针对普通冷库冷藏系统存在排气温度过高、制冷性能较低等问题,研发了一套采用微通道换热器的变频转子压缩机新型冷藏系统,研究系统在不同压缩机转速情况下、采用不同补气形式对系统制冷性能的影响.结果表明:库外温度为32℃时,压缩机转速从3 000 r/min提升至5 000 r/min过程中,分别与不补气系统对比,低压补气系统时排气温度降低了 20.54％～22.61％、压缩机功率提高了0.28％～9.19％、制冷量增加了 1.15％～4.52％、COP增加了 1.41％～3.43％;中压补气系统排气温度降低了 18％～20.42％、压缩机功率提高了 8.38％～17.29％、制冷量增加了 7.86％～18.48％、COP 增加了 5.08％～8.97％.

在人类的生产生活中，对电力的需求日益增长，为了提高电能质量，增加电能输送容量，减少输电过程的损耗，继电器被广泛应用在电力系统中。在远距离输电过程中，建立继电保护对实施安全供电具有重要的意义。本文从输电线路纵差保护的影响因素入手对纵差保护进行分析，并对输电线路中的电流进行计算，消除不良影响，为提高输电线路纵差保护的灵敏度及可靠性提出相应的补救措施。

<正>随着汽车工业和高速公路的发展,对轮胎性能要求越来越高,为满足市场对轮胎质量的高要求,需要不断改进胶料的性能。子午线轮胎胎圈上三角胶在轮胎运行过程中为主要承重部位,轮胎在运行时此处生热过大会造成轮胎早期的胎圈损坏,给企业的市场竞争带来不利影响。因此,需要不断改进三角胶的使用性能。一、实验1.主要原材料NR,牌号SMR20,马来西亚;炭黑N326,江西黑猫炭黑公司;白炭黑,山东联科白炭黑有限公司;

The load forecasting is an important task of power utilities,which is wildly used in the dispatching and operation planning of power systems,and the accurate load forecasting is helpful to the security and stability of power systems as well as to reducing the power generation costs. With the establishment and development of the power market,short-time load forecasting will play more and more important role in power systems. This paper systematically analyses relative methods of predicting loads in power system,including traditional load forecasting methods,ways based on artificial intelligence,dynamic forecasting method based on time-frequency analysis,and ways of describing dynamic process. Then basic theories,advantages and disadvantages of different methods were described. Finally,the practical forecasting method should be the combination of advantages of different ways is concluded in this paper.

TWACS is a new valuable communication technology based on power distribution networks.It does not have the limitations and constraints imposed by feeder configurations,capacitor banks or transformer winding configurations.TWACS signal exhibits very low attenuation and does not suffer from standing wave phenomenon.The theory,signal detection principle and realization method of this technology are introduced,and the feasibility is analyzed by simulation in this paper.

By brief analysis of the main factors that impact the power factor of distribution grid,it can tell that power transformers and asynchronous motors are important equipments consuming reactive power,it also points out the impact on power factor when supplying voltage exceeds the prescribed limit.This paper detailedly analyzed reactive-compensation by parallel connected capacitor,got the calculating method of compensating capacitor capability,and deduced the relation between improving power factor and reducing power loss.Meanwhile,the methods that enhance the natural power factor of the system were discussed,and four methods were given,that is,applying electrical equipments reasonably,improving maintenance quality of asynchronous motors,employing synchronous operation of synchronous or asynchronous motors to increase power factor and choosing the capacity of distribution transformers in reason,advancing operating modes of distribution transformers.Finally,the economic and social benefits by improving the power factor were outlined.

To make more effectively use of the mass data on the SIS(Supervisory Information System) platform of thermal power plant,its economical indexes are sorted into controllable and uncontrollable according to their characteristics.An optimized model of dynamically controllable indexes is built up to evaluate the selected indexes:generated power,plant electricity rate and other indicators,and the dynamic optimization strategy based on the neural network model is built up on SIS platform to evaluate the shift groups.With the SIS of a power plant as an example,by applying the optimized controllable indexes as the supervisory parameters of shift group,the optimized model of dynamically controllable indexes based on SIS data can comprehensively reflect the unit operational status and the dynamic optimization strategy based on neural network model can result in better management effectiveness than that of the traditional indicator evaluation system.

The effect of the dynamic and static load characteristics on the damping torque of low frequency oscillation in cross-regional power grid is analyzed.The dynamic and static load models are proposed.The dynamic load model is composed of the constant impedance and the induction motor considering the mechanical transient process.With the single-machine infinite-bus system(Phillips-Heffron Model) as an example,commonly used in the study of power system low-frequency oscillation,the damping torque analysis method is used to calculate the damping torque coefficient for both dynamic and static load models,and the detailed expressions are given.The damping torque and frequency of the oscillation modes in four-machine two-region system are calculated and simulated for different load models and changing parameters,and the varying tendency of damping ratio along with the increase or decrease of load characteristics is obtained.The conclusions are tested under 2008's low-flow operating mode of Central China Power Grid and the results are consistent with the theoretical analysis.

我国物料输送长期使用带式输送带,主要原因是由于带式输送带使用方便,运营成本低廉,成为连续输送物料的主力军,为国民经济发展起到积极作用.但敞开运送物料存在原料抛撒、不利于环保的缺点.

<正>随着橡胶履带产品的发展,现在各大橡胶履带生产企业的竞争开始由质量和性能的竞争转向价格和成本的拼杀。降低成本的工作主要从降低原材料成本、物料消耗和缩短硫化时间这三方面来做。

This paper presents the construction of hardware and flow chart of software of an obstacle recurrence and amplification device (ORAD) based on the digital closed-loop modification technology. The digital closed-loop modification technology is creatively applied to the process of the obstacle recurring and amplifying. In addition, the obstacle source data is accurately modified by the sampling feedback data according to the adaptive fuzzy intelligent control algorithm. The proposed two methods enable the ORAD to overcome the waveform's nonlinear distortion which is the drawback of the present devices of the same kind, such as the power amplifier, the relay test system, etc. Therefore the practicability of the ORAD is greatly enhanced.