• Progress in Superconductivity and Cryogenics
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• v.17 no.2
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• pp.25-30
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• 2015

In order to realize economical applications, it is important to reduce the ac loss of 2G high-temperature superconductor coated conductors. It seems to be reasonable that a multi-filamentary wire can decrease the magnetization loss. In this study, we prepared two samples of YBCO coated conductors with striations. We measured local superconducting properties of both samples by using Low Temperature Scanning Laser and Hall Probe Microscopy (LTSLHPM). The distribution of the local critical temperature of samples was analyzed from experimental results of Low Temperature Scanning Laser Microscopy (LTSLM) near the superconducting transition temperature. According to LTSLM results, spatial distributions of the local critical temperature of both samples are homogeneous. The local current density and the local magnetization in samples were explored from measuring stray fields by using Scanning Hall Probe Microscopy (SHPM). From SHPM results, the remanent field pattern of the one bridge sample in an external magnetic field confirms the Bean's critical state model and the three bridge sample has similar remanent field pattern of the one bridge sample. The local magnetization curve in the three bridge sample was measured from external fields from -500 Oe to 500 Oe. We visualized that the distribution of local hysteresis loss are related in the distribution of the remanent field of the three bridge sample. Although the field dependence of the critical current density must be taken into account, the relation of the local hysteresis loss and the remanent field from Bean's model was useful.

• Progress in Superconductivity and Cryogenics
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• v.15 no.3
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• pp.1-4
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• 2013

We investigated the effect of Nb substitution for Ru on the structural and magnetic properties of $(Ru_{1-x}Nb_x)\;Sr_2(Sm_{1.4}Ce_{0.6})Cu_2O_z$ Samples. X-ray diffraction measurements indicated that nearly single-phase samples are formed in the range from x = 0 to 1.0. The superconducting transition temperature determined from the inflection in the field-cooled magnetic susceptibility decreased only slightly from $T_c$ = 25 K for x = 0 to $T_c$ = 22 K for x = 1.0, in consistent with the change in room temperature thermopower of the samples. However, the Nb substitution for Ru above x = 0.25 significantly suppressed the weak ferromagnetic component of the field-cooled magnetic susceptibility. It was also found that the Nb substitution for Ru results in an enhanced diamagnetic susceptibility with Nb content above x = 0.5 in both zero field-cooled and field-cooled magnetization measurements, in contrast to the behavior of the samples with $x{\leq}0.5$ in which the diamagnetic susceptibility decreases as the Nb content increases.

• Korean Journal of Metals and Materials
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• v.48 no.2
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• pp.180-186
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• 2010

For the application of field emission display (FED), it is essential to develop a carbon nanotube (CNT) cathode with high emission current density. In this study, we developed and demonstrated a post-heat treatment (PHT) process to improve field emission properties of CNT cathodes. Since the PHT is intended to burn out organic materials covering the CNTs, the PHT was carried out by heating samples at a high temperature in an atmosphere. The PHT process is applied for samples processed by surface treatment with an adhesive tape. Compared to samples prior to the PHT, samples after the PHT at $360^{\circ}C$ showed about 17% improvement in emission current density. The major reason for the increased current density is mainly the increased aspect ratio of the CNTs because of the removal of the adhesive organic residues covering the CNTs, which were attached on the CNT surfaces during the surface treatment using the adhesive taping method.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.19 no.3
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• pp.288-296
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• 2009

We conducted validation for asbestos quality control (QC) samples made by the developed method which was presented in our published paper. The main results of the validation study are as follows. The pooled coefficient variations of analytical results in three different concentrations (low, medium, and high concentration) for amosite and chrysotile were less than 20 %, which met the sample homogenicity criteria of NIOSH. Also we confirmed the homogenicity of asbestos samples by using the relocatable field slide. To evaluate the field applicability of the developed asbestos QC samples, the field validation was performed with four proficient asbestos analysts by using the statistical methods of AIHA asbestos PAT program. All analytical results from four asbestos analysts were located in the acceptable range.

• Journal of Climate Change Research
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• v.9 no.1
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• pp.59-67
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• 2018

In this study, the $N_2O$, emitted from combustion facility, were analyzed by using simulated gas and field samples to find out how long samples can be stored in Tedlar bag. According to the results of the experiment using simulated gases (1 ppm, 5 ppm, 10 ppm) in Tedlar bag, After 144hr, $N_2O$ concentration of simulated gases changed that 1 ppm is 5.3%, 5 ppm is 12.8%, and 10ppm is 10.5%. The higher initial concentration of simulated gas was, the larger rate of $N_2O$ concentration was changed. In case of high concentration samples, it need to be careful when it was analyzed after 144 hr. Stability evaluation in Tedlar bag was carried out through field samples such as combustion facility of bituminous coal, B-C oil and LNG. The concentration rate of field samples, which is under 1 ppm of average initial concentration, was evaluated using statistical method. As a result, $N_2O$ concentrations were changed to field samples in the bag even when 96 hr had passed. And after sampling, it is necessary that sample analysis should be quickly as soon as possible.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.362-362
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• 2009

$MgB_2$ bulk samples were sintered at different ambient. In this work, high purity Ar gas was added with oxygen and hydrogen gas, which can be regarded as impurity in a sense, as a possible dopant in the $MgB_2$. It was found that oxygen in the sintering ambient leads to a decrease in the critical current density $J_c$ at self field and lower fields. However, we can obtained higher $J_c$ at higher fields. It was also noted that $MgB_2$ samples sintered with 5% hydrogen in Ar revealed the increased $J_c$ at all fields compared to those processed in pure Ar ambient. From the XRD and FESEM analysis, the impurity gas in Ar can refine the $MgB_2$ grain size and result in increased grain. boundary, which can act as a strong flux pinning sites in $MgB_2$ samples. Also discussed are the effects of sintering ambient on irreversibility field, $H_{irr}$ and the upper critical field, $H_{C2}$.

• Animal Systematics, Evolution and Diversity
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• v.5 no.1
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• pp.1-12
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• 1989

Samples of striped field mice, Apodemus agrarius Pallas, from eight localities in s southwestern islands and coasts in Korea were collected and analyzed together with samples from the mainland and Jeju island. In chromosomal analyses no variation was revealed in karyotypes among samples from Korea. In morphometric analyses samples from Wan and Bogil islands formed a large-size g group (A. agrarius chejuensis) with those from Jeju island, whereas samples from Jin and H Hajo islands formed a small-size group (A. agrarius coreae) with those from the mainland including southwestern coasts It is supposed that small-size population of striped field mice in Wan and Bogil islands w were extinct and replaced by large-szie population of striped field mice immigrated from Jeju island by humans.

• Journal of the Architectural Institute of Korea Structure & Construction
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• v.34 no.12
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• pp.57-63
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• 2018

The purpose of this study was to confirm the effects of flush-out on the reduction of Volatile Organic Compounds(VOCs) concentration in newly built residential buildings. The field measurements were conducted in two complexes of multi-residential buildings which are located suburban areas of Seoul. About three samples of residential buildings were selected in the field measurements. Two samples, B and C, had been flush-out with outdoor air more than seven days. The sample A was maintained at same condition during the flush-out because of the comparison. The indoor concentrations of VOCs in the three samples were measured at three times, before, during, and after flush-out. From the field measurements, it was confirmed that two samples' indoor VOCs' concentrations were considerably decreased after the flush-out comapred with those of the sample A in which the flush-out was not conducted. The decreases of indoor VOCs concentrations were corresponding to about 50% ~ 92% of the concentrations of before. Through the reviews for the previous studies, it was also found that the reduction effects of the flush-out is similar with the those of the bake-out which were reported in the previous studies.

• Korean Journal of Soil Science and Fertilizer
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• v.49 no.5
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• pp.555-563
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• 2016

Uniformity and leveled distributions of soil chemicals across paddy fields are critical to manage optimal crop yields, reduce environmental risks and efficiently use water in rice cultivation. In this study, an investigation of spatial distributions on soil chemical properties was conducted to evaluate the effect of land leveling on mitigation of soil chemical property heterogeneity from a remodeled paddy field. The spatial variabilities of chemical properties were analyzed by geostatistical analyses; semivariograms and kriged simulations. The soil samples were taken from a 1 ha paddy field before and after land leveling with sufficient water. The study site was located at Bon-ri site of Dalseong and river sediments were dredged from Nakdong river basins. The sediments were buried into the paddy field after 50 cm of top soils at the paddy field were removed. The top soils were recovered after the sediments were piled up. In order to obtain the most accurate spatial field information, the soil samples were taken at every 5 m by 5 m grid point and total number of samples was 100 before and after land leveling with sufficient water. Soil pH increased from 6.59 to 6.85. Geostatistical analyses showed that chemical distributions had a high spatial dependence within a paddy field. The parameters of semivariogram analysis showed similar trends across the properties except pH comparing results from before and after land leveling. These properties had smaller "sill" values and greater "range" values after land leveling than ones from before land leveling. These results can be interpreted as land leveling induced more homogeneous distributions of soil chemical properties. The homogeneous distributions were confirmed by kriged simulations and distribution maps. As a conclusion, land leveling with sufficient water may induce better managements of fertilizer and water use in rice cultivation at disturbed paddy fields.

• Bulletin of the Korean Chemical Society
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• v.29 no.1
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• pp.153-158
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• 2008

A microchip-based capillary gel electrophoresis (MCGE) technique was developed for the ultra-fast detection and differentiation of Candidatus Mycoplasma haemominutum (Candidatus M. haemominutum, California strain) and Mycoplasma haemofelis (M. haemofelis, Ohio strain) in Korean feral cats through the application of programmed field strength gradients (PFSG) in a conventional glass double-T microchip. The effects of the poly (ethyleneoxide) (PEO) concentration and electric field strength on the separation of DNA fragments were investigated. The PCR-amplified products of Candidatus M. haemominutum (202-bp) and M. haemofelis (273-bp) were analyzed by MCGE within 75 s under a constant applied electric field of 117.6 V/cm and a sieving matrix of 0.3% PEO (Mr 8 000 000). When the PFSG was applied, MCGE analysis generated results 6.8-times faster without any loss of resolution or reproducibility. The MCGE-PFSG technique was also applied to eleven samples selected randomly from 33 positive samples. The samples were detected and differentiated within 11 s. The analysis time of the MCGE-PFSG technique was approximately 980-times faster than that using conventional slab gel electrophoresis.