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Continuous-wave amplification in bismuth-oxide fiber optical parametric amplifiers
, Article 2011 IEEE Winter Topicals, WTM 2011, 10 January 2011 through 12 January 2011, Keystone, CO ; 2011 , Pages 161-162 ; 9781424484287 (ISBN) ; Jamshidifar, M ; Govan, D ; Marhic, M. E ; Sharif University of Technology
Abstract
We review our investigations on bismuth-oxide fiber as an amplifying medium for parametric amplifiers with continuous-wave pumping. The results lead to new applications in demultiplexing, which are discussed
Flow physics exploration of surface tension driven flows
, Article Colloids and Surfaces A: Physicochemical and Engineering Aspects ; Volume 518 , 2017 , Pages 30-45 ; 09277757 (ISSN) ; Moezzi Rafie, H ; Goodarzi Ardakani, V ; Javadi, A ; Miller, R ; Sharif University of Technology
Abstract
Surface tension driven passive micro-pumping relies mainly on the surface tension properties. To have control over surface tension driven passive micro-pumps (STD-PMPs), it is essential to understand the physical background of the fluid flow in these pumps. Hence, the purpose of this work is to give an exploration of the flow physics of a STD-PMP. In this regard, computer simulation is used to give detailed information about the flow pattern and physical phenomena at different conditions. To this end, a droplet of water, with a specified diameter, is placed onto an entry port connected to another droplet at the exit port via a microchannel. The results indicate that the pumping process, in...
Performance assessment and optimization of a humidification dehumidification (HDH) system driven by absorption-compression heat pump cycle
, Article Desalination ; Volume 447 , 2018 , Pages 84-101 ; 00119164 (ISSN) ; Shekari Namin, A ; Ghaebi, H ; Amidpour, M ; Sharif University of Technology
Elsevier B.V
2018
Abstract
Feasibility investigation of a humidification dehumidification (HDH) desalination system driven by an absorption-compression heat pump cycle (ACHPC) is carried out in this paper. The proposed hybrid desalination system uses both heating capacity of the discharged brine as a waste heat for the ACHPC and mechanical power of the ACHPC for the HDH system. The system's performance is investigated under different optimal design modes, using genetic algorithm (GA) as the most robust tool for optimization. A steady-state mathematical model based on the mass, energy, exergy, and exergoeconomic balance equations for components of the proposed system is developed and the predicted results are validated...
Performance of valveless diffuser micropumps under harmonic piezoelectric actuation
, Article 8th Biennial ASME Conference on Engineering Systems Design and Analysis, ESDA2006, Torino, 4 July 2006 through 7 July 2006 ; Volume 2006 , 2006 ; 0791837793 (ISBN); 9780791837795 (ISBN) ; Saidi, M. H ; Mehrabian, A ; Bazargan, M ; Kenarsari, S. D ; Sharif University of Technology
American Society of Mechanical Engineers
2006
Abstract
Valveless piezoelectric micropumps are in wide practical use due to their ability to conduct particles with absence of interior moving mechanical parts. The objective of this paper is to obtain the fluid flow response to actuation frequency of a passive diffuser valve under harmonic pressures. In this regards a 2D model of a micropump valves and chambers is analyzed. The analysis is performed for 10Kpa back pressure on micropump chamber and actuation frequencies within the range of 1Hz to 10 KHz. Results show the highest velocity in the direction of diffuser axis occurs at the narrow diffuser neck while flow direction reverses every half period. For low frequencies, a parabolic velocity...
Design optimization of diffuser type valveless micropumps
, Article 8th Biennial ASME Conference on Engineering Systems Design and Analysis, ESDA2006, Torino, 4 July 2006 through 7 July 2006 ; Volume 2006 , 2006 ; 0791837793 (ISBN); 9780791837795 (ISBN) ; Mehrabian, A ; Sharif University of Technology
American Society of Mechanical Engineers
2006
Abstract
Valveless piezoelectric micropumps are in wide practical use due to their ability to conduct particles with absence of interior moving mechanical parts. In this paper, using finite element method, an extended numerical study on fluid flow through micropump chamber and diffuser valves is conducted to find out the optimum working conditions of micropump. In order to obtain maximum generality of the reported results, an analytical study along with a dimensional analysis is presented primarily, to investigate the main dimensionless groups of parameters affecting the micropump net flux. Consequently, the parameters appeared in the main dimensionless groups have been changed in order to understand...
Effect of actuation frequency on the performance of diffuser micropumps
, Article 4th International Conference on Nanochannels, Microchannels and Minichannels, ICNMM2006, Limerick, 19 June 2006 through 21 June 2006 ; Volume 2006 B , 2006 , Pages 725-731 ; 0791847608 (ISBN); 9780791847602 (ISBN) ; Ahmadian, M. T ; Sharif University of Technology
2006
Abstract
Valveless piezoelectric micropumps are in wide practical use due to their ability to conduct particles with absence of interior moving mechanical parts. The objective of this paper is to obtain the fluid flow response to actuation frequency of a passive diffuser valve under harmonic pressures. In this regards a 2D model of a micropump valves and chambers is analyzed. The analysis is performed for 10Kpa back pressure on micropump chamber and actuation frequencies within the range of 1 Hz to 10 KHz. Results show the highest velocity in the direction of diffuser axis occurs at the narrow diffuser neck while flow direction reverses every half period. For low frequencies, a parabolic velocity...
Propose and characteristics study of a new actuation method for micropumps, using membrane buckling
, Article 4th ASME Integrated Nanosystems Conference: Design, Synthesis, and Applications, Berkeley, CA, 14 September 2005 through 16 September 2005 ; 2005 , Pages 25-26 ; 0791842088 (ISBN); 9780791842089 (ISBN) ; Ahmadian, M. T ; Salehi, H ; Monazami, R ; Zade, A. Q ; Sharif University of Technology
American Society of Mechanical Engineers
2005
Abstract
In this paper, we present a novel idea on actuation system in micropumps. The prominent goal of this paper is to propose and prove a mechanical actuation system which works in high frequency and has good ability in producing flow and pressure in micro actuation system. As like as other common micropumps, the proposed scheme is consisted of two check valves and an actuation space. The actuation space includes a volume of liquid in a chamber and a cylindrical membrane as the actuator. The main aspect of this idea is employment of buckling as a consequence of incensement of its internal pressure caused by temperature rising in the membrane. Rise of temperature is done by passing a controllable...
A 5 GHz, 1.5 Volt and very low-power cmos frequency synthesizer for wireless communications
, Article 2002 45th Midwest Symposium on Circuits and Systems, Tulsa, OK, 4 August 2002 through 7 August 2002 ; Volume 3 , 2002 , Pages III536-III539 ; Sharif University of Technology
2002
Abstract
A 5GHz, 1.5 Volt and low power CMOS frequency synthesizer with LC-tuned VCO (voltage controlled oscillator) is presented. The synthesizer consists of an LC-tuned VCO, an injection-lock frequency divider, a very low power prescaler which brings 2.5GHz range frequency to 11 MHz, a phase-frequency detector and charge-pump with improved architecture. Spiral inductors with Q-factor of 9 are used for the LC-tuned 5 GHz VCO. A fixed 2 frequency divider based on injection-locking phenomenon is used to bring 5 GHz VCO frequency to 2.5GHz. Both VCO and injection-locked divider's oscillators are tuned with NMOS varactors with their bodies are grounded, resulting in about 700 MHz tuning range....
A 1.5-V supply, 10.7-MHz, bandpass gm-C filter in a 0.6μm standard CMOS technology
, Article 14th International Conference on Microelectronics, ICM 2002, 11 December 2002 through 13 December 2002 ; Volume 2002-January , 2002 , Pages 46-49 ; 0780375734 (ISBN) ; Atarodi, M ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2002
Abstract
A 1.5-V single supply, second order continuous-time bandpass filter, on a 0.6μm standard CMOS process is designed. The THD of the transconductor for a 0.7Vpp input, is -50dB at 10-MHz. In the proposed transconductor structure, the whole circuit, apart from a dc level-shifter based on a voltage doubler, is biased by a single 1.5-V supply. Due to this structure, a high current voltage doubler is not required and the whole filter draws less than 70μm current from this doubler making an on-chip voltage doubler feasible. Also, a new linear common-mode detector with high-frequency response is designed to stabilize the output common-mode voltage. © 2002 IEEE
Performance analysis and parametric study of thermal energy storage in an aquifer coupled with a heat pump and solar collectors, for a residential complex in Tehran, Iran
, Article Applied Thermal Engineering ; Volume 62, Issue 1 , 2014 , Pages 156-170 ; ISSN: 13594311 ; Bahadori, M. N ; Saidi, M. H ; Sharif University of Technology
Abstract
Aquifers are underground porous formations containing water. Confined aquifers are the formations surrounded by two impermeable layers, called cap rocks and bed rocks. These aquifers are suitable for seasonal thermal energy storage. In the present study, a confined aquifer was considered to meet the cooling and heating energy needs of a residential complex located in Tehran, Iran. Three different alternatives were analyzed in this aquifer thermal energy storage (ATES), including: using ATES for cooling alone, for cooling and heating, as a heat pump, and for heating alone, employing flat plate solar energy collectors. A numerical simulation, based on the finite difference method, was carried...
Proposal of a new design for valveless micropumps
, Article Scientia Iranica ; Volume 18, Issue 6 , December , 2011 , Pages 1261-1266 ; 10263098 (ISSN) ; Movahhedy, M. R ; Assempour, A ; Sharif University of Technology
2011
Abstract
A new design for a valveless micropumping device has been proposed that integrates two existing pumping technologies, namely, the wall induced traveling wave and the obstacle-type valveless micropump. The liquid in the microchannel is transported by generating a traveling wave on the channel, while the placing of two asymmetric trapezoid obstacles, along the centerline of the channel inlet and outlet, leads to a significant (up to seven times) increase of the net flow rate of the device. The effectiveness of this innovative design has been proved through a verified three-dimensional finite element model. FluidStructure Interaction (FSI) analysis is performed in the framework of an Arbitrary...
Potential use of cold thermal energy storage systems for better efficiency and cost effectiveness
, Article Energy and Buildings ; Volume 42, Issue 12 , 2010 , Pages 2296-2303 ; 03787788 (ISSN) ; Mozafari, A ; Ahmadi, A ; Esmaili, P ; Shayesteh, M ; Sarkhosh, M ; Dincer, I ; Sharif University of Technology
Abstract
The present article deals with the employment of combined heat and power (CHP) micro gas turbines using natural gas and cold thermal energy storage system (CTES) in Tehran (with mild climate), Bandarabas (with hot and humid climate) and Kerman (with semi-hot climate). A micro CHP produces electricity to meet the electrical energy needs of the building, and it is also considered to meet part of the heating, cooling and domestic hot water energy needs through a heat pump and refrigeration system. A detailed study considering the effect of CTES system on the selection of micro gas turbines of a residential building located in Tehran is performed. The results show that since the number of micro...
Effect of bubble size and angle of tapering upriser pipe on the performance of airlift pumps
, Article Particulate Science and Technology ; Volume 28, Issue 4 , Aug , 2010 , Pages 332-347 ; 02726351 (ISSN) ; Saidi, M. H ; Karimi, A ; Zamiri, A ; Sharif University of Technology
2010
Abstract
Airlift pumps are devices with the ability to lift liquid phase by injecting the gas phase. Parameters that affect the performance of these pumps are divided into two groups. The first group contains design parameters such as diameter of the pipe, tapering angle of the upriser pipe, and the submergence ratio, which is the ratio of immersed length to the total length of the upriser. The second group includes operating parameters such as the gas flow rate, bubble diameter, bubble distribution, and inlet gas pressure. In this research, the performance of an airlift pump is investigated numerically for different submergence ratios and different diameter of the upriser pipe. For this purpose, an...
Investigating optical properties of one-dimensional photonic crystals containing semiconductor quantum wells
, Article International Journal of Optics ; Volume 2017 , 2017 ; 16879384 (ISSN) ; Asgari, M ; Sabatyan, A ; Sharif University of Technology
Abstract
This study examined MQWs made of InGaAs/GaAs, InAlAs/InP, and InGaAs/InP in terms of their band structure and reflectivity. We also demonstrated that the reflectivity of MQWs under normal incident was at maximum, while both using a strong pump and changing incident angle reduced it. Reflectivity of the structure for a weak probe pulse depends on polarization, intensity of the pump pulse, and delay between the probe pulse and the pump pulse. So this system can be used as an ultrafast all-optical switch which is inspected by the transfer matrix method. After studying the band structure of the one-dimensional photonic crystal, the optical stark effect (OSE) was considered on it. Due to the OSE...
Different operational alternatives of aquifer thermal energy storage system for cooling and heating of a residential complex under various climatic conditions in Iran
, Article Scientia Iranica ; Volume 26, Issue 3B , 2019 , Pages 1281-1292 ; 10263098 (ISSN) ; Bahadori, M. N ; Saidi, M. H ; Sharif University of Technology
Sharif University of Technology
2019
Abstract
In this research, a confined aquifer with low groundwater flow was considered to meet the cooling and heating requirements of residential complexes. The complexes were located in the cities of Ahvaz, Ardabil, Bandar Abbas, Esfahan, Kerman, Rasht, Tehran, and Zahedan. The complex in Ardabil mostly required heating, the ones in Ahvaz and Bandar Abbas mostly required cooling, and the complexes in other cities required both heating and cooling. Four different alternatives of Aquifer Thermal Energy Storage (ATES) were analyzed in this study. These alternatives consisted of using ATES: 1) alone for cooling, 2) coupled with a conventional refrigeration system or a chiller for cooling, 3) by...
Different operational alternatives of aquifer thermal energy storage system for cooling and heating of a residential complex under various climatic conditions in Iran
, Article Scientia Iranica ; Volume 26, Issue 3B , 2019 , Pages 1281-1292 ; 10263098 (ISSN) ; Bahadori, M. N ; Saidi, M. H ; Sharif University of Technology
Sharif University of Technology
2019
Abstract
In this research, a confined aquifer with low groundwater flow was considered to meet the cooling and heating requirements of residential complexes. The complexes were located in the cities of Ahvaz, Ardabil, Bandar Abbas, Esfahan, Kerman, Rasht, Tehran, and Zahedan. The complex in Ardabil mostly required heating, the ones in Ahvaz and Bandar Abbas mostly required cooling, and the complexes in other cities required both heating and cooling. Four different alternatives of Aquifer Thermal Energy Storage (ATES) were analyzed in this study. These alternatives consisted of using ATES: 1) alone for cooling, 2) coupled with a conventional refrigeration system or a chiller for cooling, 3) by...
Thermal performance assessment of an evaporative condenser-based combined heat pump and humidification-dehumidification desalination system
, Article Desalination ; Volume 496 , 2020 ; Shafii, M. B ; Sharif University of Technology
Elsevier B.V
2020
Abstract
A new design for heat pump integrated humidification-dehumidification (HDH-HP) desalination cycles was proposed in the current experimental study. An evaporative condenser was designed and fabricated instead of a separate humidifier, heater, and air/water-cooled condensers find in previous HDH-HP systems. Meanwhile, the air dehumidification process in this work directly occurred inside the heat pump evaporator. The effect of several operating parameters such as ambient wet-bulb temperature, spraying saline water and airflow rates, compressor speed, superheat, and evaporator saturation temperature control modes of the electronic expansion valve (EEV) on freshwater production and GOR were...
In pursuit of a replacement for conventional high-density polyethylene tubes in ground source heat pumps from their composites – a comparative study
, Article Geothermics ; Volume 87 , September , 2020 ; Fatehifar, M ; Ghasempour, R ; Noorollahi, Y ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
Ground-source heat pumps, as the most environmentally friendly and energy-efficient air conditioning technology, suffer from a great required length of ground heat exchanger, partly arising from the low thermal conductivity of high-density polyethylene tubes commonly used in ground heat exchangers. In an attempt to find a replacement with an acceptable thermal conductivity for high-density polyethylene tubes, in this study, first, a comprehensive comparative study on fillers commonly used in thermally conductive polymer composites and resulting high-density polyethylene composites was conducted. Then, based on the advantages and disadvantages presented, an appropriate composite was selected...
Multi-evaporator Joule-Thomson cryogenic refrigeration cycles created by pumping and suction mechanisms
, Article Applied Thermal Engineering ; Volume 175 , 2020 ; Gholizadeh, T ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
Due to the simple structure and low production cost of Joule-Thomson (JT) refrigeration cycles, these cryogenic systems have widely been used in many food or medicine industries. However, in many scenarios, two or even three cryogenic temperatures are needed to simultaneously supply different cryogenic cooling loads since each product has its own comfort low-temperature range. In this case, multi-evaporator JT systems can be a promising solution to address several cryogenic temperatures via employing different evaporators. Following this objective, an innovative triple-evaporator JT cycle is proposed, where the pressure difference between evaporators is created via a pumping mechanism by...
A novel ground thermal recovery system for horizontal ground heat exchangers in a hot climate
, Article Energy Conversion and Management ; Volume 224 , 2020 ; Habibi, M ; Hakkaki Fard, A ; Sharif University of Technology
Elsevier Ltd
2020
Abstract
Ground Source Heat Pumps (GSHP), as a renewable source heating, ventilating, and air conditioning (HVAC) technology, has the highest energy efficiency among different heat pump types. One of the major drawbacks of GSHPs is the long-term ground temperature variations as a result of heat accumulation or depletion in the ground. This contribution puts forward a novel ground thermal recovery system for horizontal ground heat exchangers in a hot climate. The proposed recovery system consists of open-loop horizontal Ground-Air Heat Exchangers (GAHEs) that are buried between the horizontal Ground-Water Heat Exchangers (GWHEs). A fan supplies ambient air to the GAHE pipes when the soil around GWHE...