检索结果-南通市图书馆

Dynamic Risk Spillovers in Non-Ferrous Metal Future Markets During COVID-19:A Frequency Domain Analysis

在线全文

学校读者我要写书评

暂无评论

Journal of Systems Science and Information 2024年第1期12卷 47-63页

作者： guang YANG Xiaoyu LIU Dingxuan ZHANG Yunjie wei School of Economics and Management University of Chinese Academy of SciencesBeijing 100190China Center for Research on Intelligent Perception and Computing Institute of AutomationChinese Academy of SciencesBeijing 100190China Academy of Mathematics and Systems Science Chinese Academy of SciencesBeijing 100190China

During the COVID-19 pandemic,the international financial markets experienced severe *** the background of“Made in China 2025”,substantial entity enterprises have a large demand for non-ferrous *** the enhancement of financial attributes of non-ferrous metals,it is vital to prevent financial systemic risk contagion in the non-ferrous metal *** this article,the ensemble empirical mode decomposition method is used to decompose the prices of eight important non-ferrous metals futures,and then the dynamic DY risk spillover index model is established from the perspectives of long-term and *** risk spillover between non-ferrous metals during the COVID-19 is quantitatively analyzed from different frequency *** study finds that in the long run,the risk spillover relationship between non-ferrous metals remained basically stable,and the change of it after the epidemic is *** the short run,the risk spillover relationship has different degrees of structural changes after the outbreak of the COVID-19 *** ensemble empirical mode decomposition method can distinguish the risk spillovers in different cycles,and help to formulate policies for preventing systemic risks in the non-ferrous metal markets according to the different length of terms.

关键词： COVID-19 non-ferrous metals ensemble empirical mode decomposition risk spillover index

Ti_(3)C_(2)T_(x)/SnO_(2)P–N heterostructure construction boosts room-temperature detecting formaldehyde

在线全文

学校读者我要写书评

暂无评论

Rare Metals 2024年第1期43卷 267-279页

作者： Yue Zhang Ming-Yue Wang Xiao-guang San Yan-Bai Shen Guo-sheng Wang Lei Zhang Dan Meng College of Chemical Engineering Shenyang University of Chemical TechnologyShenyang 110142China Institute for Superconducting and Electronic Materials(ISEM) Australian Institute for Innovative Materials(AIIM)University ofWollongongWollongongNSW2500Australia College of Resources and Civil Engineering Northeastern UniversityShenyang 110819China

Formaldehyde is a common atmospheric pollutant produced in industrial production and daily ***,the traditional semiconductor formaldehyde gas sensor cannot work at room temperature,which limits its practical ***,developing high-performance gas sensors for rapidly and accurately detecting formaldehyde at room temperature is an important *** this study,Ti_(3)C_(2)Tx/SnO_(2)heterostructures were constructed,which could selectively detect formaldehyde at room temperature with a response value of 29.16%(10×10^(-6)).In addition,the sensor shows a remarkable theoretical detection limit of 5.09×10^(-9)and good longterm *** functional theory(DFT)simulations reveal that SnO_(2)nano spheres provide the majority of adsorption sites that strongly interact with ***,Ti_(3)C_(2)T_(x)acting as a conductive layer facilitates the transfer of charge carriers so that they show a sensing response to formaldehyde at room ***,the formation of p-n heterostructures between SnO_(2)and Ti_(3)C_(2)T_(x)boosts the Schottky barrier at the interface,which is the critical factor in enhancing the sensing properties by turning the Schottky barrier upon introducing formaldehyde *** perspective is expected to provide instructive guidance for utilizing MXene/metal oxide nanocomposites to improve the gas sensing performance at room temperature.

关键词： Ti_(3)C_(2)T_(x)/SnO_(2)nanocomposites p-n heterostructures Formaldehyde sensing Room temperature DFT calculations

Beam based alignment using a neural network

在线全文

学校读者我要写书评

暂无评论

Nuclear Science and Techniques 2024年第4期35卷 108-118页

作者： Guan-Liang Wang Ke-Min Chen Si-wei Wang Zhe Wang Tao He Masahito Hosaka guang-Yao Feng wei Xu National Synchrotron Radiation Laboratory University of Science and Technology of ChinaHefei 230029China Diamond Light Source Oxfordshire OX110DEUK

Beams typically do not travel through the magnet centers because of errors in storage *** beam deviating from the quadrupole centers is affected by additional dipole fields due to magnetic field ***-based alignment(BBA)is often performed to determine a golden orbit where the beam circulates around the quadrupole center *** storage rings with many quadrupoles,the conventional BBA procedure is time-consuming,particularly in the commissioning phase,because of the necessary iterative *** addition,the conventional BBA method can be affected by strong coupling and the nonlinearity of the storage ring *** this study,a novel method based on a neural network was proposed to determine the golden orbit in a much shorter time with reasonable *** golden orbit can be used directly for operation or adopted as a starting point for conventional *** method was demonstrated in the HLS-II storage ring for the first time through simulations and online *** results of the experiments showed that the golden orbit obtained using this new method was consistent with that obtained using the conventional *** development of this new method and the corresponding experiments are reported in this paper.

关键词： Golden orbit Beam-based alignment Neural network Storage ring

Hydrodynamic characteristics and particle tracking of 90° lateral intakes at an inclined river slope

在线全文

学校读者我要写书评

暂无评论

Water Science and Engineering 2024年第2期17卷 197-208页

作者： wei He Si-yuan Feng Jian Zhang Hong-wu Tang Yang Xiao sheng Chen Chun-sheng Liu College of Water Conservancy and Hydropower Engineering Hohai UniversityNanjing 210098China State Key Laboratory of Hydrology Water Resources and Hydraulic Engineering Hohai UniversityNanjing 210098China Collaborative Innovation Center on Water Safety and Water Science Hohai UniversityNanjing 210098China

Lateral intakes are common in *** pump effciency and sediment deposition are determined by the local hydrodynamic characteristics and mainstream division *** hydraulic characteristics of lateral withdrawal from inclined river slopes at different intake elevations should be ***,the division width exhibits significant vertical non-uniformity at an inclined river slope,which should be ***,a three-dimensional(3-D)hydrodynamic and particle-tracking model was developed with the Open Source Field Operation and Manipulation(Open FOAM),and the model was validated with physical model tests for 90°lateral withdrawal from an inclined side *** flow fields,withdrawal sources,and division widths were investigated with different intake bottom elevations,withdrawal discharges,and main channel *** study showed that under inclined side bank conditions,water entered the intake at an oblique angle,causing significant 3-D spiral flows in the intake rather than two-dimensional closed recirculation.A lower withdrawal discharge,a lower bottom elevation of the intake,or a higher main channel velocity could further strengthen this *** average division width and turbulent kinetic energy were smaller under inclined side bank conditions than under vertical bank *** a low intake bottom elevation,a low withdrawal discharge,or a high main channel velocity,the sources of lateral withdrawal were in similar ranges near the local inclined bank in the vertical *** inclined slope conditions,sediment deposition near the intake entrance could be reduced,compared to that under vertical slope *** results provide hydrodynamic and sediment references for engineering designs for natural rivers with inclined terrains.

关键词： Lateral withdrawal Hydrodynamic characteristics Particle tracking Inclined river slope Bottom elevation of intake OpenFOAM

Chalcogen-dependent catalytic properties of RuX2 (X = S/Se/Te) nanoparticles decorated carbon nanofibers for hydrogen evolution in acidic and alkaline media

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Nano Research 2024年第4期17卷 2528-2537页

作者： Chengkai He Yue wei Jia Xu Yujie wei Tao Wang Rongfei Liu Lvlv Ji Zhun Liu sheng Wang School of Materials Science and Engineering Zhejiang Sci-Tech UniversityHangzhou 310018China Department of Physics Shaoxing UniversityShaoxing 312000China Zhejiang Kangjiesi New Material Technology Co. LTDZhuji 311800China

Transition metal dichalcogenides(TMDs),with the general formula MX_(2)(M=Mo/W/Fe/Co/Ni,etc.;X=S/Se/Te),have attracted extensive research interests for hydrogen evolution reaction(HER).Compared with numerous studies on noble-metal-free TMDs,the chalcogen-dependent HER catalytic properties of noble-metal-based TMDs are lack of sufficient research ***,a facile electrospinning-assisted synthetic strategy is proposed to synthesize ruthenium dichalcogenides(RuX_(2),X=S/Se/Te)nanoparticles decorated carbon nanofibers(CNFs).Benefiting from the identical nanofibrous morphology and exposed crystal planes of RuX_(2)(111),the catalytic activities of RuX_(2)@CNFs samples were investigated and compared in a fair and direct *** electrochemical measurements coupled with density functional theory calculations were carried out to probe their intrinsic HER catalytic activities,resulting in the catalytic activity order of RuS_(2)@CNFs>RuSe_(2)@CNFs>RuTe_(2)@CNFs in acidic media and that of RuS_(2)@CNFs>RuTe_(2)@CNFs>RuSe_(2)@CNFs in alkaline *** superior catalytic performance of RuS_(2)@CNFs mainly stems from the relative lower HER energy barriers and thereby the higher intrinsic catalytic activity of RuS_(2)(111),leading to ultralow overpotentials of 44 and 9 mV at 10 mA·cm^(-2) in acidic and alkaline media,***_(2)(111)is endowed with the more optimized Gibbs free energy of hydrogen adsorption(ΔGH*)than RuTe_(2)(111),but RuTe_(2)(111)shows enhanced catalytic property for H_(2)O dissociation and OH-desorption than RuSe_(2)(111),therefore,resulting in the altered catalytic activity sequences for RuSe_(2) and RuTe_(2) in acidic and alkaline media.

关键词： hydrogen evolution reaction transition metal dichalcogenides carbon nanofibers electrocatalysis catalytic activity

Diabetic retinopathy identification based on multi-sourcefree domain adaptation

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

International Journal of Ophthalmology(English edition) 2024年第7期17卷 1193-1204页

作者： guang-Hua Zhang guang-Ping Zhuo Zhao-Xia Zhang Bin Sun wei-Hua Yang Shao-Chong Zhang School of Big Data Intelligent Diagnosis&Treatment Industry Taiyuan UniversityTaiyuan 030032Shanxi ProvinceChina Shanxi Key Laboratory of Intelligent Optimization Computing and Blockchain Technology Taiyuan Normal UniversityTaiyuan 030619Shanxi ProvinceChina Shanxi Eye Hospital Taiyuan 030002Shanxi ProvinceChina College of Computer Science and Technology Taiyuan Normal UniversityTaiyuan 030619Shanxi ProvinceChina Shenzhen Eye Institute Shenzhen Eye HospitalJinan UniversityShenzhen 518040Guangdong ProvinceChina

AIM:To address the challenges of data labeling difficulties,data privacy,and necessary large amount of labeled data for deep learning methods in diabetic retinopathy(DR)identification,the aim of this study is to develop a source-free domain adaptation(SFDA)method for efficient and effective DR identification from unlabeled ***:A multi-SFDA method was proposed for DR *** method integrates multiple source models,which are trained from the same source domain,to generate synthetic pseudo labels for the unlabeled target ***,a softmax-consistence minimization term is utilized to minimize the intra-class distances between the source and target domains and maximize the inter-class *** is performed using three color fundus photograph datasets(APTOS2019,DDR,and EyePACS).RESULTS:The proposed model was evaluated and provided promising results with respectively 0.8917 and 0.9795 F1-scores on referable and normal/abnormal DR identification *** demonstrated effective DR identification through minimizing intra-class distances and maximizing inter-class distances between source and target ***:The multi-SFDA method provides an effective approach to overcome the challenges in DR *** method not only addresses difficulties in data labeling and privacy issues,but also reduces the need for large amounts of labeled data required by deep learning methods,making it a practical tool for early detection and preservation of vision in diabetic patients.

关键词： diabetic retinopathy multisource-free domain adaptation pseudo-label generation softmaxconsistence minimization

Enhancing reversible hydrogen storage performance of 2LiBH4–MgH2 via in-situ building heterogeneous nucleation sites

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Rare Metals 2024年第9期43卷 4367-4376页

作者： wei Chen Ya-Hui Sun Tian Xu Xue-Bin Yu guang-Lin Xia Department of Materials Science Fudan University

2LiBH4-MgH2composite is one of the most attractive reactive hydride composites with a theoretic hydrogen capacity of 10.8 wt%.However,the large nucleation restriction of MgB2during the second step of dehydrogenation results in sluggish hydrogen storage kinetics and high operating temperature,which hinders its practical application as on-board hydrogen storage ***,Al3Ti doped Al nanoparticles （AT NPs） are prepared by a facile chemical reduction reaction to improve the hydrogen storage performance of *** the initial H2desorption process,MgAlB4and TiB2that have identical crystal structure and low d-value mismatch with MgB2resulting from the reaction between AT NPs and 2LiBH4-MgH2composite serve as effective nucleation sites for the formation of *** a result,the apparent activation energy of the two-step H2desorption of AT NPs doped 2LiBH4-MgH2composite are notably decreased to （110.0±5.9） and（119.6±1.4） kJ·mol-1,which is 55.5 and 33.5 kJ·mol-1lower than that of the undoped *** importantly,a reversible hydrogen storage capacity of 9.2 wt%after 10cycles of H2desorption and adsorption could be achieved,corresponding to a capacity retention rate of 99%.The building of reactive bimetallic catalyst towards in situ formation of heterogeneous nucleation sites provides a new strategy for improving the hydrogen storage performance of reactive hydride composites.

关键词： Catalytic effects Heterogeneous nucleation Reactive hydride composites Reversible hydrogen storage

Regression Method for Rail Fastener Tightness Based on Center-Line Projection Distance Feature and Neural Network

在线全文

同方期刊数据库

学校读者我要写书评

暂无评论

Chinese Journal of Mechanical Engineering 2024年第2期37卷 356-371页

作者： Yuanhang Wang Duxin Liu sheng Guo Yifan Wu Jing Liu wei Li Hongjie Wang Robotics Research Center School of MechanicalElectronic and Control EngineeringBeijing Jiaotong UniversityBeijing 100044China China Construction Industrial&Energy Engineering Group Co. Ltd.Nanjing 210023China

In the railway system,fasteners have the functions of damping,maintaining the track distance,and adjusting the track ***,routine maintenance and inspection of fasteners are important to ensure the safe operation of track ***,assessment methods for fastener tightness include manual observation,acoustic wave detection,and image *** are limitations such as low accuracy and efficiency,easy interference and misjudgment,and a lack of accurate,stable,and fast detection *** at the small deformation characteristics and large elastic change of fasteners from full loosening to full tightening,this study proposes high-precision surface-structured light technology for fastener detection and fastener deformation feature extraction based on the center-line projection distance and a fastener tightness regression method based on neural ***,the method uses a 3D camera to obtain a fastener point cloud and then segments the elastic rod area based on the iterative closest point algorithm *** component analysis is used to calculate the normal vector of the segmented elastic rod surface and extract the point on the centerline of the elastic *** point is projected onto the upper surface of the bolt to calculate the projection ***,the mapping relationship between the projection distance sequence and fastener tightness is established,and the influence of each parameter on the fastener tightness prediction is ***,by setting up a fastener detection scene in the track experimental base,collecting data,and completing the algorithm verification,the results showed that the deviation between the fastener tightness regression value obtained after the algorithm processing and the actual measured value RMSE was 0.2196 mm,which significantly improved the effect compared with other tightness detection methods,and realized an effective fastener tightness regression.

关键词： Railway system Fasteners Tightness inspection Neural network regression 3D point cloud processing

A continuous-wave Nd:YVO_(4)-KGW intracavity Raman laser with over 34% diode-to-Stokes optical efficiency

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

High Power Laser Science and Engineering 2024年第2期12卷 62-68页

作者： Quan sheng Jingni Geng Tianchang Liu Shijie Fu wei Shi Jianquan Yao Institute of Laser and Optoelectronics School of Precision Instrument and Optoelectronics EngineeringTianjin UniversityTianjinChina Key Laboratory of Optoelectronic Information Technology(Ministry of Education) Tianjin UniversityTianjinChina

We demonstrate a continuous-wave(CW)Nd:YVO_(4)-potassium gadolinium tungstate(KGW)intracavity Raman laser with a diode-to-Stokes optical efficiency of 34.2%.By optimizing the cavity arrangement and reducing the cavity losses,8.47 W Stokes output at 1177 nm was obtained under an incident 878.6 nm diode pump power of 24.8 *** influence of cavity losses on the power and efficiency of the CW Raman laser,as well as the potential for further optimization,was investigated based on the numerical *** observation of thermally-induced output rollover was well explained by the calculation of the thermal lensing and cavity stability,indicating that the end-face curvature played an important role when the end-face of the crystal was highly reflective coated to make the cavity.A 10.9 W Stokes output under 40.9 W incident pump was also demonstrated with a cavity arrangement less sensitive to the end-face curvature,which is the highest output power of CW intracavity Raman lasers reported.

关键词： continuous wave intracavity Raman laser KGW crystal thermal lens