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**Search for:**problem-solving

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Total 398 records

#### The Role of Proof and Reasoning in Solving Real-Life Math Problems

, M.Sc. Thesis Sharif University of Technology ; Zohuri-Zangeneh, Bijan (Supervisor) ; Gooya, Zahra (Supervisor)
Abstract

The purpose of the present study was to investigate the Grade 9 students' ability to solve real-life and modelling problems, focusing on proof and reasoning. The study conducted using qualitative method in which, six volunteer students participated. The data collected via eight problems mostly chosen from Chapter 3 of the 9th grade mathematics textbook and using Adobe Connect Platform, because of Covid-19 Pandemic and schools clousure. The data were analyzed using a problem solving framework developed by Mason, Burton and Stacey (2010) including three stages of entry, attack and review. The results showed that considering these three steps, is effective to understand students' problem...

#### Has "The Work and Technology Course" in the Elementary School and Guidance School Paid Enough Attention to Improve Technological Thinking?

, M.Sc. Thesis Sharif University of Technology ; Taghavi, Mostafa (Supervisor)
Abstract

It has been five years since the new education system was started, according to which fundamental changes have been applied to school text books. The mentioned changes in the text books are based on “the fundamental transformation document” and “Iran’s national educational curriculum”. In “Iran’s national educational curriculum”, eleven fields concerning pedagogy and learning are explicitly mentioned; one of these eleven fields is “training and learning work and technology”. One of the merits which has been stressed in this field, is “technological thinking”. Nowadays, methods of extending and reinforcing the technological thinking have come to be the subject of investigations in many...

#### WiP: Floating xy-yx: An efficient thermal management routing algorithm for 3d nocs

, Article 16th IEEE International Conference on Dependable, Autonomic and Secure Computing, IEEE 16th International Conference on Pervasive Intelligence and Computing, IEEE 4th International Conference on Big Data Intelligence and Computing and IEEE 3rd Cyber Science and Technology Congress, DASC-PICom-DataCom-CyberSciTec 2018, 12 August 2018 through 15 August 2018 ; 2018 , Pages 730-735 ; 9781538675182 (ISBN) ; Shirmohammadi, Z ; Rohbani, N ; Farbeh, H ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2018

Abstract

3D Network-on-Chips (3D NoCs) have higher scalability, higher throughput, and lower power consumption over 2D NoCs. However, the reliability of data transfer in 3D NoCs is seriously threatened by thermal problems. This is due to poor heat dissipation, inappropriate traffic distribution, and cooling restriction for layers away of the chip heat-sink in 3D NoCs. To solve this problem, this paper proposes an efficient deadlock-free and traffic-And thermal-Aware routing algorithm, called Floating XY-YX. The main idea behind Floating XY-YX routing algorithm is twofold: 1) to use XY and YX routing algorithms in consecutive layers in dessicate form, and 2) to evenly load the traffic, which is...

#### Wide-band VHF nulling by five elements spiral array antenna

, Article ITST 2006 - 2006 6th International Conference on ITS Telecommunications, Proceedings, Chengdu, 21 June 2006 through 23 June 2006 ; 2006 , Pages 446-448 ; 0780395867 (ISBN); 9780780395862 (ISBN) ; Mousavi, M ; Emadi, M ; Nayebi, M. M ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2006

Abstract

Genetic algorithm for optimization of beam forming in spiral array antenna is used. The goal is to achieve a -20 dB in null over the wide frequency band. Our simulation shows -20 dB over 75 MHz Null Band width, in VHF band. © 2006 IEEE

#### What's decidable about availability languages?

, Article 35th IARCS Annual Conference on Foundations of Software Technology and Theoretical Computer Science, FSTTCS 2015, 16 December 2015 through 18 December 2015 ; Volume 45 , 2015 , Pages 192-205 ; 18688969 (ISSN) ; 9783939897972 (ISBN) ; Atig, M. F ; Meyer, R ; Salehi, M. S ; Harsha P ; Ramalingam G ; Sharif University of Technology
Schloss Dagstuhl- Leibniz-Zentrum fur Informatik GmbH, Dagstuhl Publishing
2015

Abstract

We study here the algorithmic analysis of systems modeled in terms of availability languages. Our first main result is a positive answer to the emptiness problem: it is decidable whether a given availability language contains a word. The key idea is an inductive construction that replaces availability languages with Parikh-equivalent regular languages. As a second contribution, we solve the intersection problem modulo bounded languages: given availability languages and a bounded language, it is decidable whether the intersection of the former contains a word from the bounded language. We show that the problem is NP-complete. The idea is to reduce to satisfiability of existential Presburger...

#### Weak composite Diffie-Hellman

, Article International Journal of Network Security ; Volume 7, Issue 3 , 2008 , Pages 383-387 ; 1816353X (ISSN) ; Mohajeri, J ; Salmasizadeh, M ; Sharif University of Technology
2008

Abstract

In1985, Shmuley proposed a theorem about intractability of Composite Diffie-Hellman. The theorem of Shmuley may be paraphrased as saying that if there exist a probabilistic polynomial time oracle machine which solves the Diffie-Hellman modulo an RSA-number with odd-order bases then there exist a probabilistic algorithm which factors the modulo. In the other hand Shmuely proved the theorem only for odd-order bases and left the even-order case as an open problem. In this paper we show that the theorem is also true for even-order bases. Precisely speaking we prove that even if there exist a probabilistic polynomial time oracle machine which can solve the problem only for even-order bases still...

#### Vulnerability take grant (VTG): an efficient approach to analyze network vulnerabilities

, Article Computers and Security ; Volume 26, Issue 5 , 2007 , Pages 349-360 ; 01674048 (ISSN) ; Jalili, R ; Sharif University of Technology
2007

Abstract

Modeling and analyzing information system vulnerabilities help predict possible attacks to computer networks using vulnerabilities information and the network configuration. In this paper, we propose a comprehensive approach to analyze network vulnerabilities in order to answer the safety problem focusing on vulnerabilities. The approach which is called Vulnerability Take Grant (VTG) is a graph-based model consists of subject/objects as nodes and rights/relations as edges to represent the system protection state. Each node may have properties including single vulnerabilities such as buffer overflow. We use the new concept of vulnerability rewriting rule to specify the requirements and...

#### VSPACE: VNF simultaneous placement, admission control and embedding

, Article IEEE Journal on Selected Areas in Communications ; Volume 36, Issue 3 , 2018 , Pages 542-557 ; 07338716 (ISSN) ; Parsaeefard, S ; Maddah Ali, M. A ; Mahmoodi, T ; Khalaj, B. H ; Sharif University of Technology
Institute of Electrical and Electronics Engineers Inc
2018

Abstract

In future wireless networks, network functions virtualization lays the foundations for establishing a new dynamic resource management framework to efficiently utilize network resources. In this paper, a network service can be viewed as a chain of virtual network functions (VNFs), called a service function chain (SFC), served via placement, admission control (AC), and embedding into network infrastructure, based on the resource management objectives and the state of network. To fully exploit such a potential and reach higher network performance, resource management stages should be jointly performed. To this end, two main challenges are: how to present a system model that formulates the...

#### Visibility testing and counting

, Article Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics), 28 May 2011 through 31 May 2011, Jinhua ; Volume 6681 LNCS , 2011 , Pages 343-351 ; 03029743 (ISSN) ; 9783642212031 (ISBN) ; Zarei, A ; Sharif University of Technology
2011

Abstract

For a set of n disjoint line segments S in R2, the visibility counting problem (VCP) is to preprocess S such that the number of visible segments in S from a query point p can be computed quickly. For this configuration, the visibility testing problem (VTP) is to test whether p sees a fixed segment s. These problems can be solved in logarithmic query time by using O(n4) preprocessing time and space. In this paper, we approximately solve this problem using quadratic preprocessing time and space. Our methods are superior to current approximation algorithms in terms of both approximation factor and preprocessing cost. In this paper, we propose a 2-approximation algorithm for the VCP using at...

#### Vibration-based identification of impact force using genetic algorithm

, Article 2nd International Operational Modal Analysis Conference, IOMAC 2007, Copenhagen, 30 April 2007 through 2 May 2007 ; 2007 ; 9788791606144 (ISBN) ; Hashemi, R ; Sharif University of Technology
Aalborg University
2007

Abstract

Presented within this paper is the identification of impact force acting on a simply supported beam. The force identification is an inverse problem in which the measured response of the structure is used to determine the applied force. The identification problem is formulated as an optimization problem and genetic algorithm is utilized to solve the optimization problem. The objective function is calculated on the difference between analytical and measured responses and the decision variables are the location and magnitude of the applied force. The results from simulation show the effectiveness of the approach and its robustness to the measurement noise and sensor location

#### Variable structure control with adaptive fuzzy sliding surface

, Article JVC/Journal of Vibration and Control ; Volume 12, Issue 11 , 2006 , Pages 1251-1270 ; 10775463 (ISSN) ; Talasaz, A ; Sharif University of Technology
2006

Abstract

An adaptive fuzzy sliding mode control scheme is presented in this article. Despite the advantages of sliding mode control design for uncertain dynamic systems, classical sliding mode control has a major problem in the form of chattering, produced by the rapid switching used to conduct the state trajectories toward the sliding surfaces. A variety of methods are used to achieve chattering-free motion by smoothing out the switching functions; a fuzzy method is introduced in this article. In the proposed approach, the switching functions are replaced by adaptive fuzzy control signals such that the Lyapunov stability conditions are satisfied. This adaptive fuzzy controller can improve the...

#### Valuation of dynamic reactive power support in multitransaction power systems

, Article European Transactions on Electrical Power ; Volume 17, Issue 1 , 2007 , Pages 61-79 ; 1430144X (ISSN) ; Vakilian, M ; Feuillet, R ; Hadj Said, N ; Sharif University of Technology
2007

Abstract

This paper presents a reactive power valuation method with regard to its effect on realization of MW transactions. The security constraint optimization model in which the objective function is maximization of transactions is solved by the genetic algorithm approach. The proposed scheme allocates a specific amount of MW transactions to each dynamic reactive power source. An index is introduced to derive VAr value from the calculated optimal parameters of power network. This index represents the system-wide effect of MVAr sources on MW transactions implementations. Application of proposed method has been illustrated using IEEE 30 and 14 bus test systems. Results are discussed and compared in...

#### Utilizing distributed learning automata to solve stochastic shortest path problems

, Article International Journal of Uncertainty, Fuzziness and Knowlege-Based Systems ; Volume 14, Issue 5 , 2006 , Pages 591-615 ; 02184885 (ISSN) ; Meybodi, M. R ; Sharif University of Technology
2006

Abstract

In this paper, we first introduce a network of learning automata, which we call it as distributed learning automata and then propose some iterative algorithms for solving stochastic shortest path problem. These algorithms use distributed learning automata to find a policy that determines a path from a source node to a destination node with minimal expected cost (length). In these algorithms, at each stage distributed learning automata determines which edges to be sampled. This sampling method may result in decreasing unnecessary samples and hence decreasing the running time of algorithms. It is shown that the shortest path is found with a probability as close as to unity by proper choice of...

#### Using neural network for solving of on-line economic dispatch problem

, Article CIMCA 2006: International Conference on Computational Intelligence for Modelling, Control and Automation, Jointly with IAWTIC 2006: International Conference on Intelligent Agents Web Technologies and International Commerce, Sydney, NSW, 28 November 2006 through 1 December 2006 ; 2006 , Pages 87- ; 0769527310 (ISBN); 9780769527314 (ISBN) ; Varahram, M. H ; Sharif University of Technology
IEEE Computer Society
2006

Abstract

In this study, two methods for solving economic dispatch problems, namely Hopfield neural network and X iteration method are compared. Three sample of power system with 3, 6 and 20 units have been considered. The time required for CPU, for solving economic dispatch of these two systems has been calculated. It has been shown that for on-line economic dispatch, Hopfield neural network is more efficient and the time required for convergence is considerably smaller compared to classical methods. © 2006 IEEE

#### Using fuzzy logic theory to improve construction productivity

, Article Proceedings, Annual Conference - Canadian Society for Civil Engineering, 10 June 2008 through 13 June 2008, Quebec City, QC ; Volume 1 , 2008 , Pages 585-596 ; 9781605603964 (ISBN) ; Dehghan, R ; Khoramshahi, F ; Sharif University of Technology
2008

Abstract

Fuzzy logic is a powerful problem-solving methodology that provides a remarkably simple way to draw definite conclusions from vague, ambiguous or imprecise information. This study is a review on the possibility of developing a tool to help site managers and planners in selecting the most suitable actions for construction productivity improvement in a complex construction site, using fuzzy logic theory. Improving productivity can have a large impact on the overall construction process and consequently result in significant time and cost savings, i.e. minimizing capital cost on the construction projects. Problems associated with productivity measurement such as "lack of a standard productivity...

#### Using description logics for network vulnerability analysis

, Article International Conference on Networking, International Conference on Systems and International Conference on Mobile Communications and Learning Technologies, ICN/ICONS/MCL'06, Morne, 23 April 2006 through 29 April 2006 ; Volume 2006 , 2006 ; 0769525520 (ISBN); 9780769525525 (ISBN) ; Jalili, R ; Abolhassani, H ; Shahriari, H. R ; Sharif University of Technology
2006

Abstract

The distributed nature and complexity of computer networks and various services provided via them, makes the networks vulnerable to numerous attacks. The TCP/IP presumptions which are based on using this protocol to provide a simple, open communication infrastructure in an academic and collaborative environment, causes this protocol lack of built-in mechanisms for authentication, integrity and privacy. Even though in the last few years a more systematic approach to TCP/IP network security problem has been followed, a formal approach to this problem is lacking. In this paper, we propose using Description Logics as a formal model which could be used to analyze TCP/IP networks against attacks....

#### Unsupervised grammar induction using history based approach

, Article Computer Speech and Language ; Volume 20, Issue 4 , 2006 , Pages 644-658 ; 08852308 (ISSN) ; Ghassem Sani, G ; Sharif University of Technology
2006

Abstract

Grammar induction, also known as grammar inference, is one of the most important research areas in the domain of natural language processing. Availability of large corpora has encouraged many researchers to use statistical methods for grammar induction. This problem can be divided into three different categories of supervised, semi-supervised, and unsupervised, based on type of the required data set for the training phase. Most current inductive methods are supervised, which need a bracketed data set for their training phase; but the lack of this kind of data set in many languages, encouraged us to focus on unsupervised approaches. Here, we introduce a novel approach, which we call...

#### Unit commitment using particle swarm-based-simulated annealing optimization approach

, Article 2007 IEEE Swarm Intelligence Symposium, SIS 2007, Honolulu, HI, 1 April 2007 through 5 April 2007 ; 2007 , Pages 297-302 ; 1424407087 (ISBN); 9781424407088 (ISBN) ; Hajian, M ; Zamani, M ; Sharif University of Technology
2007

Abstract

In this paper, a new approach based on hybrid Particle Swarm-Based- Simulated Annealing Optimization (PSO-B-SA) for solving thermal unit commitment (UC) problems is proposed. The PSO-B-SA presented in this paper solves the two sub-problems simultaneously and independently; unit-scheduled problem that determines on/off status of units and the economic dispatch problem for production amount of generating units. Problem formulation of UC is defined as minimization of total objective function while satisfying all the associated constraints such as minimum up and down time, production limits and the required demand and spinning reserve. Simulation results show that the proposed approach can...

#### Two parameter tuned multi-objective evolutionary algorithms for a bi-objective vendor managed inventory model with trapezoidal fuzzy demand

, Article Applied Soft Computing Journal ; Volume 30 , May , 2015 , Pages 567-576 ; 15684946 (ISSN) ; Akhavan Niaki, S. T ; Sharif University of Technology
Elsevier Ltd
2015

Abstract

This paper presents a bi-objective vendor managed inventory (BOVMI) model for a supply chain problem with a single vendor and multiple retailers, in which the demand is fuzzy and the vendor manages the retailers' inventory in a central warehouse. The vendor confronts two constraints: number of orders and available budget. In this model, the fuzzy demand is formulated using trapezoidal fuzzy number (TrFN) where the centroid defuzzification method is employed to defuzzify fuzzy output functions. Minimizing both the total inventory cost and the warehouse space are the two objectives of the model. Since the proposed model is formulated into a bi-objective integer nonlinear programming (INLP)...

#### Two-machine flow shop scheduling to minimize the sum of maximum earliness and tardiness

, Article International Journal of Production Economics ; Volume 122, Issue 2 , 2009 , Pages 763-773 ; 09255273 (ISSN) ; Mirzaee, M ; Vasei, M ; Modarres, M ; Azaron, A ; Sharif University of Technology
2009

Abstract

This paper presents optimal scheduling in a two-machine flow shop, in which the objective function is to minimize the sum of maximum earliness and tardiness (n/2/P/ETmax). Since this problem tries to minimize earliness and tardiness, the results can be useful for different production systems such as just in time (JIT). This objective function has already been considered for n jobs and m machines, but the proposed algorithms are not efficient to solve large scale problems. In this paper, neighborhood conditions are developed and the dominant set for any optimal solution is determined. The branch-and-bound (B&B) method is used to solve the problem and the proper upper and lower bounds are also...