Publications

This paper proposes an adaptive near-hover position controller for quadcopters, which can be deployed to quadcopters of very different mass, size and motor constants, and also shows rapid adaptation to unknown disturbances during runtime. The core algorithmic idea is to learn a single policy that can adapt online at test time not only to the disturbances applied to the drone, but also to the robot dynamics and hardware in the same framework. We achieve this by training a neural network to estimate a latent representation of the robot and environment parameters, which is used to condition the behaviour of the controller, also represented as a neural network. We train both networks exclusively in simulation with the goal of flying the quadcopters to goal positions and avoiding crashes to the ground. We directly deploy the same controller trained in the simulation without any modifications on two quadcopters in the real world with differences in mass, size, motors, and propellers with mass differing by 4.5 times. In addition, we show rapid adaptation to sudden and large disturbances up to one-third of the mass of the quadcopters. We perform an extensive evaluation in both simulation and the physical world, where we outperform a state-of-the-art learning-based adaptive controller and a traditional PID controller specifically tuned to each platform individually. Video results can be found at https://youtu.be/U-c-LbTfvoA.

A near-field powermeter that directly quantifies light absorption and heat transfer in single nanowires is demonstrated. The mechanism is based on the metal-insulator transition in single-crystal VO₂ microbeams, where the domain wall exhibits distinct optical contrast between the two phases. The powermeter is contactless and optically readable, allowing quick determination of optical absorbance, thermal conductivity, and contact thermal resistance of single nanostructures.

We present the results of several surveys for supernovae (SNe) in galaxy clusters. SNe discovered in deep, archival HST images were used to measure the cluster SN Ia rate to z=1. A search for SNe in nearby (0.06 < z < 0.2) Abell galaxy clusters yielded 15 SNe, 12 of which were spectroscopically confirmed. Of these, 7 are cluster SNe Ia, which we will use to measure the SN Ia rate in nearby clusters. This search has also discovered the first convincing examples of intergalactic SNe. We conclude with a brief description of ongoing and future cluster SN surveys.

A novel approach for the sensitization of singlet oxygen has been developed which utilizes indirect excitation of the photosensitizer by two-photon-excited fluorescence resonance energy transfer (FRET) from separate chromophores assembled into a dendrimer. This approach effectively enhances the two-photon excitation efficiency of a known photosensitizer, without the sort of chromophore modifications that could lead to loss of photosensitization and other desirable photophysical properties. Photosensitization of singlet oxygen via excitation wavelengths transmissive to human body tissue (750−1000 nm) could alleviate the depth limitations of photodynamic therapy. The dendritic photosensitizer was prepared by grafting two-photon-absorbing chromophores and water-solubilizing moieties to a known multivalent porphyrin photosensitizer. Efficient FRET (>99% quenching of donor emission) between the peripheral donor two-photon-absorbing chromophores and the central acceptor photosensitizer at the core of the dendrimer was demonstrated under two-photon excitation conditions in an aqueous medium. Photosensitized production of singlet oxygen was monitored through chemical trapping and oxygen luminescence. Both methods independently demonstrated enhanced two-photon-induced singlet oxygen generation upon incorporation of two-photon-absorbing chromophores capable of efficient FRET to the photosensitizer.

A dense and stable lithium deposition process is highlighted by a snowy world, where the snowflakes represent the Li ions and the branches are like the ultralight 3D copper nanowire network with a phosphidation gradient employed by Wei Lv, Quan-Hong Yang, Feiyu Kang, and co-workers in article number 1904991. The gradient surface increases the lithiophilicity and high utilization of 3D structure, enabling a dendrite-free lithium-metal anode with high energy density.

We present Hubble Space Telescope blue spectra at intermediate spectral resolution for the nuclei of 23 nearby disk galaxies. These objects were selected to have nebular emission in their nuclei, and span a range of emission-line classifications as well as Hubble types. In this paper we focus on the stellar population as revealed by the continuum spectral energy distribution measured within the central 0."13 (~8pc) of these galaxies. The data were modeled with linear combinations of single-age stellar population synthesis models. The large majority (~80%) of the surveyed nuclei have spectra whose features are consistent with a predominantly old (>5x10^9 yr) stellar population. Approximately 25% of these nuclei show evidence of a component with age younger than 1 Gyr, with the incidence of these stars related to the nebular classification. Successful model fits imply an average reddening corresponding to A_V~0.4 mag and stellar metallicity of (1--2.5) Z_sun. We discuss the implications of these results for the understanding of star formation history in the environment of quiescent and active supermassive black holes. Our findings reinforce the picture wherein Seyfert nuclei and the majority of low-ionization nuclear emission-line regions (LINERs) are predominantly accretion-powered, and suggest that much of the central star formation in Hii nuclei is actually circumnuclear.

ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTMesocellular Siliceous Foams with Uniformly Sized Cells and WindowsPatrick Schmidt-Winkel, Wayne W. Lukens,, Dongyuan Zhao, Peidong Yang, Bradley F. Chmelka, and Galen D. StuckyView Author Information Department of Chemistry, Materials Research Laboratory and Department of Chemical Engineering University of California, Santa Barbara, California 93106 Cite this: J. Am. Chem. Soc. 1999, 121, 1, 254–255Publication Date (Web):December 19, 1998Publication History Received9 September 1998Published online19 December 1998Published inissue 1 January 1999https://pubs.acs.org/doi/10.1021/ja983218ihttps://doi.org/10.1021/ja983218irapid-communicationACS PublicationsCopyright © 1999 American Chemical SocietyRequest reuse permissionsArticle Views6348Altmetric-Citations735LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-AlertscloseSupporting Info (1)»Supporting Information Supporting Information SUBJECTS:Anions,Emulsions,Liquids,Nitrogen,Phase transitions Get e-Alerts