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Finite-Difference Lattice Boltzmann Scheme for High-Speed Compressible Flow:Two-Dimensional Case

Communications in Theoretical physics 2008年第7期50卷 201-210页

作者： GAN Yan-Biao XU Ai-Guo ZHANG Guang-Cai ZHANG Ping ZHANG Lei LI Ying-Jun China University of Mining and Technology （Beijing） Beijing 100083 China State Key Laboratory of Computational Physics Institute of Applied Physics and Computational Mathematics P.O. Box 8009-26 Beijing 100088 China Fundamental Science Department North China Institute of Aerospace Engineering Langfang 065000 China

Lattice Boltzmann （LB） modeling of high-speed compressible flows has long been attempted by various authors. One common weakness of most of previous models is the instability problem when the Mach number of the flow is large. In this paper we present a finite-difference LB model, which works for flows with flexible ratios of specific heats and a wide range of Mach number, from 0 to 30 or higher. Besides the discrete-velocity-model by Watari [Physica A 382 （2007） 502], a modified Lax Wendroff finite difference scheme and an artificial viscosity are introduced. The combination of the finite-difference scheme and the adding of artificial viscosity must find a balance of numerical stability versus accuracy. The proposed model is validated by recovering results of some well-known benchmark tests： shock tubes and shock reflections. The new model may be used to track shock waves and/or to study the non-equilibrium procedure in the transition between the regular and Mach reflections of shock waves, etc.

关键词： lattice Boltzmann method high-speed compressible flow von Neumann analysis

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Predicting unfavorable deformations of bridge beams using grid technology

Predicting unfavorable deformations of bridge beams using gr...

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11th International Conference on Civil, Structural and Environmental Engineering Computing, Civil-Comp 2007

作者： Sipos, A.A. Domokos, G. Department of Mechanics Materials and Structures Center for Applied Mathematics and Computational Physics Budapest University of Technology and Economics Hungary

ISBN: (纸本)9781905088157

In this paper we apply a previously developed algorithm to predict unfavourable lateral deformations of precast concrete beams. The algorithm is robust, i.e. there is no danger of false solutions or divergent behaviour, however this reliability requires a high computational effort. This latest is partially compansated by the parallel implementation of the algorithm, namely it can be used under the Grid. The algorithm applies the rules of the Eurocode 2 standard to include the special material properties of concrete such as creep. We developed also additional componentes (a user interface and a graphical application) to enable industrial users to carry out calculations easily via a web browser. In this paper we apply our method to predict unfavourable lateral deformations of prestressed bridge beams originating from the slight asymmetry of the prefabricating technology. © 2007 Civil-Comp Press.

关键词： Forecasting

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A Bregman-Style Improved ADMM and its Linearized Version in the Nonconvex Setting:Convergence and Rate Analyses

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Journal of the Operations Research Society of China 2024年第2期12卷 298-340页

作者： Peng-Jie Liu Jin-Bao Jian Hu Shao Xiao-Quan Wang Jia-Wei Xu Xiao-Yu Wu School of Mathematics Jiangsu Center for Applied MathematicsChina University of Mining and TechnologyXuzhou 221116JiangsuChina School of Mathematics and Physics Center for Applied Mathematics of GuangxiGuangxi Minzu UniversityNanning 530006GuangxiChina Department of Civil and Environmental Engineering The Hong Kong Polytechnic UniversityHong KongChina School of Mathematics and Computational Science Xiangtan UniversityXiangtan 411105HunanChina

This work explores a family of two-block nonconvex optimization problems subject to linear *** first introduce a simple but universal Bregman-style improved alternating direction method of multipliers(ADMM)based on the iteration framework of ADMM and the Bregman ***,we utilize the smooth performance of one of the components to develop a linearized version of *** to the traditional ADMM,both proposed methods integrate a convex combination strategy into the multiplier update *** each proposed method,we demonstrate the convergence of the entire iteration sequence to a unique critical point of the augmented Lagrangian function utilizing the powerful Kurdyka–Łojasiewicz property,and we also derive convergence rates for both the sequence of merit function values and the iteration ***,some numerical results show that the proposed methods are effective and encouraging for the Lasso model.

关键词： Nonconvex optimization Alternating direction method of multipliers Kurdyka-Lojasiewicz property Convergence rate

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Phase-coherence dynamics of frequency-comb emission via high-order harmonic generation in few-cycle pulse trains

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Chinese physics B 2023年第3期32卷 205-211页

作者：梁畅通张晶晶李鹏程 Research Center for Advanced Optics and Photoelectronics Department of PhysicsCollege of ScienceShantou UniversityShantou 515063China Key Laboratory of Intelligent Manufacturing Technology of the Ministry of Education Shantou UniversityShantou 515063China Institute of Applied Physics and Computational Mathematics Beijing 100088China

Frequency-comb emission via high-order harmonic generation(HHG)provides an alternative method for the coherent vacuum ultraviolet(VUV)and extreme ultraviolet(XUV)radiation at ultrahigh repetition *** particular,the temporal and spectral features of the HHG were shown to carry profound insight into frequency-comb emission *** we present an ab initio investigation of the temporal and spectral coherence of the frequency comb emitted in HHG of He atom driven by few-cycle pulse *** find that the emission of frequency combs features a destructive and constructive coherences caused by the phase interference of HHG,leading to suppression and enhancement of frequency-comb *** results reveal intriguing and substantially different nonlinear optical response behaviors for frequency-comb emission via *** dynamical origin of frequency-comb emission is clarified by analyzing the phase coherence in HHG processes in *** results provide fresh insight into the experimental realization of selective enhancement of frequency comb in the VUV–XUV regimes.

关键词： high-order harmonic generation frequency comb time-dependent Schro¨dinger equation intense laser field systems

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Vibronic effect study of ^(1)A_(2) state of H_(2)O and D_(2)O

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Chinese physics B 2024年第5期33卷 395-399页

作者：张倍源王礼涵朱剑辉徐卫青马子茹赵小利吴勇朱林繁 Department of Modern Physics University of Science and Technology of ChinaHefei 230026China Center for Transformative Science ShanghaiTech UniversityShanghai 201210China Department of Physics Yantai UniversityYantai 264005China Institute of Applied Physics and Computational Mathematics Beijing 100088China School of Physics and Information Technology Shaanxi Normal UniversityXi'an 710119China HEDPS Center for Applied Physics and TechnologyPeking UniversityBeijing 100084China

The generalized oscillator strengths of the dipole-forbidden excitations of the ^(1)A_(2) of H_(2)O and D_(2)O were calculated with the time dependent density functional theory,by taking into account the vibronic *** is found that the vibronic effect converts the dipole-forbidden excitation of the ^(1)A_(2) into a dipole-allowed one,which enhances the intensities of the corresponding generalized oscillator strength in the small squared momentum transfer *** present investigation shows that the vibronic effect of H_(2)O is slightly stronger than that of D_(2)O,which exhibits a clear isotopic effect.

关键词： water heavy water generalized oscillator strength vibronic effect isotope effect

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4D seismic monitoring of CO2 sequestration based upon spectral-element and adjoint methods: Comparison of acoustic, elastic and poroelastic theories 80

4D seismic monitoring of CO2 sequestration based upon spectr...

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Society of Exploration Geophysicists International Exposition and 80th Annual Meeting 2010, SEG 2010

作者： Morency, Christina Luo, Yang Tromp, Jeroen Department of Geosciences Princeton University United States Department of Geosciences and Program in Applied and Computational Mathematics Princeton University United States

ISBN: (纸本)9781617389801

The key issues in CO2 sequestration monitoring involve accurate monitoring, from the injection stage to prediction & verification, of CO2 movement over time for environmental considerations. A natural non-intrusive monitoring technique is referred to as "4D seismics", which involves 3D time-lapse seismic surveys. The success of monitoring the CO2 movement is subject to a proper description of the physical properties of the structure. We realize time-lapse migrations comparing acoustic, elastic, and poroelastic simulations of 4D seismic imaging to characterize the storage zone, based solely upon the first arrival traveltime anomaly arising from the injection of CO2. This approach highlights the influence of using different physical theories on interpreting seismic data, and, more importantly, on extracting the CO2 signature from the seismic wave field. Simulations are performed using a spectral-element method, which allows for highly accurate results. Biot? Equations are implemented to account for poroelastic effects. The sensitivity of observables to the model parameters is quantified based upon finite-frequency sensitivity kernels calculated using an adjoint method. © 2010 SEG.

关键词： Carbon dioxide

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Rapid Path Extraction and Three-Dimensional Roaming of the Virtual Endonasal Endoscope

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Chinese Journal of Electronics 2021年第3期30卷 397-405页

作者： WANG Yudong HAN Jing PAN Junjun WANG Jing CAO Yi ZHU Li LUO Yanlin School of Artificial Intelligence Beijing Normal University State Key Laboratory of Virtual Reality Technology and Systems Beihang University Institute of Applied Physics and Computational Mathematics Department of Otolaryngology Head and Neck Surgery Peking University Third Hospital

Compared with traditional endonasal endoscope, Virtual endonasal endoscope(VEE) is a computerized alternative solution with the advantages of being non-invasive, affordable, no perforation, low risk of infection, and high degree of sensitivity. A Central path extraction algorithm based on Pre-planning of the roaming area(CPE-PRA) is proposed to extract the central path of the nasal cavity model efficiently. And a B-spline curve fitting algorithm based on Relative center deviation(RCD)is introduced to fit a smooth curve to the extracted path,so that the virtual camera could have both a steady turning speed and a broad vision. A series of comparison tests were conducted to evaluate the effectiveness and efficiency of the proposed algorithms.

关键词： virtual instrumentation Virtual endonasal endoscope RCD rapid path extraction nasal cavity model medical image processing VEE feature extraction path planning CPE-PRA splines (mathematics) B-spline curve fitting algorithm computerized alternative solution roaming area relative center deviation virtual camera Central path extraction algorithm curve fitting endoscopes surgery medical robotics three-dimensional roaming

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Role of XUV Photons in Atomic High-Order Above-Threshold Ionization Processes in IR+XUV Two-Color Laser Fields

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Chinese physics Letters 2017年第11期34卷 15-19页

作者：张奎刘敏王兵兵郭迎春严宗朝陈京柳晓军 Laboratory of Optical Physics Beijing National Laboratory for Condensed Matter PhysicsInstitute of PhysicsChinese Academy of SciencesBeijing 100190 Department of Physics East China Normal UniversityShanghai 200241 Department of Physics University of New BrunswickFrederictonNew BrunswickCanada State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics Wuhan Institute of Physics and MathematicsChinese Academy of SciencesWuhan 430071 Center for Cold Atom Physics Chinese Academy of SciencesWuhan 430071 HEDPS Center for Applied Physics and TechnologyPeking UniversityBeijing 100871 Institute of Applied Physics and Computational Mathematics Beijing 100088

We investigate the above-threshold ionization of an atom in a combined infrared （IR） and extreme ultraviolet （XUV） two-color laser field and focus on the role of XUV field in the high-order above-threshold ionization （HATI） process. It is demonstrated that, in stark contrast to previous studies, the XUV laser may play a significant role in atomic HATI process, and in particular, the XUV laser can accelerate the ionized electron in a quantized way during the collision between the electron and its parent ion. This process cannot be explained by the elassical three-step model Our results indicate that the previously well-established concept that HATI is an elastic recollision process is broken down.

关键词： ATI Role of XUV Photons in Atomic High-Order Above-Threshold Ionization Processes in IR+XUV Two-Color Laser Fields IR

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Terahertz Velocity and Spectroscopy Sensing with Self-mixing Interference of Quantum Cascade Lasers

Terahertz Velocity and Spectroscopy Sensing with Self-mixing...

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Optical Sensors, SENSORS 2024 - Part of Optica Sensing Congress

作者： Cai, Jiaxuan Xie, Yan Yang, Ning Chu, Weidong Wang, Yingxin Zhao, Ziran Institute of Applied Physics and Computational Mathematics Beijing100088 China National Key Laboratory of Computational Physics Beijing100088 China Department of Engineering Physics Tsinghua University Beijing100084 China

Coherence measurement system based on self-mixing interferometry with quantum cascade lasers could be employed for various of sensing applications, such as multi-target velocity and broadband terahertz spectroscopy se... 详细信息

ISBN: (纸本)9781957171364

关键词： Quantum cascade lasers

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Achieving Tunable and High-Performance Four-THz-Frequency Photodetection by Near-Field Pillars 5th

Achieving Tunable and High-Performance Four-THz-Frequency Ph...

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5th China and International Young Scientist Terahertz Conference, YTHZ 2024

作者： Wang, Yiwei Bai, Peng Yang, Ning Chu, Weidong Xie, Yan Wang, Yingxin Chen, Meng Zhao, Ziran Institute of Applied Physics and Computational Mathematics Beijing100088 China National Key Laboratory of Computational Physics Beijing100088 China Department of Engineering Physics Tsinghua University Beijing100084 China

ISBN: (纸本)9789819739127

Through theoretical simulations, we exploit an array of metal-dielectric-metal pillars which can surprisingly tune the properties of photoresponsivity spectrum by changing periods. That is, the complexity of processing can be mitigated by controlling periods instead of patch sizes. In addition, one can envision a significant enhancement of the responsivity (peak value at 0.128 A/W) compared with the unoptimized GaAs-based device, resulting in a low noise equivalent power (minimum at 0.703 pWHz−1/2) and high specific detectivity (peak value at 6.10 × 1010 Jones), which indicates that a higher operating temperature is possible. Our discovery demonstrates an efficient strategy to simplify the workflow of patchwork design for our ratchet and up-version imaging systems. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2024.

关键词： Gallium arsenide

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