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本给出了具有高密度孪晶界c取向YBa2Cu3O7-x外延薄膜存在涡旋玻璃转变及很好的标度行为的实验证据,在有a方向昌粒或45°晶界的GdBa2Cu3O7-x外延薄膜中存在涡旋玻璃转变但在转变温度附近观察到磁通蠕动和热激活磁通流的某些特征。 相似文献
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FLUX CREEP, FLUX PINNING AND CRITICAL CURRENT DENSITY OF Y-, Gd-, AND Tl-BASED SUPERCONDUCTIVE THIN FILMS 下载免费PDF全文
Magnetic hysteresis loops have been measured for YBa2Cu3O6+x, GdBa2Cu3O6+x and Tl2Ba2Ca2Cu3O10-y films at different temperatures with a vibrating sample magnetometer. Based on Bean model, magnetic critical current density Jcm has been derived approximately. The field and temperature dependence of Jcm for all samples can be written as: Jcm= Jc0(T)×f(B,T), Where f(B,T) = 1 - Aln(B/B0(T)), which is similar to the transport critical density strongly affected by flux creep: Jct = Jc0(B,t)(1 - (kBT/U0)ln(BΩd/Ec)). The extraordinary similarity suggests that Jcm is determined not only by flux pinning but also by flux creep. In the first formula, f(B,T) may be correlated with the effect of flux creep on Jcm, and Jc0(T) is determined by flux pinning. Jc0(T) is independent of magnetic field and is proportional to (Tc - T). Similar results have also been found for other samples. It may be the common characteristic of high-Tc superconductors. Magnetic relaxation of YBa2Cu3O6+x and GdBa2Cu3O6+x films has been measured at LN2 temperature. Using the equation of Hagen et al., effective activation energy U0 has been deduced, which is about 0.3eV, one order bigger than the value obtained by A = kBT/U0. U0 is almost independent of the field in the field range selected. 相似文献
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某型陀螺仪是影响武器控制舱贮存寿命的薄弱环节,针对历年统计的陀螺仪的成败型、不完全故障数据,将"保序回归"和"变样本Pearson?2拟合优度检验与极小卡方估计"相结合,得到了其寿命分布函数。结果显示,I型极大值和威布尔分布适用于陀螺仪的寿命分布,但I型极大值不具有可加速性,因而选择威布尔分布作为寿命分布。根据统计数据计算,得到了置信度0.90和可靠度0.95时陀螺仪自然贮存寿命为22.30年,得到了陀螺仪在90℃下的加速系数K=7.2695,预估了2009年和2011年生产的陀螺仪加速寿命试验时间分别为8.25月和11.56月,对加速寿命试验时间规划、经费预算具有工程实际意义。 相似文献
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Strain-induced insulator–metal transition in ferroelectric BaTiO_3(001) surface:First-principles study 下载免费PDF全文
The electronic properties of TiO_2-terminated BaTiO_3(001) surface subjected to biaxial strain have been studied using first-principles calculations based on density functional theory. The Ti ions are always inward shifted either at compressive or tension strains, while the inward shift of the Ba ions occurs only for high compressive strain, implying an enhanced electric dipole moment in the case of high compressive strain. In particular, an insulator–metal transition is predicted at a compressive biaxial strain of 0.0475. These changes present a very interesting possibility for engineering the electronic properties of ferroelectric BaTiO_3(001) surface. 相似文献
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