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RISS 인기검색어
- 검색키워드
- 저자 : Jabbar, Md. Abdul (검색결과 97 건)
- 무료
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Field investigation on load distribution and deflections of railway track sleepers
Jabbar Ali Zakeri,Javad Sadeghi 대한기계학회 2007 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.21 No.12
Despite the significant role of sleepers in railway track mechanical behavior, no thorough mechanistic approach has been presented for the development of the loading pattern they experience. The current theoretical methods in the analysis of the railway track system need further calibration and verification using field-measured data. In this paper, using specific load-cells between sleepers and the rail and beneath the sleepers, the vertical loading conditions of these main track elements are studied. The lateral resistance of the concrete sleepers in the ballasted tracks is investigated by using full scale sleeper pull-out tests. Moreover, track deflections under the sleeper as the main track analysis parameter are measured and the results are discussed. In this paper, with the results obtained from extensive field measurements, some suggestions are made leading to an improvement in the current understanding of the sleeper loading pattern and the track deflections.
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Non-resonant piezoelectric transformer based power converter for ultra-low-power electronic devices
Jabbar, Hamid,Jung, Hyun Jun,Cho, Jae Yong,Sung, Tae Hyun Elsevier 2016 Sensors and actuators. A Physical Vol.244 No.-
<P><B>Abstract</B></P> <P>Piezoelectric transformer is used in its resonance frequency range to step-up or -down the input voltage. When the transformer is operated with alternating voltage in the non-resonance frequency range, which can be a few hertz, the transformer input works as an actuator, and the isolated output as a sensor to step-down the voltage. The output voltage has a linear relationship to its input the voltage. In this paper, the piezoelectric transformer in the non-resonant and low frequency range is represented by an equivalent circuit. A power converter that steps-down the mains voltage of 220V and 60Hz to supply power to a micro-watt consuming wireless sensor node is presented. This small size, fewer component, isolated, low EMI, and no inductive component converter has total input power consumption of 31mW with 3V and 11.2μW of output voltage and power respectively.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Low-frequency and non-resonant behavior of Piezoelectric Transformer is presented. </LI> <LI> Equivalent circuit of non-resonant piezoelectric transformer is presented. </LI> <LI> The presented system can supply energy for ultra-low power electronics devices. </LI> <LI> Application specific design can improve efficiency and increase the output power. </LI> <LI> Overall power consumption of the system is very low (31mW). </LI> </UL> </P>
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Jabbar Ali Zakeri,Morvarid Fattahi,Mohammad Mehdi Ghanimoghadam 대한기계학회 2015 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.29 No.6
One of the major problems of railroad deterioration is uneven settlement which occurs due to various reasons, including existence ofdefects in substructures, using non-homogenous ballast, or being poorly drained. Sometimes, because of these problems, sleepers remainfreely as a part of vertical displacement and contact the ballast with load increase. Different models have been presented for checking theeffect of hanging sleepers on the dynamic interaction of rail and train. In this paper, a mathematical model was developed for railwaytrack and differential rail displacement with supported and unsupported sleepers was compared by modeling sleepers such as partiallysupported ones. On this basis, the motion equations of the train-track system were solved considering the non-linearity of wheel/rail contactform and using numerical integration in the time domain. Longitudinal sections of the track model were coded in Matlab softwareand the effect of one, two, or three partially supported sleepers and various spacing of sleepers on the sleepers and rail displacement wasstudied and compared with that of the unsupported one. It was shown that, with increasing the sleeper spacing from 50 to 75 cm, raildisplacement increased from 7 to 22% in the unsupported sleeper and 5 to 8% in the partially supported sleeper. Additionally, rail displacementincreased from 13 to 74% by changing the number of the unsupported sleeper from 1 to 9. Also, it increased from 6 to 24% inthe partially supported sleepers.
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Investigation on dynamic behavior of railway track in transition zone
Jabbar-Ali Zakeri,Vida Ghorbani 대한기계학회 2011 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.25 No.2
Railway track transition zone is a zone where track stiffness changes abruptly. This change occurs where the slab track connects to a conventional ballasted track, at the abutments of open-deck bridges, at the beginnings and ends of tunnels, at road and railway level crossings, and at locations where rigid culverts are placed close to the bottom of sleepers. In this paper, ballasted and slab tracks are simulated by two-dimensional model with two-layer masses. The transition zone is divided into three segments, each having a length of 6meters with different specification and stiffness. The model of track consists of a Timoshenko beam as a rail and slab, lumped mass as sleepers, and spring and damper as ballast, sub-grade, and rail pad. The results of the dynamic analysis are presented and compared in two circumstances – one considering the transition zone and the other its absence.
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Jabbar Ali Zakeri,Rauf Abbasi 대한기계학회 2012 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.26 No.12
Sleeper is one of the most important components in a railway track system. Thus, for accurate analysis and design of concrete sleepers,knowledge of imposed loading pattern is necessary. Sandy desert areas are critical regions where loading status of concrete sleeper is different from other areas. In these areas, the influence of flowing sand grains between the ballast aggregates increase the stiffness of ballast layer; consequently, rail support modulus increases, so the received share of total axle load subsequently increases on the sleeper which is placed under the wheel load. On the other hand, the pressure distribution underneath the sleeper changes considerably. In this paper, the results of a field investigation about the variation of rail support modulus and also variation of loading pattern of concrete sleeper followed by the variation of bending moment of sleepers in sandy desert regions were presented.
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Application of 2D-infinite beam elements in dynamic analysis of train-track interaction
Jabbar Ali Zakeri,He Xia 대한기계학회 2009 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.23 No.5
Railway structure is a structure with an infinite length for which its modeling is usually carried out by accepting some assumptions for boundary conditions. In practice, there are various methods of modeling by forming equations of motions and dynamic analysis. One of these methods is modeling the railway track by finite element method. Generally in such modeling, a limited length of a track is modeled and executed by implementing some boundary conditions. Assortment of boundary conditions has an effect on dynamic responses. To reduce such effects, usually the length of the track is chosen to such a measure to minimize the dynamic responses of the end points of the track elements to zero. Doing so would cause an increase in the length of the track and hence add to an equation's degrees of freedom, volume of output and prolongation of analysis time. For this reason, a combination of finite elements and infinite beam elements (two end elements) has been proposed for railway track modeling. Also, matrices of mass, damping and stiffness of one infinite element which has been laid on a visco-elastic bed, have been calculated by implementing selected shape functions. Therefore, by applying two infinite beam elements on either side of the model, a railway track is formed like a beam on an elastic bed which creates the possibility of eliminating the boundary condition effects.
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Jabbar Khalafy,Mehdi Rimaz,Mahnaz Ezzati,Rolf. H. Prager 대한화학회 2012 Bulletin of the Korean Chemical Society Vol.33 No.9
A simple regioselective synthesis of cinnoline derivatives was achieved by a one-pot three component synthetic methodology. New substituted 7,8-dihydrocinnolin-5(6H)-ones are prepared via one-pot three component reaction of arylglyoxals with 1,3-cyclohexanedione and dimedone in the presence of hydrazine hydrate in moderate to good yields.
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Jabbar Khalafy,Mehdi Rimaz,Leila Panahi,Hossein Rabiei 대한화학회 2011 Bulletin of the Korean Chemical Society Vol.32 No.7
A series of new 4-aryl-6,8-dimethylpyrimido[4,5-c]pyridazine-5,7(6H,8H)-diones have been synthesized via three component reaction of 1,3-dimethylbarbituric acid with arylglyoxals in the presence of hydrazinium dihydrochloride in ethanol. All of these derivatives may act as potential monoamine oxidase inhibitors.
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