• Korean Journal of Materials Research
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• v.28 no.11
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• pp.663-670
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• 2018

H13 tool steels are widely used as metallic mold materials due to their high hardness and thermal stability. Recently, many studies are undertaken to satisfy the demands for manufacturing the complex shape of the mold using a 3D printing technique. It is reported that the mechanical properties of 3D printed materials are lower than those of commercial forged alloys owing to micropores. In this study, we investigate the effect of microstructures and defects on mechanical properties in the 3D printed H13 tool steels. H13 tool steel is fabricated using a selective laser melting(SLM) process with a scan speed of 200 mm/s and a layer thickness of $25{\mu}m$. Microstructures are observed and porosities are measured by optical and scanning electron microscopy in the X-, Y-, and Z-directions with various the build heights. Tiny keyhole type pores are observed with a porosity of 0.4 %, which shows the lowest porosity in the center region. The measured Vickers hardness is around 550 HV and the yield and tensile strength are 1400 and 1700 MPa, respectively. The tensile properties are predicted using two empirical equations through the measured values of the Vickers hardness. The prediction of tensile strength has high accuracy with the experimental data of the 3D printed H13 tool steel. The effects of porosities and unmelted powders on mechanical properties are also elucidated by the metallic fractography analysis to understand tensile and fracture behavior.

• Korean Journal of Soil Science and Fertilizer
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• v.45 no.2
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• pp.127-134
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• 2012

Microwave remote sensing can help monitor the land surface water cycle, crop growth and soil moisture. A ground-based polarimetric scatterometer has an advantage for continuous crop using multi-polarization and multi-frequencies and various incident angles have been used extensively in a frequency range expanding from L-band to Ka-band. In this study, we analyzed the relationships between L-, C- and X-band signatures and soil moisture content over the whole soybean growth period. Polarimetric backscatter data at L-, C- and X-bands were acquired every 10 minutes. L-band backscattering coefficients were higher than those observed using C- or X-band over the period. Backscattering coefficients for all frequencies and polarizations increased until Day Of Year (DOY) 271 and then decreased until harvesting stage (DOY 294). Time serious of soil moisture content was not a corresponding with backscattering over the whole growth stage, although it increased relatively until early August (R2, DOY 224). We conducted the relationship between the backscattering coefficients of each band and soil moisture content. Backscattering coefficients for all frequencies were not correlated with soil moisture content when considered over the entire stage ($r{\leq}0.50$). However, we found that L-band HH polarization was correlated with soil moisture content (r=0.90) when Leaf Area Index (LAI)<2. Retrieval equations were developed for estimating soil moisture content using L-band HH polarization. Relation between L-HH and soil moisture shows exponential pattern and highly related with soil moisture content ($R^2=0.92$). Results from this study show that backscattering coefficients of radar scatterometer appear effective to estimate soil moisture content.

• Journal of Yeungnam Medical Science
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• v.14 no.1
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• pp.123-136
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• 1997

The purpose of this study was to examine the reliability and validity of a Korean form of Childhood Attention Problem(CAP) scale. CAP were administered to 98 normal elementary school students as control group and 98 attention deficit hyperactivity disorder patients. Male students showed high scores than female students in both subscale and total scores, but not statistically significant. There were no significant difference in CAP scale between male students and female students in attention deficit hyperactivity disorder patients. In the reliability test, the test-retest reliability coefficient was highly satisfactory and that of inattention subscale was 0.83, impulsivity subscale was 0.70 and total score was 0.82. In the reliability test by internal consistency, the Cronbach $\alpha$ coefficient was highly satisfactory and that of inattention subscale was 0.91, overactivity subscale was 0.89(p<0.05). The concurrent validity between CAP scale and ADDES-BV scale was 0.85 in attention deficit hyperactivity disorder patient group and 0.73 in normal control group(p<0.05). In discriminant validity test between attention deficit hyperactivity disorder patient group and normal control group, the patient group showed higher score(p<0.05). The total discriminant capacity of the patient group in CAP was 93.4%. In this point of view, CAP scale showed high reliability and validity in applying to Korean subjects and was proved to be the good and simple screening test tool for attention deficit hyperactivity disorder research and can help many young patient to treat early.

• Journal of The Korean Society of Grassland and Forage Science
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• v.29 no.3
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• pp.197-210
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• 2009

To improve the forage quality and reduce nitrogen input, trial was conducted on the effect of seeding method, combination, and nitrogen fertilizer with WCB (whole crop barley) and leguminous plant. Present experiment was carried out by split-split design having seeding methods for main plot, combinations for sub-plot, and nitrogen fertilizers for sub-sub plot with three replications. When WCB and leguminous plant were mixed-sown, WCB showed earlier heading and maturing than those of inter-sown, and the more nitrogen delayed growth stage a little. Occurrence of BaYMV (Barley Yellow Mosaic Virus), a serious disease caused by soil fungi and decrease barley yield, was deterred by mixed-seeding as compared to inter-sown barley a little. Inter-sown WCB increased the number of spike per $m^2$ as compared to mixed-seeding showing more spikes with nitrogen increase. WCB produced much fresh and dry matter yield at mixed-seeding than inter-seeding, and had advantage with hairy vetch (HV). Increased nitrogen showed much forage yield, however, half application of it is considerable for environmental-friendly farming. Electric conductivity (EC) decreased in inter-cropping or mixed-sowing soil with WCB and leguminous crop after harvest. But, organic matter (OM) content of soil after harvesting was vice versa. Acid detergent fiber (ADF) and Neutral detergent fiber (NDF) of WCB plant were higher at mixed-seeding than those of inter-sown ones. It showed increased tendency with time progress.

• Tuberculosis and Respiratory Diseases
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• v.59 no.3
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• pp.279-285
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• 2005

Background : Ambient particles during Asian dust events are usually less than $10{\mu}m$ in size, and known to be associated with the adverse effects on the general population. There is little evidence linking Asian dust to adverse effects on the airways. In 2002, the authors found that particulate matter during Asian dust events had an effect on the symptoms and pulmonary function of patients with bronchial asthma. An aggravating factor might be that of a viral infection, but this remains unclear. Conversely, it has been speculated that African dust may carry the virus responsible for foot and mouth disease. Asian dust events are also likely to be responsible for transporting viruses, some of which are pathogenic, and common in many environments. Therefore, in this study, air samples were screened for the presence of viruses. Methods : Air samples were collected 20 times each during Asian dust events and under non-dust conditions, for at least 6 hours per sample, using a high volume air sampler (Sibata Model HV500F), with an airflow rate of 500L/min, between April and August 2003, and between April and August 2004. The samples were then screened for the presence of targeted viruses (Influenza A, B, Hog cholera virus, and Aphthovirus) using a polymerase chain reaction method. Results : One Asian dust event occurred between April and August 2003, and 3 between April and August 2004, with a 24 hour average PM10 level of $148.0{\mu}g/m^3$. The 24 hour average PM10 level was $57{\mu}g/m^3$. There was a significant difference in the PM10 concentration between dusty and clear days. No viruses (Influenza virus, Aphthovirus, and Hog cholera virus) were identified in the air samples obtained during the dusty days. Conclusions : Although no virus was detected in this study, further studies will be needed to identify suspected viruses carried during Asian dust events, employing more appropriate virus detection conditions.

• Neonatal Medicine
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• v.17 no.2
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• pp.181-192
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• 2010

Purpose: Current studies have demonstrated the neuroprotective effects of dizocilpine (MK-801) in many animal models of brain injury, including hypoxic-ischemic (HI) encephlopathy, trauma and excitotoxicity, but limited data are available for those during the neonatal periods. Here we investigated whether dizocilpine can protect the developing rat brain from HI injury via anti-apoptosis. Methods: In an in vitro model, embryonic cortical neuronal cell culture of Sprague-Dawley (SD) rats at 18-day gestation was done. The cultured cells were divided into three groups: normoxia (N), hypoxia (H), and hypoxia treated with dizocilpine (HD). The N group was prepared in 5% $CO_2$ incubators and the other groups were placed in 1% $O_2$ incubators (94% N2, 5% $CO_2$) for 16 hours. In an in vivo model, left carotid artery ligation was done in 7-day-old SD rat pups. The animals were divided into six groups; hypoxia (N), hypoxia (H), hypoxia with sham-operation (HS), hypoxia with operation (HO), HO treated with vehicle (HV), and HO treated with dizocilpine (HD). Hypoxia was made by exposure to a 2 hour period of hypoxic incubator (92% N2, 8% $O_2$). Results: In the in vitvo and in vivo models, the expressions of Bcl-2 in the hypoxia groups were reduced compared to the normoxia group. whereas those in the dizocilpine-treated group were increased compared to the hypoxia group. However. the expressions of Bax and caspase-3 and the ratio of Bax/Bcl-2 were revealed reversely. Conclusion: Dizocilpine has neuroprotective property over perinatal HI brain injury via anti-apoptosis.

• Neonatal Medicine
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• v.18 no.1
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• pp.59-69
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• 2011

Purpose: Current studies have demonstrated the neuroprotective effects of 6-cyano-7-nitroquinoxalin-2,3-dione (CNQX) in many animal models of brain injury, including hypoxic-ischemic (HI) encephlopathy, trauma and excitotoxicity, but limited data are available for those during the neonatal periods. Here we investigated whether CNQX can protect the developing rat brain from HI injury via mediation of nitric oxide synthase. Methods: In an in vivo model, left carotid artery ligation was done in 7-day-old Sprague-Dawley (SD) rat pups. The animals were divided into six groups; normoxia (N), hypoxia (H), hypoxia with sham-operation (HS), hypoxia with operation (HO), HO treated with vehicle (HV), and HO treated with CNQX at a dose of 10 mg/kg (HC). Hypoxia was made by exposure to a 2 hr period in the hypoxic chamber (92% $N_2$, 8% $O_2$). In an in vitro model, embryonic cortical neuronal cell culture of SD rats at 18-day gestation was done. The cultured cells were divided into three groups: normoxia (N), hypoxia (H), and hypoxia treated with CNQX (HC). The N group was prepared in 5% $CO_2$ incubators and the other groups were placed in 1% $O_2$) incubators (94% $N_2$, 5% $CO_2$) for 16 hr. Results: In the in vitvo and in vivo models, the expressions of iNOS and eNOS were reduced in the hypoxia group when compared to the normoxia group, whereas they were increased in the CNQX-treated group compared to the hypoxia group. In contrast, the expression of nNOS was showed reversely. Conclusion: CNQX has neuroprotective property over perinatal HI brain injury via mediation of nitric oxide synthase.

• Food Science and Preservation
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• v.22 no.3
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• pp.443-451
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• 2015

This study was carried out to investigate the quality characteristics and identification of acetic acid bacteria for black waxy rice vinegar. Eight (8) strains of acetic acid bacteria were isolated for the production of acetic acid and their acidities were then compared with commercial acetic acid bacteria. Among them, F1, H4, and two types of commercial bacteria (four best strains by vinegar zymogen) were selected. After analyzing the 16S rRNA sequence, both F1 and H4 strains were identified as acetobacter genus. Therefore, the F-1 and H-4 strains were named as Acetobacter sp. F-1 and Acetobacter sp. H-4, respectively. Acidity of black waxy rice vinegar during fermentation was steadily increased up to 16 days and the acidity was then constant. Total acidity content was higher when used FV-1 strain. In the results of Hunter's color value of black waxy vinegar, L value was at 75.01 to 80.11, while (+a) value was at 3.34 to 3.92, and (+b) value was at 12.84 to 18.09. The major organic acid of the black waxy vinegar was acetic acid. The total organic acid content was high when used H-4, F-1, C-2 and C-1 strains. The total free amino acid content of the black waxy vinegar by strain was the highest (351.43 mg%) of F-1 vinegar strain, and the lowest (247.74 mg%) of C-2 vinegar strain. A sensory evaluation of black waxy vinegar indicated that F-1 vinegar strain was better than the other samples in aspect of flavor, color, and overall preference.

• Korean Journal of Remote Sensing
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• v.25 no.4
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• pp.383-389
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• 2009

The main objective of the research is a feasibility study on the intertidal zone using a X-band radar satellite, TerraSAR-X. The TerraSAR-X data have been acquired in the west coast of Korea where large tidal flats, Ganghwa and Yeongjong tidal flats, are developed. Investigations include: 1) waterline and backscattering characteristics of the high resolution X-band images in tidal flats; 2) polarimetric signature of halophytes (or salt marsh plants), specifically Suaeda japonica; and 3) phase and coherence of interferometric pairs. Waterlines from TerraSAR-X data satisfy the requirement of horizontal accuracy of 60 m that corresponds to 20 cm in average height difference while current other spaceborne SAR systems could not meet the requirement. HH-polarization was the best for extraction of waterline, and its geometric position is reliable due to the short wavelength and accurate orbit control of the TerraSAR-X. A halophyte or salt marsh plant, Suaeda japonica, is an indicator of local sea level change. From X-band ground radar measurements, a dual polarization of VV/VH-pol. is anticipated to be the best for detection of the plant with about 9 dB difference at 35 degree incidence angle. However, TerraSAR-X HH/TV dual polarization was turned to be more effective for salt marsh monitoring. The HH-HV value was the maximum of about 7.9 dB at 31.6 degree incidence angle, which is fairly consistent with the results of X-band ground radar measurement. The boundary of salt marsh is effectively traceable specifically by TerraSAR-X cross-polarization data. While interferometric phase is not coherent within normal tidal flat, areas of salt marsh where the landization is preceded show coherent interferometric phases regardless of seasons or tide conditions. Although TerraSAR-X interferometry may not be effective to directly measure height or changes in tidal flat surface, TanDEM-X or other future X-band SAR tandem missions within one-day interval would be useful for mapping tidal flat topography.