60 research outputs found
Flexible highly-effective energy harvester via crystallographic and computational control of nanointerfacial morphotropic piezoelectric thin film
No full textControlling the properties of piezoelectric thin films is a key aspect for designing highly efficient flexible electromechanical devices. In this study, the crystallographic phenomena of PbZr1-x Ti (x) O-3 (PZT) thin films caused by distinguished interfacial effects are deeply investigated by overlooking views, including not only an experimental demonstration but also ab initio modeling. The polymorphic phase balance and crystallinity, as well as the crystal orientation of PZT thin films at the morphotropic phase boundary (MPB), can be stably modulated using interfacial crystal structures. Here, interactions with MgO stabilize the PZT crystallographic system well and induce the texturing influences, while the PZT film remains quasi-stable on a conventional Al2O3 wafer. On the basis of this fundamental understanding, a high-output flexible energy harvester is developed using the controlled-PZT system, which shows significantly higher performance than the unmodified PZT generator. The voltage, current, and power densities are improved by 556%, 503%, and 822%, respectively, in comparison with the previous flexional single-crystalline piezoelectric device. Finally, the improved flexible generator is applied to harvest tiny vibrational energy from a real traffic system, and it is used to operate a commercial electronic unit. These results clearly indicate that atomic-scale designs can produce significant impacts on macroscopic applications.
Wavelength-decoupled geometric metasurfaces by arbitrary dispersion control
No full textConventional multicolor metaholograms suffer from the fundamental limitations of low resolution and irreducible noise because the unit structure functionality is still confined to a single wavelength. Here, we propose wavelength-decoupled metasurfaces that enables to control chromatic phase responses independently in a full range from 0 to 2�� for each wavelength. The propagation phase associated with the geometric phase of rectangular dielectric nanostructures plays a critical role to embed a dual phase response into a single nanostructure. A multicolor metahologram is also demonstrated to verify the feasibility of our method that breaks through the fundamental constraints of conventional multicolor metaholograms. Our approach can be extended to achieve complete control of chromatic phase responses in the visible for general dual-wavelength diffractive optical elements. ? 2019, The Author(s).11Ysciescopu
Trend Analysis of GPS Precipitable Water Vapor Above South Korea Over the Last 10 Years
No full textWe analyzed global positioning system (GPS)-derived precipitable water vapor (PWV) trends of the Korea Astronomy
and Space Science Institute 5 stations (Seoul, Daejeon, Mokpo, Milyang, Sokcho) where Korea Meteorological Administration
meteorological data can be obtained at the same place. In the least squares analysis, the GPS PWV time series
showed consistent positive trends (0.11 mm/year) over South Korea from 2000 to 2009. The annual increase of GPS PWV
was comparable with the 0.17 mm/year and 0.02 mm/year from the National Center for Atmospheric Research Earth
Observing Laboratory and Atmospheric InfraRed Sounder, respectively. For seasonal analysis, the increasing tendency
was found by 0.05 mm/year, 0.16 mm/year, 0.04 mm/year in spring (March-May), summer (June-August) and winter
(December-February), respectively. However, a negative trend (-0.14 mm/year) was seen in autumn (September-November).
We examined the relationship between GPS PWV and temperature which is the one of the climatic elements.
Two elements trends increased during the same period and the correlation coefficient was about 0.8. Also, we found the
temperature rise has increased more GPS PWV and observed a stronger positive trend in summer than in winter. This is
characterized by hot humid summer and cold dry winter of Korea climate and depending on the amount of water vapor
the air contains at a certain temperature. In addition, it is assumed that GPS PWV positive trend is caused by increasing
amount of saturated water vapor due to temperature rise in the Korean Peninsula. In the future, we plan to verify GPS
PWV effectiveness as a tool to monitor changes in precipitable water through cause analysis of seasonal trends and indepth/
long-term comparative analysis between GPS PWV and other climatic elements
PRESENTING SEMANTIC CHARACTERISTICS OF PERCEPTION IN VERBS IN DIFFERENT RUSSIAN LANGUAGE DICTIONARIES
No full textThe article examines main characteristics of definitions of Russian verbs with perception semantics through in Russian language dictionaries. The author characterizes verbs and their nominations in dictionaries to find similarities and differencies between word definition
Characteristics of flow velocity and flame speed in a turbulent channel flow for lean hydrogen flames
No full textDirect numerical simulations of lean premixed V-shaped hydrogen flames in a turbulent channel flow were conducted to study the characteristics of flow velocity and flame speed in lean hydrogen flames. In addition, a robust method to extract the laminar flame speed (SL) and the flow velocity just upstream of the flame front, called the approaching flow velocity (uapp) on a moving flame, was developed using the G-equation framework. The results show that SL and uapp are considerably affected by the flame front topology. The flame front is categorized into (i) the front-facing flame bulge (FFB), which refers to regions where the flame front is convex toward reactants and faces upstream, and (ii) the flame cusps (FC), which refer to regions with negative curvature. Since flashback corresponds to the relative movement of the flame, the characteristics of flashback can be studied intuitively by investigating the correlation between SL and uapp. The analysis employs a direct flashback indicator, termed the flashback velocity (uFB), defined as the difference between the x-components of the approaching flow velocity (uapp,x) and the flame speed (SL,x). An analysis of the quantified probabilities shows that uFB is scattered and can become negative (local flashback), which occurs mainly in FC regions. Flames in FC regions cannot cause global flame flashback, as flame cusps are inherently located on the rear side of the flame and are quickly destroyed by flame folding. Conversely, uFB in FFB regions tends to be skewed negatively, implying that FFB would propagate upstream relative to the average flame movement. When the flame in FFB regions propagates upstream, its topology remains bulged and continues to propagate upstream, meaning that negative uFBin FFB regions would be a strong attractor for global flame flashback.
All-Sky 1 km MODIS Land Surface Temperature Reconstruction Considering Cloud Effects Based on Machine Learning
No full textOpen AccessArticle
All-Sky 1 km MODIS Land Surface Temperature Reconstruction Considering Cloud Effects Based on Machine Learning
by Dongjin ChoORCID,Dukwon Bae,Cheolhee YooORCID,Jungho Im *ORCID,Yeonsu LeeORCID andSiwoo LeeORCID
Department of Urban and Environmental Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan 44919, Korea
*
Author to whom correspondence should be addressed.
Academic Editor: Anand Inamdar
Remote Sens. 2022, 14(8), 1815; https://doi.org/10.3390/rs14081815
Received: 9 February 2022 / Revised: 5 April 2022 / Accepted: 7 April 2022 / Published: 9 April 2022
(This article belongs to the Special Issue Land Surface Temperature Estimation Using Remote Sensing)
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Abstract
A high spatio-temporal resolution land surface temperature (LST) is necessary for various research fields because LST plays a crucial role in the energy exchange between the atmosphere and the ground surface. The moderate-resolution imaging spectroradiometer (MODIS) LST has been widely used, but it is not available under cloudy conditions. This study proposed a novel approach for reconstructing all-sky 1 km MODIS LST in South Korea during the summer seasons using various data sources, considering the cloud effects on LST. In South Korea, a Local Data Assimilation and Prediction System (LDAPS) with a relatively high spatial resolution of 1.5 km has been operated since 2013. The LDAPS model???s analysis data, binary MODIS cloud cover, and auxiliary data were used as input variables, while MODIS LST and cloudy-sky in situ LST were used together as target variables based on the light gradient boosting machine (LightGBM) approach. As a result of spatial five-fold cross-validation using MODIS LST, the proposed model had a coefficient of determination (R2) of 0.89???0.91 with a root mean square error (RMSE) of 1.11???1.39 ??C during the daytime, and an R2 of 0.96???0.97 with an RMSE of 0.59???0.60 ??C at nighttime. In addition, the reconstructed LST under the cloud was evaluated using leave-one-station-out cross-validation (LOSOCV) using 22 weather stations. From the LOSOCV results under cloudy conditions, the proposed LightGBM model had an R2 of 0.55???0.63 with an RMSE of 2.41???3.00 ??C during the daytime, and an R2 of 0.70???0.74 with an RMSE of 1.31???1.36 ??C at nighttime. These results indicated that the reconstructed LST has higher accuracy than the LDAPS model. This study also demonstrated that cloud cover information improved the cloudy-sky LST estimation accuracy by adequately reflecting the heterogeneity of the relationship between LST and input variables under clear and cloudy skies. The reconstructed all-sky LST can be used in a variety of research applications including weather monitoring and forecasting
Corrigendum: Proceedings of the 12th annual deep brain stimulation think tank: cutting edge technology meets novel applications
No full textIn the published article, there was an error in the author list and author Sarah-Anna Hescham was erroneously excluded. The corrected author list appears below. “Alfonso Enrique Martinez-Nunez 1*, Christopher J. Rozell 2, Simon Little 3, Huiling Tan 4, Stephen L. Schmidt 5, Warren M. Grill 5,6, Miroslav Pajic 5, Dennis A. Turner 5,6,7, Coralie de Hemptinne 1, Andre Machado 8,9, Nicholas D. Schiff 10, Abbey S. Holt-Becker 11, Robert S. Raike 11, Mahsa Malekmohammadi 12,13, Yagna J. Pathak 14, Lyndahl Himes 14, David Greene 15, Lothar Krinke 16,17, Mattia Arlotti 16, Lorenzo Rossi 16, Jacob Robinson 18,19, Bahne H. Bahners 20,21,22, Vladimir Litvak 23, Luka Milosevic 24,25, Saadi Ghatan 26,27, Frederic L. W. V. J. Schaper 20, Michael D. Fox 20, Nicholas M. Gregg 28, Cynthia Kubu 8, James J. Jordano 29,30,31, Nicola G. Cascella 32, YoungHoon Nho 33, Casey H. Halpern 33,34, Helen S. Mayberg 35,36,37, Ki Sueng Choi 35,36, Haneul Song 35, Jungho Cha 35, Sankaraleengam Alagapan 2, Nico U. F. Dosenbach 38,39,40,41,42,43, Evan M. Gordon 44, Jianxun Ren 45, Hesheng Liu 45,46, Lorraine V. Kalia 47,48, Sarah-Anna Hescham 49,50,51, Dorian M. Kusyk 1, Adolfo Ramirez-Zamora 1, Kelly D. Foote 1, Michael S. Okun 1 and Joshua K. Wong 1.” The authors apologize for this error and state that this does not change the scientific conclusions of the article in any way. The original article has been updated.</p
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No full textRecently, natural and anthropogenic disasters have rapidly increased due to the on-going climate change and various human activities. Remote sensing (RS) technology enables the continuous monitoring and rapid detection of disastrous events thanks to its advantages covering vast areas at high temporal resolution. Moreover, RS technology has been very actively used in disaster monitoring and assessment since cluster- and micro-satellites and drones were introduced and became popular. In this special issue, nine papers were introduced, including the processing and applications of remote sensing data for monitoring, assessment, and prediction of various natural disasters. These papers are expected to serve as useful references for disaster management in the future
Turbulent Flame Speed and Turbulent Markstein Length in the Near Field of a Harmonically Oscillating Flame
No full textThis study investigates turbulent flame speed and turbulent Markstein length using analytic and numerical methods. Using asymptotic analysis on harmonically oscillating flames, explicit expressions for the un-stretched turbulent flame speed and the turbulent Markstein length are derived. Numerical simulations using the 3D level-set method were conducted on the parameters of laminar flame speed, amplitude of oscillation of the flame holder, turbulence intensity, and longitudinal length scale of the flow. Results show that with distance downstream the un-stretched turbulent flame speed increases parabolically and Markstein length increases linearly. The explicit expressions are consistent with simulation results and offer insight into flame dynamics in the near field. In the far field, the numerical simulations show saturation of the un-stretched turbulent flame speed and the turbulent Markstein length, which are not captured by the asymptotic analysis.</p
Dysautonomia Is Linked to Striatal Dopamine Deficits and Regional Cerebral Perfusion in Early Parkinson Disease
No full textPurpose: The aim of this study was to investigate the association between autonomic dysfunction and striatal dopamine depletion or metabolic changes in de novo Parkinson disease (PD).
Methods: Based on the Composite Autonomic Severity Score (CASS), patients with de novo PD were classified into PD with (PD-AUT+) and without autonomic dysfunction (PD-AUT-) groups. We compared the dopamine transporter (DAT) availability in the striatum by quantitatively measuring F-FP-CIT PET between both groups. We also assessed the association between DAT availability and the CASS. In addition, we compared regional uptake in early-phase images of F-FP-CIT PET as well as cortical thickness between the PD-AUT+ and PD-AUT- groups.
Results: The PD-AUT+ group had significantly lower DAT availability in all striatal subregions than did the PD-AUT- group. The total CASS was significantly correlated with DAT availability in all striatal subregions. In addition, the subscores of the adrenergic component were correlated with DAT availability in all striatal subregions. The subscores of the cardiovagal component were negatively correlated with DAT availability in the caudate and ventral striatum. In early-phase F-FP-CIT PET, the PD-AUT+ group exhibited decreased regional perfusion in the parieto-occipital areas and increased regional perfusion in the pallidothalamic, pontocerebellar, inferior frontal, and primary motor areas compared with the PD-AUT- group. There were no regions of different cortical thickness between the PD groups.
Conclusions: The present study revealed that autonomic dysfunction is closely linked to striatal dopamine depletion and prominent PD-related perfusion patterns in de novo PD, suggesting a greater pathological burden in patients with dysautonomia.restrictio
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