MD simulation of nanometric cutting of copper with and without water lubrication

Three-dimensional molecular dynamics(MD)simulation was carried out to understand the mechanism of water lubrication in nanometric cutting.The water-lubricated cutting was compared with the dry cutting process in terms of lattice deformation,cutting force,heat and pressure distribution,and machined surface integrity.It was found that water molecules effectively reduce the friction between the tool and workpiece,the heat in the cutting zone and the pressure being generated on the tool surface,thus leading to prolonged tool life.Water molecules also enlarged the pressure-affected area,which decreased the roughness of the machined surface.     

The conditions for onset of beta oscillations in an extended subthalamic nucleus-globus pallidus network

The persistence of beta oscillations generated in the basal ganglia is typical pathological characteristic of Parkin-son's disease.In this paper,we construct a new network model,which is mainly composed of the subthalamic nu-cleus and the globus pallidus.Based on theory analysis,we obtained the beta shock conditions in the proposed model.It is shown that numerical simulations are in good agreement with analytical results.At last,the effects of cortex and striatum inputs on the generation of oscillations are also discussed.We hope that the obtained results may find applications to treatment of Parkinson’s disease and study of neural oscillations produced in other parts of the brain neural network.     

喷管尺寸对火箭发动机喷流噪声影响研究

为了研究喷管尺寸对火箭发动机喷流噪声声场分布的影响规律,采用LES与FW-H相结合的方法,针对不同喷管尺寸的高温燃气喷流气动声场进行了数值模拟,并分析了声场特性。数值结果表明,火箭发动机喷流远场噪声具有方向性,噪声声压级在离开喷流中心轴线40°处达到最大值;喷流噪声声场的声压级随着喷管尺寸的增大而增加。研究结果为不同尺寸的火箭发动机喷流噪声预测提供参考依据。     

壁湍流猝发事件检测与提取方法研究

在重力式低速水洞中完成了湍流边界层流场测量,并分别利用自相关方法和小波分析方法,对对数律区中一测点处的速度信号进行了分析。结果表明,自相关方法对于平均猝发周期的检测精度较高;小波分析方法可用于猝发事件的提取,但对平均猝发周期的检测精度较低。为此,进一步提出了一种同时基于自相关方法和小波分析方法的壁湍流猝发事件快速检测与提取方法,并总结了该方法的具体实施步骤。与原方法相比,该方法既能够精确检测湍流平均猝发周期,又能够提高猝发事件的提取精度。     

Porous haydite used as waste water filter medium for lake sludge

Porous haydite used as waste filter medium was prepared by dreging lake sludge to help solve the treatment problem of sludge and realize its reclamation. Several calcination regimes were considered and their effects on the pore structure and the properties such as the strength, the density, the filtering ability and the phosphate absorption ability of the haydite were investigated. For the mixture of 60% lake sludge and 40% fly ash in this experiment, the calcination regime with a pre-calcination period at about 600 °C, a temperature keeping period at 1 200 °C and a moderate cooling rate are recommended to prepare haydite with reasonable pore structure and good performances for its usage as the waste water filter media.     

利用路径优先级实现传感器网络中的拥塞避免

提出了一种基于路径优先级的多路径传感器网络拥塞避免算法.传感器节点通过监测队列剩余空间长度和拥塞状态持续时间实时更新节点的拥塞状态指数(CSI),当检测到CSI发生改变时,计算节点的路由状态指数(RP-SI)并通知其邻居节点,邻居节点更新记录下游节点的RPSI,调整下游路径的优先级.传感器节点根据信息优先级的不同,通过不同优先级的路径发送数据.仿真结果表明,提出的算法在减少网络拥塞的发生和减少网络时延等方面取得了很好的性能.     

矿井隧道中人体电容的研究

矿井隧道环境中人体静电荷的积聚与释放主要依赖于人体的电容及电阻.根据电场系统解的唯一性原理,利用电介质材料的多重镜像方法,把隧道环境等价为人体的镜像人体丛林,模拟计算了该多导体系统的人体电容.研究了隧道环境人体电容与介质环境、人体身材、隧道形状、人体与隧道的相对位置等关系.计算结果表明,隧道环境中的人体电容值与人体的外形及隧道的形状密切相关,而与人体在隧道中的相对位置关系不大,表明隧道环境中人体电容值是有意义的.人体电容还随着煤层介电常数ε的不同而变化,在相对介电常数εr=7附近(干燥煤炭的相对介电常数εr=6.3)人体电容出现一峰值,该电容值是自由环境中的1.15倍,说明煤矿环境是静电安全的敏感环境.     

一种新型灵敏度可调式光纤光栅传感器

以光纤光栅为敏感组件,设计了一种嵌入式等强度悬臂梁结构的灵敏度可调式光纤光栅传感器．将传统的感测片长度固定的传感器架构设计为感测片部分嵌入主架构的传感器,通过改变悬臂梁感测片长度来达到灵敏度调节的效果．由理论分析和振动、位移灵敏度调节实验验证,此传感器装置可以达到调节灵敏度的效果,而且可调节范围较广．     

一种基于PSO优化的RFID防碰撞算法

在射频识别(RFID)系统中,不可避免地存在碰撞问题,标签碰撞的解决对于标签的快速有效识别非常重要.提出一种基于粒子群优化的改进自适应分组和预发信号ASPS( Adaptive splitting and pre-signaling)的RFID防碰撞算法.首先建立ASPS防碰撞算法模型;然后借鉴粒子群优化算法的特点,通过将接收信号二维化,建立适合粒子群优化算法的模型,从而改进ASPS算法.实验表明,该算法运算时间短,处理碰撞的次数少,具有良好的实际应用前景.     

基于多FPGA的NoC多核处理器验证平台设计

为了能够灵活地验证和实现自主设计的基于NoC的多核处理器,缩短NoC多核处理器的设计周期,提出了设计集成4片Virtex-6-550T FPGA的NoC多核处理器原型芯片设计/验证平台.分析和评估了NoC多核处理器的规模以及对FPGA硬件资源的需求,在此基础上给出了集成4片FPGA的开发板详细设计方案,并对各主要模块如互联架构、电源、板级时钟分布、接口技术、存储资源等关键设计要点进行阐述.描述了开发板各个主要模块的测试过程和结果,表明了该设计的可行性.