CRTSⅡ型轨道板结构设计

介绍了Ⅱ型无砟轨道的主要技术特点.采用当量地基梁模型、三重叠合梁模型、梁-板模型和空间实体模型对Ⅱ型板式无砟轨道结构进行了力学计算,得出Ⅱ型轨道板设计荷载.通过不同的荷栽组合对轨道板的强度、裂缝等进行检算,最终确定轨道板的配筋.简要阐述了轨道板内钢筋绝缘和综合接地方案.可以为Ⅱ型轨道板的结构设计提供指导.     

Enforcement of law by the Port State Control (PSC)

Since the International Maritime Organization (IMO) introduced the Port State Control (PSC) programme in 1982, it has been playing a vital role in the enforcement of safety law at sea worldwide. This paper addresses the effectiveness of PSC and the effectiveness of the methods for selecting ships to be inspected adopted by regional PSC. Data on ship total loss (from 1973-2003) and on the PSC records (from 1994-2005) have been collected. The study reveals that the enforcement of PSC is effective in improving the safety level of maritime transport. The methods adopted by regional PSC are compared on their effectiveness, efficiency and stability in identifying substandard ships. Suggestions are made on the improvement of the enforcement of PSC.     

基于非线性渗流模型的管道型岩溶隧道突水机理研究北大核心CSCD

管道型岩溶突水是一个复杂的多场耦合的非线性渗流问题,致灾具有突发性。为揭示管道型岩溶突水灾害的发生机理,文章基于多物理场耦合作用机理,开展了不同溶腔水压、岩溶管道内不同填充介质、不同岩溶管道宽度及岩溶管道长度条件下的多场耦合分析。得到以下结论:(1)管道型岩溶破坏模式下发生的突水灾害,根据填充介质透水性能的异同而表现不同;(2)流体从富水溶腔中流出时流速较小,流经岩溶管道后流速逐渐增加,进入隧道后达到最大值;(3)影响突水过程的因素主要有:富水溶腔水压、岩溶管道或断层裂隙带内填充介质的种类、岩溶管道的宽度、隧道与水源的距离,其中,岩溶管道宽度及岩溶管道内填充介质类型对突水影响大于其他因素。     

Parameter optimization and parametric deviation influence for shock resistance of double-stage vibration isolation system with limiters北大核心CSCD

［Objectives］For marine nuclear power plants, the relative displacement of the pump supported by a vibration isolation system should be strictly restricted. In order to improve the shock resistance of a vibration isolation system with displacement limiters, the parameter optimization and parametric deviation influence are studied. ［Methods］The theoretical model of a double-stage vibration isolation system with typical limiter parameters is established, the analysis of the shock response characteristics of the system is carried out using the direct integration method, the optimal limiter parameters are obtained using a genetic algorithm, and the influence of parameter deviation on the shock resistance of the system is studied. ［Results］Limiter parameters significantly affect the shock response characteristics of the vibration isolation system. The optimal limiter parameters improve the shock resistance of the system, but parameter deviation has a great influence on shock resistance. Based on the influence of parameter deviation, a deviation control strategy is proposed in which the elastic parameter should have a positive deviation and the gap parameter a negative deviation. The simulation results show that the proposed strategy can effectively alleviate the shock resistance degradation caused by deviation.［Conclusions］The results of this study can be used to guide the design, manufacturing and variation control of limiters for vibration isolation systems. © 2022 Journal of Clinical Hepatology. All rights reserved.     

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%。     

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.     

Study on rail corrugation of a metro tangential track with Cologne-egg type fasteners

In Chinese metro lines, rail corrugation on both tangential and tight curved tracks with Cologne-egg type fasteners is very severe. Based on the viewpoint of friction-induced vibration causing rail corrugation, the rail corrugation on a tangential track with Cologne-egg type fasteners is studied in this paper. A vibration model of an elastic multiple-wheelset-track system with Cologne-egg type fasteners is established. Both the complex eigenvalue analysis and the transient dynamic analysis are performed to study the stability and the dynamic performance of the wheelset-track system. The simulation results show that a low rail support stiffness value is responsible for rail corrugation on the tangential track. When the Cologne-egg fasteners characterised by a lower stiffness value are replaced with the DTVI2 fasteners characterised by a higher stiffness value, rail corrugation disappears. However, rail corrugation on tight curved tracks cannot be suppressed using the same replacement. The above conclusions are consistent with the corrugation occurrences in actual metro tracks.     

Experimental investigation into the mechanism of the polygonal wear of electric locomotive wheels

Experiments were conducted at field sites to investigate the mechanism of the polygonal wear of electric locomotive wheels. The polygonal wear rule of electric locomotive wheels was obtained. Moreover, two on-track tests have been carried out to investigate the vibration characteristics of the electric locomotive's key components. The measurement results of wheels out-of-round show that most electric locomotive wheels exhibit polygonal wear. The main centre wavelength in the 1/3 octave bands is 200?mm and/or 160?mm. The test results of vibration characteristics indicate that the dominating frequency of the vertical acceleration measured on the axle box is approximately equal to the passing frequency of a polygonal wheel, and does not vary with the locomotive speed during the acceleration course. The wheelset modal analysis using the finite element method (FEM) indicates that the first bending resonant frequency of the wheelset is quite close to the main vibration frequency of the axle box. The FEM results are verified by the experimental modal analysis of the wheelset. Moreover, different plans were designed to verify whether the braking system and the locomotive's adhesion control have significant influence on the wheel polygon or not. The test results indicate that they are not responsible for the initiation of the wheel polygon. The first bending resonance of the wheelset is easy to be excited in the locomotive operation and it is the root cause of wheel polygon with centre wavelength of 200?mm in the 1/3 octave bands.     

掺石墨水泥基复合材料电磁波吸收性能研究

以水泥净浆为基体、高纯石墨粉为电磁波吸收剂,制备了掺石墨水泥基复合材料。采用矩形波导法测试不同石墨掺量下的水泥基复合材料的电磁参数,并基于传输与阻抗理论计算得到试验样品的反射损耗RL,另外又定义了损耗因子tanδ,最后根据广义匹配定律定义了M值。结果表明,15%石墨的水泥基复合材料低频段具有较高的介电常数,且其在吸波层厚度为5 mm时,出现两个吸收峰,分别为RL=-34.9 d B和RL=-53.75 d B,反射损耗RL-10 d B的频带达到0.43 GHz(3.62~3.95 GHz),有效吸收频带较窄。此外,石墨粒径组成尺寸对掺石墨水泥基复合材料吸波能力有一定影响。     

Design and evaluation of sideslip angle observer for vehicle stability control

This paper presents a method for estimating the vehicle side slip angle, which is considered as a significant signal in determining the vehicle stability region in vehicle stability control systems. The proposed method combines the model-based method and kinematics-based method. Side forces of the front and rear axles are provided as a weighted sum of directly calculated values from a lateral acceleration sensor and a yaw rate sensor and from a tire model according to the nonlinear factor, which is defined to identify the degree of nonlinearity of the vehicle state. Then, the side forces are fed to the extended Kalman filter, which is designed based on the single-track vehicle model associated with a tire model. The cornering stiffness identifier is introduced to compensate for tire force nonlinearities. A fuzzy-logic procedure is implemented to determine the nonlinear factor from the input variables: yaw rate deviation from the reference value and lateral acceleration. The proposed observer is compared with a model-based method and kinematics-based method. An 8 DOF vehicle model and Dugoff tire model are employed to simulate the vehicle state in MATLAB/SIMULINK. The simulation results shows that the proposed method is more accurate than the model-based method and kinematics-based method when the vehicle is subjected to severe maneuvers under different road conditions.