• Journal of The Korean Astronomical Society
• /
• v.37 no.5
• /
• pp.295-297
• /
• 2004

Observations with EUVE, ROSAT, and BeepoSAX have shown that some clusters of galaxies produce intense EUV emission. These findings have produced considerable interest; over 100 papers have been published on this topic in the refereed literature. A notable suggestion as to the source of this radiation is that it is a 'warm' (106 K) intracluster medium which, if present, would constitute the major baryonic component of the universe. A more recent variation of this theme is that this material is 'warm-hot' intergalactic material condensing onto clusters. Alternatively, inverse Compton scattering of low energy cosmic rays against cosmic microwave background photons has been proposed as the source of this emission. Various origins of these particles have been posited, including an old (${\~}$Giga year) population of cluster cosmic rays; particles associated with relativistic jets in the cluster; and cascading particles produced by shocks from sub-cluster merging. The observational situation has been quite uncertain with many reports of detections which have been subsequently contradicted by analyses carried out by other groups. Evidence supporting a thermal and a non-thermal origin has been reported. The existing EUV, FUV, and optical data will be briefly reviewed and clarified. Direct observational evidence from a number of different satellites now rules out a thermal origin for this radiation. A new examination of subtle details of the EUV data suggests a new source mechanism: inverse Compton scattered emission from secondary electrons in the cluster. This suggestion will be discussed in the context of the data.

• Proceedings of the KSME Conference
• /
• 2004.11a
• /
• pp.1140-1145
• /
• 2004

Laser-induced incandescence (LII) is introduced as a valuable tool for the characterization of nanoparticles in flame environments. This technique is based on the heating of the particles by a short laser pulse and the subsequent detection of the thermal radiation. It has been applied successfully for the investigation of soot in different fields of application. The evaluation of the temporal decay of the laser-induced incandescence (LII) signal from soot particles is introduced as a technique to obtain two-dimensional distributions of particle sizes and is applied to a laminar diffusion flame. This novel approach to soot sizing exhibits several theoretical and technical advantages compared with the established combination of elastic scattering and LII, especially as it yields absolute sizes of primary particles without requiring calibration. With this technique a spatially resolved 2-D measurement of soot primary particle sizes is feasible in a combination process form the ratio of emission signals obtained at two delay times after a laser pulse, as the cooling behavior is characteristic of particle size.

• Proceedings of the Korean Nuclear Society Conference
• /
• 1999.10a
• /
• pp.247-247
• /
• 1999

This paper describes a new mechanistic thermal conductivity model considering the heterogeneous microstructure of MOX fuel. Even though the thermal conductivities of MOX have been investigated numerously by experimental measurements and theoretical analyses, they show the large scattering making the performance analysis of MOX fuel difficult. Therefore, a thermal conductivity model that depends on the heterogeneous microstructure of MOX fuel has been developed by using a general two-phase thermal conductivity model. In order to apply this model for developing the thermal conductivity for heterogeneous MOX fuel, the fuel is assumed to consist of Purich particles and U02 matrix including Pu02 in solid solution. Since little relevant data on Purich particles is available, FIGARO and SiemensKWU results are only used to characterize the microstructure of unirradiated and irradiated fuel. Philliponneaus and HALDEN models are selected for the local thermal conductivities for Purich particles and matrix, respectively. Then by combining the two models, overall thermal conductivity of MOX fuel is obtained. The new proposed model estimates the MOX thermal conductivity about 10% less than the value of U02 fuel, which is in the range of MOX thermal conductivity from HALDEN. The developed thermal conductivity model has been incorporated into KAERIs fuel performance code, COSMOS, and then verified using the measured data in the FIGARO program. Comparison of predicted and measured temperatures shows the reasonable agreement within acceptable error bounds together with satisfactory results for the fission gas release and gap pressure.essure.

• Journal of the Korean Ceramic Society
• /
• v.39 no.10
• /
• pp.981-987
• /
• 2002

Monodispersed colloidal silica was prepared by Stober process. We have synthesized monodispersed colloidal silica of carious sizes (100 nm, 200 nm, 300 nm) by controlling volume ratios of TEOS(Tetraethylorthosilicate), $NH_4OH$, Ethanol and D. I. water. Shape and monodispersity of the synthesized colloidal particles were observed by Scanning Electron Microscopy(SEM) and laser light scattering particle analyzer. Self-assembled monolayer of monodispersed colloids was achieved by dipping Si substrate into a well-dispersed silica suspension. It was determined that uniformity and spatial extent of the self-assemble monolayer of monodispersed colloids are significantly influenced by the experimental parameters such as concentration, pH and surface tension of the colloidal suspension. We have observed a hexagonally well-ordered packing colloidal monolayer in a relatively large area (1.5 mm ${\times}$ 1.5 mm) as confirmed by SEM.

• Membrane Journal
• /
• v.14 no.2
• /
• pp.149-156
• /
• 2004

This work focused on the degradation of natural organic matter (NOM) present in lake water using a combined pkotocatalysisimicrofiltration (MF) process. The system performances were investigated in terms of organic removal efficiency and membrane permeability. The addition of iron oxide particles (IOP) into the photocatalytic membrane reactor improved initial NOM removal by sorption, but during photocatalysis the removal efficiency was reversed, probably due to the scattering of UV light by IOP. The modification of TiO$_2$ surfaces by IOP deposition was conducted to enhance the photocatalytic NOM removal efficiency. A minimal amount of Impregnation of IOP on TiO$_2$ surfaces was required to prevent the light scattering effect as well. The coating of MF membranes with IOP helped to improve the NOM removal efficiency while sorbing NOM by IOP. Regardless of tile operating conditions and particles addition examined, no significant fouling was occurring at a flux of 15 L/$m^2$-h during entire MF operation.

• Asian Journal of Atmospheric Environment
• /
• v.6 no.2
• /
• pp.96-103
• /
• 2012

Ambient particulate matter (PM) and particle-bound polycyclic aromatic hydrocarbon (PAH) concentrations were measured continuously for 70 days at a Korean elementary school located near a highway. The $PM_{10}$, $PM_{2.5}$, and $PM_1$ values were measured with a light-scattering, multi-channel, aerosol spectrometer (Grimm, Model 1.107). The number concentrations of the particles were measured using a scanning mobility particle sizer and counter (SMPS+C) which counted particles from 11.1 to 1083.3 nm classified in 44 channels. Particle-bound PAHs were measured with a direct reading, photoelectric aerosol sensor. The daily $NO_2$, $SO_2$, and CO concentrations were obtained from a national air-monitoring station located near the school. The average concentrations of $PM_{10}$, $PM_{2.5}$, and $PM_1$ were 75.3, 59.3, and $52.1{\mu}g/m^3$, respectively. The average number concentration of the ultrafine particles (UFPs) was $46,307/cm^3$, and the averaged particle-bound PAHs concentration was $17.9ng/cm^3$ during the study period. The ambient UFP variation was strongly associated with traffic intensity, particularly peak concentrations during the traffic rush hours. Particles <100 nm corresponded to traffic-related pollutants, including PAHs. Additional longterm monitoring of ambient UFPs and high-resolution traffic measurements should be carried out in future studies. In addition, transient variations in the ambient particle concentration should be taken into consideration in epidemiology studies in order to examine the short-term health effects of urban UFPs.

• Applied Chemistry for Engineering
• /
• v.9 no.4
• /
• pp.569-573
• /
• 1998

A water soluble polymer, polycondensate of 1-butylamine and epichlorohydrin (PBE), was synthesized by condensation of 1-butylamine and epichlorohydrin. The characteristics of PBE were determined by IR spectroscopy, low angle light scattering measurement, and $\zeta$ potential measurement. Its interactions with colloidal bentonite particles in aqueous medium were also studied. The results of the studies are as follows : PBE is a cationic polyelectrolyte carrying tertiary ammonium ions on its backbone. The average molecular weight of PBE is found to be about 1,600. The adsorption of PBE on the colloidal bentonite particles are well described with Langmuir adsorption isotherm. As the amounts of PBE adsorbed on the bentonite particles increase, the $\zeta$ potential of the particles changes its sign from negative to positive. This inversion of charge confirms that PBE is cationic in nature. The adsorption of PBE onto the bentonite particles was found to occur through cation exchange reaction. It has been shown that PBE has flocculation effects on the colloidal suspension of bentonite. It has also enhanced effects of filtrability on the digested sludge.

• Particle and aerosol research
• /
• v.10 no.1
• /
• pp.1-8
• /
• 2014

In this study, we have developed a real-time monitoring device for measuring $PM_{10/2.5/1}$ of ambient aerosol particles. The real-time PM (Particulate Matter) monitor was based on the light scattering method and had 16 channels in particle size. The laboratory and field tests were carried out to evaluate the performance of the PM monitor developed. Arizona Road Dust particles ranging from diameter of 0.1 to $20{\mu}m$ were generated as test particles in the laboratory test. The field test was carried out at the Seoul Meteorological Observatory. We can obtain the particle size and number concentration (particle size distribution) only from the real-time PM monitor developed. Therefore, the average density of aerosol particles was used to obtain the PM data from the particle size distribution. The $PM_{10/2.5/1}$ results of the PM monitor were compared with the data of the Grimm Dust Monitor (Model 1.108) and a beta ray gauge (Thermo Fisher Scientific). As a result, it was shown that the $PM_{10/2.5/1}$ results obtained by the real-time PM monitor agreed well with the data of the reference devices, and overall, the real-time PM monitor could be used as a PM monitoring device for real-time monitoring of the ambient particles.

• Journal of the Korea Computer Graphics Society
• /
• v.28 no.4
• /
• pp.13-22
• /
• 2022

In this paper, we propose a single framework based on the MPM(Material Point Method) that can represent the dynamic angular motion of the elementary particle unit. In this study, the particles can have various shapes while also describing linear and angular motion. As a result, unlike other particle-based simulations, which only represent linear movements of spherical (e.g. Circle, Sphere) particles, it is possible to express the visually dynamic motion of them. The proposed framework utilizes MPM, due to the fact that rotational motion can be decomposed and derived from large deformation. During the integration process of the presented technique, a deformation gradient tensor is decomposed by polar decomposition theory for extracting rotation tensor. By applying this together with the linear motion of each particle, as a result, it is possible to simultaneously express the angluar and linear motion of the particle itself. To verify the proposed method, we show the simulation of rotating particles scattering in the wind field, and the interaction(e.g. Collision) between a moving object and them by comparing the traditional MPM

• Journal of the Korean Society of Food Science and Nutrition
• /
• v.32 no.3
• /
• pp.370-374
• /
• 2003

Cell cracking method using a non-collision was evaluated for the possibility of new red ginseng grinding technique. Based on particle size distribution analysis by 1size shaker, the ratios of 100 mesh penetrated particles were 94.9% for hammer mill (group A) and 95.6% for cell crack (group B). The ratio of 120 mesh penetrated particle of group A was higher than that in group B. The particle size distributions for 100 mesh non-penetrated Powder between 2 groups were not significantly different, and particle size distribution analysis by laser scattering analyzer showed that the particle size ranges were 0.77~128.07 ${\mu}{\textrm}{m}$ for group A and 4.24~180.07 ${\mu}{\textrm}{m}$ for group B. The Particle size distribution in group A was more broad than that in group B. The mean particle size in group B was larger than that in group A, while the standard deviation of particle size distribution in group B was less than that in group A. Structural surface characteristics, in group A, particle size distribution was broad and the distribution curve was amorphous. The structure of individual particles was similar to unequal stone which was roughly grinded and had soft cotton-like surface. In the contrary, in group B, particle size distribution was relatively narrow and also individual size particles were ubiquitously distributed. The structure of individual particles was unequal cut stone shape.