Reliability evaluation algorithm for complex electrical distribution networks using the storage structure of adjacency multilist

A section algorithm of reliability evaluation for complex medium voltage Electrical Distribution Networks (EDNs) using adjacency multilist (AM) is proposed. The constructing method for AM is introduced. The AM can be used to store the structure data of EDNs and to solve the problem of space & time complexity. A new power flow algorithm of backward / forward sweep is proposed and a fast algorithm of forming sections in distribution network is put forward. The proposed algorithm makes a perfect combination of the power flow algorithm and the section algorithm of reliability evaluation, which makes efforts to decrease the work of programming and saves the computing time. Applying the proposed algorithm in RBTS-BUS6 system and actual EDNs, the reliability assessment results show that the algorithm has an advantage of saving time and possesses efficiency in engineering practicality.     

冰蓄冷低温送风空调系统㶲损因素分析

低温送风空调系统引进新型冰蓄冷设备,采用正丁烷作为制冷剂,制冷剂与水直接接触,换热更强烈且稳定。为了研究该系统相应㶲损因素条件下的节能薄弱环节,实现系统性能优化,基于该系统及各表冷器㶲分析模型,分析了热湿比、新风比、送风温差等㶲损因素对系统㶲效率和各表冷器㶲损率的影响。结果表明:当热湿比变化时,处理二次混风的表冷器㶲损率随之呈正比变化,其他表冷器㶲损率及系统㶲效率随之呈反比变化;当新风比变化时,处理新风的两级表冷器㶲损率随之呈正比变化,其他表冷器㶲损率及系统㶲效率随之呈反比变化;当送风温差变化时,处理一次回风的表冷器㶲损率随之呈正比变化,其他表冷器㶲损率及系统㶲效率随之呈反比变化。     

报春花属植物耐热性生理指标研究初探

报春花属植物大多喜冷凉环境,高温成为限制报春花属植物人工栽培的关键因子之一。为研究报春属植物对高温的响应机制,筛选出能反映报春花属植物耐热性差异的生理指标及耐热性强的种质,本试验测定了灰岩皱叶报春、滇北球花报春、鄂报春、黄花九轮草、小报春及岩生报春6种报春花在42℃高温胁迫下不同时间的热害指数、叶绿素含量、电导率、丙二醛含量、游离脯氨酸及可溶性蛋白的含量。结果表明：热害指数、电导率、丙二醛含量、游离脯氨酸及可溶性蛋白含量均能作为评价报春花属植物耐热性的生理指标;综合分析各指标反映出的不同种报春花耐热性的差异,灰岩皱叶报春和小报春的耐热性较强,鄂报春、岩生报春及黄花九轮草的耐热性中等,滇北球花报春的耐热性较差。     

发动机用平板型空滤器流动阻力特性分析和改进

为减小平板型空滤器流动阻力以增大进气量,对平板型空滤器流动阻力特性开展了实验研究,获得了空滤器流动阻力随流量变化的规律和阻力构成成分。阻力随流量的增大而加速增大,滤芯阻力约占整个空滤器阻力的一半,入口流量为120 m 3/h时,总阻力为915.3 Pa,滤芯阻力为426.4 Pa。在实验获得滤芯阻力参数的基础上,提出采用多孔介质跃升模型对平板型空滤器内部流场开展三维数值仿真分析,结果表明,仿真结果与实验结果比较吻合,最大误差为5.67%。滤芯阻力同样约占整个阻力的一半,另一半阻力主要为出口处阻力,其余壁面阻力约占15%。最后,在实验和仿真分析的基础上,提出了改进模型并进行了仿真分析。结果表明,改进模型阻力有较大程度的下降,入口流量为120 m 3/h时,总阻力为588.2 Pa,较原始模型下降了32.2%;增大空滤器流通横截面积是减小阻力以增大进气量的有效手段,改进空滤器壁面的平滑性是补充措施。     

Powertrain parameter design for the electric vehicle with taking the energy consumption of air conditioner into consideration

On the basis of considering the influence of air conditioner on vehicle performance,the parameter determination of the power train composed of a battery,a traction motor and a two-speed transmission of an electric car is carried out. To ensure the economy of operation,a shifting strategy with a principle which emphasizes the high work efficiency of the power train is drawn up and the gear ratios are corrected aiming at the least energy cost over the drive cycle. The simulation results indicate that the designed parameters meet the requirements moderately and the driving range is extended by 5.28% when the air conditioner is turned off and 4.29% when turned on,compared with the initial results through the correction of the gear ratios.     

农产品空气能热泵烘房温度场的数值模拟与验证

农产品热泵烘房温度场均匀性是影响农产品干燥品质的重要因素。本文选用5HGR-35型农产品热泵烘房,通过交互式CAD/CAM系统(UG)软件建立热泵烘房3D模型,运用理论分析与计算流体动力学(Computational fluid dynamics,CFD)模拟相结合的方法,研究其内部温度场分布情况,对现有结构烘房的温度场建模模拟,分析模拟结果并对现有结构进行优化。通过模拟得出结论:送风速度越大,烘房内热空气更新越快,换热效果越好。综合温度场分布以及农产品烘干要求,烘房内合理的送风速度为11 m/s左右;在11 m/s风速下,烘房空载时在15 min左右达到设定温度(65℃);小推车设计高度加大300~310 mm烘房内部温度场更均匀;烘房顶部均匀加入3块长×宽×高=2900 mm×20 mm×300 mm的挡板,可以使烘房内部温度场更均匀;小推车与烘房之间及相互之间保持30 mm左右间隙摆放更有利于烘房内部温度场的分布;验证试验中,模拟温度与实测温度吻合性良好。上述结论对烘房的进一步优化设计具有一定的指导意义。     

CFD Simulation of Air Distribution for Subway Island- platform

To provide gist of air distribution design for subway island-platform and appraise the blue print of air distribution design,a three-dimension model of typical island-platform was constructed.Then it got an appropriate temperature difference for the supply air to optimize the air conditioning system design for subway island-platform.The physical model was set up with standard turbulence.Based on factual heat and wet load,a boundary condition for the simulation was analyzed.The air flow of subway island-platform was simulated with Computational Fluid Dynamics(CFD).The Simulated temperature fields were the same as the tested temperature fields.Then the Computational Fluid Dynamics simulation can simulate and forecast subway island-platform temperature fields accurately with standard model.Thus it can provide gist for air-conditional system design of subway island-platform.     

Simulation of the penetration rate (ROP) of the air percussion drilling

It is difficult to calculate the penetration rate (ROP) of percussion drilling. In the early research, the empirical or semiempirical formulae of the ROP are derived from the laboratory or field data collected by the researchers. However, the ROP value of the formulae is not as accurate as that in the field. Benefiting from the dynamic model, the geometric structure model and the theory of the roller cone bit, the mathematical model of the hammer bit, the mathematical model of the true bottom hole and the mathematical model between the tooth and the rock of the hammer bit are established. Hence the ROP of the air percussion drilling can be predicted by simulation. Field tests show the models are reliable and the results are coincident with that in the field. The research can help to redesign the hammer bit and optimize the drilling parameters.     

果蔬强制通风预冷过程中温度场分布的分析

果蔬预冷是冷链的首要环节之一。以100 t冷库为研究对象,建立了气体区和果蔬区的数学、物理模型,采用k-ε紊流模型和非稳态求解方法,运用计算流体力学软件对果蔬预冷降温过程进行了三维非稳态数值模拟。在其他参数相同的条件下,比较分析了不同风速和送风方式下的温度场分布情况。结果表明：送风速度对库内温度场有显著影响,温度随风速的增大而降低,且温度梯度逐渐减小;对比两种送风方式,上送下回送风方式预冷均匀性较好。     

Spatial and temporal distribution of temperature of drivage roadway air after methane explosions

The spatial and temporal distribution of air temperature after methane explosions in drivage roadway is studied based on the relationship between overpressure and temperature which is found based on gas equation, dynamic and functional principles. The moment temperature distribution after methane explosions under different concentrations of methane is got through solution to the overpressure model and connection with experimental data. Based on unsteady mass and heat transfer, and other physical phenomena, the controlling equations of mass, momentum and energy are founded. The instantaneous temperature distribution after methane explosions is used as one kind of initial conditions of RNG k-ε model to solve the spatial and temporal distribution of temperature in drivage roadway. Studying on it has great meaning to understand the mechanism of sub-fire or sub-explosions induced by initial explosions. It could provide some understanding and helpful methods to prevent and control those sub-disasters.     

高寒草原草地植被物候期及其与气象因子的关系模式

为进一步探寻高寒地区草地植被物候期生长指标与气象因子间的最佳关系模型,基于近11a的气象和牧草观测资料,采用曲线估计分析法探讨了高寒地区不同年际间草地植被物候期生长指标的变化特征及其与气象因子间的关系。结果表明,不同年际间气温和降水量均无显著差异,草地植被物候期生长指标在不同年际间的表现规律不尽相同。其中2005和2010年草地植被高度显著高于2015年,而植被盖度在不同年际间无显著差异;草地植被产量的变化趋势与植被高度一致。另外,2014年草地植被各生长指标的变异系数最大,分别为85%、55%和94%;而2015年变异程度最小,分别为48%、32%和64%。此外,不同年际间高寒草地植被物候期平均气温与高度无关,而与盖度和产量呈一次函数;年平均降水量与高度、盖度和产量间的最佳拟合模型均呈一次线性方程。由此可见,季节性降水量是驱动高海拔地区草地植被高度、盖度和产量的主导因子。     

Experimental Investigation on Characteristics and Evaluation Indexes of Ground-borne Noise Induced by Subway

In-situ experiments and investigation of evaluation indexes were performed to study the subway-induced ground-borne noise in buildings along the subway lines. The characteristics of ground-borne noise in buildings were summarized from various aspects by analyzing the experimental data. The factors such as the spectrum width, the analyzing time and background noise effect on the results of evaluation indexes, were further investigated. The correlation between different evalution indexes was analyzed, and the deficiencies of the indexes of noise evaluation in the environmental noise control codes of China were discussed.     

Numerical simulation of backward flow of methane roof layer in an airway

We study methane backward flow in the laneways at various wind velocities and angles based on computational fluid dynamics theory; analyze the backward flow area length, the concentration distribution and the methane roof layer thickness. The results show that the methane roof layer would move against the airflow in a declensional ventilated airway if the downward air velocity is not large enough. The faster the airflow speed, the smaller the methane backward flow area becomes, and the methane roof layer becomes thicker and shorter. In a declensional ventilated airway, the methane/air mixing capacity increases with the increase of the inclination of the airway, and the thickness of methane roof layer decreases with the increase of the inclination of the airway.     

微波辐射技术在淀粉改性中的应用

简要介绍微波技术的原理,以及目前在淀粉改性方面的应用状况及发展趋势。     

淀粉改性方法的研究现状及进展

淀粉是来源广泛、可再生的绿色资源,在食品、医药、纺织和造纸等行业有着广泛应用,具备巨大的开发潜力。由于天然淀粉的结构特点和不足限制了其开发和应用。通过综述近年来淀粉改性的几种主要方法,包括化学改性、物理改性和酶法改性,重点介绍离子液体、挤压和酶催化在淀粉改性中的应用现状及发展趋势。     

Error Analysis and Modification of Virtual Instrument System

The errors of each parts of virtual instrument system, which are produced in the signals transfer process, are introduced. These errors include sensor error, signal conditioning error, data acquisition error and data dealing error, etc. The main error can be found by analyzing the influence of these errors on different virtual instrument system. The methods of errors modification are also discussed. It's an effective method that modifying system errors, especially nonlinear errors, by software. At last, as a good example, the error analysis and modification of Virtual Noise Analysis Instrument is given.     

酪蛋白酶解改性研究进展

酪蛋白酶法改性不仅可以提高人体对酪蛋白的消化吸收,其水解产物中含有许多生理活性肽。从酪蛋白的酶解方法和酶解产物功能性角度,综述了相关国内外研究进展。     

Study on Modification of Amino-sulfonic Acid-based Water-reducer

Amino-sulfonic acid-based water-reducer is characterized by high water-reducing rate and restraining the concrete mixture from slump loss with time. The application of amino-sulfonic acid-based waterreducer in concrete mixture was restricted due to its high bleeding. Based on principles of molecular design, the traditional superplasticizer of aminosulfonic acid series was modified by the suitable functional group introduced by monomer A and monomer U. The effects of such product on the fluidity, fluidity loss with time and bleeding rate of cement paste were tested. It was found that the modifying effect of monomer A for the superplasticizer was better than that of monomer U. The dispensability and flow retainability of superplasticizer were strong and the bleeding rate of cement paste added with superplasticizer modified by 9% monomer A was reduced obviously.     

Optimum Compound Profile Modification of Cyclodal Gear

The analysis of the existing way and amount of profile modification of cycloidal gears at present showed that the equidistance and movedistance modification is in substance really to have the profile swelled up,and the rational modification way and amount is a swelling correction within the range of zero to some limit. This paper presents a new modifying way which is optimum compound modification at separate parts. The modified profile has the most simultaneously transmission teeth,even side clearance and the longest wear-life to forming crush dressing roll and is also easyly to NC machining.