Chinese Academy of Engineering Physics

Beijing, China

Chinese Academy of Engineering Physics

Beijing, China
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Lv Z.-L.,Sichuan University | Lv Z.-L.,Henan University of Science and Technology | Cheng Y.,Sichuan University | Chen X.-R.,Sichuan University | Ji G.-F.,Chinese Academy of Engineering Physics
Computational Materials Science | Year: 2013

CdSiP2 is regarded to be a promising material for future technical applications, but many of its properties are still not well studied. In this work, electronic, bonding, elastic properties and intrinsic hardness of CdSiP2 are investigated by performing first principles calculations within the framework of generalized gradient approximation. Calculations indicate that CdSiP2 is a direct-gap semiconductor with a gap value of 1.22 eV located at the Γ-point. Combined with the density of states, the characteristics of the band structure have been analyzed and their origins have been specified, which reveal that sp3 hybridization plays an important role in the formation of the crystal. Charge analyses disclose that CdSiP2 is a crystal with ionic and covalent properties. The calculated intrinsic hardness of CdSiP2 is 10.05 GPa, agreeing well with the experimental value of 10.5 GPa. Its bulk modulus and elastic constants, together with its elastic anisotropy, are also computed and analyzed. The obtained elastic constants are larger than other theoretical ones, as a result, the bulk modulus deduced gives a value of 80.99 GPa, which is more reasonable compared with the experimentally derived value and other theoretical ones. © 2013 Elsevier B.V. All rights reserved.

Huang J.,Tsinghua University | Zhang Y.,Tsinghua University | Ma T.,Tsinghua University | Li H.,Chinese Academy of Engineering Physics | Zhang L.,Chinese Academy of Engineering Physics
Applied Physics Letters | Year: 2010

The correlation between the dielectric breakdown performance and interface polarization was studied by the measurements of the dielectric breakdown strength and impedance spectroscopy as a function of sintering temperatures in a BaO-SrO- TiO2-Al2O3-SiO2 glass ceramic system. It was found that dielectric breakdown strength strongly depends on the interface polarization. The sintering temperature dependence of breakdown strength is attributed to the variation in interfacial polarization based on the results of complex impedance analysis. © 2010 American Institute of Physics.

Hu J.,Jilin University | Dong X.,Jilin University | Dong X.,Chinese Academy of Engineering Physics | Tosto S.,ENEA
Journal of the American Ceramic Society | Year: 2012

High resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD) techniques were used to examine the crystal structure of TiB ceramic powder synthesized by a Ti-Boronizing method. The HRTEM analysis revealed that the synthesized titanium boride has fcc crystal structure, with titanium and boron atoms alternatively arranged like Na and Cl ions in NaCl-type lattice. The crystal structure of this boride phase, denoted as fcc-TiB in the paper, was confirmed also by XRD analysis and agrees with the data reported in the card PDF # 06-641. This card is present in the powder diffraction file (PDF) database, but seldom quoted in literature because the typical crystal structure of TiB that forms in situ as a phase is orthorhombic. The present work reports new experimental data on the crystal properties of pure fcc-TiB not yet reported in the literature. The lattice parameter of fcc-TiB, calculated from XRD analysis, is a 0=4.245 Å. © 2012 The American Ceramic Society.

Sekine T.,Hiroshima University | Meng C.,Chinese Academy of Engineering Physics | Zhu W.,Chinese Academy of Engineering Physics | He H.,Chinese Academy of Engineering Physics
Journal of Geophysical Research: Solid Earth | Year: 2012

Detailed wave profiles of antigorite (a serpentine mineral) under plate-impact shock loading have been measured to a pressure of 131 GPa in order to understand its dynamic behavior because serpentine is present in pristine meteorites as well as in the Earth mantle. All the profiles indicate single wave structures, and a sudden decrease in density was detected at ∼60 GPa with increasing pressure when shock-loaded for a long duration (∼0.6 s) using a thick flyer. Such a drop in density also was observed during recompression by a high-impedance window material (LiF). Although exothermic decomposition is generally considered to be fast, the decomposition of antigorite under shock loading requires a reaction time so that the Hugoniot may represent a metastable state at which stable phase cannot appear in a timely way. Based on these observations, antigorite decomposes exothermically into an assemblage of either brucite + stishovite + periclase or brucite + perovskite above a shock pressure of 60 GPa, but does not dehydrate endothermically into assemblages with water fluid. The observed dynamic behavior of serpentine, coupled with the previous results of the shock-recovered serpentines, reinforces that serpentine plays a key role to carry water within the snowline of the solar system. © 2012 by the American Geophysical Union.

Zhou Y.,Beijing Institute of Technology | Zhou Y.,Chinese Academy of Engineering Physics | Long X.-P.,Chinese Academy of Engineering Physics | Zeng Q.-X.,Beijing Institute of Technology
Polymer | Year: 2011

Dissipative particle dynamics (DPD) simulations are used to investigate the effect of nanorods on the interface of immiscible A/B homopolymer blends. The nanorods are constructed by a string of beads connected through the spring forces, and then their rigidity is achieved depending on the angle forces. For the low volume fraction and/or aspect ratio, nanorods lead to broaden the interfacial width, D and decrease the interfacial tension, γS with the increase of the volume fraction. There is also a pronounced linear relationship. For the high volume fraction and/or aspect ratio, the variation of D and γS is found to depend on Onsager's dimensionless parameter ψν, where ψ and ν are the volume fraction and aspect ratio of nanorods in the systems, respectively. Two scaling D ∼ (ψν)3 and γS ∼ (ψν)2 are constructed. These results indicate that nanorods can indeed be used as a compatibilizing agent of immiscible blends as mentioned in reference [J. Chem. Phys. 2008, 128, 054901] and improve the interfacial characteristics, only when the parameters (ψν) in the correct range are chosen. © 2011 Elsevier Ltd. All rights reserved.

Song H.X.,Chinese Academy of Engineering Physics | Geng H.Y.,Chinese Academy of Engineering Physics | Wu Q.,Chinese Academy of Engineering Physics
Physical Review B - Condensed Matter and Materials Physics | Year: 2012

Taking uranium dioxide and plutonium dioxide as prototypes, the phase stabilities of actinide dioxides under high pressures are studied with density functional theory. The calculations are carried out within the framework of Perdew-Burke-Ernzerhof (PBE) and PBE+U formalism. Beyond the cotunnite Pnma phase, two novel orthorhombic phases with space groups Cmc2 1 and Cmcm are found as the possible ground state. Both of them are low temperature distortions of the hexagonal Ni 2In phase with space group P6 3/mmc, which is a common post-cotunnite phase adopted by many AX 2 and A 2X binary compounds. According to the PBE+U calculations, the Cmc2 1 phase is stable above 120GPa in UO 2, and it transforms to the Cmcm phase at around 400GPa. In PuO 2, the Pnma phase directly transforms to the Cmcm phase at 123GPa. Symmetry analysis shows that the transitions of Cmc2 1 to Cmcm in UO 2 and Pnma to Cmcm in PuO 2 are pressure induced group-subgroup transitions. The Cmcm phase is responsible for pressure-induced metallization both in UO 2 and PuO 2, but their electronic structures are quite different during metallization. The difference is originated from their insulating nature, where UO 2 is a standard Mott-Hubbard insulator, while PuO 2 belongs to an intermediate region between the Mott-Hubbard insulator and charge-transfer insulator. The equations of state are also analyzed, together with the pressure dependence of lattice parameters, fractional atomic coordinates, electronic band gap, and magnetic moment. The results indicate that these distorted-Ni 2In phases will probably be adopted by other actinide dioxides. © 2012 American Physical Society.

Wan Z.,Hefei University of Technology | Zhou L.,Chinese Academy of Engineering Physics | Yang H.,Hefei University of Technology | Sun D.,Hefei University of Technology
Physics of Fluids | Year: 2013

Large eddy simulation is performed for investigating the local and far-field behaviors of free and swirling jets at moderate Reynolds number. By solving compressible boundary layer equations, the inflow profiles with different swirl number are calculatedthen their stability characteristics are analyzed based on linear stability theory. The amplification rates of swirling jets are higher than the free one, particularly for higher or negative azimuthal wavenumber modes. Multiple unstable modes are superimposed to construct inflow forcing. The quantities of flow and acoustic are presented and compared against the results of existed experiments and other computations, besides, the comparisons are also made among themselves. For swirling jets, the spreadings of jet half-width and vorticity thickness at the initial and transition stage are enhanced, but they are surpassed by the free jet at turbulent mixing stage. In all cases, the development of mixing layer initially is greatly influenced by frequencies f0 and f0/2 associated with upstream forcing. As the swirl intensity is increased, the growth rates of fluctuation quantities on the centerline and the nozzle lip line are raised, but the peak levels on the centerline are reduced substantially. In swirling jets, the strength of vortex pairing is decreasedthe pairing noise is weakened correspondingly. The overall sound pressure levels are lower than that of the free jet at all observation angles (φ{symbol})about 3 decibels (dB) is reduced at φ{symbol} ≃ 30° in the strong swirling case at a distance of 60 radii. The Fourier analyses of pressure and acoustic sources show that the modes are varied greatly, which suggests that the noise reduction should be corresponding to the change of instability waves. © 2013 AIP Publishing LLC.

Wang H.,Chinese Academy of Engineering Physics | Zhu H.,Chinese Academy of Engineering Physics
Nanoscale Research Letters | Year: 2014

The size evolution of Pb nanoparticles (NPs) synthesized by ion implantation in an epitaxial Al film has been experimentally investigated. The average radius R of Pb NPs was determined as a function of implantation fluence f. The R(f) data were analyzed using various growth models. Our observations suggest that the size evolution of Pb NPs is controlled by the diffusion-limited growth kinetics (R 2∝f). With increasing implantation current density, the diffusion coefficient of Pb atoms in Al is evident to be enhanced. By a comparative analysis of the R(f) data, values of the diffusion coefficient of Pb in Al were obtained. © 2014 Wang and Zhu; licensee Springer.

Chen Y.,Chinese Academy of Engineering Physics
Journal of Chromatography A | Year: 2011

A set of accurate expressions of elution-curve moments are derived from the moments of residence time and displacement in a step based on probability theory. Then the problems about residence time and displacement in a step of a solute molecule in the porous layer of capillary columns and in the moving mobile phase are described by a set of mass-balance equations respectively. The set of equations are solved in Fourier-Laplace domain, and the characteristic functions of residence time of a step, as well as the moments, are obtained by means of computing software Mathematica. At last, using numerical inverse Laplace transform, the elution curves for various conditions are calculated. In the case of large desorption constant the results entirely coincide with those of mass-balance-equation theory and in the case of small desorption constant they are equivalent to those of stochastic theory. © 2011 Elsevier B.V.

He X.,Chinese Academy of Engineering Physics | Zhang K.,Chinese Academy of Engineering Physics | Li Q.,Chinese Academy of Engineering Physics
Physical Review Special Topics - Accelerators and Beams | Year: 2011

Beam position monitors are an important diagnostics tool for particle accelerator operation and related beam dynamics research. The measurement of the beam deflection angle, or moving direction of a charged particle beam with respect to the beam pipe axis, can provide useful additional information. Beam monitors sensitive to the beam's azimuthal B-dot field (sometimes referred as B dots) are used to measure the displacement (position) of the beam centroid, as the beam generates a dipole term of the azimuthal magnetic field. Similarly, a dipole term of the axial magnetic field will be generated by the beam moving in a direction not parallel to the axis of the beam pipe. In this paper, a new method using the axial B-dot field is presented to measure the beam deflection angle directly, including the theoretical background. Simulations using the MAFIA numerical code have been performed, demonstrating a good agreement to the new established analytical model. © 2011 American Physical Society.

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