检索结果-内蒙古大学图书馆

Well/Ill-Posedness Bifurcation for the Boltzmann Equation with Constant Collision Kernel

ANNALS OF PDE 2024年第2期10卷 14页

作者： chen, xuwen Holmer, Justin Univ Rochester Dept Math Rochester NY 14627 USA Brown Univ Dept Math 151 Thayer St Providence RI 02912 USA

We consider the 3D Boltzmann equation with the constant collision kernel. We investigate the well/ill-posedness problem using the methods from nonlinear dispersive PDEs. We construct a family of special solutions, which are neither near equilibrium nor self-similar, to the equation, and prove that the well/ill-posedness threshold in H-s Sobolev space is exactly at regularity s =1, despite the fact that the equation is scale invariant at s =1/2.

关键词： Boltzmann equation Ill-posedness X-s,X-b spaces

来源：评论

学校读者我要写书评

暂无评论

Well/Ill-Posedness of the Boltzmann Equation with Soft Potential

引用

COMMUNICATIONS IN MATHEMATICAL PHYSICS 2024年第12期405卷 1-51页

作者： chen, xuwen Shen, Shunlin Zhang, Zhifei Univ Rochester Dept Math Rochester NY 14627 USA Univ Sci & Technol China Sch Math Sci Hefei 230026 Anhui Peoples R China Peking Univ Sch Math Sci Beijing 100871 Peoples R China

We consider the Boltzmann equation with the soft potential and angular cutoff. Inspired by the methods from dispersive PDEs, we establish its sharp local well-posedness and ill-posedness in Hs\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$H<^>{s}$$\end{document} Sobolev space. We find the well/ill-posedness separation at regularity s=d-12\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$s=\frac{d-1}{2}$$\end{document}, strictly 12\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\frac{1}{2}$$\end{document}-derivative higher than the scaling-invariant index s=d-22\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$s=\frac{d-2}{2}$$\end{document}, the usually expected separation point.

关键词：

来源：评论

学校读者我要写书评

暂无评论

A Time-Dependent Inclusion-Based Method for Continuous Collision Detection between Parametric Surfaces

引用

ACM TRANSACTIONS ON GRAPHICS 2024年第6期43卷 1-11页

作者： chen, xuwen Yu, cheng Ni, Xingyu Chu, Mengyu Wang, Bin chen, Baoquan Peking Univ Sch Intelligence Sci & Technol Beijing Peoples R China Peking Univ Sch Comp Sci Beijing Peoples R China Peking Univ State Key Lab Gen Artificial Intelligence Beijing Peoples R China BIGAI State Key Lab Gen Artificial Intelligence Beijing Peoples R China

Continuous collision detection (CCD) between parametric surfaces is typically formulated as a five-dimensional constrained optimization problem. In the field of CAD and computer graphics, common approaches to solving this problem rely on linearization or sampling strategies. Alternatively, inclusion-based techniques detect collisions by employing 5D inclusion functions, which are typically designed to represent the swept volumes of parametric surfaces over a given time span, and narrowing down the earliest collision moment through subdivision in both spatial and temporal dimensions. However, when high detection accuracy is required, all these approaches significantly increases computational consumption due to the Intelligence, Peking University, high-dimensional searching space. In this work, we develop a new time- dependent inclusion-based CCD framework that eliminates the need for temporal subdivision and can speedup conventional methods by a factor ranging from 36 to 138. To achieve this, we propose a novel time-dependent inclusion function that provides a continuous representation of a moving surface, along with a corresponding intersection detection algorithm that quickly identifies the time intervals when collisions are likely to occur. We validate our method across various primitive types, demonstrate its efficacy within the simulation pipeline and show that it significantly improves CCD efficiency while maintaining accuracy.

关键词： parametric surface continuous collision detection interval analysis

来源：评论

学校读者我要写书评

暂无评论

Interaction and sorption mechanisms of phthalate plasticizers and Cd²⁺ on biochar

引用

ENVIRONMENTAL POLLUTION 2025年 373卷 126176页

作者： Li, Wenjie Wang, Jian chen, xuwen Mosa, Ahmed Ling, Wanting Gao, Yanzheng Nanjing Agr Univ Inst Organ Contaminant Control & Soil Remediat Coll Resources & Environm Sci Nanjing 210095 Peoples R China Mansoura Univ Fac Agr Soils Dept Mansoura 35516 Egypt

Biochar exhibits significant potential for the remediation of soil contaminated with organic pollutants and heavy metals. A comprehensive understanding of the interfacial interactions and sorption mechanisms of lowhydrophobicity phthalate plasticizers, such as dimethyl phthalate (DMP) and diethyl phthalate (DEP), along with Cd2+ on biochar, is essential for the effective remediation of polluted soil environments. This study systematically examines the interaction and sorption mechanisms of PAEs-Cd2+ on biochar at both macro and micro levels using sorption batch experiments and molecular dynamics simulations. The sorption of contaminants by biochar occurred through a combination of physical and chemical mechanisms. The presence of coexisting pollutants reduced the sorption capacity of biochar to PAEs but had a minimal effect on Cd2+ adsorption. In the co-sorption system, PAEs and Cd2+ demonstrated distinct interaction behaviors. Due to its smaller molecular size and higher diffusion coefficient, Cd2+ readily bonded to surface sorption sites on biochar and infiltrated its pores. Although PAE-ion complexes enhanced the sorption of pollutants by biochar, PAE molecules, and cluster structures primarily accumulated on the biochar surface, interacting with heavy metals through electrostatic forces. This interaction reduced the contribution of pore filling to pollutant sorption and weakened the desorption hysteresis capacity of biochar. The intraparticle diffusion model had similar results. Thus, a larger specific surface area and an abundant pore structure are crucial factors in improving the co-sorption capacity of biochar. This study offers novel insights into the sorption behavior of PAEs and Cd2+ on biochar within organicinorganic composite pollution.

关键词： Composite pollution Biochar Phthalate esters Cd2+ Molecular dynamics

来源：评论

学校读者我要写书评

暂无评论

Fenton technology optimization for polycyclic aromatic hydrocarbons degradation in soil

引用

APPLIED SOIL ECOLOGY 2025年 210卷

作者： Zhou, Luan Wang, Tongxin Song, Weijie Ling, Wanting chen, xuwen Nanjing Agr Univ Inst Organ Contaminant Control & Soil Remediat Coll Resources & Environm Sci Nanjing 210095 Peoples R China

An effective Fenton oxidation technology was developed to degrade PAHs in the soil, and fluorene (FLU), phenanthrene (PHE), fluoranthene (FLA) and pyrene (PYR) were selected as primary pollutants. This research presented a systematic approach to optimize the key operational parameters, such as reaction time, H2O2 concentration, Fe2+/H2O2 addition ratio, pH value, and soil-water ratio, those factors altogether affected the generation of center dot OH and the overall degradation efficiency of PAHs. The optimized parameter combination of Fenton technology suitable for PAHs degradation in complex soil environments was proposed. The key parameters were as follows: soil-water ratio was 2:1, pH was 3, H2O2 concentration was 11 % of the total system, Fe2+/H2O2 addition ratio was 1/8, and reaction time was 24 h. The degradation percentages for FLU, PHE, FLA and PYR were 75.4 %, 66.2 %, 60.8 % and 93.7 % in this optimized system, respectively. As the reaction time increased, the degradation efficiency of PAHs by Fenton technology reached the maximum until it became stable or slightly decreased. Appropriate H2O2 concentration and Fe2+/H2O2 addition ratio were conducive to the maximum generation of center dot OH, thus improving the degradation efficiency of PAHs. The pH value significantly influenced the degradation of PAHs, and the soil-water ratio had important effects on the Fenton oxidation process. By optimizing these conditions, a more thorough and profound assessment of the Fenton technology's applicability in treating actual-world PAHs-polluted soils was achievable, and it was expected to reduce the restoration cost. Meanwhile, it also contributed to the development of more efficient and sustainable soil remediation strategies.

关键词： Polycyclic aromatic hydrocarbons (PAHs) Fenton technology Fenton reagents concentration pH Soil-water ratio

来源：评论

学校读者我要写书评

暂无评论

Design and Stage Analysis of a Non-Invasive Monitoring System for Determining Formaldehyde Release From Wood-Based Panels by the Chamber Method

引用

IEEE ACCESS 2024年 12卷 137952-137969页

作者： Ye, Jinfei Lu, Yang Wang, Kuokuo Jiao, Qingchun chen, xuwen Wang, Lijun Zhejiang Jinhui Digital Technol Co Ltd Hangzhou 310015 Zhejiang Peoples R China Zhejiang Light Ind Prod Inspect & Res Inst Hangzhou 310018 Zhejiang Peoples R China Zhejiang Univ Sci & Technol Sch Automat & Elect Engn Hangzhou 310023 Peoples R China Zhejiang Inst Standardizat Zhijiang Standardizat T Hangzhou 310063 Zhejiang Peoples R China Technol Innovat Ctr State Market Regulat Managemen Hangzhou 310063 Zhejiang Peoples R China

With the extensive application of wood-based panels in the home decor industry, determining formaldehyde release form wood-based panels (FRWBP) is crucial for ensuring environmental air quality and human health. This article addresses the issues of insufficient monitoring of the testing stages for FRWBP and the difficulty in tracing the operation records of operator during determining FRWBP by the chamber method. It proposes a system for monitoring and analyzing the testing stages of FRWBP based on electrical monitoring. The system employs non-invasive sensing technology that does not interfere with normal testing process to collect real-time electrical usage data from the devices. The data is uploaded to an industrial computer for storage and processing. Statistical features of the electrical time series data are extracted using a sliding window approach and optimized with Principal Component Analysis (PCA). Subsequently, the binary tree support vector machine algorithm (BTSVM) optimized by k-means clustering algorithm is used to identify the detection states of the wood-based panels. Experimental results show that the system can achieve traceability of the formaldehyde detection stage records of artificial boards, and the designed algorithm model can also effectively identify the detection status of wood-based panels. The system and methods proposed in this paper have significant prospects for implementation in monitoring and traceability management within the testing industry.

关键词： Environmental monitoring Temperature measurement Support vector machines Sensor phenomena and characterization Noninvasive treatment Formaldehyde Principal component analysis Air quality FRWBP chamber method non-invasive PCA k-means BTSVM

来源：评论

学校读者我要写书评

暂无评论

Quantitative Derivation of the Euler-Poisson Equation from Quantum Many-Body Dynamics

引用

Peking Mathematical Journal 2024年第2期7卷 643-711页

作者： xuwen chen Shunlin Shen Zhifei Zhang Department of Mathematics University of RochesterRochesterNY 14627USA School of Mathematical Sciences Peking UniversityBeijing 100871China

We study the three dimensional quantum many-body dynamics with repulsive Coulomb interaction in the mean-field *** Euler-Poisson equation is its limit as the particle number tends to infinity and Planck’s constant tends to *** a new scheme combining the hierarchy method and the modulated energy method,we establish strong and quantitative microscopic to macroscopic convergence of mass and momentum densities as well as kinetic and potential energies before the 1st blow up time of the limiting Euler-Poisson equation.

关键词： Euler-Poissonequation BBGKY hierarchy Quantum many-body dynamics Modulated energy

来源：评论

学校读者我要写书评

暂无评论

Simulation and Optimization of Magnetoelastic Thin Shells

引用

ACM TRANSACTIONS ON GRAPHICS 2022年第4期41卷 p1-18页

作者： chen, xuwen Ni, Xingyu Zhu, Bo Wang, Bin chen, Baoquan Peking Univ CFCS Beijing Peoples R China Dartmouth Coll Hanover NH 03755 USA Beijing Inst Gen Artificial Intelligence Beijing Peoples R China Peking Univ Sch AI Beijing Peoples R China

Magnetoelastic thin shells exhibit great potential in realizing versatile functionalities through a broad range of combination of material stiffness, remnant magnetization intensity, and external magnetic stimuli. In this paper, we propose a novel computational method for forward simulation and inverse design of magnetoelastic thin shells. Our system consists of two key components of forward simulation and backward optimization. On the simulation side, we have developed a new continuum mechanics model based on the Kirchhoff-Love thin-shell model to characterize the behaviors of a megnetolelastic thin shell under external magnetic stimuli. Based on this model, we proposed an implicit numerical simulator facilitated by the magnetic energy Hessian to treat the elastic and magnetic stresses within a unified framework, which is versatile to incorporation with other thin shell models. On the optimization side, we have devised a new differentiable simulation framework equipped with an efficient adjoint formula to accommodate various PDE-constraint, inverse design problems of magnetoelastic thin-shell structures, in both static and dynamic settings. It also encompasses applications of magnetoelastic soft robots, functional Origami, artworks, and meta-material designs. We demonstrate the efficacy of our framework by designing and simulating a broad array of magnetoelastic thin-shell objects that manifest complicated interactions between magnetic fields, materials, and control policies.

关键词： magnetic simulation thin shell magnetoelastic coupling

来源：评论

学校读者我要写书评

暂无评论

The Derivation of the Compressible Euler Equation from Quantum Many-Body Dynamics

引用

Peking Mathematical Journal 2024年第1期7卷 35-90页

作者： xuwen chen Shunlin Shen Jiahao Wu Zhifei Zhang Department of Mathematics University of RochesterRochesterNY 14627USA School of Mathematical Sciences Peking UniversityBeijing 100871China

We study the three-dimensional many-particle quantum dynamics in mean-field *** forge together the hierarchy method and the modulated energy *** prove rigorously that the compressible Euler equation is the limit as the particle num-ber tends to infinity and the Planck’s constant tends to *** improve the previous sufficient small time hierarchy argument to any finite time via a new iteration scheme and Strichartz bounds first raised by Klainerman and Machedon in this *** establish strong and quantitative microscopic to macroscopic convergence of mass and momentum densities up to the 1st blow up time of the limiting Euler *** justify that the macroscopic pressure emerges from the space-time averages of micro-scopic interactions via the Strichartz-type *** have hence found a physical meaning for Strichartz-type bounds.

关键词： Compressible Euler equation BBGKY hierarchy Quantum many-body dynamics Klainerman-Machedon bounds Modulated energy

来源：评论

学校读者我要写书评

暂无评论

Compressed Ru skin on atomic-ordered hexagonal Ru-Ni enabling rapid Volmer-Tafel kinetics for efficient alkaline hydrogen evolution

引用

CHEMICAL ENGINEERING JOURNAL 2024年 487卷

作者： chen, xuwen Ye, Lifan Wu, Wei chen, Suhao Wang, Zichen Zhu, Yu Jiang, Haoran chen, Runzhe cheng, Niancai Fuzhou Univ Coll Mat Sci & Engn Fuzhou 350108 Peoples R China

Ru-based materials are promising electrocatalysts for hydrogen evolution reaction (HER) owing to their low-cost (one twenty-fifth of Pt) and similar Gibbs free energy of H* adsorption (AGH*) to that of Pt. However, the inadequate ability for the water dissociation of Ru catalysts is significantly impeding the water splitting efficiency. In this work, we demonstrate an atomically ordered hexagonal Ru-Ni alloy with compressive-strained Ru skin as a high-performance HER catalyst for significantly boosting the water dissociation. The Ordered Ru-Ni achieves an optimized catalytic activity for alkaline HER with a low overpotential of 23 mV at 10 mA cm-2, Tafel slope of 25.9 mV dec-1 and superior mass activity of 4.83 A mg-Ru1, which is 15.1 times higher than Ru/C. According to DFT calculations, the ordered RuNi core imposes homogeneous compressive strain on the Ru skin, resulting in an optimum binding energy towards H*/OH* intermediates on Ru active sites for rapid Tafel step kinetics. Moreover, the decreased H2O dissociation energy barrier of Ordered Ru-Ni suggests a promoted VolmerTafel kinetics is achieved, significantly boosting the overall HER efficiency. This work provides a practical avenue for surface strain engineering of Ru-based catalysts to promote the HER activity.

关键词： Compressive strain Ru shell Ru-Ni alloy Hydrogen evolution reaction Water dissociation

来源：评论

学校读者我要写书评

暂无评论

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案：

请选择收藏分类：

通借通还

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：