Sharif Digital Repository

In this study, the properties of poly (vinyl alcohol)(PVA) films incorporated with Zataria multiflora essential oil (ZMO) as a potential antioxidant/antibacterial material was investigated. PVA films were prepared from PVA solutions (2% w/v) containing different concentrations of ZMO. Water solubility, moisture absorption, water swelling, and water vapor permeability for pure PVA films were 57 ± 1.1, 99 ± 3.2%, 337 ± 8%, and 0.453 ± 0.015 g mm/m2 h, respectively. Incorporation of ZMO into PVA films caused a significant decrease in water swelling and moisture absorption and increase in solubility and water vapor permeability. Tensile strength, elastic modulus, and elongation at break for pure... 

Respiratory drug delivery has been under the research spotlight for the past few decades, mainly due to the high incidence of pulmonary diseases and the fact that this type of delivery offers the highest efficiency for treatment. Despite its invaluable benefits, there are some major drawbacks to respiratory drug delivery, the most important of which being poor delivery efficiency and relatively high drug deposition in undesirable regions, such as the mouth cavity. One way to improve the efficiency of respiratory drug delivery with metered-dose inhalers is placing a respiratory spacer between the inhaler exit and the mouth. It is argued that high drug deposition in the immediate airways of... 

Using 3-D scanned data to analyze and extract pore network plays a vital role in investigation of porous media's characteristics. In this paper, a new simple method is developed to detect pores and throats for analyzing the connectivity and permeability of the network. This automated method utilizes some of the common and well-known image processing functions which are widely accessible by researchers and this has led to an easy algorithm implementation. In this method, after polishing and quality control of images, using city-block distance function and watershed segmentation algorithm, pores and throats are detected and 3-D network is produced. This method can also be applied on 2-D images... 

The effect of complexity level of a lumped kinetic model for heavy residue hydroconversion on estimated values of kinetic parameters was investigated in this work by imposing constraints for the parameter estimation algorithm of a complex six-lump kinetic model and deriving a simpler modified model from the complex model. Kinetic analysis was performed using available experimental data reported in the literature from a study on hydrocracking of Chinese Gudao vacuum residue in a bench-scale reactor using ammonium phosphomolybdate (APM) as a dispersed catalyst. The kinetic models also included coke formation reactions that had previously been ignored by most investigators due to the rather... 

Three new Cu(I) complexes containing bidentate N^N donor ligands with the general formula [Cu(N^N)2][PF6] (N^N = 2,3-diphenyl-6,7-di-p-tolyl-1,4,5,8-tetraazaphenanthrene (L1), 2,3-diphenyl-6,7-di(2-thienyl)-1,4,5,8-tetraazaphenanthrene (L2), and 2,3-diphenyl-6,7-di-p-fluorophenyl-1,4,5,8-tetraazaphenanthrene (L3), were prepared by the reaction of [Cu(CH3CN)4][PF6] with two equivalents of the N^N ligand. Single-crystal X-ray diffraction analysis confirmed that in each complex the metal displays a distorted tetrahedral geometry surrounded by the four N atoms of the two sterically hindered substituted tetraazaphenanthrene (TAP) ligands. Density functional theory (DFT) and time-dependent density... 

A class of networks are those with both positive and negative links. In this manuscript, we studied the interplay between positive and negative ties on mesoscopic level of these networks, i.e., their community structure. A community is considered as a tightly interconnected group of actors; therefore, it does not borrow any assumption from balance theory and merely uses the well-known assumption in the community detection literature. We found that if one detects the communities based on only positive relations (by ignoring the negative ones), the majority of negative relations are already placed between the communities. In other words, negative ties do not have a major role in community... 

For a given quantum field theory, provided the area of the entangling surface is fixed, what surface maximizes entanglement entropy? We analyze the answer to this question in four and higher dimensions. Surprisingly, in four dimensions the answer is related to a mathematical problem of finding surfaces that minimize the Willmore (bending) energy and eventually to the Willmore conjecture. We propose a generalization of the Willmore energy in higher dimensions and analyze its minimizers in a general class of topologies Sm×Sn and make certain observations and conjectures that may have some mathematical significance  

In this paper, first we present a new explanation for the relationship between logical circuits and artificial neural networks, logical circuits and fuzzy logic, and artificial neural networks and fuzzy inference systems. This shows us that neural networks are working in the same way as logical circuits when the connection between them is through the fuzzy logic. However, themain difference between them is that logical circuits can be constructed without using any kind of optimization-based learning methods. Based on these results, we propose a new neuro-fuzzy computing system. As verified by simulation results, it can effectively be implemented on the memristor crossbar structure and... 

We present fabrication, characterization, and experimental results describing electrical actuation and readout of the mechanical vibratory response of electrospun ZnO nanofibers. For a fiber with an approximate radius of 200 nm and a length of 70 ìm, a resonance frequency around 3.62 MHz with a quality factor (Q) of about 235 in air at ambient conditions is observed. It is shown that the measured frequency of the resonance is consistent with results from finite element simulations. Also, the measurements were performed in an enclosed chamber with controlled levels of ethanol vapor. The adsorption of ethanol causes a shift in the resonance frequency of the fibers, which can be related to the... 

Considerable portion of energy losses in a vehicle traced to tire. Energy losses in a tire are due to tire longitudinal slip as well as rolling resistance. Hence, both of aforementioned factors must take into the consideration to study the tire energy loss. Present paper aims to investigate the power losses in tires and to examine influence of road conditions and tire inflation pressure on them. To cover the real-world conditions, experiments were done on a gasoline-fueled passenger vehicle on an urban highway along two routes with same length and opposite gradients to comprise the change of road conditions. Then, by use of engine performance model which is prepared in dynamometer... 

An architectural modification method was utilized to improve fracture toughness of discontinuously reinforced aluminum (DRA) composites. Al-DRA composites having a structure similar to that of reinforced concrete were fabricated. The number of reinforcing DRA rods within Al matrix and volume fraction of SiC particles in DRA were altered to evaluate their effect on fracture behavior of these materials. It was found that architectural modification does not have any destructive influence on elastic modulus and yield strength of the composite. Moreover, the success of this method on toughness improvement strongly depends on the occurrence of debonding between Al and DRA regions upon loading  

Gold nanotubes/nanowires (GNT/NW) were synthesized by using the template-assisted electrodeposition technique and mixed with castor oil-polyethylene glycol based polyurethane (PU) to fabricate porous composite scaffolds for biomedical application. 100 and 50 ppm of GNT/NW were used to synthesize composites. The composite scaffolds were characterized by Fourier transform infrared spectroscopy, dynamic mechanical thermal analysis, differential scanning calorimetry, and scanning electron microscopy. Cell attachment on polyurethane-GNT/NW composites was investigated using fat-derived mesenchymal stem cells. Addition of 50 or 100 ppm GNT/NW had significant effects on thermal, mechanical, and cell... 

Gas injection is the second largest enhanced oil recovery process being applied in many reservoirs around the world. Simulation of these processes is necessary for implementation, management, and decision making. Relative permeability is one of the most important factors in numerical reservoir simulation. In this study, several core flood experiments are done and the relative permeability in carbon dioxide (CO2) injection is compared with nitrogen (N2) injection. Oil relative permeability in CO 2 injection is found to be higher than in N2 injection, but gas relative permeability in CO2 injection is found to be lower than in N2 injection. Higher oil relative permeability in CO 2 injection... 

Bioinspired materials can mimic the stem cell environment and modulate stem cell differentiation and proliferation. In this study, biomimetic micro/nanoenvironments were fabricated by cell-imprinted substrates based on mature human keratinocyte morphological templates. The data obtained from atomic force microscopy and field emission scanning electron microscopy revealed that the keratinocyte-cell-imprinted poly(dimethylsiloxane) casting procedure could imitate the surface morphology of the plasma membrane, ranging from the nanoscale to the macroscale, which may provide the required topographical cell fingerprints to induce differentiation. Gene expression levels of the genes analyzed... 

Injecting low salinity brines is regarded as an enhanced oil recovery (EOR) process through IFT reduction. However, the exact mechanism behind this process is an unsettled and complex issue that has not been well understood yet, especially for heavy crude oil system. Besides, limited information is available regarding the key heavy oil/brine interfacial tension (IFT). The present study aims to investigate the sensitivity of dead heavy crude oil/brine IFT to a wide range of properties/conditions and to reveal the underlying physicochemical mechanisms involved in enhanced oil recovery and IFT reduction by low salinity water injection into heavy oil reservoir. IFT was measured as a function of... 

The interfacial tension (IFT) of a crude oil/CO2 system is recognized as the main property affecting the efficiency of CO2 flooding during an enhanced oil recovery (EOR) process. The addition of a paraffin group hydrocarbon to asphaltenic crude oils as an asphaltene precipitant component is aimed to mimic the asphaltene precipitation process during crude oil production and transportation. Asphaltene precipitation would critically affect the interfacial behavior of crude oil/CO2 systems. In the first part of this study, the equilibrium densities of oil samples which contain n-heptane at different ratios were measured over varying pressures at 323 K. Then, the equilibrium IFT between CO2 and... 

A two dimensional rectangular microchannel with circular micropillars was modeled in the presence of an electric field. Continuity and Navier-Stokes equations were solved along with convection-diffusion equation using finite element method. Reaction phenomenon was applied via a partial differential equation on the reaction surfaces and electric force was added as a source term to the transport equations. Velocity, concentration and electric potential distributions were obtained, with the aid of which, capture efficiency and average surface concentration of reaction surfaces were calculated. To ameliorate the reaction rate, different designs of reaction surfaces were investigated; the designs... 

We outline a comprehensive numerical procedure for modeling of species transport and surface reaction kinetics in electrokinetically actuated microfluidic devices of rectangular cross section. Our results confirm the findings of previous simplified approaches that a concentration wave is created for sufficiently long microreactors. An analytical solution, developed for the wave propagation speed, shows that, when normalizing with the fluid mean velocity, it becomes a function of three parameters comprising the channel aspect ratio, the relative adsorption capacity, and the kinetic equilibrium constant. Our studies also reveal that the reactor geometry idealized as a slit, instead of a...