Optimized unequal error protection of embedded video bitstream using adaptive-hierarchical QAM

In this paper, a reliable video communication system using adaptive Hierarchical QAM (HQAM) is designed to provide optimized unequal error protection (UEP) to embedded video bitstreams. Based on the relative importance of bits, video bitstream is partitioned into two priorities, namely High Priority (HP) and Low Priority (LP) substreams. Then, the optimal value of modulation (or hierarchical) parameter (α) of HQAM, which controls the relative error protection of these substreams, is selected from a pre-designed look-up table. The proposed system adapts itself by adapting the optimal α according to the varying channel condition, without changing the modulation level. This is in contrast to conventional WiMAX and LTE systems, in which dynamic switching among multiple modulations is used to adapt the varying channel conditions. This paper proposes HQAM with adaptive α as an alternative to the multiple modulation schemes. Moreover, for fixed average transmission power, receiver demodulates symbols without the knowledge of α. In order to further improve the video quality and to reduce the effects of erroneously received LP bits, the proposed system uses another level of adaptation, in which received LP bits are adaptively considered or discarded, before decoding the video, depending on the channel conditions (or optimized α). Simulation results show that proposed system can achieve significant improvement in the video quality compared to QAM based EEP scheme and non-adaptive HQAM.     

Structural Analysis with Fuzzy Variables

Abstract: The analysis of existing structures requires engineers to model two types of uncertainty, cognitive and non-cognitive. The objective of this paper is to reexamine structural analysis methods by considering the cognitive type of uncertainty. Two analytical approaches are proposed for this purpose: (1) combining the displacement method with fuzzy arithmetic and (2) considering all possible permutations of extreme values of any uncertain variables in a structure using the displacement method. The first approach, which is based on fuzzy arithmetic, requires less computing time as compared with the permutations method but only obtains approximate solutions. However, the second approach produces the exact solution. For the purpose of illustration, the modulus of elasticity E is assumed to be an uncertain variable and is modeled as a triangular fuzzy number. The structural behavior was investigated due to this cognitive uncertainty in E. The results based on the second approach show that if E is a triangular fuzzy number, the member forces can be either fuzzy numbers or crisp values, depending on the structural type. In addition, modified definitions for fuzzy division and fuzzy subtraction are proposed in this paper. Applications of these modified definitions and proposed methods are also presented.     

Sputter deposition of self-organized nanoclusters through porous anodic alumina templates

Silver nanoparticles were sputter deposited through self organized hexagonally ordered porous anodic alumina templates that were fabricated using a two-step anodization process. The average pore diameter of the template was 90 nm and the interpore spacing was 120 nm. Atomic force microscope studies of the sputter-deposited silver nanoparticle array on a Si substrate indicate an approximate replication of the porous anodic alumina mask. The nature of the deposition depends strongly on the process parameters such as sputtering voltage, ambient pressure and substrate temperature. We report a detailed study of the sputtering conditions that lead to an optimal deposition through the template.     

Optical and structural properties of sputter-deposited nanocrystalline Cu2O films: effect of sputtering gas

We report the effect of the atomic mass of the sputtering gas (He, Ne, Ar, Kr, and Xe) on the structure and optical properties of nanocrystalline cuprous oxide (Cu2O) thin films deposited by dc magnetron sputtering. The crystal structure and surface morphology were studied by X-ray diffraction (XRD) and atomic force microscopy (AFM) respectively. We find that the atomic mass of the sputtering gas significantly affects the primary crystallite size as well as the surface morphology and texture. Optical reflectance and transmission measurements show that the nanocrystalline thin films are transparent over most of the visible region. The HOMO-LUMO gap obtained from optical absorption spectra show a size-dependent quantum shift with respect to the bulk band gap reported for Cu2O (2.1 eV).     

Effect of GTAW Parameters on Structure and Mechanical Properties of C86300 Weld Joint

In this study, the effects of heat input variation in gas tungsten arc welding (GTAW), on structure and mechanical properties of commercially C86300 (containing addition of 0.6 wt% silicon) weld joint were investigated. Following microstructural characterization of Base metal, GTAW has been performed at welding currents 50 and 60 A and flow rates of argon shielding gas (10, 14 and 18 l/min) using the same filler metal composition. Therefore six GTAW samples were performed with various welding specifications. By structural investigations and hardness profiles, effects of increasing heat input on increasing average grain size in weld zone, heat affected zone width, penetration depth and alloying element losses were indicated. However increasing heat input increases penetration depth and has a positive effect on hardness and strength of the joint. In considering wear application of this alloy castings and probable GTAW for them, pin-on-disc wear test was performed and revealed better wear resistance of weld metal in comparison with base metal. Hence the optimum values of welding current and argon flow rates (in GTAW with the same composition filler) was determined for this alloy.     

Pb(II) biosorption using DAP/EDTA-modified biopolymer (Chitosan)

Abstract

In this study, chitosan was chemically modified with only diammonium phosphate (DAP) and DAP/EDTA (ethylenediaminetetraacetic acid) mixture for the removal of Pb(II) ions from aqueous solution. Modified chitosan forms were analyzed using thermo-gravimetric analyzer (TGA), Fourier transform infrared (FTIR) spectroscopy, and scanning electron microscopy (SEM) to investigate the thermal degradation behavior, structural modifications, and the surface texture of the cross-linked chitosan adsorbents, respectively. The adsorption results were analyzed by well-known kinetic and isotherm models. The kinetics of metal adsorption followed the pseudo-second-order model. The maximum sorption capacities obtained from the Langmuir isotherm model were 126?mg/g for diammonium phosphate-modified Chitosan (DMC) and 137?mg/g for DAP/EDTA-modified chitosan (EDMC). The thermodynamic analysis showed that the metal removal process was endothermic in nature.     

Resistance upset butt welding of austenitic to martensitic stainless steels

In this research, joining austenitic to martensitic stainless steels and effect of welding power on microstructure and mechanical properties of the joint were investigated. Microstructure of the weld was studied using optical microscopy (OM) and scanning electron microscopy (SEM). Energy dispersive spectroscopy (EDS) linked to SEM was used to determine chemical composition of phases and distribution of chromium (Cr), nickel (Ni) and iron (Fe) at the joint interface. Microhardness and tensile strength tests were performed. Finally fracture surface of samples were studied by SEM. Results showed that an interlayer composed of 80% ferrite and 20% martensite has formed at the joint interface and there were three different zones in the heat affected zone (HAZ) of two steels. Different forms of austenite phase including widmanstatten austenite (W_γ), allotriomorphic austenite (A_γ) and intergranular austenite (I_γ), delta ferrite (δ-ferrite) and chromium carbide (Cr₂₃C₆) have formed in the HAZ of austenitic stainless steel. Fractography of tension samples indicated that in all samples fracture occurred in austenitic stainless steel HAZ. The strength and hardness of the joint increased and HAZ length decreased with increasing of welding power.     

Phase separation in immiscible silver–copper alloy thin films

Far from equilibrium, immiscible nanocrystalline Ag–Cu alloy thin films of nominal composition Ag–40 at.% Cu have been deposited by co-sputter deposition. Both X-ray and electron diffraction studies indicate that the as-deposited films largely consist of nanocrystalline grains of a single alloyed face-centered cubic (fcc) phase. However, detailed three-dimensional atom probe tomography studies on the same films give direct evidence of a nanoscale phase separation within the columnar grains of the as-deposited Ag–Cu films. Subsequent annealing of these films at 200 °C leads to two effects; a more pronounced nanoscale separation of the Ag and Cu phases, as well as the early stages of recrystallization leading to the breakdown of the columnar grain morphology. Finally, annealing at a higher temperature of 390 °C for a long period of time leads to complete recrystallization, grain coarsening, and a complete phase separation into fcc Cu and fcc Ag phases.