مجله علوم و فنون دریایی
سال بیستم شماره 1 (بهار 1400)

One of the most prevalent ways for studying the submarine’s hydrodynamic behavior, like maneuvering, is calculating the hydrodynamic coefficients the hydrodynamic coefficients. In this paper calculation of hydrodynamic coefficients (up to third order) of an AUV using Computational Fluid Dynamics (CFD) and Finite Volume Method(FVM) was performed. Therefore, a Myring body was chosen to simulate the unsteady maneuvering for surge, sway and yaw motions. The turbulence effects were modeled by k-ω sst turbulent model. The Planar Motion Mechanism (PMM) in two situations has been implemented to calculate the forces and moments for sway and yaw motions. Creating body motions in computational domain, the Overset mesh was used. Furthermore, the grid study was performed for investigating of the simulation accuracy. Then for calculating the coefficients, some six order polynomial equations were interpolated for forces and moments versus velocity and acceleration. The numerical results were compared with the results of (Prestero, 2001) . The relevant error for damping coefficients was between 0.8 to 12 percent. These values for added mass coefficients were between 0.8 to 37 percent.

The aim of this research is to investigate the hydrodynamic status of Mahshahr export port. Initially, the modeling of tidal streams in the starting point of Khurmousa by the tidal inputs of Rahnamaian station was performed in logical manner and the results obtained from the inner point of Khurmousa was calibrated with inputs from Imam Khomeini station port and satisfactory results were achieved. During the next stage, by considering the main aim of this research, a model specific to the area of export port of Mahshar was developed. Based on the results from field measurements and the results obtained from the model, the tidal amplitude balance in export port of Mahshahr is 4.25 meters, the maximum annual ebb is 2.25 meters and the annual minimum is 2 meters. The velocity of tidal streams in Mahshahr export port parallel to the channel and during the most part of the year is between 0.5 to 1 meters per second. The pattern of tidal streams is constant throughout the year and experiences no changes

Circumstances of Extremely shallow acceptor will have a significant impact on the diffusion of contaminants flow. In this study, diffusion and progression parameters in extremely shallow ambient have been investigated. The results showed that the diffusion coefficient decreases with increasing Froude number. This is due to increasing the fluid jet input speed and momentum. On the other hand the results show that, the fluid with a higher concentration has higher diffusion factors and less progression length under the same circumstances. Also diffusion of contaminants fluid in the acceptor ambient, were classified with the initial Froude number due to flow pattern. Studies show that in contaminants flow with Froude number greater than 5, diffusion boundaries are almost similar to the second-order parabolic equation. Coefficients a, b and c were calculated separately for each experiment. While for flows with Froude number lessr than 5, diffusion expanse of flow is almost similar to the oval equation. The 3D mathematical-experimental equation(x, y, t) was obtained for this part. More results show that at all concentrations, the progression parameters increased with increasing densitometry Froude number. While this process changes in a constant rate for all concentrations. The results also indicate dependence of progression parameter to the and Weber number. The effectiveness of Reynolds and Weber numbers on diffusion and flow region shows that they are effective in all concentrations up to specific amount, and negligible after this amount.

The study in 1393 to determine the heavy metals mercury , cadmium , lead , cobalt and vanadium in the muscles of two species Liza abu (Liza abu) and yellow fin seabream (Acanthopagrus latus) Bahmanshir River was conducted in summer and winter . Amounts of heavy metals by atomic absorption spectrophotometry Perkin Elmer 4100 took place with the help of devices.Analysis of the data was analyzed with the help of software SPSS17 help of means and analysis of variance (ANOVA One-way) were compared with each other . The results showed that the highest levels of mercury , cadmium and cobalt in Yellowfin Seabream in the summerThe highest level of lead in Liza abu in summer and in winter the highest concentration of vanadium in Yellowfin Seabream , respectively. The lowest mercury, lead and cobalt were measured in Liza abu in winter . Also the lowest amount of cadmium and vanadium in Liza abu in summer. The mercury and vanadium in muscle Liza abu and yellow fin seabream was lower compared to the threshold of global standards ,But the amount of lead and cadmium were higher than the standard limit . In general, the amount of mercury, lead, cobalt and cadmium in both species was in summer than winter , but the concentration of vanadium in winter than summer .

In this study, the effect of cooking and pre-cooking methods was done on quality and sensory factors of peeled and un peeled whiteleg western shrimp. Free fatty acids, pH indices, TBARs, volatile nitrogen bubbles (TVB-N) and sensory factors such as tissue, Odor, taste were evaluated during 16 days of storage at -18 ° C. Cooking and pre-cooking of shrimp were done by boiling, in which the shrimp was heated to 80 ° C for 5 minutes to cooking and 3 minutes to pre-cooking. The lowest of factors such thiobarbituric acid was in unpeeled raw shrimp and the highest in peeled cooking, for pH in unpeeled raw shrimp and peeled cooking, for TVB-N, unpeeled raw shrimp and the highest in peeled cooking and for FFA index peeled cooking and the highest in peeled raw shrimp. The results showed heating would maintain the quality indices during the maintenance period.

This research investigates the dynamics of excess return on vessels trip charter and time charter in travel leases and rental of the specified route in bulk dry market. Initially, using a weekly dataset between January 2003 and January 2016, a long-term co-integration relationship between temporary travel contracts and maritime-specific contracts was evaluated in the ship's temporary lease equations. Then, a new method was developed based on technical analysis to identify surplus return signals and the formation of a business strategy. Accordingly, our focus was on short-term deviations and we developed a leasing strategy for technical analysis. In particular, we designed the MMTM method and formed a rental strategy. Finally, we tested our strategy for a simple weekly entry into a specific lease. The results show that our method performs better than the benchmark strategy and reveals that a proper utilization of market price deviations will result in significant surplus returns.

Increased population growth and the creation of major economic powers has led to increase in the world's energy consumption. In 2008, 88% of the energy consumption of the world was formed by fossil fuels. Since in Iran, fuel for transportation system produces the essential pollutants, substituting these fuels with biofuels, including bioethanol and biodiesel, can effectively reduce pollution in the environment. Some species of microalgae, have the ability to store high levels of carbohydrates, rather than lipids. These microalgae are good candidates for the production of bioethanol since the carbohydrates in their biomass, can be extracted and fermented to bioethanol. The purpose of this study was to optimize the microalgae culture, to increase the production of starch. This study was performed in laboratory scale. The microalga Chlorella vulgaris was procured from Persian Type Culture Collection (PTCC) of Iranian Research Organization for Science and Technology. Culture media BBM and Z8 were selected for growth and production of starch. Optical density, cell counting and dry biomass were measured in these media. Regarding significant difference (P

In this article, spectrum of the reflection, transmission and absorption of the thin metal nano-layer by using quantum hydrodynamic equations is studied. The thin metal nano-layer can be used to cover the equipment and devices to avoid detection which coated the outer surface of the submarines, ships, planes. It is also used the nano-layers to cover the various devices such as solar cells, glass reflex. In some devices, for example the solar cells, the more increase the absorption ratio, the more increase the efficiency and in some other devices, for example the reflex glasses, it is better to be high the reflection ratio. Hence, the study of the reflection, transmission and absorption ratio of electromagnetic waves are important in quantum plasma slabs. By combining the quantum hydrodynamic equations and the Maxwell's equations in the presence of a magnetic field can be obtained the coefficients of the reflection, transmission and absorption of electromagnetic waves in thin metal nano-layer in which we have taken the slab as quantum plasma. Clearly, it is shown that by taking term of the quantum Bohm's potential cause to appearance of the quantum refractive index for the Langmuir wave that this new refractive index does not have any similar relation in the classical plasma. Using the numerical values and the Mathematica software, the absorption coefficients have drawn in various conditions. This proposed method enables us practically to control the reflection or absorption power of electromagnetic waves in quantum plasma slab by adjusting a uniform external magnetic field.

Anti-Rolling Gyro (ARG) is one of the useful equipment which is used for enhancing stability of vessels. ARG produces a moment against wave torque and reduces undesirable vessel roll based on gyroscopic concepts and using flywheel moment. The first step in designing ARG is flywheel design which exerts appropriate moment in order to reduce rolling of vessel with attention to the sea wave moments and angular velocity of the waves. According to direct relation of righting moment of gyro with mass moment inertia, in order to increase righting moment, it should be chosen a flywheel with high moment inertia, in the contrary, increasing moment inertia also leads to increasing mass of flywheel. In this study, with regards to conditions of waves of Persian Gulf, for optimizing of mass and moment inertia, non-dominated sorting multi objective genetic algorithm (NAGA-II) is used, in a way that minimum mass and maximum moment inertia will be gained. Finally, the dimension of all the flywheel optimal options are demonstrated in the form of pareto diagram, in order that performance conditions regarding parameters including mass and the number of gyros in a vessel based on gained results, are being investigated.

The aim of this study was to The Role of Port Competencies in Strategic Competitiveness on the Performance of Ports in Khuzestan Province (service competence, marketing competence and informational competence). This study is the target of numerous applied researches. According to the method of data collection, the research include descriptive preceding studies (non-experimental) and causal respectively. Methods This study library - field is the first to refer to hardware resources (such as printed books and papers valid) and software resources (such as digital books and articles from scientific websites) to review and extract indexes study and then were collected through a questionnaire. The population of the research areas of strategic and financial executives and professionals are the ports of the province. It was estimated number of 82 people. The sample size was estimated by Morgan table of 68 people. However, due to the limited size of the population for collecting information and access to the whole population, a questionnaire was distributed among all the population. In this study, data analysis, descriptive and inferential statistics in the form of software SPSS (22.0) and PLS (3) is used. The results showed that all three types of competencies (marketing, service and information) on Strategic Competitiveness positive and significant effect on both performance and strategic competitiveness of financial performance and strategic performance was effective.

In this study, effects of four concentrations of waterborne calcium (8, 25, 50, 100 mg/l) on eyed egg percentage, hatching percentage and ions (Ca, K, Cu and Mn) uptake of rainbow trout eggs in a water recirculating system were determined. Twelve experimental units, with the capacity of holding 45 liter of water were used and 21g egg introduced in each one. Different concentrations of ions (Ca,Na,K,Mg,P,Fe,Cu,Zn,Mn) in treatments were prepared by adding analytical salts (Merck) into double-de-ionized distilled water. Dissolved oxygen and water temperature variations during incubation were 9.80-11.11mg/l and 7.5-9 ºC respectively. The eyed egg percentage was not significantly (P>0.05) different among treatments. The hatching percentage of eggs were significantly (P