软土地基路堤临界高度确定方法探讨

软土地基上高速公路工程建设中存在路堤临界高度的现象,根据国内外已有的文献资料全面总结了路堤临界高度的3种确定方法:实测资料确定法、理论公式计算法和离心模型试验法。在此基础上,根据某高速公路的大量实测数据,利用多元线性回归分析方法,得到了一个路堤临界高度计算的经验公式,探讨了软土地基硬壳层和软土层厚度与路堤临界高度之间的内在联系。     

工程机械管理及维护系统的设计与开发

从预防性维护的角度出发,提出了工程机械管理及维护系统的设计与开发思路.介绍了系统的设计原理,主要功能模块,工作流程和技术特点.系统集机械台帐管理、状态检测、维护保养、故障诊断、维修等模块于一体,适用于多数公路企业的机械管理工作,对提高公路企业的管理水平和工作效率具有重要的意义.     

一种基于PLL的牵引电机速度辨识算法

提出一种基于PLL的速度辨识算法,在此算法中引入闭环转子磁链观测器和幅值归一化环节,弥补PLL本身在抗干扰能力上的不足.通过闭环转子磁链观测模型抑制了转子磁链中可能出现的直流偏置,引入幅值归一化环节抑制了可能出现的转子磁链幅值波动.在仿真软件中搭建模型进行验证,结果表明在电机速度指令突变以及负载转矩突变的情况下可以保持较好的辨识效果.通过仿真结果验证了所研究速度辨识算法的正确性和有效性.     

考虑横向漂移的船舶路径跟踪自抗扰控制

针对船舶运动系统中内部动态不确定和外部干扰等问题,进行了欠驱动船舶路径跟踪的自抗扰方法研究。利用Backstepping设计参考航向角,并通过线性扩张状态观测器对流干扰和横向运动引起的横向漂移进行估计。其次,根据自抗扰算法对航向进行控制,采用线性扩张状态观测器对外界干扰及内部不确定项进行估计。最后仿真结果表明,在风流干扰下所设计的控制器仍能使船准确地跟踪上参考路径,验证了所提控制方案的有效性。     

针片状指数对道砟直剪力学特性的影响

为研究针片状道砟在破碎情况下对道砟散体直剪力学特性的影响，通过进行不同工况下道砟直剪试验，从道砟散体剪切强度、变形及破碎特性对试验结果进行分析. 研究结果表明:（1） 随着针片状指数增加，道砟散体直剪力学性能下降，包括抗剪强度和内摩擦角（100 kPa下当针状指数由0分别提高到20%、40%时，抗剪强度分别降低10.9%、16.8%；片状指数由0分别提高到20%、40%时，抗剪强度分别降低14.7%、22.3%；针、片状道砟总值由0分别提高到20%、40%时，抗剪强度分别降低12.4%、18.9%）. （2） 随着针片状道砟含量增加，试样剪缩和剪胀量均降低. （3） 针片状道砟在直剪试验过程中易于发生破碎，且破碎类型多为整体断裂并伴随尖角破碎折断，显著影响有砟道床维修周期.      

随着伊本·白图泰的足迹 游历中世纪的非洲、欧洲和亚洲——评李光斌翻译的《异境奇观——伊本·白图泰游记》

伊本·白图泰是14世纪著名的旅行家，他从摩洛哥出发，穿过阿尔及利亚、突尼斯、利比亚、埃及、叙利亚到麦加完成第一次朝觐。后来他又到过东非各国、印度、东南亚国家和中国等。李光斌老先生翻译的《异境奇观——伊本·白图泰游记》是目前最完整的全译本，当我阅读此书时，好象是跟随伊本·白图泰游历中世纪的非洲、欧洲和亚洲。李光斌老先生不仅翻译准确，达到了“信”、“达”、“雅”的境界，而且注释详尽，在考据学上也颇有作为。     

钢棒加强式轨枕道床的纵横向阻力试验研究

为了探究钢棒加强式轨枕的纵横向阻力机理、分担以及钢棒插入深度和砟肩宽度的影响规律，为川藏铁路长大坡道韧性和稳定性增强提供新方法，通过进行一系列纵横向阻力试验得到了钢棒加强式轨枕纵横向阻力的总体特性和分担情况；通过改变钢棒插入深度和砟肩宽度探究了两者对钢棒加强式轨枕纵横向阻力的影响规律. 结果表明:与普通轨枕相比，钢棒加强式轨枕的纵横向阻力都有提高，当砟肩宽度为500 mm，堆高为0，钢棒插入深度为400 mm时，钢棒加强式轨枕纵横向阻力比肩宽为500 mm、堆高为150 mm条件下普通轨枕分别高39.2%和53.7%，枕底部分横向阻力分担比普通轨枕提升8%，纵向阻力提升26%；钢棒插入深度对道床阻力影响较大，在砟肩宽度为500 mm、堆高为0 时，插入深度由100 mm变至400 mm，相较于普通轨枕肩宽为500 mm、堆高为150 mm的工况，纵向阻力增幅由5.1%变至39.2%，横向阻力增幅由6.1%变至53.7%；砟肩宽度变化时，纵向阻力变化较小，横向阻力变化较大.      

铺缆船用电缆埋设犁土壤挖掘阻力计算

传统的计算埋设犁土壤挖掘阻力的方法一般采用经验公式计算。经验公式依赖丰富的试验数据，且只能适应特定形状和尺寸的埋设犁。由于埋设犁的形状和尺寸各不相同，基于经验公式计算土壤挖掘阻力的方法准确性不高。根据土力学基本原理，在力学分析的基础上，运用数学方法进行公式推导，得到用于计算不同形状尺寸埋设犁挖掘阻力的理论方法，解决依赖经验公式计算土壤挖掘阻力的局限性。     

Reliability Modeling and Maintenance Policy Optimization for Deteriorating System Under Random Shock

Performance degradation and random shock are commonly regarded as two dependent competing risks for system failures. One method based on effective service age is proposed to jointly model the cumulative effect of random shock and system degradation, and the reliability model of degradation system under Nonhomogeneous Poisson processes (NHPP) shocks is derived. Under the assumption that preventive maintenance (PM) is imperfective and the corrective maintenance (CM) is minimal repair, one maintenance policy which combines PM and CM is presented. Moreover, the two decision variables, PM interval and the number of PMs before replacement, are determined by a multi-objective maintenance optimization method which simultaneously maximizes the system availability and minimizes the system long-run expect cost rate. Finally, the performance of the proposed maintenance optimization policy is demonstrated via a numerical example.     

Occupant injury risk analysis at NASS/CDS database

Injury information for vehicle occupants from the body regions of the head, thorax, abdomen, and upper and lower extremities, due to the restraints and interior parts of the vehicle, were extracted from the 2009 ~ 2012 NASS/CDS database. For those cases with high occurrence frequency, a detailed and comprehensive data analysis was performed to find the relationship between the accident, occupant, vehicle, and injury data. A numerical frontal impact sled model with the Hybrid III dummy and the GHBMC human body model was constructed to simulate and identify those injury risks according to NASS/CDS. Among the 5,734 injuries to the aforementioned body regions from frontal crashes are, listed by frequency of occurrence, the lower extremity (27.8 %), upper extremity (21.3 %), thorax (15.1 %), face (10.9 %), spine (8.7 %), head (7.3 %), and abdomen (6.9 %). The main injury sources to the head were the windshield, side structure, and steering wheel. For the thorax and abdomen they were the seat belt and steering wheel. For the lower extremity it was the instrument panel. The main injury patterns for the head were the concussion and the contusion. For the thorax they were vessel laceration and lung contusion. For the abdomen they were laceration and contusion of the organs. For the lower extremity they were bone fracture and ligament rupture. The steering wheel and seat positions were main factors affecting head and thorax injury risks. From the sled impact simulation, high injury risks of the head and thorax were assessed respectively at conditions of steering column tilt down and rear most seat position, which correlated well with the findings from the NASS/CDS data analysis.