Showing papers in "Engineering Science and Technology, an International Journal in 2016"

State of the art on tribological behavior of polymer matrix composites reinforced with natural fibers in the green materials world

Abstract: Natural fiber reinforced polymer composites have emerged as a potential environmentally friendly and cost-effective alternative to synthetic fiber reinforced composites. Therefore, in the past decade, a number of major industries, such as the automotive, construction and packaging industries, have shown a considerable interest in the progress of new natural fiber reinforced composite materials. The availability of natural fibers and the ease of manufacturing have tempted researchers to study their feasibility of their application as reinforcement and the extent to which they satisfy the required specifications in tribological applications. However, less information concerning the tribological performance of natural fiber reinforced composite material is available in the literature. Hence, the aim of this bibliographic review is to demonstrate the tribological behavior of natural fiber reinforced composites and find a knowledge about their usability for various applications that tribology plays a dominant role. This review presents the reported work on natural fiber reinforced composites with special reference to the type of fibers, matrix polymers, treatment of fibers and test parameters. The results show that composites reinforced with natural fibers have an improvement in tribological properties and their properties are comparable with conventional fibers. In addition, fiber treatment and fiber orientation are two important factors can affect tribological properties where treated fibers and normal oriented fibers exhibit better friction and wear behavior. This review is trying to evaluate the effect of test parameter including normal load and sliding speed on tribological properties, and the results vary based on type of reinforcement. Generally, due to their positive economic and environmental aspects, as well as their good tribological properties, natural composites are showing a good potential for employing in several applications.

Effect of chemical reaction on MHD boundary layer flow and melting heat transfer of Williamson nanofluid in porous medium

Abstract: Radiation and chemical reaction effects on the steady boundary layer flow of MHD Williamson fluid through porous medium toward a horizontal linearly stretching sheet in the presence of nanoparticles are investigated numerically. Adequate similarity transformations are used to derive a set of nonlinear ordinary differential equations governing the flow. The resultant nondimensionalized boundary value problem is solved numerically by Runge–Kutta–Fehlberg fourth–fifth order method with Shooting technique. The profiles for velocity, temperature and concentration, which are controlled by a number of thermo-physical parameters, are presented graphically. Based on these plots the conclusions are given, and the obtained results are tested for their accuracy.

Heat and mass transfer in magnetohydrodynamic Casson fluid over an exponentially permeable stretching surface

Abstract: In this study we analyzed the flow, heat and mass transfer behavior of Casson fluid past an exponentially permeable stretching surface in presence of thermal radiation, magneticfield, viscous dissipation, heat source and chemical reaction. We presented dual solutions by comparing the results of the Casson fluid with the Newtonian fluid. The governing partial nonlinear differential equations of the flow, heat and mass transfer are transformed into ordinary differential equations by using similarity transformation and solved numerically by using Matlab bvp4c package. The effects of various non-dimensional governing parameters on velocity, temperature and concentration profiles are discussed and presented graphically. Also, the friction factor, Nusselt and Sherwood numbers are analyzed and presented in tabular form for both Casson and Newtonian fluids separately. Under some special conditions the results of the present study have an excellent agreement with existing studies for both Casson and Newtonian fluid cases.

Tribological performance of self-lubricating aluminum matrix nanocomposites: Role of graphene nanoplatelets

Abstract: In the present investigation, aluminum matrix nanocomposites reinforced by graphene nanoplatelets were synthesized by powder metallurgy method. The microstructure of the Al-Graphene nanoplatelets sample was investigated by TEM. The hardness measurements of these samples were investigated using a Rockwell hardness tester. To investigate the tribological behavior of aluminum matrix composites reinforced by graphene nanoplatelets and pure aluminum, pin-on-disk experiments were conducted on the prepared samples. In the experiments, the influence of reinforcement, volume fraction, normal load, and sliding velocity on the tribological performance was investigated. Results showed that the wear rate of Al-1wt.% GNP is increased with increasing normal loads. However, the coefficient of friction (COF) of the Al-1wt.% GNP decreased with increasing normal loads. Formation of graphene film on the worn surface of Al-1wt.% GNP sample and morphology of the worn surfaces of aluminum and composite samples were analyzed by Optical Microscope (OM) and Scanning Electron Microscope (SEM). It was found that the graphene nanoplatelets reinforced nano-composites showed superior tribological properties and demonstrated the ability of the self-lubricating nature of the composite during tribological conditions.

Firefly algorithm optimized fuzzy PID controller for AGC of multi-area multi-source power systems with UPFC and SMES

Abstract: In this paper, a Firefly Algorithm (FA) optimized fuzzy PID controller is proposed for Automatic Generation Control (AGC) of multi-area multi-source power system. Initially, a two area six units power system is used and the gains of the fuzzy PID controller are optimized employing FA optimization technique using an ITAE criterion. The superiority of the proposed FA optimized fuzzy PID controller has been demonstrated by comparing the results with some recently published approaches such as optimal control and Differential Evolution (DE) optimized PID controller for the identical interconnected power system. Then, physical constraints such as Time Delay (TD), reheat turbine and Generation Rate Constraint (GRC) are included in the system model and the superiority of FA is demonstrated by comparing the results over DE, Gravitational Search Algorithm (GSA) and Genetic Algorithm (GA) optimization techniques for the same interconnected power system. Additionally, a Unified Power Flow Controller (UPFC) is placed in the tie-line and Superconducting Magnetic Energy Storage (SMES) units are considered in both areas. Simulation results show that the system performances are improved significantly with the proposed UPFC and SMES units. Sensitivity analysis of the system is performed by varying the system parameters and operating load conditions from their nominal values. It is observed that the optimum gains of the proposed controller need not be reset even if the system is subjected to wide variation in loading condition and system parameters. Finally, the effectiveness of the proposed controller design is verified by considering different types of load patterns.

Spintronics: A contemporary review of emerging electronics devices

Abstract: Spintronics is a new field of research exploiting the influence of electron spin on the electrical conduction (or current is spin dependent). The major problem is the realization and fabrication of spintronics based devices. To meet the objective scientific community is developing the novel kind of materials that relies on magnetism instead of flow of current through electron. This paper illustrates and reviews one of the emerging technologies known as spintronics by putting few low power computing techniques altogether based on spintronics to provide a basic and meaningful understanding to the reader. The challenges of spintronics devices that has to meet for the success of electronics future are summarized.

Multi-attribute optimization of machining process parameters in powder mixed electro-discharge machining using TOPSIS and grey relational analysis

Abstract: Powder Mixed Electro-Discharge Machining (PMEDM) is a hybrid machining process where a conductive powder is mixed to the dielectric fluid to facilitate effective machining of advanced material. In the present work application of Taguchi method in combination with Technique for order of preference by similarity to ideal solution (TOPSIS) and Grey Relational Analysis (GRA) have been adopted to evaluate the effectiveness of optimizing multiple performance characteristics for PMEDM of H-11 die steel using copper electrode. The effect of process variables such as powder concentration (Cp), peak current (Ip), pulse on time (Ton), duty cycle (DC) and gap voltage (Vg) on response parameters such as Material Removal Rate (MRR), Tool Wear Rate (TWR), Electrode Wear Ratio (EWR) and Surface Roughness (SR) have been investigated using chromium powder mixed to the dielectric fluid. Analysis of variance (ANOVA) and F-test were performed to determine the significant parameters at a 95% confidence interval. Predicted results have been verified by confirmatory tests which show an improvement of 0.161689 and 0.2593 in the preference values using TOPSIS and GRA respectively. The recommended settings of process parameters is found to be Cp = 6 g/l, Ip = 6Amp, Ton = 100 µs, DC = 90% and Vg = 50 V from TOPSIS and Cp = 6 g/l, Ip = 3Amp, Ton = 150 µs, DC = 70% and Vg = 30 V from GRA. The microstructure analysis has been done for the optimal sample using Scanning Electron Microscope (SEM).

Support vector machine based fault classification and location of a long transmission line

Abstract: This paper investigates support vector machine based fault type and distance estimation scheme in a long transmission line. The planned technique uses post fault single cycle current waveform and pre-processing of the samples is done by wavelet packet transform. Energy and entropy are obtained from the decomposed coefficients and feature matrix is prepared. Then the redundant features from the matrix are taken out by the forward feature selection method and normalized. Test and train data are developed by taking into consideration variables of a simulation situation like fault type, resistance path, inception angle, and distance. In this paper 10 different types of short circuit fault are analyzed. The test data are examined by support vector machine whose parameters are optimized by particle swarm optimization method. The anticipated method is checked on a 400 kV, 300 km long transmission line with voltage source at both the ends. Two cases were examined with the proposed method. The first one is fault very near to both the source end (front and rear) and the second one is support vector machine with and without optimized parameter. Simulation result indicates that the anticipated method for fault classification gives high accuracy (99.21%) and least fault distance estimation error ( 0.29%.

Automatic generation control of multi-area power systems with diverse energy sources using Teaching Learning Based Optimization algorithm

Abstract: This paper presents the design and analysis of Proportional-Integral-Double Derivative (PIDD) controller for Automatic Generation Control (AGC) of multi-area power systems with diverse energy sources using Teaching Learning Based Optimization (TLBO) algorithm. At first, a two-area reheat thermal power system with appropriate Generation Rate Constraint (GRC) is considered. The design problem is formulated as an optimization problem and TLBO is employed to optimize the parameters of the PIDD controller. The superiority of the proposed TLBO based PIDD controller has been demonstrated by comparing the results with recently published optimization technique such as hybrid Firefly Algorithm and Pattern Search (hFA-PS), Firefly Algorithm (FA), Bacteria Foraging Optimization Algorithm (BFOA), Genetic Algorithm (GA) and conventional Ziegler Nichols (ZN) for the same interconnected power system. Also, the proposed approach has been extended to two-area power system with diverse sources of generation like thermal, hydro, wind and diesel units. The system model includes boiler dynamics, GRC and Governor Dead Band (GDB) non-linearity. It is observed from simulation results that the performance of the proposed approach provides better dynamic responses by comparing the results with recently published in the literature. Further, the study is extended to a three unequal-area thermal power system with different controllers in each area and the results are compared with published FA optimized PID controller for the same system under study. Finally, sensitivity analysis is performed by varying the system parameters and operating load conditions in the range of ±25% from their nominal values to test the robustness.

Melting heat transfer in boundary layer stagnation-point flow of nanofluid toward a stretching sheet with induced magnetic field

Abstract: A steady two-dimensional hydromagnetic stagnation-point flow of an electrically conducting nanofluid past a stretching surface with induced magnetic field, melting effect and heat generation/absorption has been analyzed numerically. The model used for the nanofluid incorporates the effects of Brownian motion and thermophoresis. The nonlinear partial differential equations are transformed into ordinary differential equations using suitable similarity transformations, before being solved numerically. Effect of pertinent parameters on different flow fields are determined and discussed in detail through several plots and a table. Obtained numerical results are compared and found to be in good agreement with previously published results in a limiting sense. Further, in the absence of melting and magnetic field effect, the skin friction co-efficient results are compared with exact solutions, which are reported earlier.

Load frequency control of large scale power system using quasi-oppositional grey wolf optimization algorithm

Abstract: This article presents a newly developed, novel and efficient optimization technique called quasi-oppositional grey wolf optimization algorithm (QOGWO) for the first time to solve load frequency control problem (LFC) of a power system. Grey wolf optimization (GWO) is a recently developed meta-heuristic optimization technique based on the effect of leadership hierarchy and hunting mechanism of wolves in nature. Two widely employed test systems; viz. two-area hydro-thermal and four-area hydro-thermal power plant, are considered to establish the effectiveness of the proposed QOGWO algorithm. Optimal proportional-integral-derivative controller (PID) is designed for each area separately using proposed algorithm employing integral time absolute error (ITAE) based fitness function. The validity of proposed QOGWO method is tangibly verified by comparing its simulation results with those of GWO and other approaches available in the literature. Time domain simulation results confirm the potentiality and efficacy of the proposed QOGWO method over other intelligent methods like fuzzy logic, artificial neural network (ANN) and adaptive neuro-fuzzy interface system (ANFIS) controller. Finally, sensitivity analysis is performed to show the robustness of the designed controller under different uncertainty conditions.

Optimal sizing and locations of capacitors in radial distribution systems via flower pollination optimization algorithm and power loss index

Abstract: In this paper, a new and powerful algorithm called Flower Pollination Algorithm (FPA) is proposed for optimal allocations and sizing of capacitors in various distribution systems. First the most candidate buses for installing capacitors are suggested using Power Loss Index (PLI). Then the proposed FPA is employed to deduce the size of capacitors and their locations from the elected buses. The objective function is designed to reduce the total cost and consequently to increase the net saving per year. The proposed algorithm is tested on 15, 69 and 118-bus radial distribution systems. The obtained results via the proposed algorithm are compared with other algorithms like Genetic Algorithm (GA), Particle Swarm Optimization (PSO), Plant Growth Simulation Algorithm (PGSA), Direct Search Algorithm (DSA), Teaching Learning-Based Optimization (TLBO), Cuckoo Search Algorithm (CSA), Artificial Bee Colony (ABC) and Harmony Search Algorithm (HSA) to highlight the benefits of the proposed algorithm. Moreover, the results are introduced to verify the effectiveness of the suggested algorithm to minimize the losses and total cost and to enhance the voltage profile and net saving for various distribution systems.

Effects of oxygen enriched combustion on pollution and performance characteristics of a diesel engine

Abstract: Oxygen enriched combustion is one of the attractive combustion technologies to control pollution and improve combustion in diesel engines. An experimental test was conducted on a single cylinder direct injection diesel engine to study the impact of oxygen enrichment on pollution and performance parameters by increasing the oxygen concentration of intake air from 21 to 27% by volume. The tests results show that the combustion process was improved as there is an increase in thermal efficiency of 4 to 8 percent and decrease in brake specific fuel consumption of 5 to 12 percent. There is also a substantial decrease in unburned hydro carbon, carbon mono-oxide and smoke density levels to the maximum of 40, 55 and 60 percent respectively. However, there is a considerable increase in nitrogen oxide emissions due to increased combustion temperature and extra oxygen available which needs to be addressed.

Variable viscosity and MHD flow in Casson fluid with Cattaneo–Christov heat flux model: Using Keller box method

Abstract: This article presents a numerical investigation of MHD flow of Casson fluid model with variable viscosity towards a stretching sheet with variable thickness. Cattaneo–Christov heat flux model is used instead of Fourier’s law to explore the heat transfer characteristics. The governing partial differential equations are transformed into nonlinear ordinary differential equations by using suitable similarity transformations. These equations are solved by using a numerical technique, known as Keller box method. The relevant physical parameters appearing in velocity and temperature distributions are analyzed and discussed through graphs. In order to check the accuracy of the method comparison has been made with some previous published results.

Methods of synthesis and performance improvement of lithium iron phosphate for high rate Li-ion batteries: A review

Abstract: Lithium ion battery technology has the potential to meet the requirements of high energy density and high power density applications. A continuous search for novel materials is pursued continually to exploit the latent potential of this technology. In this review paper, methods for preparation of Lithium Iron Phosphate are discussed which include solid state and solution based synthesis routes. The methods to improve the electrochemical performance of lithium iron phosphate are presented in detail.

An improved energy aware distributed unequal clustering protocol for heterogeneous wireless sensor networks

Abstract: In this paper, an improved version of the energy aware distributed unequal clustering protocol (EADUC) is projected. The EADUC protocol is commonly used for solving energy hole problem in multi-hop wireless sensor networks. In the EADUC, location of base station and residual energy are given importance as clustering parameters. Based on these parameters, different competition radii are assigned to nodes. Herein, a new approach has been proposed to improve the working of EADUC, by electing cluster heads considering number of nodes in the neighborhood in addition to the above two parameters. The inclusion of the neighborhood information for computation of the competition radii provides better balancing of energy in comparison with the existing approach. Furthermore, for the selection of next hop node, the relay metric is defined directly in terms of energy expense instead of only the distance information used in the EADUC and the data transmission phase has been extended in every round by performing the data collection number of times through use of major slots and mini-slots. The methodology used is of retaining the same clusters for a few rounds and is effective in reducing the clustering overhead. The performance of the proposed protocol has been evaluated under three different scenarios and compared with existing protocols through simulations. The results show that the proposed scheme outperforms the existing protocols in terms of network lifetime in all the scenarios.

An experimental investigation of shell and tube latent heat storage for solar dryer using paraffin wax as heat storage material

Abstract: In the presented study the shell and tube type latent heat storage (LHS) has been designed for solar dryer and paraffin wax is used as heat storage material. In the first part of the study, the thermal and heat transfer characteristics of the latent heat storage system have been evaluated during charging and discharging process using air as heat transfer fluid (HTF). In the last section of the study the effectiveness of the use of an LHS for drying of food product and also on the drying kinetics of a food product has been determined. A series of experiments were conducted to study the effects of flow rate and temperature of HTF on the charging and discharging process of LHS. The temperature distribution along the radial and longitudinal directions was obtained at different time during charging process to analyze the heat transfer phenomenon in the LHS. Thermal performance of the system is evaluated in terms of cumulative energy charged and discharged, during the charging and discharging process of LHS, respectively. Experimental results show that the LHS is suitable to supply the hot air for drying of food product during non-sunshine hours or when the intensity of solar energy is very low. Temperature gain of air in the range of 17 °C to 5 °C for approximately 10 hrs duration was achieved during discharging of LHS.

Estimation of solar radiation and optimum tilt angles for south-facing surfaces in Humid Subtropical Climatic Region of India

Abstract: In the present work, availability of solar radiation for south-facing flat surfaces in Humid Subtropical Climatic Region of India has been estimated. Measurements of global and diffuse solar radiation for Aligarh (27.89°N, 78.08°E) which lies in the Humid Subtropical Climatic Region were performed for over a period of three years. Monthly, seasonal and annual optimum tilt angles were estimated. Comparison of total incident solar radiation was performed between Aligarh and New Delhi (Capital of India, 28.61°N, 77.20°E). Annual optimum tilt angle for Aligarh and New Delhi was found as 27.62° and 27.95° respectively (close to the latitude of the respective location). Estimated gains in annual average solar radiation (based on monthly, seasonal and annual optimum tilt angles) in comparison to a horizontal surface were 12.92%, 11.61% and 6.51% (for Aligarh) and 13.13%, 11.80% and 7.58% (for New Delhi) respectively. A loss of 1.16% and 5.68% energy (for Aligarh) and 1.18% and 4.91% (for New Delhi) were estimated with surface at seasonal and annual optimum tilt angles respectively compared to a surface at monthly optimum tilt angle. Based on the study, it was recommended that the inclined surface must be tilted on monthly or seasonal optimum tilt angle for better utilization of solar energy.

Numerical study on flow separation in 90° pipe bend under high Reynolds number by k-ε modelling

Abstract: The present paper makes an effort to find the flow separation characteristics under high Reynolds number in pipe bends. Single phase turbulent flow through pipe bends is investigated using k-e turbulence model. After the validation of present model against existing experimental results, a detailed study has been performed to study the influence of Reynolds number on flow separation and reattachment. The separation region and the velocity field of the primary and the secondary flows in different sections have been illustrated. Numerical results show that flow separation can be clearly visualized for bend with low curvature ratio. Distributions of the velocity vector show the secondary motion clearly induced by the movement of fluid from inner to outer wall of the bend leading to flow separation. This paper provides numerical results to understand the flow characteristics of fluid flow in 90° bend pipe.

A novel symbiotic organisms search algorithm for optimal power flow of power system with FACTS devices

Abstract: In this paper, symbiotic organisms search (SOS) algorithm is proposed for the solution of optimal power flow (OPF) problem of power system equipped with flexible ac transmission systems (FACTS) devices. Inspired by interaction between organisms in ecosystem, SOS algorithm is a recent population based algorithm which does not require any algorithm specific control parameters unlike other algorithms. The performance of the proposed SOS algorithm is tested on the modified IEEE-30 bus and IEEE-57 bus test systems incorporating two types of FACTS devices, namely, thyristor controlled series capacitor and thyristor controlled phase shifter at fixed locations. The OPF problem of the present work is formulated with four different objective functions viz. (a) fuel cost minimization, (b) transmission active power loss minimization, (c) emission reduction and (d) minimization of combined economic and environmental cost. The simulation results exhibit the potential of the proposed SOS algorithm and demonstrate its effectiveness for solving the OPF problem of power system incorporating FACTS devices over the other evolutionary optimization techniques that surfaced in the recent state-of-the-art literature.

A quadrilateral inverse-shell element with drilling degrees of freedom for shape sensing and structural health monitoring

Abstract: The inverse Finite Element Method (iFEM) is a state-of-the-art methodology originally introduced by Tessler and Spangler for real-time reconstruction of full-field structural displacements in plate and shell structures that are instrumented by strain sensors. This inverse problem is commonly known as shape sensing. In this effort, a new four-node quadrilateral inverse-shell element, iQS4, is developed that expands the library of existing iFEM-based elements. This new element includes hierarchical drilling rotation degrees-of-freedom (DOF) and further extends the practical usefulness of iFEM for shape sensing analysis of large-scale structures. The iFEM/iQS4 formulation is derived from a weighted-least-squares functional that has Mindlin theory as its kinematic framework. Two validation problems, (1) a cantilevered plate under static transverse force near the free tip, and (2) a short cantilever beam under shear loading, are solved and discussed in detail. Following the validation cases, the applicability of the iQS4 element to more complex structures is demonstrated by the analysis of a thin-walled cylinder. For this problem, the effects of noisy strain measurements on the accuracy of the iFEM solution are examined using strain measurements that involve five and ten percent random noise, respectively. Finally, the effect of sensor locations, number of sensors, the discretization of the geometry, and the influence of noise on the strain measurements are assessed with respect to the solution accuracy.

Unsteady MHD radiative flow and heat transfer of a dusty nanofluid over an exponentially stretching surface

Abstract: We analyzed the unsteady magnetohydrodynamic radiative flow and heat transfer characteristics of a dusty nanofluid over an exponentially permeable stretching surface in presence of volume fraction of dust and nano particles We considered two types of nanofluids namely Cu-water and CuO-water embedded with conducting dust particles The governing equations are transformed into nonlinear ordinary differential equations by using similarity transformation and solved numerically using Runge–Kutta based shooting technique The effects of non-dimensional governing parameters namely magneticfield parameter, mass concentration of dust particles, fluid particle interaction parameter, volume fraction of dust particles, volume fraction of nano particles, unsteadiness parameter, exponential parameter, radiation parameter and suction/injection parameter on velocity profiles for fluid phase, dust phase and temperature profiles are discussed and presented through graphs Also, friction factor and Nusselt numbers are discussed and presented for two dusty nanofluids separately Comparisons of the present study were made with existing studies under some special assumptions The present results have an excellent agreement with existing studies Results indicated that the enhancement in fluid particle interaction increases the heat transfer rate and depreciates the wall friction Also, radiation parameter has the tendency to increase the temperature profiles of the dusty nanofluid

Bat algorithm optimized fuzzy PD based speed controller for brushless direct current motor

Abstract: In this paper, design of fuzzy proportional derivative controller and fuzzy proportional derivative integral controller for speed control of brushless direct current drive has been presented. Optimization of the above controllers design is carried out using nature inspired optimization algorithms such as particle swarm, cuckoo search, and bat algorithms. Time domain specifications such as overshoot, undershoot, settling time, recovery time, and steady state error and performance indices such as root mean squared error, integral of absolute error, integral of time multiplied absolute error and integral of squared error are measured and compared for the above controllers under different operating conditions such as varying set speed and load disturbance conditions. The precise investigation through simulation is performed using simulink toolbox. From the simulation test results, it is evident that bat optimized fuzzy proportional derivative controller has superior performance than the other controllers considered. Experimental test results have also been taken and analyzed for the optimal controller identified through simulation.

Fast vector quantization using a Bat algorithm for image compression

Abstract: Linde–Buzo–Gray (LBG), a traditional method of vector quantization (VQ) generates a local optimal codebook which results in lower PSNR value. The performance of vector quantization (VQ) depends on the appropriate codebook, so researchers proposed optimization techniques for global codebook generation. Particle swarm optimization (PSO) and Firefly algorithm (FA) generate an efficient codebook, but undergoes instability in convergence when particle velocity is high and non-availability of brighter fireflies in the search space respectively. In this paper, we propose a new algorithm called BA-LBG which uses Bat Algorithm on initial solution of LBG. It produces an efficient codebook with less computational time and results very good PSNR due to its automatic zooming feature using adjustable pulse emission rate and loudness of bats. From the results, we observed that BA-LBG has high PSNR compared to LBG, PSO-LBG, Quantum PSO-LBG, HBMO-LBG and FA-LBG, and its average convergence speed is 1.841 times faster than HBMO-LBG and FA-LBG but no significance difference with PSO.

Influence of CaCO3, Al2O3, and TiO2 microfillers on physico-mechanical properties of Luffa cylindrica/polyester composites

Abstract: The development of natural fibre reinforced polymer composites has gained popularity in many applications due to their environment friendly characteristics over the synthetic fibre based polymer composites. This paper describes the fabrication and physical, mechanical, three-body abrasive wear and water absorption behaviour of Luffa fibre reinforced polyester composites with and without addition of micro-fillers of Al 2 O 3 , CaCO 3 and TiO 2 . The ranking of the composite materials has been made by using Technique for order preference by similarity to ideal solution (TOPSIS) method with output parameters of their physical, mechanical and abrasive wear and water absorption attributes. The addition of microfillers has enhanced greatly the physical and mechanical properties of Luffa -fibre based composites. The addition of microfillers has influenced the physico-mechanical properties of Luffa -fibre based polyester composites in descending order of CaCO 3 , Al 2 O 3 , and TiO 2 .

Optimal setting of FACTS devices for voltage stability improvement using PSO adaptive GSA hybrid algorithm

Abstract: This paper presents a novel technique for optimizing the FACTS devices, so as to maintain the voltage stability in the power transmission systems. Here, the particle swarm optimization algorithm (PSO) and the adaptive gravitational search algorithm (GSA) technique are proposed for improving the voltage stability of the power transmission systems. In the proposed approach, the PSO algorithm is used for optimizing the gravitational constant and to improve the searching performance of the GSA. Using the proposed technique, the optimal settings of the FACTS devices are determined. The proposed algorithm is an effective method for finding out the optimal location and the sizing of the FACTS controllers. The optimal locations and the power ratings of the FACTS devices are determined based on the voltage collapse rating as well as the power loss of the system. Here, two FACTS devices are used to evaluate the performance of the proposed algorithm, namely, the unified power flow controller (UPFC) and the interline power flow controller (IPFC). The Newton–Raphson load flow study is used for analyzing the power flow in the transmission system. From the power flow analysis, bus voltages, active power, reactive power, and power loss of the transmission systems are determined. Then, the voltage stability is enhanced while satisfying a given set of operating and physical constraints. The proposed technique is implemented in the MATLAB platform and consequently, its performance is evaluated and compared with the existing GA based GSA hybrid technique. The performance of the proposed technique is tested with the benchmark system of IEEE 30 bus using two FACTS devices such as, the UPFC and the IPFC.

Reconciling viability and cost-effective shape memory alloy options – A review of copper and iron based shape memory metallic systems

Abstract: Shape memory alloys (SMAs) are group of alloys that display anthropomorphic characteristics. These alloys recover their pre-deformed morphology when heated above their transition temperatures after being deformed in their lower temperature phase (martensitic phase). This unique material behavior is explored in industrial and technological applications where capacity for strain recovery is a key design parameter. Copper and iron based SMAs are largely viewed as potential cost effective substitute to Ni–Ti SMAs judging from their promising shape memory properties, damping capacity and other functional properties. Despite their outstanding potentials, the susceptibility of copper based SMAS to phase stabilization, transition hysteresis, aging and brittleness creates doubt on the possibility of transiting from the realm of potential to functional long term use in engineering applications. On the other hand the low percentage shape recovery in the Fe based SMAs also creates a gap between the theory and potential use of these alloys. This paper takes a critical look at the science of shape memory phenomena as applicable to copper and iron based SMA systems. It also covers the limitations of these systems, the effect of processing parameters on these alloys, proposed solutions to limitations associated with this group of shape memory alloys and thoughts for future consideration.

Free convection in a square cavity filled by a porous medium saturated by a nanofluid: Viscous dissipation and radiation effects

Abstract: The influence of the viscous dissipation and radiation effects on the natural convection heat transfer in a square cavity filled with porous media saturated with a nanofluid is studied. The vertical walls of the cavity are subject to finite temperature difference while the top and bottom walls of the cavity are insulated. The Buongiorno's nanofluid model, incorporating the Brownian motion and thermophoresis effects, is employed. The governing equations, in nondimensional form, are written in the weak form and solved using the finite element method. The influences of viscous dissipation and radiation effects on the concentration distribution of nanoparticles are discussed. The average and local Nusselt numbers are reported for various values of viscous dissipation (Eckert number) and radiation effects. The results show that the Nusselt numbers at the hot and cold walls are not equal due to the presence of viscous dissipation effects. The raise of Eckert number decreases the Nusselt number at hot wall, but it increases the Nusselt number at the cold wall. It is also found that the increase of Lewis number enhances the heat transfer in the cavity.

Empirical investigation to explore factors that achieve high quality of mobile learning system based on students’ perspectives

Abstract: This study presents three frameworks for mobile learning system based on quality factors derived from the updated DeLone and McLean information system success model. This study used the questionnaire as a quantitative method to explore quality factors for mobile learning system based on perspectives of 392 students. This study opens future work for using the identified quality factors as guidelines for researchers and designers to design and develop mobile learning applications.

Flower pollination algorithm to solve combined economic and emission dispatch problems

Abstract: Economic Load Dispatch (ELD) is the process of allocating the required load between the available generation units such that the cost of operation is minimized. The ELD problem is formulated as a nonlinear constrained optimization problem with both equality and inequality constraints. The dual-objective Combined Economic Emission Dispatch (CEED) problem is considering the environmental impacts that accumulated from emission of gaseous pollutants of fossil-fuelled power plants. In this paper, an implementation of Flower Pollination Algorithm (FPA) to solve ELD and CEED problems in power systems is discussed. Results obtained by the proposed FPA are compared with other optimization algorithms for various power systems. The results introduced in this paper show that the proposed FPA outlasts other techniques even for large scale power system considering valve point effect in terms of total cost and computational time.