Mitigating Pilot Contamination for Channel Estimation in Multi-cell Massive MIMO Systems

Massive multiple-input multiple-output (MIMO) is a crucial technology platform for the fifth-generation of cellular systems (5G). However, massive MIMO systems are affected by pilot contamination, which influences the data rate of the system. This contamination is caused by the non-orthogonality of the pilot sequences transmitted by users in a cell similar to the neighboring cells. The current study proposes a channel-estimation scheme that employs comprehensive knowledge of large-scale gained by applying an orthogonal pilot reuse sequence to eliminate pilot contamination in edge users with reduced channel quality based on the approximation of large-scale fading, and the performance of this scheme is evaluated using the maximum ratio transmission and zero-forcing precoding techniques. Largely interfering users in neighboring cells are established based on an estimation of large-scale fading, and these users are included in the joint channel processing. The channel quality of users is enhanced by allocating orthogonal pilot reuse sequences to the center user and the edge users based on their levels of pilot contamination estimated from the large-scale fading to mitigate this problem when the number of antenna elements M is infinite. The findings of the simulation indicate that improved channel approximation and reduced performance loss could lead to a high data rate.

     

Synthesis and optimization of future hydrogen energy infrastructure planning in Peninsular Malaysia

The potential future use of hydrogen as an energy carrier in the transportation sector necessitates a shift in the current energy supply chain from supplying petroleum products such as gasoline and diesel, to supply hydrogen. This research was carried out to investigate hydrogen demand and determine the optimum hydrogen delivery network employing truck transportation. Peninsular Malaysia was taken as a case study. The hydrogen demand was determined using two method: Firstly, by assuming that the hydrogen demand in Peninsular Malaysia as a function of total vehicle numbers, average total distance traveled and vehicle fuel economy were measured. While the second method investigated based on the current supply of gasoline and diesel from surveys on local petrol stations in Peninsular Malaysia. As a result, the second method was found as more accurate method and adopted as the overall energy demand in Peninsular Malaysia. Objective function for total investment cost for the future hydrogen infrastructure was developed based on the production technologies, type of transport, type of storage, product phase and plant type. The model was solved based on MILP using GAMS. Finally from the result, it can be concluded that liquefied hydrogen produced by natural gas steam reforming and delivered via tanker trucks is the optimum hydrogen supply chain method due to the minimum cost.     

Effect of filler‐to‐matrix blending ratio on the mechanical strength of palm‐based biocomposite boards

The effect of the blending ratio of a polyurethane matrix and oil‐palm empty fruit bunch (EFB) fibers on the mechanical properties of biocomposite boards has been studied. The PU matrix and EFB fibers were used at blending ratios of 25:75, 30:70 and 35:65 (by weight). The mechanical property of hardness was studied. The intention of this study was to produce fiberboard from a vegetable oil‐based polyester as the matrix and biomass from the palm oil industry, namely EFB. It was found that the blending ratio with a lower filler loading (35:65) gave higher impact and flexural strengths due to better fiber encapsulation which enhanced the fiber–matrix interfacial adhesion. Copyright © 2005 Society of Chemical Industry     

MHD mixed convection flow adjacent to a vertical plate with prescribed surface temperature

The steady MHD mixed convection flow adjacent to a bounding surface immersed in an incompressible viscous fluid is considered. The governing system of partial differential equations is first transformed into a system of ordinary differential equations, before being solved numerically by a finite-difference scheme. The features of the flow and heat transfer characteristics for different values of the governing parameters are analyzed and discussed. Numerical results are obtained for the skin friction coefficient and the local Nusselt number as well as the velocity and temperature profiles. It is found that dual solutions exist for both assisting and opposing flows. The range of the mixed convection parameter for which the solution exists increases in the presence of a magnetic field.     

Microbial community analysis of mixed anaerobic microflora in suspended sludge of ASBR producing hydrogen from palm oil mill effluent

This study investigated the microbial community of an anaerobic sequencing batch reactor (ASBR) operating at mesophilic temperature under varying hydraulic retention times (HRTs) for evaluating optimal hydrogen production conditions, using palm oil mill effluent (POME) as substrate. POME sludge enriched by heat treatment with hydrogen-producing bacteria was used as inoculum and acclimated with the POME. The microbial community was determined by first isolating cultivable bacteria at each operating HRT and then using polymerase chain reaction (PCR). The PCR products were sequenced and sequence identification was performed using the BLAST algorithm and Genbank database. The findings revealed that about 50% of the isolates present were members of the genus Streptococcus, about 30% were Lactobacillus species and around 20% were identified as species of genus Clostridium. Scanning electron microscopy (SEM) analysis also confirmed the presence of spherical and rod-shaped microbial morphologies in the sludge samples of bioreactor during prolonged cultivation.     

Recent advances in cleaner hydrogen productions via thermo-catalytic decomposition of methane: Admixture with hydrocarbon

A continuous increase in the greenhouse gases concentration due to combustion of fossil fuels for energy generation in the recent decades has sparked interest among the researchers to find a quick solution to this problem. One viable solution is to use hydrogen as a clean and effective source of energy. In this paper, an extensive review has been made on the effectiveness of metallic catalyst in hydrocarbon reforming for CO_X free hydrogen production via different techniques. Among all metallic catalyst, Ni-based materials impregnated with various transition metals as promoters exhibited prolonged stability, high methane conversions, better thermal resistance and improved coke resistance. This review also assesses the effect of reaction temperature, gas hour space velocity and metal loading on the sustainability of thermocatalytic decomposition TCD of methane. The practice of co-feeding of methane with other hydrocarbons specifically ethylene, propylene, hydrogen sulphide, and ethanol are classified in this paper with the detailed overview of TCD reaction kinetics over an empirical model based on power law that has been presented. In addition, it is also expected that the outlook of TCD of methane for green hydrogen production will provide researchers with an excellent platform to the future direction of the process over Ni-based catalysts.     

Multi-objective scheduling of MapReduce jobs in big data processing

Multimedia Tools and Applications - Data generation has increased drastically over the past few years due to the rapid development of Internet-based technologies. This period has been called the...     

Mechanical properties and dynamic mechanical analysis of thermoplastic‐natural‐rubber‐reinforced short carbon fiber and kenaf fiber hybrid composites

The hybridization of thermoplastic natural rubber based on carbon fiber (CF) and kenaf fiber (KF) was investigated for its mechanical and thermal properties. Hybrid composites were fabricated with a melt‐blending method in an internal mixer. Samples with overall fiber contents of 5, 10, 15, and 20 vol % were subjected to flexural testing, and samples with up to 30% fiber content were subjected to impact testing. For flexural testing, generally, the strength and modulus increased up to 15 vol % and then declined. However, for impact testing, higher fiber contents resulted in an increment in strength in both treated and untreated composites. Thermal analysis was carried out by means of dynamic mechanical analysis on composites with 15 vol % fiber content with fractions of CF to KF of 100/0, 70/30, 50/50, 30/70, and 0/100. Generally, the storage modulus, loss modulus, and tan δ for the untreated hybrid composite were more consistent and better than those of the treated hybrid composites. The glass‐transition temperature of the treated hybrid composite was slightly lower than that of the untreated composite, which indicated poor damping properties. A scanning electron micrograph of the fracture surface of the treated hybrid composite gave insight into the damping characteristics. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Investigating corrosion effects and heat transfer enhancement in smaller size radiators using CNT-nanofluids

Nanofluids have been extensively studied in the past to enhance the heat transfer performance and efficiency of systems. However, corrosion effects have been paid very little attention and thus this work presents an experimental study on the effect of carbon nanotubes (CNT) on corrosion of three different metals under study such as aluminium alloy, stainless steel and copper, respectively. The work was further extended to study the heat transfer performance in a car radiator of two different sizes. Both the studies were performed using four different fluids such as water, ethylene glycol, 0.02 % CNT-nanofluid and 0.1 % CNT-nanofluid, respectively. It was observed that among the three metals, the highest rate of corrosion occurs to aluminium, followed by stainless steel and copper, irrespective of the fluid used. The rate of corrosion increased with the increase in temperature (27–90 °C) in all cases. The experimental results showed that the stable CNT-nanofluids prepared in this work showed better heat transfer performance in both engines. Moreover, the smaller radiator using the CNT-nanofluids depicted enhanced heat transfer rates compared to the standard radiator using water and ethylene glycol.