• 한국입자에어로졸학회지
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• 제9권3호
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• pp.133-137
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• 2013

Measuring particle size distribution is one of the primary concerns in aerosol studies. For a nano-particle size distribution measurement, many scientists use a combination of a differential mobility analyzer (DMA) and a condensation particle counter (CPC) system, which is a called scanning mobility particle sizer (SMPS). Although it has a very high particle size resolution, some issues still remain. These problems include residence time between a DMA and a CPC, discontinuity of a CPC, and disturbance due to long scanning time during the precise measurement of particles. In particular, long scanning time is not adequate for measuring particle size distribution since the particle concentration is changing during the measurement. In this study, we developed radial exhaust multi-port system (REM-system) with no scanning time and high resolution to measure real-time particle size distribution. As a result of the REM-system performed using mono-disperse particle, it is expected that this system will be suitable for measuring continuously changing aerosol. If the counting efficiency of multi-condensation particle counter (M-CPC) and data inversion matrix are completed, REM-system will be a very adequate system for unsteady aerosol, which changes for SMPS scanning time.

• 사물인터넷융복합논문지
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• 제9권3호
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• pp.1-6
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• 2023

웹 서비스 환경에서 사용자가 원하는 서비스 품질을 만족하는 경제적인 방법의 하나는 객체의 크기를 조절하는 것이다. 이를 위해 본 연구에서는 서비스 품질로 평균 응답 시간이 임의의 임계값 이하로 주어질 때, 이 제약 조건을 만족하는 최대 객체의 크기를 구한다. 시스템이 정상 상태일 때, 라운드-로빈을 사용하는 결정 모델의 평균 응답 시간은 일반 분포를 따르는 큐잉 모델에서의 평균 응답 시간과 같아질 것으로 추론할 수 있다. 이를 기반으로 최대 객체 크기를 발견하기 위한 해석적 수식과 절차를 수립한다. 웹 트래픽은 서비스 분포로 Pareto 분포가 적합하므로 M/G(Pareto)/1 모델과 지수 분포를 사용한 M/G/1/PS를 적용하여 최대 객체의 크기를 구한다. 수치 계산을 통한 성능평가는 Pareto 분포의 형상 파라미터(shaping parameter)가 커짐에 따라 M/G(Pareto)/1 모델과 M/G/1/PS 모델의 최대 객체 크기가 같아짐을 보여준다. 본 연구의 결과는 경제적인 웹 서비스 제어를 위해 객체의 크기를 조절하는 환경에 사용될 수 있다.

• 한국환경과학회지
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• 제2권3호
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• pp.201-206
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• 1993

The concentration of Total Suspended Particulates(T.S.P), size distribution of suspended particulates, and soluble anions of T.S.P in atmosphere of industrial region in Busan were investigated. T.S.P was measured by High-Volume Air Sampler and particle size distribution was measured by Anderson Air Sampler. We analyzed the chemical component of the T.S.P by ion Chromatography and measure4 the shape and size of T.S.P by Scanning Electron Micrography The small size of T.S.P mainly exist in industrial region, but the large size of T.S.P mainly exist in residentail area.

• 한국세라믹학회지
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• 제30권5호
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• pp.411-419
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• 1993

A process for the preparation of cobalt oxide powders was developed by the evaporaton of emulsion containing cobalt. The characteristics of powders were examined by means of DTA, X-ray diffracton, SEM, PSA. Cobalt oxide powders were produced by evaporating the emulsion prepared by mixing cobalt sulfate solution and organic phase consisted of kerosene, Span 80 and D2EHPA in the kerosene bath at 16$0^{\circ}C$, then the precursor obtained was calcined at 100$0^{\circ}C$. As the concentration of cobalt ions in the aqueous solution, Span 80 and the stirring speed increased, the mean size of cobalt oxide powders decreased and the size distribution was improved. At the volume ratio of one of the aqueous to organic phase, the finest mean size and the optimum size distribution was obtained. On the other hand the concentration of D2EHPA and liquid paraffin had little effect on the mean size as well as on the size distribution of powders.

• 상하수도학회지
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• 제27권6호
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• pp.805-813
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• 2013

In this study, molecular size distribution of natural organic matter (NOM) after ozonation was measured and its effect on adsorption capacity of activated carbon was investigated. According to the results, the molecular size of NOM was limitedly changed. Specifically, the molecular size of NOM between 5,000 to 10,000 Da were slightly decreased with increasing ozone doses. The adsorption capacity after ozonation was evaluated using Freundlich isotherm with ideal adsorbed solution theory (IAST) which simulated the multi components adsorption. Further, mini-column test was conducted. The Freundlich constant, K was reduced after ozonation and the non-adsorbable fraction was increased with ozonation. However, no correlation between K and ozone doses was found. The present study also agreed with the correlation between adsorption capacity and pore size characteristics of activated carbon.

• 천문학회보
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• 제35권2호
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• pp.35.1-35.1
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• 2010

Unlike the initial mass function, the initial size distribution of globular cluster (GC) systems is not well known. We calculate the evolution of the mass function (MF), radial distribution (RD), and size distribution (SD) of the Galactic GC system. By comparing the results from this calculation and the present-day MF, RD, and SD of the Galactic GC system, we infer the initial SD of the GC system. We find that a Gaussian distribution of the half-mass radius and a Gaussian distribution of the half-mass to Jacobi radius ratio are the best-fit initial SDs of the Galactic GC system.

• 한국환경보건학회지
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• 제22권4호
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• pp.55-61
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• 1996

Measurements of the seasonal variations of concentration and size distribution of TSP, $SO_4^{2-}, NO_3^-, Cl^-, NH_4^+, Na^+, K^+, Ca^{2+}$ and $Mg^{2+}$ were made by Andersen air sampler from May 1995 to April 1996 in Seoul. The size distribution of these ions was divided into four patterns. 1) Distribution was concentrated on fine particles over a year such as $NO_3^-$ component, 2) Distribution was predominated in coarse particles fraction over a year such as $Mg^{2+}$ and $Ca^{2+}$ components, 3) Distribution was differerent from various seasons such as $NH_4^+, SO_4^{2-}, Cl^-$ and $K^+$ components, 4) Distribution was bi-modal such as $Na^+$.

• 한국물환경학회지
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• 제36권3호
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• pp.185-193
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• 2020

Bimodal flocculation describes the aggregation and breakage processes of the flocculi (or primary particles) and the flocs in the water environment. Bimodal flocculation causes bimodal size distribution with the two separate peaks of the flocculi and the flocs. Extracellular polymeric substances and ionic species common in the water environment increase the occurrence of bimodal flocculation and flocculi-floc size distribution, under the flocculation mechanisms of electrostatic attraction and polymeric bridging. This study investigated bimodal flocculation and flocculi-floc size distribution, with respect to the extracellular polymeric substance concentration and ionic strength in the kaolinite-containing suspension. The batch flocculation tests comprising 0.12 g/L of kaolinite showed that the highest flocculation potential occurred at the lowest xanthan gum (as extracellular polymeric substances) concentration, under all the ionic strengths of 0.001, 0.01, and 0.1 M NaCl. Also, it was important to note that the higher ionic strength resulted in the higher flocculation potential, at all the xanthan gum concentrations. The bimodal flocculation and flocculi-floc size distribution became apparent in the experimental conditions, which had low and intermediate flocculation potential. Besides the polymeric bridging flocculation, steric stabilization increased the flocculi mass fraction against the floc mass fraction, thereby developing the bimodal size distribution.

• 상하수도학회지
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• 제22권1호
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• pp.159-168
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• 2008

A special field experiment has been carried out from March 2001 to June 2001 at the Changhowon in Kyunggi to investigate a better methodology for the estimation of dry deposition of pollutions applicable in Korea. In this study, dry deposition plate was used to measure of total and water soluble acidic mass fluxes, and CPRI(Coarse Particle Rotary Impactor), CI(Cascade Impactor) were also used to measure ambient concentrations in various particle size ranges. Sehmel-Hodgson model was used to estimate dry depostion velocity and Weibull probability distribution function was applied to get generalized particle size distribution for the size fractioned concentration data sampled by CPRI and CI. Atmospheric dry deposition fluxes of mass and ionic matters estimated by the various techniques(one-step, multi-step, equi-concentration, subdivision for only the coarse particle range, applying Weibull distribution function, etc.) were compared to flux data sampled by DDP. It was found out that the deposition fluxes estimation methodology calculated by the each particle size range devided by particle size distribution characteristics and the rapidly changed points of deposition velocity using Weibull probability distribution function was the most applicable.

• 한국농공학회논문집
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• 제48권6호
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• pp.59-67
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• 2006

Particles of soil are crushed when soil is compacted in the in-situ or lab. Among many factors that affect the crush of particles, compaction energy is a major factor. Because the crush of particles can change physical properties, the analysis of effect of compaction energy is very important. In this study, the fragmentation fractals were used for determining the change in grain size distribution and the effect due to change in grain size distribution was estimated. Compaction energy was increased by 50, 100, 200 and 300% based on the energy of standard A compaction test. As a result, grain size distribution curves were changed and fine particles increased as compaction energy were increased. Relative compaction were ranged between $93.38{\sim}107.67$. Fractal dimension of each site increased as compaction energy increased. Relative compaction is proportional to the fractal dimension but coefficients of permeability were in inverse proportional to the involution of fractal dimension.