课程文献中心 更多>>

关键词： 可见光通信   异构网络   小区缩放   功率控制   用户关联  

摘要： 基于射频（RF）的无线通信系统不断受到频谱短缺和接入拥塞的压力，而可见光通信（VLC）与RF的融合可以实现了高数据速率和广覆盖的互补优势。本文针对室内混合VLC/RF异构网络场景，提出了融合小区缩放的功率控制与用户关联联合优化方法，以实现功率和用户服务质量（QoS）约束下的系统总传输速率最大化，并将其建模成一个多变量耦合的混合整数非线性规划（MINLP）优化问题，运用优化求解器BARON有效求解了该问题。仿真结果验证了融合小区缩放的VLC/RF异构网络能提供更优的功率分配和用户关联，提高了总传输速率。

关键词： 功率放大器   可重构   双频段   超宽带   PIN开关  

摘要： 适应5G智能无线通信系统的飞速发展，提出了一种基于滤波器型偏置的可重构超宽带功率放大器。本文基于滤波器偏置原理，可重构理论和宽带输入输出匹配理论设计了一款可以工作在连续频段内的滤波器型偏置的双频段可重构功率放大器。功率放大器工作在0.7～2.2GHz和2.1～3.6GHz两个频段范围内，输入和输出分别通过基于PIN开关的单刀单掷开关和单刀双掷开关来实现切换功放工作频段。通过实测，该功放在0.7～2.2GHz和2.1～3.6GHz范围内，增益分别为11.9～13.6dB和10.7～12.4dB；功率附加效率分别为63.8%～72.7%和60.3%～68.8%；饱和输出功率均约为41dBm。本设计很好的兼顾了功放的带宽、增益、PAE和输出功率，更好的适应5G智能无线通信系统的发展。

关键词： Biomedical technology   biomedical engineering   cochlear implants   in vivo cardiac pacemaker   cardiac defibrillator   retinal prosthesis   neural recording system   biocompatibility   microwave systems   CP implantable antennas   near-field wireless  

ISBN: (数字)9781119189947 ISBN: (纸本)9781119189916

摘要： Antennas and Wireless Power Transfer Methods for Biomedical Applications Join the cutting edge of biomedical technology with this essential reference The role of wireless communications in biomedical technology is a significant one. Wireless and antenna-driven communication between telemetry components now forms the basis of cardiac pacemakers and defibrillators, cochlear implants, glucose readers, and more. As wireless technology continues to advance and miniaturization progresses, it’s more essential than ever that biomedical research and development incorporate the latest technology. Antennas and Wireless Power Transfer Methods for Biomedical Applications provides a comprehensive introduction to wireless technology and its incorporation into the biomedical field. Beginning with an introduction to recent developments in antenna and wireless technology, it analyzes the major wireless systems currently available and their biomedical applications, actual and potential. The result is an essential guide to technologies that have already improved patient outcomes and increased life expectancies worldwide. Readers will also find: Authored by internationally renowned researchers of wireless technologies Detailed analysis of CP implantable antennas, wearable antennas, near-field wireless power, and more Up to 100 figures that supplement the text Antennas and Wireless Power Transfer Methods for Biomedical Applications is a valuable introduction for biomedical researchers and biomedical engineers, as well as for research and development professionals in the medical device industry.

关键词： 电力变压器   油中溶解气体   异常数据识别   气体含量预测  

摘要： 采用神经网络模型对油中溶解气体含量进行预测是目前评估电力变压器运行状态的重要方法，数据质量是影响神经网络模型预测精度的关键因素，然而，由于变压器复杂的运行环境，使得采集到的气体数据中不可避免的存在多种类型的异常数据，进而造成数据质量下降，严重影响模型的预测精度。此外，神经网络模型的参数是否匹配也是影响其预测性能的重要因素，然而，传统依据人工经验选择参数存在主观性、低效性和不可扩展性等缺点，也在一定程度上影响了模型的预测性能。为解决上述问题，该文通过对最近邻集成隔离法(iNNE)进行修正，提出了修正最近邻集成隔离法(MiNNE)，利用MiNNE综合考虑局部度量与全局度量的特性实现气体异常数据的准确识别，有效提升数据质量。同时，对鹈鹕优化算法进行改进，提出了改进鹈鹕优化算法(IPOA)，并利用IPOA对影响神经网络模型预测精度的关键参数进行优化，有效克服了传统依据经验选参而导致模型预测精度低与传统POA易陷入局部最优的问题，提高了模型的预测性能。采用电力变压器实际运行数据对所提模型进行验证，结果表明，相较于其他模型，所提模型在7种特征气体预测中均取得了最佳的预测效果，充分证明了所提模型的优越性。

关键词： 光伏发电   时序预测   变分模态分解   门控循环单元   雾凇优化  

摘要： 针对光伏的随机性特征给高精度超短期功率预测带来的各种问题，提出IVMD-RIME-GRU自适应优化预测模型：在数据处理环节，对原始光伏功率信号进行改进的变分模态分解(improved variational mode decomposition， IVMD)，后续则对分解得到的模态信号分别进行预测，降低光伏非平稳性造成的影响。IVMD通过残差是否已接近白噪声来确定VMD分解的最优模态数，尽量减少分解造成的信息损失。在训练预测环节，采用能够处理长时间序列的门控循环单元(gated recurrent unit， GRU)进行预测，并利用雾凇（RIME）优化算法强大的寻优能力，对GRU的关键参数进行自适应优化，提升算法整体性能。最后将各模态的预测结果合并，得到实际预测输出。仿真结果表明，所提出的模型能够将原始GRU的预测性能提升70%以上，且对光伏功率的峰谷快速切换实现良好跟踪。

关键词： Threshold voltage  

摘要： This paper proposed an 8 nm N-type Double Gate MOSFET with improved characteristics. A comparative study has been done based on substrate and oxide material. The substrate and oxide material combination is Si-SiO2, SiGe-HfO2. This study discussed about which channel and oxide material is performed with better efficiency in sub-micron dimension in terms of Ioff, Ion, Ion/Ioff, Threshold Voltage (Vth), Sub-threshold Swing (SS) and Drain-Induced-Barrier-Lowering (DIBL) to obtain energy efficient and high performance circuits. All parameters are validated according to the IRDS-2020 and compare with existing literature. Based on improved performance SiGe material has been chosen for circuit level applications. In this research all the basic gates (NOT, AND, OR, XOR, XNOR) as well as universal gates (NAND, NOR) along with their performance with respect to Propagation Delay, Short Circuit power dissipation, Dynamic power dissipation, Power Delay Product (PDP), Energy Delay Product (EDP) and Noise Margin have been explored at 1 Volt supply voltage. These findings suggest that the proposed device is a suitable candidate to design high speed and low power logic circuits.

关键词： 超声换能器   压电陶瓷   COMSOL有限元仿真   压电性能   介电性能  

摘要： 采用固相法制备了PMN-PZT + x % Nb2O5压电陶瓷，其中x = 0、0.05、0.1、0.2、0.3、0.4、0.5。通过X射线衍射仪、扫描电子显微镜表征陶瓷的结构和形貌，测试陶瓷的压电常数d33、相对介电常数εr、介电损耗tanδ、相角θ、导纳曲线G-B、品质因子Qm、机电耦合系数Ke、阻抗|Z|和谐振频率fr、反谐振频率fa，并计算平面机电耦合系数kp，研究了Nb2O5掺杂量和烧结温度对压电振子的微观结构、电学综合性能的影响。基于COMSOL有限元仿真软件对压电振子的频率特性、表面声压级、位移大小、振动模态进行分析。结果表明：陶瓷的压电性能不仅与准同型相界有关，还取决于晶胞的四方度；掺杂适量Nb2O5后陶瓷发生四方相与立方相的转变；当x = 0.2且在1250 ℃烧结时，频率带宽为2.21 kHz，谐振频率fr和阻抗|Z|分别为156.8 kHz和78.38 Ω，平面机电耦合系数kp= 0.66，压电常数d33= 634 pC/N，相对介电常数εr= 5621，介电损耗tanδ = 0.0174。这项工作有望满足高功率超声换能器的应用要求。由仿真结果显示，厚度太小，压电振子位移过小，厚度太大，会导致不对称位移和形变。

关键词： 材料合成与加工工艺   超声波焊接   有限元模拟   摩擦系数   超声软化  

摘要： 采用有限元方法，以界面温度以及焊头下压位移的试验结果作为依据，探索了纯铜超声波焊接时摩擦及材料软化过程，并分析了焊接过程的温度场及塑性应变分布。结果表明，所建的模型能较好模拟焊接动态软化及摩擦系数变化过程。工件接触面的平均摩擦系数在焊接初期快速增加之后急剧下降，并在焊接时间0.2 s后呈现较平稳的波动。铜的超声软化系数在焊接初期急剧增加；之后缓慢增加，并在时间0.3 s后明显增加。超声软化是材料塑性变形的主要物理机制。

关键词： Junctionless   MCMG   MOSFET   multi-channel   multi-gate  

摘要： In this paper, a multi-gate junctionless field-effect transistor with a quad gate and multiple channels has been proposed and thoroughly simulated. The proposed device offers a lower I-off current of 4.34 x 10(-19) A, an I-on current of 4.17 x 10(-06) A with an I-on/I-off current ratio of 9.65 x 10(12), a threshold voltage of 0.86 V, a transconductance of 5 x 10(-05) S, a drain-induced barrier lowering (DIBL) of 22 mV/V, and a subthreshold slope (SS) of 61.51 mV/dec. The visual contour plots of the device are also included in this study to understand the working mechanism. The larger tunneling width between the channel drain and barrier height between the source-channel interface exhibits a lower leakage current and better performance. The performance of the proposed device is also studied when the work function between the semiconductor and gate material is altered. The work function difference improves the performance metrics. Aside from that, the effects of temperature variation on the device's performance characteristics are also being studied. When the temperature varies by 33% the threshold voltage of the proposed device drops by only 7% which shows a minimum variation in the proposed device. The results obtained from the proposed device exhibit the potential of using multi-gate multi-channel junctionless field effect transistor (MCMG) device in low-power logic circuits and memory devices.

关键词： 开关类功率放大器   Σ-△调制   开关管开关特性   失真补偿  

摘要： 开关类功率放大器（SMPA）因具有体积小、功率效率高等优点而被广泛应用。但在应用中，因其结构中开关管存在开关特性而导致性能下降，降低输出信号信噪比（SNR）。若更换开关管或修改电路设计，将面临电路成本增加和复杂度提高的问题。因此，提出一种基于Σ-Δ调制的SMPA性能失真补偿方法。该方法首先产生失真补偿查找表，其次由查找表调整Σ-△调制级，最后产生失真补偿的Σ-△调制电路。仿真结果表明，过采样比（OSR）为512，调制阶数为3阶时，理想输出信号SNR为151.8 dB，畸变输出信号SNR为75.2 dB，失真补偿后输出信号SNR提高至110.7 dB，验证了失真补偿方法有效，为低成本、低复杂度地解决SMPA性能降低问题提供了技术支撑。