789 research outputs found


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    The South China Sea policy of the United States after World War II was formed by the United States’ perception of the three events in the South China Sea before the Cold War. After events such as France’s occupation of the nine small islands in the South China Sea, Japan’s occupation of the South China Sea, and the struggle against Japan during the Pacific War, the United States has continuously deepened its understanding of the South China Sea and increasingly valued its important value. With Japan's gradual retreat in the later stages of World War II, the United States gradually gained control of the South China Sea and took a dominant position in the South China Sea dispute. With the continuous deepening of the United States' understanding of the South China Sea and the changes in its identity, status, and interests in the South China Sea region, the U.S. South China Sea policy has gradually taken shape

    Retrieving density and velocity fields of the ocean's interior from surface data

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    Author Posting. © American Geophysical Union, 2014. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research: Oceans 119 (2014): 8512–8529, doi:10.1002/2014JC010221.Using the “interior + surface quasigeostrophic” (isQG) method, the density and horizontal velocity fields of the ocean's interior can be retrieved from surface data. This method was applied to the Simple Ocean Data Assimilation (SODA) and the Hybrid Coordinate Ocean Model (HYCOM)/Navy Coupled Ocean Data Assimilation (NCODA) reanalysis data sets. The input surface data include sea surface height (SSH), sea surface temperature (SST), sea surface salinity (SSS), and a region-averaged stratification. The retrieved subsurface fields are compared with reanalysis data for three tested regions, and the results indicate that the isQG method is robust. The isQG method is particularly successful in the energetic regions like the Gulf Stream region with weak stratification, and the Kuroshio region with strong correlation between sea surface density (SSD) and SSH. It also works, though less satisfactorily, in the Agulhas leakage region. The performance of the isQG method in retrieving subsurface fields varies with season, and peaks in winter when the mixed layer is deeper and stratification is weaker. In addition, higher-resolution data may facilitate the isQG method to achieve a more successful reconstruction for the velocity retrieval. Our results suggested that the isQG method can be used to reconstruct the ocean interior from the satellite-derived SSH, SST, and SSS data in the near future.This work was jointly supported by the MOST of China (grant 2011CB403505 & 2014CB953904), the China Special Fund for Meteorological Research in the Public Interest (NO. GYHY201406008), the Strategic Priority Research Program of the Chinese Academy of Sciences (grant XDA11010304), National Natural Science Foundation of China (grant 41376021). J. Wang is supported by the National Science Foundation (NSF) through grant OCE-1234473.2015-06-1

    Mechanisms of global ocean ventilation age change during the last deglaciation

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    Marine radiocarbon (14C) is widely used to trace deep-ocean circulation, providing insight into the atmosphere–ocean exchange of CO2 during the last deglaciation. Evidence shows a significantly depleted Δ14C in the glacial deep ocean, suggesting an increased ventilation age at the Last Glacial Maximum (LGM). In this study, using two transient simulations with tracers of 14C and ideal age (IAGE), we found that the oldest ventilation age is not observed at the LGM. In contrast, the models show a modestly younger ventilation age during the LGM compared to the present day. The global mean ventilation ages averaged below 1 km are approximately 800 (630) years and 930 (2000) years at the LGM and in the present day, respectively, in two simulations. This younger glacial ventilation age is mainly caused by the stronger glacial Antarctic Bottom Water (AABW) transport associated with sea ice expansion. Notably, the ocean ventilation age is significantly older predominantly in the deep Pacific during deglaciation compared to the age at the LGM, with global mean ventilation ages peaking at 1900 and 2200 years around 14–12 ka in two simulations, primarily due to the weakening of AABW transport.</p

    Efficient Triangular Interpolation Method: Error Analysis and Applications

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    The interpolation errors of bivariate Lagrange polynomial and triangular interpolations are studied for the plane waves. The maximum and root-mean-square (RMS) errors on the right triangular, equilateral triangular and rectangular (bivariate Lagrange polynomial) interpolations are analyzed. It is found that the maximum and RMS errors are directly proportional to the (p+1)’th power of kh for both one-dimensional (1D) and two-dimensional (2D, bivariate) interpolations, where k is the wavenumber and h is the mesh size. The interpolation regions for the right triangular, equilateral triangular and rectangular interpolations are selected based on the regions with smallest errors. The triangular and rectangular interpolations are applied to evaluate the 2D singly periodic Green’s function (PGF). The numerical results show that the equilateral triangular interpolation is the most accurate interpolation method, while the right triangular interpolation is the most efficient interpolation method

    An Efficient Multilevel Fast Multipole Algorithm to Solve Volume Integral Equation for Arbitrary Inhomogeneous Bi-Anisotropic Objects

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    A volume integral equation (VIE) based on the mixed-potential representation is presented to analyze the electromagnetic scattering from objects involving inhomogeneous bi-anisotropic materials. By discretizing the objects using tetrahedrons on which the commonly used Schaubert-Wilton-Glisson (SWG) basis functions are defined, the matrix equation is derived using the method of moments (MoM) combined with the Galerkin’s testing. Further, adopting an integral strategy of tetrahedron-to-tetrahedron scheme, the multilevel fast multipole algorithm (MLFMA) is proposed to accelerate the iterative solution, which is further improved by using the spherical harmonics expansion with a faster implementation and low memory requirement. The memory requirement of the radiation patterns of basis functions in the proposed MLFMA is several times less than that in the conventional MLFMA

    Improved Diffusion-based Image Colorization via Piggybacked Models

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    Image colorization has been attracting the research interests of the community for decades. However, existing methods still struggle to provide satisfactory colorized results given grayscale images due to a lack of human-like global understanding of colors. Recently, large-scale Text-to-Image (T2I) models have been exploited to transfer the semantic information from the text prompts to the image domain, where text provides a global control for semantic objects in the image. In this work, we introduce a colorization model piggybacking on the existing powerful T2I diffusion model. Our key idea is to exploit the color prior knowledge in the pre-trained T2I diffusion model for realistic and diverse colorization. A diffusion guider is designed to incorporate the pre-trained weights of the latent diffusion model to output a latent color prior that conforms to the visual semantics of the grayscale input. A lightness-aware VQVAE will then generate the colorized result with pixel-perfect alignment to the given grayscale image. Our model can also achieve conditional colorization with additional inputs (e.g. user hints and texts). Extensive experiments show that our method achieves state-of-the-art performance in terms of perceptual quality.Comment: project page: https://piggyback-color.github.io

    Thermal discharge-created increasing temperatures alter the bacterioplankton composition and functional redundancy

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    Additional file 1: Table S1. Measurements of geochemical factors of the 10 sampling sites. Table S2. Pearson correlations between seawater temperature and biogeochemical variables. Figure S1. Pearson correlations between seawater temperature and bacterial abundance (A), DNA yield (a proxy for microbial biomass) (B), and grazing rate (C). Figure S2. Multivariate regression tree (MRT) of bacterial diversity associated with driving biogeochemical factors
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