Structural, electronic and vibrational properties of indium oxide clusters

Geometric, electronic and vibrational properties of the most stable and energetically favourable configurations of indium oxide clusters In_mO_n (1≤m, n≤4) are investigated using density functional theory. The lowest energy geometries prefer the planar arrangement of the constituent atoms with a trend to maximize the number of ionic In-O bonds. Due to the charge transfer from In to O atoms, the electrostatic repulsion occurs between the atoms with the same kind of charge. The minimization of electrostatic repulsion and the maximization of In-O bond number compete between each other and determine the location of the isometric total energy. The most stable linear In-O-In-O structure of In₂O₂ cluster is attributed to the reduced electrostatic repulsive energy at the expense of In-O bond number, while the lowest energy rhombus-like structure of In₂O₃ cluster reflects the maximized number of In-O bonds. Furthermore, the vibrational frequencies of the lowest energy clusters are calculated and compared with the available experimental results. The energy gap and the charge density distribution for clusters with varying oxygen/indium ratio are also discussed.     

Cluster synchronization in a network of non-identical dynamic systems

Cluster synchronization in a network of non-identical dynamic systems is studied in this paper, using two-cluster synchronization for detailed analysis and discussion. The results show that the common intercluster coupling condition is not always needed for the diffusively coupled network. Several sufficient conditions are obtained by using the Schur unitary triangularization theorem, which extends previous results. Some numerical examples are presented for illustration.     

Controlled quantum state sharing of arbitrary two-qubit states with five-qubit cluster states

In this paper, we propose a controlled quantum state sharing scheme to share an arbitrary two-qubit state using a five-qubit cluster state and the Bell state measurement. In this scheme, the five-qubit cluster state is shared by a sender (Alice), a controller (Charlie), and a receiver (Bob), and the sender only needs to perform the Bell-state measurements on her particles during the quantum state sharing process, the controller performs a single-qubit projective measurement on his particles, then the receiver can reconstruct the arbitrary two-qubit state by performing some appropriate unitary transformations on his particles after he has known the measured results of the sender and the controller.     

一种基于分块的遥感影像并行处理机制

高性能计算的基础是集群体系下的大规模并行计算.遥感图像处理效率的提高,依赖于并行计算技术的运用.在分析了已有网格计算环境下分布式任务分配方法的基础上,针对远海遥感影像目标物数量相对较少的特点,从软件角度利用四叉树结构对目标区域进行划分,同时采用动态负载均衡的任务分配策略与并行计算的思想,提出了对影像进行并行处理的集群体系任务分配算法模型,实验表明该集群体系下任务分配模型能有效提高图像并行处理的速度.     

Determination of Xenon in Air by a Pulse-discharge Helium Ionization Detector

A pulse-discharge helium ionization detector(Valco, PD-D3-I) was used to measure xenon concentration in air. The dependences of the detector relative response on various gas chromatograph parameters were investigated. Based on the well prepared gas connections for the detector system and optimized gas chromatography(GC) working conditions, the atmospheric xenon concentration could be measured by the cheap GC method with a detection level of 0.7?0^-9(parts by volume). Moreover, the xenon concentration in the ground level air around our laboratory was measured with the result of 0.085?0^-6(parts by volume) and RSD of 0.91%.     

Simultaneous Forecast for Three Speciations of Heavy Metal Elements Using Fuzzy Cluster-Artificial Neural Network

The three speciations(water extract, adsorption and organic speciations) of Cu, Zn, Fe and Mn in geo-chemical samples were determined by fuzzy cluster-artificial neural network(FC-ANN) method coupled with atomic absorption spectrometry. A back-propagation artificial neural network with one input node and three export nodes was constructed, which could forecaste three speciations of heavy metals simultaneously. In the learning sample set, the three speciations of each element were allowed to change in a wide concentration range and the accuracy of the analysis was apparently increased via the learning sample set optimized with the help of the fuzzy cluster analysis. The average relative errors of the three speciations of Cu, Zn, Fe or Mn from 100 geo-chemical samples were less than 5%. The relative standard deviations of the three speciations of each of four heavy metals were 0.008%―4.43%.     

中性和阳离子丁酮团簇的结构及稳定性的理论研究

使用密度泛函B3LYP方法,在6-31G*和6-311+G**基组水平上计算中性和阳离子丁酮团簇(CH_3COC_2H_5)_n和(CH_3COC_2H_5)_n~+(n 7)的稳定结构,并比较不同尺寸团簇之间的相对稳定性.中性和阳离子丁酮团簇的结构具有相似性:n=3—7时,组成团簇的丁酮的平均几何参数基本相同,单环结构最稳定;随着团簇尺寸的增加,双环结构的稳定性逐渐上升.通过平均结合能、一阶差分能、HOMO-LUMO能隙等计算分析可知:在所研究的各种尺寸团簇中,(CH_3COC_2H_5)_3是最稳定的中性团簇,与实验中的最强峰对应;(CH_3COC_2H_5)_4~+是最稳定的阳离子团簇.通过电离能计算得到丁酮分子的垂直电离能为9.535 eV与实验值相符,同时证明中性和阳离子丁酮二元团簇的结构变化较大.研究结果为实验中丁酮团簇碎片离子的形成机理提供一定的理论依据,并且为进一步研究酮类分子团簇的生长规律提供有价值的信息.     

Interactions between clusters of self-interstitial atoms via a conservative climb in BCC–Fe

We conduct kinetic Monte Carlo simulations for the conservative climb motion of a cluster of self-interstitial atoms (SIAs) towards another SIA cluster in BCC–Fe; the conservative climb velocity is inversely proportional to the fourth power of the distance between them, as per the prediction based on Einstein’s equation. The size of the climbing cluster significantly affects its conservative climb velocity, while the size of the cluster that originates the stress field does not. The activation energy for the conservative climb is considerably greater than that derived in previous studies and strongly dependent on the climbing cluster size. The results presented in this study are the atomistic evaluation of the behaviour of SIA clusters through three-dimensional motion, which cannot be achieved using molecular dynamics techniques alone.     

Helium irradiation-induced defects in deformed 316L stainless steel

Well-annealed 316L stainless steel was first cold rolled to 10% and 20% reductions in thickness and then irradiated by 50 keV He⁺ to a dose of 1 × 10²⁰ He⁺/m² at room temperature. Thermal desorption spectroscopy was used to investigate the helium desorption behaviour at different helium trapping states. The results showed that high-density dislocations had stronger inhibitory effect for helium desorption at temperatures from 800 to 1200 K. Positron annihilation Doppler broadening spectroscopy measurements were used to investigate the distribution of helium irradiation-induced defects. The S–E and ΔS–E plots clearly demonstrated that the helium irradiation-induced defects were trapped and restricted in motion by dislocations. The interaction between dislocations and helium irradiation-induced defects in deformed 316L stainless steel was investigated.     

不同构型(In,Al)GaN合金发光机理的第一性原理研究

基于第一性原理的密度泛函理论,研究了纤锌矿（In,Al）GaN合金的4种构型（均匀、短链、小团簇、团簇-链共存模型）的电子结构和发光微观机理。结果表明,在InGaN合金中,短In-N-链和小In-N团簇都局域电子在价带顶（VBM）态。当小团簇与短链共存时,前者局域电子的能力明显强于后者,是辐射复合发光中心。然而,在AlGaN合金中,电子在VBM态的局域受短Al-N链和小Al-N团簇的影响并不显著。合金微观结构的不同会引起电子局域的改变,从而影响材料的发光性能,并对带隙和弯曲系数有重要影响。