• YAKHAK HOEJI
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• v.51 no.6
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• pp.463-468
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• 2007

Chong Myung Tang is consisted of three medicinal herbs (Acori Graminei Rhizoma, Polygalae Radix and Hoelen cum Radix). It has been used as a medicine for the purpose of learning and memory improvement. In this paper, Chong Myung Tang was screened the biological activities for Alzheimer's disease. The extract (70% ethanol) of Acari Graminei Rhizoma (1 mg/ml) showed that acetylcholinesterase (AChE) and amyloid beta ($A{\beta}$) peptide aggregation inhibitory potency are 43.1% and 76.5%, respectively. The extract of Polygalae Radix showed inhibitory activity against $A{\beta}_{1-42}$ peptide aggregation (51.5%). To predict the drug-likeness, oral absorption ability; blood-brain barrier (BBB) penetraion rate, mutagenecity and carcinogenicity; in silico screening was performed against 16 compounds in the three medicinal herbs. According to the results, all compounds have appropriate chemical structures as medicines. The six compounds in Acori Graminei Rhizoma and the five compounds in Hoelen cum Radix showed excellent oral absorption rate and BBB penetration rate. The four compounds in Polygalae Radix showed excellent oral absorption rate, but their BBB penetration was presented low rate. And, the extract of Hoelen cum Radix didn't show AChE and $A{\beta}_{1-42}$ peptide aggregation inhibitory activities in vitro. Therefore, their activity in brain may be other mechanism. According to all of the results, in silico prediction technology is convenient and effective to determine biological active compounds in medicinal herbs.

• The Korean Journal of Pesticide Science
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• v.6 no.1
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• pp.16-24
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• 2002

Research trends in the measurement of foliar uptake of pesticides and the recently proposed action mechanism of the surfactant-induced uptake of pesticides were reviewed with the related reports and studies. Major techniques used in those fields are bioassay, radiotracer techniques with leaves or cuticular membrane. Recently, a new method using Congo Red as a tracer was proposed. The limiting factor in the pesticides uptake into leaves is the waxy layer which consists of the epicuticular and cuticular wax. Physico-chemical parameters such as molar volume, water solubility and partition coefficient of pesticides have limited influences on the pesticide uptake into leaves. Polydisperse ethoxylated fatty alcohol surfactants are well known as the good activator for many pesticides. It is now generally agreed that uptake activation is not related to the intrinsic surface active properties of surfactants such as surface activity, solvent property, humectancy and critical micelle concentration. Recent studies using ESR-spectroscopy revealed that the surfactants have an unspecific plasticising effect on the molecular structure of the wax and cuticular matrix, leading to increased mobilities of pesticides. Penetration of surfactants into waxy layer altered the pesticide mobility in wax and the partition coefficient of pesticide, and then the pesticides penetration into leaves was enhanced temporally. The enhancing effect of surfactant could be significantly different depending on the carbon number of aliphatic moiety and the number of ethoxy group in polyoxyethylene chain of surfactants. It is suggested that the rate of penetration of surfactants should have a significant relationship with the rate of penetration of pesticides.

• Journal of Energy Engineering
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• v.13 no.4
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• pp.281-290
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• 2004

Spent refractories from a coal gasifier after 1000 hours of operation were analyzed for crystalline phases, chemical composition and microstructures as a function of slag penetration depth, and the slag corrosion mechanism was determined. The chemical corrosion of chromia refractory occurred via reaction between Cr$_2$O$_3$ of the refractory and FeO and A1$_2$O$_3$ in the slag. The FeO reacted with Cr$_2$O$_3$ at the slare/refractory interface and formed FeCr$_2$O$_4$. After all FeO were consumed, Al in the penetrating slag substituted Cr in Cr$_2$O$_3$, forming (Al, Cr)$_2$O$_3$, at the edges of the particle, which were broken to form fragments rich in Al. The corrosion resistance of Cr$_2$O$_3$ varied with the particle size and the extent of sintering, and the higher resistance was observed in the larger and more sintered particles. There was no chemical change in ZrO$_2$, but showed the effects of physical corrosion: the grain boundaries became more wavy, and ZrO$_2$ grains were split in the corroded area. The slag penetration depth increased in the refractory samples farther down from the feed nozzles.

• Journal of the Korea Concrete Institute
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• v.17 no.6 s.90
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• pp.931-938
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• 2005

When concrete structures are exposed under marine condition for a long time, the steel in concrete is corroded due to the ingression of chlorides in the seawater. Because the damages of corrosion resulting from the chloride ion are very serious, many researches have been performed. Silver nitrate colormetric method that can measure easily penetration depth of chloride ion has been executed, recent)y. However, characteristics of silver nitrate colormetric method were not fully examined. Therefore, the objective of this paper Is to study the applicability of colormetric method. For the purpose of this, effect factors and reaction mechanism of colormetric method were investigated, and the colormetric method is applied for marine concrete structures. According to the results of silver nitrate colored method, two reactions such as white reaction of AgCl and brown reaction of AgOH were shown when $AgNO_3$ was sprayed in splited section. And velocity constant ratio(K) of two reactions appeared that white reaction, AgCl reacts with the fast speed by 3240. When the colormetric method was applied in concrete, it is reasonable that $AgNO_3$ solution more than 0.05N concentration was sprayed. It is confirmed that the colormetric method is useful tool for estimating the chloride of concrete structures in situ. The average chloride amount of colored parts indicates $0.9kg/m^3$ per concrete unit weight.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.1
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• pp.111-116
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• 2010

To improve occupants' safety in an emergency, crashworthy design is necessary to rotorcraft design and development. Especially, landing gear has the important role for crashworthy design because landing gear absorbs relatively large energy for the crash landing. In addition, military specifications require failure of landing gear shall not increase danger to any occupants by penetration of the airframe. To meet the specification requirements, crashworthiness device like failure mechanism should be prepared so that landing gear is collapsed safely and doesn't penetrate the airframe. In this study, design and design development test of the failure mechanism which is necessary for the rotorcraft landing gear was performed. First, collapse scenario was determined for the landing gear not to penetrate the airframe. Then, the failure pin which is the most important part of the failure mechanism was designed with 2 strength range in order to meet design criteria. Finally, design of the failure mechanism was verified successfully by design development test.

• Geomechanics and Engineering
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• v.23 no.2
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• pp.127-137
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• 2020

To study the reverse fault formation process and the stress evolution feature, a simulation test system of reverse fault formation is developed based on the analysis of reverse fault formation mechanism. The system mainly consists of simulation laboratory module, operation console and horizontal loading control system, and data monitoring system. It can represent the fault formation process, induce fault crack initiation and simulate faults of different throws. Simulation tests on reverse fault formation process are conducted by using the simulation test system: horizontal loading is added to one side of the model. the bottom rock layer cracks under the effect of the induction device. The crack dip angle is about 29°. A reverse fault is formed with the expansion of the crack dip angle towards the upper right along the fracture surface and the slippage of the hanging wall over the foot wall. Its formation process unfolds five stages: compressive deformation of rock, local crack initiation, reverse fault penetration, slippage of the hanging wall over the foot wall and compaction of fault plane. There is residual structural stress inside rock after fault formation. The study methods and results have guiding and referential significance for further study on reverse fault formation mechanism and rock stress evolution.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.6
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• pp.637-647
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• 2014

In pressurized water reactors, the upper head of the reactor pressure vessel (RPV) contains numerous control rod drive mechanism (CRDM) nozzles. These nozzles are fabricated by welding after being inserted into the RPV head with a room temperature shrink fit. The tensile residual stresses caused by this welding are a major factor in primary water stress corrosion cracking (PWSCC). Over the last 15 years, the incidences of cracking in alloy 600 CRDM nozzles have increased significantly. These cracks are caused by PWSCC and have been shown to be driven by the welding residual stresses and operational stresses in the weld region. Various measures are being sought to overcome these problems. The defects resulting from the welding process are often the cause of PWSCC acceleration. Therefore, any weld defects found in the RPV manufacturing process are immediately repaired by repair welding. Detailed finite-element simulations for the Korea Nuclear Reactor Pressure Vessel were conducted in order to predict the magnitudes of the repair weld residual stresses in the tube materials.

• Journal of Energy Engineering
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• v.18 no.2
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• pp.125-131
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• 2009

Physical characteristics of metals such as hardness, wear-resistance and corrosion-resistance can be artificially controlled by ion implantation. The interaction between ion and solid surface was modeled in molecular scale and simulated by the molecular dynamics method in order to understand the ion implantation mechanism. From the microscopic point of view, the molecular behaviors were observed for improving characteristics of ion implantation. For these purposes, the implantation mechanism and the influences of incident energy, surface temperature and molecular weight were discussed in this study. As the results, the penetration probability was even decreased if incident energy was exceeded any values in the case of high temperature of solid surface. Moreover, it was confirmed that ion implantation into solid surface with amorphous state could be more effective for some conditions.

• Journal of Welding and Joining
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• v.23 no.3
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• pp.76-82
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• 2005

Recently the application of laser welding technology has been considered to shipbuilding structure. However, when this technology is applied to primer coated steel, good quality weld beads are not easily obtained. Because the primer-coated layer caused the spatter, humping bead and porosity which are main part of the welding defect attributed to the powerful vaporizing pressure of zinc. So we performed experiment with objectives of understanding spatter and porosity formation mechanism and producing sound weld beads in 6mmt primer coated steels by a $CO_2$ CW laser. The effects of welding parameters; defocused distance, welding speed, coated thickness and coated position; were investigated in the bead shape and penetration depth on bead and lap welding. Alternative idea was suggested to suspend the welding defect by giving a reasonable gap clearance for primer coated thickness. The zinc of primer has a boiling point that is lower than melting point of steel. Zinc vapor builds up at the interface between the two sheets and this tends to deteriorate the quality of the weld by ejecting weld material from lap position or leaving porosity. Significant effects of primer coated position was lap side rather than surface. Therefore introducing a small gap clearance in the lap position, the zinc vapor could escape through it and sound weld beads can be acquired. In conclusion, formation and suspension mechanism of the welding defects was suggested by controling the factors.

• Archives of Pharmacal Research
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• v.22 no.2
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• pp.165-172
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• 1999

In the present work , the transport mechanism of a capsaicin derivative, DA-5018, through blood-brain barrier (BBB) has been investigated to evaluate the feasibility of potential drug development. The result of pharmacokinetic parameters obtained from the intravenous injection of plasma volume marker,$[3^H]RSA$ and $[{14}^C]DA-5018$, indicated that both AUC, area under the plasma concentration curve and VD, volume of distribution in brain of $[3^H]RSA$ agreed with those reported ($1620{\pm}10 $percentage injected dose minute per milliliter (%IDmin/ml) and $12.0{\pm}0.1{\mu}l/g$, respectively). Elimination half-life and AUC of $[{14}^C]DA-5018$is corrected by the PHLC analysis, 19.6$\pm$1.2 min and 7.69$\pm$0.85% IDmin/ml, respectively. The metabolic rate of $[{14}^C]DA-5018$was very rapid. The blood-brain barrier permeability surface area (PS) product of $[{14}^C]DA-5018$ was calculated to be 0.24$\pm$0.05 $\mu$l/min/g. The result of internal carotid artery perfusion and capillary depletion suggested that [14C]DA-5018 pass through BBB with the time increasingly. Investigation of transport mechanism of $[{14}^C]DA-5018$ using agonist and antagonist suggested that vanilloid (capsaicin) receptor did not exist in the BBB, and nutrient carrier system in the BBB has no effect on the transport of DA-5018. In conclusion, despite the fact that penetration of DA-5018 through BBB is significant, the intact drug found in the brain tissue is small because of a rapid metabolism. Therefore, for the central analgesic effect of DA-5018, the method to increase the metabolic stability in plasma and the brain permeability should be considered.