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Journal of Ocean University of China (English Edition)
Journal Prestige (SJR): 0.265  Citation Impact (citeScore): 1 Number of Followers: 1  Hybrid journal (It can contain Open Access articles)ISSN (Print) 1993-5021 - ISSN (Online) 1672-5182 Published by Springer-Verlag  [2468 journals]
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- Underwater Image Transmission Method and Realization Based on Inductively
Coupled Mooring Chain-
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Abstract: Abstract Inductively coupled mooring chain transmission technology plays a crucial role in the long-distance online monitoring of marine hydrographic information. However, the impedance characteristics of the seawater medium pose a limitation on its capability to achieve high-speed real-time transmission of underwater images. In this paper, based on the principle of inductively coupled transmission for marine applications, the selected 1920 × 1080 pixel images are segmented, packaged, and then transmitted to the sending node using the user datagram protocol (UDP), and the modulation and demodulation of the transmitted images are realized using the orthogonal frequency division multiplexing (OFDM) algorithm of least squares (LS) estimation, and eight combinations with different mapping modes and coding rates are tested in the bandwidth of 200–800 kHz and the quality of the transmitted images is evaluated using three criteria: mean squared error (MSE), peak signal to noise ratio (PSNR), and structural similarity index (SSIM). The results indicate that the image transmission quality is optimal when the mapping method is 16-quadrature amplitude modulation (16QAM), the coding rate is 1/2, and the center frequency is 800 kHz. Under these conditions, the maximum transmission rate is 0.84 Mbits−1, the SSIM criterion exceeds 0.91690 dB, and the learned perceptual image patch similarity (LPIPS) is less than 0.06000. This paper provides a solution for the underwater image transmission of inductively coupled mooring chains for marine applications.
PubDate: 2024-08-09
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- Investigating the Impact of Ocean Acidification on Anti-Stress Mechanisms
in Sepia esculenta Larvae Based on Transcriptome Profiling-
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Abstract: Abstract With the rapid development of oil, energy, power and other industries, CO2 emissions rise sharply, which will cause a large amount of CO2 in the air be absorbed by the ocean and lead to ocean acidification. The growth and development of organisms can be seriously affected by acidified seawater. Sepia esculenta is a mollusk with high nutritional and economic value and is widely cultured in offshore waters of China. Larvae are the early life forms of the organism and are more vulnerable to changes in the external environment. Too low pH will lead to some adverse reactions in larvae, which will affect metabolism, immune response and other life activities. In this study, we sequenced the transcriptome of S. esculenta subjected to acidified seawater stress and identified 1072 differentially expressed genes (DEGs). The detected atypical expression of DEGs substantiates cellular malformation and translocation in S. esculenta under low pH stimulation. Simultaneously, this also substantiates the notable impact of ocean acidification on mollusks. These DEGs were used for functional enrichment analysis of GO and KEGG, and the top twenty items of the biological process classification in GO terms and 11 KEGG signaling pathways were significantly enriched. Finally, the constructed protein-protein interaction network (PPI) was used to analyze protein-protein interactions, and 12 key DEGs and 3 hub genes were identified. The reliability of 12 genes was verified by quantitative RT-PCR. A comprehensive analysis of the KEGG signaling pathway and PPI revealed that ocean acidification leads to abnormalities in lipid metabolism in S. esculenta larvae, which can lead to cancer development and metastasis, accompanied by some degree of inflammation. The results of the study will help to further investigate the physiological processes of S. esculenta when stimulated by ocean acidification, and provide a reference to cope with the captive breeding of S. esculenta affected by acidification.
PubDate: 2024-08-01
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- Analysis of Tidal Current Energy Potential in the Major Channels of the
Bohai Strait Based on Delft3D-
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Abstract: Abstract The utilization and development of tidal current energy can help alleviate the current energy shortage, improve the global ecological environment, and maintain sustainable development. In this study, numerical simulation is carried out on a rectangular grid using Delft3D. The tidal current energy potential of the major channels in the Bohai Strait is further simulated and estimated by comparing the simulated and measured data. Results show that the flow module in Delft3D has good modeling ability for the assessment of tidal current energy potential. The average flow velocity, maximum flow velocity, and energy flow density are consistent. The Laotieshan Channel, located in the northern part of the Bohai Strait, shows a large tidal current energy potential. The maximum flow velocity of this channel can reach 2 m s−1, and the maximum energy flow density can exceed 500 W m−2. The tidal current energy in the Laotieshan Channel is more than 10 times that in other channels. Therefore, this study advocates for the continued exploration and exploitation of the tidal current energy resources in the Laotieshan Channel.
PubDate: 2024-08-01
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- Characteristics and Preliminary Causes of Tropical Cyclone Remote
Precipitation over China-
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Abstract: Abstract In this study, the characteristics and preliminary causes of tropical cyclone remote precipitation (TRP) over China during the period from 1979 to 2020 are investigated. Results indicated that approximately 72.42% of tropical cyclones (TCs) in the Western Pacific produce TRP over China. The peak months for TRP are July and August. The four key regions of TRP are the adjacent areas between the Sichuan and Shaanxi Provinces, the northern coast of the Bohai Sea, the coast of the Yellow Sea, and the southern coast area. The typical distance between the station with TRP and the TC center ranges from 1500 to 2500 km. Most of these stations are situated north to 60° west of north of the TC. The south–west water vapor transportation on the west side of the TC is crucial to TRP. TRP has a decreasing trend because of the decrease in the number of TCs that generate TRP. From the perspective of large-scale environmental conditions, a decrease in the integrated horizontal water vapor transport in Mainland China, the weakening of upward motion at approximately 25°–35°N, which is inconducive to convection, and an increase in low-level vertical wind shear, which is unfavorable for the development of TC in areas with high frequencies of TRP-related TCs, are the factors that result in the decreasing trend of TRP.
PubDate: 2024-08-01
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- Cyclic Beam Direction of Arrival Estimation Method for Ship Propeller
Noise-
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Abstract: Abstract In underwater acoustic applications, the conventional cyclic direction of arrival algorithm faces challenges, including a low signal-to-noise ratio and high bandwidth when compared with modulated frequencies. In response to these issues, this paper introduces a novel, robust, and broadband cyclic beamforming algorithm. The proposed method substitutes the conventional cyclic covariance matrix with the variance of the cyclic covariance matrix as its primary feature. Assuming that the same frequency band shares a common steering vector, the new algorithm achieves superior detection performance for targets with specific modulation frequencies while suppressing interference signals and background noise. Experimental results demonstrate a significant enhancement in the directibity index by 81% and 181% when compared with the traditional Capon beamforming algorithm and the traditional extended wideband spectral cyclic MUSIC (EWSCM) algorithm, respectively. Moreover, the proposed algorithm substantially reduces computational complexity to 1/40th of that of the EWSCM algorithm, employing frequency band statistical averaging and covariance matrix variance.
PubDate: 2024-08-01
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- Multiple Matching Attenuation Based on Curvelet Domain Extended Filtering
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Abstract: Abstract The paper develops a multiple matching attenuation method based on extended filtering in the curvelet domain, which combines the traditional Wiener filtering method with the matching attenuation method in curvelet domain. Firstly, the method uses the predicted multiple data to generate the Hilbert transform records, time derivative records and time derivative records of Hilbert transform. Then, the above records are transformed into the curvelet domain and multiple matching attenuation based on least squares extended filtering is performed. Finally, the attenuation results are transformed back into the time-space domain. Tests on the model data and field data show that the method proposed in the paper effectively suppress the multiples while preserving the primaries well. Furthermore, it has higher accuracy in eliminating multiple reflections, which is more suitable for the multiple attenuation tasks in the areas with complex structures compared to the time-space domain extended filtering method and the conventional curvelet transform method.
PubDate: 2024-08-01
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- Identification of Shell Color-Associated Genes Using Mantle
Branch-Specific RNA Sequencing of Yellow-Colored Line of Pearl Oyster
Pinctada fucata martensii-
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Abstract: Abstract The yellow-colored line of pearl oyster Pinctada fucata martensii displays a yellow prismatic layer and a white nacreous layer that can be used as an ideal model for research on shell color formation. Micro-Raman spectroscopy and transcriptome analyses were performed to explore the potential molecular mechanism underlying the phenotype differentiation. The micro-Raman spectroscopy results indicate that the prismatic layer exhibits distinct characteristic peaks of carotenoids, while these peaks are not prominent in the nacreous layer. In the transcriptome comparison of the central zone of mantle and mantle edge tissue, which function in nacreous and prismatic layer formation, respectively, 935 significantly differentially expressed genes (DEGs) were identified, with 385 genes upregulated and 227 genes downregulated (∣log2(Fold change)∣> 1 and false discovery rate < 0.05) in the mantle edge tissue. Among these genes, some were associated with melanoma/melanogenesis, such as tyrosinase, zinc metalloprotease, glutathione S-transferase, and ATP-binding cassette sub-family; some were associated with the carotenoid-related pathway, including scavenger receptors, cytochrome P450 and lipoprotein receptor. Genes associated with porphyrin metabolism, including porphobilinogen deaminase, and copper/zinc superoxide dismutase, and genes associated with shell matrix protein, including amorphous calcium carbonate binding protein, shematrin, PIF, and collagen, also exhibited significantly different expressions. It is speculated that the different colours between prismatic layer and nacreous layer in the yellow-colored line of P. f. martensii might be resulted from melanin, carotenoids and porphyrin metabolism, while genes related to shell structure and biomineralization might also affect coloration. Our results provide new insights to understand the mechanism of shell color formation in mollusca.
PubDate: 2024-08-01
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- Combined Effect of Temperature and Cadmium on Molecular Responses of Hsp70
and P-gp Genes in Crassostrea gigas-
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Abstract: Abstract To evaluate the combined effect of temperature and cadmium on the molecular responses of heat shock protein 70 (hsp70) and P-glycoprotein (P-gp) in mantle, digestive gland and gills of Crassostrea gigas, oysters were exposed to combinations of five temperature levels (10, 15, 20, 25, and 30°C) and 10 µg L−1 cadmium for 21 days. Oysters were sampled for mRNA quantification by qPCR, and the results showed that the P-gp gene expression changed significantly after treatment at different temperatures and different treatment times. The P-gp gene expression was the highest in the digestive gland. Compared with the control group, the P-gp gene expression in cadmium treatment groups at all the different temperatures were significantly higher than the control group. The control oysters (kept at 10° during the whole experiment without cadmium) expressed low levels of hsp70, but the groups treated with cadmium displayed somewhat higher levels. The present study demonstrated hsp70 and P-gp played an important role in the detoxification of Cd in C. gigas, and confirmed temperature should be considered for the assessment of Cd-induced toxicity in oysters.
PubDate: 2024-08-01
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- The Response of Carbonate System to Watershed Urbanization Process in a
Semi-Arid River-
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Abstract: Abstract Different from rivers in humid areas, the variability of riverine CO2 system in arid areas is heavily impacted by anthropogenic disturbance with the increasing urbanization and water withdrawals. In this study, the water chemistry and the controls of carbonate system in an urbanized river (the Fenhe River) on the semi-arid Loess Plateau were analyzed. The water chemistry of the river water showed that the high dissolved inorganic carbon (DIC) concentration (about 37 mg L−1) in the upstream with a karst land type was mainly sourced from carbonate weathering involved by H2CO3 and H2SO4, resulting in an oversaturated partial pressure of CO2 (pCO2) (about 800 µatm). In comparison, damming resulted in the widespread appearance of non-free flowing river segments, and aquatic photosynthesis dominated the DIC and pCO2 spatiality demonstrated by the enriched stable isotope of DIC (δ13CDIC). Especially in the mid-downstream flowing through major cities in warm and low-runoff August, some river segments even acted as an atmospheric CO2 sink. The noteworthy is wastewater input leading to a sudden increase in DIC (> 55 mg L−1) and pCO2 (> 4500 µatm) in the downstream of Taiyuan City, and in cold November the increased DIC even extended to the outlet of the river. Our results highlight the effects of aquatic production induced by damming and urban sewage input on riverine CO2 system in semi-arid areas, and reducing sewage discharge may mitigate CO2 emission from the rivers.
PubDate: 2024-08-01
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- An Improved Chromosome-Level Genome Assembly and Annotation of Belted
Beard Grunt (Hapalogenys analis)-
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Abstract: Abstract Hapalogenys analis (order Lobotiformes) is an economically and ecologically significant fish species. It is a typical sedentary rocky reef fish and is primarily found in the northern Pacific Ocean. Here, we used Hi-C and PacBio sequencing technique to assemble a high-quality, chromosome-level genome for this species. The 539 Mb genome had a contig N50 with a size of 3.43 Mb, while 755 contigs clustered into 24 chromosomal groups with an anchoring rate of 99.02%. Of the total genomic sequence, 132.74 Mb (24.39%) were annotated as repeat elements. A total of 21360 protein-coding genes were identified, of which 20787 genes (97.32%) were successfully annotated to public databases. The BUSCO evaluation indicated that 96.90% of the total orthologous genes were matched. The phylogenetic tree representing H. analis and 14 other bony fish species indicated that the H. analis genome contained 364 expanded gene families related to olfactory receptor activity, compared with the common ancestor of H. analis and Sciaenidae. Comparative genomic analysis further identified 3584 contracted gene families. Branch-site modeling identified 277 genes experiencing positive selection, which may facilitate the adaptation to rocky reef environments. The genome reported here is helpful for ecological and evolutionary studies of H. analis.
PubDate: 2024-08-01
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- Extraction of Acoustic Normal Mode Depth Functions Using Range-Difference
Method with Vertical Linear Array Data-
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Abstract: Abstract Data-derived normal mode extraction is an effective method for extracting normal mode depth functions in the absence of marine environmental data. However, when the corresponding singular vectors become nonunique when two or more singular values obtained from the cross-spectral density matrix diagonalization are nearly equal, this results in unsatisfactory extraction outcomes for the normal mode depth functions. To address this issue, we introduced in this paper a range-difference singular value decomposition method for the extraction of normal mode depth functions. We performed the mode extraction by conducting singular value decomposition on the individual frequency components of the signal’s cross-spectral density matrix. This was achieved by using pressure and its range-difference matrices constructed from vertical line array data. The proposed method was validated using simulated data. In addition, modes were successfully extracted from ambient noise.
PubDate: 2024-08-01
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- Inversion of Seabed Geotechnical Properties in the Arctic Chukchi Deep Sea
Basin Based on Time Domain Adaptive Search Matching Algorithm-
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Abstract: Abstract The chirp sub-bottom profiler, for its high resolution, easy accessibility and cost-effectiveness, has been widely used in acoustic detection. In this paper, the acoustic impedance and grain size compositions were obtained based on the chirp sub-bottom profiler data collected in the Chukchi Plateau area during the 11th Arctic Expedition of China. The time-domain adaptive search matching algorithm was used and validated on our established theoretical model. The misfit between the inversion result and the theoretical model is less than 0.067%. The grain size was calculated according to the empirical relationship between the acoustic impedance and the grain size of the sediment. The average acoustic impedance of sub-seafloor strata is 2.5026 × 106 kg (s m2)−1 and the average grain size (θ value) of the seafloor surface sediment is 7.1498, indicating the predominant occurrence of very fine silt sediment in the study area. Comparison of the inversion results and the laboratory measurements of nearby borehole samples shows that they are in general agreement.
PubDate: 2024-08-01
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- Experimental Study on the Variation of Optical Imaging Characteristics
with Zenith Angle due to Internal Solitary Waves in Sunglint-
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Abstract: Abstract Internal solitary waves (ISWs) change the roughness of the sea surface, thus producing dark and bright bands in optical images. However, reasons for changes in imaging characteristics with the solar zenith angle remain unclear. In this paper, the optical imaging pattern of ISWs in sunglint under different zenith angles of the light source is investigated by collecting optical images of ISWs through physical simulation. The experiment involves setting 10 zenith angles of the light source, which are divided into area a the optical images of ISWs in the three areas show dark-bright mode, single bright band, and bright-dark mode, which are consistent with those observed by optical remote sensing. In addition, this study analyzed the percentage of the dark and bright areas of the bands and the change in the relative gray difference and found changes in both areas under different zenith angles of the light source. The MODIS and ASAR images display a similar brightness-darkness distance of the same ISWs. Therefore, the relationship between the brightness-darkness distance and the characteristic half-width of ISWs is determined in accordance with the eKdV theory and the imaging mechanism of ISWs of the SAR image. Overall, the relationship between them in the experiment is almost consistent with the theoretical result.
PubDate: 2024-08-01
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- Dietary Supplementation of β-Carotene Reveals miRNAs Involved in the
Regulation of Carotenoid Metabolism in Crassostrea gigas-
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Abstract: Abstract Carotenoids play crucial physiological roles in animals. A comprehensive investigation into the mechanism of carotenoid metabolism in oysters will establish a theoretical foundation for further development of its carotenoid-rich traits. However, the information on the function of miRNA in β-carotene metabolism in oysters is limited. To elucidate the mechanisms underlying miRNA regulation of carotenoid metabolism in oysters, we compared the expressions of miRNA in digestive gland tissues of Pacific oyster (Crassostrea gigas) fed with a β-carotene supplemented diet and a normal diet, respectively. A total of 690 candidate miRNAs in the Pacific oyster digestive gland tissues were identified, including 590 known miRNAs and 111 unknown miRNAs. Three differentially expressed miRNAs were obtained in the carotenoid-fed and normal groups, associated to 137 differentially expressed target genes. Moreover, the GO enrichment analysis revealed that the differentially expressed target genes were mainly involved in transmembrane transport activity. KEGG enrichment showed that the differentially expressed target genes were involved in ABC transport. Analysis of the mRNA-miRNA network revealed that novel0025 played a central role in carotenoid metabolism, and it was negatively correlated with the expression of 46 mRNAs. In addition, down-regulated expression of novel0025 upregulated the expression of the lipoprotein gene LOC105342186, suggesting a potential regulatory role in carotenoid metabolism. Our results provide useful information for elucidating the miRNA regulation mechanism during carotenoids metabolism in the Pacific oyster.
PubDate: 2024-08-01
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- Spatiotemporal Distributions of Bacterioplankton Communities in the
Qiantang River (Hangzhou Section), China-
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Abstract: Abstract The spatial and temporal distribution of bacterioplankton communities plays a vital role in understanding the ecological dynamics and health of aquatic ecosystems. In this study, we conducted a comprehensive investigation of the bacterioplankton communities in the Qiantang River (Hangzhou section). Water samples were collected quarterly from seven sites over a one-year period. Physical and chemical parameters, including dissolved oxygen (DO), water temperature (WT), chemical oxygen demand (COD), nitrite (NO2−), active phosphate (PO43−) and other indices were determined. In this study, the α diversity, β diversity and abundance differences of bacterial communities were investigated using 16S rRNA high-throughput sequencing analysis. The spatial and temporal distribution characteristics and main driving factors of the bacterioplankton community structure and diversity were discussed. The results showed that a total of 57 phyla were detected in the bacterioplankton community, among which Proteobacteria and Actinomycetes were the two dominant groups with the highest relative abundance. The results of PCoA based on Bray-Curtis distance showed that the sampling season had a slightly greater effect on the changes in bacterioplankton community structure in the Qiantang River. Mantel and partial Mantel test showed that environmental variables (Mantel r = 0.6739, P < 0.0001; partial Mantel r = 0.507, P = 0.0001) were more important than geographical distance (Mantel r = 0.5322, P < 0.001; partial Mantel r = 0.1563, P = 0.001). The distance attenuation model showed that there was significant distance attenuation in all four seasons, and the maximum limit of bacterial community diffusion was found in spring. RDA analysis showed that nine environmental factors, including COD, WT and DO, significantly affected community distribution (P < 0.05). This study provides valuable insights into the spatial and temporal distribution characteristics of bacterioplankton communities, shedding light on their ecological roles in the Qiantang River. The information obtained can guide future research on the interactions between bacterioplankton and their environment, enabling the development of effective conservation strategies and sustainable management practices for aquatic ecosystems.
PubDate: 2024-08-01
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- Characterization, Expression Pattern Analysis, and Cellular Localization
of Two Homologous MUC2 Genes in Japanese Flounder (Paralichthys olivaceus)
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Abstract: Abstract As a member of mucins family, MUC2 is an important component of mucus, which is characterized by tandem and irregular repeat sequences rich in threonine and serine. It is strongly expressed by goblet cells that are involved in innate immunity. Japanese flounder is an economically important marine flatfish. In this study, two homologous genes of MUC2 were identified, named MUC2-1 and MUC2-2. Depending on phylogenetic and structural analysis, MUC2-1 and MUC2-2 were clustered in two clades, respectively. Paralichthys olivaceus MUC2-1 showed a closer relationship with MUC2 in the higher vertebrates. Various healthy tissues were analyzed to determine the expression patterns, and both MUC2 genes showed high expression levels in the gills and intestines. Following Edwardsiella tarda challenge, P. olivaceus MUC2-1 and MUC2-2 both showed significant up-regulated expression in intestine and kidney. Moreover, MUC2-1 was significantly up-regulated in gill cell lines following PGN and polyI:C stimulation, and MUC2-2 was significantly up-regulated in gill cell lines following LPS stimulation. In addition, ISH results revealed that MUC2-1 and MUC2-2 showed the same tissue localization in intestine tissues, but displayed different localization in gill. The siRNA-mediated knockdown of MUC2-1 and MUC2-2 genes in the gill cell lines of Japanese flounder affected the expressions of galnt family genes and smad pathway members that are related to mucosal immunity. The results provided a valuable insight into understanding the functions of MUC2 on mucosal immune system in response to the invasion of bacterial pathogen.
PubDate: 2024-08-01
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- Vulnerability and Conservation of Nearshore Cetaceans to Increasing Vessel
Traffic: The Indo-Pacific Humpback Dolphin in the South China Sea-
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Abstract: Abstract A comprehensive risk assessment to evaluate the vulnerability of the nearshore cetaceans to increasing marine traffic is lacking. In this study, the risk to Indo-Pacific humpback dolphins (Sousa chinensis) in the main habitats in China was assessed based on a semiquantitative spatial vulnerability analysis. 85% of the (sub)population which overlapped with the lanes of ferries and/or cargo vessels, with exposure scores of 1.23 ± 0.31 (calculated based on the proportion of sea routes that overlap the dolphin’s range). A combination of high exposure to the sea routes and sensitivity to marine traffic would render the (sub)populations to be highly vulnerable (EPRE: 5.21 and XM: 4.47). A low frequency of vessels and an awareness of the ecology assures a low vulnerability (SH: 2.43, EZ: 2.73). Uncertainty scores were commonly lower for the higher vulnerable populations, and higher for the lower vulnerable populations, suggesting additional field data and more monitoring are necessary. Six years of field data have been used to analyze the influences of various types of marine traffic on humpback dolphin behavior. Fishing and non-fishing vessels were significantly different (χ2 = 65.19, p < 0.01). The humpback dolphins were attracted by fishing vessels (83.1%) but avoided non-fishing vessels (95.2%). We recommend a management with seasonal and geographical constraints, to balance economic development and environmental conservation.
PubDate: 2024-08-01
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- Bioinspired Polarized Optical Flow Enables Turbid Underwater Target Motion
Estimation-
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Abstract: Abstract Underwater target motion estimation is a challenge for ocean military and scientific research. In this work, we propose a method based on the combination of polarization imaging and optical flow for turbid underwater target detection. Polarization imaging can reduce the influence of backscattered light and obtain high-quality images underwater. The optical flow shows the motion and structural information of the target. We use polarized optical flow to obtain the optical flow field and estimate the target motion. The experimental results of different targets under varying water turbidity levels illustrate that our method is realizable and robust. The precision is verified by comparing the results with the precise displacement data and calculating two error measures. The proposed method based on polarized optical flow can obtain accurate displacement information and a good recognition effect. Moving target segmentation based on the Otsu method further proves the superiority of the polarized optical flow under turbid water. This study is valuable for target detection and motion estimation in scattering environments.
PubDate: 2024-08-01
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- Experimental Study on Consolidation Properties of Hydrate-Bearing
Fine-Grained Sediments Collected from the Shenhu Area of the Northern
South China Sea-
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Abstract: Abstract Mechanical properties of hydrate-bearing fine-grained sediments are crucial to effectively mitigate environmental risks caused by artificial and natural decomposition of natural gas hydrates, and the decomposition can induce laterally confined deformation. To explore the effect of natural gas hydrates on laterally confined compression properties, consolidation tests are conducted on remolded hydrate-free and hydrate-bearing samples by using natural fine-grained sediments collected from the northern South China Sea as the host sediments, and empirical equations are developed based on the analyses of consolidation characteristics. The results show that vertical loading induces a reduction in void ratio, and the reduction increases with decreasing hydrate saturation when samples are subjected to the same vertical stress change. The compression index of samples is about 0.53 whether there is hydrate or not, but the yield stress of samples increases sharply with increasing hydrate saturation once beyond the critical value. The coefficient of volume compression and the coefficient of consolidation of hydrate-bearing samples both increase firstly and then decrease to a relative stable level with increasing vertical stress, and the transition occurs at 200 kPa. The average consolidation degree with elapsed time increases rapidly under low vertical stresses, slowly under median vertical stresses, and under high vertical stresses, the consolidation increases a little faster but still slower than those under low vertical stresses.
PubDate: 2024-08-01
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- Dynamic Location Method for Shallow Ocean Bottom Nodes Using the
Levenberg-Marquart Algorithm-
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Abstract: Abstract Ocean bottom node (OBN) data acquisition is the main development direction of marine seismic exploration; it is widely promoted, especially in shallow sea environments. However, the OBN receivers may move several times because they are easily affected by tides, currents, and other factors in the shallow sea environment during long-term acquisition. If uncorrected, then the imaging quality of subsequent processing will be affected. The conventional secondary positioning does not consider the case of multiple movements of the receivers, and the accuracy of secondary positioning is insufficient. The first arrival wave of OBN seismic data in shallow ocean mainly comprises refracted waves. In this study, a nonlinear model is established in accordance with the propagation mechanism of a refracted wave and its relationship with the time interval curve to realize the accurate location of multiple receiver movements. In addition, the Levenberg-Marquart algorithm is used to reduce the influence of the first arrival pickup error and to automatically detect the receiver movements, identifying the accurate dynamic relocation of the receivers. The simulation and field data show that the proposed method can realize the dynamic location of multiple receiver movements, thereby improving the accuracy of seismic imaging and achieving high practical value.
PubDate: 2024-08-01
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