فصلنامه علوم و فناوری دریا
سال بیست و چهارم شماره 93 (بهار 1399)

One way to stabilize a ship in the face of nonlinear movements in the direction of the roll is to control the fins. Due to the completely non-linear dynamics of the movement in the direction of the ship's roll angle, as well as considering the structural uncertainties and external disturbances caused by the sea waves, it is not easy to extract an accurate dynamic model. Therefore, it is difficult to design a system-based controller that, with optimal performance, applies the appropriate force as a control input to the fins and overcomes the stated structural and non-structural uncertainties. A common way to control such unreliable nonlinear systems is to use nonlinear resistant control. Control of the immersion model is one of the most widely used nonlinear resistive control methods that can overcome these uncertainties, but this control method in the practical implementation stage has disadvantages such as vibration at the control input. In this paper, in order to eliminate the undesirable phenomenon of control input vibration, the control of the immersion model is combined with the Takagi-Sugno-Kang fuzzy system. The controller of the obtained fuzzy immersion model has the advantages of controlling the immersive model and also in its implementation, there is no trace of the phenomenon of control input vibration. As a case study, in order to demonstrate the optimal performance of the proposed controllers, a favorable and challenging optimal path for the position of the roll angle has been considered and the controllers of the immersion model and fuzzy immersion model have been implemented and simulated on a warship.

Solar energy has been accepted as an alternative source of energy worldwide recently. Current researches and markets have shown that Solar Photovoltaic (PV) is the fastest growing and most promising form of renewable energy used in generating electricity. This paper presents an intelligent sun tracking system in which photo-resistors (sensors) are used to determine the direction of the sunlight along with wind sensors to specify the direction of the wind. Due to their high performance and low expense, these sensors have been preferred and used. This system generate the requested electrical energy to used in light systems in a ship. An algorithm based on fuzzy logic is designed to implement the controlling system considering all the various meteorological conditions. The results show that with the correct operation of the control system, the performance error, especially in the afternoon and early afternoon, has decreased relative to the uncontrolled mode and the PID controller.

This paper is focused on the effects of bolt pretension load and bolt torque on the behavior of hybrid bonded-bolted joints with composite adherends. For this aim by employing the finite element software of ANSYS Workbench, three dimensional model of hybrid single lap composite joint is simulated. At first for selecting an appropriate element numbers, the convergence study is performed. Then by changing the amounts of the bolted pretension load and its torque, the effectiveness of them on the stress components in bolt and nut, adhesive layer and laminated composites are investigated.To demonstrate the validity of the presented simulation results, the obtained results are compared with the researches presented in the available literature. The results of this research is indicated that, increasing the pretension load, provided that failure does not occur in the bolt or nut, causes increases in the load-bearing capacity of the joint.

Today, maintenance due to increased complexity in the production process and product variety has faced the change and caused the paradigm shift in implementation of maintenance strategies that in this procedure, maintenance strategies based on status has changed to strategies based on reliability. The aim of the study is evaluating of risk of equipment failure by a subset technique of possible risk assessment, which is called Fault Tree Analysis. Fault tree analysis is a technique based on failure and component-oriented, which started with an undesirable event, and by using a backward system process, determine the causes of this event. During this process, a fault tree is drawn to describe graphically the events and their relationship to the occurrence of the top event. Fault Tree is a qualitative model that offers a lot of useful information that cause an undesirable event. On the other hand, by using of Boolean algebra equations and by considering the relationship between the specified causes, quantitative analysis also can be done. In this study, emergency stop of gas turbine due to a malfunction in lubrication system as the top event (undesirable event) is considered and by considering the causes of failure to the occurrence of the event and drawing the fault tree, both quantitative and qualitative assessments on system failures, has been done. In addition, how to use the results of the risk assessment of failures in order to optimize the processes of maintenance management system has been presented.

War at sea is a complex situation, and apart from the use of techniques, the laws are required someday. Many of the rules of naval warfare are in common with those of other wars, but the rules of naval warfare are far more complex. The prohibition of the principles of international law, which is enshrined in the law of armed conflict within the framework of humanitarian law, comprises two basic principles: the prohibition on the use of weapons and methods that cause unnecessary harm and pain, and the prohibition on the use of military methods and equipment which They are not directly capable of separating civilian targets and property. Limiting the means of warfare means balancing the military necessity and the damage inflicted by the war to support non-combatants. In naval warfare certain tools and methods are used. Humanitarian law restricts the effects of war and, for humanitarian reasons, restricts the right of the parties to the conflict to choose and use war instruments and methods. The purpose of this brief is to examine the methods of naval warfare from the perspective of international humanitarian law, and to prove that international humanitarian law is applicable to the methods and instruments of naval warfare. The research method of this paper is analytical-descriptive method and the method of data collection is library method.

The bioactive compounds are divided into two types: primary and secondary. Primary bioactive compounds are essential for the growth of living organisms, but secondary bioactive compounds are not essential for living organisms and originate from primary bioactive compounds. Most secondary bioactive compounds contribute to survival. Marine microorganisms live freely or coexist with marine plants and animals and many marine metabolites are often produced by symbiotic microorganisms. Coexisting microorganisms with Sponge, microalgae, bacteria and sea fungi are major sources of bioactive compounds. Compounds produced by sponges include unusual steroids and nucleosides, anti-inflammatory compounds such as clathriol and halo-peptin. Omega-3 fatty acids, types of toxins, pigments and sterols are derived from microalgae. Marine bacteria produce compounds such as lobophorin, bryostatin, macrolactin, saline amide, acetogenin and astaxanthin. Sea fungi produce compounds such as dendrophiellines, pestalone ,scalusamides ermophilanes, etc. Compounds such fluostramine are also derived from bryozoa. The diversity of marine organisms and products is very high compared to terrsterial resources and marine microorganisms are important sources of new compounds. As a result, the discovery of new bioactive compounds from marine resources confirms the need for research on marine organisms.