K2O-SnO2-LiZnVO4系湿敏陶瓷特性的研究

采用共沉淀法制备出K2O-SnO2-LiZnVO4系湿敏陶瓷材料,考察了液相掺杂K 对材料湿敏特性的影响,研究了材料的灵敏度、电容特性、阻抗特性等湿敏性能.实验结果表明: K 液相掺杂为10 mol%时可使材料具有低湿电阻小,灵敏度适中的特性.测试频率对试样的阻抗-相对湿度特性曲线影响较大,100 Hz时曲线的线性度最好.试样的电容在低频范围随相对湿度的升高而增大,但高频范围几乎不随相对湿度变化.     

极小曲面力学超材料抗冲吸能特性分析

本文基于极小曲面结构构建了一类力学超材料,并研究了其准静态及动态力学特性.首先,通过对等效密度为30%、40%和50%的超材料样件进行准静态压缩试验,分析了不同等效密度下结构准静态力学特性变化规律,结果表明,结构模量及平台应力随等效密度的增长呈指数上升,其变化规律可用Gibson-Ashby模型进行精准拟合;其次,研究了不同冲击工况对极小曲面力学超材料动态力学特性的影响规律.根据动态力学特性影响因素及变化规律,分别构建了刚性-完美塑性-锁定模型和简化吸能特性预测模型,对冲击时的力学超材料强度及吸能特性进行预测.结果表明,基于三周期极小曲面的力学超材料具有良好的抗压抗冲吸能特性,且其动态力学性能可以通过建立的模型进行精确预测,为高性能防护结构设计提供了理论基础.     

SiC高温高量程MEMS加速度传感器的仿真与分析

加速度传感器材料的特性对传感器的性能影响很大,SiC作为新一代半导体材料具有优良的力学温度特性,适用于高温、高过载加速度传感器.基于SiC提出了一种可用于高温、高过载环境的加速度传感器设计方案.根据悬臂梁的相关力学理论知识,对传感器结构、尺寸进行了设计,并利用ANSYS有限元仿真软件对SiC材料传感器敏感结构进行模态分析、静力学分析、热分析.仿真结果表明,6H-SiC材料表现出了比Si材料更优异的抗高温、抗过载特性,为应用于高量程、高温环境下的加速度传感器研究提供了可靠的理论基础.     

Fe_2O_3-MgO(K_2O)陶瓷湿敏特性的研究

报导了不同含量的MgO、K_2O掺杂对Fe_2O_3为基的陶瓷材料湿敏特性影响的研究结果.确定了使材料湿敏特性得到很大改善的掺杂含量.并通过XRD、SEM的分析,对其感湿机理进行了讨论。还报导了环境温度变化对材料湿敏特性的影响情况.     

压电超材料单元设计及在弹性梁减振中的应用

超材料是将不同性质的材料按照某种规律组合在一起形成的一种周期材料.由于其对弹性波的传递会产生带隙效应,因此在噪声控制、减振隔振等领域得到重视.本文设计了一种压电超材料,通过压电材料元胞的周期性排列,产生频率带隙,以获得减振效果.结构尺寸及厚度小,可以粘贴在主结构上.首先分析了设计的压电超材料色散特性;其次,利用压电超材料对悬臂梁结构进行了减振研究,分析了若干个元胞组成的压电超材料对梁振动能量的调控,并结合压电片上的电压曲线;最后,研究了分流电路中的电阻值和电感值对压电超材料梁减振特性的影响.提出此类压电超材料的进一步改进方向.     

箔式镱大压力传感器的设计与制作

镱材料具有压阻特性,其压阻系数比锰铜、碳等压阻材料要高得多.本文介绍了利用这一特性设计制作的箔式镱大压力传感器,并介绍了其工作原理和设计制作中的关键要点,以及在工艺上需解决的关键问题.     

SiNx 和SiC 材料的红外吸收特性研究

采用LPCVD和PECVD技术制作了不同厚度的SiNx和SiC材料样品,使用傅立叶变换红外光谱仪对其进行了红外吸收特性测试,并通过离子注入的方式对其红外吸收特性进行调节.实验结果表明:LPCVD SINx材料在8～14μm波段存在吸收峰,而PECVD SiNx和SiC材料在3μm～5μm波段和8～14μm波段存在吸收峰.随着材料厚度的增加,吸收度也增加,1 μm厚的LPCVD SiNx,红外吸收度可以达到0.92.离子注入可改变材料的红外吸收能力.     

薄膜体声波谐振器(FBAR)谐振特性的模拟分析*

主要利用Mason等效电路模型对加入介质声损耗的薄膜体声波谐振器输入阻抗公式进行了推导,并利用该结果对薄膜体声波谐振器的谐振特性进行了模拟分析,分别就不同压电层材料和厚度以及不同电极材料和厚度对薄膜体声波谐振器谐振特性的影响进行了详细分析.结果表明,薄膜体声波谐振器谐振频率主要由压电材料和厚度决定但电极的影响也是很大的.在制作高频FBAR器件(5GHz以上)时,采用氮化铝作压电材料比用氧化锌作压电材料更合适.     

导电橡胶复合材料温敏特性研究

根据导电橡胶复合材料产生温阻效应的物理机理,分析了影响其温敏特性的主要因素,研究了不同导电粒子添加量、基体材料、硫化剂和改性剂等对导电橡胶温度敏感性能的影响规律.制备了具有温敏特性的导电橡胶复合材料;导电粒子填料添加量会改变复合材料的温敏性质,填充量少表现为正温度系数效应,填充量较大则呈现为负温度系数效应,存在转折温度;基体材料的粘度关系到复合材料的温度敏感程度,粘度小、电阻变化范围大、温度敏感度强,反之较弱;不同组分室温硫化硅橡胶基体的温敏特性有很大区别;不同硫化剂对温敏强度有一定影响,添加改性材料对复合材料温敏特性有显著作用.导电橡胶可作为温度传感器的敏感材料.     

水下弹性球壳回波特性的仿真研究

水下弹性球壳回波特性的研究对水下目标特征提取和识别具有重要意义.利用弹性理论和分离变量法导出弹性球壳散射声场的Bayleigh简正级数解,得到其反向散射波形态函数.由形态函数计算了高斯脉冲入射到弹性球壳的回波波形,并建立了水下弹性球壳回波特性的数学模型.通过对弹性球壳形态函数和回波结构的仿真,分析比较了不同材料和不同厚度的弹性球壳形态函数和回波特性,并讨论了水下弹性球壳回波特性的影响因素.结果表明,水下弹性球壳的回波特性与球壳材料、球壳厚度和入射信号等因素有关.     

Detection of near accidents by measurement of horizontal acceleration of the trunk

The aim of the study was to develop a method for the detection and recording of sudden movements caused by a person's effort to regain balance during slipping and tripping. The method is based on the assessment of the horizontal acceleration of the trunk. A portable device was developed for recording sudden movements at work sites. The device was tested in laboratory conditions with 20 test persons. The experiments showed that the device is capable of detecting slips and even slight losses of balance which do not lead to actual falls. The acceleration levels of the trunk increased significantly in slipping incidents compared to normal walking, both in antero-posterior and medial-lateral direction.     

Computer-aided reporting of the results of neuropsychological evaluations of traumatic brain injury

The TBI Report Assistant is designed to perform the types of routine tasks that computers do well, while freeing the skilled psychologist to concentrate on tasks best done by knowledgeable humans. The Assistant is intended for reporting the results of neuropsychological evaluation of traumatic brain injury patients using a standard battery. The program encourages the inclusion of additional information by writing to a disk file suitable for editing with a word processor, rather than directly to the printer. The resulting file contains prompts for summary and interpretive statements by the psychologist.     

收割机驱动轮轴横向力自动测量方法研究

为了获得收割机驱动轮轴作用力规律,对驱动轮轴横向力进行自动测量。将沃得双滚筒横轴流型巨龙收割机作为研究对象,通过发动机为收割机提供动力,经传动轴输入,利用驱动轮轴对各模块进行驱动。收割机驱动轮轴横向力测量通过测试装置完成,装置主要包括轴承安装座、推力轴承、螺母以及传感器。通过推力轴承把轴向力传输至芯轴,轴向力属于拉压型,利用两副推力轴承把芯轴置于驱动轮轴上。芯轴为收割机驱动轮轴横向力测量的重要零件之一,是车轴和端盖的连接,需令芯轴和车轴间保持同心。收割机驱动轮轴横向力测量传感器为整个装置的核心部件,选用上海华东电子生产的BLR-24型负荷传感器,把荷载传感器输出电压信号转变为电压值,传输给数据处理部分,设计了传感器接口电路。在轴箱上安装2个传感器,对轮对运动量进行调整。经实验验证,所提方法测试数据为在实际应用下非常有效的数据,和其它方法相比有更低的测试误差,整体性能强。     

服务业专业化集聚与服务业内部结构演进

服务业结构升级是当下中国经济面临的主要问题之一。本文试图从服务业专业化集聚的角度提供新的动力解释,研究发现服务业专业化集聚对服务业内部结构演进有正的显著的影响,它推动着服务业内部结构的升级和转型。本文先构建一个非均衡的增长模型分析服务业专业化集聚如何影响资源在各个部门间的流动,接着采用省际面板数据分析两者间的关系,最后,针对地区间指标显著的差异,采用分位数回归方法来进一步验证,结果表明,服务业专业化集聚对服务业内部结构演进有着正的影响的结论稳健可靠。     

A lattice-Boltzmann simulation study of the drag coefficient of clusters of spheres

Drag coefficients of irregularly shaped particles, constructed from spheres, were measured in lattice-Boltzmann simulations and compared to literature data. The agreement is very well. The distance between the spheres was increased to study the influence of inter-particle distance on the drag force in clusters. The drag coefficient of the clusters was found to increase with inter-particle distance. The drag force on an individual particle in a cluster is lower when that particle is shielded from the flow by other particles.     

云南省腾冲县几种蔬菜反射光谱特征的初步分析

蔬菜光谱特征的测定和分析对遥感识别蔬菜具有极其重要的意义。利用SE590地物光谱仪在野外对腾冲县的几种蔬菜进行了反射光谱值的测定,并制作了光谱曲线图,对其光谱特征进行了分析。在此基础上,对其光谱数据进行一阶导数的变换,并对各蔬菜的一阶导数的特征进行了分析。研究表明,在波长400~679 nm的范围上,可以根据其反射值的高低,将蔬菜分为两组,一组为大白菜、豌豆、牛皮菜和青菜,另一组为葱、大蒜和香菜。对于第一组而言,根据反射的峰值、谷值、坡度和反射值的高低等特征可以将它们区别开。对于第二组而言,根据其在726~1 100 nm范围上反射值的高低,可以将其区别开来。就各种蔬菜的一阶导数特征而言,大白菜、豌豆、大蒜、葱和香菜等均在特定的波段位置存在着独特的一阶导数特征,据此可以将其区别出来。而牛皮菜和青菜却没有独特的一阶导数特征。     

A study of executives' use of biometrics: an application of theory of planned behaviour

Biometrics has become an important alternative in user authentication to a system. The Brunei Government has embarked on various e-government projects. Some of these projects embed biometric mechanism for authentication. The acceptance of biometric security services appears to be affected by several factors, some of which may be the personal attitude of the users, influences of normality and context in which it is used. The study focuses on 155 executives from the 10 ministries of Brunei Darussalam to explore the behavioural intent of the executives towards biometrics through their attitudes. The theory of planned behaviour (TPB) was used as a reference framework, to understand the intention of using biometrics. The data analyses through Smart-PLS suggest that government officers’ attitudes towards biometrics is a predictor of behavioural intention, whereas, subjective norms is a predictor of attitude, perceived behavioural control, behavioural intention and behaviour, i.e. the use of the biometric technology. The implications of these findings are discussed and some conclusions are drawn.     

基于模型的机载燃油系统故障诊断研究

针对某型号飞机的燃油系统进行故障诊断,应用基于模型的故障诊断算法,采用离散的状态变量描述系统行为和功能,基于一致性算法判定系统当前行为是否正常以及冲突搜索算法对异常进行诊断.诊断过程引入故障可能性概率的函数Rank,避免了传统穷举方法,有效提高了算法的效率.诊断结果能够很好地涵盖单故障以及多故障组合,同时也能满足系统进行实时故障诊断的要求.     

Applications of artificial intelligence for optimization of compressor scheduling

This paper presents a feasibility study of evolutionary scheduling for gas pipeline operations. The problem is complex because of several constraints that must be taken into consideration during the optimization process. The objective of gas pipeline operations is to transfer sufficient gas from gas stations to consumers so as to satisfy customer demand with minimum costs. The scheduling involves selection of a set of compressors to operate during a shift. The scheduling decision has to be made so as to satisfy the dual objectives of minimizing the sum of fuel cost, start-up cost, the cost of gas wasted due to oversupply, and satisfying minimal operative and inoperative time of the compressors. The problem was decomposed into the two subproblems of gas load forecast and selection of compressors. Neural networks were used for forecasting the load; and genetic algorithms were used to search for a near optimal combination of compressors. The study was conducted on a subsystem of the pipeline network located in southeastern Saskatchewan, Canada. The results are compared with the solutions generated by an expert system and a fuzzy linear programming model.