فصلنامه علوم و فناوری دریا
سال چهاردهم شماره 56 (زمستان 1389)

Today, with increasing of oil and gas field’s development, and also installation or commissioning of related offshore technology, the need for communication and air access to these facilities has also increased. Considering by the space limitation of offshore installation, the helicopters would be an appropriate machine to accelerate the transportation. Also Helidecks on this installation would operate such as an airport, so this additional structure must be designed in a way to have a proper interaction with platforms. Hence, loading, locating and analyzing the environmental conditions can play a significant role on safe flight operations and compatibly interaction with the superstructure. In this study principles of Helidecks loading has been described with a case study of Reshadat platform at Persian Gulf in Iran.

Always oceanographers pay attention to layer structure in the sea environment. Creation of layer structures is because of some phenomenons like double diffusion, internal waves, turbulence modular mixing. In this paper with examination of vertical structure of temperature, salinity and density between Persian Gulf and Oman Sea in different seasons, layer structures appear clearly. Also countors of the same physical parameters show the existence of regular structure which prove internal waves resulting from the Persian Gulf and flow into the Oman Sea. The exchange flow through the Stait of Hormus results from horizontal density gradient between the Persian Gulf and Oman Sea. In winter the density ratio () in this nearshore region is a bout 0.7 and in offshore region is 0.2. this shows that in this area, double diffusion forms layer structures which have horizontal variations as well as in the vertical. Coastal topography also seems to affect the double diffusion processes and leads to variations of layering in horizontal directions especially between near and offshore regions.

Corrosion engineering is application of science and technology or the art of prevention or control the damages caused by the corrosion in an economical and confidential method. As the environmental condition in various industries are different. The amount of corrosion in alloys and structures and their prevention methods are different. In marine environment because of the salt existence and different contaminators, organisms, microorganisms, and the diluted gas, the corrosion is increased drastically. This problem because of the special operation an individual in comparison to other and the ability to move on the ice water and soil and the abyss areas is increased. In order to reduce the corrosion problem in these vehicles special instruction in phase of design and manufacturing and the maintenance phase must be applied. In this article affective parameter on the corrosion as material selection, cover choosing, and application of preventers, and using sealing, applying the design hints, site seeing the corrosion and tidiness of the vehicle, is identified. A comprehensive program in order to reduce the corrosion problem in hovercraft vehicle is presented.

A mechanistic study is performed to examine the coupling between the in-line and the cross flow motion of a cylindrical structure subjected to current forces. The structure represents a free span pipeline. A time domain model is formulated in which the in-line and cross-flow deflections are coupled through the axial tension which in turn is computed from the pipeline prolongation at any time. At the end the effects of resonance on the dynamic behavior of pipeline is discussed.

In this paper, Non dimensional numbers and their influence on the performance of high speed planing crafts are studied as the first stage of the design process. Then the process of designing the planing high speed crafts is studied by discussing the design algorithm for a small planing catamaran model. Continuously, some of the hull parameters like lift and drag coefficients, center of pressure position and draft variation versus boat speed changes, etc. are analyzed and then porpoising phenomena, hydrodynamic performance, and the second in which hull starts to plan over the water are determined. At the end, by the aid of the new algorithm the best position for the center of the pressure is attained with 3 percent error. Thus the power of 200 watts is attained for the example model. This amount of power, in compare with experimental data, shows 5 percent of error.

In this paper, we have analyzed physical parameters of Persian GULF water and its effect on sound wave propagation. Then we have studied an AUV (Automatic Underwater Vehicle) and its transmitter and receiver. Then by software produced, we have shown the effect of physical parameter of water on AUV communication system.

Today, the use of renewable energy in electricity production to different causes, including lack of fossil fuel resources, reduce environmental pollution, improving power quality, reduce line losses and stability of networks is growing rapidly. In recent years the above reasons as well as lack of electricity transmission networks nationwide to ships carrying fuel and limit their energy use in new vessels, researchers have been considered.The aim of this proposal is to find out the optimal value of the DG capacity to reduce line losses (LLRI) and Voltage Profile Improvement Index (VPII). To achieve this goal, integrate the particle swarm optimization (PSO) with the chaotic sequences is proposed. The application of chaotic sequences in PSO is an efficient strategy to improve the global searching capability and escaping from local minima. Calculation line losses and voltage profile was accomplished by Newton-Raphson load flow solution. The proposed method is tested on a standard IEEE-30 bus system and the results of the simulation carried out by using MATLAB are found to be encouraging. Moreover rate convergence in this method is very higher than the other methods. The method has the potential to be used for identifying the best location and rating a DG to be installed for improving power quality in an electrical power system.