Trellis-Based Equalization for Sparse ISI Channels Revisited

Sparse intersymbol-interference (ISI) channels are encountered in a variety of high-data-rate communication systems. Such channels have a large channel memory length, but only a small number of significant channel coefficients. In this paper, trellis-based equalization of sparse ISI channels is revisited. Due to the large channel memory length, the complexity of maximum-likelihood detection, e.g., by means of the Viterbi algorithm (VA), is normally prohibitive. In the first part of the paper, a unified framework based on factor graphs is presented for complexity reduction without loss of optimality. In this new context, two known reduced-complexity algorithms for sparse ISI channels are recapitulated: The multi-trellis VA (M-VA) and the parallel-trellis VA (P-VA). It is shown that the M-VA, although claimed, does not lead to a reduced computational complexity. The P-VA, on the other hand, leads to a significant complexity reduction, but can only be applied for a certain class of sparse channels. In the second part of the paper, a unified approach is investigated to tackle general sparse channels: It is shown that the use of a linear filter at the receiver renders the application of standard reduced-state trellis-based equalizer algorithms feasible, without significant loss of optimality. Numerical results verify the efficiency of the proposed receiver structure.Comment: To be presented at the 2005 IEEE Int. Symp. Inform. Theory (ISIT 2005), September 4-9, 2005, Adelaide, Australi

Design of low loss tem coaxial cavity bandpass filter

This paper presents a design of coaxial cavity bandpass filter that utilizing the method of tapped-input coupling. The design procedures have assumed lossless lowpass prototypes, thus yielding lossless bandpass filters. A systematic filter development using lowpass prototype as a starting point to produce four-pole Chebyshev bandpass response is demonstrated. The coaxial cavity filter has the center frequency of 2.5 GHz and bandwidth of 160 MHz. The insertion loss of 0.1 dB insertion loss and return loss better than 20 dB is achieved especially in the passband. This class of filter would be useful in microwave systems where the low insertion loss and high selectivity are crucial, such as in a base station, radar and satellite transceivers

Illumination and Expression Invariant Face Recognition: Toward Sample Quality-based Adaptive Fusion

The performance of face recognition schemes is adversely affected as a result of significant to moderate variation in illumination, pose, and facial expressions. Most existing approaches to face recognition tend to deal with one of these problems by controlling the other conditions. Beside strong efficiency requirements, face recognition systems on constrained mobile devices and PDA's are expected to be robust against all variations in recording conditions that arise naturally as a result of the way such devices are used. Wavelet-based face recognition schemes have been shown to meet well the efficiency requirements. Wavelet transforms decompose face images into different frequency subbands at different scales, each giving rise to different representation of the face, and thereby providing the ingredients for a multi-stream approach to face recognition which stand a real chance of achieving acceptable level of robustness. This paper is concerned with the best fusion strategy for a multi-stream face recognition scheme. By investigating the robustness of different wavelet subbands against variation in lighting conditions and expressions, we shall demonstrate the shortcomings of current non-adaptive fusion strategies and argue for the need to develop an image quality based, intelligent, dynamic fusion strategy

Image quality-based adaptive illumination normalisation for face recognition

Automatic face recognition is a challenging task due to intra-class variations. Changes in lighting conditions during enrolment and identification stages contribute significantly to these intra-class variations. A common approach to address the effects such of varying conditions is to pre-process the biometric samples in order normalise intra-class variations. Histogram equalisation is a widely used illumination normalisation technique in face recognition. However, a recent study has shown that applying histogram equalisation on well-lit face images could lead to a decrease in recognition accuracy. This paper presents a dynamic approach to illumination normalisation, based on face image quality. The quality of a given face image is measured in terms of its luminance distortion by comparing this image against a known reference face image. Histogram equalisation is applied to a probe image if its luminance distortion is higher than a predefined threshold. We tested the proposed adaptive illumination normalisation method on the widely used Extended Yale Face Database B. Identification results demonstrate that our adaptive normalisation produces better identification accuracy compared to the conventional approach where every image is normalised, irrespective of the lighting condition they were acquired

Image-Quality-Based Adaptive Face Recognition

The accuracy of automated face recognition systems is greatly affected by intraclass variations between enrollment and identification stages. In particular, changes in lighting conditions is a major contributor to these variations. Common approaches to address the effects of varying lighting conditions include preprocessing face images to normalize intraclass variations and the use of illumination invariant face descriptors. Histogram equalization is a widely used technique in face recognition to normalize variations in illumination. However, normalizing well-lit face images could lead to a decrease in recognition accuracy. The multiresolution property of wavelet transforms is used in face recognition to extract facial feature descriptors at different scales and frequencies. The high-frequency wavelet subbands have shown to provide illumination-invariant face descriptors. However, the approximation wavelet subbands have shown to be a better feature representation for well-lit face images. Fusion of match scores from low- and high-frequency-based face representations have shown to improve recognition accuracy under varying lighting conditions. However, the selection of fusion parameters for different lighting conditions remains unsolved. Motivated by these observations, this paper presents adaptive approaches to face recognition to overcome the adverse effects of varying lighting conditions. Image quality, which is measured in terms of luminance distortion in comparison to a known reference image, will be used as the base for adapting the application of global and region illumination normalization procedures. Image quality is also used to adaptively select fusion parameters for wavelet-based multistream face recognition

Natural solution to antibiotic resistance: bacteriophages ‘The Living Drugs’

Antibiotics have been a panacea in animal husbandry as well as in human therapy for decades. The huge amount of antibiotics used to induce the growth and protect the health of farm animals has lead to the evolution of bacteria that are resistant to the drug’s effects. Today, many researchers are working with bacteriophages (phages) as an alternative to antibiotics in the control of pathogens for human therapy as well as prevention, biocontrol, and therapy in animal agriculture. Phage therapy and biocontrol have yet to fulfill their promise or potential, largely due to several key obstacles to their performance. Several suggestions are shared in order to point a direction for overcoming common obstacles in applied phage technology. The key to successful use of phages in modern scientific, farm, food processing and clinical applications is to understand the common obstacles as well as best practices and to develop answers that work in harmony with nature

Electronic commerce adoption:a study of business-to-business practice in Saudi Arabia

Electronic commerce (e-commerce) has become an increasingly important initiative among organisations. The factors affecting adoption decisions have been well-documented, but there is a paucity of empirical studies that examine the adoption of e-commerce in developing economies in the Arab world. The aim of this study is to provide insights into the salient e-commerce adoption issues by focusing on Saudi Arabian businesses. Based on the Technology-Organisational-Environmental framework, an integrated research model was developed that explains the relative influence of 19 known determinants. A measurement scale was developed from prior empirical studies and revised based on feedback from the pilot study. Non-interactive adoption, interactive adoption and stabilisation of e-commerce adoption were empirically investigated using survey data collected from Saudi manufacturing and service companies. Multiple discriminant function analysis (MDFA) was used to analyse the data and research hypotheses. The analysis demonstrates that (1) regarding the non-interactive adoption of e-commerce, IT readiness, management team support, learning orientation, strategic orientation, pressure from business partner, regulatory and legal environment, technology consultants‘ participation and economic downturn are the most important factors, (2) when e-commerce interactive adoption is investigated, IT readiness, management team support, regulatory environment and technology consultants‘ participation emerge as the strongest drivers, (3) pressure from customers may not have much effect on the non-interactive adoption of e-commerce by companies, but does significantly influence the stabilisation of e-commerce use by firms, and (4) Saudi Arabia has a strong ICT infrastructure for supporting e-commerce practices. Taken together, these findings on the multi-dimensionality of e-commerce adoption show that non-interactive adoption, interactive adoption and stabilisation of e-commerce are not only different measures of e-commerce adoption, but also have different determinants. Findings from this study may be valuable for both policy and practice as it can offer a substantial understanding of the factors that enhance the widespread use of B2B e-commerce. Also, the integrated model provides a more comprehensive explanation of e-commerce adoption in organisations and could serve as a foundation for future research on information systems

Numerical Analysis of Contact Area under Slippage Conditions

في هذا البحث، تم دراسة منطقة التماس التي تتولد بين جسمين (أحدهما سطح مستو والاخر سطح نصف أسطواني) تحت تأثير الانزلاق، حيث أنها تمثل واحدة من المشاكل الهامة في الهندسة الميكانيكية وخاصة في تصميم الروبوتات. تم دراسة العديد من المعاملات مثل قوى الاحتكاك، الاجهادات المكافئة، معامل الاحتكاك، وتشوه منطقة التماس. حيث تم رصد سلوك هذه العوامل خلال الانزلاق الذي يتم إنشاؤه بين سطح مستو مصنوع من سبائك الحديد الصلب والجزء الآخر المصنوع من المطاط. أظهرت نتائج المحاكاة سلوكا هاماً، وخاصة في بداية الانزلاق وظاهرة (الالتصاق-الانزلاق) بمعنى آخر، مخرجات المحاكاة تشير إلى أن تأثير الانزلاق له سلوك هام، خاصة عندما تبدأ كل من ظاهرة الانزلاق والالتصاق بالحدوث. وتهدف هذه التحليلات إلى فهم كيفية تأثر منطقة التماس لتصميم ما يمنع حدوث الانزلاق والضرر في الاجزاء الهندسية المتماسة. In the present paper, the contact of area, which is produced between a pair of bodies (flat surface and hemi-cylindrical shape), has been studied under the effect of slippage occurrence, where it represents one of the important problems in the mechanical engineering, especially in robotic design. Many parameters have been studied, like frictional forces, equivalent stresses, friction coefficient, and contact area of deformation. The behavior of these parameters has been monitored during the slippage that is generated between the flat surface made from cast alloy steel and the other part made from rubber. The finite element method (FEM) with SOLIDWORKS software was used to simulate this contact area under the slippage effect. The results of the simulation showed a significant behavior, particularly at the beginning of slippage and the stage of (stick-slip) phenomena, in other words, the simulation outputs indicated that the slippage influence has an important behavior, especially when the phenomena of both slippage and stick-slip stage start to occur. These analyses are intended to understand how the contact area affected to design measures to prevent the slippage occurrence and the damage in contacted bodies