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Cable-driven legged landing gear for unmanned helicopter:Prototype design,optimization and performance assessment

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Science China(Technological Sciences) 2024年第4期67卷 1196-1214页

作者： TIAN BaoLin GAO HaiBo YU HaiTao SHAN HaoMin HOU JunChen YU HongYing DENG ZongQuan State Key Laboratory of Robotics and System Harbin Institute of TechnologyHarbin 150001China China Academy of Aerospace Science and innovation Beijing 100048China

Unmanned helicopters equipped with adaptive landing gear will dramatically extend their application especially in dealing with challenging *** study presents a novel cable-driven legged landing gear(CLG)with differential transmission for unmanned helicopters in complex landing *** obtain the preferred configuration of the legged mechanism,a multi-objective optimization framework for the CLG is constructed by concurrently considering terrain adaptability,landing stability and reasonable linkage of internal *** non-dominated sorting genetic algorithmⅡis employed to numerically acquire the optimal scale parameters that guide the mechanical design of the *** unmanned helicopter prototype equipped with the devised CLG is developed with key performance *** results show that the devised CLG can provide energy-efficient support over uneven terrains(totally driven torque demand less than 0.1 N m)in quasi-static landing tests,and favorable terrain adaptability(posture fluctuation of the fuselage less than±1°)in unknown slope landing *** exhibited merits give the proposed CLG the potential to enhance the landing performance of future aircraft in extreme environments.

关键词： unmanned helicopter adaptive landing gear experimental verification

Combined effects of sea urchin-like structure and mixed Cu^(+)/Cu^(0)states on promoting C_(2)formation in electrocatalytic CO_(2)reduction

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Frontiers of Chemical Science and Engineering 2024年第3期18卷 63-73页

作者： Mengqing Shan Dongsheng Lu Jiatong Dong Shen Yan Jinyu Han Hua Wang Collaborative innovation Center of Chemical Science and Engineering Key Laboratory for Green Chemical Technology of the Ministry of EducationSchool of Chemical Engineering and TechnologyTianjin UniversityTianjin300354China

Surface engineering and Cu valence regulation are essential factors in improving the C_(2)selectivity during the electrochemical reduction of CO_(2).Herein,we present a sea urchin-like CuO/Cu_(2)O catalyst derived from rhombic dodecahedra Cu_(2)O through one-step oxidation/etching method where the mixed Cu^(+)/Cu^(0)states are formed via in situ reduction during *** combined effects of the morphology and the mixed Cu^(+)/Cu^(0)states on C–C coupling are evaluated by the Faradaic efficiency of C_(2)and the C_(2)/C1 ratio obtained in an H-cell.R-Cu^(O)/Cu_(2)O exhibited 49.5%Faradaic efficiency of C_(2)with a C_(2)/C1 ratio of 3.1 at−1.4 V *** hydrogen electrode,which are 1.5 and 3.2 times higher than those of R-Cu_(2)O,*** a flow-cell,68.0%Faradaic efficiency of C_(2)is achieved at a current density of 500 mA·cm^(−2).The formation of the mixed Cu^(+)/Cu^(0)states was confirmed by in situ Raman ***,the sea urchin-like structure provides more active sites and enables faster electron *** a result,the excellent C_(2)production on R-CuO/Cu_(2)O is primarily attributed to the synergistic effects of the sea urchin-like structure and the stable mixed Cu^(+)/Cu^(0)***,this work presents an integrated strategy for developing Cu-based electrocatalysts for C_(2)production through electrochemical CO_(2)reduction.

关键词： CO_(2)electrolysis sea urchin-like structure Cu^(+)/Cu^(0) C_(2)products

Coherent link between a Ti:sapphire comb and a 1.5μm laser via nonlinear interaction in photonic crystal fiber

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Photonics Research 2024年第2期12卷 350-355页

作者： YUAN YAO HAOSEN SHI GUANG YANG BO LI CONGYU WANG HONGFU YU LONGSHENG MA YANYI JIANG State Key Laboratory of Precision Spectroscopy East China Normal UniversityShanghai 200062China Collaborative innovation Center of Extreme Optics Shanxi UniversityTaiyuan 030006China

Optical clock networks have distinct advantages for the dissemination of time/frequency,geodesy,and fundamental *** realize such a network,the telecom band and optical atomic clocks have to be coherently *** the telecom band and optical atomic clocks reside in a distinct spectral region,second-harmonic generation is usually introduced to bridge the large frequency *** this paper,we introduce a new method to coherently link a 1550 nm continuous wave laser with a Ti:sapphire mode-locked laser-based optical frequency *** coupling the 1550 nm continuous wave laser light and the Ti:sapphire comb light together into a photonic crystal fiber,nonlinear interaction takes place,and new comblike frequency components related to the 1550 nm laser frequency are generated in the visible ***,we can detect beat notes between two combs in the visible region with a signal-to-noise ratio of more than 40 dB in a resolution bandwidth of300 *** this signal,we realize an optical frequency divider for converting the frequency of optical clocks in the visible region to the telecom band at 1.55μ*** out-of-loop measurement shows that the additional noise and uncertainty induced in optical frequency conversion are 5×10^(-18)at 1 s averaging time and 2.2×10^(-19),respectively,which are limited by the uncompensated light path fluctuation but fulfill precision measurement using state-of-the-art optical clocks.

关键词： fiber interaction nonlinear

Path signature-based XAI-enabled network time series classification

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Science China(Information Sciences) 2024年第7期67卷 91-106页

作者： Le SUN Yueyuan WANG Yongjun REN Feng XIA Department of Jiangsu Collaborative innovation Center of Atmospheric Environment and Equipment Technology(CICAEET) Nanjing University of Information Science and Technology School of Computing Technologies Royal Melbourne Institute of Technology

Classifying network time series(NTS) is crucial for automating network administration and ensuring cyberspace security. It enables the detection of anomalies, the identification of network attacks,and the monitoring of performance issues, thereby providing valuable support for network protection and optimization. However, modern communication networks pose challenges for NTS classification *** include handling large-scale and complex NTS data, extracting features from intricate datasets, and addressing explainability requirements. These challenges are particularly pronounced for complex 5G networks. Notably, explainability has become crucial for the widespread deployment of network automation for 5G networks and beyond. To tackle these challenges, we propose a path-signature-based NTS classification model called recurrent signature(Recur Sig). This innovative model is designed to overcome the time-consuming feature selection problem by utilizing deep-learning(DL) techniques. Additionally, it provides a solution for addressing the black-box issue associated with DL models in network automation systems(NAS) by incorporating an explainable classification approach. Extensive experimentation on various public datasets demonstrates that Recur Sig outperforms existing models in accuracy and explainability. The results indicate its potential for application in cyberspace security and automated network management, offering an explainable solution for network protection and optimization.

关键词： network time series classification explainable artificial intelligence path signature automated network management recurrent neural network

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Asymmetric Drying and Wetting Trends in Eastern and Western China

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Advances in Atmospheric Sciences 2024年第2期41卷 221-232页

作者： Wen WU Fei JI Shujuan HU Yongli HE College of Atmospheric Sciences Lanzhou UniversityLanzhou 730000China Collaborative innovation Center for Western Ecological Safety Lanzhou UniversityLanzhou 730000China

As an important factor that directly affects agricultural production, the social economy, and policy implementation,observed changes in dry/wet conditions have become a matter of widespread concern. However, previous research has mainly focused on the long-term linear changes of dry/wet conditions, while the detection and evolution of the non-linear trends related to dry/wet changes have received less attention. The non-linear trends of the annual aridity index, obtained by the Ensemble Empirical Mode Decomposition(EEMD) method, reveal that changes in dry/wet conditions in China are asymmetric and can be characterized by contrasting features in both time and space in China. Spatially, most areas in western China have experienced transitions from drying to wetting, while opposite changes have occurred in most areas of eastern China. Temporally, the transitions occurred earlier in western China compared to eastern China. Research into the asymmetric spatial characteristics of dry/wet conditions compensates for the inadequacies of previous studies, which focused solely on temporal evolution;at the same time, it remedies the inadequacies of traditional research on linear trends over centennial timescales. Analyzing the non-linear trend also provides for a more comprehensive understanding of the drying/wetting changes in China.

关键词： aridity index EEMD dry/wet conditions asymmetric evolution

An isolated symmetrical 2T2R cell enabling high precision and high density for RRAM-based in-memory computing

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Science China(Information Sciences) 2024年第5期67卷 287-294页

作者： Yaotian LING Zongwei WANG Yuhang YANG Lin BAO Shengyu BAO Qishen WANG Yimao CAI Ru HUANG School of Integrated Circuits Beijing Advanced Innovation Center for Integrated Circuits Peking University State Key Laboratory of Information Photonics and Optical Communications Beijing University of Posts and Telecommunications

In-memory computing(IMC), leveraging emerging memories, holds significant promise in overcoming memory limitations and improving energy efficiency. However, the prevailing IMC array structure based on serially connected transistors and memory cells(1T1R/2T2R), along with the signed weight mapping scheme, can lead to asymmetrical weight sensing issues(AWS) due to electrical asymmetry within the1T1R/2T2R structure, particularly in highly scaled cells where the transistor's resistance becomes significant. In this paper, we propose and fabricate an electrically symmetric memory cell based on a physically isolated 2T2R structure for IMC. This design aims to enhance the precision and density of RRAM-based IMC arrays. The 2T2R cells are manufactured using the back-end-of-line(BEOL) process of a commercial40 nm technology platform. The feasibility of this design is verified through measured and simulated results,showcasing its capability to address the issue of AWS. Compared to conventional 2T2R cells, this design achieves a considerably smaller transistor footprint without compromising accuracy, while also improving integration density by 42.2%. These innovative memory cell advancements have the potential to further advance high-energy-efficient IMC technology.

关键词： RRAM 2T2R multi-level storage weight asymmetry in-memory computing

Manipulating the electron dynamics in the non-sequential double ionization process of Ar atoms by an orthogonal two-color laser field

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Chinese Physics B 2024年第6期33卷 338-345页

作者：王鹏昭钱丽洁孙真荣杨岩 State Key Laboratory of Precision Spectroscopy East China Normal UniversityShanghai 200241China Collaborative innovation Center of Extreme Optics Shanxi UniversityTaiyuan 030006China

Electron dynamics during non-sequential double ionization(NSDI) is one of the most attractive areas of research in the field of laser–atom or laser–molecule interaction. Based on the classic two-dimensional model, we study the process of NSDI of argon atoms driven by a few-cycle orthogonal two-color laser field composed of 800 nm and 400 nm laser pulses. By changing the relative phase of the two laser pulses, a localized enhancement of NSDI yield is observed at 0.5πand 1.5π, which could be attributed to a rapid and substantial increase in the number of electrons returning to the parent ion within extremely short time intervals at these specific phases. Through the analysis of the electron–electron momentum correlations within different time windows of NSDI events and the angular distributions of emitted electrons in different channels, we observe a more pronounced electron–electron correlation phenomenon in the recollision-induced ionization(RII) channel. This is attributed to the shorter delay time in the RII channel.

关键词： non-sequential double ionization electron dynamics few-cycle orthogonal two-color laser field

Peer-to-Peer Trading in Distribution Systems with the Utility's Operation

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CSEE Journal of Power and Energy Systems 2024年第2期10卷 629-638页

作者： Xuanyi Xiao Feng Wang Mohammad Shahidehpour Yujia Zhai Quan Zhou Department of Electrical and Information Engineering Hunan UniversityChangshaChina Robert W.Galvin Center for Electricity innovation Ilinois Institute of TechnologyChicagoIL60616USA

To realize a liberalized peer-to-peer (P2P) electricity market in distribution systems with network security, this paper develops a general framework for P2P trading in distribution systems with the utility's operation. The model is formulated as a bi-level programming. The utility's operation is an upper level problem, where a calculation method of network usage charges for P2P trading is also proposed. Peers' P2P trading is a lower level problem. An iterative algorithm based on analytical target cascading (ATC) is proposed to solve the model, where the interactions between utility and peers are presented. Numerical results on the IEEE 33-bus system demonstrate that the proposed method realizes a liberalized P2P market and ensures network security in distribution systems.

关键词： Distribution system peer-to-peer trading electricitymarket distributed energyresources(DERs) analytical target cascading(ATC)

Determinants of malaria from environmental and poverty aspects in Indonesia:A spatiotemporal perspective,2016-2020

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Asian Pacific Journal of Tropical Medicine 2024年第6期17卷 256-267页

作者： Afi Nursafingi Prima Widayani Sidiq Purwoko Andy Bhermana Research Center for Public Health and Nutrition Research Organization for HealthNational Research and Innovation AgencyJakartaIndonesia Department of Geographic Information Science Faculty of GeographyUniversitas Gadjah MadaYogyakartaIndonesia Center for Food Crops Research Organization for Agriculture and FoodNational Research and Innovation AgencyJakartaIndonesia

Objective:To investigate the environmental and social aspects of poverty contributing to malaria incidence in Indonesia from 2016 to ***:Random forest regression was used to analyse the independent variables contributing to malaria *** conditions were extracted from remotely sensed data,including vegetation,land temperature,soil moisture,precipitation,and *** contrast,the social aspects of poverty were obtained from government statistical ***:From 2016 to 2020,the contribution of each environmental and social aspect of poverty to malaria incidence fluctuated ***,the top three essential variables were people aged 15 years and above,experiencing poverty(variable importance/VI=32.0%),people experiencing poverty who work in the agricultural sector(VI=14.4%),and precipitation(VI=9.8%).It was followed by people experiencing poverty who are unemployed(VI=9.2%),land temperature(VI=5.2%),people experiencing poverty who have low education(VI=8.0%),soil moisture(VI=7.4%),elevation(VI=6.0%),and vegetation(VI=3.8%).Conclusions:Poverty and variables related to climate have become the crucial determinants of malaria in *** government must strengthen malaria surveillance through climate change mitigation and adaptation programs and accelerate poverty alleviation programs to support malaria elimination.

关键词： Malaria Poverty Climate Random forest Indonesia