• Tunnel and Underground Space
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• 제32권1호
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• pp.30-58
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• 2022

The deep geological repository for high-level radioactive waste disposal is a multi barrier system comprised of engineered barriers and a natural barrier. The long-term integrity of the deep geological repository is affected by the coupled interactions between the individual barrier components. Erosion and piping phenomena in the compacted bentonite buffer due to buffer-rock interactions results in the removal of bentonite particles via groundwater flow and can negatively impact the integrity and performance of the buffer. Rapid groundwater inflow at the early stages of disposal can lead to piping in the bentonite buffer due to the buildup of pore water pressure. The physiochemical processes between the bentonite buffer and groundwater lead to bentonite swelling and gelation, resulting in bentonite erosion from the buffer surface. Hence, the evaluation of erosion and piping occurrence and its effects on the integrity of the bentonite buffer is crucial in determining the long-term integrity of the deep geological repository. Previous studies on bentonite erosion and piping failed to consider the complex coupled thermo-hydro-mechanical-chemical behavior of bentonite-groundwater interactions and lacked a comprehensive model that can consider the complex phenomena observed from the experimental tests. In this technical note, previous studies on the mechanisms, lab-scale experiments and numerical modeling of bentonite buffer erosion and piping are introduced, and the future expected challenges in the investigation of bentonite buffer erosion and piping are summarized.

• Journal of the Korean Society of Food Science and Nutrition
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• 제44권4호
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• pp.564-572
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• 2015

Nutritional compositions, volatile compounds, and sensory attributes of Cynanchi wilfordii Radix were analyzed in order to examine its practical utilization as a food resource. In the proximate analysis, protein and lipid contents were shown to be 14.6 and 5.0 mg/100 g, respectively, in C. wilfordii Radix. Potassium was the most predominant mineral (809 mg/100 g), as determined by inductively coupled plasma-optical emission spectrometry in parallel with microwave acid digestion. Total phenolic content was found to be 410 mg/100 g. Further, arginine and linoleic acid were the most abundant amino acid and fatty acid of C. wilfordii Radix, respectively. To examine its functional properties, classical 2,2-diphenyl-1-picrylhydrazyl (DPPH) analysis was performed. As a result, the concentration of C. wilfordii Radix required to scavenge 50% of DPPH radicals was 1.16 mg of dried material. Lastly, in olfactory and sensory tests, ${\beta}$-eudesmol (woody odor) was the major flavor compound responsible for the bitter taste and sensory attributes of C. wilfordii Radix. Taken altogether, the above results provide important preliminary results for utilization of C. wilfordii Radix as a food resource.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• 제44권12호
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• pp.1071-1086
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• 2016

The safety of aircraft can be threatened by environmental factors, such as icing, turbulence, and lightning strike. Due to its adverse effects on aircraft structure and electronic components of aircraft, lightning strike is one of the biggest hazards on aircraft safety. Lightning strike can inject high voltage electric current to the aircraft, which may generate strong magnetic field and extreme hot spots, leading to severe damage of structure or other equipment in aircraft. In this work, mechanism of lightning strike and associated direct and indirect effects of lightning on aircraft were studied. First, on the basis of aircraft lightning regulations provided by Aerospace Recommended Practice (ARP), we considered different lightning waveform and zones of an aircraft. A coupled thermal-electrical computational model of ABAQUS was then used for simulating flow of heat and electric current caused by a lightning strike. A study on fuel tank, with and without lightning protection system, was also conducted using the computational model. Finally, electric current flow on two full scale airframes was analyzed using the EMA3D code.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• 제19권6호
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• pp.621-629
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• 2008

This paper presents a low temperature co-fire ceramics(LTCC) Upconverter for a Ka-band OBS satellite transponder in order for size reduction which is one of the most important requirement for satellite components. A S-band low-pass filter(LPF), a K-band band-pass filter(BPF), and an upconverting MMIC mixer are embedded in the multi-layer structure of the upconverter. All spurious can be selectively rejected by employing a modified Elliptic low pass filter with a multi-pole structure for the S-band LPF. Also an improved performance of out-of-band rejection can be obtained. At the K-band BPF design a layer coupled configuration is employed. The upconverting mixer is an MMIC diode mixer with a double-balanced configuration. Conversion loss and isolation of the upconverter are 9 dB and 51 dBc, respectively. The size of the LTCC upconverter is only $8{\times}7{\times}0.6mm^3$ which is one-third for the thin-film based upconverter.

• Journal of Environmental Health Sciences
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• 제43권4호
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• pp.257-266
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• 2017

Objectives: The hazardous metals content of medicinal herbs distributed in the Daegu area was investigated, and the place of origin and the content of herbicides and medicinal components were studied. Methods: An analysis of hazardous metals content (10 types) was carried out on 164 samples of 99 types of herbal medicines. Among the total samples, 45 were domestic and 119 were imported. Hg was analyzed by the amalgamation method. Other hazardous metals content (nine types) was digested using the microwave method and measured by inductively coupled plasma optical emission spectrometry (ICP-OES). Results: The mean values of the hazardous metals content in the herbal medicines were Pb 1.0833 mg/kg, As 0.0136 mg/kg, Cd 0.0840 mg/kg, Cr 3.7120 mg/kg, Cu 4.2666 mg/kg, Mn 40.080 mg/kg, Ni 1.4330 mg/kg, Sb 0.1053 mg/kg, Al 202.64 mg/kg and Hg 0.0062 mg/kg. Three of the samples violated the Ministry of Food and Drug Safety (MFDS) regulatory guidance on cadmium (less than 0.3 mg/kg). The measured values of heavy metals (Pb, As, Cd, Hg) showed levels below the recommended levels for herbal medicines in MFDS regulatory guidance. In the comparison of domestic samples with imported herbal medicines, it was found that one domestic and two imported samples surpassed the maximum residue limits for cadmium. The median values of the hazardous metals detected in the three medicinal parts of the root, leaf (branch), and flower (seed and fruit) were as follows. Cr, Ni, Sb and Al were highly detected in roots, Pb, Cd, Mn, Hg in leafs (branch), and As, Cu in flowers (seed and fruit). Conclusion: There were various kinds of hazardous metals which were detected at high levels according to the place of origin of the medicinal herb and the parts the plant. For hazardous metals for which no acceptance criteria have been established, safety standards should be further studied and managed to ensure the safety of herbal medicines.

• Proceedings of the Korea Water Resources Association Conference
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• 한국수자원학회 2006년도 학술발표회 논문집
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• pp.2-11
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• 2006

In the processes of hydrological cycle, when precipitation reaches the ground surface, water may become surface runoff or infiltrate into soil and then possibly further percolate into groundwater aquifer. A part of the water is returned to the atmosphere through evaporation and transpiration. Soil moisture dynamics driven climate fluctuations plays a key role in the simulation of water transfer among ground surface, unsaturated zone and aquifer. In this study, a one-layer canopy and a four-layer soil representation is used for a coupled soil-vegetation modeling scheme. A non-zero hydraulic diffusivity between the deepest soil layer modeled and groundwater table is used to couple the numerical equations of soil moisture and groundwater dynamics. Simulation of runoff generation is based on the mechanism of both infiltration excess overland flow and saturation overland flow nested in a numerical model of soil moisture dynamics. Thus, a comprehensive hydrological model integrating canopy, soil zone and aquifer has been developed to evaluate water resources in the plain region of Huaihe River basin in East China and simulate water transfer among precipitation, surface water, soil moisture and groundwater. The newly developed model is capable of calculating hydrological components of surface runoff, evapotranpiration from soil and aquifer, and groundwater recharge from precipitation and discharge into rivers. Regional parameterization is made by using two approaches. One is to determine most parameters representing specific physical values on the basis of characterization of soil properties in unsaturated zone and aquifer, and vegetations. The other is to calibrate the remaining few parameters on the basis of comparison between measured and simulated streamflow and groundwater tables. The integrated modeling system was successfully used in the Linhuanji catchment of Huaihe plain region. Study results demonstrate that (1) on the average 14.2% of precipitation becomes surface runoff and baseflow during a ten-year period from 1986 to 1995 and this figure fluctuates between only 3.0% in drought years of 1986, 1988, 1993 and 1994 to 24.0% in wet year of 1991; (2) groundwater directly deriving from precipitation recharge is about 15.0% t of the precipitation amount, and (3) about half of the groundwater recharge flows into rivers and loses through evaporation.

• Journal of Applied Biological Chemistry
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• 제51권1호
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• pp.20-27
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• 2008

The contents of lignan, protein, and oil of nine Sesamum indicum cultivars were analyzed. To determine the lignan contents, sesamin 1 and sesamolin 2 were isolated from the ethylacetate extracts of the Suwon cultivar, and the structures were fully characterized by spectral and physical methods. The seeds of nine cultivars were screened for two lignans, which were determined by HPLC using a $C_{18}$ reversed phase column coupled with a photodiode array detector. Suwon cultivar showed the highest concentration (1: $6.24{\pm}0.04$ and 2: $3.58{\pm}0.01\;mg/g$), whereas Soonheuk displayed the lowest (1: $0.91{\pm}0.01$ and 2: $0.73{\pm}0.01\;mg/g$). The average content ratio of sesamin 1 (3.64 mg/g) was significantly higher than that of sesamolin 2 (2.57 mg/g). The protein content ranged from $21.52{\pm}0.35$ to $31.22{\pm}0.25%$, Suwon containing the highest level and Soonheuk had the lowest. Kwangbaek showed the highest oil level ($49.84{\pm}0.40%$), while Soonheuk exhibited the lowest ($42.52{\pm}0.05%$). Sesamin 1 exhibited a stronger radical-scavenging activity in the ABTS ($IC_{50}:\;63.2{\pm}2.4\;{\mu}M$) than its DPPH radical-scavenging activity ($IC_{50}>200\;{\mu}M$). These results lead to the conclusion that lignan content is affected by protein and oil contents. Concentration of the chemical components in the cultivars could be a key factor in the selection process of a high quality species.

• Journal of the Korea Academia-Industrial cooperation Society
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• 제18권3호
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• pp.724-729
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• 2017

The crashworthiness of the fuel tank of a rotorcraft is verified through the crash impact test. The crash impact test has a high risk of failure due to the application of an excessive load, which can seriously affect the overall development schedule of the aircraft. Therefore, a lot of effort has been made to minimize the possibility of failure in the actual test by carrying out a numerical analysis of the crash impact test of the fuel tank in the initial design stage. Recently, an external auxiliary fuel tank was added to increase the cruising distance. In this study, the numerical analysis results of the crash impact test based on several different shapes of the external auxiliary fuel tank are presented, in order to evaluate its crashworthiness. For the numerical analysis, smoothed particle hydrodynamics (SPH), which is one of the fluid-structure coupled analysis methods, is applied and the test conditions prescribed by US military standards are reflected in the analysis conditions. In addition, the material property data previously obtained by the specimen test of the actual fuel tank is applied to the numerical analysis. As a result, the equivalent stress of the fuel tank material itself and the metal fitting is provided and the possibility of acquiring data for designing the crash-worthiness of the external auxiliary fuel tank is evaluated by examining the behavior and working load of the internal mounted components.

• Journal of the Korean Vacuum Society
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• 제15권4호
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• pp.331-337
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• 2006

Cavity-type beam position monitors were developed in collaboration with KEK to use for the future accelerators such as international linear collider (ILC) or x-ray free electron laser (XFEL) in PAL. BPM components such as BPM cavity, beam tubes, waveguides and feedthroughs were assembled by brazing at the same time to reduce mechanical errors during the fabrication. There are four screwed pins around outer rim of the cavity for the tuning of cavity frequency and x-y isolation. The resonance frequency of BPM is 6.422 GHz, the inner diameter of cavity is 53.822 mm, and the range of mechanical adjusting is $+ / - 250{\mu}m$. The x-y isolation was measured better than -40 dB after tuned. Test results of signal forms, x-y isolations, sensitivities are satisfied within requirements for the KEK ATF2 beam line.

• Journal of the Mineralogical Society of Korea
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• 제27권3호
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• pp.107-114
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• 2014

In this study, we tried to determine the origin of fine-grained sediments in Southeastern Yellow Sea Mud patch (SEYSM) using principal component analysis coupled with semi-quantitative X-ray diffraction analysis for 4 major clay minerals. We used 51 marine surface sediments from SEYSM and 33 surface sediments of rivers flowing into the Yellow Sea. We made bioplot diagram using R program with principal component 1 and component 2 because the two components might contain about 98% of all data. The content of each clay mineral in the south and north regions of SEYSM are almost similar. In the biplot, SEYSM sediments distribute close to Korean rivers sediments than Huanghe and Changjiang sediments. Based on these results, we suggest that SEYSM is originated from the Korean rivers sediments. The higher accumulation rate in the SEYSM compared to the sediment discharge from neighboring Korean rivers can be explained by erosion and reworking of surface sediments in this area. The principal component analysis can be used for the provenance research of marine sediments around the Korean Peninsula.