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dynamic motion of quadrupedal robots on challenging terrain:a kinodynamic optimization approach

Frontiers of Mechanical Engineering 2024年第3期19卷 23-40页

作者： Qi LI Lei dING Xin luo Engineering Research Center of Hubei Province for Clothing Information Wuhan 430200China school of Computer science and Artificial Intelligence Wuhan Textile UniversityWuhan 430200China state Key Laboratory of digital Manufacturing Equipment and Technology Huazhong University of Science and TechnologyWuhan 430074China

The dynamic motion of quadrupedal robots on challenging terrain generally requires elaborate spatial–temporal kinodynamic motion planning and accurate control at higher refresh rate in comparison with regular ***,conventional quadrupedal robots usually generate relatively coarse planning and employ motion replanning or reactive strategies to handle terrain *** resultant complex and computation-intensive controller may lead to nonoptimal motions or the breaking of locomotion *** this paper,a kinodynamic optimization approach is *** generate long-horizon optimal predictions of the kinematic and dynamic behavior of the quadruped robot on challenging terrain,we formulate motion planning as an optimization problem;jointly treat the foot’s locations,contact forces,and torso motions as decision variables;combine smooth motion and minimal energy consumption as the objective function;and explicitly represent feasible foothold region and friction constraints based on terrain *** track the generated motions accurately and stably,we employ a whole-body controller to compute reference position and velocity commands,which are fed forward to joint controllers of the robot’s *** verify the effectiveness of the developed approach through simulation and on a physical quadruped robot *** show that the quadruped robot can successfully traverse a 30°slope and 43% of nominal leg length high step while maintaining the rhythm of dynamic trot gait.

关键词： quadrupedal robot kinodynamic planning nonlinear optimization challenging terrain whole-body control

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Infinitely Many solutions for a Class of Quasi-linear Elliptic Problem

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Acta Mathematicae Applicatae sinica 2024年第3期40卷 728-743页

作者： Xiao-yao JIA Zhen-luo LOU school of Economics and Management Zhongyuan University of TechnologyZhengzhou 450007China Mathematics and statistics school Henan University of Science and TechnologyLuoyang 471023China

In this paper,we study the following quasi-linear elliptic equation:■where Ω?R^(N) is a bounded domain,λ>0 is a *** function ψ(|t|)t is the subcritical term,and φ(|t|)t is the critical Orlicz-sobolev growth term with respect to φ.Under appropriate conditions on φ,ψ and φ,we prove the existence of infinitely many weak solutions for quasi-linear elliptic equation,for λ∈(0,λ_(0)),where λ_(0)> 0 is a fixed constant.

关键词： quasi-linear elliptic equations variational methods Orlicz-sobolev spaces

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A simple Proof of ACC for Minimal Log discrepancies for surfaces

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Acta Mathematica sinica,English series 2024年第2期40卷 425-434页

作者： Jing Jun HAN Yu Jie luo shanghai Center for Mathematical sciences Fudan UniversityJiangwan CampusShanghai 200438P.R.China department of Mathematics Johns Hopkins UniversityBaltimoreMD 21218USA

Following shokurov's idea,we give a simple proof of the ACC conjecture for minimal log discrepancies for surfaces.

关键词： Ascending chain condition minimal log discrepancies minimal model program surface

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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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downscaling seasonal Precipitation Forecasts over East Africa with deep Convolutional Neural Networks

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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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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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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(COFspeed 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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New structure transistors for advanced technology node CMOs ICs

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National science Review 2024年第3期11卷 24-41页

作者： Qingzhu Zhang Yongkui Zhang Yanna luo Huaxiang Yin Integrated Circuit Advanced Process R&d Center Institute of Microelectronics of Chinese Academy of Sciences(IMECAS) state key Lab of Fabrication Technologies for Integrated Circuits Institute of Microelectronics of Chinese Academy of Sciences school of Integrated Circuits University of Chinese Academy of Sciences

Over recent decades, advancements in complementary metal-oxide-semiconductor integrated circuits(ICs)have mainly relied on structural innovations in transistors. From planar transistors to the fin field-effect transistor(FinFET) and gate-all-around FET(GAAFET), more gate electrodes have been added to three-dimensional(3d) channels with enhanced control and carrier conductance to provide higher electrostatic integrity and higher operating currents within the same device footprint. Beyond the 1-nm node, Moore's law scaling is no longer expected to be applicable to geometrical shrinkage. Vertical transistor stacking, e.g. in complementary FETs(CFET), 3d stack(3ds) FETs and vertical-channel transistors(VFET), for enhanced density and variable circuit or system design represents a revolutionary scaling approach for sustained IC development. Herein, innovative works on specific structures, key process breakthroughs, shrinking cell sizes and design methodologies for transistor structure research and development are reviewed. Perspectives on future innovations in advanced transistors with new channel materials and operating theories are also discussed.

关键词： transistor CMOs GAAFET CFET 3ds FET

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