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931.
The electronic structures of kinks in the [100](010) and 1/2[111](−110) edge dislocations in bcc iron containing hydrogen
are investigated by means of the first-principles DMol method and the discrete variational method. The effects of hydrogen
on the kinks are discussed. The results show that hydrogen forms weak bonding states with its neighboring host atoms, and
since hydrogen draws charge from its neighboring host atoms, the interactions between most of the host atoms are weakened
compared with those of the corresponding atomic pairs in the clean kinks. This indicates that the migration of kink, i.e.
the motion of dislocation, is easier in the doping hydrogen kink than in the clean kink, which may be the solid solution softening
effect resulting from the impurity hydrogen.
Supported by the National Basic Research Program of China (Grant No. 2006CB605102) and Science Foundation of Central South
University of Forestry & Technology (Grant No. 06y016) 相似文献
932.
The L, H and C curves in P-T phase are proposed to describe the minimal, maximal and critical characteristics of ignition time of H2/O2 combustion system, respectively. The features of H2/O2(Air) combustion system, including explosion or not as well as the time delay to achieve its explosion status, can be well
shown by explosion limits and these proposed curves. These curves can be described by 1.2k
1=k
s
[Ms], (k
11/k
10+1)k
1=k
s
[Ms], and 2k
1=k
s
[Ms], respectively, which provide a physical explanation for these curves and give another way to establish them. Based on the
contour of ignition time, the Z-type explosion limits can be explained by thermal explosion theory. Furthermore, the ignition
distance of supersonic combustion is predicted according to the ignition time obtained in a Semenov system, which is very
reasonable. 相似文献
933.
In remote sensing applications, accurate extraction of land type area after classification is very important. But for images
of land use/cover change (LUCC) obtained from the special spatial resolution remote sensing data, it will be of great significance
to obtain the land type area information with higher resolution by making use of spatial distribution characteristcs information
of the land type itself first and further scaling-down in a given scale threshold on the basis of the existing spatial resolution
data. An explicit expression of the relationship between the measurement scale, global fractal dimension and the land type
area corresponding to different measurement scales is obtained on the research basis of the authors’ histo-variogram using
the standardized area index (SAI). A good attempt has been made to obtain the land type area information with higher resolution
by merely using the spatial distribution characteristcs information of the land type in the image itself and further scaling-down
in a given scale threshold on the basis of the existing spatial resolution data.
Supported by the National Natural Science Foundation of China (Grant No. 40601068), the National Basic Research Program of
China (“973” Project) (Grant No. 2007CB714402) and the Key Science and Technology R&D Program of Qinghai Province (Grant No.
2006-6-160-01) 相似文献
934.
Safety evaluation and the static-dynamic coupling analysis of counter-arched slab in plunge pool 总被引:1,自引:0,他引:1
The stability of plunge pool slab of drainage structure is crucial to energy dissipation, but the working conditions of counter-arched
slab are very complex and its stress procedure is considerably nonlinear and coupling. Therefore, a nonlinear static and dynamic
coupling method to analyze the counter-arched slab configuration is put forward, which can reflect the coupling of dynamic
loads, slab, anchor bars, groundwork and abutment as well as the dynamic procedure of instability. Various nonlinear factors
and static-dynamic coupling are taken into consideration, and the working conditions, stress mechanism, dynamic instability
procedure and influential instability factors are revealed. The proposed method thus provides a comprehensive safety evaluation
method of plunge pool, which further provides an important theoretical basis for engineering design of counter-arched slab
in plunge pool.
Supported by the National Science Fund for Distinguished Young Scholars (Grant No. 50725929) and the National Natural Science
Foundation of China (Grant Nos. 50539060, 50679052, 50779044) 相似文献
935.
车辆-轨道-桥梁空间耦合振动引起的环境振动 总被引:1,自引:0,他引:1
首先建立了车辆-无碴轨道-桥梁系统空间耦合振动模型,通过随机振动分析得到桥墩墩底反力,然后建立了土体-建筑物的三维有限元模型,并将以上得到的墩底反力作为土体-建筑物三维有限元模型的外部激励。分析结果表明,周围土体振动强度随距离的增加而减小,且都存在反弹区 周围建筑物的振动强度随桥墩距离的增大而减小,且在建筑物低层横向和竖向振动相差不大,但是到了高层处横向振动明显大于竖向振动。 相似文献
936.
The main goal of this paper is to construct an efficient reduced-order model (ROM) for unsteady aerodynamic force modeling.
Balanced truncation (BT) is presented to address the problem. For conventional BT method, it is necessary to compute exact
controllability and observability grammians. Although it is relatively straightforward to compute these matrices in a control
setting where the system order is moderate, the technique does not extend easily to high order systems. In response to the
challenge, snapshots-BT (S-BT) method is introduced for high order system ROM construction. The outline idea of the S-BT method
is that snapshots of primary and dual system approximate the controllability and observability matrices in the frequency domain.
The method has been demonstrated for 3 high order systems: (1) unsteady motion of a two-dimensional airfoil in response to
gust, (2) AGARD 445.6 wing aeroelastic system, and (3) BACT (benchmark active control technology) standard aeroservoelastic
system. All the results indicate that S-BT based ROM is efficient and accurate enough to provide a powerful tool for unsteady
aerodynamic force modeling. 相似文献
937.
Fractal model of lightning channel for simulating lightning strikes to transmission lines 总被引:2,自引:0,他引:2
How to accurately evaluate the direct-strike lightning protection is one of the key issues in the design of transmission lines.
In this paper, three important issues in applying the fractal simulation to the lightning protection of transmission lines
were discussed, including the criteria and implementation of upward leader inception, the connection with the magnitude of
lightning current, and the calculation and control of fractal dimensions. Then we conducted the simulation iterately, leading
to statistical results, which indicate that even if the transmission line satisfies the perfect shielding condition, shielding
failure fault remains possible. Furthermore, we calculated the shielding failure fault rates of an EHV line with different
ground obliquities and distribution of strike points over the interval between two neighboring towers along a UHV-DC line
to find out the weak point of transmission-line lightning protection. This work provides a promising approach for improving
the lightning protection property of transmission lines by optimizing the configuration of shielding wires and phase or pole
conductors. 相似文献
938.
Based on Al induced crystallization (AIC) method, influences of different material structures on formation and characteristics of ploy-silicon thin films were studied and optimized. Al-Si films on glass with different structures (Si/Al/Glass, Al/Si/Glass, Si/Al/…/Si/Al/Glass) were deposited on glass substrates by sputtering method. All samples were annealed for MIC with varied time processes under 500℃ N2 environment. X-ray diffraction test and scanning electron microscope were adopted to characterize cryst... 相似文献
939.
DongJie Guo HaiTao Ding Haiju Wei Qingsong He Min Yu ZhenDong Dai 《中国科学E辑(英文版)》2009,52(10):3061-3070
This paper reports a new technique to fabricate an ion-exchange polymer-metal composite (IPMC) actuator. This technique is based on a hybrid organic-inorganic composite membrane. In the fabrication course, silica oxide particles, prepared from hydrolysis of tetraethyl orthosilicate in situ with sol-gel reaction, co-crystallize with perfluorosulfonate acid (PFSA) ionomer. Attenuated total reflectance fourier transform infrared spectroscopy (ATR-FTIR) analyses demonstrate that a highly water-saving hybrid mem... 相似文献
940.
Andre SULPICE Jean-Louis SOUBEYROUX Christophe VERWAERDE Gia Ky HOANG 《中国科学E辑(英文版)》2009,52(10):3071-3075
Two sets of internal-Sn Nb3Sn superconducting strands were fabricated through RRP method, one with 2 wt% of Ti alloyed in Sn core and the other just pure Sn. Four reaction temperatures of 650℃, 675℃, 700℃ and 725℃ and 128 h duration were applied for A15 phase formation heat treatment after Cu-Sn alloying procedure of 210℃/50 h + 340℃/25 h. For the heat-treated coil samples, transport non-Cu JC was examined through standard 4-probe technique and phase microstructure was observed by means of Field Emission Sc... 相似文献