• YAKHAK HOEJI
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• v.41 no.6
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• pp.698-703
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• 1997

Recently, l-deprenyl (selegiline), a relative new antiparkinson`s drug, has been marketed in Korea. As its metabolites, l-methamphetamine and l-amphetamine, are the enantiomers of illicit drugs,d-methamphetamine and d-amphetamine, a method for analysis of enantiomers of methamphetamine and amphetamine in rat urine was investigated. The optical isomers of methamphetamine and amphetamine were analyzed with the chiral derivatizing reagent (S)-(-)-N-(trifluoroacetyl)-prolyl chloride (l-TFP), which was used to form the diastereomers of methamphetamine and amphetamine. And all diastereomers (l-TFP -l-AM, lTFP-d-AM, l-TFP-l-MA & l-TFP-d-MA) were well resolved by capillary gas chromatography. After administration of 10mg/kg l-deprenyl to rat, l-methamphetamine and l-amphetamine were detected without autoracemization to the d form in all urine samples collected during 24hrs, and the ratios of l-amphetamine/l-methamphetamine were 1.1~3.3. l-Amphetamine was detected in only 3 out of 8 urine samples collected during 24~48hrs where as no l-methamphetamine was detected in all cases.

• Nuclear Engineering and Technology
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• v.52 no.10
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• pp.2353-2360
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• 2020

An anodic electrophoretic deposition (EPD) technique is used to create a uniform TiO₂ thin film coating on boiling thin steel plates (1.1 mm by 90 mm). All of the effective parameters except time of the EPD method are kept constant. To investigate the effect of gamma irradiation on the critical heat flux (CHF), the test specimens were irradiated in a gamma cell to different doses ranging from 100 to 300 kGy, and then SEM and BET analysis were performed. For each coated specimen, the contact angle and capillary length were measured. The specimens were then tested in a boiling pool for CHF and boiling heat transfer coefficient. It was observed that irradiation significantly decreases the maximum pore diameter while it increases the porosity, pore surface area and pore volume. These surface modifications due to gamma irradiation increased the CHF of the nano-coated surfaces compared to that of the unirradiated surfaces. The heat transfer coefficient (HTC) of the nano-coated surfaces irradiated at 300 kGy increased from 83 to 160 kW/(㎡ K) at 885 kW/㎡ wall heat flux by 100%. The CHF of the irradiated (300 kGy) and unirradiated surfaces are 2035 kW/㎡ and 1583 kW/㎡, respectively, an increase of nearly 31%.

• Carbon letters
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• v.27
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• pp.90-97
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• 2018

Electromagnetic interference (EMI) shielding is an important issue in modern daily life due to the increasing prevalence of electronic devices and their compact design. This study estimated EMI-shielding effect (EMI-SE) of small ($8-14{\times}17mm$) Hanji (Korean traditional paper) doped with carbon nanotubes (CNTs) and compared to Hanji without CNT using $^2H$ (92.1 MHz) and $^{23}Na$ (158.7 MHz) nuclear magnetic resonance (NMR) peak area data obtained from 1 M NaCl in $D_2O$ samples in capillary tubes that were wrapped in the Hanji samples. The simpler method of using the variation of reflected power and tuning frequency by inserting the sample into an NMR coil was also tested at 242.9, 158.7, and 92.1 MHz. Overall, EMI shielding was relatively more effective at the higher frequencies. Our results validated that NMR methods to be useful to evaluate EMI-SE, particularly for small, flexible shielding materials, and demonstrated that EMI shielding by absorption is dominant in Hanji mixed with CNT.

• 보존과학연구
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• s.16
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• pp.112-122
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• 1995

TEN-STORIED STONE PAGODA ON THE SITE OFWON-GAKSA(Temple) which is one of three marble pagodas in South Korea, were dated from the thirteenth year of the reign of King Sejo(1467). On the roof and surface of each the stories, there were large amount of the contaminants such as pigeon′s excretions, dust and environmental elements for a long time. The pH of contaminants is not acid, but is 7.2, neutral. To find the species of organic acidscontained in the contaminants and the degree of damaging for a marble pagoda, we analyzed the contaminants using GC-MSD method by the following procedures. Organic acids were extracted by saponifying whole contaminants. After Saponification, the organic acids were mathylated to increase their volatility upon subsequent GC-MSD analysis. The mathyl esters of the organic acids are extracted from the acidified aqueous solution. And the organic extracts were washed with adilute base solution. The washed extract were analyzed by GC(Hewlett Packard 5890)with a nonpolar capillary column(Crosslinked 5% Ph Me Silicone, $50×0.2㎜×0.33\mum$film thickness, USA) and Mass Spectrometric Detector(Hewlett Packard 5970B).As the result, it was found that 12 organic acids were the main compound in pagoda′contaminants, and the amount of organic acid were negligible.

• Journal of the Korean Society for Precision Engineering
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• v.21 no.6
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• pp.139-144
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• 2004

In order to discuss the availability of hydrostatic guideways driven by the coreless linear motor to ultra precision machine tools, a prototype of guideway is designed and tested in this research. A coreless linear DC motor with the continuous force of 156 N and a laser scale with the resolution of 0.01 ${\mu}{\textrm}{m}$ are used as the feeding system. The experiments are performed on the static stuffiness, motion accuracy, positioning accuracy, microstep response and variation of velocity. The guideway has the infinite axial stillness within 50 N of applied load, and by the motion error compensation method using the Active Controlled Capillary, 0.08 ${\mu}{\textrm}{m}$ of linear motion error and 0.1 arcsec of angular motion error are acquired. The guideway also has 0.21 ${\mu}{\textrm}{m}$ of positioning error and 0.09 ${\mu}{\textrm}{m}$ of repeatability, and it shows the stable response against the 0.01 ${\mu}{\textrm}{m}$ resolution step command. The velocity variation of feeding system is less than 0.6 %. From these results, it is confirmed that the hydrostatic guideway driven by the coreless linear motor is very useful fur the ultra precision machine tools.

• 한국신재생에너지학회:학술대회논문집
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• 2006.06a
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• pp.425-428
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• 2006

Natural gas hydrate has been a major problem for its plugging nature in the pipeline. With the demand of deep-water production, the importance of flow assurance technology, preventing hydrate, asphaltene and wax in the pipeline becomes bigger Kinetic models combined with the flow simulator are being developed to explain the nature of hydrate plug formation in the pipeline. To simulate the hydrate plug formation, each stage including the nucleation, growth and agglomeration should be considered. The hydrate nucleation is known to be stochastic and is believed hard to be predicted. Recent publications showed hydrate growth and agglomeration can be observed rigorously using a particle size analyzer. However properties of the hydrate should be investigated to model the growth and agglomeration. The attractive force between hydrate particles, supposed to be the capillary force, was revealed to be stochastic. Alternative way to model the hydrate agglomeration is to simulate by the discrete element method. Those parameters, particle size distribution, attractive force, and growth rate are embedded into the kinetic model which is combined Into the flow simulator. When compared with the flowloop experimental data, hydrate kinetic model combined into a flow simulator showed good results. With the early results, the hydrate kinetic model is promising but needs more efforts to improve it.

• Asian Journal of Turfgrass Science
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• v.9 no.3
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• pp.173-185
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• 1995

Hydroseeding technique is a very popular method of revegetating slope areas through the control of soil erosion and stability by seeding grasses. This study was conducted to select turfgrass species and cultivars for hydroseeding. Experiment plots were established on various soil types and environmental conditions at Singar-Ansan high-way construction site. The investigation was designed in three cutting, one back-filling and other three spare sites with various seed mixtures. Results indicated that combinations of seed mixtures influenced seed germination and rates of surface cover. In a view of long term, vegetation shifts should be influenced by characters of slopes and micro-climate conditions. Hydroseeding did not show good results on rocky slope areas. Revegetation was only going on where there had soil. The combination of seed mixture with a higher rate of perennial ryegrass had relatively good revegetation with faster germination and seedling growth. Improved turf-type tall fescue Arid ⓡ and Falcon ⓡ seemed to have good environ-mental adaptation and drought tolerance. Wild or old type cultivars showed relatively slow green-up in spring and growth rates at the next year of seeding. For the harmonious landscaping with surrounding area, the combination of native grass mixture with cool-season grasses had good results. Slow and low revegetation rate at hack-filling site seemed to be caused by the poor development of capillary tubes in sub-soil. It was shown that a high correlation between seed germination and revegetation rate, and between three-month later coverage rate and final rate. The evaluation of coverage rate after three month seems to he acceptable to decide the accomplishment of hydroseeding results on rode side slopes.

• Proceedings of the Ginseng society Conference
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• 2002.10a
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• pp.27-34
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• 2002

Clinical study on hemodynamics of healthy elders before and after tread mill. Using doubleblind, placebo-controlled study design. Seventy-five 50-70 years old volunteers without organic disease were divided into two groups, Ginseng group and control group. Each subject was received 3 g Korea Red Ginseng (KRG) capsules or placebo per day for 4 weeks. Before and after administration 4 weeks, the symptoms were asked and hemodynamics parameter such as pump function, systolic function, preload and afterload were recorded before and after tread mill 1,5, 10 minutes by the method of thoracic impedance cardiograph. The result showed that Ginseng could improve quality of life, had obvious effect of increasing PEP (pre-ejection period), PEP/LVET (pre-ejection period/left ventricular ejection period), PCWP (wedged pressure pulmonary capillary). The change rate of HR (heart rate), SV (stroke volume) in KRG group were much lowered, while EF (ejection fraction), LVET (left ventricular ejection period), LVEDP (left ventricular end diastolic pressure) was recovered much quickly. The circulation showed Ginseng could improve the quality of life though its promoting circulation function which are increasing both the systolic function and the preload.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.18 no.4
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• pp.304-311
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• 2006

Experiments on evaporative spray cooling on the square plate heaters with plain or micro-porous coated surfaces were performed in this study. Micro-porous coated surfaces were made by using DOM [Diamond particle, Omegabond 101, Methyl-Ethyl-Keton] method. In case of purely air-jet cooling, the micro-porous coating doesn't affect the cooling capacity. In spray cooling three different flow patterns (complete wetting, evaporative wetting, dryout) are observed on both plain and micro-porous coated surfaces. The effects of various operating conditions, such as water flow rate, particle size, and coating thickness were investigated on the micro-porous coated surfaces. It is found that the level of surface wetting is an important factor to determine the performance of spray cooling. It depends on the balance between absorbed liquid amount by capillary force over porosity and the evaporative amount. The micro-porous coated surface has largest cooling capacity, especially in the evaporative wetting zone. It is found that the effects of liquid flow rate and coating thickness are significant in evaporative wetting zone, but are not in complete wetting and dryout zones.

• Journal of Magnetics
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• v.17 no.3
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• pp.225-228
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• 2012

Muscle contusion usually results from a direct blunt impact and is frequently associated with contact sports. Muscle contusion results from microscopic muscle fiber and capillary disruption causing a microhemorrhage dissecting torn fibers and remaining viable muscle fibers. Recent studies concluded that some physical methods, including pulsed ultrasound (PU) and pulsed electromagnetic field (PEMF) treatment, accelerate and facilitate wound healing, improve scar quality and have beneficial effects on muscle and tendon healing. However, there are few studies on the effects of the early use of physical methods, such as PU and PEMF, on the expression of neurotrophic factors. The objective of this study was to investigate the effects of the early application of PU and PEMF, measured through the expression of BDNF in the muscles (gastrocnemius) and spinal cords of rats after skeletal muscle contusion. In the spinal cords and muscles, there was a significant increase of BDNF expression in the PEMF and PU groups, a greater increase was found in the PEMF group than in the PU group. In conclusion, PEMF is a useful therapeutic method that improves muscle healing after muscle contusion.