深水试验水池大型升降平台多电机同步控制

深水试验水池是开展深海装备开发必不可少的试验手段,大型升降平台是其中的关键设备.大型高精度、高转速传动系统的多电机同步控制是最为核心的问题之一.同步控制算法的优劣直接影响系统的性能与可靠性.提出深水试验水池大型升降平台多电机同步协调控制系统构成方案,并提出一种新的基于拉力死区误差均衡及中心耦合误差的升降平台多电机同步协调控制策略,实现了拉力控制和位置控制的解耦;同时,提出了多电机控制的升降平台仿真系统,其仿真结果表明:所提出的控制策略同步稳定性能高、收敛速度快,具有很高的应用价值.     

新型集装箱汽车衡称重技术与误差分析研究

为了对一辆集卡装载的2个20英尺集装箱进行分别称重,设计了新的汽车衡结构,推导出计算公式并进行实验验证,得到了一种可以保证作业安全且能为港口和货主接受的集装箱汽车衡称重方法。     

挖泥船产量计密度测量精度分析及放射源核素、活度选择研究

通过理论分析结合长江武汉航道工程局挖泥船施工现场情况提出以清水计数率作为密度测量精度的评价指标,在此基础上推导出针对不同排泥管径所需放射源活度的计算公式,据此结合现场条件建立放射源核素及活度的选择条件,为提高设备的有效性提供依据。     

烟台某工程循环水取、排水工程压水试验

为确定烟台某工程地基基岩的渗透特性,阐述水上岩体压水试验的主要操作过程、试验数据处理和试验结果分析评价方法．测定区域内的各岩层的透水率和渗透系数,给出不同风化程度岩层的渗透性评价,为设计提供防渗设计所需参数。     

Investigating micro-simulation error in activity-based travel demand forecasting: a case study of the FEATHERS framework

Activity-based models of travel demand have received considerable attention in transportation planning and forecasting in recent years. However, in most cases they use a micro-simulation approach, thereby inevitably including a stochastic error that is caused by the statistical distributions of random components. As a consequence, running a transport micro-simulation model several times with the same input will generate different outputs, which baffles practitioners in applying such a model and in interpreting the results. A common approach is therefore to run the model multiple times and to use the average value of the results. The question then becomes: what is the minimum number of model runs required to reach a stable result? In this paper, systematic experiments are carried out using Forecasting Evolutionary Activity-Travel of Households and their Environmental RepercussionS (FEATHERS), an activity-based micro-simulation modelling framework currently implemented for the Flanders region of Belgium. Six levels of geographic detail are taken into account. Three travel indices – average daily activities per person, average daily trips per person and average daily distance travelled per person, as well as their corresponding segmentations – are calculated by running the model 100 times. The results show that the more disaggregated the level, the larger the number of model runs is needed to ensure confidence. Furthermore, based on the time-dependent origin-destination table derived from the model output, traffic assignment is performed by loading it onto the Flemish road network, and the total vehicle kilometres travelled in the whole Flanders are subsequently computed. The stable results at the Flanders level provides model users with confidence that application of FEATHERS at an aggregated level requires only limited model runs.     

Instantaneous communication throughputs of vehicular ad hoc networks

Vehicular ad hoc networks (VANETs) formed by connected vehicles in a traffic stream could be applied to improve safety, mobility, and environmental impacts of a transportation system. In this paper, we present analytical models for the instantaneous communication throughputs of VANETs to measure the efficiency of information propagation under various traffic conditions at a time instant. In particular, we define broadcast and unicast communication throughputs by the wireless channel bandwith multiplied by the average probabilities that one vehicle is a successful receiver and sender in a VAENT, respectively. With a protocol communication model, we derive formulas to determine the probabilities for an equipped vehicle to be a successful broadcast receiver and a successful unicast receiver/sender, and obtain broadcast and unicast throughputs along discrete and continuous traffic streams. We further examine the impacts on communication throughputs of the transmission range and the interference range of dedicated short range communication devices as well as the market penetration rate of equipped vehicles and the percentage of senders. Finally, we investigate the influence of shock waves on communication throughputs.     

原油管线在线等质量取样系统设计及实现

为了有效解决原油长输管线反复出现的原油途耗异常问题,通过对原油油种、工艺条件和原油输送方式等的分析,设计了等质量流量比例采样系统,由该系统实现原油管线在线自动取样。系统投用后,实现了实时对量,及时发现损耗异常情况,有效控制了原油途耗不稳定的问题。采用等质量流量比例采样模式,较好地解决了多油种、边收边付、多种输送方式以及流量范围宽等不利因素影响计量的问题,具有较好的参考和推广价值。     

Logit模型在南广高铁线客流分担预测中的应用

对分担率进行科学的预测是交通运输规划的基础性工作,是制定运输决策的重要依据。文章经过比较选取多项Logit模型为分担率预测模型,介绍了模型建立与求解的方法,并运用该模型对南广高铁沿线客流分担率进行预测分析。     

船舶厨房通风空调系统的配置分析

介绍了船用厨房的设计规范,设计标准和相应的解决方法。并对厨房系统进行了分类,通过不同类型的厨房分析,采用合适的空调和通风系统。并从送/排风的方式和风量要求进行了介绍。最后从工程实际的角度上对常用的设计参数如温度,噪音,静压等参数做出了说明。     

长江口软基围堤施工的加载速率效应

针对长江口某围堤施工软土堆载过程中的稳定性问题,进行不同加载模式下的应力路径试验,分析长江口软黏土的应力-应变关系、结构损伤特性、强度及应变率发展模式,为该围堤工程的施工速率选取及施工过程中的稳定性控制提供技术依据。结果表明:在不考虑固结的前提下,土体的不排水抗剪强度几乎不受加载模式影响;最终强度与达到破坏时的应变大小无关,但与分级加载时间和分级静置时间存在相互作用关系;土体失稳时的应变率与加载速率和静置时间均有一定关系,且加载速率的影响更大;当加荷超过不排水抗剪强度的80%时,或分级最大应变率逐渐偏离加载初期的线性变化,土样濒临破坏。