فهرست مطالب

Coastal, Offshore and Environmental Engineering - Volume:8 Issue: 1, Winter 2023
  • Volume:8 Issue: 1, Winter 2023
  • تاریخ انتشار: 1401/12/24
  • تعداد عناوین: 6
  • Hossein Ramak, Maryam Soyuf Jahromi, Parastoo Akbari Pages 1-9

    In Gulf of Oman, the sinking of Persian Gulf Water mass has been reported. In the current study, the FVCOM ocean model has been used in 20 layers to investigate the phenomenon of downwelled Persian Gulf Water in the Gulf of Oman. The bathymetry of the simulated area (47˚-59.45˚E, 22˚-32˚N) was achieved from GEBCO-2019 by the resolution of 30 seconds. Triangular grid was generated in SMS. The open boundary fluctuations were also extracted from TMD. The temperature and salinity were obtained from the output of HYCOM (standard depths). Satellite data were used for the verification. The results showed the downward vertical velocity of Persain Gulf Water is higher in the area of the sudden depth change than the other parts in all seasons. This fact indicated the downwelled water was in a form of a spot. The rate of downwards penetration of water was different (winter: -2cm/s, spring: -1cm/s, summer: -1.2cm/s, autumn: -1.7cm/s). In summer, the salinity contours were very close to each other in the east of the Strait of Hormuz, or intense stratification. Therefore, the slope of the salt wedge was less. In winter, the calculated slope of the salt wedge (1.5×10-1 degrees) was greater than summer (3.8×10-2 degrees). The larger angle or slope of the salt wedge means the greater horizontal component of the weight of water (mgsinθ). It causes the displacement of saline water, and faster movement of Persian Gulf Water. Therefore, the water of the Persian Gulf moves faster to lower depths in Gulf of Oman in winter than summer

    Keywords: Water Mass, Seasonal change, Downwelled Water, Vertical Velocity, FVCOM
  • MohammadReza Khalilabadi Pages 10-15

    The abstract should include the One of the most exciting topics for researchers over the past few years is detecting underwater acoustic noises. Meanwhile, the complicated nature of the ocean makes this task very challenging. Also, making signals formatted data compatible with machine learning approaches needs much knowledge in signal processing for feature detection. This paper proposed a method to overcome these challenges, which extracts features with Convolutional Neural Network (CNN) and Mel-spectrogram (converting signal data to images). This method needless knowledge in signal processing and more knowledge in machine learning; because using CNNs find the hidden pattern and knowledge of the data automatically. The proposed approach detected the presence of the ships and categorized them into different kinds of them with 99% accuracy that is a noticeable improvement considering state of the art. The performed CNN models consist of 2 CNN layers for feature extraction and a Dense layer for classification the underwater ship noises.

    Keywords: Underwater Acoustic, Deep Learning, Recognition, Noise, CNN
  • Mahmoud Pourali, MohamadReza Kavianpour Pages 16-25

    Electric energy consumption is growing almost all over the world. Similarly, using clean resources in coastal such as wave power is also growing. The coasts of Oman Gulf in southeast of Iran is one of the most potential areas for deriving energy from waves. The sea waves are mostly generated by wind and the climate change affect the wind field. Hence evaluating climate change effects on the wave power is essential for energy extraction. In this research, the variation of monthly average in Chabahar bay wave power under the middle scenario of future climate effect has been studied. For this, the CNRM-CM6-SSP2-45 dataset has been downscaled with the Weibull technique, and with a calibrated wave model, wave characteristic has been calculated. Based on the results, the average annual wave power will reach 10.4 kW/m by an increase of 3%. Total wave energy in Chabahar is about 91,000 kWh/m during the year. which will also increase by 3% compared to the same period previous century. In the July and August, the first high energetic months, the wave power increase by 1% on average compared to the previous period. The highest monthly increase occurs in October and with a 277% increase, it reaches 5535 kW/m. The highest monthly decrease of 25% occurs in June and the energy reaches from 13041 to 9513 kW/m.

    Keywords: Wave energy, Climate change, Weibull-based bias-correction, Gulf of Chabahar, Emission scenario
  • Parvin Ghafarian Pages 26-30

    In this study, cyclogenesis was investigated over the Black Sea from synoptic-dynamic view. While the Black Sea has an important role in precipitation of northwest of Iran, a system that is formed over the Black Sea was selected and it affected Iran on 14th and 15th March 2009 (40 mm precipitation has occurred in some stations). Using archived data of NCEP / NCAR, absolute and thermal vorticity advection in 500hPa level and potential vorticity at 325 degrees Kelvin level were calculated. Within the development process the cutoff low was formed over the Black Sea and the difference between directions of the upper-level cutoff low at 250hPa level and surface low represents a strong baroclinicity which in turn supports cyclogenesis. The results show that the absolute and thermal vorticity advection in mid-level and potential vorticity anomaly has a fundamental role in creating cyclogenesis. In such a way that the absolute vorticity advection gets 15 times larger (about ), and cyclogenesis occurs when the mid-level trough axis is altered from northeast-southwest direction to northwest-southeast direction, and the polar jet will be combined with a subtropical jet. Also, a strong dependence of the cyclogenesis in initial stages occurs when a large upper level Potential Vorticity (PV) anomaly advected into a region where there is a meridional potential temperature gradient at low-level.

    Keywords: Potential vorticity, NCEP, NCAR, Heavy precipitation, Dynamic meteorology, Iran
  • Asghar Rashnodi, Aliashraf Ahmadian Pages 31-44

    The coronavirus (COVID-19) crisis, has put everything in a new and complicated situation. Businesses, especially exporters, have also been affected. The main objective of the present study is to investigate and prioritize the factors effective on the development of export strategy in the context of coronavirus (COVID-19), and to test this Phenomenon in the export firms of Iran through mixed method (qualitative-quantitative) research. To this end, 42 export firms were selected from Iranian ports and maritime industries as the statistical sample of the study and the data were gathered using questionnaire and interview and data analyzed with fuzzy Delphi methods and partial least squares technique. The research findings show that the most important inner firm factors effective on the export performance of Iranian firms in the context of the Corona crisis are: Firm’s capabilities and resources; Managerial characteristics; Marketing capacity; Strategic capability and Company human resources. The research findings have led to the identification of vital export incentives and stimuli in critical situations and finally to the introduction of a new typology of factors tailored to critical situations that can be useful for empowering businesses in possible future crises.

    Keywords: export performance, Export Critical Success Factors, critical situations, Coronavirus (COVID-19), innovativeness
  • Naser Abasi, Cyrus Ershadi, MohammadAli Lotfollahi yaghin, Alireza Mojtahedi Pages 45-60

    In designing of any system that deals with forces and displacements some of the effective parameters on hydrodynamic behavior that needs to be investigated are the degree of freedom, and the stiffness of the support systems. In the present study, the effects of degree of freedom on hydrodynamic performance of a box type floating breakwaters (FB) is investigated experimentally and numerically. The experiments were conducted in the 2D wave flume of the (SCWMRI). Regular waves were generated by a piston type wave paddle controlled by ‘DHI wave generating’ software. The effect of incident waves characteristics on efficiency of FB is examined in four configurations. In this paper, a new dimensionless parameter (DB/L2, i.e., draft times width divided by wavelength squared) is identified as an essential parameter for comparison between theories and the experimental data. Generally, the most efficient configuration is the fixed breakwater, but considering the tidal phenomenon, providing the required draft of FB will increase the cost of project. For short wavelengths, it is seen that the efficiency of pile-restrained FB is good same as the fixed type in mild conditions. Regarding the cost-effectiveness, the configuration of the FB with the pile should be considered the most efficient for design purposes in mild conditions.

    Keywords: Floating Breakwater, Degree of Freedom, Stiffness of Anchorage System, Hydrodynamic Performance, Transmission Coefficient