Sharif Digital Repository

In this study, a machine learning approach was applied to evaluate the impact of operating and design variables on dry powder inhalation efficiency. Emitted dose and fine particle fraction data were extracted from the literature for a variety of drug and carrier combinations. Carrier surface properties are obtained by image analysis of SEM images reported. Models combining artificial neural network and genetic algorithm were developed to determine the emitted dose and fine particle fraction. Design strategies for the carrier surface were also proposed to enhance the fine particle fractions. © 2021 Elsevier Ltd  

Nanowire arrays of copper oxide were first grown vertically using simple and cost effective thermal oxidation method on a copper foil. Subsequently, in order to deposit and grow PbS nanocyrstalline thin films on CuO NWs by utilizing the chemical bath deposition technique, these arrays were immersed as the substrate in the reaction solution consisting of Pb(NO3)2, (NH2)2CS and NaOH. The final products were characterized in detail by which the formation of uniform, unique arrays of CuO@PbS core–shell NWs was confirmed. Due to the nature of methods employed in synthesis of this hetero structure, the tuning of core and shell size and consequently properties of the novel structure is easily... 

Abstract: We propose a novel method for producing unequal sized droplets through breakup of droplets. This method does not have the disadvantages of the available methods and also reduces the dependence of the droplets volume ratio on the inlet velocity of the system by up to 26 percent. The employed method for investigating the proposed system relies on 3D numerical simulation using the VOF algorithm and the results have been obtained with various valve ratios for both the micro- and nanoscale. The results indicate that the droplet length during the breakup process increases linearly with time. The droplet length at the nanoscale is smaller than that at the micro scale. It has been shown... 

Parabolic trough solar collector (PTC) is one of the most mature and widely used type of solar energy harnessing devices. Therefore, investigation of the effect of various operational conditions on the overall efficiency of these devices has been topic of substantial interest in the recent decade. Moreover, utilization of nanoparticles as a useful additive to the working fluid should be examined thoroughly to optimize the collector's outputs. To do so, in the present study, energy and exergy efficiencies of a typical PTC as a function of several involving parameters are numerically calculated. These parameters are nanoparticle volume fraction (from 0 to 5 percent), environment wind speed... 

The use of superhydrophobic surfaces is one the most promising methods for reducing the friction and increasing the flow rate in fluid transfer systems. Because in such systems the surface structure plays a key role, in this study, we explore the performance of the hierarchical nanostructures. These nanostructures are inspired by the superhydrophobic surface of the lotus leaf. We consider a flow between two walls with hierarchical nanostructures and simulate the system via the molecular dynamics method. The size of the nanostructures and the distance between them have been studied to find whether a design with a maximum flow rate exists. The nanostructures have two parts, a bigger part on... 

Access to clean water is one of the challenges of the 21st century. Thus water purification is inevitable. One method of water treatment is purification by magnetic particles in the presence of magnetic field. The contaminants are attached to the magnetic particles and then by applying a magnetic field, magnetic particles and, thus, the pollutants can be collected. For the optimal design of a water treatment system, the effect of important parameters in the design, such as magnetic fields, particle size, and Reynolds number are determined numerically by modeling and simulating the water treatment process. Two methods are used to create the magnetic field: permanent magnet and coils. It is... 

Nanofluids are widely used as the continuous phase during droplet formation in microsystems due to their impressive features such as excellent thermal, magnetic, and interfacial properties. Although it is well-known that nanofluids are susceptible to exhibit non-Newtonian behavior even at a low concentration of nanoparticles, effects of non-Newtonian behavior of nanofluids have not been studied on droplet formation thus far. In this study, oil-in-water droplet formation with a relatively high viscosity ratio of the immiscible phases was studied numerically in a T-junction microchannel. To inspect the non-Newtonian effects of aqueous nanofluids on droplet formation, empirical data on the... 

Droplet-based microfluidics technologies hold great attention in a wide range of applications, including chemical analysis, drug screening, and food industries. This work aimed to describe the effects of different physical properties of the two immiscible phases on droplet formation in a flow-focusing microfluidic device and determining proper flow rates to form a droplet within the desired size range. A numerical model was developed to solve the governing equations of two-phase flow and the results were validated with previous experimental results. The results demonstrate different types of droplet formation regimes from dripping to jetting and different production rates of droplets as a... 

The humidification-dehumidification (HDH) desalination system with a Horizontal Solar Film Evaporator (HSFE) is a sustainable and economical approach to providing freshwater in remote areas where conventional energy is limited or condensation irrigation in off-grid greenhouses. The present study investigates the baffle turbulators on heat and mass transfer of the HSFE of the HDH desalination system. To this aim, a comprehensive three-dimensional transient computational fluid dynamics model of the HSFE has been developed. The model is then used to evaluate the effect of various design parameters on the performance of the HSFE. The Design of Experiments methodology is adopted to determine... 

Three-dimensional cell culture and the forming multicellular aggregates are superior over traditional monolayer approaches due to better mimicking of in vivo conditions and hence functions of a tissue. A considerable amount of attention has been devoted to devising efficient methods for the rapid formation of uniform-sized multicellular aggregates. Microfluidic technology describes a platform of techniques comprising microchannels to manipulate the small number of reagents with unique properties and capabilities suitable for biological studies. The focus of this review is to highlight recent studies of using microfluidics, especially droplet-based types for the formation, culture, and... 

This research demonstrates pulsed electrohydrodynamic drop-on-demand (DoD) printing as a novel technique for synthesizing core-shell microparticles in a controlled manner. In this regard, a multiphase and multiphysics model is presented for coaxial electrohydrodynamic printing. The governing partial differential equations of the model are discretized using the finite element method, and a suitable numerical scheme is adopted to solve the system of discretized equations. The experimental results in the literature are used to validate the numerical model. Utilizing the validated model, the effects of continuous-direct current (DC) voltage and pulsed-DC voltage are examined on the behavior of a... 

The solar humidification-dehumidification desalination system with a subsurface condenser is a promising renewable energy-based desalination system. This desalination system is particularly suitable for condensation irrigation in greenhouses, especially where conventional energy sources are limited. A computational model of the system comprising a horizontal solar film evaporator and a subsurface condenser is developed. A previously proposed hybrid analytical–numerical model for horizontal ground heat exchangers is modified for the subsurface condenser. An experimental setup of the subsurface condenser is also built and used to verify the developed model of the subsurface condenser. The... 

The 3D simulation of the hydrodynamic behavior of a rotating disc contactor (RDC) by means of computational fluid dynamics (CFD) was investigated for the n-butanol-succinic acid-water (BSW) system. For the two-phase liquid-liquid flow, the velocity distribution of the continuous phase and drop size distributions were determined using the k-ω turbulence model in conjunction with the Eulerian-Eulerian approach and MUSIG model. In this system in which the holdup of the dispersed phase is low, the continuous phase velocity was computed by simultaneously solving the Navier-Stokes equations beside the different models of turbulence. The motions of the dispersed phase was calculated while... 

The studies surrounding the concept of microdroplets have seen a dramatic increase in recent years. Microdroplets have applications in different fields such as chemical synthesis, biology, separation processes and micro-pumps. This study numerically investigates the effect of different parameters such as Capillary number, Length of droplets, and Magnetic Bond number on the splitting process of ferrofluid microdroplets in symmetric T-junctions using an asymmetric magnetic field. The use of said field that is applied asymmetrically to the T-junction center helps us control the splitting of ferrofluid microdroplets. During the process of numerical simulation, a magnetic field with various... 

Researchers usually simplify their simulations by considering the Newtonian fluid assumption in microfluidic devices. However, it is essential to study the behavior of real non-Newtonian fluids in such systems. Moreover, using the external electric or magnetic fields in these systems can be very beneficial for manipulating the droplet size. This study considers the simulation of the process of non-Newtonian droplets’ formation under the influence of an external electric field. The novelty of this study is the use of a shear-thinning fluid as the droplet phase in this process, which has been less studied despite its numerous applications. The effects of an external electric field on this... 

Droplet-based microfluidics is an attractive approach for producing microgels due to its high potential to control the size and shape of the particles and precisely entrap the substances within the hydrogel matrix. However, the microfluidic generation of monodisperse microgels with desired structures is still challenging. Indeed, the rheological and interfacial properties of the immiscible fluids, as well as the adopted gelling strategy, play important roles in microfluidic methods. Herein, sodium alginate droplets with different concentrations are generated via a microfluidic device with a flow-focusing unit. Besides, a combined in situ and ex situ strategy is optimized to crosslink sodium... 

High capacity pulse tube refrigerator (HCPTR) is a new generation of cryocoolers tailored to provide more than 250 W of cooling power at cryogenic temperatures. The most important characteristics of HCPTR when compared with other types of pulse tube refrigerators are a powerful pressure wave generator, and an accurate design. In this paper the influence of geometrical and operating parameters on the performance of a double inlet pulse tube refrigerator (DIPTR) is studied. The DIPTR is modeled applying the nodal analysis technique, using mass, momentum and energy conservation equations. The model is able to compute instantaneous flow field throughout the system and calculate cooling capacity... 

In planar perovskite solar cells (PSCs), engineering the extraction and recombination of electron–hole pairs by modification of the electron transport layer (ETL)/perovskite interface is very vital for obtaining high performance. The main idea here is to improve properties of the TiO2/perovskite interface by inserting an ultra-thin layer (UTL) of WO3 or SnO2 with the thickness of less than 10 nm by RF magnetron sputtering method. The structural and electrical characteristics of the samples were tested by XRD, AFM, FE-SEM, Mott-Schottky analysis, UV–Vis spectroscopy, J-V characterization and electrochemical impedance spectroscopy (EIS). It was found that the bilayer structured ETLs exhibit... 

In this paper, a finite point method is employed to solve the incompressible laminar Stokes flow. A moving least-squares approximation, using linear and quadratic basis functions, in conjunction with a point collocation method, has been utilized to discretize the governing equations. Two examples, including the driven cavity and the fully developed channel flow, are solved showing the accuracy and applicability of the method. In summary, the solutions for the linear basis case exhibit a large sensitivity to the size of the domain of influence of the weighting function, in contrast to the quadratic basis case