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。     

ZnO量子点／SiO2复合器件的可调控电致发光研究

在不同浓度的SiO2乙醇溶液中制备了一系列ZnO量子点／SiO2复合材料,通过匀胶方法将其制备成复合薄膜器件。器件的电致发光（EL）随着SiO2浓度的增加逐渐蓝移。通过实验,探索了发生蓝移的机制。选取一种ZnO量子点／SiO2复合材料均匀混入不同质量的纯SiO2后,测试结果表明,该蓝移现象不是SiO2自身发光引起的。通...     

MHD non-Darcian mixed convection heat and mass transfer over a non-linear stretching sheet with Soret-Dufour effects and chemical reaction

A study has been carried out to analyze the effects of variable thermal conductivity, Soret (thermal-diffusion) and Dufour (diffusion-thermo) on MHD non-Darcy mixed convection heat and mass transfer over a non-linear stretching sheet embedded in a saturated porous medium in the presence of thermal radiation, viscous dissipation, non-uniform heat source/sink and first-order chemical reaction. The governing differential equations transform into a set of non-linear coupled ordinary differential equations using similarity analysis. Similarity equations are then solved numerically using shooting algorithm with Runge-Kutta Fehlberg integration scheme over the entire range of physical parameters. A comparison with previously published work has been carried out and the results are found to be in good agreement. Graphical presentation of the local skin-friction coefficient, the local Nusselt number and the local Sherwood number as well as the temperature profiles show interesting features of the physical parameters.     

EMD端点效应的改进型混沌延拓方法及其在机械故障诊断中的应用

针对经验模态分解(Empirical Mode Decomposition,EMD)的端点效应问题,分析了三次样条插值产生端点效应的机理,指出了现有延拓方法的不足,提出采用Lyapunov指数预测模型进行边界延拓,以此减小端点效应在经验模态分解过程中产生的影响。在采用最大Lyapunov指数法进行边界延拓时,针对Lyapunov指数预测模型所表示的平均发散度仅是轨道演化规律的一个近似模型,提出采用局域发散度代替最大Lyapunov指数进行改进,以改进预测模型的预测精度。基于改进型Lyapunov指数边界延拓方法,由于引入时间序列预测模型使端点处的延拓更加合理,所延拓数据更加趋于真实,在希尔伯特-黄变换（Hilbert-Huang Transform,HHT）实现过程中仅需一次延拓,实现了准确的EMD分解。仿真计算和转子系统故障试验分析结果表明,所用方法可以有效解决EMD的端点效应问题。     

Steam reforming of acetic acid over NiKOH/Al2O3 catalyst with low nickel loading: The remarkable promotional effects of KOH on activity

In this paper, the effects of strong base (KOH) addition on the catalytic performances of Ni/Al₂O₃ catalysts in acetic acid steam reforming for hydrogen generation was investigated. The addition of KOH drastically changed the physiochemical property and catalytic performances of the nickel–based catalysts. KOH reacted with γ–Al₂O₃ during calcination, forming ɑ–Al₂O₃ with Al(OH)₃ as a reaction intermediate, which led to reconstruction of the porous structure, merge of small pores, decreased specific area and sintering of nickel. Most importantly, the catalytic activity of nickel–based catalysts were significantly enhanced by the addition KOH, especially the ones with low nickel loading. There are almost no active of 1 wt% Ni/Al₂O₃ catalyst for steam reforming of acetic acid, while, with adding 5 wt % KOH, activity of the catalyst matched that of 20 wt% Ni/Al₂O₃. In–situ DRIFTS study showed the involvement of the reactive intermediates including CH₃, CH₂, CO, COO, COC, CC and absorbed CO₂ in acetic acid steam reforming. The Ni/Al₂O₃ catalyst with low nickel loading had insufficient metallic nickel to gasify these reactive intermediates. The presence KOH effectively aided gasification of the reactive intermediates, and thus significantly promoted the catalytic activity. In addition, the KOH with varied loading significantly affect formation of catalytic coke and polymeric coke formed during the reforming reaction.     

Size effects on mass transport and storage in lithium batteries

The contribution deals with the significance of size effects for lithium-based batteries. The relevant size effects range from purely geometrical effects to effects in which the local thermodynamics is varied. In this context, several recent findings towards improved electrolytes and electrodes are discussed.     

MHD free convection flow along a vertical wavy surface with heat generation or absorption effect

We formulate the problem of free convection from a vertical wavy surface embedded in a uniform porous medium in the presence of an external magnetic field and internal heat generation or absorption effects. Using the appropriate transformations, the boundary layer equations are reduced to non-linear partial differential equations. The transformed boundary layer equations are solved numerically using Runge–Kutta integration scheme with the shooting technique. We have focused our attention on the evaluation of the local Nusselt number Nu_x, dimensionless velocity, f′, and temperature, θ. The governing parameters are the amplitude of the waviness of the surface, a, ranging from 0.0 (flat plate) to 0.3, and the heat generation absorption parameter Q ranging from − 0.25 to 0.25, and magnetic parameter Mn, ranging from 0.0 to 2.0. The effect of all these parameters are discussed and plotted.     

Nanoscale Characterization of Energy Generation from Piezoelectric Thin Films

We report on the use of nanoindentation to characterize in situ the voltage and current generation of piezoelectric thin films. This work presents the controlled observation of nanoscale piezoelectric voltage and current generation, allowing accurate quantification and mapping of force function variations. We characterize both continuous thin films and lithographically patterned nano­islands with constrained interaction area. The influence of size on energy generation parameters is reported, demonstrating that nanoislands can exhibit more effective current generation than continuous films. This quantitative finding suggests that further research into the impact of nanoscale patterning of piezoelectric thin films may yield an improved materials platform for integrated microscale energy scavenging systems.     

Gender differences in injury severity risks in crashes at signalized intersections

This paper analyzes gender differences in crash risk severities using data for signalized intersections. It estimates gender models for injury severity risks and finds that driver condition, type of crash, type of vehicle driven and vehicle safety features have different effects on females’ and males’ injury severity risks. Also, it finds some variables which are significantly related to females’ injury severity risks but not males’ and others which affect males’ injury severity risks but not females’. It concludes that better and more in-depth information about gender differences in injury severity risks is gained by estimating separate models for females and males.     

布拉格光纤激光器热效应研究

提出了布拉格光纤激光器的稳定热模型,并通过热传输方程和数值有限元方法对其温度分布特点进行了分析,并对布拉格光纤激光器的温度分布不均匀产生的热应力分布进行了计算,结果显示该型激光器的热应力小于熔点时石英的临界应力。