scholarly journals Biofouling Impacts and Toxicity of Antifouling Agents on Marine Environment: A Qualitative Study.

2021 ◽  
Vol 10 (1) ◽  
Author(s):  
Nithi E Sadan ◽  
P.S. Akash ◽  
Sunil Kumar P G
Keyword(s):  
Harmful Effect ◽  
Frictional Resistance ◽  
Offshore Structure ◽  
Marine Structures ◽  
Toxic Compounds ◽  
International Maritime Organisation ◽  
Marine Fouling ◽  
Structural Fatigue ◽  
Major Threat ◽  
Fuel Costs

Biofouling from microorganisms, plants, barnacles, mussels or algae is a major problem for marine structures. Fouling leads to increased fuel costs due to increased frictional resistance on ships, and reduces reserve buoyancy of floating offshore structure, in addition to causing cage deformation and structural fatigue, impacting endurance of materials. The intrusion of invasive aquatic species (IAS) to new environments by ships is identified as a major threat to the world’s oceans. Marine fouling affects most manmade surfaces immersed in the sea, resulting in substantial losses. Anti-fouling paints tackle this problem to a certain extent. Extensive research is in progress in the antifouling technologies in maritime sector, with new products in compliance with International Maritime Organisation (IMO) regulations being developed. The most efficient solution to minimise fouling is to make surfaces unsuitable for settlers, coating them with Antifouling (AF) Paints containing toxic compounds. Most AF agents had Tributyltin (TBT), and has been phased out by IMO since 2008 due to harmful effect on environment.  However, use of TBT in AF paints is not prohibited, though has been restricted in several countries. The environmental problems by biofouling and toxicity of existing and alternative Anti-Fouling techniques are reviewed in this paper. Further, various ship hull cleaning technologies commercially available including afloat cleaning are also introduced. Keywords— Biofouling, TBT, Antifouling (AF), IAS, IMO, AFS, Alternatives

Non-Linear Fatigue Analysis for Jacket Offshore Structures

2006 ◽  
Author(s):  
O. Gaidai ◽  
A. Naess
Keyword(s):  
Dynamic Analysis ◽  
Direct Method ◽  
Nonlinear Effects ◽  
Offshore Structures ◽  
Fatigue Analysis ◽  
Offshore Structure ◽  
Structural Fatigue ◽  
Drag Forces ◽  
Random Seas ◽  
Fatigue Estimation

This paper presents different approaches for accounting for nonlinear effects in fatigue analysis. One approach is an application of the quadratic approximation method described in [3, 4] to the stochastic fatigue estimation of jacket type offshore structures. An alternative method proposed is based on a spectral approximation, and this approximation turns out to be quite accurate and computationally simple. The stress cycles causing structural fatigue are considered to be directly related to the horizontal excursions of the fixed offshore structure in random seas. Besides inertia forces, it is important to study the effect of the nonlinear Morison type drag forces. Since no direct method for dynamic analysis with Morison type forces is available, it is a goal to find an accurate approximation, allowing efficient dynamic analysis. This has implications for long term fatigue analysis, which is an important issue for design of offshore structures.

scholarly journals Evaluation of machine learning algorithms for detection of road induced shocks buried in vehicle vibration signals

2018 ◽  
Vol 233 (4) ◽  
pp. 935-947 ◽  
Author(s):  
Julien Lepine ◽  
Vincent Rouillard ◽  
Michael Sek
Keyword(s):  
Machine Learning ◽  
Learning Algorithms ◽  
Harmful Effect ◽  
Area Under The Curve ◽  
Detection Algorithm ◽  
Machine Learning Algorithms ◽  
Gaussian Kernel ◽  
Support Vector ◽  
Structural Fatigue ◽  
Road Surfaces

Road surface imperfections and aberrations generate shocks causing vehicles to sustain structural fatigue and functional defects, driver and passenger discomfort, injuries, and damage to freight. The harmful effect of shocks can be mitigated at different levels, for example, by improving road surfaces, vehicle suspension and protective packaging of freight. The efficiency of these methods partly depends on the identification and characterisation of the shocks. An assessment of four machine learning algorithms (Classifiers) that can be used to identify shocks produced on different roads and test tracks is presented in this paper. The algorithms were trained using synthetic signals. These were created from a model made from acceleration measurements on a test vehicle. The trained Classifiers were assessed on different measurement signals made on the same vehicle. The results show that the Support Vector Machine detection algorithm used in conjunction with a Gaussian Kernel Transform can accurately detect shocks generated on the test track with an area under the curve (AUC) of 0.89 and a Pseudo Energy Ratio Fall-Out (PERFO) of 8%.

scholarly journals A Thermophilic Bacterial Esterase for Scavenging Nerve Agents: A Kinetic, Biophysical and Structural Study

Molecules ◽  
2021 ◽  
Vol 26 (3) ◽  
pp. 657
Author(s):  
Janek Bzdrenga ◽  
Elodie Trenet ◽  
Fabien Chantegreil ◽  
Kevin Bernal ◽  
Florian Nachon ◽  
...  
Keyword(s):  
Amino Acids ◽  
Structural Study ◽  
Nerve Agents ◽  
Toxic Compounds ◽  
X Ray ◽  
X Ray Crystallography ◽  
Major Threat ◽  
Skin Decontamination

Organophosphorous nerve agents (OPNA) pose an actual and major threat for both military and civilians alike, as an upsurge in their use has been observed in the recent years. Currently available treatments mitigate the effect of the nerve agents, and could be vastly improved by means of scavengers of the nerve agents. Consequently, efforts have been made over the years into investigating enzymes, also known as bioscavengers, which have the potential either to trap or hydrolyze these toxic compounds. We investigated the previously described esterase 2 from Thermogutta terrifontis (TtEst2) as a potential bioscavenger of nerve agents. As such, we assessed its potential against G-agents (tabun, sarin, and cyclosarin), VX, as well as the pesticide paraoxon. We report that TtEst2 is a good bioscavenger of paraoxon and G-agents, but is rather slow at scavenging VX. X-ray crystallography studies showed that TtEst2 forms an irreversible complex with the aforementioned agents, and allowed the identification of amino-acids, whose mutagenesis could lead to better scavenging properties for VX. In conjunction with its cheap production and purification processes, as well as a robust structural backbone, further engineering of TtEst2 could lead to a stopgap bioscavenger useful for in corpo scavenging or skin decontamination.

scholarly journals Comparative analysis of tripod offshore structure

2020 ◽  
Vol 72 (11) ◽  
pp. 1021-1030
Keyword(s):  
Comparative Analysis ◽  
Finite Elements ◽  
Velocity Profile ◽  
Wave Forces ◽  
Wave Loads ◽  
Analysis Program ◽  
Offshore Structure ◽  
Marine Structures ◽  
Finite Elements Analysis ◽  
Structural Parts

Marine structures are nowadays used in a variety of ways. The analysis of a tripod-type offshore structure sixty m in total height is performed in this study. In addition to operation-related loads, the structure is also under the effect of wind and wave loads. While the Eurocode velocity profile is used to calculate wind forces, the Airy wave velocity profile is utilized to determine wave forces. The model is created by a finite elements analysis program, and is composed of fluid and structural parts. The interaction of the parts is ensured by Coupled Eulerian Lagrangian (CEL) technique.

Semi-Active Vibration Control of a Marine Structure With Magnetorheological (MR) Dampers Utilizing LQR Method

2010 ◽  
Author(s):  
Mohammad Sajjad Daneshfard ◽  
A. Zabihollah
Keyword(s):  
Degrees Of Freedom ◽  
Structural Integrity ◽  
Dynamic Range ◽  
Active Vibration Control ◽  
Linear Quadratic Regulator ◽  
Linear Quadratic ◽  
Offshore Structure ◽  
Marine Structures ◽  
Mr Dampers ◽  
Marine Structure

The developing of technology has discovered new materials which have been applied to improve the performance of structures. The researchers have recently increased the attention in controllable fluids and its applications. Magnetorheological (MR) dampers are devices that employ rheological fluids to modify their mechanical properties. Their mechanical simplicity, high dynamic range, lower power requirements, large force capacity, robustness and safe manner operation in case of fail have made them attractive devices to passive, semi-active and active control in mechatronic, civil, aerospace and automotive applications. The characteristics of the MR damper change when the rheological fluid is exposed to a magnetic field changing its stiffness and damping coefficients. For this study, a marine structure exposed to different excitations has been considered in which some members have been substituted by the MR dampers. Prevention of serious damage of marine structures like the problems are generated by vibrations might be achieved by monitoring the loading conditions and by inspecting the structural integrity. The concept of smart structures can be applied to marine applications. There are plenty of marine structures in huge dimensions, for example, the overall length of a very large crude carrier exceeds 50 m. This offshore structure has 12 links and 21 nodes in each sides and each node has 2 degrees of freedom in X, Y directions. It is applied 7 MR dampers on critical links and controls the environmental vibrations and loading. Environmental loadings are divided into three general groups; Winds, wave and currents. All of maintained points are considered in analyzing of the offshore structure. Control the vibration of a marine structure in order to prevent the collapse of these structures is final purpose of this research. The controlling and the suppressing of this vibration have been done through Magnetorheological (MR) fluid dampers. The controlling method is used by the linear quadratic Regulator (LQR) as controller of this system and the results shows that it acceptable method in order to the amplitude of these vibrations.

Offshore Structures

2019 ◽  
pp. 69-127
Author(s):  
Mavis Sika Okyere
Keyword(s):  
Fire Resistance ◽  
Fire Protection ◽  
Fire Safety ◽  
Structural Design ◽  
Oil And Gas ◽  
Load Condition ◽  
Condition Assessment ◽  
Offshore Structures ◽  
Offshore Structure ◽  
Major Threat

Fire will always be a major threat to the offshore structure as oil and gas always passes through the installation. The design against accidental fire situation should be included in the structural design of offshore structures in collaboration with safety engineers. The design of offshore structures for fire safety involves considering fire as a load condition, assessment of fire resistance, use of fire protection materials, and so on. This chapter presents a methodology that will enable an engineer to design an offshore structure to resist fire. It aims to highlight the major requirements of design and to establish a common approach in carrying out the design.

The Change of Stress on Marine Concrete Covered with Barnacles

2014 ◽  
Vol 584-586 ◽  
pp. 1031-1034
Author(s):  
Gen Li Wang ◽  
Zheng Mao Ye ◽  
Bin Wu
Keyword(s):  
Dynamic Load ◽  
Static Load ◽  
Concrete Surface ◽  
Simplified Model ◽  
Marine Structures ◽  
Marine Fouling ◽  
Marine Concrete ◽  
Fouling Organisms

Barnacle is a major creature in marine fouling organisms, it increases static load and dynamic load of marine structures. In this paper, the change of stress on marine concrete surface covered with barnacles is studied. Moreover, a simplified model is established. The result shows that the stress of seawater increases by 0.53 times on the concrete surface, which is covered with barnacles.

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