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Existence of viscosity solutions for ~Iessian equations in exterior domains

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Frontiers of Mathematics in China 2014年第1期9卷 201-211页

作者： Boping tian Yongqiang fu Department of Mathematics Harbin Institute of Technology Harbin 150001 China

The Perron method is used to establish the existence of viscosity solutions to the exterior Dirichlet problems for a class of Hessian type equations with prescribed behavior at infinity.

关键词： Hessian equation viscosity solution exterior domain

Stochastic response analysis of damaged elastic beams

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Science China(Technological Sciences) 2012年第6期55卷 1618-1623页

作者： tian YanPing fu YiMing School of Mechanical Engineering Hangzhou Dianzi UniversityHangzhou 310018China College of Mechanical and Vehicle Engineering Hunan UniversityChangsha 410082China

Great progress has been made in study on dynamic behavior of the damaged structures subject to deterministic *** stochastic response analysis of the damaged structures,however,has not yet attracted people's *** the damaged elastic beams for example,the analysis procedure for stochastic response of the damaged structures subject to stochastic excitations is investigated in this ***,the damage constitutive relations and the corresponding damage evolution equation of one-dimensional elastic structures are briefly ***,the stochastic dynamic equation with respect to transverse displacement of the damaged elastic beams is *** finite difference method and Newmark method are adopted to solve the stochastic partially-differential equation and corresponding boundary *** stochastic response characteristic,damage evolution law,the effect of noise intensity on damage evolution and the first-passage time of damage are discussed in *** present work extends the research field of damaged structures,and the proposed procedure can be generalized to analyze the dynamic behavior of more complex structures,such as damaged plates and shells.

关键词： damaged elastic beams stochastic response Gaussian white noise first-passage time of damage finite differencemethod

Complex Behavior in a Selective Aging Neuron Model Based on Small World Networks

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Communications in Theoretical Physics 2008年第2期49卷 409-413页

作者： ZHANG gui-Qing CHEN tian-Lun Department of Physics Nankai University Tianjin 300071 China

Complex behavior in a selective aging simple neuron model based on small world networks is investigated. The basic elements of the model are endowed with the main features of a neuron function. The structure of the selective aging neuron model is discussed. We also give some properties of the new network and find that the neuron model displays a power-law behavior. If the brain network is small world-like network, the mean avalanche size is almost the same unless the aging parameter is big enough.

关键词： selective aging self-organized criticality small world networks finite-size-scaling analysis power-law

一株同步硝化反硝化菌株的筛选及其生物电化学脱氮性能研究

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南京农业大学学报 2025年第1期48卷 133-143页

作者：田瑞瑞付欢郑云黄新琦周俊雍晓雨南京工业大学生物与制药工程学院江苏南京211816 南京师范大学地理科学学院江苏南京210023

[目的]本文旨在获得具有高效脱氮性能的异养硝化-好氧反硝化(heterotrophic nitrification-aerobic denitrification,HN-AD)功能菌株,构建生物电化学-同步硝化反硝化(bio-electrochemical systems-simultaneous nitrification and denitrification,BES-SND)耦合系统,实现脱氮效率的提升。[方法]从活性污泥中筛选HN-AD菌株,鉴定后通过摇瓶试验分析其脱氮性能。然后进一步研究碳源、C/N、溶解氧等外界因素对菌株同步硝化反硝化性能的影响。将菌株接种到微生物燃料电池(microbial fuel cells,MFC)的生物阴极,分析低C/N条件下BES-SND体系的脱氮性能。[结果]从活性污泥中筛选出一株具有同步硝化反硝化性能的HN-AD菌株,命名为Alcaligenes aquatilis N3。确定该菌株发生SND反应的最适碳源为乙酸钠、C/N值为20、溶解氧为3.70 mg·L^(-1)。在BES-SND脱氮体系中,C/N值分别为2、4、6、8时,菌株*** N3的总氮去除率分别为20.51%、26.67%、37.76%和48.50%。在C/N=2的试验条件下,BES-SND系统的总氮去除速率在第5天仍为1.79 mg·L^(-1)·d^(-1)。[结论]在低碳环境下,*** N3菌株依然可以在BES-SND耦合脱氮体系中实现脱氮,降低了脱氮过程对碳源的依赖性,具有一定的实际环境应用潜力。

关键词：同步硝化反硝化异养硝化-好氧反硝化生物电化学低C/N值微生物燃料电池

Numerical investigation of Richtmyer-Meshkov instability driven by cylindrical shocks

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Acta Mechanica Sinica 2006年第1期22卷 9-16页

作者： Baolin tian Dexun fu Yanwen Ma LNM Institute of Mechanics Chinese Academy of SciencesBeijing 100080 China Institute of Applied Physics and Computational Mathematics Beijing 100088 China

In this paper, a numerical method with high order accuracy and high resolution was developed to simulate the Richtmyer-Meshkov（RM） instability driven by cylindrical shock waves. Compressible Euler equations in cylindrical coordinate were adopted for the cylindrical geometry and a third order accurate group control scheme was adopted to discretize the equations. Moreover, an adaptive grid technique was developed to refine the grid near the moving interface to improve the resolution of numerical solutions. The results of simulation exhibited the evolution process of RM instability, and the effect of Atwood number was studied. The larger the absolute value of Atwood number, the larger the perturbation amplitude. The nonlinear effect manifests more evidently in cylindrical geometry. The shock reflected from the pole center accelerates the interface for the second time, considerably complicating the interface evolution process, and such phenomena of reshock and secondary shock were studied.

关键词： Richtmyer-Meshkov instability Atwoodnumber cylindrical shock

Weak Signal Frequency Detection Based on a Fractional-Order Bistable System

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Chinese Physics Letters 2012年第6期29卷 13-16页

作者： HE gui-tian LUO Mao-Kang Department of Mathematics Sichuan UniversityChengdu 610064

We apply spectral power amplification to quantifying and investigating the phenomenon of stochastic resonance in fractional-order ***,the frequency of the weak mixed signal is detected by a stochastic resonance mechanism together with a power *** corresponding numerical results demonstrate the effectiveness of the proposed methods.

关键词： spectrum methods stochastic

Wind tunnel simulation of wind loading on a solid structure of revolution

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Acta Mechanica Sinica 2010年第4期26卷 551-558页

作者： Le-tian Yang Zhi-fu Gu State Key Laboratory of Turbulence and Complex Systems and College of Engineering Peking University 100871 Beijing China

The wind tunnel simulations of wind loading on a solid structure of revolution with one smooth and five rough surfaces were conducted using wind tunnel tests. Timemean and fluctuating pressure distributions on the surface were obtained, and the relationships between the roughness Reynolds number and pressure distributions were analyzed and discussed. The results show that increasing the surface roughness can significantly affect the pressure distribution, and the roughness Reynolds numbers play an important role in the change of flow patterns. The three flow patterns of subcritical, critical and supercritical flows can be classified based on the changing patterns of both the mean and the fluctuating pressure distributions. The present study suggests that the wind tunnel results obtained in the supercritical pattern reflect more closely those of full-scale solid structure of revolution at the designed wind speed.

关键词： Wind tunnel simulation Roughness Reynolds number Pressure distribution Solid structure of revolution

The law of strength damage and deterioration of jointed sandstone after dry-wet cycles

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Journal of Mountain Science 2023年第4期20卷 1170-1182页

作者： WANG gui-lin ZHANG tian-yu ZHANG Liang School of Civil Engineering Chongqing UniversityChongqing400045China National and Local Joint Engineering Research Center for Environmental Geological Hazard Prevention and Control in the Reservoir Area Chongqing400045China School of Architecture and Civil Engineering Xi’an University of Science and TechnologyXi’an710054China

Under the periodic rise and fall of the water level in the Three Gorges Reservoir in China,the rock mass in the ebb and flow zone of the slope is always in a state of a dry-wet *** order to explore the influence of dry-wet cycle on mechanical properties of jointed sandstone,the triaxial and uniaxial compression tests of dry-wet cycle of jointed sandstone were carried *** the experiment,four groups of samples with different numbers of joints were set up,and the jointed rock samples were subjected to 20 dry-wet *** both the triaxial compression test and the Mohr-Coulomb(M-C)rock fracture criterion,the strength envelope of the sandstone samples was fitted,and their strength degradation was further analyzed and *** results show that:(1)The peak intensity and elastic modulus of the sandstone samples decrease with increased number of dry-wet cycles.(2)The total deterioration of mechanical properties of intact rock samples is bigger than that of jointed sandstone samples as the number of dry-wet cycles increases.(3)With the increase of confining pressure,the peak intensity of intact sandstone samples increases much more than that of jointed sandstone samples,which indicates that joints and their numbers have obvious influence.(4)Joints and their numbers play an important role in guiding the damage effects of sandstone samples,which weaken the damage caused by dry-wet ***,the envelope of the M-C strength criterion of intact sandstone samples moves more than that of jointed sandstone samples.

关键词： Jointed sandstone Dry-wet cycle Triaxial compression Strength damage Deterioration mechanism

Preparation of Self-limiting Heating Cables with Excellent Processability, Mechanical Properties and PTC Effect via Thermal and Electrical Treatments

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Chinese Journal of Polymer Science 2024年第4期42卷 511-520页

作者： tian-Hao Yang Tong Wu Qiang fu State Key Laboratory of Polymer Materials Engineering College of Polymer Science and EngineeringSichuan UniversityChengdu610065China State Key Laboratory of Polymer Materials Engineering Polymer Research Institute of Sichuan UniversityChengdu610065China

Polymer/conductive filler composites have been widely used for the preparation of self-limiting heating cables with the positive temperature coefficient (PTC) effect. The control of conductive filler distribution and network in polymer matrix is the most critical for performance of PTC materials. In order to compensate for the destruction of the filler network structure caused by strong shearing during processing, an excessive conductive filler content is usually added into the polymer matrix, which in turn sacrifices its processability and mechanical properties. In this work, a facile post-treatment of the as-extruded cable, including thermal and electrical treatment to produce high-density polyethylene (HDPE)/carbon black (CB) cable with excellent PTC effect, is developed. It is found for the as-extruded sample, the strong shearing makes the CB particles disperse uniformly in HDPE matrix, and 25 wt% CB is needed for the formation of conductive paths. For the thermal-treated sample, a gradually aggregated CB filler structure is observed, which leads to the improvement of PTC effect and the notable reduction of CB content to 20 wt%. It is very interesting to see that for the sample with combined thermal and electrical treatment, CB particles are agglomerated and oriented along the electric field direction to create substantial conductive paths, which leads to a further decrease of CB content down to 15 wt%. In this way, self-limiting heating cables with excellent processability, mechanical properties and PTC effect have simultaneously been achieved.

关键词： Self-limiting heating cables Positive temperature coefficient Thermal treatment Electrical treatment