首页 | 官方网站   微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 218 毫秒
1.
《科学通报(英文版)》2008,(16):2453-2453
The past decades have witnessed the fast increase of demands on various Internet applications, which work in the open and dynamic Internet environment and enable people to share and utilize various kinds of resources such as computing power, data, software, and services. The Internet applications bring great challenges to both microelectronics and software technologies that are the two indispensable underpinnings of information technologies: microelectronics is the foundation of all hardware devices, and software plays the director role of controlling those devices to function correctly and serve human society effectively. Much progress in software and microelectronicstechnologies has been made in recent years.  相似文献   

2.
Empirical mode decomposition (EMD) is proposed to identify linear structure under non-stationary excitation,and non-white noise coefficient is introduced under the assumption of random signals consisting of white noise and non-white noise signals. The cross-correlation function of resoonse signal is decomoosed into mode functions and residue by EMD method. The identification technique of the modal parameters of single freedom degree is applied to each mode function to obtain natural frequencies, damping ratios and mode shapes. The results of identification of the five-degree freedom linear system demonstrate that the proposed method is effective in identifying the parameters of linear structures under non-stationary ambient excitation.  相似文献   

3.
A nonlinear autoregressive (NAR) model is built to model the heartbeat interval time series and the optimum model degree is proposed to be taken to evaluate the nonlinearity degree of heart rate variability (HRV). A group of healthy persons are studied and the results indicate that this method can effectively get nonlinear information from short (6—7 min) heartbeat series and consequently reflect the degree of heart rate variability, which supplies convenience in clinical application. Finally, a comparison with the traditional time domain method shows that the NAR model method can reflect the complexity of the whole signal and lessen the influence of noise and instability, in the signal.  相似文献   

4.
1 Results Micro-batteries are expected to become more and more important in numerous small-sized devices,like medical implantables,biosensors,hearing aids and autonomous network devices.Characteristic for these electronic applications is that they have to operate autonomously and reliably.Due to these requirements thin film power sources need to be rechargeable,mechanically stable for a long period of time and have a long cycle life.As the average energy consumption of these future devices will be rather small,this opens up the possibility to integrate all-solid-state rechargeable batteries,enabling a high degree of IC integration.  相似文献   

5.
Some new concepts (rank of a loop, degree of freedom of a graph, path unit and ordered path arrangement, constraint degree of path, coupling degree of a graph, basic graph, etc. ), formulas, and algorithms, are proposed in this paper. Based on these concepts, a new systematic theory and practical method for the design of topological structure, kinematics and dynamics of mechanical systems is established. Some conjectures and problems needed to be researched are also put forward. The concepts, formulae and algorithms presented in this paper will find wide potential applications.  相似文献   

6.
This study is concerned with the need for remote sensing techniques for the monitoring of oil-slick pollution on sea surfaces and the effects of oil-slick pollution on the sea.We used Daqing crude oil,Jilin crude oil,heavy oil and seawater from Dalian Bay to simulate oil-slick pollution on the sea surface and obtained multi-angle hyperspectral polarized reflectance information,from which we calculated the polarization for different kinds of crude oil,and oil-slicks of different thicknesses.By comparing the degree of polarization between oil-slicks of different thickness,and sea water,it was found that in the case of thin oil-slicks,the degree of polarization of seawater is higher than that of oil slicks with wavelengths of between 400-1000 nm.However,there was little difference at a wavelength of 785 nm.At angles of incident of 20° and 30° (the viewing angle equals the incident angle),it was easy to distinguish the changes of oil-slick thickness by the degree of polarization at 785 and 880 nm in the near-infrared band.The crude oil showed its inherent polarized characteristic as the oil-slick thickness increased to a certain degree.That is to say,the polarization of the seawater was higher than that of the oil-slick in the visible light range,but less than that in the near-infrared band.As the incident angle changed from 40° to 50°,the degree of polarization of seawater increased,and it was higher than that for the oil-sick between wavelengths of 400-1000 nm at an angle of incidence of 50°.This research on the polarized characteristics of an oil-slick on a sea surface brings new scientific techniques to the monitoring of sea-surface pollution by remote sensing.  相似文献   

7.
A microelement method for scale-span analysis of material microstructure and member macro response has been proposed. Instead of material parameter input for traditional mechanical analysis, the method is based on the input of metallographic diagram information. In order to express the material microstructure, this method arranges concentrated microelements in ordinary finite element before calculation, and transfers the node degrees of freedom of each microelement into the ones of the same finite element via compatibility conditions. This method can realize direct transition analysis from material microstructure to macro responses of members, while computation elements and degrees of freedom are equal to those of ordinary FEM. Based on the complicated microstructure diagrams proposed by material metallographic diagram, the mechanics responses of functionally graded plates are calculated and 3-D distributions of macro-mechanical variables and identical stress lines tendency on microstructure are given.  相似文献   

8.
The flowering time of Arabidopsis is sensitive to climate variability, with lighting conditions being a major determinant of the flowering time. Long-days induce early flowering, while short-days induce late flowering or even no flowers. This study investigates the intrinsic mechanisms for Arabidopsis flowering in different lighting conditions using mutual information networks and logic networks. The structure parameters of the mutual information networks show that the average degree and the average core clearly distinguish these networks. A method is then given to find the key structural genes in the mutual information networks and the logic networks respectively. Ten genes are found to possibly promote flowering with three genes that may restrain flowering. The sensitivity of this method to find the genes that promote flowering is 80%, while the sensitivity of the method to find the genes that restrain flowering is 100%  相似文献   

9.
Cohesion is one of the phenomena of the text.It is expressed through the cohesive devices.As part of Functional Grammar,the cohesive devices relate themselves naturally to the meanings,which exist both in the text and in its social context.This paper is to explore the relationship between the cohesive devices and their meanings.These meanings subsume the discourse semantics in the text and the register in the social context.  相似文献   

10.
Based on the coordinate rotation digital computer(CORDIC)algorithm,the high-speed kinematicscalculation for a six degree of freedom(DOF)space manipulator is implemented in a field programmablegate array(FPGA)co-processor.A pipeline architecture is adopted to reduce the complexity and time-consumption of the kinematics calculation .The CORDIC soft-core and the CORDIC-based pipelined kine-matics calculation co-processor are described with the very-high-speed integrated circuit hardware descrip-tion langua...  相似文献   

11.
本文采用密度泛函理论系统地研究了过渡金属原子Co和Ni单掺杂和双掺杂ZnO纳米线的结构、电子性质和磁性质.所有掺杂纳米线的束缚能都为负值,表明掺杂过程是放热的. Co原子趋于占据纳米线中间位置,而Ni原子趋于占据纳米线表面位置.所有掺杂纳米线能隙都小于纯纳米线能隙,并显示出直接带隙半导体特性.纳米线的总磁矩主要来源于磁性原子的贡献. Co掺杂纳米线出现了铁磁和反铁磁两种耦合状态;而Ni掺杂纳米线出现了铁磁、反铁磁和顺磁三种耦合状态.  相似文献   

12.
本文采用第一性原理密度泛函理论系统地研究了V原子单掺杂和双掺杂(ZnTe)12团簇的结构和磁性质.我们考虑了替代掺杂、外掺杂和内掺杂.不管是单掺杂还是双掺杂,外掺杂团簇都是最稳定结构.团簇磁矩主要来自V-3d态的贡献,4s和4p态也贡献了一小部分磁矩.由于轨道杂化,相邻的Zn和Te原子上也产生少量自旋.V原子之间的磁性耦合是短程相互作用.  相似文献   

13.
本文采用第一性原理密度泛函理论系统地研究了Fe原子单掺杂和双掺杂ZnO纳米线的电子性质和磁性质.所有掺杂纳米线的形成能都比纯纳米线的形成能低,说明掺杂过程是放热的.计算结果显示Fe原子趋于占据纳米线表面位置.纳米线的总磁矩主要来源于Fe原子3d轨道的贡献.由于杂化,相邻的O原子也产生了少量自旋.在超原胞内,Fe、O原子磁矩平行排列,表明它们之间是铁磁耦合.表面掺杂纳米线显示出半导体特性,而中间掺杂纳米线显示出半金属性,在自旋电子学领域有广泛应用.  相似文献   

14.
Using first-principles density function for molecules method (DMol) and discrete variational method (DVM) based on the density functional theory, we studied the doping effect of Re in Ni3Al. The structure relaxation and the alloying energy show that Re has a strong A1 site preference and leads to the local deformation, which is in agreement with the experimental results and other theoretical results. In addition, the charge density difference and the bond order show that Re can strongly enhance the interatomic interaction between the nearest neighbor atoms. From the density of states and the Pauli spectrum, we find that resonance states and localized states are induced by doping Re, and the doped Re atom forms the hybridized bond with the nearest neighbor atoms.  相似文献   

15.
用第一性原理计算硅烯在N和S原子共掺杂时的能带及电子态密度, 并研究硅烯量子电容与不同掺杂构型间的关系. 结果表明: 引入N/S和N/B共掺杂原子可导致Fermi能级处产生局域态; 在-0.6~0.6 V内, 用NSS,NS,NBB,NNB和NB掺杂硅烯的量子电容均增加, 其中NSS掺杂单空位硅烯在Fermi能级附近, 其量子电容为43.9 μF/cm2, 量子电容增加明显.  相似文献   

16.
Using first-principles density function for molecules method (DMol) and discrete variational method (DVM) based on the density functional theory, we studied the doping effect of Re in Ni3Al. The structure relaxation and the alloying energy show that Re has a strong Al site preference and leads to the local deformation, which is in agreement with the experimental results and other theoretical results. In addition, the charge density difference and the bond order show that Re can strongly enhance the interatomic interaction between the nearest neighbor atoms. From the density of states and the Pauli spectrum, we find that resonance states and localized states are induced by doping Re, and the doped Re atom forms the hybridized bond with the nearest neighbor atoms.  相似文献   

17.
采用基于密度泛函理论的第一性原理平面波赝势方法,对V掺杂AlN的电子结构和铁磁性质进行了研究.结果表明,V掺杂后,由于V 3d与N 2p轨道杂化在半导体能隙中产生自旋极化杂质带,材料表现出半金属铁磁性,其磁矩主要来自以V原子为中心的VN4四面体.另外,通过对V掺杂AlN的铁磁稳定性的研究发现,V原子之间为铁磁耦合时体系处于稳定的基态,并且有围绕N原子形成团簇的趋势,随着V原子间距离的增加,体系FM和AFM态的能量将趋于简并.  相似文献   

18.
采用密度泛函理论(density functional theory,DFT)中的广义梯度近似(generalized gradient approximation,GGA)对Sn11团簇的4种同分异构体(对称性分别为D5h,D5d,D4h,D4d)的几何结构、电子结构计算研究,得出对称性为D5d的团簇最稳定.将Sn11团簇的中心原子替换成过渡金属原子成为MSn10(M=Sc,Ti,V,Cr,Mn,Fe,Co,Ni)团簇,对其稳定性和磁性进行了分析.在Sn11团簇中将中心原子替换成过渡金属原子后,束缚能都变小了,说明过渡金属原子的替换提高了原锡团簇的稳定性,其中NiSn10团簇的束缚能最小,稳定性最强.过渡金属原子都具有一定的磁性,当把这些原子掺入锡团簇后,过渡金属原子的磁性都有所减弱,其中MSn10(M=Sc,Ti,V,Ni)团簇的磁性完全消失,其原因在于掺杂后,团簇中各原子的电荷分布发生了变化.  相似文献   

19.
基于第一性原理研究了Cr元素掺杂3C-SiC的电子结构和磁性,揭示了Cr元素掺杂3C-SiC的磁矩形成以及铁磁耦合的微观物理机制,发现同时引入N元素后Cr元素掺杂3C-SiC的形成能大幅降低,并对其形成能降低的机理进行了系统的讨论,给出了合理的解释,在过渡金属掺杂时引入N元素能够显著地降低磁性杂质的形成能。  相似文献   

20.
依赖强度耦合T-C模型的反聚束效应   总被引:1,自引:1,他引:0  
研究了依赖强度耦合T—C模型的反聚束效应,讨论了原子—原子间的耦合强度、初始光场强度以及原子初态与光场二阶相干度的关系,揭示了原子间的相对耦合强度、初始场强以及原子初态对光子的反聚束效应的影响.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司    京ICP备09084417号-23

京公网安备 11010802026262号