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  1. Free, publicly-accessible full text available May 20, 2023
  2. Aerial images provide important situational aware- ness for responding to natural disasters such as hurricanes. They are well-suited for providing information for damage estimation and localization (DEL); i.e., characterizing the type and spatial extent of damage following a disaster. Despite recent advances in sensing and unmanned aerial systems technology, much of post-disaster aerial imagery is still taken by handheld DSLR cameras from small, manned, fixed-wing aircraft. However, these handheld cameras lack IMU information, and images are taken opportunistically post-event by operators. As such, DEL from such imagery is still a highly manual and time-consuming process. We propose an approach tomore »both detect damage in aerial images and localize it in world coordinates, with specific focus on detecting and localizing flooding. The approach is based on using structure from motion to relate image coordinates to world coordinates via a projective transformation, using class activation mapping to detect the extent of damage in an image, and applying the projective transformation to localize damage in world coordinates. We evaluate the performance of our approach on post-event data from the 2016 Louisiana floods, and find that our approach achieves a precision of 88%. Given this high precision using limited data, we argue that this approach is currently viable for fast and effective DEL from handheld aerial imagery for disaster response.« less
    Free, publicly-accessible full text available December 1, 2022
  3. Free, publicly-accessible full text available December 1, 2022
  4. Realizing quantum speedup for practically relevant, computationally hard problems is a central challenge in quantum information science. Using Rydberg atom arrays with up to 289 qubits in two spatial dimensions, we experimentally investigate quantum algorithms for solving the Maximum Independent Set problem. We use a hardware-efficient encoding associated with Rydberg blockade, realize closed-loop optimization to test several variational algorithms, and subsequently apply them to systematically explore a class of graphs with programmable connectivity. We find the problem hardness is controlled by the solution degeneracy and number of local minima, and experimentally benchmark the quantum algorithm’s performance against classical simulated annealing.more »On the hardest graphs, we observe a superlinear quantum speedup in finding exact solutions in the deep circuit regime and analyze its origins.« less
    Free, publicly-accessible full text available May 5, 2023
  5. Abstract A new class of electromechanically coupled metamaterial is presented which relies on magnetic field interactions between the host structure and a local resonator circuit to realize novel vibration control capabilities. The metamaterial chain exhibits a highly tunable vibration band gap which can be easily placed at a desired frequency using the resonant circuit parameters, providing a robust mechanism to independently alter the band gap width, depth, and frequency of maximum attenuation. In its dissipative form, the electromechanical metamaterial is shown to exhibit electrical metadamping as a function of the local resonance circuit resistance. The impact of the damping ratiomore »as a function of the electrical resistance is characterized in frequency and time domains, and related to the infinite system dynamics. A robust experimental realization of the system is constructed which achieves electromechanical coupling through a moving coil and magnet system. The apparatus is used to show that the band gap location and depth can be readily tuned with the circuit elements. The presented metamaterial has potential for meaningful vibroacoustic practical applications in addition to revealing fundamentally new properties of damped electrically-resonant structures.« less
    Free, publicly-accessible full text available November 16, 2022
  6. Free, publicly-accessible full text available September 1, 2022
  7. Free, publicly-accessible full text available November 1, 2022
  8. Abstract Spin-valley locking in monolayer transition metal dichalcogenides has attracted enormous interest, since it offers potential for valleytronic and optoelectronic applications. Such an exotic electronic state has sparsely been seen in bulk materials. Here, we report spin-valley locking in a Dirac semimetal BaMnSb 2 . This is revealed by comprehensive studies using first principles calculations, tight-binding and effective model analyses, angle-resolved photoemission spectroscopy measurements. Moreover, this material also exhibits a stacked quantum Hall effect (QHE). The spin-valley degeneracy extracted from the QHE is close to 2. This result, together with the Landau level spin splitting, further confirms the spin-valley lockingmore »picture. In the extreme quantum limit, we also observed a plateau in the z -axis resistance, suggestive of a two-dimensional chiral surface state present in the quantum Hall state. These findings establish BaMnSb 2 as a rare platform for exploring coupled spin and valley physics in bulk single crystals and accessing 3D interacting topological states.« less
    Free, publicly-accessible full text available December 1, 2022