Event region detection is the important application for wireless sensor networks（WSNs）, where the existing faulty sensors would lead to drastic deterioration of network quality of service.Considering single-moment n...Event region detection is the important application for wireless sensor networks（WSNs）, where the existing faulty sensors would lead to drastic deterioration of network quality of service.Considering single-moment nodes fault-tolerance, a novel distributed fault-tolerant detection algorithm named distributed fault-tolerance based on weighted distance（DFWD） is proposed, which exploits the spatial correlation among sensor nodes and their redundant information.In sensor networks, neighborhood sensor nodes will be endowed with different relative weights respectively according to the distances between them and the central node.Having syncretized the weighted information of dual-neighborhood nodes appropriately, it is reasonable to decide the ultimate status of the central sensor node.Simultaneously, readings of faulty sensors would be corrected during this process.Simulation results demonstrate that the DFWD has a higher fault detection accuracy compared with other algorithms, and when the sensor fault probability is 10%, the DFWD can still correct more than 91% faulty sensor nodes, which significantly improves the performance of the whole sensor network.展开更多
In this research combustion of aluminum dust particles in a quiescent medium with spatially discrete sources distributed in a random way was studied by a numerical approach.A new thermal model was generated to estimat...In this research combustion of aluminum dust particles in a quiescent medium with spatially discrete sources distributed in a random way was studied by a numerical approach.A new thermal model was generated to estimate flame propagation speed in a lean/rich reaction medium.Flame speed for different particle diameters and the effects of various oxidizers such as carbon dioxide and oxygen on flame speed were studied.Nitrogen was considered the inert gas.In addition,the quenching distance and the minimum ignition energy(MIE) were studied as a function of dust concentration.Different burning time models for aluminum were employed and their results were compared with each other.The model was based on conduction heat transfer mechanism using the heat point source method.The combustion of single-particle was first studied and the solution was presented.Then the dust combustion was investigated using the superposition principle to include the effects of surrounding particles.It is found that larger particles have higher values of quenching distance in comparison with smaller particles in an assumed dust concentration.With the increase of dust concentration the value of MIE would be decreased for an assumed particle diameter.Considering random discrete heat sources method,the obtained results of random distribution of fuel particles in space provide closer and realistic predictions of the combustion physics of aluminum dust flame as compared with the experimental findings.展开更多
研究旨在通过仿真实验揭示红外偏振成像系统在浮空器平台海雾背景下的探测优势。首先,基于偏振双向反射分布函数,分析了偏振特性随观测角度变化的规律,研究结果表明红外偏振在浮空器斜视成像中的适用性。其次,借助蒙特卡罗方法和最小可...研究旨在通过仿真实验揭示红外偏振成像系统在浮空器平台海雾背景下的探测优势。首先,基于偏振双向反射分布函数,分析了偏振特性随观测角度变化的规律,研究结果表明红外偏振在浮空器斜视成像中的适用性。其次,借助蒙特卡罗方法和最小可分辨温差(Minimum Resolvable Temperature Difference,MRTD)模型,构建了红外偏振成像系统的最大作用距离模型,从而验证了红外偏振成像相较于红外强度成像在海雾背景下特征保持和探测距离上存在优势。为红外偏振技术在浮空器平台上的部署应用,提供了理论分析和仿真依据。展开更多
为研究长距离公路隧道电力电缆区在夏季机械通风条件下仍然存在的高温环境问题,以上海市G40长距离跨江隧道为研究对象,采用CFD模拟方法,探究电缆发热量、室外环境温度和通风量对电力电缆区温度场分布的影响规律,并提出适用于该隧道结构...为研究长距离公路隧道电力电缆区在夏季机械通风条件下仍然存在的高温环境问题,以上海市G40长距离跨江隧道为研究对象,采用CFD模拟方法,探究电缆发热量、室外环境温度和通风量对电力电缆区温度场分布的影响规律,并提出适用于该隧道结构的温度预测关联式,用于解决工程实践中面临的“高温区域覆盖范围如何界定”以及“下游温度超标临界条件如何判定”等关键问题。结果表明:1)在夏季机械排风工况下,电力电缆区的空气温度沿着隧道纵向呈现非线性增长趋势,表明气流驱动的热迁移现象显著;2)电缆发热量对隧道进排风温差呈现非线性增长特征,当电缆长期高负载运行时,电缆区排风温度将超过标准规定的安全阈值(≤40℃);3)降低隧道入口温度虽可减少排风温度,但会导致进排风温差扩大超出规范限值(≤10℃);4)通风量每增大87.81 m 3/s(即换气次数增大2次/h)可使排风温度降低约3.57℃,但过高的通风量会导致风机功耗激增,因此需要进一步研究通风策略以平衡降温效果与风机能耗之间的关系。展开更多
基金Basic research program from Institute of Earthquake Science China Earthquake Administration (690206)Social Welfare Research Program from Ministry of Science and Technology of China (2005DIB3J119)
基金supported by the National Science Foundation for Outstanding Young Scientists (60425310)the Science Foundation for Post-doctoral Scientists of Central South University (2008)
文摘Event region detection is the important application for wireless sensor networks（WSNs）, where the existing faulty sensors would lead to drastic deterioration of network quality of service.Considering single-moment nodes fault-tolerance, a novel distributed fault-tolerant detection algorithm named distributed fault-tolerance based on weighted distance（DFWD） is proposed, which exploits the spatial correlation among sensor nodes and their redundant information.In sensor networks, neighborhood sensor nodes will be endowed with different relative weights respectively according to the distances between them and the central node.Having syncretized the weighted information of dual-neighborhood nodes appropriately, it is reasonable to decide the ultimate status of the central sensor node.Simultaneously, readings of faulty sensors would be corrected during this process.Simulation results demonstrate that the DFWD has a higher fault detection accuracy compared with other algorithms, and when the sensor fault probability is 10%, the DFWD can still correct more than 91% faulty sensor nodes, which significantly improves the performance of the whole sensor network.
文摘In this research combustion of aluminum dust particles in a quiescent medium with spatially discrete sources distributed in a random way was studied by a numerical approach.A new thermal model was generated to estimate flame propagation speed in a lean/rich reaction medium.Flame speed for different particle diameters and the effects of various oxidizers such as carbon dioxide and oxygen on flame speed were studied.Nitrogen was considered the inert gas.In addition,the quenching distance and the minimum ignition energy(MIE) were studied as a function of dust concentration.Different burning time models for aluminum were employed and their results were compared with each other.The model was based on conduction heat transfer mechanism using the heat point source method.The combustion of single-particle was first studied and the solution was presented.Then the dust combustion was investigated using the superposition principle to include the effects of surrounding particles.It is found that larger particles have higher values of quenching distance in comparison with smaller particles in an assumed dust concentration.With the increase of dust concentration the value of MIE would be decreased for an assumed particle diameter.Considering random discrete heat sources method,the obtained results of random distribution of fuel particles in space provide closer and realistic predictions of the combustion physics of aluminum dust flame as compared with the experimental findings.
文摘研究旨在通过仿真实验揭示红外偏振成像系统在浮空器平台海雾背景下的探测优势。首先,基于偏振双向反射分布函数,分析了偏振特性随观测角度变化的规律,研究结果表明红外偏振在浮空器斜视成像中的适用性。其次,借助蒙特卡罗方法和最小可分辨温差(Minimum Resolvable Temperature Difference,MRTD)模型,构建了红外偏振成像系统的最大作用距离模型,从而验证了红外偏振成像相较于红外强度成像在海雾背景下特征保持和探测距离上存在优势。为红外偏振技术在浮空器平台上的部署应用,提供了理论分析和仿真依据。
文摘为研究长距离公路隧道电力电缆区在夏季机械通风条件下仍然存在的高温环境问题,以上海市G40长距离跨江隧道为研究对象,采用CFD模拟方法,探究电缆发热量、室外环境温度和通风量对电力电缆区温度场分布的影响规律,并提出适用于该隧道结构的温度预测关联式,用于解决工程实践中面临的“高温区域覆盖范围如何界定”以及“下游温度超标临界条件如何判定”等关键问题。结果表明:1)在夏季机械排风工况下,电力电缆区的空气温度沿着隧道纵向呈现非线性增长趋势,表明气流驱动的热迁移现象显著;2)电缆发热量对隧道进排风温差呈现非线性增长特征,当电缆长期高负载运行时,电缆区排风温度将超过标准规定的安全阈值(≤40℃);3)降低隧道入口温度虽可减少排风温度,但会导致进排风温差扩大超出规范限值(≤10℃);4)通风量每增大87.81 m 3/s(即换气次数增大2次/h)可使排风温度降低约3.57℃,但过高的通风量会导致风机功耗激增,因此需要进一步研究通风策略以平衡降温效果与风机能耗之间的关系。
