فصلنامه روشهای هوشمند در صنعت برق
پیاپی 17 (بهار 1393)

The purpose of this study is to design a content-based medical image retrieval system and provide a new method to reduce semantic gap between visual features and semantic concepts. Generally performance of the retrieval systems based on only visual contents decrease because these features often fail to describe the high level semantic concepts in user’s mind. In this paper this problem is solved using a new approach based on projection of relevant and irrelevant images in to a new space with low dimensionality and less overlapping in relevance feedback level. For this purpose، first we change the feature space using Principal Component Analysis (PCA) and Linear Discriminant Analysis (LDA) techniques and then classify the feedback images applying Support Vector Machine (SVM) classifier. The proposed framework has been evaluated on a database consisting of 10،000 medical X-ray images of 57 semantic classes. The obtained results show that the proposed approach significantly improves the accuracy of retrieval system.

Designing a two-phase brushless direct current motor (BLDC) and analyzing effects of stator slots structure on the motor operation are main objectives of this paper. At first BLDC motor with three different structures for stator slots is designed by using RMxprt software and efficiency of BLDC motor for different structures in full-load condition has been presented، then the BLDC motor in different conditions by using Maxwell 3D software is designed and with finite element method is analyzed electromagnetically. The results of simulations show that by varying stator slots structure efficieny and operation of motor have changed significantly therefore with correct choosing of stator slots structure intersted operation can be found.

Adaptive beamforming methods are known to degrade in the presence of steering vector and covariance matrix uncertinity. In this paper، a new approach is presented to robust adaptive minimum variance distortionless response beamforming make robust against both uncertainties in steering vector and covariance matrix. This method minimize a optimization problem that contains a quadratic objective function and a quadratic constraint. The optimization problem is nonconvex but is converted to a convex optimization problem in this paper. It is solved by the interior-point method and optimum weight vector to robust beamforming is achieved.

In this paper، the problem of 3D heart motion in beating heart surgery is resolved by proposing a parallel force-motion controller. Motion controller is designed based on neuro-adaptive approach to compensate 3D heart motion and deal with uncertainity in dynamic parameters، while an implicit force control is implemented by considering a viscoelastic tissue model. Stability analysis is proved through Lypanov’s stability theory and Barballet’s lemma. Simulation results، for D2M2 robot، which is done in nominal case and viscoelastic parameter mismatches demonstrate the robust performance of the controller.

This paper first discusses about Electric arc. the model used in this paper is a dynamic model shown with a differential equation. Then، this model is placed with power system model which is considered as a thevenin equivalent model،and whole dynamical system is derived. With linearization around the work places، Jacobian Matrix of the system was extracted and the stability of equilibrium points specificed. Infollow، restricted equation to the central manifold for system intended is achieved and using that، possible events in the system the critical values of the bifurcation parameter is investigated. At the end، the analytical result is compared with the simulation results obtained with the help of Auto software. Finally، we will conclude that، using one type of the analytical method، one split of power system is characterized، but with using Auto software، all bifurcation are identified in the power system.

In this research، a new structure of photonic crystal fibers (PCFs) will be proposed،in which instead of using the aire- holes in the cladding region، the flourine (2%) doped solid silica rods in order to reduce the problems associated with deformities of air-holes in the cladding region will be used. Also، in the following، a few of the propagation charactristics of the proposed Photonic Crystal Fiber with a conventional silica Photonic Crystal Fiber such as، Normalized frequency،effective refractive index،total dispersion and higher order dispersions (Group velocity dispersion and Third Order Dispersion) will be analyzed and compared. Finally it will be observed that، the proposed PCF structure is much simpler than the conventional one in the fabrication process. But they are not suitable for femtosecond solitons propagation. Also، it will be shown that، the situation of the conventional Photonic Crystal Fiber is much better than the proposed structure in the femtosecond optical solitons propagation.

Networked control systems are control systems which controllers and plants are connected via telecommunication network. One of the most important challenges in networked control systems is the problem of network time delay. Increasing of time delay may affect on control system performance extremely. Other important issue in networked control systems is the security problems. Since it is possible that unknown people access to network especially Internet، the probability of terrible attacks such as deception attacks is greater، therefore presentation of methods which could decrease time delay and increase system immunity are desired. In this paper a symmetric encryption with low data volume against deception attacks is proposed. This method has high security and low time delay rather than the other encryption algorithms and could improve the control system performance against deception attacks.

Joint bit allocation، relay selection and subcarrier assignment are critical for achieving full benefits of OFDM-based cooperative relay networks. In this paper، first such a problem is studied in a dual hop OFDMA cooperative network consisting in multi source nodes، multiple decode-and-forward (DF) relays and a single destination node. The aim is to minimize overall transmission power under the bit-error-rate (BER) and data rate constraints. However، the optimal solution to the optimization problem is computationally complex to obtain and may be unfair. Assuming knowledge of the instantaneous channel gains for all links in the entire network، an iterative three-step resource allocation algorithm with low complexity is proposed. It performs the privileged user selection based on fairness criterion first، and then allocates subcarrier-relay with the given constraints. Finally، power and bit are assigned to the selected subcarriers based on the water-filling algorithm. In order to guarantee the fairness of users، several fairness criteria are also proposed to provide attractive trade-offs between network performance (i. e. overall transmission power، average network lifetime and average outage probability) and fairness to all users. Numerical studies are conducted to evaluate the performance of the proposed algorithm in two practical scenarios. Simulation results show that the proposed allocation algorithm achieves an efficient trade-off between network performance and fairness among users.