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Downscaling Seasonal Precipitation Forecasts over East Africa with Deep Convolutional Neural Networks

Advances in Atmospheric Sciences 2024年第3期41卷 449-464页

作者： Temesgen Gebremariam ASFAW Jing-Jia luo Institute for Climate and Application Research(ICAR)/CIC-FEMD/KLME/ILCEC Nanjing University of Information Science and TechnologyNanjing 210044China Institute of Geophysics Space Science and Astronomy Addis Ababa UniversityAddis Ababa 1176Ethiopia

This study assesses the suitability of convolutional neural networks(CNNs) for downscaling precipitation over East Africa in the context of seasonal forecasting. To achieve this, we design a set of experiments that compare different CNN configurations and deployed the best-performing architecture to downscale one-month lead seasonal forecasts of June–July–August–September(JJAS) precipitation from the Nanjing University of Information Science and Technology Climate Forecast System version 1.0(NUIST-CFS1.0) for 1982–2020. We also perform hyper-parameter optimization and introduce predictors over a larger area to include information about the main large-scale circulations that drive precipitation over the East Africa region, which improves the downscaling results. Finally, we validate the raw model and downscaled forecasts in terms of both deterministic and probabilistic verification metrics, as well as their ability to reproduce the observed precipitation extreme and spell indicator indices. The results show that the CNN-based downscaling consistently improves the raw model forecasts, with lower bias and more accurate representations of the observed mean and extreme precipitation spatial patterns. Besides, CNN-based downscaling yields a much more accurate forecast of extreme and spell indicators and reduces the significant relative biases exhibited by the raw model predictions. Moreover, our results show that CNN-based downscaling yields better skill scores than the raw model forecasts over most portions of East Africa. The results demonstrate the potential usefulness of CNN in downscaling seasonal precipitation predictions over East Africa,particularly in providing improved forecast products which are essential for end users.

关键词： East Africa seasonal precipitation forecasting downscaling deep learning convolutional neural networks(CNNs)

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In memoriam:Shizhu Wen(1932-2023)

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Friction 2024年第7期12卷 1341-1346页

作者： Jianbin luo Yonggang MENG Yu TIAN State Key Laboratory of Tribology in Advanced Equipment Tsinghua UniversityBeijing 100084China

Professor Shizhu Wen,the winner of the 2015 Tribology Gold Medal,passed away due to illness on November 3,2023,at the age of *** was a professor of Tsinghua University,an academician of the Chinese Academy of Sciences,and the Honorary President of the Chinese Tribology Institute(CTI)from 1997 to *** Wen was born in 1932 in Jiangxi Province of China and graduated from Tsinghua University in 1955,where he was awarded the Outstanding Graduate Gold Medal and then remained as an assistant professor at the *** Wen was promoted to full professor in *** had undertaken tribology research at the Imperial College London in 1979 and *** 1985,he presided over the establishment of the State Key Laboratory of Tribology(SKLT)of Tsinghua University and served as the first director of the SKLT.

关键词： sided professor zhu

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Characteristics and Genesis of Acid Drainage Contamination from a Rock Tunneling Project Site

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Journal of Earth Science 2024年第1期35卷 190-200页

作者： Yanyun Li Zejiao luo Shihua Qi Hubei Key Laboratory of Yangtze River Basin Environmental Aquatic Science School of Environmental StudiesChina University of GeosciencesWuhan 430078China State Key Laboratory of Biogeology and Environmental Geology China University of GeosciencesWuhan 430078China

While acid mine drainage(AMD)issues have become a topic of global concern,few studies have focused on acid drainage problems of non-mining *** conducted field research and a series of laboratory experiments to investigate the characteristics,release processes and formation of acid drainage *** rock samples and adjacent surface water,groundwater,soil and sediment samples were collected at a railway tunnel construction site in central China,and various parameters,such as the p H,mineral ion concentrations,and heavy metal concentrations,were *** on the measured concentrations,surface water and sediments were seriously contaminated by acids,sulfate salts and heavy *** in surface water showed a decreasing tendency as the distance from the spoils increased,while that in sediments showed a greater influence of coprecipitation and adsorption processes of heavy metal *** eluviation experiments of three rock samples indicated that R2(silty fine sandstone)was the most likely major acid drainage *** ferrooxidans was cultured and isolated from contaminated water to study the oxidation conditions during the release *** significant release of acid drainage when air and bacteria were both in the culture container suggested that oxygen and bacteria were necessary to produce acid drainage from spoils.

关键词： acid mine drainage heavy metals leaching oxidation

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Change of probability density distributions of summer temperatures in different climate zones

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Frontiers of Earth Science 2024年第1期18卷 1-16页

作者： Xinqiu OUYANG Weilin LIAO Ming luo Guangdong Key Laboratory for Urbanization and Geo-simulation School of Geography and PlanningSun Yat-sen UniversityGuangzhou 510006China Institute of Environment Energy and SustainabilityThe Chinese University of Hong KongHong Kong 999077China

Extreme events have become increasingly frequent worldwide which are reflected in diverse changes in the shape of the temperature probability density ***,few studies have paid attention to the heterogeneity of temperature at the scale of climate ***,we use the ERA5-land data set to explore interdecadal summer temperature changes and the distribution across different climate zones from 1981 to *** the minimum(Tmin)and maximum(Tmax)temperature of 1982–1991 and 2010–2019,the results imply that Tmin and Tmax in summer maintained a notable upward trend over the past 40 years,especially *** effects of a simple shift toward a warmer climate contributed most to all climate zones,while the standard deviation,skewness and kurtosis had minor effects on extreme temperature except for *** analysis shows that the probability of extreme events in all climate zones is increasing in frequency and intensity,especially Tmin and Tmax in temperate climate *** diverse reasons for climate change can assist us with taking different measures to address extreme climate in distinct climate zones.

关键词： Climate change probability density function extreme events

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A Server Placement Algorithm for Reducing Risk and Improving Power Utilization in Data Centers

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Tsinghua Science and Technology 2024年第1期29卷 158-173页

作者： Rui Chen Huikang Huang Xiaoxuan luo Weiwei Lin School of Computer Science and Engineering South China University of TechnologyGuangzhou 510006China Peng Cheng Laboratory Shenzhen 518066China

As the power demand in data centers is increasing,the power capacity of the power supply system has become an essential resource to be *** many data centers use power oversubscription to make full use of the power capacity,there are unavoidable power supply risks associated with ***,how to improve the data center power capacity utilization while ensuring power supply security has become an important *** solve this problem,we first define it and propose a risk evaluation metric called Weighted Power Supply Risk(WPSRisk).Then,a method,named Hybrid Genetic Algorithm with Ant Colony System(HGAACS),is proposed to improve power capacity utilization and reduce power supply risks by optimizing the server placement in the power supply *** uses historical power data of each server to find a better placement solution by population *** possesses not only the remarkable local search ability of Ant Colony System(ACS),but also enhances the global search capability by incorporating genetic operators from Genetic Algorithm(GA).To verify the performance of HGAACS,we experimentally compare it with five other placement *** experimental results show that HGAACS can perform better than other algorithms in both improving power utilization and reducing the riskof powersupply system.

关键词： server placement power utilization power supply risk swarm intelligence algorithm

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Multi-UAV cooperative maneuver decision-making for pursuitevasion using improved MADRL

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Defence Technology（防务技术） 2024年第5期35卷 187-197页

作者： Delin luo Zihao Fan Ziyi Yang Yang Xu School of Aerospace Engineering Xiamen UniversityXiamen 361102China School of Civil Aviation Northwestern Polytechnical UniversityXi'an 710072China

Aiming at the problem of multi-UAV pursuit-evasion confrontation, a UAV cooperative maneuver method based on an improved multi-agent deep reinforcement learning(MADRL) is proposed. In this method, an improved Comm Net network based on a communication mechanism is introduced into a deep reinforcement learning algorithm to solve the multi-agent problem. A layer of gated recurrent unit(GRU) is added to the actor-network structure to remember historical environmental states. Subsequently,another GRU is designed as a communication channel in the Comm Net core network layer to refine communication information between UAVs. Finally, the simulation results of the algorithm in two sets of scenarios are given, and the results show that the method has good effectiveness and applicability.

关键词： Reinforcement learning UAV Maneuver decision GRU Cooperative control

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Effects of Number of Bleed Holes on Shock-Wave/Boundary-Layer Interactions in a Transonic Compressor Stator

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Journal of Thermal Science 2024年第2期33卷 611-624页

作者： LI Bai ZHOU Xun luo Lei DU Wei School of Energy Science and Engineering Harbin Institute of TechnologyHarbin150001China

An extensive numerical investigation is conducted to characterize the flow separation control in a transonic compressor cascade with a porous *** bleed holes are arranged on the suction surface in a single row,two staggered rows and three staggered *** each bleed scheme,five bleed pressure ratios are examined at an inlet Mach number of *** results indicate that the aerodynamic performance of the cascade is significantly improved by the porous *** the single-row scheme,the maximum reduction in total pressure losses is 57%.For the two-staggered-row and three-staggered-row schemes,there is an optimal bleed pressure ratio of 1.0,and the maximum reductions in total pressure loss are 68% and 75%,*** low loss in the cascade is due to the well-controlled boundary *** new local supersonic region created by the bleed hole is the key reason for the improved boundary *** vortex induced by side bleeding provides another mechanism for delaying flow *** the bleed holes could create multiple local supersonic regions,which reduce the range of the adverse pressure gradient that the boundary layer needs to *** is the reason why cascades with more bleed holes perform better.

关键词： transonic compressor stator shock wave/boundary layer interaction porous bleed number of bleed holes

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Short-time maritime target detection based on polarization scattering characteristics

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Journal of Systems Engineering and Electronics 2024年第1期35卷 55-64页

作者： CHEN Shichao luo Feng TIAN Min LYU Wanghan College of Computer and Information Engineering(College of Artificial Intelligence) Nanjing Tech UniversityNanjing 211816China Hangzhou Institute of Technology Xidian UniversityHangzhou 311200China

In this paper,a detection method combining Cameron decomposition based on polarization scattering characteristics in sea clutter background is ***,the Cameron decomposition is exploited to fuse the radar echoes of full polarization channels at the data *** to the artificial material structure on the surface of the target,it can be shown that the non-reciprocity of the target cell is stronger than that of the clutter ***,based on the analysis of the decomposition results,a new feature with scattering geometry characteristics in polarization domain,denoted as Cameron polarization decomposition scattering weight(CPD-SW),is extracted as the test statistic,which can achieve more detailed descriptions of the clutter scattering characteristics utilizing the difference between their scattering ***,the superiority of the proposed CPD-SW detector over traditional detectors in improving detection performance is verified by the IPIX measured dataset,which has strong stability under short-time observation in threshold detection and can also improve the separability of feature space zin anomaly detection.

关键词： sea clutter small target radar detection Cameron decomposition characteristics analysis

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Photoinduced superlubricity on TiO_(2) surfaces

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Friction 2024年第3期12卷 428-438页

作者： Ke HAN Liran MA Yu TIAN Jianbin luo State Key Laboratory of Tribology in Advanced Equipment Tsinghua UniversityBeijing 100084China Received:16 September 2022/Revised:28 October 2022/Accepted:27 December 2022The author(s)2022.

Superlubricity control is of great interest in both industry and scientific research,and several methods have been proposed to achieve this *** this work,ultraviolet(UV)light was introduced into titanium dioxide(TiO_(2))and silicon nitride(Si_(3)N_(4))tribosystems to accomplish photoinduced *** friction coefficients(COFs)between Si_(3)N_(4) balls and TiO_(2) plates in the mixtures of sulfuric acid(H^(2)SO_(4))solution and glycerol solution were obviously reduced,and the system entered the superlubricity region(COF<0.01)after UV illumination at a speed of 56 mm/***,the COF was much larger without UV treatment than that with UV *** formation of silica(SiO_(2))layers on the surfaces of Si_(3)N_(4) balls and the elastohydrodynamic effects were determined to be fundamental to the low friction in this experiment,and the enhancement of the combination between the TiO_(2) surface and the hydroxy group of glycerol by UV illumination was the key to the photoinduced superlubricity in this *** findings showed one method for achieving superlubricity by introducing a light field that could be further applied to special working conditions.

关键词： light control friction superlubricity glycerol titanium dioxide(TiO_(2))

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AWells-Riley/based COVID-19 infectiousrisk assessment model combining both short rangeandroom scale effects

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Building Simulation 2024年第1期17卷 93-111页

作者： Yinshuai Feng Yifan Fan Xiaoyu luo Jian Ge College of Civil Engineering and Architecture Zhejiang UniversityHangzhouChina Center for Balance Architecture Zhejiang UniversityHangzhouChina International Research Center for Green Building and Low-Carbon City International CampusZhejiang UniversityHainingChina

There is growing evidence of the high transmission potential of COVID-19 through virus-laden *** aerosols are inhaled in various concentrations,an overall assessment of transmission risks at different indoor scales is ***,a comprehensive risk assessment method that evaluates the direct link between short-range and room-scale zones is stl *** this paper,a risk assessment model combining both short-range and room-scale effects is developed to obtain effective reproduction number in confined indoor environments,called Turbulent Jet Wells Riley(TJWR)*** with the viral load data and aerosol generation data of different human respiratory activities,the Monte Carlo simulation method is applied to calculate the quanta emission rate,which further provides the input parameters of the TJWR *** known outbreaks(Hangzhou banquet hall X,Guangzhou restaurant Y,and Hong Kong restaurant Z,China)are chosen to validate the TJWR *** show that the TJWR model is more efficient than the original Wells-Riley *** average relative error of the TJWR model ranges between 9%and 44%,while for the Wells-Riley model,it ranges between 57%and 78%.The TJWR model also proves that infection risk assessments using the well-mixed assumption can systematically underestimate the transmission risk for those close to the ***,there is a significant positive linear correlation between the total number of exposed individuals at the short-range and the effective reproduction *** newly developed TJWR model has great potential for rapid and real-time overall airborne transmission risk assessment in buildings and cities.

关键词： COVID-19 airborne transmission infection risk Wells-Riley model Monte Carlo simulation

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