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RISS 인기검색어
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- 저자 : Meng Scott (검색결과 4 건)
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Kyu Thein,Meng Scott,Duran Hatice,Nanjundiah Kumar,Yandek Gregory R. The Polymer Society of Korea 2006 Macromolecular Research Vol.14 No.2
The present article describes the experimental and theoretical observations on the formation of holographic, polymer-dispersed, liquid crystals and electrically switchable, photonic crystals. A phase diagram of the starting mixture of nematic liquid crystal and photo-reactive triacrylate monomer was established by means of differential scanning calorimetry (DSC) and cloud point measurement. Photolithographic patterns were imprinted on the starting mixture of LC/triacrylate via multi-beam interference. A similar study was extended to a dendrimer/photocurative mixture as well as to a single component system (tetra-acrylate). Theoretical modeling and numerical simulation were carried out based on the combination of Flory-Huggins free energy of mixing and Maier-Saupe free energy of nematic ordering. The combined free energy densities were incorporated into the time-dependent Ginzburg-Landau (Model C) equations coupled with the photopolymerization rate equation to elucidate the spatio-temporal structure growth. The 2-D photonic structures thus simulated were consistent with the experimental observations. Furthermore, 3-D simulation was performed to guide the fabrication of assorted photonic crystals under various beam-geometries. Electro-optical performance such as diffraction efficiency was evaluated during the pattern photopolymerization process and also as a function of driving voltage.
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FINITE ELEMENT MODEL OF A HIGH-STATURE MALE PEDESTRIAN FOR SIMULATING CAR-TO-PEDESTRIAN COLLISIONS
Wansoo Pak,Yunzhu Meng,Jeremy Schap,Bharath Koya,Scott F. Gayzik,Costin D. Untaroiu 한국자동차공학회 2019 International journal of automotive technology Vol.20 No.3
Among road traffic deaths, pedestrian accounted for 22 % of all fatalities in the world, 26 % in Europe, and 22 % in the U.S. To investigate the injury risk of the high-stature population, a Finite Element (FE) model corresponding to a male 95th percentile (M95) pedestrian was developed and validated in this study. The model mesh was obtained by morphing the Global Human Body Models Consortium male 50th percentile pedestrian model to the reconstructed geometry of a recruited high-stature human subject. The lower extremity, shoulder, and upper body of the FE model were validated against the Post Mortem Human Surrogate (PMHS) test data recorded in valgus bending, lateral, and anterior-lateral blunt impact tests. Then, a vehicle-pedestrian impact simulation was performed using the whole-body model. In the component validations, the M95 pedestrian model showed higher stiffness than the PMHS test corridors developed for 50th percentile male. The kinematic trajectories predicted by the FE model were well-correlated to the corresponding PMHS test data in whole-body validation. Therefore, the model could be used to investigate various pedestrian accidents and/or to improve safety regulations and vehicle front-end design for high-stature pedestrian protection.
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Lennartson, Elizabeth M.,Wang, Jun,Gu, Juping,Castro Garcia, Lorena,Ge, Cui,Gao, Meng,Choi, Myungje,Saide, Pablo E.,Carmichael, Gregory R.,Kim, Jhoon,Janz, Scott J. Copernicus GmbH 2018 Atmospheric Chemistry and Physics Vol.18 No.20
<P><p><strong>Abstract.</strong> Spatial distribution of diurnal variations of aerosol properties in South Korea, both long term and short term, is studied by using 9 AERONET (AErosol RObotic NETwork) sites from 1999 to 2017 and an additional 10 sites during the KORUS-AQ (Korea-United States Air Quality) field campaign in May and June of 2016. The extent to which the WRF-Chem (Weather Research and Forecasting coupled with Chemistry) model and the GOCI (Geostationary Ocean Color Imager) satellite retrieval can describe these variations is also analyzed. On a daily average, aerosol optical depth (AOD) at 550<span class='thinspace'></span>nm is 0.386 and shows a diurnal variation of 20 to <span class='inline-formula'>−30</span><span class='thinspace'></span>% in inland sites, which is larger than the AOD of 0.308 and diurnal variation of <span class='inline-formula'>±20</span><span class='thinspace'></span>% seen in coastal sites. For all the inland and coastal sites, AERONET, GOCI, and WRF-Chem, and observed PM<span class='inline-formula'><sub>2.5</sub></span> (particulate matter with aerodynamic diameter less than 2.5<span class='thinspace'></span><span class='inline-formula'>µ</span>m) data generally show dual peaks for both AOD and PM<span class='inline-formula'><sub>2.5</sub></span>, one in the morning (often at <span class='inline-formula'>∼08</span>:00-10:00<span class='thinspace'></span>KST, Korea Standard Time, especially for PM<span class='inline-formula'><sub>2.5</sub>)</span> and another in the early afternoon (<span class='inline-formula'>∼14</span>:00<span class='thinspace'></span>KST, albeit for PM<span class='inline-formula'><sub>2.5</sub></span> this peak is smaller and sometimes insignificant). In contrast, Ångström exponent values in all sites are between 1.2 and 1.4 with the exception of the inland rural sites having smaller values near 1.0 during the early morning hours. All inland sites experience a pronounced increase in the Ångström exponent from morning to evening, reflecting an overall decrease in particle size in daytime. To statistically obtain the climatology of diurnal variation of AOD, a minimum requirement of <span class='inline-formula'>∼2</span> years of observation is needed in coastal rural sites, twice as long as that required for the urban sites, which suggests that the diurnal variation of AOD in an urban setting is more distinct and persistent. While Korean GOCI satellite retrievals are able to consistently capture the diurnal variation of AOD (although it has a systematically low bias of 0.04 on average and up to 0.09 in later afternoon hours), WRF-Chem clearly has a deficiency in describing the relative change of peaks and variations between the morning and afternoon, suggesting further studies for the diurnal profile of emissions. Furthermore, the ratio between PM<span class='inline-formula'><sub>2.5</sub></span> and AOD in WRF-Chem is persistently larger than the observed counterparts by 30<span class='thinspace'></span>%-50<span class='thinspace'></span>% in different sites, but spatially no consistent diurnal variation pattern of this ratio can be found. Overall, the relatively small diurnal variation of PM<span class='inline-formula'><sub>2.5</sub></span> is in high contrast with large AOD diurnal variation, which suggests the large diurnal variation of AOD-PM<span class='inline-formula'><sub>2.5</sub></span> relationships (with the PM<span class='inline-formula'><sub>2.5</sub></span><span class='thinspace'></span><span class='inline-formula'>∕</span><span class='thinspace'></span>AOD ratio being largest in the early morning, decreasing around noon, and increasing in late afternoon) and, therefore, the need to use AOD from<span id='page15126'/> geostationary satellites to constrain either modeling or estimate of surface PM<span class='inline-formula'><sub>2.5</sub></span> for air quality application.</p> </P>
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