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RISS 인기검색어
- 검색키워드
- 저자 : Vesali, Farzad (검색결과 4 건)
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Farzad Vesali 대한기계학회 2012 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.26 No.8
A universal joint also known as universal coupling, U joint, Cardan joint, Hardy-Spicer joint, or Hooke’s joint is a joint or coupling in a rigid rod that allows the rod to ‘bend’ in any direction, and is commonly used in shafts that transmit rotary motion. It consists of a pair of hinges located close together, oriented at 90o to each other, connected by a cross shaft. The Cardan joint suffers from one major problem:even when the input drive shaft rotates at a constant speed, the output drive shaft rotates at a variable speed, thus causing vibration and wear. The variation in the speed of the driven shaft depends on the configuration of the joint. Such configuration can be specified by three variables. The universal (Cardan) joints are associated with power transmission systems. They are commonly used when there needs to be angular deviations in the rotating shafts. It is the purpose of this research to study the dynamics of the universal joints and to propose some practical methods for improving their performance. The task is performed by initially deriving the motion equations associated to the universal joints. That is followed by elaborating on the oscillatory behavior in the rotational speed and the torque that transmits through the intermediary shaft. The forces in the joint bearings are calculated by using an analytical method that is also supported by the numerical modeling. Such models are also used in order to calculate the rhythm and the amount of the excess loads on the joint. This is suggested as a systematic procedure in the search for the causes of the failures in these popular bearings. With the same purpose in mind some defected bearings with deformed sections were selected for the laboratory examinations. By analyzing the loading behavior and the surface conditions of the defected bearings and by comparison with the known fatigue theories attempts are made in order to dig into the causes for the failures in these joints and their bearing surfaces. With the aim of improving the performance and the life expectancy of these popular elements of the machineries, some practical recommendations are also suggested.
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Elham Vesali-Kermani,Aziz Habibi-Yangjeh,Srabanti Ghosh 한국공업화학회 2020 Journal of Industrial and Engineering Chemistry Vol.84 No.-
Nitrogenfixation is a natural or artificial process, in which molecular nitrogen is combined with otherelements to form more-reactive compounds containing nitrogen elements. In this study, graphitic carbonnitride nanosheets were combined with nanoparticles of MgO to fabricate an efficient binary visiblelight-induced photocatalysts (abbreviated as NCN/MgO), and they were applied for the photofixation ofnitrogen gas. The synthesized photocatalysts were characterized to investigate the morphology, phasestructure, optical, and textural properties. The results displayed that the NCN/MgO (10%) nanocompositehas considerable performance in the nitrogen photofixation reaction compared with the pristine CN andNCN, which is 10.8 and 2.8 times, respectively. The stability of the optimum sample, as a vitalcharacteristic of photocatalyst, was examined in three runs. Also, the effect of MgO loading, calcinationtemperature, solvent, electron scavenger, pH, and absence of N2 in solution upon the NH4+ productionrate was examined. Finally, an anticipated mechanism was proposed for the meaningful nitrogenphotofixation enhancement.
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Dynamic response of railway bridges traversed simultaneously by opposing moving trains
Mohammad Ali Rezvani,Farzad Vesali,Atefeh Eghbali 국제구조공학회 2013 Structural Engineering and Mechanics, An Int'l Jou Vol.46 No.5
Bridges are vital components of the railroads. High speed of travel, the periodic and oscillatory nature of the loads and the comparable vehicle bridge weight ratio distinguish the railway bridges from the road bridges. The close proximity between estimations by some numerical methods and the measured data for the bridge-vehicle dynamic response under the moving load conditions has boosted the confidence in the numerical analyses. However, there is hardly any report regarding the responses of the railway bridges under the effect of the trains entering from the opposite directions while running at unequal speed and having dissimilar geometries. It is the purpose of this article to present an analytical method for the dynamic analysis of the railway bridges under the influence of two opposing series of moving loads. The bridge structural damping and many modes of vibrations are included. The concept of modal superposition is used to solve for the system motion equations. The method of solution is indeed a computer assisted analytical solution. It solves for the system motion equations and gives output in terms of the bridge deflection. Some case studies are also considered for the validation of the proposed method. Furthermore, the effects of varying some parameters such as the distance between the bogies, and the bogie wheelset distance are studied. Also, the conditions of resonance and cancellation in the dynamic response for a variety of vehiclebridge specifications are investigated.
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Dynamic response of railway bridges traversed simultaneously by opposing moving trains
Rezvani, Mohammad Ali,Vesali, Farzad,Eghbali, Atefeh Techno-Press 2013 Structural Engineering and Mechanics, An Int'l Jou Vol.46 No.5
Bridges are vital components of the railroads. High speed of travel, the periodic and oscillatory nature of the loads and the comparable vehicle bridge weight ratio distinguish the railway bridges from the road bridges. The close proximity between estimations by some numerical methods and the measured data for the bridge-vehicle dynamic response under the moving load conditions has boosted the confidence in the numerical analyses. However, there is hardly any report regarding the responses of the railway bridges under the effect of the trains entering from the opposite directions while running at unequal speed and having dissimilar geometries. It is the purpose of this article to present an analytical method for the dynamic analysis of the railway bridges under the influence of two opposing series of moving loads. The bridge structural damping and many modes of vibrations are included. The concept of modal superposition is used to solve for the system motion equations. The method of solution is indeed a computer assisted analytical solution. It solves for the system motion equations and gives output in terms of the bridge deflection. Some case studies are also considered for the validation of the proposed method. Furthermore, the effects of varying some parameters such as the distance between the bogies, and the bogie wheelset distance are studied. Also, the conditions of resonance and cancellation in the dynamic response for a variety of vehicle-bridge specifications are investigated.
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