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: 本文对高中物理教学中, 物理图像的临界点问题、 力和加速度的时间因果关系、 摩擦力中有关相对运动
的表述等常见问题进行探讨. 相似文献
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A new structural phase of MgV2O6 was obtained by a high-pressure,high-temperature(HPHT) synthesis method.The new phase was investigated by the Rietveld analysis of X-ray powder diffraction data,showing space group Pbcn(No.60) symmetry and a = 13.6113(6) (1 = 0.1 nm),b = 5.5809(1) ,c = 4.8566(3) ,V = 368.93(2) 3(Z = 4).High pressure behavior was studied by Raman spectroscopy at room temperature.Under 22.5 GPa,there was no sign of a structural phase transition in the spectra,demonstrating stability of the HPHT phase up to the highest pressure. 相似文献
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以柠檬酸为络合剂,用溶胶.凝胶法制备出纳米级上转换发光粉SrMoO4:Yb,Er。XRD、TEM确定了样品SrMoO4:Yb,Er是四方晶系,其粒径约为70nm,属于多晶。实验表明:用980nm LD对其进行激发,在室温下观察到了526,548nm附近的绿光发射和652nm附近微弱的红光发射,分别对应于Er^3+离子^2H11/2→^4I15/2,^4S3/2→^4I15/2和^4F9/2→^4I15/2的跃迁;当n(Yb)/n(Er)为7:1时,上转换发光强度最强。由激发功率与发光强度的关系得出绿光和红光发射均为双光子过程。 相似文献
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本文主要通过高压拉曼光谱研究了正铁氧体SmFeO3的晶格振动模式在外加压力作用下的行为规律,高压实验中压力最高为29.7GPa。本文采用溶胶凝胶法,制备出具有正交结构,其空间群为Pnma的SmFeO3。在外加压力作用下,所有观察到的拉曼振动模式都呈现出宽化趋势。特别是位于621.1cm-1的FeO6八面体的反弹性振动模式Ag(1)与位于452.7cm-1的FeO6八面体的弯曲振动模式B3g(3),其压力系数出现最大值。与此相反,Sm-O振动模式Ag(7)的压力系数却非常小。这说明外加压力更容易影响到FeO6八面体的晶格变化,而不是SmO12十七面体的改变。SmFeO3的这种高压下晶格振动模式变化行为类似于G型结构的CaSnO3。同时,文中还给出了所有声子零压模式下的格林爱森参数与体弹模量的比值。这些参数可用于进一步测量单轴或者双轴的应变力,可深入理解声子频率在张力作用下移动的表现行为。 相似文献
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强激光与一维多原子分子离子的相互作用及高次谐波的增强 总被引:1,自引:1,他引:0
研究强激光脉冲与一维多原子分子离子的相互作用,讨论双色激光场中高次谐波转化效率的提高,并应用经典三步模型说明高次谐波平台展宽的物理机制. 相似文献
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TiO2的光催化性能改性是水污染治理和光催化领域研究的重点方向。为了增强TiO2的光催化性能,以胶体碳球为模板,采用水热-煅烧法首次制备了TiO2空心球、硒掺杂二氧化钛(Se-TiO2)空心球和锡/硒共掺杂二氧化钛(Sn/Se-TiO2)空心球。同时,对Sn/Se-TiO2空心球的形貌、结构以及元素组成进行了表征,并以罗丹明B为模拟污染物,评价了样品的光催化性能。结果表明:TiO2为单一的锐钛矿相,Sn和Se成功地掺杂进入了TiO2晶格中;Sn/Se共掺杂形成了缺陷能级,降低了禁带宽度和电子-空穴对的复合几率,提高了可见光的响应范围。当Se掺杂2.0%(物质的量分数,下同),Sn掺杂0.5%时,样品光催化性能最好,去除率为76.92%。同等条件下空心球的光催化去除率:TiO222,说明Sn/Se共掺杂T... 相似文献
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Structural and spectroscopic properties of Sr 2 ZnTeO 6 (SZTO) were investigated by angle-dispersive synchrotron X-ray powder diffraction and Raman spectroscopy in a diamond anvil cell up to 31 GPa at room temperature. Although SZTO remained stable up to the highest pressure, the different pressure coefficients of the normalized axial compressibility were obtained as βab =8.16×10-3 GPa-1 and βc =7.61×10-3 GPa-1 . The bulk modulus B0 was determined to be 190(1) GPa by fitting the pressure-volume data using the Birch-Murnaghan equation of state. All the observed Raman modes exhibited a broadening effect under high pressure. The vibrational band υ1 around 765 cm-1 , which is associated with the Te-O stretching mode in the basal plane of the TeO6 octahedron had the largest pressure coefficient, and the Grüneisen parameters for all the observed phonon modes were also calculated and presented. These parameters could be used to measure the amount of uniaxial or biaxial strain, providing a fundamental tool for monitoring the magnitude of the shift of phonon frequencies with strains. 相似文献
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The structural and magnetic properties of SmFeO3 with B site substitution of non-magnetic atom A1 are investigated. The x-ray diffraction patterns show that SmFe(1-x)AlxO3 remains an orthorhombic structure within the whole doping range, and the unit-cell volume decreases monotonically with the increase of doped A1 concentration. Besides, the octa- hedral tilting distortions of FeO6 are found to be alleviated while the tolerance factor increases. However, the relationship between the lattice parameters and Al concentration is observed to deviate from Vegard's rule, and this may be caused by magnetostriction effects. For the doping content values in a range 0 〈 x 〈 0.6, the ferromagnetism, antiferromagnetism, and paramagnetism are observed to occur continuously. Moreover, the magnetization and the spin reorientation temperature (Tk) decrease monotonically as Al content value increases. With the doping content values being x = 0.8 and 1.0, these compounds only show paramagnetic behavior. 相似文献
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设Y_(n×m)服从矩阵正态分布N(XΘ, σ^2Σ×V),X_(n×k)是一个列满秩的矩阵,n ≥k≥3,σ^2是未知的,σ^(-2)S_p服从自由度为p的χ^2分布。当f(t)是单调非降 可微的函数, 且0≤f(t)≤2(k-2)/m(p+2)时,其列向量为Δ_i(Y)=[I_k- f(V′_iY′(X′Σ^(-1)X)^(-2)YV_iS_p_(-1)S_p (X′Σ^(-1)X)^(-1)/V′_iY′(X′Σ^(-1)X)^(-2)YV_i](X′Σ^(-1)X)^(-1)X′Σ^(-1)Y_i的估计Δ(Y)在风险函数R_1或R_2下是能够改善Θ的极大似然估计(X′Σ^(-1)X)^(-1)X′Σ^(-1)Y.同时得到了Θ和CXΘ的线性可容许估计类.
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