فصلنامه دریا فنون
سال چهارم شماره 4 (پیاپی 10، زمستان 1396)

In this paper, RCS of complex objects was calculated by using combination of physical optics theoream, physical theory of diffraction and method of eqiuvalent current. modeling of complex object was done with meshing in Abaqus Software.so first by meshing the surface of object and then meshing the edges of the object, then by transferring of these data to MATLAB software, physical optics theory was implmented to each mesh of the object surface and physical theory of diffraction and eqiuvalent current theory was implemented to object edges and by summation of electric field was seen from surface meshes and edges, total cross section of the object was obtained with consideration of edge effect. simulations results shows our algorithm has good agreement with CST-MS result and able to determine RCS features with lower complexity low time consuming

Clustering is used in radar pulse classification and de-interleaving. Proper selection of initial centers for clusters is the fundamental problem in clustering methods. In the proposed algorithm, the similarity matrix for the input data based on defined neighborhood radius is created. Then, with analysis of similarity matrix and selection of lines with the most similar code, denser clusters are separated respectively. In this way, regarding to the high stream radar pulse, without requirement to iteration, pulse strings are separated as optimal. This algorithm has capability of priority selection of dense categories in clustering. On the basis of neighborhood radius defined, data on the common border clusters, have been carefully separated.
In particular, the advantage of using this algorithm is selection of dense clusters center in radar pulse clustering. The proposed method can also be used to cluster the data in various fields. . Results of proposed method for data sample consisted of 200 radar pulse is compared with the results of clustering around the leader which is one of the main clustering algorithms in the field of radar pulses. Evaluation and measure of clustering validity such as Dunn, Silhouette and RMSSD indexes, shows efficiency of the proposed algorithm.

People around the world encountered every day with the natural events that lead to the death, injury, destruction of property and disruption of their daily activities. Flooding is known as one of these natural hazards that have long been threatened the urban communities and causes several human and financial casualties. Therefore, it is necessary to perform research studies and implement subsequent actions consistent with the nature of the river at the time of flooding. In this study, the hydraulic behavior of Aghghala city has been considered and investigated in dealing with the 100-year flooding of Gorganroud River using CCHE2D; and with defining the risk index, the required input data have been extracted to codify the rapid response planning, crisis management, and flooding insurance. The results show that regarding the flow pattern formed during the flooding and the overall hazard maps, evacuation of the entire city seems to be essential. However, regarding to the area of the zones having high risk, the predicted damages would be very heavy.

Seas and theirs risks for humans caused that warning equipments like SONAR attended by many of researchers about seabed. In this paper, a new method is introduced for sonar image processing and removal of gap region in side-scan sonar images. In the proposed method, to improve removal efficiency of gap region and target detection in sonar images, phase congurency algorithm and structural characteristics of shape are used. In this study, Haqqani port, Bandar Abbas, Iran seabed images are used to show the efficiency of phase congruency method. The proposed method is compared with classic gradient method, and the results show that the proposed method has more efficiency than classic methods. These method improved parameters like: sensitivity (4.4 %), Detected Evaluation Ratio (4 %), Detected False Evaluation Ratio (75.6 %) Algorithm running time (5.8 Sec).

Meshfree methods are particular types of numerical methods that are recently preferred over element based methods. This preference is attributed to their merits over the element based methods, when dealing with the moving boundary problems. Mixed Discrete Least Squares Meshles (MDLSM) method is a type of meshless method which has improved the accuracy of numerical solutions because of applying mixed formulation. This method, because of using strong form of equations, is completely meshless. The proposed method is based on minimization of residual function which is defined as sum of residuals of the governing equations and boundary conditions. Considering the importance of proper analysis of sea waves phenomena in designing the structures interacting with sea waves and the efficiency and high accuracy of MDLSM method, application of MDLSM method is hereby extended to analyze the linear waves in sea environment. Through solving numerical examples, efficiency and accuracy of the proposed method are evaluated. Depending on the time step, the error has been 10% to 6% for different wave heights. Furthermore, by analyzing the CPU time for constructing the shape functions and derivatives in the proposed method compared against the existing DLSM method, a remarkable reduction in CPU time is observed.

Decompression sickness is a disorder that human body and brain suffers from it. By processing electroencephalography signals, some information about neurophysiologic disorders can be extracted and suffered brain regions clearly will be identified. In this paper by using extracted features including entropy and energy of common people and diver's registered signals, a model based on brain function will be presented that is able to display the organization and brain regions connections. This model is designed by cell neural networks and shows the brain function. The results show that in intra-region connections of some regions of diver's including T7, T8, O1 and O2, )P

In this paper a high efficiency, low cost, and low THD five-level inverter is proposed. The proposed inverter has lower number of switches than the similar structures and this feature causes that the implementation cost of the proposed inverter becomes lower than the others. Also, a passive filter is proposed to decrease the THD value, and simulation results prove this fact that THD value has been decreased dramatically. As well, high switching frequency is another important feature of the proposed converter. According to the simulation results in the PSPICE and PLECS software, the proposed converter has several advantages such as high stability, high efficiency, low cost, and proper thermal specifications. Simulation results show the effectiveness of the proposed solution.