Sharif Digital Repository

Conducting polymer-based devices and scaffolds has become remarkably popular due to their properties such as conductivity, tunable electrochemical properties, and straightforward fabrication procedures. Hence, they have versatile applications and can be used as implants, biosensors, cell capture/release devices, and regenerative medicine scaffolds. This review addresses the effect of conductive polymers on cell behavior since their conductive features can be applied to simulate a cellular response. Moreover, the impact of polymer chemical and physical properties on cellular response has been discussed. Recent biomedical engineering approaches used for cell capture and release were reviewed... 

Stem cell therapy has been introduced as an emerging approach for injured tissue regeneration. This chapter addresses developing regenerative medicine techniques for controlling stem cell behavior. Recent studies have been reviewed and novel approaches have been divided into four main categories: 3D bioprinting, lithography, microfluidics, and electrospinning. Moreover, the impact of applied biophysical and/or biochemical cues to the designed scaffold on controlling stem cell activity has been discussed. The potential of using stem cells for various soft and hard tissue regenerations has been explored in different bioengineered scaffolds and the applied techniques for controlling stem cell... 

One of the most arduous challenges in tissue engineering is neovascularization, without which there is a lack of nutrients delivered to a target tissue. Angiogenesis should be completed at an optimal density and within an appropriate period of time to prevent cell necrosis. Failure to meet this challenge brings about poor functionality for the tissue in comparison with the native tissue, extensively reducing cell viability. Prior studies devoted to angiogenesis have provided researchers with some biomaterial scaffolds and cell choices for angiogenesis. For example, while most current angiogenesis approaches require a variety of stimulatory factors ranging from biomechanical to biomolecular... 

For a low-permeability carbonate formation, the acid fracture process is simulated through coupling a commercial acid fracture simulator (GOHFER) to a finite volume reservoir simulator (IMEX). Unlike LGR (Local grid refinement) approach that suffers from severe convergence problems, a dynamic up-scaling procedure is employed to convert the discrete fracture network (DFN) model into a dual continuum model for our simulation. In this paper, multiple simulations are used to optimize the acid fracture schedule parameters, such as fluid volume, flow rate, perforation location, number of injection steps, and acid type, in order to maximize the effective fracture length. For four points perforation... 

Perovskite solar cells fabrication process need inert or low humidity atmospheres. While highly efficient perovskite solar cells to overcome the photovoltaic marketing should be achieved stability at any environmental conditions. At high humidity, water molecules react with the perovskite layer and increase the degradation rate, leading to a drastic decrease in device performance and perovskite crystallinity. In this work, the effect of environmental humidity on photophysical parameters of wide bandgap, (WBG) perovskite layer and solar cells stability is systematically investigated and tBP is proposed as an additive in perovskite precursor to increase the moisture resistance and improve the... 

One way of improving the performance of diesel engines is to produce modifications in the fuel supply systems. In this article, the effects of creating rotationary flow inside the nozzle and changing fuel injection angle on the performance and emission of caterpillar diesel engine have been examined in two separate stages using AVL FIRE software. First, the injector and its spray have been simulated with various geometries. The numerical results of this step indicate that creating rotationary flow inside the nozzle decreases the penetration length, while increases fuel spray cone angle and improves atomization quality. In the subsequent step, the diesel engine has been simulated with its... 

One of the possible fluid-fluid interactions during water-flooding in oil reservoirs, that is still debated, is the effect of injected brine salinity on asphaltene destabilization. If asphaltene precipitation is induced by salinity changes in the oil reservoirs and surface facilities, this could have a massive impact on the economy of a low salinity water-flooding project. Therefore, this study aims to investigate the effect of brine salinity on the amount of asphaltene precipitation and the governing destabilization mechanisms. Direct asphaltene precipitation measurements, along with the analyses of optical microscopy images and ion chromatography (IC), indicate that the asphaltene... 

The performance of several regression methods is investigated to estimate the distribution of engineering demand parameters conditioned on intensity measures (EDP|IM) for small record sets. In particular, the performance of the multivariate ordinary least squares (OLS), a simultaneous mean-variance regression (MVR) done by a penalized weighted least-square loss function, and a mean-covariance/variance regression based on expectation maximization method (EM) are assessed. The efficiency of the introduced methods is compared with FEMA-P58 methodology. Performance assessment of EM and MVR methods shows that the overall increase in efficiency is about 25–45% for maximum inter-story drift ratios,... 

The diseases and disorders of the cornea may lead to blindness, and cornea transplantation has been an effective treatment in this regard. However, lack of cornea throughout the world makes this treatment difficult. Therefore, the first goal of the present study is to make a chitosan/gelatin hyaline film with NHS and EDC crosslinkers for transplanting the epithelial cells of the cornea. Two solutions of gelatin and chitosan were mixed homogeneously before crosslinking in ratios of 20/80, 30/70, 40/60, and 50/50 (Gel/Chi). After 24 hours, they were put in an oven to dry, then EDC and NHS were added to the mixture as crosslinker. Corneal epithelial cell morphology was assessed qualitatively... 

A huge amount of energy consumption, the cost of this usage and environmental effects have become serious issues for commercial cloud providers. Solar energy is a promising clean energy source, to provide some portion of the Internet data center's (IDC's) energy usage which can reduce environmental effects and total energy costs. Moreover, due to the high energy consumption of the cooling system, considering cooling power in job scheduling can provide efficient solutions to reduce total energy consumption. In this article, we investigate the problem of minimizing the energy cost of an IDC and propose an algorithm which schedules heterogeneous IDC workloads, by considering available renewable... 

Magnetic field effects are encountered in many engineering applications which include but are not limited to metal casting, nuclear reactor coolers, and geothermal energy extraction. On the other hand, due to their outstanding thermal performance, nanofluids have been successful in obtaining acceptability as per the new generation of heat transfer fluids in automotive cooling devices, in heat exchangers, and building heating. Therefore, this research is carried out to understand how the nanofluid flow in a cavity is affected by a magnetic field (due to a dipole placed nearby). The single-phase model is employed for modeling the nanofluid, whereas the governing partial differential equations... 

Seismic performance of postmainshock buildings considering seismic mainshock-aftershock sequences are studied. The case studies correspond to three SAC steel MRF buildings of three, nine and twenty stories. The 2-D models are able to capture important properties of deterioration of strength and stiffness. Endurance time method is used to predict the response of structures in different hazard levels. Results are compared with those from of nonlinear incremental dynamic analysis. Maximum dynamic seismic responses of structures are captured during synthetic mainshock-aftershock seismic sequences which are produced by endurance time method. Interactional-conceptual curves for different seismic... 

Due to the remarkable progress in the field of the manufacturing process, smart composites have become the desired target for high-tech engineering applications. Accordingly, for the first time, thermal buckling, critical voltage and vibration response of a thermally affected graphene nanoplatelet reinforced composite (GPLRC) microdisk in the thermal environment are explored with the aid of generalized differential quadrature method (GDQM). Also, the current microstructure is coupled with a piezoelectric actuator (PIAC). The extended form of Halpin-Tsai micromechanics is used to acquire the elasticity of the structure, whereas, the variation of thermal expansion, Poisson’s ratio, and density... 

One problem that has always been a challenge for geotechnical engineers is construction on problematic and soft soils. Traditional methods of lime and cement stabilisation can be used to treat soils with these properties. The main drawback of lime addition to the clayey soils is a significant loss in ductility of lime-treated soils. Using ductile materials such as geogrids in lime-treated soils is one of the most effective ways to increase the soil ductility. Therefore, the effect of geogrids and lime on unconfined compressive strength (UCS), failure strain (ɛf), secant modulus (Es), deformability indexes (ID), resilient modulus (Mr), bulk modulus (K), and shear modulus (G) of the treated... 

After an earthquake, the residual stiffness and strength of structural elements are typically estimated based on a qualitative visual inspection of cracks that is prone to error. In this paper a new approach is proposed to automatically estimate the updated stiffness and strength of damaged unreinforced masonry walls by characterization of crack patterns by a mathematical index. It is shown that structural and textural fractal dimensions of a crack pattern reflect the extent of cracking and the type of cracking or crushing, i.e., whether the cracks pass through joints or whether bricks have been damaged and crushed. Using results of six quasi-static cyclic tests on unreinforced brick masonry... 

The optimum design of reinforced concrete cantilever retaining walls subjected to seismic loads is an extremely important challenge in structural and geotechnical engineering, especially in seismic zones. This study proposes an adaptive sperm swarm optimization algorithm (ASSO) for economic design of retaining structure under static and seismic loading. The proposed ASSO algorithm utilizes a time-varying velocity damping factor to provide a fine balance between the explorative and exploitative behavior of the original method. In addition, the new method considers a reasonable velocity limitation to avoid the divergence of the sperm movement. The proposed algorithm is benchmarked with a set... 

Viral diseases have long been among the biggest challenges for healthcare systems around the world. The recent Coronavirus Disease 2019 (COVID-19) pandemic is an example of how complicated the situation can get if we are not prepared to combat a viral outbreak in time, which brings up the need for quick and affordable biosensing platforms and vast knowledge of potential antiviral effects and drug/gene delivery opportunities. The same challenges have also existed for nonviral immunogenic disorders. Nanomedicine is considered a novel candidate for effectively overcoming these worldwide challenges. Among the versatile nanomaterials commonly used in biomedical applications, graphene has recently... 

Fabrication of scaffolds with enhanced mechanical properties and desirable cellular compatibility is critical for numerous tissue engineering applications. This study was aimed at fabrication and characterization of a nanofiber skin substitute composed of collagen (Col)/sodium alginate (SA)/ polyethylene oxide (PEO)/Rhodotorula mucilaginosa sp. GUMS16 produced exopolysaccharides (EPS) were prepared using the biaxial electrospinning technique. This study used collagen extracted from the bovine tendon as a natural scaffold, sodium alginate as an absorber of excess wound fluids, and GUMS16 produced exopolysaccharides as an antioxidant. Collagen was characterized using FTIR and EDS analyses. The... 

Most of the vehicle pollutants during emission tests are raised from catalyst inefficiency during cold start. Catalysts usually convert harmful emissions only when their temperature reaches around 250 °C to 350 °C. In this research, the vortex tube is implemented to recover the waste heat energy of exhaust gas during the cold start to improve catalyst heating. The experiments are conducted on the turbocharged direct-injection gasoline engine to extract the boundary conditions of numerical simulations. Numerical simulations are performed to evaluate the effects of different hot exhaust mass fractions on the flow regime and waste heat recovery. The results reveal that the level of turbulence... 

A single‐cylinder marine diesel engine was modified to be operated in reactivity controlled compression ignition (RCCI) combustion mode. The engine fueling system was upgraded to a common rail fuel injection system. Natural gas (NG) was used as port fuel injection, and a die-sel/sunflower methyl ester biodiesel mixture was used for direct fuel injection. The fraction of bio-diesel in the direct fuel injection was changed from 0% (B0; 0% biodiesel and 100% diesel) to 5% (B5) and 20% (B20) while keeping the total energy input into the engine constant. The objective was to understand the impacts of the increased biodiesel fraction on the combustion characteristics and stability, emissions, and...