• Proceedings of the Korean Society of Crop Science Conference
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• 2000.11a
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• pp.3-11
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• 2000

The Asian summer monsoon has a profound social and economic impact in East Asia and its surrounding countries. The monsoon is basically a response of the atmosphere to the differential heating between the land mass of the Asian continent and the adjacent oceans. The atmospheric response, however, is quite complicated due to the interactions between the atmospheric heat sources, land-sea contrast, and topography, The occurrence of extreme summertime floods in Korea, Japan, and China in 1998 and 1999 has highlighted the range of variability of the East Asian summertime monsoon circulation and spurred interest in investigating the cause of such extreme variability. While ENSO is often considered a prime mechanism responsible for the unusual hydrological disasters in East Asia, understanding of the connection between ENSO and the East Asian monsoon is hampered by their dynamic complexities. Along with a recent phenomenon of weather abnormalities observed in many parts of the globe, Korea has seen its share of increased weather abnormalities such as the record-breaking heavy rainfalls due to a series of flash floods in the summers of 1998 and 1999, following devastating Yangtze river floods in China. A clear regime shift is found in the tropospheric mean temperature in the northern hemisphere middle latitudes and the surface temperature over the Asian continent during the summer with a sudden warming since 1977. Either decadal climate variation or climate regime shift in the Asian continent is evident and may have altered the characteristics of the East Asian summer monsoon. Considering the summertime rainfall amount in Korea is overall increased lately, the 1998/99 heavy rainfalls may not be isolated episodes related only to ENSO, but could be a part of long-term climate variation. The record-breaking heavy summer rainfalls in Korea may not be direct impact of ENSO. Instead, the effects of decadal climate variation and ENSO may be coupled to each other and also to the East Asian summer monsoon system, while their individual impacts are difficult to separate.

• The Bulletin of The Korean Astronomical Society
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• v.43 no.1
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• pp.53.1-53.1
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• 2018

During a major solar eruption, the erupting plasma is possibly out of the equilibrium ionization state because of its rapid heating or cooling. The non-equilibrium ionization process is important in a rapidly evolving system where the thermodynamical time scale is shorter than the ionization or recombination time scales. We investigate the effects of non-equilibrium ionization on EUV and X-ray observations by the Atmospheric Imaging Assembly (AIA) on board Solar Dynamic Observatory and X-ray Telescope (XRT) on board Hinode. For the investigation, first, we find the emissivities for all the lines of ions of elements using CHIANTI 8.07, and then we find the temperature responses multiplying the emissivities by the effective area for each AIA and XRT passband. Second, we obtain the ion fractions using a time-dependent ionization model (Shen et al. 2015), which uses an eigenvalue method, for all the lines of ion, as a function of temperature, and a characteristic time scale, $n_et$, where $n_e$ and t are density and time, respectively. Lastly, the ion fractions are multiplied to the temperature response for each passband, which results in a 2D grid for each combination of temperature and the characteristic time scale. This is the set of passband responses for plasma that is rapidly ionized in a current sheet or a shock. We investigate an observed event which has a relatively large uncertainty in an analysis using a differential emission measure method assuming equilibrium ionization state. We verify whether the observed coronal plasmas are in non-equilibrium or equilibrium ionization state using the passband responses.

• Journal of the Korean Wood Science and Technology
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• v.24 no.2
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• pp.46-54
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• 1996

This study was carried out to investigate the vacuum drying characteristics of 50mm- and 75mm- thick tree disks of some domestic softwoods for substituting the conventional hardwoods as the materials for wood crafts. Though the elapsed drying times from green to in-use moisture content(MC) were largely shortened by vacuum drying, the tree disks treated by EWS couldn't be dried to in-use MC, and so sapwood stains also were occurred severely. We suggest EWS treatment is undesirable for the species with very high sapwood portion or vacuum drying with hot water circulation heating system. Heart checks were slight, but sapwood checks, which have never been trouble in drying process of tree disks, were severe. For the reasonable explanation it is suggested MC differences between sapwood and heartwood were large and most of tree disks had already no barks before drying test. Ginkgo was vacuum-dried with very slight drying defects such as heart checks, sapwood checks. V-cracks and sapwood stains. In Korean red pine and pitch pine V-cracks were severely occurred. And it was found the special feature that most of these defected tree disks contained several V-cracks within one tree disk. It can be considered as the causes that the region of sapwood was defected by the several checks at the early drying stage because of the steep MC gradient along the radial direction, and then at the later drying stage the drying stresses due to differential shrinkage were concentrated on these brittle spots.

• Korean Journal of Materials Research
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• v.18 no.5
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• pp.235-240
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• 2008

This paper presents results and observations obtained from a study of the optical and thermal properties of alkali tellurite depending on the composition. Fourier transform infrared (FT-IR) spectra showed evidence of chemical modification from $TeO_4$ trigonal bipyramids (tbp) to $TeO_3$ trigonal pyramids (tp) in tellurite glasses. The optical band gaps of the different glass samples calculated using Tauc's method were found to range from 3.5-3.8 eV. The glass transition temperature (Tg) and glass stability (${\Delta}T$) of alkali tellurite glasses were investigated, as $M_2O$ [M: Li, Na, K] amounted to 25 mol%, through the use of differential thermal analysis (DTA). The coefficient of thermal expansion (CTE) was measured in a thermo mechanical analysis (TMA) with a slow heating rate after the glass samples were annealed. The results confirm that the optical band gap of alkali tellurite glasses depends on the Te-O-Te structural relaxation related to the ratio of bridging/non bridging oxygen (BO/NBO). In contrast, the thermal properties are related to the ionic field strength of the Te-O-M and M-O-M bonds, and the Te-O-Te breakage depends on the ratio of BO/NBO.

• Journal of Electrical Engineering and Technology
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• v.13 no.3
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• pp.1251-1264
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• 2018

The systematic and effective design method of a Class-D current-source resonant inverter for use in an induction cooker with zero-ripple line current is presented. The design procedure is based on the principle of the Class-D current-source resonant inverter with a simplified load network model that is a parallel equivalent circuit. An induction load characterization is obtained from a large-signal excitation test-bench based on parallel load network, which is the key to an accurate design for the induction cooker system. Accordingly, the proposed scheme provides a systematic, precise, and feasible solution than the existing design method based on series-parallel load network under low-signal excitation. Moreover, a zero-ripple condition of utility-line input current is naturally preserved without any extra circuit or control. Meanwhile, a differential-mode input electromagnetic interference (EMI) filter can be eliminated, high power quality in utility-line can be obtained, and a standard-recovery diode of bridge-rectifier can be employed. The step-by-step design procedure explained with design example. The devices stress and power loss analysis of induction cooker with a parallel load network under large-signal excitation are described. A 2,500-W laboratory prototype was developed for $220-V_{rms}/50-Hz$ utility-line to verify the theoretical analysis. An efficiency of the prototype is 96% at full load.

• Advances in nano research
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• v.16 no.4
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• pp.325-340
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• 2024

There are several novel uses for dispersing many nanoparticles into a conventional fluid, including dynamic sealing, damping, heat dissipation, microfluidics, and more. Therefore, melting heat and mass transfer characteristics of a 3-D MHD Hybrid Nanofluid flow over a rotating disc with presenting dufour and soret effects are assessed numerically in this study. In this instance, we investigated both ferric sulfate and molybdenum disulfide as nanoparticles suspended within base fluid water. The governing partial differential equations are transformed into linked higher-order non-linear ordinary differential equations by the local similarity transformation. The collection of these deduced equations is then resolved using a Chebyshev spectral collocation-based algorithm built into the Mathematica software. To demonstrate how different instances of hybrid/ nanofluid are impacted by changes in temperature, velocity, and the distribution of nanoparticle concentration, examples of graphical and numerical data are given. For many values of the material parameters, the computational findings are shown. Simulations conducted for different physical parameters in the model show that adding hybrid nanoparticle to the fluid mixture increases heat transfer in comparison to simple nanofluids. It has been identified that hybrid nanoparticles, as opposed to single-type nanoparticles, need to be taken into consideration to create an effective thermal system. Furthermore, porosity lowers the velocities of simple and hybrid nanofluids in both cases. Additionally, results show that the drag force from skin friction causes the nanoparticle fluid to travel more slowly than the hybrid nanoparticle fluid. The findings also demonstrate that suction factors like magnetic and porosity parameters, as well as nanoparticles, raise the skin friction coefficient. Furthermore, It indicates that the outcomes from different flow scenarios correlate and are in strong agreement with the findings from the published literature. Bar chart depictions are altered by changes in flow rates. Moreover, the results confirm doctors' views to prescribe hybrid nanoparticle and particle nanoparticle contents for achalasia patients and also those who suffer from esophageal stricture and tumors. The results of this study can also be applied to the energy generated by the melting disc surface, which has a variety of industrial uses. These include, but are not limited to, the preparation of semiconductor materials, the solidification of magma, the melting of permafrost, and the refreezing of frozen land.

• Economic and Environmental Geology
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• v.45 no.2
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• pp.89-104
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• 2012

The solubility of aluminum for two Andisol profiles formed on pyroclastic materials and basaltic rocks from Jeju Island, Korea was investigated. It is found that high organic carbon content and $Al_{pyrophosphate}/Al_{oxalate}$ ratios in the A horizons, suggesting the substantial amounts of reactive Al are associated with organic matter, whereas the low organic carbon content and the $Al_{pyrophosphate}/Al_{oxalate}$ ratios in the Bo horizons indicate that a major part of the reactive Al should be bound inorganically. The differential FT-IR spectra following acid-oxalate dissolution and heating up to 150 and $350^{\circ}C$, and transmission electron microscope (TEM) observation confirm that imogolite is in the Bo horizon. Our results of equilibration experiments demonstrate that the Al solubility in the Bo horizon for Andisols can be clarified by the congruent dissolution model for imogolite-type material (ITM), rather than by the simultaneous equilibrium with both ITM and Al hydroxy-interlayered aluminosilicate. With results from dialysis and aging procedures, it is noted that the formation of a proto imogolite sol showing its transformation to imogolite, which supports the congruent dissolution of ITM primarily controlling the Al solubility of Andisols in Jeju Island, Korea.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.10 no.1
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• pp.66-72
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• 2000

The behavior of nucleation and crystallization in the $Li_2O_3-SiO_2$ glass heat-treated at different condition under the conventional and microwave processing was studied by differential thermal analysis (DTA), X-ray diffractometry (XRD), optical microscopy (OM), and electrical conductivity measurement. Nucleation temperature and temperature of maximum nucleation rate in both conventionally and microwave heat-treated samples were 460~$500^{\circ}C$ and $580^{\circ}C$, respectively. It was expected that the probability for bulk crystallization increased in microwave heat-treated sample, compared to conventionally heat-treated one. Degree of crystallization increased with increasing crystallization temperature in both conventionally and microwave heat-treated samples. However, pattern of crystallization growth under microwave processing appeared to be quite different from that under the conventional one due to its internal or volumetric heating. Electrical conductivity of conventionally and microwave heat-treated samples were 1.337~2.299, 0.281~~$0.911{\times}10^{-7}\Omega {\textrm}{cm}^{-1}$, respectively.

• Environmental and Resource Economics Review
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• v.14 no.1
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• pp.167-199
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• 2005

The following policy implications can be drawn from this study: 1) The Air Pollution Emission Amount Report published by the Ministry of Environment since 1991 classifies industries into 4 sectors, i. e., heating, manufacturing, transportation and power generation. Currently, the usability of report is very low and extra efforts should be given to refine the current statistics and to improve the industrial classification. 2) Big pollution industries are as follows - s7, s17 and s20. The current air pollution control policy for these sectors compared to other sectors are found to be inefficient. This finding should be noted in the implementation of future air pollution policy. 3) s10 and s17 are found to be a big polluting industrial sector and its pollution reduction effect is also significant. 4) The effect of emission coefficient (${\Delta}f$) has the biggest impact on the reduction of emission amount change and the effect of economic growth coefficient (${\Delta}y$) has the biggest impact on the increase of emission volume. The effect of production technology factor (${\Delta}D$) and the effect of the change of the final demand structure (${\Delta}u$) are insignificant in terms of the change of emission volume. 5) Further studies on emission estimation techniques on each industry sector and the economic analysis are required to promote effective enforcement of the total volume control system of air pollutants, the differential management of pollution causing industrial sectors and the integration of environment and economy. 6) Korea's economic growth in 1990 is not pollution-driven in terms of the Barry Commoner's hypothesis, even though the overall industrial structure and the demand structure are not environmentally friendly. It indicates that environmental policies for the improvement of air quality depend mainly on the government initiatives and systematic national level consideration of industrial structures and the development of green technologies are not fully incorporated.