فصلنامه دریا فنون
سال نهم شماره 1 (پیاپی 27، بهار 1401)

The increasing use of artificial intelligence methods in automatic sonar target reco.

In this paper, a high-performance graphene dielectric plasmonic waveguide in the far infrared spectrum is proposed, which is one of the components of integrated photonic and optoelectronic circuits with various applications, including communications, military, medical, etc. The proposed waveguide geometric structure is composed of a rectangular cube layer with a semi-cylindrical ridge underneath (with a high refractive index material), rectangular cube substrate with a semi-cylindrical depression (with a low refractive index material), a sheet of graphene and the substrate of material with low refractive index, that the layers and sublayers are stacked on top of each other, respectively. Here, the surface plasmon polaritons (SPPs) modes are stimulated at the interface of graphene and dielectric. The propagation properties of SPPs modes have been investigated using the finite element method (FEM). The simulation results show that via modifying the geometrical parameters of the structure and tuning the chemical potential of the proposed graphene waveguide, a small normalized mode area ~〖10〗^(-4) and the propagation length ~〖10〗^3 μm are achieved. Therefore, it is recommended that the proposed waveguide can be used as a component of photonic devices due to relatively long propagation length and the strong confinement of light.

In this research, fresh water and power have been produced by using the heat output from the ship's engine. The cycle used in this process, the organic Rankine cycle (ORC) has been a regenerative model. The desalination system is of the type (Multi Effect desalination). This system has three stages, in each stage, with the warming and evaporation of sea water, some of the sweetened water is separated so that the salt in it is completely separated. ASPEN HYSYS software has been used to simulate this process. Energy and exergy analysis, the process is calculated for all currents to obtain the amount of exergy destruction in all equipment. The result is that the amount of production power from the Rankin Organic Cycle is 254.8 kW. The amount of water produced by the desalination system is 4899 (kg / h) and the most exergy destruction. among the equipment in Turbine LP has the highest destruction of exergy and in heat exchangers of converter (HX-1) has the highest exergy destruction by analyzing the sensitivity and effect of temperature, mass flow and pressure parameters on the production of power and freshwater, we have reached the conclusion that by increasing the mass flow and temperature increasing the fresh water and power. The amount of power per year is equal to (kW) 2370606.24 and the amount of water produced is 1741926 (kg/year) and the availability for ORC is 0.9833 and for MSF is 0.9756.

The acoustic performance of ship propellers is an important issue in ship design. Noise generated by the ship's propeller is one of the most important sources of noise when ship moving in seaway which has a higher frequency range and level than other noise sources. In this study, the fluid field around the DTMB 4119 marine propeller was simulated by the finite volume method and then by the FW-H integral method, the sound pressure level was estimated and validated with the experimental results. In the following, a standard Series B propeller in two different advanced coefficients simulated. its hydrodynamic properties investigated by velocity triangles and extracted vortex structure of the flow. The Steady and unsteady states were used to evaluate the acoustic performance of this propeller. In the steady-state condition, the noise level was lower at high frequencies, while in the unsteady state, noise levels were around 10 dB higher, which be due to ignored unsteady terms. For extrapolation of the result of acoustic noise levels from the model scale to a full scale of the propeller, the ITTC87 method was used.

Biological fouling is a significant problem to the shipping industry causing increases in frictional resistance, decreases in ship speed and increases in fuel consumption. It can cause blockage of intake pipes and heat exchangers and decrease efficiency of cooling system. Had The use of sonication is one of the most unconventional and innovative methods for preventing moss growth and reducing the amount of marine sediments. In this study, experimental experiments were carried out to investigate the effect of ultrasound on preventing moss growth on box shaped models by installing ultrasound in the real environment of the sea near the port of Bandar Abbas. The results showed that the effect of ultrasound on uncoated sheet is much better than coated sheet, so that the amount of rust and sediment accumulation in the bermetal box (without color) was 5% compared to the stainless steel cover in the 60-day period. It was also found that the duration of the waves affected the absorption of moss, so that the absorption of moss on an anti-corrosive box in the mode of intermittent radiation is 1.3 times as long as the waves are continuously emitted to the box surface.

Water temperature is an important factor in all dependent ocean/sea processes. The FVCOM 3D numerical model was applied to simulate the water temperature in the Chabahar Bay. Chabahar Bay is a semi-enclosed and shallow omega-shaped bay, located on the south-eastern coasts of Iran. The correlation coefficient (R) between the FVCOM model results and the field data is 0.95. The trend of seasonal temperature changes is affected by monsoon conditions; a sharp drop in temperature (6 °C) in a short period of time (7 days) was seen due to a sharp increase in evaporation. Self Organizing Maps (SOM) was used to classify output results of FVCOM and determine the main temperature patterns in Chabahar Bay. The number and density of SOM outputs is proportional to the dispersion and distribution of input data. In the 5×4 array of SOM, the main patterns are categorized so that the warmer patterns are on the left and the colder patterns are on the right. About 24% of the maps showed a warm core located between north and northeast of the Bay. The gradient of temperature from south to north of the Bay vary more than 10 °C (in warm maps) to below 5 °C (in cold maps). In 61% of the results related to the midpoint of Chabahar Bay, the surface and bottom temperature are in the range of 22-25 °C and 19-20 °C, respectively.