فصلنامه علوم و فناوری دریا
سال بیست و یکم شماره 82 (تابستان 1396)

Among different offshore platform concepts; FPSOs (Floating Production, Storage and Offloading units) have been more attractive these days. Stability and seakeeping are two effective hull design parameters and overall efficiency assessment of FPSOs. This study has focused on some performance factors such as, stability both intact and damage condition, hull position, displacement and acceleration due to environmental loads. The aim of this study is to achieve a systematic procedure to evaluate the quality of performance for three type of FPSO hull forms including: ship-shaped, rectangular box and oval. The procedure is done by an MCDM model with an AHP method. Models are done in Finite Element Method (FEM) and diffraction analysis have been performed. Oval type FPSO has better performance in stability and rectangular box has better performance in seakeeping assessment. Better seakeeping performance of rectangular box FPSO leads to have greater score in overall efficiency assessment among three case studies. In this study, spread mooring type with steep-s flexible riser are used for all case studies.

Many technologies to absorb wave energy is provided and there are different ways to optimize the efficiency of wave energy converters. In this study, the analysis of mooring system and its impact on the dynamics of a point absorber wave energy converter was considered.
Energy absorption from ocean waves by two-body point absorber converters depends on the relative displacement between the buoy and submerged body of a point absorber converter in the direction of heave. For this purpose, in wave energy converter is used a three-point mooring system with heave plate, Conventionally. In this paper, two types of mooring systems for a point absorber converter are considered. Then, the dynamic of two models is analyzed in the regular wave. Hydrodynamic Forces and coefficients are calculated by the discretization of boundary integral equations in the wave scattering and radiation problem.
The responses of the submerged body and buoy to regular wave were investigated. The results are validated with the available results. Extracted energy is calculated via the value difference between the relative displacement of the buoy and submerged body. The obtained results showed the significant contribution of the tension mooring system into enhanced the value of relative motion and the efficiency of the converter

This paper presents a new control algorithm for an active power filter (APF) to compensate harmonic and reactive power of a 3-phase thyristor bridge rectifier under non-ideal mains voltage scenarios. Sensing load current, dc bus voltage and source voltages compute reference currents of the APF. APF driving signals are produced with these signals via a hysteresis band current controller. Matlab/simulink power system toolbox is used to simulate the proposed system. The proposed method’s performance is compared with conventional instantaneous power (p–q) theory. The simulation results are presented and discussed showing the effectiveness of the control algorithm. The proposed algorithm is found quite satisfactory to compensate the reactive power and harmonics under non-ideal mains voltage conditions. The increased performance of the ctive power filter under different non-sinusoidal mains voltage and dynamic load conditions are extensively demonstrated.

Array factor is sum of multiplied weights to elements signal (received or transmitted). This weights be set to reduce side lobe level (with Dolph Chebyschev). Element failure disturbs the Array Factor and change the parameters of that. The side lobe level is used to cost function the main parameter influence of array failing, and then define kind of cost function (multimodal or unimodal) and show the different global optimization point for any failing mode. In this problem, the number and position of failed element be gived and Genetic Algorithm, remake the Array Factor with reduce the cost function and recalculate the weights of unfailed element to recovery of original Array Factor. In practice, 4% of elements be failed but in this paper, try to find what kind of failing mode can be recovered with Genetic Algorithm. Array Factor and Genetic Algorithm be simulated in MATLAB ver. 2014 and results (weights) can be used in design step of array antenna for: 1-define mode (number and position of failed element) of array failure, that can be recovered. 2-calculate weights of unfailed element I any failure mode. 3-make correction table from offline recovery result for using in runtime mode of array.

In the research, changes of physico-chemical and biological properties of coastal waters of Sisangan- Chalus area were evaluated. Field measurements and sampling were carried out by water sampling, and using CTD and Hach probe in depths of 5, 10 and 20 m in the southern coastal waters of the Caspian Sea during autumn 2013 to winter 2014. In autumn, the water column mainly covers the surface mixed layer and so vertical variation of the physical parameters was slight between sea surface and near the bed. The structure of physical parameters indicates vertical stratification including surface mixed layer in the water column till 20 m depth. The average parameters of temperature, salinity and density in autumn were approximately around 27.3°C, 12.3 and 1006.6 kg/m3, while in winter they were recorded around 11.4°C, 12.12 and 1008.2 kg/m3. Horizontal changes of the physical, chemical and biological parameters were not high in the study area. Physical structure of water column and physicao-chemical properties affected zooplankton in the coastal waters of the region.

The study focused on identification and, species diversity of phytoplankton, zooplankton, benthos and fishes for water quality protects in the Chitgar Lake between 2013 and 2014. This survey identified 35 phytoplankton taxa comprised of diatoms (12 genus), chlorophytes (15 genus), cyanophytes (5 genus), dinoflagellates (2 genus) and chrysophytes (1 genus) were identified. The finding showed, the chlorophyta genus dominated in the Chitgar lake. The findings showed, the 36 zooplankton taxa comprised of Arthropoda (6 genus), Protozoa (6 genus), Rotatoria (20 genus), Nematoda (1 genus), Gastrotricha (2 genus) and Oligochaeta (1 genu) were identified. The highest taxa was belonged the Rotatoria during the study. Three taxa contained of Ephemeroptera, Diptera and Oligochaeta were identified. In this study, 18 species comprised of Cyprinidae (11 species), Cichlidae (one species), Loricariidae (one species), Pangasiidae (one species), Serrasalmidae (one species), Poeciliidea (one species), Salmonidae (one species), and Scaridae (one species) were identified. Among the fishes just one native fish from Capoeta bohsei species observed during the study. Based on, the finding, the plankton taxa confirmed that the Chitgar lake water is at the high quality category. Furthermore, the fish alien species were dominated in the lake, which could raise trophy level in the future.

Resistive economy as a principle mentioned in various circles and Lectures. The study was conducted by questionnaire and the aim is evaluate the implementation of resistive economy in Port and Maritime organizations. Indicators based on the questionnaire raised by science and technology to the vice presidency. Indicators based on the questionnaire raised by science and technology to the vice presidency. The questionnaire contains 33 indicators in seven Include : jihadi approach, flexibility, opportunity, generating, endogenous, leading and extroverted. Validity of the questionnaire using content (structure) was confirmed. In a pilot study questionnaire reliability coefficient was 0.958. according to Morgan minimum sample size of 274 people. The results showed that in the Port Authority, jihad, endogenous, extroverted, flexibility, opportunity, generating leading approaches as approaches of the resistive economy, ever more has not been implemented effectively and efficient. Based on the results obtained, in order to implement appropriate resistive economy in the maritime organization Can be present suggestions that include: Organizational incentives to be considered for Implementers of resistive economy plan, the financial system to be reformed in line resistive economy, fields scientific exchanges with neighboring countries to be created, be done needed diplomacy for support the resistive economy, wider variety of services provided to external customers, resistive economic benefits to be explained for staff clearly, should be considered the planning for post- prohibition and economic risk management to be active in critical situations purposefully.