Skip to Content

Instrukcja korzystania z Biblioteki

Serwisy:

Ukryty Internet | Wyszukiwarki specjalistyczne tekstów i źródeł naukowych | Translatory online | Encyklopedie i słowniki online

Translator:

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

The most important aim for industrialists is the prevention and the evaluation of their products state since non-predicted failure is very expensive in some cases. This can be done mainly by the evaluation of the “Remaining Useful Lifetime” (RUL) by the means of prognostic approaches compensating the inconveniences of classical maintenance strategies. A proposed analytic prognostic methodology based on damage laws, such as Paris-Erdogan’s and Palmgren-Miner’s laws, is developed here to determine the RUL of the system. It permits to ensure a high availability and productivity with less cost for industrial systems. To make this approach more reliable, it is essential to introduce the stochastic description. For the case of fatigue effect where damage state is growing from macro-cracks to total failure, D(N) expresses an increasing scalar damage function in terms of loading cycles N. The RUL is estimated from a predefined threshold of damage DC. Pipelines tubes, subject to fatigue effects due to pressure-depression alternation, belong to vital mechanical systems in petrochemical industries that serve to transport natural gases or liquids. The prognostic evaluation of their states increases the tubes availability while minimizing their missions cost.

http://www.thescipub.com/abstract/10.3844/ajeassp.2013.145.160 2013/06/09 - 09:17

Engineering design under uncertainty has gained considerable attention in recent years. A great multitude of new design optimization methodologies and reliability analysis approaches are put forth with the aim of accommodating various uncertainties. Uncertainties in practical engineering applications are commonly classified into two categories, i.e., aleatory uncertainty and epistemic uncertainty. Aleatory uncertainty arises because of unpredictable variation in the performance and processes of systems, it is irreducible even adding more data or knowledge. On the other hand, epistemic uncertainty stems from lack of knowledge of the system due to limited data, measurement limitations, or simplified approximations in modeling system behavior and it can be reduced by obtaining more data or knowledge. More specifically, aleatory uncertainty is naturally represented by a statistical distribution and its associated parameters can be characterized by sufficient data. If, however, the data is limited and can be quantified in a statistical sense, epistemic uncertainty can be considered as an alternative tool in such a situation. Of the several optional treatments for epistemic uncertainty, possibility theory and evidence theory have proved to be the most computationally efficient and stable for reliability analysis and engineering design optimization. This study first attempts to provide a better understanding of uncertainty in engineering design by giving a comprehensive overview of its classifications, theories and design considerations. Then a review is conducted of general topics such as the foundations and applications of possibility theory and evidence theory. This overview includes the most recent results from theoretical research, computational developments and performance improvement of possibility theory and evidence theory with an emphasis on revealing the capability and characteristics of quantifying uncertainty from different perspectives. Possibility and evidence theory-based reliability methods have many advantages for practical engineering when compared with traditional probability-based reliability methods. They can work well under limited data while the latter need large amounts of information, more than possible in engineering practice due to aleatory and epistemic uncertainties. The possible directions for future work are summarized.

http://www.thescipub.com/abstract/10.3844/ajeassp.2013.95.136 2013/06/09 - 09:17

In this study, a novel planar µ-Negative (MNG) metamaterial structure based on Split Ring Resonators (SRRs) with improved rejection bandwidth is presented. A bridging technique is used to connect two SRR unit cells at the center to emulate a cascaded filter. The proposed structure achieved a -20 dB rejection bandwidth of 15.5% compared to 4.5% for the conventional SRRs which makes it a good candidate for integration with antennas and RF circuits that require large operational bandwidth.

http://www.thescipub.com/abstract/10.3844/ajeassp.2013.137.144 2013/06/09 - 09:17

Mammogram is the best available radiographic method to detect breast cancer in the early stage. However detecting a microcalcification clusters in the early stage is a tough task for the radiologist. Herein we present a novel approach for classifying microcalcification in digital mammograms using Nonsubsampled Contourlet Transform (NSCT) and Support Vector Machine (SVM). The classification of microcalcification is achieved by extracting the microcalcification features from the Contourlet coefficients of the image and the outcomes are used as an input to the SVM for classification. The system classifies the mammogram images as normal or abnormal and the abnormal severity as benign or malignant. The evaluation of the system is carried on using Mammography Image Analysis Society (MIAS) database. The experimental result shows that the proposed method provides improved classification rate.

http://www.thescipub.com/abstract/10.3844/ajeassp.2013.57.68 2013/06/09 - 09:17

Succession is one of the most studied processes in ecology and succession theory provides strong predictability. However, few attempts have been made to influence the course of succession thereby testing the hypothesis that the passage of one stage is essential to enter a next one. At each stage of succession ecosystem processes may be affected by the diversity of species present, but there is little empirical evidence showing that plant species diversity may affect succession. The main objective in the present study is to test if there is any effect of plant species diversity on the functioning of artificially-created grassland communities. We were mostly interested in how successful is the sowing of meadow species into newly abandoned land and how long do the effect of initial sowing persist, how is affected the set of natural colonizers, which includes both the weed species and also the later successional species arriving naturally into the zone. One of the main questions concerning succession is to which extent the trajectory may be predictable or not. What will be the consequence of the different succession pathways for ecosystem processes, such as productivity and resource utilization, as well as species composition of both above and belowground communities? What will be the subsequent effects of feed back to vegetation development through initial manipulation of vegetation after land abandonment? And, finally, how general may results be when obtained in specific conditions? Our hypothesis is that an increase in the initial plant species diversity at the start of secondary succession enhances the amount of biomass produced and consequently stimulates the soil microbial biomass and the abundance of soil invertebrates. It has been suggested that changes in plant species diversity affect several ecosystem processes, such as primary productivity, nutrient retention and vegetation dynamics. A positive impact of species diversity on plant productivity has been explained by the complementarity of resource use among plant species or their functional groups.

http://www.thescipub.com/abstract/10.3844/ajeassp.2013.69.86 2013/06/09 - 09:17

The behavior of reinforced concrete beams at failure by shear is distinctly different from their behavior by bending, which is considered to be unsafe mode of failure. The shear failure of beams is usually sudden without sufficient advanced warning and the diagonal cracks that develop due to excess shear forces are considerably wider than the flexural cracks. The cost and safety of shear reinforcement in reinforced concrete beams led to the study of other alternatives. Swimmer bar system is a new type of shear reinforcement. It is a small inclined bars, with its both ends bent horizontally for a short distance and welded to both top and bottom flexural steel reinforcement. Regardless of the number of swimmer bars used in each inclined plane, the swimmer bars form plane-crack interceptor system instead of bar-crack interceptor system when stirrups are used. Test results of several reinforced concrete beams will be presented. The effectiveness of the new swimmer bar system as related to the old stirrup system will be discussed. Beam deflection is also targeted experimentally in the lab. Several deflection measurements were taken to study the effect of using new swimmer bar system on deflection. Also the crack width of the tested reinforced concrete beams was monitored.

http://www.thescipub.com/abstract/10.3844/ajeassp.2013.87.94 2013/06/09 - 09:17

Predicting Remaining Useful Lifetime (RUL) of industrial systems becomes currently an important aim for industrialists knowing that the expensive failure can occur suddenly. As the classical strategies of maintenance are not efficient and practical because they neglect the evolving product state and environment, the recent prognostic approaches try to fill this gap. This approach shows to be important in ensuring high availability in minimum costs for industrial systems, like in aerospace, defense, petro-chemistry and automobiles. An analytic prognostic methodology based on existing damage laws in fracture mechanics, such as Paris’ and Miner’s laws, is recently developed for determining the system RUL. Damages have been assumed to be accumulated linearly, since we have considered the widely used linear Miner’s law. In this study, the nonlinear case in damage accumulation is explored to take into account the complex behavior of some materials subject to fatigue effects. It is useful especially when the nature of applied constraints and influent environment contribute to accentuate this nonlinearity. Our damage model is based on the accumulation of a damage measurement D(N) after each loading cycle N. In automobile industry, the prognostic assessment of the suspension component by this developed nonlinear approach shows its importance for the same earlier reasons.

http://www.thescipub.com/abstract/10.3844/ajeassp.2013.42.56 2013/06/09 - 09:17

In seismic prone regions, buildings are designed to maintain sufficient stiffness during moderate earthquakes and to absorb and dissipate a large amount of the energy released due to severe earthquakes. The usual steel framing systems; the moment frames require larger member sections to satisfy stiffness requirements and have large ductility capacity, the concentrically braced frames satisfy stiffness on the expense of ductility requirements, resulting in poor energy dissipation. This study deals with the eccentrically Braced Steel Frames (EBF). EBF configuration is similar to traditional braced frames with the exception that at least one end of each brace must be eccentrically connected to the frame. The energy dissipation is achieved through the yielding of a beam segment called the link, while the other frame members, including outer beam segments, braces and columns, should remain essentially elastic. EBFs offer an economical steel framing system satisfying both stiffness and ductility requirements. The study incorporates conducting nonlinear finite element analysis to study the effect of the link length and link section on the behavior of D types EBF systems. The study involves material and geometric nonlinearities.

http://www.thescipub.com/abstract/10.3844/ajeassp.2013.31.41 2013/06/09 - 09:17

Limited phase range and narrower bandwidth are the main performance limitations of reflectarray antennas for high gain applications which result in the performance to be restricted particularly in satellite and earth observatory systems. This study provides a thorough investigation on the tunability performance of reflectarrays designed in X-band frequency range using different non-linear dielectric substrates. An investigation of phase agility characteristics of reflectarray rectangular patch antenna printed above non-linear materials (0.17≤ Δε ≤0.45) is thoroughly presented. A detailed analytical study on dynamic phase range and frequency tunability of the reflectarrays is carried out based on the analytical investigation which is validated by Finite Integral Method (FIM). As the dielectric anisotropy of non-linear materials increases from 0.17-0.45 the frequency tunability performance of the reflectarray antenna is shown to increase from 372-796 MHz. The results show that LC-B1 with a dielectric anisotropy of 0.45 contributes a maximum dynamic phase range and frequency tunability performance of 160° and 796 MHz respectively. The dielectric non-linear properties presented in this study are shown to considerably affect the frequency and phase range performance of reflectarray antenna particularly for rapid dynamic phase change of terrestrial systems.

http://www.thescipub.com/abstract/10.3844/ajeassp.2013.25.30 2013/03/28 - 01:08

This study describes the impact of alternative building material envelope systems on the overall thermal performance of four selected materials used in Sana’a, Yemen. These systems included adobe, brick, stone and concrete block. After thorough on-site investigation and data collection, the information, along with regional weather data were input into the Ecotect energy simulation software for thermal performance evaluation. The objective was to search for affordable and energy-efficient construction techniques suitable for settlements and incorporating traditional cultural values in a arid upland region characterized by cold winters and warm, dry summers. This was pursued by analyzing temperature and measurements within buildings constructed from a variety of traditional and modern materials. The thermal behavior and comfort, the patterns of energy use and the appropriateness of the different building techniques and materials are analyzed, compared and discussed. We demonstrate how a building envelope reacts to outdoor conditions through graphic illustration and show ways in which the research can be extended by the creation of simulations using Ecotect software. This research contributes to the promotion of passive and low energy architecture towards a sustainable future.

http://www.thescipub.com/abstract/10.3844/ajeassp.2013.20.24 2013/03/25 - 11:02

A honeycomb core with half-circular cut-away sections at the spine (the adjoining cell walls) is designed and developed and numerically tested under axial dynamic load condition. The parametric study is invoked to identify the effect of various circular cut-away dimensions. In one embodiment a half-circular shaped cuts are removed from the top of the cell where the cell is impacted and its radius decreases toward the trailing edge of the cell. Numerical (FE) analysis was performed using explicit ANSYS/LS-DYNA and LS-DYNA codes to investigate the crushing performance, where impact angles 30° and 90° was combined with velocity of 5:3 m/sec. The crushing strength and internal energy absorption of the modified honeycomb cores with cut-away sections are then monitored to define the design parameters. The representative Y-section (axisymmetric model) is used for numerical analysis which simulates the honeycomb crushing performance. The numerical results of these innovative models show cyclic buckling effect in which crushing strength increases linearly as the rigid wall passes through. The FE results are validated with corresponding published experiments of the original unmodified honeycomb core (without cut-away).

http://www.thescipub.com/abstract/10.3844/ajeassp.2013.8.19 2013/03/12 - 22:13

Nowadays the world has experiencing global warming due to excessive energy release into atmospheres. Today, a lot of research being conducted on ways to recover or reused the energy losses. An experimental investigation has been carried out to identify the most suitable cooling system techniques to achieve a stable and sustainable power output. Four types of Thermoelectric Module (TEM) was fitted and tested on different cooling system techniques. Testing was conducted using a candle flame as a heat source to produce a suitable temperature with the maximum temperature of 200°C. An electronic circuit is used to provide a constant and sufficient power. The use of suitable cooling system and TEM was found by investigating the module parameters such as the temperature different of hot to cold side, number of thermo elements and internal resistance. This research contributes an important role in saving energy and reducing the dependency to primary energy sources (AC power or battery)."

http://www.thescipub.com/abstract/10.3844/ajeassp.2013.1.7 2013/03/08 - 17:10

With the onset of the first ever Greenhouse Gas (GHG) regulation for ships by the International Maritime Organisation (IMO) in 2011, the container shipping industry requires the combined use of technical and operational emissions reduction measures to improve the environmental performance of its vessels. Studies show that most existing measures are cost effective with a range of emissions reduction potential. However, the level of implementation is not depicted and the potential of the measures may be over-estimated. An evaluation of the emissions reduction measures is conducted through the examination of 3 factors, namely level of implementation, emissions reduction potential and cost effectiveness. Strategies to overcome the critical barriers of implementation are suggested in this study. Lastly, recommendations for companies with regards to GHG issues are made. The strong link between cost effectiveness and level of implementation is highlighted in this study. It is also shown that there is immense potential to reduce emissions from ships given the availability of measures with significant reduction potential. However, the top barriers of implementation, namely cost of measure and lack of information, need to be addressed for a higher level of adoption. This report serves as the first step to map strategy for managing GHG in the shipping industry. The importance of cost effectiveness in decision making from a ship operators perspective prompts the adoption of measures that are the most cost effective first before measures with high emissions reduction potential. It is prudent for shipping companies to adopt a more environmentally friendly operation as green is the way forward in the shipping industry.

http://www.thescipub.com/abstract/10.3844/ajeassp.2012.310.317 2013/02/15 - 03:05

Public-Private Partnerships (PPP) or Private Finance Initiatives (PFI) are increasingly becoming very popular with governments across the globe for the provision of public infrastructure and services. When contracted, the public sector client believing the private sector will act in accordance with ‘bounded rationality’, ignores the constant monitoring and review process which is an integral part of any project. However, the failures of some of these partnerships and the social and economic costs incurred due to laxity in monitoring reminds us of the need to develop the permanent bureaucratic machinery of government, who share the government’s unique objectives of end-users satisfaction rather than shareholders’, to perform the monitoring of these projects. Though the public sector has been delivering projcets for dacades, the complexities associated with the PFI strategy has opened up new challenges for its staff. Most failures and moral harzards are only discovered after scandals evoke investigations like the case of Enron or when public criticisms force the government to reverse their decision as in the case of the Skye toll bridge by which time a lot of damage would have be done. Literature has shown that when employees are trained and engaged in organisational decisions and policy planning they make policy executions easier. Therefore, considering the Theoretical ideology behind the PFI of the asset being returned to the Public sector at the end of the concession, it becomes pertinent for proper training of the public sector staff. Public sector officials, if adequately trained and motivated can perform the tasks being contracted out to private consultants thereby re-affirming government’s commitment to its Value for Money (VFM) proposition. Though the public sector staff strength has been depleted due to the adoption of New Public Management (NPM), however the remaining qualified staff can be pooled to create an ‘incubator’ from which a formidable monitoring team would evolve through the use of project management ‘Core Team concept’.

http://www.thescipub.com/abstract/10.3844/ajeassp.2012.301.309 2013/02/15 - 03:05

Public-Private Partnerships (PPP) or Private Finance Initiatives (PFI) are increasingly becoming very popular with governments across the globe for the provision of public infrastructure and services. When contracted, the public sector client believing the private sector will act in accordance with ‘bounded rationality’, ignores the constant monitoring and review process which is an integral part of any project. However, the failures of some of these partnerships and the social and economic costs incurred due to laxity in monitoring reminds us of the need to develop the permanent bureaucratic machinery of government, who share the government’s unique objectives of end-users satisfaction rather than shareholders’, to perform the monitoring of these projects. Though the public sector has been delivering projcets for dacades, the complexities associated with the PFI strategy has opened up new challenges for its staff. Most failures and moral harzards are only discovered after scandals evoke investigations like the case of Enron or when public criticisms force the government to reverse their decision as in the case of the Skye toll bridge by which time a lot of damage would have be done. Literature has shown that when employees are trained and engaged in organisational decisions and policy planning they make policy executions easier. Therefore, considering the Theoretical ideology behind the PFI of the asset being returned to the Public sector at the end of the concession, it becomes pertinent for proper training of the public sector staff. Public sector officials, if adequately trained and motivated can perform the tasks being contracted out to private consultants thereby re-affirming government’s commitment to its Value for Money (VFM) proposition. Though the public sector staff strength has been depleted due to the adoption of New Public Management (NPM), however the remaining qualified staff can be pooled to create an ‘incubator’ from which a formidable monitoring team would evolve through the use of project management ‘Core Team concept’.

http://www.thescipub.com/abstract/10.3844/ajeassp.2012.301.309 2013/02/15 - 03:05

Public-Private Partnerships (PPP) or Private Finance Initiatives (PFI) are increasingly becoming very popular with governments across the globe for the provision of public infrastructure and services. When contracted, the public sector client believing the private sector will act in accordance with ‘bounded rationality’, ignores the constant monitoring and review process which is an integral part of any project. However, the failures of some of these partnerships and the social and economic costs incurred due to laxity in monitoring reminds us of the need to develop the permanent bureaucratic machinery of government, who share the government’s unique objectives of end-users satisfaction rather than shareholders’, to perform the monitoring of these projects. Though the public sector has been delivering projcets for dacades, the complexities associated with the PFI strategy has opened up new challenges for its staff. Most failures and moral harzards are only discovered after scandals evoke investigations like the case of Enron or when public criticisms force the government to reverse their decision as in the case of the Skye toll bridge by which time a lot of damage would have be done. Literature has shown that when employees are trained and engaged in organisational decisions and policy planning they make policy executions easier. Therefore, considering the Theoretical ideology behind the PFI of the asset being returned to the Public sector at the end of the concession, it becomes pertinent for proper training of the public sector staff. Public sector officials, if adequately trained and motivated can perform the tasks being contracted out to private consultants thereby re-affirming government’s commitment to its Value for Money (VFM) proposition. Though the public sector staff strength has been depleted due to the adoption of New Public Management (NPM), however the remaining qualified staff can be pooled to create an ‘incubator’ from which a formidable monitoring team would evolve through the use of project management ‘Core Team concept’.

http://www.thescipub.com/abstract/10.3844/ajeassp.2012.291.299 2013/02/12 - 10:13

The aim of this study is to simulate and implement open loop and closed loop controlled DC-DC converter for stand-alone wind energy system. Wind turbines, however, are not always very efficient in the wind speeds that are most common to a region. Typically, wind energy systems are designed to be highly efficient in high wind speed and have a cut-off wind speed- below which no energy is captured. In remote locations where wind energy is used for battery charging, the energy lost below the cut-off wind speed could be used for trickle charging or maintaining a battery’s fully charged state. Wind turbines are most efficient when they are operated at one specific Tip-Speed to Wind-Speed Ratio (TSR). Therefore, for the efficient capture of wind power, turbine speed should be controlled to follow the ideal TSR, with an optimal operating point, which is different for every wind speed In this system, the DC-DC converter in the DC link with a constant dc voltage to the load, a DC-DC converter will allow the voltage at the output of a diode bridge rectifier to be controlled. In low wind speed conditions, the voltage may be lowered to prevent the dc link from reverse biasing the diode rectifier. Under high wind speed condition, the voltage may be increased, reducing I2R losses. In addition, adjusting the voltage on the dc rectifier will change the generator terminal voltage and thereby provide control over the current flowing out of the generator. The LCL-T resonant inverter system for both open loop and closed loop DC-to-DC converter systems are simulated using MATLAB simulink power system blocks. This converter has advantages like reduced transformer size, reduced filter size and current source characteristics. The simulation studies indicate that LCL-T type for open and closed loop DC-DC converter can be used with stand-alone wind generator. Constant voltage can be maintained at the output of DC-to-DC converter by using a PWM rectifier at the output. Embedded controlled DC to DC converter is fabricated and it is tested.

http://www.thescipub.com/abstract/10.3844/ajeassp.2012.291.300 2013/02/06 - 08:32

A finite element-finite difference numerical model is developed for predicting non-uniform temperature development in hydrating concrete with respect to time and space. The results obtained from this model can be used by structural and construction engineers to predict critical thermal stresses induced due to differential temperatures between the core and the surface of the concrete at early ages and between the zero-stress temperatures and the minimum equilibrating ambient temperatures that the concrete experiences during its service life. The prediction of zero-stress temperatures also enables to quantify the extent of built-in curl developed in concrete structures. The finite element is used to space discretization while the finite difference is used to obtain transient solutions of the model. The numerical formulations are then programmed in Matlab. The numerical results were compared with experimental results found in literature and demonstrated very good agreement.

http://www.thescipub.com/abstract/10.3844/ajeassp.2012.282.290 2013/01/02 - 21:16

Digital medical powerful tools for diagnosis, treatment and surgery and plays a vital role in modern healthcare delivery. Large storage capacity is needed for storing these images and for transmitting them. This leads to the strong demand for digital medical image compression and reliable transmission. In this study, we have applied three compression methods to medical images. In all the methods discrete wavelet transform is applied followed by the corresponding compression methods. The experiments are carried on three medical images and the quality of reconstructed images is evaluated based on Compression Ratio (CR) and Peak Signal to Noise Ratio. The results show that the SOM algorithm has higher compression ratio than FCM and FKM while maintaining the image quality and preserving the information. The results show that the SOM algorithm outperforms the existing methods FCM and FKM for medical image compression.

http://www.thescipub.com/abstract/10.3844/ajeassp.2012.275.281 2012/11/07 - 19:28

Blog is a communication tool that plays a key role in a web application. Use of blogs has resulted in a paradigm shift in the way a web application interacts with the customer. During the development of web application, there is a need to elicit and specify the requirements for the blogging functionality. In this study, we present a requirements checklist for the blog, from the perspective of integrating the blog in a web application. We follow the use case based approach for identifying the software requirement for the blog. The requirement checklist helps both the web application and the developer during the requirement elicitation of the blog’s software. The checklist is also useful during the testing phase for the validation and verification of the blog functionality."

http://www.thescipub.com/abstract/10.3844/ajeassp.2012.266.274 2012/09/14 - 23:47

Regardless of the large number of Object-Oriented (OO) modeling languages currently being used in the Information Systems (IS) modeling process, unavailability of an OO modeling language that can be used in both the analysis and design phases disintegrates the two phases. The problem is, such disintegration can lead to a high level of missing information in the real world system from the analysis phase to the design phase. The approach of this study is to propose a framework to produce design phase models from analysis phase models using ontology based Unified Modeling Language (UML), thereby integrating the two phases. The results obtained from the porposed framework involve: a consructed language which can be used in generating the analysis phase scripts; and the development of script files based on the UML constructs at the analysis and design phases to automatically generate the UML scripts for those two phases. Since this study is a part of an ongoing research study, it can be concluded that, at the end of this study (1) both analysis and design phases would be able to integrate using a common OO modeling language (2) the manual work involved in the current analysis and design modeling would be reduced (3) the complexities and difficulties faced by the modelers (By modelers we mean the analysts and designers who are doing the analysis and design phase modeling) in using UML modeling tools would be reduced.

http://www.thescipub.com/abstract/10.3844/ajeassp.2012.251.260 2012/09/14 - 23:47

A software development process is concerned primarily with the production aspect especially the management of software development. The development of a software process passes through various phases and there is a need to manage all issues particularly configuration issues during the evolution of a software process. This study makes an attempt to deal with various configuration issues with the help of an opensource configuration management tool. The analysis of different software development paradigms is also presented in order to discuss the brief explanation with respect to software process management.

http://www.thescipub.com/abstract/10.3844/ajeassp.2012.261.265 2012/09/14 - 23:47

Free-riding is a desperate and a constant menace to many P2P systems, to violate the cooperation among peers. This study proposes a grade-based approach, which expeditiously maintains fairness in the network by encouraging the high contributed peers and altogether wiping out the free-riders. The Network Contribution Ratio determines the contribution of users globally. Besides, the proposed grading algorithm uses a point-based incentive mechanism which provides credit points to the users with respect to their grade and the transfer of users between each grade is instituted.

http://www.thescipub.com/abstract/10.3844/ajeassp.2012.243.250 2012/09/03 - 14:40

Interest in Composite Content Applications has been climbing higher over the recent years due to the rising need around enabling business process improvements and addressing challenges around business process agility. Such applications can deliver substantial value by leveraging both content and process services for the better orchestration of people and processes and empower organizations to automate routine tasks and aggregate information from multiple sources in a collaborative work environment that enables rapid decision making. In this whitepaper, we have introduced Case Management and its relationship with ECM, the essential functionalities in a Case Management Product stack and expanded on leading vendors in this space along with the salient features of their case management offerings. Subsequently we have built on a sample case scenario of building a contracts management application using EMC Documentum xCelerated Composition Platform (xCP), the business needs and challenges that a well-designed Contracts Management application can address, a real-life application of xCP platform to build such a solution and the observations on the strengths and limitations of this platform, along with a few workarounds to address the limitations.

http://www.thescipub.com/abstract/10.3844/ajeassp.2012.219.229 2012/08/29 - 20:16

Performance of Wireless LAN can be improved at each layer of the protocol stack with respect to energy efficiency. The Media Access Control layer is responsible for the key functions like access control and flow control. During contention, Backoff algorithm is used to gain access to the medium with minimum probability of collision. After studying different variations of back off algorithms that have been proposed, a new variant called History based Probabilistic Backoff Algorithm is proposed. Through mathematical analysis and simulation results using NS-2, it is seen that proposed History based Probabilistic Backoff algorithm performs better than Binary Exponential Backoff algorithm.

http://www.thescipub.com/abstract/10.3844/ajeassp.2012.230.236 2012/08/29 - 20:16

Devices constituting wireless ad-hoc networks generally operate in battery power, energy efficiency is a critical research issue. IEEE 802.11 Power Save Mode is a standard recommended for energy efficient operation of wireless ad-hoc networks. When there is no data to transfer, energy is still utilized by IEEE 802.11 PSM during the ATIM window. With this work, an attempt is made to address this drawback with the proposal of a variation in the PSM. Using IEEE 802.11 PSM, each frame travels only one hop during a beacon interval, leading to huge end to end latency and energy consumption. This issue is also addressed and history based prediction method is proposed. According to this method, a data frame can travel many hops from source to destination within a beacon interval. Simulation results using Network Simulator 2 (NS-2) show that the proposed method outperforms IEEE 802.11 PSM with respect to energy efficiency and end to end latency.

http://www.thescipub.com/abstract/10.3844/ajeassp.2012.237.242 2012/08/29 - 20:16

During the last two or three decades, incidence of failure of reinforced concrete structures has been seen widely for many reasons, such as increasing service loads and/or durability problems and the economic losses due to such failures are costly. Nowadays, the size and the form of repair and rehabilitation market are too large since there has been an increased emphasis on repair and retrofitting of defected structures over demolition and new construction. For safety in concrete tunnel, periodic inspection has been conducted using many testing technologies and techniques. However, these technologies cannot replace visual inspection because of their slow and complicated procedures. For this reason, the Knowledge-Based Systems (KBS) are used with lab tests results to diagnose R.C tunnel lining corrosion crack damage (DICRCTL). In this study, we attempt to propose an alternative to the human expert, to give technical decisions in diagnosing corrosion crack damages in second segment of R.C. tunnel lining. To overcome this requirement, an expert system is developed to achieve the research aim. This proposed system was constructed on a knowledge base that incorporates with the gathered information, tests in the form of rules which is suitable to implement in an expert system environment to diagnostic advisory nature. The proposed application results show an easy, fast and satisfactory answer to engineering needs.

http://www.thescipub.com/abstract/10.3844/ajeassp.2012.198.204 2012/08/27 - 22:14

Purpose of this study is the consideration of loading and contact problems encountered at rotating machine elements and especially at toothed gears. The later are some of the most commonly used mechanical components for rotary motion and power transmission. This fact proves the necessity for improved reliability and enhanced service life, which require precise and clear knowledge of the stress field at gear tooth. This study investigates the maximum allowable stresses occurring during spur gear tooth meshing computed using Niemann’s formulas at Highest Point of Single Tooth Contact (HPSTC). Gear material, module, power rating and number of teeth are considered as variable parameters. Furthermore, the maximum allowable stresses for maximum power transmission conditions are considered keeping the other parameters constant. After the application of Niemann’s formulas to both loading cases, the derived results are compared to the respective estimations of Finite Element Method (FEM) using ANSYS software. Comparison of the results derived from Niemann’s formulas and FEM show that deviations between the two methods are kept at low level for both loading cases independently of the applied power (either random or maximum) and the respective tangential load.

http://www.thescipub.com/abstract/10.3844/ajeassp.2012.205.216 2012/08/27 - 22:14

The objective of this research is to predict rut depth in local flexible pavements. Predication model in pavement performance is the process that used to estimate the parameter values which related to pavement structure, environmental condition and traffic loading. The different local empirical models have been used to calculate permanent deformation which include environmental and traffic conditions. Finite element analysis through ANSYS computer software is used to analyze two dimensional linear elastic plane strain problem through (Plane 82) elements. Standard Axle Load (ESAL) of 18 kip (80 kN) loading on an axle with dual set of tires, the wheel spacing is 13.5 in (343 mm) with tire contact pressure of 87 psi (0.6 MPa) is used. The pavement system is assumed to be an elastic multi-layers system with each layer being isotropic, homogeneous with specified resilient modulus and Poisson ratio. Each layer is to extend to infinity in the horizontal direction and have a finite thickness except the bottom layer. The analysis of results show that, although, the stress level decrease 14% in the leveling course and 27% in the base course, the rut depth is increased by 12 and 28% in that layers respectively because the material properties is changed.

http://www.thescipub.com/abstract/10.3844/ajeassp.2012.163.169 2012/08/17 - 14:53

Fluidized bed gasification can be used to convert the solar energy stored as carboneous compounds in bio-mass into a carbon neutral fuel with reduced emissions. Canada produces 20.57 million tonnes of wheat straw annually which could be used for green energy production. Wheat straw residue gasification has the capability of replacing 7.5 % (0.62 EJ) of Canada’s annual fossil fuel consumption. To achieve efficient gasification in a fluidized bed proper fuel mixing and residence time must be achieved. The aim of this study was to investigate the effects of sand particle size, distributor plate shape and angle, bed height and fluidizing velocity on particle mixing and residence time in the fluidized bed reactor. Greater values of the residence time were obtained with course sand whereas lower values were obtained with fine sand. An in-crease in the angle of convex or a decrease in the angle of a concave of the distributor plate resulted in an increase in the residence time. Both the concave and convex distributor plates achieved vertical upward and downward movements of the bed material resulting in continuous bed material turnover and, thus, good mixing. However, the concave plate achieved longer residence time which will result in better conversion efficiency. To improve the mixing properties of the binary mixture, which has great tendency for segregation due to density differences, an angled distributor plate (concave or convex) should be used. Considerable increases in the residence time were recorded with increases in the bed height. Increasing the fluidizing velocity decreased the residence time due to the increase in the bubble velocity. However, since the conversion efficiency is affected by the degree of mixing, it will also be improved by increasing the fluidization velocity. A velocity above 1.50 Umf is recommended for better fluidization and improved mixing.

http://www.thescipub.com/abstract/10.3844/ajeassp.2012.170.183 2012/08/17 - 14:53

The purpose of this research was to experimentally characterize the flexural and tensile characteristics of fiber-reinforced Very High-Strength Concrete (VHSC) panels. The panels were made with a unique mix of cementitous materials achieving compressive strength of 26,000 psi (180 MPa) or greater. VHSC panels were reinforced with polypropylene fibers of 1 inch (25.4 mm) in length and Polyvinyl alcohol (PVA) micro-fibers of ½ inch length, incorporated at 1.5% by volume. For the flexural behavior, 17×2×¾ inch flat panels were tested under third-point loading tests, while the direct tension experiments were tested on 10×3×½ inch tension panels under a direct tensile load. Flexural tests were conducted on three panels of plain VHSC, three panels of VHSC reinforced with polypropylene fibers and three panels of VHSC reinforced with ½ inch micro-fibers. Similar testing program was used to conduct the direct tension tests. Also, compression test conducted on 2×2×2 inch cubes and compressive test conducted on 4 inch by 8 inch cylinders test were used to establish compressive strength and modulus of elasticity respectively. Results show that the compressive strength, tensile strength and fracture toughness of the VHSC panels were much greater than those normally obtained by typical concrete material. The presence of fibers increases the toughness of VHSC specimens between 80 and 190% and increases the tensile strength by 23 to 47%. The modulus of elasticity and Poisson’s ratio recorded herein were determined according to ASTM C 469-02. Laboratory experiments on flexural and tensile properties of thin, very high-strength, fiber reinforced concrete panels, were used to study the material and characterize the panels’ reaction to load. Parameters such as compressive strength, tensile strength, toughness, elastic modulus, Poisson’s ratio and first-crack strength were determined and may be considered for potential use as design parameters in future material improvements.

http://www.thescipub.com/abstract/10.3844/ajeassp.2012.184.197 2012/08/17 - 14:53

Due to wide implementation of Epoxy insulators in industrial applications and its economic implications; development of various Epoxy insulator materials has to be evaluated along with a reliable prediction methodology of their lifetimes. In this study, a new methodology based on Artificial-Neural-Networks (ANN) is developed to predict Epoxy insulators lifetime using laboratory measurements of their surface leakage current under accelerated aging. The effect of adding fillers with various concentration rates to the Epoxy insulators such as; Calcium Silicate (CaSiO2), Mica and Magnesium Oxide (Mg(OH)2) on their lifetimes is compared with the base case (no filler and dry condition). Furthermore, the lifetime of each specimen under study is examined under various weather conditions such as dry, wet, salt wet (NaCl) and hydro carbon solvent Naphtha. The obtained results are weighing against the experimental measured data based on two ANN techniques; i.e., Feed-Forward-Neural-Network (FNN) and Recurrent-Neural-Network (RNN). The results obtained from the FNN and RNN are compared to validate the proposed methodology to predict the lifetime of epoxy insulators in terms of the type and percentage concentration of filler. The obtained Epoxy insulators predicted lifetime under various filler concentrations and weather conditions are compared and conclusions are reported.

http://www.thescipub.com/abstract/10.3844/ajeassp.2012.157.162 2012/08/07 - 14:08

Animal and poultry manures have been recognized for centuries as organic fertilizers providing essential nutrients to crops and improving soil structure due to their large input of organic matter. Increasing demand for poultry and egg products has led to intensification of the poultry rearing process, resulting in large amounts of poultry manure. Drying can be used to reduce the environmental impact of poultry manure and create a value added product for the farmers (animal feed or organic fertilizer). The aim of this study was to investigate the effect of solar heated air drying on the chemical and biological characteristics of poultry manure and develop a suitable manure solar dryer. The effects of temperature (40-60°C) and manure layer depth (1-3 cm) were evaluated. At the three temperature levels studied, the time required to dry poultry manure in the 1 cm-deep layer was the shortest, followed by the 2 and 3 cm-deep layers, respectively. The optimum depth to dry manure (at which the highest drying effectiveness occurred) was 3 cm. The manure drying rate increased with increasing temperature and was the fastest at 60°C for all manure depths studied. A drying temperature-depth combination of 60°C and 3 cm was the most efficient for the thin layer drying of poultry manure. Drying poultry manure at these conditions provided an effective means of removing moisture and odor and destroying microorganisms, thereby allowing the production of a value added product. This temperature range is feasible with a solar dryer operating in the tropics. A solar dryer operating at a 3 cm manure depth would be capable of drying 336 kg/h. Drying poultry manure with solar heated air resulted in a slight decrease in protein content (from 42 to 41%), a decrease in pH (from 8.4 to 6.6), removal of Salmonellae and a 99% reduction in numbers of total bacteria, yeast, mold and E. coli. Thin layer solar drying of poultry manure proved to be an effective means of converting poultry manure into a value added product while reducing the environmental and health problems that are associated with current disposal options.

http://www.thescipub.com/abstract/10.3844/ajeassp.2012.136.150 2012/08/04 - 16:06

Spectrum sensing is the basic and important operation in Cognitive Radio (CR) to find the unused spectrum. Energy detector is a popular sensing method because it doesn’t require transmitted signal properties, channel information, of even the type of modulation. This study summarizes the performance result of energy detector over Additive White Gaussian Noise (AWGN), Rayleigh fading and Nakagami fading channels. Energy detection with soft decision and hard decision are also studied for different number of cognitive nodes as well as each cognitive node having multiple antennas. The performance of hard decision and soft decision are evaluated by means of complementary Receiver Operating Characteristic (ROC) curves. It clearly shows that the probability of missing detection decreases for increasing the number of antennas in cognitive node and also increasing of cooperated cognitive users.

http://www.thescipub.com/abstract/10.3844/ajeassp.2012.151.156 2012/08/04 - 16:06

Problem statement: This study proposes a novel Distributed Amplify and-Forward (DAF) cooperative scheme, achieving higher diver¬sity order and yet maintaining the same transmission freedom as the conventional Amplify-and-Forward (AF) scheme. In the DAF scheme, a user’s transmitted symbols are partitioned into several sequences in order to be relayed by different users. Approach: In the cooperative network, each user still uses half of their transmission for relaying others’ signals. But instead of relaying one user’s entire transmitted sequence, it helps different users for the relaying. Theoretical analysis of the DAF scheme is carried out in order to justify its advantages over the existing schemes. The outage behavior and Diversity-Multiplexing Tradeoff (DMT) analyses of the DAF scheme are presented. Results: Through outage behavior analysis, it is shown the DAF scheme achieves substantial diversity gains over the AF scheme. Furthermore, the DMT analysis justices both the scheme’s achievable diversity gains and its ability to maintain the same multiplexing gain as the AF scheme. The theoretical analyses are then extended to a general cooperative network consisting of N (N≥2) relays, showing the diversity order can be increased with respect to the number of relays but not at the expense of each user’s multiplexing gain. Conclusion: Finally, a practical coded cooperative system that integrates the DAF scheme with the concatenated Reed-Solomon Convolution Codes (RSCC) is proposed, validating the achievable performance gain offered by the DAF scheme.

http://www.thescipub.com/abstract/10.3844/ajeassp.2011.607.616 2012/08/02 - 21:14

This study reports on the effects of dry heating of oil palm fruits for the purpose of sterilization and solvent extraction with various oil parameters. Steam sterilization of oil palm fresh fruit bunches was required as a pre-treatment to deactivate enzymes that give rise to Free Fatty Acids (FFA) before the oil could be extracted. While the use of high-pressure steam was effective, large amount of water used ends up as palm oil mill effluent, which requires appropriate treatment. Dry heating of oil palm fruits was carried out in an oven for 1-4 and 5 min time duration. The heated fruits were extracted for its oil by solvent means. Oil yield, Deterioration Of Bleachability Index (DOBI), oxidative stability and FFA content were investigated. The FFA content in the oil extracted from dry heated oil palm fruits ranged from 0.59-2.89%, DOBI from 3.65-6.72 and oxidative stability from 14.3-20.2 h. Dry heated oil palm fruits yield crude oil with comparable quality to that of commercial crude palm oil, which is steam sterilized.

http://www.thescipub.com/abstract/10.3844/ajeassp.2012.128.131 2012/08/02 - 00:39

Recognition of handwritten numerals has been one of the most challenging topics in image processing. This is due to its contributions in the automation process in several applications. The aim of this study was to build a classifier that can easily recognize offline handwritten Arabic numerals to support those applications that are deal with Hindi (Arabic) numerals. A new algorithm for Hindi (Arabic) Numeral Recognition is proposed. The proposed algorithm was developed using MATLAB and tested with a large sample of handwritten numeral datasets for different writers in different ages. Pattern recognition techniques are used to identify Hindi (Arabic) handwritten numerals. After testing, high recognition rates were achieved, their ranges from 95% for some numerals and up to 99% for others. The proposed algorithm used a powerful set of features which proved to be effective in the recognition of Hindi (Arabic) numerals.

http://www.thescipub.com/abstract/10.3844/ajeassp.2012.132.135 2012/08/02 - 00:39

Problem statement: Spectrally Efficient Frequency Division Multiplexing (SEFDM) system promises bandwidth savings by multiplexing overlapped non-orthogonal sub-carriers. However, the loss of orthogonality results in increasing the complexity of generation and detection of the signal. In this work, we propose simple framework for the generation of the SEFDM signal based on the Inverse Discrete Fourier Transform (IDFT). Approach: This study further proposes the use of the Discrete Fourier Transform (DFT) as the receiver front end, specifically for extracting the statistics of the signal needed for recovering the transmitted signal. The proposed transmitter designs employ similar building blocks as Orthogonal Frequency Division Multiplexing (OFDM) based systems, hence, would facilitate an easy migration and/or coexistence with OFDMon the transmitter side. Furthermore, the proposed framework may facilitate the IDFT design for any Frequency Division Multiplexed (FDM) signal with arbitrary sub-carriers spacing. Results and Conclusion: The equivalence of the IDFT generated signal and the modulators based signal is proved mathematically, nonetheless, numerical simulations were performed to verify that equivalence and to test for the performance of the digitally generated signal in AWGN channel. Numerical results confirmed the required spectrum compression and Bit Error Rate (BER) performance at a much reduced complexity.

http://www.thescipub.com/abstract/10.3844/ajeassp.2011.598.606 2012/08/01 - 04:10

Problem statement: An important indicator of an individual’s health is respiration rate. It is the average number of times air is inhaled and exhaled per minute. Existing respiration monitoring methods require an instrument to be attached to the patient’s body during the recording. This is a discomfort to the patient and the instrument can be dislodged from its position. Approach: In this study a novel noncontact, thermal imaging based respiration rate measurement method is developed and evaluated. Facial thermal videos of 16 children (age: Median = 6.5 years, minimum = 6 months, maximum = 17 years) were processed in the study. The recordings were carried out while the children rested comfortably on a bed. The children’s respiration rates were also simultaneously measured using a number of conventional contact based methods. Results: This allowed comparisons with the thermal imaging method to be carried out. The image capture rate was 50 frames per second and the duration of a thermal video recording was 2 min per child. The thermal images were filtered and segmented to identify the nasal region. An algorithm was developed to automatically track the identified nasal area. This region was partitioned into eight equal concentric segments. The pixel values within each segment were averaged to produce a single thermal feature for that segment of the image. A respiration signal was obtained by plotting each segment’s feature against time. Conclusion: Respiration rate values were automatically calculated by determining the number of oscillations in the respiration signals per minute. A close correlation (coefficient = 0.994) was observed between the respiration rates measured using the thermal imaging method and those obtained using the most effective conventional contact based respiration method.

http://www.thescipub.com/abstract/10.3844/ajeassp.2011.586.597 2012/08/01 - 04:10

The Tyre tread pattern is the arrangement of blocks, grooves and voids, sipes and channels designed into the tread to enhance its grip on the road. Tread is the uppermost part of any tyre which contact into the road and it has its own performance towards mileage, traction, low noise and heat built up properties. It would be meaningful to conduct an extended analysis on the tyre tread blocks for its performance in static and dynamic condition to predict its behavior and wear of tread block in on-road condition. The Finite Element software Abaqus is used for the present analysis of the tread block and its behavior was studied on two different contact surfaces. The tread block is modeled in six different shapes and analyzed for is performance. The deformation stress strain characteristic of different blocks is studied which will be useful in deciding the contact behavior, friction and road grip. The regular shape/geometry has common behavior and the mixed type geometry shows a distinguished variation in the analysis. The dynamic stiffness and deformed shape was analyzed in this study and it has its own effect in tyre design. The tread block dynamics study by geometric shape would be vital in tread pattern optimization to enhance the traction, better hydroplaning and rolling resistance under all operating conditions.

http://www.thescipub.com/abstract/10.3844/ajeassp.2012.119.127 2012/07/28 - 14:12