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MPI Solver of Particle-Laden Compressible High Enthalpy Flow: Numerical Method and Validation

LI Qing, YU Zhaosheng, LIU Pengxin, LI Tingting, CHEN Jianqiang, YUAN Xianxu

Acta Scientiarum Naturalium Universitatis Pekinensis 2024, 60 (1): 89-108. DOI: 10.13209/j.0479-8023.2023.022

Abstract （67）

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Based on the theoretical equations of compressible particle-laden flow in multi-physical conditions, a MPI-Particle Solver based on dynamic linked list array is developed, which is coupled with a compressible flow solver of carried phase. The dispersed particle phase is different from the carried fluid phase, the previous one is based on the Lagrange coordinate system, while the later one is based on the Euler coordinate system. The traditional way is to use the global array to assign the memory to the dispersed particle phase to achieve the transfer between two-phase, but at expense of low computational efficiency. This paper uses dynamic linked list array to allocate memory to dispersed particle phase, achieve both problems. A series of DNS validations with references case have been done, in terms of multi-physical effects and two canonical cases at incompressible limit.

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Bi-Attention Text-Keyword Matching for Law Recommendation

DING Na, LIU Peng, SHAO Huipeng, WANG Xuekui

Acta Scientiarum Naturalium Universitatis Pekinensis 2024, 60 (1): 79-88. DOI: 10.13209/j.0479-8023.2023.077

Abstract （78）

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This paper proposed a bi-directional attention based text-keyword matching model for law recommendation (BiAKLaw). In this model, BERT is utilized as a basic matching model, bi-directional attention mechanism is implemented to extract token-level alignment features and keyword-level differential features, and these features are fused with keyword attentive semantic representations for a better matching effect. The experimental results on the traffic accident and intentional injury datasets demonstrate that, compared with BERT, the proposed model increases F1 evaluation metric by 3.74% and 3.43% respectively.

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Theoretical Analysis on the High Enthalpy Radiation Particle Laden Compressible Flow

LI Tingting, LIU Pengxin, YUAN Xianxu, ZHOU Qiang, LI Qing

Acta Scientiarum Naturalium Universitatis Pekinensis 2022, 58 (6): 989-998. DOI: 10.13209/j.0479-8023.2022.039

Abstract （363）

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The theoretical equations of particle laden compressible flow by taking into account of heat radiation and convection were derived. It is found that, the heat exchange between dispersed phase and carried fluid phase is proportional to square of Mach number. In extreme high temperature environment, the convective heat transfer between two phases is one way, which means that the isothermal particle transfers the heat into the fluid, but the fluid can not cool down the radiation-heated particle via convection. In addition, the effect of shrinking core on the particle dynamics was investigated. The shrinking core effect modifies the Stokes number of particle, therefore the time evolution of unsteady velocity of particle from rest to terminal state in a uniform flow was altered.

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Design of Secure Divider for Side Channel Defense

MA Bingwen, YAN Xuesong, LIU Hao, LIU Pengyuan, YI Jiangfang

Acta Scientiarum Naturalium Universitatis Pekinensis 2022, 58 (4): 597-601. DOI: 10.13209/j.0479-8023.2021.128

Abstract （427）

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According to the common methods of side channel timing attack and defense using arithmetic unit, based on the division algorithms of fixed delay and variable delay, a secure divider was designed. The design considered both high performance and high security. It was suitable for different working environments. Experimental results showed that the proposed divider was effective, especially for low power embedded microprocessors for IoT applications.

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Impact of Tibetan Glacier Change on the Asian Climate during the Last Glacial Maximum

WU Yubin, LIU Yonggang, YI Chaolu, LIU Peng

Acta Scientiarum Naturalium Universitatis Pekinensis 2019, 55 (1): 159-170. DOI: 10.13209/j.0479-8023.2018.094

Abstract （1052）

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Taking the climate of the Last Glacial Maximum (about 26000 years ago to 19000 years ago) as the background climate, the authors study the climatic impact of the expansion of the glacier on the Tibetan Plateau using the atmospheric general circulation model CAM4 coupled to the land surface model CLM4. The results show that in summer the increased glacier extent over Qinghai-Tibet Plateau has a significant impact on the climate in the Northern Hemisphere. Besides the significant temperature decrease on the glacier, atmospheric teleconnection can also cause significant warming near the Bering Strait. In addition, the disturbance caused by glaciers will enhance the South Asian summer monsoon and increase the precipitation there. Finally, through comparing the influence of the scale of the Qinghai-Tibetan glaciers on the climate under the different climate states of the Last Glacial Maximum (LGM) and Pre-industrial (PI) periods, it was found that their influence in the PI period was significantly less than that in the LGM period. It indicates that impact of Tibetan glaciers on climate is related with the climate state.

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Analysis of Particle Size Distribution Measurements from a Summer Campaign in Suburban Tianjin

LIANG Si,MA Nan,XU Wanyun,DENG Zhaoze,LIU Pengfei,RAN Liang,ZHAO Chunsheng

Acta Scientiarum Naturalium Universitatis Pekinensis

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A Semantic Security Policy Language for Distributed Computing Environment

LIU Peng,HU Jianbin,CHEN Zhong

Acta Scientiarum Naturalium Universitatis Pekinensis

Abstract （668）

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A semantic security policy language, called SSPL, was proposed for distributed computing environment. SSPL is represented in OWL DL. SSPL supports basic concepts of security policy-positive and negative authorization and obligation, privilege delegation and revocation, policy conflict resolution. Furthermore, SSPL supports rule-style policy, which enhances the expressiveness of SSPL. This paper also demonstrates the reasoning of SSPL policy. DL-safe rule and courteous logic program were introduced for the formal semantic of SSPL. The transformation from SSPL policy to courteous DL-safe program and the query answering procedure of the result courteous DL-safe program are presented.

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