فهرست مطالب

  • Volume:6 Issue:1, 2018
  • تاریخ انتشار: 1397/03/04
  • تعداد عناوین: 10
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  • Saeed Ranjbaran *, Alireza Roudbari, Saeed Ebadollahi Pages 1-6

    Using field calibration methods without precision laboratory equipment, systematic faults of inertial sensors can be reduced and measurement accuracy can be increased. In this paper, a simple and fast method called improved least squares is used to find calibration coefficients of an accelerometer including bias, scale factor and non-orthogonality. Simulation results show that the measurement accuracy has improved by about 60%. In this method, this principal is used that the magnitude of acceleration measured by accelerometer in static condition is equal to the magnitude of gravity vector and a cost function is then defined. Also, in gyroscope field calibration, sensor is rotated manually around all three axes separately and then it is put in the static mode. Changes in the angle obtained from gyroscope at each movement are compared with the ones obtained from the calibrated accelerometer. Calibration coefficients including bias and scale factor are obtained using least squares method. Simulation results show that accuracy of the gyroscope has increased by about 40% and comparison with the other methods proves that the proposed method performs well.

    Keywords: Accelerometer, Gyroscope, Bias, Scale factor, Non-orthogonality
  • Hashem Firoozi *, Mohsen Imanieh Pages 7-14

    In this article the function of solar cells with the structure of CuIn1xGaxSe2 is examined. CIGS solar cell consists of layers of ZnO (Layer TCO), Cd_S (buffer layer), CIGS (Absorbent layer), and Layer MO (Substrate), which Cd_S and CIGS layers form a PN Junction. CIGS Thin Film Solar Cell is simulated using SILVACO software. The absorbent layer doping was originally changed. Later doping was kept constant and P-type layer of InAsP was added. Their effect on cell function was observed and examined. It was observed that after doping some parameters of the solar cell have improved whilst some others had decreased. It was also concluded that examined increase of decrease in the amount of dopant would reduce our efficiencies of solar cell. Added the InAsP layer leads to increased open circuit voltage, short circuit current and the solar cell power, consequently gives the yields about 33.2%, which is acceptable efficiency.

    Keywords: Solar cell, CIGS, InAsP, Absorbent, Doping
  • Mohammad Abdolahi *, Morteza Zahedi Pages 15-24

    Discourse coherence modeling evaluation becomes a critical but challenging task for all content analysis tasks in Natural Language Processing subfields, such as text summarization, question answering, text generation and machine translation. Existing methods like entitybased and graph-based models are engaging in semantic and linguistic concepts of a text and cannot solve the problem very well. Since they are only very limited to available word co-occurrence information in the sequential sentences within a short part of a text. One of the greatest challenges of the above methods is their limitation in long documents coherence evaluation and being suitable for documents with low number of sentences. Our proposed method focuses on both local and global coherence. It can also assess the local topic integrity of text at the paragraph level regardless of word meaning and handcrafted rules. The global coherence in the proposed method is evaluated by sequence paragraph dependency. Applying statistical approaches and based on recent results in word embeddings, the presented method studies how to incorporate the external word correlation knowledge into short and long stories to assess both local and global coherence, simultaneously. Using the effect of combined word2vec vectors and most likely n-grams, we show that our proposed method does not depend on the language and its semantic concepts. Results indicate that the proposed method is superior to other algorithms in terms of performance, accuracy in long documents with a high number of sentences.

    Keywords: Local text coherence, Global text coherence, Word vector, Word embeddings, Word2vec algorithm
  • Farshid Yousefi Moghadam*, Behnam Afzali, Farshad Nadi, Rohullah Zallbeygi Pages 25-32

    In this paper, a microstrip lowpass filter with an ultra-wide stopband with sharp roll-off and compact size is designed and fabricated. To provide a very small dimension, T-shaped and stepped impedance have been used. The cut of frequency at -3 dB is 3.1 GHz. In the proposed structure, insertion loss is less than 0.12 and return loss is more than 15 dB. To achieve a -20dB attenuation level in the stopband, modified L-shaped structure is utilized. This filter has an ultra-wide stopband that is expanded from 3.37 GHz to 37.5 GHz also the suppression level is greater than -20dB. The size of the fabricated LPF is about 16.6 * 13.5 mm2 which corresponds to an electrical of 0.28ƛg * 0.22ƛg, where ƛg is the guided wavelength at 3.1 GHz, which is very small. The proposed filter is designed, simulated, optimized, fabricated and measured. There is good agreement between the simulated and measured results.

    Keywords: Microstrip filter, Low pass filter, Sharp roll-off, Ultra wide stopband, T-shaped structure
  • Azin Saberi nejad, Reza Tavoli * Pages 33-42

    These days, data mining one of the most significant issues. One field data mining is a mixture of computer science and statistics which is considerably limited due to increase in digital data and growth of computational power of computer. One of the domains of data mining is the software cost estimation category. In this article, classifying techniques of learning algorithm of machine and COCOMO model as the most common estimation model of software costs were presented. Then the analysis method of principal component approach are presented. This article shows that the method to increase the accuracy of software cost estimation is suitable. Then, the basic data set was decreased and was turned into a new collection by using this method. Among the features, the best were extracted. The algorithm of several classifications were assessed by applying this method. Finally, the evidence for accuracy of our claims in terms of increase in estimation accuracy of software costs was presented.

    Keywords: Increased accuracy, Software cost estimation, Principle components analysis, data mining
  • Payam Vahedi, Babak Ganji* Pages 43-52

    In the present paper, a shape design method is introduced for switched reluctance motors (SRM) by which both heat transfer and acoustic noise are improved. For evaluation of the proposed shape design method, a simulation model based on finite element method (FEM) is also developed to predict both the temperature rise within the machine and the produced noise. The simulation model is created using ANSYS finite element (FE) package and it is build up totally as a parametric model in ANSYS parametric design language. Since the convection heat transfer coefficients depend on the temperature rise, they are determined in the developed thermal model based on an iterative algorithm. The proposed shape design method is applied to a typical 8/6 SRM and simulation results including temperature distribution in various sections of the machine, displacement of stator and sound pressure level (SPL) are presented. Based on the obtained simulation results, it is illustrated that the temperature rise and the noise of the SRM could be improved significantly using the introduced shape design method.

    Keywords: Switched reluctance motor, Thermal modeling, Heat transfer, Noise reduction, Shape design
  • Maryam Feli, Fariborz Parandin * Pages 53-58

    An efficient double junction InGaN/CIGS solar cell can be simulated using Silvaco ATLAS software. In this study, a thin CdS top cover layer is used as the anti-reflector layer. To reach the current matching condition, changing the thickness of this CdS layer, we can enhance the short-circuit currents of both the top and bottom cells. To gain a desired efficiency, different design parameters, such as the doping concentrations and the thicknesses of the various layers of the cell are optimized. This cell is designed to be used in a real environmental situation. Considering the proposed structure and the simulation results, an optimum efficiency of 41.87% is achieved and also the obtained fill factor is equal to 75.16%.

    Keywords: Solar cell, Double-junction, Efficiency, Energy gap
  • Hassan Rashidi *, Mohammad Sadeghzadeh Hemayati Pages 59-76

    One of the major challenges in software engineering is how to respond to the desolate state of high-quality software development in a timely and cost-effective manner. Software quality refers to the abilities related to the properties of software products in meeting users' requirements. Many studies have been conducted in an attempt to formalize the quality of software. However, according to the recent researches, the lack of comprehensive quality model is rooted in neglecting all quality aspects. In this study, we review nineteen quality models and classify them from three different perspectives, including structural, behavioral, and basic and derived aspects. The main aim of this paper is to specify and extract the more comprehensive set of quality factors to evaluate software quality. Moreover, this paper compares the different quality models and analyzes the factors to draw the necessary aspects in comprehensive quality models. Since the software quality involves several engineering tasks and several players who deal with quality concepts during software life cycle according to their various roles, in various phases and different artifacts, comprehensive quality models must consider many factors. These factors are in different aspects such as the measurement time in different development phases, product as well as process-related quality factors, a set of quality metrics measureable on the different type of artifacts such as document, model and source code, and finally a specific mechanism to apply dynamic weights to quality factors to determine their impacts on final quality of a product based on its application domain.

    Keywords: Software, Quality, Software Engineering, Models
  • Seyed Ehsan Abdollahi *, Mehran Mirzaei Pages 77-84

    Linear induction motors (LIMs) are widely employed in rail transportation systems due to their robust, simple and low cost structure. Several methods have evaluated various topologies'' performances in the literature. These methods are more and less effective in the intended structures. In this paper, a new two-dimensional analytical method is presented in order to predict developed thrust force of a single-sided linear induction motor with a solid iron secondary. The skin and saturation effects of the induced eddy currents in the solid iron of the secondary are considered in the proposed method. The analytical results are then compared with the 2D finite element simulation and the experimental ones of the research work of Gieras et al. .Results confirm the accuracy of the proposed analytical and finite element methods for the analysis and design of linear induction motors with solid iron secondary.

    Keywords: Iron secondary, Analytical calculations, Finite element method, Eddy currents, Linear induction motors, Thrust force
  • Nasrollah Azam Baleghi, Mohammad Hossein Shafie * Pages 85-94

    In this paper, a sliding mode controller based on the disturbance estimation is designed for a class of discrete-time nonlinear affine systems. Based on two disturbance compensator schemes, static and dynamic, procedures of sliding mode controller design are proposed for the discrete-time system. In the case of measurable state variables, the instantaneous value of disturbances can be estimated based on the value of states and control signals. In two proposed control laws, there is no switching expression to induce the problem of chattering. Moreover, based on the necessary and sufficient quasi-sliding mode condition proposed by Sarpturk, boundedness and robustness of the proposed controllers is evaluated. In the case of constant or slowly time-varying disturbances, the quasi-sliding mode band converges asymptotically to zero and in this case, the proposed method is converted to the ideal sliding mode. Finally, two examples are provided to verify the proposed control laws and to compare the performance of the proposed controllers.

    Keywords: Discrete-time, Nonlinear affine systems, Quasi-sliding mode, Disturbance estimation