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The "Water-energy-food" nexus is an important content in the field of ecosystem security. Constructing and optimizing the ecological security pattern from this perspective is of great significance to alleviate the contradiction between social production and ecosystem and improve people's well-being. With the rapid economic development in the Guangdong-Hong Kong-Macao Greater Bay Area, the contradiction between supply and demand of water, energy and food resources is prominent. This study evaluates the ecosystem services in the Greater Bay Area from the three dimensions of "water-energy-food", modifies the ecological resistance surface by using Luo Jia No.1 luminous data, and constructs and optimizes the ecological security pattern of the Greater Bay Area by using the minimum cumulative resistance model. The findings are as follows: (1) The total area of ecological source in the Greater Bay Area is 9,626.1 km2, mainly distributed in the mountainous and hilly areas in the east and west of the study area, corresponding to Jiangmen City, the middle of Huizhou City and Zhaoqing City, with an average altitude of over 1,000 m above sea level and relatively high terrain, dominated by woodlands. (2) There are 38 ecological corridors in total, with a total length of 2,023.09 km, of which the shortest is 11.76 km and the longest is 304.99 km. They are concentrated in the mountainous and hilly areas with good vegetation coverage, and there are no corridors in the middle. (3) The radiation area of ecological source is 28,929.5 km2, accounting for 51.88% of the total area of the Greater Bay Area. The western part of the study area is almost completely covered, with more areas remaining uncovered in the east. In order to achieve 60% coverage, it is necessary to add a minimum of 4,524.856km2 of ecological source radiation area in both the northern and southern parts of Huizhou. (4) Based on the distribution of the "water-energy-food" nexus in different regions, it is proposed to construct an ecological security pattern optimization model with "one belt, one axis and four clusters" as the core which could provide scientific references for regional ecological space development from the perspective of "water-energy-food".

The Fuzzy C means algorithm cannot effectively segment object pixels from a non-destructive testing ( NDT) image because of the great difference between the background and the object region. Therefore, a fast fuzzy C means algorithm for segmentation of NDT image was proposed in this study. In the process of clustering, local spatial information and gray information were introduced to improve the robustness of the algorithm. The condition value was used to represent the sample size to balance clusters of different sizes and solve the cluster-size sensitivity problem. Based on the new constraints, a new form of membership degree and cluster center representation could be obtained. The execution time of image segmentation was no longer determined by the size of the image, but by the gray level of the image. The computational complexity of the algorithm was greatly reduced. NDT images and synthetic images with a large difference in cluster size were used for testing. The segmentation accuracy ( SA), F-value, G-mean and the execution time of image segmentation were used to evaluate the performance of algorithms. The experimental results showed that when the original test image was polluted by Gaussian noise, salt and pepper noise, Rayleigh noise and multiplicative noise, the proposed algorithm had better robustness, SA is 97. 93%, F-value is 88. 50%, G-mean is 93. 83%, the execution time of image segmentation was less, about 14. 06 ms. The simulation tests could verify the effectiveness of the proposed algorithm. [ABSTRACT FROM AUTHOR]

Adenine (A) and guanine (G) are mainly found in deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) and play a crucial role in genetic information transfer and protein synthesis. In this study, NH2-MIL-53(Fe)/CS/MXene nanocomposites were prepared for detecting guanine and adenine. With high specific surface area, excellent water dispersion, and numerous active sites, MXene (transition metal carbides, nitrides, and carbonitrides) provides a good platform for loading primitive metal-organic frameworks (MOFs). At the same time, the problem of poor conductivity and dispersion of MOFs is solved. The electrochemical catalytic oxidation of adenine and guanine of NH2-MIL-53 (Fe)/CS/MXene nanocomposites was carried out by differential pulse voltammetry (DPV). Operating voltage of DPV: 0.7–0.9 V (vs. Ag/AgCl) for G, 1.0–1.2 V (vs. Ag/AgCl) for A, 0.8 V (vs. Ag/AgCl), and 1.1 V (vs. Ag/AgCl) for G and A. The concentration ranges for detecting A and G were 3–118 μM and 2–120 μM with detection limits of 0.57 μM and 0.17 μM (S/N = 3), respectively. The nanocomposite was used for detecting G and A in herring sperm DNA, and the content of G and A was found to be about 9 and 11 μM; the RSD values were 3.4 and 1.3%, respectively. [ABSTRACT FROM AUTHOR]