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Kosmos
Astronomia Astrofizyka
Inne

Kultura
Sztuka dawna i współczesna, muzea i kolekcje

Metoda
Metodologia nauk, Matematyka, Filozofia, Miary i wagi, Pomiary

Materia
Substancje, reakcje, energia
Fizyka, chemia i inżynieria materiałowa

Człowiek
Antropologia kulturowa Socjologia Psychologia Zdrowie i medycyna

Wizje
Przewidywania Kosmologia Religie Ideologia Polityka

Ziemia
Geologia, geofizyka, geochemia, środowisko przyrodnicze

Życie
Biologia, biologia molekularna i genetyka

Cyberprzestrzeń
Technologia cyberprzestrzeni, cyberkultura, media i komunikacja

Działalność
Wiadomości | Gospodarka, biznes, zarządzanie, ekonomia

Technologie
Budownictwo, energetyka, transport, wytwarzanie, technologie informacyjne

American Journal of Engineering and Applied Sciences

This study presents a concept of harvesting and transferring energy to a low power electrical appliances using wireless technology where interconnecting wires are not available. This study was a ground work for the future alternative energy supply especially to the areas where supplying direct energy is a challenge such as in deep sea exploration as well as to the area where power interruption is a problem. Research was carried out to study how the waste signal and energy in the air could be collected and converted into useful energy which later could be used to supply power to electrical appliances. The approach of this research started by simulation work using PSPICE full edition that was performed to develop the design and later was used as guidelines in developing the prototype. We then harvested the Radio Frequency (RF) signal that was available in air by using RF energy harvesting circuit. This circuit harvested the energy and converted them into electricity. It was accomplished by using an antenna to capture the RF energy and a voltage doublers circuit to convert and magnify the AC input signal to larger DC output. For a start we managed to capture a 3V voltage which was stored in a rechargeable battery. The energy in this rechargeable battery was then utilized to power up low-powered electrical appliances. Germanium and Silicon diodes have been used to harvest and amplify the voltage so that a better and higher output can be achieved.

http://www.thescipub.com/abstract/10.3844/ajeassp.2008.12.15 2011/01/11 - 03:34

Problem statement: In the area of globalization the degree of competition in the market increased and many companies attempted to manufacture the products efficiently to overcome the challenges faced. Approach: Mixed model assembly line was able to provide continuous flow of material and flexibility with regard to model change. The problem under study attempted to describe the mathematical programming limitation for minimizing the overall make-span and balancing objective for set of parallel lines. Results: A proposed mixed-integer model only able to find the best job sequence in each line to meet the problem objectives for the given number of job allotted to each line. Hence using the proposed mathematical model for large size problem was time consuming and inefficient as so many job allocation values should be checked. This study presented an intelligence based genetic algorithm approach to optimize the considered problem objectives through reducing the problem complexity. A heuristic algorithm was introduced to generate the initial population for intelligence based genetic algorithm. Then, it started to find the best sequence of jobs for each line based on the generated population by heuristic algorithm. By this means, intelligence based genetic algorithm only concentrated on those initial populations that produce better solutions instead of probing the entire search space. Conclusion/Recommendations: The results obtained from intelligence based genetic algorithm were used as an initial point for fine-tuning by simulated annealing to increase the quality of solution. In order to check the capability of proposed algorithm, several experimentations on the set of problems were done. As the total objective values in most of problems could not be improved by simulated algorithm, it proved the well performing of proposed intelligence based genetic algorithm in reaching the near optimal solutions.

http://www.thescipub.com/abstract/10.3844/ajeassp.2010.15.24 2011/01/11 - 03:34

One interesting application of system identification method is to identify and control the heat transfer from the exhaust valve to the seat to keep away the valve from being damaged. In this study, two co-axial cylindrical specimens are used as exhaust valve and its seat. Using the measured temperatures at different locations of the specimens and with a semi-analytical method, the temperature distribution of the specimens is calculated and consequently, the thermal contact conductance is calculated. By applying the system identification method and having the temperatures at both sides of the contact surface, the temperature transfer function is calculated. With regard to the fact that the thermal contact has nonlinear behavior, two nonlinear black-box models called nonlinear ARX and NLN Hammerstein-Wiener models are taken for accurate estimation. Results show that the NLN Hammerstein-Wiener models with wavelet network nonlinear estimator is the best.

http://www.thescipub.com/abstract/10.3844/ajeassp.2008.16.23 2011/01/11 - 03:34

Problem statement: Repeated heat cure during assembly processes affected the Die Attach Film (DAF) material properties and the effectiveness touched area that leads to weak die bonding and delamination. Suitable die attached condition and DAF material selection had been evaluated to achieve required reliability performance in the manufacturing of the 3D Quad Flat No-Lead (QFN) stacked die package. Approach: During this study, special attention was given to the development of the residual stresses due to mismatch in the coefficients of thermal expansion of different DAF materials. Both experimental and finite element method were employed to gain a better understanding in a stress development induced between two different type of DAF, different die attach temperature and during the manufacturing process. Differential scanning calorimetry (DSC) was used to measure the changes of heat flow characteristics for both types of DAF. The die bond strength results measured using shear testing machine were compared with the finite element method prediction. Results: Although both DAF samples achieved good reliability performance and passed the Moisture Sensitivity Level 3 test (MSL3) at reflow 260°C without any sign of delamination, numerical simulation had demonstrated that the stress development were increased exponentially as the die attach temperature increased. It showed that different DAF gave different values of stresses but presented the same trend which the lowest die attached temperature (100°C in comparison with 125°C and 150°C) gave more stress to the die and possibility that the die will have weak adhesion to the substrate was high. Conclusions/Recommendations: Therefore for this case, stress can be relieved by having higher die attached temperature with an adequate bonding force and time, however die attached temperature for both DAF must be used above the glass transition temperature (128°C for DAF A and 165°C for DAF B) and being controlled not to exceed the crystallization temperature (203°C for DAF A and 204°C for DAF B) of both DAF.

http://www.thescipub.com/abstract/10.3844/ajeassp.2009.17.24 2011/01/11 - 03:34

This study describes and presents the analysis for the Source-Coupled Logic (SCL) inverter as will as the effect of submicron layout parasitics. The SCL inverter circuit model and its operation is defined. The analysis for the SCL is carried from the point of view of input/output voltage characteristics and the effect of noise margin. The inverter gate delay model is described and the effect of biasing current on the delay is shown. The result shows that, the delay of the SCL inverter is decreased as biasing current increase. The simulation is done based on the 0.18 µ Silterra PDK. Different layouts for SCL inverter have been investigated for its effect on output voltage swing, switching noise and the area. The results show an important effect on the SCL output signals. Post-Simulation was carried out on all proposed layouts using HSPICE and using 0.35 µ­ MIMOS Berhad PDK. The layout was done using Virtuous from Cadence where as the extraction done using Mentor Graphic-Caliber Interactive tool.

http://www.thescipub.com/abstract/10.3844/ajeassp.2008.24.32 2011/01/11 - 03:34

Problem Statement: Nonlinear behavior of offshore structure is attracting tremendous amount of attention in recent years. Response of these structures is strictly dependent upon behavior of their joints. Because of the lack of information about this part of a structure, most of the recent analysis and designs do not contain appropriate material in the case of joints. In most cases, joints are assumed to be fully clamped and their deformability is not accounted for in assessment of Jacket Type Offshore Platforms (JTOP) whereas, in reality there is always deformation in joints particularly when members undergo beyond elastic region. Approach: In this study, finite element modeling of tubular connections is carried out in order to assess their nonlinear behavior. As a result in a separate study, two FE models of a platform are made and effect of joint flexibility on these models is investigated analytically. Nonlinear static and dynamic analyses are performed considering joint deformation and compared to platform with clamped connections. Furthermore, some important parametric studies are carried out such as effect of joint flexibility on natural frequency of vibration of the structure and the process of plastic hinge formation in platform. Results: Results prove considerable effect of local joint deformation on nonlinear static and dynamic behavior of offshore structures. Conclusions/Recommendations: Taking into account the calculated results in this paper, it is highly recommended to consider the effect of joints in the design and analysis of offshore structures based on the importance of the project.

http://www.thescipub.com/abstract/10.3844/ajeassp.2009.25.30 2011/01/11 - 03:34

Problem statement: Fast Fourier Transform (FFT) is widely applied in OFDM trance-receiver communications system. Hence efficient FFT algorithm is always considered. Approach: This study proposed FPGA realization of high resolution high speed low latency floating point adder/subtractor for FFT in OFDM trance-receiver. The design was implemented for 32 bit pipelined adder/subtractor which satisfied IEEE-754 standard for floating-point arithmetic. The design was focused on the trade-off between the latency and speed improvement as well as resolution and silicon area for the chip implementation. In order to reduce the critical path and decrease the latency, the novel structure was designed and investigated. Results: Consequently, synthesis report indicated the latency of 4 clock cycles due to each stage operated within just one clock cycle. The unique structure of designed adder well thought out resulted 6691 equivalent gate count and lead us to obtain low area on chip. Conclusion: The synthesis Xilinx ISE software provided results representing the estimated area and delay for design when it is pipelined to various depths. The report showed the minimum delay of 3.592 ns or maximum frequency of 278.42 MHz.

http://www.thescipub.com/abstract/10.3844/ajeassp.2010.25.30 2011/01/11 - 03:34

Problem statement: Reverse osmosis is increasingly used as a separation technique in chemical and environmental engineering for the removal of organics and organic pollutants present in waste water. The removal of an organic compound, namely phenol, using a polyamide membrane was investigated in this study. Waste water containing phenol present a serious environmental problem and increasing attention is being given for its removal using RO membranes. Objective of this study is to (i) generate experimental data related to the removal of phenol using a spiral wound polyamide membrane (ii) analyze the performance of the membrane using solution-diffusion model and validate the model with the experimental data. Approach: Experiments were conducted on a laboratory scale spiral wound polyamide RO module. The permeate concentrations and rejection coefficient values were measured for various feed inlet pressures and feed concentrations. The total feed flow rate, 3.33×10-4 m3 sec-1 (20 LPM) was not varied. The transport of solvent and solute through the membranes were analyzed using solution-diffusion model taking concentration polarization into account. Results: By varying inlet pressures from 4-14 kgf cm-2) and feed concentrations of phenol from 200-1100 ppm, the rejection coefficients of the membrane were measured and found to vary from 64-91%. The solvent and solute transport parameters were determined by a graphical procedure using the experimental data and its values were 5.9×10-7 (m atm-1) and 6.54×10-7 (m sec-1) respectively. Conclusion: The model and the estimated parameter values were validated with the experimental data. The model was able to predict the rejection within 10% error. In view of the fact that not much information is available on the usage of spiral wound polyamide RO membrane modules for the removal of phenolic compounds, it may be concluded that the experimental results reported in this study is very significant in the scale up and design of RO system for treatment of industrial effluents containing phenolic compounds.

http://www.thescipub.com/abstract/10.3844/ajeassp.2010.31.36 2011/01/11 - 03:34

Monte-Carlo simulation based procedure was applied for assessing the reliability of Fibre Reinforced Polymer (FRP) confined reinforced concrete columns. Assessment of reliability provides a quantitative measure of effectiveness of repair. Problem Statement: The procedure presented in the paper could be used for assessing the reliability of reinforced concrete columns before and after the application of FRP wrap, thus helping to quantitatively assess the effectiveness of repair. The equations provided in ACI 440.2R were used for formulating the reliability equations Approach:
Java based computer program was developed to assess the reliability of circular concrete columns strengthened using FRP composites. The influence of diameter, thickness of wrap, longitudinal steel and elasticity modulus of wrap on reliability was studied. Results: The results indicated that the diameter of column and wrap thickness strongly influenced the reliability of columns Conclusions/Recommendations: The influence of internal steel reinforcement area and elasticity modulus of Fibre Reinforced Polymer on reliability was very limited. Computationally efficient formulation for estimating reliability was proposed. The new equation estimated reliability by up to 1575.2314 times faster than the common equation, thus resulting in the saving of time and computational power.

http://www.thescipub.com/abstract/10.3844/ajeassp.2009.31.38 2011/01/11 - 03:34

This research characterized the effects of air velocity and lime juice layer thickness on freezing time. In the experiment, the air velocity of the freezer and the thickness of the lime juice layer were set to be 4-12 m sec-1 and 4-10 mm, respectively. The temperatures of the lime juice were measured from 15°C until it reached -20°C and were continuously recorded during each test. The experimental freezing time curves showed a decreased freezing rate period. In addition, the mathematical model of freezing time was fit to a set of the experimental sample data, which was characterized by 6 different regression models. The results showed that the freezing times increased when decreasing air velocity. Moreover, increasing the lime juice layer thickness would also increase the freezing time of lime juice in which occurred mostly in S-2 stage. With the air velocity exceeding 8 m/s and the lime juice layer thickness less than 8 mm, the experiment gave the best operating condition for the freezing time of lime juice in this freezing process. The Model (6) was found to satisfactorily describe the curves freezing time of lime juice with R2 of 0.9656.

http://www.thescipub.com/abstract/10.3844/ajeassp.2008.33.39 2011/01/11 - 03:34

Problem statement: Moment Resisting Frame (MRF) is widely used as lateral resisting systems when sufficient ductility and deformability are to be met. Response of these structures is strictly dependent upon behavior of their joints, whereas the analysis of steel moment resisting frames generally has been performed without considering the accurate connection behavior. Approach: In this study Finite Element (FE) models had been developed to obtain the moment-rotation relations of theoretically fixed connection types which were widely utilized in Iran. Using moment-rotation relation obtained from FE analysis, 2D global structural model of MR buildings were developed afterwards to evaluate the behavior of the structures globally. Nonlinear static and dynamic analyses were carried out subsequently to investigate the structural behavior of MRFs having built-up column sections. Results: The results proved considerable effects of beam column connection behavior on nonlinear response of structures. Conclusion/Recommendations: It was recommended to consider the effects of connection properties in analysis and design of the MRF.

http://www.thescipub.com/abstract/10.3844/ajeassp.2010.37.41 2011/01/11 - 03:34

Problem Statement: The current source inverter induction motor (CSI-IM) drive was widely used in various industries. The main disadvantage of this drive was nonlinearity and complexity. This work was done to develop a simple drive systems models. Approach: The MATLAB/SIMULINK software was used for system modeling. Three reduced models were developed by choosing specific frame, neglecting stator transients and ignoring stator equations. Results: The dynamic performance of the models was examined in open loop form for a step change in control variable (the input voltage) as well as for step change in disturbance (mechanical load).Conclusion: The three models were equivalent in steady state. The error of these models in the transient response was less than 5 %, with the exception of the time performances of the transient model to step change of supply voltage. Recommendations: All three models were suggested to be used for designing torque control systems. The detailed and stator equation models were recommended to be used in speed control design.

http://www.thescipub.com/abstract/10.3844/ajeassp.2009.39.43 2011/01/11 - 03:34

Throughout the world, the disposal of used tires is a major environmental problem causing environmental hazards such as breeding ground for mosquitoes, producing uncontrolled fire and they are contaminating the soil and vegetation. Therefore, there is an urgent need to identify alternative outlets for these tyres, with the emphasis on recycling the waste tyre. Concrete is an excellent structural material and considered as essential for the modern civilization and human society. Now, the use of waste tires in concrete has become technically feasible and the concrete is being considered as light weight concrete. This study reviews the feasibility of using waste tires in the form of chips and fibers with different sizes in concrete to improve the strength as well as protecting the environment. Also it reviews the potential application in the field by exploiting its unique characteristics and properties. In this study, we outline the use of rubberized concrete in structural and non-structural members and show how it is suitable for the concrete, its uses, barriers and benefits and way to future study.

http://www.thescipub.com/abstract/10.3844/ajeassp.2008.40.44 2011/01/11 - 03:34

The Dynamic Voltage Restorer (DVR) was a power electronics device that was able to compensate voltage sags on critical loads dynamically. The DVR consists of VSC, injection transformers, passive filters and energy storage (lead acid battery). By injecting an appropriate voltage, the DVR restores a voltage waveform and ensures constant load voltage. There were so many types of the control techniques being used in DVR for mitigating voltage sags. The efficiency of the DVR depends on the efficiency of the control technique involved in switching the inverter. Problem statement: Simulation and experimental investigation toward new algorithms development based on SVPWM. Understanding the nature of DVR and performance comparisons between the various controller technologies available. The proposed controller using space vector modulation techniques obtain higher amplitude modulation indexes if compared with conventional SPWM techniques. Moreover, space vector modulation techniques can be easily implemented using digital processors. Space vector PWM can produce about 15% higher output voltage than standard Sinusoidal PWM. Approach: The purpose of this research was to study the implementation of SVPWM in DVR. The proposed control algorithm was investigated through computer simulation by using PSCAD/EMTDC software. Results: From simulation and experimental results showed the effectiveness and efficiency of the proposed controller based on SVPWM in mitigating voltage sags in low voltage distribution systems. It was concluded that its controller also works well both in balance and unbalance conditions of voltages. Conclusion/Recommendations: The simulation and experimental results of a DVR using PSCAD/EMTDC software based on SVPWM technique showed clearly the performance of the DVR in mitigating voltage sags. The DVR operates without any difficulties to inject the appropriate voltage component to correct rapidly any anomaly in the supply voltage to keep the load voltage balanced and constant at the nominal value.

http://www.thescipub.com/abstract/10.3844/ajeassp.2010.42.48 2011/01/11 - 03:34

Problem Statement: Ionospheric scintillations, which cause significant effects on satellite signals for communication and navigation, often takes place in equatorial region such as Malaysia. However, this disturbance are not fully understand due to few studies performed. This research reports the study and monitoring activity on Total Electron Content (TEC) and ionospheric scintillation in Malaysia using GPS measurements. Approach: One dual-frequency GPS receiver was positioned at the main station in Parit Raja, West Malaysia (1.86° N, 103.8° E) and Sipitang, East Malaysia (5.10° N, 115.56° E) respectively. Dual-frequency GPS data collected during the one-month ionospheric experimental campaign was used for TEC and scintillation computation and analysis. The TEC with 15 sec interval were computed from combined L1 and L2 code-pseudorange and carrier phase measurements. Whereas, the scintillation parameter S4 index was computed as a standard deviation of the received signal power normalized to average signal power every 60 sec on L1. A corrected S4 (without noise effects) was also computed and used in the analysis. Results: It was found that the daily maxima vTEC for Parit Raja (PR) ranged from 38-100 TECU, which is generally higher than those of Sipitang, which ranged from 30-42 TECU. However, a general consistency for both stations can be seen during the 1 month campaign period. Conclusions/Recommendations: In conclusion, these results show good agreement in the existence of the equatorial anomaly observed during moderate solar flux conditions and undisturbed geomagnetic condition. This will contributes to the knowledge of equatorial ionosphere and help in space weather condition. However, to better understand and characterize the ionosphere over Malaysia, more campaigns should be encouraged.

http://www.thescipub.com/abstract/10.3844/ajeassp.2009.44.49 2011/01/11 - 03:34

This study presents a study of the application of a Unified Power Flow Controller (UPFC) to control power transmission, generator terminals voltage and better damping of Low Frequency Oscillation (LFO) in Single-Machine Infinite-Bus (SMIB) power system. The UPFC integrates properties of both shunt and series compensations and can effectively alter power system parameters in a way that increases power transfer capability and stabilizes system. In practice systems use simple Proportional Integral (PI) controllers for control of UPFC. However, since the PI control parameters are usually tuned based on classical or trial-and-error approaches, they are incapable of obtaining a good dynamic performance for a wide range of operation conditions. To address this problem, in this research an optimization approach, based on the Genetic Algorithms (GA) method is proposed for the design of UPFC controllers (power-flow controller, DC-voltage regulator and generator terminals voltage controller) and also supplementary damping controller for increase damping of power system oscillations is developed. A SMIB power system installed with a UPFC is considered for case study. Several linear time-domain simulation tests visibly show the effectiveness and validity of proposed method in control of power transmission, terminal voltage of generator and enhance of LFO damping.

http://www.thescipub.com/abstract/10.3844/ajeassp.2008.45.52 2011/01/11 - 03:34

Problem statement: A cluster of small-sized Single-Gimbal Control Moment Gyros (SGCMGs) is proposed as an attitude control actuator for high-speed maneuver of small satellites. There exists a singularity problem what is peculiar to the CMG system. Approach: This study presented a simple singularity avoidance steering law using the Singular Value Decomposition (SVD) algorithm. Results: Capability of the present steering method in singularity avoidance was demonstrated with numerical simulations for fixed-star tracking control of a small satellite using four SGCMGs. Conclusion: The proposed steering law utilizes the singular value decomposition to obtain singular vectors and generates the command gimbal rate that keeps the command torque in the direction orthogonal to the singular direction with a maximum gain.

http://www.thescipub.com/abstract/10.3844/ajeassp.2010.49.55 2011/01/11 - 03:34

Problem statement: The reinforcements added to an alloy lead to variation in properties. The content and size of the reinforcement influences the properties of composites. Very little research has been carried out in hybrid composites. Work on hybrid LM6 aluminium alloy metal matrix composites (MMC) with flyash and SiC has been initiated here. The effect of the four parameters, size and weight of the reinforcements on the hardness and wear loss has been studied. Approach: Artificial neural networks, from the artificial intelligence family, is a type of information processing system, based on modeling the neural system of human brain. The effect of the parameters was investigated using ANN. Central composite rotatable method of design of experiments was used to arrive at the combination and the number of specimens. The specimens were prepared using the liquid metallurgy route and tested. Pin-on-disc apparatus was used for determining wear. Rockwell hardness on C scale was determined. The data from the experiments were used for training and testing the network. Results: The accuracy in ANN prediction was appreciable with the error estimated for wear loss and hardness being less than 2%. Conclusions/Recommendations: The ANN prediction is quick and economical way of estimating the properties.

http://www.thescipub.com/abstract/10.3844/ajeassp.2009.50.53 2011/01/11 - 03:34

Fabrication of Mg1-XZnXFe2O4 (where x = 0.2, 0.3, 0.4 and 0.5) samples using a conventional technique is reported. Oxides of magnesium, zinc and iron with purity of about 99.99% were mixed with distilled water in a milling machine for 12 hours. They were then filtered and pre-sintered at 1250°C and sintered at 1350°C for 10 h in air. The phase and the crystal structure of the as-prepared samples were identified using X-Ray Diffraction analysis (XRD). Hysteresis graph was evaluated using Vibrating Sample Magnetometer (VSM) to get the saturation magnetization (emu g-1) and coercivity (G) value. Atomic Force Microscope (AFM) was used to observe the surface morphology. The X-ray diffraction analysis showed major peak at plane (3 1 1) of the cubic structure for all the ferrites. The largest value of density achieved was 4.69 gcm-3 which was exhibited by sample with 0.5 mole fraction of zinc content. Highest saturation magnetization value (3.652emu g-1) was obtained for the 0.3 mole fraction of zinc content. A strong correlation between the saturation magnetization and zinc content was observed. We speculate that it is due to the Heisenberg super-exchange interaction of magnetic Fe3+ and non-magnetic Zn2+ occupying the tetrahedral sites. The sample was used to induce electromagnetic (EM) waves in high operating frequency (5 MHz).

http://www.thescipub.com/abstract/10.3844/ajeassp.2008.53.56 2011/01/11 - 03:34

Externally Prestressed Segmental (EPS) concrete box sections are widely used in the construction of bridge structures today. EPS concept has become an attractive tool for rehabilitation and strengthening of existing bridges which have insufficient strength and/or excessive deflection and cracking. Problem statement: EPS bridges are affected by combined stresses (bending, shear, normal, and torsional) at the joint interface between the segments. However, very limited researchers studied this type of bridges under combined stresses. Approach: This paper presented an experimental investigation of the structural behaviour of EPS bridge with shear key under torsion. Four beams were tested, each containing three segments that were presetressed using two external tendons. A parametric study of two different external tendon layouts as well as different levels of torsional force applied by different load eccentricities was conducted. Results: The effect of torsion was evaluated in terms of vertical deflections, concrete and tendon strains, failure loads and failure mechanisms. It was concluded that torsion has a significant effect in the structural behaviour of external prestressed segmental box girder beams. Torsion not only alters failure load of the beam but also changes the type of failure mechanism. It was also investigated that harp tendon layout results in better structural behaviour in term of deflection and tendon strain as compared with the straight tendon. Recommendations: It recommended including the effect of joint (flat and shear key) type as well as the effect of tendon layout under torsion to obtain comprehensive behavior of EPS bridge.

http://www.thescipub.com/abstract/10.3844/ajeassp.2009.54.60 2011/01/11 - 03:34

Problem statement: Resonance-type microscopies have been widely used to evaluate the nanoscaled or microscaled surface elastic properties of materials by the resonance-frequency shifts of an oscillator, which contacts the surface of materials by a spherical tip. Approach: The tip-specimen contact is modeled to be a spring support, whose stiffness is given by the traditional Hertzian contact theory. However, because of the influence of the oscillator vibration and the anisotropy in nanoscaled or microscaled region of materials, the predicted results from the traditional Hertzian contact theory can not coincide with the experimental observations. In order to explain this discrepancy, dynamic contact stiffness at the contact interface between a rigid sphere and a semi-infinite cubic solid is investigated. Results: An oscillating force being superposed on a biasing force excites the oscillation of the sphere contacting with the solid surface, which causes the contact radius to vary with the oscillation. The assumption of sufficiently small oscillating force compared with the biasing force yields an oscillating-contact-pressure distribution of the constant contact radius and then dynamic contact stiffness. Because the oscillating-contact-pressure distribution cannot promise the uniform contact deformation, the influence of contact-displacement conditions is discussed. Conclusion: It is shown that dynamic contact stiffness depends on the oscillating frequency and contact radius of the sphere and the solid anisotropy.

http://www.thescipub.com/abstract/10.3844/ajeassp.2010.56.63 2011/01/11 - 03:34

The study was carried out to determine the effect of pulsating frequencies on the local and average heat transfer characteristic of a heated circular air jet. The velocity profile of a heated circular pulsating air jet was measured in the first part of the study. The same set-up was used to measure the heat flux of the pulsating jet impinging on a wall. The heat flux of the heated air jet impinging on the plate was measured using a heat flux microsensor at different radial positions. Measurement of the heat flux was used to calculate the average and local Nusselt Number for different pulsating frequencies and at different flow Reynolds Number. The pulsating frequencies were between 10-80 Hz and the Reynolds number used were 16 000, 23 300 and 32 000. Results obtained show that the local Nusselt number calculated were higher at all radial position away from the stagnation point. The pulsed jet Nusselt number was higher than the average steady jet Nusselt number for all values of frequencies due to the higher localised heat transfer. The higher Nusselt number obtained at localized radial positions can be due to the higher instantaneous velocity as was shown from the velocity profile plotted in the first part of the experiment. Enhanced turbulence intensity found was due to the pulsed jet.

http://www.thescipub.com/abstract/10.3844/ajeassp.2008.57.61 2011/01/11 - 03:34

Problem statement: Drying a packed bed of porous particle at high temperature with varying humidity of hot air is an attractive process. Despite, many researches on experimental and simulation on a fixed bed drying at low and average temperature are proposed. Few studies showed drying at high temperature with humid air or using superheated steam. The latest is compared to dry air. Approach: In this study, we show an experimental and numerical study of humid air drying of a fixed bed of moist porous alumina particles. The air velocity, the air temperature and the vapor pressure were varied from 1.7-2.3 m.sec-1, 120-160°C and 0.1-0.65 bar, respectively and the experiments were performed at atmospheric pressure. Then a mathematical describing heat and mass transfer during drying is developed. This model is based on the averaging volume approach using two scale changes. Results: From the experimental works, the solid temperature and the bed moisture content have been presented at different drying conditions. The previous results show that an increase in humidity leads to an increase of the wet bulb temperature and a decrease in the drying time. At the same drying temperature, the variation in the gas velocity affects also the drying time. In addition, we note that the drying time increases if the bed depth increases. The predicted results deduced from the developed model were compared with the experiment. Conclusion: The experimental and predicted results obtained from this study describing drying of a packed bed illustrate clearly the effect of the air humidity on the drying kinetics.

http://www.thescipub.com/abstract/10.3844/ajeassp.2009.61.69 2011/01/11 - 03:34

In this study a rarefied gas flow inside a rotating circular cylinder by means of direct simulation Monte Carlo (DSMC) method is investigated. A rarefied gas is supposed to be contained in a cylindrical domain, bonded by a rotational cylinder with smooth and diffuse-reflection surface. The top and bottom ends of domain is assumed to be speculary-reflecting. Special attention is focused on the effect of parameter L/D, where L and D are the cylinder length and diameter, respectively. The investigation on the formation of various kinds of flow patterns in the range of various values of the L/D are important aims of the present work. Finally computed results such as density fields and velocity profiles are shown and discussed.

http://www.thescipub.com/abstract/10.3844/ajeassp.2008.62.65 2011/01/11 - 03:34

Problem statement: The aim of this research was to study the electrical and optical properties of N, N`-bis(Inaphthyl)-N,N`-diphenyl-1,1`-biphenyl-4,4`-diamine (NPB) organic materials often used as hole transport layer in Organic Light-Emitting Devices (OLED). Approach: The NPB layer was prepared using the thermal evaporation method. From photoluminescence spectra, two peaks at 630 and 480 nm were observed with 55 nm NPB. The electrical conductivity was strongly influenced by the layer thickness. Results: The energy band gap of each NPB layer was successfully presented in the range of 2.4-2.9 eV. Conclusion: This study successfully showed the effect of different thickness of NPB in OLED.

http://www.thescipub.com/abstract/10.3844/ajeassp.2010.64.67 2011/01/11 - 03:34

The Static Synchronous Compensator (STATCOM) provides shunt compensation in similar way to the Static VAR Compensator (SVC) but utilizes a voltage source converter rather than capacitors and reactor. In practice systems use simple Proportional-Integral (PI) controllers for control of STATCOM. However, since the PI control parameters were usually tuned based on classical or trial-and-error approaches, they were incapable of obtaining good dynamic performance for a wide range of operation conditions and various loads in power system. For this problem, in this research a robust control approach based on the Quantitative Feedback Theory (QFT) method was proposed for the design of STATCOM controllers (AC-voltage regulator and DC-voltage regulator) and also supplementary damping controller for increase of power system oscillations damping is developed. A Single-Machine Infinite-Bus (SMIB) power system installed with a STATCOM with system parametric uncertainties were considered for case study. The system parametric uncertainties were obtained by changing parameters and load by 45% simultaneously from their typical values. To show effectiveness of QFT method, the proposed method is compared with a conventional method (classical P-I controller optimized by Genetic Algorithm (GA)). Several linear and non-linear time-domain simulation tests visibly show the validity of proposed method in compare with traditional method.

http://www.thescipub.com/abstract/10.3844/ajeassp.2008.66.75 2011/01/11 - 03:34

Problem statement: Foamed concrete has become most commercial material in construction industry. People in industries were come out with the new mix design of foamed concrete to meet the specification and the requirements needed. Approach: This is because foamed concrete has the possibility as alternative of lightweight concrete for producing intermediate strength capabilities with excellent thermal insulation, freeze-thaw resistance, high-impact resistance and good shock absorption. Results: Currently Standard test to measure the compressive strength of foamed concrete is using standard unconfined compressive test. Several research has been conduct but the compressive strength using standard unconfined compressive test not capture true behavior of foamed concrete because it just achieved only low compressive strength and sample under compression failed due to brittle collapse of the sample. This paper was analyses the comparison between standard compressive test and confined compressive test. The confinement test introduced to prevent sample from brittle collapse. Foamed concrete cylindrical sample has been investigated under the standard compressive test for hard concrete (ASTM-C39). Based on the research, samples are produced under unconfined and confined condition. Analysis has been done and the result show that under standard compressive test, the sample failed due to early crack initiation and failed. Confinement condition was increase the compressive strength but this condition influence the result. Conclusion/Recommendations: Standard test is not suitable to capture the true behavior of foamed concrete, and to prevent the sample from brittle collapse during the test, new testing method was introduced to capture the true behavior of foamed concrete which is using Quasi Static Indentation Test. This test can be used to study about the behaviour of foamed concrete before it can be implemented to its final application.

http://www.thescipub.com/abstract/10.3844/ajeassp.2010.68.72 2011/01/11 - 03:34

Problem statement: The importance of diesel particulate filter has been increased later because of its ability in making emission reduction of the exhaust gasses. Diesel Particulate Filters (DPF) do two important jobs: gas emissions reduction and noise reduction, the pores spread inside the DPF store some gases and soot emissions and on the other side it prevents some sound or noise to be gone outside, so it works as a noise reduction device or unit. Diesel particulate filter is considered as a porous media, it's very important to study the flow behavior in such media in order to redesign dimensions, specifications and location of diesel particulate filter on the exhaust pipes. Approach: The flow of gasses through the Diesel Particulate Filters (DPF) unit is studied here analytically and numerically to reach for the best equation describes the real nature of flow behavior. The analytical model is built to find the velocity of flow, pressure drop and nature of flow-laminar or turbulent- at two conditions at cold conditions (25˚C) and hot conditions (500˚C). Also the problem is solved numerically using some appropriate software. A comparison was made between both analytical and numerical results especially the pressure drop effect. Some appropriate software used to describe the reality of the gasses flow through porous media. Results: It was found that the nature gases flow in DPF is laminar; a pressure drop through the DPF was occurred, gases axial velocity, vertical velocity, temperature are all decrease as such gases go through the filter. Vertical velocity's values were very small compared with the axial velocity's values. Conclusion/Recommendations: Gases pressure is decreased as such gases flow along the DPF unit and exhaust system, so there is a pressure drop. Temperature distribution and profiles showed that the values of temperature have a fluctuation along the DPF unit. Axial and vertical velocities were decreasing as the gases flow through the DPF unit and the exhaust system. It is recommended to study the flow as a non-linear 3D problem.

http://www.thescipub.com/abstract/10.3844/ajeassp.2009.70.75 2011/01/11 - 03:34

Problem statement: The urban water supply systems in Australian large cities, which generally depend on large surface water reservoirs, are highly stressed due to rapid urban growth and severe drought conditions during the current decade. To ensure the long term sustainability of urban water supply, various alternative water sources including rainwater tanks, grey water, wastewater and desalination plants are being examined in Australia. In the previous research, it has been shown that rainwater tank of appropriate size, installed in detached small dwellings, can meet a significant proportion of household water demand, but there has been limited study on water savings and financial viability of Rain Water Harvesting System (RWHS) for multistorey residential buildings. This study examines the sustainability of RWHS in multistorey residential buildings in Sydney under different scenarios such as varying roof area, number of floors in the building, water price and interest rate to identify favorable condition where RWHS proves to be sustainable. Approach: A hypothetical multistorey building was considered and various scenarios in relation to site area and floor arrangement were established. A water balance model was developed to calculate water savings for various scenarios. Finally, life cycle costing was undertaken to identify most sustainable RWHS scenario for the hypothetical multistorey building. Results: It was found that a higher roof area is more favorable in terms of water savings and financial benefits. Capital and maintenance costs account for the majority of the expenditure of a RWHS. Plumbing cost forms the largest single component of the capital cost. It is shown that lower interest and increased water price regimes enhance the financial viability of RWHS. Conclusion: It was found that it is possible to achieve “pay back” for a RWHS under some favorable scenarios and conditions thus making the RWHS for multistorey buildings in Sydney sustainable.

http://www.thescipub.com/abstract/10.3844/ajeassp.2010.73.82 2011/01/11 - 03:34

Problem statement: Fabrication of nano materials particularly nano inductors at low sintering temperature remains a challenge. This study was carried out as our initial response to obtain a nano-size inductors, which is aluminium iron garnet using low sintering temperature. Approach: The aluminum iron garnet (Al3Fe5O12) nano crystals were prepared by sol-gel technique. The starting solution is a mixture of iron nitrate Fe(NO3)3.9H2O, yttrium nitrate Y(NO3)3.6H2O and aluminum nitrate Al(NO3)3.9H2O and were dissolved in 150 mL of citric acid, C6H8O7.H2O. The mixtures were stirred continuously, at about 250 r.p.m, in room temperature until the formation of a gel was observed. The gel was dried at 110°C in an oven to remove the unneeded water. The dried powder was calcined at 600°C, for 3 h in air and was wet crushed using a Fritsch Planetary Micromill for 6 h to obtain fine particles powder. The sample was then characterized by X-Ray Diffraction analysis (XRD) to confirm the garnet phase. The sintered powder was characterized at different temperature by X-ray diffraction analysis and Raman Spectroscopy was used to study the vibration of atoms in a materials. Finally, Field Emission Scanning Electron Microscopy (FESEM) was used to study the surface morphology of the sample. Results: The XRD results showed that, the best garnet cubic phase giving [1 0 4] plane of the Al3Fe5O12 crystallite appeared at 33.30 of the 2 theta. We report a clear cubic crystal structure of less than 62 nm, which was observed possible for the first time, for this type of garnet, Al3Fe5O12. The much lower sintering temperature 800°C comparing to the conventional method was attributed to the sol gel method. Conclusion: The long stirring time (one month) that had allowed self assembly of the anions and cations to form the gelatin. In addition the small radius of aluminium prefers to occupy the tetrahedron and octahedron sites instead of the much larger dodecahedron site resulted to the clear cubic structure of the garnet.

http://www.thescipub.com/abstract/10.3844/ajeassp.2009.76.79 2011/01/11 - 03:34

To stabilize infrastructures such as tall buildings, bridges, etc., piles are used to resist lateral loads created from earth pressure, wind, waves and earthquake extensively. Pile design requires understanding of how the load is transferred from a pile to surrounding soil and vice versa. Pile properties, soil stress-strain behavior and pile-soil interaction play important roles in pile-response subjected to lateral loads. A study was carried out to investigate the effects of above-mentioned parameters on pile-soil behavior subjected to lateral forces. A comparison was made between the results derived from finite difference and equivalent spring methods by writing a computer program and using a civil engineering package, respectively.

http://www.thescipub.com/abstract/10.3844/ajeassp.2008.76.81 2011/01/11 - 03:34

The need to optimize the operation of water reservoirs is an issue that is becoming increasingly a concern for water resources planners in developing countries. This issue particularly becomes more significant in large systems with multiple reservoirs where operation of one reservoir has an impact on the others. In other word, the set of reservoirs in these systems act like a united series and require specific methods to handle various modeling issues. Problem statement: Sirvan River basin in west of Iran, standing in fifth order in respect of discharge, is an example of such a complex system. The project of water transfer from western tropical regions which is one of the large-scale projects in water resources management in Middle East, consists of a number of reservoirs and transfer systems. The matter of optimum operation of such a collection is one of the complicated and outstanding issues in water resources management. Approach: It was found that, due to increasing decision-making variables, conventional models used in optimizing water resources systems were not any longer capable of obtaining a desired solution, either because of low precision or time constraints. Hence, the intelligent random research approach "Simulated Annealing" has been used which in recent, decades has revealed appropriate results in solving major problems. Results: The results of this research indicate that the annealing approach is capable of solving such complex problems in water resources management with good precision in a reasonable period of time. Conclusions/Recommendations: The results were also compared with outputs of MODSIM which is a widely known model for solving complex water resources systems problems and benefits from "out of kilter"algorithm. The results indicate SA as a very robust and effective model in optimization of large real multi-reservoir systems.

http://www.thescipub.com/abstract/10.3844/ajeassp.2009.80.87 2011/01/11 - 03:34

Prediction of the properties other than moment carrying capacity of GFRP plated RC beams does not have any straight forward mechanism. This study presents a General Regression Neural Network (GRNN) based computational model for predicting the yield load, ultimate load, yield deflection, ultimate deflection, deflection ductility and energy ductility of such beams. Results from experimental investigations carried out on nine RC beams with steel ratios of 0.419, 0.603 and 0.905% plated 0, 3 and 5 mm thick GFRP laminates were used for generating the GRNN model. The predictions of the model closely agreed with experimental results.

http://www.thescipub.com/abstract/10.3844/ajeassp.2008.82.88 2011/01/11 - 03:34

Problem statement: This study mainly to study the effect of several commercial underfill materials to the reliability of HiCTE Flip Chip Ceramic Ball Grid Array (FC-CBGA) package due to Accelerated Thermal Cycling (ATC) effect. Approach: The warpage condition of package, die back stress, interfacial die shear stress, and solder bump fatigue for different commercial underfills were assessed and compared via a commercial Finite Element Analysis (FEA) under JEDEC Standard of ATC. The thermo-mechanical properties of underfills for simulation were obtained by using Thermal Mechanical Analyzer (TMA) and Dynamic Mechanical Analyzer (DMA). The actual package of HiCTE FC-CBGA were assembled with those underfill materials and underwent ATC to be compared with FEA result. Results: The results from FEA and experimental were discussed to characterize the performance of each underfill material. The results of this study indicate that the underfill materials investigated, those with a glass transition temperature (Tg) and a Young’s modulus of approximately above 105°C and 8-9 GPa, respectively, were appropriate for HiCTE FC-CBGA with high lead solder bumps. Conclusion: The result from FEA analysis and ATC reliability test found that the underfill materials with high and medium low Young’s modulus has high reliability in FC-CBGA package.

http://www.thescipub.com/abstract/10.3844/ajeassp.2010.83.89 2011/01/11 - 03:34

Problem statement: This study designed the pneumatic and hydraulic systems in coal fluidized bed combustor. These are fluidization of silica sand bed material, Air distributor, centrifugal fan, electric motor power drive and surface heat exchanger. Approach: The effects of increased gas velocity on silica sand and the resultant drag force formed the basic equations in fluidization. Air distributor was introduced to achieve pressure drop across the beds. Results: The constructed centrifugal fan was driven by selected electric motor based on pressure and temperature changes in the reactor. The dimensions of the heat transfer tube were calculated from fluid flow and energy balance equations. The values obtained were as the follows: Fluidization velocity (1.54 m sec-­1), gas velocity through orifice (29.52 m sec-1), the fan electric motor (2 KW, 3 ph at 1500 pm), the steam temperature obtained was 160°C from water ambient temperature of 30°C and tube length 22 m was coiled into levels in the combustor. Conclusion/Recommendation: Precise specifications of pneumatic and hydraulic systems will adequately address the environment concern of coal fired power supply as a method to address epileptic power supply in Nigeria.

http://www.thescipub.com/abstract/10.3844/ajeassp.2009.88.95 2011/01/11 - 03:34

The development of Computational Fluid Dynamics (CFD) compressible codes for 2D structured quadrilateral grid and 3D unstructured hexahedral grid is described. The high-speed flow in a nozzle blade cascade is predicted numerically by solving the 2D/3D Euler Equations in a coupled manner. The new finite volume CFD solvers employ second-order accurate central differencing scheme for spatial discretization and multi-stage Runge-Kutta technique for temporal integration with flow variables stored at the vertices. Artificial dissipations with pressure sensors are introduced to control solution stability and capture shock discontinuity. The predictions have been compared with experimental measurements and good agreement has been found.

http://www.thescipub.com/abstract/10.3844/ajeassp.2008.89.94 2011/01/11 - 03:34

Problem statement: In recent years, Greenhouse Gas (GHG) emissions and their potential effects on global climate change have been a worldwide concern. According to International Energy Agency (IEA), power generation contributes more than half of the global GHG emissions. Approach: Purpose of this study is to examine GHG emission reduction potentials in the Canadian electricity generation sector through fuel switching and adoption of advanced power generation systems. To achieve this objective, eight different scenarios were introduced. In the first scenario, existing power stations’ fuel was switched to natural gas. Existing power plants were replaced by Natural Gas Combined Cycle (NGCC), Integrated Gasification Combined Cycle (IGCC), Solid Oxide Fuel Cell (SOFC), hybrid SOFC and SOFC-IGCC hybrid power stations in scenario numbers 2 to 6, respectively. In last two scenarios, CO2 capture systems were installed in the existing power plants and in the second scenario, respectively. Results: The results showed that Canada’s GHG emissions can be reduced by 33, 59, 20, 64, 69, 29, 86 and 94% based on the first to eighth scenarios, respectively. On the other hand, the second scenario is the most practical and its technology has already matured and is available. In this scenario by replacing existing power plants by NGCC power plants, Canada can fulfill more than 25% of its 238,000 kt year-1 commitment of GHG emission reduction to the Kyoto Protocol. In addition, the GHG emission reduction potentials for each province and Canada as a whole were presented and compared. Based on the results, Alberta, Ontario and Saskatchewan are the biggest producers of GHG in Canada by emitting 49, 21 and 14% of Canada’s GHG emissions, respectively. Therefore, they have higher potential to reduce GHG emissions. The comparison of the results for different provinces revealed that based on efficiency of electricity generation and consumed fuel distribution; specific scenario(s) tend to be suitable for each province. Conclusion: The results pointed out that despite of acceptable performance of some provinces, there are still great potentials to reduce GHG emission level in Canada. In addition, the economical analysis showed that some scenarios are economically competitive with current technologies and should be considered when a new power station is to be built.

http://www.thescipub.com/abstract/10.3844/ajeassp.2010.90.97 2011/01/11 - 03:34

The ultrasonic velocity, density and viscosity measurements were carried out for the mixtures of benzamide with Propan-2-ol, butan-1-ol, 1-pentanol and n-hexanal in 1,4-dioxan at 303, 308 and 313K. The derived acoustic and thermodynamic parameters namely adiabatic compressibility, free length, free volume, internal pressure, viscous relaxation time and Gibbs free energy were evaluated with a view to investigate the nature of molecular interaction.The obtained results support the occurance of complex formation through intermolecular hydrogen bonding in these ternary liquid mixtures.

http://www.thescipub.com/abstract/10.3844/ajeassp.2008.95.99 2011/01/11 - 03:34

Problem statement: Eccentrically Braced Frames (EBFs) are usually infilled by masonry walls, but in common design, the stiffness and lateral resistance of these walls is ignored. Considering the results of carried out tests and studies, it seems that infilled masonry walls have a significant influence on the stiffness and the strength of EBFs. Since experimental test of total frame with infilled brick wall is a very expensive and time consuming process, proper numerical models which can precisely simulate the behavior of EBFs considering the effects of infilled brick wall are necessary. Approach: In this study, a proper model is made using explicit finite elements method to study the behavior of EBFs with infilled masonry wall. Because of complicated mechanical and geometrical properties of masonry walls and also because of the interaction between steel frame and masonry wall, this model is not easy to obtain. To ensure the ability of the model to precisely simulate the behavior of an EBF with infilled brick wall, initial models were made and the problems were solved comparing the results of experimental test and the results of these initial models. Firstly, material models and some basic principles of explicit finite element algorithm are used and three initial models were made: a model of a brick wall without eccentrically braced steel frame, a model of an EBF without infilled brick wall and finally a model of an EBF with infilled brick wall. Results: Using these three initial models, constitutive model for masonry and steel material and also the proper elements for modeling the behavior of mortar is obtained. Studies showed that good prediction of the behavior of a system consisting of EBF and masonry wall is possible, by minimizing the kinematical energy and using a special time scaling of explicit finite element model. Conclusion: After verifying the finite element models, the influence of masonry infilled wall on the behavior of eccentrically braced frames is studied. This investigation showed that in general, the presence of masonry wall increases the yield strength and the elastic range in the force-displacement curves. But the plastic behavior of the frame is deteriorated and due to fragile behavior of masonry materials, the total system of steel frame and masonry wall has a significant strength fall when the elastic range is passed.

http://www.thescipub.com/abstract/10.3844/ajeassp.2009.96.104 2011/01/11 - 03:34

Problem statement: The nonlinear refractive index and nonlinear absorption are two important optical phenomena which are extensively used in optical switching, optical limiting and labeling. Approach: In the present research we had measured nonlinearity of Ag nano-fluid prepared using Γ-irradiation method. The measurement was carried out using a single beam z-scan technique. Under a CW laser beam excitation operated at 532 nm with the power output of 40 mW, a closed aperture setup was used for thermal-induced nonlinear refractive index and an open aperture setup was applied for measuring nonlinearity absorption. Results: We measured the nonlinear refraction coefficient and nonlinear absorption coefficients for silver nano-fluid at concentration 6.475×10-3 M, the values obtained were -6.173×10-8 cm2 W-1 and 7.994×10-3 cm W-1 respectively. Conclusion: The nonlinear refraction coefficient with the negative sign indicates the self-defocusing phenomenon. The experimental data from open aperture measurement showed that a two photon absorption phenomenon. These results showed that the Ag nano-fluid has significant values of nonlinear refractive index and nonlinear absorption, thus it could be good candidate for optical devices.

http://www.thescipub.com/abstract/10.3844/ajeassp.2010.98.101 2011/01/11 - 03:34