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Robust high frequency seismic bandwidth extension with a deep neural network trained using synthetic data

Artificial Intelligence in Geosciences 2024年第1期5卷 64-81页

作者： Paul Zwartjes Jewoo Yoo Aramco Europe Delft Global Research CenterNetherlands

Geophysicists interpreting seismic reflection data aim for the highest resolution possible as this facilitates the interpretation and discrimination of subtle geological *** deterministic methods based on Wiener filtering exist to increase the temporal frequency bandwidth and compress the seismic wavelet in a process called spectral ***-encoder neural networks with convolutional layers have been applied to this problem,with encouraging results,but the problem of generalization to unseen data *** published works have used supervised learning with training data constructed from field seismic data or synthetic seismic data generated based on measured well logs or based on seismic wavefield *** leads to satisfactory results on datasets similar to the training data but requires re-training of the networks for unseen data with different *** this work seek to improve the generalization,not by experimenting with network architecture(we use a conventional U-net with some small modifications),but by adopting a different approach to creating the training data for the supervised learning *** the network is important,at this stage of development we see more improvement in prediction results by altering the design of the training data than by architectural *** approach we take is to create synthetic training data consisting of simple geometric shapes convolved with a seismic *** created a very diverse training dataset consisting of 9000 seismic images with between 5 and 300 seismic events resembling seismic reflections that have geophysically motived perturbations in terms of shape and *** 2D U-net we have trained can boost robustly and recursively the dominant frequency by 50%.We demonstrate this on unseen field data with different bandwidths and signal-to-noise ***,this 2D U-net can handle non-stationary wavelets and overlapping events of different bandwidth without cr

关键词： Resolution Seismic data u-Net Bandwidth extension Synthetic data

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Exploring the driving factors and their mitigation potential in global energy-related CO2 emission

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global Energy Interconnection 2020年第5期3卷 413-422页

作者： Zhiyuan Ma Shining Zhang Fangxin Hou Xin Tan Fengying Zhang Fang Yang Fei Guo global Energy Interconnection Development and Cooperation Organization No.8 Xuanwumennei StreetBeijing 100031P.R.China global Energy Interconnection Group Co. Ltd.No.8 Xuanwumennei StreetBeijing 100031P.R.China International Institute for Applied Systems Analysis(IIASA) Schlossplatz 1-A2361 LaxenburgAustria

In order to quantify the contribution of the mitigation strategies,an extended Kaya identity has been proposed in this paper for decomposing the various factors that influence the CO2 *** this end,we provided a detailed decomposition of the carbon intensity and energy intensity,which enables the quantification of clean energy development and *** logarithmic mean divisia index(LMDI)has been applied to the historical data to quantify the contributions of the various factors affecting the CO2 ***,the global energy interconnection(GEI)scenario has been introduced for providing a systematic solution to meet the 2℃goal of the Paris *** combining LMDI with the scenario analysis,the mitigation potential of the various factors for CO2 emission has been *** from the historical data indicate that economic development and population growth contribute the most to the increase in CO2 emissions,whereas improvement in the power generation efficiency predominantly helps in emission reduction.A numerical analysis,performed for obtaining the projected future carbon emissions,suggests that clean energy development and electrification are the top two factors that can decrease CO2 emissions,thus showing their great potential for mitigation in the ***,the carbon capture and storage technology serves as an important supplementary mitigation method.

关键词： CO2 emission Kaya identity Clean energy development Electrification global Energy Interconnection Mitigation potential

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Optimized Protection Strategies for HVDC Grid with Fault-blocking Modular Multilevel Converters for Overhead Line Applications

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Journal of Modern Power Systems and Clean Energy 2020年第6期8卷 1168-1177页

作者： Sheng Yan Zhiyuan He Jie Yang Ming Kong Minqiang Hu Southeast University NanjingChina global Energy Interconnection Research Institute BeijingChina

The high-voltage direct current(HVDC)grid has been recognized as an effective solution for renewable energy ***,two main development trends for HVDC grids are being studied:a DC breaker based HVDC grid and fault-blocking converter based HVDC *** the former has a perfect performance for fault clearance,its development is still highly constrained by the cost and maturity of DC *** latter can extinguish DC faults by the fault-blocking *** using DC breakers,there is no bottleneck in its technical ***,in fault scenarios,such types of HVDC grids will be blocked at length for air-deionization,which is its main *** aim of this paper is to minimize its power interruption time,by optimizing protection coordination *** cover the most complex cases,the overhead line applications,in which the reclosure actions are required to be implemented,are *** this paper,the protection requirements of HVDC grids are first discussed,then the benefits of fault-blocking modular multilevel converters(MMCs)and their fault features are *** on this,a control function is designed to reduce the air-deionization *** minimize the influence of the DC faults,a separation methodology for restarting the system is *** effectiveness of the proposed protection coordination schemes is validated by PSCAD/EMTDC simulations.

关键词： Modular multilevel converter(MMC) high-voltage direct current(HVDC) overhead line fault-blocking converter protection coordination

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Cloud Classification and Distribution of Cloud Types in Beijing Using Ka-Band Radar Data

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Advances in Atmospheric Sciences 2019年第8期36卷 793-803页

作者： Juan HUO Yongheng BI Daren Lü Shu DUAN Key Laboratory for Atmosphere and global Environment Observation Chinese Academy of Sciences

A cloud clustering and classification algorithm is developed for a ground-based Ka-band radar system in the vertically pointing mode. Cloud profiles are grouped based on the combination of a time–height clustering method and the k-means clustering method. The cloud classification algorithm, developed using a fuzzy logic method, uses nine physical parameters to classify clouds into nine types: cirrostratus, cirrocumulus, altocumulus, altostratus, stratus, stratocumulus, nimbostratus,cumulus or cumulonimbus. The performance of the clustering and classification algorithm is presented by comparison with all-sky images taken from January to June 2014. Overall, 92% of the cloud profiles are clustered successfully and the agreement in classification between the radar system and the all-sky imager is 87%. The distribution of cloud types in Beijing from January 2014 to December 2017 is studied based on the clustering and classification algorithm. The statistics show that cirrostratus clouds have the highest occurrence frequency(24%) among the nine cloud types. High-level clouds have the maximum occurrence frequency and low-level clouds the minimum occurrence frequency.

关键词： clouds clustering algorithm classification algorithm radar cloud type

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Responses of two cultivars of Trifolium repens L. to ethylene diurea in relation to ambient ozone

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Journal of Environmental Sciences 2010年第7期22卷 1096-1103页

作者： Shalini Singh Dalbir Kaur S.B.Agrawal M.Agrawal Laboratory of Air Pollution and global Climate Change Department of BotanyBanaras Hindu University

Three ethylene diurea （EDU） concentrations （0, 150 and 300 mg/L） were used to evaluate the negative impact of ozone （O3） on two cultivars of Trifoliurn repens L. cv. Vardan and Bundel grown under natural field conditions in a suburban area of Varanasi, India. Mean O3 concentrations varied from 30.3 to 46.6 μg/L during the experimental period. Higher photosynthetic pigments and ascorhic acid concentrations were noticed in both EDU-treated cultivars over non-EDU-treated ones, but a reverse trend was found for lipid peroxidation. Growth parameters and biomass also showed increments under EDU treatment of both cultivars. The ratio of variable fluorescence to maximum fluorescence increased significantly in Vardan but not in Bundel upon EDU treatment. Results revealed that EDU concentration of 300 mg/L was more effective to combat the oxidative stress as well as protecting plants from O3 injury symptoms. The test cultivar Vardan is relatively sensitive to O3, thereby can be used as a bioindicator of O3 pollution in areas having higher O3 concentrations. Results also indicated that Bundel has more efficient antioxidant defense system than Vardan and hence was more tolerant to O3 stress.

关键词： Trifolium repens ozone oxidative stress ascorbic acid photosynthetic pigments

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Heterogeneous integration of 2D materials on Si charge-coupled devices as optical memory

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Science China(Information Sciences) 2024年第6期67卷 190-197页

作者： Zheng BIAN Feng TIAN Zongwen LI Xiangwei SU Tianjiao ZHANG Jialei MIAO Bin YU Yang XU Yuda ZHAO College of Integrated Circuits Hangzhou Global Scientific and Technological Innovation CentreZhejiang University

Optical memory integrates the function of optical sensing in memory devices, remarkably promoting the interconnection between sensory and memory terminals. Silicon charge-coupled photodetectors and floating gate memory have been widely used in imaging and storage technologies, respectively. However,the heterogeneous integration of the two devices requires technological innovation and complex electrical connections. In this work, we adopt a three-dimensional layer stacking method to design a novel optical memory device. On the top of Si charge-coupled photodetectors, we successively deposit two-dimensional graphene,hexagonal boron nitride, and molybdenum disulfide as a floating gate layer, a tunneling layer, and a readout layer, respectively. By applying a gate bias on lightly doped Si, a deep depletion layer is formed with a high voltage potential drop. Under dark conditions, the depletion layer cannot be filled, and the electric field across the h-BN tunnel barrier is relatively small. Under light irradiation, the deep depletion layer is gradually filled, and the h-BN tunneling layer withstands the increasing electric field, resulting in charge storage in the floating gate layer. Based on this mechanism, the device exhibits a gate voltage-dependent operation mode, including an integrated optical sensing-memory mode and an electrically driven storage mode. Under moderate gate voltage, the device can effectively detect the optical information with varied intensity and store the optical information in the floating gate, displaying optically controlled memory characteristics. Our work demonstrates a compact device structure for optical memory and displays excellent optically controlled memory performance, which can be applied in artificial vision systems.

关键词： heterogeneous integration charge-coupled device floating gate optical memory molybdenum disulfide lightly doped silicon

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Decomposition and Approximation of Multivariate Functions on the Cube

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Acta Mathematica Sinica,English Series 2013年第1期29卷 119-136页

作者： Zhi Hua ZHANG College of global Change and Earth System Science Beijing Normal University

In this paper, we present a decomposition method of multivariate functions. This method shows that any multivariate function f on [0, 1]d is a finite sum of the form ∑jФjψj, where each Фj can be extended to a smooth periodic function, each ψj is an algebraic polynomial, and each Фjψj is a product of separated variable type and its smoothness is same as f. Since any smooth periodic function can be approximated well by trigonometric polynomials, using our decomposition method, we find that any smooth multivariate function on [0, 1]d can be approximated well by a combination of algebraic polynomials and trigonometric polynomials. Meanwhile, we give a precise estimate of the approximation error.

关键词： Decomposition of multivariate functions approximation of multivariate functions fundamental polynomial projection operator classification of boundary points

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Ocean Data Assimilation Using Intermittent Analyses and Continuous Model Error Correction

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Advances in Atmospheric Sciences 2002年第6期19卷 965-992页

作者： BohuaHuang JamesL.KinterIII PaulS.Schopf Center for Ocean-Land-Atmosphere Studies Institute of Global Environment and Society

A new data insertion approach is applied to the Derber and Rosati ocean data assimilation (ODA) system, a system that uses a variational scheme to analyze ocean temperature and provide ocean model corrections continuously. Utilizing the same analysis component as the original system, the new approach conducts analyses to derive model corrections intermittently at once-daily intervals. A technique similar to the Incremental Analysis Update (IAU) method of Bloom et al. is applied to incorporate the corrections into the model gradually and continuously. This approach is computationally more economical than the original.A 13-year global ocean analysis from 1986 to 1998 is produced using this new approach and compared with an analysis based on the original one. An examination of both analyses in the tropical Pacific Ocean shows that they have qualitatively similar annual and interannual temperature variability. However, the new approach produces smoother monthly analyses. Moreover, compared to the independent

关键词： data assimilation ocean general circulation model ocean current temperature profiles sea surface temperature

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2022 Multiple-country Monkeypox Outbreak and Its Importation Risk into China:An Assessment Based on the Risk Matrix Method

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Biomedical and Environmental Sciences 2022年第10期35卷 878-887页

作者： DU Min ZHANG Shi Mo SHANG Wei Jing YAN Wen Xin LIU Qiao QIN Chen Yuan LIU Min LIU Jue Department of Epidemiology and Biostatistics School of Public HealthPeking UniversityBeijing 100191China Institute for global Health and Development Peking UniversityBeijing 100871China global Center for Infectious Disease and Policy Research&global Health and Infectious Diseases Group Peking UniversityBeijing 100191China

Objective To analyze the 2022 multiple-country monkeypox outbreak and assess its importation risk into *** Data was from United States Centers for Disease Control and *** described the global epidemic and calculated concentration index to measure economic-related *** risk into China was evaluated and ranked by using risk matrix method and Borda count method,*** As of July 29,2022,of 79 countries or territories,39(49.37%,39/79),17(21.52%,17/79),6(7.59%,6/79),12(15.19%,12/79),and 5(6.33%,5/79)country or territories identified cases1,*** were economic-related health disparities exist in the distribution of cases(the concentration index=0.42,P=0.027),and the inequality disadvantageous to the rich(pro-poor).There were 12(15.38%,12/78),15(19.23%,15/78),6(7.69%,6/78),and 45(57.69%,45/78)countries or territories with extremely high,high,moderate,and low importation *** States and France ranked first with the highest Borda points of 156,and counts of *** Of 78 countries or territories,the key attention need be paid to the United States and France,*** the epidemic progresses,preparing prevention and control measures to further reduce importation risk was crucial.

关键词： Monkeypox Importation risk China Risk matrix method

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Trends in global health research among universities in China:a bibliometric analysis

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global Health Research and Policy 2023年第1期8卷 453-462页

作者： Chenkai Wu Lijing LYan Qian Long Yunguo Liu Jie Tan Zhexun Lou Shenglan Tang global Health Research Center Duke Kunshan UniversityAcademic Building 3038No.8 Duke AvenueKunshan 215316JiangsuChina Duke global Health Institute Duke UniversityDurhamNCUSA School of Health Sciences Wuhan UniversityWuhanHubeiChina

Background There has been considerable progress in developing global health education and research in ***,evidence of the progress of Chinese universities’contributions to global health research is *** efforts are needed to depict the progress Chinese universities have collectively made in advancing the field of global *** study aimed to examine Chinese universities’collective contributions to global health research by describing the longitudinal trends in global health research publications,uncovering research themes in global health,and exploring collaboration *** A comprehensive bibliometric analysis was conducted for original research studies of the ten founding members of the China Consortium of Universities for global Health,one of the largest networks of global health research and education in *** We found that(1)the number of research publications in the field of global health has steadily increased from 2014 to 2020,(2)non-communicable disease was the most popular research topic,accounting for over one-third of total publications,followed by maternal and child health and neurological and mental disorders and diseases,(3)less than one-fifth of papers involved primary data collection,with the majority of the study populations from low-income and lower-middle-income countries in Asia and Africa,and(4)a sizable collaboration network has been established with co-authors from over 200 oversea universities or organizations,with about one third from the *** Despite a variety of challenges and barriers,Chinese universities have been playing an increasingly important role in global health research as assessed by peer-reviewed publications over the last *** concerted efforts by multiple stakeholders,including government,private sectors,funding agencies,academic institutions,and researchers,are needed to advance the development of global health research in China.

关键词： China global health Health governance Non-communicable disease Maternal and child health

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