Sharif Digital Repository

Droplet microfluidics is a platform of microfluidics in which two immiscible fluids are used to generate droplets for various biomedical applications. This platform introduces several advantages in applications such as cell lysis, cell culture, co-culture, and cell encapsulation. The most important issues regarding droplet generation devices are the fabrication complexity and maintenance of these devices. In this study, a simple and easy-to-fabricate microdroplet generator is designed and fabricated to resolve these issues. Furthermore, since this device is easy to fabricate and use, it can play a key role in the fabrication of medical devices for controlling infectious diseases in poor and... 

The present study aims to challenge the existing finite element models in terms of one of the most important practical parameters, i.e. coverage. Important models from the literature are re-simulated and their resulted treated surfaces are carefully examined. Result of this study shows that existing finite element models could not reflect the realistic coverage. A variable dimension symmetry cell is developed in order to acquire full coverage and at the same time not increasing the computational cost. This model can successfully simulate the surface nanocrystallization by severe shot peening in which the amount of coverage is much higher than conventional shot peening  

Nowadays, cervical disorders are common due to human lifestyles. Accordingly, the cage design should be optimized as an essential issue. For an optimal design, an objective function is utilized to calculate the proper geometrical parameters. Additionally, the base material of the cage plays a key role in its functionality and final cost. Novel materials are currently introduced with more compatibility with the bone in terms of mechanical and chemical properties. In this study, a cervical cage was modeled based on PEEK material with three types of tooth designs on its surface. The cervical cage is assumed to be implanted between C6 and C7 vertebrae. The geometric parameters of the cage were... 

Achieving high efficiency and throughput in droplet-based mixing over a small characteristic length, such as microfluidic channels, is one of the crucial parameters in Lab-on-a-Chip (LOC) applications. One solution to achieve efficient mixing is to use active mixers in which an external power source is utilized to mix two fluids. One of these active methods is magnetic micromixers using ferrofluid. In this technique, magnetic nanoparticles are used to make one phase responsive to magnetic force, and then by applying a magnetic field, two fluid phases, one of which is magneto-responsive, will sufficiently mix. In this study, we investigated the effect of the magnetic field’s characteristics... 

Cell lysis is an essential primary step in cell assays. In the process of cell lysis, the cell membrane is destroyed and the substances inside the cell are extracted. By utilizing a droplet-based microfluidic platform for cell lysis, the mixer unit that is required for mixing lysis reagents with the cells can be excluded, and thus, the complexity of the fabrication process is reduced. In addition, lysing the cells within the droplets will prevent the cells from exposure to the channel walls, and as a result, cleanliness of the samples and the device is maintained. In this study, cell lysis within the droplets and the parameters affecting the efficiency of this process are investigated using... 

The beneficial effects of shot peening on fatigue life of mechanical components are well known. However, there are some reports in the literature that indicate inappropriate shot peening parameters tend to reduce the fatigue life. It is therefore, the purpose of this study to find a logical quantitative justification for these observations. Using finite element method, a dynamic elasticplastic simulation of shot peening was presented. Effect of shot velocity and size on surface morphology after shot peening were examined. Fatigue crack initiation life calculation of shot peened specimens revealed that beneficial effect of shot peening significantly vanishes in the case of high velocities and... 

Separation and lysis of RBCs play an important role in diagnosis of different diseases. Although they have been partially studied in several researches, a comprehensive study on integrating both separation and lysis units on a single chip has been seen rarely in the literature. Also, the factors related to the chemical lysis process have not been investigated in detail. In this study, we introduce a novel microfluidic channel design for sequential RBC's separation and lysis. For the separation part, an active method with an electric field was applied to the cells. Besides, a novel mixer was designed for mixing the cell solution and lysis reagent. In the lysis section, we used a mathematical... 

Nerve repositioning surgery is one of the treatments chosen for the patients with edentulous posterior atrophic mandible. Like any other treatments, this therapy has its advantages and disadvantages, indications and contraindications. The most important complication of this procedure is neurosensory disturbance. This problem may occur at different stages of the treatment. One common time when nerve damage happens is when the nerve is located outside the canal and drilling and insertion of the implant are performed. Accordingly, this report describes a simple and feasible method to retract and protect nerves outside the canal during the treatment of nerve transposition. This will reduce the... 

Nerve repositioning surgery is one of the treatments chosen for the patients with edentulous posterior atrophic mandible. Like any other treatments, this therapy has its advantages and disadvantages, indications and contraindications. The most important complication of this procedure is neurosensory disturbance. This problem may occur at different stages of the treatment. One common time when nerve damage happens is when the nerve is located outside the canal and drilling and insertion of the implant are performed. Accordingly, this report describes a simple and feasible method to retract and protect nerves outside the canal during the treatment of nerve transposition. This will reduce the... 

Knowing the rate of evaporation from surface water resources such as channels and reservoirs is essential for precise management of the water balance. Few detailed evaporation studies exist for small lakes or reservoirs in arid regions of the world. In this study, monthly evaporation was determined by Bowen Ratio Energy Budget technique (BREB) for Alghadir reservoir (Saveh, Iran) from 1995-2007 and compared with class-A pan. Daily data were obtained from IMO (Iran Meteorological Organization) weather station, located near the reservoir, for all of these years. Some variations have been observed on the estimated evaporation of the energy budget at different years, ranging from 151 cm for 1997... 

Coverage is one of the most important parameters which is always used in practice to characterize a shot peening process. At the same time however, it is the most missing parameter in the finite element simulations of this process. This study aims to relate shot peening simulation to the actual coverage that is developed during the process. Accordingly, two important models from literature are re-simulated and their capability to predict an actual coverage is assessed. Results of this study illustrate that full coverage situation is not captured by these models. Thereafter, a random finite element simulation along with a step by step examination of the treated surface is adopted in order to... 

Grinding is widely used for manufacturing of components that require fine surface finish and good dimensional accuracy. In this study a thermo-mechanical finite element analysis is conducted to find out how grinding parameters can affect temperature and residual stress distribution in the workpiece. Results of parametric study presented in this work indicate, by carefully selecting the grinding parameters, minimum thermal and mechanical damage can be achieved. Higher workpiece velocities produce higher surface residual stress. By increasing depths of cut, depth of tensile residual stresses increases. Convection heat coefficient does not have any considerable effect on surface residual stress... 

Cancer diagnosis has recently been at the forefront of recent medical research, with ongoing efforts to develop devices and technologies for detecting cancer in patients. One promising approach for cancer diagnosis is the detection of Circulating Tumor Cells (CTCs) in blood samples. Separating these rare cells from the diverse background of blood cells and analyzing them can provide valuable insights into the disease's stage and lethality. Here we present the design and fabrication of a centrifugal microfluidic platform on a polymeric disk that utilizes centrifugal forces for cell isolation. The separation units exploit both active and passive methods. In other words, in addition to... 

Motorcycles are the third most common means of transportation in the megacity of Tehran. Hence, measurements of emission factors are essential for Tehran motorcycle fleets. In this study, 60 carburetor motorcycles of various mileages and engine displacement volumes were tested in a chassis dynamometer laboratory according to cold start Euro-3 emissions certification test procedures. For almost all of the tested samples, the average carbon monoxide (CO) emission factors were about seven times higher than the limits for Euro-3 certification. No motorcycle fell within the Euro-3 certification limit on CO emissions. 125 cc engine displacement volume motorcycles, which are dominant in Tehran,... 

Passenger cars (PCs) not only are a major contributor to greenhouse gas (GHG) emissions in Iran but also pose severe energy security challenges due to their dependence on gasoline. This study aimed to understand the future trends of the gasoline demand and GHG emissions from PCs in Iran and assess the effectiveness of mitigation policies. The data were collected from multiple sources and used to develop the survival rate function of PCs. The study used back-calculation to compensate for the short period of stock data availability. The use intensity of PCs was estimated based on the gasoline consumption statistics. Econometric models were developed to project the future PC stock and use... 

Passenger cars (PCs) are a major contributor to urban air pollution, greenhouse gas emissions, and energy security challenges in megacities in developing countries because of their high growth potential. Since the PC fleet changes through time, the projection of air pollutant emissions from PCs is essential for effective emission reduction policymaking. However, the extensive amount of data and proper models are required for this purpose that are not available in many developing countries. Hence, this study develops multiple econometric and emission models and integrate them into a framework to simulate the future stock and activity of PCs and projects PCs’ air pollutants and CO2 emissions... 

As an essential step of product design, tolerance design plays a critical role in reducing manufacturing costs while ensuring mechanical assemblies’ quality and reliability. However, existing tolerance allocation approaches only are concentrated on design specification constraints during the design stage, although component degradation caused by environmental and operating conditions increases the probability of product failure during the service life. To deal with the degradation effect arising over the service life of mechanical assemblies, this paper proposes a reliability-based tolerance design approach to allocate optimal, reliable tolerances to mechanical systems. The proposed approach...