具有P型覆盖层新型超级结横向双扩散功率器件

为了设计功率集成电路所需要的低功耗横向双扩散金属氧化物半导体器件(lateral double-diffused MOSFET), 在已有的N型缓冲层超级结LDMOS(N-buffered-SJ-LDMOS)结构基础上, 提出了一种具有P型覆盖层新型超级结LDMOS结构(P-covered-SJ-LDMOS). 这种结构不但能够消除传统的N沟道SJ-LDMOS由于P型衬底产生的衬底辅助耗尽问题, 使得超级结层的N区和P区的电荷完全补偿, 而且还能利用覆盖层的电荷补偿作用, 提高N型缓冲层浓度, 从而降低了器件的比导通电阻. 利用三维仿真软件ISE分析表明, 在漂移区长度均为10 μm的情况下, P-covered-SJ-LDMOS的比导通电阻较一般SJ-LDMOS结构降低了59%左右, 较文献提出的N型缓冲层 SJ-LDMOS(N-buffered-SJ-LDMOS)结构降低了43%左右.     

反相流动注射-长光程多波长分光光度法测定饮用水中超痕量亚硝酸盐

1 引言 亚硝酸盐是致癌物质N-亚硝胺的重要前体,故国家对饮用水中亚硝酸盐的含量有严格的要求.目前通常采用重氮偶联分光光度法检测水体中亚硝酸盐但该方法检测限为1 μg/L.但是,此检测限仅略低于国标中对瓶装饮用纯净水中亚硝酸盐含量的要求(2 μg/L),该方法操作时人为误差较大.本研究将反相流动注射与LWCC相结合,建立了饮用水中超痕量亚硝酸盐的快速检测方法,并用于分析市场上常见的瓶装饮用水和自来水样品.与其他检测方法相比,本方法具有样品消耗量少(10 mL,平行测定3次);方法灵敏高,定量下限为0.09 μg/L;线性范围宽(0.09～110 μg/L);分析速度快,样品通量为45h-1;适合用于工业在线分析和实时检测等特点.     

离子色谱法测定循环冷却水中的羟基-1,1-亚乙基二磷酸

建立了循环冷却水中羟基-1,1-亚乙基二磷酸(HEDP)的离子色谱检测方法。色谱柱为IonPac AS14A阴离子交换柱,流动相为80 mmol/L NaOH水溶液,流速1.0 mL/min,抑制型电导检测器检测。方法的线性范围为0.25～25 mg/L,平均回收率为102%,检出限为0.1 mg/L;对0.25 mg/L和0.5 mg/L的HEDP标准溶液分别进行13次平行测定,相对标准偏差(RSD)分别为4.7%和3.5%。该方法具有简单、快速、灵敏、抗干扰等优点,用于循环冷却水中HEDP的检测,结果令人满意。     

High-Efficient Nd：YLF Q-Switched Laser Operating at 523.5 nm

An intracavity frequency doubling electro-optically Q-switched Nd： YLF 523.5 nm laser is developed. An appropriate cylindrical lens is employed in the oscillator to optimize the mode size and to improve the stability of the cavity. With an incident pump pulse energy of 58 mJ at a 500 Hz repetition rate, a green pulse energy of 16.8 mJ at 523.5 nm is obtained, corresponding to an optical-optical conversion efficiency of 29%. The pulse width is less than 8 ns, and the beam quality factor is M^2≤ 2.5.     

PHM技术国内外发展情况综述

随着现代武器装备复杂化、综合化、智能化程度的不断提高,传统的故障诊断技术难以适应新的需求。为了满足信息化战争对武器装备作战效能和快捷、精准、持续保障的要求,20世纪90年代中期,PHM(故障预测与健康管理)技术应运而生。从发展概况、应用成效、PHM验证评价、典型案例分析以及发展规划5个方面总结了国外PHM技术发展的应用成效;并对国内PHM技术的基础理论、工程技术与应用方面的发展状况进行了总结;通过对比国内外PHM技术的发展应用现状,总结分析了目前国内PHM技术发展现状与国外先进水平之间的差距以及未来发展的借鉴启示。     

海水中硝酸盐的无阀连续流动分析

建立了一种无阀连续流动分析方法和装置,仅用一台多通道蠕动泵传送试剂和样品,无需依靠注入阀、电磁阀和定量环进行试剂或样品的选择和定量输入.样品通过铜-镉还原柱,将硝酸盐还原为亚硝酸盐,然后用重氮-偶氮光度法进行测定.研究结果表明,硝酸盐的线性范围为5 ～ 180 μmol/L,方法检出限为0.27.μmol/L,对10和80 μmol/L硝酸盐溶液连续测定11次,相对标准偏差分别为1.4％和1.3％,不同盐度的实际水样加标回收率在99.4％ ～ 106.1％之间.测定结果与流动注射分析法相比,无显著性差异.与流动注射分析相比,无阀设计装置大大降低了成本,操作更加简便,有利于在普通实验室或现场连续监测中推广使用.本方法成功应用于厦门西港海水样品中硝酸盐的测定以及九龙江河口区的硝酸盐走航式监测.     

流动注射-固相萃取-分光光度法检测半导体工业用水中痕量硅

硅酸盐在酸性介质中与钼酸铵反应生成硅钼黄,硅钼黄还原为硅钼蓝后,可被HLB小柱定量萃取.在此基础上,建立了流动注射-固相萃取-分光光度(FI-SPE-Vis)测定水中痕量硅酸盐的新方法.反应生成的硅钼蓝经HLB小柱萃取后,用水清洗去除杂质,NaOH溶液洗脱,分光光度法检测.实验对各参数进行了优化,优化后的参数为:洗脱剂浓度0.01 mol/L;试样上柱流速28.0 mL/min;洗脱流速3.5 mL/min;反应温度45 ℃;硅钼黄与硅钼蓝反应时间均为5 min;钼酸铵混合溶液、草酸溶液、抗坏血酸溶液的用量分别为3.5,3.5和1.75 mL.本方法具有良好的重现性和灵敏度,测定含硅9.33 μg/L的硅酸盐水样7次,RSD值为1.8%;选取不同的试样富集时间,可将定量分析的线性范围扩展为0.47～117 μg/L;检出限0.18 μg/L;回收率为96.8%～105%.可满足特殊工业用水中痕量硅检测的需要.     

Discrete element crowd model for pedestrian evacuation through an exit

A series of accidents caused by crowds within the last decades evoked a lot of scientific interest in modeling the movement of pedestrian crowds. Based on the discrete element method, a granular dynamic model, in which the human body is simplified as a self-driven sphere, is proposed to simulate the characteristics of crowd flow through an exit. In this model, the repulsive force among people is considered to have an anisotropic feature, and the physical contact force due to body deformation is quantified by the Hertz contact model. The movement of the human body is simulated by applying the second Newton's law. The crowd flow through an exit at different desired velocities is studied and simulation results indicated that crowd flow exhibits three distinct states, i.e., smooth state, transition state and phase separation state. In the simulation, the clogging phenomenon occurs more easily when the desired velocity is high and the exit may as a result be totally blocked at a desired velocity of 1.6 m/s or above, leading to faster-to-frozen effect.     

Multi-grid simulation of pedestrian counter flow with topological interaction

We investigate the dynamics of pedestrian counter flow by using a multi-grid topological pedestrian counter flow model.In the model,each pedestrian occupies multi-rather than only one grid,and interacts with others in the form of topological interaction,which means that a moving pedestrian interacts with a fixed number of those nearest neighbours coming from the opposite direction to determine his/her own moving direction.Thus the discretization of space and time are much finer,the decision making process of the pedestrian is more reliable,which all together makes the moving behaviour and boundary conditions much more realistic.When compared with field observations,it can be found that the modified model is able to reproduce well fitted pedestrian collective behaviour such as dynamical variation of lane formation,clustering of pedestrians in the same direction,etc.The fundamental diagram produced by the model fits also well with field data in the free flow region.Further analyses indicate that with the increase of the size of pedestrian counter flow system,it becomes harder for the system to transit into a jamming state,while the increase of interaction range does not change the transition point from free flow to jamming flow in the multi-grid topological counter flow model.It is also found that the asymmetry of the injection rate of pedestrians on the boundaries has direct influence on the process of transition from free flow to jamming flow,i.e.,a symmetric injection makes it easier for the system to transit into jamming flow.     

高温高应变率下混凝土材料的损伤演化方程

采用?74 mm大口径分离式霍普金森压杆(SHPB)对不同温度(20、200、400℃)下的C45混凝土材料进行动态力学性能实验,得到了不同温度、不同应变率下混凝土材料的应力-应变曲线。实验结果表明:在20~400℃温度范围内,混凝土材料具有温度硬化和应变率硬化现象。基于上述实验数据给出了损伤变量关于塑性应变的关系式,并通过相关实验数据确定了不同温度、不同应变率下损伤演化方程的材料参数。将该损伤演化方程应用于混凝土材料的本构关系中,预测结果与实验数据具有较好的一致性,证明了所提出的高温、高应变率下混凝土材料损伤演化方程的合理性。