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排序方式: 共有354条查询结果,搜索用时 31 毫秒
81.
We report direct full-field magneto-optical observations of Barkhausen avalanches in Co polycrystalline thin films at criticality. We provide experimental evidence for the validity of a phenomenological model of the Barkhausen avalanche originally proposed by Cizeau, Zapperi, Durin, and Stanley [Phys. Rev. Lett. 79, 4669 (1997)]], where the model describes a 180 degrees -type flexible domain wall deformed by a localized defect with consideration of long-range dipolar interaction. The Barkhausen jump areas show a power-law scaling distribution with critical exponent tau approximately 1.33 for all the samples having different thickness from 5 to 50 nm, which is in accord with the two-dimensional prediction of the model. 相似文献
82.
We study the isentropic compressible Navier–Stokes equations with radially symmetric data in an annular domain. We first prove the global existence and regularity results on the radially symmetric weak solutions with non‐negative bounded densities. Then we prove the global existence of radially symmetric strong solutions when the initial data ρ0, u 0 satisfy the compatibility condition for some radially symmetric g ∈ L2. The initial density ρ0 needs not be positive. We also prove some uniqueness results on the strong solutions. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
83.
The dispersion polymerization of styrene has been carried out using polystyrene-block-poly(4-vinylpyridine) copolymer [P(S-b-4VP)], prepared by a reversible addition-fragmentation chain transfer (RAFT) method, as a steric stabilizer in alcohol media. These block copolymer contains a long poly(4-vinylpyridine) block and a short polystyrene block. The stable spherical particles were obtained when the block copolymer concentrations increased from 2 to 20 wt.% relative to the monomer and the average particle sizes decreased from 340 to 200 nm with increasing concentration of the block copolymer. Alcoholic solvents, from methanol to n-hexanol, are responsible for the particle size. These results indicate that the poly(S-b-4VP) block copolymer is effective for providing polystyrene nano-sized particles with a low content of it working as a good stabilizer in any kind of alcoholic medium. 相似文献
84.
The linear-type bifunctional vinyl urethane macromonomer (L-VUM: Mw; 40,453) was synthesized and applied to emulsion polymerization of styrene in DDI water. The structure of L-VUM was confirmed using 1H NMR and FT-IR. The macromonomer served as a good nonionic surfactant resulted in stable polystyrene nanospheres. Polystyrene particles were prepared with various concentrations of macromonomoer (1–30 wt% refer to monomer), initiator (0.5–2 wt%) and different temperatures (60–80 °C). Monodisperse PS nanospheres with 30 wt% L-VUM have a number-average diameter (Dn) of 200 nm with good uniformity (1.011) and molecular weight (Mw) 231,180 g/mol. The particle morphology, molecular weight and distribution, uniformity and the stability of the nanospheres upon the reaction temperature and concentration of L-VUM will be thoroughly discussed. 相似文献
85.
For the transformation for , it is proved that a real-valued function of modulus is not a multiplicative coboundary if the discontinuities of are -adic points and . It is also proved that the weakly mixing skew product transformations arising from Bernoulli shifts have Lebesgue spectrum.
86.
Choe W Pecharsky VK Pecharsky AO Gschneidner KA Young VG Miller GJ 《Physical review letters》2000,84(20):4617-4620
A temperature-dependent, single crystal x-ray diffraction study of the giant magnetocaloric material, Gd5(Si2Ge2), across its Curie temperature (276 K) reveals that the simultaneous orthorhombic to monoclinic transition occurs by a shear mechanism in which the (Si, Ge)-(Si,Ge) dimers that are richer in Ge increase their distances by 0.859(3) A and lead to twinning. The structural transition changes the electronic structure, and provides an atomic-level model for the change in magnetic behavior with temperature in the Gd5(SixGe1-x)(4). 相似文献
87.
88.
Shimada K Goto K Kawashima T Takagi N Choe YK Nagase S 《Journal of the American Chemical Society》2004,126(41):13238-13239
Nitric oxide (NO) is a messenger molecule implicated in a number of physiological processes. Nitrosation of selenoproteins has been suggested as playing an important role in NO-mediated cellular functions such as the inactivation of glutathione peroxidase (GPx), but no chemical information about Se-nitrosated species has been available to date. Here a stable Se-nitrososelenol (RSeNO), a new class of NO derivative, was synthesized and fully characterized by X-ray crystallography and spectroscopic methods. This Se-nitrososelenol can be formed by direct transnitrosation from an S-nitrosothiol to a selenol, as is the case in the proposed mechanism for the NO-mediated inactivation of GPx. 相似文献
89.
Insong Choe 《manuscripta mathematica》2001,105(4):501-506
A compact complex manifold X obtained by taking quotient of a bounded symmetric domain has an ample canonical line bundle. We prove that the dimension
of very ample pluricanonical subsystem is strictly bigger than 2n, where n is the dimension of X.
Received: 23 June 2000 / Revised version: 30 March 2001 相似文献
90.
Decay rate for the incompressible flows in half spaces 总被引:3,自引:0,他引:3
We show that the time decay rate of norm of weak solution for the Stokes equations and for the Navier–Stokes equations on the half spaces are if the initial data and for . We also show that the decay rate is determined by the linear part of the weak solution. We use the heat kernel and Ukai's
solution formula for the Stokes equations. It has been known up to now that the decay rate on the half space was , which was obtained by Borchers and Miyakawa [1] and Ukai [9].
Received: 3 November 1999; in final form: 10 May 2000 / Published online: 17 May 2001 相似文献