김재석 교수

Variations of mixing state and chemical constituents of Asian dust (AD) particles having different transport pathways were investigated by measuring hygroscopicity and volatility of size-selected (1 μm) dust particles, and their morphology and elemental composition in Gwangju, Korea. Also, hygroscopicity and volatility of possible candidate chemical species that can be included in the dust particles was measured in a laboratory for comparison with field data. A significant amount of dust particl

Abstract. The physical characteristics of aerosol particles during particle bursts observed at King Sejong Station in the Antarctic Peninsula from March 2009 to December 2016 were analyzed. This study focuses on the seasonal variation in parameters related to particle formation such as the occurrence, formation rate (FR) and growth rate (GR), condensation sink (CS) and source rate of condensable vapor. The number concentrations during new particle formation (NPF) events varied from 1707 to 83 12

Abstract. Sulfuric acid, amines and oxidized organics have been found to be important compounds in the nucleation and initial growth of atmospheric particles. Because of the challenges involved in determining the chemical composition of objects with very small mass, however, the properties of the freshly nucleated particles and the detailed pathways of their formation processes are still not clear. In this study, we focus on a challenging size range, i.e., particles that have grown to diameters

Abstract. Marine biota is an important source of atmospheric aerosol particles in the remote marine atmosphere. However, the relationship between new particle formation and marine biota is poorly quantified. Long-term observations (from 2009 to 2016) of the physical properties of atmospheric aerosol particles measured at the Antarctic Peninsula (King Sejong Station; 62.2∘ S, 58.8∘ W) and satellite-derived estimates of the biological characteristics were analyzed to identify the link between new

Abstract. Measurements of the hygroscopicity of 15–145 nm particles in a boreal forest environment were conducted using two Hygroscopicity Tandem Differential Mobility Analyzer (HTDMA) systems during the Pan-European Gas-Aerosols-climate interaction Study (PEGASOS) campaign in spring 2013. Measurements of the chemical composition of non-size segregated particles were also performed using a high-resolution aerosol mass spectrometer (HR-AMS) in parallel with hygroscopicity measurements. On average

Abstract. New particle formation driven by acid–base chemistry was initiated in the CLOUD chamber at CERN by introducing atmospherically relevant levels of gas-phase sulfuric acid and dimethylamine (DMA). Ammonia was also present in the chamber as a gas-phase contaminant from earlier experiments. The composition of particles with volume median diameters (VMDs) as small as 10 nm was measured by the Thermal Desorption Chemical Ionization Mass Spectrometer (TDCIMS). Particulate ammonium-to-dimethyl

Abstract. Seasonal variability in the physical characteristics of aerosol particles sampled from the King Sejong Station in the Antarctic Peninsula was investigated over the period between March 2009 and February 2015. Clear seasonal cycles for the total particle concentration (CN) were observed. The mean monthly concentration of particles larger than 2.5 nm (CN2.5) was highest during the austral summer, with an average value of 1080.39 ± 595.05 cm−3, and lowest during the austral winter, with a

Highly selective chemical mechanical polishing (CMP) of Si3N4 over SiO2 is achieved by using a modified silica abrasive. Controlling the removal rate of Si3N4/SiO2, chemical reaction is a dominant factor for ceria abrasive, but physical force such as repulsion/attraction is a primary one for silica abrasive. In order to maximize mechanical action in CMP process using silica slurry, we modified the surface charge of silica abrasive into having more negative charge, which resulting in −50 mV of ze

A mathematical model to analyse the saturation throughput of IEEE 802.11ac medium access control (MAC) is proposed. The main contributions of the proposed model are the integration of the transmission opportunity (TXOP) sharing mode and the consideration of variable‐length MAC protocol data units, instead of a fixed‐length assumption. By using the model, accurate results (within 2% relative error) for the IEEE 802.11ac TXOP sharing mode are achieved.

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The effects of resistant starches on the quality characteristics of cookies were investigated by the physicochemical, instrumental and sensory properties of RS-added flours and cookies. Retrograded RS3 by autoclaving-cooling cycle and cross-linked RS4 after annealing treatment were used. The protein content of RS-added flour decreased, but the ash content of RS4-added flour increased slightly with increasing RS content. The RS levels of wheat flour, RS3- and RS4-added flours were 7.0%, 9.6-13.4%

A complex pattern of coupling between fluid flow and mass transport develops when heterogeneous reactions occur. For instance, dissolution and precipitation reactions can change a porous medium's physical properties, such as pore geometry and thus permeability. These changes influence fluid flow, which in turn impacts the composition of dissolved constituents and the solid phases, and the rate and direction of advective transport. Two-dimensional modeling studies using TOUGHREACT were conducted