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991.
A red oxide phosphor, Sr2ScAlO5:Eu2+ with perovskite-type structure, for white light-emitting diodes 下载免费PDF全文
Sr2ScAlO5:Eu2+,a red oxide phosphor with a perovskite-type structure,has been synthesized through a solid-state reaction and its luminescence properties have been investigated.An absorption band centering at 450 nm is observed from the diffuse reflection spectra and the excitation spectra,indicating that the phosphor can match perfectly with the blue light of InGaN light-emitting diodes.A broad red emission band at 620 nm is found from the emission spectra,originating from the 4f 6 5d-4f 7 transition of the Eu 2+ ions.The best doping content of Eu in this material is about 5%.Sr2ScAlO5:Eu2+is a highly promising red phosphor for use in white light-emitting diodes. 相似文献
992.
Jieguang Miao Baoshan Wang Jiying Peng Huiming Tan Huikun Bian 《Optics & Laser Technology》2008,40(1):137-141
Diffusion bonded Nd:YAG/Cr:YAG composite laser crystal has been employed to perform a compact diode-pumped passively Q-switched laser. At the incident pump power of 3.3 W and pulse repetition rate of 16.3 kHz, the maximum average output of 592 mW has been obtained, corresponding to an optical-to-optical conversion efficiency of 18%. Stable passively Q-switched operation with peak power of 6.5 kW and pulse duration of 6 ns was also achieved. It has been experimentally revealed that Nd:host/Cr:YAG composite structure is a promising material for compact cost-effective Q-switched laser sources with high-peak power and short pulse duration. In addition, thermal lens effect (TLE) in the active medium and its impact on the Q-switched laser performance have been analyzed. 相似文献
993.
This work provides the first systematic test of validity of the embedded-atom potentials of Mei et al. [Phys. Rev. B 43 (1991) 4653], via a complete study of the vibrational and thermodynamic properties of isoelectronic transition (Ni, Pd, Pt) and noble (Cu, Ag, Au) metals. Phonon dispersion curves and thermal properties are studied within the quasiharmonic approximation. Results for the temperature-dependence of the lattice constants, coefficients of linear thermal expansion, isothermal and adiabatic bulk moduli, heat capacities at constant volume and constant pressure, Debye temperatures and Grüneisen parameters are presented. Electronic contribution to the specific heat is included explicitly via density-functional calculation. The calculated phonon frequencies for Ag and Cu agree well with the results from inelastic neutron scattering experiments. Despite less satisfactory agreement between calculated and measured phonon frequencies for the other four metals, isothermal and adiabatic bulk moduli and the specific heats of all metals are reproduced reasonably well by the model, while the Grüneisen parameter and Debye temperature are underestimated by about 10%. The coefficient of linear thermal expansion is underestimated with respect to measured values in most cases except for Pt and Au. The results are good for Pt up to 1000 K and for Au up to 500 K. 相似文献
994.
The deformation of an elastic rod rotating in a viscous fluid is considered, with applications related to flagellar motility. The rod is tilted relative to the rotation axis, and experiments and theory are used to study the shape transition when driven either at constant torque or at constant speed. At low applied torque, the rod bends gently and generates small propulsive force. At a critical torque, the rotation speed increases abruptly, and the rod forms a helical shape with increased propulsive force. We find good agreement between theory and experiment. A simple physical model is presented to capture and explain the essential behavior. 相似文献
995.
采用超声喷雾热分解法在石英衬底上以醋酸锌水溶液为前驱体,以硝酸银水溶液为Ag掺杂源生长了Ag掺杂ZnO(ZnO:Ag)薄膜.研究了衬底温度对所得ZnO:Ag薄膜的晶体结构、电学和光学性质的影响规律.所得ZnO:Ag薄膜结构良好,在室温光致发光谱中检测到很强的近带边紫外发光峰,透射光谱中观测到非常陡峭的紫外吸收截止边和较高的可见光区透过率,表明薄膜具有较高的晶体质量与较好的光学特性.霍尔效应测试表明,在500℃下获得了p型导电的ZnO:Ag薄膜,载流子浓度为5.30×1015cm关键词:
ZnO:Ag薄膜
p型掺杂
超声喷雾热分解
霍尔效应 相似文献
996.
化学战剂的分析测试进展 总被引:2,自引:0,他引:2
边归国 《分析测试技术与仪器》2004,10(2):87-92
综述了气相色谱、液相色谱、红外光谱、色质联用、生化传感器、核磁共振、军用侦毒设备、分光光度计、毛细管电泳等仪器对化学战剂分析测试的应用进展情况. 相似文献
997.
将基本尺度熵的方法在时间上做多尺度化的扩展,并将其应用到心跳间隔序列的分析研究中.研究发现,健康人的心率变异性是小时间尺度下的模式特定性与大时间尺度下的模式丰富性相结合的,而充盈性心衰患者则正好相反.这说明充盈性心衰患者在小时间尺度下心脏动力系统的控制不力,导致随机性增加,而在大时间尺度下对外界环境变化反应又不够丰富,从而导致生命更容易受威胁.据此提出了以小时间尺度下的基本尺度熵值相对于大时间尺度下平台区基本尺度熵值的变异参数δ作为区分健康人和充盈性心衰患者的诊断依据.通过对72例健康人和44例充盈性心衰患者的计算,发现两组样本差异显著,证明了参数δ的有效性.
关键词:
多尺度化的基本尺度熵
心跳间隔序列
心率变异性
充盈性心衰 相似文献
998.
999.
Xiaofeng He Xueqiang Zhang Yuehui Wang Lu Gao Jia Wang Bin Cui Yongbo Bian Tao Yu Qiang Zhang Hong Li Chunguang Li Junjie Li Changzhi Gu Yusheng He 《Physica C: Superconductivity and its Applications》2009,469(21):1925-1929
An ultra-narrow band eight-pole dual-mode HTS patch filter was designed and fabricated. The filter is constructed by four corner-cut square patches, each of which has two resonating modes. The influence of the change of the corner-cut position on the filter response was investigated by simulations. Four small rectangle patches were added in the topology of the filter as tuning tools. By employing this unique tuning structure, the simulated filter responses and current density distributions on the patches have been greatly improved. The filter was fabricated using double sided YBCO films on a 3 in. LaAlO3 substrate. The measured results showed satisfactory performance with center frequency 2.494 GHz, fractional bandwidth 0.2%, return loss in passband better than 16 dB, and out-of-band rejection of the filter better than 90 dB at 15 MHz away from its center frequency. 相似文献
1000.
J. B. Chu S. M. Huang D. W. Zhang Z. Q. Bian X. D. Li Z. Sun X. J. Yin 《Applied Physics A: Materials Science & Processing》2009,95(3):849-855
This paper presents further insights and observations of the chemical bath deposition (CBD) of ZnS thin films using an aqueous
medium involving Zn-salt, ammonium sulfate, aqueous ammonia, and thioure. Results on physical and chemical properties of the
grown layers as a function of ammonia concentration are reported. Physical and chemical properties were analyzed using scanning
electron microscopy (SEM), X-ray energy dispersive (EDX), and X-ray diffraction (XRD). Rapid growth of nanostructured ZnO
films on fluorine-doped SnO2 (FTO) glass substrates was developed. ZnO films crystallized in a wurtzite hexagonal structure and with a very small quantity
of Zn(OH)2 and ZnS phases were obtained for the ammonia concentration ranging from 0.75 to 2.0 M. Flower-like and columnar nanostrucured
ZnO films were deposited in two ammonia concentration ranges, respectively: one between 0.75 and 1.0 M and the other between
1.4 and 2.0 M. ZnS films were formed with a high ammonia concentration of 3.0 M. The formation mechanisms of ZnO, Zn(OH)2, and ZnS phases were discussed in the CBD process. The developed technique can be used to directly and rapidly grow nanostructured
ZnO film photoanodes. Annealed ZnO nanoflower and columnar nanoparticle films on FTO substrates were used as electrodes to
fabricate the dye sensitized solar cells (DSSCs). The DSSC based on ZnO-nanoflower film showed an energy conversion efficiency
of 0.84%, which is higher compared to that (0.45%) of the cell being constructed using a photoanode of columnar nanoparticle
ZnO film. The results have demonstrated the potential applications of CBD nanostructured ZnO films for photovoltaic cells. 相似文献