• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.36 no.12
• /
• pp.1605-1612
• /
• 2012

The distribution of a response usually depends on the distribution of the variables. When a variable shows a distribution with two different modes, the response also shows a distribution with two different modes. In this case, recently developed methods for reliability analysis assume that the distribution functions are continuous with a mode. In actual problems, however, because information is often provided in a discrete form with two or more modes, it is important to estimate the distributions for such information. In this study, we employ the finite mixture model to estimate the response distribution with two different modes, and we select the best candidate distribution through AIC. Mathematical examples are illustrated to verify the proposed method.

• Journal of environmental and Sanitary engineering
• /
• v.9 no.2
• /
• pp.24-31
• /
• 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.

• The Bulletin of The Korean Astronomical Society
• /
• v.35 no.2
• /
• pp.27.1-27.1
• /
• 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.

• Particle and aerosol research
• /
• v.11 no.3
• /
• pp.87-92
• /
• 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
• /
• v.36 no.4
• /
• pp.343-353
• /
• 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.

• Journal of the Korea Institute of Military Science and Technology
• /
• v.14 no.1
• /
• pp.147-153
• /
• 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
• /
• v.34 no.2
• /
• pp.447-452
• /
• 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
• /
• v.18 no.6
• /
• pp.600-603
• /
• 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.

• Journal of the Korean Chemical Society
• /
• v.55 no.4
• /
• pp.673-679
• /
• 2011

Bimodal high-density polyethylenes with different comonomer type and content were synthesized by polymerization of ethylene using Ziegler-Natta catalyst. Their structure and properties were studied using GPC, NMR, DSC and tensile test. It was found that ethylene/1-hexene copolymer exhibits higher tensile strength and elongation at break than that of ethylene/1-butylene copolymer with similar comonomer content. The molecular weight decreases as the comonomer content of the polymer increases. Short chain branching affects the crystallinity and thus the morphology and consequently the mechanical properties of the corresponding bimodal high-density polyethylenes. After SSA treated, the multiple endothermic peaks were observed. Multiple endothermic peaks are mainly attributed to the heterogeneity of ethylene sequence length and lamellar thickness. The difference of broadness index indicates that SCB distribution of polyethylene containing higher comonomer content has improved uniformity.

• The Korean Journal of Applied Statistics
• /
• v.24 no.3
• /
• pp.547-557
• /
• 2011

In this paper we developed a statistical model for traffic volume data which collected from a spot of specific local state road. One peculiar property of daily traffic data is that it has bimodal shape which have two peaks on times of both going to office and coming back to home. So, various mixture models of circular distribution are suggested for bimodal traffic data and EM algorithms are applied to estimate the parameters of the suggested models. To compare the accuracy of the suggested models, classical regressions with dummy variables are also considered. The suggested models for traffic volumn data can be effectively used to estimate missing values due to measuring instrument disorder.