伺服滑台驱动系统的设计

从伺服滑台驱动系统的构成讲起,简述其工作原理及在焊装行业的应用情况。阐述驱动系统性能对伺服滑台实现其功能的重要性。介绍伺服滑台驱动系统设计的一般流程,并对设计过程中的齿轮齿条副设计、伺服减速电机和滚珠导轨副选型以及润滑组件设计4个主要步骤做了较全面和详细的说明,提供一套较完整的伺服滑台驱动系统的设计方法。     

Selection bias in build-operate-transfer transportation project appraisals

Recent empirical studies have found widespread inaccuracies in traffic forecasts despite the fact that travel demand forecasting models have been significantly improved over the past few decades. We suspect that an intrinsic selection bias may exist in the competitive project appraisal process, in addition to the many other factors that contribute to inaccurate traffic forecasts. In this paper, we examine the potential for selection bias in the governmental process of Build-Operate-Transfer (BOT) transportation project appraisals. Although the simultaneous consideration of multiple criteria is typically used in practice, traffic flow estimate is usually a key criterion in these appraisals. For the purposes of this paper, we focus on the selection bias associated with the highest flow estimate criterion. We develop two approaches to quantify the level and chance of inaccuracy caused by selection bias: the expected value approach and the probability approach. The expected value approach addresses the question “to what extent is inaccuracy caused by selection bias?”. The probability approach addresses the question “what is the chance of inaccuracy due to selection bias?”. The results of this analysis confirm the existence of selection bias when a government uses the highest traffic forecast estimate as the priority criterion for BOT project selection. In addition, we offer some insights into the relationship between the extent/chance of inaccuracy and other related factors. We do not argue that selection bias is the only reason for inaccurate traffic forecasts in BOT projects; however, it does appear that it could be an intrinsic factor worthy of further attention and investigation.     

Assessing transportation user benefits with maximum trip lengths

Maximum time lengths of urban trips can be used to calculate major user benefits of transportation improvements. These benefits include those associated with reduced cost of travel, those associated with travel to additional destinations, and those associated with improved quality of destinations. Maximum trip lengths can be measured using techniques of psychological scaling.     

GSM-R基站天线的选型分析

简要介绍GSM-R系统基站使用的天线和应用方式,通过测试数据说明选用不同天线对覆盖效果的影响.特别提出了减小天线下倾角的重要性,以及天线下倾角调谐方式对减少同频干扰的作用.     

高校人事代理制度中存在的问题及对策

人事代理制度已经成为高校人事管理模式的重要方式,对高校用人多元化,提高人事代理人员素质,全面促进高校发展,起到十分重要的作用。文章分析了高校人事代理制度实施过程中的影响因素,从营造良好的氛围、提高待遇、建立公平的内部机制、统一录用标准、构建完善的档案管理平台、激发他们的主体意识等六方面提出应对措施。     

中小型船舶固定灭火系统的选配与检验

本文通过对船舶各类固定灭火系统的特性比较,根据规范的要求及经验总结,对不同类型的船舶及其不同的处所的固定灭火系统的选配,提出合理的建议,并对船舶同定灭火系统的检验,总结出检验要点。     

佳木斯至沈阳铁路客运专线速度目标值选择研究

佳木斯至沈阳客运专线位于我国东北地区黑龙江省、吉林省、辽宁省的东部,分析该项目在区域路网中的地位及作用,通过对项目在经济合理性、旅行时间市场竞争性以及与路网相关线路技术标准的适应性等方面的分析,结合项目在路网中功能定位以及沿线客流的特点,系统论述作为我国东北地区辅助客运通道铁路速度目标值选择的研究思路与方法。经综合比选,推荐该线速度目标值采用250 km/h。     

Journal of Marine Science and Application 2014 Sum. Contents

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京张高铁清华园隧道复合地层盾构机械配置研究

依据清华园隧道盾构区间的隧道参数和工程地质条件,分析盾构机刀盘和刀具对卵石土、砂、粉质黏土互层的适应性。从地层渗透系数、颗粒级配、地下水压、周边环境影响、隧道规模等方面进行综合考虑,选取泥水平衡盾构作为最终选型。考虑到刀盘跨度较大和中途换刀对盾构稳定性的影响,结合渣土特性和既有工程经验,决定采用辐条面板式刀盘,并确定了开口率和开口尺寸;此外,还给出了以切削型为主且可常压更换的刀具配置方案。最后简要介绍了常压换刀的技术流程和泥水环流系统的设计方案,总结了卵石土、砂、粉质黏土互层的盾构机械配置方案。     

集满铁路引入集宁铁路枢纽方案研究

集满铁路主要承担蒙古国塔本陶勒盖煤矿至中国河北及以远地区的煤炭运输,引入集宁铁路枢纽有利于集宁地区铁路运输网络的完善和发展。通过阐述集宁铁路枢纽内在建和规划项目,结合集满铁路运量预测分析,根据集宁地区既有站现状、货物运输通道及方向等情况提出3个接轨点方案,即芦家村站接轨方案、庙梁站接轨方案和三岔口站接轨方案,通过从线路长度、方案工程难易和工程总投资等方面进行综合比选,推荐采用芦家村站接轨方案,为集满铁路引入集宁铁路枢纽提供借鉴。