Sharif Digital Repository

In transition from concept design to detail design, designers and engineers need to find specific materials to optimize performance of the systems. The large number of materials and the wide range of manufacturing processes cause engineers always to seek new materials selection methods. In this research work a new method so called QFD method, which employs materials indices, is introduced. The method enjoys a combination of Ashby's materials selection concepts with the Quality Function Deployment (QFD) tool. The QFD method, which is modified here to fit the materials selection field, provides the designer with the required weighting factors for the material indices. Incorporation of House of... 

In this research, the effect of surface characteristics on boiling heat transfer has been investigated experimentally. For this purpose, a device with the ability to automatically record the liquid temperature of the inlet and outlet of the test area, calculate the coefficient of boiling heat transfer, and heat flux has been developed. The automatic temperature stability of the working fluid and the ability to investigate the effect of surfaces with different characteristics (in terms of material and surface structure) on the boiling heat transfer parameters are the most important features of this device. The performance of the experimental setup was evaluated by the modified "Chen" equation... 

In this research, the effect of surface characteristics on boiling heat transfer has been investigated experimentally. For this purpose, a device with the ability to automatically record the liquid temperature of the inlet and outlet of the test area, calculate the coefficient of boiling heat transfer, and heat flux has been developed. The automatic temperature stability of the working fluid and the ability to investigate the effect of surfaces with different characteristics (in terms of material and surface structure) on the boiling heat transfer parameters are the most important features of this device. The performance of the experimental setup was evaluated by the modified "Chen" equation... 

In this paper, an innovative method is proposed for material selection. This method is based on the well-known weighting properties approach while integrating a new exponential function in the method to overcome the deficiencies of previously proposed methods. Using a maximum and minimum, in each significant aspect of the problem, for scaling, the values of material properties and achieving more realistic results by not emphasizing on any of the high and low extremes and using an exponential function that ranks the candidates regardless of their number, for improving the performance of the methodology and obtaining more absolute rankings, are some of the advantages of this method. The... 

The performance of nanoparticles for biomedical applications is often assessed by their narrow size distribution, suitable magnetic saturation and low toxicity effects. In this work, superparamagnetic iron oxide nanoparticles (SPIONs) with different size, shape and saturation magnetization levels were synthesized via a co-precipitation technique using ferrous salts with a Fe3+/Fe2+ mole ratio equal to 2. A parametric study is conducted, based on a uniform design-of-experiments methodology and a critical polymer/iron mass ratio (r-ratio) for obtaining SPION with narrow size distribution, suitable magnetic saturation, and optimum biocompatibility is identified. Polyvinyl alcohol (PVA) has been... 

In this research, the galvanized steel with thickness of 2 mm was joined to the 5754 aluminum alloy with thickness of 3 mm by the cold metal transfer MIG welding–brazing process. The effect of the filler wires (AlSi3Mn, AlSi5, and AlSi12) and wire feed speeds (4.7, 5, and 5.3 m/min) on metallurgical and mechanical properties have been discussed. According to the experimental results, thickness of intermetallic compound (IMC) layer which was formed along the interface during the MIG welding–brazing was varied by changing of parameters. In addition, the results indicated that by increasing of the wire feed speed, the thickness of IMC layer at first decreased and then increased. Results... 

In this paper we propose a content-based text and image retrieval architecture using Fuzzy Adaptive Resonance Theory neural network. This method is equipped with an unsupervised mechanism for dynamic data clustering to deal with incremental information without metadata such as in web environment. Results show noticeable average precision and recall over search results. © 2006 IEEE  

In recent years, the fabrication of nanoparticles and exploration of their properties have attracted the attention of physicists, chemists, biologists and engineers. Interest in nanoparticles arise from the fact that the mechanical, chemical, electrical, optical, magnetic, electro-optical and magneto-optical properties of these particles are different from their bulk properties and depend on the particle size. There are numerous areas where nanoparticulate systems are of scientific and technological interest. This new book reviews research on the various components of superparamagnetic iron oxide nanoparticles  

As the use of superparamagnetic iron oxide nanoparticles (SPION) in biomedical applications increases (e.g. for targeting drug delivery and imaging), patients are likely to be exposed to products containing SPION. Despite their high biomedical importance, toxicity data for SPION are limited to date. The aim of this study is to investigate the cytotoxicity of SPION and its ability to change cell medium components. Bare and poly(ethylene glycol)-co-fumarate (PEGF)-coated SPION with narrow size distributions were synthesized. The particles were prepared by co-precipitation using ferric and ferrous salts with a molar Fe3+/Fe2+ ratio of 2. Dulbecco's modified Eagle's medium (DMEM) and primary... 

This paper presents the results of a thorough power quality analysis in order to determine the cause of failure in a Compressed Natural Gas (CNG) distribution transformer. The paper presents the field data and determines power quality indices of such loads based on IEEE/IEC standards. It provides steady state time-series parameters as well as transient waveforms. Different signatures of the voltage and current signals are extracted, and consequences of the distortions are described. The analysis is clarified by presenting both time domain captured waveforms and statistical power quality indices. Optimum solution for improving power quality and prevent component failure is also proposed. ©... 

In this paper we propose a neuro-fuzzy architecture for Web content taxonomy using hybrid of Adaptive Resonance Theory (ART) neural networks and fuzzy logic concept. The search engine called Kavosh1 is equipped with unsupervised neural networks for dynamic data clustering. This model was designed for retrieving images without metadata and in estimating resemblance of multimedia documents; however, in this work only text mining method is implemented. Results show noticeable average precision and recall over search results. © 2007 IEEE  

Superparamagnetic iron oxide nanoparticles (SPION) with narrow size distribution and stabilized by polyvinyl alcohol (PVA) were synthesized. The particles were prepared by a coprecipitation technique using ferric and ferrous salts with a molar Fe3+/Fe2+ ratio of 2. Using a design of experiments (DOE) approach, the effect of different synthesis parameters (stirring rate and base molarity) on the structure, morphology, saturation magnetization, purity, size, and size distribution of the synthesized magnetite nanoparticles was studied by various analysis techniques including X-ray powder diffraction (XRD), thermogravimetric analysis (TGA) with differential scanning calorimetry (DSC)... 

Recently, due to the restructuring of power systems and the high penetration level of local renewables, distribution systems have encountered with the complexity of power management. Therefore, the modern systems would be operated in a multi-agent structure which facilitates the power management as well as privacy protections of independent entities. In this structure, the distribution system is assumed to compose of several agents who independently schedule their local resources in order to maximize their own profits. Consequently, this paper provides an efficient peer-to-peer (P2P) active power management framework in a multi-agent distribution system while considering network constraints... 

In recent years, distributed structures have been developed in distribution networks as a result of privatization as well as integration of independently operated distributed energy resources (DERs) into the grid. In this context, effective management techniques seem to be necessary to enable decentralized operation of systems that have been consisted of multiple agents. Accordingly, novel management schemes should be applied in such systems to enable the distributed reactive power management, which would finally improve voltage profile in the network. As a result, this paper develops a distributed algorithm for reactive power management in multi-agent distribution systems with the aim of...