• Journal of the Korean Chemical Society
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• v.55 no.2
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• pp.204-207
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• 2011

A particle counting system that can also provide sensitive, specific chemical information, while consuming very less power, occupying less space, and being inexpensive has been developed. This system uses a microwave plasma torch (MPT) as the excitation source for atomic emission spectrometry (AES). Emission from a single particle can be detected, and the wavelength at which the emission is observed indicates the elements present in the particle. It is believed that correlating the particle size and emission intensity will allow us to estimate the particle size in addition to abovementioned capabilities of the system. In the long term, this system can be made field-portable, so that it can be used in atmospheric aerosol monitoring applications, which require real-time detection and characterization of particles at low concentrations.

• Nuclear Engineering and Technology
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• v.55 no.7
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• pp.2373-2379
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• 2023

In sodium systems, leakage is one of the safety concerns; it can cause chemical reactions, which may result in fires. There are contact and non-contact types of leak detectors, and the conventional method of non-contact type detection is by gas sampling. Because of the complexity of this method, there has always been a need for a simple gas sensor, and the resistive-type nanostructure ZnO sensor is a promising option with various advantages. In this study, a ZnO sensor was fabricated, and the concept was tested as a leak detector using a dedicated experiment facility. The experiment results showed distinctive changes in resistance with the presence of sodium aerosol under various conditions. Replacing the conventional gas sampling with the ZnO sensors is expected to enable identification of the leakage location if used as a point-wise instrumentation and to greatly reduce the total cost, making the system simple, light, and effective. For further study, more tests will be performed to evaluate the sensitivity of key parameters under various conditions.

• Particle and aerosol research
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• v.13 no.4
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• pp.159-164
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• 2017

The detection efficiency and characteristics of an optical particle counter (OPC), with various sample nozzle outlet diameters, were experimentally investigated. The OPC system, which was built with original design, was made up of a diode laser, two photodetectors, and a variety of optics such as a beam splitter and a concave mirror. The cone-shaped sampling nozzle was designed to be changeable to alter the outlet diameter, within the range of 1 to 3 mm. For samples, sets of polystyrene latex (PSL) standard particle with various sizes of 1 to $3{\mu}m$, were used. As a result, detection efficiency of the OPC greatly decreased with larger nozzle outlet diameter. Moreover, increased nozzle outlet diameter means broader sample flow, thus caused light interference and multiple scattering which results in abnormal high peaks in scattered light signal. The ratio of abnormal peaks to regular signal of single particle increased with larger nozzle outlet diameter.

• Journal of the Optical Society of Korea
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• v.19 no.6
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• pp.695-699
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• 2015

A high spectral resolution lidar (HSRL) system based on injection-seeded Nd:YAG laser and iodine absorption filter has been developed for the quantitative measurement of aerosol and cloud. The laser frequency is stabilized at 80 MHz by a frequency locking system and the absorption line of iodine cell is selected at the 1111 line with 2 GHz width. The observations show that the HSRL can provide vertical profiles of particle extinction coefficient, backscattering coefficient and lidar ratio for cloud and aerosol up to 12 km altitude, simultaneously. For the measured cases, the lidar ratios are 10~20 sr for cloud, 28~37 sr for dust, and 58~70 sr for urban pollution aerosol. It reveals the potential of HSRL to distinguish the type of aerosol and cloud. Time series measurements are given and demonstrate that the HSRL has ability to continuously observe the aerosol and cloud for day and night.

• Particle and aerosol research
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• v.10 no.3
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• pp.93-97
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• 2014

Condensation particle counter (CPC) has been one of the most important basic instrument for measuring number concentration of submicron aerosols. The principle of the CPC is to expose aerosols to a supersaturated vapor and cool down which causes adiabatic expansion. The particles grow by heterogenous nucleation to a sufficient size for easy detection by optical method. However, for growth by condensation, CPC essentially needs both saturater and condensor causing a heavy system. Therefore, it is hard to install commercial CPC to tethered balloon package system. In this study, we developed customized CPC for tethered balloon package system called Hy-CPC which is lighter and smaller in structure than commercial CPCs, and evaluated activation efficiency and detection efficiency by Hy-CPC using electrostatic method (electrometer and Faraday cup).

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.9
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• pp.1066-1074
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• 2004

With a diode corona charger, which is a component of ELPI(Electrical Low Pressure Impactor), aerosol particles are charged to make electrical detection possible before they are collected by the impactor. We designed and evaluated two cylindrical corona chargers, each of which had a central corona needle electrode. For the performance evaluation of each corona charger the polydisperse dioctyl sebacate(DOS) particles, with diameters of 0.1∼0.8 $\mu$m and NaCl particles, smaller than 0.1$\mu$m, were used. The particles were then led through an electrostatic classifier (TSI model 3081) to classify monodisperse aerosol with minimal size deviation. After evaluating the wall loss of the particles in the corona charger, we measured the product of penetration and number of charges, Pㆍn, to evaluate the corona charger efficiency at high positive voltages of 4, 5, 6 kV.

• Proceedings of the KSRS Conference
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• 1998.09a
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• pp.409-414
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• 1998

To examine the detectability of the aerosol and/or Yellow dust from China crossing over the Yellow sea, three works carried out as follows , Firstly, a comparison was made of the visible(VIS), water vapor(WV), and Infrared(IR) images of the GMS-5 and NOAA/AVHRR on the cases of yellow sand event over Korea. Secondly, the spectral radiance and reflectance(%) was observed during the yellow sand phenomena on April, 1998 in Seoul using the GER-2600 spectroradiometer, which observed the reflected radiance from 350 to 2500 nm in the atmosphere. We selected the optimum wavelength for detecting of the yellow sand from this observation, considering the effects of atmospheric absorption. Finally, the atmospheric radiance emerging from the LOWTRAN-7 radiative transfer model was simulated with and without yellow sand, where we used the estimated aerosol column optical depth ($\tau$ 673 nm) in the Meteorological Research Institute and the d'Almeida's statistical atmospheric aerosol radiative characteristics. The image analysis showed that it was very difficult to detect the yellow sand region only by the image processing because the albedo characteristics of the sand vary irregularly according to the density, size, components and depth of the yellow sand clouds. We found that the 670-680 nm band was useful to simulate aerosol characteristics considering the absorption band from the radiance observation. We are now processing the simulation of atmospheric radiance distribution in the range of 400-900 nm. The purpose of this study is to present the preliminary results of the aerosol and/or Yellow dust detectability using the Ocean Scanning Multispectral Imager(OSMI), which will be mounted on KOMPSAT-1 as the ocean color monitoring sensor with the range of 400-900 nm wavelength.

• Korean Journal of Remote Sensing
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• v.33 no.3
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• pp.257-266
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• 2017

In this study, the dust/smoke detection algorithm was developed with a multi-spectral satellite remote sensing method using Moderate resolution Imaging Spectroradiometer (MODIS) Level 1B (L1B) data and the results were validated as RGB composite images of red(R; band 1), green(G; band 4), blue(B; band 3) channels using MODIS L1B data and Cloud-Aerosol Lidar with Orthogonal Polarization Satellite Observations(CALIPSO) Vertical Feature Mask (VFM) product. In the daytime on March 30, 2007 and April 27, 2012, the consistencies between the dust/smoke detected by this algorithm and verification data were approximately 56.4 %, 72.0 %, respectively. During the nighttime, the similar consistency was 40.5 % on April 27, 2012. Although these results were analyzed for limited cases due to the spatiotemporal matching for the MODIS and CALIPSO satellites, they could be used to utilize the aerosol detection of geostationary satellites for the next generations in Korea through further research.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.22 no.11
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• pp.1564-1570
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• 1998

In-situ particle monitors(ISPMs) are widely used for monitoring contaminant particles in vacuum-based semiconductor manufacturing equipment. In the present research, the performance of a Particle Measuring Systems(PMS) Vaculaz-2 ISPM at subatmospheric pressures has been studied. We created uniform upstream conditions of particle concentration and measured the detection efficiency, the lower detection limit, and the size response of the ISPM using uniform sized methylene blue aerosol particles. The effect of particle size, particle velocity, particle concentration, and system pressure on the detection efficiency was examined. Results show that the detection efficiency of the ISPM decreases with decreasing chamber pressure, and with increasing mass flow rate. The lower detection limit of the ISPM, determined at 50 % of the measured maximum detection efficiency, was found to be about $0.15{\sim}0.2{\mu}m$, which is similar to the minimum detectable size of $0.17{\mu}$ given by the manufacturer.

• Journal of Korean Society for Atmospheric Environment
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• v.22 no.6
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• pp.851-862
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• 2006

Satellites have been valuable tool for global/regional scale atmospheric environment monitoring as well as emission source detection. In this study, we present the results of application of satellite remote sensing data for air quality forecast in Seoul metropolitan area. AOT (Aerosol Optical Thickness) data from TERRA/MODIS (Moderate Resolution Imaging Spectre-radiometer) satellite were compared to ground based $PM_{10}$ mass concentrations, and used to estimate the possibility of the aerosol forecasting in Seoul metropolitan area. Although correlation coefficient (${\sim}0.37$) between MODIS AOT products and surface $PM_{10}$ concentration data was relatively low, there was good correlation between MODIS AOT and surface PM concentration under certain atmospheric conditions, which supports the feasibility of using the high-resolution MODIS AOT for air quality forecasting. The MODIS AOT data with trajectory forecasts also can provide information on aerosol concentration trend. The success rate of the 24 hour aerosol concentration trend forecast result was about 75% in this study. Finally, application of satellite remote sensing data with ground-based air quality observations could provide promising results for air quality monitoring and more exact trend forecast methodology by high resolution satellite data and verification with long term measurement dataset.