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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

Problem statement: Shrinkage induced cracking cause damage to reinforced concrete structures. An experimental study was conducted on restrained shrinkage test of cement mortar and light weight High Performance Fiber Reinforced Cementitious Composites (HPFRCC). Approach: Two types of light weight HPFRCC and a premix mortar containing small amount of fiber were included in the experiment. Results: Results showed the multiple cracks, as many as 49, in light weight HPFRCC specimens compared to few cracks (about six cracks) in the premix mortar specimen. At the end of shrinkage test, the width of the cracks in the mortar specimen was more than 250 μm with the largest crack width of about 400 μm. However, the scenario was quite different in light weight HPFRCC specimens, where the width of almost all cracks was less than 100 μm. Conclusion: The higher number of multiple cracks with small cracks width in light weight HPFRCC specimens due to drying shrinkage was due to their strain hardening and ductile behavior compared to quasi brittle behavior of premix mortar where less number of wide cracks was observed.

http://www.thescipub.com/abstract/10.3844/ajeassp.2009.775.780 2011/01/11 - 03:35

Problem statement: Sea surface current retrieving from Synthetic Aperture Radar (SAR) is required standard methods due to the complexity of sea surface ocean imaging in SAR data. In this context, various analytical models have been developed which describe overall effects of sea surface roughness on the Doppler signal mechanisms. Nevertheless, such models are limited in the complexity of the sea surface current estimation that can be used. In fact, the resolution of the sea surface Doppler velocity in azimuth direction is typically coarser as compared to the normalized radar cross section image. Approach: This study introduced a new method to retrieve sea surface current from RADARSAT-1 SAR Standard beam mode (S2) data. The method was based on the utilization of the Wavelength Diversity Ambiguity Resolving (WDAR) and Multi Look beat Frequency (MLBF) algorithms to remove Doppler centroid (fDC) ambiguity. Results: The result showed that the proposed methods are able to correct Doppler centroid (fDC) ambiguity and produced fine spatial sea surface current variations in S2 mode data. The current velocities were ranged between 0.18 and 0.78 m sec-1 with standard error of 0.11 m sec-1. Conclusion: In conclusion, RADARSAT-1 SAR standard beam mode (S2) data can be utilized to retrieve real time sea surface current. Both WDAR and MLBF algorithms are able to provide accurately information on Doppler Centroid (fDC) in which accurately real time sea surface current can be retrieved from SAR data.

http://www.thescipub.com/abstract/10.3844/ajeassp.2009.781.788 2011/01/11 - 03:35

Problem statement: Most resent evolutionary algorithms work under weak theoretical basis and thus, they are computationally expensive. Approach: This study discussed the use of new evolutionary algorithm for automatic programming, based on theoretical definitions of program behaviors. Evolutionary process adapted fixed and self-organized input-output specification of the problem, to evolve good finite state machine that efficiently satisfies these specifications. Results: The proposed algorithm enhanced evolutionary process by simultaneously solving multi-parts from the same problem. Conclusion: The probability that the algorithm will converge to the optimal solution was highly enhanced when decomposing the main problem into multi-part.

http://www.thescipub.com/abstract/10.3844/ajeassp.2009.789.795 2011/01/11 - 03:35

Problem statement: The rainfall based design flood estimation techniques are commonly adopted in hydrological design and require a number of inputs including information on soil loss characteristics. Approach: A conceptual loss model known as the ‘Initial Loss-Continuing Loss (IL-CL) model’ is widely used in Australia. Results: The Initial Loss (IL) occurs at the beginning of the rainfall event, prior to the commencement of surface runoff and the Continuing Loss (CL) is the average rate of loss throughout the remainder of the storm. The currently recommended design loss values depicted in “Australian Rainfall and Runoff Vol. 1” for Queensland (Australia) has some basic limitations. This study investigated how more accurate CL values can be estimated and derived for medium sized tropical Queensland catchments using long term rainfall and streamflow data. Accuracy in CL estimation has got significant implications in the estimation of design floods. Conclusion/Recommendations: The results showed that CL value is not fixed and constant through out the duration of the storm but the CL value decays with the duration of the storm.

http://www.thescipub.com/abstract/10.3844/ajeassp.2009.796.803 2011/01/11 - 03:35

Problem statement: There is currently no standard design guideline to determine the number of composites needed to retrofit masonry walls in order to withstand a given explosion. Past design approaches were mainly based on simplified single-degree-of-freedom analysis. A finite element analysis was conducted for concrete masonry walls hardened with composites and subjected to short duration blast loads. Approach: The analysis focused on displacement time history responses which form the basis for retrofit design guidelines against blast loadings. The blast was determined from 0.5 kg equivalent TNT explosive at 1.83 m stand-off distance to simulate small mailroom bombs. Two and four layered retrofitted walls were investigated. Uncertainties in the finite model analysis of walls such as pressure distributions, effect of mid height explosive bursts versus near the ground explosive bursts and variations in modulus of elasticity of the wall were presented. Results: Uniformly distributed blast loads over the retrofitted wall height produced a small difference in peak displacement results when compared to the non-uniform pressure distribution. Ground explosive burst was shown to produce a 62.7% increase in energy and a higher peak displacement response when compared to mid-height explosive burst. Conclusion: The parametric study on the variation of modulus of elasticity of concrete masonry showed no significant effect on peak displacement affirming the use of the resistance deflection contribution of the composite in retrofit designs.

http://www.thescipub.com/abstract/10.3844/ajeassp.2009.804.811 2011/01/11 - 03:35

Problem statement: Power flow through an AC transmission line is influenced by three basic electrical parameters, which are line impedance, magnitudes and phase-shift angle between the sending and receiving voltages. Therefore, the change in any of the three basic parameters means a change in the power flow through the transmission line. The aims of this research paper are: increase the power transfer capability of transmission systems, minimize the transmission losses, support a good voltage profile and retain system stability under large disturbances. Study the use of eigenstructure techniques for state feedback control of the power system static compensator. Therefore, the mathematical analysis was performed for eigenvector assignment, power flow transmission line and for the static compensator analysis based on the transformation of the three-phase into d-q frame. Approach: A novel control method for regulating the power system in case of abnormal conditions was carried out. The system considered is a static synchronous compensator. The study includes a detailed mathematical analysis of the impact of the shunt compensator on the power flow; investigation of the system constraints and their effects on the static compensator control; in addition simulation of static compensator to control a transmitted active power flow on the transmission line. The conducted method provides a way of constructing the state feedback gain matrix to satisfy a certain prescribed performance. Results: The solutions of the obtained equation were conducted using the computer simulation method for both open-loop and static compensator techniques. The result shows fast tracking of the power flow transient response when using the static compensator technique comparing with open-loop technique. However, the same trend of the behavior was observed for all cases. Conclusion: A new method for developing a parameterized feedback matrix that assigns a closed-loop prespecified set of eigenvalues was obtained. It improves the overall system performance and yields a class of controllers contributing uniformly to the assignment process. The voltage could be kept constant independent of the loads with static compensator. The results show clearly the applicability of the proposed control scheme which is acceptable for the static compensator.

http://www.thescipub.com/abstract/10.3844/ajeassp.2009.812.816 2011/01/11 - 03:35

Problem statement: This study was to analyze the concept of spatial-function in courtyard
house layout and its influence to the cultural and social activities. Themes such as integration,
segregation, accessibility and zoning of the building space layout are required to be deliberated, in
order to achieve further understanding about the Kurdish social and cultural benchmarks (norms) that
might have affected by the spatial configuration of the house layouts. Approach: The study was based
on the analysis from selected samples of courtyard house layouts in Erbil city, through adopting the
theory of space syntax and its techniques (gamma analysis method). The purpose was to interpret and
identify the mutual relationship between space and social life through both scales of spatial-functional
analysis. Functionally, illustration and classification of the key zones and sectors of the house;
spatially, measuring the main syntactic characteristics of spatial systems (house layouts)and translating
it to numerical data in order to identify their effect that forming spatial patterns. Results: The
functional approach for the design of residential spaces had a clear impact on the method of formation
and organization of residential spaces (functional sectors) through the indicators of physical and
intellectual change that affected the nature of spontaneous social interaction in the traditional Kurdish
courtyard houses in the city of Erbil. Conclusion: Social variables and factors stemming from the
customs and traditions of the community have a direct impact on the residential function through the
way of forming and configuration of its interior spaces, which had supported by discovering Genotypic
spatial-functional patterns of house layouts (study sample).

http://www.thescipub.com/abstract/10.3844/ajeassp.2010.560.568 2011/01/11 - 03:35

Problem statement: The waiting space is the first point of perception and reality that users
would encounter when they visit any health institution. The users’ experience in the waiting area is
very crucial in determining their preference. The study explored the physical environment of the
waiting area which affects the people’s anxiety and perception. The physical environment which links
with the interior semantics and is part of the language of space speaks volume about the users’ needs
and preferences. The study discussed the spatial contents within the environment which give comfort
to the users. How health care is delivered particular in the first meeting point between the patients and
the institution are interpreted. Approach: Combinations of physical observation on sites and in-depth
interviews were conducted to find out the real situation of users experience. Results: The physical
waiting area characteristics contributed to the comfort or discomfort of the immediate users. The
waiting time appears to be the main concern of the users. Conclusion: The findings suggested that the
adult patrons are quite happy with the seat design that is the seat affordances the adult users. The
seating arrangement could be further enhance for better affordances.

http://www.thescipub.com/abstract/10.3844/ajeassp.2010.569.575 2011/01/11 - 03:35

Problem statement: During the last fifty years, there have been significant changes on the
perspectives of space. Space definition not only involves physical features but also deals with social
capital for human development. Regarding this matter, the research puts the perspective of space as a
subject or as a work of art that needs better comprehension rather than considering it as merely an
object or fact. Kampung Kauman is a traditional Moslem village located around the Grand Mosque in
some cities of Java. In the city of Semarang, Kauman area is an expression of human culture built up
over times and experiences for three centuries. Approach: The study applies investigative-method on
the transcendental aspects of space by using ethnography-architecture. The classification of
ethnography-architecture concentrates on single case. The method applies approaches on culture and
design and also participant observation as research tools which will be concluded with open themes.
Results: After observing Kauman Pompa Semarang, the research discovers local concepts of ‘the
charity space’ and ‘the social intensive space’. Conclusion: The research is a unique knowledge for
architecture since the approach on culture reveals the role of Islamic culture in establishing kampung
Kauman (Kauman village). Ethnography-architecture is applicable to other researches in investigating
the original space concept.

http://www.thescipub.com/abstract/10.3844/ajeassp.2010.576.587 2011/01/11 - 03:35

Problem statement: Tillage is a process of creating a desirable soil condition for seed germination and growth. The tillage of soil is considered to be one of the biggest farm operations as the tillage operation requires the most energy on the farm. Manufacturers of tillage implements tend to overdesign their products due to a lack of the proper testing and analysis of tillage tools and the technical expertise required to optimize the farm operations. Chisel plow is widely used by farmers as a primary tillage tool. Performance data for chisel plow operation is essential in order to optimize its performance and reduce the cost of tillage operation. Approach: Field experiments were conducted using a fully instrumented MS 3090 tractor to evaluate the performance of a heavy duty chisel plow in a sandy soil over wide ranges of plowing depths and forward speeds. The plowing depth, forward speed and draft were measured and recorded using an instrumentation system and data logger. Results: The effects of plowing depth and forward speeds on draft, unit draft, vertical specific draft, horizontal specific draft and coefficient of pull were evaluated. The results indicated that increasing the plowing depth and/or the forward speed increased the draft, unit draft and vertical specific draft. Also, increasing the plowing depth increased the horizontal specific draft and the coefficient of pull, while increasing the forward speed decreased the horizontal specific draft and the coefficient of pull. Conclusion: About 26.7% of the draft force was directed towards cutting the soil and 73.3% was consumed in pulverization of soil particles. The values of the vertical specific draft were much higher than those of the horizontal specific draft for all plowing depths and forward speeds. The plowing depth had more pronounced effect on the draft, unit draft, specific draft and coefficient of pull than the forward speed. The optimum forward speed was 1.75 m sec-1. The recommended plowing depth should be based on the type of crop (depth of the root system).

http://www.thescipub.com/abstract/10.3844/ajeassp.2010.588.596 2011/01/11 - 03:35

Problem statement: Soil consolidation is generally time dependent, therefore soil displacement as a result root water uptake is space and time dependent. The time-dependent nature of abstraction of ground water by vegetation need to be evaluated in order understand the effect of time elapse on matric suction a generation and subsequent ground displacement. Approach: The current approach used the theory of unsaturated soils with modification due to assumption made in the course of model formulation with two stress state variables principles. A volume change was modeled as a result of matric suction change caused by vegetative induced moisture migration. The effect of elapsed time for full cycle are simulated for periods that covers a spring/summer soil-drying phase of 6 months followed by an autumn/winter 6 month recharge phase. Results: The results of this evaluation showed that the soil matric suction and deformation increases with time spring/summer soil-drying phase of 6 months followed decreases during autumn/winter 6 month recharge phase. There is also decreased in the suction generation and ground displacement as the lateral distance from the Lime tree trunk increases. Conclusion: This study provided a valuable and a relatively accurate means to estimate the influences of vegetation on ground taking the various elapsed times into account. The effect of rainfall has been incorporated into the simulation study, as study of this kind is not complete with inclusion of rainfall data.

http://www.thescipub.com/abstract/10.3844/ajeassp.2010.597.603 2011/01/11 - 03:35

Problem statement: Change detection is the process of identifying difference of the state of an object or phenomena by observing it at different time. Essentially, it involves the ability to quantify temporal effects using multi-temporal data sets. Information about change is necessary for evaluating land cover and the management of natural resources. Approach: A neural network model based on both spectral and textural analysis is developed. Change detection system in this study is presented using modified version of back-propagation-training algorithm with dynamic learning rate and momentum. Through proposed model, the two images at different dates are fed into the input layer of neural network, in addition with Variance, Skewness and Eculedian for each image that represent different texture measure. This leads to better discrimination process. Results: The results showed that the trained network with texture measures achieve 23% higher accuracy than that without textural parameters. Conclusion: Adding textural parameters of satellite images through training phase increases the efficiently of change detection process also, it provides adequate information about the type of changes. It also found, when using dynamic momentum and learning rate, time and effort needed to select their appropriate value is reduced.

http://www.thescipub.com/abstract/10.3844/ajeassp.2010.604.610 2011/01/11 - 03:35

Problem statement: Electrical Discharge Machining (EDM) has grown over the last few decades from a novelty to a mainstream manufacturing process. Though, EDM process is very demanding but the mechanism of the process is complex and far from completely understood. It is difficult to establish a model that can accurately predict the performance by correlating the process parameters. The optimum processing parameters are essential to increase the production rate and decrease the machining time, since the materials, which are processed by EDM and even the process is very costly. This research establishes empirical relations regarding machining parameters and the responses in analyzing the machinability of the stainless steel. Approach: The machining factors used are voltage, rotational speed of electrode and feed rate over the responses MRR, EWR and Ra. Response surface methodology was used to investigate the relationships and parametric interactions between the three controllable variables on the MRR, EWR and Ra. Central composite experimental design was used to estimate the model coefficients of the three factors. The responses were modeled using a response surface model based on experimental results. The significant coefficients were obtained by performing Analysis Of Variance (ANOVA) at 95% level of significance. Results: The variation in percentage errors for developed models was found within 5%. Conclusion: The developed models show that voltage and rotary motion of electrode are the most significant machining parameters influencing MRR, EWR and Ra. These models can be used to get the desired responses within the experimental range.

http://www.thescipub.com/abstract/10.3844/ajeassp.2010.611.619 2011/01/11 - 03:35

Problem statement: Elastic cylindrical shells are common structures in the fields of civil engineering and engineering mechanics. These thin-walled constructions may undergo buckling when subjected to axial compression. Buckling limits to large extent their strength performance. This phenomenon depends hugely on the initial distributed or localized geometric imperfections that are present on the shell structure. Localized geometric imperfections result in general from the operation of welding strakes to assemble the shell structure. In this study, reliability of buckling strength as it could be affected by shell material and geometry parameters was investigated. The localized geometric imperfections were chosen to be entering and having either a triangular or a wavelet form. Interaction between three localized imperfections had also been considered. Approach: A special software package which was dedicated to buckling analysis of quasi axisymmetric shells was used in order to compute the buckling load via the linear Euler buckling procedure. A set of five factors including shell aspect ratios, defect characteristics and the distance separating the localized initial geometric imperfections had been found to govern the buckling problem. A parametric study was performed to determine their relative influence on the buckling load reduction. Reliability analysis was carried out by using first order reliability method. Results: Wavelet imperfection was found to be more severe than triangular form in the range of low amplitude imperfections. It was shown also by comparison with the single imperfection case that further diminution of the critical load is obtained for three interacting imperfections. The interval distance separating the localized geometric imperfections was found to have important influence on the reliability index. Conclusion/Recommendations: In the he range of investigated parameters, reliability was found to increase with the distance separating the localized geometric imperfections. This can help performing optimal design of assembled strakes.

http://www.thescipub.com/abstract/10.3844/ajeassp.2010.620.628 2011/01/11 - 03:35

In this abstract the following commercial aircraft 3 avionics systems will be merged together: (1) Autopilot Flight Director System (APFDS), (2) Flight Control System (FCS) and (3) Flight Management Systems (FMS). Problem statement: These systems perform functions that are dependant and related to each other, also they consists of similar hardware components. Each of these systems consists of at least one computer, control panel and displays that place on view the selection and aircraft response. They receive several similar sensor inputs, or outputs of one system are fed as input to the other system. By combining the three systems, repeated and related functions are reduced. Since these systems perform related functions, designers and programmers verify that conflict between these systems is not present. Combining the three systems will eliminate such possibility. Also used space, weight, wires and connections are decreased, consequently electrical consumption is reduced. To keep redundancy, the new system can be made of multiple channels. Approach: The new system (called Autopilot Navigation Management System, APNMS) is more efficient and resolves the above mention drawbacks. Results: The APFDS system functions (as attitude-hold or heading-hold) are merged with the FCS system main function which is controlling flight control surfaces as well as other functions as flight protection, Turn coordination and flight stability augmentation. Also the Flight Management system functions (as flight planning, aircraft flight performance/engine thrust management) are merged in the new system. All this is done through combining all 3 systems logic software’s. Conclusion/Recommendations: The new APNMS system can be installed and tested on prototype aircraft in order to verify its benefits and fruits to the aviation industry.

http://www.thescipub.com/abstract/10.3844/ajeassp.2010.629.630 2011/01/11 - 03:35

Problem statement: This study presented a jointly application of bond graph technique and wave-scattering formalism for a new realization called scattering bond graph model which has the main advantage to show up explicitly the different wave propagation. Approach: For that, we proposed to find the scattering matrix from the causal bond graph model of a low-pass filter based on Microstrip lines and with cut-off frequency 10 GHz, while starting with determination of the integro-differentials operators which is based, in their determination, on the causal ways and causal algebraic loops present in the associated bond graph model and which gives rise to the wave matrix which gathers the incident and reflected waves propagation of the studied filter. Results: The scattering parameters, founded from the wave matrix, will be checked by comparison of the simulation results. Conclusion: Thereafter, we use a procedure to model directly this scattering matrix under a special bond graph model form often called “Scattering Bond Graph Model”.

http://www.thescipub.com/abstract/10.3844/ajeassp.2010.631.642 2011/01/11 - 03:35

Problem statement: Mortar mix is a major construction material in fabrication of ferrocement
structural elements. However, there have been scarce amount of technical data available on suitable mix
proportion to achieve structural grade mortar with specific strength requirement and adequate level of
workability for proper placement into construction formwork. Moreover, current practice in ferrocement
construction work which uses mortar mix with cement: sand ratio ranging between 1:1.5 to 1:2 incurs high
requirement of cement yet producing mix with suboptimum level of compressive strength. Approach: An
experimental investigation was carried out to evaluate workability and compressive strength properties of
structural grade mortar mixes with various cement: sand ratios ranging from 1:2.0-1:2.75 and varying
water/binder ratio between 0.35 and 0.50. Throughout the laboratory investigation, a total of 28 batches of
mortar mixes with various mix proportion were designed, cast and tested in accordance to relevant standards
of practice prescribed by British Standard Institute (BSI) and American Society of Testing Material
(ASTM). Results: At the end of the laboratory investigation program, high performance mortar mix with
compressive strength exceeding 55 MPa and slump level within 50-90 mm which is suitable for heavy duty
ferrocement construction work was successfully developed. Moreover, data on mix proportion for several
other grades of mortar mixes ranging from grade 35 to grade 55 were also derived. Conclusion: It was
found that optimum cement: Sand ratio of structural mortar is 1:2.25. With the use of this cement: Sand ratio
in the production of structural grade mortar mix in fabrication of ferrocement structural elements,
consumption of cement binder will be economized hence resulting in potential savings in term of material
and production cost of mortar mix in the construction industry. Besides, it was also observed that strengths
of mortar mixes do not vary linearly with cement content of the mix.

http://www.thescipub.com/abstract/10.3844/ajeassp.2010.643.649 2011/01/11 - 03:35

Problem statement: Prestressed Concrete (PC) I section girder with Reinforced
Concrete (RC) topping slab has been widely applied to long span bridge girders for several years.
A bridge girder is subjected to severe conditions caused by an aggressive environment and
overloading. A crack can be initiated and propagate when the tensile stress exceeds the tensile
strength of concrete due to overloading. Deterioration of the girder may be caused by a wide crack
due to corrosion of the reinforcement and other mechanisms. Prestressing force and flexural
stiffness (EI) of PC-I section girder are reduced depending on the level of overloading and the
corresponding damage. Approach: Full scale tests of Type III AASHTO highway girder with a 20
cm thick RC topping slab were performed to study both the degradation process due to
overloading and also the effects of external post-tension in the recovery of structural performance
of a damaged highway PC bridge girder. Results: The results showed that degradation, loss of
internal prestressing force in the PC-I girder and flexural stiffness of the composite girder depend
directly on Damage Index (DI) expressed in terms of permanent deformation. External post
tension with three levels of prestressing forces was applied to strengthen the damaged girder to
recover its structural performance, flexural stiffness and strength. A simplified analytical model,
verified by test results, was developed to predict flexural behaviors, loss of internal prestressing
force and flexural stiffness of highway girder due to overloading and also structural performance
of the strengthened girder. Conclusion: It was found that the required external prestressing force
to effectively recover structural performance of a damaged girder depended directly on the
damage index of the girder.

http://www.thescipub.com/abstract/10.3844/ajeassp.2010.650.662 2011/01/11 - 03:35

Problem statement: The need for high performance transceiver with high Signal to Noise
Ratio (SNR) has driven the communication system to utilize latest technique identified as over
sampling systems. It was the most economical modulator and decimation in communication system. It
has been proven to increase the SNR and is used in many high performance systems such as in the
Analog to Digital Converter (ADC) for wireless transceiver. Approach: This research presented the
design of the novel class of decimation and its VLSI implementation which was the sub-component in
the over sampling technique. The design and realization of main unit of decimation stage that was the
Cascaded Integrator Comb (CIC) filter, the associated half band filters and the droop correction are
also designed. The Verilog HDL code in Xilinx ISE environment has been derived to describe the
proposed advanced CIC filter properties. Consequently, Virtex-II FPGA board was used to implement
and test the design on the real hardware. The ASIC design implementation was performed accordingly
and resulted power and area measurement on chip core layout. Results: The proposed design
focused on the trade-off between the high speed and the low power consumption as well as the
silicon area and high resolution for the chip implementation which satisfies wireless communication
systems. The synthesis report illustrates the maximum clock frequency of 332 MHz with the active
core area of 0.308×0.308 mm2. Conclusion: It can be concluded that VLSI implementation of
proposed filter architecture is an enabler in solving problems that affect communication capability in
DSP application.

http://www.thescipub.com/abstract/10.3844/ajeassp.2010.663.669 2011/01/11 - 03:35

Problem statement: Arbitrary signal generators play an important role in many
applications. Several different techniques utilizing both analog and digital approaches are being used
for the generation of periodic signals. However, all of them suffer from many drawbacks. In this study,
we present modeling, simulation and prototyping of a novel periodic arbitrary signal generation system
using FPGAs. The proposed system utilizes orthogonal functions to generate a variety of periodic
arbitrary signals. Approach: A new approach for designing arbitrary signals utilizing Walsh and
Rademacher functions had been used. The design had been done using state-of-the-art high level
design techniques and has been targeted to the latest available FPGA chips from Xilinx and Altera.
Results: The simulation results demonstrated both the digital and analog versions were presented. It
was found that all the signals generated showed precisely zero error and the signal generated was
exactly the same as the desired one. Conclusion: Excellent accuracy with zero error is achieved. The
designed and implemented Arbitrary signal Generation System is stand-alone and doesn’t require the
support of any computer hardware or software, as was needed in earlier attempts It has been concluded
that virtually any periodic signal can be generated using the technique developed.

http://www.thescipub.com/abstract/10.3844/ajeassp.2010.670.677 2011/01/11 - 03:35

Problem statement: An optimal control on two axes and design for solar tracker which
called altitude and azimuth is challenge. Approach: The phototransistor with the shade that blocks the
screen was employed as a detector of solar beam radiation. The height of the screen determined the
sensitivity operation or period of tracking in this solar tracker. The phototransistor is particularly
designed to detect solar bean radiation thoroughly through the two axes with the operating time. The
mechanism of this solar tracker is that it has a capacity of solar tracking in every 10 min,
approximately, which respond in terms of time at about 37° sec-1 with and operating point at 0.3 sec.
Results: Our solar tracker obtained an average deviation at about 2.5deg;h-1. In weak sunlight however,
the value varies and fluctuates rapidly depending on sky condition. Conclusion: The accuracy of solar
position tracking function satisfied our goal as well. There is only average of 2.5deg; error shown. The
experiment also shows that the error rate diminishes as the solar radiance expand. However, we hope
to develop this device to be more exact in the position.

http://www.thescipub.com/abstract/10.3844/ajeassp.2010.678.682 2011/01/11 - 03:35

Problem statement: In this study, a systematic study based on Technology CAD (TCAD)
was taken up for the design and Virtual Wafer Fabrication (VWF) of strain-engineered MOSFETs in
Si CMOS technology. Approach: A simple manufacturable process recipe was developed to induce
uniaxial stress in channel region to obtain enhanced performance in CMOS in 45 nm technology node.
Results: Using Synopsys Sentaurus Process simulation tool, high dopant activation and low Transient
Enhanced Diffusion (TED) during processing are fully captured. A physics-based mobility model had
been developed and implemented in Synopsys Sentaurus Device tool. Sentaurus Device was used to
simulate device DC and AC characteristics and also to extract Vth, Ion and Ioff. Conclusion: Optimum
process conditions required to meet a set of device specifications had been achieved via the Design of
Experiment (DoE) study. Process Compact Model (PCM) was used for performance and
manufacturability optimization.

http://www.thescipub.com/abstract/10.3844/ajeassp.2010.683.692 2011/01/11 - 03:35

Problem statement: The objective of this study was to optimize the geometrical parameters
of a bubble pump integrated in a solar flat plate collector. Approach: This solar bubble pump was part
of an ammonia/water/helium (NH3/H2O/He) absorption-diffusion cooling system. Results: An
empirical model was developed on the basis of momentum, mass, material equations and energy
balances. The mathematical model was solved using the simulation tool “Engineering Equation Solver
(EES)”. Conclusion/Recommendations: Using metrological data from Gabes (Tunisia) various
parameters were geometrically optimized for maximum bubble pump efficiency which was best for a
bubble pump tube diameter of 6 mm, a tube length of 1.5 m, an inclination to the horizontal between
30 and 50° of the solar flat plate collector and a submergence ratio between 0.2 and 0.3.

http://www.thescipub.com/abstract/10.3844/ajeassp.2010.693.698 2011/01/11 - 03:35

Problem statement: Each year, a major part of revenues spent on Investing in sector
development plans and State infrastructures filled with clear reduce costs and done on time Projects
leading to high savings budget plans executive and will be return on Investment. Approach: On
transportation projects, Value Engineering (VE) teamwork by involving construction, design and
maintenance staff review the construction project features and look for ways to improve quality,
control costs and time. Also this study briefly described VE and quality, cost schedule planning,
application of VE, cost parameters, relationship of value, function, cost and worth. Results: VE,
highway construction was survived and opportunities for better, less expensive means of completing
the construction projects were analyzed. The intention is to progress project quality and productivity,
foster innovation, optimize design elements, also ensure overall economical costs. Conclusion: This
study achieved to the model Value Engineering in Highway Construction (VEHC) which cause
decrease time, decrease cost and increase quality in highway it has been.

http://www.thescipub.com/abstract/10.3844/ajeassp.2010.699.703 2011/01/11 - 03:35

Problem statement: Due to the climatic variation for the year and it's sever harmattan
during the month of December to March with the high keraunic level (80-90) in the areas, it was
necessary to know the seasonal variation of soil resistivity. The seasonal variation and the nature of
soil have considerable influence on electrical characteristics and therefore affect the earthling system
performance. Approach: Eighteen sites were chosen from three main soil divisions. The soil
resistivity was taken in each of the site at depths of 0.5, 0.8 and 1.2 m using the four point test
instrument (Wenner Method). From the selected sites in the three soil divisions the temperature was
also taken at depths of 0.2, 0.5, 0.8 and 1.0 m. Results: The coefficient of seasonal variation at the
depth of 0.5 m was high and reduced drastically at a depth of 1.2 m. The soil temperature was higher
than the ambient temperature at the depth of 0.2 m during the months of December to March. From 0.8
m depth and below the temperature reduced even during the dry seasons. Conclusion: The coefficient
of seasonal variation of soil at the depth of 0.8 and 1.2 m was small (1.8-3.0) throughout the year in all
soil types. That indicates the high water level and or the permanent moisture table which gives an
advantage to low soil resistivity for buried conductors and electrodes in the area.

http://www.thescipub.com/abstract/10.3844/ajeassp.2010.704.709 2011/01/11 - 03:35

Problem statement: This study introduced a variable step-size Least Mean-Square (LMS)
algorithm in which the step-size is dependent on the Euclidian vector norm of the system output error.
The error vector includes the last L values of the error, where L is a parameter to be chosen properly
together with other parameters in the proposed algorithm to achieve a trade-off between speed of
convergence and misadjustment. Approach: The performance of the algorithm was analyzed,
simulated and compared to the Normalized LMS (NLMS) algorithm in several input environments.
Results: Computer simulation results demonstrated substantial improvements in the speed of
convergence of the proposed algorithms over other algorithms in stationary environments for the same
small level of misadjustment. In addition, the proposed algorithm shows superior tracking capability
when the system is subjected to an abrupt disturbance. Conclusion: For nonstationary environments,
the algorithm performs as well NLMS and other variable step-size algorithms.

http://www.thescipub.com/abstract/10.3844/ajeassp.2010.710.717 2011/01/11 - 03:35

Problem statement: The study addressed the problem of selecting the appropriate microassembly
techniques according to the micro-part features. Actually, in the micro-domain, the choice of
the correct assembly technique is highly dependent on the micro-part characteristics such as shape,
geometry and material. Approach: Since there was an incomplete and unstructured knowledge about
the micro-assembly, the study proposed a Decision Support System (DSS) as solution for assisting the
designer in the correct selection of the most suitable micro-assembly strategies. The first step was
establishing a structured correlation between micro-assembly techniques and part features. In particular
the phases grasping and releasing were adopted as test-study for their importance in the microassembly
process. The second step was the set up of a multistage model for the selection of the
grasping-releasing technique and the implementation of the model in an Expert System as a set of
rules. Results: The DSS was tested on some common micro-parts producing a scored list of selected
grasping-releasing methods. Conclusion: The DSS proved quite valuable in the selection and the
scoring of the micro-assembly principles that suit specific applications.

http://www.thescipub.com/abstract/10.3844/ajeassp.2010.718.722 2011/01/11 - 03:35

Problem statement: In this article, some important aspects linked to the new Ceppo
Morelli (Piemonte, Italy) future by-pass tunnel construction were considered. Approach: The article
concerned a mountainous region which in the past was affected by slope landslides and block falls that
reached a downhill roadway and two nearby villages. Results: Using risk analysis approach the
probability of block-falls down the mountain slopes was accomplished, with estimation of their
trajectories. Conclusion: Obtained results proved the need to open the new tunnel because the present
roadway is not considered risk free.

http://www.thescipub.com/abstract/10.3844/ajeassp.2010.723.727 2011/01/11 - 03:35

Problem statement: Commodity Flow Survey (CFS) was launched to collect
comprehensive freight flow data throughout the kingdom of Thailand. The survey’s database is the
most complete collection of commodity flow data in Thailand. The need to reveal interregional freight
characteristics using available data from the CFS led to the objectives of this research. Approach: An
origin destination matrix based on province was calibrated using a flexible Box-Cox function form. It
used maximum likelihood and the backward method for calibration and Root Mean Square Error
(RMSE) and Mean Relative Error (MRE) to verify the model’s performance. Independent variables
were classified into three groups: origin variable, destination variable and geographic variable. The
origin variable represented the behavior of the trip as generated at the place of origin. Some
consumption occurred at the origin. The employment and the average plant size variables were
selected for potential productivity while personal income per capita and total populations were
included to explain consumption behavior at the origin. Personal income per capita and total
populations were selected for destination variables which act as proxy for final demand at the
destination. The third category, distance, was the most conventional friction variable for geographical
variables. Results: The calibrated model revealed that origin income, origin average plant size and
origin population performed poorly. Therefore these variables were eliminated. The best developed
model included four strongly significant variables at a 5% level: origin employment, destination
population, destination income per capita and distance. Conclusion: The results showed that the
selected variables and the Box-Cox functional form were successful in explaining behavior of
interregional freight transportation in Thailand. The developed model was the first interregional freight
transportation model to be calibrated against Thailand commodity flow survey data.

http://www.thescipub.com/abstract/10.3844/ajeassp.2010.728.733 2011/01/11 - 03:35

Problem statement: Internal soil erosion is a real threat for hydraulic infrastructures. In
its final stage it develops in piping involving the formation and progression of a continuous void
inside the soil between the upstream and downstream sides. The hole erosion test was introduced to
characterize kinematics of piping in terms of the time left to rupture. Actual modeling approaches of
this test are essentially one dimensional. The wall shear stress generated by the flow is assumed to be
uniform, so that erosion rate is also uniform along the hole length. Experimental observations show
however an irregular profile of the eroded hole. Approach: In this study an axisymmetric extension
representation of the hole erosion test was performed. The biphasic flow at the origin of surface
erosion occurring in the porous soil sample was modeled by means of the renormalization group
based k-ε turbulence equations. Fluent software package was used to perform the numerical
modeling. Results: This had enabled to estimate the wall shear stress which was found to be non
uniform along the hole length. Erosion rate was then estimated by using a classical law. Its variations
as affected by the applied gradient pressure, fluid density as well as the actual fluid/soil interface
roughness were analyzed. In particular, wall roughness and clay concentration were found to
increase noticeably the erosion rate. Conclusion/Recommendations: Predicting erosion rate at the
start of piping formation can be done by the proposed model. Flow features are however very
complex in the real HET configuration. In particular, clay concentration does not vary equally along
the hole length. The erosion law coefficients are variable. Transport phenomenon of some soils
particles that detach is present in the problem. Further investigations including these aspects should
be performed in order to render more profoundly the complex physics involved in this experiment.

http://www.thescipub.com/abstract/10.3844/ajeassp.2010.734.739 2011/01/11 - 03:35

Problem statement: In this study, the behavior of abutment wall in full height frame
integral abutment bridges was investigated. It was seen that the effect of backfill soil resistance on
behavior of abutment wall movement is mostly neglected in previous studies. In this research, the final
bridge superstructure displacement under temperature-induced forces was formulated. In addition,
according to the final bridge displacement, the earth pressure that acts as a resistant force on the bridge
abutment using the new equation from British design manual for roads and bridges, BA 42/96 was
used. Besides, in the construction of integral bridges, the deck and girders are mostly encased into
abutment wall, which makes these bridge components as fixed elements. This fix connectivity makes
the top abutment wall move along with the bridge deck. Moreover, the abutment wall in integral
bridges is made of reinforced concrete and thus, it could be assumed as a rigid mass that has a linear
deformation behavior. Approach: To implement a new method to calculate the amount of abutment
wall movement at different elevations in full height frame abutment integral bridges, considering the
parameters such as temperature changes, bridge deck elongation and the backfill soil resistance. First,
internal forces of the bridge abutment were formulated. They were all presented as functions of bridge
deck final displacement. Second, different methods to calculate the soil lateral pressure were used.
Third, the numerical modeling was applied and the corresponding results due to the bridge deck
elongation were extracted. Fourth, the results obtained from phases two and three were compared to
obtain some conclusion. Results: The results derived in this study, consisted of four data sets. First, the
existing forces such as the bridge deck elongation force, the backfill soil resistance etc. were
formulated according to the bridge final displacement. Then after, the static principals revealed the
amount of deck final elongation. For the second set, different correlations such as British Standard,
Massachusetts manual and etc. which had considered the effect of deck final displacement in their
formulas were presented and with regard to the first part, the backfill reactions were obtained. For the
third set, by combining the results from set one and two, different values for the deck final
displacement were derived. For the next step, according to the fix connectivity of the abutment and the
bridge deck, the abutment top elevation displacement was set equal to the deck final displacement. For
the bottom elevation, because of the rigidity of the wall and the rotational behavior about its
foundation, the displacement was set zero. Therefore, by assuming linear deformation behavior of rigid
masses, the abutment deformation profile for different elevations was concluded. For the last set, the
bridge computer model was built using SAP2000 and the corresponding results were collected.
Conclusion: It was seen that, generally, except for some certain cases, all the used correlations in this
study were in a close agreement either with each other or with the Finite Element data. British
Standard method had the closest results to the finite element data and thus preferably it is
recommended while the others not denied.

http://www.thescipub.com/abstract/10.3844/ajeassp.2010.749.756 2011/01/11 - 03:35

Problem statement: The need for wireless communication has driven the communication
systems to high performance. However, the main bottleneck that affects the communication capability
is the Fast Fourier Transform (FFT), which is the core of most modulators. Approach: This study
presented on-chip implementation of pipeline digit-slicing multiplier-less butterfly for FFT structure.
The approach taken; in order to reduce computation complexity in butterfly, digit-slicing multiplierless
single constant technique was utilized in the critical path of Radix-2 Decimation In Time (DIT)
FFT structure. The proposed design focused on the trade-off between the speed and active silicon area
for the chip implementation. The new architecture was investigated and simulated with MATLAB
software. The Verilog HDL code in Xilinx ISE environment was derived to describe the FFT Butterfly
functionality and was downloaded to Virtex II FPGA board. Consequently, the Virtex-II FG456 Proto
board was used to implement and test the design on the real hardware. Results: As a result, from the
findings, the synthesis report indicates the maximum clock frequency of 549.75 MHz with the total
equivalent gate count of 31,159 is a marked and significant improvement over Radix 2 FFT butterfly.
In comparison with the conventional butterfly architecture, design that can only run at a maximum
clock frequency of 198.987 MHz and the conventional multiplier can only run at a maximum clock
frequency of 220.160 MHz, the proposed system exhibits better results. The resulting maximum clock
frequency increases by about 276.28% for the FFT butterfly and about 277.06% for the multiplier.
Conclusion: It can be concluded that on-chip implementation of pipeline digit-slicing multiplier-less
butterfly for FFT structure is an enabler in solving problems that affect communications capability in
FFT and possesses huge potentials for future related works and research areas.

http://www.thescipub.com/abstract/10.3844/ajeassp.2010.757.764 2011/01/11 - 03:35

Problem statement: Internal erosion occurs in soils containing fine particles under the
action of high pressure gradients that could result from water discharge. This phenomenon can yield in
its final stage to the formation of piping which constitutes a real threat for hydraulics infrastructures as
it can precipitate their entire rupture in very short time. In order to mitigate this insidious hazard, it is
important to characterize piping dynamics. In this context, the Hole Erosion Test was introduced to
assess the erosive features of soils by means of two parameters, the erosion rate and the critical shear
stress indicating the beginning of erosion. Modeling this test can enable to understand more
comprehensibly the piping phenomenology. Approach: A simplified analytical modeling of the Hole
Erosion Test was considered in this study. A closed form solution of erosion taking place during piping
was derived without resorting to the habitual cumbersome developments that are needed to achieve
complete solution of the rational equations describing this highly coupled problem. This was achieved
by assuming formal analogy between the erosive shear stress and the friction shear that develops at a
cylindrical piping wall under an axial viscous flow. The flow was assumed to be uniform along the
tube. Results: A closed form analytical formula describing erosion dynamics associated to piping was
derived. Theoretical predictions were compared with experimental results and the simplified model
was found to predict accurately the increase of flow rate that results from piping erosion.
Conclusion/Recommendations: The one-dimensional modeling that was proposed for the Hole
Erosion Test under strong simplifying assumptions was found to yield the same features as those
obtained in the literature by using other approaches. It gives furthermore the dynamics as function of
the fluid regime existing inside the tube. In order to get further insight regarding the flowing flow
action, which could be non uniform during erosion, more advanced modeling is needed.

http://www.thescipub.com/abstract/10.3844/ajeassp.2010.765.768 2011/01/11 - 03:35

Problem statement: Lifetime of standard dog-bone specimens made form steel as affected
by phasing between thermal cycles and strains cycles and by cycle duration in thermomechanical
fatigue is assessed under various conditions of loading. Approach: The methodology used was based
on finite element post-processing analysis by specialized fatigue software package that takes into
account coupling of damage from three primary sources: Fatigue, oxidation and creep. Results: A
parametric study has been conducted for various thermomechanical loadings and effects of phasing
and cycle duration on lifetime have been evaluated. The associated percentages of damage mechanisms
due to fatigue, oxidation and creep have been determined. Conclusion: It has been shown that both
phasing and cycle duration have considerable effect on lifetime. In the range of parameters investigated,
the in-phase cycles were found to reduce considerably damage in the specimen for low pressures and low
temperatures. The results have shown also that there was no way of unique comparison of the various
phasing configurations, since there exists always a case of thermomechanical loading for which one
phasing configuration yields higher damage than any another configuration.

http://www.thescipub.com/abstract/10.3844/ajeassp.2010.740.748 2011/01/11 - 03:35

Demand for lighter and stiffer products has been increasing in the last few years especially in automobile manufacturing. The closed die forging process of Metal Matrix Material (MMC) is presented as possible solution, since it produces parts with good mechanical properties and lighter weight. A computational modeling of closed die forging process using finite element method and optimization techniques makes the design optimization faster and more efficient, decreasing the use of conventional trial and error methods. In this study, the application of commercial finite element software (ANSYS) has been used to model cold closed die forging process. The model has been developed using ANSYS Parametric Design Language (APDL) to simulate a single stage axi-symmetry closed die forging process for H cross sectional shape. The material used is AlMgSi matrix with 15% SiC particles. Its flow curve and fractural strain are obtained from the literature. ANSYS Optimizer is used to obtain the maximum height in which the material can flow in the rib by changing Design Variables (DV) and State Variables (SV). Normally design variables are geometrical parameters such as, rib height to width ratio, web height to rib height ratio, fillet radii, draft angle and billet radius. State Variables (SV) are some parameters that depend on the design variables such as, the equivalent strain which must be below the fracture strain of the MMC material, and an acceptable contact gap (within the allowable tolerances range). Optimization method called Sub-Problem Approximation Method was used to find out the optimal design set. The technique used in this study can be used for newly developed materials to investigate its forgeability for much complicated shapes in closed die forging process.

http://www.thescipub.com/abstract/10.3844/ajeassp.2008.1.6 2011/01/11 - 03:34

Problem statement: Peat soil is well known to deform and fail under a light surcharge load and is characterized with low shear strength, high compressibility and high water content. With the rising demand from the construction industry, utilization of these soils is required and suitable technique needs to be found out for stabilizing them. Approach: Model study had been carried to stabilize peat soil using cement as binding agent and polypropylene fibers as additive. Due to high natural water content of the peat soil, the stabilized peat soil samples were kept at normal room temperature and relative humidity for air curing for 90 days. The improvement in the mechanical strength of the stabilized samples was studied by California Bearing Ratio (CBR) test for both, unsoaked and soaked samples. The water-cement ratio of the samples was measured for 180 days to study the improvement in strength over time. Results: The results of CBR tests showed an increase by a factor over 22 for unsoaked condition and 15 for the soaked condition of the stabilized samples. With the addition of the polypropylene fibers to the stabilized peat soil with cement not only improved the strength of the stabilized peat soil but also contributed to considerable amount of uniformity and intactness to the stabilized peat soil samples. It was also observed that as the curing time for the stabilized peat soil continued through 180 days the moisture content continued to decrease as well. Thus the water-cement (w/c) ratio reduced and as a result of cement hydration, the strength stabilized peat soil samples increased in hardness and gained strength through the curing period. Conclusion/Recommendations: Cement and polypropylene fibers can be used to improve the mechanical strength of the soft peat soil by adopting air curing technique.

http://www.thescipub.com/abstract/10.3844/ajeassp.2010.1.6 2011/01/11 - 03:34

There has been a gaining interest in the use of fuel ethanol from fermentation process. A main challenge in producing the ethanol concerned the production cost which was largely contributed by the process of water removal. Distillation could remove water to a certain level but due to ethanol-water azeotrope an extra process was needed before ethanol could be blended with gasoline. Problem statement: Pressure Swing Adsorption (PSA) process was attractive for final separation since it required less energy and lower setup cost. Despite many researches on simulation and experimental works on adsorption of water on 3A zeolite in a fixed bed, none have studied a process with the actual PSA system. Approach: The purpose of this research was to study the PSA process with two adsorbers and effects of several parameters. The research also included analysis of kinetic and thermodynamic data of ethanol-water adsorption on commercial 3A zeolites in a single fixed bed. Two-level factorial design experiment was used in this research works to preliminary screen the influence and interaction among each factor. Results: From the experimental works, it was found that the most suitable condition for water adsorption on 30 g of zeolite was at 90°C initial bed temperature, feed flow rate of 1 mL min1 and feed concentration of 95% vol ethanol. Langmuir isotherm could best predict the experimental results and the corresponding equation was proposed. In the PSA pilot test, the principal factors, which had an effect on the adsorption rate, recovery, and the enrichment of the product, were feed rate, feed concentration, adsorption pressure and the cycle time. Prediction of the process efficiency in terms of ethanol recovery and enrichment was proposed in the form of regression models. Conclusions/Recommendations: The results of the study in a fixed bed adsorber could help designing a pilot scale PSA unit. The experiments proved to be successful in terms of producing high concentration ethanol with acceptable percentage of ethanol recovery. With further simulation works, the process could be scaled up for an industrial use.

http://www.thescipub.com/abstract/10.3844/ajeassp.2009.1.7 2011/01/11 - 03:34

This research was to study the comparisons of heat transfer performance of closed-looped oscillating heat pipe and closed-looped oscillating heat pipe with check valves heat exchangers with R134a, Ethanol and water were used as the working fluids. A set of heat pipe heat exchanger (CLOHP and CLOHP/CV) were made of copper tubes in combination of following dimension: 2.03 mm inside diameter: 40 turns, with 20, 10 and 20 cm for evaporator, adiabatic and condenser sections lengths. The working fluid was filled in the tube at the filling ratio of 50%. The evaporator section was given heat by heater while the condenser section was cooled by air. The adiabatic section was properly insulated. In the test operation, it could be concluded as follows. It indicated that the heat transfer performance of closed-looped oscillating heat pipe with check valves heat exchanger better than closed-looped oscillating heat exchanger.

http://www.thescipub.com/abstract/10.3844/ajeassp.2008.7.11 2011/01/11 - 03:34

Problem statement: This study proposed a systematic model of delivering Ready Mixed Concrete (RMC) that optimizes the schedule of dispatching RMC trucks. Approach: Firstly, the factors that impact the RMC delivery process are analyzed. Secondly, a model based on Bee Colony Optimization (BCO) was developed in order to find the best dispatching schedule which minimized the total waiting duration of RMC trucks at construction sites subject to the needs of RMC deliveries from different construction sites. Results: To demonstrate its efficiency, the BCO algorithm was applied to solve two dispatching RMC problems. The simulation results obtained from the BCO are compared to those achieved from the conventional approaches i.e., Genetic Algorithm (GA) and Tabu Search (TS) algorithm. Conclusion/Recommendations: The experimental results showed that the BCO approach is can quickly generate efficient and flexible solutions to dispatching RMC trucks. Furthermore, the obtained results had higher quality solution efficiently and faster computational time than the conventional approaches.

http://www.thescipub.com/abstract/10.3844/ajeassp.2010.7.14 2011/01/11 - 03:34

Problem statement: In a competitive electricity market with limited number of producers, Generation Companies (Gencos) is facing an oligopoly market rather than a perfect competition. Under oligopoly market environment, each Genco may increase its own profit through a favorable bidding strategy. The objective of a Genco is to maximize its profit and minimize the associated risk. In order to achieve this goal, it is necessary and important for the Genco to make optimal bidding strategies with risk management before bidding into spot market to get an expected high profit, since spot prices are substantially volatile. This study propose a method to build optimal bidding strategies in a day-ahead electricity market with incomplete information and considering both risk management and unit commitment. Approach: The proposed methodology employs the Monte Carlo simulation for modeling a risk management and a strategic behavior of rival. A probability density function (pdf), Value at Risk (VaR) and Monte Carlo simulation used to build optimal bidding strategies for a Genco. Results: The result of the proposed method shows that a Genco can build optimal bidding strategies to maximize expected total profit considering unit commitment and risk management. The Genco controls the risk by setting the confidence level. If the Genco increase the confidence level, the expected total VaR of profit decrease. Conclusions/Recommendations: The proposed method for building optimal bidding strategies in a day-ahead electricity market to maximize expected total profit considering unit commitment and risk management is helpful for a Genco to make a decision to submit bidding to the Independent System Operator (ISO).

http://www.thescipub.com/abstract/10.3844/ajeassp.2009.8.16 2011/01/11 - 03:34