Materials and Energy Research CenterInternational Journal of Engineering1025-24958219950501Computer Simulation of Ammonia Cold Shot Converter16171121ENE. EsmailzadehMechanical Engineering, Sharif University of TechnologyD. MowiaChemical & Petroleum Engineering, Shiraz UniversityJ. Fathi KalajahiChemical & Petroleum Engineering, Shiraz UniversityJournal Article19700101A mathematical model is developed and tested with plant data for the ammonia cold shot converter of Razi Petrochemical Complex. The model is based on a material and energy balance in a differential element of beds and is subjected to the assumptions of uniform distribution of temperature and composition through a general cross section and negligible mass and heat transfer in axial direction. The governing differential equations are solved by Runge-Kutta of fourth order to obtain temperature and concentration profiles through the reactor. The agreement between calculated temperature and composition with plant data confirms the validity of the developed model.https://www.ije.ir/article_71121_31d0879fc71c3e9913d7ddbeadf8d7fe.pdfMaterials and Energy Research CenterInternational Journal of Engineering1025-24958219950501Tests to Determine the Joint Stiffness and Resisting Moment Capacity of Joints in Timber-Framed Houses718471122ENF. Nateghistructure, IIEESJournal Article19700101Wind and earthquake disasters in the world often cause billions of dollars of damage to buildings, most of which is to non-engineered buildings-especially homes. Wood-frame homes use connectors which exhibit partial rotational rigidity at the member ends, making analytical solutions difficult. This is due to the lack of information about the complex behavior of the connections used in this type of buildings, and the lack of a methodology to analyze light-timber frame buildings with flexible joints. In order to address the problem, tests were carried out to determine the moment rotation characteristics of wood joints made of conventional and mechanical fasteners. During testing, it was discovered that rotational stiffness of timber connections is a function of the axial load as well as the shear load. Comparison of ordinary timber connections with metal connectors were made. Resisting moment capacity of joints with different connectors were also determined. This paper presents a new method of testing for joint stiffness and the experimental results obtained during testing for stud-to-bottom-plate, rafter-to-ridge-board, and top-plate-to-rafter connections using different connectors.https://www.ije.ir/article_71122_138ea1c02f07e061ac3c4db442c9343d.pdfMaterials and Energy Research CenterInternational Journal of Engineering1025-24958219950501Investigation of Melting by Molecular Dynamics Simulation859471123ENH. AkbarzadehPhysics, Isfahan University of TechnologyS. Mohammad AminiPhysics, Isfahan University of TechnologyJournal Article19700101The melting of a 64 ion microcrystal of KCI was studied by means of a molecular dynamics computer simulation. We used a central pair interaction with an inverse power law repulsion. The thermodynamics, kinetic and structural properties such as melting temperature, latent heat, mean square displacement, diffusion constant, radial distribution function and bond angle distribution are calculated. The simulation indicated that the melting temperature of the microcrystal is lower than the experimental value of the bulk, which is consistent with the Gibbs-Thompson relation. It is shown that all the features of the melting transition which are observed in a bulk system are also exhibited by such a small microcrystal. The simulation is programmed in FORTRAN and run on a PC.https://www.ije.ir/article_71123_4c93cee29e829b54579e940baffedeaf.pdfMaterials and Energy Research CenterInternational Journal of Engineering1025-24958219950501Stress Concentration Factors in Spherical Vessels with Single Oblique Nozzle9510671124ENK. Naderan, Shahid Chamran University of AhvazJournal Article19700101Finite element method is employed to analyze the spherical vessel intersected by an oblique cylindrical nozzle. In this survey the stress and strain distributions on acute and obtuse sides of the connection under internal pressure are studied widely although axial and moment loadings on the nozzle are also studied briefly. Stress concentration factors for a wide range of geometrical ratios in term of membrane stress in the sphere are calculated and presented. Variation of these factors with angle of obliquity of the branch is also investigated. The results are compared with measured quantities and with those mentioned in other references. It is assumed that the definition of thin shell is valid for both vessel and nozzle simultaneously and that the corners are sharp without any reinforcement. ABAQUS computer program is used in this survey.https://www.ije.ir/article_71124_94ae6e8ef3bc25b82321b2012b5c1419.pdfMaterials and Energy Research CenterInternational Journal of Engineering1025-24958219950501Stress Analysis of the Human Ligamentous Lumber Spine-From Computer-Assisted Tomography to Finite Element Analysis10711271125ENC. BreauMechanical Engineering, Ecole Polytechnique Fédérale de LausanneJournal Article19700101Detailed investigation on biomechanics of a complex structure such as the human lumbar spine requires the use of advanced computer-based technique for both the geometrical reconstruction and the stress analysis. In the present study, the computer-assisted tomography (CAT) and finite element method (FEM) are merged to perform detailed three dimensional nonlinear analysis of the human ligamentous lumbar spine. The details of the development of a three dimensional model of the lumbar spine using CAT images are initially described. Then the predicted nonlinear response of the system subjected to axial compression force is presented. The stress analysis is performed using a finite element code developed by Shirazi-Adl.https://www.ije.ir/article_71125_1a2d0b7e5fb583fbe7431f6167eed9b3.pdfMaterials and Energy Research CenterInternational Journal of Engineering1025-24958219950501Robot Motion Vision Part II: Implementation11312071126ENM.A. TaalebinezhaadMIT Artificial Intelligence Laboratory, University of CambridgeJournal Article19700101The idea of Fixation introduced a direct method for general recovery of shape and motion from images without using either feature correspondence or optical flow [1,2]. There are some parameters which have important effects on the performance of fixation method. However, the theory of fixation does not say anything about the autonomous and correct choice of those parameters. This paper presents the effect of those parameters on the experimental results of implementing some of the fixation algorithms on real images where the motion is a combination of translation and rotation. The results show that important motion components can be estimated accurately if the right parameters are used. Some of the critical issues involved in the implementation of autonomous robot motion vision are also discussed. Among these are the criteria for autonomously choosing an optimum size for the fixation patch, and appropriate choice of the fixation point location. Finally, a calibration method is described for precisely determining the location of real rotation axis in imaging systems.https://www.ije.ir/article_71126_cd13bab2d720c765140a80e8d50156f7.pdf