大型数据库管理系统中主机性能测评及工作模式设计

本文针对大型数据库管理系统中缺乏平台质量评测手段的问题,建立了TPC-C基准评测体系。首先介绍了主机性能评测的通用原则,然后分析了TPC-C基准评测体系的模型结构和原理,最后提出了根据业务特点推算主机处理能力的TPC-C基准评测方法,同时设计了主机系统的工作模式。     

Time-dependent drivers’ merging behavior model in work zone merging areas

This study investigates the drivers’ merging behavior in work zone merging areas during the entire merging implementation period from the time of starting a merging maneuver to that of completing the maneuver. With the actual work zone merging traffic data, we propose a time-dependent logistic regression model considering the possible time-varying effects of influencing factors, and a standard logistic regression model for the purpose of model comparison. Model comparison results show that the time-dependent model performs better than the standard model because the former can provide higher prediction accuracy. The time-dependent model results show that seven factors exhibit time-varying effects on the drivers’ merging behavior, including merging vehicle speed, through lane lead vehicle speed and through lane lag vehicle speed, longitudinal gap between the merging and lead vehicles, longitudinal gap between the merging and through lane lead vehicles, types of through lane lead and through lane lag vehicles. Interestingly, both the through lane lead vehicle speed and the through lane lag vehicle speed are found to exhibit heterogeneous effects at different times of the merging implementation period. One important finding from this study is that the merging vehicle has a decreasing willingness to take the choice of “complete a merging maneuver” as the elapsed time increases if the through lane lead vehicle is a heavy vehicle.     

LCI型路缘石自动成型机

LCI型路缘石自动成型机是一种利用沥青混合料修筑道路路缘的专用设备。本文主要介绍了该机工作原理、技术参数、结构设计、沥青混合料的配制及施工工艺。     

煤炭集运站到发线能力计算方法探析

以某纵列式集运站为例,在分析其作业流程基础上,采用作业时分法、甘特图法、全日作业图法等方法对煤炭集运站到发线能力进行计算。研究结果表明,作业时分法是一种较为粗放式的计算方法,建议用于规划阶段及方案研究阶段车站到发线规模的核定;甘特图法和全日作业图法,能力计算结果更为真实可靠,在进入初步设计阶段(实质性工程设计阶段),应采用甘特图法和全日作业图法确定车站到发线规模。     

用科学发展观统领地方铁路工作为地方经济和社会发展做出更大贡献

“十五”期间,在铁路跨越式发展的形势下,全国地方铁路工作取得突出成绩,在地方铁路建设和满足铁路运输需求方面发挥了重要作用。按照铁路“十一五”发展规划的总体思路,地方铁路将加强行业管理力度,结合铁道部与各省、市、自治区签订的铁路建设纪要和地方铁路建设的需求,配合铁路干线的规划搞好地方铁路的规划和建设,促进区域经济的发展。2006年,地方铁路将转变发展观念,创新发展模式,提高发展质量,建立更适应地方铁路的建设模式和运营模式。     

强化机遇意识实现良好开局全面开创铁路计划工作的新局面

推进铁路跨越式发展,做好“十一五”规划的落实工作和2006年计划工作,要进一步提高对加快铁路发展的认识,增强加快铁路发展的机遇意识,继续发扬苦干实干拼命干精神,铁道部发展计划司、设计单位和建设单位要明确职责、加强协调,进一步加强资金管理,优化设计方案、降低成本,提高资金使用效益,并充分调动地方政府、合资公司等各方积极性,全面开创铁路计划工作新局面。     

广西高校体育教师工作压力的现状分析

文章采用文献资料法、问卷调查法、数理统计法等研究方法,对广西高校体育教师的工作压力进行调查分析.结果表明,广西高校体育教师普遍感受到中等程度的工作压力,不同年龄、教龄和职称的体育教师工作压力呈显著性差异.     

加强铁路法制建设促进铁路跨越式发展

加强铁路法制建设,是铁路跨越式发展战略的重要组成部分。近年来,铁道部围绕铁路跨越式发展对法制保障的需要,加大了法制建设力度,取得了一系列成果,立法取得重大突破,依法行政得到有序推进,企业的法治化管理得到加强。但也存在一些问题,铁路法规体系还不完整,依法行政理念还不深入,企业法律风险意识还不强。需要重点抓好:健全铁路法规体系、全面推进依法行政、依法推进铁路改革、依法规范铁路运输经营管理、依法保障大规模铁路建设的实施、加大法制宣传教育力度、加强法律队伍建设等工作,确保铁路跨越式发展战略的顺利实施。     

Real-time merging traffic control for throughput maximization at motorway work zones

Work zones on motorways necessitate the drop of one or more lanes which may lead to significant reduction of traffic flow capacity and efficiency, traffic flow disruptions, congestion creation, and increased accident risk. Real-time traffic control by use of green–red traffic signals at the motorway mainstream is proposed in order to achieve safer merging of vehicles entering the work zone and, at the same time, maximize throughput and reduce travel delays. A significant issue that had been neglected in previous research is the investigation of the impact of distance between the merge area and the traffic lights so as to achieve, in combination with the employed real-time traffic control strategy, the most efficient merging of vehicles. The control strategy applied for real-time signal operation is based on an ALINEA-like proportional–integral (PI-type) feedback regulator. In order to achieve maximum performance of the control strategy, some calibration of the regulator’s parameters may be necessary. The calibration is first conducted manually, via a typical trial-and-error procedure. In an additional investigation, the recently proposed learning/adaptive fine-tuning (AFT) algorithm is employed in order to automatically fine-tune the regulator parameters. Experiments conducted with a microscopic simulator for a hypothetical work zone infrastructure, demonstrate the potential high benefits of the control scheme.     

Effectiveness of graphic-aided portable changeable message signs in reducing vehicle speeds in highway work zones

Portable changeable message signs (PCMSs) have been employed in highway work zones as a temporary traffic control device for decades in the United States. Results of previous research showed that the traditional text-based PCMS had several limitations, such as having a short range of legibility and being difficult to read by elderly and non-English-speaking drivers. A few simulation studies indicated that using graphic-aided PCMSs could likely overcome these limitations. This paper presents the results of field experiments that were conducted to determine the effectiveness of graphic-aided PCMS in reducing vehicle speeds in the upstream of highway work zones. In field experiment Phase I, a full-matrix PCMS was programmed to display a work zone graphic and a flagger graphic, which were similar to the W21-1 sign and W20-7 sign, respectively, specified by the Manual on Uniform Traffic Control Devices. In field experiment Phase II, the PCMS was programmed to display two alternative work zone graphics along with the original work zone graphic. 1115 and 1600 valid vehicle speed data were collected during field experiments Phase I and Phase II, respectively. The results of data analysis suggested that graphic-aided PCMSs reduced mean vehicle speeds between 13% and 17% in the upstream of a work zone. This study provided valuable knowledge to government agencies and the transportation industry on how to regulate and implement graphic-aided PCMS in highway work zones.