Efficient Visible-to-UV Photon Upconversion Systems Based on CdS Nanocrystals Modified with Triplet Energy Mediators

Developing high-performance visible-to-UV photon upconversion systems based on triplet–triplet annihilation photon upconversion (TTA-UC) is highly desired, as it provides a potential approach for UV light-induced photosynthesis and photocatalysis. However, the quantum yield and spectral range of visible-to-UV TTA-UC based on nanocrystals (NCs) are still far from satisfactory. Here, three different sized CdS NCs are systematically investigated with triplet energy transfer to four mediators and four annihilators, thus substantially expanding the available materials for visible-to-UV TTA-UC. By improving the quality of CdS NCs, introducing the mediator via a direct mixing fashion, and matching the energy levels, a high TTA-UC quantum yield of 10.4% (out of a 50% maximum) is achieved in one case, which represents a record performance in TTA-UC based on NCs without doping. In another case, TTA-UC photons approaching 4 eV are observed, which is on par with the highest energies observed in optimized organic systems. Importantly, the in-depth investigation reveals that the direct mixing approach to introduce the mediator is a key factor that leads to close to unity efficiencies of triplet energy transfer, which ultimately governs the performance of NC-based TTA-UC systems. These findings provide guidelines for the design of high-performance TTA-UC systems toward solar energy harvesting.     

移动电话资费管制的研究

伴随着中国电信行业,特别是移动电话用户数量的高速发展和有效市场竞争格局的初步建立,移动电话资费的调整、改革与管制等问题成为近几年社会各界关注的焦点.本文从电信管制理论出发,分析和介绍了电信资费管制理论的演进过程,进而对中国电信市场特别是移动电话资费的管制实践进行了系统研究,深入地分析了中国建立的新的移动电话资费管制体系,并对未来移动电话资费管制的发展趋势作了展望.     

激光微束对球状介质粒子光阱力的计算与仿真分析

基于几何光学原理,以射线光学计算模型为基础,对几何尺寸远大于光波长的米氏球状粒子所受轴向光阱力进行了计算。在给定参量条件下,进行了数值仿真,并根据仿真结果,讨论了光束束腰半径、相对折射率、激光波长及功率等系统主要参量与光阱品质特性的关系。这些参量都是由显微镜和其他一些光学部件的特性所决定的。针对不同介质粒子合理选择上述参量,以得到较大光阱力和光阱刚度。这些仿真结果为各仪器参量的选择提供了理论依据。     

Al2O3/SiCnano纳米复合材料微结构及强韧化机理研究

纳米颗粒复合材料的“内晶型”结构中，晶内的纳米相和基体间存在的次界面对材料性能的改善有更重要作用，本文系统观察了氧化铝陶瓷和Ａｌ２Ｏ３／ＳｉＣｎａｎｏ纳米复合材料的微结构，着重研究了弥散ＳｉＣ颗粒对Ａｌ２Ｏ３基体微结构的影响，讨论了“内晶型”结构，位错组态，纳米化效应和穿晶断裂之间的关系以及材料强韧化机理。     

激光实际大气传输湍流效应相位校正一些实验结果

进行了近地面水平大气中激光传输湍流效应及其自适应光学相位校正实验，对光束振幅起伏、到达角起伏及其远场Strehl比进行了测量分析。实验结果表明，光束到达角起伏功率谱在低频段（f＜0．4υ／d）近似地满足-2/3次幂关系，而在高频段（f＞0．4υ／d）则近似满足-8／3次幂关系。在较弱湍流效应情况下时数振幅起伏方差小于0．3），相位补偿是有效的，而在较强湍流效应树数振福起伏饱和）时，自适应光学系统常常不能实现稳定闭环。由于传输场景地形复杂，湍流效应及其相位校正效果定量规律的描述还需进一步研究。     

聚焦光束稳态热晕补偿实验

进行了聚焦光束稳态热晕效应及自适应光学补偿的室内模拟实验观测，获得了在不同热畸变参数情况下，自适应光学系统开闭环时光束远场Strehl比和信标光波前方差的测量结果。测量结果表明自适应光学对聚焦光束整束热晕的补偿效果是显著的。在热畸变参数Nd大于170时，校正剩余波前大差呈非线性增长。在热畸变参数N_d与光束菲涅耳数N_f的比值大于1时，校正后的远场光斑峰值强度随入射功率的增加开始呈下降趋势。     

非致冷焦平面热成象技术及其应用

９０年代以后，非致冷红外焦平面技术的实用化成为红外热成象技术中最引入注目的突破之一，基估军事和民用领域的广泛应用前景受到国内外的普遍重视。本文综述了非致冷红外焦平面技术的两大技术途径及其特点、发展趋势和应用情况，并了发展我国非致冷红外焦平面技术的途径。     

天津本地ATM宽带业务试验网

概括地介绍了已建的天津本地ＡＴＭ宽带业务试验网的结构、特点，以及在网上进行有关技术、业务试验的情况和体会，认为通过该网积累了如何建设ＡＴＭ宽带网、如何用好ＡＴＭ宽带网、如何管理ＡＴＭ宽带网等方面丰富的经验。     

Interdiffusion behavior of Hg in HgTe/CdTe superlattices grown on Cd0.96Zn0.04 Te (211)B substrates by molecular beam epitaxy

Double-crystal x-ray rocking curve (DCRC) and secondary-ion mass-spectroscopy (SIMS) measurements have been performed to investigate the effect of rapid thermal annealing on the interdiffusion behavior of Hg in HgTe/CdTe superlattices grown on Cd_0.96Zn_0.04Te (211)B substrates by molecular beam epitaxy. The sharp satellite peaks of the DCRC measurements on a 100-period HgTe/CdTe (100Å/100Å) superlattice show a periodic arrangement of the superlattice with high-quality interfaces. The negative direction of the entropy change obtained from the diffusion coefficients as a function of the reciprocal of the temperature after RTA indicates that the Hg diffusion for the annealed HgTe/CdTe superlattice is caused by an interstitial mechanism. The Cd and the Hg concentration profiles near the annealed HgTe/CdTe superlattice interfaces, as measured by SIMS, show a nonlinear behavior for Hg, originating from the interstitial diffusion mechanism of the Hg composition. These results indicate that a nonlinear interdiffusion behavior is dominant for HgTe/CdTe superlattices annealed at 190°C and that the rectangular shape of HgTe/CdTe superlattices may change to a parabolic shape because of the intermixing of Hg and Cd due to the thermal treatment.