فصلنامه علوم و فناوری دریا
سال هفدهم شماره 68 (زمستان 1392)

In this paper we have discussed the effect of array beamforming on controlling the clutter level of active sonars in shallow waters. To show this، we have used K-distribution statistical model for modeling clutter، because in previous paper we showed that this distribution best models the clutter. The results and distribution are exhibited and we have deducted that sonar clutter can be reduced by well-defined beamforming.

In this paper numerical study on the penetration of aluminum targets with a thickness of 1 mm by projectiles with three types of nose shape، blunt، hemispherical and conical presented. Targets penetrate at different impact speed and initial velocity and residual velocity of the projectiles were measured. In additionto measuring ballistic limit، effect of projectile nose shape on the deformation of target plates was also studied. According to researches results the ballistic limit of cylindro-hemispherical projectiles is more than cylindricalprojectiles and also cylindro-conical projectiles has minimum ballistic limit. Numerical simulationfrom LS-DYNA are compared with Experimental results، that show good agreement between the experimental and numerical data.

Prediction of waves in coastal engineering and marine issues is essential. For this purpose، various methods including experimental methods، numerical methods and computational software tools exist. Experimental methods are relatively simple، but in comparison with other methods are not accurate. Numerical models are generally accurate، but use them time and money wants. In recent decades، the use of artificial neural networks have been widely applied to solve many engineering problems of the sea. It is capable in the modeling nonlinear problems. This paper conducted in Bandar Anzali، Caspian predicting in the wave height of the artificial neural network technique is used. Data obtained from the Ports and Shipping Organization and the Caspian Oil Company، in the periods 3،6، 12 and 24 h were measured by ADCP system. Network using Feed-forward three-layered networks with four neurons in the middle layer، which produces the best prediction.

Effect of Copper، Zinc and Vanadium on growth of Gracilaria salicornia were carried out over 21days under laboratory conditions. The macroalga was collected from coasts of Gheshm island in February 2012. For each treatment، the algae were inoculated into 20 litre water with diameters of 60×30×40 cm. The suspension method used for culture. All treatments (tanks) were carried out in triplicates. The length، width and weight of the thalli were measured on 2، 5، 7، 14، 21 days and relative growth was calculated. The results of this study showed significant differences on growth of G. salicornia between treatments (P<0. 05). Increased growth in low concentrations and reduce the high rate of the investigated metals shows that these metals initially as essential elements for the growth of the practice، and so increase the toxic effects too.

Sound travels to long distances in the ocean by various forms of ductedpropagation. When sound travels in a duct، it is prevented from spreading indepth and remains confined between the boundaries of the duct. The surfaceduct is a zone bounded above by the sea surface and below by the SLD. Within the surface duct، sound rays are alternatively refracted and reflected. A surface duct exists when the negative temperature gradient within it doesnot exceed a value determined by the effect of pressure on sound speed. Specifically، the surface duct is characterized by a positivesound-speed gradient. At very low frequencies، sound ceases to be trapped in the surface duct. So calculating themaximum wavelength for duct transmission is very important. In this paper we used a profile as a pattern of sound velocity distribution to calculate related parameters. Finally an optimum frequency for minimum scattering of sound channel propagation presented.

Various combinations in Cyanobacteria were reported to have antiviral effects. Polysaccharides are new sources of anti Epstein-Barr virus (EBV) reagents. Aqueous extract of Anabaena ISC 90 and Anabaena ISC 55 were significantly inhibited the transcription in EBV. In this study lipophilic extract and hydrophilic extract of Anabaena ISC 90 and Anabaena ISC 55 which are sources of polysaccharides، with silica gel were considered. They produce Nano particles with cytotoxic effects on EBV virus in Lymphoblastoid Cell Line (LCL) cell line. After extracting DNA from treated LCL cells and performing PCR test for viral capsid. It was confirmed that viral load was significantly decreased. Produced Nano particles significantly inhibited in the reproduction of EBV in low concentrations.