MgO-C continuous temperature-measuring sensors for liquid steel were made of fused magnesia with different critical particle sizes from 0.5 to 2.0 mm,thus the effects what magnesia＇s particle size affect sensors＇ pr...MgO-C continuous temperature-measuring sensors for liquid steel were made of fused magnesia with different critical particle sizes from 0.5 to 2.0 mm,thus the effects what magnesia＇s particle size affect sensors＇ properties and lifetime were studied.The result shows that the MgO-C continuous temperature-measuring sensor has good aggression resistance to basic tundish powders and meets the requirement for response time of temperature measuring practice in tundish.The sensor＇s service life,which is affected by multi-properties of material and operating environment,reached its maximum when the critical particle size of magnesia was 1.0 mm.The average lifetime of sensors was 43 or 40 h when served for casting SPHC or Q195 steel.展开更多
Parameter optimization of nodes communication is the foundation of underwater sensor networks.The packet size is an important indicator of the impact of communication performance.As a result,the optimal packet size se...Parameter optimization of nodes communication is the foundation of underwater sensor networks.The packet size is an important indicator of the impact of communication performance.As a result,the optimal packet size selection is a critical issue in improving the communication performance.This paper aims to make a model reflecting the communication characteristics as the optimization target,because underwater sensor networks have the characteristics of high time delay,high energy consumption and high bit error rate.Finally,simulation experiments and theory have demonstrated the effectiveness and timeliness of simultaneous perturbation stochastic approximation(SPSA) algorithm.展开更多
铁路轨道与车轮长期滚动接触,容易产生疲劳裂纹,导致钢轨表面剥离甚至钢轨断裂等严重问题,因此开展裂纹尺寸、扩展深度以及裂纹形状的检测与定量表征具有重要意义。设计搭建了采用阵列式传感器交流电磁场检测技术(Alternating current f...铁路轨道与车轮长期滚动接触,容易产生疲劳裂纹,导致钢轨表面剥离甚至钢轨断裂等严重问题,因此开展裂纹尺寸、扩展深度以及裂纹形状的检测与定量表征具有重要意义。设计搭建了采用阵列式传感器交流电磁场检测技术(Alternating current field measurement,ACFM)的钢轨裂纹检测系统。结合检测信号等值线彩色图研究了不同长度、不同深度、不同形状(簇状、Y形和W形)裂纹对ACFM信号的影响规律,分析了裂纹形状对交流电磁场检测信号影响机理。研究结果表明:随着裂纹长度与深度的增加,B_(x)信号谷值减小,B_(z)信号出现越来越明显的双极值特征,蝶形图中缺陷环面积逐渐增加,表明裂纹引起的磁场扰动逐渐变大,B_(z)信号相比B_(x)信号对裂纹长度与深度的变化更敏感;随簇状裂纹条数的增加,裂纹周围的B_(x)和B_(z)信号强度逐渐增加,B_(x)信号波峰位置的连线可反应裂纹走向;W形裂纹的B_(x)信号出现了三个极值,B_(z)信号出现了对称分布的极值特征;Y形裂纹的B_(x)信号出现了六个极值,B_(z)信号出现了四个极值。利用阵列式传感器ACFM信号的等值线彩色图可实现对复杂形状裂纹的识别和表征。展开更多
We consider the extension of network lifetime of battery driven wireless sensor networks by splitting the sensing area into uniform clusters and implementing heterogeneous modulation schemes at different members of th...We consider the extension of network lifetime of battery driven wireless sensor networks by splitting the sensing area into uniform clusters and implementing heterogeneous modulation schemes at different members of the clusters. A cross-layer optimization has been proposed to reduce total energy expenditure of the network;at network layer, routing is done through uniform clusters;at MAC layer, each sensor node of the cluster is assigned fixed or variable time slots and at physical layer different member of the clusters is assigned different modulation techniques. MATLAB simulation proved substantial network lifetime gains.展开更多
基金Item Sponsored by National Science and Technology Support Plan of China(2006AA040309)
文摘MgO-C continuous temperature-measuring sensors for liquid steel were made of fused magnesia with different critical particle sizes from 0.5 to 2.0 mm,thus the effects what magnesia＇s particle size affect sensors＇ properties and lifetime were studied.The result shows that the MgO-C continuous temperature-measuring sensor has good aggression resistance to basic tundish powders and meets the requirement for response time of temperature measuring practice in tundish.The sensor＇s service life,which is affected by multi-properties of material and operating environment,reached its maximum when the critical particle size of magnesia was 1.0 mm.The average lifetime of sensors was 43 or 40 h when served for casting SPHC or Q195 steel.
文摘Parameter optimization of nodes communication is the foundation of underwater sensor networks.The packet size is an important indicator of the impact of communication performance.As a result,the optimal packet size selection is a critical issue in improving the communication performance.This paper aims to make a model reflecting the communication characteristics as the optimization target,because underwater sensor networks have the characteristics of high time delay,high energy consumption and high bit error rate.Finally,simulation experiments and theory have demonstrated the effectiveness and timeliness of simultaneous perturbation stochastic approximation(SPSA) algorithm.
文摘铁路轨道与车轮长期滚动接触,容易产生疲劳裂纹,导致钢轨表面剥离甚至钢轨断裂等严重问题,因此开展裂纹尺寸、扩展深度以及裂纹形状的检测与定量表征具有重要意义。设计搭建了采用阵列式传感器交流电磁场检测技术(Alternating current field measurement,ACFM)的钢轨裂纹检测系统。结合检测信号等值线彩色图研究了不同长度、不同深度、不同形状(簇状、Y形和W形)裂纹对ACFM信号的影响规律,分析了裂纹形状对交流电磁场检测信号影响机理。研究结果表明:随着裂纹长度与深度的增加,B_(x)信号谷值减小,B_(z)信号出现越来越明显的双极值特征,蝶形图中缺陷环面积逐渐增加,表明裂纹引起的磁场扰动逐渐变大,B_(z)信号相比B_(x)信号对裂纹长度与深度的变化更敏感;随簇状裂纹条数的增加,裂纹周围的B_(x)和B_(z)信号强度逐渐增加,B_(x)信号波峰位置的连线可反应裂纹走向;W形裂纹的B_(x)信号出现了三个极值,B_(z)信号出现了对称分布的极值特征;Y形裂纹的B_(x)信号出现了六个极值,B_(z)信号出现了四个极值。利用阵列式传感器ACFM信号的等值线彩色图可实现对复杂形状裂纹的识别和表征。
文摘We consider the extension of network lifetime of battery driven wireless sensor networks by splitting the sensing area into uniform clusters and implementing heterogeneous modulation schemes at different members of the clusters. A cross-layer optimization has been proposed to reduce total energy expenditure of the network;at network layer, routing is done through uniform clusters;at MAC layer, each sensor node of the cluster is assigned fixed or variable time slots and at physical layer different member of the clusters is assigned different modulation techniques. MATLAB simulation proved substantial network lifetime gains.
