Sharif Digital Repository

In this study, application of the Response Surface Methodology and the Central Composite Design (CCD) technique for modeling and optimization of the influence of several operating variables on titanium recovery in a leaching process were investigated. The four main leaching parameters, namely temperature, acid concentration, leaching time and solid to liquid ratio, were changed during-the leaching experiments based on the CCD. A total of 30 leaching experiments were designed and carried out in the CCD method according to software-based designed matrix. According to the results, i.e., titanium recoveries with these four parameters as well as empirical model equations were developed. The model... 

In this study the effect of HPGR operational parameters on the dimensional properties of pellet feed was examined and optimized using factorial methodology. The operational parameters considered include feed moisture, specific pressure and roll speed. For this study, size and shape of particles with Blaine number in the range 1800–2200 cm2 g−1 was thoroughly investigated. It was deduced that increasing the specific pressure and decreasing the roll speed would result in reduction of D80 but would increase the Blaine number. The circularity, aspect ratio and roughness descriptors of the particles were measured by SEM micrographs and image analysis software. It was observed that particles... 

In this study the effect of HPGR operational parameters on the dimensional properties of pellet feed was examined and optimized using factorial methodology. The operational parameters considered include feed moisture, specific pressure and roll speed. For this study, size and shape of particles with Blaine number in the range 1800–2200 cm2g−1 was thoroughly investigated. It was deduced that increasing the specific pressure and decreasing the roll speed would result in reduction of D80 but would increase the Blaine number. The circularity, aspect ratio and roughness descriptors of the particles were measured by SEM micrographs and image analysis software. It was observed that particles tended... 

Response surface methodology (RSM) explores the relationships between several explanatory variables and one or more response variables. The main idea of RSM is to use a set of designed experiments to obtain an optimal response. RSM tries to simplify the original problem through some polynomial estimation over small sections of the feasible area, elaborating on optimum provision through a well known optimization technique, say Gradient Method. As the real world problems are usually very complicated, polynomial estimation may not perform well in providing a good representation of the objective function. Also, the main problem of the Gradient Method, getting trapped in local minimum (maximum),... 

The Weibull distribution plays an important role in failure distribution modeling of reliability research. While there are three parameters in the general form of this distribution, for simplicity, one of its parameters is usually omitted and as a result, the others are estimated easily. However, due to its more flexibility, when the general form of the Weibull distribution is of interest, the estimation procedure is not an easy task anymore. For example, in the maximum likelihood estimation method, the likelihood function that is formed for a three-parameter Weibull distribution is very hard to maximize. In this paper, a new hybrid methodology based on a variable neighborhood search and a... 

Forming limit diagrams (FLDs) are extensively used in industries, particularly the auto industry. The establishment of these diagrams using a predictive approach can lead to reduction in both cost and time. In the present work, Gurson-Tvergaard-Needleman (GTN), a porosity-based model, was used to predict the FLD of an interstitial-free steel via finite element simulation. Optimum values of the GTN model were obtained by applying a response surface methodology (RSM) based on central composite design. Results show that RSM is a good method for an appropriate determination of the GTN model parameters, such as initial void volume fraction, effective void volume fraction, critical void volume... 

Medical applications of rapid prototyping have an increasing trend, making the future of RP more and more promising. These applications may include design, development, and manufacture of medical devices and instrumentation, as well as implant design, anatomical modeling, surgical planning, surgical implants, and prosthesis fabrication. This paper provides a new methodology for customized hip prosthesis that could provide high accuracy of femoral canal reconstruction via 3D modeling of prosthesis stem, 3D modeling of prosthesis neck, and facilitating the communication between the designer and surgeon. Combining RP technologies and rapid tooling with this novel custom-made hip prosthesis,... 

The meshless element-free Galerkin method was generalized and an algorithm was developed for 3D dynamic modeling of deformable bodies in real time. The efficacy of the algorithm was investigated in a 3D linear viscoelastic model of human spleen subjected to a time-varying compressive force exerted by a surgical grasper. The model remained stable in spite of the considerably large deformations occurred. There was a good agreement between the results and those of an equivalent finite element model. The computational cost, however, was much lower, enabling the proposed algorithm to be effectively used in real-time applications  

Herein, magnetic metal-organic framework nanocomposite (ZIF-8@SiO2@MnFe2O4) was synthesized. The ultrasound-assisted simultaneous adsorption of Malachite Green (MG) and Methyl Orange (MO) as cationic and anionic dyes onto ZIF-8@SiO2@MnFe2O4 magnetic microporous nanocomposite (MMNC) as a novel adsorbent was investigated. The FTIR, FESEM, TEM, XRD, BET and VSM were used to characterize the prepared adsorbent. The analysis of dyes concentration in a binary mixture was investigated using zero-order and first order derivative spectrophotometry. The individual effects and possible interactions between the various parameters were investigated by response surface methodology (RSM). The optimized... 

A new methodology is presented with which the likely impact of accident in one process unit of an industry on other process units can be forecast and assessed. The methodology is based on Monte Carlo Simulation and overcomes the limitations of analytical methods, used hitherto, which were inherently limited in their ability to handle the uncertainty and the complexity associated with domino effect phenomena. The methodology has been validated and its applicability has been demonstrated with two case studies  

This work describes a novel Fe3O4@SiO2@polypyrrole magnetic nanocomposite and its application in the preconcentration of Cd(ii) and Ni(ii) ions. The parameters affecting the preconcentration procedure were optimised by a Box-Behnken design using response surface methodology. Three variables (extraction time, magnetic sorbent amount, and pH) were selected as the main factors affecting the sorption step, while four variables (type, volume and concentration of the eluent, and elution time) were selected as the main factors in the optimisation study of the elution step. Following the sorption and elution of analytes, the ions were quantified by FAAS. The limits of detection were 0.3 and 1.2 ng... 

Conjugated linoleic acid (CLA) is one of the most physiological active fatty acids due to its positive effect on prevention of diseases such as obesity, hyperlipidemia, atherosclerosis and cancer. The aim of this study was to optimize the production of conjugated linoleic acid (CLA)% in alkali isomerization of safflower oil including 71% linoleic acid (LA) using response surface methodology (RSM). The effect of three reaction variables such as temperature, reaction time and amount of KOH on CLA production was investigated using design-expert software. The optimal condition determined at this point, 72% total CLA with the yield of 84% temperature reaction time and the amount of KOH were 187.6... 

Purpose: The purpose of this paper is to evaluate the galvanic corrosion of nitinol orthodontic wires with six dental alloys in artificial saliva and consider the effect of initiated localized corrosion and real surfaces of anode and cathode on galvanic current. Design/methodology/approach: Linear polarization and cyclic polarization curves for each alloy in de-aerated Duffo and Castillo's artificial saliva are obtained. Galvanic corrosion investigation is conducted by polarization curve intersection and mixed potential theory methods. In order to verify the initiation of localized corrosion, scanning electron microscopy is used. Findings: Initiation of localized corrosion on the anode... 

TiO2 nanoparticles were synthesized by sol-gel method using titanium tetraisopropoxide. Sulfate ions were introduced on the titania by impregnation method using sulfuric acid as precursor of sulfate ions. Fourier transform infrared and energy-dispersive X-ray spectroscopy, X-ray fluorescence as well as X-ray diffraction, scanning electron microscopy, and BET methods were used for the characterization of the obtained nanoparticles. The esterification of isoamyl alcohol with acetic acid was investigated to prove the catalytic activity of the TiO2 nanoparticles under solvent-free conditions. Response surface methodology was applied to optimize the effect of some parameters such as the molar... 

A novel colorimetric nanosensor is reported for the selective and sensitive determination of cysteine using magnetic-sulfur, nitrogen graphene quantum dots (Fe3O4/S, N-GQDs), and gold nanoparticles (Au NPs). Thus, S, N-GQDs was firstly immobilized on Fe3O4 nanoparticles through its magnetization in the presence of Fe3+ in the alkali solution. The prepared Fe3O4/S, N-GQDs were dispersed in cysteine solution resulting in its quick adsorption on the surface of the Fe3O4/S, N-GQDs through hydrogen bonding interaction. Then, Au NPs solution was added to this mixture that after a short time, the color of Au NPs changed from red to blue, the intensity of surface plasmon resonance peak of Au NPs at... 

A novel colorimetric nanosensor is reported for the selective and sensitive determination of cysteine using magnetic-sulfur, nitrogen graphene quantum dots (Fe3O4/S, N-GQDs), and gold nanoparticles (Au NPs). Thus, S, N-GQDs was firstly immobilized on Fe3O4 nanoparticles through its magnetization in the presence of Fe3+ in the alkali solution. The prepared Fe3O4/S, N-GQDs were dispersed in cysteine solution resulting in its quick adsorption on the surface of the Fe3O4/S, N-GQDs through hydrogen bonding interaction. Then, Au NPs solution was added to this mixture that after a short time, the color of Au NPs changed from red to blue, the intensity of surface plasmon resonance peak of Au NPs at... 

Context constructing bespoke software development methodologies for specific project situations has become a crucial need, giving rise to Situational Method Engineering (SME). Compared with Software Engineering, SME has a long way to go yet; SME approaches are especially deficient as to support for modeling, portability, and automation. Model-Driven Development (MDD) has been effectively used for addressing these issues in Software Engineering, and is also considered a promising approach for resolving them in SME. Objective This paper aims to address the shortcomings of existing SME approaches by introducing a novel MDD approach, specifically intended for SME purposes, that uses a... 

A Software Process Line (SPrL) is potentially suitable for constructing software development methodologies by reusing core assets. However, adopting this approach without prior assessment of its suitability can lead to failure. The aim of this paper is to identify a set of requirements that can be used for deciding whether to adopt the SPrL approach in an organization. Identification of the requirements was accomplished in two stages: the characteristics important in method tailoring were first identified via a Systematic Mapping Study (SMS) that focused on analyzing 43 primary studies; the degree of importance of the identified characteristics was then determined using a questionnaire... 

Scrum is currently the most widely used agile methodology. However, it is regarded as a framework rather than a concrete process. Unfortunately, the resources available on Scrum do not explicitly define its variable parts and do not offer proper guidance on how to resolve those variabilities. Process (re)configuration is thus left to Scrum Retrospective sessions; this can delay the vital decisions that can significantly improve the process before problems arise. This paper aims to address the problems associated with configuring/reconfiguring Scrum by identifying all the variabilities (variation points) in the Scrum framework, along with the situations where a variation point can be resolved... 

Scrum is currently the most widely used agile methodology. However, it is regarded as a framework rather than a concrete process. Unfortunately, the resources available on Scrum do not explicitly define its variable parts and do not offer proper guidance on how to resolve those variabilities. Process (re)configuration is thus left to Scrum Retrospective sessions; this can delay the vital decisions that can significantly improve the process before problems arise. This paper aims to address the problems associated with configuring/reconfiguring Scrum by identifying all the variabilities (variation points) in the Scrum framework, along with the situations where a variation point can be resolved...