فصلنامه علوم و فناوری دریا
سال بیست و یکم شماره 83 (پاییز 1396)

To convert the DC voltage and current levels of DC-DC power converters is used. This is not ideal because pieces of power converters are the disadvantages that this may result in loss of productivity in them. Among the weaknesses that are discussed in this converters dissipate them. The toll that this type of converters and other power converters switching losses suffered soft switching techniques have been proposed to solve it. In fact, these methods overlap when switching voltage and current at high levels prevents the key. Moreover, the use of three-level structure causing it to drop to about half the input voltage is voltage power switches. This is also a great impact in reducing switching losses and extend the life of power converters. In this article the basic definitions and concepts of power converters, two major types of soft switching techniques are examined and compared in terms of productivity. Also went on a three-level DC-DC converters are the best examples of a MATLAB simulation software and the results of its soft switching is provided at the end.

in this paper,the design and simulation of an integrated circuit for clock and data recovery at a data rate of 5 Gbps has been dealt with in the middle phase method . clock and dat recovery circuits are of particular importance in optical communication and play a key role in high speed receivers . the proposed circuit is designed and simulated using an intermediate phase method and using CMOS technology of 0.18 micrometers in the ADS simulator.the result indicate that the circuit with the PRBS input data can recover the data in a very small time .the amount of jitter in the recoverd data is 16 pico second.

Theoretical and practical limits effect on resolution imaging systems and the effective ways to overcome these limits, super-resolution methods that have been developed at recent years. The main purpose of this paper, in addition magnified digital images, restore missing high frequency detail. In this paper, a method called single-frame resolution using a convolution neural network (CNN) based on optimization genetic algorithms (GA) provided better results to improve images than traditional super-resolution methods. Results show that our method achieved an improved performance compared to other super-resolution based methods, and the proposed method increases the quality of the image based on PSNR metric. The amount of this improvement is about 10% compared to super-resolution based approaches.

This work addresses an autonomous underwater vehicle (AUV) for applying nonlinear control that be efficient for both perfect operation of under-actuated AUV and tracking guarantees. For this purpose, controller is capable of intelligent estimation of uncertainties and ocean current disturbance rejection. We proposed adaptive radial basis function neural network (RBF NN) controller in both heading and diving to approximate unknown nonlinear dynamics. Moreover, the problem of designing an adaptive RBF NN controller was augmented with sliding mode robust term to improve trajectory tracking and regulation in presence of uncertainties. Due to under-actuated mechanism of REMUS and lack of direct actuator effect, combination of RBF NN and sliding mode robust term is applied to compensate the system’s gravity/buoyancy force and guarantee appropriate motion in Z direction. Furthermore, stability proof of proposed control scheme was shown with lyapunov theory. Furthermore, the control, design and simulation results are provided without any simplification of the entire system. Although the design approach of this paper is implemented on REMUS this point of view can be applied on any AUV using the same technique.

To monitor environmental conditions underwater and seabed and ocean vessels now be considered a special interest. These vessels designed and is used in various forms. One kind of this vessels are sea gliders. Sea gliders hull form is based on operational requirements and different environmental conditions. They were designed to meet the demand for a vehicle with low energy consumption that could be used for long-term oceanographic sampling The typical design of the underwater glider is having fixed wings internal masses, a ballast pump, and a rudder. Thus, the buoyancy-driven underwater glider controls its attitude by moving the internal masses and rudder, gliding downwards and upwards through the ocean's water column by constantly changing the buoyancy level from negative to positive buoyancy in order to change the depth. Numerous institutes have developed laboratory-scale underwater gliders for research purposes. Numerical Analysis of the gliders to further understanding of motion control and maneuverability is the very useful and important. This article examines the changes in hydrodynamic coefficients of drag coefficient (water resistance) and lift coefficient (ascending) fixed at different angles of attack that fixed wings play a major role in it, are dealt with. Glider studied in this paper is sea glider that method of performance underwater, geometric modeling, dynamic modeling, numerical analysis, and finally to investigate the hydrodynamic coefficients and its results is given below.

Today the industry to develop new methods for shaping sheet has been willing to increase production diversification. One of these methods is sheet forming progressive Where the tools rotating in directions controlled without the need to mold and shape the sheet without machining. country and in the world through numerical simulation after simulation in the present study we examined truncated pyramid in the process of using Abaqus software on a sheet of aluminum (AL1050), power versus time diagram was extracted was wrought with practical examples, finally, after obtaining the power consumed in the process and verify again the results were accepted

Presently, natural products play major role in medical and pharmaceutical sciences that among them marine derived products have been paid more attention in recent years. In comparison of these products with those that originated from other sources, more and developed compounds with biologic activities are found that is the result of more developmental opportunities of aquatic organisms than land organisms. Some of these marine natural products are antibiotic while others have anti-tumor, anti-viral, anti-coagulant, anti- gastric ulcer, sedative, lowering blood fat, immune stimulator and immunosuppresive properties. Some of these products are used as fungicide and insecticide and also used as food and cosmetic additives. Persian Gulf is a valuable and rich source that with regarding to the biodiversity of its micro- and microorganisms can be regarded as an important source for extraction of bioactive substances. In the present survey a review has been done to introduce native bacteria of Persian Gulf that can produce natural bioactive compounds