A reliable congestion control mechanism for geocasting in mobile wireless networks

In this paper, we present a reliable congestion control mechanism for geocasting in mobile wireless networks. Our protocol can be used as an extension to conventional multicasting protocols in order to overcome the problems associated with terminal mobility and the wireless environment. We present the architecture and implementation of the Multicast ACK Aggregation Method (MAAM). And test the performance of MAAM in various scenarios. Our simulation results show the efficiency and reliability of MAAM in wireless networks with high bit error rates. We further enhance the performance of MAAM by designing MAAM with local recovery (MAAM/LR). Copyright © 2003 John Wiley & Sons, Ltd.     

The histopathological picture of the liver of hamsters experimentally infected with Leishmania D. infantum on top of Schistosoma mansoni infection

No doubt, double and triple infection in a patient is not an uncommon phenomenon in the Old World. Consequently, the histopathological picture of the liver of Syrian golden hamsters experimentally infected with Leishmania. d. infantum on top of pre-infection with S. mansoni was studied. The results showed that the liver was markedly affected by the concomitant infection than infection with either parasite alone. The superadded Leishmania infection caused the early appearance of cell necrosis and fatty changes. The schistosomal granulomas were rounded in shape and well circumscribed. However, they were smaller in size and less in number when compared with schistosomal control. Also, there was a comparative decrease in the number of their cellular constitutions but without changing in the cell types. The schistosomal granulomas were surrounded with a rim of amastigotes laden macrophages. On the other hand, the leishmanial granulomas, were irregular in shape but comparatively increased in size and in number on the behalf of the schistosomal granulomas. Their cellular constitutions comparatively increased as well. So, it is concluded that the L.d. infantum infection on the top of S. mansoni infection suppressed the schistosomal pathological picture in the liver of hamsters.     

An approximate method for separated spectral analysis of connected buildings with added damping

The problem of determining maximum seismic responses, or spectral analysis, of connected adjacent structures is studied in this research. The goal of the study is twofold. First, determining when the dynamic coupling is important in such a problem and, second, establishing how to analyze each of the two structures separately when coupling is important. For tall buildings in many cases, the connecting link is intentionally accommodated with an added damping to suppress the lateral displacements. Therefore, effect of the localized damping is also accounted for in the analysis. Using essentials of modal analysis, a criterion is developed for estimation of the dynamic coupling of the two adjacent structures. Also, a procedure is developed for separated analysis of each structure incorporating the stiffness and inertial effects of the adjacent structures when coupling is important. The representative examples confirm good accuracy of the presented method.     

Bi-level optimization of laminated composite structures using particle swarm optimization algorithm

This paper presents an efficient bi-level optimization technique to obtain the optimal stacking sequence for symmetric composite structures. The proposed approach involves two levels of modeling and optimization. The first level of the optimization procedure is used to minimize the weight of the composite structure. At this level, lamination parameters and the number of plies of specified angles (0, ±45 and 90 degree) are design variables, buckling load factor is treated as a constraint, and the weight of the structure is to be minimized using continuous-discrete particle swarm optimization algorithm. Next, at the second level the location of each ply orientation through the thickness (i.e. the layup of the panel) is found. At the second level, optimum stacking sequence is sought to maximize the load bearing capacity of the structure with respect to the buckling. The proposed methodology is applied to two test cases. Results show that the approach improves the buckling load factor of the structure without any weight penalty.     

Synthesis,Characterization and Surface Activities of Cationic Polysaccharide (Aloe) Schiff Base Surfactants

Synthesis of cationic polysaccharide (Aloe) Schiff base surfactants was described and their chemical structures were confirmed by using FTIR spectroscopic, H‐NMR and UV analysis. The surface activities of these surfactants were measured, including surface tension, critical micelle concentration, effectiveness, efficiency, maximum surface excess and minimum surface area at 25 °C, interfacial tension and emulsification power at 25 °C. Adsorption and micellization free energies of these amphiphiles in their solutions showed a good tendency towards adsorption at the interfaces.     

Mechanical and barrier properties of XNBR-clay nanocomposite: a promising material for protective gloves

Carboxylated nitrile butadiene rubber (XNBR)-based gloves are commonly used to protect users’ hands from the aggressive environment in various industrial applications. Permeation resistance and mechanical properties of gloves should be simultaneously considered to accomplish adequate protection. Accordingly, in this study, XNBR was reinforced with different amounts of nanoclay and the resulting dispersion was examined using X-ray diffraction and transmission electron microscope. The results showed that, nanoclay has been appropriately dispersed in XNBR lattice and therefore, considerable enhancements in mechanical properties, including tensile strength and modulus were gained. The permeation resistance of the synthesized nanocomposites was studied by two solvents, including perchlorethylene and aniline with low and high affinity to XNBR, respectively. Using permeation test cell, parameters of breakthrough time (BT) and steady-state permeation rate (SSPR) were determined. The BT and SSPR of aniline in nanocomposites with 3 phr nanoclay in comparison with neat polymer were increased 89 % and decreased by 11 %, respectively. Degradation resistance test of nanocomposite demonstrated acceptable integrity of its barrier properties after repeated exposure to selected chemicals. Analysis of mechanical properties and permeation indices of synthesized nanocomposites illustrated that the application of these materials for manufacturing protective gloves seems promising.     

Electrodeposition of nanostructured Ti/(Ru+Ti+Ce)O_2 coatings

A nanostructured ternary coating of Ti/(Ru + Ti + Ce)O_2 was prepared by the conventional electrodeposition on the titanium substrate as the cathode with different numbers of coating layers. The main objective of this work was to study nanostructured coatings of ceramic materials. For this purpose, the amount of precursor materials in the electrolyte was a variable parameter. Furthermore, the salt of TiCl_4/RuCl_3·xH_2 O/Ce(NO_3)_3·6 H_2 O with different amounts, hydrogen peroxide, methanol, and distilled water were used as an aqueousunaqueous bath. In addition, the coated samples were put to heat at 300, 450, 650, and 850℃ in an electric furnace for1 h. The crystalline phase of the coating was characterized by X-ray diffraction(XRD). The chemical composition and microstructure of the coating were studied using energydispersive spectroscopy(EDS) and scanning electron microscopy analysis(SEM). Moreover, the electrochemical measurement of Ti/(Ru + Ti + Ce)O_2 coatings was carried out. Results show that with the increase in the number of coating layers, the quality of morphology is improved.Then, the best quality of coatings is obtained at six layers on the titanium substrate with electrolyte including TiO_2/RuO_2/CeO_2 with the molar ratio of 70:5:25 after heat treatment at 450 ℃ for 1 h. Besides,with the increase in Ce02 content from 5 wt% to 25 wt% and the number of coating layers, higher thickness of about(20.0±0.1) μm and minimum over potential for chlorine evolution were obtained.     

An investigation of structure and electrical characteristics of lanthanum strontium manganite nanopowders with different Sr2+ ion concentrations

Generally, the efficiency of solid oxide fuel cells is heavily dependent on the electrocatalytic activity of the cathode toward the oxygen reduction reaction. In order to achieve a better cathode performance, La_xSr_1-xMnO₃ (LSM) nanopowders with different Sr²⁺ ion contents varying from 0.2 to 0.8 have been synthesized using the coprecipitation method. The obtained nanoparticles were characterized by x-ray diffraction, field emission scanning electron microscopy, and electrochemical impedance spectroscopy. It was found that the LSM nanoparticles seemed to exhibit high polarization resistance with the increase of the Sr²⁺ ion molar ratios. The crystallite size was found to increase from 16.4 to 24.3 nm with increasing Sr²⁺ content from 0.2 to 0.8. The lattice parameters were decreased with Sr²⁺ ion content which may be caused by an increase in internal stress with the increasing grain size of LSM. Meanwhile, the real part impedance (Z′) was increased from 10 (Ω) at 0.2 Sr²⁺ to 24 (Ω) at 0.8 Sr²⁺ ion ratio. Alternatively, |Z| of prepared sample was increased from 12 to 26 (Ω) by increasing Sr²⁺ ion molar ratios from 0.2 to 0.8.