基于ADAMS仿真确定飞机着陆道面动荷载

为了合理确定机场刚性道面设计中的动载系数,减少道面荷载现场测试的工作量,利用ADAMS软件进行仿真研究,分析了飞机着陆时道面的竖向荷载、纵向水平荷载和横向水平荷载的动态响应规律.通过改变飞机着陆时的俯仰角、滚转角、初始下降速率和初始机轮离地距离4个主要参数,分析道面受载情况的敏感性,并利用白噪声线性滤波法生成不同等级道面,研究了不同平整度下道面的动态响应规律.研究结果表明:初始下降速率从0 m/s增大到3 m/s时,动载系数从0.677增大到1.623;着陆水平荷载主要为纵向水平荷载;飞机对H级道面的动荷载最大值比A级道面增大68.71%.     

环境友好方法制备纳米氧化镁

以MgCl2·6H2O为原料,强碱性阴离子交换树脂作为致沉剂,采用离子交换树脂法制备了纳米MgO粉体．通过单因素实验探讨了MgCl2的起始浓度、反应温度、反应时间以及煅烧温度和时间对MgO粒径及物化性能的影响,用XRD、SEM、TEM对纳米MgO进行了表征,并考查了离子交换树脂的循环利用．结果表明,制备纳米MgO的最佳工艺条件为：MgCl2浓度为0．2mol／L,反应温度为50℃,反应时间8h,煅烧温度及时间为400℃煅烧6h;在最佳工艺条件下制备的纳米MgO具有规则的六方片状结构,平均粒径大小为10nm左右;离子交换树脂的再生对MgO的产率和形貌不产生影响．与其他制备纳米MgO的方法相比,该工艺成本低、污染小、产率较高,具有一定的环保效应,适宜于工业化生产．     

内孤立波作用下潜水器运动响应数值分析

内孤立波会导致海水等密度面大振幅的垂向起伏,影响潜水器的水下适航性,甚至危及安全性.运用CFD方法开展内孤立波数值造波,并将内孤立波数值解与eKdV理论解进行比较,验证数值造波的准确性.在此基础上,模拟了内孤立波作用下处于3种不同潜深的Suboff缩比模型的运动,详细分析了不同潜深下模型在内孤立波作用下的运动响应规律....     

Numerical and experimental study of submerged supple nets: Applications to fish farms

Our aim is to investigate the behavior of submerged supple nets. This work generates many problems owing to the discontinuous and highly flexible nature of the nets. Only the action of external forces can bring an infinitely flexible structure like a net into a definite shape. When considering supple nets immersed in a fluid, these external forces themselves depend on the net geometry. A numerical method to solve this fluid-structure coupling problem is proposed, and is applied to fish farms. In order to validate the calculation model of the hydrodynamic forces on the mesh sides, we measured the hydrodynamic forces on a plane panel of netting spread across a transverse current. We thus proved that the Landweber model modified according to the Richtmeyer formula as regards friction gives good results. The calculated shape of the fixed net cage is qualitatively in accordance with flume tank observations. We have adapted the algorithm to the study of the dynamic behavior of floating fish farms.     

工程车辆智能换挡规律的仿真

以装载机为研究对象,分析了工程车辆自动变速系统的结构及原理,建立了工程车辆电控自动变速系统组成原理图。针对工程车辆的作业特点,以适应性和在线实时性等综合性能最优为控制目标,确定了工程车辆智能换挡规律控制原则。基于仿人智能模糊控制方法,对换挡规律进行了分析研究,建立了装载机动力传动系统动态仿真模型,并应用Matlab/Simulink软件进行了仿真分析。仿真结果表明,将仿人智能模糊控制方法应用于工程车辆智能变速系统具有可行性。     

Two-Layer Path Planner for AUVs Based on the Improved AAF-RRT Algorithm

As autonomous underwater vehicles (AUVs) merely adopt the inductive obstacle avoidance mechanism to avoid collisions with underwater obstacles, path planners fo...     

风场作用下趸船区域溢油动态模拟研究

以舟山定海港区某油库码头为背景建立了风场作用下的趸船区域溢油动态模型。针对趸船区域可能产生油品溢漏的位置,对趸船区域的溢油运动情况进行了模拟分析。模拟结果显示,当泄漏油品为柴油(850kg/m3,0.003825Pa·s)、泄漏点宽度为0.5m、油品泄漏速度为1m/s时,受风场作用,发生在趸船附近的溢油事故,其溢漏油品不仅随潮水运动流动,还会大量的在码头与岸线之间的区域及码头两端部附近产生积聚。在进行溢油事故快速控制和污油回收时,需要重点针对该区域进行监控防治。     

Proteus在电气信息类实验教学改革中的应用

针对电气自动化专业人才培养的特点,提出了Proteus仿真软件在电气信息类实验教学改革中的应用。通过Proteus软件在模拟电子技术、数字电子技术以及单片机课程中的应用表明,该教学改革方案不仅能提高实验教学质量,还能提高学生的创新思维和学习能力。     

装卸同步工艺下的集卡配置仿真研究

为了研究装卸同步工艺下的集卡配置,建立了包括船舶,桥吊,集卡和龙门吊等现代码头作业设备的系统仿真模型,采用Flexsim-CT软件分别对作业面与作业线下的集卡运输作业进行了在装卸同步工艺下的模型仿真,并对两种运输策略在同步装卸工艺下的集卡作业效率和整体作业时间进行了比较。经过试验得到了在不同集卡资源条件下的最优集卡配置方案,并对方案的仿真指标进行了对比分析。研究为装卸同步工艺下的集卡配置方案提供了重要的参考。     

The Contribution of Benefit-in-Kind Taxation Policy in Britain to the ‘Peak Car’ Phenomenon

Car use per person has historically grown year-on-year in Great Britain since the 1950s, with minor exceptions during fuel crises and times of economic recession. The ‘Peak Car’ hypothesis proposes that this historical trend no longer applies. The British National Travel Survey provides evidence of such an aggregate levelling off in car mileage per person since the mid-1990s, but further analysis shows that this is the result of counter trends netting out: in particular, a reduction in per capita male driving mileage being offset by a corresponding increase in female car driving mileage. A major contributory factor to the decline in male car use has been a sharp reduction in average company car mileage per person. This paper investigates this aspect in more detail. Use of company cars fell sharply in Britain from the 1990s up to the 2008 recession. Over the same period, taxation policy towards company cars became more onerous, with increasing levels of taxation on the benefit-in-kind value of the ownership of a company car and on the provision of free fuel for private use. The paper sets out the changes in taxation policy affecting company cars in the UK, and looks at the associated reductions in company car ownership (including free fuel) and patterns of use. It goes on to look in more detail at which groups of the population have kept company cars and in which parts of the country they have been most used, and how these patterns have changed over time. A preliminary investigation is also made of possible substitution effects between company car and personal car driving and between company car use and rail travel. Clearly, the role of the company car is only one of many factors that are contributing to aggregate changes in levels of car use in Great Britain, alongside demographic changes and a wide range of policy initiatives. But, company car use cannot fall below zero, so the effect of declining year-on-year company car mileage suppressing overall car traffic levels cannot continue indefinitely.