Anisotropic dilations of shift‐invariant subspaces and approximation properties in

Let A be an expansive linear map in . Approximation properties of shift‐invariant subspaces of when they are dilated by integer powers of A are studied. Shift‐invariant subspaces providing approximation order α or density order α associated to A are characterized. These characterizations impose certain restrictions on the behavior of the spectral function at the origin expressed in terms of the concept of point of approximate continuity. The notions of approximation order and density order associated to an isotropic dilation turn out to coincide with the classical ones introduced by de Boor, DeVore and Ron. This is no longer true when A is anisotropic. In this case the A‐dilated shift‐invariant subspaces approximate the anisotropic Sobolev space associated to A and α. Our main results are also new when S is generated by translates of a single function. The obtained results are illustrated by some examples.     

Sm共掺对Sr4Al14O25:M (M=Mn4+, Cr3+）荧光粉发光性能的影响

用固相反应法合成了Sr₄Al₁₄O₂₅:M和Sr₄Al₁₄O₂₅:(M+Sm³⁺)(M=Mn⁴⁺, Cr³⁺)荧光粉, 研究了其发光性能．Sm的共掺并没有改变Sr₄Al₁₄O₂₅:Cr³⁺激发带和发射带的位置, 但是显著提高了材料的发光性能;Sm共掺Sr₄Al₁₄O₂₅:Mn⁴⁺反而降低了发光强度． 对于Cr³⁺, Sm³⁺共掺的Sr₄Al₁₄O₂₅荧光粉, 呈现了从Sm³⁺到Cr³⁺ 的辐射形式的能量传递过程,说明了Sm的共掺对于Sr₄Al₁₄O₂₅:Cr³⁺荧光粉的发光强度提高的原因．     

Identities for degenerate Bernoulli polynomials and Korobov polynomials of the first kind

In this paper, we derive five basic identities for Sheffer polynomials by using generalized Pascal functional and Wronskian matrices. Then we apply twelve basic identities for Sheffer polynomials, seven from previous results, to degenerate Bernoulli polynomials and Korobov polynomials of the first kind and get some new identities. In addition, letting λ→ 0 in such identities gives us those for Bernoulli polynomials and Bernoulli polynomials of the second kind.     

N'-吡啶(噻唑)甲氧苯基-N-芳酰基脲衍生物的合成与生物活性

通过芳酰基异氰酸酯与吡啶(噻唑)甲氧苯胺的亲核加成反应,合成8个未见文献报道的N'-吡啶(噻唑)甲氧苯基-N-芳酰基脲衍生物.其结构经1H NMR,IR和元素分析表征.初步生物活性试验表明,标题化合物具有良好的杀虫活性,如5d在100mg/L浓度下,对小菜蛾(Plutellaxylostella)和棉铃虫(Heliothis armigera)具有100%的抑制活性.     

Uncertainties caused by source directivity in room-acoustic investigations

Although deviations in the measurement of acoustic parameters should be lower than the subjectively perceivable change in the corresponding parameter measured, this study reflects that directionality of sound sources could cause wide audience areas to break away from this criterion at high frequencies, even when using dodecahedron loudspeakers which meet the requirements of the ISO 3382 standard. The directivity of four different acoustic sources was measured and the influence of its accurate orientation spatially quantified in five enclosures for speech and music. By means of simulation software, the number of receivers affected by uncertainties greater than difference limens was established.     

Eigenmode Splitting in all Hydrogenated Amorphous Silicon Nitride Coupled Microcavity

Hydrogenated amorphous silicon nitride based coupled optical microcavity is investigated theoretically and ex- perimentally. The theoretical calculation of the transmittance spectra of optical microcavity with one cavity and coupled microcavity with two-cavity is performed. The optical eigenmode splitting for coupled microcavity is found due to the interaction between the neighbouring localized cavities. Experimentally, the coupled cavity samples are prepared by plasma enhanced chemical vapour deposition and characterized by photoluminescence measurements. It is found that the photoluminescence peak wavelength agrees well with the cavity mode in the calculated transmittance spectra. This eigenmode splitting is analogous to the electron state energy splitting in diatom molecules.     

On the Geometric Distance Between Quantum States with Positive Partial Transposition and Private States

We prove an analytic positive lower bound for the geometric distance between entangled positive partial transpose (PPT) states of a broad class and any private state that delivers one secure key bit. Our proof holds for any Hilbert space of finite dimension. Although our result is proven for a specific class of PPT states, we show that our bound nonetheless holds for all known entangled PPT states with non-zero distillable key rates, irrespective of whether they are in our special class or not. Thus, our result naturally leads to the conjecture of impossibility of using PPT-bound entangled state in physical implementation of quantum key distribution.     

Molecular orientation and dielectric anisotropy properties of 4-cyano-4′-n-heptylbiphenyl-TiO2 liquid crystal composite

The molecular orientation and the dielectric anisotropy of the nematic liquid crystal (LC) 4-cyano-4′-n-heptylbiphenyl (7CB) and of TiO₂-doped 7CB have been investigated. The dielectric properties of the LCs exhibit a relaxation peak that shifts to lower frequencies with increasing voltages. The relaxation frequencies of 7CB and 7CB/TiO₂ liquid crystals were calculated and found to decrease as the bias voltage increases. This is attributed to molecular reorientation. The dielectric anisotropy of the LCs changes from the positive type to negative type and the static electric permittivity and dielectric anisotropy values were found to be lower for the 7CB/TiO₂ system.     

基于一维TiO_2纳米管阵列薄膜的β伏特效应研究

介绍了一种采用宽禁带半导体二氧化钛纳米管阵列薄膜材料制备β伏特效应同位素电池的方法.通过对金属钛片的电化学阳极氧化制备了垂直定向、有序排列的二氧化钛纳米管阵列薄膜,研究了退火条件对二氧化钛纳米管阵列薄膜半导体光电性能的影响.通过与镍-63辐射源的集成封装,形成三明治结构镍-63/二氧化钛纳米管阵列薄膜/钛片的β伏特同位素电池.实验结果表明,基于氩气氛围下450?C退火的黑色二氧化钛纳米管阵列薄膜具有高的氧空位缺陷浓度和宽的可见-紫外吸收光谱.在使用β辐射总能量为10 m Ci的镍-63辐射源时,同位素电池的开路电压为1.02 V,短路电流75.52 n A,最大有效转换效率为22.48%.     

Living Free Radical Polymerisation Under a Constant Source of Gamma Radiation – An Example of Reversible Addition‐Fragmentation Chain Transfer or Reversible Termination?

The primary mechanism for living polymerisation under a source of gamma radiation at low dose rates is shown to be reversible addition‐fragmentation chain transfer. This was demonstrated by showing that the initial transfer step determines the success of the polymerisation. When an inappropriate leaving group is chosen for the RAFT agent, the polymerisation is non‐living. Under a reversible termination mechanism the ‘living’‐ness should be independent of this initial transfer step.