International Journal of Coastal, Offshore and Environmental Engineering
Volume:7 Issue: 2, Spring 2022

Ocean color satellite sensors provide the only long-term Essential Climate Variable (ECV) globally that targets Chlorophyll-a concentrations (Chl-a) as the most important biological factor in the oceans. It is difficult to develop the long-term and consistent ocean color time-series for climate studies due to the differences in characteristics, atmospheric correction, Chl-a retrieval algorithms, and limited lifespans of individual satellite sensors. Therefore, the merged multi-sensor ocean color datasets were developed by merging data from different satellite sensor products. The performance of the commonly used single-sensor and multi-sensor merged ocean color datasets is a challenging issue over highly turbid coastal waters and dusty atmospheric conditions. In this study, we compared the common single-sensor [Sea-viewing Wide Field-ofview Sensor (SeaWiFS), Moderate Resolution Imaging Spectroradiometer (MODIS), Medium Resolution Imaging Spectrometer (MERIS), Visible Imager Radiometer (VIIRS), and Sentinel-3 Ocean and Land Colour Instrument (OLCI)], and merged multi-sensor [Ocean Colour Climate Change Initiative (OC-CCI), and GlobColour weighted average (GC-AVW) and Garver-SiegelMaritorena (GC-GSM)] Chl-a datasets over the Persian Gulf, known as optically complex and highly turbid water bodies in a dusty atmospheric condition. The results indicate that the OC-CCI dataset provides more spatial and temporal coverages than the other datasets. Temporal consistency between single-sensor and merged datasets was made in two different timespans during the common period of sensors and during the continuous lifespan intersection between individual two-paired of datasets. The statistical metrics were calculated to show the temporal consistency between Chl-a datasets during the common and continuous time periods. Correlation between OC-CCI and the other datasets showed that the relationships between datasets did not change significantly during the proposed time periods. Further, it was indicated that the OC-CCI product is more constant than the other single-sensor and merged products. It was shown that OC-CCI datasets were more consistent with MERIS and GC-GSM datasets, and SeaWiFS and GC-AVW were not significantly correlated to the other datasets. The results revealed that the single sensor products that use POLYMER atmospheric correction algorithm (e.g. MERIS), and merged multi-sensor product that performs the GSM blending algorithms (e.g. GC-GSM) are more consistent and stable than the other products over the study area.

Global sea level rise of 1.5 meter by 2100 AD due to global warming and polar ice-melt has emerged as a concept and not a science. Ocean thermal expansion responsible for sea level rise has also emerged as a myth. Warming of ocean surface can produce water vapor by evaporation which is not the volumetric expansion of ocean water to raise sea level. More the thermal heating of the ocean surface water more will be the evaporation from the ocean that negates volumetric expansion of the ocean water. Global warming can alleviate ocean temperature not to expand ocean water. Global scale ocean temperature measures 28oC upto the depth of 40 m only. Below this depth temperature drastically decreases almost to 6oC at 1000 m depth trending further decrease. Science behind melting of the polar floating ice-blocks supports reoccupation of the same occupied volume of the floating ice without sea level rise. Ice-melting further reduces load from the crust of the Earth to elastically rebound for attaining isostatic equilibrium preventing sea level rise. Paleo-sea level markers in the sediment deposits occur due to the crustal subsidence and uplift for transgression and regression respectively. Prograding delta can result in apparent sea-level drop showing retreat of the sea. Geophysical spheroidal shape of the earth with equatorial bulge and polar flattening maintain a perfect hydrostatic equilibrium condition. Maximum centrifugal force and minimum gravity attraction can allow sea level to occur at about 21 km higher in the equatorial region than in the polar region preventing sea-level fluctuation.

Offshore platforms are among important structures whose performance during their life-time and beyond is of significant importance. One of the approaches for ensuring a platform’s fitness-for-purpose condition is the structural integrity management system. In this process, a wide range of risk assessment approaches can be carried out to investigate the platforms’ performance. These assessments are divided into qualitative, semi-quantitative and quantitative methods, whose outcome is the risk level of the structure under investigation. By obtaining the risk level, the condition of the platform can be surveyed and certain actions can be defined to ensure that the platform remains fit-forpurpose. In this study, a fixed offshore jacket platform located in the phase 19 of the South Pars gas field in the Persian Gulf is investigated using a semiquantitative risk assessment method. Based on certain assumptions, the risk level obtained for this platform can be categorized as intermediate. By knowing the risk level, risk mitigation actions can be carried out and inspection intervals can beefined.

Security is necessary for marine communication systems such as marine wireless sensor networks and automatic identification system which is the emerging system for automatic traffic control and collision avoidance services in the maritime transportation sector. Public key cryptography algorithms have an important role in these systems to realize secure communication systems. Public key cryptography algorithms such as RSA and Elliptic curve cryptography (ECC) have high computation costs and many works are done by researcher in order to speed up the operation. Residue number system which is a carry free system is widely used to speed up the operation in public key cryptography algorithm. In this paper, an improved RNS reverse converter for three-module set {2^n,2^n-1,2^(n-1)-1} using chinese reminder theorem with fractional is presented. Unit gate delay and area comparison of the proposed reverse converter with literature have confirmed that the proposed reverse conversion takes fewer hardware costs and higher speed.

The aim of this research was to compare the performance of a submerged obstacle and floating wave barrier in the stability of rubble mound breakwaters based on the damage parameter. The submerged obstacle was attached to the toe, and the floating wave barrier was installed 50 cm from a reshaping breakwater. We carried out tests in a 35 m flume at SCWMRI. Random waves with the JONSWAP spectrum influenced the breakwater. We then analyzed the structure's reshaping using close-range photogrammetric imaging by constructing the DEM and DSM to record the displacement of rocks. Furthermore, we obtained the eroded area and the damage parameter from the integrated model at eight cross-sections at equal distances. We showed that the damage parameter increased by 39.12 and 44.44%, respectively, by increasing the relative wave height from 0.36 to 0.48 and 0.6. Also, the damage parameter increased by 22.94 and 28.26%, respectively, by increasing the relative wave period from 0.6 to 0.8 and 1. In addition, regarding different modes, we obtained the damage parameter in the breakwater without the submerged obstacle and the floating barrier 1.116 under random waves. The damage parameter decreased to 0.701 (i.e., 37.19%) by using the submerged obstacle, while the wave barrier reduced this parameter to 0.735 (i.e., 34.14%); thus, the obstacle has outperformed the wave barrier. Using the obstacle simultaneously with the wave barrier reduced the damage parameter by 51.79%, confirming the highest efficiency and performance among models. Consequently and based on the experiments and findings in this study, this model was suggested for adoption.

In this paper underwater acoustic wave propagation is studied numerically by Differential Quadrature method. Numerical methods are different with respect to accuracy, computer costs and practical flexibility. In this study Differential Quadrature (DQ) method is applied for numerical solution of underwater acoustic wave for first time. Two experimental cases are used to validate the two-dimensional wave model, first the numerical results are verified by analytical solution and the second one showed the applicability of current method in complex domain. Comparisons demonstrate the efficiency, accuracy and robustness of the Differential Quadrature method for acoustic wave simulation.