抛物线型有损传输线频域灵敏度分析的伴随方程法

提出了一种求解含抛物线型有损非均匀线网络频域灵敏度的方法。该方法首先将抛物线型有损非均匀线用科罗达(Kuroda)等效方法变换成有损均匀线及若干集中元件组成的等效电路,然后借助伴随网络方程法求出抛物线型有损非均匀传输线等参数的频域灵敏度。给出了计算实例,并通过扰动法进行了验证。     

An efficient method of designing dual‐ and wide‐band power dividers with arbitrary power division

Capability of microstrip nonuniform transmission lines (MNTLs) for construction of dual‐band and broadband unequal Wilkinson power dividers with arbitrary‐way, arbitrary frequency band operations, and arbitrary power divisions is evaluated. Also, the MNTL transformers are introduced for dual‐band/broadband matching of the unequal output impedances of the MNTL power divider with arbitrary output terminal impedances. The strip width of MNTLs is considered variable and is written as a truncated Fourier series expansion. To show the validity of the design procedure, three experimental MNTL Wilkinson power dividers, which are dual‐band two‐ and three‐way power dividers with different power divisions working at 1 and 3.4 GHz and one broadband equal power divider working from 0.4 to 1.8 GHz, have been designed and fabricated. In the first ones with power division of 1.5, outputs isolation and ports matching of less than ?30 dB are achieved. Next, an extended recombinant structure is presented for achieving three‐way MNTL power dividers with dual‐band operation. The measured isolation between outputs and ports matching are better than 30 dB and measured forward transmissions are between ?4.87 and ?5.45 in two passbands of the divider. Also, for the proposed broadband divider, the measured isolation between the outputs is better than 13 dB in 127% desired bandwidth. © 2012 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2013.     

非均匀入流中螺旋桨噪声数值预报

将黏性多相流理论的数值方法和球形空泡辐射噪声理论相结合,进行了非均匀入流条件下螺旋桨片空化的周期形态模拟以及螺旋桨空化单极子声源辐射噪声数值预报。采用流场数值模拟方法和声场边界元数值声学方法耦合的方法,在频域上预报非均匀入流下空化和非空化条件下螺旋桨负载噪声;通过数值预报负载噪声得到非空化条件下螺旋桨噪声,将片空化单极子声源辐射噪声和空化的负载噪声在频域上进行相加得到空化条件下的螺旋桨噪声。采用某民船桨模验证了非均匀入流下螺旋桨片空化周期形态以及空化单极子声源辐射噪声预报的准确性,然后分析了民船桨在空化和非空化条件下螺旋桨噪声的叶频和二倍叶频特征。结果表明,上述方法能有效地预报螺旋桨空化和非空化噪声的叶频特征。     

A wideband rectifier array on dual‐polarized differential‐feed fractal slotted ground antenna for RF energy harvesting

This article reports a novel wideband rectenna for RF energy harvesting applications. A wideband fractal slotted ground antenna (SGA) is adopted. The operating frequency bands of the antenna are GSM, UMTS, Wi‐Fi, and LTE2600/4G bands. The antenna is fed by a dual‐polarized and differential‐feed (DP‐DF) microstrip lines disposed with an angle of 90° each relative to the other. The feed lines are etched on the bottom side of the substrate and connected to an array of four wideband RF‐to‐DC rectifiers. A nonuniform transmission lines filter ensures wideband behavior for each rectifier. The rectenna performances are simulated and measured. The experiments show an output DC voltage of 1 V at a power density of 26.6 μW/cm² over the frequency band of operation with a peak efficiency of 50%. The proposed rectenna is suitable for energy harvesting applications in urban environments.     

Simulation study of single‐cell‐gap transflective liquid crystal display with nonuniform potential

A single‐cell‐gap transflective liquid crystal display with a nonuniform electric potential is demonstrated. The top substrate has a top planar common electrode, a transparent dielectric layer with a general dielectric constant is coated on the bottom substrate, and two planar pixel electrodes with the same size are coated on the dielectric layer and the bottom substrate, respectively. With the different gaps between the two planar pixel electrodes and top planar pixel electrode, the nonuniform electric potential from the transmissive region (T region) to the reflective region (R region) is generated, while a bumpy reflector is coated under the bottom substrate. In this device, with the dielectric layer, the pixel and common electrodes generate a strong electric potential in the T region and a relatively weak electric potential in the R region. Consequently, the T and R regions accumulate the same optical phase retardation. The simulation results show that the display exhibits reasonably low operating voltage, high optical efficiency, and well‐matched voltage‐dependent transmittance and reflectance curves. Besides, the fabrication process and the driving mode of the transflective liquid crystal display are relatively simple, and it is suitable for mobile applications.     

非均匀厚度漂移区SOI高压器件及其优化设计

提出非均匀厚度漂移区SOl高压器件新结构及其优化设计方法.非均匀厚度漂移区调制SOI层的电场并增强埋层电场,从而 提高器件击穿电压.考虑到这种调制效应.提出解析模型用以优化设计该新器件的结构参数.借助解析模型,研究了电场分布和器件击穿电压与结构参数的关系.数值仿真'证实了解析模型的正确性.具有3阶梯的非均匀厚度漂移区SOl器件耐压为常规结构SOl器件的2倍,且保持较低的导通电阻.     

不均匀多导体传输线的瞬态分析

针对越来越严重的信号畸变和线间耦合问题,应用时域有限差分法（Finite Difference Time Domain,FDTD）建立了不均匀多导体传输线的仿真模型,并通过MATLAB编程对不均匀多导体传输线两端的电压响应进行了仿真分析.在此基础上,理论说明了各端口瞬态响应的波形特点.结果表明了时域有限差分法用于分析多导体传输系统电磁兼容问题的正确性和有效性,为电磁干扰的预测提供了有价值的参考信息.     

Gradient-based recursive parameter estimation for a periodically nonuniformly sampled-data Hammerstein–Wiener system based on the key-term separation

The identification of the Hammerstein–Wiener (H-W) systems based on the nonuniform input–output dataset remains a challenging problem. This article studies the identification problem of a periodically nonuniformly sampled-data H-W system. In addition, the product terms of the parameters in the H-W system are inevitable. In order to solve the problem, the key-term separation is applied and two algorithms are proposed. One is the key-term-based forgetting factor stochastic gradient (KT-FFSG) algorithm based on the gradient search. The other is the key-term-based hierarchical forgetting factor stochastic gradient (KT-HFFSG) algorithm. Compared with the KT-FFSG algorithm, the KT-HFFSG algorithm gives more accurate estimates. The simulation results indicate that the proposed algorithms are effective.     

图像区间模糊模型及其在图像检索中的应用

在HSV颜色空间下,通过非均匀量化方法,构建了图像区间模糊模型.在此模型下,图像可以看作是一个区间模糊集合(IVFS,interval-valued fuzzy set).IVFS之间相似性度量可以用来衡量图像之间的相似程度.给出一种基于LP范数距离的IVFS集合度量(简称IVFSLp)并将它应用于图像检索中.实验数据表明:IVF-SLP与直方图距离(histogram distance)和普通模糊集的相似性度量(general fuzzy similarity measure)相比具有更好的性能.     

Interpretation of infinite shear rate viscosity and a nonuniform heat sink/source on a 3D radiative cross nanofluid with buoyancy assisting/opposing flow

With respect to bionomical concerns and energy security, the performance of refrigeration systems should be enriched, which can be done by improving the characteristics of working liquids. Nanoliquids have attracted interest in the fields of engineering and industry due to their prominent thermophysical characteristics. Researchers have used nanoliquids as working liquids and noticed significant fluctuations in thermal execution. In this study,  our prime aim was to study the impact of thermal radiation and varying thermal conductivity on a cross-nanofuid with the addition of a nonuniform heat sink–source, chemical process, and activation energy (AE) together with effects of assisting and opposing buoyancy. Furthermore, the relationship of zero-mass flux together with the mechanism of thermophoresis and Brownian motion is considered. Traditionalistic transformations gave the ordinary differential equations (ODEs), which are further dealt with the approach of the Shooting Scheme to change the boundary value problem (BVP) into an initial value problem (IVP) and a numerical comparison is made with the Matlab solver package bvp4c. Bvp4c is based upon a collocation scheme, which yields numeric outcomes for nonlinear ODEs with IVP. Impacts of the involved parameters on mass transfer profile, heat, and momentum fields are shown through graphs. Mass transfer of the cross nanofluid increases with increasing values of AE parameter. Values of physical quantities like drag forces, rate of transport of heat and mass in the case of assisting/opposing flow are tabulated. The drag force magnitudes are greater for enhancing values of M, a, and n, while on the other hand, the opposing tendency is seen for We₁ and We₂. The magnitude of the rate of heat transport (Nusselt number) falls for greater values of m, σ, δ, and N_t, but in contrast, it accelerates for E, Pr, and n.