• Atmosphere
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• v.21 no.1
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• pp.35-44
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• 2011

We investigated characteristics of new particle formation and growth events observed at Gosan climate observatory using Scanning Mobility Particle Sizer (SMPS) measurements of particle number size distribution with 54 size ranges from 10 to 487 nm in October 2009. Four days (17~20 October) and five days (22~26 October) were classified into strong new particle formation and growth event ($N_S$) and weak particle formation and growth event ($N_W$), respectively. $N_S$ and $N_W$ divided by increase of aerosol number concentration in nucleation mode and continuity of growth from nucleation to Aitken mode. Particle growth rates of $N_S$ (5.34~$9.19nm\;h^{-1}$) were greater than that of $N_W$ (2.15~$3.53nm\;h^{-1}$). $N_S$ and $N_W$ were analyzed with synoptic pattern over East Asia, meteorological elements, and sulfur dioxide ($SO_2$) measured at Gosan. We found that $N_S$ was characterized by a fast and northwesterly wind accompanied cold and dry airmass, but $N_W$ was affected airmass originated from South China and come through the Korea Peninsula. The events ($N_S$ and $N_W$) occurred at conditions of high solar flux ($&gt;700W\;m^{-2}$) and low relative humidity (< 60%). The $SO_2$ concentration on $N_S$ and $N_W$ was higher than that on case of non observed new particle formation.

• Progress in Medical Physics
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• v.12 no.2
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• pp.147-153
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• 2001

We have discussed that the total body irradiation(TBI) dose distribution of 6 and 10 MV photon beams, also differences between calculation dose use of compensator sheet and measurements in humanoid phantom. Total body irradiation and hemi-body irradiation(HBI) can be effectively performed when uniformity of dose distribution is estabilished. The method of TBI and HBI dosimatry requires special considerations related to technique, long distance and very large field, machine parameter, patient positioning. TBI and HBI with megavoltage photon beams requires basic dosimatric data which have to be measured directly or derived from the standard beam data. The semiconductor detector and ion chamber were positioned at a dmax depth, mid depth, and its specific ratio was determined using a scanning data by RFA-7 3-dimensional water phantom and solid phantom. The effective source axis distance 380 cm, the field size from 120 cm to 152 cm, isodose distributions were analyzed as a function of the thickness in phantom. Also, have discussed that the measurement of basic data for clinical photon beams for dosage calculations, data calculation sheet and the use of tissue compensation to improve dose uniformity. We have improved a dose uniformity in the TBI and HBI method.

• Journal of Welding and Joining
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• v.34 no.2
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• pp.1-10
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• 2016

The use of materials for modern lightweight auto-bodies is becoming more complex than hitherto assemblies. The high strength materials nowadays frequently used for more specific fields such as the front and rear sub frames, seat belts and seats are mounted to the assembled body structure using bolt joints. It is desirable to use nuts attached to the assembled sheets by projection welding to decrease the number of loose parts which improves the quality. In this study, nut projection welding was carried out between a nut of both boron steel and carbon steel and ultra-high strength hot-stamped steel sheets. Then, the joints were characterized by optical and scanning electron microscope. The mechanical properties of the joints were evaluated by microhardness measurements and pullout tests. An indigenously designed sample fixture set-up was used for the pull-out tests to induce a tensile load in the weld. The fractography analysis revealed the dominant interfacial fracture between boron steel nut weld which is related to the shrinkage cavity and small size fusion zone. A non-interfacial fracture was observed in carbon steel nut weld, the lower hardness of HAZ caused the initiation of failure and allowed the pull-out failure which have higher in tensile strengths and superior weldability. Hence, the fracture load and failure mode characteristics can be considered as an indication of the weldability of materials in nut projection welding.

• Journal of Veterinary Clinics
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• v.37 no.5
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• pp.242-248
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• 2020

An intestinal strigeiid trematode, Apharyngostrigea pipientis, was detected from Ardea cinerea jouyi, Egretta intermedia and Nycticorax nycticorax between July, 2006 and June, 2020 in Daejeon metropolitan city and Kangwon-do, Republic of Korea. It was observed with a light and scanning electron microscope (SEM), and molecularly analyzed with 18S rRNA genes. The infection rate of the strigeiid trematode was 25.9% (7/27). The body is cylindrical in whole mount, greatly elongated in outline and shows a strong dorsal curvature. The overall measurements are: length 4.1-4.8 mm; fore-body 1.00-1.20 mm by 0.8-0.9 mm; hind-body 3.2-3.6 mm by 0.43-0.46 mm. The body is covered by a relatively thick cuticle, devoid of spines. The oral sucker leads into a short esophagus that is devoid of a muscular pharynx. The holdfast organ is enormously developed. The vitelline follicles distributed dorsal wall of fore-body and hind-body. This strigeiid trematode especially differs from other species of genus Apharyngostrigea in morphology. Although these A. pipientis are several morphological distinctions from Apharyngostrigea cornu, the partial sequence of 18S rRNA showed the sequence homology of A. pipientis (99.9%) and A. cornu (99.8%), and this result revealed their conspecific relationship between A. cornu and A. pipientis. This is the first report of A. pipientis in the Republic of Korea.

• Korean Journal of Materials Research
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• v.9 no.10
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• pp.1006-1011
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• 1999

B-doped hydrogenated amorphous silicon carbide (a-SiC:H) thin films were prepared by plasma-enhanced chemical-vapor deposition in a gas mixture of $SiH_4$, $CH_4$ and $B_2H_6$. Microstructures and chemical properties of a-SiC:H films grown with varing the volume ratio of $CH_4$ to $SiH_4$ were characterized with various analysis methods including scanning electron microscopy(SEM), X-ray diffractometry(XRD), Raman spectroscopy, Fourier-transform infrared (FTIR) spectroscopy. X-ray photoelectron spectroscopy(XPS), UV absorption spectroscopy and photoconductivity measurements. While Si:H films grown without $CH_4$ showed amorphous state, the addition of $CH_4$ during deposition enhanced the development of a microcrystalline phase. By introducing C atoms into the film, Si-Si and Si--$\textrm{H}_{n}$ bonds of a -Si:H films were gradually replaced by Si-C, C-C, and Si--$\textrm{C}_{n}\textrm{H}_{m}$ bonds. Consequently, the electrical resistivity and optical bandgap of a-SiC:H films were increased with the C concentration in the film.

• Journal of Periodontal and Implant Science
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• v.28 no.2
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• pp.351-372
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• 1998

The purpose of this study was to evaluate in vitro effects of the loss of tooth substance and root surface changes following root planing with various periodontal instruments. The 39 extracted human teeth due to severe periodontal disease were included. The total 50 root surfaces of 30 teeth were root planed with following instruments : Group 1, with Gracey curette, Group 2, with ultrasonic scaler, Group 3, with rotating root planing bur, Group 4, with Gracey curette plus rubber cup polishing, and Group 5, with ultrasonic scaler plus rubber cup polishing. Following root planing, the amount of tooth substance loss was evaluated by measuring the weight of the removed tooth substance and then 5 specimens ($5{\times}5{\times}2mm$) were randomly selected from the each group for roughness measurement. Root planed areas of each specimen were subjected to five measurements using the Profilometer and an average surface roughness values(Ra) for each group was obtained. Statistical difference for roughness values of each group was analyzed using oneway ANOVA and student t-test. For scanning electron microscopic(SEM) examination of root surface changes following root planing, 15 root surfaces of remaining 9 teeth were root planed and 3 specimens were randomly selected. The mean loss of tooth substance removed was Group 1, $7.0{\pm}1.09mg$, Group 2, $1.3{\pm}1.00mg$, Group 3, $5.8{\pm}1.72mg$, Group 4, $8.7{\pm}1.34mg$, and Group 5, $4.5{\pm}1.68mg$ following root palning, respectively. These results indicate that curette is effective instrument in the respect of diseased root substance removal. The average surface roughness values are following results : Group 1 and Group 4 were the smoothest surface ($Ra=0.34{\pm}0.06{\mu}m$, $Ra=0.34{\pm}0.04{\mu}m$, respectively) and Group 2 was the roughest surface ($Ra=2.09{\pm}0.06{\mu}m$). Statistical analysis of roughness values demonstrated a highly significant difference (P<0.05) between each experimental groups. However, no statistically significant difference in roughness values were observed between the Group 1 and Group 4. The results in this study suggest that curette and/or polishing procedure should be done after root planing with ultrasonic scaler and caution should be used with dia-mond-coated bur during routine root planing procedure.

• Publications of The Korean Astronomical Society
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• v.14 no.2
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• pp.123-128
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• 1999

The beam size and the antenna efficiency of TRAO 14m radio telescope were measured at 86.2, 98.0 and 115.2 GHz. The beam size was determined by deconvolving the azimuthal scanning data of the Venus. To test the accuracy of our deconvolution method, the beam size at 86.2 GHz was compared with that determined from the mapping data of SiO maser line and we found no difference between them. With above beam sizes, antenna efficiencies were calculated from the continuum measurements of Venus, Jupiter and Moon. The beam efficiencies at these frequencies are appeared to be 0.49, 0.45 and 0.41, respectively. On the other hand, we also suggest that an automatic focus setting can be adopted for TRAO radio telescope based on the gradual change of best focus with elevation.

• The Journal of the Petrological Society of Korea
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• v.24 no.2
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• pp.77-90
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• 2015

The fission track registration techniques for accurate determinations of uranium in solid- and liquid-state geological materials were recommended and their applicability were examined. The determination of uranium can be achieved by optical counting of neutron-induced fission tracks of $^{235}U$ registered on solid-state track detectors under high magnification. In a dry registration method using powdered pellets of rocks (e.g., granite and coal) showing good uranium-affinity, it was not easy to decide an overall mean concentration over the total sample owing to track-clusters caused by frequent presence of uranium-bearing minerals. Separate scanning for homogeneous and track-clustered parts may be an alternative choice. Assuring the homogeneity over the whole sample, high reproducibilities were confirmed both from duplicate detections using mica and Lexan polycarbonate detectors and from multiple measurements at different thermal neutron fluences. The wet registration method using sealed quartz tubes is recommended to overcome the common heterogeneity in uranium concentrations of $10^1ppm$ and more. Adopting the wet registration, the uranium homogeneity was recovered below the $10^0ppm$ level and the lower detection limit was proved to reach without difficulty the $10^2ppb$ (i.e. $ng\;g^{-1}$) level.

• Journal of the Korean Magnetics Society
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• v.13 no.4
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• pp.155-159
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• 2003

We report on the annealing effect and ferromagnetic characteristics of Zn$_{0.7}$Mn$_{0.3}$O film prepared by sol-gel method on the silicon (100) substrate using field emission-scanning electron microscopy (FE-SEM), energy dispersive spectroscopy (EDS), X-ray diffractometry (XRD) and superconducting quantum interference device (SQUID) magnetometry. Magnetic measurements show thatZn$_{0.7}$Mn$_{0.3}$O films exhibit ferromagnetism at 5 K revealing the coercive field of ∼110 Oe for as grown sample and 360, 1035 Oe for samples annealed at 700, 800 $^{\circ}C$, respectively. Our experimental evidence suggests that ferromagnetic precipitates of a manganese oxide may be responsible for the observed ferromagnetic behaviors of the film.he film.

• Particle and aerosol research
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• v.9 no.2
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• pp.39-50
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• 2013

Real-time aerosol measuring instruments have been widely used for the measurement of atmospheric aerosol, diesel particulate matter, or material synthesis. A scanning mobility particle sizer (SMPS) measures the number size distribution of particles using electrical mobility detection technique. An aerodynamic particle sizer (APS) is used to determine the number concentration and the mean aerodynamic diameter of test particles. An electrical low-pressure impactor (ELPI) is a multi-stage impaction device to separate airborne particles into aerodynamic size classes using particle charging and electrical detection techniques. In this study, the performance of these instruments were evaluated to assess their ability to obtain mass concentrations from particle number concentration measurements made as a function of particle size. The effect of determination of particle density on the measurement of mass concentration was investigated for the three instruments.