796 results on '"William L. Smith"'
Search Results
52. On the angular effect of residual clouds and aerosols in clear-sky IR window radiance observations.
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Nicholas R. Nalli, Christopher D. Barnet, Antonia Gambacorta, Eric S. Maddy, Hua Xie, Tom King, Everette Joseph, Vernon R. Morris, and William L. Smith
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- 2012
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53. 4-D cloud water content fields derived from operational satellite data.
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William L. Smith, Patrick Minnis, Stanley G. Benjamin, and Stephen S. Weygandt
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- 2010
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54. CERES MODIS Cloud Product Retrievals for Edition 4—Part II: Comparisons to CloudSat and CALIPSO
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Patrick Minnis, William L. Smith, Christopher R. Yost, Sunny Sun-Mack, and Yan Chen
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Ice cloud ,Daytime ,Meteorology ,Cloud top ,Cloud fraction ,0211 other engineering and technologies ,02 engineering and technology ,Lidar ,Spectroradiometer ,General Earth and Planetary Sciences ,Environmental science ,Cirrus ,Electrical and Electronic Engineering ,Optical depth ,021101 geological & geomatics engineering - Abstract
Assessments of the Clouds and the Earth’s Radiant Energy System Edition 4 (Ed4) cloud retrievals are critical for climate studies. Ed4 cloud parameters are evaluated using instruments in the A-Train Constellation. Cloud-Aerosol LiDAR with Orthogonal Polarization (CALIOP) and Cloud Profiling Radar (CPR) retrievals are compared with Ed4 retrievals from the Aqua Moderate-Resolution Imaging Spectroradiometer (MODIS) as a function of the CALIOP horizontal averaging (HA) scale. Regardless of the HA scale, MODIS daytime (nighttime) water cloud fraction (CF) is greater (less) than that from CALIOP. MODIS ice CF is less than CALIOP overall, with the largest differences in polar regions. Ed4 and CALIOP retrieve the same cloud phase in 70%–98% of simultaneous observations depending on the time of day, surface conditions, HA scales, and type of cloud vertical structure. Mean cloud top height (CTH) differences for single-layer water clouds over snow-/ice-free surfaces are less than 100 m. Base altitude positive biases of 170–460 m may be impacted by CPR detection limitations. Average MODIS ice CTHs are underestimated by 70 m for some deep convective clouds and up to ~2.2 km for thin cirrus. Ice cloud base altitudes are typically underestimated (overestimated) during daytime (nighttime). MODIS and CALIOP cirrus optical depths over oceans are within 46% and 5% for daytime and nighttime observations, respectively. Ice water path differences depend on the CALIOP retrieval version and warrant further investigation. Except for daytime cirrus optical depth, Ed4 cloud property retrievals are at least as accurate as other long-term operational cloud property retrieval systems.
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- 2021
55. Thermal infrared observations of a western United States biomass burning aerosol plume.
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Sorenson, Blake T., Reid, Jeffrey S., Zhang, Jianglong, Holz, Robert E., Sr., William L. Smith, and Gumber, Amanda
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BIOMASS burning ,MODIS (Spectroradiometer) ,SMOKE plumes ,TOBACCO smoke ,AEROSOLS ,TROPOSPHERIC aerosols ,LIGHT transmission - Abstract
Biomass burning smoke particles, due to their sub-micron particle size in relation to the average thermal Infrared (TIR) wavelength, theoretically have negligible signals at the TIR channels. However, near-instantaneous longwave (LW) signatures of thick smoke plumes can be frequently observed at the TIR channels from remotely sensed data, including at 10.6 micron (IR window) as well as in water vapor-sensitive wavelengths at 7.3, 6.8, and 6.3 micron (e.g., lower, middle and upper troposphere). We systematically evaluated multiple hypotheses as to causal factors of these IR signatures of biomass burning smoke using a combination of Aqua MODerate resolution Imaging Spectroradiometer (MODIS) and Cloud and the Earth Radiant Energy System (CERES), Geostationary Operational Environmental Satellite 16/17 (GOES-16/17) Advanced Baseline Imager, and Suomi-NPP Visible Infrared Imaging Radiometer Suite (VIIRS) and Cross-track Infrared Sounder (CrIS) data. The largely clear transmission of light through wildfire smoke in the near infrared indicates that coarse or giant ash particles are unlikely to be the dominant cause. Rather, clear signals in water vapor and TIR channels suggest both co-transported water vapor injected to the mid to upper troposphere and surface cooling by the reduction of surface radiation by the plume are more significant, with the surface cooling effect of smoke aloft being the most dominant. Giving consideration of the smoke impacts onto TIR/longwave, CERES indicates large wildfire aerosol plumes are more radiatively neutral. Further, this smoke induced TIR signal may be used to map very optically thick smoke plumes, where traditional aerosol retrieval methods have difficulties. [ABSTRACT FROM AUTHOR]
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- 2023
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56. Emerging Additive Manufacturing Technology for Propulsion
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Omar R. Mireles, Erin Lanigan, Paul R. Gradl, Kevin Wheeler, Timothy M. Smith, David Scannapieco, Jeremy Iten, John D. Roehling, William L. Smith, Manyalibo J. Matthews, and Anton Du Plessis
- Published
- 2022
57. 1D Radiative Transfer Model Calculations of Solar Actinic Flux Densities with Satellite Cloud Products – Comparison with Airborne Measurements on HALO
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Arthur Kremer, Birger Bohn, Rabindra Palikonda, and William L. Smith Jr.
- Abstract
Clouds are highly variable in their structure as well as phase, resulting in a potentially large influence on actinic flux densities. Chemistry-transport models rely on accurate simulations of actinic flux densities to reproduce the essential impact of photolysis processes, thus the need for accurate radiative transfer calculations in the presence of clouds arises. Current studies show that under clear sky conditions simulated and measured UV/VIS actinic flux densities are typically within 10%, independent of wavelength. On the other hand, the impact of clouds on actinic radiation is more difficult to reproduce correctly when dependent on cloud structure, phase and position, flux densities can be significantly smaller or greater compared to clear sky conditions.Following a similar approach by Ryu et al., 2016, UV/VIS spectral actinic flux densities were calculated utilizing cloud products from geostationary satellites (NASA SatCORPS). In this work, the latest version of the libRadtran model has been used, as well as aerosol properties (MODIS, MOD08_D3), surface albedos (MODIS) and total ozone columns (TEMIS, MSR-2) from polar-orbiting satellites as key input to simulate actinic flux densities in a range 280-650 nm. The evaluation of the model results is made by comparison with measured data from several campaigns with the research aircraft HALO (High Altitude and Long Range Research Aircraft) with a total of around 90 flights.Using the NASA SatCORPS products (cloud phase, cloud optical depth, cloud top height, cloud liquid or ice water content and cloud particle size) 1-D radiative transfer calculations were conducted. Radiative properties of water clouds are reliably reproduced using look-up tables based on pre-conducted radiative transfer calculations using Mie theory. On the other hand, ice clouds and their correct parametrizations are challenging because of the wide range of possible ice crystal variations. Moreover, small-scale variations captured by the highly resolved aircraft measurements cannot be reproduced completely, due to the lower spatial and temporal resolution of satellite observations. The final intent of this study is to assess the quality of the radiative transfer modelled actinic flux densities and their potential to improve chemistry-transport models.
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- 2022
58. Threshold Concept Pedagogy for Antiracist Social Studies Teaching
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William L. Smith, Jenna Cushing-Leubner, Ryan M. Crowley, and Sara B. Demoiny
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Cultural Studies ,Pedagogy ,Sociology ,Social studies - Abstract
This conceptual article explores the use of threshold concepts to help pre-service teachers develop antiracist dispositions. Threshold concepts are “troublesome knowledge” within a discipline that ...
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- 2021
59. Observational and theoretical study of spectrally resolved ocean optical properties.
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Taiping Zhang, William L. Smith Jr., Thomas P. Charlock, C. Ken Rutledge, Zhonghai Jin, Glenn Cota, and Bryan E. Fabbri
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- 2003
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60. GIFTS - the precursor geostationary satellite component of the future Earth Observing System.
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William L. Smith, F. Wallace Harrison, D. E. Hinton, Henry E. Revercomb, Gail Bingham, R. Petersen, and J. C. Dodge
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- 2002
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61. Refractive index matched polymeric and preceramic resins for height-scalable two-photon lithography
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Matthew A. Worthington, James S. Oakdale, Jean-Baptiste Forien, Siwei Liang, Swetha Chandrasekaran, Juergen Biener, Johanna J. Schwartz, Magi Mettry, William L. Smith, Sourabh K. Saha, Brian Au, and Nicholas A. Heth
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Materials science ,business.industry ,General Chemical Engineering ,Microfluidics ,02 engineering and technology ,General Chemistry ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Multiphoton lithography ,Laser ,01 natural sciences ,0104 chemical sciences ,law.invention ,Nanolithography ,Photopolymer ,Resist ,law ,Optoelectronics ,0210 nano-technology ,business ,Nanoscopic scale ,Refractive index - Abstract
Nanofabrication techniques that can generate large and complex 3D structures with nanoscale features are becoming increasingly important in the fields of biomedicine, micro-optics, and microfluidics. Direct laser writing via two-photon polymerization (DLW-TPP) is one such technique that relies on nonlinear absorption of light to form nanoscale 3D features. Although DLW-TPP provides the required nanoscale resolution, its built height is often limited to less than a millimetre. This height limitation is driven by the need to tightly focus the laser beam at arbitrary depths within the photopolymer. This requirement necessitates matching the photopolymer's refractive index to specific values but the required techniques have not been disseminated widely in the open scientific literature. To address this knowledge gap, we test two universal, different approaches to generate refractive index-matched polymeric and preceramic resins and demonstrate their performance by printing of fine submicron features in 3D structures as tall as 2.5 mm. Specifically, we achieve index-matching by mixing commercially-available resins or covalent modification of functional monomers. This work investigates the relationship of voxel shape to RI mismatch, and presents tuning of RI through mixing and covalent modification to a nonconventional material system of preceramic resin which has never been demonstrated before. We demonstrate the material flexibility by generating 3D silicon oxycarbide structures from preceramic resists while simultaneously eliminating the part-height limitation of conventional DLW-TPP.
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- 2021
62. Hyperspectral Satellite Radiance Atmospheric Profile Information Content and Its Dependence on Spectrometer Technology
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Robert O. Knuteson, Elisabeth Weisz, Joe K. Taylor, W. P. Menzel, William L. Smith, Henry E. Revercomb, and David C. Tobin
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Atmospheric Science ,satellite remote sensing ,010504 meteorology & atmospheric sciences ,Geophysics. Cosmic physics ,Multispectral image ,0211 other engineering and technologies ,02 engineering and technology ,01 natural sciences ,Information content (IC) ,Computers in Earth Sciences ,infrared (IR) hyperspectral sensors ,TC1501-1800 ,021101 geological & geomatics engineering ,0105 earth and related environmental sciences ,Remote sensing ,Atmospheric sounding ,Spectrometer ,QC801-809 ,Hyperspectral imaging ,Numerical weather prediction ,Ocean engineering ,weather prediction ,Depth sounding ,Radiance ,Environmental science ,Satellite - Abstract
Satellite vertical atmospheric sounding was initiated more than 50 years ago and has evolved to provide the most critical component of today's global observation system. However, the operational use of today's polar orbiting satellite hyperspectral infrared (IR) observations in numerical weather prediction (NWP) has been limited to a small fraction of the radiance information being provided. On the other hand, research systems are in operation that combines high vertical resolution polar hyperspectral radiance measurements with high spatial and time resolution geostationary multispectral radiance measurements that demonstrate the promise of future geo-hyperspectral sounding observations to significantly improve the forecast location and warning time for the development of localized tornadic storms. This article has a twofold objective: 1) to demonstrate that there is much more information available in current IR sounding data, than is being used to benefit the current NWP operation and 2) to illustrate the importance of the spectrometer technology (i.e., Fourier transform vs. dispersive grating) used for achieving the vertical profile resolution required to improve both extended range and localized severe weather forecasts. These objectives are achieved by performing both theoretical physics-based radiance information content (IC) studies and empirical analyses of current hyperspectral radiance measurements. The IC studies clearly demonstrate the unique importance of longwave IR (9−15 μm) radiance observations. The empirical studies demonstrate the importance of using Fourier transform spectrometers for providing the high spectral fidelity needed to resolve the small-scale vertical features in atmospheric temperature and moisture profiles, which impact weather forecast accuracy.
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- 2021
63. Age as a moderator of attitude towards technology in the workplace: work motivation and overall job satisfaction.
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Steven M. Elias, William L. Smith, and Chet E. Barney
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- 2012
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64. Simulations of Infrared Radiances over a Deep Convective Cloud System Observed during TC4: Potential for Enhancing Nocturnal Ice Cloud Retrievals.
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Patrick Minnis, Gang Hong, J. Kirk Ayers, William L. Smith, Christopher R. Yost, Andrew J. Heymsfield, Gerald M. Heymsfield, Dennis L. Hlavka, Michael D. King, Errol Korn, Matthew J. McGill, Henry B. Selkirk, Anne M. Thompson, Lin Tian, and Ping Yang 0007
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- 2012
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65. Porting and testing NPOESS CrIMSS EDR algorithms.
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Susan Kizer, Xu Liu 0018, Allen M. Larar, William L. Smith, Daniel K. Zhou, Chris Barnet, Murty Divakarla, Guang Guo, William J. Blackwell, Robert Vincent Leslie, Laura G. Jairam, and Karen St. Jermain
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- 2010
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66. Global Land Surface Emissivity Retrieved From Satellite Ultraspectral IR Measurements.
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Daniel K. Zhou, Allen M. Larar, Xu Liu 0018, William L. Smith, Larrabee L. Strow, Ping Yang 0007, Peter Schlussel, and Xavier Calbet
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- 2011
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67. CERES Edition-2 Cloud Property Retrievals Using TRMM VIRS and Terra and Aqua MODIS Data - Part I: Algorithms.
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Patrick Minnis, Szedung Sun-Mack, David F. Young, Patrick W. Heck, Donald P. Garber, Yan Chen 0002, Douglas A. Spangenberg, Robert F. Arduini, Qing Z. Trepte, William L. Smith, Kirk Ayers, Sharon Gibson, Walter F. Miller, Gang Hong, Venkatesan Chakrapani, Yoshihide Takano, Kuo-Nan Liou, Yu Xie, and Ping Yang 0007
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- 2011
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68. CERES Edition-2 Cloud Property Retrievals Using TRMM VIRS and Terra and Aqua MODIS Data - Part II: Examples of Average Results and Comparisons With Other Data.
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Patrick Minnis, Szedung Sun-Mack, Yan Chen 0002, Mandana M. Khaiyer, Yuhong Yi, J. Kirk Ayers, Ricky R. Brown, Xiquan Dong, Sharon Gibson, Patrick W. Heck, Bing Lin, Michele L. Nordeen, Louis Nguyen, Rabindra Palikonda, William L. Smith, Douglas A. Spangenberg, Qing Z. Trepte, and Baike Xi
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- 2011
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69. Geosynchronous imaging Fourier transform spectrometer (GIFTS): Imaging and tracking capability.
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Daniel K. Zhou, Allen M. Larar, Xu Liu 0018, Robert A. Reisse, Gail E. Bingham, Lorin J. Zollinger, Joe J. Tansock, William L. Smith, Henry E. Revercomb, and Ron J. Huppi
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- 2007
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70. Observational Evidence that Radiative Heating Modifies the Life Cycle of Tropical Anvil Clouds
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William L. Smith, Joel R. Norris, Mandana M. Thieman, Blaž Gasparini, Casey J. Wall, Odran Sourdeval, Université de Lille, CNRS, Laboratoire d'Optique Atmosphérique (LOA) - UMR 8518, Laboratoire d’Optique Atmosphérique - UMR 8518 (LOA), and Institut national des sciences de l'Univers (INSU - CNRS)-Université de Lille-Centre National de la Recherche Scientifique (CNRS)
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Atmospheric Science ,Observational evidence ,010504 meteorology & atmospheric sciences ,[SDU]Sciences of the Universe [physics] ,Climatology ,Convective clouds ,Deep convection ,Diurnal effects ,Cloud microphysics ,Cloud radiative effects ,Mesoscale processes ,Environmental science ,Radiant heat ,010502 geochemistry & geophysics ,01 natural sciences ,0105 earth and related environmental sciences - Abstract
A variety of satellite and ground-based observations are used to study how diurnal variations of cloud radiative heating affect the life cycle of anvil clouds over the tropical western Pacific Ocean. High clouds thicker than 2 km experience longwave heating at cloud base, longwave cooling at cloud top, and shortwave heating at cloud top. The shortwave and longwave effects have similar magnitudes during midday, but only the longwave effect is present at night, so high clouds experience a substantial diurnal cycle of radiative heating. Furthermore, anvil clouds are more persistent or laterally expansive during daytime. This cannot be explained by variations of convective intensity or geographic patterns of convection, suggesting that shortwave heating causes anvil clouds to persist longer or spread over a larger area. It is then investigated if shortwave heating modifies anvil development by altering turbulence in the cloud. According to one theory, radiative heating drives turbulent overturning within anvil clouds that can be sufficiently vigorous to cause ice nucleation in the updrafts, thereby extending the cloud lifetime. High-frequency air motion and ice-crystal number concentration are shown to be inversely related near cloud top, however. This suggests that turbulence depletes or disperses ice crystals at a faster rate than it nucleates them, so another mechanism must cause the diurnal variation of anvil clouds. It is hypothesized that radiative heating affects anvil development primarily by inducing a mesoscale circulation that offsets gravitational settling of cloud particles.
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- 2020
71. An Adaptive Bayesian Design for Personalized Dosing in a Cancer Prevention Trial
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Lili Zhao, Zora Djuric, Mack T. Ruffin, D. Kim Turgeon, Ananda Sen, Daniel P. Normolle, Dean E. Brenner, and William L. Smith
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Epidemiology ,Bayesian probability ,Cancer Prevention Trial ,Machine learning ,computer.software_genre ,01 natural sciences ,Article ,Bayesian design ,03 medical and health sciences ,0302 clinical medicine ,Neoplasms ,Inflammatory marker ,Animals ,Medicine ,Bayesian algorithm ,030212 general & internal medicine ,Dosing ,0101 mathematics ,Trial registration ,business.industry ,010102 general mathematics ,Public Health, Environmental and Occupational Health ,Bayes Theorem ,Clinical trial ,Research Design ,Artificial intelligence ,business ,computer ,Algorithms - Abstract
INTRODUCTION: In biomarker-driven clinical trials, translational strategies typically involve moving findings from animal experiments to human trials. Typically, the translation is static, using a fixed model derived from animal experiments for the duration of the trial. But Bayesian designs, capable of incorporating information external to the experiment, provide a dynamic translational strategy. The current article demonstrates an example of such a dynamic Bayesian strategy in a clinical trial. METHODS: This study explored the effect of a personalized dose of fish oil for reducing prostaglandin E(2), an inflammatory marker linked to colorectal cancer. A Bayesian design was implemented for the dose-finding algorithm that adaptively updated a dose–response model derived from a previously completed the animal study during the clinical trial. In the initial stages of the trial, the dose–response model parameters were estimated from the rodent data. The model was updated following a Bayesian algorithm after data on every ten to 15 subjects were obtained until the model stabilized. Subjects were enrolled in the study between 2013 and 2015, and the data analysis was carried out in 2016. RESULTS: Three dosing models were used for groups of 16, 15, and 15 subjects. The mean target dose significantly decreased from 6.63 g/day (Model 1) to 4.06 g/day (Model 3) (p=0.001). Compared with the static strategy of dosing with a single model, the dynamic modeling reduced the dose significantly by about 1.38 g/day, on average. CONCLUSIONS: A Bayesian design was effective in adaptively revising the dosing algorithm, resulting in a lower pill burden. TRIAL REGISTRATION: This study is registered at www.clinicaltrials.gov NCT01860352.
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- 2020
72. Assimilation of GOES-16 Radiances and Retrievals into the Warn-on-Forecast System
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Nusrat Yussouf, Patrick S. Skinner, Kristopher M. Bedka, Rabindra Palikonda, Anthony E. Reinhart, Xuguang Wang, William L. Smith, Thomas A. Jones, and Kent H. Knopfmeier
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Atmospheric Science ,Data assimilation ,010504 meteorology & atmospheric sciences ,Meteorology ,0207 environmental engineering ,Environmental science ,Assimilation (biology) ,02 engineering and technology ,020701 environmental engineering ,01 natural sciences ,0105 earth and related environmental sciences - Abstract
The increasing maturity of the Warn-on-Forecast System (WoFS) coupled with the now operational GOES-16 satellite allows for the first time a comprehensive analysis of the relative impacts of assimilating GOES-16 all-sky 6.2-, 6.9-, and 7.3-μm channel radiances compared to other radar and satellite observations. The WoFS relies on cloud property retrievals such as cloud water path, which have been proven to increase forecast skill compared to only assimilating radar data and other conventional observations. The impacts of assimilating clear-sky radiances have also been explored and shown to provide useful information on midtropospheric moisture content in the near-storm environment. Assimilation of all-sky radiances adds a layer of complexity and is tested to determine its effectiveness across four events occurring in the spring and summer of 2019. Qualitative and object-based verification of severe weather and the near-storm environment are used to assess the impact of assimilating all-sky radiances compared to the current model configuration. We focus our study through the entire WoFS analysis and forecasting cycle (1900–0600 UTC, daily) so that the impacts throughout the evolution of convection from initiation to large upscale growth can be assessed. Overall, assimilating satellite data improves forecasts relative to radar-only assimilation experiments. The retrieval method with clear-sky radiances performs best overall, but assimilating all-sky radiances does have very positive impacts in certain conditions. In particular, all-sky radiance assimilation improved convective initiation forecast of severe storms in several instances. This work represents an initial attempt at assimilating all-sky radiances into the WoFS and additional research is ongoing to further improve forecast skill.
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- 2020
73. The leadership role of teachers and environment club coordinators in promoting ecocentrism in secondary schools: Teachers as exemplars of environmental education
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William L. Smith
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business.industry ,Education ,Deep ecology ,Environmental education ,Anthropocentrism ,Pedagogy ,Sustainability ,Sociology ,Ecocentrism ,Teacher leadership ,Club ,business ,Curriculum ,General Environmental Science - Abstract
This study of Naessian ecocentrism and anthropocentrism in three environment club coordinators/science teachers, their colleagues and some parents at three secondary schools uses deep ecology and relational fields as primary frameworks for open-ended interviews. The findings reveal new insights into the affective, cognitive and behavioural characteristics of coordinators who enhance environmental education in their schools. The work presents preliminary data on leadership among sustainability coordinators who run environment clubs. It fills a gap in the literature by showing that in addition to environmental educators requiring knowledge and attitudes regarding sustainability practices, affective qualities like connectedness and love for the environment may be important to their success as sustainability exemplars. Teachers emerge as sustainability exemplars in a relational field to implement sustainability across the secondary curriculum, galvanise students, teachers and parents to connect to the Earth, and help students, teachers and parents move away from anthropocentrism. Findings suggest that if schools commit resources and time to the coordinator’s role, students experience significant benefits by becoming closer to the Earth and more empowered to act for the environment in ways consistent with deep ecology.
- Published
- 2020
74. Controlling melt pool shape, microstructure and residual stress in additively manufactured metals using modified laser beam profiles
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Rongpei Shi, Thejaswi U. Tumkur, Bey Vrancken, John D. Roehling, Joseph T. McKeown, Manyalibo J. Matthews, William L. Smith, R.K. Ganeriwala, Tien T. Roehling, Gabriel M. Guss, and Saad A. Khairallah
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Equiaxed crystals ,0209 industrial biotechnology ,Materials science ,02 engineering and technology ,010501 environmental sciences ,Laser ,Microstructure ,01 natural sciences ,law.invention ,020901 industrial engineering & automation ,Residual stress ,law ,Thermal ,Bessel beam ,General Earth and Planetary Sciences ,Composite material ,Raster scan ,0105 earth and related environmental sciences ,General Environmental Science ,Gaussian beam - Abstract
Laser powder bed fusion has proven to be an effective additive manufacturing technology for the manufacture of complex metal components. However, the local thermal history associated with Gaussian beam, raster scan processes produces heterogeneous and spatially non-uniform microstructures that differ from those produced from conventional manufacturing and often lack optimized mechanical properties. Steep thermal gradients and high cooling rates produce large thermal strains driving residual stress fields that can negatively affect the dimensional accuracy of the as-built component. Here, we present experimental and simulation methods for controlling microstructure and residual stress through tailored laser beam profiles. Elliptical and Bessel beam profiles are shown to produce more equiaxed microstructures as compared to those of Gaussian beams, while distributed diode-based illumination profiles allow for reduced residual stresses. These experimental results are supported by high-fidelity powder-scale simulation models coupled to the cellular automata and thermomechanical models that account for macroscale residual stress.
- Published
- 2020
75. A Divergence of Interests: Critical Race Theory and White Privilege Pedagogy
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William L. Smith and Ryan M. Crowley
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Race (biology) ,Divergence (linguistics) ,Publishing ,business.industry ,Critical theory ,White privilege ,Critical race theory ,Racial bias ,Sociology ,business ,Genealogy ,Education - Abstract
Background/ContextInformed by the increasing racial disparity between the nation's predominantly White teaching force and the growing number of students of color in K–12 schools, along with the well-documented struggles that White teachers have in exploring race and racial identity, the authors critique the use of White privilege pedagogy as a strategy for promoting antiracist dispositions in White pre-service teachers.Purpose/Objective/Research Question/Focus of StudyBy deploying several concepts central to critical race theory, as well as critiques that note the shortcomings of past attempts at racial reform (Brown v. Board of Education, Voting Rights Act), the authors investigate the effectiveness of White privilege pedagogy within the teacher education setting.Research DesignTo construct our conceptual critique of White privilege pedagogy within teacher education, we reviewed the extant literature that discussed the range of shortcomings to this pedagogical approach. To create a more historical and structural critique, we demonstrated how the tenets of White privilege pedagogy conflicted with key principles of critical race theory and with lessons from past racial remedies. We contend that White privilege pedagogy arises from a racial liberalist worldview and requires an untenable convergence of interests that limits its long-term impact. We parallel our critiques of White privilege pedagogy with arguments used by critical race scholars to explain the limited impact of previous efforts at racial reform.Conclusions/RecommendationsThe authors urge teacher educators to move away from the individualized and over-essentialized representations of racism inherent to White privilege pedagogy in favor of historical, structural, and intersectional discussions of race, racism, and the construction of White privilege.
- Published
- 2020
76. Atmospheric Profile Retrievals Using Grating and Interferometer Infrared and Microwave Measurements
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H.-L. Huang, William L. Smith, and Mark S. Whipple
- Abstract
Infrared radiance spectra measured by grating and interferometer devices will be widely available in the EOS (Earth Observing System) and NPOESS (National Polar Orbiting Environmental Satellite System) era. The future European polar satellite system, METOP, is scheduled to carry an interferometer to obtain infrared spectra. The Japanese satellite ADEOS (Advanced Earth Observing Satellite) launched on August 16, 1996 is also carrying an interferometer capable of measuring infrared spectra. These future infrared measurements will all possess spectral resolutions of better than 1 cm-1 and have quasi-continuous spectral coverage in the 3 μm ~ 15 μm region. With nearly thousands of spectra measurements at any single field of view, it is important to develop an innovative retrieval algorithm which cannot only handle a large volume of measurements but can also yield high precision sounding profiles.
- Published
- 2022
77. Detecting Defective Struts in Metallic Micro-Lattices Using High Speed Melt Pool Thermal Monitoring
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Jean-Baptiste Forien, Gabe Guss, Saad A. Khairallah, William L. Smith, Philip J. Depond, Manyalibo Matthews, and Nicholas P. Calta
- Published
- 2022
78. The forgotten intermediate condylar canal : anatomical study with application to skull base surgery
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William L. Smith, Przemysław A. Pękala, Joe Iwanaga, Marios Loukas, Aaron S. Dumont, Jerzy Walocha, and R. Shane Tubbs
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Adult ,Skull Base ,Occipital Bone ,Skull ,Cadaver ,Humans ,Orthopedic Procedures ,Surgery ,Neurology (clinical) ,Neurosurgical Procedures - Abstract
The intermediate condylar canal, which lies lateral to the occipital condyles and medial to the jugular foramen, is rarely mentioned in textbooks, even those devoted to the skull base. Therefore the present anatomic study was performed to better elucidate these structures.We studied 100 adult skulls (200 sides) to better understand the prevalence and anatomy of the intermediate condylar canal.An intermediate canal was found on 6 of 200 sides (3%). On average, these canals traveled 7.1 mm lateral to the occipital condyle and had a mean of 2.2 mm posteromedial to the jugular foramen. Anteriorly, these canals opened into the external surface of the hypoglossal canal and, when present, were just medial to a paracondylar process for which there was a strong positive correlation. The length of the canals ranged from 5 to 7.8 mm. In all, there were 3 partial canals and 3 complete canals. One left canal communicated anteriorly at the confluence of the inferior opening of a septated (bifurcated) hypoglossal canal and an unnamed foramen medial to the jugular foramen. These canals were distinct from posterior condylar canals when the latter was present.Knowledge of the anatomic variants at the base of the skull may help minimize complications during surgical procedures that employ a paracondylar or transcondylar approach or approaches to the jugular foramen.
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- 2022
79. 3D Printed Polymer Composites for CO2 Capture
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Jennifer M. Knipe, William L. Bourcier, Du T. Nguyen, Sarah E. Baker, Maxwell Murialdo, Roger D. Aines, Congwang Ye, Simon H. Pang, Joshuah K. Stolaroff, William L. Smith, and Katherine Hornbostel
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Aqueous solution ,Materials science ,Inkwell ,business.industry ,General Chemical Engineering ,Composite number ,3D printing ,02 engineering and technology ,General Chemistry ,021001 nanoscience & nanotechnology ,Industrial and Manufacturing Engineering ,Solvent ,chemistry.chemical_compound ,Silicone ,020401 chemical engineering ,chemistry ,Chemical engineering ,Polymer composites ,0204 chemical engineering ,0210 nano-technology ,business ,Sodium carbonate - Abstract
We have developed polymer composite inks that may be three-dimensionally (3D) printed to produce new reactor designs for CO2 capture. These inks are composed of solid sodium carbonate particles dispersed within an uncured silicone and are printed using direct ink writing (DIW). After printing, the silicone is cured, and the structures are hydrated to form aqueous sodium carbonate domains dispersed throughout the silicone. These domains enable high CO2 absorption rates by creating domains with high surface area of solvent per unit volume in the printed structures. These results demonstrate an order-of-magnitude improvement in CO2 absorption rates relative to a liquid pool of sodium carbonate. The results from this class of composite inks demonstrate the potential for the use of 3D printing to shape new and advanced CO2 capture reactors.
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- 2019
80. Global Cloud Detection for CERES Edition 4 Using Terra and Aqua MODIS Data
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Gang Hong, Patrick Minnis, Kristopher M. Bedka, Qing Z. Trepte, S. Sun-Mack, Fu-Lung Chang, Thad Chee, Yan Chen, Zhonghai Jin, William L. Smith, and Christopher R. Yost
- Subjects
Daytime ,business.industry ,Cloud cover ,Cloud fraction ,0211 other engineering and technologies ,Cloud computing ,02 engineering and technology ,Snow ,Spectroradiometer ,Lidar ,General Earth and Planetary Sciences ,Environmental science ,Satellite ,Electrical and Electronic Engineering ,business ,021101 geological & geomatics engineering ,Remote sensing - Abstract
The Clouds and Earth’s Radiant Energy System (CERES) has been monitoring clouds and radiation since 2000 using algorithms developed before 2002 for CERES Edition 2 (Ed2) products. To improve cloud amount accuracy, CERES Edition 4 (Ed4) applies revised algorithms and input data to Terra and Aqua MODerate-resolution Imaging Spectroradiometer (MODIS) radiances. The Ed4 cloud mask uses 5–7 additional channels, new models for clear-sky ocean and snow/ice-surface radiances, and revised Terra MODIS calibrations. Mean Ed4 daytime and nighttime cloud amounts exceed their Ed2 counterparts by 0.035 and 0.068. Excellent consistency between average Aqua and Terra cloud fraction is found over nonpolar regions. Differences over polar regions are likely due to unresolved calibration discrepancies. Relative to Ed2, Ed4 cloud amounts agree better with those from the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO). CALIPSO comparisons indicate that Ed4 cloud amounts are more than or as accurate as other available cloud mask systems. The Ed4 mask correctly identifies cloudy or clear areas 90%–96% of the time during daytime over nonpolar areas depending on the CALIPSO–MODIS averaging criteria. At night, the range is 88%–95%. Accuracy decreases over land. The polar day and night accuracy ranges are 90%–91% and 80%–81%, respectively. The mean Ed4 cloud fractions slightly exceed the average for seven other imager cloud masks. Remaining biases and uncertainties are mainly attributed to errors in Ed4 predicted clear-sky radiances. The resulting cloud fractions should help CERES produce a more accurate radiation budget and serve as part of a cloud property climate data record.
- Published
- 2019
81. Cerebellar Stimulation Used in 20 Spastic Cerebral Palsy Patients (4- To 5-Year Study)
- Author
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William L. Smith
- Subjects
medicine.medical_specialty ,Physical medicine and rehabilitation ,Spastic cerebral palsy ,Cerebellar stimulation ,business.industry ,medicine ,business ,medicine.disease - Published
- 2021
82. Residual stress analysis of in situ surface layer heating effects on laser powder bed fusion of 316L stainless steel
- Author
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Michael R. Hill, Maria Strantza, Manyalibo J. Matthews, Ava S. Ashby, Bey Vrancken, John D. Roehling, Joseph T. McKeown, William L. Smith, Gabriel M. Guss, Bjørn Clausen, Donald W. Brown, and R.K. Ganeriwala
- Subjects
Technology ,STRAIN ,Materials science ,Contour method ,Neutron diffraction ,Materials Science ,Biomedical Engineering ,Residual stress ,Materials Science, Multidisciplinary ,Manufacturing Engineering ,Industrial and Manufacturing Engineering ,law.invention ,Annealing (glass) ,TI-6AL-4V ,Annealing ,Stress (mechanics) ,Engineering ,law ,Powder bed fusion ,General Materials Science ,Surface layer ,Composite material ,Engineering (miscellaneous) ,TEMPERATURE ,Diode ,Science & Technology ,Laser diode ,Laser ,THERMOMECHANICAL MODEL ,Engineering, Manufacturing ,SIMULATION - Abstract
Fabricating parts using laser powder bed fusion (LPBF) is of growing interest to many fields, ranging from medical to aerospace, but this process is often plagued with residual stresses that can reach magnitudes as high as the yield strength of the material. Previous work has demonstrated the ability to reduce residual stress during LPBF by over 90% using an in situ annealing method that makes use of large area, shaped light illumination from a set of laser diodes. In this work, an in-depth analysis of the effectiveness of this in situ residual stress reduction technique is presented. A custom LPBF system was used to fabricate 316 L stainless steel parts, and the stresses of these parts were analyzed using the contour method and neutron diffraction on various planes within the samples. These spatial measurements revealed stress reductions near the edges and base of the samples in each of the three measured orthogonal stress directions, in addition to an overall reduction in stress owing to in situ application of laser diode heating. The experimental results were found to be in excellent agreement with numerical thermomechanical simulations that captured the effects of various processing parameters. Furthermore, in cases where the annealing was only performed once every 5 layers, the residual stress was similarly reduced, which indicates that further optimization might be achieved to limit additional processing time during the builds while still relieving equivalent amounts of stress.
- Published
- 2021
83. Ultra-low-density digitally architected carbon with a strutted tube-in-tube structure
- Author
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Y. Morris Wang, Maira R. Cerón, Sanjit Bhowmick, Ling Liu, Juergen Biener, Monika M. Biener, Jip van Ham, James S. Oakdale, William L. Smith, Thomas Voisin, Jianchao Ye, Patrick Onck, Joseph Lefebvre, Leonardus Bimo Bayu Aji, John D. Roehling, and Micromechanics
- Subjects
Structural material ,Materials science ,Mechanical Engineering ,chemistry.chemical_element ,Stiffness ,Topology (electrical circuits) ,General Chemistry ,Condensed Matter Physics ,Compression (physics) ,chemistry ,Mechanics of Materials ,medicine ,General Materials Science ,Composite material ,medicine.symptom ,Porous medium ,Nanoscopic scale ,Carbon ,Beam (structure) - Abstract
Porous materials with engineered stretching-dominated lattice designs, which offer attractive mechanical properties with ultra-light weight and large surface area for wide-ranging applications, have recently achieved near-ideal linear scaling between stiffness and density. Here, rather than optimizing the microlattice topology, we explore a different approach to strengthen low-density structural materials by designing tube-in-tube beam structures. We develop a process to transform fully dense, three-dimensional printed polymeric beams into graphitic carbon hollow tube-in-tube sandwich morphologies, where, similar to grass stems, the inner and outer tubes are connected through a network of struts. Compression tests and computational modelling show that this change in beam morphology dramatically slows down the decrease in stiffness with decreasing density. In situ pillar compression experiments further demonstrate large deformation recovery after 30–50% compression and high specific damping merit index. Our strutted tube-in-tube design opens up the space and realizes highly desirable high modulus–low density and high modulus–high damping material structures. A nanoscale tube-in-tube sandwich structure is generated by a two-step templating-pyrolysis process, which strengthens the log-pile carbon architecture and slows down the decrease of stiffness with decreasing density.
- Published
- 2021
84. KC model of three customer-contact dimensions: an exploratory hospital field test.
- Author
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William L. Smith and Mohammad Chowdhury
- Published
- 2007
- Full Text
- View/download PDF
85. Experiential tourism around the world and at home: definitions and standards.
- Author
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William L. Smith
- Published
- 2006
- Full Text
- View/download PDF
86. Experiential tourism standards: the perceptions of rural tourism providers.
- Author
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William L. Smith
- Published
- 2006
- Full Text
- View/download PDF
87. Geophysical parameter retrieval and validation.
- Author
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Daniel K. Zhou and William L. Smith
- Published
- 2003
- Full Text
- View/download PDF
88. Defining optimal spatial resolution for high-spectral resolution infrared sensors.
- Author
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Hung-Lung Huang, Richard A. Frey, William L. Smith, Daniel K. Zhou, and Hal J. Bloom
- Published
- 2003
- Full Text
- View/download PDF
89. Multi-year observations of shortwave and longwave radiation at the CERES ocean validation site.
- Author
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C. K. Rutledge and William L. Smith
- Published
- 2003
- Full Text
- View/download PDF
90. Evaluation of Regional Surface Energy Budget Over Ocean Derived From Satellites
- Author
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David Painemal, Fred G. Rose, William L. Smith, Seiji Kato, and Fu-Lung Chang
- Subjects
Global and Planetary Change ,ocean surface ,Science ,atmosphere-ocean coupling ,Energy balance ,Irradiance ,Flux ,Energy flux ,General. Including nature conservation, geographical distribution ,Ocean Engineering ,climatology ,Aquatic Science ,QH1-199.5 ,Oceanography ,Atmospheric sciences ,Energy budget ,Atmosphere ,Sea surface temperature ,remote sensing ,Environmental science ,energy budget ,FNET ,Physics::Atmospheric and Oceanic Physics ,Water Science and Technology - Abstract
The energy balance equation of an atmospheric column indicates that two approaches are possible to compute regional net surface energy flux. The first approach is to use the sum of surface energy flux components Fnet,c and the second approach is to use net top-of-atmosphere (TOA) irradiance and horizontal energy transport by the atmosphere Fnet,t. When regional net energy flux is averaged over the global ocean, Fnet,c and Fnet,t are, respectively, 16 and 2 Wm–2, both larger than the ocean heating rate derived from ocean temperature measurements. The difference is larger than the estimated uncertainty of Fnet,t of 11 Wm–2. Larger regional differences between Fnet,c and Fnet,t exist over tropical ocean. The seasonal variability of energy flux components averaged between 45°N and 45°S ocean reveals that the surface provides net energy to the atmosphere from May to July. These two examples demonstrates that the energy balance can be used to assess the quality of energy flux data products.
- Published
- 2021
91. Improving the CERES SYN cloud and flux products by identifying GOES-17 scan anomalies using a convolutional neural network
- Author
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William L. Smith, Konstantin V. Khlopenkov, Michele L. Nordeen, Benjamin R. Scarino, and David R. Doelling
- Subjects
Contextual image classification ,Computer science ,business.industry ,Deep learning ,Anomaly (natural sciences) ,Broadband ,Geostationary orbit ,Cloud computing ,Satellite imagery ,Artificial intelligence ,business ,Convolutional neural network ,Remote sensing - Abstract
The NASA Clouds and the Earth’s Radiant Energy System (CERES) project relies on top-of-atmosphere (TOA) broadband fluxes derived from geostationary (GEO) satellite imagery to account for the diurnal flux variations between the CERES observation intervals, and thereby produce a synoptic gridded (SYN1deg) product based on continuous temporal observations. Consistent broadband flux derivation depends on accurate radiative property measurements and cloud retrievals, which largely determine the radiance-to-flux conversion process. Therefore, it is important to ensure a high quality of cloud property input in order to maintain a reliable broadband flux record. In Edition 4 of the CERES SYN1deg product, a robust automated image anomaly detection algorithm based on inter-line and inter-pixel differences, spatial variance, and 2-D Fourier analysis has been successful in identifying imagery with linear artifacts, but the line-by-line inspection and cleaning process must still be performed by a human. Therefore, further automation of this quality assurance process is warranted, especially considering the excessive amount of additional cleaning necessitated by the GOES-17 Advance Baseline Imager (ABI) cooling system anomaly. As such, this article highlights advancement of the CERES GEO image artifact cleaning approach based on a convolutional neural network (CNN) for classification of bad scanlines. Once trained, the CNN approach is a computationally inexpensive means to ensure greater consistency in cloud retrievals, and therefore broadband flux derivation, based on GOES-17 measurements.
- Published
- 2021
92. AIRS/AMSU/HSB on the Aqua mission: design, science objectives, data products, and processing systems.
- Author
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Hartmut Aumann, Moustafa T. Chahine, Catherine Gautier, Mitchell D. Goldberg, Eugenia Kalnay, Larry M. McMillin, Henry E. Revercomb, Philip W. Rosenkranz, William L. Smith, David H. Staelin, Larrabee L. Strow, and Joel Susskind
- Published
- 2003
- Full Text
- View/download PDF
93. AIRS/AMSU/HSB validation.
- Author
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Eric J. Fetzer, Larry M. McMillin, David C. Tobin, Hartmut Aumann, Michael R. Gunson, W. Wallace McMillan, Denise Hagan, Mark D. Hofstadter, James Yoe, David N. Whiteman, John E. Barnes, Ralf Bennartz, Holger Vömel, Von Walden, Michael Newchurch, Peter J. Minnett, Robert Atlas, Francis Schmidlin, Edward T. Olsen, Mitchell D. Goldberg, Sisong Zhou, HanJung Ding, William L. Smith, and Hank Revercomb
- Published
- 2003
- Full Text
- View/download PDF
94. Extrapolating shortwave geostationary satellite imagery of clouds into nighttime using longwave observations
- Author
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Julie Haggerty, Allyson Rugg, Daniel R. Adriaansen, and William L. Smith
- Subjects
010504 meteorology & atmospheric sciences ,Terminator (solar) ,0211 other engineering and technologies ,Longwave ,Mesoscale meteorology ,Dusk ,02 engineering and technology ,01 natural sciences ,13. Climate action ,Geostationary orbit ,Range (statistics) ,General Earth and Planetary Sciences ,Environmental science ,Satellite ,Shortwave ,021101 geological & geomatics engineering ,0105 earth and related environmental sciences ,Remote sensing - Abstract
The lack of shortwave (SW, visible, and near-infrared) geostationary satellite data at night results in degradation of many weather forecasts and real-time diagnostic products. We present a method to extrapolate SW GOES-16 advanced baseline imager data through night using nighttime longwave (LW, infrared) observations and the relationships between LW and SW data observed during the previous day. The method is not a forecast since it requires LW nighttime observations but can provide continuity through day, night, and satellite terminator hours. To provide performance statistics, the algorithm is applied during the day so the SW extrapolations can be compared to observations. Typical mean absolute errors (MAEs) range from 1.0% to 12.7% reflectance depending on the SW channel. These MAEs can be predicted using a diagnostic metric called 0-h MAE which quantifies the quality of the algorithm’s input data. In addition to quantitative error statistics, three case studies are presented, including an animation of extrapolated imagery from dusk through dawn. Considerations for future improvements include use of convolutional neural networks and/or object-based extrapolations where mesoscale features are extrapolated individually.
- Published
- 2021
95. Bempedoic Acid: A New Avenue for the Treatment of Dyslipidemia
- Author
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William L. Smith, James J. Nawarskas, and Angela Cheng-Lai
- Subjects
Statin ,Cholesterol ,medicine.drug_class ,business.industry ,Fatty Acids ,General Medicine ,Pharmacology ,Placebo ,medicine.disease ,Clinical trial ,chemistry.chemical_compound ,chemistry ,Ezetimibe ,medicine ,Humans ,lipids (amino acids, peptides, and proteins) ,Dicarboxylic Acids ,Risk factor ,Cardiology and Cardiovascular Medicine ,Adverse effect ,business ,Dyslipidemia ,medicine.drug ,Dyslipidemias ,Hypolipidemic Agents - Abstract
Uncontrolled dyslipidemia, specifically elevation of low-density lipoprotein cholesterol, is a major risk factor for developing cardiovascular disease. Currently, statin therapy remains as first-line treatment for reducing both serum cholesterol levels and cardiovascular risk. However, certain patients are unable to achieve desired serum cholesterol levels despite maximally tolerated statin therapy. As a result, several nonstatin therapy avenues have been evaluated for their potential benefits in reducing cholesterol and cardiovascular risk. Bempedoic acid is one such nonstatin therapy option, which has been explored over the past few years to potentially assist patients in further reducing serum cholesterol. Bempedoic acid is a novel prodrug that inhibits cholesterol synthesis upstream of statins by inhibiting adenosine triphosphate-citrate lyase. Bempedoic acid has been studied as a single, once daily 180 mg dose. Administered as monotherapy or in combination with statin or ezetimibe, bempedoic acid significantly reduces low-density lipoprotein cholesterol. Furthermore, bempedoic acid was generally well tolerated by patients and rates of adverse events were similar to placebo with few exceptions. Despite proven reductions in cholesterol and favorable safety profile, bempedoic acid will likely remain a third- or fourth-line agent for the treatment of dyslipidemia behind other nonstatin therapies until the improvement of cardiovascular outcomes is demonstrated in future clinical trials.
- Published
- 2021
96. Stratiform Cloud-Hydrometeor Assimilation for HRRR and RAP Model Short-Range Weather Prediction
- Author
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John M. Brown, Stanley G. Benjamin, Therese T. Ladwig, Patrick Minnis, Stephen S. Weygandt, David D. Turner, Ming Hu, Eric James, Curtis R. Alexander, William L. Smith, and Andrew K. Heidinger
- Subjects
Atmospheric Science ,Data assimilation ,Meteorology ,business.industry ,Weather prediction ,Range (statistics) ,Environmental science ,Cloud computing ,business ,Visibility ,Numerical weather prediction - Abstract
Accurate cloud and precipitation forecasts are a fundamental component of short-range data assimilation/model prediction systems such as the NOAA 3-km High-Resolution Rapid Refresh (HRRR) or the 13-km Rapid Refresh (RAP). To reduce cloud and precipitation spin-up problems, a non-variational assimilation technique for stratiform clouds was developed within the Gridpoint Statistical Interpolation (GSI) data assimilation system. One goal of this technique is retention of observed stratiform cloudy and clear 3D volumes into the subsequent model forecast. The cloud observations used include cloud-top data from satellite brightness temperatures, surface-based ceilometer data, and surface visibility. Quality control, expansion into spatial information content, and forward operators are described for each observation type. The projection of data from these observation types into an observation-based cloud-information 3D gridded field is accomplished via identification of cloudy, clear, and cloud-unknown 3D volumes. Updating of forecast background fields is accomplished through clearing and building of cloud water and cloud ice with associated modifications to water vapor and temperature. Impact of the cloud assimilation on short-range forecasts is assessed with a set of retrospective experiments in warm and cold seasons using the RAPv5 model. Short-range (1-9h) forecast skill is improved in both seasons for cloud ceiling and visibility and for 2-m temperature in daytime and with mixed results for other measures. Two modifications were introduced and tested with success: use of prognostic subgrid-scale cloud fraction to condition cloud building (in response to a high bias) and removal of a WRF-based rebalancing.
- Published
- 2021
97. Impact of Atmospheric Retrievals on Hurricane Florence/Michael Forecasts in a Regional NWP Model
- Author
-
Min Shao and William L. Smith
- Subjects
Atmospheric Science ,Geophysics ,Data assimilation ,Meteorology ,Space and Planetary Science ,Earth and Planetary Sciences (miscellaneous) ,Environmental science - Published
- 2019
98. Reducing residual stress by selective large-area diode surface heating during laser powder bed fusion additive manufacturing
- Author
-
Tien T. Roehling, Bey Vrancken, William L. Smith, Michael R. Hill, Joseph T. McKeown, Gabriel M. Guss, Manyalibo J. Matthews, and John D. Roehling
- Subjects
In situ ,Technology ,0209 industrial biotechnology ,Materials science ,PREDICTION ,Annealing (metallurgy) ,Materials Science ,Residual stress ,Biomedical Engineering ,Materials Science, Multidisciplinary ,Manufacturing Engineering ,02 engineering and technology ,CONTOUR METHOD ,Industrial and Manufacturing Engineering ,Annealing ,TI-6AL-4V ,law.invention ,Engineering ,020901 industrial engineering & automation ,law ,Thermal ,General Materials Science ,Composite material ,Microstructure ,Engineering (miscellaneous) ,Diode ,Fusion ,Science & Technology ,021001 nanoscience & nanotechnology ,Laser ,Engineering, Manufacturing ,Grain growth ,0210 nano-technology - Abstract
High residual stresses are typical in additively manufactured metals and can reach levels as high as the yield strength, leading to distortions and even cracks. Here, an in situ method for controlling residual stress during laser powder bed fusion additive manufacturing was demonstrated. By illuminating the surface of a build with homogeneously intense, shaped light from a set of laser diodes, the thermal history was controlled thereby reducing the residual stress in as-built parts. 316L stainless steel bridge-shaped parts were built to characterize the effect of in situ annealing on the residual stress. A reduction in the overall residual stress value of up to 90% was realized without altering the as-built grain structure (no grain growth). Some annealing effects on the cellular-dendritic solidification structure (patterns of higher solute content) occurred in areas that experienced prolonged exposure to elevated temperature. A comparison of the in situ process to conventional post-build annealing demonstrated equivalent stress reduction compared to rule-of-thumb thermal treatments. Use of this method could reduce or remove the need for post processing to remove residual stresses.
- Published
- 2019
99. Decomposing Shortwave Top-of-Atmosphere and Surface Radiative Flux Variations in Terms of Surface and Atmospheric Contributions
- Author
-
Hailan Wang, Sunny Sun-Mack, Seiji Kato, Fred G. Rose, Norman G. Loeb, and William L. Smith
- Subjects
Surface (mathematics) ,Atmospheric Science ,010504 meteorology & atmospheric sciences ,0211 other engineering and technologies ,02 engineering and technology ,01 natural sciences ,Atmosphere ,Radiative flux ,Climatology ,Radiative transfer ,Environmental science ,Shortwave ,021101 geological & geomatics engineering ,0105 earth and related environmental sciences - Abstract
A diagnostic tool for determining surface and atmospheric contributions to interannual variations in top-of-atmosphere (TOA) reflected shortwave (SW) and net downward SW surface radiative fluxes is introduced. The method requires only upward and downward radiative fluxes at the TOA and surface as input and therefore can readily be applied to both satellite-derived and model-generated radiative fluxes. Observations from the Clouds and the Earth’s Radiant Energy System (CERES) Energy Balanced and Filled (EBAF) Edition 4.0 product show that 81% of the monthly variability in global mean reflected SW TOA flux anomalies is associated with atmospheric variations (mainly clouds), 6% is from surface variations, and 13% is from atmosphere–surface covariability. Over the Arctic Ocean, most of the variability in both reflected SW TOA flux and net downward SW surface flux anomalies is explained by variations in sea ice and cloud fraction alone (r2 = 0.94). Compared to CERES, variability in two reanalyses—the ECMWF interim reanalysis (ERA-Interim) and NASA’s Modern-Era Retrospective Analysis for Research and Applications, version 2 (MERRA-2)—show large differences in the regional distribution of variance for both the atmospheric and surface contributions to anomalies in net downward SW surface flux. For MERRA-2 the atmospheric contribution is 17% too large compared to CERES while ERA-Interim underestimates the variance by 15%. The difference is mainly due to how cloud variations are represented in the reanalyses. The overall surface contribution in both ERA-Interim and MERRA-2 is smaller than CERES EBAF by 15% for ERA-Interim and 58% for MERRA-2, highlighting limitations of the reanalyses in representing surface albedo variations and their influence on SW radiative fluxes.
- Published
- 2019
100. Estimates of entrainment in closed cellular marine stratocumulus clouds from the MAGIC field campaign
- Author
-
William L. Smith, Michael Jensen, Edwin W. Eloranta, Michele L. Nordeen, Virendra P. Ghate, Maria P. Cadeddu, and David B. Mechem
- Subjects
Atmospheric Science ,Boundary layer ,Magic (programming) ,Atmospheric sciences ,Field campaign ,Marine stratocumulus ,Geology - Published
- 2019
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