다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

The primary goal of this review is to present a clear chemical perspective of borates in order to stimulate and facilitate the discovery of new borate-based optical materials. These materials, whic...

Borates: A Rich Source for Optical Materials.

The generalization of the Local Density Approximation (LDA) method for the systems with strong Coulomb correlations is presented which gives a correct description of the Mott insulators. The LDA+U method is based on the model hamiltonian approach and allows to take into account the non-sphericity of the Coulomb and exchange interactions. parameters. Orbital-dependent LDA+U potential gives correct orbital polarization and corresponding Jahn-Teller distortion. To calculate the spectra of the strongly correlated systems the impurity Anderson model should be solved with a many-electron trial wave function. All parameters of the many-electron hamiltonian are taken from LDA+U calculations. The method was applied to NiO and has shown good agreement with experimental photoemission spectra and with the oxygen Kα X-ray emission spectrum.

http://absimage.aps.org/image/MAR06/MWS_MAR06-2005-007233.pdf

First-principles calculations of electronic structure and spectra of strongly correlated systems: the LDA+U method

With an ever increasing dependence on electrical energy for powering modern equipment and electronics, research is focused on the development of efficient methods for the generation, storage and distribution of electrical power. In this regard, the development of suitable dielectric based solid-state capacitors will play a key role in revolutionizing modern day electronic and electrical devices. Among the popular dielectric materials, anti-ferroelectrics (AFE) display evidence of being a strong contender for future ceramic capacitors. AFE materials possess low dielectric loss, low coercive field, low remnant polarization, high energy density, high material efficiency, and fast discharge rates; all of these characteristics makes AFE materials a lucrative research direction. However, despite the evident advantages, there have only been limited attempts to develop this area. This article attempts to provide a focus to this area by presenting a timely review on the topic, on the relevant scientific advancements that have been made with respect to utilization and development of anti-ferroelectric materials for electric energy storage applications. The article begins with a general introduction discussing the need for high energy density capacitors, the present solutions being used to address this problem, and a brief discussion of various advantages of anti-ferroelectric materials for high energy storage applications. This is followed by a general description of anti-ferroelectricity and important anti-ferroelectric materials. The remainder of the paper is divided into two subsections, the first of which presents various physical routes for enhancing the energy storage density while the latter section describes chemical routes for enhanced storage density. This is followed by conclusions and future prospects and challenges which need to be addressed in this particular field.

/pdf/anti-ferroelectric-ceramics-for-high-energy-density-45qwsutgr9.pdf

Anti-Ferroelectric Ceramics for High Energy Density Capacitors.

Abstract The discovery of inorganic phosphors that can be excited by GaN light emitting diodes in the wavelength range 380–460 nm is essential for improving the efficiency and light quality of solid state lighting devices. Garnets doped with Ce 3+ are of particular interest for this application. We have studied the luminescence of Ce 3+ in garnet phosphors and established a relationship between the excitation/emission wavelengths and the deviation from cubic symmetry around the rare-earth ion. Data are presented for both known yttrium aluminum and yttrium gallium garnet systems, as well as newly synthesized inverse garnets of the general formula Mg 3 Y 2− y Gd y Ge 3− z Si z O 12 :Ce (0 ⩽  y  ⩽ 2, z  = 0, 1).

http://ma.ecsdl.org/content/MA2007-02/33/1520.full.pdf

Structure-Property Correlations in Ce-Doped Garnet Phosphors for Use in Solid State Lighting

Fabrication and luminescence of BiPO4:Tb3+/Ce3+ nanofibers by electrospinning

Nearly monodisperse CaWO4 and CaWO4:Eu3+ microspheres have been synthesized in large scale by a surfactant-assisted solution route, in which cetyltrimethyl ammonium bromide (CTAB) is used. X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM) and photoluminescence (PL) were used to characterize the resulting samples. The results of XRD indicate that the CaWO4 and CaWO4:Eu3+ samples have the scheelite structures. The growth process of these nearly monodisperse spheres with an average diameter around 3.2 μm has been examined. The results of FTIR indicate that CTAB plays an important role in the formation of microspheres. The CaWO4 microspheres exhibit a blue emission band with a maximum at 423 nm. But the CaWO4:Eu3+ microspheres exhibit a red emission band with a maximum at 623 nm.

SYNTHESIS OF CaWO4 AND CaWO4:Eu MICROSPHERES BY PRECIPITATION

An abnormal laser deflection phenomenon in a copper-doped KTa1−xNbxO3 (Cu:KTN) crystal is demonstrated in this Letter. A near-50 mrad beam deflection angle was observed when a voltage of 1.2 kV was applied to a Cu:KTN block with size of 2.8 mm × 1.2 mm × 7.5 mm at room temperature. The special features of this deflection phenomenon are that the laser beam deflection direction is perpendicular to the electric field direction, and the beam deflection angle remains unchanged when the electric field direction is reversed. The operating principle of the phenomenon is investigated and the origin of the deflection phenomenon is attributed to an interaction between the graded refractivity effect and the quadratic electro-optic effect of the crystal.

Anomalous laser deflection phenomenon based on the interaction of electro-optic and graded refractivity effects in Cu-doped KTa1−xNbxO3 crystal

Synthesis and luminescent properties of Eu 3+ , Eu 3+ /Bi 3+ and Gd 3+ codoped YAG:Ce 3+ phosphors and their potential applications in warm white light-emitting diodes

PbWO 4 :Eu 3+ nanocrystals were synthesized by the hydrothermal method at different temperatures. Their luminescence properties were studied systemically. The results indicate that the particle sizes of the nanocrystals increase with increasing hydrothermal temperature. Estimated according to Scherrer's equation, the crystallite sizes are in the range of 10–15 nm, 20–30 nm, and 35–40 nm at the hydrothermal temperatures of 120 °C, 150 °C, and 180 °C, respectively. Because of the slight aggregations of powders, nanocrystal sizes observed by TEM are larger than the crystallite sizes estimated by XRD patterns. The excitation spectrum shows four excitation bands. The excitation band with the maximum at 264 nm can be attributed to the charge-transfer band of W 6+ –O 2− within the WO 4 2− group and O–Eu CT band. The bands at 372 nm, 458 nm, and 536 nm can be assigned to the electronic transitions of Eu 3+ ions. In the emission spectrum, the 5 D 0 → 7 F J transitions ( J =1, 2, 3 and 4) can be observed clearly. But the band emissions caused by tungstate groups are not observed. The concentration of europium has an influence on the luminescence of samples.

Bing Liu

Papers

Fabrication and luminescence of BiPO4:Tb3+/Ce3+ nanofibers by electrospinning

SYNTHESIS OF CaWO4 AND CaWO4:Eu MICROSPHERES BY PRECIPITATION

Anomalous laser deflection phenomenon based on the interaction of electro-optic and graded refractivity effects in Cu-doped KTa1−xNbxO3 crystal

Synthesis and luminescent properties of Eu 3+ , Eu 3+ /Bi 3+ and Gd 3+ codoped YAG:Ce 3+ phosphors and their potential applications in warm white light-emitting diodes

Luminescence properties of PbWO4:Eu3+ nanocrystals synthesized by a hydrothermal method