中小型船厂的建造计划管理及优化方法研究

针对中小型船厂,以加强建造计划管理为目的,分析船舶建造计划管理中涉及的相关问题,详述设计计划与生产计划建立的过程及彼此的关系,利用累计负荷和PERT网络方法给出对计划进行动态控制与合理优化相应的结果。研究表明,建造计划管理从整体上可控制船舶的建造节奏,使复杂过程以系统和有序的方式进行。     

基于随机骨料模型的混凝土劈拉强度数值模拟

采用随机骨料模型模拟混凝土的细观结构,利用有限元方法数值模拟混凝土劈拉的细观损伤断裂,并对其劈拉破坏过程进行了研究。结果表明：该种随机骨料的数值模拟方法基本可行．混凝土骨料与砂浆的界面是其劈拉破坏的薄弱环节。     

204国道东台段改扩建工程Superpave20沥青混合料配合比设计

Superpave沥青混合料设计方法是一种新型的混合料设计方法,Superpave是Superior Performing Asphalt Pavement的缩写,中文意思是"高性能沥青路面",是美国战略公路研究计划(SHRP)的研究成果之一。从目前国内的应用来看,它较传统的马歇尔设计方法沥青混合料性能有较大的改善,有效地防止了沥青路面早期损害的发生。该文以204国道盐城南段(东台段)改扩建工程沥青面层试验为基础,依据Superpave沥青混合料设计实例对其进行探讨,以求指导路面设计与施工。     

Effect of direct in-cylinder CO2 injection on HCCI combustion and emission characteristics

Fuel injection during negative valve overlap period was used to realize diesel homogeneous charge compression ignition (HCCI) combustion. In order to control the combustion, CO₂ in-cylinder injection was used to simulate external EGR. Effects of CO₂ injection parameters (injection timing, quantity, pressure) on HCCI combustion and emission characteristics were investigated. Experimental results revealed that CO₂ in-cylinder injection can control the start of combustion and effectively reduce NO_x emission. Either advancing CO₂ injection timing or increasing CO₂ injection quantity can reduce peak cylinder pressure and mean gas temperature, delay the starts of low temperature reaction (LTR) and high temperature reaction (HTR), and lower pressure rise rate; NO_x emission was reduced, while smoke, HC, and CO emissions increased. Since the combustion phase was improved, the indicated thermal efficiency was also improved. Injection pressure determines the amount of disturbance introduced into the cylinder. Generally, with the same injection quantity, higher injection pressure results in higher momentum flux and total momentum. Larger momentum flux and momentum has a stronger disturbance to air-fuel mixture, resulting in a more homogeneous mixture; therefore, larger injection pressure leads to lower NO_x and smoke emissions.     

Pedestrian crosswalk overflow violation in China: Characteristics and countermeasure

The phenomenon that pedestrians do not walk in the crosswalk during pedestrian green is defined as overflow violation, which is illegal but common. Broadly varying crossing positions at far-side cross-section may result in widely distributed conflict points with left-turning and right-turning vehicles, which may cause the occurrence of severe conflicts. This paper proposes a model to estimate the overflow pedestrians’ crossing positions at the far-side cross-section of signalized crosswalk, which enables us to better understand pedestrian overflow violation behavior and finally facilitate their safety. After analysis, the intersection geometry and destination are determined as the critical factors causing pedestrians to overflow. And then, Weibull distribution is employed to describe the stochastic characteristics of overflow pedestrians’ crossing position distribution at the far-side cross-section. A crossing position distribution model which takes the crosswalk length, width and distance between crosswalk and destination into account is developed. The established model is validated by comparing the observed pedestrian crossing positions with the estimated crossing positions. The validation results suggest that the established model is capable of being adopted to estimate the overflow pedestrians’ crossing positions at far-side cross-section. Based on the model, countermeasure for overflow violation can be put forward to prevent pedestrians from walking outside the crosswalk.     

基于多任务学习和层次分析法的公路隧道支护方案优化设计

为提升公路隧道施工过程中支护的实时性和合理性, 以浙江省龙丽温高速的围岩地质特征和支护方案为研究背景。 分析围岩特征与支护参数的相关性, 确定了以围岩风化程度、 坚硬程度、 岩体完整程度、 地下水状态、 围岩稳定情况为输入围岩特征, 锚杆间排距、 锚杆长度、 喷砼厚度、 钢拱架型号为输出支护参数的多任务学习模型结构。 针对多任务学习模型获得的预测支护参数, 通过层次分析法评价预测支护参数中部分强于实际支护参数, 部分弱于实际的支护设计, 结果表明预测支护参数综合得分高于实际支护参数。 研究成果为实现公路隧道快速支护方案选型和评估提供了指导。     

汽车电子液压制动系统

介绍电子液压制动系统(EHB)的发展现状、基本结构及工作原理,对EHB的优点和不足作简要分析。     

提高PLC控制系统的可靠性研究

简述了影响可编程序控制器控制系统可靠性的主要因素,并就可编程序控制器的工作环境、电源的要求、接地和连接线的方式、冗余设计和降级操作设计、控制系统的输入电路和输出电路与可编程序控制器的软件程序编制等多个方面,提出了一些可行的方法和措施.     

高速公路交通工程安全设施的探讨

主要对高速公路交通安全设施的内容及其对于交通安全的作用和本人多年来对其施工的一些心得等方面进行了描述,来充分说明交通工程的重要性,引起大家对交通工程更加重视。     

基于Flash软件的电气原理模拟软在《电气设备》和《电工电子技术》改革中的探索与实践

本文提出将基于Flash软件的电气设备应用在《电气设备》和《电工电子技术》课程中,分析了《电气设备》和《电工电子技术》课程教学现状和基于Flash软件的电气设备在《电气设备》和《电工电子技术》课程改革中的优势,将基于Flash软件的电气设备电气原理模拟接线软件应用在《电气设备》和《电工电子技术》教学中,电气设备电气原理模拟接线软件以操作简单、交互功能强大,让学习者可以通过软件进行电气设备接线训练,从而提高学习者对电气设备电路原理的理解。详细介绍了基于Flash软件的电气设备在《电气设备》和《电工电子技术》改革中的实践应用,在职业教育和企业培训中,学生实训课和企业等实操培训不仅实现了材料的零消耗,过程零隐患,更重要的是现在的实操培训可针对任何设备开展,不受时间、环境、设备体积的影响,提高学生和学员学习的积极性和主动性,取得了较好的教学效果。