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讨论了定数截尾样本下双参数指数分布环境因子的极大似然估计、区间估计和Bayes估计.以参数后验密度的商密度作为环境因子的后验密度,并结合专家经验运用Bayes方法给出了环境因子在平方损失下和LINEX损失下的Bayes估计.最后运用Monte Carlo方法对各估计结果的均方误差(MSE),进行了模拟比较.结果表明LINEX损失下环境因子的估计较好. 相似文献
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Anisotropy of elasticity and minimum thermal conductivity of monocrystal M4AlC3 (M = Ti,Zr, Hf) 下载免费PDF全文
The elastic constants, elastic anisotropy index, and anisotropic fractional ratios of Ti4AlC3, Zr4AlC3, and Hf4AlC3 are studied by using a plane wave method based on density functional theory. All compounds are characterized by the elastic anisotropy index. The bond length, population, and hardness of the three compounds are calculated. The degrees of hardness are then compared. The minimum thermal conductivity at high temperature limitation in the propagation direction of [0001](0001) is calculated by the acoustic wave velocity, which indicates that the thermal conductivity is also anisotropic. Finally, the electronic structures of the compounds are analyzed numerically. We show that the bonding of the M4AlC3 lattice exhibits mixed properties of covalent bonding, ionic bonding, and metallic bonding. Moreover, no energy gap is observed at the Fermi level, indicating that various compounds exhibit metallic conductivity at the ground state. 相似文献
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以乙醇钠作碱,用二正丁基二氯化锡或三正丁基氯化锡与二苯基硫代卡巴腙反 应,合成了二正丁基锡二(二苯基硫代卡巴腙)[(n-Bu)_2Sn(sN_4C_13H_11)_2].通 过元素分析、红外光谱、紫外光谱和核磁共振氢谱对其结构进行了表征.用X射线 单晶衍射测定了该化合物的晶体结构。化合物为单斜晶系,空间群P2_1/c,α=2 .0215(7)nm,b=1.3103(5)nm,c=2.8171 (10)nm,β=95.412(7)°,Z=8, V=7.428(5)nm~3,Dc=1.330g/cm~3,μ=0.834 mm~-l, F(OOO)=3056, R_l=0.0575, wR_2=0.0959.化合物中,中心锡原子为六配位畸变八面体构型 相似文献
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采用高温固相法在空气气氛中合成了新型Mg_(1+y)Al_(2-x)O_4:xMn~(4+),yMg~(2+)深红色荧光粉.利用X射线衍射仪、扫描电子显微镜和荧光光谱仪表征荧光粉的晶体结构和形貌,并分析了发光性质,讨论了掺杂不同浓度Mn4+和过量Mg2+对样品发光强度的影响.结果表明,在300 nm波长激发下样品发射652 nm波长的红光,归因于Mn~(4+)的~2Eg—~4A_(2g)跃迁, Mn~(4+)的最佳掺杂浓度为0.14%.采用Blasse公式计算了Mn~(4+)-Mn~(4+)之间能量传递的临界距离,讨论了可能的能量传递过程和引起浓度淬灭的原因,采用Tanabe-Sugano能级图从理论上计算和分析了Mn~(4+)的d~3电子构型的晶体场强度大小.过量Mg~(2+)可以提高荧光粉的发光强度,同时导致了荧光寿命的缩短,荧光衰减曲线呈单指数变化.探讨了过量Mg~(2+)增强发光强度的机理,阐述了深红色荧光粉MgAl_2O_4:Mn~(4+)发光效率提高的原因. 相似文献
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爆炸荷载下邻近既有层状围岩隧道的迎爆侧易发生开裂、破坏,确保既有隧道围岩在爆破扰动下的安全是隧道近接施工中的关键问题。基于弹性力学和结构力学原理,建立了既有层状围岩隧道迎爆侧最危险点的简化力学模型,得到了最危险点的应力计算表达式,分析了隧道半径与岩层厚度的比值、岩层的倾角、岩层所对应的圆心角和隧道埋深等因素对既有隧道围岩稳定性的影响规律,并依据岩体最大拉应力判据确定了既有层状隧道围岩稳定的质点临界振动速度,结合地震波传播时的衰减规律,可以得出爆破施工时的最大单响药量,从而为隧道近接爆破动力扰动施工提供理论依据。 相似文献
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2D subwavelength multilevel (2-, 4-, 8-, etc. levels) columned stairstep grating with coned spatial profile has been designed to reduce reflection. In this paper, the rigorous coupled-wave theory is employed to analyze the electromagnetic diffraction property of the columned stairstep grid grating. The structure is shown to achieve extremely low reflectance over a wide field of view and a wide light wave band. 相似文献
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学习笔记伴随着学习的全过程,随年级的提高笔记的作用越来越突出。然而在教学实践中发现,相当一部分学生不会记笔记,更不会运用笔记进行
学习,刚入高一的学生在这方面暴露的问题更加突出。 相似文献
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We have observed the thermodynamic properties of metallic
superconductive nano-particles in the grand canonical ensemble; and the
level distribution and the level correlation between the discrete electronic
energy levels are considered in the calculation of the electronic spin
susceptibility of the ensemble numerically. The quantum effect, even--odd
effect and other special effects existing in the metallic nano-particles are
also studied in this article. 相似文献