Suppression of Periodic Narrowband Interferences in Cable Partial Discharge Detections

There are background noises and interferences in the signal acquired,due to partial discharge(PD) detection system covers a broad frequency band.To suppress periodic narrowband signal which is a quite serious interference in PD measurement,the existing suppression method is introduced,the new method of wavelet packet transform is mainly studied to de-noise the periodic narrowband in XLPE cable PD detection system,which is based on the db4 basic wavelet using soft threshold.The results of the experiment show that wavelet packet transform is effective in restraining the periodic narrowband interferences to extract the PD pulses in XLPE cable PD monitoring system.     

Floyd Dijkstra Algorithm Applied to the Design of Cable Laying

On the application of F D(Floyd Dijkstra) algorithm to the design of cable laying,we provide a method to achieve optimal design of cable laying in this paper,and it is verified by practical examples.     

Prediction of crosstalk characterisation in cables bundles

Based on the heterogeneity of cable bundles and the randomness of wire spacing in cable bundles, this paper adopts the statistical theory to explore a method to predict the uneven cable bundle crosstalks. Under the assumption of electrically small and weak coupling, the mean value and standard deviation of the near end crosstalk voltage ratio are derived. 273RDSI numerical simulations are used to predict worst case crosstalk and to test the model effectiveness . The difference of the wire number and the bundles height from the ground are analyzed. The results indicate that for a given number of wires by increasing the bundle height the mean value increases, whereas the standard deviation is substantially independent of height. Moreover, the standard deviation decreases with the number of sections. By increasing the number of wires, both the mean value and the standard deviation decrease, whereas the sensitivity of the mean value to the bundle height increases.     

基于EC-Probe仪器的土壤盐分原位测定及其在河北坝上地区的应用研究

目前中国测定土壤含盐量主要使用土壤浸提液法,而这种传统的方法操作繁琐,原位测定法相对更为便捷,但应用较少。使用EC-Probe仪器原位测定河北坝上部分地区土壤电导率,部分土样采用实验室土壤浸提液电导率法建立土壤盐分与土壤电导率之间的转换模型,通过该模型对坝上地区不同土地利用类型同一深度的土壤盐度进行测量,并分析了不同深度土壤盐度分布的主要规律。结果发现沼泽、耕地、森林、河漫滩和草地的土壤含盐量依次下降,研究发现该研究区域目前各种土地利用类型的土壤盐度均未达到盐碱化标准,但沼泽地和耕地的盐碱化风险较高,需加强生态保护。     

Parametric Analysis of the Cable''s Vortex-Induced Vibration of Submerged Floating Tunnel

The cable's motion was modeled by a spring-mass-damper system. The flow field was calculated by RSM combined with the enhanced wall function model and the vibration equation of the cable was solved by the Four Step Runge-Kutta Algorithm, which was written into FLUENT software to be analyzed. It was adopted to analyse the factors influencing vortex-induced vibration of submerged floating tunnel cable, such as mass ratio, damping ratio of the cable and whether to consider streamline movement. The main conclusion included: mass ratio has little influence on the transverse vortex induced vibration amplitude of the cable, but has a big influence on the region of the reduced velocity; damping ratio almost has little influence on the region of the reduced velocity of cable's viv, but has an influence on the cable's vibration amplitude significantly; In the case of low-mass ratio, considered the impact of the cable streamline movement, the transverse vortex-induced vibration amplitude is bigger than not considered the case.     

Effect of High-frequency Thermal Disturbance on Soil Temperature around the Metro Tunnels

Soil temperature prediction model around the subway metro tunnels is constructed with the consideration of coupled heat transfer between range temperature and surrounding soil. Finite difference method is adopted for numerical solution of the model, and the solving results in certain conditions are compared to validate the analytical solution. The high-frequency thermal disturbance brought by train operation is simplified into three different forms, and the predictive model of soil temperature is used to calculate the corresponding soil temperature response. It is indicated that temperature fluctuations of range air and the wall are accompanied with high-frequency thermal disturbance, but the impact on soil temperature distribution inside is limited.     

A New Method to Measure Cable Force and Its Application in Cable Structures

In cable structures cables are very important components. The magnitude of cable pretensioning is a vital parameter in the design of cable structures and a crucial component in controlling the construction of such structures. Developing a new sensor type is an innovative theme in the monitoring and control of cable structures construction. Based on the elastic magnetic characteristics of ferromagnetic material, we introduce a theory of an elastic magnetic method to measure cable force and developed a new flux sensor. Applying this method in the model test of an hyperbolic cable net demonstrates that it can acquire the accurate cable force value conveniently. This study can provide scientific references for structural engineering.     

Comparision of Theoritical Solutions and Ultimate Span-Length between FRP Cables and Steel Cables

As the self weight of cable affects mechanical behavior obviously with the inerease of span length.FRP (fiber reinforced polymer) cable that has the lighter weight than the conventional cables has advantage for long span structures.The analysis of single cable is the fundamental theory for the design of cable structures.Based on different considerations of gravity loads.the solutions of the single cable on gravity loads have three sets of solutions: parabola solution.catenary solution and elastic catenary solution.And the equations for the three sets of solutions are derived by taking the end tension force of cable as the control parameter.The comparison between FRP cables and steel cables is conducted by elastic catenary solution.and the results show that the lager span structure can be realized by FRP cables.The precision for the parabola solution and catenary solution is compared for stay cables and horizontal cables.and the proper ranges of both approximate methods are proposed.Based on the above methods.the ultimate span length of FRP cable and steel cable are analyzed.It is concluded that the ultimate span of FRP cable is 4.4 times larger than that of steel cable.     

Nonlinear Response and the Dynamic Stability of Viscoelastic Cable

Based on one dimensional constitutive equations of Revlon materials and the motion equations of the cable, the partial differential equations of the viscoelastic cable in inner and outer of plan under the gravity are investigated. Using Galerkin's method, a system of nonlinear ordinary equations is obtained. The analysis methods of the dynamic stability of viscoelastic cable are given. Finally, the effect of dynamic response of the cable, which is produced by elastic and viscoelastic parameters, is testified by the research of digital simulation.     

The Calculation of Transient Overvoltages on the Signal Cable Conductors Ocurring Equipment Faulting in Power System

This thesis studies circuit model for calculating transient overvoltages on the signal cable conduuctors,and the computational method and program of cable parameters.The transient overvoltages on the signal cable conductors ocurring equipment faulting in a 500 kV power system is calculated by EMTP.     

A Simple Model for Predicting Daily Mean Soil Temperatures

Based on measurements in 3 different types of soil (clay, sand, peat) linear regression equations between daily air temperature (2 m) and soil temperature (2, 5, 10, 20, 50 cm depth) are calculated for all months of the growing season. The equations show a significant seasonal dependence and the best correlations in the upper 10 cm of soil. Differences depending on the type of soil are relatively small. Correction terms involving cloudiness and thermal inertia of the soil during a sudden warming or cooling period complete the prediction model. Standard deviations between predicted and measured values have been found within 1.5 K in most cases. Lastly a generally applicable method for calculating regression equations at any station is introduced. The application of this method to different sites and types of soil in Bavaria and other regions of Germany shows a good agreement with measured values.     

Method of Cable Tension Controlling in the Long span Cable stayed Bridge Construction

In allusion to the cable tension controlling problem in the parallel strand stayed cable construction, on the basis of construction techniques of applying tension loads one by one, the mechanical model of the cable girder tower in the process of construction was established. With the equal cable tension as a goal, the formula was deduced with the method of forward analysis, which could be used to calculate the initial tension of each strand in construction. The effect of temperature variations on the initial tension could be eliminated by using the formula with the method of equivalent tension. Moreover, a method was proposed to measure the cable tension in the processes of construction and performing the function. Finally, the practice in one cable stayed bridge in the north indicated that 1) the uniform cable tension could be obtained by the proposed method; 2) the tension error range of whether a single strand or the whole stayed cable was within 5%, and the result could meet the needs in construction control; 3) the method could provide reference for the similar stayed cable construction.     

Self-balance Principles and Formulae for Axle-linked Cable-car

Even if pulled by single wire rope, the axle-linked cable-car can under some conditions automatically balance the eccentric moment caused by the carried loads. This paper expounds the self-balance principles of the four-wheel axle-linked cable car, deduces the associated formulae and analyzes the conditions for its application, laying a theoretic foundation for the design of transverse container cable car.     

不同植被覆盖下土壤水分遥感监测方法的比较研究

为了研究不同植被覆盖程度下多种土壤水分遥感监测模型的适用性,提高大面积土壤水分遥感监测的可行性和精度,本研究利用辽宁省52个气象站2008—2010年土壤相对湿度人工观测资料以及对应时段的卫星遥感资料,采用热惯量、能量指数、植被供水指数法进行土壤水分的遥感监测,在低、中、高植被覆盖条件下对比3种定量反演土壤水分的遥感模型,并与人工观测资料建立线性、指数、对数拟合。结果表明：在中低植被覆盖期,热惯量法最适合,与0~20 cm的平均土壤相对湿度的对数相关最好;高植被覆盖期,能量指数法稍好于植被供水指数法,与0~10 cm的平均土壤湿度的对数相关最好。     

覆盖生态木屑对‘染井吉野’樱花根系分布特征的影响

树木的根系分布是影响灌溉效果的重要因素,为实现园林树木的科学灌溉,对‘染井吉野’樱花的根系分布特征和覆盖生态木屑对根系分布特征的影响开展研究。采用根钻法对玉渊潭公园内大面积种植的‘染井吉野’樱花根系进行定点逐层取样,利用Win-RHIZO Pro根系分析系统分析根的总长度、直径小于1 mm的根的总长度、根的投影面积、根的表面积和根尖计数等指标。结果表明：‘染井吉野’樱花的吸收根水平方向可以伸展长达6 m,垂直方向上则主要集中在0~20 cm的土层内;铺设生态木屑对土壤表层樱花根系具有明显的促进作用,铺设不同厚度生态木屑对樱花根系分布特征影响不同,覆盖5~10 cm厚生态木屑后樱花根系总长度达到(782.98±401.29) cm,是不铺生态木屑的樱花根系总长度的10倍,是其他试验组的2倍以上。樱花属于浅根系树种,城市公园环境使‘染井吉野’樱花根系主要分布于土壤表层,但分布范围甚广,能够达到树干投影面积的2倍;铺设生态木屑促使樱花根系向土壤表层集中,铺设5~10 cm厚的生态木屑可以有效促进土壤表层樱花根系生长,但对土壤深度20 cm以下的樱花根系影响较小。     

土壤含水量高光谱遥感定量反演研究进展

高光谱遥感因其光谱信息丰富,在土壤含水量的反演中得到了广泛的应用。通过对土壤含水量遥感监测方法进行了归纳总结,对比分析了微波法、热红外法、光学法和高光谱法监测土壤含水量的优缺点以及适用范围;重点分析总结了土壤含水量高光谱遥感定量方法,简要阐述了统计模型和机理模型反演土壤含水量的研究进展,特别对辐射传输模型和几何光学模型等两个机理模型进行了说明,将近年来国内外学者在基于机理模型的土壤含水量遥感反演研究中获得的成果进行了归纳总结,并提出了存在的问题以及今后的研究方向。     

Analyse critique d'une methode d'estimation de la conductivite thermique d'un sol in situ

A numerical method for determining the thermal conductivity of a soil in situ is proposed. It requires the measure of the temperature at three levels in the soil. From the knowledge of the boundary conditions (temperatures at the top and the bottom of the soil layer) and an estimation of the initial the mal profile, the temperature at the intermediate level can be calculated by integration of the monodimensional heat conduction equation with a numerical method (finite elements method). The boundary conditions are interpolated by the FOURIER series. The heat capacity is calculated according to the model of DE VRIES. The thermal conductivity is estimated by minimizing the residual sum of squares between calculated and measured temperatures at the intermediate level. The soil layer can be considered either homogeneous or stratified in two sub-layers. Using simulated temperature data, the optimal conditions of use of the method are defined and the sensitivity of the method to errors made on the measure of the temperature and on the position of the temperature probes is studied.In the case of an homogeneous soil layer, the method yields a good estimation of the thermal conductivity (error ≤1%) with a 4 hours period of estimation, whatever the position of the intermediate probe. The more precise estimation is obtained with an intermediate probe placed at the middle of the layer and with a high thermal amplitude. The method is not sensitive to errors made on temperature measures (biased or truncated measures) if the estimation is made on a period of 24 hours. It is highly sensitive to errors made on the position of the temperature probes.In the case of a stratified layer, the method allows to estimate the thermal conductivity of each sub-layer whatever the position of the intermediate probe if the period of estimation is at least 12 hours. The method is very sensitive to errors made on temperature measures (whatever the duration of the estimation period), on the position of the temperature probes and on the position of the limit between the two sub-layers. Therefore, its use for a stratified soil layer seems delicate.     

河北省无公害果品基地土壤重金属含量分析及土壤环境评价研究

摘要：本文在河北省选取12个县的无公害果品产地作为土样采集点,分析土壤中重金属Hg、As、Pb、Cr、Cd的含量及其污染状况,利用SPSS软件分析重金属元素间的相关性;以《土壤环境质量标准》GB15168—1995二级标准为评价标准,采用单项污染指数法和内梅罗综合污染指数法相结合的方法,对研究区土壤环境质量进行评价。结果表明：河北省无公害果品生产基地土壤污染综合评价值范围在0.085～0.991之间,等级范围在Ⅰ～Ⅲ级之间,其中８个县评价等级为Ⅰ级;１个县为Ⅱ级;３个县为Ⅲ级,各重金属之间除Pb与Cd在0.05水平下呈显著负相关性,其它重金属元素之间没有显著相关性。研究区土壤重金属综合污染评价状况为安全级,土壤中重金属元素含量状况可以满足无公害食品生产基地的建设要求。     

基于连接酶检测反应的NPY基因多态与清远麻鸡繁殖性状的相关性研究

基因多态性蕴藏着大量遗传信息,分型技术是研究多态性的主要研究手段。本文建立了一个基于聚合酶链反应-连接酶检测反应的基因多态性检测系统,探讨清远麻鸡神经肽Y基因（NPY）的多态性,并分析其对清远麻鸡开产日龄、开产蛋重、开产体重、40周平均蛋重、50周平均蛋重以及52周产蛋数的遗传效应。对NPY基因转录起始去4 bp的缺失突变进行基因型分型,结果同直接测序分型结果一致。不同基因型个体间仅在开产体重上存在显著差异,BB型个体的开产体重显著低于AA和AB型个体。