Cellular reuse patterns quality and efficiency comparison

Capacity enhancement and interference performance are among the most important issues in the 2nd and 3rd generation cellular networks planning. The main objective of the planning process is to reach a tradeoff between the quality and the capacity of the network. In this paper, we study and compare the CIR and spectral efficiency of different cellular reuse patterns. We also establish the exact analytical PDF expression of CIR assuming one interferer in the serving cell, we then generalize this expression to many interferer tiers. Shadowing effect is also carefully considered in the CIR distribution extension. Moreover, numerical computations are performed to estimate spectral efficiency values for the different patterns studied. Some simulations are also developed to give the comparison a concrete and a practical aspect. A reuse partitioning (RP) capacity scheme is used to serve as the basis of the study. In particular, RP sub‐cells' sizes and number of partitions are optimized in order to maximize the traffic capacity parameterized by spectral and trunking efficiency while involving the financial cost. The efficiency/cost comparison is among the main novel issues contributed by the paper. Copyright © 2006 John Wiley & Sons, Ltd.     

Long-term bond performance of GFRP bars in concrete under temperature ranging from 20 °C to 80 °C

Eighty pull-out specimens were used to study the effect of temperature ranging from 20 °C to 80 °C in dry environment on bond properties between Glass Fiber Reinforced Polymer (GFRP) bars and concrete. The pullout-test specimens were subjected during 4 and 8 months to high temperatures up to 80 °C and then compared to untreated specimens (20 °C). Experimental results showed no significant reduction on bond strength for temperatures up to 60 °C. However, a maximum of 14% reduction of the bond strength was observed for 80 °C temperature after 8 months of thermal loading. For treated specimens, the coefficient β in the CMR model, which predicts the bond–stress–displacement behavior, seems to be dependant with the temperature.     

Synthesis and characterization of new pyrochlore solid solution Bi1.5Sb1.5Cu1−xMnxO7

A new pyrochlore solid solution with formula Bi_1.5Sb_1.5Cu_1−xMn_xO₇ has been synthesized using ceramic method at 1000 °C. The cell parameter decreases linearly with increasing manganese concentration. Rietveld refinements for (B_1.5Mn_0.5)(Sb_1.5Mn_0.5)O₇ compound using X-ray powder diffraction data confirmed an overall A₂B₂O₇ cubic pyrochlore structure with a = 10.42749 (4) Å and Fd-3m symmetry. The reliability factors are R_wp = 3.48%; R_p = 2.37%; R_exp = 1.65% and R_Bragg = 1.58%. The magnetic susceptibility measurements achieved between 4 and 300 K indicate a paramagnetic behaviour with an oxidation state “2+” of the manganese ion. The electric resistance measured using complex impedance spectroscopy method put in evidence a decrease of the electric resistance with the temperature, which reached 5 × 10² Ω at 675 K. Dielectric properties depend on the variation of frequency and temperature, results indicate a conductive compound.     

Measurements of microclimatic factors inside the oasis: interception and sharing of solar radiation

The oasis climate must be given prime consideration when new cultivated land is laid out and also when attempting to increase the yield of palm groves. Measurements of the microclimatic factors at different heights in the traditional oasis (multi-storey exploitation) have been made for a period of 1 month (October 1995). We have been able to bring out the share of intercepted global radiation between the three production levels inside the oasis, so we can have an approximation of the photosynthetic efficiency. The vertical net radiation profiles give us an approximation of the evapotranspiration for the total oasis and for every storey. We have also accentuated the role of a windbreak played by the oasis and we have studied the incidence of a canopy with three storey exploitation on relative humidity and air temperature profiles.     

Characterization of nonspecific crossover in split-flow thin channel fractionation

Split-flow thin channel (SPLITT) fractionation is a technique for continuous separation of particles or macromolecules in a fluid stream into fractions according to the lateral migration induced by application of a field perpendicular to the direction of flow. Typical applications have involved isolation of different fractions from a polydisperse sample. Some specialized applications involve the separation of the fraction influenced by the transverse field from the fraction that is not. For example, immunomagnetically labeled biological cells may be separated from nonlabeled cells with the application of a transverse magnetic field gradient. In such cases, it may be critically important to minimize contamination of the labeled cells with nonlabeled cells while at the same time maximizing the throughput. Such contamination is known as nonspecific crossover (NSC) and refers to the real or apparent migration of nonmobile particles or cells across stream lines with the mobile material. The possible mechanisms for NSC are discussed, and experimental results interpreted in terms of shear-induced diffusion (SID) caused by viscous interactions between particles in a sheared flow. It is concluded that SID may contribute to NSC, but that further experiments and mathematical modeling are necessary to more fully explore the phenomenon.     

Formation of machine groups and part families in cellular manufacturing systems using a correlation analysis approach

The important step in the design of a cellular manufacturing (CM) system is to identify the part families and machine groups and consequently to form manufacturing cells. The scope of this article is to formulate a multivariate approach based on a correlation analysis for solving cell formation problem. The proposed approach is carried out in three phases. In the first phase, the correlation matrix is used as similarity coefficient matrix. In the second phase, principal component analysis (PCA) is applied to find the eigenvalues and eigenvectors on the correlation similarity matrix. A scatter plot analysis as a cluster analysis is applied to make simultaneously machine groups and part families while maximizing correlation between elements. In the third stage, an algorithm is improved to assign exceptional machines and exceptional parts using respectively angle measure and Euclidian distance. The proposed approach is also applied to the general group technology (GT) problem in which exceptional machines and part are considered. Furthermore, the proposed approach has the flexibility to consider the number of cells as a dependent or independent variable. Two numerical examples for the design of cell structures are provided in order to illustrate the three phases of proposed approach. The results of a comparative study based on multiple performance criteria show that the present approach is very effective, efficient and practical.     

Robust Delay-Derivative-Dependent Sliding Mode Observer for Fault Reconstruction : A Diesel Engine System Application

In this paper, a new delay-derivative-dependent sliding mode observer (SMO) design for a class of linear uncertain time-varying delay systems is presented. Based on this observer, a robust actuator fault reconstruction method is developed. In the meantime, the considered uncertainty is bounded and the time-delay is varying and affects the state system. Besides, the dynamic properties of the observer are analyzed and the reachability condition is satisfied. Applying the developed SMO, the \(H_\infty \) concept and a delay-derivative-dependent bounded real lemma (BRL), a robust actuator fault reconstruction is obtained wherein the effect of the uncertainty is minimized. Also, both the SMO and the BRL are delay-derivative-dependent which reduces the time-varying delay conservatism on the state estimation and on the fault reconstruction. A diesel engine system is included to illustrate the validity and the applicability of the proposed approaches.     

Fast coding unit partitioning method based on edge detection for HEVC intra-coding

High efficiency video coding (HEVC) standard is the latest video coding standard generation. It employs powerful coding tools to obtain improved compression efficiency. To better exploit the redundancies, HEVC adopts a very flexible quad-tree coding structure, allowing the encoder to use a block partition that matches the image features. This exhaustive technique may achieve a higher coding efficiency; however, it induces a significant computational complexity in the encoding engine. This paper proposes a new texture parameter for classifying digital videos as a first contribution and then introduces an efficient coding unit (CU) partitioning algorithm based on the early defined texture parameter in order to speed up the encoding process. In fact, the proposed technique is based on edge detection by performing SOBEL filtering in order to decide the appropriate CU size. Compared to the original HEVC, the average execution time-saving is about 31 % while maintaining almost the same output video quality.     

Streaming an image through the eye: The retina seen as a dithered scalable image coder

We propose the design of an original scalable image coder/decoder that is inspired from the mammalians retina. Our coder accounts for the time-dependent and also non-deterministic behavior of the actual retina. The present work brings two main contributions: As a first step, (i) we design a deterministic image coder mimicking most of the retinal processing stages and then (ii) we introduce a retinal noise in the coding process, that we model here as a dither signal, to gain interesting perceptual features. Regarding our first contribution, our main source of inspiration will be the biologically plausible model of the retina called Virtual Retina. The coder that we propose has two stages. The first stage is an image transform which is performed by the outer layers of the retina. Here we model it by filtering the image with a bank of difference of Gaussians with time-delays. The second stage is a time-dependent analog-to-digital conversion which is performed by the inner layers of the retina. The main novelty of this coder is to show that the time-dependent behavior of the retina cells could ensure, in an implicit way, scalability and bit allocation. Regarding our second contribution, we reconsider the inner layers of the retina. We emit a possible interpretation for the non-determinism observed by neurophysiologists in their output. For this sake, we model the retinal noise that occurs in these layers by a dither signal. The dithering process that we propose adds several interesting features to our image coder. The dither noise whitens the reconstruction error and decorrelates it from the input stimuli. Furthermore, integrating the dither noise in our coder allows a faster recognition of the fine details of the image during the decoding process. Our present paper goal is twofold. First, we aim at mimicking as closely as possible the retina for the design of a novel image coder while keeping encouraging performances. Second, we bring a new insight concerning the non-deterministic behavior of the retina.