Invariance property of Gaussian signals: A new interpretation, extension and applications

This paper addresses the invariance property of Gaussian signals, originally derived by Bussgang, which characterizes the input/output moment relation of a hybrid nonlinear moment (HNM) estimator based on a zero-memory nonlinearity (ZMN) g(y). Some re-derivations of this property are reviewed, and an original, direct, and simple proof is presented (Appendix 1). The paper then derives a new interpretation of this property (Theorem 1) that shows a moment-sense equivalence between g(y) and a linear mappingh ₁(y) whose coefficients a₀ and a₁ are completely characterized in terms ofg(y) and are shown to be optimal in a mean square error (MSE) sense. A direct and very interesting byproduct of this interpretation is a simple linear relationship between the input and output of the HNM estimator involved. The property is then generalized (Theorem 2) to signals other than Gaussian, resulting in an infinite cumulant series expansion of the HNM estimator output, whose coefficients are all characterized in terms ofg(y). Applications of Theorem 1 to some ZMNs commonly used in signal processing and control theory are presented that clearly illustrate the power and elegance of the invariance property. Finally, some conclusions are given.Author acknowledges financial support by KFUPM.     

Optimal filter-based detection of microcalcifications

This paper deals with the problem of texture feature extraction in digital mammograms. We use the extracted features to discriminate between texture representing clusters of microcalcifications and texture representing normal tissue. Having a two-class problem, we suggest a texture feature extraction method based on a single filter optimized with respect to the Fisher criterion. The advantage of this criterion is that it uses both the feature mean and the feature variance to achieve good feature separation. Image compression is desirable to facilitate electronic transmission and storage of digitized mammograms. In this paper, we also explore the effects of data compression on the performance of our proposed detection scheme. The mammograms in our test set were compressed at different ratios using the Joint Photographic Experts Group compression method. Results from an experimental study indicate that our scheme is very well suited for detecting clustered microcalcifications in both uncompressed and compressed mammograms. For the uncompressed mammograms, at a rate of 1.5 false positive clusters/image our method reaches a true positive rate of about 95%, which is comparable to the best results achieved so far. The detection performance for images compressed by a factor of about four is very similar to the performance for uncompressed images.     

基于矩和Gabor变换的手写体汉字识别方法

特征提取是手写体汉字识别的一个研究难点。本文提出了一种基于特征融合的新提取方法,即将Gabor变换和正交矩变换结合起来,用正交Zernike矩提取全局特征,用Gabor变换提取局部特征,然后使用主成分分析的方法进行特征压缩。由此得到的特征向量能从整体上和局部上反映汉字的特征。实验证明该方法是行之有效的。     

基于Gabor变换的中文字符特征提取方法研究

针对传统汉字字符特征提取方法的不足,提出了一种基于Gabor变换,对图像纹理特征的方向性敏感的字符特征提取方法。先将灰度字体图像进行二值化、归一化处理,再利用Gabor滤波器进行滤波,获取图像的内部纹理特征和边缘信息,进而从不同方向进行特征提取。实验证明利用gabor变换计算中文字符图像的笔画方向特征,对中文字符具有较好的分类效果。     

Guided properties and applications of photonic bandgap fibers

The authors have reviewed some of their recent studies on photonic bandgap fibers (PBGFs). PBGFs that confine light in the core by the photonic bandgap effect of cladding have potential applications in various photonic devices. In this paper, the guided properties and tuned mechanics of anti-resonant PBGFs are theoretically illustrated. The special coupling properties in multi-core PBGFs, such as decoupling and resonant coupling effect,are then introduced. Finally, fiber Bragg grating inscribed in all-solid PBGFs is theoretically and experimentally studied, and special resonant characteristics are also observed.     

A bandpass filter-based approach to crop row location and tracking

A method of locating crop rows in image sequences is described. Unlike several previously reported algorithms, the method does not rely upon the segmentation of plant material from the background on the basis of absolute brightness or colour. Rather, the periodic amplitude variation due to parallel crop rows is exploited. Given the geometry of the camera arrangement and the crop row spacing, a filter is derived which allows the crop rows to be extracted whilst attenuating the effects of partial shadowing and spurious features such as weeds. The position and orientation of the rows are tracked using an extended Kalman filter.The method has been used to guide a mechanical hoe in winter wheat with an RMS positional error of 15.6 mm at a speed of 1.6 ms⁻¹, despite the presence of complex shadows cast by the tractor in the imaged area.     

The modeling, analysis, and design of filter-based parametricfrequency dividers

A technique for the design of filter-based parametric frequency dividers is discussed. The technique combines basic divider analysis with modern nonlinear simulation techniques. In essence, the procedure allows the completion of a successful design that is based on computer simulations, but requires little or no nonlinear optimization. Specifically, divider modeling, threshold, and efficiency are investigated, and a straightforward design strategy is given     

Mechanical properties and applications of custom-built gold AFM cantilevers

Silicon and silicon nitride metal-coated cantilevers have been in use for a long time in several scanning probe microscopy applications that require electrically conductive probes. However, conventional metalized cantilevers present several drawbacks such as limited life-time of the metal layer due to wear, and increased tip radius. This work focuses on monolithic metallic cantilevers developed in order to overcome the limitations of conventional metalized atomic force microscopy (AFM) probes. These custom-made cantilevers are designed for several applications such as in current-sensing AFM (CSAFM), Kelvin probe force microscopy (KPFM), and tip-enhanced Raman spectroscopy (TERS). Determination of the dynamic and static mechanical properties of these cantilevers in a non-destructive way is reported here. Key parameters under investigation are the cantilever spring constant and the frequency response using finite element method (FEM). Gold cantilevers are selected for this study, which allow optimizing the design and the process of developing these metallic cantilevers with parameters engineered for the applications mentioned above. This work contributes to the establishment and applicability of custom-made probes in advanced scanning probe microscopy methods and their performance understanding using computer simulations.     

Electrical and acoustic properties of biological materials and biomedical applications

A survey of our research on the linear electrical and acoustic properties of biological materials including cells, tissues, and biopolymers is presented. Topics include: 1) dielectric properties of tissues and cells from dc to 20 GHz; 2) identification of the mechanism responsible for major dielectric relaxation effects observed (counter ion relaxation, Maxwell?Wagner charging of membrane interfaces, relaxation of protein bound water, and relaxation of tissue water); 3) ultrasonic properties of biopolymers and tissues (identification of macromolecular absorption as the dominant contributor to acoustic absorption); and 4) interaction of EM fields with biosystems. This, in turn, includes applications in physical medicine, investigations of field-induced force effects on cells and their response, macroscopic and microscopic dosimetry, development of safety standards, and applications of available biophysical insight to evaluate field interaction with cells, membranes, and macromolecules.     

The optoelectronic properties and applications of solution-processable titanium oxide nanoparticles

In this study, the surface modified TiO₂ nanoparticles have been prepared through microwave-assisted reaction with oleic acid as surfactant. The as-synthesized TiO₂ nanoparticles reveal uniform particle size distribution and high dispersibility in organic solvents which can be easily integrated into solution-process. The organic capped TiO₂ (OC-TiO₂) has been applied as filler for LED encapsulant and electron collection layer for organic solar cells. With 1.0 wt% loading of TiO₂ nanoparticles, the refractive index (RI) of TiO₂/silicone composites increase from 1.51 for neat silicone to 1.575. As a result, a high-power LED encapsulated with this composite showed more than 9% increase in the light output. Moreover, the organic solar cell with the OC-TiO₂ as electron collection layer shows an enhanced long-term durability due to the hydrophobic property of OC-TiO₂.     

Waveguiding properties and applications of silica nanowires in various environments

Waveguiding properties of silica nanowires in various environments are studied by solving the eigenvalue equations of a circular cross-section waveguide numericany in cylindrical coordinates. The single-mode condition, propagation constants, poynting vector and power distribution inside and outside silica nanowire are calculated. The results show that silica nanowires in water, compared with silica nanowires in air, have higher fraction of the evanescent fields. Due to the sensitivity to surrounding environment, silica nanowires arc very suitable for sensing elements, which can be used to implemept a single-mode fiber optic evanescent wave sensing element of highly sensitive and accurate measurement.     

Hydrogenated amorphous-silicon/crystalline-silicon heterojunctions:properties and applications

Fundamental properties of amorphous-silicon/crystalline-silicon heterojunctions are studied through their capacitance-voltage and current-voltage characteristics. In light of the heterojunction properties, the applicability to devices such as vidicon targets, gamma-ray detectors, solar cells, and heterojunction bipolar transistors is discussed     

仿射不变的中心投影

 考虑将区域和轮廓类不变特征提取算法结合:利用中心投影将目标转化为闭曲线,对闭曲线运用轮廓类方法提取不变特征.证明了图像经中心投影所得闭曲线保持仿射变换的结论.介绍了一种利用小波变换进行仿射不变特征提取的算法.对一些汉字、26个大写英文字母等的实验结果表明结论的有效性,与传统方法相比该算法对噪声具有较强的鲁棒性.     

pn Junction applications and transport properties in polysilicon rods

B-Doped polysilicon rods have been studied through their crystalline structure and electronic transport properties. P Diffusion data and the properties of the p-n junctions obtained are also discussed. Avalanche current distribution and reverse bias electric field spikes have been carefully studied.It is concluded that this material is quite suitable for low-cost solar cell applications, and, from preliminary experiments, could be of interest for power transient suppressors.     

Microwave properties and applications of negative conductance transferred electron devices

The transferred electron effect in epitaxial GaAs has been used to realize a semiconductor device which exhibits a stable negative conductance over a wide range of microwave frequencies and power levels. These devices have been used in conjunction with circulator coupled networks to design high-level wide-band transferred electron amplifiers which have a voltage gain bandwidth product in excess of 10 GHz for frequencies from 4.0 to about 16.0 GHz. Linear gains of 6-12 dB per stage and saturated output power levels in excess of ½ W have been realized. The physical and electrical properties of these devices are described with regard to the achievement of a stable negative conductance. The influence of several parameters (i.e., device temperature, bias voltage, circuit loading, etc.) is discussed with regard to device and circuit stability. Measurements of the terminal admittance of several typical devices as a function of the bias, input power, and frequency have been used to study their microwave properties. The large signal data are used to compute the relationship between the available device power and the magnitude of the negative conductance independent of the test circuit. This same measurement technique can provide a simulation of the performance of any nonlinear negative conductance, without the need for circuit design and load tuning. In addition, an analytical large signal model of the negative conductance has been used to predict the large signal performance of the active device (i.e., gain compression, conversion efficiency, etc.) in both oscillator and amplifier circuits.     

Semiconductor nanowhiskers: Synthesis,properties, and applications

Recent results of studying the semiconductor’s whisker nanocrystals are reviewed. Physical grounds of growing whisker nanocrystals using the mechanism vapor-liquid-crystal are given and the main epitaxial technologies of synthesis of whisker nanocrystals are described. Thermodynamic and kinetic factors controlling the morphological properties, composition, and crystal structure of whisker nanocrystals are considered in detail. The main theoretical models of the growth and structure of whisker nanocrystals are described. The data on physical properties of whisker nanocrystals and possibilities of their use in nanophotonics, nanoelectronics, and nanobiotechnology are presented.     

Extremal properties of three-dimensional sensor networks with applications

We analyze various critical transmitting/sensing ranges for connectivity and coverage in three-dimensional sensor networks. As in other large-scale complex systems, many global parameters of sensor networks undergo phase transitions. For a given property of the network, there is a critical threshold, corresponding to the minimum amount of the communication effort or power expenditure by individual nodes, above (respectively, below) which the property exists with high (respectively, a low) probability. For sensor networks, properties of interest include simple and multiple degrees of connectivity/coverage. First, we investigate the network topology according to the region of deployment, the number of deployed sensors, and their transmitting/sensing ranges. More specifically, we consider the following problems: assume that n nodes, each capable of sensing events within a radius of r, are randomly and uniformly distributed in a 3-dimensional region R of volume V, how large must the sensing range R/sub SENSE/ be to ensure a given degree of coverage of the region to monitor? For a given transmission range R/sub TRANS/, what is the minimum (respectively, maximum) degree of the network? What is then the typical hop diameter of the underlying network? Next, we show how these results affect algorithmic aspects of the network by designing specific distributed protocols for sensor networks.