• Ocean Systems Engineering
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• v.10 no.3
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• pp.333-357
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• 2020

International Maritime Organisation (IMO) regulations insist on reduced emission of CO₂, noxious and other environmentally dangerous gases from ship, which are usually let out while burning fossil fuel for running its propulsive machinery. Contrallability of ship during sailing has a direct implication on its course keeping and changing ability, and tries to have an optimised routing. Bad coursekeeping ability of a ship may lead to frequent use of rudder and resulting changes in the ship's drift angle. Consequently, it increases vessels resistance and also may lead to longer path for its journey due to zigzag movements. These adverse effects on the ship journey obviously lead to the increase in fuel consumption and higher emission. Hence, IMO has made it mandatory to evaluate the manoeuvring qualities of a ship at the designed stage itself. In this paper a numerical horizontal planar motion mechanism is simulated in CFD environment and from the force history, the hydrodynamic derivatives appearing in the manoeuvring equation of motion of a ship are estimated. These derivatives along with propeller thrust and rudder effects are used to simulate different standard manoeuvres of the vessel and check its parameters against the IMO requirements. The present study also simulates these manoeuvres by using numerical free running model for the same ship. The results obtained from both these studies are presented and discussed here.

• The Journal of the Korea Contents Association
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• v.2 no.3
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• pp.119-126
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• 2002

The QoS(Quality of Service) guarantee mechanism is one of critical issues in the wireless network. Real-time applications like VoIP(Voice over IP) in All-IP networks need smooth handoffs in order to minimize or eliminate packet loss as a Mobile Host(MH) transitions between network links. In this paper, we design a new multicasting algorithm using DB(Dynamic Buffering) mechanism for Mobile-IPv6. A key feature of the new protocol is the concepts of the DB and MRA(Multicast Routing Agent) to reduce delivery path length of the multicast datagram. Particularly, the number of tunneling and average routing length of datagram are reduced relatively, the multicast traffic load is also decreased.

• Transactions of the Korean Society of Automotive Engineers
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• v.22 no.3
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• pp.97-104
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• 2014

Automobile trunk latches enable trunks to be opened and closed by a latch mechanism, which can be selectively positioned between a locked condition and an open condition. To maintain structural and electronic performance of the trunk latch, the latch needs to endure impact load that occurs in its open and close motion, and a dynamic mechanism needs to be electronically controled by a contact switch connected with a small DC motor. A base plate, which is the most important component relating to the structural safety, commonly uses a high stiffness material SAPH440-P with high manufacturing cost. In this paper, through structural analysis and optimization, production cost is significantly reduced by replacing SAPH440-P used in some region of the base plate with engineering plastic PBT GF 20%. The optimized contact switch reduces difference between distributed pressures of its two legs, which leads to improve the electronic performance of the trunk latch.

• Biomolecules & Therapeutics
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• v.3 no.3
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• pp.199-204
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• 1995

Gastrodia elata is a medicinal plant which has been used as anticonvulsant in Korea, Japan and China. This study was conducted to examine the action mechanism of Gastrodia elata centering around the change of GABA and glutamic acid level in brain while observing the anticonvulsive effect in PTZ-induced seizure model. Seizures were reduced effectively by pretreatment of ether soluble part of methanol extract of Gastrodia elata. The pretreatment of ether soluble part inhibited not only the decrease of brain GABA level but also the increase of brain glutamic acid level observed in PTZ model of convulsive dose. Although there was not any change in glutamic acid level, the same development was also observed in the model of subconvulsive dose. From above results, it seems that the anticonvulsive component of Gastrodia elata is lipophilic, and its action mechanism is originated from both control action of GABA level and inhibition of glutaminergic neurotransmission.

• Natural Product Sciences
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• v.19 no.1
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• pp.49-53
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• 2013

Paeonia lactiflora Pall (PL) has been used as a traditional herbal medicine in China, Korea, and Japan for more 1,200 years. PL has reported to have antioxidant activity and protective effect of cells from oxidative stress, although the mechanism has not been verified. FOXO3a is a transcription factor that binds to its target gene's consensus FOXO binding site. FOXO3a protein modulates the various biological functions including cell cycle control, apoptosis, DNA repair, and ROS detoxification. Therefore, FOXO3a activity is associated with cancer, aging, diabetes, infertility, neurodegeneration, and immune system dysfunction. Here we found that FOXO3a was activated by PL extract. Transcriptional target genes such as MnSOD, p27, and GADD45 were activated by PL extract. Protein levels of MnSOD and catalase were increased, consequently, ROS level was reduced in HEF cells by PL extract. These findings suggest that PL extract has an antioxidant activity through FOXO activation and thereby activation of FOXO target genes, MnSOD and catalase.

• Journal of the Korean Ceramic Society
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• v.41 no.11
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• pp.812-818
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• 2004

This study has been undertaken with objective of studying the mechanism and condition of formation of hexagonal boron nitride from reduction of boric okide in the presence of carbon under nitrogen atmosphere. It was found that the formation of hexagonal boron nitride was started at 1400$^{\circ}C$ and almost completed its conversion at 1550$^{\circ}C$. The morphology of boron nitride synthesized in this study was very fine and platelet. It was considered as reaction pathway of hexagonal boron nitride that boron oxide was reduced to born and evaporated by activated carbon, and then it was reacted with nitrogen.

• Proceedings of the Zoological Society Korea Conference
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• 1995.10b
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• pp.82-82
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• 1995

Regulation of enzyme synthesis by transcriptional and translational control systems provides rather stable adaptation to change of amino acid level in the growth medium, while manipulation of enzyme activity through endproduct feedback inhibition represents rather short-term and reversible ways of adjusting metabolic fluctuation of amino acid level. Various control mechanisms interplay to regulate genes encoding enzymes for amino acid biosynthesis in the yeast, Sacchromyces cerevisiae. When amino acids are in short supply, genes under a cross-pathway regulatory mechanism Or general amino acid control (general control) increase their action, in which Gcn4p is the major positive regulator of gene expression. When cells are cultured in minimal medium, basal level expression is also regulated by supplementary control elements, where inorganic phosphate level is additionally involved. Most of amino acid biosynthetic genes are also regulated by the level of endproduct of the pathway. This pathway-specific regulatory mechanism is called specific amino acid control (specific controD, under which gene expression is reduced when endproduct is present in the medium. Derepression of a gene through general control can be usually overridden by repression through specific control, where the endproduct level of that particular pathway is high and not limiting. In this presentation, regulatory factors for basal level expression and general control of yeast amino acid biosynthesis will be discussed, m addition to pathway-specific repression patterns and interaction between CrOSS- and specific-control mechanisms. Preliminary results are also presented from the investigation of the cloned genes in the threonine biosynthetic pathway of the yeast. yeast.

• YAKHAK HOEJI
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• v.33 no.3
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• pp.183-190
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• 1989

Angiotensin II, adminstered (infused or injected) intravenously, elicited the antidiuretic action with the decreased parameters of renal function at a small dose ($0.01\;{\mu}g/kg/min$), whereas, at a large dose (0.03, $0.1\;{\mu}g/kg/min$ and $5.0\;{\mu}g/kg$), it produced the diuretic action accompanied the increased amounts of sodium and potassium excreted in urine ($E_{Na}\;and\;R_K$). At this time, glomerular filtration rates (GFR) were weakened slightly and renal plasma flows (RPF) were reduced markedly, and then filtration fractions (FF) were increased. Angiotensin II, infused into a renal artery, exhibited antidiuretic action at a small dose ($0.003\;{\mu}g/kg/min$), and diuretic action at a large dose ($0.01\;{\mu}g/kg/min$), only in infused (experimental) kidney. The mechanism of the action was similar to the cases of the intravenous angiotensin II. The above results suggest that angiotensin II of a large dose produced diuretic action due to mechanism inhibiting reabsorption of electrolytes in renal tubules, mainly in proximal tubule in dog.

• YAKHAK HOEJI
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• v.45 no.4
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• pp.387-396
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• 2001

The effects of ascorbic acid, thiols such as cysteine, n-acetyl-ι-cyteine, glutathione, thiourea, 2-mercaptoethanol and dithiotreithol and organic acids such as magic acid, citric acid, glycolic acid, taurine and kojic acid on polyphenol oxidate (PPO) activity were studied in order to establish if it reacts with oxidized product and/or directly inhibits the enzyme. To investigate the mechanism, the quantification of t-butylcatechol and 4-methylcatechol (phenolic compounds) as substates, their oxidized product and sulphydryl colorless additional compounds were determined by high performance liquid chromatograph (HPLC) method. Chromatographic results indicate that ascorbic acid, organic acids and lower level of cysteine reduced oxidized product of substrates back to their respective positions uf ο-diphenols. On the other hand, other thiols and high level of cysteine reacted with oxidative product of ο-diphenols and then produced sulphydryl colorless compounds. Cysteine apperars to have two types of mechanism of actions in the formation of oxidative products of substrates depending on its concentration; ascorbic acid-type and other thiols-types. The effect of ascorbic acid with thiols on polyphenol oxidase was determined by same method. Chromatographic results indicate that ascorbic acid was more reactive with oxidized product of substrates than thiols.

• Proceedings of the Zoological Society Korea Conference
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• 1995.10b
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• pp.83-83
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• 1995

The three chitin synthetases of Saccharomyces cerevisiae, Chs1, Chs2, and Chs3, participate in septum and cell wall formation of vegetative cells and in wall morphogenesis of conjugating cells and spores. Because of the differences in the nature and in the time of execution of their functions, the synthetases must be specifically and individually regulated. The nature of that regulation has been investigated by measuring changes in the levels of the three synthetases and of the messages of the three corresponding gnes, CDSI, CHS2, and CAL1/CSD2/DITl0l(referred to below as CAL1), during the budding cycles. For Chs1 and Chs3, posttranslational regulation, probably by activation of latent forms, appears to be predominant. Since Chs2, like Chs1, is found in the cell in the zymogenic form, a posttranslational activation step appears to be necessary for this synthetase also. The regulation mechanism was investigated to search the relationship of CAL1, CAL2 and CALJ which is involved in Chs3 activity us ing different assay methods other than previous one. Treatment of Chs3-containing membranes with detergents drastically reduced the enzymatic activity. Activity could, however, be restored by subsequent incubation with trypsin or other pro teases in the presence of UDPGlcNAc. Experiments wi th mutants in the three genes invoIved in Chs3 activity-CAL1, CAL2, and CALJ-showed that only CAL1 and CALJ are required for the proteaseelicited (zymogenic) activity. It is concluded that Chs3 IS a zymogen and that the CAL2 product funct ions as its activator.ivator.