Based on the structural characteristic of metal drill collar for induction logging while drilling, we have given the analytical formulae of lengthways fields Ez and Hz when the tool is located in a fan-ring shaped slo...Based on the structural characteristic of metal drill collar for induction logging while drilling, we have given the analytical formulae of lengthways fields Ez and Hz when the tool is located in a fan-ring shaped slot of drill collar by the boundary conditions of electromagnetic field, and derived the other components of electromagnetic field in and out the fan-ring slot from Ez and Hz. In the other intervals of formation, where the drill collar is a solid cylinder, the analytical formulae of field are educed through the method of variable coefficient. The total analytical solutions of field in whole space have been obtained. With the help of the analytical formulae, we have also given numerical examples and analyzed the distributive characteristic of electromagnetic field. From the computational results we find that the secondary scattering field Hz is in a linear relation with the conductivity of stratum. The characteristic of field is very useful for induction logging while drilling, which can be used to measure and analyze the logging responses of the stratum conductivity. This paper sets up a theoretical foundation for us to study the distrbutions of field and to direct the design of logging instruments.展开更多
传统的阵列波束展宽技术需要对阵元施加复加权操作,实现起来相对复杂。提出了一种基于多种群遗传算法(Multiple Population Genetic Algorithm,MPGA)的唯相加权阵列波束展宽技术,并针对均匀直线阵列和扇形圆环阵列,结合其数学模型,分别...传统的阵列波束展宽技术需要对阵元施加复加权操作,实现起来相对复杂。提出了一种基于多种群遗传算法(Multiple Population Genetic Algorithm,MPGA)的唯相加权阵列波束展宽技术,并针对均匀直线阵列和扇形圆环阵列,结合其数学模型,分别设计出适配的适应度函数,通过MPGA对阵元内各个阵元的附加相位进行优化,经仿真实现了阵列波束展宽。结果表明,该方法可以在考虑天线阵列的副瓣电平及天线效率的同时,设计实现更宽的阵列波束,且收敛速度较快、稳健性较好,充分显示了MPGA在天线阵列设计中较好的应用前景。展开更多
采用实验测试的方法研究了冷凝风机使用封闭式和半开式导流罩时冰箱的制冷与噪声性能。结果表明:冷凝风机使用半开式导流罩可以产生更大的风压和流量,获取更好的静压-流量特性,提升冷凝器的冷凝效果,从而降低冰箱的整机能耗;冷凝风机导...采用实验测试的方法研究了冷凝风机使用封闭式和半开式导流罩时冰箱的制冷与噪声性能。结果表明:冷凝风机使用半开式导流罩可以产生更大的风压和流量,获取更好的静压-流量特性,提升冷凝器的冷凝效果,从而降低冰箱的整机能耗;冷凝风机导流罩主要影响冰箱的中低和中高频段的噪声,使用半开式导流罩时冷凝风机噪声和冰箱整机噪声分别降低了3.4 d B(A)和4 d B(A);封闭式和半开式导流罩长度缩短时,冰箱噪声分别呈震荡下降和先下降后上升的趋势。冷凝风机导流罩对冰箱的制冷与噪声性能影响较大,在使用半开式导流罩时冰箱综合性能较优。展开更多
基金Supported by the National Natural Science Foundation of China(Grant No.10705049)the Beijing Natural Science Foundation(Grant No.1083011)Fund-ing Project for Academic Human Resources Development in Institutions of Higher Learning[PHR(IHLB)]
文摘Based on the structural characteristic of metal drill collar for induction logging while drilling, we have given the analytical formulae of lengthways fields Ez and Hz when the tool is located in a fan-ring shaped slot of drill collar by the boundary conditions of electromagnetic field, and derived the other components of electromagnetic field in and out the fan-ring slot from Ez and Hz. In the other intervals of formation, where the drill collar is a solid cylinder, the analytical formulae of field are educed through the method of variable coefficient. The total analytical solutions of field in whole space have been obtained. With the help of the analytical formulae, we have also given numerical examples and analyzed the distributive characteristic of electromagnetic field. From the computational results we find that the secondary scattering field Hz is in a linear relation with the conductivity of stratum. The characteristic of field is very useful for induction logging while drilling, which can be used to measure and analyze the logging responses of the stratum conductivity. This paper sets up a theoretical foundation for us to study the distrbutions of field and to direct the design of logging instruments.
文摘传统的阵列波束展宽技术需要对阵元施加复加权操作,实现起来相对复杂。提出了一种基于多种群遗传算法(Multiple Population Genetic Algorithm,MPGA)的唯相加权阵列波束展宽技术,并针对均匀直线阵列和扇形圆环阵列,结合其数学模型,分别设计出适配的适应度函数,通过MPGA对阵元内各个阵元的附加相位进行优化,经仿真实现了阵列波束展宽。结果表明,该方法可以在考虑天线阵列的副瓣电平及天线效率的同时,设计实现更宽的阵列波束,且收敛速度较快、稳健性较好,充分显示了MPGA在天线阵列设计中较好的应用前景。
文摘采用实验测试的方法研究了冷凝风机使用封闭式和半开式导流罩时冰箱的制冷与噪声性能。结果表明:冷凝风机使用半开式导流罩可以产生更大的风压和流量,获取更好的静压-流量特性,提升冷凝器的冷凝效果,从而降低冰箱的整机能耗;冷凝风机导流罩主要影响冰箱的中低和中高频段的噪声,使用半开式导流罩时冷凝风机噪声和冰箱整机噪声分别降低了3.4 d B(A)和4 d B(A);封闭式和半开式导流罩长度缩短时,冰箱噪声分别呈震荡下降和先下降后上升的趋势。冷凝风机导流罩对冰箱的制冷与噪声性能影响较大,在使用半开式导流罩时冰箱综合性能较优。
