فصلنامه علوم و فناوری دریا
سال هجدهم شماره 71 (پاییز 1393)

Tsunami waves happen every year in different locations of the seas and oceans of the world. These waves propagate with high celerity in different directions and when these waves reach the coast cause serious damage to the beach، coastal structures and facilities. Therefore understanding this complicated phenomenon and prediction of its behavior can minimize the damages. In this research a numerical simulation was performed on tsunami phenomenon. The objective of the research was to predict the wave characteristics as it reaches the coastal zone. Flow3D software was used for this purpose. Assuming viscous flow for sea water، Navier Stokes as governing equations together with volume of fluid method was used to simulate tsunami waves in FLOW 3D software. A single wave was generated using a simulated piston type wave maker in the lateral boundary of the study domain. Waves are generated in deep water and propagate towards the beach. The simulation results revealed the considerable increase in wave height in coastal zone. The rate of height increase versus slope was calculated. Furthermore effect of decrease in width of the coastal zone on wave height increase was considered.

In this investigation، we study the status of a water column in the Oman Sea (25N، 57E) with the depth of 600m. We used temperature and salinity measurement data in both warm and cold seasons for study of static stability and double diffusion processes. For study of static stability and the occurrence of double diffusion and the importance of them in the water column، the profiles of temperature، salinity، density، potential density، buoyancy frequency and turner angle in the warm and cold seasons calculated and compared.

Inverters extensively are used to control the speed of three phase induction motors in recent years. Pulse width modulation method is used for switching power semiconductor devices in inverters. There are several techniques for pulse width modulation. In this paper، we have tried to fully describe sinusoidal pulse width modulation and space vector pulse width modulation approaches، also by simulating the inverter in MATLAB software and calculating total harmonic distortion، inverter output voltages belonging to the both of pulse width modulation methods have been compared.

Influential factor in the maintenance of defense systems، navigation equipment and navigation aid providing Ideal environment to increase the throughput and efficiency of the staff، the right choice is an air conditioning system in Extremist vessels. Due to the Persian Gulf and the different climate conditions in different parts of the region and the lack of attention to the problem of determining the design capacity of the vessels conditioning systems also need to optimize class Construction. Therefore، due to the low number of vessels conditioning system cooling capacity Extremist Ndsa sailing in different locations during missions and personnel grievances، to fix this problem Research and field work in the operating area of Bandar Abbas on the basis of scientific studies that took Methods and results are presented in this paper. This paper describes the types of HVAC systems on vessels Extremist with its advantages and disadvantages are reviewed. Cooling load calculation of three tables، engineering companies، marine engineering approach to relationships Science (calculation formula) and the calculation method on this class of vessels software Carrier Extremist perform together were compared. According to our calculations based on the methods and models over the floating cabin area and volume، sex walls Floating climatic conditions and other parameters that the software method nominal capacity of 30 000 Btu/h arrived. Previous conditioning system capacity on this class of vessels under 20 000 Btu/hours or 24 000 Btu/ hours. Due to the higher accuracy computational methods، software selection based on the capacity of cooling capacity conditioning system was studied in the float. After selecting the new system installation and field testing of the vessel، the new cooling capacity this class of vessel ideally suited for floating design provides needed ventilation. In this method، 10 to 15% as a safety factor to the calculated cooling load is added. The new cooling capacity can be used to optimize the results of previous vessels and conditioning systems such an increase can be used defensively and staff morale.

Today’s with increasing of capacity of the ports and ships dimension، the needs for applying an appropriate berthing (fenders) system has been also increased. The principal function of the fender system is to prevent the vessel or the dock from being damaged during the mooring process or during the berthing periods. Forces during the vessel berthing or anchoring may be in the form of impact، abrasive action from vessels، or direct pressure. These forces may extensive damage to the ship and structure if suitable means are not employed to counteract them. The amount of energy absorbed and the maximum impact force imparted are the primary criteria applied in accepted fender design practices. So considering the design criteria this article by using a case study obtains the energy of mooring of ten general cargos.

Comb filter find application in a wide range of practical systems such as in the rejection of power-line harmonics and clutter from fixed objects in moving-target-indicator (MTI) radars. In this paper we describe three types of comb filter. These three types are FIR comb filter، IIR comb filter and FFT comb filter، and also by simulating in MATLAB software we compare these three types’ filters. At the end we describe method for improve the FFT comb filtering.