小差比率制动系数校验的优化方案

针对传统小差比率制动系数校验方法存在校验结果可能不准确的问题,从固定相位调节幅值校验方法出发,得到了其简化的等价模型,并根据校验需满足的条件,提出了一种小差比率制动系数校验新方法。该方法能保证校验过程中所测小差比率系数是母差差动动作所需满足条件中最后一个满足的条件,从而保证测得的小差比率系数必定是装置实际的小差比率制动系数门槛值。通过对常规比率差动的RCS-915AB装置和复式比率差动的BP-2CS装置的现场调试和校验,验证了所提方法的有效性和正确性。     

Phase equilibria and crystal structures of solid solutions in the system LaCoO<Subscript>3−δ</Subscript>-SrCoO<Subscript>2.5±δ</Subscript>-SrFeO<Subscript>3−δ</Subscript>-LaFeO<Subscript>3−δ</Subscript>

The composition region and structure of La_1?x Sr _x Co_1?y Fe _y O_3?δ solid solutions are determined by x-ray powder diffraction using the Rietveld profile analysis method. The solid solutions based on lanthanum cobaltite, LaCoO_3?δ, have a rhombohedrally distorted perovskite-like structure (sp. gr. R \(\bar 3\) c), and those based on lanthanum ferrite, LaFeO_3?δ, have an orthorhombically distorted structure (sp. gr. Pbnm). The rhombohedral distortion decreases with increasing strontium content, and the solid solutions with x ≥ 0.5 have an ideal cubic structure (sp. gr. Pm3m). The composition dependences of lattice parameters for the La_1?x Sr _x Co_1?y Fe _y O_3?δ solid solutions are presented, and the 1100°C isotherm of the LaCoO_3?δ-SrCoO_2.5±δ-SrFeO_3?δ-LaFeO_3?δ system in air is constructed.     

Dry сoolers and air-condensing units (Review)

The analysis of factors affecting the growth of shortage of freshwater is performed. The state and dynamics of the global market of dry coolers used at electric power plants are investigated. Substantial increase in number and maximum capacity of air-cooled condensers, which have been put into operation in the world in recent years, are noted. The key reasons facilitating the choice of developers of the dry coolers, in particular the independence of the location of thermal power plant from water sources, are enumerated. The main steam turbine heat removal schemes using air cooling are considered, their comparison of thermal efficiency is assessed, and the change of three important parameters, such as surface area of heat transfer, condensate pump flow, and pressure losses in the steam exhaust system, are estimated. It is shown that the most effective is the scheme of direct steam condensation in the heat-exchange tubes, but other schemes also have certain advantages. The air-cooling efficiency may be enhanced much more by using an air-cooling hybrid system: a combination of dry and wet cooling. The basic applied constructive solutions are shown: the arrangement of heat-exchange modules and the types of fans. The optimal mounting design of a fully shopassembled cooling system for heat-exchange modules is represented. Different types of heat-exchange tubes ribbing that take into account the operational features of cooling systems are shown. Heat transfer coefficients of the plants from different manufacturers are compared, and the main reasons for its decline are named. When using evaporative air cooling, it is possible to improve the efficiency of air-cooling units. The factors affecting the faultless performance of dry coolers (DC) and air-condensing units (ACU) and the ways of their elimination are described. A high velocity wind forcing reduces the efficiency of cooling systems and creates preconditions for the development of wind-driven devices. It is noted that global trends have a significant influence on the application of dry coolers in Russia, in view of the fact that some TPP have a surface condensers arrangement. The reasons that these systems are currently less efficient than the direct steam condensation in an air-cooled condenser are explained. It is shown that, in some cases, it is more reasonable to use mixing-type condensers in combination with a dry cooler. Measures for a full import substitution of steam exhaust heat removal systems are mentioned.     

Improving the accuracy of multisided travelling wave determination of location of a fault in a power line by means of the difference–distance-measuring technique

The double-ended travelling wave method of determination of location of a fault in electrical networks has significant errors due to changes in the propagation velocity of electromagnetic waves. We have developed a travelling wave method of improving the accuracy of location of a fault determination in power transmission lines that is based on navigation algorithms. The method is applicable to lines with branches. The distance to fault determination for the developed method is up to twice as accurate as the double-ended travelling wave location of a fault method. The accuracy of the developed method is less influenced by external factors (change of sag, soil resistance, the instantaneous value of the current at the fault time) than is the accuracy of the double-ended travelling wave location of a fault method. The proposed method allows reducing the errors in determining distance to the location of a fault, and its accuracy is less affected by external factors. The developed method can be incorporated into existing and prospective devices based on travelling wave methods of location of a fault determination.     

改性木质素磺酸盐分散剂对陶瓷料浆性能的影响

常用的陶瓷分散剂为无机盐类,其分散稳定效果不佳,而高分子分散剂价格高,有必要开发性价比优良的分散剂。本论文系统研究了改性木质素磺酸盐陶瓷分散剂(WAL)的应用性能。掺WAL的陶瓷料浆颗粒表面的Zeta总体高于掺对比样的无机盐分散剂,尤其在掺量0.35%时,掺WAL的Zeta电位绝对值为38.89mv,比无机盐分散剂的高6.0mv。掺WAL的陶瓷料浆球磨后颗粒的平均粒径由空白的19.47μm减小至12.61μm,小于掺无机盐分散剂的13.45μm。掺WAL的浆体流出时间为49.53s,比掺无机盐分散剂的缩短7.08s;通过显微镜放大1000倍也可以看出WAL的分散效果优于无机盐分散剂,浆体中絮体小且均匀。掺WAL浆体的分散稳定性指数120min时为2.5,小于无机盐分散剂的3.0;颗粒粒径沉降60min后为15.37μm,小于无机盐分散剂的16.29μm。综合表明,WAL是一种性能优良的陶瓷分散剂,有良好的应用前景。     

一种含Re单晶镍基合金的组织结构与蠕变性能

通过组织形貌观察及蠕变曲线测定,研究了一种含Re镍基单晶合金在高温的蠕变行为。结果表明,合金经完全热处理后的组织结构是立方γ′相以共格方式嵌镶在γ基体中。在试验的温度和应力范围内,与无Re合金相比较,含Re合金有较好的蠕变抗力及较长的蠕变寿命,并测算出合金在稳态期间的蠕变激活能与应力指数。通过分析位错攀移越过筏状γ′相及影响合金应变速率的因素,研究了合金在稳态蠕变期间的变形机制,其中,元素Re溶入γ基体后可有效阻碍位错运动,降低合金的应变速率,是使合金具有较低应变速率和较长蠕变寿命的主要原因。     

基于深度学习的三维模型检索算法综述

近年来,深度学习被广泛应用于各个领域并取得了显著的进展,如何利用深度学习高效管理呈爆炸式增长的三维模型一直是一个研究热点.本文介绍了发展至今主流的基于深度学习的三维模型检索算法,并根据实验得出的算法性能评估分析了其优缺点.根据检索任务的不同,可将主要的三维模型检索算法分为两类:(1)基于模型的三维模型检索方法,即检索对...     

Investigation into the properties of basalt of the Vasil’evskoe deposit in Yakutia as the raw material for obtaining continuous fibers

The results of investigations into the chemical and mineralogical composition of potentially suitable petrurgical raw materials of the Vasil’evka deposit for producing continuous basalt fibers and composite materials on its basis are presented. Electron probe microanalysis and petrographic analysis are used. The performed investigations proved the possibility of obtaining continuous basalt fibers based on basalt from the Vasil’evka deposit in Yakutia, since its composition and main characteristics correspond to requirements imposed on petrurgical raw materials by the viscosity modulus, the pyroxene composition, the presence of phase transformations, etc.