共查询到20条相似文献,搜索用时 109 毫秒
1.
Tao Liu Zuxiong Xu Zhongtao Zhao Ruzhang Ma Tiandou Hu Yaning Xie Yinghuan Guo 《中国科学A辑(英文版)》1997,40(4):395-399
The role of magnetoelastic coupling effects in nanocrystalline ferromagnets is investigated by means of high-field magnetization and Doppler-broadening spectrum measurements. For the nanocrystalline Fe73 5Cu1Nb3Si13.5B9 alloy, the results show that the pinning effects resulting from the quasidislocation dipole intensely influence the movement of domain wall; by coupling with the magnetostriction the defects-induced stress fields determine the magnetic properties at the early stage of crystallization. In view of the effective anisotropy and magnetoelastic coupling energy the optimal annealing conditions of alloys are discussed. 相似文献
2.
Wen Deng Xiaping Zhong Yuyang Huang Liangyue Xiong Shuhe Wang Jianting Guo Qiwei Long 《中国科学A辑(英文版)》1999,42(1):87-92
Positron lifetime measurements have been performed in binary Fe3Al and Fe3Al doping with Nb or Si alloys. The densities of valence electrons of the bulk and microdefects in all tested samples have
been calculated by using the positron lifetime parameters. Density of valence electron is low in the bulk of Fe3Al alloy. It indicates that, the 3d electrons in a Fe atom have strong-localized properties and tend to form covalent bonds
with Al atoms, and the bonding nature in Fe3Al is a mixture of metallic and covalent bonds. The density of valence electron is very low in the defects of Fe3Al grain boundary, which makes the bonding cohesion in grain boundary quite weak. The addition of Si to Fe3Al gives rise to the decrease of the densities of valence electrons in the bulk and the grain boundary thus the metallic bonding
cohesion. This makes the alloy more brittle. The addition of Nb to Fe3Al results in the decrease of the ordering energy of the alloy and increases the density of valence electron and the bonding
cohesion of the grain boundary. However, since the radius of Nb atom is larger than that of Fe atom, when Nb atoms substitute
for Fe atoms, they will distort the lattice and enlarge the volume of the lattice, which decreases the density of valence
electron and the cohesion of metallic bond in the bulk of the alloy.
Project supported by the National Natural Science Foundation of China (Grant No. 59561001) and the Foundation of Guangxi Education
Committee. 相似文献
3.
By X-ray diffraction and high pressure Mossbauer spectroscopy, the structure and the hyperfine parameters of Ni substituted
γ’-Fe4N were investigated. The results of X-ray diffraction indicate that single phase γ’-(Fe1-xNix)4N compounds can be prepared in the composition range of 0⩽x⩽0.6, and with the increase of Ni content the lattice parameter is fit for the relationshipa
0(x)=3.790 5-0.021 57x-0.031 67x
2. By high pressure Mossbauer spectra, effects of magnetovolume and chemical bonding of Ni atom on hyperfine magnetic field
and isomer shift of iron were distinguished for the first time, and their composition dependences for different lattice sites
were studied simultaneously. It is found that the magnetovolume and chemical bonding have different influences on the properties
of γ’-(Fe1-xNix)4N, and the latter one plays a key role in the property changes of γ’-(Fe1-xNix)4N.
Project supported by the National Natural Science Foundation of China, the Natural Science Fund of Gansu Province and the
Postdoctoral Fund of China. 相似文献
4.
Peixun Luo Yun Zhao Cunyi Xu Keliang Hu Guien Zhou Xiaoguang Li Yuheng Zhang 《中国科学A辑(英文版)》1998,41(6):656-662
The Raman and infrared spectra, resistivity as well as thermoelectric power of Y1-xNdxSr2Cu2.7Mo0.3 O7 δ(.x =0, 0.1. 0.2. 0.5, 0.8 and 1.0) are studied carefully. It was found that the structure characteristics of RSr2Cu2.7Mo0.3O7 δ cuprates are different from those of RBa2Cu307 δ. The variations of the microstructure in Y1-x NdxSr2Cu2.7Mo0.3O7 δ with Nd-doping affect the carrier distribution. so as a result the superconductivity changes. Furthermore, it is pointed
out that the microstructure variations with the large rare earth ionic substitution cause the widely existing rare earth ionic
size effect in HTSC.
Project supported by the National Natural Science Foundation of China and the National Center for R & D Superconductivity. 相似文献
5.
The decomposition of the complete graph Kv into Kr×Kc's, the products of Kr and Kc,is originated from the use of DNA library screening. In this paper, we consider the case where r=2 and c = 5, and show that such a decomposition exists if and only if v ≡ 1 (mod 25). 相似文献
6.
Limin Wang Weihua Wang Liling Sun Jianhua Zhao Daoyang Dai Wenkui Wang 《中国科学A辑(英文版)》2000,43(4):407-413
Bulk amorphous Pd41,Ni10Cu28P21, alloy has been prepared by water quenching method. The system shows excellent glass forming ability (GFA) with a high value
of reduced glass transition temperatureT
rg 0.714. Structural analyses indicate that the Pd41,Ni10Cu28,P21, alloy has a dense packing structure closer to “frozen liquid” than that of amorphous Pd40Ni40,P20, alloy. Experiments on crystallization reveal that several crystalline phases simultaneously precipitate in the early part
of crystallization. Below 710 K, a metastable phase forms, and subsequently disappears at elevated temperatures. In addition,
the influence of partial substitute of Cu for Ni on GFA has been discussed with regard to thermodynamics and kinetics 相似文献
7.
The dependence of the microstructural change and lattice space symmetry of nano-SnO2 on the annealing temperature has been studied systematically using Raman spectroscopy and X-ray diffraction. Comparing the
results of nano-SnO2 with the results of amorphous film and single crystal of SnO2, it is found that the new Raman peaks N1 and N2 are in accordance with Matossi’s force constant model completely. When the annealing temperature is near 673K, the local
lattice disorders and the density of vacant lattice decrease rapidly in the nano-SnO2 grains. The lattice distortion and the new Raman peaks disappear almost at the same time. The possible mechanisms of the
microstructural change and the new Raman peaks N1 and N2 are discussed.
Project supported by the Foundation of State Science and Technology Commission and the Natural Science Foundation of Anhui
Province. 相似文献
8.
Experiments of X-ray diffraction for liquid Cu70Ni30 alloy above and below its liquidus (l 230°C) have been carried out. By the analysis of experimental results, it is discovered
that difference between structures of liquid and undercooled Cu70Ni30 alloy is their cluster sizes. The correlation radius of cluster is 1.125 nm and the atom number of cluster is 403 at l 250—l
400°C, and they are 1.3 nm and 704 respectively at the undercooled liquid state (1 200°C). The structure of liquid Cu70Ni30 alloy is fcc short order and its solid structure, fcc, is kept from liquid fcc short order. 相似文献
9.
In this paper, the matrix of equidiagonal-dominance is defined and several theorems about ‖A
−1‖∞ and its evaluation are established. Many interesting numerical examples are given.
This work is supported by the National Natural Science Foundation of China and the Science Foundation of Academy of Engineering
Physics of China 相似文献
10.
Hong Ya GAO Shu Qing ZHOU 《数学学报(英文版)》2007,23(12):2241-2246
We obtain a new inequality for weakly (K1,K2)-quasiregular mappings by using the McShane extension method. This inequality can be used to derive the self-improving regularity of (K1, K2)-Quasiregular Mappings. 相似文献
11.
Large size C70 single crystals with the dimension of more than 5 mm are grown from the vapor phase by controlling nucleation. X-ray diffraction
and electron diffraction confirm that in the C70 single crystal a phase of the hexagonal close-packed (hcp) structure coexists with a minor face-center-cubic (fcc) phase
at room temperature. The morphologies and their formation mechanism of the C70 single crystals are investigated by means of scanning electron micrascopy and optical microscopy. The influence of growth
conditions on the morphologies of C70 single crystals is discussed.
Project supported by the National Natural Science Foundation of China (Grant No. 59772026). 相似文献
12.
Riping Liu Jianhua Zhao Xiangyi Zhang Duanwei He Zhicheng Qin Yingfan Xu Wenkui Wang 《中国科学A辑(英文版)》1999,42(1):74-79
The microstructure of Pd77.5Au6Si16.5alloy solidified both on board a Chinese Retrievable Satellite and on the earth is studied. Postmortem analyses of microstructure
presented that the same types of phases, primary phase (Pd3Si) and eutectics (Pd3Si + Pd solid solution) were formed in both cases. But the phase morphologies were quite different. It was dendritic for the
primary phase and lamellar for the eutectics under normal gravity condition. However, under microgravity condition the primary
phase was granular and the eutectic was peculiar network. Detailed analysis showed that the differences in morphologies of
the microstructure were due to the existence of gravity-induced buoyancy convection on the earth which increased the mass
transport abilities and decreased the thickness of the solute boundary in front of the solid-liquid interface during solidification
under normal gravity condition. 相似文献
13.
Jialin Zhu Liangchen Chen Richeng Yu Fengying Li Jing Liu Changqing Jin 《中国科学A辑(英文版)》2002,45(7):900-905
In situ high pressure energy dispersive X-ray diffraction measurements on the layered perovskite-like manganate Ca3Mn2O7 powder under pressures were performed by using the diamond anvil cell with synchrotron radiation. The results show that the
structure of layered perovskite-like manganate Ca3Mn2O7 is unstable under pressure due to the easy compression of NaCl-type blocks. The structure of Ca3Mn2O7 underwent two phase transitions under pressures in the range of 0–35 GPa. One was at about 1.3 GPa with the crystal structure
changing from tetragonal to orthorhombic. The other was at about 9.5 GPa with the crystal structure changing from orthorhombic
back to another tetragonal. 相似文献
14.
Shixin Gan 《数学学报(英文版)》1999,15(2):187-196
In this paper, we prove that under theF
4 conditions, anyL log+
L bounded two-parameter Banach spece valued martingale converges almost surely to an integrable Banach space valued random
variable if and only if the Banach space has the Radon-Nikodym property. We further prove that the above conclusion remains
true if theF
4 condition is replaced by the weaker localF
4 condition.
Project supported by the National Natural Science Foundation of China and the State Education Commission Ph. D. Station Foundation 相似文献
15.
Xijun Li Kebin Li Jiaju Du Xiaojun Xu Jun Fang Zhihe Wang Xiaowen Cao Jingsheng Zhu Yuheng Zhang 《中国科学A辑(英文版)》1998,41(3):308-312
The electrical resistance in zero magnetic field and magnetoresistance in different external magnetic fields have been measured
in a temperature range of 77—300 K. It is found that the temperature dependence of magnetoresistance can be well described
by a phenomenofogical formula of
where the fitting parameters α, β vary as the external magnetic fieldH changes,E
0 is the activation energy,E
0/k
B = 1160 K,M
s is the saturation magnetization, the temperature and magnetic field dependence ofM/M
s is obtained by the mean-field expression.
Project supported by the National Natural Science Foundation of China and partly by the Chinese Academy of Sciences. 相似文献
16.
ChangJian Zhao 《中国科学A辑(英文版)》2008,51(12):2172-2188
In this paper the author first introduce a new concept of L
p
-dual mixed volumes of star bodies which extends the classical dual mixed volumes. Moreover, we extend the notions of L
p
intersection body to L
p
-mixed intersection body. Inequalities for L
p
-dual mixed volumes of L
p
-mixed intersection bodies are established and the results established here provide new estimates for these type of inequalities.
This work was supported by the Natural Science Foundation of Zhejiang Province of China (Grant No. Y605065) and the Foundation
of the Education Department of Zhejiang Province of China (Grant No. 20050392) 相似文献
17.
Duanwei He Fuxiang Zhang Xiangyi Zhang Ming Zhang Riping Liu Yingfan Xu Wenkui Wang 《中国科学A辑(英文版)》1998,41(4):405-410
C3N4 crystals with the size of several micrometers have been synthesized from C3N4H4 in the presence of nickel-based alloy or cobalt as catalyst under high pressure of 7 GPa and temperature of about 1400°C
for 10 min. Scanning electron microscopy, energy-disperse X-ray analysis, and X-ray diffraction were used to examine the grown
crystals. The general rule on selecting the starting materials for synthesis of carbon nitride crystals at high pressures
and high temperatures is suggested. 相似文献
18.
We study the L
p
-saturation for the linear combination of Bernstein-Kantorovich operators. As a result we obtain the saturation class by using
K-functional as well as some modulus of smoothness.
Research supported by National Natural Science Foundation of China (10671019) and Zhejiang Provincial Natural Science Foundation
of China (102005). 相似文献
19.
A successful experimental synthesis of pure crystalline β- and α-C3N4 films on Si(100) substrate was carried out by bias-assisted hot filament chemical vapor deposition (bias-HFCVD). It is found
that a mixed-phase C3-I-SixNy buffer layer was formed between the Si substrate and the C-N film. A “lattice match selection” was proposed to study the
growth mechanism of C3N4 clusters composed of many crystal columns with hexagonal facets.
Project supported by the National Natural Science Foundation of China and the Chinese Academy of Sciences. 相似文献
20.
Jing Ping YANG Shi Hong CHENG Xiao Qian WANG 《数学学报(英文版)》2007,23(3):467-478
This paper investigates bivariate recursive equations on excess-of-loss reinsurance. For an insurance portfolio, under the assumptions that the individual claim severity distribution has bounded continuous density and the number of claims belongs to R1 (a, b) family, bivariate recursive equations for the joint distribution of the cedent's aggregate claims and the reinsurer's aggregate claims are obtained. 相似文献