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    Abrupt PN Junctions: Analytical solutions under equilibrium and non-equilibrium

    , Article Solid-State Electronics ; Volume 122 , 2016 , Pages 37-44 ; 00381101 (ISSN) Khorasani, S ; Sharif University of Technology
    Elsevier Ltd  2016
    We present an explicit solution of carrier and field distributions in abrupt PN junctions under equilibrium. An accurate logarithmic numerical method is implemented and results are compared to the analytical solutions. Analysis of results shows reasonable agreement with numerical solution as well as the depletion layer approximation. We discuss extensions to the asymmetric junctions. Approximate relations for differential capacitance C-V and current-voltage I-V characteristics are also found under non-zero external bias  

    Improved passivity criterion in haptic rendering: influence of coulomb and viscous friction [electronic resource]

    , Article Advanced Robotics ; 2014 Volume 28, Issue 10 Mashayekhi, A. (Ahmad) ; R. Bozorgmehry, R ; Nahvi, A ; Meghdari, A ; Asgari, P ; Sharif University of Technology
    In this paper, a new criterion for passivity of haptic devices is obtained. This criterion creates a relationship between Coulomb friction coefficient, viscous friction coefficient, sampling rate, and the maximum simulated stiffness. The process of derivation of the passivity criterion is described in detail. This criterion is improved compared with other existing criteria and predicts passivity in haptic rendering more accurately. In particular, for speeds of less than 5 cm/s, the new passivity criterion should replace the previous criteria to avoid unwanted vibrations of stiff virtual walls. Analytical and numerical investigations are presented to validate the new criterion. A specific... 

    Nonlinear charging and transport times in doped nanotubes junctions

    , Article Journal of the Physical Society of Japan ; Volume 74, Issue 2 , 2005 , Pages 515-518 ; 00319015 (ISSN) Esfarjani, K ; Farajian, A. A ; Kawazoe, Y ; Chui, S. T ; Sharif University of Technology
    The nonlinear capacitance in doped nanotube junctions is calculated self consistently. A negative differential capacitance is observed when the applied bias becomes larger than the pseudogap of the metallic armchair nanotube. For this device, one can deduce a relaxation time of approximately 0.1 fs. Because of its negative differential resistance (NDR), a switching time of less than a femtosecond, i.e., at least three orders smaller than present-day switching times, can also be estimated. This effect is important in designing ultrafast nano-electronic components. ©2005 The Physical Society of Japan  

    Design of a robotic cameraman with three actuators for laparoscopic surgery

    , Article Proceedings of Frontiers in Biomedical Devices Conference, NanoBio06, Irvine, CA, 8 June 2006 through 9 June 2006 ; Volume 2006 , 2006 Mirbagheri, A ; Farahmand, F ; Meghdari, A ; Sayyaadi, H ; Savoj, L ; Mirbagheri, E ; Sharif University of Technology
    American Society of Mechanical Engineers  2006

    Interference management in D2D-enabled heterogeneous cellular networks using matching theory

    , Article IEEE Transactions on Mobile Computing ; 2018 ; 15361233 (ISSN) Shamaei, S ; Bayat, S ; Hemmatyar, A. M. A ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2018
    To support the increasing data traffic demand in wireless communications networks, a multi-tier architecture that consists of multiple small cells is adopted in traditional (macro) cellular networks. Nevertheless, due to the expansion of various wireless devices and services, there is still a need to increase the network capacity in new generation networks such as 5G. Hence, the integration of Device-to-Device (D2D) communication as a promising technology with heterogeneous networks has been proposed. This integration not only increases network capacity but also improves spectral efficiency and alleviates the traffic load of base stations. However, the co/cross-tier interferences between D2D... 

    Dual-pipe damper

    , Article Journal of Constructional Steel Research ; Volume 85 , 2013 , Pages 81-91 ; 0143974X (ISSN) Maleki, S ; Mahjoubi, S ; Sharif University of Technology
    In this paper, a new passive earthquake energy dissipative device, called the dual-pipe damper (DPD), is introduced, tested and analytically studied. The device consists of two pipes welded at selected locations and loaded in shear. The inelastic cyclic deformation dissipates energy mainly through flexure of the pipe body. However, at large displacements a tension diagonal forms in the middle of the device which further adds to stiffness and strength. The strength, stiffness and energy dissipation of the DPD is more than two single pipe dampers that were previously studied. Cyclic quasi-static tests were performed on four samples of DPD. Excellent ductility, energy absorption and stable... 

    Efficient Offloading in Ambient Cloud

    , M.Sc. Thesis Sharif University of Technology Golkarifard, Morteza (Author) ; Movaghar Rahimabadi, Ali (Supervisor)
    Execution speed seriously bothers application developers and users for wearable devices such as Google Glass. Intensive applications like Mobile Augmented Reality (MAR) suffer from significant delays when CPU is busy. Energy is another concern when the devices are in low battery level but users need them for urgency use. To ease such pains, one approach is to expand the computational power by cloud offloading. This paradigm works well when the available Internet access has enough bandwidth. Another way, however, is to leverage nearby devices for computation offloading, which is known as device-to-device (D2D) offloading. In this paper, we present Dandelion, a unified code offloading system... 

    Carbon nanotube-based nano-fluidic devices

    , Article Journal of Physics D: Applied Physics ; Vol. 47, issue. 8 , 2014 ; ISSN: 00223727 Masoud Seyyed Fakhrabadi, M ; Rastgoo, A ; Ahmadian, M. T ; Sharif University of Technology
    The paper investigates the influences of fluid flow on static and dynamic behaviours of electrostatically actuated carbon nanotubes (CNTs) using strain gradient theory. This nonclassical elasticity theory is applied in order to obtain more accurate results possessing higher agreement with the experimental data. The effects of various fluid parameters such as the fluid viscosity, velocity, mass and temperature on the pull-in properties of the CNTs with two cantilever and doubly clamped boundary conditions are studied. The results reveal the applicability of the proposed nano-system as nano-valves or nano-fluidic sensors  

    Nonlinear analysis of carbon nanotube-based nanoelectronics devices

    , Article Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science ; Vol. 228, issue. 13 , 2014 , p. 2426-2439 Fakhrabadi, M. M. S ; Rastgoo, A ; Ahmadian, M. T ; Sharif University of Technology
    The paper deals with the investigation of nonlinear static and dynamic behaviors of electrostatically actuated carbon nanotubes with different geometries and boundary conditions. The deflection and pull-in properties are studied in detail in the presence of DC and combined DC+AC electrostatic voltages accompanying the interatomic interactions. The considered nano system can be applied in a wide range of nanoelectronics devices such as nano switches, nano resonators, nano transistors, nano capacitors and random access memories. Moreover, a useful mathematical model of the nano sensor application of the studied nano system to sense the stiffness of the nano particles is presented  

    Highly efficient and stable perovskite solar cells based on a low-cost carbon cloth

    , Article Advanced Energy Materials ; Volume 6, Issue 20 , 2016 ; 16146832 (ISSN) Gholipour, S ; Correa Baena, J. P ; Domanski, K ; Matsui, T ; Steier, L ; Giordano, F ; Tajabadi, F ; Tress, W ; Saliba, M ; Abate, A ; Morteza Ali, A ; Taghavinia, N ; Grätzel, M ; Hagfeldt, A ; Sharif University of Technology
    Wiley-VCH Verlag  2016
    A low-cost carbon cloth is applied in perovskite solar cells (PSC) as a collector composite and degradation inhibitor. This study incorporates carbon fibers as a back contact in perovskite solar cells, which results in enhancement in all photovoltaic parameters. This material is suitable for large-scale fabrication of PSCs as it has shown an improved long-term stability when compared to the gold counterpart under elevated temperatures  

    Improving sit-to-stand transition by the saddle-assistive device in the spinal cord injury: A case study

    , Article Proceedings of the Institution of Mechanical Engineers, Part H: Journal of Engineering in Medicine ; Volume 235, Issue 7 , 2021 , Pages 735-742 ; 09544119 (ISSN) Hojjati Najafabadi, A ; Amini, S ; Farahmand, F ; Sharif University of Technology
    SAGE Publications Ltd  2021
    Physical problems caused by fractures, aging, stroke, and accidents can reduce foot power; these, in the long term, can dwindle the muscles of the waist, thighs, and legs. These conditions provide the basis for the invalidism of the harmed people. In this study, a saddle-walker was designed and evaluated to help people suffering from spinal cord injury and patients with lower limb weakness. This S-AD works based on body weight support against the previously report designs. This saddle-walker consisted of a non-powered four-wheel walker helping to walk and a powered mechanism for the sit-to-stand (STS) transfer. A set of experiments were done on the STS in the use of the standard walker and... 

    Rapid design space exploration of DSP applications using programmable SOC devices - A case study

    , Article 15th Annual IEEE International ASIC/SOC Conference, ASIC/SOC 2002, 25 September 2002 through 28 September 2002 ; Volume 2002-January , 2002 , Pages 273-277 ; 10630988 (ISSN); 0780374940 (ISBN) Hashempour, M ; Sharifì, S ; Gudarzi, M ; Hessabi, S ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2002
    In this paper, we present results of our experiments in implementation of a widely used DSP primitive on a programmable SoC (System-on-a-Chip) Device. The DSP primitive is a 16-bit digital FIR filter which we implemented on Triscend E5 CSoC® family. Experimental results show that by properly breaking the DSP task into hardware and software parts, one can achieve higher throughput compared to DSP processor implementations, while having more flexibility and less time-to-design compared to full-hardware realizations. Programmable SoC device facilitates rapid design-space exploration, which we employed to optimize our mixed hardware-software architecture. We compared our filter throughput to... 

    Flopcoin: a cryptocurrency for computation offloading

    , Article IEEE Transactions on Mobile Computing ; 2017 ; 15361233 (ISSN) Chatzopoulos, D ; Ahmadi, M ; Kosta, S ; Hui, P ; Sharif University of Technology
    During the last years, researchers have proposed solutions to help smartphones improve execution time and reduce energy consumption by offloading heavy tasks to remote entities. Lately, inspired by the promising results of message forwarding in opportunistic networks, many researchers have proposed strategies for task offloading towards nearby mobile devices, giving birth to the Device-to-Device offloading paradigm. None of these strategies, though, offers any mechanism that considers selfish users and, most importantly, that motivates and defrays the participating devices who spend their resources. In this paper, we address these problems and propose the design of a framework that... 

    Modified distributed mediation device for low power consumption in large scale sensor networks

    , Article 2nd International Conference on Intelligent Sensing and Information Processing, ICISIP'05, Chennai, 4 January 2005 through 7 January 2005 ; Volume 2005 , 2005 , Pages 7-12 ; 0780388402 (ISBN); 9780780388406 (ISBN) Shahmansouri, V ; Ghannad Rezaie, M ; Pakravan, H. R ; Sharif University of Technology
    This paper proposes a new medium-access control (MAC) protocol designed for wireless sensor networks. A wireless sensor network is an array of large number of sensors interconnected by a multi-hop ad-hoc network. The fundamental objective for sensor network is low-power consumption while latency is usually less important. This characteristic of sensor network motivates different MAC laver design from the conventional wireless network to reduce power consumption. In this paper novel algorithm based on distributed mediation device (DMD) protocol has been introduced that utilized distributed node scheduling strategy to dramatically increase energy saving principally in intermediate devices... 

    Performance analysis of network coding-based content delivery in dual interface cellular networks

    , Article 2018 Iran Workshop on Communication and Information Theory, IWCIT 2018, 25 April 2018 through 26 April 2018 ; 2018 , Pages 1-6 ; 9781538641491 (ISBN) Amerimehr, M. H ; Shariatpanahi, S. P ; Jafari Siavoshani, M ; Ashtiani, F ; Mazoochi, M ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2018
    We consider a group of mobile users, in closed proximity, who are interested in downloading a common content (e.g., a video file). We address a cooperative solution where each mobile device is equipped with both cellular and Wi-Fi interfaces. The users exploit the cellular link to download different shares of the content from the based-station and leverage on Wi-Fi link to exchange the received data. In order to expedite content delivery, the base-station transmits random linear network-coded data to users. This paper presents an analytical study of the average completion time, i.e., the time necessary for all devices to successfully retrieve the data. We propose an analytical model to... 

    Microfluidics-Enabled multimaterial maskless stereolithographic bioprinting

    , Article Advanced Materials ; Volume 30, Issue 27 , 2018 ; 09359648 (ISSN) Miri, A. K ; Nieto, D ; Iglesias, L ; Goodarzi Hosseinabadi, H ; Maharjan, S ; Ruiz Esparza, G. U ; Khoshakhlagh, P ; Manbachi, A ; Dokmeci, M. R ; Chen, S ; Shin, S. R ; Zhang, Y. S ; Khademhosseini, A ; Sharif University of Technology
    Wiley-VCH Verlag  2018
    A stereolithography-based bioprinting platform for multimaterial fabrication of heterogeneous hydrogel constructs is presented. Dynamic patterning by a digital micromirror device, synchronized by a moving stage and a microfluidic device containing four on/off pneumatic valves, is used to create 3D constructs. The novel microfluidic device is capable of fast switching between different (cell-loaded) hydrogel bioinks, to achieve layer-by-layer multimaterial bioprinting. Compared to conventional stereolithography-based bioprinters, the system provides the unique advantage of multimaterial fabrication capability at high spatial resolution. To demonstrate the multimaterial capacity of this... 

    Microfluidic devices as invitro microenvironments for -stem cell culture

    , Article Proceedings of the IASTED International Conference on Biomedical Engineering, BioMed 2014 ; 2014 , pp. 83-88 Shamloo, A ; Abeddoust, M ; Mehboudi, N ; Sharif University of Technology
    Many potential therapies are currently being studied that may promote neural regeneration and guide regenerating axons to form correct connections following injury. It has been shown that adult neurons have some limited regenerative capabilities, and the lack of connection formation between neurons is not an intrinsic inability of these cells to form axons after being damaged, but rather the inhibitory microenvironment of the injured tissue prevents regeneration. In this study, the polarization and chemotaxis of neuronal stem cells (NSC) in response to quantified gradients of nerve growth factor (NGF) was examined. To accomplish this, a microfluidic device was designed and fabricated to... 

    Neuronal cell navigation within a microfluidic device

    , Article Middle East Conference on Biomedical Engineering, MECBME ; 17-20 February , 2014 , pp. 261-264 Shamloo, A ; Sharif University of Technology
    In this study, the polarization and navigation of neuronal cells was studied in response to quantified gradients of nerve growth factor (NGF). To accomplish this, a microfluidic device was designed and fabricated to generate stable concentration gradients of biomolecules in a cell culture chamber within a 3D microenvironment. Numerical simulation was implemented to optimize the device geometry for generating a uniform concentration gradient of NGF which was found to remain stable for multiple hours. Neural Stem/ Progenitor Cell (NSCs) migration and differentiation was studied within this microfluidic device in response to NGF concentration and within a 3D environment of collagen matrix.... 

    Maximum clique-based resource allocation in device-to-device communications

    , Article IEEE International Symposium on Personal, Indoor and Mobile Radio Communications, PIMRC, 30 August 2015 through 2 September 2015 ; Volume 2015-December , Sept , 2015 , Pages 1195-1200 ; 9781467367820 (ISBN) Elhami, G ; Zehni, M ; Pakravan, M. R ; Sharif University of Technology
    Institute of Electrical and Electronics Engineers Inc  2015
    Device-to-Device communication (D2D) integrated in cellular networks emerges as a new trend in response to notable rise in traffic demand. Resource allocation is one of the important challenges in deployment of D2D networks. In this paper, we formulate an optimization problem for optimal resource allocation and then propose a novel algorithm namely maximum clique based resource allocation (MCRA) for improving the spectral reuse based on graph theoretic concept of maximum clique. Practical application of D2D communications requires each node to receive and transmit signals during the communication process. We have considered this issue in constructing the interference graph and mathematical... 

    Numerical optimization and inverse study of a microfluidic device for blood plasma separation

    , Article European Journal of Mechanics, B/Fluids ; Volume 57 , 2016 , Pages 31-39 ; 09977546 (ISSN) Shamloo, A ; Vatankhah, P ; Bijarchi, M. A ; Sharif University of Technology
    Elsevier Ltd  2016
    In this paper, a passive microfluidic device for continuous real time blood plasma separation has been studied and optimized. A numerical model is used to solve both the fluid flow and the particles confined within it. Red blood cells are considered as particles with diameter of 7μm. A parametric study is performed in order to characterize the effect of different parameters on separation and purity efficiency. In this study, four different variables were introduced to design the microfluidic device for blood plasma separation including: the angle between the daughter channels and the main channel, the widths, the diffuse angle and the number of daughter channels. Results show that the...