The response of clamped-clamped microbeams under mechanical shock

We present modeling, simulation, and characterization for the dynamic response of clamped-clamped microbeams under mechanical shock. A Galerkin-based reduced-order model is utilized and its results are verified by comparing to finite-element results. The results indicate that the response of a microbeam to mechanical shock is inherently non-linear because of the dominating effect of mid-plane stretching. The effect of the shock pulse shape is investigated. It is concluded that the shape of the shock pulse can result in significant dynamic amplification in the response of the microbeam even in cases where the shock load is considered quasi-static.The combined effect of the electrostatic force and mechanical shock is investigated. The results show that this combined effect can lead to early instability in microelectromechanical systems (MEMS) devices through dynamic pull-in. This could explain some of the reported experimental evidences for the existence of strange modes of failure of MEMS devices under mechanical shock and impact. These failures are characterized by overlaps between moving microstructures and stationary electrodes, which cause electrical shorts. The shock-electrostatic interaction is shown to be promising to design smart MEMS switches triggered at predetermined level of shock and acceleration. Finally, the mechanical shock combined with the packaging effect of MEMS devices is analyzed. A single-degree-of-freedom model representing the motion of the package, which is mounted over a printed circuit board, coupled with the continuous beam model is utilized. Our results reveal that neglecting the effect of the package motion on the response of microbeams can overestimate or underestimate their response. It is concluded that a poor design of the package may result in severe amplification of the shock effect leading to a device failure.     

以第一原理研究二氧化钛纳米粒子热动力学性质(英文)

利用第一原理分子动力学研究了二氧化钛纳米粒子(TiO2)n(n=1～6)的热动力性质.使用分子动力学(molecular dynamics)和火焰算法(FIRE algorithm)获得二氧化钛纳米粒子的最低能量结构,再利用密度泛函理论(density functional theory)进一步计算得到更精确的最低能量结构.研究得到二氧化钛纳米粒子的几何和结构的热力学效应.     

First-principle study of native defects in CuScO2 and CuYO2

This paper studies the electronic structure and native defects in transparent conducting oxides CuScO2 and CuYO2 using the first-principle calculations. Some typical native copper-related and oxygen-related defects, such as vacancy, interstitials, and antisites in their relevant charge state are considered. The results of calculation show that, CuMO2（M = Sc, Y） is impossible to show n-type conductivity ability. It finds that copper vacancy and oxygen interstitial have relatively low formation energy and they are the relevant defects in CuScO2 and CuYO2. Copper vacancy is the most efficient acceptor, and under O-rich condition oxygen antisite also becomes important acceptor and plays an important role in p-type conductivity.     

Synthesis, Crystal Structure and Quantum Chemistry Study of Tri（o-bromobenzyl）tin Ferrocenecarboxylate

A novel complex tri(o-bromobenzyl)tin ferrocenecarboxylate has been synthesized and its crystal structure was determined by X-ray diffraction. It belongs to orthorhombic, space group Pbca with a = 1.1340(3), b = 1.7823 (4), c = 3.0119(8) nm, V = 6.088(3) nm3, Mr = 857.81, Z = 8, Dc = 1.872 g/cm3, μ(MoKα) = 52.63 cm-1, F(000) = 3328, R = 0.0683 and wR = 0.1057. The tin atom adopts a distorted tetrahedral coordination geometry. Further studies on the title com- plex have been performed with quantum chemistry calculation at the Lanl2dz basis set level using G98W package. The stability of the complex, some frontier molecular orbital energies and com- position characteristics of some frontier molecular orbitals have been investigated.     

Irradiation preservation of Hangzhou White Chrysanthemum Dendranthema morifolium (Ramat. Tzvel)

A study on the irradiation preservation of Hangzhou White Chrysanthemum (HWC for short) was carried out to keep the quality of HWC and prolong its shelf life. The results showed that: 1). γ-irradiation with proper dosage was one of the key steps to prolong the shelf-life of HWC. After γ - treatment at the dose level of 3–5kGy, the laminated plastic film packed HWC could be stored in ambient temperature for over 300 days, remaining its original colour, aroma and taste. 2). Different dose rate had no effect on the treatment results. 3). The main quality indexes of HWC treated with 10.0 kGy γ - rays were not changed, moreover, it had the higher hygienic qualities.     

Thermal hazard evaluation for methyl ethyl ketone peroxide mixedwith inorganic acids

Methyl ethyl ketone peroxide (MEKPO) possesses complex structures which have caused many incidents involving fires or explosions by mixing with incompatible substances, external fires, and others. In this study, reactivities or incompatibilities of MEKPO with inorganic acids (HCl, HNO₃, H₃PO₄ and H₂SO₄) were assessed by differential scanning calorimetry (DSC) and vent sizing package 2 (VSP2). Parameters obtained by the above-mentioned devices could be readily employed to discuss the runaway reaction, such as onset temperature (T ₀), heat of reaction (ΔH _d), time to maximum rate (TMR), maximum self heat rate (dT/dt)_max, adiabatic temperature rise (ΔT _ad), maximum pressure of decomposition (P _max) and so on. Mixing MEKPO with hydrochloric acid resulted in the lowest T ₀ among inorganic acids. Nitric acid not only lowered the T ₀ but also delivered the highest heat releasing rate or self heat rate (dT/dt), which was concluded to be the worst case in terms of contamination hazards during storage or transportation of MEKPO.     

基于VSP2的液体有机过氧化物不稳定性分级研究

本文通过对国内外危险化学品不稳定性分级进行研究,提出了一种新的有机过氧化物不稳定性分级方法(OPIC),此方法基于泄放尺寸包绝热量热仪(VSP2)测量数据,将反应初始温度(Tonset)作为反应可能性指数(RPI),最大功密度(MPD)(包含反应热(ΔH)和最大反应速率max(dr/dt))、绝热温升(ΔTad)、最大压力上升速率max(dp/dt)和总压力变化(ΔP)等参数通过层次分析法综合为反应严重度指数(RSI),并将前人统计的采用这些参数准确分级的次数代入层次分析法(AHP)中,得到这些参数在反应严重度指数(RSI)中的权重。将RPI指数与RSI指数采用风险矩阵的方法得到最终的有机过氧化物不稳定分级,能更加全面的表征有机过氧化物的不稳定性。根据VSP2实验和计算结果分析证明:利用本文提出的有机过氧化物分级方法(OPIC)对液体有机过氧化物进行分级更符合实际情况,该方法为化学品的本质安全筛选提供了可靠的技术支持。     

大功率远程荧光粉型白光LED散热封装设计

针对大功率远程荧光粉型白光LED存在的散热问题,研究了其封装结构的散热设计方法。在分析现有远程荧光粉型白光LED封装结构及散热特点的基础上,提出将荧光粉层与芯片热隔离的同时开辟独立的荧光粉层散热路径的热设计方法。仿真分析结果表明:新的设计能够在不增加灯珠径向尺寸的同时改善荧光粉层的散热能力。在相同边界条件下,改进设计后的荧光粉层温度较改进前降低了10.7℃,芯片温度降低了0.55℃。在芯片基座上设置热隔离槽对芯片和荧光粉层温度的影响可以忽略。为了达到最优的芯片和荧光粉层温度配置,对荧光粉层与芯片之间封装胶层厚度进行优化是必要的。新的封装方法将芯片和荧光粉层的散热问题相互独立出来,既避免了二者的相互加热问题,又增加了灯珠光学设计的自由度。     

电磁监测试验卫星阻滞势分析器探测技术

依据电磁监测试验卫星的任务要求,自主研发了等离子体分析仪,首次实现电离层等离子体原位探测.作为等离子体分析仪的重要组成部分,阻滞势分析器主要用于探测电离层等离子体的密度、沿轨道方向漂移速度、温度以及成分等参数.阻滞势分析器传感器栅网材料选用铍铜,表面镀金处理,并通过仿真验证了多层栅网总透过率与理论计算的一致性.依据技术指标,详细设计了阻滞势分析器传感器的窗口半径、收集极半径、有效高度及扫描电压等参数.在电子学电路设计时通过前放电路三个可调量程的设计,保证了电路测量精度.在此基础上,借助意大利国家天体物理研究院行星际物理研究所的地面等离子体环境,完成了阻滞势分析器的等离子体环境测试.测试结果表明,该阻滞势分析器的性能指标满足设计要求,能够实现电磁监测试验卫星的任务需求.     

电子封装中材料的几何尺寸对翘曲的影响

电子器件的封装技术是制约集成电路发展的关键环节之一。封装中各材料（基底、粘结层、芯片及封装材料）的几何尺寸、材料性能的差异引起的翘曲问题严重影响芯片的可靠性和焊接性能。本文采用数值分析方法,并考虑玻璃态转化温度（Tg）对材料性能（弹性模量和热膨胀系数）的影响,研究了尺寸变化对芯片翘曲的影响。分析表明基底与芯片厚度比和封装材料与芯片厚度比的变化对翘曲的影响较大,基底与芯片面积比和粘结层与芯片高度比的变化对整体翘曲的影响较小,本文结果为进一步封装设计提供理论依据。