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Highly c-axis oriented MgB2 thin films with Tc^onset of 39.6K were fabricated by magnesium diffusing into pulsedlaser-deposited boron precursors.The estimation of critical current density Jc,using hysteresis loops and the Bean model,has given the value of 10^7A/cm^2(15K,0T),which is one of the highest values ever reported.The x-ray photoemission study of the MgB2 thin films has revealed that the binding energies of Mg 2p and B 1s are at 49.4eV and 186.9eV,which are close to those of metallic Mg and transition-metal diborides,respectively. 相似文献
23.
SrO doped zirconia (20%) was synthesized by n-butanol soft-template method using both NaOH and ammonia solution as precipitants. The high-temperature phase stability was investigated following further heat treatment at 1000°C for 2 h. XRD and Raman spectra were used to characterize the crystal form of zirconia. In addition, TEM was used to characterize the dispersibility of SrO doped zirconia. The results indicated that the concentration of OH? introduced into the ZrO2 lattice was the main factor controlling the crystal form of nanosized zirconia. The NaOH solution precipitant could improve the dispersibility of SrO doped t-ZrO2, and could also prevent the phase transformation of zirconia from t-ZrO2 to m-ZrO2 effectively. 相似文献
24.
Shigehiro Morikawa Toshiro Inubushi Kan Takahashi Hisanari Ishii Shino Shigemori 《Magnetic resonance imaging》1996,14(10):1197-1204
The relationships among tissue edema, lactate accumulation, and intracellular pH in middle cerebral artery (MCA)-occluded rats were investigated with multiecho 1H magnetic resonance imaging and spatially resolved metabolic images constructed by 1H and 31P nuclear magnetic resonance (NMR) chemical shift imaging (CSI). For the effective and sensitive detection of NMR signals from the brain, outer volume suppression (OVS), reduced k-space sampling and proton irradiation were incorporated into the CSI sequences. The consecutive three measurements of calculated T2 image, lactate image, and pH image which were required for 3.75 h were repeated for four cycles of 1–16 h after MCA occlusion. Tissue edema and lactate accumulation in the infarcted region were gradually and consistently increased during the 15-h observation period. In contrast, severe acidosis was already detected on the first pH image (2–4.7 h after MCA occlusion); thereafter, the degree of acidosis became milder and showed no further progression. The dissociation between the time courses of the lactate accumulation and pH decrease was clearly demonstrated by the NMR metabolic images. Acid-base balance in cerebral infarction might be affected not only by lactate production but also by complicated interactions with tissue edema and some other factors. 相似文献
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Jin Xue Nanxi Li Kan Wu Jia Haur Wong Chunmei Ouyang Sheel Aditya Perry Ping Shum 《Optics Communications》2012,285(2):153-157
This paper investigates the effectiveness of phase noise suppression by incoherent addition in a passively mode-locked fiber laser. Incoherent addition is achieved by using an interferometer external to the mode-locked laser. Two different types of interferometers, Mach–Zehnder and ring, are investigated experimentally for different background phase noise levels. Measurements show that both types of interferometers can achieve good phase noise reduction for a background phase noise level above ? 130 dBc/Hz. Effects of dispersion management and pulse train intensity ratio in the interferometers are also discussed. Multi-stage cascaded interferometers are proposed for supermode noise suppression of harmonically actively mode-locked lasers. 相似文献
27.
Kangli Min Fengzhen Huang Xiaomei Lu Yi Kan Junting Zhang Song Peng Yaoyang Liu Jie Su Chao Zhang Zijian Liu Jinsong Zhu 《Solid State Communications》2012,152(4):304-306
KNb0.95Co0.05O3 (KN–Co) ceramic was prepared via a solid-state reaction method, and the effect of cobalt dopant on the structural, electric, and magnetic properties was studied. The KN–Co ceramic with polycrystalline perovskite structure exhibited ferromagnetic and ferroelectric properties simultaneously at room temperature, and the coupling of them was confirmed by a large magnetocapacitance effect (about 13%) near the Curie temperature. The possible causes for the magnetism and magnetoelectric properties are discussed. 相似文献
28.
采用密度泛函方法,研究了MnxSny(x=2,3,4; y=18,24,30)团簇的几何结构. 发现MnxSn6x+6(x=2,3,4)倾向于形成 Mn 原子内掺入D3d Sn团簇单笼结构,即Mn2Sn18, Mn3Sn24 和Mn4Sn30.而MnxSn6x+12(x=2,3)则倾向于形成由两个小笼连接 而成的双笼结构,即MnSn12-MnSn12 和MnSn12-Mn2Sn18.因此,可望通过控制掺杂Mn 原子的数量来组装成不同结构的MnxSny一维纳米线. 相似文献
29.
紧拓扑半群上概率测度卷积序列的极限性质 总被引:4,自引:1,他引:4
本文讨论紧拓扑半群上概率测度卷积序列的若干重要极限性质.在第1节中,我们讨论测度集的代数结构与其支撑集代数结构的关系.第2节的定理1,通过支撑集的代数结构给出组合收敛测度序列的一个极限定理.在定理2中我们讨论独立同分布时的情形,建立了一类紧半群上的Kawada-It型结果.这些定理推广了紧群、紧交换半群、紧L-X半群上一些相应的结论. 相似文献
30.
采用二维磁驱动数值模拟程序MDSC2,对大电流脉冲装置聚龙一号上的151发次磁驱动370 m厚铝飞片实验、164发次磁驱动330 m厚铝飞片实验进行了数值模拟和分析。数值模拟表明:370 m厚铝飞片和330 m厚铝飞片的磁驱动过程中, VISAR测量的速度不是飞片自由面的速度,而是飞片中邻近自由面最近的固体反射面的速度。这是由于磁驱动飞片发射过程中,飞片自由面部分被烧蚀,密度低于固体密度状态,而飞片自由面和加载面中间的飞片还保持固体密度状态。VISAR测量的激光将穿过自由面的低于固体密度状态的飞片部分,到达飞片自由面最近的固体密度位置再反射回去,获得这一位置的飞片速度。数值模拟的飞片固体反射面速度历史和VISAR测量的速度历史相吻合。 相似文献