三维船体曲面模型建立方法及程序实现

该文对应用实体造型技术建立船体曲面模型的方法进行了研究。在So lidW orks建模环境中使用VB作为二次开发工具,通过应用程序实现了三维NURBS船体曲面模型的建立。并用实例验证了程序的适用性,为进一步建立数字化的船体曲面产品模型奠定了基础。     

关于安全态度的哲学思考

人的安全态度本质在于“防”。这一思想的产生既是历史的必然,也是二千多年前东方先哲智慧的结晶。而“防”的思想又决定着人的安全态度。基于以上思想,笔者对构建“未雨绸缪”、“如履薄冰”、“按部就班”、“防微杜渐”、“安分守己”、“深思熟虑”、“勤勤恳恳”、“学而不厌”、“唇亡齿寒”九种安全态度的必要性进行了论述。     

宋瑞琴 助推铁路机务信息化

在推进中国铁路现代化进程中，有一个与铁路机务结下30年情缘并为铁路机务信息化作出突出贡献的优秀女企业家，她就是北京金京铭科技有限公司董事长宋瑞琴。请看本刊记者采写的报道——[编者按]     

AutoCAD在船舶设计中的二次开发和应用

本软件是在AutoCADDcL平台上,利用对话框控制语言和Aut01isp语言来编制机舱原理图设计的软件包,该软件包包括燃油系统计算、滑油系统计算、冷却水系统计算及压缩空气系统计算四部分。该软刊:以中文对话框的方式来进行操作,实现了人机交互。     

针叶树绿化栽植技术的探讨

针对目前针叶树栽植成活率比较低的现状,笔者深入绿化工地,对针叶树栽植的整地、选苗、运苗、栽植、养护等一系列过程进行了观察和研究,找出了针叶树成活率低的原因,从而达到提高针叶树绿化景观的目的.     

基于负荷平衡的流水线生产节拍设计

提出了在有排序约束和无排序约束两种情况下的流水线节拍设计方案,能有效解决流水线负荷平衡问题.该设计方案通过优化选取工作节点和工作节拍、有效组合任务元素、降低工作节点间等待时间等有效措施,来提高设备利用率、实现流水线负荷的平衡,进而达到提高流水线生产产量的目的.     

Effect of Heavy-Duty Diesel Engine Operating Parameters on Particle Number and Size Distribution at Low Speed Condition

Experiments and simulations were used to investigate the effect of a range of engine operating parameters and fuel characteristics on the particle size and particle number (PN) concentration at low speed and idle speed condition. The occurrence, size, and concentration of particles were tested against a range of parameters including start of injection (SOI), common rail pressure, exhaust gas recirculation (EGR) ratio and load. The results showed that the homogeneity of the mixture had the greatest impact on particle size and number concentration. The performance of particle is different at different levels of load. The particle were of nucleation mode at idle condition, and the cold idle particles had a slightly larger diameter than those produced at hot idle. By using the diesel and under high load, at EGR ratios of less than 20 %, most particles were of nucleation mode. At EGR ratios exceeding 20 %, nucleation-mode particles were gradually replaced by accumulation-mode particles. At EGR ratios above 30 %, most particles were of the accumulation mode. Under the same load, gasoline compression ignition produced particles of smaller size and reduced particulate mass (PM). The use of gasoline extended ignition delay, as the high volatility and octane number of the fuel improved the homogeneity of the mixture. Finally, a linear relationship was found between PM and PN. The relative contribution of the different factors to the formation of nucleationor accumulation-mode particles was investigated.     

Effect of Charge Density on Spray Characteristics,Combustion Process,and Emissions of Heavy-Duty Diesel Engines

In-cylinder charge density at top dead center is an important parameter of diesel engines and is influenced by intake pressure, intake temperature, and compression ratio. The effects of charge density on fuel spray, combustion process, and emissions were investigated by using a constant volume bomb and a heavy-duty diesel engine. Spray development resistance increased with the increase of the charge density in the constant volume bomb. It was found that short spray penetration was accompanied by a large spray cone angle in the former stage with high charge density. However, the equivalence ratio was lowered and the degree of homogeneity of the mixture was increased in the later stage owing to the rapid interaction of fuel and gas at a high mixing rate. Combining the first law of thermodynamics and the second law of thermodynamics for analysis, as the charge density increased, the gross indicated thermal efficiency (ITEg) was improved. However, pumping loss had to be considered with higher charge density. Under this condition, the brake thermal efficiency (BTE) trend was increased initially and decreased subsequently. Under high-load operation (1200 r/min BMEP, 2.0 MPa), the minimum charge density value of 44.8 kg/m³ was found to be reasonable. This charge density was suitable for combustion and brought about minimum exhaust energy and trade-off emissions. Moreover, by analyzing two operation conditions in terms of the maximum BTE with the Miller and the conventional cycles, compression temperature and combustion temperature were reduced in the Miller cycle with the charge density 44.8 kg/m³. A high C_p/C_v could improve the cylinder exergy/power conversion process by its positive effect of increasing the specific heat ratio. Owing to the interaction between a high C_p/C_v and exergy loss to heat transfer, the condition with the minimal charge density could produce more piston work.     

美国海战场综合电子信息系统概况及其启示

美军综合电子信息系统是由多个信息系统综合集成的、为诸军种联合作战提供信息作战能力的一体化军事信息系统.首先描述了美军建设一体化C4ISR系统的总框架,美国海军C4ISR体系的建设、主要的电子信息系统和美国海军一体化C4ISR系统的发展趋势.最后就我国海战场综合电子信息系统的发展进行了简单探讨.     

跨文化传播的桥梁:中国近代海关洋员与中西文化交流

以往研究中国近代海关史大多从制度沿革及政治经济层面进行考察,较少从文化维度进行分析.本文用全球化视野首次考察中国海关洋员在中西文化交流进程中的桥梁特征和作用,论述中突破了传统学界所持的"文化侵略"、"文化殖民"等传统单向话语,建构再现了早期全球化进程中跨文化双向传播这一鲜为人知的历史,不仅对深化中国近代海关史研究,而且对中国近代史和当今文化全球化理论研究都不无裨益.