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Search Results: 1 - 10 of 496240 matches for " br>刘志祥 "
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地铁隧道附属广告设施的活塞风作用时变特性
Time Variant Characteristics of Piston Wind for Billboards Affiliated with Subway Tunnels

祝福,, 曹瑞洲, <br>ZHU Fu, YU Zhixiang, CAO Ruizhou, LIU Zhixiang
- , 2018, DOI: 10.3969/j.issn.0258-2724.2018.05.023
Abstract: 为了预测地铁隧道内由活塞风效应引起的广告牌表面风荷载的时变特性,采用计算流体动力学(computational fluid dynamics,CFD)开展了活塞风三维非稳态流动模拟.基于用户自定义函数(user-defined functions,UDF)定义了列车运行控制与动网格控制程序,搭建了精度更高的活塞风模拟方法,并结合以往的实验与仿真,验证了方法的合理性.在此基础上根据实际隧道断面建立了全尺寸动网格模型,考虑了不同运行速度下由列车运动引起的流场变化,重点关注地铁隧道内不同位置广告牌表面的静压变化.研究结果表明,列车经过广告牌时表面静压由正变负,速度增加时会导致广告牌表面的静压显著增大,对于80 km/h的工况静压幅值能超过500 Pa;对于部分以120 km/h运行的地铁,静压幅值超过1 kPa.
:In order to predict the time-variant characteristics of a piston wind for billboards in subway tunnels,a simulation based on computational fluid dynamics was employed to solve the three-dimensional unsteady flow problem. User-defined functions were used to define the movement manipulating the train and the dynamic mesh,thereby leading to the establishment of a more accurate simulation method for the piston wind. The rationality of the method was verified according to previously conducted experiments and simulations by Kim. A full-scale tunnel model was then set up based on a real tunnel cross-section. Different train speeds were taken into account to analyse the flow field changes caused by train movements,thus focusing on the changes of the static pressure on the billboard surfaces in subway tunnels. The results show that speed increases cause the static pressure on the billboards to increase significantly,thus changing from positive to negative when the train passes by. The static pressure amplitudes exceed 500 Pa for train speeds of 80 km/h and 1 kPa for some subways at an operating speed of 120 km/h
The Eigenvalue Problems of Biharmonic Equations
双调和方程特征值问题

Liu Xiangqing,Huang Yisheng,Deng Zhiying,<br>,黄毅生,
数学物理学报(A辑) , 2009,
Abstract: 该文讨论Navier边值条件下的双调和特征值问题{△2u=a(x)u+f(x,u), x∈Ω,解的存在性,其中Q C RN(N≥5)是有界光滑区域,△2为双调和算子,权函数a(x)>0a.e.于Ω,且a(x)∈Lr(Ω)(r≥N/4).应用变分方法,得出了在f(x,u)=0的情况下方程的第二特征值,并研究了它的结构.同时在f(x,u)满足一定的条件下,得出了共振与非共振情形下方程非零解的存在性.
Progress of biogas technology and engineering
生物燃气技术及工程的发展现状

Xiaofeng Liu,Yuexiang Yuan,Zhiying Yan,<br>晓风,袁月,
生物工程学报 , 2010,
Abstract: Dwindling supplies of conventional energy sources and the demand to increase the share of renewable energy for sustainability have increased the significance of biogas, the product of synergistic fermentation of biodegrable organic wastes from municipal, agricultural and industrial activities by microbial populations under anaerobic conditions. With extensive research and engineering practice, many technologies and modes have been developed for biogas production and application. Currently, the most widely used mode is the complete-mixing mesophilic fermentation. Europe, especially Germany, is leading the world in the combined heat and power production (CHP) from biogas. In this paper, updated progress in biogas technologies is reviewed, with focuses on anaerobic microorganisms, bioreactor configurations and process development, biogas production and applications, in which perspectives of biogas as a clean and renewable energy are projected.
STUDY ON FRACTAL GRADATION OF TAILINGS AND KNOWLEDGE BANK OF ITS CEMENTING STRENGTH
尾砂分形级配与胶结强度的知识库研究

LIU Zhi-xiang,LI Xi-bing,<br>,李夕兵
岩石力学与工程学报 , 2005,
Abstract: Characteristics of tailings gradation are studied by using fractal theory. Experimental data about the fractal gradations of tailings material and their cementing strength from a lot of mines are analyzed. Neural network is used to establish the model of knowledge bank which embodies the relations between strengths of cemented tailings and content of cement,consistence,fractal dimension of porosity and correlation coefficient of fractal dimension. Combining grading method with chaotic optimization,the neural network model achieves rapid training and avoids local minimum when there are a lot of samples to be trained. Research results show that the strengths of cemented tailings increase with the decrease of fractal dimension of porosity and with the increase of the correlation coefficients of fractal dimension. Because fractal dimension of porosity and its correlation coefficient embody the global distribution information of tailing granule,they can be used as a standard of rationality of gradation. According to gradation of tailings,the knowledge bank model can predict the strengths of cemented tailings in different contents of cement or consistence,and guide filling design in mine.
RESEARCH ON CHAOS AND INTELLIGENT IDENTIFICATION OF ACOUSTIC EMISSION IN ROCK MASS
岩体声发射混沌与智能辨识研究

LI Xi-bing,LIU Zhi-xiang,<br>李夕兵,
岩石力学与工程学报 , 2005,
Abstract: Acoustic emission(AE) in rock specimen was tested under loading and breakage,and AE in rock engineering was surveyed. Action laws of AE in rock mass were researched with chaotic kinetics,and chaotic attractors of AE in different stages were calculated during deformation and breakage in rock engineering. By coupling chaos with neural network,a prediction model of AE was established. According to characteristics of AE in different stages,an intelligent identification model for analyzing stability in rock engineering was created. Research results show that there are four different stages in AE activities,i. e.,stable period,earlier active period, intensely active period,and reversal period. Breakage occurs in the reversal period with abnormal AE and diminishing value of chaotic attractor. In-situ case verifies that chaotic kinetics can reflect the characteristics of and the intelligent identification model proposed in this paper is able to predict and analyze stability in rock engineering,especially in deep mining.
PLASTIC LIMIT ANALYSIS OF DUCTILE COMPOSITES BASED ON HOMOGENIZATION THEORY
基于均匀化理论韧性复合材料塑性极限分析

Li Huaxiang Liu Yinghua Feng Xiqiao Cen Zhangzhi,<br>李华,应华,冯西桥,岑章
力学学报 , 2002,
Abstract: This paper is to determine the bearing capacities of ductile composites by means of the homogenization theory of micromechanics and the plastic limit analysis. To reflect the microstructures of a composite, a representative volume element (RVE) is first selected. According to the homogenization theory, the overall fields are decomposed into macroscopic average and microscopic fluctuation terms, which can reflect the relation between macroscopic and microscopic scales. Then, by introducing the homogenization theory into the plastic limit analysis, a strategy for the direct computation of the limit load of a microstructure RVE is put forward. For such ductile composites as metal matrix composites (MMC), the constitutions is assumed as rigid-perfectly plastic solids and obey the von Mises yield criterion. By means of the kinematic limit approach and finite element method, the numerical modeling of the plastic limit analysis of a composite is formulated as a nonlinear mathematical programming with equality-constraint conditions, which can be solved by a direct iterative algorithm developed. Numerical examples show the validity of the method and the high effectivity of the algorithm. It can be concluded from numerical results that the macroscopic strength of a composite is mainly determined by weak constitutions in the plane model and that the reinforced effects of fibers are most intensive in the off-axis direction. The method presents an effective tool for the strength analysis of ductile composites.
Spray of Emulsion Suppressant for Controlling Dust in the Roadway of the Shangrdong Aluminium Mine
BS-Ⅰ型乳液抑尘剂防治矿山运输路面扬尘

Ren Xiaohua,<br>任晓华,殷秀文,,崔云山,焕勇,王家进
环境科学 , 1992,
Abstract: Spray with a dosage of 0.8-2.0 kg/m2 of the emulsified suppressant prepared from 2.0-5.0% pretreated heavy oil, water and 0.05% emulphor could make the concentration of dust in the atmosphere above the roadway of the Shandong Aluminium Mine reduced from 9.6-33.3 mg/m3 to lower than 10 mg/m3 (average 4.3-5.8 mg/m3) within 15 day. Futher exploration found that the excellent dust suppressing effect resulted from the physicochemical characters of the emulsion.
燃料电池机车热管理系统建模和动态分析
Modeling and Dynamic Analysis of Thermal Management System for Fuel Cell Locomotive

郭爱, 陈维荣, , 李奇<br>GUO Ai, CHEN Weirong, LIU Zhixiang, LI Qi
- , 2015,
Abstract: 摘要: 为了提高燃料电池机车的工作效率和动态性能,根据燃料电池机车热管理工作原理,利用物质守恒定律、热力学第一定理和相似原理,建立了包含散热器风机和冷却液循环泵的面向控制模型,研究了旁路阀门开度、冷却液循环泵电压和散热器风机电压对电堆温度、温度差以及系统效率的影响.研究结果表明:旁路阀可以局部调节电堆温度、温度差以及系统调节时间,但几乎不影响稳态效率;循环泵可以调节电堆的温度差,在保证温度差条件下,循环泵电压越小系统效率越高;散热器风机可以调节电堆温度和响应时间,电压越小系统效率越高.
Abstract: To improve the efficiency and dynamic performance of fuel cell locomotives, a control-oriented thermal management model with a fan in the radiator and a coolant circulation pump was built by the law of mass conservation, the first law of thermodynamics, and the affinity law. Based on this model, the influences of the control parameters including the bypass ratio, the coolant circulation pump voltage, and the radiator fan voltage on the stack temperature, temperature difference, and system efficiency were studied. The results showed that, the bypass valve would influence the stack temperature and its temperature difference partially, and change the response time of the thermal system, but almost has no effect on the system efficiency; the circulation pump was able to adjust the temperature difference between the inlet and outlet of the stack to make it to be a proper value; with the same temperature difference, the system efficiency will be higher with lower circulation pump voltage; the radiator fan could not only adjust the stack temperature and the response time of thermal system, but also influence the temperature difference and system efficiency
掺杂tio_2纳米线及其可见光催化性能

武汉理工大学学报 , 2007,
Abstract: ?采用二次阳极氧化工艺制备了高度有序的多孔氧化铝模板,通过模板法与溶胶-电泳沉积法结合的组装技术,合成了具有高比表面积的糖葫芦状m/tio2(m=fe3+,zn2+,cu2+,cr3+)纳米线数组体系。采用sem对样品进行了表征,sem测试结果表明m/tio2纳米线数组保持了模板的有序性,直径分布均匀一致,为70nm左右,长为15μm左右,取向性很好。以甲基橙为目标降解物,在可见光下考察该金属离子掺杂纳米线的催化活性,确定了每种离子的最佳掺杂量。结果显示此掺杂纳米线数组体系具有非常优良的可见光催化性能,这也使得在可见光下纳米线具有更大的应用前景和优势。m/tio2薄膜的紫外-可见吸收光谱测试结果显示氧化钛的吸收带边红移至了可见光区,并通过相关公式进行了禁带宽度的估算。结合对不同离子掺杂纳米线的可见光催化活性的比较,从不同角度对于过渡金属离子掺杂改性的机理进行了初步探讨。
Quark phase transition in supernova and the effect of quark mass on the process
超新星核中的夸克相变及夸克质量效应

Lai Xiang-Jun,Luo Zhi-Quan,Liu Jing-Jing,Liu Hong-Lin,<br>赖,,晶晶,宏林
物理学报 , 2008,
Abstract: Based on constituent quark mass and current quark mass model, the phase transition of two-flavor quark matter to more stable three-flavor quark matter in the core of supernova is studied. It is shown that the timescale of the process is shorter than 10-8 seconds for both cases, and the smaller the quark mass (current quark mass), the quicker the process; and the equilibrium parameters, except the temperature, such as s-quark abundance, neutrino abundance and total neutrino energy in supernova core, have a slight increase compared to the former result after the conversion according to constituent quark mass model. But the values of those parameters (including temperature) increase significantly based on current quark mass model. The current quark mass will be more favorable for the success of the delayed neutrino-heating mechanism for the explosion.
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