ALBERT

Description: Author(s): Y. Y. Chin, H.-J. Lin, Z. Hu, Masanori Nagao, Yongping Du, Xiangang Wan, B.-J. Su, L. Y. Jang, T. S. Chan, H.-Y. Chen, Y. L. Soo, and C. T. Chen The x-ray absorption spectra at the Bi- L 1 and S- K edges of LaO 1 − x F x BiS 2 show a decrease of spectral weight close to the absorption thresholds upon F substitution for O, indicating a reduction of the unoccupied Bi 6 p and S 3 p states, as expected for electron doping. This doping-induced spectral weigh… [Phys. Rev. B 94, 035150] Published Mon Jul 25, 2016

Description: Author(s): Q. Q. Ge, H. C. Xu, X. P. Shen, M. Xia, B. P. Xie, F. Chen, Y. Zhang, R. Kato, T. Tsumuraya, T. Miyazaki, M. Matsunami, S. Kimura, and D. L. Feng The electronic structure of a quantum spin liquid compound, EtMe3Sb[Pd(dmit)2]2, has been studied with angle-resolved photoemission spectroscopy, together with two other Pd(dmit)2 salts in the valence bond solid or antiferromagnetic state. EtMe3Sb[Pd(dmit)2]2, being a Mott insulator, has its lower H... [Phys. Rev. B 89, 075105] Published Wed Feb 05, 2014

Description: Author(s): R. Wang, Y. J. Jin, J. Z. Zhao, Z. J. Chen, Y. J. Zhao, and H. Xu The interplay between symmetry and magnetization directions in ferromagnetic materials provides an exotic platform to investigate the symmetry-protected topological order. In this work, we propose that unexpected ferromagnetic topological features, such as triple fermions and type-I and type-II Weyl... [Phys. Rev. B 97, 195157] Published Thu May 31, 2018

Description: Author(s): V. Thampy, X. M. Chen, Y. Cao, C. Mazzoli, A. M. Barbour, W. Hu, H. Miao, G. Fabbris, R. D. Zhong, G. D. Gu, J. M. Tranquada, I. K. Robinson, S. B. Wilkins, and M. P. M. Dean Charge-density-wave (CDW) correlations feature prominently in the phase diagram of the cuprates, motivating competing theories of whether fluctuating CDW correlations aid superconductivity or whether static CDW order coexists with superconductivity in inhomogeneous or spatially modulated states. Her… [Phys. Rev. B 95, 241111(R)] Published Wed Jun 21, 2017

Description: Author(s): J. B. He, Y. Fu, L. X. Zhao, H. Liang, D. Chen, Y. M. Leng, X. M. Wang, J. Li, S. Zhang, M. Q. Xue, C. H. Li, P. Zhang, Z. A. Ren, and G. F. Chen We report a study of the magnetic and magnetotransport properties of layered transition-metal pnictide CaMnSb 2 . CaMnSb 2 is a quasi-two-dimensional system with an orthorhombic crystal structure, containing two distinct layers of a distorted Sb square sheet and an edge-sharing MnSb 4 tetrahedron. It wa… [Phys. Rev. B 95, 045128] Published Tue Jan 17, 2017

Description: Author(s): R. Y. Chen, Y. G. Shi, P. Zheng, L. Wang, T. Dong, and N. L. Wang RuP single crystals of MnP-type orthorhombic structure were synthesized by the Sn flux method. Temperature-dependent x-ray diffraction measurements reveal that the compound experiences two structural phase transitions, which are further confirmed by enormous anomalies shown in temperature-dependent ... [Phys. Rev. B 91, 125101] Published Mon Mar 02, 2015

Description: A formulation of finite-rate ablation surface boundary conditions, including oxidation, nitridation, and sublimation of carbonaceous material with pyrolysis gas injection, has been developed based on surface species mass conservation. These surface boundary conditions are discretized and integrated with a Navier-Stokes solver. This numerical procedure can predict aerothermal heating, chemical species concentration, and carbonaceous material ablation rate over the heatshield surface of re-entry space vehicles. In this study, the gas-gas and gas-surface interactions are established for air flow over a carbon-phenolic heatshield. Two finite-rate gas-surface interaction models are considered in the present study. The first model is based on the work of Park, and the second model includes the kinetics suggested by Zhluktov and Abe. Nineteen gas phase chemical reactions and four gas-surface interactions are considered in the present model. There is a total of fourteen gas phase chemical species, including five species for air and nine species for ablation products. Three test cases are studied in this paper. The first case is a graphite test model in the arc-jet stream; the second is a light weight Phenolic Impregnated Carbon Ablator at the Stardust re-entry peak heating conditions, and the third is a fully dense carbon-phenolic heatshield at the peak heating point of a proposed Mars Sample Return Earth Entry Vehicle. Predictions based on both finite-rate gas- surface interaction models are compared with those obtained using B' tables, which were created based on the chemical equilibrium assumption. Stagnation point convective heat fluxes predicted using Park's finite-rate model are far below those obtained from chemical equilibrium B' tables and Zhluktov's model. Recession predictions from Zhluktov's model are generally lower than those obtained from Park's model and chemical equilibrium B' tables. The effect of species mass diffusion on predicted ablation rate is also examined.

Description: A multi-dimensional, coupled thermal response modeling system for analysis of hypersonic entry vehicles is presented. The system consists of a high fidelity Navier-Stokes equation solver (GIANTS), a two-dimensional implicit thermal response, pyrolysis and ablation program (TITAN), and a commercial finite element thermal and mechanical analysis code (MARC). The simulations performed by this integrated system include hypersonic flowfield, fluid and solid interaction, ablation, shape change, pyrolysis gas generation and flow, and thermal response of heatshield and structure. The thermal response of the heatshield is simulated using TITAN, and that of the underlying structural is simulated using MARC. The ablating heatshield is treated as an outer boundary condition of the structure, and continuity conditions of temperature and heat flux are imposed at the interface between TITAN and MARC. Aerothermal environments with fluid and solid interaction are predicted by coupling TITAN and GIANTS through surface energy balance equations. With this integrated system, the aerothermal environments for an entry vehicle and the thermal response of the entire vehicle can be obtained simultaneously. Representative computations for a flat-faced arc-jet test model and a proposed Mars sample return capsule are presented and discussed.

Description: A fully implicit ablation and thermal response program has been developed for the simulation of one-dimensional transient transport of thermal energy in a multilayer stack of isotropic materials and structure which can ablate from a front surface and decompose in-depth. Equations and numerical procedures for solution are described. Solutions are compared with those of Aerotherm Charring Material Thermal Response and Ablation Program, and with the arcjet data. The code is numerically more stable, and solves much wider range of problems compared with the existing explicit code. Applications of the code for the analysis of aeroshell heatshields of Stardust, Mars 2001, and Mars Microprobe using the advanced Light Weight Ceramic Ablators developed at the NASA Ames Research Center are presented and discussed in detail.

Description: A system is presented for multi-dimensional, fully-coupled thermal response modeling of hypersonic entry vehicles. The system consists of a two-dimensional implicit thermal response, pyrolysis and ablation program (TITAN), a commercial finite-element thermal and mechanical analysis code (MARC), and a high fidelity Navier-Stokes equation solver (GIANTS). The simulations performed by this integrated system include hypersonic flow-field, fluid and solid interaction, ablation, shape change, pyrolysis gas generation and flow, and thermal response of heatshield and structure. The thermal response of the ablating and charring heatshield material is simulated using TITAN, and that of the underlying structural is simulated using MARC. The ablating heatshield is treated as an outer boundary condition of the structure, and continuity conditions of temperature and heat flux are imposed at the interface between TITAN and MARC. Aerothermal environments with fluid and solid interaction are predicted by coupling TITAN and GIANTS through surface energy balance equations. With this integrated system, the aerothermal environments for an entry vehicle and the thermal response of both the heatshield and the structure can be obtained simultaneously. Representative computations for a proposed blunt body earth entry vehicle are presented and discussed in detail.