Measured properties of bare and insulated antennas in sand

An experimental system for measuring the electrical properties of antennas embedded in moist sand is described. Measured antenna input admittances for bare linear and circular-loop antennas in sand are compared with theory. Insulated linear and circular-loop antennas with the dielectric constant of the insulation comparable to that of the surrounding medium are considered. Measured input admittances of linear antennas with different insulation sizes and dielectric constants are used to illustrate the effect of the insulation on the admittance. Measured input admittances for the spherically insulated circular-loop antenna are compared with theory and are found to be in good agreement.     

Probability of Error in Binary Communication Systems with Causal Band-Limiting Filters--Part I: Nonreturn-to-Zero Signal

Upper and lower bounds to probability of error in binary communication systems with intersymbol interference are presented. Closed-form formulas are given for systems with filters having a finite number of lumped elements. Explicit results are given when the filters are Butterworth filters of orderN = 1, 2,..., 10. Four systems are considered: with a sample detector (SD), with an integrate-integrated-and-dump detector (IDD), with a filter in receiver only, and with filters in receiver and transmitter. The transmitted signal is assumed to be of the nonreturn-nonreturn-to-zero (NRZ) form.     

背景风场和温度梯度对重力波传播的影响

运用射线跟踪方法，计算了背景风场和温度梯度共同影响下大气重力波的传播射线，结果表明，在顺风传播情况下，较小波长的重力波在１００ｋｍ左右的高度上被捕获，较大波长时可穿透传播到热层，但射线在水平方向拉伸；在逆风传播情况下，较长波长的波在１２０ｋｍ之下的高度发生无环反射，较短波长的波在２００ｋｍ以上的高度发生有环反射，而介于两种反射波的波长之间的波则穿透传播到热层高度，射线变陡。分析表明，上述波的反射、     

Full-wave solutions for the depolarization of the scattered radiation fields by rough surfaces of arbitrary slope

Employing a variable coordinate system associated with the local features of two-dimensionally rough surfaces with arbitrary slope, full-wave solutions are derived for the depolarization of the scattered radiation fields. An outline of the analytical procedures used in the derivations of the solutions are presented. Furthermore, the engineer who is not familiar with them can also use the final result which is expressed as a definite integral whose integrand is given explicitly and in closed form. These full-wave solutions are compared with the quasi-optics solution and the iterative or perturbational solutions for slightly rough surfaces, and they are shown to bridge the wide gap that exists between them. The full-wave solutions are consistent with energy conservation, duality, and reciprocity relationships in electromagnetic theory. These solutions account for upward and downward scattering of the incident waves with respect to the horizontal reference plane, thus shadowing and multiple scattering are considered. Applications to two-dimensionally periodic structures and random rough surfaces are also presented. The fullwave solutions are examined for Brewster, grazing, and specular angles and backscatter. Special consideration is also given to good conducting boundaries.     

InGaN nanoinclusions in an AlGaN matrix

GaN-based structures with InGaN quantum dots in the active region emitting in the near-ultraviolet region are studied. In this study, two types of structures, namely, with InGaN quantum dots in a GaN or AlGaN matrix, are compared. Photoluminescence spectra are obtained for both types of structures in a temperature range of 80–300 K and at various pumping densities, and electroluminescence spectra are obtained for light-emitting (LED) structures with various types of active region. It is shown that the structures with quantum dots in the AlGaN matrix are more stable thermally due to the larger localization energy compared with quantum dots in the GaN matrix. Due to this, the LED structures with quantum dots in an AlGaN matrix are more effective.     

Implementation of first-order and second-order microwave differentiators

Simple and accurate formulations are employed to represent discrete-time infinite impulse response processes of both first- and second-order differentiators in the Z-domain. These formulations, in conjunction with the representations of transmission-line elements in the Z-domain, lead to transmission-line configurations that are eligible for wide-band microwave differentiators. Both the first- and second-order differentiators in microstrip circuits are implemented to verify this method. The experimental results are in good agreement with simulation values.     

Measurement of the circuit properties of insulated linear antennas in a dissipative medium

The experimental system for measuring the electrical properties of antennas embedded in a dissipative medium is discussed. Measured input admittances of linear antennas with insulations of different sizes and dielectric constants are compared with the theoretical results. Measured current distributions of insulated antennas with the dielectric constant of the insulation comparable to that of the surrounding medium are compared with theory and are found to be in good agreement. The uncertainties in the measurement are discussed.     

Experimental identification of inertial and friction parameters for electro-hydraulic motion simulators

The fullness of dynamics equations and the degree of uncertainty in dynamic parameters are important factors in application of the identified models to model-based control strategies. Therefore, in this paper, the experimental identification of inertial parameters and friction coefficients are dealt with for an electro-hydraulic motion simulator, normally consisting of the Stewart platform. The model with arbitrary geometry, inertia distribution and frictions are obtained based on a structured Boltzmann-Hamel-d’Alembert formulation, and then the estimation equations are explicitly expressed in terms of a linear form with respect to the base parameters of minimal dimension to be identified. The identified parameters are obtained through solving the estimation equations by simple least square method. Moreover, exciting trajectories are also designed respectively in the actuating space and task space. Finally, the identified parameters are used to validate the developed model by comparing the predicted forces with respect to the actuating forces for a random trajectory.     

Matched swept-frequency digital modulation for binary signaling in inhomogeneous dispersive media

A digital modulation technique which is most suitable for binary signaling through inhomogeneous dispersive media is introduced. Space-time rays are used to synthesize frequency-modulated input pulses that are either compressed in the medium with enhanced output or dispersed in the medium with widely spread output. The synthesized binary signals are shown to be in the form of swept-frequency signals which are matched to the dispersive properties of the medium. For media with quadratic phase functions, or under narrow-band conditions, the matched binary signals are linearly frequency modulated (chirp) with sweep rates that are related to the medium dispersion. The medium response to the matched chirp-modulated signals is investigated in detail. Conditions for the enhancement of the performance of the proposed modulation technique due to the available bandwidth are also discussed.     

远距离复杂背景鲁棒的步态特征提取与表示方法

远距离复杂背景下步态图像通常受到噪声的影响很大。Gabor特征在此类步态识别中显示了良好的特性,然而一些基于Gabor特征的算法使用较多的模板从而导致计算量增大。为解决这个问题,本文提出了一种新的基于改进Gabor特征的步态特征提取与表示方法。首先突出步态能量图中的有效区域,并抑制易受噪声干扰的区域。然后构造一个同时具有两个方向互补特性的基本的滤波器,经过缩放和旋转,生成一系列滤波器。使用这些滤波器对改进的步态能量图以及步态差异图像进行卷积,得到两个特征向量集合以表示此步态对象。使用最近邻分类计算出本文方法在USF步态数据库上的识别率,与相关算法的比较证实了此步态特征提取与表示方法的有效性。对算法的计算量分析表明,本文算法所需的计算量比相关算法有较大降低。      

On-Chip Power Distribution Grids With Multiple Supply Voltages for High-Performance Integrated Circuits

On-chip power distribution grids with multiple supply voltages are discussed in this paper. Two types of interdigitated and paired power distribution grids with multiple supply voltages and multiple grounds are presented. Analytic models are also developed to estimate the loop inductance in four types of proposed power delivery schemes. Two proposed schemes, fully and pseudo-interdigitated power delivery, reduce power supply voltage drops as compared to conventional interdigitated power distribution systems with dual supplies and a single ground by, on average, 15.3% and 0.3%, respectively. The performance of the proposed on-chip power distribution grids is compared to a reference power distribution grid with a single supply and a single ground. The voltage drop in fully interdigitated and fully paired power distribution grids with multiple supplies and multiple grounds is reduced, on average, by 2.7% and 2.3%, respectively, as compared to the voltage drop of an interdigitated power distribution grid with a single supply and a single ground. The proposed power distribution grids are a better alternative to a single supply voltage and a single ground power distribution system. On-chip resonances in power distribution grids with decoupling capacitors are intuitively explained in this paper, and circuit design implications are provided. It is also noted that fully interdigitated and fully paired power distribution grids with multiple supply voltages and multiple grounds are recommended to decouple power supply voltages.     

Intranuclear localization of hepatoma chromatin antigens not detected in liver chromatin

Localization of malignant cell antigens which are not detected in the liver chromatin was investigated by antibodies to chromatin of Zajdela ascite hepatoma and solid hepatoma 27. Antibodies to chromatin of Zajdela ascite hepatoma do not interact with nuclear matrix of both hepatoma and liver cells. Zajdela ascite hepatoma and solid hepatoma 27 chromatin regions hypersensitive to DNase I and endogenous Mg2+-dependent nuclease are enriched with immunogenic proteins. Antibodies to hepatoma chromatins pretreated with liver chromatin show that hepatoma chromatin antigens which are not detected in liver chromatin are localized in chromatin regions hypersensitive to nucleases but are absent (or scanty) in actively transcribed regions.     

利用星载激光雷达研究中国海及其周边海域的云层分布

利用2007~2010年4年间的CALIPSO 5 km二级云数据对中国海及其周边海域层数不同的云的出现概率（COF）随年度、月份和区域的变化进行了统计分析,并将2007年、2008年的部分统计结果与MODIS数据的统计结果相比较。结果表明：在研究区域,不同年份的层数相同的云的出现概率差别小于3%,且不同年份的出现概率区域分布相近,在靠近赤道的海域高于80%,在20°N附近海域低于50%,这与MODIS数据的统计结果相一致;同一年不同月份的出现概率差异明显,但是4年都是在6、7月出现最大值,层数相同的云的出现概率随纬度变化而明显变化。     

Nonlinear bilateral teleoperators with non-collocated remote controller over delayed network

Remote robots in bilateral teleoperation systems are utilized to accomplish various missions in different locations, which are generally far away from local robots collocated with a human operator. In order to enhance flexibility of teleoperators with extensive applicability, this paper proposed a novel control framework, where the remote controller is non-collocated with the robot in the environment. In contrast to traditional teleoperation systems, the remote robot only needs to send out sensory information and receive control commands from the local side. Stability and transparency of the proposed teleoperators are studied for PD-like controller with fixed time delays, and P-like controller with time-varying delays. If the control gains are contingent to upper bounds of time delays, then the system is stable with guaranteed position tracking and force reflection. Numerical simulations and experiments were conducted to demonstrate the effectiveness of the proposed control algorithms in bilateral teleoperation.     

海量超声数据体可视化研究

近年来,随着科学数据的快速增长,海量数据的可视化分析成了急需解决的难题.越来越多的处理海量数据的方法向着并行、分布式处理的方向发展.本文提出了一种混合的框架来处理海量的超声数据,该框架通过整合多种硬件环境和计算资源来处理海量数据;所有的数据都存放在一个基于高速网络环境的数据共享中心,具有高性能显卡的前端工作站将耗时的处理任务分配到网络中的计算结点,而自身处理显示和交互的操作;同时基于OpenCL和OpenMP实现了可视化算法在GPU和CPU上的并行计算;核外算法应用在本框架中来处理海量的体数据.实验结果表明,本文提出的框架不仅可以处理海量数据,而且具有较高的交互性能.     

Epidemic Simulation for Training in Public Health Management

Epidemiological simulation models to be used primarily to augment the teaching of epidemiology to medical students and other individuals concerned with public health and control of epidemics are presented. Interactive simulations are used to expose students to ``realistic' epidemic situations and permit them to experiment with various control strategies. Criteria by which simulations for such teaching purposes may be evaluated are proposed and operating simulations, MEASLES and INFLU, are described in detail. Information is provided regarding user experience with the above simulations.     

Approximate reconstruction of randomly sampled signals

We study the use of polynomial interpolation to approximate a function specified by samples taken at random moments satisfying a Poisson distribution with uniform mean sampling rate. Two different selection schemes are considered to determine which samples should be used in the construction of the polynomials, and detailed error estimates are derived for each case. The results are compared with the classical interpolation methods of convolution with a smoothing window. It is concluded that only low order polynomials are useful for interpolation in the presence of noise, but that they are comparable or superior to nonadaptive convolution in most cases, as well as computationally more efficient. Some simulation experiments are presented to support the theoretical estimates.     

Costs and cost scaling in time-domain integral-equation analysis ofelectromagnetic scattering

Computation of scattering from multi-wavelength bodies is expensive, and costs scale with up to the sixth power of the incident frequency. Conventional integral-equation time-domain methods have costs scaling with the fifth power. Here are described modifications to the IETD approach that offer the prospect of a reduction in cost scaling, to possibly the third power of frequency, and an associated large reduction in cost. The approach exploits the pulsed nature of the illumination, which results in surface fields that are small most of the time over most of the body, on bodies that are electrically large. Neglect of these produces some modest increase in error, but allows large reductions in cost and storage requirements. In the examples shown, cost reductions by amounts approaching two orders of magnitude are obtained, with the factor by which costs are reduced itself increasing with roughly the square of the body size; storage requirements are rendered essentially negligible     

A study of microstrip array antennas with the feed network

The radiation and losses in microstrip antennas with a corporate feed network are studied. A surface current approach is applied in which the electrical currents in the feed lines are modeled as in ideal transmission lines. The free-space radiation and the surface-wave excitation of typical segments in printed feed networks are studied. A four-element array antenna with its printed feed network is analyzed and predicted radiation patterns, directivity, and gain are presented and compared with experimental results. The gain and directivity of large arrays of 16, 64, 256 and 1024 elements are calculated and measurements in the frequency range of 10 to 35 GHz are reported