Mechanism of defect evolution in H+ and He+ implanted InP

The defect evolution in InP with the 75 keV H⁺ and 115 keV He⁺ implantation at room temperature after subsequent annealing has been investigated in detail. With the same ion implantation fluence, the He⁺ implantation caused much broader damage distribution accompanied by much higher out-of-plane strain with respect to the H⁺ implanted InP. After annealing, the H⁺ implanted InP did not show any blistering or exfoliation on the surface even at the high fluence and the H₂ molecules were stored in the heterogeneously oriented platelet defects. However, the He molecules were stored into the large bubbles which relaxed toward the free surface, creating blisters at the high fluence.     

An Adaptive Rank Aggregation-Based Ensemble Multi-Filter Feature Selection Method in Software Defect Prediction

Feature selection is known to be an applicable solution to address the problem of high dimensionality in software defect prediction (SDP). However, choosing an appropriate filter feature selection (FFS) method that will generate and guarantee optimal features in SDP is an open research issue, known as the filter rank selection problem. As a solution, the combination of multiple filter methods can alleviate the filter rank selection problem. In this study, a novel adaptive rank aggregation-based ensemble multi-filter feature selection (AREMFFS) method is proposed to resolve high dimensionality and filter rank selection problems in SDP. Specifically, the proposed AREMFFS method is based on assessing and combining the strengths of individual FFS methods by aggregating multiple rank lists in the generation and subsequent selection of top-ranked features to be used in the SDP process. The efficacy of the proposed AREMFFS method is evaluated with decision tree (DT) and naïve Bayes (NB) models on defect datasets from different repositories with diverse defect granularities. Findings from the experimental results indicated the superiority of AREMFFS over other baseline FFS methods that were evaluated, existing rank aggregation based multi-filter FS methods, and variants of AREMFFS as developed in this study. That is, the proposed AREMFFS method not only had a superior effect on prediction performances of SDP models but also outperformed baseline FS methods and existing rank aggregation based multi-filter FS methods. Therefore, this study recommends the combination of multiple FFS methods to utilize the strength of respective FFS methods and take advantage of filter–filter relationships in selecting optimal features for SDP processes.     

缺陷单层和双层石墨烯的拉曼光谱及其激发光能量色散关系

拉曼光谱作为一种无破坏性、快速且敏锐的测试技术已经成 为表征石墨烯样品和研究其缺陷的最重要的实验手段之一. 本论文用离子注入在单层和双层石墨烯中产生缺陷, 并利用拉曼光谱研究了存在缺陷时单层和双层石墨烯的一阶和二阶拉曼模, 单层石墨烯的D模为双峰结构, 而双层石墨烯的D模具有四峰结构. 同时, 利用四条激光线系统地研究了本征和缺陷单层和双层石墨烯的拉曼峰频率的激发光能量依赖关系, 并基于石墨材料的双共振拉曼散射机理指认了离子注入后样品各拉曼峰的物理根源. 关键词： 石墨烯 缺陷 拉曼光谱 能量色散关系     

ZnMgO/ZnO异质结构中二维电子气的研究

论文根据ZnMgO/ZnO异质结构二维电子气的能带结构及相关理论模型, 采用一维Poisson-Schrodinger方程的自洽求解, 模拟计算了ZnMgO/ZnO异质结构中二维电子气的分布及其对ZnMgO势垒层厚度及Mg组分的依赖关系. 研究发现该异质结构中ZnMgO势垒层厚度存在一最小临界值: 当垒层厚度小于该临界值时, 二维电子气消失, 当垒层厚度大于该临界值时, 其二维电子气密度随着该垒层厚度的增加而增大; 同时研究发现ZnMgO势垒层中Mg组分的增加将显著增强其二维电子气的行为, 导致二维电子气密度的明显增大; 论文对模拟计算获得的结果与相关文献报道的实验结果进行了比较, 并从极化效应和能带结构的角度进行了分析和讨论, 给出了合理的解释. 关键词： 氧化锌 二维电子气 异质结构 理论计算     

Structural studies on banana oil,isoamyl acetate,by means of microwave spectroscopy and quantum chemical calculations

The rotational spectrum of isoamyl acetate, H₃C–COO–(CH₂)₂–CH(CH₃)₂, has been recorded and assigned using a molecular beam Fourier transform microwave (MB-FTMW) spectrometer in the frequency range of 3–26.5?GHz. One conformer has been observed. By comparing the spectroscopic data with the quantum chemical data, it was found that the conformer observed does not have C_s symmetry. The rotational and centrifugal distortion constants were determined. The barrier to internal rotation of the acetate methyl group was found to be 93.98?cm^?1. Due to the high number of the conformers, a systematic nomenclature will be presented.     

High-resolution,near-infrared CW-CRDS,and ab initio investigations of N2O–HDO

We have investigated the N₂O–HDO molecular complex using ab initio calculations at the CCSD(T)-F12a/aug-cc-pVTZ level of theory and using cavity ring-down spectroscopy to probe an HDO/N₂O/Ar supersonic jet around 1.58 μm. A single a-type vibrational band was observed, 13 cm^?1 redshifted compared to the OH+OD excited band in HDO, and 173 vibration-rotation lines were assigned (T_rot ≈ 20 K). A weighted fit of existing microwave and present near infrared (NIR) data was achieved using a standard Watson's Hamiltonian (σ = 1.26), producing ground and excited states rotational constants. The comparison of the former with those calculated ab initio suggests a planar geometry in which the OD rather than the OH bond in water is almost parallel to NNO. The equilibrium geometry and dissociation energy (D_e = –11.7 kJ/mol) of the water–nitrous oxide complex were calculated. The calculations further demonstrate and allow characterising another minimum, 404 cm^?1 (ΔE₀) higher in energy. Harmonic vibrational frequencies and dissociation energies, D₀, were calculated for various conformers and isotopic forms of the complex, in both minima. The absence of N₂O–D₂O from dedicated NIR experiments is reported and discussed.     

Theoretical study of stabilities,electronic, and catalytic performance of supported platinum on modified graphene

The geometry, electronic structure, and catalytic properties for CO oxidation of Pt atom supported on pri-graphene (PG), Haeckelite (H), and Stone–Wales-defect-graphene are investigated by density functional theory (DFT) calculations. In contrast to a Pt atom on PG, defective graphene, especially the Haeckelite, strongly stabilises the Pt atom and makes it more positive and thus the CO poisoning. At the same time the catalytic activities are as high as the pristine one. Langmuir–Hinshelwood mechanisms are favoured as the starting state and are followed by the Eley–Rideal reaction. The results indicate the benefit of Haeckelite as a substrate for the Pt atom and validate the reactivity of catalysts on the atomic scale with low cost and high activity.     

On the interaction of the Dirac oscillator with the Aharonov–Casher system in topological defect backgrounds

In this paper, we study the influence of the Aharonov–Casher effect [Y. Aharonov, A. Casher, Phys. Rev. Lett. 53 (1984) 319] on the Dirac oscillator in three different scenarios of general relativity: the Minkowski spacetime, the cosmic string spacetime and the cosmic dislocation spacetime. In this way, we solve the Dirac equation and obtain the energy levels for bound states and the Dirac spinors for positive-energy solutions. We show that the relativistic energy levels depend on the Aharonov–Casher geometric phase. We also discuss the influence of curvature and torsion on the relativistic energy levels and the Dirac spinors due to the topology of the cosmic string and cosmic dislocation spacetimes.     

The resonant secondary emission of the F center in alkali halides

The secondary radiation after resonant excitation of F center and its linear polarization P correlated to the polarization of resonant light have been measured for five alkali halides at low temperatures. In KC1, the spectrum of P over the whole Stokes region is divided into three successive regions, the depolarization range at the one-phonon Raman scattering, the near plateau range, and the depolarization range down to vanishing. The former two have common relevance to resonant energy and symmetries of coupled phonons. These relevances are interpreted adopting a configuration coordinate model for 2s- and 2p-like excited states.