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Aerosol concentrations and composition in the North Pacific marine boundary layer
Choi, Yongjoo,Rhee, Tae Siek,Collett Jr., Jeffrey L.,Park Jr., Taehyun,Park Jr., Seung-Myung,Seo Jr., Beom-Keun,Park Jr., Gyutae,Park Jr., Keyhong,Lee Jr., Taehyoung Elsevier 2017 Atmospheric environment Vol.171 No.-
<P>Ship-borne measurements of inorganic and organic aerosols, including methanesulfonic acid (MSA), were conducted over the Northern Pacific using a High Resolution Time of Flight Aerosol Mass Spectrometer (AMS). This study, conducted aboard the Korean ice breaker R/V Araon, was part of the SHIP borne Pole-to-Pole Observations (SHIPPO) project. Based on air mass source region, the cruise track could be divided into five sections. Overall, the South Asia and Northern Japan ship transects showed higher aerosol concentrations due to continental pollution and biomass burning sources, respectively. In all five regions, the average mass concentrations of sulfate and organic aerosols (OA) were much higher than concentrations of nitrate and ammonium. Positive matrix factorization (PMF) analysis distinguished two organic aerosol factors as hydrocarbon-like and oxidized OA (HOA and OOA). HOA peaked in South Asia under the influence of anthropogenic pollution source areas, such as China and Korea, and generally decreased with increasing latitude across the full study region. OOA concentrations peaked in Northern Japan near the Tsugaru Strait and appear to reflect fine particle contributions from biomass burning. The mean HOA concentration in the clean marine area (Aleutian Island to Siberia) was 0.06 mu g/m(3) and comprised approximately 8% of the OA mass fraction. The highest MSA concentrations peaked in the Aleutian Islands at nearly 15 mu g/m(3), suggesting influence from higher dimethyl sulfide (DMS) emissions resulting from biological nutrient uptake during summer. The MSA/sulfate ratio, an indicator of the relative fine particle contributions of DMS and anthropogenic sources, revealed a sharp gradient as the ship approached the clean marine areas where the dominance of DMS increased. The patterns in OOA, HOA, and MSA concentrations found in this study provide a better understanding of the characteristics of inorganic and organic aerosols in the Northern Pacific Ocean. (C) 2017 Elsevier Ltd. All rights reserved.</P>
Park, Shin-Young,Lee, Hyo-Jung,Kang, Jeong-Eon,Lee, Taehyoung,Kim, Cheol-Hee Elsevier 2018 Atmospheric environment Vol.172 No.-
<P>The online model, Weather Research and Forecasting Model with Chemistry (WRF-Chem) is employed to interpret the effects of aerosol-cloud-precipitation interaction on mesoscale meteorological fields over Northeast Asia during the Megacity Air Pollution Study-Seoul (MAPS-Seoul) 2015 campaign. The MAPS-Seoul campaign is a pre-campaign of the Korea-United States Air Quality (KORUS-AQ) campaign conducted over the Korean Peninsula. We validated the WRF-Chem simulations during the campaign period, and analyzed aerosol-warm cloud interactions by diagnosing both aerosol direct, indirect, and total effects. The results demonstrated that aerosol directly decreased downward shortwave radiation up to -44% (-282 W m(-2)) for this period and subsequently increased downward longwave radiation up to + 15% (similar to 52 W m(-2)) in the presence of low-level clouds along the thematic area. Aerosol increased cloud fraction indirectly up to similar to 24% with the increases of both liquid water path and the droplet number mixing ratio. Precipitation properties were altered both directly and indirectly. Direct effects simply changed cloud-precipitation quantities via simple updraft process associated with perturbed radiation and temperature, while indirect effects mainly suppressed precipitation, but sometimes increased precipitation in the higher relative humidity atmosphere or near vapor-saturated condition. The total aerosol effects caused a time lag of the precipitation rate with the delayed onset time of up to 9 h. This implies the importance of aerosol effects in improving mesoscale precipitation rate prediction in the online approach in the presence of non-linear warm cloud.</P>
Taehyoung Kim,Sung-Ho Jin,Jongwook Park,Kwon Taek Lim,Sang Youl Kim,Yeong-Soon Gal 한국공업화학회 2020 Journal of Industrial and Engineering Chemistry Vol.87 No.-
A new ionic polyacetylene having perfluorinated benzyl substituent, poly(2-ethynyl-N-heptafluor-obenzylpyridinium iodide), was synthesized via the direct polymerization of the quaterinazed acetylenicpyridinium monomers. The polymerization proceeded homogeneously without any additional initiatoror catalyst to give a moderate yield of polymer. The results of instrumental analyses on the molecularstructure of polymer revealed that the polymer have polyacetylene backbone system with Nheptafluorobenzylicpyridiniumiodide as substituent. The photoluminescence (PL) spectra of polymerexhibited that the PL peak is located at 550 nm, corresponding to a photon energy of 2.26 eV. Theirreversible electrochemical behaviors of polymer between the doped and undoped peaks were observedin the cyclic voltammograms of polymer. The initial oxidation and reduction of poly(EHFBPI) occurred at0.53 V and -0.75 V (vs Ag/AgNO3). HOMO level of poly(EHFBPI) was 5.27 eV.
Traffic convexity aware cellular networks: a vehicular heavy user perspective
Taehyoung Shim,Jihong Park,Seung-Woo Ko,Seong-Lyun Kim,Beomhee Lee,Jingu Choi IEEE 2016 IEEE wireless communications Vol.23 No.1
<P>Rampant mobile traffic increase in modern cellular networks is largely due to large-sized multimedia contents. Recent advancements in smart devices as well as radio access technologies promote the consumption of bulky content, even for passengers in moving vehicles, referred to as vehicular heavy users. In this article the emergence of vehicular heavy user traffic is observed by field experiments conducted in 2012 and 2015 in Seoul, Korea. The experiments reveal that such traffic is becoming dominant, as shown by the 8.62 times increase in vehicular heavy user traffic while total traffic increased just 3.04 times. To resolve this so-called VHP, we propose a cell association algorithm that exploits user demand diversity for different velocities. This user traffic pattern is discovered first by our field trials, which is convex-shaped over velocity, that is, walking user traffic is less than stationary or vehicular user traffic. As VHP becomes severe, our numerical evaluation verifies that the proposed cell association outperforms in practice a well-known load balancing association, cell range expansion. In addition to cell association, several complementary techniques are suggested in line with the technical trend toward 5G.</P>