Sharif Digital Repository

Multiphase flows appear in many scientific and engineering applications. On the other hand, there has been a tremendous experimental and numerical investigation trying to understand complex fluid-fluid interfaces better. However, conventional CFD have certain limitations in complicated situations. Fortunately in the past two decades, new approaches, namely SPH and LBM (sometimes called meshless methods) have been developed. Since they are mesoscopic, they have been able to perform much better than conventional CFD. Especially, LBM is becoming more and more popular and has already been divided to many branches  

Among the various approaches, ZnS treatment is the most convenient method for reducing the charge recombination in quantum dot-sensitized solar cells (QDSSCs). Here an improved method of ZnS treatment is explained for efficiency enhancement in QDSSCs. To get to the goal of device performance improvement, it is essential to have a uniform deposited layer. We utilized Triton X-100 (TX-100) as a surfactant to the convenient aqueous precursors during ZnS deposition by successive ionic layer adsorption and reaction method. It helps to decrease in contact angle and increase in wettability of the aqueous precursor and results in a more uniform deposited layer. The effect of modified ZnS treatment... 

This paper addresses a real-world problem faced by the public healthcare sector. The problem consists of both the patients’ and service provider's requirements (i.e., accessibility vs. costs) for locating healthcare facilities, allocating service units to those facilities, and determining the facilities’ capacities. The main contribution of this study is capturing both short-term and long-term uncertainties at the modelling stage. The queuing theory is incorporated to consider stochastic demand and service time as a short-term uncertainty, as well as a service level measurement. The developed nonlinear model is then converted into a linear model after introducing a new set of decision... 

The high demand for radiotherapy services, combined with the limited capacity of available resources, patient unpunctuality, and series of appointments, makes Patient Appointment Scheduling (PAS) in radiotherapy centers very challenging. Although most centers use a First-Come-First-Serve (FCFS) policy for appointment scheduling, this approach does not consider patients’ behaviors, and consequently, it performs poorly. This type of inappropriate scheduling usually leads to inefficiency at the center and/or patient dissatisfaction. This study provides a data-driven approach to patient appointment scheduling to deal with the challenges mentioned above, and it considers patients’ histories of... 

In this research heating, cooling and electrical demands of a residential tower are evaluated for Iran various weather conditions. For this purpose, several cities are selected as the representative of the specific weather conditions. To meet the cooling demand, desiccant cooling system plus alternative systems are applied. To analyze desiccant wheel, outlet humidity and temperature have been modeled. Also, the effect of rotational speed and regeneration temperature on entropy generation of the desiccant wheel has been studied based on the obtained results. It is deduced that the entropy generation may be increased by increasing the regeneration temperature and the rotational speed. To... 

In this study the first and the second laws of thermodynamics are evaluated for a single effect absorption chiller. Entropy generation and COP are selected as the objective functions and their variations are studied by varying the generator temperature for various condensing temperatures. For this purpose, the enthalpy and the entropy data of the super-heated steam, saturated steam and the saturated water are formulated in the mathematical equations. Also to provide the required steam of generator, prime mover in the form of internal combustion engine is applied and its partial load conditions are analyzed. A residential tower is considered as the case study for selecting the proper prime... 

In this paper, the advantages of numerical simulation to improve the process of copper electroforming are demonstrated. In this regard, the finite element model of copper electroforming for a rotating cone electrode was first prepared and then, the effect of the key parameters, such as applied current density, solution conductivity, electrode spacing, and anode height, on the uniformity of the thickness was investigated. The model combines tertiary current distribution with Bulter–Volmer electrode kinetics and computational fluid dynamics at the turbulent condition. In order to validate the model, a cone-shaped shell was produced by electroforming method in the laboratory. The obtained... 

In this research, the effect of adding graphene-based aerogel ((G)A) nanoparticles on the tensile and fatigue behavior of the epoxy polymer was investigated. Specimens of nanocomposites were prepared by adding 0.05, 0.1, 0.2, 0.5, 1, and 2 wt.-% (G)A nanoparticles to the epoxy polymer. Tensile tests revealed that the 0.1 wt.-% graphene-based aerogel/ epoxy ((G)A/E) nanocomposites had the highest increase in tensile strength with 19 % growth compared to neat epoxy. Also, the tensile modulus increased by 15 % in the 0.5 wt.-% (G)A/E nanocomposites. A substantial improvement in fatigue life of the epoxy polymer was observed on adding 0.1 wt.-% (G)A nanoparticles. For instance, the fatigue life... 

We study the interdiction of illegal product distribution in a network with multiple sources (origins) and sinks (destinations). This work contributes to the literature of dynamic maximum flow interdiction problems by addressing multiple commodities in a network of relationships. The related distribution network consists of (1) criminals, who are hierarchically connected, and seeking to maximize the total profit flow from origins to destinations, and (2) enforcement officers aiming to minimize criminals’ long-term success by monitoring and arresting them, using the limited resources at their disposal. Considering several real-world operational details, we first propose a mixed-integer... 

We study the interdiction of illegal product distribution in a network with multiple sources (origins) and sinks (destinations). This work contributes to the literature of dynamic maximum flow interdiction problems by addressing multiple commodities in a network of relationships. The related distribution network consists of (1) criminals, who are hierarchically connected, and seeking to maximize the total profit flow from origins to destinations, and (2) enforcement officers aiming to minimize criminals’ long-term success by monitoring and arresting them, using the limited resources at their disposal. Considering several real-world operational details, we first propose a mixed-integer... 

We study the interdiction of illegal product distribution in a network with multiple sources (origins) and sinks (destinations). This work contributes to the literature of dynamic maximum flow interdiction problems by addressing multiple commodities in a network of relationships. The related distribution network consists of (1) criminals, who are hierarchically connected, and seeking to maximize the total profit flow from origins to destinations, and (2) enforcement officers aiming to minimize criminals’ long-term success by monitoring and arresting them, using the limited resources at their disposal. Considering several real-world operational details, we first propose a mixed-integer... 

In United States (U.S.), government-funded organizations, such as NLDAC, reimburse travel and subsistence expenses incurred during living-organ donation process. However, in Iran, there is a non-governmental organization called Iranian Kidney Foundation (IKF) that funds the direct and indirect costs of donors through charitable donations and contributions from participants in the exchange program. In this article, for countries outside the U.S. that currently use an equality approach, we propose a potential new compensation-apportionment approach (equitable approach) for kidney-exchange chains and compare it with the currently available system (equality approach) in terms of the... 

The receptivity of supersonic/hypersonic flows over blunt noses to freestream disturbances is performed by means of spectral collocation methods. The unsteady flow computations are made through solving the full Navier-Stokes equations in 2D. A shock-fitting technique is used to compute unsteady shock motion and its interaction with freestream disturbances accurately in the receptivity study. The computational results for receptivity of a semi-cylinder at Mach 8 is presented and validated by comparison with available theoretical and numerical results. The study shows significant effects of the viscosity on the receptivity process  

The purpose of this paper is to study and identify suitable outflow boundary conditions for the numerical simulation of viscous supersonic/hypersonic flow over blunt bodies, governed by the compressible Navier-Stokes equations, with an emphasis motivated primarily by the use of spectral methods without any filtering. The subsonic/supersonic composition of the outflow boundary requires a dual boundary treatment for well-posedness. All compatibility relations, modified to undertake the hyperbolic/parabolic behaviour of the governing equations, are used for the supersonic part of the outflow. Regarding the unknown downstream information in the subsonic region, different subsonic outflow... 

Sleep Spindle is the hallmark of the second stage of sleep in EEG signal. It had been analyzed using different methods, including Fourier transform, parametric and non-parametric models, higher order statistics and spectra, and also time-frequency methods such as wavelet transform, and matching pursuit. In this study, bump modeling has been used to analyze sleep spindle. Bump modeling is a method which represents the time-frequency map of signals with a number of elementary functions. Results of this work demonstrate that bump modeling is capable of analyzing different sleep spindle patterns in sleep EEG signals successfully  

Drop formation in cross-junction micro-channels is numerically studied using the lattice Boltzmann method with pseudo-potential model. To verify the simulation, the results are compared to previous numerical and experimental data. Furthermore, the effects of capillary number, flow rate ratio, contact angle, and viscosity ratio on the flow patterns, drop length, and interval between drops are investigated and highlighted. The results show that the drop forming process has different regimes, namely, jetting, drop, and squeezing regimes. Also, it is shown that increasing in the flow rate ratio in the squeezing regime causes increment in drop length and decrement in drops interval distance. On... 

This study reports on the simulation of temperature distribution of human tooth under a laser beam based on non-Fourier models. The temperature in the tooth depth that directly results from the conduction heat transfer process is caused by the lengthy thermal relaxation time in the tooth layers. A detailed tooth composed of enamel, dentin, and pulp with unstructured shape, uneven boundaries, and realistic thicknesses was considered. A finite difference scheme was separately adopted to solve time-dependent equations in solid layers and soft tissue of the tooth. In this study, a dual-phase-lag non-Fourier heat conduction model was applied to evaluate temperature distribution induced by laser... 

In this study, a dental short pulse laser with a Gaussian beam profile was applied normally to the top surface of a mineral organ i.e. the human tooth for a root canal therapy. A numerical method of finite difference is adopted to solve the time-dependent heat transfer equation. The real boundary conditions of thermal insulation on the sharp segment of the root canal and periodic heat flux on the top boundary of the tooth were applied. The comparison of a three-phase-lag (TPL) bio-heat transfer model with other heat transfer studies has shown that this new bio-heat model (TPL) could accurately predict the thermal behaviour of a non-homogeneous structure such as the human tooth. It was... 

The authors report the simulation of temperature distribution and thermally induced stress in the premolar tooth under ND-YAG pulsed laser beam. The Three-Phase-Lag (TPL) non-Fourier model is proposed to describe the heat conduction in the human tooth with nonhomogeneous inner structures. A premolar tooth comprising enamel, dentin, and pulp with real shapes and thicknesses are considered and a numerical method of finite difference was adopted to solve the time-dependent TPL bio-heat transfer, strain and stress equations. The surface heating scheme is applied for simulation of laser therapy. The aim of this laser therapy is that the temperature of pulp reaches to 47oC. The results are... 

Blood availability in hospitals is of high humanitarian importance, thus blood shortage is not desired at all. High wastage rate of blood in hospitals is an important issue, which becomes more important as the standards of health care services becomes higher. In order to address blood shortage and wastage issues in a hospital, this paper develops a new inventory management model as a decision making tool to help making tactical and operational level decisions for a Hospital Blood Bank (HBB) inventory management. These decisions include issuance and ordering policy and the aim of the model is to reduce blood wastage and shortage. For this purpose, a multi period, multi-product inventory...