提高PLC控制系统可靠性的措施

本文分析了影响PLC控制系统可靠性的主要因素。针对这些因素,探讨了解决这些问题的方法,给出了提高PLC控制系统可靠性的硬、软件措施。     

产品全生命周期评价方法研究前景的探讨

首先总结了全生命周期评价方法的研究和应用现状。在此基础上,指出了与国外发达国家相比,国内在生命周期评价方法研究和应用上的不足。为了弥补这些不足,展望了未来国内在全生命周期评价研究领域的主要研究方向。这些方向包括关注产品生命周期设计方法和产品再循环设计方法的研究,建立产品生命周期评价所需数据库,增加产品社会影响因素的评价指标和深入挖掘统计数据背后的影响作用。这些分析为今后开展全生命周期评价研究提供了建设性意见。     

移动机器人的导航与路径规划的研究

本文对移动机器人的导航与规划的方法进行了总结和比较,并且讨论了这些方法的优缺点。     

基于区域的超声图像处理技术

分析了超声图像的特点,然后根据这些特点和实际对这些图像处理所要达到的要求,提出了一种基于区域的串行方法.对界面进行了识别,通过实际处理效果表明该方法不但抑制了噪声的影响,而且探测出的界面吻合效果较好.     

基于区域的超声图像处理技术

分析了超声图像的特点,然后根据这些特点和实际对这些图像处理所要达到的要求,提出了一种基于区域的串行方法.对界面进行了识别,通过实际处理效果表明该方法不但抑制了噪声的影响,而且探测出的界面吻合效果较好.     

军品用步入式温湿度试验系统的故障分析

本文介绍了军品用步入式温湿度试验系统在使用中所产生的各种故障现象及故障原因,分析了这些故障对该温湿度试验系统性能的影响,以及解决这些故障的方法与措施,提出了对步入式温湿度试验系统的维修与保养方法。     

环境试验设备的故障分析

叙述环境试验设备在运行中所发生的各种故障,同时,分析了这些故障对该设备主要技术参数的影响,以及解决这些故障的方法与措施,并且,提出了对使用中的环境试验设备的维修与保养的方法。     

煤基车用替代燃料的润滑性评定方法的研究

燃料润滑性是用作压燃式发动机的燃料的重要特性之一.煤基燃料二甲醚、甲醇和F-T柴油都是压燃式发动机的良好清洁代用燃料,但是这些煤基代用燃料的物理化学特性与传统的柴油燃料不同,当前的燃料润滑性评定方法可能不是非常适用于这些煤基燃料,因此研究这些煤基燃料润滑性的评定方法是当务之急.分析了国际上通用的燃料润滑性评定方法HFRR、BOCLE和SLBOCLE方法的优缺点,并指出油泵试验法可能是一种较适合煤基车用替代燃料润滑性评定的方法.     

基于ObjectARX程序的直线打断方法

列出了几种常用的直线打断处理方法,并指出这些方法所存在的不足,提出了一种比较稳定的直线打断处理程序方法,取得了较好的效果。     

汽车空调故障诊断方法的研究

对汽车空调制冷系统的检修方法和一般流程进行了分析和研究。通过案例介绍了经验诊断、仪表测量诊断等方法,说明了这些方法的实用性。     

打破民国高等教育体系的院系调整——以中国现代科学家于院系调整前后在高校的分布为解读

“院系调整”时,在高校的中国现代科学家有四分之三被调离本校,名牌大学无一不伤筋动骨。此举是为了打破民国遗留下来的高等教育体系,为新政权确立在高校的实际权威扫清道路。院系调整造成了长期形成的大学传统的断裂,影响了大师的造就。     

The surface structure of mouse peritoneal cells--a study with the scanning electron microscope

Normal and stimulated peritoneal cells have been examined with the Stereo-scan scanning electron microscope. Normal lymphocytes were identified by their small size; some had numerous small stubby or pointed processes on their surfaces. Macrophages were larger and had ridge-like processes. Many of the stimulated cells showed no significant deviation from normal. Others, all macrophages, showed a marked deviation from the normal spherical shape. Ridge-like processes were more prominent on their surfaces, and large flange-like processes and a few finger-like processes were seen. This suggests that on stimulation peritoneal cells become more deformable and therefore irregular in shape, and that their surfaces become rougher.     

The 1990 changes in the electrical units and the temperature scale

The SI units are dynamic, with small adjustments being made from time to time to bring their experimentally realized values into agreement with their definitions. On January 1, 1990, by international agreement the electrical units and the temperature scale were adjusted to bring them into better harmony with the SI definitions. Although small, the changes are potentially significant. This paper will discuss the changes and the actions that were taken in the United States to bring about a smooth transition.     

乌头碱、中乌头碱、次乌头碱及水解产物的电喷雾质谱裂解机制研究

目的:研究乌头碱、中乌头碱和次乌头碱及其水解产物的质谱裂解机制。方法:采用直接进样(FAB)-电喷雾(ESI)-质谱(MS)的方法,在正离子模式下对3种双酯碱和其水解产物进行了多级质谱检测。结果:均产生了[M+H]~+准分子离子,裂解过程中以失掉水,甲醇,一氧化碳中性分子为主。结论:该数据有利于进一步研究乌头属生物碱的化学成分和质量标准的建立。     

Influence of the carbon content on the corrosion and tribocorrosion performance of Ti-DLC coatings for biomedical alloys

Biomedical alloys are prone to suffer corrosion and wear phenomena coming from the hostile environment of the body and friction processes, respectively. Diamond-like carbon (DLC) coatings are known to be excellent candidates for using as protective coatings on biomedical alloys, not only due to their excellent tribological properties but also due to their chemical composition and stability. In this work, three Ti-DLC PVD coatings with different compositions were deposited on Ti6Al4V alloy and their corrosion and tribocorrosion responses were evaluated in simulated body fluid. Excellent tribocorrosion response has been found especially in case of coatings with high carbon content. Additionally significative reduction of friction and wear has been obtained in comparison to the substrate response.     

全合成左旋士的宁六种关键中间体的电喷雾离子阱质谱研究

采用电喷雾离子阱质谱法(ESI—MS)对不对称全合成左旋士的宁的六种中间体进行了深入探讨,获得了它们的结构碎片信息,通过比较它们的异同对其质谱裂解途径进行解析。结果表明:以正离子检测方式下可以得到较强的准分子离子[M+H]+峰,并检测到各自少量的加合离子。它们的(+)ESI—MSn(n=1～3)质谱主要产生氧醚键C-O和硫醚键S-C断裂的碎片。这些特征为全合成士的宁的关键中间体及其结构类似物的结构推断提供了有力的证据,有助于提高合成工作效率。     

Using two-stage clustering of acoustic-emission signals for the detection of weld flaws

A two-stage method for the clustering of acoustic-emission (AE) signals using their parameters and digitized shapes was considered. AE signals were initially clustered according to a set of their informative parameters; the primary clusters that were obtained using these parameters were then subjected to clustering using their digitized AE signal shape. The use of two-stage clustering for the processing of AE signals that were recorded at the moment of welding allowed the calculation time to be reduced without loss of localization accuracy.     

Morphogenesis of the different types of photoreceptors of the chicken (Gallus domesticus) retina and the effect of amblyopia in neonatal chicken

Despite the great variety in chicken photoreceptors, existing morphogenetic studies only deal with two types: rods and cones. We have therefore examined by scanning electron microscopy the first appearance and maturation of different retinal photoreceptors in 36 chicken embryos (Gallus domesticus), aged 5-19 days prehatching. On day 5 of incubation, chicken retinae were only composed of proliferating ventricular cells devoid of photoreceptors. On day 8, outer mitotic cells were separated from inner differentiating photoreceptors, by the transient layer of Chievitz. Ball-like protrusions appeared at the ventricular surface, representing the first signs of photoreceptor inner segment formation. From day 10 onward, double cones, single cones, and rods could be clearly distinguished, and occasional cilia were detected at their tip. On day 12, inner segments had increased in length and diameter, and frequently carried a cilium representing the beginning of outer segment formation. On day 14, most photoreceptors displayed a distinct outer segment. On day 19, photoreceptors had essentially assumed adult morphology. Based on the shape of their outer segments, two subtypes of cones and three subtypes of double cones could be distinguished. Throughout development, we observed microvilli close to maturing photoreceptors, either originating from their lateral sides, from their tip, or from Müller cells. Microvillus density peaked between day 12 and 14, indicating an important role in photoreceptor morphogenesis. Unilateral occlusion of the eyes of posthatching chicken reduced the proportion of double cones to single cones in the retina, indicating dependence of retinal morphogenesis upon functional activity of visual cells.     

液压马达中活塞与缸体的密封结构有限元分析

应用有限元法,借助ANSYS软件分析液压马达中活塞和缸体间O形圈加密封环的组合密封和新型膨胀环密封2种典型密封结构,获得2种密封结构在不同工作压力下的变形以及密封圈接触面的应力分布规律,并对2种密封结构的密封效果进行了比较。分析结果表明：随着油压的升高,2种密封结构的范.米塞斯（Von M ises）应力都随之增加,均具有很好的自适应能力,但膨胀环密封更优;2种密封都达到了密封的效果,新型膨胀环密封的密封性能要好于组合密封结构,即使膨胀环密封由于局部应力过高可能造成磨损,但楔形结构可保证其密封效果得到自动补偿。     

Histological and immunocytochemical localization of serotonin-like immunoreactivity in the brain and optic ganglia of the Indian white shrimp, Fenneropenaeus indicus

Serotonin is one of the important neurotransmitter and neuromodulator so far studied in crustacean models. With its secretory sites well-studied in higher crustaceans, its function in controlling the release of metabolic hormones from their storage and release sites has been well proved. The present study attempts to localize serotonin-like immunoreactivity in Fenneropenaeus indicus, a commercially important shrimp species and a natural inhabitant of the Indian oceans. Histological studies were employed to visualize the different types of neurosecretory cells and their regions of occurrence in brain and optic ganglia on the basis of their size, shape, and tinctorial properties. Immunocytochemical studies were performed in the brain and optic ganglia with specific antisera against serotonin in combination with peroxidase anti-peroxidase to map the serotonin-like immunoreactive cells. Variations in the immunoreactivity were observed on comparing the cells of brain and optic ganglia. Medulla terminalis region had intense serotonin immunoreactivity suggesting it to be the primary source of the neurotransmitter.