谈PLC可编程控制器的原理和工业应用

介绍了PLC可编程控制器的结构和工作原理及优点，说明PLC在工业生产中的广泛应用，可实现生产的集中控制和管理，降低工人劳动强度，改善劳动条件，为提高工业生产的可靠性，提供了有力保障。     

1981-2020年我国高校图书馆现代化服务研究文献计量分析

根据中国知网18种图书情报领域核心期刊近40年的文献数据信息,通过领域专家构建高校图书馆现代化服务研究的重要关键词,以作者提供的关键词为主,同时利用知识图谱工具从题目和摘要中抽取重要关键词作为补充,绘制该领域的关键词共现网络图,并以技术发展脉络为主要依据,结合国家发展大局,将40年划分为4个不同时期,对每个时期的热点研究主题、主要发文机构以及作者等情况进行分析,最后总结该领域近40年来的研究规律,并对领域发展进行展望。     

Numerical Modeling of Response and Damage of Masonry Walls to Blast Loading

To model the damage process of masonry walls under blast loading, a dynamic continuum damage material model is constructed for brick and mortar separately. The degradation of both the stiffness and strength are governed by a damage variable. By using the proposed material model, damage and fragmentation of a typical masonry wall under blast loading at different scaled distances is calculated. The hazard level of the masonry wall to blast loading is evaluated by analyzing the numerical results.     

Strength and Toughness of Steel Fibre Reinforced Reactive Powder Concrete Under Blast Loading

The blast resistance of structures used in buildings needs to be investigated due to the increased threat of a terrorist attack. The damage done by Composition B or Powergel to steel fibre reinforced reactive powder concrete (SFRPC) panels and ordinary reinforced concrete (RC) panels of equivalent static flexural strength is compared. A 0.5 kg charge was detonated at a distance of 0.1 m from the 1.3 m×1.0 m×0. 1 m (thick) panels, which were simply supported and spaning 1.3m. Dynamic displacement measurements, high-speed video recording and visual examination of the panels for spall and breach were undertaken. The SFRPC panels withstood the bare charge blast better than the reinforced ordinary concrete panels. Neither type of panel was breached using a 0.5 kg charge. The RC panel exhibited more spalling when Composition B was used. Under successive Composition B loading conditions, the RC panel was breached. In comparison the SFRPC panel was not breached. Exposure to fragmenting charge loading conditions confirmed these performance differences between the SFRPC panel and the reinforced ordinary concrete panel.     

Enhancing rice resistance to fungal pathogens by transformation with cell wall degrading enzyme genes from Trichoderma atroviride

Three genes encoding for fungal cell wall degrading enzymes (CWDEs), ech42, nag70 and gluc78 from the biocontrol fungus Trichoderma atroviride were inserted into the binary vector pCAMBIA1305.2 singly and in all possible combinations and transformed to rice plants. More than 1800 independently regenerated plantlets in seven different populations (for each of the three genes and each of the four gene combinations) were obtained. The ech42 gene encoding for an endochitinase increased resistance to sheath blight caused by Rhizoctonia solani, while the exochitinase-encoding gene, nag70, had lesser effect. The expression level of endochitinase but exochitinase was correlated with disease resistance. Nevertheless, exochitinase enhanced the effect of endochitinase on disease resistance when the two genes co-expressed in transgenics. Resistance to Magnaporthe grisea was found in all kinds of regenerated plants including that with single gluc78. A few lines expressing either ech42 or nag70 gene were immune to the disease. Transgenic plants are being tested to further evaluate disease resistance at field level. This is the first report of multiple of expression of genes encoding CWDEs from Trichoderma atroviride that result in resistance to blast and sheath blight in rice.     

A Blast Shock Isolation System with MRFD and Its Semi-Active Control Analysis

To effectively reduce the damage to people and devices in civil defense engineering subjected to blast shock, a blast shock isolation system with magnetorheological fluid dampers (MRFD) is proposed. MRFD can provide continuously adjustable Coulomb friction and has many advantages for semi-active control. Numerical simulation of this isolation system is finished using Matlab simulink toolbox. General semi-active control algorithms are consided based on instantaneous optimal active control algorithm. And the results indicate that the shock isolation system can work efficiently, decreasing about 93% of the peak acceleration of the isolation floor.     

虚拟全景的链接——“虚拟现实”系列之三

该文通过实例介绍了虚拟全景之间、虚拟现实全景与URL以及静止图片之间的链接技术     

废气再循环式柴油热风炉热交换系统的研制

介绍一种利用废气再循环以提高柴油热风炉热效率的方法,及其自行研制一种适用于温室内的全数字微机智能监控柴油热风炉废气再循环热交换系统。它由微电脑控制间歇地分流大部分、乃至全部已燃废气到进气管的装置。该系统采用新型的数字式温、湿度一体化传感器(LTM8901)和一线总线结构,由微处理器(89C51)自动智能监控。从系统的原理、结构设计出发,开发了独特用于柴油热风炉的废气再循环热交换系统,找到了最佳工作状况。当控制EGR率在50％～70％范围时,能提高热利用率17．6％,节约能源,并且还降低了排放污染。     

Dynamic Responses Analysis of a Building Structure Subjected to Ground Shock from a Tunnel Explosion

Dynamic responses of a multi-storey building without or with a sliding base-isolation device for ground shock induced by an in-tunnel explosion are numerically analyzed. The effect of an adjacent tunnel in between the building and the explosion tunnel, which affects ground shock propagation, is considered in the analysis. Different modeling methods, such as the eight-node equal-parametric finite element and mass-lumped system, are used to establish the coupling model consisting of the two adjacent tunnels, the surrounding soil medium with the Lysmer viscous boundary condition, and the multi-storey building with or without the sliding base-isolation device. In numerical calculations, a continuous friction model, which is different from the traditional Coulomb friction model, is adopted to improve the computational efficiency and reduce the accumulated errors. Some example analyses are subsequently performed to study the response characteristics of the building and the sliding base-isolation device to ground shock. The effect of the adjacent tunnel in between the building and the explosion tunnel on the ground shock wave propagation is also investigated. T.he final conclusions based on the numerical results will provide some guidance in engineering practice.     

矿渣微粉对混凝土性能影响的试验研究

通过试验，利用不同细度、不同掺量的矿渣微粉等量置换混凝土中的水泥，研究混凝土性能变化趋势，以期达到优化矿渣微粉应用参数和使用效果的目的。试验结果表明：在配制C40混凝土时，矿渣细度控制在500m^2/kg左右，掺量20％∽60％时，混凝土的工作性和力学性能均得到较好的发挥。