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Michelle Lee

Publications and source records attributed to Michelle Lee.

7 recordsLinked to original sources
arXiv2026

Redundant contacts and force redistribution stabilize limbless vertical climbing

Animals navigating complex vertical environments must secure stable footholds, a challenge for species without feet. While arboreal climbing has evolved repeatedly in snakes, the physical mechanisms they use to scale broad, nearly flat surfaces remain poorly understood. By measuring three-dimensional body kinematics and per-contact forces on a smooth vertical wall with protruding posts, we show that cornsnakes climb by dynamically balancing forces across a highly redundant network of 5 to 16 simultaneous contacts--far exceeding the three contacts minimally required for physical stability. Using a computational model and a robotic climber, we demonstrate that while simple body undulations and passive friction are mechanically sufficient to climb this terrain, snakes systematically deviate from this passive baseline. While downward climbing relies primarily on friction, ascending snakes actively generate positive mechanical work at their contacts to propel themselves. Furthermore, we found that whenever a snake engages a new contact, it triggers a stereotyped, system-wide redistribution of force that seamlessly integrates the new foothold without disrupting whole-body balance. These results reveal how a continuous, flexible body can transform sparse environmental features into a robust, fault-tolerant network. This mechanism provides a biomechanical framework for understanding the repeated evolution of limbless climbing and offers physical principles for designing agile robots for unstructured terrain.

physics.bio-ph↗
arXiv2025

TabRAG: Improving Tabular Document Question Answering for Retrieval Augmented Generation via Structured Representations

Incorporating external knowledge bases in traditional retrieval-augmented generation (RAG) relies on parsing the document, followed by querying a language model with the parsed information via in-context learning. While effective for text-based documents, question answering on tabular documents often fails to generate plausible responses. Standard parsing techniques lose the two-dimensional structural semantics critical for cell interpretation. In this work, we present TabRAG, a parsing-based RAG framework designed to improve tabular document question answering via structured representations. Our framework consists of layout segmentation that decomposes the document inputs into a series of components, enabling fine-grained extraction. Subsequently, a vision language model parses and extracts the document tables into a hierarchically structured representation. In order to cater various table styles and formats, we integrate a self-generated in-context learning module that guides the table extraction process. Experimental results demonstrate that TabRAG outperforms existing popular parsing techniques across a broad suite of evaluation and ablation benchmarks. Code is available at: https://github.com/jacobyhsi/TabRAG.

cs.CL↗
arXiv2015

Single Crystal Functional Oxides on Silicon

Single crystalline thin films of complex oxides show a rich variety of functional properties such as ferroelectricity, piezoelectricity, ferro and antiferromagnetism etc. that have the potential for completely new electronic applications (1-2). Direct synthesis of such oxides on Si remains challenging due to the fundamental crystal chemistry and mechanical incompatibility of dissimilar interfaces (3-16). Here we report integration of thin (down to 1 unit cell) single crystalline, complex oxide films onto Si substrates, by epitaxial transfer at room temperature. In a field effect transistor using a transferred Pb0.2Zr0.8TiO3 (PZT) layer as the gate insulator, we demonstrate direct reversible control of the semiconductor channel charge with polarization state. These results represent the realization of long pursued but yet to be demonstrated single crystal functional oxides on-demand on silicon.

cond-mat.mtrl-sci↗
arXiv2014

Amalgam Anosov representations

Let $\Gamma$ be a one-ended, torsion-free hyperbolic group and let $G$ be a semisimple Lie group with finite center. Using the canonical JSJ splitting due to Sela, we define amalgam Anosov representations of $\Gamma$ into $G$ and prove that they form a domain of discontinuity for the action of $\mathrm{Out}(\Gamma)$. In the appendix, we prove, using projective Anosov Schottky groups, that if the restriction of the representation to every Fuchsian or rigid vertex group of the JSJ splitting of $\Gamma$ is Anosov, with respect to a fixed pair of opposite parabolic subgroups, then $\rho$ is amalgam Anosov.

math.GT↗
arXiv2013

Separable-stable representations of a compression body

Let M be a hyperbolizable, nontrivial compression body without toroidal boundary components. In this paper, we characterize which discrete and faithful representations of the fundamental group of M into PSL(2,C) are separable-stable. The set of separable-stable representations forms a domain of discontinuity for the action of the outer automorphism group of the fundamental group of M on the PSL(2,C)-character variety of M.

math.GT↗
arXiv2011

Dynamics on the PSL(2,C)-character variety of a twisted I-bundle

Let M be a twisted interval bundle over a nonorientable hyperbolizable surface. Let X(M) be the PSL(2,C)-character variety of π_1(M). We examine the dynamics of the action of Out(π_1(M)) on X(M), and in particular, we find an open set on which the action is properly discontinuous that is strictly larger than the interior of the deformation space of marked hyperbolic manifolds homotopy equivalent to M. Further, we identify which discrete and faithful representations can lie in a domain of discontinuity for the action of Out(π_1(M)) on X(M).

math.GT↗