1,722,812 research outputs found
Jun Won Lee
No full text학위논문(석사)--아주대학교 일반대학원 :의학과,2009. 2Ⅰ. INTRODUCTION
Ⅱ. MATERIALS AND METHODS
Ⅱ.1 Outlining of structures
Ⅱ.2 Filling of outlines with color
Ⅱ.3 Surface reconstruction of outlined structures
Ⅱ.4 Assembling and refining of surface models
Ⅱ.5 Picturing of not outlined structures
Ⅲ. RESULT
Ⅳ. DISCUSSION
Ⅴ. CONCLUSION
REFERENCES
국문요약Maste
Classification of flat bands according to the band-crossing singularity of Bloch wave functions
Full text linkWe show that flat bands can be categorized into two distinct classes, that is, singular and nonsingular flat bands, by exploiting the singular behavior of their Bloch wave functions in momentum space. In the case of a singular flat band, its Bloch wave function possesses immovable discontinuities generated by the band-crossing with other bands, and thus the vector bundle associated with the flat band cannot be defined. This singularity precludes the compact localized states from forming a complete set spanning the flat band. Once the degeneracy at the band crossing point is lifted, the singular flat band becomes dispersive and can acquire a finite Chern number in general, suggesting a new route for obtaining a nearly flat Chern band. On the other hand, the Bloch wave function of a nonsingular flat band has no singularity, and thus forms a vector bundle. A nonsingular flat band can be completely isolated from other bands while preserving the perfect flatness. All one-dimensional flat bands belong to the nonsingular class. We show that a singular flat band displays a novel bulk-boundary correspondence such that the presence of the robust boundary mode is guaranteed by the singularity of the Bloch wave function. Moreover, we develop a general scheme to construct a flat band model Hamiltonian in which one can freely design its singular or nonsingular nature. Finally, we propose a general formula for the compact localized state spanning the flat band, which can be easily implemented in numerics and offer a basis set useful in analyzing correlation effects in flat bands. © 2019 American Physical Societ
A study on the suppression of the vortex in ladle and the measurement of melt velocity by electromagnetic field
No full text학위논문(박사) - 한국과학기술원 : 재료공학과, 2000.2, [ iv, 171 p. ]한국과학기술원 : 재료공학과
Sparse Signal Recovery via Tree Search Matching Pursuit
No full textRecently, greedy algorithm has received much attention as a cost-effective means to reconstruct the sparse signals from compressed measurements. Much of previous work has focused on the investigation of a single candidate to identify the support (index set of nonzero elements) of the sparse signals. Well-known drawback of the greedy approach is that the chosen candidate is often not the optimal solution due to the myopic decision in each iteration. In this paper, we propose a tree search based sparse signal recovery algorithm referred to as the tree search matching pursuit (TSMP). Two key ingredients of the proposed TSMP algorithm to control the computational complexity are the pre-selection to put a restriction on columns of the sensing matrix to be investigated and the tree pruning to eliminate unpromising paths from the search tree. In numerical simulations of Internet of Things (IoT) environments, it is shown that TSMP outperforms conventional schemes by a large margin. © 2011 KICS.1
Geometric characterization of anomalous Landau levels of isolated flat bands
No full text© 2021, The Author(s).According to the Onsager’s semiclassical quantization rule, the Landau levels of a band are bounded by its upper and lower band edges at zero magnetic field. However, there are two notable systems where the Landau level spectra violate this expectation, including topological bands and flat bands with singular band crossings, whose wave functions possess some singularities. Here, we introduce a distinct class of flat band systems where anomalous Landau level spreading (LLS) appears outside the zero-field energy bounds, although the relevant wave function is nonsingular. The anomalous LLS of isolated flat bands are governed by the cross-gap Berry connection that measures the wave-function geometry of multi bands. We also find that symmetry puts strong constraints on the LLS of flat bands. Our work demonstrates that an isolated flat band is an ideal system for studying the fundamental role of wave-function geometry in describing magnetic responses of solids.11Nsciescopu
RECUP Net: RECUrsive Prediction Network for Surrounding Vehicle Trajectory Prediction with Future Trajectory Feedback
No full textIn order to predict the behavior of human drivers accurately, the autonomous vehicle should he able to understand the reasoning and decision process of motion generation of human drivers. However, most of the conventional prediction methods overlook this and focus on improving the prediction results using the given data, the historical information. In contrast, human drivers not only depend on the historical motion but also consider future predictions when handling interactions with other vehicles. In this paper, we propose a novel recursive RNN encoder-decoder prediction model that takes the initial future prediction results as inputs of second prediction computation. This feedback mechanism can he interpreted as a network sharing, which allows the model to refine or correct the predicted results iteratively. We use two encoders to analyze both of the historical information and future information, and the attention mechanism is employed to interpret interaction. Our experimental results with the NGSIM dataset demonstrate the recursive structure enhances prediction results effectively compare to the baselines based on the ablation study and state-of-the-art methods. Furthermore, we observe that the results improve successively as the model iterates
Unified bulk-boundary correspondence for band insulators
Full text linkThe bulk-boundary correspondence, a topic of intensive research interest over the past decades, is one of the quintessential ideas in the physics of topological quantum matter. Nevertheless, it has not been proven in all generality and has in certain scenarios even been shown to fail, depending on the boundary profiles of the terminated system. Here, we introduce bulk numbers that capture the exact number of in-gap modes, without any such subtleties in one spatial dimension. Similarly, based on these 1D bulk numbers, we define a new 2D winding number, which we call the pole winding number, that specifies the number of robust metallic surface bands in the gap as well as their topological character. The underlying general methodology relies on a simple continuous extrapolation from the bulk to the boundary, while tracking the evolution of Green's function's poles in the vicinity of the bulk band edges. As a main result we find that all the obtained numbers can be applied to the known insulating phases in a unified manner regardless of the specific symmetries. Additionally, from a computational point of view, these numbers can be effectively evaluated without any gauge fixing problems. In particular, we directly apply our bulk-boundary correspondence construction to various systems, including 1D examples without a traditional bulk-boundary correspondence, and predict the existence of boundary modes on various experimentally studied graphene edges, such as open boundaries and grain boundaries. Finally, we sketch the 3D generalization of the pole winding number by in the context of topological insulators
Perfect transmission and Aharanov-Bohm oscillations in topological insulator nanowires with nonuniform cross section
Full text linkTopological insulator nanowires with uniform cross section, combined with a magnetic flux, can host both a perfectly transmitted mode and Majorana zero modes. Here we consider nanowires with rippled surfaces- specifically, wires with a circular cross section with a radius varying along its axis-and we calculate their transport properties. At zero doping, chiral symmetry places the clean wires (no impurities) in the AIII symmetry class, which results in a Z topological classification. A magnetic flux threading the wire tunes between the topologically distinct insulating phases, with perfect transmission obtained at the phase transition. We derive an analytical expression for the exact flux value at the transition. Both doping and disorder break the chiral symmetry and the perfect transmission. At finite doping, the interplay of surface ripples and disorder with the magnetic flux modifies quantum interference such that the amplitude of Aharonov-Bohm oscillations reduces with increasing flux, in contrast to wires with uniform surfaces where it is flux-independent
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