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Ye Z.,New York University | Mao H.,New York University | Lin C.-J.,Lamar University | Youn Kim S.,Korea Institute of SandT Evaluation and Planning KISTEP
Atmospheric Chemistry and Physics | Year: 2016

A box model incorporating a state-of-the-art chemical mechanism for atmospheric mercury (Hg) cycling was developed to investigate the oxidation of gaseous elemental mercury (GEM) at three locations in the northeastern United States: Appledore Island (AI; marine), Thompson Farm (TF; coastal, rural), and Pack Monadnock (PM; inland, rural, elevated). The chemical mechanism in this box model included the most up-to-date Hg and halogen chemistry. As a result, the box model was able to simulate reasonably the observed diurnal cycles of gaseous oxidized mercury (GOM) and chemical speciation bearing distinct differences between the three sites. In agreement with observations, simulated GOM diurnal cycles at AI and TF showed significant daytime peaks in the afternoon and nighttime minimums compared to flat GOM diurnal cycles at PM. Moreover, significant differences in the magnitude of GOM diurnal amplitude (AI < TF < PM) were captured in modeled results. At the coastal and inland sites, GEM oxidation was predominated by O3 and OH, contributing 80-99% of total GOM production during daytime. H2O2-initiated GEM oxidation was significant (∼33% of the total GOM) at the inland site during nighttime. In the marine boundary layer (MBL) atmosphere, Br and BrO became dominant GEM oxidants, with mixing ratios reaching 0.1 and 1 pptv, respectively, and contributing ∼70% of the total GOM production during midday, while O3 dominated GEM oxidation (50-90% of GOM production) over the remaining day when Br and BrO mixing ratios were diminished. The majority of HgBr produced from GEMCBr was oxidized by NO2 and HO2 to form brominated GOM species. Relative humidity and products of the CH3O2CBrO reaction possibly significantly affected the mixing ratios of Br or BrO radicals and subsequently GOM formation. Gas-particle partitioning could potentially be important in the production of GOM as well as Br and BrO at the marine site. © 2016 Author(s). Source


Hu J.W.,Incheon National University | Chun S.-S.,Korea Institute of SandT Evaluation and Planning KISTEP | Noh M.-H.,POSCO
Journal of Mechanical Science and Technology | Year: 2013

One of the most significant behavioral characteristics for bolted connections results in prying action and slip in that ultimate strength capacity as well as energy dissipation can be determined based on these mechanisms. The experimental programs considered herein were performed to isolate the heavy clip-angle component of bolted moment connections so that an economic parametric investigation on prying action and slip mechanism should be conducted. So, in this paper, the proposed prying and slip model are evaluated by comparing their predictions to the results of experimental component tests with respects to failure modes, ultimate clip-angle capacity, and slip resistance. Thus, the adequacy of both proposed models generally used for connection design is validated through the comparison. © 2013 The Korean Society of Mechanical Engineers and Springer-Verlag Berlin Heidelberg. Source


Chang M.-R.,Korea Research Institute of Standards and Science | Lee W.H.,Seoul National University | Rhee W.J.,Incheon National University | Park T.H.,Seoul National University | And 2 more authors.
Korean Journal of Chemical Engineering | Year: 2013

Macrophages participate in several inflammatory pathologies such as sepsis and arthritis. We investigated the effect of silkworm hemolymph (SH) on the LPS-induced pro-inflammatory macrophages. SH inhibits LPS-induced nitric oxide (NO) production in RAW 264.7 cells and murine peritoneal macrophages. The decreased NO was reflected as a decreased amount of inducible nitric oxide synthase (iNOS) mRNA and protein. It was also found that SH inhibited pro-inflammatory cytokines, IL-1β, IL-6, and TNF-α production. To elucidate the mechanism by which SH inhibits NO production and iNOS expression, we investigated that SH suppressed IκB phosphorylation, which leads to the activation of NF-κB followed by degradation of IκB. This observation suggests that SH is a potential therapeutic modulator for inflammation-associated disorders. © 2013 Korean Institute of Chemical Engineers, Seoul, Korea. Source


Hu J.W.,Korea Institute of SandT Evaluation and Planning KISTEP | Kim D.K.,Hanyang University | Leon R.T.,Georgia Institute of Technology | Choi E.,Hongik University
ISIJ International | Year: 2011

This study presents the development of refined three dimensional (3D) finite element (FE) models with the ability to reliably simulate the mechanical behavior of full-scale bolted T-stub connections. FE models incorporated material nonlinearity, geometric nonlinear behavior, several contact interactions between faying surfaces, and prescribed displacements for generating initial bolt pretension. These FE models were used to compare experimental test results, which verify that advanced FE modeling methods make a notable contribution to reproducing the overall behavior of connections and components accurately, including the moment-rotation curves. In addition, the FE models provide some useful information which is difficult to obtain during physical testing, i.e., the distribution of stress and strain, friction forces between shear faying surfaces, and bolt reaction forces. The validated FE models are also used for additional parametric studies so as to comprehensively understand their response mechanisms. Moreover, the observation of FE analysis results supports the statement that connection models presented herein were designed to reach the yielding of connection components when the structural beam produces its full plastic moment at the plastic hinge. © 2011 ISIJ. Source


Park T.,Hanyang University | Hwang W.-S.,Inha University | Leon R.T.,Georgia Institute of Technology | Hu J.W.,Korea Institute of SandT Evaluation and Planning KISTEP
KSCE Journal of Civil Engineering | Year: 2011

Concrete Filled steel Tube (CFT) columns have been widely used in moment resisting frame structures located on non-seismic zones or high seismic zones. This paper discusses the design of such composite members based on the advanced methods which are introduced in the 2005 America Institute of Steel Construction (AISC) Specification and the 2005 AISC Seismic Provisions. These design specifications explicitly allow the use of the full plastic capacities of CFT columns, and so they require column members with more slender steel walls than ones allowed in previous specification. In addition, this study focuses particularly on damage evaluation following nonlinear frame analyses. The paper begins with an examination of design interaction curves including the length effect and the full plastic strength demand in CFT beam-column members. Based on advanced computational simulations of a series of 3-, 9-, and 20-story SAC composite-special moment frames, this paper then investigates new techniques to evaluate the damage of CFT columns during a strong earthquake. The paper concludes with some discussion of (a) step by step procedures to compute the interactive ratios of the individual CFT beam-columns and (b) member vs. seismic performance evaluation. © 2011 Korean Society of Civil Engineers and Springer-Verlag Berlin Heidelberg. Source

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