Sharif Digital Repository

Governments in developing countries have invested in institutions of higher learning in order to develop homegrown, high technology products. Among these, the National University of Malaysia (Universiti Kebangsaan Malaysia), recognized as a Research University, is actively involved in projects related to medical technology through its various faculties. The net result of these activities is impressing from the point of view of patents and publications, but unfortunately not yet in terms of commercialization. This paper starts by presenting the main obstacles towards the objective of bringing a laboratory prototype to the market in the context of Malaysia. Then, a framework is presented... 

In this research FeCl2/FeCl3/Perlite magnetic nanoparticles (FeCl2/FeCl3/PMNs), as a novel magnetic nanocomposite adsorbent was used for the removal of green malachite (GM) dye from aqueous solution in a batch and fixed bed column. Firstly, FeCl2/FeCl3/PMNs adsorption properties were investigated. Therefore, the solution of FeCl2·4H2O and FeCl3·6H2O by ratio 2/1 was mixed with perlite nanoparticles. The study investigates the effect of process parameters such as pH, adsorbent dosage, contact time and GM dye initial concentration. Next, GM dye was quantitatively evaluated by using the Langmuir, Freundlich and BET isotherms and pseudo-first- and pseudo-second-order kinetic model. The... 

In this paper, we prove the existence of capacity achieving linear codes with random binary sparse generating matrices over the Binary Symmetric Channel (BSC). The results on the existence of capacity achieving linear codes in the literature are limited to the random binary codes with equal probability generating matrix elements and sparse parity-check matrices. Moreover, the codes with sparse generating matrices reported in the literature are not proved to be capacity achieving for channels other than Binary Erasure Channel. As opposed to the existing results in the literature, which are based on optimal maximum a posteriori decoders, the proposed approach is based on a different decoder... 

Recycling of wastepaper is an effective way to achieve the sustainable paper manufacturing regarding sustainable development goals. Focusing on the mixed wastepaper sorting, recovery of suitable papers for deinking purpose and minimizing the impurities were developed in this study. In a wastepaper sorting process, each equipment has its own role in increasing recycling performance. In this study, disc screen was applied and evaluated for sorting of the mixed wastepaper considering independent variables such as inclination, velocity and moisture content. Response surface method was applied for design of the experiments. Sorting efficiency of 100% was achieved in two conditions: 1–20%... 

Recycling of wastepaper is an effective way to achieve the sustainable paper manufacturing regarding sustainable development goals. Focusing on the mixed wastepaper sorting, recovery of suitable papers for deinking purpose and minimizing the impurities were developed in this study. In a wastepaper sorting process, each equipment has its own role in increasing recycling performance. In this study, disc screen was applied and evaluated for sorting of the mixed wastepaper considering independent variables such as inclination, velocity and moisture content. Response surface method was applied for design of the experiments. Sorting efficiency of 100% was achieved in two conditions: 1–20%... 

The present study is focused on the investigation of the absorption properties of the bi-layer absorber with different thickness and orientation approaches. Improvement in absorption exclusively depends on the various parameters as interfacial polarization, multiple reflections among layers, conduction loss, phase cancellations, and shape anisotropy, etc. By considering these parameters. Calcium titanate micro-cubes CaTiO3 (CTO) and polypyrrole nanotubes (PPy) nanocomposites were prepared and microwave absorption from single layer coaxial absorbers having M1 = CaTiO3+15 wt% polymer and M2 = CaTiO3+30 wt% polymer were determined. Different layer orientations and thicknesses of the bi-layer... 

Many high performance steganographic schemes work at a limited or sparsely distributed set of embedding rates. We have shown that some steganographic changes will be wasted as these schemes are utilized individually for messages of various lengths. To measure the wasted changes and compare different schemes in this respect, we have built a framework based on two new criteria: the Relative Change Waste (RCW) and the Expected Changes per Pixel (ECP). To decrease the wasted changes a systematic combination of schemes is introduced and proved to be equivalent to nonlinear interpolation of points in a two-dimensional space. We have proved that a special case which leads to a linear interpolation... 

A family of matrix embedding steganographic schemes for digital images is investigated. The target schemes are applied to blocks of n pixels in a cover image. In every block, at most m pixels are allowed to change with q-ary steps. We have derived some upper bounds on the embedding efficiency of these schemes for different values on m. It is also shown that these upper bounds approach the general upper bound on the embedding efficiency of q-ary steganography. For the case of q=3, we have shown that there is no feasible optimum member of the family for m=2, although for m=1, a well-known example exists. Instead, for m=2, a new close-to-bound scheme in the family is presented which exploits... 

In this paper, a numerical optimization method has been carried out to optimize the shape and efficiency of a propeller. For analysis of the hydrodynamic performance parameters, an extended vortex lattice method was used by implementing an open-source code which is called OpenProp. The method of optimization is a non-gradient based algorithm. After a trade-off between a few gradient-based and non-gradient based algorithms, it is found that the problem of being trapped in local optimum solutions can be easily solved by choosing nongradient based ones. Hence, modified Genetic algorithm is used to implement the so-called hydrodynamic performance analyzer code. The objective function is to... 

A four stage LC-ring oscillator is presented. Eight different phases are generated in which there in 45 degrees phase difference between consecutive outputs and direction of phases is defined. Nmos capacitors in parallel with constant capacitors are used for coupling between stages. The control voltage is applied to Pmos varactors to adjust the oscillation frequency. The advantages of this structure are the rather small inductors size, low power consumption, and tuning curve linearity. The proposed structure is simulated in 0.18um CMOS technology. Power consumption for each stage is 4.8mW from a 1.8B supply. The proposed VCO has a phase noise of -121dBc/Hz at 1MHz offset from the center... 

The objective of this paper is to demonstrate a topology optimization method subject to displacement and stress constraints. The method does not rely on pseudo-densities; instead it exploits the concept of topological level-set where 'partial' elements are avoided. Consequently: (1) the stresses are well-defined at all points within the evolving topology, and (2) the finite-element analysis is robust and efficient. Further, in the proposed method, a series of topologies of decreasing volume fractions are generated in a single optimization run. The method is illustrated through numerical experiments in 2D  

A novel class AB architecture for single stage multipath differential amplifier is presented. The proposed amplifier combines the flipped voltage follower(FVF) for differential input and the nonlinear current mirror for active load. Applying these techniques to telescopic-cascode amplifier increases the unity-gain bandwidth, the DC gain and the slew rate while the same power consumption as the conventional telescopic cascade is achieved  

The performance of a three-dimensional optical code-division multiple-access system based on polarization-wavelength-time codes is investigated. The unwanted effects of multiple access interference are first studied and an accurate enough expression is given for the upper bound of the bit error rate. The proposed expression is obtained by decomposing the three-dimensional polarization-wavelength-time codes into horizontally and vertically polarized two-dimensional wavelength-time codes that are assumed to be statistically independent. It is shown by Monte Carlo simulation that the assumption of independence gives accurate enough bit error rate, whenever the number of chips is much larger... 

The performance of the adaptive spatial resolution technique is improved by making the resolution function of the coordinate transformation as smooth as possible. To this end, the smoothness of the resolution function is probed and a quantitative criterion is proposed to make the jump points; which were conventionally equidistant from each other, regularized. The here-proposed regularization is applied to two different recent formulations and its effects on the overall convergence rate and on the presence of numerical artifacts in analysis of highly conducting gratings are studied. Dielectric and metallic gratings at optical and microwave frequencies are considered and the helpfulness of the... 

This article deals with the design and optimization of a cascade thermoacoustic Stirling engine. Different configurations for cascade thermoacoustic Stirling heat engine are investigated. A simplified model is proposed to enable initial design guidelines. The most important characteristics of the cascade system are examined. The results indicate that the thermoacoustic engines in cascade configuration may achieve very low onset temperatures. A suitable configuration is selected and the locations and dimensions of different thermoacoustic units are optimized to achieve low onset temperatures as well as high values for the acoustic power output and efficiency. The results support the... 

Traditionally, the members of a supply chain compete to reduce their individual costs. However, as collaborative supply chain approach is urged within industries to reduce the overall costs, either full cooperation or partial coopetition is considered by the members. In cooperative approach, members benefit from lower overall costs and lower cost variations. But individually, some seem better off in a competitive approach in a single period considering their local costs. Coopetition, or partial cooperation, may be suggested as a compromise to lower overall supply chain costs, while members choose alliances towards lower average costs and cost variations. A multi-stage, multi-member,... 

A circuit model is proposed for periodic 1-D array of metallic strips in the sub-wavelength regime. The parameters of the proposed circuit and their dependence on frequency are all explicitly given by closed form expressions. The necessity of using numerical simulation to extract model parameters is thus sidestepped. It is demonstrated that the proposed model is valid at different incident angles and for arbitrary surrounding mediums given that there is only one propagating diffracted order outside the grating and only one guided mode supported by the slits. Both major polarizations are studied in this paper  

Members in a traditional supply chain compete to reduce their individual costs. But total cost is minimized in a cooperative, or a corporate managed, supply chain. A lower average cost and a lower cost variation are achieved by cooperative individual members in the long-run. The problem is formulated and solved as an integrated flow network. Previous research is expanded to include multi-period and multi-product cooperative supply chain with possibility of holding inventory in a multi-stage, multi-member setup. A Cooperative Supply Optimizer System (CSOS), a software-based coordination mechanism, is developed for large chains. It gathers operational information from members of the supply... 

The graph colouring problem, as an important NP-complete problem, is considered in this paper and a hybrid meta-heuristic approach is developed to solve it. The initial solution of the algorithm, generated by a heuristic method, is used by a simulated annealing (SA) approach to generate new solutions until no progress in a number of solutions reported. At this stage, the algorithm will use a tabu search routine and this local search operator will be followed for some iterations. After finding a better solution, the algorithm is again followed through SA. Efficiency of the algorithm is showed through various experiments on well-known benchmark problems of DIMACS. Comparison with the available... 

Here a propeller design method based on a vortex lattice algorithm is developed, and two gradient-based and non-gradient-based optimization algorithms are implemented to optimize the shape and efficiency of two propellers. For the analysis of the hydrodynamic performance parameters, a vortex lattice method was used by implementing a computer code. In the first problem, one of the Sequential Unconstraint Minimization Techniques (SUMT) is employed to minimize the torque coefficient as an objective function, while keeping the thrust coefficient constant as a constraint. Also, chord distribution is considered as a design variable, namely 11 design variables. In the second problem, a modified...