Phase change analysis of an underwater glider propelled by the ocean's thermal energy

The phase change characteristic of the power source of an underwater glider propelled by the ocean's thermal energy is the key factor in glider attitude control. A numerical model has been established based on the enthalpy method to analyze the phase change heat transfer process under convective boundary conditions. Phase change is not an isothermal process,but one that occurs at a range of temperature. The total melting time of the material is very sensitive to the surrounding temperature. When the temperature of the surroundings decreases 8 degrees,the total melting time increases 1.8 times. But variations in surrounding temperature have little effect on the initial temperature of phase change,and the slope of the temperature time history curve remains the same. However,the temperature at which phase change is completed decreases significantly. Our research shows that the phase change process is also affected by container size,boundary conditions,and the power source's cross sectional area. Materials stored in 3 cylindrical containers with a diameter of 38mm needed the shortest phase change time. Our conclusions should be helpful in effective design of underwater glider power systems.     

Phase change analysis of an underwater glider propelled by the ocean＇s thermal energy

The phase change characteristic of the power source of an underwater glider propelled by the ocean＇s thermal energy is the key factor in glider attitude control. A numerical model has been established based on the enthalpy method to analyze the phase change heat transfer process under convective boundary conditions. Phase change is not an isothermal process, but one that occurs at a range of temperature. The total melting time of the material is very sensitive to the surrounding temperature. When the temperature of the surroundings decreases 8 degrees, the total melting time increases 1.8 times. But variations in surrounding temperature have little effect on the initial temperature of phase change, and the slope of the temperature time history curve remains the same. However, the temperature at which phase change is completed decreases significantly. Our research shows that the phase change process is also affected by container size, boundary conditions, and the power source＇s cross sectional area. Materials stored in 3 cylindrical containers with a diameter of 38ram needed the shortest phase change time. Our conclusions should be helpful in effective design of underwater glider power systems.     

Time Domain Calculation of Connector Loads of a Very Large Floating Structure

Loads generated after an air crash, ship collision, and other accidents may destroy very large floating structures(VLFSs) and create additional connector loads. In this study, the combined effects of ship collision and wave loads are considered to establish motion differential equations for a multi-body VLFS. A time domain calculation method is proposed to calculate the connector load of the VLFS in waves. The Longuet–Higgins model is employed to simulate the stochastic wave load. Fluid force and hydrodynamic coefficient are obtained with DNV Sesam software. The motion differential equation is calculated by applying the time domain method when the frequency domain hydrodynamic coefficient is converted into the memory function of the motion differential equation of the time domain. As a result of the combined action of wave and impact loads, high-frequency oscillation is observed in the time history curve of the connector load. At wave directions of 0° and 75°, the regularities of the time history curves of the connector loads in different directions are similar and the connector loads of C1 and C2 in the X direction are the largest. The oscillation load is observed in the connector in the Y direction at a wave direction of 75° and not at 0°. This paper presents a time domain calculation method of connector load to provide a certain reference function for the future development of Chinese VLFS     

Improving Mobility Management for AII-IP Radio Heterogeneous Network Using SCTP

Mobility management is a very important function of mobile communication in all-IP radio heterogeneous network. In order to achieve an efficient mobility management, with low delay and low beacon overhead, a micromobile stream control transmission protocol （mmSCTP） scheme was proposed. This scheme reasonably utilizes SCTP features and elaborately designs execution-steps for vertical handoff. Moreover, it provides fast locating for idle mobile node when a session is initiated by the correspondent node. The analytical and simulation results show that the proposed scheme is effective in supporting fast vertical handoff and effective location management.     

浙江省公路、水路交通科技“九五”发展状况和“十五”展望

本从四个方面回顾总结了“九五”期间浙江省公路、水路交通科技发展状况,分析了存在了问题和面临的形势,简要论述了“十五”发展目标和主要任务。     

深圳市BRT定位、发展模式及近期建设标准建议

快速公交系统（BRT）在国内尚属新生事物,各城市都在探索中,并无成功的案例。在对国外典型的BRT系统研究的基础上,针对深圳实际情况,对深圳市BRT定位、发展模式和近期建标等提出建议,具有重要意义。     

电气化铁路接触网机械化检修问题探讨

比较详细的论述了电气化铁路接触网机械化检修的重要性及目前实施机械化检修中存在的问题，最后提出了解决措施和建议。     

海上深层水泥拌和船定位系统的型号选择

通过调研当代海上打桩、抛石、水泥土搅拌、定位等施工作业情况，浅议了定位的基本原理，进行了现行产品的型号比选，并结合烟台港水泥土搅拌作业的需要，就系统的型号提出了具体的意见。     

Ignition models and simulation of solid propellant of thermodynamic undersea vehicle

The starting characteristics of thermodynamic undersea vehicle systems are determined by the geometry, size and combustion area of solid propellants, which directly effect liquid propellant pipeline design. It is necessary to establish accurate burning models for solid propellants. Based on combustion models using powder rings and two different solid ignition grains, namely star-shaped ignition grains and stuffed ignition grains, a mathematic model of the ignition process of the propulsion system was built. With the help of Matlab, a series of calculations were made to determine the effects of different grains on ignition characteristics. The results show that stuffed ignition grain is best suited to be the ignition grain of a thermodynamic undersea vehicle system.     

高职高专轨道交通类专业的办学模式探讨

高职高专轨道交通类专业的专业性较强,就业面较窄,对毕业生身体素质与心理素质要求较高,毕业生的就业压力较大,严重制约了开办相应专业的院校的办学规模和专业建设.校企合作联办"订单班",确定岗位标准和培养目标,确定班别和学生,确定验收标准,是此类专业办学的一种途径与方式,有利于出好人才、快出人才.