Sharif Digital Repository

In this study, the flow of a fiber filled viscoelastic matrix through planar contractions is investigated. It was found that by adding fiber to the matrix vortex, the intensity increases. Fiber orientation along "x" and "y" axes was studied too. It was found that fiber orientation could be used for determining the flow regime through the contraction geometry. The rigidity condition of fibers, which needs the trace of the orientation tensor to be unity everywhere in the domain, is correct except near walls and the reentrant corner, which is slightly less than one. In these regions, the stress magnitude is higher, which results in more numerical errors, and which further leads to some error in... 

Contraction flow is one of important geometries in fluid flow both in Newtonian and non-Newtonian fluids. In this study, flow of a viscoelastic fluid through a planar 4:1 contraction with rounded corners was investigated. Six different rounding ratios (RR =0, 0.125, 0.25, 0.375, 0.438, 0.475, 0.488) was examined using the linear PTT constitutive equation at creeping flow and isothermal condition. Then the resulting PDE set including continuity, momentum, and PTT constitutive equations were implemented to the OpenFOAM software. The results clearly show vortex deterioration with increasing rounding diameter, so that when rounding corner exceeds a critical value, the vortex disappears... 

The Weibel instability plays an important role in stopping hot electrons and energy deposition mechanism in fast ignition of inertial fusion process. In this paper, the ion Weibel instability in counter propagating electron-ion plasmas is investigate. The obtained results show that the growth rate of Weibel instability will be decreased about 40% with the anisotropy velocity as vxe = 2vze = 20; the ion density ratio, b = n0i1/n0i2, and density gradient, are increasing 50 and 90% respectively. The ion streaming in density gradient of dense plasma leads to increasing the Weibel instability growth rate and its amplification through ion streaming in the large wavenumber. The maximum unstable... 

Esterification of Phthalic anhydride with 2-Octanol and Sebacic acid with Ethanol has been studied in the presence of Sulfated Titania. This study showed that Sulfated Titania has strong catalytic effect on esterification reactions. The effect of some factors such as reaction temperature, molar ratio of acid to alcohol, amount of catalyst used, reaction time, calcination temperature, drying temperature and calcination atmosphere has been investigated. Equilibrium composition achieved in 80 min for Diethyl Sebacate and 20 min for Dioctyl Phthalate in various conditions. © 2005 Elsevier B.V. All rights reserved  

In this paper, new polymer composites were synthesized by template copolymerization of aniline and metanilic acid in the presence of prepared melamine triacetic acid and poly(melamine-co-citric acid) as polyacids and dopants. The properties of the poly(aniline-co-metanilic acid) composites were studied by Fourier transform infrared, X-ray diffraction, scanning electron microscope, CV, and differential scanning calorimeter analysis. The four-point probe technique was used for evaluating the electrical conductivity of the composites. The scanning electron micrographs disclosed that the products had the morphology with agglomerated distorted spherical shapes with the average size of 40–50 nm.... 

In this paper, new polymer composites were synthesized by template copolymerization of aniline and metanilic acid in the presence of prepared melamine triacetic acid and poly(melamine-co-citric acid) as polyacids and dopants. The properties of the poly(aniline-co-metanilic acid) composites were studied by Fourier transform infrared, X-ray diffraction, scanning electron microscope, CV, and differential scanning calorimeter analysis. The four-point probe technique was used for evaluating the electrical conductivity of the composites. The scanning electron micrographs disclosed that the products had the morphology with agglomerated distorted spherical shapes with the average size of 40–50 nm.... 

Polysaccharides (PSA) have taken specific position among biomaterials for advanced applications in medicine. Nevertheless, poor mechanical properties are known as the main drawback of PSA, which highlights the need for PSA modification. Nanocomposites PSA (NPSA) are a class of biomaterials widely used as biomedical platforms, but despite their importance and worldwide use, they have not been reviewed. Herein, we critically reviewed the application of NPSA by categorizing them into generic and advanced application realms. First, the application of NPSA as drug and gene delivery systems, along with their role in the field as an antibacterial platform and hemostasis agent is discussed. Then,... 

The effects of insulated and isothermal thin baffles on pseudosteady-state natural convection within spherical containers were studied computationally. The computations are based on an iterative, finite-volume numerical procedure using primitive dependent variables. Natural convection effect is modeled via the Boussinesq approximation. Parametric studies were performed for a Prandtl number of 0.7. For Rayleigh numbers of 104, 105, 106, and 107, baffles with three lengths positioned at five different locations were investigated (120 cases). The fluid that is heated adjacent to the sphere rises replacing the colder fluid, which sinks downward through the stratified stable thermal layer. For... 

In this study, a new type of magnetite nanocomposite with a core-shell structure was synthesized using Fe3O4 nanoparticles as a core and polyaniline (PANI) as a shell. For this propose, the surface of Fe3O4 was chemically modified with hexamethylenediisocyanate (HMDI) to improve its compatibility and interphase interaction with the polymeric matrix. Thereafter, the PANI was reacted with modified Fe3O4 to anchor them to PANI by covalent bands which acted as a shell. In the second step, the poly (maleic acid-co-acrylic acid) (P(MAc-co-AA)) as polymeric dopant for the PANI was synthesized. Finally, the PANI anchored to Fe3O4 was immersed in an aqueous solution of poly (maleic... 

In this study, a new type of magnetite nanocomposite with a core–shell structure was synthesized using Fe3O4 nanoparticles as a core and polyaniline (PANI) as a shell. For this propose, the surface of Fe3O4 was chemically modified with hexamethylenediisocyanate (HMDI) to improve its compatibility and interphase interaction with the polymeric matrix. Thereafter, the PANI was reacted with modified Fe3O4 to anchor them to PANI by covalent bands which acted as a shell. In the second step, the poly (maleic acid-co-acrylic acid) (P(MAc-co-AA)) as polymeric dopant for the PANI was synthesized. Finally, the PANI anchored to Fe3O4 was immersed in an aqueous solution of poly (maleic... 

Background and Objective: During the manufacture and storage of probiotic products, there are always possibilities that probiotics be exposed to harmful stresses such as high temperature, low pH, various osmotic pressures and high oxygen levels, which can decrease the number of living cells. Encapsulation is one of the methods used to protect living cells such as probiotic bacteria from environmental challenges. Up-to-date, various compounds with abilities to protect bacteria during freeze-drying and to increase viability during storage have been identified. In this study, alginate with calcium chloride was used to encapsulate probiotic bacteria using extrusion method. Then, effects of... 

Uncertainty of kidney exchange programs (KEP) is one of the main challenges that cause failure in most planned transplants to proceed to surgery. Unfortunately, this challenge usually decreases KEP performance in the real world. To face this challenge, we develop an efficient approach, consisting of scheduling methodology and recourse actions, to recover failing pairs and improve the number of successful transplants in KEPs. The developed policy can be implemented in two different schemes. The first scheme receives an optimal matching as an input and determines recourse actions and the sequence of disjoint cycles and chains for the given optimal matching. However, the second scheme does not... 

A supramolecular linear-dendritic copolymer consisting of a polystyrene backbone and hanging hyperbranched polyglycerols was prepared and characterized. Host-guest interactions between β-cyclodextrin incorporated in the core of polyglycerol as a host and aromatic rings of polystyrene as guests lead to the formation of a supramolecular linear-dendritic copolymer. Supramolecules formed micelles in aqueous solutions which were able to encapsulate and transfer paclitaxel with a high loading capacity  

In this paper a two level supply chain system is studied, in which the final demand is assumed to be fuzzy with triangular membership function. The inventory control policy of (r, Q) is followed for this system and unsatisfied demand is assumed to be back ordered. The objective is to minimize the total cost of the system, including ordering, holding and shortage costs. The model happens to be a nonlinear programming. Considering the complexity arising from the model, we also develop a genetic algorithm to obtain a near-optimal solution. The method is illustrated through some numerical examples  

This paper puts forward a new methodology for time-variant seismic risk analysis of transportation networks. Risk here denotes the probability of exceeding the sum of direct loss due to repair costs of bridges in the network and indirect loss due to the reduced capacity for traffic flow. The proposed methodology employs reliability methods and a host of probabilistic models for earthquake events, damage, repair cost, downtime, and travel time, while accounting for time-varying phenomena of aging and discounting. A comprehensive application on the transportation network of Isfahan, Iran, is presented that features 64 bridges subject to seismicity from seven sources. © 2018 Taylor & Francis... 

This paper puts forward a new methodology for time-variant seismic risk analysis of transportation networks. Risk here denotes the probability of exceeding the sum of direct loss due to repair costs of bridges in the network and indirect loss due to the reduced capacity for traffic flow. The proposed methodology employs reliability methods and a host of probabilistic models for earthquake events, damage, repair cost, downtime, and travel time, while accounting for time-varying phenomena of aging and discounting. A comprehensive application on the transportation network of Isfahan, Iran, is presented that features 64 bridges subject to seismicity from seven sources. © 2018, © 2018 Taylor &... 

The high prevalence of shoulder pain in using walkers in patients who have spinal cord injury (SCI). Also, the limited options available to economically measure grip forces in walkers, which drove the need to create one. This article describes a method to obtain upper-extremities’ forces and moments in a person with SCI by designing an appropriate instrumented walker. First, since the commercial multidirectional loadcells are too expensive, custom loadcells are fabricated. Ultimately, a complete gait analysis by means of VICON motion analysis and using inverse dynamic method has been held to measure upper-extremities’ efforts. The results for a person with SCI using a two-wheel walker in low... 

The high prevalence of shoulder pain in using walkers in patients who have spinal cord injury (SCI). Also, the limited options available to economically measure grip forces in walkers, which drove the need to create one. This article describes a method to obtain upper-extremities’ forces and moments in a person with SCI by designing an appropriate instrumented walker. First, since the commercial multidirectional loadcells are too expensive, custom loadcells are fabricated. Ultimately, a complete gait analysis by means of VICON motion analysis and using inverse dynamic method has been held to measure upper-extremities’ efforts. The results for a person with SCI using a two-wheel walker in low... 

Solvatochromic parameters (E T N , normalized polarity parameter; π, dipolarity/polarizability; β, hydrogen-bond acceptor basicity; α, hydrogen-bond donor acidity) have been determined for binary mixtures of propan-2-ol, propan-1-ol, ethanol, methanol and water with recently synthesized ionic liquid (IL; 2-hydroxyethylammonium formate) at 25 °C. In all solutions except aqueous solution, E T N values of the media increase abruptly with the ILs mole fraction and then increase gradually to the value of pure IL. A synergistic behavior is observed for the α parameter in all solutions. The behavior of π and β are nearly ideal for all solutions except for solutions of methanol with the IL. The...