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961.
Over a long period of exploration, the successful observation of quantized version of anomalous Hall effect (AHE) in thin film of magnetically doped topological insulator (TI) completed a quantum Hall trio—quantum Hall effect (QHE), quantum spin Hall effect (QSHE), and quantum anomalous Hall effect (QAHE). On the theoretical front, it was understood that the intrinsic AHE is related to Berry curvature and U(1) gauge field in momentum space. This understanding established connection between the QAHE and the topological properties of electronic structures characterized by the Chern number. With the time-reversal symmetry (TRS) broken by magnetization, a QAHE system carries dissipationless charge current at edges, similar to the QHE where an external magnetic field is necessary. The QAHE and corresponding Chern insulators are also closely related to other topological electronic states, such as TIs and topological semimetals, which have been extensively studied recently and have been known to exist in various compounds. First-principles electronic structure calculations play important roles not only for the understanding of fundamental physics in this field, but also towards the prediction and realization of realistic compounds. In this article, a theoretical review on the Berry phase mechanism and related topological electronic states in terms of various topological invariants will be given with focus on the QAHE and Chern insulators. We will introduce the Wilson loop method and the band inversion mechanism for the selection and design of topological materials, and discuss the predictive power of first-principles calculations. Finally, remaining issues, challenges and possible applications for future investigations in the field will be addressed. 相似文献
962.
Jun Lu Daikun Xi Rui Huang Liangbin Li 《Journal of Macromolecular Science: Physics》2013,52(5):1018-1030
High-pressure crystallized bisphenol-A polycarbonate (BAPC) samples were investigated using wide-angle X-ray diffraction (WAXD), differential scanning calorimetry (DSC), and scanning electron microscopy (SEM). The results showed that BAPC chain-extended crystals with c-axis thickness around 2.0 μm were developed through the melt crystallization. Furthermore, a high-crystallinity BAPC sample with a wide variety of microstructures was obtained by a stepwise double-heat treatment at high pressure. In the sample, individual spherulites can be easily exposed and isolated with selective etching, which results in open porous microspheres. These spheres provide the possibility to study the spherulite structure in three dimensions. The open porous microspheres may have functional applications, such as catalyst support and for other surface active materials. 相似文献
963.
We have used vibrational spectroscopy to study the formula and molecular structure of the mineral penkvilksite Na 2TiSi 4O 11·2H 2O. Penkvilksite is a mineral which may be used in the uptake of radioactive elements. Both Raman and infrared spectroscopies identify a band at ~3638 cm?1 attributed to an OH-stretching vibration of hydroxyl units. The inference is that OH units are involved in the structure of penkvilksite. The formula may be well written as Na 2TiSi 4O 10(OH)2·H 2O. The mineral is characterised by a very intense Raman band at 1085 cm?1 and a broad infrared band at 1080 cm?1 assigned to SiO-stretching vibrations. Raman bands at 620, 667 and 711 cm?1 are attributed to SiO and TiO chain bonds. Water-stretching vibrations are observed as Raman bands at 3197, 3265, 3425 and 3565 cm?1. Vibrational spectroscopy enables aspects of the molecular structure of the mineral penkvilksite to be ascertained. Penkvilksite is a mineral which can incorporate actinides and lanthanides from radioactive waste. 相似文献
964.
Jinghao Zhao Hang Zhou Jiangwei Cui Qiwen Zheng Ying Wei Shanxue Xi 《辐射效应与固体损伤》2013,168(7-8):606-616
ABSTRACTThe authors perform gamma ray irradiation and hot carrier stress on RH H-Gate PD (partially depleted) SOI NMOSFETs as the experimental group and commercial strip-shaped gate PD SOI NMOSFETs as the control group. They analyse HCI degradation in samples and conclude that radiation could enhance HCI degradation in RH H-gate samples. Moreover, the mechanism is explained as the coupling effect between the front gate and back gate caused by TID radiation-induced trap charges in the buried oxide. 相似文献
965.
966.
Jing Xi Ruriko Yoshida David Haws 《Annals of the Institute of Statistical Mathematics》2013,65(4):763-783
In 2005, Chen et al. introduced a sequential importance sampling (SIS) procedure to analyze zero-one two-way tables with given fixed marginal sums (row and column sums) via the conditional Poisson (CP) distribution. They showed that compared with Monte Carlo Markov chain (MCMC)-based approaches, their importance sampling method is more efficient in terms of running time and also provides an easy and accurate estimate of the total number of contingency tables with fixed marginal sums. In this paper, we extend their result to zero-one multi-way ( $d$ -way, $d \ge 2$ ) contingency tables under the no $d$ -way interaction model, i.e., with fixed $d-1$ marginal sums. Also, we show by simulations that the SIS procedure with CP distribution to estimate the number of zero-one three-way tables under the no three-way interaction model given marginal sums works very well even with some rejections. We also applied our method to Samson’s monks data set. 相似文献
967.
Chang Chang Xi 《Mathematische Zeitschrift》2013,273(3-4):1025-1052
In this paper, we use ${\mathcal D}$ -split sequences and derived equivalences to provide formulas for calculation of higher algebraic K-groups (or mod-p K-groups) of certain matrix subrings which occur both in commutative algebra as the endomorphism rings of direct sums of Prüfer modules or of chains of Glaz–Vasconcelos ideals and in noncommutative geometry as an essential ingredient of the study of singularities of orders over surfaces. In our results, we do not assume any homological requirements on rings and ideals under investigation, and therefore extend sharply many existing results of this type in the algebraic K-theory literature to a more general context. 相似文献
968.
In this note we will introduce our recent work on the existence of approximate Hermitian-Einstein structures on semi-stable Higgs bundles, and the asymptotic behavior of the Yang-Mills-Higgs flow for Higgs pairs at infinity. 相似文献
969.
Electronic speckle pattern interferometry (ESPI) is a nondestructive, whole-field optical measurement technique. The removal of speckle noise is fundamental to extract measurement information accurately. In this letter, two filtering methods based on the oriented feature of ESPI fringes, i.e., the second-order oriented partial differential equation (SOOPDE) and oriented, regularized quadratic-cost function filtering methods, are first proven to be consistent. An important question in solving partial differential equation, i.e., how to select suitable parameters in an adaptive manner, is then discussed. The computer-simulated and experimentally obtained ESPI fringe patterns and phase map are processed by the SOOPDE filtering model with adaptive selective parameters. The qualitative and quantitative analyses demonstrate that the parameters selected by the adaptive method are effective and suitable for the SOOPDE filtering model. 相似文献
970.
An optical bandpass filter (OBF) is an important element whose properties considerably influence the output performance of a single side band multicarrier source based on a re-circulating frequency shifter. The influence of the OBF in the loop on the output spectrum is theoretically analyzed. Numerical simulations and experiments are Mso carried out. Results show that the steepness and deepness of a nonflat-top filter influence the stability of the spectrum of an output multicarrier. To obtain multicarrier output with tone to noise ratio (TNR) 〉26 dB and error vector magnitude (EVM) 〈0.25, the steepness ratio of the filter should be greater than 0.75 and deepness should be larger than 0.99. 相似文献