平面运动机构试验的数值模拟

获取水动力导数是预报船舶操纵性的关键,平面运动机构试验是主要的测量方法.该文通过商业软件FLUENT提供的动网格功能对DTMB5415模型的平面运动机构试验进行了数值模拟,忽略了自由面兴波,计算得到的侧向力及转首力矩的变化与实验结果吻合良好,为使用CFD预报船舶操纵性提供了相关经验.     

水利水电工程通航技术研究进展

随着我国水利水电工程向具有供水、防洪、发电、通航等多目标开发方向的发展,高坝通航技术得到了迅猛发展。总结了通航建筑物船闸及升船机的技术研究进展,特别是具有国际领先水平的船闸输水形式及阀门防空化新技术,湿运全平衡钢丝绳卷扬提升式垂直升船机、齿轮齿条爬升式升船机和水力浮动式升船机新技术。我国高坝通航升船机及船闸建设水平已跃居世界前列。     

自主湖水环境监测船的运动控制系统设计

设计自主湖水环境监测船的运动控制系统,包括由GPS和电子罗盘构成的导航系统、超声传感器避障系统、太阳能和蓄电池配合的自主能源供给系统。采用超声、红外传感器和机械卡环设计自动泊位装置。基于坐标系变换,建立自主船的运动学模型。针对双电机的转速控制,设计实现三层递阶控制器及滑膜变结构转速控制算法。实验结果表明,滑膜控制能较好地排除水流速度的突变干扰,差动转向平稳,自主船可实现自动泊位和能源自给,运动控制系统稳定,速度响应小于4 s,大角度转向响应小于13 s。     

新建隧道穿越既有桥梁桩基时的主动预支护技术

随着我国城市化进程的加快,新建隧道穿越既有桥梁桩基的工程越来越多.介绍一种具有防御性的主动预支护技术,在新建隧道穿越既有桥梁桩基时,对采取一般技术手段无有效控制把握,有可预见的大变形,地质条件复杂或重要性桥梁等情况时,可以采取"先加固,后开挖"的施工顺序以及"支顶为主,注浆为辅"的桥梁保护方案,控制桥梁上部结构的变形,以保证桥梁在隧道开挖过程中的正常使用.     

桃花江航运枢纽整体水力学试验研究

桃花江旅游景观船闸在布置上因受到枢纽地形与河道防洪的限制,难以满足规范要求.采用几何比尺为1∶25的整体水工模型进行了试验研究,2座枢纽的控制运行条件均为最高通航水位组合,主河道中流速较大,特别是上下游口门处引航道的横向流速较大,不能满足规范要求.修改方案主要通过减小2座船闸上下游引航道与桃花江主河道夹角,并对口门附近地形进行了相应的疏浚.试验结果表明,修改方案有效降低了2座船闸上游口门处横向流速等不利因素.     

南水北调丹江口升船机电力拖动系统设计及应用

介绍了丹江口水电站过坝垂直升船机和斜面升船机的概况及组成,对电力拖动系统进行了分析,依据当前电力拖动的技术发展,采用先进的技术,对电力拖动系统进行选型、配置,设计了完善的操作方式,具有独特的特点。经厂内及机电联调试验验证,电力拖动系统设计合理、满足要求。     

Vessel motion thresholds for maintaining physical and cognitive performance: a study of naval personnel at sea

Methods and results are reported from a study of ships companies' exposure to low-frequency motions on three vessels of the Royal Navy. The aim of the study was to investigate relationships between deck accelerations and the incidence of problems such as difficulties with physical tasks, cognitive activities, motion sickness, and work effort. Ship motions were recorded continuously during sea patrols of 10-14 days. The data collected from the three vessels comprised 105 days of ship motions over 12 patrols, with 779 associated daily diaries from 78 participants. Problems most strongly associated with vessel motions were related to the difficulties with physical tasks. Some cognitive aspects of task performance and motion sickness were associated with vertical acceleration magnitudes, but the correlations were less strong than with physical tasks. Practitioner Summary: Little is known about the severity of ship motions that degrade physical and mental performance. The paper offers preliminary estimates of the motion threshold values below which the performance will not be degraded by motion.     

Effect of ship motion on spinal loading during manual lifting

This study investigated the effects of ship motion on peak spinal loading during lifting. All measurements were done on a ship at sea. In 1-min trials, which were repeated over a wide range of sailing conditions, subjects lifted an 18 kg box five times. Ship motion, whole body kinematics, ground reaction forces and electromyography were measured and the effect of ship motion on peak spinal moments and compression forces was investigated. To investigate whether people time their lifts in order to reduce the effect of ship motion on back loading, trials were performed at a free and at a constrained (lifting every 10s) work pace. With increase of the (local) vertical ship acceleration, increased moments and compression forces were found. Furthermore, lifting at a free work pace did not result in smaller effects of ship motion on spinal moments and compression forces than working at a constrained work pace.     

An iterative calibration method for nonlinear coefficients of marine triaxial accelerometers

Single-axis rotation technique is often used in the marine laser inertial navigation system so as to modulate the constant biases of non-axial gyroscopes and accelerometers to attain better navigation performance. However, two significant accelerometer nonlinear errors need to be attacked to improve the modulation effect. Firstly, the asymmetry scale factor inaccuracy enlarges the errors of frequent zero-cross oscillating specific force measured by non-axial accelerometers. Secondly, the traditional linear model of accelerometers can hardly measure the continued or intermittent acceleration accurately. These two nonlinear errors degrade the high-precision specific force measurement and the calibration of nonlinear coefficients because triaxial accelerometers is urgent for the marine navigation. Based on the digital signal sampling property, the square coefficients and cross-coupling coefficients of accelerometers are considered. Meanwhile, the asymmetry scale factors are considered in the I-F conversion unit. Thus, a nonlinear model of specific force measurement is established compared to the linear model. Based on the three-axis turntable, the triaxial gyroscopes are utilized to measure the specific force observation for triaxial accelerometers. Considering the nonlinear combination, the standard calibration parameters and asymmetry factors are separately estimated by a two-step iterative identification procedure. Besides, an efficient specific force calculation model is approximately derived to reduce the real-time computation cost. Simulation results illustrate the sufficient estimation accuracy of nonlinear coefficients. The experiments demonstrate that the nonlinear model shows much higher accuracy than the linear model in both the gravimetry and sway navigation validations.     

多弧离子镀在海洋船舶装备材料上的应用

离子镀膜技术作为一项正在发展的表面镀膜技术,具有良好的耐摩擦、磨损性能。多孤离子镀是最先进的镀膜技术之一,通过阐述分析多弧离子镀的原理、技术优点,研究其应用领域,探求多弧离子镀在海洋船舶材料中的应用,并对该技术进行展望。