The glassy state of the amorphous V2O5–NiO–TeO2 samples

The glass transition temperature dependence to heating rate and therefore the activation energy (ΔH^?) of the glass transition of (60-x)V₂O₅–xNiO–40TeO₂ oxide glasses with 0≤x≤20 (in mol%) were investigated at heating rates φ (=3 6, 9, 10 and 12 K/min) using differential scanning calorimetry (DSC). The heating rate dependence of T_g was used to investigate the applicability of different theoretical models describing the glass transition. Using the application of Moynihan and Kissinger et al. models to the present data, different values of (ΔH^?) at each different heating-rate regions were obtained. The fragility parameter (m=ΔH^?/R T_g) was ∼24.98 for x=10 mol%, suggesting that this glass may be considered as a rather strong glass (fragility index m∼>20 is an indication of fragile glass). Also the compositional dependence of T_g and ΔH^? was investigated.     

The characteristics for H<Subscript> 2</Subscript><Superscript> +</Superscript>-like impurities confined by spherical quantum dots

The energy spectra of H₂ ⁺-like impurities confined in finite spherical quantum dots have been calculated as a function of the distance between nuclear with different sizes on the basis of effective-mass approximation by linear variational method. B-splines have been used as basis functions, which can easily construct the trial wavefunctions with appropriate boundary and cusp conditions. The quantitative analyses of the partial wave weights for ground state and some low lying states have been done.     

双波长敏感的光致聚合物全息存储材料

介绍了一种以聚乙烯醇为粘结剂,丙烯酰胺和亚甲基双丙烯酰胺作为单体,赤藓红和亚甲基蓝作为光引发剂,三乙醇胺作为共引发剂的光致聚合物材料。材料能同时对红光和绿光敏感,用红光和绿光分别对材料曝光,测得的两种衍射效率分别不低于30％,灵敏度不低于25cm^2／J。该材料对红光的最大响应空间频率为2274 lp／mm,相应的衍射效率为27．73％,响应范围为1600∽2800lp／mm;对绿光的最大响应空间频率为2350 lp／mm．相应的衍射效率为25、72％,响应范围为1700∽3000 lp／mm。在材料的同一点上进行红光和绿光的波长复用全息存储,当用红光或绿光再现时单幅图像清晰,信噪比高,两幅图像之间无任何干扰,该材料适合双波长全息存储。     

Structural and magnetic ordering in the VxNb1+yS2 system

The influence of composition on the structural ordering and magnetism in the V_xNb_1+yS₂ system has been investigated by X-ray diffraction and magnetic measurements. Stoichiometric V_1/3NbS₂ did not exhibit the structural ordering of vanadium between the NbS₂ layers. In the ordered structure, the vanadium composition deviated from the ideal value of to both higher and lower values, while the niobium composition was in the range of 0.05?y?0.18. Excess niobium, y>0, is thought to play an essential role in the structural ordering in this system. For samples with excess niobium and ordered structures, a magnetic transition was observed at 20-50 K, depending on the composition. The spontaneous magnetization of 3-5×10⁻³ μ_B/V atom is thought to be intrinsic to this system. The magnetization curves consisted of a constant and a proportional parts of the magnetic field, which correspond to the spontaneous magnetization and high-field susceptibility, respectively. The magnetization curves and the temperature dependencies of the high-field susceptibility were quite similar to those of the canted antiferromagnetic NiS₂. A correlation between the structural and magnetic ordering is suggested.     

Optical bistability at angular incidence in a one-dimensional photonic crystal containing single negative materials

Nonlinear wave propagation is studied theoretically in a one-dimensional photonic band gap structure containing single negative materials. It is found that Kerr nonlinearity is greatly enhanced near the lower edge of a recently explored angular gap for transverse magnetic polarized light. Consequently, optical bistability is achieved at very low values of input intensity in a periodic structure composed of only a few repeating units. The characteristics of optical bistability are affected only slightly with the variation of the incident angle and thickness ratio of the layers. The effect of losses is also found to be relatively insignificant in such a small structure.     

Photoluminescence of CdGeP2 and (Cd,Mn)GeP2

Photoluminescence of CdGeP₂ (112) single crystal and CdGeP₂ epitaxial film grown on GaAs (001) substrate have been studied and their spectral similarity found. Spectral bands associated with donor/acceptor transitions peak at close energies for both substances and all are lower than the energy gap of the chalcopyrite crystal.On the other hand, the growth of (Cd,Mn)GeP₂ ferromagnetic layer on CdGeP₂ (112) single crystal was performed to make it possible observation of PL from both the ferromagnetic layer and substrate. The green laser excitation (514, 532 nm) produces a proper photoluminescence similar to that in the undoped CdGeP₂ crystal and film. An extra emission from the ferromagnetic-nonmagnetic heterojunction occurs to extend up to photon energies exceeding E_g of the host semiconductor. The short wavelength photoluminescence is to be due to (Cd,Mn)GeP₂ dilute magnetic semiconductor (DMS). This fact states that Mn-doped II-IV-V₂ chalcopyrites are closer to II-VI DMS than to another group III-V DMS, where the heavy Mn-doping suppresses photoluminescence at all. Features of the observed short wavelength emission are discussing based on the temperature and spectral analyses.     

渐变段倾角对渐变复合腔特性影响的分析

利用模式耦合理论,在考虑多模耦合的情况下,对渐变结构复合腔进行了冷腔分析,计算了H51-H52模式对下,各个模式的耦合及场幅值分布情况,分析了渐变段的倾角对渐变复合腔的Q值及场幅值分布的影响。研究表明：渐变段的倾角对渐变结构复合腔的高频特性有很大的影响,特别是各模式的场分布及Q值,合适地选择渐变角度,能使场幅值放大率比较大,这将有利于提高注-波互作用效率。     

Structural and elastic properties of the filled tetrahedral semiconductors LiZnX (X=N, P, and As)

We report on first-principles study of the structural and elastic properties of the Nowotny-Juza filled tetrahedral compounds LiZnX (X=N, P, As) using the full-potential linearized augmented plane wave method within the local density approximations. Our results indicate that the energetically favourable α-LiZnX materials are slightly softer than their binary analogous GaX and the sound speeds are quantitatively similar for LiZnAs and GaAs.     

Spintronic properties of the Ti2CoB Heusler compound by density functional theory

The electronic structure and magnetic properties of the Ti₂CoB Heusler compound with a high-ordered CuHg₂Ti structure were investigated using the self-consistent full potential linearized augmented plane wave (FPLAPW) method within the density functional theory (DFT). Spin-polarized calculations show that the Ti₂CoB compound is half-metallic ferromagnetic with a magnetic moment of 2 μ_B at the equilibrium lattice constant, a=5.74 Å. The Ti₂CoB Heusler compound is ferromagnetic below the equilibrium lattice constant and ferrimagnetic above the equilibrium lattice constant. A large peak in majority-spin DOS and an energy gap in minority-spin DOS are observed at the Fermi level, yielding a spin polarization of 100%. A spin polarization higher than 90% is achieved for a wide range of lattice constants between 5.6 and 6.0 Å.     

Polynomial integrability of the Hamiltonian systems with homogeneous potential of degree − 3

In this paper, we study the polynomial integrability of natural Hamiltonian systems with two degrees of freedom having a homogeneous potential of degree k given either by a polynomial, or by an inverse of a polynomial. For k=−2,−1,…,3,4, their polynomial integrability has been characterized. Here, we have two main results. First, we characterize the polynomial integrability of those Hamiltonian systems with homogeneous potential of degree −3. Second, we extend a relation between the nontrivial eigenvalues of the Hessian of the potential calculated at a Darboux point to a family of Hamiltonian systems with potentials given by an inverse of a homogeneous polynomial. This relation was known for such Hamiltonian systems with homogeneous polynomial potentials. Finally, we present three open problems related with the polynomial integrability of Hamiltonian systems with a rational potential.