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Fuzzy hierarchical location-allocation models for congested systems [electronic resource]
, Article Scientia Iranica ; January 2006, Scientia Iranica, Vol. 13, No. 1, pp. 14-24 Journal of Industrial and Systems Engineering ; 2007, Vol. 1 No. 2, pp 171-189 ; Mahlouji, Hashem ; Eshghi, Kourosh ; Khanmohammadi, S ; Sharif Universitty Of Technology
Abstract
There exist various service systems that have hierarchical structure. In hierarchical service networks, facilities at different levels provide different types of services. For example, in health care systems, general centers provide low-level services such as primary health care services, while the specialized hospitals provide high-level services. Because of demand congestion in service networks, location of servers and allocation of demand nodes have a strong impact on the length of queues at servers as well as on the response times to service calls. The thrust of this article is the development of hierarchical location-allocation models for congested systems by employing queueing theory...
A cellular cardiac matrix-based porous microcarrier as a cell delivery system in myocardial tissue engineering application
, Article Iranian Polymer Journal (English Edition) ; Volume 31, Issue 9 , 2022 , Pages 1079-1091 ; 10261265 (ISSN) ; Mashayekhan, S ; Khanmohammadi, M ; Sharif University of Technology
Springer Science and Business Media Deutschland GmbH
2022
Abstract
Myocardial infarction (MI) causes a high mortality rate in the world every year. Myocardial tissue engineering using extracellular matrix-derived substrate and cytocompatible biopolymers is a promising approach for treating MI. Besides, injectable porous microspheres are developing engineer constructs to use as dual-purpose microcarriers for cell culture and injectable scaffolds in trivial invasiveness for tissue implantation. This study aimed to fabricate porous microcarriers composed of myocardial extracellular matrix and chitosan using an electrospraying technique. The effect of electrospraying parameters, including extracellular matrix/chitosan ratio and voltage, on MCs diameter was...
A Framework to Evaluate the Resilience of Hospitals
, M.Sc. Thesis Sharif University of Technology ; Kashani, Hamed (Supervisor)
Abstract
In the aftermath of earthquakes, hospitals serve the critical role of treating casualties and reducing mortalities and severe injuries. A hospital must be resilient to play its role correctly after the earthquake. A resilient hospital is able to maintain its functionality at an acceptable level and provide service to the injured. In order to enhance the resilience of a hospital, an appropriate framework is needed to evaluate the hospital resilience and determines the impact of modification actions. This framework should characterize the serviceability of a hospital in terms of an appropriate metric. In this framework, the behavior of a given hospital building in the event of an earthquake as...
A system dynamics approach to the seismic resilience enhancement of hospitals
, Article International Journal of Disaster Risk Reduction ; Volume 31 , 2018 , Pages 220-233 ; 22124209 (ISSN) ; Farahmand, H ; Kashani, H ; Sharif University of Technology
Elsevier Ltd
2018
Abstract
In the aftermath of earthquakes, hospitals serve the critical role of treating casualties. In many cases, the key components of a hospital (i.e., the building, staff, medicine inventory, technical systems, and medical equipment) are affected by an earthquake. To handle the demand surge, affected hospitals should recover in an effective manner. Hospital recovery is a complex and dynamic process because each component requires specific types and amount of resources to recover. Furthermore, the recovery of each component not only affects its performance but also plays a role in the overall hospital recovery. Hospital administrators need to model the complex recovery process after a future...
On the existence of nowhere-zero vectors for linear transformations
, Article Bulletin of the Australian Mathematical Society ; 2010 , Pages 1-8 ; 00049727 (ISSN) ; Hassani Monfared, K ; Jamaali, M ; Khanmohammadi, E ; Kiani, D ; Sharif University of Technology
2010
Abstract
A matrix A over a field F is said to be an AJT matrix if there exists a vector x over F such that both x and Ax have no zero component. The Alon-Jaeger-Tarsi (AJT) conjecture states that if F is a finite field, with |F|≥4, and A is an element of GL n (F), then A is an AJT matrix. In this paper we prove that every nonzero matrix over a field F, with |F|≥3, is similar to an AJT matrix. Let AJTn (q) denote the set of n×n, invertible, AJT matrices over a field with q elements. It is shown that the following are equivalent for q≥3 : (i) AJTn (q)=GL n (q) ; (ii) every 2n×n matrix of the form (A{divides}B)t has a nowhere-zero vector in its image, where A,B are n×n, invertible, upper and lower...
Production of uniform size cell-enclosing silk derivative vehicles through coaxial microfluidic device and horseradish crosslinking reaction
, Article European Polymer Journal ; Volume 172 , 2022 ; 00143057 (ISSN) ; Hosseini, M ; Varaa, N ; Mahmoodi, N ; Goodarzi, A ; Taghdiri Nooshabadi, V ; Hassanzadeh, S ; Arabpour, Z ; Khanmohammadi, M ; Sharif University of Technology
Elsevier Ltd
2022
Abstract
Silk fibroin (SF) as a natural biopolymer holds great potential in biomedical research because of its biocompatibility, easy processability and high strength properties. However, slow gelation time has narrowed its applications, specifically in cell-laden microparticle production due to insufficient crosslinkable moieties. This study aimed to develop cell-laden silk fibroin-phenol (SF-Ph) microparticle through co-flow microfluidic system using SF conjugated Ph moieties whereas covalent crosslinking is mediated with horseradish peroxidase (HRP) in the presence of hydrogen peroxide (H2O2). For this, the SF-Ph was synthesized through carbodiimide condensation crosslinking reaction. Aqueous...
Design, Fabrication and Evaluation of Polymeric Microcapsules Containing Cells to Use in Cell Therapy in Heart
, M.Sc. Thesis Sharif University of Technology ; Mashayekhan, Shohreh (Supervisor) ; Sharifi, Ali Mohammad (Supervisor) ; Khanmohammadi, Mehdi (Co-Supervisor)
Abstract
Because of the inability of conventional methods to regenerate the infarcted part of the heart, regenerative medicine based on using scaffolds and hydrogels incorporation with cells and biological factors emerges as a promising approach. Micro-structures, especially hollow microcapsules created by the microfluidic system, has received a great deal of attention due to their inspired biomimetic structures, providing complete coverage cells, and preventing an immune response, consequently. This study aimed to use a microfluidic system to fabricate hollow microcapsules and investigate the behavior of rat cardiomyoblast cells (H9C2) along with exosomes within these structures. These structures'...
The relationship between an EFL teacher's gender and students' willingness to communicate
, Article International Journal of Communication and Linguistic Studies ; Volume 10, Issue 4 , 2013 , Pages 17-29 ; 23277882 (ISSN) ; Pakzadian, S. S
Common Ground Publishing
2013
Abstract
Learning a foreign language encompasses a process of trial and error that can lead to the progression of the learner's interlanguage, meaning that the learners make use of their language knowledge that receives feedback and brings about progress through diagnosis of the problems and being corrected by the teacher. Therefore, there exists a need to analyze the underlying reasons causing the students to remain taciturn with a low willingness to communicate (WTC) during a language class. There has been much work done investigating the role of the learner's stable personal characteristics (traits) along with their situational changes at a specific time (states) that influence the student's...
An automated simple algorithm for realistic pore network extraction from micro-tomography images
, Article Journal of Petroleum Science and Engineering ; Vol. 123, issue , 2014 , pp. 164-171 ; ISSN: 09204105 ; Jamshidi, S ; Salehi, S
2014
Abstract
Using 3-D scanned data to analyze and extract pore network plays a vital role in investigation of porous media's characteristics. In this paper, a new simple method is developed to detect pores and throats for analyzing the connectivity and permeability of the network. This automated method utilizes some of the common and well-known image processing functions which are widely accessible by researchers and this has led to an easy algorithm implementation. In this method, after polishing and quality control of images, using city-block distance function and watershed segmentation algorithm, pores and throats are detected and 3-D network is produced. This method can also be applied on 2-D images...
Discrimination of heart arrhythmias using novel features in heart rate phase space
, Article Computing in Cardiology ; Volume 40 , Sept , 2013 , Pages 1035-1038 ; 23258861 (ISSN); 9781479908844 (ISBN) ; Rezaei, S ; Salavatian, S
2013
Abstract
In this paper, we try to recognize and distinguish different groups of arrhythmia using novel features which have been obtained from the heart rate's phase space in recent years. For this purpose, we used Triangular Phase Space Mapping (TPSM) and Parabolic Phase Space Mapping (PPSM). For recognition, we used three groups of 15 subjects using the Physionet database (Arrhythmia, Congestive Heart Failure (CHF), and Atrial Fibrillation (AF)) with Normal Sinus Rhythm (NSR). The obtained features discriminate arrhythmia from NSR by p
An intelligent hybrid classification algorithm integrating fuzzy rule-based extraction and harmony search optimization: Medical diagnosis applications
, Article Knowledge-Based Systems ; Volume 220 , 2021 ; 09507051 (ISSN) ; Abdullah, S ; Akhavan Niaki, S. T ; Banihashemi, S ; Sharif University of Technology
Elsevier B.V
2021
Abstract
Uncertainty is a critical factor in medical datasets needed to be overcome for increasing diagnosis efficiency. This paper proposes an intelligent classification algorithm comprising a fuzzy rule-based approach, a harmony search (HS) algorithm, and a heuristic algorithm to classify medical datasets intelligently. Two fuzzy approaches, as well as orthogonal and triangular fuzzy sets, are first utilized to define the attributes of data. Then, an HS algorithm is integrated with a heuristic to generate fuzzy rules to select the best rules in the fuzzy rule-based systems. Moreover, to improve the performance of the proposed classification approach, a three-phase parameter tuning approach is...
Performance evaluation of shared hosting security methods
, Article Proc. of the 11th IEEE Int. Conference on Trust, Security and Privacy in Computing and Communications, TrustCom-2012 - 11th IEEE Int. Conference on Ubiquitous Computing and Communications ; 2012 , Pages 1310-1315 ; 9780769547459 (ISBN) ; Arshad, S ; Khoshkdahan, S ; Sharif University of Technology
2012
Abstract
Shared hosting is a kind of web hosting in which multiple websites reside on one webserver. It is cost-effective and makes the administration easier for websites' owners. However, shared hosting has some performance and security issues. In default shared hosting configuration, all websites' scripts are executed under the webserver's user account regardless of their owners. Therefore, a website is able to access other websites' resources. This security problem arises from lack of proper isolation between different websites hosted on the same webserver. In this survey, we have examined different methods for handling mentioned security issue. Also we evaluated the performance of mentioned...
The behaviour of an artificially cemented sandy gravel
, Article Geotechnical and Geological Engineering ; Volume 23, Issue 5 , 2005 , Pages 537-560 ; 09603182 (ISSN) ; Hosseini, S. M ; Toll, D. G ; Yasrebi, S. S ; Sharif University of Technology
2005
Abstract
The major section of the city of Tehran, Iran has been developed on cemented coarse-grained alluvium. This deposit consists of gravely sand to sandy gravel with some cobbles and is dominantly cemented by carbonaceous materials. In order to understand the mechanical behaviour of this soil, a series of undrained triaxial compression tests and unconfined compression tests were performed on uncemented and artificially cemented samples. Portland cement type I was used as the cementation agent for preparing artificially cemented samples. Uncemented samples and lightly cemented samples (1.5% cement) tested at high confining pressure showed contractive behaviour accompanied with positive excess pore...
An imperialist competitive algorithm approach for multi-objective optimization of direct coupling photovoltaic-electrolyzer systems
, Article International Journal of Hydrogen Energy ; Vol. 39, Issue 33 , 11 November , 2014 , pp. 18743-18757 ; ISSN: 03603199 ; Sayedin, F ; Khavas, S. S
2014
Abstract
In the context of sustainable clean hydrogen production pathways, photovoltaic-electrolyzer systems are one of the most promising alternatives for acquiring hydrogen from renewable energy sources. In fact, determining the optimal set of design and operating variables are always a key issue while coupling directly renewable electricity sources to PEM electrolyzers. Few previous studies have attempted to find the optimal size and operational condition of directly coupled photovoltaic-electrolyzer (PV/El) systems in order to maximize the hydrogen production or to minimize energy transfer loss between photovoltaic devices and the electrolyzer. Nevertheless an easy and efficient approach still...
Kalman filter based packet loss replacement in presence of additive noise
, Article 2012 25th IEEE Canadian Conference on Electrical and Computer Engineering: Vision for a Greener Future, CCECE 2012 ; 2012 ; 9781467314336 (ISBN) ; Ghorshi, S ; Tahaei, A
2012
Abstract
A major problem in real-time packet-based communication systems, is misrouted or delayed packets which results in degraded perceived voice quality. If packets are not available on time, the packets are considered as lost. The easiest solution in a network terminal receiver is to replace silence for the duration of lost speech segments. In a high quality communication system, to avoid degradation in speech quality due to packet loss, a suitable method or algorithm is needed to replace the missing segments of speech. In this paper, we introduce an adaptive filter for replacement of lost speech segment. In this method Kalman filter as a state-space based method will be used to predict the...
Investigation of Mesh Sensitivity Influence to Determine Crack Characteristic by Finite Element Methods
, Article Journal of Failure Analysis and Prevention ; Volume 16, Issue 3 , 2016 , Pages 506-512 ; 15477029 (ISSN) ; Mirjavadi, S. S ; Asli, S. A ; Sharif University of Technology
Springer New York LLC
2016
Abstract
In this research, an extended finite element model has been investigated. Investigation of opening and closure stress always has been one of the difficult parameters to analysis of results; therefore, the utilization of finite element methods would be a good and logical alternative for this purpose. In addition, linear elastic fracture criteria are used for validation of numerical results from the simulation. In this work, a detailed analysis of the influence of different parameters in the results of a specific specimen with a semi-elliptical tooling groove in terms of closure and opening stress is presented, and the impact of optimum element size in fracture characteristic in various load...
Investigation of the effect of nanosilica on rheological, thermal, mechanical, structural, and piezoelectric properties of poly(vinylidene fluoride) nanofibers fabricated using an electrospinning technique
, Article Industrial and Engineering Chemistry Research ; Volume 56, Issue 44 , 2017 , Pages 12596-12607 ; 08885885 (ISSN) ; Ahmad Ramazani, S. A ; Talebi, S ; Fattahpour, S ; Hasany, M ; Sharif University of Technology
2017
Abstract
The effects of different nano-SiO2 contents on the rheological properties of poly(vinylidene fluoride) (PVDF) solution and mechanical, thermal, structural, and piezoelectric properties of composite nanofibers were investigated. Results showed an increase in fiber diameter (∼125 to 350 nm) and ∼450% increase in tensile strength as the content of nano-SiO2 particles increased. The degree of crystallinity decreased by 19% as the nano-SiO2 content increased by 2% (w/w). Further investigation demonstrated that silica could significantly improve the piezoelectric properties of PVDF nanofibers as the output voltage showed an increase in the presence of silica attributed to change in the crystalline...
A method for real-time safe navigation in noisy environments
, Article 2013 18th International Conference on Methods and Models in Automation and Robotics, MMAR 2013, Miedzyzdroje ; 2013 , Pages 329-333 ; 9781467355063 (ISBN) ; Kamali, E ; Niknezhad, M. R ; Monfared, S. S. M. S ; Sharif University of Technology
2013
Abstract
The challenge of finding an optimized and reliable path dates back to emersion of mobile robots. Several approaches have been developed that have partially answered this need. Satisfying results in previous implementations has led to an increased utilization of sampling-based motion planning algorithms in recent years, especially in high degrees of freedom (DOF), fast evolving environments. Another advantage of these algorithms is their probabilistic completeness that guarantees delivery of a path in sufficient time, if one exists. On the other hand, sampling based motion planners leave no comment on safety of the planned path. This paper suggests biasing the Rapidly-exploring Random Trees...
A generalization of the swartz equality
, Article Glasgow Mathematical Journal ; Vol. 56, issue. 2 , May , 2014 , pp. 381-386 ; ISSN: 00170895 ; Fakhari, S. A. S ; Yassemi, S ; Sharif University of Technology
2014
Abstract
For a given (d-1)-dimensional simplicial complex Γ, we denote its h-vector by h(Γ)=(h 0(Γ),h 1(Γ),...,hd (Γ)) and set h -1(Γ)=0. The known Swartz equality implies that if Δ is a (d-1)-dimensional Buchsbaum simplicial complex over a field, then for every 0 ≤ i ≤ d, the inequality ihi (Δ)+(d-i+1)h i-1(Δ) ≥ 0 holds true. In this paper, by using these inequalities, we give a simple proof for a result of Terai (N. Terai, On h-vectors of Buchsbaum Stanley-Reisner rings, Hokkaido Math. J. 25(1) (1996), 137-148) on the h-vectors of Buchsbaum simplicial complexes. We then generalize the Swartz equality (E. Swartz, Lower bounds for h-vectors of k-CM, independence, and broken circuit complexes, SIAM J....
Hardware-in-the-loop optimization of an active vibration controller in a flexible beam structure using evolutionary algorithms
, Article Journal of Intelligent Material Systems and Structures ; Vol. 25, issue. 10 , 2014 , p. 1211-1223 ; Hosseini Kordkheili, S. A ; Afshari, S. S ; Sharif University of Technology
2014
Abstract
In this study, active vibration control of a cantilevered flexible beam structure equipped with bonded piezoelectric sensor/actuators is investigated. The linear quadratic regulator technique together with an observer is adopted to design the controller as well as to provide the full-state feedback. Two different approaches are subsequently used for simultaneously integrated optimization of the controller and observer parameters. In the first approach, a linear experimental model of the system is obtained using identification techniques, and the optimization is then performed based on a computer simulation of the system. However, in the second approach, a hardware-in-the-loop optimization...