卡塞格伦天线系统中波束指向角度和天线座机械角度关系的研究与分析

文中介绍的卡塞格伦天线系统中,波束指向角度和天线座机械角度有着复杂的数学关系.采用球面三角法推导了这些关系,作为雷达伺服系统测量和控制波束指向角度的基础.     

油田钻井设备常出现的故障及解决策略

在日常生产实践中,油田钻井机械设备常出现损坏等问题,直接致使钻井作业被迫中断,设备的整修与恢复期限较为长久,在很大程度上损害油田生产的效益。本文首先分析油田钻井设备常遇到的故障表现及其原因,接着就防范和解决这些故障提出合理化建议。     

浅谈无卤素环保PCB的制作

无卤素环保PCB将随着绿色电子的推行而越来越受客户和消费者的青睐，但因其材料的特沫性，无卤素板较普通板在制作上增加了难度，主要是与机械力有关的制程，加工效率大大降低，品质也很难达到要求。本文就针对无卤素板的制作难点进行分析，并提出改善方案。     

渭河特大桥44m节段拼装膺架设计与受力分析

膺架法结合节段拼装技术进行大跨度简支箱梁的施工,具有施工速度快、可操作性强、经济和安全等优点,文中结合渭河特大桥施工,介绍节段拼装膺架设计及受力分析。     

Transactions,standardisation and competition: Establishing uniform sizes in the British wire industry c.1880

When science could not provide a solution to transaction problems in the British wire industry c.1880, market groups had to negotiate a business solution. This involved converging towards a ‘one-size-fits-all’ standard: a process requiring compromises and cooperation between competitive firms, and solving coordination failure through state intervention. This paper demonstrates how different groups held different notions of ‘ideal’ standards depending on the incentives they faced. Reconciling these differences was an institutional, rather than a technological, process. The paper also analyses why, historically, dominant producers cooperated to set industry standards when faced with an imminent lock-in on ‘wrong’ standards imposed on the industry.     

Trust Promoting Seals in Electronic Markets

Abstract

In order to promote web sales, companies conducting electronic commerce are constantly seeking viable and efficient ways to increase web traffic. One approach is to build consumers' trust, and ultimately to increase web sales. Many business-to-consumer online merchants follow this approach and display trust-promoting seals on their websites. However, whether these seals really fulfill the tasks they have promised has remained unexplored. This study empirically examines the influence of trust-promoting seals on consumers' online purchasing decisions. The results show that the trust-promoting seals are generally effective in promoting web sales, and some seals enhance promotion better than others.     

一种半履带式单臂无线数据采集机器人的设计与实现

给出了一种带有机械手臂并能采集环境温度、湿度等信息的半履带式机器人的控制设计方案。其关键是硬件电路特别是多个多种电机的控制与构成,无线通信控制、软件设计等。文章详细给出了关键部分的设计与实现过程。     

集装袋老化力学性能试验研究及其灰色预测

考虑粮食集装袋不同的使用环境，通过老化试验对集装袋的老化行为进行研究，探讨了自然暴露和不同温度条件对集装袋性能的影响。结果表明，随着老化时间的增加，集装袋基布的抗拉强度、断裂伸长率下降。自然暴露对基材性能的影响最为显著，高温环境下次之，低温环境下最不显著。基布的抗老化性能与气候条件的变化密切相关，随着温度的升高、光照强度增强，基布老化加剧。同时，基于灰色预测理论，对集装袋横向基布自然老化力学性能进行预测，预测结果精度较高。     

机械工程当中液压系统的维护保养

本文作者根据多年的工作实践,从几个方面探讨了大多数机械工程当中的液压系统如何维护保养。     

多层次模糊评价方法在机械产品质量管理中的应用研究

质量管理对于机械产品的生产至关重要,本文针对机械产品质量中存在的模糊不确定因素,应用模糊数学的概念和方法,建立了机械产品质量的多层次模糊评价模型,并应用实例,对具体的车床质量进行了多层次模糊评价。结果表明,该方法具有较强的实用性和可操作性。