Universiti Putra Malaysia
Download Latest Complete Journal - JST Vol. 25 (4) Oct. 2017
Foreword by the Chief Executive Editor
No.ArticlesDownloads
1
Full Article
(Downloads: 66)
Abstract (Viewed: 6)Non-invasive imaging modalities for wound assessment have become increasingly popular over the past two decades. The wounds can be developed superficially or from within deep tissues, depending on the nature of the dominant risk factors. Developing a reproducible quantitative method to assess wound-healing status has demonstrated to be a convoluted task. Advances in High-Frequency Ultrasound (HFU) skin scanners have expanded their application as they are cost-effective and reproducible diagnostic tools in dermatology, including for the measurement of skin thickness, the assessment of skin tumours, the estimation of the volume of melanoma and non-melanoma skin cancers, the visualisation of skin structure and the monitoring of the healing of acute and chronic wounds. Previous studies have revealed that HFU images carry dominant parameters and depict the phenomena occurring within deep tissue layers during the wound-healing process. However, the investigations have mostly focussed on the validation of HFU images, and few studies have utilised HFU imaging in quantitative assessment of wound generation and healing. This paper is an introductory review of the important studies proposed by the researchers in the context of wound assessment. The principles of dermasonography are briefly explained, followed by a review of the relevant literature that investigated the wound-healing process and tissue structures within the wound using HFU imaging. Wound assessment, High-frequency ultrasound, Dermatologic sonography, Wound healing
2
Full Article
(Downloads: 23)
Abstract (Viewed: 1)The enormous attention and interest by both academics and industrial field for greener, biodegradable and renewable materials implicate a persuasive trends towards the encroachment of nano-materials science and technology in the polymer composite field. Nanocomposites creates high impacts on the development of nano materials with advanced features to solve potential risks with their wider industrial applications. Nano fibres are highly engineered fibres with diameters less than 100 nm that offer several advantages over conventional fibres. One dimensional (1D) nanostructure fillers such as carbon nanofibre and cellulose nanofibre are the most common, promising and unique for developing multifunctional nanocomposites with better properties and extensive applications compared to micro size fibres. Nano fibre technology brings revolution by providing products that are completely safe, truly greener, reliable and environmentally friendly for industries, researchers and users. This review article is intended to present valuable literature data on research and trend in the fields of carbon and cellulose nano fiber, nanocomposites with specific focus on various applications for a sustainable and greener environment.Nano filler, nanofibre, nanofibres processing, carbon nanofibre, cellulosic nanofibre, nanocomposites
3
Full Article
(Downloads: 15)
Abstract (Viewed: 1)Dispersibility of nanoparticles is the key problem in nanotechnology industries, and thus warrants attention on the techniques of dispersion. This review paper presents dispersibility of treated nanoparticles in polymer resin. Dispersibility of nanoparticles in polymer media is crucial in order to enhance the mechanical and thermal properties of nanocomposite. This paper concentrates on several preparations on how to incorporate nanoparticles in polymer to overcome the problem described in this review. A few techniques are discussed in this paper such as by using ultra sonication or even directly mixing nanoparticles into polymer matrix. Dispersion, nanoparticles, polymer
4
Full Article
(Downloads: 14)
Abstract (Viewed: 1)The growing interest, environmental consciousness and high performance demands on engineering have led to extensive research and development of new and improved materials. Among the most commonly used natural fibres are kenaf, oil palm, sugar palm, pineapple leaf fibre, flax, hemp, sisal, coir and jute. These fibres are used to reinforce thermoplastic polymer matrices such as polystyrene (PS), polypropylene (PP), polyethylene (PE) and polyvinyl chloride (PVC). Meanwhile, phenolic, unsaturated polyester vinyl ester and epoxy resin are for thermosetting polymer matrices. The objective of this paper is to solicit works that cover major class of natural fibres, thermosetting polymers matrices, which detail about unsaturated polyester resin and hybrid biocomposites industry. Natural fibres, modification, polymer matrices, unsaturated polyester, hybrid biocomposites
5
Full Article
(Downloads: 15)
Abstract (Viewed: 1)Environmental issues have motivated researchers to replace synthetic fibres with natural fibres in the fabrication of polymer composites. However, natural fibres demonstrate weak mechanical or thermal properties which limit their different applications. Researchers have suggested fabrication of hybrid composites in order to improve the mechanical and thermal properties of natural fibre-based composites. Hybrid composites are made up by two or more fibres in one matrix or two polymer blends and with one natural fibre reinforcement. By hybridising one natural fibre with another natural fibre/synthetic fibre in one matrix, the resulting composite is a unique product (hybrid composites) that displays better mechanical and thermal properties in comparison with individual fibre-reinforced polymer composites. The advantages of developing hybrid composites are that they are more reliable for different applications and more environmental friendly. In this review paper, we present some recently published works related to mechanical and thermal properties of natural/natural fibres, and natural/synthetic fibre-based hybrid composites. Hybrid composites are one of the emerging fields in material science which has attracted attention for their different engineering applications. Fibres, composites, hybrid composites, mechanical properties, thermal properties
6
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(Downloads: 23)
Abstract (Viewed: 4)Older adults are at risk of osteoporotic fractures. Osteoporotic vertebral fractures are associated with a reduced cross-sectional area and muscle strength of the back extensor muscles, increased intramuscular fat infiltration and thoracic and lumbar curvature alterations. This study proposed a protocol to examine in more detail the contributions of altered spinal morphological, physical performance and biochemical markers to the risk of developing osteoporotic vertebral fractures. In this cross-sectional study, we plan to recruit 100 adults aged 50 years and above from an orthopaedic clinic, Hospital CanselorTuankuMuhriz, UniversitiKebangsaan Malaysia. The fracture prediction tool (FRAX) will be used to categorise high and low risk groups. Back muscle strength will be quantified using a load cell system. Thoracolumbar curvatures will be examined using an electromagnetic tracking system and intramuscular fat infiltration in the lumbar muscles will be measured using Magnetic Resonance Imaging. The Short Physical Performance Battery and JAMA dynamometer will quantify physical performance and the European Quality of Life Questionnaire will be used to assess self-perceived quality of life. Biochemical markers of serum C terminal telopeptide and N terminal propeptide of type I procollagen will be assessed using an enzyme-linked immunosorbent assays kit. A spine-specific model using regression analysis will be developed to predict osteoporotic vertebral fractures using the measured parameters in the present study.Biochemical markers, intramuscular fat infiltration, osteoporotic fracture, physical performance, spinal morphology, quality of life
7
Full Article
(Downloads: 15)
Abstract (Viewed: 1)This study presents an empirical approach for estimating sea surface salinity (SSS) from remote sensing of ocean colour. The analysis is based on two important empirical relationships of in-water optical properties. The first involves the behaviour of the optical properties of coloured dissolved organic matter (CDOM) under conservative mixing along the salinity gradient. The second is the tight relationship between CDOM and water-leaving radiance. Our results showed that CDOM absorption coefficients in ultra-violet wavelengths (350 and 380 nm) can be best estimated using the blue-green band ratio Rrs(412/547) with a R2 value of 0.87. It was also found that the absorption coefficient of CDOM in the study area was tightly correlated with the salinity (R2≈0.83); however, the data indicate that this relationship may be dependent on freshwater flow and the intensity of vertical mixing. During the wet and well-mixed season (Northeast monsoon), CDOM was almost conservative with salinity but tended to behave non-conservatively during the dry and stratified season (Southwest monsoon). These resulting empirical relationships allow CDOM and salinity in the study area to be estimated from satellite ocean colour data. Validation using independent datasets showed that the algorithms for CDOM and salinity perform relatively well with the RMS error of 0.04 m-1 and 0.30`, respectively, over a range of salinity from 30` to 33`. The ability of the algorithm to predict salinity as those presented in this study can be further improved using more independent tests with in-situ and satellite bio-optical measurements. Salinity, ocean colour, empirical algorithms, coloured dissolved organic matter, South China Sea
8
Full Article
(Downloads: 10)
Abstract (Viewed: 1)Circular data analysis is a particular branch of statistics that sits somewhere between the analysis of linear data and the analysis of spherical data. Circular data are used in many scientific fields. The efficiency of the statistical methods that are applied depends on the accuracy of the data in the study. However, circular data may have outliers that cannot be deleted. If this is the case, we have two ways to avoid the effect of outliers. First, we can apply robust methods for statistical estimations. Second, we can adjust the outliers using the other clean data points in the dataset. In this paper, we focus on adjusting outliers in circular data using the circular distance between the circular data points and the circular mean direction. The proposed procedure is tested by applying it to a simulation study and to real data sets. The results show that the proposed procedure can adjust outliers according to the measures used in the paper. Directional data, circular data, circular mean, circular distance, outlier
9
Full Article
(Downloads: 12)
Abstract (Viewed: 2)Microalgae (MA) has huge potential use as feedstock for producing biodiesel. However, harvesting of MA is still a major obstacle. This paper presents a performance evaluation of flocculation and membrane processes for harvesting of MA. The experiments were conducted using Chlamydomonas sp., which was cultured in an open pond. Chitosan was used as flocculants, while microfiltration and ultrafiltration membrane were used during filtration using membrane. The results showed that the harvesting efficiency of MA using flocculation was within the range of 74.2-81.2%. The harvesting of MA using membrane processes resulted in efficiency within the range of 86.8-91.1% and around 99% for MF and UF, respectively. The harvesting efficiency of the combination of flocculation and MF was comparable with UF only i.e. ˜99%. The performance of flocculation process was influenced by the concentration of the flocculant, the agitation rate and the agitation time. Flocculation installed before MF membrane improved the resulting normalised flux of microfiltration membrane as well as increased harvesting efficiency. Microalgae harvesting, membrane filtration, flocculation, fouling, microfiltration, ultrafiltration
10
Full Article
(Downloads: 10)
Abstract (Viewed: 1)The artificial immune system (AIS) algorithm is a heuristic technique inspired by the biological immune system. The biological immune system has been proven to be a robust system that defends our body from any pathogen attacks. This paper presents a hybrid paradigm by implementing the Hopfield neural network integrated with enhanced AIS for solving a 3-Satisfiability (3-SAT) problem. Fundamentally, a 3-Satisfiability problem is used as an ideal optimisation problem by neural network practitioners in their research. The core impetus of this study was to compare the performance of artificial immune system (AIS) algorithm and brute-force search (BFS) algorithm in doing 3-SAT logic programming. Microsoft Visual C++ 2013 was used as a dynamic platform for training, simulating and testing of the network. We restricted our analysis to 3-Satisfiability (3-SAT) clauses. The performances of both paradigms were analysed according to the following measures, namely, global minima ratio, global Hamming distance, fitness landscape value and computational time. The experimental results successfully depicted the robustness of the AIS compared to the BFS algorithm. The work presented here has profound implications for future studies of AIS to solve more complicated NP problems. Artificial immune system algorithm, brute-force search algorithm, Hopfield network, 3-Satisfiability, logic programming
11
Full Article
(Downloads: 13)
Abstract (Viewed: 2)The cart-and-pendulum system is a highly nonlinear and under-actuated system that is a great source of interest and motivation for researchers all over the world. There are various configurations of the cart-and-pendulum system that finds wide applications in areas of manufacturing, robotics and control. This paper presents an offline mode control of the Flexible Inverted Pendulum (FIP), which is an extended version of conventional rigid-link pendulum system. The flexibility induced in the pole gives an additional degree of freedom to the system. The nonlinear differential equations were derived using Newton's second law of motion. The study inculcates Fuzzy-based Adaptive Neuro Fuzzy Inference System (ANFIS) controllers for achieving the desired objective. The performance of controllers was measured and compared in a Matlab-Simulink environment. The study considered the effect of friction during motion of the proposed system. The results clearly showed that the ANFIS controller effectively mimics and optimises the behaviour of the Fuzzy controller. The number of Fuzzy rules were also significantly reduced using the ANFIS techniques. FIP, Fuzzy logic, ANFIS, membership function, Matlab-Simulink
12
Full Article
(Downloads: 20)
Abstract (Viewed: 4)Glycerolysis can be a useful alternative for lowering free fatty acid (FFA) content present in waste cooking oil. In the present work, the effect of mass ratio of co-solvent hexane to oil on glycerolysis of waste cooking oil was investigated to enhance the miscibility of the oil and glycerol phases. The experimental results showed that the addition of hexane as co-solvent affected the glycerolysis reaction rate. However, a suitable amount of co-solvent must be added to achieve an optimum of FFA conversion. The use of 0.125:1 of mass ratio of co-solvent to oil leads to higher rate constant of approximately two times compared to glycerolysis without a co-solvent. The glycerolysis reduces the FFA content, peroxide and saponification values of oil; however, it does not change the density and kinematic viscosity as well as the fatty acid composition of oil. Co-solvent, free fatty acid, glycerolysis, waste cooking oil
13
Full Article
(Downloads: 15)
Abstract (Viewed: 2)Pulse Width Modulation (PWM) techniques are widely used in PV-operated, inverter-controlled AC motor drives. The frequency and magnitude of the voltage applied to the motors are controlled using PWM-based PV-operated drives. PWM is the standard approach for operating the inverter in order to generate high quality output voltage. In past decades, the performance of the PWM techniques were determined using power factor, transient response and efficiency, which play a major role in the regulation of PWM inverters so that a dynamic response can be obtained in grid-connected facilities. Conventional PWM such as PWM, Sinusoidal PWM (SPWM) and Space-Vector PWM (SVPWM) perform satisfactorily in terms of average switching frequency requirement, switching losses and DC bus current ripple, with respect to driving AC induction motors. However, they have poor harmonic characteristics leading to degradation of torque and speed profile of AC motor. In order to overcome the aforementioned drawback, the proposed work investigated the harmonic contents of the mentioned PWM techniques, torque and speed profiles with regards to the AC drive applications. The simulation study revealed that the 2nd, 5th and 8th order (negative sequence) harmonics introduced more problems related to torque and the 4th and 7th (positive sequence) harmonics created more heating problems. Further, the 3rd, 6th and 9th (zero sequence) harmonics caused heat due to addition of voltage and/or current in a neutral conductor. The main objective of the paper was to compare the three well established PWM methods with respect to the AC drive application in the context of effect of harmonics, by analysing their ease of implementation, output harmonic spectra voltage and Total Harmonic Distortion (THD). AC motor, pulse width modulation, speed, torque, total harmonic distortion
14
Full Article
(Downloads: 15)
Abstract (Viewed: 1)This study was attempted to evaluate infiltration methods based on irrigation advance for furrow irrigation. Irrigation advance data were collected at Latif farm, Sindh Agriculture University, Tandojam for three irrigation events. To achieve the objectives of the study two different methods viz. Upadhyaya and Raghuwanshi and Valiantzas one-point, were tested against the two-point method. Evaluation of employed methods was undertaken to know the best method for the prediction of cumulative infiltration and advance. The results revealed that Upadhyaya and Raghuwanshi (ME=-5.25) and Valiantzas one-point (ME=-0.99) are unsuitable for silt loam soil with their original constants as these methods show great scatter when compared with reference method and measured data. Thus, it is suggested that these methods must be evaluated before use. Infiltration characteristics, furrow irrigation, advance, two-point method, Upadhyaya and Raghuwanshi, Valiantzas one-point, Tandojam
15
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(Downloads: 10)
Abstract (Viewed: 1)Modification of thermoplastic starch with other natural polymer is a promising research since the combination of both material will produce a fully green polymer with modified properties. The aim of this paper is to investigate the effects of agar on physical properties of thermoplastic sugar palm starch (SPS). Various types of thermoplasctic SPS based polymer were prepared by blending SPS and agar with the presence of glycerol as a plasticiser. Agar with various contents (10, 20, 30, and 40 wt%) were mixed with thermoplastic SPS via melt mixing before compression moulded into 3 mm mould plate. The prepared laminates were characterised for the moisture content, density, water absorption, thickness swelling and water solubility. Results showed that incorporation of agar has slightly increased the moisture content and water absorption capacity of the blends. Slight increment in thickness swelling was observed for thermoplastic SPS after incorporation with agar (40 wt%). Water solubility of thermoplastic SPS was slightly increased with incorporation of agar (40 wt%). Similar density was recorded for all ratios of agar, which indicated that the incorporation of agar did not influence the density of thermoplastic SPS. In conclusion, the incorporation of agar has slightly increased the hydrophilic behaviour of thermoplastic SPS. Agar, starch, thermoplastic, thickness swelling, water absorption
16
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(Downloads: 9)
Abstract (Viewed: 1)The formation of intermetallic compound (IMC) layer at the interfaces of pad finishes has been studied. The growth of IMC layer as a reflow process and its properties were also discussed. In this study, solder alloy SAC237 (Sn: 99 wt.%, Ag: 0.3 wt.%, Cu: 0.7 wt.%), reinforced with 0.01 wt.% Multi-Walled Carbon Nanotubes (MWCNTs), was mixed to form a composite solder paste and soldered on Electroless Nickel Immersion Gold (ENIG) and Immersion Tin (ImSn) pad finishes. Reflow process was conducted in oven with specific reflow profile. The growth and properties of IMC layer were analysed using optical microscope with image analyser. Results showed that the thickness of IMC layer for ENIG and ImSn were 1.49 and 2.51 ┬Ám, respectively. Floating IMC and voids within the solder bulk and IMC layer were also identified in the samples. In addition, the measured wetting angle for ENIG and ImSn were 16.21° and 34.32°, respectively. As reflow, ENIG, SAC237, immersion tin, intermetallic compound, multi-walled carbon nanotubes
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(Downloads: 17)
Abstract (Viewed: 1)In the recent years, electronic packaging provides significant research and development challenges across multiple disciplines such as performance, materials, reliability, thermals and interconnections. New technologies and techniques frequently adopted can be implemented in soldering alloys of semiconductor sectors in terms of optimisation. Wetting contact angle or wettability of solder alloys is one of the important factors which has got the attention of scholars. Hence in this study, due to the remarkable similarity over classical solder alloys (Pb-Sn), Bi-Ag solder was investigated. Data were collected through the effects of aging time variation and different weight percentages of Ag in solder alloys. The contact angle of the alloys with Cu plate was measured by optical microscopy. Artificial neural networks (ANNs) were applied on the measured datasets to develop a numerical model for further simulation. Results of the experiments and simulations showed that the coefficient of determination (R2) is around 0.97, which signifies that the ANN set up is appropriate for the evaluation. Artificial neural networks, Bi-Ag alloy, lead free soldering alloy, wetting angle
18
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(Downloads: 9)
Abstract (Viewed: 1)This research investigates the strength of kenaf or epoxy composite filled with mesoporous silica and studies the hybrid effects between mesoporous silica orkenaf in epoxy matrix. The volume of kenaf woven mat is maintained constantly at 7.2vol%, whereas proportion of epoxy is varied with inclusion of mesoporous silica and silicon, keeping constant the volume of the composite at 67.5cm3. The proportion of mesoporous silica is altered from 0.5vol%, 1.0vol%, 3.0vol% and 5.0vol%, while silicon is kept constant at 3.0vol%. A total of 11 specimens were produced, each with its distinctive composition and mechanical strengths. Variation of fillers composition affects the mechanical strengths of the composite. SEM analysis shows that epoxy bonds well with silicon, kenaf and mesoporous silica. Some de-bonding among the components is observed within the composite although there is also some tearing of fibres and impregnation of epoxy within fibre, proving that the components have good interaction and do not act individually. Flexural test shows that mesoporous silica improves the flexural strength of the composite, where the highest value is 35.14MPa, obtained at 5.0vol% Mesoporous Silica in Kenaf/Epoxy (SiaK/Ep). It also improves the flexural modulus, where the highest value is 1569.48MPa, obtained at 3.0vol% SiaK/Ep. DMA result reveals that adding mesoporous silica increases the Tg of the composite produced. Highest Tg is obtained at 0.5vol% Mesoporous Silica in Kenaf/Epoxy modofied Silicon (SiaK/Ep-Si) with the value of 87.54°C. Epoxy, hybrid composite, kenaf, natural fibre reinforced polymer
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(Downloads: 9)
Abstract (Viewed: 1)Cellulose I can be irreversible transformed into cellulose II via mercerisation or regeneration treatments. In the past few decades, mercerisation was used mainly to improve fibre properties for textile industries. A few studies have focused on the effects of mercerisation treatment on the cellulose polymorph itself and after it was downscaled to nanosize. This study aims to characterise the micro size crystalline cellulose after complete polymorph conversion via mercerisation technique and investigate its effects on isolation to nanosize crystalline cellulose. A microcrystalline cellulose (MCC) was purchased and converted into cellulose II via mercerisation technique. Sulphuric acid hydrolysis was carried-out to produce nanocrystalline cellulose (NCC). The MCC and NCC of different polymorphs were then characterised and analysed for its crystallography, morphology, particles size distribution and thermal stability using wide-angle X-ray diffraction (WXRD), electron microscopes, dynamic light scattering analyser and thermogravimetric analyser, respectively. Both MCC and NCC fibres showed complete conversion of cellulose I to cellulose II and decrement of crystallinity index (CI). Electron micrographs revealed that both cellulose II polymorph fibres (MCC II and NCC II) were morphological affected. The analysis of size distribution and dimension measurement confirmed that mercerisation treatment causing increment in fibre diameter and shortened length. The thermal stability of both cellulose II polymorph fibres (MCC II and NCC II) was also found to be improved. Nanocrystalline cellulose, microcrystalline cellulose, mercerization, alkaline treatment, cellulose polymorph
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(Downloads: 10)
Abstract (Viewed: 2)The Stochastic Alpha Beta Rho (SABR) is a popular stochastic volatility model for pricing interest rate derivatives. In contrast to local volatility models, the SABR model correctly captures the movement of the volatility smile. The model's density can be approximated by the solution of a one-dimensional partial differential equation (pde). Solving for the density using the Crank-Nicolson discretisation results in loss of accuracy in computation of European option prices. This paper proposes a non-oscillatory scheme for approximating the density function using an exponential time integration scheme. The non-oscillatory property leads to an efficient scheme for option valuation via quadrature of the density function. Numerical examples illustrate that European option prices can be computed with high accuracy. CEV, exponential time integration, Quadrature, SABR, volatility smiles and skews
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(Downloads: 9)
Abstract (Viewed: 1)This paper presents a design of low power low voltage positive second generation current conveyor (CCII) which is based on Miller compensated Operational Transconductance Amplifier (OTA). The OTA realisation is carried out using low power techniques bulk-driven (BD) and bulk-driven quasi-floating gate (BDQFG) for a comparison of aforementioned techniques. The use of bulk-driven approach facilitates the proposed CCII design operable at sub-volt supply. Furthermore, CCII realisations using BD and BDQFG have been done so as to have a fair comparison of advantage of using BDQFG over BD in terms of improving transconductance and frequency response. The proposed CCII operates at 0.4V. The complete analysis has been carried out in 0.18 ?mCMOS technology with the help of HSpice simulator. Bandwidth, Bulk Driven, Current conveyor, Floating gate, Impedance, Quasi-floating gate
22
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(Downloads: 13)
Abstract (Viewed: 1)Satellite communication is an emerging field of communication. It is used for many applications, such as broadcasting, messaging, telephony, and for communication between military troops. The satellite communication is prone to impersonate attacks as the access to the satellite does not require a physical connection. Hence, there is a foremost need to restrict the access to only legitimate users. This study aims to solve achieve this. The proposed scheme is based on elliptic curve cryptography (ECC) and assures access to legitimate users only and also claims to be lightweight in working. The analysis indicates that the proposed technique is free from various attacks including internal and external attacks. Also, the performance analysis confirms the proposed authentication scheme as more reliable and robust against attacks compared with existing techniques. Authentication, elliptic curve cryptography, hash function, Kerberos, satellite communication
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(Downloads: 9)
Abstract (Viewed: 1)Confront exercise deals with the influence of parameters, such as polarity, electrode type, concentration of abrasive powder, peak current, voltage and duty cycle by using Taguchi's L36 mixed orthogonal array on M2 tool steel with 99% copper and powder metallurgy copper-titanium (Cu-Ti) by electric discharge machining (EDM) process with and without abrasive powder mixed dielectric for material removal rate (MRR), tool wear rate (TWR) and surface roughness (SR). The parameters affecting the MRR, TWR and SR should be recognised and optimised for desired results using Main effects plot for Means and analysis of variance (ANOVA). Grey relation analysis optimises the results by following normalised, dev. Seq. Δ and Grey relational coefficient Φ values to convert into single Grade. The confirmation experiment test can be done to formalise the present work with optimal set of parameters and Rank. Grey relation analysis found that the copper-titanium tool electrode gives better results with powder mixed dielectric and to meliorate machining performance and shows improvement in overall outcomes up to 17-27%. Scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) analysis are employed for the work surface quality assurance in this research. Abrasives, ANOVA, EDM, EDS, Grey relational analysis, Powder metallurgy, SEM
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(Downloads: 15)
Abstract (Viewed: 4)Heterogeneous networks continue to be operate thanks to the various services they offer, especially in terms of mobility, wide coverage and rapid deployment. However, quality of service (QoS) is a major challenge for these networks, which often consist of different technologies (WiMAX, WIFI, UMTS, LTE, etc.). This study measures and evaluates the behaviour of Web-based applications in a vertical handover context between 802.16e and 802.11e technologies, taking into account all possible QoS mechanisms. The evaluation scenarios were performed using OPNET Modeler. The applications used are: Dynamic web (HTTP + database) and mail flow. The evaluation criteria used are: TCP delay, HTTP load page delay, DB query delay, mail download and upload delay.802.16e, 802.11e, HTTP, OPNET Modeler, QoS, Vertical Handover; Web-Based
25
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(Downloads: 16)
Abstract (Viewed: 2)The satellite orbit determination approach involves a set of techniques which measure the satellite motion in terms of its velocity and position. In this paper, we have elaborated the method of determining an accurate ephemeris for an orbiting satellite which involves estimating the position and velocity of the satellite from a sequence of observations. To observe perturbations in the orbit due to different types of gravitational and non-gravitational effect, we have applied the prediction algorithm and analysed the changes in the Kepler's elements. Dynamic and static errors are the limiting factors for estimation techniques, such as the geo-potential model errors and atmospheric drag model errors, depending on the dynamic environment of the satellite. The proposed prediction model can help to prevent the loss of control over the satellite due to orbital variations. Atmospheric drag, Estimation techniques, Gauss theory, Inter Satellite Distance, Kalman filtering, Kepler elements, Non-gravitational forces
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(Downloads: 16)
Abstract (Viewed: 1)To ensure reliable and efficient operations of encryption and hash codes, a unique approach of formulating a security key from Deoxyribonucleic acid (DNA) of an individual is presented in this paper. The fusion of DNA sequence with Linear Congruential Generator (LCG) sequence ensures uniqueness in the keys generated and eradicates the problem of duplicate keys. The obtained key is significant due to its optimum length and robust algorithm. Simulation results reveal that keys produced thus pass the criteria of being random, by a significant coefficient value. Uniqueness is verified through avalanche test, which assures generation of a unique key every time. Authentication, Biometrics, Confidentiality, DNA, Linear Congruential Generator

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