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171.
根据大型柔性构件存在着建立运动方程自由度多,整体结构参数不宜测量等特点,文中研究了基于子结构的振动特征结构配置.为克服以往在拼装子结构时由于界面耦合作用,造成振动能量相互传递,破坏原有各子控制器设计性能的缺陷,作者提出了通过在界面上安装控制执行器,以割断子结构间能量传递的分散解耦控制法,保证了子控制器的设计特性在装配后不会改变 相似文献
172.
A. Bello M. Fabiane D. Dodoo-Arhin K.I. Ozoemena N. Manyala 《Journal of Physics and Chemistry of Solids》2014
Silver metal nanoparticles were decorated by electron beam evaporation on graphene foam (GF) grown by chemical vapour deposition. X-ray diffraction, Raman spectroscopy, scanning and transmission electron microscopy, and atomic force microscopy were used to investigate the structure and morphology of the graphene foam/silver nanoparticles (GF/Ag). Both samples were tested as electrodes for supercapacitors. The GF/Ag exhibited a significantly higher capacitive performance, including a specific capacitance value of (~110 Fg−1) and excellent cyclability in a three-electrode electrochemical cell. These results demonstrate that graphene foam could be an excellent platform for metal particles for investigating improved electrochemical performance. 相似文献
173.
基于惯性约束聚变强激光装置中金属化膜脉冲电容器"自愈"的失效机理,提出了更为适合的冲击模型金属化膜脉冲电容器可靠性评估方法。现有的加速退化试验中,失效阈值往往是事先确定的,但考虑可靠性产品个体差异及环境影响的不同,这是不合理的,针对此问题提出了基于随机阈值的冲击模型金属化膜脉冲电容器退化建模的方法。由于模型过于复杂,采用MCMC方法进行参数估计。最后通过对电容器的仿真实验,将随机阈值下的评估结果与固定阈值的情况相对比,说明了该模型和方法的合理性,并进一步分析了不同的阈值分布均值和方差对产品可靠性的影响。 相似文献
174.
粒子加速器由于受地基振动、环境温度、热效应等因素的影响,导致束流位置探头(BPM)所在真空盒的机械中心相对四极铁磁中心的漂移较大,因此很难提高束流轨道的绝对测量精度。探索利用电容式探头实时检测该漂移量的方法。首先分析了电容式探头的测量原理,并设计了轨道振动同步诊断方案,然后设计了专用探头,并利用数据采集设备对探头的线性度、精度和频率响应进行实验室测试。结果显示电容式探头能检测到2μm的相对位移,且可有效检测300Hz以下的振动频率,可用于束流轨道与相关环境参数的同步诊断。 相似文献
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177.
Paul S Vinod Chandran C Bräuniger T Madhu PK 《Journal of magnetic resonance (San Diego, Calif. : 1997)》2011,209(2):261-268
We present here a bimodal Floquet theoretical and experimental investigation of the direction of sweep in the swept-frequency two pulse phase modulated (SW(f)-TPPM) scheme used for heteronuclear dipolar decoupling in solid-state NMR. The efficiency of the decoupling turns out to be independent of the sweep direction. 相似文献
178.
We prove a variant of a Johnson‐Lindenstrauss lemma for matrices with circulant structure. This approach allows to minimize the randomness used, is easy to implement and provides good running times. The price to be paid is the higher dimension of the target space k = O(ε?2 log3 n) instead of the classical bound k = O(ε?2 log n). © 2011 Wiley Periodicals, Inc. Random Struct. Alg., 2011 相似文献
179.
A fresh analysis of literature data shows how the influences of temperature and pressure on ion transport and structural relaxation in glass-forming systems may be combined within the framework of ‘master plots’ based on the equation EA = M · VA, to reveal new insights into coupling and decoupling effects in a wide range of systems. EA,σ and VA,σ are, respectively, instantaneous activation energies and volumes for ionic conductivity and the parameter, Mσ, is a corresponding ‘process modulus’. For structural relaxations occurring at the glass transition, the appropriate modulus is given by Ms = Tg · dP/dTg. We can now identify typical behaviour patterns for fragile liquids on the one hand, and typical inorganic glasses on the other. Thus, the parameters, Mσ and Ms, for fragile systems such as molten Ca(NO3)2:KNO3 (CKN) or a typical polymer electrolyte such as a complex of LiCF3SO3 in PPG, are found to remain constant over a wide range of temperatures down to Tg, despite changes in the temperature (and pressure) dependences of the ionic conductivities, as indicated for example by a return to Arrhenius behaviour in the case of CKN, or by so-called Stickel plots and changes in the VTF parameters for the polymer electrolytes. If E* and V* are activation energies and volumes assigned to elementary steps, when again E* = M · V*, we can go further and identify the microscopic processes driving forward structural relaxation. In the case of inorganic glasses, where usually we find the decoupling index Rτ ≈ 1012, we identify two distinct decoupling paradigms represented by strong and fragile systems respectively, where in both cases the activation volumes for ion transport are very similar to the corresponding ionic volumes. In the former case (typified by the strongly cross-linked silicate and aluminosilicate systems), the negative activation volumes for structural relaxation (negative values of dTg/dP) are clearly indicative of a ‘water-like’ behaviour attributable to the collapse of the network under pressure. On the other hand, for the more fragile fast-ion conducting silver iodomolybdate glass, the experimental results show that Ms (at Tg) ≈ Mσ (in glass), implying some recoupling of structural relaxation to ion transport. Arguments based on the dynamic structure model lead us to predict that a similar close link should exist between Ms (at Tg) and Mσ in the relatively fragile lithium and sodium borate glasses, thus highlighting the need for more information concerning the effects of pressure on the glass transition temperatures of common inorganic glasses. 相似文献
180.
《天然气化学杂志》2014,(6):809-815
The effects of magnetic fields on electrochemical processes have made a great impact on both theoretical and practical significances in im- proving capacitor performance. In this study, active carbon/Fe304-NPs nanocomposites (AC/Fe304-NPs) were synthesized using a facile hy- drothermal method and ultrasonic technique. Transmission electron micrographs (TEM) showed that Fe304 nanoparticles (Fe304-NPs) grew along the edge of AC. AC/Fe304-NPs nanocomposites were further used as an electrochemical electrode, and its electrochemical performance was tested under magnetization and non-magnetization conditions, respectively, in a three-electrode electrochemical device. Micro-magnetic field could improve the electric double-layer capacitance, reduce the charge transfer resistance, and enhance the discharge performance. The capacitance enhancement of magnetized electrode was increased by 33.1% at the current density of 1 A/g, and the energy density was improved to 15.97 Wh/kg, due to the addition of magnetic particles. 相似文献