Sharif Digital Repository

In the present work, N-rich activated carbon was synthesized using hydrothermal carbonization of egg white biomass in the presence of sucrose, followed by chemical activation and magnetization of hydrochar in the presence of iron (II) and (III) at NaOH solution. The results showed that the sucrose has a critical role in hydrochar yield by increasing of sucrose content. This claim also proved by SEM analysis, which hydrochar morphology was changed from the layered to fused carbon spheres morphology that confirmed the increasing of nucleation site. The materials were characterized with VSM, SEM, CHN, FTIR, Raman spectroscopy and XRD techniques. Capacity of prepared magnetic activated carbon... 

The paper presents a systematic approach to designing an imaging dish for a concentrator photovoltaic (CPV) system to minimize exergy destruction. The designed CPV system uniformly distributes light rays on the receiver (TPV/multi-junction PV) to enhance the conversion technology efficiency and lifetime. To this end, a parametric dish is designed using imaging optics and the numerical solution of a differential equation. Afterward, a Monte Carlo simulation is used to estimate the output energy and exergy of the CPV system with the parametric dish. Finally, an optimization algorithm finds the optimal design parameters to minimize the system's exergy destruction. The optimal design leads to a... 

The paper presents a conceptual study on modification of the electric arc furnace (EAF) slag doors in order to allow removal of the excess slag from the EAF. The idea behind additional slag doors is to allow deslagging of the bath in certain unfavorable cases when the slag height is too great. Slags which exceed the optimal height cause unnecessary refractory corrosion and additional energy losses. The study proposes symmetric slag doors comprised of two hatches, i.e. upper and lower. The upper hatch is intended to decrease the slag height to the optimal level, while the lower hatch can be used to completely deslag the EAF at tapping. In this manner, tilting of the EAF is not necessary. A... 

In this paper, a conceptual study and quantification of using a thermophotovoltaic system (TPV) to convert incident radiation on furnace panels to electrical energy is presented. In typical electric arc furnaces (EAF), a considerable amount of energy is wasted during the melting process, that is, steel enthalpy, off-gas extraction, vessel cooling, slag enthalpy, and others. Although a remarkable share of the energy is wasted in circulating water, the contained exergy is simply too low to be considered for heat recovery (under 0.5% of input exergy) in comparison to energy content of the extracted gasses and slag. In the performed study, a TPV power output is calculated as a function of arc... 

This paper presents an electric arc furnace (EAF) optimization framework intended to define optimal control profiles for the EAF, in order to increase its efficiency and thus reduce the energy consumption. The framework aims to minimize controllable losses and to maximize energy transfer to the bath and, consequently, minimize the operational costs. This is achieved through improved actuation of the EAF inputs, i.e., transformer power, oxygen lancing, and carbon addition. To achieve maximal energy transfer to the bath and to reduce the heat losses from the arcs, proper properties of the slag, such as foaminess and basicity, are a subject of considerable attention. The framework is designed... 

This article aims at developing a semi-analytic approach for studying the free and forced vibrations of a pseudoelastically behaving shape memory alloy beam. Based on the Euler–Bernoulli beam theory, equations of motion were derived through Hamilton principle, and the obtained partial differential equations were decomposed by applying the Galerkin approach and were solved using Newmark integration method. A three-dimensional phenomenological model of shape memory alloy, which is capable of identifying the main properties of the shape memory alloy, was employed to model the behavior of the shape memory alloy beam. A closed-form numerical algorithm was introduced to simulate the governing... 

In this study Al2O3-SiC micro/nanocomposites have been fabricated by mixing alumina nanopowders and silicon carbide micro/nanopowders, followed by hot pressing at 1550, 1600, 1650 and 1700°C. The density, mechanical properties and fracture mode of Al2O3-SiC composites containing different volume fractions (2.5%, 5%, 7.5%, 10% and 15%) of micro/nanoscale SiC particles were investigated and compared with those of alumina. The relative density of composites could reach values very close to theoretical density, especially after sintering at 1700°C. However, relative density declined by increasing the SiC fraction at the same sintering temperature. The flexural strength of composites was best for... 

Purpose: The purpose of this paper is to apply a hybrid neuro-fuzzy paradigm called self-organizing neuro-fuzzy multilayered classifier (SONeFMUC) to classify the operating faults of a hydraulic system. The main motivation behind the use of SONeFMUC is to attest the capabilities of neuro-fuzzy classifier for handling the difficulties associated with fault diagnosis of hydraulic circuits. Design/methodology/approach: In the proposed methodology, first, the neuro-fuzzy nodes at each layer of the SONeFMUC are trained separately using two well-known bio-inspired algorithms, i.e. a semi deterministic method with random walks called co-variance matrix adaptation evolutionary strategy (CMA-ES) and... 

The major application of stochastic intelligent methods in optimisation, control and management of complex systems is transparent. Many researchers try to develop collective intelligent techniques and hybrid meta-heuristic models for improving the reliability of such optimisation algorithms. In this paper, a new optimisation method that is the simulation of 'the great salmon run' (TGSR) is developed. This simulation provides a powerful tool for optimising complex multi-dimensional and multi-modal problems. For demonstrating the high robustness and acceptable quality of TGSR, it is compared with most of the well-known proposed optimisation techniques such as parallel migrating genetic... 

In the last decade, technological innovations have resulted in considering distributed generation with heat recovery capability in addition to centralised generation. This work aims to develop a comprehensive model analysing techno-economic parameters of energy supply in an office building. The energy model is developed on the basis of the reference energy system with the linear programming technique. The objective function is the annual value of total costs of the energy supply system. The results of the model for the building of Sharif Energy Research Institute indicate that the most appropriate generation technology is an internal combustion engine of 461 kW and a water boiler of 152 kW.... 

Serious and challengeable role in markets of low power supplies for cellular phones and other small portable devices is expected for single fuel cell in future. Single fuel cell voltage level is extremely low in comparison with its output current. According to the extremely low level of the voltage, a suitable dc/dc boost converter must be used for increasing the voltage. In this paper, a model for a single fuel cell is presented and the effect of external load variation and changing of reactant pressure on cell performance is investigated. Moreover, a predictive voltage controller for boost convertor of PEM fuel cell is presented, simulated and validated using MATLAB/Simulink. The results... 

In the last decade, technological innovations have resulted in considering distributed generation with heat recovery capability in addition to centralised generation. This work aims to develop a comprehensive model analysing techno-economic parameters of energy supply in an office building. The energy model is developed on the basis of the reference energy system with the linear programming technique. The objective function is the annual value of total costs of the energy supply system. The results of the model for the building of Sharif Energy Research Institute indicate that the most appropriate generation technology is an internal combustion engine of 461 kW and a water boiler of 152 kW.... 

The paper studies the effects of solid and liquid steel properties on the heat transfer coefficient (HTC) in electric arc furnaces (EAFs). Mathematically speaking, the HTC is a function of solid and liquid steel properties. Different velocities of the bath cause different flow paths around the solid particles and therefore different HTCs - a computational issue that has not been addressed yet. Therefore, a simplified calculation model is proposed, intended for HTC estimation according to the EAF conditions. Although many studies investigated this topic, most of them either assume unconventional conditions for the EAF operation, are computationally complex or focus on a specific case; and... 

The present study evaluates the application of top-down steel demand estimation in developing countries. The anticipated steel demand for the case of Iran is calculated by three methods, including the growth model (GM), the intensity of use hypothesis (IUH), and the fixed stock paradigm (FCP). GM shows a broad range of apparent steel demand based on the assumed growth factor. When the gross domestic product (GDP) per capita reaches 13,000 dollars per person (constant 2010 US$), the IUH method estimates the consumption peak consumption at around 500 kg steel per capita per year, which is being expected between 2040 and 2060 depending on the economic growth assumptions. Since fluctuations in... 

Coronavirus disease 2019 (COVID-19) is now of global concern due to its rapid dissemination across the globe. The rapid spread of this viral infection, along with many of its unknown aspects, has posed new challenges to the health care systems. The main challenging effects of COVID-19 are rapid dissemination through close contact and varying clinical severity among different individuals. Furthermore, the medical staff in endemic areas are becoming exhausted and deal with a considerable level of job burnout, which can negatively affect their medical decision making. Also, due to the variable pulmonary manifestations of COVID-19, some physicians may misdiagnose patients. To overcome these... 

University (Educational) buildings comprise a considerable contribution of commercial buildings energy consumption. Optimizing operational measures are widely suggested for energy saving in university buildings. Hence, in this study, a bi-level energy-efficient occupancy profile optimization method using a metaheuristic algorithm, integrated with a demand-driven control strategy adjusted with dynamic set-point temperature is proposed to optimize the energy consumption within in a university departmental building. To proceed with the proposed energy saving strategies; first, building's thermal behavior and AHU system performance are identified and modeled through Artificial Neural Networks... 

Loess as a subcategory of collapsible soils is a well-known aeolian deposit generally characterized as a highly-porous medium with relatively low natural density and water content and a high percentage of fine-grained particles. Such collapsible soil sustains large stresses under a dry condition with natural water content. However, it can experience high and relatively sudden decreases in its volume once it reaches a certain water content under a certain load and therefore, the natural condition of the soil might not be suitable for construction if the possibility of the exposure of the soil to excessive water exists during the lifetime of the project. This research presents the utilization... 

Proton Exchange Membrane (PEM) Fuel Cells are attracting most of the electricity consumers because of high efficiency, zero carbon emissions and high reliability. There are many parameters influencing on this power source's operation. A model of PEM fuel cell will be presented and the sensitivity of the fuel cell's parameters will be analyzed. Multi Parameters Sensitivity Analysis is used next to examine the relative importance of the influential parameters on the PEM fuel cell operation  

This paper presents a formulation for in-plane modal characteristics of non-uniform thickness annular elliptic and circular plates for all classical boundary conditions. The investigations are performed for elastic and isotropic annular elliptic plates on the basis of two- dimensional linear plane stress theory of elasticity. Two-dimensional boundary characteristic orthogonal polynomials (BCOP) are used in the Rayleigh-Ritz method to obtain the natural frequencies and associated mode shapes. The proposed method, not only can find solution for those simple cases of annular circular plates available in literature as a simplified case study, but also it finds some natural frequencies which can... 

The paper aims to present a supply model to satisfy the required household final energy carriers, freshwater and industrial cooling loads for a deprived area of access that is located in hot and humid climate. To this aim, a multi-generation hybrid solar thermophotovoltaic integrated system with capability of adjusting heat to power ratio dynamically is introduced. Appropriate analytical tools are developed to obtain the optimal capacity of any systems and energy flows subject to the technology and demand constraints, the financial limitation and the constraints defined by the politicians and local government. The demand constraints are identified through the field studies and the comfort...