一种面向智能校园网的IPv6过渡技术

分析了双栈协议、隧道技术和NAT-PT技术这3种常用的过渡机制,并通过一个IPv6实验床的建设,利用IPv6双栈协议和隧道技术过渡机制,有效地实现了校园网从IPv4向IPv6的平滑过渡。与已有的技术相比,该方法实现了IPv4和IPv6的共存及协同运行。     

复杂城市场地下大跨度桥梁总体设计关键技术研究

以常德沅江六桥总体设计为例，分析了基于复杂城市场地下大跨度桥梁设计特点及需考虑的各方面因素，阐述沅江六桥方案的设计思路。综合考虑规划路网、沿线高压电走廊、沅江水文条件、地震断裂带等因素，对大桥的规划桥位进行优化调整，提出推荐桥位方案。根据通航要求和规划码头等条件，确定推荐方案的桥梁跨径和桥型。简要介绍桥梁结构设计，并验证主要结构的科学合理性。     

Mechanical model and characteristics of deep-water drilling riser-wellhead system under internal solitary waves

Internal solitary waves with a huge amount of energy easily trigger the large dynamic responses of riser-wellhead system and threaten its structural safety. However, previous studies have only focused on the dynamic response of the riser under internal solitary waves. The riser may experience excessive traction from the platform, especially from the mooring platform, in response to the arrival of internal solitary waves. The bottom of the riser connects to the wellhead system, which in turn exerts a reaction force on the riser. To address this problem, a coupled dynamic model of deep-water drilling mooring platform-riser-wellhead system under internal solitary waves is developed in this paper. A dynamic response analysis method based on the fourth-order Runge-Kutta method and finite element method is also proposed for the mooring platform-riser-wellhead system. A dynamical solver for the coupled system is then developed using MATLAB. The dynamic response characteristics of the riser-wellhead system under internal solitary waves are calculated. Results show that the displacement and bending moment of the system initially increases and then decreases along with the propagation of internal solitary waves, and finally reach equilibrium position. The displacement and bending moment reach their peak before the trough of internal solitary waves passes through the riser-wellhead system. The dynamic responses of the riser-wellhead system under the influence of internal solitary wave loads are much larger than those without the effect of internal solitary wave loads. The riser system experiences shearing loads at the interface of internal solitary waves, which trigger a step-like bending moment variation. The bending moment of the conductor under the mudline is greatly increased by the internal solitary waves.