The storage pressure and reconstruction of the mesostructure of gas-bearing sediments are key factors in the study of shallow gas geohazards. Using an industrial CT scanning test system, vertical rotational (SR) scanning is used, with the position of the microfocus X-ray source fixed and the sample rotated at a constant speed of 360° along the XY plane, with a set rotation step of 0.3° per second, the gas-bearing samples in the reactor are pressurized to 2 MPa, 4 MPa, and 6 MPa, taking into account the best resolution of the sample imaging, the best detection range and other. The results show that the slices and reconstructed images obtained from the CT scan have good experimental results; the greyscale values of small bubbles increase when pressurized to 2 MPa; the overall greyscale values of gas increase significantly when pressurized to 6 MPa; the number of bubbles decrease with increasing bubble radius during the pressurization process; the pressurization process lead to local changes in the solid-liquid-gas phase, which show that the volume of pore gas and pore water changes more than that of the soil skeleton. The overall change is greater than that of the soil skeleton, and the microscopic local location will have a greater rise or decrease. When the gas content at different locations rises and dominates, it will drive the reduction of pore water and the movement of the soil skeleton.

Tuna is an important fishing target in China’s pelagic fishery. Its morphological indexes are of great significance for the study of the growth, development and life history of tunas. Manual measurement of morphological index is a very tedious and inefficient measurement method, while computer vision is an efficient and objective automatic measurement method. Therefore, in this paper, images of three Thunnus species are preprocessed by the computer vision library (OpenCV). It mainly uses image processing techniques such as bilateral filter, gray transformation, image binarization and contour extraction to obtain the contour image of tuna. According to the pre-selected feature points, the computer vision technology is used to traversal all the pixel points on the contour image, and 17 pre-selected feature points of each contour image are automatically located. By using the computer vision technology, the pixel length of the morphological index of the three species of tuna is automatically measured and the actual length of the morphological index is calculated. The absolute error and relative error between automatic measurement and manual measurement are compared and analyzed. The results show that the computer vision technique is effective in the automatic measurement of the morphological indexes of the three Thunnus species. The absolute error ranges of 12 morphological indices of Thunnus obesus, Thunnus albacores and Thunnus alalunga are 0.00−1.46 cm, 0−1.73 cm and 0−1.32 cm, respectively, and the relative error ranges are 0.01%−5.84%, 0%−6.17% and 0%−6.89%, respectively. It is expected to provide a basis for intelligent identification of tuna and a basic reference for automatic measurement of other fish.

In order to explore the effects of low temperature stress on the expression of genes related to lipid synthesis and catabolism in cobia (Rachycentron canadum), the experiment set up a normal temperature group (30.5±1.0)°C and a low temperature group (20.0±0.5)°C, and used real-time fluorescent quantitative PCR (qRT-PCR) to analyze the expression levels of 5 target genes in liver, muscle and intraperitoneal fat (IPF). The results showed that at 1 d, the expression of carnitine palmitoyl transferase-1 and hormone-sensitive lipase genes of liver, carnitine palmitoyl transferase-1, hormone-sensitive lipase and monoacylglycerol lipase genes of muscle were up-regulated (p<0.05), acetyl-CoA carboxylase and fatty acid synthase genes of liver, muscle and 5 lipid metabolism related genes of IPF were significantly down-regulated (p<0.05); at 4 d, the expression of carnitine palmitoyl transferase-1, hormone-sensitive lipase and monoacylglycerol lipase genes of liver, and hormone-sensitive lipase, monoacylglycerol lipase, acetyl-CoA carboxylase, fatty acid synthase genes of muscle and carnitine palmitoyl transferase-1, hormone-sensitive lipase, monoacylglycerol lipase, acetyl-CoA carboxylase genes of IPF were up-regulated (p<0.05), acetyl-CoA carboxylase and fatty acid synthase gene of liver were down-regulated (p<0.05); at 7 d, the expressions of carnitine palmitoyl transferase-1, hormone-sensitive lipase, monoacylglycerol lipase, acetyl-CoA carboxylase genes of liver and IPF, and hormone-sensitive lipase, monoacylglycerol lipase, acetyl-CoA carboxylase genes of muscle were up-regulated (p<0.05), carnitine palmitoyl transferase-1 gene of muscle and fatty acid synthase genes of liver were down-regulated (p<0.05). The results showed that cobia responded to low temperature stress by inhibiting lipid synthesis and metabolism, promoting lipid hydrolysis in the liver and muscle, and inhibiting the lipid hydrolysis of IPF in the early stage of low temperature stress; in the late period of low temperature stress, cobia lipid synthesis and catabolism were significantly increased, and the main tissue that used fatty acids to provide energy was transformed from the liver and muscle to liver and IPF.

The community structure of scleractinian corals in the southwest seawaters the of the Weizhou Island was analyzed with the data collected in a survey conducted with the method of line intercept transect from May 14 to 22, 2019. The results showed that 38 species of scleractinian corals in 9 families were found, dominated by mass corals such as porites sp., favites abdita, goniopora stutchburyi etc. The coverage of the living scleractinian corals ranged from 5.20% to 31.20%, the average coverage were 16.66%, higher at the sites far from or close to the shore but with deeper water. The living scleractinian coral had low recruitment rate, few diseases and low mortality rate. Species diversity, dominance and evenness of the scleractinian coral communities were positively correlated one another (p<0.05). The coverage and biodiversity of the living scleractinian corals were higher at the sites where anthropogenic disturbance was less, i.e. closer to the cliff, deeper water, fewer boating and diving etc. The living scleractinian corals closer to sandy beach influenced severely by suspended sediment on eroded coast and diving had the lowest coverage, the highest dominance of the dominant species and relatively lower diversity. Human activities, southwest monsoon, storm surge, suspended sediment on eroded coast and extreme weather are the main influential factors on the coral reef ecosystem in the southwest seawaters of the Weizhou Island.

Numerous engineering projects show that beach nourishment is a common method against coastal erosion. Beach nourishment is an artificial process of adding sediment to a beach to increase beach width and protect it from erosion. In this paper, a 1D numerical model for beach profile was established and verified by the results of physical model experiment. In addition, the rates of profile change to equilibrium profile on different positions and different sand volume schemes were calculated, and the efficiency was compared and analyzed. To analyze the protection effects of beach nourishment, the profiles in nourishment schemes and no nourishment schemes after storm condition were compared. It turned out that when the nourishment volume was large the efficiency of bar nourishment under the calm condition was higher than of berm nourishment, and the nourishment effect under the storm condition was better. This study has important implications to save construction costs and raise working efficiency during the practical nourishment engineering. In the meantime, it sheds light on evaluating the effect of beach nourishment.

Tropical cyclone disaster is one of the most serious natural disasters, and its impact mainly depends on the center location and the intensity. Monitoring the location and the intensity of tropical cyclones is of great significance for improving the accuracy of tropical cyclone forecast and for reducing the impact of tropical cyclone disasters. In this paper, the characteristics of the HY-2B scatterometer wind field, as well as its divergence and curl, are analyzed. It is found that the divergence or curl of the wind field near the cyclone center shows remarkable signatures, such that a new method is proposed to identify the cyclone center, and then the results are compared with the conventional method. Moreover, a method for estimating the size of the tropical cyclone is introduced to evaluate the cyclone intensity. Finally, the remote sensing data of Typhoon Francisco and Typhoon Bualoi are used to verify the proposed methods. The results show that the difference between the cyclone center position determined by the scatterometer and the one of the optimal path is generally less than 20 km. Meanwhile, the determined wind radii correspond well with the development of the tropical cyclone.

China-France Oceanography Satellite scatterometer (CSCAT) is the first rotating fan beam scatterometer internationally, which was flown onboard China-France Oceanography Satellite (CFOSAT) on October 2018. Based on the maximum likelihood estimation wind inversion algorithm, the residual characteristics of the CSCAT sea surface wind inversion cost function in detail, focuses on the influence of the new observation geometry on the wind inversion residual and wind quality is analyzed in this article, we establish the likelihood probability model function of the ambiguous solutions. The results show that the residual characteristic of the CSCAT wind inversion varies with the position of the wind vector cell (WVC) across the swath. The exponential distribution of the ambiguous solution likelihood probability model function is between −0.4 and −1.8. The results provide an important reference for the quality control of CSCAT and the refinement adjustment of the two dimensional variational ambiguity removal algorithm.

Sea fog is a kind of disastrous weather phenomenon which occurs on the sea surface. Mastering the distribution and dynamic changes of sea fog can effectively reduce the disasters caused by sea fog. Satellite remote sensing observation has the characteristics of near real time, wide coverage, continuous observation and so on. Especially the geostationary satellite remote sensing observation with high time resolution, which can continuously and dynamically track the occurrence, development and extinction of sea fog. The sea fog events in the Yellow Sea and Bohai Sea are taken from 2018 to 2019 as examples in this paper. Based on the analysis of the multi-channel bright temperature radiation characteristics of sea fog in the Yellow Sea and Bohai Sea by using Himawari-8 (H-8) geostationary satellite data, the separation index of sea fog and cloud, the separation index of sea fog and water, the slope index of multi-band brightness temperature difference and texture index of mid-infrared bright temperature are defined through the difference and ratio combination of different bands, and the night sea fog monitoring algorithm based on multi-exponential probability distribution is proposed to realize the automatic identification of sea fog at night. The algorithm is applied to H-8 and GEO-KOMPSAT2A (GK-2A) geostationary satellite data respectively. The position distribution and coverage area of sea fog identify by multi-time satellite observations of six sea fog events from February to June 2020 are compared to achieve mutual verification. The results show that the algorithm proposed in this paper can effectively recognize sea fog at night. The monitoring results every 10 minutes of continuous observations of H-8 and GK-2A at night on April 29, 2020 are selected to follow up and analyze the area where sea fog occurred, it shows the occurrence, development and evolution of the sea fog event clearly. It indicates that the algorithm can monitor the distribution of sea fog and track the development and change of fog. It can provide scientific basis and decision-making basis for the prevention and mitigation of sea fog.

Data measured by ultrasonic anemometer moored at a fixed platform near Maoming City, Guangdong Province from February 15 to May 8, 2012 has been used to analyze turbulence within wave boundary layer. The results confirmed that under swell conditions, there are areas obviously affected by swell in the cospectrum and Ogive curves. Furthermore, the sign change of wave-induced Reynolds stress is related to wave age. This paper presents the statistical distribution of the sign reversal of the Reynolds stress caused by the waves in the along-wind and cross-wind directions with wave age. In addition, this paper extracts the wave-induced Reynolds stress τ_swell based on cospectrum method, and compares it with the wave-induced Reynolds stress τ_*swell calculated by traditional method. The results show that the value of τ_swell is 2−3 orders of magnitude larger than that of τ_*swell, which indicates that the traditional method significantly underestimates the wave-induced Reynolds stress, and the traditional method needs to be improved.

Using the 3-D numerical model Ecom-si, saltwater intrusion in the Changjiang Estuary and water take in the Qingcaosha Reservoir under different wind speeds are studied. Model results show that the high saline water in Subei is transported southward to the Changjiang Estuary. Ekman transport drives a surge along the coast and a horizontal circulation in the Changjiang Estuary, which enters the North Channel (NC) and exit through the South Channel. This process increases salinity in the NC. Under the mean river discharge in the dry season (11 900 m³/s), the net water flux across the mouth of the NC is landward when wind speed exceeds 10 m/s, and the saltwater in the NC can spill over into the South Channel when wind speed exceeds 11 m/s. When wind speed is 0, the 15-day averaged salinity in the NC is only 0.97 and the elevation at the mouth of the NC is only 0.13 m. When wind speed increases to 14 m/s, salinity in the NC increases to 27.4 and the elevation at the mouth of the NC increases to 0.42 m. North wind reduces the number of days that the Qingcaosha Reservoir could take water from Changjiang within a month. When wind speed is 0, the number of days is 29.4 and when wind speed exceeds 10 m/s, the number of days is 0. The salinity in the NC increases with the strength of north wind, which is unfavorable to water take in the Qingcaosha Reservoir.