The Ediacaran Doushantuo Formation(ca. 635–551 Ma) deposited immediately after the last Neoproterozoic glaciations and recorded the most prominent negative excursions of carbonate carbon isotopic composition(δ^...The Ediacaran Doushantuo Formation(ca. 635–551 Ma) deposited immediately after the last Neoproterozoic glaciations and recorded the most prominent negative excursions of carbonate carbon isotopic composition(δ^(13)C(carb)). These excursions have been interpreted as a result of widespread remineralization of a large dissolved organic carbon(DOC) reservoir in the Ediacaran deep oceans. However, there is no direct evidence so far found in rocks for the proposed DOC reservoir, which devalues such an interpretation. Here, we conducted a detailed study on the glow-curves characteristics and signal origins of spurious thermoluminescence(TL) of the Doushantuo Formation at Jiulongwan in Yangtze Gorges area, South China, through sequential tests under CO2, N2 and air. Spurious TL intensities for test samples before and after removing soluble organic matter via accelerated solvent extraction(ASE) are nearly identical. Further, significant positive correlation between the spurious TL intensity and total inorganic carbon(TIC) content(R^2=0.7) indicate that the Doushantuo spurious TL with the characteristic peak at 393.5 °C from the sequential test is chemiluminescence(CL) which is derived from the oxidation of a type of non-volatile organic matter strongly associated with carbonate mineral lattice(termed as “X-OM”). A most likely explanation is that the X-OM is a type of dissolved organic matter which co-precipitated with carbonate minerals into sediments in the Ediacaran Doushantuo Ocean. Furthermore, a significant exponential negative correlation(R^2=0.55) is observed between the CL data and the isotopic difference between carbonate and coexisting bulk organic matter(i.e., Δ^(13)C(carb-org), a proxy for remineralization degree of DOC reservoir in proposed DOC hypothesis), suggesting that the X-OM was derived from the oxidation of the DOC reservoir in the Ediacaran Ocean. We thus propose that the X-OM and its CL detected in our study may have recorded the e展开更多
Recent years have witnessed the great success of self-supervised learning(SSL)in recommendation systems.However,SSL recommender models are likely to suffer from spurious correlations,leading to poor generalization.To ...Recent years have witnessed the great success of self-supervised learning(SSL)in recommendation systems.However,SSL recommender models are likely to suffer from spurious correlations,leading to poor generalization.To mitigate spurious correlations,existing work usually pursues ID-based SSL recommendation or utilizes feature engineering to identify spurious features.Nevertheless,ID-based SSL approaches sacrifice the positive impact of invariant features,while feature engineering methods require high-cost human labeling.To address the problems,we aim to automatically mitigate the effect of spurious correlations.This objective requires to 1)automatically mask spurious features without supervision,and 2)block the negative effect transmission from spurious features to other features during SSL.To handle the two challenges,we propose an invariant feature learning framework,which first divides user-item interactions into multiple environments with distribution shifts and then learns a feature mask mechanism to capture invariant features across environments.Based on the mask mechanism,we can remove the spurious features for robust predictions and block the negative effect transmission via mask-guided feature augmentation.Extensive experiments on two datasets demonstrate the effectiveness of the proposed framework in mitigating spurious correlations and improving the generalization abilities of SSL models.展开更多
With the wide application of the fifth-generation mobile communication system(5G)technology,wireless communication equipment tends to develop in miniaturization,high frequency,and low loss.In this paper,a surface acou...With the wide application of the fifth-generation mobile communication system(5G)technology,wireless communication equipment tends to develop in miniaturization,high frequency,and low loss.In this paper,a surface acoustic wave(SAW)filter with a center frequency of 3.5 GHz was designed.Firstly,the acoustic waveguide structure of the longitudinal leaky SAW(LLSAW)excitation is determined,and the two-dimensional(2D)theoretical model of the device is established by COMSOL Multiphysics.Secondly,the influence of electrode parameters on the performance of the device is studied,and the electrode parameters are optimized on this basis.By setting the device structure parameters reasonably,the spurious in the passband can be effectively suppressed.Finally,the center frequency of the mirror T-structure LLSAW filter is 3.536 GHz,the insertion loss is-1.414 dB,the bandwidth of-3 dB is 276 MHz,and the out-of-band rejection is greater than-30 dB.展开更多
Using the Radon transform and morphological image processing, an algorithm for ship's wake detection in the SAR (synthetic aperture radar) image is developed. Being manipulated in the Radon space to invert the gra...Using the Radon transform and morphological image processing, an algorithm for ship's wake detection in the SAR (synthetic aperture radar) image is developed. Being manipulated in the Radon space to invert the gray-level and binary images, the linear texture of ship wake in oceanic clutter can be well detected. It has been applied to the automatic detection of a moving ship from the SEASAT SAR image. The results show that this algorithm is well robust in a strong noisy background and is not very sensitive to the threshold parameter and the working window size.展开更多
基金supported by the Chinese 973 Program (No. 2013CB955704)the National Natural Science Foundation of China (No. 41172030)
文摘The Ediacaran Doushantuo Formation(ca. 635–551 Ma) deposited immediately after the last Neoproterozoic glaciations and recorded the most prominent negative excursions of carbonate carbon isotopic composition(δ^(13)C(carb)). These excursions have been interpreted as a result of widespread remineralization of a large dissolved organic carbon(DOC) reservoir in the Ediacaran deep oceans. However, there is no direct evidence so far found in rocks for the proposed DOC reservoir, which devalues such an interpretation. Here, we conducted a detailed study on the glow-curves characteristics and signal origins of spurious thermoluminescence(TL) of the Doushantuo Formation at Jiulongwan in Yangtze Gorges area, South China, through sequential tests under CO2, N2 and air. Spurious TL intensities for test samples before and after removing soluble organic matter via accelerated solvent extraction(ASE) are nearly identical. Further, significant positive correlation between the spurious TL intensity and total inorganic carbon(TIC) content(R^2=0.7) indicate that the Doushantuo spurious TL with the characteristic peak at 393.5 °C from the sequential test is chemiluminescence(CL) which is derived from the oxidation of a type of non-volatile organic matter strongly associated with carbonate mineral lattice(termed as “X-OM”). A most likely explanation is that the X-OM is a type of dissolved organic matter which co-precipitated with carbonate minerals into sediments in the Ediacaran Doushantuo Ocean. Furthermore, a significant exponential negative correlation(R^2=0.55) is observed between the CL data and the isotopic difference between carbonate and coexisting bulk organic matter(i.e., Δ^(13)C(carb-org), a proxy for remineralization degree of DOC reservoir in proposed DOC hypothesis), suggesting that the X-OM was derived from the oxidation of the DOC reservoir in the Ediacaran Ocean. We thus propose that the X-OM and its CL detected in our study may have recorded the e
文摘Recent years have witnessed the great success of self-supervised learning(SSL)in recommendation systems.However,SSL recommender models are likely to suffer from spurious correlations,leading to poor generalization.To mitigate spurious correlations,existing work usually pursues ID-based SSL recommendation or utilizes feature engineering to identify spurious features.Nevertheless,ID-based SSL approaches sacrifice the positive impact of invariant features,while feature engineering methods require high-cost human labeling.To address the problems,we aim to automatically mitigate the effect of spurious correlations.This objective requires to 1)automatically mask spurious features without supervision,and 2)block the negative effect transmission from spurious features to other features during SSL.To handle the two challenges,we propose an invariant feature learning framework,which first divides user-item interactions into multiple environments with distribution shifts and then learns a feature mask mechanism to capture invariant features across environments.Based on the mask mechanism,we can remove the spurious features for robust predictions and block the negative effect transmission via mask-guided feature augmentation.Extensive experiments on two datasets demonstrate the effectiveness of the proposed framework in mitigating spurious correlations and improving the generalization abilities of SSL models.
文摘With the wide application of the fifth-generation mobile communication system(5G)technology,wireless communication equipment tends to develop in miniaturization,high frequency,and low loss.In this paper,a surface acoustic wave(SAW)filter with a center frequency of 3.5 GHz was designed.Firstly,the acoustic waveguide structure of the longitudinal leaky SAW(LLSAW)excitation is determined,and the two-dimensional(2D)theoretical model of the device is established by COMSOL Multiphysics.Secondly,the influence of electrode parameters on the performance of the device is studied,and the electrode parameters are optimized on this basis.By setting the device structure parameters reasonably,the spurious in the passband can be effectively suppressed.Finally,the center frequency of the mirror T-structure LLSAW filter is 3.536 GHz,the insertion loss is-1.414 dB,the bandwidth of-3 dB is 276 MHz,and the out-of-band rejection is greater than-30 dB.
基金This project was supported by the National Natural Science Foundation of China (No. 49831060).
文摘Using the Radon transform and morphological image processing, an algorithm for ship's wake detection in the SAR (synthetic aperture radar) image is developed. Being manipulated in the Radon space to invert the gray-level and binary images, the linear texture of ship wake in oceanic clutter can be well detected. It has been applied to the automatic detection of a moving ship from the SEASAT SAR image. The results show that this algorithm is well robust in a strong noisy background and is not very sensitive to the threshold parameter and the working window size.