One of the major tasks of monitoring production well operations is to determine bottom-hole flowing pressure.The overwhelming majority of wells in the Perm Krai are serviced using borehole pumps,which makes it difficu...One of the major tasks of monitoring production well operations is to determine bottom-hole flowing pressure.The overwhelming majority of wells in the Perm Krai are serviced using borehole pumps,which makes it difficult to take direct bottom-hole flowing pressure measurements.The bottomhole filtration pressure(BHFP)in these wells is very often determined by recalculating the parameters measured at the well mouth(annulus pressure,dynamic fluid level depth).The recalculation is done by procedures based on analytically determining the characteristics of the gas-liquid mixture in the wellbore,which is very inconsistent to perform due to the mixture's complex behavior.This article proposes an essentially different approach to BHFP measurements that relies on the mathematical processing of the findings of more than 4000 parallel mouth and deep investigations of the oil production wells of a large oil-production region.As a result,multivariate mathematical models are elaborated that allow reliably determining the BHFP of oil-production wells in operation.展开更多
The data on any aspect of public health, including that on infant mortality, has inbuilt hierarchical structure. Using traditional regression approach in data analysis, i.e., ignoring hierarchical structure, either at...The data on any aspect of public health, including that on infant mortality, has inbuilt hierarchical structure. Using traditional regression approach in data analysis, i.e., ignoring hierarchical structure, either at micro (individual) or at macro (community) level will be avoiding desired assumption related to independence of records. Accordingly, this may result into distortion in the results due to probable underestimation of standard error of the regression coefficients. To be more specific, an irrelevant co-variate may emerge as an important covariate leading to inappropriate public health implications. To overcome this problem, the objective of the present work was to deal with multilevel analysis of the data on infant mortality available under second round of National family Health Survey and notify changes in results under traditional regression analysis that ignores hierarchical structure of data. This method provides more accurate results leading to meaningful public health implications. In addition, estimation of variability at different levels and their covariance are also obtained. The results indicate that the community (e.g., state) level characteristics still have major role regarding infant mortality in India. Further, if computational facilities are available, multilevel analysis may be preferred in dealing with data involving hierarchical structure leading to accurate results having meaningful public health implications.展开更多
开展针对基于模块化多电平换流器的高压直流(modular multilevel converter based high voltage direct current,M M C-HVDC)输电系统的损耗研究,对高压直流输电系统的设计与优化具有重要意义。提出一种基于模块化多电平换流器的高压直...开展针对基于模块化多电平换流器的高压直流(modular multilevel converter based high voltage direct current,M M C-HVDC)输电系统的损耗研究,对高压直流输电系统的设计与优化具有重要意义。提出一种基于模块化多电平换流器的高压直流输电系统损耗计算的实用方法。首先,根据MMC-HVDC输电系统的拓扑结构和器件参数建立M M C-HVDC输电系统及其各个器件的损耗计算模型,并通过仿真计算精确求解M M C-HVDC输电系统及其器件不同运行工况的损耗系列数据;然后再利用数据拟合的方法得到便于工程应用的损耗计算公式;最后,针对厦门柔性直流输电系统工程,采用本文方法求得损耗计算公式,并与实测结果进行了对比分析。分析表明,利用该损耗拟合公式计算和评估MMC-HVDC输电系统的损耗可满足工程精度要求。展开更多
文摘One of the major tasks of monitoring production well operations is to determine bottom-hole flowing pressure.The overwhelming majority of wells in the Perm Krai are serviced using borehole pumps,which makes it difficult to take direct bottom-hole flowing pressure measurements.The bottomhole filtration pressure(BHFP)in these wells is very often determined by recalculating the parameters measured at the well mouth(annulus pressure,dynamic fluid level depth).The recalculation is done by procedures based on analytically determining the characteristics of the gas-liquid mixture in the wellbore,which is very inconsistent to perform due to the mixture's complex behavior.This article proposes an essentially different approach to BHFP measurements that relies on the mathematical processing of the findings of more than 4000 parallel mouth and deep investigations of the oil production wells of a large oil-production region.As a result,multivariate mathematical models are elaborated that allow reliably determining the BHFP of oil-production wells in operation.
文摘The data on any aspect of public health, including that on infant mortality, has inbuilt hierarchical structure. Using traditional regression approach in data analysis, i.e., ignoring hierarchical structure, either at micro (individual) or at macro (community) level will be avoiding desired assumption related to independence of records. Accordingly, this may result into distortion in the results due to probable underestimation of standard error of the regression coefficients. To be more specific, an irrelevant co-variate may emerge as an important covariate leading to inappropriate public health implications. To overcome this problem, the objective of the present work was to deal with multilevel analysis of the data on infant mortality available under second round of National family Health Survey and notify changes in results under traditional regression analysis that ignores hierarchical structure of data. This method provides more accurate results leading to meaningful public health implications. In addition, estimation of variability at different levels and their covariance are also obtained. The results indicate that the community (e.g., state) level characteristics still have major role regarding infant mortality in India. Further, if computational facilities are available, multilevel analysis may be preferred in dealing with data involving hierarchical structure leading to accurate results having meaningful public health implications.
文摘开展针对基于模块化多电平换流器的高压直流(modular multilevel converter based high voltage direct current,M M C-HVDC)输电系统的损耗研究,对高压直流输电系统的设计与优化具有重要意义。提出一种基于模块化多电平换流器的高压直流输电系统损耗计算的实用方法。首先,根据MMC-HVDC输电系统的拓扑结构和器件参数建立M M C-HVDC输电系统及其各个器件的损耗计算模型,并通过仿真计算精确求解M M C-HVDC输电系统及其器件不同运行工况的损耗系列数据;然后再利用数据拟合的方法得到便于工程应用的损耗计算公式;最后,针对厦门柔性直流输电系统工程,采用本文方法求得损耗计算公式,并与实测结果进行了对比分析。分析表明,利用该损耗拟合公式计算和评估MMC-HVDC输电系统的损耗可满足工程精度要求。
