Sharif Digital Repository

This research studies multi-objective master production schedule (MPS) and advanced order commitment (AOC) in two-stage supply chains. Simulation-based experimental analysis evaluates the impact of environmental and MPS design factors on schedule cost and instability. The results provide insight into multi-objective MPS design considerations through rolling schedule policies. The study reveals that the manufacturers production smoothness utility coefficient and its interaction with other experimental factors considerably impact on the systems performance. In addition, it introduces a simulation framework with embedded mixed integer programming models that could be used as a framework for... 

Inbound marketing is the process of attracting the probable customers to a business before they have any intention to become customers. An effective method for inbound marketing is creation of a positive psychological business environment to attract the customers. A significant portion of traditional business environment is moving online and the new business environment is the company website. One of the major elements in online inbound marketing is the website address and the website logo, which are the first factors of brand personality that the visitor to the company website encounters when looking up the website in a search engine. In this paper, a framework for inbound e-marketing using... 

Recently, numerous studies have focused on simulation and optimisation of combined cooling, heat, and power (CCHP) systems. This research, from a different perspective, aims to conduct a comprehensive review of the studies performed in the field of solar, geothermal or combined sources, and subsequently analysing the multi-objective evolutionary algorithms to identify the most efficient situation, which satisfy researchers' needs in order to attain a better performance in their ongoing or future research projects. It is worth noting that multi-objective optimisation in these cycles is based on optimising a thermodynamic term (exergy efficiency, thermal efficiency, etc.) and an economic term... 

The present study investigated a counter-flow cooling tower performance by integrating the Artificial Neural Networks and Intelligent Optimisation Algorithms (ANN-IOAs). For this purpose, two scenarios were evaluated. In the first scenario, inlet air wet-bulb temperature (T aw), inlet air dry bulb temperature (T ad), water to the air mass flow rate ratio (mw /ma), and rotor speed (υ) were the input parameters for the ANNs, while the output temperature (T wo) was the ANNs output. In the second scenario, the same input parameters applied for the first scenario were used as input variables and the tower efficiency (ε) was considered as an output parameter. The well-known IOAs methods, namely,... 

The present study investigated a counter-flow cooling tower performance by integrating the Artificial Neural Networks and Intelligent Optimisation Algorithms (ANN-IOAs). For this purpose, two scenarios were evaluated. In the first scenario, inlet air wet-bulb temperature (T aw), inlet air dry bulb temperature (T ad), water to the air mass flow rate ratio (mw /ma), and rotor speed (υ) were the input parameters for the ANNs, while the output temperature (T wo) was the ANNs output. In the second scenario, the same input parameters applied for the first scenario were used as input variables and the tower efficiency (ε) was considered as an output parameter. The well-known IOAs methods, namely,... 

Simultaneous extraction of zinc and cadmium by a mixture of di-2-ethyl hexyl phosphoric acid (DEHPA) and mono-2-ethyl hexyl phosphoric acid (MEHPA), and the synergistic effect of MEHPA on co-extraction of zinc and cadmium with DEHPA have been investigated. It was shown that the extraction of zinc and cadmium by DEHPA and/or MEHPA can be increased by an increase of pH. The results also illustrate that the pH0.5 of zinc, by increase in MEHPA from 0.1 to 8 vol%, did not vary significantly while that of cadmium varies from 0.63 to 2.4. In other words MEHPA prevents selective extraction of zinc from aqueous media containing both zinc and cadmium. Studies on the selective separation parameter... 

The present work is concerned with the steady incompressible flow through a parallel plate channel with stretching walls under an externally applied magnetic field. The governing continuity and Navier-Stokes equations are reduced to a fourth order nonlinear differential equation by using vorticity definition and similarity solution transformation. The obtained equations are solved by applying the analytical homotopy perturbation method (HPM). The method is called order of magnitude suggested for simplifying series solution to finite expression that is useful in engineering problems. The results are verified by comparing with numerical solutions and demonstrate a good accuracy of the obtained... 

In the last decade, many potent analytical methods have been utilized to find the approximate solution of nonlinear differential equations. Some of these methods are energy balance method (EBM), homotopy perturbation method (HPM), variational iteration method (VIM), amplitude frequency formulation (AFF), and max-min approach (MMA). Besides the methods mentioned above, the Akbari-Ganji method (AGM) is a highly efficient analytical method to solve a wide range of nonlinear equations, including heat transfer, mass transfer, and vibration problems. In this study, it was constructed the approximate analytic solution for movement of two mechanical oscillators by employing the AGM. In the derived... 

At SCN 2018, Fiore and Pagnin proposed a generic compiler (called “Matrioska”) allowing to transform sufficiently expressive single-key homomorphic signatures (SKHSs) into multi-key homomorphic signatures (MKHSs) under falsifiable assumptions in the standard model. Matrioska is designed for homomorphic signatures that support programs represented as circuits. The MKHS schemes obtained through Matrioska support the evaluation and verification of arbitrary circuits over data signed from multiple users, but they require the underlying SKHS scheme to work with circuits whose size is exponential in the number of users, and thus can only support a constant number of users. In this work, we propose... 

The ride comfort of high-speed trains passing over railway bridges is studied in this paper. A parametric study is carried out using a time domain model. The effects of some design parameters are investigated such as damping and stiffness of the suspension system and also ballast stiffness. The influence of the track irregularity and train speed on two comfort indicators, namely Sperling's comfort index and the maximum acceleration level are also studied. Two types of railway bridges, a simple girder and an elastically supported bridge are considered. Timoshenko beam theory is used for modelling the rail and bridge and two layers of parallel damped springs in conjunction with a layer of mass... 

Purpose: The purpose of this paper is to investigate natural convection in a porous wavy-walled enclosure that is including a cylinder cavity in the middle of it and filled with a hybrid nanofluid contains 1-Butanol as the base fluid and MoS2–Fe3O4 hybrid nanoparticles. Design/methodology/approach: The domain of interest is bounded by constant temperature horizontal corrugated surfaces and isothermal vertical flat surfaces. The numerical outputs are explained in the type of isotherms, streamline and average Nusselt number with variations of the Rayleigh number, Hartmann number, nanoparticle shape factor and porosity of the porous medium. For solving the governing equations, the finite... 

Direct Simulation Monte Carlo (DSMC) method is applied to evaluate the performance of a new micro gas sensor (MIKRA) for mass analysis of ammonia in the rarefied gas. In order to simulate a rarefied gas inside the micro gas detector, Boltzmann equation is applied to obtain high precision results. This study performed comprehensive studies to reveal the main mechanism of force generation and applied this for the analysis of the gas mixture. Our findings show that value of generated Knudsen force significantly varies when the percentage of the NH3 varies in the mixture. According to obtained results, the maximum Knudsen force increases when the fraction of the ammonia decreases. Our findings... 

This paper deals with the mixed convective heat transfer of nanofluids through a concentric vertical annulus. Because of the non-adherence of the fluid-solid interface in the presence of nanoparticle migrations, known as slip condition, the Navier's slip boundary condition was considered at the pipe walls. The employed model for nanofluid includes the modified two-component four-equation non-homogeneous equilibrium model that fully accounts for the effects of nanoparticles volume fraction distribution. Assuming the fully developed flow and heat transfer, the basic partial differential equations including continuity, momentum, and energy equations have been reduced to two-point ordinary... 

Residual stresses, created in a steel beam by elastic-plastic bending, are predicted using an approximate analysis and the finite element method. The predictions are compared to experimental measurements obtained from the application of incremental centre hole drilling, deep hole drilling and neutron diffraction methods. Finite element simulations of the incremental centre hole drilling and deep hole drilling methods applied to the predicted residual stresses permitted an assessment of their ability to reconstruct the stresses. An analytical reconstruction analysis using an Airy stress function together with boundary and equilibrium conditions is developed and applied to the predictions and... 

A typical process in many industrial applications is rising bubble dynamic in viscous liquids like two-phase reactors. Examining the physical behavior of bubbles may improve the understanding of systems regarding design and operation. This study focused on the splitting of bubbles resulting from their impact on solid obstacles. Fragmentation of the bubbles appears in many applications such as lab on a chip in small scale or slug bubbly flow moving upward in a tube in large scales. Using a new index-function model in Lattice Boltzmann technique proposed by “He”, we simulated the deformation and motion of a bubble in different regimes, through which, we accurately captured a sharp interface... 

In this paper, Direct Simulation Monte Carlo (DSMC) simulations were applied to investigate the mechanism of the force generation inside a low-pressure gas sensor. The flow feature and force generation mechanism inside a rectangular enclosure with heat and cold arms as the non-isothermal walls are comprehensively explained. In addition, extensive parametric studies are done to study the effects of physical parameters on the performance and characteristics of this device in different operating conditions. In this research, the Knudsen number is varied from 0.1 to 4.5 (0.5 to 11torr) to reveal all the characteristics of the thermally driven force inside the MEMS sensor. In order to simulate a... 

One of the major challenges in the manufacturing parts, especially metals, is turning with good/excellent surface quality, which has a significant effect on the fatigue strength of the industrial components. Selecting incorrect or unsuitable values of machining parameters leads to vibration instability in the cutting tool and as a result, excessive roughness is created on the product’s surface. Therefore, one of the ways to reduce the roughness factor and increase the product fatigue life is to control the relative slip and vibration between the cutting tool and the workpiece. To achieve this goal, the authors attempted to investigate the simultaneous effects of tool overhang and cutting... 

Recently, an inequality satisfied by noncontextual hidden-variable models and violated by quantum mechanics for all states of a four-level system has been derived based on an information-theoretic distance approach to nonclassical correlations. In this Rapid Communication, we experimentally demonstrate the violation of this inequality with single photons. Our experiment offers a method to study a distinction between quantum and classical correlations from an information-theoretic perspective. © 2020 American Physical Society