IP网络的QOS技术探讨

在早期计算机网络和分组转发网中，网络只提 供尽力而为(Best Effort)的业务。对进人网络的业 务流，都以先来先服务(FIFO)的方式对业务流分组 进行服务，即IP网尽量把数据包从源端转发到目的 端，但对所能够提供的包转发的服务质量(QoS)不 做任何承诺〔。因此，IP网提供的服务     

基于MATLAB、C++、Vega的减摇鳍控制系统的视觉仿真

针对船舶减鳍系统,运用PID控制理论设计了控制器,利用MATLAB模拟了随机海浪和鳍相互作用对船舶的影响,将C 作为中间环节,实现了MATLAB与Vega之间的数据传输,从而实现了减摇仿真的视觉效果。经仿真试验表明,该仿真系统的结果是令人满意的。     

中国铁路实现跨越式发展的资金保障分析

中国铁路实现跨越式发展的资金保障包括资金筹集和资金节约两方面。一方面,铁路建设的投融资应采取政府主导的多元化投资模式,其中项目融资是实现投资主体多元化和投资方式市场化的重要途径;另一方面,应使铁路建设项目的工程寿命周期成本达到最低,关键是强本简末,严格控制投资规模以及铁路建设项目的工程造价,采取有效的工程项目管理模式。     

安全诚信管理——水上安全监管新模式

中华人民共和国海事局2003年6月1日开展评选安全诚信船舶以来,在一定程度上提高了船舶单位安全生产水平,但这种制度并没有得到长足发展。客观地说,这种安全诚信做法还没有为广大海事执法人员所认同,本文旨在进一步转变执法人员观念,提高对安全诚信的认识,助推船舶单位构建安全诚信管理体系,实现水运的持续快速发展。     

Measurement of soot oxidation with No<Subscript>2</Subscript>-O<Subscript>2</Subscript>-H<Subscript>2</Subscript>O in a flow reactor simulating diesel engine DPF

Understanding the mechanism of carbon oxidation is important for the successful modeling of diesel particulate filter regeneration. Characteristics of soot oxidation were investigated with carbon black (Printex-U). A flow reactor system that could simulate the condition of a diesel particulate filter and diesel exhaust gas was designed. Kinetic constants were derived and the reaction mechanisms were proposed using the experimental results and a simple reaction scheme, which approximated the overall oxidation process in TPO as well as CTO. From the experiments, the apparent activation energy for carbon oxidation with NO₂-O₂-H₂O was determined to be 40±2 kJ/mol, with the first order of carbon in the range of 10∼90% oxidation and a temperature range of 250∼500°C. This value was exceedingly lower than the activation energy of NO₂-O₂ oxidation, which was 60±3 kJ/mol. When NO₂ exists with O₂ and H₂O, the reaction rate increases in proportion to NO₂. It increases nonlinearly with O₂ or H₂O concentration when the other two oxidants are fixed.     

超长桩有效桩长问题的探讨

超长桩在大型桥梁和高层建筑中得到了越来越广泛的应用,实际工程中往往会出现桩越来越长的现象,有时桩太长会造成浪费,且不科学,所以有必要研究超长桩的有效桩长问题.运用数学和力学知识,在假定计算模型的基础上,从理论上推导了超长桩的有效桩长的计算公式.结果表明,有效桩长与工作荷载下的桩顶沉降、桩身刚度、桩顶工作荷载及桩侧土体性质有关.这对软土地区超长桩的设计有着重要的指导意义和适用价值.     

拱圈喷射混凝土施工工艺及操作经验

介绍了旧桥加固改造拱圈喷射混凝土的施工经验,提出材料控制是前提,合适的喷射混凝土配合比是关键,喷射方式是重点.     

Visco‐elastic traffic flow model

To increase our understanding of the operations of traffic system, a visco‐elastic traffic model was proposed in analogy of non‐Newtonian fluid mechanics. The traffic model is based on mass and momentum conservations, and includes a constitutive relation similar to that of linear visco‐elastic fluids. The further inclusion of the elastic effect allows us to describe a high‐order traffic model more comprehensively because the use of relaxation time indicates that vehicle drivers adjust their time headway in a reasonable and safe range. The self‐organizing behaviour is described by introducing the effects of pressure and visco‐elasticity from the point of view in fluid mechanics. Both the viscosity and elasticity can be determined by using the relaxation time and the traffic sound speed. The sound speed can be approximately represented by the road operational parameters including the free‐flow speed, the jam density, and the density of saturation if the jam pressure in traffic flows is identical to the total pressure at the flow saturation point. A linear stability analysis showed that the traffic flow should be absolutely unstable for disturbances with short spatial wavelengths. There are two critical points of regime transition in traffic flows. The first point happens at the density of saturation, and the second point occurs at a density relating on the sound speed and the fundamental diagram of traffic flows. By using a triangular form flow–density relation, a numerical test based on the new model is carried out for congested traffic flows on a loop road without ramp effect. The numerical results are discussed and compared with the result of theoretical analysis and observation data of traffic flows. Copyright © 2011 John Wiley & Sons, Ltd.     

邮轮旅客登船桥型式及特点分析

能够为邮轮旅客提供便捷、舒适登离船服务的大型现代化邮轮登船桥在国外的发展已有近20年的历史,由于各个邮轮码头所处的地理位置、海水潮差大小、邮轮码头工艺布局以及接待邮轮类别的不同,邮轮登船桥虽然均能满足海港接待邮轮的要求,但却具有各自不同的主体结构形式。本文按照两种不同的分类方法,对国外现有的登船桥型式进行了分类,并阐述了各种登船桥的特点。     

大管桩与抛石体相互作用的模型方试验研究

高桩码头施工中的抛石过程会对大管桩的受力产生较大的影响,这将给码头的正常使用带来隐患.模型实验用沙子模拟抛石体,用PVC管模拟大管桩,利用应变片电测技术,测量了不同工况下PVC管中的应变,并分析得出了作用在PVC管上载荷的分布规律.通过模型实验,给出了大管桩与抛石体相互作用的经验公式,并指出引起PVC管侧向弯曲的主要原因是沙子对PVC管存在侧向集中力,产生该集中力的原因是PVC管前后沙子高度差的存在.此外,通过验证实验和数值模拟,得出了与模型实验相同的结论,从而进一步证明了模型实验所得规律的正确性.