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991.
利用解析方法和电路模拟方法研究了阻抗变换器功率传输效率的优化设计。电路计算中,采用了脉冲上升沿等效的正半周正弦波作为输入波形的假设,并忽略了水介质能量损失的影响。首先对比了线性、饱和型变化和陡变型变化3种典型阻抗的功率和能量传输效率,分析讨论了影响指数型阻抗变换器功率传输效率的关键影响因素,并得到了功率传输效率最大化的中间参数和符合系数的参数范围。讨论了实际设计中应注意的绝缘安全系数的结构设计、杂散参数对阻抗计算的影响、水介质能量损失等问题。 相似文献
992.
993.
共吸附剂修饰纳晶TiO2薄膜电极是目前染料敏化太阳电池研究的一个热点. 本文通过平带电势和电化学阻抗研究了二(3,3-二甲基丁基)次膦酸和鹅脱氧胆酸两种共吸附剂修饰对TiO2薄膜电极的平带电势和电极表面钝化能力的影响及其在染料敏化太阳电池中的应用. 结果表明, 二(3,3-二甲基丁基)次膦酸能更有效地钝化TiO2薄膜表面, 并使TiO2薄膜平带电势负移. 电化学阻抗谱测试结果表明, 在染料敏化太阳电池中, 相对于鹅脱氧胆酸, 二(3,3-二甲基丁基)次膦酸能更显著地提高器件的电子寿命和开路电压. 相似文献
994.
Gold nanoparticle (Au‐NPs)‐Titanium oxide nanotube (TiO2‐NTs) electrodes are prepared by using galvanic deposition of gold nanoparticles on TiO2‐NTs electrodes as support. Scanning electron microscopy and energy‐dispersive X‐ray spectroscopy results indicate that nanotubular TiO2 layers consist of individual tubes of about 60–90 nm diameters and gold nanoparticles are well‐dispersed on the surface of TiO2‐NTs support. The electrooxidation of hydroquinone of Au‐NPs/TiO2‐NTs electrodes is investigated by different electrochemical methods. Au‐NPs/TiO2‐NTs electrode can be used repeatedly and exhibits stable electrocatalytic activity for the hydroquinone oxidation. Also, determination of hydroquinone in skin cream using this electrode was evaluated. Results were found to be satisfactory and no matrix effects are observed during the determination of hydroquinone content of the “skin cream” samples. 相似文献
995.
A simple cell, consisting of two insulated wire electrodes placed in a PTFE tube through which the test gaseous phase flows, has been applied to capacitively coupled contactless conductometric detection (C4D) and determination of water vapour in the air, to examine the possibilities of the use of C4D for analyses of gaseous samples. It has been found that the measurement is sufficiently sensitive and reliable for determinations of common concentrations of water in the air. The dynamic characteristics and the signal stability demonstrate that the cell will be suitable for long‐term continuous monitoring of the air humidity. Qualitative tests indicate that vapours of organic solvents can also be monitored. To the authors knowledge, this is the first attempt to use C4D in gas analyses. 相似文献
996.
利用高压X射线衍射和高压原位电化学阻抗谱法研究了AlN纳米线的高压结构和电学性质.研究结果表明:AlN纳米线的电学参数均在22.6 GPa发生了突变,该突变与样品发生了从纤锌矿到岩盐矿的结构相变相关.岩盐相中晶格对电子的散射在电传导中起主导作用;不同于纤锌相中的长程传导,岩盐相中存在短程传导,且其作用随压力增加而增大;纤锌相的介电损耗峰在1Hz且不受压力影响;岩盐相的介电损耗峰随压力减小且向低频方向移动.本研究将为AlN及其相关材料的进一步研究和应用提供实验依据. 相似文献
997.
基于电阻抗成像技术和生物阻抗谱技术,提出一种面向生物组织检测的生物阻抗谱成像方法.该方法将目标区域可视化并精准识别目标种类,可用于肺癌早期检测,协助临床医生对早期肺癌进行精准检测,提高早期肺癌的治愈率.本文通过数值仿真的方法验证生物阻抗谱成像方法在肺癌早期检测中的可行性和有效性,仿真结果表明:1)生物阻抗谱成像方法可以实现早期肺癌区域的可视化,并精确判别出早期肺癌种类; 2)生物阻抗谱成像方法中阻抗谱的最佳采集模式是4次循环采集,最佳分类器是Linear-SVM, 5折交叉验证的平均分类准确率可以达到99.9%.为了验证仿真结果,本文选取3种具有不同电学特性的生物组织模拟癌变区域进行了检测.实验结果表明该方法可以对生物组织区域可视化,并判别出生物组织的种类.该方法可以兼顾电阻抗成像和生物阻抗谱方法的优点,有望用于肺癌早期检测. 相似文献
998.
This paper considers the problem of joint power allocation and antenna selection (J-PA-AS) for downlink (DL) and uplink (UL) clustered non-orthogonal multiple-access (NOMA) networks. In particular, the goal is to perform antenna selection for each user cluster and allocate transmit power to its users so as to maximize the network sum-rate in the DL and UL directions, while satisfying quality-of-service (QoS) requirements. The formulated problem happens to be non-convex and NP-hard, and thus, there is no systematic or computationally-efficient approach to solve it directly. In turn, a low-complexity two-stage algorithm is proposed. Specifically, the first stage optimally solves the sum-rate maximizing power allocation for each (antenna, user cluster) pair. After that, antenna selection is optimally solved in polynomial-time complexity via the Kuhn–Munkres with backtracking (KMB) algorithm. Extensive simulation results are provided to validate the proposed algorithm, which is shown to efficiently yield the optimal network sum-rate in each link direction, in comparison to the optimal J-PA-AS scheme (solved via a global optimization package), and superior to other benchmark schemes. Light is also shed on the impact of spatial-diversity on the network sum-rate, where it is shown that the greater the number of base-station antennas is, the higher the network sum-rate, and the lower the outage events. Additionally, the significance of decoupling antenna selection in each link direction on the network sum-rate is highlighted. Lastly, the cases of imperfect channel state information (CSI) and imperfect successive interference cancellation (SIC) have been investigated, where it is demonstrated that spatial-diversity gains reduce the adverse effects of imperfect CSI and SIC on the network sum-rate. 相似文献
999.
1000.
R. Padhee 《Phase Transitions》2013,86(9):865-880
This paper highlights the electrical properties of two new complex tungsten bronze ceramics (K2Pb2Eu2W2Ti4Nb4O30 and K2Pb2Pr2W2Ti4Nb4O30) which were prepared by high temperature mixed oxide method. Variation of impedance parameters with temperature (27–500 °C) and frequency (1 kHz to 5 MHz) shows the grain and grain boundary effects in the samples. The variation of dielectric parameters with frequency is also studied. The ac conductivity variation with temperature clearly exhibits that the materials have thermally activated transport properties of Arrhenius type. 相似文献