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Saline Water Irrigation Scheduling Through a Crop-Water-Salinity Production Function and a Soil-Water-Salinity Dynamic Model 被引量:16
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作者 WANG Yang-Ren KANG Shao-Zhong +2 位作者 LI Fu-Sheng ZHANG Lu ZHANG Jian-Hua 《Pedosphere》 SCIE CAS CSCD 2007年第3期303-317,共15页
Using a crop-water-salinity production function and a soil-water-salinity dynamic model, optimal irrigation scheduling was developed to maximize net return per irrigated area. Plot and field experiments were used to o... Using a crop-water-salinity production function and a soil-water-salinity dynamic model, optimal irrigation scheduling was developed to maximize net return per irrigated area. Plot and field experiments were used to obtain the crop water sensitivity index, the salinity sensitivity index, and other parameters. Using data collected during 35 years to calculate the 10-day mean precipitation and evaporation, the variation in soil salinity concentrations and in the yields of winter wheat and cotton were simulated for 49 irrigation scheduling that were combined from 7 irrigation schemes over 3 irrigation dates and 7 salinity concentrations of saline irrigation water (fresh water and 6 levels of saline water). Comparison of predicted results with irrigation data obtained from a large area of the field showed that the model was valid and reliable. Based on the analysis of the investment cost of the irrigation that employed deep tube wells or shallow tube wells, a saline water irrigation schedule and a corresponding strategy for groundwater development and utilization were proposed. For wheat or cotton, if the salinity concentration was higher than 7.0 g L-1 in groundwater, irrigation was needed with only fresh water; if about 5.0 g L-1, irrigation was required twice with fresh water and once with saline water; and if not higher than 3.0 g L-1, irrigation could be solely with saline water. 展开更多
关键词 crop-water-salinity production function irrigation scheduling saline water irrigation water-salinity dy- namic model
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DECAY ESTIMATES FOR ISENTROPIC COMPRESSIBLE MAGNETOHYDRODYNAMIC EQUATIONS IN BOUNDED DOMAIN 被引量:4
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作者 Mohamed Ahmed Abdallah 江飞 谭忠 《Acta Mathematica Scientia》 SCIE CSCD 2012年第6期2211-2220,共10页
In this paper, under the hypothesis that y is upper bounded, we construct a Lyapunov functional for the multidimensional isentropic compressible magnetohydrodynamic equations and show that the weak solutions decay exp... In this paper, under the hypothesis that y is upper bounded, we construct a Lyapunov functional for the multidimensional isentropic compressible magnetohydrodynamic equations and show that the weak solutions decay exponentially to the equilibrium state in L2 norm. Our result verifies that the method of Daoyuan Fang, Ruizhao Zi and Ting Zhang I1] can be adapted to magnetohydrodynamic equations. 展开更多
关键词 Navier-Stokes equations weak solution decay estimates magnetohydrody-namic
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Thermodynamic assessment of Ni-Ta-C ternary system
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作者 崔予文 金展鹏 《中国有色金属学会会刊:英文版》 EI CSCD 1999年第4期757-763,共7页
By means of the CALPHAD technique, an ideal calculation, i. e. without ternary interaction parameter, was applied to assess the Ni-Ta-C ternary system. The calculated and experimental data were in reasonable agreement... By means of the CALPHAD technique, an ideal calculation, i. e. without ternary interaction parameter, was applied to assess the Ni-Ta-C ternary system. The calculated and experimental data were in reasonable agreements. It proved the CALPHAD technique of a Powerful approach of the extrapolation, as well as the good feasibility of the thermodynamic descriptions of three binary systems, Ni-C, Ni-Ta and Ta-C. 展开更多
关键词 nickel-tantalum-carbon systems PHASE DIAGRAMS thermody namics
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THE MODAL SYNTHESIS IN THE ANALYSISOF ROBOT KINETO-ELASTODYNAMICS
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作者 姜剑虹 《Journal of Southeast University(English Edition)》 EI CAS 1994年第1期34-40,共7页
THEMODALSYNTHESISINTHEANALYSISOFROBOTKINETO-ELASTODYNAMICSJiangJianhons(姜剑虹)(NanjingEngineeringInstituteofEn... THEMODALSYNTHESISINTHEANALYSISOFROBOTKINETO-ELASTODYNAMICSJiangJianhons(姜剑虹)(NanjingEngineeringInstituteofEngineeringCorps)TH... 展开更多
关键词 ROBOT FINITE ELEMENT MODAL SYNTHESIS method/Kineto-elastody-namics
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Secure Multi-keyword Search Supporting Dynamic Update and Ranked Retrieval
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作者 Jingbo Yan Yuqing Zhang Xuefeng Liu 《China Communications》 SCIE CSCD 2016年第10期209-221,共13页
As cloud computing is becoming prevalent, data owners are motivated to delegate complex data managements to the commercial cloud for economic savings. Sensitive data is usually encrypted before being uploaded to the c... As cloud computing is becoming prevalent, data owners are motivated to delegate complex data managements to the commercial cloud for economic savings. Sensitive data is usually encrypted before being uploaded to the cloud, which unfortunately makes the frequently-used search function a challenging problem. In this paper, we present a new multi-keyword dynamic search scheme with result ranking to make search over encrypted data more secure and practical. In the scheme, we employ a powerful function-hiding inner product encryption to enhance the security by preventing the leakage of search pattern. For the concern of efficiency, we adopt a tree-based index structure to facilitate the searching process and updating operations. A comprehensive security analysis is provided and experiments over the real world data show that our scheme is efficient. 展开更多
关键词 secure search ranked search dynamic update cloud computing
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Modal Analysis and Structural Dynamic Modification of Hollow Spindle
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作者 吴文英 吴强 +1 位作者 叶国铭 蔡旭初 《Journal of China Textile University(English Edition)》 EI CAS 1999年第3期93-95,共3页
Dynamic parameters of hollow spindle are identified and sensitivities to mass and stiffness are calculated by using modal analysis based on CRAS system. A method of adjusting resonance frequency is also presented. All... Dynamic parameters of hollow spindle are identified and sensitivities to mass and stiffness are calculated by using modal analysis based on CRAS system. A method of adjusting resonance frequency is also presented. All of the work is useful for optimizing design hollow spindle. 展开更多
关键词 HOLLOW SPINDLE MODAL analysis STRUCTURAL dy-namic MODIFICATION
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Apoptosis Induced by Photodynamic Therapy with Benzoporphyrin Derivative Monoacid Ring A and Exploration of its Potential Mechanism in Bladder Cancer Cells
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作者 Chuanshan Xu Shiming Wu +3 位作者 Zhigang Wang Lehua Yu Qing Yang Xiabo Zeng 《Chinese Journal of Clinical Oncology》 CSCD 2005年第6期837-841,共5页
OBJECTIVE To investigate apoptosis induced by photodynamic therapy with benzoporphyrin derivative monoacid ring A (BPD-MA) and explore its potential mechanism in human bladder cancer cells. METHODS Photosensitizatio... OBJECTIVE To investigate apoptosis induced by photodynamic therapy with benzoporphyrin derivative monoacid ring A (BPD-MA) and explore its potential mechanism in human bladder cancer cells. METHODS Photosensitization of BPD-MA was activated with a red light Laser (632.8nm) delivered at 10 mW/cm^2 to give a total dose of 2.4 J/cm^2. Cellular apoptosis was measured with flow cytometry analysis and an insitu terminal deoxyuridine nick end-labeling (TUNEL) assay. Changes in mitochondrial membrane potential (△φm) were monitored by a flow cy-tometric method with Rhodamine 123 staining and the expression of bcl- 2 in BIU-87 cells was detected with immunocytochemical staining. RESULTS At 8 h following photodynamic treatment, the degree of apoptosis was significantly increased when analyzed with flow cytometry and TUNEL assay. Treatment of the BIU-87 cells by PDT with BPD-MA resulted in the collapse of the △φm and a decrease of bcl-2 expression. CONCLUSION BPD-MA-mediated PDT can effectively induce apoptosis in BIU-87 cells. The mechanism probably is through a mitochondrial-initiated pathway. 展开更多
关键词 photoch/namic therapy BPD-MA human bladder cancer cell APOPTOSIS mitochondrial membrane potential bcl-2.
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System modeling and dynamic analysis of ISG hybrid power shafting
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作者 周久焱 孙逢春 +1 位作者 程夕明 王志福 《Journal of Beijing Institute of Technology》 EI CAS 2013年第2期163-170,共8页
A system model is established to analyze the dynamic performance of an integrated starter and generator (ISG) hybrid power shafting. The model couples the electromechanical coupling shaft dynamics, the bearing hydro... A system model is established to analyze the dynamic performance of an integrated starter and generator (ISG) hybrid power shafting. The model couples the electromechanical coupling shaft dynamics, the bearing hydrodynamic lubrication and the engine block stiffness. The model is com- pared with the model based on ADAMS or the model neglecting the bearing hydrodynamics. The bearing eccentricity and the oil film pressure have been calculated under different hybrid conditions or at the different motor power levels. It' s found that the bearing hydrodynamics decreases the cal- culation results of the bearing peak load. Changes of the hybrid conditions or the motor power have no significant effect on the main bearing, but have impact on the motor bearing. A hybrid power sys- tem composed of a 1.6 L engine and a 45 kW ISG motor can operate safely. 展开更多
关键词 system modeling integrated starter and generator (ISG) hybrid power system dy-namic analysis
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Dynamics of an ensemble of clumps embedded in a magnetized ADAF
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作者 Fazeleh Khajenabi Mina Rahmani 《Research in Astronomy and Astrophysics》 SCIE CAS CSCD 2015年第12期2187-2192,共6页
We investigate the effects of a global magnetic field on the dynamics of an ensemble of clumps within a magnetized advection-dominated accretion flow by ignoring interactions between the clumps and then solving the co... We investigate the effects of a global magnetic field on the dynamics of an ensemble of clumps within a magnetized advection-dominated accretion flow by ignoring interactions between the clumps and then solving the collisionless Boltzman equation. In the strong-coupling limit, in which the averaged radial and rotational velocities of the clumps follow dynamics described by an Advection-Dominated Accretion Flow (ADAF), the root mean square radial velocity of the clumps is cal- culated analytically for different magnetic field configurations. The value of the root mean square radial velocity of the clumps increases by increasing the strength of the radial or vertical components of the magnetic field, but a purely toroidal magnetic field geometry leads to a reduction in the value of the root mean square radial velocity of the clumps in the inner parts by increasing the strength of this component. Moreover, dynamics of the clumps strongly depend on the amount of advected energy so that the value of the root mean square radial velocity of the clumps increases in the presence of a global magnetic field as the flow becomes more advective. 展开更多
关键词 accretion -- accretion disk -- black hole physics -- magnetohydrody- namics
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Criterion of aerodynamic performance of large-scale offshore horizontal axis wind turbines
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作者 程兆雪 李仁年 +1 位作者 杨从新 胡文瑞 《Applied Mathematics and Mechanics(English Edition)》 SCIE EI 2010年第1期13-20,共8页
With the background of offshore wind energy projects, this paper studies aerodynamic performance and geometric characteristics of large capacity wind turbine rotors (1 to 10 MW), and the main characteristic paramete... With the background of offshore wind energy projects, this paper studies aerodynamic performance and geometric characteristics of large capacity wind turbine rotors (1 to 10 MW), and the main characteristic parameters such as the rated wind speed, blade tip speed, and rotor solidity. We show that the essential criterion of a high- performance wind turbine is a highest possible annual usable energy pattern factor and a smallest possible dimension, capturing the maximum wind energy and producing the maximum annual power. The influence of the above-mentioned three parameters on the pattern factor and rotor geometry of wind turbine operated in China's offshore meteoro- logical environment is investigated. The variation patterns of aerodynamic and geometric parameters are obtained, analyzed, and compared with each other. The present method for aerodynamic analysis and its results can form a basis for evaluating aerodynamic performance of large-scale offshore wind turbine rotors. 展开更多
关键词 offshore wind energy project horizontal axis wind turbine rotor aerody-namic design annual usable energy pattern factor power coefficient wind turbine rotor wind turbine blade
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大跨度公铁双层斜拉桥主梁涡激共振机理与控制 被引量:1
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作者 刘志文 周威 +3 位作者 刘振标 严爱国 夏正春 陈政清 《湖南大学学报(自然科学版)》 EI CAS CSCD 北大核心 2024年第1期1-13,共13页
以拟建的某主跨808 m公铁双层斜拉桥为工程依托,采用节段模型风洞试验研究不同攻角下双层桁架梁断面的涡振性能及5种气动控制措施的抑振效果,结合计算流体动力学(CFD)静态绕流模拟,对比分析双层桁架梁断面的涡振机理及控制方法.研究表明... 以拟建的某主跨808 m公铁双层斜拉桥为工程依托,采用节段模型风洞试验研究不同攻角下双层桁架梁断面的涡振性能及5种气动控制措施的抑振效果,结合计算流体动力学(CFD)静态绕流模拟,对比分析双层桁架梁断面的涡振机理及控制方法.研究表明:主梁断面原设计方案在+3°和0°风攻角下存在明显的竖向和扭转涡振现象,且振幅超过规范允许值;间隔封闭上层桥面栏杆或增设抑流板可有效抑制主梁扭转涡振,但竖向涡振振幅仍不满足规范要求;上弦杆外侧增设风嘴可有效抑制主梁竖向和扭转涡振,而下弦杆外侧增设风嘴对主梁涡振抑振效果有限.气流经主梁原设计断面上层桥面分离后,在其上下表面形成周期性脱落的大尺度旋涡,并在上层桥面后部再附,这是主梁发生竖向涡振的主要诱因;上弦杆外侧增设风嘴可引导气流平稳通过上层桥面,消除了周期性的旋涡脱落,并在其上表面形成一段狭长“回流区”,从而有效抑制了涡振的发生. 展开更多
关键词 桥梁工程 涡激共振机理 风洞试验 双层桁架主梁 气动控制措施 计算流体动力学
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基于无差拍预测算法的双向隔离型AC-DC矩阵变换器高动态电流控制策略 被引量:1
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作者 梅杨 张家奇 《高电压技术》 EI CAS CSCD 北大核心 2024年第3期1090-1099,共10页
针对双向隔离型AC-DC矩阵变换器采用传统双闭环控制策略存在的控制参数多、整定困难等问题,提出了一种基于无差拍预测算法的高动态电流控制策略,通过引入无差拍预测算法对网侧电流进行控制,以减少控制器参数,消除数字控制时延。考虑到... 针对双向隔离型AC-DC矩阵变换器采用传统双闭环控制策略存在的控制参数多、整定困难等问题,提出了一种基于无差拍预测算法的高动态电流控制策略,通过引入无差拍预测算法对网侧电流进行控制,以减少控制器参数,消除数字控制时延。考虑到算法中电压电流检测量众多,故采用输入电压观测器以降低检测成本,减小采样误差的影响。变换器采用后级单重移相的调制方法来协调配合无差拍预测算法,其中参考输入电流指令与移相角为双射函数关系,简单易实现。仿真和实验结果表明:采用所提控制策略可以实现网侧电流正弦,功率因数接近于1;直流侧电压稳定,电流纹波率小于1%;直流电流在参考值突变时,跟踪快速且无超调、无振荡;同时,在变换器功率正向传输、反向传输以及正反向切换过程中,采用所提控制策略相比于传统的双闭环控制策略,电流动态调节时间分别缩短了69%、85%、67%。由此证明所提控制策略可以保证变换器良好的输入输出性能,并且相比于传统的双闭环控制策略在切换过程中动态性能得到显著提升。 展开更多
关键词 矩阵变换器 预测控制 控制器参数 无差拍预测算法 功率因数 动态性能
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中国省域文化产业与经济高质量发展的动态响应及协调效应研究
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作者 苏晓智 周克勤 《资源开发与市场》 CAS 2024年第8期1239-1249,共11页
在当前国家提出高质量发展的战略背景下,文化产业成为推动经济高质量发展的重要资源之一。以中国30个省区市为研究对象,采用熵权法测度2012—2021年中国省域文化产业与经济高质量发展水平,继而采用PVAR模型探讨了二者的互动响应关系,最... 在当前国家提出高质量发展的战略背景下,文化产业成为推动经济高质量发展的重要资源之一。以中国30个省区市为研究对象,采用熵权法测度2012—2021年中国省域文化产业与经济高质量发展水平,继而采用PVAR模型探讨了二者的互动响应关系,最后利用修正的耦合协调模型和马尔科夫链深入剖析了二者协同发展的时空演变特征。结果表明:①中国省域文化产业与经济高质量发展综合水平稳步上升,经济高质量发展整体水平高于文化产业,年均增长速度低于文化产业。中国省域文化产业与经济高质量发展均呈现较为显著的空间异质性,整体表现为“由西向东”梯度式递增的格局;②中国省域文化产业与经济高质量发展之间存在双向互动关系,短期内二者受自身发展的影响较大,长期来看彼此间的交互影响不断增强。前期文化产业与经济高质量发展主要依靠自身发展,后期经济高质量发展对文化产业的作用不断增强,文化产业对经济高质量发展的影响稳定在有限区间;③中国省域文化产业与经济高质量发展的总体耦合协调发展水平较低。耦合协调度在空间层面呈现出“东南高,西北低”的空间分异格局;④中国省域文化产业与经济高质量发展的耦合协调度维持原有状态的概率最大,存在“马太效应”和“俱乐部收敛”现象,难以实现跨越等级式的演化。 展开更多
关键词 文化产业 经济高质量发展 PVAR模型 耦合协调度 马尔科夫链 动态效应
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平面并联机器人离线PID控制优化研究
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作者 刘一扬 王春燕 《机械设计与制造》 北大核心 2024年第5期156-160,共5页
为了使平面并联机器人在闭环控制系统中具有更稳定的控制性能。对此,这里构建了平面五杆并联机器人动力学模型及其控制系统模型,给出了控制系统的增益矢量p。对机器人系统模型进行离线PID控制优化,通过控制增益来设计控制系统中的增益矢... 为了使平面并联机器人在闭环控制系统中具有更稳定的控制性能。对此,这里构建了平面五杆并联机器人动力学模型及其控制系统模型,给出了控制系统的增益矢量p。对机器人系统模型进行离线PID控制优化,通过控制增益来设计控制系统中的增益矢量p,从而实现非线性单目标动态优化(NLMODOP)。在NLMODOP中加入动态约束,采用带约束处理机制的差分进化(DE)算法求解平面并联机器人的非线性规划问题,进而处理不稳定的动态优化。对机器人模型中的五个连杆进行仿真实验,并对有无DE算法控制的仿真结果进行了比较。结果表明:相比于无DE算法,采用DE算法下的机器人系统模型的连杆跟踪位移基本无跟踪误差。说明基于差分进化算法的平面并联机器人离线PID控制优化具有较好的控制精度和跟踪性能。 展开更多
关键词 平面五杆并联机器人 离线PID控制优化 非线性单目标动态优化 差分进化算法
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HAN基ECSP凝胶模型的构建与分子动力学模拟 被引量:2
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作者 李门 李天鹏 +2 位作者 郭爱强 刘建国 高欣宝 《装备环境工程》 CAS 2024年第2期28-36,共9页
目的从微观分子的角度对硝酸羟胺(HAN)基电控固体推进剂(Electrically Controlled Solid Propellants,ECSP)的性能参数进行模拟与计算。方法利用分子表面静电势(ESP)对HAN分子2种可能的构型进行优化和稳定性分析。通过真空非周期性分子... 目的从微观分子的角度对硝酸羟胺(HAN)基电控固体推进剂(Electrically Controlled Solid Propellants,ECSP)的性能参数进行模拟与计算。方法利用分子表面静电势(ESP)对HAN分子2种可能的构型进行优化和稳定性分析。通过真空非周期性分子动力学模拟得到聚乙烯醇(PVA)分子稳定构型,并以HAN基ECSP的主要成分按一定比例构建凝胶模型。基于RESP(Restrained Electrostatic Potential)电荷生成更准确的凝胶模型拓扑文件,并进行凝胶模型的分子动力学模拟、模型稳定分析以及模型参数计算。结果凝胶模型总能量相对平均值的周期性波动不超过7%。由于三维PVA链的包裹,H_(2)O分子的扩散系数被大幅削弱。氢键分析和径向分布函数表明氢键键长主要分布在0.2826 nm附近,PVA与H_(2)O间的氢键较少,H_(2)O与HAN、H_(2)O与H_(2)O之间的氢键较多。模型密度为1.405 g/cm^(3),与实验值吻合度高。在283、293、303 K下,HAN基ECSP凝胶模型的拉伸模量依次降低,剪切模量先增后减。在15 K/600 ps冷却速率下,HAN基ECSP凝胶模型的拉伸模量和剪切模量均增大。结论ECSP制备结束后,冷却过程中的环境温度不宜过高,否则容易造成ECSP力学性能的快速下降,快速冷却可以提高ECSP的力学性能。 展开更多
关键词 电控固体推进剂 硝酸羟胺 聚乙烯醇 凝胶模型 分子动力学模拟 力学性能 静电势
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电推进涵道风扇气动快速求解方法及性能分析研究
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作者 刘乾 刘汉儒 +1 位作者 尚珣 王掩刚 《推进技术》 EI CAS CSCD 北大核心 2024年第3期131-138,共8页
随着绿色航空发展,为了能在设计阶段快速获得涵道风扇气动性能参数和非定常流场特征,有必要开发一种高效的数值求解方法。基于小型电推进风扇内流弱可压和尾迹耗散特性,本文将转子和涵道的面元与尾迹涡粒子耦合,使用面元法求解固壁流场... 随着绿色航空发展,为了能在设计阶段快速获得涵道风扇气动性能参数和非定常流场特征,有必要开发一种高效的数值求解方法。基于小型电推进风扇内流弱可压和尾迹耗散特性,本文将转子和涵道的面元与尾迹涡粒子耦合,使用面元法求解固壁流场,使用涡量输运方程求解远场尾迹传播特征,克服了有限体积法尾迹耗散快的问题。研究表明,本文发展的面元-涡粒子耦合方法对涵道风扇叶表压力与有限体积法趋势一致,整体推力误差为7.83%,能满足工程快速预测需求。本文发展的高效非定常计算方法的尾迹计算数值耗散低,能揭示更为复杂的非定常流动现象,仿真结果显示风扇涵道对尾迹发展有明显约束,而当尾迹传播至外部时,涡量呈现出明显的收缩和对称分布特征。在计算效率方面,本文发展的耦合方法非定常计算效率高,计算相同非定常时间步耗时仅为有限体积法的1/6,具有潜在的涵道动力非定常设计应用价值。 展开更多
关键词 电推进系统 涵道风扇 面元-涡粒子法 非定常气动计算 快速预测方法
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2000—2021年图木舒克市生态环境质量动态监测与评价
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作者 王剑 管瑶 +5 位作者 贺兴宏 代云豪 陈艺伟 王育强 李会文 范德宝 《干旱区地理》 CSCD 北大核心 2024年第3期465-473,共9页
为客观评价新疆图木舒克市驱动因素对其生态环境质量的影响,选取图木舒克市2000、2011年和2021年3期Landsat影像数据,耦合归一化植被指数(NDVI)、土壤湿度(WET)、干度(NDSI)、地表温度(LST)4个指标,分析主成分构建遥感生态指数(RSEI),... 为客观评价新疆图木舒克市驱动因素对其生态环境质量的影响,选取图木舒克市2000、2011年和2021年3期Landsat影像数据,耦合归一化植被指数(NDVI)、土壤湿度(WET)、干度(NDSI)、地表温度(LST)4个指标,分析主成分构建遥感生态指数(RSEI),结合研究区自然因素和社会经济因素,对图木舒克市近22 a来生态环境质量进行动态监测与评价。结果表明:(1)图木舒克市近22 a来RSEI均值从0.406升至0.476,生态环境质量变好面积远大于变差面积,改善区域主要分布在研究区中部、东南、西北地区,近22 a生态环境质量得到有效改善。(2)通过对图木舒克市驱动因素进行分析,当地生态环境质量受人口、国内生产总值(GDP)、耕地面积、气候等因素影响,在驱动因素中社会经济因素对当地生态环境质量有显著影响。(3)通过构建RSEI并分析其驱动因素对生态环境质量的影响,可以高效、准确地对当地生态环境质量进行动态监测与客观评价。 展开更多
关键词 图木舒克市 遥感生态指数 生态环境质量 驱动因素 动态监测
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湖南省印支运动应力场特征及其动力机制 被引量:3
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作者 柏道远 李彬 +1 位作者 曾广乾 杨俊 《华南地质》 CAS 2024年第2期252-269,共18页
长期以来,华南中部湖南印支运动的构造表现暨上古生界盖层褶皱的形成时代备受研究者关注,但至今仍存在显著的认识分歧。鉴此,本文在作者多年研究成果基础上,对湖南省印支运动早、晚两幕褶皱相关的区域应力场特征及厘定依据进行了系统总... 长期以来,华南中部湖南印支运动的构造表现暨上古生界盖层褶皱的形成时代备受研究者关注,但至今仍存在显著的认识分歧。鉴此,本文在作者多年研究成果基础上,对湖南省印支运动早、晚两幕褶皱相关的区域应力场特征及厘定依据进行了系统总结和阐释,并探讨了应力场形成的动力机制以及印支运动的其他相关问题,取得以下主要认识:(1)印支运动早幕发生于中三叠世后期,区域最大主应力方向变化很大,省境中带,自湘西北往南东至湘中、湘东南东部,总体由NNW向—近SN向→NW向→NWW向弧形偏转;南西带,由湘西南的NW向→湘中南的EW向→湘东南西部的EW向变化;北东带,由湘东北的SN向转为湘东地区的NW向、NWW向。印支运动晚幕发生于晚三叠世,区域最大主应力为SN向,湘中局部地区为NNE向。(2)印支运动早幕区域挤压应力场主要与华北地块向南、思茅-印支地块向北以及古太平洋板块向北西的挤压有关,呈NE向—NNE向展布的各次级块体之间的继发性陆内汇聚、NW向基底隐伏断裂左行走滑以及加里东期越城岭和苗儿山花岗质岩体的阻挡等也具有重要的控制作用。印支运动晚幕SN向区域挤压应力场与华北地块向南的挤压、思茅-印支地块向北的挤压有关,局部NNE向最大主应力与NW向常德-安仁、郴州-邵阳基底隐伏断裂右行走滑有关。(3)古太平洋板块的NW向挤压或许是华南印支期NE向褶皱最好的动力学解释;湘中地区NE向褶皱发育程度远高于EW向褶皱,是前者早于后者的重要证据;湘中高挂山—四明山NE向构造隆起带是印支运动晚幕SN向挤压下,先期NE向构造软弱带横向压扁和垂向拉伸而形成。 展开更多
关键词 印支运动早幕 印支运动晚幕 区域挤压应力场 动力机制 华南地块 湖南
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无动力髋关节助力外骨骼设计与分析
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作者 杨洁 王旭鹏 +1 位作者 唐欣尧 张文洁 《机械传动》 北大核心 2024年第8期70-81,共12页
为了提高现有助力外骨骼人机协同性,基于人体运动步态试验数据采集,建立人体下肢逆运动学、逆动力学模型,分析了髋关节行走时的角度、力矩、动势能等参数;根据相关参数分析,进行储能元件选型和设计,提出了一种储能元件为变刚度弹簧的无... 为了提高现有助力外骨骼人机协同性,基于人体运动步态试验数据采集,建立人体下肢逆运动学、逆动力学模型,分析了髋关节行走时的角度、力矩、动势能等参数;根据相关参数分析,进行储能元件选型和设计,提出了一种储能元件为变刚度弹簧的无动力髋关节助力外骨骼;利用Adams开展了人机耦合模拟试验,验证了所设计外骨骼的人机协同性。模拟结果表明,所设计的无动力髋关节助力外骨骼具有较好的人机协同性。之后,进行外骨骼实物加工,开展了外骨骼穿戴试验。试验结果表明,穿戴外骨骼后,髋关节力矩在步态周期内平均减少5.6%,做功平均减少6.25%。以此证明,无动力髋关节助力外骨骼对人体行走有积极的助力效果。 展开更多
关键词 髋关节助力外骨骼 变刚度弹簧 逆运动学 逆动力学 仿真
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Influence of bathymetry evolution on position of tidal shear front and hydrodynamic characteristics around the Yellow River estuary 被引量:3
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作者 Yucen LU Yongming SHEN 《Frontiers of Earth Science》 SCIE CAS CSCD 2012年第4期405-419,共15页
A three dimensional numerical model based on the hydrodynamic module of finite-volume coastal ocean (FVCOM) was established for the Yellow River estuary. The model has been calibrated by observed data and proved to ... A three dimensional numerical model based on the hydrodynamic module of finite-volume coastal ocean (FVCOM) was established for the Yellow River estuary. The model has been calibrated by observed data and proved to be suitable to reflect the hydrodynamic force in the research area. We employed the model to simulate the tidal shear front off the Yellow River estuary and analyzed the formation, spread and duration of two different types of shear front. To examine the effect ofbathymetry evolution on the position of tidal shear front, subaqueous bathymetry of the Yellow River estuary was changed according to the changing patterns obtained from the past few years. Tidal shear front was modeled on both the original and the changed bathymetry. The results show that the position of shear front moved from a shallow to a deep area due to the deposition of bathymetry. The influence of bathymetry evolution on hydrodynamic characteristics including the distribution of salinity and the movement of particles was studied. We found the dispersion areas of low salinity became larger after changing bathymetry and the particles on the surface, middle and bottom layer are able to move further both north and west of Laizhou Bay on the changed bathymetry. 展开更多
关键词 Yellow River estuary shear front hydrody- namic force bathymetry evolution SALINITY
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