一种橙光磷光铱(Ⅲ)配合物的合成、晶体结构及光电性质研究

采用二氯甲烷为溶剂,无水碳酸钾为缚酸剂,在25℃温和条件下,以2-苯基-4-甲基喹啉铱(III)氯桥二聚体[(4m2pq)2Ir(μ-Cl)2Ir(4m2pq)2]和乙酰丙酮(Hacac)进行配位,反应合成了新型铱(Ⅲ)配合物[(4m2pq)2Ir(acac)]。通过核磁共振氢谱(1H NMR)、碳谱(13C NMR)、X射线单晶衍射等确定分子结构,利用紫外-可见吸收光谱、发射光谱对其光物理性质进行研究。结果表明:(4m2pq)2Ir(acac)的单晶结构属三斜晶系,空间群为P1;(4m2pq)2Ir(acac)在二氯甲烷溶液中呈橙光发射,发射峰为597 nm,磷光寿命0.33μs,量子效率达50.4%。以(4m2pq)2Ir(acac)为客体掺杂在CBP中,制备了结构为ITO/NPB(30 nm)/CBP:(4m2pq)2Ir(acac)(质量分数6%和8%,20 nm)/BCP(10 nm)/Alq3(20 nm)/LiF(1 nm)/Al(150 nm)的橙色磷光有机电致发光器件,器件的最大亮度达到39 667 cd/m2,发射峰位于597 nm,最大电流效率为14.2 cd/A,最大功率效率为8.1 lm/W。     

用氨基酸加和法计算多肽的脂水分配系数

Based on amino acid addition model, a set of hydrophobicity contributions of amino acids was obtained from the multivariate linear regression analysis of peptides' octanol/water partition coefficients. Multivariate regression was performed on a training set of 219 peptides including dipeptides to pentapeptides which we compose 21 natural amino acids. The correlation coefficients for the whole set fitting are 0. 978 and 0- 974, for log P and log D respectively. In addition, a new test method -evolution test-for regression analysis was discussed. The result of evolution test for amino acid addition model shows the advantage of this new test method.     

端元提取技术在高光谱图像压缩中的应用

高光谱图像海量数据如何实现大比例有效压缩是限制其应用的主要问题之一,而现有有损压缩方法存在大压缩比与光谱特性信息准确保留的矛盾,即使现有最优有损压缩方法也不能够得到令人满意的结果。文章基于混合像元分解的思想提出基于端元提取技术的数据有损压缩方法来解决该矛盾,首先用顶点成分分析(VCA)方法提取场景中地物的端元光谱,根据各端元与观测像元之间的光谱间余弦角相似性度量方法估计各端元的丰度,接着对端元光谱及丰度数据进行无损压缩,最后利用JPEG2000有损压缩方法对高光谱图像的所有单波段图像进行空间维大比例有损压缩。AVIRIS高光谱图像的仿真结果表明,压缩比得到大幅度提高,光谱信息得到有效恢复。在实现压缩比为50∶1时,大部分像元的光谱角误差在2%左右。     

Theoretical study of thermoelectric properties of MoS2Theoretical study of thermoelectric properties of MoS2Theoretical study of thermoelectric properties of MoS2

We systematically studied the thermoelectric properties of MoS2 with doping based on the Boltzmann transport theory and first-principles calculations. We obtained an optimal doping region （around 1019 cm-3） for thermoelectric properties along in-plane and cross-plane directions. MoS2 in the optimal doping region has a vanishingly small anisotropy of ther- mopower possibly due to the decoupling of in-plane and cross-plane conduction channels, but big anisotropies of electrical conductivity cr and electronic thermal conductivity ke arising from the anisotropic electronic scattering time. The ~ is comparable to the lattice counterpart k1 in the plane, while tq dominates over tee across the plane, The figure of merit ZT can reach 0.1 at around 700 K with in-plane direction preferred by doping.     

Luminescence Properties of Nanostructure ZnO-Covered Carbon Fibers Prepared by Thermal Oxidation

We report on ZnO nanosheets and nanorods synthesized by thermal oxidation of zinc films deposited on carbon fiber surfaces. The structure and optical properties are characterized by x-ray diffraction, scanning electron microscopy and photoluminescence spectrum. An orange-red emission around 683 nm is found in the PL spectrum when the sample prepaxs at 400℃ for four hours in air. With annealing temperature increasing from 400℃ to 500℃, the blue shift is observed.     

用于火星电离层探测的星-星无线电掩星技术

火星和地球类似,周围束缚了不同密度的电离层.利用无线电掩星技术可以对火星电离层进行观测.星-地无线电掩星在探测精度和探测区域方面都受到一定的限制.中俄联合火星探测计划将于2011年10月一箭双星发射俄罗斯的Phobos-Grunt探测器和中国的萤火1号火星探测器.该计划将开展国际上首次火星电离层的星-星无线电掩星观测试验,重点是对星-地无线电掩星无法观测的正午和子夜区域的火星电离层进行探测.星-星无线电掩星观测试验采用双频工作模式,接收机灵敏度为-145dBm,相位测量精度优于5%周.在地面对接收机进行了动态模拟测试,测试得到的相位数据能很好地反演出火星电离层电子密度廓线.     

铂基氧还原电催化剂的结构演变

质子交换膜燃料电池的商业化有望在不久的将来实现更清洁的能源社会.然而,氧还原反应缓慢的反应动力学和苛刻的条件对质子交换膜燃料电池的寿命和成本产生了巨大的挑战.之前大多数铂基催化剂的设计都将重点更多地放在提高活性上.随着质子交换膜燃料电池的商业化,寿命问题也受到了更多的关注.对整个生命周期中结构演变进行深入地了解,有助于...     

Stacking stability of MoS_2 bilayer: An ab initio study

The study of the stacking stability of bilayer MoS2 is essential since a bilayer has exhibited advantages over single layer MoS2 in many aspects for nanoelectronic applications. We explored the relative stability, optimal sliding path between different stacking orders of bilayer MoS2, and （especially） the effect of inter-layer stress, by combining first-principles density functional total energy calculations and the climbing-image nudge-elastic-band （CI-NEB） method. Among five typical stacking orders, which can be categorized into two kinds （I： AA＇, AB and II： AA＇, AB＇, A＇B）, we found that stacking orders with Mo and S superposing from both layers, such as AA＇ and AB, is more stable than the others. With smaller computational efforts than potential energy profile searching, we can study the effect of inter-layer stress on the stacking stability. Under isobaric condition, the sliding barrier increases by a few eV/（uc.GPa） from AA＇ to ABt, compared to 0.1 eV/（uc.GPa） from AB to [AB]. Moreover, we found that interlayer compressive stress can help enhance the transport properties of AA＇. This study can help understand why inter-layer stress by dielectric gating materials can be an effective means to improving MoS2 on nanoelectronic applications.     

用氨基酸加和法计算多肽的脂水分配系数

在药物设计中,化合物的流水性是值得考虑的一种重要的性质．目前常使用化合物在正辛醇和水两相间的分配系数的对数值（logP）来度量其流水性．仅从化合物的结构出发来预测其脂水分配系数具有重要的意义,已有多种计算方法见诸报导’‘,“．对于普通的有机化合物,它们能给出较好的结果．多肽是一类具有重要生物功能的化合物．在药物设计中,多肽也是常用的物系．目前预测一般有机化合物脂水分配系数的方法对于多肽尚不能给出满意的结果．鉴于多肽类化合物特殊的重要性,专门发展一种方法来预测多肽的脂水分配系数也是十分必要的．在这方…