Anomalous Excess Heat Capacities of Ethanol + Alkane Mixtures

A thermodynamic study at atmospheric pressure on the ethanol + n-dodecane and ethanol + n-tridecane binary systems near their liquid-liquid critical points has been carried out. To this end, densities and speeds of sound were determined in the temperature range from 288.15 to 308.15 K, whereas differential scanning calorimetry was used to obtain isobaric heat capacities per unit volume from 288.15 to 303.15 K as well as liquid-liquid equilibrium curves. All these results for the mentioned properties were obtained over the complete composition range. They were used to obtain molar volumes, isentropic compressibilities, isobaric thermal expansivities, isothermal compressibilities, isochoric heat capacities, and the excess quantities of all these properties. An untypical behavior of the excess heat capacities at the lowest measuring temperatures resulting from the critical behavior of the isobaric heat capacity is observed. No clear anomalies for the excess volumetric properties are detected.     

大兴安岭地区初霜冻成因及预报

霜冻的出现一般都是范围广、危害性强、损失大，特别是大兴安岭区地处高纬度地区，初霜来得比较早，对初霜冻的预报就显得格外重要。选取了该区近35a出现初霜的资料，经过分析研究发现，初霜冻的出现和高空环流形势及地面的天空状况有直接的关系。     

Theoretical method for estimation of mean pressure on contact area between rolling tools and workpiece in cross wedge rolling processes

The paper gives a new method no determine the mean unit contact pressures on a material—tool contact surface in cross wedge rolling processes (CWR). The dependencies worked out on the basis of the energy and the upper bound methods permits rolling forces to be determined which are comparable to experimentally measured ones. The analysis provides equations which relate the mean contact pressure q_m to the basic process parameters, namely the forming angle α, the spreading angle β, the relative reduction of a portion δ and the shear friction factors m and m_k.     

行人大腿冲击器的生物仿真度

针对汽车行人保护碰撞试验中大腿冲击器的生物力学特性问题,采用THUMS(total human model for safety)人体模型与大腿冲击器进行对比仿真分析.模拟THUMS-SUV行人交通事故,并对THUMS人体模型大腿所受冲击力和弯矩进行了输出.根据事故中行人大腿初始碰撞条件和行人大腿最低能量状态,分别建立两种工况的行人大腿冲击器碰撞模型并进行模拟,对比分析行人大腿冲击器和THUMS人体模型大腿的动态响应、最大瞬间冲击力和最大弯矩.仿真结果表明:相对THUMS人体模型而言,大腿冲击器的最大瞬间冲击力偏高而最大弯矩偏低,行人小腿和上身的运动和接触作用,会影响大腿部位的接触力和最大弯矩,因此大腿冲击器的生物仿真度有待提高.     

原料上料系统自动化控制的改造实施

某水泥厂建厂时,在原料上料系统流程上采用了传统的机旁手动操作方式。几年来,手动操作控制逐渐显露出很多弊端,于是将手动按钮启停控制更换为机旁优先的自动控制方式。详细介绍了自动控制方式的实施方案和控制原理,系统改造后,画面友好、操作简单、控制灵活,改造效果良好。     

宏岩煤矿工作面上隅角瓦斯来源测定分析

工作面上隅角易于瓦斯积聚,影响工作面安全生产。根据宏岩煤矿4406工作面实际地质情况,运用理论分析,结合现场监测对工作面上隅角瓦斯来源进行了分析,研究表明,工作面上隅角瓦斯涌出量与工作面状态（动、静）、作业工序、顶板运动等因素有关。     

基于单片机的蜂箱蜜蜂监测系统设计

针对蜜蜂养殖业及科学研究中存在的蜂箱内蜜蜂数量监测困难的问题,提出一种用于监测蜂箱中蜜蜂数量的监测系统。系统采用STC89C52单片机作为控制核心,用光电传感器H42B6感应外界光线的变化,通过触发单片机的外部中断识别蜜蜂的经过,根据触发顺序判断蜜蜂的进出方向,通过单片机进行数据处理,并将处理后的数据送入串口,最终通过串口调试工具显示在上位机界面上。实验结果证明:该系统能精确地统计出蜂箱中蜜蜂的进出数目,给养蜂者的管理提供准确依据。     

蹬空上提面矿压显现规律的数值模拟研究

提高工作面回采上限是节约煤炭资源的重要途径之一。针对既蹬空又提高上限的工作面,回采前需研究其矿压显现规律。通过FLAC3D数值模拟能很好地分析蹬空、上提对工作面回采的影响。数值计算结果表明:蹬空上提段超前支承压力峰值较蹬空非上提段大,蹬空上提对工作面顶板下沉量的影响较蹬空非上提大。     

制造执行系统(MES)集成性探讨

MES的广泛应用使得企业在整体信息化方面面临了更多的挑战,面对挑战,企业与产品厂商都将MES与其他信息化系统的集成推进作为应对的主要方案。从MES的概念、集成性、同其他信息化系统的集成以及集成发展的趋势,为MES集成的相关工作,阐述MES集成应关注的更多知识。     

Approximations in a semigroup by using a neighbourhood system

Let S be a semigroup. We consider the relation γ and its transitive closure γ*. The relation γ is the smallest equivalence relation on S so that S/γ* is a commutative semigroup. Based on the relation γ, we define a neighbourhood system for each element of S, and we present a general framework of the study of approximations in semigroups. The connections between semigroups and operators are examined.