基于零序电流差动量的矿井低压电网选择性漏电保护新方案

针对现有矿井低压电网选择性漏电保护装置存在可靠性及灵敏度低的问题,提出一种基于零序电流差动量的选择性漏电保护新方案。该方案通过对矿井低压电网发生单相漏电故障时各支路不同采集点的零序电流值做差,根据差动量的幅值及相位在故障支路与非故障支路中的差异性实现漏电保护的横向选择及区段定位。Matlab/Simulink仿真实验及快速傅里叶变换结果表明,该方案不受电网负载容量、三相电源电压初始相位角的影响,在故障选线及区段定位方面具有较高的可靠性及灵敏度。

阻水河区水流模式动量变差方程及壅水特征值解

根据原型和模型观测,经过概化,本文确立了阻水河区水流模式,通过流束分解,运用流体力学基本原理,建立了壅水质量力—动量变差方程,提出了壅水特征值解法。经过实践验证,可有效应用于防洪治河,河道工程规划设计、河道管理和清障等方面的水文水力计算。

输电线路计算功率法差动保护方法研究

文章针对传统方法在输电线路差动保护应用中输电线路差流值较大,起到的差动保护效果比较差的问题进行了研究。首先根据输电线路双端口U型等值电路特征,建立输电线路数学模型;然后利用计算功率法计算发生金属性接地故障和相间金属性短路故障时输电线路功率的差动量和制动量,并判断输电线路故障是区内故障还是区外故障;在此基础上设计了高定值差动保护和低定值差动保护两种保护策略,根据相应保护原则确定差动保护定值,完成输电线路计算功率法差动保护。经实验证明,应用设计方法后输电线路差流值小于传统方法,在保护输电线路稳定运行方面具有良好的应用效果,具有较好的可靠性和灵敏性。

变压器保护T60比率制动原理

介绍了变压器差动保护比率制动特性中差动量及制动量的计算过程,分析了差动保护中零序分量滤除的必要性。根据变压器保护T60差动保护中比率制动原理,分析了差动电流的幅值补偿、相位补偿以及零序分量滤除原理及相应的计算公式,对差动保护中的比率制动曲线特性以及相对应的定值进行整定,并推导出制动特性中过渡曲线的计算方法。

略论“文化整合力”与旅游业的可持续发展

本文从文化对于旅游业发展的整合作用出发,说明了旅游业实现可持续发展战略必须以文化开发为中心,弘扬民族文化,开发丰富多彩的文化旅游资源。

ANALYSIS AND MEASUREMENT FOR THE DYNAMIC ERRORS OF COORDINATE MEASURING MACHINES

The analysis and calculating method of dynamic errors of CMMs during probing are discussed.To relate the dynamic displacement errors with the dynamic rotational errors a method for obtaining the displacement errors at the probing position from dynamic rotational errors is presented.It is pointed out that the finite element method might be used for modeling dynamic errors.However,dynamic errors are difficult to be modeled so a combined practical and theoretical approach is needed.In addition,the dynamic errors are measured with inductive position sensors.

Precipitation kinetics of 2519A aluminum alloy based on aging curves and DSC analysis

The precipitation kinetics of 2519 A aluminum alloy after different cold rolling reductions before aging was investigated by hardness test and differential scanning calorimetry（DSC）. The activation energy was calculated according to DSC curves using single heating rate method. The microstructures of as-rolled and peak-aged alloys were observed by transmission electron microscopy（TEM）. The result shows that the age hardenability reduces and the activation energy rises with increasing the reduction from 7% to 40%. Nonuniform dislocations are found in as-rolled alloy and inhomogeneous distribution of θ′ phase is revealed in peak-aged alloy when the reduction is 15%. The inhomogeneous distribution of θ′ phase may be related to the age hardenability reducing and activation energy rising.

A New Clock-Driven ECO Placement Algorithm Based on Table-Lookup Delay Model

A new clock-driven ECO placement algorithm is pr es ented for standard-cell layout design based on the table-lookup delay model.It considers useful clock skew information in the placement stage.It also modifies the positions of cells locally to make better preparation for the clock routing . Experimental results show that with little influence to other circuit performa nce,the algorithm can improve permissible skew range distribution evidently.

Theoretical Analysis of Neutron Double-Differential Cross Section of n ＋^19F at 14.2 MeV

A new light nuclear reaction model has been developed and the double-differential measurements of lp shell nuclei have been analyzed successfully. Now, the application of this model is expanded to 19F of the 2s-ld shell nucleus. The double-differential cross section of total outgoing neutron for n ＋^19F reactions at En=14.2 MeV has been calculated and analyzed, which agrees fairly well with the experimental measurements. In this paper, the contributions from different reaction channels to the double-differential cross sections have been analyzed in detail. The calculations indicate that this light nudear reaction model is also able to be used for the 2s-ld shell nucleus so long as the related level scheme couM be provided sufficiently.

平衡孔板孔数和分布研究

采用数值模拟方法研究平衡孔板平衡孔数量和圆心圆直径的最佳取值。以管径D=100 mm、等效开孔直径比β=0.6工况为例,介绍了获得最佳平衡孔数量和圆心圆直径比的方法和过程。取定圆心圆直径比情况下(K=0.67),对比不同平衡孔数量时流出系数、压力损失和动量差等指标,得到最佳开孔数量为N=10;取定平衡孔数量情况下(N=10),对比不同圆心圆直径比时上述评判指标,得到最佳圆心圆直径比为K=0.67。文中给出了DN50~DN1000五种管道规格和6个等效开孔直径比各种工况组合的最佳结构参数,平衡孔最佳开孔数量为8或10个,最佳圆心圆直径比K的取值在0.64~0.73之间(多数情况下取值在0.66~0.70之间)。文中提出了动量差概念用于进行平衡孔性能的评判,对比结果表明,以动量差ΔM达到最小值作为某个结构参数取得最佳的辅助依据是可行的。研究结果对于平衡孔板结构设计具有参考价值。

Calculation of Scale of Fluctuation and Variance Reduction Function

The scale of fluctuation is one of the vital parameters for the application of random field theory to the reliability analysis of geotechnical engineering. In the present study, the fluctuation function method and weighted curve fitting method were presented to make the calculation more simple and accurate. The vertical scales of fluctuation of typical layers of Tianjin Port were calculated based on a number of engineering geotechnical investigation data, which can be guidance to other projects in this area. Meanwhile, the influences of sample interval and type of soil index on the scale of fluctuation were analyzed, according to which, the principle of determining the scale of fluctuation when the sample interval changes was defined. It can be obtained that the scale of fluctuation is the basic attribute reflecting spatial variability of soil, therefore, the scales of fluctuation calculated according to different soil indexes should be basically the same. The non-correlation distance method was improved, and the principle of determining the variance reduction function was also discussed.

Assessment of parameters for precipitation simulation of heat treatable aluminum alloys using differential scanning calorimetry

Differential scanning calorimetry （DSC） has been used extensively to study different solid state reactions. The signals measured in DSC are associated with the growth and dissolution of different precipitates during a specific heat cycle. The time-temperature dependence of heat cycles and the corresponding heat flow evolution measured in the sample by DSC provide valuable experimental information about the phase evolution and the precipitation kinetics in the material. The thermo-kinetic computer simulation was used to predict the DSC signals of samples taken from 6xxx and 2xxx alloys. In the model, the evolution of different metastable and stable phases and the role and influence of excess quenched-in vacancies in the early stage of precipitation were taken into account. Transmission electron microscopy （TEM） and high-resolution TEM were used to verify the existence of precipitates, their size and number density at specific points of the DSC curves.

MULTI-RESOLUTION MOTION ESTIMATION AND COMPENSATION BASED ON ADJACENT PREDICTION OF FRAME DIFFERENCE IN WAVELET DOMAIN

Aiming at the higher bit-rate occupation of motion vector encoding and more time load of full-searching strategies, a multi-resolution motion estimation and compensation algorithm based on adjacent prediction of frame difference was proposed.Differential motion detection was employed to image sequences and proper threshold was adopted to identify the connected region.Then the motion region was extracted to carry out motion estimation and motion compensation on it.The experiment results show that the encoding efficiency of motion vector is promoted, the complexity of motion estimation is reduced and the quality of the reconstruction image at the same bit-rate as Multi-Resolution Motion Estimation(MRME) is improved.

Research on thermal decomposition of 1,3,5-trinitro-1,3,5-triazinane based on differential scanning calorimetry

In order to test the thermal decomposition of 1,3,5-trinitro-1,3,5-triazinane(RDX),the linear temperature rise experiment of RDX was carried out by differential scanning calorimeter under different heating rate conditions.The kinetic calculation of RDX thermal decomposition curve was carried out by Kissinger and Ozawa methods,respectively,and the thermal analysis software was used to calculate the parameters such as self-accelerating decomposition temperature.The results show that the initial decomposition temperature range,decomposition peak temperature range,and decomposition completion temperature range of RDX are 208.4-214.2,225.7-239.3 and 234.0-252.4℃,respectively,and the average decomposition enthalpy is 362.9 J·g^-1.Kissinger method was used to calculate the DSC experimental data of RDX,the apparent activation energy obtained is 190.8 kJ·mol^-1,which is coincident with the results calculated by Ozawa method at the end of the reaction,indicating that the apparent activation energy calculated by the two methods is relatively accurate.When the packaging mass values are 1.0,2.0 and 5.0 kg,respectively,the self-accelerating decomposition temperatures are 97.0,93.0 and 87.0℃,respectively,indicating that with the increase of packaging mass,the self-accelerating decomposition temperature gradually decreases,and the risk increases accordingly.

Solubility of red palm oil in supercritical carbon dioxide： Measurement and modelling

The solubility of red palm oil （RPO） in supercritical carbon dioxide （scCO2） was determined using a dynamic method at 8.5-25 MPa and, 313.15-333.15 K and at a fixed scCO2 flow rate of 2.9 g. mn -1 using a full factorial design. The solubility was determined under low pressures and temperatures as a preliminary study for RPO par- ticle formation using scCO2. The solubility of RPO was 0.5-11.3 mg. （g CO2） -1 and was significantly affected by the pressure and temperature. RPO solubility increased with pressure and decreased with temperature. The Adachi-Lu model showed the best-fit for RPO solubility data with an average relative deviation of 14% with a high coefficient of determination, R2 of 0.9667, whereas the Peng-Robinson equation of state thermodynamic model recorded deviations of 17%-30%.

GPS Rapid Static and Kinematic Positioning Based on GPS Active Network

This paper presents a data processing strategy for GPS kinematic positioning by using a GPS active network to model the GPS errors in double difference observable.Firstly,the double difference residuals are estimated between the reference stations in the active network.Then the errors at a user station are predicted as the network corrections to user measurements,based on the location of the user.Finally conventional kinematic positioning algorithms can be applied to determine the position of the user station.As an example,continuous 24_hour GPS data in March 2001 has been processed by this method.It clearly demonstrates that,after applying these corrections to a user within the network,both the success rate for ambiguity resolution and the positioning accuracy have been significantly improved.

Dynamic error research and application of an angular measuring system belonging to a high precision excursion test turntable

Angular measuring system is the most important component of a servo turntable in inertial test apparatus. Its function and precision determine the turntable＇ s function and precision. It attaches importance to research on inertial test equipment. This paper introduces the principle of the angular measuring system using amplitude discrimination mode. The dynamic errors axe analyzed from the aspects of inductosyn, amplitude and function error of double-phase voltage and wavefonn distortion. Through detailed calculation, theory is provided for practical application; system errors are allocated and the angular measuring system meets the accuracy requirement. As a result, the schedule of the angular measuring system can be used in practice.

Designing the Instrument Crank-Coupler Mechanism of Linear Output with Least Transmission Ratio Error

Movement accuracy is the key factor to be considered in designing precision instrument linkage and mini-linkage mechanisms. Although manufacturing errors, elastic deformation, kinematic pair clearance and friction factors all will have synthesis effect on the position accuracy of the mechanical system, the essential factor to guarantee the movement precision remains the kinematic dimensions. Combining the classical theory of mechanical synthesis with the modern error theory and the numerical method, the authors put forward a systematic and complete process and method of computer aided design for the instrument crank-coupler mechanism in which the follower takes the linear displacement approximately within a certain limited domain, with the design result of least transmission ratio error.

Research of the Thermal Parameters and the Accuracy of Flow Measurement of the Biological Fuel

The heat parameters, the thermoanemometric flow-meter （TAF） errors and the experimental characteristics have been defined. The results of experiments were conducted with the help of physically-informational models allowing to realize all major thermal methods and their inherent informative options. The metrological evaluation was made and the sensitivity to the consumption of gas and liquid have been defined, their static and dynamic errors, followed by the comparison of costs according to these criteria. The developed method provides accurate measurement of volumetric flow of motor fuel 1.0-1.5% at heater temperature measurement accuracy of 1%.

Comparison of SCS-CN Determination Methodologies in a Heterogeneous Catchment

The aim of this study was to assess the runoff amount from a catchment characterized by diverse land uses by using the Soil Conservation Service Curve Number(SCS-CN) method based on Curve Number(CN) defined for dominant homogeneous elementary sub-regions.The calculations employed the SCS-CN method,involving the division of the catchment in two homogeneous parts and determining the runoff amount.The obtained results were compared with the results provided by three other CN determination methods,i.e.the Hawkins function,the kinetics equation,and a complementary error function peak.The catchment is located in a mountain dominated by forest land cover.Empirical CN-Precipitation(CN_(emp)-P) data pairs were analyzed using the mentioned methods,and the highest quality score was achieved from model 1.The results suggest that dividing a catchment into two homogeneous areas and determining their separate CN parameters,used later on to calculate the runoff by means of the presented approach,could be an alternative to the standard methods.The described method is relatively easy,and as it does not require an adoption of numerous parameters,and it can be employed for designing hydraulic facilities.