A non-incremental time-space algorithm is proposed for numerical. analysis of forming process with the inclusion of geometrical, material, contact-frictional nonlinearities. Unlike the widely used Newton-Raphso...A non-incremental time-space algorithm is proposed for numerical. analysis of forming process with the inclusion of geometrical, material, contact-frictional nonlinearities. Unlike the widely used Newton-Raphson counterpart, the present scheme features an iterative solution procedure on entire time and space domain. Validity and feasibility of foe present scheme are further justiced by the numerical investigation herewith presented.展开更多
Let W be a standard Brownian motion,and define Y(t) =∫t 0 ds W(s) as Cauchy' s principal value related to the local time of W.We study some limitresults on lag increments of Y(t) and obtain various results all...Let W be a standard Brownian motion,and define Y(t) =∫t 0 ds W(s) as Cauchy' s principal value related to the local time of W.We study some limitresults on lag increments of Y(t) and obtain various results all of which are related to earlier work by Hanson and Russo in 1 983展开更多
In recent years, MIMO technology has emerged as one of the technical breakthroughs in the field of wireless communications. Two famous MIMO techniques have become investigated thoroughly throughout the literature;Spat...In recent years, MIMO technology has emerged as one of the technical breakthroughs in the field of wireless communications. Two famous MIMO techniques have become investigated thoroughly throughout the literature;Spatial Multiplexing, and Space Time Block Coding. On one hand, Spatial Multiplexing offers high data rates. On the other hand, Space Time Block Coding presents transmission fidelity. This imposes a fundamental tradeoff between capacity and reliability. Adaptive MIMO Switching schemes have been proposed to select the MIMO scheme that best fits the channel conditions. However, the switching schemes presented in the literature directly switch between the MIMO endpoints. In this paper, an adaptive MIMO system that incrementally switches from multiplexing towards diversity is proposed. The proposed scheme is referred to as incremental diversity and can be set to operate in two different modes;Rate-Adaptive, and Energy-Conservative Incremental Diversity. Results indicate that the proposed incremental diversity framework achieves transmission reliability offered by MIMO diversity, while maintaining a gradual increase in spectral efficiency (in the Rate-Adaptive mode) or a reduction in required number of received symbols (in the Energy-Conservative mode) with increase in the SNR.展开更多
耐震时程分析(endurance time analysis,ETA)法作为结构响应分析领域的有效简化方法,基于频域地震动反应谱合成的耐震时程曲线无法准确反映时域的脉冲特性,限制了其在近断层脉冲型地震中的应用。为将ETA法应用到近断层脉冲型地震动作用...耐震时程分析(endurance time analysis,ETA)法作为结构响应分析领域的有效简化方法,基于频域地震动反应谱合成的耐震时程曲线无法准确反映时域的脉冲特性,限制了其在近断层脉冲型地震中的应用。为将ETA法应用到近断层脉冲型地震动作用下斜拉桥动力响应分析中,基于增量动力分析(incremental dynamic analysis,IDA)法研究了不同峰值下脉冲、高频分量对斜拉桥动力响应的贡献程度,构建了考虑脉冲和强度特性的斜拉桥动力响应预测模型,利用ETA法模拟高频分量下的斜拉桥动力响应并结合预测模型,预测了近断层脉冲型地震动下斜拉桥的动力响应。结果表明:建立的预测模型可以精确表达不同强度下高频分量与原始地震动响应之间的定量关系;基于ETA模型和IDA法计算出0.6 g下的平均动力响应最大相对误差不超过10%,具有良好的预测精度。研究成果为高效合理地计算近断层脉冲型地震动下斜拉桥的动力响应提供了技术支撑。展开更多
In the study on functional low-carbon ergonomic validity in buildings,ergonomic validity is different from resource validity which is easy for quantitative analysis. To eliminate the complexity and uncertainty impacts...In the study on functional low-carbon ergonomic validity in buildings,ergonomic validity is different from resource validity which is easy for quantitative analysis. To eliminate the complexity and uncertainty impacts of human factors on quantitative study,it proposes a method of building a parameter of ergonomic validity—multi-effect time by using cardiotachometer to record heart rate change,being used to evaluate the functional low-carbon ergonomic validity targeting at the ontological characteristics of kitchen. This method is used to determine the physical consumption intensity( multi-effect) through heart rate incremental relation based on the principles of physiology and ergonomics,and to confirm the ergonomic validity of environmental factors by the time to complete standard work as well as multi-effect quantitative analysis. The test results show that,under the kitchen operating conditions,the multi-effect( ME) can properly reflect the real-time status of the operator and is easily operated; the parameters obtained are not significantly related to the physiological status of the operator,and multi-effect time( MT) is sensitive to the physical consumption brought about to the operator due to kitchen environmental factors; thus,it can be taken as an objective index,which is simple and easy to operate in residential kitchen functional low-carbon evaluation.展开更多
风电参与系统调频是提升新能源高占比电力系统频率安全稳定水平的关键措施之一。然而风电机组的现有调频控制策略难以适应系统多样化的功率扰动,未能充分发挥风电机组的快速频率支撑能力。建立了直驱型风电机组调频控制的通用电磁暂态模...风电参与系统调频是提升新能源高占比电力系统频率安全稳定水平的关键措施之一。然而风电机组的现有调频控制策略难以适应系统多样化的功率扰动,未能充分发挥风电机组的快速频率支撑能力。建立了直驱型风电机组调频控制的通用电磁暂态模型,并对现有调频控制策略下风电机组的动态特性进行了分析,明确了限制其调频能力的原因。在此基础上,通过建立计及风电调频的改进系统频率响应模型,实现了系统功率扰动程度的评估,并进一步提出了基于该评估结果的风电机组的主动频率支撑控制策略。该策略基于扰动发生后的最大频率变化率(rate of change of frequency, RoCoF)判断系统功率扰动程度,结合风电机组的运行模式,选择不同的调频控制组合,能够在充分发挥风电机组的主动频率支撑能力的同时,显著降低系统频率的二次跌落风险。仿真结果表明,相比于定参数调频策略和传统自适应调频策略,所提方法在不同扰动程度下的调频性能优势明显,证明了方法的有效性。展开更多
为克服筒仓结构在地震易损性评估时需要进行大量非线性时程分析的不足,采用基于耐震时程法(endurance time method,ETM)的易损性分析方法对筒仓结构进行易损性的快速评估。以IV类场地柱承式筒仓为研究对象,选取实际天然地震动记录为目...为克服筒仓结构在地震易损性评估时需要进行大量非线性时程分析的不足,采用基于耐震时程法(endurance time method,ETM)的易损性分析方法对筒仓结构进行易损性的快速评估。以IV类场地柱承式筒仓为研究对象,选取实际天然地震动记录为目标反应谱合成3条耐震时程曲线,利用有限元软件ABAQUS建立柱承式筒仓模型并输入耐震时程曲线,将ETM分析结果与增量动力分析方法(incremental dynamic analysis,IDA)结果进行对比。结果表明:ETM分析结果与IDA分析结果的中位值相匹配,满足筒仓结构抗震性能分析精度要求;筒仓不同支承柱在地震作用下的基底剪力分配情况与储料质量无关,仅取决于支承柱位置;ETM所得的筒仓地震易损性曲线与IDA易损性曲线基本吻合,耐震时程法可作为柱承式筒仓抗震性能分析、预测和评估的高效方法。展开更多
时变干扰问题在风洞流场控制中较为常见,其中典型的例子是跨声速连续变迎角试验中迎角变化对马赫数控制造成的干扰。为提高存在时变干扰情况下的流场控制精度,本文创新性地提出一种新型的前馈+反馈复合控制方案。该方案中,前馈控制采用...时变干扰问题在风洞流场控制中较为常见,其中典型的例子是跨声速连续变迎角试验中迎角变化对马赫数控制造成的干扰。为提高存在时变干扰情况下的流场控制精度,本文创新性地提出一种新型的前馈+反馈复合控制方案。该方案中,前馈控制采用基于超前校正的增量式扩张状态观测器(Lead Correction based Incremental Extend State Observer,LIESO),反馈控制则采用增量式比例积分(Proportional–Integral,PI)控制。针对1.2 m跨超声速风洞连续变迎角试验,对该复合控制方法进行了试验验证。结果表明:LIESO+PI复合控制能够有效抑制时变干扰,鲁棒性良好,在不同模型堵塞度和试验马赫数下均表现出较好的适应性,具备较高的工程应用价值。展开更多
文摘A non-incremental time-space algorithm is proposed for numerical. analysis of forming process with the inclusion of geometrical, material, contact-frictional nonlinearities. Unlike the widely used Newton-Raphson counterpart, the present scheme features an iterative solution procedure on entire time and space domain. Validity and feasibility of foe present scheme are further justiced by the numerical investigation herewith presented.
文摘Let W be a standard Brownian motion,and define Y(t) =∫t 0 ds W(s) as Cauchy' s principal value related to the local time of W.We study some limitresults on lag increments of Y(t) and obtain various results all of which are related to earlier work by Hanson and Russo in 1 983
文摘In recent years, MIMO technology has emerged as one of the technical breakthroughs in the field of wireless communications. Two famous MIMO techniques have become investigated thoroughly throughout the literature;Spatial Multiplexing, and Space Time Block Coding. On one hand, Spatial Multiplexing offers high data rates. On the other hand, Space Time Block Coding presents transmission fidelity. This imposes a fundamental tradeoff between capacity and reliability. Adaptive MIMO Switching schemes have been proposed to select the MIMO scheme that best fits the channel conditions. However, the switching schemes presented in the literature directly switch between the MIMO endpoints. In this paper, an adaptive MIMO system that incrementally switches from multiplexing towards diversity is proposed. The proposed scheme is referred to as incremental diversity and can be set to operate in two different modes;Rate-Adaptive, and Energy-Conservative Incremental Diversity. Results indicate that the proposed incremental diversity framework achieves transmission reliability offered by MIMO diversity, while maintaining a gradual increase in spectral efficiency (in the Rate-Adaptive mode) or a reduction in required number of received symbols (in the Energy-Conservative mode) with increase in the SNR.
基金Sponsored by the "Twelfth Five-year" National Science and Technology Supoort Programe(Grant No.2011BAJ05B02-03)
文摘In the study on functional low-carbon ergonomic validity in buildings,ergonomic validity is different from resource validity which is easy for quantitative analysis. To eliminate the complexity and uncertainty impacts of human factors on quantitative study,it proposes a method of building a parameter of ergonomic validity—multi-effect time by using cardiotachometer to record heart rate change,being used to evaluate the functional low-carbon ergonomic validity targeting at the ontological characteristics of kitchen. This method is used to determine the physical consumption intensity( multi-effect) through heart rate incremental relation based on the principles of physiology and ergonomics,and to confirm the ergonomic validity of environmental factors by the time to complete standard work as well as multi-effect quantitative analysis. The test results show that,under the kitchen operating conditions,the multi-effect( ME) can properly reflect the real-time status of the operator and is easily operated; the parameters obtained are not significantly related to the physiological status of the operator,and multi-effect time( MT) is sensitive to the physical consumption brought about to the operator due to kitchen environmental factors; thus,it can be taken as an objective index,which is simple and easy to operate in residential kitchen functional low-carbon evaluation.
文摘风电参与系统调频是提升新能源高占比电力系统频率安全稳定水平的关键措施之一。然而风电机组的现有调频控制策略难以适应系统多样化的功率扰动,未能充分发挥风电机组的快速频率支撑能力。建立了直驱型风电机组调频控制的通用电磁暂态模型,并对现有调频控制策略下风电机组的动态特性进行了分析,明确了限制其调频能力的原因。在此基础上,通过建立计及风电调频的改进系统频率响应模型,实现了系统功率扰动程度的评估,并进一步提出了基于该评估结果的风电机组的主动频率支撑控制策略。该策略基于扰动发生后的最大频率变化率(rate of change of frequency, RoCoF)判断系统功率扰动程度,结合风电机组的运行模式,选择不同的调频控制组合,能够在充分发挥风电机组的主动频率支撑能力的同时,显著降低系统频率的二次跌落风险。仿真结果表明,相比于定参数调频策略和传统自适应调频策略,所提方法在不同扰动程度下的调频性能优势明显,证明了方法的有效性。
文摘为克服筒仓结构在地震易损性评估时需要进行大量非线性时程分析的不足,采用基于耐震时程法(endurance time method,ETM)的易损性分析方法对筒仓结构进行易损性的快速评估。以IV类场地柱承式筒仓为研究对象,选取实际天然地震动记录为目标反应谱合成3条耐震时程曲线,利用有限元软件ABAQUS建立柱承式筒仓模型并输入耐震时程曲线,将ETM分析结果与增量动力分析方法(incremental dynamic analysis,IDA)结果进行对比。结果表明:ETM分析结果与IDA分析结果的中位值相匹配,满足筒仓结构抗震性能分析精度要求;筒仓不同支承柱在地震作用下的基底剪力分配情况与储料质量无关,仅取决于支承柱位置;ETM所得的筒仓地震易损性曲线与IDA易损性曲线基本吻合,耐震时程法可作为柱承式筒仓抗震性能分析、预测和评估的高效方法。
文摘时变干扰问题在风洞流场控制中较为常见,其中典型的例子是跨声速连续变迎角试验中迎角变化对马赫数控制造成的干扰。为提高存在时变干扰情况下的流场控制精度,本文创新性地提出一种新型的前馈+反馈复合控制方案。该方案中,前馈控制采用基于超前校正的增量式扩张状态观测器(Lead Correction based Incremental Extend State Observer,LIESO),反馈控制则采用增量式比例积分(Proportional–Integral,PI)控制。针对1.2 m跨超声速风洞连续变迎角试验,对该复合控制方法进行了试验验证。结果表明:LIESO+PI复合控制能够有效抑制时变干扰,鲁棒性良好,在不同模型堵塞度和试验马赫数下均表现出较好的适应性,具备较高的工程应用价值。
