共查询到20条相似文献,搜索用时 15 毫秒
1.
Kebin Li Rongsheng Cheng Shouguo Wang Zhixiang Chen Jun Fang Zhihe Wang Xiaowen Cao Xiaojun Xu Jingsheng Zhu Yuheng Zhang 《中国科学A辑(英文版)》1999,42(1):99-105
Epitaxial La2/3Ca1/3MnO3 thin films were prepared on NdGaO3(1lO) substrates by d.c. magnetron sputtering method. The measurements of magnetoresistance ρ(H) upon magnetic field at different temperatures were carried out in the field range of 0–8 T. It is found that ρ(H) obeys the following relations: when the temperature (T) is higher than the Curie temperature
below
and
whenT is far WowT
c. It is suS8ested that the negative magnetoresistive effect is mainly due to enhancement of the magnetoconductance.
Project supported by the National Natural Science Foundation of China (Grant No. 19504012) and the Chinese Academy of Sciences. 相似文献
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Caoshui Xiong Li Pi Yeqing Tang Hong Zhu Denggang Zong Junfeng Zhang Yunfei Deng Jingsheng Zhu Yuheng Zhang 《中国科学A辑(英文版)》1999,42(1):106-112
The La0,67Sr0.33Mn03 +δ/Pr0.7Cao.3Mn03+δ/La0.67Sr0.33Mn03+δ(LPL) trilayered films on (100)LaA-1O3 substrates are prepared by using direct current (DC) magnetron sputtering method. The results obtained by means of X-ray
powder diffractometer show that all films are the high quality epitaxial films. The results gained by SQUID magnetometer indicate
that there is a magnetic coupling in the LPL trilayered films. The resistivities of LSMO, PC-MO and LPL films are measured
using standard four-probe method and analyzed logp-1/T curve. From the results it is concluded that the middle-layered PCMO which is ferromagnetic may play a role of intra-magnetic
field, which weakens the paramagnetism of LSMO film, lowersp
max and enlargesT
p
which is the transition temperature from metal to insulator, just as the applied magnetic field does. And the middle-layered
PCMO may induce the change of the density of states in the LSMO’s gap. The two reasons above make the resistivity andT
p
of the samples in zero field change with the thickness of PCMO layers.
Project supported by the Chinese Academy of Sciences and the Foundation of State Science and Technology Commission of China. 相似文献
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Journal of Fourier Analysis and Applications - For a fixed singular Borel probability measure $$\mu $$ on $$(-1/2, 1/2)$$ , we give several characterizations of when an entire function is the... 相似文献
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田正平 《数学的实践与认识》1988,(1)
考虑所有的N元数组(x_0,x_1,…,x_(N-1))的集合F_3~N。若对任意的z∈F_3~N,在F_3~N的子集合S中都存在一个元素,这个元素和z最多只相差一个坐标,则称S覆盖F_3~N。设A(N)表示覆盖F_3~N的子集S的最小数|S|。本文证明了A((3′-1)/2)=3~((3′-1)/2-1) ,其中r是正整数。 相似文献
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Hans-werner Henn 《K-Theory》1999,16(4):299-359
We compute the cohomology of SL(3, [1/2]) with coefficients in the prime fields and in the integers. On the way we obtain the cohomology of certain mod-2 congruence subgroups of SL(3, ) with coefficients in
p for p>2. Finally we compute the cohomology of GL(3, [1/2]). 相似文献
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众所周知,在△ABC中,有不等式 tgA/2+tgB/2+tgc/2≥3~(1/2) (1) 当且仅当△ABC为正三角形时取等号。本文介绍不等式(1)的一种新证法。证明∵tgC/2=(1-tgA/2tgB/2)/tgA/2+tgB/2) 相似文献
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K. L. Zarembo 《Theoretical and Mathematical Physics》1992,91(3):613-617
The model of a scalar field with interaction potential exp (-1/22) ind-dimensional spacetime (d2) is considered. It is shown that the Green's functions of the model are the same as the Green's functions of the free field.Physicotechnical Institute, Moscow. Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 91, No. 3, pp. 411–417, June, 1992. 相似文献
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A. N. Vasil'ev S. É. Derkachev N. A. Kivel' A. S. Stepanenko 《Theoretical and Mathematical Physics》1993,94(2):127-136
Using the conformal invariance of the Green's functions for the fields in the Gross-Neveu model in the critical regime that was proved earlier, we now use the conformal-bootstrap method for arbitrary space dimensiond to calculate the critical dimension of the master field (index ) in order 1/n
3 and of the auxiliary field in order 1/n
2, i.e., to an order higher by one than the previously known results.In memory of M. K. PolivanovSt Petersburg State University. Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 94, No. 2, pp. 179–192, February, 1993. 相似文献
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Watcharaphong Ananchuen Nawarat Ananchuen Louis Caccetta 《Graphs and Combinatorics》2010,26(3):315-328
Let γ c (G) denote the minimum cardinality of a connected dominating set for G. A graph G is k-γ c -critical if γ c (G) = k, but γ c (G + xy) < k for ${xy \in E(\overline {G})}$ . Further, for integer r ≥ 2, G is said to be k-(γ c , r)-critical if γ c (G) = k, but γ c (G + xy) < k for each pair of non-adjacent vertices x and y that are at distance at most r apart. k-γ c -critical graphs are k-(γ c , r)-critical but the converse need not be true. In this paper, we give a characterization of 3-(γ c , 2)-critical claw-free graphs which are not 3-γ c -critical. In fact, we show that there are exactly four classes of such graphs. 相似文献
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This paper investigates the semi-online machine covering problem on three special uniform machines with the known largest size. Denote by sj the speed of each machine, j = 1, 2, 3. Assume 0 < s1 = s2 = r ≤ t = s3, and let s = t/r be the speed ratio. An algorithm with competitive ratio max{2, (3s+6)/(s+6) } is presented. We also show the lower bound is at least max{2, (3s)/(s+6)}. For s ≤ 6, the algorithm is an optimal algorithm with the competitive ratio 2. Besides, its overall competitive ratio is 3 which matches the overall lower bound. The algorithm and the lower bound in this paper improve the results of Luo and Sun. 相似文献
15.
Let Σ_1 and Σ_2 be m and n dimensional Riemannian manifolds of constant curvature respectively. We assume that w is a unit constant m-form in Σ_1 with respect to which Σ_0 is a graph. We set v = 〈e_1 ∧ … ∧ e_m, 〉), where {e_1, …, e_m} is a normal frame on Σ_t. Suppose that Σ_0 has bounded curvature. If v(x, 0) ≥ v0 > \frac{\sqrt{p}}{2} for all x, then the mean curvature flow has a global solution F under some suitable conditions on the curvatrue of Σ_1 and Σ_2. 相似文献
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Geometriae Dedicata - We show that an open subset $${\mathfrak {F}}_4''$$ of the $$\mathrm{PU}(2,1)$$ configuration space of four points in $$S^3$$ is in bijection with an open subset of... 相似文献
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Tunneling planer Hall (TPH) effect in Ni81 Fe19/Al2O3/NixFe1−x trilayer junction is different from general planer Hall effect in single-layer film or two-layer junction. This effect concerns
the spin-polarized transport, so that the TPH voltage depends on the angle between magnetic vectors of two ferromagnetic layers.
The TPH effect is reported to be influenced by composition and magnetic properties of FM layers and the thickness of the insulating
layer. 相似文献