Sharif Digital Repository

An optical amplifier followed by a bistable element has been statistically analyzed before [1]. In this manuscript, output noise analysis represents, then signal to noise ratios (SNR) are calculated either for input or output. It will be shown that noise reduction, can be achieved by a proper selection of parameters  

In this research, low density polyethylene (LDPE) and poly(ethylene-co-vinyl acetate) (EVA) were used as polymeric materials. The methods used to produce LDPE and EVA was film blowing and thermal-dry phase inversion. The amount of permeability, diffusivity and solubility of O2 and CO2 through above polymers were obtained and also the effect of temperature, pressure and film thickness for LDPE was measured. To study film cross-section morphology in EVA, scanning electron microscopy (SEM) was applied. The results showed that the amount of permeability and solubility were decreased by increasing film thickness but diffusivity was increased. However, by increasing temperature, permeability,... 

This study presents a seasonal multi-product multi-period inventory control model with inventory costs obtained under inflation and all-unit discount policy. The products are delivered in boxes of known quantities and both backorder and lost-sale quantities are considered in case of shortage. The goal is to find a representative set of Pareto optimal solutions (including the ordering quantities) in different periods and to minimize both the total inventory cost (i.e. ordering, holding, shortage, and purchasing costs) and the total storage space, simultaneously. Three multi-objective optimization algorithms of non-dominated sorting genetic algorithm (NSGA-II), non-dominated ranked genetic... 

A label-free electrochemical biosensor was developed for the rapid detection of the matrix metalloproteinase 9 (MMP-9) biomarker on the basis of antibody immobilizing on the zinc oxide (ZnO) nanoparticle and ZnO nanorod electrodes. The charge transfer resistance (Rct) of the electrodes was used as the indicator for MMP-9 concentration, which was obtained through cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The ZnO nanorod-based biosensor exhibited linear behavior in the MMP-9 concentration range of 1–1000 ng/ml, which is a wider range than the available concentration ranges for most of the conventional methods. The biosensor sensitivity was 32.5 μA/(decade × cm2)... 

The effects of external resistance on the recruitment of trunk muscles and the role of intrinsic and reflexive mechanisms to ensure the spinal stability are significant issues in spinal biomechanics. A computational model of spine under the control of 48 anatomically oriented muscle actions was used to simulate iso-resistive trunk movements. Neural excitation of muscles was attained based on inverse dynamics approach along with the stability-based optimization. The effect of muscle spindle reflex response on the trunk movement stability was evaluated upon the application of a perturbation moment. In this study, the trunk extension movement at various resistance levels while extending from... 

We propose a solvable generalization of the Tonks-Girardeau model that describes a coherent one-dimensional (1D) gas of cold two-level bosons which interact with two external fields in a Ramsey interferometer. They also interact among themselves by idealized, infinitely strong contact potentials, with interchange of momentum and internal state. We study the corresponding Ramsey fringes and the quantum projection noise which, essentially unaffected by the interactions, remains that for ideal bosons. The dual system of this gas, an ideal gas of two-level fermions coupled by the interaction with the separated fields, produces the same fringes and noise fluctuations. The cases of time-separated... 

In this study, an industrial acetylene hydrogenation unit is simulated utilizing three available kinetic models. The results are compared against six-day experimental data and the best model is selected. Effects of feed temperature and the amount of injected hydrogen on ethylene selectivity are also studied. According to the simulation results, the unit is not working under its optimum conditions. Furthermore, by reduction of the hydrogen flow rate to 52 kg/h, process selectivity is increased. In addition, a new approach is proposed to modify the hydrogenation process and reduce undesired by-products. In the simulation of the modified process, hydrogenation reactors temperature, hydrogen... 

This paper presents a three-dimensional phenomenological constitutive model for magnetic shape memory alloys (MSMAs), developed within the framework of irreversible continuum thermodynamics. To this end, a proper set of internal variables is introduced to reflect the microstructural consequences on the material macroscopic behavior. Moreover, a stress-dependent thermodynamic force threshold for variant reorientation is introduced which improves the model accuracy. Preassumed kinetic equations for magnetic domain volume fractions, decoupled equations for magnetization unit vectors and appropriate presentation of the limit function for martensite variant reorientation lead to a simple... 

Adaptation of Penicillium simplicissimum with different heavy metals present in a spent hydrocracking catalyst, as well as one-step, two-step, and spent medium bioleaching of the spent catalyst by the adapted fungus, was examined in batch cultures. Adaptation experiments with the single metal ions Ni, Mo, Fe, and W showed that the fungus could tolerate up to 1500. mg/L Ni, 8000. mg/L Mo, 3000. mg/L Fe, and 8000. mg/L W. In the presence of multi-metals, the fungus was able to tolerate up to 300. mg/L Ni, 200. mg/L Mo, 150. mg/L Fe and 2500. mg/L W. A total of 3% (w/v) spent catalyst generally gave the maximum extraction yields in the two-step bioleaching process (100% of W, 100% of Fe, 92.7%... 

In this article, a capacitated location allocation problem is considered in which the demands and the locations of the customers are uncertain. The demands are assumed fuzzy, the locations follow a normal probability distribution, and the distances between the locations and the customers are taken Euclidean and squared Euclidean. The fuzzy expected cost programming, the fuzzy β-cost minimization model, and the credibility maximization model are three types of fuzzy programming that are developed to model the problem. Moreover, two closed-form Euclidean and squared Euclidean expressions are used to evaluate the expected distance between customers and facilities. In order to solve the problem... 

The quantity of spent hydroprocessing catalysts discarded as solid wastes in the petroleum refining industries has increased remarkably due to a steady increase in the processing of heavier feedstock. The adaptation of Penecillum Simplicissimum BBRC1-20019 with different heavy metals present in spent hydrocracking catalysts was studied. Adaptation experiments with single metals showed that the fungus could tolerate ≤ 1500 mg/L Ni, 8000 mg/L Mo, 3000 mg/L Fe, and 8000 mg/L W. In the presence of a mixture of these metals, the fungus tolerated ≤ 300 mg/L Ni, 200 mg/L Mo, 150 mg/L Fe, and 2500 mg/L W. The presence of multi-metals acted cumulatively to enhance the toxic effect in the growth of... 

This study was designed to compare one-step, two-step and spent medium bioleaching of spent catalyst by adapted Penecillum simplicissimum in batch cultures. Penecillum simplicissimum which was adapted to heavy metal ions Ni, Mo, Fe, and W grew in the presence of up to 5 %w/v of spent catalyst in the medium. The main lixiviant in bioleaching was gluconic acid which was produced mainly in present and absence of spent catalyst. A total of 3 %w/v spent catalyst generally gave maximum extraction yields in two-step bioleaching process, which the amounts of leached metals were 100 % of W, 100 % of Fe, 92.7 % of Mo, 66.43 % of Ni, and 25 % of Al. The red pigment produced by fungus could also... 

This research aims to expand the body of information that researchers require before starting electronic waste (E-waste) recovery experiments. With this purpose, the basic metal contents, alkalinity, polymer components, iron magnetic separation, metal recovery priority and economic values of different types of waste printed circuit boards (PCBs) were investigated. The selected wastes were computer PCBs (CPCBs), CPCBs with wires, mobile phone PCBs (MPPCBs), television PCBs (TVPCBs), fax machine PCBs (FPCBs), copy machine PCBs (COPCBs) and central processing units (CPUs). These E-wastes were prepared in the three fraction sizes of F1<1 mm, 1 < F2<3 mm, and 3 < F3<8 mm to evaluate the metal... 

Polystyrene, acrylonitrile butadiene styrene, and polypropylene are the main polymers in E-waste, existing about 31%, 16%, and 13%, respectively. In this research, the effects of the elimination of low-density materials (such as polymers and plastics) were studied using the shaking table method. Bioleaching of Cu and Ni against the original sample (Sample #1) and pre-treated sample without low-density materials (Sample #2) was compared. The amount of bioleached metals and growth characteristics (including pH, Eh, bacterial count) was investigated within 25 days. The analysis of Sample #1 showed that at pulp density of 15 g/l, 94% and 79% of Cu and Ni were recovered maximally, respectively,... 

The oxidation of ferrous iron in solution using Acidithiobacillus ferrooxidans has industrial applications in the regeneration of ferric iron as an oxidant agent for the removal of hydrogen sulfide from waste gases, desulphurization of coal, leaching of non-ferrous metallic sulfides and treatment of acid mine drainage. The aim of this attempt was to increase the biooxidation rate of ferrous sulfate by using immobilized cells. Rate of ferrous iron oxidation was determined in a packed-bed reactor configuration with low density polyethylene (LDPE) particles as support material in order to find the most practical system for scale-up. The present work studies the influence of basic parameters on... 

The purpose of this research is to explain the surface modification of fabricated polyamide reverse osmosis (RO) membranes using UV-initiated graft polymerization at different irradiation times (15, 30, 60, and 90 s) and various acrylamide concentrations (10, 20, and 30 g L−1). Also, coating of membranes surface with various concentrations of TiO2 nanoparticles (10, 20, 30, and 50 ppm) followed by the same UV irradiation times was investigated. After that, the membranes modification was done by grafting of acrylamide blended with TiO2 nanoparticles via UV irradiation. The characterization of membranes surface properties and their performance were systematically carried out. The results... 

This study was designed to compare one-step, two-step and spent medium bioleaching of spent catalyst by adapted Aspergillus niger in batch cultures. Aspergillus niger, which was adapted to heavy metal ions, Ni, Mo, Fe, and W, was grown in medium containing up to 5% (w/v) of spent catalyst. The main lixiviant in bioleaching was gluconic acid, which was produced at all pulp densities in the one-step bioleaching process. Gluconic acid was also produced in the two-step bioleaching process when the spent catalyst was present at pulp densities greater than 1% (w/v). In the spent medium leaching, however, the primary agent was citric acid. The pulp density of the spent catalyst was varied, and this... 

In this study, the Geocoat™ technology was used for the extraction of zinc from a mineral concentrate obtained from the Kooshk mine (Yazd, Iran) by a culture dominated by the mesophilic bacterium Acidithiobacillus ferrooxidans in a packed column bioreactor. A low grade sphalerite ore was used as support for the concentrate coating. During the 100 days of leaching pH, Fe3+, Fetotal, microbial population density and zinc extraction were measured. The final zinc extraction from concentrate and low grade support was 97% and 78%, respectively, and it was found that leaching from the support does not proceed significantly before leaching from the coating is completed  

Controllability analysis of a network through its topology has recently been a popular issue in the systems and control community. In this regard, the zero extension rule is introduced in this paper, which provides a sufficient number of control nodes to ensure the controllability of certain families of undirected networks through the notion of their balancing sets. Moreover, some lower bounds on the dimension of the controllable subspace are provided. Finally, based on the generalized zero extension rule, some controllability conditions for such special structure of networks as the path, cycle, and three-branch tree are derived  

In this present research work, a new configuration of the hybrid magnetorheological (MR) brake via T-shaped drum with an arc form surface boundary - the biomechanical geometric design of the hybrid MR brake as a prosthetic knee - is discussed and experimentally tested. The main purpose of this study is to develop a prosthetic knee with one rotary disc to fulfill the desired objective. To achieve this, three steps are considered. In the first step, to model the brake, slab method modeling is used to calculate the braking torque due to the arc surface. In the second step, the biomechanical geometric design is adjusted as an optimization problem to maximize the braking torque, minimize the...