WorldWideScience

Sample records for anisotropic conduction properties

  1. Effects of anisotropic thermal conduction on wind properties in hot accretion flow

    Science.gov (United States)

    Bu, De-Fu; Wu, Mao-Chun; Yuan, Ye-Fei

    2016-06-01

    Previous works have clearly shown the existence of winds from black hole hot accretion flow and investigated their detailed properties. In extremely low accretion rate systems, the collisional mean-free path of electrons is large compared with the length-scale of the system, thus thermal conduction is dynamically important. When the magnetic field is present, the thermal conduction is anisotropic and energy transport is along magnetic field lines. In this paper, we study the effects of anisotropic thermal conduction on the wind production in hot accretion flows by performing two-dimensional magnetohydrodynamic simulations. We find that thermal conduction has only moderate effects on the mass flux of wind. But the energy flux of wind can be increased by a factor of ˜10 due to the increase of wind velocity when thermal conduction is included. The increase of wind velocity is because of the increase of driving forces (e.g. gas pressure gradient force and centrifugal force) when thermal conduction is included. This result demonstrates that thermal conduction plays an important role in determining the properties of wind.

  2. Effects of anisotropic thermal conduction on wind properties in hot accretion flow

    CERN Document Server

    Bu, De-Fu; Yuan, Ye-Fei

    2016-01-01

    Previous works have clearly shown the existence of winds from black hole hot accretion flow and investigated their detailed properties. In extremely low accretion rate systems, the collisional mean-free path of electrons is large compared with the length-scale of the system, thus thermal conduction is dynamically important. When the magnetic field is present, the thermal conduction is anisotropic and energy transport is along magnetic field lines. In this paper, we study the effects of anisotropic thermal conduction on the wind production in hot accretion flows by performing two-dimensional magnetohydrodynamic simulations. We find that thermal conduction has only moderate effects on the mass flux of wind. But the energy flux of wind can be increased by a factor of $\\sim 10$ due to the increase of wind velocity when thermal conduction is included. The increase of wind velocity is because of the increase of driving forces (e.g. gas pressure gradient force and centrifugal force) when thermal conduction is includ...

  3. Conductivities in an anisotropic medium

    CERN Document Server

    Khimphun, Sunly; Park, Chanyong

    2016-01-01

    In order to imitate anisotropic medium of a condensed matter system, we take into account an Einstein-Maxwell-dilaton-axion model as a dual gravity theory where the anisotropy is caused by different momentum relaxations. This gravity model allows an anisotropic charged black hole solution. On this background, we investigate how the linear responses of vector modes like electric, thermoelectric, and thermal conductivities rely on the anisotropy. We find that the electric conductivity in low frequency limit shows a Drude peak and that in the intermediate frequency regime it reveals the power law behavior. Especially, when the anisotropy increases the exponent of the power law becomes smaller. In addition, we find that there exist a critical value for the anisotropy at which the DC conductivity reaches to its maximum value.

  4. Mussel-Inspired Anisotropic Nanocellulose and Silver Nanoparticle Composite with Improved Mechanical Properties, Electrical Conductivity and Antibacterial Activity

    Directory of Open Access Journals (Sweden)

    Hoang-Linh Nguyen

    2016-03-01

    Full Text Available Materials for wearable devices, tissue engineering and bio-sensing applications require both antibacterial activity to prevent bacterial infection and biofilm formation, and electrical conductivity to electric signals inside and outside of the human body. Recently, cellulose nanofibers have been utilized for various applications but cellulose itself has neither antibacterial activity nor conductivity. Here, an antibacterial and electrically conductive composite was formed by generating catechol mediated silver nanoparticles (AgNPs on the surface of cellulose nanofibers. The chemically immobilized catechol moiety on the nanofibrous cellulose network reduced Ag+ to form AgNPs on the cellulose nanofiber. The AgNPs cellulose composite showed excellent antibacterial efficacy against both Gram-positive and Gram-negative bacteria. In addition, the catechol conjugation and the addition of AgNP induced anisotropic self-alignment of the cellulose nanofibers which enhances electrical and mechanical properties of the composite. Therefore, the composite containing AgNPs and anisotropic aligned the cellulose nanofiber may be useful for biomedical applications.

  5. Simultaneous Measurement of Thermal Diffusivity and Thermal Conductivity by Means of Inverse Solution for One-Dimensional Heat Conduction (Anisotropic Thermal Properties of CFRP for FCEV)

    Science.gov (United States)

    Kosaka, Masataka; Monde, Masanori

    2015-11-01

    For safe and fast fueling of hydrogen in a fuel cell electric vehicle at hydrogen fueling stations, an understanding of the heat transferred from the gas into the tank wall (carbon fiber reinforced plastic (CFRP) material) during hydrogen fueling is necessary. Its thermal properties are needed in estimating heat loss accurately during hydrogen fueling. The CFRP has anisotropic thermal properties, because it consists of an adhesive agent and layers of the CFRP which is wound with a carbon fiber. In this paper, the thermal diffusivity and thermal conductivity of the tank wall material were measured by an inverse solution for one-dimensional unsteady heat conduction. As a result, the thermal diffusivity and thermal conductivity were 2.09 × 10^{-6}{ m}2{\\cdot }{s}^{-1} and 3.06{ W}{\\cdot }{m}{\\cdot }^{-1}{K}^{-1} for the axial direction, while they were 6.03 × 10^{-7} {m}2{\\cdot }{s}^{-1} and 0.93 {W}{\\cdot }{m}^{-1}{\\cdot }{K}^{-1} for the radial direction. The thermal conductivity for the axial direction was about three times higher than that for the radial direction. The thermal diffusivity shows the same trend in both directions because the thermal capacity, ρ c, is independent of direction, where ρ is the density and c is the heat capacity.

  6. Anisotropic Transport Properties of Complex Metallic Alloys

    OpenAIRE

    Smontara, Ana; Dolinšek, Janez

    2010-01-01

    Anisotropic transport properties (electrical resistivity, ρ, and thermal conductivity, κ) of the Y-phase Al-Ni-Co, o-Al13Co4 and Al4(Cr,Fe) complex metallic alloys were investigated. They belong to the class of decagonal approximant phases with stacked-layer crystallographic structure and allowed us to study the evolution of anisotropic transport properties with increasing structural complexity and the unit cell size.

  7. Anisotropic conductivity tensor imaging using magnetic induction tomography

    International Nuclear Information System (INIS)

    Magnetic induction tomography aims to reconstruct the electrical conductivity distribution of the human body using non-contact measurements. The potential of the method has been demonstrated by various simulation studies and a number of phantom experiments. These studies have all relied on models having isotropic distributions of conductivity, although the human body has a highly heterogeneous structure with partially anisotropic properties. Therefore, whether the conventional modeling approaches used so far are appropriate for clinical applications or not is still an open question. To investigate the problem, we performed a simulation study to investigate the feasibility of (1) imaging anisotropic perturbations within an isotropic medium and (2) imaging isotropic perturbations inside a partially anisotropic background. The first is the case for the imaging of anomalies that have anisotropic characteristics and the latter is the case e.g. in lung imaging where an anisotropic skeletal muscle tissue surrounds the lungs and the rib cage. An anisotropic solver based on the singular value decomposition was used to attain conductivity tensor images to be compared with the ones obtained from isotropic solvers. The results indicate the importance of anisotropic modeling in order to obtain satisfactory reconstructions, especially for the imaging of the anisotropic anomalies, and address the resolvability of the conductivity tensor components

  8. Anisotropic thermal conductivity of magnetic fluids

    Institute of Scientific and Technical Information of China (English)

    Xiaopeng Fang; Yimin Xuan; Qiang Li

    2009-01-01

    Considering the forces acting on the particles and the motion of the particles, this study uses a numerical simulation to investigate the three-dimensional microstructure of the magnetic fluids in the presence of an external magnetic field. A method is proposed for predicting the anisotropic thermal conductivity of magnetic fluids. By introducing an anisotropic structure parameter which characterizes the non-uniform distribution of particles suspended in the magnetic fluids, the traditional Maxwell formula is modified and extended to calculate anisotropic thermal conductivity of the magnetic fluids. The results show that in the presence of an external magnetic field the magnetic nanoparticles form chainlike clusters along the direction of the external magnetic field, which leads to the fact that the thermal conduc-tivity of the magnetic fluid along the chain direction is bigger than that along other directions. The thermal conductivity of the magnetic fluids presents an anisotropic feature. With the increase of the magnetic field strength the chainlike clusters in the magnetic fluid appear to be more obvious, so that the anisotropic feature of heat conduction in the fluids becomes more evident.

  9. Transient combined radiation and conduction in a one-dimensional non-gray participating medium with anisotropic optical properties subjected to radiative flux at the boundaries

    Science.gov (United States)

    Asllanaj, Fatmir; Brige, Xavier; Jeandel, Gérard

    2007-09-01

    Transient combined heat transfer by radiation and conduction is investigated in non-gray participating media with anisotropic optical properties. The medium is irradiated by a time-dependent source. Different kinds of boundaries are considered: black, opaque, transparent and semi-transparent. The heat transfer equations are solved numerically in a one-dimensional configuration. Comparisons are made with test cases taken from the literature, and the results obtained demonstrate the accuracy of the present numerical model. The influence of transparent, semi-transparent and opaque boundaries on an insulating fibrous medium is also studied.

  10. Highly anisotropic thermal conductivity of arsenene: An ab initio study

    Science.gov (United States)

    Zeraati, Majid; Vaez Allaei, S. Mehdi; Abdolhosseini Sarsari, I.; Pourfath, Mahdi; Donadio, Davide

    2016-02-01

    Elemental two-dimensional (2D) materials exhibit intriguing heat transport and phononic properties. Here we have investigated the lattice thermal conductivity of newly proposed arsenene, the 2D honeycomb structure of arsenic, using ab initio calculations. Solving the Boltzmann transport equation for phonons, we predict a highly anisotropic thermal conductivity of 30.4 and 7.8 W/mK along the zigzag and armchair directions, respectively, at room temperature. Our calculations reveal that phonons with mean free paths between 20 nm and 1 μ m provide the main contribution to the large thermal conductivity in the zigzag direction; mean free paths of phonons contributing to heat transport in the armchair directions range between 20 and 100 nm. The obtained anisotropic thermal conductivity and feasibility of synthesis, in addition to high electron mobility reported elsewhere, make arsenene a promising material for nanoelectronic applications and thermal management.

  11. Mussel-Inspired Anisotropic Nanocellulose and Silver Nanoparticle Composite with Improved Mechanical Properties, Electrical Conductivity and Antibacterial Activity

    OpenAIRE

    Hoang-Linh Nguyen; Yun Kee Jo; Minkyu Cha; Yun Jeong Cha; Dong Ki Yoon; Naresh D. Sanandiya; Ekavianty Prajatelistia; Dongyeop X. Oh; Dong Soo Hwang

    2016-01-01

    Materials for wearable devices, tissue engineering and bio-sensing applications require both antibacterial activity to prevent bacterial infection and biofilm formation, and electrical conductivity to electric signals inside and outside of the human body. Recently, cellulose nanofibers have been utilized for various applications but cellulose itself has neither antibacterial activity nor conductivity. Here, an antibacterial and electrically conductive composite was formed by generating catech...

  12. A BEM FOR TRANSIENT HEAT CONDUCTION PROBLEM OF ANISOTROPIC FGM

    OpenAIRE

    Azis, Mohammad Ivan

    2014-01-01

    A boundary element method (BEM) for the solution of a certain class of nonlinear parabolic initial boundary value problems for a certain class of anisotropic functionally graded media is derived. The method is then used to obtain numerical values for some particular transient 2-D heat conduction problems for anisotropic functionally graded materials (FGM).

  13. Effective Dirac Hamiltonian for anisotropic honeycomb lattices: Optical properties

    Science.gov (United States)

    Oliva-Leyva, M.; Naumis, Gerardo G.

    2016-01-01

    We derive the low-energy Hamiltonian for a honeycomb lattice with anisotropy in the hopping parameters. Taking the reported Dirac Hamiltonian for the anisotropic honeycomb lattice, we obtain its optical conductivity tensor and its transmittance for normal incidence of linearly polarized light. Also, we characterize its dichroic character due to the anisotropic optical absorption. As an application of our general findings, which reproduce the previous case of uniformly strained graphene, we study the optical properties of graphene under a nonmechanical distortion.

  14. Anisotropic thermal conduction in galaxy clusters with MHD in Gadget

    CERN Document Server

    Arth, Alexander; Beck, Alexander M; Petkova, Margarita; Lesch, Harald

    2014-01-01

    We present an implementation of thermal conduction including the anisotropic effects of magnetic fields for SPH. The anisotropic thermal conduction is mainly proceeding parallel to magnetic fields and suppressed perpendicular to the fields. We derive the SPH formalism for the anisotropic heat transport and solve the corresponding equation with an implicit conjugate gradient scheme. We discuss several issues of unphysical heat transport in the cases of extreme ansiotropies or unmagnetized regions and present possible numerical workarounds. We implement our algorithm into the GADGET code and study its behaviour in several test cases. In general, we reproduce the analytical solutions of our idealised test problems, and obtain good results in cosmological simulations of galaxy cluster formations. Within galaxy clusters, the anisotropic conduction produces a net heat transport similar to an isotropic Spitzer conduction model with an efficiency of one per cent. In contrast to isotropic conduction our new formalism ...

  15. Anisotropic nanomaterials preparation, properties, and applications

    CERN Document Server

    Li, Quan

    2015-01-01

    In this book anisotropic one-dimensional and two-dimensional nanoscale building blocks and their assembly into fascinating and qualitatively new functional structures embracing both hard and soft components are explained. Contributions from leading experts regarding important aspects like synthesis, assembly, properties and applications of the above materials are compiled into a reference book. The anisotropy, i.e. the direction-dependent physical properties, of materials is fascinating and elegant and has sparked the quest for anisotropic materials with useful properties. With such a curiosi

  16. Anisotropic thermal conductivity in uranium dioxide.

    Science.gov (United States)

    Gofryk, K; Du, S; Stanek, C R; Lashley, J C; Liu, X-Y; Schulze, R K; Smith, J L; Safarik, D J; Byler, D D; McClellan, K J; Uberuaga, B P; Scott, B L; Andersson, D A

    2014-08-01

    The thermal conductivity of uranium dioxide has been studied for over half a century, as uranium dioxide is the fuel used in a majority of operating nuclear reactors and thermal conductivity controls the conversion of heat produced by fission events to electricity. Because uranium dioxide is a cubic compound and thermal conductivity is a second-rank tensor, it has always been assumed to be isotropic. We report thermal conductivity measurements on oriented uranium dioxide single crystals that show anisotropy from 4 K to above 300 K. Our results indicate that phonon-spin scattering is important for understanding the general thermal conductivity behaviour, and also explains the anisotropy by coupling to the applied temperature gradient and breaking cubic symmetry.

  17. Thermal conduction in single-layer black phosphorus: highly anisotropic?

    International Nuclear Information System (INIS)

    The single-layer black phosphorus is characteristic for its puckered structure, which has led to distinct anisotropy in its optical, electronic, and mechanical properties. We use the non-equilibrium Green's function approach and the first-principles method to investigate the thermal conductance for single-layer black phosphorus in the ballistic transport regime, in which the phonon–phonon scattering is neglected. We find that the anisotropy in the thermal conduction is very weak for the single-layer black phosphorus—the difference between two in-plane directions is less than 4%. Our phonon calculations disclose that the out-of-plane acoustic phonon branch has lower group velocities in the direction perpendicular to the pucker, as the black phosphorus is softer in this direction, leading to a weakening effect for the thermal conductance in the perpendicular direction. However, the longitudinal acoustic phonon branch behaves abnormally; i.e., the group velocity of this phonon branch is higher in the perpendicular direction, although the single-layer black phosphorus is softer in this direction. The abnormal behavior of the longitudinal acoustic phonon branch is closely related to the highly anisotropic Poisson's ratio in the single-layer black phosphorus. As a result of the counteraction between the out-of-plane phonon mode and the in-plane phonon modes, the thermal conductance in the perpendicular direction is weaker than the parallel direction, but the anisotropy is pretty small. (paper)

  18. Optimal anisotropic three-phase conducting composites: Plane problem

    CERN Document Server

    Cherkaev, Andrej

    2010-01-01

    The paper establishes tight lower bound for effective conductivity tensor $K_*$ of two-dimensional three-phase conducting anisotropic composites and defines optimal microstructures. It is assumed that three materials are mixed with fixed volume fractions and that the conductivity of one of the materials is infinite. The bound expands the Hashin-Shtrikman and Translation bounds to multiphase structures, it is derived using the technique of {\\em localized polyconvexity} that is a combination of Translation method and additional inequalities on the fields in the materials; similar technique was used by Nesi (1995) and Cherkaev (2009) for isotropic multiphase composites. This paper expands the bounds to the anisotropic composites. The lower bound of conductivity (G-closure) is a piece-wise analytic function of eigenvalues of $K_*$, that depends only on conductivities of components and their volume fractions. Also, we find optimal microstructures that realize the bounds, developing the technique suggested earlier ...

  19. Anisotropic thermal conductivity of thin polycrystalline oxide samples

    Energy Technology Data Exchange (ETDEWEB)

    Tiwari, A., E-mail: abhishektiwariiitr@gmail.com [Groupe d’Etudes des Matériaux Hétérogènes (GEMH, EA 3178), Ecole Nationale Supérieure de Céramique Industrielle, 12, Rue Atlantis, 87068 Limoges Cedex (France); Department of Mechanical and Aerospace Engineering, Monash University, Melbourne, VIC 3800 (Australia); Boussois, K.; Nait-Ali, B.; Smith, D. S.; Blanchart, P. [Groupe d’Etudes des Matériaux Hétérogènes (GEMH, EA 3178), Ecole Nationale Supérieure de Céramique Industrielle, 12, Rue Atlantis, 87068 Limoges Cedex (France)

    2013-11-15

    This paper reports about the development of a modified laser-flash technique and relation to measure the in-plane thermal diffusivity of thin polycrystalline oxide samples. Thermal conductivity is then calculated with the product of diffusivity, specific heat and density. Design and operating features for evaluating in-plane thermal conductivities are described. The technique is advantageous as thin samples are not glued together to measure in-plane thermal conductivities like earlier methods reported in literature. The approach was employed to study anisotropic thermal conductivity in alumina sheet, textured kaolin ceramics and montmorillonite. Since it is rare to find in-plane thermal conductivity values for such anisotropic thin samples in literature, this technique offers a useful variant to existing techniques.

  20. Optical Conductivity of Anisotropic Quantum Dots in Magnetic Fields

    Institute of Scientific and Technical Information of China (English)

    GUO Kang-Xian; CHEN Chuan-Yu

    2005-01-01

    @@ Optical conductivity of anisotropic double-parabolic quantum dots is investigated with the memory-function approach, and the analytic expression for the optical conductivity is derived. With characteristic parameterspertaining to GaAs, the numerical results are presented. It is shown that: (1) the larger the optical phonon frequency ωLO, the stronger the peak intensity of the optical conductivity, and the more asymmetric the shape of the optical conductivity; (2) the magnetic field enhances the optical conductivity for levels l = 0 and l = 1, with or without electron-LO-phonon interactions; (3) the larger the quantum dot thickness lz, the smaller the optical conductivity σ(ω).

  1. Accurately simulating anisotropic thermal conduction on a moving mesh

    CERN Document Server

    Kannan, Rahul; Pakmor, Rüdiger; Marinacci, Federico; Vogelsberger, Mark

    2015-01-01

    We present a novel implementation of an extremum preserving anisotropic diffusion solver for thermal conduction on the unstructured moving Voronoi mesh of the AREPO code. The method relies on splitting the one-sided facet fluxes into normal and oblique components, with the oblique fluxes being limited such that the total flux is both locally conservative and extremum preserving. The approach makes use of harmonic averaging points and a simple, robust interpolation scheme that works well for strong heterogeneous and anisotropic diffusion problems. Moreover, the required discretisation stencil is small. Efficient fully implicit and semi-implicit time integration schemes are also implemented. We perform several numerical tests that evaluate the stability and accuracy of the scheme, including applications such as point explosions with heat conduction and calculations of convective instabilities in conducting plasmas. The new implementation is suitable for studying important astrophysical phenomena, such as the co...

  2. Anisotropic Optical Properties of Layered Germanium Sulfide

    CERN Document Server

    Tan, Dezhi; Wang, Feijiu; Mohamed, Nur Baizura; Mouri, Shinichiro; Sandhaya, Koirala; Zhang, Wenjing; Miyauchi, Yuhei; Ohfuchi, Mari; Matsuda, Kazunari

    2016-01-01

    Two-dimensional (2D) layered materials, transition metal dichalcogenides and black phosphorus, have attracted much interest from the viewpoints of fundamental physics and device applications. The establishment of new functionalities in anisotropic layered 2D materials is a challenging but rewarding frontier, owing to their remarkable optical properties and prospects for new devices. Here, we report the anisotropic optical properties of layered 2D monochalcogenide of germanium sulfide (GeS). Three Raman scattering peaks corresponding to the B3g, A1g, and A2g modes with strong polarization dependence are demonstrated in the GeS flakes, which validates polarized Raman spectroscopy as an effective method for identifying the crystal orientation of anisotropic layered GeS. Photoluminescence (PL) is observed with a peak at around 1.66 eV that originates from the direct optical transition in GeS at room temperature. Moreover, determination of the polarization dependent characteristics of the PL and absorption reveals...

  3. Existence and uniqueness in anisotropic conductivity reconstruction with Faraday's law

    KAUST Repository

    Lee, Min-Gi

    2015-03-18

    We show that three sets of internal current densities are the right amount of data that give the existence and the uniqueness at the same time in reconstructing an anisotropic conductivity in two space dimensions. The curl free equation of Faraday’s law is taken instead of the usual divergence free equation of the electrical impedance to- mography. Boundary conditions related to given current densities are introduced which complete a well determined problem for conductivity reconstruction together with Fara- day’s law.

  4. Accurately simulating anisotropic thermal conduction on a moving mesh

    Science.gov (United States)

    Kannan, Rahul; Springel, Volker; Pakmor, Rüdiger; Marinacci, Federico; Vogelsberger, Mark

    2016-05-01

    We present a novel implementation of an extremum preserving anisotropic diffusion solver for thermal conduction on the unstructured moving Voronoi mesh of the AREPO code. The method relies on splitting the one-sided facet fluxes into normal and oblique components, with the oblique fluxes being limited such that the total flux is both locally conservative and extremum preserving. The approach makes use of harmonic averaging points and a simple, robust interpolation scheme that works well for strong heterogeneous and anisotropic diffusion problems. Moreover, the required discretization stencil is small. Efficient fully implicit and semi-implicit time integration schemes are also implemented. We perform several numerical tests that evaluate the stability and accuracy of the scheme, including applications such as point explosions with heat conduction and calculations of convective instabilities in conducting plasmas. The new implementation is suitable for studying important astrophysical phenomena, such as the conductive heat transport in galaxy clusters, the evolution of supernova remnants, or the distribution of heat from black hole-driven jets into the intracluster medium.

  5. Reciprocal relations for effective conductivities of anisotropic media

    Science.gov (United States)

    Nevard, John; Keller, Joseph B.

    1985-11-01

    Any pair of two-dimensional anisotropic media with local conductivity tensors that are functions of position and that are related to one another in a certain reciprocal way are considered. It is proved that their effective conductivity tensors are related to each other in the same way for both spatially periodic media and statistically stationary random media. An inequality involving the effective conductivity tensors of two three-dimensional media that are reciprocally related is also proved. These results extend the corresponding results for locally isotropic media obtained by Keller, Mendelsohn, Hansen, Schulgasser, and Kohler and Papanicolau. They also yield a relation satisfied by the effective conductivity tensor of a medium reciprocal to a translated or rotated copy of itself.

  6. Heat Conductance is Strongly Anisotropic for Pristine Silicon Nanowires

    DEFF Research Database (Denmark)

    Markussen, Troels; Jauho, Antti-Pekka; Brandbyge, Mads

    2008-01-01

    We compute atomistically the heat conductance for ultrathin pristine silicon nanowires (SiNWs) with diameters ranging from 1 to 5 nm. The room temperature thermal conductance is found to be highly anisotropic: wires oriented along the 110 direction have 50−75% larger conductance than wires oriented...... instead use the Tersoff empirical potential model (TEP). For the smallest wires, the thermal conductances obtained from DFT and TEP calculations agree within 10%. The presented results could be relevant for future phonon-engineering of nanowire devices....... along the 100 and 111 directions. We show that the anisotropies can be qualitatively understood and reproduced from the bulk phonon band structure. Ab initio density functional theory (DFT) is used to study the thinnest wires, but becomes computationally prohibitive for larger diameters, where we...

  7. Image theory for electric dipoles above a conducting anisotropic earth

    Science.gov (United States)

    Mahmoud, S. F.

    1984-07-01

    New image representations for vertical electric dipoles (VED) above an imperfectly conducting and axially anisotropic earth are developed. These include multidiscrete images at different depths below the air-earth interface and multipole image sources. It is shown that, in contrast with the available image representations in the literature, the developed ones predict the correct behavior of the fields in the far zone along the earth's surface. Extension to a layered earth's model is made. The theory is also extended to the horizontal electric dipole with similar conclusions to the case of the vertical dipole.

  8. Measurement of the anisotropic thermal conductivity of the porcine cornea.

    Science.gov (United States)

    Barton, Michael D; Trembly, B Stuart

    2013-10-01

    Accurate thermal models for the cornea of the eye support the development of thermal techniques for reshaping the cornea and other scientific purposes. Heat transfer in the cornea must be quantified accurately so that a thermal treatment does not destroy the endothelial layer, which cannot regenerate, and yet is responsible for maintaining corneal transparency. We developed a custom apparatus to measure the thermal conductivity of ex vivo porcine corneas perpendicular to the surface and applied a commercial apparatus to measure thermal conductivity parallel to the surface. We found that corneal thermal conductivity is 14% anisotropic at the normal state of corneal hydration. Small numbers of ex vivo feline and human corneas had a thermal conductivity perpendicular to the surface that was indistinguishable from the porcine corneas. Aqueous humor from ex vivo porcine, feline, and human eyes had a thermal conductivity nearly equal to that of water. Including the anisotropy of corneal thermal conductivity will improve the predictive power of thermal models of the eye.

  9. Anisotropic Transport Properties of the Orthorhombic Al13Co4 Approximant to the Decagonal Quasicrystal

    OpenAIRE

    Lukatela, Jagoda; Stanić, Denis; Popčević, Petar; Ivkov, Jovica; Dolinšek, Janez; Gille, Peter

    2010-01-01

    Anisotropic transport properties (electrical resistivity, thermoelectric power, Hall coefficient and thermal conductivity) of the o-Al13Co4 orthorhombic approximant to the decagonal phase were investigated. The crystalline-direction-dependent measurements were performed along the a, b and c directions of the orthorhombic unit cell, where (b, c) atomic planes are stacked along the perpendicular a direction. Anisotropic electrical and thermal conductivities are the highest along the stacking a ...

  10. Micromechanics model for predicting anisotropic electrical conductivity of carbon fiber composite materials

    Science.gov (United States)

    Haider, Mohammad Faisal; Haider, Md. Mushfique; Yasmeen, Farzana

    2016-07-01

    Heterogeneous materials, such as composites consist of clearly distinguishable constituents (or phases) that show different electrical properties. Multifunctional composites have anisotropic electrical properties that can be tailored for a particular application. The effective anisotropic electrical conductivity of composites is strongly affected by many parameters including volume fractions, distributions, and orientations of constituents. Given the electrical properties of the constituents, one important goal of micromechanics of materials consists of predicting electrical response of the heterogeneous material on the basis of the geometries and properties of the individual phases, a task known as homogenization. The benefit of homogenization is that the behavior of a heterogeneous material can be determined without resorting or testing it. Furthermore, continuum micromechanics can predict the full multi-axial properties and responses of inhomogeneous materials, which are anisotropic in nature. Effective electrical conductivity estimation is performed by using classical micromechanics techniques (composite cylinder assemblage method) that investigates the effect of the fiber/matrix electrical properties and their volume fractions on the micro scale composite response. The composite cylinder assemblage method (CCM) is an analytical theory that is based on the assumption that composites are in a state of periodic structure. The CCM was developed to extend capabilities variable fiber shape/array availability with same volume fraction, interphase analysis, etc. The CCM is a continuum-based micromechanics model that provides closed form expressions for upper level length scales such as macro-scale composite responses in terms of the properties, shapes, orientations and constituent distributions at lower length levels such as the micro-scale.

  11. Computational Study of Subdural Cortical Stimulation: Effects of Simulating Anisotropic Conductivity on Activation of Cortical Neurons.

    Directory of Open Access Journals (Sweden)

    Hyeon Seo

    Full Text Available Subdural cortical stimulation (SuCS is an appealing method in the treatment of neurological disorders, and computational modeling studies of SuCS have been applied to determine the optimal design for electrotherapy. To achieve a better understanding of computational modeling on the stimulation effects of SuCS, the influence of anisotropic white matter conductivity on the activation of cortical neurons was investigated in a realistic head model. In this paper, we constructed pyramidal neuronal models (layers 3 and 5 that showed primary excitation of the corticospinal tract, and an anatomically realistic head model reflecting complex brain geometry. The anisotropic information was acquired from diffusion tensor magnetic resonance imaging (DT-MRI and then applied to the white matter at various ratios of anisotropic conductivity. First, we compared the isotropic and anisotropic models; compared to the isotropic model, the anisotropic model showed that neurons were activated in the deeper bank during cathodal stimulation and in the wider crown during anodal stimulation. Second, several popular anisotropic principles were adapted to investigate the effects of variations in anisotropic information. We observed that excitation thresholds varied with anisotropic principles, especially with anodal stimulation. Overall, incorporating anisotropic conductivity into the anatomically realistic head model is critical for accurate estimation of neuronal responses; however, caution should be used in the selection of anisotropic information.

  12. Deformation characterization of conductive particles in anisotropically conductive adhesive simulated by FEM

    Institute of Scientific and Technical Information of China (English)

    Yanli Wang; Junpin Lin; Zhi Lin; Xinfa Cui; Guoliang Chen

    2005-01-01

    The deformation behavior and the contact area of conductive particles in anisotropically conductive adhesives (ACA) were investigated by finite element method (FEM). The solid conductive particles are made of pure Ni and Cu. The results indicate that the deformation of the conductive particles is inhomogeneous during fabrication. When the reduction in height is small the deformation concentrates in the area near the contact area. As the reduction in height increases, the strain in the area near the contact area increases, and the metal flows toward the circumference, resulting in the increase of the contact area between the conductive particles and pad. The higher the degree of deformation, the larger the contact area. The regression equations were offered to express the relations between the bounding force and the contact area or the reduction in height. An approach of how to obtain the maximum contact area in ACA was discussed.

  13. Cellulose-Templated Graphene Monoliths with Anisotropic Mechanical, Thermal, and Electrical Properties.

    Science.gov (United States)

    Zhang, Rujing; Chen, Qiao; Zhen, Zhen; Jiang, Xin; Zhong, Minlin; Zhu, Hongwei

    2015-09-01

    Assembling particular building blocks into composites with diverse targeted structures has attracted considerable interest for understanding its new properties and expanding the potential applications. Anisotropic organization is considered as a frequently used targeted architecture and possesses many peculiar properties because of its unusual shapes. Here, we show that anisotropic graphene monoliths (AGMs), three-dimensional architectures of well-aligned graphene sheets obtained by a dip-coating method using cellulose acetate fibers as templates show thermal-insulating, fire-retardant, and anisotropic properties. They exhibit a feature of higher mechanical strength and thermal/electrical conductivities in the axial direction than in the radial direction. Elastic polymer resins are then introduced into the pores of the AGMs to form conductive and flexible composites. The composites, as AGMs, retain the unique anisotropic properties, revealing opposite resistance change under compressions in different directions. The outstanding anisotropic properties of AGMs make them possible to be applied in the fields of thermal insulation, integrated circuits, and electromechanical devices. PMID:26284380

  14. Anisotropic properties of aligned SWNT modified poly (methyl methacrylate) nanocomposites

    Indian Academy of Sciences (India)

    Weixue Li; Qing Wang; Jianfeng Dai

    2006-06-01

    The poly (methyl methacrylate) (PMMA)/single-walled carbon nanotube (SWNT) composites with good uniformity, dispersion and alignment of SWNT were fabricated in an improved figuration process. The semidried mixture was stretched along one direction at a drawing ratio of 50 before it was dried, and then folded along the same direction stretching repeatedly for 100 times. The transmission electron microscopic (TEM) observation demonstrated that SWNT in the PMMA/SWNT composite tends to align in the stretching direction owing to a torque exerting on it in the stretching process. The electrical and mechanical properties of PMMA/SWNT composite were studied as a function of SWNT orientation and concentration. The aligned SWNT modified PMMA/SWNT composite presented highly anisotropic properties. The experimental results showed that the electrical conductivity and mechanical properties of composite rise with the increase of SWNT concentration, and that composite films showed higher conductivity and higher mechanical draw ratios along the stretched direction than perpendicular to it. The thermogravimetric analysis (TGA) revealed that embedding the SWNTs into the PMMA matrix also improves the thermal stability of the composite.

  15. Thermal conductivity of anisotropic snow measured by three independent methods

    Directory of Open Access Journals (Sweden)

    F. Riche

    2012-05-01

    Full Text Available The thermal conductivity of snow determines the temperature gradient, and by this the rate of snow metamorphism. It is therefore a key property of snow. However, parameterizations of thermal conductivity measured with the transient needle probe and the steady-state heat-flux plate show a bias. In addition, it is not clear to which degree thermal anisotropy is relevant. Until now, no physically convincing argument for the existence of this bias could be found. In this study, we investigated three independent methods to measure snow thermal conductivity and its anisotropy: a needle probe with a long heating time, a guarded heat flux plate, and direct numerical simulation at the level of the pore and ice structure. The three methods were applied to identical snow samples, apart from the different measurement volumes of each methods. We analyzed the consistency and the difference between these methods. We found a distinct change from horizontal thermal anisotropy in small rounded grains and vertical anisotropy in depth hoar. The anisotropy between vertical and horizontal conductivity ranges between 0.5–2. This anisotropy can cause a difference of up to −25 % to + 25 % if the thermal conductivity is calculated only from a horizontally inserted needle probe. Based on these measurements, the direct numerical simulation is the most reliable method as the tensorial components of the thermal conductivity can be calculated, the corresponding microstructure is precisely known and the homogeneity of the sample can be determined.

  16. Spin conductivity of the two-dimensional anisotropic frustrated Heisenberg model in the honeycomb lattice

    Science.gov (United States)

    Lima, L. S.

    2016-07-01

    We use the SU(3) Schwinger's boson theory to study the spin transport properties of the two-dimensional anisotropic frustrated Heisenberg model in a honeycomb lattice at T=0. We have investigated the behavior of the spin conductivity for this model which presents a single-ion anisotropy and J1 and J2 exchange interactions. We study the spin transport in the Bose-Einstein condensation regime where we have that the tz bosons are condensed and the following condition is valid: = = t. Our results show a metallic spin transport for ω > 0 and a superconductor spin transport in the limit of DC conductivity, ω → 0, where σ(ω) tends to infinity in this limit of ω.

  17. Strain-engineering the anisotropic electrical conductance in ReS2 monolayer

    Science.gov (United States)

    Yu, Sheng; Zhu, Hao; Eshun, Kwesi; Shi, Chen; Zeng, Min; Li, Qiliang

    2016-05-01

    Rhenium disulfide (ReS2) is a semiconducting layered transition metal dichalcogenide that exhibits a stable distorted 1 T (Re in octahedral coordination) phase. The reduced symmetry in ReS2 leads to in-plane anisotropy in various material properties. In this work, we performed a comprehensive first-principle computational study of strain effect on the anisotropic mechanical and electronic properties of ReS2 monolayers. We found that the anisotropic ratio in electron mobility along two principle axes is 2.36 while the ratio in hole mobility reaches 7.76. The study of strain applied along different directions shows that the elastic modulus is largest for out-of-plane direction, and the strain along a-direction induces indirect bandgap while strain along b- or c-direction does not. In addition, the carrier mobility can be significantly improved by the c-direction tensile strain. This study indicates that the ReS2 monolayer has promising applications in nanoscale strain sensor and conductance-switch FETs.

  18. Relative acceleration approach for conduction failure of cardiac excitation propagation on anisotropic curved surfaces

    CERN Document Server

    Chun, Sehun

    2012-01-01

    In cardiac electrophysiology, it is important to predict the necessary conditions for conduction failure, the failure of the cardiac excitation propagation even in the presence of normal excitable tissue, in high-dimensional anisotropic space because these conditions may provide feasible mechanisms for abnormal excitation propagations such as atrial re-entry and, subsequently, atrial fibrillation even without taking into account the time-dependent refractory region. Some conditions of conduction failure have been studied for anisotropy or simple curved surfaces, but the general conditions on anisotropic curved surfaces (anisotropic and curved surface) remain unknown. To predict and analyze conduction failure on anisotropic curved surfaces, a new analytic approach is proposed, called the relative acceleration approach borrowed from spacetime physics. Motivated by a discrete model of cardiac excitation propagation, this approach is based on the hypothesis that a large relative acceleration can translate to a dr...

  19. Properties and evolution of anisotropic structures in collisionless plasmas

    CERN Document Server

    Karimov, A R; Stenflo, L

    2016-01-01

    A new class of exact electrostatic solutions of the Vlasov-Maxwell equations based on the Jeans's theorem is proposed for studying the evolution and properties of two-dimensional anisotropic plasmas that are far from thermodynamic equilibrium. In particular, the free expansion of a slab of electron-ion plasma into vacuum is investigated.

  20. Geometric tuning of thermal conductivity in three-dimensional anisotropic phononic crystals.

    Science.gov (United States)

    Wei, Zhiyong; Wehmeyer, Geoff; Dames, Chris; Chen, Yunfei

    2016-10-01

    Molecular dynamics simulations are performed to investigate the thermal transport properties of a three-dimensional (3D) anisotropic phononic crystal consisting of silicon nanowires and films. The calculation shows that the in-plane thermal conductivity is negatively correlated with the out-of-plane thermal conductivity upon making geometric changes, whether varying the nanowire diameter or the film thickness. This enables the anisotropy ratio of thermal conductivity to be tailored over a wide range, in some cases by more than a factor of 20. Similar trends in thermal conductivity are also observed from an independent phonon ray tracing simulation considering only diffuse boundary scattering effects, though the range of anisotropy ratios is smaller than that obtained in MD simulation. By analyzing the phonon dispersion relation with varied geometric parameters, it is found that increasing the nanowire diameter increases the out-of-plane acoustic phonon group velocities, but reduces the in-plane longitudinal and fast transverse acoustic phonon group velocities. The calculated phonon irradiation further verified the negative correlation between the in-plane and the out-of-plane thermal conductivity. The proposed 3D phononic crystal may find potential application in thermoelectrics, energy storage, catalysis and sensing applications owing to its widely tailorable thermal conductivity.

  1. The Effect of Anisotropic Conduction on the Thermal Instability in the Interstellar Medium

    CERN Document Server

    Choi, Ena

    2011-01-01

    Thermal instability (TI) can strongly affect the structure and dynamics of the interstellar medium (ISM) in the Milky Way and other disk galaxies. Thermal conduction plays an important role in the TI by stabilizing small scales and limiting the size of the smallest condensates. In the magnetized ISM, however, heat is conducted anisotropically (primarily along magnetic field lines). We investigate the effects of anisotropic thermal conduction on the nonlinear regime of the TI by performing two-dimensional magnetohydrodynamic simulations. We present models with magnetic fields of different initial geometries and strengths, and compare them to hydrodynamic models with isotropic conduction. We find anisotropic conduction does not significantly alter the overall density and temperature statistics in the saturated state of the TI. However, it can strongly affect the shapes and sizes of cold clouds formed by the TI. For example, for uniform initial fields long filaments of cold gas are produced that are reminiscent ...

  2. Numerical Investigation of Characteristic of Anisotropic Thermal Conductivity of Natural Fiber Bundle with Numbered Lumens

    Directory of Open Access Journals (Sweden)

    Guan-Yu Zheng

    2014-01-01

    Full Text Available Natural fiber bundle like hemp fiber bundle usually includes many small lumens embedded in solid region; thus, it can present lower thermal conduction than that of conventional fibers. In the paper, characteristic of anisotropic transverse thermal conductivity of unidirectional natural hemp fiber bundle was numerically studied to determine the dependence of overall thermal property of the fiber bundle on that of the solid region phase. In order to efficiently predict its thermal property, the fiber bundle was embedded into an imaginary matrix to form a unit composite cell consisting of the matrix and the fiber bundle. Equally, another unit composite cell including an equivalent solid fiber was established to present the homogenization of the fiber bundle. Next, finite element thermal analysis implemented by ABAQUS was conducted in the two established composite cells by applying proper thermal boundary conditions along the boundary of unit cell, and influences of the solid region phase and the equivalent solid fiber on the composites were investigated, respectively. Subsequently, an optional relationship of thermal conductivities of the natural fiber bundle and the solid region was obtained by curve fitting technique. Finally, numerical results from the obtained fitted curves were compared with the analytic Hasselman-Johnson’s results and others to verify the present numerical model.

  3. Microscopic understanding of the anisotropic conductivity of PEDOT:PSS thin films

    NARCIS (Netherlands)

    Nardes, A.M.; Kemerink, M.; Janssen, R.A.J.; Bastiaansen, J.J.A.M.; Kiggen, N.M.M.; Langeveld, B.M.W.; Breemen, A.J.J.M. van; Kok, M.M. de

    2007-01-01

    The anisotropic conductivity of spin-coated poly(3,4- ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) thin films by temperature-dependent conductivity measurements, has been analyzed. A detailed 3D morphological model was derived from topographic scanning tunneling microscopy (STM) and cr

  4. Anisotropic mechanical properties of graphene sheets from molecular dynamics

    International Nuclear Information System (INIS)

    Anisotropic mechanical properties are observed for a sheet of graphene along different load directions. The anisotropic mechanical properties are attributed to the hexagonal structure of the unit cells of the graphene. Under the same tensile loads, the edge bonds bear larger load in the longitudinal mode (LM) than in the transverse mode (TM), which causes fracture sooner in LM than in TM. The Young's modulus and the third order elastic modulus for the LM are slightly larger than that for the TM. Simulation also demonstrates that, for both LM and TM, the loading and unloading stress-strain response curves overlap as long as the graphene is unloaded before the fracture point. This confirms that graphene sustains complete elastic and reversible deformation in the elongation process.

  5. Anisotropic diffusive transport: connecting microscopic scattering and macroscopic transport properties

    OpenAIRE

    Alerstam, Erik

    2013-01-01

    This work concerns the modeling of radiative transfer in anisotropic turbid media using diffusion theory. A theory for the relationship between microscopic scattering properties (i.e., an arbitrary differential scattering cross-section) and the macroscopic diffusion tensor, in the limit of independent scatterers, is presented. The theory is accompanied by a numerical method capable of performing the calculations. In addition, a boundary condition appropriate for modeling systems with anisotro...

  6. Anisotropic lattice thermal conductivity in chiral tellurium from first principles

    Science.gov (United States)

    Peng, Hua; Kioussis, Nicholas; Stewart, Derek A.

    2015-12-01

    Using ab initio based calculations, we have calculated the intrinsic lattice thermal conductivity of chiral tellurium. We show that the interplay between the strong covalent intrachain and weak van der Waals interchain interactions gives rise to the phonon band gap between the lower and higher optical phonon branches. The underlying mechanism of the large anisotropy of the thermal conductivity is the anisotropy of the phonon group velocities and of the anharmonic interatomic force constants (IFCs), where large interchain anharmonic IFCs are associated with the lone electron pairs. We predict that tellurium has a large three-phonon scattering phase space that results in low thermal conductivity. The thermal conductivity anisotropy decreases under applied hydrostatic pressure.

  7. Strain-Engineering the Anisotropic Electrical Conductance of Few-Layer Black Phosphorus

    Science.gov (United States)

    Fei, Ruixiang; Yang, Li

    2014-05-01

    Newly fabricated monolayer phosphorene and its few-layer structures are expected to be promising for electronic and optical applications because of their finite direct band gaps and sizable but anisotropic electronic mobility. By first-principles simulations, we show that this unique anisotropic conductance can be controlled by using simple strain conditions. With the appropriate biaxial or uniaxial strain, we can rotate the preferred conducting direction by 90 degrees. This will be of useful for exploring quantum Hall effects, and exotic electronic and mechanical applications based on phosphorene.

  8. Anisotropic Conductance of a Surface Quantum-Wire Array

    Science.gov (United States)

    Weitering, Hanno; Yoo, Kwonjae

    2001-03-01

    The Ga/Si(112)6x1 interface consists of a self-assembled, mesoscopic array of atomic Ga wires on a high-index Si(112) surface. The structural uniformity of this atomic-wire- or quantum-wire array is far superior to those created by nano-lithography or STM atom manipulation. The details of electron transport in these quantum wires should be very interesting. Si atoms also possess dangling bonds. Since the trivalent Ga atoms are threefold coordinated, their dangling bond orbitals are empty and hence, they should not contribute significantly to the conductivity. However, quasi one-dimensional metallic transport might be possible in the silicon dangling bonds because each dangling bond contributes one electron. These dangling bonds can form a quasi one-dimensional, half-filled electronic band. One of the interesting questions is whether this surface is indeed a quasi 1D metal or whether the Si chains undergo a Jahn-Teller or buckling distortion that opens up a band gap. We have measured the conductance of this mesoscopic wire array as a function of temperature parallel and perpendicular to the Ga chains. Transport measurements reveal a strong conductance anisotropy as expected. However, the conduction channels are orthogonal to the crystallographic chains. This counterintuitive result is in excellent agreement with electronic structure calculations by Ortega and Flores. The theoretical band structure was confirmed independently with photoemission spectroscopy.

  9. Effective Heat and Mass Transport Properties of Anisotropic Porous Ceria for Solar Thermochemical Fuel Generation

    OpenAIRE

    Sophia Haussener; Aldo Steinfeld

    2012-01-01

    High-resolution X-ray computed tomography is employed to obtain the exact 3D geometrical configuration of porous anisotropic ceria applied in solar-driven thermochemical cycles for splitting H2O and CO2. The tomography data are, in turn, used in direct pore-level numerical simulations for determining the morphological and effective heat/mass transport properties of porous ceria, namely: porosity, specific surface area, pore size distribution, extinction coefficient, thermal conductivity, conv...

  10. Growth of anisotropic gold nanostructures on conducting glass surfaces

    Indian Academy of Sciences (India)

    P R Sajanlal; T Pradeep

    2008-01-01

    In this paper, we describe a method for the growth of gold nanowires and nanoplates starting from a bilayer array of gold seeds, anchored on electrically conducting indium tin oxide (ITO) substrates. This is based on a seed-mediated growth approach, where the nanoparticles attached on the substrate through molecular linkages are converted to nanowires and nanoplates at certain cetyltrimethylammonium bromide (CTAB) concentration. Our modified approach can be used to make nanowires of several tens of micrometers length at a lower CTAB concentration of 0.1 M. The length of the nanowires can be varied by adjusting the time of the reaction. As the concentration of CTAB was increased to 0.25 M, the nanoparticles got converted to nanoplates. These Au nanoplates are (111) oriented and are aligned parallel to the substrate.

  11. Interconnection of multichannel polyimide electrodes using anisotropic conductive films (ACFs) for biomedical applications.

    Science.gov (United States)

    Baek, Dong-Hyun; Park, Ji Soo; Lee, Eun-Joong; Shin, SuJung; Moon, Jin-Hee; Pak, James Jungho; Lee, Sang-Hoon

    2011-05-01

    In this paper, we propose a method for interconnecting soft polyimide (PI) electrodes using anisotropic conductive films (ACFs). Reliable and automated bonding was achieved through development of a desktop thermocompressive bonding device that could simultaneously deliver appropriate temperatures and pressures to the interconnection area. The bonding conditions were optimized by changing the bonding temperature and bonding pressure. The electrical properties were characterized by measuring the contact resistance of the ACF bonding area, yielding a measure that was used to optimize the applied pressure and temperature. The optimal conditions consisted of applying a pressure of 4 kg f/cm(2) and a temperature of 180 °C for 20 s. Although ACF base bonding is widely used in industry (e.g., liquid crystal display manufacturing), this study constitutes the first trial of a biomedical application. We performed a preliminary in vivo biocompatibility investigation of ACF bonded area. Using the optimized temperature and pressure conditions, we interconnected a 40-channel PI multielectrode device for measuring electroencephalography (EEG) signals from the skulls of mice. The electrical properties of electrode were characterized by measuring the impedance. Finally, EEG signals were measured from the mice skulls using the fabricated devices to investigate suitability for application to biomedical devices.

  12. Interconnection of multichannel polyimide electrodes using anisotropic conductive films (ACFs) for biomedical applications.

    Science.gov (United States)

    Baek, Dong-Hyun; Park, Ji Soo; Lee, Eun-Joong; Shin, SuJung; Moon, Jin-Hee; Pak, James Jungho; Lee, Sang-Hoon

    2011-05-01

    In this paper, we propose a method for interconnecting soft polyimide (PI) electrodes using anisotropic conductive films (ACFs). Reliable and automated bonding was achieved through development of a desktop thermocompressive bonding device that could simultaneously deliver appropriate temperatures and pressures to the interconnection area. The bonding conditions were optimized by changing the bonding temperature and bonding pressure. The electrical properties were characterized by measuring the contact resistance of the ACF bonding area, yielding a measure that was used to optimize the applied pressure and temperature. The optimal conditions consisted of applying a pressure of 4 kg f/cm(2) and a temperature of 180 °C for 20 s. Although ACF base bonding is widely used in industry (e.g., liquid crystal display manufacturing), this study constitutes the first trial of a biomedical application. We performed a preliminary in vivo biocompatibility investigation of ACF bonded area. Using the optimized temperature and pressure conditions, we interconnected a 40-channel PI multielectrode device for measuring electroencephalography (EEG) signals from the skulls of mice. The electrical properties of electrode were characterized by measuring the impedance. Finally, EEG signals were measured from the mice skulls using the fabricated devices to investigate suitability for application to biomedical devices. PMID:21189231

  13. Anisotropic mechanical properties and Stone-Wales defects in graphene monolayer: A theoretical study

    Energy Technology Data Exchange (ETDEWEB)

    Fan, B.B. [School of Materials Science and Engineering, Zhengzhou University, Henan 450001 (China); Yang, X.B. [Department of Physics, South China University of Technology, Guangzhou 510640 (China); Zhang, R., E-mail: zhangray@zzu.edu.c [School of Materials Science and Engineering, Zhengzhou University, Henan 450001 (China); Zhengzhou Institute of Aeronautical Industry Management, Henan 450046 (China)

    2010-06-14

    We investigate the mechanical properties of graphene monolayer via the density functional theoretical (DFT) method. We find that the strain energies are anisotropic for the graphene under large strain. We attribute the anisotropic feature to the anisotropic sp{sup 2} hybridization in the hexagonal lattice. We further identify that the formation energies of Stone-Wales (SW) defects in the graphene monolayer are determined by the defect concentration and also the direction of applied tensile strain, correlating with the anisotropic feature.

  14. Interplay among Cooling, AGN Feedback and Anisotropic Conduction in the Cool Cores of Galaxy Clusters

    CERN Document Server

    Yang, H -Y K

    2015-01-01

    Feedback from the active galactic nuclei (AGN) is one of the most promising heating mechanisms to circumvent the cooling-flow problem in galaxy clusters. However, the role of thermal conduction remains unclear. Previous studies have shown that anisotropic thermal conduction in cluster cool cores (CC) could drive the heat-flux driven buoyancy instabilities (HBI) that re-orient the field lines in the azimuthal directions and isolate the cores from conductive heating from the outskirts. However, how the AGN interacts with the HBI is still unknown. To understand these interwined processes, we perform the first 3D magnetohydrodynamic (MHD) simulations of isolated CC clusters that include anisotropic conduction, radiative cooling, and AGN feedback. We find that: (1) For realistic magnetic field strengths in clusters, magnetic tension can suppress a significant portion of HBI-unstable modes and thus the HBI is either completely inhibited or significantly impaired, depending on the unknown magnetic field coherence le...

  15. Effects of anisotropic thermal conductivity in magnetohydrodynamics simulations of a reversed-field pinch.

    Science.gov (United States)

    Onofri, M; Malara, F; Veltri, P

    2010-11-19

    A compressible magnetohydrodynamics simulation of the reversed-field pinch is performed including anisotropic thermal conductivity. When the thermal conductivity is much larger in the direction parallel to the magnetic field than in the perpendicular direction, magnetic field lines become isothermal. As a consequence, as long as magnetic surfaces exist, a temperature distribution is observed displaying a hotter confined region, while an almost uniform temperature is produced when the magnetic field lines become chaotic. To include this effect in the numerical simulation, we use a multiple-time-scale analysis, which allows us to reproduce the effect of a large parallel thermal conductivity. The resulting temperature distribution is related to the existence of closed magnetic surfaces, as observed in experiments. The magnetic field is also affected by the presence of an anisotropic thermal conductivity. PMID:21231314

  16. Dipole estimation errors due to not incorporating anisotropic conductivities in realistic head models for EEG source analysis

    Energy Technology Data Exchange (ETDEWEB)

    Hallez, Hans; Staelens, Steven; Lemahieu, Ignace [Department of Electronics and Information Systems, Institute of Broadband Technology (IBBT) Medical Image and Signal Processing (MEDISIP), Ghent University, Sint-Pietersnieuwstraat 41, 9000 Ghent (Belgium)], E-mail: hans.hallez@ugent.be

    2009-10-21

    EEG source analysis is a valuable tool for brain functionality research and for diagnosing neurological disorders, such as epilepsy. It requires a geometrical representation of the human head or a head model, which is often modeled as an isotropic conductor. However, it is known that some brain tissues, such as the skull or white matter, have an anisotropic conductivity. Many studies reported that the anisotropic conductivities have an influence on the calculated electrode potentials. However, few studies have assessed the influence of anisotropic conductivities on the dipole estimations. In this study, we want to determine the dipole estimation errors due to not taking into account the anisotropic conductivities of the skull and/or brain tissues. Therefore, head models are constructed with the same geometry, but with an anisotropically conducting skull and/or brain tissue compartment. These head models are used in simulation studies where the dipole location and orientation error is calculated due to neglecting anisotropic conductivities of the skull and brain tissue. Results show that not taking into account the anisotropic conductivities of the skull yields a dipole location error between 2 and 25 mm, with an average of 10 mm. When the anisotropic conductivities of the brain tissues are neglected, the dipole location error ranges between 0 and 5 mm. In this case, the average dipole location error was 2.3 mm. In all simulations, the dipole orientation error was smaller than 10 deg. We can conclude that the anisotropic conductivities of the skull have to be incorporated to improve the accuracy of EEG source analysis. The results of the simulation, as presented here, also suggest that incorporation of the anisotropic conductivities of brain tissues is not necessary. However, more studies are needed to confirm these suggestions.

  17. Dipole estimation errors due to not incorporating anisotropic conductivities in realistic head models for EEG source analysis

    International Nuclear Information System (INIS)

    EEG source analysis is a valuable tool for brain functionality research and for diagnosing neurological disorders, such as epilepsy. It requires a geometrical representation of the human head or a head model, which is often modeled as an isotropic conductor. However, it is known that some brain tissues, such as the skull or white matter, have an anisotropic conductivity. Many studies reported that the anisotropic conductivities have an influence on the calculated electrode potentials. However, few studies have assessed the influence of anisotropic conductivities on the dipole estimations. In this study, we want to determine the dipole estimation errors due to not taking into account the anisotropic conductivities of the skull and/or brain tissues. Therefore, head models are constructed with the same geometry, but with an anisotropically conducting skull and/or brain tissue compartment. These head models are used in simulation studies where the dipole location and orientation error is calculated due to neglecting anisotropic conductivities of the skull and brain tissue. Results show that not taking into account the anisotropic conductivities of the skull yields a dipole location error between 2 and 25 mm, with an average of 10 mm. When the anisotropic conductivities of the brain tissues are neglected, the dipole location error ranges between 0 and 5 mm. In this case, the average dipole location error was 2.3 mm. In all simulations, the dipole orientation error was smaller than 10 deg. We can conclude that the anisotropic conductivities of the skull have to be incorporated to improve the accuracy of EEG source analysis. The results of the simulation, as presented here, also suggest that incorporation of the anisotropic conductivities of brain tissues is not necessary. However, more studies are needed to confirm these suggestions.

  18. A multipoint flux approximation of the steady-state heat conduction equation in anisotropic media

    KAUST Repository

    Salama, Amgad

    2013-03-20

    In this work, we introduce multipoint flux (MF) approximation method to the problem of conduction heat transfer in anisotropic media. In such media, the heat flux vector is no longer coincident with the temperature gradient vector. In this case, thermal conductivity is described as a second order tensor that usually requires, at least, six quantities to be fully defined in general three-dimensional problems. The two-point flux finite differences approximation may not handle such anisotropy and essentially more points need to be involved to describe the heat flux vector. In the framework of mixed finite element method (MFE), the MFMFE methods are locally conservative with continuous normal fluxes. We consider the lowest order Brezzi-Douglas-Marini (BDM) mixed finite element method with a special quadrature rule that allows for nodal velocity elimination resulting in a cell-centered system for the temperature. We show comparisons with some analytical solution of the problem of conduction heat transfer in anisotropic long strip. We also consider the problem of heat conduction in a bounded, rectangular domain with different anisotropy scenarios. It is noticed that the temperature field is significantly affected by such anisotropy scenarios. Also, the technique used in this work has shown that it is possible to use the finite difference settings to handle heat transfer in anisotropic media. In this case, heat flux vectors, for the case of rectangular mesh, generally require six points to be described. Copyright © 2013 by ASME.

  19. The anisotropic compressive mechanical properties of the rabbit patellar tendon.

    Science.gov (United States)

    Williams, Lakiesha N; Elder, Steven H; Bouvard, J L; Horstemeyer, M F

    2008-01-01

    In this study, we examine the transverse and longitudinal compressive mechanical behavior of the rabbit patellar tendon. The anisotropic compressive properties are of interest, because compression occurs where the tendon attaches to bone and where the tendon wraps around bone leading to the development of fibro-cartilaginous matrices. We quantified the time dependent viscoelastic and anisotropic behavior of the tendon under compression. For both orientations, sections of patellar tendon were drawn from mature male white New Zealand rabbits in preparation for testing. The tendons were sequentially compressed to 40% strain at strain rates of 0.1, 1 and 10% strain(s) using a computer-controlled stepper motor driven device under physiological conditions. Following monotonic loading, the tendons were subjected to stress relaxation. The tendon equilibrium compressive modulus was quantified to be 19.49+/-11.46 kPa for the transverse direction and 1.11+/-0.57 kPa for the longitudinal direction. The compressive modulus at applied strain rates of 0.1, 1 and 10% strain(s) in the transverse orientation were 13.48+/-2.31, 18.24+/-4.58 and 20.90+/-8.60 kPa, respectively. The compressive modulus at applied strain rates of 0.1, 1 and 10% strain/s in the longitudinal orientation were 0.19+/-0.11, 1.27+/-1.38 and 3.26+/-3.49 kPa, respectively. The modulus values were almost significantly different for the examination of the effect of orientation on the equilibrium modulus (p=0.054). Monotonic loading of the tendon showed visual differences of the strain rate dependency; however, no significant difference was shown in the statistical analysis of the effect of strain rate on compressive modulus. The statistical analysis of the effect of orientation on compressive modulus showed a significant difference. The difference shown in the orientation analysis validated the anisotropic nature of the tendon. PMID:19065006

  20. Strongly Anisotropic Thermal and Electrical Conductivities of Self-assembled Silver Nanowire Network

    OpenAIRE

    Cheng, Zhe; Han, Meng; Yuan, Pengyu; Xu, Shen; Cola, Baratunde A.; Wang, Xinwei

    2016-01-01

    Heat dissipation issues are the emerging challenges in the field of flexible electronics. Thermal management of flexible electronics creates a demand for flexible materials with highly anisotropic thermal conductivity, which work as heat spreaders to remove excess heat in the in-plane direction and as heat shields to protect human skin or device components under them from heating. This study proposes a self-assembled silver nanowire network with high thermal and electrical anisotropy with the...

  1. KINEMATIC WAVE PROPERTIES OF ANISOTROPIC DYNAMICS MODEL FOR TRAFFIC FLOW

    Institute of Scientific and Technical Information of China (English)

    姜锐; 吴清松; 朱祚金

    2002-01-01

    The analyses of kinematic wave properties of a new dynamics model for traffic flow are carried out. The model does not exhibit the problem that one characteristic speed is always greater than macroscopic traffic speed, and therefore satisfies the requirement that traffic flow is anisotropic. Linear stability analysis shows that the model is stable under certain condition and the condition is obtained. The analyses also indicate that the model has a hierarchy of first-and second-order waves, and allows the existence of both smooth traveling wave and shock wave. However, the model has a distinctive criterion of shock wave compared with other dynamics models, and the distinction makes the model more realistic in dealing with some traffic problems such as wrong-way travel analysis.

  2. Anisotropic electrical conductivity tensor of granular high-Tc superconductors in an effective-medium theory

    International Nuclear Information System (INIS)

    The earliest high-Tc oxide superconductors were generally studied in the form of porous polycrystalline pellets. As material preparation technology improved, resulting in samples with orientational order and a smaller concentration of impurity phases, the effects of granular behaviour did not disappear. In both the cases of disordered and partially-ordered structures, an important question arises as to how to interpret measured low-field resistivities in terms of the underlying anisotropic single-crystal values. This paper provides the answer to this question within the context of an effective-medium theory. The authors version of the effective-medium approximation attempts to describe the electrical properties of an inhomogeneous medium, consisting of a mixture of several types of anisotropic polycrystals with different degrees of orientational order. (author)

  3. Unusual Properties of Anisotropic Hall Gas: Implication to Metrology of the Integer Quantum Hall Effect

    OpenAIRE

    Ishikawa, K; Maeda, N.

    2001-01-01

    Physical properties of anisotropic compressible quantum Hall states and their implications to integer quantum Hall effect are studied based on a mean field theory on the von Neumann lattice. It is found that the Hall gas has unusual thermodynamic properties such as negative pressure and negative compressibility and unusual transport properties. Transport properties and density profile of Hall gas states at half fillings agree with those of anisotropic states discovered experimentally in highe...

  4. Thermal conductivities of sub-micron Bi2Te3 films sputtered on anisotropic substrates

    Science.gov (United States)

    Yan, Dan; Wu, Ping; Zhang, Shiping; Pei, Yili; Yang, Fan; Wang, Li

    2016-07-01

    Approximately 450 nm thick Bi2Te3 films were deposited on flat Al2O3 substrate and nanochannel alumina (NCA) templates with different pore diameters through radio-frequency magnetron sputtering. The structure and morphology of Bi2Te3 films were investigated by x-ray diffraction and field-emission scanning electron microscopy. Moreover, the thermal conductivities of the films deposited on anisotropic substrates were evaluated by micro-Raman method combined with numerical simulation and optimization conducted by COMSOL Multiphysics. The thermal conductivities of Bi2Te3 films deposited on NCA templates with discontinuous Φ20 and Φ100 nm pores and flat Al2O3 substrate were 0.80, 0.99 and 1.54 Wm‑1 K‑1, respectively. The lower thermal conductivities of Bi2Te3 films deposited on NCA templates are attributed to much smaller grain size, bottom porous layers, and rougher surfaces through analysis.

  5. Anisotropic electronic, mechanical, and optical properties of monolayer WTe2

    Science.gov (United States)

    Torun, E.; Sahin, H.; Cahangirov, S.; Rubio, A.; Peeters, F. M.

    2016-02-01

    Using first-principles calculations, we investigate the electronic, mechanical, and optical properties of monolayer WTe2. Atomic structure and ground state properties of monolayer WTe2 (Td phase) are anisotropic which are in contrast to similar monolayer crystals of transition metal dichalcogenides, such as MoS2, WS2, MoSe2, WSe2, and MoTe2, which crystallize in the H-phase. We find that the Poisson ratio and the in-plane stiffness is direction dependent due to the symmetry breaking induced by the dimerization of the W atoms along one of the lattice directions of the compound. Since the semimetallic behavior of the Td phase originates from this W-W interaction (along the a crystallographic direction), tensile strain along the dimer direction leads to a semimetal to semiconductor transition after 1% strain. By solving the Bethe-Salpeter equation on top of single shot G0W0 calculations, we predict that the absorption spectrum of Td-WTe2 monolayer is strongly direction dependent and tunable by tensile strain.

  6. Anisotropic thermoelectric properties in layered complex nitrides with α-NaFeO2-type structure

    Science.gov (United States)

    Ohkubo, Isao; Mori, Takao

    2016-10-01

    Electronic structures and thermoelectric transport properties of α-NaFeO2-type d0-electron layered complex nitrides AMN2 (A = Sr or Na; M = Zr, Hf, Nb, Ta) were evaluated using density-functional theory and Boltzmann theory calculations. Despite the layered crystal structure, all materials had three-dimensional electronic structures. Sr(Zr, Hf)N2 exhibited isotropic electronic transport properties because of the contribution of the Sr 4d orbitals to the conduction band minimums (CBMs) in addition to that of the Zr 4d (Hf 5d) orbitals. Na(Nb,Ta)N2 showed weak anisotropic electronic transport properties due to the main contribution of the Nb 4d (Ta 5d) and N 2p orbitals to the CBMs and no contribution of the Na orbitals.

  7. Anisotropic vanadium dioxide sculptured thin films with superior thermochromic properties

    Science.gov (United States)

    Sun, Yaoming; Xiao, Xiudi; Xu, Gang; Dong, Guoping; Chai, Guanqi; Zhang, Hua; Liu, Pengyi; Zhu, Hanmin; Zhan, Yongjun

    2013-01-01

    VO2 (M) STF through reduction of V2O5 STF was prepared. The results illustrate that V2O5 STF can be successfully obtained by oblique angle thermal evaporation technique. After annealing at 550°C/3 min, the V2O5 STF deposited at 85° can be easily transformed into VO2 STF with slanted columnar structure and superior thermochromic properties. After deposition SiO2 antireflective layer, Tlum of VO2 STF is enhanced 26% and ΔTsol increases 60% compared with that of normal VO2 thin films. Due to the anisotropic microstructure of VO2 STF, angular selectivity transmission of VO2 STF is observed and the solar modulation ability is further improved from 7.2% to 8.7% when light is along columnar direction. Moreover, the phase transition temperature of VO2 STF can be depressed into 54.5°C without doping. Considering the oblique incidence of sunlight on windows, VO2 STF is more beneficial for practical application as smart windows compared with normal homogenous VO2 thin films. PMID:24067743

  8. Electron beam curing of acrylated epoxy resins for anisotropic conductive film application

    International Nuclear Information System (INIS)

    Radiation curable acrylated epoxy oligomer was found to be an effective resin system for application to electron beams (EB) on curing of anisotropic conducting film. To study curing degree as a function of EB dosage, we irradiated bisphenol-A type acrylate epoxy oligomer samples with doses of 5 to 600 kGy of EB. To investigate the effect of a metal barrier for potential industrial application, a 3 mm thick Al plate was placed in front of the samples, and the curing parameters were compared with the ones irradiated without an Al plate. As the dosage of the EB irradiation was increased, the glass transition temperature of the sample ranged from 46.8 to 62.2 °C for the epoxy composites without placing an Al plate, and from 46.4 to 64.1 °C for their counterparts with a 3 mm thick Al plate. These results confirm that enhancement of the curing degree with increasing EB irradiation is possible even in the presence of a metal plate. The scanning electron microscope images of the fracture surfaces are presented as evidence of the morphological changes of the EB cured epoxy samples. - Highlights: ► Acrylated epoxy oligomer was cured by irradiation of the electron beam. ► Curing degree was increased with increasing dosage of the electron beam. ► Electron beam can be used for the bonding of anisotropic conducting films

  9. Probing Anisotropic Surface Properties of Molybdenite by Direct Force Measurements.

    Science.gov (United States)

    Lu, Zhenzhen; Liu, Qingxia; Xu, Zhenghe; Zeng, Hongbo

    2015-10-27

    Probing anisotropic surface properties of layer-type mineral is fundamentally important in understanding its surface charge and wettability for a variety of applications. In this study, the surface properties of the face and the edge surfaces of natural molybdenite (MoS2) were investigated by direct surface force measurements using atomic force microscope (AFM). The interaction forces between the AFM tip (Si3N4) and face or edge surface of molybdenite were measured in 10 mM NaCl solutions at various pHs. The force profiles were well-fitted with classical DLVO (Derjaguin-Landau-Verwey-Overbeek) theory to determine the surface potentials of the face and the edge surfaces of molybdenite. The surface potentials of both the face and edge surfaces become more negative with increasing pH. At neutral and alkaline conditions, the edge surface exhibits more negative surface potential than the face surface, which is possibly due to molybdate and hydromolybdate ions on the edge surface. The point of zero charge (PZC) of the edge surface was determined around pH 3 while PZC of the face surface was not observed in the range of pH 3-11. The interaction forces between octadecyltrichlorosilane-treated AFM tip (OTS-tip) and face or edge surface of molybdenite were also measured at various pHs to study the wettability of molybdenite surfaces. An attractive force between the OTS-tip and the face surface was detected. The force profiles were well-fitted by considering DLVO forces and additional hydrophobic force. Our results suggest the hydrophobic feature of the face surface of molybdenite. In contrast, no attractive force between the OTS-tip and the edge surface was detected. This is the first study in directly measuring surface charge and wettability of the pristine face and edge surfaces of molybdenite through surface force measurements. PMID:26434695

  10. Anisotropic and inhomogeneous thermal conduction in suspended thin-film polycrystalline diamond

    Science.gov (United States)

    Sood, Aditya; Cho, Jungwan; Hobart, Karl D.; Feygelson, Tatyana I.; Pate, Bradford B.; Asheghi, Mehdi; Cahill, David G.; Goodson, Kenneth E.

    2016-05-01

    While there is a great wealth of data for thermal transport in synthetic diamond, there remains much to be learned about the impacts of grain structure and associated defects and impurities within a few microns of the nucleation region in films grown using chemical vapor deposition. Measurements of the inhomogeneous and anisotropic thermal conductivity in films thinner than 10 μm have previously been complicated by the presence of the substrate thermal boundary resistance. Here, we study thermal conduction in suspended films of polycrystalline diamond, with thicknesses ranging between 0.5 and 5.6 μm, using time-domain thermoreflectance. Measurements on both sides of the films facilitate extraction of the thickness-dependent in-plane ( κ r ) and through-plane ( κ z ) thermal conductivities in the vicinity of the coalescence and high-quality regions. The columnar grain structure makes the conductivity highly anisotropic, with κ z being nearly three to five times as large as κ r , a contrast higher than that reported previously for thicker films. In the vicinity of the high-quality region, κ r and κ z range from 77 ± 10 W/m-K and 210 ± 50 W/m-K for the 1 μm thick film to 130 ± 20 W/m-K and 710 ± 120 W/m-K for the 5.6 μm thick film, respectively. The data are interpreted using a model relating the anisotropy to the scattering on the boundaries of columnar grains and the evolution of the grain size considering their nucleation density and spatial rate of growth. This study aids in the reduction in the near-interfacial resistance of diamond films and efforts to fabricate diamond composites with silicon and GaN for power electronics.

  11. Effects of spark plasma sintering conditions on the anisotropic thermoelectric properties of bismuth antimony telluride

    DEFF Research Database (Denmark)

    Han, Li; Hegelund Spangsdorf, Steeven; Van Nong, Ngo;

    2016-01-01

    -rate) using spark plasma sintering (SPS). The effects of SPS conditions on the anisotropic thermoelectric properties and microstructure evolutions were systematically investigated. The change of sintering temperature showed stronger influence than other sintering parameters to the resulting thermoelectric...

  12. A Study on the Nanofiber-Sheet Anisotropic Conductive Films (NS-ACFs) for Ultra-Fine-Pitch Interconnection Applications

    Science.gov (United States)

    Lee, Sang-Hoon; Paik, Kyung-Wook

    2016-09-01

    Nanofiber-sheet anisotropic conductive films (NS-ACFs) were invented to overcome the limitations of high joint resistance and short-circuit issues of ultra-fine-pitch interconnections. The NS-ACFs have great advantages in terms of suppressing conductive particle movement during the flip-chip bonding process. In a 20-μm ultra-fine-pitch with 7-μm bump spacing ultra-fine-pitch chip-on-glass assembly, suppression effects of conductive particle movement were significantly improved by using the NS-ACFs because an unmelted NS inside the ACFs suppressed the mobility of conductive particles so that they would not flow out during the bonding process. The NS-ACFs could significantly increase the capture rate of conductive particles from 31% up to 81% compared to conventional ACFs. Moreover, excellent electrical contact properties were obtained without melting the nanofiber material which was essential for the conventional nanofiber ACFs. The NS-ACFs are promising interconnection materials for ultra-fine-pitch packaging applications.

  13. Effective Heat and Mass Transport Properties of Anisotropic Porous Ceria for Solar Thermochemical Fuel Generation

    Directory of Open Access Journals (Sweden)

    Sophia Haussener

    2012-01-01

    Full Text Available High-resolution X-ray computed tomography is employed to obtain the exact 3D geometrical configuration of porous anisotropic ceria applied in solar-driven thermochemical cycles for splitting H2O and CO2. The tomography data are, in turn, used in direct pore-level numerical simulations for determining the morphological and effective heat/mass transport properties of porous ceria, namely: porosity, specific surface area, pore size distribution, extinction coefficient, thermal conductivity, convective heat transfer coefficient, permeability, Dupuit-Forchheimer coefficient, and tortuosity and residence time distributions. Tailored foam designs for enhanced transport properties are examined by means of adjusting morphologies of artificial ceria samples composed of bimodal distributed overlapping transparent spheres in an opaque medium.

  14. Numerical simulations of buoyancy instabilities in galaxy cluster plasmas with cosmic rays and anisotropic thermal conduction

    CERN Document Server

    Rasera, Yann

    2008-01-01

    In clusters of galaxies, the specific entropy of intracluster plasma increases outwards. Nevertheless, a number of recent studies have shown that the intracluster medium is subject to buoyancy instabilities due to the effects of cosmic rays and anisotropic thermal conduction. In this paper, we present a new numerical algorithm for simulating such instabilities. This numerical method treats the cosmic rays as a fluid, accounts for the diffusion of heat and cosmic rays along magnetic field lines, and enforces the condition that the temperature and cosmic-ray pressure remain positive. We carry out several tests to ensure the accuracy of the code, including the detailed matching of analytic results for the eigenfunctions and growth rates of linear buoyancy instabilities. This numerical scheme will be useful for simulating convection driven by cosmic-ray buoyancy in galaxy cluster plasmas and may also be useful for other applications, including fusion plasmas, the interstellar medium, and supernovae remnants.

  15. Three discontinuous Galerkin schemes for the anisotropic heat conduction equation on non-aligned grids

    CERN Document Server

    Held, Markus; Steigmeir, Andreas

    2015-01-01

    We present and discuss three discontinuous Galerkin (dG) discretizations for the anisotropic heat conduction equation on non-aligned cylindrical grids. Our most favourable scheme relies on a self-adjoint local dG (LDG) discretization of the elliptic operator. It conserves the energy exactly and converges with arbitrary order. The pollution by numerical perpendicular heat fluxes degrades with superconvergence rates. We compare this scheme with aligned schemes that are based on the flux-coordinate independent approach for the discretization of parallel derivatives. Here, the dG method provides the necessary interpolation. The first aligned discretization can be used in an explicit time-integrator. However, the scheme violates conservation of energy and shows up stagnating convergence rates for very high resolutions. We overcome this partly by using the adjoint of the parallel derivative operator to construct a second self-adjoint aligned scheme. This scheme preserves energy, but reveals unphysical oscillations ...

  16. Reliability of flip-chip bonded RFID die using anisotropic conductive paste hybrid material

    Institute of Scientific and Technical Information of China (English)

    Jun-Sik LEE; Jun-Ki KIM; Mok-Soon KIM; Namhyun KANG; Jong-Hyun LEE

    2011-01-01

    A reliability of flip-chip bonded die as a function of anisotropic conductive paste (ACP) hybrid materials. bonding conditions, and antenna pattern materials was investigated during the assembly of radio frequency identification(RFID) inlay. The optimization condition for flip-chip bonding was determined from the behavior of bonding strength. Under the optimized condition,the shear strength for the antenna printed with paste-type Ag ink was larger than that for Cu antenna. Furthermore, an identification distance was varied from the antenna materials. Comparing with the Ag antenna pattern, the as-bonded die on Cu antenna showed a larger distance of identification, However, the long-term reliability of inlay using the Cu antenna was decreased significantly as a function of aging time at room temperature because of the bended shape of Cu antenna formed during the flip-chip bonding process.

  17. Pulse splitting in nonlinear media with anisotropic dispersion properties

    DEFF Research Database (Denmark)

    Bergé, L.; Juul Rasmussen, J.; Schmidt, M.R.

    1998-01-01

    to a singularity in the transverse plane. Instead, the pulse spreads out along the direction of negative dispersion and splits up into small-scale cells, which may undergo further splitting events. The analytical results are supported by direct numerical solutions of the three dimensional cubic Schrodinger......The nonlinear self-focusing of beams in media with anisotropic (mix-signed) dispersion is investigated. Theoretical predictions employing virial-type arguments and self-similar techniques suggest that a pulse propagating in a nonlinear medium with anisotropic dispersion will not collapse...

  18. Transport Properties of Anisotropic Polar Fluids: 1. Quadrupolar Interaction

    CERN Document Server

    Fernandez, G A; Hasse, H

    2009-01-01

    Equilibrium molecular dynamics simulation and the Green-Kubo formalism were used to calculate self-diffusion coefficient, shear viscosity,and thermal conductivity for 30 different quadrupolar two-center Lennard-Jones fluids along the bubble line and in the homogeneous liquid. It was systematically investigated how anisotropy, i.e. elongation, and quadrupole momentum influence the transport properties. The reduced elongation L* was varied from 0 to 0.8 and the reduced squared quadrupole momentum Q*2 from 0 to 4, i.e. in the entire range in which parameters for real fluids are expected. The statistical uncertainty of the reported data varies with transport property, for self-diffusion coefficient data the error bars are typically lower than 3 %, for shear viscosity and thermal conductivity they are about 8 and 12 %, respectively.

  19. Transport Properties of Anisotropic Polar Fluids: 1. Quadrupolar Interaction

    OpenAIRE

    Fernandez, G. A.; Vrabec, J.; Hasse, H.

    2009-01-01

    Equilibrium molecular dynamics simulation and the Green-Kubo formalism were used to calculate self-diffusion coefficient, shear viscosity,and thermal conductivity for 30 different quadrupolar two-center Lennard-Jones fluids along the bubble line and in the homogeneous liquid. It was systematically investigated how anisotropy, i.e. elongation, and quadrupole momentum influence the transport properties. The reduced elongation L* was varied from 0 to 0.8 and the reduced squared quadrupole moment...

  20. 电子封装中各向异性导电胶的可靠性%Reliability aspects of electronics packaging technology using anisotropic conductive adhesives

    Institute of Scientific and Technical Information of China (English)

    刘建影; 路秀真; 曹立强

    2007-01-01

    Anisotropic conductive adhesive technology for electronics packaging and interconnect application has significantly been developed during the last few years. It is time to make a summary of what has been done in this field. The present paper reviews the technology development, especially from the reliability point of view. It is pointed out that anisotropic conductive adhesives are now widely used in many applications and the reliability data and models have been developed to a large extent for anisotropic conductive adhesives in various applications.

  1. Measurement of the anisotropic thermal conductivity of molybdenum disulfide by the time-resolved magneto-optic Kerr effect

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Jun, E-mail: junliu@illinois.edu; Choi, Gyung-Min; Cahill, David G. [Department of Materials Science and Engineering and Materials Research Laboratory, University of Illinois, Urbana, Illinois 61801 (United States)

    2014-12-21

    We use pump-probe metrology based on the magneto-optic Kerr effect to measure the anisotropic thermal conductivity of (001)-oriented MoS{sub 2} crystals. A ≈20 nm thick CoPt multilayer with perpendicular magnetization serves as the heater and thermometer in the experiment. The low thermal conductivity and small thickness of the CoPt transducer improve the sensitivity of the measurement to lateral heat flow in the MoS{sub 2} crystal. The thermal conductivity of MoS{sub 2} is highly anisotropic with basal-plane thermal conductivity varying between 85–110 W m{sup -1} K{sup -1} as a function of laser spot size. The basal-plane thermal conductivity is a factor of ≈50 larger than the c-axis thermal conductivity, 2.0±0.3 W m{sup -1} K{sup -1}.

  2. Growth and anisotropic transport properties of self-assembled InAs nanostructures in InP

    Energy Technology Data Exchange (ETDEWEB)

    Bierwagen, O.

    2007-12-20

    Self-assembled InAs nanostructures in InP, comprising quantum wells, quantum wires, and quantum dots, are studied in terms of their formation and properties. In particular, the structural, optical, and anisotropic transport properties of the nanostructures are investigated. The focus is a comprehending exploration of the anisotropic in-plane transport in large ensembles of laterally coupled InAs nanostructures. The self-assembled Stranski-Krastanov growth of InAs nanostructures is studied by gas-source molecular beam epitaxy on both nominally oriented and vicinal InP(001). Optical polarization of the interband transitions arising from the nanostructure type is demonstrated by photoluminescence and transmission spectroscopy. The experimentally convenient four-contact van der Pauw Hall measurement of rectangularly shaped semiconductors, usually applied to isotropic systems, is extended to yield the anisotropic transport properties. Temperature dependent transport measurements are performed in large ensembles of laterally closely spaced nanostructures. The transport of quantum wire-, quantum dash- and quantum dot containing samples is highly anisotropic with the principal axes of conductivity aligned to the <110> directions. The direction of higher mobility is [ anti 110], which is parallel to the direction of the quantum wires. In extreme cases, the anisotropies exceed 30 for electrons, and 100 for holes. The extreme anisotropy for holes is due to diffusive transport through extended states in the [ anti 110], and hopping transport through laterally localized states in the [110] direction, within the same sample. A novel 5-terminal electronic switching device based on gate-controlled transport anisotropy is proposed. The gate-control of the transport anisotropy in modulation-doped, self-organized InAs quantum wires embedded in InP is demonstrated. (orig.)

  3. Growth and anisotropic transport properties of self-assembled InAs nanostructures in InP

    International Nuclear Information System (INIS)

    Self-assembled InAs nanostructures in InP, comprising quantum wells, quantum wires, and quantum dots, are studied in terms of their formation and properties. In particular, the structural, optical, and anisotropic transport properties of the nanostructures are investigated. The focus is a comprehending exploration of the anisotropic in-plane transport in large ensembles of laterally coupled InAs nanostructures. The self-assembled Stranski-Krastanov growth of InAs nanostructures is studied by gas-source molecular beam epitaxy on both nominally oriented and vicinal InP(001). Optical polarization of the interband transitions arising from the nanostructure type is demonstrated by photoluminescence and transmission spectroscopy. The experimentally convenient four-contact van der Pauw Hall measurement of rectangularly shaped semiconductors, usually applied to isotropic systems, is extended to yield the anisotropic transport properties. Temperature dependent transport measurements are performed in large ensembles of laterally closely spaced nanostructures. The transport of quantum wire-, quantum dash- and quantum dot containing samples is highly anisotropic with the principal axes of conductivity aligned to the directions. The direction of higher mobility is [ anti 110], which is parallel to the direction of the quantum wires. In extreme cases, the anisotropies exceed 30 for electrons, and 100 for holes. The extreme anisotropy for holes is due to diffusive transport through extended states in the [ anti 110], and hopping transport through laterally localized states in the [110] direction, within the same sample. A novel 5-terminal electronic switching device based on gate-controlled transport anisotropy is proposed. The gate-control of the transport anisotropy in modulation-doped, self-organized InAs quantum wires embedded in InP is demonstrated. (orig.)

  4. Quasielastic Light Scattering Measurements of the Anisotropic Mechanical Properties of a Polymer Nematic Liquid Crystal.

    Science.gov (United States)

    Taratuta, Victor Gregory

    An experimental investigation of macroscopic mechanical properties of a polymer nematic liquid crystal was conducted on nematic solutions formed from rigid or semiflexible main chain polymers that are fully extended in a solution. The particular system under investigation is a poly-(gamma) -benzyl glutamate (PBG) which belongs to a class of synthetic polypeptides. Quasielastic Rayleigh light scattering on well aligned nematic single crystals of PBG was used to measure the elastic constants and the anisotropic viscosities as a function of concentration. The elastic constants are measured from the intensity of the scattered light which is determined by the amplitude of thermally excited director fluctuations. That amplitude depends on the energy of the fluctuation which is proportional to the appropriate elastic constant. The viscosities associated with the elastic deformation modes are computed from the characteristic relaxation times of the fluctuations by measuring their temporal autocorrelation function. The splay and bend elastic constants were found to be very similar in magnitude; both showed a linear dependence on concentration. The twist elastic constant was much smaller than either splay or bend and showed only a weak concentration dependence. Four out of five independent Leslie viscosities were measured (except the elongational flow viscosity (alpha)(,1)). The viscosities were found to exhibit very large anisotropies. Different types of viscosities showed distinctly different patterns of concentration dependence. (gamma)(,1) and (eta)(,c) were quadratic in concentration, (eta)(,a) was linear in concentration, and (eta)(,b) did not show any strong concentration dependence. The viscosity data indicate that even at a moderate length to diameter ratio studied (L/D - 30), the PBG approaches a behavior predicted for a system composed of infinitely long molecular chains. The concentration dependence data for the elastic constants and the anisotropic viscosities

  5. Evaluation of a multi-electrode bioimpedance spectroscopy tensor probe to detect the anisotropic conductivity spectra of biological tissues

    International Nuclear Information System (INIS)

    This paper presents bioimpedance spectroscopy measurements of anisotropic tissues using a 16 electrode probe and reconstruction method of estimating the anisotropic impedance spectrum in a local region just underneath the center of the probe. This may enable in-vivo surface bioimpedance measurements with similar performance to the ex-vivo gold standard that requires excising and placing the entire tissue sample in a unit measurement cell with uniform electric field. The multiple surface electrodes enable us to create a focused current pattern so that the resulting measured voltage is more sensitive to a local region and less sensitive to other areas. This is exploited in a reconstruction method to provide improved bioimpedance and anisotropy measurements. In this paper, we describe the current pattern for localized electrical energy concentration, performance with the spring loaded pin electrodes, data calibration and experimental results on anisotropic agar phantoms and different tissue types. The anisotropic conductivity spectra are able to differentiate insulating films of different thickness and detect their orientation. Bioimpedance spectra of biological tissues are in agreement with published data and reference instruments. The anisotropy expressed as the ratio of eigenvalues and the orientation of eigenfunctions were reconstructed at 45° intervals. This information is used to predict the underlying anisotropy of the region under the probe. Tissue measurements clearly demonstrate the expected higher anisotropy of muscle tissue compared to liver tissue and spectral changes. (paper)

  6. Evaluation of a multi-electrode bioimpedance spectroscopy tensor probe to detect the anisotropic conductivity spectra of biological tissues

    Science.gov (United States)

    Karki, Bishal; Wi, Hun; McEwan, Alistair; Kwon, Hyeuknam; In Oh, Tong; Woo, Eung Je; Seo, Jin Keun

    2014-07-01

    This paper presents bioimpedance spectroscopy measurements of anisotropic tissues using a 16 electrode probe and reconstruction method of estimating the anisotropic impedance spectrum in a local region just underneath the center of the probe. This may enable in-vivo surface bioimpedance measurements with similar performance to the ex-vivo gold standard that requires excising and placing the entire tissue sample in a unit measurement cell with uniform electric field. The multiple surface electrodes enable us to create a focused current pattern so that the resulting measured voltage is more sensitive to a local region and less sensitive to other areas. This is exploited in a reconstruction method to provide improved bioimpedance and anisotropy measurements. In this paper, we describe the current pattern for localized electrical energy concentration, performance with the spring loaded pin electrodes, data calibration and experimental results on anisotropic agar phantoms and different tissue types. The anisotropic conductivity spectra are able to differentiate insulating films of different thickness and detect their orientation. Bioimpedance spectra of biological tissues are in agreement with published data and reference instruments. The anisotropy expressed as the ratio of eigenvalues and the orientation of eigenfunctions were reconstructed at 45° intervals. This information is used to predict the underlying anisotropy of the region under the probe. Tissue measurements clearly demonstrate the expected higher anisotropy of muscle tissue compared to liver tissue and spectral changes.

  7. Evolution, Interaction, and Intrinsic Properties of Dislocations in Intermetallics: Anisotropic 3D Dislocation Dynamics Approach

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Qian [Iowa State Univ., Ames, IA (United States)

    2008-01-01

    The generation, motion, and interaction of dislocations play key roles during the plastic deformation process of crystalline solids. 3D Dislocation Dynamics has been employed as a mesoscale simulation algorithm to investigate the collective and cooperative behavior of dislocations. Most current research on 3D Dislocation Dynamics is based on the solutions available in the framework of classical isotropic elasticity. However, due to some degree of elastic anisotropy in almost all crystalline solids, it is very necessary to extend 3D Dislocation Dynamics into anisotropic elasticity. In this study, first, the details of efficient and accurate incorporation of the fully anisotropic elasticity into 3D discrete Dislocation Dynamics by numerically evaluating the derivatives of Green's functions are described. Then the intrinsic properties of perfect dislocations, including their stability, their core properties and disassociation characteristics, in newly discovered rare earth-based intermetallics and in conventional intermetallics are investigated, within the framework of fully anisotropic elasticity supplemented with the atomistic information obtained from the ab initio calculations. Moreover, the evolution and interaction of dislocations in these intermetallics as well as the role of solute segregation are presented by utilizing fully anisotropic 3D dislocation dynamics. The results from this work clearly indicate the role and the importance of elastic anisotropy on the evolution of dislocation microstructures, the overall ductility and the hardening behavior in these systems.

  8. Anisotropic Adhesion Properties of Triangular-Tip-Shaped Micropillars

    KAUST Repository

    Kwak, Moon Kyu

    2011-06-01

    Directional dry adhesive microstructures consisting of high-density triangular-tip-shaped micropillars are described. The wide-tip structures allow for unique directional shear adhesion properties with respect to the peeling direction, along with relatively high normal adhesion. © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. 75 FR 78915 - Conduct on Postal Property

    Science.gov (United States)

    2010-12-17

    ... in 39 CFR 232.1. 1. Paragraph (f) Gambling: The prohibition of lottery ticket sales contains an... vending operations on federal property be permitted to sell tickets ``for any lottery authorized by State... property, the operation of gambling devices, the conduct of a lottery or pool, or the selling or...

  10. Anisotropic vanadium dioxide sculptured thin films with superior thermochromic properties

    OpenAIRE

    Sun, Yaoming; Xiao, Xiudi; Xu, Gang; Dong, Guoping; Chai, Guanqi; Zhang, Hua; Liu, Pengyi; Zhu, Hanmin; Zhan, Yongjun

    2013-01-01

    VO2 (M) STF through reduction of V2O5 STF was prepared. The results illustrate that V2O5 STF can be successfully obtained by oblique angle thermal evaporation technique. After annealing at 550°C/3 min, the V2O5 STF deposited at 85° can be easily transformed into VO2 STF with slanted columnar structure and superior thermochromic properties. After deposition SiO2 antireflective layer, Tlum of VO2 STF is enhanced 26% and ΔTsol increases 60% compared with that of normal VO2 thin films. Due to the...

  11. Anisotropic mechanical properties of a polymer nematic liquid crystal

    Science.gov (United States)

    Taratuta, Victor G.; Lonberg, Franklin; Meyer, Robert B.

    1988-03-01

    A concentration dependence of elastic and viscous properties of nematic poly-γ-benzyl glutamate (PBG) was studied experimentally. The splay and bend constants are similar in magnitude, both linear in concentration. The twist constant is much smaller and constant. Viscosities exhibit large anisotropies. γ1 and ηc are roughly quadratic in concentration, ηa is linear, while ηb is constant. The data are self-consistently interpreted in terms of the theoretical models for nematics of semi flexible chains rather than those of rigid rods.

  12. Direct current electric potential in an anisotropic half-space with vertical contact containing a conductive 3D body

    Directory of Open Access Journals (Sweden)

    Li Ping

    2004-01-01

    Full Text Available Detailed studies of anomalous conductors in otherwise homogeneous media have been modelled. Vertical contacts form common geometries in galvanic studies when describing geological formations with different electrical conductivities on either side. However, previous studies of vertical discontinuities have been mainly concerned with isotropic environments. In this paper, we deal with the effect on the electric potentials, such as mise-à-la-masse anomalies, due to a conductor near a vertical contact between two anisotropic regions. We also demonstrate the interactive effects when the conductive body is placed across the vertical contact. This problem is normally very difficult to solve by the traditional numerical methods. The integral equations for the electric potential in anisotropic half-spaces are established. Green's function is obtained using the reflection and transmission image method in which five images are needed to fit the boundary conditions on the vertical interface and the air-earth surface. The effects of the anisotropy of the environments and the conductive body on the electric potential are illustrated with the aid of several numerical examples.

  13. Electrospun PCL nanofibers with anisotropic mechanical properties as a biomedical scaffold

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Geun Hyung [Department of Mechanical Engineering, Chosun University, 375 Seosok-dong, Dong-gu, Kwangju (Korea, Republic of)], E-mail: gkim@chosun.ac.kr

    2008-06-01

    To design an ideal scaffold, various factors should be considered, such as pore size and morphology, mechanical properties versus porosity, surface properties and appropriate biodegradability. Of these factors, the importance of mechanical properties on cell growth is particularly obvious in tissues such as bone, cartilage, blood vessels, tendons and muscles. Although electrospun nanofibers provide easily applicable nano-sized structures which could be used as biomedical scaffolds, the mechanical properties are poor since an increased pore size and porosity are generally accompanied by a decrease in mechanical properties. In addition, the general electrospinning has been limited to the fabrication of a variety of anisotropic mechanical properties, which are extremely important parameters for designing a musculoskeletal system. In this study, scaffolds consisting of variously oriented nanofibers were produced using an electrospinning process modified with an auxiliary electrode and a two-axis robot collecting system. Using an auxiliary electrode, a stable Taylor cone and initial spun jets were obtained. The influence of the electrode was evaluated with electric field simulation. Using the modified electrospinning process, various directions of orientation of electrospun fibers could be acquired and the fabricated oriented nanofiber webs showed a mechanically anisotropic behavior and a higher hydrophilic property compared to randomly distributed fibrous mats.

  14. Anisotropic dielectric properties of two-dimensional matrix in pseudo-spin ferroelectric system

    Science.gov (United States)

    Kim, Se-Hun

    2016-10-01

    The anisotropic dielectric properties of a two-dimensional (2D) ferroelectric system were studied using the statistical calculation of the pseudo-spin Ising Hamiltonian model. It is necessary to delay the time for measurements of the observable and the independence of the new spin configuration under Monte Carlo sampling, in which the thermal equilibrium state depends on the temperature and size of the system. The autocorrelation time constants of the normalized relaxation function were determined by taking temperature and 2D lattice size into account. We discuss the dielectric constants of a two-dimensional ferroelectric system by using the Metropolis method in view of the Slater-Takagi defect energies.

  15. Deformation and recrystallization textures and anisotropic plastic properties of Zircaloy sheet

    International Nuclear Information System (INIS)

    Crystallographic textures and anisotropic mechanical properties of cold-rolled and recrystallized Zircaloy-4 sheets have been characterized. The mechanical anisotropy parameters of the sheets were determined using grid analysis tests while the textures were characterized using x-ray pole figures and crystallite orientation distribution functions (CODF's). These CODF's, in conjunction with appropriate plasticity models, were employed to predict the anisotropy parameters (R and P) assuming the dominance of various individual slip systems. The experimental results were correlated with the model predictions. (author)

  16. Electrical Properties of PPy-Coated Conductive Fabrics for Human Joint Motion Monitoring

    Directory of Open Access Journals (Sweden)

    Jiyong Hu

    2016-03-01

    Full Text Available Body motion signals indicate several pathological features of the human body, and a wearable human motion monitoring system can respond to human joint motion signal in real time, thereby enabling the prevention and treatment of some diseases. Because conductive fabrics can be well integrated with the garment, they are ideal as a sensing element of wearable human motion monitoring systems. This study prepared polypyrrole conductive fabric by in situ polymerization, and the anisotropic property of the conductive fabric resistance, resistance–strain relationship, and the relationship between resistance and the human knee and elbow movements are discussed preliminarily.

  17. A Model of Anisotropic Property of Seepage and Stress for Jointed Rock Mass

    Directory of Open Access Journals (Sweden)

    Pei-tao Wang

    2013-01-01

    Full Text Available Joints often have important effects on seepage and elastic properties of jointed rock mass and therefore on the rock slope stability. In the present paper, a model for discrete jointed network is established using contact-free measurement technique and geometrical statistic method. A coupled mathematical model for characterizing anisotropic permeability tensor and stress tensor was presented and finally introduced to a finite element model. A case study of roadway stability at the Heishan Metal Mine in Hebei Province, China, was performed to investigate the influence of joints orientation on the anisotropic properties of seepage and elasticity of the surrounding rock mass around roadways in underground mining. In this work, the influence of the principal direction of the mechanical properties of the rock mass on associated stress field, seepage field, and damage zone of the surrounding rock mass was numerically studied. The numerical simulations indicate that flow velocity, water pressure, and stress field are greatly dependent on the principal direction of joint planes. It is found that the principal direction of joints is the most important factor controlling the failure mode of the surrounding rock mass around roadways.

  18. The thermal instability in a sheared magnetic field - Filament condensation with anisotropic heat conduction. [solar physics

    Science.gov (United States)

    Van Hoven, G.; Mok, Y.

    1984-01-01

    The condensation-mode growth rate of the thermal instability in an empirically motivated sheared field is shown to depend upon the existence of perpendicular thermal conduction. This typically very small effect (perpendicular conductivity/parallel conductivity less than about 10 to the -10th for the solar corona) increases the spatial-derivative order of the compressible temperature-perturbation equation, and thereby eliminates the singularities which appear when perpendicular conductivity = 0. The resulting growth rate is less than 1.5 times the controlling constant-density radiation rate, and has a clear maximum at a cross-field length of order 100 times and a width of about 0.1 the magnetic shear scale for solar conditions. The profiles of the observable temperature and density perturbations are independent of the thermal conductivity, and thus agree with those found previously. An analytic solution to the short-wavelength incompressible case is also given.

  19. Preparation and magnetic properties of anisotropic (Sm,Pr)Co5/Co composite particles

    International Nuclear Information System (INIS)

    Anisotropic (Sm,Pr)Co5/Co nanocomposite particles have been fabricated by chemical coating the 2 h ball milled (Sm,Pr)Co5 flakes with Co nanoparticles. The Co nanoparticles were synthesized with mean particle sizes in the range of 20–50 nm. The nanocomposite particles present [0 0 1] out-of-plane texture and improved magnetic properties, e.g., an enhanced remanent magnetization of 72 emu/g for (Sm,Pr)Co5/Co and 66 emu/g for (Sm,Pr)Co5. In addition, by using the 8 h ball milled powders (much smaller than the 2 h ball milled powders) as the starting materials, Co nanoparticles can also be successfully coated on the surface of the flakes. A plausible mechanism for the formation of Co nanoparticles on the surface of (Sm,Pr)Co5 flakes is discussed. - Highlights: ► Nanocomposite (Sm,Pr)Co5/Co flakes have been prepared through the liquid-phase method. ► Anisotropic nanocomposite particles are showing improved magnetic properties. ► Plausible mechanism for the formation of Co nanoparticles is discussed.

  20. Preparation and magnetic properties of anisotropic (Sm,Pr)Co{sub 5}/Co composite particles

    Energy Technology Data Exchange (ETDEWEB)

    Wang Xiaoliang; He Huanlong; Wang Fengqing; Chen Yan; Xu Lei [State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, 066004 Qinhuangdao (China); Li Xiaohong [College of Physics Science and Technology, Hebei University, 071002 Baoding (China); Zhang Xiangyi, E-mail: xyzh66@ysu.edu.cn [State Key Laboratory of Metastable Materials Science and Technology, Yanshan University, 066004 Qinhuangdao (China)

    2012-03-15

    Anisotropic (Sm,Pr)Co{sub 5}/Co nanocomposite particles have been fabricated by chemical coating the 2 h ball milled (Sm,Pr)Co{sub 5} flakes with Co nanoparticles. The Co nanoparticles were synthesized with mean particle sizes in the range of 20-50 nm. The nanocomposite particles present [0 0 1] out-of-plane texture and improved magnetic properties, e.g., an enhanced remanent magnetization of 72 emu/g for (Sm,Pr)Co{sub 5}/Co and 66 emu/g for (Sm,Pr)Co{sub 5}. In addition, by using the 8 h ball milled powders (much smaller than the 2 h ball milled powders) as the starting materials, Co nanoparticles can also be successfully coated on the surface of the flakes. A plausible mechanism for the formation of Co nanoparticles on the surface of (Sm,Pr)Co{sub 5} flakes is discussed. - Highlights: Black-Right-Pointing-Pointer Nanocomposite (Sm,Pr)Co{sub 5}/Co flakes have been prepared through the liquid-phase method. Black-Right-Pointing-Pointer Anisotropic nanocomposite particles are showing improved magnetic properties. Black-Right-Pointing-Pointer Plausible mechanism for the formation of Co nanoparticles is discussed.

  1. Nanostructured SnS with inherent anisotropic optical properties for high photoactivity

    Science.gov (United States)

    Patel, Malkeshkumar; Chavda, Arvind; Mukhopadhyay, Indrajit; Kim, Joondong; Ray, Abhijit

    2016-01-01

    In view of the worldwide energy challenge in the 21st century, the technology of semiconductor-based photoelectrochemical (PEC) water splitting has received considerable attention as an alternative approach for solar energy harvesting and storage. Two-dimensional (2D) structures such as nanosheets have the potential to tap the solar energy by unlocking the functional properties at the nanoscale. Tin(ii) sulfide is a fascinating solar energy material due to its anisotropic material properties. In this manuscript, we report on exploiting the 2D structure modulated optical properties of nanocrystalline SnS thin film synthesized by chemical spray pyrolysis using ambient transport in the harvesting of solar energy. We obtained the nanostructured SnS with well-preserved dimensions and morphologies with one step processing. The work demonstrates that the intrinsically ordered SnS nanostructure on FTO coated glass can tap the incident radiation in an efficient manner. The structure-property relationship to explain the photo-response in nanocrystalline-SnS is verified experimentally and theoretically. The novel design scheme for antireflection coating along with the anisotropic properties of SnS is conceived for realizing a PEC cell. The developed PEC cell consists of a SnS photoanode which shows considerably high photocurrent density of 7 mA cm-2 with aqueous media under AM 1.5G, 100 mW cm-2 exposure with notably stable operation. Electrochemical impedance spectroscopy revealed that a non-ideal capacitive behavior as well as drift assisted transport across the solid-state interface is responsible for such a high photo-current density in the nanocrystalline-SnS photoanode.In view of the worldwide energy challenge in the 21st century, the technology of semiconductor-based photoelectrochemical (PEC) water splitting has received considerable attention as an alternative approach for solar energy harvesting and storage. Two-dimensional (2D) structures such as nanosheets have the

  2. Experimental evaluation of electrical conductivity imaging of anisotropic brain tissues using a combination of diffusion tensor imaging and magnetic resonance electrical impedance tomography

    Science.gov (United States)

    Sajib, Saurav Z. K.; Jeong, Woo Chul; Kyung, Eun Jung; Kim, Hyun Bum; Oh, Tong In; Kim, Hyung Joong; Kwon, Oh In; Woo, Eung Je

    2016-06-01

    Anisotropy of biological tissues is a low-frequency phenomenon that is associated with the function and structure of cell membranes. Imaging of anisotropic conductivity has potential for the analysis of interactions between electromagnetic fields and biological systems, such as the prediction of current pathways in electrical stimulation therapy. To improve application to the clinical environment, precise approaches are required to understand the exact responses inside the human body subjected to the stimulated currents. In this study, we experimentally evaluate the anisotropic conductivity tensor distribution of canine brain tissues, using a recently developed diffusion tensor-magnetic resonance electrical impedance tomography method. At low frequency, electrical conductivity of the biological tissues can be expressed as a product of the mobility and concentration of ions in the extracellular space. From diffusion tensor images of the brain, we can obtain directional information on diffusive movements of water molecules, which correspond to the mobility of ions. The position dependent scale factor, which provides information on ion concentration, was successfully calculated from the magnetic flux density, to obtain the equivalent conductivity tensor. By combining the information from both techniques, we can finally reconstruct the anisotropic conductivity tensor images of brain tissues. The reconstructed conductivity images better demonstrate the enhanced signal intensity in strongly anisotropic brain regions, compared with those resulting from previous methods using a global scale factor.

  3. A study of phonon anisotropic scattering effect on silicon thermal conductivity at nanoscale

    Energy Technology Data Exchange (ETDEWEB)

    Bong, Victor N-S; Wong, Basil T. [Swinburne Sarawak Research Centre for Sustainable Technologies, Faculty of Engineering, Computing & Science, Swinburne University of Technology Sarawak Campus, 93350 Kuching, Sarawak (Malaysia)

    2015-08-28

    Previous studies have shown that anisotropy in phonon transport exist because of the difference in phonon dispersion relation due to different lattice direction, as observed by a difference in in-plane and cross-plane thermal conductivity. The directional preference (such as forward or backward scattering) in phonon propagation however, remains a relatively unexplored frontier. Our current work adopts a simple scattering probability in radiative transfer, which is called Henyey and Greenstein probability density function, and incorporates it into the phonon Monte Carlo simulation to investigate the effect of directional scattering in phonon transport. In this work, the effect of applying the anisotropy scattering is discussed, as well as its impact on the simulated thermal conductivity of silicon thin films. While the forward and backward scattering will increase and decrease thermal conductivity respectively, the extent of the effect is non-linear such that forward scattering has a more obvious effect than backward scattering.

  4. Nanostructured SnS with inherent anisotropic optical properties for high photoactivity.

    Science.gov (United States)

    Patel, Malkeshkumar; Chavda, Arvind; Mukhopadhyay, Indrajit; Kim, Joondong; Ray, Abhijit

    2016-01-28

    In view of the worldwide energy challenge in the 21(st) century, the technology of semiconductor-based photoelectrochemical (PEC) water splitting has received considerable attention as an alternative approach for solar energy harvesting and storage. Two-dimensional (2D) structures such as nanosheets have the potential to tap the solar energy by unlocking the functional properties at the nanoscale. Tin(ii) sulfide is a fascinating solar energy material due to its anisotropic material properties. In this manuscript, we report on exploiting the 2D structure modulated optical properties of nanocrystalline SnS thin film synthesized by chemical spray pyrolysis using ambient transport in the harvesting of solar energy. We obtained the nanostructured SnS with well-preserved dimensions and morphologies with one step processing. The work demonstrates that the intrinsically ordered SnS nanostructure on FTO coated glass can tap the incident radiation in an efficient manner. The structure-property relationship to explain the photo-response in nanocrystalline-SnS is verified experimentally and theoretically. The novel design scheme for antireflection coating along with the anisotropic properties of SnS is conceived for realizing a PEC cell. The developed PEC cell consists of a SnS photoanode which shows considerably high photocurrent density of 7 mA cm(-2) with aqueous media under AM 1.5G, 100 mW cm(-2) exposure with notably stable operation. Electrochemical impedance spectroscopy revealed that a non-ideal capacitive behavior as well as drift assisted transport across the solid-state interface is responsible for such a high photo-current density in the nanocrystalline-SnS photoanode. PMID:26745636

  5. Dispersion properties of transverse anisotropic liquid crystal core photonic crystal fibers

    Science.gov (United States)

    Karasawa, Naoki

    2016-04-01

    The dispersion properties of liquid crystal core photonic crystal fibers for different core diameters have been calculated by a full vectorial finite difference method. In calculations, air holes are assumed to be arranged in a regular hexagonal array in fused silica and a central hole is filled with liquid crystal to create a core. In this study, three types of transverse anisotropic configurations, where liquid crystal molecules are oriented in a transverse plane, and a planar configuration, where liquid crystal molecules are oriented in a propagation direction, are considered. The large changes of the dispersion properties are found when the orientation of the liquid crystal molecules is changed from a planar configuration to a uniform configuration, where all molecules are oriented in the same direction in a transverse plane. Since the orientation of liquid crystal molecules may be controlled by applying an electric field, it could be utilized for various applications including the spectral control of supercontinuum generation.

  6. Anisotropic Poly(Vinyl Alcohol) Hydrogel: Connection Between Structure and Bulk Mechanical Properties

    Science.gov (United States)

    Hudson, Stephen; Hutter, Jeffrey; Millon, Leonardo; Wan, Wankei; Nieh, Mu-Ping

    2009-03-01

    Poly(vinyl alcohol) (PVA) hydrogels are formed from PVA solution by creation of physical cross-links during freeze/thaw cycling. By choosing a suitable freeze/thaw protocol and applying a strain during thermal processing, gels with permanent, anisotropic bulk mechanical properties matching those of cardiovascular tissues can be made, making them useful for applications ranging from artificial heart valves to vascular grafts. We have performed small- and ultra small-angle neutron scattering (SANS and USANS) measurements covering length scales from 2 nm to 10 μm, and modeled the structure as interconnected PVA blobs of size 20 to 50 nm arranged in fractal aggregates extending to at least 10 μm. Here, we discuss the relationship between the microstructure and bulk mechanical properties. Strength increases with the number of thermal cycles due to reinforcement of the small-scale gel phase, while anisotropy is due to elongation of the much larger fractal aggregates.

  7. The value and cost of complexity in predictive modelling: role of tissue anisotropic conductivity and fibre tracts in neuromodulation

    Science.gov (United States)

    Salman Shahid, Syed; Bikson, Marom; Salman, Humaira; Wen, Peng; Ahfock, Tony

    2014-06-01

    Objectives. Computational methods are increasingly used to optimize transcranial direct current stimulation (tDCS) dose strategies and yet complexities of existing approaches limit their clinical access. Since predictive modelling indicates the relevance of subject/pathology based data and hence the need for subject specific modelling, the incremental clinical value of increasingly complex modelling methods must be balanced against the computational and clinical time and costs. For example, the incorporation of multiple tissue layers and measured diffusion tensor (DTI) based conductivity estimates increase model precision but at the cost of clinical and computational resources. Costs related to such complexities aggregate when considering individual optimization and the myriad of potential montages. Here, rather than considering if additional details change current-flow prediction, we consider when added complexities influence clinical decisions. Approach. Towards developing quantitative and qualitative metrics of value/cost associated with computational model complexity, we considered field distributions generated by two 4 × 1 high-definition montages (m1 = 4 × 1 HD montage with anode at C3 and m2 = 4 × 1 HD montage with anode at C1) and a single conventional (m3 = C3-Fp2) tDCS electrode montage. We evaluated statistical methods, including residual error (RE) and relative difference measure (RDM), to consider the clinical impact and utility of increased complexities, namely the influence of skull, muscle and brain anisotropic conductivities in a volume conductor model. Main results. Anisotropy modulated current-flow in a montage and region dependent manner. However, significant statistical changes, produced within montage by anisotropy, did not change qualitative peak and topographic comparisons across montages. Thus for the examples analysed, clinical decision on which dose to select would not be altered by the omission of anisotropic brain conductivity

  8. Characterization of three-dimensional anisotropic heart valve tissue mechanical properties using inverse finite element analysis.

    Science.gov (United States)

    Abbasi, Mostafa; Barakat, Mohammed S; Vahidkhah, Koohyar; Azadani, Ali N

    2016-09-01

    Computational modeling has an important role in design and assessment of medical devices. In computational simulations, considering accurate constitutive models is of the utmost importance to capture mechanical response of soft tissue and biomedical materials under physiological loading conditions. Lack of comprehensive three-dimensional constitutive models for soft tissue limits the effectiveness of computational modeling in research and development of medical devices. The aim of this study was to use inverse finite element (FE) analysis to determine three-dimensional mechanical properties of bovine pericardial leaflets of a surgical bioprosthesis under dynamic loading condition. Using inverse parameter estimation, 3D anisotropic Fung model parameters were estimated for the leaflets. The FE simulations were validated using experimental in-vitro measurements, and the impact of different constitutive material models was investigated on leaflet stress distribution. The results of this study showed that the anisotropic Fung model accurately simulated the leaflet deformation and coaptation during valve opening and closing. During systole, the peak stress reached to 3.17MPa at the leaflet boundary while during diastole high stress regions were primarily observed in the commissures with the peak stress of 1.17MPa. In addition, the Rayleigh damping coefficient that was introduced to FE simulations to simulate viscous damping effects of surrounding fluid was determined. PMID:27173827

  9. Giant dipole moment in a triad system. mechanisms of anisotropic photoresponse in the transient dc conductivity of dipolar solutes

    Energy Technology Data Exchange (ETDEWEB)

    Smirnov, S.N.; Braun, C.L. [Dartmouth College, Hanover, NH (United States); Greenfield, S.R.; Svec, W.A.; Wasielewski, M.R. [Argonne National Lab.,IL (United States)

    1996-07-25

    A transient dc conductivity method was used to observe formation of a giant dipole moment for the triad molecule MA-ANI-NI (ethoxyaniline-aminonaphthalimide-dimethylphenyl-naphthalenediimide-octyl) in toluene. The independence of the dipole moment on excitation wavelength indicates high efficiency of intramolecular energy or (and) electron transfer. The effect of light polarization on the DC conductivity signal caused by a photoinduced increase in solute dipole moment is considered in detail. It is shown that the time variation of the signal includes information about structural anomalies in the angular distribution function of molecular dipoles and depends on light polarization even for zero ground state dipole moment. Nonzero ground state dipole moment and (or) electric field dependence of the charge transfer rate constants give an additional source for an anisotropic photoresponse signal. Analysis of the photoresponse and its anisotropy for the triad gives ground ({mu}{sub g}), first ({mu}{sub l}), and second ({mu}{sub 2}) excited state dipole moments as follows: {mu}{sub g} = 12{+-}5 D, {mu}{sub l} = 35{+-}10, and {mu}{sub 2} = 87{+-}6 D. The lifetime of the giant dipole state is {tau} = 290{+-}10 ns, and the molecule`s rotational time is {tau}{sub r} = 1.6{+-}0.15 ns. 14 refs., 7 figs., 2 tabs.

  10. Propagation properties of an optical vortex carried by a Bessel-Gaussian beam in anisotropic turbulence.

    Science.gov (United States)

    Cheng, Mingjian; Guo, Lixin; Li, Jiangting; Huang, Qingqing

    2016-08-01

    Rytov theory was employed to establish the transmission model for the optical vortices carried by Bessel-Gaussian (BG) beams in weak anisotropic turbulence based on the generalized anisotropic von Karman spectrum. The influences of asymmetry anisotropic turbulence eddies and source parameters on the signal orbital angular momentum (OAM) mode detection probability of partially coherent BG beams in anisotropic turbulence were discussed. Anisotropic characteristics of the turbulence could enhance the OAM mode transmission performance. The spatial partially coherence of the beam source would increase turbulent aberration's effect on the optical vortices. BG beams could dampen the influences of the turbulence because of their nondiffraction and self-healing characteristics. PMID:27505641

  11. High Tg and fast curing epoxy-based anisotropic conductive paste for electronic packaging

    Science.gov (United States)

    Keeratitham, Waralee; Somwangthanaroj, Anongnat

    2016-03-01

    Herein, our main objective is to prepare the fast curing epoxy system with high glass transition temperature (Tg) by incorporating the multifunctional epoxy resin into the mixture of diglycidyl ether of bisphenol A (DGEBA) as a major epoxy component and aromatic diamine as a hardener. Furthermore, the curing behavior as well as thermal and thermomechanical properties were investigated by differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA) and thermomechanical analysis (TMA). It was found that Tg obtained from tan δ of DGEBA/aromatic diamine system increased from 100 °C to 205 °C with the presence of 30 percentage by weight of multifunctional epoxy resin. Additionally, the isothermal DSC results showed that the multifunctional epoxy resin can accelerate the curing reaction of DGEBA/aromatic diamine system. Namely, a high degree of curing (˜90%) was achieved after a few minutes of curing at low temperature of 130 °C, owing to a large number of epoxy ring of multifunctional epoxy resin towards the active hydrogen atoms of aromatic diamine.

  12. Anisotropic transport properties in the phase-separated La0.67Ca0.33MnO3/NdGaO3 (001) films

    Science.gov (United States)

    Hong-Rui, Zhang; Yuan-Bo, Liu; Shuan-Hu, Wang; De-Shun, Hong; Wen-Bin, Wu; Ji-Rong, Sun

    2016-07-01

    The anisotropic transport property was investigated in a phase separation La0.67Ca0.33MnO3 (LCMO) film grown on (001)-oriented NdGaO3 (NGO) substrate. It was found that the resistivity along the b-axis is much higher than that along the a-axis. Two resistivity peaks were observed in the temperature dependent measurement along the b-axis, one located at 91 K and the other centered at 165 K. Moreover, we also studied the response of the resistivities along the two axes to various electric currents, magnetic fields, and light illuminations. The resistivities along the two axes are sensitive to the magnetic field. However, the electric current and light illumination can influence the resistivity along the b-axis obviously, but have little effect on the resistivity along the a-axis. Based on these results, we believe that an anisotropic-strain-controlled MnO6 octahedra shear-mode deformation may provide a mechanism of conduction filaments paths along the a-axis, which leads to the anisotropic transport property. Project supported by the National Basic Research Program of China (Grant Nos. 2011CB921801, 2012CB921403, and 2013CB921701) and the National Natural Science Foundation of China (Grant Nos. 11074285, 51372064, and 11134007).

  13. Anisotropic structural and electrical properties of strained SrTiO3 films on sapphire

    International Nuclear Information System (INIS)

    The electronic properties of oxide films strongly depend on the composition, structure and structural imperfections. Since lattice constants and thermal expansion coefficient of substrate and films are usually different, mechanical strain is imposed on the growing films. In this work we examine the strain of epitaxially grown SrTiO3 films on sapphire and its impact on the ferroelectric properties of the film. The lattice mismatch of about 10% between SrTiO3 and sapphire is reduced via a buffer layer, CeO2. The strain induced modification of the structure is determined via XRD measurements. High-resolution Pole-figure measurements demonstrate the anisotropic and thickness dependent (i.e., relaxation) distortion of the SrTiO3 lattice. Electronic characterization of the dielectric properties reveal the resulting anisotropy of the polarizability of film. Furthermore, it demonstrates that ferroelectric can be induced via strain in the originally incipient ferroelectric SrTiO3 up to high temperatures well above 200 K.

  14. Anisotropic mechanical properties of zircon and the effect of radiation damage

    Science.gov (United States)

    Beirau, Tobias; Nix, William D.; Bismayer, Ulrich; Boatner, Lynn A.; Isaacson, Scott G.; Ewing, Rodney C.

    2016-06-01

    This study provides new insights into the relationship between radiation-dose-dependent structural damage due to natural U and Th impurities and the anisotropic mechanical properties (Poisson's ratio, elastic modulus and hardness) of zircon. Natural zircon samples from Sri Lanka (see Muarakami et al. in Am Mineral 76:1510-1532, 1991) and synthetic samples, covering a dose range of zero up to 6.8 × 1018 α-decays/g, have been studied by nanoindentation. Measurements along the [100] crystallographic direction and calculations, based on elastic stiffness constants determined by Özkan (J Appl Phys 47:4772-4779, 1976), revealed a general radiation-induced decrease in stiffness (~54 %) and hardness (~48 %) and an increase in the Poisson's ratio (~54 %) with increasing dose. Additional indentations on selected samples along the [001] allowed one to follow the amorphization process to the point that the mechanical properties are isotropic. This work shows that the radiation-dose-dependent changes of the mechanical properties of zircon can be directly correlated with the amorphous fraction as determined by previous investigations with local and global probes (Ríos et al. in J Phys Condens Matter 12:2401-2412, 2000a; Farnan and Salje in J Appl Phys 89:2084-2090, 2001; Zhang and Salje in J Phys Condens Matter 13:3057-3071, 2001). The excellent agreement, revealed by the different methods, indicates a large influence of structural and even local phenomena on the macroscopic mechanical properties. Therefore, this study indicates the importance of acquiring better knowledge about the mechanical long-term stability of radiation-damaged materials.

  15. Investigation of low field dielectric properties of anisotropic porous Pb(Zr,Ti)O3 ceramics: Experiment and modeling

    Science.gov (United States)

    Olariu, C. S.; Padurariu, L.; Stanculescu, R.; Baldisserri, C.; Galassi, C.; Mitoseriu, L.

    2013-12-01

    Anisotropic porous Pb(Zr,Ti)O3 ceramics with various porosity degrees have been studied in order to determine the role of the pore shape and orientation on the low-field dielectric properties. Ceramic samples with formula Pb(Zr0.52Ti0.48)0.976Nb0.024O3 with different porosity degrees (dense, 10%, 20%, 40% vol.) have been prepared by solid state reaction. Taking into consideration the shape and orientation of the pore inclusions, the dielectric properties of porous ceramics have been described by using adapted mixing rules models. Rigorous bounds, derived on the basis on Variational Principle, were used to frame dielectric properties of porous composites. The finite element method (FEM) was additionally used to simulate the dielectric response of the porous composites under various applied fields. Among the few effective medium approximation models adapted for anisotropic oriented inclusions, the best results were obtained in case of needle-like shape inclusions (which do not correspond to the real shape of microstructure inclusions). The general case of Wiener bounds limited well the dielectric properties of anisotropic porous composites in case of parallel orientation. Among the theoretical approaches, FEM technique allowed to simulate the distribution of potential and electric field inside composites and provided a very good agreement between the computed permittivity values and experimental ones.

  16. Anisotropic effective medium properties from interacting Ag nanoparticles in silicon dioxide.

    Science.gov (United States)

    Menegotto, Thiago; Horowitz, Flavio

    2014-05-01

    Films containing a layer of Ag nanoparticles embedded in silicon dioxide were produced by RF magnetron sputtering. Optical transmittance measurements at several angles of incidence (from normal to 75°) revealed two surface plasmon resonance (SPR) peaks, which depend on electric field direction: one in the ultraviolet and another red-shifted from the dilute Ag/SiO₂ system resonance at 410 nm. In order to investigate the origin of this anisotropic behavior, the structural properties were determined by transmission electron microscopy, revealing the bidimensional plane distribution of Ag nanoparticles with nearly spherical shape as well as the filling factor of metal in the composite. A simple model linked to these experimental parameters allowed description of the most relevant features of the SPR positions, which, depending on the field direction, were distinctly affected by the coupling of oscillations between close nanoparticles, as described by a modified Drude-Lorentz dielectric function introduced into the Maxwell-Garnett relation. This approach allowed prediction of the resonance for light at 75° incidence from the SPR position for light at normal incidence, in good agreement with experimental observation. PMID:24921871

  17. Crack path predictions and experiments in plane structures considering anisotropic properties and material interfaces

    Directory of Open Access Journals (Sweden)

    P.O. Judt

    2015-10-01

    Full Text Available In many engineering applications special requirements are directed to a material's fracture behavior and the prediction of crack paths. Especially if the material exhibits anisotropic elastic properties or fracture toughnesses, e.g. in textured or composite materials, the simulation of crack paths is challenging. Here, the application of path independent interaction integrals (I-integrals, J-, L- and M-integrals is beneficial for an accurate crack tip loading analysis. Numerical tools for the calculation of loading quantities using these path-invariant integrals are implemented into the commercial finite element (FE-code ABAQUS. Global approaches of the integrals are convenient considering crack tips approaching other crack faces, internal boundaries or material interfaces. Curved crack faces require special treatment with respect to integration contours. Numerical crack paths are predicted based on FE calculations of the boundary value problem in connection with an intelligent adaptive re-meshing algorithm. Considering fracture toughness anisotropy and accounting for inelastic effects due to small plastic zones in the crack tip region, the numerically predicted crack paths of different types of specimens with material interfaces and internal boundaries are compared to subcritically grown paths obtained from experiments.

  18. Anisotropic stress rupture properties of the nickel-base single crystal superalloy SRR99

    International Nuclear Information System (INIS)

    The influence of orientation on the stress rupture properties of a single crystal superalloy SRR99 was investigated at temperatures of 760 and 1040 deg. C. It is found that the creep anisotropic behaviour is pronounced at the lower temperature of 760 deg. C and the stress rupture life ranks in the order [0 0 1] > [1 1 1] > [0 1 1]. Despite the anisotropy of stress rupture life is evidently reduced at the higher temperature, the [1 1 1] orientation exhibits the longest life. At 760 deg. C, EBSD (electron back scattered diffraction) was adopted to measure the lattice rotation and the deduced results indicate that the dominant slip systems are {1 1 1} during stress rupture test. At 1040 deg. C, the ranking order of the stress rupture life is [1 1 1] > [0 0 1] > [0 1 1] and the single crystal close to [0 1 1] orientation still shows the poorest life. In the [0 0 1] and [1 1 1] samples, regular γ' raft structure is formed compared with [0 1 1] samples. Further observations made by TEM investigations reveal the underlying deformation mechanisms for crystals with orientations near [0 0 1], [0 1 1] and [1 1 1] under two test conditions.

  19. Characterization of anisotropic elastic properties of the arteries by exponential and polynomial strain energy functions.

    Science.gov (United States)

    Hudetz, A G; Monos, E

    1981-01-01

    Three-dimensional quasi-static mechanical measurements were carried out on cylindrical segments of the dog carotid and iliac arteries for determination of the passive anisotropic elastic properties of the vessel wall. On the basis of passive characteristics of outer diameter vs. intraluminal pressure, and axial extending force vs. intraluminal pressure, picked up at various fixed initial vascular length values, the incremental Young moduli and poisson ratios of the vessel wall were calculated in the 0--33 kPa (0--250 mm Hg) pressure range. The strain energy function of the arteries was approximated by polynomial and exponential models. We found that an exponential energy function with 4-parameters gives more accurate results than the 7- or 12-parameter polynomial functions. According to the results the axial modulus reaches higher values than the tangential and radial moduli at a low tangential stretch level, while at high tangential stretch the tangential modulus is the highest in both carotid and iliac arteries. After elevation of the initial tangential stretch the increase in the tangential modulus is the most pronounced, while the values of radial and axial moduli increased less. A change in the initial axial stretch influences the axial and radial moduli to a similar extent, but has no substantial effect on the value of the tangential modulus. The values of corresponding poisson ratios depend in a similar way on the initial deformation state. The different behaviour of the two Poisson ratios characterizing the mechanical coupling between tangential and axial directions, indicates that the structural coupling between the two main directions is asymmetrical. It is assumed that this property of the passive vascular structure can be explained by the network arrangement of collagen fibres in the vessel wall.

  20. New membrane structures with proton conducting properties

    DEFF Research Database (Denmark)

    Nørgaard, Casper Frydendal

    for these membranes is restricted by the loss of conductivity and dimensional stability as the temperature reaches the boiling point of water and the glass transition temperature of the polymer. At low relative humidity the membranes dehydrate, resulting in loss of conductivity and reduced dimensions. High...... [1, 2, 3]. Improved fuel cell performance from incorporation of hygroscopic oxides or solid proton conductors (e.g. zirconium phosphates) has been reported. The poster exhibits upcoming work in the field of composite electrolyte membranes at the University of Southern Denmark, combining radiation...

  1. Thermal Properties of Asphalt Mixtures Modified with Conductive Fillers

    Directory of Open Access Journals (Sweden)

    Byong Chol Bai

    2015-01-01

    Full Text Available This paper investigates the thermal properties of asphalt mixtures modified with conductive fillers used for snow melting and solar harvesting pavements. Two different mixing processes were adopted to mold asphalt mixtures, dry- and wet-mixing, and two conductive fillers were used in this study, graphite and carbon black. The thermal conductivity was compared to investigate the effects of asphalt mixture preparing methods, the quantity, and the distribution of conductive filler on thermal properties. The combination of conductive filler with carbon fiber in asphalt mixture was evaluated. Also, rheological properties of modified asphalt binders with conductive fillers were measured using dynamic shear rheometer and bending beam rheometer at grade-specific temperatures. Based on rheological testing, the conductive fillers improve rutting resistance and decrease thermal cracking resistance. Thermal testing indicated that graphite and carbon black improve the thermal properties of asphalt mixes and the combined conductive fillers are more effective than the single filler.

  2. Assessing the influence of van der Waals corrected exchange-correlation functionals on the anisotropic mechanical properties of coinage metals

    Science.gov (United States)

    Lee, Ji-Hwan; Park, Jong-Hun; Soon, Aloysius

    2016-07-01

    Current materials-related calculations employ density-functional theory (DFT), commonly using the (semi-)local-density approximations for the exchange-correlation (xc) functional. The difficulties in arriving at a reasonable description of van der Waals (vdW) interactions by DFT-based models is to date a big challenge. In this work, we use various flavors of vdW-corrected DFT xc functionals—ranging from the quasiempirical force-field add-on vdW corrections to self-consistent nonlocal correlation functionals—to study the bulk lattice and mechanical properties (including the elastic constants and anisotropic indices) of the coinage metals (copper, silver, and gold). We critically assess the reliability of the different vdW-corrected DFT methods in describing their anisotropic mechanical properties which have been less reported in the literature. In the context of this work, we regard that our results reiterate the fact that advocating a so-called perfect vdW-inclusive xc functional for describing the general physics and chemistry of these coinage metals could be a little premature. These challenges to modern-day functionals for anisotropically strained coinage metals (e.g., at the faceted surfaces of nanostructures) may well be relevant to other strained material systems.

  3. Macroscopic properties of isotropic and anisotropic fracture networks from the percolation threshold to very large densities

    Science.gov (United States)

    Adler, P. M.; Thovert, J.; Mourzenko, V.

    2011-12-01

    The main purpose of this review paper is to summarize some recent studies of fracture networks. Progress has been made possible thanks to a very versatile numerical technique based on a three-dimensional discrete description of the fracture networks. Any network geometry, any boundary condition, and any distribution of the fractures can be addressed. The first step is to mesh the fracture network as it is by triangles of a controlled size. The second step consists in the discretization of the conservation equations by the finite volume technique. Two important properties were systematically studied, namely the percolation threshold rho_c and the macroscopic permeability K_n of the fracture network. Dimensionless quantities are denoted by a prime. The numerical results are interpreted in a systematic way with the concept of excluded volume which enables us to define a dimensionless fracture density rho' equal in the average to the average number of intersections per fracture. 1. Isotropic networks of identical fractures The dimensionless percolation threshold rho'_c of such networks was systematically studied for fractures of various shapes. rho'_c was shown to be almost independent of the shape except when one has very elongated rectangles. A formula is proposed for rho'_c. The permeability of these networks was calculated for a wide range of fracture densities and shapes. K'_n(rho') is almost independent of the fracture shape; an empirical formula is proposed for any value of rho' between rho'_c and infinity. For large rho', K_n is well approximated by the Snow formula initially derived for infinite fractures. 2. Anisotropic networks of identical fractures The fracture orientations are supposed to follow a Fisher distribution characterized by the parameter kappa; when kappa=0, the fractures are isotropic; when kappa=infinity, the fractures are perpendicular to a given direction. rho'_c does not depend significantly on kappa and the general formula proposed in 1

  4. Transport properties in network models with perfectly conducting channels

    International Nuclear Information System (INIS)

    We study the transport properties of disordered electron systems that contain perfectly conducting channels. Two quantum network models that belong to different universality classes, unitary and symplectic, are simulated numerically. The perfectly conducting channel in the unitary class can be realized in zigzag graphene nano-ribbons and that in the symplectic class is known to appear in metallic carbon nanotubes. The existence of a perfectly conducting channel leads to novel conductance distribution functions and a shortening of the conductance decay length.

  5. Transport properties in network models with perfectly conducting channels

    Energy Technology Data Exchange (ETDEWEB)

    Kobayashi, K; Hirose, K; Ohtsuki, T [Department of Physics, Sophia University, 102-8554 Tokyo (Japan); Obuse, H [Department of Physics, Kyoto University, 606-8501 Kyoto (Japan); Slevin, K [Department of Physics, Osaka University, 560-0043 Osaka (Japan)], E-mail: k-koji@sophia.ac.jp

    2009-02-01

    We study the transport properties of disordered electron systems that contain perfectly conducting channels. Two quantum network models that belong to different universality classes, unitary and symplectic, are simulated numerically. The perfectly conducting channel in the unitary class can be realized in zigzag graphene nano-ribbons and that in the symplectic class is known to appear in metallic carbon nanotubes. The existence of a perfectly conducting channel leads to novel conductance distribution functions and a shortening of the conductance decay length.

  6. Effects of substrate temperature and annealing on the anisotropic magnetoresistive property of NiFe films

    Institute of Scientific and Technical Information of China (English)

    WU Ping; WANG Fengping; QIU Hong; PAN Liqing; TIAN Yue

    2003-01-01

    Ni83Fe17 films with a thickness of about 100 nm were deposited on thermal oxidized silicon substrates at ambient temperature, 240, 350, and 410℃ by DC magnetron sputtering. The deposition rate was about 0.11 nm/s. The as-deposited films were annealed at 450, 550, and 650℃, respectively, in a vacuum lower than 3 x 10-3 Pa for 1 h. The Ni83Fe17 films mainly grow with a crystalline orientation of [111] in the direction of the film growth. With the annealing temperature increasing, the [ 111] orientation enhances. For films deposited at all four different temperatures, the significant improvement on anisotropic magnetoresistance occurs at the annealing temperature higher than 550℃. But for films deposited at ambient temperatures and 240℃, the anisotropic magnetoresistance can only rise to about 1% after 650℃ annealing. For films deposited at 350℃ and 410℃, the anisotropic magnetoresistance rises to about 3.8% after 650℃ annealing. The atomic force microscopy (AFM) observation shows a significant increase in grain size of the film deposited at 350℃ atter 650℃annealing. The decrease in resistivity and the increase in anisotropic magnetoresistance are caused by the decrease in point defects, the increase in grain size, and the improvement in lattice structure integrity of the films.

  7. An anisotropically and heterogeneously aligned patterned electrospun scaffold with tailored mechanical property and improved bioactivity for vascular tissue engineering.

    Science.gov (United States)

    Xu, He; Li, Haiyan; Ke, Qinfei; Chang, Jiang

    2015-04-29

    The development of vascular scaffolds with controlled mechanical properties and stimulatory effects on biological activities of endothelial cells still remains a significant challenge to vascular tissue engineering. In this work, we reported an innovative approach to prepare a new type of vascular scaffolds with anisotropically and heterogeneously aligned patterns using electrospinning technique with unique wire spring templates, and further investigated the structural effects of the patterned electrospun scaffolds on mechanical properties and angiogenic differentiation of human umbilical vein endothelial cells (HUVECs). Results showed that anisotropically aligned patterned nanofibrous structure was obtained by depositing nanofibers on template in a structurally different manner, one part of nanofibers densely deposited on the embossments of wire spring and formed cylindrical-like structures in the transverse direction, while others loosely suspended and aligned along the longitudinal direction, forming a three-dimensional porous microstructure. We further found that such structures could efficiently control the mechanical properties of electrospun vascular scaffolds in both longitudinal and transverse directions by altering the interval distances between the embossments of patterned scaffolds. When HUVECs were cultured on scaffolds with different microstructures, the patterned scaffolds distinctively promoted adhesion of HUVECs at early stage and proliferation during the culture period. Most importantly, cells experienced a large shape change associated with cell cytoskeleton and nuclei remodeling, leading to a stimulatory effect on angiogenesis differentiation of HUVECs by the patterned microstructures of electrospun scaffolds, and the scaffolds with larger distances of intervals showed a higher stimulatory effect. These results suggest that electrospun scaffolds with the anisotropically and heterogeneously aligned patterns, which could efficiently control the

  8. Anisotropic thermoelectric properties of layered compounds in SnX2 (X = S, Se): a promising thermoelectric material.

    Science.gov (United States)

    Sun, Bao-Zhen; Ma, Zuju; He, Chao; Wu, Kechen

    2015-11-28

    Thermoelectrics interconvert heat to electricity and are of great interest in waste heat recovery, solid-state cooling and so on. Here we assessed the potential of SnS2 and SnSe2 as thermoelectric materials at the temperature gradient from 300 to 800 K. Reflecting the crystal structure, the transport coefficients are highly anisotropic between a and c directions, in particular for the electrical conductivity. The preferred direction for both materials is the a direction in TE application. Most strikingly, when 800 K is reached, SnS2 can show a peak power factor (PF) of 15.50 μW cm(-1) K(-2) along the a direction, while a relatively low value (11.72 μW cm(-1) K(-2)) is obtained in the same direction of SnSe2. These values are comparable to those observed in thermoelectrics such as SnSe and SnS. At 300 K, the minimum lattice thermal conductivity (κmin) along the a direction is estimated to be about 0.67 and 0.55 W m(-1) K(-1) for SnS2 and SnSe2, respectively, even lower than the measured lattice thermal conductivity of Bi2Te3 (1.28 W m(-1) K(-1) at 300 K). The reasonable PF and κmin suggest that both SnS2 and SnSe2 are potential thermoelectric materials. Indeed, the estimated peak ZT can approach 0.88 for SnSe2 and a higher value of 0.96 for SnS2 along the a direction at a carrier concentration of 1.94 × 10(19) (SnSe2) vs. 2.87 × 10(19) cm(-3) (SnS2). The best ZT values in SnX2 (X = S, Se) are comparable to that in Bi2Te3 (0.8), a typical thermoelectric material. We hope that this theoretical investigation will provide useful information for further experimental and theoretical studies on optimizing the thermoelectric properties of SnX2 materials.

  9. A Numerical Study on the Anisotropic Thermal Conduction by Phonon Mean Free Path Spectrum of Silicon in Silicon-on-Insulator Transistor

    Energy Technology Data Exchange (ETDEWEB)

    Kang, Hyung Sun; Koh, Young Ha; Jin, Jae Sik [Chosun Univ., Kwangju (Korea, Republic of)

    2016-02-15

    The primary concern of this research is to examine the phonon mean free path (MFP) spectrum contribution to heat conduction. The size effect of materials is determined by phonon MFP, and the size effect appears when the phonon MFP is similar to or less than the characteristic length of materials. Therefore, knowledge of the phonon MFP is essential to increase or decrease the heat conduction of a material for engineering applications, such as micro/nanosystems. In this study, frequency dependence of the phonon transport is considered using the Boltzmann transport equation based on a full phonon dispersion model. Additionally, the phonon MFP spectrums of in-plane and out-of plane heat transport are investigated by varying the film thickness of the silicon layer from 41 nm to 177 nm. This will increase the understanding of anisotropic heat conduction in a SOI (Silicon-on-Insulator) transistor.

  10. Tensile and electrical properties of high-strength high-conductivity copper alloys

    Energy Technology Data Exchange (ETDEWEB)

    Zinkle, S.J.; Eatherly, W.S. [Oak Ridge National Lab., TN (United States)

    1998-09-01

    Electrical conductivity and tensile properties have been measured on an extruded and annealed CuCrNb dispersion strengthened copper alloy which has been developed for demanding aerospace high heat flux applications. The properties of this alloy are somewhat inferior to GlidCop dispersion strengthened copper and prime-aged CuCrZr over the temperature range of 20--500 C. However, if the property degradation in CuCrZr due to joining operations and the anisotropic properties of GlidCop in the short transverse direction are taken into consideration, CuCrNb may be a suitable alternative material for high heat flux structural applications in fusion energy devices. The electrical conductivity and tensile properties of CuCrZr that was solution annealed and then simultaneously aged and diffusion bonded are also summarized. A severe reduction in tensile elongation is observed in the diffusion bonded joint, particularly if a thin copper shim is not placed in the diffusion bondline.

  11. Magnetic Cellulose Nanocrystal Based Anisotropic Polylactic Acid Nanocomposite Films: Influence on Electrical, Magnetic, Thermal, and Mechanical Properties.

    Science.gov (United States)

    Dhar, Prodyut; Kumar, Amit; Katiyar, Vimal

    2016-07-20

    This paper reports a single-step co-precipitation method for the fabrication of magnetic cellulose nanocrystals (MGCNCs) with high iron oxide nanoparticle content (∼51 wt % loading) adsorbed onto cellulose nanocrystals (CNCs). X-ray diffraction (XRD), Fourier transform infrared (FTIR), and Raman spectroscopic studies confirmed that the hydroxyl groups on the surface of CNCs (derived from the bamboo pulp) acted as anchor points for the adsorption of Fe3O4 nanoparticles. The fabricated MGCNCs have a high magnetic moment, which is utilized to orient the magnetoresponsive nanofillers in parallel or perpendicular orientations inside the polylactic acid (PLA) matrix. Magnetic-field-assisted directional alignment of MGCNCs led to the incorporation of anisotropic mechanical, thermal, and electrical properties in the fabricated PLA-MGCNC nanocomposites. Thermomechanical studies showed significant improvement in the elastic modulus and glass-transition temperature for the magnetically oriented samples. Differential scanning calorimetry (DSC) and XRD studies confirmed that the alignment of MGCNCs led to the improvement in the percentage crystallinity and, with the absence of the cold-crystallization phenomenon, finds a potential application in polymer processing in the presence of magnetic field. The tensile strength and percentage elongation for the parallel-oriented samples improved by ∼70 and 240%, respectively, and for perpendicular-oriented samples, by ∼58 and 172%, respectively, in comparison to the unoriented samples. Furthermore, its anisotropically induced electrical and magnetic properties are desirable for fabricating self-biased electronics products. We also demonstrate that the fabricated anisotropic PLA-MGCNC nanocomposites could be laminated into films with the incorporation of directionally tunable mechanical properties. Therefore, the current study provides a novel noninvasive approach of orienting nontoxic bioderived CNCs in the presence of low

  12. Magnetic Cellulose Nanocrystal Based Anisotropic Polylactic Acid Nanocomposite Films: Influence on Electrical, Magnetic, Thermal, and Mechanical Properties.

    Science.gov (United States)

    Dhar, Prodyut; Kumar, Amit; Katiyar, Vimal

    2016-07-20

    This paper reports a single-step co-precipitation method for the fabrication of magnetic cellulose nanocrystals (MGCNCs) with high iron oxide nanoparticle content (∼51 wt % loading) adsorbed onto cellulose nanocrystals (CNCs). X-ray diffraction (XRD), Fourier transform infrared (FTIR), and Raman spectroscopic studies confirmed that the hydroxyl groups on the surface of CNCs (derived from the bamboo pulp) acted as anchor points for the adsorption of Fe3O4 nanoparticles. The fabricated MGCNCs have a high magnetic moment, which is utilized to orient the magnetoresponsive nanofillers in parallel or perpendicular orientations inside the polylactic acid (PLA) matrix. Magnetic-field-assisted directional alignment of MGCNCs led to the incorporation of anisotropic mechanical, thermal, and electrical properties in the fabricated PLA-MGCNC nanocomposites. Thermomechanical studies showed significant improvement in the elastic modulus and glass-transition temperature for the magnetically oriented samples. Differential scanning calorimetry (DSC) and XRD studies confirmed that the alignment of MGCNCs led to the improvement in the percentage crystallinity and, with the absence of the cold-crystallization phenomenon, finds a potential application in polymer processing in the presence of magnetic field. The tensile strength and percentage elongation for the parallel-oriented samples improved by ∼70 and 240%, respectively, and for perpendicular-oriented samples, by ∼58 and 172%, respectively, in comparison to the unoriented samples. Furthermore, its anisotropically induced electrical and magnetic properties are desirable for fabricating self-biased electronics products. We also demonstrate that the fabricated anisotropic PLA-MGCNC nanocomposites could be laminated into films with the incorporation of directionally tunable mechanical properties. Therefore, the current study provides a novel noninvasive approach of orienting nontoxic bioderived CNCs in the presence of low

  13. Transport properties in network models with perfectly conducting channels

    OpenAIRE

    Kobayashi, Koji; Hirose, Kosuke; Obuse, Hideaki; Ohtsuki, Tomi; Slevin, Keith

    2008-01-01

    We study the transport properties of disordered electron systems that contain perfectly conducting channels. Two quantum network models that belong to different universality classes, unitary and symplectic, are simulated numerically. The perfectly conducting channel in the unitary class can be realized in zigzag graphene nano-ribbons and that in the symplectic class is known to appear in metallic carbon nanotubes. The existence of a perfectly conducting channel leads to novel conductance dist...

  14. Critical properties of the metal-insulator transition in anisotropic systems

    OpenAIRE

    Milde, Frank; Römer, Rudolf A.; Schreiber, Michael; Uski, Ville

    1999-01-01

    We study the three-dimensional Anderson model of localization with anisotropic hopping, i.e., weakly coupled chains and weakly coupled planes. In our extensive numerical study we identify and characterize the metal-insulator transition by means of the transfer-matrix method. The values of the critical disorder $W_c$ obtained are consistent with results of previous studies, including multifractal analysis of the wave functions and energy level statistics. $W_c$ decreases from its isotropic val...

  15. Anisotropic Elastic Properties of Flexible Metal-Organic Frameworks: How Soft are Soft Porous Crystals?

    OpenAIRE

    Ortiz, Aurélie U.; Boutin, Anne; Fuchs, Alain H; Coudert, François-Xavier

    2012-01-01

    We performed ab initio calculations of the elastic constants of five flexible metal-organic frameworks: MIL-53(Al), MIL-53(Ga), MIL-47 and the square and lozenge structures of DMOF-1. Tensorial analysis of the elastic constants reveal a highly anisotropic elastic behavior, some deformation directions exhibiting very low Young's modulus and shear modulus. This anisotropy can reach a 400:1 ratio between the most rigid and weakest directions, in stark contrast with the case of non-flexible MOFs ...

  16. Inverse estimation of the elastic and anelastic properties of the porous frame of anisotropic open-cell foams.

    Science.gov (United States)

    Cuenca, Jacques; Göransson, Peter

    2012-08-01

    This paper presents a method for simultaneously identifying both the elastic and anelastic properties of the porous frame of anisotropic open-cell foams. The approach is based on an inverse estimation procedure of the complex stiffness matrix of the frame by performing a model fit of a set of transfer functions of a sample of material subjected to compression excitation in vacuo. The material elastic properties are assumed to have orthotropic symmetry and the anelastic properties are described using a fractional-derivative model within the framework of an augmented Hooke's law. The inverse estimation problem is formulated as a numerical optimization procedure and solved using the globally convergent method of moving asymptotes. To show the feasibility of the approach a numerically generated target material is used here as a benchmark. It is shown that the method provides the full frequency-dependent orthotropic complex stiffness matrix within a reasonable degree of accuracy.

  17. Magnetic Imaging of Applied and Propagating Action Currents in Cardiac Tissue Slices: Determination of Anisotropic Electrical Conductivities in a Two-Dimensional Bidomain.

    Science.gov (United States)

    Staton, Daniel Joseph

    We describe the first, high-resolution magnetic images of applied currents and propagating action currents in slices of canine cardiac tissue. This tissue was maintained in vitro at 37^circC. Our main conclusions are summarized as follows: the action currents produce magnetic fields which are measurable; during the initial stages of the propagating action potential, small, expanding, quatrefoil loops of current develop; the magnetic fields produced by repolarization currents are larger than previously anticipated. Most of the current associated with the propagating action potential is confined within the wavefront and should be magnetically silent; however, differences in the intracellular and extracellular electrical conductivities, in both the longitudinal and transverse fiber directions, are great enough that expanding quatrefoil current densities are associated with the wavefront and produce measurable magnetic fields. Since action currents are affected by the electrical conductivities, it is of interest to determine their values, which depend not only upon the tissue characteristics, but also on the mathematical model used to interpret the measured data. In our analysis of current injection, we use the anisotropic bidomain model which incorporates a passive, linear membrane. We introduce theoretical techniques to calculate the anisotropic conductivities of a two-dimensional bidomain. To apply these techniques to magnetic fields resulting from current injection into cardiac tissue slices, we need to improve the higher spatial frequency content of our present measurements. This may be done by measuring the magnetic field closer to the cardiac slice (presently 2.5 mm), decreasing the sampling interval of the measurement, and increasing the sampling area of the field. Magnetic fields are produced by propagating action currents, which are in turn the result of the propagating action potential. From the magnetic field, we directly image isochronal transmembrane

  18. Anisotropic magnetic, transport and thermodynamic properties of novel tetragonal Ce{sub 2}RhGa{sub 12} compound

    Energy Technology Data Exchange (ETDEWEB)

    Nallamuthu, S.; Rashid, T.P. [Department of Physics, National Institute of Technology, Tiruchirappalli 620 0015 (India); Krishnakumar, V. [Department of Physics, Periyar University, Salem 636 011 (India); Besnard, Celine [Laboratory of Crystallography, University of Geneva, 24 Quai Ernest-Ansermet, CH-1211 Geneva 4 (Switzerland); Hagemann, Hans [Department of Physical Chemistry, University of Geneva, Geneva (Switzerland); Reiffers, Marian [Faculty of Humanities and Natural Sciences, Presov University, Presov (Slovakia); Nagalakshmi, R., E-mail: nagaphys@yahoo.com [Department of Physics, National Institute of Technology, Tiruchirappalli 620 0015 (India)

    2014-08-01

    Highlights: • Ce{sub 2}RhGa{sub 12} crystallizes in tetragonal structure having space-group P4/nbm. • Anisotropic magnetic, transport and thermodynamic properties are investigated. • The antiferromagnetic ordering temperature is 3.5 K. • Sommerfeld parameter γ ≈ 423 mJ/mol K{sup 2}. - Abstract: We report on a comprehensive study of the magnetization, resistivity and heat capacity on the single crystals of Ce{sub 2}RhGa{sub 12} synthesized using Ga flux. Single crystal X-ray diffraction data confirm the tetragonal Pb/nbm structure of Ce{sub 2}RhGa{sub 12}, which is isostructural to Ce{sub 2}PdGa{sub 12}. Ce{sub 2}RhGa{sub 12} orders antiferromagnetically at T{sub N} = 3.5 K and exhibits anisotropic magnetic behavior, inferred from the magnetization and resistivity data, taken along the two principal crystallographic directions of the crystal, viz., along [1 0 0] and [0 0 1]. The anisotropic magnetic response of Ce{sub 2}RhGa{sub 12} establishes [0 0 1] as the easy axis of magnetization, and a weak meta-magnetic transition is also observed in the magnetic isotherm at 2 K along the same axis. A sharp peak in specific heat signals the bulk antiferromagnetic transition at T{sub N} = 3.5 K, which shifts to lower temperatures in low applied fields. The electrical resistivity along the two directions shows metallic behavior from 300 K down to 1.8 K and establishes Ce{sub 2}RhGa{sub 12} as a normal, trivalent cerium compound.

  19. Influence of Coalescence on the Anisotropic Mechanical and Electrical Properties of Nickel Powder/Polydimethylsiloxane Composites

    Directory of Open Access Journals (Sweden)

    Sung-Hwan Jang

    2016-03-01

    Full Text Available Multifunctional polymer-based composites have been widely used in various research and industrial applications, such as flexible and stretchable electronics and sensors and sensor-integrated smart structures. This study investigates the influence of particle coalescence on the mechanical and electrical properties of spherical nickel powder (SNP/polydimethylsiloxane (PDMS composites in which SNP was aligned using an external magnetic field. With the increase of the volume fraction of the SNP, the aligned SNP/PDMS composites exhibited a higher tensile strength and a lower ultimate strain. In addition, the composites with aligned SNP showed a lower percolation threshold and a higher electrical conductivity compared with those with randomly dispersed SNP. However, when the concentration of the SNP reached a certain level (40 vol. %, the anisotropy of the effective material property became less noticeable than that of the lower concentration (20 vol. % composites due to the change of the microstructure of the particles caused by the coalescence of the particles at a high concentration. This work may provide rational methods for the fabrication of aligned composites.

  20. Crystal growth and anisotropic magnetic properties of V3O7

    International Nuclear Information System (INIS)

    Needle-like crystals of V3O7 up to 2 mm in length were grown by a chemical vapor transport method using NH4Cl as a transport agent. The anisotropic magnetic susceptibility was measured for the first time. At 2 K, a spin-flop transition occurs under a magnetic field of 0.1 T. V3O7 is proved to be a uniaxial antiferromagnet with its easy axis parallel to the b-axis of monoclinic structure. A spin structure with antiferromagnetic interaction between (101-bar) layers and ferromagnetic interaction in the layers below the Neel temperature (5.2 K) is suggested. - Graphical abstract: The temperature dependence of the magnetic susceptibility of V3O7 for (H-parallel b) and (H-perpendicular b), respectively, at 0.1 T. The inset shows crystals of V3O7 grown by using NH4Cl as the transport agent.

  1. Anisotropic elastic properties of flexible metal-organic frameworks: how soft are soft porous crystals?

    Science.gov (United States)

    Ortiz, Aurélie U; Boutin, Anne; Fuchs, Alain H; Coudert, François-Xavier

    2012-11-01

    We performed ab initio calculations of the elastic constants of five flexible metal-organic frameworks (MOFs): MIL-53(Al), MIL-53(Ga), MIL-47, and the square and lozenge structures of DMOF-1. Tensorial analysis of the elastic constants reveals a highly anisotropic elastic behavior, some deformation directions exhibiting very low Young's modulus and shear modulus. This anisotropy can reach a 400:1 ratio between the most rigid and weakest directions, in stark contrast to the case of nonflexible MOFs such as MOF-5 and ZIF-8. In addition, we show that flexible MOFs can display extremely large negative linear compressibility. These results uncover the microscopic roots of stimuli-induced structural transitions in flexible MOFs, by linking the local elastic behavior of the material and its multistability. PMID:23215398

  2. Investigation of new ion-conducting ORMOLYTES : structure and properties

    OpenAIRE

    Dahmouche, Karim; Atik, Mohamed; Mello, Nilson C.; Bonagamba, Tito J.; Panepucci, Horacio; Aegerter, Michel A.; Judeinstein, Patrick

    1997-01-01

    Two families of hybrid organic-inorganic composites exhibiting Li+ ionic conduction (ORMOLYTES) have been prepared by the sol-gel process. The first family, prepared from a mixture of 3-isocyanatopropyltriethoxysilane, O,O''Bis (2-aminopropyl)-polyethyleneglycol (or O,O'Bis (2-aminopropyl)-polypropyleneglycol) and lithium salt, presents chemical bonds between the organic and the inorganic phase and an ionic conductivity σ higher than 10-4 S m-1 at room temperature. Their properties have...

  3. Investigation of ion-conducting ormolytes : structure-property relationships

    OpenAIRE

    Judeinstein, Patrick; Schmidt, Helmut K.; Titman, J.; Stamm, M.

    1994-01-01

    Hybrid organic-inorganic composites with ionic properties, so called ormolytes (organically modified electrolytes) have been prepared by the sol-gel process from mixtures of tetraethoxysilane, tetraethylene glycol, and lithium salt. They show ionic conductivity up to 5 x 10-5 Ω-1 cm-1, with activation energies around 0.6 eV. Their properties have been related to their structure using a multitechnique approach (IR, DSC, NMR, SAXS). These materials can be described as diphasic systems wit...

  4. Soil hydraulic properties near saturation, an improved conductivity model

    DEFF Research Database (Denmark)

    Børgesen, Christen Duus; Jacobsen, Ole Hørbye; Hansen, Søren;

    2006-01-01

    The hydraulic properties near saturation can change dramatically due to the presence of macropores that are usually difficult to handle in traditional pore size models. The purpose of this study is to establish a data set on hydraulic conductivity near saturation, test the predictive capability...... of commonly used hydraulic conductivity models and give suggestions for improved models. Water retention and near saturated and saturated hydraulic conductivity were measured for a variety of 81 top and subsoils. The hydraulic conductivity models by van Genuchten [van Genuchten, 1980. A closed-form equation...... for predicting the hydraulic conductivity of unsaturated soils. Soil Sci. Soc. Am. J. 44, 892–898.] (vGM) and Brooks and Corey, modified by Jarvis [Jarvis, 1991. MACRO—A Model of Water Movement and Solute Transport in Macroporous Soils. Swedish University of Agricultural Sciences. Department of Soil Sciences...

  5. Analytical Evalution of Heat Transfer Conductivity with Variable Properties

    DEFF Research Database (Denmark)

    Rahimi, Masoume; Hosseini, Mohammad Javad; Barari, Amin;

    2011-01-01

    The homotopy analysis method (HAM) as a new technique which is powerful and easy-to-use, is applied to solve heat transfer problems. In this paper, we use HAM for heat transfer conductivity equation with variable properties which may contain highly nonlinear terms. The obtained results are also...

  6. NMR Properties of the Polar Phase of Superfluid ^3He in Anisotropic Aerogel Under Rotation

    Science.gov (United States)

    Mineev, V. P.

    2016-09-01

    The polar phase of superfluid ^3He is stable in "nematically ordered" densed aerogel. A rotating vessel with the polar superfluid can be filled either by an array of the single quantum vortices or by an array of the half-quantum vortices. It is shown that the inhomogeneous distribution of the spin part of the order parameter arising in an array of half-quantum vortices in strong enough magnetic field tilted to the average direction of aerogel strands leads to the appearance of a satellite in the NMR signal shifted in the negative direction with respect to the Larmor frequency. The satellite is absent in the case of an array of single quantum vortices which allows to distinguish these two configurations. The polar state in the anisotropic aerogel with lower density transforms at lower temperatures to the axipolar state. The array of half-quantum vortices created in the polar phase keeps its structure under transition to the axipolar state. The temperature dependence of the vortex-satellite NMR frequency is found to be slower below the transition temperature to the axipolar state.

  7. Magnetic properties of anisotropic Ba-Zn-Li system W-type hexagonal ferrites; Ihosei Ba-Zn-Li kei W gata ropposho ferrite no jiki tokusei

    Energy Technology Data Exchange (ETDEWEB)

    Yamamoto, H.; Chono, M. [Meiji University, Tokyo (Japan). School of Science and Technology

    1997-06-15

    This paper describes effects of composition and in-air sintering conditions of anisotropic Ba-Zn-Li system W-type ferrites on their magnetic and mechanical properties. Single W-phase was obtained during semi-sintering by displacing 2Zn{sup 2+} with Li{sup +} and Fe{sup 3+} in the Ba[Zn2(1-x)(LiFe)x]Fe(18)O(27) compound. Phases except W-phase were formed during sintering of the obtained specimen. When the displacement amount of LiFe, x=0.3, the magnetic property (BH)max reached the maximum value. There was not a remarkable improvement compared with the case without displacement. When BaO was added after semi-sintering, the single W-phase could be obtained at lower temperature and the (BH)max value became larger than that before its addition. When the displacement amount of LiFe, x=0.3 in Ba[Zn2(1-x)(LiFe)x]Fe(18)O(27) and 3wt% BaO was added after the semi-sintering, the optimum magnetic property was obtained. For the fabrication conditions, the semi-sintering was conducted at 1275degC for 1 hour in air, and the sintering was conducted at 1225degC for 0.5h in air. A value of (BH)max, 20.40 kJ/m{sup 3} was obtained. 20 refs., 9 figs., 3 tabs.

  8. Molecular anisotropic magnetoresistance

    Science.gov (United States)

    Otte, Fabian; Heinze, Stefan; Mokrousov, Yuriy

    2015-12-01

    Using density functional theory calculations, we demonstrate that the effect of anisotropic magnetoresistance (AMR) can be enhanced by orders of magnitude with respect to conventional bulk ferromagnets in junctions containing molecules sandwiched between ferromagnetic leads. We study ballistic transport in metal-benzene complexes contacted by 3 d transition-metal wires. We show that a gigantic AMR can arise from spin-orbit coupling effects in the leads, drastically enhanced by orbital-symmetry filtering properties of the molecules. We further discuss how this molecular anisotropic magnetoresistance (MAMR) can be tuned by the proper choice of materials and their electronic properties.

  9. Preparation and properties of PAn/ATTP/PE conductive composites

    Institute of Scientific and Technical Information of China (English)

    QIU Jian-hui; FENG Hui-xia

    2006-01-01

    Polyaniline/Attapugite/ PE(PAn-ATTP/PE)composites containing particles with core-shell structure were obtained via the two-step blending processs. The experimental condition is as follows: Organo-attapulgite and PAn was obtained by modifying attapulgite with laury benzenesulfonic acid sodium salt and,then added to PE. The electrical conductivity,structure and properties of the composites were studied. Under the function of shear stress,core-shell structure particles with ATTP as the core and PAn as the shell were formed in the composites. The structure of PAn-ATTP/PE composites were characterized by FTIR,XRD,SEM,etc,respectively. The effects of concentration of doping agent on the conductivity and mechanical property of the composites were investigated. The mechanical properties and impact fracture surface of the ternary composites were studied by means of the tensile tester,SEM,etc. The results show that polyaniline encapsulated ATTP enhances the strength of the PE. And the conductivity of PAn-ATTP/PE composites of is improved effectively when polyaniline encapsulated ATTP is added. The composite have good conductivity when 10% polyaniline encapsulated ATTP is added.

  10. Effect of cryogenic treatment on thermal conductivity properties of copper

    Science.gov (United States)

    Nadig, D. S.; Ramakrishnan, V.; Sampathkumaran, P.; Prashanth, C. S.

    2012-06-01

    Copper exhibits high thermal conductivity properties and hence it is extensively used in cryogenic applications like cold fingers, heat exchangers, etc. During the realization of such components, copper undergoes various machining operations from the raw material stage to the final component. During these machining processes, stresses are induced within the metal resulting in internal stresses, strains and dislocations. These effects build up resistance paths for the heat carriers which transfer heat from one location to the other. This in turn, results in reduction of thermal conductivity of the conducting metal and as a result the developed component will not perform as per expectations. In the process of cryogenic treatment, the metal samples are exposed to cryogenic temperature for extended duration of time for 24 hours and later tempered. During this process, the internal stresses and strains are reduced with refinement of the atomic structure. These effects are expected to favourably improve thermal conductivity properties of the metal. In this experimental work, OFHC copper samples were cryotreated for 24 hours at 98 K and part of them were tempered at 423K for one hour. Significant enhancement of thermal conductivity values were observed after cryotreating and tempering the copper samples.

  11. On the Relativistic anisotropic configurations

    CERN Document Server

    Shojai, F; Stepanian, A

    2016-01-01

    In this paper we study anisotropic spherical polytropes within the framework of general relativity. Using the anisotropic Tolman-Oppenheimer-Volkov (TOV) equations, we explore the relativistic anisotropic Lane-Emden equations. We find how the anisotropic pressure affects the boundary conditions of these equations. Also we argue that the behaviour of physical quantities near the center of star changes in the presence of anisotropy. For constant density, a class of exact solution is derived with the aid of a new ansatz and its physical properties are discussed.

  12. On the relativistic anisotropic configurations

    Energy Technology Data Exchange (ETDEWEB)

    Shojai, F. [University of Tehran, Department of Physics, Tehran (Iran, Islamic Republic of); Institute for Research in Fundamental Sciences (IPM), Foundations of Physics Group, School of Physics, Tehran (Iran, Islamic Republic of); Kohandel, M. [Alzahra University, Department of Physics and Chemistry, Tehran (Iran, Islamic Republic of); Stepanian, A. [University of Tehran, Department of Physics, Tehran (Iran, Islamic Republic of)

    2016-06-15

    In this paper we study anisotropic spherical polytropes within the framework of general relativity. Using the anisotropic Tolman-Oppenheimer-Volkov equations, we explore the relativistic anisotropic Lane-Emden equations. We find how the anisotropic pressure affects the boundary conditions of these equations. Also we argue that the behavior of physical quantities near the center of star changes in the presence of anisotropy. For constant density, a class of exact solution is derived with the aid of a new ansatz and its physical properties are discussed. (orig.)

  13. Properties of axial surface waves along dielectrically coated conducting cylinders

    OpenAIRE

    Siart, U.; Adrian, S.; Eibert, T.

    2012-01-01

    In this paper the fundamental properties of surface waves along conducting cylinders with and without dielectric coating are investigated for cylinder diameters in the centimeter range and frequencies in the gigahertz range and higher. Analytical results for the phase constant and attenuation versus the cylinder radius are derived and cutoff frequencies of various TE, TM, and hybrid waves are computed. The radial power distribution is computed in order to investi...

  14. Microwave conductance properties of aligned multiwall carbon nanotube textile sheets

    Science.gov (United States)

    Brown, Brian L.; Martinez, Patricia; Zakhidov, Anvar A.; Shaner, Eric A.; Lee, Mark

    2015-07-01

    Understanding the conductance properties of multi-walled carbon nanotube (MWNT) textile sheets in the microwave regime is essential for their potential use in high-speed and high-frequency applications. To expand current knowledge, complex high-frequency conductance measurements from 0.01 to 50 GHz and across temperatures from 4.2 K to 300 K and magnetic fields up to 2 T were made on textile sheets of highly aligned MWNTs with strand alignment oriented both parallel and perpendicular to the microwave electric field polarization. Sheets were drawn from 329 and 520 μm high MWNT forests that resulted in different DC resistance anisotropy. For all samples, the microwave conductance can be modeled approximately by a shunt capacitance in parallel with a frequency-independent conductance, but with no inductive contribution. This is consistent with diffusive Drude conduction as the primary transport mechanism up to 50 GHz. Further, it is found that the microwave conductance is essentially independent of both temperature and magnetic field.

  15. Electrical conductivity and dielectric properties of potassium sulfamate single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, A.S.; Iype, L.; Rajesh, R. [School of Pure and Applied Physics, Mahatma Gandhi University, Kottayam (India); Varughese, G. [Department of Physics, Catholicate College, Pathanamthitta, Kerala (India); Joseph, G. [Department of Physics, Sacred Heart College, Thevera, Cochin, Kerala (India); Louis, G. [Department of Physics, Cochin University of Science and Technology, Cochin (India)

    2011-10-15

    Single crystals of potassium sulfamate are grown by the method of slow evaporation at constant temperature. AC electrical conductivity of potassium sulfamate is measured in the temperature range 300-430 K and in the frequency region between 100 Hz and 3 MHz along the a, b and c-axes. Complex impedance spectroscopy is used to investigate the frequency response of the electrical properties of the potassium sulfamate single crystal. Temperature variation of AC conductivity and dielectric measurements show a slope change around 345 K for both heating and cooling run and this anomaly is attributed as phase transition, which is well supported by the DSC measurements. Value of loss tangent in the temperature region 330-400 K is found to be very low. Activation energies for the conduction process are calculated along the a, b and c-axes. (copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  16. Anisotropic In-Plane Conductivity and Dichroic Gold Plasmon Resonance in Plasma-Assisted ITO Thin Films e-Beam-Evaporated at Oblique Angles.

    Science.gov (United States)

    Parra-Barranco, Julián; García-García, Francisco J; Rico, Víctor; Borrás, Ana; López-Santos, Carmen; Frutos, Fabián; Barranco, Angel; González-Elipe, Agustín R

    2015-05-27

    ITO thin films have been prepared by electron beam evaporation at oblique angles (OA), directly and while assisting their growth with a downstream plasma. The films microstructure, characterized by scanning electron microscopy, atomic force microscopy, and glancing incidence small-angle X-ray scattering, consisted of tilted and separated nanostructures. In the plasma assisted films, the tilting angle decreased and the nanocolumns became associated in the form of bundles along the direction perpendicular to the flux of evaporated material. The annealed films presented different in-depth and sheet resistivity as confirmed by scanning conductivity measurements taken for the individual nanocolumns. In addition, for the plasma-assisted thin films, two different sheet resistance values were determined by measuring along the nanocolumn bundles or the perpendicular to it. This in-plane anisotropy induces the electrochemical deposition of elongated gold nanostructures. The obtained Au-ITO composite thin films were characterized by anisotropic plasmon resonance absorption and a dichroic behavior when examined with linearly polarized light. PMID:25938593

  17. Predicting saturated hydraulic conductivity using soil morphological properties

    Directory of Open Access Journals (Sweden)

    Gülay Karahan

    2016-01-01

    Full Text Available Many studies have been conducted to predict soil saturated hydraulic conductivity (Ks by parametric soil properties such as bulk density and particle-size distribution. Although soil morphological properties have a strong effect on Ks, studies predicting Ks by soil morphological properties such as type, size, and strength of soil structure; type, orientation and quantity of soil pores and roots and consistency are rare. This study aimed at evaluating soil morphological properties to predict Ks. Undisturbed soil samples (15 cm length and 8.0 cm id. were collected from topsoil (0-15 cm and subsoil (15-30 cm (120 samples with a tractor operated soil sampler at sixty randomly selected sampling sites on a paddy field and an adjecent grassland in Central Anatolia (Cankırı, Turkey. Synchronized disturbed soil samples were taken from the same sampling sites and sampling depths for basic soil analyses. Saturated hydraulic conductivity was measured on the soil columns using a constant-head permeameter. Following the Ks measurements, the upper part of soil columns were covered to prevent evaporation and colums were left to drain in the laboratory. When the water flow through the column was stopped, a subsample were taken for bulk density and then soil columns were disturbed for describing the soil morphological properties. In addition, soil texture, bulk density, pH, field capacity, wilting point, cation exchange capacity, specific surface area, aggregate stability, organic matter, and calcium carbonate were measured on the synchronized disturbed soil samples. The data were divided into training (80 data values and validation (40 data values sets. Measured values of Ks ranged from 0.0036 to 2.14 cmh-1 with a mean of 0.86 cmh-1. The Ks was predicted from the soil morphological and parametric properties by stepwise multiple linear regression analysis. Soil structure class, stickiness, pore-size, root-size, and pore-quantity contributed to the Ks prediction

  18. Investigation of Mechanical Properties of Magneto-Rheological Ethylene Propylene Diene Monomer and Natural Rubber Type Synthetic Rubbers for Both Isotropic and Anisotropic Situations

    Directory of Open Access Journals (Sweden)

    Uğur Mazlum

    2015-12-01

    Full Text Available Magneto-rheological (MR materials are in a smart material class that has the rheological properties to be quickly and reversibly controlled with the external magnetic field applications. Considering the technological developments the rubber-like smart materials has had a more functional usage area with magneto- rheological effect. This study investigates the axial mechanical properties of magneto-rheological Ethylene Propylene Diene Monomer (EPDM and Natural Rubber (NR type synthetic rubbers for isotropic and anisotropic situations. Also, these composite materials were built by means of hot press systems as either isotropic or anisotropic using magnetic field application after addition of ferromagnetic powders. The influence of magnetic field was investigated. In this study, NR rubber was found to be more susceptible in terms of smart material properties unlike EPDM synthetic rubber.

  19. Dynamics of Anisotropic Universes

    CERN Document Server

    Pérez, J

    2006-01-01

    We present a general study of the dynamical properties of Anisotropic Bianchi Universes in the context of Einstein General Relativity. Integrability results using Kovalevskaya exponents are reported and connected to general knowledge about Bianchi dynamics. Finally, dynamics toward singularity in Bianchi type VIII and IX universes are showed to be equivalent in some precise sence.

  20. Electrical properties of the anisotropic n-ТiО2/P-CdTe heterojunctions

    OpenAIRE

    Брус, Віктор Васильович; Ілащук, Марія Іванівна; Ковалюк, Захар Дмитрович; Мар’янчук, Павло Дмитрович; Ульяницький, Костянтин Сергійович; Кафанов, Анатолій Михайлович

    2012-01-01

    The electrical properties of the n-ТіО2/p-CdTe, prepared by deposition of TiO2 film onto freshly cleaved CdTe single crystal substrates were investigated. The electric current in the heterojunctions is induced by generation-recombination processes within the depletion region and tunneling of carriers

  1. Mechanical properties of cancellous bone in the human mandibular condyle are anisotropic

    DEFF Research Database (Denmark)

    Giesen, EB; Ding, Ming; Dalstra, M;

    2001-01-01

    ). Archimedes' principle was applied to determine bone density parameters. The cancellous bone was in axial loading 3.4 times stiffer and 2.8 times stronger upon failure than in transverse loading. High coefficients of correlation were found among the various mechanical properties and between them...

  2. Preparation and Magnetic Properties of Anisotropic (Sm,PrCo5/Fe Nanocomposites Particles via Electroless Plating

    Directory of Open Access Journals (Sweden)

    Shi Wang

    2014-01-01

    Full Text Available Anisotropic (Sm,PrCo5/Fe nanocomposites particles were prepared by electroless plating iron on the surface of (Sm,PrCo5 nanoflakes after being prepared by ball milling for 4 h. A uniform and continuous coating layer was obtained due to the addition of complexing agent and the particle size of the reduced Fe particles was in the range of 10~20 nm. When the nominal addition of Fe was 15 wt%, the nanocomposites show enhanced remnant and saturation magnetization: Mr=53.35 emu/g, Ms=73.08 emu/g compared to the noncoated nanoflakes with Mr=48.52 emu/g, Ms=60.15 emu/g, while the coercivity drops from 10.33 kOe to 8.89 kOe. The effect of Fe content on the magnetic properties of the magnets is also discussed.

  3. Averaging anisotropic cosmologies

    International Nuclear Information System (INIS)

    We examine the effects of spatial inhomogeneities on irrotational anisotropic cosmologies by looking at the average properties of anisotropic pressure-free models. Adopting the Buchert scheme, we recast the averaged scalar equations in Bianchi-type form and close the standard system by introducing a propagation formula for the average shear magnitude. We then investigate the evolution of anisotropic average vacuum models and those filled with pressureless matter. In the latter case we show that the backreaction effects can modify the familiar Kasner-like singularity and potentially remove Mixmaster-type oscillations. The presence of nonzero average shear in our equations also allows us to examine the constraints that a phase of backreaction-driven accelerated expansion might put on the anisotropy of the averaged domain. We close by assessing the status of these and other attempts to define and calculate 'average' spacetime behaviour in general relativity

  4. Physical properties of Li ion conducting polyphosphazene based polymer electrolytes

    Energy Technology Data Exchange (ETDEWEB)

    Sanderson, S.; Zawodzinski, T.; Hermes, R.; Davey, J.; Dai, Hongli

    1996-12-31

    We report a systematic study of the transport properties and the underlying physical chemistry of some polyphosphazene (PPhz)-based polymer electrolytes. We synthesized MEEP and variants which employed mixed combinations of different length oxyethylene side-chains. We compare the conductivity and ion-ion interactions in polymer electrolytes obtained with lithium triflate and lithium bis(trifluoromethanesulfonyl)imide (TFSI) salts added to the polymer. The combination of the lithium imide salt and MEEP yields a maximum conductivity of 8 x 10{sup -5} {Omega}{sup -1} cm{sup -1} at room temperature at a salt loading of 8 monomers per lithium. In one of the mixed side-chain variations, a maximum conductivity of 2 x 10{sup -4} {Omega}{sup -1} cm{sup -1} was measured at the same molar ratio. Raman spectral analysis shows some ion aggregation and some polymer - ion interactions in the PPhz-LiTFSI case but much less than observed with Li CF{sub 3}SO{sub 3}. A sharp increase in the Tg as salt is added corresponds to concentrations above which the conductivity significantly decreases and ion associations appear.

  5. Field-dependent anisotropic microrheological and microstructural properties of dilute ferrofluids.

    Science.gov (United States)

    Yendeti, Balaji; Thirupathi, G; Vudaygiri, Ashok; Singh, R

    2014-08-01

    We have measured microrheological and microstructural properties of a superparamagnetic ferrofluid made of Mn0.75Zn0.25Fe2O4 (MZF) nanoparticles, using passive microrheology in a home-built inverted microscope. Thermal motion of a probe microsphere was measured for different values of an applied external magnetic field and analysed. The analysis shows anisotropy in magneto-viscous effect. Additional microrheological properties, such as storage modulus and loss modulus and their transition are also seen. We have also obtained microstructural properties such as elongational flow coefficient [Formula: see text] , relaxation time constant [Formula: see text] , coefficient of dissipative magnetization [Formula: see text] , etc., using the analysis given in Oliver Muller et al., J. Phys.: Condens. Matter 18, S2623, (2006) and Stefan Mahle et al., Phys. Rev. E 77, 016305 (2008) over our measured viscosity data. Our values for the above parameters are in agreement with earlier theoretical calculations and macro-rheological experimental measurements. These theoretical calculations consider an ideal situation of zero-shear limit, which is best approximated only in the passive microrheology technique described here and a first time measurement of all these parameters with passive microrheology. PMID:25117500

  6. Influence of anisotropic grain boundary properties on the evolution of grain boundary character distribution during grain growth—a 2D level set study

    International Nuclear Information System (INIS)

    The present study elaborates on a 2D level set model of polycrystal microstructures that was recently established by adding the influence of anisotropic grain boundary energy and mobility on microstructure evolution. The new model is used to trace the evolution of grain boundary character distribution during grain growth. The employed level set formulation conveniently allows the grain boundary characteristics to be quantified in terms of coincidence site lattice (CSL) type per unit of grain boundary length, providing a measure of the distribution of such boundaries. In the model, both the mobility and energy of the grain boundaries are allowed to vary with misorientation. In addition, the influence of initial polycrystal texture is studied by comparing results obtained from a polycrystal with random initial texture against results from a polycrystal that initially has a cube texture. It is shown that the proposed level set formulation can readily incorporate anisotropic grain boundary properties and the simulation results further show that anisotropic grain boundary properties only have a minor influence on the evolution of CSL boundary distribution during grain growth. As anisotropic boundary properties are considered, the most prominent changes in the CSL distributions are an increase of general low-angle Σ1 boundaries as well as a more stable presence of Σ3 boundaries. The observations also hold for the case of an initially cube-textured polycrystal. The presence of this kind of texture has little influence over the evolution of the CSL distribution. Taking into consideration the anisotropy of grain boundary properties, grain growth alone does not seem to be sufficient to promote any significantly increased overall presence of CSL boundaries. (paper)

  7. Anisotropic magnetic properties of single crystals of SmRh4B4

    International Nuclear Information System (INIS)

    The magnetic susceptibility of single crystals of SmRh4B4 has been measured for two orientations of the crystals with respect to the applied field H. At low temperatures, the easy direction of magnetization is perpendicular to the tetragonal c axis, while for temperatures higher than 73 K, the easy axis of magnetization is parallel to the c axis. The data have been analyzed by including intermediate coupling of the lowest three J manifolds of the Sm/sup 3+/ ion, crystal-field interactions, and conduction-electron polarization effects. The anisotropy crossover is shown to result primarily from a competition between the anisotropy of the crystal-field energy levels in the ground (J = (5/2) manifold and the anisotropy of Van Vleck terms due to mixing of the J = (5/2 and J = 7) / 2 manifolds

  8. Anisotropic magneto-optical properties of vanadium in Bi4Ge3O12

    Science.gov (United States)

    Petkova, P.

    2016-07-01

    The paper deals with the investigation of the magneto-optical effect and photochromism in vanadium doped Bi4Ge3O12 (BGO) single crystals in a wide spectral range. It has been found out that the photosensitivity of doped crystals is significantly shifted to the visible wavelengths. This investigation reports the experimental results of Faraday rotation in the case of vanadium doped Bi4Ge3O12. The rotation angle of the polarization plane of the crystal plate has been investigated in the magnetic field in an illuminated state, obtained by exposure with ultraviolet (UV) light and an annealed state developed after annealing at 400 °C. We have observed the strong appearance of vanadium impurity in the spectral range 380-700 nm. The experimental determination of magneto-optical properties of V4+ ions gives us an opportunity for calculation of the refractive index n of the doped BGO.

  9. Anisotropic tensile properties of tungsten fiber reinforced Zr based metallic glass composites

    International Nuclear Information System (INIS)

    The tensile properties and deformation behaviors of Zr based metallic glass composites containing different tungsten fiber orientations were investigated. The angles (θf) between tungsten fiber orientation and loading axial direction are 0°, 15°, 30°, 45°, 60°, 75° and 90°, respectively. The results show that the strength and the failure modes vary with θf. The tensile strength of the composite decreases as the θf increases. The tensile strength of the composite at θf=90° is only 253 MPa. The plasticity of all the composites do not be improved. The composites failed approximately 90° normal fault at θf=0°/15°, while the composites failed along the tungsten fiber when the θf is bigger than or equal to 30° because of the low axial grain boundary strength of the elongated W grains

  10. Electrical dissipation and material properties of in-plane anisotropic superconducting YBCO films

    CERN Document Server

    Czerwinka, P S

    2001-01-01

    vortex liquid-to-glass phase transition model (VG). In all cases, the data can be successfully collapsed when scaled under the VG algorithm forming the expected master curves for temperatures above and below the vortex-glass 'transition' temperature T sub V sub G (B). However, between film systems we observe wide variations of the critical exponent z(theta,B) and T sub V sub G (B) as a function of field strength (B) and field orientation (theta). This lack of 'universality' does not allow interpretation of the scaling as evidence for a vortex liquid-to-glass phase transition. We find quantitative evidence in support of alternative scaling models which are based upon conventional flux-flow/creep theories and distributions of vortex-pinning strength. We investigate the growth, material and electrical properties of a wide variety of YBa sub 2 Cu sub 3 O sub 7 sub - subdelta films (40-480nm). The films range from c-axis normal to c-axis parallel to the film plane and were grown upon SrTiO sub 3 (STO) and LaSrGaO ...

  11. Nonlinear conductive properties and scaling behavior of conductive particle filled high-density polyethylene composites

    Institute of Scientific and Technical Information of China (English)

    ZHENG Qiang; SHEN Lie; LI Wenchun; SONG Yihu; YI Xiaosu

    2005-01-01

    The blends prepared by incorporation of carbon black (CB) or graphite powder (GP) inHto high-density polyethylene (HDPE) matrix have been novel and extensively applied polymeric positive temperature coefficient (PTC) composites. A phenomenological model was proposed on the basis of the GEM equation and the dilution effect of filler volume fraction due to the thermal volume expansion of the polymer matrix. Accordingly, the contribution of the thermal expansion of the matrix to the jump-like PTC transition of the composites was quantitatively estimated and a mechanical explanation was given. It was proved that the contribution of the volume expansion to PTC effect decreased for HDPE/CB composites crosslinked through electron-beam irradiation. Furthermore, the influences of the filler content, temperature and crosslinking on the self-heating behavior as well as the nonlinear conduction characteristics at electrical-thermal equilibrium state were examined. Based on the electric-field and initial resistivity dependence of the self-heating temperature and resistance dependence of the critical field, the mechanisms of the self-heating of the polymeric PTC materials were evaluated. The intrinsic relations between macroscopic electrical properties and microscopic percolation network at electrical-thermal equilibrium state were discussed according to the scaling relationship between the self-heating critical parameter and the conductivity of materials.

  12. Pristine Basal- and Edge-Plane-Oriented Molybdenite MoS2 Exhibiting Highly Anisotropic Properties.

    Science.gov (United States)

    Tan, Shu Min; Ambrosi, Adriano; Sofer, Zdenĕk; Huber, Štěpán; Sedmidubský, David; Pumera, Martin

    2015-05-01

    The layered structure of molybdenum disulfide (MoS2 ) is structurally similar to that of graphite, with individual sheets strongly covalently bonded within but held together through weak van der Waals interactions. This results in two distinct surfaces of MoS2 : basal and edge planes. The edge plane was theoretically predicted to be more electroactive than the basal plane, but evidence from direct experimental comparison is elusive. Herein, the first study comparing the two surfaces of MoS2 by using macroscopic crystals is presented. A careful investigation of the electrochemical properties of macroscopic MoS2 pristine crystals with precise control over the exposure of one plane surface, that is, basal plane or edge plane, was performed. These crystals were characterized thoroughly by AFM, Raman spectroscopy, X-ray photoelectron spectroscopy, voltammetry, digital simulation, and DFT calculations. In the Raman spectra, the basal and edge planes show anisotropy in the preferred excitation of E2g and A1g phonon modes, respectively. The edge plane exhibits a much larger heterogeneous electron transfer rate constant k(0) of 4.96×10(-5) and 1.1×10(-3)  cm s(-1) for [Fe(CN)6 ](3-/4-) and [Ru(NH3 )6 ](3+/2+) redox probes, respectively, compared to the basal plane, which yielded k(0) tending towards zero for [Fe(CN)6 ](3-/4-) and about 9.3×10(-4)  cm s(-1) for [Ru(NH3 )6 ](3+/2+) . The industrially important hydrogen evolution reaction follows the trend observed for [Fe(CN)6 ](3-/4-) in that the basal plane is basically inactive. The experimental comparison of the edge and basal planes of MoS2 crystals is supported by DFT calculations. PMID:25821017

  13. Hydraulic Conductivity Distributions for Anisotropic Systems and Application to Tc Transport at the U.S. Department of Energy Hanford Site

    International Nuclear Information System (INIS)

    At the United States Department of Energy Hanford Site a spill of radioactive Technetium has been migrating horizontally in the vadose zone rather than flowing vertically to the water table. This result has been interpreted as being due to horizontal anisotropy in the hydraulic conductivity, K, (a tendency for fluids to migrate more easily in the horizontal direction) due to high horizontal connectivity of sedimentary deposits with a tendency for larger values of K. Such layers have larger components of silt and clay than the predominantly sandy soils at the Hanford site. It is generally accepted that effects of such anisotropy tend to be greater at smaller length scales, probably because of the lack of perfect correlations at large length scales. It has also been suggested that this anisotropy in K is maximized under relatively dry conditions when finer soils (with smaller pores) trap moisture more effectively than sands and gravels. The random component of the distribution of the Hanford flood deposits requires a probabilistic framework for the calculation of K. The work on this project had two main components: (1) to use continuum percolation theory applied to random fractal models to produce a general framework for calculating distributions of K under anisotropic conditions and as a function of system scale, (2) to apply the scheme for calculation to the Hanford site. The results of the general calculation (submitted for publication in Philosophical Magazine) are that the mean horizontal and vertical K values become equal in the limit of large system size (in agreement with general perception above) while the distributions of K values cause significant overlap of expected experimental values of K in the vertical and horizontal directions already at intermediate length scales. In order to make these calculation specific to the Hanford site, however, values of the appropriate length scales to describe the Hanford subsurface as well as to describe the maximum

  14. The Properties of Normal Conducting Cathodes in FZD Superconducting Gun

    CERN Document Server

    Xiang, R; Buettig, H; Janssen, D; Justus, M; Lehnert, U; Michel, P; Murcek, P; Schamlott, A; Schneider, Ch; Schurig, R; Staufenbiel, F; Teichert, J

    2009-01-01

    The superconducting radio frequency photoinjector (SRF photoinjector) is one of the latest applications of SC technology in the accelerator field. Since superconducting cathodes with high QE are not available up to now, normal conducting cathode material is the main choice for the SRF photoinjectors. However, the compatibility between the cathode and the cavity is one of the challenges for this concept. The SRF gun with Cs2Te cathode has been successfully operated under the collaboration of BESSY, DESY, FZD, and MBI. In this paper, some experience gained in the gun commissioning will be concluded. The results of the properties of Cs2Te photocathode in the cavity will be presented, such as the Q.E., the life time, the dark current and the thermal emittance.

  15. The Derived Equivalent Circuit Model for Magnetized Anisotropic Graphene

    CERN Document Server

    Cao, Ying S; Ruehli, Albert E

    2015-01-01

    Due to the static magnetic field, the conductivity for graphene becomes a dispersive and anisotropic tensor, which complicates most modeling methodologies. In this paper, a novel equivalent circuit model is proposed for graphene with the magnetostatic bias based on the electric field integral equation (EFIE). To characterize the anisotropic property of the biased graphene, the resistive part of the unit circuit is replaced by a resistor in series with current control voltage sources (CCVSs). The CCVSs account for the off-diagonal parts of the surface conductivity tensor for the magnetized graphene. Furthermore, the definitions of the absorption cross section and the scattering cross section are revisited to make them feasible for derived circuit analysis. This proposed method is benchmarked with several numerical examples. This paper also provides a new equivalent circuit model to deal with dispersive and anisotropic materials.

  16. Interpreting equilibrium-conductivity and conductivity-relaxation measurements to establish thermodynamic and transport properties for multiple charged defect conducting ceramics.

    Science.gov (United States)

    Zhu, Huayang; Ricote, Sandrine; Coors, W Grover; Kee, Robert J

    2015-01-01

    A model-based interpretation of measured equilibrium conductivity and conductivity relaxation is developed to establish thermodynamic, transport, and kinetics parameters for multiple charged defect conducting (MCDC) ceramic materials. The present study focuses on 10% yttrium-doped barium zirconate (BZY10). In principle, using the Nernst-Einstein relationship, equilibrium conductivity measurements are sufficient to establish thermodynamic and transport properties. However, in practice it is difficult to establish unique sets of properties using equilibrium conductivity alone. Combining equilibrium and conductivity-relaxation measurements serves to significantly improve the quantitative fidelity of the derived material properties. The models are developed using a Nernst-Planck-Poisson (NPP) formulation, which enables the quantitative representation of conductivity relaxations caused by very large changes in oxygen partial pressure.

  17. Anisotropic universe with anisotropic sources

    Energy Technology Data Exchange (ETDEWEB)

    Aluri, Pavan K.; Panda, Sukanta; Sharma, Manabendra; Thakur, Snigdha, E-mail: aluri@iucaa.ernet.in, E-mail: sukanta@iiserb.ac.in, E-mail: manabendra@iiserb.ac.in, E-mail: snigdha@iiserb.ac.in [Department of Physics, IISER Bhopal, Bhopal - 462023 (India)

    2013-12-01

    We analyze the state space of a Bianchi-I universe with anisotropic sources. Here we consider an extended state space which includes null geodesics in this background. The evolution equations for all the state observables are derived. Dynamical systems approach is used to study the evolution of these equations. The asymptotic stable fixed points for all the evolution equations are found. We also check our analytic results with numerical analysis of these dynamical equations. The evolution of the state observables are studied both in cosmic time and using a dimensionless time variable. Then we repeat the same analysis with a more realistic scenario, adding the isotropic (dust like dark) matter and a cosmological constant (dark energy) to our anisotropic sources, to study their co-evolution. The universe now approaches a de Sitter space asymptotically dominated by the cosmological constant. The cosmic microwave background anisotropy maps due to shear are also generated in this scenario, assuming that the universe contains anisotropic matter along with the usual (dark) matter and vacuum (dark) energy since decoupling. We find that they contribute dominantly to the CMB quadrupole. We also constrain the current level of anisotropy and also search for any cosmic preferred axis present in the data. We use the Union 2 Supernovae data to this extent. An anisotropy axis close to the mirror symmetry axis seen in the cosmic microwave background data from Planck probe is found.

  18. Material Induced Anisotropic Damage

    NARCIS (Netherlands)

    Niazi, M.S.; Wisselink, H.H.; Meinders, V.T.; Boogaard, van den A.H.; Hora, P.

    2012-01-01

    The anisotropy in damage can be driven by two different phenomena; anisotropic defor-mation state named Load Induced Anisotropic Damage (LIAD) and anisotropic (shape and/or distribution) second phase particles named Material Induced Anisotropic Damage (MIAD). Most anisotropic damage models are based

  19. Electrochromic properties of a novel low band gap conductive copolymer

    Energy Technology Data Exchange (ETDEWEB)

    Yigitsoy, Basak; Varis, Serhat; Tanyeli, Cihangir; Akhmedov, Idris M.; Toppare, Levent [Department of Chemistry, Middle East Technical University, 06531 Ankara (Turkey)

    2007-07-10

    A copolymer of 2,5-di(thiophen-2-yl)-1-p-tolyl-1H-pyrrole (DTTP) with 3,4-ethylene dioxythiophene (EDOT) was electrochemically synthesized. The resultant copolymer P(DTTP-co-EDOT) was characterized via cyclic voltammetry, FTIR, SEM, conductivity measurements and spectroelectrochemistry. Copolymer film has distinct electrochromic properties. It has four different colors (chestnut, khaki, camouflage green, and blue). At the neutral state {lambda}{sub max} due to the {pi}-{pi}{sup *} transition was found to be 487 nm and E{sub g} was calculated as 1.65 eV. Double potential step chronoamperometry experiment shows that copolymer film has good stability, fast switching time (less than 1 s) and good optical contrast (20%). An electrochromic device based on P(DTTP-co-EDOT) and poly(3,4-ethylenedioxythiophene) (PEDOT) was constructed and characterized. The device showed reddish brown color at -0.6 V when the P(DTTP-co-EDOT) layer was in its reduced state; whereas blue color at 2.0 V when PEDOT was in its reduced state and P(DTTP-co-EDOT) layer was in its oxidized state. At 0.2 V intermediate green state was observed. Maximum contrast (%{delta}T) and switching time of the device were measured as 18% and 1 s at 615 nm. ECD has good environmental and redox stability. (author)

  20. Electrochemical Properties for Co-Doped Pyrite with High Conductivity

    Directory of Open Access Journals (Sweden)

    Yongchao Liu

    2015-09-01

    Full Text Available In this paper, the hydrothermal method was adopted to synthesize nanostructure Co-doped pyrite (FeS2. The structural properties and morphology of the synthesized materials were characterized using X-ray diffraction (XRD and scanning electron microscopy (SEM, respectively. Co in the crystal lattice of FeS2 could change the growth rate of different crystal planes of the crystal particles, which resulted in various polyhedrons with clear faces and sharp outlines. In addition, the electrochemical performance of the doping pyrite in Li/FeS2 batteries was evaluated using the galvanostatic discharge test, cyclic voltammetry and electrochemical impedance spectroscopy. The results showed that the discharge capacity of the doped material (801.8 mAh·g−1 with a doping ratio of 7% was significantly higher than that of the original FeS2 (574.6 mAh·g−1 because of the enhanced conductivity. Therefore, the doping method is potentially effective for improving the electrochemical performance of FeS2.

  1. Ionic Conductivity and Dielectric Properties of the PAN-Ion Conducting Polymers

    Institute of Scientific and Technical Information of China (English)

    N.M.Ali; L.Othman; K.B.Md; Isa; A.Ahmad; Z.Osman

    2007-01-01

    1 Results In this work, the ion conducting films of polyacrylonitrile (PAN) containing lithium triflate (LiCF3SO3) and sodium triflate (NaCF3SO3) were prepared by the solution casting technique. The ionic conductivity measurements were carried out using impedance spectroscopy. The room temperature conductivity for pure polyacrylonitrile film is 1.51×10-11 S·cm-1. The room temperature conductivity for the highest conducting film in the PAN-LiCF3SO3 and PAN-NaCF3SO3 systems is 1.51×10-5 and 7.99×10-6 S·...

  2. Review on Optical and Electrical Properties of Conducting Polymers

    Directory of Open Access Journals (Sweden)

    Manisha Bajpai

    2016-01-01

    Full Text Available We reviewed optical and electrical properties of conjugated polymers. The charge transport models to describe the hole and electron transport mechanism are also included in the electrical properties of conjugated polymers. The effect of optical and electrical properties after doping is also indexed in this paper.

  3. Anisotropic Stars Exact Solutions

    CERN Document Server

    Dev, K; Dev, Krsna; Gleiser, Marcelo

    2000-01-01

    We study the effects of anisotropic pressure on the properties of spherically symmetric, gravitationally bound objects. We consider the full general relativistic treatment of this problem and obtain exact solutions for various form of equations of state connecting the radial and tangential pressures. It is shown that pressure anisotropy can have significant effects on the structure and properties of stellar objects. In particular, the maximum value of 2M/R can approach unity (2M/R < 8/9 for isotropic objects) and the surface redshift can be arbitrarily large.

  4. Nanoionics phenomenon in proton-conducting oxide: Effect of dispersion of nanosize platinum particles on electrical conduction properties

    Directory of Open Access Journals (Sweden)

    Hiroshige Matsumoto et al

    2007-01-01

    Full Text Available High-temperature proton conductors are oxides in which low-valence cations are doped as electron acceptors; the incorporation of water molecules into the oxides results in the formation of protonic defects that act as charge carriers. Since the protons thus formed are in equilibrium with other electronic defects, electrons and holes, the oxides possibly have different proton-conduction properties at and near boundaries when they are in contact with another phase. In this paper, we present our recent experimental observation of a marked change in the electrical properties of a proton conductor upon the dispersal of fine platinum particles in the oxide. First, the material shows extremely low electrical conductivity in comparison with the original proton-conducting perovskite. Second, there was a threshold amount of platinum at which such a drop in conductivity occurred. A percolation model is employed to explain these experimental results; the fine platinum particles dispersed in the proton-conducting oxide wears highly resistive skin that is formed due to shifts in defect equilibriums, which prevents ionic/electronic conduction. The experiments suggest that the ion-conducting properties of oxides can be varied by introducing interfaces at a certain density; nanoionics is a key to yielding enhanced and/or controlled ionic conduction in solids.

  5. Studies and Properties of Ceramics with High Thermal Conductivity

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The sintering technology of the AlN ceramics power were discussed. It is discussed that the compound sintering aids is consistent with the enhancement of the the thermal conductivity of AlN ceramics, and sintering technics is helped to the improvement of density. It is analyzed how to sinter machinable AlN ceramics with high thermal conductivity. And the microstructure of compound ceramics based on AlN was studied.

  6. Synthesis of Conductive Nanofillers/Nanofibers and Electrical Properties of their Conductive Polymer Composites

    Science.gov (United States)

    Sarvi, Ali

    Thanks to their corrosion resistance, light weight, low cost, and ease of processing, electrically conducting polymer composites (CPCs) have received significant attention for the replacement of metals and inorganic materials for sensors, actuators, supercapacitors, and electromagnetic interference (EMI) shields. In this PhD thesis, high aspect ratio conductive nanofillers namely copper nanowires (CuNWs) and multiwall carbon nanotubes (MWCNTs) were coated with polyaniline (PANi) using solution mixing and in-situ polymerization method, respectively. Transmission electron microscopy (TEM) showed a smooth polyaniline nano-coating between 5--18 nm in thickness on the nanofillers' surface. The coating thickness and; consequently, electrical conductivity was controlled and tuned by polyaniline/aniline concentration in solution. Composites with tunable conductivity may be used as chemisensors, electronic pressure sensors and switches. Coated nanofillers demonstrated better dispersion in polystyrene (PS) and provided lower electrical percolation threshold. Dispersion of nanofillers in PS was investigated using rheological measurements and confirmed with electron micrographs and nano-scale images of CPCs. Polyaniline (PANi), when used as a coating layer, was able to attenuate electromagnetic (EM) waves via absorption and store electrical charges though pseudocapacitance mechanism. The dielectric measurements of MWCNT-PANi/PS composites showed one order of magnitude increase in real electrical permittivity compared to that of MWCNT/PS composites making them suitable for charge storage purposes. Incorporation of PANi also brought a new insight into conductive network formation mechanism in electrospun mats where the orientation of conductive high aspect ratio nanofillers is a major problem. Conductive nanofibers of poly(vinylidene fluoride) (PVDF) filled with coated multiwall carbon nanotubes (MWCNTs) were fabricated using electrospinning. These highly oriented PVDF

  7. Preparation and Magnetic Properties of Anisotropic (Sm,Pr)Co5/Fe Nanocomposites Particles via Electroless Plating

    OpenAIRE

    Shi Wang; Jin-Ming Ma; Yan Chen

    2014-01-01

    Anisotropic (Sm,Pr)Co5/Fe nanocomposites particles were prepared by electroless plating iron on the surface of (Sm,Pr)Co5 nanoflakes after being prepared by ball milling for 4 h. A uniform and continuous coating layer was obtained due to the addition of complexing agent and the particle size of the reduced Fe particles was in the range of 10~20 nm. When the nominal addition of Fe was 15 wt%, the nanocomposites show enhanced remnant and saturation magnetization: Mr=53.35 emu/g, Ms=73.08 emu/g ...

  8. The filler-rubber interface in styrene butadiene nanocomposites with anisotropic silica particles: morphology and dynamic properties.

    Science.gov (United States)

    Tadiello, L; D'Arienzo, M; Di Credico, B; Hanel, T; Matejka, L; Mauri, M; Morazzoni, F; Simonutti, R; Spirkova, M; Scotti, R

    2015-05-28

    Silica-styrene butadiene rubber (SBR) nanocomposites were prepared by using shape-controlled spherical and rod-like silica nanoparticles (NPs) with different aspect ratios (AR = 1-5), obtained by a sol-gel route assisted by a structure directing agent. The nanocomposites were used as models to study the influence of the particle shape on the formation of nanoscale immobilized rubber at the silica-rubber interface and its effect on the dynamic-mechanical behavior. TEM and AFM tapping mode analyses of nanocomposites demonstrated that the silica particles are surrounded by a rubber layer immobilized at the particle surface. The spherical filler showed small contact zones between neighboring particles in contact with thin rubber layers, while anisotropic particles (AR > 2) formed domains of rods preferentially aligned along the main axis. A detailed analysis of the polymer chain mobility by different time domain nuclear magnetic resonance (TD-NMR) techniques evidenced a population of rigid rubber chains surrounding particles, whose amount increases with the particle anisotropy, even in the absence of significant differences in terms of chemical crosslinking. Dynamic measurements demonstrate that rod-like particles induce stronger reinforcement of rubber, increasing with the AR. This was related to the self-alignment of the anisotropic silica particles in domains able to immobilize rubber. PMID:25899456

  9. A single-source precursor route to anisotropic halogen-doped zinc oxide particles as a promising candidate for new transparent conducting oxide materials.

    Science.gov (United States)

    Lehr, Daniela; Wagner, Markus R; Flock, Johanna; Reparaz, Julian S; Sotomayor Torres, Clivia M; Klaiber, Alexander; Dekorsy, Thomas; Polarz, Sebastian

    2015-01-01

    Numerous applications in optoelectronics require electrically conducting materials with high optical transparency over the entire visible light range. A solid solution of indium oxide and substantial amounts of tin oxide for electronic doping (ITO) is currently the most prominent example for the class of so-called TCOs (transparent conducting oxides). Due to the limited, natural occurrence of indium and its steadily increasing price, it is highly desired to identify materials alternatives containing highly abundant chemical elements. The doping of other metal oxides (e.g., zinc oxide, ZnO) is a promising approach, but two problems can be identified. Phase separation might occur at the required high concentration of the doping element, and for successful electronic modification it is mandatory that the introduced heteroelement occupies a defined position in the lattice of the host material. In the case of ZnO, most attention has been attributed so far to n-doping via substitution of Zn(2+) by other metals (e.g., Al(3+)). Here, we present first steps towards n-doped ZnO-based TCO materials via substitution in the anion lattice (O(2-) versus halogenides). A special approach is presented, using novel single-source precursors containing a potential excerpt of the target lattice 'HalZn·Zn3O3' preorganized on the molecular scale (Hal = I, Br, Cl). We report about the synthesis of the precursors, their transformation into halogene-containing ZnO materials, and finally structural, optical and electronic properties are investigated using a combination of techniques including FT-Raman, low-T photoluminescence, impedance and THz spectroscopies. PMID:26665089

  10. A single-source precursor route to anisotropic halogen-doped zinc oxide particles as a promising candidate for new transparent conducting oxide materials

    Directory of Open Access Journals (Sweden)

    Daniela Lehr

    2015-11-01

    Full Text Available Numerous applications in optoelectronics require electrically conducting materials with high optical transparency over the entire visible light range. A solid solution of indium oxide and substantial amounts of tin oxide for electronic doping (ITO is currently the most prominent example for the class of so-called TCOs (transparent conducting oxides. Due to the limited, natural occurrence of indium and its steadily increasing price, it is highly desired to identify materials alternatives containing highly abundant chemical elements. The doping of other metal oxides (e.g., zinc oxide, ZnO is a promising approach, but two problems can be identified. Phase separation might occur at the required high concentration of the doping element, and for successful electronic modification it is mandatory that the introduced heteroelement occupies a defined position in the lattice of the host material. In the case of ZnO, most attention has been attributed so far to n-doping via substitution of Zn2+ by other metals (e.g., Al3+. Here, we present first steps towards n-doped ZnO-based TCO materials via substitution in the anion lattice (O2− versus halogenides. A special approach is presented, using novel single-source precursors containing a potential excerpt of the target lattice 'HalZn·Zn3O3' preorganized on the molecular scale (Hal = I, Br, Cl. We report about the synthesis of the precursors, their transformation into halogene-containing ZnO materials, and finally structural, optical and electronic properties are investigated using a combination of techniques including FT-Raman, low-T photoluminescence, impedance and THz spectroscopies.

  11. AC Conductivity and Dielectric Properties of Borotellurite Glass

    Science.gov (United States)

    Taha, T. A.; Azab, A. A.

    2016-10-01

    Borotellurite glasses with formula 60B2O3-10ZnO-(30 - x)NaF- xTeO2 ( x = 0 mol.%, 5 mol.%, 10 mol.%, and 15 mol.%) have been synthesized by thermal melting. X-ray diffraction (XRD) analysis confirmed that the glasses were amorphous. The glass density ( ρ) was determined by the Archimedes method at room temperature. The density ( ρ) and molar volume ( V m) were found to increase with increasing TeO2 content. The direct-current (DC) conductivity was measured in the temperature range from 473 K to 623 K, in which the electrical activation energy of ionic conduction increased from 0.27 eV to 0.48 eV with increasing TeO2 content from 0 mol.% to 15 mol.%. The dielectric parameters and alternating-current (AC) conductivity ( σ ac) were investigated in the frequency range from 1 kHz to 1 MHz and temperature range from 300 K to 633 K. The AC conductivity and dielectric constant decreased with increasing TeO2 content from 0 mol.% to 15 mol.%.

  12. Understanding hopping transport and thermoelectric properties of conducting polymers

    Science.gov (United States)

    Ihnatsenka, S.; Crispin, X.; Zozoulenko, I. V.

    2015-07-01

    We calculate the conductivity σ and the Seebeck coefficient S for the phonon-assisted hopping transport in conducting polymers poly(3,4-ethylenedioxythiophene) or PEDOT, experimentally studied by Bubnova et al. [J. Am. Chem. Soc. 134, 16456 (2012)], 10.1021/ja305188r. We use the Monte Carlo technique as well as the semianalytical approach based on the transport energy concept. We demonstrate that both approaches show a good qualitative agreement for the concentration dependence of σ and S . At the same time, we find that the semianalytical approach is not in a position to describe the temperature dependence of the conductivity. We find that both Gaussian and exponential density of states (DOS) reproduce rather well the experimental data for the concentration dependence of σ and S giving similar fitting parameters of the theory. The obtained parameters correspond to a hopping model of localized quasiparticles extending over 2-3 monomer units with typical jumps over a distance of 3-4 units. The energetic disorder (broadening of the DOS) is estimated to be 0.1 eV. Using the Monte Carlo calculation we reproduce the activation behavior of the conductivity with the calculated activation energy close to the experimentally observed one. We find that for a low carrier concentration a number of free carriers contributing to the transport deviates strongly from the measured oxidation level. Possible reasons for this behavior are discussed. We also study the effect of the dimensionality on the charge transport by calculating the Seebeck coefficient and the conductivity for the cases of three-, two-, and one-dimensional motion.

  13. Anisotropic structural and optical properties of semi-polar (11-22) GaN grown on m-plane sapphire using double AlN buffer layers.

    Science.gov (United States)

    Zhao, Guijuan; Wang, Lianshan; Yang, Shaoyan; Li, Huijie; Wei, Hongyuan; Han, Dongyue; Wang, Zhanguo

    2016-01-01

    We report the anisotropic structural and optical properties of semi-polar (11-22) GaN grown on m-plane sapphire using a three-step growth method which consisted of a low temperature AlN buffer layer, followed by a high temperature AlN buffer layer and GaN growth. By introducing double AlN buffer layers, we substantially improve the crystal and optical qualities of semi-polar (11-22) GaN, and significantly reduce the density of stacking faults and dislocations. The high resolution x-ray diffraction measurement revealed that the in-plane anisotropic structural characteristics of GaN layer are azimuthal dependent. Transmission electron microscopy analysis showed that the majority of dislocations in the GaN epitaxial layer grown on m-sapphire are the mixed-type and the orientation of GaN layer was rotated 58.4° against the substrate. The room temperature photoluminescence (PL) spectra showed the PL intensity and wavelength have polarization dependence along parallel and perpendicular to the [1-100] axis (polarization degrees ~ 0.63). The realization of a high polarization semi-polar GaN would be useful to achieve III-nitride based lighting emission device for displays and backlighting.

  14. Effects of anisotropic interaction-induced properties of hydrogen-rare gas compounds on rototranslational Raman scattering spectra: Comprehensive theoretical and numerical analysis.

    Science.gov (United States)

    Głaz, Waldemar; Bancewicz, Tadeusz; Godet, Jean-Luc; Gustafsson, Magnus; Haskopoulos, Anastasios; Maroulis, George

    2016-07-21

    A comprehensive study is presented of many aspects of the depolarized anisotropic collision induced (CI) component of light scattered by weakly bound compounds composed of a dihydrogen molecule and a rare gas (Rg) atom, H2-Rg. The work continues a series of earlier projects marking the revival of interest in linear light scattering following the development of new highly advanced tools of quantum chemistry and other theoretical, computational, and experimental means of spectral analyses. Sophisticated ab initio computing procedures are applied in order to obtain the anisotropic polarizability component's dependence on the H2-Rg geometry. These data are then used to evaluate the CI spectral lines for all types of Rg atoms ranging from He to Xe (Rn excluded). Evolution of the properties of CI spectra with growing polarizability/masses of the complexes studied is observed. Special attention is given to the heaviest, Kr and Xe based, scatterers. The influence of specific factors shaping the spectral lines (e.g., bound and metastable contribution, potential anisotropy) is discussed. Also the share of pressure broadened allowed rotational transitions in the overall spectral profile is taken into account and the extent to which it is separable from the pure CI contribution is discussed. We finish with a brief comparison between the obtained results and available experimental data. PMID:27448883

  15. Effects of anisotropic interaction-induced properties of hydrogen-rare gas compounds on rototranslational Raman scattering spectra: Comprehensive theoretical and numerical analysis

    Science.gov (United States)

    Głaz, Waldemar; Bancewicz, Tadeusz; Godet, Jean-Luc; Gustafsson, Magnus; Haskopoulos, Anastasios; Maroulis, George

    2016-07-01

    A comprehensive study is presented of many aspects of the depolarized anisotropic collision induced (CI) component of light scattered by weakly bound compounds composed of a dihydrogen molecule and a rare gas (Rg) atom, H2-Rg. The work continues a series of earlier projects marking the revival of interest in linear light scattering following the development of new highly advanced tools of quantum chemistry and other theoretical, computational, and experimental means of spectral analyses. Sophisticated ab initio computing procedures are applied in order to obtain the anisotropic polarizability component's dependence on the H2-Rg geometry. These data are then used to evaluate the CI spectral lines for all types of Rg atoms ranging from He to Xe (Rn excluded). Evolution of the properties of CI spectra with growing polarizability/masses of the complexes studied is observed. Special attention is given to the heaviest, Kr and Xe based, scatterers. The influence of specific factors shaping the spectral lines (e.g., bound and metastable contribution, potential anisotropy) is discussed. Also the share of pressure broadened allowed rotational transitions in the overall spectral profile is taken into account and the extent to which it is separable from the pure CI contribution is discussed. We finish with a brief comparison between the obtained results and available experimental data.

  16. Relativistic heat conduction and thermoelectric properties of nonuniform plasmas

    CERN Document Server

    Honda, M

    2003-01-01

    Relativistic heat transport in electron-two-temperature plasmas with density gradients has been investigated. The Legendre expansion analysis of relativistically modified kinetic equations shows that strong inhibition of heat flux appears in relativistic temperature regimes, suppressing the classical Spitzer-H{\\"a}rm conduction. The Seebeck coefficient, the Wiedemann-Franz law, and the thermoelectric figure of merit are derived in the relativistic regimes.

  17. Inferring single neuron properties in conductance-based balanced networks

    OpenAIRE

    Germán eMato; Roman eRossi Pool

    2011-01-01

    Balanced states in large networks are a usual hypothesis for explaining the variability of neural activity in cortical systems. In this regime the statistics of the inputs is characterized by static and dynamic fluctuations. The dynamic fluctuations have a Gaussian distribution. Such statistics allows to use reverse correlation methods, by recording synaptic inputs and the spike trains of ongoing spontaneous activity without any additional input. By using this method, properties of the single...

  18. The Spectroscopic and Conductive Properties of Ru(II Complexes with Potential Anticancer Properties

    Directory of Open Access Journals (Sweden)

    Adebayo A. Adeniyi

    2014-01-01

    Full Text Available Different density functional methods (DFT have been used to optimize and study the chemistry of five potential anticancer complexes in terms of their electronic, conductive, and spectroscopic properties. Many of the computed properties in addition to the IR and QTAIM analysis of the NMR are dipole moment vector (μi, linear polarizability tensor (αij, first hyperpolarizability tensors (βijk, polarizability exaltation index (Γ, and chemical hardness (η of the complexes. Stable low energy geometries are obtained using basis set with effective core potential (ECP approximation but, in the computation of atomic or molecular properties, the metal Ru atom is better treated with higher all electron basis set like DGDZVP. The spectroscopic features like the IR of the metal-ligand bonds and the isotropic NMR shielding tensor of the coordinated atoms are significantly influenced by the chemical environment of the participating atoms. The carboxylic and pyrazole units are found to significantly enhance the polarizabilities and hyperpolarizabilities of the complexes while the chloride only improves the polarity of the complexes. Fermi contacts (FC have the highest effect followed by the PSO among all the four Ramsey terms which defined the total spin-spin coupling constant J (HZ of these complexes.

  19. Configurational temperature and local properties of the anisotropic Gay-Berne liquid crystal model: Applications to the isotropic liquid/vapor interface and isotropic/nematic transition

    Science.gov (United States)

    Ghoufi, Aziz; Morineau, Denis; Lefort, Ronan; Malfreyt, Patrice

    2011-01-01

    Molecular simulations in the isothermal statistical ensembles require that the macroscopic thermal and mechanical equilibriums are respected and that the local values of these properties are constant at every point in the system. The thermal equilibrium in Monte Carlo simulations can be checked through the calculation of the configurational temperature, {k_BT_{conf}={}/{}}, where nabla _r is the nabla operator of position vector r. As far as we know, T_{conf} was never calculated with the anisotropic Gay-Berne potential, whereas the calculation of T_{conf} is much more widespread with more common potentials (Lennard Jones, electrostatic, …). We establish here an operational expression of the macroscopic and local configurational temperatures, and we investigate locally the isotropic liquid phase, the liquid / vapor interface, and the isotropic-nematic transition by Monte Carlo simulations.

  20. Conducting polymers. VI. Effect of doping with iodine on the dielectrical and electrical conduction properties of polyacrylonitrile

    Science.gov (United States)

    El-Ghamaz, N. A.; Diab, M. A.; Zoromba, M. Sh.; El-Sonbati, A. Z.; El-Shahat, O.

    2013-10-01

    The effect of doping of polyacrylonitrile (PAN) with iodine on the dielectical properties and ac conductivity as a function of temperature and frequency is investigated. Thermogravimetric analysis, TGA, and FTIR measurements show that PAN undergoes degradation starting at 523 K. Doping PAN with I2 enhances the ac electrical conductivity σac in the temperature range under investigation due to oligomerization of the nitrile groups giving a conjugated polyimine. The thermal activation energy, ΔE, is calculated for PAN and PAN/I2 and found to be in the range 0.16-1.16 eV at 0.1 kHz. The correlated barrier hopping (CBH) conduction mechanism is found to be the dominant conduction mechanism for PAN and PAN/I2 samples.

  1. Synthesis of polymer nanostructures with conductance switching properties

    Energy Technology Data Exchange (ETDEWEB)

    Su, Kai; Nuraje, Nurxat; Zhang, Lingzhi; Matsui, Hiroshi; Yang, Nan Loh

    2015-03-03

    The present invention is directed to crystalline organic polymer nanoparticles comprising a conductive organic polymer; wherein the crystalline organic polymer nanoparticles have a size of from 10 nm to 200 nm and exhibits two current-voltage states: (1) a high resistance current-voltage state, and (2) a low resistance current-voltage state, wherein when a first positive threshold voltage (V.sub.th1) or higher positive voltage, or a second negative threshold voltage (V.sub.th2) or higher negative voltage is applied to the nanoparticle, the nanoparticle exhibits the low-resistance current-voltage state, and when a voltage less positive than the first positive threshold voltage or a voltage less negative than the second negative threshold voltage is applied to the nanoparticle, the nanoparticle exhibits the high-resistance current-voltage state. The present invention is also directed methods of manufacturing the nanoparticles using novel interfacial oxidative polymerization techniques.

  2. Formation of conductive networks with both segregated and double-percolated characteristic in conductive polymer composites with balanced properties.

    Science.gov (United States)

    Zhang, Shuangmei; Deng, Hua; Zhang, Qin; Fu, Qiang

    2014-05-14

    Morphological control of conductive networks involves the construction of segregated or double-percolated conductive networks is often reported to reduce the electrical percolation threshold of conductive polymer composites (CPCs) for better balance among electrical conductivity, mechanical properties, and filler content. Herein, the construction of conductive networks with both segregated and double-percolated characteristics is achieved based on polypropylene (PP)/polyethylene (PE) and multi-wall carbon nanotubes (CNTs). CNTs were firstly dispersed in PE; then PE/CNTs were compounded with PP particles well below the melting temperature of PP. It is observed that the percolation threshold (pc) decreases with increasing PP particle size (size 3.6 mm, pc=0.08 wt %), which agrees with previous theoretical prediction and experiment in much smaller particle size range. To further study this, the amount of CNTs in PE is varied. It is shown that the degree of PE/CNTs coating on PP particles varies with CNTs as well as PE content in these composites, and have significant influence on the final electrical property. Furthermore, a model combines classical percolation theory and model for segregated network has been proposed to analyze the effect of particle size, degree of coating and thickness of coating on the percolation behavior of these CPCs. In such a model the percolation of CNTs in PE phase as well as PENT phase in the segregated structure can be described. Overall, through such method, a much better balance among mechanical property, conductivity, and filler content is achieved in these CPCs comparing with the results in literature. PMID:24745303

  3. Anisotropic modulation of magnetic properties and the memory effect in a wide-band (011)-Pr0.7Sr0.3MnO3/PMN-PT heterostructure

    Science.gov (United States)

    Zhao, Ying-Ying; Wang, Jing; Kuang, Hao; Hu, Feng-Xia; Liu, Yao; Wu, Rong-Rong; Zhang, Xi-Xiang; Sun, Ji-Rong; Shen, Bao-Gen

    2015-04-01

    Memory effect of electric-field control on magnetic behavior in magnetoelectric composite heterostructures has been a topic of interest for a long time. Although the piezostrain and its transfer across the interface of ferroelectric/ferromagnetic films are known to be important in realizing magnetoelectric coupling, the underlying mechanism for nonvolatile modulation of magnetic behaviors remains a challenge. Here, we report on the electric-field control of magnetic properties in wide-band (011)-Pr0.7Sr0.3MnO3/0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 heterostructures. By introducing an electric-field-induced in-plane anisotropic strain field during the cooling process from room temperature, we observe an in-plane anisotropic, nonvolatile modulation of magnetic properties in a wide-band Pr0.7Sr0.3MnO3 film at low temperatures. We attribute this anisotropic memory effect to the preferential seeding and growth of ferromagnetic (FM) domains under the anisotropic strain field. In addition, we find that the anisotropic, nonvolatile modulation of magnetic properties gradually diminishes as the temperature approaches FM transition, indicating that the nonvolatile memory effect is temperature dependent. By taking into account the competition between thermal energy and the potential barrier of the metastable magnetic state induced by the anisotropic strain field, this distinct memory effect is well explained, which provides a promising approach for designing novel electric-writing magnetic memories.

  4. Anisotropic modulation of magnetic properties and the memory effect in a wide-band (011)-Pr0.7Sr0.3MnO3/PMN-PT heterostructure

    KAUST Repository

    Zhao, Ying-Ying

    2015-04-24

    Memory effect of electric-field control on magnetic behavior in magnetoelectric composite heterostructures has been a topic of interest for a long time. Although the piezostrain and its transfer across the interface of ferroelectric/ferromagnetic films are known to be important in realizing magnetoelectric coupling, the underlying mechanism for nonvolatile modulation of magnetic behaviors remains a challenge. Here, we report on the electric-field control of magnetic properties in wide-band (011)-Pr0.7Sr0.3MnO3/0.7Pb(Mg1/3Nb2/3)O3-0.3PbTiO3 heterostructures. By introducing an electric-field-induced in-plane anisotropic strain field during the cooling process from room temperature, we observe an in-plane anisotropic, nonvolatile modulation of magnetic properties in a wide-band Pr0.7Sr0.3MnO3 film at low temperatures. We attribute this anisotropic memory effect to the preferential seeding and growth of ferromagnetic (FM) domains under the anisotropic strain field. In addition, we find that the anisotropic, nonvolatile modulation of magnetic properties gradually diminishes as the temperature approaches FM transition, indicating that the nonvolatile memory effect is temperature dependent. By taking into account the competition between thermal energy and the potential barrier of the metastable magnetic state induced by the anisotropic strain field, this distinct memory effect is well explained, which provides a promising approach for designing novel electric-writing magnetic memories.

  5. Numerical experiments for the conductive properties of saturated rock

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The reservoir evaluation as a key technology in oil exploration and production is based on the electrical transport property (ETP) of saturated rock that is described in a mathematical form with Arhcie’s equa-tion. But there have been increasing cases observed in many researches indicating that the ETP is non-Archie especially for the complex reservoir with low porosity and permeability. In this paper,the numerical experiments based on the Lattice Boltzmann method (LBM) have been employed to study the effect of porous structure and fluids on the ETP for revealing the nature of non-Archie phenomenon in micro-scale. The results of numerical experiments have proved that the saturation exponent n is a function of water saturation and porosity instead of being a constant in Archie’s equation. And then,a new formula has been developed for the EPT through combining the result of numerical simulation with that of laboratory measurements. The calculations from the new formula show very good agreement with laboratory measurements to demonstrate the efficiency of the new formula over the conventional methods in non-Archie rock.

  6. Fluctuation theory for transport properties in multicomponent mixtures: thermodiffusion and heat conductivity

    DEFF Research Database (Denmark)

    Shapiro, Alexander

    2004-01-01

    The theory of transport properties in multicomponent gas and liquid mixtures, which was previously developed for diffusion coefficients, is extended onto thermodiffusion coefficients and heat conductivities. The derivation of the expressions for transport properties is based on the general statis...... of the heat conductivity coefficient for ideal gas. (C) 2003 Elsevier B.V. All rights reserved....

  7. Anisotropically structured magnetic aerogel monoliths

    Science.gov (United States)

    Heiligtag, Florian J.; Airaghi Leccardi, Marta J. I.; Erdem, Derya; Süess, Martin J.; Niederberger, Markus

    2014-10-01

    Texturing of magnetic ceramics and composites by aligning and fixing of colloidal particles in a magnetic field is a powerful strategy to induce anisotropic chemical, physical and especially mechanical properties into bulk materials. If porosity could be introduced, anisotropically structured magnetic materials would be the perfect supports for magnetic separations in biotechnology or for magnetic field-assisted chemical reactions. Aerogels, combining high porosity with nanoscale structural features, offer an exceptionally large surface area, but they are difficult to magnetically texture. Here we present the preparation of anatase-magnetite aerogel monoliths via the assembly of preformed nanocrystallites. Different approaches are proposed to produce macroscopic bodies with gradient-like magnetic segmentation or with strongly anisotropic magnetic texture.Texturing of magnetic ceramics and composites by aligning and fixing of colloidal particles in a magnetic field is a powerful strategy to induce anisotropic chemical, physical and especially mechanical properties into bulk materials. If porosity could be introduced, anisotropically structured magnetic materials would be the perfect supports for magnetic separations in biotechnology or for magnetic field-assisted chemical reactions. Aerogels, combining high porosity with nanoscale structural features, offer an exceptionally large surface area, but they are difficult to magnetically texture. Here we present the preparation of anatase-magnetite aerogel monoliths via the assembly of preformed nanocrystallites. Different approaches are proposed to produce macroscopic bodies with gradient-like magnetic segmentation or with strongly anisotropic magnetic texture. Electronic supplementary information (ESI) available: Digital photographs of dispersions and gels with different water-to-ethanol ratios; magnetic measurements of an anatase aerogel containing 0.25 mol% Fe3O4 nanoparticles; XRD patterns of the iron oxide and

  8. Thermoelectric properties, electronic structure and optoelectronic properties of anisotropic Ba{sub 2}Tl{sub 2}CuO{sub 6} single crystal from DFT approach

    Energy Technology Data Exchange (ETDEWEB)

    Reshak, A.H. [New Technologies - Research Center, University of West, Bohemia, Univerzitni 8, 30614 Pilsen (Czech Republic); Center of Excellence Geopolymer and Green Technology, School of Material Engineering, University Malaysia Perlis, 01007 Kangar, Perlis (Malaysia); Khan, Saleem Ayaz, E-mail: sayaz_usb@yahoo.com [New Technologies - Research Center, University of West, Bohemia, Univerzitni 8, 30614 Pilsen (Czech Republic)

    2014-03-15

    First principle calculation was performed for the electronic structure, electronic charge density, Fermi surface, optical and thermoelectric properties of Ba{sub 2}Tl{sub 2}CuO{sub 6} compound. From the electronic band structure the two overlapping bands and the density of state at Fermi level (29.2 states/Ryd-cell) confirms the superconducting behavior. Colors of the Fermi surface elucidate speed of electrons and strength of the superconductivity as well. The bonding nature was investigated using the calculated charge density contour plot, it shows mixed ionic-covalent nature of Cu3O and Tl3O while Ba3O shows dominant ionic nature with small covalency. The optical properties were calculated and discussed in details. The calculated uniaxial anisotropy value (0.7913) clarifies a considerable anisotropy between two dominant tensor components of dielectric function. Moreover the evaluation of Seebeck coefficient and thermal conductivity conform that the compound is much suitable for thermoelectric applications. - Highlights: • DFT calculation, for density of state at Fermi level confirm the superconducting behavior of Ba{sub 2}Tl{sub 2}CuO{sub 6}. • Colors of the Fermi surface show speed of electrons and strength of superconductor. • Electronic charge density was obtained which illuminate bonding nature. • The calculated uniaxial anisotropy is 0.7913, indicating the strong anisotropy. • Seebeck coefficient and thermal conductivity were calculated and discussed.

  9. Rate dependence of electrical and mechanical properties of conductive polymer nanocomposites

    OpenAIRE

    Foley J.R.; Stilson C.L.; Smith K.K.G.; McKinion C.M.; Chen C.; Ganguli S; Roy A.K

    2015-01-01

    Conductive polymer nanocomposites with enhanced electrical and thermal properties show promise as an alternative solution for electronic materials. For example, electronic interconnect materials will have comparable electrical and thermal conductivity to solder with an increased operating range of strain and temperature. This paper documents the fabrication and experimental evaluation of a prototype conductive polymer nanocomposite. Material selection, fabrication processes, and initial chara...

  10. Algebraically explicit analytical solutions of unsteady conduction with variable thermal properties in cylindrical coordinate

    Institute of Scientific and Technical Information of China (English)

    CAI Ruixian; ZHANG Na

    2004-01-01

    The analytical solutions of unsteady heat conduction with variable thermal properties(thermal conductivity,density and specific heat are functions of temperature or coordinates)are meaningful in theory.In addition,they are very useful to the computational heat conduction to check the numerical solutions and to develop numerical schemes,grid generation methods and so forth.Such solutions in rectangular coordinates have been derived by the authors.Some other solutions for 1-D and 2-D axisymmetrical heat conduction in cylin drical coordinates are given in this paper to promote the heat conduction theory and to develop the relative computational heat conduction.

  11. Effects of physical properties on electrical conductivity of compacted lateritic soil

    Institute of Scientific and Technical Information of China (English)

    Wei Bai; Lingwei Kong; Aiguo Guo

    2013-01-01

    Natural soils of various types have different electrical properties due to the composition, structure, water content, and temperature. In order to investigate the electrical properties of lateritic soil, electrical con-ductivity experiments have been conducted on a self-developed testing device. Test results show that the electrical conductivity of laterite increases with the increase of water content, degree of saturation and dry density. When the water content is below the optimum water content, the electrical conductivity of soils increases nonlinearly and the variation rate increases dramatically. However, when the water content, degree of saturation, or dry density increases to a certain value, the electrical conductivity tends to be a constant. In addition, soil electrical conductivity increases with the increase of temperature, and it is observed that the electrical conductivity decreases with the increase of the number of wetting-drying cycles.

  12. Anisotropic electrical and thermal conductivity in Bi{sub 2}AE{sub 2}Co{sub 2}O{sub 8+δ} [AE = Ca, Sr{sub 1−x}Ba{sub x} (x = 0.0, 0.25, 0.5, 0.75, 1.0)] single crystals

    Energy Technology Data Exchange (ETDEWEB)

    Dong, Song-Tao [National Laboratory of Solid State Microstructures and Department of Materials Science and Engineering, Nanjing University, Nanjing 210093 (China); Institute of Material Science and Engineering, Jiangsu University of Science and Technology, Zhenjiang 212003 (China); Zhang, Bin-Bin; Lv, Yang-Yang; Zhou, Jian; Zhang, Shan-Tao [National Laboratory of Solid State Microstructures and Department of Materials Science and Engineering, Nanjing University, Nanjing 210093 (China); Xiong, Ye [College of Physical Science and Technology, Nanjing Normal University, Nanjing 210097 (China); Yao, Shu-Hua, E-mail: shyao@nju.edu.cn, E-mail: ybchen@nju.edu.cn [National Laboratory of Solid State Microstructures and Department of Materials Science and Engineering, Nanjing University, Nanjing 210093 (China); State Key laboratory of Crystal Material, Shandong University, Jinan, 250100 (China); Chen, Y. B., E-mail: shyao@nju.edu.cn, E-mail: ybchen@nju.edu.cn [National Laboratory of Solid State Microstructure and Department of Physics, Nanjing University, Nanjing 210093 (China); Chen, Yan-Feng [National Laboratory of Solid State Microstructures and Department of Materials Science and Engineering, Nanjing University, Nanjing 210093 (China); Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093 (China)

    2015-09-28

    Bi{sub 2}AE{sub 2}Co{sub 2}O{sub 8+δ} (AE represents alkaline earth), constructed by stacking of rock-salt Bi{sub 2}AE{sub 2}O{sub 4} and triangle CoO{sub 2} layers alternatively along c-axis, is one of promising thermoelectric oxides. The most impressive feature of Bi{sub 2}AE{sub 2}Co{sub 2}O{sub 8+δ}, as reported previously, is their electrical conductivity mainly lying along CoO{sub 2} plane, adjusting Bi{sub 2}AE{sub 2}O{sub 4} layer simultaneously manipulates both thermal conductivity and electrical conductivity. It in turn optimizes thermoelectric performance of these materials. In this work, we characterize the anisotropic thermal and electrical conductivity along both ab-plane and c-direction of Bi{sub 2}AE{sub 2}Co{sub 2}O{sub 8+δ} (AE = Ca, Sr, Ba, Sr{sub 1−x}Ba{sub x}) single crystals. The results substantiate that isovalence replacement in Bi{sub 2}AE{sub 2}Co{sub 2}O{sub 8+δ} remarkably modifies their electrical property along ab-plane; while their thermal conductivity along ab-plane only has a slightly difference. At the same time, both the electrical conductivity and thermal conductivity along c-axis of these materials also have dramatic changes. Certainly, the electrical resistance along c-axis is too high to be used as thermoelectric applications. These results suggest that adjusting nano-block Bi{sub 2}AE{sub 2}O{sub 4} layer in Bi{sub 2}AE{sub 2}Co{sub 2}O{sub 8+δ} cannot modify the thermal conductivity along high electrical conductivity plane (ab-plane here). The evolution of electrical property is discussed by Anderson localization and electron-electron interaction U. And the modification of thermal conductivity along c-axis is attributed to the microstructure difference. This work sheds more light on the manipulation of the thermal and electrical conductivity in the layered thermoelectric materials.

  13. Averaging anisotropic cosmologies

    CERN Document Server

    Barrow, J D; Barrow, John D.; Tsagas, Christos G.

    2006-01-01

    We examine the effects of spatial inhomogeneities on irrotational anisotropic cosmologies by looking at the average properties of pressure-free Bianchi-type models. Adopting the Buchert averaging scheme, we identify the kinematic backreaction effects by focussing on spacetimes with zero or isotropic spatial curvature. This allows us to close the system of the standard scalar formulae with a propagation equation for the shear magnitude. We find no change in the already known conditions for accelerated expansion. The backreaction terms are expressed as algebraic relations between the mean-square fluctuations of the models' irreducible kinematical variables. Based on these we investigate the early evolution of averaged vacuum Bianchi type $I$ universes and those filled with pressureless matter. In the latter case we show that the backreaction effects can modify the familiar Kasner-like singularity and potentially remove Mixmaster-type oscillations. We also discuss the possibility of accelerated expansion due to ...

  14. Anisotropic and heterogeneous mechanical properties of a stratified shale/limestone sequence at Nash Point, South Wales: A case study for hydraulic fracture propagation through a layered medium

    Science.gov (United States)

    Forbes Inskip, Nathaniel; Meredith, Philip; Gudmundsson, Agust

    2016-04-01

    While considerable effort has been expended on the study of fracture propagation in rocks in recent years, our understanding of how fractures propagate through layered sedimentary rocks with different mechanical and elastic properties remains poorly constrained. Yet this is a key issue controlling the propagation of both natural and anthropogenic hydraulic fractures in layered sequences. Here we report measurements of the contrasting mechanical and elastic properties of the Lower Lias at Nash Point, South Wales, which comprises an interbedded sequence of shale and limestone layers, and how those properties may influence fracture propagation. Elastic properties of both materials have been characterised via ultrasonic wave velocity measurements as a function of azimuth on samples cored both normal and parallel to bedding. The shale is highly anisotropic, with P-wave velocities varying from 2231 to 3890 m s-1, giving an anisotropy of ~55%. By contrast, the limestone is essentially isotropic, with a mean P-wave velocity of 5828 m s-1 and an anisotropy of ~2%. The dynamic Young's modulus of the shale, calculated from P- and S-wave velocity data, is also anisotropic with a value of 36 GPa parallel to bedding and 12 GPa normal to bedding. The modulus of the limestone is again isotropic with a value of 80 GPa. It follows that for a vertical fracture propagating (i.e. normal to bedding) the modulus contrast is 6.6. This is important because the contrast in elastic properties is a key factor in controlling whether fractures arrest, deflect, or propagate across interfaces between layers in a sequence. There are three principal mechanisms by which a fracture may deflect across or along an interface, namely: Cook-Gordon debonding, stress barrier, and elastic mismatch. Preliminary numerical modelling results (using a Finite Element Modelling software) of induced fractures at Nash Point suggest that all three are important. The results demonstrate a rotation of the maximum

  15. Saturated hydraulic conductivity in relation to physical properties of soils in the Nsukka Plains, SE Nigeria

    International Nuclear Information System (INIS)

    The objective of the study is to develop and validate statistical models for estimating the saturated hydraulic conductivity of soils with high water intake rates from more easily-determined properties and to test the hypothesis that it is equal to Philip transmissivity term and the steady infiltration rate. The results of the study show that the dominant physical property influencing saturated hydraulic conductivity of the investigated soils is the macroporosity. 37 refs, 6 figs, 5 tabs

  16. Anisotropic Model Colloids

    Science.gov (United States)

    van Kats, C. M.

    2008-10-01

    The driving forces for fundamental research in colloid science are the ability to manage the material properties of colloids and to unravel the forces that play a role between colloids to be able to control and understand the processes where colloids play an important role. Therefore we are searching for colloidal materials with specific physical properties to better understand our surrounding world.Until recently research in colloid science was mainly focused on spherical (isotropic) particles. Monodisperse spherical colloids serve as a model system as they exhibit similar phase behaviour as molecular and atomic systems. Nevertheless, in many cases the spherical shape is not sufficient to reach the desired research goals. Recently the more complex synthesis methods of anisotropic model colloids has strongly developed. This thesis should be regarded as a contribution to this research area. Anisotropic colloids can be used as a building block for complex structures and are expected not only to lead to the construction of full photonic band gap materials. They will also serve as new, more realistic, models systems for their molecular analogues. Therefore the term ‘molecular colloids” is sometimes used to qualify these anisotropic colloidal particles. In the introduction of this thesis, we give an overview of the main synthesis techniques for anisotropic colloids. Chapter 2 describes the method of etching silicon wafers to construct monodisperse silicon rods. They subsequently were oxidized and labeled (coated) with a fluorescent silica layer. The first explorative phase behaviour of these silica rods was studied. The particles showed a nematic ordering in charge stabilized suspensions. Chapter 3 describes the synthesis of colloidal gold rods and the (mesoporous) silica coating of gold rods. Chapter 4 describes the physical and optical properties of these particles when thermal energy is added. This is compared to the case where the particles are irradiated with

  17. Ab initio study of anisotropic mechanical properties of LiCoO{sub 2} during lithium intercalation and deintercalation process

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Linmin; Zhang, Jing, E-mail: jz29@iupui.edu [Department of Mechanical Engineering, Indiana University-Purdue University Indianapolis, Indianapolis, Indiana 46202 (United States)

    2015-12-14

    The mechanical properties of Li{sub x}CoO{sub 2} under various Li concentrations and associated anisotropy have been systematically studied using the first principles method. During the lithium intercalation process, the Young's modulus, bulk modulus, shear modulus, and ultimate strength increase with increasing lithium concentration. Strong anisotropy of mechanical properties between a-axis and c-axis in Li{sub x}CoO{sub 2} is identified at low lithium concentrations, and the anisotropy decreases with increasing lithium concentration. The observed lithium concentration dependence and anisotropy are explained by analyzing the charge transfer using Bader charge analysis, bond order analysis, and bond strength by investigating partial density of states and charge density difference. With the decrease of Li concentration, the charge depletion in the bonding regions increases, indicating a weaker Co-O bond strength. Additionally, the Young's modulus, bulk modulus, shear modulus, and toughness are obtained by simulating ab initio tensile tests. From the simulated stress-strain curves, Li{sub x}CoO{sub 2} shows the highest toughness, which is in contraction with Pugh criterion prediction based on elastic properties only.

  18. Effect of Curing Procedure on the Properties of Copper-Powder-Filled Conductive Adhesives

    Institute of Scientific and Technical Information of China (English)

    ZHENG Xiaoling; ZHANG Lulu; YOU Min; WU Jianhao; YU Haizhou; YANG Derong; MAO Yuping

    2008-01-01

    By means of testing the shear strength with single lap joint, measuring electrical resistivity for cured products and the curing strain with strain gauges, the effect of cure parameters on the properties of HT1012 conductive adhesive filled with copper powder was investigated, and the residual stress in the conductive adhesives was also estimated. The experimental results show that the properties such as shear strength of the adhesives, electrical resistivity of products as well as the residual stress of cured HT1012 copper-filled conductive adhesive were evidently affected by curing temperature and time. The diagrams of scanning electron microscopy (SEM) and Fourier transform infrared (FT-IR) were also used to determine the properties. The higher mechanical property was achieved under the condition of curing the adhesive 3h at 60℃ as the density of the hydrogen links or linkages existed in the adhesive was relatively higher and the lower electrical resistivity occurred at 80℃.

  19. The porosity effect on properties of sintered materials as their conductivity and Youngs modulus of elasticity

    International Nuclear Information System (INIS)

    A set of equations derived demonstrates quantitatively the influence of closed pores on the conductivity as well as on Youngsmodulus of elasticity of sintered materials. There are three microstructural parameters following from the theoretical derivation controlling the porosity effect on the properties, which are the total porosity, the form factor and the orientation factor of the pores. By quantitative microstructure analysis these factors become available providing together with the equations the tool - to calculate the conductivity and Youngs modulus of elasticity from microstructural quantities of sintered materials thus substituting direct property measurements by quantitative microstructure analysis if desired - to endeaver technologically optimum microstructures to obtain theoretically predicted special property values and to precalculate property alterations by microstructure variations ('taylor-made-materials') - to supplement the conventional microstructural quality control by calculated property data. (orig.)

  20. Anisotropic phenomena in gauge/gravity duality

    International Nuclear Information System (INIS)

    In this thesis we use gauge/gravity duality to model anisotropic effects realised in nature. Firstly we analyse transport properties in holographic systems with a broken rotational invariance. Secondly we discuss geometries dual to IR fixed points with anisotropic scaling behaviour, which are related to quantum critical points in condensed matter systems. Gauge/gravity duality relates a gravity theory in Anti-de Sitter space to a lower dimensional strongly coupled quantum field theory in Minkowski space. Over the past decade this duality provided many insights into systems at strong coupling, e.g. quark-gluon plasma and condensed matter close to quantum critical points. One very important result computed in this framework is the value of the shear viscosity divided by the entropy density in strongly coupled theories. The quantitative result agrees very well with measurements of the ratio in quark-gluon plasma. However, for isotropic two derivative Einstein gravity it is temperature independent. We show that by breaking the rotational symmetry of a system we obtain a temperature dependent shear viscosity over entropy density. This is important to make contact with real world systems, since substances in nature display such dependence. In addition, we derive various transport properties in strongly coupled anisotropic systems using the gauge/gravity dictionary. The most notable results include an electrical conductivity with Drude behaviour in the low frequency region. This resembles conductors with broken translational invariance. However, we did not implement the breaking explicitly. Furthermore, our analysis shows that this setup models effects, resembling the piezoelectric and exoelectric effects, known from liquid crystals. In a second project we discuss a geometry with non-trivial scaling behaviour in order to model an IR fixed point of condensed matter theories. We construct the UV completion of this geometry and analyse its properties by computing the

  1. Rate dependence of electrical and mechanical properties of conductive polymer nanocomposites

    Science.gov (United States)

    Foley, J. R.; Stilson, C. L.; Smith, K. K. G.; McKinion, C. M.; Chen, C.; Ganguli, S.; Roy, A. K.

    2015-09-01

    Conductive polymer nanocomposites with enhanced electrical and thermal properties show promise as an alternative solution for electronic materials. For example, electronic interconnect materials will have comparable electrical and thermal conductivity to solder with an increased operating range of strain and temperature. This paper documents the fabrication and experimental evaluation of a prototype conductive polymer nanocomposite. Material selection, fabrication processes, and initial characterization of a low Tg polymer with a high fill ratio of carbon nanotubes is presented. The electrical and thermal properties of the composite are measured and compared with predictions. The mechanical properties are measured using dynamic mechanical analysis (DMA) over a wide temperature range. The mechanical and electrical responses of the conductive polymer composite are simultaneously measured at higher strain rates using a modified split Hopkinson pressure bar (SHPB) apparatus. The dynamic stress-strain response is obtained using traditional analytic methods (e.g., two- and three-wave analysis). The electrical response is observed using constant current excitation with high bandwidth (>500 kHz) instrumentation. The dynamic compression data implies the change in electrical resistance is solely a function of the material deformation, i.e., the material exhibits constant electrical conductivity and is insensitive to the applied loads. DMA and SHPB dynamic data are used to estimate the parameters in a Mulliken-Boyce constitutive model, and the resulting behavior is critically evaluated. Finally, progress towards improving the polymer composite's mechanical, electrical, and thermal properties are discussed.

  2. Electrochemical evaluation of the p-Si/conducting polymer interfacial properties

    Science.gov (United States)

    Nagasubramanian, G.; Distefano, S.; Moacanin, J.

    1988-01-01

    Results are presented from an experimental investigation of the contact resistance and interfacial properties of a p-Si/conducting polymer interface for solar cell applications. The electronic character of the polymer/semiconductor function is determined by studying the electrochemical behavior of both poly(isothianapthene) (PITN) and polypyrrole (PP) in an acetonitrile solution on p-silicon electrodes. The results obtained indicate that while PITN is intrinsically more conductive than PP, neither passivates surface states nor forms ohmic contact.

  3. In-plane anisotropic effect of magnetoelectric coupled PMN-PT/FePt multiferroic heterostructure: Static and microwave properties

    Science.gov (United States)

    Vargas, Jose M.; Gómez, Javier

    2014-10-01

    The effects of the electric and magnetic field variation on multiferroic heterostructure were studied in this work. Thin films of polycrystalline Fe50Pt50 (FePt) were grown by dc-sputtering on top of the commercial slabs of lead magnesium niobate-lead titanate (PMN-PT). The sample was a (011)-cut single crystal and had one side polished. In this condition, the PMN-PT/FePt operates in the L-T (longitudinal magnetized-transverse polarized) mode. A FePt thin film of 20 nm was used in this study to avoid the characteristic broad microwave absorption line associated with these films above thicknesses of 40 nm. For the in-plane easy magnetization axis (01-1), a microwave magnetoelectric (ME) coupling of 28 Oe cm kV -1 was estimated, whereas a value of 42 Oe cm kV -1 was obtained through the hard magnetization axis (100). Insight into the effects of the in-plane strain anisotropy on the ME coupling is obtained from the dc-magnetization loops. It was observed that the trend was opposite along the easy and hard magnetic directions. In particular, along the easy-magnetic axis (01-1), a square and narrow loop with a factor of Mr/MS of 0.96 was measured at 10 kV/cm. Along the hard-magnetic axis, a factor of 0.16 at 10 kV/cm was obtained. Using electric tuning via microwave absorption at X-band (9.78 GHz), we observe completely different trends along the easy and hard magnetic directions; Multiple absorption lines along the latter axis compared to a single and narrower absorption line along the former. In spite of its intrinsic complexity, we propose a model which gives good agreement both for static and microwave properties. These observations are of fundamental interest for future ME microwave components, such as filters, phase-shifters, and resonators.

  4. In-plane anisotropic effect of magnetoelectric coupled PMN-PT/FePt multiferroic heterostructure: Static and microwave properties

    Directory of Open Access Journals (Sweden)

    Jose M. Vargas

    2014-10-01

    Full Text Available The effects of the electric and magnetic field variation on multiferroic heterostructure were studied in this work. Thin films of polycrystalline Fe50Pt50 (FePt were grown by dc-sputtering on top of the commercial slabs of lead magnesium niobate-lead titanate (PMN-PT. The sample was a (011-cut single crystal and had one side polished. In this condition, the PMN-PT/FePt operates in the L-T (longitudinal magnetized-transverse polarized mode. A FePt thin film of 20 nm was used in this study to avoid the characteristic broad microwave absorption line associated with these films above thicknesses of 40 nm. For the in-plane easy magnetization axis (01-1, a microwave magnetoelectric (ME coupling of 28 Oe cm kV −1 was estimated, whereas a value of 42 Oe cm kV −1 was obtained through the hard magnetization axis (100. Insight into the effects of the in-plane strain anisotropy on the ME coupling is obtained from the dc-magnetization loops. It was observed that the trend was opposite along the easy and hard magnetic directions. In particular, along the easy-magnetic axis (01-1, a square and narrow loop with a factor of Mr/MS of 0.96 was measured at 10 kV/cm. Along the hard-magnetic axis, a factor of 0.16 at 10 kV/cm was obtained. Using electric tuning via microwave absorption at X-band (9.78 GHz, we observe completely different trends along the easy and hard magnetic directions; Multiple absorption lines along the latter axis compared to a single and narrower absorption line along the former. In spite of its intrinsic complexity, we propose a model which gives good agreement both for static and microwave properties. These observations are of fundamental interest for future ME microwave components, such as filters, phase-shifters, and resonators.

  5. Effect of the rheological properties of carbon nanotube dispersions on the processing and properties of transparent conductive electrodes.

    Science.gov (United States)

    Maillaud, Laurent; Poulin, Philippe; Pasquali, Matteo; Zakri, Cécile

    2015-06-01

    Transparent conductive films are made from aqueous surfactant stabilized dispersions of carbon nanotubes using an up-scalable rod coating method. The processability of the films is governed by the amount of surfactant which is shown to alter strongly the wetting and viscosity of the ink. The increase of viscosity results from surfactant mediated attractive interactions between the carbon nanotubes. Links between the formulation, ink rheological properties, and electro-optical properties of the films are determined. The provided guidelines are generalized and used to fabricate optimized electrodes using conductive polymers and carbon nanotubes. In these electrodes, the carbon nanotubes act as highly efficient viscosifiers that allow the optimized ink to be homogeneously spread using the rod coating method. From a general point of view and in contrast to previous studies, the CNTs are optimally used in the present approach as conductive additives for viscosity enhancements of electronic inks. PMID:25961667

  6. Anisotropic conductance at improper ferroelectric domain walls

    NARCIS (Netherlands)

    Meier, D.; Seidel, J.; Cano, A.; Delaney, K.; Kumagai, Y.; Mostovoy, M.; Spaldin, N. A.; Ramesh, R.; Fiebig, M.

    2012-01-01

    Transition metal oxides hold great potential for the development of new device paradigms because of the field-tunable functionalities driven by their strong electronic correlations, combined with their earth abundance and environmental friendliness. Recently, the interfaces between transition-metal

  7. Determination of relationships between thermal conductivity and material properties of rocks

    Institute of Scientific and Technical Information of China (English)

    Kazim G(o)rgülü

    2004-01-01

    Energy transfer between the adjacent parts of rocks in underground mines is widely influenced by the thermal conductivity of rocks. The relationships between the thermal conductivity and some material properties of rocks such as the uniaxial compressive strength, unit mass, tensile strength, cohesion, Young's modulus, point load strength, Schmidt rebound hardness, Shore scleroscope hardness and toughness strength were investigated. The statistical analysis of the data obtained in laboratory tests shows that the thermal conductivity increases with increasing the uniaxial compressive strength, unit mass, tensile strength, cohesion, Young's modulus, point load strength, Schmidt rebound hardness and Shore scleroscope hardness, and decreases with increasing the toughness strength.

  8. Anisotropic transport and optical spectroscopy study on antiferromagnetic triangular lattice EuCd2As2 : An interplay between magnetism and charge transport properties

    Science.gov (United States)

    Wang, H. P.; Wu, D. S.; Shi, Y. G.; Wang, N. L.

    2016-07-01

    We present anisotropic transport and optical spectroscopy studies on EuCd2As2 . The measurements reveal that EuCd2As2 is a low carrier density semimetal with moderate anisotropic resistivity ratio. The charge carriers experience very strong scattering from Eu magnetic moments, resulting in a Kondo-like increase of resistivity at low temperature. Below the antiferromagnetic transition temperature at TN=9.5 K, the resistivity drops sharply due to the reduced scattering from the ordered Eu moments. Nevertheless, the anisotropic ratio of ρc/ρa b keeps increasing, suggesting that the antiferromagnetic coupling is along the c axis. The optical spectroscopy measurement further reveals, besides an overdamped reflectance plasma edge at low energy, a strong coupling between phonon and electronic continuum. Our study suggests that EuCd2As2 is a promising candidate displaying intriguing interplay among charge, magnetism, and the underlying crystal lattice.

  9. Anisotropic Stars II Stability

    CERN Document Server

    Dev, K; Dev, Krsna; Gleiser, Marcelo

    2003-01-01

    We investigate the stability of self-gravitating spherically symmetric anisotropic spheres under radial perturbations. We consider both the Newtonian and the full general-relativistic perturbation treatment. In the general-relativistic case, we extend the variational formalism for spheres with isotropic pressure developed by Chandrasekhar. We find that, in general, when the tangential pressure is greater than the radial pressure, the stability of the anisotropic sphere is enhanced when compared to isotropic configurations. In particular, anisotropic spheres are found to be stable for smaller values of the adiabatic index $\\gamma$.

  10. Predicting thermal conductivity of rocks from the Los Azufres geothermal field, Mexico, from easily measurable properties

    Energy Technology Data Exchange (ETDEWEB)

    Garcia, Alfonso; Contreras, Enrique; Dominquez, Bernardo A.

    1988-01-01

    A correlation is developed to predict thermal conductivity of drill cores from the Los Azufres geothermal field. Only andesites are included as they are predominant. Thermal conductivity of geothermal rocks is in general scarce and its determination is not simple. Almost all published correlations were developed for sedimentary rocks. Typically, for igneous rocks, chemical or mineral analyses are used for estimating conductivity by using some type of additive rule. This requires specialized analytical techniques and the procedure may not be sufficiently accurate if, for instance, a chemical analysis is to be changed into a mineral analysis. Thus a simple and accurate estimation method would be useful for engineering purposes. The present correlation predicts thermal conductivity from a knowledge of bulk density and total porosity, properties which provide basic rock characterization and are easy to measure. They may be determined from drill cores or cuttings, and the procedures represent a real advantage given the cost and low availability of cores. The multivariate correlation proposed is a quadratic polynomial and represents a useful tool to estimate thermal conductivity of igneous rocks since data on this property is very limited. For porosities between 0% and 25%, thermal conductivity is estimated with a maximum deviation of 22% and a residual mean square deviation of 4.62E-3 n terms of the log{sub 10}(k{rho}{sub b}) variable. The data were determined as part of a project which includes physical, thermal and mechanical properties of drill cores from Los Azufres. For the correlation, sixteen determinations of thermal conductivity, bulk density and total porosity are included. The conductivity data represent the first determinations ever made on these rocks.

  11. Manipulating dispersion and distribution of graphene in PLA through Novel Interface Engineering for improved conductive properties

    Science.gov (United States)

    This study aimed to enhance the conductive properties of PLA nanocomposite by controlling the dispersion and distribution of graphene within the minor phase of the polymer blend. Functionalized graphene (f-GO) was achieved by reacting graphene oxide (GO) with various silanes under the aid of an ioni...

  12. Theoretical study of anisotropic MHD turbulence with low magnetic Reynolds number

    Science.gov (United States)

    Sukoriansky, Semion; Zemach, Efi

    2016-03-01

    Flows of electrically conducting fluids under the action of external magnetic field present an example of strongly anisotropic turbulence. Such flows are not only important for different engineering applications, but also provide an interesting framework for studies of quasi-two-dimensional turbulence with strongly modified transport properties in easily controllable laboratory experiments. We present theoretical results that advance our understanding of magnetohydrodynamic (MHD) flows with low magnetic Reynolds number by treating this phenomenon within the quasi-normal scale elimination (QNSE) theory. Previous applications of the theory to turbulent flows with stable stratification and solid body rotation have demonstrated that QNSE is a powerful tool for studies of anisotropic turbulent flows. We derive expressions for scale-dependent eddy viscosities and eddy diffusivities in the directions parallel and normal to the external magnetic field and investigate progressive anisotropization of turbulent transport of momentum and passive scalar. The theory yields analytical expressions for anisotropic one-dimensional spectra of MHD turbulence. In particular, the theory sheds light upon the modification of the Kolmogorov k-5/3 spectrum by anisotropic Ohmic (Joule) dissipation.

  13. First-principles calculations of the superconducting properties in Li-decorated monolayer graphene within the anisotropic Migdal-Eliashberg formalism

    Science.gov (United States)

    Zheng, Jing-Jing; Margine, E. R.

    2016-08-01

    The ab initio anisotropic Migdal-Eliashberg formalism has been used to examine the pairing mechanism and the nature of the superconducting gap in the recently discovered lithium-decorated monolayer graphene superconductor. Our results provide evidence that the superconducting transition in Li-decorated monolayer graphene can be explained within a standard phonon-mediated mechanism. We predict a single anisotropic superconducting gap and a critical temperature Tc=5.1 -7.6 K , in very good agreement with the experimental results.

  14. Ti3C2Tx Filler Effect on the Proton Conduction Property of Polymer Electrolyte Membrane.

    Science.gov (United States)

    Liu, Yahua; Zhang, Jiakui; Zhang, Xiang; Li, Yifan; Wang, Jingtao

    2016-08-10

    Conductive polymer electrolyte membranes are increasingly attractive for a wide range of applications in hydrogen-relevant devices, for instance hydrogen fuel cells. In this study, two-dimensional Ti3C2Tx, a typical representative of the recently developed MXene family, is synthesized and employed as a universal filler for its features of large specific surface area, high aspect ratio, and sufficient terminated -OH groups. The Ti3C2Tx is incorporated into polymer matrix to explore its function on membrane microstructure and proton conduction property. Both phase-separated (acidic Nafion and sulfonated poly(ether ether ketone)) and non-phase-separated (basic chitosan) polymers are utilized as membrane matrixes. The microstructures, physicochemical properties, and proton conduction properties of the membranes are extensively investigated. It is demonstrated that Ti3C2Tx generates significant promotion effect on proton conduction of the composite membrane by facilitating both vehicle-type and Grotthuss-type proton transfer, yielding several times increased proton conductivity for every polymer-based composite membrane under various conditions, and the composite membrane achieves elevated hydrogen fuel cell performance. The stable Ti3C2Tx also reinforces the thermal and mechanical stabilities of these composite membranes. Since the MXene family includes more than 70 members, this exploration is expected to open up new perspectives for expanding their applications, especially as membrane modifiers and proton conductors. PMID:27430190

  15. Structural, dielectric and AC conductivity properties of Co2+ doped mixed alkali zinc borate glasses

    Science.gov (United States)

    Madhu, B. J.; Banu, Syed Asma; Harshitha, G. A.; Shilpa, T. M.; Shruthi, B.

    2013-02-01

    The Co2+ doped 19.9ZnO+5Li2CO3+25Na2CO3+50B2O3 (ZLNB) mixed alkali zinc borate glasses have been prepared by a conventional melt quenching method. The structural (XRD & FT-IR), dielectric and a.c. conductivity (σac) properties have been investigated. Amorphous nature of these glasses has been confirmed from their XRD pattern. The dielectric properties and electrical conductivity (σac) of these glasses have been studied from 100Hz to 5MHz at the room temperature. Based on the observed trends in the a.c. conductivities, the present glass samples are found to exhibit a non-Debye behavior.

  16. IONIC CONDUCTIVITY AND ELECTRICAL PROPERTIES OF CARBOXYMETHYL CELLULOSE - NH4Cl SOLID POLYMER ELECTROLYTES

    Directory of Open Access Journals (Sweden)

    N. H. AHMAD

    2016-06-01

    Full Text Available In this present work, carboxymethyl cellulose (CMC – ammonium chloride (NH4Cl solid polymer electrolyte (SPE films were prepared by solution casting method. The ionic conductivity and electrical properties of SPE films were investigated using Electrical Impedance Spectroscopy. SPE film containing 16 wt. % NH4Cl exhibited the highest ionic conductivity of 1.43 x 10-3 S/cm at ambient temperature, 303K. The temperature dependence SPE films showed an Arrhenius-type relation where the regression values obtained from the log conductivity versus reciprocal temperature is close to unity (R2≈1. The electrical properties have been measured as a function of frequency of Ԑr,Ԑi, Mr, Mi shown a non-Debye type behavior

  17. Dielectric properties and electrical conductivity of flat micronic graphite/polyurethane composites

    Science.gov (United States)

    Plyushch, Artyom; Macutkevic, Jan; Kuzhir, Polina P.; Banys, Juras; Fierro, Vanessa; Celzard, Alain

    2016-03-01

    Results of broadband dielectric spectroscopy of flat micronic graphite (FMG)/polyurethane (PU) resin composites are presented in a wide temperature range (25-450 K). The electrical percolation threshold was found to lie between 1 and 2 vol. % of FMG. Above the percolation threshold, the composites demonstrated a huge hysteresis of properties on heating and cooling from room temperature up to 450 K, along with extremely high values of dielectric permittivity and electrical conductivity. Annealing proved to be a very simple but powerful tool for significantly improving the electrical properties of FMG-based composites. In order to explain this effect, the distributions of relaxation times were calculated by the complex impedance formalism. Below room temperature, both dielectric permittivity and electrical conductivity exhibited a very low temperature dependence, mainly caused by the different thermal properties of FMG and pure PU matrix.

  18. Anisotropic pressure and hyperons in neutron stars

    CERN Document Server

    Sulaksono, A

    2014-01-01

    We study the effects of anisotropic pressure on properties of the neutron stars with hyperons inside its core within the framework of extended relativistic mean field. It is found that the main effects of anisotropic pressure on neutron star matter is to increase the stiffness of the equation of state, which compensates for the softening of the EOS due to the hyperons. The maximum mass and redshift predictions of anisotropic neutron star with hyperonic core are quite compatible with the result of recent observational constraints if we use the parameter of anisotropic pressure model $h \\le 0.8$[1] and $\\Lambda \\le -1.15$ [2]. The radius of the corresponding neutron star at $M$=1.4 $M_\\odot$ is more than 13 km, while the effect of anisotropic pressure on the minimum mass of neutron star is insignificant. Furthermore, due to the anisotropic pressure in the neutron star, the maximum mass limit of higher than 2.1 $M_\\odot$ cannot rule out the presence of hyperons in the neutron star core.

  19. Nanoparticle-Structured Highly Sensitive and Anisotropic Gauge Sensors.

    Science.gov (United States)

    Zhao, Wei; Luo, Jin; Shan, Shiyao; Lombardi, Jack P; Xu, Yvonne; Cartwright, Kelly; Lu, Susan; Poliks, Mark; Zhong, Chuan-Jian

    2015-09-16

    The ability to tune gauge factors in terms of magnitude and orientation is important for wearable and conformal electronics. Herein, a sensor device is described which is fabricated by assembling and printing molecularly linked thin films of gold nanoparticles on flexible microelectrodes with unusually high and anisotropic gauge factors. A sharp difference in gauge factors up to two to three orders of magnitude between bending perpendicular (B(⊥)) and parallel (B(||)) to the current flow directions is observed. The origin of the unusual high and anisotropic gauge factors is analyzed in terms of nanoparticle size, interparticle spacing, interparticle structure, and other parameters, and by considering the theoretical aspects of electron conduction mechanism and percolation pathway. A critical range of resistivity where a very small change in strain and the strain orientation is identified to impact the percolation pathway in a significant way, leading to the high and anisotropic gauge factors. The gauge anisotropy stems from molecular and nanoscale fine tuning of interparticle properties of molecularly linked nanoparticle assembly on flexible microelectrodes, which has important implication for the design of gauge sensors for highly sensitive detection of deformation in complex sensing environment or on complex curved surfaces such as wearable electronics and skin sensors. PMID:26037089

  20. Polypropylene/Graphene and Polypropylene/Carbon Fiber Conductive Composites: Mechanical, Crystallization and Electromagnetic Properties

    Directory of Open Access Journals (Sweden)

    Chien-Lin Huang

    2015-11-01

    Full Text Available This study aims to examine the properties of composites that different carbon materials with different measurements can reinforce. Using a melt compounding method, this study combines polypropylene (PP and graphene nano-sheets (GNs or carbon fiber (CF to make PP/GNs and PP/CF conductive composites, respectively. The DSC results and optical microscopic observation show that both GNs and CF enable PP to crystalize at a high temperature. The tensile modulus of PP/GNs and PP/CF conductive composites remarkably increases as a result of the increasing content of conductive fillers. The tensile strength of the PP/GNs conductive composites is inversely proportional to the loading level of GNs. Containing 20 wt% of GNs, the PP/GNs conductive composites have an optimal conductivity of 0.36 S/m and an optimal EMI SE of 13 dB. PP/CF conductive composites have an optimal conductivity of 10−6 S/m when composed of no less than 3 wt% of CF, and an optimal EMI SE of 25 dB when composed of 20 wt% of CF.

  1. Evaluation of three-dimensional anisotropic head model for mapping realistic electromagnetic fields of brain tissues

    Directory of Open Access Journals (Sweden)

    Woo Chul Jeong

    2015-08-01

    Full Text Available Electromagnetic fields provide fundamental data for the imaging of electrical tissue properties, such as conductivity and permittivity, in recent magnetic resonance (MR-based tissue property mapping. The induced voltage, current density, and magnetic flux density caused by externally injected current are critical factors for determining the image quality of electrical tissue conductivity. As a useful tool to identify bio-electromagnetic phenomena, precise approaches are required to understand the exact responses inside the human body subject to an injected currents. In this study, we provide the numerical simulation results of electromagnetic field mapping of brain tissues using a MR-based conductivity imaging method. First, we implemented a realistic three-dimensional human anisotropic head model using high-resolution anatomical and diffusion tensor MR images. The voltage, current density, and magnetic flux density of brain tissues were imaged by injecting 1 mA of current through pairs of electrodes on the surface of our head model. The current density map of anisotropic brain tissues was calculated from the measured magnetic flux density based on the linear relationship between the water diffusion tensor and the electrical conductivity tensor. Comparing the current density to the previous isotropic model, the anisotropic model clearly showed the differences between the brain tissues. This originates from the enhanced signals by the inherent conductivity contrast as well as the actual tissue condition resulting from the injected currents.

  2. Anisotropic Contrast Optical Microscope

    CERN Document Server

    Peev, D; Kananizadeh, N; Wimer, S; Rodenhausen, K B; Herzinger, C M; Kasputis, T; Pfaunmiller, E; Nguyen, A; Korlacki, R; Pannier, A; Li, Y; Schubert, E; Hage, D; Schubert, M

    2016-01-01

    An optical microscope is described that reveals contrast in the Mueller matrix images of a thin, transparent or semi-transparent specimen located within an anisotropic object plane (anisotropic filter). The specimen changes the anisotropy of the filter and thereby produces contrast within the Mueller matrix images. Here we use an anisotropic filter composed of a semi-transparent, nanostructured thin film with sub-wavelength thickness placed within the object plane. The sample is illuminated as in common optical microscopy but the light is modulated in its polarization using combinations of linear polarizers and phase plate (compensator) to control and analyze the state of polarization. Direct generalized ellipsometry data analysis approaches permit extraction of fundamental Mueller matrix object plane images dispensing with the need of Fourier expansion methods. Generalized ellipsometry model approaches are used for quantitative image analyses. We demonstrate the anisotropic contrast optical microscope by mea...

  3. Defined-size DNA triple crossover construct for molecular electronics: modification, positioning and conductance properties

    International Nuclear Information System (INIS)

    We present a novel, defined-size, small and rigid DNA template, a so-called B-A-B complex, based on DNA triple crossover motifs (TX tiles), which can be utilized in molecular scale patterning for nanoelectronics, plasmonics and sensing applications. The feasibility of the designed construct is demonstrated by functionalizing the TX tiles with one biotin-triethylene glycol (TEG) and efficiently decorating them with streptavidin, and furthermore by positioning and anchoring single thiol-modified B-A-B complexes to certain locations on a chip via dielectrophoretic trapping. Finally, we characterize the conductance properties of the non-functionalized construct, first by measuring DC conductivity and second by utilizing AC impedance spectroscopy in order to describe the conductivity mechanism of a single B-A-B complex using a detailed equivalent circuit model. This analysis also reveals further information about the conductivity of DNA structures in general.

  4. Prediction of Geomechanical Properties from Thermal Conductivity of Low-Permeable Reservoirs

    Science.gov (United States)

    Chekhonin, Evgeny; Popov, Evgeny; Popov, Yury; Spasennykh, Mikhail; Ovcharenko, Yury; Zhukov, Vladislav; Martemyanov, Andrey

    2016-04-01

    A key to assessing a sedimentary basin's hydrocarbon prospect is correct reconstruction of thermal and structural evolution. It is impossible without adequate theory and reliable input data including among other factors thermal and geomechanical rock properties. Both these factors are also important in geothermal reservoirs evaluation and carbon sequestration problem. Geomechanical parameters are usually estimated from sonic logging and rare laboratory measurements, but sometimes it is not possible technically (low quality of the acoustic signal, inappropriate borehole and mud conditions, low core quality). No wonder that there are attempts to correlate the thermal and geomechanical properties of rock, but no one before did it with large amount of high quality thermal conductivity data. Coupling results of sonic logging and non-destructive non-contact thermal core logging opens wide perspectives for studying a relationship between the thermal and geomechanical properties. More than 150 m of full size cores have been measured at core storage with optical scanning technique. Along with results of sonic logging performed with Sonic Scanner in different wells drilled in low permeable formations in West Siberia (Russia) it provided us with unique data set. It was established a strong correlation between components of thermal conductivity (measured perpendicular and parallel to bedding) and compressional and shear acoustic velocities in Bazhen formation. As a result, prediction of geomechanical properties via thermal conductivity data becomes possible, corresponding results was demonstrated. The work was supported by the Russian Ministry of Education and Science, project No. RFMEFI58114X0008.

  5. Reflecting and Polarizing Properties of Conductive Fabrics in Ultra-High Frequency Range

    Directory of Open Access Journals (Sweden)

    Oleg Kiprijanovič

    2015-09-01

    Full Text Available The system based on ultra-wide band (UWB signals was employed for qualitative estimation of attenuating, reflecting and polarizing properties of conductive fabrics, capable to prevent local static charge accumulation. Pulsed excitation of triangle monopole antenna of 6.5 cm height by rectangular electric pulses induced radiation of UWB signals with spectral density of power having maximum in ultra-high frequency (UHF range. The same antenna was used for the radiated signal receiving. Filters and amplifiers of different passband were employed to divide UHF range into subranges of 0.3-0.55 GHz, 0.55-1 GHz, 1-2 GHz and 2-4 GHz bands. The free space method, when conductive fabric samples of 50x50 cm2 were placed between transmitting and receiving antennas, was used to imitate a practical application. Received wideband signals corresponding to the defined range were detected by unbiased detectors. The fabrics made of two types of warps, containing different threads with conductive yarns, were investigated. It was estimated attenuation and reflective properties of the fabrics when electric field is collinear or perpendicular to thread direction. In the UHF range it was revealed good reflecting properties of the fabrics containing metallic component in the threads. The system has advantages but not without a certain shortcoming. Adapting it for specific tasks should lead to more effective usage, including yet unused properties of the UWB signals.

  6. Field Theory of Anisotropic Quantum Hall Gas: Metrology and a Novel Quantum Hall Regime

    OpenAIRE

    Ishikawa, K; Aoyama, T.; Ishizuka, Y.; Maeda, N.

    2003-01-01

    The von Neumann lattice representation is a convenient representation for studying several intriguing physics of quantum Hall systems. In this formalism, electrons are mapped to lattice fermions. A topological invariant expression of the Hall conductance is derived and is used for the proof of the integer quantum Hall effect in the realistic situation. Anisotropic quantum Hall gas is investigated based on the Hartree-Fock approximation in the same formalism. Thermodynamic properties, transpor...

  7. Anisotropic pseudopotential for polarized dilute quantum gases

    International Nuclear Information System (INIS)

    An anisotropic pseudopotential arising in the context of collisions of two particles polarized by an external field is rigorously derived and its properties are investigated. Such a low-energy pseudopotential may be useful in describing collective properties of dilute quantum gases, such as molecules polarized by an electric field or metastable 3P2 atoms polarized by a magnetic field. The pseudopotential is expressed in terms of the reactance (K) matrix and derivatives of the Dirac δ function. In most applications, it may be represented as a sum of a traditional spherically symmetric contact term and an anisotropic part. The former contribution may be parametrized by a generalized scattering length. The anisotropic part of the pseudopotential may be characterized by the off-diagonal scattering length for dipolar interactions and off-diagonal scattering volume for quadrupolar interactions. The two-body matrix element of the pseudopotential in a basis of plane waves is also derived

  8. Anisotropic Flow Measurements in ALICE at the Large Hadron Collider

    NARCIS (Netherlands)

    Bilandzic, A.

    2012-01-01

    Anisotropic flow is one of the observables which is sensitive to the properties of the created hot and dense system in heavy-ion collisions. In noncentral heavy-ion collisions the initial volume of the interacting system is anisotropic in coordinate space. Due to multiple interactions this anisotropy

  9. Studies on conductivity and dielectric properties of polyaniline–zinc sulphide composites

    Indian Academy of Sciences (India)

    H C Pant; M K Patra; S C Negi; A Bhatia; S R Vadera; N Kumar

    2006-08-01

    In the present paper, we report electrical conductivity and dielectric studies on the composites of conducting polyaniline (PANI) with crystalline semiconducting ZnS powder, wherein PANI has been taken as inclusion and ZnS crystallites as the host matrix. From the studies, it has been observed that the value of room temperature d.c. conductivity of the composites with volume fraction of PANI > 0.65 shows an unusual behaviour wherein, conductivity values of the composites exceed that of PANI itself with maximum value as high as 6 times that of PANI at the volume fraction of 0.85. A similar trend has also been observed for the real and imaginary parts of complex dielectric constant values of the composites. This unusual behaviour in the d.c. conductivity and dielectric properties has been attributed to the enhancement in the degree of crystallinity of PANI as a consequence of its interfacial interaction with ZnS matrix. The results of optical microscopy show coating of PANI all around the ZnS particles. The temperature dependent conductivity studies suggest the quasi one-dimensional VRH conduction in PANI as well as its composites with ZnS. FTIR and XRD studies have also been reported.

  10. Correlation of Electrical and Swelling Properties with Nano Free Volume Structure of Conductive Silicone Rubber Composites

    International Nuclear Information System (INIS)

    The present study focuses on finding a correlation between the positron annihilation parameters in silicone rubber based on Poly dimethyl siloxane (PDMS) composites loaded with different conductive fillers and their swelling and electrical properties. Four types of conductive fillers have been used in this study: carbon black, graphite, copper, and nickel powders. The maximum degree of swelling Qm %, the penetration rate, P, as well as the diffusion coefficient, D, decrease with increasing the filler content due to the reduction of the size of free volume, as observed through a decrease of the probability of ortho-positronium (o-Ps) formation I3 and the o-Ps lifetime Τ3, representing the size of free volume measured by the positron annihilation lifetime technique (PAL). The electrical conductivity ln (Σ) is positively correlated with the probability of free annihilation of positrons at interfaces I2, thus suggesting an increase in the electron density with the filler content. The activation energy of conduction, Ea, is found to decrease with the increase in the loading of conductive filler and the particle size of the filler. A correlation between the free-volume Vf, and the d.c. electrical conductivity ln (Σ) is found to be in accordance with Miyamoto and Shibayma model of ion conduction.

  11. Remarks on inhomogeneous anisotropic cosmology

    Science.gov (United States)

    Kaya, Ali

    2016-08-01

    Recently a new no-global-recollapse argument was given for some inhomogeneous and anisotropic cosmologies that utilizes surface deformation by the mean curvature flow. In this paper we discuss important properties of the mean curvature flow of spacelike surfaces in Lorentzian manifolds. We show that singularities may form during cosmic evolution, and the theorems forbidding the global recollapse lose their validity. The time evolution of the spatial scalar curvature that may kinematically prevent the recollapse is determined in normal coordinates, which shows the impact of inhomogeneities explicitly. Our analysis indicates a caveat in numerical solutions that give rise to inflation.

  12. CoCl2 reinforced polymeric nanocomposites of conjugated polymer (polyaniline) and its conductive properties

    Indian Academy of Sciences (India)

    M Majhi; R B Choudhary; P Maji

    2015-09-01

    Polyaniline (PANI) was synthesized by chemical oxidative polymerization of aniline using ammonium persulphate as an oxidant in acidic aqueous medium. Cobalt chloride hexahydrate (CoCl2⋅6H2O)-doped PANI composite was synthesized by in-situ oxidative polymerization process by using various concentrations of CoCl2. Its chemical, structural and morphological properties were examined by X-ray diffraction, energydispersive X-ray spectroscopy, Fourier transform infrared spectroscopy and field-emission scanning electron microscopy techniques. These results confirmed the successful formation of PANI and CoCl2-doped PANI nanocomposites. The morphology of CoCl2-doped PANI nanocomposite was found to be spherical in nature. The dielectric properties were examined using LCR-HITESTER in the frequency range 50 Hz–5 MHz. The optical properties were examined by UV–visible spectroscopic techniques in the wavelength range of 200–800 nm. The high dielectric properties and alternating current conductivity of the composite was studied in the temperature range 313–373 K. It was found that the synthesized polymeric nanocomposite owned fairly suitable dielectric and optical properties for its application in actuators, conductive paints and for many other purposes.

  13. Effects of annealing process on electrical conductivity and mechanical property of Cu-Te alloys

    Institute of Scientific and Technical Information of China (English)

    ZHU Da-chuan; TANG Ke; SONG Ming-zhao; TU Ming-jing

    2006-01-01

    The effects of annealing process on the electrical conductivity and mechanical properties of Cu-Te alloys were studied via AG-10TA electronic universal machine, SB2230 digital electric bridge, SEM and EDS. The results show that recrystallization and precipitation occur simultaneously during the annealing process of Cu-Te alloys. Tellurium precipitates as Cu2Te second phase. The grain size increases with the increasing of annealing temperature and time. The electrical conductivity increases monotonously. The tensile strength of Cu-Te alloy is higher than that of pure copper.

  14. Plate Fin Heat Exchanger Model with Axial Conduction and Variable Properties

    CERN Document Server

    Hansen, B J; Klebaner, A; 10.1063/1.4706971

    2012-01-01

    Future superconducting radio frequency (SRF) cavities, as part of Project X at Fermilab, will be cooled to superfluid helium temperatures by a cryogenic distribution system supplying cold supercritical helium. To reduce vapor fraction during the final Joule-Thomson (J-T) expansion into the superfluid helium cooling bath, counter-flow, plate-fin heat exchangers will be utilized. Due to their compact size and ease of fabrication, plate-fin heat exchangers are an effective option. However, the design of compact and high-effectiveness cryogenic heat exchangers operating at liquid helium temperatures requires consideration of axial heat conduction along the direction of flow, in addition to variable fluid properties. Here we present a numerical model that includes the effects of axial conduction and variable properties for a plate fin heat exchanger. The model is used to guide design decisions on heat exchanger material choice and geometry. In addition, the J-T expansion process is modeled with the heat exchanger ...

  15. Synthesis, Characterization, Electrical Conductivity and Fluorescence Properties of Polyimine Bearing Phenylacetylene Units.

    Science.gov (United States)

    Şenol, Dilek; Kolcu, Feyza; Kaya, İsmet

    2016-09-01

    In this study, a Schiff base was synthesized by the condensation reaction of 4-bromobenzaldehyde and 4-aminophenol. Then, phenylacetylene substituted Schiff base monomer (IPA) was obtained by HBr elimination reaction of IPA with phenylacetylene through Sonogashira reaction. IPA was polymerized via chemical oxidative polycondensation reaction. FT-IR and NMR measurements were used for the structural analyses of the synthesized substances. Fluorescence and UV-Vis analyses were carried out for optical characterization. Electrochemical characteristics, electrical conductivities and thermal properties were determined using cyclic voltammetry (CV), four-point probe conductometer, TG-DTA and DSC methods. The main purpose of the present study was to investigate the effects of phenylacetylene bearing units on the properties of conjugated aromatic polyimines. The spectral analysis signified a green light emission behavior when irradiated at different wavelengths. Combined with fluorescent behavior and good thermal stability, the electrical conductivity was found to be very crucial for π-conjugated polymer.

  16. Synthesis, Characterization, Electrical Conductivity and Fluorescence Properties of Polyimine Bearing Phenylacetylene Units.

    Science.gov (United States)

    Şenol, Dilek; Kolcu, Feyza; Kaya, İsmet

    2016-09-01

    In this study, a Schiff base was synthesized by the condensation reaction of 4-bromobenzaldehyde and 4-aminophenol. Then, phenylacetylene substituted Schiff base monomer (IPA) was obtained by HBr elimination reaction of IPA with phenylacetylene through Sonogashira reaction. IPA was polymerized via chemical oxidative polycondensation reaction. FT-IR and NMR measurements were used for the structural analyses of the synthesized substances. Fluorescence and UV-Vis analyses were carried out for optical characterization. Electrochemical characteristics, electrical conductivities and thermal properties were determined using cyclic voltammetry (CV), four-point probe conductometer, TG-DTA and DSC methods. The main purpose of the present study was to investigate the effects of phenylacetylene bearing units on the properties of conjugated aromatic polyimines. The spectral analysis signified a green light emission behavior when irradiated at different wavelengths. Combined with fluorescent behavior and good thermal stability, the electrical conductivity was found to be very crucial for π-conjugated polymer. PMID:27338948

  17. A Study of the Preparation and Properties of Antioxidative Copper Inks with High Electrical Conductivity.

    Science.gov (United States)

    Tsai, Chia-Yang; Chang, Wei-Chen; Chen, Guan-Lin; Chung, Cheng-Huan; Liang, Jun-Xiang; Ma, Wei-Yang; Yang, Tsun-Neng

    2015-12-01

    Conductive ink using copper nanoparticles has attracted much attention in the printed electronics industry because of its low cost and high electrical conductivity. However, the problem of easy oxidation under heat and humidity conditions for copper material limits the wide applications. In this study, antioxidative copper inks were prepared by dispersing the nanoparticles in the solution, and then conductive copper films can be obtained after calcining the copper ink at 250 °C in nitrogen atmosphere for 30 min. A low sheet resistance of 47.6 mΩ/□ for the copper film was measured by using the four-point probe method. Importantly, we experimentally demonstrate that the electrical conductivity of copper films can be improved by increasing the calcination temperature. In addition, these highly conductive copper films can be placed in an atmospheric environment for more than 6 months without the oxidation phenomenon, which was verified by energy-dispersive X-ray spectroscopy (EDS). These observations strongly show that our conductive copper ink features high antioxidant properties and long-term stability and has a great potential for many printed electronics applications, such as flexible display systems, sensors, photovoltaic cells, and radio frequency identification. PMID:26370132

  18. Estimation of radiative and conductive properties of a semitransparent medium using genetic algorithms

    Science.gov (United States)

    Braiek, A.; Adili, A.; Albouchi, F.; Karkri, M.; Ben Nasrallah, S.

    2016-06-01

    The aim of this work is to simultaneously identify the conductive and radiative parameters of a semitransparent sample using a photothermal method associated with an inverse problem. The identification of the conductive and radiative proprieties is performed by the minimization of an objective function that represents the errors between calculated temperature and measured signal. The calculated temperature is obtained from a theoretical model built with the thermal quadrupole formalism. Measurement is obtained in the rear face of the sample whose front face is excited by a crenel of heat flux. For identification procedure, a genetic algorithm is developed and used. The genetic algorithm is a useful tool in the simultaneous estimation of correlated or nearly correlated parameters, which can be a limiting factor for the gradient-based methods. The results of the identification procedure show the efficiency and the stability of the genetic algorithm to simultaneously estimate the conductive and radiative properties of clear glass.

  19. Scaling of material properties for Yucca Mountain: literature review and numerical experiments on saturated hydraulic conductivity

    Energy Technology Data Exchange (ETDEWEB)

    McKenna, S.A.; Rautman, C.A.

    1996-08-01

    A review of pertinent literature reveals techniques which may be practical for upscaling saturated hydraulic conductivity at Yucca Mountain: geometric mean, spatial averaging, inverse numerical modeling, renormalization, and a perturbation technique. Isotropic realizations of log hydraulic conductivity exhibiting various spatial correlation lengths are scaled from the point values to five discrete scales through these techniques. For the variances in log{sub 10} saturated hydraulic conductivity examined here, geometric mean, numerical inverse and renormalization adequately reproduce point scale fluxes across the modeled domains. Fastest particle velocities and dispersion measured on the point scale are not reproduced by the upscaled fields. Additional numerical experiments examine the utility of power law averaging on a geostatistical realization of a cross-section similar to the cross-sections that will be used in the 1995 groundwater travel time calculations. A literature review on scaling techniques for thermal and mechanical properties is included. 153 refs., 29 figs., 6 tabs.

  20. The colored and bleached properties of tungsten oxide electrochromic films with different substrate conductivities

    International Nuclear Information System (INIS)

    Tungsten oxide films have been deposited by reactive RF magnetron sputtering. The electrochromic properties were characterized by cyclic voltammetry and UV-visible spectrometry. The oxide films were deposited on substrates with different electrical conductivities. The sheet resistances of the ITO electrodes used in this study were 10, 50 and180 Ω/cm2, respectively. Experimental results demonstrate that the electrical conductivity of the electrode material strongly influences the response time of the WO3 electrochromic film, which is explained by the different numbers of lithium ions transported at the different electrode conductivities. The ITO material with 10 Ω/cm2 gave the best response time of the WO3 electrochromic films

  1. The colored and bleached properties of tungsten oxide electrochromic films with different substrate conductivities

    Energy Technology Data Exchange (ETDEWEB)

    Lu, Y.-M. [Graduate Institute of Electro-Optical and Materials Science, National Formosa University, Huwei, Taiwan (China)], E-mail: ymlumit@yahoo.com.tw; Hu, C.-P. [Department of Engineering Science, National Cheng Kung University, Tainan, Taiwan (China)

    2008-01-31

    Tungsten oxide films have been deposited by reactive RF magnetron sputtering. The electrochromic properties were characterized by cyclic voltammetry and UV-visible spectrometry. The oxide films were deposited on substrates with different electrical conductivities. The sheet resistances of the ITO electrodes used in this study were 10, 50 and180 {omega}/cm{sup 2}, respectively. Experimental results demonstrate that the electrical conductivity of the electrode material strongly influences the response time of the WO{sub 3} electrochromic film, which is explained by the different numbers of lithium ions transported at the different electrode conductivities. The ITO material with 10 {omega}/cm{sup 2} gave the best response time of the WO{sub 3} electrochromic films.

  2. AC conductivity and dielectric properties of bulk tungsten trioxide (WO{sub 3})

    Energy Technology Data Exchange (ETDEWEB)

    El-Nahass, M.M. [Department of Physics, Faculty of Education, Ain Shams University, Roxy 11757, Cairo (Egypt); Ali, H.A.M., E-mail: hend2061@yahoo.com [Department of Physics, Faculty of Education, Ain Shams University, Roxy 11757, Cairo (Egypt); Saadeldin, M.; Zaghllol, M. [Physics Department, Faculty of Science, Cairo University, Giza 12613 (Egypt)

    2012-11-15

    AC conductivity and dielectric properties of tungsten trioxide (WO{sub 3}) in a pellet form were studied in the frequency range from 42 Hz to 5 MHz with a variation of temperature in the range from 303 K to 463 K. AC conductivity, {sigma}{sub ac}({omega}) was found to be a function of {omega}{sup s} where {omega} is the angular frequency and s is the frequency exponent. The values of s were found to be less than unity and decrease with increasing temperature, which supports the correlated barrier hopping mechanism (CBH) as the dominant mechanism for the conduction in WO{sub 3}. The dielectric constant ({epsilon} Prime ) and dielectric loss ({epsilon} Double-Prime ) were measured. The Cole-Cole diagram determined complex impedance for different temperatures.

  3. Proton-conducting Microcrystalline Cellulose Doped with Imidazole. Thermal and Electrical Properties

    International Nuclear Information System (INIS)

    Highlights: • A microcrystalline cellulose was doped with imidazole molecules • Thermal and electrical properties of newly synthesized material were determined • The doped cellulose exhibits four times higher conductivity than a pure cellulose • The highest proton conductivity of about 2 × 10−4 S/m was measured at 160 °C • The thermal stability was determined to be in the range from 110 to about 150 °C - ABSTRACT: A new biodegradable polymeric material (Cell-Im) consisting of microcrystalline cellulose (Cell) and imidazole (Im) dopant was successfully synthesized. The thermal properties and proton conductivity of Cell-Im were determined and compared with that of pure microcrystalline cellulose. It was found that the Cell-Im exhibits close to four orders of magnitude higher conductivity than a pure cellulose sample, up to approximately 2 × 10−4 S/m at 160 °C under anhydrous conditions. Thermal stability of Cell-Im was confirmed above water boiling point in a temperature range from 110 to about 150 °C. The Cell-Im is inexpensive to obtain, non-hazardous and environmentally friendly and can have potential for possible application as a solid electrolyte in electrochemical devices

  4. Effect of conducting polypyrrole on the transport properties of carbon nanotube yarn

    Energy Technology Data Exchange (ETDEWEB)

    Foroughi, Javad, E-mail: foroughi@uow.edu.au [ARC Centre of Excellence for Electromaterials Science, Intelligent Polymer Research Institute, University of Wollongong, Wollongong, NSW 2519 (Australia); Information and communication Technology Research Institute, University of Wollongong, Wollongong, NSW 2519 (Australia); Kimiaghalam, Bahram [Information and communication Technology Research Institute, University of Wollongong, Wollongong, NSW 2519 (Australia); Ghorbani, Shaban Reza [Department of Physics, Hakim Sabzevari University, P.O. Box 397, Sabzevar (Iran, Islamic Republic of); Safaei, Farzad [Information and communication Technology Research Institute, University of Wollongong, Wollongong, NSW 2519 (Australia); Abolhasan, Mehran [Faculty of Engineering and IT University of Technology Sydney, Sydney, NSW Australia (Australia)

    2012-10-01

    Experiments were conducted to measure the electrical conductivity in three types of pristine and carbon nanotube-polypyrrole (CNT-PPy) composite yarns and its dependence on over a wide temperature range. The experimental results fit well with the analytical models developed. The effective energy separation between localized states of the pristine CNT yarn is larger than that for both the electrochemically and chemically prepared CNT-PPy yarns. It was found that all samples are in the critical regime in the insulator-metal transition, or close to the metallic regime at low temperature. The electrical conductivity results are in good agreement with a Three Dimensional Variable Range Hopping model at low temperatures, which provides a strong indication that electron hopping is the main means of current transfer in CNT yarns at T < 100 K. We found that the two shell model accurately describes the electronic properties of CNT and CNT-PPy composite yarns in the temperature range of 5-350 K. - Highlights: Black-Right-Pointing-Pointer We developed hybrid carbon nanotube conducting polypyrrole composite yarns. Black-Right-Pointing-Pointer The main current transfer scheme in yarn is via three dimensional electrons hopping. Black-Right-Pointing-Pointer Two shell model describes well electronic properties of yarns in range of 5-350 K.

  5. A Numerical Method for Analyzing Electromagnetic Scattering Properties of a Moving Conducting Object

    Directory of Open Access Journals (Sweden)

    Lei Kuang

    2014-01-01

    Full Text Available A novel numerical approach is developed to analyze electromagnetic scattering properties of a moving conducting object based on the finite-difference time-domain (FDTD algorithm. Relativistic boundary conditions are implemented into the FDTD algorithm to calculate the electromagnetic field on the moving boundary. An improved technique is proposed to solve the scattered field in order to improve the computational efficiency and stability of solutions. The time-harmonic scattered field from a one-dimensional moving conducting surface is first simulated by the proposed approach. Numerical results show that the amplitude and frequency of the scattered field suffer a modulation shift. Then the transient scattered field is calculated, and broadband electromagnetic scattering properties of the moving conducting surface are obtained by the fast Fourier transform (FFT. Finally, the scattered field from a two-dimensional moving square cylinder is analyzed. The numerical results demonstrate the Doppler effect of a moving conducting object. The simulated results agree well with analytical results.

  6. Piezoelectric and pyroelectric properties of conductive polyethylene oxide-lead titanate composites

    Science.gov (United States)

    Khanbareh, H.; van der Zwaag, S.; Groen, W. A.

    2015-04-01

    Polymer-ceramic composites with pyroelectric sensitivity are presented as promising candidates for sensing applications. Selection of the appropriate ceramic filler and the polymer matrix is one of the key parameters in the development of optimized materials for specific applications. In this work lead-titanate (PT) ceramic particulate is incorporated into a polymer matrix, polyethylene oxide (PEO) with a relatively high electrical conductivity to develop sensitive and at the same time flexible composites. PT particles are dispersed in PEO at varying volume fractions, and composite materials are cast in the form of films to measure their dielectric, piezoelectric and pyroelectric properties. From these data the piezoelectric voltage coefficients as well as pyroelctric figures of merit of the composite films have been determined. In order to determine the effect of electrical conductivity of the polymer matrix on the poling efficiency and the final properties, a poling study has been performed. Improving the electrical conductivity of the polymer phase enhances the poling process significantly. It is found that both the piezoelectric and the pyroelectric figures of merit increase with concentration of PT. PT-PEO composites show superior pyroelectric sensitivity compared to other composites with less conductive polymer matrices.

  7. Porous polymer electrolytes with high ionic conductivity and good mechanical property for rechargeable batteries

    Science.gov (United States)

    Liang, Bo; Jiang, Qingbai; Tang, Siqi; Li, Shengliang; Chen, Xu

    2016-03-01

    Porous polymer electrolytes (PPEs) are attractive for developing lithium-ion batteries because of the combined advantages of liquid and solid polymer electrolytes. In the present study, a new porous polymer membrane doped with phytic acid (PA) is prepared, which is used as a crosslinker in polymer electrolyte matrix and can also plasticize porous polymer electrolyte membranes, changing them into soft tough flexible materials. A PEO-PMMA-LiClO4-x wt.% PA (x = weight of PA/weight of polymer, PEO: poly(ethylene oxide); PMMA: poly(methyl methacrylate)) polymer membrane is prepared by a simple evaporation method. The effects of the ratio of PA to PEO-PMMA on the properties of the porous membrane, including morphology, porous structure, and mechanical property, are systematically studied. PA improves the porous structure and mechanical properties of polymer membrane. The maximum tensile strength and elongation of the porous polymer membranes are 20.71 MPa and 45.7% at 15 wt.% PA, respectively. Moreover, the PPEs with 15 wt.% PA has a conductivity of 1.59 × 10-5 S/cm at 20 °C, a good electrochemical window (>5 V), and a low interfacial resistance. The results demonstrate the compatibility of the mechanical properties and conductivity of the PPEs, indicating that PPEs have good application prospects for lithium-ion batteries.

  8. SPATIAL DEPENDENCE OF ELECTRICAL CONDUCTIVITY AND CHEMICAL PROPERTIES OF THE SOIL BY ELECTROMAGNETIC INDUCTION

    Directory of Open Access Journals (Sweden)

    Flavia Cristina Machado

    2015-08-01

    Full Text Available Brazilian soils have natural high chemical variability; thus, apparent electrical conductivity (ECa can assist interpretation of crop yield variations. We aimed to select soil chemical properties with the best linear and spatial correlations to explain ECa variation in the soil using a Profiler sensor (EMP-400. The study was carried out in Sidrolândia, MS, Brazil. We analyzed the following variables: electrical conductivity - EC (2, 7, and 15 kHz, organic matter, available K, base saturation, and cation exchange capacity (CEC. Soil ECa was measured with the aid of an all-terrain vehicle, which crossed the entire area in strips spaced at 0.45 m. Soil samples were collected at the 0-20 cm depth with a total of 36 samples within about 70 ha. Classical descriptive analysis was applied to each property via SAS software, and GS+ for spatial dependence analysis. The equipment was able to simultaneously detect ECa at the different frequencies. It was also possible to establish site-specific management zones through analysis of correlation with chemical properties. We observed that CEC was the property that had the best correlation with ECa at 15 kHz.

  9. Conductivity and properties of polysiloxane-polyether cluster-LiTFSI networks as hybrid polymer electrolytes

    Science.gov (United States)

    Boaretto, Nicola; Joost, Christine; Seyfried, Mona; Vezzù, Keti; Di Noto, Vito

    2016-09-01

    This report describes the synthesis and the properties of a series of polymer electrolytes, composed of a hybrid inorganic-organic matrix doped with LiTFSI. The matrix is based on ring-like oligo-siloxane clusters, bearing pendant, partially cross-linked, polyether chains. The dependency of the thermo-mechanic and of the transport properties on several structural parameters, such as polyether chains' length, cross-linkers' concentration, and salt concentration is studied. Altogether, the materials show good thermo-mechanical and electrochemical stabilities, with conductivities reaching, at best, 8·10-5 S cm-1 at 30 °C. In conclusion, the cell performances of one representative sample are shown. The scope of this report is to analyze the correlations between structure and properties in networked and hybrid polymer electrolytes. This could help the design of optimized polymer electrolytes for application in lithium metal batteries.

  10. Surface instabilities during straining of anisotropic materials

    DEFF Research Database (Denmark)

    Legarth, Brian Nyvang; Richelsen, Ann Bettina

    2006-01-01

    The development of instabilities in traction-free surfaces is investigated numerically using a unit cell model. Full finite strain analyses are conducted using isotropic as well as anisotropic yield criteria and both plane strain tension and compression are considered. In the load range of tension...

  11. Field dependent spin transport of anisotropic Heisenberg chain

    Science.gov (United States)

    Rezania, H.

    2016-04-01

    We have addressed the static spin conductivity and spin Drude weight of one-dimensional spin-1/2 anisotropic antiferromagnetic Heisenberg chain in the finite magnetic field. We have investigated the behavior of transport properties by means of excitation spectrum in terms of a hard core bosonic representation. The effect of in-plane anisotropy on the spin transport properties has also been studied via the bosonic model by Green's function approach. This anisotropy is considered for exchange constants that couple spin components perpendicular to magnetic field direction. We have found the temperature dependence of the spin conductivity and spin Drude weight in the gapped field induced spin-polarized phase for various magnetic field and anisotropy parameters. Furthermore we have studied the magnetic field dependence of static spin conductivity and Drude weight for various anisotropy parameters. Our results show the regular part of spin conductivity vanishes in isotropic case however Drude weight has a finite non-zero value and the system exhibits ballistic transport properties. We also find the peak in the static spin conductivity factor moves to higher temperature upon increasing the magnetic field at fixed anisotropy. The static spin conductivity is found to be monotonically decreasing with magnetic field due to increase of energy gap in the excitation spectrum. Furthermore we have studied the temperature dependence of spin Drude weight for different magnetic field and various anisotropy parameters.

  12. Electronic and transport properties of noncollinear magnetic monatomic Mn chains: Fano resonances in the superlattice of noncollinear magnetic barriers and magnetic anisotropic bands

    Energy Technology Data Exchange (ETDEWEB)

    Dai, C.J. [College of Science, Nanjing University of Aeronautics and Astronautics, Nanjing 210016 (China); Yan, X.H., E-mail: xhyan@nuaa.edu.cn [College of Science, Nanjing University of Aeronautics and Astronautics, Nanjing 210016 (China); College of Electronic Science and Engineering, Nanjing University of Posts and Telecommunications, Nanjing 210046 (China); Xiao, Y. [College of Science, Nanjing University of Aeronautics and Astronautics, Nanjing 210016 (China); Guo, Y.D. [College of Electronic Science and Engineering, Nanjing University of Posts and Telecommunications, Nanjing 210046 (China)

    2015-04-01

    By means of the density functional theory combined with non-equilibrium Green's function method, ballistic transport properties of one-dimensional noncollinear magnetic monatomic chains were investigated using the single-atomic Mn chains as a model system. Fano resonances are found to exist in the monatomic Mn chains with spin-spiral structure. Furthermore, in the monatomic Mn chains with magnetic soliton lattice, Fano resonances are enhanced and cause the conductance splitting in the transmission spectra. The Fano resonances in the noncollinear magnetic single-atomic Mn chains are arising from the coupling of the localized d-states and the extended states of the quantum channels. By constructing a theoretical model and calculating its conductance, it is found that the phenomena of Fano resonances and the accompanying conductance splitting exist universally in the superlattice of one-dimensional noncollinear magnetic barriers, due to the interference of the incident waves and reflected waves by the interfaces between the neighboring barriers. Moreover, the band structures of the ferromagnetic and spin-spiral monatomic Mn chains exhibit a strong dependence on the spatial arrangement of the magnetic moments of Mn atoms when spin–orbit coupling is considered. - Highlights: • Transport properties of noncollinear magnetic monatomic Mn chains are studied. • Fano resonances are found in the noncollinear magnetic monatomic Mn chains. • Magnetic soliton lattice leads to conductance splitting in the transmission curve. • Fano resonances exist in the superlattice of noncollinear magnetic barriers. • Effect of SOC on the band structure of FM and spin-spiral Mn chains are studied.

  13. Electrical Properties of Conductive Cotton Yarn Coated with Eosin Y Functionalized Reduced Graphene Oxide.

    Science.gov (United States)

    Kim, Eunju; Arul, Narayanasamy Sabari; Han, Jeong In

    2016-06-01

    This study reports the fabrication and investigation of the electrical properties of two types of conductive cotton yarns coated with eosin Y or eosin B functionalized reduced graphene (RGO) and bare graphene oxide (GO) using dip-coating method. The surface morphology of the conductive cotton yarn coated with reduced graphene oxide was observed by Scanning Electron Microscope (SEM). Due to the strong electrostatic attractive forces, the negatively charged surface such as the eosin Y functionalized reduced graphene oxide or bare GO can be easily coated to the positively charged polyethyleneimine (PEI) treated cotton yarn. The maximum current for the conductive cotton yarn coated with eosin Y functionalized RGO and bare GO with 20 cycles repetition of (5D + R) process was found to be 793.8 μA and 3482.8 μA. Our results showed that the electrical conductivity of bare GO coated conductive cotton yarn increased by approximately four orders of magnitude with the increase in the dipping cycle of (5D+R) process.

  14. Electrical Properties of Conductive Cotton Yarn Coated with Eosin Y Functionalized Reduced Graphene Oxide.

    Science.gov (United States)

    Kim, Eunju; Arul, Narayanasamy Sabari; Han, Jeong In

    2016-06-01

    This study reports the fabrication and investigation of the electrical properties of two types of conductive cotton yarns coated with eosin Y or eosin B functionalized reduced graphene (RGO) and bare graphene oxide (GO) using dip-coating method. The surface morphology of the conductive cotton yarn coated with reduced graphene oxide was observed by Scanning Electron Microscope (SEM). Due to the strong electrostatic attractive forces, the negatively charged surface such as the eosin Y functionalized reduced graphene oxide or bare GO can be easily coated to the positively charged polyethyleneimine (PEI) treated cotton yarn. The maximum current for the conductive cotton yarn coated with eosin Y functionalized RGO and bare GO with 20 cycles repetition of (5D + R) process was found to be 793.8 μA and 3482.8 μA. Our results showed that the electrical conductivity of bare GO coated conductive cotton yarn increased by approximately four orders of magnitude with the increase in the dipping cycle of (5D+R) process. PMID:27427672

  15. Quasiparticle anisotropic hydrodynamics

    CERN Document Server

    Alqahtani, Mubarak

    2016-01-01

    We study an azimuthally-symmetric boost-invariant quark-gluon plasma using quasiparticle anisotropic hydrodynamics including the effects of both shear and bulk viscosities. We compare results obtained using the quasiparticle method with the standard anisotropic hydrodynamics and viscous hydrodynamics. We consider the predictions of the three methods for the differential particle spectra and mean transverse momentum. We find that the three methods agree for small shear viscosity to entropy density ratio, $\\eta/s$, but show differences at large $\\eta/s$. Additionally, we find that the standard anisotropic hydrodynamics method shows suppressed production at low transverse-momentum compared to the other two methods, and the bulk-viscous correction can drive the primordial particle spectra negative at large $p_T$ in viscous hydrodynamics.

  16. Thermal conductivity and mechanical properties of AlN-based thin films

    Science.gov (United States)

    Moraes, V.; Riedl, H.; Rachbauer, R.; Kolozsvári, S.; Ikeda, M.; Prochaska, L.; Paschen, S.; Mayrhofer, P. H.

    2016-06-01

    While many research activities concentrate on mechanical properties and thermal stabilities of protective thin films, only little is known about their thermal properties being essential for the thermal management in various industrial applications. Based on the 3ω-method, we show the influence of Al and Cr on the temperature dependent thermal conductivity of single-phase cubic structured TiN and single-phase wurtzite structured AlN thin films, respectively, and compare them with the results obtained for CrN thin films. The dc sputtered AlN thin films revealed a highly c-axis oriented growth for deposition temperatures of 250 to 700 °C. Their thermal conductivity was found to increase strongly with the film thickness, indicating progressing crystallization of the interface near amorphous regions during the sputtering process. For the 940 nm AlN film, we found a lower boundary for the thermal conductivity of 55.3 W m-1 K-1 . By the substitution of only 10 at. % Al with Cr, κ significantly reduces to ˜5.0 W m-1 K-1 , although the single-phase wurtzite structure is maintained. The single-phase face centered cubic TiN and Ti0.36Al0.64N thin films exhibit κ values of 3.1 W m-1 K-1 and 2.5 W m-1 K-1 , respectively, at room temperature. Hence, also here, the substitutional alloying reduces the thermal conductivity, although at a significantly lower level. Single-phase face centered cubic CrN thin films show κ values of 3.6 W m-1 K-1 . For all nitride based thin films investigated, the thermal conductivity slightly increases with increasing temperature between 200 and 330 K. This rather unusual behavior is based on the high defect density (especially point defects) within the thin films prepared by physical vapor deposition.

  17. Anisotropic elastic plates

    CERN Document Server

    Hwu, Chyanbin

    2010-01-01

    As structural elements, anisotropic elastic plates find wide applications in modern technology. The plates here are considered to be subjected to not only in plane load but also transverse load. In other words, both plane and plate bending problems as well as the stretching-bending coupling problems are all explained in this book. In addition to the introduction of the theory of anisotropic elasticity, several important subjects have are discussed in this book such as interfaces, cracks, holes, inclusions, contact problems, piezoelectric materials, thermoelastic problems and boundary element a

  18. Mixture of Anisotropic Fluids

    Science.gov (United States)

    Florkowski, W.; Maj, R.

    The recently introduced approach describing coupled quark and gluon anisotropic fluids is generalized to include explicitly the transitions between quarks and gluons. We study the effects of such processes on the thermalization rate of anisotropic systems. We find that the quark-gluon transitions may enhance the overall thermalization rate in the cases where the initial momentum anisotropies correspond to mixed oblate-prolate or prolate configurations. On the other hand, no effect on the thermalization rate is found in the case of oblate configurations. The observed regularities are connected with the late-time behavior of the analyzed systems which is described either by the exponential decay or the power law.

  19. Mixture of anisotropic fluids

    CERN Document Server

    Florkowski, Wojciech

    2013-01-01

    The recently introduced approach describing coupled quark and gluon anisotropic fluids is generalized to include explicitly the transitions between quarks and gluons. We study the effects of such processes on the thermalization rate of anisotropic systems. We find that the quark-gluon transitions may enhance the overall thermalization rate in the cases where the initial momentum anisotropies correspond to mixed oblate-prolate or prolate configurations. On the other hand, no effect on the thermalization rate is found in the case of oblate configurations. The observed regularities are connected with the late-time behavior of the analyzed systems which is described either by the exponential decay or the power law.

  20. Anisotropic Weyl invariance

    CERN Document Server

    Pérez-Nadal, Guillem

    2016-01-01

    We consider a non-relativistic free scalar field theory with a type of anisotropic scale invariance in which the number of coordinates "scaling like time" is generically greater than one. We propose the Cartesian product of two curved spaces, with the metric of each space parameterized by the other space, as a notion of curved background to which the theory can be extended. We study this type of geometries, and find a family of extensions of the theory to curved backgrounds in which the anisotropic scale invariance is promoted to a local, Weyl-type symmetry.

  1. Identification of conduction and hot electron property in ZnS, ZnO and SiO2

    International Nuclear Information System (INIS)

    The impact excitation and ionization is the most important process in layered optimization scheme and solid state cathodoluminescence. The conduction property (semiconductor property) of SiO2, ZnS and ZnO is studied based on organic/inorganic electroluminescence. The hot electron property (acceleration and multiplication property) of SiO2 and ZnS is investigated based on the solid state cathodoluminescence. The results show that the SiO2 has the fine hot electron property and the conduction property is not as good as ZnO and ZnS

  2. Obtuse triangle suppression in anisotropic meshes

    KAUST Repository

    Sun, Feng

    2011-12-01

    Anisotropic triangle meshes are used for efficient approximation of surfaces and flow data in finite element analysis, and in these applications it is desirable to have as few obtuse triangles as possible to reduce the discretization error. We present a variational approach to suppressing obtuse triangles in anisotropic meshes. Specifically, we introduce a hexagonal Minkowski metric, which is sensitive to triangle orientation, to give a new formulation of the centroidal Voronoi tessellation (CVT) method. Furthermore, we prove several relevant properties of the CVT method with the newly introduced metric. Experiments show that our algorithm produces anisotropic meshes with much fewer obtuse triangles than using existing methods while maintaining mesh anisotropy. © 2011 Elsevier B.V. All rights reserved.

  3. Gravitational stresses in anisotropic rock masses

    Science.gov (United States)

    Amadei, B.; Savage, W.Z.; Swolfs, H.S.

    1987-01-01

    This paper presents closed-form solutions for the stress field induced by gravity in anisotropic rock masses. These rocks are assumed to be laterally restrained and are modelled as a homogeneous, orthotropic or transversely isotropic, linearly elastic material. The analysis, constrained by the thermodynamic requirement that strain energy be positive definite, gives the following important result: inclusion of anisotropy broadens the range of permissible values of gravity-induced horizontal stresses. In fact, for some ranges of anisotropic rock properties, it is thermodynamically admissible for gravity-induced horizontal stresses to exceed the vertical stress component; this is not possible for the classical isotropic solution. Specific examples are presented to explore the nature of the gravity-induced stress field in anisotropic rocks and its dependence on the type, degree and orientation of anisotropy with respect to the horizontal ground surface. ?? 1987.

  4. Physico-mechanical and electrical properties of conductive carbon black reinforced chlorosulfonated polyethylene vulcanizates

    Directory of Open Access Journals (Sweden)

    2008-12-01

    Full Text Available The present work deals with the effect of conductive carbon black (Ensaco 350G on the physico-mechanical and electrical properties of chlorosulfonated polyethylene (CSM rubber vulcanizates. The physico-mechanical properties like tensile strength, tear strength, elongation at break, compression set, hardness and abrasion resistance have been studied before and after heat ageing. Up to 30 parts per hundred rubber (phr filler loading both tensile and tear strength increases beyond which it shows a decreasing trend whereas modulus gradually increases with the filler loading. Incorporation of carbon black increases the hysteresis loss of filled vulcanizates compared to gum vulcanizates. Unlike gum vulcanizate, in filled vulcanizates the rate of relaxation shows increasing trend. The bound rubber content is found to increase with increase in filler loading. Dielectric relaxation spectra were used to study the relaxation behavior as a function of frequency (100 to 106 Hz at room temperature. Variation in real and imaginary parts of electric modulus has been explained on the basis of interfacial polarization of fillers in the polymer medium. The percolation limit of the conductive black as studied by ac conductivity measurements has also been reported.

  5. Calculation of the transport properties of carbon dioxide. II. Thermal conductivity and thermomagnetic effects

    Science.gov (United States)

    Bock, Steffen; Bich, Eckard; Vogel, Eckhard; Dickinson, Alan S.; Vesovic, Velisa

    2004-05-01

    The transport properties of pure carbon dioxide have been calculated from the intermolecular potential using the classical trajectory method. Results are reported in the dilute-gas limit for thermal conductivity and thermomagnetic coefficients for temperatures ranging from 200 K to 1000 K. Three recent carbon dioxide potential energy hypersurfaces have been investigated. Since thermal conductivity is influenced by vibrational degrees of freedom, not included in the rigid-rotor classical trajectory calculation, a correction for vibration has also been employed. The calculations indicate that the second-order thermal conductivity corrections due to the angular momentum polarization (Bukowski et al. (1999) are in good agreement with the available experimental data. They underestimate the best experimental data at room temperature by 1% and in the range up to 470 K by 1%-3%, depending on the data source. Outside this range the calculated values, we believe, may be more reliable than the currently available experimental data. Our results are consistent with measurements of the thermomagnetic effect at 300 K only when the vibrational degrees of freedom are considered fully. This excellent agreement for these properties indicates that particularly the potential surface of Bukowski et al. provides a realistic description of the anisotropy of the surface.

  6. Prediction of thermal conductivity of rock through physico-mechanical properties

    Energy Technology Data Exchange (ETDEWEB)

    Singh, T.N. [Department of Earth Sciences, Indian Institute of Technology, Bombay 400 076 (India); Sinha, S.; Singh, V.K. [Institute of Technology, Banaras Hindu University, Varanasi 221 005 (India)

    2007-01-15

    The transfer of energy between two adjacent parts of rock mainly depends on its thermal conductivity. Present study supports the use of artificial neural network (ANN) and adaptive neuro fuzzy inference system (ANFIS) in the study of thermal conductivity along with other intrinsic properties of rock due to its increasing importance in many areas of rock engineering, agronomy and geo environmental engineering field. In recent years, considerable effort has been made to develop techniques to determine these properties. Comparative analysis is made to analyze the capabilities among six different models of ANN and ANFIS. ANN models are based on feedforward backpropagation network with training functions resilient backpropagation (RP), one step secant (OSS) and Powell-Beale restarts (CGB) and radial basis with training functions generalized regression neural network (GRNN) and more efficient design radial basis network (NEWRB). A data set of 136 has been used for training different models and 15 were used for testing purposes. A statistical analysis is made to show the consistency among them. ANFIS is proved to be the best among all the networks tried in this case with average absolute percentage error of 0.03% and regression coefficient of 1, whereas best performance shown by the FFBP (RP) with average absolute error of 2.26%. Thermal conductivity is predicted using P-wave velocity, porosity, bulk density, uniaxial compressive strength of rock as input parameters. (author)

  7. Electrical conductivity and thermal properties of functionalized carbon nanotubes/polyurethane composites

    Directory of Open Access Journals (Sweden)

    Aline M. F. Lima

    2012-01-01

    Full Text Available Multi-walled carbon nanotubes (MWCNTs functionalized with amine and carboxyl groups were used to prepare polyurethane/MWCNT nanocomposites in two distinct concentrations: a lower value of 1 mass% (spray coating and a higher one of ~50 mass% (buckypaper based. The MWCNT-NH2 sample contained only 0.5 mass% of amine groups, whereas MWCNT-COOH contained 5 mass% of carboxyl groups. The MWCNT functionalized with low amine group content showed improved thermal properties when compared to neat thermoplastic polyurethane (TPU and MWCNT-COOH based nanocomposites. The electrical conductivity of the polyurethane elastomer was greatly increased from 10-12 to ~10-5 S cm-1in the 1 mass% nanotube composite and to 7 S cm-1for the MWCNT-NH2 buckypaper-based nanocomposite. Furthermore, the relative high content of functional groups in the MWCNT-COOH sample, which disrupt the sp²structure in the nanotube walls, led to inferior properties; for instance the conductivity of the buckypaper based composite is one order of magnitude lower when using MWCNT-COOH in comparison with the MWCNT-NH2. These results show the range of property design possibilities available with the elastomeric polyurethane nanocomposite by tailoring the functional group content and the carbon nanotube load.

  8. Properties of TiO{sub 2}-based transparent conducting oxides

    Energy Technology Data Exchange (ETDEWEB)

    Hitosugi, Taro [Kanagawa Academy of Science and Technology (KAST), 213-0012 Kawasaki (Japan); Advanced Institute for Materials Research (WPI-AIMR), Tohoku University, 980-8577 Sendai (Japan); Yamada, Naoomi; Nakao, Shoichiro [Kanagawa Academy of Science and Technology (KAST), 213-0012 Kawasaki (Japan); Hirose, Yasushi; Hasegawa, Tetsuya [Kanagawa Academy of Science and Technology (KAST), 213-0012 Kawasaki (Japan); Department of Chemistry, University of Tokyo, 113-0033 Tokyo (Japan)

    2010-07-15

    The development and properties of titanium dioxide (TiO{sub 2})-based transparent conducting oxides (TCO), which exhibit properties comparable to those of In{sub 2-x}Sn{sub x}O{sub 3} (ITO), are reviewed in this article. An epitaxial thin film of anatase Ti{sub 0.94}Nb{sub 0.06}O{sub 2} exhibited a resistivity ({rho}) of 2.3 x 10{sup -4}{omega} cm and internal transmittance of {proportional_to}95% in the visible light region. Furthermore, we prepared polycrystalline films with {rho} of 6.4 x 10{sup -4}{omega} cm at room temperature on glass substrates by using sputtering. We focus on characteristics unique to TiO{sub 2}-based TCO, such as a high refractive index, high transmittance in infrared, and high stability in reducing atmospheres. Possible applications of TiO{sub 2}-based TCOs, as well as the mechanism of the transparent conducting properties found in this d-electron-based TCO, are discussed in this review. Photograph showing TiO{sub 2}-based TCO on a transparent plastic film. Note that the film appears greenish due to interference in the film originating from its high refractive index. This high refractive index is one of the unique characteristics of TiO{sub 2}-based TCO. (Abstract Copyright [2010], Wiley Periodicals, Inc.)

  9. Properties of polyacrylic acid-coated silver nanoparticle ink for inkjet printing conductive tracks on paper with high conductivity

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Qijin [Ningbo Institute of Material Technology and Engineering, Chinese Academy of Sciences, Ningbo, Zhejiang 315201 (China); Shen, Wenfeng, E-mail: wfshen@nimte.ac.cn [Ningbo Institute of Material Technology and Engineering, Chinese Academy of Sciences, Ningbo, Zhejiang 315201 (China); Xu, Qingsong [Ningbo Institute of Material Technology and Engineering, Chinese Academy of Sciences, Ningbo, Zhejiang 315201 (China); Tan, Ruiqin [Faculty of Information Science and Engineering, Ningbo University, Ningbo, Zhejiang 315211 (China); Song, Weijie, E-mail: weijiesong@nimte.ac.cn [Ningbo Institute of Material Technology and Engineering, Chinese Academy of Sciences, Ningbo, Zhejiang 315201 (China)

    2014-10-15

    Silver nanoparticles with a mean diameter of approximately 30 nm were synthesized by reduction of silver nitrate with triethanolamine in the presence of polyacrylic acid. Silver nanoparticle-based ink was prepared by dispersing silver nanoparticles into a mixture of water and ethylene glycol. The mechanism for the dispersion and aggregation of silver nanoparticles in ink is discussed. The strong electrostatic repulsions of the carboxylate anions of the adsorbed polyacrylic acid molecules disturbed the aggregation of metal particles in solutions with a high pH value (pH > 5). An inkjet printer was used to deposit this silver nanoparticle-based ink to form silver patterns on photo paper. The actual printing qualities of the silver tracks were then analyzed by variation of printing passes, sintering temperature and time. The results showed that sintering temperature and time are associated strongly with the conductivity of the inkjet-printed conductive patterns. The conductivity of printed patterns sintered at 150 °C increased to 2.1 × 10{sup 7} S m{sup −1}, which was approximately one third that of bulk silver. In addition, silver tracks on paper substrate also showed better electrical performance after folding. This study demonstrated that the resulting ink-jet printed patterns can be used as conductive tracks in flexible electronic devices. - Highlights: • An ink from silver nanoparticles coated with polyacrylic acid was prepared. • The ink was used for inkjet-printed tracks at varying printing parameters. • The conductivity of printed tracks sintered at 150 °C increased to 2.1 × 10{sup 7} S/m. • Mechanism for dispersion and aggregation of the nanoparticles in ink is discussed.

  10. Anisotropic models for compact stars

    CERN Document Server

    Maurya, S K; Ray, Saibal; Dayanandan, Baiju

    2015-01-01

    In the present paper we obtain an anisotropic analogue of Durgapal-Fuloria (1985) perfect fluid solution. The methodology consists of contraction of anisotropic factor $\\Delta$ by the help of both metric potentials $e^{\

  11. Anisotropic magnetization and transport properties of RAgSb{sub 2} (R=Y, La-Nd, Sm, Gd-Tm)

    Energy Technology Data Exchange (ETDEWEB)

    Myers, Kenneth D.

    1999-11-08

    This study of the RAgSb{sub 2} series of compounds arose as part of an investigation of rare earth intermetallic compounds containing antimony with the rare earth in a position with tetragonal point symmetry. Materials with the rare earth in a position with tetragonal point symmetry frequently manifest strong anisotropies and rich complexity in the magnetic properties, and yet are simple enough to analyze. Antimony containing intermetallic compounds commonly possess low carrier densities and have only recently been the subject of study. Large single grain crystals were grown of the RAgSb{sub 2} (R=Y, La-Nd, Sm, Gd-Tm) series of compounds out of a high temperature solution. This method of crystal growth, commonly known as flux growth is a versatile method which takes advantage of the decreasing solubility of the target compound with decreasing temperature. Overall, the results of the crystal growth were impressive with the synthesis of single crystals of LaAgSb{sub 2} approaching one gram. However, the sample yield diminishes as the rare earth elements become smaller and heavier. Consequently, no crystals could be grown with R=Yb or Lu. Furthermore, EuAgSb{sub 2} could not be synthesized, likely due to the divalency of the Eu ion. For most of the RAgSb{sub 2} compounds, strong magnetic anisotropies are created by the crystal electric field splitting of the Hund's rule ground state. This splitting confines the local moments to lie in the basal plane (easy plane) for the majority of the members of the series. Exceptions to this include ErAgSb{sub 2} and TmAgSb{sub 2}, which have moments along the c-axis (easy axis) and CeAgSb{sub 2}, which at intermediate temperatures has an easy plane, but exchange coupling at low temperatures is anisotropic with an easy axis. Additional anisotropy is also observed within the basal plane of DyAgSb{sub 2}, where the moments are restricted to align along one of the {l_angle}110{r_angle} axes. Most of the RAgSb{sub 2} compounds

  12. Microstructural and electrical conductivity properties of cubic zirconia doped with various amount of titania

    Directory of Open Access Journals (Sweden)

    M. Gürü

    2007-12-01

    Full Text Available Purpose: A dopant concentration higher than the optimum may reduce the number of mobile oxygen ions because of defect association causing conductivity degredation. In this study, the effect of TiO2 addition on the microstructure and electrical conductivity of cubic zirconia was investigated.Design/methodology/approach: The cubic zirconia powders with 0-10 wt% TiO2 were prepared by a colloidal processing and pressureless sintering. The effect of TiO2 addition on the microstructure and electrical conductivity of cubic zirconia was investigated. Sintered specimens were characterized by XRD, SEM and impedance spectroscopy.Findings: The experimental results showed that when the TiO2 amount was less than 5 wt %, the specimens were entirely single cubic phase; further addition of TiO2 (5 wt% or more destabilized cubic zirconia phase and caused the formation of tetragonal phase. Grain size measurements for undoped and TiO2 doped cubic zirconia specimens showed that grain size decreased with increasing TiO2 content. The electrical conductivity of TiO2 doped cubic zirconia decreased with increasing TiO2 content and increased with increasing test temperature.Research limitations/implications: The measurement of electrical conductivity is one of the important requirements for the electrolyte in solid oxide fuel cells. Generally, the ac impedance of an ionic conductor contains the contributions from grain, grain boundary and electrode-electrolyte interface at high, intermediate and low frequencies, respectively, which can be reflected in a complex plane by three successive arcs[6].Originality/value: Determination of the microstructural and electrical conductivity properties of cubic zirconia doped with various amount of titania.

  13. Acoustic properties of pistonphones at low frequencies in the presence of pressure leakage and heat conduction

    Science.gov (United States)

    Zhang, Fan; He, Wen; He, Longbiao; Rong, Zuochao

    2015-12-01

    The wide concern on absolute pressure calibration of acoustic transducers at low frequencies prompts the development of the pistonphone method. At low frequencies, the acoustic properties of pistonphones are governed by the pressure leakage and the heat conduction effects. However, the traditional theory for these two effects applies a linear superposition of two independent correction models, which differs somewhat from their coupled effect at low frequencies. In this paper, acoustic properties of pistonphones at low frequencies in full consideration of the pressure leakage and heat conduction effects have been quantitatively studied, and the explicit expression for the generated sound pressure has been derived. With more practical significance, a coupled correction expression for these two effects of pistonphones has been derived. In allusion to two typical pistonphones, the NPL pistonphone and our developed infrasonic pistonphone, comparisons were done for the coupled correction expression and the traditional one, whose results reveal that the traditional one produces maximum insufficient errors of about 0.1 dB above the lower limiting frequencies of two pistonphones, while at lower frequencies, excessive correction errors with an explicit limit of about 3 dB are produced by the traditional expression. The coupled correction expression should be adopted in the absolute pressure calibration of acoustic transducers at low frequencies. Furthermore, it is found that the heat conduction effect takes a limiting deviation of about 3 dB for the pressure amplitude and a small phase difference as frequency decreases, while the pressure leakage effect remarkably drives the pressure amplitude to attenuate and the phase difference tends to be 90° as the frequency decreases. The pressure leakage effect plays a more important role on the low frequency property of pistonphones.

  14. Estimating saturated hydraulic conductivity and air permeability from soil physical properties using state-space analysis

    DEFF Research Database (Denmark)

    Poulsen, Tjalfe; Møldrup, Per; Nielsen, Don;

    2003-01-01

    Estimates of soil hydraulic conductivity (K) and air permeability (k(a)) at given soil-water potentials are often used as reference points in constitutive models for K and k(a) as functions of moisture content and are, therefore, a prerequisite for predicting migration of water, air, and dissolved...... and gaseous chemicals in the vadose zone. In this study, three modeling approaches were used to identify the dependence of saturated hydraulic conductivity (K-S) and air permeability at -100 cm H2O soil-water potential (k(a100)) on soil physical properties in undisturbed soil: (i) Multiple regression, (ii...... at -100 cm H2O soil-water potential (epsilon(100)). Similarly, k(a100) could be predicted from nearby values of k(a100) and epsilon(100). Including soil total porosity in the state-space modeling did not improve prediction accuracy. Thus, macro-porosity (epsilon(100)) was the key porosity parameter...

  15. Measurement of thermal radiative and conductive properties of semitransparent materials using a photothermal crenel method

    Energy Technology Data Exchange (ETDEWEB)

    Cheheb, Zied [Ecole Nationale d' Ingenieurs de Monastir, Laboratoire d' Etudes des Systemes Thermiques et Energetiques, Avenue Ibn Eljazzar, 5019 Monastir (Tunisia)], E-mail: zied_cheheb@yahoo.fr; Albouchi, Fethi; Ben Nasrallah, Sassi [Ecole Nationale d' Ingenieurs de Monastir, Laboratoire d' Etudes des Systemes Thermiques et Energetiques, Avenue Ibn Eljazzar, 5019 Monastir (Tunisia)

    2008-03-15

    This paper deals with a theoretical and an experimental study allowing the measurement of the radiative and the conductive properties of semitransparent materials. The method consists of applying a crenel heat flux on the front face of a semitransparent sample and recording the temperature at the rear face using an open thermocouple junction. Parameter identification is performed by the minimization of the ordinary least-squares function comparing the measured and the calculated temperatures. This later is obtained from the thermal model describing the heat transfer by conduction and radiation in the medium. This model is built by the thermal quadrupole formalism. Measurements are reported on commercial glasses and plexiglass samples, and the used iterative algorithm is based on the Gauss-Newton method.

  16. Measurement of thermal radiative and conductive properties of semitransparent materials using a photothermal crenel method

    International Nuclear Information System (INIS)

    This paper deals with a theoretical and an experimental study allowing the measurement of the radiative and the conductive properties of semitransparent materials. The method consists of applying a crenel heat flux on the front face of a semitransparent sample and recording the temperature at the rear face using an open thermocouple junction. Parameter identification is performed by the minimization of the ordinary least-squares function comparing the measured and the calculated temperatures. This later is obtained from the thermal model describing the heat transfer by conduction and radiation in the medium. This model is built by the thermal quadrupole formalism. Measurements are reported on commercial glasses and plexiglass samples, and the used iterative algorithm is based on the Gauss-Newton method

  17. Nanofluidic Diodes with Dynamic Rectification Properties Stemming from Reversible Electrochemical Conversions in Conducting Polymers.

    Science.gov (United States)

    Pérez-Mitta, Gonzalo; Marmisollé, Waldemar A; Trautmann, Christina; Toimil-Molares, María Eugenia; Azzaroni, Omar

    2015-12-16

    The use of solid state nanochannels as nanofluidic diodes is currently a topic of large interest in nanotechnology. Particularly, there is a focus in the development of nanochannels with surface functionalities that make them responsive to multiple environmental variables. Here, we present for the first time the construction of electrochemical potential- and pH-responsive nanofluidic diodes using a novel approach based on a controlled electrochemical polymerization of aniline on gold-coated polycarbonate asymmetric nanochannels. The polyaniline-modified nanochannels showed three different levels of reversible ionic rectification corresponding to the degrees of oxidation of the conducting polymer. Our results demonstrate that this strategy enables an accurate and reversible control of the rectification properties due to the well-defined and predictable electrochemical conversion of charged species generated on the pore walls. We envision that these results will create novel avenues to fabricate electrochemically modulated nanofluidic diodes using conducting polymers integrated into single conical nanopores.

  18. Transparent conducting film: Effect of mechanical stretching to optical and electrical properties of carbon nanotube mat

    Indian Academy of Sciences (India)

    Tsuyoshi Saotome; Hansang Kim; David Lashmore; H Thomas Hahn

    2011-07-01

    We describe in this paper a transparent conducting film (TCF). It is a fibrous layer of multiwalled carbon nanotubes (MWNTs), labeled a dilute CNT mat, that was prepared and unidirectionally stretched to improve both the optical and electrical properties. After stretching by 80% strain, transmittance at 550 nm wavelength was improved by 37% and sheet resistance was reduced to 71% of the original value. The improvement of the transmittance can be explained by increased area of the CNT mat after stretch, and the reduced sheet resistance can be explained by increased density of the CNT alignment in lateral direction due to contraction. Based on the microscopic observation before and after stretch, models to describe the phenomena are proposed. By further expanding on this method, it may be possible to obtain a transparent conducting carbon nanotube film which is crack-resistant for solar cell applications.

  19. MORPHOLOGY, CONDUCTIVITY AND ELECTROCHEMICAL PROPERTIES OF HYDROTHERMAL CARBONIZED POROUS CARBON MATERIALS

    Directory of Open Access Journals (Sweden)

    N. I. Nagirna

    2016-07-01

    Full Text Available The paper studies the morphology, conductivity and electrochemical properties of carbon materials, obtained from raw plant materials at different condition of hydrothermal carbonization, using low-temperature porometry, impedance spectroscopy and galvanostatic charge/discharge. It is set, that in porous structure of carbon materials micropores are dominant; when carbonization temperature increased the specific surface and pore volume decrease more than 10 times. The temperature growth results in increasing the electrical conductivity of the carbon material more than 6 orders. It is found, that the maximal value of specific capacity (1138 mА·h/g has an electrochemical system based on porous carbon carbonized at 1023 K.

  20. Determination of density of states, conduction mechanisms and dielectric properties of nickel disulfide nanoparticles

    Science.gov (United States)

    Jamil, Arifa; Batool, S. S.; Sher, F.; Rafiq, M. A.

    2016-05-01

    Temperature and frequency dependent ac electrical measurements were used to explore density of states, conduction mechanisms and dielectric properties of nickel disulfide (NiS2) nanoparticles. The NiS2 nanoparticles were prepared by conventional one step solid state reaction method at 250 °C. X-ray diffraction (XRD) confirmed cubic phase of prepared nanoparticles. Scanning electron microscope (SEM) images revealed presence of irregular shaped nanoparticles as small as 50 nm. The ac electrical measurements were carried out from 300 K to 413 K. Two depressed semicircular arcs from 20 Hz to 2 MHz showed presence of bulk and grain boundary phases in NiS2 nanoparticles at all temperatures. Small polaron hopping conduction from 300 K to 393 K and correlated barrier hopping conduction mechanism at temperatures higher than 393 K was observed. High value of density of states (of the order of 1024 eV-1cm-3) was calculated from ac conductivity. At low frequencies high values (of the order of 104-107) of real part of dielectric constant (ɛ') were observed at different temperatures. These observations suggest that NiS2 nanoparticles may find applications in electronic devices.

  1. Effect of Ce on castability, mechanical properties and electric conductivity of commercial purity aluminum

    Institute of Scientific and Technical Information of China (English)

    Chang-lue LV; Heng-cheng Liao; Ye Liu; Qi-gui Wang

    2015-01-01

    Effects of Ce addition on microstructure, castability (lfuidity and hot tearing sensitivity), mechanical properties and electric conductivity of commercial purity aluminum (CP-Al) were investigated through microstructure observation and performance tests. Results show that adding Ce in a CP-Al can considerably reifne the grains, and has an important inlfuence on the amount, crystallographic forms, and distribution of secondary phases. Addition of Ce also has a large impact on the lfuidity and hot tearing sensitivity (HTS) of the CP-Al. With the addition of Ce from 0.1wt.%to 0.5wt.%, the lfuidity of CP-Al is ifrst increased remarkably and then decreased, and the HTS has an opposite response. The best castability of the studied alloys appears to be at 0.2wt.%-0.3wt.%Ce addition. The remarkable improvement in castability is attributed to the considerable reifnement of grain structure. Ce addition can also lead to a signiifcant rise in electric conductivity. The maximum conductivity of the as-cast CP-Al is 59.7% IACS with an addition of 0.2wt.%Ce. The T7 heat treatment can further improves the conductivity to 60.7% IACS. The Ce-induced evolution of the secondary phases is believed to be the mechanism for it.

  2. Dynamic-Mechanical and Impact Properties of Conductive Polymer Blends Based on Polypropylene

    Science.gov (United States)

    Acierno, Domenico; Russo, Pietro

    2007-04-01

    Plastic materials with significant electrical properties are getting more and more interest as witnessed by the wide spectra of industrial applications such as high performance textiles, fabrics for military, electronics and display technologies, automotive field (fuel delivery lines, exterior body panels) and so on. In this context, in the last decade an increasing interest has been devoted to the use of intrinsically conductive polymers such as polyaniline (PANI). In this work melt blended formulations based on polypropylene, containing 5% and 10% by weight of PANI, were investigated in terms of dynamic-mechanical and impact properties. Preliminary results indicate that, besides the processing conditions, inclusions of PANI make a general worsening of the dumping behaviour, especially in the rubbery region. Anyway, it is evident a clear improvement of the impact resistance with respect to the matrix, processed under the same conditions and taken as a reference, for the 5wt % system.

  3. Modeling properties of chromospheric evaporation driven by thermal conduction fronts from reconnection shocks

    CERN Document Server

    Brannon, Sean

    2014-01-01

    Magnetic reconnection in the corona results in contracting flare loops, releasing energy into plasma heating and shocks. The hydrodynamic shocks so produced drive thermal conduction fronts (TCFs) which transport energy into the chromosphere and drive upflows (evaporation) and downflows (condensation) in the cooler, denser footpoint plasma. Observations have revealed that certain properties of the transition point between evaporation and condensation (the "flow reversal point" or FRP), such as temperature and velocity-temperature derivative at the FRP, vary between different flares. These properties may provide a diagnostic tool to determine parameters of the coronal energy release mechanism and the loop atmosphere. In this study, we develop a 1-D hydrodynamical flare loop model with a simplified three-region atmosphere (chromosphere/transition region/corona), with TCFs initiated by shocks introduced in the corona. We investigate the effect of two different flare loop parameters (post-shock temperature and tra...

  4. Inorganic Solid-State Electrolytes for Lithium Batteries: Mechanisms and Properties Governing Ion Conduction.

    Science.gov (United States)

    Bachman, John Christopher; Muy, Sokseiha; Grimaud, Alexis; Chang, Hao-Hsun; Pour, Nir; Lux, Simon F; Paschos, Odysseas; Maglia, Filippo; Lupart, Saskia; Lamp, Peter; Giordano, Livia; Shao-Horn, Yang

    2016-01-13

    This Review is focused on ion-transport mechanisms and fundamental properties of solid-state electrolytes to be used in electrochemical energy-storage systems. Properties of the migrating species significantly affecting diffusion, including the valency and ionic radius, are discussed. The natures of the ligand and metal composing the skeleton of the host framework are analyzed and shown to have large impacts on the performance of solid-state electrolytes. A comprehensive identification of the candidate migrating species and structures is carried out. Not only the bulk properties of the conductors are explored, but the concept of tuning the conductivity through interfacial effects-specifically controlling grain boundaries and strain at the interfaces-is introduced. High-frequency dielectric constants and frequencies of low-energy optical phonons are shown as examples of properties that correlate with activation energy across many classes of ionic conductors. Experimental studies and theoretical results are discussed in parallel to give a pathway for further improvement of solid-state electrolytes. Through this discussion, the present Review aims to provide insight into the physical parameters affecting the diffusion process, to allow for more efficient and target-oriented research on improving solid-state ion conductors.

  5. On the Newtonian anisotropic configurations

    Energy Technology Data Exchange (ETDEWEB)

    Shojai, F. [University of Tehran, Department of Physics, Tehran (Iran, Islamic Republic of); Institute for Research in Fundamental Sciences (IPM), Foundations of Physics Group, School of Physics, Tehran (Iran, Islamic Republic of); Fazel, M.R.; Stepanian, A. [University of Tehran, Department of Physics, Tehran (Iran, Islamic Republic of); Kohandel, M. [Alzahra University, Department of Sciences, Tehran (Iran, Islamic Republic of)

    2015-06-15

    In this paper we are concerned with the effects of an anisotropic pressure on the boundary conditions of the anisotropic Lane-Emden equation and the homology theorem. Some new exact solutions of this equation are derived. Then some of the theorems governing the Newtonian perfect fluid star are extended, taking the anisotropic pressure into account. (orig.)

  6. Anisotropic Lyra cosmology

    Indian Academy of Sciences (India)

    B B Bhowmik; A Rajput

    2004-06-01

    Anisotropic Bianchi Type-I cosmological models have been studied on the basis of Lyra's geometry. Two types of models, one with constant deceleration parameter and the other with variable deceleration parameter have been derived by considering a time-dependent displacement field.

  7. Lévy Flights due to Anisotropic Disorder in Graphene

    Science.gov (United States)

    Gattenlöhner, S.; Gornyi, I. V.; Ostrovsky, P. M.; Trauzettel, B.; Mirlin, A. D.; Titov, M.

    2016-07-01

    We study transport properties of graphene with anisotropically distributed on-site impurities (adatoms) that are randomly placed on every third line drawn along carbon bonds. We show that stripe states characterized by strongly suppressed backscattering are formed in this model in the direction of the lines. The system reveals Lévy-flight transport in the stripe direction such that the corresponding conductivity increases as the square root of the system length. Thus, adding this type of disorder to clean graphene near the Dirac point strongly enhances the conductivity, which is in stark contrast with a fully random distribution of on-site impurities, which leads to Anderson localization. The effect is demonstrated both by numerical simulations using the Kwant code and by an analytical theory based on the self-consistent T -matrix approximation.

  8. 各向异性圆锥体的平面光波散射特性%Scattering Property of Anisotropic Medium Cone in Plane Optical Wave

    Institute of Scientific and Technical Information of China (English)

    李应乐; 李瑾; 王明军; 董群峰

    2011-01-01

    基于通用的矢量电位和标量电位与介电常数张量无关的原理,由激发的电偶极子与位函数的关系得到了任意各向异性目标散射场的表达式.得到了通用的介电常数张量的变换关系,具体地给出了介电常数张量在球坐标系中的表达式,将目标的内外电场展为级数,得到了各向异性晶体圆锥体一级散射场的解析表达式.理论结果与文献一致,验证了算法的正确性.在光波波长与粒子尺寸相近的情况下,对所得结果进行了仿真,表明各向异性圆锥体的散射具有偶极辐射的特点.所得结果简单、通用,为研究形状更为复杂的各向异性目标、纳米粒子等的光散射研究提供了理论基础.%Based on the principle that both scalar potential and vector potential are independent of the dielectric tensor, by using the relation between electric dipoles and their potentials, the analytical expression of scattering field for the anisotropic medium target is developed. The transformation of dielectric tensor is researched. The expression of a tensor in spherical coordinate system is presented in detail. The electric fields inside and outside the target are expanded in series, and then the primary scattering field from the anisotropic gypsum cone is presented. The theoretical result coincides with those in literatures and its validity is tested. When the wavelength is near to the size of the nanoparticle, some simulations are carried out, the result shows that the scattering of anisotropic cones has the characteristic of dipole radiation. The method used is simple and universal. The result has provided a theory for studying the laser scattering from a complex anisotropic target.

  9. Statistical properties of Joule heating rate, electric field and conductances at high latitudes

    Directory of Open Access Journals (Sweden)

    A. T. Aikio

    2009-07-01

    Full Text Available Statistical properties of Joule heating rate, electric field and conductances in the high latitude ionosphere are studied by a unique one-month measurement made by the EISCAT incoherent scatter radar in Tromsø (66.6 cgmlat from 6 March to 6 April 2006. The data are from the same season (close to vernal equinox and from similar sunspot conditions (about 1.5 years before the sunspot minimum providing an excellent set of data to study the MLT and Kp dependence of parameters with high temporal and spatial resolution.

    All the parameters show a clear MLT variation, which is different for low and high Kp conditions. Our results indicate that the response of morning sector conductances and conductance ratios to increased magnetic activity is stronger than that of the evening sector. The co-location of Pedersen conductance maximum and electric field maximum in the morning sector produces the largest Joule heating rates 03–05 MLT for Kp≥3. In the evening sector, a smaller maximum occurs at 18 MLT. Minimum Joule heating rates in the nightside are statistically observed at 23 MLT, which is the location of the electric Harang discontinuity.

    An important outcome of the paper are the fitted functions for the Joule heating rate as a function of electric field magnitude, separately for four MLT sectors and two activity levels (Kp<3 and Kp≥3. In addition to the squared electric field, the fit includes a linear term to study the possible anticorrelation or correlation between electric field and conductance. In the midday sector, positive correlation is found as well as in the morning sector for the high activity case. In the midnight and evening sectors, anticorrelation between electric field and conductance is obtained, i.e. high electric fields are associated with low conductances. This is expected to occur in the return current regions adjacent to

  10. Diagnostic properties of nerve conduction tests in population-based carpal tunnel syndrome

    Directory of Open Access Journals (Sweden)

    Johnsson Ragnar

    2003-05-01

    Full Text Available Abstract Background Numerous nerve conduction tests are used for the electrodiagnosis of carpal tunnel syndrome (CTS, with a wide range of sensitivity and specificity reported for each test in clinical studies. The tests have not been assessed in population-based studies. Such information would be important when using electrodiagnosis in epidemiologic research. The purpose of this study was to compare the diagnostic accuracy of various nerve conduction tests in population-based CTS and determine the properties of the most accurate test. Methods In a population-based study a questionnaire was mailed to a random sample of 3,000 persons. Of 2,466 responders, 262 symptomatic (numbness/tingling in the radial fingers and 125 randomly selected asymptomatic responders underwent clinical and electrophysiologic examinations. A standardized hand diagram was administered to the symptomatic persons. At the clinical examination, the examining surgeon identified 94 symptomatic persons as having clinically certain CTS. Nerve conduction tests were then performed on the symptomatic and the asymptomatic persons by blinded examiners. Analysis with receiver operating characteristic (ROC curves was used to compare the diagnostic accuracy of the nerve conduction tests in distinguishing the persons with clinically certain CTS from the asymptomatic persons. Results No difference was shown in the diagnostic accuracy of median nerve distal motor latency, digit-wrist sensory latency, wrist-palm sensory conduction velocity, and wrist-palm/forearm sensory conduction velocity ratio (area under curve, 0.75–0.76. Median-ulnar digit-wrist sensory latency difference had a significantly higher diagnostic accuracy (area under curve, 0.80. Using the optimal cutoff value of 0.8 ms for abnormal sensory latency difference shown on the ROC curve the sensitivity was 70%, specificity 82%, positive predictive value 19% and negative predictive value 98%. Based on the clinical diagnosis

  11. Electron beam induced modifications in conductivity and dielectric property of polymer electrolyte film

    International Nuclear Information System (INIS)

    This paper describes the effect of 8 MeV of electron beam (EB) energy irradiation on the electrical conductivity and dielectric properties of sodium fluoride NaF-doped polyethylene oxide (PEO) film. The structural and chemical characterizations were employed using X-ray diffractometry (XRD) and Fourier Transform Infrared (FTIR) techniques respectively before and after irradiation. The morphology study carried out using Scanning Electronic Microscopy (SEM) analysis. The DC electrical conductivity showed increases with dose and temperature and was consistent with Arrhenius behavior. The maximum conductivity of 1.1 × 10−5 S/cm and minimum activation energy of 0.25 eV were obtained at 25 kGy, 338 K; further increases in the dose resulted in a reduction in conductivity. The real (ε′) and imaginary (ε″) part of the dielectric constant suddenly decreased in a low frequency region (40–640 Hz), subsequently independent at higher frequency. The AC conductivity showed increases with frequency and temperature for all films. The dielectric constant and AC conductivity increased at the 25 kGy dose due to chain scission. Further increases in dose such as 50 and 75 kGy, resulted in a decrease in dielectric constant and AC conductivity due to cross-linking. The electric modulus approach was used to calculate the dielectric relaxation time (τ), which decreased at 25 kGy and then increased at 50 and 75 kGy doses. The modulus data were fitted using a non-exponential Kohlrausch–Williams–Watts (KWW) function ϕ (t), and the results indicate the existence of a non-Debye relaxation. - Highlights: • Film is exposed to 8 MeV Electron Beam with the doses of 25, 50, and 75 kGy. • Morphology changes of the film conformed from Scanning Electronic Microscopy (SEM). • AC conductivity shows increases with frequency as well as electron fluence. • The dielectric constant was satisfying the universal law of dielectric constant. • The dielectric relaxation time (τ) decreases

  12. Electromagnetism on anisotropic fractal media

    Science.gov (United States)

    Ostoja-Starzewski, Martin

    2013-04-01

    Basic equations of electromagnetic fields in anisotropic fractal media are obtained using a dimensional regularization approach. First, a formulation based on product measures is shown to satisfy the four basic identities of the vector calculus. This allows a generalization of the Green-Gauss and Stokes theorems as well as the charge conservation equation on anisotropic fractals. Then, pursuing the conceptual approach, we derive the Faraday and Ampère laws for such fractal media, which, along with two auxiliary null-divergence conditions, effectively give the modified Maxwell equations. Proceeding on a separate track, we employ a variational principle for electromagnetic fields, appropriately adapted to fractal media, so as to independently derive the same forms of these two laws. It is next found that the parabolic (for a conducting medium) and the hyperbolic (for a dielectric medium) equations involve modified gradient operators, while the Poynting vector has the same form as in the non-fractal case. Finally, Maxwell's electromagnetic stress tensor is reformulated for fractal systems. In all the cases, the derived equations for fractal media depend explicitly on fractal dimensions in three different directions and reduce to conventional forms for continuous media with Euclidean geometries upon setting these each of dimensions equal to unity.

  13. Anisotropic Diffusion in Mesh-Free Numerical Magnetohydrodynamics

    CERN Document Server

    Hopkins, Philip F

    2016-01-01

    We extend recently-developed mesh-free Lagrangian methods for numerical magnetohydrodynamics (MHD) to arbitrary anisotropic diffusion equations, including: passive scalar diffusion, Spitzer-Braginskii conduction and viscosity, cosmic ray diffusion/streaming, anisotropic radiation transport, non-ideal MHD (Ohmic resistivity, ambipolar diffusion, the Hall effect), and turbulent 'eddy diffusion.' We study these as implemented in the code GIZMO for both new meshless finite-volume Godunov schemes (MFM/MFV) as well as smoothed-particle hydrodynamics (SPH). We show the MFM/MFV methods are accurate and stable even with noisy fields and irregular particle arrangements, and recover the correct behavior even in arbitrarily anisotropic cases. They are competitive with state-of-the-art AMR/moving-mesh methods, and can correctly treat anisotropic diffusion-driven instabilities (e.g. the MTI and HBI, Hall MRI). We also develop a new scheme for stabilizing anisotropic tensor-valued fluxes with high-order gradient estimators ...

  14. Effect of ionic conductivity of zirconia electrolytes on polarization properties of various electrodes in SOFC

    Energy Technology Data Exchange (ETDEWEB)

    Watanabe, Masahiro; Uchida, Hiroyuki; Yoshida, Manabu [Yamanashi Univ., Kofu (Japan)

    1996-12-31

    Solid oxide fuel cells (SOFCs) have been intensively investigated because, in principle, their energy conversion efficiency is fairly high. Lowering the operating temperature of SOFCs from 1000{degrees}C to around 800{degrees}C is desirable for reducing serious problems such as physical and chemical degradation of the constructing materials. The object of a series of the studies is to find a clue for achieving higher electrode performances at a low operating temperature than those of the present level. Although the polarization loss at electrodes can be reduced by using mixed-conducting ceria electrolytes, or introducing the mixed-conducting (reduced zirconia or ceria) laver on the conventional zirconia electrolyte surface, no reports are available on the effect of such an ionic conductivity of electrolytes on electrode polarizations. High ionic conductivity of the electrolyte, of course, reduces the ohmic loss. However, we have found that the IR-free polarization of a platinum anode attached to zirconia electrolytes is greatly influenced by the ionic conductivity, {sigma}{sub ion}, of the electrolytes used. The higher the {sigma}{sub ion}, the higher the exchange current density, j{sub 0}, for the Pt anode in H{sub 2} at 800 {approximately} 1000{degrees}C. It was indicated that the H{sub 2} oxidation reaction rate was controlled by the supply rate of oxide ions through the Pt/zirconia interface which is proportional to the {sigma}{sub ion}. Recently, we have proposed a new concept of the catalyzed-reaction layers which realizes both high-performances of anodes and cathodes for medium-temperature operating SOFCs. We present the interesting dependence of the polarization properties of various electrodes (the SDC anodes with and without Ru microcatalysts, Pt cathode, La(Sr)MnO{sub 3} cathodes with and without Pt microcatalysts) on the {sigma}{sub ion} of various zirconia electrolytes at 800 {approximately} 1000{degrees}C.

  15. A review of the electrical properties of semiconductor nanowires: insights gained from terahertz conductivity spectroscopy

    Science.gov (United States)

    Joyce, Hannah J.; Boland, Jessica L.; Davies, Christopher L.; Baig, Sarwat A.; Johnston, Michael B.

    2016-10-01

    Accurately measuring and controlling the electrical properties of semiconductor nanowires is of paramount importance in the development of novel nanowire-based devices. In light of this, terahertz (THz) conductivity spectroscopy has emerged as an ideal non-contact technique for probing nanowire electrical conductivity and is showing tremendous value in the targeted development of nanowire devices. THz spectroscopic measurements of nanowires enable charge carrier lifetimes, mobilities, dopant concentrations and surface recombination velocities to be measured with high accuracy and high throughput in a contact-free fashion. This review spans seminal and recent studies of the electronic properties of nanowires using THz spectroscopy. A didactic description of THz time-domain spectroscopy, optical pump-THz probe spectroscopy, and their application to nanowires is included. We review a variety of technologically important nanowire materials, including GaAs, InAs, InP, GaN and InN nanowires, Si and Ge nanowires, ZnO nanowires, nanowire heterostructures, doped nanowires and modulation-doped nanowires. Finally, we discuss how THz measurements are guiding the development of nanowire-based devices, with the example of single-nanowire photoconductive THz receivers.

  16. Manipulating dispersion and distribution of graphene in PLA through novel interface engineering for improved conductive properties.

    Science.gov (United States)

    Fu, Yu; Liu, Linshu; Zhang, Jinwen

    2014-08-27

    This study aimed to enhance the conductive properties of PLA nanocomposite by controlling the dispersion and distribution of graphene within the minor phase of the polymer blend. Functionalized graphene (f-GO) was achieved by reacting graphene oxide (GO) with various silanes under the aid of an ionic liquid. Ethylene/n-butyl acrylate/glycidyl methacrylate terpolymer elastomer (EBA-GMA) was introduced as the minor phase to tailor the interface of matrix/graphene through reactive compatibilization. GO particles were predominantly dispersed in PLA in a self-agglomerating pattern, while f-GO was preferentially located in the introduced rubber phase or at the PLA/EBA-GMA interfaces through the formation of the three-dimensional percolated structures, especially for these functionalized graphene with reactive groups. The selective localization of the f-GO also played a crucial role in stabilizing and improving the phase morphology of the PLA blend through reducing the interfacial tension between two phases. The establishment of the percolated network structures in the ternary system was responsible for the improved AC conductivity and better dielectric properties of the resulting nanocomposites. PMID:25014782

  17. Electrical conductivity and luminescence properties of two silver(I) coordination polymers with heterocyclic nitrogen ligands

    International Nuclear Information System (INIS)

    The synthesis and X-ray structural characterization of two novel silver(I) coordination polymers, [Ag(NO3)(quin)]n (1) and [Ag8(HL)2(H2O)4(mpyz)]·3H2O (2) are reported, where quin=5,6,7,8-tetrahydroquinoxaline, H6L=cyclohexane-1,2,3,4,5,6-hexacarboxylic acid and mpyz=2-methyl pyrazine. The single crystal diffraction analyses showed that complex 1 is a 2D layered structure, while 2 presents a 3D polymeric architecture. In complex 2 the network is stabilized by argentophilic interactions and hydrogen bonding. Electrical conductivity of order 3×10−4 Scm−1 (1) and 1.6×10−4 Scm−1 (2) is measured on thin film specimen at room temperature. The photoluminescence and thermal properties of the complexes have also been studied. - Graphical abstract: Two new 1D and 3D coordination polymers of Ag(I) have been synthesized and characterized by X-ray analysis. The electrical, luminescence and thermal properties have been studied. - Highlights: • 1 is 2D layered while 2 present a 3D polymeric architecture. • The network in 2 is stabilized by argentophilic interactions and hydrogen bonding. • Electrical conductivity measurement is quite interesting. • Argentophilic interaction and intra-ligand π⁎–π CT explains emission behavior of 2

  18. A generalized anisotropic deformation formulation for geomaterials

    Science.gov (United States)

    Lei, Z.; Rougier, Esteban; Knight, E. E.; Munjiza, A.; Viswanathan, H.

    2016-04-01

    In this paper, the combined finite-discrete element method (FDEM) has been applied to analyze the deformation of anisotropic geomaterials. In the most general case geomaterials are both non-homogeneous and non-isotropic. With the aim of addressing anisotropic material problems, improved 2D FDEM formulations have been developed. These formulations feature the unified hypo-hyper elastic approach combined with a multiplicative decomposition-based selective integration for volumetric and shear deformation modes. This approach is significantly different from the co-rotational formulations typically encountered in finite element codes. Unlike the co-rotational formulation, the multiplicative decomposition-based formulation naturally decomposes deformation into translation, rotation, plastic stretches, elastic stretches, volumetric stretches, shear stretches, etc. This approach can be implemented for a whole family of finite elements from solids to shells and membranes. This novel 2D FDEM based material formulation was designed in such a way that the anisotropic properties of the solid can be specified in a cell by cell basis, therefore enabling the user to seed these anisotropic properties following any type of spatial variation, for example, following a curvilinear path. In addition, due to the selective integration, there are no problems with volumetric or shear locking with any type of finite element employed.

  19. On the swelling properties of proton conducting membranes for direct methanol fuel cells

    Energy Technology Data Exchange (ETDEWEB)

    Saarinen, V.; Kreuer, K.D.; Merkle, R.; Maier, J. [Max-Planck-Institut fuer Festkoerperforschung, Heisenbergstr. 1, D-70569 Stuttgart (Germany); Schuster, M. [FuMA-Tech GmbH, Am Grubenstollen 11, D-66386 St. Ingbert (Germany)

    2007-04-15

    The swelling properties of different fluorinated (Nafion 117, poly(ethylene-alt-tetrafluoroethylene) and poly(vinylidene fluoride)-graft-poly(styrene sulfonic acid)) and hydrocarbon (sulfonated poly(phenylene sulfone)) proton conducting ionomers were investigated in alcohol (MeOH, EtOH, 2-propanol, tBuOH)-water and H{sub 2}SO{sub 4}-water mixtures. Solvent uptake and its water/alcohol selectivity were determined by thermal desorption using combined thermogravimetry (TGA) and mass spectrometry (MS). Clear trends are observed for the selectivity: preferential water uptake (alcohol rejection) correlates with high IEC (ion exchange capacity) and low solvent uptake (swelling) indicating a preferred interaction of the ionic groups (-SO{sub 3}{sup -}, H{sup +}) and the groups on the polymerbackbone carrying partial charges (e.g. sulfone units (-SO{sub 2}-) in the sulfonated poly(phenylene sulfone)) with water. The total swelling significantly decreases in the presence of H{sub 2}SO{sub 4} indicating osmosis being a major driving force in the swelling process. This is particularly low for ETFE-SA, which is highlighting its supreme mechanical properties and its high selectivity for water uptake (selectivity coefficients up to 10 for {lambda} = 7). Unlike Nafion, which shows high swelling in alcohol-water mixtures and almost no selectivity, high selectivity coefficients (up to 8) are observed for sulfonated poly(phenylene sulfone) even at medium solvent uptake ({lambda} = 12). The total solvent uptake in these highly polar ionomers even decreases with methanol mole fraction and is virtually independent of temperature (up to T = 120 C). Together with the high proton conductivity and high hydrolytic stability reported in the literature, the swelling properties presented in this work are making sulfonated poly(phenylene sulfone) interesting membrane materials for DMFC applications. (author)

  20. Water uptake, ionic conductivity and swelling properties of anion-exchange membrane

    Energy Technology Data Exchange (ETDEWEB)

    Duan, QJ; Ge, SH; Wang, CY

    2013-12-01

    Water uptake, ionic conductivity and dimensional change of the anion-exchange membrane made by Tokuyama Corporation (A201 membrane) are investigated at different temperatures and water activities. Specifically, the amount of water taken up by membranes exposed to water vapor and membranes soaked in liquid water is determined. The water uptake of the A201 membrane increases with water content as well as temperature. In addition, water sorption data shows Schroeder's paradox for the AEMs investigated. The swelling properties of the A201 membrane exhibit improved dimensional stability compared with Nafion membrane. Water sorption of the A201 membrane occurs with a substantial negative excess volume of mixing. The threshold value of hydrophilic fraction in the A201 membrane for ionic conductivity is around 0.34, above which, the conductivity begins to rise quickly. This indicates that a change in the connectivity of the hydrophilic domains occurs when hydrophilic fraction approaches 0.34. (C) 2013 Elsevier B.V. All rights reserved.

  1. Pyroelectric properties and electrical conductivity in samarium doped BiFeO 3 ceramics

    KAUST Repository

    Yao, Yingbang

    2012-06-01

    Samarium (Sm 3+) doped BiFeO 3 (BFO) ceramics were prepared by a modified solid-state-reaction method which adopted a rapid heating as well as cooling during the sintering process. The pyroelectric coefficient increased from 93 to 137 μC/m 2 K as the Sm 3+ doping level increased from 1 mol% to 8 mol%. Temperature dependence of the pyroelectric coefficient showed an abrupt decrease above 80 °C in all samples, which was associated with the increase of electrical conductivity with temperature. This electrical conduction was attributed to oxygen vacancy existing in the samples. An activation energy of ∼0.7 eV for the conduction process was found to be irrespective of the Sm 3+ doping level. On the other hand, the magnetic Néel temperature (T N) decreased with increasing Sm 3+ doping level. On the basis of our results, the effects of Sm doping level on the pyroelectric and electrical properties of the BFO were revealed. © 2011 Elsevier Ltd. All rights reserved.

  2. Electrical properties of polypropylene-based composites controlled by multilayered distribution of conductive particles.

    Science.gov (United States)

    Gao, Wanli; Zheng, Yu; Shen, Jiabin; Guo, Shaoyun

    2015-01-28

    Materials consisting of alternating layers of pure polypropylene (PP) and carbon black filled polypropylene (PPCB) were fabricated in this work. The electrical behaviors of the multilayered composites were investigated from two directions: (1) Parallel to interfaces. The confined layer space allowed for a more compact connection between CB particles, while the conductive pathways tended to be broken up with increasing number of layers leading to a distinct enhancement of the electrical resistivity due to the separation of insulated PP layers. (2) Vertical to interfaces. The alternating assemblies of insulated and conductive layers like a parallel-plate capacitor made the electrical conductivity become frequency dependent. Following the layer multiplication process, the dielectric permittivity was significantly enhanced due to the accumulation of electrical charges at interfaces. Thus, as a microwave was incident on the dielectric medium, the interfacial polarization made the main contribution to inherent dissipation of microwave energy, so that the absorbing peak became strengthened when the material had more layers. Furthermore, the layer interfaces in the multilayered system were also effective to inhibit the propagation of cracks in the stretching process, leading to a larger elongation at the break than that of the PP/CB conventional system, which provided a potential route to fabricate electrical materials with optimal mechanical properties.

  3. AC conductivity and dielectric properties of Te doped LaMnO3

    International Nuclear Information System (INIS)

    We have studied the structural and dielectric properties of La1-xTexMnO3 (x=0.00, 0.10 and 0.20) samples. All the samples show a rhombohedral structure with space group R3-bar c, at room temperature. The dielectric constant and the ac conductivity are measured at room temperature as a function of frequency, ranging from (75 KHz-7MHz).The dielectric constant shows a normal behaviour and the dielectric loss tangent exhibit anomalous behaviour. The ac conductivity obeys super linear power law σ(ω)= Bωn. The real part (ω'), imaginary part (ω) of dielectric constant, loss tangent, and ac conductivity have been explained on the basis of space charge polarization according to Maxwell-Wagner's two layer model and Koops phenomenological theory. The occurrence of giant or colossal dielectric constant is most likely due to electrode polarization or interface polarization effect. The depletion layers arising due to the formation of Schottky diodes at the metallic contacts of semiconducting samples, which may be formed by grain boundaries, can give rise to Maxwell-Wagner type relaxation and apparently very high dielectric constants. (author)

  4. Investigation of thermal conductivity and rheological properties of nanofluids containing graphene nanoplatelets.

    Science.gov (United States)

    Mehrali, Mohammad; Sadeghinezhad, Emad; Latibari, Sara Tahan; Kazi, Salim Newaz; Mehrali, Mehdi; Zubir, Mohd Nashrul Bin Mohd; Metselaar, Hendrik Simon Cornelis

    2014-01-01

    In the present study, stable homogeneous graphene nanoplatelet (GNP) nanofluids were prepared without any surfactant by high-power ultrasonic (probe) dispersion of GNPs in distilled water. The concentrations of nanofluids were maintained at 0.025, 0.05, 0.075, and 0.1 wt.% for three different specific surface areas of 300, 500, and 750 m2/g. Transmission electron microscopy image shows that the suspensions are homogeneous and most of the materials have been well dispersed. The stability of nanofluid was investigated using a UV-visible spectrophotometer in a time span of 600 h, and zeta potential after dispersion had been investigated to elucidate its role on dispersion characteristics. The rheological properties of GNP nanofluids approach Newtonian and non-Newtonian behaviors where viscosity decreases linearly with the rise of temperature. The thermal conductivity results show that the dispersed nanoparticles can always enhance the thermal conductivity of the base fluid, and the highest enhancement was obtained to be 27.64% in the concentration of 0.1 wt.% of GNPs with a specific surface area of 750 m2/g. Electrical conductivity of the GNP nanofluids shows a significant enhancement by dispersion of GNPs in distilled water. This novel type of nanofluids shows outstanding potential for replacements as advanced heat transfer fluids in medium temperature applications including solar collectors and heat exchanger systems. PMID:24410867

  5. Transport properties and photo- conductivity of nanocrystalline PbTe(In) films

    Energy Technology Data Exchange (ETDEWEB)

    Dobrovolsky, Alexandr; Chernichkin, Vladimir; Belogorokhov, Ivan; Ryabova, Ludmila; Khokhlov, Dmitry [Faculty of Physics, M. V. Lomonosov Moscow State University, Leninskie Gory, 119991 Moscow (Russian Federation); Dashevsky, Zinovi; Kasiyan, Vladimir [Department of Materials Engineering, Ben-Gurion University, 84105 Beer-Sheva (Israel)

    2010-04-15

    Microstructure, charge transport and photoelectric properties are studied for PbTe(In) films deposited on amorphous substrates kept at different temperatures T{sub s} during deposition. All the films have a column-like structure with the mean column diameter increasing from 60 nm at the lowest T{sub s}=-120 C up to 300 nm at the maximal T{sub s}=250 C. The substrate temperature increase results in appearance of a preferred orientation of grains and in an inversion of the conductivity type from hole to electron. Electric transport and photoelectric properties of the films were studied in the temperature interval 4.2-300 K in DC and AC modes at frequencies varied from 20 Hz up to 1 MHz. The impedance spectra analysis was done in terms of the equivalent circuit model. Modification of charge transport mechanisms is correlated with the variation of microstructure of the films grown at different substrate temperatures. Films with disordered grains possess all features of non-homogeneous systems, while the films with a preferred orientation of grains are analogous to PbTe(In) single crystals in their transport and photoelectric properties. Mechanisms of the persistent photoconductivity observed in the films are qualitatively distinguished. (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  6. Magnetron sputtering of transparent conductive zinc oxide: relation between the sputtering parameters and the electronic properties

    International Nuclear Information System (INIS)

    Magnetron sputtering of transparent conductive oxides (zinc oxide, indium tin oxide, tin oxide) is a promising technique which allows the deposition of films at low temperatures with good optical and electronic properties. A special advantage is the scalability to large areas. The principles underlying magnetron sputtering are reviewed in this paper. The growth process during magnetron sputtering is characterized by the bombardment of the growing film with species from the sputtering target and from the plasma. In addition to sputtered atoms with energies in the eV range, ions from the plasma (mostly argon) and neutral atoms (also argon) reflected at the target hit the growing film. Depending on the energy of these species and on the ion-to-neutral ratio the properties of the films vary. High energies (≥100 eV), which occur mainly at low sputtering pressures lead to damage of the growing film, connected with mechanical stress, small crystallites and bad electrical parameters. Ion assisted growth with low ion energies (below about 50 eV) is advantageous as is a high ion-to-neutral ratio. A compilation of resistivities of magnetron sputtered zinc oxide films yields a limiting resistivity of 2x10-4 Ω cm for polycrystalline films. Based on the correlation between plasma parameters and film properties new search fields are anticipated. (author)

  7. Autofocus imaging: Experimental results in an anisotropic austenitic weld

    Science.gov (United States)

    Zhang, J.; Drinkwater, B. W.; Wilcox, P. D.; Hunter, A.

    2012-05-01

    The quality of an ultrasonic array image, especially for anisotropic material, depends on accurate information about acoustic properties. Inaccuracy of acoustic properties causes image degradation, e.g., blurring, errors in locating of reflectors and introduction of artifacts. In this paper, for an anisotropic austenitic steel weld, an autofocus imaging technique is presented. The array data from a series of beacons is captured and then used to statistically extract anisotropic weld properties by using a Monte-Carlo inversion approach. The beacon and imaging systems are realized using two separated arrays; one acts as a series of beacons and the other images these beacons. Key to the Monte-Carlo inversion scheme is a fast forward model of wave propagation in the anisotropic weld and this is based on the Dijkstra algorithm. Using this autofocus approach a measured weld map was extracted from an austenitic weld and used to reduce location errors, initially greater than 6mm, to less than 1mm.

  8. DC conductivity and magnetic properties of piezoelectric-piezomagnetic composite system

    Science.gov (United States)

    Hemeda, O. M.; Tawfik, A.; A-Al-Sharif; Amer, M. A.; Kamal, B. M.; El Refaay, D. E.; Bououdina, M.

    2012-11-01

    A series of composites (1-x) (Ni0.8Zn0.2Fe2O4)+x (BaTiO3), where x=0%, 20%, 40%, 60%, 80% and 100% BT content, have been prepared by the standard ceramic technique, then sintered at 1200 °C for 8 h. X-ray diffraction analysis shows that the prepared composites consist of two phases, ferrimagnetic and ferroelectric. DC electrical resistivity, thermoelectric power, charge carriers concentration and charge carrier mobility have been studied at different temperatures. It was found that the DC electrical conductivity increases with increasing BT content. The values of the thermoelectric power were positive and negative for the composites indicating that there are two conduction mechanisms, hopping and band conduction, respectively. Using the values of DC electrical conductivity and thermoelectric power, the values of charge carrier mobility and the charge carrier concentration were calculated. Magnetic measurements (hysteresis loop and magnetic permeability) show that the magnetization decreases by increasing BT content. M-H loop of pure Ni0.6 Zn0.4 Fe2O4 composite indicates that it is paramagnetic at room temperature and that the magnetization is diluted by increasing the BT content in the composite system. The value of magnetoelectric coefficient for the composites decreases by increasing BT content for all the compositions except for 40% BT content, which may be due to the low resistivity of magnetic phase compared with the BT phase that causes a leakage of induced charges on the piezoelectric phase. Since both ferroelectric and magnetic phases preserve their basic properties in the bulk composite, the present BT-NZF composite are potential candidates for applications as pollution sensors and electromagnetic waves.

  9. Spin superfluidity in the anisotropic XY model in the triangular lattice

    Science.gov (United States)

    Lima, L. S.

    2016-07-01

    We use the SU(3) Schwinger's boson theory to study the spin transport properties in the two-dimensional anisotropic frustrated Heisenberg model in the triangular lattice at T=0. We have investigated the behavior of the spin conductivity for this model which presents an single-ion anisotropy. We study the spin transport in the Bose-Einstein condensation regime where we have that the tz bosons are condensed and the following condition is valid: = = t . Our results show a metallic spin transport for ω > 0 and a superfluid spin transport in the limit of DC conductivity, ω → 0 , where σ(ω) tends to infinity in this limit of ω.

  10. Inhomogeneous Anisotropic Cosmology

    CERN Document Server

    Kleban, Matthew

    2016-01-01

    In homogeneous and isotropic Friedmann-Robertson-Walker cosmology, the topology of the universe determines its ultimate fate. If the Weak Energy Condition is satisfied, open and flat universes must expand forever, while closed cosmologies can recollapse to a Big Crunch. A similar statement holds for homogeneous but anisotropic (Bianchi) universes. Here, we prove that ${\\it arbitrarily}$ inhomogeneous and anisotropic cosmologies with "flat" (including toroidal) and "open" (including compact hyperbolic) spatial topology that are initially expanding must continue to expand forever at least in some region, despite the presence of arbitrarily large density fluctuations and/or the formation of black holes. Because the set of 3-manifold topologies is countable, a single integer determines the ultimate fate of the universe, and, in a specific sense, most 3-manifolds are "flat" or "open". Our result has important implications for inflation: if there is a positive cosmological constant (or suitable inflationary potenti...

  11. Molecular anisotropic magnetoresistance

    OpenAIRE

    Otte, Fabian; Heinze, Stefan; Mokrousov, Yuriy

    2015-01-01

    Using density functional theory calculations, we demonstrate that the effect of anisotropic magnetoresistance (AMR) can be enhanced by orders of magnitude with respect to conventional bulk ferromagnets in junctions containing molecules sandwiched between ferromagnetic leads. We study ballistic transport in metal-benzene complexes contacted by $3d$ transition-metal wires. We show that the gigantic AMR can arise from spin-orbit coupling effects in the leads, drastically enhanced by orbital-symm...

  12. Magnetic properties of the α -T3 model: Magneto-optical conductivity and the Hofstadter butterfly

    Science.gov (United States)

    Illes, E.; Nicol, E. J.

    2016-09-01

    The α -T3 model interpolates between the pseudospin S =1 /2 honeycomb lattice of graphene and the pseudospin S =1 dice lattice via parameter α . We present calculations of the magnetic properties of this hybrid pseudospin model, namely the absorptive magneto-optical conductivity and the Hofstadter butterfly spectra. In the magneto-optics curves, signatures of the hybrid system include a doublet structure present in the peaks, resulting from differing Landau level energies in the K and K' valleys. In the Hofstadter spectra, we detail the evolution of the Hofstadter butterfly as it changes its periodicity by a factor of three as we vary between the two limiting cases of the α -T3 model.

  13. Bulk-Quantity Synthesis and Conductive Properties of Comb-Like Dendritic ZnO Nanostructures

    Institute of Scientific and Technical Information of China (English)

    LIAO Zhi-Min; ZHANG Hong-Zhou; XU Jun; YU Da-Peng

    2005-01-01

    @@ Adopting a simple low-temperature (~ 500℃) vapour process, we have synthesized bulk quantity comb-like dendritic ZnO nanostructures in large area.An atomic force microscope equipped with Au-coated probes was employed to elucidate the current-voltage characteristic of the individual ZnO nanocomb.The connection electrodes were defined by depositing Pt wires using focused ion beam (FIB).A rectification effect was observed,while it was slightly suppressed compared with that of the previous reports.The good conductive properties of the sample can be attributed to the Ga+ ions implantation through the FIB process of electrode definition.We suggest that the material and the FIB method can be developed to fabricate novel nanosized devices.

  14. Property-Transfer Modeling to Estimate Unsaturated Hydraulic Conductivity of Deep Sediments at the Idaho National Laboratory, Idaho

    Science.gov (United States)

    Perkins, Kim S.; Winfield, Kari A.

    2007-01-01

    The unsaturated zone at the Idaho National Laboratory is complex, comprising thick basalt flow sequences interbedded with thinner sedimentary layers. Understanding the highly nonlinear relation between water content and hydraulic conductivity within the sedimentary interbeds is one element in predicting water flow and solute transport processes in this geologically complex environment. Measurement of unsaturated hydraulic conductivity of sediments is costly and time consuming, therefore use of models that estimate this property from more easily measured bulk-physical properties is desirable. A capillary bundle model was used to estimate unsaturated hydraulic conductivity for 40 samples from sedimentary interbeds using water-retention parameters and saturated hydraulic conductivity derived from (1) laboratory measurements on core samples, and (2) site-specific property transfer regression models developed for the sedimentary interbeds. Four regression models were previously developed using bulk-physical property measurements (bulk density, the median particle diameter, and the uniformity coefficient) as the explanatory variables. The response variables, estimated from linear combinations of the bulk physical properties, included saturated hydraulic conductivity and three parameters that define the water-retention curve. The degree to which the unsaturated hydraulic conductivity curves estimated from property-transfer-modeled water-retention parameters and saturated hydraulic conductivity approximated the laboratory-measured data was evaluated using a goodness-of-fit indicator, the root-mean-square error. Because numerical models of variably saturated flow and transport require parameterized hydraulic properties as input, simulations were run to evaluate the effect of the various parameters on model results. Results show that the property transfer models based on easily measured bulk properties perform nearly as well as using curve fits to laboratory-measured water

  15. Electrical conductivity and luminescence properties of two silver(I) coordination polymers with heterocyclic nitrogen ligands

    Energy Technology Data Exchange (ETDEWEB)

    Rana, Abhinandan; Kumar Jana, Swapan [Department of Chemistry and Chemical Technology, Vidyasagar University, Midnapore 721102, West Bengal (India); Pal, Tanusri [Department of Physics, Midnapore College, Midnapore 721101, West Bengal (India); Puschmann, Horst [Department of Chemistry, Durham University, Durham DH1 3LE (United Kingdom); Zangrando, Ennio [Dipartimento di Scienze Chimiche e Farmaceutiche, University of Trieste, 34127 Trieste (Italy); Dalai, Sudipta, E-mail: sudipta@mail.vidyasagar.ac.in [Department of Chemistry and Chemical Technology, Vidyasagar University, Midnapore 721102, West Bengal (India)

    2014-08-15

    The synthesis and X-ray structural characterization of two novel silver(I) coordination polymers, [Ag(NO{sub 3})(quin)]{sub n} (1) and [Ag{sub 8}(HL){sub 2}(H{sub 2}O){sub 4}(mpyz)]·3H{sub 2}O (2) are reported, where quin=5,6,7,8-tetrahydroquinoxaline, H{sub 6}L=cyclohexane-1,2,3,4,5,6-hexacarboxylic acid and mpyz=2-methyl pyrazine. The single crystal diffraction analyses showed that complex 1 is a 2D layered structure, while 2 presents a 3D polymeric architecture. In complex 2 the network is stabilized by argentophilic interactions and hydrogen bonding. Electrical conductivity of order 3×10{sup −4} Scm{sup −1} (1) and 1.6×10{sup −4} Scm{sup −1} (2) is measured on thin film specimen at room temperature. The photoluminescence and thermal properties of the complexes have also been studied. - Graphical abstract: Two new 1D and 3D coordination polymers of Ag(I) have been synthesized and characterized by X-ray analysis. The electrical, luminescence and thermal properties have been studied. - Highlights: • 1 is 2D layered while 2 present a 3D polymeric architecture. • The network in 2 is stabilized by argentophilic interactions and hydrogen bonding. • Electrical conductivity measurement is quite interesting. • Argentophilic interaction and intra-ligand π{sup ⁎}–π CT explains emission behavior of 2.

  16. Anisotropic polyurethane magnetorheological elastomer prepared through in situ polycondensation under a magnetic field

    Science.gov (United States)

    Wu, Jinkui; Gong, Xinglong; Fan, Yanceng; Xia, Hesheng

    2010-10-01

    Highly filled polytetramethylene ether glycol (PTMEG)-based polyurethane (PU) magnetorheological elastomers (MREs) with anisotropic structure and good mechanical properties were prepared. The difficulty in dispersion and orientation of iron particles in the PU elastomer was overcome by ball milling mixing and further in situ one-step polycondensation under a magnetic field. The microstructure and properties of the composite were characterized in detail. Scanning electron microscopy (SEM) showed that a chain-like structure of carbonyl iron was formed in the PU matrix after orientation under a magnetic field of 1.2 T. The aligned chain-like structure of carbonyl iron in PU greatly enhanced the thermal conductivity, the compression properties and the magnetorheological (MR) effect of anisotropic PU MREs compared to that of the isotropic one. When the test frequency is 1 Hz, the maximum absolute and relative MR effect of anisotropic PU MREs with 26 wt% hard segment and 70 wt% carbonyl iron were ~ 1.3 MPa and ~ 21%, respectively.

  17. Anisotropic polyurethane magnetorheological elastomer prepared through in situ polycondensation under a magnetic field

    International Nuclear Information System (INIS)

    Highly filled polytetramethylene ether glycol (PTMEG)-based polyurethane (PU) magnetorheological elastomers (MREs) with anisotropic structure and good mechanical properties were prepared. The difficulty in dispersion and orientation of iron particles in the PU elastomer was overcome by ball milling mixing and further in situ one-step polycondensation under a magnetic field. The microstructure and properties of the composite were characterized in detail. Scanning electron microscopy (SEM) showed that a chain-like structure of carbonyl iron was formed in the PU matrix after orientation under a magnetic field of 1.2 T. The aligned chain-like structure of carbonyl iron in PU greatly enhanced the thermal conductivity, the compression properties and the magnetorheological (MR) effect of anisotropic PU MREs compared to that of the isotropic one. When the test frequency is 1 Hz, the maximum absolute and relative MR effect of anisotropic PU MREs with 26 wt% hard segment and 70 wt% carbonyl iron were ∼ 1.3 MPa and ∼ 21%, respectively

  18. The thermal properties of a carbon nanotube-enriched epoxy: Thermal conductivity, curing, and degradation kinetics

    KAUST Repository

    Ventura, Isaac Aguilar

    2013-05-31

    Multiwalled carbon nanotube-enriched epoxy polymers were prepared by solvent evaporation based on a commercially available epoxy system and functionalized multiwalled carbon nanotubes (COOH-MWCNTs). Three weight ratio configurations (0.05, 0.5, and 1.0 wt %) of COOH-MWCNTs were considered and compared with neat epoxy and ethanol-treated epoxy to investigate the effects of nano enrichment and processing. Here, the thermal properties of the epoxy polymers, including curing kinetics, thermal conductivity, and degradation kinetics were studied. Introducing the MWCNTs increased the curing activation energy as revealed by differential scanning calorimetry. The final thermal conductivity of the 0.5 and 1.0 wt % MWCNT-enriched epoxy samples measured by laser flash technique increased by up to 15% compared with the neat material. The activation energy of the degradation process, investigated by thermogravimetric analysis, was found to increase with increasing CNT content, suggesting that the addition of MWCNTs improved the thermal stability of the epoxy polymers. © 2013 Wiley Periodicals, Inc.

  19. LOW-POTENTIAL ELECTROSYNTHESIS OF CONDUCTING AND ELECTROACTIVE OLIGOCATECHOLBORANE WITH BLUE LIGHT-EMITTING PROPERTIES

    Institute of Scientific and Technical Information of China (English)

    Bao-yang Lu; Shuai Chen; Lei-qiang Qin; Yao Huang; Jing-kun Xu

    2013-01-01

    Novel conducting oligocatecholborane (OCOB) with electrical conductivity of 3.73 × 10-2 S cm-1 was successfully synthesized by low-potential electropolymerization of catecholborane (COB) in boron trifluoride diethyl etherate at 0.70 V versus Ag/AgC1.FT-IR and 1H-NMR spectra,together with the computational results,proved that COB was polymerized through the coupling at C(4) and C(5) positions and the reactive B-H bond was stable during the electrochemical polymerization.The resulting product was mainly composed of oligomers with short chain lengths by GPC and mass spectral results.The as-formed OCOB film showed good electrochemistry in monomer-free electrolytes with the electrochromic property from opaque blue to sap green.Fluorescence studies indicated that soluble OCOB can emit bright blue light under excitation of 365 nm UV light with the maximum emission at 396 nm and a fluorescence quantum yield of 0.21.The deposited OCOB also exhibited favorable thermal stability and smooth and compact morphology even at high magnifications.

  20. Electric conductivity and dielectric properties of HDPE-TlInS2 composites

    International Nuclear Information System (INIS)

    Polymer-semiconductor composites are prepared from a homogeneous mixture of powders of high density polyethylene (HDPE) and the TlInS2 semiconductor. The electric conductivity (σac) and dielectric properties (ε'and ε) of the composites as a function of the volume fraction of the TlInS2 ferroelectric (0-60%), temperature (20-150 degrees Celsius), and frequency (102-106 Hz) of the measured electric field are studied. The semi logarithmic plot of the temperature dependence of conductivity, i.e., the lnσac-temperature curve, comprises three regions; one of them corresponds to the low temperature portion of the curve where σac weakly depends on temperature, while in the other two regions σac exhibits a strong temperature dependence. The plot of the frequency dependence of σac for the HDPE-TlInS2 composites shows that σac increases exponentially and nonlinearly at low and high frequencies, respectively. The observed decrease in ε' with increasing frequency is representative of a dielectric relaxation process. The occurrence of this relaxation process is also confirmed by the fact that the ε(f) plot exhibits a maximum at 10 kHz. It is assumed that the relaxation processes in the HDPE-TlInS2 composite structures are attributed to interfacial polarization and the local mobility of the polar components and short segments of the polymer backbone. (authors)

  1. Lightweight cordierite–mullite refractories with low coefficients of thermal conductivity and high mechanical properties

    Indian Academy of Sciences (India)

    Wen Yan; Junfeng Chen; Nan Li; BingqiangHan Han; Yaowu Wei

    2015-04-01

    Lightweight cordierite–mullite refractories with low coefficients of thermal conductivity (CTCs), high strengths and high thermal-shock resistances were prepared using porous cordierite ceramics as aggregates. Phase compositions and microstructures of lightweight refractories were measured by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS), etc. The effect of the relative mullite content of matrix (RMCM) on the microstructures and properties of lightweight refractories was investigated. It was found that the RMCM has a strong effect on the CTC and the mechanical properties. With an increase of RMCM, the compressive and flexural strengths of specimen increase. The thermal-shock resistance is the highest when the RMCM is 22 wt%, and also improved slightly when the RMCM is 46 wt% comparing with the specimen without mullite. When the RMCM is 46 wt%, the CTC reaches the minimum. Specimen with the RMCM of 46 wt% is the most appropriate mode, which has a moderate apparent porosity of 30%, a high compressive strength of 135.1 MPa, a high flexural strength of 20.5 MPa, a good thermal-shock resistance and a low CTC of 0.61 W mK−1.

  2. Deep rooting plants influence on soil hydraulic properties and air conductivity over time

    Science.gov (United States)

    Uteau, Daniel; Peth, Stephan; Diercks, Charlotte; Pagenkemper, Sebastian; Horn, Rainer

    2014-05-01

    Crop sequences are commonly suggested as an alternative to improve subsoil structure. A well structured soil can be characterized by enhanced transport properties. Our main hypothesis was, that different root systems can modify the soil's macro/mesopore network if enough cultivation time is given. We analyzed the influence of three crops with either shallower roots (Festuca arundinacea, fescue) or taproots (Cichorium intybus, chicory and Medicago sativa, alfalfa). The crops where cultivated on a Haplic Luvisol near Bonn (Germany) for one, two or three years. Undisturbed soil cores were taken for measurement of unsaturated hydraulic conductivity and air permeability. The unsaturated conductivity was measured using the evaporation method, monitoring the water content and tension at two depths of each undisturbed soil core. The van Genuchten-Mualem model (1991) was fitted to the measured data. Air permeability was measured in a permeameter with constant flow at low pressure gradient. The measurements were repeated at -1, -3, -6, -15, -30 and -50 kPa matric tension and the model of Ball et al. (1988) was used to describe permeability as function of matric tension. Furthermore, the cores equilibrated at -15 kPa matric tension were scanned with X-Ray computer tomography. By means of 3D image analysis, geometrical features as pore size distribution, tortuosity and connectivity of the pore network was analyzed. The measurements showed an increased unsaturated hydraulic conductivity associated to coarser pores at the taprooted cultivations. A enhanced pore system (related to shrink-swell processes) under alfalfa was observed in both transport measurements and was confirmed by the 3D image analysis. This highly functional pore system (consisting mainly of root paths, earthworm channels and shrinking cracks) was clearly visible below the 75 cm of depth and differentiated significantly from the other two treatments only after three years of cultivation, which shows the time

  3. Mechanical Properties and Electrical Conductivity of TiN-Al2O3 Composites

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    TIN-Al2O3 composite powders with different TiN contents (0,10 vol%,20 vol%,30 vol% and 40 vol%) were prepared with micrometer TiN and α-Al2O3 powder (their purities were 99%) as starting materials by wet ball milling for 5 h.TiN-Al2O3 com-posite were then prepared by pressing the above composite powders,drying at 200 ℃ for 12 h and firing at 1 800 ℃ for 3 h in nitrogen atmosphere in hot-pressing furnace.The influences of TiN content on mechanical properties and electrical conductivity of TiN-Al2O3 com-posites were studied.The results showed that the me-chanical properties of the composite increased with TiN content increasing,while the resistivity of composites de-creased.A composite with 40% TiN had 498 MPa ben-ding strength,4.285 MPa·m1/2 fracture toughness,1.34×10-3 Ω·cm resistivity.The SEM analysis showed that the fine TiN crystals distributed among the crystal boundary of Al2O3 matrix.They bonded together forming a net-like structure which played a role of re-straining Al2O3 grains from growing up,toughening and strengthening,so the mechanical properties of TIN -Al2O3 composite were enhanced.

  4. Q-factor and absorption enhancement for plasmonic anisotropic nanoparticles

    CERN Document Server

    Liu, Wei; Miroshnichenko, Andrey E

    2016-01-01

    We investigate the scattering and absorption properties of anisotropic metal-dielectric core-shell nanoparticles. It is revealed that the radially anisotropic dielectric layer can accelerate the evanescent decay of the localized resonant surface modes, leading to Q-factor and absorption rate enhancement. Moreover, the absorption cross section can be maximized to reach the single resonance absorption limit. We further show that such artificial anisotropic cladding materials can be realized by isotropic layered structures, which may inspire many applications based on scattering and absorption of plasmonic nanoparticles.

  5. Renormalized anisotropic exchange for representing heat assisted magnetic recording media

    Energy Technology Data Exchange (ETDEWEB)

    Jiao, Yipeng; Liu, Zengyuan; Victora, R. H., E-mail: victora@umn.edu [MINT Center, Electrical and Computer Engineering, University of Minnesota, Minneapolis, Minnesota 55455 (United States)

    2015-05-07

    Anisotropic exchange has been incorporated in a description of magnetic recording media near the Curie temperature, as would be found during heat assisted magnetic recording. The new parameters were found using a cost function that minimized the difference between atomistic properties and those of renormalized spin blocks. Interestingly, the anisotropic exchange description at 1.5 nm discretization yields very similar switching and magnetization behavior to that found at 1.2 nm (and below) discretization for the previous isotropic exchange. This suggests that the increased accuracy of anisotropic exchange may also reduce the computational cost during simulation.

  6. Renormalized anisotropic exchange for representing heat assisted magnetic recording media

    International Nuclear Information System (INIS)

    Anisotropic exchange has been incorporated in a description of magnetic recording media near the Curie temperature, as would be found during heat assisted magnetic recording. The new parameters were found using a cost function that minimized the difference between atomistic properties and those of renormalized spin blocks. Interestingly, the anisotropic exchange description at 1.5 nm discretization yields very similar switching and magnetization behavior to that found at 1.2 nm (and below) discretization for the previous isotropic exchange. This suggests that the increased accuracy of anisotropic exchange may also reduce the computational cost during simulation

  7. Electrochemical Impedance of a Battery Electrode with Anisotropic Active Particles

    CERN Document Server

    Song, J

    2013-01-01

    Electrochemical impedance spectra for battery electrodes are usually interpreted using models that assume isotropic active particles, having uniform current density and symmetric diffusivities. While this can be reasonable for amorphous or polycrystalline materials with randomly oriented grains, modern electrode materials increasingly consist of highly anisotropic, single-crystalline, nanoparticles, with different impedance characteristics. In this paper, analytical expressions are derived for the impedance of anisotropic particles with tensorial diffusivities and orientation-dependent surface reaction rates and capacitances. The resulting impedance spectrum contains clear signatures of the anisotropic material properties and aspect ratio, as well as statistical variations in any of these parameters.

  8. Hydraulic Conductivity Functions in Relation to Some Chemical Properties in a Cultivated Oxisols of a Humid Region, Delta State, Nigeria

    Directory of Open Access Journals (Sweden)

    Egbuchua, C. N.

    2014-04-01

    Full Text Available The study was conducted to evaluate hydraulic conductivity functions in relation to some soil chemical properties in an oxisols of the tropics. Field and laboratory studies were carried out and data collected, subjected to statistical analytical procedure for computing coefficient of variability and correlation among soil properties. Results of the study showed that hydraulic conductivity functions varied spatially and temporarily across the experimental points with a moderate mean value of 0.0026 cm/h and a coefficient o variation of 31.45% soil chemical properties showed that the soils were acidic with a mean pH value of 5.12. Organic carbon, total nitrogen and available phosphorus were low with mean values of 1.29%, 0.68% and 4.43 mgkg-1. Coefficient of variability among soil properties indicated less to moderately variable. Soil pH had negative correlation with all the soil properties evaluated.

  9. Anisotropic Babinet-invertible metasurfaces to realize transmission-reflection switching for orthogonal polarizations of light

    CERN Document Server

    Nakata, Yosuke; Okimura, Kunio; Nakanishi, Toshihiro; Takeda, Mitsuo Wada; Kitano, Masao

    2016-01-01

    The electromagnetic properties of an extremely thin metallic checkerboard drastically change from resonant reflection (transmission) to resonant transmission (reflection) when the local electrical conductivity at the interconnection points of the checkerboard is switched. To date, such critical transitions of metasurfaces have been applied only when they have 4-fold rotational symmetry, and their application to polarization control, which requires anisotropy, has been unexplored. To overcome this applicability limitation and open up new pathways for dynamic deep-subwavelength polarization control by utilizing critical transitions of checkerboard-like metasurfaces, we introduce a universal class of anisotropic Babinet-invertible metasurfaces enabling transmission-reflection switching for each orthogonally polarized wave. As an application of anisotropic Babinet-invertible metasurfaces, we experimentally realize a reconfigurable terahertz polarizer whose transmitting axis can be dynamically rotated by $90^\\circ...

  10. Bianchi -V space-time with anisotropic dark energy in general relativity

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Chandra Prakash [Department of Applied Mathematics, Delhi Technological University (Formerly Delhi College of Engineering), Delhi (India)

    2011-12-15

    In a spatially homogeneous and anisotropic Bianchi type-V space-time the consequences of the presence of dynamically anisotropic dark energy and perfect fluid with heat-conduction are studied. We assume that dark energy is minimally interacting with matter and has an equation of state which is modified in a consistent way with the conservation of energy momentum tensor. Exact solutions of Einstein field equations are obtained by taking constant value of deceleration parameter. We find that this assumption is reasonable for the observation of the present day universe. The physical and geometrical properties of the models, the behavior of the anisotropy of dark energy and the thermodynamical relations that govern such solutions are discussed in detail. (author)

  11. Emergence of anisotropic heavy fermions in antiferromagnetic Kondo lattice CeIn3 revealed by photoemission

    Science.gov (United States)

    Zhang, Yun; Lu, Haiyan; Zhu, Xiegang; Tan, Shiyong; Chen, Qiuyun; Feng, Wei; Xie, Donghua; Luo, Lizhu; Zhang, Wen; Lai, Xinchun; Donglai Feng Team; Huiqiu Yuan Team

    One basic concept in heavy fermions systems is the entanglement of localized spin state and itinerant electron state. It can be tuned by two competitive intrinsic mechanisms, Kondo effect and Ruderman-Kittel-Kasuya-Yosida interaction, with external disturbances. The key issue regarding heavy fermions properties is how the two mechanisms work in the same phase region. To investigate the relation of the two mechanisms, the cubic antiferromagnetic heavy fermions compound CeIn3 was investigated by soft x-ray angle resolved photoemission spectroscopy. The hybridization between f electrons and conduction bands in the paramagnetic state was observed directly, providing compelling evidence for Kondo screening scenario and coexistence of two mechanisms. The hybridization strength shows slight and regular anisotropy in K space, implying that the two mechanisms are competitive and anisotropic. This work illuminates the concomitant and competitive relation between the two mechanisms and supplies some evidences for the anisotropic superconductivity of CeIn3

  12. DC conductivity and magnetic properties of piezoelectric-piezomagnetic composite system

    Energy Technology Data Exchange (ETDEWEB)

    Hemeda, O.M., E-mail: omhemeda@yahoo.co.uk [Tanta University, Faculty of Science, Physics Department (Egypt); Taif University, Faculty of Science, Physics Department (Saudi Arabia); Tawfik, A. [Taif University, Faculty of Science, Physics Department (Saudi Arabia); A-Al-Sharif [Moata University, Faculty of Science, Physics Department (Jordan); Amer, M.A. [Taif University, Faculty of Science, Physics Department (Saudi Arabia); Kamal, B.M.; El Refaay, D.E. [Suez Canal University, Faculty of Science, Physics Department (Egypt); Bououdina, M. [Nanotechnology Centre, College of Science, University of Bahrain, PO Box 32038 (Bahrain); Department of Physics, College of Science, University of Bahrain, PO Box 32038 (Bahrain)

    2012-11-15

    A series of composites (1-x) (Ni{sub 0.8}Zn{sub 0.2}Fe{sub 2}O{sub 4})+x (BaTiO{sub 3}), where x=0%, 20%, 40%, 60%, 80% and 100% BT content, have been prepared by the standard ceramic technique, then sintered at 1200 Degree-Sign C for 8 h. X-ray diffraction analysis shows that the prepared composites consist of two phases, ferrimagnetic and ferroelectric. DC electrical resistivity, thermoelectric power, charge carriers concentration and charge carrier mobility have been studied at different temperatures. It was found that the DC electrical conductivity increases with increasing BT content. The values of the thermoelectric power were positive and negative for the composites indicating that there are two conduction mechanisms, hopping and band conduction, respectively. Using the values of DC electrical conductivity and thermoelectric power, the values of charge carrier mobility and the charge carrier concentration were calculated. Magnetic measurements (hysteresis loop and magnetic permeability) show that the magnetization decreases by increasing BT content. M-H loop of pure Ni{sub 0.6} Zn{sub 0.4} Fe{sub 2}O{sub 4} composite indicates that it is paramagnetic at room temperature and that the magnetization is diluted by increasing the BT content in the composite system. The value of magnetoelectric coefficient for the composites decreases by increasing BT content for all the compositions except for 40% BT content, which may be due to the low resistivity of magnetic phase compared with the BT phase that causes a leakage of induced charges on the piezoelectric phase. Since both ferroelectric and magnetic phases preserve their basic properties in the bulk composite, the present BT-NZF composite are potential candidates for applications as pollution sensors and electromagnetic waves. - Highlights: Black-Right-Pointing-Pointer Studied composite has a high magnetoelectric coefficient compared with other composites. Black-Right-Pointing-Pointer A p-n transition is observed

  13. Electric and magnetic fields from two-dimensional anisotropic bisyncytia.

    OpenAIRE

    Sepulveda, N G; Wikswo, J.P.

    1987-01-01

    Cardiac tissue can be considered macroscopically as a bidomain, anisotropic conductor in which simple depolarization wavefronts produce complex current distributions. Since such distributions may be difficult to measure using electrical techniques, we have developed a mathematical model to determine the feasibility of magnetic localization of these currents. By applying the finite element method to an idealized two-dimensional bisyncytium with anisotropic conductivities, we have calculated th...

  14. POLYNOMIAL PRESERVING RECOVERY FOR ANISOTROPIC AND IRREGULAR GRIDS

    Institute of Scientific and Technical Information of China (English)

    Zhimin Zhang

    2004-01-01

    Some properties of a newly developed polynomial preserving gradient recovery technique are discussed. Both practical and theoretical issues are addressed. Bounded-ness property is considered especially under anisotropic grids. For even-order finite element space, an ultra-convergence property is established under translation invariant meshes; for linear element, a superconvergence result is proven for unstructured grids generated by the Delaunay triangulation.

  15. Mesoscopic Phase Separation in Anisotropic Superconductors

    OpenAIRE

    V. I. Yukalov; Yukalova, E. P.

    2005-01-01

    General properties of anisotropic superconductors with mesoscopic phase separation are analysed. The main conclusions are as follows: Mesoscopic phase separation can be thermodynamically stable only in the presence of repulsive Coulomb interactions. Phase separation enables the appearance of superconductivity in a heterophase sample even if it were impossible in pure-phase matter. Phase separation is crucial for the occurrence of superconductivity in bad conductors. Critical temperature for a...

  16. Model anisotropic quantum Hall states

    OpenAIRE

    Qiu, R. -Z.; Haldane, F.D.M.; Wan, Xin; Yang, Kun; Yi, Su

    2012-01-01

    Model quantum Hall states including Laughlin, Moore-Read and Read-Rezayi states are generalized into appropriate anisotropic form. The generalized states are exact zero-energy eigenstates of corresponding anisotropic two- or multi-body Hamiltonians, and explicitly illustrate the existence of geometric degrees of in the fractional quantum Hall effect. These generalized model quantum Hall states can provide a good description of the quantum Hall system with anisotropic interactions. Some numeri...

  17. Light transport and rotational diffusion in optically anisotropic colloidal suspensions

    OpenAIRE

    Sandomirski, Kirill

    2006-01-01

    We have investigated for the first time the influence of magnetic field on rotational diffusion in anisotropic colloidal suspensions by the method of diffusing wave spectroscopy. It has been established that the change of static properties of the sample in magnetic field exceeds the influence of rotational Brawnian motion of colloidal particles.The main dependencies of magnitude and direction of a magnetic field B on anisotropic diffusion of light has been established. It has been shown that...

  18. Duals of Orphan-Free Anisotropic Voronoi Diagrams are Triangulations

    CERN Document Server

    Canas, Guillermo D

    2011-01-01

    We show that, under mild conditions on the underlying metric, duals of appropriately defined anisotropic Voronoi diagrams are embedded triangulations. Furthermore, they always triangulate the convex hull of the vertices, and have other properties that parallel those of ordinary Delaunay triangulations. These results apply to the duals of anisotropic Voronoi diagrams of any set of vertices, so long as the diagram is orphan-free.

  19. Gamma-beam propagation in the anisotropic medium

    OpenAIRE

    V.A. Maisheev

    1997-01-01

    Propagation of gamma-beam in the anisotropic medium is considered. The simpliest example of such a medium of the general type is a combination of the two linearly polarized monochromatic laser waves with different frequencies (dichromatic wave). The optical properties of this combination are described with the use of the permittivity tensor. The refractive indices and polarization characteristics of normal electromagnetic waves propagating in the anisotropic medium are found. The relations, d...

  20. Modeling operations back extrusion billets thick-walled anisotropic

    OpenAIRE

    ПЛАТОНОВ В.И.; Яковлев, С. С.

    2014-01-01

    The mathematical model is an inverse extrusion thick-walled tube blanks of material having anisotropic mechanical properties cylindrical. Relations are given to assess the kinematics of course materials la, stress and strain states, power operation modes reverse extrusion. The results of theoretical investigations of power modes. You are the manifest effects of process parameters on the power mode of operation isothermal reverse extrusion billets of high anisotropic materials in the short-ter...

  1. Spin and Orbital angular momentum propagation in anisotropic media: theory

    OpenAIRE

    Picón, Antonio; Benseny, Albert; Mompart, Jordi; Calvo, Gabriel F.

    2011-01-01

    This paper is devoted to study the propagation of light beams carrying orbital angular momentum in optically anisotropic media. We first review some properties of homogeneous anisotropic media, and describe how the paraxial formalism is modified in order to proceed with a new approach dealing with a general setting of paraxial propagation along uniaxial inhomogeneous media. This approach is suitable for describing the space-variant-optical-axis phase plates.

  2. Material Induced Anisotropic Damage in DP600

    NARCIS (Netherlands)

    Niazi, M.S.; Wisselink, H.H.; Meinders, V.T.; Boogaard, van den A.H.

    2013-01-01

    Plasticity induced damage development in metals is anisotropic by nature. The anisotropy in damage is driven by two different phenomena; anisotropic deformation state i.e. Load Induced Anisotropic Damage (LIAD) and anisotropic microstructure i.e. Material Induced Anisotropic Damage (MIAD). The contr

  3. Influence of the Chemical Composition on Electrical Conductivity and Mechanical Properties of the Hypoeutectic Al-Si-Mg Alloys

    OpenAIRE

    Dybowski B.; Szymszal J.; Poloczek Ł.; Kiełbus A.

    2016-01-01

    Due to low density and good mechanical properties, aluminium alloys are widely applied in transportation industry. Moreover, they are characterized by the specific physical properties, such as high electrical conductivity. This led to application of the hypoeutectic Al-Si-Mg alloys in the power generation industry. Proper selection of the alloys chemical composition is an important stage in achievement of the demanded properties. The following paper presents results of the research on the inf...

  4. Gold-ionic liquid nanofluids with preferably tribological properties and thermal conductivity

    Directory of Open Access Journals (Sweden)

    Wang Baogang

    2011-01-01

    Full Text Available Abstract Gold/1-butyl-3-methylimidazolium hexafluorophosphate (Au/[Bmim][PF6] nanofluids containing different stabilizing agents were fabricated by a facile one-step chemical reduction method, of which the nanofluids stabilized by cetyltrimethylammonium bromide (CTABr exhibited ultrahighly thermodynamic stability. The transmission electron microscopy, UV-visible absorption, Fourier transform infrared, and X-ray photoelectron characterizations were conducted to reveal the stable mechanism. Then, the tribological properties of these ionic liquid (IL-based gold nanofluids were first investigated in more detail. In comparison with pure [Bmim][PF6] and the nanofluids possessing poor stability, the nanofluids with high stability exhibited much better friction-reduction and anti-wear properties. For instance, the friction coefficient and wear volume lubricated by the nanofluid with rather low volumetric concentration (1.02 × 10-3% stabilized by CTABr under 800 N are 13.8 and 45.4% lower than that of pure [Bmim][PF6], confirming that soft Au nanoparticles (Au NPs also can be excellent additives for high performance lubricants especially under high loads. Moreover, the thermal conductivity (TC of the stable nanofluids with three volumetric fraction (2.55 × 10-4, 5.1 × 10-4, and 1.02 × 10-3% was also measured by a transient hot wire method as a function of temperature (33 to 81°C. The results indicate that the TC of the nanofluid (1.02 × 10-3% is 13.1% higher than that of [Bmim][PF6] at 81°C but no obvious variation at 33°C. The conspicuously temperature-dependent and greatly enhanced TC of Au/[Bmim][PF6] nanofluids stabilized by CTABr could be attributed to micro-convection caused by the Brownian motion of Au NPs. Our results should open new avenues to utilize Au NPs and ILs in tribology and the high-temperature heat transfer field.

  5. Molecular mechanics of DNA bricks: in situ structure, mechanical properties and ionic conductivity

    Science.gov (United States)

    Slone, Scott Michael; Li, Chen-Yu; Yoo, Jejoong; Aksimentiev, Aleksei

    2016-05-01

    The DNA bricks method exploits self-assembly of short DNA fragments to produce custom three-dimensional objects with subnanometer precision. In contrast to DNA origami, the DNA brick method permits a variety of different structures to be realized using the same library of DNA strands. As a consequence of their design, however, assembled DNA brick structures have fewer interhelical connections in comparison to equivalent DNA origami structures. Although the overall shape of the DNA brick objects has been characterized and found to conform to the features of the target designs, the microscopic properties of DNA brick objects remain yet to be determined. Here, we use the all-atom molecular dynamics method to directly compare the structure, mechanical properties and ionic conductivity of DNA brick and DNA origami structures different only by internal connectivity of their consistituent DNA strands. In comparison to equivalent DNA origami structures, the DNA brick structures are found to be less rigid and less dense and have a larger cross-section area normal to the DNA helix direction. At the microscopic level, the junction in the DNA brick structures are found to be right-handed, similar to the structure of individual Holliday junctions (HJ) in solution, which contrasts with the left-handed structure of HJ in DNA origami. Subject to external electric field, a DNA brick plate is more leaky to ions than an equivalent DNA origami plate because of its lower density and larger cross-section area. Overall, our results indicate that the structures produced by the DNA brick method are fairly similar in their overall appearance to those created by the DNA origami method but are more compliant when subject to external forces, which likely is a consequence of their single crossover design.

  6. Anisotropically Inflating Universes

    CERN Document Server

    Barrow, J D; Barrow, John D.; Hervik, Sigbjorn

    2008-01-01

    We show that in theories of gravity that add quadratic curvature invariants to the Einstein-Hilbert action there exist expanding vacuum cosmologies with positive cosmological constant which do not approach the de Sitter universe. Exact solutions are found which inflate anisotropically. This behaviour is driven by the Ricci curvature invariant and has no counterpart in the general relativistic limit. These examples show that the cosmic no-hair theorem does not hold in these higher-order extensions of general relativity and raises new questions about the ubiquity of inflation in the very early universe and the thermodynamics of gravitational fields.

  7. Structural anisotropic properties of a-plane GaN epilayers grown on r-plane sapphire by molecular beam epitaxy

    Energy Technology Data Exchange (ETDEWEB)

    Lotsari, A.; Kehagias, Th.; Katsikini, M.; Arvanitidis, J.; Ves, S.; Komninou, Ph.; Dimitrakopulos, G. P., E-mail: gdim@auth.gr [Physics Department, Aristotle University of Thessaloniki, 54124 Thessaloniki (Greece); Tsiakatouras, G.; Tsagaraki, K.; Georgakilas, A. [Department of Physics, Microelectronics Research Group, University of Crete, P.O. Box 2208, GR 71003, Greece and IESL, FORTH, P.O. Box 1385, GR71110 Heraklion (Greece); Christofilos, D. [Physics Division, School of Technology, Aristotle University of Thessaloniki, GR54124 Thessaloniki (Greece)

    2014-06-07

    Heteroepitaxial non-polar III-Nitride layers may exhibit extensive anisotropy in the surface morphology and the epilayer microstructure along distinct in-plane directions. The structural anisotropy, evidenced by the “M”-shape dependence of the (112{sup ¯}0) x-ray rocking curve widths on the beam azimuth angle, was studied by combining transmission electron microscopy observations, Raman spectroscopy, high resolution x-ray diffraction, and atomic force microscopy in a-plane GaN epilayers grown on r-plane sapphire substrates by plasma-assisted molecular beam epitaxy (PAMBE). The structural anisotropic behavior was attributed quantitatively to the high dislocation densities, particularly the Frank-Shockley partial dislocations that delimit the I{sub 1} intrinsic basal stacking faults, and to the concomitant plastic strain relaxation. On the other hand, isotropic samples exhibited lower dislocation densities and a biaxial residual stress state. For PAMBE growth, the anisotropy was correlated to N-rich (or Ga-poor) conditions on the surface during growth, that result in formation of asymmetric a-plane GaN grains elongated along the c-axis. Such conditions enhance the anisotropy of gallium diffusion on the surface and reduce the GaN nucleation rate.

  8. Thermal conductivity and heat transport properties of nitrogen-doped graphene.

    Science.gov (United States)

    Goharshadi, Elaheh K; Mahdizadeh, Sayyed Jalil

    2015-11-01

    In the present study, the thermal conductivity (TC) and heat transport properties of nitrogen doped graphene (N-graphene) were investigated as a function of temperature (107-400K) and N-doped concentration (0.0-7.0%) using equilibrium molecular dynamics simulation based on Green-Kubo method. According to the results, a drastic decline in TC of graphene observed at very low N-doped concentration (0.5 and 1.0%). Substitution of just 1.0% of carbon atoms with nitrogens causes a 77.2, 65.4, 59.2, and 53.7% reduction in TC at 107, 200, 300, and 400K, respectively. The values of TC of N-graphene at different temperatures approach to each other as N-doped concentration increases. The results also indicate that TC of N-graphene is much less sensitive to temperature compared with pristine graphene and the sensitivity decreases as N-doped concentration increases. The phonon-phonon scattering relaxation times and the phonon mean free path of phonons were also calculated. The contribution of high frequency optical phonons for pristine graphene and N-graphene with 7.0% N-doped concentration is 0-2% and 4-8%, respectively. These findings imply that it is potentially feasible to control heat transfer on the nanoscale when designing N-graphene based thermal devices.

  9. Scattering and Transmission Properties of a Complex 3-D Slot in a Thick Conducting Plane

    Institute of Scientific and Technical Information of China (English)

    NIE Xiaochun; GE Debiao; YUAN Ning

    2001-01-01

    A new technique which combinesthe generalized network formulation along with theboundary integral method and the connection algo-rithm is proposed to deal with the electromagneticcharacterization of the transmission and scatteringproperties of a complex 3-D (three-dimensional) slotin a thick conducting plane.First,the interior cav-ity of the slot is divided into sections according to itsconfiguration and filling characteristics and the gener-alized admittance matrix of each section is computedby the boundary integral method.Using the connec-tion algorithm,the interior admittance matrix of theoverall slot can be derived by cascading the admit-tance matrices of individual sections.Then the aper-ture equivalent magnetic currents,the backscatteredfield and the transmitted field can be obtained by thegeneralized network formulation.Numerical examplesare presented to demonstrate the validity,versatilityand capability of the technique.The technique can beused to not only efficiently handle arbitrary slot re-gardless of its geometry and material properties butalso greatly reduce the memory requirement and com-putation time.

  10. The anisotropic properties analysis of the rock mass surrounding the roadway' s in seepage and stress field%巷道围岩渗流场和应力场各向异性特征分析及应用

    Institute of Scientific and Technical Information of China (English)

    杨天鸿; 师文豪; 于庆磊; 李海洲; 郑超; 夏冬

    2012-01-01

    依托范各庄煤矿12号煤层底板的砂岩巷道工程实际,应用岩体结构面非接触测量(Sha-peMetriX3D)系统,对巷道开挖面进行岩体结构面数字摄影测量及识别,得到岩体结构面的几何分布参数;在此基础上,利用Mont-Carlo方法生成裂隙网络,分别利用离散介质渗流方法和几何损伤理论计算岩体的渗透张量和弹性张量,研究了岩体力学参数各向异性和尺度效应;最后,建立了平面应变情况下的巷道围岩各向异性渗流力学模型,采用COMSOL Multiphysics多物理场分析软件,计算得到了可以考虑节理分布特征的巷道围岩应力场和渗流场,并讨论了岩体力学性质主方向对围岩应力场、渗流场及损伤区的影响。研究表明,岩体的各向异性对数值模拟结果影响显著,等效连续介质的各向异性模型能考虑岩体结构面的影响,更符合工程实际。%Depending on the sandstone roadway on the floor of No. 12 coal seam in Fangezhuang Coal Mine,a 3D con- tact-free measuring system, named as ShapeMetriX3D, was employed to capture discontinuities on the face of the road- way and obtain statistical parameters for each set of discontinuities. And then, fracture network was generated by Mont- Carlo method. Permeability tensor of rock mass was calculated by the discrete medium seepage method, and the elastic- ity tensor of rock mass was obtained by geometrical damage theory. Then, scale effect and anisotropic behaviors of rock mass were studied. Finally, an anisotropic percolation mechanics model of surrounding rock mass of the roadway was built under plane strain condition. Using COMSOL multiphysics code, the stress field and seepage field surrounding the roadway were obtained, which can take into account the influence of orientation of discontinuities. Furthermore, the in- fluences of principal direction of rock mass properties on stress, seepage and damage zone were discussed. The results show that the

  11. Anisotropic wetting of copper alloys induced by one-step laser micro-patterning

    Energy Technology Data Exchange (ETDEWEB)

    Hans, M., E-mail: michael.hans@mx.uni-saarland.de [Chair of Functional Materials, Faculty of Natural Sciences and Technology, Saarland University, 66123 Saarbruecken (Germany); Mueller, F.; Grandthyll, S.; Huefner, S. [Experimental Physics, Faculty of Natural Sciences and Technology, Saarland University, 66123 Saarbruecken (Germany); Muecklich, F. [Chair of Functional Materials, Faculty of Natural Sciences and Technology, Saarland University, 66123 Saarbruecken (Germany)

    2012-12-15

    Highlights: Black-Right-Pointing-Pointer One-step, contactless micro-patterning of copper alloys has been achieved. Black-Right-Pointing-Pointer Anisotropic wetting properties are tailored by line-like structures. Black-Right-Pointing-Pointer Both topographical and chemical patterns contribute to the phenomenon. Black-Right-Pointing-Pointer The topographic shape and homogeneity are found to be governing factors. - Abstract: Copper alloys (CuSn8, CuZn23Al3Co) have been micro-patterned with line-like geometries by Laser Interference Surface Structuring (LISS). In the presented study two high power pulsed laser beams are recombined to create unique, line-like intensity distributions with a chosen, constant periodicity of 10 {mu}m at varying laser fluencies. Anisotropic wetting properties on these surfaces have been confirmed by drop shape analysis and static contact angle measurements, which were conducted parallel and perpendicular to the structures revealing up to 25% difference in contact angle. The topography and chemistry of the tailored line structures have been characterized and analyzed by white light interferometry, spatial frequency distribution, AFM and X-ray photoelectron spectroscopy. The topographic shape and homogeneity are considered as key parameters for anisotropic wetting design, although it is concluded that both, the geometry as well as the locally varying chemical composition of the surface structures contribute to the phenomenon. Parallel capillarity effects and perpendicular contact line pinning are found to be the governing mechanisms.

  12. Anisotropic Thermal Diffusion

    Science.gov (United States)

    Gardiner, Thomas

    2013-10-01

    Anisotropic thermal diffusion in magnetized plasmas is an important physical phenomena for a diverse set of physical conditions ranging from astrophysical plasmas to MFE and ICF. Yet numerically simulating this phenomenon accurately poses significant challenges when the computational mesh is misaligned with respect to the magnetic field. Particularly when the temperature gradients are unresolved, one frequently finds entropy violating solutions with heat flowing from cold to hot zones for χ∥ /χ⊥ >=102 which is substantially smaller than the range of interest which can reach 1010 or higher. In this talk we present a new implicit algorithm for solving the anisotropic thermal diffusion equations and demonstrate its characteristics on what has become a fairly standard set of test problems in the literature. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000. SAND2013-5687A.

  13. Inhomogeneous anisotropic cosmology

    Science.gov (United States)

    Kleban, Matthew; Senatore, Leonardo

    2016-10-01

    In homogeneous and isotropic Friedmann-Robertson-Walker cosmology, the topology of the universe determines its ultimate fate. If the Weak Energy Condition is satisfied, open and flat universes must expand forever, while closed cosmologies can recollapse to a Big Crunch. A similar statement holds for homogeneous but anisotropic (Bianchi) universes. Here, we prove that arbitrarily inhomogeneous and anisotropic cosmologies with ``flat'' (including toroidal) and ``open'' (including compact hyperbolic) spatial topology that are initially expanding must continue to expand forever at least in some region at a rate bounded from below by a positive number, despite the presence of arbitrarily large density fluctuations and/or the formation of black holes. Because the set of 3-manifold topologies is countable, a single integer determines the ultimate fate of the universe, and, in a specific sense, most 3-manifolds are ``flat'' or ``open''. Our result has important implications for inflation: if there is a positive cosmological constant (or suitable inflationary potential) and initial conditions for the inflaton, cosmologies with ``flat'' or ``open'' topology must expand forever in some region at least as fast as de Sitter space, and are therefore very likely to begin inflationary expansion eventually, regardless of the scale of the inflationary energy or the spectrum and amplitude of initial inhomogeneities and gravitational waves. Our result is also significant for numerical general relativity, which often makes use of periodic (toroidal) boundary conditions.

  14. Anisotropic fluid from nonlocal tidal effects

    CERN Document Server

    Culetu, Hristu

    2014-01-01

    The Shiromizu et al. \\cite{SMS} covariant decomposition formalism is used to find out the brane properties rooted from the 5-dimensional Witten bubble spacetime. The non-local tensor $E_{ab}$ generated by the 5-dimensional Weyl tensor gives rise at an anisotropic energy-momentum tensor on the brane with negative energy density and $p = \\rho/3$ as equation of state. The tidal acceleration is towards the brane and that is in accordance with the negative energy density on the brane. The anisotropic fluid has vanishing "bulk" viscosity but the shear viscosity coefficient is $r$- and $t$- dependent. The brane is endowed with an apparent horizon which is exactly the radial null geodesic.

  15. Polarimetric characterization of optically anisotropic flexible substrates

    Energy Technology Data Exchange (ETDEWEB)

    Stchakovsky, M. [HORIBA Jobin-Yvon SAS, Z.A. de la Vigne aux Loups, 5 Avenue Arago, 91380 Chilly-Mazarin (France)], E-mail: michel.stchakovsky@jobinyvon.fr; Caillaud, C. [HORIBA Jobin-Yvon SAS, Z.A. de la Vigne aux Loups, 5 Avenue Arago, 91380 Chilly-Mazarin (France); Foldyna, M.; Ossikovski, R.; Garcia-Caurel, E. [Laboratoire de Physique des Interfaces et des Couches Minces, Ecole Polytechnique, 91128 Palaiseau (France)

    2008-02-15

    Phase Modulated Spectroscopic Ellipsometry as well as Liquid Crystal Mueller Matrix Polarimetry in reflection and in transmission configurations were used to systematically study five types of anisotropic polymer sheets: polyethylene-terephtalate (PET), polyethylene-naphtalate (PEN), polycarbonate (PC), polypropylene (PP) and triacetylcellulose (TAC). The measurements were performed at different sample azimuths in two ellipsometric configurations giving access to both standard ellipsometric data as well as to the entire Mueller matrix. Biaxial anisotropy, a common characteristic to all polymer types, as well as the in-depth optical properties, inhomogeneity present in the sheets were clearly evidenced. The data were interpreted in terms of a model consisting of a thick substrate (several microns) coated with a simple layer. Both, substrate and layer were anisotropic and characterized by a triplet of principal refractive indexes. The orientation of the principal indexes of the bulk and the layer were different revealing the in-depth inhomogeniety of the samples.

  16. Thermodynamics of anisotropic branes

    CERN Document Server

    Ávila, Daniel; Patiño, Leonardo; Trancanelli, Diego

    2016-01-01

    We study the thermodynamics of flavor D7-branes embedded in an anisotropic black brane solution of type IIB supergravity. The flavor branes undergo a phase transition between a `Minkowski embedding', in which they lie outside of the horizon, and a `black hole embedding', in which they fall into the horizon. This transition depends on two independent dimensionless ratios, which are formed out of the black hole temperature, its anisotropy parameter, and the mass of the flavor degrees of freedom. It happens either at a critical temperature or at a critical anisotropy. A general lesson we learn from this analysis is that the anisotropy, in this particular realization, induces similar effects as the temperature. In particular, increasing the anisotropy bends the branes more and more into the horizon. Moreover, we observe that the transition becomes smoother for higher anisotropies.

  17. Influence of mashed potato dielectric properties and circulating water electric conductivity on radio frequency heating at 27 MHz.

    Science.gov (United States)

    Wang, Jian; Olsen, Robert G; Tang, Juming; Tang, Zhongwei

    2008-01-01

    Experiments and computer simulations were conducted to systematically investigate the influence of mashed potato dielectric properties and circulating water electric conductivity on electromagnetic field distribution, heating rate, and heating pattern in packaged food during radio frequency (RF) heating processes in a 6 kW, 27 MHz laboratory scale RF heating system. Both experimental and simulation results indicated that for the selected food (mashed potato) in this study, the heating rate decreased with an increase of electric conductivity of circulating water and food salt content. Simplified analytical calculations were carried out to verify the simulation results, which further indicated that the electric field distribution in the mashed potato samples was also influenced by their dielectric properties and the electric conductivity of the surrounding circulating water. Knowing the influence of water electric conductivity and mashed potato dielectric properties on the heating rate and heating pattern is helpful in optimizing the radio frequency heating process by properly adjusting these factors. The results demonstrate that computer simulation has the ability to demonstrate influence on RF heat pattern caused by the variation of material physical properties and the potential to aid the improvement on construction and modification of RF heating systems.

  18. Highly conducting poly(methyl methacrylate) / carbon nanotubes composites: Investigation on their thermal, dynamic-mechanical, electrical and dielectric properties

    OpenAIRE

    Logakis, E.; Pandis, Ch.; Pissis, P.; Pionteck, J.; Pötschke, P.

    2011-01-01

    Abstract Nanocomposites of poly(methyl methacrylate) (PMMA) containing various multi-walled carbon nanotubes (MWCNT) contents were prepared using melt mixing. Several techniques were employed to study the influence of the MWCNT addition on the thermal, mechanical, electrical and dielectric properties of the PMMA matrix. The electrical percolation threshold (pc) was found to be 0.5 vol.% by performing AC and DC conductivity measurements. Significantly high conductivity levels (?dc) ...

  19. Interface trap characterization and electrical properties of Au-ZnO nanorod Schottky diodes by conductance and capacitance methods

    OpenAIRE

    Hussain, I.; Soomro, Muhammad Yousuf; Bano, Nargis; Nur, Omer; Willander, Magnus

    2012-01-01

    Schottky diodes with Au/ZnO nanorod (NR)/n-SiC configurations have been fabricated and their interface traps and electrical properties have been investigated by current-voltage (I-V), capacitance-voltage (C-V), capacitance-frequency (C-f), and conductance-frequency (G(p)/omega-omega) measurements. Detailed and systematic analysis of the frequency-dependent capacitance and conductance measurements was performed to extract the information about the interface trap states. The discrepancy between...

  20. Effect of the processing conditions on the mechanical and electrical properties of extruded conductive PP tape and filament

    OpenAIRE

    Silva, Marco Aurélio Pinto; R. S. Martins; Nóbrega, J. M.; Carvalho, Helder; Lanceros-Méndez, S.

    2011-01-01

    Polypropylene (PP) shows a number of desirable properties that make it a versatile material among thermoplastic polymers. Due to its low cost and density, it is an excellent resin for conductive polymer composites (CPCs).[1] CPCs mainly consist on a polymer matrix with incorporated carbonaceous fillers. These multifunctional materials are routinely employed in various commercial applications due to their good electrical conductivity, corrosion resistance, light weight and enhanced mechanical...

  1. Electrochemical properties of mixed conducting (La,M)(CoFe) oxide perovskites (M=3DSr, Ca, and Ba)

    Energy Technology Data Exchange (ETDEWEB)

    Stevenson, J.W.; Armstrong, T.R.; Bates, J.L. [and others

    1996-04-01

    Electrical properties and oxygen permeation properties of solid mixed-conducting electrolytes (La,M)(CoFe) oxide perovskites (M=3DSr, Ca, and Ba) have been characterized. These materials are potentially useful as passive membranes to separate high purity oxygen from air and as the cathode in a fuel cell. Dilatometric linear expansion measurements were performed as a function of temperature and oxygen partial pressure to evaluate the stability.

  2. Review of anisotropic flow correlations in ultrarelativistic heavy-ion collisions

    CERN Document Server

    Zhou, You

    2016-01-01

    Anisotropic flow phenomena is a key probe of the existence of Quark-Gluon Plasma. Several new observable associated with correlations between anisotropic flow harmonics are developed, which are expected to be sensitive to the initial fluctuations and transport properties of the created matter in heavy ion collisions. I review recent developments of correlations of anisotropic flow harmonics. The experimental measurements, together with the comparisons to theoretical model calculations, open up new opportunities of exploring novel QCD dynamics in heavy-ion collisions.

  3. Investigations on electrical conductivity and dielectric properties of Na doped ZnO synthesized from sol gel method

    Energy Technology Data Exchange (ETDEWEB)

    Tabib, Asma; Sdiri, Nasr [Laboratoire de Physico-Chimie des Matériaux Minéraux et leurs Applications, Centre National de Recherches en Sciences des Matériaux, B.P. 95 Hammam-Lif, 2050 (Tunisia); Elhouichet, Habib, E-mail: habib.elhouichet@fst.rnu.tn [Laboratoire de Physico-Chimie des Matériaux Minéraux et leurs Applications, Centre National de Recherches en Sciences des Matériaux, B.P. 95 Hammam-Lif, 2050 (Tunisia); Département de Physique, Faculté des Sciences de Tunis, University Tunis El Manar, Tunis 2092 (Tunisia); Férid, Mokhtar [Laboratoire de Physico-Chimie des Matériaux Minéraux et leurs Applications, Centre National de Recherches en Sciences des Matériaux, B.P. 95 Hammam-Lif, 2050 (Tunisia)

    2015-02-15

    Highlights: • ZnO nanoparticles doped with Na were prepared from sol-gel method. • Electric conductivity and dielectric properties were investigated. • The ZnO conductivity is estimated to be of p-type for critical Na doping of 1.5% at. - Abstract: Na doped ZnO nanoparticles (NPs) were elaborated by sol gel technique. The X-ray diffraction patterns show that the peaks are indexed to the hexagonal structure without any trace of an extra phase. Electric and dielectric properties were investigated using complex impedance spectroscopy. The impedance spectra were analyzed in terms of equivalent circuits involving resistors, capacitors and constant phase elements (CPE). The contribution of grain boundary resistance to the total resistance of the system is remarkable. The AC conductivity increases with temperature following the Arrhenius law, with single apparent activation energy for conduction process. The frequency dependence of the electric conductivity follows a simple power law behavior, in according to relation σ{sub AC}(ω) = σ(0) + A ω{sup s}, where s is smaller than 1. The analysis of dc conductivity indicates that the conduction is ionic in nature. The study of its variation, at fixed temperature, with Na content shows sharp decrease which is explained by the formation of Na{sub Zn} acceptor. It was found that the dc conductivity reaches its minimum value for critical Na concentration of 1.5% at which the conductivity is estimated to be of p-type. Impedance and modulus study reveals the temperature dependent non-Debye type relaxation phenomenon. Dielectric studies revealed a promising dielectric properties (relatively high ε′ at low frequencies and low loss at high frequencies). In the low-frequency region, the values of M′ tends to zero suggesting negligible or absent electrode polarization phenomenon. The frequency dependent maxima in the imaginary modulus are found to obey to Arrhenius law.

  4. Shielding properties of conductive plastic housings loaded with printed circuit boards

    OpenAIRE

    Lozano Guerrero, Antonio José; Robinson, Martin Paul; Díaz Morcillo, Alejandro Benedicto; Monzó Cabrera, Juan; Clemente Fernández, Francisco Javier; Balbastre Tejedor, Juan Vicente

    2012-01-01

    In this paper the benefits of using conductive plastics in enclosure configurations have been evaluated taking into account the influence of internal printed circuit boards. Conductive plastic enclosures are a very attractive alternative to traditional metallic enclosures to protect electronic systems against electromagnetic interference. A wide range of conductivities can be obtained with these materials to satisfy a required design. An equivalent model for the printed circuit board has b...

  5. Anisotropic Inflation with General Potentials

    CERN Document Server

    Shi, Jiaming; Qiu, Taotao

    2015-01-01

    Anomalies in recent observational data indicate that there might be some "anisotropic hair" generated in an inflation period. To obtain general information about the effects of this anisotropic hair to inflation models, we studied anisotropic inflation models that involve one vector and one scalar using several types of potentials. We determined the general relationship between the degree of anisotropy and the fraction of the vector and scalar fields, and concluded that the anisotropies behave independently of the potentials. We also generalized our study to the case of multi-directional anisotropies.

  6. ARTc: Anisotropic reflectivity and transmissivity calculator

    Science.gov (United States)

    Malehmir, Reza; Schmitt, Douglas R.

    2016-08-01

    While seismic anisotropy is known to exist within the Earth's crust and even deeper, isotropic or even highly symmetric elastic anisotropic assumptions for seismic imaging is an over-simplification which may create artifacts in the image, target mis-positioning and hence flawed interpretation. In this paper, we have developed the ARTc algorithm to solve reflectivity, transmissivity as well as velocity and particle polarization in the most general case of elastic anisotropy. This algorithm is able to provide reflectivity solution from the boundary between two anisotropic slabs with arbitrary symmetry and orientation up to triclinic. To achieve this, the algorithm solves full elastic wave equation to find polarization, slowness and amplitude of all six wave-modes generated from the incident plane-wave and welded interface. In the first step to calculate the reflectivity, the algorithm solves properties of the incident wave such as particle polarization and slowness. After calculation of the direction of generated waves, the algorithm solves their respective slowness and particle polarization. With this information, the algorithm then solves a system of equations incorporating the imposed boundary conditions to arrive at the scattered wave amplitudes, and thus reflectivity and transmissivity. Reflectivity results as well as slowness and polarization are then tested in complex computational anisotropic models to ensure their accuracy and reliability. ARTc is coded in MATLAB ® and bundled with an interactive GUI and bash script to run on single or multi-processor computers.

  7. Pulsed EM Field Response of a Thin, High-Contrast, Finely Layered Structure With Dielectric and Conductive Properties

    NARCIS (Netherlands)

    De Hoop, A.T.; Jiang, L.

    2009-01-01

    The response of a thin, high-contrast, finely layered structure with dielectric and conductive properties to an incident, pulsed, electromagnetic field is investigated theoretically. The fine layering causes the standard spatial discretization techniques to solve Maxwell's equations numerically to b

  8. Optimization of electrical conduction and passivity properties of stainless steels used for PEM fuel cell bipolar plates

    International Nuclear Information System (INIS)

    Among the new technologies for energy for sustainable development, PEMFC (proton exchange membrane fuel cells) offer seducing aspects. However, in order to make this technology fit large scale application requirements, it has to comply with stringent cost, performance, and durability criteria. In such a frame, the goal of this work was to optimize electrical conduction properties and passivity of stainless steels for the conception of PEMFC bipolar plates, used instead of graphite, the reference material. This work presents the possible ways of performance loss when using stainless steels and some methods to solve this problem. Passive film properties were studied, as well as their modifications by low cost industrial surface treatments, without deposition. Ex situ characterizations of corrosion resistance and electrical conduction were performed. Electrochemical impedance spectroscopy, water analysis, surface analysis by microscopy and photoelectron spectroscopy allowed to study the impact of ageing on two alloys in different states, and several conditions representative of an exposure to PEMFC media. Correlations between semi-conductivity properties, composition, and structure of passive layers were considered, but not leading to clear identification of all parameters responsible for electrical conduction and passivity. The plate industrial state is not convenient for direct use in fuel cell to comply with durability and performance requirements. A surface modification studied improves widely electrical conduction at initial state. The performance is degraded with ageing, but maintaining a level higher than the initial industrial state. This treatment increases also corrosion resistance, particularly on the anode side. (author)

  9. Anisotropic Tomography of Portugal (West Iberia) from ambient seismic noise

    Science.gov (United States)

    Silveira, Graça; Stutzmann, Éléonore; Schimmel, Martin; Dias, Nuno; Kiselev, Sergey; Custódio, Susana; Dundar, Suleyman

    2016-04-01

    Located on the western Iberian Peninsula, Portugal constitutes a key area for accretionary terrane and basin research, providing the best opportunity to probe a crustal formation shaped by the Paleozoic Variscan orogeny followed by the Mesozoic-Cenozoic extensions. The geology of Portugal documents a protracted history from Paleozoic basement formation to the Mesozoic opening of the North Atlantic Ocean. The inheritance of such complex geologic history is yet to be fully determined, playing an important role in the current geodynamic framework influencing, for example, the observed regional seismicity. The physical properties of its crust have largely remained undetermined so far, with unevenly distributed knowledge on the spatial distributions of a detailed crustal structure. Also, the deep seismic reflection/refraction surveys conducted in Western Iberia do not provide a clear picture of the regional characteristics of the crust. Using Seismic Broad Band observations from a dense temporary deployment, conducted between 2010 and 2012 in the scope of the WILAS project and covering the entire Portuguese mainland, we computed a 3D anisotropic model from ambient seismic noise. The dispersion measurements were computed for each station pair using empirical Green's functions generated by cross-correlating one-day-length seismic ambient-noise records. After dispersion analysis, group velocity measurements were regionalized to obtain 2D anisotropic tomographic images. Afterwards, the dispersion curves, extracted from each cell of the 2D group velocity maps, were inverted as a function of depth to obtain a 3D shear wave anisotropic model, using a bayesian approach. A simulated annealing method, in which the number of splines that describes the model, is adapted within the inversion. The models are jointly interpreted with the models gathered from Ps receiver functions as well as with the regional seismicity, enabling to obtain a more detailed picture of the crustal

  10. Anisotropic surface roughness enhances the bending response of ionic polymer-metal composite (IPMC) artificial muscles

    Science.gov (United States)

    Stoimenov, Boyko L.; Rossiter, Jonathan M.; Mukai, Toshiharu

    2007-01-01

    Demands from the fields of bio-medical engineering and biologically-inspired robotics motivate a growing interest in actuators with properties similar to biological muscle, including ionic polymer-metal composites (IPMC), the focus of this study. IPMC actuators consist of an ion-conductive polymer membrane, coated with thin metal electrodes on both sides and bend when voltage is applied. Some of the advantages of IPMC actuators are their softness, lack of moving parts, easy miniaturization, light weight and low actuation voltage. When used in bio-mimetic robotic applications, such as a snake-like swimming robot, locomotion speed can be improved by increasing the bending amplitude. However, it cannot be improved much by increasing the driving voltage, because of water electrolysis. To enhance the bending response of IPMCs we created a "preferred" bending direction by anisotropic surface modification. Introduction of anisotropic roughness with grooves across the length of the actuator improved the bending response by a factor of 2.1. Artificially introduced cracks on the electrodes in direction, in which natural cracks form by bending, improved bending response by a factor of 1.6. Anisotropic surface modification is an effective method to enhance the bending response of IPMC actuators and does not compromise their rigidity under loads perpendicular to the bending plane.

  11. Dislocation structures and electrical conduction properties of low angle tilt grain boundaries in LiNbO3

    Science.gov (United States)

    Furushima, Yuho; Nakamura, Atsutomo; Tochigi, Eita; Ikuhara, Yuichi; Toyoura, Kazuaki; Matsunaga, Katsuyuki

    2016-10-01

    Dislocations in crystalline materials constitute unique, atomic-scale, one-dimensional structure and have a potential to induce peculiar physical properties that are not found in the bulk. In this study, we fabricated LiNbO3 bicrystals with low angle tilt grain boundaries and investigated the relationship between the atomic structure of the boundary dislocations and their electrical conduction properties. Observations by using transmission electron microscopy revealed that dislocation structures at the (0001) low angle tilt grain boundaries depend on the tilt angle of the boundaries. Specifically, the characteristic dislocation structures with a large Burgers vector were formed in the boundary with the tilt angle of 2°. It is noteworthy that only the grain boundary of 2° exhibits distinct electrical conductivity after reduction treatment, although LiNbO3 is originally insulating. This unique electrical conductivity is suggested to be due to the characteristic dislocation structures with a large Burgers vector.

  12. Electric double layer of anisotropic dielectric colloids under electric fields

    Science.gov (United States)

    Han, M.; Wu, H.; Luijten, E.

    2016-07-01

    Anisotropic colloidal particles constitute an important class of building blocks for self-assembly directed by electrical fields. The aggregation of these building blocks is driven by induced dipole moments, which arise from an interplay between dielectric effects and the electric double layer. For particles that are anisotropic in shape, charge distribution, and dielectric properties, calculation of the electric double layer requires coupling of the ionic dynamics to a Poisson solver. We apply recently proposed methods to solve this problem for experimentally employed colloids in static and time-dependent electric fields. This allows us to predict the effects of field strength and frequency on the colloidal properties.

  13. Studies on the Dielectric and Transport Properties of PEO/Chitosan Proton Conducting Polymer Electrolyte

    Institute of Scientific and Technical Information of China (English)

    M.F.Z.Abdul; Kadir; A.K.Arof

    2007-01-01

    1 Results The effect of ammonium nitrate (NH4NO3) content in 40 wt.% PEO and 60 wt.% chitosan blend has been analyzed in this study.The sample containing 40 wt.% NH4NO3 exhibited the highest room temperature conductivity.In order to ascertain that water does not influence the conductivity,the samples were dried in a dessicator and the conductivity determined daily until it shows a constant value.Results are as shown in Fig.1.Samples containing other salt concentrations were also kept in the dessicator f...

  14. Properties of a conductive cellular chloride pathway in the skin of the toad (Bufo bufo)

    DEFF Research Database (Denmark)

    Larsen, Erik Hviid; Kristensen, P

    1978-01-01

    of the steady-state conductance and the steady-state chloride current reveal that the chloride pathway has maximum conductance for V approximately -80 mV (outside of the skin being negative) and approaches a non-conducting safe for V greater than 0 mV. This strong outward going rectification is a steady......-compartment model indicate that the strong steady-state chloride current rectification cannot be obtained if only the intracellular chloride concentration and the membrane potentials are allowed to vary ("Goldman-rectification"). It is suggested, therefore, that the premeability of the chloride pathway varies...

  15. Photon states in anisotropic media

    Indian Academy of Sciences (India)

    Deepak Kumar

    2002-08-01

    Quantum aspects of optical polarization are discussed for waves traveling in anisotropic dielectric media with a view to relate the dynamics of polarization with that of photon spin and its manipulation by classical polarizers.

  16. Gradient expansion for anisotropic hydrodynamics

    CERN Document Server

    Florkowski, Wojciech; Spaliński, Michał

    2016-01-01

    We compute the gradient expansion for anisotropic hydrodynamics. The results are compared with the corresponding expansion of the underlying kinetic-theory model with the collision term treated in the relaxation time approximation. We find that a recent formulation of anisotropic hydrodynamics based on an anisotropic matching principle yields the first three terms of the gradient expansion in agreement with those obtained for the kinetic theory. This gives further support for this particular hydrodynamic model as a good approximation of the kinetic-theory approach. We further find that the gradient expansion of anisotropic hydrodynamics is an asymptotic series, and the singularities of the analytic continuation of its Borel transform indicate the presence of non-hydrodynamic modes.

  17. Properties of unirradiated fuel element graphites H-451 and SO818. [Bulk density, tensile properties, thermal expansion, thermal conductivity

    Energy Technology Data Exchange (ETDEWEB)

    Engle, G.B.; Johnson, W.R.

    1976-10-08

    Nuclear graphites H-451, lot 440 (Great Lakes Carbon Corporation (GLCC)), and SO818 (Airco Speer Division, Air Reduction Corporation (AS)) are described, and physical, mechanical, and chemical property data are presented for the graphites in the unirradiated state. A summary of the mean values of the property data and of data on TS-1240 and H-451, lot 426, is tabulated. A direct comparison of H-451, lot 426, chosen for Fort St. Vrain (FSV) fuel reload production, TS-1240, and SO818 may be made from the table. (auth)

  18. Explicit analytical solutions of the anisotropic Brinkman model for the natural convection in porous media (Ⅱ)

    Institute of Scientific and Technical Information of China (English)

    CAI; Ruixian; GOU; Chenhua; ZHANG; Na

    2005-01-01

    Some algebraically explicit analytical solutions are derived for the anisotropic Brinkman model―an improved Darcy model―describing the natural convection in porous media. Besides their important theoretical meaning (for example, in analyzing the non-Darcy and anisotropic effects on the convection), such analytical solutions can be the benchmark solutions that can promote the development of computational heat and mass transfer. Some solutions considering the anisotropic effect of permeability have been given previously by the authors, and this paper gives solutions including the anisotropic effect of thermal conductivity and the effect of heat sources.

  19. Effect of methyl red dye on dielectric and conductivity properties of PEO/CdCl2 electrolytes

    Science.gov (United States)

    Kamath, Archana; Devendrappa, H.

    2016-05-01

    In this report the conductivity and dielectric properties of polyethylene oxide-cadmium chloride (PEO/CdCl2) polymer electrolyte films doped with an azo dye methyl red (MR) are discussed. The films were prepared by solution casting technique at different concentrations of the dye in PEO/CdCl2 electrolyte. The thermal behavior, chemical interaction of the dye with the electrolyte and surface morphology were studied by differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) respectively. The conductivity and dielectric properties were measured as a function of composition and temperature using complex impedance spectroscopy. The temperature dependent electrical conductivity of the films exhibited Arrhenius type behavior. Conductivity and dielectric results also signify the enhancement in the amorphous phase of the polymer electrolyte dye systems. The value of highest conductivity observed is 1.21x10-4 at 343K and the conductivity of the film was enhanced by a three orders of magnitude.

  20. Magnetic properties and critical behavior of the conductivity near the M-I transition

    Energy Technology Data Exchange (ETDEWEB)

    Sarachik, M.

    1993-04-01

    Results of studies of resistivity, magnetoresistance, and Hall coefficient of Si:B are reported. Experiments in the insulating phase (hopping conduction) were done on various materials (in-type CdSe, doped Si, GaAs, etc.)

  1. Conductivity and Discharge Guiding Properties of Mid-IR Laser Filaments

    CERN Document Server

    Mongin, Denis; Ališauskas, Skirmantas; Pugzlys, Audrius; Schubert, Elise; kasparian, jerome; Wolf, Jean Pierre; Baltuska, Andrius

    2016-01-01

    The electric conductivity, HV discharge triggering and guiding capabilities of filaments at 3.9 micrometer in air are investigated in the perspective of lightning control applications, and compared to near-IR filaments in identical conditions

  2. Properties and processing by extrusion of electrically conductive multilayer filaments comprising polymer composites

    OpenAIRE

    R. S. Martins; Gonçalves, Renato Ferreira; Azevedo, Tiago; Nóbrega, J. M.; Carvalho, Helder; Lanceros-Méndez, S.; Rocha, J. G.

    2013-01-01

    This work describes the production and characterization of three-layer piezoelectric filaments using two different electrically conductive polymers. The filaments were produced in a filament extrusion line, equipped with a coextrusion die that enabled a coaxial arrangement for a three-layer filament. For the inner and outer layers two different electrically conductive compounds were used, and the middle layer was made of the electroactive polymer PVDF. The produced filament can be used as a p...

  3. Mechanical identification of layer-specific properties of mouse carotid arteries using 3D-DIC and a hyperelastic anisotropic constitutive model

    CERN Document Server

    Badel, Pierre; Lessner, Susan; Sutton, Michael A; 10.1080/10255842.2011.586945

    2012-01-01

    The role of mechanics is known to be of primary order in many arterial diseases; however, determining mechanical properties of arteries remains a challenge. This paper discusses the identifiability of the passive mechanical properties of a mouse carotid artery, taking into account the orientation of collagen fibres in the medial and adventitial layers. On the basis of 3D digital image correlation measurements of the surface strain during an inflation/extension test, an inverse identification method is set up. It involves a 3D finite element mechanical model of the mechanical test and an optimisation algorithm. A two-layer constitutive model derived from the Holzapfel model is used, with five and then seven parameters. The five-parameter model is successfully identified providing layer-specific fibre angles. The seven-parameter model is over parameterised, yet it is shown that additional data from a simple tension test make the identification of refined layer-specific data reliable.

  4. A micro-mechanical analysis of thermo-elastic properties and local residual stresses in ductile iron based on a new anisotropic model for the graphite nodules

    Science.gov (United States)

    Andriollo, Tito; Thorborg, Jesper; Tiedje, Niels; Hattel, Jesper

    2016-06-01

    In this paper, the thermo-elastic behavior of the graphite nodules contained in ductile iron is derived on the basis of recent transmission electron microscopy investigations of their real internal structure. The proposed model is initially validated by performing a finite element homogenization analysis to verify its consistency with the room-temperature elastic properties of ductile iron measured at the macro scale. Subsequently, it is used to investigate the formation of local residual stresses around the graphite particles by simulating the manufacturing process of a typical ferritic ductile iron grade, and the results are compared with preliminary measurements using synchrotron x-rays. Finally, the obtained accurate description of the stress & strain field at the micro scale is used to shed light on common failure modes reported for the nodules and on some peculiar properties observed in ductile iron at both micro and macro scale.

  5. Recovery of microstructure properties: random variability of soil solid thermal conductivity

    Directory of Open Access Journals (Sweden)

    Stefaniuk Damian

    2016-03-01

    Full Text Available In this work, the complex microstructure of the soil solid, at the microscale, is modeled by prescribing the spatial variability of thermal conductivity coefficient to distinct soil separates. We postulate that the variation of thermal conductivity coefficient of each soil separate can be characterized by some probability density functions: fCl(λ, fSi(λ, fSa(λ, for clay, silt and sand separates, respectively. The main goal of the work is to recover/identify these functions with the use of back analysis based on both computational micromechanics and simulated annealing approaches. In other words, the following inverse problem is solved: given the measured overall thermal conductivities of composite soil find the probability density function f(λ for each soil separate. For that purpose, measured thermal conductivities of 32 soils (of various fabric compositions at saturation are used. Recovered functions f(λ are then applied to the computational micromechanics approach; predicted conductivities are in a good agreement with laboratory results.

  6. Finite element equations and numerical simulation of elastic wave propagation in two-phase anisotropic media

    Institute of Scientific and Technical Information of China (English)

    刘洋; 魏修成

    2003-01-01

    Based on Biot theory of two-phase anisotropic media and Hamilton theory about dynamic problem, finite elementequations of elastic wave propagation in two-phase anisotropic media are derived in this paper. Numerical solutionof finite element equations is given. Finally, properties of elastic wave propagation are observed and analyzedthrough FEM modeling.

  7. On Radiative Fluids in Anisotropic Spacetimes

    CERN Document Server

    Shogin, Dmitry

    2016-01-01

    We apply the second-order Israel-Stewart theory of relativistic fluid- and thermodynamics to a physically realistic model of a radiative fluid in a simple anisotropic cosmological background. We investigate the asymptotic future of the resulting cosmological model and review the role of the dissipative phenomena in the early Universe. We demonstrate that the transport properties of the fluid alone, if described appropriately, do not explain the presently observed accelerated expansion of the Universe. Also, we show that, in constrast to the mathematical fluid models widely used before, the radiative fluid does approach local thermal equilibrium at late times, although very slowly, due to the cosmological expansion.

  8. A transitioning universe with anisotropic dark energy

    Science.gov (United States)

    Yadav, Anil Kumar

    2016-08-01

    In this paper, we present a model of transitioning universe with minimal interaction between perfect fluid and anisotropic dark energy in Bianchi I space-time. The two sources are assumed to minimally interacted and therefore their energy momentum tensors are conserved separately. The explicit expression for average scale factor are considered in hybrid form that gives time varying deceleration parameter which describes both the early and late time physical features of universe. We also discuss the physical and geometrical properties of the model derived in this paper. The solution is interesting physically as it explain accelerating universe as well as singularity free universe.

  9. A transitioning universe with anisotropic dark energy

    CERN Document Server

    Yadav, Anil Kumar

    2016-01-01

    In this paper, we present a model of transitioning universe with minimal interaction between perfect fluid and anisotropic dark energy in Bianchi I space-time. The two sources are assumed to minimally interacted and therefore their energy momentum tensors are conserved separately. The explicit expression for average scale factor are considered in hybrid form that gives time varying deceleration parameter which describes both the early and late time physical features of universe. We also discuss the physical and geometrical properties of the model derived in this paper. The solution is interesting physically as it explain accelerating universe as well as singularity free universe.

  10. Rheological properties and thermal conductivity of AlN-poly(propylene glycol) suspensions

    Science.gov (United States)

    Wozniak, Maciej; Rutkowski, Pawel; Kata, Dariusz

    2016-01-01

    Nanofluids have recently attracted researches' attention as a new generation of heat-transferring fluids used in heat exchangers and for energy storage. Also aluminium nitride is commonly known for its considerable heat conductivity, as high as 320 W/(m K). Because of that, the compound might be a preferable dispersed phase of heat-transferring fluids. This presented studies are focused on nano-AlN-poly(propylene glycol) dispersions which can be applied as potential cooling fluids. The rheological response of the suspensions on shearing and their thermal conductivity in the function of solids concentration and temperature were measured and discussed. The most desired result of the studies is to produce dispersions with Newtonian-like flow at increased temperature and at higher shear rate. All the aforementioned parameters conjugated with significant thermal conductivity of such nanofluids could predispose them to be used as effective cooling media.

  11. Studies of YBa2Cu3O6+x degradation and surface conductivity properties by Scanning Spreading Resistance Microscopy

    International Nuclear Information System (INIS)

    Local surface conductivity properties and surface degradation of c-axis oriented YBa2Cu3O6+x (YBCO) thin films were studied by Scanning Spreading Resistance Microscopy (SSRM). For the surface degradation studies, the YBCO surface was cleaned by ion beam etching and the SSRM surface conductivity map has been subsequently repeatedly measured over several hours in air and pure nitrogen. Average surface conductivity of the scanned area was gradually decreasing over time in both cases, faster in air. This was explained by oxygen out-diffusion in both cases and chemical reactions with water vapor in air. The obtained surface conductivity images also revealed its high inhomogenity on micrometer and nanometer scale with numerous regions of highly enhanced conductivity compared to the surroundings. Furthermore, it has been shown that the size of these conductive regions considerably depends on the applied voltage. We propose that such inhomogeneous surface conductivity is most likely caused by varying thickness of degraded YBCO surface layer as well as varying oxygen concentration (x parameter) within this layer, what was confirmed by scanning Auger electron microscopy (SAM). In our opinion the presented findings might be important for analysis of current-voltage and differential characteristics measured on classical planar junctions on YBCO as well as other perovskites.

  12. Effect of epoxidation level on thermal properties and ionic conductivity of epoxidized natural rubber solid polymer nanocomposite electrolytes

    Energy Technology Data Exchange (ETDEWEB)

    Harun, Fatin; Chan, Chin Han; Winie, Tan [Faculty of Applied Sciences, UniversitiTeknologi MARA (UiTM), Shah Alam, 40450 Selangor Darul Ehsan (Malaysia); Sim, Lai Har; Zainal, Nurul Fatahah Asyqin [Center of Foundation Studies, PuncakAlam Campus, UniversitiTeknologi MARA, 40430 Selangor Darul Ehsan (Malaysia)

    2015-08-28

    Effect of epoxide content on the thermal and conductivity properties of epoxidized natural rubber (ENR) solid polymer nanocomposite electrolytes was investigated. Commercial available epoxidized natural rubber having 25 (ENR25) and 50 mole% (ENR50) epoxide, respectively were incorporated with lithium perchlorate (LiClO{sub 4}) salt and titanium dioxide (TiO{sub 2}) nanofiller via solution casting method. The solid polymer nanocomposite electrolytes were characterized by differential scanning calorimetry (DSC) and impedance spectroscopy (IS) for their thermal properties and conductivity, respectively. It was evident that introduction of LiClO{sub 4} causes a greater increase in glass transition temperature (T{sub g}) and ionic conductivity of ENR50 as compared to ENR25. Upon addition of TiO{sub 2} in ENR/LiClO{sub 4} system, a remarkable T{sub g} elevation was observed for both ENRs where ENR50 reveals a more pronounced changes. It is interesting to note that they exhibit different phenomenon in ionic conductivity with TiO{sub 2} loading where ENR25 shows enhancement of conductivity while ENR50 shows declination.

  13. Effect of helium gas pressure on dc conduction mechanism and EMI shielding properties of nanocrystalline carbon thin films

    International Nuclear Information System (INIS)

    This paper reports the effect of helium partial pressures ∼1.2 × 10−5 (base pressure), 1.4 × 10−4, 8.6 × 10−3 and 0.1 mbar on the variable range hopping conduction in nanocrystalline carbon thin films deposited by filtered cathodic jet carbon arc technique. High resolution transmission electron microscopy studies suggest the random distribution of nanocrystallites (∼3–7 nm) in the amorphous matrix. The DC conduction behavior of the deposited nanocrystalline films has been studied in the light of Mott's variable range hopping (VRH) model and found to obey three dimensional VRH conduction. The randomly distributed nanocrystallites in amorphous matrix may lead to change in the distribution of density of states near Fermi level and hence, the conduction behavior. The enhanced electrical conductivity of the deposited films due to the helium environment makes them suitable for electromagnetic interference shielding applications. The sample deposited at a helium partial pressure of 0.1 mbar has a value of shielding effectiveness ∼7.84 dB at 18 GHz frequency. - Highlights: • Nanocrystalline carbon thin films (NCTF) has been deposited by FCJCA technique. • Effect of helium gas pressure has been studied on the properties of NCTF. • Investigation of EMI shielding properties of NCTF has been carried out

  14. Effect of helium gas pressure on dc conduction mechanism and EMI shielding properties of nanocrystalline carbon thin films

    Energy Technology Data Exchange (ETDEWEB)

    Rawal, Ishpal, E-mail: rawalishpal@gmail.com [Department of Physics, Kirori Mal College, University of Delhi, Delhi 110007 (India); Panwar, O.S., E-mail: ospanwar@mail.nplindia.ernet.in [Polymorphic Carbon Thin Films Group, Physics of Energy Harvesting Division, CSIR-National Physical Laboratory, Dr. K. S. Krishnan Road, New Delhi 110012 (India); Tripathi, R.K. [Polymorphic Carbon Thin Films Group, Physics of Energy Harvesting Division, CSIR-National Physical Laboratory, Dr. K. S. Krishnan Road, New Delhi 110012 (India); Singh, Avanish Pratap; Dhawan, S.K. [Polymeric and Soft Materials Group, Physics Engineering of Carbon, CSIR-National Physical Laboratory, Dr. K. S. Krishnan Road, New Delhi 110012 (India); Srivastava, A.K. [Electron and Ion Microscopy, Sophisticated and Analytical Instruments, CSIR-National Physical Laboratory, Dr. K. S. Krishnan Road, New Delhi 110012 (India)

    2015-05-05

    This paper reports the effect of helium partial pressures ∼1.2 × 10{sup −5} (base pressure), 1.4 × 10{sup −4}, 8.6 × 10{sup −3} and 0.1 mbar on the variable range hopping conduction in nanocrystalline carbon thin films deposited by filtered cathodic jet carbon arc technique. High resolution transmission electron microscopy studies suggest the random distribution of nanocrystallites (∼3–7 nm) in the amorphous matrix. The DC conduction behavior of the deposited nanocrystalline films has been studied in the light of Mott's variable range hopping (VRH) model and found to obey three dimensional VRH conduction. The randomly distributed nanocrystallites in amorphous matrix may lead to change in the distribution of density of states near Fermi level and hence, the conduction behavior. The enhanced electrical conductivity of the deposited films due to the helium environment makes them suitable for electromagnetic interference shielding applications. The sample deposited at a helium partial pressure of 0.1 mbar has a value of shielding effectiveness ∼7.84 dB at 18 GHz frequency. - Highlights: • Nanocrystalline carbon thin films (NCTF) has been deposited by FCJCA technique. • Effect of helium gas pressure has been studied on the properties of NCTF. • Investigation of EMI shielding properties of NCTF has been carried out.

  15. Effect of epoxidation level on thermal properties and ionic conductivity of epoxidized natural rubber solid polymer nanocomposite electrolytes

    International Nuclear Information System (INIS)

    Effect of epoxide content on the thermal and conductivity properties of epoxidized natural rubber (ENR) solid polymer nanocomposite electrolytes was investigated. Commercial available epoxidized natural rubber having 25 (ENR25) and 50 mole% (ENR50) epoxide, respectively were incorporated with lithium perchlorate (LiClO4) salt and titanium dioxide (TiO2) nanofiller via solution casting method. The solid polymer nanocomposite electrolytes were characterized by differential scanning calorimetry (DSC) and impedance spectroscopy (IS) for their thermal properties and conductivity, respectively. It was evident that introduction of LiClO4 causes a greater increase in glass transition temperature (Tg) and ionic conductivity of ENR50 as compared to ENR25. Upon addition of TiO2 in ENR/LiClO4 system, a remarkable Tg elevation was observed for both ENRs where ENR50 reveals a more pronounced changes. It is interesting to note that they exhibit different phenomenon in ionic conductivity with TiO2 loading where ENR25 shows enhancement of conductivity while ENR50 shows declination

  16. A micro-mechanical analysis of thermo-elastic properties and local residual stresses in ductile iron based on a new anisotropic model for the graphite nodules

    DEFF Research Database (Denmark)

    Andriollo, Tito; Thorborg, Jesper; Tiedje, Niels Skat;

    2016-01-01

    analysis to verify its consistency with the room-temperature elastic properties of ductile iron measured at the macro scale. Subsequently, it is used to investigate the formation of local residual stresses around the graphite particles by simulating the manufacturing process of a typical ferritic ductile......In this paper, the thermo-elastic behavior of the graphite nodules contained in ductile iron is derived on the basis of recent transmission electron microscopy investigations of their real internal structure. The proposed model is initially validated by performing a finite element homogenization...

  17. Electrically Anisotropic Layered Perovskite Single Crystal

    KAUST Repository

    Li, Ting-You

    2016-04-01

    Organic-inorganic hybrid perovskites (OIHPs), which are promising materials for electronic and optoelectronic applications (1-10), have made into layered organic-inorganic hybrid perovskites (LOIHPs). These LOIHPs have been applied to thin-film transistors, solar cells and tunable wavelength phosphors (11-18). It is known that devices fabricated with single crystal exhibit the superior performance, which makes the growth of large-sized single crystals critical for future device applications (19-23). However, the difficulty in growing large-sized LOIHPs single crystal with superior electrical properties limits their practical applications. Here, we report a method to grow the centimeter-scaled LOIHP single crystal of [(HOC2H4NH3)2PbI4], demonstrating the potentials in mass production. After that, we reveal anisotropic electrical and optoelectronic properties which proved the carrier propagating along inorganic framework. The carrier mobility of in-inorganic-plane (in-plane) devices shows the average value of 45 cm2 V–1 s–1 which is about 100 times greater than the record of LOIHP devices (15), showing the importance of single crystal in device application. Moreover, the LOIHP single crystals show its ultra-short carrier lifetime of 42.7 ps and photoluminescence quantum efficiency (PLQE) of 25.4 %. We expect this report to be a start of LOIHPs for advanced applications in which the anisotropic properties are needed (24-25), and meets the demand of high-speed applications and fast-response applications.

  18. Excellent thermal conductivity and dielectric properties of polyimide composites filled with silica coated self-passivated aluminum fibers and nanoparticles

    Science.gov (United States)

    Zhou, Yongcun; Bai, Yuanyuan; Yu, Ke; Kang, Yan; Wang, Hong

    2013-06-01

    A polymer based composite was prepared by using modified aluminum fibers and aluminum nanoparticles as fillers in polyimide matrix that resulted in the high thermal conductivity and low relative permittivity. It was found that silica coated aluminum fibers with the multilayer coating structures can significantly reduce the relative permittivity (about 19.6 at 1 MHz) of the composite while keeping lower dielectric loss (0.024 at 1 MHz). The thermal conductivity of composites was significantly increased to 15.2 W/m K. This work shows a useful way to choose proper modifier fillers to improve the composite properties for electronic packaging composite materials.

  19. Dynamic properties of silica aerogels as deduced from specific-heat and thermal-conductivity measurements

    DEFF Research Database (Denmark)

    Bernasconi, A.; Sleator, T.; Posselt, D.;

    1992-01-01

    The specific heat C(p) and the thermal conductivity lambda of a series of base-catalyzed silica aerogels have been measured at temperatures between 0.05 and 20 K. The results confirm that the different length-scale regions observed in the aerogel structure are reflected in the dynamic behavior...

  20. Conductivity properties of proton transfer and influence of temperature on it in hydrogen-bonded systems

    Institute of Scientific and Technical Information of China (English)

    PANG Xiao-feng; YU Jia-feng

    2004-01-01

    We study and calculate the mobility and conductivity of proton transfer and influence of temperature on it by pang's dynamic model in hydrogen bonded systems, which coincide with experiments. We further study the mechanism of magnetization of ciguid water in the basis of this model.

  1. Effect of ageing treatment on wear properties and electrical conductivity of Cu–Cr–Zr alloy

    Indian Academy of Sciences (India)

    Ibrahim Sağlam; Dursun Özyürek; Kerim Çetinkaya

    2011-12-01

    In this study, the effect of ageing processes on the wear behaviour and electrical conductivity was investigated. Prior to solid solution heat treatment at 920°C and ageing at 470°C, 500°C and 530°C for 1 h, 2 h and 3 h, respectively, the prepared samples were homogenized at 920°C for 1 h. After the ageing processes, all samples were characterized in terms of electrical conductivity, scanning electron microscope (with energy dispersive X-ray spectrum (EDS)) and hardness (HV5). In wear tests, pin-on-disc type standard wearing unit was used. As a result, starting from 1 h aged specimens, orderly increase of electrical conductivity was defined. From EDS analyses it was observed that Cr rate increases as precipitates grow. With increase of Cr rate there was also a defined rise of electrical conductivity. From the wear tests, it was observed that the least wear loss was in Cu–Cr–Zr alloy aged at 500°C for 2 h and the most wear loss was in specimens aged at 530°C for 2 h. Furthermore, it was observed that the friction coefficient values resulting from wear rate were overlapped with hardness results and there is a decrease tendency of friction coefficient as wear distance increases.

  2. Effect of interfacial treatment on the thermal properties of thermal conductive plastics

    Directory of Open Access Journals (Sweden)

    2007-09-01

    Full Text Available In this paper, ZnO, which is processed by different surface treatment approaches, is blended together with polypropylene to produce thermal conductive polymer composites. The composites are analyzed by Fourier transform infrared (FTIR spectroscopy and scanning electron microscopy (SEM to investigate the surface modification of filler, their distribution in the matrix and the condition of two-phase interface. Optimized content of filler surface modifier is investigated as well. The results showed that using low-molecular coupling agent produces positive effect to improve the interface adhesion between filler and matrix, and the thermal conductivity of the composite as well. Macro-molecular coupling agent can strongly improve two-phase interface, but it is not beneficial at obtaining a high thermal conductivity. The blend of ZnO without modification and polypropylene has many defects in the two-phase interface, and the thermal conductivity of the composite is between those of composites produced by previous two approaches. The surface treatment of the filler also allowed producing the composites with lower coefficient of thermal expansion (CTE. As for the content of low-molecular coupling agent, it obtains the best effect at 1.5 wt%.

  3. Effect of thermomechanical treatment on mechanical properties and electrical conductivity of a CuCrZr alloy

    Indian Academy of Sciences (India)

    G Durashevich; V Cvetkovski; V Jovanovich

    2002-02-01

    The CuCrZr alloy undergoes processes of precipitation during ageing. Besides precipitation hardening the strength is affected by cold deformation which is performed before and after ageing. The cold deformation (1) before ageing accelerates the process of strength hardening, since it induces higher rate of precipitation from the saturated -solid solution. Cold deformation (2) after ageing primarily affects the alloy strength. In this paper the results of the effect of thermomechanical treatment on mechanical properties and electrical conductivity of a CuCrZr alloy are presented. The aim of the paper was to evaluate the most suitable combination of thermomechanical treatment and alloy properties.

  4. Synthesis of rock-salt type lithium borohydride and its peculiar Li+ ion conduction properties

    Directory of Open Access Journals (Sweden)

    R. Miyazaki

    2014-05-01

    Full Text Available The high energy density and excellent cycle performance of lithium ion batteries makes them superior to all other secondary batteries and explains why they are widely used in portable devices. However, because organic liquid electrolytes have a higher operating voltage than aqueous solution, they are used in lithium ion batteries. This comes with the risk of fire due to their flammability. Solid electrolytes are being investigated to find an alternative to organic liquid. However, the nature of the solid-solid point contact at the interface between the electrolyte and electrode or between the electrolyte grains is such that high power density has proven difficult to attain. We develop a new method for the fabrication of a solid electrolyte using LiBH4, known for its super Li+ ion conduction without any grain boundary contribution. The modifications to the conduction pathway achieved by stabilizing the high pressure form of this material provided a new structure with some LiBH4, more suitable to the high rate condition. We synthesized the H.P. form of LiBH4 under ambient pressure by doping LiBH4 with the KI lattice by sintering. The formation of a KI - LiBH4 solid solution was confirmed both macroscopically and microscopically. The obtained sample was shown to be a pure Li+ conductor despite its small Li+ content. This conduction mechanism, where the light doping cation played a major role in ion conduction, was termed the “Parasitic Conduction Mechanism.” This mechanism made it possible to synthesize a new ion conductor and is expected to have enormous potential in the search for new battery materials.

  5. Soil physical property estimation from soil strength and apparent electrical conductivity sensor data

    Science.gov (United States)

    Quantification of soil physical properties through soil sampling and laboratory analyses is time-, cost-, and labor-consuming, making it difficult to obtain the spatially-dense data required for precision agriculture. Proximal soil sensing is an attractive alternative, but many currently available s...

  6. Transient hyperbolic heat conduction in thick-walled FGM cylinders and spheres with exponentially-varying properties

    Energy Technology Data Exchange (ETDEWEB)

    Keles, I. [Department of Mechanical Engineering, Ondokuz Mayis University, Samsun (Turkey); Conker, C. [Department of Mechanical Engineering, Mustafa Kemal University, Hatay (Turkey)

    2011-05-15

    This paper focuses on non-Fourier hyperbolic heat conduction analysis for heterogeneous hollow cylinders and spheres made of functionally graded material (FGM). All the material properties vary exponentially across the thickness, except for the thermal relaxation parameter which is taken to be constant. The cylinder and sphere are considered to be cylindrically and spherically symmetric, respectively, leading to one-dimensional heat conduction problems. The problems are solved analytically in the Laplace domain, and the results obtained are transformed to the real-time space using the modified Durbin's numerical inversion method. The transient responses of temperature and heat flux are investigated for different inhomogeneity parameters and relative temperature change values. The comparisons of temperature distribution and heat flux between various time and material properties are presented in the form of graphs. (authors)

  7. Anisotropic physical properties of PrRhAl4Si2 single crystal: A non-magnetic singlet ground state compound

    Science.gov (United States)

    Maurya, Arvind; Kulkarni, R.; Thamizhavel, A.; Dhar, S. K.

    2016-08-01

    We have grown the single crystal of PrRhAl4Si2, which crystallizes in the tetragonal crystal structure. From the low temperature physical property measurements like, magnetic susceptibility, magnetization, heat capacity and electrical resistivity, we found that this compound does not show any magnetic ordering down to 70 mK. Our crystal field calculations on the magnetic susceptibility and specific heat measurements reveal that the 9-fold degenerate (2 J + 1) levels of Pr atom in PrRhAl4Si2 split into 7 levels, with a singlet ground state and a well-separated excited doublet state at 123 K, with a overall level splitting energy of 320 K.

  8. Influence of surface properties on the electrical conductivity of silicon nanomembranes

    Directory of Open Access Journals (Sweden)

    Zhao Xiangfu

    2011-01-01

    Full Text Available Abstract Because of the large surface-to-volume ratio, the conductivity of semiconductor nanostructures is very sensitive to surface chemical and structural conditions. Two surface modifications, vacuum hydrogenation (VH and hydrofluoric acid (HF cleaning, of silicon nanomembranes (SiNMs that nominally have the same effect, the hydrogen termination of the surface, are compared. The sheet resistance of the SiNMs, measured by the van der Pauw method, shows that HF etching produces at least an order of magnitude larger drop in sheet resistance than that caused by VH treatment, relative to the very high sheet resistance of samples terminated with native oxide. Re-oxidation rates after these treatments also differ. X-ray photoelectron spectroscopy measurements are consistent with the electrical-conductivity results. We pinpoint the likely cause of the differences. PACS: 73.63.-b, 62.23.Kn, 73.40.Ty

  9. Conductivity and electrical properties of corn starch-chitosan blend biopolymer electrolyte incorporated with ammonium iodide

    Science.gov (United States)

    Yusof, Y. M.; Shukur, M. F.; Illias, H. A.; Kadir, M. F. Z.

    2014-03-01

    This work focuses on the characteristics of polymer blend electrolytes based on corn starch and chitosan doped with ammonium iodide (NH4I). The electrolytes were prepared using the solution cast method. A polymer blend comprising 80 wt% starch and 20 wt% chitosan was found to be the most amorphous blend and suitable to serve as the polymer host. Fourier transform infrared spectroscopy analysis proved the interaction between starch, chitosan and NH4I. The highest room temperature conductivity of (3.04 ± 0.32) × 10-4 S cm-1 was obtained when the polymer host was doped with 40 wt% NH4I. This result was further proven by field emission scanning electron microscopy study. All electrolytes were found to obey the Arrhenius rule. Dielectric studies confirm that the electrolytes obeyed non-Debye behavior. The temperature dependence of the power law exponent s for the highest conducting sample follows the quantum mechanical tunneling model.

  10. Preparation and properties of proton conducting blending polymers with fluorous block copolymers as compatibilizers

    Energy Technology Data Exchange (ETDEWEB)

    Shi, K. [National Research Council of Canada, Vancouver, BC (Canada). Inst. for Fuel Cell Innovation; Murphy, J.; Sieb, N.; Holdcroft, S. [Simon Fraser Univ., Burnaby, BC (Canada). Dept. of Chemistry]|[National Research Council of Canada, Vancouver, BC (Canada). Inst. for Fuel Cell Innovation

    2005-07-01

    This paper presented the results of an experiment in which 3 series of membranes were prepared by blending polyvinylidene difluoride (PVDF) or poly(vinylidene difluoride-co-hexafluoropropylene) (P(VDF/HFP)) with sulfonated poly(ether ether ketone) (S-PEEK), sulfonated polysulfone (SPU), or sulfonated polystyrene in order to develop novel Proton Exchange Membranes (PEMs) suitable for melt processing. The incorporation of fluorine-containing block copolymer into the blended system resulted in the preparation of acceptable proton conductivity and low water containing PEM materials. The effect of sulfonated poly([vinylidene difluoride-co-hexafluoropropylene]-b-styrene block copolymers as compatibilizers was also investigated. It was observed that conductivity was enhanced for S-PEEK/fluoropolymer blends. Microstructures for the blends were examined by transmission electron microscope and scanning electron microscope.

  11. Fabrication, characterization, and electrical conductivity properties of Pr6O11 nanoparticles

    Institute of Scientific and Technical Information of China (English)

    Bahaa M.Abu-Zied; Youssef A.Mohamed; Abdullah M.Asiri

    2013-01-01

    Pr6O11 nanoparticles were obtained by subsequent thermal decomposition of the as-prepared precipitate formed under ambient temperature and pressure using NaOH as precipitant.The calcination process was affected,for 1 h in static air atmosphere,at 400-700 ℃ temperature range.The different samples were characterized using X-ray diffraction (XRD),transmission electron microscopy (TEM),field emission scanning electron microscopy (FE-SEM),thermogravimetric analysis (TGA),in situ electrical conductivity,and N2 adsorption/desorption.The obtained results demonstrated that nano-crystalline Pr6O1 1,with crystallites size of 6-12 nm,started to form at 500 ℃.Such value increased to 20-33 nm for the sample calcined at 700 ℃.The as-synthesized Pr6O11 nanoparticles presented high electrical conductivity due to electron hopping between Pr(Ⅲ)-Pr(Ⅳ) pairs.

  12. Crystal structure and ion conducting properties of La5NbMo2O16

    KAUST Repository

    Vu, T.D.

    2016-01-29

    The new compound La5NbMo2O16 with high ionic conduction has been discovered during the study of the ternary phase diagram of La2O3-MoO3-Nb2O5. The material crystallizes in the cubic space group Pn 3n (no 222) with the unit cell parameter a=11.2250(1) Å. La5NbMo2O16 is a new analogue of the R5Mo3O16 series (R=Pr, Nd). The structure was refined from a combined data X-ray and neutron powder diffraction. The ionic conductivity of the compound is then measured on sintered pellets, by means of complex impedance spectroscopy. © 2016 Elsevier Inc. All rights reserved.

  13. Pulsed EM Field Response of a Thin, High-Contrast, Finely Layered Structure With Dielectric and Conductive Properties

    OpenAIRE

    De Hoop, A.T.; Jiang, L.

    2009-01-01

    The response of a thin, high-contrast, finely layered structure with dielectric and conductive properties to an incident, pulsed, electromagnetic field is investigated theoretically. The fine layering causes the standard spatial discretization techniques to solve Maxwell's equations numerically to be practically inapplicable. To overcome this difficulty, an approximate method is proposed that models the interaction of the layer with an incident electromagnetic field via a boundary condition t...

  14. A Study on Properties of Electrical Conductive Bricks for Direct Current Electrical Arc Furnace

    Institute of Scientific and Technical Information of China (English)

    1999-01-01

    In this expeiment,the effects of temperature and graphite content on the electricl conductivity of MgO-C materials are studied,Experimental results indicated:the proper ontent of graphite is 10%-12%,The specific electrical resistance of MgO-C materials tends to decrease as the preheat treatment temerature rises.After heat treatment,the specific electrical resistance of MgO-C materials is nearly independent of temperature.

  15. Effect of antioxidant on PTC properties of conductive carbon black/polyethylene composites

    International Nuclear Information System (INIS)

    Complete text of publication follows. Carbon black (CB)-filled high-density polyethylene (HDPE) composites have been used as self resetting fuse for a number of years. The main features of the positive temperature coefficient (PTC) materials are affected by crystallinity of the polymer. The crystallinity of the polymer is changed with thermal treatment. The HDPE/CB composites should be resistant to the severe conditions of high temperature. HDPE with a melt index of 0.35 was selected as the polymer matrix in this work. Carbon black with an average particle size of 86 nm was used. The CB and polymer were mixed in a Brabender Plastograph at 160 deg C for 15 min. The CB/polymer blend thus produced was sandwiched between a pair of copper foils (0.04 mm thick), that served as electrodes. Thermal aging of PTC samples was conducted in an oven at range from 50 deg C to 140 deg C in air. The composites containing 0.5 - 3wt% of Irganox as antioxidant were irradiated under nitrogen at room temperature with different doses of gamma rays from a Co60 source. The conductive composites with thermal aging treatment have the lower resistivity. The reproducibility of the conductive composites depended on the amount of antioxidants

  16. Thermal Properties Capability Development Workshop Summary to Support the Implementation Plan for PIE Thermal Conductivity Measurements

    Energy Technology Data Exchange (ETDEWEB)

    Braase, Lori [Idaho National Lab. (INL), Idaho Falls, ID (United States); Papesch, Cynthia [Idaho National Lab. (INL), Idaho Falls, ID (United States); Hurley, David [Idaho National Lab. (INL), Idaho Falls, ID (United States)

    2015-04-01

    The Department of Energy (DOE)-Office of Nuclear Energy (NE), Idaho National Laboratory (INL), and associated nuclear fuels programs have invested heavily over the years in infrastructure and capability development. With the current domestic and international need to develop Accident Tolerant Fuels (ATF), increasing importance is being placed on understanding fuel performance in irradiated conditions and on the need to model and validate that performance to reduce uncertainty and licensing timeframes. INL’s Thermal Properties Capability Development Workshop was organized to identify the capability needed by the various nuclear programs and list the opportunities to meet those needs. In addition, by the end of fiscal year 2015, the decision will be made on the initial thermal properties instruments to populate the shielded cell in the Irradiated Materials Characterization Laboratory (IMCL).

  17. Low-Frequency Dependence of Conductivity and Dielectric Properties of Polyaniline/ZnFe2O4 Nanocomposites

    Institute of Scientific and Technical Information of China (English)

    G. D. Prasanna; H. S. Jayanna; Ashok R Lamani; M. L. Dinesha; C. S. Naveen; G. J. Shankaramurthy

    2011-01-01

    Conducting polyaniline/ZnFe2O4 nanocomposites are synthesized by using a simple and inexpensive one-step in-situ polymerization method in the presence of ZnFe2O4 nanoparticles.The structural,morphological and electrical properties of the samples are characterized by x-ray diffraction,Fourier transform infrared spectra and scanning electron microscopy.These results reveal the formation of polyaniline/ZnFe2O4 nanocomposites.The morphology of these samples is studied by scanning electron microscopy.Further,the ac conductivity (σac) of these composites is investigated in the frequency range of 1 kHz-10 MHz.The presence of polarons and bipolarons are responsible for the frequency dependence of ac conductivity in these nanocomposites.The ac conductivity is found to be constant up to 1 MHz and thereafter it increases steeply.The ac conductivity of 0.695S·cm-1 at room temperature is observed as the maxima for the polyaniline with 40wt% of the ZnFe2O4 nanocomposite.Polymers are known,in general,as a class of heat sensitive,flexible,electrically insulating,amorphous or semicrystalline materials.The electrical properties of polymers can be modified by the addition of inorganic materials.Nanoscale particles as fillers are attractive due to their intriguing properties arising from the nanosize and resulting large surface area.The insertion of nanoscale materials may improve the electrical and dielectric properties of the host polymers.[1]A large number of polymers are now included in the list of conducting polymers,including polyaniline,polypyrrole,polythiophene,polyparaphenylene,polyphenylene sulphide,polyphenylene vinylene,etc.%Conducting polyaniline/ZnFe2O4 nanocomposites are synthesized by using a simple and inexpensive one-step in-situ polymerization method in the presence of ZnFe2OA nanoparticles. The structural, morphological and electrical properties of the samples are characterized by x-ray diffraction, Fourier transform infrared spectra and scanning electron

  18. Low firing temperature thick-film piezoresistive composites: properties and conduction mechanism

    OpenAIRE

    Vionnet Menot, Sonia; Ryser, Peter

    2007-01-01

    Thick-film technology has found applications on miniaturised hybrid circuits in various fields (automotive electronics, televisions, ...). This technology is also now widely used for the fabrication of force and pressure sensors that use the piezoresistive properties of thick-film resistors. The goal of this work has been generated by the fact that usual piezoresistive pastes / inks were optimised for applications on alumina, which is the standard substrate for thick-film technology, but ill ...

  19. Effect of a proton conducting filler on the physico-chemical properties of SPEEK-based membranes

    Energy Technology Data Exchange (ETDEWEB)

    Mecheri, B.; Chen, F.; Traversa, E. [Department of Chemical Science and Technology, University of Rome ' ' Tor Vergata' ' , Via della Ricerca Scientifica 1, 00133 Roma (Italy); D' Epifanio, A. [Department of Chemical Science and Technology, University of Rome ' ' Tor Vergata' ' , Via della Ricerca Scientifica 1, 00133 Roma (Italy); Hunter College of the City University of New York, New York, NY 10065 (United States); Pisani, L. [CRS4 Parco Scientifico e Tecnologico, POLARIS, 09010 Pula(CA) (Italy); Weise, F.C.; Greenbaum, S. [Hunter College of the City University of New York, New York, NY 10065 (United States); Licoccia, S.

    2009-08-15

    Composite membranes based on sulphonated polyetherether ketone (SPEEK) having a 60% degree of sulphonation (DS=0.6) and containing 23 and 50 wt.-% hydrated tin oxide (SnO{sub 2}.nH{sub 2}O) were prepared and characterised. The lower water uptake (WU) and the higher conductivity values recorded for the composite membranes with respect to pure SPEEK reference suggested the involvement of SnO{sub 2}.nH{sub 2}O in the proton conduction mechanism. Pulsed-field-gradient spin-echo (PFGSE) NMR was employed to obtain a direct measurement of water self-diffusion coefficient in the membranes. Differences were observed between the unfilled SPEEK and the composites, including departures from the normal correlation between water diffusivity and proton conductivity in the case of composites. To better understand the SnO{sub 2}.nH{sub 2}O effect on the proton transport properties of the SPEEK-based membrane, we employed an analytical model that predicts the membrane conductivity as a function of its hydration level and porous structure. The comparison of the model results with the experimental proton conductivity values demonstrated that the tin oxide phase provides additional paths between the water clusters for proton transport, resulting in reduced tortuosity and enhanced proton conductivity. Moreover, the composite showed reduced methanol crossover with respect to the unfilled membrane. (Abstract Copyright [2009], Wiley Periodicals, Inc.)

  20. Influence of sputtering gas pressure on properties of transparent conducting Si-doped zinc oxide films

    Energy Technology Data Exchange (ETDEWEB)

    Qin, Hua; Liu, Hunfa; Lei, Chengxin [Shandong Univ. of Technology, Zibo (China). Dept. of Sciences

    2013-10-15

    Si-doped zinc oxide (SZO, Si 3%) thin films were deposited on glass substrates by means of direct current magnetron sputtering under different pressures. The influence of sputtering pressure on structure, morphology, optical and electrical properties of SZO thin films was investigated. The results reveal that the sputtering pressures have a significant impact on the growth rate, crystal quality and electrical properties of the films, but have little impact on the optical properties of the films. SZO thin film samples grown on glasses are polycrystalline with a hexagonal wurtzite structure and have a preferred orientation along the c-axis perpendicular to the substrate. When the sputtering pressure increases from 2 to 8 Pa, the film surface becomes compact and smooth, the degree of crystallization of the films increases, and the resistivity of films decreases. However, when the sputtering pressure continues to increase from 8 to 10 Pa, the degree of crystallization of the films decreases, the grain size decreases, and the resistivity of the films increases. SZO(3%) thin film deposited at a sputtering pressure of 8 Pa shows the largest carrier concentration, the largest mobility, the lowest resistivity of 3.0 x 10{sup -4} {Omega} cm and a high overall transmission of 93.3% in the visible range. (orig.)

  1. Influence of anisotropic piezoelectric actuators on wing aerodynamic forces

    Institute of Scientific and Technical Information of China (English)

    GUAN De; LI Min; LI Wei; WANG MingChun

    2008-01-01

    Changing the shape of an airfoil to enhance overall aircraft performance has always been s goal of aircraft designers.Using smart material to reshape the wing can improve aerodynamic performance.The influence of anisotropic effects of piezo-electric actuators on the aerodynamic characteristics of a simplified HALE wing model was investigated.Test verification was conducted.

  2. Quark–gluon plasma phenomenology from anisotropic lattice QCD

    Energy Technology Data Exchange (ETDEWEB)

    Skullerud, Jon-Ivar; Kelly, Aoife [Department of Mathematical Physics, Maynooth University, Maynooth, Co Kildare (Ireland); Aarts, Gert; Allton, Chris; Amato, Alessandro; Evans, P. Wynne M.; Hands, Simon [Department of Physics, Swansea University, Swansea SA2 8PP, Wales (United Kingdom); Burnier, Yannis [Institut de Théorie des Phénomènes Physiques, Ecole Polytechnique Fédérale de Lausanne, CH–1015 Lausanne (Switzerland); Giudice, Pietro [Institut für Theoretische Physik, Universität Münster, D–48149 Münster (Germany); Harris, Tim; Ryan, Sinéad M. [School of Mathematics, Trinity College, Dublin 2 (Ireland); Kim, Seyong [Department of Physics, Sejong University, Seoul 143-747 (Korea, Republic of); Lombardo, Maria Paola [INFN–Laboratori Nazionali di Frascati, I–00044 Frascati (RM) (Italy); Oktay, Mehmet B. [Department of Physics and Astronomy, University of Iowa, Iowa City, Iowa 52242 (United States); Rothkopf, Alexander [Institut für Theoretische Physik, Universität Heidelberg, Philosophenweg 16, D–69120 Heidelberg (Germany)

    2016-01-22

    The FASTSUM collaboration has been carrying out simulations of N{sub f} = 2 + 1 QCD at nonzero temperature in the fixed-scale approach using anisotropic lattices. Here we present the status of these studies, including recent results for electrical conductivity and charge diffusion, and heavy quarkonium (charm and beauty) physics.

  3. Influence of anisotropic piezoelectric actuators on wing aerodynamic forces

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Changing the shape of an airfoil to enhance overall aircraft performance has always been a goal of aircraft designers. Using smart material to reshape the wing can improve aerodynamic performance. The influence of anisotropic effects of piezoelectric actuators on the aerodynamic characteristics of a simplified HALE wing model was investigated. Test verification was conducted.

  4. Anisotropic behavior of quantum transport in graphene superlattices

    DEFF Research Database (Denmark)

    Pedersen, Jesper Goor; Cummings, Aron W.; Roche, Stephan

    2014-01-01

    We report on the possibility to generate highly anisotropic quantum conductivity in disordered graphene-based superlattices. Our quantum simulations, based on an efficient real-space implementation of the Kubo-Greenwood formula, show that in disordered graphene superlattices the strength of multi...

  5. Quark–gluon plasma phenomenology from anisotropic lattice QCD

    International Nuclear Information System (INIS)

    The FASTSUM collaboration has been carrying out simulations of Nf = 2 + 1 QCD at nonzero temperature in the fixed-scale approach using anisotropic lattices. Here we present the status of these studies, including recent results for electrical conductivity and charge diffusion, and heavy quarkonium (charm and beauty) physics

  6. Quark-gluon plasma phenomenology from anisotropic lattice QCD

    CERN Document Server

    Skullerud, Jon-Ivar; Allton, Chris; Amato, Alessandro; Burnier, Yannis; Evans, P Wynne M; Giudice, Pietro; Hands, Simon; Harris, Tim; Kelly, Aoife; Kim, Seyong; Lombardo, Maria Paola; Oktay, Mehmet B; Rothkopf, Alexander; Ryan, Sinéad M

    2015-01-01

    The FASTSUM collaboration has been carrying out simulations of N_f=2+1 QCD at nonzero temperature in the fixed-scale approach using anisotropic lattices. Here we present the status of these studies, including recent results for electrical conductivity and charge diffusion, and heavy quarkonium (charm and beauty) physics.

  7. Research on the Relationship between Density of States and Conducting Properties of Single-walled Carbon Nanotubes

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    The analytical expression of the electronic density of states (DOS) for single-walled carbon nanotubes (SWNTs) has been derived on the basis of graphene approximation of the energy E(k) near the Fermi level EF. The distinctive properties of the DOS, the normalized differential conductivity and the current vs bias for SWNTs are deduced and analyzed theoretically.The singularities in the DOS (or in the normalized differential conductivity) predict that the jump structure of current (or conductance)-bias of SWNTs exists. All conclusions from the theoretical analysis are in well agreement with the experimental results of SWNT's electronic structure and electronic transport. In other words, the simple theoretical model in this paper can be applied to understand a range of spectroscopic and other measurement data related to the DOS of SWNTs.

  8. Electronic and Thermal Transport Properties of Complex Structured Cu-Bi-Se Thermoelectric Compound with Low Lattice Thermal Conductivity

    Directory of Open Access Journals (Sweden)

    Jae-Yeol Hwang

    2013-01-01

    Full Text Available Monoclinic Cux+yBi5−ySe8 structure has multiple disorders, such as randomly distributed substitutional and interstitial disorders by Cu as well as asymmetrical disorders by Se. Herein, we report the correlation of electronic and thermal properties with the structural complexities of Cux+yBi5−ySe8. It is found that the interstitial Cu site plays an important role not only to increase the electrical conductivity due to the generation of electron carriers but also to reduce the thermal conductivity mainly due to the phonon scattering by mass fluctuation. With impurity doping at the interstitial Cu site, an extremely low lattice thermal conductivity of 0.32 W·m−1·K−1 was achieved at 560 K. These synergetic effects result in the enhanced dimensionless figure of merit (ZT.

  9. SU(3) Polyakov linear-sigma model: Conductivity and viscous properties of QCD matter in thermal medium

    CERN Document Server

    Tawfik, Abdel Nasser; Hussein, M T

    2016-01-01

    In mean field approximation, the grand canonical potential of SU(3) Polyakov linear-$\\sigma$ model (PLSM) is analysed for chiral phase-transition, $\\sigma_l$ and $\\sigma_s$ and for deconfinement order-parameters, $\\phi$ and $\\phi^*$ of light- and strange-quarks, respectively. Various PLSM parameters are determined from the assumption of global minimization of the real part of the potential. Then, we have calculated the subtracted condensates ($\\Delta_{l,s}$). All these results are compared with recent lattice QCD simulations. Accordingly, essential PLSM parameters are determined. The modelling of the relaxation time is utilized in estimating the conductivity properties of the QCD matter in thermal medium, namely electric [$\\sigma_{el}(T)$] and heat [$\\kappa(T)$] conductivities. We found that the PLSM results on the electric conductivity and on the specific heat agree well with the available lattice QCD calculations. Also, we have calculated bulk and shear viscosities normalized to the thermal entropy, $\\xi/s$...

  10. Temperature-dependent ionic conductivity and transport properties of LiClO4-doped PVA/modified cellulose composites

    Indian Academy of Sciences (India)

    Sunil G Rathod; R F Bhajantri; V Ravindrachary; P K Pujari; G K Nagaraja; Jagadish Naik; Vidyashree Hebbar; H Chandrappa

    2015-09-01

    This paper presents the investigation on physicochemical properties and ionic conductivity of LiClO4-doped poly(vinyl alcohol) (PVA)/modified cellulose composites. The percolative behaviour of LiClO4 with dc conductivity (dc) for different LiClO4 weight fractions (p) related to transport dimensionality was also focused. The highest ionic conductivity of 9.79 × 10–6 S cm–1 was observed for 20 wt% LiClO4 doping level at room temperature. The activation energies (g) were estimated using temperature-dependent conductivity, which follows the Arrhenius and Vogel–Tammann–Fulcher (VTF) relation. The dynamic fragility () and activation energy (g) vs. g of polymer composites using equivalence of the both Williams–Landel–Ferry (WLF) and VTF equations were also correlated. Transport properties such as travel time of ions between sites (o), mobility (), diffusion coefficient () and number of transitions per unit time () for normal cationic (Li+) hopping process of LiClO4-doped PVA/mCellulose composites have been investigated using the Rice and Roth model.

  11. FORTRAN 77 programs for conductive cooling of dikes with temperature-dependent thermal properties and heat of crystallization

    Science.gov (United States)

    Delaney, P.T.

    1988-01-01

    Temperature histories obtained from transient heat-conduction theory are applicable to most dikes despite potential complicating effects related to magma flow during emplacement, groundwater circulation, and metamorphic reaction during cooling. Here. machine-independent FORTRAN 77 programs are presented to calculate temperatures in and around dikes as they cool conductively. Analytical solutions can treat thermal-property contrasts between the dike and host rocks, but cannot address the release of magmatic heat of crystallization after the early stages of cooling or the appreciable temperature dependence of thermal conductivity and diffusivity displayed by most rock types. Numerical solutions can incorporate these additional factors. The heat of crystallization can raise the initial temperature at the dike contact, ??c1, about 100??C above that which would be estimated if it were neglected, and can decrease the rate at which the front of solidified magma moves to the dike center by a factor of as much as three. Thermal conductivity and diffusivity of rocks increase with decreasing temperature and, at low temperatures, these properties increase more if the rocks are saturated with water. Models that treat these temperature dependencies yield estimates of ??c1 that are as much as 75??C beneath those which would be predicted if they were neglected. ?? 1988.

  12. Reconstruction of apparent orthotropic conductivity tensor image using magnetic resonance electrical impedance tomography

    International Nuclear Information System (INIS)

    Magnetic resonance electrical impedance tomography visualizes current density and/or conductivity distributions inside an electrically conductive object. Injecting currents into the imaging object along at least two different directions, induced magnetic flux density data can be measured using a magnetic resonance imaging scanner. Without rotating the object inside the scanner, we can measure only one component of the magnetic flux density denoted as Bz. Since the biological tissues such as skeletal muscle and brain white matter show strong anisotropic properties, the reconstruction of anisotropic conductivity tensor is indispensable for the accurate observations in the biological systems. In this paper, we propose a direct method to reconstruct an axial apparent orthotropic conductivity tensor by using multiple Bz data subject to multiple injection currents. To investigate the anisotropic conductivity properties, we first recover the internal current density from the measured Bz data. From the recovered internal current density and the curl-free condition of the electric field, we derive an over-determined matrix system for determining the internal absolute orthotropic conductivity tensor. The over-determined matrix system is designed to use a combination of two loops around each pixel. Numerical simulations and phantom experimental results demonstrate that the proposed algorithm stably determines the orthotropic conductivity tensor

  13. Reconstruction of apparent orthotropic conductivity tensor image using magnetic resonance electrical impedance tomography

    Energy Technology Data Exchange (ETDEWEB)

    Sajib, Saurav Z. K.; Kim, Ji Eun; Jeong, Woo Chul; Kim, Hyung Joong; Woo, Eung Je [Department of Biomedical Engineering, Kyung Hee University, Yongin, Gyeonggi (Korea, Republic of); Kwon, Oh In, E-mail: oikwon@konkuk.ac.kr [Department of Mathematics, Konkuk University, Seoul (Korea, Republic of)

    2015-03-14

    Magnetic resonance electrical impedance tomography visualizes current density and/or conductivity distributions inside an electrically conductive object. Injecting currents into the imaging object along at least two different directions, induced magnetic flux density data can be measured using a magnetic resonance imaging scanner. Without rotating the object inside the scanner, we can measure only one component of the magnetic flux density denoted as B{sub z}. Since the biological tissues such as skeletal muscle and brain white matter show strong anisotropic properties, the reconstruction of anisotropic conductivity tensor is indispensable for the accurate observations in the biological systems. In this paper, we propose a direct method to reconstruct an axial apparent orthotropic conductivity tensor by using multiple B{sub z} data subject to multiple injection currents. To investigate the anisotropic conductivity properties, we first recover the internal current density from the measured B{sub z} data. From the recovered internal current density and the curl-free condition of the electric field, we derive an over-determined matrix system for determining the internal absolute orthotropic conductivity tensor. The over-determined matrix system is designed to use a combination of two loops around each pixel. Numerical simulations and phantom experimental results demonstrate that the proposed algorithm stably determines the orthotropic conductivity tensor.

  14. Breast ultrasound despeckling using anisotropic diffusion guided by texture descriptors.

    Science.gov (United States)

    Gómez Flores, Wilfrido; Pereira, Wagner Coelho de Albuquerque; Infantosi, Antonio Fernando Catelli

    2014-11-01

    Breast ultrasound (BUS) is considered the most important adjunct method to mammography for diagnosing cancer. However, this image modality suffers from an intrinsic artifact called speckle noise, which degrades spatial and contrast resolution and obscures the screened anatomy. Hence, it is necessary to reduce speckle artifacts before performing image analysis by means of computer-aided diagnosis systems, for example. In addition, the trade-off between smoothing level and preservation of lesion contour details should be addressed by speckle reduction schemes. In this scenario, we propose a BUS despeckling method based on anisotropic diffusion guided by Log-Gabor filters (ADLG). Because we assume that different breast tissues have distinct textures, in our approach we perform a multichannel decomposition of the BUS image using Log-Gabor filters. Next, the conduction coefficient of anisotropic diffusion filtering is computed using texture responses instead of intensity values as stated originally. The proposed algorithm is validated using both synthetic and real breast data sets, with 900 and 50 images, respectively. The performance measures are compared with four existing speckle reduction schemes based on anisotropic diffusion: conventional anisotropic diffusion filtering (CADF), speckle-reducing anisotropic diffusion (SRAD), texture-oriented anisotropic diffusion (TOAD), and interference-based speckle filtering followed by anisotropic diffusion (ISFAD). The validity metrics are the Pratt's figure of merit, for synthetic images, and the mean radial distance (in pixels), for real sonographies. Figure of merit and mean radial distance indices should tend toward '1' and '0', respectively, to indicate adequate edge preservation. The results suggest that ADLG outperforms the four speckle removal filters compared with respect to simulated and real BUS images. For each method--ADLG, CADF, SRAD, TOAD and ISFAD--the figure of merit median values are 0.83, 0.40, 0.39, 0

  15. DFT study of the conductance of molecular wire: The effect of coupling geometry and intermolecular interaction on the transport properties

    Institute of Scientific and Technical Information of China (English)

    QI; Yuanhua; GUAN; Daren; LIU; Chengbu

    2006-01-01

    The density functional theory (DFT) combining with the non-equilibrium Green functions (NEGF) method is applied to the study of the electronic transport properties for a Di-thiol-benzene (DTB) molecule coupled to two Au(111) surfaces. The dependence of the transport properties on the bias, the coupling geometry of the molecule-electrode interface, and the intermolecular interaction are examined in detail. The results show that the existence of the hydrogen atom at the end of the DTB molecule would significantly decrease the transmission coefficients, and then the differential conductance (dI/dV). By changing the position of the DTB molecule located between two electrodes a maximum value of calculated current is observed. It is also found that the intermolecular interaction will strongly influence the transport properties of the system studied.

  16. Self-collimation in photonic crystals with anisotropic constituents

    Institute of Scientific and Technical Information of China (English)

    J. W. Haus; M. Siraj; P. Prasad; P. Markowicz

    2007-01-01

    @@ In a photonic crystal composed of anisotropic constituents we quantify the range of input angles and the degree of collimation of the beam inside the crystal. The optical properties of a photobleached 4-dimethylamino-N-methyl-4-stilbazolium-tosylate (DAST) crystal are used in our model to demonstrate the efficacy of the self-collimation features.

  17. Effect of anisotropic plasticity on mixed mode interface crack growth

    DEFF Research Database (Denmark)

    Tvergaard, Viggo; Legarth, Brian Nyvang

    2007-01-01

    different anisotropic yield criteria to account for the plastic anisotropy. Conditions of small-scale yielding are assumed, and due to the mismatch of elastic properties across the interface the corresponding oscillating stress singularity field is applied as boundary conditions on the outer edge...

  18. Anisotropic Fractional Brownian Random Fields as White Noise Functionals

    Institute of Scientific and Technical Information of China (English)

    Zhi-yuan Huang; Chu-jin Li

    2005-01-01

    This investigation aims at a new construction of anisotropic fractional Brownisn random fields by the white noise approach. Moreover, we investigate its distribution and sample properties (stationariness of increments, self-similarity, sample continuity) which will furnish some useful views to future applications.

  19. Anisotropic rock physics models for interpreting pore structures in carbonate reservoirs

    Institute of Scientific and Technical Information of China (English)

    Li Sheng-Jie; Shao Yu; Chen Xu-Qiang

    2016-01-01

    We developed an anisotropic effective theoretical model for modeling the elastic behavior of anisotropic carbonate reservoirs by combining the anisotropic self-consistent approximation and differential effective medium models. By analyzing the measured data from carbonate samples in the TL area, a carbonate pore-structure model for estimating the elastic parameters of carbonate rocks is proposed, which is a prerequisite in the analysis of carbonate reservoirs. A workfl ow for determining elastic properties of carbonate reservoirs is established in terms of the anisotropic effective theoretical model and the pore-structure model. We performed numerical experiments and compared the theoretical prediction and measured data. The result of the comparison suggests that the proposed anisotropic effective theoretical model can account for the relation between velocity and porosity in carbonate reservoirs. The model forms the basis for developing new tools for predicting and evaluating the properties of carbonate reservoirs.%♦Corresponding author: Li Sheng-Jie (Email: Richard@cup.edu.cn)

  20. Investigation of the lithium ion mobility in cyclic model compounds and their ion conduction properties

    Energy Technology Data Exchange (ETDEWEB)

    Thielen, Joerg

    2011-07-27

    In view of both, energy density and energy drain, rechargeable lithium ion batteries outperform other present accumulator systems. However, despite great efforts over the last decades, the ideal electrolyte in terms of key characteristics such as capacity, cycle life, and most important reliable safety, has not yet been identified. Steps ahead in lithium ion battery technology require a fundamental understanding of lithium ion transport, salt association, and ion solvation within the electrolyte. Indeed, well defined model compounds allow for systematic studies of molecular ion transport. Thus, in the present work, based on the concept of immobilizing ion solvents, three main series with a cyclotriphosphazene (CTP), hexaphenylbenzene (HBP), and tetramethylcyclotetrasiloxane (TMS) scaffold were prepared. Lithium ion solvents, among others ethylene carbonate (EC), which has proven to fulfill together with propylene carbonate safety and market concerns in commercial lithium ion batteries, were attached to the different cores via alkyl spacers of variable length. All model compounds were fully characterized, pure and thermally stable up to at least 235 C, covering the requested broad range of glass transition temperatures from -78.1 C up to +6.2 C. While the CTP models tend to rearrange at elevated temperatures over time, which questions the general stability of alkoxide related (poly)phosphazenes, both, the HPB and CTP based models show no evidence of core stacking. In particular the CTP derivatives represent good solvents for various lithium salts, exhibiting no significant differences in the ionic conductivity {sigma}{sub dc} and thus indicating comparable salt dissociation and rather independent motion of cations and ions. In general, temperature-dependent bulk ionic conductivities investigated via impedance spectroscopy follow a William-Landel-Ferry (WLF) type behavior. Modifications of the alkyl spacer length were shown to influence ionic conductivities only in

  1. Structure degradation and conducting properties of the perovskite phase of yttrium ceramics

    CERN Document Server

    Kalanov, M U

    2002-01-01

    It is shown, that under normal conditions the perovskite phase of the yttrium ceramics of the [(Y,Ba)CuO sub 3 sub - subDELTA sub / sub 3] sub 3 is metastable and degrades in time. The degradation results in the YBa sub 2 Cu sub 3 O sub 7 sub - subdelta orthorhombic phase with transition into the superconducting state at T sub c = 91 K. The conductivity type changes thereby from the mixed metal-semiconductor character to the metallic one within the temperature interval of 100-300 K

  2. COATING THE CONDUCTIVITY MATERIALS TO IMPROVING THE ELECTROCHEMICAL PROPERTIES OF LiFePO4

    OpenAIRE

    WAN LIN WANG; EN MEI JIN; HAL-BON GU

    2013-01-01

    LiFePO4 cathode materials were prepared by a solid-state method followed by one-step heat treatment. To improve the electrochemical properties of the LiFePO4, acetylene black (AB), citric acid (CA), and pyrene are added as carbon source, respectively. The cyclic voltammetry (CV), AC impedance and galvanostatic charge/discharge testing results showed that using the LiFePO4-C composite such as the AB carbon source exhibits higher discharge capacity and stability than the other composite. Synthe...

  3. Optical Properties of Fluid Hydrogen at the Transition to a Conducting State

    Science.gov (United States)

    McWilliams, R. Stewart; Dalton, D. Allen; Mahmood, Mohammad F.; Goncharov, Alexander F.

    2016-06-01

    We use fast transient transmission and emission spectroscopies in the pulse laser heated diamond anvil cell to probe the energy-dependent optical properties of hydrogen at pressures of 10-150 GPa and temperatures up to 6000 K. Hydrogen is absorptive at visible to near-infrared wavelengths above a threshold temperature that decreases from 3000 K at 18 GPa to 1700 K at 110 GPa. Transmission spectra at 2400 K and 141 GPa indicate that the absorptive hydrogen is semiconducting or semimetallic in character, definitively ruling out a first-order insulator-metal transition in the studied pressure range.

  4. Transparent conducting properties of SrSnO3 and ZnSnO3

    Directory of Open Access Journals (Sweden)

    Khuong P. Ong

    2015-06-01

    Full Text Available We report optical properties of doped n-type SrSnO3 and ZnSnO3 in relation to potential application as transparent conductors. We find that the orthorhombic distortion of the perovskite structure in SrSnO3 leads to absorption in the visible as the doping level is increased. This arises from interband transitions. We find that strain tuning could modify this absorption, but does not eliminate it. On the other hand, we find that ZnSnO3 although also having a non-cubic structure, can retain excellent transparency when doped, making it a good candidate transparent conductor.

  5. Transparent conducting properties of SrSnO3 and ZnSnO3

    Science.gov (United States)

    Ong, Khuong P.; Fan, Xiaofeng; Subedi, Alaska; Sullivan, Michael B.; Singh, David J.

    2015-06-01

    We report optical properties of doped n-type SrSnO3 and ZnSnO3 in relation to potential application as transparent conductors. We find that the orthorhombic distortion of the perovskite structure in SrSnO3 leads to absorption in the visible as the doping level is increased. This arises from interband transitions. We find that strain tuning could modify this absorption, but does not eliminate it. On the other hand, we find that ZnSnO3 although also having a non-cubic structure, can retain excellent transparency when doped, making it a good candidate transparent conductor.

  6. Tunable waveguide bends with graphene-based anisotropic metamaterials

    KAUST Repository

    Chen, Zhao-xian

    2016-01-15

    We design tunable waveguide bends filled with graphene-based anisotropic metamaterials to achieve a nearly perfect bending effect. The anisotropic properties of the metamaterials can be described by the effective medium theory. The nearly perfect bending effect is demonstrated by finite element simulations of various structures with different bending curvatures and shapes. This effect is attributed to zero effective permittivity along the direction of propagation and matched effective impedance at the interfaces between the bending part and the dielectric waveguides. We envisage that the design will be applicable in the far-infrared and terahertz frequency ranges owing to the tunable dielectric responses of graphene.

  7. Thermoelectric properties of ultra-low thermal conductivity half-Heusler alloy

    Science.gov (United States)

    Mallick, Md. Mofasser; Vitta, Satish

    2016-05-01

    The half-Heusler alloy HfNiGe has been synthesized by arc melting from high purity elements followed by annealing at 1000 K for 6 days to homogenize completely. The X-ray diffraction pattern indicates the presence of mainly an orthorhombic phase with small amount of other binary phases. The electrical resistivity is found to be low and increases slightly with temperature from 14 µΩ-m to 24 µΩ-m, indicating a semi metallic behavior. As a result the Seebeck coefficient is found to be low and also increases with temperature from -11 µV K-1 to -19.5 µV K-1. The thermal conductivity has been determined using a combination of heat capacity and thermal diffusivity. It decreases from ~ 1.9 Wm-1K-1 at room temperature to ~ 0.007 Wm-1K-1 at 843 K, an extremely low value for a half-Heusler alloy. The thermal conductivity reduction is found to be mainly due to a sharp decrease in heat capacity for T> 650 K. This leads to a divergence of figure of merit at high temperatures, >800K, from ~0.05 to 2 at 843 K.

  8. Study of Liquid Mixtures Electrical Properties as a Function of Electrical Conductivity using Capacitive Sensor

    Directory of Open Access Journals (Sweden)

    P. Azimi Anaraki

    2014-01-01

    Full Text Available In this study design and operation of a capacitive cell sensor for liquid mixture monitoring is reported. Operation of the capacitance measurement module for such probe is based on the charge and discharge method. The capacitive effect of small drop of different liquids in tap water was studied using this capacitive sensor. A small percentage of contaminating agents such as oil in tap water is determined with a good sensitivity. Comparison of the measured resistances for different liquid mixtures shows a decrease by increasing Total Dissolved Solids (TDS. In another study the electrical capacitance of different solutions, mixture of ethanol and water, mixture of methanol and water, mixture of petroleum and water and other liquid mixtures were studied. It must be pointed out that the measuring capacitance of the sensor is different from that of the liquid capacitance, but the samples electrical characteristics can be compared relatively with each other. The effects of the electrical conductivity on the permittivity and conductance of different liquid mixtures are also investigated. The experimental results are promising concerning water liquids and verify the successful operation of such device as a liquid sensor and are a useful method for checking the electrical quality of the water mixture that is required for different applications.

  9. Conductivity and electrical properties of corn starch–chitosan blend biopolymer electrolyte incorporated with ammonium iodide

    International Nuclear Information System (INIS)

    This work focuses on the characteristics of polymer blend electrolytes based on corn starch and chitosan doped with ammonium iodide (NH4I). The electrolytes were prepared using the solution cast method. A polymer blend comprising 80 wt% starch and 20 wt% chitosan was found to be the most amorphous blend and suitable to serve as the polymer host. Fourier transform infrared spectroscopy analysis proved the interaction between starch, chitosan and NH4I. The highest room temperature conductivity of (3.04 ± 0.32) × 10−4 S cm−1 was obtained when the polymer host was doped with 40 wt% NH4I. This result was further proven by field emission scanning electron microscopy study. All electrolytes were found to obey the Arrhenius rule. Dielectric studies confirm that the electrolytes obeyed non-Debye behavior. The temperature dependence of the power law exponent s for the highest conducting sample follows the quantum mechanical tunneling model. (paper)

  10. Continuum mechanics of anisotropic materials

    CERN Document Server

    Cowin, Stephen C

    2013-01-01

    Continuum Mechanics of Anisotropic Materials(CMAM) presents an entirely new and unique development of material anisotropy in the context of an appropriate selection and organization of continuum mechanics topics. These features will distinguish this continuum mechanics book from other books on this subject. Textbooks on continuum mechanics are widely employed in engineering education, however, none of them deal specifically with anisotropy in materials. For the audience of Biomedical, Chemical and Civil Engineering students, these materials will be dealt with more frequently and greater accuracy in their analysis will be desired. Continuum Mechanics of Anisotropic Materials' author has been a leader in the field of developing new approaches for the understanding of anisotropic materials.

  11. Magnetic properties of conducting polymer doped with manganese zinc ferrite nanoparticles

    Science.gov (United States)

    Poddar, P.; Wilson, J. L.; Srikanth, H.; Morrison, S. A.; Carpenter, E. E.

    2004-10-01

    The magnetic properties of superparamagnetic particles are influenced by the supporting matrix. We have systematically studied the DC magnetic properties of loosely packed manganese-zinc ferrite (Mn0.68Zn0.25Fe2.07O3) nanoparticles synthesized using a reverse micelle technique. The results have been compared with those for particles suspended in paraffin wax and embedded in a polypyrrole matrix. The polypyrrole-doped particles were prepared using an in situ ultraviolet irradiation method and spin-coated into thin films. The loosely packed particles showed no resolvable coercivity even well below the blocking temperature. On the other hand, the same particles in wax showed the opening up of a large coercivity below the blocking temperature. However, both the samples showed characteristic superparamagnetic transition peaks in the temperature-dependent susceptibility nearly at the same temperature. The particles in the polypyrrole matrix showed a remarkable increase in the blocking temperature and large hysteresis at 300 K. The structural characterization of the polymer-doped sample showed clustering of the nanoparticles.

  12. Effect of heat treatments on the tensile and electrical properties of high-strength, high-conductivity copper alloys

    Energy Technology Data Exchange (ETDEWEB)

    Zinkle, S.J.; Eatherly, W.S. [Oak Ridge National Lab., TN (United States)

    1997-08-01

    The unirradiated tensile properties of CuCrZr produced by two different vendors have been measured following different heat treatments. Room temperature electrical resistivity measurements were also performed in order to estimate the thermal conductivity of these specimens. The thermomechanical conditions studied included solution quenched, solution quenched and aged (ITER reference heat treatment), simulated slow HIP thermal cycle ({approximately}1{degrees}C/min cooling from solutionizing temperature) and simulated fast HIP thermal cycle ({approximately}100{degrees}C/min cooling from solutionizing temperature). Specimens from the last two heat treatments were tested in both the solution-cooled condition and after subsequent precipitate aging at 475{degrees}C for 2 h. Both of the simulated HIP thermal cycles caused a pronounced decreases in the strength and electrical conductivity of CuCrZr. The tensile and electrical properties were unchanged by subsequent aging in the slow HIP thermal cycles caused a pronounced decrease in the strength and electrical conductivity of CuCrZr. The tensile and electrical properties were unchanged by subsequent aging in the slow HIP thermal cycle specimens, whereas the strength and conductivity following aging in the fast HIP thermal cycle improved to {approximately}65% of the solution quenched and aged CuCrZr values. Limited tensile and electrical resistivity measurements were also made on two new heats of Hycon 3HP CuNiBe. High strength but poor uniform and total elongations were observed at 500{degrees}C on one of these new heats of CuNiBe, similar to that observed in other heats.

  13. Formulation of cross-anisotropic failure criterion for soils

    Directory of Open Access Journals (Sweden)

    Yi-fei SUN

    2013-10-01

    Full Text Available Inherently anisotropic soil fabric has a considerable influence on soil strength. To model this kind of inherent anisotropy, a three-dimensional anisotropic failure criterion was proposed, employing a scalar-valued anisotropic variable and a modified general three- dimensional isotropic failure criterion. The scalar-valued anisotropic variable in all sectors of the deviatoric plane was defined by correlating a normalized stress tensor with a normalized fabric tensor. Detailed comparison between the available experimental data and the corresponding model predictions in the deviatoric plane was conducted. The proposed failure criterion was shown to well predict the failure behavior in all sectors, especially in sector II with the Lode angle ranging between 60º and 120º, where the prediction was almost in accordance with test data. However, it was also observed that the proposed criterion overestimated the strength of dense Santa Monica Beach sand in sector III where the intermediate principal stress ratio b varied from approximately 0.2 to 0.8, and slightly underestimated the strength when b was between approximately 0.8 and 1. The difference between the model predictions and experimental data was due to the occurrence of shear bending, which might reduce the measured strength. Therefore, the proposed anisotropic failure criterion has a strong ability to characterize the failure behavior of various soils and potentially allows a better description of the influence of the loading direction with respect to the soil fabric.

  14. Latest developments in anisotropic hydrodynamics

    CERN Document Server

    Tinti, Leonardo

    2015-01-01

    We discuss the leading order of anisotropic hydrodynamics expansion. It has already been shown that in the (0+1) and (1+1)-dimensional cases it is consistent with the second order viscous hydrodynamics, and it provides a striking agreement with the exact solutions of the Boltzmann equation. Quite recently, a new set of equations has been proposed for the leading order of anisotropic hydrodynamics, which is consistent with the second order viscous hydrodynamics in the most general (3+1)-dimensional case, and does not require a next-to-leading treatment for describing pressure anisotropies in the transverse plane.

  15. Dynamical analysis of anisotropic inflation

    Science.gov (United States)

    Karčiauskas, Mindaugas

    2016-06-01

    The inflaton coupling to a vector field via the f(φ)2F μνFμν term is used in several contexts in the literature, such as to generate primordial magnetic fields, to produce statistically anisotropic curvature perturbation, to support anisotropic inflation, and to circumvent the η-problem. In this work, I perform dynamical analysis of this system allowing for the most general Bianchi I initial conditions. I also confirm the stability of attractor fixed points along phase-space directions that had not been investigated before.

  16. Anisotropic hydrodynamics: Motivation and methodology

    International Nuclear Information System (INIS)

    In this proceedings contribution I review recent progress in our understanding of the bulk dynamics of relativistic systems that possess potentially large local rest frame momentum-space anisotropies. In order to deal with these momentum-space anisotropies, a reorganization of relativistic viscous hydrodynamics can be made around an anisotropic background, and the resulting dynamical framework has been dubbed “anisotropic hydrodynamics”. I also discuss expectations for the degree of momentum-space anisotropy of the quark–gluon plasma generated in relativistic heavy ion collisions at RHIC and LHC from second-order viscous hydrodynamics, strong-coupling approaches, and weak-coupling approaches

  17. Tubular array, dielectric, conductivity and electrochemical properties of biodegradable gel polymer electrolyte

    International Nuclear Information System (INIS)

    Highlights: • A new finding of tubular array of 10–20 μm in length and 1–2 μm in thickness of gel polymer electrolyte (GPE) having 2.2 × 10−3 S cm−1 conductivity is reported. • Thermal and electrochemical characterizations of GPEs show good interaction among the polymer, plasticizer and salt. • GPE based supercapacitor demonstrates high capacitance of 186 F g−1. • Low temperature studies did not influence much on capacitance values obtained from AC impedance studies. • Charge–discharge exhibits high capacity with excellent cyclic stability and energy density. -- Abstract: A supercapacitor based on a biodegradable gel polymer electrolyte (GPE) has been fabricated using guar gum (GG) as the polymer matrix, LiClO4 as the doping salt and glycerol as the plasticizer. The scanning electron microscopy (SEM) images of the gel polymer showed an unusual tubular array type surface morphology. FTIR, DSC and TGA results of the GPE indicated good interaction between the components used. Highest ionic conductivity and lowest activation energy values were 2.2 × 10−3 S cm−1 and 0.18 eV, respectively. Dielectric studies revealed ionic behavior and good capacitance with varying frequency of the GPE system. The fabricated supercapacitor showed a maximum specific capacitance value of 186 F g−1 using cyclic voltammetry. Variation of temperature from 273 K to 293 K did not significantly influence the capacitance values obtained from AC impedance studies. Galvanostatic charge–discharge study of supercapacitor indicated that the device has good stability, high energy density and power density

  18. Macroporous conductive polymer films fabricated by electrospun nanofiber templates and their electromechanical properties

    Energy Technology Data Exchange (ETDEWEB)

    Zhou Jian; Gao Qiang; Fukawa, Tadashi; Shirai, Hirofusa; Kimura, Mutsumi, E-mail: mkimura@shinshu-u.ac.jp [Department of Functional Polymer Science, Faculty of Textile Science and Technology, Shinshu University, Ueda 386-8567 (Japan)

    2011-07-08

    We demonstrate a facile method to fabricate macroporous poly (3,4-ethylenedioxythiophene)/poly (4-styrene sulfonate) (PEDOT/PSS) films with empty channels by using electrospun nanofiber as a sacrificial template. The channels within the PEDOT/PSS films were prepared by depositing PEDOT/PSS aqueous dispersion onto poly (vinyl pyrrolidone)/poly(methyl methacrylate) (PVP/PMMA) nanofiber template, and then the nanofibers were removed by solvent extraction. The average diameter of the channels is 313 {+-} 45 nm, which is almost the same as the parent PVP/PMMA nanofibers. The macroporous PEDOT/PSS film with the empty channels showed an enhancement of electromechanical properties compared to the nonporous PEDOT/PSS film.

  19. Thermo-mechanical properties of mixed ion-electron conducting membrane materials

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Bingxin

    2011-07-01

    The thesis presents thermo-mechanical properties of La{sub 0.58}Sr{sub 0.4}Co{sub 0.2}Fe{sub 0.8}O{sub 3-{delta}} (LSCF) and Ba{sub 0.5}Sr{sub 0.5}Co{sub 0.8}Fe{sub 0.2}O{sub 3-{delta}} (BSCF) perovskite materials, which are considered as oxygen transport membranes (OTM) for gas separation units. Ring-on-ring bending test with disk-shaped samples and depth-sensitive micro-indentation have been used as macroscopic and microscopic tests, respectively. In addition, the thermo-mechanical properties of a third OTM candidate material La{sub 2}NiO{sub 4+{delta}} (LNO) were investigated. The results of the thermo-mechanical measurements with the BSCF revealed an anomaly between 200 C and 400 C. In particular, the temperature dependence of Young's modulus shows a minimum at {proportional_to} 200 C. Fracture stress and toughness exhibit a qualitatively similar behavior with a minimum between 200 C and 400 C, before recovering between 500 C and 800 C. X-ray diffraction analyses verified that BSCF remains cubic in the relevant temperature range. Hence the anomalies were assumed to be related to the transition of Co{sup 3+} spin states reported for other Co-containing perovskites. This assumption could be experimentally confirmed by magnetic susceptibility measurements. The fracture surfaces of the specimens are not affected by the mechanical anomalies at intermediate temperatures, since only a transgranular fracture mode has been observed. Complementary to the mechanical characterization of BSCF, also the temperature dependency of fracture stress and elastic behavior of LSCF have been determined. Phase compositions of LSCF have been studied by in-situ high temperature XRD. Changes in phase composition with temperature are observed. At ambient temperature the LSCF perovskite material comprises two phases: rhombohedral and cubic symmetry. The ratio of the two phases depends on both cooling rate and atmosphere. The transition of rhombohedral to cubic occurs between 700 C and

  20. On the optical properties of carbon nanotubes. Part I. A general formula for the dynamical optical conductivity

    Energy Technology Data Exchange (ETDEWEB)

    Rasmussen, Morten Grud, E-mail: morteng@math.aau.dk [Department of Mathematical Sciences, Aalborg University, Fredrik Bajers Vej 7G, 9220 Aalborg (Denmark); Ricaud, Benjamin, E-mail: benjamin.ricaud@epfl.ch [Laboratoire de Traitement des Signaux 2, École Polytechnique Fédérale de Lausanne, Lausanne, Vaud (Switzerland); Savoie, Baptiste, E-mail: baptiste.savoie@gmail.com [Dublin Institute for Advanced Studies, School of Theoretical Physics, 10 Burlington Road, Dublin 04 (Ireland)

    2016-02-15

    This paper is the first one in a series of two articles in which we revisit the optical properties of single-walled carbon nanotubes (SWNTs). Produced by rolling up a graphene sheet, SWNTs owe their intriguing properties to their cylindrical quasi-one-dimensional (quasi-1D) structure (the ratio length/radius is experimentally of order of 10{sup 3}). We model SWNT by circular cylinders of small diameters on the surface of which the conduction electron gas is confined by the electric field generated by the fixed carbon ions. The pair-interaction potential considered is the 3D Coulomb potential restricted to the cylinder. To reflect the quasi-1D structure, we introduce a 1D effective many-body Hamiltonian which is the starting-point of our analysis. To investigate the optical properties, we consider a perturbation by a uniform time-dependent electric field modeling an incident light beam along the longitudinal direction. By using Kubo’s method, we derive within the linear response theory an asymptotic expansion in the low-temperature regime for the dynamical optical conductivity at fixed density of particles. The leading term only involves the eigenvalues and associated eigenfunctions of the (unperturbed) 1D effective many-body Hamiltonian and allows us to account for the sharp peaks observed in the optical absorption spectrum of SWNT.

  1. On the optical properties of carbon nanotubes. Part I. A general formula for the dynamical optical conductivity

    International Nuclear Information System (INIS)

    This paper is the first one in a series of two articles in which we revisit the optical properties of single-walled carbon nanotubes (SWNTs). Produced by rolling up a graphene sheet, SWNTs owe their intriguing properties to their cylindrical quasi-one-dimensional (quasi-1D) structure (the ratio length/radius is experimentally of order of 103). We model SWNT by circular cylinders of small diameters on the surface of which the conduction electron gas is confined by the electric field generated by the fixed carbon ions. The pair-interaction potential considered is the 3D Coulomb potential restricted to the cylinder. To reflect the quasi-1D structure, we introduce a 1D effective many-body Hamiltonian which is the starting-point of our analysis. To investigate the optical properties, we consider a perturbation by a uniform time-dependent electric field modeling an incident light beam along the longitudinal direction. By using Kubo’s method, we derive within the linear response theory an asymptotic expansion in the low-temperature regime for the dynamical optical conductivity at fixed density of particles. The leading term only involves the eigenvalues and associated eigenfunctions of the (unperturbed) 1D effective many-body Hamiltonian and allows us to account for the sharp peaks observed in the optical absorption spectrum of SWNT

  2. Anisotropic metamaterials for microwave antennas and infrared nanostructured thin films

    Science.gov (United States)

    Jian, Zhihao

    Wave-matter interactions have long been investigated to discover unknown physical phenomena and exploited to achieve improved device performance throughout the electromagnetic spectrum ranging from quasi-static limit to microwave frequencies, and even at infrared and optical wavelengths. As a nascent but fast growing field, metamaterial technology, which relies on clusters of artificially engineered subwavelength structures, has been demonstrated to provide a wide variety of exotic electromagnetic properties unattainable in natural materials. This dissertation presents the research on novel anisotropic metamaterials for tailoring microwave radiation and infrared scattering of nanostructured thin films. First, a new inversion algorithm is proposed for retrieving the anisotropic effective medium parameters of a slab of metamaterial. Secondly, low-loss anisotropic metamaterial lenses and coatings are introduced for improving the gain and/or bandwidth for a variety of antennas. In particular, a quad-beam high-gain lens for a quarter-wave monopole, a low-profile grounded leaky metamaterial coating for slot antenna, and an ultra-thin anisotropic metamaterial bandwidth-enhancing coating for a quarter-wave monopole are experimentally demonstrated. In the infrared regime, novel nanostructured metamaterial free-standing thin-films, which are inherently anisotropic, are introduced for achieving exotic index properties and further for practical photonic devices. In particular, a low-loss near-infrared fishnet zero-index metamaterial, a dispersionengineered optically-thin, low-loss broadband metamaterial filter with a suppressed group delay fluctuation in the mid-infrared, and a conformal dual-band near-perfectly absorbing coating in the mid-infrared are experimentally demonstrated. These explorations show the great promise anisotropic metamaterials hold for the flexible manipulation of electromagnetic waves and their broad applicability in a wide spectrum range.

  3. Frequency dependent capacitance and conductance properties of Schottky diode based on rubrene organic semiconductor

    Science.gov (United States)

    Barış, Behzad

    2013-10-01

    Al/rubrene/p-Si Schottky diode has been fabricated by forming a rubrene layer on p type Si by using the spin coating method. The frequency dependent capacitance-voltage (C-V-f) and conductance-voltage (G-V-f) characteristics of Al/rubrene/p-Si Schottky diyotes has been investigated in the frequency range of 5 kHz-500 kHz at room temperature. The C-V plots show a peak for each frequency. The capacitance of the device decreased with increasing frequency. The decrease in capacitance results from the presence of interface states. The plots of series resistance-voltage (Rs-V) gave a peak in the depletion region at all frequencies. The density of interface states (Nss) and relaxation time (τ) distribution profiles as a function of applied voltage bias have been determined from the C-V and G-V measurements. The values of the Nss and τ have been calculated in the ranges of 8.37×1011-4.85×1011 eV-1 cm-2 and 5.17×10-6-1.02×10-5 s, respectively.

  4. Coating the Conductivity Materials to Improving the Electrochemical Properties of LiFePO4

    Science.gov (United States)

    Wang, Wan Lin; Jin, En Mei; Gu, Hal-Bon

    2013-03-01

    LiFePO4 cathode materials were prepared by a solid-state method followed by one-step heat treatment. To improve the electrochemical properties of the LiFePO4, acetylene black (AB), citric acid (CA), and pyrene are added as carbon source, respectively. The cyclic voltammetry (CV), AC impedance and galvanostatic charge/discharge testing results showed that using the LiFePO4-C composite such as the AB carbon source exhibits higher discharge capacity and stability than the other composite. Synthesized LiFePO4-C/Li cells (with AB) showed that initial discharge capacity was 140.65 mA h g-1 and at the 2nd cycle were 145.87 mA h g-1, respectively. Morphology and electrochemical performance of the LiFePO4 cathode materials were investigated. Furthermore, the cell was subjected to current density studies (0.1 mA cm-2) that suggested excellent capacity retention of the cell at 25°C.

  5. Holographic transports and stability in anisotropic linear axion model

    CERN Document Server

    Ge, Xian-Hui; Niu, Chao; Sin, Sang-Jin

    2014-01-01

    We study thermoelectric conductivities and shear viscosities in a holographically anisotropic model. Momentum relaxation is realized through perturbing the linear axion field. AC conductivity exhibits a conherent/incoherent metal transition. The longitudinal shear viscosity for prolate anisotropy violates the bound conjectured by Kovtun-Son-Starinets. We also find that thermodynamic and dynamical instabilities are not always equivalent, which provides a counter example of the Gubser-Mitra conjecture.

  6. Anomalous Propagation of Electromagnetic Waves in Anisotropic Media with a Unique Dispersion Relation

    Institute of Scientific and Technical Information of China (English)

    SHU Wei-Xing; LUO Hai-Lu; LI Fei; REN Zhong-Zhou

    2006-01-01

    @@ We investigate the propagation of electromagnetic waves at the interface between an isotropic material and the anisotropic medium with a unique dispersion relation. We show that the refraction behaviour of E-polarized waves is opposite to that of H-polarized waves, though the dispersion relations for E- and H-polarized waves are the same. It is found that waves exhibit different propagation properties in anisotropic media with different sign combinations of the permittivity and permeability tensors. Some interesting properties of propagation are also found in the special anisotropic media, leading to potential applications.

  7. Arsenic compromises conducting airway epithelial barrier properties in primary mouse and immortalized human cell cultures.

    Directory of Open Access Journals (Sweden)

    Cara L Sherwood

    Full Text Available Arsenic is a lung toxicant that can lead to respiratory illness through inhalation and ingestion, although the most common exposure is through contaminated drinking water. Lung effects reported from arsenic exposure include lung cancer and obstructive lung disease, as well as reductions in lung function and immune response. As part of their role in innate immune function, airway epithelial cells provide a barrier that protects underlying tissue from inhaled particulates, pathogens, and toxicants frequently found in inspired air. We evaluated the effects of a five-day exposure to environmentally relevant levels of arsenic {<4μM [~300 μg/L (ppb] as NaAsO2} on airway epithelial barrier function and structure. In a primary mouse tracheal epithelial (MTE cell model we found that both micromolar (3.9 μM and submicromolar (0.8 μM arsenic concentrations reduced transepithelial resistance, a measure of barrier function. Immunofluorescent staining of arsenic-treated MTE cells showed altered patterns of localization of the transmembrane tight junction proteins claudin (Cl Cl-1, Cl-4, Cl-7 and occludin at cell-cell contacts when compared with untreated controls. To better quantify arsenic-induced changes in tight junction transmembrane proteins we conducted arsenic exposure experiments with an immortalized human bronchial epithelial cell line (16HBE14o-. We found that arsenic exposure significantly increased the protein expression of Cl-4 and occludin as well as the mRNA levels of Cl-4 and Cl-7 in these cells. Additionally, arsenic exposure resulted in altered phosphorylation of occludin. In summary, exposure to environmentally relevant levels of arsenic can alter both the function and structure of airway epithelial barrier constituents. These changes likely contribute to the observed arsenic-induced loss in basic innate immune defense and increased infection in the airway.

  8. Electrochemical properties of a thermally expanded magnetic graphene composite with a conductive polymer.

    Science.gov (United States)

    Ahmed, Mahmoud M M; Imae, Toyoko

    2016-04-21

    A magnetic graphene composite derived from stage-1 FeCl3-graphite intercalation compounds was thermally treated for up to 75 min at 400 °C or for 2 min at high temperatures up to 900 °C. These heat-treatments of the magnetic graphene composite gave rise to the cubical expansion of graphene with the enlargement of inter-graphene distances. The specific capacitance of the magnetic graphene composite increased upon heating and reached 42 F g(-1) at a scan rate of 5 mV s(-1) in 1.0 M NaCl, after being treated for 2 min at 900 °C. This value corresponds to 840% increase in the capacitance activity superior to that (5 F g(-1)) of the pristine magnetic graphene composite before heat-treatment. This capacitance enhancement can play a significant role in the increase of the surface area that reached 17.2 m(2) g(-1) during the non-defective inter-graphene exfoliation. Moreover, the magnetic graphene composite heated at 900 °C was hybridized with polyaniline by in situ polymerization of aniline to reach a specific capacitance of 253 F g(-1) at 5 mV s(-1). The current procedure of heat-treatment and hybridization with a conductive polymer can be an effective method for attaining a well-expanded magnetic graphene composite possessing an enhanced electrochemical activity with a relatively high energy density (141 W h kg(-1) in 1.0 M NaCl) and an excellent stability (99% after 9000 cycles of 20 A g(-1)). PMID:27030519

  9. Magnetic relaxation in anisotropic magnets

    DEFF Research Database (Denmark)

    Lindgård, Per-Anker

    1971-01-01

    The line shape and the kinematic and thermodynamic slowing down of the critical and paramagnetic relaxation in axially anisotropic materials are discussed. Kinematic slowing down occurs only in the longitudinal relaxation function. The thermodynamic slowing down occurs in either the transverse or...

  10. Anisotropic Poisson Processes of Cylinders

    CERN Document Server

    Spiess, Malte

    2010-01-01

    Main characteristics of stationary anisotropic Poisson processes of cylinders (dilated k-dimensional flats) in d-dimensional Euclidean space are studied. Explicit formulae for the capacity functional, the covariance function, the contact distribution function, the volume fraction, and the intensity of the surface area measure are given which can be used directly in applications.

  11. Failure in imperfect anisotropic materials

    DEFF Research Database (Denmark)

    Legarth, Brian Nyvang

    2005-01-01

    The fundamental cause of crack growth, namely nucleation and growth of voids, is investigated numerically for a two phase imperfect anisotropic material. A unit cell approach is adopted from which the overall stress strain is evaluated. Failure is observed as a sudden stress drop and depending...

  12. Well-integrated ZnO nanorod arrays on conductive textiles by electrochemical synthesis and their physical properties

    Science.gov (United States)

    Ko, Yeong Hwan; Kim, Myung Sub; Park, Wook; Yu, Jae Su

    2013-01-01

    We reported well-integrated zinc oxide (ZnO) nanorod arrays (NRAs) on conductive textiles (CTs) and their structural and optical properties. The integrated ZnO NRAs were synthesized by cathodic electrochemical deposition on the ZnO seed layer-coated CT substrate in ultrasonic bath. The ZnO NRAs were regularly and densely grown as well as vertically aligned on the overall surface of CT substrate, in comparison with the grown ZnO NRAs without ZnO seed layer or ultrasonication. Additionally, their morphologies and sizes can be efficiently controlled by changing the external cathodic voltage between the ZnO seed-coated CT substrate and the counter electrode. At an external cathodic voltage of -2 V, the photoluminescence property of ZnO NRAs was optimized with good crystallinity and high density.

  13. Thermophysical properties of alkali metal vapours. Part II - assessment of experimental data on thermal conductivity and viscosity

    OpenAIRE

    Fialho, Paulo; Ramires, Maria de Lurdes V.; Nieto de Castro, Carlos A.; João M. N. A. Fareleira; Mardolcar, Umesh V.

    1994-01-01

    Copyright © 1994 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim. Article first published online: 8 MAY 2010. An analysis of the available data on the viscosity and thermal conductivity coefficients of the alkali metal vapours is presented. The analysis is based upon theoretical calculations of the properties of the monatomic systems, described in the preceding parts I and I.A of the present paper, and making use of the kinetic theory of a binary gas reacting mixture. A summary of the measur...

  14. Anisotropic pseudo-potential for polarized dilute quantum gases

    OpenAIRE

    Derevianko, Andrei

    2002-01-01

    Anisotropic pseudopotential relevant to collisions of two particles polarized by external field is rigorously derived and its properties are investigated. Such low-energy pseudopotential may be useful in describing collective properties of dilute quantum gases, such as molecules polarized by electric field or metastable $^3P_2$ atoms polarized by magnetic field. The pseudopotential is expressed in terms of reactance (K--) matrix and derivatives of Dirac delta-function. In most applications it...

  15. Conductive reduced graphene oxide/MnO2 carbonized cotton fabrics with enhanced electro -chemical, -heating, and -mechanical properties

    Science.gov (United States)

    Tian, Mingwei; Du, Minzhi; Qu, Lijun; Zhang, Kun; Li, Hongliang; Zhu, Shifeng; Liu, Dongdong

    2016-09-01

    Versatile and ductile conductive carbonized cotton fabrics decorated with reduced graphene oxide (rGO)/manganese dioxide (MnO2) are prepared in this paper. In order to endow multifunction to cotton fabric, graphene oxide (GO) is deposited on cotton fibers by simple dip-coating route. MnO2 nanoparticles are assembled on the surface of cotton fabric through in-situ chemical solution deposition. MnO2/GO@cotton fabrics are carbonized to achieve conductive fabric (MnO2/rGO@C). The morphologies and structures of obtained fabrics are characterized by SEM, XRD, ICP and element analysis, and their electro-properties including electro-chemical, electro-heating and electro-mechanical properties are evaluated. The MnO2/rGO@C yields remarkable specific capacitance of 329.4 mA h/g at the current density of 100 mA/g, which is more than 40% higher than that of the control carbonized cotton fabric (231 mA h/g). Regarding electro-heating properties, the temperature of MnO2/rGO@C fabric could be monotonically increased to the steady-state maximum temperatures (ΔTmax) of 36 °C within 5 min under the applied voltage 15 V while the ΔTmax = 17 °C of the control case. In addition, MnO2/rGO@C exhibits repeatable electro-mechanical properties and its normalized resistance (R-R0)/R0 could reach 0.78 at a constant strain (curvature = 0.6 cm-1). The MnO2/rGO@C fabric is versatile, scalable, and adaptable to a wide variety of smart textiles applications.

  16. Anisotropic Internal Friction Damping

    CERN Document Server

    Peters, R D

    2003-01-01

    The mechanical damping properties of sheet polaroid material have been studied with a physical pendulum. The polaroid samples were placed under the knife-edges of the pendulum, which was operated in free-decay at a period in the vicinity of 10 s. With the edges oriented parallel to the direction of the long molecular chains in the polaroid, it was found that the damping was more than 10% smaller than when oriented perpendicular to the chains.

  17. Finite-difference schemes for anisotropic diffusion

    Energy Technology Data Exchange (ETDEWEB)

    Es, Bram van, E-mail: es@cwi.nl [Centrum Wiskunde and Informatica, P.O. Box 94079, 1090GB Amsterdam (Netherlands); FOM Institute DIFFER, Dutch Institute for Fundamental Energy Research, Association EURATOM-FOM (Netherlands); Koren, Barry [Eindhoven University of Technology (Netherlands); Blank, Hugo J. de [FOM Institute DIFFER, Dutch Institute for Fundamental Energy Research, Association EURATOM-FOM (Netherlands)

    2014-09-01

    In fusion plasmas diffusion tensors are extremely anisotropic due to the high temperature and large magnetic field strength. This causes diffusion, heat conduction, and viscous momentum loss, to effectively be aligned with the magnetic field lines. This alignment leads to different values for the respective diffusive coefficients in the magnetic field direction and in the perpendicular direction, to the extent that heat diffusion coefficients can be up to 10{sup 12} times larger in the parallel direction than in the perpendicular direction. This anisotropy puts stringent requirements on the numerical methods used to approximate the MHD-equations since any misalignment of the grid may cause the perpendicular diffusion to be polluted by the numerical error in approximating the parallel diffusion. Currently the common approach is to apply magnetic field-aligned coordinates, an approach that automatically takes care of the directionality of the diffusive coefficients. This approach runs into problems at x-points and at points where there is magnetic re-connection, since this causes local non-alignment. It is therefore useful to consider numerical schemes that are tolerant to the misalignment of the grid with the magnetic field lines, both to improve existing methods and to help open the possibility of applying regular non-aligned grids. To investigate this, in this paper several discretization schemes are developed and applied to the anisotropic heat diffusion equation on a non-aligned grid.

  18. Stress singularity analysis of anisotropic multi-material wedges under antiplane shear deformation using the symplectic approach

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    Symplectic approach has emerged a popular tool in dealing with elasticity problems especially for those with stress singularities. However, anisotropic material problem under polar coordinate system is still a bottleneck. This paper presents a subfield method coupled with the symplectic approach to study the anisotropic material under antiplane shear deformation. Anisotropic material around wedge tip is considered to be consisted of many subfields with constant material properties which can be handled by th...

  19. Scaling Argument of Anisotropic Random Walk

    Institute of Scientific and Technical Information of China (English)

    XU Bing-Zhen; JIN Guo-Jun; WANG Fei-Feng

    2005-01-01

    In this paper, we analytically discuss the scaling properties of the average square end-to-end distance for anisotropic random walk in D-dimensional space ( D ≥ 2), and the returning probability Pn(ro) for the walker into a certain neighborhood of the origin. We will not only give the calculating formula for and Pn (ro), but also point out that if there is a symmetric axis for the distribution of the probability density of a single step displacement, we always obtain ~ n, where ⊥ refers to the projections of the displacement perpendicular to each symmetric axes of the walk; in D-dimensional space with D symmetric axes perpendicular to each other, we always have ~ n and the random walk will be like a purely random motion; if the number of inter-perpendicular symmetric axis is smaller than the dimensions of the space, we must have ~ n2 for very large n and the walk will be like a ballistic motion. It is worth while to point out that unlike the isotropic random walk in one and two dimensions, which is certain to return into the neighborhood of the origin, generally there is only a nonzero probability for the anisotropic random walker in two dimensions to return to the neighborhood.

  20. First-Principles Study of Lattice Thermal Conductivity of Td-WTe2

    OpenAIRE

    Liu, Gang; Sun, Hong Yi; Zhou, Jian; Li, Qing Fang; Wan, X. G.

    2015-01-01

    The structural and thermal properties of bulk Td-WTe2 have been studied by using first-principles calculations. We find that the lattice thermal conductivity of WTe2 is anisotropic, with the highest value along a-axis and lowest one along the c-axis at 300 K. Our calculated size dependent thermal conductivity shows that nanostructuring of WTe2 can possibly further decrease the lattice thermal conductivity. Such extremely low thermal conductivity, even much lower than WSe2, makes WTe2 attracti...