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    Covering orthogonal polygons with sliding k-transmitters

    , Article Theoretical Computer Science ; Volume 815 , May , 2020 , Pages 163-181 Mahdavi, S. S ; Seddighin, S ; Ghodsi, M ; Sharif University of Technology
    Elsevier B. V  2020
    Abstract
    In this paper, we consider a new variant of covering in an orthogonal art gallery problem where each guard is a sliding k-transmitter. Such a guard can travel back and forth along an orthogonal line segment, say s, inside the polygon. A point p is covered by this guard if there exists a point q∈s such that pq‾ is a line segment normal to s, and has at most k intersections with the boundary walls of the polygon. The objective is to minimize the sum of the lengths of the sliding k-transmitters to cover the entire polygon. In other words, the goal is to find the minimum total length of trajectories on which the guards can travel to cover the entire polygon. We prove that this problem is NP-hard... 

    The investigation of laser shock peening effects on corrosion and hardness properties of ANSI 316L stainless steel

    , Article International Journal of Advanced Manufacturing Technology ; Volume 88, Issue 5-8 , 2017 , Pages 1557-1565 ; 02683768 (ISSN) Ebrahimi, M ; Amini, S ; Mahdavi, S. M ; Sharif University of Technology
    Springer London  2017
    Abstract
    Laser shock peening (LSP) is known as a post processing surface treatment which can improve the mechanical properties of some materials. Shock waves are generated by confining the laser-induced plasma to cause a large pressure shock wave over a significant surface area. In the present study, effects of LSP on the electrochemical corrosion and micro hardness properties of 316L stainless steel alloy were investigated by changing the laser parameters such as the laser spot size, the average number of impacts, and the laser intensity. Since laser parameters do not cover the desired region of LSP, we have to use the proper design of experiment method, in which the D-optimal design of MATLAB was... 

    An efficient down-sampling method for multiresolution image completion

    , Article 2011 7th Iranian Conference on Machine Vision and Image Processing, MVIP 2011 - Proceedings ; 2011 ; 9781457715358 (ISBN) Shariatzadeh, S. M ; Kasaei, S ; Mahdavi Amiri, N ; Sharif University of Technology
    2011
    Abstract
    Image completion is an active subject in image and video processing, which deals with recovering the missing or removed parts of a given 2-D or 3-D data. Here, we present a method to efficiently build the multiresolution pyramid for a partially-missing image, by which, multiresolution image completion can be efficiently initialized and performed. Using this approach, we improve our previous algorithm for multiresolution image completion, especially when the inputs suffer spread missing areas. In comparison with the overall process of image completion, the computational and space complexity of the proposed method for building multiresolution pyramid is eligible. The obtained results of our... 

    Effects of paraffinic group on interfacial tension behavior of CO 2-asphaltenic crude oil systems

    , Article Journal of Chemical and Engineering Data ; Vol. 59, issue. 8 , 2014 , Pages 2563-2569 ; ISSN: 00219568 Mahdavi, E ; Zebarjad, F. S ; Taghikhani, V ; Ayatollahi, S ; Sharif University of Technology
    2014
    Abstract
    The interfacial tension (IFT) of a crude oil/CO2 system is recognized as the main property affecting the efficiency of CO2 flooding during an enhanced oil recovery (EOR) process. The addition of a paraffin group hydrocarbon to asphaltenic crude oils as an asphaltene precipitant component is aimed to mimic the asphaltene precipitation process during crude oil production and transportation. Asphaltene precipitation would critically affect the interfacial behavior of crude oil/CO2 systems. In the first part of this study, the equilibrium densities of oil samples which contain n-heptane at different ratios were measured over varying pressures at 323 K. Then, the equilibrium IFT between CO2 and... 

    Experimental investigation on the effect of asphaltene types on the interfacial tension of co2-hydrocarbon systems

    , Article Energy and Fuels ; Volume 29, Issue 12 , November , 2015 , Pages 7941-7947 ; 08870624 (ISSN) Mahdavi, E ; Zebarjad, F. S ; Ayatollahi, S ; Taghikhani, V ; Sharif University of Technology
    American Chemical Society  2015
    Abstract
    Interfacial tension (IFT) is known as the critical parameter affecting the efficiency of CO2 flooding during the enhanced oil recovery (EOR) process. Besides, the asphaltene precipitation phenomenon is reported as the most significant problem during CO2 injection into asphaltenic oil reservoirs. Accordingly, it is important to examine the effect of asphaltene precipitation on the IFT behavior of the oil-CO2 system at reservoir conditions. The main objective of this research work is to study of the effect of asphaltene and its type on the IFT behavior of the oil-CO2 system. The IFT between pure CO2 and a model oil both with and without asphaltene was measured using an axisymmetric drop shape... 

    Experimental Investigation on the Effect of Asphaltene Types on the Interfacial Tension of CO2-Hydrocarbon Systems

    , Article Energy and Fuels ; Volume 29, Issue 12 , 2015 , Pages 7941-7947 ; 08870624 (ISSN) Mahdavi, E ; Zebarjad, F. S ; Ayatollahi, S ; Taghikhani, V ; Sharif University of Technology
    American Chemical Society  2015
    Abstract
    Interfacial tension (IFT) is known as the critical parameter affecting the efficiency of CO2 flooding during the enhanced oil recovery (EOR) process. Besides, the asphaltene precipitation phenomenon is reported as the most significant problem during CO2 injection into asphaltenic oil reservoirs. Accordingly, it is important to examine the effect of asphaltene precipitation on the IFT behavior of the oil-CO2 system at reservoir conditions. The main objective of this research work is to study of the effect of asphaltene and its type on the IFT behavior of the oil-CO2 system. The IFT between pure CO2 and a model oil both with and without asphaltene was measured using an axisymmetric drop shape... 

    Optoelectrical and structural characterization of Cu2SnS3 thin films grown via spray pyrolysis using stable molecular ink

    , Article Solar Energy ; Volume 224 , 2021 , Pages 218-229 ; 0038092X (ISSN) Heidariramsheh, M ; Gharabeiki, S ; Mahdavi, S. M ; Taghavinia, N ; Sharif University of Technology
    Elsevier Ltd  2021
    Abstract
    This work focused on the spray pyrolysis deposition of Cu2SnS3 (CTS) thin films using a stable basic solution. The effect of the most important parameters including the substrate temperature and copper concentration on the structural, optical and electrical properties of as-deposited thin films was investigated. Qualified thin films with suitable microstructure and composition could be deposited at 370℃. XRD and Raman analysis while confirming the pure CTS film formation, show that as the Cu/Sn decreases, the crystal structure layers are changed from the tetragonal phase to the cubic phase mixed with Sn-rich phases. The optical study shows its band gap between 1.08 and 1.2 eV for different... 

    Clearing an orthogonal polygon to find the evaders

    , Article Theoretical Computer Science ; Volume 847 , December , 2020 , Pages 175-184 Mahdavi, S. S ; Ghodsi, M ; Sharif University of Technology
    Elsevier B. V  2020
    Abstract
    In a multi-robot system, a number of autonomous robots would sense, communicate, and decide to move within a given domain to achieve a common goal. In the pursuit-evasion problem, a polygonal region is given and a robot called a pursuer tries to find some mobile targets called evaders. The goal of this problem is to design a motion strategy for the pursuer such that it can detect all the evaders. In this paper, we consider a new variant of the pursuit-evasion problem in which the robots (pursuers) each moves back and forth along an orthogonal line segment inside a simple orthogonal polygon P. We assume that P includes unpredictable, moving evaders that have bounded speed. We propose the... 

    New half-pixel accuracy motion estimation algorithms for low bitrate video communications

    , Article Scientia Iranica ; Volume 15, Issue 6 , 2008 , Pages 507-516 ; 10263098 (ISSN) Mahdavi Nasab, H ; Kasaei, S ; Sharif University of Technology
    Sharif University of Technology  2008
    Abstract
    Fractional-pixel accuracy Motion Estimation (ME) has been shown to result in higher quality reconstructed image sequences in hybrid video coding systems. However, the higher quality is achieved by notably increased Motion Field (MF) bitrate and more complex computations. In this paper, new half-pixel block matching ME algorithms are proposed to improve the rate-distortion characteristics of low bitrate video communications. The proposed methods tend to decrease the required video bandwidth, while improving the motion compensation quality. The key idea is to put a deeper focus on the search origin of the ME process, based on center-bias characteristics of low bitrate video MFs. To employ the... 

    Half-pixel accuracy block matching motion estimation algorithms for low bitrate video communications

    , Article First IEEE and IFIP International Conference in Central Asia on Internet, 2005, Bishkek, 26 September 2005 through 28 September 2005 ; Volume 2005 , 2005 ; 0780391799 (ISBN); 9780780391796 (ISBN) Mahdavi Nasab, H ; Kasaei, S ; Sharif University of Technology
    2005
    Abstract
    Motion estimation at fractional-pixel accuracy results in higher quality video sequences. However, the higher quality is achieved by more computations and increased required motion field bitrates. In this paper, new half-pixel accuracy block matching-based motion estimation algorithms are proposed to improve the rate-distortion characteristics of low-bitrate video communications. The proposed methods especially tend to decrease the required video bandwidth, with no degradation in quality of reconstructed image sequences. The key idea is to put a deeper focus on the origin (zero motion) based on the center-bias characteristics of low bitrate video motion fields. The experimental results show... 

    An efficient adaptive interpolation scheme for fast mesh-based motion estimation

    , Article First IEEE and IFIP International Conference in Central Asia on Internet, 2005, Bishkek, 26 September 2005 through 28 September 2005 ; Volume 2005 , 2005 , Pages 4-7 ; 0780391799 (ISBN); 9780780391796 (ISBN) Mahdavi Nasab, H ; Kasaei, S ; Sharif University of Technology
    IEEE Computer Society  2005
    Abstract
    Motion estimation and compensation is an essential part of existing video coding systems. Compared to the widely used block-matching algorithms (BMA), the mesh-based motion estimation (MME) produces better subjective and objective qualified image sequences in many cases, especially at low bitrates. However, the iterative refinement step of the MME is computationally too expensive. In this paper, we propose a fast MME scheme, which adjusts its interpolation patterns to the motion features of image sequences to achieve higher quality reconstructed results. Experimental results show notable rate-distortion improvement over both the BMA and the conventional non-iterative MME schemes, especially... 

    Emerging bioengineering strategies for regulating stem cell fate: Scaffold physical and biochemical cues

    , Article Tissue Engineering: Current Status and Challenges ; 2022 , Pages 125-156 ; 9780128240649 (ISBN) Sharareh Mahdavi, S ; Mashayekhan, S ; Sharif University of Technology
    Elsevier  2022
    Abstract
    Stem cell therapy has been introduced as an emerging approach for injured tissue regeneration. This chapter addresses developing regenerative medicine techniques for controlling stem cell behavior. Recent studies have been reviewed and novel approaches have been divided into four main categories: 3D bioprinting, lithography, microfluidics, and electrospinning. Moreover, the impact of applied biophysical and/or biochemical cues to the designed scaffold on controlling stem cell activity has been discussed. The potential of using stem cells for various soft and hard tissue regenerations has been explored in different bioengineered scaffolds and the applied techniques for controlling stem cell... 

    Agent-based web service for the design of a dynamic coordination mechanism in supply networks

    , Article Journal of Intelligent Manufacturing ; Volume 20, Issue 6 , 2009 , Pages 727-749 ; 09565515 (ISSN) Mahdavi, I ; Mohebbi, S ; Zandakbari, M ; Cho, N ; Mahdavi Amiri, N ; Sharif University of Technology
    2009
    Abstract
    The theory of network coordination presents an effective approach to improve the business processes within supply networks. The automation of the negotiation process among buyers and suppliers has become an important policy in the transactional networks. This leads to assessing the roles of both quantifiable and non-quantifiable parameters in coordination mechanisms with the aim of achieving higher performance. Here, we develop an e-based supply chain multi-agent model for the design of mass-customized on-line services. The model addresses the bullwhip effect in multi-stage supply chain and also clarifies the evaluation of inventory policies in various supply and demand uncertainties. To... 

    Kinetics and mechanisms of nanoparticle formation and growth in vapor phase condensation process

    , Article Materials and Design ; Volume 28, Issue 3 , 2007 , Pages 850-856 ; 02613069 (ISSN) Simchi, A ; Ahmadi, R ; Reihani, S. M. S ; Mahdavi, A ; Sharif University of Technology
    Elsevier Ltd  2007
    Abstract
    Design of nanoparticle synthesis by inert-gas condensation process was studied according to the mechanisms and kinetics of nucleation and growth in the vapor phase. The effect of process parameters, e.g., source temperature, evaporation rate, and the inert-gas pressure, on the particle size and particle shape was examined at the example for silver and copper-tin alloy. The synthesized nanopowders had near spherical shape with particle size range from 10 to 60 nm dependent on the processing condition. Scanning and transmission electron microscopy (SEM and TEM) analyses showed that the crystallites are subunits of larger agglomerate particles, and relatively large particles display crystal... 

    Duality results and a dual simplex method for linear programming problems with trapezoidal fuzzy variables

    , Article Fuzzy Sets and Systems ; Volume 158, Issue 17 , 2007 , Pages 1961-1978 ; 01650114 (ISSN) Mahdavi Amiri, N ; Nasseri, S. H ; Sharif University of Technology
    2007
    Abstract
    Linear programming problems with trapezoidal fuzzy variables (FVLP) have recently attracted some interest. Some methods have been developed for solving these problems by introducing and solving certain auxiliary problems. Here, we apply a linear ranking function to order trapezoidal fuzzy numbers. Then, we establish the dual problem of the linear programming problem with trapezoidal fuzzy variables and hence deduce some duality results. In particular, we prove that the auxiliary problem is indeed the dual of the FVLP problem. Having established the dual problem, the results will then follow as natural extensions of duality results for linear programming problems with crisp data. Finally,... 

    Duality in fuzzy number linear programming by use of a certain linear ranking function

    , Article Applied Mathematics and Computation ; Volume 180, Issue 1 , 2006 , Pages 206-216 ; 00963003 (ISSN) Mahdavi Amiri, N ; Nasseri, S. H ; Sharif University of Technology
    2006
    Abstract
    We explore some duality properties in fuzzy number linear programming problems. By use of a linear ranking function we introduce the dual of fuzzy number linear programming primal problems. We then present several duality results. © 2006 Elsevier Inc. All rights reserved  

    On the suitability of modeling approaches for power electronic converters

    , Article International Symposium on Industrial Electronics 2006, ISIE 2006, Montreal, QC, 9 July 2006 through 13 July 2006 ; Volume 2 , 2006 , Pages 1486-1491 ; 1424404975 (ISBN); 9781424404971 (ISBN) Poshtan, M ; Kaboli, S ; Mahdavi, J ; Sharif University of Technology
    2006
    Abstract
    This paper is a summary and in-depth evaluation of some popular models for power electronic converters. Proper examples are given to support the evaluation with a complete comparison between the actual and simulated results. The paper presents the effort behind the design and analysis of DC-DC Converters and discuses their features. Some advantages and disadvantages of the studied models and the complicities of the nonlinear structure of the switching function of the converters are explained here. The paper offers some useful criteria for future selection and development on different DC-DC Converters. © 2006 IEEE  

    Duality in fuzzy variable linear programming

    , Article Wec 05: Fourth World Enformatika Conference, Istanbul, 24 June 2005 through 26 June 2005 ; Volume 6 , 2005 , Pages 115-117 ; 9759845857 (ISBN) Mahdavi Amiri, N ; Nasseri, S. H ; Sharif University of Technology
    2005
    Abstract
    Recently, fuzzy variable linear programming problems have attracted some interests. We introduce the dual of fuzzy variable linear programming problem, and then deduce some important duality results. COPYRIGHT © ENFORMATIKA  

    Engineered conducting polymer-based scaffolds for cell release and capture

    , Article International Journal of Polymeric Materials and Polymeric Biomaterials ; 2022 ; 00914037 (ISSN) Mahdavi, S. S ; Abdekhodaie, M. J ; Sharif University of Technology
    Taylor and Francis Ltd  2022
    Abstract
    Conducting polymer-based devices and scaffolds has become remarkably popular due to their properties such as conductivity, tunable electrochemical properties, and straightforward fabrication procedures. Hence, they have versatile applications and can be used as implants, biosensors, cell capture/release devices, and regenerative medicine scaffolds. This review addresses the effect of conductive polymers on cell behavior since their conductive features can be applied to simulate a cellular response. Moreover, the impact of polymer chemical and physical properties on cellular response has been discussed. Recent biomedical engineering approaches used for cell capture and release were reviewed... 

    Designing a dynamic buyer-supplier coordination model in electronic markets using stochastic petri nets

    , Article International Journal of Information Systems and Supply Chain Management ; Volume 1, Issue 3 , 2008 , Pages 1-20 ; 19355726 (ISSN) Mahdavi, I ; Mohebbi, S ; Cho, N ; Paydar, M. M ; Mahdavi Amiri, N ; Sharif University of Technology
    2008
    Abstract
    Functional relationship between supplier and buyer in an open market place leads to investigate the role of both quantifiable and non-quantifiable parameters in coordination mechanism with the aim of achieving higher performance in supply chain activities. Here, we develop a supply chain model and a new agent to analyze and simulate the players' behavior in the network. A cooperative game theory framework is utilized between buyer and supplier in order to increase the supply chain performance. The study is supported by presenting SC Net Optimizer as a tool for implementing the proposed coordination mechanism and evaluates the performance of the chain by simulation using stochastic Petri nets...