• 환경위생공학
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• 제9권2호
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• pp.24-31
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• 1994

Aerosol size distribution were determined in Seoul by Anderson sampler from October 1989 to September 1991 for the major ionic species(SO$_{4}$$^{2-}$, NO$_{3}$$^{-}$, Cl$^{-}$, Na$^{+}$, Na$^{+}$, K$^{+}$, Ca$^{2+}$ and Mg$^{2+}$) and TSP( Total Suspended Particles ). The seasonal variations in concentrations and size distribution have been investigated. The size distributions of TSP and each of ionic species were bimodal throughout the year. The size distribution of these ions were divided as follows; (1) fine- mode dominant for SO$_{4}$$^{2-}$ and N%'. (2) coarse- mode dominant for NO$_{3}$$^{-}$, Cl$^{-}$, Ca$^{2+}$ and Mg$^{2+}$. (3) both- mode dominant for TSP.

• 대한기계학회논문집A
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• 제36권12호
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• pp.1605-1612
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• 2012

신뢰성해석에서 응답의 분포는 변수의 분포에 따라 달라진다. 특히 변수의 분포가 바이모달 분포일 때 대부분 응답의 분포 또한 바이모달 분포이다. 이런 문제에 대해 기존의 신뢰성해석 기법은 변수를 하나의 모드를 갖고 연속함수로 정의되는 특정 확률분포로 가정하고 신뢰성해석을 수행한다. 하지만 실제 문제에서 변수들은 이산정보이면서 한 개 이상의 모드를 갖는 경우가 많기 때문에 변수의 분포에 대한 가정을 하지 않고 한 개 이상의 모드를 고려한 신뢰성해석을 수행하는 것은 매우 중요하다. 본 연구에서는 바이모달 이산정보를 고려한 신뢰성해석을 위해 유한 혼합 모델을 후보 분포로 사용한 아카이케정보척도 기반 신뢰성해석 기법을 제안한다. 수학예제를 통해 제안한 기법의 정확도를 검증하고 유용성을 확인한다.

• 천문학회보
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• 제35권2호
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• pp.27.1-27.1
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• 2010

Globular cluster (GC) systems in most galaxies, particularly in ellipticals, show bimodal color distributions. Because broadband colors trace metallicity at old ages, this phenomenon has been commonly interpreted as bimodal metallicity distributions, implying the presence of two sub-populations in the globular cluster system within a galaxy. However, a new explanation has recently been proposed, in which the non-linear nature of color-metallicity relations induced by horizontal-branch stars can produce bimodal color distributions even from unimodal metallicity distributions. In this study, we put these two explanations to the test on the origin of color bimodality, using multi-band (U,B,V and I) photometry of globular clusters in NGC 1399, the central giant elliptical galaxy in Fornax galaxy cluster. We find significant changes in the morphology of color distributions when using different colors. The observation is also well reproduced by the Monte Carlo realization of GC color when a unimodal metallicity distribution and the theoretical non-linear color-metallicity relations are assumed. We discuss the implications regarding theories on galaxy formation and evolution.

• 한국입자에어로졸학회지
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• 제11권3호
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• pp.87-92
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• 2015

MCM-41 (Mobil Composition of Matter) and SBA-15 (Santa Barbara Amorphous) were used as a supported catalyst for ethylene polymerization due to their combination of large surface area and wide range of pore size distribution. The morphology of supports was used to control the morphology of the resulting polymer. Different molar ratios of Al/Ti were used for ethylene polymerization at $60^{\circ}C$ under atmospheric pressure. The effect of different mass ratios of MCM-41/SBA-15 and 1-hexene concentration on polymerization activity and polymer properties was investigated. The catalytic activity and the crystallinity reached the highest value at Al/Ti of 480. Upon incorporation of MCM-41 and SBA-15 into $MgCl_2/TiCl_4$ catalyst, the molecular weight and crystallinity of polyethylene were enhanced. The obtained polyethylene showed melting temperature between 130 and $135^{\circ}C$. The polyethylene with replication structure of support and bimodal MWD was expected.

• Geomechanics and Engineering
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• 제36권4호
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• pp.343-353
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• 2024

The hydraulic anisotropic behavior of unsaturated soil has not been fully explored in relation to the grain-size distribution. The present study conducted laboratory assessments to examine the hydraulic anisotropy condition of statically compacted specimens in various initial states. The investigation incorporated the concept of hydraulic anisotropy by employing two discrete forms of soil stratification: horizontal-layering (HL) and vertical-layering (VL). The examined soils comprised sandy silt and silty sand, exhibiting either unimodal or bimodal soil-water characteristic curve (SWCC). This study aimed to investigate the potential correlation between the hydraulic anisotropy ratio and soil properties. The present study established a correlation between the hydraulic anisotropy ratio and several soil parameters, including fine content, dry density, plastic limit, and liquid limit. The study results indicate a non-linear relationship between the percentage of fine and dry density in soils with unimodal and bimodal soil-water characteristic curve (SWCC) and hydraulic anisotropy ratio.

• 한국군사과학기술학회지
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• 제14권1호
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• pp.147-153
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• 2011

A series of nonequilibrium molecular dynamics(NEMD) simulations are performed to investigate the kinetic energy and velocity distributions of molecules in shock waves. In the simulations, argon molecules are used as a medium gas through which shock waves are propagating. The kinetic energy distribution profiles reveals that as a strong shock wave whose Mach number is 27.1 is applied, 39.6% of argon molecules inside the shock wave have larger kinetic energy than molecular ionization energy. This indicates that an application of a strong shock wave to argon gas can give rise to an intense light. The velocity distribution profiles in z direction along which shock waves propagate clearly represent two Maxwell-Boltzmann distributions of molecular velocities in two equilibrium regions and one bimodal velocity distribution profile that is attributed to a nonequilibrium region. The peak appearing in the directional temperature in z direction is discussed on a basis of the bimodal velocity distribution in the nonequilibrium region.

• Bulletin of the Korean Chemical Society
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• 제34권2호
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• pp.447-452
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• 2013

In this study we report a new method for the synthesis of a silica monolithic column bed with bimodal pores (throughpores and mesopores). The template induced synthesis method was used to direct bimodal pores simultaneously instead of the usual post base-treating method. Block polymer Pluronic F127 was chosen as a dual-function template to form hierarchically porous silica monolith with both macropores and mesopores. This is a simplification of the method of monolithic column preparation. Poly(ethylene glycol) was used as a partial substitute for F127 can effectively prevent shrinkage during the monolith aging process without losing much surface area (944 $m^2/g$ to 807 $m^2/g$). More importantly, the resultant material showed a much narrower mesopore size (centered at 6 nm) distribution than that made using only F127 as the template reagent, which helps the mass transfer process. The solvent washing method was used to remove the remaining organic template, and it was proved to be effective enough. The new synthesis method makes the fabrication of the silica monolithic column (especially capillary column) much easier. All the structure parameters indicate that monolith PFA05 prepared by the above method is a good material for separation, with the merits of much higher surface area than usual commercial HPLC silica particles, suitable mesopore volume, narrow mesopore size distribution, low shrinkage and it is easily prepared.

• Bulletin of the Korean Chemical Society
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• 제18권6호
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• pp.600-603
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• 1997

Spherical, submicrometer particles of barium-titanyl oxalate were homogeneously precipitated by thermal decomposition of diethyl oxalate in acidic aqueous solutions. The rates of oxalate ion generations, determined by various combinations of temperature and initial concentration of diethyl oxalate had a very important effect on the particle size distribution. Monosized, bimodal, or broad unimodal powders were obtained under certain combinations of experimental variables.

• 대한화학회지
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• 제55권4호
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• pp.673-679
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• 2011

지글러-나타 촉매를 사용하여 에틸렌을 중합함으로써 다양한 공단량체의 종류와 조성을 갖는 이중 분자량 분포의 고밀도 폴리에틸렌이 합성되었다. 이들의 구조와 물성을 GPC, NMR, DSC, 인장 측정기를 이용하여 연구하였다. 에틸렌/1-헥센 공중합체가 에틸렌/1-부텐 공중합체보다 비슷한 조성을 가질 경우 높은 인장강도와 파단연신율을 가짐을 확인 하였다. 분자량은 고분자의 공단량체 비율이 증가할수록 감소하였다. 짧은 곁사슬은 결정화도에 영향을 주어 결과적으로 이중 분자량 분포를 갖는 고밀도 폴리에틸렌의 모폴로지와 기계적 물성에 영향을 미쳤다. SSA로 처리 후 다수의 발열 곡선이 관찰되었으며 이는 주로 에틸렌 배열길이와 라멜라 두께의 불균일성에 기인한다. 분포지수의 차이로부터 공단량체의 조성이 높은 폴리에틸렌의 SCB 분포가 균일도를 향상시킴을 알 수 있었다.

• 응용통계연구
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• 제24권3호
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• pp.547-557
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• 2011

본 논문에서는 우리나라 지방국도의 특정지점에서 수집된 교통량 자료를 이용하여 일일 시간교통량 추정모형을 개발하였다. 본 연구의 특징은 일일 24시의 시간변수를 원형변수로 취급하고, 지방부 교통량 자료의 특성상 출퇴근 시간에 교통량이 집중되는 이봉형의 현상을 감안하여 원형분포의 혼합모형을 고려하였다. 또한 시간대별 교통량의 분포가 요일에 따라 유사한 패턴을 가지는 데 착안하여 요일별 모형을 제시하였다. 혼합원형분포의 모수추정에는 EM알고리즘이 사용되었으며, 모형의 성능비교를 위해 가변수 회귀모형과의 비교를 실시하였다. 제시된 요일별 지방국도의 시간교통량 적합모형은 계측기의 손상 등으로 인한 교통량 결측자료의 추정에 효과적으로 사용될 수 있다.