Sharif Digital Repository

Powder metallurgy is one of the most important and most usable methods in industries. Nowadays, many of the specimens are made this way. In this method, after powder compaction stage, because of sintering in high temperature, crystallographical structure of the material changes. This change results in poorer strength than initial powde. In order to avoid change and decrease in powder strength, shock consolidation is used. In this research, because of complication of this phenomenon and final quality of the specimen, shock consolidation of metal powders is investigated and analysed. This phenomenon is modeled, simulated, analysed and optimized mathematically.Various methods are used to create... 

In this article, research has been carried out on the control technique of autonomous mobile robots to navigate in unknown environments, avoiding static and moving obstacles using eight ultrasonic sensors for obstacle recognition.
In this article we used simple three wheeled robots. Each robot has a passive caster wheel and two active fixed wheels which can act independently. In addition robots have holonomic constraints like maximum acceleration, maximum speed and maximum angular velocity, so robot’s speed and orientation change independently and these changes are small in each time step. Each robot has eight ultrasonic sensors, each of them cover 22.5 degree of space from robot‘s... 

Recently, the use of mass spectrometry imaging (MSI) has been introduced as a powerful tool to study the compounds in biological and environmental samples. The lack of need to sample preparation have made it possible to quantify and qualify these compounds in complex matrix such as biological matrices. This technique will also allow analyzing the compounds in a very wide mass range and precise structural information this method gives leads to employ this method widely for quantification and qualification of wide variety compounds. Accuracy and precision of results obtained by this method beside unique information it gives about system lead to wide use of this method in scientific... 

One of the most important targets in bio-informatics is the analysis of biological networks. These networks are modeled by graphs. Comparing networks with mapping is a useful tool for analyzing. The mapping between the nodes of a network that preserves some topological and functional structures, is called network alignment. Network alignment has various applications in different fields; such as pattern recognition, social networks, biological networks, and etc. The alignment of the protein-protein interaction network is one of the substantial problems. There are many static algorithms for the alignment of PPI networks. Because of the developments of computer science in recent years,... 

Nowadays, the use of vehicles is inevitable for all people including pregnant females. Vehicle vibrations during passing road bumps and holes is one of the pregnant females’ concerns. The aim of the present study is to develop a biomechanical model of a Uterus and Fetus Set (UFS) to evaluate its response to the inferior excitation, caused by the vehicle passing over speed bumps. The most important innovation of this research is "Analysis of the effect of vehicle speed and speed bumps characteristics on the risk of injury to the fetus." "Modeling the pregnant uterus complex separately from other abdominal organs", "Biomechanical modeling based on CT scan data from a real subject", "Providing... 

In this research, multi-disciplinary design optimization (MDO) of a flying vehicle has been done based on the flight simulation. A meta-heuristic algorithm called Multi-objective Adaptive Real-coded Memetic Algorithm (MARCOMA) has been used for optimization. Since solving a MDO problem is a time consuming process, a RBF neural network has been used in the optimization algorithm as a surrogate model. The new algorithm, called MARCOMA+NN, has been tested with some standard benchmarks. MDO problem has six disciplines consists structure, aerodynamic, propulsion, guidance, control, and fire control. The MDO problem has 31 design variables and two objective functions. The objective functions are... 

A cooperative aerial system to defense a Ground Station (GS), against an Incoming aerial Targets (IT) is presented. GS is surrounded by given terrains and a group of homogenous Unmanned Aerial Vehicles (UAVs) are employed using a novel online guidance algorithm in a decentralized manner. The proposed algorithm includes loiter, midcourse and terminal phases. During loiter; UAVs follow an optimal circular path. IT is supposed to approach GS along an optimal low altitude trajectory with respect to the terrains. UAVs are informed the initial position and velocity of IT and they are unaware of IT trajectory. Each UAV decides on whether to engage with IT or not, and shares its decision with other... 

PVDF (polyvinylidene fluoride) magnetic nanocomposite films were prepared by solution casting using two types of nanomagnetic particles: (i) magnetic nanoparticles synthesized by using an alkaline solution of mixed ferrous/ferric salts along with oleic acid as a coating agent at 70˚C; (ii) Fe3O4 nanoparticles prepared by hydrolysis of aqueous solution of ferrous/ferric salts with potassium hydroxide at room temprature. Scanning electron microscopy (SEM) showed that the PVDF magnetic nanocomposite had a porous structure with Fe3O4 nanoparticles dispersed inside the porous polymer matrix. The presence of crystalline magnetite within the polymer matrix was confirmed by X-Ray diffraction method...