Sharif Digital Repository

MADI is new engineering material with very desirable properties such as higher strength at the same hardness compared to regular ductile iron, significantly better fatigue performance than regular ductile iron or austempered ductile iron, better machinability than regular austempered ductile iron and similar to as cast ductile iron. In this study,fatigue properties of Machinable Austempering Ductile was investigated using rotary -bend fatigue testing device. Chemical composition of sample was selected on the base of previous work which results in good mechanical properties and low hardness after austempering process. The results of this study,indicates that for an austempered ductile iron... 

ADI have been used for a wide variety of application in automotive,rail,and heavy engineering industry because of its excellent mechanical properties such as high strength with good ductility,good wear resistance,and good fatigue properties. The properties of austempered ductile iron are dependent on both chemistry and heat treatment, which has lead to invention of MADI (machinable austempered ductile iron). MADI is a new class of ductile iron with superior mechanical property than regular ductile iron with the same machinability characteristic. In this study Different cycles of austempering process (austenitization and austempering cycle) applied Due to the effect of heat treatment cycle on... 

In this paper, we consider to seek vulnerabilities and we conduct possible attacks on the crucial and essential parts of Android OSs architecture including the framework and the Android kernel layers. As a regard, we explain the Binder component of Android OS from security point of view. Then, we demonstrate how to penetrate into the Binder and control data exchange mechanism in Android OS by proposing a kernel level attack model based on the hooking method. As a result, by implementing the attack model, it is illustrated that the Android processes are detectable and the data can be extracted from any process and system calls. © 2016 IEEE  

Thermal dependency of material characteristics in micro electromechanical systems strongly affects their performance, design, and control. Hence, it is essential to understand and model that in MEMS devices to optimize their designs. A thermal phenomenon introduces two main effects: damping due to internal friction, and softening due to Young modulus temperature relation. Based on some reported theoretical and experimental results, we model the thermal phenomena and use two Lorentzian functions to describe the restoring and damping forces caused by thermal phenomena. In order to emphasize the thermal effects, a nonlinear model of the MEMS, by considering capacitor nonlinearity, have been... 

Welding is an important manufacturing process that can be automated and optimized. In this paper we discuss the Gas Metal Arc Welding (GMAW) control and modeling problem. For modeling the process recently developed highly nonlinear fifth order mathematical model is used, for controlling the GMAW process we use a new Mixed Fuzzy Control (MFC) structure. In this work first a Traditional Fuzzy Controller (TFC) is designed from the viewpoint of a Single-Input Single-Output (SISO) system for controlling each state of GMAW process. Then, an appropriate coupling fuzzy controller is also designed according to the characteristics of gas metal arc welding process and incorporated into a TFC. We then... 

This research deals with a flexible flowshop scheduling problem with the arrival and delivery of jobs in groups and processing them individually. Each group of jobs has a specific release time. Due to the special characteristics of each job, only a specific group of machines in each stage are eligible to process that job. All jobs in a group should be delivered at the same time after processing. The objectives of the problem are the minimization of the sum of the completion time of groups on one hand and the minimization of sum of the differences between the completion time of jobs and the delivery time of the group containing that job (waiting period) on the other hand. The problem can be... 

The variation of effective parameters in Micro Electro Mechanical Systems strongly affects their performance, design, and control. Hence, it is essential to understand and model the effective parameters in MEMS devices to optimize their designs. Typical MEMS (Microresonator) employ a parallel-plate capacitor, in which one plate is actuated electrically and its motion is detected by capacitive changes. In this paper we investigate nonlinear modelling of microresonators. The nonlinearities from capacitor (quadratic) and midplane stretch were considered for this purpose. The achieved microbeam′s equations are nondimensionalized and by using the multiple scales method received to the equations... 

In this paper, a one-dimensional numerical approach is used to study the effect of various parameters such as micro combustor diameter, mass flow rate and external convection heat transfer coefficient on the temperature and species mass fraction profiles. A premixed mixture of H2-Air with a multi-step chemistry (9 species and 19 reactions) is used and thermal conductivity of the mixture is considered as a function of species thermal conductivity and temperature by using a set of new relations. The transient gas phase energy and species conservation equations result in an Advection-Diffusion-Reaction system (A-D-R) that leads to two stiff systems of PDEs, which can not be solved by... 

Identification and minimization of error sources are important issues in experimental investigations. Mainly in micro-scale problems, precise settings should be applied to high-tech test beds to reduce disturbance and induced motion. An experimental study is conducted to assess the role of induced forces and velocity fields in a particulate system used for particle identification and separation. Two main effects caused by disturbances are sampling errors and induced motion in the channel, either on fluid or dispersed phases. Different disturbance scenarios are implemented on the test bed and then the system response is reported. In order to assess induced motion as a result of applied... 

Magnetic convection heat transfer in a two-dimensional square cavity induced by magnetic field gradient is investigated numerically using a semi-implicit finite volume method. The side walls of the cavity are heated with different temperatures, the top and bottom walls are isolated, and a permanent magnet is located near the bottom wall. Thermal buoyancy-induced flow is neglected due to the nongravity condition on the plane of the cavity. Conditions for the different values of non-dimensional variables in a variety of ferrofluid properties and magnetic field parameters are studied. Based on this numerical analysis, a general correlation for the overall Nusselt number on the side walls is... 

Heteropoly acid was found to be an effective and efficient catalyst for the ring opening reaction of epoxides with various aromatic amines to produce the corresponding β-amino alcohols in moderate to excellent yields in water. This method provides a new and efficient protocol in terms of mild reaction conditions, clean reaction profiles, small quantity of catalyst, and simple work-up procedure  

A simple, rapid, atom economy and highly efficient procedure has been developed for thiolysis of epoxides by aromatic and aliphatic thiols under solvent-free conditions. A high regioselectivity in favor of nucleophilic attack at the benzylic carbon atom of aromatic epoxides, such as styrene oxide, is observed. However, aliphatic unsymmetrical alkenyl oxides undergo selective nucleophilic attack at the sterically less hindered carbon atom. A variety of β-hydroxy sulfides were obtained in short reaction time and excellent yields with nearly complete regioselectivity  

A new mathematical method is proposed to model the transport of polydisperse submicron aerosol particles in a heterogeneous porous media, and as an example, it is applied to study the transport of mainstream smoke aerosol particles in the cigarette tobacco column. The tobacco column is composed of randomly distributed pores and the aerosol particle transport is modeled utilizing a pore sub-model and taking into account aerosol particle coagulation and deposition. Copyright © 2009 Begell House, Inc  

The solid LiClO4-mediated one-pot reaction of aldehydes with secondary amines and C nucleophiles afforded the corresponding aminoalkylation products in high yields. Unlike the previous reported procedure, the aminoalkylation of aldehyde was achieved in the presence of only 0.5 equivalents of solid lithium perchlorate in dichloromethane as the solvent with good to high yields at room temperature. © Springer-Verlag 2003  

The reactions of different dithiocarbamate anions with epoxides were investigated in water. With this method, β-hydroxy dithiocarbamate derivatives were synthesized in high yields. The reaction was also carried out in DMF in the presence of lithium perchlorate with a simple work-up procedure, and the results are compared  

A simple, rapid, and highly regioselective green protocols for the synthesis of β-hydroxylnitriles by the direct reaction of epoxides with trimethylsilyl cyanide in the presence of catalytic amount of lithium perchlorate under solvent free conditions in high to quantitative yield is reported  

Treatment of aliphatic and aromatic aldehydes with chiral amines and trimethylsilyl cyanide in the absence or in the presence of Lewis acids (including lithium perchlorate) under solvent-free conditions afforded the corresponding α-aminonitriles in good yields and with a diastereoselectivity of 68 to 86%  

An experimental investigation has been performed to realize thorough behavior of a vortex tube system. In this work attention has been focussed on the classification of the parameters affecting vortex tube operation. The effective parameters are divided into two different types, namely geometrical and thermo-physical ones. A reliable test rig has been designed and constructed to investigate the effect of geometrical parameters i.e. diameter and length of main tube, diameter of outlet orifice, shape of entrance nozzle. Thermo-physical parameters which have been designated and studied are inlet gas pressure, type of gas, cold gas mass ratio and moisture of inlet gas. The effects of these... 

An operationally simple and entirely green protocol for heteropoly acid catalyst conjugate addition of indoles and pyrrole to unsaturated carbonyl compounds and nitro-alkene in water was investigated. It is important that the products arising from 1,2-addition were not observed under the reaction conditions. Pyrroles also readily underwent Michael addition at Α-positions under the same reaction conditions. Indole and many of its derivatives are present in many substances commonly found in nature. Micheal addition reactions are performed in organic solvents with the reactions in water are relatively scarce. The Michael addition between indole and methyl vinyl ketone in the presence of...