呼和浩特市汽车4S店发展的探讨

针对内蒙古呼和浩特市汽车4S店的发展及现状,指出目前存在的问题,并提出解决问题的对策与建议。     

CET-4虚拟语气考题分析与归纳

本文结合1998￣2003年CET-4考题,对虚拟语气的考查重点进行了分析与归纳,旨在使学生熟练掌握其解题技巧。     

用新观点研究预测中国2010—2011年车市发展

为分析研究2011年及近期车市发展趋势,供汽车产销单位经营决策参考,采用"车市波动分析法",用车市季度主要参数表和年度车市波动图分析车市实际走势。肯定了汽车产销量超美的成绩。指出2010年车市逐季度大幅回落趋势,分析了罕见的"波形异常"问题的影响及原因。对2011年面临形势进行了分析和预测:车市处于扩张后期,中下等市场,2011年后车市仍有可能小幅回升,对"十二五"期间车市发展持审慎乐观态度。     

交流能量互馈试验台网侧变流器仿真研究

简要介绍了交流传动互馈试验台的主要优点、电气结构和实现原理,对网侧变流器的工作原理和控制方法进行了说明。通过计算机仿真对试验台中变压器和网侧变流器部分进行了实际工况的模拟。仿真结果表明网侧变流器的性能良好,满足互馈试验台的需要,同时也说明本试验台的网侧能量互馈的可行性。     

SS6B型电力机车牵引电动机环火原因及防止措施

对SS6B型电力机车ZD114型脉流牵引电动机第一次中修后运用时所发生环火故障进行分析,并且探讨在设计、制造、运用及检修方面是否存在不同程度的缺陷。根据实际运用及检修经验,在此提出一些防止措施,已经取得一些初步效果。     

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。     

Remaining fatigue life assessment of corroded mooring chains using crack growth modelling

Failures caused by the combined actions of fatigue, corrosion and wear are important safety concerns for mooring chains used on floating structures in the oil and gas industry. Prediction of remaining corrosion fatigue life based on surface condition could therefore be a useful tool for the continued safe operation of corroded chains. This paper investigates the use of crack growth modelling for estimating the remaining corrosion fatigue life of mooring chains that exhibit significant pitting corrosion damage. A crack growth modelling approach is used to produce remaining fatigue life estimates for a selection of severely pitted mooring chains. Using fatigue crack growth rate test results for grade R4 high strength mooring chain steel, empirical crack growth laws are presented for free corrosion and cathodic protection conditions at load ratio R = 0.1. Two different methods for establishing equivalent cracks from surface scans of corrosion damage are presented. The mooring chains are proof loaded as part of their manufacturing process. Residual stresses introduced during this process have therefore been determined by finite element analysis and accounted for in the fatigue crack growth predictions. One of the equivalent crack models, accounting for the single dominant corrosion pit, provided quite accurate fatigue life predictions when compared with full scale test results.     

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.     

Hydrodynamic modelling of a multi-body wave energy converter using the Moving Frame Method

Significant wave energy conversion may be achieved with multiple floats with several modes of motion combining constructively to generate power. With the M4 system, power take off is at hinges to absorb resulting pitch motions. Complexity increases with number of floats and conventional vectorial multi-body dynamics may be conveniently replaced by the recently formulated moving frame method based on the calculus of variations to avoid free-body diagrams and joint reaction forces. Furthermore by utilising group theory to gather spatial rotations and angular velocities in a common structure, the obtained notation is general and straight-forward to apply for single and multi-body systems. This paper lays the foundations for incorporating hydrodynamic forces into the moving frame method. The method is applied to 3, 6 and 8 float cases in regular and irregular waves with results compared to the vectorial method and experimental measurements, showing close agreement. It is suggested that this is a more natural and general approach for complex multi-body, multi-hinge hydrodynamics systems.     

Design and model test of a soft-connected lattice-structured floating solar photovoltaic concept for harsh offshore conditions

Various types of floating solar photovoltaic (FPV) devices have been previously proposed, designed and constructed with applications primarily limited to onshore water bodies or near-shore regions with benign environmental conditions. This paper proposes a novel FPV concept which can survive harsh environmental conditions with extreme wave heights above 10 m. This concept uses standardised lightweight semi-submersible floats made of circular materials as individual modules. The floating modules are soft connected with ropes to form an FPV array. We first present the conceptual design of the floats and the connection systems, including hydrostatic, hydrodynamic, and structural assessments of the floats. To verify the motion response performance, we carried out 1:60 scaled model tests for a 2 by 3 array under regular and irregular wave conditions. From the time series and response spectra, the motion characteristics of the array and the mooring responses are analysed in detail. The proposed concept exhibits excellent performances in terms of modular motions with limited wave overtopping and no contact is observed between adjacent modules under the extreme wave conditions. The findings of this study can serve as a valuable reference to developing reliable and cost-effective FPV technologies for offshore conditions.