雷电流幅值概率计算公式

雷电流幅值概率是表征雷电活动频度,计算雷击闪络率的必要参数.通过累积概率函数和概率密度函数比较了实际雷电流幅值分布和规程中概率分布公式计算结果,发现实测值所对应的雷电流幅值概率和规程法公式存在很大的差异,该差异随雷电流幅值的减少而增大.通过比较实测值和IEEE标准推荐公式等其他类似公式,认为上述公式与实测雷电流概率分布...     

对凝汽器传热系数公式修正的研究

在凝汽器传热系数的计算中,通常采用的是前苏联别尔曼公式,通过实例发现别尔曼公式中凝汽器蒸汽负荷和循环水流量对传热系数的修正不足,造成了别尔曼公式计算结果与实际运行值存在偏差.针对别尔曼公式在循环水流量和蒸汽符合偏离设计值时产生的偏差给出了改进的修正系数,并对原有修正存在偏差给出了理论解释,计算证明改进的修正系数获得了良好的效果.     

焊接结点短裂纹疲劳强度的研究

本文在研究焊接结点切口根部短裂纹和焊接残余应力对结点疲劳强度影响的基础上,推导出了计算结点有效应力集中系数卢的公式.应用这一公式计算了几类焊接结点的β值,经与实验结果比较,计算值与实验值吻合较好,本文研究结果,对工程应用有参考价值.     

电厂锅炉烟气Yong值计算公式的讨论与分析

本文从热量Ｙｏｎｇ和工质Ｙｏｎｇ两个基本概念出发，论证了计算电厂锅炉烟气Ｙｏｎｇ值两种方法的理论依据，证明了两种计算方法的等效性。同时指出文献〈１〉〈２Ｍ〉中计算烟气Ｙｏｎｇ值的公式有误，文献〈３〉中计算烟气Ｙｏｎｇ值的公式是正确的。     

计算架空线路分布参数的新方法

提出一种考虑土壤电阻率影响的架空输电线路分布参数计算新方法。介绍和分析了Carson公式和Dubanton公式,提出用函数代替的方法简化Carson校正项来避免Carson公式计算困难、Dubanton公式误差较大的问题,总结出一种计算精度较高的架空线路分布参数计算新方法。误差分析表明,该方法的计算公式简单、计算值连续、计算结果较精确。该方法可替代Dubanton公式进行相应的计算和分析,在电力系统分析、仿真及计算中具有很强的实用价值。     

电站燃煤锅炉煤粉细度控制值研究

提出了一定条件下煤粉颗粒完全燃尽临界直径的概念,并依据煤粉颗粒分布特性和煤粉颗粒燃尽临界直径计算得出不同煤粉细度分布下的未燃尽率,分析了煤粉颗粒燃尽临界直径、煤粉细度、挥发分含量等对未燃尽率的影响。分析表明,对于低挥发分难燃煤种,按挥发分确定煤粉细度的经验公式计算值与经济煤粉细度值相比偏大;对于Vdaf>35%的燃煤,按挥发分确定煤粉细度的经验公式计算值与经济煤粉细度值相比偏小;对于其它燃煤,按挥发分确定煤粉细度的经验公式计算的煤粉细度值在经济煤粉细度值范围内,但经济煤粉细度值需要通过试验确定。     

基于二维水动力模型与经验公式的桥梁壅水计算及其对比分析

本文以海南省南渡江六座桥梁为例,利用MIKE21数值模型计算不同频率洪水下各桥的桥前壅水值,并与经验公式计算结果进行对比分析。结果表明:MIKE21数值模型能够较好地模拟复杂地形,率定与验证过程中相对误差均小于5%,纳西效率系数均大于0.8;与二维模型计算结果相比,D’Aubuisson与Henderson经验公式计算结果偏小,在桥墩阻水面积比小于10%的情况下,Henderson公式计算结果比D’Aubuisson公式计算结果更接近二维模型计算值;而铁科院陆浩公式计算结果偏大。因此,对于处在复杂地形或是所在河道具有重要防洪任务的桥梁,建议采用数学模型计算壅水值,以便求得更加合理的计算结果,为防洪影响评价工作提供分析计算的依据。     

PM_(2.5)对理论盐密值的影响研究

根据污闪事故发生时的环境监测数据,大气环境污染及其污染性质也是影响输变电设备外绝缘表面污秽程度的因素,而污染物粒径较小的地区积污增长速度较大。因此,针对某些学者提出的理论盐密值与大气环境参数间的经验公式,提出了纳入PM_(2.5)后的经验公式修正建议。分别根据纳入PM_(2.5)的经验公式和未纳入PM_(2.5)的经验公式,计算了理论盐密值,并与安装在监测点附近的光传感器盐密在线监测装置的实测数据进行了对比分析。利用纳入PM_(2.5)后的经验公式的ESDD理论计算值与实际值较为吻合,而未纳入PM_(2.5)的ESDD理论计算值与实际测量结果差异率较大。在可实时获取大气环境参数的地区,可以考虑利用纳入PM_(2.5)后的经验公式推算该地区的理论盐密值的实时变化情况,及时掌握该地区电网污秽等级的变化。     

关于电感值的工程变通计算和测试法

简要介绍用常规方法计算电感值存在的困难,推导出一种计算电感的公式,从而绕开了对磁材磁性能指标如Bs及μ值的准确了解,顺利计算出所需的电感值.     

矩形接地网接触电势的解析计算法

此文提出了计算矩形接地网最大接触电势的新公式。验证计算表明，当矩形地网的长宽比ε≤１６时，新公式的计算值对计算机数值计算法的计算误差小于１０％。     

电厂EAM设计模型研究

电厂MIS已成为新建电厂工程设计的一个重要组成部分,企业资产管理系统(EAM)作为新建电厂MIS的重要组成部分,需要研究一个面向电厂企业级EAM设计模型,探索一个既有针对资产密集型电厂实施的资产管理先进思想,又有针对满足企业适应市场机制需要的ERP管理思想的电厂EAM设计模型,为新建电厂MIS设计提供了一个途径。     

SO2,NOx与CO2排气罚款的应有数量级

作为推广环保措施的辅助手段之一，对污染物排放实施罚款在现阶段是一种行之有效的途径。为了切实收到促进环保之效，必须定出合理的罚款数量级。本文结合我国电力工业的具体国情，从两种不同角度分析探讨了燃煤电站常见污染气体的应有罚款尺度：一是罚款数额应至少与污染治理投资费用相当；二是罚款数额只应比电厂收入低一至两个数量级。从两个角度所得结论基本一致：对ＳＯ２及ＮＯｘ的罚款应不少于１０００元／吨，而对ＣＯ２的罚款应不少于１０元／吨。这些结论对考虑电站建设与制定我国相应的环保法律与法规有参考价值。     

Extinction coefficients of hemoglobin for near-infrared spectroscopy of tissue.

Extinction coefficients of hemoglobin have been studied for five decades by clinical chemists and biochemists, particularly for laboratory spectrophotometric measurements. In the last ten to 15 years, near infrared spectroscopy (NIRS) and imaging for tissue vascular oxygenation, breast tumor detection, and functional brain imaging have been intensively developed for in vivo measurements by groups of physicists, biomedical engineers, and mathematicians. In the approach of NIRS, NIR light in the wavelength range of 650-900 nm is utilized to illuminate tissue in vivo, and the transmitted or reflected light through tissue is recorded for the quantification of hemoglobin concentrations of the measured tissue vasculature. In order to achieve mathematical conversion from the detected light intensity at different wavelengths to hemoglobin concentration, extinction coefficients of hemoglobin, /spl epsiv/, must be used. While the engineers and physicists working in the NIR field have found the correct /spl epsiv/ values to use, there has been controversy on what /spl epsiv/ values should be used for in vivo NIRS in comparison with the conventional e/spl epsiv/ that most biochemists have used in the laboratories for in vitro measurements. The purpose of this article is to address this issue and help biomedical engineers and physicists gain a better understanding of e to be used for NIRS and NIR imaging.     

利用旋挖工艺优化嵌岩桩的勘测方案

现行的标准对端承桩的勘探点间距与持力层层面坡度的变化情况做出了严格的规定,但在以基岩作为桩端持力层的场地,由于受沉积环境与地质构造的影响,持力岩层的层面变化较大,如果严格按打入桩的要求来控制,则勘察工作量将大幅增加,而且也很难做到。旋挖桩的成孔过程客观上起到了钻探的作用,在施工过程中可以很好进行桩端持力岩层风化程度的鉴别,有效地控制进入持力层的深度,确保桩侧与桩端阻力的发挥。本文结合工程实例,探讨了在基岩地区采用旋挖桩时,可以对勘探点间距与持力层层面坡度变化的规定作适当的放宽处理,旨在为旋挖桩的勘测方案优化积累一些有益的经验。     

Probability distributions of outputs of stochastic economic dispatch

This paper introduces an approach to carry the uncertainty about the wind speed through the optimization for the economic dispatching. This approach uses simulated wind speed data points for inputs to economic dispatch models and produces data for estimating the probability distributions of optimal fossil fuel generation outputs, transmission loss, and total cost of power generation. Large samples of simulated data allow statistical analyses of the outputs such as the mean, median, percentiles, and confidence intervals for each output variable, plots of distributions of all output variables, and correlation measures for examining relationships between pairs of the output variables. Through the proposed algorithm, a generation expansion planner can perform useful analyses without executing the algorithm repeatedly. The algorithm and its results are illustrated through an example of an economic dispatch model and a model for the distribution of the wind speed based on a forecast for the planning target time.     

Domain of stability of ac/dc power systems

The domain of stability (DOS) of a dynamic system is the sub-state space within which the system converges to a stable equilibrium state if the operating point varies because of a disturbance. The cell mapping technique has been widely used to find the DOS of second-order systems. However, there is no generic method reported in the literature for finding the DOS of any system of order greater than two, other than for ac power systems or for ac/dc power systems with dc dynamics omitted. For these two systems, the DOS can be found using the transient energy function (TEF) because a TEF has been available only for ac-dynamics-only systems. The DOS for ac/dc systems with dc dynamics has not been found because a TEF for dc systems with dc dynamics was not available until the authors recently derived one. In this paper, the existing cell mapping technique is improved to find the DOS of systems of order greater than two. This improved cell mapping technique and the recently developed TEF for dc systems have been used to find the domains of stability of ac/dc systems.     

Verification of the seismic resistance of gas-insulated switchgear(GIS)

A brief introduction to the background of seismic requirements is given, and the test procedure for demonstrating the capability of gas-insulated switchgear (GIS) to withstand seismic stresses up to highest ground accelerations of 0.75 g. are described. The verification methods for checking the test object after test are also described. As vibrational tests are very cost-intensive and therefore can only be performed with a representative switchgear arrangement, a calculation method for demonstrating the seismic withstand behavior of practical switchgear arrangements is presented. The tests and calculation results demonstrate the suitability of a three-pole common enclosed GIS design for 145/170 kV for horizontal ground accelerations up to 0.75 g     

FIDIC合同条件下国际承包工程的延期及其费用索赔

以巴基斯坦巴罗塔工程C-03合同为背景，简述了在FIDIC施工合同条件（1999年版）下，承包商由于非自身原因提出延长工期索赔的合同依据，以及在延期索赔过程中应遵循的程序和原则。还介绍了承包商在巴罗塔C-03合同下成功地完成延长工期索赔的步骤，对时间索赔报告和费用索赔报告的编制原则和方法进行了总结。     

Planning and Protection Implications of Reduced Fault-Withstand Time of Power Transformers

The recent revisions (1980-1983) to the standards for power transformers in both the U.S.A. and Canada call for corresponding revisions in many related planning and protection practices. Particularly, it is found that the reduction to 2 seconds for maximum through faults on transformers and the necessity to include a value for system impedance in the specification of the larger transformers will have significant effects on previous practices for planning, protection, operations, loading and specification. This paper discusses a number of these effects, with an emphasis from a protection point of view.     

Evaluation of the stability of intracortical microelectrode arrays.

In order to use recorded neural activities from the brain as control signals for neuroprosthesis devices, it is important to maintain a stable interface between chronically implanted microelectrodes and neural tissue. Our previous paper introduced a method to quantify the stability of the recording microelectrodes. In this paper, the method is refined 1) by incorporating stereotypical behavioral patterns into the spike sorting program and 2) by using a classifier based on Bayes theorem for assigning the recorded action potentials to the underlying neural generators. An improved method for calculating stability index is proposed. The results for the stability of microelectrode arrays that differ in structure are presented.