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A spatially periodic structure of heterogeneous elastic rods that periodically oscillate along their axes is proposed as a time-modulated phononic crystal. Each rod is a bi-material cylinder, consisting of periodically distributed slices with significantly different elastic properties. The rods are imbedded in an elastic matrix. Using a plane wave expansion, it is shown that the dispersion equation for sound waves is obtained from the solutions of a quadratic eigenvalue problem over the eigenfrequency ω. The coefficients of the corresponding quadratic polynomial are represented by infinite matrices defined in the space spanned by the reciprocal lattice vectors, where elements depend on the velocity of translation motion of the rods and Bloch vector k. The calculated band structure exhibits both ω and k bandgaps. If a frequency gap overlaps with a momentum gap, a mixed gap is formed. Within a mixed gap, ω and k acquire imaginary parts. A method of analysis of the dispersion equation in complex ω−k space is proposed. As a result of the high elastic contrast between the materials in the bi-material rods, a substantial depth of modulation is achieved, leading to a large gap to midgap ratio for the frequency, momentum, and mixed bandgaps. 

Visual localization, the task of determining the position and orientation of a camera, typically involves three core components: offline construction of a keyframe database, efficient online keyframes retrieval, and robust local feature matching. However, significant challenges arise when there are large viewpoint disparities between the query view and the database, such as attempting localization in a corridor previously build from an opposing direction. Intuitively, this issue can be addressed by synthesizing a set of virtual keyframes that cover all viewpoints. However, existing methods for synthesizing novel views to assist localization often fail to ensure geometric accuracy under large viewpoint changes. In this paper, we introduce a confidence-aware geometric prior into 2D Gaussian splatting to ensure the geometric accuracy of the scene. Then we can render novel views through the mesh with clear structures and accurate geometry, even under significant viewpoint changes, enabling the synthesis of a comprehensive set of virtual keyframes. Incorporating this geometry-preserving virtual keyframe database into the localization pipeline significantly enhances the robustness of visual localization. 

The photophysics of thiobases—nucleobases in which one or more oxygen atoms are replaced with sulfur atoms— vary greatly depending on the location of sulfonation. Not only are direct dynamics of a neutral thiobase impacted, but also the dynamics of excess electron accommodation. In this work, time-resolved photoelectron spectroscopy is used to measure binary anionic clusters of iodide and 4-thiouracil, I− · 4TU. We investigate charge transfer dynamics driven by excitation at 3.88 eV, corresponding to the lowest ππ* transition of the thiouracil, and at 4.16 eV, near the cluster vertical detachment energy. The photoexcited state dynamics are probed by photodetachment with 1.55 and 3.14 eV pulses. Excitation at 3.88 eV leads to a signal from a valence-bound ion only, indicating a charge accommodation mechanism that does not involve a dipole-bound anion as an intermediate. Excitation at 4.16 eV rapidly gives rise to dipole-bound and valence-bound ion signals, with a second rise in the valence-bound signal corresponding to the decay of the dipole-bound signal. The dynamics associated with the low energy ππ* excitation of 4-thiouracil provide a clear experimental proof for the importance of localized excitation and electron backfilling in halide–nucleobase clusters.