• 대한기계학회논문집B
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• 제20권6호
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• pp.2014-2022
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• 1996

Flow characteristics of the wake behind a finite circular cylinder(FC) mounted on a flat plate was experimentally investigated. Three finite cylinder models having aspect ratio (length to diameter ratio, L/D) of 6,10 and 13 were tested in this study. Wake velocity was measured by a hot-wire anemometry at Reynolds number of 20,000, and the results were compared with those of two-dimensional circular cylinder. As a result, the free-end effect on the wake structure becomes more dominant with decreasing the aspect ratio(L/D) of the finite cylinder. Invisid flow entrained into the wake region decreases the turbulence intensity and periodicity of the vortex shedding due to existence of the free end. From spectral analysis and cross correlation of the velocity signals, vortices having 24Hz frequency characteristics are found in the down wash flow just behind the free end. There exists very complicated flow near the free end due to interaction between the entrained flow and streamwise vortices. Vortex formation region is destroyed significantly in the near wake and shows quite different wake structures from those of 2-D cylinder.

• 로봇학회논문지
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• 제3권2호
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• pp.106-111
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• 2008

This paper presents a decentralized coordination for a small-scale mobile robot teams performing a task through cooperation. Robot teams are required to generate and maintain various geometric patterns adapting to an environment and/or a task in many cooperative applications. In particular, all robots must continue to strive toward achieving the team's mission even if some members fail to perform their role. Toward this end, given the number of robots in a team, an effective coordination is investigated for decentralized formation control strategies. Specifically, all members are required first to reach agreement on their coordinate system and have an identifier (ID) for role assignment in a self-organizing way. Then, employing IDs on individual robots within a common coordinate system, a decentralized neighbor-referenced formation control is realized to generate, keep, and switch between different geometric shapes. This approach is verified using an in-house simulator and physical mobile robots. We detail and evaluate the formation control approach, whose common features include self-organization, robustness, and flexibility.

• 생약학회지
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• 제40권4호
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• pp.382-387
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• 2009

Enhanced formation and accumulation of advanced glycation end products (AGEs) have been implicated as a major pathogenesis process leading to diabetic complications, normal aging, atherosclerosis and Alzheimer's disease. In our ongoing project to discover novel treatments for diabetic complications from natural sources, we have investigated on the inhibitory activity of 67 ethanol extracts from 57 Korean herbal medicines against the formation of AGEs in vitro. Of these, 22 extracts were found to have a significant AGEs inhibitory activity ($IC_{50}$<50 ${\mu}g$/ml) compared with aminoguanidine ($IC_{50}$=75.98 ${\mu}g$/ml). Particularly, 6 extracts from 3 herbal medicines, Castanea crenata (flower, leaf, bark-twig), Acer tatarium subsp. ginnala (fruit) and Sapium japonicum (leaf, twig) showed (approximately 8-17 fold) stronger inhibitory activity than that of aminoguanidine.

• Journal of Nutrition and Health
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• 제49권4호
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• pp.233-240
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• 2016

항산화, 항암 및 항염증 효능 등의 생리 활성이 보고된 우엉 뿌리의 열수 추출물을 제조하여 advanced glycation end products (AGEs) 형성 저해 효과를 확인하였다. AGEs는 bovine serum albumin (BSA)과 단당류인 glucose, fructose, galactose를 혼합하여 $37^{\circ}C$에서 3주간 배양하여 생성하였고 매주 형광도 측정, fructosamine 분석, ${\alpha}$-dicarbonyl compounds 함량 분석을 통해 AGEs의 생성량을 확인하였다. 우엉 뿌리 추출물의 AGEs 생성 저해능을 AGEs 생성 억제제로 알려져 있는 aminoguanidine (AG)의 저해능과 비교하였다. 우엉 뿌리 추출물은 BSA와 단당류인 glucose, fructose, galactose 각각의 당화반응을 억제하였으며 특히 배양 3주차에서 BSA와 glucose의 당화반응 결과물인 AGEs 생성을 유의적으로 저해하였다. 농도 2 mg/mL 이상의 우엉 뿌리 추출물은 1 mM AG보다 AGEs 생성 저해능이 우수하였으며 농도 4 mg/mL의 우엉 뿌리 추출물은 배양 3주차에서 AGEs 생성을 약 80% 이상 억제하는 효능을 나타냈다. 체내 혈당은 당뇨병과 같은 질환과 식이의 영향을 받으므로 다양한 glucose 농도에서 우엉 뿌리 추출물의 AGEs 생성 억제능을 조사하였다. 그 결과 AGEs 생성은 glucose의 농도에 비례하여 증가하였으며 우엉 뿌리 추출물은 당뇨환자의 식후에 관찰되는 혈당인 25 mM glucose 군에서 1 mM의 AG보다 높은 우수한 저해 효과를 확인하였다. 본 연구 결과는 우엉 뿌리 추출물의 AGEs 생성 억제라는 새로운 기능성을 밝히며 향후 당뇨 합병증 예방 효능을 가진 기능성 식품으로의 개발 가능성을 제시한다.

• Bulletin of the Korean Chemical Society
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• 제9권3호
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• pp.167-171
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• 1988

Formation of intermolecular charge-transfer complexes between 7,7,8,8-tetracyanoquinodimethane (TCNQ) and two different series of stilbene derivatives has been studied spectroscopically at $25^{\circ}$C in 1,2-dichloroethane. The compounds of Series I include stilbene and derivatives which have fused phenyl rings on one end of the central ethylene structure and a phenyl ring on the other end. The other Series, II, is comprised of stilbenes which have various para substituents on one of the two phenyl rings. The equilibrium constant, $K_c^{AD}$ and the molar extinction coefficient, ${\varepsilon}_{\lambda}^{AD}$, were determined using the Scott equation. The values of the charge-transfer transition frequency, ${\vu}_AD$ and $K_c{AD}$ correlated well respectively with the ionization potentials of the fused rings of Series Ⅰ or of the compounds of Series II and with the values of ${\sigma}_p$, the Hammett constants of the Series II substituents. trans-4-N,N-Dimethylaminostilbene and trans-4-nitrostilbene were found to be able to participate in electron transfer reaction with TCNQ forming the corresponding anion radical, TCNQ$^-$:

• 천문학회지
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• 제14권2호
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• pp.55-71
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• 1981

On the basis of observational constraints, particularly the relationship between metal abundance and cumulative stellar mass, a simple two-zone disk-halo model for the chemical evolution of our Galaxy was investigated, assuming different chemical processes in the disk and halo and the infall rates of the halo gas defined by the halo evolution. The main results of the present model calculations are: (i) The halo formation requires more than 80% of the initial galactic mass and it takes a period of $2{\sim}3{\times}10^9$ yrs. (ii) The halo evolution is divided into two phases, a fast collapse phase ($t=2{\sim}3{\times}10^8$ yrs) during which period most of the halo stars $({\sim}95%)$ are formed and a later slow collapse phase which is characterized by the chemical enrichment due to the inflow of external matter to the halo. (iii) The disk evolution is also divided into two phases, an active disk formation phase with a time-dependent initial mass function (IMF) up to $t{\approx}6{\times}10^9$ yrs and a later steady slow formation phase with a constant IMF. It is found that at the very early time $t{\approx}5{\times}10^8$ yrs, the metal abundance in the disk is rapidly increased to ${\sim}1/3$ of the present value but the total stellar mass only to ${\sim}10%$ of the present value, finally reaching about 80% of the present values toward the end of the active formation phase.

• 한국기계가공학회지
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• 제17권3호
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• pp.1-6
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• 2018

Micro prism pattern is applying in order to get increase of luminance, control the light, and so forth especially in optics and display industry. Most patterns are fabricated by lithography, planning, and EDM, but they have limitations on the productivity or the unit cost of produce. However, ultra precision mold is one of the processes able to replace it, and assure high productivity required by industries. In this investigation, micro prismatic end-milling is suggested in order to fabricate the pattern effectively. Micro prism pattern having $100{\mu}m$ of pitch and height was machined on STD-11. After machining, the flank and boundary wear on micro end mill were measured and analyzed, as well as burr formation and dimensional accuracy of fabricated pattern were evaluated. Thus the optimal cutting conditions were derived.

• Restorative Dentistry and Endodontics
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• 제22권1호
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• pp.305-324
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• 1997

Numerous materials such as amalgam, IRM, SuperEBA, dessicated ZOE, and Ketac-Silver have been used as a root-end filling material or to repair furcation perforations. But so far no material has been found to satisfy all of the requirements of an ideal restorative material. Recently, mineral trioxide aggregate (MTA) has been suggested for use as a root end filling material and for the repair of furcation perforations. The purpose of this study was to compare the effect of MTA on the proliferation of MC3T3/E1 osteoblastic cell, formation of bone nodule, alkaline phosphatase activity, and finally the tissue reaction of bone with those of amalgam, IRM, SuperEBA, dessicated ZOE, and Ketac-Silver. The following conclusions were drawn within the limits of the experimental results : 1. MTA showed a excellent proliferation of osteoblastic cell and Ketac-Silver showed moderate proliferation of osteoblastic cell. The rest of test materials showed no proliferation of osteoblastic cell. 2. Many of definite bone nodules were found in the MTA group. In contrast, Ketac-Silver group showed no definite bone formation but only showed mild sign of bone formation. 3. Alkaline phosphatase activity of Ketac-Silver and MTA showed similar results. But both of them showed higher activity than that of other materials (p<0.005). 4. The tissue reaction to implanted MTA in the calbarium of mouse was milder than that observed with other materials. The tissue reaction of dessicated ZOE showed the worst results among the test materials.

• 한국식품영양과학회지
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• 제28권3호
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• pp.638-645
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• 1999

This study was done to investigate effects of ${\gamma}$ irradiated beef feeding on the formation of gluta thione S transferase placental form positive(GST P+) foci, lipid peroxidation, cytochrome P450 system and microsomal glucose 6 phosphate activity in diethylnitrosamine(DEN) initiated rat hepatocarci nogenesis. Weaning Sprague Dawley male rats were fed the diet containing ${\gamma}$ irradiatied ground beef at the dose of 0, 3, 5kGy as a 20% of protein source for 8 weeks. One week after feeding, rats were intraperitoneally injected twice with a dose of DEN(50mg/kg BW). As a promoter, 0.05% phenobarbital was fed in drinking water from one week after DEN treatment until the end of experiment. At the end of 8th week, rats were sacrificed and hepatic GST P+ foci, microsomal malondialdehyde(MDA) and conjugated diene contents were determined. In addition, cytochrome P450 content and the activities of NADPH cytochrome P450 reductase and glucose 6 phosphatase were also measured. There was no significant effect by gamma irradiation on microsomal MDA content, conjugated diene, cytochrome P450 content and activities of NADPH cytochrome P450 reductase and glucose 6 phosphatase. However with DEN treatment, microsomal MDA content and conjugated diene contents were significantly changed. Cytochrome P450 content was also significantly increased while microsomal glucose 6 phophatase activity was significantly decreased with DEN treatment. However activity of NADPH cytochrome P450 reductase was not affected. An interesting finding in this study was that the number and area of hepatic GST P+ foci of the rats fed gamma irradiated beef were significantly(p<0.05) lower than those of the control. Such a lowering effect on GST P+ foci formation was highest at the dose of 3kGy than others. Overall results suggest that the consumption of low dose of gamma irradiated beef does not affect the formation of lipid peroxide, cytochrome P450 system and membrane stability.

• 대한본초학회지
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• 제32권3호
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• pp.63-69
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• 2017

Objectives : Advanced glycation end product (AGEs) is combine formation of glucose and protein. AGEs and reactive oxygen species are potential therapeutic targets for the various disease such as diabetic complications, renal injury, skin damage. The aim of this study was investigated the AGEs inhibitory activity and antioxidant activity of water extracts from 40 Korean medicines and 5 heating-processed Korean medicines. Methods: AGEs formation inhibitory activities of Korean medicines measured using bovine serum albumin (BSA), glucose, and fructose. Then, five effective Korean medicines were selected and heated with 30% ethanol. The AGEs inhibitory activities of heated Korean medicine were measured compared with not-heated Korean medicines. The antioxidant activities were evaluated through radical scavenging assays using 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) radicals. Furthermore, we examined total phenol and flavonoids contents. Results: Scutellariae Radix, Corni Fructus, Persimmon Fruit, Paeoniae Radix, Mori Folium respectively reduced AGEs production. Morever, heating-processed Scutellariae Radix has AGEs inhibitory activities better than not-processed Scutellariae Radix. Heating- processed Scutellariae Radix scavenged DPPH and ABTS effectively and $IC_{50}$ of DPPH and ABTS radical scavenging activity of Heat processed Scutellariae Radix were $15.47{\pm}0.26{\mu}g/m{\ell}$ and $12.07{\pm}1.23{\mu}g/m{\ell}$. It caused heat processing methods of Scutellariae Radix up regulated total phenol and flavonoids contents ($26.68{\pm}0.01$ to $46.15{\pm}0.10$, $20.30{\pm}0.38$ to $64.20{\pm}0.52$). Conclusion: It has AGEs inhibitory activities that 20 kind of medicinal plants of 40 medicinal plants. Especially, heat processed Scutellariae Radix has excellent AGEs inhibitory activities and antioxidant effect.