Output-feedback online optimal control for a class of nonlinear systems

In this paper an output-feedback model-based reinforcement learning (MBRL) method for a class of second-order nonlinear systems is developed. The control technique uses exact model knowledge and integrates a dynamic state estimator within the model-based reinforcement learning framework to achieve output-feedback MBRL. Simulation results demonstrate the efficacy of the developed method

Opheodrys aestivus

Number of Pages: 14Integrative BiologyGeological Science

Multimodal dynamics : self-supervised learning in perceptual and motor systems

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2006.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Includes bibliographical references (leaves 178-192).This thesis presents a self-supervised framework for perceptual and motor learning based upon correlations in different sensory modalities. The brain and cognitive sciences have gathered an enormous body of neurological and phenomenological evidence in the past half century demonstrating the extraordinary degree of interaction between sensory modalities during the course of ordinary perception. We develop a framework for creating artificial perceptual systems that draws on these findings, where the primary architectural motif is the cross-modal transmission of perceptual information to enhance each sensory channel individually. We present self-supervised algorithms for learning perceptual grounding, intersensory influence, and sensorymotor coordination, which derive training signals from internal cross-modal correlations rather than from external supervision. Our goal is to create systems that develop by interacting with the world around them, inspired by development in animals. We demonstrate this framework with: (1) a system that learns the number and structure of vowels in American English by simultaneously watching and listening to someone speak. The system then cross-modally clusters the correlated auditory and visual data.(cont.) It has no advance linguistic knowledge and receives no information outside of its sensory channels. This work is the first unsupervised acquisition of phonetic structure of which we are aware, outside of that done by human infants. (2) a system that learns to sing like a zebra finch, following the developmental stages of a juvenile zebra finch. It first learns the song of an adult male and then listens to its own initially nascent attempts at mimicry through an articulatory synthesizer. In acquiring the birdsong to which it was initially exposed, this system demonstrates self-supervised sensorimotor learning. It also demonstrates afferent and efferent equivalence - the system learns motor maps with the same computational framework used for learning sensory maps.by Michael Harlan Coen.Ph.D

Prevalence of Periodontitis and Associated Factors among Pregnant Women: A cross sectional survey in Southern Province, Rwanda

Background The literature has shown the relationship between maternal periodontitis and complications associated with pregnancy. Thus, prevalence estimates and risk factor identification for periodontitis during pregnancy in Rwanda are paramount. Aim The aim of the current study was to determine the prevalence of periodontitis and identify related risk factors among pregnant women in Rwanda. Methods A cross sectional study was conducted to determine the prevalence of periodontal diseases in a convenience sample of 400 pregnant women in the Southern Province of Rwanda. A logistic regression analysis using a hierarchical approach was performed to assess the risk factors for periodontal disease. Socio demographic factors were put in the regression model first followed by a second step for other potential factors. Results The overall prevalence of periodontitis was 60.5%. Multivariable logistic regression showed that age OR=2.48 (95% CI. 1.18-5.22), education level OR=82.15 (95% CI. 8.21-822.11), socio economic status OR=2.28 (95% CI. 1.49-6.62), employment status OR=7.3 (95% CI. 1.38-38.74, and tobacco use OR=6.89 (95% CI. 1.78-60.65) were significantly associated with periodontitis. Conclusion Periodontitis appears to be a common problem among pregnant women in Rwanda. Risk factor screening could help identify pregnant women at higher risk of periodontal disease. Rwanda J Med Health Sci 2021;4(1):131-15

Atmospheric oxidation chemistry and ozone production: Results from SHARP 2009 in Houston, Texas

This study considers whether spikes in nitrate in snow sampled at Summit, Greenland, from August 2000 to August 2002 are related to solar proton events. After identifying tropospheric sources of nitrate on the basis of correlations with sulfate, ammonium, sodium, and calcium, we use the three-dimensional global Whole Atmosphere Community Climate Model (WACCM) to examine unaccounted for nitrate spikes. Model calculations confirm that solar proton events significantly impact HOx, NOx, and O3 levels in the mesosphere and stratosphere during the weeks and months following the major 9 November 2000 solar proton event. However, solar proton event (SPE)-enhanced NOy calculated within the atmospheric column is too small to account for the observed nitrate peaks in surface snow. Instead, our WACCM results suggest that nitrate spikes not readily accounted for by measurement correlations are likely of anthropogenic origin. These results, consistent with other recent studies, imply that nitrate spikes in ice cores are not suitable proxies for individual SPEs and motivate the need to identify alternative proxies

Student and Faculty Perceptions of Live Synchronous Distance Education for Allied Health Students Following Program Expansion to a Rural Campus

Background & Purpose: Distance education (DE) is a means to meet allied health workforce needs in rural locations where healthcare worker shortages are apparent. Five allied health programs were expanded to a rural campus teaching synchronously using distance education technology. The purpose of this convergent parallel mixed methods study was to explore perceptions of allied health students and faculty at two campus locations. Methods: Quantitative and qualitative information were collected through a survey of students and faculty (physical therapy, physician assistant, and medical imaging [diagnostic medical sonography, radiography, magnetic resonance imaging] programs). Both campuses served as live and distance sites depending on instructor location and area of content expertise. For example, morning courses may be taught live from one campus, and afternoon classes taught live from the other campus. Only one program, physical therapy, offered labs by distance education. Response distributions were compared for questions by campus using Cochran-Armitage trend tests and analyzed de-identified qualitative comments using constant comparisons to establish themes. Results: Student (n=121) and faculty (n=19) mostly agreed distance education technology was effective for teaching and learning. Significant differences were found in student opinions about receiving a similar educational experience between the two campuses. More students at the Main campus somewhat or strongly disagreed (n=34, 37%) it was similar compared to the Rural campus (n= 5, 17%, p=0.024). There were no comments specifically related to the physical therapy lab experience. Open-ended comment themes included training, purposeful engagement of both campus locations, and setting clear expectations. Conclusions: Although differences in learning experiences exist between the main and rural campus locations; the results indicated using distance education technology is an effective means to deliver the curriculum. Both students and faculty commented about the lack of experience with the educational technology before implementation. Synchronous, distance education offers the opportunity for program expansion and effective delivery of curriculum content. Using the results of this study can enhance future education in allied health professions using synchronous distance education technology

Nitrate deposition to surface snow at Summit, Greenland, following the 9 November 2000 solar proton event

Abstract This study considers whether spikes in nitrate in snow sampled at Summit, Greenland, from August 2000 to August 2002 are related to solar proton events. After identifying tropospheric sources of nitrate on the basis of correlations with sulfate, ammonium, sodium, and calcium, we use the three-dimensional global Whole Atmosphere Community Climate Model (WACCM) to examine unaccounted for nitrate spikes. Model calculations confirm that solar proton events significantly impact HOx, NOx, and O3 levels in the mesosphere and stratosphere during the weeks and months following the major 9 November 2000 solar proton event. However, solar proton event (SPE)-enhanced NOy calculated within the atmospheric column is too small to account for the observed nitrate peaks in surface snow. Instead, our WACCM results suggest that nitrate spikes not readily accounted for by measurement correlations are likely of anthropogenic origin. These results, consistent with other recent studies, imply that nitrate spikes in ice cores are not suitable proxies for individual SPEs and motivate the need to identify alternative proxies. Key Points A global model simulates nitrate deposition from solar proton events Soluble ion correlations in Summit snow identify tropospheric sources of nitrate Nitrate ions in snow are found not to be a good proxy for solar proton events