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M. H. Ehsani M. E. Ghazi P. Kameli F. S. Razavi 《Journal of Superconductivity and Novel Magnetism》2013,26(10):3151-3157
The Co-doped bilayered LaSr2Mn2O7 manganite at low Co concentrations (0–0.15) was synthesized by the sol–gel process. The X-ray diffraction (XRD) technique confirms phase formation for all the samples under investigation. The results of ac magnetic susceptibility measurements indicate the effect of Co doping on the magnetic ordering phases. The indications of charge ordering (CO) transitions were observed in all the prepared compounds. The CO magnetic phase transition temperature was observed systematically shift to lower temperatures as the Co concentration increases. There was an anomalous oscillating magnetic behavior in all samples with a few peaks before the CO temperature in the paramagnetic (PM) region so that with an increasing Co doping, the number of peaks and amplitude were decreased. Also, the ac susceptibility measurements were performed in the presence of an applied dc magnetic field to further study of this oscillating behavior. 相似文献
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W. P. Liu M. T. Li C. T. Lin 《Journal of Superconductivity and Novel Magnetism》2014,27(11):2419-2426
We report the structure, transport, and magnetic properties of K x Fe2?y Se2?z Te z single crystals grown by optical floating zone technique. The phase separation phenomena were observed in the Te-doped samples. With increasing Te doping level, the c-axis lattice parameter expands for both insulating/semiconducting and superconducting phases while the superconducting transition temperature (T c) decreases and eventually vanishes at z = 0.51. The critical current density was estimated to be 103–104 A/cm2 for the all doped samples. The upper critical field and anisotropic superconducting ratio increase with Te doping. We compared the results of critical current density J c, upper critical field μ 0 H c2 and apparent thermally activated energy U 0 for the samples with z = 0, 0.09, and 0.16. The influence of Te doping on the vortex pinning and the implication of U 0 versus μ 0 H is discussed. 相似文献
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窃电给供电企业造成巨大的经济损失。常规的防窃电方式已经很难有效的防止窃电。本文论述了几种常见的窃电方式,并阐述了当前常见的几种智能防窃电技术。 相似文献
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《Materials Letters》1988,6(10):331-335
The cation concentration ratio in the individual grains (1 to 25 μm) of four Y1Ba2Cu3O7−z pellets was investiga spectroscopy. A spread in the cation composition was observed even in a sample showing a narrow superconducting transition. The concentrations of Y, Ba and Cu were in the ranges 12–20, 30–35 and 48–53 at%, respectively. It is, therefore, likely that the Y1Ba2Cu3O7−z structure covers a finite area on the YO1.5-BaO-CuO phase diagram. 相似文献
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The Glass rods with nominal composition of (Bi
2-
Tl
)Sr
2
Ca
2
Cu
3
O
10+z
, where =0.15, 0.25 and 0.35, have been prepared by melt casting technique. Preferably c-axis oriented grains were grown after the sintering process. The thermal conductivity (T) measurements were performed between 30K and 290K and calculations were made using Wiedemann-Franz law. The (T) values of the samples varied between 3.8 to 8.9 mW/cm.K and showed strong dependence to the heating temperatures and compositions. The best T
c
and T
zero
were obtained to be 122 K and 115 K respectively. 相似文献
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Mg3Sb2化合物具有良好的热电性能和成本优势, 受到研究者的广泛关注。由于Mg元素具有很高的饱和蒸汽压和化学反应活性, 因此Mg3Sb2在合成过程中含量难以精确控制。本研究利用固相反应/球磨结合放电等离子体烧结制备了不同Mg含量的Mg3(1+z)Sb2(z=0, 0.02, 0.04, 0.06和0.08)样品, 通过物相结构分析和热电性能测试, 研究了Mg含量对Mg3Sb2化合物热电性能的影响规律。结果表明, 随着名义Mg含量的增加, 实际Mg含量在Mg3Sb2化合物中由缺失状态转变为过量状态, Mg3(1+z)Sb2(z=0, 0.02, 0.04)样品存在Mg空位(${{\text{{V}'}}_{\text{Mg}}}$), 表现为p型传导; 而Mg3(1+z)Sb2 (z=0.06, 0.08)样品中存在间隙Mg($\text{Mg}_{\text{i}}^{\centerdot \centerdot }$), 表现为n型传导。Mg3(1+0.04)Sb2样品在较宽温区(室温至770 K)内保持最高的热电优值, 该样品最接近本征p型Mg3Sb2化合物的组成和热电性能。本研究表明, Mg含量对Mg3(1+z)Sb2化合物载流子类型和浓度以及迁移率具有一定的调控作用。 相似文献
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《计量技术》辑编部: 根据机械工业部部标《渐开线圆柱齿轮精度》(JB179—83)要求,确定渐开线齿形测量部位,一般用两种方法;第一、按共轭齿轮啮合时的工作圆计算;第二、在相配齿轮不清楚时,按与标准齿条啮合时的工作圆计算。在按第二种方法计算齿廓起测点展开弧长b_1(或展开角φ_1,下同)时,一般都认为:齿数z≤16齿的齿轮,基圆半径r_b大于齿轮与标准齿条啮合时的工作圆半径R(即过齿条齿顶线与啮合线的交点T的圆,如图1所示),这时不需计 相似文献
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研究了层间“离位”附载多孔薄膜结构形式增韧层的大厚度纤维预成型体中等代流体(树脂)沿预成型体厚度方向(z向)的流动行为,通过压力传感器监测z向流动RTM(z-RTM)工艺注射过程中进、出胶口压力的变化规律,进一步反推树脂在层间“离位”增韧与非增韧预成型体中的宏观流动及微观浸润模式。结果表明,在 z-RTM工艺注射过程中,树脂在沿纤维束间z向快速流动的同时完成对纤维丝束内部的浸润。层间“离位”附载的增韧层虽延缓了树脂的宏观流动,但使流动前锋曲面更加平滑。层间“离位”增韧预成型体z向渗透率为3.5×10-15m2,与非增韧预成型体的z向渗透率2.9×10-14m2相比,降低约一个数量级。 相似文献
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W. T. Jin S. J. Hao X. J. Zhang Y. Zhao H. Zhang 《Journal of Superconductivity and Novel Magnetism》2010,23(5):847-850
Single-phase samples of a self-compensating Y1?x Ca x Ba2?x La x Cu3O z system were synthesized through a solid-state reaction method with x<0.4. The structure of all samples were characterized by X-ray diffraction and refined by the Rietveld method. Superconducting properties have been investigated by the DC magnetization measurement. The critical temperature (T c ) decreases evidently with the increment of x although the carrier concentration remains constant in the samples for different doping level. Careful study of the chemical bonds in the crystalline lattice demonstrates that the T c is closely correlated to four pairs of bond angles in the unit cell. The analysis indicates that crystalline structure is one of the important factors to high-T c superconductivity, and its influence is independent of the carrier concentration. 相似文献
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Conditions for temperature-gradient epitaxial growth of Al
x
Ga
y
In1 – x – y
Sb1 – z
Bi
z
/InSb heterostructures are examined. The factors are established which determine the initial melt undercooling required for preventing the thermal degradation of the substrate. 相似文献
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目的通过图像分割方法得到纸张z向截面中印刷墨层区域的图像,利于更好地分析研究油墨在纸张中的分布。方法利用物理切割方法和超景深显微镜拍摄,得到高分辨率的纸张z向截面彩色图像,将该图像从RGB颜色空间转换到HIS空间,采用欧式距离作为相似性度量,实现油墨层的分割。结果在HIS空间对油墨层图像进行分割时,分割阈值选取为3倍样本标准差最大值时,分割图像精确;当分割阈值取4倍或者2倍、1倍时,出现了过度分割或者欠分割。结论分割得到的油墨层图像有利于定量计算油墨的渗透深度及渗透分布,为进一步定量研究油墨与纸张的相互作用奠定了一定的基础。 相似文献