WorldWideScience

Sample records for splittings shell structure

  1. 7 CFR 51.2002 - Split shell.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 2 2010-01-01 2010-01-01 false Split shell. 51.2002 Section 51.2002 Agriculture... Standards for Grades of Filberts in the Shell 1 Definitions § 51.2002 Split shell. Split shell means a shell... of the shell, measured in the direction of the crack. ...

  2. Shell-like structures

    CERN Document Server

    Altenbach, Holm

    2011-01-01

    In this volume, scientists and researchers from industry discuss the new trends in simulation and computing shell-like structures. The focus is put on the following problems: new theories (based on two-dimensional field equations but describing non-classical effects), new constitutive equations (for materials like sandwiches, foams, etc. and which can be combined with the two-dimensional shell equations), complex structures (folded, branching and/or self intersecting shell structures, etc.) and shell-like structures on different scales (for example: nano-tubes) or very thin structures (similar

  3. Temporal structures in shell models

    DEFF Research Database (Denmark)

    Okkels, F.

    2001-01-01

    The intermittent dynamics of the turbulent Gledzer, Ohkitani, and Yamada shell-model is completely characterized by a single type of burstlike structure, which moves through the shells like a front. This temporal structure is described by the dynamics of the instantaneous configuration of the shell...

  4. Plate shell structures of glass

    DEFF Research Database (Denmark)

    Bagger, Anne

    to their curved shape. A plate shell structure maintains a high stiffness-to-weight ratio, while facilitating the use of plane structural elements. The study focuses on using laminated glass panes for the load bearing facets. Various methods of generating a plate shell geometry are suggested. Together with Ghent......, such as facet size, imperfections, and connection characteristics. The critical load is compared to that of a similar, but smoothly curved, shell structure. Based on the investigations throughout the study, a set of guidelines for the structural design of plate shells of glass is proposed.......This thesis is a study of plate shell structures -- a type of shell structure with a piecewise plane geometry, organized so that the load bearing system is constituted by distributed in-plane forces in the facets. The high stiffness-to-weight ratio of smoothly curved shell structures is mainly due...

  5. Dynamic Hydrogen Production from Methanol/Water Photo-Splitting Using Core@Shell-Structured CuS@TiO2 Catalyst Wrapped by High Concentrated TiO2 Particles

    Directory of Open Access Journals (Sweden)

    Younghwan Im

    2013-01-01

    Full Text Available This study focused on the dynamic hydrogen production ability of a core@shell-structured CuS@TiO2 photocatalyst coated with a high concentration of TiO2 particles. The rectangular-shaped CuS particles, 100 nm in length and 60 nm in width, were surrounded by a high concentration of anatase TiO2 particles (>4~5 mol. The synthesized core@shell-structured CuS@TiO2 particles absorbed a long wavelength (a short band gap above 700 nm compared to that pure TiO2, which at approximately 300 nm, leading to easier electronic transitions, even at low energy. Hydrogen evolution from methanol/water photo-splitting over the core@shell-structured CuS@TiO2 photocatalyst increased approximately 10-fold compared to that over pure CuS. In particular, 1.9 mmol of hydrogen gas was produced after 10 hours when 0.5 g of 1CuS@4TiO2 was used at pH = 7. This level of production was increased to more than 4-fold at higher pH. Cyclic voltammetry and UV-visible absorption spectroscopy confirmed that the CuS in CuS@TiO2 strongly withdraws the excited electrons from the valence band in TiO2 because of the higher reduction potential than TiO2, resulting in a slower recombination rate between the electrons and holes and higher photoactivity.

  6. Structural basis of photosynthetic water-splitting

    International Nuclear Information System (INIS)

    Photosynthetic water-splitting takes place in photosystem II (PSII), a membrane protein complex consisting of 20 subunits with an overall molecular mass of 350 kDa. The light-induced water-splitting reaction catalyzed by PSII not only converts light energy into biologically useful chemical energy, but also provides us with oxygen indispensible for sustaining oxygenic life on the earth. We have solved the structure of PSII at a 1.9 Å resolution, from which, the detailed structure of the Mn 4 CaO 5 -cluster, the catalytic center for water-splitting, became clear. Based on the structure of PSII at the atomic resolution, possible mechanism of light-induced water-splitting was discussed

  7. Stokes shift and fine-structure splitting in CdSe/CdTe invert type-II ...

    Indian Academy of Sciences (India)

    Using the atomistic tight-binding (TB) theory and configuration interaction (CI) description, it is showed that the Stokes shift and fine-structure splitting (FSS) in semiconductor core/shell nanocrystals are predominantly affected by the shell thickness and band profiles. CdSe/CdTe invert type-II and CdTe/CdSe type-II core/shell ...

  8. Splitting method for computing coupled hydrodynamic and structural response

    International Nuclear Information System (INIS)

    Ash, J.E.

    1977-01-01

    A numerical method is developed for application to unsteady fluid dynamics problems, in particular to the mechanics following a sudden release of high energy. Solution of the initial compressible flow phase provides input to a power-series method for the incompressible fluid motions. The system is split into spatial and time domains leading to the convergent computation of a sequence of elliptic equations. Two sample problems are solved, the first involving an underwater explosion and the second the response of a nuclear reactor containment shell structure to a hypothetical core accident. The solutions are correlated with experimental data

  9. Shell structure of octupole deformation

    International Nuclear Information System (INIS)

    Zhang Xizhen; Dong Baoguo

    1992-01-01

    A convenient definition of intrinsic frame of an octupole deformed shape was proposed recently. The octupole deformation potential was expanded on the bases of irreducible representations of group O h . Based on the parameterization given in previous paper, the shell structures of octupole deformation which cover all possible octupole deformed shapes were studied

  10. Core-shell photoanode developed by atomic layer deposition of Bi₂O₃ on Si nanowires for enhanced photoelectrochemical water splitting.

    Science.gov (United States)

    Weng, Baicheng; Xu, Fenghua; Xu, Jianguang

    2014-11-14

    Core-shell nanowire (NW) arrays, which feature a vertically aligned n-type Si NW core and a p-type α-Bi₂O₃ shell, are developed as a highly efficient photoanode that is suitable for water splitting. The morphology and structure of the heterostructure were characterized by scanning electron microscopy (SEM), energy-dispersive x-ray spectroscopy (EDS), high-resolution transmission electron microscopy (HRTEM), x-ray photoelectron spectroscopy (XPS), and x-ray diffraction (XRD). The deposition of Bi₂O₃ nanolayers on the surface of the smooth Si NWs causes the surface of the NWs to become rough. The as-prepared core-shell NW photoelectrode has a relatively low reflectance in the visible light region, suggesting good light absorption. The core-shell NW arrays show greatly improved photoelectrochemical water-splitting performance. Photoelectrochemical stability for over 16 h under constant light illumination and fixed bias potential was achieved, illustrating the good stability of this core-shell NW photoanode. These Si/Bi₂O₃ core-shell NW arrays effectively combine the light absorption ability of the Si NWs and the wide energy gap and chemical stability of Bi₂O₃ for water splitting. This study furthers the attempts to design photoanodes from low-cost, abundant materials for applications in water splitting and photovoltaics.

  11. Giant Rabi Splitting of Whispering Gallery Polaritons in GaN/InGaN Core-Shell Wire.

    Science.gov (United States)

    Gong, Su-Hyun; Ko, Suk-Min; Jang, Min-Ho; Cho, Yong-Hoon

    2015-07-08

    The hybrid nature of exciton polaritons opens up possibilities for developing a new concept nonlinear photonic device (e.g., polariton condensation, switching, and transistor) with great potential for controllability. Here, we proposed a novel type of polariton system resulting from strong coupling between a two-dimensional exciton and whispering gallery mode photon using a core-shell GaN/InGaN hexagonal wire. High quality, nonpolar InGaN multiple-quantum wells (MQWs) were conformally formed on a GaN core nanowire, which was spatially well matched with whispering gallery modes inside the wire. Both high longitudinal-transverse splitting of nonpolar MQWs and high spatial overlap with whispering gallery modes lead to unprecedented large Rabi splitting energy of ∼180 meV. This structure provides a robust polariton effect with a small footprint; thus, it could be utilized for a wide range of interesting applications.

  12. Stokes shift and fine-structure splitting in CdSe / CdTe invert type-II ...

    Indian Academy of Sciences (India)

    Worasak Sukkabot

    2018-01-09

    Jan 9, 2018 ... that the Stokes shift and fine-structure splitting (FSS) in semiconductor core/shell nanocrystals are predominantly affected by the shell thickness and band profiles. CdSe/CdTe invert type-II and CdTe/CdSe type-II core/shell nanocrystals are used as the simulated candidates in order to obtain the different ...

  13. Engineered Magnetic Core-Shell Structures.

    Science.gov (United States)

    Alavi Nikje, Mir Mohammad; Vakili, Maryam

    2015-01-01

    In recent years, engineered magnetic core-shell structures are playing an important role in the wide range of various applications. These magnetic core-shell structures have attracted considerable attention because of their unique properties and various applications. Also, the synthesis of engineered magnetic core-shell structures has attracted practical interest because of potential applications in areas such as ferrofluids, medical imaging, drug targeting and delivery, cancer therapy, separations, and catalysis. So far a large number of engineered magnetic core-shell structures have been successfully synthesized. This review article focuses on the recent progress in synthesis and characterization of engineered magnetic core-shell structures. Also, this review gives a brief description of the various application of these structures. It is hoped that this review will play some small part in helping future developments in important field.

  14. Plate shell structures - statics and stability

    DEFF Research Database (Denmark)

    Almegaard, Henrik

    2008-01-01

    This paper describes the basic structural system, statics and spatial stability of plate shells. The structural system can be considered as a single layer of planar elements, where each element only transfers in-plane (membrane) forces to its neighbouring elements. External out-of-plane loads...... system is dual to that of a spatial truss system, which means the stringer system [1] can be applied to plate-shell structures....

  15. Split mandrel versus split sleeve coldworking: Dual methods for extending the fatigue life of metal structures

    Science.gov (United States)

    Rodman, Geoffrey A.; Creager, Matthew

    1994-01-01

    It is common practice to use split sleeve coldworking of fastener holes as a means of extending the fatigue life of metal structures. In search of lower manufacturing costs, the aerospace industry is examining the split mandrel (sleeveless) coldworking process as an alternative method of coldworking fastener holes in metal structures. The split mandrel process (SpM) significantly extends the fatigue life of metal structures through the introduction of a residual compressive stress in a manner that is very similar to the split sleeve system (SpSl). Since the split mandrel process is significantly less expensive than the split sleeve process and more adaptable to robotic automation, it will have a notable influence upon other new manufacture of metal structures which require coldworking a significant number of holes, provided the aerospace community recognizes that the resulting residual stress distributions and fatigue life improvement are the same for both processes. Considerable testing has validated the correctness of that conclusion. The findings presented in this paper represent the results of an extensive research and development program, comprising data collected from over 400 specimens fabricated from 2024-T3 and 7075-T651 aluminum alloys in varied configurations, which quantify the benefits (fatigue enhancement and cost savings) of automating a sleeveless coldworking system.

  16. Structural shell analysis understanding and application

    CERN Document Server

    Blaauwendraad, Johan

    2014-01-01

    The mathematical description of the properties of a shell is much more elaborate than those of beam and plate structures. Therefore many engineers and architects are unacquainted with aspects of shell behaviour and design, and are not familiar with sufficiently reliable shell theories for the different shell types as derived in the middle of the 20th century. Rather than contributing to theory development, this university textbook focuses on architectural and civil engineering schools. Of course, practising professionals will profit from it as well. The book deals with thin elastic shells, in particular with cylindrical, conical and spherical types, and with elliptic and hyperbolic paraboloids. The focus is on roofs, chimneys, pressure vessels and storage tanks. Special attention is paid to edge bending disturbance zones, which is indispensable knowledge in FE meshing. A substantial part of the book results from research efforts in the mid 20th century at Delft University of Technology. As such, it is a valua...

  17. Si/PEDOT hybrid core/shell nanowire arrays as photoelectrodes for photoelectrochemical water-splitting.

    Science.gov (United States)

    Li, Xiaojuan; Lu, Wenhui; Dong, Weiling; Chen, Qi; Wu, Dan; Zhou, Wenzheng; Chen, Liwei

    2013-06-21

    Si/poly(3,4-ethylenedioxythiophene) (PEDOT) core/shell nanowire arrays have been prepared by chemical etching of Si nanowires followed by vapor-phase polymerization of PEDOT as hybrid photoanodes for photoelectrochemical water-splitting. The PEDOT layer is employed as a multi-functional coating to prevent photocorrosion of Si nanowires, collect photogenerated holes and catalyze the water oxidation reaction. The amino silane modified Si nanowire surface improves PEDOT layer adhesion, and the resulting photoanode exhibits better photoresponse and improved stability. By tuning the length of the nanowires, we identify that the competition between the carrier recombination and catalytic water oxidation reaction is the primary factor determining the photoelectrocatalytic activity of the hybrid photoanode.

  18. Stability of Ag@SiO2 core–shell particles in conditions of photocatalytic overall water-splitting

    NARCIS (Netherlands)

    Park, Sun Young; Han, Kai; O'Neill, Devin B.; Mul, Guido

    2017-01-01

    Core–shell nanoparticles containing plasmonic metals (Ag or Au) have been frequently reported to enhance performance of photo-electrochemical (PEC) devices. However, the stability of these particles in water-splitting conditions is usually not addressed. In this study we demonstrate that Ag@SiO2

  19. UHPFRC in large span shell structures

    NARCIS (Netherlands)

    Ter Maten, R.N.; Grunewald, S.; Walraven, J.C.

    2013-01-01

    Ultra-High Performance Fibre-Reinforced Concrete (UHPFRC) is an innovative concrete type with a high compressive strength and a far more durable character compared to conventional concrete. UHPFRC can be applied in structures with aesthetic appearance and high material efficiency. Shell structures

  20. Conceptual Design Tool for Concrete Shell Structures

    DEFF Research Database (Denmark)

    Holst, Malene Kirstine; Kirkegaard, Poul Henning

    2011-01-01

    This paper focuses on conceptual tools for concrete shell structures when working within the span of performance-based design and computational morphogenesis. The designer, referred to as the Architect-Engineer, works through several iterations parallel with aesthetic, functional and technical...

  1. Engineered bamboo for shell structures

    OpenAIRE

    Sharma, B; Konstantatou, Marina; Reynolds, M; Ramage, M

    2015-01-01

    Engineered bamboo combines the benefits of a natural material with the advantages of a laminated composite, resulting in an efficient, light material well-suited to gridshell structures. Bamboo is a rapidly renewable material that can be harvested every 4-5 years. The round culm can either be used as is or it can be processed into a variety of laminated products. Engineered bamboo is currently promoted as a structural alternative to timber and glue-laminated timber, but also has potential in ...

  2. Drift-shell splitting of energetic ions injected at pseudo-substorm onsets

    International Nuclear Information System (INIS)

    Takahashi, K.; Anderson, B.J.; Ohtani, S.; Reeves, G.D.; Takahashi, S.; Sarris, T.E.; Mursula, K.

    1997-01-01

    One feature of a magnetospheric substorm is the injection of energetic particles into closed drift orbits. Injections are routinely observed by geosynchronous satellites and have been used to identify the occurrence of substorms and the local time of particle energization. In this study we examine pitch angle distributions of ion injections in the 50-to 300-keV energy range observed by the Active Magnetospheric Particle Tracer Explorers Charge Composition Explorer (AMPTE/CCE) satellite, hereinafter CCE. In a dipole field, all pitch angles follow the same drift shell, but the day night asymmetry of the magnetospheric magnetic field introduces a pitch angle dependence in particle drift orbits, so that particles with different pitch angles disperse radially as they drift. The effect is known as drift-shell splitting. For satellite observations near noon at a fixed geocentric distance, the guiding center orbits of ions detected at small pitch angles intersect the midnight meridian at larger geocentric distances than do ions with near-90 degree pitch angles. The ion pitch angle distributions detected on the dayside therefore provide information about the radial distance of the nightside acceleration region. We apply this principle to study ion injection events observed on September 17 - 18, 1984, in association with pseudo-substorm onsets. CCE was at 13 hours local time near its apogee (8.8R E ) and observed a series of ion flux enhancements. Energy dispersion of the timing of the flux increases assures that they are due to injections on the nightside. The flux increases were observed only at pitch angles from 0 degree to 60 degree. We calculate drift orbits of protons using the Tsyganenko 89c magnetic field model and find that the drift orbits for 60 degree pitch angle protons observed at the satellite pass through midnight at 9R E , well outside of geostationary orbit, indicating that the ion injections occurred tailward of 9R E . Energetic ion data from geostationary

  3. Radial Diffusion Caused by Pitch Angle Scattering and Drift Shell Splitting - Simulation and Van Allen Probes Observations

    Science.gov (United States)

    Henderson, M. G.; Morley, S.; Cunningham, G.; Tu, W.; Reeves, G. D.; Fennell, J. F.; Claudepierre, S. G.; Blake, J. B.; Spence, H.; Baker, D. N.

    2013-12-01

    In realistic asymmetric magnetic fields, particles with different pitch angles starting on the same field line will trace out different drift shells. As a result of this drift shell splitting, pitch angle scattering automatically leads to additional radial diffusion. At a given position on a drift shell, the instantaneous DLL associated with this process is related to the gradient of L* with respect to equatorial pitch angle and the local value of the bounce averaged Daa diffusion coefficient. The final DLL associated with pitch angle scattering is then obtained by drift averaging. We show initial results of computed DLL coefficients and simulations using the DREAM diffusion code. The results are compared with Phase Space Densities measured with the recently launched Van Allen Probes.

  4. Methodology of shell structure reinforcement layout optimization

    Science.gov (United States)

    Szafrański, Tomasz; Małachowski, Jerzy; Damaziak, Krzysztof

    2018-01-01

    This paper presents an optimization process of a reinforced shell diffuser intended for a small wind turbine (rated power of 3 kW). The diffuser structure consists of multiple reinforcement and metal skin. This kind of structure is suitable for optimization in terms of selection of reinforcement density, stringers cross sections, sheet thickness, etc. The optimisation approach assumes the reduction of the amount of work to be done between the optimization process and the final product design. The proposed optimization methodology is based on application of a genetic algorithm to generate the optimal reinforcement layout. The obtained results are the basis for modifying the existing Small Wind Turbine (SWT) design.

  5. Balsam-pear-like rutile/anatase core/shell titania nanorod arrays for photoelectrochemical water splitting

    Science.gov (United States)

    Wen, Wei; Yao, Jin-Cheng; Gu, Yi-Jie; Sun, Tu-Lai; Tian, He; Zhou, Qi-Lai; Wu, Jin-Ming

    2017-11-01

    In this work, a solution combustion followed by dissolution in hydrogen peroxide is adopted to achieve a precursor for decorating anatase TiO2 nanosheets along single-crystalline rutile TiO2 nanorods, which achieves balsam-pear-like core/shell nanorod arrays with enhanced photoelectrochemical water splitting. The enhanced photoelectrochemical performance is attributed to the novel nanoarchitecture, which can simultaneously offer a high surface area, enhanced light-harvesting, a rutile/anatase junction for charge carrier separation and a conductive pathway for charge carrier collection. The photoanode design can also give hints to other functional materials.

  6. Compact complex surfaces with geometric structures related to split quaternions

    International Nuclear Information System (INIS)

    Davidov, Johann; Grantcharov, Gueo; Mushkarov, Oleg; Yotov, Miroslav

    2012-01-01

    We study the problem of existence of geometric structures on compact complex surfaces that are related to split quaternions. These structures, called para-hypercomplex, para-hyperhermitian and para-hyperkähler, are analogs of the hypercomplex, hyperhermitian and hyperkähler structures in the definite case. We show that a compact 4-manifold carries a para-hyperkähler structure iff it has a metric of split signature together with two parallel, null, orthogonal, pointwise linearly independent vector fields. Every compact complex surface admitting a para-hyperhermitian structure has vanishing first Chern class and we show that, unlike the definite case, many of these surfaces carry infinite-dimensional families of such structures. We provide also compact examples of complex surfaces with para-hyperhermitian structures which are not locally conformally para-hyperkähler. Finally, we discuss the problem of non-existence of para-hyperhermitian structures on Inoue surfaces of type S 0 and provide a list of compact complex surfaces which could carry para-hypercomplex structures.

  7. Compact complex surfaces with geometric structures related to split quaternions

    Energy Technology Data Exchange (ETDEWEB)

    Davidov, Johann, E-mail: jtd@math.bas.bg [Institute of Mathematics and Informatics, Bulgarian Academy of Sciences, 1113 Sofia (Bulgaria); ' L. Karavelov' Civil Engineering Higher School, 175 Suhodolska Str., 1373 Sofia (Bulgaria); Grantcharov, Gueo, E-mail: grantchg@fiu.edu [Department of Mathematics and Statistics, Florida International University, Miami, FL 33199 (United States); Mushkarov, Oleg, E-mail: muskarov@math.bas.bg [Institute of Mathematics and Informatics, Bulgarian Academy of Sciences, 1113 Sofia (Bulgaria); Yotov, Miroslav, E-mail: yotovm@fiu.edu [Department of Mathematics and Statistics, Florida International University, Miami, FL 33199 (United States)

    2012-12-11

    We study the problem of existence of geometric structures on compact complex surfaces that are related to split quaternions. These structures, called para-hypercomplex, para-hyperhermitian and para-hyperkaehler, are analogs of the hypercomplex, hyperhermitian and hyperkaehler structures in the definite case. We show that a compact 4-manifold carries a para-hyperkaehler structure iff it has a metric of split signature together with two parallel, null, orthogonal, pointwise linearly independent vector fields. Every compact complex surface admitting a para-hyperhermitian structure has vanishing first Chern class and we show that, unlike the definite case, many of these surfaces carry infinite-dimensional families of such structures. We provide also compact examples of complex surfaces with para-hyperhermitian structures which are not locally conformally para-hyperkaehler. Finally, we discuss the problem of non-existence of para-hyperhermitian structures on Inoue surfaces of type S{sup 0} and provide a list of compact complex surfaces which could carry para-hypercomplex structures.

  8. Red-Light-Driven Water Splitting by Au(Core)-CdS(Shell) Half-Cut Nanoegg with Heteroepitaxial Junction.

    Science.gov (United States)

    Naya, Shin-Ichi; Kume, Takahiro; Akashi, Ryo; Fujishima, Musashi; Tada, Hiroaki

    2018-01-31

    A key material for artificial photosynthesis including water splitting is heteronanostructured (HNS) photocatalysts. The photocatalytic activity depends on the geometry and dimension, and the quality of junctions between the components. Here we present a half-cut Au(core)-CdS(shell) (HC-Au@CdS) nanoegg as a new HNS plasmonic photocatalyst for water splitting. UV-light irradiation of Au nanoparticle (NP)-loaded ZnO (Au/ZnO) at 50 °C induces the selective deposition of hexagonal CdS on the Au surface of Au/ZnO with an epitaxial (EPI) relation of CdS{0001}/Au{111}. The subsequent selective dissolution of the ZnO support at room temperature yields HC-Au@CdS with the Au NP size and EPI junction (#) retained. Red-light irradiation (λ ex = 640 nm) of HC-Au@#CdS gives rise to continuous stoichiometric water splitting with an unprecedentedly high external quantum yield of 0.24%.

  9. Solar water splitting with III-N nanocolumn structures

    Science.gov (United States)

    Medvedev, O. S.; Puzyk, M. V.; Usikov, A. S.; Helava, H.; Makarov, Yu N.

    2017-11-01

    HVPE – grown GaN/AlGaN p-n structures with nanocolumns fabricated on the top (1.0 μm of height and 100-130 nm of diameter) were used in a photoelectrochemical process to investigate direct water splitting. The H2 production rate of 0.56 ml/cm2 × h was measured for the GaN/AlGaN structures in KOH electrolyte under the Xe-lamp illumination. H2 evolution was observed at the Pt electrode. However an etching and a small amount of generated gas was observed at the working electrode. Possible mechanisms of corrosion in GaN/AlGAN nanocolumn structures are discussed. A sacrificial agent (like HBr) or the surface passivation by nitrogen atoms is needed to prevent oxidation and etching of the III-N materials.

  10. Micromagnetic studies of three-dimensional pyramidal shell structures

    International Nuclear Information System (INIS)

    Knittel, A; Franchin, M; Fischbacher, T; Fangohr, H; Nasirpouri, F; Bending, S J

    2010-01-01

    We present a systematic numerical analysis of the magnetic properties of pyramidal-shaped core-shell structures in a size range below 400 nm. These are three-dimensional structures consisting of a ferromagnetic shell which is grown on top of a non-magnetic core. The standard micromagnetic model without the magnetocrystalline anisotropy term is used to describe the properties of the shell. We vary the thickness of the shell between the limiting cases of an ultra-thin shell and a conventional pyramid and delineate different stable magnetic configurations. We find different kinds of single-domain states, which predominantly occur at smaller system sizes. In analogy to equivalent states in thin square films we term these onion, flower, C and S states. At larger system sizes, we also observe two types of vortex states, which we refer to as symmetric and asymmetric vortex states. For a classification of the observed states, we derive a phase diagram that specifies the magnetic ground state as a function of structure size and shell thickness. The transitions between different ground states can be understood qualitatively. We address the issue of metastability by investigating the stability of all occurring configurations for different shell thicknesses. For selected geometries and directions hysteresis measurements are analysed and discussed. We observe that the magnetic behaviour changes distinctively in the limit of ultra-thin shells. The study has been motivated by the recent progress made in the growth of faceted core-shell structures.

  11. Synthesis and characterization of core-shell metal oxide nanoparticles for efficient electrochemical water splitting

    OpenAIRE

    Nong, Hong Nhan

    2016-01-01

    Electrocatalytic water splitting is expected to emerge as a key technology for the storage of excess electricity from renewable sources in form of hydrogen or for production of sustainable hydrogen fuel as part of a solar refinery. In particular, polymer electrolyte membrane (PEM) electrolyzers, owing to their high voltage efficiency, high current density, good partial loading range, compact system design, high gas purity and rapid system response, will likely play a critically important role...

  12. The split coaxial linac structure and its RF modes

    International Nuclear Information System (INIS)

    Mueller, R.W.

    1989-01-01

    The Split Coaxial Cavity structure has been invented and applied for the first time in the heavy-ion RFQ linac MAXILAC of GSI. It has an ideally flat RF voltage distribution and a good power economy. From another standpoint, it is a member of the small family of linac structures where the two modes, the wanted one and the unflatness mode, are clearly and strictly separable. The unflatness or ''Q Line'' mode is analyzed in more detail in this paper. It is necessary for the understanding of the interaction of the beam with the cavity, possible beam instabilities resulting from it, and for curing these instabilities with the chance of obtaining improved beams. (orig.)

  13. Periodic transmission peak splitting in one dimensional disordered photonic structures

    Science.gov (United States)

    Kriegel, Ilka; Scotognella, Francesco

    2016-08-01

    In the present paper we present ways to modulate the periodic transmission peaks arising in disordered one dimensional photonic structures with hundreds of layers. Disordered structures in which the optical length nd (n is the refractive index and d the layer thickness) is the same for each layer show regular peaks in their transmission spectra. A proper variation of the optical length of the layers leads to a splitting of the transmission peaks. Notably, the variation of the occurrence of high and low refractive index layers, gives a tool to tune also the width of the peaks. These results are of highest interest for optical application, such as light filtering, where the manifold of parameters allows a precise design of the spectral transmission ranges.

  14. Shell model description of band structure in 48Cr

    International Nuclear Information System (INIS)

    Vargas, Carlos E.; Velazquez, Victor M.

    2007-01-01

    The band structure for normal and abnormal parity bands in 48Cr are described using the m-scheme shell model. In addition to full fp-shell, two particles in the 1d3/2 orbital are allowed in order to describe intruder states. The interaction includes fp-, sd- and mixed matrix elements

  15. Process to make core-shell structured nanoparticles

    Science.gov (United States)

    Luhrs, Claudia; Phillips, Jonathan; Richard, Monique N

    2014-01-07

    Disclosed is a process for making a composite material that contains core-shell structured nanoparticles. The process includes providing a precursor in the form of a powder a liquid and/or a vapor of a liquid that contains a core material and a shell material, and suspending the precursor in an aerosol gas to produce an aerosol containing the precursor. In addition, the process includes providing a plasma that has a hot zone and passing the aerosol through the hot zone of the plasma. As the aerosol passes through the hot zone of the plasma, at least part of the core material and at least part of the shell material in the aerosol is vaporized. Vapor that contains the core material and the shell material that has been vaporized is removed from the hot zone of the plasma and allowed to condense into core-shell structured nanoparticles.

  16. Using a Combination of FEM and Perturbation Method in Frequency Split Calculation of a Nearly Axisymmetric Shell with Middle Surface Shape Defect

    Directory of Open Access Journals (Sweden)

    D. S. Vakhlyarskiy

    2016-01-01

    Full Text Available This paper proposes a method to calculate the splitting of natural frequency of the shell of hemispherical resonator gyro. (HRG. The paper considers splitting that arises from the small defect of the middle surface, which makes the resonator different from the rotary shell. The presented method is a combination of the perturbation method and the finite element method. The method allows us to find the frequency splitting caused by defects in shape, arbitrary distributed in the circumferential direction. This is achieved by calculating the perturbations of multiple natural frequencies of the second and higher orders. The proposed method allows us to calculate the splitting of multiple frequencies for the shell with the meridian of arbitrary shape.A developed finite element is an annular element of the shell and has two nodes. Projections of movements are used on the axis of the global cylindrical system of coordinates, as the unknown. To approximate the movements are used polynomials of the second degree. Within the finite element the geometric characteristics are arranged in a series according to the small parameter of perturbations of the middle surface geometry.Movements on the final element are arranged in series according to the small parameter, and in a series according to circumferential angle. With computer used to implement the method, three-dimensional arrays are used to store the perturbed quantities. This allows the use of regular expressions for the mass and stiffness matrices, when building the finite element, instead of analytic dependencies for each perturbation of these matrices of the required order with desirable mathematical operations redefined in accordance with the perturbation method.As a test task, is calculated frequency splitting of non-circular cylindrical resonator with Navier boundary conditions. The discrepancy between the results and semi-analytic solution to this problem is less than 1%. For a cylindrical shell is

  17. Interface Fracture in Adhesively Bonded Shell Structures

    DEFF Research Database (Denmark)

    Jensen, Henrik Myhre

    2007-01-01

    Two methods for the prediction of crack propagation through the interface of adhesively bonded shells are discussed. One is based on a fracture mechanics approach; the other is based on a cohesive zone approach. Attention is focussed on predicting the shape of the crack front and the critical...... to take into account effects such as plastic deformation in the adhering shells, and to take into account effects of large local curvatures of the interface crack front. The comparison shows a convergence of the results based on the cohesive zone model towards the results based on a fracture mechanics...

  18. Communication: spin-orbit splittings in degenerate open-shell states via Mukherjee's multireference coupled-cluster theory: a measure for the coupling contribution.

    Science.gov (United States)

    Mück, Leonie Anna; Gauss, Jürgen

    2012-03-21

    We propose a generally applicable scheme for the computation of spin-orbit (SO) splittings in degenerate open-shell systems using multireference coupled-cluster (MRCC) theory. As a specific method, Mukherjee's version of MRCC (Mk-MRCC) in conjunction with an effective mean-field SO operator is adapted for this purpose. An expression for the SO splittings is derived and implemented using Mk-MRCC analytic derivative techniques. The computed SO splittings are found to be in satisfactory agreement with experimental data. Due to the symmetry properties of the SO operator, SO splittings can be considered a quality measure for the coupling between reference determinants in Jeziorski-Monkhorst based MRCC methods. We thus provide numerical insights into the coupling problem of Mk-MRCC theory. © 2012 American Institute of Physics

  19. Radar attenuation in Europa's ice shell: obstacles and opportunities for constraining shell thickness and thermal structure

    Science.gov (United States)

    Kalousova, Klara; Schroeder, Dustin M.; Soderlund, Krista M.; Sotin, Christophe

    2016-10-01

    With its strikingly young surface and possibly recent endogenic activity, Europa is one of the most exciting bodies within our Solar System and a primary target for spacecraft exploration. Future missions to Europa are expected to carry ice penetrating radar instruments which are powerful tools to investigate the subsurface thermophysical structure of its ice shell.Several authors have addressed the 'penetration depth' of radar sounders at icy moons, however, the concept and calculation of a single value penetration depth is a potentially misleading simplification since it ignores the thermal and attenuation structure complexity of a realistic ice shell. Here we move beyond the concept of a single penetration depth by exploring the variation in two-way radar attenuation for a variety of potential thermal structures of Europa's ice shell as well as for a low loss and high loss temperature-dependent attenuation model. The possibility to detect brines is also investigated.Our results indicate that: (i) for all ice shell thicknesses investigated (5-30 km), a nominal satellite-borne radar sounder will penetrate between 15% and 100% of the total thickness, (ii) the maximum penetration depth strongly varies laterally with the deepest penetration possible through the cold downwellings, (iii) the direct detection of the ice/ocean interface might be possible for shells of up to 15 km if the radar signal travels through the cold downwelling, (iv) even if the ice/ocean interface is not detected, the penetration through most of the shell could constrain the deep shell structure through the loss of signal, and (v) for all plausible ice shells the two-way attenuation to the eutectic point is ≤30 dB which shows a robust potential for longitudinal investigation of the ice shell's shallow structure.Part of this work has been performed at the Jet Propulsion Laboratory, California Institute of Technology, under contract to NASA. K.K. acknowledges support by the Grant Agency of the

  20. A structure-preserving split finite element discretization of the split 1D linear shallow-water equations

    Science.gov (United States)

    Bauer, Werner; Behrens, Jörn

    2017-04-01

    We present a locally conservative, low-order finite element (FE) discretization of the covariant 1D linear shallow-water equations written in split form (cf. tet{[1]}). The introduction of additional differential forms (DF) that build pairs with the original ones permits a splitting of these equations into topological momentum and continuity equations and metric-dependent closure equations that apply the Hodge-star. Our novel discretization framework conserves this geometrical structure, in particular it provides for all DFs proper FE spaces such that the differential operators (here gradient and divergence) hold in strong form. The discrete topological equations simply follow by trivial projections onto piecewise constant FE spaces without need to partially integrate. The discrete Hodge-stars operators, representing the discretized metric equations, are realized by nontrivial Galerkin projections (GP). Here they follow by projections onto either a piecewise constant (GP0) or a piecewise linear (GP1) space. Our framework thus provides essentially three different schemes with significantly different behavior. The split scheme using twice GP1 is unstable and shares the same discrete dispersion relation and similar second-order convergence rates as the conventional P1-P1 FE scheme that approximates both velocity and height variables by piecewise linear spaces. The split scheme that applies both GP1 and GP0 is stable and shares the dispersion relation of the conventional P1-P0 FE scheme that approximates the velocity by a piecewise linear and the height by a piecewise constant space with corresponding second- and first-order convergence rates. Exhibiting for both velocity and height fields second-order convergence rates, we might consider the split GP1-GP0 scheme though as stable versions of the conventional P1-P1 FE scheme. For the split scheme applying twice GP0, we are not aware of a corresponding conventional formulation to compare with. Though exhibiting larger

  1. Topology optimization of 3D shell structures with porous infill

    DEFF Research Database (Denmark)

    Clausen, Anders; Andreassen, Erik; Sigmund, Ole

    2017-01-01

    This paper presents a 3D topology optimization approach for designing shell structures with a porous or void interior. It is shown that the resulting structures are significantly more robust towards load perturbations than completely solid structures optimized under the same conditions. The study...... indicates that the potential benefit of using porous structures is higher for lower total volume fractions. Compared to earlier work dealing with 2D topology optimization, we found several new effects in 3D problems. Most notably, the opportunity for designing closed shells significantly improves...

  2. Atomic oxygen fine-structure splittings with tunable far-infrared spectroscopy

    Science.gov (United States)

    Zink, Lyndon R.; Evenson, Kenneth M.; Matsushima, Fusakazu; Nelis, Thomas; Robinson, Ruth L.

    1991-01-01

    Fine-structure splittings of atomic oxygen (O-16) in the ground state have been accurately measured using a tunable far-infrared spectrometer. The 3P0-3pl splitting is 2,060,069.09 (10) MHz, and the 3Pl-3P2 splitting is 4,744,777.49 (16) MHz. These frequencies are important for measuring atomic oxygen concentration in earth's atmosphere and the interstellar medium.

  3. Dynamic characteristics of cylindrical shells considering Fluid-structure interaction

    International Nuclear Information System (INIS)

    Jhung, Myung Jo; Kim, Wal Tae; Ryu, Yong Ho

    2009-01-01

    To assure the reliability of cylinders or shells with fluid-filled annulus, it is necessary to investigate the modal characteristics considering fluid-structure interaction effect. In this study, theoretical background and several finite element models are developed for cylindrical shells with fluid-filled annulus considering fluid-structure interaction. The effect of the inclusion of the fluid-filled annulus on the natural frequencies is investigated, which frequencies are used for typical dynamic analyses such as responses spectrum, power spectral density and unit load excitation. Their response characteristics are addressed with respect to the various representations of the fluid-structure interaction effect

  4. Facile Spray-Pyrolysis Synthesis of Yolk-Shell Earth-Abundant Elemental Nickel-Iron-Based Nanohybrid Electrocatalysts for Full Water Splitting.

    Science.gov (United States)

    Li, Hao; Ci, Suqin; Zhang, Mengtian; Chen, Junxiang; Lai, Keyuan; Wen, Zhenhai

    2017-12-08

    The development of high-activity electrocatalysts for water splitting that comprise only inexpensive, earth-abundant elements is critical but remains a daunting challenge. In this work, yolk-shell Ni 3 Fe/Ni 3 FeN was prepared by a spray-pyrolysis technique, which could be scaleable. The yolk-shell Ni 3 Fe/Ni 3 FeN presents excellent catalytic activity for the oxygen evolution reaction (OER) and the hydrogen evolution reaction (HER) with overpotentials of 268 and 166 mV at 10 mA cm -2 , respectively, and bears a prominent electrochemical durability. Overall water splitting with an electrolyzer containing the yolk-shell Ni 3 Fe/Ni 3 FeN as the cathode and anode only requires a cell voltage of 1.62 V to reach a current density of 10 mA cm -2 . The present research not only introduces a new route for the synthesis of advanced functional electrocatalysts for overall water splitting but also sheds light on their potential commercial applications. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Oxide-supported IrNiO(x) core-shell particles as efficient, cost-effective, and stable catalysts for electrochemical water splitting.

    Science.gov (United States)

    Nong, Hong Nhan; Oh, Hyung-Suk; Reier, Tobias; Willinger, Elena; Willinger, Marc-Georg; Petkov, Valeri; Teschner, Detre; Strasser, Peter

    2015-03-02

    Active and highly stable oxide-supported IrNiO(x) core-shell catalysts for electrochemical water splitting are presented. IrNi(x)@IrO(x) nanoparticles supported on high-surface-area mesoporous antimony-doped tin oxide (IrNiO(x)/Meso-ATO) were synthesized from bimetallic IrNi(x) precursor alloys (PA-IrNi(x) /Meso-ATO) using electrochemical Ni leaching and concomitant Ir oxidation. Special emphasis was placed on Ni/NiO surface segregation under thermal treatment of the PA-IrNi(x)/Meso-ATO as well as on the surface chemical state of the particle/oxide support interface. Combining a wide array of characterization methods, we uncovered the detrimental effect of segregated NiO phases on the water splitting activity of core-shell particles. The core-shell IrNiO(x)/Meso-ATO catalyst displayed high water-splitting activity and unprecedented stability in acidic electrolyte providing substantial progress in the development of PEM electrolyzer anode catalysts with drastically reduced Ir loading and significantly enhanced durability. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Electronic shell structure and chemisorption on gold nanoparticles

    DEFF Research Database (Denmark)

    Larsen, Ask Hjorth; Kleis, Jesper; Thygesen, Kristian Sommer

    2011-01-01

    to distort considerably, creating large band gaps at the Fermi level. For up to 200 atoms we consider structures generated with a simple EMT potential and clusters based on cuboctahedra and icosahedra. All types of cluster geometry exhibit jelliumlike electronic shell structure. We calculate adsorption...

  7. Electron refrigeration in hybrid structures with spin-split superconductors

    Science.gov (United States)

    Rouco, M.; Heikkilä, T. T.; Bergeret, F. S.

    2018-01-01

    Electron tunneling between superconductors and normal metals has been used for an efficient refrigeration of electrons in the latter. Such cooling is a nonlinear effect and usually requires a large voltage. Here we study the electron cooling in heterostructures based on superconductors with a spin-splitting field coupled to normal metals via spin-filtering barriers. The cooling power shows a linear term in the applied voltage. This improves the coefficient of performance of electron refrigeration in the normal metal by shifting its optimum cooling to lower voltage, and also allows for cooling the spin-split superconductor by reverting the sign of the voltage. We also show how tunnel coupling spin-split superconductors with regular ones allows for a highly efficient refrigeration of the latter.

  8. Overview of Hanford Single Shell Tank (SST) Structural Integrity

    Energy Technology Data Exchange (ETDEWEB)

    Rast, Richard S.; Washenfelder, Dennis J.; Johnson, Jeremy M.

    2013-11-14

    To improve the understanding of the single-shell tanks (SSTs) integrity, Washington River Protection Solutions, LLC (WRPS), the USDOE Hanford Site tank contractor, developed an enhanced Single-Shell Tank Integrity Project (SSTIP) in 2009. An expert panel on SST integrity, consisting of various subject matters experts in industry and academia, was created to provide recommendations supporting the development of the project. This panel developed 33 recommendations in four main areas of interest: structural integrity, liner degradation, leak integrity and prevention, and mitigation of contamination migration, Seventeen of these recommendations were used to develop the basis for the M-45-10-1 Change Package for the Hanford Federal Agreement and Compliance Order, which is also known as the Tri-Party Agreement. The structural integrity of the tanks is a key element in completing the cleanup mission at the Hanford Site. There are eight primary recommendations related to the structural integrity of Hanford Single-Shell Tanks. Six recommendations are being implemented through current and planned activities. The structural integrity of the Hanford is being evaluated through analysis, monitoring, inspection, materials testing, and construction document review. Structural evaluation in the form of analysis is performed using modern finite element models generated in ANSYS. The analyses consider in-situ, thermal, operating loads and natural phenomena such as earthquakes. Structural analysis of 108 of 149 Hanford Single-Shell Tanks has concluded that the tanks are structurally sound and meet current industry standards. Analysis of the remaining Hanford Single-Shell Tanks is scheduled for FY2014. Hanford Single-Shell Tanks are monitored through a dome deflection program. The program looks for deflections of the tank dome greater than 1/4 inch. No such deflections have been recorded. The tanks are also subjected to visual inspection. Digital cameras record the interior surface of

  9. Identification of genomic indels and structural variations using split reads

    Directory of Open Access Journals (Sweden)

    Urban Alexander E

    2011-07-01

    Full Text Available Abstract Background Recent studies have demonstrated the genetic significance of insertions, deletions, and other more complex structural variants (SVs in the human population. With the development of the next-generation sequencing technologies, high-throughput surveys of SVs on the whole-genome level have become possible. Here we present split-read identification, calibrated (SRiC, a sequence-based method for SV detection. Results We start by mapping each read to the reference genome in standard fashion using gapped alignment. Then to identify SVs, we score each of the many initial mappings with an assessment strategy designed to take into account both sequencing and alignment errors (e.g. scoring more highly events gapped in the center of a read. All current SV calling methods have multilevel biases in their identifications due to both experimental and computational limitations (e.g. calling more deletions than insertions. A key aspect of our approach is that we calibrate all our calls against synthetic data sets generated from simulations of high-throughput sequencing (with realistic error models. This allows us to calculate sensitivity and the positive predictive value under different parameter-value scenarios and for different classes of events (e.g. long deletions vs. short insertions. We run our calculations on representative data from the 1000 Genomes Project. Coupling the observed numbers of events on chromosome 1 with the calibrations gleaned from the simulations (for different length events allows us to construct a relatively unbiased estimate for the total number of SVs in the human genome across a wide range of length scales. We estimate in particular that an individual genome contains ~670,000 indels/SVs. Conclusions Compared with the existing read-depth and read-pair approaches for SV identification, our method can pinpoint the exact breakpoints of SV events, reveal the actual sequence content of insertions, and cover the whole

  10. Structural qualification of the multifunctional instrument tree for installation in double-shell and 100-series single-shell tanks

    International Nuclear Information System (INIS)

    Strohlow, J.P.

    1995-12-01

    This document provides the technical basis and methodology for qualifying the multifunctional instrument tree (MIT) structure for installation in double-shell and 100-series single-shell tanks. Structural qualification for MIT installations in specific tanks are also contained in this document

  11. The effect of mesh size on failure for shell structures

    NARCIS (Netherlands)

    Walters, C.L.; Schipperen, J.H.A.

    2012-01-01

    More than any other application, simulation of crash events depends on the precise representation of fracture. At the same time, practical considerations typically force the crash analyst to use shell elements for many types of thin-walled structures, such as cars, aircraft, and ships. For these

  12. "Shell and space structures in modern engineering: Challenges and ...

    African Journals Online (AJOL)

    "Shell and space structures in modern engineering: Challenges and opportunities" - An Inaugural Lecture. A Zingoni. Abstract. An Inaugural Lecture Given in the University of Zimbabwe On 4 July 2001. Full Text: EMAIL FULL TEXT EMAIL FULL TEXT · DOWNLOAD FULL TEXT DOWNLOAD FULL TEXT.

  13. Active Sites Intercalated Ultrathin Carbon Sheath on Nanowire Arrays as Integrated Core-Shell Architecture: Highly Efficient and Durable Electrocatalysts for Overall Water Splitting.

    Science.gov (United States)

    Hou, Jungang; Wu, Yunzhen; Cao, Shuyan; Sun, Yiqing; Sun, Licheng

    2017-12-01

    The development of active bifunctional electrocatalysts with low cost and earth-abundance toward oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) remains a great challenge for overall water splitting. Herein, metallic Ni 4 Mo nanoalloys are firstly implanted on the surface of NiMoO x nanowires array (NiMo/NiMoO x ) as metal/metal oxides hybrid. Inspired by the superiority of carbon conductivity, an ultrathin nitrogen-doped carbon sheath intercalated NiMo/NiMoO x (NC/NiMo/NiMoO x ) nanowires as integrated core-shell architecture are constructed. The integrated NC/NiMo/NiMoO x array exhibits an overpotential of 29 mV at 10 mA cm -2 and a low Tafel slope of 46 mV dec -1 for HER due to the abundant active sites, fast electron transport, low charge-transfer resistance, unique architectural structure and synergistic effect of carbon sheath, nanoalloys, and oxides. Moreover, as OER catalysts, the NC/NiMo/NiMoO x hybrids require an overpotential of 284 mV at 10 mA cm -2 . More importantly, the NC/NiMo/NiMoO x array as a highly active and stable electrocatalyst approaches ≈10 mA cm -2 at a voltage of 1.57 V, opening an avenue to the rational design and fabrication of the promising electrode materials with architecture structures toward the electrochemical energy storage and conversion. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Investigation of stresses in facetted glass shell structures

    DEFF Research Database (Denmark)

    Bagger, Anne; Jönsson, Jeppe; Wester, Ture

    2007-01-01

    system, while the glass merely serves as a separation of the inside environment from the outside. In this paper facetted glass shell structures with three way vertices, i.e. with three adjoining edges in each vertex are considered, since the load carrying ability of such a structure is achieved primarily......The typical use of triangular and quadrangular facets in doubly curved facetted shells requires the use of triangulated truss systems or quadrangular truss framing with diagonals or cross tension cabling. In such a structure, the load carrying ability is based on concentrated forces in the framing...... by in-plane forces in the facets and the transfer of distributed in-plane forces across the joints. It is described how these facets work structurally, specifically how bending moments develop and cause possible stress concentrations in the corners, which are subjected to uplift. Apart from local...

  15. Cu cluster shell structure at elevated temperatures

    DEFF Research Database (Denmark)

    Christensen, Ole Bøssing; Jacobsen, Karsten Wedel; Nørskov, Jens Kehlet

    1991-01-01

    Equilibrium structures of small (3–29)-atom Cu clusters are determined by simulated annealing, and finite-temperature ensembles are simulated by Monte Carlo techniques using the effective-medium theory for the energy calculation. Clusters with 8, 18, and 20 atoms are found to be particularly stab...

  16. Preparation of porous carbon particle with shell/core structure

    Directory of Open Access Journals (Sweden)

    2007-05-01

    Full Text Available Porous carbon particles with a shell/core structure have been prepared successfully by controlled precipitation of the polymer from droplets of oil-in-water emulsion, followed by curing and carbonization. The droplets of the oil phase are composed of phenolic resin (PFR, a good solvent (ethyl acetate and porogen (Poly(methyl methacrylate, PMMA. The microstructure was characterized in detail by scanning electron microscopy (SEM, transmission electron microscopy (TEM, nitrogen adsorption, and thermo gravimetric analysis (TGA. The obtained carbon particles have a capsular structure with a microporous carbon shell and a mesoporous carbon core. The BET surface area and porous volume are calculated to be 499 m2g-1 and 0.56 cm3g-1, respectively. The effects of the amount of porogen (PMMA, co-solvent (acetone and surfactant on the resultant structure were studied in detail.

  17. Fast and low-cost synthesis of 1D ZnO–TiO{sub 2} core–shell nanoarrays: Characterization and enhanced photo-electrochemical performance for water splitting

    Energy Technology Data Exchange (ETDEWEB)

    Hernández, Simelys, E-mail: simelys.hernandez@iit.it [Center for Space Human Robotics (IIT-POLITO), Istituto Italiano di Tecnologia, Corso Trento 21, 10129 Torino (Italy); Cauda, Valentina; Hidalgo, Diana; Farías Rivera, Vivian; Manfredi, Diego; Chiodoni, Angelica [Center for Space Human Robotics (IIT-POLITO), Istituto Italiano di Tecnologia, Corso Trento 21, 10129 Torino (Italy); Pirri, Fabrizio C. [Center for Space Human Robotics (IIT-POLITO), Istituto Italiano di Tecnologia, Corso Trento 21, 10129 Torino (Italy); Applied Science and Technology Department, Politecnico di Torino, Corso Duca degli Abruzzi 24, 10129 Torino (Italy)

    2014-12-05

    Highlights: • Simple, fast and low-cost synthesis of 1-D ZnO–TiO{sub 2} core–shell heterostructures. • ZnO NWs completely covered with a shell of anatase TiO{sub 2} nanocrystals in only 3 min. • The TiO{sub 2} shell thickness depends on the impregnation time in the titania synthesis bath. • 2-fold enhancement of photo-electrochemical activity and better stability of ZnONWs. • Forty- times higher photocurrent densities than TiO{sub 2} nanoparticles film. - Abstract: We report on a simple, fast and low-cost synthesis procedure for the complete covering of zinc oxide (ZnO) 1D nanostructures with a protective shell of titania (TiO{sub 2}) nanoparticles. ZnO nanowires (NWs) were grown on transparent F-doped Tin Oxide (FTO) conductive layer on glass by seed layer-assisted hydrothermal route in aqueous media, while the titania shell was deposited on the ZnO NWs through an in situ non-acid sol–gel synthesis. The nanowires impregnation time in the titania sol was varied from 3 to 10 min. The resulting core–shell ZnO–TiO{sub 2} structures were characterized by different techniques, including Scanning and Transmission Electron Microscopy, X-ray diffraction and UV–Vis spectroscopy, confirming the uniform coverage of the wurzite ZnO NWs with anatase TiO{sub 2} nanoparticles (NPs), with a shell thickness dependent on the impregnation time in the titania synthesis bath. Photoelectrochemical (PEC) tests of the ZnO–TiO{sub 2} material, used as anode for the water splitting reaction, confirmed the formation of the heterojunction by the enhanced photocurrent densities, reaching values of about 0.7 mA/cm{sup 2} under simulated solar light (AM1.5G, 100mW/cm{sup 2}). The core–shell photo-anodes performance was about twice and forty- times better than the ones with a film of equivalent thickness of bare ZnO NWs and TiO{sub 2} NPs, respectively. Steady-state measures of the photocurrent over the time and FESEM analysis confirmed that this procedure could be

  18. Material Distribution Optimization for the Shell Aircraft Composite Structure

    Science.gov (United States)

    Shevtsov, S.; Zhilyaev, I.; Oganesyan, P.; Axenov, V.

    2016-09-01

    One of the main goal in aircraft structures designing isweight decreasing and stiffness increasing. Composite structures recently became popular in aircraft because of their mechanical properties and wide range of optimization possibilities.Weight distribution and lay-up are keys to creating lightweight stiff strictures. In this paperwe discuss optimization of specific structure that undergoes the non-uniform air pressure at the different flight conditions and reduce a level of noise caused by the airflowinduced vibrations at the constrained weight of the part. Initial model was created with CAD tool Siemens NX, finite element analysis and post processing were performed with COMSOL Multiphysicsr and MATLABr. Numerical solutions of the Reynolds averaged Navier-Stokes (RANS) equations supplemented by k-w turbulence model provide the spatial distributions of air pressure applied to the shell surface. At the formulation of optimization problem the global strain energy calculated within the optimized shell was assumed as the objective. Wall thickness has been changed using parametric approach by an initiation of auxiliary sphere with varied radius and coordinates of the center, which were the design variables. To avoid a local stress concentration, wall thickness increment was defined as smooth function on the shell surface dependent of auxiliary sphere position and size. Our study consists of multiple steps: CAD/CAE transformation of the model, determining wind pressure for different flow angles, optimizing wall thickness distribution for specific flow angles, designing a lay-up for optimal material distribution. The studied structure was improved in terms of maximum and average strain energy at the constrained expense ofweight growth. Developed methods and tools can be applied to wide range of shell-like structures made of multilayered quasi-isotropic laminates.

  19. Magnetic Core-Shell Morphology of Structurally Uniform Magnetite Nanoparticles

    Science.gov (United States)

    Krycka, Kathryn

    2011-03-01

    Magnetic nanoscale structures are intriguing, in part, because of the exotic properties that emerge compared with bulk. The reduction of magnetic moment per atom in magnetite with decreasing nanoparticle size, for example, has been hypothesized to originate from surface disordering to anisotropy-induced radial canting, which are difficult to distinguish using conventional magnetometry. Small-angle neutron scattering (SANS) is ideal for probing structure, both chemical and magnetic, from nm to microns across an ensemble of particles. Adding polarization analysis (PASANS) of the neutron spin orientation before and after interaction with the scattering particles allows the magnetic structure to be separated into its vector components. Application of this novel technique to 9 nm magnetite nanoparticles closed-packed into face-centered crystallites with order of a micron revealed that at nominal saturation the missing magnetic moments unexpectedly interacted to form well-ordered shells 1.0 to 1.5 nm thick canted perpendicular to their ferrimagnetic cores between 160 to 320 K. These shells additionally displayed intra-particle ``cross-talk'', selecting a common orientation over clusters of tens of nanoparticles. However, the shells disappeared when the external field was removed and interparticle magnetic interactions were negligible (300 K), confirming their magnetic origin. This work has been carried out in collaboration with Ryan Booth, Julie Borchers, Wangchun Chen, Liv Dedon, Thomas Gentile, Charles Hogg, Yumi Ijiri, Mark Laver, Sara Majetich, James Rhyne, and Shannon Watson.

  20. Relativistic and perturbational calculations of fine structure splittings in F2 and F2

    Science.gov (United States)

    Mark, F.; Marian, C.; Schwarz, W. H. E.

    Dirac-Fock calculations near the SCF limit using the recently developed basis set expansion technique of Mark and Schwarz have been performed on the F2 ground state with particular consideration of the relativistic splitting of the πg and πu orbitals. The magnetic contribution to the Breit interaction has been included by first-order perturbation theory. Fine structure splittings of the ionic states F2+(X 2Πg) and F2+(A 2Πu) have been calculated by first-order perturbation theory within the Breit-Pauli framework at three levels of approximation for the zero-order wavefunction. The results of the Dirac-Breit and the Breit-Pauli approaches are compared with experimental data. The calculated splittings are analysed by partitioning them into physically meaningful contributions. Aided by results of numerical Dirac-Fock calculations on atoms the general conclusion is drawn that ionic reorganization of the wavefunction increases the fine structure splitting at the Breit-Pauli level, whereas it decreases the splitting at the Dirac-Breit level. Using a model of Ishiguro and Kobori the ratios of Πg and Πu spin-orbit splittings of halogen molecular ions X2+ are discussed.

  1. Shell structure of potassium isotopes deduced from their magnetic moments

    CERN Document Server

    Papuga, J.; Kreim, K; Barbieri, C; Blaum, K; De Rydt, M; Duguet, T; Garcia Ruiz, R F; Heylen, H; Kowalska, M; Neugart, R; Neyens, G; Nortershauser, W; Rajabali, M M; Sanchez, R; Smirnova, N; Soma, V; Yordanov, D T

    2014-09-29

    $\\textbf{Background:}$ Ground-state spins and magnetic moments are sensitive to the nuclear wave function, thus they are powerful probes to study the nuclear structure of isotopes far from stability. \\\\ \\\\ $\\textbf{Purpose:}$ Extend our knowledge about the evolution of the $1/2^+$ and $3/2^+$ states for K isotopes beyond the $N = 28$ shell gap. \\\\ \\\\ $\\textbf{Method:}$ High-resolution collinear laser spectroscopy on bunched atomic beams. \\\\ \\\\ $\\textbf{Results:}$ From measured hyperfine structure spectra of K isotopes, nuclear spins and magnetic moments of the ground states were obtained for isotopes from $N = 19$ up to $N = 32$. In order to draw conclusions about the composition of the wave functions and the occupation of the levels, the experimental data were compared to shell-model calculations using SDPF-NR and SDPF-U effective interactions. In addition, a detailed discussion about the evolution of the gap between proton $1d_{3/2}$ and $2s_{1/2}$ in the shell model and $\\textit{ab initio}$ framework is al...

  2. Magnetization processes in core/shell exchange-spring structures.

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, J. S.

    2015-03-27

    The magnetization reversal processes in cylindrical and spherical soft core/hard shell exchange-spring structures are investigated via the analytical nucleation theory, and are verified with numerical micromagnetic simulations. At small core sizes, the nucleation of magnetic reversal proceeds via the modified bulging mode, where the transverse component of the magnetization is only semi-coherent in direction and the nucleation field contains a contribution from self-demagnetization. For large core sizes, the modified curling mode, where the magnetization configuration is vortex-like, is favored at nucleation. The preference for the modified curling mode is beneficial in that the fluxclosure allows cylindrical and spherical core/shell exchange-spring elements to be densely packed into bulk permanent magnets without affecting the nucleation field, thereby offering the potential for high energy product.

  3. Pore structure of the activated coconut shell charcoal carbon

    Science.gov (United States)

    Budi, E.; Nasbey, H.; Yuniarti, B. D. P.; Nurmayatri, Y.; Fahdiana, J.; Budi, A. S.

    2014-09-01

    The development of activated carbon from coconut shell charcoal has been investigated by using physical method to determine the influence of activation parameters in term of temperature, argon gas pressure and time period on the pore structure of the activated carbon. The coconut shell charcoal was produced by pyrolisis process at temperature of about 75 - 150 °C for 6 hours. The charcoal was activated at various temperature (532, 700 and 868 °C), argon gas pressure (6.59, 15 and 23.4 kgf/cm2) and time period of (10, 60 and 120 minutes). The results showed that the pores size were reduced and distributed uniformly as the activation parameters are increased.

  4. Suppression of the water splitting back reaction on GaN:ZnO photocatalysts loaded with core/shell cocatalysts, investigated using a μ-reactor

    DEFF Research Database (Denmark)

    Dionigi, Fabio; Vesborg, Peter Christian Kjærgaard; Pedersen, Thomas

    2012-01-01

    Using silicon-based l-reactors, we have studied the photocatalytic water splitting reaction and the catalytic back reaction on the same catalysts. GaN:ZnO without cocatalyst and loaded with Rh, Pt, Cr2O3/Rh, Cr2O3/Pt, and Rh–Cr mixed oxide has been tested for gas-phase photocatalytic water...... splitting. The results confirm the high activity observed in liquid-phase experiments with Cr2O3/Rh and Rh–Cr mixed oxide as cocatalysts. To investigate the reason of this enhanced activity, the back reaction was studied by reacting stoichiometric H2/O2 and monitoring the water molecules produced....... The comparison of the two experiments shows that the suppression of the back reaction with the core/shell cocatalysts and the Rh–Cr mixed oxide corresponds to an increase in the net photocatalytic water splitting activity. The fact that the back reaction is not completely suppressed with Cr2O3/Pt compared to Cr2...

  5. Temperature-dependent fine structure splitting in InGaN quantum dots

    Science.gov (United States)

    Wang, Tong; Puchtler, Tim J.; Zhu, Tongtong; Jarman, John C.; Kocher, Claudius C.; Oliver, Rachel A.; Taylor, Robert A.

    2017-07-01

    We report the experimental observation of temperature-dependent fine structure splitting in semiconductor quantum dots using a non-polar (11-20) a-plane InGaN system, up to the on-chip Peltier cooling threshold of 200 K. At 5 K, a statistical average splitting of 443 ± 132 μeV has been found based on 81 quantum dots. The degree of fine structure splitting stays relatively constant for temperatures less than 100 K and only increases above that temperature. At 200 K, we find that the fine structure splitting ranges between 2 and 12 meV, which is an order of magnitude higher than that at low temperatures. Our investigations also show that phonon interactions at high temperatures might have a correlation with the degree of exchange interactions. The large fine structure splitting at 200 K makes it easier to isolate the individual components of the polarized emission spectrally, increasing the effective degree of polarization for potential on-chip applications of polarized single-photon sources.

  6. Magnetic mirror structure for testing shell-type quadrupole coils

    Energy Technology Data Exchange (ETDEWEB)

    Andreev, N.; Barzi, E.; Bossert, R.; Chlachidze, G.; Kashikhin, V.S.; Kashikhin, V.V.; Lamm, M.J.; Nobrega, F.; Novitski, I.; Tartaglia, N.; Turrioni, D.; /Fermilab

    2009-10-01

    This paper presents magnetic and mechanical designs and analyses of the quadrupole mirror structure to test single shell-type quadrupole coils. Several quadrupole coils made of different Nb{sub 3}Sn strands, cable insulation and pole materials were tested using this structure at 4.5 and 1.9 K. The coils were instrumented with voltage taps, spot heaters, temperature sensors and strain gauges to study their mechanical and thermal properties and quench performance. The results of the quadrupole mirror model assembly and test are reported and discussed.

  7. Adsorption of copper to different biogenic oyster shell structures

    International Nuclear Information System (INIS)

    Wu, Qiong; Chen, Jie; Clark, Malcolm; Yu, Yan

    2014-01-01

    Graphical abstract: - Highlights: • Adsorption of copper to waste oyster shell occurs rapidly at pH 5.5. • Copper adsorbs to the different structures of oyster shell at different rates. • The prismatic layer dominates copper sorption rather than the nacreous layer. • SEM analysis shows a porous open network structure to the prismatic layer. • Surface ζ-potentials establish electrostatic attraction to drive copper sorption. - Abstract: The removal of copper from solution by oyster shell powder was investigated for potential wastewater treatment uses. In particular, adsorption behavior differences between the prismatic (PP) and nacreous (NP) shell layers, and how this affects copper removal, were investigated. Experimental results indicated that copper adsorption was highly pH-dependent with optimal copper removal at pH 5.5, where the powdered whole raw shell (RP) removed up to 99.9% of the copper within 24 h at a 10 mg/L initial copper concentration. Langmuir and Freundlich models were used to analyze the isotherm PP, NP and RP data. These results showed a strong homogeneous Langmuir model for low initial copper concentrations (5–30 mg/L) to both RP and PP layer, while strong agreement with a heterogeneous Freundlich model for high initial copper concentrations (30–200 mg/L); nevertheless, a homogeneous Langmuir model provided the best fit for the more dense NP layer across the initial concentration range (5–200 mg/L). The distribution coefficient (K d ) value of PP layer for each initial concentration investigated was substantially higher than the NP layer and it was also found that the PP layer dominated the adsorption process with an adsorption capacity of 8.9 mg/g, while the adsorption capacity of the NP layer was 2.6 mg/g. These differences are believed to be because of the more porous structure of the PP layer, which was confirmed by scanning electron microscopy, infrared spectroscopy, energy-dispersive X-ray spectroscopy, and

  8. Structural and magnetic properties of core-shell iron-iron oxide nanoparticles

    DEFF Research Database (Denmark)

    Kuhn, Luise Theil; Bojesen, A.; Timmermann, L.

    2002-01-01

    We present studies of the structural and magnetic properties of core-shell iron-iron oxide nanoparticles. alpha-Fe nanoparticles were fabricated by sputtering and subsequently covered with a protective nanocrystalline oxide shell consisting of either maghaemite (gamma-Fe2O3) or partially oxidized...... magnetite (Fe3O4). We observed that the nanoparticles were stable against further oxidation, and Mossbauer spectroscopy at high applied magnetic fields and low temperatures revealed a stable form of partly oxidized magnetite. The nanocrystalline structure of the oxide shell results in strong canting...... of the spin structure in the oxide shell, which thereby modifies the magnetic properties of the core-shell nanoparticles....

  9. Structural Dynamics of the Oxygen-Evolving Complex of Photosystem II in Water-Splitting Action.

    Science.gov (United States)

    Wilson, Andrew J; Jain, Prashant K

    2018-04-17

    Oxygenic photosynthesis in nature occurs via water splitting catalyzed by the oxygen-evolving complex (OEC) of photosystem II. To split water, the OEC cycles through a sequence of oxidation states (S i , i = 0-4), the structural mechanism of which is not fully understood under physiological conditions. We monitored the OEC in visible-light-driven water-splitting action by using in situ, aqueous-environment surface-enhanced Raman scattering (SERS). In the unexplored low-frequency region of SERS, we found dynamic vibrational signatures of water binding and splitting. Specific snapshots in the dynamic SERS correspond to intermediate states in the catalytic cycle, as determined by density functional theory and isotopologue comparisons. We assign the previously ambiguous protonation configuration of the S 0 -S 3 states and propose a structural mechanism of the OEC's catalytic cycle. The findings address unresolved questions about photosynthetic water splitting and introduce spatially resolved, low-frequency SERS as a chemically sensitive tool for interrogating homogeneous catalysis in operando.

  10. Continuous one-pot synthesis of sandwich structured core-shell particles and transformation to yolk-shell particles.

    Science.gov (United States)

    Ko, You Na; Kang, Yun Chan; Park, Seung Bin

    2013-05-10

    Scalable continuous ultrasonic spray pyrolysis is used to develop a facile one-pot method of synthesizing sandwich structured core-shell particles consisting of a Pd core, a V2O5 inner layer, and a porous SiO2 outer layer. Pd@SiO2 yolk-shell particles are easily formed by removing the V2O5 inner layer.

  11. Core/Shell Structured Magnetic Nanoparticles for Biological Applications

    International Nuclear Information System (INIS)

    Park, Jeong Chan; Jung, Myung Hwan

    2013-01-01

    Magnetic nanoparticles have been widely used for biomedical applications, such as magnetic resonance imaging (MRI), hyperthermia, drug delivery and cell signaling. The surface modification of the nanomaterials is required for biomedical use to give physiogical stability, surface reactivity and targeting properties. Among many approaches for the surface modification with materials, such as polymers, organic ligands and metals, one of the most attractive ways is using metals. The fabrication of metal-based, monolayer-coated magnetic nanoparticles has been intensively studied. However, the synthesis of metal-capped magnetic nanoparticles with monodispersities and controllable sizes is still challenged. Recently, gold-capped magnetic nanoparticles have been reported to increase stability and to provide biocompatibility. Magnetic nanoparticle with gold coating is an attractive system, which can be stabilized in biological conditions and readily functionalized in biological conditions and readily functionalized through well-established surface modification (Au-S) chemistry. The Au coating offers plasmonic properties to magnetic nanoparticles. This makes the magnetic/Au core/shell combinations interesting for magnetic and optical applications. Herein, the synthesis and characterization of gold capped-magnetic core structured nanomaterials with different gold sources, such as gold acetate and chloroauric acid have been reported. The core/shell nanoparticles were transferred from organic to aqueous solutions for biomedical applications. Magnetic core/shell structured nanoparticles have been prepared and transferred from organic phase to aqueous solutions. The resulting Au-coated magnetic core nanoparticles might be an attractive system for biomedical applications, which are needed both magnetic resonance imaging and optical imaging

  12. Structured Arrangement Supporting the Development of Splitting Level in Doing Multiplication by Number up to 20

    Science.gov (United States)

    Meryansumayeka; Darmawijoyo; Ilma, Ratu; den Hertog, Jaap

    2011-01-01

    In guiding students to construct a mathematical concept themselves, learning process should be started by a context which is suit with the concept. In this research, we focused on structured arrangement which was believed to be able to support students ages 8-9 years old developing splitting strategy in doing multiplication. This study was a…

  13. Experimental evidence for a shell structure of the proton

    Energy Technology Data Exchange (ETDEWEB)

    Levintov, I.I.

    1983-11-01

    Spin effects in nucleon-nucleon scattering are explained by the interaction of Fock configurations of the type (qqQQ-barq), having the structure of p shells. The number of nucleon p shells is N = n/sub f/ -1 (n/sub f/ is the number of flavors). The strong spin effect in p/sub arrow-up/p/sub arrow-up/ scattering for p/sup 2//sub perpendicular/ > or approx. =4 (GeV/c)/sup 2/ (the Argonne effect) is explained by the presence of the configuration (qqcc-barq) in the proton. An analogous effect in the region p/sup 2//sub perpendicular/ > or approx. =100 (GeV/c)/sup 2/, due to the configuration (qqbb-barq), is predicted. In scattering of unpolarized hadrons by a polarized proton target for constant theta/sub cms/ and variation of s (i.e., p/sup 2//sub perpendicular/), it is predicted that there are structures in the asymmetry in the region p/sup 2//sub perpendicular/ approx.4m/sup 2//sub Q/ (Q = c, b, ...).

  14. Light Modulation and Water Splitting Enhancement Using a Composite Porous GaN Structure.

    Science.gov (United States)

    Yang, Chao; Xi, Xin; Yu, Zhiguo; Cao, Haicheng; Li, Jing; Lin, Shan; Ma, Zhanhong; Zhao, Lixia

    2018-02-14

    On the basis of the laterally porous GaN, we designed and fabricated a composite porous GaN structure with both well-ordered lateral and vertical holes. Compared to the plane GaN, the composite porous GaN structure with the combination of the vertical holes can help to reduce UV reflectance and increase the saturation photocurrent during water splitting by a factor of ∼4.5. Furthermore, we investigated the underlying mechanism for the enhancement of the water splitting performance using a finite-difference time-domain method. The results show that the well-ordered vertical holes can not only help to open the embedded pore channels to the electrolyte at both sides and reduce the migration distance of the gas bubbles during the water splitting reactions but also help to modulate the light field. Using this composite porous GaN structure, most of the incident light can be modulated and trapped into the nanoholes, and thus the electric fields localized in the lateral pores can increase dramatically as a result of the strong optical coupling. Our findings pave a new way to develop GaN photoelectrodes for highly efficient solar water splitting.

  15. Active vibration control of ring-stiffened cylindrical shell structure using macro fiber composite actuators.

    Science.gov (United States)

    Sohn, Jung Woo; Jeon, Juncheol; Choi, Seung-Bok

    2014-10-01

    Vibration control performance of the ring-stiffened cylindrical shell structure is experimentally evaluated in this work. In order to achieve high control performance, advanced flexible piezoelectric actuator whose commercial name is Macro-Fiber Composite (MFC) is adapted to the shell structure. Governing equation is derived by finite element method and dynamic characteristics are investigated from the modal analysis results. Ring-stiffened cylindrical shell structure is then manufactured and modal test is conducted to verify modal analysis results. An optimal controller is designed and experimentally realized to the proposed shell structure system. Vibration control performance is experimentally evaluated in time domain and verified by simulated control results.

  16. Fabrication of bimodal porous silicate with silicalite-1 core/mesoporous shell structures and synthesis of nonspherical carbon and silica nanocases with hollow core/mesoporous shell structures.

    Science.gov (United States)

    Yu, Jong-Sung; Yoon, Suk Bon; Lee, Yun Jo; Yoon, Kyung Byung

    2005-04-21

    In this work, an attempt has been made to modify the shape and nanostructure of core-shell materials, which have been usually generated on the basis of amorphous spherical cores. Novel core-shell silicate particles, each of which consists of a silicalite-1 zeolite crystal core and mesoporous shell (ZCMS), were synthesized for the first time. The ZCMS core-shell particles are unique because they are of pseudohexagonal prismatic shape and have hierarchical porosity of both a uniform microporous core and a mesoporous shell coexisting in a particle framework. The nonspherical bimodal porous core-shell particles were then utilized as templates to fabricate a new carbon replica structure. Interestingly, the pore replication process was carried out only through the mesopores in the shell, and not through the micropores due to the narrower micropore size in the core, resulting in nonspherical carbon nanocases with a hollow core and mesoporous shell (HCMS) structure. Nonspherical silica nanocases with HCMS structure were also generated by replication using the carbon nanocases as templates, which are not possible to synthesize through other synthetic methods. Interestingly, the pseudohexagonal prismatic shape of the zeolite crystals was transferred onto the carbon and silica nanocases.

  17. Active constrained layer damping treatments for shell structures: a deep-shell theory, some intuitive results, and an energy analysis

    Science.gov (United States)

    Shen, I. Y.

    1997-02-01

    This paper studies vibration control of a shell structure through use of an active constrained layer (ACL) damping treatment. A deep-shell theory that assumes arbitrary Lamé parameters 0964-1726/6/1/011/img1 and 0964-1726/6/1/011/img2 is first developed. Application of Hamilton's principle leads to the governing Love equations, the charge equation of electrostatics, and the associated boundary conditions. The Love equations and boundary conditions imply that the control action of the ACL for shell treatments consists of two components: free-end boundary actuation and membrane actuation. The free-end boundary actuation is identical to that of beam and plate ACL treatments, while the membrane actuation is unique to shell treatments as a result of the curvatures of the shells. In particular, the membrane actuation may reinforce or counteract the boundary actuation, depending on the location of the ACL treatment. Finally, an energy analysis is developed to determine the proper control law that guarantees the stability of ACL shell treatments. Moreover, the energy analysis results in a simple rule predicting whether or not the membrane actuation reinforces the boundary actuation.

  18. Overview Of Hanford Single Shell Tank (SST) Structural Integrity - 12123

    International Nuclear Information System (INIS)

    Rast, R.S.; Rinker, M.W.; Washenfelder, D.J.; Johnson, J.B.

    2012-01-01

    To improve the understanding of the single-shell tanks (SSTs) integrity, Washington River Protection Solutions, LLC (WRPS), the USDOE Hanford Site tank contractor, developed an enhanced Single-Shell Tank Integrity Project in 2009. An expert panel on SST integrity, consisting of various subject matters experts in industry and academia, was created to provide recommendations supporting the development of the project. This panel developed 33 recommendations in four main areas of interest: structural integrity, liner degradation, leak integrity and prevention, and mitigation of contamination migration. Seventeen of these recommendations were used to develop the basis for the M-45-10-1 Change Package for the Hanford Federal Agreement and Compliance Order, which is also known as the Tri-Party Agreement. The structural integrity of the tanks is a key element in completing the cleanup mission at the Hanford Site. There are eight primary recommendations related to the structural integrity of Hanford SSTs. Six recommendations are being implemented through current and planned activities. The structural integrity of the Hanford SSTs is being evaluated through analysis, monitoring, inspection, materials testing, and construction document review. Structural evaluation in the form of analysis is performed using modern finite element models generated in ANSYS(reg s ign) The analyses consider in-situ, thermal, operating loads and natural phenomena such as earthquakes. Structural analysis of 108 of 149 Hanford SSTs has concluded that the tanks are structurally sound and meet current industry standards. Analyses of the remaining Hanford SSTs are scheduled for FY2013. Hanford SSTs are monitored through a dome deflection program. The program looks for deflections of the tank dome greater than 1/4 inch. No such deflections have been recorded. The tanks are also subjected to visual inspection. Digital cameras record the interior surface of the concrete tank domes, looking for cracks and

  19. OVERVIEW OF HANFORD SINGLE SHELL TANK (SST) STRUCTURAL INTEGRITY - 12123

    Energy Technology Data Exchange (ETDEWEB)

    RAST RS; RINKER MW; WASHENFELDER DJ; JOHNSON JB

    2012-01-25

    To improve the understanding of the single-shell tanks (SSTs) integrity, Washington River Protection Solutions, LLC (WRPS), the USDOE Hanford Site tank contractor, developed an enhanced Single-Shell Tank Integrity Project in 2009. An expert panel on SST integrity, consisting of various subject matters experts in industry and academia, was created to provide recommendations supporting the development of the project. This panel developed 33 recommendations in four main areas of interest: structural integrity, liner degradation, leak integrity and prevention, and mitigation of contamination migration. Seventeen of these recommendations were used to develop the basis for the M-45-10-1 Change Package for the Hanford Federal Agreement and Compliance Order, which is also known as the Tri-Party Agreement. The structural integrity of the tanks is a key element in completing the cleanup mission at the Hanford Site. There are eight primary recommendations related to the structural integrity of Hanford SSTs. Six recommendations are being implemented through current and planned activities. The structural integrity of the Hanford SSTs is being evaluated through analysis, monitoring, inspection, materials testing, and construction document review. Structural evaluation in the form of analysis is performed using modern finite element models generated in ANSYS{reg_sign} The analyses consider in-situ, thermal, operating loads and natural phenomena such as earthquakes. Structural analysis of 108 of 149 Hanford SSTs has concluded that the tanks are structurally sound and meet current industry standards. Analyses of the remaining Hanford SSTs are scheduled for FY2013. Hanford SSTs are monitored through a dome deflection program. The program looks for deflections of the tank dome greater than 1/4 inch. No such deflections have been recorded. The tanks are also subjected to visual inspection. Digital cameras record the interior surface of the concrete tank domes, looking for cracks and

  20. A refined element-based Lagrangian shell element for geometrically nonlinear analysis of shell structures

    Directory of Open Access Journals (Sweden)

    Woo-Young Jung

    2015-04-01

    Full Text Available For the solution of geometrically nonlinear analysis of plates and shells, the formulation of a nonlinear nine-node refined first-order shear deformable element-based Lagrangian shell element is presented. Natural co-ordinate-based higher order transverse shear strains are used in present shell element. Using the assumed natural strain method with proper interpolation functions, the present shell element generates neither membrane nor shear locking behavior even when full integration is used in the formulation. Furthermore, a refined first-order shear deformation theory for thin and thick shells, which results in parabolic through-thickness distribution of the transverse shear strains from the formulation based on the third-order shear deformation theory, is proposed. This formulation eliminates the need for shear correction factors in the first-order theory. To avoid difficulties resulting from large increments of the rotations, a scheme of attached reference system is used for the expression of rotations of shell normal. Numerical examples demonstrate that the present element behaves reasonably satisfactorily either for the linear or for geometrically nonlinear analysis of thin and thick plates and shells with large displacement but small strain. Especially, the nonlinear results of slit annular plates with various loads provided the benchmark to test the accuracy of related numerical solutions.

  1. Synergetic effect of organic cores and inorganic shells for core/shell structured composite abrasives for chemical mechanical planarization

    Science.gov (United States)

    Chen, Yang; Li, Zhina; Miao, Naiming

    2014-09-01

    Core/shell structured organic/inorganic composite microspheres has an important potential application in efficient and damage-free chemical mechanical planarization/polishing (CMP) as a kind of novel abrasive due to its uniform non-rigid mechanical property. However, the synergistic effect of material removal between organic cores and inorganic shells of composite abrasives is ambiguous. In this work, oxide-CMP performances of various slurries, containing polystyrene (PS) spheres, solid abrasives (SiO2 or CeO2), mixed abrasives ((PS + SiO2) or (PS + CeO2)), core/shell composites (PS/SiO2 or PS/CeO2), were investigated by atomic force microscopy. Experiment results indicated that the surfaces polished by composite abrasives exhibited lower surface roughness, fewer scratches as well as lower topographical variations than those by other type of abrasives. The core/shell structure of composite abrasives plays an important role in improving CMP behavior. Moreover, the organic cores are mainly beneficial to decrease surface roughness and mechanical damages, and the inorganic shells are in favor of improving material removal rate.

  2. Determination of Core-Shell Structures in Pd-Hg Nanoparticles by STEM-EDX

    DEFF Research Database (Denmark)

    Deiana, Davide; Verdaguer Casadevall, Arnau; Malacrida, Paolo

    2015-01-01

    The structural and elemental configuration of a high-performing Pd-Hg electrocatalyst for oxygen reduction to hydrogen peroxide has been studied by means of high-resolution scanning transmission electron microscopy. Pd-Hg nanoparticles are shown to have a crystalline core-shell structure, with a Pd...... core and a Pd-Hg ordered alloy shell. The ordered shell is responsible for the high oxygen reduction selectivity to H2O2....

  3. Exact free oscillation spectra, splitting functions and the resolvability of Earth's density structure

    Science.gov (United States)

    Akbarashrafi, F.; Al-Attar, D.; Deuss, A.; Trampert, J.; Valentine, A. P.

    2018-04-01

    Seismic free oscillations, or normal modes, provide a convenient tool to calculate low-frequency seismograms in heterogeneous Earth models. A procedure called `full mode coupling' allows the seismic response of the Earth to be computed. However, in order to be theoretically exact, such calculations must involve an infinite set of modes. In practice, only a finite subset of modes can be used, introducing an error into the seismograms. By systematically increasing the number of modes beyond the highest frequency of interest in the seismograms, we investigate the convergence of full-coupling calculations. As a rule-of-thumb, it is necessary to couple modes 1-2 mHz above the highest frequency of interest, although results depend upon the details of the Earth model. This is significantly higher than has previously been assumed. Observations of free oscillations also provide important constraints on the heterogeneous structure of the Earth. Historically, this inference problem has been addressed by the measurement and interpretation of splitting functions. These can be seen as secondary data extracted from low frequency seismograms. The measurement step necessitates the calculation of synthetic seismograms, but current implementations rely on approximations referred to as self- or group-coupling and do not use fully accurate seismograms. We therefore also investigate whether a systematic error might be present in currently published splitting functions. We find no evidence for any systematic bias, but published uncertainties must be doubled to properly account for the errors due to theoretical omissions and regularization in the measurement process. Correspondingly, uncertainties in results derived from splitting functions must also be increased. As is well known, density has only a weak signal in low-frequency seismograms. Our results suggest this signal is of similar scale to the true uncertainties associated with currently published splitting functions. Thus, it seems

  4. The influence of MOVPE growth conditions on the shell of core-shell GaN microrod structures

    Science.gov (United States)

    Schimpke, Tilman; Avramescu, Adrian; Koller, Andreas; Fernando-Saavedra, Amalia; Hartmann, Jana; Ledig, Johannes; Waag, Andreas; Strassburg, Martin; Lugauer, Hans-Jürgen

    2017-05-01

    A core-shell geometry is employed for most next-generation, three-dimensional opto-electric devices based on III-V semiconductors and grown by metal organic vapor phase epitaxy (MOVPE). Controlling the shape of the shell layers is fundamental for device optimization, however no detailed analysis of the influence of growth conditions has been published to date. We study homogeneous arrays of gallium nitride core-shell microrods with height and diameter in the micrometer range and grown in a two-step selective area MOVPE process. Changes in shell shape and homogeneity effected by deliberately altered shell growth conditions were accurately assessed by digital analysis of high-resolution scanning electron microscope images. Most notably, two temperature regimes could be established, which show a significantly different behavior with regard to material distribution. Above 900 °C of wafer carrier temperature, the shell thickness along the growth axis of the rods was very homogeneous, however variations between vicinal rods increase. In contrast, below 830 °C the shell thickness is higher close to the microrod tip than at the base of the rods, while the lateral homogeneity between neighboring microrods is very uniform. This temperature effect could be either amplified or attenuated by changing the remaining growth parameters such as reactor pressure, structure distance, gallium precursor, carrier gas composition and dopant materials. Possible reasons for these findings are discussed with respect to GaN decomposition as well as the surface and gas phase diffusion of growth species, leading to an improved control of the functional layers in next-generation 3D V-III devices.

  5. On the origin of second-peak splitting in the static structure factor of metallic glasses

    NARCIS (Netherlands)

    van de Waal, B.W.

    1995-01-01

    It is proposed that the splitting of the second peak of the total static structure factor, S(k), of many metallic glasses is essentially the same feature as the indentation at kσ = (9/2)π in the function (sin k σ + α−1 sin kασ), caused by the coincidence of the fourth minimum of the second term with

  6. Theory of elastic thin shells solid and structural mechanics

    CERN Document Server

    Gol'Denveizer, A L; Dryden, H L

    1961-01-01

    Theory of Elastic Thin Shells discusses the mathematical foundations of shell theory and the approximate methods of solution. The present volume was originally published in Russian in 1953, and remains the only text which formulates as completely as possible the different sets of basic equations and various approximate methods of shell analysis emphasizing asymptotic integration. The book is organized into five parts. Part I presents the general formulation and equations of the theory of shells, which are based on the well-known hypothesis of the preservation of the normal element. Part II is

  7. Tuning structure and mobility of solvation shells surrounding tracer additives.

    Science.gov (United States)

    Carmer, James; Jain, Avni; Bollinger, Jonathan A; van Swol, Frank; Truskett, Thomas M

    2015-03-28

    Molecular dynamics simulations and a stochastic Fokker-Planck equation based approach are used to illuminate how position-dependent solvent mobility near one or more tracer particle(s) is affected when tracer-solvent interactions are rationally modified to affect corresponding solvation structure. For tracers in a dense hard-sphere fluid, we compare two types of tracer-solvent interactions: (1) a hard-sphere-like interaction, and (2) a soft repulsion extending beyond the hard core designed via statistical mechanical theory to enhance tracer mobility at infinite dilution by suppressing coordination-shell structure [Carmer et al., Soft Matter 8, 4083-4089 (2012)]. For the latter case, we show that the mobility of surrounding solvent particles is also increased by addition of the soft repulsive interaction, which helps to rationalize the mechanism underlying the tracer's enhanced diffusivity. However, if multiple tracer surfaces are in closer proximity (as at higher tracer concentrations), similar interactions that disrupt local solvation structure instead suppress the position-dependent solvent dynamics.

  8. Reduction of the Radiating Sound of a Submerged Finite Cylindrical Shell Structure by Active Vibration Control

    Directory of Open Access Journals (Sweden)

    Seung-Bok Choi

    2013-02-01

    Full Text Available In this work, active vibration control of an underwater cylindrical shell structure was investigated, to suppress structural vibration and structure-borne noise in water. Finite element modeling of the submerged cylindrical shell structure was developed, and experimentally evaluated. Modal reduction was conducted to obtain the reduced system equation for the active feedback control algorithm. Three Macro Fiber Composites (MFCs were used as actuators and sensors. One MFC was used as an exciter. The optimum control algorithm was designed based on the reduced system equations. The active control performance was then evaluated using the lab scale underwater cylindrical shell structure. Structural vibration and structure-borne noise of the underwater cylindrical shell structure were reduced significantly by activating the optimal controller associated with the MFC actuators. The results provide that active vibration control of the underwater structure is a useful means to reduce structure-borne noise in water.

  9. New Insight of Northern Apennines (Italy): SKS Splitting Measurements Reveal a Complex Anisotropic Structure

    Science.gov (United States)

    Salimbeni, S.; Pondrelli, S.; Margheriti, L.; Levin, V.; Park, J.; Plomerova, J.

    2006-12-01

    The multidisciplinary RETREAT project (REtreating-Trench, Extension and Accretion Tectonics) is focused on the development of a 3D self-consistent dynamic model of the syn-convergent extension in the Northern Apennines. The seismological deployment of the Project started on 2003 and closed on September 2006, using 10 instruments lent by the GFU and 25 instruments lent by PASSCAL, added to the permanent stations of the Italian National Network. Many of the stations were deployed along a NE-SW transect across the Apennine chain. We present here new results of seismic anisotropy analysis obtained from SKS core-refracted shear waves. The study of SKS splitting is applied on twenty teleseismic earthquakes; for all of them we calculate the anisotropic parameters (delay time and fast polarization direction) by minimizing the energy in the transverse component. Our analysis assesses uncertainty by testing the parameters for stability to noise. Previous studies of splitting analysis have found in the study region evidence for tectonic domains in which a coherent splitting signal can be found. The Tuscany domain (Tyrrhenian side) shows homogeneous NW-SE fast axes directions; the Po-Plain domain (Eastern side of the Apennines) shows a N-S to NE-SW directions, here strongly influenced by backazimuth. To better define the complex structure that may exist below the Northern Apennines and Po Plain we apply the cross convolution method of Menke and Levin (2003) to discriminate whether a two-layer anisotropic model fits the splitting pattern more convincingly that a simple one-layer model. Previous analysis suggested that structure beneath the Tuscany side is simpler; a single anisotropic layer with a NW-SE fast polarization direction is in agreement with all the dataset. Beneath the Po Plain the complexity of the structure is confirmed in the analysis of most stations.

  10. Diffraction inspired unidirectional and bidirectional beam splitting in defect-containing photonic structures without interface corrugations

    Energy Technology Data Exchange (ETDEWEB)

    Colak, Evrim [Electrical Engineering Department, Ankara University, Golbasi, 06830 Ankara (Turkey); Serebryannikov, Andriy E., E-mail: andser@amu.edu.pl [Faculty of Physics, Adam Mickiewicz University, 61-614 Poznań (Poland); Usik, P. V. [Institute of Radio Astronomy, National Academy of Sciences of Ukraine, 61002 Kharkiv (Ukraine); Ozbay, Ekmel [Nanotechnology Research Center—NANOTAM, Bilkent University, 06800 Ankara (Turkey)

    2016-05-21

    It is shown that strong diffractions and related dual-beam splitting can be obtained at transmission through the nonsymmetric structures that represent two slabs of photonic crystal (PhC) separated by a single coupled-cavity type defect layer, while there are no grating-like corrugations at the interfaces. The basic operation regimes include unidirectional and bidirectional splitting that occur due to the dominant contribution of the first positive and first negative diffraction orders to the transmission, which is typically connected with different manifestations of the asymmetric transmission phenomenon. Being the main component of the resulting transmission mechanism, diffractions appear owing to the effect exerted by the defect layer that works like an embedded diffractive element. Two mechanisms can co-exist in one structure, which differ, among others, in that whether dispersion allows coupling of zero order to a wave propagating in the regular, i.e., defect-free PhC segments or not. The possibility of strong diffractions and efficient splitting related to it strongly depend on the dispersion properties of the Floquet-Bloch modes of the PhC. Existence of one of the studied transmission scenarios is not affected by location of the defect layer.

  11. Outer shell structure in nearly zero magnetostrictive amorphous microwires

    Science.gov (United States)

    Óvári, T.-A.; Chiriac, H.; Lostun, Mihaela

    2009-04-01

    Nearly zero magnetostrictive microwires have been proven to be very versatile, due to their extremely soft magnetic properties, the changes in their magnetization mechanism with dimensions, and the appearance of sensitive application-related effects, such as the large Barkhausen and the giant magnetoimpedance effects. Their sensitive magnetoimpedance response originates in the specific domain structure, composed of an inner core and an outer shell (OS), since the OS with a circumferential easy axis is the main region involved in the magnetoimpedance effect. The circumferential OS is believed to display a bamboolike structure with consecutive rings circumferentially magnetized in opposite directions. However, earlier theoretical studies predicted a uniformly magnetized OS as being energetically favored. This paper aims to clarify this contradiction. The variation of the magnetostatic energy from the bamboo domain to the uniformly magnetized state has been calculated and it has been found to be null. Therefore, a uniformly magnetized OS has lower energy due to the absence of domain walls. Calculation results are supported by magneto-optical Kerr effect surface domain images and surface hysteresis loops. For large values of the metallic nucleus diameter, as well as for microwires with the glass coating removed, the OS vanishes, being replaced with a surface region with helical magnetization, which expands toward the microwire surface.

  12. Numerical analysis of stiffened shells of revolution. Volume 2: Users' manual for STAR-02S - shell theory automated for rotational structures - 2 (statics), digital computer program

    Science.gov (United States)

    Svalbonas, V.

    1973-01-01

    A procedure for the structural analysis of stiffened shells of revolution is presented. A digital computer program based on the Love-Reissner first order shell theory was developed. The computer program can analyze orthotropic thin shells of revolution, subjected to unsymmetric distributed loading or concentrated line loads, as well as thermal strains. The geometrical shapes of the shells which may be analyzed are described. The shell wall cross section can be a sheet, sandwich, or reinforced sheet or sandwich. General stiffness input options are also available.

  13. A curved finite element for general thin shell structures

    International Nuclear Information System (INIS)

    Jones, R.F. Jr.

    1978-01-01

    This work describes the development of a curved quadrilateral shell finite element which demonstrates very good convergence properties. A general description is used in deriving the element so that it may be applied to any thin shell problem. The element is shown to be very efficient. It has a total of 36 degrees-of-freedom with 9 at each of the corners of the element. There are several distinct advantages that the element offers for practical applications. Most of the shell elements that have been presented in the past are limited to problems in which the coordinates on the shell surface are orthogonal. The element that is described in the paper is derived using a general description so that it may be applied to any thin shell problem including those in which the shell coordinates are not orthogonal. The degree-of-freedom at each of the four nodes are the three Cartesian displacements and their first derivatives with respect to the two surface coordinates. The imposition of boundary conditions is simplified since each of the degrees-of-freedom can be can be associated with a quantity which has a simple physical meaning. During the course of the derivation of the element, the strain displacement relationships are derived in a very simple manner consistent with Love's first approximation for thin shells. The derivation in the paper starts from basic principles and should help to shed some light on the proper form for the bending strain. Two primary contributions are presented in this work. The first is the presentation of a procedure for the development of a general quadrilateral shell element. The second is the simple derivation of the bending strain for the thin shells which apparently has not been presented previously. (Auth.)

  14. Modeling plate shell structures using pyFormex

    DEFF Research Database (Denmark)

    Bagger, Anne; Verhegghe, Benedict; Hertz, Kristian Dahl

    2009-01-01

    (plate shells and triangulated lattice shells) may not differ in complexity regarding the topology, but when it comes to the practical generation of the geometry, e.g. in CAD, the plate shell is far more troublesome to handle than the triangulated geometry. The free software tool “pyFormex”, developed...... element analysis software Abaqus as a Python script, which translates the information to an Abaqus CAE-model. In pyFormex the model has been prepared for applying the meshing in Abaqus, by allocation of edge seeds, and by defining geometry sets for easy handling....

  15. Gross shell structure at high spin in heavy nuclei

    International Nuclear Information System (INIS)

    Deleplanque, Marie-Agnes; Frauendorf, Stefan; Pashkevich, Vitaly V.; Chu, S.Y.; Unzhakova, Anja

    2003-01-01

    Experimental nuclear moments of inertia at high spins along the yrast line have been determined systematically and found to differ from the rigid-body values. The difference is attributed to shell effect and these have been calculated microscopically. The data and quantal calculations are interpreted by means of the semiclassical Periodic Orbit Theory. From this new perspective, features in the moments of inertia as a function of neutron number and spin, as well as their relation to the shell energies can be understood. Gross shell effects persist up to the highest angular momenta observed

  16. Decoupling capabilities of split-loop resonator structure for 7 Tesla MRI surface array coils

    Science.gov (United States)

    Hurshkainen, A.; Kurdjumov, S.; Simovski, C.; Glybovski, S.; Melchakova, I.; van den Berg, C. A. T.; Raaijmakers, A.; Belov, P.

    2017-09-01

    In this work we studied electromagnetic properties of one-dimentional periodic structures composed of split-loop res-onators (SLRs) and investigated their capabilities in decoupling of two dipole antennas for full-body magnetic resonance imaging (MRI). Two different finite structures comprising a single-SLR and a double-SLR constitutive elements were studied. Numerical simulations of the structures were performed to evaluate their decoupling capabilities. As it was demonstrated two dipole antennas equipped with either a single or a double-SLR structure exhibit high isolation even for an electrically short distance between the dipoles. Double-SLR structure while dramatically improving isolation of the dipoles keeps the field created by each of the decoupled dipoles comparable with one of a single dipole inside the target area.

  17. Design, fabrication and test of a lightweight shell structure, phase 3

    Science.gov (United States)

    1977-01-01

    Progress is reported in the construction of lightweight orthogrid shells. Graphite/epoxy panels are being used in the fabrication. The shell structure is diagramed in detail. Panel laminates, and panel stiffener flanges are described while illustrations delineate panel assembly procedures.

  18. High thermal stability of core-shell structures dominated by negative interface energy.

    Science.gov (United States)

    Zhu, Yong-Fu; Zhao, Ning; Jin, Bo; Zhao, Ming; Jiang, Qing

    2017-03-29

    Nanoscale core/shell structures are of interest in catalysis due to their superior catalytic properties. Here we investigated the thermal stability of the coherent core-shell structures in a thermodynamic way by considering the impact from the core with the bulk melting point T m (∞) lower or higher than the shell. When a low-T m (∞) core is adopted, core-shell melting induced by the melting depression of the core does not occur upon heating because of the superheating, although the melting depression of the core can be triggered ultimately by the preferential melting of the high-T m (∞) shell for small cores. The superheating of the core is contributed by the negative solid-solid interface energy, while the depression is originated from the positive solid-liquid interface energy. Owing to the presence of the negative interface energy, moreover, the low-T m (∞)-core structure possesses a low difference in thermal expansion between the core and the shell, high activation energy of outward atomic diffusion from the core to shell, and low heat capacity. This result is beneficial for the core-shell structure design for its application in catalysis.

  19. Core-Shell-structured Dendritic Mesoporous Silica Nanoparticles for Combined Photodynamic Therapy and Antibody Delivery.

    Science.gov (United States)

    Abbaraju, Prasanna Lakshmi; Yang, Yannan; Yu, Meihua; Fu, Jianye; Xu, Chun; Yu, Chengzhong

    2017-07-04

    Multifunctional core-shell-structured dendritic mesoporous silica nanoparticles with a fullerene-doped silica core, a dendritic silica shell and large pores have been prepared. The combination of photodynamic therapy and antibody therapeutics significantly inhibits the cancer cell growth by effectively reducing the level of anti-apoptotic proteins. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  20. Analysis of Completely Prevaporized Spray Flames with Water/Octane Core/Shell Structured Droplets

    Directory of Open Access Journals (Sweden)

    Chung-Yao Hsuan

    2015-01-01

    Full Text Available A series of studies on laminar flame propagation in off-stoichiometric dilute sprays of monodispersed inert or fuel drops had been investigated by large activation energy asymptotics. The present study extends previous theoretical model to consider water/octane core/shell structured drops instead of single-phase drops. The core/shell structured drops are composed of core fluid (water encased by a layer of shell fluid (n-octane. In this study, we only deal with the case that core/shell structured drops are vaporized completely just at flame location. Namely, the discussions of this paper are restricted to the completely prevaporized mode. By varying parameters of core water radius, core-to-shell ratio, the amount of liquid loading, and the stoichiometric ratio (lean or rich burning, we examine the gasification of core water and shell fuel of core/shell structured drops upstream of the bulk flame and its relation to the internal heat transfer. The effects of drop radius, core-to-shell ratio, liquid loading, and overall heat loss or gain on flame propagation flux are reported and discussed.

  1. Shell-like structures advanced theories and applications

    CERN Document Server

    Eremeyev, Victor

    2017-01-01

    The book presents mathematical and mechanical aspects of the theory of plates and shells, applications in civil, aero-space and mechanical engineering, as well in other areas. The focus relates to the following problems: • comprehensive review of the most popular theories of plates and shells, • relations between three-dimensional theories and two-dimensional ones, • presentation of recently developed new refined plates and shells theories (for example, the micropolar theory or gradient-type theories), • modeling of coupled effects in shells and plates related to electromagnetic and temperature fields, phase transitions, diffusion, etc., • applications in modeling of non-classical objects like, for example, nanostructures, • presentation of actual numerical tools based on the finite element approach.

  2. Anisotropic Velocity Structure near the Alpine Fault, New Zealand, from Shear Wave Splitting of Local Earthquakes

    Science.gov (United States)

    Savage, M. K.; Boese, C. M.; Townend, J.

    2015-12-01

    We use shear wave splitting of local earthquakes to characterize seismic anisotropy along the central portion of the transpressive, plate-bounding Alpine Fault and surrounding the Deep Fault Drilling Project (DFDP) boreholes. We combine data from the SAMBA network of 2 Hz borehole seismometers, the DFDP10 short-period surface network, and the GeoNet broadband network. Using the MFAST automatic shear wave splitting program applied to hand-picked S arrivals, 1.5 years of data yielded 15,902 measurements. Of these, 1291 measurements from 23 stations were of high quality (grades of A or B); their fast azimuths exhibit three predominant trends: one NE/SW, subparallel to the Alpine Fault, one perpendicular to it and the third E-W. The last of these, observed at the six stations closest to the fault, is roughly parallel to the maximum principal stress direction. Some stations show a single population of fast directions and others show two or more populations. We consider that the orientations are likely caused by a combination of stress-controlled, crack-induced anisotropy and structure-controlled anisotropy associated with the fault fabric and its interaction with the dominantly schistose rocks in the region. Delay times for the highest-quality measurements average 0.067±0.002 s, consistent with small splitting of the high-frequency phases (dominant frequencies 6.9±0.07 Hz) with short path lengths (4.5±0.09 s travel-time). If the anisotropy is present along the entire path, the percentage anisotropy is 1. 5%. However, delay times do not increase much with hypocentral distance, suggesting near-surface effects are dominant and hence that anisotropy is larger near the surface. To ensure the shear-wave splitting results do not depend on the particular algorithm used, a second semi-automated processing routine with different shear-wave splitting criteria is applied. A comparison of the results is anticipated to help to eliminate any possible artefacts.

  3. Editorial Core-Shell Nano structures: Modeling, Fabrication, Properties, and Applications

    International Nuclear Information System (INIS)

    Qi, W.; Luo, L.; Qian, H.; Ouyang, G.; Nanda, K.K.; Obare, S.O.

    2012-01-01

    Core-shell nano structures, a family of nano materials, have attracted increasing research interest due to their unique structural features that consist of an inner core and an external shell of different chemical compositions. These structural features allow the possibility of combining distinctive properties of varied materials. Comparatively, core-shell nano structures have exhibited improved physical and chemical properties relative to their single-component counterparts. The inherent emergent chemical and physical properties of core-shell nano structures are of great importance to a potentially broader range of applications including electronics, magnetism, optics, and catalysis. So far a large number of core-shell nano structures have been successfully fabricated using approaches ranging from laser ablation and high-temperature evaporation to carbothermal reduction and hydrothermal methods. Structural characterization of these nano structures and determination of their unique properties for various applications have been well documented. This special issue is devoted to describing a number of unique properties and applications of core-shell nano structures by introducing a few research papers in this field.

  4. Core-Shell Structured Electro- and Magneto-Responsive Materials: Fabrication and Characteristics

    Directory of Open Access Journals (Sweden)

    Hyoung Jin Choi

    2014-11-01

    Full Text Available Core-shell structured electrorheological (ER and magnetorheological (MR particles have attracted increasing interest owing to their outstanding field-responsive properties, including morphology, chemical and dispersion stability, and rheological characteristics of shear stress and yield stress. This study covers recent progress in the preparation of core-shell structured materials as well as their critical characteristics and advantages. Broad emphasises from the synthetic strategy of various core-shell particles to their feature behaviours in the magnetic and electric fields have been elaborated.

  5. Monte Carlo Shell Model for ab initio nuclear structure

    Directory of Open Access Journals (Sweden)

    Abe T.

    2014-03-01

    Full Text Available We report on our recent application of the Monte Carlo Shell Model to no-core calculations. At the initial stage of the application, we have performed benchmark calculations in the p-shell region. Results are compared with those in the Full Configuration Interaction and No-Core Full Configuration methods. These are found to be consistent with each other within quoted uncertainties when they could be quantified. The preliminary results in Nshell = 5 reveal the onset of systematic convergence pattern.

  6. Probing atomic structure in magnetic core/shell nanoparticles using synchrotron radiation.

    Science.gov (United States)

    Baker, S H; Roy, M; Thornton, S C; Qureshi, M; Binns, C

    2010-09-29

    Core/shell Fe/Cu and Fe/Au nanoparticles were prepared directly by deposition from the gas phase. A detailed study of the atomic structure in both the cores and shells of the nanoparticles was undertaken by means of extended absorption fine structure (EXAFS) measurements. For Fe/Cu nanoparticles, a Cu shell ∼ 20 monolayers thick appears similar in structure to bulk Cu and is sufficient to cause the structure in the Fe core to switch from body centred cubic (bcc; as in bulk Fe) to face centred cubic. This is not the case for thinner Cu shells, 1-2 monolayers in thickness, in which there is a considerable contraction in nearest-neighbour interatomic distance as the shell structure changes to bcc. In Fe/Au nanoparticles, the crystal structure in the Fe core remains bcc for all Au thicknesses although there is some stretching of the lattice. In thin Au shells ∼ 2 monolayers thick, there is strong contraction in interatomic distances. There does not appear to be significant alloying at the Fe/Au interface.

  7. Water-assisted and controllable synthesis of core/shell/shell structured carbon-based nanohybrids, and their magnetic and microwave absorption properties.

    Science.gov (United States)

    Qi, Xiaosi; Yang, Erqi; Cai, Hongbo; Xie, Ren; Bai, Zhongchen; Jiang, Yang; Qin, Shuijie; Zhong, Wei; Du, Youwei

    2017-08-29

    By controlling the pyrolysis temperature, core/shell/shell structured Fe/Fe 5 C 2 /carbon nanotube bundles (Fe/Fe 5 C 2 /CNTBs), Fe/Fe 3 C/helical carbon nanotubes (Fe/Fe 3 C/HCNTs) and Fe/Fe 3 C/chain-like carbon nanospheres (Fe/Fe 3 C/CCNSs) with high encapsulation efficiency could be selectively synthesized in large-scale by water-assisted chemical vapor deposition method. Water vapor was proved to play an important role in the growth process. Because of α-Fe nanoparticles tightly wrapped by two layers, the obtained core/shell/shell structured nanohybrids showed high stabilities and good magnetic properties. The minimum reflection loss values of the as-prepared nanohybrids reached approximately -15.0, -46.3 and -37.1 dB, respectively. The excellent microwave absorption properties of the as-prepared core/shell/shell structured nanohybrids were considered to the quarter-wavelength matching model. Moreover, the possible enhanced microwave absorption mechanism of the as-prepared Fe/Fe 3 C/HCNTs and Fe/Fe 3 C/CCNSs were discussed in details. Therefore, we proposed a simple, inexpensive and environment-benign strategy for the synthesis of core/shell/shell structured carbon-based nanohybrids, exhibiting a promising prospect as high performance microwave absorbing materials.

  8. ECO-TECHNIQUE OF SEWER RENOVATION USING COMPOSITE SHELLS: STRUCTURAL ANALYSIS

    Directory of Open Access Journals (Sweden)

    B. Attaf

    2015-07-01

    Full Text Available An eco-technical renovation of the sewage system is developed in this paper; this technique involves incorporating into the existing sewer a series of jointed prefabricated sandwich or composite shells. The purpose of his study is to determine the structural shell deflection, the high displacement areas and to validate the non-failure criterion for each ply constituting the inner and outer laminate facings. The numerical results were obtained at low cost by using the finite element method. Studies have focused on structural analysis of a typical shell unit with an ovoid form (egg-shaped section when it is subjected, during annular space filling operation, to pressure forces generated by wet concrete. To ensure the safety of the composite shell structure, Tsai-Hill criterion function is applied and results are presented for the most stressed plies

  9. Verification of split spectrum technique for ultrasonic inspection of welded structures in nuclear reactors

    International Nuclear Information System (INIS)

    Ericsson, L.; Stepinski, T.

    1992-01-01

    Ultrasonic nondestructive inspection of materials is often limited by the presence of backscattered echoes from the material structure. A digital signal processing technique for removal of this material noise, referred to as split spectrum processing (SSP), has been developed and verified using simple laboratory experiments during the last decade. However, application of the split spectrum processing algorithm to industrial conditions has been rarely reported. In the paper the results of the practical evaluation of the SSP technique are presented. A number of different ultrasonic transducers were used for acquiring echoes from artificial flaws as well as natural cracks. The flaws were located in test blocks employed by the Swedish Nuclear Power Companies as reference during ultrasonic inspection of nuclear reactor vessels. The acquired ultrasonic A-scan signals were processed off-line using specially developed algorithms on a personal computer (PC). The experiments show evidence that properly tuned SSP algorithms result in a considerable improvement of the signal to material noise ratio. The enhancements were similar irrespective of the features of the transducer used or the nature of the inspected flaw. The problems related to the development of self-tuning SSP algorithms for on-line processing of B-scans are discussed. (author)

  10. ProteinSplit: splitting of multi-domain proteins using prediction of ordered and disordered regions in protein sequences for virtual structural genomics

    International Nuclear Information System (INIS)

    Wyrwicz, Lucjan S; Koczyk, Grzegorz; Rychlewski, Leszek; Plewczynski, Dariusz

    2007-01-01

    The annotation of protein folds within newly sequenced genomes is the main target for semi-automated protein structure prediction (virtual structural genomics). A large number of automated methods have been developed recently with very good results in the case of single-domain proteins. Unfortunately, most of these automated methods often fail to properly predict the distant homology between a given multi-domain protein query and structural templates. Therefore a multi-domain protein should be split into domains in order to overcome this limitation. ProteinSplit is designed to identify protein domain boundaries using a novel algorithm that predicts disordered regions in protein sequences. The software utilizes various sequence characteristics to assess the local propensity of a protein to be disordered or ordered in terms of local structure stability. These disordered parts of a protein are likely to create interdomain spacers. Because of its speed and portability, the method was successfully applied to several genome-wide fold annotation experiments. The user can run an automated analysis of sets of proteins or perform semi-automated multiple user projects (saving the results on the server). Additionally the sequences of predicted domains can be sent to the Bioinfo.PL Protein Structure Prediction Meta-Server for further protein three-dimensional structure and function prediction. The program is freely accessible as a web service at http://lucjan.bioinfo.pl/proteinsplit together with detailed benchmark results on the critical assessment of a fully automated structure prediction (CAFASP) set of sequences. The source code of the local version of protein domain boundary prediction is available upon request from the authors

  11. Broadband absorption and enhanced photothermal conversion property of octopod-like Ag@Ag2S core@shell structures with gradually varying shell thickness.

    Science.gov (United States)

    Jiang, Qian; Zeng, Wenxia; Zhang, Canying; Meng, Zhaoguo; Wu, Jiawei; Zhu, Qunzhi; Wu, Daxiong; Zhu, Haitao

    2017-12-19

    Photothermal conversion materials have promising applications in many fields and therefore they have attracted tremendous attention. However, the multi-functionalization of a single nanostructure to meet the requirements of multiple photothermal applications is still a challenge. The difficulty is that most nanostructures have specific absoprtion band and are not flexible to different demands. In the current work, we reported the synthesis and multi-band photothermal conversion of Ag@Ag 2 S core@shell structures with gradually varying shell thickness. We synthesized the core@shell structures through the sulfidation of Ag nanocubes by taking the advantage of their spatially different reactivity. The resulting core@shell structures show an octopod-like mopgorlogy with a Ag 2 S bulge sitting at each corner of the Ag nanocubes. The thickness of the Ag 2 S shell gradually increases from the central surface towards the corners of the structure. The synthesized core@shell structures show a broad band absorption spectrum from 300 to 1100 nm. Enhanced photothermal conversion effect is observed under the illuminations of 635, 808, and 1064 nm lasers. The results indicate that the octopod-like Ag@Ag 2 S core@shell structures have characteristics of multi-band photothermal conversion. The current work might provide a guidance for the design and synthesis of multifunctional photothermal conversion materials.

  12. Effect of core-shell structure on optical properties of Au-Cu2O nanoparticles

    Science.gov (United States)

    Sai, Cong Doanh; Ngac, An Bang

    2018-03-01

    Solid Au-Cu2O core-shell nanoparticles were synthesized using gold nanoparticles of 16.6 nm in size as the core. The core-shell structure of the synthesized particles was confirmed and characterized by TEM and HRTEM images. Due to their similar crystal structure, the (111) planes of Cu2O are nucleated and grown epitaxially on the {111} facets of Au nanoparticles with the lattice mismatch of about 4.3% resulting in a polycrystallized Cu2O shell covering the Au nanocore. Due to the quantum confinement effect, the band gap energy Eg of the synthesized Cu2O shells is blue-shifted from 2.35 to 2.70 eV as the shell thickness decreases from of 24.6±3.6 to 9.0±1.7 nm. The localized SPR (Surface Plasmon Resonance) peak of the Au nanocore undergoes a large red shift of the order of a hundred of nm due to both the high refractive index and the increase of the thickness of Cu2O shell. Theoretical models within the Drude framework significantly underestimate the experimental data and predict a wrong rate of change of the SPR peak position with respect to the shell thickness.

  13. A study on the nonlinear finite element analysis of reinforced concrete structures: shell finite element formulation

    Energy Technology Data Exchange (ETDEWEB)

    Lee, Sang Jin; Seo, Jeong Moon

    2000-08-01

    The main goal of this research is to establish a methodology of finite element analysis of containment building predicting not only global behaviour but also local failure mode. In this report, we summerize some existing numerical analysis techniques to be improved for containment building. In other words, a complete description of the standard degenerated shell finite element formulation is provided for nonlinear stress analysis of nuclear containment structure. A shell finite element is derived using the degenerated solid concept which does not rely on a specific shell theory. Reissner-Mindlin assumptions are adopted to consider the transverse shear deformation effect. In order to minimize the sensitivity of the constitutive equation to structural types, microscopic material model is adopted. The four solution algorithms based on the standard Newton-Raphson method are discussed. Finally, two numerical examples are carried out to test the performance of the adopted shell medel.

  14. Coupled mixed-field laminate theory and finite element for smart piezoelectric composite shell structures

    Science.gov (United States)

    Saravanos, Dimitris A.

    1996-01-01

    Mechanics for the analysis of laminated composite shells with piezoelectric actuators and sensors are presented. A new mixed-field laminate theory for piezoelectric shells is formulated in curvilinear coordinates which combines single-layer assumptions for the displacements and a layerwise representation for the electric potential. The resultant coupled governing equations for curvilinear piezoelectric laminates are described. Structural mechanics are subsequently developed and an 8-node finite-element is formulated for the static and dynamic analysis of adaptive composite structures of general laminations containing piezoelectric layers. Evaluations of the method and comparisons with reported results are presented for laminated piezoelectric-composite plates, a closed cylindrical shell with a continuous piezoceramic layer and a laminated composite semi-circular cantilever shell with discrete cylindrical piezoelectric actuators and/or sensors.

  15. Compact and Wide Stopband Lowpass Filter Using Open Complementary Split Ring Resonator and Defected Ground Structure

    Directory of Open Access Journals (Sweden)

    S. S. Karthikeyan

    2015-09-01

    Full Text Available A compact (0.16 λg x 0.08 λg and wide stop¬band lowpass filter design using open complementary split ring resonator (OCSRR and defected ground structure (DGS is presented in this paper. Low pass filter is con-structed using two cascaded stages of OCSRR. Since the rejection bandwidth of the OCSRR is narrow, tapered dumbbell shaped DGS section is placed under the OCSRR to enhance the bandwidth. The cutoff frequency (fc of the proposed lowpass filter is 1.09 GHz. The rejection band¬width of the filter covers the entire ultra wideband spec¬trum. Hence the spurious passband suppression is achieved up to 10 fc. The designed filter has been fabri¬cated and validated by experimental results

  16. Diverse and tunable electronic structures of single-layer metal phosphorus trichalcogenides for photocatalytic water splitting

    International Nuclear Information System (INIS)

    Liu, Jian; Li, Xi-Bo; Wang, Da; Liu, Li-Min; Lau, Woon-Ming; Peng, Ping

    2014-01-01

    The family of bulk metal phosphorus trichalcogenides (APX 3 , A = M II , M 0.5 I M 0.5 III ; X = S, Se; M I , M II , and M III represent Group-I, Group-II, and Group-III metals, respectively) has attracted great attentions because such materials not only own magnetic and ferroelectric properties, but also exhibit excellent properties in hydrogen storage and lithium battery because of the layered structures. Many layered materials have been exfoliated into two-dimensional (2D) materials, and they show distinct electronic properties compared with their bulks. Here we present a systematical study of single-layer metal phosphorus trichalcogenides by density functional theory calculations. The results show that the single layer metal phosphorus trichalcogenides have very low formation energies, which indicates that the exfoliation of single layer APX 3 should not be difficult. The family of single layer metal phosphorus trichalcogenides exhibits a large range of band gaps from 1.77 to 3.94 eV, and the electronic structures are greatly affected by the metal or the chalcogenide atoms. The calculated band edges of metal phosphorus trichalcogenides further reveal that single-layer ZnPSe 3 , CdPSe 3 , Ag 0.5 Sc 0.5 PSe 3 , and Ag 0.5 In 0.5 PX 3 (X = S and Se) have both suitable band gaps for visible-light driving and sufficient over-potentials for water splitting. More fascinatingly, single-layer Ag 0.5 Sc 0.5 PSe 3 is a direct band gap semiconductor, and the calculated optical absorption further convinces that such materials own outstanding properties for light absorption. Such results demonstrate that the single layer metal phosphorus trichalcogenides own high stability, versatile electronic properties, and high optical absorption, thus such materials have great chances to be high efficient photocatalysts for water-splitting

  17. Structural Color Palettes of Core-Shell Photonic Ink Capsules Containing Cholesteric Liquid Crystals.

    Science.gov (United States)

    Lee, Sang Seok; Seo, Hyeon Jin; Kim, Yun Ho; Kim, Shin-Hyun

    2017-06-01

    Photonic microcapsules with onion-like topology are microfluidically designed to have cholesteric liquid crystals with opposite handedness in their core and shell. The microcapsules exhibit structural colors caused by dual photonic bandgaps, resulting in a rich variety of color on the optical palette. Moreover, the microcapsules can switch the colors from either core or shell depending on the selection of light-handedness. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Effects of finite element formulation on optimal plate and shell structural topologies

    CSIR Research Space (South Africa)

    Long, CS

    2009-09-01

    Full Text Available quantitatively to avoid simply comparing topologies visually. Special attention is paid to plate and shell problems and it is therefore appro- priate to give some background on structural topology optimization of plate and shell problems at this point... to automatically generate not only good, but optimal designs, topology optimization has been receiving unprecedented attention of late. However, we believe that an aspect of the problem which has not received sufficient attention is the effect of the the actual...

  19. Economic Development through Globalisation in Nigeria : An analysis of Shell & the IMF Structural Adjustment Programs

    OpenAIRE

    Bokhari, Sven; Del Duca, Fabrizio

    2008-01-01

    Date: 2008/06/03 Level: Master thesis in International Business and Entrepreneurship, 10p (15ECTS) Authors: Sven Bokhari Fabrizio Del Duca Title: Economic Development through globalisation in Nigeria. An analysis of Shell & the IMF Structural Adjustment Programs Tutor: Leif Linnskog, Ph.D. Research Question: Can globalisation be seen as positive or negative for the Economic Development of Nigeria? A focus on Shell and the International Monetary Fund Research Issue: Globalisation in its cu...

  20. Insights into Shallow Anisotropic Structure in the Forearc Hikurangi Subduction Zone, New Zealand via Splitting of Teleseisms

    Science.gov (United States)

    Karalliyadda, S.; Savage, M. K.

    2013-12-01

    We use a recent transect that consists of 10 broadband stations across the northeast of Wellington region to explore the anisotropic structure of the forearc of the Hikurangi subduction zone in the southern North Island (NI), New Zealand from shear-wave splitting of SKS, ScS and teleseismic S phases. These measurements are then integrated with the previous splitting measurements in northwest of the transect. Splitting parameters from teleseismic S-phases revealed an abrupt lateral variation in the anisotropic structure. The general trend of splitting agrees well with the previous studies around this area, with NE-SW trench-parallel fast direction (φ). The range of delay times ( 0.5 - 3.0 s) and slightly varying SKS φ across the southeast of NI suggest a laterally varying anisotropic structure. As inferred by splitting variations from long period (>7 s) phases across the profile, the upper-plate Wairarapa fault and basin area appear to be characterized by a distinct anisotropic structure that is possibly localized at crustal depths. The sharp change in delay time (δt) around this fault zone divides the region in to two distinct domains of eastern and western sides. The average δt on the eastern side (2.05 × 0.45 s) is ~0.6 s higher than that measured in the western side (1.44 × 0.24 s) of the Wairarapa fault. This change takes place between two stations that are separated by ~3 km. Clear frequency dependent splitting from ScS and teleseismic S-phases suggests that the anisotropic structure is either stratified or governed by more complex anisotropy. Multilayer models are unable to explain the observations adequately, suggesting a more complex structure. We think that this complex structure is governed in part by the laterally-varying crustal contribution of anisotropy and this lateral variation is likely associated with the multilayer anisotropy to form a more complex structure. We suggest that the subduction structure is dominated by the mantle flow in the

  1. Methanol oxidation reaction on core-shell structured Ruthenium-Palladium nanoparticles: Relationship between structure and electrochemical behavior

    Science.gov (United States)

    Kübler, Markus; Jurzinsky, Tilman; Ziegenbalg, Dirk; Cremers, Carsten

    2018-01-01

    In this work the relationship between structural composition and electrochemical characteristics of Palladium(Pd)-Ruthenium(Ru) nanoparticles during alkaline methanol oxidation reaction is investigated. The comparative study of a standard alloyed and a precisely Ru-core-Pd-shell structured catalyst allows for a distinct investigation of the electronic effect and the bifunctional mechanism. Core-shell catalysts benefit from a strong electronic effect and an efficient Pd utilization. It is found that core-shell nanoparticles are highly active towards methanol oxidation reaction for potentials ≥0.6 V, whereas alloyed catalysts show higher current outputs in the lower potential range. However, differential electrochemical mass spectrometry (DEMS) experiments reveal that the methanol oxidation reaction on core-shell structured catalysts proceeds via the incomplete oxidation pathway yielding formaldehyde, formic acid or methyl formate. Contrary, the alloyed catalyst benefits from the Ru atoms at its surface. Those are found to be responsible for high methanol oxidation activity at lower potentials as well as for complete oxidation of CH3OH to CO2 via the bifunctional mechanism. Based on these findings a new Ru-core-Pd-shell-Ru-terrace catalyst was synthesized, which combines the advantages of the core-shell structure and the alloy. This novel catalyst shows high methanol electrooxidation activity as well as excellent selectivity for the complete oxidation pathway.

  2. Super-paramagnetic core-shell material with tunable magnetic behavior by regulating electron transfer efficiency and structure stability of the shell

    Directory of Open Access Journals (Sweden)

    Wenyan Zhang

    Full Text Available In this work, a spherical nano core-shell material was constructed by encapsulating Fe3O4 microsphere into conductive polymer-metal composite shell. The Fe3O4 microspheres were fabricated by assembling large amounts of Fe3O4 nano-crystals, which endowed the microspheres with super-paramagnetic property and high saturation magnetization. The polymer-metal composite shell was constructed by inserting Pt nano-particles (NPs into the conductive polymer polypyrrole (PPy. As size and dispersion of the Pt NPs has an important influence on their surface area and surface energy, it was effective to enlarge the interface area between PPy and Pt NPs, enhance the electron transfer efficiency of PPy/Pt composite shell, and reinforced the shell’s structural stability just by tuning the size and dispersion of Pt NPs. Moreover, core-shell structure of the materials made it convenient to investigate the PPy/Pt shell’s shielding effect on the Fe3O4 core’s magnetic response to external magnetic fields. It was found that the saturation magnetization of Fe3O4/PPy/Pt core-shell material could be reduced by 20.5% by regulating the conductivity of the PPy/Pt shell. Keywords: Super-paramagnetic, Conductivity, Magnetic shielding, Structural stability

  3. Surface energy effect on free vibration of nano-sized piezoelectric double-shell structures

    Science.gov (United States)

    Fang, Xue-Qian; Zhu, Chang-Song; Liu, Jin-Xi; Liu, Xiang-Lin

    2018-01-01

    Combining Goldenveizer-Novozhilov shell theory, thin plate theory and electro-elastic surface theory, the size-dependent vibration of nano-sized piezoelectric double-shell structures under simply supported boundary condition is presented, and the surface energy effect on the natural frequencies is discussed. The displacement components of the cylindrical nano-shells and annular nano-plates are expanded as the superposition of standard Fourier series based on Hamilton's principle. The total stresses with consideration of surface energy effect are derived, and the total energy function is obtained by using Rayleigh-Ritz energy method. The free vibration equation is solved, and the natural frequency is analyzed. In numerical examples, it is found that the surface elastic constant, piezoelectric constant and surface residual stress show different effects on the natural frequencies. The effect of surface piezoelectric constant is the maximum. The effect of dimensions of the double-shell under different surface material properties is also examined.

  4. Synthesis, structural, optical and photocatalytic properties of CdS/ZnS core/shell nanoparticles

    Science.gov (United States)

    Reddy, Ch. Venkata; Shim, Jaesool; Cho, Migyung

    2017-04-01

    CdS, ZnS and CdS/ZnS core/shell nanoparticles were successfully synthesized via two-step synthesis method. The as-prepared CdS, ZnS and CdS/ZnS core/shell nanoparticles were used to study the structural, morphological, and optical properties by PXRD, TEM, HRTEM, UV-vis spectroscopy, N2 adsorption-desorption, FT-IR, PL and Raman spectroscopy measurements. The XRD pattern confirms the crystal structure of the prepared ZnS, CdS, and CdS/ZnS core/shell nanoparticles. The crystallinity of the as-prepared samples is confirmed by PXRD, TEM and HRTEM analysis. The BET analysis showed that the CdS/ZnS core/shell nanoparticles had larger surface area and pore diameter than CdS and ZnS. The Raman and FT-IR spectra confirm the fundamental vibrational modes of CdS and ZnS respectively. Compared to pure CdS and ZnS, CdS/ZnS core/shell nanoparticles exhibited higher photocatalytic activity for the degradation of methyl orange (MO). The enhancement of photocatalytic activity in the CdS/ZnS core/shell nanoparticles is due to the interface actions between CdS and ZnS, which greatly reduces the recombination of photogenerated electrons-holes pair. The proposed mechanism for degradation of MO dye is discussed in detail.

  5. Embryo splitting

    OpenAIRE

    Karl Illmensee; Mike Levanduski

    2010-01-01

    Mammalian embryo splitting has successfully been established in farm animals. Embryo splitting is safely and efficiently used for assisted reproduction in several livestock species. In the mouse, efficient embryo splitting as well as single blastomere cloning have been developed in this animal system. In nonhuman primates embryo splitting has resulted in several pregnancies. Human embryo splitting has been reported recently. Microsurgical embryo splitting under Institutional Review Board appr...

  6. Large hh-lh splitting energy for InAs/AlSb/GaSb based N-structure photodetectors

    Science.gov (United States)

    Akel, K.; Hostut, M.; Tansel, T.; Ergun, Y.

    2018-01-01

    We investigate the band properties of InAs/AlSb/GaSb (N-structure) and InAs/GaSb material based type II superlattice (T2SL) photodedectors. The superlattice empirical pseudopotential method is used to define band-structures such as the bandgap and heavy hole-light hole (hh-lh) splitting energies in the mid-wavelength infrared range (MWIR) and long wavelength range (LWIR). The calculations are carried out on the variation of AlSb/GaSb layer thickness for (InAs)10.5/(AlSb)x/(GaSb)9-x and the variation of InAs layer thickness for (InAs)x/(AlSb)3/(GaSb)6 T2SL structures at 77 K. For the same bandgap energy of 229 meV (5.4 μm in wavelength), hh-lh splitting energy is calculated as 194 meV for the (InAs)7.5/(AlSb)3/(GaSb)6 structure compared to the (InAs)10.5/(GaSb)9 structure with hh-lh splitting energy of 91 meV within the MWIR. Long wavelength performance of InAs/AlSb/GaSb structure shows superior electronic properties over the standard InAs/GaSb T2SL structure with larger hh-lh splitting energy which is larger than the bandgap energy. The best result is obtained for (InAs)17/(AlSb)3/(GaSb)6 with the minimum bandgap of 128 meV with hh-lh splitting energy of 194 meV, which is important for suppressing the Auger recombination process. These values are very promising for a photodetector design in both MWIR and LWIR in high temperature applications.

  7. Shell structure at high spin and the influence on nuclear shapes

    International Nuclear Information System (INIS)

    Khoo, T.L.; Chowdhury, P.; Ahmad, I.

    1982-01-01

    Nuclear structure at high spin is influenced by a combination of liquid-drop and shell-structure effects. For N 90. The competition between oblate and prolate driving effects leads to a prolate-to-oblate shape transition in 154 Dy 88 . The role of rotation-aligned configurations in the shape change is discussed

  8. Tomographic TR-PIV measurement of coherent structure spatial topology utilizing an improved quadrant splitting method

    Science.gov (United States)

    Yang, ShaoQiong; Jiang, Nan

    2012-10-01

    In this paper, we calculated the spatial local-averaged velocity strains along the streamwise direction at four spatial scales according to the concept of spatial local-averaged velocity structure function by using the three-dimensional three-component database of time series of velocity vector field in the turbulent boundary layer measured by tomographic time-resolved particle image velocimetry. An improved quadrant splitting method, based on the spatial local-averaged velocity strains together with a new conditional sampling phase average technique, was introduced as a criterion to detect the coherent structure topology. Furthermore, we used them to detect and extract the spatial topologies of fluctuating velocity and fluctuating vorticity whose center is a strong second-quadrant event (Q2) or a fourth-quadrant event (Q4). Results illustrate that a closer similarity of the multi-scale coherent structures is present in the wall-normal direction, compared to the one in the other two directions. The relationship among such topological coherent structures and Reynolds stress bursting events, as well as the fluctuating vorticity was discussed. When other burst events are surveyed (the first-quadrant event Q1 and the third-quadrant event Q3), a fascinating bursting period circularly occurs: Q4-S-Q2-Q3-Q2-Q1-Q4-S-Q2-Q3-Q2-Q1 in the center of such topological structures along the streamwise direction. In addition, the probability of the Q2 bursting event occurrence is slightly higher than that of the Q4 event occurrence. The spatial instable singularity that almost simultaneously appears together with typical Q2 or Q4 events has been observed, which is the main character of the mutual induction mechanism and vortex auto-generation mechanism explaining how the turbulence is produced and maintained.

  9. Research advances in polymer emulsion based on "core-shell" structure particle design.

    Science.gov (United States)

    Ma, Jian-zhong; Liu, Yi-hong; Bao, Yan; Liu, Jun-li; Zhang, Jing

    2013-09-01

    In recent years, quite many studies on polymer emulsions with unique core-shell structure have emerged at the frontier between material chemistry and many other fields because of their singular morphology, properties and wide range of potential applications. Organic substance as a coating material onto either inorganic or organic internal core materials promises an unparalleled opportunity for enhancement of final functions through rational designs. This contribution provides a brief overview of recent progress in the synthesis, characterization, and applications of both inorganic-organic and organic-organic polymer emulsions with core-shell structure. In addition, future research trends in polymer composites with core-shell structure are also discussed in this review. Copyright © 2013 Elsevier B.V. All rights reserved.

  10. Embryo splitting

    Directory of Open Access Journals (Sweden)

    Karl Illmensee

    2010-04-01

    Full Text Available Mammalian embryo splitting has successfully been established in farm animals. Embryo splitting is safely and efficiently used for assisted reproduction in several livestock species. In the mouse, efficient embryo splitting as well as single blastomere cloning have been developed in this animal system. In nonhuman primates embryo splitting has resulted in several pregnancies. Human embryo splitting has been reported recently. Microsurgical embryo splitting under Institutional Review Board approval has been carried out to determine its efficiency for blastocyst development. Embryo splitting at the 6–8 cell stage provided a much higher developmental efficiency compared to splitting at the 2–5 cell stage. Embryo splitting may be advantageous for providing additional embryos to be cryopreserved and for patients with low response to hormonal stimulation in assisted reproduction programs. Social and ethical issues concerning embryo splitting are included regarding ethics committee guidelines. Prognostic perspectives are presented for human embryo splitting in reproductive medicine.

  11. Tests of a niobium split-ring superconducting heavy ion accelerating structure

    Energy Technology Data Exchange (ETDEWEB)

    Benaroya, R.; Bollinger, L.M.; Jaffey, A.H.; Khoe, T.K.; Olesen, M.C.; Scheibelhut, C.H.; Shepard, K.W.; Wesolowski, W.A.

    1976-01-01

    A niobium split-ring accelerating structure designed for use in the Argonne superconducting heavy-ion energy booster was successfully tested. The superconducting resonator has a resonant frequency of 97 MHz and an optimum particle velocity ..beta.. = 0.11. Ultimate performance is expected to be limited by peak surface fields, which in this structure are 4.7 E/sub a/ electric and 170 E/sub a/ (Gauss) magnetic, where E/sub a/ is the effective accelerating gradient in MV/m. The rf losses in two demountable superconducting joints severely limited performance in initial tests. Following independent measurements of the rf loss properties of several types of demountable joints, one demountable joint was eliminated and the other modified. Subsequently, the resonator could be operated continuously at E/sub a/ = 3.6 MV/m (corresponding to an energy gain of 1.3 MeV per charge) with 10W rf input power. Maximum field level was limited by electron loading. The mechanical stability of the resonator under operating conditions is excellent: vibration induced eigenfrequency noise is less than 120 Hz peak to peak, and the radiation pressure induced frequency shift is ..delta..f/f = 1.6 x 10/sup -6/ E/sub a//sup 2/.

  12. Tests of a niobium split-ring superconducting heavy ion accelerating structure

    International Nuclear Information System (INIS)

    Benaroya, R.; Bollinger, L.M.; Jaffey, A.H.; Khoe, T.K.; Olesen, M.C.; Scheibelhut, C.H.; Shepard, K.W.; Wesolowski, W.A.

    1976-01-01

    A niobium split-ring accelerating structure designed for use in the Argonne superconducting heavy-ion energy booster was successfully tested. The superconducting resonator has a resonant frequency of 97 MHz and an optimum particle velocity β = 0.11. Ultimate performance is expected to be limited by peak surface fields, which in this structure are 4.7 E/sub a/ electric and 170 E/sub a/ (Gauss) magnetic, where E/sub a/ is the effective accelerating gradient in MV/m. The rf losses in two demountable superconducting joints severely limited performance in initial tests. Following independent measurements of the rf loss properties of several types of demountable joints, one demountable joint was eliminated and the other modified. Subsequently, the resonator could be operated continuously at E/sub a/ = 3.6 MV/m (corresponding to an energy gain of 1.3 MeV per charge) with 10W rf input power. Maximum field level was limited by electron loading. The mechanical stability of the resonator under operating conditions is excellent: vibration induced eigenfrequency noise is less than 120 Hz peak to peak, and the radiation pressure induced frequency shift is Δf/f = 1.6 x 10 -6 E/sub a/ 2

  13. Thermal Stability of Co-Pt and Co-Au Core-Shell Structured Nanoparticles: Insights from Molecular Dynamics Simulations.

    Science.gov (United States)

    Wen, Yu-Hua; Huang, Rao; Shao, Gui-Fang; Sun, Shi-Gang

    2017-09-07

    Co-Pt and Co-Au core-shell nanoparticles were heated by molecular dynamics simulations to investigate their thermal stability. Two core structures, that is, hcp Co and fcc Co, have been addressed. The results demonstrate that the hcp-fcc phase transition happens in the hcp-Co-core/fcc-Pt-shell nanoparticle, while it is absent in the hcp-Co-core/fcc-Au-shell one. The stacking faults appear in both Pt and Au shells despite different structures of the Co core. The Co core and Pt shell concurrently melt and present an identical melting point in both Co-Pt core-shell nanoparticles. However, typical two-stage melting occurs in both Co-Au core-shell nanoparticles. Furthermore, the Au shell in the hcp-Co-core/fcc-Au-shell nanoparticle exhibits a lower melting point than that in the fcc-Co-core/fcc-Au-shell one, while the melting points are closely equal for both hcp and fcc Co cores. All of these observations suggest that their thermal stability strongly depends on the structure of the core and the element of the shell.

  14. Spin State as a Marker for the Structural Evolution of Nature's Water-Splitting Catalyst.

    Science.gov (United States)

    Krewald, Vera; Retegan, Marius; Neese, Frank; Lubitz, Wolfgang; Pantazis, Dimitrios A; Cox, Nicholas

    2016-01-19

    In transition-metal complexes, the geometric structure is intimately connected with the spin state arising from magnetic coupling between the paramagnetic ions. The tetramanganese-calcium cofactor that catalyzes biological water oxidation in photosystem II cycles through five catalytic intermediates, each of which adopts a specific geometric and electronic structure and is thus characterized by a specific spin state. Here, we review spin-structure correlations in Nature's water-splitting catalyst. The catalytic cycle of the Mn4O5Ca cofactor can be described in terms of spin-dependent reactivity. The lower "inactive" S states of the catalyst, S0 and S1, are characterized by low-spin ground states, SGS = 1/2 and SGS = 0. This is connected to the "open cubane" topology of the inorganic core in these states. The S2 state exhibits structural and spin heterogeneity in the form of two interconvertible isomers and is identified as the spin-switching point of the catalytic cycle. The first S2 state form is an open cubane structure with a low-spin SGS = 1/2 ground state, whereas the other represents the first appearance of a closed cubane topology in the catalytic cycle that is associated with a higher-spin ground state of SGS = 5/2. It is only this higher-spin form of the S2 state that progresses to the "activated" S3 state of the catalyst. The structure of this final metastable catalytic state was resolved in a recent report, showing that all manganese ions are six-coordinate. The magnetic coupling is dominantly ferromagnetic, leading to a high-spin ground state of SGS = 3. The ability of the Mn4O5Ca cofactor to adopt two distinct structural and spin-state forms in the S2 state is critical for water binding in the S3 state, allowing spin-state crossing from the inactive, low-spin configuration of the catalyst to the activated, high-spin configuration. Here we describe how an understanding of the magnetic properties of the catalyst in all S states has allowed conclusions on

  15. Structural instability of shell-like assemblies of a keplerate-type polyoxometalate induced by ionic strength.

    Science.gov (United States)

    Veen, Sandra J; Kegel, Willem K

    2009-11-19

    We demonstrate a new structural instability of shell-like assemblies of polyoxometalates. Besides the colloidal instability, that is, the formation of aggregates that consist of many single layered POM-shells, these systems also display an instability on a structural scale within the shell-like assemblies. This instability occurs at significantly lower ionic strength than the colloidal stability limit and only becomes evident after a relatively long time. For the polyoxometalate, abbreviated as {Mo(72)Fe(30)}, it is shown that the structural stability limit of POM-shells lies between a NaCl concentration of 1.00 and 5.00 mM in aqueous solution.

  16. Harnessing the bistable composite shells to design a tunable phononic band gap structure

    Science.gov (United States)

    Li, Yi; Xu, Yanlong

    2018-02-01

    By proposing a system composed of an array of bistable composite shells immersed in air, we develop a new class of periodic structure to control the propagation of sound. Through numerical investigation, we find that the acoustic band gap of this system can be switched on and off by triggering the snap through deformation of the bistable composite shells. The shape of cross section and filling fraction of unit cell can be altered by different number of bistable composite shells, and they have strong impact on the position and width of the band gap. The proposed concept paves the way of using the bistable structures to design a new class of metamaterials that can be enable to manipulate sound.

  17. Study of thermal diffusivity of nanofluids with bimetallic nanoparticles with Au(core)/Ag(shell) structure

    International Nuclear Information System (INIS)

    Gutierrez Fuentes, R.; Pescador Rojas, J.A.; Jimenez-Perez, J.L.; Sanchez Ramirez, J.F.; Cruz-Orea, A.; Mendoza-Alvarez, J.G.

    2008-01-01

    The thermal diffusivity of Au/Ag nanoparticles with core/shell structure, at different compositions (Au/Ag = 3/1, 1/1, 1/3, 1/6), was measured by using the mismatched mode of the dual-beam thermal lens (TL) technique. This study determines the effect of the bimetallic composition on the thermal diffusivity of the nanofluids. In these results we find a lineal increment of the nanofluid it thermal diffusivity when the Ag shell thickness is increased. Our results show that the nanoparticle structure is an important parameter to improve the heat transport in composites and nanofluids. These results could have importance for applications in therapies and photothermal deliberation of drugs. Complementary measurements with UV-vis spectroscopy and TEM, were used to characterize the Au(core)/Ag(shell) nanoparticles

  18. Study of CRFP Shell Structures under Dynamic Loading in Shock Tube Setup

    Directory of Open Access Journals (Sweden)

    H. A. Khawaja

    2014-01-01

    Full Text Available The paper gives the study of the response of carbon fiber reinforced polymers (CRFP quasi-isotropic shell structures under the influence of dynamic loading. The quasi-isotropic CRFP shell specimens are fabricated using Multipreg E720 laminates. These laminates are laid in such a way that shell structure has equal strength and mechanical properties in the two-dimensional (2D plane and hence can be regarded as quasi-isotropic. In this study, the dynamic loading is generated using shock waves in a shock tube experimental setup. The strain and pressure data is collected from the experiments. Additional tests are carried out using Material Test System (MTS for both tensile and flexural response of CRFP. Results obtained from experiments are compared with numerical simulations using ANSYS Multiphysics 14.0 finite element method (FEM package. The numerical simulation and experimental results are found to be in good agreement.

  19. Nuclear Shell Structure and Beta Decay I. Odd A Nuclei II. Even A Nuclei

    Science.gov (United States)

    Mayer, M.G.; Moszkowski, S.A.; Nordheim, L.W.

    1951-05-01

    In Part I a systematics is given of all transitions for odd A nuclei for which sufficiently reliable data are available. The allowed or forbidden characters of the transitions are correlated with the positions of the initial and final odd nucleon groups in the nuclear shell scheme. The nuclear shells show definite characteristics with respect to parity of the ground states. The latter is the same as the one obtained from known spins and magnetic moments in a one-particle interpretation. In Part II a systematics of the beta transitions of even-A nuclei is given. An interpretation of the character of the transitions in terms of nuclear shell structure is achieved on the hypothesis that the odd nucleon groups have the same structure as in odd-A nuclei, together with a simple coupling rule between the neutron and proton groups in odd-odd nuclei.

  20. Shell and membrane theories in mechanics and biology from macro- to nanoscale structures

    CERN Document Server

    Mikhasev, Gennadi

    2015-01-01

    This book presents the latest results related to shells  characterize and design shells, plates, membranes and other thin-walled structures, a multidisciplinary approach from macro- to nanoscale is required which involves the classical disciplines of mechanical/civil/materials engineering (design, analysis, and properties) and physics/biology/medicine among others. The book contains contributions of a meeting of specialists (mechanical engineers, mathematicians, physicists and others) in such areas as classical and non-classical shell theories. New trends with respect to applications in mechanical, civil and aero-space engineering, as well as in new branches like medicine and biology are presented which demand improvements of the theoretical foundations of these theories and a deeper understanding of the material behavior used in such structures.

  1. Core-Shell Structure in Doped Inorganic Nanoparticles: Approaches for Optimizing Luminescence Properties

    Directory of Open Access Journals (Sweden)

    Dini Xie

    2013-01-01

    Full Text Available Doped inorganic luminescent nanoparticles (NPs have been widely used in both research and application fields due to their distinctive properties. However, there is an urgent demand to improve their luminescence efficiency, which is greatly reduced by surface effects. In this paper, we review recent advances in optimizing luminescence properties of doped NPs based on core-shell structure, which are basically classified into two categories: one is by use of surface coating with nonmetal materials to weaken the influence of surface effect and the other is with metal shell via metal enhanced luminescence. Different materials used to coat NPs are surveyed, and their advantages and disadvantages are both commented on. Moreover, problems in current core-shell structured luminescent NPs are pointed out and strategies furthering the optimization of luminescence properties are suggested.

  2. Steady-State Response of Acoustic Cavities Bounded by Piezoelectric Composite Shell Structures

    Science.gov (United States)

    Kaljević, I.; Saravanos, D. A.

    1997-07-01

    A formulation to calculate the coupled response of composite shells with embedded piezoelectric layers and an enclosed acoustic fluid is presented in this paper. The methodology consists of three parts: (1) a formulation for the electro-mechanical response of piezoelectric shells; (2) a formulation for the three-dimensional acoustic response of the enclosed fluid; and (3) the combination of the formulations (1) and (2) to calculate the coupled smart structure-acoustic fluid response. A recently developed mixed field laminate theory is adapted for the analysis of piezoelectric shells. The theory combines the first order shear theory kinematic assumptions with a layer-wise approximation for the electric potential. Shell geometry is described in an orthogonal curvilinear co-ordinate system and general piezoelectric material descriptions and laminate configurations are considered. A boundary element formulation is developed to calculate the acoustic response of the enclosed fluid. Quadratic conforming boundary elements are used to discretize the fluid boundary. Advanced numerical integration techniques are employed to calculate singular elements in boundary element matrices. The treatment of distributed acoustic sources is also presented. A formulation to calculate the coupled fluid-structure response is also developed. Relations between the structural and acoustic variable on the structure-fluid interface are utilized to generate the coupled system of equations in terms of the kinematic shell variables and acoustic pressures on the fluid boundary. The convergence of the present developments is established by studying a circular cylindrical shell with an attached piezoelectric layer. The coupled response is investigated for various types of mechanical loads and active voltage patterns.

  3. Structural characterization of Pt–Pd core–shell nanoparticles by Cs-corrected STEM

    International Nuclear Information System (INIS)

    Esparza, R.; García-Ruiz, Amado F.; Velázquez Salazar, J. J.; Pérez, R.; José-Yacamán, M.

    2013-01-01

    Pt–Pd core–shell nanoparticles were synthesized using a modified polyol method. A thermal method under refluxing, carrying on the reaction up to 285 °C, has been performed to reduce metallic salts using ethylene glycol as reducer and poly(N-vinyl-2-pyrrolidone) as protective reagent of the formed bimetallic nanoparticles. According to other works, this type of structure has been studied and utilized to successfully increase the catalytic properties of monometallic nanoparticles Pt or Pd. Core–shell bimetallic nanoparticles were structurally characterized using aberration-corrected scanning transmission electron microscopy (Cs-STEM) equipped with a high-angle annular dark field detector, energy-dispersive X-ray spectrometry (EDS), and electron energy-loss spectroscopy (EELS). The high-resolution elemental line scan and mappings were carried out using a combination of STEM–EDS and STEM–EELS. The obtained results show the growth of the Pd shell on the Pt core with polyhedral morphology. The average size of the bimetallic nanoparticles was 13.5 nm and the average size of the core was 8.5 nm; consequently, the thickness of the shell was around 2.5 nm. The growth of the Pd shell on the Pt core is layer by layer, suggesting a Frank-van der Merwe growth mechanism.

  4. Structural characterization of Pt-Pd core-shell nanoparticles by Cs-corrected STEM

    Energy Technology Data Exchange (ETDEWEB)

    Esparza, R., E-mail: resparza@fata.unam.mx [Universidad Nacional Autonoma de Mexico, Centro de Fisica Aplicada y Tecnologia Avanzada (Mexico); Garcia-Ruiz, Amado F. [UPIICSA-COFAA, Instituto Politecnico Nacional (Mexico); Velazquez Salazar, J. J. [University of Texas at San Antonio, Department of Physics and Astronomy (United States); Perez, R. [Universidad Nacional Autonoma de Mexico, Centro de Fisica Aplicada y Tecnologia Avanzada (Mexico); Jose-Yacaman, M. [The University of Texas at San Antonio, Department of Physics and Astronomy (United States)

    2013-01-15

    Pt-Pd core-shell nanoparticles were synthesized using a modified polyol method. A thermal method under refluxing, carrying on the reaction up to 285 Degree-Sign C, has been performed to reduce metallic salts using ethylene glycol as reducer and poly(N-vinyl-2-pyrrolidone) as protective reagent of the formed bimetallic nanoparticles. According to other works, this type of structure has been studied and utilized to successfully increase the catalytic properties of monometallic nanoparticles Pt or Pd. Core-shell bimetallic nanoparticles were structurally characterized using aberration-corrected scanning transmission electron microscopy (Cs-STEM) equipped with a high-angle annular dark field detector, energy-dispersive X-ray spectrometry (EDS), and electron energy-loss spectroscopy (EELS). The high-resolution elemental line scan and mappings were carried out using a combination of STEM-EDS and STEM-EELS. The obtained results show the growth of the Pd shell on the Pt core with polyhedral morphology. The average size of the bimetallic nanoparticles was 13.5 nm and the average size of the core was 8.5 nm; consequently, the thickness of the shell was around 2.5 nm. The growth of the Pd shell on the Pt core is layer by layer, suggesting a Frank-van der Merwe growth mechanism.

  5. Synthesis of magnetically separable Sn doped magnetite/silica core-shell structure and photocatalytic property

    International Nuclear Information System (INIS)

    Wang, Wei-Wei; Yao, Jia-Liang

    2010-01-01

    Sn doped Fe 3 O 4 /SiO 2 core-shell structures with the magnetic and photocatalytic properties have been successfully synthesized using Fe 3 O 4 microspheres as the precursor. The morphology, phase and structure of the bifunctional products were investigated by X-ray powder diffraction, transmission electron microscopy, selected-area electron diffraction, high-resolution transmission electron microscopy, energy dispersive spectroscopy, and scanning electron microscopy. The effects of the amount and hydrolysis rate of tetraethyl orthosilicate on the preparation of the Fe 3 O 4 /SiO 2 core-shell structures were investigated. Low concentration and slow hydrolysis rate of tetraethyl orthosilicate were useful to obtain the uniform silica coated Fe 3 O 4 . The magnetic measurements indicated that the Sn doped Fe 3 O 4 /SiO 2 core-shell structures showed ferromagnetic property and the magnetic saturation value slightly decreased after coated the silica layer. The magnetic Sn doped Fe 3 O 4 /SiO 2 core-shell structures exhibited good photocatalytic activity in the degradation of methyl orange and could be separated by applying an appropriate magnetic field.

  6. In situ preparation of nickel/carbon core–shell structure by chemical vapor deposition

    Energy Technology Data Exchange (ETDEWEB)

    Cao, Fuyang [Key Laboratory of Advanced Technologies of Materials, Ministry of Education of China, Superconductivity and New Energy R and D Center, Southwest Jiaotong University, Chengdu 610031 (China); Jiang, Qi, E-mail: jiangqi66@163.com [Key Laboratory of Advanced Technologies of Materials, Ministry of Education of China, Superconductivity and New Energy R and D Center, Southwest Jiaotong University, Chengdu 610031 (China); Fang, Yuan; Ban, Shengguang; Ou, Shisheng; Qian, Hongxia [Key Laboratory of Advanced Technologies of Materials, Ministry of Education of China, Superconductivity and New Energy R and D Center, Southwest Jiaotong University, Chengdu 610031 (China); Zhao, Yong [School of Materials Science and Engineering, University of New South Wales, Sydney, 2052 NSW (Australia)

    2013-10-15

    Nickel/carbon core–shell structure with uniform diameter has been synthesized by galvanostatic electrodeposition nickel on its surface followed by chemical vapor deposition. We proposed the growth mechanism of the core–shell structure that the precipitation of carbon from metal catalysts during the high temperature growth period lifts up metal particles leading to the formation of core–shell structure or carbon nanotubes with respect to the diameter of catalyst particles. The substrate with deposited nickel was characterized by optical microscope. The elements and features of the substrate were studied by energy dispersive X-ray spectroscopy and X-ray diffraction respectively. The morphology of the resulting material was examined by field emitting scanning electron microscopy. In addition, the electrochemical performance of the core–shell structure modified electrodes was also investigated. The result shows that electrodes modified with core structure have better electrochemical property than the bare electrodes in the [Fe(CN){sub 6}]{sup 3−}/[Fe(CN){sub 6}]{sup 4−} solution at a scan rate of 20 mV s{sup −1}.

  7. Numerical analysis of stiffened shells of revolution. Volume 3: Users' manual for STARS-2B, 2V, shell theory automated for rotational structures, 2 (buckling, vibrations), digital computer programs

    Science.gov (United States)

    Svalbonas, V.

    1973-01-01

    The User's manual for the shell theory automated for rotational structures (STARS) 2B and 2V (buckling, vibrations) is presented. Several features of the program are: (1) arbitrary branching of the shell meridians, (2) arbitrary boundary conditions, (3) minimum input requirements to describe a complex, practical shell of revolution structure, and (4) accurate analysis capability using a minimum number of degrees of freedom.

  8. The shell structure effects in neutron cross section calculation by a ...

    African Journals Online (AJOL)

    The role of the shell structure properties of the nucleus in the calculation of neutron-induced reaction cross-section data based on nuclear reaction theory has been investigated. In this investigation, measured, evaluated and calculated (n.p) reaction cross-section data on la spherical nucleus (i.e. 112Sn) and a deformed ...

  9. Nuclear structure of s-d shell nuclei: what is new?

    International Nuclear Information System (INIS)

    Shanmugam, G.

    1995-01-01

    In this paper the shape evolution of the even-even s-d shell nuclei with temperature and spin is studied using Landau theory of phase transitions. The most important thermal fluctuations are incorporated in this study. The ground state pairing is also included in the calculations. Both the summation and Strutinsky methods are used for extracting the Landau constants. Both yield qualitatively similar results. To conclude, Landau theory of phase transitions can be effectively and economically used to study the structure of excited s-d shell nuclei. 10 refs., 2 tabs., 8 figs

  10. Exploring the changing of shell structure of nuclei at N=50

    International Nuclear Information System (INIS)

    Here it is reported an experimental study of the excited structures of the neutron-rich N=50 and 51 isotones. New experimental information has been obtained on a wide range of nuclei close to the N=50 shell closure by means of multi-nucleon transfer and deep-inelastic collisions. The reaction mechanism allows the population of medium and high-spin yrast states. The systematic of the N=51 single-neutron states, extended down to the Z=34, can be used to test the predictions of the shell evolution based on the effects of the tensor interactions as well as of the different effective interactions

  11. Ab initio and shell model studies of structural, thermoelastic and vibrational properties of SnO2 under pressure.

    Science.gov (United States)

    Casali, R A; Lasave, J; Caravaca, M A; Koval, S; Ponce, C A; Migoni, R L

    2013-04-03

    The pressure dependences of the structural, thermoelastic and vibrational properties of SnO2 in its rutile phase are studied, as well as the pressure-induced transition to a CaCl2-type phase. These studies have been performed by means of ab initio (AI) density functional theory calculations using the localized basis code SIESTA. The results are employed to develop a shell model (SM) for application in future studies of nanostructured SnO2. A good agreement of the SM results for the pressure dependences of the above properties with the ones obtained from present and previous AI calculations as well as from experiments is achieved. The transition is characterized by a rotation of the Sn-centered oxygen octahedra around the tetragonal axis through the Sn. This rotation breaks the tetragonal symmetry of the lattice and an orthorhombic distortion appears above the critical pressure P(c). A zone-center phonon of B1g symmetry in the rutile phase involves such rotation and softens on approaching Pc. It becomes an Ag mode which stabilizes with increasing pressure in the CaCl2 phase. This behavior, together with the softening of the shear modulus (C11-C12)/2 related to the orthorhombic distortion, allows a precise determination of a value for Pc. An additional determination is provided by the splitting of the basal plane lattice parameters. Both the AI and the experimentally observed softening of the B(1g) mode are incomplete, indicating a small discontinuity at the transition. However, all results show continuous changes in volume and lattice parameters, indicating a second-order transition. All these results indicate that there should be sufficient confidence for the future employment of the shell model.

  12. Ab initio and shell model studies of structural, thermoelastic and vibrational properties of SnO2 under pressure

    International Nuclear Information System (INIS)

    Casali, R A; Ponce, C A; Lasave, J; Koval, S; Migoni, R L; Caravaca, M A

    2013-01-01

    The pressure dependences of the structural, thermoelastic and vibrational properties of SnO 2 in its rutile phase are studied, as well as the pressure-induced transition to a CaCl 2 -type phase. These studies have been performed by means of ab initio (AI) density functional theory calculations using the localized basis code SIESTA. The results are employed to develop a shell model (SM) for application in future studies of nanostructured SnO 2 . A good agreement of the SM results for the pressure dependences of the above properties with the ones obtained from present and previous AI calculations as well as from experiments is achieved. The transition is characterized by a rotation of the Sn-centered oxygen octahedra around the tetragonal axis through the Sn. This rotation breaks the tetragonal symmetry of the lattice and an orthorhombic distortion appears above the critical pressure P c . A zone-center phonon of B 1g symmetry in the rutile phase involves such rotation and softens on approaching P c . It becomes an A g mode which stabilizes with increasing pressure in the CaCl 2 phase. This behavior, together with the softening of the shear modulus (C 11 −C 12 )/2 related to the orthorhombic distortion, allows a precise determination of a value for P c . An additional determination is provided by the splitting of the basal plane lattice parameters. Both the AI and the experimentally observed softening of the B 1g mode are incomplete, indicating a small discontinuity at the transition. However, all results show continuous changes in volume and lattice parameters, indicating a second-order transition. All these results indicate that there should be sufficient confidence for the future employment of the shell model. (paper)

  13. Buckling Design and Imperfection Sensitivity of Sandwich Composite Launch-Vehicle Shell Structures

    Science.gov (United States)

    Schultz, Marc R.; Sleight, David W.; Myers, David E.; Waters, W. Allen, Jr.; Chunchu, Prasad B.; Lovejoy, Andrew W.; Hilburger, Mark W.

    2016-01-01

    Composite materials are increasingly being considered and used for launch-vehicle structures. For shell structures, such as interstages, skirts, and shrouds, honeycomb-core sandwich composites are often selected for their structural efficiency. Therefore, it is becoming increasingly important to understand the structural response, including buckling, of sandwich composite shell structures. Additionally, small geometric imperfections can significantly influence the buckling response, including considerably reducing the buckling load, of shell structures. Thus, both the response of the theoretically perfect structure and the buckling imperfection sensitivity must be considered during the design of such structures. To address the latter, empirically derived design factors, called buckling knockdown factors (KDFs), were developed by NASA in the 1960s to account for this buckling imperfection sensitivity during design. However, most of the test-article designs used in the development of these recommendations are not relevant to modern launch-vehicle constructions and material systems, and in particular, no composite test articles were considered. Herein, a two-part study on composite sandwich shells to (1) examine the relationship between the buckling knockdown factor and the areal mass of optimized designs, and (2) to interrogate the imperfection sensitivity of those optimized designs is presented. Four structures from recent NASA launch-vehicle development activities are considered. First, designs optimized for both strength and stability were generated for each of these structures using design optimization software and a range of buckling knockdown factors; it was found that the designed areal masses varied by between 6.1% and 19.6% over knockdown factors ranging from 0.6 to 0.9. Next, the buckling imperfection sensitivity of the optimized designs is explored using nonlinear finite-element analysis and the as-measured shape of a large-scale composite cylindrical

  14. Optimal design of hollow core–shell structural active materials for lithium ion batteries

    Directory of Open Access Journals (Sweden)

    Wenjuan Jiang

    2015-01-01

    Full Text Available To mitigate mechanical and chemical degradation of active materials, hollow core–shell structures have been applied in lithium ion batteries. Without embedding of lithium ions, the rigid coating shell can constrain the inward volume deformation. In this paper, optimal conditions for the full use of inner hollow space are identified in terms of the critical ratio of shell thickness and inner size and the state of charge. It is shown that the critical ratios are 0.10 and 0.15 for Si particle and tube (0.12 and 0.18 for Sn particle and tube, and above which there is lack of space for further lithiation.

  15. 7 CFR 51.2731 - U.S. Spanish Splits.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 2 2010-01-01 2010-01-01 false U.S. Spanish Splits. 51.2731 Section 51.2731... STANDARDS) United States Standards for Grades of Shelled Spanish Type Peanuts Grades § 51.2731 U.S. Spanish Splits. “U.S. Spanish Splits” consists of shelled Spanish type peanut kernels which are split or broken...

  16. What explains the structure of Enceladus's ice shell and can it be in equilibrium?

    Science.gov (United States)

    Hemingway, D.; Mittal, T.

    2017-12-01

    Over the course of the Cassini mission, a series of geodetic measurements [1-3] have revealed that Enceladus's ongoing south polar eruptions are likely sourced from a global subsurface liquid water ocean [2-6]. The extent of the ocean and the structure of the overlying ice shell are of particular importance as they speak to the nature of the eruptions and the thermal state and evolution of Enceladus. How quickly is Enceladus cooling? Is the ocean a recent, perhaps transient phenomenon, or has it been present for billions of years? Based on shape, gravity, and libration observations, the floating ice shell is inferred to be thickest at the equator, where it is perhaps 35-45 km thick at the sub- and anti-Saturnian points, and thinnest at the poles, especially beneath the broad topographic depression associated with the South Polar Terrain (SPT), where the shell is likely less—perhaps much less—than 10 km thick [6,7]. Although tidal heating is assumed to be the mechanism primarily responsible for the observed shell structure, and whereas several theoretical studies have been carried out [e.g., 8], a clear match between theory and observations has yet to be demonstrated. Likewise, the question of whether or not the current configuration can be in equilibrium, remains open. Here we model the effects of tidal heating on Enceladus's ice shell, showing that the expected equilibrium ice shell structure is largely consistent with the structure inferred from shape, gravity, and libration observations. We consider the nature of the north-south polar asymmetry in shell structure and geologic activity, and we address the question of whether or not the current structure can be maintained in spite of ongoing relaxation. In light of our results, we discuss implications for the heat budget and thermal evolution of Enceladus. [1] P. Thomas et al., Icarus 190 (2), 573-584, Oct. 2007. [2] L. Iess et al., Science 344 (6179), 78-80, 2014. [3] P. C. Thomas et al., Icarus 264, 37

  17. Strain-induced structural defects and their effects on the electrochemical performances of silicon core/germanium shell nanowire heterostructures.

    Science.gov (United States)

    Lin, Yung-Chen; Kim, Dongheun; Li, Zhen; Nguyen, Binh-Minh; Li, Nan; Zhang, Shixiong; Yoo, Jinkyoung

    2017-01-19

    We report on strain-induced structural defect formation in core Si nanowires of a Si/Ge core/shell nanowire heterostructure and the influence of the structural defects on the electrochemical performances in lithium-ion battery anodes based on Si/Ge core/shell nanowire heterostructures. The induced structural defects consisting of stacking faults and dislocations in the core Si nanowire were observed for the first time. The generation of stacking faults in the Si/Ge core/shell nanowire heterostructure is observed to prefer settling in either only the Ge shell region or in both the Ge shell and Si core regions and is associated with the increase of the shell volume fraction. The relaxation of the misfit strain in the [112] oriented core/shell nanowire heterostructure leads to subsequent gliding of Shockley partial dislocations, preferentially forming the twins. The observation of crossover of defect formation is of great importance for understanding heteroepitaxy in radial heterostructures at the nanoscale and for building three dimensional heterostructures for the various applications. Furthermore, the effect of the defect formation on the nanomaterial's functionality is investigated using electrochemical performance tests. The Si/Ge core/shell nanowire heterostructures enhance the gravimetric capacity of lithium ion battery anodes under fast charging/discharging rates compared to Si nanowires. However, the induced structural defects hamper lithiation of the Si/Ge core/shell nanowire heterostructure.

  18. Shell Layer Thickness-Dependent Photocatalytic Activity of Sputtering Synthesized Hexagonally Structured ZnO-ZnS Composite Nanorods.

    Science.gov (United States)

    Liang, Yuan-Chang; Lo, Ya-Ru; Wang, Chein-Chung; Xu, Nian-Cih

    2018-01-07

    ZnO-ZnS core-shell nanorods are synthesized by combining the hydrothermal method and vacuum sputtering. The core-shell nanorods with variable ZnS shell thickness (7-46 nm) are synthesized by varying ZnS sputtering duration. Structural analyses demonstrated that the as-grown ZnS shell layers are well crystallized with preferring growth direction of ZnS (002). The sputtering-assisted synthesized ZnO-ZnS core-shell nanorods are in a wurtzite structure. Moreover, photoluminance spectral analysis indicated that the introduction of a ZnS shell layer improved the photoexcited electron and hole separation efficiency of the ZnO nanorods. A strong correlation between effective charge separation and the shell thickness aids the photocatalytic behavior of the nanorods and improves their photoresponsive nature. The results of comparative degradation efficiency toward methylene blue showed that the ZnO-ZnS nanorods with the shell thickness of approximately 17 nm have the highest photocatalytic performance than the ZnO-ZnS nanorods with other shell layer thicknesses. The highly reusable catalytic efficiency and superior photocatalytic performance of the ZnO-ZnS nanorods with 17 nm-thick ZnS shell layer supports their potential for environmental applications.

  19. Corrugated Shell Displacements During the Passage of a Vehicle Along a Soil-Steel Structure

    Directory of Open Access Journals (Sweden)

    Machelski Czesław

    2016-12-01

    Full Text Available Corrugated steel plates are highly rigid and as the constructions can be immersed in soil, they can be used as soil-steel structures. With an increase of cover depth, the effectiveness of operating loads decreases. A substantial reduction of the impacts of vehicles takes place as a road or rail surface with its substructure is crucial. The scope of load’s impact greatly exceeds the span L of a shell. This article presents the analysis of deformations of the upper part of a shell caused by a live load. One of the assumptions used in calculations performed in Plaxis software was the circle-shaped shell and the circumferential segment of the building structure in the 2D model. The influence lines of the components of vertical and horizontal displacements of points located at the highest place on the shell were used as a basis of analysis. These results are helpful in assessing the results of measurements carried out for the railway structure during the passage of two locomotives along the track. This type of load is characterized by a steady pressure onto wheels with a regular wheel base. The results of measurements confirmed the regularity of displacement changes during the passage of this load.

  20. Strong 1.54 μm cathodoluminescence from core-shell structures of silicon nanoparticles and erbium

    Science.gov (United States)

    Hoang, Tuan; Elhalawany, Noha; Enders, Brian; Bahceci, Ersin; Abuhassan, Laila; Nayfeh, Munir H.

    2016-12-01

    We report on the development of efficient infrared-active core-shell Er2O3-Si nanoparticle architecture. Sub 3-nm H-terminated Si nanoparticles are used to reduce/deposit Er3+ ions on the nanoparticles, which in an aqueous environment simultaneously oxidize to produce the core-shells. Our results show strong cathodoluminance at 1543 nm while being able to resolve the Stark splitting. The strong luminescence afforded by the core-shell architecture in which the Si-Er interspacing drops appreciably supports a sensitive interspacing-dependent dipole-dipole energy transfer interaction model, while the hydrogenated silicon-core allows increased loading and reduced segregation of Er as in amorphous silicon material. The room temperature-wet procedure, with pre-prepared and -sorted Si nanostructures affords promising applications in electronic and optical technologies.

  1. Form-finding of shell structures generated from physical models

    NARCIS (Netherlands)

    Li, Q.; Su, Y; Wu, Y; Borgart, A.; Rots, J.G.

    2017-01-01

    Vector form intrinsic finite element is a recently developed and promising numerical method for the analysis of complicated structural behavior. Taking the cable-link element as example, the framework of the vector form intrinsic finite element is explained first. Based on this, a constant strain

  2. Preparation and characteristics of core-shell structure cobalt/silica nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Fu Wuyou [National Laboratory of Superhard Materials, Jilin University, Changchun 130012 (China); Yang Haibin [National Laboratory of Superhard Materials, Jilin University, Changchun 130012 (China) and Henan Polytechnic University, Hennan Jiaozuo 454000 (China)]. E-mail: yanghb@jlu.edu.cn; Hari-Bala [College of Chemistry, Jilin University, Changchun 130023 (China); Liu Shikai [Henan Polytechnic University, Hennan Jiaozuo 454000 (China); Li, Minghui [National Laboratory of Superhard Materials, Jilin University, Changchun 130012 (China); Zou Guangtian [National Laboratory of Superhard Materials, Jilin University, Changchun 130012 (China)

    2006-12-10

    The silica nanolayer with different thickness was coated on the spherical cobalt nanoparticles (an average diameter of 67 nm) to form core-shell structure by the controlled hydrolysis and condensation of tetraethyl orthosilicate (TEOS). This coating process was based on the use of silane coupling agent 3-mercaptopropyltrimethoxysilane (HS-(CH{sub 2}){sub 3}Si(OCH{sub 3}){sub 3}, MPTS) as a primer to render the cobalt surface vitreophilic, thus rendering cobalt surface compatible with silica. The control over the silica coating layer thickness can be achieved by varying the reaction time. The cobalt nanoparticles and the cobalt coated with silica shell were confirmed by transmission electron microscopy (TEM). X-ray photoelectron spectroscopy (XPS) was used to gain insight into the way in which the MPTS is bound to the surface of the cobalt nanoparticles. Result of the thermogravimetric analysis (TGA) and differential thermal analysis (DTA) indicate that the thermal stability of cobalt/silica is better than that of pure cobalt nanoparticles. Magnetic properties of these powders have been evaluated. These cobalt/silica core-shell nanoparticles can be utilized as precursors for making property-tunable magnetic nanoparticles, thin films, and multilayered core-shell structure nanocomposites.

  3. Lowering of ground state induced by core-shell structure in strontium titanate

    Science.gov (United States)

    Kiat, J. M.; Hehlen, B.; Anoufa, M.; Bogicevic, C.; Curfs, C.; Boyer, B.; Al-Sabbagh, M.; Porcher, F.; Al-Zein, A.

    2016-04-01

    A new ground state of textbook compound strontium titanate (SrTi O3) is obtained by inducing a specific core-shell structure of the particles. Using a combination of high energy synchrotron and neutron diffraction, we demonstrate a lowering of the ferroelastic ground state towards a new antiferrodistortive phase, accompanied with strong shifts of the critical temperature. This new phase is discussed within the Landau theory and compared with the situation in thin films and during pressure experiments. The crucial competition between particle shape anisotropy, surface tension, and shear strain is analyzed. Inducing a specific core-shell structure is therefore an easy way to tailor structural properties and to stabilize new phases that cannot exist in bulk material, just like film deposition on a substrate.

  4. The scale dependence of single-nucleon shell structure

    Energy Technology Data Exchange (ETDEWEB)

    Somà, V., E-mail: vittorio.soma@cea.fr [Centre de Saclay, IRFU/Service de Physique Nucléaire, 91191 Gif-sur-Yvette (France); Duguet, T. [Centre de Saclay, IRFU/Service de Physique Nucléaire, 91191 Gif-sur-Yvette (France); KU Leuven, Instituut voor Kern-en Stralingsfysica, 3001 Leuven (Belgium); Department of Physics and Astronomy, Michigan State University, East Lansing, Michigan 48824-1321 (United States); NSCL, Michigan State University, East Lansing, Michigan 48824-1321 (United States); Hergert, H. [NSCL, Michigan State University, East Lansing, Michigan 48824-1321 (United States); The Ohio State University, Columbus, Ohio 43210 (United States); Holt, J. D. [TRIUMF, 4004 Wesbrook Mall, Vancouver, BC, V6T 2A3 (Canada)

    2015-10-15

    We address the scale dependence of (effective) single-particle energies, non-observable quantities that are commonly used for interpreting nuclear structure observables measured in experiments and computed in many-body theories. We first demonstrate their scale dependence on a formal level, making them intrinsically theoretical objects, before illustrating this point via ab initio calculations in the oxygen isotopes. Finally, we consider a modified definition of effective single-particle energy and investigate its running properties.

  5. Interfacial Structural Transition in Hydration Shells of a Polarizable Solute.

    Science.gov (United States)

    Dinpajooh, Mohammadhasan; Matyushov, Dmitry V

    2015-05-22

    Electrostatics of polar solvation is typically described by harmonic free energy functionals. Polarizability contributes a negative polarization term that can make the harmonic free energy negative. The harmonic truncation fails in this regime. Simulations of polarizable ideal dipoles in water show that water's susceptibility passes through a maximum in the range of polarizabilities zeroing the harmonic term out. The microscopic origin of the nonmonotonic behavior is an interfacial structural transition involving the density collapse of the first hydration layer and enhanced number of dangling OH bonds.

  6. Cu–Ni core–shell nanoparticles: structure, stability, electronic, and magnetic properties: a spin-polarized density functional study

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Qiang, E-mail: wangqiang@njtech.edu.cn; Wang, Xinyan; Liu, Jianlan; Yang, Yanhui [Nanjing Tech University, School of Chemistry and Molecular Engineering, Institute of Advanced Synthesis (IAS) (China)

    2017-02-15

    Bimetallic core–shell nanoparticles (CSNPs) have attracted great interest not only because of their superior stability, selectivity, and catalytic activity but also due to their tunable properties achieved by changing the morphology, sequence, and sizes of both core and shell. In this study, the structure, stability, charge transfer, electronic, and magnetic properties of 13-atom and 55-atom Cu and Cu–Ni CSNPs were investigated using the density functional theory (DFT) calculations. The results show that Ni@Cu CSNPs with a Cu surface shell are more energetically favorable than Cu@Ni CSNPs with a Ni surface shell. Interestingly, three-shell Ni@Cu{sub 12}@Ni{sub 42} is more stable than two-shell Cu{sub 13}@Ni{sub 42}, while two-shell Ni{sub 13}@Cu{sub 42} is more stable than three-shell Cu@Ni{sub 12}@Cu{sub 42}. Analysis of Bader charge illustrates that the charge transfer increases from Cu core to Ni shell in Cu@Ni NPs, while it decreases from Ni core to Cu shell in Ni@Cu NPs. Furthermore, the charge transfer results that d-band states have larger shift toward the Fermi level for the Ni@Cu CSNPs with Cu surface shell, while the Cu@Ni CSNPs with Ni surface shell have similar d-band state curves and d-band centers with the monometallic Ni NPs. In addition, the Cu–Ni CSNPs possess higher magnetic moment when the Ni atoms aggregated at core region of CSNPs, while having lower magnetic moment when the Ni atoms segregate on surface region. The change of the Cu atom location in CSNPs has a weak effect on the total magnetic moment. Our findings provide useful insights for the design of bimetallic core–shell catalysts.

  7. Ionic core–shell dendrimers with a polycationic core: structural aspects and host–guest binding properties

    NARCIS (Netherlands)

    van de Coevering, R.; Bruijnincx, P.C.A.; Lutz, M.; Spek, A.L.; van Koten, G.; Klein Gebbink, R.J.M.

    2007-01-01

    The structural aspects and host–guest binding properties of ionic core–shell dendrimers [1]Br8 and [2]Br4, which bear a polycationic core and a neutral shell of Fréchet-type poly(benzyl aryl ether) dendrons, have been investigated by means of dendritic wedges [3]Br2 and [4]Br, that resemble one of

  8. Quadratic solid-shell elements for nonlinear structural analysis and sheet metal forming simulation

    Science.gov (United States)

    Wang, Peng; Chalal, Hocine; Abed-Meraim, Farid

    2017-01-01

    In this paper, two quadratic solid-shell (SHB) elements are proposed for the three-dimensional modeling of thin structures. These consist of a 20-node hexahedral solid-shell element, denoted SHB20, and its 15-node prismatic counterpart, denoted SHB15. The formulation of these elements is extended in this work to include geometric and material nonlinearities, for application to problems involving large displacements and rotations as well as plasticity. For this purpose, the SHB elements are coupled with large-strain anisotropic elasto-plastic constitutive equations for metallic materials. Although based on a purely three-dimensional approach, several modifications are introduced in the formulation of these elements to provide them with interesting shell features. In particular, a special direction is chosen to represent the thickness, along which a user-defined number of integration points are located. Furthermore, for efficiency requirements and for alleviating locking phenomena, an in-plane reduced-integration scheme is adopted. The resulting formulations are implemented into the finite element software ABAQUS/Standard and, to assess their performance, a variety of nonlinear benchmark problems are investigated. Attention is then focused on the simulation of various complex sheet metal forming processes, involving large strain, anisotropic plasticity, and double-sided contact. From all simulation results, it appears that the SHB elements represent an interesting alternative to traditional shell and solid elements, due to their versatility and capability of accurately modeling selective nonlinear benchmark problems as well as complex sheet metal forming processes.

  9. Modified Anderson orthogonality catastrophe power law in the presence of shell structure

    Science.gov (United States)

    Bandopadhyay, Swarnali; Hentschel, Martina

    2011-01-01

    We study Anderson orthogonality catastrophe (AOC) for parabolic quantum dots and focus on the effects of degeneracies, realized through the inherent shell structure of their energy levels that can be lifted through an external magnetic field, on the Anderson overlap. We find rich and interesting behaviors as a function of the strength and position of the perturbation, the system size, and the applied magnetic field. In particular, even for weak perturbations, we observe a pronounced AOC that is related to the degeneracy of energy levels. Most importantly, the power-law decay of the Anderson overlap as a function of the number of particles is modified in comparison to the metallic case due to the rearrangement of the energy-level shell structure. We support our analytical results by numerical calculations and also study the distribution of Anderson overlaps.

  10. Nonobservable nature of the nuclear shell structure: Meaning, illustrations, and consequences

    Science.gov (United States)

    Duguet, T.; Hergert, H.; Holt, J. D.; Somà, V.

    2015-09-01

    Background: The concept of single-nucleon shells constitutes a basic pillar of our understanding of nuclear structure. Effective single-particle energies (ESPEs) introduced by French [Proceedings of the International School of Physics "Enrico Fermi," Course XXXVI, Varenna 1965, edited by C. Bloch (Academic Press, New York, 1966)] and Baranger [Nucl. Phys. A 149, 225 (1970), 10.1016/0375-9474(70)90692-5] represent the most appropriate tool to relate many-body observables to a single-nucleon shell structure. As briefly discussed in Duguet and Hagen [Phys. Rev. C 85, 034330 (2012), 10.1103/PhysRevC.85.034330], the dependence of ESPEs on one-nucleon transfer probability matrices makes them purely theoretical quantities that "run" with the nonobservable resolution scale λ employed in the calculation. Purpose: Given that ESPEs provide a way to interpret the many-body problem in terms of simpler theoretical ingredients, the goal is to specify the terms, i.e., the exact sense and conditions, in which this interpretation can be conducted meaningfully. Methods: While the nuclear shell structure is both scale and scheme dependent, the present study focuses on the former. A detailed discussion is provided to illustrate the scale (in)dependence of observables and nonobservables and the reasons why ESPEs, i.e., the shell structure, belong to the latter category. State-of-the-art multireference in-medium similarity renormalization group and self-consistent Gorkov Green's function many-body calculations are employed to corroborate the formal analysis. This is done by comparing the behavior of several observables and of nonobservable ESPEs (and spectroscopic factors) under (quasi) unitary similarity renormalization group transformations of the Hamiltonian parametrized by the resolution scale λ . Results: The formal proofs are confirmed by the results of ab initio many-body calculations in their current stage of implementation. In practice, the unitarity of the similarity

  11. On the absence of an α-nucleus structure in a two-centre shell model

    International Nuclear Information System (INIS)

    Gupta, R.K.; Sharma, M.K.; Antonenko, N.V.; Scheid, W.

    1999-01-01

    The two-centre shell model, used within the Strutinsky macro-microscopic method, is a valid prescription for calculating adiabatic or diabatic potential energy surfaces. It is shown, however, that this model does not contain the appropriate α-nucleus structure effects, very much required for collisions between light nuclei. A possible way to incorporate such effects is suggested. (author). Letter-to-the-editor

  12. Effects of Pt shell thicknesses on the atomic structure of Ru-Pt core-shell nanoparticles for methanol electrooxidation applications.

    Science.gov (United States)

    Chen, Tsan-Yao; Lin, Tsang-Lang; Luo, Tzy-Jiun Mark; Choi, Yongjae; Lee, Jyh-Fu

    2010-08-02

    In this research, core-shell electrocatalysts comprising a Ru core covered with precisely controlled 1.5-3.6 atomic layers (ALs)-thick Pt atoms are synthesized. The sample with 1.5 ALs shows a 3.2-fold improvement in CO-tolerance and 2.4-fold current enhancement at the conventional battery operation potential (I(300), at 300 mV vs Ag/AgCl) during methanol oxidation as compared with conventional all-Pt nanoparticles. The origin of the enhanced performance and the atomic structure of the core-shell nanoparticles are elucidated to be mainly dominated by the lattice strain (possibly some slight effect of heteroatomic interactions) then by the combination of ligand effects and bifunctional mechanisms when the shell crystal is thicker than 2.7 ALs.

  13. Design of cryogenic tanks for space vehicles shell structures analytical modeling

    Science.gov (United States)

    Copper, Charles; Mccarthy, K.; Pilkey, W. D.; Haviland, J. K.

    1991-01-01

    The initial objective was to study the use of superplastically formed corrugated hat section stringers and frames in place of integrally machined stringers over separate frames for the tanks of large launch vehicles subjected to high buckling loads. The ALS was used as an example. The objective of the follow-on project was to study methods of designing shell structures subjected to severe combinations of structural loads and thermal gradients, with emphasis on new combinations of structural arrangements and materials. Typical applications would be to fuselage sections of high speed civil transports and to cryogenic tanks on the National Aerospace Plane.

  14. Preparation of TiC/W core–shell structured powders by one-step activation and chemical reduction process

    International Nuclear Information System (INIS)

    Ding, Xiao-Yu; Luo, Lai-Ma; Huang, Li-Mei; Luo, Guang-Nan; Zhu, Xiao-Yong; Cheng, Ji-Gui; Wu, Yu-Cheng

    2015-01-01

    Highlights: • A novel wet chemical method was used to prepare TiC/W core–shell structure powders. • TiC nanoparticles were well-encapsulated by W shells. • TiC phase was present in the interior of tungsten grains. - Abstract: In the present study, one-step activation and chemical reduction process as a novel wet-chemical route was performed for the preparation of TiC/W core–shell structured ultra-fine powders. The XRD, FE-SEM, TEM and EDS results demonstrated that the as-synthesized powders are of high purity and uniform with a diameter of approximately 500 nm. It is also found that the TiC nanoparticles were well-encapsulated by W shells. Such a unique process suggests a new method for preparing X/W (X refers the water-insoluble nanoparticles) core–shell nanoparticles with different cores

  15. A Structural Design Concept for a Multi-Shell Blended Wing Body with Laminar Flow Control

    Directory of Open Access Journals (Sweden)

    Majeed Bishara

    2018-02-01

    Full Text Available Static and fatigue analyses are presented for a new blended wing body (BWB fuselage concept considering laminar flow control (LFC by boundary layer suction in order to reduce the aerodynamic drag. BWB aircraft design concepts profit from a structurally beneficial distribution of lift and weight and allow a better utilization of interior space over conventional layouts. A structurally efficient design concept for the pressurized BWB cabin is a vaulted layout that is, however, aerodynamically disadvantageous. A suitable remedy is a multi-shell design concept with a separate outer skin. The synergetic combination of such a multi-shell BWB fuselage with a LFC via perforation of the outer skin to attain a drag reduction appears promising. In this work, two relevant structural design aspects are considered. First, a numerical model for a ribbed double-shell design of a fuselage segment is analyzed. Second, fatigue aspects of the perforation in the outer skin are investigated. A design making use of controlled fiber orientation is proposed for the perforated skin. The fatigue behavior is compared to perforation methods with conventional fiber topologies and to configurations without perforations.

  16. Rapid Synthesis and Formation Mechanism of Core-Shell-Structured La-Doped SrTiO3 with a Nb-Doped Shell

    Directory of Open Access Journals (Sweden)

    Nam-Hee Park

    2015-07-01

    Full Text Available To provide a convenient and practical synthesis process for metal ion doping on the surface of nanoparticles in an assembled nanostructure, core-shell-structured La-doped SrTiO3 nanocubes with a Nb-doped surface layer were synthesized via a rapid synthesis combining a rapid sol-precipitation and hydrothermal process. The La-doped SrTiO3 nanocubes were formed at room temperature by a rapid dissolution of NaOH pellets during the rapid sol-precipitation process, and the Nb-doped surface (shell along with Nb-rich edges formed on the core nanocubes via the hydrothermal process. The formation mechanism of the core-shell-structured nanocubes and their shape evolution as a function of the Nb doping level were investigated. The synthesized core-shell-structured nanocubes could be arranged face-to-face on a SiO2/Si substrate by a slow evaporation process, and this nanostructured 10 μm thick thin film showed a smooth surface.

  17. Rapid Synthesis and Formation Mechanism of Core-Shell-Structured La-Doped SrTiO₃ with a Nb-Doped Shell.

    Science.gov (United States)

    Park, Nam-Hee; Akamatsu, Takafumi; Itoh, Toshio; Izu, Noriya; Shin, Woosuck

    2015-07-02

    To provide a convenient and practical synthesis process for metal ion doping on the surface of nanoparticles in an assembled nanostructure, core-shell-structured La-doped SrTiO₃ nanocubes with a Nb-doped surface layer were synthesized via a rapid synthesis combining a rapid sol-precipitation and hydrothermal process. The La-doped SrTiO₃ nanocubes were formed at room temperature by a rapid dissolution of NaOH pellets during the rapid sol-precipitation process, and the Nb-doped surface (shell) along with Nb-rich edges formed on the core nanocubes via the hydrothermal process. The formation mechanism of the core-shell-structured nanocubes and their shape evolution as a function of the Nb doping level were investigated. The synthesized core-shell-structured nanocubes could be arranged face-to-face on a SiO₂/Si substrate by a slow evaporation process, and this nanostructured 10 μm thick thin film showed a smooth surface.

  18. Damage detection strategies for aircraft shell-like structures based on propagation guided elastic waves

    International Nuclear Information System (INIS)

    Zak, A; Ostachowicz, W; Krawczuk, M

    2011-01-01

    Damage of aircraft structural elements in any form always present high risks. Failures of these elements can be caused by various reasons including material fatigue or impact leading to damage initiation and growth. Detection of these failures at their earliest stage of development, estimation of their size and location, are one of the most crucial factors for each damage detection method. Structural health monitoring strategies based on propagation of guided elastic waves in structures and wave interaction with damage related discontinuities are very promising tools that offer not only damage detection capabilities, but are also meant to provide precise information about the state of the structures and their remaining lifetime. Because of that various techniques are employed to simulate and mimic the wave-discontinuity interactions. The use of various types of sensors, their networks together with sophisticated contactless measuring techniques are investigated both numerically and experimentally. Certain results of numerical simulations obtained by the use of the spectral finite element method are presented by the authors and related with propagation of guided elastic waves in shell-type aircraft structures. Two types of structures are considered: flat 2D panels with or without stiffeners and 3D shell structures. The applicability of two different damage detection approaches is evaluated in order to detect and localise damage in these structures. Selected results related with the use of laser scanning vibrometry are also presented and discussed by the authors.

  19. Optical and structural investigation of ZnO@ZnS core–shell nanostructures

    Energy Technology Data Exchange (ETDEWEB)

    Flores, Efracio Mamani; Raubach, Cristiane W.; Gouvea, Rogério [CCAF, Instituto de Física e Matemática (IFM), Departamento de Física, Universidade Federal de Pelotas, Campus Capão do Leão PO Box 354, CEP: 96010970, Pelotas, RS (Brazil); Longo, Elson [INCTMN-UNESP, Universidade Estadual Paulista, P.O. Box 355, Araraquara 14801-907, SP (Brazil); Cava, Sergio [CCAF, Centro de Desenvolvimento Tecnológico, Universidade Federal de Pelotas, Rua Félix da Cunha 809, Pelotas, RS (Brazil); Moreira, Mário L., E-mail: mlucio3001@gmail.com [CCAF, Instituto de Física e Matemática (IFM), Departamento de Física, Universidade Federal de Pelotas, Campus Capão do Leão PO Box 354, CEP: 96010970, Pelotas, RS (Brazil)

    2016-04-15

    In the present work, are reported the experimental study of ZnO@ZnS core–shell synthesised by a microwave-assisted solvothermal (MAS) method. Some synthesis parameters such as, time, precursor concentration and temperature were fixed. In order to investigate the effect of growing shell on the structural and optical properties, the samples were grown with two different solvent (water or ethylene glycol). The characterizations were performed by X-ray diffraction, absorption spectroscopy in the UV–vis range, scanning electron microscopy, and photoluminescence spectroscopy. The results show that both ZnO and ZnS diffractions are present for all samples, however the crystallinity degree of ZnS shell are too low. The better decorations of ZnS (shell) on the ZnO (core) are obtained for ethylene glycol (EG) solvent, which is verified through FE-SEM images of ZnO@ZnS (EG). On the other hand, non morphological solvent dependence was observed for ZnO multi-wires. Also the luminescent emission for decorated system in water were more intense and leads to form a type-II band alignment for ZnO@ZnS core–shell system. - Highlights: • Obtation of ZnO@ZnS decorated systens using different solvents by MAS methodology. • Growth solvent dependence of hexagonal and cubic phases for ZnS. • Potential application of ZnO@ZnS decorated nanostructures as replacement material for solar cells. • Control over band alignment between ZnO and ZnS.

  20. A novel member of the split betaalphabeta fold: Solution structure of the hypothetical protein YML108W from Saccharomyces cerevisiae.

    Science.gov (United States)

    Pineda-Lucena, Antonio; Liao, Jack C C; Cort, John R; Yee, Adelinda; Kennedy, Michael A; Edwards, Aled M; Arrowsmith, Cheryl H

    2003-05-01

    As part of the Northeast Structural Genomics Consortium pilot project focused on small eukaryotic proteins and protein domains, we have determined the NMR structure of the protein encoded by ORF YML108W from Saccharomyces cerevisiae. YML108W belongs to one of the numerous structural proteomics targets whose biological function is unknown. Moreover, this protein does not have sequence similarity to any other protein. The NMR structure of YML108W consists of a four-stranded beta-sheet with strand order 2143 and two alpha-helices, with an overall topology of betabetaalphabetabetaalpha. Strand beta1 runs parallel to beta4, and beta2:beta1 and beta4:beta3 pairs are arranged in an antiparallel fashion. Although this fold belongs to the split betaalphabeta family, it appears to be unique among this family; it is a novel arrangement of secondary structure, thereby expanding the universe of protein folds.

  1. A novel member of the split betaalphabeta fold: Solution structure of the hypothetical protein YML108W from Saccharomyces cerevisiae

    International Nuclear Information System (INIS)

    Pineda-Lucena, Antonio; Liao, Jack; Cort, John R.; Yee, Adelinda; Kennedy, Michael A.; Edwards, Aled M.

    2003-05-01

    As part of the Northeast Structural Genomics Consortium pilot project focused on small eukaryotic proteins and protein domains, we have determined the NMR structure of the protein encoded by open reading frame YML108W from Saccharomyces cerevisiae. YML108W belongs to one of the numerous structural proteomics targets whose biological function is unknown. Moreover, this protein does not have sequence similarity to any other protein. The NMR structure of YML108W consists of a four-stranded b-sheet with strand order 2143 and two a-helices, with an overall topology of bbabba. Strand b1 runs parallel to b4, and b2:b1 and b4:b3 pairs are arranged in an antiparallel fashion. While this fold belongs to the split bab family, it appears to be unique among this family; it is a novel arrangement of secondary structure, thereby expanding the universe of protein folds

  2. Yolk-shell structured composite for fast and selective lithium ion sieving.

    Science.gov (United States)

    Li, Na; Lu, Deli; Zhang, Jinlong; Wang, Lingzhi

    2018-06-15

    Yolk-shell structured C@Li 4 Ti 5 O 12 microspheres composed of carbon core (ca. 500 nm) and sea urchin-like Li 4 Ti 5 O 12 shell (ca. 400-500 nm) are formed by hydrothermally treating the core-shell structured C@TiO 2 in the EtOH/H 2 O solution of LiOH and calcining it in N 2 atmosphere. Yolk-shell structured TiO 2 -type lithium ion sieve is further transformed from C@Li 4 Ti 5 O 12 through the acid treatment, which have a high specific surface area of 201.74 m 2 /g. The composite shows adsorption capacity towards Li + proportional to the pH value in the range of 7-13. The adsorption reaches equilibrium within 2 h with a high equilibrium adsorption capacity of 28.46 mg/g under alkaline conditions, which is ca. 8 times the value of ordinary TiO 2 lithium ion sieve with comparable size and surface area, demonstrating the enhanced adsorption is attributed to the generation of more accessible surficial voids by replacing internal part with light carbon core. The adsorption follows Freundlich and pseudo-second-order kinetic models with a high rate constant of 0.015 g/(mg·min). The selective adsorption to Li + is verified in the presence of K + , Na + , Ca 2+ and Mg 2+ . Copyright © 2018 Elsevier Inc. All rights reserved.

  3. Controllable dielectric and electrical performance of polymer composites with novel core/shell-structured conductive particles through biomimetic method

    International Nuclear Information System (INIS)

    Yang, Dan; Tian, Ming; Wang, Wencai; Li, Dongdong; Li, Runyuan; Liu, Haoliang; Zhang, Liqun

    2013-01-01

    Highlights: ► Conductive core/shell-structured particles were synthesized by biomimetic method. ► These particles with silica/poly(dopamine)/silver core and poly(dopamine) shell. ► Dielectric composites were prepared with resulted particles and silicone elastomer. ► The dielectric properties of the composites can be controlled by shell thickness. ► This biomimetic method is simple, nontoxic, efficient and easy to control. - Abstract: Novel silica/poly(dopamine)/silver (from inner to outer) (denoted as SiO 2 /PDA/Ag) conductive micro-particles were first synthesized by biomimetic poly(dopamine) coating. These micro-particles were then coated with a poly(dopamine) layer to form core/shell-structured particles, with silica/poly(dopamine)/silver core and poly(dopamine) shell (denoted as SiO 2 /PDA/Ag/PDA). This multilayer core/shell micro-particles were confirmed by scanning electron microscopy, X-ray photoelectron spectroscopy, X-ray diffraction, and transmission electron microscope. Polymer composites were then prepared by mechanical blending of poly(dimethyl siloxane) and the core/shell-structured particles. It was found that the silver layer and the poly(dopamine) shell had good adhesion with substrate and they kept intact even under violent shearing stress during mechanical mixing. The effect of the thickness of outermost poly(dopamine) shell as well as the loading amount of this filler on the dielectric and electrical properties of the composites was further studied. The results showed that the dielectric constant, dielectric loss, and conductivity of the composites decreased with increasing shell thickness (10–53 nm) at the same loading level. And the maximal dielectric constant of composites was achieved in the composites filled with SiO 2 /PDA/Ag/PDA (with 10–15 nm PDA shell) particles, which was much larger than that of the composite filled with SiO 2 /PDA/Ag particles without insulative PDA shell. At the same time, the composites can change

  4. The impact of core-shell nanotube structures on fracture in ceramic nanocomposites

    International Nuclear Information System (INIS)

    Liang, Xin; Yang, Yingchao; Lou, Jun; Sheldon, Brian W.

    2017-01-01

    Multi-wall carbon nanotubes (MWCNTs) can be used to create ceramic nanocomposites with improved fracture toughness. In the present work, atomic layer deposition (ALD) was employed to deposit thin oxide layers on MWCNTs. These core-shell structures were then used to create nanocomposites by using a polymer derived ceramic (PDC) to produce the matrix. Variations in both the initial MWCNT structure and the oxide layers led to substantial differences in fiber-pullout behavior. Single tube pullout tests also showed that the oxide coatings led to stronger bonding with the ceramic matrix. With high defect density MWCNTs, this led to shorter pull-out lengths which is consistent with the conventional understanding of fracture in ceramic matrix composites. However, with low defect density MWCNTs longer pullout lengths were observed with the oxide layers. To interpret the different trends that were observed, we believe that the ALD coatings should not be viewed simply as a means of altering the interfacial properties. Instead, the coated MWCNTs should be viewed as more complex core-shell fibers where both interface and internal properties can be controlled with the ALD layers. - Graphical abstract: Fracture properties of core-shell nanotubes reinforced ceramic nanocomposites.

  5. Synthesis of Core-shell Structured Amorphous Si Nanoparticles by Induction Thermal Plasmas

    Science.gov (United States)

    Okamoto, Daisuke; Kageyama, Takuya; Tanaka, Manabu; Sone, Hirotaka; Watanabe, Takayuki

    2015-09-01

    Core-shell structured amorphous Si nanoparticles were synthesized by induction thermal plasma. Crystalline Si powder with 3 μm of average diameter was injected into the induction thermal plasma at 4 MHz. The Si raw materials immediately evaporate in the high temperature plasma region and nanoparticles were produced through the quenching process. Counterflow quenching gas was injected from downstream of the torch with its direction against the plasma flow. The effect of the operating parameter such as flow rate of quenching gas and input power was investigated. Collected particles were characterized by X-ray diffraction, transmission electron microscopy, electron energy-loss spectroscopy, and Raman spectroscopy. Obtained results indicate that amorphization degree of the synthesized nanoparticles is more than 90% when additional quenching gas of 20 L/min is injected. The quenching rate of the prepared nanoparticles in the growth region have an important role on determining the amorphization degree. Moreover, EELS and Raman analyses showed the synthesized nanoparticles were coated by the SiO2 shell with thickness of 2-4 nm. These findings indicated that amorphous Si/SiO2 core-shell structured nanoparticles were successfully synthesized by induction thermal plasma in single step.

  6. A phase transfer identification of core-shell structures in Au-Ru nanoparticles

    International Nuclear Information System (INIS)

    Yang, J.; Lee, Jim Yang; Too, Heng-Phon

    2005-01-01

    The difference between the transfer of citrate-stabilized Au and Ru nanoparticles from the aqueous phase to toluene was used to develop a simple experimental procedure that can positively identify the formation of bimetallic Au-Ru nanoparticles with the core-shell structure formed in the seed-mediated growth process. The procedure was independently verified by UV-vis spectroscopy, transmission electron microscopy (TEM), energy dispersive X-ray analysis (EDX) and X-ray photoelectron spectroscopy (XPS). The experimental results clearly showed that core-shell nanoparticles of Au-Ru were formed by the seed mediated growth method using Au nanoparticle seeds. The reverse order of using Ru nanoparticles as the seeds, on the contrary, could only produce a physical mixture of isolated nanoparticles of Ru and Au under the same experimental conditions

  7. Charge radii of magnesium isotopes by laser spectroscopy a structural study over the $sd$ shell

    CERN Multimedia

    Schug, M; Krieger, A R

    We propose to study the evolution of nuclear sizes and shapes over the magnesium chain by measuring the root-mean-square charge radii of $^{21 - 32}$Mg, essentially covering the entire $\\textit{sd}$ shell. Our goal is to detect the structural changes, which in the neutron-deficient isotopes may originate from clustering, in a way similar to neon, and on the neutron-rich side would characterize the transition to the "island of inversion". We will combine, for the first time, the sensitive $\\beta$-detection technique with traditional fluorescence spectroscopy for isotope-shift measurements and in such a way gain access to the exotic species near the ${N}$ = 8 and ${N}$ = 20 shell closures.

  8. Dynamic Stability of Structures: Application to Frames, Cylindrical Shells and Other Systems.

    Science.gov (United States)

    1982-02-01

    13. 1.11 2.2 I .2 BiI~~11.62-i IIg MICROCOPY RESOLUTION TESI CHART NATI, NAt HI t, ’,IA I A W th . - A AFWAL-TR-81-3155 DYNAMIC STABILITY OF STRUCTURES...are demonstrated through several structural configurations, such as eccentri- cally loaded simple two- bar frames, geometrically imperfect, thin...IWO- BAR FRAMES UNDER SUDDENLY APPLIED LOADS. 7 III. STIFFENED AND UNSTIFFENED, IMPERFECT CYLINDRICAL SHELLS 27 UNDER SUDDENLY APPLIED LOADS. The

  9. Ply-based Optimization of Laminated Composite Shell Structures under Manufacturing Constraints

    DEFF Research Database (Denmark)

    Sørensen, Rene; Lund, Erik

    2012-01-01

    This work concerns a new ply-based parameterization for performing simultaneous material selection and topology optimization of fiber reinforced laminated composite structures while ensuring that a series of different manufacturing constraints are fulfilled. The material selection can either...... be performed on the basis of different materials, and/or consist of discrete selection of the same orthotropic material with different orientations of the fibers. The problem considered is the optimization of a general laminated composite shell structure with respect to maximum stiffness (minimum compliance...

  10. Shear wave splitting as a diagnostic of variable anisotropic structure of the upper mantle beneath central Fennoscandia

    Czech Academy of Sciences Publication Activity Database

    Vecsey, Luděk; Plomerová, Jaroslava; Kozlovskaya, E.; Babuška, Vladislav

    2007-01-01

    Roč. 438, č. 1-4 (2007), s. 57-77 ISSN 0040-1951 R&D Projects: GA AV ČR IAA3012405; GA AV ČR(CZ) KJB300120605 Grant - others:Academy of Finland(FI) 208068; Academy of Finland(FI) 107991 Institutional research plan: CEZ:AV0Z30120515 Source of funding: V - iné verejné zdroje ; V - iné verejné zdroje Keywords : shear wave splitting * joint inversion of body wave anisotropic parameters * 3D anisotropic model of mantle lithosphere Subject RIV: DC - Siesmology, Volcanology, Earth Structure Impact factor: 1.729, year: 2007

  11. Effects of variation of hyperfine splitting(structure) in atomic physics

    International Nuclear Information System (INIS)

    Alavi, S A

    2009-01-01

    The possible variation of the fundamental constants is currently a very popular research topic. Theories unifying gravity and other interactions suggest the possibility of spatial and temporal variation of physics constants in the universe. Current interest is high because in superstring theories which have additional dimensions compactified on tiny scales any variation of the size of the extra dimensions results in changes in the 3-dimensional coupling constants. String theory also suggest the space to be noncommutative i.e., the space coordinates do not commute with each other. In this paper we study the hyperfine splitting in the framework of the noncommutative quantum mechanics(NCQM) developed in the literature. We show that the energy difference between two excited F = I + 1/2 and the ground F I - 1/2 states in a noncommutative space(NCS) is bigger than the one in commutative case, so the radiation wavelength in NCS s must be shorter than the radiation wavelength in commutative spaces. We also find an upper bound for the non-commutativity parameter. Since in the very tiny string scale or at very high energy situation the effects of non-commutativity of space may appear so the hyperfine splitting is not constant and changes as energy changes(high energy situation). The results would be of interest both for theoretical and optical spectroscopists.

  12. Structural Insight into the Photochemistry of Split Green Fluorescent Proteins: A Unique Role for a His-Tag.

    Science.gov (United States)

    Deng, Alan; Boxer, Steven G

    2018-01-10

    Oligohistidine affinity tags (His-tags) are commonly fused to proteins to aid in their purification via metal affinity chromatography. These His-tags are generally assumed to have minimal impact on the properties of the fusion protein, as they have no propensity to form ordered elements, and are small enough not to significantly affect the solubility or size. Here we report structures of two variants of truncated green fluorescent protein (GFP), i.e., split GFP with a β-strand removed, that were found to behave differently in the presence of light. In these structures, the N-terminal His-tag and several neighboring residues play a highly unusual structural and functional role in stabilizing the truncated GFP by substituting as a surrogate β-strand in the groove vacated by the native strand. This finding provides an explanation for the seemingly very different peptide binding and photodissociation properties of split proteins involving β-strands 10 and 11. We show that these truncated GFPs can bind other non-native sequences, and this promiscuity invites the possibility for rational design of sequences optimized for strand binding and photodissociation, both useful for optogenetic applications.

  13. Coded Splitting Tree Protocols

    DEFF Research Database (Denmark)

    Sørensen, Jesper Hemming; Stefanovic, Cedomir; Popovski, Petar

    2013-01-01

    This paper presents a novel approach to multiple access control called coded splitting tree protocol. The approach builds on the known tree splitting protocols, code structure and successive interference cancellation (SIC). Several instances of the tree splitting protocol are initiated, each...... instance is terminated prematurely and subsequently iterated. The combined set of leaves from all the tree instances can then be viewed as a graph code, which is decodable using belief propagation. The main design problem is determining the order of splitting, which enables successful decoding as early...... as possible. Evaluations show that the proposed protocol provides considerable gains over the standard tree splitting protocol applying SIC. The improvement comes at the expense of an increased feedback and receiver complexity....

  14. Shell-structure and pairing interaction in superheavy nuclei: rotational properties of the z=104 nucleus (256)rf.

    Science.gov (United States)

    Greenlees, P T; Rubert, J; Piot, J; Gall, B J P; Andersson, L L; Asai, M; Asfari, Z; Cox, D M; Dechery, F; Dorvaux, O; Grahn, T; Hauschild, K; Henning, G; Herzan, A; Herzberg, R-D; Heßberger, F P; Jakobsson, U; Jones, P; Julin, R; Juutinen, S; Ketelhut, S; Khoo, T-L; Leino, M; Ljungvall, J; Lopez-Martens, A; Lozeva, R; Nieminen, P; Pakarinen, J; Papadakis, P; Parr, E; Peura, P; Rahkila, P; Rinta-Antila, S; Ruotsalainen, P; Sandzelius, M; Sarén, J; Scholey, C; Seweryniak, D; Sorri, J; Sulignano, B; Theisen, Ch; Uusitalo, J; Venhart, M

    2012-07-06

    The rotational band structure of the Z=104 nucleus (256)Rf has been observed up to a tentative spin of 20ℏ using state-of-the-art γ-ray spectroscopic techniques. This represents the first such measurement in a superheavy nucleus whose stability is entirely derived from the shell-correction energy. The observed rotational properties are compared to those of neighboring nuclei and it is shown that the kinematic and dynamic moments of inertia are sensitive to the underlying single-particle shell structure and the specific location of high-j orbitals. The moments of inertia therefore provide a sensitive test of shell structure and pairing in superheavy nuclei which is essential to ensure the validity of contemporary nuclear models in this mass region. The data obtained show that there is no deformed shell gap at Z=104, which is predicted in a number of current self-consistent mean-field models.

  15. In situ synthesis of WC–Co nanocomposite powder via core–shell structure formation

    Energy Technology Data Exchange (ETDEWEB)

    Lin, Hua, E-mail: lh2004@swu.edu.cn [State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 610054 (China); School of Materials Science and Engineering, Southwest University, Chongqing 400715 (China); Tao, Bowan [State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 610054 (China); Li, Qing [School of Materials Science and Engineering, Southwest University, Chongqing 400715 (China); Li, Yanrong, E-mail: yrli@uestc.edu.cn [State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 610054 (China)

    2012-11-15

    Highlights: ► The hydrothermal method was firstly used to synthesize core–shell structured precursor to prepare WC–Co powder. ► WC–Co nanocomposite powder was obtained through in situ reduction and carbonization of the precursor in vacuum at 950 °C for 1 h. ► Particles of WC–Co composite indicated to have a crystallite size of 30–50 nm. -- Abstract: Cemented carbide WC–Co nanocomposite powders were synthesized through in situ reduction and carbonization of a core/shell precursor in vacuum. Samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and high-resolution transmission electron microscopy (HRTEM). The results revealed that WC–Co composite powders can be obtained at 950 °C for 1 h and the particle size is in the range from 30 to 50 nm with good dispersion. The formation mechanism of the WC–Co composite by in situ reduction and carbonization reactions was proposed. The preparation process could be divided into three steps: first, the reagents were dissolved and mixed to an aqueous solution; second step is to synthesize a carbon encapsulated core/shell nanostructure precursor using hydrothermal route, and finally, in situ reduction and carbonization of the precursor to the desired nanocomposite powders in vacuum.

  16. Visible near-infrared light scattering of single silver split-ring structure made by nanosphere lithography.

    Science.gov (United States)

    Okamoto, Toshihiro; Fukuta, Tetsuya; Sato, Shuji; Haraguchi, Masanobu; Fukui, Masuo

    2011-04-11

    We succeeded in making a silver split-ring (SR) structure of approximately 130 nm in diameter on a glass substrate using a nanosphere lithography technique. The light scattering spectrum in visible near-infrared region of a single, isolated SR was measured using a microscope spectroscopy optical system. The electromagnetic field enhancement spectrum and distribution of the SR structure were simulated by the finite-difference time-domain method, and the excitation modes were clarified. The long wavelength peak in the light scattering spectra corresponded to a fundamental LC resonance mode excited by an incident electric field. It was shown that a single SR structure fabricated as abovementioned can operate as a resonator and generate a magnetic dipole. © 2011 Optical Society of America

  17. Collagen structural alterations contribute to stiffening of tissue after split-thickness skin grafting.

    Science.gov (United States)

    Rosin, Nicole L; Agabalyan, Natacha; Olsen, Katherine; Martufi, Giampaol; Gabriel, Vincent; Biernaskie, Jeff; Di Martino, Elena S

    2016-03-01

    The gold standard treatment for full thickness injuries of the skin is autologous split-thickness skin grafting. This involves harvesting the epidermis and superficial dermis from healthy skin and transplanting it onto the prepared wound bed. The donor site regenerates spontaneously, but the appendages and cellular components from the dermal layer are excluded from the graft. As a result, the new tissue is inferior; the healed graft site is dry/itchy, has decreased elasticity, increased fragility, and altered sensory function. Because this dermal layer is composed of collagen and other extracellular matrix proteins, the aim was to characterize the changes in the dermal collagen after split thickness grafting that could contribute to a deficit in functionality. This will serve as a baseline for future studies designed to improve skin function using pharmacological or cell-based therapies for skin repair. A xenograft model whereby human split-thickness grafts were implanted into full-thickness defects on immunocompromised (athymic Nu/Nu) mice was used. The grafts were harvested 4 and 8 weeks later. The collagen microstructure was assessed with second harmonic generation with dual-photon microscopy and light polarization analysis. Collagen fiber stiffness and engagement stretch were estimated by fitting the results of biaxial mechanical tensile tests to a histo-mechanical constitutive model. The stiffness of the collagen fibril-proteoglycan complex increased from 682 ± 226 kPa/sr to 1016 ± 324 kPa/sr between 4 and 8 weeks postgrafting. At the microstructural level there were significant decreases in both thickness of collagen fibers (3.60 ± 0.34 μm vs. 2.10 ± 0.27 μm) and waviness ratio (2.04 ± 0.17 vs. 1.43 ± 0.08) of the collagen fibers postgrafting. The decrease of the macroscopic engagement stretch from 1.19 ± 0.11 to 1.09 ± 0.08 over time postgrafting mirrored the decrease in waviness measured at the microscopic level

  18. Splitting statistical potentials into meaningful scoring functions: Testing the prediction of near-native structures from decoy conformations

    Directory of Open Access Journals (Sweden)

    Oliva Baldo

    2009-11-01

    Full Text Available Abstract Background Recent advances on high-throughput technologies have produced a vast amount of protein sequences, while the number of high-resolution structures has seen a limited increase. This has impelled the production of many strategies to built protein structures from its sequence, generating a considerable amount of alternative models. The selection of the closest model to the native conformation has thus become crucial for structure prediction. Several methods have been developed to score protein models by energies, knowledge-based potentials and combination of both. Results Here, we present and demonstrate a theory to split the knowledge-based potentials in scoring terms biologically meaningful and to combine them in new scores to predict near-native structures. Our strategy allows circumventing the problem of defining the reference state. In this approach we give the proof for a simple and linear application that can be further improved by optimizing the combination of Zscores. Using the simplest composite score ( we obtained predictions similar to state-of-the-art methods. Besides, our approach has the advantage of identifying the most relevant terms involved in the stability of the protein structure. Finally, we also use the composite Zscores to assess the conformation of models and to detect local errors. Conclusion We have introduced a method to split knowledge-based potentials and to solve the problem of defining a reference state. The new scores have detected near-native structures as accurately as state-of-art methods and have been successful to identify wrongly modeled regions of many near-native conformations.

  19. Biphasic-to-monophasic successive Co-assembly approach to yolk-shell structured mesoporous organosilica nanoparticles.

    Science.gov (United States)

    Dang, Meng; Teng, Zhaogang; Su, Xiaodan; Tao, Jun; Hao, Qing; Ma, Xiaobo; Zhang, Yunlei; Li, Yanjiao; Tian, Ying; Zhang, Junjie; Lu, Guangming; Wang, Lianhui

    2017-12-01

    In this work, we report a facile biphasic-to-monophasic successive co-assembly approach to synthesize yolk-shell structured mesoporous organosilica nanoparticles (MONs). The yolk-shell structured MONs possess ethane-bridged frameworks, high surface area (1023m 2 g -1 ), radially oriented mesochannels (3.8nm), large pore volume (0.99cm 3 g -1 ), and tunable diameter (147-324nm) and shell thickness (23-53nm). The biphasic-to-monophasic successive co-assembly method is intrinsically simple and requires neither sacrificial templates nor multistep coating processes. The key of the method is that the interiors of the mesostructured organosilica nanospheres grown in the biphasic system have a lower condensation degree and Si-C-C-Si species content than the outer shells formed in the monophasic system. Thus, the interior layer is attracted by OH -1 anions and dissolved in the monophasic system, forming the yolk-shell structures. In vitro cytotoxicity and haemolysis assays demonstrate that the ethane-bridged yolk-shell MONs possess excellent biocompatibility. Furthermore, the chemotherapy drug doxorubicin (DOX) is loaded into the yolk-shell MONs to kill drug-resistant MCF-7/ADR human breast cancer cells. Compared with free DOX and DOX-loaded typical MONs, the DOX-loaded yolk-shell MONs have higher chemotherapeutic efficacy against MCF-7/ADR cells, suggesting the great potential of yolk-shell MONs synthesized via the biphasic-to-monophasic successive co-assembly approach in the biomedical field. Copyright © 2017 Elsevier Inc. All rights reserved.

  20. Chemical Structure, Ensemble and Single-Particle Spectroscopy of Thick-Shell InP-ZnSe Quantum Dots.

    Science.gov (United States)

    Reid, Kemar R; McBride, James R; Freymeyer, Nathaniel J; Thal, Lucas B; Rosenthal, Sandra J

    2018-02-14

    Thick-shell (>5 nm) InP-ZnSe colloidal quantum dots (QDs) grown by a continuous-injection shell growth process are reported. The growth of a thick crystalline shell is attributed to the high temperature of the growth process and the relatively low lattice mismatch between the InP core and ZnSe shell. In addition to a narrow ensemble photoluminescence (PL) line-width (∼40 nm), ensemble and single-particle emission dynamics measurements indicate that blinking and Auger recombination are reduced in these heterostructures. More specifically, high single-dot ON-times (>95%) were obtained for the core-shell QDs, and measured ensemble biexciton lifetimes, τ 2x ∼ 540 ps, represent a 7-fold increase compared to InP-ZnS QDs. Further, high-resolution energy dispersive X-ray (EDX) chemical maps directly show for the first time significant incorporation of indium into the shell of the InP-ZnSe QDs. Examination of the atomic structure of the thick-shell QDs by high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) reveals structural defects in subpopulations of particles that may mitigate PL efficiencies (∼40% in ensemble), providing insight toward further synthetic refinement. These InP-ZnSe heterostructures represent progress toward fully cadmium-free QDs with superior photophysical properties important in biological labeling and other emission-based technologies.

  1. Bending and splitting of spoof surface acoustic waves through structured rigid surface

    Science.gov (United States)

    Xie, Sujun; Ouyang, Shiliang; He, Zhaojian; Wang, Xiaoyun; Deng, Ke; Zhao, Heping

    2018-03-01

    In this paper, we demonstrated that a 90°-bended imaging of spoof surface acoustic waves with subwavelength resolution of 0.316λ can be realized by a 45° prism-shaped surface phononic crystal (SPC), which is composed of borehole arrays with square lattice in a rigid plate. Furthermore, by combining two identical prism-shaped phononic crystal to form an interface (to form a line-defect), the excited spoof surface acoustic waves can be split into bended and transmitted parts. The power ratio between the bended and transmitted surface waves can be tuned arbitrarily by adjusting the defect size. This acoustic system is believed to have potential applications in various multifunctional acoustic solutions integrated by different acoustical devices.

  2. Vibration Characteristics Analysis of Cylindrical Shell-Plate Coupled Structure Using an Improved Fourier Series Method

    Directory of Open Access Journals (Sweden)

    Yipeng Cao

    2018-01-01

    Full Text Available A simple yet accurate solution procedure based on the improved Fourier series method (IFSM is applied to the vibration characteristics analysis of a cylindrical shell-circular plate (S-P coupled structure subjected to various boundary conditions. By applying four types of coupling springs with arbitrary stiffness at the junction of the coupled structure, the mechanical coupling effects are completely considered. Each of the plate and shell displacement functions is expressed as the superposition of a two-dimensional Fourier series and several supplementary functions. The unknown series-expansion coefficients are treated as the generalized coordinates and determined using the familiar Rayleigh-Ritz procedure. Using the IFSM, a unified solution for the S-P coupled structure with symmetrical and asymmetrical boundary conditions can be derived directly without the need to change either the equations of motion or the expressions of the displacements. This solution can be verified by comparing the current results with those calculated by the finite-element method (FEM. The effects of several significant factors, including the restraint stiffness, the coupling stiffness, and the situation of coupling, are presented. The forced vibration behaviors of the S-P coupled structure are also illustrated.

  3. STRUCTURAL SHELL OPTIMIZATION STUDIES. VOLUME I. SURVEY OF BUCKLING DATA FOR MONOCOQUE CIRCULAR CYLINDRICAL SHELLS SUBJECTED TO UNIFORM EXTERNAL PRESSURE.

    Science.gov (United States)

    subjected to uniform external pressure. A simple, approximate method of analysis for the buckling of such a shell is offered for the purpose of...stress analysis. The loading with hydrostatic external pressure is considered as a special case of the interaction relation, and the method of analysis for...are included in which properly selected test data are evaluated. A diagramatic comparison of the suggested method of analysis and the test data shows a reasonably close agreement. (Author)

  4. Numerical analysis of stiffened shells of revolution. Volume 4: Engineer's program manual for STARS-2S shell theory automated for rotational structures - 2 (statics) digital computer program

    Science.gov (United States)

    Svalbonas, V.; Ogilvie, P.

    1973-01-01

    The engineering programming information for the digital computer program for analyzing shell structures is presented. The program is designed to permit small changes such as altering the geometry or a table size to fit the specific requirements. Each major subroutine is discussed and the following subjects are included: (1) subroutine description, (2) pertinent engineering symbols and the FORTRAN coded counterparts, (3) subroutine flow chart, and (4) subroutine FORTRAN listing.

  5. Hysteresis and compensation behaviors of mixed spin-2 and spin-1 hexagonal Ising nanowire core–shell structure

    International Nuclear Information System (INIS)

    Masrour, R.; Jabar, A.; Benyoussef, A.; Hamedoun, M.; Bahmad, L.

    2015-01-01

    The magnetic behaviors of a mixed spins (2-1) hexagonal Ising nanowire with core–shell structure are investigated by using the Monte Carlo simulations. The thermal magnetizations, the magnetic susceptibilities and the transition temperatures of core–shell are studied for different values of crystal field and exchange interactions. The thermal and magnetic hysteresis cycles are given for different values of the crystal field. - Highlights: • Critical temperature increase when exchange interaction increasing in core-shell. • Hysteresis loop areas decrease at above transition temperature. • Magnetic coercive field decrease when crystal field increasing. • Magnetic coercive field increase when exchange interaction increasing

  6. Fabrication of unique hollow silicate nanoparticles with hierarchically micro/mesoporous shell structure by a simple double template approach.

    Science.gov (United States)

    Rivera-Virtudazo, R V; Fuji, M; Takai, C; Shirai, T

    2012-12-07

    An innovative type of hollow silicate nanoparticle with a micro/mesoporous shell wall (NSHPMS) was synthesized at room temperature via an eco-friendly double template approach, followed by simple acid reflux. TEM observations of NSHPMSs showed hollow interior nanoparticles (wormhole-like shell structure. The nitrogen gas (N(2)) adsorption/desorption isotherm exhibited a unique two-step pattern: the first step (0.2 wormhole mesoporous shell wall provided sufficient spaces that contribute to high adsorption capacities and faster adsorption rates. One can envision that larger quantities of framework composition can be obtained using our NSHPMSs.

  7. Analysis of intelligent hinged shell structures: deployable deformation and shape memory effect

    International Nuclear Information System (INIS)

    Shi, Guang-Hui; Yang, Qing-Sheng; He, X Q

    2013-01-01

    Shape memory polymers (SMPs) are a class of intelligent materials with the ability to recover their initial shape from a temporarily fixable state when subjected to external stimuli. In this work, the thermo-mechanical behavior of a deployable SMP-based hinged structure is modeled by the finite element method using a 3D constitutive model with shape memory effect. The influences of hinge structure parameters on the nonlinear loading process are investigated. The total shape memory of the processes the hinged structure goes through, including loading at high temperature, decreasing temperature with load carrying, unloading at low temperature and recovering the initial shape with increasing temperature, are illustrated. Numerical results show that the present constitutive theory and the finite element method can effectively predict the complicated thermo-mechanical deformation behavior and shape memory effect of SMP-based hinged shell structures. (paper)

  8. Degenerated shell element for geometrically nonlinear analysis of thin-walled piezoelectric active structures

    International Nuclear Information System (INIS)

    Marinković, D; Köppe, H; Gabbert, U

    2008-01-01

    Active piezoelectric thin-walled structures, especially those with a notably higher membrane than bending stiffness, are susceptible to large rotations and transverse deflections. Recent investigations conducted by a number of researchers have shown that the predicted behavior of piezoelectric structures can be significantly influenced by the assumption of large displacements and rotations of the structure, thus demanding a geometrically nonlinear formulation in order to investigate it. This paper offers a degenerated shell element and a simplified formulation that relies on small incremental steps for the geometrically nonlinear analysis of piezoelectric composite structures. A set of purely mechanical static cases is followed by a set of piezoelectric coupled static cases, both demonstrating the applicability of the proposed formulation

  9. The Kernel and Shell Structure as a Tool for Improving the Graph of Transportation Connections

    Directory of Open Access Journals (Sweden)

    Barbara Mażbic-Kulma

    2013-01-01

    Full Text Available A model of a transportation system is expected to be useful in simulations of a real system to solve given transportation tasks. A connection graph is routinely used to describe a transportation system. Vertices can be train stations, bus stops, airports etc. The edges show direct connections between vertices. A direct approach can be difficult and computational problems can arise in attempts to organize or optimize such a transportation system. Therefore, a method for aggregating such graphs was introduced, using a general kernel and shell structure and its particular instances: α-clique structured graphs of connections and a hub and spoke transformation of the source graph. These structures enable the concentration and ordering of transport between vertices and reduction of the analyzed graph. To obtain the desired structures, several versions of a specialized evolutionary algorithm were developed and applied. (original abstract

  10. Preparation and microwave adsorption properties of core–shell structured barium titanate/polyaniline composite

    Energy Technology Data Exchange (ETDEWEB)

    Hongxia, Jing, E-mail: jhx820215@126.com [Department of Chemistry, College of Science, North University of China, Taiyuan 030051 (China); Qiaoling, Li [Department of Chemistry, College of Science, North University of China, Taiyuan 030051 (China); Yun, Ye [College of Material Science and Engineering, North University of China, Taiyuan Shanxi 030051 (China); Zhiwu, Guo; Xiaofeng, Yang [Department of Chemistry, College of Science, North University of China, Taiyuan 030051 (China)

    2013-04-15

    Nano-BaTiO{sub 3} particles were prepared by the sol–gel method. The core–shell structured BaTiO{sub 3}/polyaniline (PANI) composites were synthesized by in-situ polymerization with as-prepared BaTiO{sub 3} nano-particles. The structural, morphology and microwave adsorption properties of the obtained composites were investigated in detail by X-ray diffraction, Fourier transform infrared spectroscopy, transmission electron microscopy and vector network analyzer. The average particle size of the BaTiO{sub 3} nanoparticles was measured to be 60 nm and the thickness of shell was 40 nm. The complex permittivity, permeability and reflection loss of the composites were measured at different microwave frequencies in 0–6000 MHz. The effect of the mass ratio of BaTiO{sub 3}/PANI on the microwave loss properties of the composites was investigated. For the sample obtained by the mass ratio of BaTiO{sub 3} to PANI of 4:1, the value of reflection loss peaks is up to −14.5 dB. The width of the −5 and −10 dB is up to 1200 and 750 MHz, respectively. This reveals that the BaTiO{sub 3} nanoparticles in the polyaniline matrix affect the microwave absorption properties of the nanocomposites. - Highlights: ► Nano-BaTiO{sub 3} particles were prepared by the sol–gel method. ► The core–shell structured BaTiO{sub 3}/polyaniline composites were synthesized by in-situ polymerization. ► The effect of the mass ratio of BaTiO{sub 3}/PANI on the microwave loss properties of the composites was investigated.

  11. Consistent linearization of the element-independent corotational formulation for the structural analysis of general shells

    Science.gov (United States)

    Rankin, C. C.

    1988-01-01

    A consistent linearization is provided for the element-dependent corotational formulation, providing the proper first and second variation of the strain energy. As a result, the warping problem that has plagued flat elements has been overcome, with beneficial effects carried over to linear solutions. True Newton quadratic convergence has been restored to the Structural Analysis of General Shells (STAGS) code for conservative loading using the full corotational implementation. Some implications for general finite element analysis are discussed, including what effect the automatic frame invariance provided by this work might have on the development of new, improved elements.

  12. Core–shell and multilayered magnetite nanoparticles—Structural and Mössbauer studies

    Energy Technology Data Exchange (ETDEWEB)

    Kalska-Szostko, B., E-mail: kalska@uwb.edu.pl [Institute of Chemistry, Hurtowa 1, 15-399 Białystok (Poland); Wykowska, U. [Institute of Chemistry, Hurtowa 1, 15-399 Białystok (Poland); Satuła, D. [Faculty of Physics, Lipowa 41, 15-424 Białystok (Poland)

    2014-07-01

    In the paper, we present the effective method of the preparation of nanosized core–shell or multilayered nanoparticles with various layer compositions. Metals like Cu, Ag and Au have been used as a surface or spacer material in magnetite based particles. In further steps, functionalization of obtained nanoparticles was done. The resulting nanoparticles were structurally examined by X-ray diffraction, infra-red spectroscopy, transmission electron microscopy and differential scanning calorimetry. Magnetic properties of the nanoparticles were tested by Mössbauer spectroscopy.

  13. Shell supports

    DEFF Research Database (Denmark)

    Almegaard, Henrik

    2004-01-01

    A new statical and conceptual model for membrane shell structures - the stringer system - has been found. The principle was first published at the IASS conference in Copenhagen (OHL91), and later the theory has been further developed (ALMO3)(ALMO4). From the analysis of the stringer model it can...... be concluded that all membrane shells can be described by a limited number of basic configurations of which quite a few have free edges....

  14. Investigation of the structure change of atomic shells due to uranium ionization by the Dirac-Fock-Slater method

    International Nuclear Information System (INIS)

    Shchornak, G.

    1979-01-01

    The influence of outer vacancies in the atomic shells of uranium on the atomic shell structure is claculated by the Dirac-Fock-Slater method. It is found out that the energy of the X-ray transitions increases due to the detachment of the electrons with the lowest binding energies. The electron detachment from the subshells of the 4f level gives rise to negative energy shifts of the X-ray transitions.(author)

  15. Subscale and Full-Scale Testing of Buckling-Critical Launch Vehicle Shell Structures

    Science.gov (United States)

    Hilburger, Mark W.; Haynie, Waddy T.; Lovejoy, Andrew E.; Roberts, Michael G.; Norris, Jeffery P.; Waters, W. Allen; Herring, Helen M.

    2012-01-01

    New analysis-based shell buckling design factors (aka knockdown factors), along with associated design and analysis technologies, are being developed by NASA for the design of launch vehicle structures. Preliminary design studies indicate that implementation of these new knockdown factors can enable significant reductions in mass and mass-growth in these vehicles and can help mitigate some of NASA s launch vehicle development and performance risks by reducing the reliance on testing, providing high-fidelity estimates of structural performance, reliability, robustness, and enable increased payload capability. However, in order to validate any new analysis-based design data or methods, a series of carefully designed and executed structural tests are required at both the subscale and full-scale level. This paper describes recent buckling test efforts at NASA on two different orthogrid-stiffened metallic cylindrical shell test articles. One of the test articles was an 8-ft-diameter orthogrid-stiffened cylinder and was subjected to an axial compression load. The second test article was a 27.5-ft-diameter Space Shuttle External Tank-derived cylinder and was subjected to combined internal pressure and axial compression.

  16. Yolk-shell structured Sb@C anodes for high energy Na-ion batteries

    Energy Technology Data Exchange (ETDEWEB)

    Song, Junhua; Yan, Pengfei; Luo, Langli; Qi, Xingguo; Rong, Xiaohui; Zheng, Jianming; Xiao, Biwei; Feng, Shuo; Wang, Chongmin; Hu, Yong-Sheng; Lin, Yuehe; Sprenkle, Vincent L.; Li, Xiaolin

    2017-10-01

    Despite great advances in sodium-ion battery developments, the search for high energy and stable anode materials remains a challenge. Alloy or conversion-typed anode materials are attractive candidates of high specific capacity and low voltage potential, yet their applications are hampered by the large volume expansion and hence poor electrochemical reversibility and fast capacity fade. Here, we use antimony (Sb) as an example to demonstrate the use of yolk-shell structured anodes for high energy Na-ion batteries. The Sb@C yolk-shell structure prepared by controlled reduction and selective removal of Sb2O3 from carbon coated Sb2O3 nanoparticles can accommodate the Sb swelling upon sodiation and improve the structural/electrical integrity against pulverization. It delivers a high specific capacity of ~554 mAh•g-1, good rate capability (315 mhA•g-1 at 10C rate) and long cyclability (92% capacity retention over 200 cycles). Full-cells of O3-Na0.9[Cu0.22Fe0.30Mn0.48]O2 cathodes and Sb@C-hard carbon composite anodes demonstrate a high specific energy of ~130 Wh•kg-1 (based on the total mass of cathode and anode) in the voltage range of 2.0-4.0 V, ~1.5 times energy of full-cells with similar design using hard carbon anodes.

  17. Structural defect induced peak splitting in gold-copper bimetallic nanorods during growth by single particle spectroscopy.

    Science.gov (United States)

    Thota, Sravan; Chen, Shutang; Zhou, Yadong; Zhang, Yong; Zou, Shengli; Zhao, Jing

    2015-09-21

    A single particle level study of bimetallic nanoparticle growth provides valuable information that is usually hidden in ensemble measurements, helping to improve the understanding of a reaction mechanism and overcome the synthetic challenges. In this study, we use single particle spectroscopy to monitor the changes in the scattering spectra of Au-Cu alloy nanorods during growth. We found that the unique features of the single particle scattering spectra were due to atomic level geometric defects in the nanorods. Electrodynamics simulations have demonstrated that small structural defects of a few atomic layers split the scattering peaks, giving rise to higher order modes, which do not exist in defect-free rods of similar geometry. The study shows that single particle scattering technique is as sensitive as high-resolution electron microscopy in revealing atomic level structural defects.

  18. Shell structure of natural rubber particles: evidence of chemical stratification by electrokinetics and cryo-TEM.

    Science.gov (United States)

    Rochette, Christophe N; Crassous, Jérôme J; Drechsler, Markus; Gaboriaud, Fabien; Eloy, Marie; de Gaudemaris, Benoît; Duval, Jérôme F L

    2013-11-26

    The interfacial structure of natural rubber (NR) colloids is investigated by means of cryogenic transmission electron microscopy (cryo-TEM) and electrokinetics over a broad range of KNO3 electrolyte concentrations (4-300 mM) and pH values (1-8). The asymptotic plateau value reached by NR electrophoretic mobility (μ) in the thin double layer limit supports the presence of a soft (ion- and water-permeable) polyelectrolytic type of layer located at the periphery of the NR particles. This property is confirmed by the analysis of the electron density profile obtained from cryo-TEM that evidences a ∼2-4 nm thick corona surrounding the NR polyisoprene core. The dependence of μ on pH and salt concentration is further marked by a dramatic decrease of the point of zero electrophoretic mobility (PZM) from 3.6 to 0.8 with increasing electrolyte concentration in the range 4-300 mM. Using a recent theory for electrohydrodynamics of soft multilayered particles, this "anomalous" dependence of the PZM on electrolyte concentration is shown to be consistent with a radial organization of anionic and cationic groups across the peripheral NR structure. The NR electrokinetic response in the pH range 1-8 is indeed found to be equivalent to that of particles surrounded by a positively charged ∼3.5 nm thick layer (mean dissociation pK ∼ 4.2) supporting a thin and negatively charged outermost layer (0.6 nm in thickness, pK ∼ 0.7). Altogether, the strong dependence of the PZM on electrolyte concentration suggests that the electrostatic properties of the outer peripheral region of the NR shell are mediated by lipidic residues protruding from a shell containing a significant amount of protein-like charges. This proposed NR shell interfacial structure questions previously reported NR representations according to which the shell consists of either a fully mixed lipid-protein layer, or a layer of phospholipids residing exclusively beneath an outer proteic film.

  19. Design, fabrication and test of lightweight shell structure. [axial compression loads and torsion stress

    Science.gov (United States)

    Lager, J. R.

    1975-01-01

    A cylindrical shell structure 3.66 m (144 in.) high by 4.57 m (180 in.) diameter was designed using a wide variety of materials and structural concepts to withstand design ultimate combined loading 1225.8 N/cm (700 lb/in.) axial compression and 245.2 N/cm (140 lb/in.) torsion. The overall cylinder geometry and design loading are representative of that expected on a high performance space tug vehicle. The relatively low design load level results in designs that use thin gage metals and fibrous-composite laminates. Fabrication and structural tests of small panels and components representative of many of the candidate designs served to demonstrate proposed fabrication techniques and to verify design and analysis methods. Three of the designs evaluated, honeycomb sandwich with aluminum faceskins, honeycomb sandwich with graphite/epoxy faceskins, and aluminum truss with fiber-glass meteoroid protection layers, were selected for further evaluation.

  20. Analysis of field coordination on heat exchanger shell side with different diameter tubes and holding structure

    International Nuclear Information System (INIS)

    Li Jing; Lu Minshan; Dong Qiwu

    2009-01-01

    In order to overcome the disadvantages of the rod-baffle heat exchanger, which achieves the high heat transfer efficiency only at high flow velocity, and which with non compact layout of tubes and is weak in the resistance of operation mode changes, this paper proposed two sizes of heat exchange tubes and holding and support structures to replace the traditional rod-baffle support unit, to increase the heat exchange coefficient on shell side and the heat exchange effectiveness. Three-dimensional numerical simulation was conducted on the shellside flow field and heat exchange field by the CFD software, and the calculation method was proposed for the included angle for the shellside velocity-temperature gradient fields of the vertical flow heat exchanger with complex structure. The quantitative relationship of the field coordination angle for the shellside velocity field and temperature gradient field was obtained and it is proved that the new structure is with better field coordination relation. (authors)

  1. Nonlinear Shell Modeling of Thin Membranes with Emphasis on Structural Wrinkling

    Science.gov (United States)

    Tessler, Alexander; Sleight, David W.; Wang, John T.

    2003-01-01

    Thin solar sail membranes of very large span are being envisioned for near-term space missions. One major design issue that is inherent to these very flexible structures is the formation of wrinkling patterns. Structural wrinkles may deteriorate a solar sail's performance and, in certain cases, structural integrity. In this paper, a geometrically nonlinear, updated Lagrangian shell formulation is employed using the ABAQUS finite element code to simulate the formation of wrinkled deformations in thin-film membranes. The restrictive assumptions of true membranes, i.e. Tension Field theory (TF), are not invoked. Two effective modeling strategies are introduced to facilitate convergent solutions of wrinkled equilibrium states. Several numerical studies are carried out, and the results are compared with recent experimental data. Good agreement is observed between the numerical simulations and experimental data.

  2. Seniority structure of the cranked shell model wave function and the pairing phase transition

    International Nuclear Information System (INIS)

    Wu, C.S.; Zeng, J.Y.; Center of Theoretical Physics, China Center of Advanced Science and Technology

    1989-01-01

    The accurate solutions to the low-lying eigenstates of the cranked shell model Hamiltonian are obtained by the particle-number-conserving treatment, in which a many-particle configuration truncation is adopted instead of the conventional single-particle level truncation. The variation of the seniority structures of low-lying eigenstates with rotational frequency ω is analyzed. The gap parameter of the yrast band decreases with ω very slowly, though the seniority structure has undergone a great change. It is suggested to use the seniority structure to indicate the possible pairing phase transition from a superconducting state to a normal state. The important blocking effects on the low-lying eigenstates are discussed

  3. 7 CFR 51.2753 - U.S. Virginia Splits.

    Science.gov (United States)

    2010-01-01

    ... 7 Agriculture 2 2010-01-01 2010-01-01 false U.S. Virginia Splits. 51.2753 Section 51.2753... STANDARDS) United States Standards for Shelled Virginia Type Peanuts Grades § 51.2753 U.S. Virginia Splits. “U.S. Virginia Splits” consists of shelled Virginia type peanut kernels of similar varietal...

  4. Core-shell structure in (La/Ce)CrO3 nanoparticles: evidences from macroscopic, microscopic and mesoscopic studies

    International Nuclear Information System (INIS)

    Manna, P.K.; Yusuf, S.M.; Mukadam, M.D.; Kohlbrecher, J.

    2013-01-01

    The fundamental properties of a magnetic material vary considerably at the nanoscale as compared to its bulk counterpart. This is often ascribed to the presence of disordered spins at the surface of the nanoparticles. The magnetic behavior of these surface-spins is different from the core-spins, and hence we can consider such nanoparticles as a core-shell type. However, it is difficult to get an evidence of this shell in a 'bare' nanoparticle system, because the magnetization-contributions of core and shell become indistinguishable in most cases. We have used a combination of microscopic neutron diffraction, mesoscopic polarized neutron small angle scattering (SANSPOL), and macroscopic dc-magnetization techniques to investigate core-shell structure in 'bare' La 0.2 Ce 0.8 CrO 3 nanoparticles, synthesized by using a two-step method. It is noteworthy to mention here that, in our study, the La 0.2 Ce 0.8 CrO 3 nanoparticles showed a novel coexistence of magnetization and exchange-bias-field sign-reversal, which might have an application in designing volatile and thermally assisted magnetic memory elements. The first evidence of a possible core-shell structure was obtained from the presence of surface roughness/defects in the high resolution transmission electron microscopy images. Microscopic neutron diffraction study depicted that these nanoparticles are antiferromagnetic in nature. However, the SANSPOL data at 2.5 K under a 3.5-T magnetic field show the presence of a pronounced asymmetric scattering in the iso-intensity plot signifying the presence of a strong interference between nuclear and magnetic scattering amplitudes. It has been argued that the presence of such asymmetric scattering in the SANSPOL data of these antiferromagnetic nanoparticles arises from the shell. The mean core diameter and shell thickness are found to be 12.3 ± 1.1, and 2.8 ± 0.4 nm, respectively. The net magnetization (observed from the dc magnetization study), arising from the shell of

  5. Bio-inspired passive actuator simulating an abalone shell mechanism for structural control

    International Nuclear Information System (INIS)

    Yang, Henry T Y; Lin, Chun-Hung; Bridges, Daniel; Randall, Connor J; Hansma, Paul K

    2010-01-01

    An energy dispersion mechanism called 'sacrificial bonds and hidden length', which is found in some biological systems, such as abalone shells and bones, is the inspiration for new strategies for structural control. Sacrificial bonds and hidden length can substantially increase the stiffness and enhance energy dissipation in the constituent molecules of abalone shells and bone. Having been inspired by the usefulness and effectiveness of such a mechanism, which has evolved over millions of years and countless cycles of evolutions, the authors employ the conceptual underpinnings of this mechanism to develop a bio-inspired passive actuator. This paper presents a fundamental method for optimally designing such bio-inspired passive actuators for structural control. To optimize the bio-inspired passive actuator, a simple method utilizing the force–displacement–velocity (FDV) plots based on LQR control is proposed. A linear regression approach is adopted in this research to find the initial values of the desired parameters for the bio-inspired passive actuator. The illustrative examples, conducted by numerical simulation with experimental validation, suggest that the bio-inspired passive actuator based on sacrificial bonds and hidden length may be comparable in performance to state-of-the-art semi-active actuators

  6. A novel approach to preparing magnetic protein microspheres with core-shell structure

    Energy Technology Data Exchange (ETDEWEB)

    Jiang Wei, E-mail: climentjw@126.co [National Special Superfine Powder Engineering Research Center, Nanjing University of Science and Technology, Nanjing 210094 (China); Sun Zhendong; Li Fengsheng [National Special Superfine Powder Engineering Research Center, Nanjing University of Science and Technology, Nanjing 210094 (China); Chen Kai; Liu Tianyu; Liu Jialing [Department of Physics, Nanjing University of Science and Technology, Nanjing 210094 (China); Zhou Tianle [Department of Materials Science and Engineering, Nanjing University of Science and Technology, Nanjing 210094 (China); Guo Rui [Department of Mechanical Engineering, Nanjing University of Science and Technology, Nanjing 210094 (China)

    2011-03-15

    Magnetic protein microspheres with core-shell structure were prepared through a novel approach based on the sonochemical method and the emulsion solvent evaporation method. The microspheres are composed of the oleic acid and undecylenic acid modified Fe{sub 3}O{sub 4} cores and coated with globular bovine serum albumin (BSA). Under an optimized condition, up to 57.8 wt% of approximately 10 nm superparamagnetic Fe{sub 3}O{sub 4} nanoparticles could be uniformly encapsulated into the BSA microspheres with the diameter of approximately 160 nm and the high saturation magnetization of 38.5 emu/g, besides of the abundant functional groups. The possible formation mechanism of magnetic microspheres was discussed in detail. - Research Highlights: Magnetic protein microspheres with core-shell structure were prepared through a novel approach based on the sonochemical method and the emulsion solvent evaporation method. The microspheres are composed of the oleic acid and undecylenic acid modified Fe{sub 3}O{sub 4} cores and coated with globular bovine serum albumin (BSA). 57.8 wt% of approximately 10 nm superparamagnetic Fe{sub 3}O{sub 4} nanoparticles could be uniformly encapsulated into the BSA microspheres with the diameter of approximately 160 nm and the high saturation magnetization of 38.5 emu/g, besides the abundant functional groups.

  7. A novel approach to preparing magnetic protein microspheres with core-shell structure

    International Nuclear Information System (INIS)

    Jiang Wei; Sun Zhendong; Li Fengsheng; Chen Kai; Liu Tianyu; Liu Jialing; Zhou Tianle; Guo Rui

    2011-01-01

    Magnetic protein microspheres with core-shell structure were prepared through a novel approach based on the sonochemical method and the emulsion solvent evaporation method. The microspheres are composed of the oleic acid and undecylenic acid modified Fe 3 O 4 cores and coated with globular bovine serum albumin (BSA). Under an optimized condition, up to 57.8 wt% of approximately 10 nm superparamagnetic Fe 3 O 4 nanoparticles could be uniformly encapsulated into the BSA microspheres with the diameter of approximately 160 nm and the high saturation magnetization of 38.5 emu/g, besides of the abundant functional groups. The possible formation mechanism of magnetic microspheres was discussed in detail. - Research Highlights: → Magnetic protein microspheres with core-shell structure were prepared through a novel approach based on the sonochemical method and the emulsion solvent evaporation method.→ The microspheres are composed of the oleic acid and undecylenic acid modified Fe 3 O 4 cores and coated with globular bovine serum albumin (BSA).→ 57.8 wt% of approximately 10 nm superparamagnetic Fe 3 O 4 nanoparticles could be uniformly encapsulated into the BSA microspheres with the diameter of approximately 160 nm and the high saturation magnetization of 38.5 emu/g, besides the abundant functional groups.

  8. The role of Argopecten purpuratus shells structuring the soft bottom community in shallow waters of southern Peru

    Science.gov (United States)

    Lomovasky, Betina J.; Gamero, Patricia A.; Romero, Leonardo; Firstater, Fausto N.; Gamarra Salazar, Alex; Hidalgo, Fernando; Tarazona, Juan; Iribarne, Oscar O.

    2015-12-01

    Accumulation of Argopecten purpuratus shells often occurs after El Niño events in shallow waters of Independencia Bay (14°17‧S-76°10‧W; Pisco, Peru). Here we experimentally investigate the effects of their shell accumulation on macrobenthos assemblages in soft bottom, shallow areas of the bay. A field experiment (from May 2006 to May 2007), including four treatments with different coverage levels of empty shells of A. purpuratus, were randomly arranged in: (1) areas devoid of shells ("Empty" treatment: experimental control), (2) 50% of the plot area covered with shells haphazardly distributed over the bottom ("medium" treatment), (3) 100% of the plot area covered with shells, forming a 10 cm valve layer ("full" treatment) and (4) "natural control". We found a total of 124 taxa throughout the experiment. Polychaetes, crustaceans and mollusks were the most abundant groups in "natural controls", dominated by the gastropod Nassarius gayi and the polychaetes Prionospio peruana, Platynereis bicanaliculata and Mediomastus branchiferus. The abundance of individuals (N) and the species richness (S) were higher in the "medium" treatment, but only in one month under positive sea bottom thermal anomalies. Similarity analysis (Bray-Curtis) showed that "natural control", "empty" and "full" treatments were more similar among them than the "medium" treatment. Multidimensional analysis showed no clear species association among treatments and a higher grouping among the samplings of Jun-06, Aug-06 and Nov-06. Our results also showed that the commercial crab Romaleon polyodon and the polyplacophora Tonicia elegans were positively affected by shell accumulations ("medium" treatment), while the limpet Fissurella crassa was negatively affected. Our study shows that directly by changing habitat structure or indirectly by changing sediment characteristics, the addition of scallop shells to the soft bottom can modify the macrobenthic assemblage; however, the seasonal oceanographic

  9. Synthesis, structural, and optical properties of type-II ZnO–ZnS core–shell nanostructure

    Energy Technology Data Exchange (ETDEWEB)

    Sookhakian, M., E-mail: m.sokhakian@gmail.com [Department of Physics, University of Malaya, Kuala Lumpur 50603 (Malaysia); Amin, Y.M. [Department of Physics, University of Malaya, Kuala Lumpur 50603 (Malaysia); Basirun, W.J. [Department of Chemistry, University of Malaya, Kuala Lumpur 50603 (Malaysia); Nanotechnology and Catalysis Research Centre (NanoCat), Institute of Postgraduate Studies, University Malaya, 50603 Kuala Lumpur (Malaysia); Tajabadi, M.T. [Department of Chemistry, University of Malaya, Kuala Lumpur 50603 (Malaysia); Kamarulzaman, N. [Centre for Nanomaterials Research Institute of Science, Level 3 Block C (Old Engineering Building), Universiti Teknologi MARA (UiTM), 40450 Shah Alam, Selangor (Malaysia)

    2014-01-15

    We demonstrate a facile one-step method for the preparation of ZnO–ZnS core–shell type-II nanostructures, pure ZnS quantum dots and pure ZnO nanoparticles with different experimental conditions. Treatment with sodium hydroxide as a capping agent is investigated systematically during the synthesis of ZnS quantum dots (QDs). The thickness of the ZnS shell is controlled by the concentration of the sodium sulphide during the synthesis of ZnO–ZnS core–shell nanostructures. The morphology and structure of samples are verified by X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM) and energy dispersive X-ray analysis (EDX). The UV–vis absorption spectra of the pure ZnS QDs exhibit a blue shift in the absorption edge due to the quantum confinement effect. The PL emission spectra of the ZnO–ZnS core–shell nanostructure are compared with the ZnO nanoparticles. The ZnO–ZnS core–shell nanostructures show decrease in the UV and green emissions with the appearance of a blue emission, which are not found in the ZnO nanoparticles. -- Highlights: • It has synthesised ZnO–ZnS core–shell type II in one-step for the first time. • The as-synthesised samples were characterised by using XRD, UV–vis. • The photoluminescence properties of ZnO–ZnS core–shell was compared with ZnO. • The UV and green emission in the PL spectrum of ZnO–ZnS core–shell decreased. • The blue emission in the PL spectrum of ZnO–ZnS core–shell appeared.

  10. Synthesis, structural, and optical properties of type-II ZnO–ZnS core–shell nanostructure

    International Nuclear Information System (INIS)

    Sookhakian, M.; Amin, Y.M.; Basirun, W.J.; Tajabadi, M.T.; Kamarulzaman, N.

    2014-01-01

    We demonstrate a facile one-step method for the preparation of ZnO–ZnS core–shell type-II nanostructures, pure ZnS quantum dots and pure ZnO nanoparticles with different experimental conditions. Treatment with sodium hydroxide as a capping agent is investigated systematically during the synthesis of ZnS quantum dots (QDs). The thickness of the ZnS shell is controlled by the concentration of the sodium sulphide during the synthesis of ZnO–ZnS core–shell nanostructures. The morphology and structure of samples are verified by X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM) and energy dispersive X-ray analysis (EDX). The UV–vis absorption spectra of the pure ZnS QDs exhibit a blue shift in the absorption edge due to the quantum confinement effect. The PL emission spectra of the ZnO–ZnS core–shell nanostructure are compared with the ZnO nanoparticles. The ZnO–ZnS core–shell nanostructures show decrease in the UV and green emissions with the appearance of a blue emission, which are not found in the ZnO nanoparticles. -- Highlights: • It has synthesised ZnO–ZnS core–shell type II in one-step for the first time. • The as-synthesised samples were characterised by using XRD, UV–vis. • The photoluminescence properties of ZnO–ZnS core–shell was compared with ZnO. • The UV and green emission in the PL spectrum of ZnO–ZnS core–shell decreased. • The blue emission in the PL spectrum of ZnO–ZnS core–shell appeared

  11. LOAD CARRYING CAPABILITY OF LIQUID FILLED CYLINDRICAL SHELL STRUCTURES UNDER AXIAL COMPRESSION

    Directory of Open Access Journals (Sweden)

    QASIM H. SHAH

    2011-08-01

    Full Text Available Empty and water filled cylindrical Tin (Sn coated steel cans were loaded under axial compression at varying loading rates to study their resistance to withstand accidental loads. Compared to empty cans the water filled cans exhibit greater resistance to axially applied compression loads before a complete collapse. The time and load or stroke and load plots showed three significant load peaks related to three stages during loading until the cylinder collapse. First peak corresponds to the initial structural buckling of can. Second peak occurs when cylindrical can walls gradually come into full contact with water. The third peak shows the maximum load carrying capability of the structure where pressurized water deforms the can walls into curved shape until can walls fail under peak pressure. The collapse process of water filled cylindrical shell was further studied using Smooth Particle Hydrodynamics (SPH technique in LSDYNA. Load peaks observed in the experimental work were successfully simulated which substantiated the experimental work.

  12. Optimal Sensor Placement for Latticed Shell Structure Based on an Improved Particle Swarm Optimization Algorithm

    Directory of Open Access Journals (Sweden)

    Xun Zhang

    2014-01-01

    Full Text Available Optimal sensor placement is a key issue in the structural health monitoring of large-scale structures. However, some aspects in existing approaches require improvement, such as the empirical and unreliable selection of mode and sensor numbers and time-consuming computation. A novel improved particle swarm optimization (IPSO algorithm is proposed to address these problems. The approach firstly employs the cumulative effective modal mass participation ratio to select mode number. Three strategies are then adopted to improve the PSO algorithm. Finally, the IPSO algorithm is utilized to determine the optimal sensors number and configurations. A case study of a latticed shell model is implemented to verify the feasibility of the proposed algorithm and four different PSO algorithms. The effective independence method is also taken as a contrast experiment. The comparison results show that the optimal placement schemes obtained by the PSO algorithms are valid, and the proposed IPSO algorithm has better enhancement in convergence speed and precision.

  13. Preparation, and Luminescence Properties of SiO2@Sm(MABA-Siphen Core-Shell Structure Nanometer Composite

    Directory of Open Access Journals (Sweden)

    Feng Li-Na

    2018-01-01

    Full Text Available A novel ternary samarium complex was prepared using HOOCC6H4N(CONH(CH23Si- (OCH2CH332 (MABA-Si as first ligand, and phen as second ligand. The corresponding SiO2@Sm(MABA-Siphen core-shell structure nanometer composite was synthesized as well, and the silica spheres was the core, and the ternary samarium complex was the shell layer. The ternary samarium complex has been characterized by element analysis, molar conductivity and IR spectra. The results show that the chemical formula of the complex is Sm(MABA-Si(phen2(ClO43·2H2O. The fluorescent spectra illustrat that the luminescence properties of the samarium complex are superior. The core-shell structure of SiO2@Sm(MABA-Siphen nanometer composite is characterized by SEM, TEM and IR spectra. The SiO2@Sm(MABA-Siphen core-shell structure composites exhibit stronger emission intensity than the ternary samarium complex. The fluorescence lifetime of the complex and core-shell structure composite is measured as well.

  14. Core/shell nano-structuring of metal oxide semiconductors and their photocatalytic studies

    Science.gov (United States)

    Balakumar, S.; Rakkesh, R. Ajay

    2013-02-01

    Core/Shell Nanostructures of Metal Oxide Semiconductors (MOS) have attracted much attention because of their most fascinating tunable applications. These core shell morphologies can be easily engineered to enhance the unique properties of the metal-oxide nanostructures, which make them suitable as photocatalyst due to their high catalytic activity, substantial stability, and brilliant perspective in applications. This paper provides an overview on our work on the synthesis of some interesting core/ shell nanostructures of MOS such as ZnO-TiO2, ZnO-MoO3, and V2O5-TiO2 using a low temperature wet chemical route and hydrothermal techniques and their photocatalytic properties from the aspects of different shell materials and shell thicknesses. The effect of process parameters such as pH, temperature, and ratio of core and shell materials, was systematically studied. Here the evidence for the core shell formation with different shell thicknesses came from the X-ray diffraction peak intensities. The shell thickness variation was also confirmed by Transmission Electron Microscopic studies. Effect of shell thickness on optical band gap of the core shell fabricated was also investigated using DRS UV-Visible spectroscopy. A comprehensive study was carried out for the photocatalytic efficiency of core shell nanostructures by evaluating the photo-degradation of Acridine Orange (AO) dye in aqueous solution under visible and solar light irradiations. These results offered simple approaches to the nanoscale engineering and synthesis of MOS hybrid systems to serve as better photocatalytic materials.

  15. Load requirements for maintaining structural integrity of Hanford single-shell tanks during waste feed delivery and retrieval activities

    International Nuclear Information System (INIS)

    JULYK, L.J.

    1999-01-01

    This document provides structural load requirements and their basis for maintaining the structural integrity of the Hanford Single-Shell Tanks during waste feed delivery and retrieval activities. The requirements are based on a review of previous requirements and their basis documents as well as load histories with particular emphasis on the proposed lead transfer feed tanks for the privatized vitrification plant

  16. Load requirements for maintaining structural integrity of Hanford single-shell tanks during waste feed delivery and retrieval activities

    Energy Technology Data Exchange (ETDEWEB)

    JULYK, L.J.

    1999-09-22

    This document provides structural load requirements and their basis for maintaining the structural integrity of the Hanford Single-Shell Tanks during waste feed delivery and retrieval activities. The requirements are based on a review of previous requirements and their basis documents as well as load histories with particular emphasis on the proposed lead transfer feed tanks for the privatized vitrification plant.

  17. Analysis of Chemical Bonding and Structural Network of Gold Silicide in Core-Shell Silicon Nanowire

    Science.gov (United States)

    Swain, Bibhu P.; Swain, Bhabani S.

    2018-02-01

    The Au-catalyzed core-shell silicon nanowires (Si-NWs) were synthesized by chemical vapor deposition by using SiH4 and H2 precursor gases. The TEM and FTIR studies revealed that the Si-NWs consist of core silicon surrounded by a thick oxide sheath and Au distributed at the a-SiOx/Si interface. The x-ray photoelectron spectroscopy (XPS) was used to study the chemical composition and electronic environments of gold silicide in the a-SiO x /Si-NWs. The elemental analysis and chemical network of gold silicide of core-shell Si-NWs were explained on the basis of the random atomic distribution of Si, O and Au atoms. The Raman spectra and XRD peak reveal the crystalline core of Si-NWs. The individual contribution to the Au (4d) core orbital was deconvoluted to Au-Si-Au, Au-Si-O, Au-Au, Au-O-Au, Au-O-Si and Au=O/Au-O2 bonding structure. The analysis shows that the O linked with Si and Au has also contributed to growth of Si-NWs.

  18. Wear Resistance and Mechanical Behaviour of Epoxy/Mollusk Shell Biocomposites developed for Structural Applications

    Directory of Open Access Journals (Sweden)

    I.O. Oladele

    2016-09-01

    Full Text Available Epoxy resin is one of the strongest commercially exploitable thermosetting polymers in the polymer family; however its expensive nature in comparison with other thermosetting polymers such as vinylester and polyester limits its applications as a structural material. Inexpensive fillers on the other hand, especially those derived from agro-industrial wastes are very important in reducing the overall cost of polymer composites and furthermore influential in enhancing some of their engineering properties. In the present study, the wear resistance and mechanical behaviour of epoxy polymer matrix filled with <75 and 75 μm calcined particles of African land snail shells have been comparatively investigated. The wear resistance and the mechanical behaviour of the composites were studied via Taber Abraser and INSTRON universal testing machine. Also, the elemental constituents of the calcined snail shell and the epoxy biocomposites were characterized by X-Ray Fluorescence Spectroscopy and Scanning Electron Microscopy/Energy Dispersion Spectroscopy. From the experimental results, it was observed that, at the highest filler loading, smaller particle size presented a biocomposite with significant enhancement in wear and mechanical properties. However, it was also observed that increase in particle size showed no significant enhancement in the mechanical properties of the biocomposites.

  19. Nickel oxide/polypyrrole/silver nanocomposites with core/shell/shell structure: Synthesis, characterization and their electrochemical behaviour with antimicrobial activities

    Energy Technology Data Exchange (ETDEWEB)

    Das, Dhaneswar; Nath, Bikash C. [Department of Chemical Sciences, Tezpur University, Tezpur 784028, Assam (India); Phukon, Pinkee [Department of Molecular Biology and Biotechnology, Tezpur University, Tezpur 784028, Assam (India); Saikia, Bhaskar J.; Kamrupi, Isha R. [Department of Chemical Sciences, Tezpur University, Tezpur 784028, Assam (India); Dolui, Swapan K., E-mail: dolui@tezu.ernet.in [Department of Chemical Sciences, Tezpur University, Tezpur 784028, Assam (India)

    2013-10-01

    Magnetic and conducting Nickel oxide–polypyrrole (NiO/PPy) nanoparticles with core–shell structure were prepared in the presence of Nickel oxide (NiO) in aqueous solution containing sodium dodecyl benzenesulfonate (SDBS) as a surfactant as well as dopant. A stable dispersion of silver (Ag) nanoparticles was synthesized by chemical (citrate reduction) method. NiO/PPy nanocomposites were added to the Ag colloid under stirring. Ag nanoparticles could be electrostatically attracted on the surface of NiO/PPy nanocomposites, leading to formation of NiO/PPy/Ag nanocomposites with core/shell/shell structure. The morphology, structure, particle size and composition of the products were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, cyclic voltammetry (CV) and current–voltage (I–V) analysis. The resultant nanocomposites have the good conductivity and excellent electrochemical and catalytic properties of PPy and Ag nanoparticles. Furthermore, the nanocomposites showed excellent antibacterial behaviour due to the presence of Ag nanoparticles in the composite. The thermal stability of NiO–PPy as well as NiO/PPy/Ag nanocomposites was higher than that of pristine PPy. Studies of IR spectra suggest that the increased thermal stability may be due to interactions between NiO and Ag nanoparticles with the PPy backbone. - Highlights: • NiO nanoparticles were synthesized by two step soft chemical synthesis route. • Ag nanoparticles were prepared by using citrate reduction method. • NiO/PPy nanocomposites are synthesized by chemical oxidative polymerization process. • NiO/PPy/Ag nanocomposites can be used in the water purification technology.

  20. Nickel oxide/polypyrrole/silver nanocomposites with core/shell/shell structure: Synthesis, characterization and their electrochemical behaviour with antimicrobial activities

    International Nuclear Information System (INIS)

    Das, Dhaneswar; Nath, Bikash C.; Phukon, Pinkee; Saikia, Bhaskar J.; Kamrupi, Isha R.; Dolui, Swapan K.

    2013-01-01

    Magnetic and conducting Nickel oxide–polypyrrole (NiO/PPy) nanoparticles with core–shell structure were prepared in the presence of Nickel oxide (NiO) in aqueous solution containing sodium dodecyl benzenesulfonate (SDBS) as a surfactant as well as dopant. A stable dispersion of silver (Ag) nanoparticles was synthesized by chemical (citrate reduction) method. NiO/PPy nanocomposites were added to the Ag colloid under stirring. Ag nanoparticles could be electrostatically attracted on the surface of NiO/PPy nanocomposites, leading to formation of NiO/PPy/Ag nanocomposites with core/shell/shell structure. The morphology, structure, particle size and composition of the products were characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, cyclic voltammetry (CV) and current–voltage (I–V) analysis. The resultant nanocomposites have the good conductivity and excellent electrochemical and catalytic properties of PPy and Ag nanoparticles. Furthermore, the nanocomposites showed excellent antibacterial behaviour due to the presence of Ag nanoparticles in the composite. The thermal stability of NiO–PPy as well as NiO/PPy/Ag nanocomposites was higher than that of pristine PPy. Studies of IR spectra suggest that the increased thermal stability may be due to interactions between NiO and Ag nanoparticles with the PPy backbone. - Highlights: • NiO nanoparticles were synthesized by two step soft chemical synthesis route. • Ag nanoparticles were prepared by using citrate reduction method. • NiO/PPy nanocomposites are synthesized by chemical oxidative polymerization process. • NiO/PPy/Ag nanocomposites can be used in the water purification technology

  1. Core-Shell Structuring of Pure Metallic Aerogels towards Highly Efficient Platinum Utilization for the Oxygen Reduction Reaction.

    Science.gov (United States)

    Cai, Bin; Hübner, René; Sasaki, Kotaro; Zhang, Yuanzhe; Su, Dong; Ziegler, Christoph; Vukmirovic, Miomir B; Rellinghaus, Bernd; Adzic, Radoslav R; Eychmüller, Alexander

    2018-03-05

    The development of core-shell structures remains a fundamental challenge for pure metallic aerogels. Here we report the synthesis of Pd x Au-Pt core-shell aerogels composed of an ultrathin Pt shell and a composition-tunable Pd x Au alloy core. The universality of this strategy ensures the extension of core compositions to Pd transition-metal alloys. The core-shell aerogels exhibited largely improved Pt utilization efficiencies for the oxygen reduction reaction and their activities show a volcano-type relationship as a function of the lattice parameter of the core substrate. The maximum mass and specific activities are 5.25 A mg Pt -1 and 2.53 mA cm -2 , which are 18.7 and 4.1 times higher than those of Pt/C, respectively, demonstrating the superiority of the core-shell metallic aerogels. The proposed core-based activity descriptor provides a new possible strategy for the design of future core-shell electrocatalysts. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Study on core–shell–shell structured nanoparticles with magnetic and luminescent features: Construction, characterization and oxygen-sensing behavior

    International Nuclear Information System (INIS)

    Min, BU; Wenzhong, Ma

    2013-01-01

    In this paper, we construct core–shell–shell structured nanoparticles, where magnetic Fe 3 O 4 nanoparticles are used as the inner core, mesoporous silica functionalized with phosphorescent Ru(II) complex is used as the outer shell, and the middle shell which is composed of amorphous silica is introduced to minimize the negative effect from the inner core on the sensing probes. The obtained magnetic–luminescent composite nanoparticles are characterized by XRD analysis, IR spectrum, electron microscopy, fluorescence microscopy, thermogravimetric analysis and nitrogen adsorption and desorption, confirming the core–shell–shell structure. The magnetic and photophysical properties of the composite nanoparticles are investigated in detail. Data suggest that the nanoparticles show a smaller saturation magnetization value compared with that of Fe 3 O 4 nanoparticles. The composite namoparticles are red-emitting ones, and the emission is sensitive towards oxygen concentration variations with sensitivity of 4.1 and response time of 7 s. -- Highlights: • Core–shell–shell structured nanoparticles have been constructed. • The nanoparticles have been fully characterized and studied. • The nanoparticles own magnetic, luminescent and oxygen-sensing features. • Good sensitivity, short response time and high photostability have been realized

  3. Coaxial Electrospinning and Characterization of Core-Shell Structured Cellulose Nanocrystal Reinforced PMMA/PAN Composite Fibers

    Science.gov (United States)

    Li, Chao; Li, Qingde; Ni, Xiaohui; Liu, Guoxiang; Cheng, Wanli; Han, Guangping

    2017-01-01

    A modified coaxial electrospinning process was used to prepare composite nanofibrous mats from a poly(methyl methacrylate) (PMMA) solution with the addition of different cellulose nanocrystals (CNCs) as the sheath fluid and polyacrylonitrile (PAN) solution as the core fluid. This study investigated the conductivity of the as-spun solutions that increased significantly with increasing CNCs addition, which favors forming uniform fibers. This study discussed the effect of different CNCs addition on the morphology, thermal behavior, and the multilevel structure of the coaxial electrospun PMMA + CNCs/PAN composite nanofibers. A morphology analysis of the nanofibrous mats clearly demonstrated that the CNCs facilitated the production of the composite nanofibers with a core-shell structure. The diameter of the composite nanofibers decreased and the uniformity increased with increasing CNCs concentrations in the shell fluid. The composite nanofibrous mats had the maximum thermal decomposition temperature that was substantially higher than electrospun pure PMMA, PAN, as well as the core-shell PMMA/PAN nanocomposite. The BET (Brunauer, Emmett and Teller) formula results showed that the specific surface area of the CNCs reinforced core-shell composite significantly increased with increasing CNCs content. The specific surface area of the composite with 20% CNCs loading rose to 9.62 m2/g from 3.76 m2/g for the control. A dense porous structure was formed on the surface of the electrospun core-shell fibers. PMID:28772933

  4. Coaxial Electrospinning and Characterization of Core-Shell Structured Cellulose Nanocrystal Reinforced PMMA/PAN Composite Fibers.

    Science.gov (United States)

    Li, Chao; Li, Qingde; Ni, Xiaohui; Liu, Guoxiang; Cheng, Wanli; Han, Guangping

    2017-05-24

    A modified coaxial electrospinning process was used to prepare composite nanofibrous mats from a poly(methyl methacrylate) (PMMA) solution with the addition of different cellulose nanocrystals (CNCs) as the sheath fluid and polyacrylonitrile (PAN) solution as the core fluid. This study investigated the conductivity of the as-spun solutions that increased significantly with increasing CNCs addition, which favors forming uniform fibers. This study discussed the effect of different CNCs addition on the morphology, thermal behavior, and the multilevel structure of the coaxial electrospun PMMA + CNCs/PAN composite nanofibers. A morphology analysis of the nanofibrous mats clearly demonstrated that the CNCs facilitated the production of the composite nanofibers with a core-shell structure. The diameter of the composite nanofibers decreased and the uniformity increased with increasing CNCs concentrations in the shell fluid. The composite nanofibrous mats had the maximum thermal decomposition temperature that was substantially higher than electrospun pure PMMA, PAN, as well as the core-shell PMMA/PAN nanocomposite. The BET (Brunauer, Emmett and Teller) formula results showed that the specific surface area of the CNCs reinforced core-shell composite significantly increased with increasing CNCs content. The specific surface area of the composite with 20% CNCs loading rose to 9.62 m²/g from 3.76 m²/g for the control. A dense porous structure was formed on the surface of the electrospun core-shell fibers.

  5. One-pot reverse microemulsion synthesis of core-shell structured YVO4:Eu3+@SiO2 nanocomposites

    Science.gov (United States)

    Liu, Lina; Yue, Surong; Zhang, Yongsheng; Qin, Ruifei; Liu, Lishuang; Zhang, Dongmei; Sun, Ruirui; Chen, Linfeng

    2015-01-01

    Core-shell structured YVO4:Eu3+@SiO2 nanocomposite particles were synthesized using a one-pot reverse microemulsion method and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), UV absorption spectra, and photoluminescent spectra. The nanocomposite particles are well-dispersed and about 20 nm in average size. The synthesis method is of one-pot, simplifying the preparation of this kind of core-shell structured nanocomposites. The formation process of these nanocomposite particles is suggested and the photoluminescence properties of them are studied and compared with those of uncoated YVO4:Eu3+ sample.

  6. Physical mechanism of surface roughening of the radial Ge-core/Si-shell nanowire heterostructure and thermodynamic prediction of surface stability of the InAs-core/GaAs-shell nanowire structure.

    Science.gov (United States)

    Cao, Y Y; Ouyang, G; Wang, C X; Yang, G W

    2013-02-13

    As a promising and typical semiconductor heterostructure at the nanoscale, the radial Ge/Si NW heterostructure, that is, the Ge-core/Si-shell NW structure, has been widely investigated and used in various nanodevices such as solar cells, lasers, and sensors because of the strong changes in the band structure and increased charge carrier mobility. Therefore, to attain high quality radial semiconductor NW heterostructures, controllable and stable epitaxial growth of core-shell NW structures has become a major challenge for both experimental and theoretical evaluation. Surface roughening is usually undesirable for the epitaxial growth of high quality radial semiconductor NW heterostructures, because it would destroy the core-shell NW structures. For example, the surface of the Ge-core/Si-shell NWs always exhibits a periodic modulation with island-like morphologies, that is, surface roughening, during epitaxial growth. Therefore, the physical understanding of the surface roughening behavior during the epitaxial growth of core-shell NW structures is essential and urgent for theoretical design and experimentally controlling the growth of high quality radial semiconductor NW heterostructures. Here, we proposed a quantitative thermodynamic theory to address the physical process of epitaxial growth of core-shell NW structures and surface roughening. We showed that the transformation from the Frank-van der Merwe mode to the Stranski-Krastanow mode during the epitaxial growth of radial semiconductor NW heterostructures is the physical origin of surface roughening. We deduced the thermodynamic criterion for the formation of the surface roughening and the phase diagram of growth and showed that the radius of the NWs and the thickness of the shell layer can not only determine the formation of the surface roughening in a core-shell NW structure, but also control the periodicity and amplitude of the surface roughness. The agreement between the theoretical results and the

  7. Accelerated safety analyses - structural analyses Phase I - structural sensitivity evaluation of single- and double-shell waste storage tanks

    International Nuclear Information System (INIS)

    Becker, D.L.

    1994-11-01

    Accelerated Safety Analyses - Phase I (ASA-Phase I) have been conducted to assess the appropriateness of existing tank farm operational controls and/or limits as now stipulated in the Operational Safety Requirements (OSRs) and Operating Specification Documents, and to establish a technical basis for the waste tank operating safety envelope. Structural sensitivity analyses were performed to assess the response of the different waste tank configurations to variations in loading conditions, uncertainties in loading parameters, and uncertainties in material characteristics. Extensive documentation of the sensitivity analyses conducted and results obtained are provided in the detailed ASA-Phase I report, Structural Sensitivity Evaluation of Single- and Double-Shell Waste Tanks for Accelerated Safety Analysis - Phase I. This document provides a summary of the accelerated safety analyses sensitivity evaluations and the resulting findings

  8. Brake performance of core–shell structured carbonyl iron/silica based magnetorheological suspension

    International Nuclear Information System (INIS)

    Nguyen, Phuong-Bac; Do, Xuan-Phu; Jeon, Juncheol; Choi, Seung-Bok; Liu, Ying Dan; Choi, Hyoung Jin

    2014-01-01

    Chemically stable core–shell structured magnetic particles were synthesized by coating soft-magnetic carbonyl iron (CI) microspheres with silica through a sol–gel reaction, and applied as magnetorheological (MR) materials for a specially designed small-sized MR brake. The dynamic yield stress of the MR suspension containing the synthesized particles was also measured using a rotational rheometer under an applied magnetic field. The performance characteristics of the MR brake, including field dependent torque, hysteresis, time and torque tracking control responses were examined. The results showed that with the exception of the settling time, the other response times were faster than those of the pristine CI based MR fluid. - Highlights: • Silica coated magnetic particle was fabricated as magnetorheological (MR) material. • Small-sized MR brake of disc-type was specially designed. • MR fluid based on silica coated particles exhibited improved tracking accuracy

  9. A 3-NODE PIEZOELECTRIC SHELL ELEMENT FOR LINEAR AND GEOMETRICALLY NONLINEAR DYNAMIC ANALYSIS OF SMART STRUCTURES

    Directory of Open Access Journals (Sweden)

    Gil Rama

    2017-04-01

    Full Text Available Composite laminates consisting of passive and multi-functional materials represent a powerful material system. Passive layers could be made of isotropic materials or fiber-reinforced composites, while piezoelectric ceramics are considered here as a multi-functional material. The paper is focused on  linear and geometrically nonlinear dynamic analysis of smart structures made of such a material system. For this purpose, a linear 3-node shell element is used. It employs the Mindlin-Reissner kinematics and the discrete shear gap (DSG technique to alleviate the transverse shear locking effects. The electric potential is assumed to vary linearly through the thickness for each piezoelectric layer. A co-rotational formulation is used to handle the geometrically nonlinear effects. A number of examples involving actuator and sensor application of piezoelectric layers are considered. For the validation purposes, the results available in the literature and those computed in Abaqus are used as a reference.

  10. Manifestation of shell structure in the characteristics of the products of the reaction Zn+Sn

    Energy Technology Data Exchange (ETDEWEB)

    Zodan, H.; Luk' yanov, S. M.; Penionzhkevich, Y. E.; Salamatin, V. S.; Chubaryan, G. G.; Heidel, K.; Pop, A.; Schilling, K. D.; Will, E.; Gippner, P.; and others

    1989-01-01

    We report measurements of the yield of products as a function of their mass and total kinetic energy (TKE) in reactions induced by /sup 64/Zn ions in targets of silver, tin, and lanthanum at various beam energies above the Coulomb barrier. In the dependences presented for reactions with magic nuclei of tin, in contrast to those measured in other targets, a yield of projectile-like and target-like products is observed at TKE values less than the entrance Coulomb barrier. The observed properties of the spectrum shapes can be associated with the structure of the interacting nuclei, specifically with the /ital Z/=50 shell of tin nuclei, which is responsible for preserving the individual properties of the target nuclei.

  11. A novel approach to preparing magnetic protein microspheres with core-shell structure

    Science.gov (United States)

    Jiang, Wei; Sun, Zhendong; Li, Fengsheng; Chen, Kai; Liu, Tianyu; Liu, Jialing; Zhou, Tianle; Guo, Rui

    2011-03-01

    Magnetic protein microspheres with core-shell structure were prepared through a novel approach based on the sonochemical method and the emulsion solvent evaporation method. The microspheres are composed of the oleic acid and undecylenic acid modified Fe 3O 4 cores and coated with globular bovine serum albumin (BSA). Under an optimized condition, up to 57.8 wt% of approximately 10 nm superparamagnetic Fe 3O 4 nanoparticles could be uniformly encapsulated into the BSA microspheres with the diameter of approximately 160 nm and the high saturation magnetization of 38.5 emu/g, besides of the abundant functional groups. The possible formation mechanism of magnetic microspheres was discussed in detail.

  12. Soil structure interaction analysis for the Hanford Site 241-SY-101 double-shell waste storage tanks

    International Nuclear Information System (INIS)

    Giller, R.A.; Weiner, E.O.

    1991-09-01

    The 241-SY-101 tank is a double-shell waste storage tank buried in the 241-SY tank farm in the 200 West Area of the Hanford Site. This analysis addresses the effects of seismic soil-structure interaction on the tank structure and includes a parametric soil-structure interaction study addressing three configurations: two-dimensional soil structure, a two-dimensional structure-soil-structure, and a three-dimensional soil-structure interaction. This study was designed to determine an optimal method for addressing seismic-soil effects on underground storage tanks. The computer programs calculate seismic-soil pressures on the double-shell tank walls and and seismic acceleration response spectra in the tank. The results of this soil-structure interaction parametric study as produced by the computer programs are given in terms of seismic soil pressures and response spectra. The conclusions of this soil-structure interaction evaluation are that dynamically calculated soil pressures in the 241-SY-101 tank are significantly reduce from those using standard hand calculation methods and that seismic evaluation of underground double-shell waste storage tanks must consider soil-structure interaction effects in order to predict conservative structural response. Appendixes supporting this study are available in Volume 2 of this report

  13. Core-shell structure of degradable, thermosensitive polymeric micelles studied by small-angle neutron scattering.

    Science.gov (United States)

    Ramzi, Aissa; Rijcken, Cristianne J F; Veldhuis, Theo F J; Schwahn, Dietmar; Hennink, Wim E; van Nostrum, Cornelus F

    2008-01-24

    The structure of assemblies of block copolymers composed of thermosensitive, biodegradable poly(N-(2-hydroxypropyl) methacrylamide-dilactate) and poly(ethylene glycol) (pHPMAmDL-b-PEG) has been studied by small-angle neutron scattering (SANS). Three amphiphilic copolymers with a fixed PEG of 5 kDa and a partially deuterated pHPMAmDL(d) block of 6700, 10400, or 21200 Da were used to form micelles in aqueous media by heating the polymeric solution from below to above the cloud point temperature (around 10 degrees C) of the thermosensitive block. Simultaneous and quantitative analysis of the scattering cross sections obtained at three different solvent contrasts is expedited using core-shell model, which assumed a homogeneous core of uniform scattering length density. The mean core radius increased from 13 to 18.5 nm with the molecular weight of the pHPMAmDL(d) block, while the thickness of the stabilizing PEG layer was around 8 nm for the three investigated assemblies. In addition, the volume fraction values of the stabilizing PEG chains in the shell are low and decreased from 31% to 14% with increasing the size of pHPMAmDL(d) block which shows that the shell layer of the assemblies is highly hydrated. The corresponding PEG chain grafting densities decreased from 0.22 to 0.11 nm-2 and the distance between PEG chains on the nanoparticles surface increased from 2.4 to 3.4 nm. The pHPMAmDL-b-PEG micelles showed a controlled instability due to hydrolysis of the lactic acid side groups in the thermosensitive block; that is, an increase of the degradation time leads to an increase of the size of the core which becomes less hydrophobic and consequently more hydrated. Neutron experiments supplied accurate information on how the size of the core and the micelle's aggregation number changed with the incubation time. This feature and the initially small size and dense structure in aqueous solution make the polymeric micelles suitable as carriers for hydrophobic drugs.

  14. Numerical simulation of deformation and fracture of space protective shell structures from concrete and fiber concrete under pulse loading

    International Nuclear Information System (INIS)

    Radchenko, P A; Batuev, S P; Radchenko, A V; Plevkov, V S

    2015-01-01

    This paper presents results of numerical simulation of interaction between aircraft Boeing 747-400 and protective shell of nuclear power plant. The shell is presented as complex multilayered cellular structure comprising layers of concrete and fiber concrete bonded with steel trusses. Numerical simulation was held three-dimensionally using the author's algorithm and software taking into account algorithms for building grids of complex geometric objects and parallel computations. The dynamics of stress-strain state and fracture of structure were studied. Destruction is described using two-stage model that allows taking into account anisotropy of elastic and strength properties of concrete and fiber concrete. It is shown that wave processes initiate destruction of shell cellular structure—cells start to destruct in unloading wave, originating after output of compression wave to the free surfaces of cells. (paper)

  15. Gate voltage and structure parameter modulated spin splitting in AlGaN/GaN quantum wells

    Energy Technology Data Exchange (ETDEWEB)

    Li, M.; Zhang, R.; Zhang, Z.; Liu, B.; Fu, Deyi; Zhao, C.Z.; Xie, Z.L.; Xiu, X.Q.; Zheng, Y.D. [Nanjing National Lab of Microstructures, Jiangsu Provincial Key Laboratory of Advanced Photonic and Electronic Materials and Department of Physics, Nanjing University, Nanjing 210093 (China)

    2011-01-15

    In this paper, considerable magnitude of spin splitting for the conduction subband at the Fermi energy is obtained in AlGaN quantum wells (QWs) grown along the c-axis. We have analyzed how the magnitude of spin splitting of the first electron subband in AlGaN QWs with different sheet carrier concentration changes as a function of applied gate voltage, well width, and Al content in the barrier. It is also found that the contribution to spin splitting from Dresselhaus term is much larger than that from Rashba term, the contribution of Dresselhaus term to the total spin splitting depends greatly on the carrier concentrations, the change of well width has little effect on total spin splitting, and the magnitude of spin splitting can be greatly modulated by Al content in the barrier, gate voltage, and sheet carrier concentration. The internal polarized electric field is crucial for considerable spin splitting in III-nitride QWs. Moreover, the magnitude of total spin splitting calculated here is comparable with other theoretical and experimental values observed in III-nitride heterostructures. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  16. Core-shell structured titanium-nitrogen alloys with high strength, high thermal stability and good plasticity.

    Science.gov (United States)

    Zhang, Y S; Zhao, Y H; Zhang, W; Lu, J W; Hu, J J; Huo, W T; Zhang, P X

    2017-01-06

    Multifunctional materials with more than two good properties are widely required in modern industries. However, some properties are often trade-off with each other by single microstructural designation. For example, nanostructured materials have high strength, but low ductility and thermal stability. Here by means of spark plasma sintering (SPS) of nitrided Ti particles, we synthesized bulk core-shell structured Ti alloys with isolated soft coarse-grained Ti cores and hard Ti-N solid solution shells. The core-shell Ti alloys exhibit a high yield strength (~1.4 GPa) comparable to that of nanostructured states and high thermal stability (over 1100 °C, 0.71 of melting temperature), contributed by the hard Ti-N shells, as well as a good plasticity (fracture plasticity of 12%) due to the soft Ti cores. Our results demonstrate that this core-shell structure offers a design pathway towards an advanced material with enhancing strength-plasticity-thermal stability synergy.

  17. Enhancing oxidative stability in heated oils using core/shell structures of collagen and α-tocopherol complex.

    Science.gov (United States)

    Gim, Seo Yeong; Hong, Seungmi; Kim, Jisu; Kwon, YongJun; Kim, Mi-Ja; Kim, GeunHyung; Lee, JaeHwan

    2017-11-15

    In this study, collagen mesh structure was prepared by carrying α-tocopherol in the form of core/shell complex. Antioxidant properties of α-tocopherol loaded carriers were tested in moisture added bulk oils at 140°C. From one gram of collagen core/shell complex, 138mg α-tocopherol was released in medium chain triacylglycerol (MCT). α-Tocopherol was substantially protected against heat treatment when α-tocopherol was complexed in collagen core/shell. Oxidative stability in bulk oil was significantly enhanced by added collagen mesh structure or collagen core/shell complex with α-tocopherol compared to that in control bulk oils (pshell with α-tocopherol (p>0.05). Results of DPPH loss in methanol demonstrated that collagen core/shell with α-tocopherol had significantly (pshell complex is a promising way to enhance the stability of α-tocopherol and oxidative stability in oil-rich foods prepared at high temperature. Copyright © 2017 Elsevier Ltd. All rights reserved.

  18. Controlled growth of Ni/NiO core–shell nanoparticles: Structure, morphology and tuning of magnetic properties

    Energy Technology Data Exchange (ETDEWEB)

    D’Addato, S., E-mail: sergio.daddato@unimore.it [CNR-NANO, S3, via G. Campi 213/a, Modena (Italy); Dipartimento FIM, Università di Modena e Reggio Emilia, via G. Campi 213/a, Modena (Italy); Spadaro, M.C. [CNR-NANO, S3, via G. Campi 213/a, Modena (Italy); Dipartimento FIM, Università di Modena e Reggio Emilia, via G. Campi 213/a, Modena (Italy); Luches, P. [CNR-NANO, S3, via G. Campi 213/a, Modena (Italy); Grillo, V. [CNR-NANO, S3, via G. Campi 213/a, Modena (Italy); CNR-IMEM, Parco Area delle Scienze 37/A, 43100 Parma (Italy); Frabboni, S.; Valeri, S. [CNR-NANO, S3, via G. Campi 213/a, Modena (Italy); Dipartimento FIM, Università di Modena e Reggio Emilia, via G. Campi 213/a, Modena (Italy); Ferretti, A.M.; Capetti, E.; Ponti, A. [CNR-ISTM, Laboratorio di Nanotecnologie, via G. Fantoli 16/15, 20138 Milano (Italy)

    2014-07-01

    We performed a detailed study of Ni/NiO core–shell nanoparticles (NP) obtained with a gas aggregation source. The NP oxide shells were produced by oxidizing the NP with different procedures: deposition in oxygen atmosphere, post-annealing in air, sequential deposition of (a) first NiO layer, (b) Ni NP and (c) third NiO Layer. X-ray photoelectron spectroscopy from Ni 2p core-level gave information about the chemical state of Ni in the core and in the oxide shell, while scanning electron microscopy was used for investigation of the NP morphology. High quality scanning transmission electron microscopy in high angle annular dark field mode data demonstrated core–shell structure also for NiO/Ni NP/NiO samples. Field-cooled/zero-field-cooled magnetization curves and field-cooled isothermal hysteresis cycles at T = 5 K were recorded by a SQUID magnetometer. In this way, the relation between magnetic properties and oxide shell structure was assessed, showing the role played by the control of the formation of oxide on the exchange bias and interparticle magnetic interaction.

  19. Controlled growth of Ni/NiO core–shell nanoparticles: Structure, morphology and tuning of magnetic properties

    International Nuclear Information System (INIS)

    D’Addato, S.; Spadaro, M.C.; Luches, P.; Grillo, V.; Frabboni, S.; Valeri, S.; Ferretti, A.M.; Capetti, E.; Ponti, A.

    2014-01-01

    We performed a detailed study of Ni/NiO core–shell nanoparticles (NP) obtained with a gas aggregation source. The NP oxide shells were produced by oxidizing the NP with different procedures: deposition in oxygen atmosphere, post-annealing in air, sequential deposition of (a) first NiO layer, (b) Ni NP and (c) third NiO Layer. X-ray photoelectron spectroscopy from Ni 2p core-level gave information about the chemical state of Ni in the core and in the oxide shell, while scanning electron microscopy was used for investigation of the NP morphology. High quality scanning transmission electron microscopy in high angle annular dark field mode data demonstrated core–shell structure also for NiO/Ni NP/NiO samples. Field-cooled/zero-field-cooled magnetization curves and field-cooled isothermal hysteresis cycles at T = 5 K were recorded by a SQUID magnetometer. In this way, the relation between magnetic properties and oxide shell structure was assessed, showing the role played by the control of the formation of oxide on the exchange bias and interparticle magnetic interaction.

  20. Structural Changes in the Mn4Ca Cluster and the Mechanism of Photosynthetic Water Splitting

    Energy Technology Data Exchange (ETDEWEB)

    Pushkar, Y.; Yano, J.; Sauer, K.; Boussac, A.; Yachandra, V.K.

    2007-10-25

    Photosynthetic water oxidation, where water is oxidized to dioxygen, is a fundamental chemical reaction that sustains the biosphere. This reaction is catalyzed by a Mn4Ca complex in the photosystem II (PS II) oxygen-evolving complex (OEC): a multiproteinassembly embedded in the thylakoid membranes of green plants, cyanobacteria, and algae. The mechanism of photosynthetic water oxidation by the Mn4Ca cluster in photosystem II is the subject of much debate, although lacking structural characterization of the catalytic intermediates. Biosynthetically exchanged Ca/Sr-PS II preparations and x-ray spectroscopy, including extended x-ray absorption fine structure (EXAFS), allowed us to monitor Mn-Mn and Ca(Sr)-Mn distances in the four intermediate S states, S0 through S3, of the catalytic cycle that couples the one-electron photochemistry occurring at the PS II reaction center with the four-electron water-oxidation chemistry taking place at the Mn4Ca(Sr) cluster. We have detected significant changes in the structure of the complex, especially in the Mn-Mn and Ca(Sr)-Mn distances, on the S2-to-S3 and S3-to-S0 transitions. These results implicate the involvement of at least one common bridging oxygen atom between the Mn-Mn and Mn-Ca(Sr) atoms in the O-O bond formation. Because PS II cannot advance beyond the S2 state in preparations that lack Ca(Sr), these results show that Ca(Sr) is one of the critical components in the mechanism of the enzyme. The results also show that Ca is not just a spectator atom involved in providing a structural framework, but is actively involved in the mechanism of water oxidation and represents a rare example of a catalytically active Ca cofactor.

  1. Isolation and Structural Characterization of a Mackay 55-Metal-Atom Two-Shell Icosahedron of Pseudo-Ih Symmetry, Pd55L12(μ3-CO)20 (L = PR3, R = Isopropyl): Comparative Analysis with Interior Two-Shell Icosahedral Geometries in Capped Three-Shell Pd145, Pt-Centered Four-Shell Pd-Pt M165, and Four-Shell Au133 Nanoclusters.

    Science.gov (United States)

    Erickson, Jeremiah D; Mednikov, Evgueni G; Ivanov, Sergei A; Dahl, Lawrence F

    2016-02-10

    We present the first successful isolation and crystallographic characterization of a Mackay 55-metal-atom two-shell icosahedron, Pd55L12(μ3-CO)20 (L = PPr(i)3) (1). Its two-shell icosahedron of pseudo-Ih symmetry (without isopropyl substituents) enables a structural/bonding comparison with interior 55-metal-atom two-shell icosahedral geometries observed within the multi-shell capped 145-metal-atom three-shell Pd145(CO)72(PEt3)30 and 165-metal-atom four-shell Pt-centered (μ12-Pt)Pd164-xPtx(CO)72(PPh3)20 (x ≈ 7) nanoclusters, and within the recently reported four-shell Au133(SC6H4-p-Bu(t))52 nanocluster. DFT calculations carried out on a Pd55(CO)20(PH3)12 model analogue, with triisopropyl phosphine substituents replaced by H atoms, revealed a positive +0.84 e charge for the entire Pd55 core, with a highly positive second-shell Pd42 surface of +1.93 e.

  2. Effect of the STereoLithography file structure on the ear shell production for hearing aids according to DICOM images

    Energy Technology Data Exchange (ETDEWEB)

    KIm, Hyeong Gyun [Dept. of Radiological Science, Far East University, Eumseong (Korea, Republic of)

    2017-03-15

    A technique for producing the ear shell for a hearing aid using DICOM (Digital Imaging and Communication in Medicine) image and a 3D printing was studied. It is a new application method, and is an application technique that can improve the safety and infection of hearing aid users and can reduce the production time and process stages. In this study, the effects on the shape surface were examined before and after the printing of the ear shell using a 3D printer based on the values obtained from the raw data of the DICOM images at the volumes of 0.5 mm, 1.0 mm, and 2.0 mm, respectively. Before the printing, relative relationship was compared with respect to the STL (STereoLithography) file structure; and after the printing, the intervals of the layered structure of the ear shell shape surface were compared by magnifying them using a microscope. For the STL file structure, the numbers of triangular vertices, more than five intersecting points, and maximum intersecting points were large in the order of 0.5 mm, 1.0 m, and 2.0 mm, respectively; and the triangular structure was densely distributed in the order of the bending, angle, and crest regions depending on the sinuosity of the external auditory meatus shape. As for the ear shell shape surface examined by the digital microscope, the interval of the layered structure was thick in the order of 2.0 mm, 1.0 mm, and 0.5 mm. For the STL surface structure mentioned above, the intersecting STL triangular structure was denser as the sinuosity of the 3D ear shell shape became more irregular and the volume of the raw data decreased.

  3. Effect of the STereoLithography file structure on the ear shell production for hearing aids according to DICOM images

    International Nuclear Information System (INIS)

    KIm, Hyeong Gyun

    2017-01-01

    A technique for producing the ear shell for a hearing aid using DICOM (Digital Imaging and Communication in Medicine) image and a 3D printing was studied. It is a new application method, and is an application technique that can improve the safety and infection of hearing aid users and can reduce the production time and process stages. In this study, the effects on the shape surface were examined before and after the printing of the ear shell using a 3D printer based on the values obtained from the raw data of the DICOM images at the volumes of 0.5 mm, 1.0 mm, and 2.0 mm, respectively. Before the printing, relative relationship was compared with respect to the STL (STereoLithography) file structure; and after the printing, the intervals of the layered structure of the ear shell shape surface were compared by magnifying them using a microscope. For the STL file structure, the numbers of triangular vertices, more than five intersecting points, and maximum intersecting points were large in the order of 0.5 mm, 1.0 m, and 2.0 mm, respectively; and the triangular structure was densely distributed in the order of the bending, angle, and crest regions depending on the sinuosity of the external auditory meatus shape. As for the ear shell shape surface examined by the digital microscope, the interval of the layered structure was thick in the order of 2.0 mm, 1.0 mm, and 0.5 mm. For the STL surface structure mentioned above, the intersecting STL triangular structure was denser as the sinuosity of the 3D ear shell shape became more irregular and the volume of the raw data decreased

  4. The influence of the sagittal split osteotomy on the condylar cartilage structure and the subchondral vascularization of the temporomandibular joint: a preliminary study in goats.

    NARCIS (Netherlands)

    Borstlap, W.A.; Maltha, J.C.; Stoelinga, P.J.W.; Hoff, J.W. Von den

    2005-01-01

    OBJECTIVE: The concern that a sagittal split osteotomy of the mandibular ramus could compromise the subchondral vascularization and especially the venous outflow in the condylar area, which in turn could influence the structure of the condylar cartilage, prompted this preliminary study on goats.

  5. Splitting Descartes

    DEFF Research Database (Denmark)

    Schilhab, Theresa

    2007-01-01

    Kognition og Pædagogik vol. 48:10-18. 2003 Short description : The cognitivistic paradigm and Descartes' view of embodied knowledge. Abstract: That the philosopher Descartes separated the mind from the body is hardly news: He did it so effectively that his name is forever tied to that division....... But what exactly is Descartes' point? How does the Kartesian split hold up to recent biologically based learning theories?...

  6. Nanospheres with a smectic hydrophobic core and an amorphous PEG hydrophilic shell: structural changes and implications for drug delivery

    Energy Technology Data Exchange (ETDEWEB)

    Murthy, N. Sanjeeva [New Jersey Center for Biomaterials; Rutgers; The State University of New Jersey; Piscataway; USA; Zhang, Zheng [New Jersey Center for Biomaterials; Rutgers; The State University of New Jersey; Piscataway; USA; Borsadia, Siddharth [New Jersey Center for Biomaterials; Rutgers; The State University of New Jersey; Piscataway; USA; Kohn, Joachim [New Jersey Center for Biomaterials; Rutgers; The State University of New Jersey; Piscataway; USA

    2018-01-01

    The structural changes in nanospheres with a crystalline core and an amorphous diffuse shell were investigated by small-angle neutron scattering (SANS), small-, medium-, and wide-angle X-ray scattering (SAXS, MAXS and WAXS), and differential scanning calorimetry (DSC).

  7. Rheological properties of magnetorheological suspensions based on core–shell structured polyaniline-coated carbonyl iron particles

    Czech Academy of Sciences Publication Activity Database

    Sedlačík, M.; Pavlínek, V.; Sáha, P.; Švrčinová, Petra; Filip, Petr; Stejskal, Jaroslav

    2010-01-01

    Roč. 19, č. 11 (2010), s. 115008 ISSN 0964-1726 R&D Projects: GA ČR GA202/09/1626 Institutional research plan: CEZ:AV0Z20600510; CEZ:AV0Z40500505 Keywords : magnetorheology * core - shell structure * polyaniline Subject RIV: BK - Fluid Dynamics Impact factor: 2.094, year: 2010

  8. Facile Synthesis of Yolk/Core-Shell Structured TS-1@Mesosilica Composites for Enhanced Hydroxylation of Phenol

    KAUST Repository

    Zou, Houbing

    2015-12-14

    © 2015 by the authors. In the current work, we developed a facile synthesis of yolk/core-shell structured TS-1@mesosilica composites and studied their catalytic performances in the hydroxylation of phenol with H2O2 as the oxidant. The core-shell TS-1@mesosilica composites were prepared via a uniform coating process, while the yolk-shell TS-1@mesosilica composite was prepared using a resorcinol-formaldehyde resin (RF) middle-layer as the sacrificial template. The obtained materials were characterized by X-ray diffraction (XRD), N2 sorption, Fourier transform infrared spectoscopy (FT-IR) UV-Visible spectroscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The characterization results showed that these samples possessed highly uniform yolk/core-shell structures, high surface area (560–700 m2 g−1) and hierarchical pore structures from oriented mesochannels to zeolite micropores. Importantly, owing to their unique structural properties, these composites exhibited enhanced activity, and also selectivity in the phenol hydroxylation reaction.

  9. Determination of the bending and buckling effect in the stress analysis of shell structures accessible from one side only

    Science.gov (United States)

    Dose, A

    1941-01-01

    The present report describes a device for ascertaining the bending and buckling effect in stress measurements on shell structures accessible from one side only. Beginning with a discussion of the relationship between flexural strain and certain parameters, the respective errors of the test method for great or variable skin curvature within the test range are analyzed and illustrated by specimen example.

  10. Nonisothermal elasto-visco-plastic response of shell-type structures

    Science.gov (United States)

    Simitses, G. J.; Carlson, R. L.; Riff, R.

    1987-01-01

    A mathematical model and solution methodologies for analyzing structural response of thin, metallic shell-type structures under large transient, cyclic or static thermomechanical loads is disussed. Among the system responses, which are associated with these load conditions, are thermal buckling and creep buckling. Thus, geometric as well as material-type nonlinearities (of high order) can be anticipated and have been considered in the development of the mathematical model. Furthermore, this was accommodated in the solution procedures. A complete true ab-inito rate theory of kinematics and kinetics for continuum and curved thin structures, without any restriction on the magnitude of the strains or the deformation, was formulated. The time dependence and large strain behavior are incorporated through the introduction of the time rates of the metric and curvature in two coordinate systems, a fixed (spatial) one and a convected (material) coordinate system. The relations between the time derivative and the covariant derivatives (gradients) have been developed for curved space and motion, so that the velocity components supply the connection between the equations of motion and the time rate of change of the metric and curvature tensors.

  11. Dynamic Creep Buckling: Analysis of Shell Structures Subjected to Time-dependent Mechanical and Thermal Loading

    Science.gov (United States)

    Simitses, G. J.; Carlson, R. L.; Riff, R.

    1985-01-01

    The objective of the present research is to develop a general mathematical model and solution methodologies for analyzing the structural response of thin, metallic shell structures under large transient, cyclic, or static thermomechanical loads. Among the system responses associated with these loads and conditions are thermal buckling, creep buckling, and ratcheting. Thus geometric and material nonlinearities (of high order) can be anticipated and must be considered in developing the mathematical model. A complete, true ab-initio rate theory of kinematics and kinetics for continuum and curved thin structures, without any restriction on the magnitude of the strains or the deformations, was formulated. The time dependence and large strain behavior are incorporated through the introduction of the time rates of metric and curvature in two coordinate systems: fixed (spatial) and convected (material). The relations between the time derivative and the covariant derivative (gradient) were developed for curved space and motion, so the velocity components supply the connection between the equations of motion and the time rates of change of the metric and curvature tensors.

  12. Organic-Inorganic Hydrophobic Nanocomposite Film with a Core-Shell Structure

    Directory of Open Access Journals (Sweden)

    Peng Liu

    2016-12-01

    Full Text Available A method to prepare novel organic-inorganic hydrophobic nanocomposite films was proposed by a site-specific polymerization process. The inorganic part, the core of the nanocomposite, is a ternary SiO2–Al2O3–TiO2 nanoparticles, which is grafted with methacryloxy propyl trimethoxyl silane (KH570, and wrapped by fluoride and siloxane polymers. The synthesized samples are characterized by transmission electron microscopy (TEM, Fourier transform infrared (FTIR spectrscopy, X-ray diffractometry (XRD, contact angle meter (CA, and scanning electron microscope (SEM. The results indicate that the novel organic-inorganic hydrophobic nanocomposite with a core-shell structure was synthesized successfully. XRD analysis reveals the nanocomposite film has an amorphous structure, and FTIR analysis indicates the nanoparticles react with a silane coupling agent (methacryloxy propyl trimethoxyl silane KH570. Interestingly, the morphology of the nanoparticle film is influenced by the composition of the core. Further, comparing with the film synthesized by silica nanoparticles, the film formed from SiO2–Al2O3–TiO2 nanoparticles has higher hydrophobic performance, i.e., the contact angle is greater than 101.7°. In addition, the TEM analysis reveals that the crystal structure of the particles can be changed at high temperatures.

  13. Energy storage in ferroelectric polymer nanocomposites filled with core-shell structured polymer@BaTiO3 nanoparticles: understanding the role of polymer shells in the interfacial regions.

    Science.gov (United States)

    Zhu, Ming; Huang, Xingyi; Yang, Ke; Zhai, Xing; Zhang, Jun; He, Jinliang; Jiang, Pingkai

    2014-11-26

    The interfacial region plays a critical role in determining the electrical properties and energy storage density of dielectric polymer nanocomposites. However, we still know a little about the effects of electrical properties of the interfacial regions on the electrical properties and energy storage of dielectric polymer nanocomposites. In this work, three types of core-shell structured polymer@BaTiO3 nanoparticles with polymer shells having different electrical properties were used as fillers to prepare ferroelectric polymer nanocomposites. All the polymer@BaTiO3 nanoparticles were prepared by surface-initiated reversible-addition-fragmentation chain transfer (RAFT) polymerization, and the polymer shells were controlled to have the same thickness. The morphology, crystal structure, frequency-dependent dielectric properties, breakdown strength, leakage currents, energy storage capability, and energy storage efficiency of the polymer nanocomposites were investigated. On the other hand, the pure polymers having the same molecular structure as the shells of polymer@BaTiO3 nanoparticles were also prepared by RAFT polymerization, and their electrical properties were provided. Our results show that, to achieve nanocomposites with high discharged energy density, the core-shell nanoparticle filler should simultaneously have high dielectric constant and low electrical conductivity. On the other hand, the breakdown strength of the polymer@BaTiO3-based nanocomposites is highly affected by the electrical properties of the polymer shells. It is believed that the electrical conductivity of the polymer shells should be as low as possible to achieve nanocomposites with high breakdown strength.

  14. Chaotic interaction dynamics of three structures: Two cylindrical shells nested into each other and their reinforcing local rib

    Science.gov (United States)

    Krysko, V. A.; Vetsel', S. S.; Dobriyan, V. V.; Saltykova, O. A.

    2017-05-01

    This paper studies the chaotic dynamics of two cylindrical shells nested into each other with a gap and their reinforcing beam, also with a gap, which is subjected to a distributed alternating load. The problem is solved using methods of nonlinear dynamics and the qualitative theory of differential equations. The Novozhilov equations for geometrically nonlinear structures are used as the governing equations. Contact pressure is determined by Kantor's method. Using finite elements in spatial variables, the partial differential equations for the beam and shells are reduced to the Cauchy problem, which is solved by explicit integration (Euler's method). The chaotic synchronization of this system is studied.

  15. Spatially-resolved study of the luminescence from ZnO/MgO core-shell nanocrystal structures

    International Nuclear Information System (INIS)

    Panin, Gennady; Baranov, Andrey; Kapitanova, Olesya; Kang, Taewon

    2012-01-01

    The luminescent properties of core-shell nanocrystal structures were investigated with high spatial resolution. The composites consisting of ZnO/MgO core/shell nanoheteroparticles showed an increase in the relative intensity of the green luminescence after annealing while a suppression of green luminescence from samples of ZnO tetrapods in a MgO nanoparticle matrix was observed. Combined spatially-resolved combined through-the-lens-detector (TLD) and cathodoluminescence (CL) measurements revealed that the depletion of electrons in the ZnO nanocrystals could lead to a suppression of the luminescence.

  16. Protected Light-Trapping Silicon by a Simple Structuring Process for Sunlight-Assisted Water Splitting.

    Science.gov (United States)

    Santinacci, Lionel; Diouf, Maïmouna W; Barr, Maïssa K S; Fabre, Bruno; Joanny, Loïc; Gouttefangeas, Francis; Loget, Gabriel

    2016-09-21

    Macroporous layers are grown onto n-type silicon by successive photoelectrochemical etching in HF-containing solution and chemical etching in KOH. This specific latter treatment gives highly antireflective properties of the Si surface. The duration of the chemical etching is optimized to render the surface as absorbent as possible, and the morphology of the as-grown layer is characterized by scanning electron microscopy. Further functionalization of such structured Si surface is carried out by atomic layer deposition of a thin conformal and homogeneous TiO2 layer that is crystallized by an annealing at 450 °C. This process allows using such surfaces as photoanodes for water oxidation. The 40 nm thick TiO2 film acts indeed as an efficient protective layer against the photocorrosion of the porous Si in KOH, enhances its wettability, and improves the light absorption of the photoelectrode. The macroporous dual-absorber TiO2/Si has a beneficial effect on water oxidation in 1 M KOH and leads to a considerable negative shift of the onset potential of ∼400 mV as well as a 50% increase in photocurrent at 1 V vs SCE.

  17. Size dependent structural, vibrational and magnetic properties of BiFeO3 and core-shell structured BiFeO3@SiO2 nanoparticles

    International Nuclear Information System (INIS)

    Chauhan, Sunil; Kumar, Manoj; Chhoker, Sandeep; Katyal, S. C.

    2014-01-01

    Bulk BiFeO 3 , BiFeO 3 nanoparticles and core-shell structured BiFeO 3 @SiO 2 nanoparticles were synthesized by solid state reaction method, sol-gel and Stöber process (SiO 2 shell) respectively. Transmission electron microscopy image confirmed the core-shell structure of BiFeO 3 @SiO 2 nanoparticles with BiFeO3 core ∼50-90 nm and SiO 2 shell ∼16 nm. X-ray diffraction and FTIR spectroscopy results showed the presence of distorted rhombohedral structure with R3c space group in all three samples. The magnetic measurement indicated the existence of room-temperature weak ferromagnetism in core-shell BiFeO 3 @SiO 2 nanoparticles and BiFeO3 nanoparticles, whereas bulk BiFeO 3 showed antiferromagnteic nature. Electron Spin Resonance results confirmed the enhancement in magnetic properties of coreshell structured BiFeO 3 @SiO 2 nanoparticles in comparison with BiFeO 3 nanoparticles and bulk BiFeO 3

  18. Preliminary structural investigations of the Eut-L shell protein of the ethanolamine ammonia-lyase metabolosome of Escherichia coli

    International Nuclear Information System (INIS)

    Nikolakakis, Kiel; Ohtaki, Akashi; Newton, Keith; Chworos, Arkadiusz; Sagermann, Martin

    2009-01-01

    Preliminary X-ray analysis of crystals of the bacterial microcompartment shell protein Eut-L from Escherichia coli is reported. The ethanolamine ammonia-lyase microcompartment is composed of five different shell proteins that have been proposed to assemble into symmetrically shaped polyhedral particles of varying sizes. Here, preliminary X-ray analysis of crystals of the bacterial microcompartment shell protein Eut-L from Escherichia coli is reported. Cloning, overexpression and purification resulted in highly pure protein that crystallized readily under many different conditions. In all cases the protein forms thin hexagonal plate-shaped crystals belonging to space group P3 that are of unusually high stability against different solvent conditions. The crystals diffracted to a resolution of 2.0 Å using synchrotron radiation but proved to be radiation-sensitive. Preparations of heavy-atom-derivatized crystals for use in determining the three-dimensional structure are under way

  19. Split Malcev algebras

    Indian Academy of Sciences (India)

    We study the structure of split Malcev algebras of arbitrary dimension over an algebraically closed field of characteristic zero. We show that any such algebras is of the form M = U + ∑ j I j with U a subspace of the abelian Malcev subalgebra and any I j a well described ideal of satisfying [ I j , I k ] = 0 if ≠ .

  20. Inferring Enceladus' ice shell strength and structure from Tiger Stripe formation

    Science.gov (United States)

    Rhoden, A.; Hurford, T., Jr.; Spitale, J.; Henning, W. G.

    2017-12-01

    The tiger stripe fractures (TSFs) of Enceladus are four, roughly parallel, linear fractures that correlate with plume sources and high heat flows measured by Cassini. Diurnal variations of plume eruptions along the TSFs strongly suggest that tides modulate the eruptions. Several attempts have been made to infer Enceladus' ice shell structure, and the mechanical process of plume formation, by matching variations in the plumes' eruptive output with tidal stresses for different interior models. Unfortunately, the many, often degenerate, unknowns make these analyses non-unique. Tidal-interior models that best match the observed plume variability imply very low tidal stresses (<14 kPa), much lower than the 1 MPa tensile strength of ice implied by lab experiments or the 100 kPa threshold inferred for Europa's ice. In addition, the interior models that give the best matches are inconsistent with the constraints from observed librations. To gain more insight into the interior structure and rheology of Enceladus and the role of tidal stress in the development of the south polar terrain, we utilize the orientations of the TSFs themselves as observational constraints on tidal-interior models. While the initial formation of the TSFs has previously been attributed to tidal stress, detailed modeling of their formation has not been performed until now. We compute tidal stresses for a suite of rheologically-layered interior models, consistent with Enceladus' observed librations, and apply a variety of failure conditions. We then compare the measured orientations at 6391 points along the TSFs with the predicted orientations from the tidal models. Ultimately, we compute the likelihood of forming the TSFs with tidal stresses for each model and failure condition. We find that tidal stresses are a good match to the observed orientations of the TSFs and likely led to their formation. We also find that the model with the highest likelihood changes depending on the failure criterion

  1. Stress- and Structure-Induced Anisotropy in Southern California From Two Decades of Shear Wave Splitting Measurements

    Science.gov (United States)

    Li, Zefeng; Peng, Zhigang

    2017-10-01

    We measure shear wave splitting (SWS) parameters (i.e., fast direction and delay time) using 330,000 local earthquakes recorded by more than 400 stations of the Southern California Seismic Network (1995-2014). The resulting 232,000 SWS measurements (90,000 high-quality ones) provide a uniform and comprehensive database of local SWS measurements in Southern California. The fast directions at many stations are consistent with regional maximum compressional stress σHmax. However, several regions show clear deviations from the σHmax directions. These include linear sections along the San Andreas Fault and the Santa Ynez Fault, geological blocks NW to the Los Angeles Basin, regions around the San Jacinto Fault, the Peninsular Ranges near San Diego, and the Coso volcanic field. These complex patterns show that regional stresses and active faults cannot adequately explain the upper crustal anisotropy in Southern California. Other types of local structures, such as local rock types or tectonic features, also play significant roles.

  2. Facile one-step synthesis and photoluminescence properties of Ag–ZnO core–shell structure

    International Nuclear Information System (INIS)

    Zhai, HongJu; Wang, LiJing; Han, DongLai; Wang, Huan; Wang, Jian; Liu, XiaoYan; Lin, Xue; Li, XiuYan; Gao, Ming; Yang, JingHai

    2014-01-01

    Graphical abstract: The PL of the Ag–ZnO core-shell nanostructure showed obvious increase of UV emission and slight decrease of visible light emission compared to that of the pure ZnO. With the calcination temperature increasing from 300 to 600 °C, the primary peak located at 380 nm became stronger and sharper, indicating that the increasing calcination temperature made the samples crystallize better. - Highlights: • Ag-ZnO core-shell structure was obtained via a simple one-step solvothermal process. • The approach was simple, mild, low cost, reproducible and easy-to-handle. • The obvious enhancement of UV luminescent has been observed. • Effects of the calcining temperature to luminescence were investigated in detail. - Abstract: Ag–ZnO core–shell structures were gained via one-step solvothermal process. The products were characterized by means of X-ray diffraction (XRD), transmission electron microscopy (TEM), Raman spectroscopy, photoluminescence (PL) and UV–vis spectroscopy, respectively. It was shown that the properties were greatly changed compared to pure ZnO from the PL and Raman spectra, which indicated the strong interfacial interaction between ZnO and Ag. The work provides a feasible method to synthesize Ag–ZnO core–shell structure photocatalyst, which is promising in the further practical application of ZnO-based photocatalytic materials

  3. Mapping of Force: A Process of Parametric Design from the Prototype Mechanical Mechanism to the Structural Form of a Woven HYPAR Shell

    Directory of Open Access Journals (Sweden)

    Lin Kang Qiang

    2016-01-01

    Full Text Available From a new perspective of structural engineering, with the integration of the 1st and 3rd principal stress distribution of HYPAR shell structure into the selection of texture variation zone, this paper analyzes and demonstrates the key questions of how to establish the association between the force-flow, the texture direction and the form parameters; how to develop a dynamic, performance-optimized and adaptive iteration model of HYPAR shell structural form by setting and adjusting structurally sensitive parameters; and how to realize the process of parametric design from the mechanical mechanism of the prototype to the structural form of the woven HYPAR shell.

  4. Structure and stability of nickel/nickel oxide core-shell nanoparticles

    International Nuclear Information System (INIS)

    D'Addato, S; Grillo, V; Valeri, S; Frabboni, S; Altieri, S; Tondi, R

    2011-01-01

    The results of a combined x-ray photoelectron spectroscopy (XPS) and high resolution transmission electron microscopy (HR-TEM) study of Ni nanoparticles (NP), before and after oxidation, are presented. An experimental set-up was realized for the preparation and study of pre-formed NP films, concentrating the attention on Ni NP in the diameter range between 4 and 8 nm. The XPS data were taken in situ from NPs after different stages of oxidation, including controlled dosing of O 2 gas in the experimental system and exposure to the atmosphere. The Ni 2p structure is a combination of spectra from metallic Ni in the NP core and from the oxide shell. The signal from the NP core was observed even for samples after exposure to air. From the comparison of HR-TEM experimental images with theoretical simulations, it was found that the Ni NP core has a regular multitwinned icosahedral structure, composed of single-crystal tetrahedra with (111) faces. The NiO phase is clearly observed forming islands on the NP surface.

  5. Modeling and numerical analysis of a three-dimensional shape memory alloy shell structure

    Science.gov (United States)

    Zhao, Pengtao; Qiu, Jinhao; Ji, Hongli; Wang, Mingyi; Nie, Rui

    2012-04-01

    In this paper, modeling and numerical analysis of a three dimensional shell structure made of shape memory alloy (SMA) are introduced. As a new smart material, SMA material has been applied in many fields due to two significant macroscopic phenomena which are called the shape memory effect (SME) and pseudoelasticity. The material of SMA exhibits two-way shape memory effect (TWSME) after undergoing especial heat treatment and thermo-mechanical training. This work investigates the numerical simulation and application of the SMA component: SMA strip, which has been pre-curved in the room temperature. The component is expected to extend upon heating and shorten on cooling along the curve. Hence the shape memory effect can be used to change the shape of the structure. The return mapping algorithm of the 3-D SMA thermomechanical constitutive equations based on Boyd-Lagoudas model is used in the finite element analysis to describe the material features of the SMA. In this paper, the ABAQUS finite element program has been utilized with a user material subroutine (UMAT) which is written in the FORTRAN code for the modeling of the SMA strip. The SMA component which has a certain initial transformation strain can emerge considerable deflection during the reverse phase transformation inducing by the temperature.

  6. Structure-property relationship in core-shell rubber toughened epoxy nanocomposites

    Science.gov (United States)

    Gam, Ki Tak

    The structure-property relationships of epoxy nanocomposites with inorganic layer-structure nanofillers have been studied to obtain the fundamental understanding of the role of nanofillers and the physics of polymer nanocomposites in this dissertation. Several polymer nanocomposite systems with modified montmorillonite (MMT) or alpha-zirconium phosphate (ZrP) nanofillers were prepared with epoxy matrices of different ductility and properties. The successful nanofiller's exfoliations were confirmed with X-ray diffraction and transmission electronic microscopy (TEM). Dynamic mechanical analysis (DMA) on the prepared epoxy nanocomposites revealed the significant increase in rubbery plateau moduli of the epoxy nanocomposite systems above Tg, as high as 4.5 times, and tensile test results showed improved modulus by the nanofiller addition, while the fracture toughness was not affected or slightly decreased by nanofillers. The brittle epoxy nanocomposite systems were toughened with core shell rubber (CSR) particles and showed remarkable increase in fracture toughness (KIC) value up to 270%. The CSR toughening is more effective at ductile matrices, and TEM observation indicates that major toughening mechanisms induced by the CSR addition involve a large scale CSR cavitation, followed by massive shear deformation of the matrix.

  7. SANS study of PLA-mPEG core-shell structured nanoparticles for targeted drug delivery

    International Nuclear Information System (INIS)

    Wang, Yichao; Li, Puwang; Kong, Lingxue

    2009-01-01

    Full text: Colorectal cancer (CRC), referring to cancers that affect the colon and the rectum, is the third most common form of cancer and second leading cause of cancer-related death in the western world (Fortina et al 2007). Currently there are many therapeutic methods, however, most of the traditional methods have enormous side effects, partly because they significantly damage the healthy cells. Therefore, there is an urgent demand to develop a more effective drug delivery mechanism to alleviate these side effects. PLA-mPEG core-shell nanoparticles will be used to deliver the therapeutic agent to the specific area. Materials preparation will include the deuteration of L-Iactic acid monomer and ring opening polymerization to prepare the block copolymer. The drug loaded nanoparticles will be fabricated by double emulsion and solvent evaporation method. The processing parameters will be varied and optimized to maximize the encapsulation efficiency and drug loading. With SANS, we will identify the internal structure of PLA-mPEG nanoparticles with a diameter of 50- 1 00 n m, an important aspect to control the release of the drugs. At the same time, we will relate how the different process parameters affect the core size. The relationship between drug release profile and structure of the encapsulation materials will also be studied using the data from SANS.

  8. Advanced Deployable Shell-Based Composite Booms for Small Satellite Structural Applications Including Solar Sails

    Science.gov (United States)

    Fernandez, Juan M.

    2017-01-01

    State of the art deployable structures are mainly being designed for medium to large size satellites. The lack of reliable deployable structural systems for low cost, small volume, rideshare-class spacecraft severely constrains the potential for using small satellite platforms for affordable deep space science and exploration precursor missions that could be realized with solar sails. There is thus a need for reliable, lightweight, high packaging efficiency deployable booms that can serve as the supporting structure for a wide range of small satellite systems including solar sails for propulsion. The National Air and Space Administration (NASA) is currently investing in the development of a new class of advanced deployable shell-based composite booms to support future deep space small satellite missions using solar sails. The concepts are being designed to: meet the unique requirements of small satellites, maximize ground testability, permit the use of low-cost manufacturing processes that will benefit scalability, be scalable for use as elements of hierarchical structures (e.g. trusses), allow long duration storage, have high deployment reliability, and have controlled deployment behavior and predictable deployed dynamics. This paper will present the various rollable boom concepts that are being developed for 5-20 m class size deployable structures that include solar sails with the so-called High Strain Composites (HSC) materials. The deployable composite booms to be presented are being developed to expand the portfolio of available rollable booms for small satellites and maximize their length for a given packaged volume. Given that solar sails are a great example of volume and mass optimization, the booms were designed to comply with nominal solar sail system requirements for 6U CubeSats, which are a good compromise between those of smaller form factors (1U, 2U and 3U CubeSats) and larger ones (12 U and 27 U future CubeSats, and ESPA-class microsatellites). Solar

  9. Structures in the K-shell delta electron spectrum near threshold for ionization by fast charged particles

    International Nuclear Information System (INIS)

    Amundsen, P.A.; Aashamar, K.

    Results of calculations of the delta electron spectrum for K-shell ionization of atoms by fast charged particles for target charges in the range 6 2 <=40 are presented. Appreciable structure is found in the spectrum near the ionization threshold, in particular for fast projectiles and heavy target elements. The structure can be quite sensitive to the details of the effective atomic potentials. (Auth.)

  10. Immobilization of cholesterol oxidase on magnetic fluorescent core-shell-structured nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Jun, E-mail: hjun@whut.edu.cn; Liu, Huichao; Zhang, Peipei; Zhang, Pengfei; Li, Mengshi; Ding, Liyun

    2015-12-01

    The magnetic fluorescent core-shell structured nanoparticles, Fe{sub 3}O{sub 4}@SiO{sub 2}(F)@meso–SiO{sub 2} nanoparticles, were prepared. Cholesterol oxidase (COD) was immobilized on their surface to form Fe{sub 3}O{sub 4}@SiO{sub 2}(F)@meso–SiO{sub 2}@COD nanoparticles. Optimal immobilization was achieved with 2.5% (v/v) APTES, 2.0% (v/v) GA, 10 mg COD (in 15 mg carrier) and solution pH of 7.0. Fe{sub 3}O{sub 4}@SiO{sub 2}(F)@meso–SiO{sub 2}@COD nanoparticles showed maximal catalytic activity at pH 7.0 and 50 °C. The thermal, storage and operational stabilities of COD were improved greatly after its immobilization. After the incubation at 50 °C for 5 h, the nanoparticles and free COD retained 80% and 46% of its initial activity, respectively. After kept at 4 °C for 30 days, the nanoparticles and free COD maintained 86% and 65% of initial activity, respectively. The nanoparticles retained 71% of its initial activity after 7 consecutive operations. Since Fe{sub 3}O{sub 4}@SiO{sub 2}(F)@meso–SiO{sub 2}@COD nanoparticles contained tris(2,2-bipyridyl)dichloro-ruthenium(II) hexahydrate (Ru(bpy){sub 3}Cl{sub 2}) and were optical sensitive to oxygen in solution, it might be used as the sensing material and has the application potential in multi parameter fiber optic biosensor based on enzyme catalysis and oxygen consumption. - Highlights: • COD was immobilized on magnetic fluorescent core-shell structured nanoparticles. • The nanoparticles were optical sensitive to oxygen in water solution. • The nanoparticles have remarkable improved stability compared with free COD. • The nanoparticles can probably be used in multi parameter fiber optic Biosensor.

  11. State-of-the-art Sn2+-based ternary oxides as photocatalysts for water splitting: electronic structures and optoelectronic properties

    KAUST Repository

    Noureldine, Dalal

    2016-09-19

    Developing visible light responsive metal oxide photocatalysts is a challenge that must be conquered to achieve high efficiency for water splitting or hydrogen evolution reactions. Valence band engineering is possible by forming ternary oxides using the combination of a metal cation with an s2d10 electronic configuration and a transition metal oxide with a d0 configuration. Many (Sn2+, Bi3+, Pb2+)-based ternary metal oxide photocatalysts have been reported for hydrogen and/or oxygen evolution under visible irradiation. Sn2+-based materials have attracted particular attention because tin is inexpensive, abundant and more environmentally friendly than lead or bismuth. In this review, we provide a fruitful library for Sn2+-based photocatalysts that have been reported to evolve hydrogen using sacrificial reagents, including SnNb2O6, Sn2Nb2O7, SnTaxNb2−xO6, SnTa2O6, Sn2Ta2O7, SnWO4 (α and β phases), SnSb2O6·nH2O, and Sn2TiO4. The synthesis method used in the literature and the resultant morphology and crystal structure of each compound are discussed. The density functional theory (DFT) calculations of the electronic structure and density of states are provided, and the consequent optoelectronic properties such as band gap, nature of the bandgap, dielectric constant, and effective masses are summarized. This review will help highlight the main challenges for Sn2+-based materials.

  12. Dual yolk-shell structure of carbon and silica-coated silicon for high-performance lithium-ion batteries

    Science.gov (United States)

    Yang, L. Y.; Li, H. Z.; Liu, J.; Sun, Z. Q.; Tang, S. S.; Lei, M.

    2015-06-01

    Silicon batteries have attracted much attention in recent years due to their high theoretical capacity, although a rapid capacity fade is normally observed, attributed mainly to volume expansion during lithiation. Here, we report for the first time successful synthesis of Si/void/SiO2/void/C nanostructures. The synthesis strategy only involves selective etching of SiO2 in Si/SiO2/C structures with hydrofluoric acid solution. Compared with reported results, such novel structures include a hard SiO2-coated layer, a conductive carbon-coated layer, and two internal void spaces. In the structures, the carbon can enhance conductivity, the SiO2 layer has mechanically strong qualities, and the two internal void spaces can confine and accommodate volume expansion of silicon during lithiation. Therefore, these specially designed dual yolk-shell structures exhibit a stable and high capacity of 956 mA h g-1 after 430 cycles with capacity retention of 83%, while the capacity of Si/C core-shell structures rapidly decreases in the first ten cycles under the same experimental conditions. The novel dual yolk-shell structures developed for Si can also be extended to other battery materials that undergo large volume changes.

  13. 2-D differential quadrature solution for vibration analysis of functionally graded conical, cylindrical shell and annular plate structures

    Science.gov (United States)

    Tornabene, Francesco; Viola, Erasmo; Inman, Daniel J.

    2009-12-01

    This paper focuses on the dynamic behavior of functionally graded conical, cylindrical shells and annular plates. The last two structures are obtained as special cases of the conical shell formulation. The first-order shear deformation theory (FSDT) is used to analyze the above moderately thick structural elements. The treatment is developed within the theory of linear elasticity, when materials are assumed to be isotropic and inhomogeneous through the thickness direction. The two-constituent functionally graded shell consists of ceramic and metal that are graded through the thickness, from one surface of the shell to the other. Two different power-law distributions are considered for the ceramic volume fraction. The homogeneous isotropic material is inferred as a special case of functionally graded materials (FGM). The governing equations of motion, expressed as functions of five kinematic parameters, are discretized by means of the generalized differential quadrature (GDQ) method. The discretization of the system leads to a standard linear eigenvalue problem, where two independent variables are involved without using the Fourier modal expansion methodology. For the homogeneous isotropic special case, numerical solutions are compared with the ones obtained using commercial programs such as Abaqus, Ansys, Nastran, Straus, Pro/Mechanica. Very good agreement is observed. Furthermore, the convergence rate of natural frequencies is shown to be very fast and the stability of the numerical methodology is very good. Different typologies of non-uniform grid point distributions are considered. Finally, for the functionally graded material case numerical results illustrate the influence of the power-law exponent and of the power-law distribution choice on the mechanical behavior of shell structures.

  14. Sound-structure interaction analysis of an infinite-long cylindrical shell submerged in a quarter water domain and subject to a line-distributed harmonic excitation

    Science.gov (United States)

    Guo, Wenjie; Li, Tianyun; Zhu, Xiang; Miao, Yuyue

    2018-05-01

    The sound-structure coupling problem of a cylindrical shell submerged in a quarter water domain is studied. A semi-analytical method based on the double wave reflection method and the Graf's addition theorem is proposed to solve the vibration and acoustic radiation of an infinite cylindrical shell excited by an axially uniform harmonic line force, in which the acoustic boundary conditions consist of a free surface and a vertical rigid surface. The influences of the complex acoustic boundary conditions on the vibration and acoustic radiation of the cylindrical shell are discussed. It is found that the complex acoustic boundary has crucial influence on the vibration of the cylindrical shell when the cylindrical shell approaches the boundary, and the influence tends to vanish when the distances between the cylindrical shell and the boundaries exceed certain values. However, the influence of the complex acoustic boundary on the far-field sound pressure of the cylindrical shell cannot be ignored. The far-field acoustic directivity of the cylindrical shell varies with the distances between the cylindrical shell and the boundaries, besides the driving frequency. The work provides more understanding on the vibration and acoustic radiation behaviors of cylindrical shells with complex acoustic boundary conditions.

  15. Simulation of Material and Structural Instability Phenomena During the Flaring Process of Cylindrical Shells

    Science.gov (United States)

    Daxner, T.; Rammerstorfer, F. G.; Fischer, F. D.

    2004-06-01

    Pushing a conical die into a pipe, a forming process also known as `flaring', is a way of changing the shape of a thin cylindrical tube into that of a conical shell. Interest in predicting the forming limits for this specific process motivated the present study, in which experiments and Finite Element simulations were employed for the identification of two limiting mechanisms: (a) diffuse necking caused by local loss of material stability at the free, expanding end of the pipe, and (b) loss of global stability due to elasto-plastic `Concertina' buckling of the straight pipe part. The former mechanism leads to the formation of periodic necks and subsequent failure by strain localization and rupture, while the latter mechanism is characterized by a periodic buckling pattern that is similar to the one observed in typical crash elements. Whether collapse or rupture is the limiting factor depends on geometrical parameters and material parameters, such as, for example, the hardening exponent in the Ludwik law. There are some publications of analytical considerations of the flaring process, describing the load displacement behavior of the stamp and the development of plastic deformations in the tube. However, the aspect of material and structural instability requires a deeper insight into the problem, which is provided by the experimental results and the numerical studies presented here. It appears to be important to take the tridimensionality of the stress and strain states into account when reliable predictions of necking and rupture limits are to be made.

  16. Reinforcement of Natural Rubber with Core-Shell Structure Silica-Poly(Methyl Methacrylate Nanoparticles

    Directory of Open Access Journals (Sweden)

    Qinghuang Wang

    2012-01-01

    Full Text Available A highly performing natural rubber/silica (NR/SiO2 nanocomposite with a SiO2 loading of 2 wt% was prepared by combining similar dissolve mutually theory with latex compounding techniques. Before polymerization, double bonds were introduced onto the surface of the SiO2 particles with the silane-coupling agent. The core-shell structure silica-poly(methyl methacrylate, SiO2-PMMA, nanoparticles were formed by grafting polymerization of MMA on the surface of the modified SiO2 particles via in situ emulsion, and then NR/SiO2 nanocomposite was prepared by blending SiO2-PMMA and PMMA-modified NR (NR-PMMA. The Fourier transform infrared spectroscopy results show that PMMA has been successfully introduced onto the surface of SiO2, which can be well dispersed in NR matrix and present good interfacial adhesion with NR phase. Compared with those of pure NR, the thermal resistance and tensile properties of NR/SiO2 nanocomposite are significantly improved.

  17. Pion–nucleon correlations in finite nuclei in a relativistic framework: Effects on the shell structure

    Directory of Open Access Journals (Sweden)

    Elena Litvinova

    2016-04-01

    Full Text Available The relativistic particle-vibration coupling (RPVC model is extended by the inclusion of isospin-flip excitation modes into the phonon space, introducing a new mechanism of dynamical interaction between nucleons with different isospin in the nuclear medium. Protons and neutrons exchange by collective modes which are formed by isovector π and ρ-mesons, in turn, softened considerably because of coupling to nucleons of the medium. These modes are investigated within the proton–neutron relativistic random phase approximation (pn-RRPA and relativistic proton–neutron time blocking approximation (pn-RTBA. The appearance of isospin-flip states with sizable transition probabilities at low energies points out that they are likely to couple to the single-particle degrees of freedom and, in addition to isoscalar low-lying phonons, to modify their spectroscopic characteristics. Such a coupling is quantified for the shell structure of 100,132Sn and found significant for the location of the dominant single-particle states.

  18. Hydrogen peroxide sensing using ultrathin platinum-coated gold nanoparticles with core@shell structure.

    Science.gov (United States)

    Li, Yongxin; Lu, Qiufang; Wu, Shengnan; Wang, Lun; Shi, Xianming

    2013-03-15

    Ultrathin platinum-coated gold (Pt@Au) nanoparticles with core@shell structure have been developed by under-potential deposition (UPD) redox replacement technique. A single UPD Cu replacement with Pt(2+) produced a uniform Pt monolayer on the surface of gold nanoparticles, which are immobilized on glassy carbon electrode (GCE) surface based on electrostatic interaction. The ultrathin Pt@Au nanoparticles were confirmed by cyclic voltammetry and X-ray photoelectron spectroscopy (XPS). Voltammetry and amperometric methodologies were used to evaluate the electrocatalytic activity of the Pt@Au nanoparticles modified electrode towards the reduction of hydrogen peroxide under the physiological condition. The present results show that ultrathin Pt coating greatly enhances the electrocatalytic activity towards the reduction of hydrogen peroxide, which can be utilized to fabricate the hydrogen peroxide sensor. Chronoamperometric experiments showed that at an applied potential of 0.08 V (vs. Ag/AgCl), the current reduction of hydrogen peroxide was linear to its concentration in the range of 1-450 μΜ, and the detection limit was found to be 0.18 μM (signal-to-noise ratio, S/N=3). Copyright © 2012 Elsevier B.V. All rights reserved.

  19. Core – Shell structures in Sb – doped BaTiO3

    Directory of Open Access Journals (Sweden)

    Castro, M. S.

    2002-02-01

    Full Text Available In this work, fine – grained microstructures have been obtained after sintering BaTiO3 doped with an organic precursor of antimonium. In this compound, the development of a core – shell structure in the grains takes place influencing on the final grain size and electrical properties of the material. Samples were characterised by Scanning Electron Microscopy (SEM, X – ray diffraction (XRD analysis, and dielectric constant – temperature curves. Strong inhibition of the grain growth is observed in Sb-doped BaTiO3. Besides, dielectric constant vs temperature curves show the contribution of two regions, corresponding to the grain boundaries and the grain bulk. According to the observed properties, the contribution belonging to the shell region becomes more important as the dopant content and the sintering temperature rise.En el presente trabajo se han obtenido materiales de BaTiO3 dopados con antimonio a partir de un precursor orgánico que presentaron una microestructura homogénea y con tamaño de grano pequeño. En este compuesto se desarrolla una estructura de tipo “core-shell” en los granos que afecta tanto al tamaño de grano final como a las propiedades eléctricas del material. Las muestras fueron analizadas mediante Microscopía Electrónica de Barrido, difracción de rayos-X y la respuesta de la constante dieléctrica frente a la temperatura. Se observó una fuerte inhibición del crecimiento cristalino con la incorporación de antimonio. La respuesta de la constante dieléctrica frente a la temperatura presenta dos contribuciones, una asociada al borde de grano y otra al interior de grano. De acuerdo con las propiedades observadas, la contribución del borde de grano (región “shell” crece en importancia a medida que la concentración de dopante y la temperatura de sinterización aumentan.

  20. Experimental approach towards shell structure at 100Sn and 78Ni

    International Nuclear Information System (INIS)

    Grawe, H.; Gorska, M.; Fahlander, C.

    2000-07-01

    The status of experimental approach to 100 Sn and 78 Ni is reviewed. Revised single particle energies for neutrons are deduced for the N=Z=50 shell closure and evidence for low lying I π =2 + and 3 - states is presented. Moderate E2 polarisation charges of 0.1 e and 0.6 e are found to reproduce the experimental data when core excitation of 100 Sn is properly accounted for in the shell model. For the neutron rich Ni region no conclusive evidence for a N=40 subshell is found, whereas firm evidence for the persistence of the N=50 shell at 78 Ni is inferred from the existence of seniority isomers. The disappearance of this isomerism in the mid νg 9/2 shell is discussed. (orig.)

  1. Core-shell structured mZVI/Ca(OH)2 particle: Morphology, aggregation and corrosion.

    Science.gov (United States)

    Wei, Cai-Jie; Wang, Xiao-Mao; Li, Xiao-Yan

    2018-01-15

    A calcium hydroxide shell was coated onto the surface of micro-sized zero valent iron (mZVI) particles by hydrothermal approach in oversaturated Ca(OH) 2 solution. The heterogeneous nucleation of nano-scale Ca(OH) 2 particle on micro-scale spherical ZVI surface was clearly observed by scanning electronic microscope (SEM). The moderate solubility of Ca(OH) 2 was demonstrated as the crucial factor in inducing slow nucleation rate and in facilitating the abundant growth of Ca(OH) 2 nuclei on mZVI surface. The growth of shell thickness was found to obey the zero order kinetics with the rate constant at about 15nm/h. The Ca(OH) 2 shell was demonstrated to be anticorrosive to protect reactive Fe 0 from oxidation based on standard corrosion test. In addition, the instant aggregation process of mZVI within 120s was slowed down after Ca(OH) 2 shell coating. The saturation magnetization of mZVI, measured by a vibrating sample magnetometer (VSM), was gradually diminished along with the shell formation with a 32% reduction after excluding the Fe 0 content change effect. This indicated that Ca(OH) 2 shell coating can partially eliminated particle-particle or cluster-cluster magnetic attraction force to enhance the dispersion stability and resultantly facilitate the transportation. The dissolution of Ca(OH) 2 shell was greatly dependent on the pH value of the background water environment. The pH gradient change resulted from the Ca(OH) 2 shell dissolution along mZVI particle transport was illustrated by a conceptual model. Copyright © 2017 Elsevier Inc. All rights reserved.

  2. On the structural behavior of ship's shell structures due to impact loading

    Directory of Open Access Journals (Sweden)

    Hyung Kyun Lim

    2018-01-01

    Full Text Available When collision accident between ships or between ship and offshore platform occurs, a common phenomenon that occurs in structures is the plastic deformation accompanied by a large strain such as fracture. In this study, for the rational design against accidental limit state, the plastic material constants of steel plate which is heated by line heating and steel plate formed by cold bending procedure have been defined through the numerical simulation for the high speed tension test. The usefulness of the material constants included in Cowper–Symonds model and Johnson–Cook model and the assumption that strain rate can be neglected when strain rate is less than the intermediate speed are verified through free drop test as well as comparing with numerical results in several references. This paper ends with describing the future study.

  3. Constructing Repairable Meta-Structures of Ultra-Broad-Band Electromagnetic Absorption from Three-Dimensional Printed Patterned Shells.

    Science.gov (United States)

    Song, Wei-Li; Zhou, Zhili; Wang, Li-Chen; Cheng, Xiao-Dong; Chen, Mingji; He, Rujie; Chen, Haosen; Yang, Yazheng; Fang, Daining

    2017-12-13

    Ultra-broad-band electromagnetic absorption materials and structures are increasingly attractive for their critical role in competing with the advanced broad-band electromagnetic detection systems. Mechanically soft and weak wax-based materials composites are known to be insufficient to serve in practical electromagnetic absorption applications. To break through such barriers, here we developed an innovative strategy to enable the wax-based composites to be robust and repairable meta-structures by employing a three-dimensional (3D) printed polymeric patterned shell. Because of the integrated merits from both the dielectric loss wax-based composites and mechanically robust 3D printed shells, the as-fabricated meta-structures enable bear mechanical collision and compression, coupled with ultra-broad-band absorption (7-40 and 75-110 GHz, reflection loss  smaller than -10 dB) approaching state-of-the-art electromagnetic absorption materials. With the assistance of experiment and simulation methods, the design advantages and mechanism of employing such 3D printed shells for substantially promoting the electromagnetic absorption performance have been demonstrated. Therefore, such universal strategy that could be widely extended to other categories of wax-based composites highlights a smart stage on which high-performance practical multifunction meta-structures with ultra-broad-band electromagnetic absorption could be envisaged.

  4. Atomic structure and thermal stability of Pt-Fe bimetallic nanoparticles: from alloy to core/shell architectures.

    Science.gov (United States)

    Huang, Rao; Wen, Yu-Hua; Shao, Gui-Fang; Sun, Shi-Gang

    2016-06-22

    Bimetallic nanoparticles comprising noble metal and non-noble metal have attracted intense interest over the past few decades due to their low cost and significantly enhanced catalytic performances. In this article, we have explored the atomic structure and thermal stability of Pt-Fe alloy and core-shell nanoparticles by molecular dynamics simulations. In Fe-core/Pt-shell nanoparticles, Fe with three different structures, i.e., body-centered cubic (bcc), face-centered cubic (fcc), and amorphous phases, has been considered. Our results show that Pt-Fe alloy is the most stable configuration among the four types of bimetallic nanoparticles. It has been discovered that the amorphous Fe cannot stably exist in the core and preferentially transforms into the fcc phase. The phase transition from bcc to hexagonal close packed (hcp) has also been observed in bcc-Fe-core/Pt-shell nanoparticles. In contrast, Fe with the fcc structure is the most preferred as the core component. These findings are helpful for understanding the structure-property relationships of Pt-Fe bimetallic nanoparticles, and are also of significance to the synthesis and application of noble metal based nanoparticle catalysts.

  5. Preparation and characterization of core-shell structured TiO 2-BaCO 3 particles

    Science.gov (United States)

    Gablenz, Silvio; Damm, Cornelia; Müller, Franz Werner; Israel, Gunter; Rössel, Michael; Röder, Andreas; Abicht, Hans-Peter

    2001-03-01

    Preparation of core-shell structured TiO 2-BaCO 3 particles as precursor of BaTiO 3 genesis, proceeds using a two step procedure, by first coating the TiO 2 core by Ba(OH) 2 shell followed by conversion of the shell region with CO 2 gas by the formation of BaCO 3. Straightforward experimental results reveal environmental scanning electron microscopy (ESEM) and scanning transmission electron microscopy (STEM) as suitable methods for analytical characterization of the core and shell regions from individual TiO 2-BaCO 3 grains. Evidence of coating the whole ensemble of TiO 2 particles is possible using Photo Electro Motive Force (Photo EMF, PEMF) measurements. This method is able to indicate very sensitively changes of surface properties of TiO 2 after coating with Ba(OH) 2 and BaCO 3, respectively. PEMF measurements were used for the first time with concern to this topic.

  6. Phase-change core/shell structured nanofibers based on eicosane/poly(vinylidene fluoride) for thermal storage applications

    Energy Technology Data Exchange (ETDEWEB)

    Do, Cong Van [Vietnam Academy of Science and Technology, Hanoi (Viet Nam); Nguyen, Thuy Thu Thi; Park, Jun Seo [Hankyong National University, Anseong (Korea, Republic of)

    2013-07-15

    We fabricated eicosane/poly(vinylidene fluoride) (PVDF) core/shell nanofibers by melt coaxial electrospinning as potential heat-storage applications. Eicosane, a hydrocarbon with melting point near the human body temperature and high latent heat, was chosen as the core material. Melted eicosane and PVDF solutions were coaxially electrospun using a double spinneret, in which melted eicosane was fed at 0.090-0.210 mL/h while the feeding rate of PVDF solution was maintained constant at 1.500 mL/h. The applied voltage and working distance were maintained constant at 12 kV and 17 cm, respectively. Good core/shell structure of nanofibers was observed at core feed rates of 0.090-0.180mL/h by transmission electron microscopy. Differential scanning calorimetry and thermogravimetric analysis values indicated good thermal stability and high energy-storage capacity of the obtained nanofibers. The highest amount of eicosane encapsulated in the electrospun core/shell nanofibers reached 32.5 wt% at core feed rate 0.180 mL/h and had a latent heat of 77 J/g at melting point 39.2 .deg. C. These shape-stabilized core/shell composite nanofibers showed good thermoregulating properties and had sufficiently high tensile strength for potential energy-storage applications, especially in smart textiles.

  7. Solvent-surface interactions control the phase structure in laser-generated iron-gold core-shell nanoparticles.

    Science.gov (United States)

    Wagener, Philipp; Jakobi, Jurij; Rehbock, Christoph; Chakravadhanula, Venkata Sai Kiran; Thede, Claas; Wiedwald, Ulf; Bartsch, Mathias; Kienle, Lorenz; Barcikowski, Stephan

    2016-03-23

    This work highlights a strategy for the one-step synthesis of FeAu nanoparticles by the pulsed laser ablation of alloy targets in the presence of different solvents. This method allows particle generation without the use of additional chemicals; hence, solvent-metal interactions could be studied without cross effects from organic surface ligands. A detailed analysis of generated particles via transmission electron microscopy in combination with EDX elemental mapping could conclusively verify that the nature of the used solvent governs the internal phase structure of the formed nanoparticles. In the presence of acetone or methyl methacrylate, a gold shell covering a non-oxidized iron core was formed, whereas in aqueous media, an Au core with an Fe3O4 shell was generated. This core-shell morphology was the predominant species found in >90% of the examined nanoparticles. These findings indicate that fundamental chemical interactions between the nanoparticle surface and the solvent significantly contribute to phase segregation and elemental distribution in FeAu nanoparticles. A consecutive analysis of resulting Fe@Au core-shell nanoparticles revealed outstanding oxidation resistance and fair magnetic and optical properties. In particular, the combination of these features with high stability magnetism and plasmonics may create new opportunities for this hybrid material in imaging applications.

  8. Solvent-surface interactions control the phase structure in laser-generated iron-gold core-shell nanoparticles

    Science.gov (United States)

    Wagener, Philipp; Jakobi, Jurij; Rehbock, Christoph; Chakravadhanula, Venkata Sai Kiran; Thede, Claas; Wiedwald, Ulf; Bartsch, Mathias; Kienle, Lorenz; Barcikowski, Stephan

    2016-03-01

    This work highlights a strategy for the one-step synthesis of FeAu nanoparticles by the pulsed laser ablation of alloy targets in the presence of different solvents. This method allows particle generation without the use of additional chemicals; hence, solvent-metal interactions could be studied without cross effects from organic surface ligands. A detailed analysis of generated particles via transmission electron microscopy in combination with EDX elemental mapping could conclusively verify that the nature of the used solvent governs the internal phase structure of the formed nanoparticles. In the presence of acetone or methyl methacrylate, a gold shell covering a non-oxidized iron core was formed, whereas in aqueous media, an Au core with an Fe3O4 shell was generated. This core-shell morphology was the predominant species found in >90% of the examined nanoparticles. These findings indicate that fundamental chemical interactions between the nanoparticle surface and the solvent significantly contribute to phase segregation and elemental distribution in FeAu nanoparticles. A consecutive analysis of resulting Fe@Au core-shell nanoparticles revealed outstanding oxidation resistance and fair magnetic and optical properties. In particular, the combination of these features with high stability magnetism and plasmonics may create new opportunities for this hybrid material in imaging applications.

  9. Broadband perfect light trapping in the thinnest monolayer graphene-MoS2 photovoltaic cell: the new application of spectrum-splitting structure

    Science.gov (United States)

    Wu, Yun-Ben; Yang, Wen; Wang, Tong-Biao; Deng, Xin-Hua; Liu, Jiang-Tao

    2016-02-01

    The light absorption of a monolayer graphene-molybdenum disulfide photovoltaic (GM-PV) cell in a wedge-shaped microcavity with a spectrum-splitting structure is investigated theoretically. The GM-PV cell, which is three times thinner than the traditional photovoltaic cell, exhibits up to 98% light absorptance in a wide wavelength range. This rate exceeds the fundamental limit of nanophotonic light trapping in solar cells. The effects of defect layer thickness, GM-PV cell position in the microcavity, incident angle, and lens aberration on the light absorptance of the GM-PV cell are explored. Despite these effects, the GM-PV cell can still achieve at least 90% light absorptance with the current technology. Our proposal provides different methods to design light-trapping structures and apply spectrum-splitting systems.

  10. Morphology-controlled synthesis of Ti3+ self-doped yolk–shell structure titanium oxide with superior photocatalytic activity under visible light

    International Nuclear Information System (INIS)

    Wang, Shixiong; Yang, Xiangjun; Wang, Yapeng; Liu, Lixiang; Guo, Yuanyuan; Guo, Hong

    2014-01-01

    Ti 3+ self-doped yolk–shell structure titanium oxide nanoparticle aggregates are fabricated through an environmental template-free route and the reduction reaction at low temperature subsequently. After the Ti 3+ doping, the reduced TiO 2 sample exhibits a wide visible-light absorption ranged from 400 nm to 800 nm. The intrinsic hollow core–shell microstructure can make multiple reflections of light within the chamber, and thus results in more efficient use of the light source compared with solid structure. Besides, the large surface area can render the sample with a high activity. Therefore, Ti 3+ self-doped yolk–shell structure titanium oxide exhibits a superior photocatalytic activity under visible light. This strategy is simple, cheap and mass-productive, which may shed light on a new avenue for large scale production of self-doped yolk–shell structural nano functional materials for catalyst, sensors, energy storage and other new applications. - Graphical abstract: A facile generic strategy is employed to prepare Ti 3+ self-doped yolk–shell structure titanium oxide nanoparticle aggregates with the superior photocatalytic activity under visible light. - Highlights: • Yolk–shell TiO 2 mesospheres are synthesized by solvothermal alcoholysis. • Ti 3+ self-doped yolk–shell structure titanium oxide is obtained at low temperature. • It exhibits a remarkable photocatalytic activity

  11. Nitrite sensing composite systems based on a core-shell emissive-superamagnetic structure: Construction, characterization and sensing behavior.

    Science.gov (United States)

    Yang, Yan; Liu, Liang; Zha, Jianhua; Yuan, Ningyi

    2017-04-15

    Two recyclable nitrite sensing composite samples were designed and constructed through a core-shell structure, with Fe 3 O 4 nanoparticles as core, silica molecular sieve MCM-41 as shell and two rhodamine derivatives as chemosensors, respectively. These samples and their structure were identified with their electron microscopy images, N 2 adsorption/desorption isotherms, magnetic response, IR spectra and thermogravimetric analysis. Their nitrite sensing behavior was discussed based on emission intensity quenching, their limit of detection was found as low as 1.2μM. Further analysis suggested a static sensing mechanism between nitrite and chemosensors through an additive reaction between NO + and chemosensors. After finishing their nitrite sensing, these composite samples and their emission could be recycled and recovered by sulphamic acid. Copyright © 2017 Elsevier B.V. All rights reserved.

  12. Stokes shift and fine structure splitting in composition-tunable Zn{sub x}Cd{sub 1−x}Se nanocrystals: Atomistic tight-binding theory

    Energy Technology Data Exchange (ETDEWEB)

    Sukkabot, Worasak, E-mail: w.sukkabot@gmail.com

    2017-02-01

    I report on the atomistic correlation of the structural properties and excitonic splitting of ternary alloy Zn{sub x}Cd{sub 1−x}Se wurtzite nanocrystals using the sp{sup 3}s* empirical tight-binding method with the description of the first nearest neighbouring interaction and bowing effect. Based on a successful model, the computations are presented under various Zn compositions (x) and diameters of alloy Zn{sub x}Cd{sub 1−x}Se nanocrystals with the experimentally synthesized compositions and sizes. With increasing Zn contents (x), the optical band gaps and electron-hole coulomb energies are improved, while ground electron-hole wave function overlaps, electron-hole exchange energies, stokes shift and fine structure splitting are reduced. A composition-tunable emission from blue to yellow wavelength is obviously demonstrated. The optical band gaps, ground electron-hole wave function overlaps, electron-hole interactions, stokes shift and fine structure splitting are progressively decreased with the increasing diameters. Alloy Zn{sub x}Cd{sub 1−x}Se nanocrystal with Zn rich and large diameter is the best candidate to optimistically be used as a source of entangled photon pairs. The agreement with the experimental data is remarkable. Finally, the present systematic study on the structural properties and excitonic splitting predominantly opens a new perspective to understand the size- and composition-dependent properties of Zn{sub x}Cd{sub 1−x}Se nanocrystals with a comprehensive strategy to design the optoelectronic devices.

  13. Triple layered core–shell structure with surface fluorinated ZnO-carbon nanotube composites and its electron emission properties

    International Nuclear Information System (INIS)

    Wang, H.Y.; Chua, Daniel H.C.

    2013-01-01

    Highlights: ► The effects of CF 4 plasma on ZnO-CNT core–shell structures were studied. ► ZnO was effective in protecting the aligned CNTs core for as long as 30 min of plasma etching. ► SEM showed the surface morphology was nearly similar between pristine, 2 min and 30 min plasma etched specimens. ► F was observed to displace O in ZnO. ► This is the first report of an ultra long plasma etch of fluorine onto ZnO surface. - Abstract: Core-shelled structures such as zinc oxide (ZnO) on carbon nanotubes (CNTs) give rise to interesting material properties. In this work, a triple-layered core–shell–shell structure is presented where the effects of fluorine (F) incorporation on the outmost shell of the ZnO-CNT structure are studied. The samples prepared ranged from a short 2 min to a 30 min immersion in carbon tetraflouride (CF 4 ) plasma. In addition, its effects on the electron emission properties also studied and it is shown that the plasma immersions create thinner field emitters with sharp tiny wrinkles giving rise to more electron emission sites and higher enhancement factor. In addition, X-ray photoelectron spectroscopy measurements showed that F ions replace O in ZnO coatings during immersion process, thus increasing the electrical conductivity and shifts the Fermi level of ZnO upwards. Both physical and electronic effects further contribute to a lower threshold field.

  14. Evidence of a core-shell structure in the antiferromagnetic La0.2Ce0.8CrO3 nanoparticles by neutron scattering

    International Nuclear Information System (INIS)

    Manna, P.K.; Yusuf, S.M.; Mukadam, M.D.; Kohlbrecher, J.

    2012-01-01

    We report the evidence of a core-shell structure in the antiferromagnetic La 0.2 Ce 0.8 CrO 3 nanoparticles by using a combination of neutron diffraction, polarized neutron small angle scattering (SANSPOL), and dc magnetization techniques. The neutron diffraction study establishes that the present nanoparticles are antiferromagnetic in nature. The magnetic scattering in the SANSPOL study arises from the shell part of the nanoparticles due to the disordered surface spins. The analysis of the SANSPOL data shows that these nanoparticles have a mean core diameter of 12.3±1.1 nm, and a shell thickness of 2.8±0.4 nm, giving a core-shell structure with an antiferromagnetic core, and a shell with a net magnetic moment under an applied magnetic field. (orig.)

  15. Evidence of a core-shell structure in the antiferromagnetic La0.2Ce0.8CrO3 nanoparticles by neutron scattering

    Science.gov (United States)

    Manna, P. K.; Yusuf, S. M.; Mukadam, M. D.; Kohlbrecher, J.

    2012-11-01

    We report the evidence of a core-shell structure in the antiferromagnetic La0.2Ce0.8CrO3 nanoparticles by using a combination of neutron diffraction, polarized neutron small angle scattering (SANSPOL), and dc magnetization techniques. The neutron diffraction study establishes that the present nanoparticles are antiferromagnetic in nature. The magnetic scattering in the SANSPOL study arises from the shell part of the nanoparticles due to the disordered surface spins. The analysis of the SANSPOL data shows that these nanoparticles have a mean core diameter of 12.3±1.1 nm, and a shell thickness of 2.8±0.4 nm, giving a core-shell structure with an antiferromagnetic core, and a shell with a net magnetic moment under an applied magnetic field.

  16. Synthesis and performance of core-shell structured ZnO/In{sub 2}O{sub 3} composites in situ growth

    Energy Technology Data Exchange (ETDEWEB)

    Zhao Yunlong [School of Materials Science and Engineering, Zhengzhou University, Zhengzhou 450002 (China); Lu Hongxia, E-mail: luhx@zzu.edu.cn [School of Materials Science and Engineering, Zhengzhou University, Zhengzhou 450002 (China); Yu Xiujun; Fan Bingbing; Chen Deliang [School of Materials Science and Engineering, Zhengzhou University, Zhengzhou 450002 (China); Zhang Liwei [School of Materials Science and Engineering, Zhengzhou University, Zhengzhou 450002 (China); Xinxiang University, Xinxiang 453003 (China); Wang Hailong; Yang Daoyuan; Xu Hongliang [School of Materials Science and Engineering, Zhengzhou University, Zhengzhou 450002 (China); Zhang Rui [School of Materials Science and Engineering, Zhengzhou University, Zhengzhou 450002 (China); Zhengzhou Institute of Aeronautical Industry Management, Zhengzhou 450015 (China)

    2011-10-01

    Core-shell structured ZnO/In{sub 2}O{sub 3} composites were successfully synthesized via situ growth method. Phase structure, morphology, microstructure and property of the products were investigated by X-ray diffraction (XRD), TG-DTA, field emission scanning electron microscopy (FESEM), energy-dispersive spectrometry (EDS), transmission electron microscope (TEM) and photoluminescence (PL). Results show that the core-shell structures consist of spindle-like ZnO with about 800 nm in length and 200 nm in diameter, and In{sub 2}O{sub 3} particles with a diameter of 50 nm coated on the surface of ZnO uniformly. HMTA plays an important role in the formation of core-shell structures and the addition of In{sub 2}O{sub 3} has a great effect on PL spectrum. Possible mechanism for the formation of core-shell structures is also proposed in this paper.

  17. Preparation and characterization of core-shell structured α-Fe2O3/SiC spheres

    International Nuclear Information System (INIS)

    Wu Xiangyang; Jin Guoqiang; Guan Lianxiu; Cao Hu; Guo Xiangyun

    2006-01-01

    Fe 2 O 3 /SiC composite microspheres with a core-shell structure were prepared by the carbothermal reduction reaction between poly(styrene sulfonic acid) iron salt and silica. X-ray diffraction, scanning electron microscope and magnetic properties measurement system were employed to characterize the morphology, structure and magnetic properties of the microspheres. From the results, the microspheres with a diameter of 150-400 μm have an α-Fe 2 O 3 core and a SiC shell of tens of microns in thickness. The magnetism of the core-shell structured spheres at 10 4 Oe is much larger than that of pure α-Fe 2 O 3 spheres prepared under the same conditions and the increment in magnetism is attributed to the introduction of iron silicides and SiC. By further chemical treatment, the α-Fe 2 O 3 /SiC microspheres can change into SiC hollow spheres, which have diameters similar to the magnetic spheres and mainly consist of irregular SiC particles. The formation mechanism of the composite and hollow spheres was also discussed

  18. Preparation of core-shell structured CaCO3 microspheres as rapid and recyclable adsorbent for anionic dyes

    Science.gov (United States)

    Zhao, Mengen; Chen, Zhenhua; Lv, Xinyan; Zhou, Kang; Zhang, Jie; Tian, Xiaohan; Ren, Xiuli; Mei, Xifan

    2017-09-01

    Core-shell structured CaCO3 microspheres (MSs) were prepared by a facile, one-pot method at room temperature. The adsorbent dosage and adsorption time of the obtained CaCO3 MSs were investigated. The results suggest that these CaCO3 MSs can rapidly and efficiently remove 99-100% of anionic dyes within the first 2 min. The obtained CaCO3 MSs have a high Brunauer-Emmett-Teller surface area (211.77 m2 g-1). In addition, the maximum adsorption capacity of the obtained CaCO3 MSs towards Congo red was 99.6 mg g-1. We also found that the core-shell structured CaCO3 MSs have a high recycling capability for removing dyes from water. Our results demonstrate that the prepared core-shell structured CaCO3 MSs can be used as an ideal, rapid, efficient and recyclable adsorbent to remove dyes from aqueous solution.

  19. Electrochemical Synthesis of Core-Shell-Structured NbC-Fe Composite Powder for Enforcement in Low-Carbon Steel.

    Science.gov (United States)

    Li, Hongmei; Song, Qiushi; Xu, Qian; Chen, Ying; Xu, Liang; Man, Tiannan

    2017-11-01

    An NbC-Fe composite powder was synthesized from an Nb₂O₅/Fe/C mixture by electrochemical reduction and subsequent carbonization in molten CaCl₂-NaCl. The composite has a core-shell structure, in which NbC acts as the cores distributing in the Fe matrix. A strong bonding between NbC and Fe is benefit from the core-shell structure. The sintering and electrochemical reduction processes were investigated to probe the mechanism for the reactions. The results show that NbC particles about several nanometers were embraced by the Fe shell to form a composite about 100 nm in size. This featured structure can feasibly improve the wettability and sinterability of NbC as well as the uniform distribution of the carbide in the cast steel. By adding the composite into steel in the casting process, the grain size of the casted steel was markedly deceased from 1 mm to 500 μm on average, favoring the hardening of the casted steel.

  20. Anti-wear properties of the molluscan shell Scapharca subcrenata: Influence of surface morphology, structure and organic material on the elementary wear process

    International Nuclear Information System (INIS)

    Tian, Limei; Tian, Ximei; Wang, Yinci; Hu, Guangliang; Ren, Luquan

    2014-01-01

    As a typical natural biological mineralisation material, molluscan shells have excellent wear-resistance properties that result from the interactions amongst biological coupling elements such as morphology, structure and material. The in-depth study of the wear-resistance performance of shells and the contribution made by each coupling element may help to promote the development of new bionic wear-resistant devices. The objective of this study was to investigate the influence of surface morphology (rib distribution on the shell), structure (rib coupled with nodules) and material (organic matter) on the anti-wear performance of the molluscan Scapharca subcrenata shell. The effect and contribution of each of these biological coupling elements were systematically investigated using the comparative experiment method. All three were found to exert significant effects on the shell's wear-resistance ability, and their individual contributions to that ability were revealed. Organic material can be classified as the principal coupling element, rib morphology as the secondary coupling element and the combined rib-nodule structure as the general coupling element. - Highlights: • We found that the S. subcrenata shell has an anti-wear ability. • This is related to the morphology, structure and material of the shell surface. • Organic material is the principal coupling element in its anti-wear ability. • Rib morphology could be considered the secondary coupling element. • The coupled structure could be regarded as the general coupling element

  1. PARCS - A pre-stressed and reinforced concrete shell element for analysis of containment structures

    International Nuclear Information System (INIS)

    Buragohain, D.N.; Mukherjee, A.

    1993-01-01

    Containment structures are designed as pressure vessels against a huge internal pressure build up in the event of a postulated LOCA. In such situations the containment structures experience predominantly in-plane stress in tension. Therefore, pre-stressed concrete has been very frequently used for the construction of containment. For larger plants a dual containment with a pre-stressed concrete inner containment and a reinforced concrete outer containment has been adopted. These structures are required to perform within very stringent safety requirements under extremely severe loading. Naturally, their design has attracted a lot of investigators and a huge volume of literature has been published in previous SMiRT conferences. However, it seems that the structural modeling of the containment has not developed accordingly. It is a common practice to consider the concrete section only in the model and the effects of pre-stress and reinforcements are usually neglected. This is due to the difficulty in including these effects without generating an unduly large model. To include these effects using the existing software, the concrete can be modeled with 3D elements. The reinforcements can be included in the model as bar or cable elements. However, that would require a nodal line along every reinforcement. Therefore, this method would generate a huge model unmanageable even with modern computing facilities. Alternatively, the reinforcements can be assumed to be smeared uniformly within the structure and an average property can be included. This model is acceptable when the reinforcements are very closely spaced. However, for sparsely spaced reinforcements it would result in loss of accuracy, especially in important areas like the vicinity of large openings. In this paper a shell element for the analysis of pre-stressed and reinforced concrete structures has been proposed which alleviates this difficulty. This element can accommodate the reinforcing bars or cables anywhere

  2. (3He,α) reaction mechanism at high energy and neutron inner shell structure

    International Nuclear Information System (INIS)

    Wiele, J. van de.

    1980-01-01

    The ( 3 He,α) reaction on 12 C, 16 O, 28 Si, 58 Ni, 90 Zr, 118 Sn, 124 Sn and 208 Pb targets has been studied at Esub( 3 He) = 217 MeV (or 205 MeV) in order to investigate the reaction mechanism at high energy and large momentum transfer. The reaction yields large cross sections at very forward angles and strongly enhances the largest orbital momentum transfer. The angular distribution shapes are well reproduced in the frame-work of the Z-R- D.W.B.A. analysis if we use a unique empirical α-potential: Vsub(α)(Esub(α)) = Vsub( 3 He)(3/4 Esub(α)) + Vsub(n)(1/4 Esub(α)). The excitation energy spectra have been measured up to 100 MeV in the residual light and medium nuclei and up to about 16 MeV in heavy nuclei. In addition to the well-known low-lying levels, peaks or broad structures are observed for each nucleus at higher excitation energies. They are attributed to pick up from inner shells: 1s( 11 C and 15 O), 1p( 27 Si), 1d5/2 + 1p( 57 Ni), 1f7/2( 89 Zr) 1g9/2 117 Sn, 123 Sn and 1h11/2( 207 Pb). Selectivity and localization of direct and indirect pick up ( 3 He,α) reactions were studied. Finite range calculations show that this reaction is not very sensitive to the details of the range from function but only to D 0 coefficient and range R. A microscopic α-nucleus optical potential calculated with n-n dependent and independent density forces is able to reproduce both elastic scattering and pick up reaction angular distributions [fr

  3. Shell-structure influence on the multinucleon transfer in nucleon transfer matrix elements

    International Nuclear Information System (INIS)

    Muminov, A.I.; Utamuratov, R.K.; Kalandarov, Sh.A.; Nasirov, V.K.; Nasirov, A.K.

    2004-01-01

    Full text: An analysis of the experimental data on the charge (mass) distributions of products in nuclear reactions with heavy ions [1], dependence of yield of fragments on their isotope numbers and ones of projectile- and target nuclei [2], and cross sections of the formation of evaporation residues at synthesis of new superheavy elements [3] shows that the individual peculiarities (shell structure, N/Z-ratio) of interacting nuclei play decisive role at formation and evolution of dinuclear system. Therefore, the appropriate microscopic model should be used for the theoretical analysis of the above mentioned effects. The main quantities which must be included into model are the realistic scheme of single-particle states, nucleon separation energy, single-particle matrix elements of nucleon transitions in nuclei and nucleon exchange between them caused by influence of the mean-field of partner-nucleus. In this work the nucleon transfer matrix elements were calculated for the Wood-Saxon potential for spherical nucleus. The eigenvalues and wave functions of single-particle states were obtained by numerical solving Schroedinger's equation. The integral estimation of the matrix elements is found by comparing the calculated width of the charge distributions of the reaction products with the experimental data. In the early paper [4], the same matrix elements were calculated analytically using an approximation for wave functions: authors have used wave functions of the spherical potential well. The numerical values of squares of proton transfer matrix elements found in this work are nearly in coincidence with that presented in [4]. There is a difference between curves of dependencies of the matrix elements under discussion on the relative distance between centres of nuclei when this distance is smaller than sum of nuclei radii

  4. Nuclear structure in the vicinity of shell closures far from stability

    International Nuclear Information System (INIS)

    Grawe, H.; Gorska, M.; Doering, J.

    2000-09-01

    The status of experimental approach to 100 Sn and 78 Ni is reviewed. Revised single particle energies for neutrons are deduced for the N=Z=50 shell closure and evidence for low lying I π =2 + and 3 - states is presented. Moderate E2 polarization charges of 0.1 e and 0.6 e are found to reproduce the experimental data when core excitation of 100 Sn is properly accounted for in the shell model. For the neutron rich Ni region no conclusive evidence for an N=40 subshell is found, whereas firm evidence for the persistence of the N=50 shell at 78 Ni is inferred from the existence of seniority isomers. The disappearance of this isomerism in the mid νg 9/2 shell is discussed. The spectroscopy of 216 Th disproves the existence of a Z=92 shell gap as predicted by some recent mean field calculations. Inversion of the πh 9/2 and f 7/2 orbitals at Z=90 is ascribed to the coupling of the f 7/2 (and i 13/2 ) protons to the low-lying 3 - state (ℎω 3 =1.69 MeV). (orig.)

  5. Facile and green synthesis of core-shell structured magnetic chitosan submicrospheres and their surface functionalization.

    Science.gov (United States)

    Li, Yiya; Yuan, Dongying; Dong, Mingjie; Chai, Zhihua; Fu, Guoqi

    2013-09-17

    Submicrometer-sized magnetite colloid nanocrystal clusters (MCNCs) provide a new avenue for constructing uniformly sized and highly magnetic composite submicrospheres. Herein, a facile and eco-friendly method is described for the synthesis of Fe3O4@poly(acrylic acid) (PAA)/chitosan (CS) core-shell submicrospheres using MCNCs bearing carboxyl groups as the magnetic cores. It is based on the self-assembly of positively charged CS chains on the surface of the oppositely charged MCNCs dispersed in the aqueous solution containing acrylic acid (AA) and a cross-linker N,N'-methylenebis(acrylamide) (MBA), followed by radical induced cross-linking copolymerization of AA and MBA along the CS chains. The resulting polymer shell comprises a medium shell of cross-linked PAA/CS polyelectrolyte complexes and an outer shell of protonated CS chains. It was found that the shell thickness could be tuned by varying either the concentration of radical initiator or the molar ratio of AA to aminoglucoside units of CS. To the surface of thus obtained Fe3O4@PAA/CS particles, Au nanoparticles, a variety of functional groups such as fluorescein, carboxyl, quaternary ammonium, and aliphatic bromide, and even functional polymer chains were successfully introduced. Therefore, such Fe3O4@PAA/CS submicrospheres may be used as versatile magnetic functional scaffolds in biorelated areas like bioseparation and medical assay, considering the unique features of CS like nontoxicity and biocompatibility.

  6. Supersaturation-controlled surface structure evolution of Pd@Pt core-shell nanocrystals: enhancement of the ORR activity at a sub-10 nm scale

    Science.gov (United States)

    Qi, Kun; Zheng, Weitao; Cui, Xiaoqiang

    2016-01-01

    Here, we designed and implemented a facile strategy for controlling the surface evolution of Pd@Pt core-shell nanostructures by simply adjusting the volume of OH- to control the reducing ability of ascorbic acid and finally manipulating the supersaturation in the reaction system. The surface structure of the obtained Pd@Pt bimetallic nanocrystals transformed from a Pt {111} facet-exposed island shell to a conformal Pt {100} facet-exposed shell by increasing the pH value. The as-prepared well aligned Pd@Pt core-island shell nanocubes present both significantly enhanced electrocatalytic activity and favorable long-term stability toward the oxygen reduction reaction in alkaline media.Here, we designed and implemented a facile strategy for controlling the surface evolution of Pd@Pt core-shell nanostructures by simply adjusting the volume of OH- to control the reducing ability of ascorbic acid and finally manipulating the supersaturation in the reaction system. The surface structure of the obtained Pd@Pt bimetallic nanocrystals transformed from a Pt {111} facet-exposed island shell to a conformal Pt {100} facet-exposed shell by increasing the pH value. The as-prepared well aligned Pd@Pt core-island shell nanocubes present both significantly enhanced electrocatalytic activity and favorable long-term stability toward the oxygen reduction reaction in alkaline media. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr07940c

  7. Au@Pd core-shell nanobricks with concave structures and their catalysis of ethanol oxidation.

    Science.gov (United States)

    Wang, Wenjin; Zhang, Jie; Yang, Shengchun; Ding, Bingjun; Song, Xiaoping

    2013-10-01

    Au@Pd core-shell nanobricks (CNBs) with concave surfaces and Pd shells with a thickness of approximately 5 nm were synthesized by co-reduction of HAuCl4 and H2 PdCl4 in the presence of Au seeds and Ag ions. These as-synthesized concave CNBs exhibit significantly enhanced catalytic activity for the electrooxidation of ethanol in alkaline media compared to the commercially-used Pd black. The improved performance of the Au@Pd CNBs can be attributed to the exposed stepped surfaces, high-index facets, and the synergistic effects of the core and shell metals. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Thermal Stability of Platinum-Cobalt Bimetallic Nanoparticles: Chemically Disordered Alloys, Ordered Intermetallics, and Core-Shell Structures.

    Science.gov (United States)

    Huang, Rao; Shao, Gui-Fang; Zhang, Yang; Wen, Yu-Hua

    2017-04-12

    Pt-Co bimetallic nanoparticles are promising candidates for Pt-based nanocatalysts and magnetic-storage materials. By using molecular dynamics simulations, we here present a detailed examination on the thermal stabilities of Pt-Co bimetallic nanoparticles with three configurations including chemically disordered alloy, ordered intermetallics, and core-shell structures. It has been revealed that ordered intermetallic nanoparticles possess better structural and thermal stability than disordered alloyed ones for both Pt 3 Co and PtCo systems, and Pt 3 Co-Pt core-shell nanoparticles exhibit the highest melting points and the best thermal stability among Pt-Co bimetallic nanoparticles, although their meltings all initiate at the surface and evolve inward with increasing temperatures. In contrast, Co-Pt core-shell nanoparticles display the worst thermal stability compared with the aforementioned nanoparticles. Furthermore, their melting initiates in the core and extends outward surface, showing a typical two-stage melting mode. The solid-solid phase transition is discovered in Co core before its melting. This work demonstrates the importance of composition distribution to tuning the properties of binary nanoparticles.

  9. Synthesis and characterization of self-crosslinking fluorinated polyacrylate soap-free latices with core-shell structure

    Science.gov (United States)

    Xu, Wei; An, Qiufeng; Hao, Lifen; Zhang, Dan; Zhang, Min

    2013-03-01

    Novel self-crosslinking fluorinated polyacrylate soap-free latices (FMBN) with core-shell structure were synthesized by semicontinuous seeded emulsion polymerization method from dodecafluoroheptyl methacrylate (DFMA), methyl methacrylate (MMA), butyl acrylate (BA), and N-methylolamide (NMA) in the presence of a polymerizable emulsifier-ammonium allyloxtmethylate nonylphenol ethoxylates sulfate (DNS-86). Effects of the DNS-86 and DFMA amounts on stability and properties of the FMBN emulsions were studied. Besides, the latices and their film were characterized by Fourier transform infrared (FTIR) spectroscopy, nuclear magnetic resonance (1H NMR) spectrum, scanning electron microscopy (SEM), transmission electron microscopy (TEM), laser particle size analyzer, differential scanning calorimetry (DSC), thermogravimetry analysis (TGA), contact angle goniometer, X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM), respectively. FT-IR spectra and 1H NMR spectrum showed that DFMA successfully participated in soap-free emulsion polymerization and monomers formed the fluorinated acrylate copolymer. The resulted latex particles had the core-shell structure. The films formed from the FMBN latices thus had two Tg. Their thermal stability and Tg of the shell phase increased gradually with augment of DFMA amount in polymer. XPS, AFM and hydrophobicity analyses indicated the fluoroalkyl groups had the tendency to enrich at the film-air interface. This enrichment of fluorine at the film-air interface was more evident after the annealing process. Water contact angles of the FMBN film before and after the annealing process could attain 115.5° and 117.5°, individually.

  10. Pulse electrodeposition to prepare core-shell structured AuPt@Pd/C catalyst for formic acid fuel cell application

    Science.gov (United States)

    Lu, Xueyi; Luo, Fan; Song, Huiyu; Liao, Shijun; Li, Hualing

    2014-01-01

    A novel core-shell structured AuPt@Pd/C catalyst for the electrooxidation of formic acid is synthesized by a pulse electrodeposition process, and the AuPt core nanoparticles are obtained by a NaBH4 reduction method. The catalyst is characterized with X-ray powder diffraction and transmission electron microscopy, thermogravimetric analysis, cyclic voltammetry, CO stripping and X-ray photoelectron spectroscopy. The core-shell structure of the catalyst is revealed by the increase in particle size resulting from a Pd layer covering the AuPt core, and by a negative shift in the CO stripping peaks. The addition of a small amount of Pt improves the dispersion of Au and results in smaller core particles. The catalyst's activity is evaluated by cyclic voltammetry in formic acid solution. The catalyst shows excellent activity towards the anodic oxidation of formic acid, the mass activity reaches 4.4 A mg-1Pd and 0.83 A mg-1metal, which are 8.5 and 1.6 times that of commercial Pd/C. This enhanced electrocatalytic activity could be ascribed to the good dispersion of Au core particles resulting from the addition of Pt, as well as to the interaction between the Pd shell layer and the Au and Pt in the core nanoparticles.

  11. Glass transition of poly (methyl methacrylate) filled with nanosilica and core-shell structured silica

    DEFF Research Database (Denmark)

    Song, Yihu; Bu, Jing; Zuo, Min

    2017-01-01

    Core-shell (CS) nanocomposite particles with 53.4 wt% cross-linked poly (methyl methacrylate) (PMMA) shell of 11.6 nm in thickness were fabricated via miniemulsion polymerization of methyl methacrylate in the presence of modified nanosilica. The influence of nanosilica and CS nanoparticles on glass...... transition and segmental dynamics of PMMA in the nanocomposites prepared via solution casting was compared. The remarkable depression (≥10 °C) of glass transition temperature (Tg) induced by the incorporation of SiO2 and CS was both observed at low loadings. Here, different mechanisms were responsible...

  12. Large-scale micromagnetic simulation of Nd-Fe-B sintered magnets with Dy-rich shell structures

    Directory of Open Access Journals (Sweden)

    T. Oikawa

    2016-05-01

    Full Text Available Large-scale micromagnetic simulations have been performed using the energy minimization method on a model with structural features similar to those of Dy grain boundary diffusion (GBD-processed sintered magnets. Coercivity increases as a linear function of the anisotropy field of the Dy-rich shell, which is independent of Dy composition in the core as long as the shell thickness is greater than about 15 nm. This result shows that the Dy contained in the initial sintered magnets prior to the GBD process is not essential for enhancing coercivity. Magnetization reversal patterns indicate that coercivity is strongly influenced by domain wall pinning at the grain boundary. This observation is found to be consistent with the one-dimensional pinning theory.

  13. Monte Carlo simulation of magnetic properties of a ferrimagnetic nanoisland with hexagonal prismatic core-shell structure

    Science.gov (United States)

    Wang, Wei; Peng, Zhou; Lin, Shan-shan; Li, Qi; Lv, Dan; Yang, Sen

    2018-01-01

    Using Monte Carlo simulation, the magnetic and thermodynamic properties of a ferrimagnetic nanoisland with hexagonal prismatic core-shell structure, consisting of the bilayer with a core of spin-5/2 atoms surrounded by shell of spin-2 atoms in the external magnetic field have been studied. We have investigated the effects of the single-ion anisotropies, the exchange coupling and the magnetic field on the magnetization, susceptibility, internal energy and blocking temperature of the nanoisland. A great number of interesting behaviors, such as various types of magnetization curves, have been obtained depending on different values of the physical parameters. The magnetic hysteresis loop behaviors are the main focus of the research. The system exhibits multiple hysteresis loop behaviors, such as double, triple and quadruple hysteresis loops for certain parameters.

  14. Facile synthesis of core-shell Cu2O@ ZnO structure with enhanced photocatalytic H2 production

    Science.gov (United States)

    Zhang, Yong-Hui; Jiu, Bei-Bei; Gong, Fei-Long; Lu, Kuan; Jiang, Nan; Zhang, Hao-Li; Chen, Jun-Li

    2018-05-01

    Core-shell Cu2O@ZnO composites were synthesized successfully based on a one-pot hydrothermal method in the presence of dioctyl sulfosuccinate sodium salt (AOT) surfactant. The Cu2O can be converted to rough core-shell Cu2O@ZnO structure by adjusting the amount of zinc powder added. The as-synthesized Cu2O@ZnO composites exhibited excellent photocatalytic activity and the amount of H2 generated using these composites was 4.5-fold more than that produced with Cu2O cubes. A possible photocatalytic mechanism for the Cu2O@ZnO composites with enhanced photocatalytic activity could be the separation by ZnO of the effective charge carriers.

  15. Laser spectroscopy of cadmium isotopes: probing the nuclear structure between the neutron 50 and 82 shell closures

    CERN Multimedia

    Blaum, K; Stroke, H H; Krieger, A R

    We propose to study the isotopic chain of cadmium with high-resolution laser spectroscopy for the first time. Our goal is to determine nuclear spins, moments and root-mean-square charge radii of ground and isomeric states between the neutron 50 and 82 shell closures, contributing decisively to a better understanding of the nuclear structure in the vicinity of the doubly-magic $^{100}$Sn and $^{132}$Sn. On the neutron-rich side this is expected to shed light on a shell-quenching hypothesis and consequently on the duration of the r-process along the waiting-point nuclei below $^{130}$Cd. On the neutron-deficient side it may elucidate the role of the cadmium isotopes in the rp-process for rapidly accreting neutron stars.

  16. PREFACE: 11th International Spring Seminar on Nuclear Physics: Shell Model and Nuclear Structure - achievements of the past two decades

    Science.gov (United States)

    2015-02-01

    The 11th International Seminar on Nuclear Physics was held in Ischia from May 12 to May 16, 2014. This Seminar was dedicated to Aldo Covello, who has been the promoter of this series of meetings, which started in Sorrento in 1986 and continued with meetings held every two or three years in the Naples area. Aldo's idea was to offer to a group of researchers, actively working in selected fields of Nuclear Physics, the opportunity to confront their points of view in a lively and informal way. The choice for the period of the year, Spring, as well as the sites chosen reflected this intent. The first meeting was of a purely theoretical nature, but it was immediately clear that the scope of these conferences needed to be enlarged calling into play the experimental community. Then, starting from the second meeting, all the following ones have been characterized by fruitful discussion between theoretical and experimental researchers on current achievements and future developments of nuclear structure. This may be read, in fact, as one of the motivating factors for Aldo's election as Fellow of the American Physical Society in 2008 "... for his outstanding contributions to the international nuclear physics community by providing, for over two decades, a venue for theorists and experimentalists to share their latest ideas." The present meeting, organized by Aldo's former students and with the benefit of his suggestions, has maintained this tradition. The title "Shell model and nuclear structure: achievements of the past two decades" recalls that of the 2nd International Spring Seminar "Shell Model and Nuclear Structure: where do we stand?". The main aim of this 11th Seminar was, in fact, to discuss the changes of the past two decades on our view of nuclei in terms of shell structure as well as the perspectives of the shell model, which has been one of the key points in Aldo's research. This point is well accounted by the Opening Speech of Igal Talmi, one of the fathers of the

  17. Studies on II-VI and III-V semiconductor nanostructures. Introduction of the core/shell/shell structure and development of CdSe nanocrystals in an automatized procedure; Untersuchungen an II-VI und III-V Halbleiternanostrukturen. Einfuehrung der Core/shell/shell-Struktur und Darstellung von CdSe-Nanokristallen in einem automatisierten Verfahren

    Energy Technology Data Exchange (ETDEWEB)

    Mekis, I.

    2005-11-15

    The work in this dissertation is focused on the development and characterization of fluorescent II-VI and III-V-Nanomaterials. Highly luminescent and photostable Nanocrystals with narrow size distributions were prepared. It was shown that nearly monodisperse CdSe-Nanocrystals could be prepared from Cd(Ac){sub 2} and TOPSe in a mixture of TOPO/TOP/HDA/TDPA. Nearly monodisperse CdSe/CdS-Core/shell-Nanocrystals have been prepared in a one-pot-synthesis by injection of H{sub 2}S-Gas into a freshly prepared crude solution of CdSe. The passivation of the CdSe-core with an inorganic shell of CdS resulted in the drastic improvement of the photoluminescence-efficiency of the colloidal solution. Reproducible room-temperature quantum yields reached up to a value of 85%. Photostability investigations have proved the enhanced stability of CdSe/CdS-Nanocrystals compared to CdSe-Nanocrystals under illumination with UV-Light. A novel type of luminescent semiconductor nanocrystal structure has been developed, consisting of a CdSe core and two anorganic shells. Highly fluorescent and nearly monodisperse CdSe/CdS/ZnS- and CdSe/ZnSe/ZnS-Core/shell/shell-nanocrystals have been prepared via organometallic- and acetate-precursors. The Core/she ll/shell particles reached reproducible room-temperature quantum yields up to 85%. Photostability investigations among CdSe-core, CdSe/CdS-Core/shell- and CdSe/CdS/ZnS- Core/shell/-shell-nanocrystals under illumination with UV-light have proved the highest photostability of the Core/shell/shell-particles. The photostabilities of CdSe/ZnSe/ZnS-and CdSe/ZnS-nanocrystals were compared under illumination with intense laser-beam in air. Another part of this work focused on the development of an automated synthesis procedure of CdSe-nanocrystals by constructing and implementing a flow-reactor system. The size and structure of prepared nanocrystals depended considerably on the Cd:Se-precursorratio and the flow-rate. The preparation of CdSe using Cd(Ac)2

  18. Splitting rules for the 2nd hierarchy structure of the electronic spectra of 2D FC(n) quasicrystals

    Science.gov (United States)

    Li, Feng; Yang, Xiangbo

    2004-06-01

    On the basis of our former work and by means of the decomposition-decimation method, we study the splitting rules for the second hierarchy of the electronic energy spectra for two-dimensional Fibonacci-class quasicrystals with one kind of atom and two bond lengths. It is found that every line of the sub-spectra for n x n and ( n + 1) x ( n + 1) clusters of FC(n) (n ≥ 2) splits according to the type Y‘( n-1)-2-1 and type Y n-2-1 respectively. The one for n x ( n + 1) clusters of FC(n) consists of three sub-subbands when n le 2, and five sub-subbranches when n ge 3. The general formulae of the number of energy levels for the spectra of the second hierarchy are obtained. The analytical results are confirmed by numerical simulations.

  19. Split Photosystem Protein, Linear-Mapping Topology, and Growth of Structural Complexity in the Plastid Genome of Chromera velia

    Czech Academy of Sciences Publication Activity Database

    Janouškovec, J.; Sobotka, Roman; Lai, De Hua; Flegontov, Pavel; Koník, P.; Komenda, Josef; Ali, S.; Prášil, Ondřej; Pain, A.; Oborník, Miroslav; Lukeš, Julius; Keeling, P. J.

    2013-01-01

    Roč. 30, č. 11 (2013), s. 2447-2462 ISSN 0737-4038 R&D Projects: GA ČR GAP506/12/1522; GA ČR GBP501/12/G055; GA MŠk(CZ) ED2.1.00/03.0110 Institutional support: RVO:61388971 ; RVO:60077344 Keywords : plastid genome evolution * Chromera velia * split protein Subject RIV: CE - Biochemistry Impact factor: 14.308, year: 2013

  20. Preparation and Structural Studies on Hybrid Core-Shell Nanoparticles Consisting of Silica Core and Conjugated Block Copolymer Shell Prepared by Surface-Initiated Polymerization

    Science.gov (United States)

    Chatterjee, Sourav; Karam, Tony; Rosu, Cornelia; Li, Xin; Do, Changwoo; Youm, Sang Gil; Haber, Louis; Russo, Paul; Nesterov, Evgueni

    Controlled Kumada catalyst-transfer polymerization occurring by chain-growth mechanism was developed for the synthesis of conjugated polymers and block copolymers from the surface of inorganic substrates such as silica nanoparticles. Although synthesis of conjugated polymers via Kumada polymerization became an established method for solution polymerization, carrying out the same reaction in heterogeneous conditions to form monodisperse polymer chains still remains a challenge. We developed and described a simple and efficient approach to the preparation of surface-immobilized layer of catalytic Ni(II) initiator, and demonstrated using it to prepare polymers and block copolymers on silica nanoparticle. The structure of the resulting hybrid nanostructures was thoroughly studied using small-angle neutron and X-ray scattering, thermal analysis, and optical spectroscopy. The photoexcitation energy transfer processes in the conjugated polymer shell were studied via steady-state and time resolved transient absorption spectroscopy. This study uncovered important details of the energy transfer, which will be discussed in this presentation.

  1. 3D structured Mo-doped Ni3S2 nanosheets as efficient dual-electrocatalyst for overall water splitting

    Science.gov (United States)

    Wu, Chengrong; Liu, Bitao; Wang, Jun; Su, Yongyao; Yan, Hengqing; Ng, Chuntan; Li, Cheng; Wei, Jumeng

    2018-05-01

    Searching for a cost-effective, high efficient and stable bifunctional electrocatalyst for overall water-splitting is critical to renewable energy systems. In this study, three-dimensional (3D) curved nanosheets of Mo-doped Ni3S2 grown on nickel foam were successfully synthesized via a one-step hydrothermal process. The hydrogen-evolution reaction (HER) and the oxygen-evolution reaction (OER) in alkaline environment of this 3D catalyst are investigated in detail. The results show that it possesses lower overpotential, high current densities and small Tafel slopes both in OER and HER. For HER, the catalysts show excellent electrochemical performance, demonstrating a low over-potential of 212 mV at 10 mA cm-2 with a large decrease of 127 mV compared to the undoped Ni3S2. And it also shows a lower overpotential of 260 mV at 10 mA cm-2 which decreases 30 mV for OER. In addition, it is only need 1.67 V for the overall water splitting at 10 mA cm-2 which is 70 mV. It found that the Mo element would change the morphology of Ni3S2 and induce much more active sites for HER and OER. The as-prepared Mo-doped Ni3S2 bi-functional electrocatalyst could act as the promising electrode materials for water splitting.

  2. Structural and magnetic properties of CoO-Pt core-shell nanoparticles

    Czech Academy of Sciences Publication Activity Database

    Zeleňáková, A.; Zeleňák, V.; Michalik, Štefan; Kováč, J.; Meisel, M. W.

    2014-01-01

    Roč. 89, č. 10 (2014), "104417-1"-"104417-10" ISSN 1098-0121 Institutional support: RVO:68378271 Keywords : CoO-Pt core shell nanoparticles * superparamagnetism * superspin glass state * x-ray diffraction * x-ray absorption spectroscopy Subject RIV: BG - Nuclear, Atomic and Molecular Physics, Colliders Impact factor: 3.736, year: 2014

  3. Palm-Kernel Shell Concrete For Structural Use – A Preliminary ...

    African Journals Online (AJOL)

    The paper reports on the results of an investigation into the physical and strength characteristics of concrete (norminal mixes), which contains crushed palm-kernel shell as fine aggregates instead of normal river sand. 66 No beams of 100mm x 100mm x 500mm sizes and 396 No 100mm cubes as well were tested with ...

  4. Thermal and magnetic properties of ternary mixed Ising nanoparticles with core–shell structure: Effective-field theory approach

    International Nuclear Information System (INIS)

    Kantar, Ersin; Keskin, Mustafa

    2014-01-01

    We propose a ternary Ising spins (1/2, 1, 3/2) model to investigate the thermal and magnetic properties of magnetic nanoparticles with core–shell structure within the framework of the effective-field theory with correlations. The center site of the core is occupied by σ=±1/2 spin, while those surrounding the center site are occupied by S=±1, 0 spins and the shell sites are occupied by m=±1/2,±3/2 spins. Thermal behaviors of the core and shell magnetizations, susceptibilities and internal energies as well as total magnetization are examined. In order to confirm the stability of the solutions we also investigate the free energy of the system. According to the values of Hamiltonian parameters, the system undergoes first- and second-order phase transitions. Phase diagrams are calculated and discussed in detail. We find that the system exhibits a tricritical point, reentrant and five different type (Q, P, R, S and W) of compensation behaviors that strongly depend on interaction parameters. The results are in good agreement with some experimental and theoretical results. - Highlights: • Thermal and magnetic properties of ternary Ising nanoparticles are studied. • Phase diagrams within the EFT with correlations are calculated and discussed. • The effects of the exchange interactions and crystal field have been studied. • Reentrant phenomena and compensation behaviors have been found

  5. Thermal and magnetic properties of ternary mixed Ising nanoparticles with core–shell structure: Effective-field theory approach

    Energy Technology Data Exchange (ETDEWEB)

    Kantar, Ersin [Department of Physics, Erciyes University, 38039 Kayseri (Turkey); Institute of Science, Erciyes University, 38039 Kayseri (Turkey); Keskin, Mustafa, E-mail: keskin@erciyes.edu.tr [Department of Physics, Erciyes University, 38039 Kayseri (Turkey)

    2014-01-15

    We propose a ternary Ising spins (1/2, 1, 3/2) model to investigate the thermal and magnetic properties of magnetic nanoparticles with core–shell structure within the framework of the effective-field theory with correlations. The center site of the core is occupied by σ=±1/2 spin, while those surrounding the center site are occupied by S=±1, 0 spins and the shell sites are occupied by m=±1/2,±3/2 spins. Thermal behaviors of the core and shell magnetizations, susceptibilities and internal energies as well as total magnetization are examined. In order to confirm the stability of the solutions we also investigate the free energy of the system. According to the values of Hamiltonian parameters, the system undergoes first- and second-order phase transitions. Phase diagrams are calculated and discussed in detail. We find that the system exhibits a tricritical point, reentrant and five different type (Q, P, R, S and W) of compensation behaviors that strongly depend on interaction parameters. The results are in good agreement with some experimental and theoretical results. - Highlights: • Thermal and magnetic properties of ternary Ising nanoparticles are studied. • Phase diagrams within the EFT with correlations are calculated and discussed. • The effects of the exchange interactions and crystal field have been studied. • Reentrant phenomena and compensation behaviors have been found.

  6. Symplectic no-core configuration interaction framework for ab initio nuclear structure. I. Convergence behavior in p-shell nuclei

    Science.gov (United States)

    McCoy, Anna E.; Caprio, Mark A.; Dytrych, Tomas

    2017-09-01

    A major challenge in quantitatively predicting nuclear structure ab initio, directly from realistic nucleon-nucleon interactions, arises due to an explosion in the dimension of the traditional configuration interaction basis as the number of nucleons and included shells increases. The need for including highly excited configurations exists, in large part, because the kinetic energy induces strong coupling across shells. However, the kinetic energy conserves symplectic symmetry. Combining symplectic symmetry with the no-core configuration interaction (NCCI) framework provides a means of identifying and restricting the basis to include only the highly excited configurations which dominantly contribute to the nuclear wavefunction, thereby reducing the size of basis necessary to obtain accurate results. We present a framework for ab initio symplectic no-core configuration interaction (SpNCCI) calculations of the nuclear problem and explore convergence behavior of calculations of p-shell nuclei in this framework. Supported by the US DOE under Award No. DE-FG02-95ER-40934 and the Czech Science Foundation under Grant No. 16-16772S.

  7. Population Structure and Growth of the Threatened Pen Shell, Pinna rudis (Linnaeus, 1758 in a Western Mediterranean Marine Protected Area

    Directory of Open Access Journals (Sweden)

    E. NEBOT COLOMER

    2016-11-01

    Full Text Available Coastal ecosystems are being extensively degraded by human activities. Benthic, slow-growing and long-lived species are highly vulnerable to these impacts. Marine protected areas might avoid biodiversity losses through habitat protection. The pen shell Pinna rudis is a protected species, but scarce data are available on its ecology and biology. The present study is a comprehensive ecological study encompassing several unknown aspects of the growth and inner record in relation to habitat types, density and size distribution. A total of 418 strip transects were conducted by scuba diving in the Marine Protected Area of Cabrera National Park (39.14° N, 2.96° E, during the summers of 2011, 2012 and 2013. Sampling was conducted across different habitats and depths exploring 152,146.35 m2 in total. Densities varied spatially within the park (from 0 to 6.89 ind./100 m2 corresponding to a wide range of sizes and ages. Most pen shells were patchily distributed and mainly concentrated in caves. Two hotspots with high densities represent the highest densities ever recorded worldwide, showing a possible link to high larval accumulation and settlement. The population size structure showed a unimodal distribution with shell width ranging from 6.2 to 25.0 cm, with an average shell width of 16.0 ± 3.4 cm. The absolute growth was asymptotic, with a maximum age and length of 28-31 years and 45 cm, respectively. This study on the biology and ecology of a well-established population of Pinna rudis in the Western Mediterranean could set a baseline for the conservation of this species in other areas.

  8. An ultrasonic methodology for in-service inspection of shell weld of core support structure in a sodium cooled fast reactor

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Anish, E-mail: anish@igcar.gov.in; Rajkumar, K.V.; Sharma, Govind K.; Dhayalan, R.; Jayakumar, T.

    2015-02-15

    Highlights: • We demonstrate a novel ultrasonic methodology for in-service inspection of shell weld of core support structure in a sodium cooled fast breeder reactor. • The methodology comprises of the inspection of shell weld immersed in sodium from the outside surface of the main vessel using ultrasonic guided wave. • The formation and propagation of guided wave modes are validated by finite element simulation of the inspection methodology. • A defect down to 20% of 30 mm thick wall (∼6 mm) in the shell weld can be detected reliably using the developed methodology. - Abstract: The paper presents a novel ultrasonic methodology developed for in-service inspection (ISI) of shell weld of core support structure of main vessel of 500 MWe prototype fast breeder reactor (PFBR). The methodology comprises of the inspection of shell weld immersed in sodium from the outsider surface of the main vessel using a normal beam longitudinal wave ultrasonic transducer. Because of the presence of curvature in the knuckle region of the main vessel, the normal beam longitudinal wave enters the support shell plate at an angle and forms the guided waves by mode conversion and multiple reflections from the boundaries of the shell plate. Hence, this methodology can be used to detect defects in the shell weld of the core support structure. The successful demonstration of the methodology on a mock-up sector made of stainless steel indicated that an artificial defect down to 20% of 30 mm thick wall (∼6 mm) in the shell weld can be detected reliably.

  9. Spectral element modelling of wave propagation in isotropic and anisotropic shell-structures including different types of damage

    International Nuclear Information System (INIS)

    Schulte, R T; Fritzen, C-P; Moll, J

    2010-01-01

    During the last decades, guided waves have shown great potential for Structural Health Monitoring (SHM) applications. These waves can be excited and sensed by piezoelectric elements that can be permanently attached onto a structure offering online monitoring capability. However, the setup of wave based SHM systems for complex structures may be very difficult and time consuming. For that reason there is a growing demand for efficient simulation tools providing the opportunity to design wave based SHM systems in a virtual environment. As usually high frequency waves are used, the associated short wavelength leads to the necessity of a very dense mesh, which makes conventional finite elements not well suited for this purpose. Therefore in this contribution a flat shell spectral element approach is presented. By including electromechanical coupling a SHM system can be simulated entirely from actuator voltage to sensor voltage. Besides a comparison to measured data for anisotropic materials including delamination, a numerical example of a more complex, stiffened shell structure with debonding is presented.

  10. Formation of an Anti-Core–Shell Structure in Layered Oxide Cathodes for Li-Ion Batteries

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Hanlei [Materials; amp, Department; NorthEast; Omenya, Fredrick [NorthEast; Whittingham, M. Stanley [NorthEast; Wang, Chongmin [Environmental; Zhou, Guangwen [Materials; amp, Department; NorthEast

    2017-10-20

    The layered → rock-salt phase transformation in the layered dioxide cathodes for Li-ion batteries is believed to result in a “core-shell” structure of the primary particles, in which the core region maintains as the layered phase while the surface region undergoes the phase transformation to the rock-salt phase. Using transmission electron microscopy, here we demonstrate the formation of an “anti-core-shell” structure in cycled primary particles with a formula of LiNi0.80Co0.15Al0.05O2, in which the surface and subsurface regions remain as the layered structure while the rock-salt phase forms as domains in the bulk with a thin layer of the spinel phase between the rock-salt core and the skin of the layered phase. Formation of this anti-core-shell structure is attributed to the oxygen loss at the surface that drives the migration of oxygen from the bulk to the surface, thereby resulting in localized areas of significantly reduced oxygen levels in the bulk of the particle, which subsequently undergoes the phase transformation to the rock-salt domains. The formation of the anti-core-shell rock-salt domains is responsible for the reduced capacity, discharge voltage and ionic conductivity in cycled cathode.

  11. Hydrothermal preparation of blue molybdenum bronze nanoribbons: structural changes in mother crystals, related to solid-state conversion and crystallite splitting to nanomorphology

    Science.gov (United States)

    Nishida, Takamasa; Eda, Kazuo

    2018-02-01

    Hydrothermal syntheses of alkali-metal blue molybdenum bronze nanoribbons, which are expected to exhibit unique properties induced by a combined effect of extrinsic and intrinsic low-dimensionalities, from hydrated-alkali-metal molybdenum bronzes were investigated. Nanoribbons grown along the quasi-one-dimensional (1D) conductive direction of Cs0.3MoO3, which is difficult to prepare by the conventional methods, were first synthesized. The nanomorphology formation is achieved by a solid-state conversion (or crystallite splitting) and subsequent crystallite growth, and the structural changes of the starting material related to the conversion were first observed by powder X-ray diffraction and scanning transmission electron microscopy as a result of finely tuned reaction system and preparation conditions. The structural changes were analyzed by model simulations and were attributed to the structural modulations that were concerned with the intralayer packing disorder and with two-dimensional long-range ordered structure, formed in MoO3 sheets of the hydrated molybdenum bronze. Moreover, the modulations were related to displacement defects of the Mo-O framework units generated along the [100] direction in the hydrated molybdenum bronze. Then, it was suggested that the solid-state conversion into blue molybdenum bronze and the crystallite splitting to nanomorphology were initiated by the breaking of the Mo-O-Mo bonds at the defects. [Figure not available: see fulltext.

  12. A comparison study on the performance of lower order solid finite element for elastic analysis of plate and shell structures

    International Nuclear Information System (INIS)

    Lee, Young Jung; Lee, Sang Jin; Choun, Young Sun; Seo, Jeong Moon

    2003-05-01

    The objective of this research is to assess the performance of lower order solid finite elements which will be ultimately applied into the safety analysis of nuclear containment building. For the safety analysis of large structures such as nuclear containment building, efficient lower order finite element is necessarily required to calculate the structural response of containment building with low computational cost. In this study, the state of the art formulations of lower order solid finite element are throughly reviewed and the best possible solid finite element is adopted into the development of nuclear containment analysis system. Three 8-node solid finite elements based on standard strain-displacement relationship, B-bar method and EAS method are implemented as computer modules and completely tested with various plate and shell structures. The present results can be directly applied into the analysis code development for general reinforced concrete structures

  13. Role of the first coordination shell in determining the equilibrium structure and dynamics of simple liquids

    DEFF Research Database (Denmark)

    Toxværd, Søren; Dyre, J. C.

    2011-01-01

    . Lett. 103, 170601 (2009);10.1103/PhysRevLett.103.170601 J. Chem. Phys. 134, 214503 (2011)10.1063/1.3592709] . We present simulations of the standard Lennard-Jones liquid at several condensed-fluid state points, including a fairly low density state and a very high density state, as well as simulations......The traditional view that the physical properties of a simple liquid are determined primarily by its repulsive forces was recently challenged by Berthier and Tarjus, who showed that in some cases ignoring the attractions leads to large errors in the dynamics [L. Berthier and G. Tarjus, Phys. Rev...... are included in the simulations. What matters is whether or not interactions are included from all particles within the first coordination shell – the attractive forces can thus be ignored, but only at extremely high densities. The recognition of the importance of a local shell in condensed fluids goes back...

  14. Intrinsic Ge nanowire nonvolatile memory based on a simple core-shell structure

    Science.gov (United States)

    Chen, Wen-Hua; Liu, Chang-Hai; Li, Qin-Liang; Sun, Qi-Jun; Liu, Jie; Gao, Xu; Sun, Xuhui; Wang, Sui-Dong

    2014-02-01

    Intrinsic Ge nanowires (NWs) with a Ge core covered by a thick Ge oxide shell are utilized to achieve nanoscale field-effect transistor nonvolatile memories, which show a large memory window and a high ON/OFF ratio with good retention. The retainable surface charge trapping is considered to be responsible for the memory effect, and the Ge oxide shell plays a key role as the insulating tunneling dielectric which must be thick enough to prevent stored surface charges from leaking out. Annealing the device in air is demonstrated to be a simple and effective way to attain thick Ge oxide on the Ge NW surface, and the Ge-NW-based memory corresponding to thick Ge oxide exhibits a much better retention capability compared with the case of thin Ge oxide.

  15. Structural and Optical Properties of Core-Shell TiO2/CdS Prepared by Chemical Bath Deposition

    Science.gov (United States)

    Al-Jawad, Selma M. H.

    2017-10-01

    Titanium dioxide (TiO2) nanorod arrays (NRAs) sensitized with cadmium sulfide (CdS) nanoparticles (NPs) were deposited by chemical bath deposition (CBD). TiO2 NRAs were also obtained by using the same method on glass substrates coated with fluorine-doped tin oxide (FTO). The structure of the FTO/TiO2/CdS core-shell was characterized by x-ray diffraction (XRD), atomic force microscopy, scanning electron microscopy, ultraviolet-visible (UV-Vis) absorption spectroscopy, photoluminescence, and photoelectrocatalysis of FTO/TiO2 and FTO/TiO2/CdS. The FTO/TiO2 conformed to anatase and rutile phase structures for different pH values and also with annealing. XRD patterns of the FTO/TiO2/CdS sample exhibited two peaks corresponding to hexagonal (100) and (101) for CdS. Scanning electron micrographs showed nanorod structures for the TiO2 thin films deposited at a pH value equal 0.7. Optical results showed the CdS deposited on nanorod TiO2 exhibited increased absorption ability in the visible light, indicating an increased photocatalytic activity for TiO2/CdS core-shell nanorods in the visible light. When illuminated with a UV-Vis light source, the TiO2/CdS core-shell films displayed high responses. A composite exists between the TiO2 nanostructure and CdS NPs because the film absorbs the incident light located in both the visible and UV-Vis regions. A higher response to UV-Vis light was attained with the use of TiO2 NRAs/CdS NPs films prepared by CBD. This approach offers a technique for fabricating photoelectrodes.

  16. Shell structure and level migrations in zinc studied using collinear laser spectroscopy

    CERN Multimedia

    Tungate, G; De rydt, M A E; Flanagan, K; Rajabali, M M; Hammen, M; Blaum, K; Froemmgen, N E; Kowalska, M; Campbell, P; Neugart, R; Kreim, K D; Stroke, H H; Krieger, A R; Procter, T J

    We propose to perform collinear laser spectroscopy of zinc isotopes to measure the nuclear spin, magnetic dipole moment, electric quadrupole moment and mean-square charge radius. The yield database indicates that measurements of the isotopes $^{60-81}$Zn will be feasible. These measurements will cross the N = 50 shell closure and provide nuclear moments in a region where an inversion of ground-state spin has been identified in neighbouring chains.

  17. Investigation on Spin Dependent Transport Properties of Core-Shell Structural Fe3O4/ZnS Nanocomposites for Spintronic Application

    Science.gov (United States)

    Liu, Er; Yuan, Honglei; Kou, Zhaoxia; Wu, Xiumei; Xu, Qingyu; Zhai, Ya; Sui, Yunxia; You, Biao; Du, Jun; Zhai, Hongru

    2015-01-01

    The core-shell structural Fe3O4/ZnS nanocomposites with controllable shell thickness were well-fabricated via seed-mediate growth method. Structural and morphological characterizations reveal the direct deposition of crystalline II-VI compound semiconductor ZnS shell layer on Fe3O4 particles. Spin dependent electrical transport is studied on Fe3O4/ZnS nanocomposites with different shell thickness, and a large magnetoresistance (MR) ratio is observed under the magnetic field of 1.0 T at room temperature and 100 K for the compacted sample by Fe3O4/ZnS nanocomposites, which is 50% larger than that of sample with pure Fe3O4 particles, indicating that the enhanced MR is contributed from the spin injection between Fe3O4 and ZnS layer. PMID:26053888

  18. Core-shell structured high-k polymer nanocomposites for energy storage and dielectric applications.

    Science.gov (United States)

    Huang, Xingyi; Jiang, Pingkai

    2015-01-21

    High-k polymer nanocomposites have considerable potential in energy storage and dielectric applications because of their ease of processing, flexibility, and low cost. Core-shell nanoarchitecture strategies are versatile and powerful tools for the design and synthesis of advanced high-k polymer nanocomposites. Recent and in-progress state-of-the-art advancements in the application of core-shell nanoarchitecture strategies to design and prepare high-k polymer nanocomposites are summarized. Special focus is directed to emphasizing their advantages over conventional melt-mixing and solution-mixing methods: first, homogeneous nanoparticle dispersion can be easily achieved even in highly loaded nanocomposites; second, the dielectric constant of the nanocomposites can be effectively enhanced and meanwhile the high breakdown strength can be well-preserved; third, for nanocomposites filled with electrically conductive nanoparticles, dielectric loss can be effectively surpressed, and meanwhile a high dielectric constant can be achieved. In addition, fundamental insights into the roles of the interfaces on the dielectric properties of the nanocomposites can be probed. The last part of the article is concluded with current problems and future perspectives of utilizing the core-shell nanoarchitecture strategies for the development of high-k polymer nanocomposites. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Preparation, optical properties, magnetic properties and thermal stability of core-shell structure cobalt/zinc oxide nanocomposites

    International Nuclear Information System (INIS)

    Bala, Hari; Fu Wuyou; Yu Yanhui; Yang Haibin; Zhang Yishun

    2009-01-01

    Cobalt nanoparticles coated with zinc oxide can form composite spheres with core-shell structure. This coating process was based on the use of silane coupling with agent 3-mercaptopropyltrimethoxysilane (HS-(CH 2 ) 3 Si(OCH 3 ) 3 , MPTS) as a primer to render the cobalt surface vitreophilic, thus it renders cobalt surface compatible with ZnO. X-ray photoelectron spectroscopy (XPS) was used to gain insight into the way in which the MPTS is bound to the surface of the cobalt nanoparticles. The morphological structure, chemical composition, optical properties and magnetic properties of the product were investigated by using transmission electron microscopy (TEM), X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), photoluminescence (PL) spectroscope and vibrating sample magnetometer (VSM). It was found that the Co/ZnO core-shell structure nanocomposites exhibited both of favorable magnetism and photoluminescence properties. Results of the thermogravimetric analysis (TGA) and differential thermal analysis (DTA) indicated that the thermal stability of cobalt/zinc oxide was better than that of pure cobalt nanoparticles.

  20. Phase and structural transformations in a low-carbon steel that occur upon the collapse of a cylindrical shell

    Science.gov (United States)

    Kheifets, A. E.; Zel'dovich, V. I.; Frolova, N. Yu.; Dolgikh, S. M.; Gaan, K. V.; Shorokhov, E. V.

    2017-07-01

    An experiment has been performed on the collapse of a thick-walled shell (tube) made of steel 20 (Fe-0.2 wt % C) to a continuous cylinder under the action of explosion. The changes of the microstructure of the cylinder have been investigated that arise under the effect of two factors, i.e., a shock wave, which causes the initial pulse to the collapse, and high-strain-rate deformation upon the subsequent inertial convergence of the shell walls. Changes in the time-dependent temperature distribution in the cylinder have been calculated. As a result of the deformation, the new structure has been obtained in steel 20 due to barothermic quenching that consists of fine crystals of the α phase, which arise during the quenching at the place of free ferrite, and of regions of the retained initial pearlite. It has been shown that the uncommon order of the occurrence of the α → γ transformation is explained by the different degree of heating of the structural constituents of the steel (free ferrite; and pearlite). The conclusion has been drawn that the high-strain-rate deformation that occurs in this experiment can be used as the method that makes it possible not only to differently deform but also to differently heat the different structural components of multiphase materials.

  1. Preparation, optical properties, magnetic properties and thermal stability of core-shell structure cobalt/zinc oxide nanocomposites

    Science.gov (United States)

    Bala, Hari; Fu, Wuyou; Yu, Yanhui; Yang, Haibin; Zhang, Yishun

    2009-01-01

    Cobalt nanoparticles coated with zinc oxide can form composite spheres with core-shell structure. This coating process was based on the use of silane coupling with agent 3-mercaptopropyltrimethoxysilane (HS-(CH 2) 3Si(OCH 3) 3, MPTS) as a primer to render the cobalt surface vitreophilic, thus it renders cobalt surface compatible with ZnO. X-ray photoelectron spectroscopy (XPS) was used to gain insight into the way in which the MPTS is bound to the surface of the cobalt nanoparticles. The morphological structure, chemical composition, optical properties and magnetic properties of the product were investigated by using transmission electron microscopy (TEM), X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), photoluminescence (PL) spectroscope and vibrating sample magnetometer (VSM). It was found that the Co/ZnO core-shell structure nanocomposites exhibited both of favorable magnetism and photoluminescence properties. Results of the thermogravimetric analysis (TGA) and differential thermal analysis (DTA) indicated that the thermal stability of cobalt/zinc oxide was better than that of pure cobalt nanoparticles.

  2. Preparation, optical properties, magnetic properties and thermal stability of core-shell structure cobalt/zinc oxide nanocomposites

    Energy Technology Data Exchange (ETDEWEB)

    Bala, Hari [Institute of Materials Science and Engineering, Henan Polytechnic University, Jiaozuo 454000 (China); State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022 (China)], E-mail: hari@hpu.edu.cn; Fu Wuyou [National Laboratory for Superhard Materials, JiIin University, Changchun 130023 (China); Yu Yanhui [Institute of Materials Science and Engineering, Henan Polytechnic University, Jiaozuo 454000 (China); Yang Haibin [Institute of Materials Science and Engineering, Henan Polytechnic University, Jiaozuo 454000 (China); National Laboratory for Superhard Materials, JiIin University, Changchun 130023 (China); Zhang Yishun [Institute of Materials Science and Engineering, Henan Polytechnic University, Jiaozuo 454000 (China)

    2009-01-15

    Cobalt nanoparticles coated with zinc oxide can form composite spheres with core-shell structure. This coating process was based on the use of silane coupling with agent 3-mercaptopropyltrimethoxysilane (HS-(CH{sub 2}){sub 3}Si(OCH{sub 3}){sub 3}, MPTS) as a primer to render the cobalt surface vitreophilic, thus it renders cobalt surface compatible with ZnO. X-ray photoelectron spectroscopy (XPS) was used to gain insight into the way in which the MPTS is bound to the surface of the cobalt nanoparticles. The morphological structure, chemical composition, optical properties and magnetic properties of the product were investigated by using transmission electron microscopy (TEM), X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), photoluminescence (PL) spectroscope and vibrating sample magnetometer (VSM). It was found that the Co/ZnO core-shell structure nanocomposites exhibited both of favorable magnetism and photoluminescence properties. Results of the thermogravimetric analysis (TGA) and differential thermal analysis (DTA) indicated that the thermal stability of cobalt/zinc oxide was better than that of pure cobalt nanoparticles.

  3. Visible light-induced electronic structure modulation of Nb- and Ta-doped α-Fe2O3 nanorods for effective photoelectrochemical water splitting

    Science.gov (United States)

    Chang, Han-Wei; Fu, Yanming; Lee, Wan-Yi; Lu, Ying-Rui; Huang, Yu-Cheng; Chen, Jeng-Lung; Chen, Chi-Liang; Chou, Wu Ching; Chen, Jin-Ming; Lee, Jyh-Fu; Shen, Shaohua; Dong, Chung-Li

    2018-02-01

    The photoelectrochemical (PEC) water splitting activity of Nb and Ta-doped hematite (α-Fe2O3) nanorods was investigated with reference to electronic structures by in situ synchrotron x-ray absorption spectroscopy (XAS). Current density-potential measurements demonstrate that the PEC activity of α-Fe2O3 nanorods depends strongly on the species and concentrations of dopants. The doping of α-Fe2O3 nanorods with a low level of Nb or Ta can improve their electrical conductivity and thereby facilitate charge transport and reduced electron-hole recombination therein. The photoconversion effects of Nb and Ta-doped α-Fe2O3 by in situ XAS in the dark and under illumination revealed opposite evolutions of the spectral intensities of the Fe L-edge and Nb/Ta L-edge, indicating that charge transfer and a conduction pathway are involved in the photoconversion. Analytic in situ XAS results reveal that the α-Fe2O3 that is doped with a low level of Nb has a greater photoconversion efficiency than that doped with Ta because Nb sites are more active than Ta sites in α-Fe2O3. The correlation between PEC activity and the electronic structure of Nb/Ta-doped α-Fe2O3 is examined in detail using in situ XAS and helps to elucidate the mechanism of PEC water splitting in terms of the electronic structure.

  4. Porous Structured Ni-Fe-P Nanocubes Derived from a Prussian Blue Analogue as an Electrocatalyst for Efficient Overall Water Splitting.

    Science.gov (United States)

    Xuan, Cuijuan; Wang, Jie; Xia, Weiwei; Peng, Zongkai; Wu, Zexing; Lei, Wen; Xia, Kedong; Xin, Huolin L; Wang, Deli

    2017-08-09

    Exploring nonprecious metal electrocatalysts to replace the noble metal-based catalysts for full water electrocatalysis is still an ongoing challenge. In this work, porous structured ternary nickel-iron-phosphide (Ni-Fe-P) nanocubes were synthesized through one-step phosphidation of a Ni-Fe-based Prussian blue analogue. The Ni-Fe-P nanocubes exhibit a rough and loose porous structure on their surface under suitable phosphating temperature, which is favorable for the mass transfer and oxygen diffusion during the electrocatalysis process. As a result, Ni-Fe-P obtained at 350 °C with poorer crystallinity offers more unsaturated atoms as active sites to expedite the absorption of reactants. Additionally, the introduction of nickel improved the electronic structure and then reduced the charge-transfer resistance, which would result in a faster electron transport and an enhancement of the intrinsic electrocatalytic activities. Benefiting from the unique porous nanocubes and the chemical composition, the Ni-Fe-P nanocubes exhibit excellent hydrogen evolution reaction and oxygen evolution reaction activities in alkaline medium, with low overpotentials of 182 and 271 mV for delivering a current density of 10 mA cm -2 , respectively. Moreover, the Ni-Fe-P nanocubes show outstanding stability for sustained water splitting in the two-electrode alkaline electrolyzer. This work not only provides a facile approach for designing bifunctional electrocatalysts but also further extends the application of metal-organic frameworks in overall water splitting.

  5. Effects of size reduction on the structure and magnetic properties of core–shell Ni3Si/silica nanoparticles prepared by electrochemical synthesis

    International Nuclear Information System (INIS)

    Pigozzi, Giancarlo; Mukherji, Debashis; Elerman, Yalçin; Strunz, Pavel; Gilles, Ralph; Hoelzel, Markus; Barbier, Bruno; Schmutz, Patrik

    2014-01-01

    Highlights: • β 1 -Ni 3 Si nanoparticles were produced by electrochemical selective phase dissolution. • A core–shell structure with ordered Ni 3 Si core and silica shell is obtained. • The ordered L1 2 crystal structure is maintained upon size reduction down to 20 nm. • Bulk Ni 3 Si is ferromagnetic below 260 K with low saturation magnetization (2 emu/g). • Nanoparticles are superparamagnetic (T B ∼ 9–11 K) with magnetization >20 emu/g. -- Abstract: Nanostructured nickel silicides find application in electronics, high-temperature alloys, electrode materials and catalysis. In this work, the effect of size reduction on the structure and magnetic properties of β 1 -Ni 3 Si intermetallic phase nanoparticles is studied. Electrochemical selective phase dissolution (ESPD) was used to produce the β 1 -Ni 3 Si nanoparticles of different sizes (from 20 to 215 nm) by extracting β 1 nano-size precipitates from two-phase Ni–Si and Ni–Si–Al precursor alloys. The extracted nanoparticles have a core–shell structure with β 1 -Ni 3 Si core and an amorphous silica shell. Particles size and shape are controlled by the composition and thermal treatment of the precursor alloys. Precipitates size is scaled without modifying the ordered L1 2 lattice structure. The bulk β 1 -Ni 3 Si is ferromagnetic below 260 K with low saturation magnetization (2 emu/g), while the core–shell Ni 3 Si/silica nanoparticles are superparamagnetic at low temperatures ( 20 emu/g at 5 T. It is suggested that weak particle magnetic moments and low magnetic anisotropy of the L1 2 structure are responsible for these properties. The shell on one hand protects the core from degradation; however the oxidation of the core/shell interface region can influence the magnetic behavior of the nano-powders

  6. Self-Assembly of Crystalline Structures of Magnetic Core-Shell Nanoparticles for Fabrication of Nanostructured Materials.

    Science.gov (United States)

    Xue, Xiaozheng; Wang, Jianchao; Furlani, Edward P

    2015-10-14

    A theoretical study is presented of the template-assisted formation of crystalline superstructures of magnetic-dielectric core-shell particles. The templates produce highly localized gradient fields and a corresponding magnetic force that guides the assembly with nanoscale precision in particle placement. The process is studied using two distinct and complementary computational models that predict the dynamics and energy of the particles, respectively. Both mono- and polydisperse colloids are studied, and the analysis demonstrates for the first time that although the particles self-assemble into ordered crystalline superstructures, the particle formation is not unique. There is a Brownian motion-induced degeneracy in the process wherein various distinct, energetically comparable crystalline structures can form for a given template geometry. The models predict the formation of hexagonal close packed (HCP) and face centered cubic (FCC) structures as well as mixed phase structures due to in-plane stacking disorders, which is consistent with experimental observations. The polydisperse particle structures are less uniform than the monodisperse particle structures because of the irregular packing of different-sized particles. A comparison of self-assembly using soft- and hard-magnetic templates is also presented, the former being magnetized in a uniform field. This analysis shows that soft-magnetic templates enable an order-of-magnitude more rapid assembly and much higher spatial resolution in particle placement than their hard-magnetic counterparts. The self-assembly method discussed is versatile and broadly applies to arbitrary template geometries and multilayered and multifunctional mono- and polydisperse core-shell particles that have at least one magnetic component. As such, the method holds potential for the bottom-up fabrication of functional nanostructured materials for a broad range of applications. This work provides unprecedented insight into the assembly

  7. The influence of the shell closure on the microscopic structure of even-even Hg isotopes

    International Nuclear Information System (INIS)

    Burghardt, A.J.C.

    1989-01-01

    Muonic X-ray data were obtained for 198 200 202 204 Hg at high-intensity muon-beam facility of SIN and an electron-scattering study was performed on 204 Hg with the 500 MeV, high-resolution electron-scattering facility of NIKHEF-K in a q-range from 0.4 to 2.9 fm -1 . The combined analysis of the elastic electron-scattering and muonic X-ray data has yielded the ground-state charge distribution of 204 Hg. Hartree-Fock calculations with four different interactions, with and without the inclusion of pairing correlations, are compared to this experimental result. The charge-density difference between 206 Pb (determined elsewhere) and 204 Hg is then used ot investigate the filling of the last proton orbit before the Z=82 shell closure, the 3s 1/2 orbit. The interpretation of this difference, also in terms of Hartree-Fock calculations, is discussed in conjunction with the earlier study of Frois et al. concerning 206 Pb and 205 Tl. Many excited states have been observed in the spectra of 204 Hg. The experimental excitation energies and the spins and parities assigned to a number of states are presented. From the cross-section data for these states transition charge distributions have been extracted. Shell-model predictions are compared with the observed level scheme and the shell-model calculation performed by Poppelier is used to interpret transition charge distributions of six states. 101 refs.; 32 figs.; 41 figs

  8. Semiconductor Nanowires for Photoelectrochemical Water Splitting

    Science.gov (United States)

    Hwang, Yun Jeong

    Photolysis of water with semiconductor materials has been investigated intensely as a clean and renewable energy resource by storing solar energy in chemical bonds such as hydrogen. One-dimensional (1D) nanostructures such as nanowires can provide several advantages for photoelectrochemical (PEC) water splitting due to their high surface areas and excellent charge transport and collection efficiency. This dissertation discusses various nanowire photoelectrodes for single or dual semiconductor systems, and their linked PEC cells for self-driven water splitting. After an introduction of solar water splitting in the first chapter, the second chapter demonstrates water oxidative activities of hydrothermally grown TiO2 nanowire arrays depending on their length and surface properties. The photocurrents with TiO2 nanowire arrays approach saturation due to their poor charge collection efficiency with longer nanowires despite increased photon absorption efficiency. Epitaxial grains of rutile atomic layer deposition (ALD) shell on TiO2 nanowire increase the photocurrent density by 1.5 times due to improved charge collection efficiency especially in the short wavelength region. Chapter three compares the photocurrent density of the planar Si and Si nanowire arrays coated by anatase ALD TiO 2 thin film as a model system of a dual bandgap system. The electroless etched Si nanowire coated by ALD TiO2 (Si EENW/TiO2) shows 2.5 times higher photocurrent density due to lower reflectance and higher surface area. Also, this chapter illustrates that n-Si/n-TiO2 heterojunction is a promising structure for the photoanode application of a dual semiconductor system, since it can enhance the photocurrent density compared to p-Si/n-TiO 2 junction with the assistance of bend banding at the interface. Chapter four demonstrates the charge separation and transport of photogenerated electrons and holes within a single asymmetric Si/TiO2 nanowire. Kelvin probe force microscopy measurements show

  9. Structure of the ground state of nuclei A=13 with 2 p-shell

    International Nuclear Information System (INIS)

    Ismatov, E.I.; Kim, G.; Mannanov, D.E.; Khugaev, A.V.

    1995-01-01

    The result of investigation of wave functions of 13 C and 13 N with 2p-shell are presented. The expressions for the magnetic momenta log ft for β-decay 13 N to 13 C, and vertex constants of neutron separation from nuclear 13 C and elastic longitudinal and transversal form factors of electron scattering on the nucleus 13 C (expressed through transition density) are obtained. A good description of the experimental data is obtained, in particular, for the M1 form factor. (author). 1 fig.; 18 refs

  10. Growth control, structure, chemical state, and photoresponse of CuO-CdS core-shell heterostructure nanowires.

    Science.gov (United States)

    El Mel, A A; Buffière, M; Bouts, N; Gautron, E; Tessier, P Y; Henzler, K; Guttmann, P; Konstantinidis, S; Bittencourt, C; Snyders, R

    2013-07-05

    The growth of single-crystal CuO nanowires by thermal annealing of copper thin films in air is studied. We show that the density, length, and diameter of the nanowires can be controlled by tuning the morphology and structure of the copper thin films deposited by DC magnetron sputtering. After identifying the optimal conditions for the growth of CuO nanowires, chemical bath deposition is employed to coat the CuO nanowires with CdS in order to form p-n nanojunction arrays. As revealed by high-resolution TEM analysis, the thickness of the polycrystalline CdS shell increases when decreasing the diameter of the CuO core for a given time of CdS deposition. Near-edge x-ray absorption fine-structure spectroscopy combined with transmission x-ray microscopy allows the chemical analysis of isolated nanowires. The absence of modification in the spectra at the Cu L and O K edges after the deposition of CdS on the CuO nanowires indicates that neither Cd nor S diffuse into the CuO phase. We further demonstrate that the core-shell nanowires exhibit the I-V characteristic of a resistor instead of a diode. The electrical behavior of the device was found to be photosensitive, since increasing the incident light intensity induces an increase in the collected electrical current.

  11. Synthesis, characterization and nitrite ion sensing performance of reclaimable composite samples through a core-shell structure

    Science.gov (United States)

    Cui, Xiao; Yuqing, Zhao; Cui, Jiantao; Zheng, Qian; Bo, Wang

    2018-02-01

    The following paper reported and discussed a nitrite ion optical sensing platform based on a core-shell structure, using superamagnetic nanoparticles as the core, a silica molecular sieve MCM-41 as the shell and two rhodamine derivatives as probe, respectively. This superamagnetic core made this sensing platform reclaimable after finishing nitrite ion sensing procedure. This sensing platform was carefully characterized by means of electron microscopy images, porous structure analysis, magnetic response, IR spectra and thermal stability analysis. Detailed analysis suggested that the emission of these composite samples was quenchable by nitrite ion, showing emission turn off effect. A static sensing mechanism based on an additive reaction between chemosensors and nitrite ion was proposed. These composite samples followed Demas quenching equation against different nitrite ion concentrations. Limit of detection value was obtained as low as 0.4 μM. It was found that, after being quenched by nitrite ion, these composite samples could be reclaimed and recovered by sulphamic acid, confirming their recyclability.

  12. Structural and Morphological Description of Sn/SnOxCore-Shell Nanoparticles Synthesized and Isolated from Ionic Liquid.

    Science.gov (United States)

    Soulmi, Nadia; Dambournet, Damien; Rizzi, Cécile; Sirieix-Plénet, Juliette; Duttine, Mathieu; Wattiaux, Alain; Swiatowska, Jolanta; Borkiewicz, Olaf J; Groult, Henri; Gaillon, Laurent

    2017-08-21

    The potential application of high capacity Sn-based electrode materials for energy storage, particularly in rechargeable batteries, has led to extensive research activities. In this scope, the development of an innovative synthesis route allowing to downsize particles to the nanoscale is of particular interest owing to the ability of such nanomaterial to better accommodate volume changes upon electrochemical reactions. Here, we report on the use of room temperature ionic liquid (i.e., [EMIm + ][TFSI - ]) as solvent, template, and stabilizer for Sn-based nanoparticles. In such a media, we observed, using Cryo-TEM, that pure Sn nanoparticles can be stabilized. Further washing steps are, however, mandatory to remove residual ionic liquid. It is shown that the washing steps are accompanied by the partial oxidation of the surface, leading to a core-shell structured Sn/SnO x composite. To understand the structural features of such a complex architecture, HRTEM, Mössbauer spectroscopy, and the pair distribution function were employed to reveal a crystallized β-Sn core and a SnO and SnO 2 amorphous shell. The proportion of oxidized phases increases with the final washing step with water, which appeared necessary to remove not only salts but also the final surface impurities made of the cationic moieties of the ionic liquid. This work highlights the strong oxidation reactivity of Sn-based nanoparticles, which needs to be taken into account when evaluating their electrochemical properties.

  13. Synthesis, characterization and nitrite ion sensing performance of reclaimable composite samples through a core-shell structure.

    Science.gov (United States)

    Cui, Xiao; Yuqing, Zhao; Cui, Jiantao; Zheng, Qian; Bo, Wang

    2018-02-15

    The following paper reported and discussed a nitrite ion optical sensing platform based on a core-shell structure, using superamagnetic nanoparticles as the core, a silica molecular sieve MCM-41 as the shell and two rhodamine derivatives as probe, respectively. This superamagnetic core made this sensing platform reclaimable after finishing nitrite ion sensing procedure. This sensing platform was carefully characterized by means of electron microscopy images, porous structure analysis, magnetic response, IR spectra and thermal stability analysis. Detailed analysis suggested that the emission of these composite samples was quenchable by nitrite ion, showing emission turn off effect. A static sensing mechanism based on an additive reaction between chemosensors and nitrite ion was proposed. These composite samples followed Demas quenching equation against different nitrite ion concentrations. Limit of detection value was obtained as low as 0.4μM. It was found that, after being quenched by nitrite ion, these composite samples could be reclaimed and recovered by sulphamic acid, confirming their recyclability. Copyright © 2017 Elsevier B.V. All rights reserved.

  14. The effect of oxide shell thickness on the structural, electronic, and optical properties of Si-SiO2 core-shell nano-crystals: A (time dependent)density functional theory study

    International Nuclear Information System (INIS)

    Nazemi, Sanaz; Soleimani, Ebrahim Asl; Pourfath, Mahdi; Kosina, Hans

    2016-01-01

    Due to their tunable properties, silicon nano-crystals (NC) are currently being investigated. Quantum confinement can generally be employed for size-dependent band-gap tuning at dimensions smaller than the Bohr radius (∼5 nm for silicon). At the nano-meter scale, however, increased surface-to-volume ratio makes the surface effects dominant. Specifically, in Si-SiO 2 core-shell semiconductor NCs the interfacial transition layer causes peculiar electronic and optical properties, because of the co-existence of intermediate oxidation states of silicon (Si n+ , n = 0–4). Due to the presence of the many factors involved, a comprehensive understanding of the optical properties of these NCs has not yet been achieved. In this work, Si-SiO 2 NCs with a diameter of 1.1 nm and covered by amorphous oxide shells with thicknesses between 2.5 and 4.75 Å are comprehensively studied, employing density functional theory calculations. It is shown that with increased oxide shell thickness, the low-energy part of the optical transition spectrum of the NC is red shifted and attenuated. Moreover, the absorption coefficient is increased in the high-energy part of the spectrum which corresponds to SiO 2 transitions. Structural examinations indicate a larger compressive stress on the central silicon cluster with a thicker oxide shell. Examination of the local density of states reveals the migration of frontier molecular orbitals from the oxide shell into the silicon core with the increase of silica shell thickness. The optical and electrical properties are explained through the analysis of the density of states and the spatial distribution of silicon sub-oxide species.

  15. Iron Oxide Nanoparticles: Tunable Size Synthesis and Analysis in Terms of the Core-Shell Structure and Mixed Coercive Model

    Science.gov (United States)

    Phong, P. T.; Oanh, V. T. K.; Lam, T. D.; Phuc, N. X.; Tung, L. D.; Thanh, Nguyen T. K.; Manh, D. H.

    2017-04-01

    Iron oxide nanoparticles (NPs) are currently a very active research field. To date, a comprehensive study of iron oxide NPs is still lacking not only on the size dependence of structural phases but also in the use of an appropriate model. Herein, we report on a systematic study of the structural and magnetic properties of iron oxide NPs prepared by a co-precipitation method followed by hydrothermal treatment. X-ray diffraction and transmission electron microscopy reveal that the NPs have an inverse spinel structure of iron oxide phase (Fe3O4) with average crystallite sizes ( D XRD) of 6-19 nm, while grain sizes ( D TEM) are of 7-23 nm. In addition, the larger the particle size, the closer the experimental lattice constant value is to that of the magnetite structure. Magnetic field-dependent magnetization data and analysis show that the effective anisotropy constants of the Fe3O4 NPs are about five times larger than that of their bulk counterpart. Particle size ( D) dependence of the magnetization and the non-saturating behavior observed in applied fields up to 50 kOe are discussed using the core-shell structure model. We find that with decreasing D, while the calculated thickness of the shell of disordered spins ( t ˜ 0.3 nm) remains almost unchanged, the specific surface areas S a increases significantly, thus reducing the magnetization of the NPs. We also probe the coercivity of the NPs by using the mixed coercive Kneller and Luborsky model. The calculated results indicate that the coercivity rises monotonously with the particle size, and are well matched with the experimental ones.

  16. Compressive elastic moduli and polishing performance of non-rigid core/shell structured PS/SiO2 composite abrasives evaluated by AFM

    International Nuclear Information System (INIS)

    Chen, Ailian; Mu, Weibin; Chen, Yang

    2014-01-01

    The core/shell structured polystyrene (PS)/SiO 2 composite microspheres with different silica shell morphology were synthesized by a modified Stöber method. As confirmed by transmission electron microscopy (TEM), the rough discontinuous shell consisted of separate SiO 2 nanoparticles for composite-A, while the smooth continuous one was composed of amorphous silica network for composite-B. Atomic force microscopy (AFM) was employed to probe the compressive Young's moduli (E) and chemical mechanical polishing (CMP) performances of the as-prepared PS/SiO 2 composite microspheres. On the basis of the Hertzian contact mechanics, the calculated E values of the PS microspheres, composite-A and composite-B were 2.9 ± 0.4, 5.1 ± 1.2 and 6.0 ± 1.2 GPa, respectively. Compared to traditional abrasives, thermally grown silicon oxide wafers after polished by the core/shell PS/SiO 2 composite abrasives obtained a lower root mean square roughness and a higher material removal rate value. In addition, there is an obvious effect of shell morphology of the composites on oxide CMP performance and structural stability during polishing process. This approach would provide a basis for understanding the actual role of organic/inorganic core/shell composite abrasives in the material removal process of CMP.

  17. Monodisperse and core-shell-structured SiO2@YBO3:Eu3+ spherical particles: synthesis and characterization.

    Science.gov (United States)

    Lin, Cuikun; Kong, Deyan; Liu, Xiaoming; Wang, Huan; Yu, Min; Lin, Jun

    2007-04-02

    Y0.9Eu0.1BO3 phosphor layers were deposited on monodisperse SiO2 particles of different sizes (300, 570, 900, and 1200 nm) via a sol-gel process, resulting in the formation of core-shell-structured SiO2@Y0.9Eu0.1BO3 particles. X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), photoluminescence (PL), and cathodoluminescence (CL) spectra as well as lifetimes were employed to characterize the resulting composite particles. The results of XRD, FE-SEM, and TEM indicate that the 800 degrees C annealed sample consists of crystalline YBO3 shells and amorphous SiO2 cores, in spherical shape with a narrow size distribution. Under UV (240 nm) and VUV (172 nm) light or electron beam (1-6 kV) excitation, these particles show the characteristic 5D0-7F1-4 orange-red emission lines of Eu3+ with a quantum yield ranging from 36% (one-layer Y0.9Eu0.1BO3 on SiO2) to 54% (four-layer Y0.9Eu0.1BO3 on SiO2). The luminescence properties (emission intensity and color coordinates) of Eu3+ ions in the core-shell particles can be tuned by the coating number of Y0.9Eu0.1BO3 layers and SiO2 core particle size to some extent, pointing out the great potential for these particles applied in displaying and lightening fields.

  18. Spin Splitting in Different Semiconductor Quantum Wells

    International Nuclear Information System (INIS)

    Hao Yafei

    2012-01-01

    We theoretically investigate the spin splitting in four undoped asymmetric quantum wells in the absence of external electric field and magnetic field. The quantum well geometry dependence of spin splitting is studied with the Rashba and the Dresselhaus spin-orbit coupling included. The results show that the structure of quantum well plays an important role in spin splitting. The Rashba and the Dresselhaus spin splitting in four asymmetric quantum wells are quite different. The origin of the distinction is discussed in this work. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

  19. Improved Solar-Driven Photocatalytic Performance of Highly Crystalline Hydrogenated TiO2 Nanofibers with Core-Shell Structure

    Science.gov (United States)

    Wu, Ming-Chung; Chen, Ching-Hsiang; Huang, Wei-Kang; Hsiao, Kai-Chi; Lin, Ting-Han; Chan, Shun-Hsiang; Wu, Po-Yeh; Lu, Chun-Fu; Chang, Yin-Hsuan; Lin, Tz-Feng; Hsu, Kai-Hsiang; Hsu, Jen-Fu; Lee, Kun-Mu; Shyue, Jing-Jong; Kordás, Krisztián; Su, Wei-Fang

    2017-01-01

    Hydrogenated titanium dioxide has attracted intensive research interests in pollutant removal applications due to its high photocatalytic activity. Herein, we demonstrate hydrogenated TiO2 nanofibers (H:TiO2 NFs) with a core-shell structure prepared by the hydrothermal synthesis and subsequent heat treatment in hydrogen flow. H:TiO2 NFs has excellent solar light absorption and photogenerated charge formation behavior as confirmed by optical absorbance, photo-Kelvin force probe microscopy and photoinduced charge carrier dynamics analyses. Photodegradation of various organic dyes such as methyl orange, rhodamine 6G and brilliant green is shown to take place with significantly higher rates on our novel catalyst than on pristine TiO2 nanofibers and commercial nanoparticle based photocatalytic materials, which is attributed to surface defects (oxygen vacancy and Ti3+ interstitial defect) on the hydrogen treated surface. We propose three properties/mechanisms responsible for the enhanced photocatalytic activity, which are: (1) improved absorbance allowing for increased exciton generation, (2) highly crystalline anatase TiO2 that promotes fast charge transport rate, and (3) decreased charge recombination caused by the nanoscopic Schottky junctions at the interface of pristine core and hydrogenated shell thus promoting long-life surface charges. The developed H:TiO2 NFs can be helpful for future high performance photocatalysts in environmental applications.

  20. Reinforced PEI/PVdF Multicore-Shell Structure Composite Membranes by Phase Prediction on a Ternary Solution

    Directory of Open Access Journals (Sweden)

    Jihye Chae

    2018-04-01

    Full Text Available To construct a polyetherimide (PEI-reinforced polyvinylidene fluoride (PVdF composite membrane with multicore-shell structure, a ternary solution was prepared and electrospun by single-nozzle electrospinning. A theoretical prediction was made for the feasibility of complete distinction of two phases. The diameters of the membrane fibers and the PEI multi-core fibrils varied with the PEI ratio and the spinning time, respectively. The tensile strength and modulus were improved to 48 MPa and 1.5 GPa, respectively. The shrinkage of the membrane was only 6.6% at 180 °C, at which temperature the commercial PE separator melted down. The reinforcement in mechanical and thermal properties is associated with multiple PEI nanofibrils oriented along the fiber axis. Indeed, the unique morphology of self-assembled multicore-shell fibers plays an important role in their properties. All in all, PEI/PVdF membranes are appropriate for a lithium-ion battery application due to their high mechanical strength, excellent thermal stability, and controllable textural properties.

  1. The Fabrication and High-Efficiency Electromagnetic Wave Absorption Performance of CoFe/C Core-Shell Structured Nanocomposites

    Science.gov (United States)

    Wan, Gengping; Luo, Yongming; Wu, Lihong; Wang, Guizhen

    2018-03-01

    CoFe/C core-shell structured nanocomposites (CoFe@C) have been fabricated through the thermal decomposition of acetylene with CoFe2O4 as precursor. The as-prepared CoFe@C was characterized by X-ray powder diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, transmission electron microscopy, and thermogravimetric analysis. The results demonstrate that the carbon shell in CoFe@C has a poor crystallization with a thickness about 5-30 nm and a content approximately 48.5 wt.%. Due to a good combination between intrinsic magnetic properties and high-electrical conductivity, the CoFe@C exhibits not only excellent absorption intensity but also wide frequency bandwidth. The minimum RL value of CoFe@C can reach - 44 dB at a thickness of 4.0 mm, and RL values below - 10 dB is up to 4.3 GHz at a thickness of 2.5 mm. The present CoFe@C may be a potential candidate for microwave absorption application.

  2. Structural vibration a uniform accurate solution for laminated beams, plates and shells with general boundary conditions

    CERN Document Server

    Jin, Guoyong; Su, Zhu

    2015-01-01

    This book develops a uniform accurate method which is capable of dealing with vibrations of laminated beams, plates and shells with arbitrary boundary conditions including classical boundaries, elastic supports and their combinations. It also provides numerous solutions for various configurations including various boundary conditions, laminated schemes, geometry and material parameters, which fill certain gaps in this area of reach and may serve as benchmark solutions for the readers. For each case, corresponding fundamental equations in the framework of classical and shear deformation theory are developed. Following the fundamental equations, numerous free vibration results are presented for various configurations including different boundary conditions, laminated sequences and geometry and material properties. The proposed method and corresponding formulations can be readily extended to static analysis.

  3. Synthesis, structural characterization and photocatalytic application of ZnO@ZnS core-shell nanoparticles

    OpenAIRE

    Sadollahkhani, Azar; Kazeminezhad, Iraj; Lu, Jun; Nur, Omer; Hultman, Lars; Willander, Magnus

    2014-01-01

    ZnO nanoparticles were synthesized by co-precipitation with no capping agent followed by covering with ZnS using a solution-based chemical method at low temperature. By variation of the solution concentrations it was found that the fully-covering ZnS shell forms by a reaction of Na2S with ZnO NPs followed by the formation of ZnS nano-crystals by the reaction of Na2S with ZnCl2. The mechanism that led to full coverage of the ZnO core is proposed to be the addition of ZnCl2 at a later stage of ...

  4. Structural characterization of Pt-Pd and Pd-Pt core-shell nanoclusters at atomic resolution.

    Science.gov (United States)

    Sanchez, Sergio I; Small, Matthew W; Zuo, Jian-min; Nuzzo, Ralph G

    2009-06-24

    We describe the results of a study at atomic resolution of the structures exhibited by polymer-capped monometallic and bimetallic Pt and Pd nanoclusters--models for nanoscale material electrocatalysts--as carried out using an aberration-corrected scanning transmission electron microscope (STEM). The coupling of sub-nanometer resolution with Z-contrast measurements provides unprecedented insights into the atomic structures and relative elemental speciation of Pt and Pd within these clusters. The work further defines the nature of deeply quenched states that prevent facile conversions of core-shell motifs to equilibrium alloys and the nature of nonidealities such as twinning (icosahedral cores) and atomic segregation that these structures can embed. The nature of the facet structure present in these model systems is revealed by theory directed modeling in which experimental intensity profiles obtained in Z-contrast measurements at atomic resolution are compared to simulated intensity profiles using theoretically predicted cluster geometries. These comparisons show close correspondences between experiment and model and highlight striking structural complexities in these systems that are compositionally sensitive and subject to amplification by subsequent cluster growth processes. The work demonstrates an empowering competency in nanomaterials research for STEM measurements carried out using aberration corrected microscopes, approaches that hold considerable promise for characterizing the structure of these and other important catalytic materials systems at the atomic scale.

  5. Dietary Probiotics Affect Gastrointestinal Microbiota, Histological Structure and Shell Mineralization in Turtles.

    Directory of Open Access Journals (Sweden)

    Mateusz Rawski

    Full Text Available Probiotics are widely used in nutrition, and their mode of action is intensively studied in mammals and birds; however, it is almost unknown in reptiles. In the present study, Trachemys scripta scripta and Sternotherus odoratus were used to assess the effects of dietary probiotics on chelonian gastrointestinal tract microecology. In the first, 20-week experiment, 40 young T. s. scripta were randomly distributed to four experimental groups: 1st, (CON--with no additives; 2nd, (SSPA with Bacillus subtilis PB6; 3rd, (MSP--with multiple strain probiotic; and 4th, (SSPB with Bacillus subtilis C-3102. The first study has shown that SSPA and MSP decreased the numbers of total bacteria, Enterobacteriace, Staphylococcus sp. and Streptococcus sp. excreted to water and increased the villous height and mucosa thickness in duodenum. SSPB improved the duodenal microstructure; however, it also increased numbers of kanamycin and vancomycin resistant bacteria, Staphylococcus sp. and Streptococcus sp., in water. In the second, 52-week experiment, 30 S. odoratus were randomly assigned to three dietary treatments. CON, SSPA and MSP groups. The MSP preparation increased the body weight gain, crude ash, Ca and P share in the turtles' shells. Both probiotics affected duodenal histomorphology. SSPA decreased the villous height, while MSP increased the villous height and mucosa thickness, and decreased the crypt depth. SSPA decreased the concentrations of bacteria excreted to water. In the case of intestinal microbiota, bacteria suppressing effects were observed in the case of both probiotics. MSP increased the number of Bifidobacterium sp. and Lactobacillus sp./Enteroccoccus sp., and decreased the number of Clostridium perfringens and Campylobacter sp. in the small intestine. In the large intestine it lowered, amongst others, Bacteroides-Pervotella cluster, Clostridium leptum subgroup and Clostridium perfringens numbers. The above-mentioned results suggest that

  6. Dietary Probiotics Affect Gastrointestinal Microbiota, Histological Structure and Shell Mineralization in Turtles.

    Science.gov (United States)

    Rawski, Mateusz; Kierończyk, Bartosz; Długosz, Jakub; Świątkiewicz, Sylwester; Józefiak, Damian

    2016-01-01

    Probiotics are widely used in nutrition, and their mode of action is intensively studied in mammals and birds; however, it is almost unknown in reptiles. In the present study, Trachemys scripta scripta and Sternotherus odoratus were used to assess the effects of dietary probiotics on chelonian gastrointestinal tract microecology. In the first, 20-week experiment, 40 young T. s. scripta were randomly distributed to four experimental groups: 1st, (CON)--with no additives; 2nd, (SSPA) with Bacillus subtilis PB6; 3rd, (MSP)--with multiple strain probiotic; and 4th, (SSPB) with Bacillus subtilis C-3102. The first study has shown that SSPA and MSP decreased the numbers of total bacteria, Enterobacteriace, Staphylococcus sp. and Streptococcus sp. excreted to water and increased the villous height and mucosa thickness in duodenum. SSPB improved the duodenal microstructure; however, it also increased numbers of kanamycin and vancomycin resistant bacteria, Staphylococcus sp. and Streptococcus sp., in water. In the second, 52-week experiment, 30 S. odoratus were randomly assigned to three dietary treatments. CON, SSPA and MSP groups. The MSP preparation increased the body weight gain, crude ash, Ca and P share in the turtles' shells. Both probiotics affected duodenal histomorphology. SSPA decreased the villous height, while MSP increased the villous height and mucosa thickness, and decreased the crypt depth. SSPA decreased the concentrations of bacteria excreted to water. In the case of intestinal microbiota, bacteria suppressing effects were observed in the case of both probiotics. MSP increased the number of Bifidobacterium sp. and Lactobacillus sp./Enteroccoccus sp., and decreased the number of Clostridium perfringens and Campylobacter sp. in the small intestine. In the large intestine it lowered, amongst others, Bacteroides-Pervotella cluster, Clostridium leptum subgroup and Clostridium perfringens numbers. The above-mentioned results suggest that probiotics are useful in

  7. Split photosystem protein, linear-mapping topology, and growth of structural complexity in the plastid genome of chromera velia

    KAUST Repository

    Janouškovec, Jan

    2013-08-22

    The canonical photosynthetic plastid genomes consist of a single circular-mapping chromosome that encodes a highly conserved protein core, involved in photosynthesis and ATP generation. Here, we demonstrate that the plastid genome of the photosynthetic relative of apicomplexans, Chromera velia, departs from this view in several unique ways. Core photosynthesis proteins PsaA and AtpB have been broken into two fragments, which we show are independently transcribed, oligoU-tailed, translated, and assembled into functional photosystem I and ATP synthase complexes. Genome-wide transcription profiles support expression of many other highly modified proteins, including several that contain extensions amounting to hundreds of amino acids in length. Canonical gene clusters and operons have been fragmented and reshuffled into novel putative transcriptional units. Massive genomic coverage by paired-end reads, coupled with pulsed-field gel electrophoresis and polymerase chain reaction, consistently indicate that the C. velia plastid genome is linear-mapping, a unique state among all plastids. Abundant intragenomic duplication probably mediated by recombination can explain protein splits, extensions, and genome linearization and is perhaps the key driving force behind the many features that defy the conventional ways of plastid genome architecture and function. © The Author 2013.

  8. The defect structures and mechanical properties of Cu and Cu–Al alloys processed by split Hopkinson pressure bar

    International Nuclear Information System (INIS)

    Tao, Jingmei; Yang, Kai; Xiong, Haiwu; Wu, Xiaoxiang; Zhu, Xinkun; Wen, Cuie

    2013-01-01

    Pure Cu, Cu-5 at%Al, Cu-10 at%Al and Cu-15 at%Al with different stacking fault energy (SFE) of 78, 37, 7 and 5 mJ/m 2 , respectively, were processed through split Hopkinson pressure bar (SHPB) with the strain rate of 10 3 /sec. The influence of high strain rate on the evolution of microstructures and mechanical properties of Cu and Cu–Al alloys was investigated. X-ray diffraction measurements indicate that, the microstructures of Cu and Cu–Al alloys have been refined to the nano scale after deformed by SHPB, and with decreasing SFE, the average grain size decreases gradually from 72 to 40 nm, while the dislocation density increases from 0.55×10 14 to 4.4×10 14 m −2 and the twin density increases from 0.04% to 1.07%. The formation of deformation twins is an additional factor that contributes to the microhardness and strength of Cu and Cu–Al alloys except the solid solution strengthening effect. Cu-15 at%Al has the biggest strain hardening rate at larger strains due to its lowest SFE which results in the highest twin density. The results confirm that lower SFE improves both strength and strain hardening rate of materials

  9. Synthesis of novel core-shell structured dual-mesoporous silica nanospheres and their application for enhancing the dissolution rate of poorly water-soluble drugs

    International Nuclear Information System (INIS)

    Wu, Chao; Sun, Xiaohu; Zhao, Zongzhe; Zhao, Ying; Hao, Yanna; Liu, Ying; Gao, Yu

    2014-01-01

    Novel core-shell dual-mesoporous silica nanospheres (DMSS) with a tunable pore size were synthesized successfully using a styrene monomer as a channel template for the core and cetyltrimethyl ammonium bromide (CTAB) as a channel template for the shell in order to improve the dissolution rate of poorly water-soluble drugs. Simvastatin was used as a model drug and loaded into DMSS and the mesoporous core without the shell (MSC) by the solvent evaporation method. The drug loading efficiency of DMSS and MSC were determined by thermogravimetric analysis (TGA) and ultraviolet spectroscopy (UV). Characterization, using scanning electron microscopy (SEM), transmission electron microscopy (TEM), nitrogen adsorption, powder X-ray diffraction (XRD), differential scanning calorimetry (DSC), and Fourier transform infrared spectroscopy (FTIR) showed that simvastatin adsorbed in DMSS and MSC was in an amorphous state, and in vitro release test results demonstrated that both DMSS and MSC increased the water solubility and dissolution rate of simvastatin. The shell structure of DMSS was able to regulate the release of simvastatin compared with MSC. It is worth noting that DMSS has significant potential as a carrier for improving the dissolution of poorly water-soluble drugs and reducing the rapid release. - Highlights: • A novel core-shell DMSS is prepared for improving the dissolution rate of simvastatin. • The diffusional resistance of the mesoporous shell can delay and regulate drug release. • Simvastatin absorbed in DMSS exists in amorphous form due to spatial confinement

  10. Synthesis of novel core-shell structured dual-mesoporous silica nanospheres and their application for enhancing the dissolution rate of poorly water-soluble drugs

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Chao, E-mail: wuchao27@126.com [Department of Pharmaceutics, Liaoning Medical University, 40 Songpo Road, Linghe District, Jinzhou, Liaoning Province 121001 (China); Sun, Xiaohu [Management Center for Experiments, Bohai University, 19 Keji Road, Songshan District, Jinzhou, Liaoning Province 121000 (China); Zhao, Zongzhe; Zhao, Ying; Hao, Yanna; Liu, Ying [Department of Pharmaceutics, Liaoning Medical University, 40 Songpo Road, Linghe District, Jinzhou, Liaoning Province 121001 (China); Gao, Yu, E-mail: gaoyu_1116@163.com [Department of Medical Oncology, First Affiliated Hospital of Liaoning Medical University, 40 Songpo Road, Linghe District, Jinzhou, Liaoning Province 121001 (China)

    2014-11-01

    Novel core-shell dual-mesoporous silica nanospheres (DMSS) with a tunable pore size were synthesized successfully using a styrene monomer as a channel template for the core and cetyltrimethyl ammonium bromide (CTAB) as a channel template for the shell in order to improve the dissolution rate of poorly water-soluble drugs. Simvastatin was used as a model drug and loaded into DMSS and the mesoporous core without the shell (MSC) by the solvent evaporation method. The drug loading efficiency of DMSS and MSC were determined by thermogravimetric analysis (TGA) and ultraviolet spectroscopy (UV). Characterization, using scanning electron microscopy (SEM), transmission electron microscopy (TEM), nitrogen adsorption, powder X-ray diffraction (XRD), differential scanning calorimetry (DSC), and Fourier transform infrared spectroscopy (FTIR) showed that simvastatin adsorbed in DMSS and MSC was in an amorphous state, and in vitro release test results demonstrated that both DMSS and MSC increased the water solubility and dissolution rate of simvastatin. The shell structure of DMSS was able to regulate the release of simvastatin compared with MSC. It is worth noting that DMSS has significant potential as a carrier for improving the dissolution of poorly water-soluble drugs and reducing the rapid release. - Highlights: • A novel core-shell DMSS is prepared for improving the dissolution rate of simvastatin. • The diffusional resistance of the mesoporous shell can delay and regulate drug release. • Simvastatin absorbed in DMSS exists in amorphous form due to spatial confinement.

  11. Synthesis of core-shell hematite (α-Fe2O3) nanoplates: Quantitative analysis of the particle structure and shape, high coercivity and low cytotoxicity

    Science.gov (United States)

    Tadic, Marin; Kopanja, Lazar; Panjan, Matjaz; Kralj, Slavko; Nikodinovic-Runic, Jasmina; Stojanovic, Zoran

    2017-05-01

    Hematite core-shell nanoparticles with plate-like morphology were synthesized using a one-step hydrothermal synthesis. An XRPD analysis indicates that the sample consist of single-phase α-Fe2O3 nanoparticles. SEM and TEM measurements show that the hematite sample is composed of uniform core-shell nanoplates with 10-20 nm thickness, 80-100 nm landscape dimensions (aspect ratio ∼5) and 3-4 nm thickness of the surface shells. We used computational methods for the quantitative analysis of the core-shell particle structure and circularity shape descriptor for the quantitative shape analysis of the nanoparticles from TEM micrographs. The calculated results indicated that a percentage of the shell area in the nanoparticle area (share [%]) is significant. The determined values of circularity in the perpendicular and oblique perspective clearly show shape anisotropy of the nanoplates. The magnetic properties revealed the ferromagnetic-like properties at room temperature with high coercivity HC = 2340 Oe, pointing to the shape and surface effects. These results signify core-shell hematite nanoparticles' for practical applications in magnetic devices. The synthesized hematite plate-like nanoparticles exhibit low cytotoxicity levels on the human lung fibroblasts (MRC5) cell line demonstrating the safe use of these nanoparticles for biomedical applications.

  12. Vanadium fine-structure K-shell electron impact ionization cross sections for fast-electron diagnostic in laser–solid experiments

    Energy Technology Data Exchange (ETDEWEB)

    Palmeri, P., E-mail: patrick.palmeri@umons.ac.be [Astrophysique et Spectroscopie, Université de Mons - UMONS, B-7000 Mons (Belgium); Quinet, P., E-mail: pascal.quinet@umons.ac.be [Astrophysique et Spectroscopie, Université de Mons - UMONS, B-7000 Mons (Belgium); IPNAS, Université de Liège, B-4000 Liège (Belgium); Batani, D., E-mail: batani@celia.u-bordeaux1.fr [CELIA, Université de Bordeaux, F-33400 Talence (France)

    2015-09-15

    The K-shell electron impact ionization (EII) cross section, along with the K-shell fluorescence yield, is one of the key atomic parameters for fast-electron diagnostic in laser–solid experiments through the K-shell emission cross section. In addition, in a campaign dedicated to the modeling of the K lines of astrophysical interest (Palmeri et al. (2012)), the K-shell fluorescence yields for the K-vacancy fine-structure atomic levels of all the vanadium isonuclear ions have been calculated. In this study, the K-shell EII cross sections connecting the ground and the metastable levels of the parent vanadium ions to the daughter ions K-vacancy levels considered in Palmeri et al. (2012) have been determined. The relativistic distorted-wave (DW) approximation implemented in the FAC atomic code has been used for the incident electron kinetic energies up to 20 times the K-shell threshold energies. Moreover, the resulting DW cross sections have been extrapolated at higher energies using the asymptotic behavior of the modified relativistic binary encounter Bethe model (MRBEB) of Guerra et al. (2012) with the density-effect correction proposed by Davies et al. (2013)

  13. Structural characterization and self-assembly into superlattices of iron oxide-gold core-shell nanoparticles synthesized via a high-temperature organometallic route

    International Nuclear Information System (INIS)

    Chiang, I-C; Chen, D-H

    2009-01-01

    Iron oxide-gold core-shell nanocrystals have been synthesized by the thermal decomposition of iron pentacarbonyl and the subsequent reduction of gold acetate by 1,2-hexadecanediol with oleic acid and oleylamine as stabilizers. Their size, structure, composition, and optical and magnetic properties were characterized. The resultant nanoparticles were nearly monodisperse with a complete core-shell structure, and the shell thickness could be tuned via the seed-mediated growth. Also, they exhibited an absorption band at 520 nm owing to the surface plasmon resonance of Au shells and were nearly superparamagnetic due to the presence of the iron cores. By analyzing the x-ray adsorption near-edge structure (XANES) spectrum and the x-ray photoelectron spectroscopy (XPS) spectra of the fast etching mode, the iron cores were shown to be oxidized but the oxidation was incomplete in the inner region. Noteworthily, the iron oxide-Au nanoparticles could self-assemble into 2D and 3D superlattices. The packing density increased while approaching the center of assembly, leading to the variation of superstructures from a 2D nearly hcp monolayer to a 3D hcp superlattice and a 3D hexagonal superlattice. Moreover, hydrophilic iron oxide-Au core-shell nanoparticles were also obtained by surface modification with mercaptoacetic acid via a phase transfer route.

  14. 3D Atomic-Scale Insights into Anisotropic Core-Shell-Structured InGaAs Nanowires Grown by Metal-Organic Chemical Vapor Deposition.

    Science.gov (United States)

    Qu, Jiangtao; Du, Sichao; Burgess, Tim; Wang, Changhong; Cui, Xiangyuan; Gao, Qiang; Wang, Weichao; Tan, Hark Hoe; Liu, Hui; Jagadish, Chennupati; Zhang, Yingjie; Chen, Hansheng; Khan, Mansoor; Ringer, Simon; Zheng, Rongkun

    2017-08-01

    III-V ternary InGaAs nanowires have great potential for electronic and optoelectronic device applications; however, the 3D structure and chemistry at the atomic-scale inside the nanowires remain unclear, which hinders tailoring the nanowires for specific applications. Here, atom probe tomography is used in conjunction with a first-principles simulation to investigate the 3D structure and chemistry of InGaAs nanowires, and reveals i) the nanowires form a spontaneous core-shell structure with a Ga-enriched core and an In-enriched shell, due to different growth mechanisms in the axial and lateral directions; ii) the shape of the core evolves from hexagon into Reuleaux triangle and grows larger, which results from In outward and Ga inward interdiffusion occurring at the core-shell interface; and iii) the irregular hexagonal shell manifests an anisotropic growth rate on {112}A and {112}B facets. Accordingly, a model in terms of the core-shell shape and chemistry evolution is proposed, which provides fresh insights into the growth of these nanowires. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Form and formation of flares and parabolae based on new observations of the internal shell structure in lytoceratid and perisphinctid ammonoids

    Directory of Open Access Journals (Sweden)

    Gregor Radtke

    2016-08-01

    Full Text Available The ultrastructure of pristine shells of Jurassic and Cretaceous lytoceratid and perisphinctid ammonoids indicates that flares and parabolae represent homologous structures. Both mark an interruption of shell growth. We dismiss earlier interpretations of parabolae as actual aperture, relics of resorbed apophyses or superstructure of the musculature associated to a semi-internal shell. Instead we propose an episodic growth model including several growth stops at the aperture during the formation of a frill-like aperture for parabolae and flares. Such an aperture is composed of the outer prismatic layer, the nacreous layer and an apertural prismatic coating. Here, we observed the apertural prismatic coating for the first time as an integral part of flares and parabolae. The apertural prismatic coating covers only the inner surface of the frill and was secreted by a permanent mantle cover indicating a prolonged period without the production of new shell material. Parabolae differ from flares by their general shape and the presence of ventro-lateral parabolic notches and nodes. The notches were formed by folding of the frill and had the potential to form semi-open spines. The corresponding parabolic nodes are caused by an outward swelling of the shell-secreting mantle tissue producing new shell material at the position of the folding. New shell material that belongs to the conch tube is attached to the base of flares and parabolae after withdrawal of the mantle edge representing the continuation of shell growth. Usually, the frilled aperture associated with flares and parabolae were removed during lifetime. This study reports on flares in Argonauticeras for the first time. In this genus they are typically associated with varices.

  16. Shell structure in the vicinity of the doubly magic {sup 100}Sn via Coulomb excitation at PreSPEC

    Energy Technology Data Exchange (ETDEWEB)

    Guastalla, Giulia

    2014-11-17

    The PreSPEC setup in combination with the high intensity primary beams available at GSI provided unique opportunities for the key nuclear structure studies on exotic nuclei. The experiment performed on the neutron deficient {sup 104}Sn aimed to deduce the reduced transition probability of the first excited 2{sup +} state quantified by the B(E2; 0{sup +} → 2{sup +}) value. This result is the central point in the discussion of the evolution of nuclear structure in proximity of the doubly magic nucleus {sup 100}Sn. As {sup 100}Sn is not yet accessible for such measurements, a series of experiments have been performed for neutron-deficient Sn isotopes over the past few years. These data showed excessive experimental B(E2) strength compared to shell model calculations below neutron number N=64 and they are therefore not excluding a constant or even increasing collectivity below {sup 106}Sn. Hence, the measurement of the B(E2) value in the next even-even isotope toward {sup 100}Sn, i.e. {sup 104}Sn, was a crucial step to verify the robustness of the shell gap of {sup 100}Sn. Moreover, {sup 104}Sn is the heaviest isotope of the Sn isotopic chain for which a shell model calculation without significant truncation of the valence space can be performed and therefore with this experimental value the validity of Large Scale Shell Model (LSSM) calculations could be tested. As a main result of the experiment a B(E2) value corresponding to 0.10(4) e{sup 2}b{sup 2} has been extracted for {sup 104}Sn. The experimental value showed a very good agreement with the predicted one and, despite the large error bar, it clearly established a downward trend of the B(E2) values of the Sn isotopic chain toward A=100. This implied enhanced stability of the N = Z = 50 shell closure against ph-excited quadrupole modes. However, an experiment of this kind is very challenging for several reasons. First, {sup 104}Sn lies in proximity of the proton drip line and has therefore a small production

  17. Pulsed laser deposited porous nano-carpets of indium tin oxide and their use as charge collectors in core-shell structures for dye sensitized solar cells

    Science.gov (United States)

    Garvey, Timothy R.; Farnum, Byron H.; Lopez, Rene

    2015-01-01

    Porous In2O3:Sn (ITO) films resembling from brush carpets to open moss-like discrete nanostructures were grown by pulsed laser deposition under low to high background gas pressures, respectively. The charge transport properties of these mesoporous substrates were probed by pulsed laser photo-current and -voltage transient measurements in N719 dye sensitized devices. Although the cyclic voltammetry and dye adsorption measurements suggest a lower proportion of electro-active dye molecules for films deposited at the high-end background gas pressures, the transient measurements indicate similar electron transport rates within the films. Solar cell operation was achieved by the deposition of a conformal TiO2 shell layer by atomic layer deposition (ALD). Much of the device improvement was shown to be due to the TiO2 shell blocking the recombination of photoelectrons with the electrolyte as recombination lifetimes increased drastically from a few seconds in uncoated ITO to over 50 minutes in the ITO with a TiO2 shell layer. Additionally, an order of magnitude increase in the electron transport rate in ITO/TiO2 (core/shell) films was observed, giving the core-shell structure a superior ratio of recombination/transport times.Porous In2O3:Sn (ITO) films resembling from brush carpets to open moss-like discrete nanostructures were grown by pulsed laser deposition under low to high background gas pressures, respectively. The charge transport properties of these mesoporous substrates were probed by pulsed laser photo-current and -voltage transient measurements in N719 dye sensitized devices. Although the cyclic voltammetry and dye adsorption measurements suggest a lower proportion of electro-active dye molecules for films deposited at the high-end background gas pressures, the transient measurements indicate similar electron transport rates within the films. Solar cell operation was achieved by the deposition of a conformal TiO2 shell layer by atomic layer deposition (ALD). Much

  18. Optimization of wall thickness and lay-up for the shell-like composite structure loaded by non-uniform pressure field

    Science.gov (United States)

    Shevtsov, S.; Zhilyaev, I.; Oganesyan, P.; Axenov, V.

    2017-01-01

    The glass/carbon fiber composites are widely used in the design of various aircraft and rotorcraft components such as fairings and cowlings, which have predominantly a shell-like geometry and are made of quasi-isotropic laminates. The main requirements to such the composite parts are the specified mechanical stiffness to withstand the non-uniform air pressure at the different flight conditions and reduce a level of noise caused by the airflow-induced vibrations at the constrained weight of the part. The main objective of present study is the optimization of wall thickness and lay-up of composite shell-like cowling. The present approach assumes conversion of the CAD model of the cowling surface to finite element (FE) representation, then its wind tunnel testing simulation at the different orientation of airflow to find the most stressed mode of flight. Numerical solutions of the Reynolds averaged Navier-Stokes (RANS) equations supplemented by k-w turbulence model provide the spatial distributions of air pressure applied to the shell surface. At the formulation of optimization problem the global strain energy calculated within the optimized shell was assumed as the objective. A wall thickness of the shell had to change over its surface to minimize the objective at the constrained weight. We used a parameterization of the problem that assumes an initiation of auxiliary sphere with varied radius and coordinates of the center, which were the design variables. Curve that formed by the intersection of the shell with sphere defined boundary of area, which should be reinforced by local thickening the shell wall. To eliminate a local stress concentration this increment was defined as the smooth function defined on the shell surface. As a result of structural optimization we obtained the thickness of shell's wall distribution, which then was used to design the draping and lay-up of composite prepreg layers. The global strain energy in the optimized cowling was reduced in2

  19. Structural aspects of the solvation shell of lysine and acetylated lysine: A Car-Parrinello and classical molecular dynamics investigation

    International Nuclear Information System (INIS)

    Carnevale, V.; Raugei, S.

    2009-01-01

    Lysine acetylation is a post-translational modification, which modulates the affinity of protein-protein and/or protein-DNA complexes. Its crucial role as a switch in signaling pathways highlights the relevance of charged chemical groups in determining the interactions between water and biomolecules. A great effort has been recently devoted to assess the reliability of classical molecular dynamics simulations in describing the solvation properties of charged moieties. In the spirit of these investigations, we performed classical and Car-Parrinello molecular dynamics simulations on lysine and acetylated-lysine in aqueous solution. A comparative analysis between the two computational schemes is presented with a focus on the first solvation shell of the charged groups. An accurate structural analysis unveils subtle, yet statistically significant, differences which are discussed in connection to the significant electronic density charge transfer occurring between the solute and the surrounding water molecules.

  20. Effects of Alloying Elements on the Formation of Core-Shell-Structured Reinforcing Particles during Heating of Al–Ti Powder Compacts

    Science.gov (United States)

    Chen, Tijun; Gao, Min; Tong, Yunqi

    2018-01-01

    To prepare core-shell-structured Ti@compound particle (Ti@compoundp) reinforced Al matrix composite via powder thixoforming, the effects of alloying elements, such as Si, Cu, Mg, and Zn, on the reaction between Ti powders and Al melt, and the microstructure of the resulting reinforcements were investigated during heating of powder compacts at 993 K (720 °C). Simultaneously, the situations of the reinforcing particles in the corresponding semisolid compacts were also studied. Both thermodynamic analysis and experiment results all indicate that Si participated in the reaction and promoted the formation of Al–Ti–Si ternary compounds, while Cu, Mg, and Zn did not take part in the reaction and facilitated Al3Ti phase to form to different degrees. The first-formed Al–Ti–Si ternary compound was τ1 phase, and then it gradually transformed into (Al,Si)3Ti phase. The proportion and existing time of τ1 phase all increased as the Si content increased. In contrast, Mg had the largest, Cu had the least, and Si and Zn had an equivalent middle effect on accelerating the reaction. The thicker the reaction shell was, the larger the stress generated in the shell was, and thus the looser the shell microstructure was. The stress generated in (Al,Si)3Ti phase was larger than that in τ1 phase, but smaller than that in Al3Ti phase. So, the shells in the Al–Ti–Si system were more compact than those in the other systems, and Si element was beneficial to obtain thick and compact compound shells. Most of the above results were consistent to those in the semisolid state ones except the product phase constituents in the Al–Ti–Mg system and the reaction rate in the Al–Ti–Zn system. More importantly, the desirable core-shell structured Ti@compoundp was only achieved in the semisolid Al–Ti–Si system. PMID:29342946

  1. Effects of Alloying Elements on the Formation of Core-Shell-Structured Reinforcing Particles during Heating of Al-Ti Powder Compacts.

    Science.gov (United States)

    Chen, Tijun; Gao, Min; Tong, Yunqi

    2018-01-15

    To prepare core-shell-structured Ti@compound particle (Ti@compound p ) reinforced Al matrix composite via powder thixoforming, the effects of alloying elements, such as Si, Cu, Mg, and Zn, on the reaction between Ti powders and Al melt, and the microstructure of the resulting reinforcements were investigated during heating of powder compacts at 993 K (720 °C). Simultaneously, the situations of the reinforcing particles in the corresponding semisolid compacts were also studied. Both thermodynamic analysis and experiment results all indicate that Si participated in the reaction and promoted the formation of Al-Ti-Si ternary compounds, while Cu, Mg, and Zn did not take part in the reaction and facilitated Al₃Ti phase to form to different degrees. The first-formed Al-Ti-Si ternary compound was τ1 phase, and then it gradually transformed into (Al,Si)₃Ti phase. The proportion and existing time of τ1 phase all increased as the Si content increased. In contrast, Mg had the largest, Cu had the least, and Si and Zn had an equivalent middle effect on accelerating the reaction. The thicker the reaction shell was, the larger the stress generated in the shell was, and thus the looser the shell microstructure was. The stress generated in (Al,Si)₃Ti phase was larger than that in τ1 phase, but smaller than that in Al₃Ti phase. So, the shells in the Al-Ti-Si system were more compact than those in the other systems, and Si element was beneficial to obtain thick and compact compound shells. Most of the above results were consistent to those in the semisolid state ones except the product phase constituents in the Al-Ti-Mg system and the reaction rate in the Al-Ti-Zn system. More importantly, the desirable core-shell structured Ti@compound p was only achieved in the semisolid Al-Ti-Si system.

  2. Investigation of CuInSe2 nanowire arrays with core-shell structure electrodeposited at various duty cycles into anodic alumina templates

    Science.gov (United States)

    Cheng, Yu-Song; Wang, Na-Fu; Tsai, Yu-Zen; Lin, Jia-Jun; Houng, Mau-Phon

    2017-02-01

    Copper indium selenide (CuInSe2) nanowire (NW) arrays were prepared at various electrolyte duty cycles by filling anodic alumina templates through the pulsed electrodeposition technique. X-ray diffraction and scanning electron microscopy (SEM) images showed that the nucleation mechanism of CuInSe2 NW arrays was affected by the electrodeposition duty cycle. Moreover, SEM images showed that the diameter and length of the NWs were 80 nm and 2 μm, respectively. Furthermore, PEDOT/CuInSe2 NW core-shell arrays were fabricated using surfactant-modified CuInSe2 NW surfaces showing the lotus effect. Transmission electron microscopy images confirmed that a core-shell structure was achieved. Current-voltage plots revealed that the CuInSe2 NW arrays were p-type semiconductors; moreover, the core-shell structure improved the diode ideality factor from 3.91 to 2.63.

  3. Synthesis of BiFeO3/ZnO core-shell hetero-structures using ZnO nanorod positive templates.

    Science.gov (United States)

    Chen, Shih-Wei; Lee, Chia-Ching; Chen, Ming-Teng; Wu, Jenn-Ming

    2011-03-18

    We report the synthesis, morphology, and magnetization characteristics of BiFeO(3) (BFO)-covered ZnO nanorod arrays (ZNAs). High quality and well-aligned ZNAs were grown by a hydrothermal method. BFO shells were deposited by sputtering at ambient temperature and then annealing in an oxygen atmosphere. The BFO shells crystallized to form a perovskite structure at 450 °C. Scanning electron microscopy and high resolution transmission electron microscopy demonstrated that the BFO shell was polycrystalline and randomly oriented, covering the ZnO nanorods well. The magnetization-magnetic field loops measured at 5 and 300 K indicate that the BFO/ZNA hetero-structure exhibits ferromagnetic order. The BFO/ZNA displays enhanced coercivity and saturated magnetization as compared with BFO thin films.

  4. Quadrupole hyperfine structure and splitting of Δ-levels in the microwave spectra of KOH, RbOH and CsOH in the 100 GHz region

    International Nuclear Information System (INIS)

    Kuijpers, P.; Dymanus, A.; Toerring, T.

    1977-01-01

    Hyperfine structure of rotational transitions of KOH, RbOH and CsOH in various v 2 - and l-states has been carefully measured in the 100 GHz range. From the observed splittings and broadenings information about quadrupole coupling constant (eqQ) of the K nucleus in KOH and about the spacing (Esub(Δ) - Esub(Σ)) between Σ and Δ levels in the vibrational spectrum of KOH, RbOH and CsOH has been derived. The measured value of the eqQ of KOH is close to that of KF. The separation between Σ and Δ levels is found to be rather similar for the group of the alkali hydroxides increasing gradually when progressing from LiOH to CsOH. (orig.) [de

  5. Hole-level structure of double {delta}-doped quantum wells in Si: The influence of the split-off band

    Energy Technology Data Exchange (ETDEWEB)

    Rodriguez-Vargas, I. [Facultad de Ciencias, Universidad Autonoma del Estado de Morelos, Av. Universidad 1001, Col. Chamilpa, 62210 Cuernavaca, Mor. (Mexico); Gaggero-Sager, L.M. [Facultad de Ciencias, Universidad Autonoma del Estado de Morelos, Av. Universidad 1001, Col. Chamilpa, 62210 Cuernavaca, Mor. (Mexico)]. E-mail: lgaggero@buzon.uaem.mx

    2007-02-15

    We present the electronic structure calculation of two closely p-type {delta}-doped quantum wells within the lines of the Thomas-Fermi-Dirac (TFD) theory. The distance between the impurity planes as well as the impurity density of the {delta}-doped wells is varied. The exchange effects are also considered in the present study. We have paid special attention to the split-off band and its influence on the subband hole levels. We also calculate the mobility ratio of double {delta}-doped (DDD) quantum wells in Si with respect to a single {delta}-doped (SDD) one, finding the optimum distance between the wells for maximum mobility. Our results are in a good agreement with respect to the experimental data available.

  6. On split Lie triple systems

    Indian Academy of Sciences (India)

    Lie triple system; system of roots; root space; split Lie algebra; structure theory. 1. Introduction and previous definitions. Throughout this paper, Lie triple systems T are considered of arbitrary dimension and over an arbitrary field K. It is worth to mention that, unless otherwise stated, there is not any restriction on dim Tα or {k ...

  7. WC-Co Composite Coating Deposited by Cold Spraying of a Core-Shell-Structured WC-Co Powder

    Science.gov (United States)

    Luo, Xiao-Tao; Li, Cheng-Xin; Shang, Fu-Lin; Yang, Guan-Jun; Wang, Yu-Yue; Li, Chang-Jiu

    2015-01-01

    In this study, a core-shell-structured WC-Co powder was used to develop a heterogeneously structured WC-Co coating with tens micrometers of WC-10Co as strengthening phase and Co-rich WC-Co as the binder in order to realize simultaneous strengthening and toughening. Spray powder particles contain WC-10Co core coated with a Co-rich WC-Co shell by mechanical milling. WC-Co coating with dual-scale strengthening phases was deposited by cold spraying. Post-spray annealing was carried out to further modify the coating microstructure. Microstructures of the spray powder and the coating were characterized by SEM. Mechanical properties of the coating in terms of microhardness and fracture toughness were examined. Results show that a biomodal WC-Co coating with a porosity of only 0.7% was deposited by cold spray. The Co-rich matrix phase contains submicrometer-sized carbide and primary hard phase is WC-10Co particles. The measurement yielded a Vickers microhardness of 1493 ± 76.7 HV0.1 for WC-10Co core and 693 ± 47.3 HV0.1 for Co-rich binder phase. After annealed at 900 °C for 5 h, a remarkable increase in fracture toughness from 21.2 ± 3.8 to 35.7±5.2 MPa m-0.5 was achieved while no evident change occurred to the hardness of WC-10Co cores.

  8. Pseudospin-orbit splitting and its consequences for the central depression in nuclear density

    Science.gov (United States)

    Li, Jia Jie; Long, Wen Hui; Song, Jun Ling; Zhao, Qiang

    2016-05-01

    The occurrence of the bubble-like structure has been studied, in the light of pseudospin degeneracy, within the relativistic Hartree-Fock-Bogoliubov (RHFB) theory. It is concluded that the charge/neutron bubble-like structure is predicted to occur in the mirror system of {34Si,34Ca } commonly by the selected Lagrangians, due to the persistence of Z (N )=14 subshell gaps above which the π (ν ) 2 s1 /2 states are not occupied. However, for the popular candidate 46Ar, the RHFB Lagrangian PKA1 does not support the occurrence of the bubble-like structure in the charge (proton) density profiles, due to the almost degenerate pseudospin doublet {π 2 s1 /2,π 1 d3 /2} and coherent pairing effects. The formation of a semibubble in heavy nuclei is less possible as a result of small pseudospin-orbit (PSO) splitting, while it tends to appear at Z =120 superheavy systems which coincides with large PSO splitting of the doublet {π 3 p3 /2,π 2 f5 /2} and couples with significant shell effects. Pairing correlations, which can work against bubble formation, significantly affect the PSO splitting. Furthermore, we found that the influence on semibubble formation due to different types of pairing interactions is negligible. The quenching of the spin-orbit splitting in the p orbit has been also stressed, and it may be considered the hallmark for semibubble nuclei.

  9. Dye-sensitized solar cells employing a SnO2-TiO2 core-shell structure made by atomic layer deposition.

    Science.gov (United States)

    Karlsson, Martin; Jõgi, Indrek; Eriksson, Susanna K; Rensmo, Håkan; Boman, Mats; Boschloo, Gerrit; Hagfeldt, Anders

    2013-01-01

    This paper describes the synthesis and characterization of core-shell structures, based on SnO2 and TiO2, for use in dye-sensitized solar cells (DSC). Atomic layer deposition is employed to control and vary the thickness of the TiO2 shell. Increasing the TiO2 shell thickness to 2 nm improved the device performance of liquid electrolyte-based DSC from 0.7% to 3.5%. The increase in efficiency originates from a higher open-circuit potential and a higher short-circuit current, as well as from an improvement in the electron lifetime. SnO2-TiO2 core-shell DSC devices retain their photovoltage in darkness for longer than 500 seconds, demonstrating that the electrons are contained in the core material. Finally core-shell structures were used for solid-state DSC applications using the hole transporting material 2,2',7,7',-tetrakis(N, N-di-p-methoxyphenyl-amine)-9,9',-spirofluorene. Similar improvements in device performance were obtained for solid-state DSC devices.

  10. Designing of luminescent GdPO4:Eu@LaPO4@SiO2 core/shell nanorods: Synthesis, structural and luminescence properties

    Science.gov (United States)

    Ansari, Anees A.; Labis, Joselito P.; Aslam Manthrammel, M.

    2017-09-01

    GdPO4:Eu3+ (core) and GdPO4:Eu@LaPO4 (core/shell) nanorods (NRs) were successfully prepared by urea based co-precipitation process at ambient conditions which was followed by coating with amorphous silica shell via the sol-gel chemical route. The role of surface coating on the crystal structure, crystallinity, morphology, solubility, surface chemistry and luminescence properties were well investigated by means of X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive X-ray (EDX) analysis, Fourier Transform Infrared (FTIR), UV-Vis, and photoluminescence spectroscopy. XRD pattern revealed highly purified, well-crystalline, single phase-hexagonal-rhabdophane structure of GdPO4 crystal. The TEM micrographs exhibited highly crystalline and narrow size distributed rod-shaped GdPO4:Eu3+ nanostructures with average width 14-16 nm and typical length 190-220 nm. FTIR spectra revealed characteristic infrared absorption bands of amorphous silica. High absorbance in a visible region of silica modified core/shell/Si NRs in aqueous environment suggests the high solubility along with colloidal stability. The photoluminescence properties were remarkably enhanced after growth of undoped LaPO4 layers due to the reduction of nonradiative transition rate. The advantages of presented high emission intensity and high solubility of core/shell and core/shell/Si NRs indicated the potential applications in monitoring biological events.

  11. Highly selective and sensitive methanol gas sensor based on molecular imprinted silver-doped LaFeO3 core-shell and cage structures

    Science.gov (United States)

    Rong, Qian; Zhang, Yumin; Lv, Tianping; Shen, Kaiyuan; Zi, Baoye; Zhu, Zhongqi; Zhang, Jin; Liu, Qingju

    2018-04-01

    Silver-doped LaFeO3 molecularly imprinted polymers (SLMIPs) were synthesized by a sol-gel method combined with molecularly imprinted technology as precursors. The precursors were then used to prepare SLMIPs cage (SLM-cage) and SLMIPs core-shell (SLM-core-shell) structures by using a carbon sphere as the template and hydrothermal synthesis, respectively. The structures, morphologies, and surface areas of these materials were determined, as well as their gas-sensing properties and related mechanisms. The SLM-cage and SLM-core-shell samples exhibited good responses to methanol gas, with excellent selectivity. The response and optimum working temperature were 16.98 °C and 215 °C, 33.7 °C and 195 °C, respectively, with corresponding response and recovery times of 45 and 50 s (SLM-cage) and 42 and 57 s (SLM-core-shell) for 5 ppm methanol gas. Notably, the SLM-cage and SLM-core-shell samples exhibited lower responses (≤5 and ≤7, respectively) to other gases, including ethanol, ammonia, benzene, acetone, and toluene. Thus, these materials show potential as practical methanol detectors.

  12. Core-shell structure and magnetic properties of magnetite magnetic fluids stabilized with dextran

    International Nuclear Information System (INIS)

    Xu, X.Q.; Shen, H.; Xu, J.R.; Xu, J.; Li, X.J.; Xiong, X.M.

    2005-01-01

    The adsorption process of different dextran molecules onto the surface of in water dispersed magnetite nanoparticles has been investigated to optimize the preparation of magnetite magnetic fluids (MMFs). An average magnetite core size of 7.1 nm was found by X-ray diffraction and that of 8 nm was found by transmission electron microscopy for the samples prepared at 90 deg. C. An average hydrodynamic diameter of 25 nm was observed by scanning electron microscopy and that of 25-300 nm was obtained by photon correlation spectroscopy. The dextran was adsorbed by physical adsorption, a molecular weight of 20 kDa gave the best stability of these MMFs. The shell layer of the particles was weakly negatively charged in buffer solutions of pH values between 5.5 and 9.5. The particles seem to be mainly stabilized by sterical repulsion. The maximum available saturation magnetization of the MMFs was 3.5 kA/m

  13. Theoretical Elastic Stress Distributions Arising from Discontinuities and Edge Loads in Several Shell-Type Structures

    Science.gov (United States)

    Johns, Robert H.; Orange, Thomas W.

    1961-01-01

    The deformation and complete stress distribution are determined for each of the following edge loaded thin shells of revolution: (1) a right circular cylinder, (2) a frustum of a right circular cone, and (3) a portion of a sphere. The locations of the maximum circumferential and meridional stresses on both the inner and outer surfaces are also found. The basic equations for the above were selected from the published literature on the subject and expanded to produce to resultant-stress equations in closed from where practicable to do so. Equations are also developed for the discontinuity shear force and bending moment at each of the following junction: (1) axial change of thickness in a circular cylinder, (2) axial change of thickness in a cone, (3) change of thickness in a portion of a sphere, (4) a cylinder and a cone, (5) a cylinder and a portion of a sphere(6) a cylinder and a flat head, and (7) a cone and a portion of a sphere.

  14. Core-Shell Nanocatalysts Obtained in Reverse Micelles: Structural and Kinetic Aspects

    Directory of Open Access Journals (Sweden)

    Concha Tojo

    2015-01-01

    Full Text Available Ability to control the metal arrangement in bimetallic nanocatalysts is the key to improving their catalytic activity. To investigate how metal distribution in nanostructures can be modified, we developed a computer simulation model on the synthesis of bimetallic nanoparticles obtained in microemulsions by a one-pot method. The calculations allow predicting the metal arrangement in nanoparticle under different experimental conditions. We present results for two couples of metals, Au/Pt (Δε=0.26 V and Au/Ag (Δε=0.19 V, but conclusions can be generalized to other bimetallic pairs with similar difference in standard reduction potentials. It was proved that both surface and interior compositions can be controlled at nanometer resolution easily by changing the initial reactant concentration inside micelles. Kinetic analysis demonstrates that the confinement of reactants inside micelles has a strong effect on the reaction rates of the metal precursors. As a result, the final nanocatalyst shows a more mixed core and a better defined shell as concentration is higher.

  15. Morphogenesis of the turtle shell: the development of a novel structure in tetrapod evolution.

    Science.gov (United States)

    Gilbert, S F; Loredo, G A; Brukman, A; Burke, A C

    2001-01-01

    The turtle shell is an evolutionary novelty that is synapomorphic for chelonians. The carapace is initiated by the entrapment of the ribs by the carapacial ridge (CR), a lateral bulge of the dorsal ectoderm and dermal mesoderm. The mechanisms by which the CR is initiated, the ribs entrapped and the dorsal dermis ossified, remains unknown. Similarly, the formation of the plastron remains unexplained. Here, we present a series of anatomical investigations into plastron and carapace formation in the red-eared slider, Trachemys scripta, and the snapping turtle, Chelydra serpentina. We document the entrapment of the ribs by the CR and the formation of the plastron and carapacial bones by intramembranous ossification. We note the formation of the ossification centers around each rib, which suggest that the rib is organizing dermal ossification by secreting paracrine factors. The nuchal ossification center is complex and appears to involve multiple bone-forming regions. Individual ossification centers at the periphery of the carapace form the peripheral and pygial bones. The intramembranous ossification of the plastron proceeds from nine distinct ossification centers, and there appear to be interactions between the spicules of apposing centers as they draw near each other.

  16. Structural Analysis on Reduced Graphene Oxide Prepared from Old Coconut Shell by Synchrotron X-Ray Scattering

    Science.gov (United States)

    Yogi Nugraheni, Ananda; Jayanti, Dwi Noor; Kurniasari; Soontaranon, Siriwat; Giri Rachman Putra, Edy; Darminto

    2017-05-01

    This work is aimed to identify the distribution of size and structure of the reduced graphene oxide (rGO) particles before and after the mechanical exfoliation process from coconut shell. The burnt sample was heated at 400°C in ambient air, followed by sonication and centrifugation method for various concentration. The characterization were performed by using wide angle X-ray scattering (WAXS) and synchrotron small angle X-ray scattering (SAXS). Based on SAXS result, the structure of rGO showed that in low range of momentum transfer (Q), the particle size was too big to be measured using SAXS. In the high Q, the graph shown the apparent absence of change in curvature which indicates that the small particles are typically seen on high Q range, having aggregate with a new shape and big particles. The average fitting slope is -3.3, implying that the particles structure tends to be fractal (rough) surface, where the particles form aggregates to become bigger size and irregular structure. Further, the WAXS characterization shows that the exfoliation step has not affected the rGO phase formed.

  17. Phylogeography of Ivory shell (Babylonia areolata in the Gulf of Thailand revealed by COI gene structure and differentiation of shell color by ITS1 DNA

    Directory of Open Access Journals (Sweden)

    Amornrat Phongdara

    2008-03-01

    Full Text Available Babylonia areolata is an aquatic mollusk in the genus of the gastropod family Buccinidae. Genetic variations were observed in the 542 base pairs of the sequences from its cytochrome oxidase subunit I (COI gene of mtDNA. COI alignments showed that there were two monophyletic clades on the phylogenetic tree, referred as B. areolata. These results point towards the possibility of B. areolata being a single species with strong phylogeographic subdivisions. About 520 base pairs of the internal transcribed spacer 1 (ITS1 sequence were able to distinguish between the shell colors (brown, cream and white of B. areolata.

  18. Optimization of the Manufacturing Process of Conical Shell Structures Using Prepreg Laminatees

    Science.gov (United States)

    Khakimova, Regina; Zimmermann, Rolf; Burau, Florian; Siebert, Marc; Arbelo, Mariano; Castro, Saullo; Degenhardt, Richard

    2014-06-01

    The design and manufacture of an unstiffened composite conical structure which is a scaled-down version of the Ariane 5 Midlife Evolution Equipment Bay Structure is presented. For such benchmarking structures the fiber orientation error is critical and then the manufacturing process becomes a big challenge. The paper therefore is focused on the implementation of a tailoring study and on the manufacturing process. The conical structure will be tested to validate a new design approach.This study contributes to the European Union (EU) project DESICOS, whose aim is to develop less conservative design guidelines for imperfection sensitive thin-walled structures.

  19. I. Fission Probabilities, Fission Barriers, and Shell Effects. II. Particle Structure Functions

    Energy Technology Data Exchange (ETDEWEB)

    Jing, Kexing [Univ. of California, Berkeley, CA (United States)

    1999-05-01

    In Part I, fission excitation functions of osmium isotopes 185,186, 187, 189 Os produced in 3He +182,183, 184, 186W reactions, and of polonium isotopes 209,210, 211, 212Po produced in 3He/4He + 206, 207, 208Pb reactions, were measured with high precision. These excitation functions have been analyzed in detail based upon the transition state formalism. The fission barriers, and shell effects for the corresponding nuclei are extracted from the detailed analyses. A novel approach has been developed to determine upper limits of the transient time of the fission process. The upper limits are constrained by the fission probabilities of neighboring isotopes. The upper limits for the transient time set with this new method are 15x 10–21 sec and 25x 10–21 sec for 0s and Po compound nuclei, respectively. In Part II, we report on a search for evidence of the optical modulations in the energy spectra of alpha particles emitted from hot compound nuclei. The optical modulations are expected to arise from the ~-particle interaction with the rest of the nucleus as the particle prepares to exit. Some evidence for the modulations has been observed in the alpha spectra measured in the 3He-induced reactions, 3He + natAg in particular. The identification of the modulations involves a technique that subtracts the bulk statistical background from the measured alpha spectra, in order for the modulations to become visible in the residuals. Due to insufficient knowledge of the background spectra, however, the presented evidence should only be regarded as preliminary and tentative.

  20. Comparative studies on different nanofiber photocatalysts for water splitting

    Science.gov (United States)

    Alharbi, Abdulaziz; Alarifi, Ibrahim M.; Khan, Waseem S.; Asmatulu, Ramazan

    2016-04-01

    Water splitting using photocatalyst has become a topic of recent investigation since it has the potential of producing hydrogen for clean energy from sunlight. An extensive number of solid photocatalysts have been studied for overall water splitting in recent years. In this study, two methods were employed to synthesize two different photocatalysts for water splitting. The first method describes the synthesis of nickel oxide-loaded strontium titanate (NiO-SrTiO3) particles on electrospun polyacrylonitrile (PAN) nanofibers incorporated with graphene nanoplatelets for water splitting. The electrospun PAN fibers were first oxidized at 270°C for two hours and subsequently immersed in a solution containing ethanol, titanium (IV)-isopropoxide [C12H28O4Ti] and strontium nitrate [Sr(NO3)2]. This solution was then treated with NiO nanoparticles dispersed in toluene. The surface treated PAN fibers were annealed at 600°C in air for 1 hour to transform fibers into a crystalline form for improved photocatalyst performance. In the second method, coaxial electrospinning process was used to produce core/shell strontium titanate/nickel oxide (SrTiO3-NiO) nanofibers. In coaxial method, poly (vinyl pyrrolidone) (PVP) was dissolved in deionized (DI) water, and then titanium (IV) isopropoxide [C12H28O4Ti] and strontium nitrate [Sr(NO3)2] were added into the solution to form the inner (core) layer. For outer (shell) solution, polyacrylonitrile (PAN) polymer was dissolved in dimethylformamide (DMF) at a weight ratio of 10:90 and then nickel oxide was mixed with the solution. Ultraviolet (UV) spectrophotometry and static contact angle measurement techniques were employed to characterize the structural properties of photocatalysts produced by both methods and a comparison was made between the two photocatalysts. The morphology and diameter of the nanofibers were observed by scanning electron microscopy (SEM). The structure and crystallinity of the calcined nanofibers were also observed

  1. Catalyst-free fabrication of novel ZnO/CuO core-Shell nanowires heterojunction: Controlled growth, structural and optoelectronic properties

    Science.gov (United States)

    Khan, Muhammad Arif; Wahab, Yussof; Muhammad, Rosnita; Tahir, Muhammad; Sakrani, Samsudi

    2018-03-01

    Development of controlled growth and vertically aligned ZnO/CuO core-shell heterojunction nanowires (NWs) with large area by a catalyst free vapor deposition and oxidation approach has been investigated. Structural characterization reveals successful fabrication of a core ZnO nanowire having single crystalline hexagonal wurtzite structure along [002] direction and CuO nanostructure shell with thickness (8-10 nm) having polycrystalline monoclinic structure. The optical property analysis suggests that the reflectance spectrum of ZnO/CuO heterostructure nanowires is decreased by 18% in the visible range, which correspondingly shows high absorption in this region as compared to pristine ZnO nanowires. The current-voltage (I-V) characteristics of core-shell heterojunction nanowires measured by conductive atomic force microscopy (C-AFM) shows excellent rectifying behavior, which indicates the characteristics of a good p-n junction. The high-resolution transmission electron microscopy (HRTEM) has confirmed the sharp junction interface between the core-shell heterojunction nanowire arrays. The valence band offset and conduction band offset at ZnO/CuO heterointerfaces are measured to be 2.4 ± 0.05 and 0.23 ± 0.005 eV respectively, using X-ray photoelectron spectroscopy (XPS) and a type-II band alignment structure is found. The results of this study contribute to the development of new advanced device heterostructures for solar energy conversion and optoelectronics applications.

  2. Hierarchical core-shell structure of ZnO nanorod@NiO/MoO₂ composite nanosheet arrays for high-performance supercapacitors.

    Science.gov (United States)

    Hou, Sucheng; Zhang, Guanhua; Zeng, Wei; Zhu, Jian; Gong, Feilong; Li, Feng; Duan, Huigao

    2014-08-27

    A hierarchical core-shell structure of ZnO nanorod@NiO/MoO2 composite nanosheet arrays on nickel foam substrate for high-performance supercapacitors was constructed by a two-step solution-based method involving two hydrothermal processes followed by a calcination treatment. Compared to one composed of pure NiO/MoO2 composite nanosheets, the hierarchical core-shell structure electrode displays better pseudocapacitive behaviors in 2 M KOH, including high areal specific capacitance values of 1.18 F cm(-2) at 5 mA cm(-2) and 0.6 F cm(-2) at 30 mA cm(-2) as well as relatively good rate capability at high current densities. Furthermore, it also shows remarkable cycle stability, remaining at 91.7% of the initial value even after 4000 cycles at a current density of 10 mA cm(-2). The enhanced pseudocapacitive behaviors are mainly due to the unique hierarchical core-shell structure and the synergistic effect of combining ZnO nanorod arrays and NiO/MoO2 composite nanosheets. This novel hierarchical core-shell structure shows promise for use in next-generation supercapacitors.

  3. The Core/Shell Structure of CdSe/ZnS Quantum Dots Characterized by X-Ray Absorption Fine Spectroscopy

    Directory of Open Access Journals (Sweden)

    Huijing Wei

    2015-01-01

    Full Text Available Understanding the chemical and physical properties of core/shell nanocrystal quantum dots (QDs is key for their use in light-emission applications. In this paper, a single-step injection-free scalable synthetic method is applied to prepare high-quality core/shell QDs with emission wavelengths of 544 nm, 601 nm, and 634 nm. X-ray absorption fine structure spectra are used to determine the core/shell structure of CdSe/ZnS quantum dots. Moreover, theoretical XANES spectra calculated by FEFF.8.20 are used to determine the structure of Se and S compounds. The QD samples displayed nearly spherical shapes with diameters of approximately 3.4 ± 0.5 nm (634 nm, 4.5 ± 0.4 nm (601 nm, and 5.5 ± 0.5 nm (544 nm. With XANES results and MS calculations, it is indicated that sphalerite ZnS capped with organic sulfur ligands should be the shell structure. Wurtzite CdSe is the main core structure with a Cd-Se bond length of 2.3 Å without phase shift. This means that different emission wavelengths are only due to the crystal size with single-step injection-free synthesis. Therefore, single-step injection-free synthesis could generate a nearly ideal core/shell structure of CdSe/ZnS QDs capped with an organic sulfur ligand.

  4. Effect of laser radiation on multi-wall carbon nanotubes: study of shell structure and immobilization process

    Energy Technology Data Exchange (ETDEWEB)

    Gyoergy, Enikoe, E-mail: egyorgy@icmab.es; Perez del Pino, Angel [Instituto de Ciencia de Materiales de Barcelona, Consejo Superior de Investigaciones Cientificas (ICMAB-CSIC) (Spain); Roqueta, Jaume; Ballesteros, Belen [Centro de Investigaciones en Nanociencia y Nanotecnologia, Consejo Superior de Investigaciones Cientificas (CIN2-CSIC) (Spain); Cabana, Laura; Tobias, Gerard [Instituto de Ciencia de Materiales de Barcelona, Consejo Superior de Investigaciones Cientificas (ICMAB-CSIC) (Spain)

    2013-08-15

    Multi-wall carbon nanotubes (MWCNTs) with diameters between 10 and 15 nm were transferred and immobilized onto SiO{sub 2} glass substrates by ultraviolet matrix assisted pulsed laser evaporation (UV-MAPLE). Toluene was chosen as solvent material for the preparation of the composite MAPLE targets. An UV KrF* ({lambda} = 248 nm, {tau}{sub FWHM} {approx_equal} 25 ns, {nu} = 10 Hz) excimer laser source was used for the irradiation experiments. The effects of incident laser fluence on the structure of the laser transferred MWCNTs was investigated by high resolution transmission electron microscopy and Raman spectroscopy. The surface morphology of the laser processed MWCNTs was investigated by field emission scanning electron microscopy and atomic force microscopy in acoustic (dynamic) configuration. Network-like structures constituted by individual nanotubes and nanotube bundles were created onto solid substrates. Changes in the nanotubes' shell structure can be induced through the tuning of the laser fluence value incident onto the composite MAPLE targets.

  5. Preparation of Acid-Resistant Microcapsules with Shell-Matrix Structure to Enhance Stability of Streptococcus Thermophilus IFFI 6038.

    Science.gov (United States)

    Zhou, Huan Bin; Chen, Jiashu; Li, Shunyi; Zhang, Jianpan; Zhu, Chun E; Ran, Hao; Luo, Meihua; Pan, Xin; Hu, Haiyan; Wu, Chuanbin

    2017-08-01

    Microencapsulation is an effective technology used to protect probiotics against harsh conditions. Extrusion is a commonly used microencapsulation method utilized to prepare probiotics microcapsules that is regarded as economical and simple to operate. This research aims to prepare acid-resistant probiotic microcapsules with high viability after freeze-drying and optimized storage stability. Streptococcus thermophilus IFFI 6038 (IFFI 6038) cells were mixed with trehalose and alginate to fabricate microcapsules using extrusion. These capsules were subsequently coated with chitosan to obtain chitosan-trehalose-alginate microcapsules with shell-matrix structure. Chitosan-alginate microcapsules (without trehalose) were also prepared using the same method. The characteristics of the microcapsules were observed by measuring the freeze-dried viability, acid resistance, and long-term storage stability of the cells. The viable count of IFFI 6038 in the chitosan-trehalose-alginate microcapsules was 8.34 ± 0.30 log CFU g -1 after freeze-drying (lyophilization), which was nearly 1 log units g -1 greater than the chitosan-alginate microcapsules. The viability of IFFI 6038 in the chitosan-trehalose-alginate microcapsules was 6.45 ± 0.09 log CFU g -1 after 120 min of treatment in simulated gastric juices, while the chitosan-alginate microcapsules only measured 4.82 ± 0.22 log CFU g -1 . The results of the long-term storage stability assay indicated that the viability of IFFI 6038 in chitosan-trehalose-alginate microcapsules was higher than in chitosan-alginate microcapsules after storage at 25 °C. Trehalose played an important role in the stability of IFFI 6038 during storage. The novel shell-matrix chitosan-trehalose-alginate microcapsules showed optimal stability and acid resistance, demonstrating their potential as a delivery vehicle to transport probiotics. © 2017 Institute of Food Technologists®.

  6. Fe/amorphous ceramics core/shell structured nanoflakes-assembled rod-like architecture for efficient microwave absorber

    Science.gov (United States)

    Li, Xiaolong; Li, Zhenxing; Liu, Xianguo; Zhang, Shihong; Ran, Songlin

    2017-12-01

    A rod-like architecture self-assembled from Fe/amorphous ceramics core/shell structured nanoflakes has been prepared by arc discharging steelmaking slag in an Ar/H2 atmosphere, in which the amorphous ceramic shell is composed of MgO, Al2O3, MgSiO3 and CaSiO3. The electromagnetic absorbing performance of the rod-like architecture is evaluated over the range of 2–18 GHz. Multiple dielectric relaxation of the permittivity is attributed to the size distribution and novel morphology of the rod-like architecture. The experimental permeability is in good agreement with the calculated curves based on the Landau–Lifshitz–Gilbert equation. The magnetic loss ability is superior to the dielectric loss ability, due to the planar anisotropy of flake-shaped particles. At a thickness of 2.4 mm, the minimal reflection loss (RL) can reach  ‑35.04 dB at 10.96 GHz. In particular, the effective bandwidth with RL exceeding  ‑10 dB remains at least 2.56 GHz at a thickness of 1.6–4.1 mm, and exhibits a red shift phenomenon as layer thickness increases. Such efficient EM absorption performances originate from magnetic/dielectric loss ability accompanied by 1/4-wave elimination. The represented work not only provides a good reference for efficient microwave absorption, but also broadens the application of steelmaking slag.

  7. Design aids for stiffened composite shells with cutouts

    CERN Document Server

    Sahoo, Sarmila

    2017-01-01

    This book focuses on the free vibrations of graphite-epoxy laminated composite stiffened shells with cutout both in terms of the natural frequencies and mode shapes. The dynamic analysis of shell structures, which may have complex geometry and arbitrary loading and boundary conditions, is solved efficiently by the finite element method, even including cutouts in shells. The results may be readily used by practicing engineers dealing with stiffened composite shells with cutouts. Several shell forms viz. cylindrical shell, hypar shell, conoidal shell, spherical shell, saddle shell, hyperbolic paraboloidal shell and elliptic paraboloidal shell are considered in the book. The dynamic characteristics of stiffened composite shells with cutout are described in terms of the natural frequency and mode shapes. The size of the cutouts and their positions with respect to the shell centre are varied for different edge constraints of cross-ply and angle-ply laminated composite shells. The effects of these parametric variat...

  8. High spin structure of nuclei near N = 50 shell gap and search for high-spin isomers using time stamped data

    International Nuclear Information System (INIS)

    Saha, S.; Palit, R.; Trivedi, T.; Sethi, J.; Joshi, P.K.; Naidu, B.S.; Donthi, R.; Jadhav, S.; Nanal, V.; Pillay, R.G.; Jain, H.C.; Kumar, S.; Biswas, D.C.; Mukherjee, G.; Saha, S.

    2011-01-01

    Information on the high-spin states of nuclei promises to provide stringent test of the interaction of the Hamiltonian used in the calculation due to smaller basis space for high J-values. It is reported in a recent shell model review that no interaction is optimized for the region of interest around N = 50 and Z = 40 shell closure. The detailed spectroscopic information of the medium and high spin states in these nuclei is required to understand the shape transition between spherical and deformed shapes at N =60 as the higher orbitals are filled. Structure of isomers near shell closure carries important information of, for example, the extent of core excitation. In the present work, the spectroscopic study of the high spin states of 89 Zr isotope have been discussed

  9. Synthesis of In2O3-In2S3 core-shell nanorods with inverted type-I structure for photocatalytic H2 generation.

    Science.gov (United States)

    Yang, Xia; Xu, Jun; Wong, Tailun; Yang, Qingdan; Lee, Chun-Sing

    2013-08-14

    In2O3-In2S3 core-shell nanostructures were prepared via a simple hydrothermal process at low temperatures. Ultraviolet photoelectron spectroscopy (UPS) shows that the In2O3-In2S3 nanorod is an inverted type I nanostructure. The energy potential in this structure would drive both the photo-generated holes and electrons towards the shell to facilitate photocatalytic H2 generation. Such inverted type-I nanostructure is firstly used for hydrogen generation. Comparing with reported indium-based photocatalysts upon UV-Vis illumination, the core-shell In2O3-In2S3 nanostructure obtained here exhibits a good H2 evolution rate of 61.4 μmol h(-1) g(-1).

  10. Core-Shell Nano structure of a-Fe2O3/Fe3O4: Synthesis and Photo catalysis for Methyl Orange

    International Nuclear Information System (INIS)

    Tian, Y.; Wu, D.; Yu, B.; Jia, X.; Zhan, S.

    2011-01-01

    Fe 3 O 4 nanoparticle was synthesized in the solution involving water and ethanol. Then, a-Fe 2 O 3 shell was produced in situ on the surface of the Fe 3 O 4 nanoparticle by surface oxidation in molten salts, forming α-Fe 2 O 3 /Fe 3 O 4 core-shell nano structure. It was showed that the magnetic properties transformed from ferromagnetism to superparamagnetism after the primary Fe 3 O 4 nanoparticles were oxidized. Furthermore, the obtained a-Fe 2 O 3 /Fe 3 O 4 core-shell nanoparticles were used to photo catalyse solution of methyl orange, and the results revealed that a-Fe 2 O 3 /Fe 3 O 4 nanoparticles were more efficient than the self-prepared α-Fe 2 O 3 nanoparticles. At the same time, the photo catalyzer was recyclable by applying an appropriate magnetic field.

  11. Benefits of Silica Core-Shell Structures on the Temperature Sensing Properties of Er,Yb:GdVO4 Up-Conversion Nanoparticles.

    Science.gov (United States)

    Savchuk, Oleksandr A; Carvajal, Joan J; Cascales, C; Aguiló, M; Díaz, F

    2016-03-23

    We studied the temperature-dependent luminescence of GdVO4 nanoparticles co-doped with Er(3+) (1 mol %) and Yb(3+) (20 mol %) and determined their thermal sensing properties through the fluorescence intensity ratio (FIR) technique. We also analyzed how a silica coating, in a core-shell structure, affects the temperature sensing properties of this material. Spectra were recorded in the range of biological temperatures (298-343 K). The absolute sensitivity for temperature determination calculated for the core-shell nanoparticles is double the one calculated for bare nanoparticles, achieving a thermal resolution of 0.4 K. Moreover, silica-coated nanoparticles show good dispersibility in different solvents, such as water, DMSO, and methanol. Also, they show good luminescence stability without interactions with solvent molecules. Furthermore, we also observed that the silica coating shell prevents progressive heating of the nanoparticles during prolonged excitation periods with the 980 nm laser, preventing effects on their thermometric applications.

  12. Optimizing LiFePO₄@C core-shell structures via the 3-aminophenol-formaldehyde polymerization for improved battery performance.

    Science.gov (United States)

    Chi, Zi-xiang; Zhang, Wei; Wang, Xu-sheng; Cheng, Fu-quan; Chen, Ji-tao; Cao, An-min; Wan, Li-jun

    2014-12-24

    Polyanion-type cathode materials are well-known for their low electronic conductivity; accordingly, the addition of conductive carbon in the cathode materials becomes an indispensable step for their application in lithium ion batteries. To maximize the contribution of carbon, a core-shell structure with a full coverage of carbon should be favorable due to an improved electronic contact between different particles. Here, we report the formation of a uniform carbon nanoshell on a typical cathode material, LiFePO4, with the shell thickness precisely defined via the 3-aminophenol-formaldehyde polymerization process. In addition to the higher discharge capacity and the improved rate capability as expected from the carbon nanoshell, we identified that the core-shell configuration could lead to a much safer cathode material as revealed by the obviously reduced iron dissolution, much less heat released during the cycling, and better cyclability at high temperature.

  13. Core/shell structure NiCo2O4@MnCo2O4 nanofibers fabricated by different temperatures for high-performance supercapacitors

    Science.gov (United States)

    Wang, Qing; Qin, Xuefeng; Jiang, Pengcheng; Dai, Jianfeng; Li, Weixue; Gao, Haoran

    2018-03-01

    Core/shell structure NiCo2O4@MnCo2O4 nanofibers (NiCo2O4@MnCo2O4 NFs) were prepared by a facile co-electrospinning method and heat treatment. The composites annealed at 500 °C have a complete, continuously obvious core/shell structure, and clear interface of composites with good morphology, while annealed at 600 °C were stacked on each other and were unable to sustain three-dimensional network structures and 700 °C calcination have completely lost one-dimensional structure. The core NiCo2O4 is about 70 nm in diameter and the MnCo2O4 shell behaves a thickness about 60 nm. When investigated as an electrode material for supercapacitors, the NiCo2O4@MnCo2O4 NFs annealed at 500 °C exihibited the specific capacitance of 463 F g‑1 (0.926 F cm‑2) at 1 A g‑1, higher than that annealed at 600 °C 362 F g‑1, 1 A g‑1 (0.724 F cm‑2, 1 A g‑1) and 700 °C 283 F g‑1, 1 A g‑1 (0.566 F cm‑2, 1 A g‑1). These results suggest that core/shell NiCo2O4@MnCo2O4 NFs annealed at 500 °C have formed a good morphology with continuously complete core/shell structure which lead to good properties would be potential electrodes for supercapacitors.

  14. Tubular House - Form Follows Technology, Concrete Shell Structure with Inner Thermal Insulation

    Science.gov (United States)

    Idem, Robert; Kleczek, Paweł; Pawłowski, Krzysztof; Chudoba, Piotr

    2017-10-01

    The aim of this paper is the theoretical analysis of the possibilities and limitations of using an unconventional technology and the original architectural form stemming from it - the building with external construction and internal insulation. In Central European climatic conditions, the traditional solution for the walls of heated buildings relies on using external thermal insulation. This stems from building physics: it prevents interstitial condensation of water vapour in the wall. Internal insulation is used exceptionally. This is done e.g. in historical buildings undergoing thermal modernization (due to the impossibility of interfering with facade). In such cases, a thermal insulation layer is used on the internal wall surface, along with an additional layer of vapour barrier. The concept of building concerns the intentional usage of an internal insulation. In this case, the construction is a tight external reinforced concrete shell. The architectural form of such building is strongly interrelated with the technology, which was used to build it. The paper presents the essence of this concept in descriptive and drawing form. The basic elements of such building are described (the external construction, the internal insulation and ventilation). As a case study, authors present a project of a residential building along with the description of the applied materials and installation solutions, and the results obtained from thermal, humidity and energetic calculations. The discussion presents the advantages and disadvantages of the proposed concept. The basic advantage of this solution is potentially low building cost. This stems from minimizing the ground works, the simplicity of the joints and the outer finish, as well as from the possibility of prefabrication of the elements. The continuity of the thermal insulation allows to reduce the amount of thermal bridges. The applied technology and form are applicable most of all for small buildings, due to limited

  15. Investigation of dynamic characteristics of shells with holes and added mass

    Directory of Open Access Journals (Sweden)

    Seregin Sergey Valer’evich

    2014-04-01

    Full Text Available Thin cylindrical shells are widely used in construction, engineering and other industries. In case of designing a reservoir for the isothermal storage of liquefied gases such cases are inevitable, when housing requires various technical holes. A point wise added mass can appear into practice in the form of suspended spotlights, radar, architectural inclusions in buildings and structures of various purposes. It is known, that the dynamic asymmetry as an initial irregular geometric shape, including holes, and the added mass leads to specific effects in shells. In the paper the impact of a cut on the frequency and form of its own vibrations of thin circular cylindrical shells is theoretically examined with the help of the equations of linear shallow shell theory. For modal equations with Nav’e boundary conditions, we used the Bubnov - Galerkin method. The authors have expressed a formula for finding the lowest of the split-frequency vibrations of a shell with a cutout. It is stated, that in case of an appropriate choice of added mass value the lower frequencies are comparable with the case of vibrations of a shell with a hole. By numerical and experimental modeling and finite element method in the environment of MSC "Nastran" oscillation frequencies a shell supporting a concentrated mass and a shell with a cutout were compared. It is shown, that the results of the dynamic analysis of shells with holes with a suitable choice of the attached mass values are comparable with the results of the analysis of shells carrying a point mass. It was concluded that the edges in the holes, significantly affect the reduction in the lowest frequency, and need to be strengthened.

  16. Ultra-high-performance core–shell structured Ru@Pt/C catalyst prepared by a facile pulse electrochemical deposition method

    Science.gov (United States)

    Chen, Dan; Li, Yuexia; Liao, Shijun; Su, Dong; Song, Huiyu; Li, Yingwei; Yang, Lijun; Li, Can

    2015-01-01

    Core–shell structured catalysts, made by placing either a monolayer or a thin layer of a noble metal on relatively cheap core-metal nanoparticles, are fascinating and promising fuel cell catalysts due to their high utilization of noble metals. Here, we report our development of a core–shell structured catalyst, Ru@Pt/C, generated by a novel and facile pulse electrochemical deposition (PED) approach. We demonstrate that compared with a commercial Pt/C catalyst, this novel catalyst achieves over four times higher mass activity towards the anodic oxidation of methanol, and 3.6 times higher mass activity towards the cathodic reduction of oxygen. Importantly, we find that the intrinsic activity of Pt in this Ru@Pt/C catalyst is doubled due to the formation of the core–shell structure. The catalyst also shows superior stability: even after 2000 scans, it still retains up to 90% of the peak current. Our findings demonstrate that this novel PED approach is a promising method for preparing high-performance core–shell catalysts for fuel cell applications. PMID:26235385

  17. Enhanced rate capability and cycling stability of core/shell structured CoFe2O4/onion-like C nanocapsules for lithium-ion battery anodes

    International Nuclear Information System (INIS)

    Liu, Xianguo; Wu, Niandu; Cui, Caiyun; Zhou, Pingping; Sun, Yuping

    2015-01-01

    Highlights: • Core/shell-structured CoFe 2 O 4 /onion-like carbon nanocapsules have been prepared. • CoFe 2 O 4 /C nanocapsules possess good reversibility even when the current density is up to 4C. • CoFe 2 O 4 /C nanocapsules obtain a discharge capacity of 914.2 mA h g −1 after 500 cycles at 0.1C. - Abstract: In this work, core/shell structured CoFe 2 O 4 /onion-like C nanocapsules have been successfully fabricated by the arc discharge method and air-annealing process and confirmed by X-ray diffraction and high-resolution transmission electron microscopy. The core/shell structure effectively withstands the volume change of CoFe 2 O 4 nanoparticles during the cycling process. Moreover, the onion-like C shells reduce the charge transfer resistance and facilitate electron and ion transport throughout the electrode. As a result, CoFe 2 O 4 /onion-like C nanocapsules exhibit excellent performance as a potential anode material for lithium ion batteries and deliver a reversible capacity of 914.2 mA h g −1 at 0.1C, even after 500 cycles and recover its original capacity when the rate returns from 4C to the initial 0.1C after 120 cycles

  18. Structural acceptance criteria for the evaulation of existing double-shell waste storage tanks located at the Hanford site, Richland, Washington

    International Nuclear Information System (INIS)

    Julyk, L.J.; Day, A.D.; Dyrness, A.D.; Moore, C.J.; Peterson, W.S.; Scott, M.A.; Shrivastava, H.P.; Sholman, J.S.; Watts, T.N.

    1995-09-01

    The structural acceptance criteria contained herein for the evaluation of existing underground double-shell waste storage tanks located at the Hanford Site is part of the Life Management/Aging Management Program of the Tank Waste Remediation System. The purpose of the overall life management program is to ensure that confinement of the waste is maintained over the required service life of the tanks. Characterization of the present condition of the tanks, understanding and characterization of potential degradation mechanisms, and development of tank structural acceptance criteria based on previous service and projected use are prerequisites to assessing tank integrity, to projecting the length of tank service, and to developing and applying prudent fixes or repairs. The criteria provided herein summarize the requirements for the analysis and structural qualification of the existing double-shell tanks for continued operation. Code reconciliation issues and material degradation under aging conditions are addressed. Although the criteria were developed for double-shell tanks, many of the provisions are equally applicable to single-shell tanks. However, the criteria do not apply to the evaluation of tank appurtenances and buried piping

  19. Composites Based on Core-Shell Structured HBCuPc@CNTs-Fe3O4 and Polyarylene Ether Nitriles with Excellent Dielectric and Mechanical Properties

    Science.gov (United States)

    Pu, Zejun; Zhong, Jiachun; Liu, Xiaobo

    2017-10-01

    Core-shell structured magnetic carbon nanotubes (CNTs-Fe3O4) coated with hyperbranched copper phthalocyanine (HBCuPc) (HBCuPc@CNTs-Fe3O4) hybrids were prepared by the solvent-thermal method. The results indicated that the HBCuPc molecules were decorated on the surface of CNTs-Fe3O4 through coordination behavior of phthalocyanines, and the CNTs-Fe3O4 core was completely coaxial wrapped by a functional intermediate HBCuPc shell. Then, polymer-based composites with a relatively high dielectric constant and low dielectric loss were fabricated by using core-shell structured HBCuPc@CNTs-Fe3O4 hybrids as fillers and polyarylene ether nitriles (PEN) as the polymer matrix. The cross-sectional scanning electron microscopy (SEM) images of composites showed that there is almost no agglomeration and internal delamination. In addition, the rheological analysis reveals that the core-shell structured HBCuPc@CNTs-Fe3O4 hybrids present better dispersion and stronger interface adhesion with the PEN matrix than CNTs-Fe3O4, thus resulting in significant improvement of the mechanical, thermal and dielectric properties of polymer-based composites.

  20. Plate/shell structure topology optimization of orthotropic material for buckling problem based on independent continuous topological variables

    Science.gov (United States)

    Ye, Hong-Ling; Wang, Wei-Wei; Chen, Ning; Sui, Yun-Kang

    2017-10-01

    The purpose of the present work is to study the buckling problem with plate/shell topology optimization of orthotropic material. A model of buckling topology optimization is established based on the independent, continuous, and mapping method, which considers structural mass as objective and buckling critical loads as constraints. Firstly, composite exponential function (CEF) and power function (PF) as filter functions are introduced to recognize the element mass, the element stiffness matrix, and the element geometric stiffness matrix. The filter functions of the orthotropic material stiffness are deduced. Then these filter functions are put into buckling topology optimization of a differential equation to analyze the design sensitivity. Furthermore, the buckling constraints are approximately expressed as explicit functions with respect to the design variables based on the first-order Taylor expansion. The objective function is standardized based on the second-order Taylor expansion. Therefore, the optimization model is translated into a quadratic program. Finally, the dual sequence quadratic programming (DSQP) algorithm and the global convergence method of moving asymptotes algorithm with two different filter functions (CEF and PF) are applied to solve the optimal model. Three numerical results show that DSQP&CEF has the best performance in the view of structural mass and discretion.

  1. Structure and interactions of calcite spherulites with {alpha}-chitin in the brown shrimp (Penaeus aztecus) shell

    Energy Technology Data Exchange (ETDEWEB)

    Heredia, A. [Instituto de Ciencias Nucleares, Departamento de Quimica de Radiaciones y Radioquimica, UNAM, Circuito Exterior C.U. Apdo., Postal 70-543, 04510 Mexico, D.F. (Mexico); Physikalisches Institut and Center for Nanotechnology, Universitaet Muenster, Gievenbecker Weg 11, 48149 Muenster (Germany); Aguilar-Franco, M. [Instituto de Fisica, Depto de Fisicoquimica, UNAM, Circuito Exterior s/n, Ciudad Universitaria Apartado Postal 20-364 01000 Mexico D.F. (Mexico); Magana, C. [Instituto de Fisica, Depto de Estado Solido, UNAM, Circuito Exterior s/n, Ciudad Universitaria Apartado Postal 20-364 01000 Mexico D.F. (Mexico); Flores, C. [Instituto de Investigaciones en Materiales, Depto de Estado Solido, Laboratorio de Biomateriales, UNAM, Circuito Exterior C.U. S/N CP 04510 Mexico, D.F. (Mexico); Pina, C. [Instituto de Investigaciones en Materiales, Depto de Estado Solido, Laboratorio de Biomateriales, UNAM, Circuito Exterior C.U. S/N CP 04510 Mexico, D.F. (Mexico); Velazquez, R. [Centro de Fisica Aplicada Tecnologia Avanzada, UNAM, Km. 15 Carretera Queretaro-San Luis Potosi, C.P. 76230, Queretaro, Qro. (Mexico); Schaeffer, T.E. [Physikalisches Institut and Center for Nanotechnology, Universitaet Muenster, Gievenbecker Weg 11, 48149 Muenster (Germany); Bucio, L. [Instituto de Fisica, Depto de Estado Solido, UNAM, Circuito Exterior s/n, Ciudad Universitaria Apartado Postal 20-364 01000 Mexico D.F. (Mexico); Basiuk, V.A. [Instituto de Ciencias Nucleares, Departamento de Quimica de Radiaciones y Radioquimica, UNAM, Circuito Exterior C.U. Apdo., Postal 70-543, 04510 Mexico, D.F. (Mexico)

    2007-01-15

    White spots form in the brown shrimp (Penaeus aztecus, Decapoda) shell during frozen storage. The mineral formed consists of calcite incorporated into an amorphous {alpha}-chitin matrix. We studied mechanisms of interaction of amorphous {alpha}-chitin macromolecules with hkl crystal planes to form highly ordered structures, as well as the role of specific sites in the biopolymer, which can be related to nucleation and spheroidal crystal growth. We used low vacuum scanning electron microscopy (LVSEM), X-ray powder diffraction (XRD), atomic force microscopy (AFM), Fourier-transform infrared spectroscopy (FT-IR), and molecular mechanics modeling (MM+ method). AFM images showed fingerprint distances in the biopolymer and a highly layered structure in the crystalline material. The presence of {alpha}-chitin, with a specific spatial distribution of radicals, is thought to be responsible for nucleation and to thermodynamically stabilize ions to form the spherulite crystalline phase, which are usually oval to spherical (0.10 to 200 {mu}m in diameter). Our models of crystal-biopolymer interaction found high affinity of CO{sub 3} {sup 2-} anions in the (104) crystalline plane (the main plane in calcite monocrystals) to NH- groups of the biopolymer, as well as of the C=O in the biopolymer to Ca{sup 2+} cations in the crystalline structure. These interactions explain the spherical growth and inhibition in some planes. The specific physicochemical interactions (docking of groups depending on their geometrical distribution) suggest that the biomineral structure is controlled by the biopolymer on a local scale. This information is useful for further design and improvement of (hybrid) materials for versatile application, from nanotechnology to biomedicine and engineering.

  2. Structure and interactions of calcite spherulites with α-chitin in the brown shrimp (Penaeus aztecus) shell

    International Nuclear Information System (INIS)

    Heredia, A.; Aguilar-Franco, M.; Magana, C.; Flores, C.; Pina, C.; Velazquez, R.; Schaeffer, T.E.; Bucio, L.; Basiuk, V.A.

    2007-01-01

    White spots form in the brown shrimp (Penaeus aztecus, Decapoda) shell during frozen storage. The mineral formed consists of calcite incorporated into an amorphous α-chitin matrix. We studied mechanisms of interaction of amorphous α-chitin macromolecules with hkl crystal planes to form highly ordered structures, as well as the role of specific sites in the biopolymer, which can be related to nucleation and spheroidal crystal growth. We used low vacuum scanning electron microscopy (LVSEM), X-ray powder diffraction (XRD), atomic force microscopy (AFM), Fourier-transform infrared spectroscopy (FT-IR), and molecular mechanics modeling (MM+ method). AFM images showed fingerprint distances in the biopolymer and a highly layered structure in the crystalline material. The presence of α-chitin, with a specific spatial distribution of radicals, is thought to be responsible for nucleation and to thermodynamically stabilize ions to form the spherulite crystalline phase, which are usually oval to spherical (0.10 to 200 μm in diameter). Our models of crystal-biopolymer interaction found high affinity of CO 3 2- anions in the (104) crystalline plane (the main plane in calcite monocrystals) to NH- groups of the biopolymer, as well as of the C=O in the biopolymer to Ca 2+ cations in the crystalline structure. These interactions explain the spherical growth and inhibition in some planes. The specific physicochemical interactions (docking of groups depending on their geometrical distribution) suggest that the biomineral structure is controlled by the biopolymer on a local scale. This information is useful for further design and improvement of (hybrid) materials for versatile application, from nanotechnology to biomedicine and engineering

  3. Shelling of Homogeneous Media

    CERN Document Server

    Grimm, U

    2005-01-01

    A homogeneous medium is characterised by a point set in Euclidean space (for the atomic positions, say), together with some self-averaging property. Crystals and quasicrystals are homogeneous, but also many structures with disorder still are. The corresponding shelling is concerned with the number of points on shells around an arbitrary, but fixed centre. For non-periodic point sets, where the shelling depends on the chosen centre, a more adequate quantity is the averaged shelling, obtained by averaging over points of the set as centres. For homogeneous media, such an average is still well defined, at least almost surely (in the probabilistic sense). Here, we present a two-step approach for planar model sets.

  4. Enhanced Water Splitting by Fe2O3-TiO2-FTO Photoanode with Modified Energy Band Structure

    Directory of Open Access Journals (Sweden)

    Eul Noh

    2013-01-01

    Full Text Available The effect of TiO2 layer applied to the conventional Fe2O3/FTO photoanode to improve the photoelectrochemical performance was assessed from the viewpoint of the microstructure and energy band structure. Regardless of the location of the TiO2 layer in the photoanodes, that is, Fe2O3/TiO2/FTO or TiO2/Fe2O3/FTO, high performance was obtained when α-Fe2O3 and H-TiNT/anatase-TiO2 phases existed in the constituent Fe2O3 and TiO2 layers after optimized heat treatments. The presence of the Fe2O3 nanoparticles with high uniformity in the each layer of the Fe2O3/TiO2/FTO photoanode achieved by a simple dipping process seemed to positively affect the performance improvement by modifying the energy band structure to a more favorable one for efficient electrons transfer. Our current study suggests that the application of the TiO2 interlayer, together with α-Fe2O3 nanoparticles present in the each constituent layers, could significantly contribute to the performance improvement of the conventional Fe2O3 photoanode.

  5. Structural Performance of Fiber-Placed, Variable-Stiffness Composite Conical and Cylindrical Shells

    NARCIS (Netherlands)

    Blom, A.W.

    2010-01-01

    The use of fiber-reinforced composites in aerospace structures has increased dramatically over the past decades. The high specific strength and stiffness, the tailorability, and the possibilities to integrate parts and reduce the number of fasteners give composites an advantage over metals.

  6. Ply-based Optimization of Laminated Composite Shell Structures under Manufacturing Constraints

    DEFF Research Database (Denmark)

    Sørensen, Rene; Lund, Erik

    2012-01-01

    This work concerns a new ply-based parameterization for performing simultaneous material selection and topology optimization of fiber reinforced laminated composite structures while ensuring that a series of different manufacturing constraints are fulfilled. The material selection can either......) with an additional constraint on the maximum allowable amount mass....

  7. Study of the modes of adsorption and electronic structure of hydrogen peroxide and ethanol over TiO2 rutile (110) surface within the context of water splitting

    Science.gov (United States)

    Alghamdi, H.; Idriss, H.

    2018-03-01

    While photocatalytic water splitting over many materials is favourable thermodynamically the kinetic of the reaction is very slow. One of the proposed reasons linked to the slow oxidation reaction rate is H2O2 formation as a reaction intermediate. Using Density Functional Theory (DFT) H2O2 is investigated on TiO2 rutile (110) surface to determine its most stable adsorption modes: molecular, (H)O(H)O - (a), partially dissociated, (H)OO - (a), and fully dissociated (a) - OO - (a). We then compare H2O2 interaction to that of a fast hole scavenger molecule, ethanol. Geometry, electronic structure, charge density difference and work function determination of both adsorbates are presented and compared using DFT with different functionals (PBE, PBE-D, PBE-U, and HSE + D). H2O2 is found to be strongly adsorbed on TiO2 rutile (110) surface with adsorption energies reaching 0.95 eV, comparable to that of ethanol (0.89 eV); using GGA PBE. The negative changes in the work function upon adsorption were found to be highest for molecular adsorption ( - 1.23 eV) and lowest for the fully dissociated mode ( - 0.54 eV) of H2O2. This may indicate that electrons flow from the surface to the adsorbate in order to make O(s)-H partially offset the overall magnitude of the oxygen lone pair interaction (of H2O2) with Ti4+ cations. Examination of the electronic structure through density of states (DOS) at the PBE level of computation, indicates that the H2O2 highest occupied molecular orbital (HOMO) level is not overlapping with oxygen atoms of TiO2 surface at any of its adsorption modes and at any of the computation methods. Some overlap is seen using the HSE + D computational method. On the other hand the dissociated mode of ethanol (ethoxides) does overlap with all computational methods used. The high adsorption energy and the absence of overlapping of the HOMO level of H2O2 with TiO2 rutile (110) surface may explain why water splitting is slow.

  8. Characterization of core/shell structures based on CdTe and GaAs nanocrystalline layers deposited on SnO2 microwires

    Science.gov (United States)

    Ghimpu, L.; Ursaki, V. V.; Pantazi, A.; Mesterca, R.; Brâncoveanu, O.; Shree, Sindu; Adelung, R.; Tiginyanu, I. M.; Enachescu, M.

    2018-04-01

    We report the fabrication and characterization of SnO2/CdTe and SnO2/GaAs core/shell microstructures. CdTe or GaAs shell layers were deposited by radio-frequency (RF) magnetron sputtering on core SnO2 microwires synthesized by a flame-based thermal oxidation method. The produced structures were characterized by scanning electron microscopy (SEM), high-resolution scanning transmission electron microscope (HR-STEM), X-ray diffraction (XRD), Raman scattering and FTIR spectroscopy. It was found that the SnO2 core is of the rutile type, while the shells are composed of CdTe or GaAs nanocrystallites of zincblende structure with the dimensions of crystallites in the range of 10-20 nm. The Raman scattering investigations demonstrated that the quality of the porous nanostructured shell is improved by annealing at temperatures of 420-450 °C. The prospects of implementing these microstructures in intrinsic type fiber optic sensors are discussed.

  9. Structural and photoluminescence properties of tin oxide and tin oxide: C core–shell and alloy nanoparticles synthesised using gas phase technique

    Directory of Open Access Journals (Sweden)

    Mehar Bhatnagar

    2016-09-01

    Full Text Available In the present study, we report a controlled growth of tin oxide and tin oxide: carbon nanoparticles by an integrated method comprising of the gas phase agglomeration, electrical mobility based size selection, and in–flight sintering steps. The effect of in-flight sintering temperature and variation in growth environment (N2, H2 and O2 during nanoparticle formation, morphology and composition has been investigated by carrying out High Resolution Transmission Electron microscopy and X-Ray diffraction studies. The results highlight the novelty of the present technique to grow alloy and core-shell nanoparticles in which the stoichiometery (x of SnOx and the mode of incorporation of carbon into the tin oxide lattice (alloy or core-shell structure, along with well-defined size can be controlled independently. Detailed Photoluminescence (PL studies of well sintered monocrystalline SnO, SnOx and SnO2 nanoparticles along with SnOx:C and SnO2:C alloy and C@SnO core-shell nanoparticle has been carried out. The shift in the position and nature of PL peaks due to band edge, Sn interstitials and oxygen vacancy defect level energy states has been understood as a function of stoichiometery and nanoparticle structure (alloy and core-shell. These results suggest the possibility of tailoring the position of these levels by controlling the size, composition and alloying which is potentially important for gas sensing, photoconductivity and photo-electrochemical applications.

  10. Investigation of the electromagnetic absorption properties of Ni@TiO2 and Ni@SiO2 composite microspheres with core-shell structure.

    Science.gov (United States)

    Zhao, Biao; Shao, Gang; Fan, Bingbing; Zhao, Wanyu; Zhang, Rui

    2015-01-28

    In this work, amorphous TiO2 and SiO2-coated Ni composite microspheres were successfully prepared by a two-step method. The phase purity, morphology, and structure of composite microspheres are characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDS), thermogravimetric analysis (TGA), and transmission electron microscopy (TEM). Due to the presence of the insulator SiO2 shell, the core-shell Ni-SiO2 composite microspheres exhibit better antioxidation capability than that of pure Ni microspheres. The core-shell Ni-SiO2 composite microspheres show the best microwave absorption properties than those of pure Ni microspheres and Ni-TiO2 composites. For Ni-SiO2 composite microspheres, an optimal reflection loss (RL) as low as -40.0 dB (99.99% absorption) was observed at 12.6 GHz with an absorber thickness of only 1.5 mm. The effective absorption (below -10 dB, 90% microwave absorption) bandwidth can be adjusted between 3.1 GHz and 14.4 GHz by tuning the absorber thickness in the range of 1.5-4.5 mm. The excellent microwave absorption abilities of Ni-SiO2 composite microspheres are attributed to a higher attenuation constant, Debye relaxation, interface polarization of the core-shell structure and synergistic effects between high dielectric loss and high magnetic loss.

  11. Structures of chlorophyll catabolites in bananas (Musa acuminata) reveal a split path of chlorophyll breakdown in a ripening fruit.

    Science.gov (United States)

    Moser, Simone; Müller, Thomas; Holzinger, Andreas; Lütz, Cornelius; Kräutler, Bernhard

    2012-08-27

    The disappearance of chlorophyll is a visual sign of fruit ripening. Yet, chlorophyll breakdown in fruit has hardly been explored; its non-green degradation products are largely unknown. Here we report the analysis and structure elucidation of colorless tetrapyrrolic chlorophyll breakdown products in commercially available, ripening bananas (Musa acuminata, Cavendish cultivar). In banana peels, chlorophyll catabolites were found in an unprecedented structural richness: a variety of new fluorescent chlorophyll catabolites (FCCs) and nonfluorescent chlorophyll catabolites (NCCs) were detected. As a rule, FCCs exist only "fleetingly" and are hard to observe. However, in bananas several of the FCCs (named Mc-FCCs) were persistent and carried an ester function at the propionate side-chain. NCCs were less abundant, and exhibited a free propionic acid group, but functional modifications elsewhere. The modifications of NCCs in banana peels were similar to those found in NCCs from senescent leaves. They are presumed to be introduced by enzymatic transformations at the stage of the mostly unobserved, direct FCC-precursors. The observed divergent functional group characteristics of the Mc-FCCs versus those of the Mc-NCCs indicated two major "late" processing lines of chlorophyll breakdown in ripening bananas. The "last common precursor" at the branching point to either the persistent FCCs, or towards the NCCs, was identified as a temporarily abundant "secondary" FCC. The existence of two "downstream" branches of chlorophyll breakdown in banana peels, and the striking accumulation of persistent Mc-FCCs call for attention as to the still-elusive biological roles of the resulting colorless linear tetrapyrroles. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. Structures of Chlorophyll Catabolites in Bananas (Musa acuminata) Reveal a Split Path of Chlorophyll Breakdown in a Ripening Fruit

    Science.gov (United States)

    Moser, Simone; Müller, Thomas; Holzinger, Andreas; Lütz, Cornelius; Kräutler, Bernhard

    2012-01-01

    Abstract The disappearance of chlorophyll is a visual sign of fruit ripening. Yet, chlorophyll breakdown in fruit has hardly been explored; its non-green degradation products are largely unknown. Here we report the analysis and structure elucidation of colorless tetrapyrrolic chlorophyll breakdown products in commercially available, ripening bananas (Musa acuminata, Cavendish cultivar). In banana peels, chlorophyll catabolites were found in an unprecedented structural richness: a variety of new fluorescent chlorophyll catabolites (FCCs) and nonfluorescent chlorophyll catabolites (NCCs) were detected. As a rule, FCCs exist only "fleetingly" and are hard to observe. However, in bananas several of the FCCs (named Mc-FCCs) were persistent and carried an ester function at the propionate side-chain. NCCs were less abundant, and exhibited a free propionic acid group, but functional modifications elsewhere. The modifications of NCCs in banana peels were similar to those found in NCCs from senescent leaves. They are presumed to be introduced by enzymatic transformations at the stage of the mostly unobserved, direct FCC-precursors. The observed divergent functional group characteristics of the Mc-FCCs versus those of the Mc-NCCs indicated two major "late" processing lines of chlorophyll breakdown in ripening bananas. The "last common precursor" at the branching point to either the persistent FCCs, or towards the NCCs, was identified as a temporarily abundant "secondary" FCC. The existence of two "downstream" branches of chlorophyll breakdown in banana peels, and the striking accumulation of persistent Mc-FCCs call for attention as to the still-elusive biological roles of the resulting colorless linear tetrapyrroles. PMID:22807397

  13. Size dependent structural, vibrational and magnetic properties of BiFeO{sub 3} and core-shell structured BiFeO{sub 3}@SiO{sub 2} nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Chauhan, Sunil, E-mail: sunilchauhanjiit@gmail.com; Kumar, Manoj, E-mail: sunilchauhanjiit@gmail.com; Chhoker, Sandeep, E-mail: sunilchauhanjiit@gmail.com; Katyal, S. C., E-mail: sunilchauhanjiit@gmail.com [Department of Physics and Materials Science and Engineering, Jaypee Institute of Information Technology, Noida- 201307 (India)

    2014-04-24

    Bulk BiFeO{sub 3}, BiFeO{sub 3} nanoparticles and core-shell structured BiFeO{sub 3}@SiO{sub 2} nanoparticles were synthesized by solid state reaction method, sol-gel and Stöber process (SiO{sub 2} shell) respectively. Transmission electron microscopy image confirmed the core-shell structure of BiFeO{sub 3}@SiO{sub 2} nanoparticles with BiFeO3 core ∼50-90 nm and SiO{sub 2} shell ∼16 nm. X-ray diffraction and FTIR spectroscopy results showed the presence of distorted rhombohedral structure with R3c space group in all three samples. The magnetic measurement indicated the existence of room-temperature weak ferromagnetism in core-shell BiFeO{sub 3}@SiO{sub 2} nanoparticles and BiFeO3 nanoparticles, whereas bulk BiFeO{sub 3} showed antiferromagnteic nature. Electron Spin Resonance results confirmed the enhancement in magnetic properties of coreshell structured BiFeO{sub 3}@SiO{sub 2} nanoparticles in comparison with BiFeO{sub 3} nanoparticles and bulk BiFeO{sub 3}.

  14. Wrinkling of Pressurized Elastic Shells

    KAUST Repository

    Vella, Dominic

    2011-10-01

    We study the formation of localized structures formed by the point loading of an internally pressurized elastic shell. While unpressurized shells (such as a ping-pong ball) buckle into polygonal structures, we show that pressurized shells are subject to a wrinkling instability. We study wrinkling in depth, presenting scaling laws for the critical indentation at which wrinkling occurs and the number of wrinkles formed in terms of the internal pressurization and material properties of the shell. These results are validated by numerical simulations. We show that the evolution of the wrinkle length with increasing indentation can be understood for highly pressurized shells from membrane theory. These results suggest that the position and number of wrinkles may be used in combination to give simple methods for the estimation of the mechanical properties of highly pressurized shells. © 2011 American Physical Society.

  15. Investigation of CuInSe{sub 2} nanowire arrays with core–shell structure electrodeposited at various duty cycles into anodic alumina templates

    Energy Technology Data Exchange (ETDEWEB)

    Cheng, Yu-Song [Institute of Microelectronics, Department of Electrical Engineering, National Cheng-Kung University, Tainan 701, Taiwan (China); Wang, Na-Fu; Tsai, Yu-Zen [Department of Electronic Engineering, Cheng Shiu University, 840 Chengcing Rd., Niaosong District, Kaohsiung City 833, Taiwan (China); Lin, Jia-Jun [Institute of Microelectronics, Department of Electrical Engineering, National Cheng-Kung University, Tainan 701, Taiwan (China); Houng, Mau-Phon, E-mail: mphoung@eembox.ncku.edu.tw [Institute of Microelectronics, Department of Electrical Engineering, National Cheng-Kung University, Tainan 701, Taiwan (China)

    2017-02-28

    Highlights: • The present paper reports that CuInSe2 NW arrays were fabricated through pulsed electrode position onto an AAO template with various duty cycles, and a pore-filling ratio of approximately 92% was achieved. • GIXRD patterns showed that all CuInSe2 NW arrays were chalcopyrite and SAED images confirmed that the CuInSe2 NWs were polycrystalline. • PEDOT/CuInSe2 NW core–shell arrays were fabricated using surfactant-modified CuInSe2 NW surfaces showing the lotus effect. • Current–voltage plots revealed that the CuInSe2 NW arrays were p-type semiconductors; moreover, the core–shell structure improved the diode ideality factor from 3.91 to 2.63. - Abstract: Copper indium selenide (CuInSe{sub 2}) nanowire (NW) arrays were prepared at various electrolyte duty cycles by filling anodic alumina templates through the pulsed electrodeposition technique. X-ray diffraction and scanning electron microscopy (SEM) images showed that the nucleation mechanism of CuInSe{sub 2} NW arrays was affected by the electrodeposition duty cycle. Moreover, SEM images showed that the diameter and length of the NWs were 80 nm and 2 μm, respectively. Furthermore, PEDOT/CuInSe{sub 2} NW core–shell arrays were fabricated using surfactant-modified CuInSe{sub 2} NW surfaces showing the lotus effect. Transmission electron microscopy images confirmed that a core–shell structure was achieved. Current–voltage plots revealed that the CuInSe{sub 2} NW arrays were p-type semiconductors; moreover, the core–shell structure improved the diode ideality factor from 3.91 to 2.63.

  16. Investigation of CuInSe2 nanowire arrays with core–shell structure electrodeposited at various duty cycles into anodic alumina templates

    International Nuclear Information System (INIS)

    Cheng, Yu-Song; Wang, Na-Fu; Tsai, Yu-Zen; Lin, Jia-Jun; Houng, Mau-Phon

    2017-01-01

    Highlights: • The present paper reports that CuInSe2 NW arrays were fabricated through pulsed electrode position onto an AAO template with various duty cycles, and a pore-filling ratio of approximately 92% was achieved. • GIXRD patterns showed that all CuInSe2 NW arrays were chalcopyrite and SAED images confirmed that the CuInSe2 NWs were polycrystalline. • PEDOT/CuInSe2 NW core–shell arrays were fabricated using surfactant-modified CuInSe2 NW surfaces showing the lotus effect. • Current–voltage plots revealed that the CuInSe2 NW arrays were p-type semiconductors; moreover, the core–shell structure improved the diode ideality factor from 3.91 to 2.63. - Abstract: Copper indium selenide (CuInSe 2 ) nanowire (NW) arrays were prepared at various electrolyte duty cycles by filling anodic alumina templates through the pulsed electrodeposition technique. X-ray diffraction and scanning electron microscopy (SEM) images showed that the nucleation mechanism of CuInSe 2 NW arrays was affected by the electrodeposition duty cycle. Moreover, SEM images showed that the diameter and length of the NWs were 80 nm and 2 μm, respectively. Furthermore, PEDOT/CuInSe 2 NW core–shell arrays were fabricated using surfactant-modified CuInSe 2 NW surfaces showing the lotus effect. Transmission electron microscopy images confirmed that a core–shell structure was achieved. Current–voltage plots revealed that the CuInSe 2 NW arrays were p-type semiconductors; moreover, the core–shell structure improved the diode ideality factor from 3.91 to 2.63.

  17. Creep-fatigue design studies for a sodium-cooled fast reactor with tube sheet-to shell structure subjected to elevated temperature service

    Energy Technology Data Exchange (ETDEWEB)

    Koo, Gyeong Hoi; Lee, Jae Han [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2010-03-15

    In this paper, creep-fatigue damage under elevated temperatures is investigated for a tube sheet-to-shell structure, which is one of the main structures under Gen-IV class 1 components. To do this, detailed step-by-step procedures, including the elastic structural analysis and the ASME-NH code application, are described for a defined representative load cycle. From the sensitivity studies for various design parameters, such as hold time duration, shell thickness, and operating temperature, it is found that a reduction of thickness can decrease the thermal bending stresses, but the negative effect is that it may increase the primary stress and enhance the creep damage. The normal operating temperature is the most significant parameter in the creep-fatigue design

  18. Core–Shell Structure and Aggregation Number of Micelles Composed of Amphiphilic Block Copolymers and Amphiphilic Heterografted Polymer Brushes Determined by Small-Angle X-ray Scattering

    Energy Technology Data Exchange (ETDEWEB)

    Szymusiak, Magdalena; Kalkowski, Joseph; Luo, Hanying; Donovan, Alexander J.; Zhang, Pin; Liu, Chang; Shang, Weifeng; Irving, Thomas; Herrera-Alonso, Margarita; Liu, Ying (JHU); (IIT); (UIC)

    2017-08-31

    A large group of functional nanomaterials employed in biomedical applications, including targeted drug delivery, relies on amphiphilic polymers to encapsulate therapeutic payloads via self-assembly processes. Knowledge of the micelle structures will provide critical insights into design of polymeric drug delivery systems. Core–shell micelles composed of linear diblock copolymers poly(ethylene glycol)-b-poly(caprolactone) (PEG-b-PCL), poly(ethylene oxide)-b-poly(lactic acid) (PEG-b-PLA), as well as a heterografted brush consisting of a poly(glycidyl methacrylate) backbone with PEG and PLA branches (PGMA-g-PEG/PLA) were characterized by dynamic light scattering (DLS) and small-angle X-ray scattering (SAXS) measurements to gain structural information regarding the particle morphology, core–shell size, and aggregation number. The structural information at this quasi-equilibrium state can also be used as a reference when studying the kinetics of polymer micellization.

  19. Core–Shell Structure and Aggregation Number of Micelles Composed of Amphiphilic Block Copolymers and Amphiphilic Heterografted Polymer Brushes Determined by Small-Angle X-ray Scattering

    Energy Technology Data Exchange (ETDEWEB)

    Szymusiak, Magdalena [Department; Kalkowski, Joseph [Department; Luo, Hanying [Department; Donovan, Alexander J. [Department; Zhang, Pin [Department; Liu, Chang [Department; Shang, Weifeng [Department; Irving, Thomas [Department; Herrera-Alonso, Margarita [Department; Liu, Ying [Department; Department

    2017-08-16

    A large group of functional nanomaterials employed in biomedical applications, including targeted drug delivery, relies on amphiphilic polymers to encapsulate therapeutic payloads via self-assembly processes. Knowledge of the micelle structures will provide critical insights into design of polymeric drug delivery systems. Core–shell micelles composed of linear diblock copolymers poly(ethylene glycol)-b-poly(caprolactone) (PEG-b-PCL), poly(ethylene oxide)-b-poly(lactic acid) (PEG-b-PLA), as well as a heterografted brush consisting of a poly(glycidyl methacrylate) backbone with PEG and PLA branches (PGMA-g-PEG/PLA) were characterized by dynamic light scattering (DLS) and small-angle X-ray scattering (SAXS) measurements to gain structural information regarding the particle morphology, core–shell size, and aggregation number. The structural information at this quasi-equilibrium state can also be used as a reference when studying the kinetics of polymer micellization.

  20. Split Cord Malformations

    Directory of Open Access Journals (Sweden)

    Yurdal Gezercan

    2015-06-01

    Full Text Available Split cord malformations are rare form of occult spinal dysraphism in children. Split cord malformations are characterized by septum that cleaves the spinal canal in sagittal plane within the single or duplicated thecal sac. Although their precise incidence is unknown, split cord malformations are exceedingly rare and represent %3.8-5 of all congenital spinal anomalies. Characteristic neurological, urological, orthopedic clinical manifestations are variable and asymptomatic course is possible. Earlier diagnosis and surgical intervention for split cord malformations is associated with better long-term fuctional outcome. For this reason, diagnostic imaging is indicated for children with associated cutaneous and orthopedic signs. Additional congenital anomalies usually to accompany the split cord malformations. Earlier diagnosis, meticuolus surgical therapy and interdisciplinary careful evaluation and follow-up should be made for good prognosis. [Cukurova Med J 2015; 40(2.000: 199-207

  1. A numerical approach for simulating fluid structure interaction of flexible thin shells undergoing arbitrarily large deformations in complex domains

    Energy Technology Data Exchange (ETDEWEB)

    Gilmanov, Anvar, E-mail: agilmano@umn.edu [Saint Anthony Falls Laboratory, University of Minnesota, Minneapolis, MN 55414 (United States); Le, Trung Bao, E-mail: lebao002@umn.edu [Saint Anthony Falls Laboratory, University of Minnesota, Minneapolis, MN 55414 (United States); Sotiropoulos, Fotis, E-mail: fotis@umn.edu [Saint Anthony Falls Laboratory, University of Minnesota, Minneapolis, MN 55414 (United States); Department of Civil, Environmental and Geo-Engineering, University of Minnesota, Minneapolis, MN 55414 (United States)

    2015-11-01

    We present a new numerical methodology for simulating fluid–structure interaction (FSI) problems involving thin flexible bodies in an incompressible fluid. The FSI algorithm uses the Dirichlet–Neumann partitioning technique. The curvilinear immersed boundary method (CURVIB) is coupled with a rotation-free finite element (FE) model for thin shells enabling the efficient simulation of FSI problems with arbitrarily large deformation. Turbulent flow problems are handled using large-eddy simulation with the dynamic Smagorinsky model in conjunction with a wall model to reconstruct boundary conditions near immersed boundaries. The CURVIB and FE solvers are coupled together on the flexible solid–fluid interfaces where the structural nodal positions, displacements, velocities and loads are calculated and exchanged between the two solvers. Loose and strong coupling FSI schemes are employed enhanced by the Aitken acceleration technique to ensure robust coupling and fast convergence especially for low mass ratio problems. The coupled CURVIB-FE-FSI method is validated by applying it to simulate two FSI problems involving thin flexible structures: 1) vortex-induced vibrations of a cantilever mounted in the wake of a square cylinder at different mass ratios and at low Reynolds number; and 2) the more challenging high Reynolds number problem involving the oscillation of an inverted elastic flag. For both cases the computed results are in excellent agreement with previous numerical simulations and/or experiential measurements. Grid convergence tests/studies are carried out for both the cantilever and inverted flag problems, which show that the CURVIB-FE-FSI method provides their convergence. Finally, the capability of the new methodology in simulations of complex cardiovascular flows is demonstrated by applying it to simulate the FSI of a tri-leaflet, prosthetic heart valve in an anatomic aorta and under physiologic pulsatile conditions.

  2. Sol-gel preparation and characterization of uniform core-shell structured LaInO3:Sm3+/Tb3+-SiO2 phosphors

    International Nuclear Information System (INIS)

    Shang Yongchen; Yang Piaoping; Wang Wenxin; Wang Yanli; Niu Na; Gai Shili; Lin Jun

    2011-01-01

    Graphical abstract: The core-shell structured LaInO 3 :Ln 3+ -SiO 2 phosphors were realized by coating LaInO 3 :Ln 3+ phosphors on the surface of silica microspheres via a modified Pechini sol-gel process. Display Omitted Research highlights: → A facile and low-cost sol-gel process was used to fabricate fluorescent microspheres. → Uniform core-shell structured phosphors with bright PL emissions were obtained. → The possible formation scheme for the core-shell structured spheres is presented. - Abstract: The core-shell structured LaInO 3 :Ln 3+ -SiO 2 (Ln 3+ = Sm 3+ , Tb 3+ ) phosphors were realized by coating LaInO 3 :Ln 3+ phosphors on the surface of silica microspheres via a modified Pechini sol-gel process. The phase, structure, morphology, and fluorescent properties of the materials were well characterized by means of X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), Fourier transform IR spectroscopy (FT-IR), photoluminescence (PL) spectra, cathodoluminescence (CL) spectra, and the kinetic decays, respectively. The results reveal that the obtained core-shell structured phosphors consist of amorphous silica core and crystalline LaInO 3 :Ln 3+ shell, which keep the uniform spherical morphology of pure silica spheres with narrow size distribution. Upon excitation by ultraviolet (UV) irradiation or electron beam, the phosphors show the characteristic emission lines of Sm 3+ ( 4 G 5/2 - 6 H 5/2,7/2,9/2 , orange) in LaInO 3 :Sm 3+ -SiO 2 and characteristic emissions of Tb 3+ ( 5 D 4 - 7 F 6,5,4,3 , green) in LaInO 3 :Tb 3+ -SiO 2 , respectively. This kind of phosphors may have potential applications in field emission displays (FEDs) based on their uniform shape, low-cost synthetic route, and diverse luminescent properties.

  3. Fine structural observation on the oogenesis and vitellogenesis of the Chinese soft-shelled turtle ( Pelodiseus sinensis).

    Science.gov (United States)

    Hei, Nainan; Yang, Ping; Yang, Yang; Liu, Jinxiong; Bao, Huijun; Liu, Haili; Zhang, Hui; Chen, Qiusheng

    2010-05-01

    Fine structure observations were performed by means of electron microscopy on oogenesis and vitellogenesis and the special functions of follicular cells in the Chinese soft-shelled turtle (Pelodiseus sinensis). Histological examination of the ovary showed a well developed lacunae system containing fine granules, fibres or gelatiniform materials with one or two germinal beds dispersed on the dorsal surface of the ovarian cortex. The process of oogenesis comprised 10 consecutive phases according to the morphology of the yolk platelets, follicular cells and zona pellucida (ZP). Electron microscopy of vitellogenesis revealed some of the mitochondria gradually being transformed into yolk granules. In the advanced stage of vitellogenesis, large amounts of rough endoplasmic reticula, Golgiosomes and other cell organelles that are involved in synthesis and secretion were observed in follicular cells. The ZP was formed by microvilli, thus increasing the absorptive surface of the oocyte and facilitating transport of nutrients from the follicular epithelium to the ooplasm. This study demonstrated that the ovaries of members of the Testudinidae share more features with Archosaurs than with Squamates, indicating that these features were phylogenetically conserved in the Archosauria. The present observations suggest that the accumulation of yolk materials was controlled by the intrinsic and extrinsic pathways as well as by the activity of follicular cells. These results might also support a sibling relationship of the Testudinidae with the Archosauria and not with all extant reptiles.

  4. Electronic structure of the 3d metals. An investigation by L-shell-photoionisation

    Energy Technology Data Exchange (ETDEWEB)

    Richter, T.S.

    2007-12-03

    The 3d transition metal elements from Sc to Cu have been investigated by both photo electron emission and photo absorption. Experimental spectra in the 2p energy range are discussed based on atomic multiplet models and Hartree- Fock calculations. The samples have been evaporated from an electron bombardment crucible and excited/ionized by monochromatized synchrotron radiation. Fundamental effects and the main interactions which govern the electronic structure of the 3d metal atoms are covered. Common spectral features and trends in the series are discussed as well as the importance of many body electron correlation effects. (orig.)

  5. Core-Shell Zn/ZnO Structures with Improved Photocatalytic Properties Synthesized by Aqueous Solution Method

    Science.gov (United States)

    Huang, Yuan Ming; Ma, Qing-Lan; Zhai, Bao-Gai

    2013-08-01

    A facile and green method was utilized to synthesize core-shelled Zn/ZnO microspheres by boiling Zn microparticles in water for improving the photocatalytic activity of ZnO. The synthesized Zn/ZnO core-shells were investigated by means of scanning electron microscope, X-ray diffractometer and photoluminescence spectrometer, respectively. The morphology analysis showed that the metallic Zn core was about 6 μm in diameter while the ZnO shell was about 600 nm in thickness. Compared to ZnO nanoparticles, the core-shelled Zn/ZnO microspheres exhibited improved photocatalytic activity in degrading methyl orange in water. Our results suggest that the metal-semiconductor junction formed at the Zn/ZnO interface is responsible for the enhanced photocatalytic activity of ZnO.

  6. Eduardo Torroja y la International Association for Shell and Spatial Structures (IASS

    Directory of Open Access Journals (Sweden)

    Astudillo, R.

    2014-12-01

    Full Text Available Eduardo Torroja’s legacy doesn’t limit to his innovative designs, or to his contributions to concrete structures and their codes development. Throw his life, he founded, or contributed to found, several associations, national and international, which as IASS (1959 are working nowadays leading the progress of civil and architectural construction.El legado de Eduardo Torroja no se limita a sus innovadores proyectos, o a sus aportaciones al cálculo y desarrollo del hormigón armado y pretensado. A lo largo de su vida, fundó, o contribuyó a fundar, diversas asociaciones, nacionales e internacionales que, como la IASS (1959, continúan vivas liderando el progreso de la construcción civil y arquitectónica.

  7. Probing nuclear shell structure beyond the N=40 subshell using multiple Coulomb excitation and transfer experiments

    Energy Technology Data Exchange (ETDEWEB)

    Hellgartner, Stefanie Christine

    2015-11-13

    In this work, the N=40 subshell closure is investigated with two complementary methods using a radioactive {sup 72}Zn ISOLDE beam: One- and two-neutron transfer reactions and multiple Coulomb excitation. In the one-neutron transfer reaction, two new levels of {sup 73}Zn were discovered. The two-neutron transfer channel allowed to study the differential cross section of the ground state and the 2{sup +}{sub 1} state of {sup 74}Zn. In the Coulomb excitation experiment, the measured B(E2) values and quadrupole moments of {sup 72}Zn showed that the yrast states 0{sup +}{sub 1}, 2{sup +}{sub 1} and 4{sup +}{sub 1} are moderately collective. Contrary, the 0{sup +}{sub 2} state has a different structure, since it features a stronger closed N=40 configuration compared to the ground state.

  8. Enhancing photocatalytic activity by using TiO2-MgO core-shell-structured nanoparticles

    International Nuclear Information System (INIS)

    Jung, Hyun Suk; Lee, Jung-Kun; Nastasi, Michael; Kim, Jeong-Ryeol; Lee, Sang-Wook; Kim, Jin Young; Park, Jong-Sung; Hong, Kug Sun; Shin, Hyunho

    2006-01-01

    Hygroscopic Mg(OH) 2 gel was topotactically decomposed on TiO 2 particle surfaces, resulting in highly nanoporous MgO-coated TiO 2 particles. The highly hygroscopic and nanoporous MgO shell absorbed more water molecules and hydroxyl groups from the environment to yield an improved photocatalytic property of the core-shell particles as compared to the uncoated TiO 2 counterpart

  9. Reviving near infra-red emission of Ag2S nanoparticles using interfacial defects in the Ag2S@CdS core-shell structure.

    Science.gov (United States)

    Karimipour, M; Izadian, L; Molaei, M

    2018-02-01

    Ag 2 S@CdS core-shell particles were synthesized with different Cd source content as a measure of shell thickness using a pulsed microwave irradiation method. The particles were verified structurally using X-ray diffraction, energy dispersive X-ray analysis and transmission electron microscopy. Optical spectroscopy revealed that core-shells show an absorption peak at 750 nm and an emission peak located around 800 nm after 6 min of microwave irradiation. With continued microwave treatment, the NIR luminescence first vanished but it was revived after 12 min of irradiation, which was 100 nm red shifted. This new type of NIR emission in Ag 2 S with sizes greater than 5 nm is due to the proximity of a highly deficient CdS shell with strong red emission that was stable for more than 6 months in water. A mechanism has been suggested for this type of emission. Copyright © 2017 John Wiley & Sons, Ltd.

  10. The Shell Structure Effect on the Vapor Selectivity of Monolayer-Protected Gold Nanoparticle Sensors

    Directory of Open Access Journals (Sweden)

    Rui-Xuan Huang

    2014-02-01

    Full Text Available Four types of monolayer-protected gold nanoclusters (MPCs were synthesized and characterized as active layers of vapor sensors. An interdigitated microelectrode (IDE and quartz crystal microbalance (QCM were used to measure the electrical resistance and mass loading changes of MPC films during vapor sorption. The vapor sensing selectivity was influenced by the ligand structure of the monolayer on the surface of gold nanoparticles. The responses of MPC-coated QCM were mainly determined according to the affinity between the vapors and surface ligands of MPCs. The responses to the resistance changes of the MPC films were due to the effectiveness of the swelling when vapor was absorbed. It was observed that resistive sensitivity to polar organics could be greatly enhanced when the MPC contained ligands that contain interior polar functional groups with exterior nonpolar groups. This finding reveals that reducing interparticle attraction by using non-polar exterior groups could increase effective swelling and therefore enhance the sensitivity of MPC-coated chemiresistors.

  11. Effective enhancement of gas separation performance in mixed matrix membranes using core/shell structured multi-walled carbon nanotube/graphene oxide nanoribbons

    Science.gov (United States)

    Xue, Qingzhong; Pan, Xinglong; Li, Xiaofang; Zhang, Jianqiang; Guo, Qikai

    2017-02-01

    Novel core/shell structured multi-walled carbon nanotube/graphene oxide nanoribbons (MWCNT@GONRs) nanohybrids were successfully prepared using a modified chemical longitudinal unzipping method. Subsequently, the MWCNT@GONRs nanohybrids were used as fillers to enhance the gas separation performance of polyimide based mixed matrix membranes (MMMs). It is found that MMMs concurrently exhibited higher gas selectivity and higher gas permeability compared to pristine polyimide. The high gas selectivity could be attributed to the GONRs shell, which provided a selective barrier and large gas adsorbed area, while the high gas permeability resulted from the hollow structured MWCNTs core with smooth internal surface, which acted as a rapid transport channel. MWCNT@GONRs could be promising candidates to improve gas separation performance of MMMs due to the unique microstructures, ease of synthesis and low filling loading.

  12. Probing the structure of CuInS{sub 2}-ZnS core-shell and similar nanocrystals by Raman spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Dzhagan, Volodymyr, E-mail: dzhagan@isp.kiev.ua [Semiconductor Physics, Technische Universität Chemnitz, 09107 Chemnitz (Germany); V. E. Lashkaryov Institute of Semiconductors Physics, National Academy of Sciences of Ukraine, Kyiv 03028 (Ukraine); Kempken, Björn [Energy and Semiconductor Research Laboratory, Department of Physics, Carl von Ossietzky University of Oldenburg, 26111 Oldenburg (Germany); Valakh, Mykhailo [V. E. Lashkaryov Institute of Semiconductors Physics, National Academy of Sciences of Ukraine, Kyiv 03028 (Ukraine); Parisi, Jürgen; Kolny-Olesiak, Joanna [Energy and Semiconductor Research Laboratory, Department of Physics, Carl von Ossietzky University of Oldenburg, 26111 Oldenburg (Germany); Zahn, Dietrich R.T. [Semiconductor Physics, Technische Universität Chemnitz, 09107 Chemnitz (Germany)

    2017-02-15

    CuInS{sub 2}/ZnS core-shell and alloyed nanocrystals (NCs) are promising candidates for applications in biolabeling, photocatalysis, solar energy conversion, and light emitting diodes. The growth mechanism and subsequent internal structure of such heterogeneous NCs are therefore of crucial importance, as it strongly affects their optical and electronic properties. Here, we investigated using resonant Raman spectroscopy the structure of CuInS{sub 2}/ZnS and Cu-Zn-In-S/ZnS core-shell NCs, as well as the evolution of Cu{sub 2−x}S NCs into CuInS{sub 2}via the heterogeneous Cu{sub 2−x}S/CuInS{sub 2} phase. We demonstrate that the particular phases can be distinguished based on their characteristic Raman modes and tuning the exciting laser energy into resonance with the bandgap of the particular phase.

  13. Spherical carbon capsules with hollow macroporous core and mesoporous shell structures as a highly efficient catalyst support in the direct methanol fuel cell.

    Science.gov (United States)

    Chai, Geun Seok; Yoon, Suk Bon; Kim, Jung Ho; Yu, Jong-Sung

    2004-12-07

    Carbon capsules with hollow core and mesoporous shell (HCMS) structures were used as a support material for Pt(50)-Ru(50) catalyst, and the catalytic performance of the HCMS supported catalyst in the direct methanol fuel cell was described; the HCMS carbon supported catalysts exhibited much higher specific activity for methanol oxidation than the commonly used E-TEK catalyst by about 80%, proving that the HCMS carbon capsules are an excellent support for electrode catalysts in DMFC.

  14. Palladium nanoparticles encapsulated in core-shell silica: A structured hydrogenation catalyst with enhanced activity for reduction of oxyanion water pollutants

    KAUST Repository

    Wang, Yin

    2014-10-03

    Noble metal nanoparticles have been applied to mediate catalytic removal of toxic oxyanions and halogenated hydrocarbons in contaminated water using H2 as a clean and sustainable reductant. However, activity loss by nanoparticle aggregation and difficulty of nanoparticle recovery are two major challenges to widespread technology adoption. Herein, we report the synthesis of a core-shell-structured catalyst with encapsulated Pd nanoparticles and its enhanced catalytic activity in reduction of bromate (BrO3-), a regulated carcinogenic oxyanion produced during drinking water disinfection process, using 1 atm H2 at room temperature. The catalyst material consists of a nonporous silica core decorated with preformed octahedral Pd nanoparticles that were further encapsulated within an ordered mesoporous silica shell (i.e., SiO2@Pd@mSiO2). Well-defined mesopores (2.3 nm) provide a physical barrier to prevent Pd nanoparticle (6 nm) movement, aggregation, and detachment from the support into water. Compared to freely suspended Pd nanoparticles and SiO2@Pd, encapsulation in the mesoporous silica shell significantly enhanced Pd catalytic activity (by a factor of 10) under circumneutral pH conditions that are most relevant to water purification applications. Mechanistic investigation of material surface properties combined with Langmuir-Hinshelwood modeling of kinetic data suggest that mesoporous silica shell enhances activity by promoting BrO3- adsorption near the Pd active sites. The dual function of the mesoporous shell, enhancing Pd catalyst activity and preventing aggregation of active nanoparticles, suggests a promising general strategy of using metal nanoparticle catalysts for water purification and related aqueous-phase applications.

  15. Split Malcev algebras

    Indian Academy of Sciences (India)

    project of the Spanish Ministerio de Educación y Ciencia MTM2007-60333. References. [1] Calderón A J, On split Lie algebras with symmetric root systems, Proc. Indian. Acad. Sci (Math. Sci.) 118(2008) 351–356. [2] Calderón A J, On split Lie triple systems, Proc. Indian. Acad. Sci (Math. Sci.) 119(2009). 165–177.

  16. Quasi-chemical theory of F-(aq): The "no split occupancies rule" revisited

    Science.gov (United States)

    Chaudhari, Mangesh I.; Rempe, Susan B.; Pratt, Lawrence R.

    2017-10-01

    We use ab initio molecular dynamics (AIMD) calculations and quasi-chemical theory (QCT) to study the inner-shell structure of F-(aq) and to evaluate that single-ion free energy under standard conditions. Following the "no split occupancies" rule, QCT calculations yield a free energy value of -101 kcal/mol under these conditions, in encouraging agreement with tabulated values (-111 kcal/mol). The AIMD calculations served only to guide the definition of an effective inner-shell constraint. QCT naturally includes quantum mechanical effects that can be concerning in more primitive calculations, including electronic polarizability and induction, electron density transfer, electron correlation, molecular/atomic cooperative interactions generally, molecular flexibility, and zero-point motion. No direct assessment of the contribution of dispersion contributions to the internal energies has been attempted here, however. We anticipate that other aqueous halide ions might be treated successfully with QCT, provided that the structure of the underlying statistical mechanical theory is absorbed, i.e., that the "no split occupancies" rule is recognized.

  17. Fast defluorination and removal of norfloxacin by alginate/Fe@Fe3O4 core/shell structured nanoparticles.

    Science.gov (United States)

    Niu, Hongyun; Dizhang; Meng, Zhaofu; Cai, Yaqi

    2012-08-15

    Alginate-Fe(2+)/Fe(3+) polymer coated Fe(3)O(4) magnetic nanoparticles (Fe(3)O(4)@ALG/Fe MNPs) with core/shell structure are prepared and used as heterogeneous Fenton nanocatalyst to degrade norfloxacin (NOF). The Fenton-like process based on Fe(3)O(4)@ALG/Fe shows much higher efficiency on NOF degradation. Compared with Fe(3)O(4) nanoparticle-H(2)O(2) system, NOF degradation in Fe(3)O(4)@AlG/Fe-H(2)O(2) system can be conducted in a wide pH range (pH 3.5-6.5) and independent on temperature. With 0.98 mM H(2)O(2) and 0.4 g L(-1) Fe(3)O(4)@ALG/Fe, 100% of NOF and 90% of TOC is removed within 60 min, and the fluorine element in NOF molecule changes into F(-) ions within 1 min, indicating that NOF degradation in this Fenton-like reaction is performed through direct defluorination pathway. XPS analysis shows that TOC removal in reaction solution mainly results from the adsorption of NOF degradation intermediates on catalyst. Due to the paramagneticity and high saturation magnetization of Fe(3)O(4)@ALG/Fe, the used catalyst with adsorbed NOF intermediate is collected from aqueous solution by applying an external magnetic field, leading to complete removal of NOF from water samples. As being composed of inorganic materials and biopolymer, Fe(3)O(4)@ALG/Fe MNPs are robust, thermo-stable, nontoxic and environmentally friendly. These attractive features endow Fe(3)O(4)@ALG/Fe as a potent Fenton-like catalyst for fluoroquinolones degradation. Copyright © 2012 Elsevier B.V. All rights reserved.

  18. Enhanced visible light photocatalytic activity in SnO{sub 2}@g-C{sub 3}N{sub 4} core-shell structures

    Energy Technology Data Exchange (ETDEWEB)

    Shen, Hao; Zhao, Xiaoru, E-mail: xrzhao@nwpu.edu.cn; Duan, Libing; Liu, Ruidi; Li, Hui

    2017-04-15

    Highlights: • Novel SnO{sub 2}@g-C{sub 3}N{sub 4} core-shell structures were successfully synthesized. • The core-shell structures exhibited enhanced visible light photocatalytic activity. • The enhanced photocatalytic activity was due to synergic action of SnO{sub 2} and g-C{sub 3}N{sub 4}. - Abstract: SnO{sub 2}@g-C{sub 3}N{sub 4} core-shell structures were successfully synthesized by simple calcination of SnO{sub 2} microspheres and urea in a muffle furnace. The investigation of morphologies and microstructures showed that g-C{sub 3}N{sub 4} was wrapped tightly on the surface of SnO{sub 2} microspheres with large intimate interface contact areas between the g-C{sub 3}N{sub 4} shells and SnO{sub 2} cores. The X-ray photoelectron spectroscopy results and photoluminescence spectra demonstrated that the intimate interface contacts could facilitate the transfer and separation of the photogenerated charge carriers at their interface, thus the recombination of the photogenerated electron-hole pairs was impeded. The photocatalytic activity of the synthesized composites was evaluated by the photodegradation of methyl orange under visible light irradiation. It was found that SnO{sub 2}@g-C{sub 3}N{sub 4} exhibited higher photodegradation rate (k = 0.013 min{sup −1}) than that of g-C{sub 3}N{sub 4} (k = 0.008 min{sup −1}) and pure SnO{sub 2}. The enhanced photocatalytic activity could be attributed to the synergic action of SnO{sub 2} and g-C{sub 3}N{sub 4}.

  19. Similarities of artificial photosystems by ruthenium oxo complexes and native water splitting systems

    Science.gov (United States)

    Tanaka, Koji; Isobe, Hiroshi; Yamanaka, Shusuke; Yamaguchi, Kizashi

    2012-01-01

    The nature of chemical bonds of ruthenium(Ru)–quinine(Q) complexes, mononuclear [Ru(trpy)(3,5-t-Bu2Q)(OH2)](ClO4)2 (trpy = 2,2′:6′,2′′-terpyridine, 3,5-di-tert-butyl-1,2-benzoquinone) (1), and binuclear [Ru2(btpyan)(3,6-di-Bu2Q)2(OH2)]2+ (btpyan = 1,8-bis(2,2′:6′,2′′-terpyrid-4′-yl)anthracene, 3,6-t-Bu2Q = 3,6-di-tert-butyl-1,2-benzoquinone) (2), has been investigated by broken-symmetry (BS) hybrid density functional (DFT) methods. BS DFT computations for the Ru complexes have elucidated that the closed-shell structure (2b) Ru(II)–Q complex is less stable than the open-shell structure (2bb) consisting of Ru(III) and semiquinone (SQ) radical fragments. These computations have also elucidated eight different electronic and spin structures of tetraradical intermediates that may be generated in the course of water splitting reaction. The Heisenberg spin Hamiltonian model for these species has been derived to elucidate six different effective exchange interactions (J) for four spin systems. Six J values have been determined using total energies of the eight (or seven) BS solutions for different spin configurations. The natural orbital analyses of these BS DFT solutions have also been performed in order to obtain natural orbitals and their occupation numbers, which are useful for the lucid understanding of the nature of chemical bonds of the Ru complexes. Implications of the computational results are discussed in relation to the proposed reaction mechanisms of water splitting reaction in artificial photosynthesis systems and the similarity between artificial and native water splitting systems. PMID:22761310

  20. Flow Cytometric Bead Sandwich Assay Based on a Split Aptamer.

    Science.gov (United States)

    Shen, Luyao; Bing, Tao; Liu, Xiangjun; Wang, Junyan; Wang, Linlin; Zhang, Nan; Shangguan, Dihua

    2018-01-24

    A few aptamers still bind their targets after being split into two moieties. Split aptamers have shown great potential in the development of aptameric sensors. However, only a few split aptamers have been generated because of lack of knowledge on the binding structure of their parent aptamers. Here, we report the design of a new split aptamer and a flow cytometric bead sandwich assay using a split aptamer instead of double antibodies. Through DMS footprinting and mutation assay, we figured out the target-binding moiety and the structure-stabilizing moiety of the l-selectin aptamer, Sgc-3b. By separating the duplex strand in the structure-stabilizing moiety, we obtained a split aptamer that bound l-selectin. After optimization of one part of the split sequence to eliminate the nonspecific binding of the split sequence pair, we developed a split-aptamer-based cytometric bead assay (SACBA) for the detection of soluble l-selectin. SACBA showed good sensitivity and selectivity to l-selectin and was successfully applied for the detection of spiked l-selectin in the human serum. The strategies for generating split aptamers and designing the split-aptamer-based sandwich assay are simple and efficient and show good practicability in aptamer engineering.

  1. High performance and durability of order-structured cathode catalyst layer based on TiO{sub 2}@PANI core-shell nanowire arrays

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Ming; Wang, Meng; Yang, Zhaoyi [State Key Laboratory of Advanced Metallurgy, University of Science and Technology Beijing, 30 College Road, Beijing 100083 (China); School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, 30 College Road, Beijing 100083 (China); Wang, Xindong, E-mail: echem@ustb.edu.cn [State Key Laboratory of Advanced Metallurgy, University of Science and Technology Beijing, 30 College Road, Beijing 100083 (China); School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, 30 College Road, Beijing 100083 (China)

    2017-06-01

    Highlights: • TiO{sub 2}@PANI core-shell nanowire arrays were prepared and applied as catalyst support. • As-prepared Pt-TiO{sub 2}@PANI core-shell nanowire arrays were applied as order-structured cathode catalyst layer. • The novel cathode catalyst structure without Nafion{sup ®} ionomer enhance the performance and durability of PEMFC. - Abstract: In this paper, an order-structured cathode catalyst layer consisting of Pt-TiO{sub 2}@PANI core-shell nanowire arrays that in situ grown on commercial gas diffusion layer (GDL) are prepared and applied to membrane electrode assembly (MEA) of proton exchange membrane fuel cell (PEMFC). In order to prepare the TiO{sub 2}@PANI core-shell nanowire arrays with suitable porosity and prominent conductivity, the morphologies of the TiO{sub 2} nanoarray and electrochemical polymerization process of aniline are schematically investigated. The MEA with order-structured cathode catalyst layer is assembled in the single cell to evaluate the electrochemical performance and durability of PEMFC. As a result, the PEMFC with order-structured cathode catalyst layer shows higher peak power density (773.54 mW cm{sup −2}) than conventional PEMFC (699.30 mW cm{sup −2}). Electrochemically active surface area (ECSA) and charge transfer impedance (R{sub ct}) are measured before and after accelerated degradation test (ADT), and the corresponding experimental results indicate the novel cathode structure exhibits a better stability with respect to conventional cathode. The enhanced electrochemical performance and durability toward PEMFC can be ascribed to the order-structured cathode nanoarray structure with high specific surface area increases the utilization of catalyst and reduces the tortuosity of transport pathways, and the synergistic effect between TiO{sub 2}@PANI support and Pt nanoparticles promotes the high efficiency of electrochemical reaction and improves the stability of catalyst. This research provides a facile and

  2. Double-shell Fe2O3 hollow box-like structure for enhanced photo-Fenton degradation of malachite green dye

    Science.gov (United States)

    Jiang, De Bin; Liu, Xiaoying; Xu, Xuan; Zhang, Yu Xin

    2018-01-01

    In this work we demonstrate the synthesis of novel Fe2O3 nanosheets with double-shell hollow morphology by replica molding from diatomite framework. The nanostructures of Fe2O3 nanosheets were examined by focused-ion-beam scanning electron microscopy (FIB/SEM), X-ray diffraction spectroscopy (XRD), Brunauer-Emmett-Teller (BET) specific surface area measurements and Fourier transform infrared (FT-IR) spectroscopy. The results reveal that (1) Pure Fe2O3 nanosheets were successfully obtained; (2) The double-shell Fe2O3 hollow structure achieved via the NaOH etching silica method was observed; (3) Fe2O3 nanosheets possessed uniformly distributed porous nanosheets. Such structural features enlarged the specific surface area of Fe2O3 nanosheets and led to more catalytic active sites. In the heterogeneous photo-Fenton reaction, the double-shell Fe2O3 hollow morphology exhibited excellent catalytic capability for the degradation of malachite green (MG) at circumneutral pH condition. Under optimum condition, MG solution was almost completely decolorized in 60 min (99.9%). The Fe2O3 nanosheets also showed good stability and recyclability, demonstrating great potential as a promising photo-Fenton catalyst for the effective degradation of MG dye in wastewater.

  3. Synthesis and photoluminescence properties of Eu3+-doped silica@coordination polymer core-shell structures and their calcinated silica@Gd2O3:Eu and hollow Gd2O3:Eu microsphere products.

    Science.gov (United States)

    Lee, Hee Jung; Park, Ju-Un; Choi, Sora; Son, Juhee; Oh, Moonhyun

    2013-02-25

    The conjugation of Eu(3+)-doped coordination polymers constructed from Gd(3+) and isophthalic acid (H(2)IPA) with silica particles is investigated for the production of luminescent microspheres. A series of doping ratio-controlled silica@coordination polymer core-shell spheres is easily synthesized by altering the amounts of metal nodes used in the reactions, where the ratios of Gd(3+) and Eu(3+) are 10:0 (1a), 9:1 (1b), 8:2 (1c), 7:3 (1d), 5:5 (1e), and 0:10 (1f). The formation of monodisperse uniform core-shell structures is achieved throughout the entirety of a series. Investigations of the photoluminescence property of the resulting series of silica@coordination polymer core-shell spheres reveal that 20% Eu(3+)-doped product (1c) has the strongest emission intensity. The subsequent calcination process on the silica@coordination polymer core-shell structures (1a-f) results in the formation of a series of doping ratio-controlled silica@Gd(2)O(3):Eu core-shell microspheres (2a-f) with uniform shell thickness. During the calcination step, the coordination polymers within silica@coordination polymer core-shells are transformed into metal oxides, resulting in silica@Gd(2)O(3):Eu core-shell structures. The final etching process on the silica@Gd(2)O(3):Eu core-shell microspheres (2a-f) produces a series of hollow Gd(2)O(3):Eu microspheres (3a-f) as a result of the elimination of silica cores. The luminescence intensities of silica@Gd(2)O(3):Eu core-shell (2a-f) and hollow Gd(2) O(3):Eu microspheres (3a-f) also vary depending upon the doping ratio of Eu(3+) ions. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Reverse micelle-derived Cu-doped Zn(1-x)Cd(x)S quantum dots and their core/shell structure.

    Science.gov (United States)

    Kim, Jong-Uk; Kim, Young Kwan; Yang, Heesun

    2010-01-01

    Reverse micelle chemistry-derived Cu-doped Zn(1-x)Cd(x)S quantum dots (QDs) with the composition (x) of 0, 0.5, 1 are reported. The Cu emission was found to be dependent on the host composition of QDs. While a dim green/orange emission was observed from ZnS:Cu QDs, a relatively strong red emission could be obtained from CdS:Cu and Zn(0.5)Cd(0.5)S:Cu QDs. Luminescent properties of undoped QDs versus Cu-doped ones and quantum yields of alloyed ZnCdS versus CdS QDs are compared and discussed. To enhance Cu-related red emission of CdS:Cu and Zn(0.5)Cd(0.5)S:Cu core QDs, core/shell structured QDs with a wider band gap of ZnS shell are also demonstrated.

  5. Polydopamine-Based 3D Colloidal Photonic Materials: Structural Color Balls and Fibers from Melanin-Like Particles with Polydopamine Shell Layers.

    Science.gov (United States)

    Kohri, Michinari; Yanagimoto, Kenshi; Kawamura, Ayaka; Hamada, Kosuke; Imai, Yoshihiko; Watanabe, Takaichi; Ono, Tsutomu; Taniguchi, Tatsuo; Kishikawa, Keiki

    2018-03-07

    Nature creates beautiful structural colors, and some of these colors are produced by nanostructural arrays of melanin. Polydopamine (PDA), an artificial black polymer produced by self-oxidative polymerization of dopamine, has attracted extensive attention because of its unique properties. PDA is a melanin-like material, and recent studies have reported that photonic materials based on PDA particles showed structural colors by enhancing color saturation through the absorption of scattered light. Herein, we describe the preparation of three-dimensional (3D) colloidal photonic materials, such as structural color balls and fibers, from biomimetic core-shell particles with melanin-like PDA shell layers. Structural color balls were prepared through the combined use of membrane emulsion and heating. We also demonstrated the use of microfluidic emulsification and solvent diffusion for the fabrication of structural color fibers. The obtained 3D colloidal materials, i.e., balls and fibers, exhibited angle-independent structural colors due to the amorphous assembly of PDA-containing particles. These findings provide new insight for the development of dye-free technology for the coloration of various 3D colloidal architectures.

  6. Mean field theory of nuclei and shell model. Present status and future outlook

    International Nuclear Information System (INIS)

    Nakada, Hitoshi

    2003-01-01

    Many of the recent topics of the nuclear structure are concerned on the problems of unstable nuclei. It has been revealed experimentally that the nuclear halos and the neutron skins as well as the cluster structures or the molecule-like structures can be present in the unstable nuclei, and the magic numbers well established in the stable nuclei disappear occasionally while new ones appear. The shell model based on the mean field approximation has been successfully applied to stable nuclei to explain the nuclear structure as the finite many body system quantitatively and it is considered as the standard model at present. If the unstable nuclei will be understood on the same model basis or not is a matter related to fundamental principle of nuclear structure theories. In this lecture, the fundamental concept and the framework of the theory of nuclear structure based on the mean field theory and the shell model are presented to make clear the problems and to suggest directions for future researches. At first fundamental properties of nuclei are described under the subtitles: saturation and magic numbers, nuclear force and effective interactions, nuclear matter, and LS splitting. Then the mean field theory is presented under subtitles: the potential model, the mean field theory, Hartree-Fock approximation for nuclear matter, density dependent force, semiclassical mean field theory, mean field theory and symmetry, Skyrme interaction and density functional, density matrix expansion, finite range interactions, effective masses, and motion of center of mass. The subsequent section is devoted to the shell model with the subtitles: beyond the mean field approximation, core polarization, effective interaction of shell model, one-particle wave function, nuclear deformation and shell model, and shell model of cross shell. Finally structure of unstable nuclei is discussed with the subtitles: general remark on the study of unstable nuclear structure, asymptotic behavior of wave

  7. Estimation Of Young’s Modulus Of Elesticity By The Form Finding Of Grid Shell Structures By The Dynamic Relaxation Method

    Directory of Open Access Journals (Sweden)

    Grančičová Ivana

    2015-12-01

    Full Text Available The paper is basically focused on the process of form finding by the dynamic relaxation method (DRM with the aid of computational tools that enable us to make many calculations with different inputs. There are many important input values with a significant impact on the course of the calculations and the resulting displacement of a structure. One of these values is Young’s modulus of elasticity. This value has a considerable impact on the final displacement of a grid shell structure and the resulting internal forces.

  8. Crystal structure of a blue laccase from Lentinus tigrinus: evidences for intermediates in the molecular oxygen reductive splitting by multicopper oxidases

    Directory of Open Access Journals (Sweden)

    Golovleva Ludmila A

    2007-09-01

    Full Text Available Abstract Background Laccases belong to multicopper oxidases, a widespread class of enzymes implicated in many oxidative functions in pathogenesis, immunogenesis and morphogenesis of organisms and in the metabolic turnover of complex organic substances. They catalyze the coupling between the four one-electron oxidations of a broad range of substrates with the four-electron reduction of dioxygen to water. These catalytic processes are made possible by the contemporaneous presence of at least four copper ion sites, classified according to their spectroscopic properties: one type 1 (T1 site where the electrons from the reducing substrates are accepted, one type 2 (T2, and a coupled binuclear type 3 pair (T3 which are assembled in a T2/T3 trinuclear cluster where the electrons are transferred to perform the O2 reduction to H2O. Results The structure of a laccase from the white-rot fungus Lentinus (Panus tigrinus, a glycoenzyme involved in lignin biodegradation, was solved at 1.5 Å. It reveals a asymmetric unit containing two laccase molecules (A and B. The progressive reduction of the copper ions centers obtained by the long-term exposure of the crystals to the high-intensity X-ray synchrotron beam radiation under aerobic conditions and high pH allowed us to detect two sequential intermediates in the molecular oxygen reduction pathway: the "peroxide" and the "native" intermediates, previously hypothesized through spectroscopic, kinetic and molecular mechanics studies. Specifically the electron-density maps revealed the presence of an end-on bridging, μ-η1:η1 peroxide ion between the two T3 coppers in molecule B, result of a two-electrons reduction, whereas in molecule A an oxo ion bridging the three coppers of the T2/T3 cluster (μ3-oxo bridge together with an hydroxide ion externally bridging the two T3 copper ions, products of the four-electrons reduction of molecular oxygen, were best modelled. Conclusion This is the first structure of a

  9. Atomic Structure of Wurtzite CdSe (Core)/CdS (Giant Shell) Nanobullets Related to Epitaxy and Growth

    NARCIS (Netherlands)

    Bladt, Eva; Moes, Relinde; Peters, Joep; Montanarella, Federico; De Mello Donega, Celso; Vanmaekelbergh, Daniël; Bals, Sara

    2016-01-01

    Heteronanocrystals consisting of a CdSe core and a giant CdS shell have shown remarkable optical properties which are promising for applications in opto-electrical devices. Since these properties sensitively depend on the size and shape, a morphological characterization is of high interest. Here, we

  10. Colours and metallic sheen in beetle shells - A biomimetic search for material structuring principles causing light interference

    DEFF Research Database (Denmark)

    Lenau, Torben Anker; Barfoed, Michael

    2008-01-01

    metallic surfaces that do not feel so cold to touch as their metallic counterparts and that do not represent an electrical shock hazard. The present paper presents a cross disciplinary biomimetic review of research results that explain the materials and nanostructure in beetle shells and the mechanisms...

  11. Hierarchical super-structure identified by polarized light microscopy, electron microscopy and nanoindentation: Implications for the limits of biological control over the growth mode of abalone sea shells

    Directory of Open Access Journals (Sweden)

    Schneider Andreas S

    2012-09-01

    Full Text Available Abstract Background Mollusc shells are commonly investigated using high-resolution imaging techniques based on cryo-fixation. Less detailed information is available regarding the light-optical properties. Sea shells of Haliotis pulcherina were embedded for polishing in defined orientations in order to investigate the interface between prismatic calcite and nacreous aragonite by standard materialographic methods. A polished thin section of the interface was prepared with a defined thickness of 60 μm for quantitative birefringence analysis using polarized light and LC-PolScope microscopy. Scanning electron microscopy images were obtained for comparison. In order to study structural-mechanical relationships, nanoindentation experiments were performed. Results Incident light microscopy revealed a super-structure in semi-transparent regions of the polished cross-section under a defined angle. This super-structure is not visible in transmitted birefringence analysis due to the blurred polarization of small nacre platelets and numerous organic interfaces. The relative orientation and homogeneity of calcite prisms was directly identified, some of them with their optical axes exactly normal to the imaging plane. Co-oriented "prism colonies" were identified by polarized light analyses. The nacreous super-structure was also visualized by secondary electron imaging under defined angles. The domains of the super-structure were interpreted to consist of crystallographically aligned platelet stacks. Nanoindentation experiments showed that mechanical properties changed with the same periodicity as the domain size. Conclusions In this study, we have demonstrated that insights into the growth mechanisms of nacre can be obtained by conventional light-optical methods. For example, we observed super-structures formed by co-oriented nacre platelets as previously identified using X-ray Photo-electron Emission Microscopy (X-PEEM [Gilbert et al., Journal of the

  12. Structural and magnetic properties of CoFe{sub 2}O{sub 4}/NiFe{sub 2}O{sub 4} core/shell nanocomposite prepared by the hydrothermal method

    Energy Technology Data Exchange (ETDEWEB)

    Sattar, A.A. [Department of Physics, Faculty of Science, Ain Shams University, 11566 Abbasia, Cairo (Egypt); EL-Sayed, H.M., E-mail: h_m_elsaid@hotmail.com [Department of Physics, Faculty of Science, Ain Shams University, 11566 Abbasia, Cairo (Egypt); ALsuqia, Ibrahim [Department of Physics, Faculty of Education and Applied Science, Hajjah University, Alshahli, Hajjah (Yemen)

    2015-12-01

    CoFe{sub 2}O{sub 4}/NiFe{sub 2}O{sub 4} core/shell magnetic nanocomposite was synthesized by using hydrothermal method.The analysis of XRD indicated the coexistence of CoFe{sub 2}O{sub 4}, NiFe{sub 2}O{sub 4}as core/shell composite. The core/shell structure of the composite sample has been confirmed by HR-TEM images, EDX and FT-IR measurements. The size of obtained core/shell nanoparticles was 17 nm in core diameter and about 3 nm in shell thickness. The magnetization measurements showed that both the coercive field and the saturation magnetization of the resulting core/shell nanocomposite were slightly decreased compared to those of the CoFe{sub 2}O{sub 4} core but the thermal stability is of the magnetization parameter was enhanced. Furthermore, superparamagnetic phase is established at temperatures higher than the room temperature. The results were discussed in terms of the surface pinning and the magnetic interaction at the interface between the core and shell. - Highlights: • CoFe{sub 2}O{sub 4}/NiFe{sub 2}O{sub 4} core/shell could be prepared by hydrothermal method. • The structural analysis proved the formation of NiFe{sub 2}O{sub 4} shell with thickness 3 nm. • The thermal stability of M{sub s} and H{sub c} is enhanced due to the presence of NiFe{sub 2}O{sub 4} as a shell. • Super paramagnetic transition is confirmed and the effective magnetic anisotropy was calculated.

  13. Aspects of Split Supersymmetry

    CERN Document Server

    Arkani-Hamed, N; Giudice, Gian Francesco; Romanino, A

    2005-01-01

    We explore some fundamental differences in the phenomenology, cosmology and model building of Split Supersymmetry compared with traditional low-scale supersymmetry. We show how the mass spectrum of Split Supersymmetry naturally emerges from theories where the dominant source of supersymmetry breaking preserves an $R$ symmetry, characterize the class of theories where the unavoidable $R$-breaking by gravity can be neglected, and point out a new possibility, where supersymmetry breaking is directly communicated at tree level to the visible sector via renormalizable interactions. Next, we discuss possible low-energy signals for Split Supersymmetry. The absence of new light scalars removes all the phenomenological difficulties of low-energy supersymmetry, associated with one-loop flavor and CP violating effects. However, the electric dipole moments of leptons and quarks do arise at two loops, and are automatically at the level of present limits with no need for small phases, making them accessible to several ongo...

  14. MM and subMM molecular line observations of the southwest lobe of L1551: evidence of a shell structure

    International Nuclear Information System (INIS)

    Rainey, R.; White, G.J.; Richardson, K.J.; Griffin, M.J.; Cronin, J.; Hilton, J.; Monteiro, T.S.; Newcastle-upon-Tyne Univ., England)

    1986-01-01

    Observations have been made of the southwest outflow lobe of L1551 in several millimeter and submillimeter molecular lines. Maps have been made in the J=3-2 and J=2-1 transitions of CO over areas of 7.5 by 2.5 arc minutes and 5 by 5 arc minutes respectively at UKIRT. More detailed maps have also been made in the J=2-1 CO transition over an area of about 6 by 3.5 arc minutes at the NRAO 12m telescope. Additional observations of the J=4-3 transitions of HCN, HCO(+) abd H(13)CO(+) were made at selected positions. The HC(+) J=4-3 transition was detected at several positions along the outflow axis and at the position of IRS 5. Similarly the HCN J=4-3 transition was detected at the position of IRS 5 and also at a position close to HH29. However, the J=4-3 transition of H(13)CO(+) was bit detected at the position of IRS 5 even through it was observed at the position close to HH29 with a peak corrected antenna temperature of 0.23K at a V(LSR) of 1 km s(-1). The detection of the J=4-3 transitions of both HCO(+) and H(13)CO(+) close to the position of HH29 suggest the presence of very dense gas in this region. LVG analysis of the various molecular lines observed give a kinetic temperature between 10 and 15K and a density from 10(5) to 10(6) cm(-3) at the position of IRS 5 at the ambient cloud velocity. At the position close to HH29 LVG analysis of the CO observations gives a density between 10(3) and 10(4) cm(-3) at a kinetic temperature of 25k for a V(LSR) of 0 km s(-1). To the southwest of HH29 there is a large decrease in both the linewidth and intensity of CO emission. This may be due to the interaction between the outflow and a dense clump of gas which gives rise to HH29. The maps of the CO J=3-2 and CO J=2-1 emission integrated in 3.25 km s intervals show the shell structure postulated by Snell and Schloerb (1985)

  15. Core/Shell Structured TiO2/CdS Electrode to Enhance the Light Stability of Perovskite Solar Cells.

    Science.gov (United States)

    Hwang, Insung; Baek, Minki; Yong, Kijung

    2015-12-23

    In this work, enhanced light stability of perovskite solar cell (PSC) achieved by the introduction of a core/shell-structured CdS/TiO2 electrode and the related mechanism are reported. By a simple solution-based process (SILAR), a uniform CdS shell was coated onto the surface of a TiO2 layer, suppressing the activation of intrinsic trap sites originating from the oxygen vacancies of the TiO2 layer. As a result, the proposed CdS-PSC exhibited highly improved light stability, maintaining nearly 80% of the initial efficiency after 12 h of full sunlight illumination. From the X-ray diffraction analyses, it is suggested that the degradation of the efficiency of PSC during illumination occurs regardless of the decomposition of the perovskite absorber. Considering the light-soaking profiles of the encapsulated cells and the OCVD characteristics, it is likely that the CdS shell had efficiently suppressed the undesirable electron kinetics, such as trapping at the surface defects of the TiO2 and preventing the resultant charge losses by recombination. This study suggests that further complementary research on various effective methods for passivation of the TiO2 layer would be highly meaningful, leading to insight into the fabrication of PSCs stable to UV-light for a long time.

  16. Precise Tuning of the Nanostructured Surface leading to the Luminescence Enhancement in SrAl2O4Based Core/Shell Structure.

    Science.gov (United States)

    Rojas-Hernandez, Rocío Estefanía; Rubio-Marcos, Fernando; Serrano, Aida; Del Campo, Adolfo; Fernandez, José Francisco

    2017-03-28

    Intensive research has been focused on the synthesis of long-lasting SrAl 2 O 4 :EuDy in luminescent materials field. Traditionally, SrAl 2 O 4 :EuDy is synthesized in bulk form by solid state. However, their development remains restrained due to this technique is not compatible with large-scale production, sustainability and nanometer-scale requirements. Despite nano-range particles have been obtained by chemical routes, photoluminescence response decreases and application became unpractical. It remains a challenge to synthesize nonrare-earth (RE) phosphors with high photoluminescence. One major challenge for the luminescent materials community is to devise methods to deliver innovative, sustainable and cost effective solutions for the reduction of RE because of the lack of RE availability. Here, we suggest a solution based on molten salts, obtaining nanosheets or micro/nanostructured SrAl 2 O 4 :Eu, Dy particles with core-shell structure, employing only 50% of standard amounts of RE. Core-size and shell thickness and crystallinity can be tuned by post-thermal treatment, through which can be modulated the Eu +2 fraction. We find that our methodology leads the functional features of the analogous micron counterpart. These results can be considered a great achievement to scale-up the process. Besides, the harmful collateral effect of nanotechnology must be addressed by using new safe by design core-shell nanostructures.

  17. Polyaniline/multi-walled carbon nanotubes composite with core-shell structures as a cathode material for rechargeable lithium-polymer cells

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Pan [School of Marine Science and Technology, Harbin Institute of Technology, Weihai 264209 (China); Han, Jia-Jun, E-mail: hanjiajunhitweihai@163.com [School of Marine Science and Technology, Harbin Institute of Technology, Weihai 264209 (China); Jiang, Li-Feng [Dalian Chemical Institute of Chinese Academy of Sciences, Dalian 116011 (China); Li, Zhao-Yu; Cheng, Jin-Ning [School of Marine Science and Technology, Harbin Institute of Technology, Weihai 264209 (China)

    2017-04-01

    Highlights: • The polyaniline multi-walled carbon nanotubes composite with core-shell structures was synthetized via in situ chemical oxidative polymerization, and the materials were characterized by physical and chemical methods. • The PANI/WMCNTs was synthetized via in situ chemical oxidative polymerization with core-shell structures. • The WMCNTs highly enhanced the conductivity of composites. • The comopsites were more conducive to the intercalation and deintercalation of anions and cations. • The much better performance as the cathode for lithium-ion cells was acquired for the composites. • The composites are low cost and eco-friendly which have a good prospect in future. - Abstract: The aniline was polymerized onto functionalized multi-walled carbon nanotubes in order to obtain a cathode material with core-shell structures for lithium batteries. The structure and morphology of the samples were investigated by Fourier transform infrared spectroscopy analysis, scanning electron microscope, transmission electron microscope and X-ray diffraction. The electrochemical properties of the composite were characterized by the cyclic voltammetry, the charge/discharge property, coulombic efficiency, and ac impedance spectroscopy in detail. At a constant current density of 0.2 C, the first specific discharge capacity of the reduced and oxidized PANI/WMCNTs were 181.8 mAh/g and 135.1 mAh/g separately, and the capacity retention rates were corresponding to 76.75% and 86.04% for 100 cycles with 99% coulombic efficiency. It was confirmed that the CNTs obviously enhanced the conductivity and electrochemical performance of polyaniline, and compared with the pure PANI, the reduced composite possessed a quite good performance for the cathode of lithium batteries.

  18. Development of Mortar Simulator with Shell-In-Shell System – Problem of External Ballistics

    Directory of Open Access Journals (Sweden)

    A. Fedaravicius

    2007-01-01

    Full Text Available The shell-in-shell system used in the mortar simulator raises a number of non-standard technical and computational problems starting from the requirement to distribute the propelling blast energy between the warhead and the ballistic barrel, finishing with the requirement that the length of warhead's flight path must be scaled to combat shell firing tables. The design problem of the simulator is split into two parts – the problem of external ballistics where the initial velocities of the warhead must be determined, and the problem of internal ballistics – where the design of the cartridge and the ballistic barrel must be performed.

  19. Core-shell structural nanodiamond@TiN supported Pt nanoparticles as a highly efficient and stable electrocatalyst for direct methanol fuel cells

    International Nuclear Information System (INIS)

    Zhao, Yuling; Wang, Yanhui; Dong, Liang; Zhang, Yan; Huang, Junjie; Zang, Jianbing; Lu, Jing; Xu, Xipeng

    2014-01-01

    Highlights: • Core-shell structural nanodiamond@TiN was used as a novel support for Pt catalysts. • The ND@TiN support possessed a high electrochemical stability than carbon black. • The Pt/ND@TiN showed a higher catalytic activity for MOR and ORR than the Pt/C. • The Pt/ND@TiN demonstrated a much better durability compared with the Pt/C. - Abstract: A novel core-shell support material was designed with nanodiamond (ND) as core possessed excellent stability and TiN as shell improved the conductivity of support. The nano-TiN shell was decorated on the surface of ND by annealing TiO 2 in nitrogen atmosphere, and the obtained ND@TiN was employed to support Pt nanoparticles (NPs). The ND@TiN support and Pt/ND@TiN electrocatalyst were characterized by X-ray diffraction and transmission electron microscopy. ND particles were coated uniformly by the TiN layer and Pt NPs with a mean size of 4.2 nm were highly dispersed on the surface of ND@TiN. The electrochemical results confirmed that the ND@TiN support possessed a much more stability than the carbon black and exhibited a bigger background current density than the ND. The Pt/ND@TiN catalyst showed higher catalytic activity and better stability in methanol oxidation and oxygen reduction reactions compared with the Pt/C and Pt/ND

  20. Construction of hierarchically porous graphitized carbon-supported NiFe layered double hydroxides with a core-shell structure as an enhanced electrocatalyst for the oxygen evolution reaction.

    Science.gov (United States)

    Ni, Yuanman; Yao, Lihua; Wang, Yin; Liu, Bing; Cao, Minhua; Hu, Changwen

    2017-08-17

    The oxygen evolution reaction (OER) is a vital half-reaction in water splitting and metal-air batteries. Developing earth-abundant, high