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Precise Positioning Method for Seafloor Geodetic Stations Based on the Temporal Variation of Sound Speed Structure 被引量:1
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作者 Shuang ZHAO Zhenjie WANG +3 位作者 Zhixi NIE Kaifei HE Huimin LIU Zhen SUN 《Journal of Geodesy and Geoinformation Science》 CSCD 2023年第2期81-92,共12页
At present,GNSS-Acoustic(GNSS-A)combined technology is widely used in positioning for seafloor geodetic stations.Based on Sound Velocity Profiles(SVPs)data,the equal gradient acoustic ray-tracing method is applied in ... At present,GNSS-Acoustic(GNSS-A)combined technology is widely used in positioning for seafloor geodetic stations.Based on Sound Velocity Profiles(SVPs)data,the equal gradient acoustic ray-tracing method is applied in high-precision position inversion.However,because of the discreteness of the SVPs used in the forementioned method,it ignores the continuous variation of sound velocity structure in time domain,which worsens the positioning accuracy.In this study,the time-domain variation of Sound Speed Structure(SSS)has been considered,and the cubic B-spline function is applied to characterize the perturbed sound velocity.Based on the ray-tracing theory,an inversion model of“stepwise iteration&progressive corrections”for both positioning and sound speed information is proposed,which conducts the gradual correction of seafloor geodetic station coordinates and disturbed sound velocity.The practical data was used to test the effectiveness of our method.The results show that the Root Mean Square(RMS)errors of the residual values of the traditional methods without sound velocity correction,based on quadratic polynomial correction and based on cubic B-spline function correction are 1.43 ms,0.44 ms and 0.21 ms,respectively.The inversion model with sound velocity correction can effectively eliminate the systematic error caused by the change of SSS,and significantly improve the positioning accuracy of the seafloor geodetic stations. 展开更多
关键词 GNSS-Acoustic sound speed structure temporal variation seafloor positioning
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Multi-layer structure formation of relativistic electron beams in plasmas
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作者 Xiaojuan WANG Zhanghu HU Younian WANG 《Plasma Science and Technology》 SCIE EI CAS CSCD 2022年第2期10-16,共7页
A two-dimensional electromagnetic particle-in-cell simulation model is proposed to study the density evolution and collective stopping of electron beams in background plasmas.We show here the formation of the multi-la... A two-dimensional electromagnetic particle-in-cell simulation model is proposed to study the density evolution and collective stopping of electron beams in background plasmas.We show here the formation of the multi-layer structure of the relativistic electron beam in the plasma due to the different betatron frequency from the beam front to the beam tail.Meanwhile,the nonuniformity of the longitudinal wakefield is the essential reason for the multi-layer structure formation in beam phase space.The influences of beam parameters(beam radius and transverse density profile)on the formation of the multi-layer structure and collective stopping in background plasmas are also considered. 展开更多
关键词 multi-layer structure beam phase space relativistic electron beam plasma based beam dump PIC
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A Novel Conceptual Telescopic Positioning Pile for VLFS Deployed in Shallow Water:Structure Design
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作者 XU Sheng-wen LIU Xiao-lei +1 位作者 WANG Xue-feng DENG Yan-fei 《China Ocean Engineering》 SCIE EI CSCD 2020年第4期526-536,共11页
A conceptual design of using novel telescopic piles to position a multi-modular very large floating structure(VLFS),which is supposed to be severed as a movable floating airport,is proposed.The telescopic piles can au... A conceptual design of using novel telescopic piles to position a multi-modular very large floating structure(VLFS),which is supposed to be severed as a movable floating airport,is proposed.The telescopic piles can automatically plug in the soil to resist the environmental loads and pull out from the soil to evacuate or move on to the next operational sea.The feasibility demonstration of the conceptual design includes two parts:function verification and structure design.In the latter part of the conceptual design,a time-domain structural analysis is firstly conducted by using Abaqus software.The simulation results suggest that the preliminary structure scheme is not optimum due to the insufficient structure utilization,although both structure safety of the piles and positioning accuracy are guaranteed.To realize a cost reduction of construction and installation,a Genetic Algorithm-Finite Element Analysis(GA-FEA)method is employed to perform structural optimization.After optimization,31 percent of the weight of each pile is reduced and higher structure utilization is maintained.The difference of the self-weight and allowable buoyancy of a single module(SMOD)of a semisubmersible-type VLFS is much larger than the weight of the piles.Combined with the function verification in our previous work,the conceptual design of using the novel telescopic pile to position VLFS is demonstrated to be feasible. 展开更多
关键词 novel telescopic positioning pile feasibility demonstration structural optimization very large floating structure(VLFS)
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Uncertainties in landslide susceptibility prediction:Influence rule of different levels of errors in landslide spatial position 被引量:1
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作者 Faming Huang Ronghui Li +3 位作者 Filippo Catani Xiaoting Zhou Ziqiang Zeng Jinsong Huang 《Journal of Rock Mechanics and Geotechnical Engineering》 SCIE CSCD 2024年第10期4177-4191,共15页
The accuracy of landslide susceptibility prediction(LSP)mainly depends on the precision of the landslide spatial position.However,the spatial position error of landslide survey is inevitable,resulting in considerable ... The accuracy of landslide susceptibility prediction(LSP)mainly depends on the precision of the landslide spatial position.However,the spatial position error of landslide survey is inevitable,resulting in considerable uncertainties in LSP modeling.To overcome this drawback,this study explores the influence of positional errors of landslide spatial position on LSP uncertainties,and then innovatively proposes a semi-supervised machine learning model to reduce the landslide spatial position error.This paper collected 16 environmental factors and 337 landslides with accurate spatial positions taking Shangyou County of China as an example.The 30e110 m error-based multilayer perceptron(MLP)and random forest(RF)models for LSP are established by randomly offsetting the original landslide by 30,50,70,90 and 110 m.The LSP uncertainties are analyzed by the LSP accuracy and distribution characteristics.Finally,a semi-supervised model is proposed to relieve the LSP uncertainties.Results show that:(1)The LSP accuracies of error-based RF/MLP models decrease with the increase of landslide position errors,and are lower than those of original data-based models;(2)70 m error-based models can still reflect the overall distribution characteristics of landslide susceptibility indices,thus original landslides with certain position errors are acceptable for LSP;(3)Semi-supervised machine learning model can efficiently reduce the landslide position errors and thus improve the LSP accuracies. 展开更多
关键词 Landslide susceptibility prediction Random landslide position errors Uncertainty analysis multi-layer perceptron Random forest Semi-supervised machine learning
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Micrometer-sized ferrosilicon composites wrapped with multi-layered carbon nanosheets as industrialized anodes for high energy lithium-ion batteries 被引量:2
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作者 Meng Li Jingyi Qiu +6 位作者 Songtong Zhang Pengcheng Zhao Zhaoqing Jin Anbang Wang Yue Wang Yusheng Yang Hai Ming 《Journal of Energy Chemistry》 SCIE EI CAS CSCD 2020年第11期286-295,共10页
Various nanostructured architectures have been demonstrated to be effective to address the issues of high capacity Si anodes. However, the scale-up of these nano-Si materials is still a critical obstacle for commercia... Various nanostructured architectures have been demonstrated to be effective to address the issues of high capacity Si anodes. However, the scale-up of these nano-Si materials is still a critical obstacle for commercialization. Herein, we use industrial ferrosilicon as low-cost Si source and introduce a facile and scalable method to fabricate a micrometer-sized ferrosilicon/C composite anode, in which ferrosilicon microparticles are wrapped with multi-layered carbon nanosheets. The multi-layered carbon nanosheets could effectively buffer the volume variation of Si as well as create an abundant and reliable conductivity framework, ensuring fast transport of electrons. As a result, the micrometer-sized ferrosilicon/C anode achieves a stable cycling with 805.9 m Ah g-1 over 200 cycles at 500 mA g-1 and a good rate capability of455.6 mAh g-1 at 10 A g-1. Therefore, our approach based on ferrosilicon provides a new opportunity in fabricating cost-effective, pollution-free, and large-scale Si electrode materials for high energy lithium-ion batteries. 展开更多
关键词 FERROSILICON multi-layered carbon nanosheets Micrometer-sized Si Material structural design Anode Lithium-ion batteries
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POSITIVE INVERSION STRUCTURE OF THE CENTRAL STRUCTURE BELT IN TURPAN-HAMI BASIN 被引量:2
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作者 ZHU Wenbin , MA Ruishi, GUO Lingzhi, SUN Yan, XU Mingjie and HU Dezhao(Department of Earth Sciences, Nanjing University, Nanjing, JS 210093, China) 《Geotectonica et Metallogenia》 2003年第1期179-190,共12页
The central structure belt in Turpan-Hami basin is composed of the Huoyanshan structure and Qiketai structure formed in late Triassic-early Jurassic, and is characterized by extensional tectonics. The thickness of str... The central structure belt in Turpan-Hami basin is composed of the Huoyanshan structure and Qiketai structure formed in late Triassic-early Jurassic, and is characterized by extensional tectonics. The thickness of strata in the hanging wall of the growth fault is obviously larger than that in the footwall,and a deposition center was evolved in the Taibei sag where the hanging wall of the fault is located. In late Jurassic the collision between Lhasa block and Eurasia continent resulted in the transformation of the Turpan-Hami basin from an extensional structure into a compressional structure, and consequently in the tectonic inversion of the central structure belt of the Turpan-Hami basin from the extensional normal fault in the earlier stage to the compressive thrust fault in the later stage. The Tertiary collision between the Indian plate and the Eurasian plate occurred around 55Ma, and this Himalayan orogenic event has played a profound role in shaping the Tianshan area, only the effect of the collision to this area was delayed since it culminated here approximately in late Oligocene-early Miocene. The central structure belt was strongly deformed and thrusted above the ground as a result of this tectonic event. 展开更多
关键词 Turpan-Hami Basin central structure belt growth fault positive inversion structure
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The Intrinsic Electron with Its Properties Such as Inner Structure and Self-Mass Is in Conflict with Quantum Field Theory
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作者 Victor Vaguine 《Journal of High Energy Physics, Gravitation and Cosmology》 2023年第3期583-595,共13页
The quantum field theory (QFT) is one of branches of the Standard Model. According to QFT, quantum fields are the primary entities and particles are the excitations of these fields, coming in discrete lumps with no in... The quantum field theory (QFT) is one of branches of the Standard Model. According to QFT, quantum fields are the primary entities and particles are the excitations of these fields, coming in discrete lumps with no inner structures and with properties assigned by declaration. Such view is in conflict with the observed vacuum energy density, 140 orders of magnitudes less than required by the QFT. In addition, such view is challenged by Aphysical Quantum Mechanics (AQM), a deeper quantum theory. According to AQM, the fundamental understanding of quantum reality is expanded by the addition of two fundamental categories, aphysical and elementary consciousness of elementary particles. Based on AQM and as an example, the total ontology of the intrinsic (fundamental) electron is presented with its inner structure of perfect geometry consisting of the physical charged c-ring and aphysical cylinder, and with its properties such as self-mass, spin, magneto-electrostatic field configuration and magnetic moment. The position parameter in the inner structure demonstrates that there are no two identical intrinsic electrons in the Universe thus placing a question mark over the QFT principle of indistinguishability. 展开更多
关键词 Quantum Reality Physical-Aphysical Intrinsic Electron Charged C-Ring Aphysical Cylinder Elementary Consciousness position Parameter Constant U Ontology Self-Mass Indistinguishable Inner structure
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Position-Aware and Subgraph Enhanced Dynamic Graph Contrastive Learning on Discrete-Time Dynamic Graph
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作者 Jian Feng Tian Liu Cailing Du 《Computers, Materials & Continua》 SCIE EI 2024年第11期2895-2909,共15页
Unsupervised learning methods such as graph contrastive learning have been used for dynamic graph represen-tation learning to eliminate the dependence of labels.However,existing studies neglect positional information ... Unsupervised learning methods such as graph contrastive learning have been used for dynamic graph represen-tation learning to eliminate the dependence of labels.However,existing studies neglect positional information when learning discrete snapshots,resulting in insufficient network topology learning.At the same time,due to the lack of appropriate data augmentation methods,it is difficult to capture the evolving patterns of the network effectively.To address the above problems,a position-aware and subgraph enhanced dynamic graph contrastive learning method is proposed for discrete-time dynamic graphs.Firstly,the global snapshot is built based on the historical snapshots to express the stable pattern of the dynamic graph,and the random walk is used to obtain the position representation by learning the positional information of the nodes.Secondly,a new data augmentation method is carried out from the perspectives of short-term changes and long-term stable structures of dynamic graphs.Specifically,subgraph sampling based on snapshots and global snapshots is used to obtain two structural augmentation views,and node structures and evolving patterns are learned by combining graph neural network,gated recurrent unit,and attention mechanism.Finally,the quality of node representation is improved by combining the contrastive learning between different structural augmentation views and between the two representations of structure and position.Experimental results on four real datasets show that the performance of the proposed method is better than the existing unsupervised methods,and it is more competitive than the supervised learning method under a semi-supervised setting. 展开更多
关键词 Dynamic graph representation learning graph contrastive learning structure representation position representation evolving pattern
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THE STRUCTURE AND ELECTRICAL PROPERTIES IN POLYMER-LAYERED SILICATE NANOCOMPOSITES
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作者 陈文 《Journal of Wuhan University of Technology(Materials Science)》 SCIE EI CAS 1999年第3期16-22,共7页
The polymer-layered silicate nanocom- posites (PLSN) are preparedby the polymer melt interca- lation in layered silicate. By theanalyses of XRD, DSC, IR, NMR and Ac in pedance measurements etc, theex- Perimental resul... The polymer-layered silicate nanocom- posites (PLSN) are preparedby the polymer melt interca- lation in layered silicate. By theanalyses of XRD, DSC, IR, NMR and Ac in pedance measurements etc, theex- Perimental results show that polymer (PEO) can intercalate Intothe silicate interlayer in melt state, which leads to the Addition ofthe repeated distance of silicate. 展开更多
关键词 polymer-layered silicate nanocom posite MODIFICATION structure
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Influence of Anthesis Date and Boll Branch Position on Qualities and Super-molecular Structure of Cotton Fiber
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作者 SHAN Shi-hua, SHI Pei, SUN Xue-zhen, ZHOU Zhi-guo and BIAN Dong-cai(Agronomy Department of Shandong Agricultural University, Taian 271018 , P. R . China Tianjin Institute of Textile , Tianjin 300160 , P.R. China ) 《Agricultural Sciences in China》 CAS CSCD 2002年第6期636-641,共6页
The influences of the anthesis date and the fruiting branch positions on parameters of cotton fiber quality and super-molecular structure were studied. Fiber quality parameters, such as cotton fiber length, micronair,... The influences of the anthesis date and the fruiting branch positions on parameters of cotton fiber quality and super-molecular structure were studied. Fiber quality parameters, such as cotton fiber length, micronair, maturity and fiber strength deteriorated with postponing the anthesis date and decreasing temperature. When anthesis happened on the same date, the fruiting branch positions affected the fiber quality parameters, and the fiber quality parameters of the lower portion turned out to be higher than that of the upper portion, although the difference was insignificant. The super-molecular structure of the lower portion turned out to be superior to that of the upper portion at the early anthesis date and high temperature, which is in accordance with what was mentioned above, but the fruiting branch positions did not affect the impact of the anthesis date on the super-molecular structure. 展开更多
关键词 COTTON Anthesis date Fruiting branch positions Fiber qualities Super-molecular structure
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Magnetoacoustic position imaging for liquid metal in animal interstitial structure
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作者 Xiao-He Zhao Guo-Qiang Liu +1 位作者 Hui Xia Yan-Hong Li 《Chinese Physics B》 SCIE EI CAS CSCD 2020年第5期346-353,共8页
Magnetoacoustic tomography with magnetic induction(MAT-MI),as a new kind of in-vivo imaging method,has potential application value in interstitial fluid research.In this paper,we propose the application of MAT-MI with... Magnetoacoustic tomography with magnetic induction(MAT-MI),as a new kind of in-vivo imaging method,has potential application value in interstitial fluid research.In this paper,we propose the application of MAT-MI with liquid metal serving as a tracer of the interstitial structure to study its fluid behavior,and use it to implement the positional imaging of the spatial distribution of liquid metal.Owing to the particularity of liquid metal magnetoacoustic pressure(MAP)signals,we propose an envelope analysis method to extract the rising edge of the amplitude envelope of the detected waveform as effective position data.And for the first time,we propose the method of superpositing pixel matrix to achieve the position imaging of liquid metal.Finally,the positional imaging of the liquid metal sample embedded in the gel is achieved to have relatively accurate results.This study provides a method of effectively extracting data and implementing the position imaging for liquid metal in the interstitial structure in the frame of MAT-MI. 展开更多
关键词 magnetic acoustic tomography with magnetic induction(MAT-MI) liquid metal interstitial structure position imaging
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The Influence of Surface Building's Relative Position on the Seismic Response of Subway Structures
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作者 Li Fangjie Zhao Fengxin Zhang Yushan You Hongbing 《Earthquake Research in China》 2011年第2期250-259,共10页
By using the finite element method and viscoelastic artificial boundary, a soil-structure interaction system is established to simulate the influence of surface buildings on the seismic response of subway structures. ... By using the finite element method and viscoelastic artificial boundary, a soil-structure interaction system is established to simulate the influence of surface buildings on the seismic response of subway structures. The conditions of different relative positions between ground building and subway structure are analyzed. The result~ indicate that when considering the existence of surface buildings, the relative story displacements and internal forces of subway structures are changed greatly. Further the influence of surface buildings on subway structure changes as the distance increases. 展开更多
关键词 Subway structure Ground building Relative position Seismic response
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Multi-layer hierarchical cellulose nanofibers/carbon nanotubes/vinasse activated carbon composite materials for supercapacitors and electromagnetic interference shielding 被引量:2
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作者 Tianxu Wang Chuanyin Xiong +4 位作者 Yongkang Zhang Bo Wang Qing Xiong Mengjie Zhao Yonghao Ni 《Nano Research》 SCIE EI CSCD 2024年第3期904-912,共9页
Developing porous self-supporting electrodes with excellent conductivity,good mechanical properties,and high electrochemical activity is crucial for constructing electrode materials with lightweight,ultra-thin,flexibl... Developing porous self-supporting electrodes with excellent conductivity,good mechanical properties,and high electrochemical activity is crucial for constructing electrode materials with lightweight,ultra-thin,flexible,and high capacitance performance.In this work,we prepared a cellulose nanofibers(CNFs)/carbon nanotubes(CNTs)/vinasse activated carbon(VAC)(CCV)composite material with a multi-layer hierarchical conductive structure through simple vacuum filtration and freeze-drying.In this composite material,the self-assembly of CNF provides the main skeleton structure of a multi-layer hierarchical structure.CNT provides a fast path for the rapid transfer of electrons and is beneficial for the loss of electromagnetic waves.VAC provides sufficient double layer performance.The synergistic effect of the above three endows CCV composite materials with excellent energy storage performance and electromagnetic interference(EMI)shielding performance.In addition,we endowed the CCV composite with a certain shape and performance by introducing a vitrimer polymer with a dynamic cross-linked network structure.In summary,thanks to the synergistic effect of various components in the multi-layer hierarchical structure,CCV composite materials exhibit excellent integration performance,especially stable energy storage performance and EMI shielding performance.These significant properties make CCV composite materials have great application prospects in the fields of energy storage and intelligent EMI shielding. 展开更多
关键词 self-supporting electrodes multi-layer hierarchical structure SUPERCAPACITORS electromagnetic interference shielding
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A Study of Structure and Mechanism of a Meso-beta-scale Convective Vortex and Associated Heavy Rainfall in the Dabie Mountain Area Part I: Diagnostic Analysis of the Structure 被引量:5
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作者 徐文慧 倪允琪 +3 位作者 汪小康 邱学兴 宝兴华 金文岩 《Advances in Atmospheric Sciences》 SCIE CAS CSCD 2011年第5期1159-1176,共18页
An analysis was conducted on the evolutional process of a mesoscale convective vortex (MCV) and associated heavy rainfall in the Dabie Mountain area on 21-22 June 2008,as well as their structural characteristics in ... An analysis was conducted on the evolutional process of a mesoscale convective vortex (MCV) and associated heavy rainfall in the Dabie Mountain area on 21-22 June 2008,as well as their structural characteristics in different stages,by using the mesoscale reanalysis data with 3 km and 1 h resolution generated by the Local Analysis and Prediction System (LAPS) in the Southern China Heavy Rainfall Experiment.The results showed that the latent heat released by convection in the midtroposphere was the main energy source for the development of a low-level vortex.There was a positive feedback interaction between the convection and the vortex,and the evolution of the MCV was closely related to the strength of the positive interaction.The most typical characteristics of the thermal structure in different stages were that,there was a relatively thin diabatic heating layer in the midtroposphere in the formative stage;the thickness of diabatic heating layer significantly increased in the mature stage;and it almost disappeared in the decay stage.The characteristics of the dynamic structure were that,in the formative stage,there was no anticyclonic circulation at the high level;in the mature stage,an anticyclonic circulation with strong divergence was formed at the high level;in the decay stage,the anticyclonic circulation was damaged and the high-level atmosphere was in a disordered state of turbulence.Finally,the structural schematics of the MCV in the formative and mature stage were established respectively. 展开更多
关键词 mesoscale reanalysis data mesoscale convective vortex (MCV) strong convection positive feedback structural schematics
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Defect feature recognition method of glass fibre-reinforced structure based on visual image analysis 被引量:1
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作者 HUANG Jingde 《Journal of Measurement Science and Instrumentation》 CAS CSCD 2022年第1期61-67,共7页
Glass fibre-reinforced(GFR)structure is extensively used in radome,spoiler and some other equipment.In engineering practice,due to the influence of wear,aging,impact,chemical corrosion of surface structure and other f... Glass fibre-reinforced(GFR)structure is extensively used in radome,spoiler and some other equipment.In engineering practice,due to the influence of wear,aging,impact,chemical corrosion of surface structure and other factors,the internal structure of this kind of structure gradually evolves into a defect state and expands to form defects such as bubbles,scratches,shorts,cracks,cavitation erosion,stains and other defects.These defects have posed a serious threat to the quality and performance of GFR structure.From the propagation process of GFR structure defects,its duration is random and may be very short.Therefore,designing a scientific micro defect intelligent detection system for GFR structure to enhance the maintainability of GFR structure will not only help to reduce emergencies,but also have positive theoretical significance and application value to ensure safe production and operation.Firstly,the defect detection mechanism of GFR structure is discussed,and the defect detection principle and defect area identification method are analyzed.Secondly,the processing process of defect edge signal is discussed,a classifier based on MLP is established,and the algorithm of the classifier is designed.Finally,the effectiveness of this method is proved by real-time monitoring and defect diagnosis of a typical GFR structure.The experimental results show that this method improves the efficiency of defect detection and has high defect feature recognition accuracy,which provides a new idea for the on-line detection of GFR structure defects. 展开更多
关键词 glass fibre-reinforced(GFR)structure multi-layer perceptron(MLP) machine vision defect detection
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A Novel Sliding Mode Variable Structure Controller Based on a Genetic Algorithm 被引量:1
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作者 LIU Hong-yan HUANG Yu-mei +1 位作者 SHI Wen-hao ZHAO Xing-wen 《International Journal of Plant Engineering and Management》 2007年第2期87-92,共6页
A novel control method has been proposed by using the genetic algorithm (GA) for nonlinear and complex plants. The proposed control strategy is based on a variable structure control, it overcomes the defects of othe... A novel control method has been proposed by using the genetic algorithm (GA) for nonlinear and complex plants. The proposed control strategy is based on a variable structure control, it overcomes the defects of other adaptive methods such as strong dependence to the system. A GA is used to learn to optimally select integral coefficient C. Simulation results verified the effectiveness of the controller. For position control of Direct Current (DC) motor in practice, this method has good performance and strong robustness, and both dynamic and steady performances were improved. 展开更多
关键词 variable structure control position control genetic algorithm DC motor
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Influencing factors on elastic-plastic deformation of multi-layered surfaces under sliding contact
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作者 YAN Li PAN Xin-xiang XU Jiu-jun CHENG Dong 《中国有色金属学会会刊:英文版》 CSCD 2004年第z1期472-477,共6页
Stress distribution in the gradient multi-layered surface under a sliding contact was investigated using finite element method(FEM). The main structure parameters of layered surface discussed are total layer thickness... Stress distribution in the gradient multi-layered surface under a sliding contact was investigated using finite element method(FEM). The main structure parameters of layered surface discussed are total layer thickness,layer number and elastic modulus ratio of layer to the substrate. A model of multi-layered surface contact with rough slider was studied. The effect of the surface structure parameters on the elastic-plastic deformation was analyzed. 展开更多
关键词 GRADIENT multi-layered SURFACE ELASTIC-PLASTIC DEFORMATION SURFACE structure PARAMETER FEM
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A simple model for approximate bandgap structure calculation of all-solid photonic bandgap fibre based on an array of rings
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作者 方宏 娄淑琴 +3 位作者 郭铁英 姚磊 李宏雷 简水生 《Chinese Physics B》 SCIE EI CAS CSCD 2008年第1期232-237,共6页
A simple model for approximate bandgap structure calculation of all-solid photonic bandgap fibre based on an array of rings is proposed. In this model calculated are only the potential modes of a unit cell, which is a... A simple model for approximate bandgap structure calculation of all-solid photonic bandgap fibre based on an array of rings is proposed. In this model calculated are only the potential modes of a unit cell, which is a high-index ring in the low-index background for this fibre, rather than the whole cladding periodic structure based on Bloch's theorem to find the bandgap. Its accuracy is proved by comparing its results with the results obtained by using the accurate full-vector plane-wave method. High speed in computation is its great advantage over the other exact methods, because it only needs to find the roots of one-dimensional analytical expressions. And the results of this model, mode plots, offer an ideal environment to explore the basic properties of photonie bandgap clearly. 展开更多
关键词 photonic bandgap fibre bandgap structure multi-layer waveguide plane-wave method
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Partition of Forecast Error into Positional and Structural Components
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作者 Isidora JANKOV Scott GREGORY +2 位作者 Sai RAVELA Zoltan TOTH Malaquías PEÑA 《Advances in Atmospheric Sciences》 SCIE CAS CSCD 2021年第6期1012-1019,共8页
Weather manifests in spatiotemporally coherent structures.Weather forecasts hence are affected by both positional and structural or amplitude errors.This has been long recognized by practicing forecasters(cf.,e.g.,Tro... Weather manifests in spatiotemporally coherent structures.Weather forecasts hence are affected by both positional and structural or amplitude errors.This has been long recognized by practicing forecasters(cf.,e.g.,Tropical Cyclone track and intensity errors).Despite the emergence in recent decades of various objective methods for the diagnosis of positional forecast errors,most routine verification or statistical post-processing methods implicitly assume that forecasts have no positional error.The Forecast Error Decomposition(FED)method proposed in this study uses the Field Alignment technique which aligns a gridded forecast with its verifying analysis field.The total error is then partitioned into three orthogonal components:(a)large scale positional,(b)large scale structural,and(c)small scale error variance.The use of FED is demonstrated over a month-long MSLP data set.As expected,positional errors are often characterized by dipole patterns related to the displacement of features,while structural errors appear with single extrema,indicative of magnitude problems.The most important result of this study is that over the test period,more than 50%of the total mean sea level pressure forecast error variance is associated with large scale positional error.The importance of positional error in forecasts of other variables and over different time periods remain to be explored. 展开更多
关键词 forecast error orthogonal decomposition positional structurAL
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Logging and topographic effects on tree community structure and habitat associations in a tropical upland evergreen forest,Ghana
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作者 P.Addo-Fordjour E.K.Boakye Z.B.Rahmad 《Journal of Forestry Research》 SCIE CAS CSCD 2021年第4期1361-1372,共12页
We determined the response of tree community structure to logging disturbance and topography,and the patterns of tree-habitat associations in Tano Offin Forest Reserve,Ghana.We sampled trees in 27 20 m× 20 m plot... We determined the response of tree community structure to logging disturbance and topography,and the patterns of tree-habitat associations in Tano Offin Forest Reserve,Ghana.We sampled trees in 27 20 m× 20 m plots randomly and equally distributed in three topographic habitats(slope,valley,and hilltop) in each of two forests:logged and unlogged.Two topographic features,altitude and degree of slope,were measured and related with species composition.Overall,there were significant effects of logging and topographic habitat and their interaction on species diversity and composition,with the unlogged forest and valley habitat supporting higher diversity.Tree diversity varied among the topographic habitats in the logged but not in the unlogged forest.There were topographic effects on abundance of individual species but not on tree community abundance and basal area.Logging and its interaction with topographic habitat showed significant effects on tree abundance and basal area.Some species were associated with specific topographic habitats or a combination in the logged and unlogged forests.However,the patterns of habitat associations of the species differed between the logged and unlogged forests. 展开更多
关键词 ALTITUDE Community structure DISTURBANCE Habitat heterogeneity Slope Topographic position
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