Lookup tables-based detection of range spread targets in compound Gaussian environment with multiple-pulse non-coherent integration

The paper deals with detection of range spread targets embedded in K-distributed clutter with unknown parameters. A two-step detection algorithm based on multiple-pulse cell-averaging scheme and using lookup tables is proposed. First, the threshold factors that maintain a constant probability of false alarm for various clutter parameters are offline computed and stored. Then, at the detection stage, the most appropriate threshold factor is selected through the estimation of actual environment parameters. We assume that the target energy is spread over a finite number of cells, according to the multiple dominant scattering (MDS) centers model. Next, an expression for the overall reflected target energy, following the multiple-pulse integration, is derived. Finally, we proposed a specific binary hypothesis test by taking into account the number of primary cells, the target energy profile and the number of pulses. The performances analysis of the proposed detector is carried out using Monte Carlo simulations for different clutter parameters and various MDS models. The obtained results are then compared to those of the order statistics-based generalized likelihood ratio test (OS-GLRT). Simulations indicate that the performances of the proposed detector are closely related to the radar resolution, the target energy profile and the number of integrated pulses.     

Reducing saturation and congestion in VANET networks: Alliance‐based approach and comparisons

A vehicular ad hoc network (VANET) is composed mainly of fixed roadside entities (RSUs) and mobile entities (vehicles). In order to exchange information and data relating to the safety and comfort of road users, these different entities must establish communications between them. In these communications, one of the main problems is related to congestion and saturation of RSUs. In this paper, we first study the main protocols that involve RSUs in their strategy of routing by classifying them according to four levels. Furthermore, to deal with the problem of saturation of RSUs, we present a new approach of cooperation between the RSUs of a VANET in order to reduce its congestion and avoid as much as possible the saturation of these entities. This approach, called “D2A2RS” (defensive alliance–based approach for reducing RSUs saturation), is based on the concept of defensive alliances in graphs that ensures effective collaboration between RSUs. To evaluate the performance of the proposed approach, we conduct a comparative analysis by using both analytical models and simulations. The obtained comparison results have shown the efficiency and the performance of our approach compared with other concurrent approaches in the literature in terms of packet loss/success rate, end‐to‐end transmission delay, and network scalability.     

Reactive and adaptive monitoring to secure aggregation in wireless sensor networks

Data aggregation is considered as one of the fundamental distributed data processing procedures for saving the energy and minimizing the medium access layer contention in wireless sensor networks. However, sensor networks are likely to be deployed in an untrusted environment, which make them vulnerable against several attacks. A compromised node may forge arbitrary aggregation value and mislead the base station into trusting a false reading. Secure in-network aggregation can detect such manipulation. But, as long as such subversive activity is, reliable aggregation result can not be obtained. In contrast, the collection of individual sensor node values is robust and solves the problem of availability, but in an inefficient way. Our work seeks to bridge this gap in secure data collection. We propose a framework that enhances availability with efficiency close to that of in-network aggregation avoiding over-reliance on sensors. To achieve this, we design a scheme that is built on one core concept: no trust is supposed in any sensor. Therefore, we design a two hierarchical levels of monitoring to ensure the integrity and the accuracy of aggregate result, only when necessary, i.e. only when malicious activities are detected. Relying on this new type of monitoring mechanism, the framework has the ability to recover from aggregator failure without neglecting energy efficiency, providing thus much higher availability than other security protocols.     

Characterisation and comparison of the micromixing efficiency in torus and batch stirred reactors

The mixing at a molecular scale (micromixing) plays an important role on selectivity, yield and quality of final products of a large range of competing fast chemical reactions. In this study, we have compared, by the use of iodide–iodate reaction tests, the micromixing in two reactors, the first one is the standard batch stirred reactor and the second is the torus reactor. Various conditions of agitation and feed locations were used for this study. A comparative analysis of the micromixedness ratio (α) in the two reactors was carried out on the basis of the local rate of specific energy dissipation.     

Study of the miscibility of poly(ethyl methacrylate-co-4-vinylpyridine)/poly(styrene-co-cinnamic acid) blends

Summary The miscibility of a series of poly(ethyl methacrylate-co-4-vinylpyridine) with poly(styrene-co-cinnamic acid), is investigated by differential scanning calorimetry. The results show that each blend is miscible as ascertained by a single composition dependent glass transition temperature. The Tg's of the blends exhibit positive deviations from the weight average Tg's of the blend components. The thermograms data exploited according to the Kwei and Schneider approaches suggest the occurrence of strong specific intermolecular attractive interactions within the binary systems. The strength of these interactions, as estimated from the Kwei q-values, increases with the proton donor and proton acceptor contents in the copolymers. Received: 23 January 1999/Revised version: 29 April 1999/Accepted: 1 June 1999     

Evaluation of anti‐proliferative activity of Cheddar cheeses using colon adenocarcinoma (HCT‐116) cell line

The present study was planned to evaluate anti‐proliferative activity of water‐soluble peptides (WSPs) extracts of Cheddar cheeses made with buffalo and cow milk using a colon adenocarcinoma cell line. Cheese extracts were prepared at different stages of ripening up to six months. Anti‐proliferative activity of extracts was evaluated through cell viability assay, cell cycle arrest and apoptosis induction using colon cancer (HCT‐116) cell line. A dose‐dependent increase in activity was observed till five months of ripening. Cells population was relatively higher at G₀/G₁ phase of cell cycle. Moreover, apoptosis induction was also observed in a dose‐dependent manner.     

Surface treatment with amino acids of porous collagen based scaffolds to improve cell adhesion and proliferation

The purpose of this study was to improve the biocompatibility of glutaraldehyde (GA) cross‐linked chitosan coated collagen scaffold for cartilage tissue regeneration. In order to prevent the potential toxicity of GA, we treated the designed scaffold with either glutamic acid or glycine. Amino acid treated scaffolds were characterized by scanning electron microscopy (SEM) techniques. Afterward, chondrocyte interaction with the composite scaffold was investigated assessing cell adhesion and proliferation using Hoechst staining and MTT cell proliferation assay, respectively. The SEM analyses of the scaffolds’ surface and cross‐section confirmed the adhesion of amino acids on the surface of the scaffolds. We also observed that scaffolds’ porosity was reduced due to the coverage of the pores by chitosan and amino acids, leading to low porosity. The use of amino acid improved the chondrocyte adhesion and proliferation inside the scaffolds’ pores when cells were cultured onto the chitosan‐coated collagen scaffolds. Overall, our in vitro results suggest the use of amino acid to improve the biocompatibility of natural polymer composite scaffold being crosslinked with glutaraldehyde. Such scaffold has improved mechanical properties; biocompatibility thus may be useful for tissue regeneration such as cartilage.

     

Factors affecting the adsorption of cationic dyes on polymeric hydrogels prepared by gamma irradiation

The adsorption of the cationic dyes Rhodamine B (RB) and Crystal Violet (CV) on polyacrylamide/poly(acrylic acid) (poly(AAm/AAc), 25:25 % weightwise) and polyacrylamide/poly(sodium acrylate) (poly(AAm/AAcNa), 25:25 % weightwise) hydrogels was studied, employing the Langmuir and Freundlich isotherms. The results of swelling tests at pH 5.5 indicate that poly(AAm/AAcNa) hydrogel shows maximum percentage swelling (%S) was 4400 %. Moreover, the results show that the adsorption capacity is pH‐ and concentration‐dependent. At pH >5 adsorption of RB and CV increases due to ionization of ? COOH and ? COONa groups of (poly(AAm/AAc) and (poly(AAm/AAcNa) and interactions with the cationic groups of the dyes. However, at pH lower than 5, adsorption is still high, which can be explained by considering the formation of hydrogen bonds between the amino groups of the dyes and the ? COOH groups of the polymeric hydrogels. Moreover, the kinetics of adsorption follows a first‐order equation. Furthermore, scanning electron microscopy (SEM) micrographs of polymeric hydrogels doped with CV and RB have morphological differences from the pure form. Our data show that Rhodamine B adsorbs more efficiently on both polyacrylamide/poly(acrylic acid) and polyacrylamide/poly(sodium acrylate) hydrogels than CV. Copyright © 2004 Society of Chemical Industry     

Mechanical properties of paper sheets prepared from carbamoylethylated wood pulp

Carbamoylethylation of wood pulp was carried out at different conditions including acrylamide concentration, time of impregnation, and medium of the reaction (aqueous and nonaqueous). Mechanical properties of paper sheets prepared from the carbamoyethylated cellulose were examined. Carbamoyethylated paper sheets showed improved double-fold breaking length and burst factor irrespective of the reaction medium. Tear strength remained practically unaltered with aqueous carbamoylethylation but decreased in the case of non-aqueous carbamoylethylation. Water retention value (WRV) decreased by carbamoylethylation especially when the latter was performed in nonaqueous medium.     

Use of radiation grafted PVC–acrylamide membranes in radioactive waste treatment

Acrylamide monomer (AAm) was grafted onto poly(vinyl chloride) (PVC) films using γ‐radiation to produce high performance functional membranes which can be employed as ion‐exchangers. The preparation and characterization of the synthetic membranes are investigated. To elucidate their possible applications, some selected properties have been studied. In addition, thermal properties have been studied using thermogravimetric analysis and differential scanning calorimetry; X‐ray diffraction has been used to determine changes in polymer morphology. The selectivity of such membranes towards different radionuclides has also been investigated. On the basis of these investigations, the applicability of the prepared membranes is determined and discussed. The prepared PVC‐g‐PAAm has a great tendency to remove ⁶⁰Co from a radioactive liquid waste containing both ⁶⁰Co and ¹³⁷Cs. © 2002 Society of Chemical Industry