Method for Caution Values Calculation of Dissolved Gases in Transformers Based on Statistical Distribution and Correlation Analysis

Before diagnosed by DGA (dissolved gas analysis) methods, gas caution values, which index the level of gas formation, must be used to evaluate the possibility of incipient faults to reduce the misdiagnosis in the normal state. However, the calculation of these values is now only based on cumulative percentile method without taking into account operating conditions. To overcome this disadvantage, a new approach to calculate the transformer caution values is presented. This approach is based on statistical distribution and correlation analysis, and it takes the individual variation and fluctuation caused by internal and external factors into consideration. Then 6550 transformer DGA data collected from North China Power Grid are analyzed in this paper. The results show that the volume fraction of TH (total hydrocarbon) approximately obeys normal distribution when the 3-sigma rule is used to calculate its caution value. The volume fraction of CO has a strong positive correlation with oil temperature. For H2, the negative correlation with oil temperature is significant when the volume fraction is not very low. The caution value curves for CO and H2 are obtained by regression analyses. Thus, the gas caution values/curves obtained using the new method are not always constant, but vary with oil temperature, which is an advantage of the proposed method compared with cumulative percentile method. The variation of gas caution values/curves also reflects the influence of the external factors, for instance, va- rying with monitoring time ensures that the gas caution values are always consistent with operating status.

The Role of Service Quality,Perceived Value and Trust on Calculative Commitment and Loyalty Intention

Global mobile communication is one of the most dynamic and important service markets.Several researchers suggest using a theoretical approach to develop a much deeper insight into key marketing constructs,such as service quality,customer perceived value,customer satisfaction,perceived switching costs,corporate image,and customer loyalty,is vital to the mobile communications market.This paper aims to investigate the role of service quality,trust,and perceived value on calculative commitment and loyalty intention in the customers of mobile telephone network service providers(MTNSPs).To notify the meaningful factors for the calculative commitment and loyalty intention of the users in using mobile phones,this study focuses on the effect of service quality and perceived value in the trust and identifying the role of trust in forming customer loyalty.As many as 125 users of mobile phone users—house wife were surveyed in Coimbatore,Tamil Nadu,India.The data are analyzed by path analysis.This study shows that service quality has a direct and positive effect on trust,trust has a direct and positive effect on calculative commitment,calculative commitment has a direct and positive effect on loyalty,and direct and positive relationship between perceived value and calculative commitment,perceived value,and loyalty are also confirmed.In terms of mobile telecommunication systems,it is found that the users may exhibit noticeable differences in using this service.This study provides important hints to strengthen the relationship between the network service providers and their customers.

THE SELECTION OF CROWNING VALUES FOR HELICAL GEAR DRIVES

Gear crowning takes an important part in alleviating the concentration of local stresses when misalignment of the flanks exists. It is known that an excessive crowning will lead to a high local stress while an insufficient value will not be able to compensate the alignment error resulting in concentration. The selection of the crowning value is always based on empirical estimation. This paper deals with a theoretical method to determine the crowning value. The distribution forms of contact stresses on the flanks of a crowned pinion and a gear are treated as a series of complete or portions of semi-ellipsoids with the same size. The total volume of which equals the whole contact load. From this point of view a series of equations for the computation of the maximum stress is obtained. The calculation of contact stresses considering the existence of alignment errors gives insight into the selection ora proper crowning value for a gear drive.

Automatic Calculation of Dimension Chains in AutoCAD

In the course of mechanical part designing, process p lanning and assembling designing, we often have to calculate and analyse a dimen sion chain. Traditionally, a dimension chain is established and calculated m anually. With wide computer application in the field of mechanical design and ma nufacture, people began to use a computer to acquire and calculate a dimension c hain automatically. In reported work, a dimension chain can be established and c alculated automatically. However, dimension text values of dimensions composing a dimension chain and these dimensions’ tolerance’s upper values and lower valu es are put into a computer manually, which is inefficient and easy to make mis takes. In order to overcome above difficulties. it is very important to acquir e noted dimensions automatically, furthermore analyse and calculate a dimens ion chain, then show results. At present AutoCAD softwares of Autodesk company h ave been used popularly in mechanical designing. For automatically acquiring noted dimensions, analyzing and calculating a dimension chain in a design draw in AutoCAD, this paper introduces the solvable scheme of automatic dimension acq uisition and dimension chain calculation in AutoCAD by ObjectARX. ObjectARX is a developing tool for AutoCAD. In this paper a dimension chain is expressed b y three matrixes, which respectively stand for dimension text value matrix, tole rance’s upper value matrix and tolerance’s lower value matrix. The developed p rogram can be used to both calculate a assembling dimension chain, and a process dimension chain. When the program running in AutoCAD, noted dimensions comp osing a dimension chain in AutoCAD are selected in turn with a mouse, then the c omputer begin to calculate the dimension chain and results are shown in a dialog box. A running example is given in this paper.

Determination of the Critical Value of Deflection for Embedded Cylindrical Structures

An embedded cylinder is a large-diameter cylinder embedded in a soil foundation. The state of failure of such an embedded cylindrical structure shows large deflection instead of slide and overturn of the traditional gravity type of structure placed on a rubble base or foundation base. The critical value of deflection of the embedded cylindrical structure, which is the maximum allowable deflection for stability calculation of the cylinder, is a vital control value. Through investigation on deflection and soil pressures on an embedded cylinder by model experiments, the variations of the angle of rotation θ of a cylinder with effective anti-overturning ratio η and moment MH of thrust are discussed. On the basis of experimental study, the critical value of deflection of the cylindrical structure is proposed in the paper. Meanwhile, the formulas for calculating deflection of cylinders are derived.

Two Modifications of Weight Calculation of the Non-Local Means Denoising Method

The non-local means (NLM) denoising method replaces each pixel by the weighted average of pixels with the sur-rounding neighborhoods. In this paper we employ a cosine weighting function instead of the original exponential func-tion to improve the efficiency of the NLM denoising method. The cosine function outperforms in the high level noise more than low level noise. To increase the performance more in the low level noise we calculate the neighborhood si-milarity weights in a lower-dimensional subspace using singular value decomposition (SVD). Experimental compari-sons between the proposed modifications against the original NLM algorithm demonstrate its superior denoising per-formance in terms of peak signal to noise ratio (PSNR) and histogram, using various test images corrupted by additive white Gaussian noise (AWGN).

中国大健康产业统计分类与产业规模再测算

由于产业间深度融合,新业态、新模式持续涌现,健康产业的边界不断拓展,原有的健康产业统计分类已不能满足大健康产业的统计需要,官方统计也未测算出健康产业增加值,无法全面、及时反映大健康产业的发展状况。因此,文章首先在健康产业基础上从供给和需求角度界定并拓展大健康产业的内涵及外延;其次,在《健康产业统计分类(2019)》的基础上,基于国民经济核算理论,引入“大健康总产品”概念,聚焦“全生命周期”和“全人群”两个着力点,从全产业链产品供给及全口径人群健康需求两个视角探讨大健康产业统计分类标准,补充和完善大健康产业统计分类;最后,依据现有的投入产出表、经济普查及统计年鉴数据,计算各行业的大健康分离系数,据此推算我国大健康产业及健康服务业增加值。结果显示:2018年我国大健康产业增加值为10.27万亿元,其中健康服务业增加值为7.04万亿元,预测2020年、2030年健康服务业增加值分别为8.46万亿元、21.27万亿元,基本符合《“健康中国2030”规划纲要》对健康服务业发展规模的预期。

基于贝叶斯攻击图的油气生产物联网系统风险评估

针对油气生产物联网系统动态风险评估问题,提出一种基于贝叶斯攻击图的油气生产物联网系统风险评估模型。首先通过对系统进行风险分析,得到入侵证据及系统漏洞,结合入侵证据和漏洞利用成功概率,采用EM算法对训练数据进行数据补全并动态更新贝叶斯攻击图的条件概率参数表,通过条件概率表可计算得出先验概率,结合入侵证据计算得到节点的后验概率,进而得到系统的风险值,考虑资源利用的相关性对风险值进行最终修正。仿真结果分析证明了该模型的有效性和准确性。

波浪能发电装置垂荡浮子PTO系统的建模与计算

为了便捷求出垂荡式波浪能发电装置垂荡浮子的平均功率,对现有的设计计算方法进行了研究。基于波浪理论和Froude-Krylov假定法求解波浪力,应用单自由度有阻尼系统受迫振动理论,将波浪激励力作为对垂荡浮体的输入动力,将发电机的电磁阻力作为主要的阻尼力,建立了质量-弹簧-阻尼振动力学模型,确定了垂荡浮子响应的计算方法,并对实际波浪能发电装置垂荡浮子Power Take Off(PTO)系统列举出计算实例。在算例基础上,对假设条件进行了扩展,应用频率响应曲线、MATLAB软件做出不同参数条件下平均功率三维曲线和输出平均功率数值表,清晰地表明了系统响应状况。研究显示,在波高和频率比一定的条件下,PTO系统平均机械功率随着浮体质量和阻尼力矩的变化具有峰值,围绕峰值区域设计装置的各项参数,能够取得较理想的效果。该建模与计算方法可为实际工程优化设计提供参考。

地基承载力特征值确定土变形模量的探讨

目前我国地基沉降计算主要采用土压缩模量来计算,再用经验系数对计算结果进行修正。这种方法对于一些结构性较强的硬土地基误差较大,主要原因是取样扰动影响。为此,探讨了变形模量与地基承载力特征值的理论联系,在笔者提出的确定变形模量经验方法基础上,总结出依据地基承载力特征值确定变形模量的方法,该方法具有理论依据,可便捷地通过岩土工程勘察报告中常提供的地基承载力特征值确定土的变形模量,能够更为准确计算地基沉降值。采用不同方法(压板试验法、压缩模量推求法、标贯击数法、承载力经验法、依据地基承载力特征值确定变形模量法)计算了若干试验案例,通过对不同方法结果的对比,初步验证了依据地基承载力特征值确定变形模量法是可行的。

储煤筒仓内钢制螺旋溜槽脱落事故分析

螺旋溜槽是块煤仓防碎的重要手段,但在其应用过程中,事故的发生却屡见不鲜。针对某储煤筒仓内钢制螺旋溜槽脱落事故,在现场踏勘的基础上,通过检测、有限元分析和理论计算,分析了钢制螺旋溜槽脱落的原因。结果表明:荷载取值不当是造成此次事故的直接原因,而框架和溜槽结构选型和连接构造不合理是间接原因。溜槽支架宜采用多边形框架结构,也可加设框架间支撑体系;其结构宜选用底板宽度较小的U形或L形;计算时,应取溜槽底板投影一个螺距范围内的全部贮料重力且应考虑放料时的动压;螺旋溜槽计算模型应按空间螺旋曲梁计算,并充分考虑扭矩的影响。

基于仿真技术的在线接地装置阻抗值确定

为了获得运行中变电站接地装置准确接地阻抗值,提出一种基于现场测量数据与CDEGS软件计算模拟结果对比验证,确定接地阻抗值的方法。通过现场测量获得所在地区视在土壤电阻率曲线和运行中接地装置视在接地阻抗值测量曲线。使用CDEGS软件建立包含接地系统及周边构筑物等系统在内的计算模拟模型,基于CDEGS仿真模型,重现现场接地阻抗值测量过程,并计算得到接地阻抗值仿真计算曲线。在仿真计算曲线与现场测量曲线对比吻合后,最终确定接地装置在线接地阻抗实际值。通过实际应用验证了此方法有效性。

中国数字经济核心产业规模再测算研究

针对现有文献在数字经济规模的测算方法方面存在的分歧,首先基于国家统计局发布的《数字经济及其核心产业统计分类(2021)》,明确了投入产出表中的部门分类与数字经济核心产业各细分行业的对应关系;然后基于官方发布的投入产出表及投入产出延长表、学者编制的时间序列投入产出表,结合历次经济普查数据,采取将数字经济核心产业各细分行业的增加值按比例从国民经济各行业增加值中剥离出来的做法,测算了中国1981—2020年数字经济核心产业的规模及其各细分行业的占比;并与代表性文献在同口径下进行了比较,验证了测算结果的稳健性。在此基础上,预测了“十四五”时期各年中国数字经济核心产业可能达到的规模及其各细分行业的占比,并对未来数字经济核心产业的发展趋势以及数字经济统计制度建设进行了展望。

基于MMC平均值仿真模型的损耗快速评估方法

针对模块化多电平换流器(modular multilevel converter,MMC)损耗计算精度和速度难以兼顾的问题,提出一种MMC损耗快速在线评估方法。首先,基于确定的调制和电容电压平衡策略,构建开关频率曲面以反映任意稳态工况下的开关频率;其次,利用平均值模型计算开关频率上限和开关损耗功率上限;再次,结合计算结果和开关频率曲面,近似快速计算实际开关损耗,兼顾计算精度和计算效率;然后,考虑到损耗对仿真结果的影响,利用串联在桥臂上的受控电压源吸收的能量表征损耗,同时提出一种基于衰减函数的开关损耗注入方法,避免产生注入电压尖峰并改善注入效果。最后,在PSCAD中搭建计及损耗注入的MMC平均值仿真模型,验证所提方法的计算效率和准确性。

黑龙江省数字经济核心产业的核算及启示

数字经济是引领未来的新经济形态,是经济提质增效的新变量。选取《黑龙江投入产出表》《中国经济普查年鉴》《中国高技术产业统计年鉴》《黑龙江统计年鉴》以及《中国工业统计年鉴》相关数据,依据《数字经济及其核心产业统计分类(2021)》对黑龙江省数字经济核心产业增加值进行规模测算和结构分析,并与全国整体水平、其他省份的数字经济核心产业进行对比。针对黑龙江省数字经济发展中存在的问题,提出根据自身优势优化数字经济内部结构,引进人才,提高对数据价值的重视程度等相关建议。

高压大功率IGBT器件绝缘结构的电场计算研究综述

随着高压直流输电技术的发展,高压大功率绝缘栅双极型晶体管(insulated gate bipolar transistor,IGBT)器件被广泛应用于各类高压大容量电力换流和控制装备中。然而,在高压大功率IGBT器件的研制过程以及工程应用中,器件内部局部放电现象乃至击穿现象频繁发生,给器件绝缘设计带来巨大挑战。要想实现良好器件绝缘设计,就需要获得器件内部的电场分布,因此实现器件内部电场的准确计算至关重要。文中全面回顾器件内部绝缘结构的建模和计算方法的发展历程,从封装绝缘电场计算、芯片绝缘电场计算以及芯片和封装绝缘耦合电场计算3个方面介绍相关研究的发展历程、适用范围以及相应的不足,最后展望未来器件内绝缘结构电场计算的发展方向。

中国文化产业投入产出表编制、规模测度及波及效应研究

文章基于2002—2020年我国投入产出表数据,运用最新的国民经济行业分类和文化产业分类标准,将传统的投入产出表转换为以文化产业为核心的投入产出表,运用分劈系数将文化产业从国民经济其他行业中剥离出来,测算出文化产业增加值,并进一步对文化产业的波及效应进行分析。结果显示:2002—2020年,我国文化产业增加值规模从2002年的1.07万亿元增加至2020年的8.67万亿元,文化产业已成为我国国民经济发展中的支柱产业;文化产业核心层部门在总产出和增加值规模上远高于文化产业相关层部门以及其他非文化产业部门。波及效应分析结果表明,我国文化产业核心层部门呈现高拉动力、高推动力特征,基础性产业特征显著;而文化产业相关层部门呈现低拉动力、低推动力特征,对其他产业的影响较小。

基于换相角预测计算的高压直流输电双桥共同换相预判方法

高压直流输电系统交流故障下出现双桥共同换相会增大换相失败的风险,提前判断双桥共同换相的发生有利于及时采取措施避免换相失败。为获取对双桥共同换相进行预判所需的高精度换相角预测计算结果,利用拉格朗日中值定理建立换相角与中值时刻的关系,并构造虚拟换相过程用于确定中值时刻。仿真结果表明,所提换相角预测计算方法具有良好的鲁棒性和精度,用于双桥共同换相预判中能有效预判双桥共同换相的发生。

直驱风电并网系统小信号建模与次同步振荡特性

为研究直驱风电经串补线路并网系统的次同步振荡(SSO)问题,以直驱风电-串补系统为研究对象,利用Matlab/Simulink搭建系统小信号模型,计算模型初值,基于特征值分析法研究了不同参数对系统SSO阻尼特性的影响。结果表明,直驱风电-串补系统存在一个频率为40.44 Hz,阻尼比为-0.039的SSO模式。当系统滤波电感和直流电容增大时,系统的SSO阻尼增大,当系统串补度、GSC直流电压控制参数增大时和系统的SSO阻尼减小。