فصلنامه علوم و فناوری دریا
سال نوزدهم شماره 74 (تابستان 1394)

One of the main methods of mineral processing is flotation process that occurs in aquatic environments. Iran has a few fresh water resources، and many of the rich mines are located in areas with limited freshwater resources. Since Iran is connected to the Caspian Sea and Persian Gulf from the north and the south، respectively، therefore، the best solution seems to be using the sea water and recycled water in the industry. The purpose of this study was to identify the major challenges of flotation of sulfide copper - molybdenum in seawater and its recent improvements. In this study، the effect of water quality، including pH and concentration of salt (NaCl) and divalent cation on flotation operation was studied. Results reveal that recovery of copper maintained almost at the same level in both mediums. Moreover، the floatability of molybdenum was affected negatively above the pH 9. 5-10. Recovery reduction of molybdenum was suggested to occur because of the magnesium hydroxide complexes and magnesium hydroxide precipitate.

In this study، the changes of seawater parameters such as temperature، salinity، density، dissolved oxygen and turbidity was studied. Field measurements were carried out using a CTD probe in the coastal waters of Nowshahr in the autumn 2013 to winter 2014. Based on the results، the average parameters of temperature، salinity، density، dissolved oxygen and turbidity in autumn were respectively; 27. 28°C، 12. 29 1006. 61 kg/m3، 8. 26 mg/l، and 10. 73، and in winter، 11. 44°C، 19. 12، 1008. 17 kg/m3، 12. 94 mg/l، and 5. 74. In the autumn، the water column mainly covers the surface mixed layer and so vertical variation of the physical parameters was slight between sea surface and bed. The structure of physical parameters indicates vertical stratification including surface mixed layer and thermocline in the water column. Horizontal changes of the parameters were influenced by local factors such as local river discharge and plume in the study area.

Gyros for recognizing angular motion are used in vessel’s gyrocompasses، submarine inertial، airplane automatic pilots and space-vehicle attitude systems. The dynamics of gyro is a very exciting nonlinear problem in classical mechanics and control engineering. In this study، control and synchronization of two gyroscope systems with two degrees of freedom is studied. It is shown that the mentioned gyroscope system has nonlinear and chaotic dynamics. For tackle the problems of nonlinearities and chaotic behavior، in this research sliding mode control (SMC) is proposed for control and synchronization purpose. The simulation results confirm that sliding mode based controller provides good synchronization without chattering phenomena.

This paper presents a review on commercial vessel generated waste. In this context various ship waste categories are identified (oily wastes، Black water، Grey water، Ballast water، Garbage، Air emission)، their variation between different vessel types is pinpointed and the legal framework and guidelines for their management and handling are drafted adequately. Ship waste shall be refer to any harmful substance (for both the marine environment and the public health)، which is generated during the usual day-to-day ship operation. Past experience has proven that these wastes accumulate significant quantities and therefore potential for marine pollution. Thus، only after recent significant environment damage (e. g. in Alaska، the Caribbean Sea etc) has occurred، did the international maritime community turn its attention on the matter. Only Through an international marine forum marine pollution from ships can be satisfactorily tackles. That forum is the International Maritime Organization (IMO) whose twin objectives are maritime safety and the prevention of marine pollution caused by ships. Finally، more attention should be calculated to ship waste streams، monitoring of the illegal outputs and ship waste reception facilities on the beach with a common framework، to be proposed.

Nowaday there is the gantry cranes in harbor and waterfront of commercial and military widely hence with the aim of increasing efficiency and reduce the risk of their performance increased level of automation and intelligent control them is important. The most important goals for this type of crane control system is increase the speed of the object during the oscillatory motion control and accuracy in placing the object in the desired position، hence control system design methods that are classified into three main categories including classical methods، modern methods and soft computing among fuzzy logic control is provided for this purpose. In this paper، the dynamic model of a gantry crane samples were extracted at laboratory scale and system performance results with the installation of classic PID، LQR and Fuzzy logic controller have been compared with others that indicating the superiority of fuzzy method.

One of the destructive effects of nonlinear loads is producing harmonics that makes a lot of problems in power systems. Varieties of methods for reducing harmonic have been suggested in different articles. For decreasing the harmonic produced by the rectifier that is one of the most important sources in producing harmonics in power systems، different types of electrical filter have been used. In this article in addition to describing the act of single tuned passive filters we completely defined the essential formulas for this type of filter and with the help of simulations in MATLAB، the impact of passive filter in decreasing the current harmonics and improving the power quality has been evaluated.