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efficiency
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Fog harvesting: combination and comparison of different methods to maximize the collection efficiency
, Article SN Applied Sciences ; Volume 3, Issue 4 , 2021 ; 25233971 (ISSN) ; Kazerooni, H ; Sharif University of Technology
Springer Nature
2021
Abstract
Fog harvesting is an unconventional source of water that can be used in some regions with water scarcity to overcome water shortages. The most commonly used collectors are meshes which have intrinsic limitations, the most important of which are clogging and aerodynamic deviation of droplets around the wires. Here, three techniques are compared and combined to overcome these limitations, i.e., replacing the mesh with an array of vertical wires, addition of a hydrophobic layer to the wires, and forcing the ionized droplets to move toward the wires by applying an electric field. The combination of these techniques was found to result in higher fog harvesting efficiency compared to each...
Binary Taylor Diagrams: An efficient implementation of Taylor expansion Diagrams
, Article IEEE International Symposium on Circuits and Systems 2005, ISCAS 2005, Kobe, 23 May 2005 through 26 May 2005 ; 2005 , Pages 424-427 ; 02714310 (ISSN) ; Shamshiri, S ; Alisafaee, M ; Lotfi Kamran, P ; Naderi, M ; Navabi, Z ; Alizadeh, B ; Sharif University of Technology
2005
Abstract
This paper presents an efficient way of implementing Taylor expansion Diagrams (TED) that is called Binary Taylor Diagrams (BTD). BTD is based on Taylor series like TED, but uses a binary data structure. So BTD functions are simpler than those of TED. © 2005 IEEE
The effect of non-uniform magnetic field on the efficiency of mixing in droplet-based microfluidics: a numerical investigation
, Article Micromachines ; Volume 13, Issue 10 , 2022 ; 2072666X (ISSN) ; Nouri, M ; Hassani Gangaraj, M ; Shamloo, A ; Nasiri, R ; Sharif University of Technology
MDPI
2022
Abstract
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...
A bi-objective model for scheduling of multiple projects under multi-skilled workforce for distributed load energy usage
, Article Operational Research ; Volume 22, Issue 3 , 2022 , Pages 2245-2280 ; 11092858 (ISSN) ; Afshar Nadjafi, B ; Taghi Akhavan Niaki, S ; Sharif University of Technology
Springer Science and Business Media Deutschland GmbH
2022
Abstract
Satisfying the clients' uncompromising priorities is a challenge for decision makers of organizations that face multiple projects. This paper considers an organization with a multi-skilled workforce working on several predetermined projects under time-of-use energy tariffs where distributed load energy usage is the primary concern of energy suppliers. This paper also considers different time-of-use energy tariffs, which are among the most common strategies to reach a more balanced energy utilization. The problem is stated as a bi-objective mixed-integer programming model containing two conflicting objectives; to minimize the total cost of the multi-skilled workforce and obtain a sustainable...
An approach to targeting cryptocurrency mining loads for energy efficiency enhancement
, Article IET Generation, Transmission and Distribution ; Volume 16, Issue 23 , 2022 , Pages 4775-4790 ; 17518687 (ISSN) ; Azimi Hosseini, K ; Hajipour, E ; Vakilian, M ; Sharif University of Technology
John Wiley and Sons Inc
2022
Abstract
In recent years, the mining of cryptocurrencies such as Bitcoin has attracted much global attention due to the simplicity and high profitability of this business, especially in countries with low electricity rates. The process of cryptocurrency mining using cryptocurrency mining devices requires a significant amount of computing power. This industry, which is increasingly growing in energy and carbon emissions, can cause environmental concerns. Common ways to reduce this amount of energy consumption are to prohibit mining and charge these loads at a higher electricity rate; however, these solution methods are not feasible and applicable in many countries. This paper presents an energy...
Testing Real Estate Market Efficiency in Iran
, M.Sc. Thesis Sharif University of Technology ; Nili, Masoud (Supervisor) ; Keshavarz Haddad, Gholamreza (Supervisor)
Abstract
The primary aim of this research is to test the weak form of Efficient Market Hypothesis in Iran’s Housing Market. Average price of one square meter of residential property is provided by The Ministry of Housing and Urban Development in urban areas of Iran with different frequencies. The data is available in the form of quarterly time series for the metropolitan districts of capital of Tehran, semi-annual time series for five major mega cities and annual time series for a group of eighteen cities. The econometric tests performed to evaluate the market efficiency can be grouped to two main categories i.e. tests performed on time series data and tests performed on panel data. Three alternative...
, M.Sc. Thesis Sharif University of Technology ; Alavi, Babak (Supervisor) ; Feyzbakhsh, Alireza (Supervisor)
Abstract
Entrepreneurship is a process that requires high motivation for success. Self-efficacy is to believe the person's ability to organize and carry out certain types of activities to produce specific outcomes. Thus helping to increase self-efficacy beliefs in people who have attempted to entrepreneurship can increase their chances of success. On the other hand Self-leadership has been defined as “the process” of influencing oneself to establish the self-direction and self-motivation needed to perform. And include three major strategies named Behavioral focused strategies, Intrinsic motivation (Natural Reward) strategies, Constructive thought pattern strategies and some specific behaviors in each...
Optimal Model of Energy and Exergy of Iran’s Economic Activities and their Impact on the Environment
, M.Sc. Thesis Sharif University of Technology ; Saboohi, Yadollah (Supervisor)
Abstract
The economic activities in a country involved with depletion of natural resources and emission of pollutants and gases to the environment. Depletion of exhaustible resources and environmental pollutions are two determinants of sustainability of development. The present research work is aimed at studying the sustainability of Iranian economy in 2009. The analysis of sustainable development of economy is based the concept of exergy, exergy efficiency and ecological exergy efficiency. Exergy efficiency is the ratio of the exergy of a product in economic activity to the exergy of input streams to that section of economy. Ecological exergy efficiency is defined as the ratio of exergy of product...
Cost and Profit Efficiency of Iranian Banking Sector Using Parametric and Non-Parametric Methods
, M.Sc. Thesis Sharif University of Technology ; Keshavarz Haddad, Gholamreza (Supervisor)
Abstract
In this research, by employing DEA non-parametric and SFA parametric methods, the cost and profit efficiency of Iranian banking system are estimated in the period 2002-2007. Afterwards, the results are evaluated and analyzed via six aspects proposed in consistency conditions. Furthermore, we take advantage of standard non-frontier performance measures namely the cost to assets ratio (TC/A) and profit to assets (/A) for comparing them with estimated cost and profit efficiencies. The findings suggest the high degree of consistency between the results of parametric and non-parametric methods; meanwhile, any significant correlation is not seen between ownership (public/private) and type of...
Exergy analysis of a flat plate solar collector in combination with heat pipe
, Article International Journal of Environmental Research ; Vol. 8, Issue. 1 , 2014 , Pages 39-48 ; ISSN: 17356865 ; Shafii, M. B ; Rahni, M. T ; Abbaspour, M ; Sharif University of Technology
Abstract
The use of solar collectors in combination with heat pipes is rapidly growing in recent years. Heat pipes, as heat transfer components, have undeniable advantages in comparison with other alternatives. The most important advantage is their high rate of heat transfer at minor temperature differences. Although there have been numerous studies on the heat analysis or first thermodynamic analysis of flat plate solar collectors in combination with heat pipes, the exergy analysis of these collectors is needed to be investigated. In this work, energy and exergy analysis of a flat plate solar collector with a heat pipe is conducted theoretically. Next, the exergy efficiency of pulsating heat pipe...
Efficient and reliable ray tracing, some challenges and proposed solutions. ا
, Article 8th European Conference on Antennas and Propagation, EuCAP 2014 ; April , 2014 , PP. 1589-1592 ; ISBN: 978-8890701849 ; Shishegar, A. A ; Sharif University of Technology
Abstract
Ray tracing has been widely accepted as a versatile and reliable method for indoor propagation modeling. Several published articles have addressed the computational efficiency and reliability as the most challenging problems of ray tracing and have presented various solutions. Such challenges are discussed in this paper and some possible solutions are presented
Terahertz spectrum splitting by a graphene-covered array of rectangular grooves
, Article Optics Letters ; Volume 42, Issue 23 , 2017 , Pages 4808-4811 ; 01469592 (ISSN) ; Saba, A ; Jafargholi, A ; Khavasi, A ; Sharif University of Technology
Abstract
We propose a bidirectional terahertz (THz) spectrum splitter using a practically simple metamaterial structure consisting of rectangular grooves covered by graphene. Thanks to the graphene optoelectronic tunability and by adjusting the grooves width, this structure provides nearly 2π phase shift. At the same time, the reflection efficiency is acceptable throughout the phase shifts. We design each of the meta-atoms using a circuit model, and then we synthesize the final supercell based on the generalized Snell’s law so that the structure reflects different frequency waves to totally different directions. The full-wave simulations demonstrate the beam splitting with a remarkable efficiency of...
Efficiency measurement in data envelopment analysis in the presence of ordinal and interval data
, Article Neural Computing and Applications ; Volume 30, Issue 6 , 2018 , Pages 1971-1982 ; 09410643 (ISSN) ; Tavana, M ; Rahmani, M ; Santos Arteaga, F. J ; Sharif University of Technology
Springer London
2018
Abstract
Several methods have been proposed in data envelopment analysis (DEA) for measuring efficiency in problems with interval or ordinal data. In this study, we review the weaknesses and drawbacks of these methods and show how converting ordinal or interval data into precise data can lead to violations of established DEA axioms. One of the axioms violated by these conversion processes is the inclusion of observations axiom, which requires a consistent definition of the production possibility set. We describe the special properties of ordinal and interval data together with their effect on the DEA-based rankings using a theorem and an example. We also propose a new algorithm and apply random...
Solar energy systems – Potential of nanofluids
, Article Journal of Molecular Liquids ; Volume 289 , 2019 ; 01677322 (ISSN) ; Hassan, A ; Qasim, M. A ; Ali, H. M ; Babar, H ; Sajid, M. U ; Sharif University of Technology
Elsevier B.V
2019
Abstract
Global warming escalation has extended average temperature of earth beyond its safe limit. To avert this environmental-threat, solar energy has acquired substantial attention of remarkable researchers in this century. To effectively utilize solar energy by transforming into thermal and electrical energy, the involvement of nanofluids having intensified thermal, optical and magnetic properties, has become very popular. The foremost objective of this article is to provide a comprehensive review on the applications of nanofluids in solar energy systems like solar collectors, photovoltaic cells, solar stills, and thermal energy storage, which are thoroughly discussed in this paper. The effect of...
Resource allocation and power control for underlay device-to-device communication in fractional frequency reuse cellular networks
, Article Telecommunication Systems ; 2016 , Pages 1-21 ; 10184864 (ISSN) ; Khazali, A ; Kalbkhani, H ; Shayesteh, M. G ; Solouk, V ; Sharif University of Technology
Springer New York LLC
2016
Abstract
The current state of device-to-device (D2D) communication in the presence of cellular network addresses two major challenges of interference as well as throughput inadequacy. Specifically, a D2D communication underlaying fractional frequency reuse (FFR) cellular network exhibits rather high interferences due to higher occurrence of band crossing within a shared spectrum. However, due to the considerable impact of D2D communications on spectral efficiency and system capacity, the remedy for those issues may include efficient techniques of interference mitigation and average spectral efficiency maximization. In this paper, we propose a resource block (RB) allocation scheme to reduce the...
Experimental investigation of the effects of corona wind on the performance of an air-cooled PV/T
, Article Renewable Energy ; Volume 127 , 2018 , Pages 284-297 ; 09601481 (ISSN) ; Kasaeian, A ; Amidpour, M ; Nasirivatan, S ; Mousavi, S ; Sharif University of Technology
Abstract
In the present study, enhancing the heat transfer is experimentally investigated by the electro-hydrodynamics (EHD) through a single-pass air-cooled PV/T (Photovoltaic/Thermal System). The corona wind increases the heat transfer coefficient by producing a secondary flow and vortex, and consequently, increases the PV/T system efficiency. The effects of the corona wind are studied by changing the voltage values and the flow rates in the air channel. The results show that the corona wind is effective on enhancing the system performance; so that the heat transfer coefficient increases by 65% in natural flow regime by applying 11 kV voltage in the pilot setup. Totally, the thermal efficiency of...
Exergy analysis of parabolic trough solar collectors using Al2O3/synthetic oil nanofluid
, Article Solar Energy ; Volume 173 , 2018 , Pages 1236-1247 ; 0038092X (ISSN) ; Shamloo, A ; Kazemzadeh Hannani, S ; Sharif University of Technology
Elsevier Ltd
2018
Abstract
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...
Investigation of the performance of modified organic Rankine cycles (ORCs) and modified trilateral flash cycles (TFCs) assisted by a solar pond
, Article Solar Energy ; Volume 182 , 2019 , Pages 361-381 ; 0038092X (ISSN) ; Akbari, A ; Khalilian, M ; Sharif University of Technology
Elsevier Ltd
2019
Abstract
Solar pond is a type of solar collector that stores solar energy in the form of heat. The solar pond can be used as a low-temperature heat source for electricity generation. In this paper, to find the most suitable power cycle for power generation from the solar pond, the performance of the Organic Rankine Cycle (ORC), Trilateral Flash Cycle (TFC) and their modified forms with an open feed liquid heater and an internal heat exchanger for different working fluids was investigated. Water was considered as the heat transfer fluid which transfers the stored heat from the solar pond to the working fluid of the cycle. The results indicate that in all cases, the energy and exergy efficiency of the...
A numerical study on a photovoltaic thermal system integrated with a thermoelectric generator module
, Article Renewable Energy ; Volume 153 , 2020 , Pages 1261-1271 ; Parcheforosh, A ; Hakkaki Fard, A ; Amadeh, A ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
In this work, a three-dimensional numerical model is developed to investigate the performance of a photovoltaic thermal system integrated with a thermoelectric generator module (PVT/TE). Furthermore, the effects of various operating parameters such as solar radiation, coolant mass flow rate, and inlet and ambient temperatures on the performance of both the PVT and PVT/TE systems are investigated and compared. Based on the obtained results, the electrical efficiency of the PVT/TE system, when exposed to solar radiation of 600 and 1000 W/m2, is 6.23% and 10.41% higher than that of the PVT system, respectively. Besides, the electrical efficiency of the PVT and PVT/TE by increasing the inlet...
Heat transfer intensification of turbulent forced convection by inserting discontinuous twisted tapes in a wavy tube; hydrothermal and thermodynamics analysis
, Article Chemical Engineering and Processing - Process Intensification ; Volume 181 , 2022 ; 02552701 (ISSN) ; Sadrhosseini, H ; Kazemzadeh Hannani, S ; Sharif University of Technology
Elsevier B.V
2022
Abstract
The current study presents a numerical investigation on turbulent hydrothermal characteristics in a wavy passage equipped with discontinuous twisted tapes. The working fluid is water and passage walls are kept under constant wall temperature. The effect of Reynolds number (Re = 2500, 4500, 6500, 8500 and 10500), twist angle (TA = 90∘ and 180∘) and inclination angle (IA = 15∘ and 30∘) on velocity fields and streamlines, temperature contours, Nusselt number, friction factor, turbulent kinetic energy (TKE), thermal performance factor (TPF), energy efficiency factor (EEF) and entropy generation rate are evaluated. More uniform temperature and velocity fields can be found as both wavy passage and...