基于PLC的步进电机转速控制方法研究

概述了PLC控制的优点、步进电机的工作原理。提出了一种基于PLC的四相步进电机控制方法,介绍了系统的硬件组成以及相应的I/O分配。软件设计包括脉冲产生和控制、脉冲分配及步数设定三大模块,用软件完成脉冲分配功能,可以减少硬件资源,控制参数改变方便灵活,提高了系统控制的可靠性和灵活性。     

本能冲动与精神之恋——浅析《日瓦戈医生》的精神分析线索

弗洛伊德的精神分析学是20世纪的重要理论。他所提出的俄狄浦斯情结、力比多理论以及其对梦的解析都为当代的文学作品解读提供了一种独特的视角。本文试图从精神分析学的角度来阐释小说《日瓦戈医生》中所体现出的人的本能冲动与精神之爱的双重发展,并借助弗洛伊德的相关理论来分析日瓦戈与拉拉的复杂心理与梦境。     

NiCr-ZrO_2复合材料的制备及其热胀性能研究

以ZrOCl2.8H2O和Ni(NO3)2.6H2O,Cr2O3,NH4HCO3为原料,采用缓冲溶液法(一种改进的共沉淀法)制备出复合氢氧化物,将其焙烧得到复合氧化物粉末,最后通过高温还原制备得到NiCr-ZrO2复合粉体材料.通过TG-DSC,XRD,激光粒度仪等现代分析技术对材料的热物性、组成、粒度分布进行测定并研究复合材料热胀系数与其成分组成之间的关系.结果表明,NiCr-ZrO2复合材料的热胀系数随其金属含量的增加而增大.     

法治视野下儒家和谐思想的价值反思

儒家文化包含丰富的和谐思想底蕴和精华,对建设现代社会主义和谐社会具有重要的启迪和借鉴意义。本文以现代法治视角,对社会主义和谐社会理论和传统儒家和谐思想进行深入解读,剖析儒家和谐思想与现代社会的不相适宜,并以马克思主义、中国特色社会主义理论体系以及现代民主法治理念为指导,对儒家和谐思想的现代转换和科学构建作出一些思考。     

Preparation and crystallization action of SiO2 -Al2O3 -CaO-ZnO-R2O porous glass-ceramics

Using powder-sintering method,SiO2-Al2O3-CaO-ZnO-R2O porous glass-ceramics were produced for analysis. Five samples with different SiO2 /CaO ratios were used in the research. The mechanical properties, microstructures and textures of porous glass-ceramics are investigated by using differential thermogravimetric analysis/differential thermal analysis ( TGA/SDTA) ,X-ray diffraction ( XRD) ,and scanning electron microsco- py ( SEM) . The activity energy of crystallization ( E) and crystallization kinetics parameter ( k) were calculated based on the modified JMA equation. The Avrami parameter n was obtained according to Augis-Bennett function. The results show that the k value of No. 1 sample ( SiO2 /CaO = 61∶ 18) is the largest among all samples, which tends to crystallize more easily,and crystallization processes of all samples are observed bulk crystallization. The main crystal phase observed is parawollastonite ( clinorhombic system) with puncheon shape. Poreforming agents decomposed at 100 - 500 ℃ form a large number of closed pores with micron dimension and several semi-open pores distribute uniformly in the glass-ceramics matrix. This work may be expected to be favorable for industrial scale applications of porous glass-ceramics in the field of building thermal insulation.     

基于PSK调制的扩频通信研究

基于PSK调制,以直接序列扩频通信系统为研究对象,在MATLAB仿真环境下分析了直接序列扩频前后的通信系统模型的误码率性能。给出了直接扩频通信系统误码率与信噪比的关系曲线,仿真结果表明,直接序列扩频信号要比不扩频信号,更准确、可靠,因此直扩系统具有更好的性能。     

复杂网络上的动态传播

采用一种新的方法来研究文化传播,结合动力学和复杂网络的知识对文化在不同结构社区中的传播做了数值仿真和分析。发现文化的传播速度在随机结构,BA结构,小世界结构和规则结构的社区中依次减慢,且核心人物对BA结构社区中的文化传播起着重要的作用。     

Robust H_∞ output feedback controller design for linear uncertain discrete-time switched systems via state reset

This paper studies the problem of robust H∞ output feedback controller via state-reset for linear uncertain discrete-time switched systems. Using multiple Lyapunov functions,we address an output feedback controller under arbitrary switching signals,in which an H∞ performance is required. The condition is shown in the form of linear matrix inequalities (LMI). Finally,a numerical example shows the feasibility of the designed controller and illustrates that the new sufficient condition has lower conservation and more optimized H∞ tfperformance.     

Crack elongation and its width of large depth reinforced concrete beams

In order to meet the requirement of structural inspection,the crack spacing and crack width at various heights in the tensile zone of six large depth reinforced concrete beams were measured under several loading levels of serviceability state.The effects of the depth of normal section beams on the crack spacing and crack width were analyzed,and the modified model is proposed for calculating the average crack spacing by thinking about the depth of normal section,the reinforcement arrangement and the effective reinforcement ratio.The relationships of crack widths at any position in the tensile zone and at the reinforcement level on the side surface of beam were studied.By theoretical and statistical analysis,a method is proposed to calculate the ratios of crack widths between any position and the reinforcement level on the side surface of large depth reinforced concrete beams.     

Application of structural curvature of coalbed floor on CBM development in the Zaoyuan block of the southern Qinshui Basin

Based on controls of structural style and the position in coalbed methane(CBM)development,we used a method of curvatures to study its relations with CBM development parameters.We calculated structural curvatures of contours of the No.3coal seam floor of the Shanxi Formation in the Zaoyuan block of the Qinshui Basin and analyzed its relations with development parameters of coalbed methane wells.The results show that structural curvature is negatively related to coal reservoir pressure,while positively related to permeability.With an increase in structural curvature,the average production of coalbed methane wells increases at first and then decreases,reaching the highest production at 0.02 m-1 of structural curvature.Therefore,structural curvature can be an important index for potential evaluation of coalbed methane development and provide a basis for siting coalbed methane wells.