345 research outputs found
Effect of resonant acoustic powder mixing on delay time of W–KClO4–BaCrO4 mixtures
No full textThis study investigates the impact of resonant acoustic powder mixing on the delay time of the W-KClO4-BaCrO4 (WKB) mixture and its potential implications for powder and material synthesis. Through thermal analysis, an inverse linear relationship was found between thermal conductivity and delay time, allowing us to use thermal conductivity as a reliable proxy for delay time. By comparing the thermal conductivity of WKB mixtures mixed manually and using an acoustic powder mixer, we found that acoustic powder mixing resulted in minimal deviations in thermal conductivity, proving more uniform mixing. Furthermore, differential scanning calorimeter analysis and Sestak-Berggren modeling demonstrated consistent reaction dynamics with a constant activation energy as the reaction progressed in samples mixed using acoustic waves. These findings underscore the critical role of uniform powder mixing in enhancing the thermodynamic quality of the WKB mixture and emphasize the importance of developing novel methods for powder and material synthesis. (c) 2024 Author(s). All article content, except where otherwise noted, is licensed under a Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).
Colloidal Single-Layer Quantum Dots with Lateral Confinement Effects on 2D Exciton
No full textControlled lateral quantum confinement in single-layer transition-metal chalcogenides (TMCs) can potentially combine the unique properties of two-dimensional (2D) exciton with the size-tunability of exciton energy, creating the single-layer quantum dots (SQDs) of 2D TMC materials. However, exploring such opportunities has been challenging due to the limited ability to produce well-defined SQDs with sufficiently high quality and size control, in conjunction with the commonly observed inconsistency in the optical properties. Here, we report an effective method to synthesize high-quality and size-controlled SQDs of WSe2 via multilayer quantum dots (MQDs) precursors, which enables grasping a clear picture of the role of lateral confinement on the optical properties of the 2D exciton. From the single-particle optical spectra and polarization anisotropy of WSe2 SQDs of varying sizes in addition to their ensemble data, we reveal how the properties of 2D exciton in single-layer TMCs evolve with increasing lateral quantum confinement. © 2016 American Chemical Society110111sciescopu
Preference learning for guiding the tree search in continuous POMDPs
No full textA robot operating in a partially observable environment must perform sensing actions to achieve a goal, such as clearing the objects in front of a shelf to better localize a target object at the back, and estimate its shape for grasping. A POMDP is a principled framework for enabling robots to perform such information-gathering actions. Unfortunately, while robot manipulation domains involve high-dimensional and continuous observation and action spaces, most POMDP solvers are limited to discrete spaces. Recently, POMCPOW [1] has been proposed for continuous POMDPs, which handles continuity using sampling and progressive widening [2]. However, for robot manipulation problems involving camera observations and multiple objects, POMCPOW is too slow to be practical. We take inspiration from the recent work in learning to guide task and motion planning [3] to propose a framework that learns to guide POMCPOW from past planning experience. Our method uses preference learning [4, 5, 6, 7] that utilizes both success and failure trajectories, where the preference label is given by the results of the tree search. We demonstrate the efficacy of our framework in several continuous partially observable robotics domains, including real-world manipulation, where our framework explicitly reasons about the uncertainty in off-the-shelf segmentation and pose estimation algorithms. Details of the project are accessible in the following URL: https://sites.google.com/view/preference-guided-pomcpow?usp=sharing
HANSEN: Human and AI Spoken Text Benchmark for Authorship Analysis
No full textAuthorship Analysis, also known as stylometry, has been an essential aspect of Natural Language Processing (NLP) for a long time. Likewise, the recent advancement of Large Language Models (LLMs) has made authorship analysis increasingly crucial for distinguishing between human-written and AI-generated texts. However, these authorship analysis tasks have primarily been focused on written texts, not considering spoken texts. Thus, we introduce the largest benchmark for spoken texts - HANSEN (Human ANd ai Spoken tExt beNchmark).
HANSEN encompasses meticulous curation of existing speech datasets accompanied by transcripts, alongside the creation of novel AI-generated spoken text datasets. Together, it comprises 17 human datasets, and AI-generated spoken texts created using 3 prominent LLMs: ChatGPT, PaLM2, and Vicuna13B. To evaluate and demonstrate the utility of HANSEN, we perform Authorship Attribution (AA) & Author Verification (AV) on human-spoken datasets and conducted Human vs. AI spoken text detection using state-of-the-art (SOTA) models. While SOTA methods, such as, character ngram or Transformer-based model, exhibit similar AA & AV performance in human-spoken datasets compared to written ones, there is much room for improvement in AI-generated spoken text detection. The HANSEN benchmark is available at: https://huggingface.co/datasets/HANSEN-REPO/HANSEN
Mitigating Foreground Bias to the CMB Lensing Power Spectrum for a CMB-HD Survey
No full textA promising way to measure the distribution of matter on small scales (k ~ 10
hMpc^-1) is to use gravitational lensing of the Cosmic Microwave Background
(CMB). CMB-HD, a proposed high-resolution, low-noise millimeter survey over
half the sky, can measure the CMB lensing auto spectrum on such small scales
enabling measurements that can distinguish between a cold dark matter (CDM)
model and alternative models designed to solve problems with CDM on small
scales. However, extragalactic foregrounds can bias the CMB lensing auto
spectrum if left untreated. We present a foreground mitigation strategy that
provides a path to reduce the bias from two of the most dominant foregrounds,
the thermal Sunyaev-Zel'dovich effect (tSZ) and the Cosmic Infrared Background
(CIB). Given the level of realism included in our analysis, we find that the
tSZ alone and the CIB alone bias the lensing auto spectrum by 0.6 sigma and 1.1
sigma respectively, in the lensing multipole range of L in [5000,20000] for a
CMB-HD survey; combined these foregrounds yield a bias of only 1.3 sigma.
Including these foregrounds, we also find that a CMB-HD survey can distinguish
between a CDM model and a 10^-22 eV FDM model at the 5 sigma level. These
results provide an important step in demonstrating that foreground
contamination can be sufficiently reduced to enable a robust measurement of the
small-scale matter power spectrum with CMB-HD.Comment: 14 pages, 6 figures; power spectra and lensing covariance matrix from
this analysis are public at https://github.com/dwhan89/hdlensin
The usefulness and ergonomics of a new robotic system for flexible ureteroscopy and laser lithotripsy for treating renal stones
No full textPURPOSE: To investigate the usefulness and ergonomics of a newly developed robotic system for flexible ureteroscopy (easyUretero). MATERIALS AND METHODS: During in vitro testing, six participants performed renal stone removal four times in an artificial kidney-ureter-bladder model. Each participant manipulated a single-use digital flexible ureteroscope (LithoVue) with their hands and the robotic system, sequentially. We compared the task completion times of each participant. The ergonomics of and operational satisfaction with each procedure were assessed by questionnaires. In vivo tests evaluated the operability and safety of the robotic system in two live female pigs. We checked that all the steps of flexible lithotomy for renal stones could be completed individually. RESULTS: The task completion time with the robotic system during in vitro testing was significantly longer than with manual ureteroscopy regardless of the operator’s competence level (expert professors: 282.6±92.4 seconds vs. 73.6±43.3 seconds, p<0.001; fellows: 247.5±57.7 seconds vs. 95.8±43.7 seconds, p<0.001; residents: 281.3±111.0 seconds vs. 188.6±138.6 seconds, p<0.001). The residents took more time to remove the upper and mid caliceal stones with the robotic system. The ergonomic evaluation was better for the robotic system, but operational satisfaction was lower, and there was no statistical difference among the groups. In vivo tests showed that all the steps of robotic flexible ureteroscopy could be completed without difficulty. No safety issues were encountered during the procedure. CONCLUSIONS: The robotic system (easyUretero) was ergonomic and safe for flexible ureteroscopy and laser lithotripsy for renal stones
Distributed Feedback Master Oscillator Power Amplifier using Interface Polaritons
No full textCharacterization and simulation of an innovative solid-state distributed feedback master oscillator power amplifier (solid-state DFB MOPA) are presented, using interface polaritons (IPs) that enhance wave propagations at gain-loss interfaces in active layers. The author set up the design of the fabricated device, and a company, Freedom photonics, collaborated with us, allowing me to modify some of their designed MOPA systems. The master oscillator (MO) consists of a patterned grating on a waveguiding region to transfer only a single mode of 1.550 μm wavelength. The power amplifier (PA) is fabricated with the MO to reduce power loss and tapered to amplify a single low-power mode from the MO. This PA region has a difference from other tapered PAs, containing an unpumped central area to have additional IPs. The simulation analyzes modeling characteristics of output light power, responding to different geometric parameters. The characterization includes far-field profiles, LIV, spectrum, and FWHM of the new device measured from experiments, compared with counterparts of a standard model
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