Browsing by Author "Pan, Y."
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Item Q-Mat+: An Error-Controllable and Feature-Sensitive Simplification Algorithm for Medial Axis Transform(Elsevier B.V.) Pan, Y.; Wang, B.; Guo, Xiaohu; Zeng, H.; Ma, Y.; Wang, W.; Guo, XiaohuThe medial axis transform (MAT), as an intrinsic shape representation, plays an important role in shape approximation, recognition and retrieval. Q-MAT is a state-of-the-art algorithm driven by quadratic error minimization to compute a geometrically precise, structurally concise, and compact representation of the MAT for 3D shapes. In this work we extend the technique to make it more robust, controllable, and name it Q-MAT+. Combining shape diameter function (SDF) and other mesh information, Q-MAT+ gets a more complete and accurate initial MAT than Q-MAT, even for extreme thin features, such as wires and sheets. Q-MAT+ could quickly remove insignificant branches while preserving significant ones to get a simple and faithful piecewise linear approximation of the MAT. Moreover, it performs the medial axis simplification with explicit maintenance and the control of Hausdorff error, which is not originally supported in Q-MAT. We further demonstrate the outstanding efficiency and accuracy of our method compared with other existing approaches for MAT generation and simplification. ©2019 Elsevier B.V.Item WSe₂ Homojunctions and Quantum Dots Created by Patterned Hydrogenation of Epitaxial Graphene Substrates(IOP Publishing Ltd, 2019-01-17) Pan, Y.; Fölsch, S.; Lin, Y. -C; Jariwala, B.; Robinson, J. A.; Nie, Yifan; Cho, Kyeongjiae; Feenstra, R. M.; 0000-0003-2698-7774 (Cho, K); 0000-0003-4771-3633 (Nie, Y); Nie, Yifan; Cho, KyeongjiaeScanning tunneling microscopy (STM) at 5 K is used to study WSe₂ layers grown on epitaxial graphene which is formed on Si-terminated SiC(0 0 0 1). Specifically, a partial hydrogenation process is applied to intercalate hydrogen at the SiC-graphene interface, yielding areas of quasi-free-standing bilayer graphene coexisting with bare monolayer graphene. We find that an abrupt and structurally perfect homojunction (band-edge offset ∼0.25 eV) is formed when WSe₂ overgrows a lateral junction between adjacent monolayer and quasi-free-standing bilayer areas in the graphene. The band structure modulation in the WSe₂ overlayer arises from the varying work function (electrostatic potential) of the graphene beneath. Scanning tunneling spectroscopy measurements reveal that this effect can be also utilized to create WSe₂ quantum dots that confine either valence or conduction band states, in agreement with first-principles band structure calculations. ©2019 IOP Publishing Ltd.