检索结果-南通市图书馆

Science China(Technological Sciences) 2011年第1期54卷 63-69页

作者： ban Qun Martin hANKER Dietmar BORChERT ShEN hui Institute for Solar Energy System Sun Yat-sen University Guangzhou 510006 China Fraunhofer Institute for Solar Energy Systems Laboratory and Service Center Gelsenkirchen 45884 Germany

A series of hydrogenated microcrystalline silicon （μc-Si：h） p-layers for back surface field in crystalline silicon solar cells were deposited on glass substrates by the developed large area （45 cm×45 cm） plasma enhanced chemical vapour deposition processor operating at 13.56 Mhz and various values of source gas trimethylboron （TMB） to h2 flowratio. The influence of deposition parameters on the large area p-layer performance was intensively studied, as well as the thin film uniformity, optical, electrical and structural performances by Raman, PTIR, Ellipsometry, etc. Arrhenius and Tauc plots were used to discuss the μc-Si：h thin film＇s activation energy and the defects state distribution. When amorphous-microcrystalline transition state was obtained, the deposited p-doped μc-Si：h layers showed specific resistance of 38.3 Ω^-1cm1 at the flowratio of 0.66% and high crystallinity of 45%-50% with no further treatment. The effect of source gas flowratio, deposition rate, and source gas partial pressure on μc-Si：h thin film＇s performance was also investigated.

关键词： μc-Si:h flowratio uniformity band structure

One-dimensional Ga N nanomaterials transformed from one-dimensional Ga_2O_3 and Ga nanomaterials

在线全文

学校读者我要写书评

暂无评论

Nano-Micro Letters 2009年第1期1卷 4-8页

作者： X.y.han y.h.Gao X.h.Zhang Wuhan National Laboratory for Optoelectronics-Shool of Physics Huazhong University of Science and Technology Wuhan National Laboratory for Optoelectronics & Col ege of Optoelectronic Science and Engineering Huazhong University of Science and Technology

One-dimensional(1D) GaN nanomaterials exhibiting various morphologies and atomic structures were prepared via ammoniation of either Ga_2O_3 nanoribbons, Ga_2O_3 nanorods or Ga nanowires filled into carbon nanotubes(CNTs). The 1D GaN nanomaterials transformed from Ga_2O_3 nanoribbons consisted of numerous GaN nanoplatelets having the close-packed plane, i.e.(0002)2h or(111)3C parallel to the axes of starting nanoribbons. The 1D GaN nanomaterials converted from Ga_2O_3 nanorods were polycrystalline rods covered with GaN nanoparticles along the axes. The 1D GaN nanomaterials prepared from Ga nanowires filled into CNTs displayed two dominant morphologies:(i) single crystalline Ga N nanocolumns coated by CNTs, and(ii) pure single crystalline Ga N nanowires. The cross-sectional shape of Ga N nanowires were analyzed through the transmission electron microscopy(TEM) images. Formation mechanism of all-mentioned 1D GaN nanomaterials is then thoroughly discussed.

关键词： GaN One-dimensional Ga2O3 Nanostructures

Multiple feature fusion for unimodal emotion recognition

在线全文

学校读者我要写书评

暂无评论

The Journal of China Universities of Posts and Telecommunications 2019年第2期26卷 17-29页

作者： yang Lingzhi ban Xiaojuan Michele Mukeshimana Chen Zhe School of Computer and Communication Engineering Beijing Key Laboratory of Knowledge Engineering for Materials ScienceUniversity of Science and Technology BeijingBeijing 10083China Citic Pacific Special Steel holdings Qingdao Special Iron and Steel Company Limited Faculity of Engineering Sciences University of BurundiBujumbura P.0.Box 1550 BujumburaBurundi Qingdao hisense Group Company Limited Qingdao 266000China

A new semi-serial fusion method of multiple feature based on learning using privileged information(LUPI) model was put *** exploitation of LUPI paradigm permits the improvement of the learning accuracy and its stability,by additional information and computations using optimization *** execution time is also reduced,by sparsity and dimension of testing *** essence of improvements obtained using multiple features types for the emotion recognition(speech expression recognition),is particularly applicable when there is only one modality but still need to improve the *** results show that the LUPI in unimodal case is effective when the size of the feature is *** comparison to other methods using one type of features or combining them in a concatenated way,this new method outperforms others in recognition accuracy,execution reduction,and stability.

关键词： multiple feature LUPI emotion recognition semi-serial fusion method

Channel Estimation for Full-Duplex Relay Transmission in Cloud Radio Access Networks

在线全文

学校读者我要写书评

暂无评论

China Communications 2015年第11期12卷 35-42页

作者： hU Chunjing LI Jian MAO Zhendong ban yourong Key Laboratory of Universal Wireless Communication Ministry of EducationBeijing University of Posts and Telecommunications Department of Electrical Engineering University of Arkansas

Relay in full-duplex(FD) mode can achieve higher spectrum efficiency than that in half-duplex mode,while it is crucial to suppress relay self-interference to ensure transmission quality which requires instantaneous channel state information(CSI). In this paper,the channel estimation issue in FD amplify-andforward relay networks is considered,where the training-based estimation technique is adopted. Firstly,the least square(LS) estimation is implemented to obtain composite channel coefficients of source-relay-destination(SRD) channel and relay loop-interference(LI) channel in order to assist destination in performing data detection. Secondly,both LS and maximum likelihood estimation methods are utilized to perform individual channel estimation aiming at supporting successive interference cancelation at destination. Finally,simulation results demonstrate the effectiveness of both composite and individual channel estimation,and the presented ML method can achieve lower MSEs than LS solution.

关键词： channel estimation full-duplex cloud radio access networks

First principles calculations on the thermoelectric properties of bulk Au2S with ultra-low lattice thermal conductivity

在线全文

学校读者我要写书评

暂无评论

Chinese Physics B 2020年第8期29卷 108-114页

作者： y y Wu X L Zhu h y yang Z G Wang y h Li B T Wang School of Nuclear Science and Technology Lanzhou UniversityLanzhou 730000China Institute of high Energy Physics Chinese Academy of SciencesBeijing 100049China Spallation Neutron Source Science Center Dongguan 523808China School of Materials Science and Engineering Hunan University of Science and TechnologyXiangtan 411201China Institute of Modern Physics Chinese Academy of SciencesLanzhou 730000China Collaborative Innovation Center of Extreme Optics Shanxi UniversityTaiyuan 030006China

Sulfide nanocrystals and their composites have shown great potential in the thermoelectric(TE)field due to their extremely low thermal *** a solid and hollow metastable Au2S nanocrystalline has been successfully ***,we study the TE properties of this bulk Au2S by first-principles calculations and semiclassical Boltzmann transport theory,which provides the basis for its further experimental *** results indicate that the highly twofold degeneracy of the bands appears at theΓpoint in the Brillouin zone,resulting in a high Seebeck ***,Au2S exhibits an ultra-low lattice thermal conductivity(~0.88 W·m^-1·K^-1 at 700 K).At 700 K,the thermoelectric figure of merit of the optimal p-type doping is close to 1.76,which is higher than 0.8 of ZrSb at 700 K and 1.4 of PtTe at 750 *** work clearly demonstrates the advantages of Au2S as a TE material and would greatly inspire further experimental studies and verifications.

关键词： first principles calculation thermodynamic transport properties

ON FATIGUE CRACK PATh DEVIATION AT ELEVATED TEMPERATURE IN ELECTRON BEAM REPAIRED WELDMENTS OF TURBINE DISK

在线全文

学校读者我要写书评

暂无评论

Acta Metallurgica Sinica(English Letters) 2004年第4期17卷 584-590页

作者： h.Q.Zhang h.y.Zhao y.h.Zhang L.h.Li X.A.Zhang Department of Mechanical Engineering Tsinghua University Beijing 100084 ChinaDepartment of Mechanical Engineering Tsinghua University Beijing 100084 ChinaSchool of Mechanical Engineering and Automation Beijing University of Aeronautics and AstronauticsBeijing 100083 ChinaSchool of Mechanical Engineering and Automation Beijing University of Aeronautics and AstronauticsBeijing 100083 ChinaBeijing Institute of Aeronautical Materials Beijing 100095 China

Fatigue crack growth behaviors in electron beam weldments of a nickel-base superalloy are studied. The objective of this paper is to discuss effects of the inhomogeneity of mechanical performance on fatigue crack growth (FCG) rate and crack path deviation (CPD). The base metal served in a turbine disk of aerospace engine was selected to fabricate bead-on-plate weldments by using electron beam welding. Some wedge-type opening loading specimens, notched in three different zone of weld metal, hAZ and base metal, were employed and performed fatigue crack growth tests at 650℃. The results show that the fatigue crack growth of electron beam welded joints is instable due to the influence of mechanical heterogeneities. Owing to the crack deviation at the weld metal and heat-affected-zone (hAZ), the effective growth driving force at the tip of fatigue crack was reduced with the reduction of the effective stress intensity factor (SIF) which finally causes fatigue crack rate decrease. Fatigue crack was strongly affected by size and the symmetrical characteristics of the plastic zone at the crack tip, which means that the integrity of the welded structure containing the fatigue crack mainly depended on the toughness of the low strength zone.

关键词： fatigue crack growth crack path deviation electron beam welding inhomogeneity of mechanical performance

Analysis of one dimensional and two dimensional fuzzy controllers

在线全文

学校读者我要写书评

暂无评论

Journal of Systems Engineering and Electronics 2006年第2期17卷 362-373页

作者： ban Xiaojun Gao Xiaozhi huang Xianlin Wu Tianbao Dept. of Control Theory and Engineering Harbin Inst. of Technology Harbin 150001 P. R. China Inst. of Intelligent Power Electronics Helsinki Univ. of Technology Espoo Finland

The analytical structures and the corresponding mathematical properties of the one dimensional and two dimensional fuzzy controllers are first investigated in detail. The nature of these two kinds of fuzzy controllers is next probed from the perspective of control engineering. For the one dimensional fuzzy controller, it is concluded that this controller is a combination of a saturation element and a nonlinear proportional controller, and the system that employs the one dimensional fuzzy controller is the combination of an open-loop control system and a closedloop control system. For the latter case, it is concluded that it is a hybrid controller, which comprises the saturation part, zero-output part, nonlinear derivative part, nonlinear proportional part, as well as nonlinear proportional-derivative part, and the two dimensional fuzzy controller-based control system is a loop-varying system with varying number of control loops.

关键词： one dimensional fuzzy controller two dimensional fuzzy controller analytical structures fuzzy inference control system analysis.

APPLICABILITy OF CREEP CONSTITUTIVE EQUATIONS TOCREEP CURVES UNDER CONSTANT LOAD

在线全文

学校读者我要写书评

暂无评论

Acta Metallurgica Sinica(English Letters) 1998年第6期11卷 397-404页

作者： y.Kurata h.Utsumi Japan Atomic Energy Research Inst Ibaraki-ken Japan

Applicability of the following creep constitutive equations was investigated for normal type creep curves of Ni-18.5Cr alloy and tertiary creep dominant curves of Ni-18.5Cr16W alloy under constant load: the θ projection method describing a creep curse by a sum of two exponential terms, modified θ method describing a primary creep stage by an exponential term and a tertiary creep stage by a logarithmic term, modified Ω method describing a creep curve by a sum of two logarithmic term, 2θ method with only a tertiary creep component and Ω method. The θ, modified θ and modified Ω methods can describe normal type and tertiary creep dominant curves. Tertiary creep dominant curves of Ni-18.5Cr-16W alloy at 900℃ are also described using 2θ and Ω methods. Applicability of the modified θ and modified Ω methods is superior for constant load creep curves because they can predict creep curves up to rupture and rupture life accurately and conservatively.

关键词： creep equation θ projection method Ω method Ni-18.5Cr alloy,Ni-18.5Cr-16W alloy

The Cauchy problem for non-autonomous nonlinear Schr(o)dinger equations

在线全文

学校读者我要写书评

暂无评论

Science China Mathematics 2005年第4期48卷 522-538页

作者： Peter y. h. Pang Department of Mathematics

In this paper we study the Cauchy problem for cubic nonlinear Schr(o)dinger equation with space-and time-dependent coefficients on Rm and Tm. By an approximation argument we prove that for suitable initial values, the... 详细信息

关键词： non-autonomous Schr(o)dinger equations, local existence, global existence.

Creep Behavior and Microstructure Evolution of Sand–Cast Mg–4y–2.3Nd–1Gd–0.6Zr Alloy Crept at 523–573 K

在线全文

学校读者我要写书评

暂无评论

Journal of Materials Science & Technology 2017年第1期33卷 79-89页

作者： y.h.Kang h.yan R.S.Chen The Group of Magnesium Alloys and Their Applications Institute of Metal ResearchChinese Academy of SciencesShenyang 110016China University of the Chinese Academy of Sciences Beijing 100049China

high temperature tensile-creep behavior of Mg-4y-2.3Nd-IGd-O.6Zr （wt%, WE43（T6）） alloy at 523- 573 K was investigated. The creep stress exponent is equal to 4.6, suggesting the underlying dislocation creep mechanism. The activation energy is （199 _＋ 23） kJ/mol, which is higher than that for self- diffusion in Mg and is believed to be associated with precipitates coarsening or cross slip. The creep mechanism is further suggested to be dislocation climb at 523 K, while a cross slip at 573 K is possible. The metastable 13＇ and ~]1 phases in the WE43（T6） alloy were relatively thermal stable at 523 K and could be effective to hinder the dislocation climb, which contributed to its excellent creep resistance. however, at 573 K it readily transforms into equilibrium/3e phase and coarsens within two hours, thereby causing a decrease of creep resistance. In addition, precipitate free zones approximately normal to applied stress direction （directional PFZs） developed during the creep deformation, especially at 573 K. Those zones became preferential sites to nucleate, extend and connect microcracks and cavities, which lead to the intergranular creep fracture. Improving the thermal stability of precipitates or introducing thermally stable fine plate-shaped precipitates on the basal planes of Mg matrix could enhance the high temperature creep resistance.

关键词： WE43 alloy Creep PFZs Precipitate Fracture