基于遗传算法的盾构隧道管片接头刚度反演研究北大核心CSCD

梁-弹簧模型在管片衬砌结构计算中应用较广泛,目前接头刚度取值方法主要有模型试验法及经验取值法,模型试验法耗时长、成本高昂,而依据经验取值难免存在一定主观性。鉴于此,利用C++编程语言,基于遗传算法开发了盾构隧道管片结构位移反分析程序,首先通过弹性模量值反演算例,得出反演值与理论值误差为1.4%,验证了算法和程序的可行性。利用程序将反演接头刚度值与实际设计案例管片接头刚度值进行对比,反演计算结果表明:正弯矩下管片环向接头转动刚度值反演误差为2.6%,负弯矩下管片环向接头转动刚度值反演误差为4.3%。     

大直径盾构隧道穿越建筑物群变形分析与控制措施北大核心CSCD

大直径盾构隧道掘进施工对土体造成扰动,导致地表产生沉降或隆起,继而严重威胁上部建筑物群的结构安全。文章依托某大直径盾构隧道穿越老旧小区密集建筑物群工程,首先利用二维有限元软件计算关键断面房屋的沉降变形,再对比三维有限元软件的计算结果,分析两种计算方法的适用范围;然后基于三维模型探究了不同初期荷载释放率对盾构穿越引起的地表和房屋变形的影响,最后利用Peck公式计算的理论地表沉降数据,梳理初期荷载释放率、地表沉降、地层损失率三者的内部联系并提出了控制变形的相关措施。研究结果表明,初期荷载释放率越小,地表及房屋沉降也越小,对应的地层损失也越小;对于控制地表变形,减小荷载释放率等同于减小地层损失率;初期荷载释放率、地表沉降、地层损失率这三者减小的量值呈线性关系。     

Experimental research on dynamic responses characteristics and influence laws of gear transmission-propulsion system under gear excitation北大核心CSCD

［Objective］In order to study the dynamic response characteristics and influence laws of a marine gear transmission-propulsion system, a series of bench tests is carried out.［Methods］First, a biaxial gear transmission-propulsion system test bench including a cross connection gear is built. Experiments to test the acceleration response of the gearbox body and propulsion shaft system are then carried out, and the influence of speed, driving mode, axial static thrust, axial dynamic excitation force from the propeller and other factors on the dynamic response characteristics of the system are compared and analyzed. ［Results］The experimental results show that the transmission law of the vibration acceleration response of the gear transmission-propulsion system is mainly at the meshing frequency and its multipliers, as well as peaks in the low frequency band of 30–80 Hz under certain working conditions. ［Conclusion］This study can provide technical support for the vibration and noise reduction design of gear transmission-propulsion systems. © 2022 Journal of Clinical Hepatology. All rights reserved.     

Application study on a control strategy for a hybrid electric public bus

This paper first describes the control strategy used in a hybrid electric public bus and then proposes a torque-balancing control strategy. Simulations were performed using the designed control strategies, and the results were analyzed under different conditions. The torque-balancing control strategy was improved on the basis of the efficiency-first ideas of the hybrid system. Finally, experiments were performed to verify that the efficiency-first and torque-balancing control strategy (EFCS) is both feasible and reliable. The simulation results showed that, compared with a conventional public bus, the hybrid electric bus could save approximately 27.3 percent on fuel consumption using the EFCS control strategy in a public bus in China, while under the Wuhan urban driving cycle.     

Drive control system design for stability and maneuverability of a 6WD/6WS vehicle

This paper describes a drive controller designed to improve the lateral vehicle stability and maneuverability of a 6-wheel drive / 6-wheel steering (6WD/6WS) vehicle. The drive controller consists of upper and lower level controllers. The upper level controller is based on sliding control theory and determines both front and middle steering angle, additional net yaw moment, and longitudinal net force according to the reference velocity and steering angle of a manual drive, remotely controlled, autonomous controller. The lower level controller takes the desired longitudinal net force, yaw moment, and tire force information as inputs and determines the additional front steering angle and distributed longitudinal tire force on each wheel. This controller is based on optimal distribution control and takes into consideration the friction circle related to the vertical tire force and friction coefficient acting on the road and tire. Distributed longitudinal/lateral tire forces are determined as proportion to the size of the friction circle according to changes in driving conditions. The response of the 6WD/6WS vehicle implemented with this drive controller has been evaluated via computer simulations conducted using the Matlab/Simulink dynamic model. Computer simulations of an open loop under turning conditions and a closed-loop driver model subjected to double lane change have been conducted to demonstrate the improved performance of the proposed drive controller over that of a conventional DYC.     

不同加载方式的斜齿轮接触分析

以一对相互啮合的渐开线斜齿轮为研究对象,通过APDL语言生成参数化几何模型,研究映射网格划分方式并建立了斜齿轮接触的有限元模型,基于非线性接触算法在不同加载方式下对齿轮啮合齿面的接触应力进行了分析,将仿真与赫兹计算结果进行了比较,讨论了不同加载方式对接触应力的影响.     

Experimental assessment of the ultimate strength of a box girder subjected to severe corrosion

The objective of this paper is to describe the experimental assessment of the ultimate strength of a severely corroded box girder subjected to a uniform bending moment resulting from four-point loading. Three box girders that could simulate the behaviour of midship sections have been deteriorated in corrosive seawater environment to simulate different levels of corrosion degradation of ageing ship structures. During the deterioration process, various parameters have been controlled and the total weight lost was registered. Corroded plate thicknesses have been measured in 212 points and a statistical analysis has been performed. The resulting corrosion wastage has been fitted by a non-linear time variant degradation model. The experimental results of the ultimate strength test of a severely corroded box girder subjected to a four-point loading have been analysed. The load-displacement and moment-curvature relationship is discussed, different failure modes are identified, and the strain gauges readings are analysed.     

The implications of the re-establishment of direct links across the Taiwan Strait on the aviation industries in Greater China

This paper investigates the economic implications of the liberalization of air transportation across the Taiwan Strait to the region's aviation industries. Our analysis suggests that (1) liberalization has brought substantial benefits to airports and airlines in Mainland China and Taiwan. Negative impacts to Hong Kong are largely compensated by traffic increase in routes linking Mainland China. (2) In general, Taiwanese airports and airlines have benefited more from liberalization compared to airports and airlines on the mainland and Hong Kong. Such asymmetric effect is due to the larger size of the Mainland Chinese aviation market, which allows Taiwanese airlines to exploit network-related benefits. (3) Our investigation suggests that foreign hub carriers and medium sized Chinese airports will benefit most from China's future liberalizations.