为解决在高精度计量校准领域采用三同轴法测试通信电缆转移阻抗的过程中由于外筒分布参数、接头连接参数等因素严重影响量值溯源准确性的问题,通过分别测量夹具校准件和待测电缆S参数,运用网络级联算法计算屏蔽衰减,最后计算转移阻抗的...为解决在高精度计量校准领域采用三同轴法测试通信电缆转移阻抗的过程中由于外筒分布参数、接头连接参数等因素严重影响量值溯源准确性的问题,通过分别测量夹具校准件和待测电缆S参数,运用网络级联算法计算屏蔽衰减,最后计算转移阻抗的方法能有效消除测量误差,从而提升转移阻抗测量准确性。由三同轴法测量原理出发,分析标准测试方案,详细论述二端口S矩阵与A矩阵换算和网络级联算法,推导出转移阻抗精确测量方案。最后通过实验进行了验证,并采用蒙特卡洛法(Monte Carlo Method,MCM)进行测量不确定度评定,评定结果为Ur=8%(k=2)。展开更多
在政策与市场的推动下,我国电动汽车充电基础设施保有量大幅增长。本文从运营商视角出发,运用因子分析对赣州市下属县级区域公共充电站进行效能评估。本文以赣州市周边县及区域充电站为对象,并与加入部分中心城区站点对比。首先本文筛...在政策与市场的推动下,我国电动汽车充电基础设施保有量大幅增长。本文从运营商视角出发,运用因子分析对赣州市下属县级区域公共充电站进行效能评估。本文以赣州市周边县及区域充电站为对象,并与加入部分中心城区站点对比。首先本文筛选并确认充电站运营评估指标体系,指标数据由供电局提供。然后运用spss软件对数据进行因子分析,经因子分析得出KMO取样适切性量数大于0.6,表明数据适合进行因子分析,并得出站点效益性和设备稳定性两个主因子。通过加权平均计算每个站点综合得分,综合得分大于0的站点代表高于平均水平,发现综合得分大于0的站点占比35.7%,其中县级区域仅8个,占县及区域总数的25%,表明县级区域大多数站点效能水平较低,提升空间大。最后,从运营商和政府层面、充电站规划建设方面制定提出建议。Driven by policies and the market, the retention volume of charging infrastructures for electric vehicles in China has increased significantly. From the perspective of operators, this paper conducts an efficiency evaluation of public charging stations in county-level regions under Ganzhou City using factor analysis. This paper takes the charging stations in the surrounding counties and regions of Ganzhou City as the object and makes a comparison by adding some central urban area stations. Firstly, this paper screens and confirms the operation evaluation index system of charging stations, and the index data is provided by the power supply bureau. Then, SPSS software is used to conduct factor analysis on the data. Through factor analysis, it is concluded that the KMO sampling adequacy measure is greater than 0.6, indicating that the data is suitable for factor analysis, and two main factors, namely site efficiency and equipment stability, are obtained. By calculating the comprehensive score of each station through weighted average, stations with a comprehensive score greater than 0 represent a level above the average. It is found that the proportion of stations with a comprehensive score greater than 0 is 35.7%, of which only 8 are in county-level regions, accounting for 25% of the total number of counties and regions, indicating that the efficiency level of most stations in county-level regions is low and there is a large space for improvement. Finally, suggestions are formulated and proposed from the aspects of operators and the government, as well as the planning and construction of charging stations.展开更多
背景:以往的研究表明经皮神经电刺激对缓解多种疾病引起的疼痛症状有效,但其对缓解膝骨关节炎患者疼痛的确切疗效仍存在争议。且经皮神经电刺激可分为高频和低频两种模式,目前关于其分别针对膝骨关节炎疼痛的疗效尚不明确。目的:荟萃分...背景:以往的研究表明经皮神经电刺激对缓解多种疾病引起的疼痛症状有效,但其对缓解膝骨关节炎患者疼痛的确切疗效仍存在争议。且经皮神经电刺激可分为高频和低频两种模式,目前关于其分别针对膝骨关节炎疼痛的疗效尚不明确。目的:荟萃分析高频经皮神经电刺激与低频经皮神经电刺激缓解膝骨关节炎疼痛的作用。方法:计算机检索Pub Med,Embase和Cochrane数据库以及手工检索国内外公开发表的有关经皮神经电刺激缓解膝骨关节炎疼痛的随机对照试验,所有检索截止至2014年2月。严格评价纳入研究的方法学质量并提取数据,2名研究人员独立运用Rev Man 5.2软件对数据进行统计分析。结果与结论:共纳入10项随机对照试验,累计519例研究对象。荟萃分析结果显示,与对照组相比,高频经皮神经电刺激可显著缓解膝骨关节炎患者的疼痛[MD=-0.56,95%CI(-0.98,-0.15),P=0.008];与对照组相比,低频经皮神经电刺激并未缓解膝骨关节炎患者的疼痛[MD=-0.13,95%CI(-1.63,1.38),P=0.87];与低频经皮神经电刺激相比,高频经皮神经电刺激可显著缓解膝骨关节炎患者的疼痛[MD=-0.85,95%CI(-1.32,-0.37),P=0.000 5]。提示高频经皮神经电刺激可一定程度缓解膝骨关节炎患者的疼痛症状,而对比高频经皮神经电刺激,低频经皮神经电刺激对缓解膝骨关节炎患者的疼痛症状无明显作用。但由于样本量较小,纳入各研究在参数选择存在差异,存在一定局限性,此结论未来尚需更多高质量的随机对照试验进一步证实。展开更多
文摘为解决在高精度计量校准领域采用三同轴法测试通信电缆转移阻抗的过程中由于外筒分布参数、接头连接参数等因素严重影响量值溯源准确性的问题,通过分别测量夹具校准件和待测电缆S参数,运用网络级联算法计算屏蔽衰减,最后计算转移阻抗的方法能有效消除测量误差,从而提升转移阻抗测量准确性。由三同轴法测量原理出发,分析标准测试方案,详细论述二端口S矩阵与A矩阵换算和网络级联算法,推导出转移阻抗精确测量方案。最后通过实验进行了验证,并采用蒙特卡洛法(Monte Carlo Method,MCM)进行测量不确定度评定,评定结果为Ur=8%(k=2)。
文摘在政策与市场的推动下,我国电动汽车充电基础设施保有量大幅增长。本文从运营商视角出发,运用因子分析对赣州市下属县级区域公共充电站进行效能评估。本文以赣州市周边县及区域充电站为对象,并与加入部分中心城区站点对比。首先本文筛选并确认充电站运营评估指标体系,指标数据由供电局提供。然后运用spss软件对数据进行因子分析,经因子分析得出KMO取样适切性量数大于0.6,表明数据适合进行因子分析,并得出站点效益性和设备稳定性两个主因子。通过加权平均计算每个站点综合得分,综合得分大于0的站点代表高于平均水平,发现综合得分大于0的站点占比35.7%,其中县级区域仅8个,占县及区域总数的25%,表明县级区域大多数站点效能水平较低,提升空间大。最后,从运营商和政府层面、充电站规划建设方面制定提出建议。Driven by policies and the market, the retention volume of charging infrastructures for electric vehicles in China has increased significantly. From the perspective of operators, this paper conducts an efficiency evaluation of public charging stations in county-level regions under Ganzhou City using factor analysis. This paper takes the charging stations in the surrounding counties and regions of Ganzhou City as the object and makes a comparison by adding some central urban area stations. Firstly, this paper screens and confirms the operation evaluation index system of charging stations, and the index data is provided by the power supply bureau. Then, SPSS software is used to conduct factor analysis on the data. Through factor analysis, it is concluded that the KMO sampling adequacy measure is greater than 0.6, indicating that the data is suitable for factor analysis, and two main factors, namely site efficiency and equipment stability, are obtained. By calculating the comprehensive score of each station through weighted average, stations with a comprehensive score greater than 0 represent a level above the average. It is found that the proportion of stations with a comprehensive score greater than 0 is 35.7%, of which only 8 are in county-level regions, accounting for 25% of the total number of counties and regions, indicating that the efficiency level of most stations in county-level regions is low and there is a large space for improvement. Finally, suggestions are formulated and proposed from the aspects of operators and the government, as well as the planning and construction of charging stations.
文摘背景:以往的研究表明经皮神经电刺激对缓解多种疾病引起的疼痛症状有效,但其对缓解膝骨关节炎患者疼痛的确切疗效仍存在争议。且经皮神经电刺激可分为高频和低频两种模式,目前关于其分别针对膝骨关节炎疼痛的疗效尚不明确。目的:荟萃分析高频经皮神经电刺激与低频经皮神经电刺激缓解膝骨关节炎疼痛的作用。方法:计算机检索Pub Med,Embase和Cochrane数据库以及手工检索国内外公开发表的有关经皮神经电刺激缓解膝骨关节炎疼痛的随机对照试验,所有检索截止至2014年2月。严格评价纳入研究的方法学质量并提取数据,2名研究人员独立运用Rev Man 5.2软件对数据进行统计分析。结果与结论:共纳入10项随机对照试验,累计519例研究对象。荟萃分析结果显示,与对照组相比,高频经皮神经电刺激可显著缓解膝骨关节炎患者的疼痛[MD=-0.56,95%CI(-0.98,-0.15),P=0.008];与对照组相比,低频经皮神经电刺激并未缓解膝骨关节炎患者的疼痛[MD=-0.13,95%CI(-1.63,1.38),P=0.87];与低频经皮神经电刺激相比,高频经皮神经电刺激可显著缓解膝骨关节炎患者的疼痛[MD=-0.85,95%CI(-1.32,-0.37),P=0.000 5]。提示高频经皮神经电刺激可一定程度缓解膝骨关节炎患者的疼痛症状,而对比高频经皮神经电刺激,低频经皮神经电刺激对缓解膝骨关节炎患者的疼痛症状无明显作用。但由于样本量较小,纳入各研究在参数选择存在差异,存在一定局限性,此结论未来尚需更多高质量的随机对照试验进一步证实。
