oalib

Publish in OALib Journal

ISSN: 2333-9721

APC: Only $99

Submit

Any time

2020 ( 8 )

2019 ( 31 )

2018 ( 23 )

2017 ( 18 )

Custom range...

Search Results: 1 - 10 of 2629 matches for " Abbas;Djeddi "
All listed articles are free for downloading (OA Articles)
Page 1 /2629
Display every page Item
Study of water entry of circular cylinder by using analytical and numerical solutions
Ghadimi, Parviz;Dashtimanesh, Abbas;Djeddi, Seyed Reza;
Journal of the Brazilian Society of Mechanical Sciences and Engineering , 2012, DOI: 10.1590/S1678-58782012000300001
Abstract: water impact phenomenon in the case of a circular cylinder is an important issue in offshore industry where cross members may be in the splash zone of the incident wave. an analytical method as well as a numerical solution are employed to study the water entry problem of a circular section. the procedure for derivation of the analytical formulas is demonstrated step by step. the volume of fluid (vof) simulation of the water entry problem is also performed to offer comparison of the results of the linearized analytical solution with a fully nonlinear and viscous fluid flow solution. to achieve this, the flow-3d code is utilized. some consideration has also been given to the points of intersection of the free surface and the body, where the singularities exist in the free surface deformation and velocities, as predicted by the linear theory. these singularities appear to be avoided in the real fluid by the formation of jets which quickly break up into sprays under the action of surface tension. slamming force, free surface profile, impact force, pressure distribution and evolution of intersection points are also presented and comparisons of the obtained results against the results of previous studies illustrate favorable agreements.
Three-Dimensional Mathematical Investigation of Dynamic and Hydrostatic Pressure Distributions on Planing Hulls
Parviz Ghadimi,Sasan Tavakoli,Abbas Dashtimanesh,Seyed Reza Djeddi
Journal of Computational Engineering , 2013, DOI: 10.1155/2013/868252
Abstract: A mathematical model is utilized in order to calculate three-dimensional pressure distributions on planing hulls. This type of modeling is able to determine the hydrodynamic and hydrostatic pressures acting on the bottom of these hulls. As a result, the total 3-dimensional pressure exerted on the planing hull as a sum of hydrostatic and hydrodynamic pressures can be evaluated. Empirical equations introduced in previous works have been used as the fundamentals for the present mathematical modeling method. The obtained results are compared against available experimental results and results of empirical equations in order to validate the proposed method. The outcome of the -squared tests conducted on these comparisons shows favorable accuracy of the results. After evaluation of hydrodynamic pressure, the effects of trim and deadrise angles and wetted length on the 3-dimensional pressure distribution are analyzed. Finally, the total pressure on planing hull and the effect of velocity coefficients are studied. 1. Introduction Determining the exerted pressure on the planing hulls is essential to the study of their dynamics. By computing this pressure, it becomes possible to calculate the lift force, center of pressure, vessel’s dynamic, and water spray. Complexities concerned with 3-dimensional pressure distributions have made their direct calculation improbable, if not impossible. Therefore, a common approach is to first measure the pressure distribution using 2-dimensional longitudinal and transverse solutions which can be later used for calculation of 3-dimensional pressure distribution acting on the planing hull. Additionally, experimental methods can be used for calculation of pressure distribution in this type of vessel. Among these experimental works, results of Kapryan and Boyd [1] and Smiley [2, 3] are of high importance. On the other hand, Wagner [4] used analytical methods to evaluate pressure distribution over a wedge in a water-entry problem which is identical to the pressure distribution acting on an infinite planing plane. It was proved in Smiley’s experiments [3] that the longitudinal pressure distribution on the side sections of the center line is less than that on the other sections. Based on these results, empirical equations for evaluation of longitudinal pressure distribution were proposed. Later, Kapryan and Boyd [1] showed in their experimental studies that pressure on planing hulls will be reduced with an increase in the deadrise angle. With the advances in computational and computer resources, mathematical modeling methods for the
Conventional and Fractal Variogram Based on Time—Space Analysis of Seismicity Distribution—Case Study: Algeria Seismicity (1673-2010)  [PDF]
Moh-Amokrane Aitouche, Mabrouk Djeddi
Journal of Geoscience and Environment Protection (GEP) , 2018, DOI: 10.4236/gep.2018.611012
Abstract: Geostatistics belongs to the wide class of statistical methods. It is used and applied to analyze and predict the values associated with spatial or spatio-temporal phenomena such as seismological events. Thus, in addition to its adaptability to perform spatial data analysis based on the principles of variography, many other methods more representative of the spatial distributions of the epicentres have been experimented. The unidirectional or isotropic fractal variogram associates the criterion of variance with the fractal dimension which is a better descriptive parameter of the spatial organization of events. The same analysis procedure carried out through a directional or azimuthal variogram introduces the context of a preferential direction of earthquake evolution. Moreover, b-value is a privileged seismological parameter that can be studied alone or in combination with other more advanced geostatistical analysis factors such as fractals, fractal dimensions and the anisotropic variogram. All these concepts were used as methodology for a protocol of analysis of the catalog of the Algeria seismicity including 1919 events for the period extending from 1673 to 2010. This catalog is provided by the compilation of partial catalogs synthesized by the CRAAG (Research Centre in Astronomy, Astrophysics and Geophysics).
Uniaxial Modelling of Behavior of the Concrete in Fast Dynamics: Approach to Seismic Behavior  [PDF]
Abdelhak Baraka, Mohammed Benali Benmansour, Yazid Abdelaziz, Fakhreddine Djeddi
Engineering (ENG) , 2011, DOI: 10.4236/eng.2011.36066
Abstract: The advantages of the computer enable us to simulate of complex structures subjected to dynamic loading. To come up to the necessity to know the real behavior of such material, we exploit these advantages basing on experimental data available in the literature. Since the response of the material depends on stress velocity, so it is essential to provide a computational code with dynamic behavior. To perform such simulations, we have elaborated a behavior law governed by loading velocity effect on concrete and their attitudes cyclic non elastic, for an approach of seismic behavior. This paper shows the processes we have followed to formulate this viscous damage law whose aim is behavior prediction for concrete under dynamic stresses. Then, the model is validated with experimental results and simulations of some available tests on Hopkinson’s bar.
Interpretation of VLF-EM anomalies of 3D structures by using linear filtering techniques
M. Djeddi,H. A. Baker,A. Tabbagh
Annals of Geophysics , 1998, DOI: 10.4401/ag-4329
Abstract: For almost four decades now, the VLF-EM method has been used to locate different conducting structures. The interpretation is usually carried out on a profile anomaly where a possible estimation of the depth and the dip can be obtained. The maps are only used, after applying the Fraser filter, to best position the anomaly and no further quantitative interpretation is given. In this paper a linear filtering technique is developed based on the X and Y derivatives of the VLF-EM anomaly. This technique helps in determining the exact dimensions of the causative structures as well as their depths regardless of their conductivities. This work also shows that the known Fraser filter that is usually applied on a profile data can be adapted, for the first time, in studying quantitatively 3D structures if it is applied to raw data in the X and Y directions. It can now be used to estimate the dimensions of the targets.
A Comment on Link Dynamics and Protocol Design in a Multi-Hop Mobile Environment  [PDF]
Abbas Nayebi
Wireless Sensor Network (WSN) , 2011, DOI: 10.4236/wsn.2011.33012
Abstract: This paper is a supplementary document for “Link Dynamics and Protocol Design in a Multi-Hop Mobile Environment” (ref. [1]), which presents an analytic model to obtain link lifetime in mobile wireless networks. The model outcome is used as groundwork for several mobility-related evaluations. Here, it is discussed how an improper assumption in the probabilistic model led to some errors in the resultant expressions. After a detailed description of the erratic assumption, a modification is proposed to correct the derivations. The results of the new model are verified by the simulation results provided at the original paper.
Quintessence of Traditional and Agile Requirement Engineering  [PDF]
Jalil Abbas
Journal of Software Engineering and Applications (JSEA) , 2016, DOI: 10.4236/jsea.2016.93005
Abstract: Requirement gathering for software development project is the most crucial stage and thus requirement engineering (RE) occupies the chief position in the software development. Countless techniques concerning the RE processes exist to make sure the requirements are coherent, compact and complete in all respects. In this way different aspects of RE are dissected and detailed upon. A comparison of RE in Agile and RE in Waterfall is expatiated and on the basis of the literature survey the overall Agile RE process is accumulated. Agile being a technique produces high quality software in relatively less time as compared to the conventional waterfall methodology. The paramount objective of this study is to take lessons from RE that Agile method may consider, if quality being the cardinal concern. The study is patterned on the survey of the previous research reported in the coexisting literature and the practices which are being pursued in the area.
Developing Innovative Concepts for Measuring and Assessing Transit System Maturity  [PDF]
Khaled Abbas
Journal of Transportation Technologies (JTTs) , 2017, DOI: 10.4236/jtts.2017.72013
Abstract: In this research three new innovative concepts are introduced and developed: the first defined as Transit System Maturity Components (TSMC), the second referred to as Transit System Maturity Scale (TSMS) and the third labeled as Transit System Maturity Index (TSMI). The TSMC is meant to conceptualise the main strategic generic components characterising the maturity of transit systems. The TSMS is an S shaped scaling system for measuring maturity of transit system components. The TSMI presents an innovative index meant to assess the overall level of maturity of a city transit system. Such framework is envisaged to be used to determine and compare the overall maturity levels of transit systems in cities of the world as well as to act as a basis to identify strengths & gaps that need to be addressed/completed. Furthermore, it can also act as an ingredient in shaping and developing future road maps for transit system in cities across the world. The research concludes by demonstrating the applicability of TSMC, TSMS, and TSMI in conducting an initial assessment of the Transit System Maturity for the fast growing city of Dubai.
Assessment & Improvement of Children Road Safety: A Pyramid & Honeycomb Structure Approach  [PDF]
Khaled Abbas
Journal of Transportation Technologies (JTTs) , 2017, DOI: 10.4236/jtts.2017.73017
Abstract: In this research, a 4 hierarchical pyramid structure approach is proposed to assess children road safety. The first is referred to as the road safety pyramid representing children road safety components and levels including root, at accident and post accident levels and factors. The second, referred to as the children road safety assessment pyramid, includes 3 cornerstones that are required to represent a detailed methodological children road safety diagnostics. These 3 cornerstones include children safety culture, safety indicators and accident data analysis. The third pyramid, referred to as the children road safety indicators, shows the levels and types of indicators that when computed can be used for in depth analysis and historical comparison of children road safety. The core of the paper is the development of a conceptual model of factors affecting the road behavior of children including traffic exposure and experience, cognitive skills and abilities, perceptual skills, knowledge and attitude. Towards this end, the paper presents the fourth pyramid, referred to as the children road safety behavior pyramid. This includes a 7-level hierarchal structure starting from exposure leading to experience and then skills/abilities, to knowledge to perception to attitudes and eventually culminating into children road safety behavior. The paper concludes by developing a generic integrated children road safety package of policies, measures, initiatives. The package is composed of 18 fields of action. In pursuing such integrated safety package this research also enhanced the classical 3Es concept (Engineering—Education—Enforcement) and introduced instead the 14Es honeycomb structure including (Engineer-ing—Education—Environment—Enforcement—Egalitarianism—Exposure—Ethics—Emergency—Ergonomics—Encouragement—Empowerment—Enabling—Economics—Evaluation). All in all this is meant to act as a generic benchmark guide/checklist for countries in compiling and tailoring children road safety programmes.
Comprehensive Information System on Mobile Devices via Bluetooth Application Server  [PDF]
Abbas Ali Lotfi Neyestanak
iBusiness (IB) , 2010, DOI: 10.4236/ib.2010.23039
Abstract: Advantage of cell phones and their rapid progress on facilities and applications, made a technical trend to develop software implementations for this kind of systems. On the other hand, Java package with some efficient tools and products made it quite desirable for producers in a wide range of applications. In this paper the Bluetooth technology has been studied and its defects and premiums and security threats are investigated and compared with other technologies. Finally a comprehensive information system is designed, simulated and implemented based on cell phone communications. This system actually utilizes the Bluetooth technology to send and receive variety of packets such as data, image, and sound between computer and cell phone. These transferred data are then processes at the either sides and the revealed data is presented to the user. Wide 100 meter coverage has been considered for this system utilizing advanced automatic traffic management routines.
Page 1 /2629
Display every page Item


Home
Copyright © 2008-2017 Open Access Library. All rights reserved.