ocean environment
Recently Published Documents


TOTAL DOCUMENTS

594
(FIVE YEARS 132)

H-INDEX

32
(FIVE YEARS 4)

2022 ◽  
Vol 247 ◽  
pp. 106177
Author(s):  
Jennifer L. Cudney ◽  
Charles W. Bangley ◽  
Andrea Dell’Apa ◽  
Eric Diaddorio ◽  
Roger A. Rulifson

2022 ◽  
Vol 245 ◽  
pp. 110511
Author(s):  
Shuo Qiao ◽  
Lina Qing ◽  
Zongming Zhu ◽  
Yao Wu ◽  
Yuanwen Li ◽  
...  

2022 ◽  
Vol 10 (1) ◽  
pp. 76
Author(s):  
Ruigeng Hu ◽  
Xiuhai Wang ◽  
Hongjun Liu ◽  
Hao Leng

A novel scour protection approach for pipeline using the Ionic Soil Stabilizer (ISS) solidified soil was proposed in this study. The ISS-solidified slurry can be poured adjacent to the pipeline immediately after it was placed, or in the growing scour holes. In the present study, the first type was utilized as the scour protection layer around the pipeline. A series of laboratory flume tests were conducted to validate the protective capacity of ISS-solidified slurry for the pipeline in waves and combined waves and current. Then, the scanning electron microscope (SEM) tests and pore size tests were carried out, respectively, to investigate the mechanism of ISS-solidified slurry for scour protection around the pipeline. Finally, the effects of the ISS-solidified layer for liquefaction stability of non-cohesive subsoil were evaluated. The results indicated that the ISS-solidified slurry is a reliable, economic approach for scour protection around pipelines in the ocean environment. It is noteworthy that if a non-cohesive soil layer underlies the ISS-solidified slurry, it is vulnerable to suffer accumulated liquefaction due to the dense crust structure of the ISS-solidified layer, so the adverse effects for accumulated liquefaction should be considered carefully due to the set of the ISS-solidified layer.


2022 ◽  
Vol 72 (1) ◽  
pp. 122-132
Author(s):  
Remadevi M. ◽  
N. Sureshkumar ◽  
R. Rajesh ◽  
T. Santhanakrishnan

Towed array sonars are preferred for detecting stealthy underwater targets that emit faint acoustic signals in the ocean, especially in shallow waters. However, the towing ship being near to the array behaves as a loud target, introducing additional interfering signals to the array, severely affecting the detection and classification of potential targets. Canceling this underlying interference signal is a challenging task and is investigated in this paper for a shallow ocean operational scenario where the problem is more critical due to the multipath phenomenon. A method exploiting the eigenvector analysis of spatio-temporal covariance matrix based on space time adaptive processing is proposed for suppressing tow ship interference and thus improving target detection. The developed algorithm learns the interference patterns in the presence of target signals to mitigate the interference across azimuth and to remove the spectral leakage of own-ship. The algorithm is statistically analyzed through a set of relevant metrics and is tested on simulated data that are equivalent to the data received by a towed linear array of acoustic sensors in a shallow ocean. The results indicate a reduction of 20-25dB in the tow ship interference power while the detection of long-range low SNR targets remain largely unaffected with minimal power-loss. In addition, it is demonstrated that the spectral leakage of tow ship, on multiple beams across the azimuth, due to multipath, is also alleviated leading to superior classification capabilities. The robustness of the proposed algorithm is validated by the open ocean experiment in the coastal shallow region of the Arabian Sea at Off-Kochi area of India, which produced results in close agreement with the simulations. A comparison of the simulation and experimental results with the existing PCI and ECA methods is also carried out, suggesting the proposed method is quite effective in suppressing the tow ship interference and is immensely beneficial for the detection and classification of long-range targets.


2021 ◽  
Vol 44 (4) ◽  
pp. 485-495
Author(s):  
V. N. Ekzaryan ◽  
A. K. Akhmadiev

The oil and gas industry has been evolving for 150 years. Despite the predictions on the diminishing role of hydrocarbons in the second half of the 21st century, today they play a leading role in the global energy sector. In view of this there is some interest to study current development trends of the industry. This paper reviews and analyses data for the period from 2011 to 2021, which relate to the development of hydrocarbon resources in the marine and ocean environment. It was important for the authors to consider how the trends they highlighted are affecting or will affect ecosystems. The conducted research has showed that today there are three main development trends in hydrocarbon mining in the World ocean: development of the marine Arctic, continental shelf and the possibility to organize commercial production in the deep sea areas of the World ocean. For each of the directions both existing and potential ecological risks have been identified. They include loss of marine biodiversity, activation of dangerous geological processes, unpredictability of ocean environment, man-made accidents and disasters, discharges of drilling and other industrial waste, etc. The work has also identified the challenges facing the oil and gas industry. These include the search for new technologies for deep-sea production, poorly understood depth of the World ocean, need for new approaches in environmental risk management, as well as the creation of a legal framework for subsoil use regulation in new environments and areas.


Author(s):  
Abhishek Kumar Tewari ◽  
R Vijayakumar

Underwater Radiated Noise (URN) emanating from surface and underwater marine platforms has become a significant concern for all the Nations in view of the global requirement to minimise the increasing adverse impact on marine mammals and fishes and maintain ecological balance in the ‘Silent’ ocean environment. Ambient noise level in the sea, in 10 to 300 Hz frequency band, has increased by 20 to 30 dB due to shipping (Wittekind, 2009). Marine propeller (in non- cavitating and cavitating regime) is a potential contributor to the ships noise and a lot of scientific research has been undertaken and considerable progress has been achieved in estimating the hydro-acoustic performance of marine propellers. In light of this, the scope of this paper is to review and critically examine the various methods used for estimating the hydro-acoustic performance of marine propellers, particularly in the non-cavitating regime, over the past many years. This review paper brings out the details, applicability, merits and demerits of various methods, extrapolation laws to obtain full scale results, scientific conclusion of all the know-how on this subject and the scope of further research as perceived by the authors. This paper also presents a numerical methodology to estimate the noise radiated by a DTMB 4119 model propeller in the non-cavitating regime in open water condition. The hydrodynamic analysis of the propeller was performed using commercial CFD software STARCCM+, closure was achieved using standard k-ε turbulence model and hydro-acoustic predictions have been performed using FWH acoustic analogy. The results compare very well with the published literature.


2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Benshuo Yang ◽  
Haojun Xu

PurposeJapan's decision to release nuclear wastewater into the Pacific Ocean in 2023 has sparked strong opposition at home and abroad. In this study, Graph Model for Conflict Resolution (GMCR) method is adopted to analyze the conflict problem, and reasonable equilibrium solutions are given to solve the conflict event.Design/methodology/approachIn this study, GMCR is adopted to solve the conflict problem. First, identify the key decision-makers (DMs) on the issue of nuclear effluent and the relevant options they might adopt. Second, the options of each DM are arranged and combined to form a set of feasible states. Thirdly, the graph model is constructed according to the change of DM's options, and the relative preference of each DM is determined. Finally, the conflict problem is solved according to the definition of GMCR equilibrium.FindingsDischarging nuclear wastewater into the ocean is not the right choice to solve the problem. Developing more space to store nuclear wastewater is more conducive to the protection of the ocean environment.Practical implicationsIt is undesirable for the Japanese government to unilaterally discharge nuclear wastewater into the ocean. Objectively assessing the radioactivity of nuclear wastewater and the cooperation of relevant stakeholders can better solve this conflict.Originality/valueThe problem arising from Japan's releasing plan is complicated because of a lack of information and the existence of multiple stakeholders, while GMCR can help us with a better view of the current circumstance in the conflict.


2021 ◽  
Author(s):  
Qinghua Luo ◽  
Xiaozhen Yan ◽  
Chenxu Wang ◽  
Yang Shao ◽  
Zhiquan Zhou ◽  
...  

Abstract The navigation and positioning subsystem offers important position information for an autonomous underwater vehicle (AUV) system. It plays a crucial role during the underwater exploration and operations of AUV. Many scholars research underwater navigation and positioning. And many promising methods and systems were presented. However, as the diversity of ocean environment, the random drift of the gyroscope, error accumulation, the diversity of tasks, and other negative factors, the navigation and positioning result is uncertain and incredible. The accuracy, stability and robustness are not guaranteed, which can not meet the increasing application requirement. Therefore, we put forward a SINS/DVL/USBL integrated navigation and positioning IoT system with multiple resource fusion and a federated Kalman filter. In this method, we first present an improved SINS/DVL combined subsystem with filtering gain compensation strategy. The accuracy and stability of the navigation and position system can be enhanced. Secondly, We proposed a USBL positioning subsystem with the Kalman filtering acoustic signals to improve USBL positioning performance. Lastly, we present a federated Kalman Filter to fuse the positioning information from the SINS/DVL combined positioning subsystem and the USBL positioning subsystem. Through the above three methods, we can improve the positioning accuracy and robustness. Comprehensive simulation results indicated the feasibility and effectiveness of the proposed SINS/DVL/USBL integrated navigation and positioning system.


2021 ◽  
Vol 12 ◽  
Author(s):  
Shigekatsu Suzuki ◽  
Masanobu Kawachi ◽  
Chinatsu Tsukakoshi ◽  
Atsushi Nakamura ◽  
Kyoko Hagino ◽  
...  

Marine phytoplankton are major primary producers, and their growth is primarily limited by nitrogen in the oligotrophic ocean environment. The haptophyte Braarudosphaera bigelowii possesses a cyanobacterial endosymbiont (UCYN-A), which plays a major role in nitrogen fixation in the ocean. However, host-symbiont interactions are poorly understood because B. bigelowii was unculturable. In this study, we sequenced the complete genome of the B. bigelowii endosymbiont and showed that it was highly reductive and closely related to UCYN-A2 (an ecotype of UCYN-A). We succeeded in establishing B. bigelowii strains and performed microscopic observations. The detailed observations showed that the cyanobacterial endosymbiont was surrounded by a single host derived membrane and divided synchronously with the host cell division. The transcriptome of B. bigelowii revealed that B. bigelowii lacked the expression of many essential genes associated with the uptake of most nitrogen compounds, except ammonia. During cultivation, some of the strains completely lost the endosymbiont. Moreover, we did not find any evidence of endosymbiotic gene transfer from the endosymbiont to the host. These findings illustrate an unstable morphological, metabolic, and genetic relationship between B. bigelowii and its endosymbiont.


2021 ◽  
Vol 241 ◽  
pp. 110050
Author(s):  
Peng Yao ◽  
Liyan Qiu ◽  
Jiaping Qi ◽  
Rui Yang

Sign in / Sign up

Export Citation Format

Share Document