مجله رایانش نرم و فناوری اطلاعات
سال ششم شماره 2 (پاییز و زمستان 1396)

Based on the researches performed on search engines, most user queries contain more than one word. For queries with more than one word, two models can be presented. In the first model, query words are assumed to be independent of each other, and in the second model, the place and the order of words are assumed to be dependent. Experiments show that there are dependencies among most query words. One of the parameters that can determine the dependency between query words is the distance between the query words in the document. In this paper, a new distance definition based on the minimum displacement of the document words in order to match the query is presented. Also, given that most ranking algorithms use the word frequency in the documents (Term Frequency) to score the documents and since there is no clear definition for this parameter for queries with more than one word; in this paper, the frequency of the occurrence of a phrase (Phrase Frequency) and Inverted Document Frequency are defined according to the new concept of distance and the proper algorithms are presented to calculate them. Also, the results of the proposed algorithm are compared with the algorithm implemented by the open source Lucene indexer, which shows a good increase in the mean accuracy

Abstract- In this paper, a novel model is proposed to solve dynamic expansion planning of resources and electrical transmission network in multi carrier energy systems. In the proposed model, optimal capacity and sitting of generation resources as well as new electrical transmission lines are determined for a multi-year horizon. The considered optimization problem aiming at minimizing the total operation and capital costs is formulated as a mixed integer linear program (MILP) model and then is solved by mathematical method. Impacts of modeling of electrical transmission network on expansion planning in the presence of combined heat and power (CHP) and thermal furnaces are investigated in an integrated system consisting of various multi carriers. Network losses, overall system efficiency and system reliability are used as metrics to analysis performance of the proposed model. Simulation results confirm that the way for modeling of electric network has important influence on expansion of resources as well as operation costs of CHP

Intelligent optimization methods effectively explore and review the response space using past experiences a population of search agents. These population-based techniques can solve complex optimization problems with a defined number of iterations. This paper evaluates the performance of different types of common and powerful optimization algorithms in the system identification problem in order to optimal design and modeling of Infinite Impulse Response digital filters. Assumed methods include the Genetic Algorithm and Differential Evolution both based on evolutionary strategy along with six swarm intelligence algorithms, Particle Swarm Optimization, Gravitational Search Algorithm, Inclined Planes system Optimization, Ant Lion Optimizer, Teaching-Learning-Based Optimization, and, for the first time, Biogeography-Based Optimization. In the present study, the IIR system identification problem is assumed as a single-objective optimization function. It is evaluated for two experimental and challenging IIR models for the equivalent and reduced order modeling. To evaluate the efficiency and performance of the algorithms, the simulation results are evaluated in terms of Indicator of Success and Degree of Reliability with Mean Square Error. Also, the effect of reducing search agents on the performance of algorithms is analyzed. The overall estimation of the results confirms the acknowledgment of the effectiveness of the proposed evaluation indexes and the desirable performance of the proposed methods, especially for the PSO, IPO and BBO algorithms in terms of convergence characteristics, average runtime, average values of MSE, and IoS and DoR indices; GA and GSA algorithms in terms of convergence, runtime and DoR; DE method for running time; ALO algorithm for the mean of MSE, and TLBO algorithm in terms of the convergence characteristics, mean IoS, and DoR percent

Among renewable energies, wind energy is considered as the least costly source of available energy. Savonius wind turbine is a vertical axis wind turbine type which its performance is not dependent on wind direction. In this paper, the effect of overlap ratios in the common semi-cylindrical Savonius wind turbine is investigated with a new attitude. In this regard, positive and negative overlap ratios are considered by maintaining the rotor diameter. Numerical modeling is conducted using Ansys-Fluent commercial software and sliding mesh method. Simulations are carried out by using RANS method and Realizable K-ε turbulence model. By examining the velocity contours around the blades in different overlap ratios, it is found that the perturbation is higher in the circumference of the blades with negative overlap ratios. This reduces the useful net momentum. Moreover, according to the torque and power coefficients, it is found that in general, geometry with an overlap ratio of 0.15 could be more appropriate

In this paper, an online Persian isolated letter recognition by using discrete Markov models and language-based features is presented. In the proposed method, the preprocessing includes the extraction of dots, the removal of ending-bends, the normalization of the main body dimension, and the main body smoothing. The direction of the pen for the main body, and also the location and the number of secondary movements and dots of letters are used as the observable features in order to train and test models. No alphabet grouping has been used in the proposed method. In order to produce appropriate discrete observation sequences for the hidden Markov models, the proposed codebook is based on the characteristics of the Persian language. To improve the recognition accuracy, the proposed post-processing checks the recognized character in terms of the number and location of the secondary movements and dots. The final recognition rate is obtained more than 98% for the test dataset and outperforms other methods applied to this dataset

With the increasing growth of multimedia communications on the Internet, on the one hand, and with the expansion of deployment of wireless networks on the other hand, the quality of video transmission on these networks has become a major challenge. The 802.11e standard proposes a framework to provide the Quality of Service (QoS) in accordance with the type of traffic and which is used by next variants of the standard, namely, 802.11n and 802.11ac. One of the channel access mechanisms in this standard is EDCA, which has predicted four separate queues for different types of traffic. This mechanism defines distinct channel access parameters in each queue. In this paper, a dynamic method is provided for tunning the access parameters in each queue, such as the size of the Contention Window (CW), and Arbitration Inter-Frame Space (AIFS), which calculates their decrease or increase based on the varying network conditions. However, the average collision rate is used to determine the network load conditions. This criterion is calculated with a weighted average of each queue at each station and updated every time the packet is sent. The simulation results in NS2 indicate that the proposed method improves the quality of video transmission from the point of view of multiple criteria, including PSNR, throughput, packet loss rate and the end-to-end delay

In this paper, designing a neuro-fuzzy controller for generalized unified power flow controller (GUPFC) to improve transient stability has been investigated. For this purpose, a controllable compensator has been designed by using lyapunov stability criterion to increase transient stability margin and damp transient oscillation in such systems. Since transient energy function of system is a suitable tool for investigating the stability issue, optimization of GUPFC energy function has been noticed in order to reach the highest margin of transient stability. This idea is the basis of producing required teaching information in ANFIS network and can be used as a GUPFC controller. In this paper, the impact of GUPFC on single machine system, infinite bus (SMIB) and 9-bus system (Anderson and Fouad, 1977) has been studied by using proposed method. Moreover, by simulating the other FACTS devices such as UPFC and IPFC, the priority of GUPFC was proved. Keywords