高功率CO_2激光焊接等离子体控制实验研究

采用精密的侧吹辅助气体调节和控制装置，实验研究了等离子体控制的各种工艺参数；采用光电晶体管检测熔池表面及小孔内等离子体光强变化；从理论上分析了等离子体控制的机理．结果表明：当辅助气体流量变化时，等离子体控制效果呈现三个区间．无论采用何种气体，只要辅助气体的操作压力稍大于金属蒸气压力，等离子体即被最佳控制     

Search space pruning and global optimisation of multiple gravity assist spacecraft trajectories

We introduce and describe the Multiple Gravity Assist problem, a global optimisation problem that is of great interest in the design of spacecraft and their trajectories. We discuss its formalization and we show, in one particular problem instance, the performance of selected state of the art heuristic global optimisation algorithms. A deterministic search space pruning algorithm is then developed and its polynomial time and space complexity derived. The algorithm is shown to achieve search space reductions of greater than six orders of magnitude, thus reducing significantly the complexity of the subsequent optimisation. This work was partially funded under the Ariadna scheme of the European Space Agency, contract number 18138/04/NL/MV.     

基于车载CAN总线的倒车雷达单元设计

倒车雷达在汽车中得到广泛应用,但没有与车载CAN总线网络相联系,造成其功能不完善。用PIC18F258单片机设计一个倒车雷达单元,使倒车雷达能够被车载网络识别,实现与CAN总线的数据通信与资源共享,完成倒车雷达的自动刹车功能。     

Experimental investigation of the difference in B-term dominated band broadening between fully porous and porous-shell particles for liquid chromatography using the Effective Medium Theory

The difference in B-term diffusion between fully porous and porous-shell particles is investigated using the physically sound diffusion equations originating from the Effective Medium Theory (EMT). Experimental data of the B-term diffusion obtained via peak parking measurements on six different commercial particle types have been analyzed (3 porous and 3 non porous). All particles were investigated using the same experimental design and test analytes, over a very broad range of retention factor values. First, the B-term reducing effect of the solid core (inducing an additional obstruction compared to fully porous particles) has been quantified using the Hashin-Shtrikman expression, showing that the presence of a solid core can account for a reduction of about 11% when the core diameter makes up 63% of the total particle diameter (Halo and Poroshell-particles) and a reduction of 16% when the core diameter makes up 73% (Kinetex). Remaining differences can be attributed to differences in the microscopic structure of the meso-porous material (meso-pore diameter, internal porosity or relative void volume). The much lower B-term diffusion of Halo and Kinetex particles compared to the fully porous Acquity particles (some 20-40% difference, of which about 10-15% can be attributed to the presence of the solid core) can hence largely be attributed to the much smaller internal porosity and the smaller pore size of the meso-porous material making up the shell of these particles.     

基于嵌入式的智能停车场远程监控系统

针对现阶段的停车场的管理存在管理复杂、工作效率低等问题,设计了一种基于嵌入式和ZigBee技术的智能停车场远程监控系统,以实现停车场的智能化控制。该系统通过ZigBee传感器网络采集停车场中停车位的信息,利用嵌入式系统和GSM模块进行数据的处理和传输,并通过上位机对整个停车场进行远程监控。介绍了系统的设计方案和工作原理,详细阐述了系统框架,硬件设计和软件设计。通过数据传输性能和整体性能的测试表明,该系统完全达到停车场监控系统的应用要求。     

一种低成本城市停车诱导系统中区域性Zigbee网络的设计

为降低城市级停车诱导系统的建设、运营成本,提出一种无需建立管理控制中心的系统架构,采用LPC11C14和CC2530作为核心芯片设计了系统中的重要组成部分——区域性Zigbee网络。通过所开发出的测试系统的实验,表明该Zigbee网络可准确接收用户手机发出的停车请求,并能根据停车场内车位状态向用户反馈最佳车位信息,从用户发送请求到收到反馈信息的时间不超过10s。     

基于降低失效停放区比率的共享单车系统稳定性研究

共享单车失效停放区使得用户无法取车或还车,影响共享单车系统运营稳定性。本文基于排队论与马尔科夫链构建了共享单车系统稳定状态平均场方程组并求解稳态解,发现停放区交互作用使得失效停放区对相邻停放区产生需求溢出效应,增加系统失效停放区比率,影响系统运营稳定性。本文以降低系统失效停放区比率目标,引入(M,S)交互策略,调节失效停放区对相邻停放区的交互作用程度。进一步,以算例分析比较相同类型与不同类型停放区交互作用、(M,S)交互策略下共享单车系统的失效停放区比率。结果表明(M,S)交互策略能够有效降低失效停放区比率,提高系统运营稳定性。本研究为共享单车企业运营稳定性决策提供了有价值的参考。     

Hydrodynamic assist and the dynamic contact angle in the coalescence of liquid drops

^** Email: decentsp{at}for.mat.bham.ac.uk The coalescence of two viscous liquid drops in an inviscid gasor in a vacuum is studied using the interface formation model.In the very early stages of coalescence during the formationof the ‘liquid-bridge’ connecting the two drops,this model predicts a moving contact line and a dynamic contactangle. This paper examines the dynamic evolution of this contactangle, and for small Reynolds number and small Capillary number,relevant particularly in micro-fluidics, a non-linear differentialequation is derived for the contact angle and solved computationally.It is found that the contact angle evolution can only be evaluatedby determining information about the flow away from the contactline. This is a manifestation of so-called hydrodynamic assist,studied experimentally in the context of curtain coating byBlake et al. (1999 Experimental evidence of non-local hydrodynamicinfluence on the dynamic contact angle. Phys. Fluids, 11, 1995–2007).For small Capillary number and small Reynolds number, the free-surfaceevolution is determined for the coalescence of two cylindersof equal radius. Finally, some comments are made on experimentsin coalescence, as well as on issues arising in a computationalsolution of the full model described here.     

基于CAN总线的智能停车场通信系统

智能停车场是解决我国大中城市停车问题的有效手段。对停车设施进行合理地规划,对车辆停放进行有效地管理,提高城市交通系统的效率,是立体停车场迫切解决的问题。智能停车场管理系统采用先进技术和高度自动化的机电设备,将机械、电子计算机和自控设备以及智能IC卡技术有机地结合起来,通过电脑管理可实现车辆出入管理、自动存储数据等功能,实现脱机运行并提供一种高效管理。文中介绍了智能停车场控制系统组成及功能,给出了基于CAN（控制器局域网）总线智能停车场通信系统的设计与实现方案。该方案可以实现停车场车位管理动态智能化,所有车位状态都可实时监控,最大程度发挥集中调度和管理优势。     

使用物体交互模型的车辆违停事件检测

随着平安城市与监控摄像头的发展,车辆违章停靠事件的自动检测在视频自动检测方法中具有重要意义.当前的目标检测算法,例如基于特征+分类器、基于视频背景差分、基于深度学习的方法等,大多关注车牌、交通标志的定位与识别,而忽略了对车辆违章等事件的判别.因此,发展了一种基于物体交互模型的车辆违章停靠事件检测方法:首先基于轮廓提取和SVM进行车牌检测;其次基于形状和颜色进行交通标志检测;最后基于物体交互模型来判断是否违停.上述方法在真实视频场景中的实验验证了方法的有效性和可靠性.