A heuristic homotopic path simplification algorithm

, Article Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics), 20 June 2011 through 23 June 2011 ; Volume 6784 LNCS, Issue PART 3 , June , 2011 , Pages 132-140 ; 03029743 (ISSN) ; 9783642219306 (ISBN) Daneshpajouh, S ; Ghodsi, M ; Sharif University of Technology

2011

Abstract

We study the well-known problem of approximating a polygonal path P by a coarse one, whose vertices are a subset of the vertices of P. In this problem, for a given error, the goal is to find a path with the minimum number of vertices while preserving the homotopy in presence of a given set of extra points in the plane. We present a heuristic method for homotopy-preserving simplification under any desired measure for general paths. Our algorithm for finding homotopic shortcuts runs in O( mlog(n + m) + nlogn log(nm) + k) time, where k is the number of homotopic shortcuts. Using this method, we obtain an O(n 2 + mlog(n + m) + nlogn log(nm)) time algorithm for simplification under the Hausdorff...

A note on the minimum interval cost flow problem

, Article Applied Mathematics and Computation ; Volume 217, Issue 17 , 2011 , Pages 7051-7052 ; 00963003 (ISSN) Daneshpajouh, H ; Alimomeni, M ; Sharif University of Technology

2011

Abstract

We reduce the problem of minimum interval cost flow problem (MICFP) introduced by Hashemi et al. (2006) to the well-known minimum cost flow problem (MCFP)

Algorithms for Path Simplification

, Ph.D. Dissertation Sharif University of Technology Daneshpajouh, Shervin (Author) ; Ghodsi, Mohammad (Supervisor)

Abstract

In this thesis, we present different algorithms for path simplification. We first study this problem under area measures. We present an approximation algorithm for sum-area measure and an optimal algorithm for diff-area measure. Both of these algorithms can be applied on general paths. Moreover, we study the homotopic path simplification. We present a general framework for path simplification which work for desired error measure. We first present a strongly homotopic simplification algorithm for x-monotone paths. Also, we study the strongly homotopic simplification for general paths. We present a geometric tree data structure and present an algorithm based on this data structure....

Modeling of Dynamic Kill in Gas-Condensate Well

, M.Sc. Thesis Sharif University of Technology Daneshpajouh, Abouzar (Author) ; Shad, Saeed (Supervisor)

Abstract

By exploring huge gas-condensate reservoirs, three-phase transient flow modeling demonstrates its crucial role in designing dynamic kill, relief well parameters and kill procedure of such wells. Controlling gas-condensate well needs robust transient three phase models capable of capturing discontinuities in density, geometry and velocity of phases. In this paper, two phase Advection-Upstream-Splitting-Method hybrid scheme is extended to three-phase model capable of modeling blowout and dynamic kill in gas-condensate-water wells. Density and viscosity changes are calculated using Peng-Robinson equation of state and in according, flow model parameters are corrected.The capability of this model...

Computing polygonal path simplification under area measures

, Article Graphical Models ; Volume 74, Issue 5 , September , 2012 , Pages 283-289 ; 15240703 (ISSN) Daneshpajouh, S ; Ghodsi, M ; Zarei, A ; Sharif University of Technology

2012

Abstract

In this paper, we consider the restricted version of the well-known 2D line simplification problem under area measures and for restricted version. We first propose a unified definition for both of sum-area and difference-area measures that can be used on a general path of n vertices. The optimal simplification runs in O(n 3) under both of these measures. Under sum-area measure and for a realistic input path, we propose an approximation algorithm of O n2 time complexity to find a simplification of the input path, where is the absolute error of this algorithm compared to the optimal solution. Furthermore, for difference-area measure, we present an algorithm that finds the optimal...

Path simplification under difference area measure

, Article 2009 14th International CSI Computer Conference, CSICC 2009, 20 October 2009 through 21 October 2009, Tehran ; 2009 , Pages 276-279 ; 9781424442621 (ISBN) Daneshpajouh, S ; Zarei, A ; Ghodsi, M ; Sharif University of Technology

2009

Abstract

In this paper, we consider path simplification problem under difference area (diff-area) measure. Diff-area measure is defined as AA(Q) AB(Q) , where AA(Q) is the area under Q and above P and AB(Q) is the area above Q and under P (sec Figure 1). Bose et al. [1] presented an approximation algorithm for finding a simplificd path with at most k verticcs that minimizes the cliff-area measure which only works on i-monotone paths. The constraint of being i-monotone is restrictive in some applications like tracking bird migration paths or map boundary simplification. Here, we extend the method of Rosc et al. [1] and present algorithms with the same time complexities as theirs for gcneral paths....

A fast community based algorithm for generating web crawler seeds set

, Article WEBIST 2008 - 4th International Conference on Web Information Systems and Technologies, Funchal, Madeira, 4 May 2008 through 7 May 2008 ; Volume 2 , 2008 , Pages 98-105 ; 9789898111265 (ISBN) Daneshpajouh, S ; Nasiri, M. M ; Ghodsi, M ; Sharif University of Technology

2008

Abstract

In this paper, we present a new and fast algorithm for generating the seeds set for web crawlers. A typical crawler normally starts from a fixed set like DMOZ links, and then continues crawling from URLs found in these web pages. Crawlers are supposed to download more good pages in less iterations. Crawled pages are good if they have high PageRanks and are from different communities. In this paper, we present a new algorithm with O(n) running time for generating crawler's seeds set based on HITS algorithm. A crawler can download qualified web pages, from different communities, starting from generated seeds set using our algorithm in less iteration

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) Khosravizadeh, P ; 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 Rabbani, A ; 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) Moharreri, S ; 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) Mousavi, S. M ; 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) Mirheidari, S. A ; 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) Haeri, S. M ; 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 Maroufmashat, A ; 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) Miralavi, S. R ; 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) Azimi, M ; 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) Haddadi, S. A ; 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) Neyshabouri, S. A. S ; 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 Pournaki, M. R ; 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 Nobahari, H ; 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...