Atomistic simulation of fatigue in face centred cubic metals
International Nuclear Information System (INIS)
Fan, Zhengxuan
2016-01-01
Fatigue is one of the major damage mechanisms of metals. It is characterized by strong environmental effects and wide lifetime dispersions which must be better understood. Different face centred cubic metals, al, Cu, Ni, and Ag are analyzed. The mechanical behaviour of surface steps naturally created by the glide of dislocations subjected to cyclic loading is examined using molecular dynamics simulations in vacuum and in air for Cu and Ni. an atomistic reconstruction phenomenon is observed at these surface steps which can induce strong irreversibility. Three different mechanisms of reconstruction are defined. Surface slip irreversibility under cyclic loading is analyzed. all surface steps are intrinsically irreversible under usual fatigue laboratory loading amplitude without the arrival of opposite sign dislocations on direct neighbor plane.With opposite sign dislocations on non direct neighbour planes, irreversibility cumulates cycle by cycle and a micro-notch is produced whose depth gradually increases.Oxygen environment affects the surface (first stage of oxidation) but does not lead to higher irreversibility as it has no major influence on the different mechanisms linked to surface relief evolution.a rough estimation of surface irreversibility is carried out for pure edge dislocations in persistent slip bands in so-called wavy materials. It gives an irreversibility fraction between 0.5 and 0.75 in copper in vacuum and in air, in agreement with recent atomic force microscopy measurements.Crack propagation mechanisms are simulated in inert environment. Cracks can propagate owing to the irreversibility of generated dislocations because of their mutual interactions up to the formation of dislocation junctions. (author) [fr
Some aspects of plasticity in hardened face-centred cubic metals
International Nuclear Information System (INIS)
Jackson, P.J.; Nathanson, P.D.K.
1978-01-01
The plasticity of crystals of f.c.c. metals hardened by solute atoms, neutron irradiation, quenching and by dislocation distributions not characteristic of the active mode of testing is reviewed, with emphasis being placed on the simiularity of slip after various hardening treatments. Normal work hardening is not treated. The reasons for this exclusion are discussed. It is concluded that correlated slip is a normal aspect of deformation, and that diffuse uncorrelated slip occurs only when secondary dislocation multiplication is promoted, e.g. by obstacles introduced by prior slip, or by the presence of hard impenetrable obstacles of another material or phase [af
Pamato, Martha G; Wood, Ian G; Dobson, David P; Hunt, Simon A; Vočadlo, Lidunka
2018-04-01
On the basis of ab initio computer simulations, pre-melting phenomena have been suggested to occur in the elastic properties of hexagonal close-packed iron under the conditions of the Earth's inner core just before melting. The extent to which these pre-melting effects might also occur in the physical properties of face-centred cubic metals has been investigated here under more experimentally accessible conditions for gold, allowing for comparison with future computer simulations of this material. The thermal expansion of gold has been determined by X-ray powder diffraction from 40 K up to the melting point (1337 K). For the entire temperature range investigated, the unit-cell volume can be represented in the following way: a second-order Grüneisen approximation to the zero-pressure volumetric equation of state, with the internal energy calculated via a Debye model, is used to represent the thermal expansion of the 'perfect crystal'. Gold shows a nonlinear increase in thermal expansion that departs from this Grüneisen-Debye model prior to melting, which is probably a result of the generation of point defects over a large range of temperatures, beginning at T / T m > 0.75 (a similar homologous T to where softening has been observed in the elastic moduli of Au). Therefore, the thermodynamic theory of point defects was used to include the additional volume of the vacancies at high temperatures ('real crystal'), resulting in the following fitted parameters: Q = ( V 0 K 0 )/γ = 4.04 (1) × 10 -18 J, V 0 = 67.1671 (3) Å 3 , b = ( K 0 ' - 1)/2 = 3.84 (9), θ D = 182 (2) K, ( v f /Ω)exp( s f / k B ) = 1.8 (23) and h f = 0.9 (2) eV, where V 0 is the unit-cell volume at 0 K, K 0 and K 0 ' are the isothermal incompressibility and its first derivative with respect to pressure (evaluated at zero pressure), γ is a Grüneisen parameter, θ D is the Debye temperature, v f , h f and s f are the vacancy formation volume, enthalpy and entropy
Phonons in face-centred cubic calcium and strontium
International Nuclear Information System (INIS)
Singh, S.P.; Rathore, R.P.S.
1984-01-01
The axially symmetric and unpaired forces are employed to analyse the phonon dispersion and elastic behaviour of face centred cubic calcium and strontium which have so far not been studied adequately. The model with three parameters predicts the results which agree marvellously with the recently measured data. (author)
International Nuclear Information System (INIS)
Miszczyk, M.; Paul, H.; Driver, J.H.; Maurice, C.
2015-01-01
Graphical abstract: For Ni, Cu and Cu-2%Al and (1 1 0)[0 0 −1] and (1 1 0)[1 −1 −2] initial orientations at the initial stages of recrystallization, the appearance of a specific number of new orientation groups of new grains has been demonstrated. The orientation relations across the recrystallization front are characterized by a high proportion of angles in the range 25–35° and 45–55° around axes mostly grouped about the 〈1 2 2〉, 〈1 1 1〉, 〈1 2 3〉 and 〈1 1 2〉 directions. A local minimum was noted for the disorientation angle densities close to 40° in all cases. For a single isolated nucleus of uniform orientation, the rotation axes are usually grouped around one of the normals of all four {1 1 1} planes but do not (or only rarely) coincide with them. The orientation of the growing new grain quickly transforms through the formation of a first generation twins. The most frequent situation occurs when the normal of the twinning face plane is situated near the rotation axis, around which the crystal lattice of the ‘primary nuclei’ rotates. Based on the anisotropy of grain growth a possible mechanism of orientation generation and grain growth by thermally activation movement of dislocation families, on {1 1 1} planes is proposed. - Abstract: The early stages of recrystallization have been systematically characterized in single crystal metals of medium and low stacking fault energy. Goss {1 1 0}〈0 0 1〉 and brass {1 1 0}〈1 1 2〉 oriented samples of Ni, Cu and Cu–2 wt.% Al alloy were deformed in a channel die to a logarithmic strain of 0.51 to develop a homogeneous structure composed of two sets of symmetrical primary microbands and then lightly annealed. Scanning electron microscopy/electron backscattered diffraction analyses demonstrate a strong relation between as-deformed orientations and the limited number of recrystallized grain orientations. The disorientation angles across the recrystallization front are mostly grouped in
Size effect on deformation twinning in face-centred cubic single crystals: Experiments and modelling
International Nuclear Information System (INIS)
Liang, Z.Y.; De Hosson, J.T.M.; Huang, M.X.
2017-01-01
In addition to slip by dislocation glide, deformation twinning in small-sized metallic crystals also exhibits size effect, namely the twinning stress increases with decreasing sample size. In order to understand the underpinning mechanisms responsible for such effect, systematic experiments were carried out on the small-sized single-crystalline pillars of a twinning-induced plasticity steel with a face-centred cubic structure. The flow stress increases considerably with decreasing pillar diameter from 3 to 0.5 μm, demonstrating a substantial size effect with a power exponent of 0.43. Detailed microstructural characterization reveals that the plastic deformation of the present pillars is dominant by twinning, primarily via twin growth, indicating that the size effect should be related to deformation twinning instead of slip by dislocation glide. Subsequent modelling works indicate that twinning can be accomplished by the dissociation of the ion-radiation-induced vacancy Frank loops in the damaged subsurface layer of the pillars, and the size effect is attributed to the ion-radiation-induced compressive stress in the subsurface layer, which decreases with pillar diameter.
A kinematical model for the plastic deformation of face-centred cubic polycrystals
International Nuclear Information System (INIS)
Leffers, T.
1975-01-01
During the plastic deformation of a polycrystalline material the deformation of the individual grain must be adjusted to the deformation of the surrounding grains so that material continuity is maintained. This continuity condition is the essential feature distinguishing polycrystal deformation from single-crystal deformation. In the present work it is attempted to explain how the continuity condition is fulfilled in face-centred cubic polycrystals. The early treatments of the plastic deformation of polycrystalline materials were aimed directly at the formulation of a ''dynamical'' theory, i.e. it was the intention to cover the magnitude of the stresses involved as well as the slip processes producing the deformation. It is argued that rolling texture is a good tool for a necessary intermediate stage of establishing a ''kinematical'' model describing the slip processes, but not the magnitude of the necessary stresses. Three aspects of rolling texture are considered: (a) the development of the rolling textures found experimentally in face-centred cubic materials can be computer-simulated on the basis of models for the plastic deformation that only involve (111) slip; (b) experimentally that the widely accepted twinning theory for the transition in f.c.c. rolling texture does not reflect the behaviour of real materials; and (c) it is shown that the texture transition is thermally activated with an activation energy corresponding to that of cross slip. An electron-microscopical investigation of the slip process operating during rolling of f.c.c. polycrystals is also included. On the basis of the computer simulation of the texture formation supplemented by the experimental results a kinematical model is developed for the plastic deformation of f.c.c. polycrystals by rolling. In the proposed model the material continuity is maintained by inhomogeneous slip processes, combined with homogeneous multiple glide when the cross-slip frequency is high. (author)
International Nuclear Information System (INIS)
Luo Xinjun; Sholl, C A
2003-01-01
Magnetization recoveries for nuclear spin relaxation of like spins due to magnetic dipolar coupling and diffusion on inequivalent sites involve a sum of exponentials. The theory is applied to diffusion on octahedral and tetrahedral interstitial sites in the face-centred cubic structure. Monte Carlo simulations have been used to generate relaxation data for parameters typical for H in metals. It is found that only a single exponential would be observable in the high- and low-temperature limits, but that two-exponential recoveries could be observable in the vicinity of the maximum in the relaxation rate as a function of temperature. The Monte Carlo relaxation data has been fitted using a Bloembergen-Pound-Purcell (BPP) model to assess the accuracy of the BPP model
Dupraz, Maxime; Beutier, Guillaume; Rodney, David; Mordehai, Dan; Verdier, Marc
2015-06-01
Crystal defects induce strong distortions in diffraction patterns. A single defect alone can yield strong and fine features that are observed in high-resolution diffraction experiments such as coherent X-ray diffraction. The case of face-centred cubic nanocrystals is studied numerically and the signatures of typical defects close to Bragg positions are identified. Crystals of a few tens of nanometres are modelled with realistic atomic potentials and 'relaxed' after introduction of well defined defects such as pure screw or edge dislocations, or Frank or prismatic loops. Diffraction patterns calculated in the kinematic approximation reveal various signatures of the defects depending on the Miller indices. They are strongly modified by the dissociation of the dislocations. Selection rules on the Miller indices are provided, to observe the maximum effect of given crystal defects in the initial and relaxed configurations. The effect of several physical and geometrical parameters such as stacking fault energy, crystal shape and defect position are discussed. The method is illustrated on a complex structure resulting from the simulated nanoindentation of a gold nanocrystal.
Anomalous diffusion in body-centred and face-centred cubic metals
International Nuclear Information System (INIS)
Zanghi, J.-P.
1975-10-01
The initial rates of contraction due to self-irradiation damage at 4.2K in three PuSc alloys (5, 12, 18 at % Sc) stabilized in f.c.c. delta-phase were measured. The high negative value of the formation volume of a Frenkel pair which is deduced by extrapolating for pure Pu, can only be explained by assuming that the interstitial Pu may partly recover its distortion energy by creating bonds with its neighbours, by a localized enhancement of the d.f. hybridization and especially by provoking the formation of bonds between its very neighbours. It is shown that about twenty atoms around the interstitial Pu are affected by these bonds. The self-irradiation at 4.2K of a b.c.c. UPuMo alloy was also studied. The activation volume for self-diffusion of Pu in b.c.c. PuZr alloys (10 and 40 at % Zr) was determined. So the validity of Nachtrieb's melting-diffusion correlation could be checked. Indeed, in the Pu 40 at % Zr alloy, which has a pressure temperature diagram the liquidus of which has a positive slope, a positive activation volume was found, whereas in pure epsilon Pu which as a negative slope, the activation volume is negative. A self-diffusion mechanism in PuZr alloys is proposed. A study of the diffusion of Am in these alloys showed that Am and Pu likely diffuse by the same mechanism [fr
Lee, Hyun A; Castro-Aceituno, Veronica; Abbai, Ragavendran; Moon, Seong Soo; Kim, Yeon-Ju; Simu, Shakina Yesmin; Yang, Deok Chun
2018-03-29
The water extract of Anemarrhena asphodeloides, the traditional oriental medicinal plant, mediated the eco-friendly synthesis of silver nanoparticles (Aa-AgNPs) and gold nanoparticles (Aa-AuNPs). First, its therapeutic rhizome was powdered prior to water extraction and then silver, gold nanoparticles were synthesized. Aa-AgNPs and Aa-AuNPs were found to be spherical, face-centred cubic nanocrystals with a Z-average hydrodynamic diameter of 190 and 258 nm, respectively. In addition, proteins and aromatic biomolecules were the plausible players associated with the production and stabilization of Aa-AgNPs; instead, phenolic compounds were responsible for the synthesis and stability of Aa-AuNPs. In vitro cytotoxic analysis revealed that up to 50 μg.mL -1 concentration Aa-AuNPs did not exhibit any toxicity on 3T3-L1, HT29 and MCF7 cell lines, while being specifically cytotoxic to A549 cell line. On the contrary, Aa-AgNPs displayed a significantly higher toxicity in comparison to Aa-AuNPs in all cell lines specially MCF7 cell line. Since cancer cells were more sensitive to Aa-Au/AgNPs treatments, further evaluation was done in order to determine their anticancer potential. Reactive oxygen species (ROS) generation was not affected by Aa-AuNPs, on the other hand, Aa-AgNPs treatment exhibited a higher potential to induce oxidative stress in A549 cells than HT29 and MCF7 cells. In addition, Aa-Ag/AuNPs reduced cell migration in A549 cells at 10 and 50 μg.mL -1 , respectively. So far, this is the only report uncovering the ability of A. asphodeloides to synthesize silver and gold nanoparticles with anticancer potential and also indirectly enabling its large-scale utilization with value addition.
Temperature dependence of critical resolved shear stress for cubic metals
International Nuclear Information System (INIS)
Rashid, H.; Fazal-e-Aleem; Ali, M.
1996-01-01
The experimental measurements for critical resolved shear stress of various BCC and FCC metals have been explained by using Radiation Model. The temperature dependence of CRSS for different cubic metals is found to the first approximation, to upon the type of the crystal. A good agreement between experimental observations and predictions of the Radiation Model is found. (author)
Plasmon polaritons in cubic lattices of spherical metallic nanoparticles
Lamowski, Simon; Mann, Charlie-Ray; Hellbach, Felicitas; Mariani, Eros; Weick, Guillaume; Pauly, Fabian
2018-03-01
We theoretically investigate plasmon polaritons in cubic lattices of spherical metallic nanoparticles. The nanoparticles, each supporting triply-degenerate localized surface plasmons, couple through the Coulomb dipole-dipole interaction, giving rise to collective plasmons that extend over the whole metamaterial. The latter hybridize with photons forming plasmon polaritons, which are the hybrid light-matter eigenmodes of the system. We derive general analytical expressions to evaluate both plasmon and plasmon-polariton dispersions and the corresponding eigenstates. These are obtained within a Hamiltonian formalism, which takes into account retardation effects in the dipolar interaction between the nanoparticles and considers the dielectric properties of the nanoparticles as well as their surrounding. Within this model we predict polaritonic splittings in the near-infrared to the visible range of the electromagnetic spectrum that depend on polarization, lattice symmetry, and wave-vector direction. Finally, we show that the predictions of our model are in excellent quantitative agreement with conventional finite-difference frequency-domain simulations, but with the advantages of analytical insight and significantly reduced computational cost.
Energy landscape of defects in body-centered cubic metals
International Nuclear Information System (INIS)
Alexander, Rebecca
2016-01-01
The structural materials in nuclear reactors are subjected to severe irradiation conditions, leading to changes in their mechanical properties. The aging of these materials raises important issues such as those related to the safety of existing plants and future reactors. In many cases, materials with body-centered cubic bcc crystal structure are used with iron, tungsten, vanadium and tantalum as base metal. Collisions between irradiating particles and atoms constituting materials generate point defects whose migration leads to the formation of clusters responsible for aging. In this thesis, we studied the energetic properties of point defects in the bcc metals mentioned above at the atomic scale. Modeling point defects at the atomic scale can be achieved with different methods that differ only in the quality of the description of the interaction between atoms. Studies using accurate atomic interactions such ab initio calculations are computationally costly making it impossible to directly study clusters of large sizes. The modeling of atomic interactions using semi-empirical potentials reduces the reliability of predictive calculations but allow calculations for large-sized clusters. In this thesis we have developed a unique energy model for dislocation loops as well as for three-dimensional interstitial cluster of type C15. The resulting model has no size limit and can be set entirely by ab initio calculations. To test its robustness for large sizes of clusters we also set this model with semi-empirical potentials calculations and compared the predictions of the model to atomic simulations. With our development we have determined: (i) The relative stability of interstitial dislocation loops according to their Burgers vectors. (ii) The stability of the clusters C15 compared to the type of cluster loop. We showed that the C15 type clusters are more stable when they involve less than 41 interstitials in iron. (iii) In Ta we were able to show the same stability till
On metal-insulator transition in cubic fullerides
Iwahara, Naoya; Chibotaru, Liviu
The interplay between degenerate orbital and electron correlation is a key to characterize the electronic phases in, for example, transition metal compounds and alkali-doped fullerides. Besides, the degenerate orbital couples to spin and lattice degrees of freedom ,giving rise to exotic phenomena. Here, we develop the self-consistent Gutzwiller approach for the simultaneous treatment of the Jahn-Teller effect and electron correlation, and apply the methodology to reveal the nature of the ground electronic state of fullerides. For small Coulomb repulsion on site U, the fulleride is quasi degenerate correlated metal. With increase of U, we found the quantum phase transition from the metallic phase to JT split phase. In the latter, the Mott transition (MT) mainly develops in the half-filled subband, whereas the empty and the completely filled subbands are almost uninvolved. Therefore, we can qualify the metal-insulator transition in fullerides as an orbital selective MT induced by JT effect.
Influence of a hydrostatic pressure on the diffusion in metals having a cubic structure
International Nuclear Information System (INIS)
Beyeler, M.
1969-01-01
In view of obtaining informations on the structure of vacancies. We have determined, by diffusion experiments under high pressure, the activation volumes for self diffusion in different face centered cubic metals: silver, gold, copper, aluminium and in body centered cubic uranium (gamma phase). Activation volumes for noble metals diffusion in aluminium have also been investigated. The experimental results on gold, silver and copper are in good agreement with most of the theoretical models. The estimated activation volume for gamma uranium seems to indicate a vacancy mechanism.The results on aluminium for both self and impurity diffusion agree quite well with Friedel's theoretical predictions [fr
International Nuclear Information System (INIS)
Rovere, Florian; Mayrhofer, Paul H; Music, Denis; Ershov, Sergey; Baben, Moritz to; Schneider, Jochen M; Fuss, Hans-Gerd
2010-01-01
The phase stability of Al-containing cubic transition metal (TM) nitrides, where Al substitutes for TM (i.e. TM 1-x Al x N), is studied as a function of the TM valence electron concentration (VEC). X-ray diffraction and thermal analyses data of magnetron sputtered Ti 1-x Al x N, V 1-x Al x N and Cr 1-x Al x N films indicate increasing phase stability of cubic TM 1-x Al x N at larger Al contents and higher temperatures with increasing TM VEC. These experimental findings can be understood based on first principle investigations of ternary cubic TM 1-x Al x N with TM = Sc, Ti, V, Cr, Y, Zr and Nb where the TM VEC and the lattice strain are systematically varied. However, our experimental data indicate that, in addition to the decomposition energetics (cubic TM 1-x Al x N → cubic TMN + hexagonal AlN), future stability models have to include nitrogen release as one of the mechanisms that critically determine the overall phase stability of TM 1-x Al x N.
Nano- and microsized cubic gel particles from cyclodextrin metal-organic frameworks.
Furukawa, Yuki; Ishiwata, Takumi; Sugikawa, Kouta; Kokado, Kenta; Sada, Kazuki
2012-10-15
Sweet cube o' mine: Bottom-up control of gel particles has been regarded as a great challenge. By employing internal cross-linking of cyclodextrin metal-organic frameworks, cubic sugar gels were formed with sharp edges that reflect the shape of the crystals. This enabled the fabrication of shape- and size-controlled polymer gels from porous crystals (see picture). Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Pressure-driven insulator-metal transition in cubic phase UO2
Huang, Li; Wang, Yilin; Werner, Philipp
2017-09-01
Understanding the electronic properties of actinide oxides under pressure poses a great challenge for experimental and theoretical studies. Here, we investigate the electronic structure of cubic phase uranium dioxide at different volumes using a combination of density functional theory and dynamical mean-field theory. The ab initio calculations predict an orbital-selective insulator-metal transition at a moderate pressure of ∼45 GPa. At this pressure the uranium's 5f 5/2 state becomes metallic, while the 5f 7/2 state remains insulating up to about 60 GPa. In the metallic state, we observe a rapid decrease of the 5f occupation and total angular momentum with pressure. Simultaneously, the so-called “Zhang-Rice state”, which is of predominantly 5f 5/2 character, quickly disappears after the transition into the metallic phase.
Shear response of Σ3{112} twin boundaries in face-centered-cubic metals
Wang, J.; Misra, A.; Hirth, J. P.
2011-02-01
Molecular statics and dynamics simulations were used to study the mechanisms of sliding and migration of Σ3{112} incoherent twin boundaries (ITBs) under applied shear acting in the boundary in the face-centered-cubic (fcc) metals, Ag, Cu, Pd, and Al, of varying stacking fault energies. These studies revealed that (i) ITBs can dissociate into two phase boundaries (PBs), bounding the hexagonal 9R phase, that contain different arrays of partial dislocations; (ii) the separation distance between the two PBs scales inversely with increasing stacking fault energy; (iii) for fcc metals with low stacking fault energy, one of the two PBs migrates through the collective glide of partials, referred to as the phase-boundary-migration (PBM) mechanism; (iv) for metals with high stacking energy, ITBs experience a coupled motion (migration and sliding) through the glide of interface disconnections, referred to as the interface-disconnection-glide (IDG) mechanism.
International Nuclear Information System (INIS)
Yu Xiao-Xiang; Wang Chong-Yu
2013-01-01
An effective multiscale simulation which concurrently couples the quantum-mechanical and molecular-mechanical calculations based on the position continuity of atoms is presented. By an iterative procedure, the structure of the dislocation core in face-centered cubic metal is obtained by first-principles calculation and the long-range stress is released by molecular dynamics relaxation. Compared to earlier multiscale methods, the present work couples the long-range strain to the local displacements of the dislocation core in a simpler way with the same accuracy. (condensed matter: electronic structure, electrical, magnetic, and optical properties)
High dose effects in neutron irradiated face-centered cubic metals
International Nuclear Information System (INIS)
Garner, F.A.; Toloczko, M.B.
1993-06-01
During neutron irradiation, most face-centered cubic metals and alloys develop saturation or quasi-steady state microstructures. This, in turn, leads to saturation levels in mechanical properties and quasi-steady state rates of swelling and creep deformation. Swelling initially plays only a small role in determining these saturation states, but as swelling rises to higher levels, it exerts strong feedback on the microstructure and its response to environmental variables. The influence of swelling, either directly or indirectly via second order mechanisms, such as elemental segregation to void surfaces, eventually causes major changes, not only in irradiation creep and mechanical properties, but also on swelling itself. The feedback effects of swelling on irradiation creep are particularly complex and lead to problems in applying creep data derived from highly pressurized creep tubes to low stress situations, such as fuel pins in liquid metal reactors
Migration energy barriers of symmetric tilt grain boundaries in body-centered cubic metal Fe
International Nuclear Information System (INIS)
Wu, Minghui; Gu, Jianfeng; Jin, Zhaohui
2015-01-01
Graphical abstract: DFT calculated migration energy barrier (left) for symmetric grain boundary in metals is an essential physical property to measure the trend of grain boundary migration, in particular, in terms of the classical homogeneous nucleation model of GB dislocation/disconnection loops (right). - Migration energy barriers of two symmetric tilt grain boundaries in body-centered cubic metal Fe are obtained via first-principles calculations in combination with the nudged elastic band methods. Although the two grain boundaries show similar grain boundary energies, the migration energy barriers are different. Based on a homogeneous nucleation theory of grain-boundary dislocation loops, the calculated energy barrier provides a measure of intrinsic grain-boundary mobility and helps to evaluate effects due to vacancy and interstitial atoms such as carbon
Aray, Yosslen; Paredes, Ricardo; Álvarez, Luis Javier; Martiz, Alejandro
2017-06-14
The electron density localization in insulator and semiconductor elemental cubic materials with diamond structure, carbon, silicon, germanium, and tin, and good metallic conductors with face centered cubic structure such as α-Co, Ni, Cu, Rh, Pd, Ag, Ir, Pt, and Au, was studied using a localized electrons detector defined in the local moment representation. Our results clearly show an opposite pattern of the electron density localization for the cubic ceramic and transition metal materials. It was found that, for the elemental ceramic materials, the zone of low electron localization is very small and is mainly localized on the atomic basin edges. On the contrary, for the transition metals, there are low-valued localized electrons detector isocontours defining a zone of highly delocalized electrons that extends throughout the material. We have found that the best conductors are those in which the electron density at this low-value zone is the lowest.
The quantitative representation of fiber-and sheet-texture in metals of cubic system
International Nuclear Information System (INIS)
Kim, H.J.; Kim, S.C.; Chun, B.C.; Lee, C.Y.
1983-01-01
This is the first article of a series dealing with studies on the quantitative representation of fiber-and sheet-type textures in metals of cubic crystal system. Texture measurements by neutron diffraction method are analyzed using Bunge's series expansion method and the effect of series truncation is studied for samples of various texture sharpness. The present article describes two computer programs, TXFIB and TXSHT, develped for the analysis of the respective fiber-and sheet-type texture. Using these computer programs, the orientation distribution function can be expanded in the series of generalized spherical harmonics up to 58th term from 6 experimental pole figures as input. Estimations of various errors involved in the texture analysis and texture sharpness index are also included in the programs. (Author)
Defect production rates by electrons, ions and neutrons in cubic metals
International Nuclear Information System (INIS)
Jung, P.; Nielsen, B.R.; Andersen, H.H.
1982-01-01
The results of an interlaboratory program to study low temperature damage rates in dilute alloys of 300 ppM Zr in vanadium, niobium and molybdenum with electrons, light ions, fission neutrons and high energy neutrons are summarized. Additional experiments and literature data supplied complete sets of data also for the fcc metals Al, Cu and Pt. From the initial damage rates, displacement functions for each material were derived which give the number of stable defects produced by a recoil event of a certain knock-on energy. The low and high energy part of the displacement function was determined from the results of the electron and neutron irradiations, respectively, while the light ion data supplied information on the intermediate energy range. The displacement function allows the reliable calculation of atomic displacement rates also for particles and/or energies not employed in this program. For all metals the displacement rates for high energy neutrons scaled reasonably with the minimum displacement energies. This allows to estimate neutron damage rates also for those cubic metals where no high energy neutron results are available. For stainless steel, e.g., an average displacement energy of about 120 eV is deduced. The results are suggested to find practical use in defect calculations for fusion reactor first wall technology and in correlating the corresponding simulation experiments
Martensitic cubic → tetragonal transition
International Nuclear Information System (INIS)
Schumann, H.
1983-01-01
Indium-thallium alloys containing 14 to 30% At. Tl have a cubic face-centred beta phase wich changes into a tetragonal face-centred alpha martensite during solidification. The martensite contains twin crystals that are large enough to be seen by means of a light microscope. The phenomenological crystallographic martensite theory was used to calculate Miller's index of the habit plane, the formation of the surface relief, the orientation relations and the critical thickness ratio of the twins. In a beta monocrystal frequently only one of the 24 crystallographic possible habit planes are formed at one end of the sample and migrate through the whole crystal when the temperature drops. Externally applied tension and compression influence in different ways the direction in which the habit plane moves and can even destroy the twinned structure, i.e. they can modify the substructure of the martensite crystal. This induces superelasticity, an effect that has also been described quantitatively. (author)
Texture evolution maps for upset deformation of body-centered cubic metals
International Nuclear Information System (INIS)
Lee, Myoung-Gyu; Wang, Jue; Anderson, Peter M.
2007-01-01
Texture evolution maps are used as a tool to visualize texture development during upset deformation in body-centered cubic metals. These maps reveal initial grain orientations that tend toward normal direction (ND)|| versus ND|| . To produce these maps, a finite element analysis (FEA) with a rate-dependent crystal plasticity constitutive relation for tantalum is used. A reference case having zero workpiece/die friction shows that ∼64% of randomly oriented grains rotate toward ND|| and ∼36% rotate toward ND|| . The maps show well-established trends that increasing strain rate sensitivity and decreasing latent-to-self hardening ratio reduce both and percentages, leading to more diffuse textures. Reducing operative slip systems from both {1 1 0}/ and {1 1 2}/ to just {1 1 0}/ has a mixed effect: it increases the percentage but decreases the percentage. Reducing the number of slip systems and increasing the number of FEA integration points per grain strengthen - texture bands that are observed experimentally
Control of in-plane texture of body centered cubic metal thin films
International Nuclear Information System (INIS)
Harper, J.M.; Rodbell, K.P.; Colgan, E.G.; Hammond, R.H.
1997-01-01
We show that dramatically different in-plane textures can be produced in body centered cubic (bcc) metal thin films deposited on amorphous substrates under different deposition conditions. The crystallographic orientation distribution of polycrystalline bcc metal thin films on amorphous substrates often has a strong left-angle 110 right-angle fiber texture, indicating that {110} planes are parallel to the substrate plane. When deposition takes place under bombardment by energetic ions or atoms at an off-normal angle of incidence, the left-angle 110 right-angle fiber texture develops an in-plane texture, indicating nonrandom azimuthal orientations of the crystallites. Three orientations in Nb films have been observed under different deposition geometries, in which the energetic particle flux coincides with channeling directions in the bcc crystal structure. In-plane orientations in Mo films have also been obtained in magnetron sputtering systems with various configurations. These are described, and an example is given in which the in-plane orientation of Mo films deposited in two different in-line magnetron sputtering systems differs by a 90 degree rotation. In these two cases, there is a strong left-angle 110 right-angle fiber texture, but the in-plane left-angle 100 right-angle direction is oriented parallel to the scan direction in one system, and perpendicular to the scan direction in the other system. The conditions which produce such different in-plane textures in two apparently similar sputtering systems are discussed. copyright 1997 American Institute of Physics
Polycrystal plasticity as applied to the problem of in-plane anisotropy in rolled cubic metals
International Nuclear Information System (INIS)
Rollett, A.D.; Stout, M.G.; Kocks, U.F.
1989-01-01
A fundamental property of cubic metals is that slip occurs on close-packed planes in close-packed directions, which for the f.c.c. case results in 12 /111/ slip systems. This crystallographic restriction on the plastic behavior causes significant crystallographic preferred orientation (texture), hence anisotropy, to develop once a large strain has been imposed. Moreover, whereas annealing can generally ''reset'' the flow stress and ductility, it does not generally randomize the texture: therefore most metallic materials have some degree of texture and consequent anisotropy. The problem of tearing in deep drawing can be simply related to the variation of r-value with angle from the rolling direction, i.e. the in-plane anisotropy of the sheet. The r-value can be calculated from a given texture with the use of a polycrystal plasticity model. The Los Alamos polycrystal plasticity (LApp) code is based on the Bishop-Hill single crystal yield surface (SCYS) but with a mildly strain-rate sensitive modification where the stress exponent is of order 30. This modification of the SCYS removes the ambiguity of slip system selection inherent in the Bishop-Hill formulation and permits other phenomena to be treated such as latent hardening and pencil glide. The use of LApp to simulate texture formation and consequent anisotropy is described. Experimental textures in the form of X-ray pole figures are analyzed with a Williams-Imhof-Matthies-Vinel (WIMV) code, as implemented by Kallend, to give full orientation distributions (OD's). The OD obtained this way contains approximately 5000 points on a 5/degree/ by 5/degree/ lattice; this is used to assign weights to approximately 1000 discrete orientations for calculations with LApp. 11 refs., 2 figs
Teii, Kungen; Kawamoto, Shinsuke; Fukui, Shingo; Matsumoto, Seiichiro
2018-04-01
Metal-insulator-metal capacitor structures using thick hexagonal and cubic boron nitride (hBN and cBN) films as dielectrics are produced by plasma jet-enhanced chemical vapor deposition, and their electrical transport and capacitance characteristics are studied in a temperature range of 298 to 473 K. The resistivity of the cBN film is of the order of 107 Ω cm at 298 K, which is lower than that of the hBN film by two orders of magnitude, while it becomes the same order as the hBN film above ˜423 K. The dominant current transport mechanism at high fields (≥1 × 104 V cm-1) is described by the Frenkel-Poole emission and thermionic emission models for the hBN and cBN films, respectively. The capacitance of the hBN film remains stable for a change in alternating-current frequency and temperature, while that of the cBN film has variations of at most 18%. The dissipation factor as a measure of energy loss is satisfactorily low (≤5%) for both films. The origin of leakage current and capacitance variation is attributed to a high defect density in the film and a transition interlayer between the substrate and the film, respectively. This suggests that cBN films with higher crystallinity, stoichiometry, and phase purity are potentially applicable for dielectrics like hBN films.
Knezevic, Marko
Crystal plasticity physics-based constitutive theories are used in understanding and predicting the evolution of the underlying microstructure and the concomitant anisotropic stress-strain response in polycrystalline metals subjected to finite plastic strains. A new scheme for efficient crystal plasticity computations for both cubic and hexagonal polycrystalline metals subjected to arbitrary deformation modes has been developed in this thesis. This new computational scheme involves building material databases comprised of spectral coefficients. These spectral coefficients are computed using discrete Fourier transforms (DFTs) and allow for compact representation and fast retrieval of crystal plasticity solutions for a crystal of any orientation subjected to any deformation mode. The novel approach is able to speed up the conventional crystal plasticity computations by two orders of magnitude. Furthermore, mathematical procedures for delineation of property closures that identify the complete set of theoretically feasible combinations of macroscale effective properties has been developed for a broad set of mechanical properties. Subsequently, these constructs were used in microstructure design for identifying an optimal microstructure for selected performance criteria. And finally, hybrid processing recipes that transform a given initial microstructure into a member of the set of optimal microstructures that exhibit superior properties or performance characteristics have been described. Insights and tremendous potential of these novel materials knowledge systems are discussed and demonstrated through specific case-studies. The anisotropic stress-strain response measured in simple compression and simple tension tests in different sample directions on an annealed, strongly textured, AZ31 sheet has been studied. New insights into the mechanical response of this material were obtained by correlating the changes in the measured strain-hardening rates in the different
Park, Yong-Jin; Cho, Ju-Young; Jeong, Min-Woo; Na, Sekwon; Joo, Young-Chang
2016-02-23
The novel discovery of a current-induced transition from insulator to metal in the crystalline phase of Ge2Sb2Te5 and GeSb4Te7 have been studied by means of a model using line-patterned samples. The resistivity of cubic phase Ge-Sb-Te compound was reduced by an electrical current (~1 MA/cm(2)), and the final resistivity was determined based on the stress current density, regardless of the initial resistivity and temperature, which indicates that the conductivity of Ge-Sb-Te compound can be modulated by an electrical current. The minimum resistivity of Ge-Sb-Te materials can be achieved at high kinetic rates by applying an electrical current, and the material properties change from insulating to metallic behavior without a phase transition. The current-induced metal transition is more effective in GeSb4Te7 than Ge2Sb2Te5, which depends on the intrinsic vacancy of materials. Electromigration, which is the migration of atoms induced by a momentum transfer from charge carriers, can easily promote the rearrangement of vacancies in the cubic phase of Ge-Sb-Te compound. This behavior differs significantly from thermal annealing, which accompanies a phase transition to the hexagonal phase. This result suggests a new pathway for modulating the electrical conductivity and material properties of chalcogenide materials by applying an electrical current.
Clean Grain Boundary Found in C14/Body-Center-Cubic Multi-Phase Metal Hydride Alloys
Directory of Open Access Journals (Sweden)
Hao-Ting Shen
2016-06-01
Full Text Available The grain boundaries of three Laves phase-related body-center-cubic (bcc solid-solution, metal hydride (MH alloys with different phase abundances were closely examined by scanning electron microscopy (SEM, transmission electron microscopy (TEM, and more importantly, electron backscatter diffraction (EBSD techniques. By using EBSD, we were able to identify the alignment of the crystallographic orientations of the three major phases in the alloys (C14, bcc, and B2 structures. This finding confirms the presence of crystallographically sharp interfaces between neighboring phases, which is a basic assumption for synergetic effects in a multi-phase MH system.
Face Centred Cubic Multi-Component Equiatomic Solid Solutions in the Au-Cu-Ni-Pd-Pt System
Directory of Open Access Journals (Sweden)
Jens Freudenberger
2017-04-01
Full Text Available A single-phase solid solution is observed in quaternary and quinary alloys obtained from gold, copper, nickel, palladium and platinum. The lattice parameters of the alloys follow the linear rule of mixture when considering the lattice parameters of the elements and their concentration. The elements are a priori not homogeneously distributed within the respective alloys resulting in segregations. These segregations cause a large broadening of X-ray lines, which is accessed in the present article. This correlation is visualized by the help of local element mappings utilizing scanning electron microscopy including energy dispersive X-ray analysis and their quantitative analysis.
Insights on activation enthalpy for non-Schmid slip in body-centered cubic metals
International Nuclear Information System (INIS)
Hale, Lucas M.; Lim, Hojun; Zimmerman, Jonathan A.; Battaile, Corbett C.; Weinberger, Christopher R.
2015-01-01
We use insights gained from atomistic simulation to develop an activation enthalpy model for dislocation slip in body-centered cubic iron. Using a classical potential that predicts dislocation core stabilities consistent with ab initio predictions, we quantify the non-Schmid stress-dependent effects of slip. The kink-pair activation enthalpy is evaluated and a model is identified as a function of the general stress state. Our model enlarges the applicability of the classic Kocks activation enthalpy model to materials with non-Schmid behavior
The lattice distortion around the divacancy in cubic metals using the method of lattice statics
International Nuclear Information System (INIS)
Yoshioki, S.
1976-01-01
The lattice distortion produced by a divacancy in FCC metals (Al, Cu, Ag and Au) and in BCC metals (Fe, Mo and V) has been calculated using the method of lattice statics. The model assumes non-equilibrium pairwise interactions extending out to second nearest neighbours. Roughly speaking, the relaxation volumes associated with the divacancy are twice the values for the isolated vacancy. (author)
Evolution of microstructure in face centered cubic metals during irradiation: A review
International Nuclear Information System (INIS)
Garner, F.A.
1993-06-01
When fcc metals and alloys are irradiated at elevated temperatures, they tend to evolve toward saturation microstructures that are independent of the starting state of the metal and the early details of irradiation history. This leads to property changes and rates of dimensional change that also eventually become independent of the starting state. The evolution of microstructure in complex alloys, especially during the transient regime, is usually determined by the complex interaction of many microstructural and microchemical processes. The more complex the alloy, the more difficult it is to-identify and define the separate influence of each participating mechanism. The use of irradiation studies conducted on simple metals or model alloys assists in understanding the behavior of alloys of engineering relevance. A review of such studies shows that a number of prevailing perceptions of radiation-induced microstructural evolution are not universally correct
Mesoscale plastic texture in body-centered cubic metals under uniaxial load
Czech Academy of Sciences Publication Activity Database
Gröger, Roman; Vitek, V.; Lookman, T.
2017-01-01
Roč. 1, č. 6 (2017), s. 063601 E-ISSN 2475-9953 R&D Projects: GA MŠk(CZ) LQ1601; GA ČR(CZ) GA16-13797S Institutional support: RVO:68081723 Keywords : dislocations * mesoscale * bcc metals Subject RIV: BM - Solid Matter Physics ; Magnetism OBOR OECD: Condensed matter physics (including formerly solid state physics, supercond.)
International Nuclear Information System (INIS)
Luthi, Berengere
2017-01-01
In order to improve our understanding of alloy plasticity, it is important to describe at the atomic scale the dislocation-solute interactions and their effect on the dislocation mobility. This work focuses on the body-centered cubic (BCC) transition metals in presence of interstitial solute atoms, in particular the Fe-C system. Using Density Functional Theory (DFT) calculations, the core structure of the screw dislocation of Burgers vector b=1/2<111> was investigated in iron in presence of boron, carbon, nitrogen and oxygen solute atoms, and in BCC metals from group 5 (V, Nb, Ta) and 6 (Mo, W) in presence of carbon solutes. A core reconstruction is evidenced in iron and group 6 metals, along with a strong attractive dislocation-solute interaction energy: the dislocation goes from easy to hard configuration where the solute atoms are at the center of trigonal prisms along the dislocation line. A different behavior is observed in group 5 metals, for which the most stable configuration for the carbon atom is an octahedral site in the vicinity of the dislocation, without any core reconstruction. This group tendency is linked to the structure of mono-carbides. Consequences of the strongly attractive dislocation-solute interactions in Fe(C) were then investigated. First the equilibrium segregation close to the dislocation core was studied using a mean-field model and Monte Carlo simulations. Over a wide temperature range, from 200 to 700 K, a strong segregation is predicted with every other prismatic site occupied by a carbon atom. Then, the mobility of the dislocation in presence of carbon atoms was investigated by modeling the double-kink mechanism with DFT, in relation with experimental data obtained with transmission electron microscopy. The activation energy obtained for this atomic scale mechanism is in good agreement with experimental values for the dynamic strain aging. (author) [fr
Slip systems, dislocation boundaries and lattice rotations in deformed metals
DEFF Research Database (Denmark)
Winther, Grethe
2009-01-01
Metals are polycrystals and consist of grains, which are subdivided on a finer scale upon plastic deformation due to formation of dislocation boundaries. The crystallographic alignment of planar dislocation boundaries in face centred cubic metals, like aluminium and copper, deformed to moderate...... of the mechanical anisotropy of rolled sheets. The rotation of the crystallographic lattice in each grain during deformation also exhibits grain orientation dependence, originating from the slip systems. A combined analysis of dislocation boundaries and lattice rotations concludes that the two phenomena are coupled...
Energy Technology Data Exchange (ETDEWEB)
Kong, Bo, E-mail: kong79@yeah.net, E-mail: yachao.zhang@pku.edu.cn [School of Physics and Electronic Sciences, Guizhou Education University, Guiyang 550018 (China); Guizhou Provincial Key Laboratory of Computational Nano-Material Science, Guizhou Education University, Guiyang 550018 (China); Zhang, Yachao, E-mail: kong79@yeah.net, E-mail: yachao.zhang@pku.edu.cn [Guizhou Provincial Key Laboratory of Computational Nano-Material Science, Guizhou Education University, Guiyang 550018 (China)
2016-07-07
The electronic structures of the cubic GdH{sub 3} are extensively investigated using the ab initio many-body GW calculations treating the Gd 4f electrons either in the core (4f-core) or in the valence states (4f-val). Different degrees of quasiparticle (QP) self-consistent calculations with the different starting points are used to correct the failures of the GGA/GGA + U/HSE03 calculations. In the 4f-core case, GGA + G{sub 0}W{sub 0} calculations give a fundamental band gap of 1.72 eV, while GGA+ GW{sub 0} or GGA + GW calculations present a larger band gap. In the 4f-val case, the nonlocal exchange-correlation (xc) functional HSE03 can account much better for the strong localization of the 4f states than the semilocal or Hubbard U corrected xc functional in the Kohn–Sham equation. We show that the fundamental gap of the antiferromagnetic (AFM) or ferromagnetic (FM) GdH{sub 3} can be opened up by solving the QP equation with improved starting point of eigenvalues and wave functions given by HSE03. The HSE03 + G{sub 0}W{sub 0} calculations present a fundamental band gap of 2.73 eV in the AFM configuration, and the results of the corresponding GW{sub 0} and GW calculations are 2.89 and 3.03 eV, respectively. In general, for the cubic structure, the fundamental gap from G{sub 0}W{sub 0} calculations in the 4f-core case is the closest to the real result. By G{sub 0}W{sub 0} calculations in the 4f-core case, we find that H or Gd defects can strongly affect the band structure, especially the H defects. We explain the mechanism in terms of the possible electron correlation on the hydrogen site. Under compression, the insulator-to-metal transition in the cubic GdH{sub 3} occurs around 40 GPa, which might be a satisfied prediction.
A constitutive description of the thermo-viscoplastic behavior of body-centered cubic metals
International Nuclear Information System (INIS)
Gao, C.Y.; Lu, W.R.; Zhang, L.C.; Yan, H.X.
2012-01-01
Highlights: ► Established a new physics-based constitutive model for the plasticity of BCC crystals. ► The new model is better than the R–K, Abed, Z–A and J–C models. ► The new model is simpler and easier to use than the original MTS model. ► The material parameters are determined by a global optimization algorithm. ► Provided a precise description of the flow stress of HSLA-65 steel as well as Tantalum. -- Abstract: The Johnson–Cook (J–C) equation, which is obtained from the phenomenological observations of experimental data at relatively low strain rates, cannot well describe the dynamic thermo-mechanical response of many materials at high strain rates, especially under the situations of high or low temperatures. This paper develops a new physics-based model for the constitutive description of BCC metals through a thermal activation analysis of the dislocation motion in the plastic deformation of crystalline materials with the use of the mechanical threshold stress (MTS) as an internal state variable. It was found that the new model can effectively reflect the plastic deformation mechanism of BCC crystals because it directly relates the macroscopic state variables in the constitutive model with the micromechanical characteristics of materials. The material parameters of the model are efficiently determined by an optimization method to guarantee that the material parameters are globally optimal in their theoretically allowed ranges. The application of the model to HSLA-65 steel and Tantalum shows that it is much easier to apply than the MTS model, that its flow stress predictions are better than the Rusinek and Klepaczko (R–K), Abed, Zerilli and Armstrong (Z–A) and J–C models, and that the present model predictions are in good agreement with the experimental data in a broad range of strain rate, temperature and strain.
International Nuclear Information System (INIS)
Seeger, A.
1995-01-01
The strong temperature and strain-rate dependence of the flow stress of high-purity refractory body-centred cubic metals has been shown to be an intrinsic property and is usually ascribed to a high Peierls barrier of a o left angle 111 right angle /2 screw dislocations. These barriers are overcome by the formation of kink pairs on the screw dislocations. The paper reports on recent, very complete flow-stress data on ultra-high purity Mo crystals obtained by two different experimental techniques and covering the temperature range 4 K to 460 K. The results are in accord with earlier work of Brunner and Diehl on α-Fe, who showed that below the so-called knee temperature, T K , three regimes in the temperature variation of the flow-stress should be distinguished. Two of them are fully accounted for by the same glide mechanism, namely elementary glide steps on {211} planes. The so-called upper bend separating these two regimes in an inherent feature of the theory of kink-pair formation and does not indicate a change in the glide mechanism. There is, however, strong evidence that the so-called lower bend, separating the range of {211} elementary glide steps from the low-temperature flow-stress regime, is due to a change in the glide mechanism. It is argued that at the lower bend the screw-dislocation cores undergo a ''first-order phase transition'' from a low-temperature configuration that allows glide of a given screw dislocation on any of its three {110} glide planes to a high-temperature configuration that can glide only on one definite {211} plane. Between T K and the lower-bend temperature, T, bcc metals may show the unique phenomena of alloy and irradiation softening. With regard to the latter phenomenon, Brunner and Diehl distinguish between ''primary'' and ''secondary'' softening. It is shown that alloy softening and the ''secondary irradiation softening'' of bcc metals may be explained by an ''overheating'' of the phase transition in the dislocation core. (orig./WL)
Study of helium diffusion, implanted at a cyclotron, in face-centered cubic metals: Au, Ag and Al
International Nuclear Information System (INIS)
Sciani, V.
1985-01-01
Helium in metals is produced by nuclear reactions of energetic particles. In nuclear technology the interest on helium in metals is import, due to its production by (n, α) reaction. Because helium has extremely low solubility in metals, the precipitation in the form of filled bubbles at elevated temperatures occurs, which have detrimental effects on mechanical properties and may limit the lifetime of structural components. One typical example is the high temperature embrittlement. The nucleation and growth of the bubbles strongly depends on the mobility of the helium. This work presents the study of helium diffusion in Au, Ag and Al at temperatures above room temperature. The helium created by (n, α) reactions has been simulated by homogeneous alpha particles implantation in cyclotron, at room temperature, in specimens of thicknesses between 5 and 50 μm and helium concentration between 10 -3 to 10 ppm. After implantation, the specimens were dropped in a furnace in a UHV-chamber and the diffusion was measured by observing the He-release during linear and isothermal annealings. The occurence of free diffusion was comparing the dependence of release kinetics on helium concentration, sample thickness, time and heating rate to diffusion theory and is clearly separeted from agglomeration process. The diffusion constants of helium in Au, Ag and Al follow an Arrhenius behavior, with: Au:D o =10 -1.0 cm 2 /s ΔH=1.70eV Ag:D 0 =10 -1.2 cm 2 /s ΔH=1.51eV Al:D o =10 +0.5 cm 2 /s ΔH=1.40eV. The results are compared to self-diffusion and to the diffusion of other gases in these metals. Comparison with theoretical estimates favours the vacancy mechanism for helium diffusion in Au, Ag and Al. (author) [pt
International Nuclear Information System (INIS)
Zhou, Xiuquan; Gall, Daniel; Khare, Sanjay V.
2014-01-01
Highlights: • We use DFT to model the anti-ReO 3 structured transition metal nitrides M 3 N. • We predict their lattice constants, electronic structures and mechanical properties. • We correlate the metal d and nitrogen 2p orbitals with stability and hardness. • We established a high-throughput database for materials design. - Abstract: We report a systematic study of the anti-ReO 3 structured transition metal nitrides, M 3 N, using ab initio density functional theory computations in the local density approximation. Here M denotes all the 3d, 4d and 5d transition metals. Our calculations indicate that all M 3 N compounds except V 3 N of group 5 and Zn 3 N and Hg 3 N of group 12 are mechanically stable. For the stable M 3 N compounds, we report a database of predictions for their lattice constants, electronic properties and mechanical properties including bulk modulus, Young’s modulus, shear modulus, ductility, hardness and Debye temperature. It is found that most M 3 N compounds exhibit ductility with Vickers hardness between 0.4 GPa and 11.2 GPa. Our computed lattice constant for Cu 3 N, the only M 3 N compound where experiments exist, agrees well with the experimentally reported values. We report ratios of the melting points of all M 3 N compounds to that of Cu 3 N. The local density of states for all M 3 N compounds are obtained, and electronic band gaps are observed only for M of group 11 (Cu, Ag and Au) while the remaining M 3 N compounds are metallic without band gaps. Valence electron density along with the hybridization of the metal d and nitrogen 2p orbitals play an important role in determining the stability and hardness of different compounds. Our high-throughput databases for the cubic anti-ReO 3 structured transition metal nitrides should motivate future experimental work and shorten the time to their discovery
International Nuclear Information System (INIS)
Borges, J.F.A.; Padilha, A.F.; Imakuma, K.
1988-03-01
An X-rays diffraction method was applied to measure the Stacking Fault Energies (SFE) of the AISI 304, AISI 316, AISI 347 and DIN-WERKSTOFF 1.4970 Austenitic Stainless Steels. The SFE determination plays an important role in the research of the mecanichal behaviour of the Metal and Alloys, their deformation mechanisms, stability of micro-structure and electronic configuration. The method is based on the relationship between the SFE and the ratio of the Mean Square Strains to the Stacking-Fault probability. The Mean Square Strain was evaluated by Fourier Analysis of X-rays Diffaction profiles, corrected to reduce instrumental effects, followed by the application of the Warren-Averbach method to the Fourier Coefficients. The Stacking-Fault probabilities were derived from the changes of peak separations between cold-worked and annealed specimens. (author) [pt
A unified picture of the crystal structures of metals
Söderlind, Per; Eriksson, Olle; Johansson, Börje; Wills, J. M.; Boring, A. M.
1995-04-01
THE crystal structures of the light actinides have intrigued physicists and chemists for several decades1. Simple metals and transition metals have close-packed, high-symmetry structures, such as body-centred cubic, face-centred cubic and hexagonal close packing. In contrast, the structures of the light actinides are very loosely packed and of low symmetry-tetragonal, orthorhombic and monoclinic. To understand these differences, we have performed total-energy calculations, as a function of volume, for both high-and low-symmetry structures of a simple metal (aluminium), a non-magnetic transition metal (niobium), a ferromagnetic transition metal (iron) and a light actinide (uranium). We find that the crystal structure of all of these metals is determined by the balance between electrostatic (Madelung) interactions, which favour high symmetry, and a Peierls distortion of the crystal lattice, which favours low symmetry. We show that simple metals and transition metals can adopt low-symmetry structures on expansion of the lattice; and we predict that, conversely, the light actinides will undergo transitions to structures of higher symmetry on compression.
A unified picture of the crystal structures of metals
International Nuclear Information System (INIS)
Soederlind, P.; Eriksson, O.; Johansson, B.; Wills, J.M.; Boring, A.M.
1995-01-01
The crystal structures of the light actinides have intrigued physicists and chemists for several decades. Simple metals and transition metals have close-packed, high-symmetry structures, such as body-centred cubic, face-centred cubic hexagonal close packing. In contrast, the structures of the light actinides are very loosely packed and of low symmetry -tetragonal, orthorhombic and monoclinic. To understand these differences, we have have performed total-energy calculations, as a function of volume, for both high- and low-symmetry structures of a simple metal (aluminium), a non-magnetic transition metal (niobium), a ferromagnetic transition metal (iron) and a light actinide (uranium). We find that the crystal structure of all these metals is determined by the balance between electrostatic (Madelung) interactions, which favour high symmetry, and a Peierls distortion of the crystal lattice, which favours low symmetry. We show that simple metals and transition metals can adopt low-symmetry structures on expansion of the lattice; and we predict that, conversely, the light actinides will undergo transitions to structures of higher symmetry on compression. (author)
International Nuclear Information System (INIS)
Warner, D.H.; Curtin, W.A.
2009-01-01
The linking of atomistic simulations of stress-driven processes to experimentally observed mechanical behavior via the computation of activation energy barriers is a topic of intense current research. Using dislocation nucleation from a crack tip as the reaction process, long-time multiscale molecular dynamics simulations show that the activation barrier can exhibit significant temperature dependence. Using an analytic model for the nucleation process and computing the relevant material properties (elastic constants and stacking fault energies), the temperature dependence is shown to arise primarily from the temperature dependence of the material parameters for both Al and Ni. After thermally activated emission of the first partial dislocation, there is then a competition between two other thermally activated processes: twinning and full dislocation emission. Because the activation barriers depend on temperature, this transition is more complex than usually envisioned. Simulations in Al reveal that a transition from twinning to full dislocation emission back to twinning occurs with increasing temperature, which is counter to traditional metallurgical wisdom. Temperature-dependent activation energies are thus essential to accurate understanding and prediction of those phenomena that control fracture and deformation in metals at realistic loading rates.
Directory of Open Access Journals (Sweden)
Y. Yang
2016-12-01
Full Text Available Molecular dynamics simulations are performed to evaluate the influence of the stacking fault energy (SFE as a single variable parameter on defect formation by collision cascades in face-centered cubic metals. The simulations are performed for energies of a primary knock-on atom (EPKA up to 50keV at 100K by using six sets of the recently developed embedded atom method–type potentials. Neither the number of residual defects nor their clustering behavior is found to be affected by the SFE, except for the mean size of the vacancy clusters at EPKA=50keV. The mean size increases as the SFE decreases because of the enhanced formation of large vacancy clusters, which prefer to have stacking faults inside them. On the other hand, the ratio of glissile self-interstitial atom (SIA clusters decreases as the SFE increases. At higher SFEs, both the number of Frank loops and number of perfect loops tend to decrease; instead, three-dimensional irregular clusters with higher densities appear, most of which are sessile. The effect of SFE on the number of Frank loops becomes apparent only at a high EPKA of 50keV, where comparably large SIA clusters can be formed with a higher density.
Energy Technology Data Exchange (ETDEWEB)
Tatarenko, V.A.; Tsysman, C.L.; Oltarzhevskaya, Y.T. [Institute for Metal Physics, Kiev (Ukraine)
1994-12-31
The calculations in a majority of previous works for the fulleride (AqC{sub 60}) crystals were performed within the framework of the rigid-lattice model, neglecting the distoration relaxation of the host fullerene (C{sub 60}) crystal caused by the interstitial alkali-metal (A) cations. However, an each cation is a source of a static distoration field, and the resulting field is a superposition of such fields generated by all cations. This is a reason why the host-crystal distortions depend on the A-cations configurations, i.e. on a type of a spatial bulk distribution of interstitial cations. This paper seeks to find a functional relation between the amplitudes of the doping-induced structure-distortion waves and of statistic concentration ones. A semiphenomenological model is constructed here within the scope of statistical-thermodynamic treatment and using the lattice-statistics simulation method. In this model the effects due to the presence of q solute A cations over available interstices (per unit cell) on the statistic inherent reorientation and/or displacements of the solvent molecules from the average-lattice sites as well as on the lattice parameter a of the elastically-anysotropic cubic C{sub 60} crystal are taken into account.
International Nuclear Information System (INIS)
Bui, Huy Duong
1969-01-01
In this research thesis on metal strain hardening, the author first discusses the issue of passing from microscopic values to corresponding macroscopic values. If there is generally a correspondence between them, it is not the case for plastic strain. Thus, the author studies the general properties of the boundary of the macroscopic plastic field with respect to single-crystal elastic boundaries. In the second part, the author reports an experimental study of the evolution of the elastic field boundary. In the third part, he develops elastic-plastic behaviour laws for an aggregate of cubic crystals. The objectives are to report experimental results in a more satisfying way than previous studies, and to obtain acceptable physical laws while keeping some properties of conventional laws in order to ensure the solution uniqueness, and to establish minimum principles similar to those of Nodge-Prager and of Greenberg. In order to do so, he introduces a new hypothesis: there is a statistic scattering in initial thresholds of crystals
International Nuclear Information System (INIS)
Liu, Z T Y; Khare, S V; Zhou, X; Gall, D
2014-01-01
We report systematic results from ab initio calculations with density functional theory on three cubic structures, zincblende (zb), rocksalt (rs) and cesium chloride (cc), of the ten 3d transition metal nitrides. We computed lattice constants, elastic constants, their derived moduli and ratios that characterize mechanical properties. Experimental measurements exist in the literature of lattice constants for rs-ScN, rs-TiN and rs-VN and of elastic constants for rs-TiN and rs-VN, all of which are in good agreement with our computational results. Similarly, computed Vickers hardness (H V ) values for rs-TiN and rs-VN are consistent with earlier experimental results. Several trends were observed in our rich data set of 30 compounds. All nitrides, except for zb-CrN, rs-MnN, rs-FeN, cc-ScN, cc-CrN, cc-NiN and cc-ZnN, were found to be mechanically stable. A clear correlation in the atomic density with the bulk modulus (B) was observed with maximum values of B around FeN, MnN and CrN. The shear modulus, Young’s modulus, H V and indicators of brittleness showed similar trends and all showed maxima for cc-VN. The calculated value of H V for cc-VN was about 30 GPa, while the next highest values were for rs-ScN and rs-TiN, about 24 GPa. A relation (H V ∝θ D 2 ) between H V and Debye temperature (θ D ) was investigated and verified for each structure type. A tendency for anti-correlation of the elastic constant C 44 , which strongly influences stability and hardness, with the number of electronic states around the Fermi energy was observed. (paper)
Energy Technology Data Exchange (ETDEWEB)
Beyeler, M [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires
1969-07-01
In view of obtaining informations on the structure of vacancies. We have determined, by diffusion experiments under high pressure, the activation volumes for self diffusion in different face centered cubic metals: silver, gold, copper, aluminium and in body centered cubic uranium (gamma phase). Activation volumes for noble metals diffusion in aluminium have also been investigated. The experimental results on gold, silver and copper are in good agreement with most of the theoretical models. The estimated activation volume for gamma uranium seems to indicate a vacancy mechanism.The results on aluminium for both self and impurity diffusion agree quite well with Friedel's theoretical predictions. [French] Pour preciser la structure des lacunes, on a, par des etudes de diffusion sous haute pression determine les volumes d'activation correspondant a l'autodiffusion dans des metaux de structure cubique face centree: argent, or, cuivre et aluminium et dans un metal de structure cubique centree: l'uranium gamma. On a egalement determine les volumes d'activation pour l'heterodiffusion des metaux nobles dans l'aluminium. Les resultats obtenus pour l'or, l'argent et le cuivre sont en accord avec la plupart des modeles theoriques classiques. Le volume d'activation d'autodiffusion evalue pour l'uranium gamma est compatible avec une diffusion par lacune. Les resultats concernant l'aluminium et l'heterediffusion des metaux nobles dans l'aluminium verifient assez bien les previsions theoriques de Friedel. (auteur)
Energy Technology Data Exchange (ETDEWEB)
Beyeler, M. [Commissariat a l' Energie Atomique, Saclay (France). Centre d' Etudes Nucleaires
1969-07-01
In view of obtaining informations on the structure of vacancies. We have determined, by diffusion experiments under high pressure, the activation volumes for self diffusion in different face centered cubic metals: silver, gold, copper, aluminium and in body centered cubic uranium (gamma phase). Activation volumes for noble metals diffusion in aluminium have also been investigated. The experimental results on gold, silver and copper are in good agreement with most of the theoretical models. The estimated activation volume for gamma uranium seems to indicate a vacancy mechanism.The results on aluminium for both self and impurity diffusion agree quite well with Friedel's theoretical predictions. [French] Pour preciser la structure des lacunes, on a, par des etudes de diffusion sous haute pression determine les volumes d'activation correspondant a l'autodiffusion dans des metaux de structure cubique face centree: argent, or, cuivre et aluminium et dans un metal de structure cubique centree: l'uranium gamma. On a egalement determine les volumes d'activation pour l'heterodiffusion des metaux nobles dans l'aluminium. Les resultats obtenus pour l'or, l'argent et le cuivre sont en accord avec la plupart des modeles theoriques classiques. Le volume d'activation d'autodiffusion evalue pour l'uranium gamma est compatible avec une diffusion par lacune. Les resultats concernant l'aluminium et l'heterediffusion des metaux nobles dans l'aluminium verifient assez bien les previsions theoriques de Friedel. (auteur)
DEFF Research Database (Denmark)
Birkedal, Lars; Bizjak, Aleš; Clouston, Ranald
2016-01-01
This paper improves the treatment of equality in guarded dependent type theory (GDTT), by combining it with cubical type theory (CTT). GDTT is an extensional type theory with guarded recursive types, which are useful for building models of program logics, and for programming and reasoning...... with coinductive types. We wish to implement GDTT with decidable type-checking, while still supporting non-trivial equality proofs that reason about the extensions of guarded recursive constructions. CTT is a variation of Martin-L\\"of type theory in which the identity type is replaced by abstract paths between...... terms. CTT provides a computational interpretation of functional extensionality, is conjectured to have decidable type checking, and has an implemented type-checker. Our new type theory, called guarded cubical type theory, provides a computational interpretation of extensionality for guarded recursive...
DEFF Research Database (Denmark)
Birkedal, Lars; Bizjak, Aleš; Clouston, Ranald
2016-01-01
This paper improves the treatment of equality in guarded dependent type theory (GDTT), by combining it with cubical type theory (CTT). GDTT is an extensional type theory with guarded recursive types, which are useful for building models of program logics, and for programming and reasoning...... with coinductive types. We wish to implement GDTT with decidable type checking, while still supporting non-trivial equality proofs that reason about the extensions of guarded recursive constructions. CTT is a variation of Martin-L\\"of type theory in which the identity type is replaced by abstract paths between...... terms. CTT provides a computational interpretation of functional extensionality, enjoys canonicity for the natural numbers type, and is conjectured to support decidable type-checking. Our new type theory, guarded cubical type theory (GCTT), provides a computational interpretation of extensionality...
Directory of Open Access Journals (Sweden)
M. N. Singh
2015-08-01
Full Text Available We report anomalous x-ray diffraction studies on Co ferrite with composition Co1.5Fe1.5O4 to obtain the distribution of transition metal ions in tetrahedral and octahedral sites. We synthesize spinel oxide (Co1.5Fe1.5O4 through co-precipitation and subsequent annealing route. The imaginary part (absorption of the energy dependent anomalous form factor is measured and the real part is calculated theoretically through Kramers–Krönig transformation to analyze anomalous x-ray diffraction peak intensities. Fe and Co K-edge x-ray absorption near edge structure (XANES spectra are used to estimate charge states of transition metals. Our analysis, within experimental errors, suggests 44% of the tetrahedral sites contain Co in +2 oxidation state and the rest 56% sites contain Fe in +2 and +3 oxidation states. Similarly, 47% of the octahedral sites contain Fe in +3 oxidation states, whereas, the rest of the sites contain Co in +2 and +3 oxidation states. While a distinct pre-edge feature in the Fe K-edge XANES is observed, Co pre-edge remains featureless. Implications of these results to magnetism are briefly discussed.
International Nuclear Information System (INIS)
Borges, J.F.A.
1985-01-01
An X-rays diffraction method was applied to measure the Stacking-Fault Energies (SFE) of the AISI 304, AISI 316, AISI 347 and DIN-WERKSTOFF 1.4970 Austenitic Stainless Steels. The SFE determination plays an important role in the research of the mechanical behaviour of the Metal and Alloys, their deformation mechanisms, stability of microstructure amd electronic configuration. The method is based on the relationship between the SFE and the ratio of the Mean Square Strain to the Stacking-Fault probability. The Mean Square Strain was evaluated by Fourier Analysis of X-rays Diffraction profiles, corrected to reduce instrumental effects, followed by the application of the Warren-Averbach method to the Fourier Coefficients. The Stacking-Fault probabilities were derived from the changes of peak separations between cold-worked and annealed specimens. (author) [pt
Neutron diffraction study of cubic titanium carbohydride at the homogeneity lower limit
International Nuclear Information System (INIS)
Khidirov, I.; Mirzaev, B.B.; Mukhtarova, N.N.
2004-01-01
Cubic carbohydride TiC 0.47H0.22 was prepared by means of quenching from 1200 deg.C followed by the heat treatment using special regime for preventing the hydrogen yield out the lattice. It is shown that at the lower limit of homogeneity range of the cubic carbohydride, hydrogen atoms occupy the tetrahedral interstices 8(c) of the disordered cubic structure with space group of Fm3m. It is found that carbon and hydrogen atoms are partially ordered by annealing at 900-700 deg.C. The ordered structure is face-centred cubic lattice with the parameter a ≅2a 0 , where a 0 is the lattice parameter in disordered structure. The crystal structure of the disordered phase is described within the framework of space group Fd3m, where the carbon atoms occupy mainly (70%) octahedral interstices 16(c) and another ones of carbon and all hydrogen atoms occupy the octahedral interstices 16(d). (author)
Near transferable phenomenological n-body potentials for noble metals.
Pontikis, Vassilis; Baldinozzi, Gianguido; Luneville, Laurence; Simeone, David
2017-09-06
We present a semi-empirical model of cohesion in noble metals with suitable parameters reproducing a selected set of experimental properties of perfect and defective lattices in noble metals. It consists of two short-range, n-body terms accounting respectively for attractive and repulsive interactions, the former deriving from the second moment approximation of the tight-binding scheme and the latter from the gas approximation of the kinetic energy of electrons. The stability of the face centred cubic versus the hexagonal compact stacking is obtained via a long-range, pairwise function of customary use with ionic pseudo-potentials. Lattice dynamics, molecular statics, molecular dynamics and nudged elastic band calculations show that, unlike previous potentials, this cohesion model reproduces and predicts quite accurately thermodynamic properties in noble metals. In particular, computed surface energies, largely underestimated by existing empirical cohesion models, compare favourably with measured values, whereas predicted unstable stacking-fault energy profiles fit almost perfectly ab initio evaluations from the literature. All together the results suggest that this semi-empirical model is nearly transferable.
Energy Technology Data Exchange (ETDEWEB)
Hueger, E.
2005-08-26
In this work ultrathin metallic films with a crystal phase different to their natural bulk structure were produced by hetero-epitaxial growth on metallic substrates. A further aim of this work was to understand the initiation, growth and stability of crystal phase modifications of these films. there exist cases where the films turn beyond the pseudomorphic-growth to a crystal phase different from their natural bulk structure. The present work presents and discusses such a case in addition to the general phenomenon of pseudomorphic-growth. In particular it is shown that metals whose natural phase is face centred cubic (fcc) can be grown in body centred tetragonal (bct) or hexagonal close packed (hcp) phases in the form of thin films on (001) surfaces of appropriate substrates. The growth behavior, electron diffraction analysis, appearance conditions, geometric fit considerations, examples and a discussion of the phase stability of non-covered films and superlattices is given reviewing all epitaxial-systems whose diffraction pattern can be explained by the hexagonal or pseudomorphic bct phase. (orig.)
Pabari, Ritesh M; Ramtoola, Zebunnissa
2012-07-01
A two factor, three level (3(2)) face centred, central composite design (CCD) was applied to investigate the main and interaction effects of tablet diameter and compression force (CF) on hardness, disintegration time (DT) and porosity of mannitol based orodispersible tablets (ODTs). Tablet diameters of 10, 13 and 15 mm, and CF of 10, 15 and 20 kN were studied. Results of multiple linear regression analysis show that both the tablet diameter and CF influence tablet characteristics. A negative value of regression coefficient for tablet diameter showed an inverse relationship with hardness and DT. A positive value of regression coefficient for CF indicated an increase in hardness and DT with increasing CF as a result of the decrease in tablet porosity. Interestingly, at the larger tablet diameter of 15 mm, while hardness increased and porosity decreased with an increase in CF, the DT was resistant to change. The optimised combination was a tablet of 15 mm diameter compressed at 15 kN showing a rapid DT of 37.7s and high hardness of 71.4N. Using these parameters, ODTs containing ibuprofen showed no significant change in DT (ANOVA; p>0.05) irrespective of the hydrophobicity of the ibuprofen. Copyright © 2012 Elsevier B.V. All rights reserved.
Interpolation of natural cubic spline
Directory of Open Access Journals (Sweden)
Arun Kumar
1992-01-01
Full Text Available From the result in [1] it follows that there is a unique quadratic spline which bounds the same area as that of the function. The matching of the area for the cubic spline does not follow from the corresponding result proved in [2]. We obtain cubic splines which preserve the area of the function.
Mizutani, U.; Sato, H.
2018-05-01
Many face-centred cubic elements and compounds with the number of atoms per unit cell N equal to 8, 12 and 16 are known to be stabilised by forming either a band gap or a pseudogap at the Fermi level. They are conveniently expressed as cF8, cF12 and cF16, respectively, in the Pearson symbol. From the cF8 family, we worked on three tetravalent elements C (diamond), Si and Ge, SZn-type AsGa compound and NaCl-type compounds like BiLu, AsSc, etc. From the cF12 family, more than 80 compounds were selected, with a particular emphasis on ABC- and half-Heusler-type ternary equiatomic compounds. Among cF16 compounds, both the Heusler compounds ABC2 and Zintl compounds were studied. We revealed that, regardless of whether or not the transition metal (TM) and/or rare-earth (RE) elements are involved as constituent elements, the energy gap formation mechanism for cF8, cF12 and cF16 compounds can be universally discussed in terms of interference phenomenon of itinerant electrons with set of reciprocal lattice planes with ? = 8, 11 and 12, where ? refers to square of the critical reciprocal of lattice vector of an fcc lattice. The number of itinerant electrons per unit cell, e/uc, for all these band gap/pseudogap-bearing compounds is found to fall on a universal line called "3/2-power law" when plotted against ? on a logarithmic scale. This proves the validity of the fulfilment of the interference condition ? in conformity with other pseudogap compounds with different crystal symmetries and different sizes of the unit cell reported in literature.
Energy Technology Data Exchange (ETDEWEB)
Eichler, B
2003-01-01
Volatilization properties of elements with the atomic numbers Z=104 to 116 are determined on the basis of empirical relations. These empirical correlations are deduced from the analysis of thermochemical data of metallic elements in the periodic table and their relations to the material constant: Structure specific connections are shown to exist between the electron densities at the 'Wigner-Seitz' cell borders of metals and the specific surface energies of solid metals with hexagonal, cubic face-centred, cubic body-centred and rhombohedral lattices. Analogously, structure specific relations can be found between the standard enthalpies of the gaseous monoatomic metals and their surface energies. Linear correlations with exceptionally high correlation coefficients are observed between the standard sublimation enthalpies of isotypic metals in the dimeric state and the surface energies. Volatilization properties are deduced for the transactinides on the basis of these established relations, applying a predicted structure and further empirical correlations. These volatilization properties are in detail: the standard enthalpies of the gaseous monomers; the standard sublimation enthalpies of the dimers; the standard dissociation enthalpies of the dimers; the standard enthalpies of adsorption on metal surfaces; the volatilization enthalpies from molten metals, and the standard formation enthalpies of hetero binuclear intermetallic molecules. Thermochemical constants required for the calculation of the intermetallic interactions are determined using the Miedema model. The closed systematic approach facilitate: the assessment of the calculated data considering the agreement with known rules of metal chemistry, trends in the 7{sup t}h row and along the groups of the periodic table, the coherence of the data, and the action of closed shell effects in the electron configurations. From the obtained data conclusions are possible regarding the design of volatilization
Hawkins, John A.; Rittenhouse, Jeffrey L.; Soper, Linda M.; Rittenhouse, Robert C.
2008-01-01
One of the most important crystal structures adopted by metals is characterized by the "abcabc"...stacking of close-packed layers. This structure is commonly referred to in textbooks as the cubic close-packed (ccp) or face-centered cubic (fcc) structure, since the entire lattice can be generated by replication of a face-centered cubic unit cell…
The planar cubic Cayley graphs
Georgakopoulos, Agelos
2018-01-01
The author obtains a complete description of the planar cubic Cayley graphs, providing an explicit presentation and embedding for each of them. This turns out to be a rich class, comprising several infinite families. He obtains counterexamples to conjectures of Mohar, Bonnington and Watkins. The author's analysis makes the involved graphs accessible to computation, corroborating a conjecture of Droms.
Nedolya, Anatoliy V; Bondarenko, Natalya V
2016-12-01
Energy change of an iron face-centred cubic subnanocluster was evaluated using molecular mechanics method depending on the position of a carbon interstitial atom and substitutional atoms of nickel. Calculations of all possible positions of impurity atoms show that the energy change of the system are discrete and at certain positions of the atoms are close to continuous.In terms of energy, when all impurity atoms are on the same edge of an atomic cluster, their positions are more advantageous. The presence of nickel atoms on the edge of a cubic cluster resulted in decrease of potential barrier for a carbon atom and decrease in energy in the whole cluster. A similar drift of a carbon atom from central octahedral interstitial site to the surface in the direction occurred under the influence of surface factors.Such configuration corresponds to decreasing symmetry and increasing the number of possible energy states of a subnanocluster, and it corresponds to the condition of spontaneous crystallization process in an isolated system.Taking into account accidental positions of the nickel atom in the iron cluster, such behaviour of the carbon atom can explain the mechanism of growth of a new phase and formation of new clusters in the presence of other kind of atoms because of surface influence.
Directory of Open Access Journals (Sweden)
Gary R. Nicklason
2015-07-01
Full Text Available We consider center conditions for plane polynomial systems of Abel type consisting of a linear center perturbed by the sum of 2 homogeneous polynomials of degrees n and 2n-1 where $n \\ge 2$. Using properties of Abel equations we obtain two general systems valid for arbitrary values on n. For the cubic n=2 systems we find several sets of new center conditions, some of which show that the results in a paper by Hill, Lloyd and Pearson which were conjectured to be complete are in fact not complete. We also present a particular system which appears to be a counterexample to a conjecture by Zoladek et al. regarding rational reversibility in cubic polynomial systems.
Cubication of conservative nonlinear oscillators
International Nuclear Information System (INIS)
Belendez, Augusto; Alvarez, Mariela L; Fernandez, Elena; Pascual, Inmaculada
2009-01-01
A cubication procedure of the nonlinear differential equation for conservative nonlinear oscillators is analysed and discussed. This scheme is based on the Chebyshev series expansion of the restoring force, and this allows us to approximate the original nonlinear differential equation by a Duffing equation in which the coefficients for the linear and cubic terms depend on the initial amplitude, A, while in a Taylor expansion of the restoring force these coefficients are independent of A. The replacement of the original nonlinear equation by an approximate Duffing equation allows us to obtain an approximate frequency-amplitude relation as a function of the complete elliptic integral of the first kind. Some conservative nonlinear oscillators are analysed to illustrate the usefulness and effectiveness of this scheme.
Numbers for reducible cubic scrolls
Directory of Open Access Journals (Sweden)
Israel Vainsencher
2004-12-01
Full Text Available We show how to compute the number of reducible cubic scrolls of codimension 2 in (math blackboard symbol Pn incident to the appropriate number of linear spaces.Mostramos como calcular o número de rolos cúbicos redutíveis de codimensão 2 em (math blackboard symbol Pn incidentes a espaços lineares apropriados.
Randomized Block Cubic Newton Method
Doikov, Nikita; Richtarik, Peter
2018-01-01
We study the problem of minimizing the sum of three convex functions: a differentiable, twice-differentiable and a non-smooth term in a high dimensional setting. To this effect we propose and analyze a randomized block cubic Newton (RBCN) method, which in each iteration builds a model of the objective function formed as the sum of the natural models of its three components: a linear model with a quadratic regularizer for the differentiable term, a quadratic model with a cubic regularizer for the twice differentiable term, and perfect (proximal) model for the nonsmooth term. Our method in each iteration minimizes the model over a random subset of blocks of the search variable. RBCN is the first algorithm with these properties, generalizing several existing methods, matching the best known bounds in all special cases. We establish ${\\cal O}(1/\\epsilon)$, ${\\cal O}(1/\\sqrt{\\epsilon})$ and ${\\cal O}(\\log (1/\\epsilon))$ rates under different assumptions on the component functions. Lastly, we show numerically that our method outperforms the state-of-the-art on a variety of machine learning problems, including cubically regularized least-squares, logistic regression with constraints, and Poisson regression.
Randomized Block Cubic Newton Method
Doikov, Nikita
2018-02-12
We study the problem of minimizing the sum of three convex functions: a differentiable, twice-differentiable and a non-smooth term in a high dimensional setting. To this effect we propose and analyze a randomized block cubic Newton (RBCN) method, which in each iteration builds a model of the objective function formed as the sum of the natural models of its three components: a linear model with a quadratic regularizer for the differentiable term, a quadratic model with a cubic regularizer for the twice differentiable term, and perfect (proximal) model for the nonsmooth term. Our method in each iteration minimizes the model over a random subset of blocks of the search variable. RBCN is the first algorithm with these properties, generalizing several existing methods, matching the best known bounds in all special cases. We establish ${\\\\cal O}(1/\\\\epsilon)$, ${\\\\cal O}(1/\\\\sqrt{\\\\epsilon})$ and ${\\\\cal O}(\\\\log (1/\\\\epsilon))$ rates under different assumptions on the component functions. Lastly, we show numerically that our method outperforms the state-of-the-art on a variety of machine learning problems, including cubically regularized least-squares, logistic regression with constraints, and Poisson regression.
Cubic colloids : Synthesis, functionalization and applications
Castillo, S.I.R.
2015-01-01
This thesis is a study on cubic colloids: micron-sized cubic particles with rounded corners (cubic superballs). Owing to their shape, particle packing for cubes is more efficient than for spheres and results in fascinating phase and packing behavior. For our cubes, the particle volume fraction when
Cubic metaplectic forms and theta functions
Proskurin, Nikolai
1998-01-01
The book is an introduction to the theory of cubic metaplectic forms on the 3-dimensional hyperbolic space and the author's research on cubic metaplectic forms on special linear and symplectic groups of rank 2. The topics include: Kubota and Bass-Milnor-Serre homomorphisms, cubic metaplectic Eisenstein series, cubic theta functions, Whittaker functions. A special method is developed and applied to find Fourier coefficients of the Eisenstein series and cubic theta functions. The book is intended for readers, with beginning graduate-level background, interested in further research in the theory of metaplectic forms and in possible applications.
Cathodoluminescence of cubic boron nitride
International Nuclear Information System (INIS)
Tkachev, V.D.; Shipilo, V.B.; Zajtsev, A.M.
1985-01-01
Three optically active defects are detected in mono- and polycrystal cubic boron nitride (β-BN). Analysis of intensity of temperature dependences, halfwidth and energy shift of 1.76 eV narrow phononless line (center GC-1) makes it possible to interprete the observed cathodoluminescence spectra an optical analog of the Moessbaner effect. Comparison of the obtained results with the known data for diamond monocrystals makes it possible to suggest that the detected center GC-1 is a nitrogen vacancy . The conclusion, concerning the Moessbauer optical spectra application, is made to analyze structural perfection of β-BN crystal lattice
International Nuclear Information System (INIS)
Wang, S.; Wang, M.P.; Chen, C.; Xiao, Z.; Jia, Y.L.; Li, Z.; Wang, Z.X.
2014-01-01
The orientation dependence of the deformation microstructure has been investigated in commercial pure molybdenum. After deformation, the dislocation boundaries of compressed molybdenum can be classified, similar to that in face-centered cubic metals, into three types: dislocation cells (Type 2), and extended planar boundaries parallel to (Type 1) or not parallel to (Type 3) a (110) trace. However, it shows a reciprocal relationship between face-centered cubic metals and body-centered cubic metals on the orientation dependence of the deformation microstructure. The higher the strain, the finer the microstructure is and the smaller the inclination angle between extended planar boundaries and the compression axis is. - Highlights: • A reciprocal relationship between FCC metals and BCC metals is confirmed. • The dislocation boundaries can be classified into three types in compressed Mo. • The dislocation characteristic of different dislocation boundaries is different
Cathodoluminescence of cubic boron nitride
International Nuclear Information System (INIS)
Tkachev, V.D.; Shipilo, V.B.; Zaitsev, A.M.
1985-01-01
Three types of optically active defect were observed in single-crystal and polycrystalline cubic boron nitride (β-BN). An analysis of the temperature dependences of the intensity, half-width, and energy shift of a narrow zero-phonon line at 1.76 eV (GC-1 center) made it possible to interpret the observed cathodoluminescence spectra as an optical analog of the Moessbauer effect. A comparison of the results obtained in the present study with the available data on diamond single crystals made it possible to identify the observed GC-1 center as a nitrogen vacancy. It was concluded that optical Moessbauer-type spectra can be used to analyze structure defects in the crystal lattice of β-BN
Topics in Cubic Special Geometry
Bellucci, Stefano; Roychowdhury, Raju
2011-01-01
We reconsider the sub-leading quantum perturbative corrections to N=2 cubic special Kaehler geometries. Imposing the invariance under axion-shifts, all such corrections (but the imaginary constant one) can be introduced or removed through suitable, lower unitriangular symplectic transformations, dubbed Peccei-Quinn (PQ) transformations. Since PQ transformations do not belong to the d=4 U-duality group G4, in symmetric cases they generally have a non-trivial action on the unique quartic invariant polynomial I4 of the charge representation R of G4. This leads to interesting phenomena in relation to theory of extremal black hole attractors; namely, the possibility to make transitions between different charge orbits of R, with corresponding change of the supersymmetry properties of the supported attractor solutions. Furthermore, a suitable action of PQ transformations can also set I4 to zero, or vice versa it can generate a non-vanishing I4: this corresponds to transitions between "large" and "small" charge orbit...
Cubical local partial orders on cubically subdivided spaces - existence and construction
DEFF Research Database (Denmark)
Fajstrup, Lisbeth
The geometric models of Higher Dimensional Automata and Dijkstra's PV-model are cubically subdivided topological spaces with a local partial order. If a cubicalization of a topological space is free of immersed cubic Möbius bands, then there are consistent choices of direction in all cubes, such ...... that the underlying geometry of an HDA may be quite complicated....
Cubical local partial orders on cubically subdivided spaces - Existence and construction
DEFF Research Database (Denmark)
Fajstrup, Lisbeth
2006-01-01
The geometric models of higher dimensional automata (HDA) and Dijkstra's PV-model are cubically subdivided topological spaces with a local partial order. If a cubicalization of a topological space is free of immersed cubic Möbius bands, then there are consistent choices of direction in all cubes...... that the underlying geometry of an HDA may be quite complicated....
International Nuclear Information System (INIS)
Klotsman, S.M.; Timofeev, A.N.
2008-01-01
Measured changes (ε vac ) i,j of vibrational energy on vacancies formation in i-fields (in volumes and nuclei of crystallite conjugation regions of polycrystalline metals (CCR-PM)): Cr, Mo, Ta, W, Cu, Ir are presented. Changes ε vol of vibrational energy of vacancy nearest environment formed in the metal volume, changes ε FCC of vibrational energy when vacancies formation in CCR nuclei of BCC- and FCC lattices transition metals are discussed. Measured changes ε FCC of vibrational energy, u FCC potential energy and determined sign of interatomic distances changes Δa FCC when formation of split vacancy in the FCC-lattice CCR-PM, changes ε BCC of vibrational energy, u BCC potential energy and determined sign of Δa BCC changes of interatomic distances when vacancies formation in the BCC-lattice CCR-PM are demonstrated. It is noted that the increase of interatomic distances when vacancies formation in the BCC-lattice CCR nucleus of transition metals is conditioned by the the appearance of vacancies alternative structure. Properties of CCR-PM nuclei are more sensitive to interatomic distances changes in the vacancies environment, than to changes of its nearest neighbours numbers [ru
Pinot, Y; Tuilier, M-H; Pac, M-J; Rousselot, C; Thiaudière, D
2015-11-01
Titanium and aluminium nitride films deposited by magnetron sputtering generally grow as columnar domains made of oriented nanocrystallites with cubic or hexagonal symmetry depending on Al content, which are embedded in more disordered grain boundaries. The substitution of Al atoms for Ti in the cubic lattice of the films improves their resistance to wear and oxidation, allowing their use as protective coatings. Ti K-edge X-ray absorption spectroscopy, which probes both crystallized and more disordered grain boundaries, and X-ray diffraction anomalous fine structure, which is sensitive to short- and long-range order within a given crystallized domain, are carried out on a set of Ti(1-x)AlxN films deposited by magnetron sputtering on Si substrates. Attention is paid to the shape of the pre-edge region, which is sensitive to the symmetry of the site occupied by Ti atoms, either octahedral in face-centred-cubic Ti-rich (TiN, Ti0.54Al0.46N) samples or tetrahedral in hexagonal-close-packed Al-rich (Ti0.32Al0.68N) films. In order to obain information on the titanium environment in the well crystallized areas, subtraction of the smooth part of the energy-dependent structure factor for the Bragg reflections is applied to the pre-edge region of the diffraction anomalous data in order to restore their spectroscopic appearance. A flat pre-edge is related to the typical octahedral environment of Ti atoms for cubic reflections. The difference observed between pre-edge spectra associated with face-centred-cubic 200 and 111 Bragg reflections of Ti0.54Al0.46N is assigned to Ti enrichment of 111 large well ordered domains compared with the more disordered 200 ones. The sharp peak observed in the spectrum recorded from the hexagonal 002 peak of Ti0.32Al0.68N can be regarded as a standard for the pure tetrahedral Ti environment in hexagonal-close-packed nitride.
Cubical sets as a classifying topos
DEFF Research Database (Denmark)
Spitters, Bas
Coquand’s cubical set model for homotopy type theory provides the basis for a computational interpretation of the univalence axiom and some higher inductive types, as implemented in the cubical proof assistant. We show that the underlying cube category is the opposite of the Lawvere theory of De...... Morgan algebras. The topos of cubical sets itself classifies the theory of ‘free De Morgan algebras’. This provides us with a topos with an internal ‘interval’. Using this interval we construct a model of type theory following van den Berg and Garner. We are currently investigating the precise relation...
Generalized Vaidya spacetime for cubic gravity
Ruan, Shan-Ming
2016-03-01
We present a kind of generalized Vaidya solution of a new cubic gravity in five dimensions whose field equations in spherically symmetric spacetime are always second order like the Lovelock gravity. We also study the thermodynamics of its spherically symmetric apparent horizon and get its entropy expression and generalized Misner-Sharp energy. Finally, we present the first law and second law hold in this gravity. Although all the results are analogous to those in Lovelock gravity, we in fact introduce the contribution of a new cubic term in five dimensions where the cubic Lovelock term is just zero.
Cubic Pencils and Painlev\\'e Hamiltonians
Kajiwara, Kenji; Masuda, Tetsu; Noumi, Masatoshi; Ohta, Yasuhiro; Yamada, Yasuhiko
2004-01-01
We present a simple heuristic method to derive the Painlev\\'e differential equations from the corresponding geometry of rational surafces. We also give a direct relationship between the cubic pencils and Seiberg-Witten curves.
A Note on Cubic Convolution Interpolation
Meijering, E.; Unser, M.
2003-01-01
We establish a link between classical osculatory interpolation and modern convolution-based interpolation and use it to show that two well-known cubic convolution schemes are formally equivalent to two osculatory interpolation schemes proposed in the actuarial literature about a century ago. We also discuss computational differences and give examples of other cubic interpolation schemes not previously studied in signal and image processing.
Cubical version of combinatorial differential forms
DEFF Research Database (Denmark)
Kock, Anders
2010-01-01
The theory of combinatorial differential forms is usually presented in simplicial terms. We present here a cubical version; it depends on the possibility of forming affine combinations of mutual neighbour points in a manifold, in the context of synthetic differential geometry.......The theory of combinatorial differential forms is usually presented in simplicial terms. We present here a cubical version; it depends on the possibility of forming affine combinations of mutual neighbour points in a manifold, in the context of synthetic differential geometry....
Purely cubic action for string field theory
Horowitz, G. T.; Lykken, J.; Rohm, R.; Strominger, A.
1986-01-01
It is shown that Witten's (1986) open-bosonic-string field-theory action and a closed-string analog can be written as a purely cubic interaction term. The conventional form of the action arises by expansion around particular solutions of the classical equations of motion. The explicit background dependence of the conventional action via the Becchi-Rouet-Stora-Tyutin operator is eliminated in the cubic formulation. A closed-form expression is found for the full nonlinear gauge-transformation law.
Nonlinear dynamics of quadratically cubic systems
International Nuclear Information System (INIS)
Rudenko, O V
2013-01-01
We propose a modified form of the well-known nonlinear dynamic equations with quadratic relations used to model a cubic nonlinearity. We show that such quadratically cubic equations sometimes allow exact solutions and sometimes make the original problem easier to analyze qualitatively. Occasionally, exact solutions provide a useful tool for studying new phenomena. Examples considered include nonlinear ordinary differential equations and Hopf, Burgers, Korteweg–de Vries, and nonlinear Schrödinger partial differential equations. Some problems are solved exactly in the space–time and spectral representations. Unsolved problems potentially solvable by the proposed approach are listed. (methodological notes)
Surface relaxation and surface energy of face –centered Cubic ...
African Journals Online (AJOL)
DR. MIKE HORSFALL
Surface relaxation and surface energy of face –centered Cubic metals. 1AGHEMENLO H E; *2IYAYI, S E; 3AVWIRI ,G O. 1, 3 Department of Physics, Ambrose Alli University, Ekpoma, Nigeria. 2 Department of Physics, University of Benin, Benin City, Nigeria. 3 Department of Physics, University of Port Harcourt, PH, Nigeria.
Park, Yeonjoon (Inventor); Kim, Hyun Jung (Inventor); Skuza, Jonathan R. (Inventor); Lee, Kunik (Inventor); King, Glen C. (Inventor); Choi, Sang Hyouk (Inventor)
2017-01-01
An X-ray defraction (XRD) characterization method for sigma=3 twin defects in cubic semiconductor (100) wafers includes a concentration measurement method and a wafer mapping method for any cubic tetrahedral semiconductor wafers including GaAs (100) wafers and Si (100) wafers. The methods use the cubic semiconductor's (004) pole figure in order to detect sigma=3/{111} twin defects. The XRD methods are applicable to any (100) wafers of tetrahedral cubic semiconductors in the diamond structure (Si, Ge, C) and cubic zinc-blend structure (InP, InGaAs, CdTe, ZnSe, and so on) with various growth methods such as Liquid Encapsulated Czochralski (LEC) growth, Molecular Beam Epitaxy (MBE), Organometallic Vapor Phase Epitaxy (OMVPE), Czochralski growth and Metal Organic Chemical Vapor Deposition (MOCVD) growth.
Dipaths and dihomotopies in a cubical complex
DEFF Research Database (Denmark)
Fajstrup, Lisbeth
2005-01-01
In the geometric realization of a cubical complex without degeneracies, a $\\Box$-set, dipaths and dihomotopies may not be combinatorial, i.e., not geometric realizations of combinatorial dipaths and equivalences. When we want to use geometric/topological tools to classify dipaths on the 1-skeleton...
Some elements go cubic under pressure
Czech Academy of Sciences Publication Activity Database
Legut, Dominik
2007-01-01
Roč. 60, č. 10 (2007), s. 17-17 ISSN 0031-9228 Institutional research plan: CEZ:AV0Z20410507 Keywords : ab initio * polonium * cubic structure Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 5.133, year: 2007
The Exact Limit of Some Cubic Towers
DEFF Research Database (Denmark)
Anbar Meidl, Nurdagül; Beelen, Peter; Nguyen, Nhut
2017-01-01
Recently, a new explicit tower of function fields was introduced by Bassa, Beelen, Garcia and Stichtenoth (BBGS). This resulted in currently the best known lower bound for Ihara’s constant in the case of non-prime finite fields. In particular over cubic fields, the tower’s limit is at least as go...
Ab Initio Guided Low Temperature Synthesis Strategy for Smooth Face–Centred Cubic FeMn Thin Films
Directory of Open Access Journals (Sweden)
Friederike Herrig
2018-05-01
Full Text Available The sputter deposition of FeMn thin films with thicknesses in the range of hundred nanometres and beyond requires relatively high growth temperatures for the formation of the face-centred cubic (fcc phase, which results in high thin film roughness. A low temperature synthesis strategy, based on local epitaxial growth of a 100 nm thick fcc FeMn film as well as a Cu nucleation layer on an α-Al2O3 substrate at 160 °C, enables roughness values (Ra as low as ~0.6 nm, which is in the same order of magnitude as the pristine substrate (~0.1 nm. The synthesis strategy is guided by ab initio calculations, indicating very strong interfacial bonding of the Cu nucleation layer to an α-Al2O3 substrate (work of separation 5.48 J/m²—which can be understood based on the high Cu coordination at the interface—and between fcc FeMn and Cu (3.45 J/m². Accompanied by small lattice misfits between these structures, the strong interfacial bonding is proposed to enable the local epitaxial growth of a smooth fcc FeMn thin film. Based on the here introduced synthesis strategy, the implementation of fcc FeMn based thin film model systems for materials with interface dominated properties such as FeMn steels containing κ-carbide precipitates or secondary phases appears meaningful.
Elastic properties of cubic perovskite BaRuO{sub 3} from first-principles calculations
Energy Technology Data Exchange (ETDEWEB)
Han Deming; Liu Xiaojuan; Lv Shuhui; Li Hongping [State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022 (China); Meng Jian, E-mail: jmeng@ciac.jl.c [State Key Laboratory of Rare Earth Resource Utilization, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022 (China)
2010-08-01
We present first-principles investigations on the structural and elastic properties of the cubic perovskite BaRuO{sub 3} using density-functional theory within both local density approximation (LDA) and generalized gradient approximation (GGA). Basic physical properties, such as lattice constant, shear modulus, elastic constants (C{sub ij}) are calculated. The calculated energy band structures show that the cubic perovskite BaRuO{sub 3} is metallic. We have also predicted the Young's modulus (Y), Poisson's ratio ({upsilon}), and Anisotropy factor (A).
Effective-medium theory for nonlinear magneto-optics in magnetic granular alloys: cubic nonlinearity
International Nuclear Information System (INIS)
Granovsky, Alexander B.; Kuzmichov, Michail V.; Clerc, J.-P.; Inoue, Mitsuteru
2003-01-01
We propose a simple effective-medium approach for calculating the effective dielectric function of a magnetic metal-insulator granular alloy in which there is a weakly nonlinear relation between electric displacement D and electric field E for both constituent materials of the form D i =ε i (0) E i +χ i (3) |E i | 2 E i . We assume that linear ε i (0) and cubic nonlinear χ i (3) dielectric functions are diagonal and linear with magnetization non-diagonal components. For such metal-insulator composite magneto-optical effects depend on a light intensity and the effective cubic dielectric function χ eff (3) can be significantly greater (up to 10 3 times) than that for constituent materials. The calculation scheme is based on the Bergman and Stroud-Hui theory of nonlinear optical properties of granular matter. The giant cubic magneto-optical nonlinearity is found for composites with metallic volume fraction close to the percolation threshold and at a resonance of optical conductivity. It is shown that a composite may exhibit nonlinear magneto-optics even when both constituent materials have no cubic magneto-optical nonlinearity
Effective-medium theory for nonlinear magneto-optics in magnetic granular alloys: cubic nonlinearity
Energy Technology Data Exchange (ETDEWEB)
Granovsky, Alexander B. E-mail: granov@magn.ru; Kuzmichov, Michail V.; Clerc, J.-P.; Inoue, Mitsuteru
2003-03-01
We propose a simple effective-medium approach for calculating the effective dielectric function of a magnetic metal-insulator granular alloy in which there is a weakly nonlinear relation between electric displacement D and electric field E for both constituent materials of the form D{sub i}={epsilon}{sub i}{sup (0)}E{sub i} +{chi}{sub i}{sup (3)}|E{sub i}|{sup 2}E{sub i}. We assume that linear {epsilon}{sub i}{sup (0)} and cubic nonlinear {chi}{sub i}{sup (3)} dielectric functions are diagonal and linear with magnetization non-diagonal components. For such metal-insulator composite magneto-optical effects depend on a light intensity and the effective cubic dielectric function {chi}{sub eff}{sup (3)} can be significantly greater (up to 10{sup 3} times) than that for constituent materials. The calculation scheme is based on the Bergman and Stroud-Hui theory of nonlinear optical properties of granular matter. The giant cubic magneto-optical nonlinearity is found for composites with metallic volume fraction close to the percolation threshold and at a resonance of optical conductivity. It is shown that a composite may exhibit nonlinear magneto-optics even when both constituent materials have no cubic magneto-optical nonlinearity.
Helium release from metals with face-centered cubic structure
International Nuclear Information System (INIS)
Sciani, V.; Lucki, G.; Jung, P.
1984-01-01
The helium release from gold sheets of 5 and 54 μm of thickness and helium concentrations from 10 -9 to 10 -5 ap of He during the isothermal and linear annealing is studied. The helium was put in the sample through the implantation of alpha particles, with variable energy,in the cyclotron. The free diffusion of the atoms of the helium, where the diffusion coefficient follows an Arrhenius law is studied. (E.G.) [pt
Integrable peakon equations with cubic nonlinearity
International Nuclear Information System (INIS)
Hone, Andrew N W; Wang, J P
2008-01-01
We present a new integrable partial differential equation found by Vladimir Novikov. Like the Camassa-Holm and Degasperis-Procesi equations, this new equation admits peaked soliton (peakon) solutions, but it has nonlinear terms that are cubic, rather than quadratic. We give a matrix Lax pair for V Novikov's equation, and show how it is related by a reciprocal transformation to a negative flow in the Sawada-Kotera hierarchy. Infinitely many conserved quantities are found, as well as a bi-Hamiltonian structure. The latter is used to obtain the Hamiltonian form of the finite-dimensional system for the interaction of N peakons, and the two-body dynamics (N = 2) is explicitly integrated. Finally, all of this is compared with some analogous results for another cubic peakon equation derived by Zhijun Qiao. (fast track communication)
Quasiparticle Interference on Cubic Perovskite Oxide Surfaces.
Okada, Yoshinori; Shiau, Shiue-Yuan; Chang, Tay-Rong; Chang, Guoqing; Kobayashi, Masaki; Shimizu, Ryota; Jeng, Horng-Tay; Shiraki, Susumu; Kumigashira, Hiroshi; Bansil, Arun; Lin, Hsin; Hitosugi, Taro
2017-08-25
We report the observation of coherent surface states on cubic perovskite oxide SrVO_{3}(001) thin films through spectroscopic-imaging scanning tunneling microscopy. A direct link between the observed quasiparticle interference patterns and the formation of a d_{xy}-derived surface state is supported by first-principles calculations. We show that the apical oxygens on the topmost VO_{2} plane play a critical role in controlling the coherent surface state via modulating orbital state.
HRTEM studies of dislocations in cubic BN
International Nuclear Information System (INIS)
Nistor, L.C.; Tendeloo, G. van; Dinca, G.
2004-01-01
The atomic structure of dislocations in cubic boron nitride has been investigated by high resolution transmission electron microscopy. Most of the perfect dislocations, screw and 60 edge, are dissociated. A 60 dislocation which was undissociated has been analysed. Computer simulation is performed in an attempt to characterise the core structure. Twinning dislocations and dislocations resulting from the intersection of stacking faults are also revealed. (copyright 2004 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)
HRTEM studies of dislocations in cubic BN
Energy Technology Data Exchange (ETDEWEB)
Nistor, L.C. [National Institute for Materials Physics, P.O. Box MG-7 Magurele, 077125 Bucharest (Romania); Tendeloo, G. van [University of Antwerp, EMAT, Groenenborgerlaan 171, 2020 Antwerp (Belgium); Dinca, G. [Dacia Synthetic Diamond Factory, Timisoara av. 5, P.O. Box 58-52, 077350 Bucharest (Romania)
2004-09-01
The atomic structure of dislocations in cubic boron nitride has been investigated by high resolution transmission electron microscopy. Most of the perfect dislocations, screw and 60 edge, are dissociated. A 60 dislocation which was undissociated has been analysed. Computer simulation is performed in an attempt to characterise the core structure. Twinning dislocations and dislocations resulting from the intersection of stacking faults are also revealed. (copyright 2004 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)
Minimal knotted polygons in cubic lattices
International Nuclear Information System (INIS)
Van Rensburg, E J Janse; Rechnitzer, A
2011-01-01
In this paper we examine numerically the properties of minimal length knotted lattice polygons in the simple cubic, face-centered cubic, and body-centered cubic lattices by sieving minimal length polygons from a data stream of a Monte Carlo algorithm, implemented as described in Aragão de Carvalho and Caracciolo (1983 Phys. Rev. B 27 1635), Aragão de Carvalho et al (1983 Nucl. Phys. B 215 209) and Berg and Foester (1981 Phys. Lett. B 106 323). The entropy, mean writhe, and mean curvature of minimal length polygons are computed (in some cases exactly). While the minimal length and mean curvature are found to be lattice dependent, the mean writhe is found to be only weakly dependent on the lattice type. Comparison of our results to numerical results for the writhe obtained elsewhere (see Janse van Rensburg et al 1999 Contributed to Ideal Knots (Series on Knots and Everything vol 19) ed Stasiak, Katritch and Kauffman (Singapore: World Scientific), Portillo et al 2011 J. Phys. A: Math. Theor. 44 275004) shows that the mean writhe is also insensitive to the length of a knotted polygon. Thus, while these results for the mean writhe and mean absolute writhe at minimal length are not universal, our results demonstrate that these values are quite close the those of long polygons regardless of the underlying lattice and length
Neutrosophic Cubic MCGDM Method Based on Similarity Measure
Directory of Open Access Journals (Sweden)
Surapati Pramanik
2017-06-01
Full Text Available The notion of neutrosophic cubic set is originated from the hybridization of the concept of neutrosophic set and interval valued neutrosophic set. We define similarity measure for neutrosophic cubic sets and prove some of its basic properties.
Spinning solitons in cubic-quintic nonlinear media
Indian Academy of Sciences (India)
Spinning solitons in cubic-quintic nonlinear media ... features of families of bright vortex solitons (doughnuts, or 'spinning' solitons) in both conservative and dissipative cubic-quintic nonlinear media. ... Pramana – Journal of Physics | News.
International Nuclear Information System (INIS)
Song, T.; Ma, Q.; Sun, X.W.; Liu, Z.J.; Fu, Z.J.; Wei, X.P.; Wang, T.; Tian, J.H.
2016-01-01
The phase transition, electronic band structure, and equation of state (EOS) of cubic TcN are investigated by first-principles pseudopotential method based on density-functional theory. The calculated enthalpies show that TcN has a transformation between zincblende and rocksalt phases and the pressure determined by the relative enthalpy is 32 GPa. The calculated band structure indicates the metallic feature and it might make cubic TcN a better candidate for hard materials. Particular attention is paid to the predictions of volume, bulk modulus and its pressure derivative which play a central role in the formulation of approximate EOSs using the quasi-harmonic Debye model. - Highlights: • The phase transition pressure and electronic band structure for cubic TcN are determined. • Particular attention is paid to investigate the equation of state parameters for cubic TcN. • The thermodynamic properties up to 80 GPa and 3000 K are successfully predicted.
Successful synthesis and thermal stability of immiscible metal Au-Rh, Au-Ir andAu-Ir-Rh nanoalloys
Shubin, Yury; Plyusnin, Pavel; Sharafutdinov, Marat; Makotchenko, Evgenia; Korenev, Sergey
2017-05-01
We successfully prepared face-centred cubic nanoalloys in systems of Au-Ir, Au-Rh and Au-Ir-Rh, with large bulk miscibility gaps, in one-run reactions under thermal decomposition of specially synthesised single-source precursors, namely, [AuEn2][Ir(NO2)6], [AuEn2][Ir(NO2)6] х [Rh(NO2)6]1-х and [AuEn2][Rh(NO2)6]. The precursors employed contain all desired metals ‘mixed’ at the atomic level, thus providing significant advantages for obtaining alloys. The observations using high-resolution transmission electron microscopy show that the nanoalloy structures are composed of well-dispersed aggregates of crystalline domains with a mean size of 5 ± 3 nm. Еnergy dispersive x-ray spectroscopy and x-ray powder diffraction (XRD) measurements confirm the formation of AuIr, AuRh, AuIr0.75Rh0.25, AuIr0.50Rh0.50 and AuIr0.25Rh0.75 metastable solid solutions. In situ high-temperature synchrotron XRD (HTXRD) was used to study the formation mechanism of nanoalloys. The observed transformations are described by the ‘conversion chemistry’ mechanism characterised by the primary development of particles comprising atoms of only one type, followed by a chemical reaction resulting in the final formation of a nanoalloy. The obtained metastable nanoalloys exhibit essential thermal stability. Exposure to 180 °C for 30 h does not cause any dealloying process.
Black holes in a cubic Galileon universe
Energy Technology Data Exchange (ETDEWEB)
Babichev, E.; Charmousis, C.; Lehébel, A.; Moskalets, T., E-mail: eugeny.babichev@th.u-psud.fr, E-mail: christos.charmousis@th.u-psud.fr, E-mail: antoine.lehebel@th.u-psud.fr, E-mail: tetiana.moskalets@th.u-psud.fr [Laboratoire de Physique Théorique, CNRS, Univ. Paris-Sud, Université Paris-Saclay, 91405 Orsay (France)
2016-09-01
We find and study the properties of black hole solutions for a subclass of Horndeski theory including the cubic Galileon term. The theory under study has shift symmetry but not reflection symmetry for the scalar field. The Galileon is assumed to have linear time dependence characterized by a velocity parameter. We give analytic 3-dimensional solutions that are akin to the BTZ solutions but with a non-trivial scalar field that modifies the effective cosmological constant. We then study the 4-dimensional asymptotically flat and de Sitter solutions. The latter present three different branches according to their effective cosmological constant. For two of these branches, we find families of black hole solutions, parametrized by the velocity of the scalar field. These spherically symmetric solutions, obtained numerically, are different from GR solutions close to the black hole event horizon, while they have the same de-Sitter asymptotic behavior. The velocity parameter represents black hole primary hair.
Cubic phase control of ultrashort laser pulses
International Nuclear Information System (INIS)
Mecseki, K.; Erdelyi, M.; Kovacs, A.P.; Szabo, G.
2006-01-01
Complete test of publication follows. The temporal shape of an ultrashort laser pulse may change upon propagating through a linear dispersive medium having a phase shift ψω. The change can be characterized by the Taylor-coefficients of the phase shift which are calculated around the central frequency ω 0 of the pulse. Measurements and independent control of the group delay dispersion (GDD, ψ'(ω 0 )) and the third order dispersion (TOD, ψ'(ω 0 )) are important in several research fields, particularly in the generation of ultrashort laser pulses by chirped pulse amplification (CPA) and pulse shaping for molecular control. The GDD and the TOD of an ideal pulse compressor are equal to the negative of the corresponding dispersion coefficients of the medium. However, in the case of prism-pair and grating-pair compressor is different from the ratio of the coefficients of the medium to be compensated for. Therefore it is necessary to develop so-called cubic compressors that are able to control the TOD of the pulse, yet, do not affect the GDD. In this paper a new cubic compressor setup is investigated theoretically and experimentally, which resembles the set-up proposed by White, however, we control the GDD and the TOD by the position of a birefringent, semi-cylinder crystal place around the focal point of an achromatic lens. For the evaluation of the phase shift introduced by the proposed cubic compressor, a ray tracing program was written. The program allows optimizing the compressor parameters, such as the radius of the crystal, magnification of the lens etc. Calcite was applied because it is a strong birefringent material. Calculations showed that there is a trajectory, along which shifting the crystal the TOD can be tuned independently of the GDD. The value of the TOD changed in a relatively wide range between -3.15 x 10 5 fs 3 and -1.67 x 10 5 fs 3 . Although the defocus also affects the angular dispersion of the pulse leaving the compressor, if does not exceed
Cubic martensite in high carbon steel
Chen, Yulin; Xiao, Wenlong; Jiao, Kun; Ping, Dehai; Xu, Huibin; Zhao, Xinqing; Wang, Yunzhi
2018-05-01
A distinguished structural characteristic of martensite in Fe-C steels is its tetragonality originating from carbon atoms occupying only one set of the three available octahedral interstitial sites in the body-centered-cubic (bcc) Fe lattice. Such a body-centered-tetragonal (bct) structure is believed to be thermodynamically stable because of elastic interactions between the interstitial carbon atoms. For such phase stability, however, there has been a lack of direct experimental evidence despite extensive studies of phase transformations in steels over one century. In this Rapid Communication, we report that the martensite formed in a high carbon Fe-8Ni-1.26C (wt%) steel at room temperature induced by applied stress/strain has actually a bcc rather than a bct crystal structure. This finding not only challenges the existing theories on the stability of bcc vs bct martensite in high carbon steels, but also provides insights into the mechanism for martensitic transformation in ferrous alloys.
Expansion into lattice harmonics in cubic symmetries
Kontrym-Sznajd, G.
2018-05-01
On the example of a few sets of sampling directions in the Brillouin zone, this work shows how important the choice of the cubic harmonics is on the quality of approximation of some quantities by a series of such harmonics. These studies led to the following questions: (1) In the case that for a given l there are several independent harmonics, can one use in the expansion only one harmonic with a given l?; (2) How should harmonics be ordered: according to l or, after writing them in terms of (x4 + y4 + z4)n (x2y2z2)m, according to their degree q = n + m? To enable practical applications of such harmonics, they are constructed in terms of the associated Legendre polynomials up to l = 26. It is shown that electron momentum densities, reconstructed from experimental data for ErGa3 and InGa3, are described much better by harmonics ordered with q.
BDA: A novel method for identifying defects in body-centered cubic crystals.
Möller, Johannes J; Bitzek, Erik
2016-01-01
The accurate and fast identification of crystallographic defects plays a key role for the analysis of atomistic simulation output data. For face-centered cubic (fcc) metals, most existing structure analysis tools allow for the direct distinction of common defects, such as stacking faults or certain low-index surfaces. For body-centered cubic (bcc) metals, on the other hand, a robust way to identify such defects is currently not easily available. We therefore introduce a new method for analyzing atomistic configurations of bcc metals, the BCC Defect Analysis (BDA). It uses existing structure analysis algorithms and combines their results to uniquely distinguish between typical defects in bcc metals. In essence, the BDA method offers the following features:•Identification of typical defect structures in bcc metals.•Reduction of erroneously identified defects by iterative comparison to the defects in the atom's neighborhood.•Availability as ready-to-use Python script for the widespread visualization tool OVITO [http://ovito.org].
Cubic mesoporous Ag@CN: a high performance humidity sensor.
Tomer, Vijay K; Thangaraj, Nishanthi; Gahlot, Sweta; Kailasam, Kamalakannan
2016-12-01
The fabrication of highly responsive, rapid response/recovery and durable relative humidity (%RH) sensors that can precisely monitor humidity levels still remains a considerable challenge for realizing the next generation humidity sensing applications. Herein, we report a remarkably sensitive and rapid %RH sensor having a reversible response using a nanocasting route for synthesizing mesoporous g-CN (commonly known as g-C 3 N 4 ). The 3D replicated cubic mesostructure provides a high surface area thereby increasing the adsorption, transmission of charge carriers and desorption of water molecules across the sensor surfaces. Owing to its unique structure, the mesoporous g-CN functionalized with well dispersed catalytic Ag nanoparticles exhibits excellent sensitivity in the 11-98% RH range while retaining high stability, negligible hysteresis and superior real time %RH detection performances. Compared to conventional resistive sensors based on metal oxides, a rapid response time (3 s) and recovery time (1.4 s) were observed in the 11-98% RH range. Such impressive features originate from the planar morphology of g-CN as well as unique physical affinity and favourable electronic band positions of this material that facilitate water adsorption and charge transportation. Mesoporous g-CN with Ag nanoparticles is demonstrated to provide an effective strategy in designing high performance %RH sensors and show great promise for utilization of mesoporous 2D layered materials in the Internet of Things and next generation humidity sensing applications.
Mesostructured germanium with cubic pore symmetry
Energy Technology Data Exchange (ETDEWEB)
Armatas, G S; Kanatzidis, M G [Michigan State Univ., Michigan (United States), Dept. of Chemistry
2006-11-15
Regular mesoporous oxide materials have been widely studied and have a range of potential applications, such as catalysis, absorption and separation. They are not generally considered for their optical and electronic properties. Elemental semiconductors with nanopores running through them represent a different form of framework material with physical characteristics contrasting with those of the more conventional bulk, thin film and nanocrystalline forms. Here we describe cubic meso structured germanium, MSU-Ge-l, with gyroidal channels containing surfactant molecules, separated by amorphous walls that lie on the gyroid (G) minimal surface as in the mesoporous silica MCM-48. Although Ge is a high-meltin covalent semiconductor that is difficult to prepare from solution polymerization, we succeeded in assembling a continuous Ge network using a suitable precursor for Ge{sup 4-} atoms. Our results indicate that elemental semiconductors from group 14 of the periodic table can be made to adopt meso structured forms such as MSU-Ge-1, which features two three-dimensional labyrinthine tunnels obeying la3d space group symmetry and separated by a continuous germanium minimal surface that is otherwise amorphous. A consequence of this new structure for germanium, which has walls only one nanometre thick, is a wider electronic energy bandgap (1.4 eV versus 0.66 eV) than has crystalline or amorphous Ge. Controlled oxidation of MSU-Ge-1 creates a range of germanium suboxides with continuously varying Ge:O ratio and a smoothly increasing energy gap. (author)
Topological Oxide Insulator in Cubic Perovskite Structure
Jin, Hosub; Rhim, Sonny H.; Im, Jino; Freeman, Arthur J.
2013-01-01
The emergence of topologically protected conducting states with the chiral spin texture is the most prominent feature at the surface of topological insulators. On the application side, large band gap and high resistivity to distinguish surface from bulk degrees of freedom should be guaranteed for the full usage of the surface states. Here, we suggest that the oxide cubic perovskite YBiO3, more than just an oxide, defines itself as a new three-dimensional topological insulator exhibiting both a large bulk band gap and a high resistivity. Based on first-principles calculations varying the spin-orbit coupling strength, the non-trivial band topology of YBiO3 is investigated, where the spin-orbit coupling of the Bi 6p orbital plays a crucial role. Taking the exquisite synthesis techniques in oxide electronics into account, YBiO3 can also be used to provide various interface configurations hosting exotic topological phenomena combined with other quantum phases. PMID:23575973
Bifurcation of limit cycles for cubic reversible systems
Directory of Open Access Journals (Sweden)
Yi Shao
2014-04-01
Full Text Available This article is concerned with the bifurcation of limit cycles of a class of cubic reversible system having a center at the origin. We prove that this system has at least four limit cycles produced by the period annulus around the center under cubic perturbations
Kinks in systems with cubic and quartic anharmonicity
International Nuclear Information System (INIS)
Kashcheev, V.N.
1988-01-01
For a classical system of interacting particles with on-site cubic or quartic anharmonicity explicit analytic solutions of the d'Alembert equation are obtained in the form of kinks in the presence of dissipation (viscous or Rayleigh) and a constant force. These kinks will be asymptotically stable in the case of quartic anharmonicity and unstable in the case cubic anharmonicity
Optical characterisation of cubic silicon carbide
International Nuclear Information System (INIS)
Jackson, S.M.
1998-09-01
The varied properties of Silicon Carbide (SiC) are helping to launch the material into many new applications, particularly in the field of novel semiconductor devices. In this work, the cubic form of SiC is of interest as a basis for developing integrated optical components. Here, the formation of a suitable SiO 2 buried cladding layer has been achieved by high dose oxygen ion implantation. This layer is necessary for the optical confinement of propagating light, and hence optical waveguide fabrication. Results have shown that optical propagation losses of the order of 20 dB/cm are obtainable. Much of this loss can be attributed to mode leakage and volume scattering. Mode leakage is a function of the effective oxide thickness, and volume scattering related to the surface layer damage. These parameters have been shown to be controllable and so suggests that further reduction in the waveguide loss is feasible. Analysis of the layer growth mechanism by RBS, XTEM and XPS proves that SiO 2 is formed, and that the extent, of formation depends on implant dose and temperature. The excess carbon generated is believed to exit the oxide layer by a number of varying mechanisms. The result of this appears to be a number of stable Si-C-O intermediaries that, form regions to either depth extreme of the SiO 2 layer. Early furnace tests suggest a need to anneal at, temperatures approaching the melting point of the silicon substrate, and that the quality of the virgin material is crucial in controlling the resulting oxide growth. (author)
Neutron Dose Measurement Using a Cubic Moderator
International Nuclear Information System (INIS)
Sheinfeld, M.; Mazor, T.; Cohen, Y.; Kadmon, Y.; Orion, I.
2014-01-01
The Bonner Sphere Spectrometer (BSS), introduced In July 1960 by a research group from Rice University, Texas, is a major approach to neutron spectrum estimation. The BSS, also known as multi-sphere spectrometer, consists of a set of a different diameters polyethylene spheres, carrying a small LiI(Eu) scintillator in their center. What makes this spectrometry method such widely used, is its almost isotropic response, covering an extraordinary wide range of energies, from thermal up to even hundreds of MeVs. One of the most interesting and useful consequences of the above study is the 12'' sphere characteristics, as it turned out that the response curve of its energy dependence, have a similar shape compared with the neutron's dose equivalent as a function of energy. This inexplicable and happy circumstance makes it virtually the only monitoring device capable providing realistic neutron dose estimates over such a wide energy range. However, since the detection mechanism is not strictly related to radiation dose, one can expect substantial errors when applied to widely different source conditions. Although the original design of the BSS included a small 4mmx4mmO 6LiI(Eu) scintillator, other thermal neutron detectors has been used over the years: track detectors, activation foils, BF3 filled proportional counters, etc. In this study we chose a Boron loaded scintillator, EJ-254, as the thermal neutron detector. The neutron capture reaction on the boron has a Q value of 2.78 MeV of which 2.34 MeV is shared by the alpha and lithium particles. The high manufacturing costs, the encasement issue, the installation efficiency and the fabrication complexity, led us to the idea of replacing the sphere with a cubic moderator. This article describes the considerations, as well as the Monte-Carlo simulations done in order to examine the applicability of this idea
Electrical properties of cubic InN and GaN epitaxial layers as a function of temperature
International Nuclear Information System (INIS)
Fernandez, J.R.L.; Chitta, V.A.; Abramof, E.
2000-01-01
Carrier concentration and mobility were measured for intrinsic cubic InN and GaN, and for Si-doped cubic GaN as a function of temperature. Metallic n-type conductivity was found for the InN, while background p-type conductivity was observed for the intrinsic GaN layer. Doping the cubic GaN with Si two regimes were observed. For low Si-doping concentrations, the samples remain p-type. Increasing the Si-doping level, the background acceptors are compensated and the samples became highly degenerated n-type. From the carrier concentration dependence on temperature, the activation energy of the donor and acceptor levels was determined. Attempts were made to determine the scattering mechanisms responsible for the behavior of the mobility as a function of temperature
Shape Preserving Interpolation Using C2 Rational Cubic Spline
Directory of Open Access Journals (Sweden)
Samsul Ariffin Abdul Karim
2016-01-01
Full Text Available This paper discusses the construction of new C2 rational cubic spline interpolant with cubic numerator and quadratic denominator. The idea has been extended to shape preserving interpolation for positive data using the constructed rational cubic spline interpolation. The rational cubic spline has three parameters αi, βi, and γi. The sufficient conditions for the positivity are derived on one parameter γi while the other two parameters αi and βi are free parameters that can be used to change the final shape of the resulting interpolating curves. This will enable the user to produce many varieties of the positive interpolating curves. Cubic spline interpolation with C2 continuity is not able to preserve the shape of the positive data. Notably our scheme is easy to use and does not require knots insertion and C2 continuity can be achieved by solving tridiagonal systems of linear equations for the unknown first derivatives di, i=1,…,n-1. Comparisons with existing schemes also have been done in detail. From all presented numerical results the new C2 rational cubic spline gives very smooth interpolating curves compared to some established rational cubic schemes. An error analysis when the function to be interpolated is ft∈C3t0,tn is also investigated in detail.
On q-power cycles in cubic graphs
DEFF Research Database (Denmark)
Bensmail, Julien
2017-01-01
In the context of a conjecture of Erdos and Gyárfás, we consider, for any q ≥ 2, the existence of q-power cycles (i.e. with length a power of q) in cubic graphs. We exhibit constructions showing that, for every q ≥ 3, there exist arbitrarily large cubic graphs with no q-power cycles. Concerning...... the remaining case q = 2 (which corresponds to the conjecture of Erdos and Gyárfás), we show that there exist arbitrarily large cubic graphs whose only 2-power cycles have length 4 only, or 8 only....
Joo, Jang Ho; Kim, Byung-Ho; Lee, Jae-Seung
2017-11-01
A novel room-temperature aqueous synthesis for gold nanoparticle-embedded silver cubic mesh nanostructures using AgCl templates via a template-assisted coreduction method is developed. The cubic AgCl templates are coreduced in the presence of AuCl 4 - and Ag + , resulting in the reduction of AuCl 4 - into gold nanoparticles on the outer region of AgCl templates, followed by the reduction of AgCl and Ag + into silver cubic mesh nanostructures. Removal of the template clearly demonstrates the delicately designed silver mesh nanostructures embedded with gold nanoparticles. The synthetic mechanism, structural properties, and surface functionalization are spectroscopically investigated. The plasmonic photocatalysis of the cubic mesh nanostructures for the degradation of organic pollutants and removal of highly toxic metal ions is investigated; the photocatalytic activity of the cubic mesh nanostructures is superior to those of conventional TiO 2 catalysts and they are catalytically functional even in natural water, owing to their high surface area and excellent chemical stability. The synthetic development presented in this study can be exploited for the highly elaborate, yet, facile design of nanomaterials with outstanding properties. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Shear-induced anisotropic plastic flow from body-centred-cubic tantalum before melting
Wu, Christine J.; Söderlind, Per; Glosli, James N.; Klepeis, John E.
2009-03-01
There are many structural and optical similarities between a liquid and a plastic flow. Thus, it is non-trivial to distinguish between them at high pressures and temperatures, and a detailed description of the transformation between these phenomena is crucial to our understanding of the melting of metals at high pressures. Here we report a shear-induced, partially disordered viscous plastic flow from body-centred-cubic tantalum under heating before it melts into a liquid. This thermally activated structural transformation produces a unique, one-dimensional structure analogous to a liquid crystal with the rheological characteristics of Bingham plastics. This mechanism is not specific to Ta and is expected to hold more generally for other metals. Remarkably, this transition is fully consistent with the previously reported anomalously low-temperature melting curve and thus offers a plausible resolution to a long-standing controversy about melting of metals under high pressures.
Cubic Gallium Nitride on Micropatterned Si (001) for Longer Wavelength LEDs
Energy Technology Data Exchange (ETDEWEB)
Durniak, Mark T. [Rensselaer Polytechnic Inst., Troy, NY (United States). Dept. of Materials Science and Engineering; Chaudhuri, Anabil [Univ. of New Mexico, Albuquerque, NM (United States). Center for High Technology Materials; Smith, Michael L. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States). Advanced Material Sciences; Allerman, Andrew A. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States). Advanced Material Sciences; Lee, S. C. [Univ. of New Mexico, Albuquerque, NM (United States). Center for High Technology Materials; Brueck, S. R. J. [Univ. of New Mexico, Albuquerque, NM (United States). Center for High Technology Materials; Wetzel, Christian [Rensselaer Polytechnic Inst., Troy, NY (United States). Dept. of Physics, Applied Physics, and Astronomy and Dept. of Materials Science and Engineering
2016-03-01
GaInN/GaN heterostructures of cubic phase have the potential to overcome the limitations of wurtzite structures commonly used for light emitting and laser diodes. Wurtzite GaInN suffers from large internal polarization fields, which force design compromises ( 0001 ) towards ultra-narrow quantum wells and reduce recombination volume and efficiency. Cubic GaInN microstripes grown at Rensselaer Polytechnic Institute by metal organic vapor phase epitaxy on micropatterned Si , with {111} v-grooves oriented along Si ( 001 ) , offer a system free of internal polarization fields, wider quantum wells, and smaller <00$\\bar1$> bandgap energy. We prepared 6 and 9 nm Ga _{x} In _{1-x} N/GaN single quantum well structures with peak wavelength ranges from 520 to 570 nm with photons predominately polarized perpendicular to the grooves. We estimate a cubic InN composition range of 0 < x < 0.5 and an upper limit of the internal quantum efficiency of 50%. Stripe geometry and polarization may be suitable for mode confinement and reduced threshold stimulated emission.
Ab initio pseudopotential studies of cubic BC2N under high pressure
International Nuclear Information System (INIS)
Pan Zicheng; Sun Hong; Chen Changfeng
2005-01-01
We present the results of a systematic study of the structural, electronic, and vibrational properties of various cubic BC 2 N phases under high pressure. Ab initio pseudopotential total-energy and phonon calculations have been carried out to examine the changes in the structural parameters, bonding behaviours, band structures, and dynamic instabilities caused by phonon softening in these phases. We find that an experimentally synthesized high-density phase of cubic BC 2 N exhibits outstanding stability in the structural and electronic properties up to very high pressures. On the other hand, another experimentally identified phase with lower density and lower symmetry undergoes a dramatic structural transformation with a volume and bond-length collapse and a concomitant semi-metal to semiconductor transition. A third phase is predicted to be favourable over the above-mentioned lower-density phase by the enthalpy calculations. However, the dynamic phonon calculations reveal that it develops imaginary phonon modes and, therefore, is unstable in the experimental pressure range. The calculations indicate that its synthesis may be achieved at reduced pressures. These results provide a comprehensive understanding for the high-pressure behaviour of the cubic BC 2 N phases and reveal their interesting properties that can be verified by experiments
Plastic fluctuations in empty crystals formed by cubic wireframe particles
McBride, John M.; Avendaño, Carlos
2018-05-01
We present a computer simulation study of the phase behavior of colloidal hard cubic frames, i.e., particles with nonconvex cubic wireframe geometry interacting purely by excluded volume. Despite the propensity of cubic wireframe particles to form cubic phases akin to their convex counterparts, these particles exhibit unusual plastic fluctuations in which a random and dynamic fraction of particles rotate around their lattice positions in the crystal lattice while the remainder of the particles remains fully ordered. We argue that this unexpected effect stems from the nonconvex geometry of the particles in which the faces of a particle can be penetrated by the vertices of the nearest neighbors even at high number densities.
Bicontinuous cubic liquid crystalline nanoparticles for oral delivery of Doxorubicin
DEFF Research Database (Denmark)
Swarnakar, Nitin K; Thanki, Kaushik; Jain, Sanyog
2014-01-01
PURPOSE: The present study explores the potential of bicontinous cubic liquid crystalline nanoparticles (LCNPs) for improving therapeutic potential of doxorubicin. METHODS: Phytantriol based Dox-LCNPs were prepared using hydrotrope method, optimized for various formulation components, process...
A cubic boron nitride film-based fluorescent sensor for detecting Hg2+
Liu, W. M.; Zhao, W. W.; Zhang, H. Y.; Wang, P. F.; Chong, Y. M.; Ye, Q.; Zou, Y. S.; Zhang, W. J.; Zapien, J. A.; Bello, I.; Lee, S. T.
2009-05-01
Cubic boron nitride (cBN) film-based sensors for detecting Hg2+ ions were developed by surface functionalization with dansyl chloride. To immobilize dansyl chloride, 3-aminopropyltriethoxy silane was modified on hydroxylated cBN surfaces to form an amino-group-terminated self-assembled monolayer. The covalent attachment of the amino groups was confirmed by x-ray photoelectron spectroscopy. The selectivity and sensitivity of the sensors to detect diverse metal cations in ethanol solutions were studied by using fluorescence spectroscopy, revealing a great selectivity to Hg2+ ions. Significantly, the dansyl-chloride-functionalized cBN film sensors were recyclable after the sensing test.
First-principles comparison of the cubic and tetragonal phases of Mo3Sb7
Nazir, Safdar; Auluck, Sushil V.; Pulikkotil, Jiji Thomas Joseph; Singh, Nirpendra; Schwingenschlö gl, Udo
2011-01-01
Using ab initio density functional based methods, we study the normal metal state properties of the ∼3 K Mo3Sb7 superconductor, in its high temperature cubic and low temperature tetragonal structures. Although the density of states at the Fermi energy is reasonably high in both structures, our calculations unequivocally show that there exists no long range magnetic ordering in this system. We also address the optical properties of the compound. The magnetism in Mo3Sb7 is studied by fixed spin moment calculations, which yield a shallow non-magnetic minimum, thus inferring propensity to a magnetic instability. © 2011 Elsevier B.V. All rights reserved.
International Nuclear Information System (INIS)
Yang, Z.Q.; Chisholm, M.F.; He, L.L.; Pennycook, S.J.; Ye, H.Q.
2012-01-01
We report experimental investigations on interactions/reactions between dislocations and twin boundaries in Al. The absorption of screw dislocations via cross-slip and the production of stair-rods via reactions with non-screw dislocations were verified by atomic resolution imaging. Importantly, the resulting partial dislocations moving along twin boundaries can produce secondary sessile defects. These immobile defects act as obstacles to other dislocations and also serve to pin the twin boundaries. These findings show the atomic-level dynamics of the dislocation–twin boundary processes and the unique strengthening mechanism of twin boundaries in face-centered cubic metals.
First-principles comparison of the cubic and tetragonal phases of Mo3Sb7
Nazir, Safdar
2011-03-01
Using ab initio density functional based methods, we study the normal metal state properties of the ∼3 K Mo3Sb7 superconductor, in its high temperature cubic and low temperature tetragonal structures. Although the density of states at the Fermi energy is reasonably high in both structures, our calculations unequivocally show that there exists no long range magnetic ordering in this system. We also address the optical properties of the compound. The magnetism in Mo3Sb7 is studied by fixed spin moment calculations, which yield a shallow non-magnetic minimum, thus inferring propensity to a magnetic instability. © 2011 Elsevier B.V. All rights reserved.
Spinor bose gases in cubic optical lattice
International Nuclear Information System (INIS)
Mobarak, Mohamed Saidan Sayed Mohamed
2014-01-01
In recent years the quantum simulation of condensed-matter physics problems has resulted from exciting experimental progress in the realm of ultracold atoms and molecules in optical lattices. In this thesis we analyze theoretically a spinor Bose gas loaded into a three-dimensional cubic optical lattice. In order to account for different superfluid phases of spin-1 bosons with a linear Zeeman effect, we work out a Ginzburg-Landau theory for the underlying spin-1 Bose-Hubbard model. To this end we add artificial symmetry-breaking currents to the spin-1 Bose-Hubbard Hamiltonian in order to break the global U (1) symmetry. With this we determine a diagrammatic expansion of the grand-canonical free energy up to fourth order in the symmetry-breaking currents and up to the leading non-trivial order in the hopping strength which is of first order. As a cross-check we demonstrate that the resulting grand-canonical free energy allows to recover the mean-field theory. Applying a Legendre transformation to the grand-canonical free energy, where the symmetry-breaking currents are transformed to order parameters, we obtain the effective Ginzburg-Landau action. With this we calculate in detail at zero temperature the Mott insulator-superfluid quantum phase boundary as well as condensate and particle number density in the superfluid phase. We find that both mean-field and Ginzburg-Landau theory yield the same quantum phase transition between the Mott insulator and superfluid phases, but the range of validity of the mean-field theory turns out to be smaller than that of the Ginzburg-Landau theory. Due to this finding we expect that the Ginzburg-Landau theory gives better results for the superfluid phase and, thus, we restrict ourselves to extremize only the effective Ginzburg-Landau action with respect to the order parameters. Without external magnetic field the superfluid phase is a polar (ferromagnetic) state for anti-ferromagnetic (ferromagnetic) interactions, i.e. only the
Nanodefects in ultrahard crystalline cubic boron nitride
International Nuclear Information System (INIS)
Nistor, S. V.; Stefan, M.; Goovaerts, E.; Schoemaker, D.
2002-01-01
Cubic boron nitride (cBN), the second hardest known material after diamond, exhibits high thermal conductivity and an excellent ability to be n or p doped, which makes it a strong candidate for the next generation of high-temperature micro optical and micro electronic devices. According to recent studies, cBN exhibits a better resistance to radiation damage than diamond, which suggests potential applications in extreme radiation environments. Crystalline cBN powders of up to 0.5 mm linear size is obtained in a similar way as diamond, by catalytic conversion of hexagonal BN (hBN) to cBN at even higher pressures (> 5GPa) and temperatures (∼ 1900 K). Considering the essential role played by the nanodefects (point defects and impurities) in determining its physical properties, it is surprising how limited is the amount of published data concerning the properties of nanodefects in this material, especially by Electron Paramagnetic Resonance (EPR) spectroscopy, the most powerful method for identification and characterization of nanodefects in both insulators and semiconductors. This seems to be due mainly to the absence of natural cBN gems and the extreme difficulties in producing even mm 3 sized synthetic crystals. We shall present our recent EPR studies on cBN crystalline powders, performed in a broad temperature range from room temperature (RT) down to 1.2 K on several sorts of large size cBN powder grits of yellow and amber color for industrial applications. Previous multifrequency (9.3 GHz and 95 GHz) EPR studies of brown to black cBN crystallites prepared with excess of boron, resulted in the discovery of two new types of paramagnetic point defects with different spectral properties, called the D1 and D2 centers. Our X(9.3 GHz)-band EPR investigations resulted in the observation in amber cBN crystalline powders of a spectrum with a strong temperature dependence of the lineshape. It was found that for high and low temperatures, respectively, the numerical
The Combinatorial Rigidity Conjecture is False for Cubic Polynomials
DEFF Research Database (Denmark)
Henriksen, Christian
2003-01-01
We show that there exist two cubic polynomials with connected Julia sets which are combinatorially equivalent but not topologically conjugate on their Julia sets. This disproves a conjecture by McMullen from 1995.......We show that there exist two cubic polynomials with connected Julia sets which are combinatorially equivalent but not topologically conjugate on their Julia sets. This disproves a conjecture by McMullen from 1995....
Interaction of dispersed cubic phases with blood components
DEFF Research Database (Denmark)
Bode, J C; Kuntsche, Judith; Funari, S S
2013-01-01
The interaction of aqueous nanoparticle dispersions, e.g. based on monoolein/poloxamer 407, with blood components is an important topic concerning especially the parenteral way of administration. Therefore, the influence of human and porcine plasma on dispersed cubic phases was investigated. Part...... activity of cubic phases based on monoolein and poloxamer 188, on soy phosphatidylcholine, glycerol dioleate and polysorbate 80 or the parenteral fat emulsion Lipofundin MCT 20%....
Transdermal delivery of paeonol using cubic gel and microemulsion gel
Luo, Maofu; Shen, Qi; Chen, Jinjin
2011-01-01
Background The aim of this study was to develop new systems for transdermal delivery of paeonol, in particular microemulsion gel and cubic gel formulations. Methods Various microemulsion vehicles were prepared using isopropyl myristate as an oil phase, polyoxyethylated castor oil (Cremophor® EL) as a surfactant, and polyethylene glycol 400 as a cosurfactant. In the optimum microemulsion gel formulation, carbomer 940 was selected as the gel matrix, and consisted of 1% paeonol, 4% isopropyl myristate, 28% Cremophor EL/polyethylene glycol 400 (1:1), and 67% water. The cubic gel was prepared containing 3% paeonol, 30% water, and 67% glyceryl monooleate. Results A skin permeability test using excised rat skins indicated that both the cubic gel and microemulsion gel formulations had higher permeability than did the paeonol solution. An in vivo pharmacokinetic study done in rats showed that the relative bioavailability of the cubic gel and microemulsion gel was enhanced by about 1.51-fold and 1.28-fold, respectively, compared with orally administered paeonol suspension. Conclusion Both the cubic gel and microemulsion gel formulations are promising delivery systems to enhance the skin permeability of paeonol, in particular the cubic gel. PMID:21904450
International Nuclear Information System (INIS)
Hueger, E.; Osuch, K.
2005-01-01
The morphology and crystal structure of noble metal nano-films deposited on oxygen contaminated and oxygen-free Nb(001) surfaces have been studied with angle-resolved ultraviolet photoelectron spectroscopy, X-ray photo-electron diffraction, and reflection high energy electron diffraction. In the both cases a deposited noble metal film aligns its direction with the [110] direction of the Nb(001) surface. But, while a noble metal grows on an oxygen contaminated Nb(001) surface with the hexagonal close-packed (hcp) (111) planes parallel to the surface (i.e. in the (111)-oriented face centred cubic phase (fcc)), on a non-contaminated Nb(001) it grows with its hcp planes perpendicular to the surface. The latter happens because in the initial stages of the epitaxy the first two monolayers (MLs) of the noble metal grow pseudomorphically on a contamination-free Nb(001). The pseudomorphic layer is strongly extended parallel to the Nb(001) surface in comparison to its natural fcc (001) plane. As a consequence of the atomic volume conservation principle the out-of-plane lattice of the pseudomorphic layer is contracted. Thus, its body centred tetragonal (110) planes, which stay perpendicular to the surface, contract into denser-packed planes, i.e. in hcp ones. In the direction perpendicular to the surface, where the substrate does not have a direct influence on the film, the pseudomorphic layer relaxes into its natural close-packed phase, i.e. into hcp atomic planes. These planes appear as soon as the third pseudomorphic ML begins to grow. The stacking axis of the planes lies in the (100) surface of Nb and is locked by it. The fact that thick nano-films of Cu (up to 50 MLs), Ag and Au (up to 100 MLs) grow in the (112-bar0)-oriented hcp phase can be attributed to a much better fit of the hcp than of fcc stacking sequence to the four-fold symmetry of the Nb(001) surface
[Multimodal medical image registration using cubic spline interpolation method].
He, Yuanlie; Tian, Lianfang; Chen, Ping; Wang, Lifei; Ye, Guangchun; Mao, Zongyuan
2007-12-01
Based on the characteristic of the PET-CT multimodal image series, a novel image registration and fusion method is proposed, in which the cubic spline interpolation method is applied to realize the interpolation of PET-CT image series, then registration is carried out by using mutual information algorithm and finally the improved principal component analysis method is used for the fusion of PET-CT multimodal images to enhance the visual effect of PET image, thus satisfied registration and fusion results are obtained. The cubic spline interpolation method is used for reconstruction to restore the missed information between image slices, which can compensate for the shortage of previous registration methods, improve the accuracy of the registration, and make the fused multimodal images more similar to the real image. Finally, the cubic spline interpolation method has been successfully applied in developing 3D-CRT (3D Conformal Radiation Therapy) system.
Deformation of the cubic open string field theory
Energy Technology Data Exchange (ETDEWEB)
Lee, Taejin, E-mail: taejin@kangwon.ac.kr
2017-05-10
We study a consistent deformation of the cubic open bosonic string theory in such a way that the non-planar world sheet diagrams of the perturbative string theory are mapped onto their equivalent planar diagrams of the light-cone string field theory with some length parameters fixed. An explicit evaluation of the cubic string vertex in the zero-slope limit yields the correct relationship between the string coupling constant and the Yang–Mills coupling constant. The deformed cubic open string field theory is shown to produce the non-Abelian Yang–Mills action in the zero-slope limit if it is defined on multiple D-branes. Applying the consistent deformation systematically to multi-string world sheet diagrams, we may be able to calculate scattering amplitudes with an arbitrary number of external open strings.
Deformation of the cubic open string field theory
Directory of Open Access Journals (Sweden)
Taejin Lee
2017-05-01
Full Text Available We study a consistent deformation of the cubic open bosonic string theory in such a way that the non-planar world sheet diagrams of the perturbative string theory are mapped onto their equivalent planar diagrams of the light-cone string field theory with some length parameters fixed. An explicit evaluation of the cubic string vertex in the zero-slope limit yields the correct relationship between the string coupling constant and the Yang–Mills coupling constant. The deformed cubic open string field theory is shown to produce the non-Abelian Yang–Mills action in the zero-slope limit if it is defined on multiple D-branes. Applying the consistent deformation systematically to multi-string world sheet diagrams, we may be able to calculate scattering amplitudes with an arbitrary number of external open strings.
Cubic interactions of Maxwell-like higher spins
Energy Technology Data Exchange (ETDEWEB)
Francia, Dario [Scuola Normale Superiore and INFN,Piazza dei Cavalieri, 7 I-56126 Pisa (Italy); Monaco, Gabriele Lo [Dipartimento di Fisica, Università di Pisa,Piazza Fibonacci, 3, I-56126, Pisa (Italy); Dipartimento di Fisica, Università di Milano-Bicocca,Piazza della Scienza 3, I-20126 Milano (Italy); Mkrtchyan, Karapet [Max Planck Institut für Gravitationsphysik,Am Mühlenberg 1, Potsdam 14476 (Germany)
2017-04-12
We study the cubic vertices for Maxwell-like higher-spins in flat and (A)dS background spaces of any dimension. Reducibility of their free spectra implies that a single cubic vertex involving any three fields subsumes a number of couplings among different particles of various spins. The resulting vertices do not involve traces of the fields and in this sense are simpler than their Fronsdal counterparts. We propose an extension of both the free theory and of its cubic deformation to a more general class of partially reducible systems, that one can obtain from the original theory upon imposing trace constraints of various orders. The key to our results is a version of the Noether procedure allowing to systematically account for the deformations of the transversality conditions to be imposed on the gauge parameters at the free level.
Deformation of the cubic open string field theory
International Nuclear Information System (INIS)
Lee, Taejin
2017-01-01
We study a consistent deformation of the cubic open bosonic string theory in such a way that the non-planar world sheet diagrams of the perturbative string theory are mapped onto their equivalent planar diagrams of the light-cone string field theory with some length parameters fixed. An explicit evaluation of the cubic string vertex in the zero-slope limit yields the correct relationship between the string coupling constant and the Yang–Mills coupling constant. The deformed cubic open string field theory is shown to produce the non-Abelian Yang–Mills action in the zero-slope limit if it is defined on multiple D-branes. Applying the consistent deformation systematically to multi-string world sheet diagrams, we may be able to calculate scattering amplitudes with an arbitrary number of external open strings.
Energy Technology Data Exchange (ETDEWEB)
Sahli, B. [Laboratoire de Génie Physique, Université Ibn Khaldoun, Tiaret, 14000 (Algeria); Laboratoire des Matériaux Magnétiques, Université Djillali Liabés, Sidi Bel-Abbes 22000 (Algeria); Bouafia, H., E-mail: hamza.tssm@gmail.com [Laboratoire de Génie Physique, Université Ibn Khaldoun, Tiaret, 14000 (Algeria); Abidri, B.; Abdellaoui, A. [Laboratoire des Matériaux Magnétiques, Université Djillali Liabés, Sidi Bel-Abbes 22000 (Algeria); Hiadsi, S.; Akriche, A. [Laboratoire de Microscope Electronique et Sciences des Matériaux, Université des Sciences et de la Technologie Mohamed Boudiaf, département de Génie Physique, BP1505 El m’naouar, Oran (Algeria); Benkhettou, N.; Rached, D. [Laboratoire des Matériaux Magnétiques, Université Djillali Liabés, Sidi Bel-Abbes 22000 (Algeria)
2015-06-25
Highlights: • The ground state properties of SrUO{sub 3}-Perovskite were investigated. • Elastic constants and their related parameters were calculated. • Electronic properties are treated using GGA-PBEsol + U approach. - Abstract: In this paper, we investigate bulk properties of the cubic SrUO{sub 3}-Perovskite in their nonmagnetic (NM), antiferromagnetic (AFM) and ferromagnetic (FM) states using all-electron self consistent Full Potential Augmented Plane Waves plus local orbital (FP-(L)APW + lo) method within PBEsol Generalized Gradiant density approximations. Our calculation allowed us to predict that the more stable magnetic state of the cubic SrUO{sub 3}-Perovskite is that of the ferromagnetic (FM). This work is the first prediction of elastic constants and their related parameters (Young modulus, shear modulus, Poisson ratio, Zener anisotropy and the Debye temperature) for this cubic compound using Mehl method. We have employed the GGA(PBEsol) and GGA(PBEsol) + U to investigate the electronic band structure, density of states and electronic charge density of SrUO{sub 3}-Perovskite. The electronic band structure calculations revealed that SrUO{sub 3} exhibits metallic behavior. On the other hand the charge density plots for [1 1 0] direction indicates a strong ionic character along the Sr–O bond while the U–O bond has strong covalent character. Finally, we have analyzed the thermodynamic properties using the quasi-harmonic Debye model to complete the fundamental characterization of cubic SrUO{sub 3}-Perovskite.
Generalized Born-Infeld actions and projective cubic curves
Energy Technology Data Exchange (ETDEWEB)
Ferrara, S. [Department of Physics, CERN Theory Division, CH - 1211 Geneva 23 (Switzerland); INFN - Laboratori Nazionali di Frascati, Via Enrico Fermi 40, I-00044, Frascati (Italy); Porrati, M. [CCPP, Department of Physics, NYU, 4 Washington Pl., New York, NY, 10003 (United States); Sagnotti, A. [Department of Physics, CERN Theory Division, CH - 1211 Geneva 23 (Switzerland); Stora, R. [Department of Physics, CERN Theory Division, CH - 1211 Geneva 23 (Switzerland); Laboratoire d' Annecy-le-Vieux de Physique Theorique (LAPTH), F-74941, Annecy-le-Vieux, Cedex (France); Yeranyan, A. [INFN - Laboratori Nazionali di Frascati, Via Enrico Fermi 40, I-00044, Frascati (Italy); Centro Studi e Ricerche Enrico Fermi, Via Panisperna 89A, 00184, Roma (Italy)
2015-04-01
We investigate U(1){sup n} supersymmetric Born-Infeld Lagrangians with a second non-linearly realized supersymmetry. The resulting non-linear structure is more complex than the square root present in the standard Born-Infeld action, and nonetheless the quadratic constraints determining these models can be solved exactly in all cases containing three vector multiplets. The corresponding models are classified by cubic holomorphic prepotentials. Their symmetry structures are associated to projective cubic varieties. (copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)
3D confocal imaging in CUBIC-cleared mouse heart
Energy Technology Data Exchange (ETDEWEB)
Nehrhoff, I.; Bocancea, D.; Vaquero, J.; Vaquero, J.J.; Lorrio, M.T.; Ripoll, J.; Desco, M.; Gomez-Gaviro, M.V.
2016-07-01
Acquiring high resolution 3D images of the heart enables the ability to study heart diseases more in detail. Here, the CUBIC (clear, unobstructed brain imaging cocktails and computational analysis) clearing protocol was adapted for thick mouse heart sections to increase the penetration depth of the confocal microscope lasers into the tissue. The adapted CUBIC clearing of the heart lets the antibody penetrate deeper into the tissue by a factor of five. The here shown protocol enables deep 3D highresolution image acquisition in the heart. This allows a much more accurate assessment of the cellular and structural changes that underlie heart diseases. (Author)
Eisenstein Series Identities Involving the Borweins' Cubic Theta Functions
Directory of Open Access Journals (Sweden)
Ernest X. W. Xia
2012-01-01
Full Text Available Based on the theories of Ramanujan's elliptic functions and the (p, k-parametrization of theta functions due to Alaca et al. (2006, 2007, 2006 we derive certain Eisenstein series identities involving the Borweins' cubic theta functions with the help of the computer. Some of these identities were proved by Liu based on the fundamental theory of elliptic functions and some of them may be new. One side of each identity involves Eisenstein series, the other products of the Borweins' cubic theta functions. As applications, we evaluate some convolution sums. These evaluations are different from the formulas given by Alaca et al.
Regularizing cubic open Neveu-Schwarz string field theory
International Nuclear Information System (INIS)
Berkovits, Nathan; Siegel, Warren
2009-01-01
After introducing non-minimal variables, the midpoint insertion of Y Y-bar in cubic open Neveu-Schwarz string field theory can be replaced with an operator N ρ depending on a constant parameter ρ. As in cubic open superstring field theory using the pure spinor formalism, the operator N ρ is invertible and is equal to 1 up to a BRST-trivial quantity. So unlike the linearized equation of motion Y Y-bar QV = 0 which requires truncation of the Hilbert space in order to imply QV = 0, the linearized equation N ρ QV = 0 directly implies QV = 0.
3D confocal imaging in CUBIC-cleared mouse heart
International Nuclear Information System (INIS)
Nehrhoff, I.; Bocancea, D.; Vaquero, J.; Vaquero, J.J.; Lorrio, M.T.; Ripoll, J.; Desco, M.; Gomez-Gaviro, M.V.
2016-01-01
Acquiring high resolution 3D images of the heart enables the ability to study heart diseases more in detail. Here, the CUBIC (clear, unobstructed brain imaging cocktails and computational analysis) clearing protocol was adapted for thick mouse heart sections to increase the penetration depth of the confocal microscope lasers into the tissue. The adapted CUBIC clearing of the heart lets the antibody penetrate deeper into the tissue by a factor of five. The here shown protocol enables deep 3D highresolution image acquisition in the heart. This allows a much more accurate assessment of the cellular and structural changes that underlie heart diseases. (Author)
Total Positivity of the Cubic Trigonometric Bézier Basis
Directory of Open Access Journals (Sweden)
Xuli Han
2014-01-01
Full Text Available Within the general framework of Quasi Extended Chebyshev space, we prove that the cubic trigonometric Bézier basis with two shape parameters λ and μ given in Han et al. (2009 forms an optimal normalized totally positive basis for λ,μ∈(-2,1]. Moreover, we show that for λ=-2 or μ=-2 the basis is not suited for curve design from the blossom point of view. In order to compute the corresponding cubic trigonometric Bézier curves stably and efficiently, we also develop a new corner cutting algorithm.
Specific heat of the simple-cubic Ising model
Feng, X.; Blöte, H.W.J.
2010-01-01
We provide an expression quantitatively describing the specific heat of the Ising model on the simple-cubic lattice in the critical region. This expression is based on finite-size scaling of numerical results obtained by means of a Monte Carlo method. It agrees satisfactorily with series expansions
Higher-Order Approximation of Cubic-Quintic Duffing Model
DEFF Research Database (Denmark)
Ganji, S. S.; Barari, Amin; Babazadeh, H.
2011-01-01
We apply an Artificial Parameter Lindstedt-Poincaré Method (APL-PM) to find improved approximate solutions for strongly nonlinear Duffing oscillations with cubic-quintic nonlinear restoring force. This approach yields simple linear algebraic equations instead of nonlinear algebraic equations...
C2-rational cubic spline involving tension parameters
Indian Academy of Sciences (India)
preferred which preserves some of the characteristics of the function to be interpolated. In order to tackle such ... Shape preserving properties of the rational (cubic/quadratic) spline interpolant have been studied ... tension parameters which is used to interpolate the given monotonic data is described in. [6]. Shape preserving ...
Initial post dynamic buckling of a quadratic-cubic column ...
African Journals Online (AJOL)
In this investigation, we determine the dynamic buckling load of an imperfect finite column resting on a mixed quadratic-cubic nonlinear elastic foundation trapped by an explicitly time dependent sinusoidally slowly varying dynamic load .The resultant coefficients are dynamically slowly varying and the formulation contains ...
One billion cubic meters of gas produced in Kikinda area
Energy Technology Data Exchange (ETDEWEB)
Vicicevic, M; Duric, N
1969-10-01
The Kikinda gas reservoir has just passed a milestone in producing one billion cubic meters of natural gas. The reservoir was discovered in 1962, and its present production amounts to 26 million cu m. One of the biggest problems was formation of hydrates, which has successfully been solved by using methanol. Four tables show production statistics by years and productive formations.
Physical vapor deposition of cubic boron nitride thin films
International Nuclear Information System (INIS)
Kester, D.J.
1991-01-01
Cubic boron nitride was successfully deposited using physical vapor-deposition methods. RF-sputtering, magnetron sputtering, dual-ion-beam deposition, and ion-beam-assisted evaporation were all used. The ion-assisted evaporation, using boron evaporation and bombardment by nitrogen and argon ions, led to successful cubic boron nitride growth over the widest and most controllable range of conditions. It was found that two factors were important for c-BN growth: bombardment of the growing film and the presence of argon. A systematic study of the deposition conditions was carried out. It was found that the value of momentum transferred into the growing from by the bombarding ions was critical. There was a very narrow transition range in which mixed cubic and hexagonal phase films were prepared. Momentum-per-atom value took into account all the variables involved in ion-assisted deposition: deposition rate, ion energy, ion flux, and ion species. No other factor led to the same control of the process. The role of temperature was also studied; it was found that at low temperatures only mixed cubic and hexagonal material are deposited
Particle Creation in Oscillating Cavities with Cubic and Cylindrical Geometry
Setare, M. R.; Dinani, H. T.
2008-04-01
In the present paper we study the creation of massless scalar particles from the quantum vacuum due to the dynamical Casimir effect by oscillating cavities with cubic and cylindrical geometry. To the first order of the amplitude we derive the expressions for the number of the created particles.
Global Well-Posedness for Cubic NLS with Nonlinear Damping
Antonelli, Paolo
2010-11-04
We study the Cauchy problem for the cubic nonlinear Schrödinger equation, perturbed by (higher order) dissipative nonlinearities. We prove global in-time existence of solutions for general initial data in the energy space. In particular we treat the energy-critical case of a quintic dissipation in three space dimensions. © Taylor & Francis Group, LLC.
Influence of strontium on the cubic to ordered hexagonal phase
Indian Academy of Sciences (India)
... Refresher Courses · Symposia · Live Streaming. Home; Journals; Bulletin of Materials Science; Volume 23; Issue 6. Influence of strontium on the cubic to ordered hexagonal phase transformation in barium magnesium niobate. M Thirumal A K Ganguli. Phase Transitions Volume 23 Issue 6 December 2000 pp 495-498 ...
Exact solutions for the cubic-quintic nonlinear Schroedinger equation
International Nuclear Information System (INIS)
Zhu Jiamin; Ma Zhengyi
2007-01-01
In this paper, the cubic-quintic nonlinear Schroedinger equation is solved through the extended elliptic sub-equation method. As a consequence, many types of exact travelling wave solutions are obtained which including bell and kink profile solitary wave solutions, triangular periodic wave solutions and singular solutions
Estimating the board foot to cubic foot ratio
Steve P. Verrill; Victoria L. Herian; Henry N. Spelter
2004-01-01
Certain issues in recent softwood lumber trade negotiations have centered on the method for converting estimates of timber volumes reported in cubic meters to board feet. Such conversions depend on many factors; three of the most important of these are log length, diameter, and taper. Average log diameters vary by region and have declined in the western United States...
A Unified Approach to Teaching Quadratic and Cubic Equations.
Ward, A. J. B.
2003-01-01
Presents a simple method for teaching the algebraic solution of cubic equations via completion of the cube. Shows that this method is readily accepted by students already familiar with completion of the square as a method for quadratic equations. (Author/KHR)
Tangent Lines without Derivatives for Quadratic and Cubic Equations
Carroll, William J.
2009-01-01
In the quadratic equation, y = ax[superscript 2] + bx + c, the equation y = bx + c is identified as the equation of the line tangent to the parabola at its y-intercept. This is extended to give a convenient method of graphing tangent lines at any point on the graph of a quadratic or a cubic equation. (Contains 5 figures.)
Hardness and thermal stability of cubic silicon nitride
DEFF Research Database (Denmark)
Jiang, Jianzhong; Kragh, Flemming; Frost, D. J.
2001-01-01
The hardness and thermal stability of cubic spinel silicon nitride (c-Si3N4), synthesized under high-pressure and high-temperature conditions, have been studied by microindentation measurements, and x-ray powder diffraction and scanning electron microscopy, respectively The phase at ambient...
Chemically ordered face-centred tetragonal Fe–Pt nanoparticles ...
Indian Academy of Sciences (India)
2012-02-21
Feb 21, 2012 ... Heat treatment of Fe/Pt co-doped films in air caused generation of Pt NPs first. At this stage, Fe .... water to salt can be varied from 26 to 28) and mixed with ..... electron diffraction (SAED) pattern (grey scale inverted; fig- ure 5c) ...
On the use of distorted fcc structures for describing high-pressure phases
International Nuclear Information System (INIS)
Gerward, L.; Staun Olsen, J.; Benedict, U.
1986-01-01
The paper describes distorted lattices that can be derived from the face-centred cubic Bravais lattice. Crystallographic principles are outlined and it is discussed how various lattices can be identified from the observed splitting of X-ray powder diffraction lines. Examples are taken from recent high-pressure studies of actinide rocksalt structure compounds and cerium metal. (orig.)
High activity of cubic PtRh alloys supported on graphene towards ethanol electrooxidation.
Rao, Lu; Jiang, Yan-Xia; Zhang, Bin-Wei; Cai, Yuan-Rong; Sun, Shi-Gang
2014-07-21
Cubic PtRh alloys supported on graphene (PtxRhy/GN) with different atomic ratio of Pt and Rh were directly synthesized for the first time using the modified polyol method with Br(-) for the shape-directing agents. The process didn't use surface-capping agents such as PVP that easily occupy the active sites of electrocatalysts and are difficult to remove. Graphene is the key factor for cubic shape besides Br(-) and keeping catalysts high-dispersed. The X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscope (TEM) were used to characterize the structure and morphology of these electrocatalysts. The results showed that they were composed of homogeneous cubic PtRh alloys. Traditional electrochemical methods, such as cyclic voltammetry and chronoamperometry, were used to investigate the electrocatalytic properties of PtxRhy/GN towards ethanol electrooxidation. It can be seen that PtxRhy/GN with all atomic ratios exhibited high catalytic activity, and the most active one has a composition with Pt : Rh = 9 : 1 atomic ratio. Electrochemical in situ FTIR spectroscopy was used to evaluate the cleavage of C-C bond in ethanol at room temperature in acidic solutions, the results illustrated that Rh in an alloy can promote the split of C-C bond in ethanol, and the alloy catalyst with atomic ratio Pt : Rh = 1 : 1 showed obviously better performance for the C-C bond breaking in ethanol and higher selectivity for the enhanced activity of ethanol complete oxidation to CO2 than alloys with other ratios of Pt and Rh. The investigation indicates that high activity of PtxRhy/GN electrocatalyst towards ethanol oxidation is due to the specific shape of alloys and the synergistic effect of two metal elements as well as graphene support.
Cationic Phospholipids Forming Cubic Phases: Lipoplex Structure and Transfection Efficiency
Energy Technology Data Exchange (ETDEWEB)
Koynova, Rumiana; Wang, Li; MacDonald, Robert C. (NWU)
2008-10-29
The transfection activity and the phase behavior of two novel cationic O-alkyl-phosphatidylcholines, 1,2-dioleoyl-sn-glycero-3-hexylphosphocholine (C6-DOPC) and 1,2-dierucoyl-sn-glycero-3-ethylphosphocholine (di22:1-EPC), have been examined with the aim of more completely understanding the mechanism of lipid-mediated DNA delivery. Both lipids form cubic phases: C6-DOPC in the entire temperature range from -10 to 90 C, while di22:1-EPC exhibits an irreversible lamellar-cubic transition between 50 and 70 C on heating. The lipoplexes formed by C6-DOPC arrange into hexagonal phase, while the lipoplexes of di22:1-EPC are lamellar. Both lipids exhibit lower transfection activity than the lamellar-forming 1,2-dioleoyl-sn-glycero-3-ethylphosphocholine (EDOPC). Thus, for the studied cationic phospholipid-DNA systems, the lipoplex phase state is a factor that does not seem to correlate with transfection activity. The parameter that exhibits better correlation with the transfection activity within the present data set is the phase state of the lipid dispersion prior to the addition of DNA. Thus, the lamellar lipid dispersion (EDOPC) produces more efficient lipoplexes than the dispersion with coexisting lamellar and cubic aggregates (diC22:1-EPC), which is even more efficient than the purely cubic dispersions (C6-DOPC; diC22:1-EPC after heating). It could be inferred from these data and from previous research that cubic phase lipid aggregates are unlikely to be beneficial to transfection. The lack of correlation between the phase state of lipoplexes and their transfection activity observed within the present data set does not mean that lipid phase state is generally unimportant for lipofection: a viewpoint now emerging from our previous studies is that the critical factor in lipid-mediated transfection is the structural evolution of lipoplexes within the cell, upon interacting and mixing with cellular lipids.
Cationic phospholipids forming cubic phases: lipoplex structure and transfection efficiency.
Koynova, Rumiana; Wang, Li; Macdonald, Robert C
2008-01-01
The transfection activity and the phase behavior of two novel cationic O-alkyl-phosphatidylcholines, 1,2-dioleoyl- sn-glycero-3-hexylphosphocholine (C6-DOPC) and 1,2-dierucoyl- sn-glycero-3-ethylphosphocholine (di22:1-EPC), have been examined with the aim of more completely understanding the mechanism of lipid-mediated DNA delivery. Both lipids form cubic phases: C6-DOPC in the entire temperature range from -10 to 90 degrees C, while di22:1-EPC exhibits an irreversible lamellar-cubic transition between 50 and 70 degrees C on heating. The lipoplexes formed by C6-DOPC arrange into hexagonal phase, while the lipoplexes of di22:1-EPC are lamellar. Both lipids exhibit lower transfection activity than the lamellar-forming 1,2-dioleoyl- sn-glycero-3-ethylphosphocholine (EDOPC). Thus, for the studied cationic phospholipid-DNA systems, the lipoplex phase state is a factor that does not seem to correlate with transfection activity. The parameter that exhibits better correlation with the transfection activity within the present data set is the phase state of the lipid dispersion prior to the addition of DNA. Thus, the lamellar lipid dispersion (EDOPC) produces more efficient lipoplexes than the dispersion with coexisting lamellar and cubic aggregates (diC22:1-EPC), which is even more efficient than the purely cubic dispersions (C6-DOPC; diC22:1-EPC after heating). It could be inferred from these data and from previous research that cubic phase lipid aggregates are unlikely to be beneficial to transfection. The lack of correlation between the phase state of lipoplexes and their transfection activity observed within the present data set does not mean that lipid phase state is generally unimportant for lipofection: a viewpoint now emerging from our previous studies is that the critical factor in lipid-mediated transfection is the structural evolution of lipoplexes within the cell, upon interacting and mixing with cellular lipids.
INVESTIGATION OF CURVES SET BY CUBIC DISTRIBUTION OF CURVATURE
Directory of Open Access Journals (Sweden)
S. A. Ustenko
2014-03-01
Full Text Available Purpose. Further development of the geometric modeling of curvelinear contours of different objects based on the specified cubic curvature distribution and setpoints of curvature in the boundary points. Methodology. We investigate the flat section of the curvilinear contour generating under condition that cubic curvature distribution is set. Curve begins and ends at the given points, where angles of tangent slope and curvature are also determined. It was obtained the curvature equation of this curve, depending on the section length and coefficient c of cubic curvature distribution. The analysis of obtained equation was carried out. As well as, it was investigated the conditions, in which the inflection points of the curve are appearing. One should find such an interval of parameter change (depending on the input data and the section length, in order to place the inflection point of the curvature graph outside the curve section borders. It was determined the dependence of tangent slope of angle to the curve at its arbitrary point, as well as it was given the recommendations to solve a system of integral equations that allow finding the length of the curve section and the coefficient c of curvature cubic distribution. Findings. As the result of curves research, it is found that the criterion for their selection one can consider the absence of inflection points of the curvature on the observed section. Influence analysis of the parameter c on the graph of tangent slope angle to the curve showed that regardless of its value, it is provided the same rate of angle increase of tangent slope to the curve. Originality. It is improved the approach to geometric modeling of curves based on cubic curvature distribution with its given values at the boundary points by eliminating the inflection points from the observed section of curvilinear contours. Practical value. Curves obtained using the proposed method can be used for geometric modeling of curvilinear
What will we do with 104,000,000 cubic feet of Fernald waste?
International Nuclear Information System (INIS)
Motl, G.P.; Krieger, G.J.
1995-01-01
The Fernald Site, a Department of Energy (DOE) uranium metal production facility that ceased production in 1989, is now being remediated by the DOE under terms of a Consent Agreement with the United States Environmental Protection Agency (USEPA) and a Consent Decree with the State of Ohio. It is estimated that the cleanup will generate 104,000,000 cubic feet of low-level radioactive waste including construction debris, pit sludge, radium residue and a huge volume of uranium contaminated soil. The waste handling strategy for this huge volume of waste includes minimizing remedial waste generation, recycling material when economically feasible, free-releasing clean material and volume reduction. It is anticipated that large scale radium residue vitrification and sludge drying equipment/facilities will be constructed onsite for waste treatment prior to off-site disposal. Fernald waste disposition will include both onsite disposal (if approved under CERCLA) and off-site disposal at both commercial and DOE waste disposal facilities. The waste disposition strategy selected reflects a diverse variety of technical, political, regulatory and economic factors. This presentation will describe the current views at Fernald on open-quotes what will we do with 104,000,000 cubic feet of Fernald waste.close quotes
Size-dependent plastic deformation of twinned nanopillars in body-centered cubic tungsten
Xu, Shuozhi; Startt, Jacob K.; Payne, Thomas G.; Deo, Chaitanya S.; McDowell, David L.
2017-05-01
Compared with face-centered cubic metals, twinned nanopillars in body-centered cubic (BCC) systems are much less explored partly due to the more complicated plastic deformation behavior and a lack of reliable interatomic potentials for the latter. In this paper, the fault energies predicted by two semi-empirical interatomic potentials in BCC tungsten (W) are first benchmarked against density functional theory calculations. Then, the more accurate potential is employed in large scale molecular dynamics simulations of tensile and compressive loading of twinned nanopillars in BCC W with different cross sectional shapes and sizes. A single crystal, a twinned crystal, and single crystalline nanopillars are also studied as references. Analyses of the stress-strain response and defect nucleation reveal a strong tension-compression asymmetry and a weak pillar size dependence in the yield strength. Under both tensile and compressive loading, plastic deformation in the twinned nanopillars is dominated by dislocation slip on {110} planes that are nucleated from the intersections between the twin boundary and the pillar surface. It is also found that the cross sectional shape of nanopillars affects the strength and the initial site of defect nucleation but not the overall stress-strain response and plastic deformation behavior.
Effects of Aperture Size on Q factor and Shielding Effectiveness of a Cubic Resonator
Directory of Open Access Journals (Sweden)
S. Parr
2017-09-01
Full Text Available The EMC properties of a cubic metallic shield are highly affected by its resonances. At the resonant frequencies, the shielding effectiveness (SE collapses, which results in high field strengths inside the cavity. This can cause failure or even breakdown of electronic devices inside the shield. The resonant behaviour is mainly determined by the quality or Q factor of the shield. In this paper, the effects of the aperture size on the Q factor and the SE of an electrically large, cubic shield are analysed. At first, a method is developed in order to determine the Q factor based on the resonance behaviour of the shield in time domain. Only the first resonance of the shield is considered therefore. The results are evaluated for different aperture diameters and compared with theory for the Q factor. The dominant coupling mechanism of electromagnetic energy into the shield is thus identified. Then the effect of aperture size on the SE is analysed. The excitation of resonances is very probable if the interfering signal is an ultrawideband (UWB pulse, which constitutes a typical intentional electromagnetic interference (IEMI scenario. Therefore, the relation between aperture size and SE is analysed using the theory of the transient SE for a broadband signal with a constant spectral density distribution. The results show, that a worst case aperture size exists, where the SE has its minimum.
Different magnetic properties of rhombohedral and cubic Ni2+ doped indium oxide nanomaterials
Directory of Open Access Journals (Sweden)
Qingbo Sun
2011-12-01
Full Text Available Transition metal ions doped indium oxide nanomaterials were potentially used as a kind of diluted magnetic semiconductors in transparent spintronic devices. In this paper, the influences of Ni2+ doped contents and rhombohedral or cubic crystalline structures of indium oxide on magnetic properties were investigated. We found that the magnetic properties of Ni2+ doped indium oxide could be transferred from room temperature ferromagnetisms to paramagnetic properties with increments of doped contents. Moreover, the different crystalline structures of indium oxide also greatly affected the room temperature ferromagnetisms due to different lattice constants and almost had no effects on their paramagnetic properties. In addition, both the ferromagnetic and paramagnetic properties were demonstrated to be intrinsic and not caused by impurities.
Ab initio study of cubic complex Bi2CrCuO6 perovskite
International Nuclear Information System (INIS)
Fajardo, F.; Cardona, R.; Landinez Tellez, D.A.; Arbey Rodriguez M, J.; Roa-Rojas, J.
2008-01-01
We report a detailed calculation of the structural and electronic properties for the cubic complex Bi 2 CrCuO 6 perovskite material by density functional theory. The exchange-correlation potential was included through the generalized gradient approximation. From the adjusting of Murnaghan state equation to the energy as a function of volume data, we obtain an ideal lattice parameter of 7.763 A. The density of states study was carried out considering the two spin polarizations. Results reveal that this material behaves as a conductor to the spin-down polarization and evidence a semiconductor tendency to the spin-up configuration. This tendency to the half-metallicity character is corroborated by the integer number of magnetic moment (3.0 μ B ), which is attributed to the Cr-spin-up orbital contribution
Spectral intensities in cubic systems. I. Progressions based upon parity vibrational modes
International Nuclear Information System (INIS)
Acevedo, R.; Vasquez, S.O.; Meruane, T.; Poblete, V.; Pozo, J.
1998-01-01
The well-resolved emission and absorption spectra of centrosymmetric coordination compounds of the transition metal ions have been used widely to provide the experimental data against which to test theoretical models of vibronic intensities. With reference to the 2 E g → 4 A 2g luminescence transition, at a perfect octahedral site in Cs 2 SiF 6 , over than one hundred vibronic lines are observed with line widths of a few wavenumber spread over some 3000 cm -1 . This paper reports a through examination of both the electronic and vibrational factors, which influences the observed vibronic intensities of the various assigned and identified lines in the spectra of the MnF 6 2- complex ion in the Cs 2 SiF 6 cubic lattice. The origin and nature of higher order vibronic interactions are analysed on the basis of a symmetrized vibronic crystal field-ligand polarization model. (Author)
Plasma simulation with the Differential Algebraic Cubic Interpolated Propagation scheme
Energy Technology Data Exchange (ETDEWEB)
Utsumi, Takayuki [Japan Atomic Energy Research Inst., Tokai, Ibaraki (Japan). Tokai Research Establishment
1998-03-01
A computer code based on the Differential Algebraic Cubic Interpolated Propagation scheme has been developed for the numerical solution of the Boltzmann equation for a one-dimensional plasma with immobile ions. The scheme advects the distribution function and its first derivatives in the phase space for one time step by using a numerical integration method for ordinary differential equations, and reconstructs the profile in phase space by using a cubic polynomial within a grid cell. The method gives stable and accurate results, and is efficient. It is successfully applied to a number of equations; the Vlasov equation, the Boltzmann equation with the Fokker-Planck or the Bhatnagar-Gross-Krook (BGK) collision term and the relativistic Vlasov equation. The method can be generalized in a straightforward way to treat cases such as problems with nonperiodic boundary conditions and higher dimensional problems. (author)
Highly Aminated Mesoporous Silica Nanoparticles with Cubic Pore Structure
Suteewong, Teeraporn
2011-01-19
Mesoporous silica with cubic symmetry has attracted interest from researchers for some time. Here, we present the room temperature synthesis of mesoporous silica nanoparticles possessing cubic Pm3n symmetry with very high molar ratios (>50%) of 3-aminopropyl triethoxysilane. The synthesis is robust allowing, for example, co-condensation of organic dyes without loss of structure. By means of pore expander molecules, the pore size can be enlarged from 2.7 to 5 nm, while particle size decreases. Adding pore expander and co-condensing fluorescent dyes in the same synthesis reduces average particle size further down to 100 nm. After PEGylation, such fluorescent aminated mesoporous silica nanoparticles are spontaneously taken up by cells as demonstrated by fluorescence microscopy.
Polarization Change in Face-Centered Cubic Opal Films
Wolff, Christian; Romanov, Sergei; Küchenmeister, Jens; Peschel, Ulf; Busch, Kurt
2011-10-01
Artificial opals are a popular platform for investigating fundamental properties of Photonic Crystals (PhC). In this work, we provide a theoretical analysis of polarization-resolved transmission experiments through thin opal films. Despite the full cubic symmetry of the PhC, this system provides a very efficient mechanism for manipulating the polarization state of light. Based on band structure calculations and Bloch mode analysis, we find that this effect closely resembles classical birefringence. Due to the cubic symmetry, however, a description using tensorial quantities is not possible. This indicates fundamental limitations of effective material models for Photonic Crystals and demonstrates the importance of accurately modelling the microscopic geometry of such systems.
Highly Aminated Mesoporous Silica Nanoparticles with Cubic Pore Structure
Suteewong, Teeraporn; Sai, Hiroaki; Cohen, Roy; Wang, Suntao; Bradbury, Michelle; Baird, Barbara; Gruner, Sol M.; Wiesner, Ulrich
2011-01-01
Mesoporous silica with cubic symmetry has attracted interest from researchers for some time. Here, we present the room temperature synthesis of mesoporous silica nanoparticles possessing cubic Pm3n symmetry with very high molar ratios (>50%) of 3-aminopropyl triethoxysilane. The synthesis is robust allowing, for example, co-condensation of organic dyes without loss of structure. By means of pore expander molecules, the pore size can be enlarged from 2.7 to 5 nm, while particle size decreases. Adding pore expander and co-condensing fluorescent dyes in the same synthesis reduces average particle size further down to 100 nm. After PEGylation, such fluorescent aminated mesoporous silica nanoparticles are spontaneously taken up by cells as demonstrated by fluorescence microscopy.
Trace spaces in a pre-cubical complex
DEFF Research Database (Denmark)
Raussen, Martin
2009-01-01
In directed algebraic topology, directed irreversible (d)-paths and spaces consisting of d-paths are studied from a topological and from a categorical point of view. Motivated by models for concurrent computation, we study in this paper spaces of d-paths in a pre-cubical complex. Such paths...... are equipped with a natural arc length which moreover is shown to be invariant under directed homotopies. D-paths up to reparametrization (called traces) can thus be represented by arc length parametrized d-paths. Under weak additional conditions, it is shown that trace spaces in a pre-cubical complex...... are separable metric spaces which are locally contractible and locally compact. Moreover, they have the homotopy type of a CW-complex....
A local cubic smoothing in an adaptation mode
International Nuclear Information System (INIS)
Dikoussar, N.D.
2001-01-01
A new approach to a local curve approximation and the smoothing is proposed. The relation between curve points is defined using a special cross-ratio weight functions. The coordinates of three curve points are used as parameters for both the weight functions and the tree-point cubic model (TPS). A very simple in computing and stable to random errors cubic smoother in an adaptation mode (LOCUS) is constructed. The free parameter of TPS is estimated independently of the fixed parameters by recursion with the effective error suppression and can be controlled by the cross-ratio parameters. Efficiency and the noise stability of the algorithm are confirmed by examples and by comparison with other known non-parametric smoothers
3D Medical Image Interpolation Based on Parametric Cubic Convolution
Institute of Scientific and Technical Information of China (English)
无
2007-01-01
In the process of display, manipulation and analysis of biomedical image data, they usually need to be converted to data of isotropic discretization through the process of interpolation, while the cubic convolution interpolation is widely used due to its good tradeoff between computational cost and accuracy. In this paper, we present a whole concept for the 3D medical image interpolation based on cubic convolution, and the six methods, with the different sharp control parameter, which are formulated in details. Furthermore, we also give an objective comparison for these methods using data sets with the different slice spacing. Each slice in these data sets is estimated by each interpolation method and compared with the original slice using three measures: mean-squared difference, number of sites of disagreement, and largest difference. According to the experimental results, we present a recommendation for 3D medical images under the different situations in the end.
Perfect 3-colorings of the cubic graphs of order 10
Directory of Open Access Journals (Sweden)
Mehdi Alaeiyan
2017-10-01
Full Text Available Perfect coloring is a generalization of the notion of completely regular codes, given by Delsarte. A perfect m-coloring of a graph G with m colors is a partition of the vertex set of G into m parts A_1, A_2, ..., A_m such that, for all $ i,j \\in \\lbrace 1, ... , m \\rbrace $, every vertex of A_i is adjacent to the same number of vertices, namely, a_{ij} vertices, of A_j. The matrix $A=(a_{ij}_{i,j\\in \\lbrace 1,... ,m\\rbrace }$, is called the parameter matrix. We study the perfect 3-colorings (also known as the equitable partitions into three parts of the cubic graphs of order 10. In particular, we classify all the realizable parameter matrices of perfect 3-colorings for the cubic graphs of order 10.
Global Sufficient Optimality Conditions for a Special Cubic Minimization Problem
Directory of Open Access Journals (Sweden)
Xiaomei Zhang
2012-01-01
Full Text Available We present some sufficient global optimality conditions for a special cubic minimization problem with box constraints or binary constraints by extending the global subdifferential approach proposed by V. Jeyakumar et al. (2006. The present conditions generalize the results developed in the work of V. Jeyakumar et al. where a quadratic minimization problem with box constraints or binary constraints was considered. In addition, a special diagonal matrix is constructed, which is used to provide a convenient method for justifying the proposed sufficient conditions. Then, the reformulation of the sufficient conditions follows. It is worth noting that this reformulation is also applicable to the quadratic minimization problem with box or binary constraints considered in the works of V. Jeyakumar et al. (2006 and Y. Wang et al. (2010. Finally some examples demonstrate that our optimality conditions can effectively be used for identifying global minimizers of the certain nonconvex cubic minimization problem.
Magnetic ground states in nanocuboids of cubic magnetocrystalline anisotropy
Energy Technology Data Exchange (ETDEWEB)
Bonilla, F.J., E-mail: fbonilla@cicenergigune.com; Lacroix, L.-M.; Blon, T., E-mail: thomas.blon@insa-toulouse.fr
2017-04-15
Flower and easy-axis vortex states are well-known magnetic configurations that can be stabilized in small particles. However, <111> vortex (V<111>), i.e. a vortex state with its core axis along the hard-axis direction, has been recently evidenced as a stable configuration in Fe nanocubes of intermediate sizes in the flower/vortex transition. In this context, we present here extensive micromagnetic simulations to determine the different magnetic ground states in ferromagnetic nanocuboids exhibiting cubic magnetocrystalline anisotropy (MCA). Focusing our study in the single-domain/multidomain size range (10–50 nm), we showed that V<111> is only stable in nanocuboids exhibiting peculiar features, such as a specific size, shape and magnetic environment, contrarily to the classical flower and easy-axis vortex states. Thus, to track experimentally these V<111> states, one should focused on (i) nanocuboids exhibiting a nearly perfect cubic shape (size distorsion <12%) made of (ii) a material which combines a zero or positive MCA and a high saturation magnetization, such as Fe or FeCo; and (iii) a low magnetic field environment, V<111> being only observed in virgin or remanent states. - Highlights: • The <111> vortex is numerically determined in nanocubes of cubic anisotropy. • It constitutes an intermediate state in the single-domain limit. • Such a vortex can only be stabilized in perfect or slightly deformed nanocuboids. • It exists in nanocuboids made of materials with zero or positive cubic anisotropy. • The associated magnetization reversal is described by a rotation of the vortex axis.
Synthesis and Optical Properties of Cubic Gold Nanoframes
Au, Leslie; Chen, Yeechi; Zhou, Fei; Camargo, Pedro H. C.; Lim, Byungkwon; Li, Zhi-Yuan; Ginger, David S.; Xia, Younan
2008-01-01
This paper describes a facile method of preparing cubic Au nanoframes with open structures via the galvanic replacement reaction between Ag nanocubes and AuCl2−. A mechanistic study of the reaction revealed that the formation of Au nanoframes relies on the diffusion of both Au and Ag atoms. The effect of the edge length and ridge thickness of the nanoframes on the localized surface plasmon resonance peak was explored by a combination of discrete dipole approximation calculations and single na...
Orientational anharmonicity of interatomic interaction in cubic monocrystals
International Nuclear Information System (INIS)
Belomestnykh, Vladimir N.; Tesleva, Elena P.
2010-01-01
Anharmonicity of interatomic interaction from a position of physical acoustics under the standard conditions is investigated. It is shown that the measure of anharmonicity of interatomic interaction (Grilneisen parameter) is explicitly expressed through velocities of sound. Calculation results of orientation anharmonicity are shown on the example of 116 cubic monocrystals with different lattice structural type and type of chemical bond. Two types of anharmonicity interatomic interaction anisotropy are determined. Keywords: acoustics, orientational anharmonicity, Gruneisen parameter, velocity of sound
Light scattering by cubical particle in the WKB approximation
Directory of Open Access Journals (Sweden)
redouane lamsoudi
2017-11-01
Full Text Available In this work, we determined the analytical expressions of the form factor of a cubical particle in the WKB approximation. We adapted some variables (size parameter, refractive index, the scattering angle and found the form factor in the approximation of Rayleigh-Gans-Debye (RGD, Anomalous Diffraction (AD, and determined the efficiency factor of the extinction. Finally, to illustrate our formalism, we analyzed some numerical examples
Bifurcation of rupture path by linear and cubic damping force
Dennis L. C., C.; Chew X., Y.; Lee Y., C.
2014-06-01
Bifurcation of rupture path is studied for the effect of linear and cubic damping. Momentum equation with Rayleigh factor was transformed into ordinary differential form. Bernoulli differential equation was obtained and solved by the separation of variables. Analytical or exact solutions yielded the bifurcation was visible at imaginary part when the wave was non dispersive. For the dispersive wave, bifurcation of rupture path was invisible.
Dry Powder Precursors of Cubic Liquid Crystalline Nanoparticles (cubosomes)
International Nuclear Information System (INIS)
Spicer, Patrick T.; Small, William B.; Small, William B.; Lynch, Matthew L.; Burns, Janet L.
2002-01-01
Cubosomes are dispersed nanostructured particles of cubic phase liquid crystal that have stimulated significant research interest because of their potential for application in controlled-release and drug delivery. Despite the interest, cubosomes can be difficult to fabricate and stabilize with current methods. Most of the current work is limited to liquid phase processes involving high shear dispersion of bulk cubic liquid crystalline material into sub-micron particles, limiting application flexibility. In this work, two types of dry powder cubosome precursors are produced by spray-drying: (1) starch-encapsulated monoolein is produced by spray-drying a dispersion of cubic liquid crystalline particles in an aqueous starch solution and (2) dextran-encapsulated monoolein is produced by spray-drying an emulsion formed by the ethanol-dextran-monoolein-water system. The encapsulants are used to decrease powder cohesion during drying and to act as a soluble colloidal stabilizer upon hydration of the powders. Both powders are shown to form (on average) 0.6 μm colloidally-stable cubosomes upon addition to water. However, the starch powders have a broader particle size distribution than the dextran powders because of the relative ease of spraying emulsions versus dispersions. The developed processes enable the production of nanostructured cubosomes by end-users rather than just specialized researchers and allow tailoring of the surface state of the cubosomes for broader application
International Nuclear Information System (INIS)
Navarro C, H.; Perez C, M.; Rodriguez, A. G.; Lopez L, E.; Vidal, M. A.
2012-01-01
Cubic In N samples were grown on Mg O (001) substrates by gas source molecular beam epitaxy. In general, we find that In N directly deposited onto the Mg O substrate results in polycrystalline or columnar films of hexagonal symmetry. We find that adequate conditions to grow the cubic phase of this compound require the growth of an initial cubic Ga N buffer interlayer (β-t Ga N) on the Mg O surface. Subsequently, the growth conditions were optimized to obtain good photoluminescence (Pl) emission. The resultant In N growth is mostly cubic, with very small hexagonal inclusions, as confirmed by X-ray diffraction and scanning electron microscopy studies. Good crystalline quality requires that the samples to be grown under rich Indium metal flux. The cubic β-t In N/Ga N/Mg O samples exhibit a high signal to noise ratio for Pl at low temperatures (20 K). The Pl is centered at O.75 eV and persist at room temperature. (Author)
Ultralight metallic microlattices.
Schaedler, T A; Jacobsen, A J; Torrents, A; Sorensen, A E; Lian, J; Greer, J R; Valdevit, L; Carter, W B
2011-11-18
Ultralight (nickel plating, and subsequently etching away the template. The resulting metallic microlattices exhibit densities ρ ≥ 0.9 milligram per cubic centimeter, complete recovery after compression exceeding 50% strain, and energy absorption similar to elastomers. Young's modulus E scales with density as E ~ ρ(2), in contrast to the E ~ ρ(3) scaling observed for ultralight aerogels and carbon nanotube foams with stochastic architecture. We attribute these properties to structural hierarchy at the nanometer, micrometer, and millimeter scales.
Bond-order potential for magnetic body-centered-cubic iron and its transferability
Lin, Yi-Shen; Mrovec, M.; Vitek, V.
2016-06-01
We derived and thoroughly tested a bond-order potential (BOP) for body-centered-cubic (bcc) magnetic iron that can be employed in atomistic calculations of a broad variety of crystal defects that control structural, mechanical, and thermodynamic properties of this technologically important metal. The constructed BOP reflects correctly the mixed nearly free electron and covalent bonding arising from the partially filled d band as well as the ferromagnetism that is actually responsible for the stability of the bcc structure of iron at low temperatures. The covalent part of the cohesive energy is determined within the tight-binding bond model with the Green's function of the Schrödinger equation determined using the method of continued fractions terminated at a sufficient level of the moments of the density of states. This makes the BOP an O (N ) method usable for very large numbers of particles. Only d d bonds are included explicitly, but the effect of s electrons on the covalent energy is included via their screening of the corresponding d d bonds. The magnetic part of the cohesive energy is included using the Stoner model of itinerant magnetism. The repulsive part of the cohesive energy is represented, as in any tight-binding scheme, by an empirical formula. Its functional form is physically justified by studies of the repulsion in face-centered-cubic (fcc) solid argon under very high pressure where the repulsion originates from overlapping s and p closed-shell electrons just as it does from closed-shell s electrons in transition metals squeezed into the ion core under the influence of the large covalent d bonding. Testing of the transferability of the developed BOP to environments significantly different from those of the ideal bcc lattice was carried out by studying crystal structures and magnetic states alternative to the ferromagnetic bcc lattice, vacancies, divacancies, self-interstitial atoms (SIAs), paths continuously transforming the bcc structure to
X-Ray Elastic Constants for Cubic Materials
Energy Technology Data Exchange (ETDEWEB)
Malen, K
1974-10-15
The stress-strain relation to be used in X-ray stress measurements in anisotropic texture-free media is studied. The method for evaluation of appropriate elastic constants for a cubic medium is described. Some illustrative numerical examples have been worked out including line broadening due to elastic anisotropy. The elastic stress and strain compatibility at grain boundaries is taken into account using Kroner's method. These elastic constants obviously only apply when no internal stresses due to plastic deformation are present. The case of reorientation of free interstitials in the stress field can be taken into account
Inhomogeneous atomic Bose-Fermi mixtures in cubic lattices
International Nuclear Information System (INIS)
Cramer, M.; Eisert, J.; Illuminati, F.
2004-01-01
We determine the ground state properties of inhomogeneous mixtures of bosons and fermions in cubic lattices and parabolic confining potentials. For finite hopping we determine the domain boundaries between Mott-insulator plateaux and hopping-dominated regions for lattices of arbitrary dimension within mean-field and perturbation theory. The results are compared with a new numerical method that is based on a Gutzwiller variational approach for the bosons and an exact treatment for the fermions. The findings can be applied as a guideline for future experiments with trapped atomic Bose-Fermi mixtures in optical lattices
Inhomogeneous atomic Bose-Fermi mixtures in cubic lattices.
Cramer, M; Eisert, J; Illuminati, F
2004-11-05
We determine the ground state properties of inhomogeneous mixtures of bosons and fermions in cubic lattices and parabolic confining potentials. For finite hopping we determine the domain boundaries between Mott-insulator plateaux and hopping-dominated regions for lattices of arbitrary dimension within mean-field and perturbation theory. The results are compared with a new numerical method that is based on a Gutzwiller variational approach for the bosons and an exact treatment for the fermions. The findings can be applied as a guideline for future experiments with trapped atomic Bose-Fermi mixtures in optical lattices.
Universal centers in the cubic trigonometric Abel equation
Directory of Open Access Journals (Sweden)
Jaume Giné
2014-02-01
Full Text Available We study the center problem for the trigonometric Abel equation $d \\rho/ d \\theta= a_1 (\\theta \\rho^2 + a_2(\\theta \\rho^3,$ where $a_1(\\theta$ and $a_2(\\theta$ are cubic trigonometric polynomials in $\\theta$. This problem is closely connected with the classical Poincaré center problem for planar polynomial vector fields. A particular class of centers, the so-called universal centers or composition centers, is taken into account. An example of non-universal center and a characterization of all the universal centers for such equation are provided.
X-Ray Elastic Constants for Cubic Materials
Energy Technology Data Exchange (ETDEWEB)
Malen, K.
1974-10-15
The stress-strain relation to be used in X-ray stress measurements in anisotropic texture-free media is studied. The method for evaluation of appropriate elastic constants for a cubic medium is described. Some illustrative numerical examples have been worked out including line broadening due to elastic anisotropy. The elastic stress and strain compatibility at grain boundaries is taken into account using Kroner's method. These elastic constants obviously only apply when no internal stresses due to plastic deformation are present. The case of reorientation of free interstitials in the stress field can be taken into account
X-Ray Elastic Constants for Cubic Materials
International Nuclear Information System (INIS)
Malen, K.
1974-10-01
The stress-strain relation to be used in X-ray stress measurements in anisotropic texture-free media is studied. The method for evaluation of appropriate elastic constants for a cubic medium is described. Some illustrative numerical examples have been worked out including line broadening due to elastic anisotropy. The elastic stress and strain compatibility at grain boundaries is taken into account using Kroner's method. These elastic constants obviously only apply when no internal stresses due to plastic deformation are present. The case of reorientation of free interstitials in the stress field can be taken into account
Trapping of cubic ZnO nanocrystallites at ambient conditions
DEFF Research Database (Denmark)
Decremps, F.; Pellicer-Porres, J.; Datchi, F.
2002-01-01
Dense powder of nanocrystalline ZnO has been recovered at ambient conditions in the metastable cubic structure after a heat treatment at high pressure (15 GPa and 550 K). Combined x-ray diffraction (XRD) and x-ray absorption spectroscopy (XAS) experiments have been performed to probe both long......-range order and local crystallographic structure of the recovered sample. Within uncertainty of these techniques (about 5%), all the crystallites are found to adopt the NaCl structure. From the analysis of XRD and XAS spectra, the cell volume per chemical formula unit is found to be 19.57(1) and 19...
Synthesis and Optical Properties of Cubic Gold Nanoframes.
Au, Leslie; Chen, Yeechi; Zhou, Fei; Camargo, Pedro H C; Lim, Byungkwon; Li, Zhi-Yuan; Ginger, David S; Xia, Younan
2008-12-01
This paper describes a facile method of preparing cubic Au nanoframes with open structures via the galvanic replacement reaction between Ag nanocubes and AuCl(2) (-). A mechanistic study of the reaction revealed that the formation of Au nanoframes relies on the diffusion of both Au and Ag atoms. The effect of the edge length and ridge thickness of the nanoframes on the localized surface plasmon resonance peak was explored by a combination of discrete dipole approximation calculations and single nanoparticle spectroscopy. With their hollow and open structures, the Au nanoframes represent a novel class of substrates for applications including surface plasmonics and surface-enhanced Raman scattering.
Topological Characterization of Carbon Graphite and Crystal Cubic Carbon Structures.
Siddiqui, Wei Gao Muhammad Kamran; Naeem, Muhammad; Rehman, Najma Abdul
2017-09-07
Graph theory is used for modeling, designing, analysis and understanding chemical structures or chemical networks and their properties. The molecular graph is a graph consisting of atoms called vertices and the chemical bond between atoms called edges. In this article, we study the chemical graphs of carbon graphite and crystal structure of cubic carbon. Moreover, we compute and give closed formulas of degree based additive topological indices, namely hyper-Zagreb index, first multiple and second multiple Zagreb indices, and first and second Zagreb polynomials.
The cyclicity of a cubic system with nonradical Bautin ideal
Levandovskyy, Viktor; Romanovski, Valery G.; Shafer, Douglas S.
We present a method for investigating the cyclicity of an elementary focus or center of a polynomial system of differential equations by means of complexification of the system and application of algorithms of computational algebra, showing an approach to treating the case that the Bautin ideal B of focus quantities is not a radical ideal (more precisely, when the ideal B is not radical, where B is the ideal generated by the shortest initial string of focus quantities that, like the Bautin ideal, determines the center variety). We illustrate the method with a family of cubic systems.
Multi-dimensional cubic interpolation for ICF hydrodynamics simulation
International Nuclear Information System (INIS)
Aoki, Takayuki; Yabe, Takashi.
1991-04-01
A new interpolation method is proposed to solve the multi-dimensional hyperbolic equations which appear in describing the hydrodynamics of inertial confinement fusion (ICF) implosion. The advection phase of the cubic-interpolated pseudo-particle (CIP) is greatly improved, by assuming the continuities of the second and the third spatial derivatives in addition to the physical value and the first derivative. These derivatives are derived from the given physical equation. In order to evaluate the new method, Zalesak's example is tested, and we obtain successfully good results. (author)
Method of forming an abrasive compact of cubic boron nitride
International Nuclear Information System (INIS)
Bell, F.R.
1976-01-01
This patent concerns an abrasive compact comprising diamond or cubic boron nitride or mixtures thereof held in a matrix of a refractory substance and a substance which dissolves the abrasive particle to at least a limited extent. The compact may be made by subjecting a powdered mixture of the ingredients to conditions of temperature and pressure at which the abrasive particle is crystallographically stable and the solvent substance acts to dissolve the abrasive particle. The refractory substance and solvent substance are preferably so chosen that during compact manufacture there is interaction resulting in the formation of a hard material
Cubic Plus Association Equation of State for Flow Assurance Projects
DEFF Research Database (Denmark)
dos Santos, Leticia Cotia; Abunahman, Samir Silva; Tavares, Frederico Wanderley
2015-01-01
Thermodynamic hydrate inhibitors such as methanol, ethanol, (mono) ethylene glycol (MEG), and triethylene glycol (TEG) are widely used in the oil and gas industry. On modeling these compounds, we show here how the CPA equation of state was implemented in an in-house process simulator as an in......-built model: To validate the implementation, we show calulations for binary systems containing hydrate inhibitors and water or hydrocarbons using the Cubic Plus Association (CPA) and Soave-Redlich-Kwong (SRK) equation of states, also comparing against experimental data. For streams containing natural gas...
Rotary Ultrasonic Machining of Poly-Crystalline Cubic Boron Nitride
Directory of Open Access Journals (Sweden)
Kuruc Marcel
2014-12-01
Full Text Available Poly-crystalline cubic boron nitride (PCBN is one of the hardest material. Generally, so hard materials could not be machined by conventional machining methods. Therefore, for this purpose, advanced machining methods have been designed. Rotary ultrasonic machining (RUM is included among them. RUM is based on abrasive removing mechanism of ultrasonic vibrating diamond particles, which are bonded on active part of rotating tool. It is suitable especially for machining hard and brittle materials (such as glass and ceramics. This contribution investigates this advanced machining method during machining of PCBN.
Soliton interaction in quadratic and cubic bulk media
DEFF Research Database (Denmark)
Johansen, Steffen Kjær; Bang, Ole
2000-01-01
Summary form only given. The understanding of how and to what extend the cubic nonlinearity affects beam propagation and spatial soliton formation in quadratic media is of vital importance in fundamental and applied nonlinear physics. We consider beam propagation under type-I SHG conditions...... in lossless bulk second order nonlinear optical materials with a nonvanishing third order nonlinearity. It is known that in pure second order systems a single soliton can never collapse whereas in systems with both nonlinearities and that stable single soliton propagation can only in some circumstances...
Bistable Helmholtz solitons in cubic-quintic materials
International Nuclear Information System (INIS)
Christian, J. M.; McDonald, G. S.; Chamorro-Posada, P.
2007-01-01
We propose a nonlinear Helmholtz equation for modeling the evolution of broad optical beams in media with a cubic-quintic intensity-dependent refractive index. This type of nonlinearity is appropriate for some semiconductor materials, glasses, and polymers. Exact analytical soliton solutions are presented that describe self-trapped nonparaxial beams propagating at any angle with respect to the reference direction. These spatially symmetric solutions are, to the best of our knowledge, the first bistable Helmholtz solitons to be derived. Accompanying conservation laws (both integral and particular forms) are also reported. Numerical simulations investigate the stability of the solitons, which appear to be remarkably robust against perturbations
Compressibility and thermal expansion of cubic silicon nitride
DEFF Research Database (Denmark)
Jiang, Jianzhong; Lindelov, H.; Gerward, Leif
2002-01-01
The compressibility and thermal expansion of the cubic silicon nitride (c-Si3N4) phase have been investigated by performing in situ x-ray powder-diffraction measurements using synchrotron radiation, complemented with computer simulations by means of first-principles calculations. The bulk...... compressibility of the c-Si3N4 phase originates from the average of both Si-N tetrahedral and octahedral compressibilities where the octahedral polyhedra are less compressible than the tetrahedral ones. The origin of the unit cell expansion is revealed to be due to the increase of the octahedral Si-N and N-N bond...
Work function of elemental metals and its face dependence ...
African Journals Online (AJOL)
The calculated work functions for the flat surface of the metals were in perfect agreement with experimental values for metals in the low-density limit and the agreement with experimental values decreased towards the high-density limit. The calculated work functions for the body centred cubic metals were in good agreement ...
Carbon-supported cubic CoSe2 catalysts for oxygen reduction reaction in alkaline medium
International Nuclear Information System (INIS)
Feng Yongjun; Alonso-Vante, Nicolas
2012-01-01
Highlights: ► Cubic CoSe 2 a non-precious metal electrocatalyst for oxygen reduction in KOH. ► The catalyst shows four-electron transfer pathway in overall reaction. ► Catalyst has higher methanol tolerance than commercial Pt/C catalyst. - Abstract: A Carbon-supported CoSe 2 nanocatalyst has been developed as an alternative non-precious metal electrocatalyst for oxygen reduction reaction (ORR) in alkaline medium. The catalyst was prepared via a surfactant-free route and its electrocatalytic activity for the ORR has been investigated in detail in 0.1 M KOH electrolyte at 25 °C using rotating disk electrode (RDE) and rotating ring-disk electrode (RRDE) techniques. The prepared catalyst showed promising catalytic activity towards ORR in a four-electron transfer pathway and higher tolerance to methanol compared to commercial Pt/C catalyst in 0.1 M KOH. To some extent, the increase of CoSe 2 loading on the electrode favors a faster reduction of H 2 O 2 intermediate to H 2 O.
Hypersonic vibrations of Ag@SiO2 (cubic core)-shell nanospheres.
Sun, Jing Ya; Wang, Zhi Kui; Lim, Hock Siah; Ng, Ser Choon; Kuok, Meng Hau; Tran, Toan Trong; Lu, Xianmao
2010-12-28
The intriguing optical and catalytic properties of metal-silica core-shell nanoparticles, inherited from their plasmonic metallic cores together with the rich surface chemistry and increased stability offered by their silica shells, have enabled a wide variety of applications. In this work, we investigate the confined vibrational modes of a series of monodisperse Ag@SiO(2) (cubic core)-shell nanospheres synthesized using a modified Stöber sol-gel method. The particle-size dependence of their mode frequencies has been mapped by Brillouin light scattering, a powerful tool for probing hypersonic vibrations. Unlike the larger particles, the observed spheroidal-like mode frequencies of the smaller ones do not scale with inverse diameter. Interestingly, the onset of the deviation from this linearity occurs at a smaller particle size for higher-energy modes than for lower-energy ones. Finite element simulations show that the mode displacement profiles of the Ag@SiO(2) core-shells closely resemble those of a homogeneous SiO(2) sphere. Simulations have also been performed to ascertain the effects that the core shape and the relative hardness of the core and shell materials have on the vibrations of the core-shell as a whole. As the vibrational modes of a particle have a bearing on its thermal and mechanical properties, the findings would be of value in designing core-shell nanostructures with customized thermal and mechanical characteristics.
Plastic deformation of cubic zirconia single crystals at 1400 C
International Nuclear Information System (INIS)
Baufeld, B.; Baither, D.; Bartsch, M.; Messerschmidt, U.
1998-01-01
Cubic zirconia single crystals stabilized with 11 mol% yttria were deformed in air at 1400 C and around 1200 C at different strain rates along [1 anti 12] and [100] compression directions. The strain rate sensitivity of the flow stress was determined by strain rate cycling and stress relaxation tests. The microstructure of the deformed specimens was investigated by transmission high-voltage electron microscopy, including contrast extinction analysis for determining the Burgers vectors as well as stereo pairs and wide-angle tilting experiments to find the active slip planes. At deformation along [1 anti 12], the primary and secondary slip planes are of {100} type. Previous experiments had shown that the dislocations move easily on these planes in an athermal way. During deformation along [100], mainly dislocations on {100} planes are activated, which move in a viscous way by the aid of thermal activation. The discussion of the different deformation behaviours during deformation along [1 anti 12] and [100] is based on the different dynamic properties of dislocations and the fact that recovery is an essential feature of the deformation of cubic zirconia at 1400 C. The results on the shape of the deformation curve and the strain rate sensitivity of the flow stress are partly at variance with those of previous authors. (orig.)
Efficient LBM visual simulation on face-centered cubic lattices.
Petkov, Kaloian; Qiu, Feng; Fan, Zhe; Kaufman, Arie E; Mueller, Klaus
2009-01-01
The Lattice Boltzmann method (LBM) for visual simulation of fluid flow generally employs cubic Cartesian (CC) lattices such as the D3Q13 and D3Q19 lattices for the particle transport. However, the CC lattices lead to suboptimal representation of the simulation space. We introduce the face-centered cubic (FCC) lattice, fD3Q13, for LBM simulations. Compared to the CC lattices, the fD3Q13 lattice creates a more isotropic sampling of the simulation domain and its single lattice speed (i.e., link length) simplifies the computations and data storage. Furthermore, the fD3Q13 lattice can be decomposed into two independent interleaved lattices, one of which can be discarded, which doubles the simulation speed. The resulting LBM simulation can be efficiently mapped to the GPU, further increasing the computational performance. We show the numerical advantages of the FCC lattice on channeled flow in 2D and the flow-past-a-sphere benchmark in 3D. In both cases, the comparison is against the corresponding CC lattices using the analytical solutions for the systems as well as velocity field visualizations. We also demonstrate the performance advantages of the fD3Q13 lattice for interactive simulation and rendering of hot smoke in an urban environment using thermal LBM.
Defect ordering in aliovalently doped cubic zirconia from first principles
International Nuclear Information System (INIS)
Bogicevic, A.; Wolverton, C.; Crosbie, G.M.; Stechel, E.B.
2001-01-01
Defect ordering in aliovalently doped cubic-stabilized zirconia is studied using gradient corrected density-functional calculations. Intra- and intersublattice ordering interactions are investigated for both cation (Zr and dopant ions) and anion (oxygen ions and vacancies) species. For yttria-stabilized zirconia, the crystal structure of the experimentally identified, ordered compound δ-Zr 3 Y 4 O 12 is established, and we predict metastable zirconia-rich ordered phases. Anion vacancies repel each other at short separations, but show an energetic tendency to align as third-nearest neighbors along directions. Calculations with divalent (Be, Mg, Ca, Sr, Ba) and trivalent (Y, Sc, B, Al, Ga, In) oxides show that anion vacancies prefer to be close to the smaller of the cations (Zr or dopant ion). When the dopant cation is close in size to Zr, the vacancies show no particular preference, and are thus less prone to be bound preferentially to any particular cation type when the vacancies traverse such oxides. This ordering tendency offers insight into the observed high conductivity of Y 2 O 3 - and Sc 2 O 3 -stabilized zirconia, as well as recent results using, e.g., lanthanide oxides. The calculations point to In 2 O 3 as a particularly promising stabilizer for high ionic conductivity. Thus we are able to directly link (thermodynamic) defect ordering to (kinetic) ionic conductivity in cubic-stabilized zirconia using first-principles atomistic calculations
Polyamorphism in metalic glass.
Energy Technology Data Exchange (ETDEWEB)
Sheng, H. W.; Liu, H. Z.; Cheng, Y. Q.; Wen, J.; Lee, P.L.; Luo, W.K.; Shastri, S.D.; Ma, E.; X-Ray Science Division; Johns Hopkins Univ.; Chinese Academy of Sciences
2007-03-01
A metal, or an alloy, can often exist in more than one crystal structure. The face-centered-cubic and body-centered-cubic forms of iron (or steel) are a familiar example of such polymorphism. When metallic materials are made in the amorphous form, is a parallel 'polyamorphism' possible? So far, polyamorphic phase transitions in the glassy state have been observed only in glasses involving directional and open (such as tetrahedral) coordination environments. Here, we report an in situ X-ray diffraction observation of a pressure-induced transition between two distinct amorphous polymorphs in a Ce{sub 55}Al{sub 45} metallic glass. The large density difference observed between the two polyamorphs is attributed to their different electronic and atomic structures, in particular the bond shortening revealed by ab initio modeling of the effects of f-electron delocalization. This discovery offers a new perspective of the amorphous state of metals, and has implications for understanding the structure, evolution and properties of metallic glasses and related liquids. Our work also opens a new avenue towards technologically useful amorphous alloys that are compositionally identical but with different thermodynamic, functional and rheological properties due to different bonding and structural characteristics.
Energy Technology Data Exchange (ETDEWEB)
Moreno, M [Departamento de Ciencias de la Tierra y Fisica de la Materia Condensada, Universidad de Cantabria, 39005 Santander (Spain); Barriuso, M T [Departamento de Fisica Moderna, Universidad de Cantabria, 39005 Santander (Spain); Aramburu, J A [Departamento de Ciencias de la Tierra y Fisica de la Materia Condensada, Universidad de Cantabria, 39005 Santander (Spain); GarcIa-Fernandez, P [Departamento de Ciencias de la Tierra y Fisica de la Materia Condensada, Universidad de Cantabria, 39005 Santander (Spain); GarcIa-Lastra, J M [Departamento de Fisica Moderna, Universidad de Cantabria, 39005 Santander (Spain)
2006-05-03
This article reviews the microscopic origin of properties due to transition-metal (TM) impurities, M, in insulator materials. Particular attention is paid to the influence of pressure upon impurity properties. Basic concepts such as the electronic localization in an MX{sub N} complex, the electrostatic potential, V{sub R}, arising from the rest of the lattice ions or the elastic coupling of the complex to the host lattice are initially exposed. The dependence of optical and magnetic parameters on the impurity-ligand distance, R, in cubic lattices is discussed in a first step. Emphasis is put on the actual origin of the R dependence of 10Dq. Examples revealing that laws for strict cubic symmetry cannot in general be transferred to lower symmetries are later given. This relevant fact is shown to come from allowed hybridizations like nd-(n+1)s as well as the influence of V{sub R}. As a salient feature the different colour in ruby and emerald is stressed to arise from distinct V{sub R} potentials in Al{sub 2}O{sub 3} and Be{sub 3}Si{sub 6}Al{sub 2}O{sub 18}. The last part of this review deals with electronic instabilities. The phenomena associated with the Jahn-Teller (JT) effect in cubic lattices, the origin of the energy barrier among equivalent minima and the existence of coherent tunnelling in systems like MgO:Cu{sup 2+} are discussed. An increase of elastic coupling is pointed out to favour a transition from an elongated to a compressed equilibrium conformation. Interestingly the equilibrium geometry of JT ions in non-cubic lattices is shown to be controlled by mechanisms different to those in cubic systems, V{sub R} playing again a key role. The relevance of first principles calculations for clarifying the subtle mechanisms behind off-centre instabilities is also pointed out. Examples concern monovalent and divalent TM impurities in lattices with the CaF{sub 2} structure. The instability due to the transition from the ground to an excited state is finally
International Nuclear Information System (INIS)
Moreno, M; Barriuso, M T; Aramburu, J A; GarcIa-Fernandez, P; GarcIa-Lastra, J M
2006-01-01
This article reviews the microscopic origin of properties due to transition-metal (TM) impurities, M, in insulator materials. Particular attention is paid to the influence of pressure upon impurity properties. Basic concepts such as the electronic localization in an MX N complex, the electrostatic potential, V R , arising from the rest of the lattice ions or the elastic coupling of the complex to the host lattice are initially exposed. The dependence of optical and magnetic parameters on the impurity-ligand distance, R, in cubic lattices is discussed in a first step. Emphasis is put on the actual origin of the R dependence of 10Dq. Examples revealing that laws for strict cubic symmetry cannot in general be transferred to lower symmetries are later given. This relevant fact is shown to come from allowed hybridizations like nd-(n+1)s as well as the influence of V R . As a salient feature the different colour in ruby and emerald is stressed to arise from distinct V R potentials in Al 2 O 3 and Be 3 Si 6 Al 2 O 18 . The last part of this review deals with electronic instabilities. The phenomena associated with the Jahn-Teller (JT) effect in cubic lattices, the origin of the energy barrier among equivalent minima and the existence of coherent tunnelling in systems like MgO:Cu 2+ are discussed. An increase of elastic coupling is pointed out to favour a transition from an elongated to a compressed equilibrium conformation. Interestingly the equilibrium geometry of JT ions in non-cubic lattices is shown to be controlled by mechanisms different to those in cubic systems, V R playing again a key role. The relevance of first principles calculations for clarifying the subtle mechanisms behind off-centre instabilities is also pointed out. Examples concern monovalent and divalent TM impurities in lattices with the CaF 2 structure. The instability due to the transition from the ground to an excited state is finally considered. For complexes with significant elastic coupling
Moreno, M; Barriuso, M T; Aramburu, J A; García-Fernández, P; García-Lastra, J M
2006-05-03
This article reviews the microscopic origin of properties due to transition-metal (TM) impurities, M, in insulator materials. Particular attention is paid to the influence of pressure upon impurity properties. Basic concepts such as the electronic localization in an MX(N) complex, the electrostatic potential, V(R), arising from the rest of the lattice ions or the elastic coupling of the complex to the host lattice are initially exposed. The dependence of optical and magnetic parameters on the impurity-ligand distance, R, in cubic lattices is discussed in a first step. Emphasis is put on the actual origin of the R dependence of 10Dq. Examples revealing that laws for strict cubic symmetry cannot in general be transferred to lower symmetries are later given. This relevant fact is shown to come from allowed hybridizations like nd-(n+1)s as well as the influence of V(R). As a salient feature the different colour in ruby and emerald is stressed to arise from distinct V(R) potentials in Al(2)O(3) and Be(3)Si(6)Al(2)O(18). The last part of this review deals with electronic instabilities. The phenomena associated with the Jahn-Teller (JT) effect in cubic lattices, the origin of the energy barrier among equivalent minima and the existence of coherent tunnelling in systems like MgO:Cu(2+) are discussed. An increase of elastic coupling is pointed out to favour a transition from an elongated to a compressed equilibrium conformation. Interestingly the equilibrium geometry of JT ions in non-cubic lattices is shown to be controlled by mechanisms different to those in cubic systems, V(R) playing again a key role. The relevance of first principles calculations for clarifying the subtle mechanisms behind off-centre instabilities is also pointed out. Examples concern monovalent and divalent TM impurities in lattices with the CaF(2) structure. The instability due to the transition from the ground to an excited state is finally considered. For complexes with significant elastic coupling
Hairy black holes in cubic quasi-topological gravity
Energy Technology Data Exchange (ETDEWEB)
Dykaar, Hannah [Department of Physics and Astronomy, University of Waterloo,200 University Avenue West, Waterloo, ON, N2L 3G1 (Canada); Department of Physics, McGill University,3600 rue University, Montreal, QC, H3A 2T8 (Canada); Hennigar, Robie A.; Mann, Robert B. [Department of Physics and Astronomy, University of Waterloo,200 University Avenue West, Waterloo, ON, N2L 3G1 (Canada)
2017-05-09
We construct a class of five dimensional black hole solutions to cubic quasi-topological gravity with conformal scalar hair and study their thermodynamics. We find these black holes provide the second example of black hole λ-lines: a line of second order (continuous) phase transitions, akin to the fluid/superfluid transition of {sup 4}He. Examples of isolated critical points are found for spherical black holes, marking the first in the literature to date. We also find various novel and interesting phase structures, including an isolated critical point occurring in conjunction with a double reentrant phase transition. The AdS vacua of the theory are studied, finding ghost-free configurations where the scalar field takes on a non-zero constant value, in notable contrast to the five dimensional Lovelock case.
Bifurcation diagram of a cubic three-parameter autonomous system
Directory of Open Access Journals (Sweden)
Lenka Barakova
2005-07-01
Full Text Available In this paper, we study the cubic three-parameter autonomous planar system $$displaylines{ dot x_1 = k_1 + k_2x_1 - x_1^3 - x_2,cr dot x_2 = k_3 x_1 - x_2, }$$ where $k_2, k_3$ are greater than 0. Our goal is to obtain a bifurcation diagram; i.e., to divide the parameter space into regions within which the system has topologically equivalent phase portraits and to describe how these portraits are transformed at the bifurcation boundaries. Results may be applied to the macroeconomical model IS-LM with Kaldor's assumptions. In this model existence of a stable limit cycles has already been studied (Andronov-Hopf bifurcation. We present the whole bifurcation diagram and among others, we prove existence of more difficult bifurcations and existence of unstable cycles.
Supersymmetry breaking and Nambu-Goldstone fermions with cubic dispersion
Sannomiya, Noriaki; Katsura, Hosho; Nakayama, Yu
2017-03-01
We introduce a lattice fermion model in one spatial dimension with supersymmetry (SUSY) but without particle number conservation. The Hamiltonian is defined as the anticommutator of two nilpotent supercharges Q and Q†. Each supercharge is built solely from spinless fermion operators and depends on a parameter g . The system is strongly interacting for small g , and in the extreme limit g =0 , the number of zero-energy ground states grows exponentially with the system size. By contrast, in the large-g limit, the system is noninteracting and SUSY is broken spontaneously. We study the model for modest values of g and show that under certain conditions spontaneous SUSY breaking occurs in both finite and infinite chains. We analyze the low-energy excitations both analytically and numerically. Our analysis suggests that the Nambu-Goldstone fermions accompanying the spontaneous SUSY breaking have cubic dispersion at low energies.
Lipidic cubic phase serial millisecond crystallography using synchrotron radiation
Directory of Open Access Journals (Sweden)
Przemyslaw Nogly
2015-03-01
Full Text Available Lipidic cubic phases (LCPs have emerged as successful matrixes for the crystallization of membrane proteins. Moreover, the viscous LCP also provides a highly effective delivery medium for serial femtosecond crystallography (SFX at X-ray free-electron lasers (XFELs. Here, the adaptation of this technology to perform serial millisecond crystallography (SMX at more widely available synchrotron microfocus beamlines is described. Compared with conventional microcrystallography, LCP-SMX eliminates the need for difficult handling of individual crystals and allows for data collection at room temperature. The technology is demonstrated by solving a structure of the light-driven proton-pump bacteriorhodopsin (bR at a resolution of 2.4 Å. The room-temperature structure of bR is very similar to previous cryogenic structures but shows small yet distinct differences in the retinal ligand and proton-transfer pathway.
A cubic autocatalytic reaction in a continuous stirred tank reactor
Energy Technology Data Exchange (ETDEWEB)
Yakubu, Aisha Aliyu; Yatim, Yazariah Mohd [School of Mathematical Sciences, Universiti Sains Malaysia, 11800 USM, Penang Malaysia (Malaysia)
2015-10-22
In the present study, the dynamics of the cubic autocatalytic reaction model in a continuous stirred tank reactor with linear autocatalyst decay is studied. This model describes the behavior of two chemicals (reactant and autocatalyst) flowing into the tank reactor. The behavior of the model is studied analytically and numerically. The steady state solutions are obtained for two cases, i.e. with the presence of an autocatalyst and its absence in the inflow. In the case with an autocatalyst, the model has a stable steady state. While in the case without an autocatalyst, the model exhibits three steady states, where one of the steady state is stable, the second is a saddle point while the last is spiral node. The last steady state losses stability through Hopf bifurcation and the location is determined. The physical interpretations of the results are also presented.
The electric field of a uniformly charged cubic shell
McCreery, Kaitlin; Greenside, Henry
2018-01-01
As an integrative and insightful example for undergraduates learning about electrostatics, we discuss how to use symmetry, Coulomb's law, superposition, Gauss's law, and visualization to understand the electric field E (x ,y ,z ) produced by a uniformly charged cubic shell. We first discuss how to deduce qualitatively, using freshman-level physics, the perhaps surprising fact that the interior electric field is nonzero and has a complex structure, pointing inwards from the middle of each face of the shell and pointing outwards towards each edge and corner. We then discuss how to understand the quantitative features of the electric field by plotting an analytical expression for E along symmetry lines and on symmetry surfaces of the shell.
Quantum-Carnot engine for particle confined to cubic potential
Energy Technology Data Exchange (ETDEWEB)
Sutantyo, Trengginas Eka P., E-mail: trengginas.eka@gmail.com; Belfaqih, Idrus H., E-mail: idrushusin21@gmail.com; Prayitno, T. B., E-mail: teguh-budi@unj.ac.id [Department of Physics, State University of Jakarta, Jl. Pemuda No.10, Rawamangun, Jakarta Timur 13220 (Indonesia)
2015-09-30
Carnot cycle consists of isothermal and adiabatic processes which are reversible. Using analogy in quantum mechanics, these processes can be well explained by replacing variables in classical process with a quantum system. Quantum system which is shown in this paper is a particle that moves under the influence of a cubic potential which is restricted only to the state of the two energy levels. At the end, the efficiency of the system is shown as a function of the width ratio between the initial conditions and the farthest wall while expanding. Furthermore, the system efficiency will be considered 1D and 2D cases. The providing efficiencies are different due to the influence of the degeneration of energy and the degrees of freedom of the system.
Quantum-Carnot engine for particle confined to cubic potential
International Nuclear Information System (INIS)
Sutantyo, Trengginas Eka P.; Belfaqih, Idrus H.; Prayitno, T. B.
2015-01-01
Carnot cycle consists of isothermal and adiabatic processes which are reversible. Using analogy in quantum mechanics, these processes can be well explained by replacing variables in classical process with a quantum system. Quantum system which is shown in this paper is a particle that moves under the influence of a cubic potential which is restricted only to the state of the two energy levels. At the end, the efficiency of the system is shown as a function of the width ratio between the initial conditions and the farthest wall while expanding. Furthermore, the system efficiency will be considered 1D and 2D cases. The providing efficiencies are different due to the influence of the degeneration of energy and the degrees of freedom of the system
Quantum corrections for the cubic Galileon in the covariant language
Energy Technology Data Exchange (ETDEWEB)
Saltas, Ippocratis D. [Institute of Astrophysics and Space Sciences, Faculty of Sciences, Campo Grande, PT1749-016 Lisboa (Portugal); Vitagliano, Vincenzo, E-mail: isaltas@fc.ul.pt, E-mail: vincenzo.vitagliano@ist.utl.pt [Multidisciplinary Center for Astrophysics and Department of Physics, Instituto Superior Técnico, University of Lisbon, Av. Rovisco Pais 1, 1049-001 Lisboa (Portugal)
2017-05-01
We present for the first time an explicit exposition of quantum corrections within the cubic Galileon theory including the effect of quantum gravity, in a background- and gauge-invariant manner, employing the field-reparametrisation approach of the covariant effective action at 1-loop. We show that the consideration of gravitational effects in combination with the non-linear derivative structure of the theory reveals new interactions at the perturbative level, which manifest themselves as higher-operators in the associated effective action, which' relevance is controlled by appropriate ratios of the cosmological vacuum and the Galileon mass scale. The significance and concept of the covariant approach in this context is discussed, while all calculations are explicitly presented.
Explosive attractor solutions to a universal cubic delay equation
Sanz-Orozco, D.; Berk, H. L.
2017-05-01
New explosive attractor solutions have been found in a universal cubic delay equation that has been studied in both the plasma and the fluid mechanics literature. Through computational simulations and analytic approximations, it is found that the oscillatory component of the explosive mode amplitude solutions are described through multi-frequency Fourier expansions with respect to a pseudo-time variable. The spectral dependence of these solutions as a function of a system parameter, ϕ , is studied. The mode amplitude that is described in the explosive regime has two main features: a well-known envelope ( t 0 - t ) - 5 / 2 , with t0 the blow-up time of the amplitude, and a spectrum of discrete oscillations with ever-increasing frequencies, which may give experimental information about the properties of a system's equilibrium.
THERMODYNAMIC PARAMETERS OF LEAD SULFIDE CRYSTALS IN THE CUBIC PHASE
Directory of Open Access Journals (Sweden)
T. O. Parashchuk
2016-07-01
Full Text Available Geometric and thermodynamic parameters of cubic PbS crystals were obtained using the computer calculations of the thermodynamic parameters within density functional theory method DFT. Cluster models for the calculation based on the analysis of the crystal and electronic structure. Temperature dependence of energy ΔE and enthalpy ΔH, Gibbs free energy ΔG, heat capacity at constant pressure CP and constant volume CV, entropy ΔS were determined on the basis of ab initio calculations of the crystal structure of molecular clusters. Analytical expressions of temperature dependences of thermodynamic parameters which were approximated with quantum-chemical calculation points have been presented. Experimental results compared with theoretically calculated data.
Perbaikan Metode Penghitungan Debit Sungai Menggunakan Cubic Spline Interpolation
Directory of Open Access Journals (Sweden)
Budi I. Setiawan
2007-09-01
Full Text Available Makalah ini menyajikan perbaikan metode pengukuran debit sungai menggunakan fungsi cubic spline interpolation. Fungi ini digunakan untuk menggambarkan profil sungai secara kontinyu yang terbentuk atas hasil pengukuran jarak dan kedalaman sungai. Dengan metoda baru ini, luas dan perimeter sungai lebih mudah, cepat dan tepat dihitung. Demikian pula, fungsi kebalikannnya (inverse function tersedia menggunakan metode. Newton-Raphson sehingga memudahkan dalam perhitungan luas dan perimeter bila tinggi air sungai diketahui. Metode baru ini dapat langsung menghitung debit sungaimenggunakan formula Manning, dan menghasilkan kurva debit (rating curve. Dalam makalah ini dikemukaan satu canton pengukuran debit sungai Rudeng Aceh. Sungai ini mempunyai lebar sekitar 120 m dan kedalaman 7 m, dan pada saat pengukuran mempunyai debit 41 .3 m3/s, serta kurva debitnya mengikuti formula: Q= 0.1649 x H 2.884 , dimana Q debit (m3/s dan H tinggi air dari dasar sungai (m.
Experimental core electron density of cubic boron nitride
DEFF Research Database (Denmark)
Wahlberg, Nanna; Bindzus, Niels; Bjerg, Lasse
as well as experimental result. The redistribution of electron density will, if not accounted for, result in increased thermal parameters. It is estimated that 1.7-2 electrons is transferred from boron to nitrogen. [1]: N. Bindzus, T. Straasø, N. Wahlberg, J. Becker, L. Bjerg, N. Lock, A.-C. Dippel, and B......Experimental core electron density of cubic boron nitride Nanna Wahlberg*, Niels Bindzus*, Lasse Bjerg*, Jacob Becker*, and Bo B. Iversen* *Aarhus University, Department of Chemistry, CMC, Langelandsgade 140, 8000 Århus, Denmark The resent progress in powder diffraction provides data of quality...... obtained. The displacement parameters reported here are significantly lower than those previously reported, stressing the importance of an adequate description of the core density. The charge transfer from boron to nitrogen clearly affects the inner electron density, which is evident from theoretical...
Electron–soliton dynamics in chains with cubic nonlinearity
International Nuclear Information System (INIS)
Sales, M O; Moura, F A B F de
2014-01-01
In our work, we consider the problem of electronic transport mediated by coupling with solitonic elastic waves. We study the electronic transport in a 1D unharmonic lattice with a cubic interaction between nearest neighboring sites. The electron-lattice interaction was considered as a linear function of the distance between neighboring atoms in our study. We numerically solve the dynamics equations for the electron and lattice and compute the dynamics of an initially localized electronic wave-packet. Our results suggest that the solitonic waves that exist within this nonlinear lattice can control the electron dynamics along the chain. Moreover, we demonstrate that the existence of a mobile electron–soliton pair exhibits a counter-intuitive dependence with the value of the electron-lattice coupling. (paper)
Scattering of quantized solitary waves in the cubic Schrodinger equation
International Nuclear Information System (INIS)
Dolan, L.
1976-01-01
The quantum mechanics for N particles interacting via a delta-function potential in one space dimension and one time dimension is known. The second-quantized description of this system has for its Euler-Lagrange equations of motion the cubic Schrodinger equation. This nonlinear differential equation supports solitary wave solutions. A quantization of these solitons reproduces the weak-coupling limit to the known quantum mechanics. The phase shift for two-body scattering and the energy of the N-body bound state is derived in this approximation. The nonlinear Schrodinger equation is contrasted with the sine-Gordon theory in respect to the ideas which the classical solutions play in the description of the quantum states
Linear electro-optic effect in cubic silicon carbide
Tang, Xiao; Irvine, Kenneth G.; Zhang, Dongping; Spencer, Michael G.
1991-01-01
The first observation is reported of the electrooptic effect of cubic silicon carbide (beta-SiC) grown by a low-pressure chemical vapor deposition reactor using the hydrogen, silane, and propane gas system. At a wavelength of 633 nm, the value of the electrooptic coefficient r41 in beta-SiC is determined to be 2.7 +/- 0.5 x 10 (exp-12) m/V, which is 1.7 times larger than that in gallium arsenide measured at 10.6 microns. Also, a half-wave voltage of 6.4 kV for beta-SiC is obtained. Because of this favorable value of electrooptic coefficient, it is believed that silicon carbide may be a promising candidate in electrooptic applications for high optical intensity in the visible region.
Point defects in cubic boron nitride after neutron irradiation
International Nuclear Information System (INIS)
Atobe, Kozo; Honda, Makoto; Ide, Munetoshi; Yamaji, Hiromichi; Matsukawa, Tokuo; Fukuoka, Noboru; Okada, Moritami; Nakagawa, Masuo.
1993-01-01
The production of point defects induced by reactor neutrons and the thermal behavior of defects in sintered cubic boron nitride are investigated using the optical absorption and electron spin resonance (ESR) methods. A strong structureless absorption over the visible region was observed after fast neutron irradiation to a dose of 5.3 x 10 16 n/cm 2 (E > 0.1 MeV) at 25 K. This specimen also shows an ESR signal with g-value 2.006 ± 0.001, which can be tentatively identified as an electron trapped in a nitrogen vacancy. On examination of the thermal decay of the signal, the activation energy for recovery of the defects was determined to be about 1.79 eV. (author)
Spatial 't Hooft loop to cubic order in hot QCD
Giovannangeli, P.
2002-01-01
Spatial 't Hooft loops of strength k measure the qualitative change in the behaviour of electric colour flux in confined and deconfined phase of SU (N) gauge theory. They show an area law in the deconfined phase, known analytica lly to two loop order with a ``k-scaling'' law k(N-k). In this paper we comput e the O(g^3) correction to the tension. It is due to neutral gluon fields that get their mass through interaction with the wall. The simple k-scaling is lost in cubic order. The generic problem of non-convexity shows up in this order an d the cure is provided. The result for large N is explicitely given. We show tha t nonperturbative effects appear at O(g^5).
Bistable dark solitons of a cubic-quintic Helmholtz equation
International Nuclear Information System (INIS)
Christian, J. M.; McDonald, G. S.; Chamorro-Posada, P.
2010-01-01
We provide a report on exact analytical bistable dark spatial solitons of a nonlinear Helmholtz equation with a cubic-quintic refractive-index model. Our analysis begins with an investigation of the modulational instability characteristics of Helmholtz plane waves. We then derive a dark soliton by mapping the desired asymptotic form onto a uniform background field and obtain a more general solution by deploying rotational invariance laws in the laboratory frame. The geometry of the new soliton is explored in detail, and a range of new physical predictions is uncovered. Particular attention is paid to the unified phenomena of arbitrary-angle off-axis propagation and nondegenerate bistability. Crucially, the corresponding solution of paraxial theory emerges in a simultaneous multiple limit. We conclude with a set of computer simulations that examine the role of Helmholtz dark solitons as robust attractors.
G2 cubic transition between two circles with shape control
Habib, Zulfiqar; Sakai, Manabu
2009-01-01
This paper describes a method for joining two circles with an S-shaped or with a broken back C-shaped transition curve, composed of at most two spiral segments. In highway and railway route design or car-like robot path planning, it is often desirable to have such a transition. It is shown that a single cubic curve can be used for blending or for a transition curve preserving G2 continuity with local shape control parameter and more flexible constraints. Provision of the shape parameter and flexibility provide freedom to modify the shape in a stable manner which is an advantage over previous work by Meek, Walton, Sakai and Habib.
Dynamic Displacement Disorder of Cubic BaTiO3
Paściak, M.; Welberry, T. R.; Kulda, J.; Leoni, S.; Hlinka, J.
2018-04-01
The three-dimensional distribution of the x-ray diffuse scattering intensity of BaTiO3 has been recorded in a synchrotron experiment and simultaneously computed using molecular dynamics simulations of a shell model. Together, these have allowed the details of the disorder in paraelectric BaTiO3 to be clarified. The narrow sheets of diffuse scattering, related to the famous anisotropic longitudinal correlations of Ti ions, are shown to be caused by the overdamped anharmonic soft phonon branch. This finding demonstrates that the occurrence of narrow sheets of diffuse scattering agrees with a displacive picture of the cubic phase of this textbook ferroelectric material. The presented methodology allows one to go beyond the harmonic approximation in the analysis of phonons and phonon-related scattering.
Principal spectra describing magnetooptic permittivity tensor in cubic crystals
Energy Technology Data Exchange (ETDEWEB)
Hamrlová, Jana [Nanotechnology Centre, VSB – Technical University of Ostrava, listopadu 15, Ostrava, 708 33 Czech Republic (Czech Republic); IT4Innovations Centre, VSB – Technical University of Ostrava, listopadu 15, Ostrava, 708 33 Czech Republic (Czech Republic); Legut, Dominik [IT4Innovations Centre, VSB – Technical University of Ostrava, listopadu 15, Ostrava, 708 33 Czech Republic (Czech Republic); Veis, Martin [Faculty of Mathematics and Physics, Charles University, Ke Karlovu 3, Prague, 121 16 Czech Republic (Czech Republic); Pištora, Jaromír [Nanotechnology Centre, VSB – Technical University of Ostrava, listopadu 15, Ostrava, 708 33 Czech Republic (Czech Republic); Hamrle, Jaroslav, E-mail: jaroslav.hamrle@vsb.cz [IT4Innovations Centre, VSB – Technical University of Ostrava, listopadu 15, Ostrava, 708 33 Czech Republic (Czech Republic); Faculty of Mathematics and Physics, Charles University, Ke Karlovu 3, Prague, 121 16 Czech Republic (Czech Republic); Department of Physics, VSB – Technical University of Ostrava, 17. listopadu 15, Ostrava, 708 33 Czech Republic (Czech Republic)
2016-12-15
We provide unified phenomenological description of magnetooptic effects being linear and quadratic in magnetization. The description is based on few principal spectra, describing elements of permittivity tensor up to the second order in magnetization. Each permittivity tensor element for any magnetization direction and any sample surface orientation is simply determined by weighted summation of the principal spectra, where weights are given by crystallographic and magnetization orientations. The number of principal spectra depends on the symmetry of the crystal. In cubic crystals owning point symmetry we need only four principal spectra. Here, the principal spectra are expressed by ab initio calculations for bcc Fe, fcc Co and fcc Ni in optical range as well as in hard and soft x-ray energy range, i.e. at the 2p- and 3p-edges. We also express principal spectra analytically using modified Kubo formula.
Structure and energetics of nanotwins in cubic boron nitrides
Energy Technology Data Exchange (ETDEWEB)
Zheng, Shijian, E-mail: sjzheng@imr.ac.cn, E-mail: zrf@buaa.edu.cn; Ma, Xiuliang [Shenyang National Laboratory for Materials Science, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China); Zhang, Ruifeng, E-mail: sjzheng@imr.ac.cn, E-mail: zrf@buaa.edu.cn [School of Materials Science and Engineering, and International Research Institute for Multidisciplinary Science, Beihang University, Beijing 100191 (China); Huang, Rong [Key Laboratory of Polar Materials and Devices, Ministry of Education, East China Normal University, Shanghai 200062 (China); Taniguchi, Takashi [National Institute for Materials Science, Tsukuba, Ibaraki 305-0044 (Japan); Ikuhara, Yuichi [Nanostructures Research Laboratory, Japan Fine Ceramics Center, Nagoya 456-8587 (Japan); Institute of Engineering Innovation, The University of Tokyo, Tokyo 113-8656 (Japan); Beyerlein, Irene J. [Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)
2016-08-22
Recently, nanotwinned cubic boron nitrides (NT c-BN) have demonstrated extraordinary leaps in hardness. However, an understanding of the underlying mechanisms that enable nanotwins to give orders of magnitude increases in material hardness is still lacking. Here, using transmission electron microscopy, we report that the defect density of twin boundaries depends on nanotwin thickness, becoming defect-free, and hence more stable, as it decreases below 5 nm. Using ab initio density functional theory calculations, we reveal that the Shockley partials, which may dominate plastic deformation in c-BNs, show a high energetic barrier. We also report that the c-BN twin boundary has an asymmetrically charged electronic structure that would resist migration of the twin boundary under stress. These results provide important insight into possible nanotwin hardening mechanisms in c-BN, as well as how to design these nanostructured materials to reach their full potential in hardness and strength.
Multilayer gyroid cubic membrane organization in green alga Zygnema.
Zhan, Ting; Lv, Wenhua; Deng, Yuru
2017-09-01
Biological cubic membranes (CM), which are fluid membranes draped onto the 3D periodic parallel surface geometries with cubic symmetry, have been observed within subcellular organelles, including mitochondria, endoplasmic reticulum, and thylakoids. CM transition tends to occur under various stress conditions; however, multilayer CM organizations often appear associated with light stress conditions. This report is about the characterization of a projected gyroid CM in a transmission electron microscopy study of the chloroplast membranes within green alga Zygnema (LB923) whose lamellar form of thylakoid membrane started to fold into multilayer gyroid CM in the culture at the end of log phase of cell growth. Using the techniques of computer simulation of transmission electron microscopy (TEM) and a direct template matching method, we show that these CM are based on the gyroid parallel surfaces. The single, double, and multilayer gyroid CM morphologies are observed in which space is continuously divided into two, three, and more subvolumes by either one, two, or several parallel membranes. The gyroid CM are continuous with varying amount of pseudo-grana with lamellar-like morphology. The relative amount and order of these two membrane morphologies seem to vary with the age of cell culture and are insensitive to ambient light condition. In addition, thylakoid gyroid CM continuously interpenetrates the pyrenoid body through stalk, bundle-like, morphologies. Inside the pyrenoid body, the membranes re-folded into gyroid CM. The appearance of these CM rearrangements due to the consequence of Zygnema cell response to various types of environmental stresses will be discussed. These stresses include nutrient limitation, temperature fluctuation, and ultraviolet (UV) exposure.
Dian, Linghui; Yang, Zhiwen; Li, Feng; Wang, Zhouhua; Pan, Xin; Peng, Xinsheng; Huang, Xintian; Guo, Zhefei; Quan, Guilan; Shi, Xuan; Chen, Bao; Li, Ge; Wu, Chuanbin
2013-01-01
In order to improve the oral bioavailability of ibuprofen, ibuprofen-loaded cubic nanoparticles were prepared as a delivery system for aqueous formulations. The cubic inner structure was verified by cryogenic transmission electron microscopy. With an encapsulation efficiency greater than 85%, the ibuprofen-loaded cubic nanoparticles had a narrow size distribution around a mean size of 238 nm. Differential scanning calorimetry and X-ray diffraction determined that ibuprofen was in an amorphous and molecular form within the lipid matrix. The in vitro release of ibuprofen from cubic nanoparticles was greater than 80% at 24 hours, showing sustained characteristics. The pharmacokinetic study in beagle dogs showed improved absorption of ibuprofen from cubic nanoparticles compared to that of pure ibuprofen, with evidence of a longer half-life and a relative oral bioavailability of 222% (P ibuprofen-loaded cubic nanoparticles provide a promising carrier candidate with an efficient drug delivery for therapeutic treatment. PMID:23468008
Electric quadrupole interaction in cubic BCC α-Fe
Energy Technology Data Exchange (ETDEWEB)
Błachowski, A.; Komędera, K. [Mössbauer Spectroscopy Division, Institute of Physics, Pedagogical University, ul. Podchorążych 2, PL-30-084 Kraków (Poland); Ruebenbauer, K., E-mail: sfrueben@cyf-kr.edu.pl [Mössbauer Spectroscopy Division, Institute of Physics, Pedagogical University, ul. Podchorążych 2, PL-30-084 Kraków (Poland); Cios, G.; Żukrowski, J. [AGH University of Science and Technology, Academic Center for Materials and Nanotechnology, Av. A. Mickiewicza 30, PL-30-059 Kraków (Poland); Górnicki, R. [RENON, ul. Gliniana 15/15, PL-30-732 Kraków (Poland)
2016-07-15
Mössbauer transmission spectra for the 14.41-keV resonant line in {sup 57}Fe have been collected at room temperature by using {sup 57}Co(Rh) commercial source and α-Fe strain-free single crystal as an absorber. The absorber was magnetized to saturation in the absorber plane perpendicular to the γ-ray beam axis applying small external magnetic field. Spectra were collected for various orientations of the magnetizing field, the latter lying close to the [110] crystal plane. A positive electric quadrupole coupling constant was found practically independent on the field orientation. One obtains the following value V{sub zz} = +1.61(4) × 10{sup 19} Vm{sup −2} for the (average) principal component of the electric field gradient (EFG) tensor under assumption that the EFG tensor is axially symmetric and the principal axis is aligned with the magnetic hyperfine field acting on the {sup 57}Fe nucleus. The nuclear spectroscopic electric quadrupole moment for the first excited state of the {sup 57}Fe nucleus was adopted as +0.17 b. Similar measurement was performed at room temperature using as-rolled polycrystalline α-Fe foil of high purity in the zero external field. Corresponding value for the principal component of the EFG was found as V{sub zz} = +1.92(4) × 10{sup 19} Vm{sup −2}. Hence, it seems that the origin of the EFG is primarily due to the local (atomic) electronic wave function distortion caused by the spin–orbit interaction between effective electronic spin S and incompletely quenched electronic angular momentum L. It seems as well that the lowest order term proportional to the product L·λ·S dominates, as no direction dependence of the EFG principal component is seen. The lowest order term is isotropic for a cubic symmetry as one has λ=λ 1 for cubic systems with the symbol 1 denoting unit operator and λ being the coupling parameter. - Highlights: • Precision of MS the same as MAPON • Real scans versus magnetization direction • A challenge
Electric quadrupole interaction in cubic BCC α-Fe
International Nuclear Information System (INIS)
Błachowski, A.; Komędera, K.; Ruebenbauer, K.; Cios, G.; Żukrowski, J.; Górnicki, R.
2016-01-01
Mössbauer transmission spectra for the 14.41-keV resonant line in "5"7Fe have been collected at room temperature by using "5"7Co(Rh) commercial source and α-Fe strain-free single crystal as an absorber. The absorber was magnetized to saturation in the absorber plane perpendicular to the γ-ray beam axis applying small external magnetic field. Spectra were collected for various orientations of the magnetizing field, the latter lying close to the [110] crystal plane. A positive electric quadrupole coupling constant was found practically independent on the field orientation. One obtains the following value V_z_z = +1.61(4) × 10"1"9 Vm"−"2 for the (average) principal component of the electric field gradient (EFG) tensor under assumption that the EFG tensor is axially symmetric and the principal axis is aligned with the magnetic hyperfine field acting on the "5"7Fe nucleus. The nuclear spectroscopic electric quadrupole moment for the first excited state of the "5"7Fe nucleus was adopted as +0.17 b. Similar measurement was performed at room temperature using as-rolled polycrystalline α-Fe foil of high purity in the zero external field. Corresponding value for the principal component of the EFG was found as V_z_z = +1.92(4) × 10"1"9 Vm"−"2. Hence, it seems that the origin of the EFG is primarily due to the local (atomic) electronic wave function distortion caused by the spin–orbit interaction between effective electronic spin S and incompletely quenched electronic angular momentum L. It seems as well that the lowest order term proportional to the product L·λ·S dominates, as no direction dependence of the EFG principal component is seen. The lowest order term is isotropic for a cubic symmetry as one has λ=λ 1 for cubic systems with the symbol 1 denoting unit operator and λ being the coupling parameter. - Highlights: • Precision of MS the same as MAPON • Real scans versus magnetization direction • A challenge for ab initio calculations
Characterization, Microstructure, and Dielectric properties of cubic pyrochlore structural ceramics
Li, Yangyang
2013-05-01
The (BMN) bulk materials were sintered at 1050°C, 1100°C, 1150°C, 1200°C by the conventional ceramic process, and their microstructure and dielectric properties were investigated by Scanning electron microscopy (SEM), X-ray diffraction (XRD), Raman spectroscopy, Transmission electron microscopy (TEM) (including the X-ray energy dispersive spectrometry EDS and high resolution transmission electron microscopy HRTEM) and dielectric impedance analyzer. We systematically investigated the structure, dielectric properties and voltage tunable property of the ceramics prepared at different sintering temperatures. The XRD patterns demonstrated that the synthesized BMN solid solutions had cubic phase pyrochlore-type structure when sintered at 1050°C or higher, and the lattice parameter (a) of the unit cell in BMN solid solution was calculated to be about 10.56Å. The vibrational peaks observed in the Raman spectra of BMN solid solutions also confirmed the cubic phase pyrochlore-type structure of the synthesized BMN. According to the Scanning Electron Microscope (SEM) images, the grain size increased with increasing sintering temperature. Additionally, it was shown that the densities of the BMN ceramic tablets vary with sintering temperature. The calculated theoretical density for the BMN ceramic tablets sintered at different temperatures is about 6.7521 . The density of the respective measured tablets is usually amounting more than 91% and 5 approaching a maximum value of 96.5% for sintering temperature of 1150°C. The microstructure was investigated by using Scanning Transmission Electron Microscope (STEM), X-ray diffraction (XRD). Combined with the results obtained from the STEM and XRD, the impact of sintering temperature on the macroscopic and microscopic structure was discussed. The relative dielectric constant ( ) and dielectric loss ( ) of the BMN solid solutions were measured to be 161-200 and (at room temperature and 100Hz-1MHz), respectively. The BMN solid
Detwinning mechanisms for growth twins in face-centered cubic metals
Energy Technology Data Exchange (ETDEWEB)
Wang, J., E-mail: wangj6@lanl.gov [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Li, N.; Anderoglu, O. [Department of Mechanical Engineering, Materials Science and Engineering Program, Texas A and M University, College Station, TX 77843-3123 (United States); Zhang, X., E-mail: zhangx@tamu.edu [Department of Mechanical Engineering, Materials Science and Engineering Program, Texas A and M University, College Station, TX 77843-3123 (United States); Misra, A. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Huang, J.Y. [Sandia National Laboratories, Albuquerque, NM 87185 (United States); Hirth, J.P. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States)
2010-04-15
Using in situ transmission electron microscopy, we studied the stability of growth twins. We observed the rapid migration of incoherent twin boundaries (ITBs), indicating that nanotwins are unstable. Topological analysis and atomistic simulations are adopted to explore detwinning mechanisms. The results show that: (i) the detwinning process is accomplished via the collective glide of multiple twinning dislocations that form an ITB; (ii) detwinning can easily occur for thin twins, and the driving force is mainly attributed to a variation of the excess energy of a coherent twin boundary; (iii) shear stresses enable ITBs to migrate easily, causing the motion of coherent twin boundaries; and (iv) the migration velocity depends on stacking fault energy. The results imply that detwinning becomes the dominant deformation mechanism for growth twins of the order of a few nanometers thick.
Dislocation structures of Σ3 {112} twin boundaries in face centered cubic metals
Wang, J.; Anderoglu, O.; Hirth, J. P.; Misra, A.; Zhang, X.
2009-07-01
High resolution transmission electron microscopy of nanotwinned Cu films revealed Σ3 {112} incoherent twin boundaries (ITBs), with a repeatable pattern involving units of three {111} atomic planes. Topological analysis shows that Σ3 {112} ITBs adopt two types of atomic structure with differing arrangements of Shockley partial dislocations. Atomistic simulations were performed for Cu and Al. These studies revealed the structure of the two types of ITBs, the formation mechanism and stability of the associated 9R phase, and the influence of stacking fault energies on them. The results suggest that Σ3 {112} ITBs may migrate through the collective glide of partial dislocations.
Meraj, Md; Pal, Snehanshu
2017-10-11
In this paper, the creep behavior of nanocrystalline Ni having bimodal grain structure is investigated using molecular dynamics simulation. Analysis of structural evolution during the creep process has also been performed. It is observed that an increase in size of coarse grain causes improvement in creep properties of bimodal nanocrystalline Ni. Influence of bimodality (i.e., size difference between coarse and fine grains) on creep properties are found to be reduced with increasing creep temperature. The dislocation density is observed to decrease exponentially with progress of creep deformation. Grain boundary diffusion controlled creep mechanism is found to be dominant at the primary creep region and the initial part of the secondary creep region. After that shear diffusion transformation mechanism is found to be significantly responsible for deformation as bimodal nanocrystalline Ni transforms to amorphous structure with further progress of the creep process. The presence of , , and distorted icosahedra has a significant influence on creep rate in the tertiary creep regime according to Voronoi cluster analysis.
Magnetostriction of some cubic rare earth-Co2 compounds in high magnetic fields
International Nuclear Information System (INIS)
Moral, A. del; Melville, D.
1975-01-01
Magnetostriction measurements have been carried out in the cubic Laves phase compounds DyCo 2 , HoCo 2 and ErCo 2 from 10 K to well above their respective Neel temperatures Tsub(N). Pulsed magnetic fields up to 15 T (150kOe) were applied. The observed magnetostrictions are very large (approximately 10 -3 ) being similar to those found in the RFe 2 compounds. The measurements confirm the extremely high anisotropy of these materials. At the highest fields the polycrystalline samples are still undergoing rotational magnetization processes. The expected values of the saturation magnetostriction at O K are similar in sign and magnitude to those found in the corresponding rare earth metals. This fact and the scaling of magnetostriction with rare earth sublattice magnetization indicates that the rare earth ion is the main source of the magnetostriction. The metamagnetic transition above Tsub(N) has been studied, the relation between critical field and temperature being nonlinear for HoCo 2 and ErCo 2 . The compounds are highly anisotropic above Tsub(N) and all the features indicate that the field-induced phases are likely to be ferrimagnetic. (author)
Spectral intensities in cubic systems. I. Progressions based upon parity vibrational modes
Energy Technology Data Exchange (ETDEWEB)
Acevedo, R.; Vasquez, S.O. [Department of Basic Chemistry, Faculty of Physical and Mathematical Sciences, University of Chile. Tupper 2069, Casilla 2777, Santiago, Chile (Chile); Meruane, T. [Department of Chemistry, Universidad Metropolitana de Ciencias de la Educacion. Av. J.P. Alessandri 774, Casilla 147, C. Santiago, Chile (Chile); Poblete, V. [Department of Nuclear Materials, Lo Aguirre, Comision Chilena de Energia Nuclear. Amunategui 95, Casilla 188-D, Santiago, Chile (Chile); Pozo, J. [Facultad de Ciencias de la Ingenieria. Universidad Diego Portales. Casilla 298-V, Santiago, Chile (Chile)
1998-12-01
The well-resolved emission and absorption spectra of centrosymmetric coordination compounds of the transition metal ions have been used widely to provide the experimental data against which to test theoretical models of vibronic intensities. With reference to the {sup 2} E{sub g} {yields} {sup 4} A{sub 2g} luminescence transition, at a perfect octahedral site in Cs{sub 2}SiF{sub 6}, over than one hundred vibronic lines are observed with line widths of a few wavenumber spread over some 3000 cm{sup -1}. This paper reports a through examination of both the electronic and vibrational factors, which influences the observed vibronic intensities of the various assigned and identified lines in the spectra of the MnF{sub 6} {sup 2-} complex ion in the Cs{sub 2}SiF{sub 6} cubic lattice. The origin and nature of higher order vibronic interactions are analysed on the basis of a symmetrized vibronic crystal field-ligand polarization model. (Author)
High-pressure synthesis of fully occupied tetragonal and cubic tungsten bronze oxides
Energy Technology Data Exchange (ETDEWEB)
Ikeuchi, Yuya; Takatsu, Hiroshi; Tassel, Cedric; Goto, Yoshihiro; Murakami, Taito; Kageyama, Hiroshi [Graduate School of Engineering, Kyoto University (Japan)
2017-05-15
A high-pressure reaction yielded the fully occupied tetragonal tungsten bronze K{sub 3}W{sub 5}O{sub 15} (K{sub 0.6}WO{sub 3}). The terminal phase shows an unusual transport property featuring slightly negative temperature-dependence in resistivity (dρ/dT<0) and a large Wilson ratio of R{sub W}=3.2. Such anomalous metallic behavior possibly arises from the low-dimensional electronic structure with a van Hove singularity at the Fermi level and/or from enhanced magnetic fluctuations by geometrical frustration of the tungsten sublattice. The asymmetric nature of the tetragonal tungsten bronze K{sub x}WO{sub 3}-K{sub 0.6-y}Ba{sub y}WO{sub 3} phase diagram implies that superconductivity for x≤0.45 originates from the lattice instability because of potassium deficiency. A cubic perovskite KWO{sub 3} phase was also identified as a line phase - in marked contrast to Na{sub x}WO{sub 3} and Li{sub x}WO{sub 3} with varying quantities of x (<1). This study presents a versatile method by which the solubility limit of tungsten bronze oxides can be extended. (copyright 2017 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim)
Atomistic simulations of diffusional creep in a nanocrystalline body-centered cubic material
International Nuclear Information System (INIS)
Millett, Paul C.; Desai, Tapan; Yamakov, Vesselin; Wolf, Dieter
2008-01-01
Molecular dynamics (MD) simulations are used to study diffusion-accommodated creep deformation in nanocrystalline molybdenum, a body-centered cubic metal. In our simulations, the microstructures are subjected to constant-stress loading at levels below the dislocation nucleation threshold and at high temperatures (i.e., T > 0.75T melt ), thereby ensuring that the overall deformation is indeed attributable to atomic self-diffusion. The initial microstructures were designed to consist of hexagonally shaped columnar grains bounded by high-energy asymmetric tilt grain boundaries (GBs). Remarkably the creep rates, which exhibit a double-exponential dependence on temperature and a double power-law dependence on grain size, indicate that both GB diffusion in the form of Coble creep and lattice diffusion in the form of Nabarro-Herring creep contribute to the overall deformation. For the first time in an MD simulation, we observe the formation and emission of vacancies from high-angle GBs into the grain interiors, thus enabling bulk diffusion
Electronic band structure and optical properties of the cubic, Sc, Y and La hydride systems
International Nuclear Information System (INIS)
Peterman, D.J.
1980-01-01
Electronic band structure calculations are used to interpret the optical spectra of the cubic Sc, Y and La hydride systems. Self-consistent band calculations of ScH 2 and YH 2 were carried out. The respective joint densities of states are computed and compared to the dielectric functions determined from the optical measurements. Additional calculations were performed in which the Fermi level or band gap energies are rigidly shifted by a small energy increment. These calculations are then used to simulate the derivative structure in thermomodulation spectra and relate the origin of experimental interband features to the calculated energy bands. While good systematic agreement is obtained for several spectral features, the origin of low-energy interband transitions in YH 2 cannot be explained by these calculated bands. A lattice-size-dependent premature occupation of octahedral sites by hydrogen atoms in the fcc metal lattice is suggested to account for this discrepancy. Various non-self-consistent calculations are used to examine the effect of such a premature occupation. Measurements of the optical absorptivity of LaH/sub x/ with 1.6 2 lattice. These experimental results also suggest that, in contrast to recent calculations, LaH 3 is a small-band-gap semiconductor
Experimental evidence of body centered cubic iron in Earth's core
Hrubiak, R.; Meng, Y.; Shen, G.
2017-12-01
The Earth's core is mainly composed of iron. While seismic evidence has shown a liquid outer core and a solid inner core, the crystalline nature of the solid iron at the core condition remains debated, largely due to the difficulties in experimental determination of exact polymorphs at corresponding pressure-temperature conditions. We have examined crystal structures of iron up to 220 GPa and 6000 K with x-ray diffraction using a double-sided laser heating system at HPCAT, Advanced Photon Source. The iron sample is confined in a small chamber surrounded by single crystal MgO. The laser power can be modulated together with temperature measurements. The modulated heating of iron in an MgO single crystal matrix allows for microstructure analysis during heating and after the sample is quenched. We present experimental evidence of a body-centered-cubic (BCC) iron from about 100 GPa and 3000 K to at least 220 GPa and 4000 K. The observed BCC phase may be consistent with a theoretically predicted BCC phase that is dynamically stable in similar pressure-temperature conditions [1]. We will discuss the stability region of the BCC phase and the melting curve of iron and their implications in the nature of the Earth's inner core. References: A. B. Belonoshko et al., Nat. Geosci., 1-6 (2017).
Cubic-quintic solitons in the checkerboard potential
International Nuclear Information System (INIS)
Driben, Rodislav; Zyss, Joseph; Malomed, Boris A.; Gubeskys, Arthur
2007-01-01
We introduce a two-dimensional (2D) model which combines a checkerboard potential, alias the Kronig-Penney (KP) lattice, with the self-focusing cubic and self-defocusing quintic nonlinear terms. The beam-splitting mechanism and soliton multistability are explored in this setting, following the recently considered 1D version of the model. Families of single- and multi-peak solitons (in particular, five- and nine-peak species naturally emerge in the 2D setting) are found in the semi-infinite gap, with both branches of bistable families being robust against perturbations. For single-peak solitons, the variational approximation (VA) is developed, providing for a qualitatively correct description of the transition from monostability to the bistability. 2D solitons found in finite band gaps are unstable. Also constructed are two different species of stable vortex solitons, arranged as four-peak patterns ('oblique' and 'straight' ones). Unlike them, compact 'crater-shaped' vortices are unstable, transforming themselves into randomly walking fundamental beams
Tunable surface configuration of skyrmion lattices in cubic helimagnets
Wan, Xuejin; Hu, Yangfan; Wang, Biao
2018-06-01
In bulk helimagnets, the presence of magnetic skyrmion lattices is always accompanied by a periodic stress field due to the intrinsic magnetoelastic coupling. The release of this nontrivial stress field at the surface causes a periodic displacement field, which characterizes a novel particle-like property of skyrmion: its surface configuration. Here, we derive the analytical solution of this displacement field for semi-infinite cubic helimagnet with the skyrmion magnetization approximated by the triple-Q representation. For MnSi, we show that the skyrmion lattices have a bumpy surface configuration characterized by periodically arranged peaks with a characteristic height of about 10‑13 m. The pattern of the peaks can be controlled by varying the strength of the applied magnetic field. Moreover, we prove that the surface configuration varies together with the motion and deformation of the skyrmion lattices. As a result, the surface configuration can be tuned by application of electric current, mechanical loads, as well as any other effective external fields for skyrmion lattices.
Twinning of cubic diamond explains reported nanodiamond polymorphs
Németh, Péter; Garvie, Laurence A. J.; Buseck, Peter R.
2015-12-01
The unusual physical properties and formation conditions attributed to h-, i-, m-, and n-nanodiamond polymorphs has resulted in their receiving much attention in the materials and planetary science literature. Their identification is based on diffraction features that are absent in ordinary cubic (c-) diamond (space group: Fd-3m). We show, using ultra-high-resolution transmission electron microscope (HRTEM) images of natural and synthetic nanodiamonds, that the diffraction features attributed to the reported polymorphs are consistent with c-diamond containing abundant defects. Combinations of {113} reflection and rotation twins produce HRTEM images and d-spacings that match those attributed to h-, i-, and m-diamond. The diagnostic features of n-diamond in TEM images can arise from thickness effects of c-diamonds. Our data and interpretations strongly suggest that the reported nanodiamond polymorphs are in fact twinned c-diamond. We also report a new type of twin ( rotational), which can give rise to grains with dodecagonal symmetry. Our results show that twins are widespread in diamond nanocrystals. A high density of twins could strongly influence their applications.
Electrical leakage phenomenon in heteroepitaxial cubic silicon carbide on silicon
Pradeepkumar, Aiswarya; Zielinski, Marcin; Bosi, Matteo; Verzellesi, Giovanni; Gaskill, D. Kurt; Iacopi, Francesca
2018-06-01
Heteroepitaxial 3C-SiC films on silicon substrates are of technological interest as enablers to integrate the excellent electrical, electronic, mechanical, thermal, and epitaxial properties of bulk silicon carbide into well-established silicon technologies. One critical bottleneck of this integration is the establishment of a stable and reliable electronic junction at the heteroepitaxial interface of the n-type SiC with the silicon substrate. We have thus investigated in detail the electrical and transport properties of heteroepitaxial cubic silicon carbide films grown via different methods on low-doped and high-resistivity silicon substrates by using van der Pauw Hall and transfer length measurements as test vehicles. We have found that Si and C intermixing upon or after growth, particularly by the diffusion of carbon into the silicon matrix, creates extensive interstitial carbon traps and hampers the formation of a stable rectifying or insulating junction at the SiC/Si interface. Although a reliable p-n junction may not be realistic in the SiC/Si system, we can achieve, from a point of view of the electrical isolation of in-plane SiC structures, leakage suppression through the substrate by using a high-resistivity silicon substrate coupled with deep recess etching in between the SiC structures.
Anisotropic cubic lattice potts ferromagnet: renormalisation group treatment
International Nuclear Information System (INIS)
Tsallis, C.; Schwaccheim, G.; Silva, L.R. da; Rio Grande do Norte Univ., Natal
1983-01-01
Within a real space renormalisation group framework, the criticality of the fully anisotropic (arbitrary J sub(x), J sub(y) and J sub(z)) q-state Potts ferromagnet in simple cubic lattice is discussed. Several already known exact results for the d=1 and d=2 particular cases are recovered. Furthermore it is obtained: (i) the q-dependence of the d=3 correlation length critical exponent ν 3 (in particular, if q→0, ν 3 (q) approximatelly ν 3 (0)+ν 3 '(0)q) where the present approximate values are ν 3 (0) or approx.= 1.105 and ν 3 '(0) or approx.=-0.66; (ii) the q-dependence d=2 d=3 crossover critical exponent phi 23 (in particular, phi 23 varies as 1/√q if q Q→0); (iii) through a convenient numerical extrapolation, a quite accurate proposal for the critical temperatures corresponding to arbitrary ratios J sub(y)/ J sub(x) and J sub(z) / J sub(x) and values of q. (Author) [pt
Hyperfine interactions in the cubic semiconductor CdO
International Nuclear Information System (INIS)
Desimoni, J.; Bibiloni, A.G.; Massolo, C.P.; Renteria, M.
1990-01-01
The time-differential perturbed angular correlation technique has been applied using 111 In probes, which decay through electron capture to 111 Cd, to study the hyperfine interaction in cubic cadmium oxide, in the temperature range RT--740 degree C (RT denotes room temperature). The main fraction of probes are located in perfect-lattice sites, with null electric field gradient in agreement with crystalline-structure considerations. Around 25% of the total intensity shows an electric-field-gradient distribution around V zz =0. This corresponds to probes located in sites perturbed by the vicinity of oxygen vacancies in the lattice. The temperature-independent behavior of the measured hyperfine parameters is discussed in terms of conductivity and band-structure properties of the semiconductor. No time-dependent interaction arising from nuclear electron-capture aftereffects are seen in this experiment. This is in agreement with a previously reported model of aftereffect processes which states that only holes trapped in impurity levels inside the band gap of the semiconductor can give rise to detectable fluctuating interactions
Hyperfine interactions in the cubic semiconductor CdO
Energy Technology Data Exchange (ETDEWEB)
Desimoni, J.; Bibiloni, A.G.; Massolo, C.P.; Renteria, M. (Departamento de Fisica, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, Casilla de Correo No. 67, 1900 La Plata, Argentina (AR))
1990-01-15
The time-differential perturbed angular correlation technique has been applied using {sup 111}In probes, which decay through electron capture to {sup 111}Cd, to study the hyperfine interaction in cubic cadmium oxide, in the temperature range RT--740 {degree}C (RT denotes room temperature). The main fraction of probes are located in perfect-lattice sites, with null electric field gradient in agreement with crystalline-structure considerations. Around 25% of the total intensity shows an electric-field-gradient distribution around {ital V}{sub {ital zz}}=0. This corresponds to probes located in sites perturbed by the vicinity of oxygen vacancies in the lattice. The temperature-independent behavior of the measured hyperfine parameters is discussed in terms of conductivity and band-structure properties of the semiconductor. No time-dependent interaction arising from nuclear electron-capture aftereffects are seen in this experiment. This is in agreement with a previously reported model of aftereffect processes which states that only holes trapped in impurity levels inside the band gap of the semiconductor can give rise to detectable fluctuating interactions.
Cubic Interactions of Massless Bosonic Fields in Three Dimensions
Mkrtchyan, Karapet
2018-06-01
In this Letter, we take the first step towards construction of nontrivial Lagrangian theories of higher-spin gravity in a metriclike formulation in three dimensions. The crucial feature of a metriclike formulation is that it is known how to incorporate matter interactions into the description. We derive a complete classification of cubic interactions for arbitrary triples s1 , s2 , s3 of massless fields, which are the building blocks of any interacting theory with massless higher spins. We find that there is, at most, one vertex for any given triple of spins in 3D (with one exception, s1=s2=s3=1 , which allows for two vertices). Remarkably, there are no vertices for spin values that do not respect strict triangle inequalities and contain at least two spins greater than one. This translates into selection rules for three-point functions of higher-spin conserved currents in two dimensional conformal field theory. Furthermore, universal coupling to gravity for any spin is derived. Last, we argue that this classification persists in arbitrary Einstein backgrounds.
STROPHOIDS, A FAMILY OF CUBIC CURVES WITH REMARKABLE PROPERTIES
Directory of Open Access Journals (Sweden)
STACHEL Hellmuth
2015-06-01
On each strophoid there is a symmetric relation of points, so-called ‘associated’ points, with a series of properties: The lines connecting associated points P and P’ are tangent of the negative pedal curve. Tangents at associated points intersect at a point which again lies on the cubic. For all pairs (P, P’ of associated points, the midpoints lie on a line through the node N. For any two pairs (P, P’ and (Q, Q’ of associated points, the points of intersection between the lines PQ and P’Q’ as well as between PQ’ and P’Q are again placed on the strophoid and mutually associated. The lines PQ and PQ’ are symmetric with respect to the line connecting P with the node. Thus, strophoids generalize Apollonian circles: For given non-collinear points A, A’ and N the locus of points X such that one angle bisector of the lines XA and XA’ passes through N is a strophoid.
Research of Cubic Bezier Curve NC Interpolation Signal Generator
Directory of Open Access Journals (Sweden)
Shijun Ji
2014-08-01
Full Text Available Interpolation technology is the core of the computer numerical control (CNC system, and the precision and stability of the interpolation algorithm directly affect the machining precision and speed of CNC system. Most of the existing numerical control interpolation technology can only achieve circular arc interpolation, linear interpolation or parabola interpolation, but for the numerical control (NC machining of parts with complicated surface, it needs to establish the mathematical model and generate the curved line and curved surface outline of parts and then discrete the generated parts outline into a large amount of straight line or arc to carry on the processing, which creates the complex program and a large amount of code, so it inevitably introduce into the approximation error. All these factors affect the machining accuracy, surface roughness and machining efficiency. The stepless interpolation of cubic Bezier curve controlled by analog signal is studied in this paper, the tool motion trajectory of Bezier curve can be directly planned out in CNC system by adjusting control points, and then these data were put into the control motor which can complete the precise feeding of Bezier curve. This method realized the improvement of CNC trajectory controlled ability from the simple linear and circular arc to the complex project curve, and it provides a new way for economy realizing the curve surface parts with high quality and high efficiency machining.
Nature and strength of defect interactions in cubic stabilized zirconia
International Nuclear Information System (INIS)
Bogicevic, A.; Wolverton, C.
2003-01-01
The intrinsic ordering tendencies that limit ionic conduction in doped zirconia electrolytes are fully elucidated using first-principles calculations. A detailed analysis of nearly 300 yttria- and scandia-stabilized cubic-zirconia-ordered vacancy compounds reveals a delicate balance between competing elastic and electrostatic interactions. These results explain several outstanding experimental observations and provide substantial insight needed for improving ionic conduction and enabling low-temperature operation of zirconia-based electrolytes. We show that the surprising vacancy ordering in dilute solid solutions is a consequence of repulsive electrostatic and attractive elastic interactions that balance at third-neighbor vacancy separations. In contrast, repulsive elastic vacancy-dopant interactions prevail over electrostatic attraction at all probed defect separations in YSZ and lead to very weak ordering preferences in ScSZ. The total electronic contribution to the defect interactions is shown to be strongly dominated by simple point-charge electrostatics, leaving speciation of defect ordering for a given class of aliovalent dopants to the elastic term. Thus, ion size becomes a critical parameter in controlling the ionic conductivity of doped oxide electrolytes
Twinning of cubic diamond explains reported nanodiamond polymorphs.
Németh, Péter; Garvie, Laurence A J; Buseck, Peter R
2015-12-16
The unusual physical properties and formation conditions attributed to h-, i-, m-, and n-nanodiamond polymorphs has resulted in their receiving much attention in the materials and planetary science literature. Their identification is based on diffraction features that are absent in ordinary cubic (c-) diamond (space group: Fd-3m). We show, using ultra-high-resolution transmission electron microscope (HRTEM) images of natural and synthetic nanodiamonds, that the diffraction features attributed to the reported polymorphs are consistent with c-diamond containing abundant defects. Combinations of {113} reflection and rotation twins produce HRTEM images and d-spacings that match those attributed to h-, i-, and m-diamond. The diagnostic features of n-diamond in TEM images can arise from thickness effects of c-diamonds. Our data and interpretations strongly suggest that the reported nanodiamond polymorphs are in fact twinned c-diamond. We also report a new type of twin ( rotational), which can give rise to grains with dodecagonal symmetry. Our results show that twins are widespread in diamond nanocrystals. A high density of twins could strongly influence their applications.
Defect structure of cubic solid solutions of alkaline earth and rare earth fluorides
DenHartog, HW
1996-01-01
In this paper we will consider the disorder in some cubic solid solutions consisting of one of the alkaline earth fluorides and one of the rare earth fluorides. This is an attractive group of model materials, because these materials have a rather simple overall cubic structure. We will discuss the
Eliminating cubic terms in the pseudopotential lattice Boltzmann model for multiphase flow
Huang, Rongzong; Wu, Huiying; Adams, Nikolaus A.
2018-05-01
It is well recognized that there exist additional cubic terms of velocity in the lattice Boltzmann (LB) model based on the standard lattice. In this work, elimination of these cubic terms in the pseudopotential LB model for multiphase flow is investigated, where the force term and density gradient are considered. By retaining high-order (≥3 ) Hermite terms in the equilibrium distribution function and the discrete force term, as well as introducing correction terms in the LB equation, the additional cubic terms of velocity are entirely eliminated. With this technique, the computational simplicity of the pseudopotential LB model is well maintained. Numerical tests, including stationary and moving flat and circular interface problems, are carried out to show the effects of such cubic terms on the simulation of multiphase flow. It is found that the elimination of additional cubic terms is beneficial to reduce the numerical error, especially when the velocity is relatively large. Numerical results also suggest that these cubic terms mainly take effect in the interfacial region and that the density-gradient-related cubic terms are more important than the other cubic terms for multiphase flow.
On the number of longest and almost longest cycles in cubic graphs
DEFF Research Database (Denmark)
Chia, Gek Ling; Thomassen, Carsten
2012-01-01
We consider the questions: How many longest cycles must a cubic graph have, and how many may it have? For each k >= 2 there are infinitely many p such that there is a cubic graph with p vertices and precisely one longest cycle of length p-k. On the other hand, if G is a graph with p vertices, all...
Cubic Invariant Spherical Surface Harmonics in Conjunction With Diffraction Strain Pole-Figures
Brakman, C.M.
1986-01-01
Four kinds of cubic invariant spherical surface harmonics are introduced. It has been shown previously that these harmonics occur in the equations relating measured diffraction (line-shift) elastic strain and macro-stresses generating these strains for the case of textured cubic materials. As a
Synthesis of nano-scale fast ion conducting cubic Li7La3Zr2O12.
Sakamoto, Jeff; Rangasamy, Ezhiylmurugan; Kim, Hyunjoung; Kim, Yunsung; Wolfenstine, Jeff
2013-10-25
A solution-based process was investigated for synthesizing cubic Li7La3Zr2O12 (LLZO), which is known to exhibit the unprecedented combination of fast ionic conductivity, and stability in air and against Li. Sol-gel chemistry was developed to prepare solid metal-oxide networks consisting of 10 nm cross-links that formed the cubic LLZO phase at 600 ° C. Sol-gel LLZO powders were sintered into 96% dense pellets using an induction hot press that applied pressure while heating. After sintering, the average LLZO grain size was 260 nm, which is 13 times smaller compared to LLZO prepared using a solid-state technique. The total ionic conductivity was 0.4 mS cm(-1) at 298 K, which is the same as solid-state synthesized LLZO. Interestingly, despite the same room temperature conductivity, the sol-gel LLZO total activation energy is 0.41 eV, which 1.6 times higher than that observed in solid-state LLZO (0.26 eV). We believe the nano-scale grain boundaries give rise to unique transport phenomena that are more sensitive to temperature when compared to the conventional solid-state LLZO.
Electrical properties of MBE grown Si{sub 3}N{sub 4}-cubic GaN MIS structures
Energy Technology Data Exchange (ETDEWEB)
Zado, A.; Lischka, K.; As, D.J. [University of Paderborn, Faculty of Science, Department of Physics, Warburger Str. 100, 33098 Paderborn (Germany)
2012-03-15
In this work we report on the electrical characterization of non-polar cubic GaN metal-insulator-semiconductor (MIS) structures. Si{sub 3}N{sub 4} layers were deposited in-situ on top of cubic GaN grown on 3C-SiC (001) substrates. The electric characteristics of the MIS structures are measured by capacitance and admittance spectroscopy techniques. From the hysteresis in the capacitance-voltage curves and the peak height of the conductance G{sub p} -{omega} frequency curves the interface state densities are calculated. We find interface traps about 0.3 eV below the conduction band. The density of these traps is D{sub it} = 2.5x10{sup 11} cm{sup -2}eV{sup -1}. This is one order of magnitude lower than in MIS structures with a Si{sub 3}N{sub 4} insulator produced by plasma enhanced vapour deposition and two orders of magnitude lower than in MIS structures on c-GaN with SiO{sub 2} as insulator (copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)
Non-spherical micelles in an oil-in-water cubic phase
DEFF Research Database (Denmark)
Leaver, M.; Rajagopalan, V.; Ulf, O.
2000-01-01
phase, both with and without SDS, was established by NMR self-diffusion. In addition H-2 NMR relaxation experiments have demonstrated that the micelles in the cubic phase are non-spherical, having grown and changed shape upon formation of the cubic phase from the micellar solution. Small angle...... associated with the micellar cubic phase, Pm3n and Fd3m. The micellar volumes calculated for these space groups are similar and are consistent with a change in micellar geometry from spherical to prolate.......The cubic phase formed between the microemulsion and hexagonal phases of the ternary pentaethylene glycol dodecyl ether (C12E5)-decane-water system and that doped with small amounts of sodium dodecylsulfate (SDS) have been investigated. The presence of discrete oil-swollen micelles in the cubic...
On tension-compression asymmetry in ultrafine-grained and nanocrystalline metals
Gurses, Ercan; El Sayed, Tamer S.
2010-01-01
We present a physically motivated computational study explaining the tension/compression (T/C) asymmetry phenomenon in nanocrystalline (nc) and ultrafine-grained (ufg) face centered cubic (fcc) metals utilizing a variational constitutive model where
Role of Adsorption Phenomena in Cubic Tricalcium Aluminate Dissolution.
Myers, Rupert J; Geng, Guoqing; Li, Jiaqi; Rodríguez, Erich D; Ha, Juyoung; Kidkhunthod, Pinit; Sposito, Garrison; Lammers, Laura N; Kirchheim, Ana Paula; Monteiro, Paulo J M
2017-01-10
The workability of fresh Portland cement (PC) concrete critically depends on the reaction of the cubic tricalcium aluminate (C 3 A) phase in Ca- and S-rich pH >12 aqueous solution, yet its rate-controlling mechanism is poorly understood. In this article, the role of adsorption phenomena in C 3 A dissolution in aqueous Ca-, S-, and polynaphthalene sulfonate (PNS)-containing solutions is analyzed. The zeta potential and pH results are consistent with the isoelectric point of C 3 A occurring at pH ∼12 and do not show an inversion of its electric double layer potential as a function of S or Ca concentration, and PNS adsorbs onto C 3 A, reducing its zeta potential to negative values at pH >12. The S and Ca K-edge X-ray absorption spectroscopy (XAS) data obtained do not indicate the structural incorporation or specific adsorption of SO 4 2- on the partially dissolved C 3 A solids analyzed. Together with supporting X-ray ptychography and scanning electron microscopy results, a model for C 3 A dissolution inhibition in hydrated PC systems is proposed whereby the formation of an Al-rich leached layer and the complexation of Ca-S ion pairs onto this leached layer provide the key inhibiting effect(s). This model reconciles the results obtained here with the existing literature, including the inhibiting action of macromolecules such as PNS and polyphosphonic acids upon C 3 A dissolution. Therefore, this article advances the understanding of the rate-controlling mechanism in hydrated C 3 A and thus PC systems, which is important to better controlling the workability of fresh PC concrete.
Study of nonlinear waves described by the cubic Schroedinger equation
International Nuclear Information System (INIS)
Walstead, A.E.
1980-01-01
The cubic Schroedinger equation (CSE) is ubiquitous as a model equation for the long-time evolution of finite-amplitude near-monochromatic dispersive waves. It incorporates the effects of the radiation field pressure on the constitutive properties of the supporting medium in a self-consistent manner. The properties of the uniformly transiating periodic wave solutions of the one-dimensional CSE are studied here. These (so-called cnoidal) waves are characterized by the values of four parameters. Whitham's averaged variational principle is used to derive a system of quasilinear evolution equations (the modulational equations) for the values of these parameters when they are slowly varying in space and time. Explicit expressions for the characteristic velocities of the modulational equations are obtained for the full set of cnoidal waves. Riemann invariants are obtained for several limits for the stable case, and growth rates are obtained for several limits, including the solitary wave chain, for the unstable case. The results for several nontrivial limiting cases agree with those obtained by independent methods by others. The dynamics of the CSE generalized to two spatial dimensions are studied for the unstable case. A large class of similarity solutions with cylindrical symmetry are obtained systematically using infinitesimal transformation group techniques. The methods are adapted to obtain the symmetries of the action functional of the CSE and to deduce nine integral invariants. A numerical study of the self-similar solutions reveals that they are modulationally unstable and that singularities dominate the dynamics of the CSE in two dimensions. The CSE is derived using perturbation theory for a specific problem in plasma physics: the evolution of the envelope of a near-monochromatic electromagnetic wave in a cold magnetized plasma. 13 figures, 2 tables
Study of nonlinear waves described by the cubic Schroedinger equation
Energy Technology Data Exchange (ETDEWEB)
Walstead, A.E.
1980-03-12
The cubic Schroedinger equation (CSE) is ubiquitous as a model equation for the long-time evolution of finite-amplitude near-monochromatic dispersive waves. It incorporates the effects of the radiation field pressure on the constitutive properties of the supporting medium in a self-consistent manner. The properties of the uniformly transiating periodic wave solutions of the one-dimensional CSE are studied here. These (so-called cnoidal) waves are characterized by the values of four parameters. Whitham's averaged variational principle is used to derive a system of quasilinear evolution equations (the modulational equations) for the values of these parameters when they are slowly varying in space and time. Explicit expressions for the characteristic velocities of the modulational equations are obtained for the full set of cnoidal waves. Riemann invariants are obtained for several limits for the stable case, and growth rates are obtained for several limits, including the solitary wave chain, for the unstable case. The results for several nontrivial limiting cases agree with those obtained by independent methods by others. The dynamics of the CSE generalized to two spatial dimensions are studied for the unstable case. A large class of similarity solutions with cylindrical symmetry are obtained systematically using infinitesimal transformation group techniques. The methods are adapted to obtain the symmetries of the action functional of the CSE and to deduce nine integral invariants. A numerical study of the self-similar solutions reveals that they are modulationally unstable and that singularities dominate the dynamics of the CSE in two dimensions. The CSE is derived using perturbation theory for a specific problem in plasma physics: the evolution of the envelope of a near-monochromatic electromagnetic wave in a cold magnetized plasma. 13 figures, 2 tables.
Shearman, Gemma C; Khoo, Bee J; Motherwell, Mary-Lynn; Brakke, Kenneth A; Ces, Oscar; Conn, Charlotte E; Seddon, John M; Templer, Richard H
2007-06-19
Inverse bicontinuous cubic lyotropic phases are a complex solution to the dilemma faced by all self-assembled water-amphiphile systems: how to satisfy the incompatible requirements for uniform interfacial curvature and uniform molecular packing. The solution reached in this case is for the water-amphiphile interfaces to deform hyperbolically onto triply periodic minimal surfaces. We have previously suggested that although the molecular packing in these structures is rather uniform the relative phase behavior of the gyroid, double diamond, and primitive inverse bicontinuous cubic phases can be understood in terms of subtle differences in packing frustration. In this work, we have calculated the packing frustration for these cubics under the constraint that their interfaces have constant mean curvature. We find that the relative packing stress does indeed differ between phases. The gyroid cubic has the least packing stress, and at low water volume fraction, the primitive cubic has the greatest packing stress. However, at very high water volume fraction, the double diamond cubic becomes the structure with the greatest packing stress. We have tested the model in two ways. For a system with a double diamond cubic phase in excess water, the addition of a hydrophobe may release packing frustration and preferentially stabilize the primitive cubic, since this has previously been shown to have lower curvature elastic energy. We have confirmed this prediction by adding the long chain alkane tricosane to 1-monoolein in excess water. The model also predicts that if one were able to hydrate the double diamond cubic to high water volume fractions, one should destabilize the phase with respect to the primitive cubic. We have found that such highly swollen metastable bicontinuous cubic phases can be formed within onion vesicles. Data from monoelaidin in excess water display a well-defined transition, with the primitive cubic appearing above a water volume fraction of 0.75. Both of
International Nuclear Information System (INIS)
Tamura, R.; Shibata, K.; Nishimoto, K.; Takeuchi, S.; Edagawa, K.; Saitoh, K.; Isobe, M.; Ueda, Y.
2005-01-01
An antiparallel orientational transition is reported for an intermetallic compound, i.e., Cd 6 Ca crystal, which is a 1/1-1/1-1/1 crystalline approximant to the icosahedral quasicrystal Cd 5.7 Ca. A group theoretical analysis based on the Landau theory predicts that the space group of the low-temperature phase is either C2/c or C2/m, in good agreement with the observations. Accordingly, two types of orientational orderings of Cd 4 tetrahedra, which are located in the center of icosahedral clusters, may occur below 100 K: In both cases, the Cd 4 tetrahedra are orientationally ordered in an antiparallel fashion along the [110] direction of the high temperature body-centered-cubic phase. Such a transition in a metal is reminiscent of orientational transitions in molecular solids
Radiation response of cubic mesoporous silicate and borosilicate thin films
Manzini, Ayelén; Alurralde, Martín; Luca, Vittorio
2018-01-01
The radiation response has been studied of cubic mesoporous silicate and borosilicate thin films having different boron contents prepared using the block copolymer template Brij 58 and the dip coating technique. The degree of pore ordering of the films was analysed using low-angle X-ray diffraction and film thickness measured by X-ray reflectivity. For films calcined at 350 °C, the incorporation of boron resulted in a reproducible oscillatory variation in the d-spacing and intensity of the primary reflection as a function of boron content. A clear peak was observed in the d-spacing at 5-10 mol% boron incorporation. For borosilicate films of a given composition an overall suppression of d-spacing was observed as a function of aging time relative to films that did not contain boron. This was ascribed to a slow condensation process. The films were irradiated in pile with neutrons and with iodine ions at energies of 180 keV and 70 MeV. Neutron irradiation of the silicate thin films for periods up to 30 days and aged for 400 days resulted in little reduction in either d-spacing or intensity of the primary low-angle X-ray reflection indicating that the films retained their mesopore ordering. In contrast borosilicate films for which the B (n, α) reaction was expected to result in enhanced displacement damage showed much larger variations in X-ray parameters. For these films short irradiation times resulted in a reduction of the d-spacing and intensity of the primary reflections considerably beyond that observed through aging. It is concluded that prolonged neutron irradiation and internal α irradiation have only a small, although measurable, impact on mesoporous borosilicate thin films increasing the degree of condensation and increasing unit cell contraction. When these borosilicate films were irradiated with iodine ions, more profound changes occurred. The pore ordering of the films was significantly degraded when low energy ions were used. In some cases the degree
Study of the cubic - to - monoclinic transformation in magnesia partially stabilized zirconia
International Nuclear Information System (INIS)
Muccillo, R.
1988-01-01
The transformation of the cubic phase to the stable monoclinic phase in ZrO 2 : 3%MgO quenched from 1450 0 C to RT has been studied by X-ray diffractometry in order to explain the thermal hysteresis in the electrical conductivity. The monoclinic-to-cubic ratio has been measured for samples annealed in the 500 0 C-1000 0 C temperature range. The results show that the decrease in the cubic phase content is the main responsible for the thermal hysteresis in the electrical conductivity of the magnesia partially stabilized zirconia solid electrolytes. (author) [pt
P-union and P-intersection of neutrosophic cubic sets
Florentin Smarandache; Chang Su Kim
2015-01-01
Conditions for the P-intersection and P-intersection of falsity-external (resp. indeterminacy-external and truth-external) neutrosophic cubic sets to be an falsity-external (resp. indeterminacy-external and truth- external) neutrosophic cubic set are provided. Conditions for the P-union and the P-intersection of two truth-external (resp. indeterminacy-external and falsity-external) neutrosophic cubic sets to be a truth-internal (resp. indeterminacy-internal and falsity-internal) neutrosoph...
Structural study on cubic-tetragonal transition of CH3NH3PbI3
International Nuclear Information System (INIS)
Kawamura, Yukihiko; Mashiyama, Hiroyuki; Hasebe, Katsuhiko
2002-01-01
The cubic-tetragonal phase transition of CH 3 NH 3 PbI 3 was investigated by single crystal X-ray diffractometry. The crystal structure was refined at five temperatures in the tetragonal phase. The PbI 6 octahedron rotates around the c-axis alternatively to construct the SrTiO 3 -type tetragonal structure. A methylammonium ion is partially ordered; 24 disordered states in the cubic phase are reduced to 8. With decreasing temperature, the rotation angle of the octahedron increases monotonically, which indicates it is an order parameter of the cubic-tetragonal transition. (author)
d and f electrons in a qp-quantized cubical field
International Nuclear Information System (INIS)
Kibler, M.; Sztucki, J.
1993-03-01
A procedure for qp-quantizing a crystal-field potential V with an arbitrary symmetry G is developed. Such a procedure is applied to the case where V involves cubic components (G=0) of the degrees 4 and 6. This case corresponds to d and f electrons in a qp-quantized cubical potential. It is shown that the qp-quantization of the considered cubical potential is equivalent to a symmetry breaking of type O→D 4 . A general conjecture about this symmetry breaking phenomenon is given. (author) 21 refs
Pang, Maolin
2012-08-15
In this work, we carry out an investigation on shape-controlled growth of In III- and Ga III-based square-octahedral metal-organic frameworks (soc-MOFs). In particular, controllable crystal morphological evolution from simple cubes to complex octadecahedra has been achieved, and resultant highly uniform crystal building blocks promise new research opportunities for preparation of self-assembled MOF materials and related applications. © 2012 American Chemical Society.
Pang, Maolin; Cairns, Amy; Liu, Yunling; Belmabkhout, Youssef; Zeng, Huachun; Eddaoudi, Mohamed
2012-01-01
In this work, we carry out an investigation on shape-controlled growth of In III- and Ga III-based square-octahedral metal-organic frameworks (soc-MOFs). In particular, controllable crystal morphological evolution from simple cubes to complex octadecahedra has been achieved, and resultant highly uniform crystal building blocks promise new research opportunities for preparation of self-assembled MOF materials and related applications. © 2012 American Chemical Society.
The effect of voids on the hardening of body-centered cubic Fe
Energy Technology Data Exchange (ETDEWEB)
Nakai, Ryosuke, E-mail: ryosuke.nakai@jupiter.qse.tohoku.ac.jp [Department of Quantum Science and Energy Engineering, Tohoku University, 6-6-01-2, Aramaki-Aza-Aoba, Aobaku, Sendai, Miyagi, 980-8579 (Japan); Yabuuchi, Kiyohiro, E-mail: k-yabuuchi@iae.kyoto-u.ac.jp [Department of Quantum Science and Energy Engineering, Tohoku University, 6-6-01-2, Aramaki-Aza-Aoba, Aobaku, Sendai, Miyagi, 980-8579 (Japan); Institute of Advanced Energy, Kyoto University, Gokasho, Uji, Kyoto, 611-0011 (Japan); Nogami, Shuhei, E-mail: shuhei.nogami@qse.tohoku.ac.jp [Department of Quantum Science and Energy Engineering, Tohoku University, 6-6-01-2, Aramaki-Aza-Aoba, Aobaku, Sendai, Miyagi, 980-8579 (Japan); Hasegawa, Akira, E-mail: akira.hasegawa@qse.tohoku.ac.jp [Department of Quantum Science and Energy Engineering, Tohoku University, 6-6-01-2, Aramaki-Aza-Aoba, Aobaku, Sendai, Miyagi, 980-8579 (Japan)
2016-04-01
The mechanical properties of metals are affected by various types of defects. Hardening is usually described through the interaction between dislocations and obstacles, in the so-called line tension theory. The strength factor in the line tension theory represents the resistance of a defect against the dislocation motion. In order to understand hardening from the viewpoint of the microstructure, an accurate determination of the strength factor of different types of defects is essential. In the present study, the strength factor of voids in body-centered cubic (BCC) Fe was investigated by two different approaches: one based on the Orowan equation to link the measured hardness with the average size and density of voids, and the other involving direct observation of the interaction between dislocations and voids by transmission electron microscope (TEM). The strength factor of voids induced by ion irradiation estimated by the Orowan equation was 0.6, whereas the strength factor estimated by the direct TEM approach was 0.8. The difference in the strength factors measured by the two approaches is due to the positional relationship between dislocations and voids: the central region of a void is stronger than the tip. Moreover, the gliding plane and the direction of dislocation may also affect the strength factor of voids. This study determined the strength factor of voids in BCC Fe accurately, and suggested that the contribution of voids to the irradiation hardening is larger than that of dislocation loops and Cu-rich precipitates. - Highlights: • The strength factor of voids in BCC Fe was experimentally investigated. • The strength factor of voids estimated by the line tension theory was 0.6. • The strength factor of voids estimated by the bowing angle of dislocations was 0.8. • The different strength factors are due to the positional relationship.
Optically resonant magneto-electric cubic nanoantennas for ultra-directional light scattering
Energy Technology Data Exchange (ETDEWEB)
Sikdar, Debabrata, E-mail: debabrata.sikdar@monash.edu; Premaratne, Malin [Advanced Computing and Simulation Laboratory (A chi L), Department of Electrical and Computer Systems Engineering, Monash University, Clayton 3800, Victoria (Australia); Cheng, Wenlong [Department of Chemical Engineering, Faculty of Engineering, Monash University, Clayton 3800, Victoria (Australia); The Melbourne Centre for Nanofabrication, 151 Wellington Road, Clayton 3168, Victoria (Australia)
2015-02-28
Cubic dielectric nanoparticles are promising candidates for futuristic low-loss, ultra-compact, nanophotonic applications owing to their larger optical coefficients, greater packing density, and relative ease of fabrication as compared to spherical nanoparticles; besides possessing negligible heating at nanoscale in contrast to their metallic counterparts. Here, we present the first theoretical demonstration of azimuthally symmetric, ultra-directional Kerker's-type scattering of simple dielectric nanocubes in visible and near-infrared regions via simultaneous excitation and interference of optically induced electric- and magnetic-resonances up to quadrupolar modes. Unidirectional forward-scattering by individual nanocubes is observed at the first generalized-Kerker's condition for backward-scattering suppression, having equal electric- and magnetic-dipolar responses. Both directionality and magnitude of these unidirectional-scattering patterns get enhanced where matching electric- and magnetic-quadrupolar responses spectrally overlap. While preserving azimuthal-symmetry and backscattering suppression, a nanocube homodimer provides further directionality improvement for increasing interparticle gap, but with reduced main-lobe magnitude due to emergence of side-scattering lobes from diffraction-grating effect. We thoroughly investigate the influence of interparticle gap on scattering patterns and propose optimal range of gap for minimizing side-scattering lobes. Besides suppressing undesired side-lobes, significant enhancement in scattering magnitude and directionality is attained with increasing number of nanocubes forming a linear chain. Optimal directionality, i.e., the narrowest main-scattering lobe, is found at the wavelength of interfering quadrupolar resonances; whereas the largest main-lobe magnitude is observed at the wavelength satisfying the first Kerker's condition. These unique optical properties of dielectric nanocubes thus can
Energy Technology Data Exchange (ETDEWEB)
Chen, Shouhui, E-mail: csh2k@jxnu.edu.cn; Zhou, Rihui; Chen, Yaqin; Fu, Yuanyuan; Li, Ping; Song, Yonghai; Wang, Li, E-mail: lwanggroup@aliyun.com [Jiangxi Normal University, College of Chemistry and Chemical Engineering (China)
2017-04-15
In this work, Prussian blue nanocrystals, a kind of cubic metal-organic frameworks, was firstly covered by a uniform layer of resorcinol-formaldehyde (RF) resin, and then followed with heat treatment at different pyrolysis temperatures. The effects of pyrolysis temperature on the morphologies, phase, pore size, and electrochemical performance of the pyrolysis products were studied in this work. The composite generated at 600 {sup ∘}C, FexC600, was a hollow cubic composite of Fe{sub 3}O{sub 4} covered by a thin RF-derived carbon layer. The carbon layer on FexC600 was a robust and conductive protective layer, which can accommodate Fe{sub 3}O{sub 4} NPs and withstand the huge volume change of Fe{sub 3}O{sub 4} during the process of discharge and charge. When used as anodes for lithium-ion batteries, FexC600 showed excellent electrochemical performance. It delivered a discharge capacity of 1126 mAh g{sup −1} with a coulombic efficiency of 98.8% at the current density of 100 mA g{sup −1} after 100 times discharge/charge cycling. It even delivered a capacity of 492 mAh g{sup −1} at the current density of 500 mA g{sup −1}. This cubic hollow composite would be a promising alternative anode material for lithium-ion batteries.
Energy Technology Data Exchange (ETDEWEB)
Deluque Toro, C.E., E-mail: deluquetoro@gmail.com [Grupo de Nuevos Materiales, Universidad Popular del Cesar, Valledupar (Colombia); Rodríguez M, Jairo Arbey [Grupo de Estudios de Materiales—GEMA, Departamento de Física, Universidad Nacional de Colombia, AA 5997 Bogotá DC (Colombia); Landínez Téllez, D.A. [Grupo de Física de Nuevos Materiales, Departamento de Física, Universidad Nacional de Colombia, AA 5997 Bogotá DC (Colombia); Moreno Salazar, N.O. [Departamento de Física, Universidade Federal de Sergipe (Brazil); Roa-Rojas, J. [Grupo de Física de Nuevos Materiales, Departamento de Física, Universidad Nacional de Colombia, AA 5997 Bogotá DC (Colombia)
2014-12-15
The Ba{sub 2}YTaO{sub 6} double perovskite presents a transition from cubic (Fm−3m) to tetragonal structure (I4/m) at high temperature. In this work, we present a detailed study of the structural and electronic properties of the double perovskite Ba{sub 2}YTaO{sub 6} in space group Fm−3m and I4/m. Calculations were made with the Full-Potential Linear Augmented Plane Wave method (FP-LAPW) within the framework of the Density Functional Theory (DFT) with exchange and correlation effects in the Generalized Gradient (GGA) and Local Density (LDA) approximations. From the minimization of energy as a function of volume and the fitting of the Murnaghan equation some structural characteristics were determined as, for example, total energy, lattice parameter (a=8.50 Å in cubic phase and a=5.985 Å and c=8.576 Å in tetragonal), bulk modulus (135.6 GPa in cubic phase and 134.1 GPa in tetragonal phase) and its derivative. The study of the electronic characteristics was performed from the analysis of the electronic density of states (DOS). We find a non-metallic behavior for this with a direct band gap of approximately 3.5 eV and we found that the Ba{sub 2}YTaO{sub 6} (I4/m) phase is the most stable one. {sup ©} 2013 Elsevier Science. All rights reserved.
Stefan, Mariana; Vlaicu, Ioana Dorina; Nistor, Leona Cristina; Ghica, Daniela; Nistor, Sergiu Vasile
2017-12-01
We have shown in previous investigations that the low temperature collective magnetism observed in mesoporous cubic ZnS:Mn nanocrystalline powders prepared by colloidal synthesis, with nominal doping concentrations above 0.2 at.%, is due to the formation of Mn2+ clusters with distributed antiferromagnetic coupling localized in an amorphous phase found between the cubic ZnS:Mn nanocrystals. Here we investigate the composition, origin and thermal annealing behavior of this amorphous phase in such a mesoporous ZnS:Mn sample doped with 5 at.% Mn nominal concentration. Correlated analytical transmission electron microscopy, multifrequency electron paramagnetic resonance and Fourier transform infrared spectroscopy data show that the amorphous nanomaterial consists of unreacted precursor hydrated zinc and manganese acetates trapped inside the pores and on the surface of the cubic ZnS nanocrystals. The decomposition of the acetates under isochronal annealing up to 270 °C, where the mesoporous structure is still preserved, lead to changes in the nature and strength of the magnetic interactions between the aggregated Mn2+ ions. These results strongly suggest the possibility to modulate the magnetic properties of such transition metal ions doped II-VI mesoporous structures by varying the synthesis conditions and/or by post-synthesis thermochemical treatments.
International Nuclear Information System (INIS)
Chen, Shouhui; Zhou, Rihui; Chen, Yaqin; Fu, Yuanyuan; Li, Ping; Song, Yonghai; Wang, Li
2017-01-01
In this work, Prussian blue nanocrystals, a kind of cubic metal-organic frameworks, was firstly covered by a uniform layer of resorcinol-formaldehyde (RF) resin, and then followed with heat treatment at different pyrolysis temperatures. The effects of pyrolysis temperature on the morphologies, phase, pore size, and electrochemical performance of the pyrolysis products were studied in this work. The composite generated at 600 "∘C, FexC600, was a hollow cubic composite of Fe_3O_4 covered by a thin RF-derived carbon layer. The carbon layer on FexC600 was a robust and conductive protective layer, which can accommodate Fe_3O_4 NPs and withstand the huge volume change of Fe_3O_4 during the process of discharge and charge. When used as anodes for lithium-ion batteries, FexC600 showed excellent electrochemical performance. It delivered a discharge capacity of 1126 mAh g"−"1 with a coulombic efficiency of 98.8% at the current density of 100 mA g"−"1 after 100 times discharge/charge cycling. It even delivered a capacity of 492 mAh g"−"1 at the current density of 500 mA g"−"1. This cubic hollow composite would be a promising alternative anode material for lithium-ion batteries.
International Nuclear Information System (INIS)
Deluque Toro, C.E.; Rodríguez M, Jairo Arbey; Landínez Téllez, D.A.; Moreno Salazar, N.O.; Roa-Rojas, J.
2014-01-01
The Ba 2 YTaO 6 double perovskite presents a transition from cubic (Fm−3m) to tetragonal structure (I4/m) at high temperature. In this work, we present a detailed study of the structural and electronic properties of the double perovskite Ba 2 YTaO 6 in space group Fm−3m and I4/m. Calculations were made with the Full-Potential Linear Augmented Plane Wave method (FP-LAPW) within the framework of the Density Functional Theory (DFT) with exchange and correlation effects in the Generalized Gradient (GGA) and Local Density (LDA) approximations. From the minimization of energy as a function of volume and the fitting of the Murnaghan equation some structural characteristics were determined as, for example, total energy, lattice parameter (a=8.50 Å in cubic phase and a=5.985 Å and c=8.576 Å in tetragonal), bulk modulus (135.6 GPa in cubic phase and 134.1 GPa in tetragonal phase) and its derivative. The study of the electronic characteristics was performed from the analysis of the electronic density of states (DOS). We find a non-metallic behavior for this with a direct band gap of approximately 3.5 eV and we found that the Ba 2 YTaO 6 (I4/m) phase is the most stable one. © 2013 Elsevier Science. All rights reserved
Explicit Gaussian quadrature rules for C^1 cubic splines with symmetrically stretched knot sequence
Ait-Haddou, Rachid; Barton, Michael; Calo, Victor M.
2015-01-01
We provide explicit expressions for quadrature rules on the space of C^1 cubic splines with non-uniform, symmetrically stretched knot sequences. The quadrature nodes and weights are derived via an explicit recursion that avoids an intervention
Modeling the dispersion of atmospheric pollution using cubic splines and chapeau functions
Energy Technology Data Exchange (ETDEWEB)
Pepper, D W; Kern, C D; Long, P E
1979-01-01
Two methods that can be used to solve complex, three-dimensional, advection-diffusion transport equations are investigated. A quasi-Lagrangian cubic spline method and a chapeau function method are compared in advecting a passive scalar. The methods are simple to use, computationally fast, and reasonably accurate. Little numerical dissipation is manifested by the schemes. In simple advection tests with equal mesh spacing, the chapeau function method maintains slightly more accurate peak values than the cubic spline method. In tests with unequal mesh spacing, the cubic spline method has less noise, but slightly more damping than the standard chapeau method has. Both cubic splines and chapeau functions can be used to solve the three-dimensional problem of gaseous emissions dispersion without excessive programing complexity or storage requirements. (10 diagrams, 39 references, 2 tables)
Unified treatment of coupled optical and acoustic phonons in piezoelectric cubic materials
DEFF Research Database (Denmark)
Willatzen, Morten; Wang, Zhong Lin
2015-01-01
A unified treatment of coupled optical and acoustic phonons in piezoelectric cubic materials is presented whereby the lattice displacement vector and the internal ionic displacement vector are found simultaneously. It is shown that phonon couplings exist in pairs only; either between the electric...... piezoelectricity in a cubic structured material slab. First, it is shown that isolated optical phonon modes generally cannot exist in piezoelectric cubic slabs. Second, we prove that confined acousto-optical phonon modes only exist for a discrete set of in-plane wave numbers in piezoelectric cubic slabs. Third...... potential and the lattice displacement coordinate perpendicular to the phonon wave vector or between the two other lattice displacement components. The former leads to coupled acousto-optical phonons by virtue of the piezoelectric effect. We then establish three new conjectures that entirely stem from...
Physics and Technology of Transparent Ceramic Armor: Sintered Al2O3 vs Cubic Materials
National Research Council Canada - National Science Library
Krell, Andreas; Hutzler, Thomas; Klimke, Jens
2006-01-01
Sintered sub-micrometer alumina (alpha-Al2O3) is the hardest transparent armor. However, its trigonal structure gives rise to a strong thickness effect that makes thicker components translucent. Cubic ceramics (no birefringence...
Effects of quadratic and cubic nonlinearities on a perfectly tuned parametric amplifier
DEFF Research Database (Denmark)
Neumeyer, Stefan; Sorokin, Vladislav; Thomsen, Jon Juel
2016-01-01
We consider the performance of a parametric amplifier with perfect tuning (two-to-one ratio between the parametric and direct excitation frequencies) and quadratic and cubic nonlinearities. A forced Duffing–Mathieu equation with appended quadratic nonlinearity is considered as the model system......, and approximate analytical steady-state solutions and corresponding stabilities are obtained by the method of varying amplitudes. Some general effects of pure quadratic, and mixed quadratic and cubic nonlinearities on parametric amplification are shown. In particular, the effects of mixed quadratic and cubic...... nonlinearities may generate additional amplitude–frequency solutions. In this case an increased response and a more phase sensitive amplitude (phase between excitation frequencies) is obtained, as compared to the case with either pure quadratic or cubic nonlinearity. Furthermore, jumps and bi...
Cubic and quartic planar differential systems with exact algebraic limit cycles
Directory of Open Access Journals (Sweden)
Ahmed Bendjeddou
2011-01-01
Full Text Available We construct cubic and quartic polynomial planar differential systems with exact limit cycles that are ovals of algebraic real curves of degree four. The result obtained for the cubic case generalizes a proposition of [9]. For the quartic case, we deduce for the first time a class of systems with four algebraic limit cycles and another for which nested configurations of limit cycles occur.
Forbidden transitions in the EPR spectrum of the ferric ion cubic symmetry in magesium oxide
Energy Technology Data Exchange (ETDEWEB)
de Biasi, R S [Instituto Militar de Engenharia, Rio de Janeiro (Brazil). Secao de Engenharia e Ciencia dos Materiais
1979-03-01
The spectrum of the ..delta..m /sub s/=2 transitions of Fe/sup 3 +/ in cubic symmetry sites in MgO has been measured at 9.25GHz. The orientation dependence of the transitions is found to be consistent with a spin Hamiltonian of cubic symmetry with g=2.0037(isotropic), a=0.0205/sup +/-0.00005 cm/sup -1/.
Sridhar Budhi; Chia-Ming Wu; Dan Zhao; Ranjit T. Koodali
2015-01-01
Titania containing cubic MCM-48 mesoporous materials were synthesized successfully at room temperature by a modified Stöber method. The integrity of the cubic mesoporous phase was retained even at relatively high loadings of titania. The TiO2-MCM-48 materials were extensively characterized by a variety of physico-chemical techniques. The physico-chemical characterization indicate that Ti4+ ions can be substituted in framework tetrahedral positions. The relative amount of Ti4+ ions in tetrahe...
Extraordinary high strength Ti-Zr-Ta alloys through nanoscaled, dual-cubic spinodal reinforcement.
Biesiekierski, Arne; Ping, Dehai; Li, Yuncang; Lin, Jixing; Munir, Khurram S; Yamabe-Mitarai, Yoko; Wen, Cuie
2017-04-15
While titanium alloys represent the current state-of-the-art for orthopedic biomaterials, concerns still remain over their modulus. Circumventing this via increased porosity requires high elastic admissible strains, yet also limits traditional thermomechanical strengthening techniques. To this end, a novel β-type Ti-Zr-Ta alloy system, comprised of Ti-45Zr-10Ta, Ti-40Zr-14Ta, Ti-35Zr-18Ta and Ti-30Zr-22Ta, was designed and characterized mechanically and microstructurally. As-cast, this system displayed extremely high yield strengths and elastic admissible strains, up to 1.4GPa and potentially 1.48%, respectively. This strength was attributed to a nanoscaled, cuboidal structure of semi-coherent, dual body-centered cubic (BCC) phases, arising from the thermodynamics of interaction between Ta and Zr; this morphology occurring with dual BCC-phases is heretofore unreported in Ti-based alloys. Further, cell proliferation investigated by MTS assay suggests this was achieved without sacrificing biocompatibility, with no significant difference to either empty-well or commercially-pure Ti controls noted. The current research details microstructural, mechanical, and biological investigations into four novel biomedical alloys in a hitherto uninvestigated region of the Ti-Zr-Ta alloy system; Ti-45Zr-10Ta, Ti-40Zr-14Ta, Ti-35Zr-18Ta and Ti-30Zr-22Ta. We find that the investigated alloys display 0.2% yield strengths of up to 1.40GPa and elastic admissible strains of up to 1.48%, along with biological properties comparable to that seen in the conventional metallic biomaterial ASTM Grade-2 CP-Ti, achieved in the complete absence of traditional thermomechanical processing techniques. This is attributed to the presence of a dual-BCC cuboidal nanostructure, achieved via spinodal decomposition; while similar structures have been reported in e.g. Ni-based superalloys, we believe this is the first such structure investigated in a Ti-based material. As such, this work is felt to be of
On Application of Non-cubic EoS to Compositional Reservoir Simulation
DEFF Research Database (Denmark)
Yan, Wei; Michelsen, Michael Locht; Stenby, Erling Halfdan
Compositional reservoir simulation uses almost exclusively cubic equations of state (EoS) such as the SRK EoS and the PR EoS. This is in contrast with process simulation in the downstream industry where more recent and advanced thermodynamic models are quickly adopted. Many of these models are non-cubic...... EoS, such as the PC-SAFT EoS. A major reason for the use of the conventional cubic EoS in reservoir simulation is the concern over computation time. Flash computation is the most time consuming part in compositional reservoir simulation, and the extra complexity of the non-cubic EoS may significantly...... increase the time consumption. In addition to this, the non-cubic EoS also needs a C7+ characterization. The main advantage of the non-cubic EoS is that it provides for a more accurate descrition of fluid properties, and it is therefore of interest to investigate the computational aspects of using...
International Nuclear Information System (INIS)
Kostela, J.; Elmgren, M.; Almgren, M.
2005-01-01
The objective of this study was to investigate the electrochemical behaviour of the divalent redox active surfactant, N-cetyl-N'-methylviologen (CMV), in bicontinuous cubic and lamellar phases. The liquid crystalline phases were prepared from the system glycerolmonooleate (GMO)-water (and brine)-cationic surfactant. A comparison of the phase behaviour of GMO with the monovalent cetyltrimethylammonium bromide (CTAB) and the divalent CMV surfactant showed that the surfactants gave about the same effect at the same surface charge density. The electrochemical measurements were made with a mixture of CTAB and CMV as the surfactant. Cyclic voltammetry was used to study the electrochemistry of CMV incorporated in the cubic and lamellar phases that were spread on a gold electrode. The E 0 -values in the cubic samples were more negative (-0.55 V versus SCE) than in the lamellar samples (-0.53 V versus SCE). This can be explained by the higher charge density in the lamellar phase. The diffusion coefficients were also measured in the cubic phase. The mass transport is slowed down about fifty times in the cubic phase compared to in the pure electrolyte. The concentration dependence on the diffusion coefficient was also investigated. No electron hopping could be observed, which suggest that diffusional movement of the redox probe is the main source of charge transport. By placing the samples on a conducting glass slide, spectroelectrochemical investigations were performed. In the lamellar phase strong dimerization was detected at high concentration of viologen, but much less in the cubic phase
International Nuclear Information System (INIS)
Gorondy-Novak, Sofia Maria
2017-01-01
The presence of helium produced during the operation of future fast reactors and fusion reactors in core structural materials induces a deterioration of their mechanical properties (hardening, swelling, embrittlement). In order to pursue the development of the metallic structural alloys, it is necessary to comprehend the He interaction with the metal lattice thus the point in common is the study of the metallic components with body-centered cubic structure (bcc) of future alloys, such as iron and/or vanadium. Ion implantation of ions "4He was employed with the aim of simulating the damaging effects associated with the helium accumulation, the point defects' creation (vacancies, self-interstitials) and the He cluster formation in future reactors. Helium evolution in pure iron and pure vanadium has been revealed from the point of view of the trapping sites' nature and well as the helium migration mechanisms and the nucleation/growth of bubbles. These phenomena were studied by coupling different complementary techniques. Despite of the fact that some mechanisms involved seem to be similar for both bcc metals, the comparison between the helium behavior in iron and vanadium shows certain differences. Microstructural defects, including grain boundaries and implanted helium concentration (dose) in both bcc metals will play significant roles on the helium behavior at high temperature. The acquired experimental data coupled with simulation methods contribute to the future development in terms of kinetic and thermodynamic data management of helium behavior in the metal components of the alloys of nuclear interest. (author) [fr
Growth and characterization of cubic AlGaN/GaN based devices
Energy Technology Data Exchange (ETDEWEB)
Potthast, S.
2006-11-15
Cubic GaN and AlGaN layers are grown by radio frequency plasma assisted molecular beam epitaxy on freestanding 3C-SiC (001) substrates. Detailed analysis of the substrate quality reveal a direct dependence of the roughness of the 3C-SiC on the dislocation density. Additionally a strong influence of the substrate quality on the quality of cubic GaN layers is found. GaN, AlGaN and AlN buffer layers grown at different temperatures are used to improve the structural properties of the c-GaN buffer. Best values are obtained for AlN buffers deposited at T{sub Subs}=720 C. Furthermore, the growth temperature of the buffer itself is varied. Optimized results are found for T{sub Subs}=720 C grown under a Ga coverage of one monolayer. On top of the GaN buffer, AlGaN films (0
Metallic substrates for high temperature superconductors
Truchan, Thomas G.; Miller, Dean J.; Goretta, Kenneth C.; Balachandran, Uthamalingam; Foley, Robert
2002-01-01
A biaxially textured face-centered cubic metal article having grain boundaries with misorientation angles greater than about 8.degree. limited to less than about 1%. A laminate article is also disclosed having a metal substrate first rolled to at least about 95% thickness reduction followed by a first annealing at a temperature less than about 375.degree. C. Then a second rolling operation of not greater than about 6% thickness reduction is provided, followed by a second annealing at a temperature greater than about 400.degree. C. A method of forming the metal and laminate articles is also disclosed.
Mastail, C.; David, M.; Nita, F.; Michel, A.; Abadias, G.
2017-11-01
We use ab initio calculations to determine the preferred nucleation sites and migration pathways of Ti, Al and N adatoms on cubic NaCl-structure (B1) AlN surfaces, primary inputs towards a further thin film growth modelling of the TiAlN alloy system. The potential energy landscape is mapped out for both metallic species and nitrogen adatoms for two different AlN surface orientations, (001) and (110), using density functional theory. For all species, the adsorption energies on AlN(011) surface are larger than on AlN(001) surface. Ti and Al adatom adsorption energy landscapes determined at 0 K by ab initio show similar features, with stable binding sites being located in, or near, epitaxial surface positions, with Ti showing a stronger binding compared to Al. In direct contrast, N adatoms (Nad) adsorb preferentially close to N surface atoms (Nsurf), thus forming strong N2-molecule-like bonds on both AlN(001) and (011). Similar to N2 desorption mechanisms reported for other cubic transition metal nitride surfaces, in the present work we investigate Nad/Nsurf desorption on AlN(011) using a drag calculation method. We show that this process leaves a Nsurf vacancy accompanied with a spontaneous surface reconstruction, highlighting faceting formation during growth.
Plasma deposition of cubic boron nitride films from non-toxic material at low temperatures
International Nuclear Information System (INIS)
Karim, M.Z.; Cameron, D.C.; Murphy, M.J.; Hashmi, M.S.J.
1991-01-01
Boron nitride has become the focus of a considerable amount of interest because of its properties which relate closely to those of carbon. In particular, the cubic nitride phase has extreme hardness and very high thermal conductivity similar to the properties of diamond. The conventional methods of synthesis use the highly toxic and inflammable gas diborane (B 2 H 6 ) as the reactant material. A study has been made of the deposition of thin films of boron nitride (BN) using non-toxic material by the plasma-assisted chemical vapour deposition technique. The source material was borane-ammonia (BH 3 -NH 3 ) which is a crystalline solid at room temperature with a high vapour pressure. The BH 3 -NH 3 vapour was decomposed in a 13.56 MHz nitrogen plasma coupled either inductively or capacitively with the system. The composition of the films was assessed by measuring their IR absorption when deposited on silicon and KBr substrates. The hexagonal (graphitic) and cubic (diamond-like) allotropes can be distinguished by their characteristic absorption bands which occur at 1365 and 780 cm -1 (hexagonal) and 1070 cm -1 (cubic). We have deposited BN films consisting of a mixture of hexagonal and cubic phases; the relative content of the cubic phase was found to be directly dependent on r.f. power and substrate bias. (orig.)
Phase transformation of metastable cubic γ-phase in U-Mo alloys
International Nuclear Information System (INIS)
Sinha, V.P.; Hegde, P.V.; Prasad, G.J.; Dey, G.K.; Kamath, H.S.
2010-01-01
Over the past decade considerable efforts have been put by many fuel designers to develop low enriched uranium (LEU 235 ) base U-Mo alloy as a potential fuel for core conversion of existing research and test reactors which are running on high enriched uranium (HEU > 85%U 235 ) fuel and also for the upcoming new reactors. U-Mo alloy with minimum 8 wt% molybdenum shows excellent metastability with cubic γ-phase in cast condition. However, it is important to characterize the decomposition behaviour of metastable cubic γ-uranium in its equilibrium products for in reactor fuel performance point of view. The present paper describes the phase transformation behaviour of cubic γ-uranium phase in U-Mo alloys with three different molybdenum compositions (i.e. 8 wt%, 9 wt% and 10 wt%). U-Mo alloys were prepared in an induction melting furnace and characterized by X-ray diffraction (XRD) method for phase determination. Microstructures were developed for samples in as cast condition. The alloys were hot rolled in cubic γ-phase to break the cast structure and then they were aged at 500 o C for 68 h and 240 h, so that metastable cubic γ-uranium will undergo eutectoid decomposition to form equilibrium phases of orthorhombic α-uranium and body centered tetragonal U 2 Mo intermetallic compound. U-Mo alloy samples with different ageing history were then characterized by XRD for phase and development of microstructure.
Moreno, M.; Barriuso, M. T.; Aramburu, J. A.; García-Fernández, P.; García-Lastra, J. M.
2006-05-01
This article reviews the microscopic origin of properties due to transition-metal (TM) impurities, M, in insulator materials. Particular attention is paid to the influence of pressure upon impurity properties. Basic concepts such as the electronic localization in an MXN complex, the electrostatic potential, VR, arising from the rest of the lattice ions or the elastic coupling of the complex to the host lattice are initially exposed. The dependence of optical and magnetic parameters on the impurity-ligand distance, R, in cubic lattices is discussed in a first step. Emphasis is put on the actual origin of the R dependence of 10Dq. Examples revealing that laws for strict cubic symmetry cannot in general be transferred to lower symmetries are later given. This relevant fact is shown to come from allowed hybridizations like nd-(n+1)s as well as the influence of VR. As a salient feature the different colour in ruby and emerald is stressed to arise from distinct VR potentials in Al2O3 and Be3Si6Al2O18. The last part of this review deals with electronic instabilities. The phenomena associated with the Jahn-Teller (JT) effect in cubic lattices, the origin of the energy barrier among equivalent minima and the existence of coherent tunnelling in systems like MgO:Cu2+ are discussed. An increase of elastic coupling is pointed out to favour a transition from an elongated to a compressed equilibrium conformation. Interestingly the equilibrium geometry of JT ions in non-cubic lattices is shown to be controlled by mechanisms different to those in cubic systems, VR playing again a key role. The relevance of first principles calculations for clarifying the subtle mechanisms behind off-centre instabilities is also pointed out. Examples concern monovalent and divalent TM impurities in lattices with the CaF2 structure. The instability due to the transition from the ground to an excited state is finally considered. For complexes with significant elastic coupling vibrational frequencies
Numerical Simulation of Sloshing Phenomena in Cubic Tank with Multiple Baffles
Directory of Open Access Journals (Sweden)
Mi-An Xue
2012-01-01
Full Text Available A two-phase fluid flow model solving Navier-Stokes equations was employed in this paper to investigate liquid sloshing phenomena in cubic tank with horizontal baffle, perforated vertical baffle, and their combinatorial configurations under the harmonic motion excitation. Laboratory experiment of liquid sloshing in cubic tank with perforated vertical baffle was carried out to validate the present numerical model. Fairly good agreements were obtained from the comparisons between the present numerical results and the present experimental data, available numerical data. Liquid sloshing in cubic tank with multiple baffles was investigated numerically in detail under different external excitation frequencies. Power spectrum of the time series of free surface elevation was presented with the aid of fast Fourier transform technique. The dynamic impact pressures acting on the normal and parallel sidewalls were discussed in detail.
Growth of cubic InN on r-plane sapphire
International Nuclear Information System (INIS)
Cimalla, V.; Pezoldt, J.; Ecke, G.; Kosiba, R.; Ambacher, O.; Spiess, L.; Teichert, G.; Lu, H.; Schaff, W.J.
2003-01-01
InN has been grown directly on r-plane sapphire substrates by plasma-enhanced molecular-beam epitaxy. X-ray diffraction investigations have shown that the InN layers consist of a predominant zinc blende (cubic) structure along with a fraction of the wurtzite (hexagonal) phase which content increases with proceeding growth. The lattice constant for zinc blende InN was found to be a=4.986 A. For this unusual growth of a metastable cubic phase on a noncubic substrate an epitaxial relationship was proposed where the metastable zinc blende phase grows directly on the r-plane sapphire while the wurtzite phase arises as the special case of twinning in the cubic structure
Testing a generalized cubic Galileon gravity model with the Coma Cluster
Energy Technology Data Exchange (ETDEWEB)
Terukina, Ayumu; Yamamoto, Kazuhiro; Okabe, Nobuhiro [Department of Physical Sciences, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8526 (Japan); Matsushita, Kyoko; Sasaki, Toru, E-mail: telkina@theo.phys.sci.hiroshima-u.ac.jp, E-mail: kazuhiro@hiroshima-u.ac.jp, E-mail: okabe@hiroshima-u.ac.jp, E-mail: matusita@rs.kagu.tus.ac.jp, E-mail: j1213703@ed.tus.ac.jp [Department of Physics, Tokyo University of Science, 1-3 Kagurazaka, Shinjuku-ku, Tokyo 162-8601 (Japan)
2015-10-01
We obtain a constraint on the parameters of a generalized cubic Galileon gravity model exhibiting the Vainshtein mechanism by using multi-wavelength observations of the Coma Cluster. The generalized cubic Galileon model is characterized by three parameters of the turning scale associated with the Vainshtein mechanism, and the amplitude of modifying a gravitational potential and a lensing potential. X-ray and Sunyaev-Zel'dovich (SZ) observations of the intra-cluster medium are sensitive to the gravitational potential, while the weak-lensing (WL) measurement is specified by the lensing potential. A joint fit of a complementary multi-wavelength dataset of X-ray, SZ and WL measurements enables us to simultaneously constrain these three parameters of the generalized cubic Galileon model for the first time. We also find a degeneracy between the cluster mass parameters and the gravitational modification parameters, which is influential in the limit of the weak screening of the fifth force.
Vibrational effects on surface energies and band gaps in hexagonal and cubic ice
International Nuclear Information System (INIS)
Engel, Edgar A.; Needs, Richard J.; Monserrat, Bartomeu
2016-01-01
Surface energies of hexagonal and cubic water ice are calculated using first-principles quantum mechanical methods, including an accurate description of anharmonic nuclear vibrations. We consider two proton-orderings of the hexagonal and cubic ice basal surfaces and three proton-orderings of hexagonal ice prism surfaces, finding that vibrations reduce the surface energies by more than 10%. We compare our vibrational densities of states to recent sum frequency generation absorption measurements and identify surface proton-orderings of experimental ice samples and the origins of characteristic absorption peaks. We also calculate zero point quantum vibrational corrections to the surface electronic band gaps, which range from −1.2 eV for the cubic ice basal surface up to −1.4 eV for the hexagonal ice prism surface. The vibrational corrections to the surface band gaps are up to 12% smaller than for bulk ice.
Conformal Interpolating Algorithm Based on Cubic NURBS in Aspheric Ultra-Precision Machining
International Nuclear Information System (INIS)
Li, C G; Zhang, Q R; Cao, C G; Zhao, S L
2006-01-01
Numeric control machining and on-line compensation for aspheric surface are key techniques in ultra-precision machining. In this paper, conformal cubic NURBS interpolating curve is applied to fit the character curve of aspheric surface. Its algorithm and process are also proposed and imitated by Matlab7.0 software. To evaluate the performance of the conformal cubic NURBS interpolation, we compare it with the linear interpolations. The result verifies this method can ensure smoothness of interpolating spline curve and preserve original shape characters. The surface quality interpolated by cubic NURBS is higher than by line. The algorithm is benefit to increasing the surface form precision of workpieces in ultra-precision machining
Advanced CUBIC protocols for whole-brain and whole-body clearing and imaging.
Susaki, Etsuo A; Tainaka, Kazuki; Perrin, Dimitri; Yukinaga, Hiroko; Kuno, Akihiro; Ueda, Hiroki R
2015-11-01
Here we describe a protocol for advanced CUBIC (Clear, Unobstructed Brain/Body Imaging Cocktails and Computational analysis). The CUBIC protocol enables simple and efficient organ clearing, rapid imaging by light-sheet microscopy and quantitative imaging analysis of multiple samples. The organ or body is cleared by immersion for 1-14 d, with the exact time required dependent on the sample type and the experimental purposes. A single imaging set can be completed in 30-60 min. Image processing and analysis can take whole-brain neural activities at single-cell resolution using Arc-dVenus transgenic (Tg) mice. CUBIC informatics calculated the Venus signal subtraction, comparing different brains at a whole-organ scale. These protocols provide a platform for organism-level systems biology by comprehensively detecting cells in a whole organ or body.
Mass-induced instability of SAdS black hole in Einstein-Ricci cubic gravity
Myung, Yun Soo
2018-05-01
We perform the stability analysis of Schwarzschild-AdS (SAdS) black hole in the Einstein-Ricci cubic gravity. It shows that the Ricci tensor perturbations exhibit unstable modes for small black holes. We call this the mass-induced instability of SAdS black hole because the instability of small black holes arises from the massiveness in the linearized Einstein-Ricci cubic gravity, but not a feature of higher-order derivative theory giving ghost states. Also, we point out that the correlated stability conjecture holds for the SAdS black hole by computing the Wald entropy of SAdS black hole in Einstein-Ricci cubic gravity.
Energy Technology Data Exchange (ETDEWEB)
Kostela, J. [Uppsala University, Department of Physical Chemistry, Box 579, S-75123 Uppsala (Sweden)]. E-mail: johan.kostela@fki.uu.se; Elmgren, M. [Uppsala University, Department of Physical Chemistry, Box 579, S-75123 Uppsala (Sweden); Almgren, M. [Uppsala University, Department of Physical Chemistry, Box 579, S-75123 Uppsala (Sweden)
2005-05-30
The objective of this study was to investigate the electrochemical behaviour of the divalent redox active surfactant, N-cetyl-N'-methylviologen (CMV), in bicontinuous cubic and lamellar phases. The liquid crystalline phases were prepared from the system glycerolmonooleate (GMO)-water (and brine)-cationic surfactant. A comparison of the phase behaviour of GMO with the monovalent cetyltrimethylammonium bromide (CTAB) and the divalent CMV surfactant showed that the surfactants gave about the same effect at the same surface charge density. The electrochemical measurements were made with a mixture of CTAB and CMV as the surfactant. Cyclic voltammetry was used to study the electrochemistry of CMV incorporated in the cubic and lamellar phases that were spread on a gold electrode. The E {sup 0}-values in the cubic samples were more negative (-0.55 V versus SCE) than in the lamellar samples (-0.53 V versus SCE). This can be explained by the higher charge density in the lamellar phase. The diffusion coefficients were also measured in the cubic phase. The mass transport is slowed down about fifty times in the cubic phase compared to in the pure electrolyte. The concentration dependence on the diffusion coefficient was also investigated. No electron hopping could be observed, which suggest that diffusional movement of the redox probe is the main source of charge transport. By placing the samples on a conducting glass slide, spectroelectrochemical investigations were performed. In the lamellar phase strong dimerization was detected at high concentration of viologen, but much less in the cubic phase.
Cs and Ag co-incorporation in cubic silicon carbide
Londono-Hurtado, Alejandro; Heim, Andrew J.; Kim, Sungtae; Szlufarska, Izabela; Morgan, Dane
2013-08-01
those calculated for simple Cs and Ag defect clusters in SiC and to identify the most stable Cs/Ag-O-V defect clusters in SiC. Although some error will be associated with the formation energies due the limitations discussed above, these do not undermine the qualitative objectives of this work.Oxygen and Iodine chemical potential: In order to calculate the formation energies for Cs/Ag-O defect clusters, it is necessary to define the reference states that will be used in Eq. (1). We make the approximation that the reference for Cs and Ag is their pure metal form. The reference cancels from all comparisons between direct and co-incorporation and therefore only plays a role when considering formation energies for estimating solubility. These reference states can be justified as a bounding case for solubility calculations since it can be argued that if Ag and Cs are not in metal form in the TRISO particle, it is because they are in a more stable state. Therefore, by choosing the metal form of Cs and Ag as the reference, formation energies can be viewed as an upper bound of their chemical potential. As a consequence, formation energies calculated using this reference provide the lower bound for the true formation energy (i.e., the true formation energy would be more positive, leading to lower solubility) [11]. For the anions O and I we use the gas phase O2 and I2 molecules as the reference states, which are calculated as follows:The chemical potential of O is calculated as proposed by Lee et al. [32]: μ={1}/{2}EOVASP+ΔhO0+[H(T,P0)-H(T0,P0)]-TS(T,P0)+kTln(P/P0) where EOVASP is the T = 0 K energy as obtained from the DFT calculations, ΔhO0 is the correction for errors of the oxygen energy in O2 molecules vs. a solid, H is the O2 gas enthalpy, S is the O2 gas entropy, P is the oxygen partial pressure (P0 = 1 atm), T is the temperature (T0 = 298.15 K), and k is the Boltzman constant. The term [H(T,P0)-H(T0,P0)]-TS(T,P0) constitutes the free energy per O of O2 gas relative to
Changing the cubic ferrimagnetic domain structure in temperature region of spin flip transition
International Nuclear Information System (INIS)
Djuraev, D.R.; Niyazov, L.N.; Saidov, K.S.; Sokolov, B.Yu.
2011-01-01
The transformation of cubic ferrimagnetic Tb 0.2 Y 2.8 Fe 5 O 12 domain structure has been studied by magneto optic method in the temperature region of spontaneous spin flip phase transition (SPT). It has been found that SPT occurs in a finite temperature interval where the coexistence of low- and high- temperature magnetic phase domains has observed. A character of domain structure evolution in temperature region of spin flip essentially depends on the presence of mechanical stresses in crystal. Interpretation of experimental results has been carried out within the framework of SPT theory for a cubic crystal. (authors)
Limit cycles from a cubic reversible system via the third-order averaging method
Directory of Open Access Journals (Sweden)
Linping Peng
2015-04-01
Full Text Available This article concerns the bifurcation of limit cycles from a cubic integrable and non-Hamiltonian system. By using the averaging theory of the first and second orders, we show that under any small cubic homogeneous perturbation, at most two limit cycles bifurcate from the period annulus of the unperturbed system, and this upper bound is sharp. By using the averaging theory of the third order, we show that two is also the maximal number of limit cycles emerging from the period annulus of the unperturbed system.
Cubic systems with invariant affine straight lines of total parallel multiplicity seven
Directory of Open Access Journals (Sweden)
Alexandru Suba
2013-12-01
Full Text Available In this article, we study the planar cubic differential systems with invariant affine straight lines of total parallel multiplicity seven. We classify these system according to their geometric properties encoded in the configurations of invariant straight lines. We show that there are only 17 different topological phase portraits in the Poincar\\'e disc associated to this family of cubic systems up to a reversal of the sense of their orbits, and we provide representatives of every class modulo an affine change of variables and rescaling of the time variable.
Lattice vibrations and cubic to tetragonal phase transition in ZrO2
International Nuclear Information System (INIS)
Negita, K.
1989-01-01
On the basis of analyses of phonon modes in ZrO 2 , it is suggested that condensation of a phonon X 2 - at the cubic Brillouin zone boundary X point, (0, 0, 2 π/a), is associated with the cubic to tetragonal phase transition in ZrO 2 . Free energy consideration shows that spontaneous volume and shear strains, e Alg = (e 1 +e 2 +e 3 ) and e Eg = (2e 3 - e 1 - e 2 )/ Λ3, are induced in the tetragonal phase as a result of indirect couplings of the X 2 - mode to homogeneous elastic strains; the tetragonal phase is improper ferroelastic
Exact optical solitons in (n + 1)-dimensions with anti-cubic nonlinearity
Younis, Muhammad; Shahid, Iram; Anbreen, Sumaira; Rizvi, Syed Tahir Raza
2018-02-01
The paper studies the propagation of optical solitons in (n + 1)-dimensions under anti-cubic law of nonlinearity. The bright, dark and singular optical solitons are extracted using the extended trial equation method. The constraint conditions, for the existence of these solitons, are also listed. Additionally, a couple of other solutions known as singular periodic and Jacobi elliptic solutions, fall out as a by-product of this scheme. The obtained results are new and reported first time in (n + 1)-dimensions with anti-cubic law of nonlinearity.
On the structure of critical energy levels for the cubic focusing NLS on star graphs
International Nuclear Information System (INIS)
Adami, Riccardo; Noja, Diego; Cacciapuoti, Claudio; Finco, Domenico
2012-01-01
We provide information on a non-trivial structure of phase space of the cubic nonlinear Schrödinger (NLS) on a three-edge star graph. We prove that, in contrast to the case of the standard NLS on the line, the energy associated with the cubic focusing Schrödinger equation on the three-edge star graph with a free (Kirchhoff) vertex does not attain a minimum value on any sphere of constant L 2 -norm. We moreover show that the only stationary state with prescribed L 2 -norm is indeed a saddle point. (fast track communication)
Curvature and bottlenecks control molecular transport in inverse bicontinuous cubic phases
Assenza, Salvatore; Mezzenga, Raffaele
2018-02-01
We perform a simulation study of the diffusion of small solutes in the confined domains imposed by inverse bicontinuous cubic phases for the primitive, diamond, and gyroid symmetries common to many lipid/water mesophase systems employed in experiments. For large diffusing domains, the long-time diffusion coefficient shows universal features when the size of the confining domain is renormalized by the Gaussian curvature of the triply periodic minimal surface. When bottlenecks are widely present, they become the most relevant factor for transport, regardless of the connectivity of the cubic phase.
AdS5/CFT4 four-point functions of chiral primary operators: Cubic vertices
International Nuclear Information System (INIS)
Lee, Sangmin
1999-01-01
We study the exchange diagrams in the computation of four-point functions of all chiral primary operators in D=4, N=4 super Yang-Mills using AdS/CFT correspondence. We identify all supergravity fields that can be exchanged and compute the cubic couplings. As a byproduct, we also rederive the normalization of the quadratic action of the exchanged fields. The cubic couplings computed in this paper and the propagators studied extensively in the literature can be used to compute almost all the exchange diagrams explicitly. Some issues in computing the complete four-point function in the 'massless sector' are discussed
Efficient Algorithms for gcd and Cubic Residuosity in the Ring of Eisenstein Integers
DEFF Research Database (Denmark)
Damgård, Ivan Bjerre; Frandsen, Gudmund Skovbjerg
2003-01-01
We present simple and efficient algorithms for computing gcd and cubic residuosity in the ring of Eisenstein integers, bf Z[ ]i.e. the integers extended with , a complex primitive third root of unity. The algorithms are similar and may be seen as generalisations of the binary integer gcd and deri......We present simple and efficient algorithms for computing gcd and cubic residuosity in the ring of Eisenstein integers, bf Z[ ]i.e. the integers extended with , a complex primitive third root of unity. The algorithms are similar and may be seen as generalisations of the binary integer gcd...
The n-component cubic model and flows: subgraph break-collapse method
International Nuclear Information System (INIS)
Essam, J.W.; Magalhaes, A.C.N. de.
1988-01-01
We generalise to the n-component cubic model the subgraph break-collapse method which we previously developed for the Potts model. The relations used are based on expressions which we recently derived for the Z(λ) model in terms of mod-λ flows. Our recursive algorithm is similar, for n = 2, to the break-collapse method for the Z(4) model proposed by Mariz and coworkers. It allows the exact calculation for the partition function and correlation functions for n-component cubic clusters with n as a variable, without the need to examine all of the spin configurations. (author) [pt
Cubic interaction in extended theories of massless higher-spin fields
Energy Technology Data Exchange (ETDEWEB)
Fradkin, E S; Vasiliev, M A
1987-08-17
A cubic interaction of all massless higher-spin fields with s greater than or equal to 1 is constructed, based on the extended higher-spin superalgebras suggested previously by one of us (M.V.). This interaction incorporates gravitational and Yang-Mills interactions of massless higher-spin fields, which turn out to be consistent in the cubic order. An essential novel feature of the gravitational higher-spin interaction is its non-analyticity in the cosmological constant. An explicit form is found for deformed higher-spin gauge transformations leaving the action invariant.
Analysis of moderately thin-walled beam cross-sections by cubic isoparametric elements
DEFF Research Database (Denmark)
Høgsberg, Jan Becker; Krenk, Steen
2014-01-01
In technical beam theory the six equilibrium states associated with homogeneous tension, bending, shear and torsion are treated as individual load cases. This enables the formulation of weak form equations governing the warping from shear and torsion. These weak form equations are solved...... numerically by introducing a cubic-linear two-dimensional isoparametric element. The cubic interpolation of this element accurately represents quadratic shear stress variations along cross-section walls, and thus moderately thin-walled cross-sections are effectively discretized by these elements. The ability...
The influence of a cubic building on a roof mounted wind turbine
Micallef, D.; Sant, Tonio; Simao Ferreira, C.
2016-01-01
The performance of a wind turbine located above a cubic building is not well understood. This issue is of fundamental importance for the design of small scale wind turbines. One variable which is of particular importance in this respect is the turbine height above roof level. In this work, the power performance of a small wind turbine is assessed as a function of the height above the roof of a generic cubic building. A 3D Computational Fluid Dynamics model of a 10m x 10m x 10m building is use...
Preconditioning cubic spline collocation method by FEM and FDM for elliptic equations
Energy Technology Data Exchange (ETDEWEB)
Kim, Sang Dong [KyungPook National Univ., Taegu (Korea, Republic of)
1996-12-31
In this talk we discuss the finite element and finite difference technique for the cubic spline collocation method. For this purpose, we consider the uniformly elliptic operator A defined by Au := -{Delta}u + a{sub 1}u{sub x} + a{sub 2}u{sub y} + a{sub 0}u in {Omega} (the unit square) with Dirichlet or Neumann boundary conditions and its discretization based on Hermite cubic spline spaces and collocation at the Gauss points. Using an interpolatory basis with support on the Gauss points one obtains the matrix A{sub N} (h = 1/N).
DEFF Research Database (Denmark)
Ulrich, Michael; Overgaard, Søren; Penny, Jeannette
2014-01-01
In Denmark 4,456 metal-on-metal (MoM) hip prostheses have been implanted. Evidence demonstrates that some patients develope adverse biological reactions causing failures of MoM hip arthroplasty. Some reactions might be systemic. Failure rates are associated with the type and the design of the Mo...
International Nuclear Information System (INIS)
Gibala, R.; Sethi, V.K.; Fournier, R.
1977-01-01
New results obtained in surface oxide softening of the Group VB refractory metals and mechanical behavior of Nb-H and Nb-D alloys are presented. The results include: (a) experimental verification of a model of surface oxide softening of body-centered cubic metals; (b) determination of a stress-differential effect in surface oxide softening; and (c) characterization of hydrogen and deuterium strengthening in Nb and Nb-O alloys. The second section reviews major contributions in topics on: interstitials in metals, mechanical behavior of body-centered cubic metals, solute-defect interactions and internal friction mechanisms in solids
International Nuclear Information System (INIS)
1977-01-01
Progress is reported in the areas of (a) the effect of neutron damage on the dislocation kinetics in bcc metals and their alloys, and (b) the effect of 3 He on the deformation characteristics of body centered cubic metals and their alloys. Results obtained from these projects are discussed
Metallated metal-organic frameworks
Energy Technology Data Exchange (ETDEWEB)
Bury, Wojciech; Farha, Omar K.; Hupp, Joseph T.; Mondloch, Joseph E.
2017-08-22
Porous metal-organic frameworks (MOFs) and metallated porous MOFs are provided. Also provided are methods of metallating porous MOFs using atomic layer deposition and methods of using the metallated MOFs as catalysts and in remediation applications.
Determination of asphaltene onset conditions using the cubic plus association equation of state
DEFF Research Database (Denmark)
Arya, Alay; von Solms, Nicolas; Kontogeorgis, Georgios M.
2015-01-01
The cubic-plus-association (CPA) equation of state (EoS) has already been proven to be a successful model for phase equilibrium calculations for systems containing associating components and has already been applied for asphaltene modeling by few researchers. In the present work, we apply the CPA...
A modified linear algebraic approach to electron scattering using cubic splines
International Nuclear Information System (INIS)
Kinney, R.A.
1986-01-01
A modified linear algebraic approach to the solution of the Schrodiner equation for low-energy electron scattering is presented. The method uses a piecewise cubic-spline approximation of the wavefunction. Results in the static-potential and the static-exchange approximations for e - +H s-wave scattering are compared with unmodified linear algebraic and variational linear algebraic methods. (author)
On the dynamic Stability of a quadratic-cubic elastic model structure ...
African Journals Online (AJOL)
The main substance of this investigation is the determination of the dynamic buckling load of an imperfect quadratic-cubic elastic model structure , which ,in itself, is a Mathematical generalization of some of the many physical structures normally encountered in engineering practice and allied fields. The load function in ...
Darboux integrability and rational reversibility in cubic systems with two invariant straight lines
Directory of Open Access Journals (Sweden)
Dumitru Cozma
2013-01-01
Full Text Available We find conditions for a singular point O(0,0 of a center or a focus type to be a center, in a cubic differential system with two distinct invariant straight lines. The presence of a center at O(0,0 is proved by using the method of Darboux integrability and the rational reversibility.
DEFF Research Database (Denmark)
Kruger, Francois; Kontogeorgis, Georgios M.; von Solms, Nicolas
2018-01-01
Accurate thermodynamic predictions for systems containing glycols are essential for the design and commissioning of novel subsea natural gas dehydration units. Previously it has been shown that the Cubic-Plus-Association (CPA) equation of state can be used to model VLE, SLE and LLE for mixtures...
Qualitative analysis on a cubic predator-prey system with diffusion
Directory of Open Access Journals (Sweden)
Qunyi Bie
2011-04-01
Full Text Available In this paper, we study a cubic predator-prey model with diffusion. We first establish the global stability of the trivial and nontrivial constant steady states for the reaction diffusion system, and then prove the existence and non-existence results concerning non-constant positive stationary solutions by using topological argument and the energy method, respectively.
The bulk modulus of cubic spinel selenides: an experimental and theoretical study
DEFF Research Database (Denmark)
Waskowska, A.; Gerward, Leif; Olsen, J.S.
2009-01-01
It is argued that mainly the selenium sublattice determines the overall compressibility of the cubic spinel selenides, AB2Se4, and that the bulk modulus for these compounds is about 100GPa. The hypothesis is supported by experiments using high-pressure X-ray diffraction and synchrotron radiation...
Limit cycles bifurcating from the periodic annulus of cubic homogeneous polynomial centers
Directory of Open Access Journals (Sweden)
Jaume Llibre
2015-10-01
Full Text Available We obtain an explicit polynomial whose simple positive real roots provide the limit cycles which bifurcate from the periodic orbits of any cubic homogeneous polynomial center when it is perturbed inside the class of all polynomial differential systems of degree n.
Analytic smoothing effect for the cubic hyperbolic Schrodinger equation in two space dimensions
Directory of Open Access Journals (Sweden)
Gaku Hoshino
2016-01-01
Full Text Available We study the Cauchy problem for the cubic hyperbolic Schrodinger equation in two space dimensions. We prove existence of analytic global solutions for sufficiently small and exponential decaying data. The method of proof depends on the generalized Leibniz rule for the generator of pseudo-conformal transform acting on pseudo-conformally invariant nonlinearity.
DEFF Research Database (Denmark)
Arya, Alay; Liang, Xiaodong; von Solms, Nicolas
2017-01-01
In this study, different modeling approaches using the Cubic Plus Association (CPA) equation of state (EoS) are developed to calculate the asphaltene precipitation onset condition and asphaltene yield from degassed crude oil during the addition of n-paraffin. A single model parameter is fitted...
CENTER CONDITIONS AND CYCLICITY FOR A FAMILY OF CUBIC SYSTEMS: COMPUTER ALGEBRA APPROACH.
Ferčec, Brigita; Mahdi, Adam
2013-01-01
Using methods of computational algebra we obtain an upper bound for the cyclicity of a family of cubic systems. We overcame the problem of nonradicality of the associated Bautin ideal by moving from the ring of polynomials to a coordinate ring. Finally, we determine the number of limit cycles bifurcating from each component of the center variety.
Carlsson, Nils; Winge, Ann-Sofie; Engström, Sven; Akerman, Björn
2005-10-06
We used a cubic liquid crystal formed by the nonionic monoglyceride monoolein and water as a porous matrix for the electrophoresis of oligonucleotides. The diamond cubic phase is thermodynamically stable when in contact with a water-rich phase, which we exploit to run the electrophoresis in the useful submarine mode. Oligonucleotides are separated according to size and secondary structure by migration through the space-filling aqueous nanometer pores of the regular liquid crystal, but the comparatively slow migration means the cubic phase will not be a replacement for the conventional DNA gels. However, our demonstration that the cubic phase can be used in submarine electrophoresis opens up the possibility for a new matrix for electrophoresis of amphiphilic molecules. From this perspective, the results on the oligonucleotides show that water-soluble particles of nanometer size, typical for the hydrophilic parts of membrane-bound proteins, may be a useful separation motif. A charged contamination in the commercial sample of monoolein, most likely oleic acid that arises from its hydrolysis, restricts useful buffer conditions to a pH below 5.6.
Estimating cubic volume of small diameter tree-length logs from ponderosa and lodgepole pine.
Marlin E. Plank; James M. Cahill
1984-01-01
A sample of 351 ponderosa pine (Pinus ponderosa Dougl. ex Laws.) and 509 lodgepole pine (Pinus contorta Dougl. ex Loud.) logs were used to evaluate the performance of three commonly used formulas for estimating cubic volume. Smalian's formula, Bruce's formula, and Huber's formula were tested to determine which...
On the reflection of solitons of the cubic nonlinear Schrödinger equation
Katsaounis, Theodoros; Mitsotakis, Dimitrios
2016-01-01
In this paper, we perform a numerical study on the interesting phenomenon of soliton reflection of solid walls. We consider the 2D cubic nonlinear Schrödinger equation as the underlying mathematical model, and we use an implicit-explicit type Crank
Tran, Nhiem; Zhai, Jiali; Conn, Charlotte E; Mulet, Xavier; Waddington, Lynne J; Drummond, Calum J
2018-05-29
The transition between the lyotropic liquid crystalline lamellar and the bicontinuous cubic mesophase drives multiple fundamental cellular processes involving changes in cell membrane topology including endocytosis and membrane budding. While several theoretical models have been proposed to explain this dynamic transformation, experimental validation of these models has been challenging due to the short lived nature of the intermediates present during the phase transition. Herein, we report the direct observation of a lamellar to bicontinuous cubic phase transition in nanoscale dispersions using a combination of cryogenic transmission electron microscopy and static small angle X-ray scattering. The results represent the first experimental confirmation of a theoretical model which proposed that the bicontinuous cubic phase originates from the centre of a lamellar vesicle, then propagates outward via the formation of inter-lamellar attachments and stalks. The observation was possible due to the precise control of the lipid composition to place the dispersion systems at the phase boundary of a lamellar and a cubic phase, allowing for the creation of long-lived structural intermediates. By surveying the nanoparticles using cryogenic transmission electron microscopy, a complete phase transition sequence was established.
Least square fitting of low resolution gamma ray spectra with cubic B-spline basis functions
International Nuclear Information System (INIS)
Zhu Menghua; Liu Lianggang; Qi Dongxu; You Zhong; Xu Aoao
2009-01-01
In this paper, the least square fitting method with the cubic B-spline basis functions is derived to reduce the influence of statistical fluctuations in the gamma ray spectra. The derived procedure is simple and automatic. The results show that this method is better than the convolution method with a sufficient reduction of statistical fluctuation. (authors)
Energy Technology Data Exchange (ETDEWEB)
Lee, H.; Habas, S.E.; Somorjai, G.A.; Yang, P.
2008-03-20
Binary Pt/Pd nanoparticles were synthesized by localized overgrowth of Pd on cubic Pt seeds for the investigation of electrocatalytic formic acid oxidation. The binary particles exhibited much less self-poisoning and a lower activation energy relative to Pt nanocubes, consistent with the single crystal study.
Rakhimov, Abdulla; Askerzade, Iman N
2014-09-01
We have shown that the critical temperature of a Bose-Einstein condensate to a normal phase transition of noninteracting bosons in cubic optical lattices has a linear dependence on the filling factor, especially at large densities. The condensed fraction exhibits a linear power law dependence on temperature in contrast to the case of ideal homogeneous Bose gases.
Polarized infrared reflectance study of free standing cubic GaN grown by molecular beam epitaxy
International Nuclear Information System (INIS)
Lee, S.C.; Ng, S.S.; Hassan, H. Abu; Hassan, Z.; Zainal, N.; Novikov, S.V.; Foxon, C.T.; Kent, A.J.
2014-01-01
Optical properties of free standing cubic gallium nitride grown by molecular beam epitaxy system are investigated by a polarized infrared (IR) reflectance technique. A strong reststrahlen band, which reveals the bulk-like optical phonon frequencies, is observed. Meanwhile, continuous oscillation fringes, which indicate the sample consists of two homogeneous layers with different dielectric constants, are observed in the non-reststrahlen region. By obtaining the first derivative of polarized IR reflectance spectra measured at higher angles of incidence, extra phonon resonances are identified at the edges of the reststrahlen band. The observations are verified with the theoretical results simulated based on a multi-oscillator model. - Highlights: • First time experimental studies of IR optical phonons in bulk like, cubic GaN layer. • Detection of extra phonon modes of cubic GaN by polarized IR reflectance technique. • Revelation of IR multiphonon modes of cubic GaN by first derivative numerical method. • Observation of multiphonon modes requires very high angle of incidence. • Resonance splitting effect induced by third phonon mode is a qualitative indicator
Extension of the cubic-plus-association (CPA) equation of state to amines
DEFF Research Database (Denmark)
Kaarsholm, Mads Kristian; Derawi, Samer; Michelsen, Michael Locht
2005-01-01
The cubic-plus-association (CPA) equation of state has been extended to modeling mixtures containing amines. Special focus was given to primary and secondary amines, which are known to self-associate, thus forming hydrogen bonds in mixtures with alkanes. Pure-compound parameters have been determi...
DEFF Research Database (Denmark)
Castelli, Ivano Eligio; Landis, David; Thygesen, Kristian Sommer
2012-01-01
screening of around 19 000 oxides, oxynitrides, oxysulfides, oxyfluorides, and oxyfluoronitrides in the cubic perovskite structure with PEC applications in mind. We address three main applications: light absorbers for one- and two-photon water splitting and high-stability transparent shields to protect...
Calculated Pourbaix Diagrams of Cubic Perovskites for Water Splitting: Stability Against Corrosion
DEFF Research Database (Denmark)
Castelli, Ivano Eligio; Thygesen, Kristian Sommer; Jacobsen, Karsten Wedel
2014-01-01
We use density functional theory calculations to investigate the stability of cubic perovskites for photo-electrochemical water splitting taking both materials in their bulk crystal structure and dissolved phases into account. The method is validated through a detailed comparison of the calculated...
Effect of shear on cubic phases in gels of a diblock copolymer
DEFF Research Database (Denmark)
Hamley, I.W.; Pople, J.A.; Fairclough, J.P.A.
1998-01-01
The effect of shear on the orientation of cubic micellar phases formed by a poly(oxyethylene)poly(oxybutylene) diblock copolymer in aqueous solution has been investigated using small-angle x-ray scattering (SAXS) and small-angle neutron scattering (SANS). SAXS was performed on samples oriented in...
Robustness of Multiple High Speed TCP CUBIC Connections Under Severe Operating Conditions
DEFF Research Database (Denmark)
Pilimon, Artur; Ruepp, Sarah Renée; Berger, Michael Stübert
2015-01-01
We study the adaptation capabilities and robustness of the high-speed TCP CUBIC algorithm. For this purpose we consider a network environment with variable and high random packet loss and a large Bandwidth-Delay product, shared by multiple heterogeneous TCP connections. The analysis is based on a...
Ogbonnaya, Ugorji I.; Mogari, David L.; Machisi, Eric
2013-01-01
In this study, repeated measures design was employed to compare low performing students' achievements in factoring cubic polynomials using three strategies. Twenty-five low-performing Grade 12 students from a secondary school in Limpopo province took part in the study. Data was collected using achievement test and was analysed using repeated…
Pore direction in relation to anisotropy of mechanical strength in a cubic starch compact
Wu, Yu San; van Vliet, Lucas J; Frijlink, Henderik W; Stokroos, Ietse; van der Voort Maarschalk, Kees
The purpose of this research was to evaluate the relation between preferential direction of pores and mechanical strength of cubic starch compacts. The preferential pore direction was quantified in SEM images of cross sections of starch compacts using a previously described algorithm for
Unusually large unit cell of lipid bicontinuous cubic phase: towards nature's length scales
Kim, Hojun; Leal, Cecilia
Lipid bicontinuous cubic phases are of great interest for drug delivery, protein crystallization, biosensing, and templates for directing hard material assembly. Structural modulations of lipid mesophases regarding phase identity and unit cell size are often necessary to augment loading and gain pore size control. One important example is the need for unit cells large enough to guide the crystallization of bigger proteins without distortion of the templating phase. In nature, bicontinuous cubic constructs achieve unit cell dimensions as high as 300 nm. However, the largest unit cell of lipid mesophases synthesized in the lab is an order of magnitude lower. In fact, it has been predicted theoretically that lipid bicontinuous cubic phases of unit cell dimensions exceeding 30 nm could not exist, as high membrane fluctuations would damp liquid crystalline order. Here we report non-equilibrium assembly methods of synthesizing metastable bicontinuous cubic phases with unit cell dimensions as high as 70 nm. The phases are stable for very long periods and become increasingly ordered as time goes by without changes to unit cell dimensions. We acknowledge the funding source as a NIH.
Criticality of the anisotropic quantum Heisenberg model on a simple cubic lattice
International Nuclear Information System (INIS)
Mariz, A.M.; Santos, R.M.Z. dos; Tsallis, C.; Santos, R.R. dos.
1984-01-01
Within a Real Space Renormalization group framework, the criticality (phase diagram, and critical thermal and crossover exponents) of the spin 1/2 - anisotropic quantum Heisenberg ferromagnet on a simple cubic lattice is studied. The results obtained are in satisfactory agreement with known results whenever available. (Author) [pt
Criticality of the anisotropic quantum Heisenberg model on a simple cubic lattice
International Nuclear Information System (INIS)
Mariz, A.M.; Tsallis, C.; Santos, R.M.Z. dos; Santos, Raimundo R. dos.
1984-11-01
Within a Real Space Renormalization Group Framework, the criticality (phase diagram, and critical thermal and crossover exponents) of the spin 1/2 - anisotropic quantum Heisenberg ferromagnet on a simple cubic lattice is studied. The results obtained are in antisfactory agreement with known results whenever available. (Author) [pt
The influence of a cubic building on a roof mounted wind turbine
Micallef, D.; Sant, Tonio; Simao Ferreira, C.
2016-01-01
The performance of a wind turbine located above a cubic building is not well understood. This issue is of fundamental importance for the design of small scale wind turbines. One variable which is of particular importance in this respect is the turbine height above roof level. In this work, the
Face-centered-cubic Nb-Si solid solutions produced by picosecond pulsed laser quenching
International Nuclear Information System (INIS)
Wang, W.K.; Spaepen, F.
1985-01-01
Face-centered-cubic Nb/sub 100-x/Si/sub x/ solid solutions (10 2 . The lattice parameters of these solutions suggest that the solute atoms can be interstitial or substitutional, probably as a result of a change in the quenching conditions
The surface oxidation kinetics of zirconium-niobium alloys and aα-Fe with prevailing cubical texture
International Nuclear Information System (INIS)
Mukhambetov, D.G.; Kargin, D.B.; Chalaya, O. V.; Berber, N.N.
2002-01-01
It is known, that the kinetics of oxidation of zirconium at formed heating is characterized by two consecutive stages. At the initial stage the thin protecting film will be derived. The relation of its depth from time h (t) is described predominantly by parabolic law. Some time later there can be a transition to the linear law of oxidation. The time moment divided these areas on the kinetic relation is called as a point of break. The film is formed at the second stage, has a developed grid of pores or cracks, can be flake away and be crumbled by losing its protective properties. At the oxidation of the surface shells of the heat generating elements and the technological channels of atomic boilers both stages are proceeded simultaneously. This phenomenon is called modular corrosion. Its consequences can be dangerous for the equipment. Its mechanism is not clear till now. Similar dependencies h(t), with the break point, beginning from which the thin film is transformed into the thick one were found by us at the oxidation α-Fe with prevailing cubical texture. The task of the work was to study the oxide film growth laws in order to clarify the mechanisms of transition of the thin film into the oxide layer on the α-Fe surface and Zr-Nb alloy modular corrosion emergence. Low-carbonate steel with contents 99.43 % of α-Fe was used as a model object of our research. In the texture of the steel surface planar direction [100] was prevalent. Its part accounted for about 40 %. The isothermal air oxidation was carried out in the interval of 450-500 deg. C . Phase composition of the film was determined with X-ray diffraction. The mathematical treatment of the dependencies h(t) obtained by experiment showed that the kinetics of the film growth can be conditionally divided into 4-stages. The initial stage is described by function logarithmic function, the other stages - by the power mode h n =A n ·t, namely, the second stage - is described by function close to cubical (n≅3
Reese, Caleb W; Strango, Zachariah I; Dell, Zachary R; Tristram-Nagle, Stephanie; Harper, Paul E
2015-04-14
Using DSC (differential scanning calorimetry), we measure the kinetics of the cubic-HII phase transition of monoolein in bulk sucrose solutions. We find that the transition temperature is dramatically lowered, with each 1 mol kg(-1) of sucrose concentration dropping the transition by 20 °C. The kinetics of this transition also slow greatly with increasing sucrose concentration. For low sucrose concentrations, the kinetics are asymmetric, with the cooling (HII-cubic) transition taking twice as long as the heating (cubic-HII) transition. This asymmetry in transition times is reduced for higher sucrose concentrations. The cooling transition exhibits Avrami exponents in the range of 2 to 2.5 and the heating transition shows Avrami exponents ranging from 1 to 3. A classical Avrami interpretation would be that these processes occur via a one or two dimensional pathway with variable nucleation rates. A non-classical perspective would suggest that these exponents reflect the time dependence of pore formation (cooling) and destruction (heating). New density measurements of monoolein show that the currently accepted value is about 5% too low; this has substantial implications for electron density modeling. Structural calculations indicate that the head group area and lipid length in the cubic-HII transition shrink by about 12% and 4% respectively; this reduction is practically the same as that seen in a lipid with a very different molecular structure (rac-di-12:0 β-GlcDAG) that makes the same transition. Thermodynamic considerations suggest there is a hydration shell about one water molecule thick in front of the lipid head groups in both the cubic and HII phases.
An explicit approximate solution to the Duffing-harmonic oscillator by a cubication method
International Nuclear Information System (INIS)
Belendez, A.; Mendez, D.I.; Fernandez, E.; Marini, S.; Pascual, I.
2009-01-01
The nonlinear oscillations of a Duffing-harmonic oscillator are investigated by an approximated method based on the 'cubication' of the initial nonlinear differential equation. In this cubication method the restoring force is expanded in Chebyshev polynomials and the original nonlinear differential equation is approximated by a Duffing equation in which the coefficients for the linear and cubic terms depend on the initial amplitude, A. The replacement of the original nonlinear equation by an approximate Duffing equation allows us to obtain explicit approximate formulas for the frequency and the solution as a function of the complete elliptic integral of the first kind and the Jacobi elliptic function, respectively. These explicit formulas are valid for all values of the initial amplitude and we conclude this cubication method works very well for the whole range of initial amplitudes. Excellent agreement of the approximate frequencies and periodic solutions with the exact ones is demonstrated and discussed and the relative error for the approximate frequency is as low as 0.071%. Unlike other approximate methods applied to this oscillator, which are not capable to reproduce exactly the behaviour of the approximate frequency when A tends to zero, the cubication method used in this Letter predicts exactly the behaviour of the approximate frequency not only when A tends to infinity, but also when A tends to zero. Finally, a closed-form expression for the approximate frequency is obtained in terms of elementary functions. To do this, the relationship between the complete elliptic integral of the first kind and the arithmetic-geometric mean as well as Legendre's formula to approximately obtain this mean are used.
Energy Technology Data Exchange (ETDEWEB)
Arief, Injamamul; Mukhopadhyay, P.K., E-mail: pkm@bose.res.in
2014-06-01
Cubic and spherical Fe{sub 55}Co{sub 45} alloyed microstructures were synthesized by borohydride reduction from aqueous solutions of metallic precursors, using stabilizers and polymer. Monosodium citrate, sodium acetate and PEG 6000 were utilized as electrostatic stabilizers and polymeric surface modifier. Suitable reaction conditions were maintained for synthesis of predominantly larger particles (0.7 µm to 1.2 µm), that facilitates use in magnetorheological fluids. Surface morphological studies by scanning electron microscopy revealed well shaped cubic and spherical geometry for the citrate and polymer-stabilized Fe{sub 55}Co{sub 45} alloys, while the alloy compositions remained nearly the same for both. X-ray diffractions of the as-prepared and annealed samples under various temperatures showed high degree of crystallinity with increasing temperatures. Studies of D.C. magnetization of the systems reveal that the particles have a core–shell structure, with inner magnetic core having a diameter around 30 nm with a log-normal distribution. Magnetorheological studies were performed with 8 vol% suspensions of as-synthesized particles dispersed in silicone oil (viscosity 30 mPa s at 25 °C) under different magnetic fields. Detailed studies of the magnetorheological properties were studied on these systems for practical use.
The phase space of the focused cubic Schroedinger equation: A numerical study
Energy Technology Data Exchange (ETDEWEB)
Burlakov, Yuri O. [Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
1998-05-01
In a paper of 1988 [41] on statistical mechanics of the nonlinear Schroedinger equation, it was observed that a Gibbs canonical ensemble associated with the nonlinear Schroedinger equation exhibits behavior reminiscent of a phase transition in classical statistical mechanics. The existence of a phase transition in the canonical ensemble of the nonlinear Schroedinger equation would be very interesting and would have important implications for the role of this equation in modeling physical phenomena; it would also have an important bearing on the theory of weak solutions of nonlinear wave equations. The cubic Schroedinger equation, as will be shown later, is equivalent to the self-induction approximation for vortices, which is a widely used equation of motion for a thin vortex filament in classical and superfluid mechanics. The existence of a phase transition in such a system would be very interesting and actually very surprising for the following reasons: in classical fluid mechanics it is believed that the turbulent regime is dominated by strong vortex stretching, while the vortex system described by the cubic Schroedinger equation does not allow for stretching. In superfluid mechanics the self-induction approximation and its modifications have been used to describe the motion of thin superfluid vortices, which exhibit a phase transition; however, more recently some authors concluded that these equations do not adequately describe superfluid turbulence, and the absence of a phase transition in the cubic Schroedinger equation would strengthen their argument. The self-induction approximation for vortices takes into account only very localized interactions, and the existence of a phase transition in such a simplified system would be very unexpected. In this thesis the authors present a numerical study of the phase transition type phenomena observed in [41]; in particular, they find that these phenomena are strongly related to the splitting of the phase space into
Nonlinear bias compensation of ZiYuan-3 satellite imagery with cubic splines
Cao, Jinshan; Fu, Jianhong; Yuan, Xiuxiao; Gong, Jianya
2017-11-01
Like many high-resolution satellites such as the ALOS, MOMS-2P, QuickBird, and ZiYuan1-02C satellites, the ZiYuan-3 satellite suffers from different levels of attitude oscillations. As a result of such oscillations, the rational polynomial coefficients (RPCs) obtained using a terrain-independent scenario often have nonlinear biases. In the sensor orientation of ZiYuan-3 imagery based on a rational function model (RFM), these nonlinear biases cannot be effectively compensated by an affine transformation. The sensor orientation accuracy is thereby worse than expected. In order to eliminate the influence of attitude oscillations on the RFM-based sensor orientation, a feasible nonlinear bias compensation approach for ZiYuan-3 imagery with cubic splines is proposed. In this approach, no actual ground control points (GCPs) are required to determine the cubic splines. First, the RPCs are calculated using a three-dimensional virtual control grid generated based on a physical sensor model. Second, one cubic spline is used to model the residual errors of the virtual control points in the row direction and another cubic spline is used to model the residual errors in the column direction. Then, the estimated cubic splines are used to compensate the nonlinear biases in the RPCs. Finally, the affine transformation parameters are used to compensate the residual biases in the RPCs. Three ZiYuan-3 images were tested. The experimental results showed that before the nonlinear bias compensation, the residual errors of the independent check points were nonlinearly biased. Even if the number of GCPs used to determine the affine transformation parameters was increased from 4 to 16, these nonlinear biases could not be effectively compensated. After the nonlinear bias compensation with the estimated cubic splines, the influence of the attitude oscillations could be eliminated. The RFM-based sensor orientation accuracies of the three ZiYuan-3 images reached 0.981 pixels, 0.890 pixels, and 1
Adriano, Domy; VANGRONSVELD, Jaco; Bolan, N.S.; Wenzel, W.W.
2005-01-01
- Sources of Metals in the Environment - Environmental Contamination - Retention and Dynamics of Metals in Soils - Adsorption - Complexation - Precipitation - Bioavailability–Natural Attenuation Interactions - Biological Response to Metals - Soil Remediation
High-temperature and high-pressure cubic zirconia anvil cell for Raman spectroscopy.
Chen, Jinyang; Zheng, Haifei; Xiao, Wansheng; Zeng, Yishan
2003-10-01
A simple and inexpensive cubic zirconia anvil cell has been developed for the performance of in situ Raman spectroscopy up to the conditions of 500 degrees C and 30 kbar pressure. The design and construction of this cell are fully described, as well as its applications for Raman spectroscopy. Molybdenum heater wires wrapped around ceramic tubes encircling two cubic zirconia anvils are used to heat samples, and the temperatures are measured and controlled by a Pt-PtRh thermocouple adhered near the sample chamber and an intelligent digital control apparatus. With this cell, Raman spectroscopic measurements have been satisfactorily performed on water at 6000 bar pressure to 455 degrees C and on ice of room temperature to 24 kbar, in which the determinations of pressures make use of changes of the A1 Raman modes of quartz and the shift of the sharpline (R-line) luminescence of ruby, respectively.
Analytic cubic and quartic force fields using density-functional theory
Energy Technology Data Exchange (ETDEWEB)
Ringholm, Magnus; Gao, Bin; Thorvaldsen, Andreas J.; Ruud, Kenneth [Centre for Theoretical and Computational Chemistry (CTCC), Department of Chemistry, University of Tromsø—The Arctic University of Norway, 9037 Tromsø (Norway); Jonsson, Dan [Centre for Theoretical and Computational Chemistry (CTCC), Department of Chemistry, University of Tromsø—The Arctic University of Norway, 9037 Tromsø (Norway); High Performance Computing Group, University of Tromsø—The Arctic University of Norway, 9037 Tromsø (Norway); Bast, Radovan [Theoretical Chemistry and Biology, School of Biotechnology, Royal Institute of Technology, AlbaNova University Center, S-10691 Stockholm, Sweden and PDC Center for High Performance Computing, Royal Institute of Technology, S-10044 Stockholm (Sweden); Ekström, Ulf; Helgaker, Trygve [Center for Theoretical and Computational Chemistry (CTCC), Department of Chemistry, University of Oslo, P.O. Box 1033, Blindern, 0315 Oslo (Norway)
2014-01-21
We present the first analytic implementation of cubic and quartic force constants at the level of Kohn–Sham density-functional theory. The implementation is based on an open-ended formalism for the evaluation of energy derivatives in an atomic-orbital basis. The implementation relies on the availability of open-ended codes for evaluation of one- and two-electron integrals differentiated with respect to nuclear displacements as well as automatic differentiation of the exchange–correlation kernels. We use generalized second-order vibrational perturbation theory to calculate the fundamental frequencies of methane, ethane, benzene, and aniline, comparing B3LYP, BLYP, and Hartree–Fock results. The Hartree–Fock anharmonic corrections agree well with the B3LYP corrections when calculated at the B3LYP geometry and from B3LYP normal coordinates, suggesting that the inclusion of electron correlation is not essential for the reliable calculation of cubic and quartic force constants.
Energy Technology Data Exchange (ETDEWEB)
Lastras-Martinez, L.F.; Balderas-Navarro, R.E.; Castro-Garcia, R.; Herrera-Jasso, R.; Lastras-Martinez, A. [Instituto de Investigacion en Comunicacion Optica, Universidad Autonoma de San Luis Potosi, Alvaro Obregon 64, 78000 San Luis Potosi, S.L.P. (Mexico); Chavira-Rodriguez, M. [Departamento de Fisico Matematicas, Universidad Autonoma de San Luis Potosi, Alvaro Obregon 64, 78000 San Luis Potosi, S.L.P. (Mexico)
2011-01-15
The technique to measure optical anisotropies (OA) in cubic semiconductors is termed either reflectance difference spectroscopy (RDS) or reflectance anisotropy spectroscopy (RAS). In this paper we report on the application of RDS/RAS to a number of cubic semiconductors. We discuss RD spectra of GaAs, Si, CdTe, GaP, InP and GaSb (001) surfaces, induced by an uniaxial stress applied along [110] crystal directions. We show that all RD spectra can be explained in terms of a phenomenological model based on a perturbative Hamiltonian. We further report on measurements of spatial-resolved RDS measurements of GaAs employing a newly developed micro-RD spectrometer with a spatial resolution of 5 {mu}m. (Copyright copyright 2011 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)
Salmasi, Mahbod; Potter, Michael
2018-07-01
Maxwell's equations are discretized on a Face-Centered Cubic (FCC) lattice instead of a simple cubic as an alternative to the standard Yee method for improvements in numerical dispersion characteristics and grid isotropy of the method. Explicit update equations and numerical dispersion expressions, and the stability criteria are derived. Also, several tools available to the standard Yee method such as PEC/PMC boundary conditions, absorbing boundary conditions, and scattered field formulation are extended to this method as well. A comparison between the FCC and the Yee formulations is made, showing that the FCC method exhibits better dispersion compared to its Yee counterpart. Simulations are provided to demonstrate both the accuracy and grid isotropy improvement of the method.
ISAR Imaging of Ship Targets Based on an Integrated Cubic Phase Bilinear Autocorrelation Function
Directory of Open Access Journals (Sweden)
Jibin Zheng
2017-03-01
Full Text Available For inverse synthetic aperture radar (ISAR imaging of a ship target moving with ocean waves, the image constructed with the standard range-Doppler (RD technique is blurred and the range-instantaneous-Doppler (RID technique has to be used to improve the image quality. In this paper, azimuth echoes in a range cell of the ship target are modeled as noisy multicomponent cubic phase signals (CPSs after the motion compensation and a RID ISAR imaging algorithm is proposed based on the integrated cubic phase bilinear autocorrelation function (ICPBAF. The ICPBAF is bilinear and based on the two-dimensionally coherent energy accumulation. Compared to five other estimation algorithms, the ICPBAF can acquire higher cross term suppression and anti-noise performance with a reasonable computational cost. Through simulations and analyses with the synthetic model and real radar data, we verify the effectiveness of the ICPBAF and corresponding RID ISAR imaging algorithm.
Energy Technology Data Exchange (ETDEWEB)
Jayakumar, S., E-mail: sjayakumar.physics@gmail.com [Research and Development Centre, Bharathiar University, Coimbatore 641 014 (India); Department of Physics, Pollachi Institute of Engineering and Technology, Pollachi 642 205 (India); Ananthapadmanabhan, P.V.; Thiyagarajan, T.K. [Laser and Plasma Technology Division, BARC, Trombay, Mumbai 400 085 (India); Perumal, K. [Vision for Wisdom, Temple of Consciousness, Aliyar 642 101 (India); Mishra, S.C. [Department of Metallurgical and Materials Engg, National Institute of Technology, Rourkela 769 008 (India); Suresh, G. [Department of Physics, Park College of Engineering and Technology, Coimbatore 641 659 (India); Su, L.T.; Tok, A.I.Y. [School of Materials Science and Engg, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639 798 (Singapore)
2013-06-15
Pure zirconium oxide powders with particle size 2–33 nm are synthesized by reactive plasma processing. Transmission electron microscopy investigation of these particles revealed size dependent behavior for their phase stabilization. The monoclinic phase is found to be stable when particle size is ≥20 nm; Tetragonal is found to be stabilized in the range of 7–20 nm and as the particle size decreases to 6 nm and less, the cubic phase is stabilized. - Highlights: ► Direct conversion of micron-sized zirconium hydride powder to single crystal ZrO{sub 2} nanopowder. ► Size dependent stabilization of cubic, tetragonal and monoclinic phases in the reactive plasma synthesized ZrO{sub 2} nanopowder. ► Transmission electron microscopic investigation to identify particles of different sizes and their corresponding phase structure.
International Nuclear Information System (INIS)
Mittal, R.C.; Rohila, Rajni
2016-01-01
In this paper, we have applied modified cubic B-spline based differential quadrature method to get numerical solutions of one dimensional reaction-diffusion systems such as linear reaction-diffusion system, Brusselator system, Isothermal system and Gray-Scott system. The models represented by these systems have important applications in different areas of science and engineering. The most striking and interesting part of the work is the solution patterns obtained for Gray Scott model, reminiscent of which are often seen in nature. We have used cubic B-spline functions for space discretization to get a system of ordinary differential equations. This system of ODE’s is solved by highly stable SSP-RK43 method to get solution at the knots. The computed results are very accurate and shown to be better than those available in the literature. Method is easy and simple to apply and gives solutions with less computational efforts.
Canavos, G. C.
1974-01-01
A study is made of the extent to which the size of the sample affects the accuracy of a quadratic or a cubic polynomial approximation of an experimentally observed quantity, and the trend with regard to improvement in the accuracy of the approximation as a function of sample size is established. The task is made possible through a simulated analysis carried out by the Monte Carlo method in which data are simulated by using several transcendental or algebraic functions as models. Contaminated data of varying amounts are fitted to either quadratic or cubic polynomials, and the behavior of the mean-squared error of the residual variance is determined as a function of sample size. Results indicate that the effect of the size of the sample is significant only for relatively small sizes and diminishes drastically for moderate and large amounts of experimental data.
pH-responsive lyotropic liquid crystals for the preparation of pure cubic zirconia nanoparticles
Energy Technology Data Exchange (ETDEWEB)
He, Wei Yan; Liu, Jin Rong; He, Zhang; Cao, Zhen Zhu; Li, Cai Hong; Gao, Yan Fang [Inner Mongolia University of Technology, School of Chemical Engineering, Hohhot (China)
2016-07-15
We present a lyotropic liquid crystal system consisting of SDS/Triton X-100/water at 25 C. This system is respond to pH variations with a phase switch. When pH is altered from alkaline (pH 13) to acidic (pH 2) conditions, phase change occurs from a bicontinuous hexagonal phase to a partially hexagonal phase until it disappears. The hexagonal phase under alkaline conditions is stable. Thus, this system is an ideal candidate for the preparation of pure cubic ZrO{sub 2} nanoparticles. XRD results confirm that the as-synthesized powder is composed of pure cubic ZrO{sub 2}. These nanoparticles also exhibit a thermal stability of up to 800 C. The size and morphological characteristics of the nanoparticles are greatly affected by ZrOCl{sub 2} concentration. The mechanism of zirconia nanoparticle synthesis in a lyotropic hexagonal phase was proposed. (orig.)
Directory of Open Access Journals (Sweden)
Qin Guo-jie
2014-08-01
Full Text Available Sample-time errors can greatly degrade the dynamic range of a time-interleaved sampling system. In this paper, a novel correction technique employing a cubic spline interpolation is proposed for inter-channel sample-time error compensation. The cubic spline interpolation compensation filter is developed in the form of a finite-impulse response (FIR filter structure. The correction method of the interpolation compensation filter coefficients is deduced. A 4GS/s two-channel, time-interleaved ADC prototype system has been implemented to evaluate the performance of the technique. The experimental results showed that the correction technique is effective to attenuate the spurious spurs and improve the dynamic performance of the system.
Cubic Zig-Zag Enrichment of the Classical Kirchhoff Kinematics for Laminated and Sandwich Plates
Nemeth, Michael P.
2012-01-01
A detailed anaylsis and examples are presented that show how to enrich the kinematics of classical Kirchhoff plate theory by appending them with a set of continuous piecewise-cubic functions. This analysis is used to obtain functions that contain the effects of laminate heterogeneity and asymmetry on the variations of the inplane displacements and transverse shearing stresses, for use with a {3, 0} plate theory in which these distributions are specified apriori. The functions used for the enrichment are based on the improved zig-zag plate theory presented recently by Tessler, Di Scuva, and Gherlone. With the approach presented herein, the inplane displacements are represented by a set of continuous piecewise-cubic functions, and the transverse shearing stresses and strains are represented by a set of piecewise-quadratic functions that are discontinuous at the ply interfaces.
High-pressure phase of the cubic spinel NiMn2O4
DEFF Research Database (Denmark)
Åsbrink, S.; Waskowska, A.; Olsen, J. Staun
1998-01-01
experimental uncertainty, there is no volume change at the transition. The cia ratio of the tetragonal spinel is almost independent of pressure and equal to 0.91. The phase transition is attributed to the Jahn-Teller-type distortion and the ionic configurationcan be assumed as (Mn3+)(tetr)[Ni2+Mn3+](oct......It has been observed that the fee spinel NiMn2O4 transforms to a tetragonal structure at about 12 GPa. The tetragonal phase does not revert to the cubic phase upon decompression and its unit-cell constants at ambient pressure are a(0)=8.65(8) and c(0)=7.88(15) Angstrom (distorted fee). Within thr......). The bulk modulus of the cubic phase is 206(4) GPa....
Rotated domain network in graphene on cubic-SiC(001)
International Nuclear Information System (INIS)
Chaika, Alexander N; Aristov, Victor Y; Molodtsova, Olga V; Zakharov, Alexei A; Marchenko, Dmitry; Sánchez-Barriga, Jaime; Varykhalov, Andrei; Babenkov, Sergey V; Portail, Marc; Zielinski, Marcin; Murphy, Barry E; Krasnikov, Sergey A; Lübben, Olaf; Shvets, Igor V
2014-01-01
The atomic structure of the cubic-SiC(001) surface during ultra-high vacuum graphene synthesis has been studied using scanning tunneling microscopy (STM) and low-energy electron diffraction. Atomically resolved STM studies prove the synthesis of a uniform, millimeter-scale graphene overlayer consisting of nanodomains rotated by ±13.5° relative to the 〈110〉-directed boundaries. The preferential directions of the domain boundaries coincide with the directions of carbon atomic chains on the SiC(001)-c(2 × 2) reconstruction, fabricated prior to graphene synthesis. The presented data show the correlation between the atomic structures of the SiC(001)-c(2 × 2) surface and the graphene/SiC(001) rotated domain network and pave the way for optimizing large-area graphene synthesis on low-cost cubic-SiC(001)/Si(001) wafers. (paper)
Influence of Urban Traffic Driving Conditions and Vehicle Cubic Capacity on CO and VOC Emissions
Directory of Open Access Journals (Sweden)
Arina Negoitescu
2013-09-01
Full Text Available The reports regarding the global warming warn on the urgent need to reduce pollutant emissions and in particular greenhouse emissions. The performed analysis shows that cars equipped with engines operating on petrol, lead to a lower level of pollution, from the point of view of CO (carbon monoxide and VOCs (volatile organic compounds emissions at speeds above 50km/ h. Since driving in urban traffic mode involves driving with a speed up to 50km/h, it was comparatively analyzed the automobile engines operation with different cubic capacities. In conclusion, in terms of the analyzed emissions in accordance with the emission standards requirements for urban driving situations, it results that the accepted values of these emissions are recorded for automobile engines of low cubic capacities (under 1.4 l.
The influence of a cubic building on a roof mounted wind turbine
International Nuclear Information System (INIS)
Micallef, Daniel; Sant, Tonio; Ferreira, Carlos
2016-01-01
The performance of a wind turbine located above a cubic building is not well understood. This issue is of fundamental importance for the design of small scale wind turbines. One variable which is of particular importance in this respect is the turbine height above roof level. In this work, the power performance of a small wind turbine is assessed as a function of the height above the roof of a generic cubic building. A 3D Computational Fluid Dynamics model of a 10m x 10m x 10m building is used with the turbine modelled as an actuator disc. Results have shown an improvement in the average power coefficient even in cases where the rotor is partially located within the roof separation zone. This goes against current notions of small wind turbine power production. This study can be of particular importance to guide the turbine installation height on building roof tops. (paper)
Analysis of cubic and orthorhombic C3A hydration in presence of gypsum and lime
Kirchheim, A. P.
2009-02-26
Field emission scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD) have been used to study the microstructural changes and phase development that take place during the hydration of cubic (pure) and orthorhombic (Na-doped) tricalcium aluminate (C3A) and gypsum in the absence and presence of lime. The results demonstrate that important differences occur in the hydration of each C3A polymorph and gypsum when no lime is added; orthorhombic C3A reacts faster with gypsum than the cubic phase, forming longer ettringite needles; however, the presence of lime slows down the formation of ettringite in the orthorhombic sample. Additional rheometric tests showed the possible effects on the setting time in these cementitious mixes.
Analysis of cubic and orthorhombic C3A hydration in presence of gypsum and lime
Kirchheim, A. P.; Fernà ndez-Altable, V.; Monteiro, P. J. M.; Dal Molin, D. C. C.; Casanova, I.
2009-01-01
Field emission scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD) have been used to study the microstructural changes and phase development that take place during the hydration of cubic (pure) and orthorhombic (Na-doped) tricalcium aluminate (C3A) and gypsum in the absence and presence of lime. The results demonstrate that important differences occur in the hydration of each C3A polymorph and gypsum when no lime is added; orthorhombic C3A reacts faster with gypsum than the cubic phase, forming longer ettringite needles; however, the presence of lime slows down the formation of ettringite in the orthorhombic sample. Additional rheometric tests showed the possible effects on the setting time in these cementitious mixes.
Tran Hy, J
1998-01-01
This thesis describes some new studies of the effects of cubic nonlinearities arising from image-charge forces and octupole magnets on the transverse beam dynamics of proton synchrotrons and storage rings, and also a study of the damping of coherent oscillations using a feed-back damper. In the latter case, various corrective algorithms were modeled using linear one-turn maps. Kicks of fixed amplitude but appropriate sign were shown to provide linear damping and no coherent tune shift, though the rate predicted analytically was somewhat higher than that observed in simulations. This algorithm gave much faster damping (for equal power) than conventional proportional kicks, which damp exponentially. Two single-particle effects of the image-change force were investigated: distortion of the momentum dispersion function and amplitude dependence of the betatron tunes (resulting in tune spread). The former is calculated using transfer maps and the method of undetermined coefficients, the latter by solving the cubic ...
Enzymatic biofuel cell based on electrodes modified with lipid liquid-crystalline cubic phases
Nazaruk, Ewa; Smoliński, Sławomir; Swatko-Ossor, Marta; Ginalska, Grażyna; Fiedurek, Jan; Rogalski, Jerzy; Bilewicz, Renata
Two glassy carbon electrodes modified with enzymes embedded in lyotropic liquid-crystalline cubic phase were used for the biofuel cell construction. The monoolein liquid-crystalline film allowed to avoid separators in the biofuel cell. Glucose and oxygen as fuels, and glucose oxidase and laccase as anode and cathode biocatalysts, respectively were used. The biofuel cell parameters were examined in McIlvaine buffer, pH 7 solution containing 15 mM of glucose and saturated with dioxygen. A series of mediators were tested taking into account their formal potentials, stability in the cubic phase and efficiency of mediation. Most stable was the biofuel cell based on tetrathiafulvalene (TTF) and 2,2‧-azino-bis(3-ethylbenzothiazoline-6-sulfonate) (ABTS) as anode and cathode mediators, respectively. The open-circuit voltage was equal to 450 ± 40 mV. The power densities and current densities were measured for all the systems studied.
Theoretical study on recoilless fractions of simple cubic monatomic nanocrystalline particles
International Nuclear Information System (INIS)
Huang Jianping; Wang Luya
2002-01-01
Recoilless fractions of simple cubic monatomic nanocrystalline particles are calculated by using displacement-displacement Green's function. The numerical results show that the recoilless fractions on the surface of monatomic nanocrystalline particles are smaller than those in the inner, and they decrease when the particle size increase, the recoilless fractions of whole monatomic nanocrystalline particles increase when the particle size increase. These effects are more evident when the temperature is higher
Inelastic collision of two solitons for generalized BBM equation with cubic nonlinearity
Directory of Open Access Journals (Sweden)
Jingdong Wei
2015-06-01
Full Text Available We study the inelastic collision of two solitary waves of different velocities for the generalized Benjamin-Bona-Mahony (BBM equation with cubic nonlinearity. It shows that one solitary wave is smaller than the other one in the H^1(R energy space. We explore the sharp estimates of the nonzero residue due to the collision, and prove the inelastic collision of two solitary waves and nonexistence of a pure 2-soliton solution.
Analysis of RIA standard curve by log-logistic and cubic log-logit models
International Nuclear Information System (INIS)
Yamada, Hideo; Kuroda, Akira; Yatabe, Tami; Inaba, Taeko; Chiba, Kazuo
1981-01-01
In order to improve goodness-of-fit in RIA standard analysis, programs for computing log-logistic and cubic log-logit were written in BASIC using personal computer P-6060 (Olivetti). Iterative least square method of Taylor series was applied for non-linear estimation of logistic and log-logistic. Hear ''log-logistic'' represents Y = (a - d)/(1 + (log(X)/c)sup(b)) + d As weights either 1, 1/var(Y) or 1/σ 2 were used in logistic or log-logistic and either Y 2 (1 - Y) 2 , Y 2 (1 - Y) 2 /var(Y), or Y 2 (1 - Y) 2 /σ 2 were used in quadratic or cubic log-logit. The term var(Y) represents squares of pure error and σ 2 represents estimated variance calculated using a following equation log(σ 2 + 1) = log(A) + J log(y). As indicators for goodness-of-fit, MSL/S sub(e)sup(2), CMD% and WRV (see text) were used. Better regression was obtained in case of alpha-fetoprotein by log-logistic than by logistic. Cortisol standard curve was much better fitted with cubic log-logit than quadratic log-logit. Predicted precision of AFP standard curve was below 5% in log-logistic in stead of 8% in logistic analysis. Predicted precision obtained using cubic log-logit was about five times lower than that with quadratic log-logit. Importance of selecting good models in RIA data processing was stressed in conjunction with intrinsic precision of radioimmunoassay system indicated by predicted precision. (author)
Cubic spline numerical solution of an ablation problem with convective backface cooling
Lin, S.; Wang, P.; Kahawita, R.
1984-08-01
An implicit numerical technique using cubic splines is presented for solving an ablation problem on a thin wall with convective cooling. A non-uniform computational mesh with 6 grid points has been used for the numerical integration. The method has been found to be computationally efficient, providing for the care under consideration of an overall error of about 1 percent. The results obtained indicate that the convective cooling is an important factor in reducing the ablation thickness.
A splitting algorithm for the wavelet transform of cubic splines on a nonuniform grid
Sulaimanov, Z. M.; Shumilov, B. M.
2017-10-01
For cubic splines with nonuniform nodes, splitting with respect to the even and odd nodes is used to obtain a wavelet expansion algorithm in the form of the solution to a three-diagonal system of linear algebraic equations for the coefficients. Computations by hand are used to investigate the application of this algorithm for numerical differentiation. The results are illustrated by solving a prediction problem.
On the accurate fast evaluation of finite Fourier integrals using cubic splines
International Nuclear Information System (INIS)
Morishima, N.
1993-01-01
Finite Fourier integrals based on a cubic-splines fit to equidistant data are shown to be evaluated fast and accurately. Good performance, especially on computational speed, is achieved by the optimization of the spline fit and the internal use of the fast Fourier transform (FFT) algorithm for complex data. The present procedure provides high accuracy with much shorter CPU time than a trapezoidal FFT. (author)
Deformation behaviour of body centered cubic Fe nanowires under tensile and compressive loading
Sainath, G.; Choudhary, B. K.; Jayakumar, T.
2014-01-01
Molecular Dynamics (MD) simulations have been carried out to investigate the deformation behaviour of /{111} body centered cubic (BCC) Fe nanowires under tensile and compressive loading. An embedded atom method (EAM) potential was used to describe the interatomic interactions. The simulations were carried out at 10 K with a constant strain rate of $1\\times10^{8}$ $s^{-1}$. The results indicate a significant differences in deformation mechanisms under tensile and compressive loading. Under ten...
Explicit Gaussian quadrature rules for C^1 cubic splines with symmetrically stretched knot sequence
Ait-Haddou, Rachid
2015-06-19
We provide explicit expressions for quadrature rules on the space of C^1 cubic splines with non-uniform, symmetrically stretched knot sequences. The quadrature nodes and weights are derived via an explicit recursion that avoids an intervention of any numerical solver and the rule is optimal, that is, it requires minimal number of nodes. Numerical experiments validating the theoretical results and the error estimates of the quadrature rules are also presented.
Ion-induced stress relaxation during the growth of cubic boron nitride thin films
Energy Technology Data Exchange (ETDEWEB)
Abendroth, B.E.
2004-08-01
in this thesis the deposition of cubic boron nitride films by magnetron sputtering is described. The deposition process is analyzed by Langmuir-probe measurement and energy resolved mass spectroscopy. the films are studied by stress measurement, spectroscopic ellipsometry, infrared spectroscopy, elastic recoil detection analysis, Rutherford backscattering spectroscopy, X-ray absorption near edge spectroscopy, X-ray diffraction, and transmission electron microscopy. Discussed are the stress relaxation and the microstructure and bonding characteristics together with the effects of ion bombardement. (HSI)
Solutions to the equations describing materials with competing quadratic and cubic nonlinearities
International Nuclear Information System (INIS)
Li-Na, Zhao; Ji, Lin; Zi-Shuang, Tong
2009-01-01
The Lie group theoretical method is used to study the equations describing materials with competing quadratic and cubic nonlinearities. The equations share some of the nice properties of soliton equations. From the elliptic functions expansion method, we obtain large families of analytical solutions, in special cases, we have the periodic, kink and solitary solutions of the equations. Furthermore, we investigate the stability of these solutions under the perturbation of amplitude noises by numerical simulation
Ignatenko, A. N.; Irkhin, V. Yu.
2016-01-01
We have studied the Heisenberg antiferromagnets characterized by the magnetic structures with the periods being two times larger than the lattice period. We have considered all the types of the Bravais lattices (simple cubic, bcc and fcc) and divided all these antiferromagnets into 7 classes i.e. 3 plus 4 classes denoted with symbols A and B correspondingly. The order parameter characterizing the degeneracies of the magnetic structures is an ordinary Neel vector for A classes and so-called 4-...
On the reflection of solitons of the cubic nonlinear Schrödinger equation
Katsaounis, Theodoros
2016-07-05
In this paper, we perform a numerical study on the interesting phenomenon of soliton reflection of solid walls. We consider the 2D cubic nonlinear Schrödinger equation as the underlying mathematical model, and we use an implicit-explicit type Crank-Nicolson finite element scheme for its numerical solution. After verifying the perfect reflection of the solitons on a vertical wall, we present the imperfect reflection of a dark soliton on a diagonal wall.
Criticality of the bond-diluted Ising ferromagnet in a semi-infinite simple cubic lattice
International Nuclear Information System (INIS)
Silva, L.R. da; Tsallis, C.; Sarmento, E.F.
1987-01-01
We study the phase diagram and universality classes of the quenched bond-diluted spin 1/2 Ising ferromagnetic in a semi-infinite simple cubic lattice with a (0,0,1) free surface. We observe that surface ferromagnetism persists below the d=2 percolation threshold p c 2D = 1/2, in fact down to pc∼0,42. (M.W.O.) [pt
Curvelet-domain multiple matching method combined with cubic B-spline function
Wang, Tong; Wang, Deli; Tian, Mi; Hu, Bin; Liu, Chengming
2018-05-01
Since the large amount of surface-related multiple existed in the marine data would influence the results of data processing and interpretation seriously, many researchers had attempted to develop effective methods to remove them. The most successful surface-related multiple elimination method was proposed based on data-driven theory. However, the elimination effect was unsatisfactory due to the existence of amplitude and phase errors. Although the subsequent curvelet-domain multiple-primary separation method achieved better results, poor computational efficiency prevented its application. In this paper, we adopt the cubic B-spline function to improve the traditional curvelet multiple matching method. First, select a little number of unknowns as the basis points of the matching coefficient; second, apply the cubic B-spline function on these basis points to reconstruct the matching array; third, build constraint solving equation based on the relationships of predicted multiple, matching coefficients, and actual data; finally, use the BFGS algorithm to iterate and realize the fast-solving sparse constraint of multiple matching algorithm. Moreover, the soft-threshold method is used to make the method perform better. With the cubic B-spline function, the differences between predicted multiple and original data diminish, which results in less processing time to obtain optimal solutions and fewer iterative loops in the solving procedure based on the L1 norm constraint. The applications to synthetic and field-derived data both validate the practicability and validity of the method.
First-principles cluster variation calculations of tetragonal-cubic transition in ZrO2
International Nuclear Information System (INIS)
Mohri, Tetsuo; Chen, Ying; Kiyokane, Naoya
2013-01-01
Highlights: ► Cluster variation method is extended to study displacive transition. ► Electronic structure total energy calculations are performed on ZrO2. ► Tetragonal-cubic transition is studied within the framework of order -disorder transition. -- Abstract: It is attempted to extend the basic idea of continuous displacement cluster variation method (CDCVM) to the study of a displacive phase transition. As a preliminary study, we focus on cubic to tetragonal transition in ZrO 2 in which oxygen atoms on the cubic lattice are displaced alternatively in the opposite direction (upward and downward) along the tetragonal axis. Within the CDCVM, displaced atoms are regarded as different atomic species, and two distinguished atoms, A-oxygen (upward shifting) and B-oxygen (downward shifting), are introduced in the description of the free energy. FLAPW electronic structure total energy calculations are performed to extract effective interaction energies among displaced oxygen atoms, and by combing them with CDCVM, the transition temperature is calculated from the first-principles
On the magnetization process and the associated probability in anisotropic cubic crystals
Energy Technology Data Exchange (ETDEWEB)
Khedr, D.M., E-mail: doaamohammed88@gmail.com [Department of Basic Science, Modern Academy of Engineering and Technology at Maadi, Cairo (Egypt); Aly, Samy H.; Shabara, Reham M. [Department of Physics, Faculty of Science at Damietta, University of Damietta, Damietta (Egypt); Yehia, Sherif [Department of Physics, Faculty of Science at Helwan, University of Helwan, Helwan (Egypt)
2017-05-15
We present a theoretical method to calculate specific magnetic properties, e.g. magnetization curves, magnetic susceptibility and probability landscapes along the [100], [110] and [111] crystallographic directions of a crystal of cubic symmetry. The probability landscape displays the evolution of the most probable angular orientation of the magnetization vector, for selected temperatures and magnetic fields. Our method is based on the premises of classical statistical mechanics. The energy density, used in the partition function, is the sum of magnetic anisotropy and Zeeman energies, however no other energies e.g. elastic or magnetoelastic terms are considered in the present work. Model cubic systems of diverse anisotropies are analyzed first, and subsequently material magnetic systems of cubic symmetry; namely iron, nickel and Co{sub x} Fe{sub 100−x} compounds, are discussed. We highlight a correlation between magnetization curves and the associated probability landscapes. In addition, determination of easiest axes of magnetization, using energy consideration, is done and compared with the results of the present method.
The influence of coordinated defects on inhomogeneous broadening in cubic lattices
Energy Technology Data Exchange (ETDEWEB)
Matheson, P. L., E-mail: phil.matheson@uvu.edu; Sullivan, Francis P.; Evenson, William E. [Utah Valley University, Department of Physics (United States)
2016-12-15
The joint probability distribution function (JPDF) of electric field gradient (EFG) tensor components in cubic materials is dominated by coordinated pairings of defects in shells near probe nuclei. The contributions from these inner shell combinations and their surrounding structures contain the essential physics that determine the PAC-relevant quantities derived from them. The JPDF can be used to predict the nature of inhomogeneous broadening (IHB) in perturbed angular correlation (PAC) experiments by modeling the G{sub 2} spectrum and finding expectation values for V{sub zz} and η. The ease with which this can be done depends upon the representation of the JPDF. Expanding on an earlier work by Czjzek et al. (Hyperfine Interact. 14, 189–194, 1983), Evenson et al. (Hyperfine Interact. 237, 119, 2016) provide a set of coordinates constructed from the EFG tensor invariants they named W{sub 1} and W{sub 2}. Using this parameterization, the JPDF in cubic structures was constructed using a point charge model in which a single trapped defect (TD) is the nearest neighbor to a probe nucleus. Individual defects on nearby lattice sites pair with the TD to provide a locus of points in the W{sub 1}−W{sub 2} plane around which an amorphous-like distribution of probability density grows. Interestingly, however, marginal, separable PDFs appear adequate to model IHB relevant cases. We present cases from simulations in cubic materials illustrating the importance of these near-shell coordinations.
Particle linear theory on a self-gravitating perturbed cubic Bravais lattice
International Nuclear Information System (INIS)
Marcos, B.
2008-01-01
Discreteness effects are a source of uncontrolled systematic errors of N-body simulations, which are used to compute the evolution of a self-gravitating fluid. We have already developed the so-called ''particle linear theory''(PLT), which describes the evolution of the position of self-gravitating particles located on a perturbed simple cubic lattice. It is the discrete analogue of the well-known (Lagrangian) linear theory of a self-gravitating fluid. Comparing both theories permits us to quantify precisely discreteness effects in the linear regime. It is useful to develop the PLT also for other perturbed lattices because they represent different discretizations of the same continuous system. In this paper we detail how to implement the PLT for perturbed cubic Bravais lattices (simple, body, and face-centered) in a cubic simulation box. As an application, we will study the discreteness effects--in the linear regime--of N-body simulations for which initial conditions have been set up using these different lattices.
Synthesis and characterization of gold cubic nanoshells using water-soluble GeO₂templates.
Wang, Cen; Tang, Peisong; Ge, Mingyuan; Xu, Xiaobin; Cao, Feng; Jiang, J Z
2011-04-15
Size-tunable GeO₂ nanocubes were initially prepared by a modified sono-assisted reverse micelle method and then functionalized with an amino-terminated silanizing agent. Subsequently, gold decorated GeO₂ nanocomposites were prepared at pH ≈ 7 and 80 °C. It was found that well-dispersed gold nanoparticles on GeO₂ nanocubes could be obtained only if gold salt is abundant to favor simultaneous, homogeneous nucleation of gold particles. Additional gold ions were reduced onto these attached 'seed' particles accompanied by synchronous dissolution of water-soluble GeO₂ cores, resulting in gold hollow cubic shells. The GeO₂ nanocubes and Au/GeO₂ nanocomposites as well as gold hollow cubic shells were characterized by transmission electron microscopy, scanning electron microscopy, x-ray diffraction and UV-visible spectroscopy. In particular, gold hollow cubic shells feature a plasmon resonance peak at above 900 nm, which renders it quite promising in biochemical applications.
Synthesis and characterization of gold cubic nanoshells using water-soluble GeO2 templates
Wang, Cen; Tang, Peisong; Ge, Mingyuan; Xu, Xiaobin; Cao, Feng; Jiang, J. Z.
2011-04-01
Size-tunable GeO2 nanocubes were initially prepared by a modified sono-assisted reverse micelle method and then functionalized with an amino-terminated silanizing agent. Subsequently, gold decorated GeO2 nanocomposites were prepared at pH ≈ 7 and 80 °C. It was found that well-dispersed gold nanoparticles on GeO2 nanocubes could be obtained only if gold salt is abundant to favor simultaneous, homogeneous nucleation of gold particles. Additional gold ions were reduced onto these attached 'seed' particles accompanied by synchronous dissolution of water-soluble GeO2 cores, resulting in gold hollow cubic shells. The GeO2 nanocubes and Au/GeO2 nanocomposites as well as gold hollow cubic shells were characterized by transmission electron microscopy, scanning electron microscopy, x-ray diffraction and UV-visible spectroscopy. In particular, gold hollow cubic shells feature a plasmon resonance peak at above 900 nm, which renders it quite promising in biochemical applications.
Synthesis and characterization of gold cubic nanoshells using water-soluble GeO2 templates
International Nuclear Information System (INIS)
Wang Cen; Ge Mingyuan; Xu Xiaobin; Jiang, J Z; Tang Peisong; Cao Feng
2011-01-01
Size-tunable GeO 2 nanocubes were initially prepared by a modified sono-assisted reverse micelle method and then functionalized with an amino-terminated silanizing agent. Subsequently, gold decorated GeO 2 nanocomposites were prepared at pH ∼ 7 and 80 deg. C. It was found that well-dispersed gold nanoparticles on GeO 2 nanocubes could be obtained only if gold salt is abundant to favor simultaneous, homogeneous nucleation of gold particles. Additional gold ions were reduced onto these attached 'seed' particles accompanied by synchronous dissolution of water-soluble GeO 2 cores, resulting in gold hollow cubic shells. The GeO 2 nanocubes and Au/GeO 2 nanocomposites as well as gold hollow cubic shells were characterized by transmission electron microscopy, scanning electron microscopy, x-ray diffraction and UV-visible spectroscopy. In particular, gold hollow cubic shells feature a plasmon resonance peak at above 900 nm, which renders it quite promising in biochemical applications.
Effect of electrostatic interactions on phase stability of cubic phases of biomembranes.
Li, Shu Jie; Masum, Shah Md; Yamashita, Yuko; Tamba, Yukihiro; Yamazaki, Masahito
2002-06-01
We investigated effect of electrostatic interactions due to surfacecharges on structures and stability of cubic phases of monoolein (MO)membrane using the small-angle X-ray scattering method. Firstly, wechanged the surface charge density of the membrane by usingdioleoylphosphatidic acid (DOPA). As increasing DOPA concentration in themembrane at 30 wt % lipid concentration, a Q(224) to Q(229) phasetransition occurred at 0.6 mol % DOPA, and at and above 25 mol %, DOPA/MOmembranes were in the L(α) phase. NaCl in the bulk phase reduced theeffect of DOPA. These results indicate that as the electrostaticinteractions increase, the most stable phase changes as follows: Q(224)⇒ Q(229) ⇒ L(α). The increase in DOPAconcentration reduced the absolute value of spontaneous curvature of themembrane, | H(0) |. Secondly, we changed the surface charge of themembrane by adding a de novo designed peptide, which has netpositive charges and a binding site on the electrically neutral membraneinterface. The peptide-1 (WLFLLKKK) induced a Q(224) to Q(229)phase transition in the MO membrane at low peptide concentration. As NaClconcentration increases, the MO/peptide-1 membrane changed from Q(229)to Q(224) phase. The increase in peptide-1 concentration reduced |H(0) |. Based on these results, the stability of the cubic phases and themechanism of phase transition between cubic phase and L(α) phase arediscussed.
Application of Cubic Box Spline Wavelets in the Analysis of Signal Singularities
Directory of Open Access Journals (Sweden)
Rakowski Waldemar
2015-12-01
Full Text Available In the subject literature, wavelets such as the Mexican hat (the second derivative of a Gaussian or the quadratic box spline are commonly used for the task of singularity detection. The disadvantage of the Mexican hat, however, is its unlimited support; the disadvantage of the quadratic box spline is a phase shift introduced by the wavelet, making it difficult to locate singular points. The paper deals with the construction and properties of wavelets in the form of cubic box splines which have compact and short support and which do not introduce a phase shift. The digital filters associated with cubic box wavelets that are applied in implementing the discrete dyadic wavelet transform are defined. The filters and the algorithme à trous of the discrete dyadic wavelet transform are used in detecting signal singularities and in calculating the measures of signal singularities in the form of a Lipschitz exponent. The article presents examples illustrating the use of cubic box spline wavelets in the analysis of signal singularities.
CubiCal - Fast radio interferometric calibration suite exploiting complex optimisation
Kenyon, J. S.; Smirnov, O. M.; Grobler, T. L.; Perkins, S. J.
2018-05-01
It has recently been shown that radio interferometric gain calibration can be expressed succinctly in the language of complex optimisation. In addition to providing an elegant framework for further development, it exposes properties of the calibration problem which can be exploited to accelerate traditional non-linear least squares solvers such as Gauss-Newton and Levenberg-Marquardt. We extend existing derivations to chains of Jones terms: products of several gains which model different aberrant effects. In doing so, we find that the useful properties found in the single term case still hold. We also develop several specialised solvers which deal with complex gains parameterised by real values. The newly developed solvers have been implemented in a Python package called CubiCal, which uses a combination of Cython, multiprocessing and shared memory to leverage the power of modern hardware. We apply CubiCal to both simulated and real data, and perform both direction-independent and direction-dependent self-calibration. Finally, we present the results of some rudimentary profiling to show that CubiCal is competitive with respect to existing calibration tools such as MeqTrees.
Investigation of the validity of radiosity for sound-field prediction in cubic rooms
Nosal, Eva-Marie; Hodgson, Murray; Ashdown, Ian
2004-12-01
This paper explores acoustical (or time-dependent) radiosity using predictions made in four cubic enclosures. The methods and algorithms used are those presented in a previous paper by the same authors [Nosal, Hodgson, and Ashdown, J. Acoust. Soc. Am. 116(2), 970-980 (2004)]. First, the algorithm, methods, and conditions for convergence are investigated by comparison of numerous predictions for the four cubic enclosures. Here, variables and parameters used in the predictions are varied to explore the effect of absorption distribution, the necessary conditions for convergence of the numerical solution to the analytical solution, form-factor prediction methods, and the computational requirements. The predictions are also used to investigate the effect of absorption distribution on sound fields in cubic enclosures with diffusely reflecting boundaries. Acoustical radiosity is then compared to predictions made in the four enclosures by a ray-tracing model that can account for diffuse reflection. Comparisons are made of echograms, room-acoustical parameters, and discretized echograms. .
Electronic, elastic, acoustic and optical properties of cubic TiO2: A DFT approach
International Nuclear Information System (INIS)
Mahmood, Tariq; Cao, Chuanbao; Tahir, Muhammad; Idrees, Faryal; Ahmed, Maqsood; Tanveer, M.; Aslam, Imran; Usman, Zahid; Ali, Zulfiqar; Hussain, Sajad
2013-01-01
The electronic, elastic, acoustic and optical properties of cubic phases TiO 2 fluorite and pyrite are investigated using the first principles calculations. We have employed five different exchange–correlation functions within the local density and generalized gradient approximations using the ultrasoft plane wave pseudopotential method. The calculated band structures of cubic-TiO 2 elucidate that the TiO 2 fluorite and pyrite are direct and indirect semiconductors in contrast to the previous findings. From our studied properties such as bulk and shear moduli, elastic constants C 44 and Debye temperature for TiO 2 fluorite and pyrite, we infer that both the cubic phases are not superhard materials and the pyrite phase is harder than fluorite. The longitudinal and transversal acoustic wave speeds for both phases in the directions [100], [110] and [111] are determined using the pre-calculated elastic constants. In addition, we also calculate the optical properties such as dielectric function, absorption spectrum, refractive index and energy loss function using the pre-optimized structure. On the observation of optical properties TiO 2 fluorite phase turn out to be more photocatalytic than pyrite
Mechanical and Thermophysical Properties of Cubic Rock-Salt AlN Under High Pressure
Lebga, Noudjoud; Daoud, Salah; Sun, Xiao-Wei; Bioud, Nadhira; Latreche, Abdelhakim
2018-03-01
Density functional theory, density functional perturbation theory, and the Debye model have been used to investigate the structural, elastic, sound velocity, and thermodynamic properties of AlN with cubic rock-salt structure under high pressure, yielding the equilibrium structural parameters, equation of state, and elastic constants of this interesting material. The isotropic shear modulus, Pugh ratio, and Poisson's ratio were also investigated carefully. In addition, the longitudinal, transverse, and average elastic wave velocities, phonon contribution to the thermal conductivity, and interesting thermodynamic properties were predicted and analyzed in detail. The results demonstrate that the behavior of the elastic wave velocities under increasing hydrostatic pressure explains the hardening of the corresponding phonons. Based on the elastic stability criteria under pressure, it is found that AlN with cubic rock-salt structure is mechanically stable, even at pressures up to 100 GPa. Analysis of the Pugh ratio and Poisson's ratio revealed that AlN with cubic rock-salt structure behaves in brittle manner.
International Nuclear Information System (INIS)
Li, Gang; Li, Xiao-Sen; Li, Bo; Wang, Yi
2014-01-01
The combination forms of the hydrate dissociation methods in different well systems are divided into 6 main patterns. Dissociation processes of methane hydrate in porous media using the inverted five-spot water flooding method (Pattern 4) are investigated by the experimental observation and numerical simulation. In situ methane hydrate is synthesized in the Cubic Hydrate Simulator (CHS), a 5.832-L cubic reactor. A center vertical well is used as the hot water injection well, while the four vertical wells at the corner are the gas and water production wells. The gas production begins simultaneously with the hot water injection, while after approximately 20 min of compression, the water begins to be produced. One of the common characteristics of the inverted five-spot water flooding method is that both the gas and water production rates decrease with the reduction of the hydrate dissociation rate. The evaluation of the energy efficiency ratio might indicate the inverted five-spot water flooding as a promising gas producing method from the hydrate reservoir. - Highlights: • A three-dimensional 5.8-L cubic pressure vessel is developed. • Gas production of hydrate using inverted five-spot flooding method is studied. • Water/gas production rate and energy efficiency ratio are evaluated. • Temperature distributions of numerical simulation and experiment agree well. • Hydrate dissociation process is a moving boundary problem in this study
Grajeda, Laura M; Ivanescu, Andrada; Saito, Mayuko; Crainiceanu, Ciprian; Jaganath, Devan; Gilman, Robert H; Crabtree, Jean E; Kelleher, Dermott; Cabrera, Lilia; Cama, Vitaliano; Checkley, William
2016-01-01
Childhood growth is a cornerstone of pediatric research. Statistical models need to consider individual trajectories to adequately describe growth outcomes. Specifically, well-defined longitudinal models are essential to characterize both population and subject-specific growth. Linear mixed-effect models with cubic regression splines can account for the nonlinearity of growth curves and provide reasonable estimators of population and subject-specific growth, velocity and acceleration. We provide a stepwise approach that builds from simple to complex models, and account for the intrinsic complexity of the data. We start with standard cubic splines regression models and build up to a model that includes subject-specific random intercepts and slopes and residual autocorrelation. We then compared cubic regression splines vis-à-vis linear piecewise splines, and with varying number of knots and positions. Statistical code is provided to ensure reproducibility and improve dissemination of methods. Models are applied to longitudinal height measurements in a cohort of 215 Peruvian children followed from birth until their fourth year of life. Unexplained variability, as measured by the variance of the regression model, was reduced from 7.34 when using ordinary least squares to 0.81 (p linear mixed-effect models with random slopes and a first order continuous autoregressive error term. There was substantial heterogeneity in both the intercept (p modeled with a first order continuous autoregressive error term as evidenced by the variogram of the residuals and by a lack of association among residuals. The final model provides a parametric linear regression equation for both estimation and prediction of population- and individual-level growth in height. We show that cubic regression splines are superior to linear regression splines for the case of a small number of knots in both estimation and prediction with the full linear mixed effect model (AIC 19,352 vs. 19
Cubic AlGaN/GaN structures for device application
Energy Technology Data Exchange (ETDEWEB)
Schoermann, Joerg
2007-05-15
The aim of this work was the growth and the characterization of cubic GaN, cubic AlGaN/GaN heterostructures and cubic AlN/GaN superlattice structures. Reduction of the surface and interface roughness was the key issue to show the potential for the use of cubic nitrides in futur devices. All structures were grown by plasma assisted molecular beam epitaxy on free standing 3C-SiC (001) substrates. In situ reflection high energy electron diffraction was first investigated to determine the Ga coverage of c-GaN during growth. Using the intensity of the electron beam as a probe, optimum growth conditions were found when a 1 monolayer coverage is formed at the surface. GaN samples grown under these conditions reveal excellent structural properties. On top of the c-GaN buffer c-AlGaN/GaN single and multiple quantum wells were deposited. The well widths ranged from 2.5 to 7.5 nm. During growth of Al{sub 0.15}Ga{sub 0.85}N/GaN quantum wells clear reflection high energy electron diffraction oscillations were observed indicating a two dimensional growth mode. We observed strong room-temperature, ultraviolet photoluminescence at about 3.3 eV with a minimum linewidth of 90 meV. The peak energy of the emission versus well width is reproduced by a square-well Poisson- Schroedinger model calculation. We found that piezoelectric effects are absent in c-III nitrides with a (001) growth direction. Intersubband transition in the wavelength range from 1.6 {mu}m to 2.1 {mu}m was systematically investigated in AlN/GaN superlattices (SL), grown on 100 nm thick c-GaN buffer layers. The SLs consisted of 20 periods of GaN wells with a thickness between 1.5 nm and 2.1 nm and AlN barriers with a thickness of 1.35 nm. The first intersubband transitions were observed in metastable cubic III nitride structures in the range between 1.6 {mu}m and 2.1 {mu}m. (orig.)
Study on the formation of cubic texture in Ni-7 at.% W alloy substrates by powder metallurgy routes
DEFF Research Database (Denmark)
Zhao, Yue; Suo, HongLi; Zhu, YongHua
2009-01-01
One of the main challenges for coated conductor applications is to produce sharp cubic textured alloy substrates with high strength and low magnetism. In this work, the cubic textured Ni–7 at.% W substrates were prepared from different powder metallurgy ingots by rolling-assisted biaxially textured...... substrate processing. The fabrication processes of cubic texture in the Ni–7 at.% W tapes by two powder metallurgy routes are described in detail. Through the optimized process, full width at half maximum values of 6.7° and 5.0° were obtained, as estimated by X-ray (1 1 1) phi scan and (2 0 0) rocking curve...
Possible significance of cubic water-ice, H2O-Ic, in the atmospheric water cycle of Mars
Gooding, James L.
1988-01-01
The possible formation and potential significance of the cubic ice polymorph on Mars is discussed. When water-ice crystallizes on Earth, the ambient conditions of temperature and pressure result in the formation of the hexagonal ice polymorph; however, on Mars, the much lower termperature and pressures may permit the crystallization of the cubic polymorph. Cubic ice has two properties of possible importance on Mars: it is an excellant nucleator of other volatiles (such as CO2), and it undergoes an exothermic transition to hexagonal ice at temperatures above 170 K. These properties may have significant implications for both martian cloud formation and the development of the seasonal polar caps.
Energy Technology Data Exchange (ETDEWEB)
Hegde, Ganesh, E-mail: ghegde@purdue.edu; Povolotskyi, Michael; Kubis, Tillmann; Klimeck, Gerhard, E-mail: gekco@purdue.edu [Network for Computational Nanotechnology (NCN), Department of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana 47907 (United States); Boykin, Timothy [Department of Electrical and Computer Engineering, University of Alabama, Huntsville, Alabama (United States)
2014-03-28
Semi-empirical Tight Binding (TB) is known to be a scalable and accurate atomistic representation for electron transport for realistically extended nano-scaled semiconductor devices that might contain millions of atoms. In this paper, an environment-aware and transferable TB model suitable for electronic structure and transport simulations in technologically relevant metals, metallic alloys, metal nanostructures, and metallic interface systems are described. Part I of this paper describes the development and validation of the new TB model. The new model incorporates intra-atomic diagonal and off-diagonal elements for implicit self-consistency and greater transferability across bonding environments. The dependence of the on-site energies on strain has been obtained by appealing to the Moments Theorem that links closed electron paths in the system to energy moments of angular momentum resolved local density of states obtained ab initio. The model matches self-consistent density functional theory electronic structure results for bulk face centered cubic metals with and without strain, metallic alloys, metallic interfaces, and metallic nanostructures with high accuracy and can be used in predictive electronic structure and transport problems in metallic systems at realistically extended length scales.
International Nuclear Information System (INIS)
Hegde, Ganesh; Povolotskyi, Michael; Kubis, Tillmann; Klimeck, Gerhard; Boykin, Timothy
2014-01-01
Semi-empirical Tight Binding (TB) is known to be a scalable and accurate atomistic representation for electron transport for realistically extended nano-scaled semiconductor devices that might contain millions of atoms. In this paper, an environment-aware and transferable TB model suitable for electronic structure and transport simulations in technologically relevant metals, metallic alloys, metal nanostructures, and metallic interface systems are described. Part I of this paper describes the development and validation of the new TB model. The new model incorporates intra-atomic diagonal and off-diagonal elements for implicit self-consistency and greater transferability across bonding environments. The dependence of the on-site energies on strain has been obtained by appealing to the Moments Theorem that links closed electron paths in the system to energy moments of angular momentum resolved local density of states obtained ab initio. The model matches self-consistent density functional theory electronic structure results for bulk face centered cubic metals with and without strain, metallic alloys, metallic interfaces, and metallic nanostructures with high accuracy and can be used in predictive electronic structure and transport problems in metallic systems at realistically extended length scales
Hegde, Ganesh; Povolotskyi, Michael; Kubis, Tillmann; Boykin, Timothy; Klimeck, Gerhard
2014-03-01
Semi-empirical Tight Binding (TB) is known to be a scalable and accurate atomistic representation for electron transport for realistically extended nano-scaled semiconductor devices that might contain millions of atoms. In this paper, an environment-aware and transferable TB model suitable for electronic structure and transport simulations in technologically relevant metals, metallic alloys, metal nanostructures, and metallic interface systems are described. Part I of this paper describes the development and validation of the new TB model. The new model incorporates intra-atomic diagonal and off-diagonal elements for implicit self-consistency and greater transferability across bonding environments. The dependence of the on-site energies on strain has been obtained by appealing to the Moments Theorem that links closed electron paths in the system to energy moments of angular momentum resolved local density of states obtained ab initio. The model matches self-consistent density functional theory electronic structure results for bulk face centered cubic metals with and without strain, metallic alloys, metallic interfaces, and metallic nanostructures with high accuracy and can be used in predictive electronic structure and transport problems in metallic systems at realistically extended length scales.
International Nuclear Information System (INIS)
Bitzek, Erik; Gumbsch, Peter
2004-01-01
Atomistic simulations of an accelerating edge dislocation were carried out to study the effects of drag and inertia. Using an embedded atom potential for nickel, the Peierls stress, the effective mass and the drag coefficient of an edge dislocation were determined for different temperatures and stresses in a simple slab geometry. The effect of {1 1 1} surfaces on an intersecting edge dislocation were studied by appropriately cutting the slab. A dislocation intersecting a surface step was used as a model system to demonstrate the importance of inertial effects for dynamically overcoming short range obstacles. Significant effects were found even at room temperature. A simple model based on the dislocation-obstacle interaction energies was used to describe the findings
International Nuclear Information System (INIS)
Sciani, V.; Lucki, G.; Jung, P.
1984-01-01
Helium has been homogeneously introduced into gold foils at room temperature by alpha implantation in a CV-28 cyclotron. After implantation the helium release was observed in isothermal and linear heating experiments. The diffusion coefficient follows an Arrhenius behaviour with D sub(o) = 0.1 cm 2 /s and ΔH = 1.7 eV. Possible diffusion mechanisms are discussed. (Author) [pt
Xu, Yong-Qiang; Wu, Shao-Yi; Ding, Chang-Chun; Wu, Li-Na; Zhang, Gao-Jun
2018-03-01
The geometric structures, band structures, density of states and optical absorption spectra are studied for cubic and orthorhombic KNbO3 (C- and O-KNO) crystals by using first-principles calculations. Based on the above calculation results, the mechanisms of photocatalytic properties for both crystals are further theoretically investigated to deepen the understandings of their photocatalytic activity from the electronic level. Calculations for the effective masses of electron and hole are carried out to make comparison in photocatalytic performance between cubic and orthorhombic phases. Optical absorption in cubic phase is found to be stronger than that in orthorhombic phase. C-KNO has smaller electron effective mass, higher mobility of photogenerated electrons, lower electron-hole recombination rate and better light absorption capacity than O-KNO. So, the photocatalytic activity of cubic phase can be higher than orthorhombic one. The present work may be beneficial to explore the series of perovskite photocatalysts.
Crosta, M.
2011-12-05
We characterize the full family of soliton solutions sitting over a background plane wave and ruled by the cubic-quintic nonlinear Schrödinger equation in the regime where a quintic focusing term represents a saturation of the cubic defocusing nonlinearity. We discuss the existence and properties of solitons in terms of catastrophe theory and fully characterize bistability and instabilities of the dark-antidark pairs, revealing mechanisms of decay of antidark solitons into dispersive shock waves.
Crosta, M.; Fratalocchi, Andrea; Trillo, S.
2011-01-01
We characterize the full family of soliton solutions sitting over a background plane wave and ruled by the cubic-quintic nonlinear Schrödinger equation in the regime where a quintic focusing term represents a saturation of the cubic defocusing nonlinearity. We discuss the existence and properties of solitons in terms of catastrophe theory and fully characterize bistability and instabilities of the dark-antidark pairs, revealing mechanisms of decay of antidark solitons into dispersive shock waves.
Charles E. Keegan; Todd A. Morgan; Keith A. Blatner; Jean M. Daniels
2010-01-01
This article describes trends in board foot Scribner volume per cubic foot of timber for logs processed by sawmills in the western United States. Board foot to cubic foot (BF/CF) ratios for the period from 2000 through 2006 ranged from 3.70 in Montana to 5.71 in the Four Corners Region (Arizona, Colorado, New Mexico, and Utah). Sawmills in the Four Corners Region,...
Zhang, Ling; Niu, Wenxin; Zhao, Jianming; Zhu, Shuyun; Yuan, Yali; Hua, Lianzhe; Xu, Guobao
2013-01-01
A new type of concave cubic Pd@Au core-shell nanocrystals is synthesized through a kinetically controlled growth process. Pd nanocubes of 56 nm are used as the inner core, and CTAC and Br(-) are used as the capping agent and selective adsorbent, respectively. A suitable ratio of HAuCl4 and cubic Pd seeds and the presence of Br(-) anions are critical to the growth of the concave cubic Pd@Au core-shell nanocrystals. The fast deposition rate on the corners of the cubic Pd seeds promotes the overgrowth of the Au outer shell along the direction, leading to the formation of concave cubic nanostructures. The reduction process is monitored by the surface plasmon resonance spectra of the nanocrystals, and the extinction band became broader and red shifted as the nanocrystals became larger. The electrocatalytic properties of the concave cubic Pd@Au core-shell nanocrystals were investigated with the cathodic electrochemiluminescence reaction of luminol and H2O2. A possible electrocatalytic mechanism was proposed and analyzed.
International Nuclear Information System (INIS)
Bergqvist, U.
1983-12-01
The aim of this report is to estimate the exposure to various metals and metal compounds and discuss the available information of the possible toxic effects of these metals and compounds. In the first section, some metals are defined as those with either a large or a fast increasing exposure to living organisms. The available information on toxicity is discussed in the second section. In the third section interesting metals are defined as compounds having a large exposure and an apparent insufficient knowledge of their possible toxic effects. Comments on each of these metals are also to be found in the third section. (G.B.)
Stability of cubic zirconia in a granitic system under high pressure and temperature
International Nuclear Information System (INIS)
Gibb, F. G. F.; Burakov, B. E.; Taylor, K. J.; Domracheva, Y.
2008-01-01
Cubic zirconia is a well known, highly durable material with potential uses as an actinide host phase in ceramic waste forms and inert matrix fuels and in containers for very deep borehole disposal of some highly radioactive wastes. To investigate the behaviour of this material under the conditions of possible use, a cube of ∼2.5 mm edge was made from a single crystal of Yttria stabilized cubic zirconia doped with 0.3 wt.% CeO 2 . The cube was enclosed in powdered granite within a gold capsule and a small amount of H 2 O added before sealing. The sealed capsule was held for 4 months in a cold-seal pressure vessel at a temperature of 780 deg. C and a pressure 150 MPa, simulating both the conditions of a deep borehole disposal involving partial melting of the host rock and the conditions under which the actinide waste form might be encapsulated in granite prior to disposal. At the end of the experiment the quenched, largely glassy, sample was cut into thin slices and studied by optical microscopy, EMPA, SEM and cathodoluminescence methods. The results show that no corrosion of the zirconia crystal or reaction with the granite melt occurred and that no detectable diffusion of elements, including Ce, in or out of the zirconia took place on the timescale of the experiment. Consequently, it appears that cubic zirconia could perform most satisfactorily as both an actinide host waste form for encapsulation in solid granite for very deep disposal and as a container material for deep borehole disposal of highly radioactive wastes (HLW), including spent fuel. (authors)
Morphology control and negative thermal expansion in cubic ZrWMoO8 powders
International Nuclear Information System (INIS)
Liu, Qinqin; Yang, Juan; Sun, Xiujuan; Cheng, Xiaonong
2008-01-01
Cubic ZrWMoO 8 powders with rod-like aggregate and thin fasciculus-like and flower-like rod cluster morphologies have been successfully fabricated with different amounts of (NH 4 ) 2 HPO 4 as surfactant using a hydrothermal method. X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy and differential scanning calorimetry were utilized to investigate the influence of the addition of (NH 4 ) 2 HPO 4 on the crystallization process and crystal morphology of the resulting products. The results show that the purity and the thermal expansion property of the resulting products are not influenced by the addition of (NH 4 ) 2 HPO 4 . The cubic ZrWMoO 8 powders with both rod-like aggregate and flower-like rod cluster morphologies show a positive thermal expansion property in the temperature range from room temperature to 120 C, while they show a negative thermal expansion property in the temperature range from 120 C to 700 C. The abnormal thermal expansion property of cubic ZrWMoO 8 below 120 C is caused by the presence of water molecules. Investigations also show that the essence of the different morphologies of the ZrWMoO 8 particles obtained is the result of the different aggregation modes of the nanorods, which act as nuclei, and the corresponding aggregation process is dominated by the addition of (NH 4 ) 2 HPO 4 and its amount. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)
Directory of Open Access Journals (Sweden)
Azza A. Matloub
2018-02-01
Full Text Available The present study involves the preparation of cubic liquid crystalline nanoparticles (cubsomes for liver targeting to assess the potential of a formulated bioactive polysaccharide isolated from the hot aqueous extract of Ulva fasciata as an alternative natural agent with anti-hyperlipidaemic activity. Cubosomal nanoparticles were prepared by disrupting the cubic gel phase of the polysaccharide and water in the presence of a surfactant. Different lipid matrices and stabilizers were tested. All the formulations were in the nanosize range and showed sufficient negative charge to inhibit the aggregation of the cubosomes. Drug entrapment efficiencies (EEs% were determined and in vitro release studies were performed. Transmission electron microscopy (TEM and differential scanning calorimetry were used to analyze the loaded cubosomal nanoparticles containing glyceryl monostearate (GMO 2.25 g, poloxamer 407 (0.25 g and 50 mg of the polysaccharide. A preclinical study comparing the cubic liquid crystalline nanoparticles containing polysaccharide to fluvastatin as a reference drug in hyperlipidaemic rats was conducted. The rats treated with the polysaccharide- loaded cubosomes showed significant decreases in total cholesterol (TC, triglycerides (TG and total lipid (TL compared to the untreated HL rats. In addition, oxidative stress and antioxidant biomarkers were measured in the HL rats. Compared to the untreated HL rats, the cubosome treated rats showed a significant reduction in malondialdehyde (MDA, whereas insignificant changes were detected in nitric oxide (NO, glutathione (GSH levels and total antioxidant capacity (TAC. Further, vascular and intercellular adhesion molecules (VCAM, ICAM, and myeloperoxidase were demonstrated. A histopathological examination was conducted to study the alterations in histopathological lesions and to document the biochemical results. In conclusion, this study demonstrates the superiority of using a natural lipid
Zhang, Yuan
2013-08-06
Cubic bismuth pyrochlores in the Bi2O3 Bi 2O3-MgO-Nb2O5 Nb2O 5 system have been investigated as promising dielectric materials due to their high dielectric constant and low dielectric loss. Here, we report on the dielectric properties and microstructures of cubic pyrochlored Bi 1.5 MgNb 1.5 O 7 Bi1.5MgNb1.5O7 (BMN) ceramic samples synthesized via solid-state reactions. The dielectric constant (measured at 1 MHz) was measured to be ∼ 120 ∼120 at room temperature, and the dielectric loss was as low as 0.001. X-ray diffraction patterns demonstrated that the BMN samples had a cubic pyrochlored structure, which was also confirmed by selected area electron diffraction (SAED) patterns. Raman spectrum revealed more than six vibrational models predicted for the ideal pyrochlore structure, indicating additional atomic displacements of the A and O′ O\\' sites from the ideal atomic positions in the BMN samples. Structural modulations of the pyrochlore structure along the [110] and [121] directions were observed in SAED patterns and high-resolution transmission electron microscopy (HR-TEM) images. In addition, HR-TEM images also revealed that the grain boundaries (GBs) in the BMN samples were much clean, and no segregation or impure phase was observed forming at GBs. The high dielectric constants in the BMN samples were ascribed to the long-range ordered pyrochlore structures since the electric dipoles formed at the superstructural direction could be enhanced. The low dielectric loss was attributed to the existence of noncontaminated GBs in the BMN ceramics. © 2013 Springer-Verlag Berlin Heidelberg.
Ground-state ordering of the J1-J2 model on the simple cubic and body-centered cubic lattices
Farnell, D. J. J.; Götze, O.; Richter, J.
2016-06-01
The J1-J2 Heisenberg model is a "canonical" model in the field of quantum magnetism in order to study the interplay between frustration and quantum fluctuations as well as quantum phase transitions driven by frustration. Here we apply the coupled cluster method (CCM) to study the spin-half J1-J2 model with antiferromagnetic nearest-neighbor bonds J1>0 and next-nearest-neighbor bonds J2>0 for the simple cubic (sc) and body-centered cubic (bcc) lattices. In particular, we wish to study the ground-state ordering of these systems as a function of the frustration parameter p =z2J2/z1J1 , where z1 (z2) is the number of nearest (next-nearest) neighbors. We wish to determine the positions of the phase transitions using the CCM and we aim to resolve the nature of the phase transition points. We consider the ground-state energy, order parameters, spin-spin correlation functions, as well as the spin stiffness in order to determine the ground-state phase diagrams of these models. We find a direct first-order phase transition at a value of p =0.528 from a state of nearest-neighbor Néel order to next-nearest-neighbor Néel order for the bcc lattice. For the sc lattice the situation is more subtle. CCM results for the energy, the order parameter, the spin-spin correlation functions, and the spin stiffness indicate that there is no direct first-order transition between ground-state phases with magnetic long-range order, rather it is more likely that two phases with antiferromagnetic long range are separated by a narrow region of a spin-liquid-like quantum phase around p =0.55 . Thus the strong frustration present in the J1-J2 Heisenberg model on the sc lattice may open a window for an unconventional quantum ground state in this three-dimensional spin model.
Hydrothermal synthesis and white light emission of cubic ZrO2:Eu3+ nanocrystals
International Nuclear Information System (INIS)
Meetei, Sanoujam Dhiren; Singh, Shougaijam Dorendrajit
2014-01-01
Highlights: • White light emitting cubic ZrO 2 :Eu 3+ nanocrystal is synthesized by hydrothermal technique. • Eu 3+ is used to stabilize crystalline phase and to get red counterpart of the white light. • Defect emission and Eu 3+ emission combined to give white light. • The white light emitted from this nanocrystal resembles vertical daylight of the Sun. • Lifetime corresponding to red counterpart of the sample is far longer than conventional white light emitters. -- Abstract: Production of white light has been a promising area of luminescence studies. In this work, white light emitting nanocrystals of cubic zirconia doped with Eu 3+ are synthesized by hydrothermal technique. The dopant Eu 3+ is used to stabilize crystalline phase to cubic and at the same time to get red counterpart of the white light. The synthesis procedure is simple and precursor required no further annealing for crystallization. X-ray diffraction patterns show the crystalline phase of ZrO 2 :Eu 3+ to be cubic and it is confirmed by Fourier Transform Infrared spectroscopy. From transmission electron microscopy images, size of the crystals is found to be ∼5 nm. Photoluminescence emission spectrum of the sample, on monitoring excitation at O 2− –Eu 3+ charge transfer state shows broad peak due to O 2− of the zirconia and that of Eu 3+ emission. Commission Internationale de l’éclairage co-ordinate of this nanocrystal (0.32, 0.34) is closed to that of the ideal white light (0.33, 0.33). Correlated color temperature of the white light (5894 K) is within the range of vertical daylight. Lifetime (1.32 ms) corresponding to 5 D 0 energy level of the Eu 3+ is found to be far longer than conventional red counterparts of white light emitters. It suggests that the ZrO 2 :Eu 3+ nanocrystals synthesized by hydrothermal technique may find applications in simulating the vertical daylight of the Sun
Synthesis of cubic Y zeolite using a pulsed microwave heating system
Directory of Open Access Journals (Sweden)
Araújo L.R.G. de
1999-01-01
Full Text Available Cubic Y zeolite were successfully synthesized using microwave heating for 18 - 25 min, whereas 10 - 50 h are required by hydrothermal heating technique depending upon the lattice Si/Al ratio. To this end, we used a commercial microwave oven modified in order to provide pulsed microwave pumping on the synthesis mixtures. The obtained samples were analyzed by X-ray diffraction, BET surface area and infrared spectroscopy measurements. As a result, we verify that Y zeolite samples obtained from hydrogels containing low aluminum contents, present a good degree of crystallinity and then can be suitable for using in adsorption and catalysis experiments.
Maximal independent set graph partitions for representations of body-centered cubic lattices
DEFF Research Database (Denmark)
Erleben, Kenny
2009-01-01
corresponding to the leaves of a quad-tree thus has a smaller memory foot-print. The adjacency information in the graph relieves one from going up and down the quad-tree when searching for neighbors. This results in constant time complexities for refinement and coarsening operations.......A maximal independent set graph data structure for a body-centered cubic lattice is presented. Refinement and coarsening operations are defined in terms of set-operations resulting in robust and easy implementation compared to a quad-tree-based implementation. The graph only stores information...
Cubic scaling algorithms for RPA correlation using interpolative separable density fitting
Lu, Jianfeng; Thicke, Kyle
2017-12-01
We present a new cubic scaling algorithm for the calculation of the RPA correlation energy. Our scheme splits up the dependence between the occupied and virtual orbitals in χ0 by use of Cauchy's integral formula. This introduces an additional integral to be carried out, for which we provide a geometrically convergent quadrature rule. Our scheme also uses the newly developed Interpolative Separable Density Fitting algorithm to further reduce the computational cost in a way analogous to that of the Resolution of Identity method.
Dual Effect of the Cubic Ag₃PO₄ Crystal on Pseudomonas syringae Growth and Plant Immunity
Directory of Open Access Journals (Sweden)
Mi Kyung Kim
2016-04-01
Full Text Available We previously found that the antibacterial activity of silver phosphate crystals on Escherichia coli depends on their structure. We here show that the cubic form of silver phosphate crystal (SPC can also be applied to inhibit the growth of a plant-pathogenic Pseudomonas syringae bacterium. SPC pretreatment resulted in reduced in planta multiplication of P. syringae. Induced expression of a plant defense marker gene PR1 by SPC alone is suggestive of its additional plant immunity-stimulating activity. Since SPC can simultaneously inhibit P. syringae growth and induce plant defense responses, it might be used as a more effective plant disease-controlling agent.
Nonlinear stochastic heat equations with cubic nonlinearities and additive Q-regular noise in R^1
Directory of Open Access Journals (Sweden)
Henri Schurz
2010-09-01
Full Text Available Semilinear stochastic heat equations perturbed by cubic-type nonlinearities and additive space-time noise with homogeneous boundary conditions are discussed in R^1. The space-time noise is supposed to be Gaussian in time and possesses a Fourier expansion in space along the eigenfunctions of underlying Lapace operators. We follow the concept of approximate strong (classical Fourier solutions. The existence of unique continuous L^2-bounded solutions is proved. Furthermore, we present a procedure for its numerical approximation based on nonstandard methods (linear-implicit and justify their stability and consistency. The behavior of related total energy functional turns out to be crucial in the presented analysis.
Gevrey multiscale expansions of singular solutions of PDEs with cubic nonlinearity
Directory of Open Access Journals (Sweden)
Alberto Lastra
2018-02-01
Full Text Available We study a singularly perturbed PDE with cubic nonlinearity depending on a complex perturbation parameter $\\epsilon$. This is a continuation of the precedent work [22] by the first author. We construct two families of sectorial meromorphic solutions obtained as a small perturbation in $\\epsilon$ of two branches of an algebraic slow curve of the equation in time scale. We show that the nonsingular part of the solutions of each family shares a common formal power series in $\\epsilon$ as Gevrey asymptotic expansion which might be different one to each other, in general.
A reduction method for phase equilibrium calculations with cubic equations of state
Directory of Open Access Journals (Sweden)
D. V. Nichita
2006-09-01
Full Text Available In this work we propose a new reduction method for phase equilibrium calculations using a general form of cubic equations of state (CEOS. The energy term in the CEOS is a quadratic form, which is diagonalized by applying a linear transformation. The number of the reduction parameters is related to the rank of the matrix C with elements (1-Cij, where Cij denotes the binary interaction parameters (BIPs. The dimensionality of the problem depends only on the number of reduction parameters, and is independent of the number of components in the mixture.
International Nuclear Information System (INIS)
Chame, A.M.N.; Tsallis, C.
1988-01-01
The behaviour of the spontaneous surface and bulk magnetizations as function of the temperature for the Ising ferromagnet in a semi-infinitre cubic lattice for various ratios JS/JB (JS and JB are the surface and bulk coupling constants, respectively), is studied. The extraordinary transition where the surface maintains its magnetization as the bulk disorders, was study, in particular; a discontinuity on the first derivative of the surface magnetization at the bulk transition temperature was found. The criticality of the system (universality classes, critical exponents and amplitudes) is discussed. An unexpected slight lack of monotonicity of the surface magnetization as a function of JS/JB for JS/JB [pt
Bounds on Cubic Lorentz-Violating Terms in the Fermionic Dispersion Relation
Bertolami, O.; Rosa, J. G.
2004-01-01
We study the recently proposed Lorentz-violating dispersion relation for fermions and show that it leads to two distinct cubic operators in the momentum. We compute the leading order terms that modify the non-relativistic equations of motion and use experimental results for the hyperfine transition in the ground state of the ${}^9\\textrm Be^+$ ion to bound the values of the Lorentz-violating parameters $\\eta_1$ and $\\eta_2$ for neutrons. The resulting bounds depend on the value of the Lorenz-...
Ab initio phonon dispersions of face centered cubic Pb: effects of spin-orbit coupling
International Nuclear Information System (INIS)
Dal Corso, Andrea
2008-01-01
I present the ab initio phonon dispersions of face centered cubic Pb calculated within the framework of density functional perturbation theory, with plane waves and a fully relativistic ultrasoft pseudopotential which includes spin-orbit coupling effects. I find that, within the local density approximation, the theory gives phonon frequencies close to the experimental inelastic neutron scattering data. Many of the anomalies present in these dispersions are well reproduced by the fully relativistic pseudopotential theory and can be shown to appear only for small values of the smearing parameter that controls the sharpness of the Fermi surface.
Face centered cubic SnSe as a Z2 trivial Dirac nodal line material
Tateishi, Ikuma; Matsuura, Hiroyasu
2018-01-01
The presence of Dirac nodal line in the time-reversal and inversion symmetric system is dictated by Z2 index when spin-orbit interaction is absent. With the first principles calculation, we show that the Dirac nodal line can emerge in Z2 trivial material by calculating the band structure of SnSe of face centered cubic lattice as an example and it becomes a topological crystalline insulator when spin-orbit interaction is taken into account. We clarify the origin of the Dirac nodal line by obta...
Energy Technology Data Exchange (ETDEWEB)
Borghi, F.; Lenardi, C.; Podestà, A.; Milani, P., E-mail: pmilani@mi.infn.it [CIMAINA and Dipartimento di Fisica, Università degli Studi di Milano, via Celoria 16, 20133 Milano (Italy); Sogne, E. [CIMAINA and Dipartimento di Fisica, Università degli Studi di Milano, via Celoria 16, 20133 Milano (Italy); European School of Molecular Medicine (SEMM), IFOM-IEO, Milano (Italy); Merlini, M. [Dipartimento di Scienze della Terra “Ardito Desio”, Università degli Studi di Milano, via Mangiagalli 32, 20133 Milano (Italy); Ducati, C. [Department of Materials Science and Metallurgy, University of Cambridge, 27 Charles Babbage Road, Cambridge CB3 0FS (United Kingdom)
2016-08-07
Nanostructured zirconium dioxide (zirconia) films are very promising for catalysis and biotechnological applications: a precise control of the interfacial properties of the material at different length scales and, in particular, at the nanoscale, is therefore necessary. Here, we present the characterization of cluster-assembled zirconia films produced by supersonic cluster beam deposition possessing cubic structure at room temperature and controlled nanoscale morphology. We characterized the effect of thermal annealing in reducing and oxidizing conditions on the crystalline structure, grain dimensions, and topography. We highlight the mechanisms of film growth and phase transitions, which determine the observed interfacial morphological properties and their resilience against thermal treatments.
An EOQ model for weibull distribution deterioration with time-dependent cubic demand and backlogging
Santhi, G.; Karthikeyan, K.
2017-11-01
In this article we introduce an economic order quantity model with weibull deterioration and time dependent cubic demand rate where holding costs as a linear function of time. Shortages are allowed in the inventory system are partially and fully backlogging. The objective of this model is to minimize the total inventory cost by using the optimal order quantity and the cycle length. The proposed model is illustrated by numerical examples and the sensitivity analysis is performed to study the effect of changes in parameters on the optimum solutions.
Pseudo-cubic thin-plate type Spline method for analyzing experimental data
Energy Technology Data Exchange (ETDEWEB)
Crecy, F de
1994-12-31
A mathematical tool, using pseudo-cubic thin-plate type Spline, has been developed for analysis of experimental data points. The main purpose is to obtain, without any a priori given model, a mathematical predictor with related uncertainties, usable at any point in the multidimensional parameter space. The smoothing parameter is determined by a generalized cross validation method. The residual standard deviation obtained is significantly smaller than that of a least square regression. An example of use is given with critical heat flux data, showing a significant decrease of the conception criterion (minimum allowable value of the DNB ratio). (author) 4 figs., 1 tab., 7 refs.
Pseudo-cubic thin-plate type Spline method for analyzing experimental data
International Nuclear Information System (INIS)
Crecy, F. de.
1993-01-01
A mathematical tool, using pseudo-cubic thin-plate type Spline, has been developed for analysis of experimental data points. The main purpose is to obtain, without any a priori given model, a mathematical predictor with related uncertainties, usable at any point in the multidimensional parameter space. The smoothing parameter is determined by a generalized cross validation method. The residual standard deviation obtained is significantly smaller than that of a least square regression. An example of use is given with critical heat flux data, showing a significant decrease of the conception criterion (minimum allowable value of the DNB ratio). (author) 4 figs., 1 tab., 7 refs
Confalonieri, Sara
2015-01-01
Sara Confalonieri presents an overview of Cardano's mathematical treatises and, in particular, discusses the writings that deal with cubic equations. The author gives an insight into the latest of Cardano's algebraic works, the De Regula Aliza (1570), which displays the attempts to overcome the difficulties entailed by the casus irreducibilis. Notably some of Cardano's strategies in this treatise are thoroughly analyzed. Far from offering an ultimate account of De Regula Aliza, by one of the most outstanding scholars of the 16th century, the present work is a first step towards a better understanding.
Face Centered Cubic and Hexagonal Close Packed Skyrmion Crystals in Centrosymmetric Magnets
Lin, Shi-Zeng; Batista, Cristian D.
2018-02-01
Skyrmions are disklike objects that typically form triangular crystals in two-dimensional systems. This situation is analogous to the so-called pancake vortices of quasi-two-dimensional superconductors. The way in which Skyrmion disks or "pancake Skyrmions" pile up in layered centrosymmetric materials is dictated by the interlayer exchange. Unbiased Monte Carlo simulations and simple stabilization arguments reveal face centered cubic and hexagonal close packed Skyrmion crystals for different choices of the interlayer exchange, in addition to the conventional triangular crystal of Skyrmion lines. Moreover, an inhomogeneous current induces a sliding motion of pancake Skyrmions, indicating that they behave as effective mesoscale particles.
Ricci cubic gravity in d dimensions, gravitons and SAdS/Lifshitz black holes
Energy Technology Data Exchange (ETDEWEB)
Ghodsi, Ahmad; Najafi, Farzaneh [Ferdowsi University of Mashhad, Department of Physics, Mashhad (Iran, Islamic Republic of)
2017-08-15
A special class of higher curvature theories of gravity, Ricci cubic gravity (RCG), in general d dimensional space-time has been investigated in this paper. We have used two different approaches, the linearized equations of motion and the auxiliary field formalism to study the massive and massless graviton propagating modes of the AdS background. Using the auxiliary field formalism, we have found the renormalized boundary stress tensor to compute the mass of the Schwarzschild-AdS and Lifshitz black holes in RCG theory. (orig.)
A cubic B-spline Galerkin approach for the numerical simulation of the GEW equation
Directory of Open Access Journals (Sweden)
S. Battal Gazi Karakoç
2016-02-01
Full Text Available The generalized equal width (GEW wave equation is solved numerically by using lumped Galerkin approach with cubic B-spline functions. The proposed numerical scheme is tested by applying two test problems including single solitary wave and interaction of two solitary waves. In order to determine the performance of the algorithm, the error norms L2 and L∞ and the invariants I1, I2 and I3 are calculated. For the linear stability analysis of the numerical algorithm, von Neumann approach is used. As a result, the obtained findings show that the presented numerical scheme is preferable to some recent numerical methods.
Motion of a Rigid Rod Rocking Back and Forth Cubic-Quintic Duffing Oscillators
DEFF Research Database (Denmark)
Ganji, S. S.; Barari, Amin; Karimpour, S.
2012-01-01
In this work, we implemented the first-order approximation of the Iteration Perturbation Method (IPM) for approximating the behavior of a rigid rod rocking back and forth on a circular surface without slipping as well as Cubic-Quintic Duffing Oscillators. Comparing the results with the exact...... solution, has led us to significant consequences. The results reveal that the IPM is very effective, simple and convenient to systems of nonlinear equations. It is predicted that IPM can be utilized as a widely applicable approach in engineering....
International Nuclear Information System (INIS)
Borghi, F.; Lenardi, C.; Podestà, A.; Milani, P.; Sogne, E.; Merlini, M.; Ducati, C.
2016-01-01
Nanostructured zirconium dioxide (zirconia) films are very promising for catalysis and biotechnological applications: a precise control of the interfacial properties of the material at different length scales and, in particular, at the nanoscale, is therefore necessary. Here, we present the characterization of cluster-assembled zirconia films produced by supersonic cluster beam deposition possessing cubic structure at room temperature and controlled nanoscale morphology. We characterized the effect of thermal annealing in reducing and oxidizing conditions on the crystalline structure, grain dimensions, and topography. We highlight the mechanisms of film growth and phase transitions, which determine the observed interfacial morphological properties and their resilience against thermal treatments.
Borghi, F.; Sogne, Elisa; Lenardi, C.; Podestà , A.; Merlini, M.; Ducati, C.; Milani, P.
2016-01-01
Nanostructured zirconium dioxide (zirconia) films are very promising for catalysis and biotechnological applications: a precise control of the interfacial properties of the material at different length scales and, in particular, at the nanoscale, is therefore necessary. Here, we present the characterization of cluster-assembled zirconia films produced by supersonic cluster beam deposition possessing cubic structure at room temperature and controlled nanoscale morphology. We characterized the effect of thermal annealing in reducing and oxidizing conditions on the crystalline structure, grain dimensions, and topography. We highlight the mechanisms of film growth and phase transitions, which determine the observed interfacial morphological properties and their resilience against thermal treatments. Published by AIP Publishing.
Etching of semiconductor cubic crystals: Determination of the dissolution slowness surfaces
Tellier, C. R.
1990-03-01
Equations of the representative surface of dissolution slowness for cubic crystals are determined in the framework of a tensorial approach of the orientation-dependent etching process. The independent dissolution constants are deduced from symmetry considerations. Using previous data on the chemical etching of germanium and gallium arsenide crystals, some possible polar diagrams of the dissolution slowness are proposed. A numerical and graphical simulation method is used to obtain the derived dissolution shapes. The influence of extrema in the dissolution slowness on the successive dissolution shapes is also examined. A graphical construction of limiting shapes of etched crystals appears possible using the tensorial representation of the dissolution slowness.
Borghi, F.
2016-08-05
Nanostructured zirconium dioxide (zirconia) films are very promising for catalysis and biotechnological applications: a precise control of the interfacial properties of the material at different length scales and, in particular, at the nanoscale, is therefore necessary. Here, we present the characterization of cluster-assembled zirconia films produced by supersonic cluster beam deposition possessing cubic structure at room temperature and controlled nanoscale morphology. We characterized the effect of thermal annealing in reducing and oxidizing conditions on the crystalline structure, grain dimensions, and topography. We highlight the mechanisms of film growth and phase transitions, which determine the observed interfacial morphological properties and their resilience against thermal treatments. Published by AIP Publishing.
Self-similar optical pulses in competing cubic-quintic nonlinear media with distributed coefficients
International Nuclear Information System (INIS)
Zhang Jiefang; Tian Qing; Wang Yueyue; Dai Chaoqing; Wu Lei
2010-01-01
We present a systematic analysis of the self-similar propagation of optical pulses within the framework of the generalized cubic-quintic nonlinear Schroedinger equation with distributed coefficients. By appropriately choosing the relations between the distributed coefficients, we not only retrieve the exact self-similar solitonic solutions, but also find both the approximate self-similar Gaussian-Hermite solutions and compact solutions. Our analytical and numerical considerations reveal that proper choices of the distributed coefficients could make the unstable solitons stable and could restrict the nonlinear interaction between the neighboring solitons.
Laser sintered thin layer graphene and cubic boron nitride reinforced nickel matrix nanocomposites
Hu, Zengrong; Tong, Guoquan
2015-10-01
Laser sintered thin layer graphene (Gr)-cubic boron nitride (CBN)-Ni nanocomposites were fabricated on AISI 4140 plate substrate. The composites fabricating process, composites microstructure and mechanical properties were studied. Scanning electron microscopy (SEM), X-ray diffraction (XRD) and Raman spectroscopy were employed to study the micro structures and composition of the composites. XRD and Raman tests proved that graphene and CBN were dispersed in the nanocomposites. Nanoindentation test results indicate the significant improvements were achieved in the composites mechanical properties.
Complete three-dimensional photonic bandgap in a simple cubic structure
International Nuclear Information System (INIS)
Lin, Shawn-Yu; Fleming, J. G.; Lin, Robin; Sigalas, M. M.; Biswas, R.; Ho, K. M.
2001-01-01
The creation of a three-dimensional (3D) photonic crystal with simple cubic (sc) symmetry is important for applications in the signal routing and 3D waveguiding of light. With a simple stacking scheme and advanced silicon processing, a 3D sc structure was constructed from a 6-in. silicon wafer. The sc structure is experimentally shown to have a complete 3D photonic bandgap in the infrared wavelength. The finite size effect is also observed, accounting for a larger absolute photonic bandgap
Large-eddy simulation of plume dispersion within regular arrays of cubic buildings
Nakayama, H.; Jurcakova, K.; Nagai, H.
2011-04-01
There is a potential problem that hazardous and flammable materials are accidentally or intentionally released within populated urban areas. For the assessment of human health hazard from toxic substances, the existence of high concentration peaks in a plume should be considered. For the safety analysis of flammable gas, certain critical threshold levels should be evaluated. Therefore, in such a situation, not only average levels but also instantaneous magnitudes of concentration should be accurately predicted. In this study, we perform Large-Eddy Simulation (LES) of plume dispersion within regular arrays of cubic buildings with large obstacle densities and investigate the influence of the building arrangement on the characteristics of mean and fluctuating concentrations.
Structures of glide-set 90 deg. partial dislocation cores in diamond cubic semiconductors
International Nuclear Information System (INIS)
Beckman, S.P.; Chrzan, D.C.
2003-01-01
Two core reconstructions of the 90 deg. partial dislocations in diamond cubic semiconductors, the so-called single- and double-period structures, are often found to be nearly degenerate in energy. This near degeneracy suggests the possibility that both core reconstructions may be present simultaneously along the same dislocation core, with the domain sizes of the competing reconstructions dependent on temperature and the local stress state. To explore this dependence, a simple statistical mechanics-based model of the dislocation core reconstructions is developed and analyzed. Predictions for the temperature-dependent structure of the dislocation core are presented
Elastic energy and metastable phase equilibria for coherent mixtures in cubic systems
International Nuclear Information System (INIS)
Williams, R.O.
1979-02-01
Expressions were derived for the elastic energy due to coherency for cubic systems for an isotropic structure and for (100) or (111) habit planes for a lamellar structure. For the metastable equilibria the usual tangent compositions are replaced by compositions that are tangent to the elastic energy curve. For a loss of coherency there is an energy decrease due to the elastic effects and a further decrease associated with compositional changes. Information contained within this treatment permits calculation of the x-ray diffraction effects for such structures
Sadjadi, Seyed Jafar; Hamidi Hesarsorkh, Aghil; Mohammadi, Mehdi; Bonyadi Naeini, Ali
2015-06-01
Coordination and harmony between different departments of a company can be an important factor in achieving competitive advantage if the company corrects alignment between strategies of different departments. This paper presents an integrated decision model based on recent advances of geometric programming technique. The demand of a product considers as a power function of factors such as product's price, marketing expenditures, and consumer service expenditures. Furthermore, production cost considers as a cubic power function of outputs. The model will be solved by recent advances in convex optimization tools. Finally, the solution procedure is illustrated by numerical example.
Growth of InAs Wurtzite Nanocrosses from Hexagonal and Cubic Basis
DEFF Research Database (Denmark)
Krizek, Filip; Kanne, Thomas; Razmadze, Davydas
2017-01-01
. Two methods use conventional wurtzite nanowire arrays as a 6-fold hexagonal basis for growing single crystal wurtzite nanocrosses. A third method uses the 2-fold cubic symmetry of (100) substrates to form well-defined coherent inclusions of zinc blende in the center of the nanocrosses. We show......Epitaxially connected nanowires allow for the design of electron transport experiments and applications beyond the standard two terminal device geometries. In this Letter, we present growth methods of three distinct types of wurtzite structured InAs nanocrosses via the vapor-liquid-solid mechanism...
On the theory of phonoriton in cubic semiconductors with a degenerate valence band
International Nuclear Information System (INIS)
Nguyen Ai Viet; Nguyen Thi Que Huong; Le Qui Thong
1992-10-01
The ''phonoriton'' is an elementary excitation constructed from an exciton polariton and phonon in semiconductors under intense excitation by an electromagnetic wave near the exciton resonance (L.V. Keldysh and A.L. Ivanov, 1982). In this paper we develop a theory of phonoriton in direct band gap cubic semiconductor with a degenerate valence band using the simple model of J.L. Birman and B.S. Wang (1990). In addition to experimental proofs of the existence of phonoriton we propose an experiment to measure its flight time. (author). 33 refs
Energy Technology Data Exchange (ETDEWEB)
Maghribi, Mariam N. (Livermore, CA); Krulevitch, Peter (Pleasanton, CA); Hamilton, Julie (Tracy, CA)
2008-12-09
A system for providing metal features on silicone comprising providing a silicone layer on a matrix and providing a metal layer on the silicone layer. An electronic apparatus can be produced by the system. The electronic apparatus comprises a silicone body and metal features on the silicone body that provide an electronic device.
Gaussian quadrature for splines via homotopy continuation: Rules for C2 cubic splines
Barton, Michael
2015-10-24
We introduce a new concept for generating optimal quadrature rules for splines. To generate an optimal quadrature rule in a given (target) spline space, we build an associated source space with known optimal quadrature and transfer the rule from the source space to the target one, while preserving the number of quadrature points and therefore optimality. The quadrature nodes and weights are, considered as a higher-dimensional point, a zero of a particular system of polynomial equations. As the space is continuously deformed by changing the source knot vector, the quadrature rule gets updated using polynomial homotopy continuation. For example, starting with C1C1 cubic splines with uniform knot sequences, we demonstrate the methodology by deriving the optimal rules for uniform C2C2 cubic spline spaces where the rule was only conjectured to date. We validate our algorithm by showing that the resulting quadrature rule is independent of the path chosen between the target and the source knot vectors as well as the source rule chosen.
Radiation effects in cubic zirconia: A model system for ceramic oxides
Thomé, L.; Moll, S.; Sattonnay, G.; Vincent, L.; Garrido, F.; Jagielski, J.
2009-06-01
Ceramics are key engineering materials for electronic, space and nuclear industry. Some of them are promising matrices for the immobilization and/or transmutation of radioactive waste. Cubic zirconia is a model system for the study of radiation effects in ceramic oxides. Ion beams are very efficient tools for the simulation of the radiations produced in nuclear reactors or in storage form. In this article, we summarize the work made by combining advanced techniques (RBS/C, XRD, TEM, AFM) to study the structural modifications produced in ion-irradiated cubic zirconia single crystals. Ions with energies in the MeV-GeV range allow exploring the nuclear collision and electronic excitation regimes. At low energy, where ballistic effects dominate, the damage exhibits a peak around the ion projected range; it accumulates with a double-step process by the formation of a dislocation network. At high energy, where electronic excitations are favored, the damage profiles are rather flat up to several micrometers; the damage accumulation is monotonous (one step) and occurs through the creation and overlap of ion tracks. These results may be generalized to many nuclear ceramics.
Numerical Studies on Natural Convection Heat Losses from Open Cubical Cavities
Directory of Open Access Journals (Sweden)
M. Prakash
2013-01-01
Full Text Available The natural convection heat losses occurring from cubical open cavities are analysed in this paper. Open cubical cavities of sides 0.1 m, 0.2 m, 0.25 m, 0.5 m, and 1 m with constant temperature back wall boundary conditions and opening ratio of 1 are studied. The Fluent CFD software is used to analyse the three-dimensional (3D cavity models. The studies are carried out for cavities with back wall temperatures between 35°C and 100°C. The effect of cavity inclination on the convective loss is analysed for angles of 0° (cavity facing sideways, 30°, 45°, 60°, and 90° (cavity facing vertically downwards. The Rayleigh numbers involved in this study range between 4.5 × 105 and 1.5 × 109. The natural convection loss is found to increase with an increase in back wall temperature. The natural convection loss is observed to decrease with an increase in cavity inclination; the highest convective loss being at 0° and the lowest at 90° inclination. This is observed for all cavities analysed here. Nusselt number correlations involving the effect of Rayleigh number and the cavity inclination angle have been developed from the current studies. These correlations can be used for engineering applications such as electronic cooling, low- and medium-temperature solar thermal systems, passive architecture, and also refrigeration systems.
Gaussian quadrature for splines via homotopy continuation: Rules for C2 cubic splines
Barton, Michael; Calo, Victor M.
2015-01-01
We introduce a new concept for generating optimal quadrature rules for splines. To generate an optimal quadrature rule in a given (target) spline space, we build an associated source space with known optimal quadrature and transfer the rule from the source space to the target one, while preserving the number of quadrature points and therefore optimality. The quadrature nodes and weights are, considered as a higher-dimensional point, a zero of a particular system of polynomial equations. As the space is continuously deformed by changing the source knot vector, the quadrature rule gets updated using polynomial homotopy continuation. For example, starting with C1C1 cubic splines with uniform knot sequences, we demonstrate the methodology by deriving the optimal rules for uniform C2C2 cubic spline spaces where the rule was only conjectured to date. We validate our algorithm by showing that the resulting quadrature rule is independent of the path chosen between the target and the source knot vectors as well as the source rule chosen.
Self-oriented Ag-based polycrystalline cubic nanostructures through polymer stabilization
Alonso, Amanda; Vigués, Núria; Rodríguez-Rodríguez, Rosalía; Borrisé, Xavier; Muñoz, María; Muraviev, Dmitri N.; Mas, Jordi; Muñoz-Berbel, Xavier
2016-10-01
This paper presents the study of the dynamics of the formation of polymer-assisted highly-orientated polycrystalline cubic structures (CS) by a fractal-mediated mechanism. This mechanism involves the formation of seed Ag@Co nanoparticles by InterMatrix Synthesis and subsequent overgrowth after incubation at a low temperature in chloride and phosphate solutions. These ions promote the dissolution and recrystallization in an ordered configuration of pre-synthetized nanoparticles initially embedded in negatively-charged polymeric matrices. During recrystallization, silver ions aggregate in AgCl@Co fractal-like structures, then evolve into regular polycrystalline solid nanostructures (e.g. CS) in a single crystallization step on specific regions of the ion exchange resin (IER) which maintain the integrity of polycrystalline nanocubes. Here, we study the essential role of the IER in the formation of these CS for the maintenance of their integrity and stability. Thus, this synthesis protocol may be easily expanded to the composition of other nanoparticles providing an interesting, cheap and simple alternative for cubic structure formation and isolation.
Data fitting by G1 rational cubic Bézier curves using harmony search
Directory of Open Access Journals (Sweden)
Najihah Mohamed
2015-07-01
Full Text Available A metaheuristic algorithm, called Harmony Search (HS is implemented for data fitting by rational cubic Bézier curves. HS is a derivative-free real parameter optimization algorithm, and draws an inspiration from the musical improvisation process of searching for a perfect state of harmony. HS is suitable for multivariate non-linear optimization problem. It is mainly achieved by data fitting using rational cubic Bézier curves with G1 continuity for every joint of segments of the whole data sets. This approach has significant contributions in making the technique automated. HS is used to optimize positions of middle points and values of the shape parameters. Test outline images and comparative experimental analysis are presented to show effectiveness and robustness of the proposed method. Statistical testing between HS and two other different metaheuristic algorithms is used in the analysis on several outline images. All of the algorithms improvised a near optimal solution but the result that is obtained by the HS is better than the results of the other two algorithms.
Rapid hydrothermal route to synthesize cubic-phase gadolinium oxide nanorods
International Nuclear Information System (INIS)
Hazarika, Samiran; Paul, Nibedita; Mohanta, Dambarudhar
2014-01-01
An inexpensive fabrication route and growth mechanism is being reported for obtaining quality gadolinium oxide ( Gd 2 O 3 ) nanoscale rods. The elongated nanoscale systems, as produced via a hydrothermal process, were characterized by X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM), optical absorption spectroscopy, photoluminescence (PL) spectroscopy, Raman spectroscopy and magnetic hysteresis measurements. XRD patterns of the nanorods, as-prepared from independent precursors of different pH, depict a cubic crystal phase and an average crystallite size of 5-6.5 nm. As revealed from HRTEM micrographs, diameter of the nanorods prepared at pH = 13.3 (∼7 nm) was much smaller than the rods prepared at pH = 10.8 (∼19 nm). However, the aspect ratio was more than double in the former case than the latter case. PL response was found to be dominated by defect mediated emissions, whereas Raman spectrum of a given specimen (pH = 10.8) has revealed characteristic F g + A g modes of cubic phase of Gd 2 O 3 nanorods, apart from other independent modes. Furthermore, M ∼ H plot of the nanorod system (pH = 10.8) exhibited slight departure from the ideal superparamagnetic behaviour, with low remanence and coercive field values. The exploitation of one-dimensional Gd 2 O 3 nanorods have immense potential in the production of advanced contrast agents, smart drives and also in making novel ferrofluids of technological relevance. (author)
Simulation of the relationship between porosity and tortuosity in porous media with cubic particles
International Nuclear Information System (INIS)
Tang Xiao-Wu; Sun Zu-Feng; Cheng Guan-Chu
2012-01-01
Tortuosity is an important parameter used in areas such as vascular medicine, neurobiology, and the field of soil permeability and diffusion to express the mass transport in porous media. It is a function of the porosity and the shape and distribution of particles. In this paper, the tortuosity of cubic particles is calculated. With the assumption that the porous medium is homogeneous, the problem is converted to the micro-level over a unit cell, and geometry models of flow paths are proposed. In three-dimensional (3D) cells, the flow paths are too complicated to define. Hence, the 3D models are converted to two-dimensional (2D) models to simplify the calculation process. It is noticed that the path in the 2D model is shorter than that in the 3D model. As a result, triangular particles and the interaction are also taken into consideration to account for the longer distance respectively. We have proposed quadrate particle and interaction (QI) and quadrate and triangular particle (QT) models with cubic particles. Both models have shown good agreement with the experimental data. It is also found that they can predict the toruosities of some kinds of porous media, like freshwater sediment and Negev chalk
Facão, M.; Carvalho, M. I.
2017-10-01
In this work, we present parameter regions for the existence of stable plain solitons of the cubic complex Ginzburg-Landau equation (CGLE) with higher-order terms associated with a fourth-order expansion. Using a perturbation approach around the nonlinear Schrödinger equation soliton and a full numerical analysis that solves an ordinary differential equation for the soliton profiles and using the Evans method in the search for unstable eigenvalues, we have found that the minimum equation allowing these stable solitons is the cubic CGLE plus a term known in optics as Raman-delayed response, which is responsible for the redshift of the spectrum. The other favorable term for the occurrence of stable solitons is a term that represents the increase of nonlinear gain with higher frequencies. At the stability boundary, a bifurcation occurs giving rise to stable oscillatory solitons for higher values of the nonlinear gain. These oscillations can have very high amplitudes, with the pulse energy changing more than two orders of magnitude in a period, and they can even exhibit more complex dynamics such as period-doubling.
Energy Technology Data Exchange (ETDEWEB)
Arroyo Rojas Dasilva, Yadira; Kozak, Roksolana; Erni, Rolf; Rossell, Marta D., E-mail: marta.rossell@empa.ch
2017-05-15
The development of new electro-optical devices and the realization of novel types of transistors require a profound understanding of the structural characteristics of new semiconductor heterostructures. This article provides a concise review about structural defects which occur in semiconductor heterostructures on the basis of micro-patterned Si substrates. In particular, one- and two-dimensional crystal defects are being discussed which are due to the plastic relaxation of epitaxial strain caused by the misfit of crystal lattices. Besides a few selected examples from literature, we treat in particular crystal defects occurring in GaAs/Si, Ge/Si and β-SiC/Si structures which are studied by high-resolution annular dark-field scanning transmission electron microscopy. The relevance of this article is twofold; firstly, it should provide a collection of data which are of help for the identification and characterization of defects in cubic semiconductors by means of atomic-resolution imaging, and secondly, the experimental data shall provide a basis for advancing the understanding of device characteristics with the aid of theoretical modelling by considering the defective nature of strained semiconductor heterostructures. - Highlights: • The heterogeneous integration of high-quality compound semiconductors remains a challenge. • Lattice defects cause severe degradation of the semiconductor device performances. • Aberration-corrected HAADF-STEM allows atomic-scale characterization of defects. • An overview of lattice defects found in cubic semiconductors is presented. • Theoretical modelling and calculations are needed to determine the defect properties.
International Nuclear Information System (INIS)
Fiske, David R
2006-01-01
Computing spherical harmonic decompositions is a ubiquitous technique that arises in a wide variety of disciplines and a large number of scientific codes. Because spherical harmonics are defined by integrals over spheres, however, one must perform some sort of interpolation in order to compute them when data are stored on a cubic lattice. Misner (2004 Class. Quantum Grav. 21 S243) presented a novel algorithm for computing the spherical harmonic components of data represented on a cubic grid, which has been found in real applications to be both efficient and robust to the presence of mesh refinement boundaries. At the same time, however, practical applications of the algorithm require knowledge of how the truncation errors of the algorithm depend on the various parameters in the algorithm. Based on analytic arguments and experience using the algorithm in real numerical simulations, I explore these dependences and provide a rule of thumb for choosing the parameters based on the truncation errors of the underlying data. I also demonstrate that symmetries in the spherical harmonics themselves allow for an even more efficient implementation of the algorithm than was suggested by Misner in his original paper
Atomistic aspects of ductile responses of cubic silicon carbide during nanometric cutting.
Goel, Saurav; Luo, Xichun; Reuben, Robert L; Rashid, Waleed Bin
2011-11-11
Cubic silicon carbide (SiC) is an extremely hard and brittle material having unique blend of material properties which makes it suitable candidate for microelectromechanical systems and nanoelectromechanical systems applications. Although, SiC can be machined in ductile regime at nanoscale through single-point diamond turning process, the root cause of the ductile response of SiC has not been understood yet which impedes significant exploitation of this ceramic material. In this paper, molecular dynamics simulation has been carried out to investigate the atomistic aspects of ductile response of SiC during nanometric cutting process. Simulation results show that cubic SiC undergoes sp3-sp2 order-disorder transition resulting in the formation of SiC-graphene-like substance with a growth rate dependent on the cutting conditions. The disorder transition of SiC causes the ductile response during its nanometric cutting operations. It was further found out that the continuous abrasive action between the diamond tool and SiC causes simultaneous sp3-sp2 order-disorder transition of diamond tool which results in graphitization of diamond and consequent tool wear.
Visualization of membrane protein crystals in lipid cubic phase using X-ray imaging
International Nuclear Information System (INIS)
Warren, Anna J.; Armour, Wes; Axford, Danny; Basham, Mark; Connolley, Thomas; Hall, David R.; Horrell, Sam; McAuley, Katherine E.; Mykhaylyk, Vitaliy; Wagner, Armin; Evans, Gwyndaf
2013-01-01
A comparison of X-ray diffraction and radiographic techniques for the location and characterization of protein crystals is demonstrated on membrane protein crystals mounted within lipid cubic phase material. The focus in macromolecular crystallography is moving towards even more challenging target proteins that often crystallize on much smaller scales and are frequently mounted in opaque or highly refractive materials. It is therefore essential that X-ray beamline technology develops in parallel to accommodate such difficult samples. In this paper, the use of X-ray microradiography and microtomography is reported as a tool for crystal visualization, location and characterization on the macromolecular crystallography beamlines at the Diamond Light Source. The technique is particularly useful for microcrystals and for crystals mounted in opaque materials such as lipid cubic phase. X-ray diffraction raster scanning can be used in combination with radiography to allow informed decision-making at the beamline prior to diffraction data collection. It is demonstrated that the X-ray dose required for a full tomography measurement is similar to that for a diffraction grid-scan, but for sample location and shape estimation alone just a few radiographic projections may be required
Dicyanamide Salts that Adopt Smectic, Columnar, or Bicontinuous Cubic Liquid-Crystalline Mesophases.
Park, Geonhui; Goossens, Karel; Shin, Tae Joo; Bielawski, Christopher W
2018-04-25
Although dicyanamide (i.e., [N(CN) 2 ] - ) has been commonly used to obtain low-viscosity, halogen-free, room-temperature ionic liquids, liquid-crystalline salts containing such anions have remained virtually unexplored. Here we report a series of amphiphilic dicyanamide salts that, depending on their structures and compositions, adopt smectic, columnar, or bicontinuous cubic thermotropic liquid-crystalline mesophases, even at room temperature in some cases. Their thermal properties were explored by polarized light optical microscopy, differential scanning calorimetry, thermogravimetric analysis (including evolved gas analysis), and variable-temperature synchrotron X-ray diffraction. Comparison of the thermal phase characteristics of these new liquid-crystalline salts featuring "V-shaped" [N(CN) 2 ] - anions with those of structural analogues containing [SCN] - , [BF 4 ] - , [PF 6 ] - , or [CF 3 SO 3 ] - anions indicated that not only the size of the counterion but also its shape should be considered in the development of mesomorphic salts. Collectively, these discoveries may be expected to facilitate the design of thermotropic ionic liquid crystals that form inverted-type bicontinuous cubic and other sophisticated liquid-crystalline phases. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.