小型船舶操控面板的设计与实现

本文介绍了一套小型游船操控面板的设计。本文操控面板的MCU采用STM32系列微控制器,通过合理的接口设计和功能调配,并采用数码管作为信息显示机制,相对于普通按键的面板具有结构紧凑、可批量生产、经济性好、智能化程度高的优点。     

电力系统选择性保护仿真研究

针对船舶电力系统的特性,建立了电力系统选择性保护的断路器和熔断器数学模型,利用电磁暂态仿真软件搭建了全系统仿真模型。仿真分析了典型故障下各种瞬动保护设置方案的保护结果,得出了最优的瞬动保护设置方案。     

AB控制器与D445通讯性能测试研究

AB的控制器与西门子的传动系统采用Profibus_DP网络进行系统集成时,必须采用第三方设备进行通信连接,本文讲述了在实现系统通信功能的情况下,采用不同的第三方模块、不同的参数设置时系统通讯性能测试结果。     

Integrated analysis of land-use and transport policy interventions

Analysing the impact of urban policy interventions on urban growth, land use and transport (LUT) is crucial for urban planners, transport planners and policy-makers, especially in rapidly growing cities. This paper presents a cellular automata-based land-use/transport interaction model – Metronamica-LUTI – for Jeddah that is used to analyse the impact of different proposed policy interventions under two urban growth scenarios for the period 2011–2031. Used as an integrated policy impact assessment tool, the model demonstrates a strong reciprocal relationship between LUT in Jeddah. This study shows that relevant spatial information and integrated policy impact assessment can provide rich insights into the interaction between LUT, the appropriate policy to consider in place and time which traditional planning practice and typical static urban models cannot do.     

Severity of pedestrian injuries due to traffic crashes at signalized intersections in Hong Kong: a Bayesian spatial logit model

The present study intended to (1) investigate the injury risk of pedestrian casualties involved in traffic crashes at signalized intersections in Hong Kong; (2) determine the effect of pedestrian volumes on the severity levels of pedestrian injuries; and (3) explore the role of spatial correlation in econometric crash‐severity models. The data from 1889 pedestrian‐related crashes at 318 signalized intersections between 2008 and 2012 were elaborately collected from the Traffic Accident Database System maintained by the Hong Kong Transport Department. To account for the cross‐intersection heterogeneity, a Bayesian hierarchical logit model with uncorrelated and spatially correlated random effects was developed. An intrinsic conditional autoregressive prior was specified for the spatial correlation term. Results revealed that (1) signalized intersections with greater pedestrian volumes generally exhibited a lower injury risk; (2) ignoring the spatial correlation potentially results in reduced model goodness‐of‐fit, an underestimation of variability and standard error of parameter estimates, as well as inconsistent, biased, and erroneous inference; (3) special attention should be paid to the following factors, which led to a significantly higher probability of pedestrians being killed or sustaining severe injury: pedestrian age greater than 65 years, casualties with head injuries, crashes that occurred on footpaths that were not obstructed/overcrowded, heedless or inattentive crossing, crashes on the two‐way carriageway, and those that occurred near tram or light‐rail transit stops. Copyright © 2017 John Wiley & Sons, Ltd.     

The digital revolution and worthwhile use of travel time: implications for appraisal and forecasting

Savings in travel time and more specifically their monetary value typically constitute the main benefit to justify major investment in transport schemes. However, worthwhile use of travel time is an increasingly prominent phenomenon of the digital age. Accordingly, questions are increasingly being asked regarding whether values of time used by countries around the world based on their appraisal approaches are too high. This paper offers the most comprehensive examination of our theoretical and empirical understandings of international appraisal approaches and how they account for worthwhile use of travel time. It combines the economics perspective with wider social science insight and reaches the conclusion that past revolutions in transport that have made longer and quicker journeys possible are now joined by a digital revolution that is reducing the disutility of travel time. This revolution offers potential economic benefit that comes at a fraction of the cost of major investments in transport that are predicated on saving travel time. The paper highlights the challenges faced in both current and indeed potential alternative future appraisal approaches. Such challenges are rooted in the difficulty of measuring time use and productivity with sufficient accuracy and over time to credibly account for how travel time factors into the economic outcomes from social and working practices in the knowledge economy. There is a need for further research to: establish how improvements in the opportunities for and the quality of worthwhile use of travel time impact on the valuation of travel time savings for non-business travel; improve our understanding of how productive use of time impacts on the valuation of time savings for business travellers; and estimate how these factors have impacted on the demand for different modes of travel.     

PFI增压汽油机机油稀释试验研究

在一款1．0 L 气道喷射增压汽油机上研究了机油稀释的分布区域及其产生机理,发现机油稀释严重的区域主要集中在高速大负荷工况。通过对喷油器喷孔直径、喷油相位、VVT 动作角、空燃比、水泵流量、机油冷却器散热量、曲轴箱强制通风系统 PCV 阀补气量等相关特性参数的调整验证,发现喷油相位靠后、空燃比过浓是机油稀释严重的主要原因,水泵流量、PCV 阀补气量、VVT 动作角、机油冷却器散热量对机油稀释也有一定的影响,喷油器喷孔直径的变化对机油稀释无影响。最终在该款发动机上综合采用优化喷油相位、水泵流量、PCV 阀补气量、机油冷却器散热量的措施,最大机油稀释水平控制在5％以下。     

One-dimensional model on fuel penetration in diesel sprays with gas flow

In diesel engine, spray penetration is usually changed by in-cylinder gas flow. Accurate prediction on diesel spray with gas flow is important to the optimal design of diesel fuel injection system. This paper presents a theory investigation focusing on the penetration of diesel spray with gas flow. In order to understand the effect of gas flow on the penetration of diesel spray, a one-dimensional spray model is developed from an idealized diesel spray, which is able to predict the spray behavior under different gas flow conditions. The ambient gas flow is simplified as ideal flow that has only constant flow velocity along x-axial and y-axial directions of spray. The x-axial and y-axial directions are respectively defined as along and vertical spray directions. The main assumption is that the y-axial direction gas flow has no effect on the penetration of spray along x-axial direction. The principles of conservation of mass and momentum are used in the derivation. Momentum of in-cylinder air flow is also taken into consideration. Validation of the model at stable condition is achieved by comparing model predictions with experimental measurements of diesel spray without gas flow from Naber's experiments. Furthermore, CFD simulations on penetration of diesel spray with gas flow were performed with the commercial code AVL-fire. The onedimensional model is validated by the penetration results with gas flow from CFD calculation. Results show that a reasonable estimation of the spray evolution can be obtained for both with and without ambient gas flow conditions.     

Experimental study of EGR cooler regeneration aided by oxygen-fed NTP and air-fed NTP

Based on non-thermal plasma (NTP) technology fed by oxygen and air as the gas source respectively, the experimental system of exhaust gas recirculation (EGR) cooler regeneration was built to do a study at different regeneration temperatures. By measuring the concentration of main active substance and CO_x in regeneration process, the influence of temperature on regeneration aided by oxygen-fed NTP and air-fed NTP was investigated. The experimental results indicate that EGR cooler can be regenerated both by air-fed NTP and oxygen-fed NTP at a wide temperature range of 18 °C ～ 300 °C. By comparison of the regeneration with oxygen-fed NTP and air-fed NTP, it can be easily known that the regeneration effect is most remarkable at 150 °C with oxygen-fed NTP and at 120 °C with air-fed NTP. In addition, when the temperature is below 150 °C especially at 120 °C, the regeneration efficiency of air-fed NTP is lower than oxygen-fed NTP, nevertheless, when the temperature is above 150 °C, air-fed NTP has a superiority in regeneration and the higher the temperature is, the more obvious the superiority will be.     

Multi-axle vehicle dynamics stability control algorithm with all independent drive wheel

The stability driving characteristic and the tire wear of 8-axle vehicle with 16-independent driving wheels are discussed in this paper. The lateral stability of 8-axle vehicle can be improved by the direct yaw moment which is generated by the 16 independent driving wheels. The hierarchical controller is designed to determine the required yaw torque and driving force of each wheel. The upper level controller uses feed-forward and feed-backward control theory to obtain the required yaw torque. The fuzzification weight ratio of two control objective is built in the upper level controller to regulate the vehicle yaw and lateral motions. The rule-based yaw moment distribution strategy and the driving force adjustment based on the safety of vehicle are proposed in the lower level controller. The influence of rear steering angle is considered in the distribution of driving force of the wheel. Simulation results of a vehicle double lane change show the stability of 8-axle vehicle under the proposed control algorithm. The wear rate of tire is calculated by the interaction force between the tire and ground. The wear of tire is different from each other for the vehicle with the stability controller or not.