저공해 사이클론 연소기 설계를 위한 유동해석 연구

전영남,백원석,김승호,김미환 조선대학교 환경연구소 2001 環境硏究 Vol.17 No.2

Cyclone combustors are being used for burning a wide range of fuel such as, low calorific value gas, waste water, sludge, coal, etc. The 3-dimensional swirling flow in a tangential inlet cyclone combustor with different inlet conditions and dimensions are simulated using a standard k-e turbulence model. The main parameters considered in this work are inlet velocity, inlet number, exit diameter, body length, vortex finder length and inlet area. The results show that the change of parameters has an influence on the shape and size of recirculation zones, vortex core and flow field, which are important factors for combustion efficiency and emissions. The application of this kind of computer program looks promising as a potential tool for optimum design of a cyclone combustor with high level of the swirling flow.

유백피 메탄올 추출물에 의한 Melanin 합성 조절

정승일,김춘관,전병훈,백승화,우원홍,천현자 대한동의병리학회 2001 동의생리병리학회지 Vol.15 No.5

Melanogenesis is a physiological process resulted in the synthesis of melanin pigments, which have a role in protecting skin from the damaging effect of ultra-violet(UV) radiation. The main aim of the present study was to examine the effect of Ulmus davidiana var. japonica on melanogenesis. Cells were cultured in the presence of methanol extracts from Ulmus davidiana var. japonica for 48 h, and there were estimated total melanin content as a final product and activity of tyrosinase, a key enzyme, in melanogenesis. Methanol extracts of the bark Ulmus davidiana var. japonica increased tyrosinase activity and melanin contents in a dose-dependent manner. Especially, It was observed that only 100 μg/ml methanol extract stimulates melanin secretion in B16/F10 melanoma cells by 140% at 48 h treatment and activity of tyrosinase increased by 250 % in the presence of same concentration.

CNC 라우터 베드 구조해석에 관한 연구

백승엽(Seung-Yup Baek),윤태현(Tae-Hyun Yoon),양부열(Bu-Yeol Yang),김성현(Seong-Hyun Kim),최승건(Seung-Geon Choi),최웅걸(Woong-Kirl Choi),전광호(Kwang-Ho Chun),진다솜(Da-Som Jin) 한국산학기술학회 2015 한국산학기술학회 학술대회 Vol.2015 No.1

기존 판형 사인에서 고급 입체 사인물의 수요 변화로 아크릴 및 비금속 소재와 판형 금속 소재의 가공 수요는 증가하고 있지만, 이를 동시에 가공할 수 있는 복합 장비는 극히 제한적인 수준이다. 또한, 기존의 수동 복합기의 경우 사용상의 어려움 및 낮은 효율성으로 실질적인 수요가 없는 편이다. 본 논문에서는 가공 공정을 최적화하면서 수익률 증가를 보장할 수 있는 CNC 라우터 복합 시스템의 개발을 위해 기초 단계로서 베드의 구조에 따른 구조해석을 진행하였다. 베드의 스크류의 개수 및 위치에 따른 하중 해석을 진행하였으며, 해석 결과를 바탕으로 CNC 라우터 시스템의 개발을 진행할 것이다.

Inhibitory effects of ethanol extract of Atractylodis Rhizoma on melanogenesis in B16/F10 melanoma cells

Chun, Hyun-Ja,Lee, Jeong-Ho,Choi, Eun-Young,Baek, Seung-Hwa Kyung Hee Oriental Medicine Research Center 2003 Oriental pharmacy and experimental medicine Vol.3 No.2

The inhibitory effect of Atractylodis Rhizoma alba extract(AM) on melanogenesis was studied by using B16/F10 melanoma in culture. Cells were cultured in the presence of various concentrations of AM for 48 hrs, and the experiment of total melanin content as a final product and activity of tyrosinase, a key enzyme, in melanogenesis. AM significantly inhibited tyrosinase activity, and melanin content in a dose-dependent manner. These results show that Atractylodes macrocephala extract could be developed as skin whitening components of cosmetics.

Biological Activities of Methyl-4-[[(2E)-3,7-dimethyl-oxy]-3-hydroxybenzoate

Baek, Seung-Hwa,Oh, Hyun-Ju,Lim, Jin-A,Chun, Hyun-Ja,Lee, Hyun-Ok,Ahn, Jong-Woong,Perry, Nigel B.,Kim, Hyung-Min Korean Chemical Society 2004 Bulletin of the Korean Chemical Society Vol.25 No.2

Methyl-4-[[(2E)-3,7-dimethyl-2,6-octadienyl]oxy]-3-hydroxybenzoate (5) has been identified from the New Zealand liverwort Trichocolea hatcheri (T. hatcheri) on the basis of spectroscopic evidence. This compound was tested for its growth inhibitory effects against tumor cell lines, using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-2H-tetrazolium bromide (MTT) assay. It showed growth inhibition activity against Staphylococcus epidermidis (MIC, 1,000 ${\mu}$g/mL). These results suggest that compound 5 possesses antitumoral , antimicrobial and antioxidative activities.

Room-Temperature Ring-Opening of Quinoline, Isoquinoline, and Pyridine with Low-Valent Titanium

Baek, Seung-yeol,Kurogi, Takashi,Kang, Dahye,Kamitani, Masahiro,Kwon, Seongyeon,Solowey, Douglas P.,Chen, Chun-Hsing,Pink, Maren,Carroll, Patrick J.,Mindiola, Daniel J.,Baik, Mu-Hyun American Chemical Society 2017 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.139 No.36

<P>The complex (PNP)Ti=(CHBu)-Bu-t((CH2Bu)-Bu-t) (PNP = N[2-P(i)p(r2)-4-methylphenyl](2-)) dehydrogenates cyclohexane to cyclohexene by forming a transient low-valent titanium-alkyl species, [(PNP)Ti((CH2Bu)-Bu-t)], which reacts with 2 equiv of quinoline (Q) at room temperature to form (H3CBu)-Bu-t and a Ti(IV) species where the less hindered C-2=N-1 bond of Qis ruptured and coupled to another equivalent of Q, The product isolated from this reaction is an imide with a tethered cycloamide group, (PNP)Ti=N[C18H13N] (1). Under photolytic conditions, intramolecular C-H bond activation across the imide moiety in 1 occurs to form 2, and thermolysis reverses this process. The reaction of 2 equiv of isoquinoline (Iq) with intermediate [(PNP)Ti((CH2Bu)-Bu-t)] results in regioselective cleavage of the C-I=N-2 and C-1-H bonds, which eventually couple to form complex 3, a constitutional isomer of 1. Akin to 1, the transient [(PNP)Ti((CH2Bu)-Bu-t)] complex can ring-open and couple two pyridine molecules, to produce a close analogue of 1, complex (PNP)Ti=N[C10H9N] (4). Multinudear and multidimensional NMR spectra confirm structures for complexes 1-4, whereas solid-state structural analysis reveals the structures of 2, 3, and 4. DFT calculations suggest an unprecedented Mechanism for ring-opening of Q wheat the reactive intermediate in the low-spin manifold crosses over to the high-spin surface to access a low-energy transition state but returns to the low-spin surface immediately. This double spin-crossover constitutes a rare example of a two-state reactivity, which is key for enabling the reaction at room temperature. The regioselective behavior of Iq ring-opening is found to be due to electronic effects, where the aromatic resonance of the bicycle is maintained during the key C-C coupling event.</P>

Detection of Methomyl, a Carbamate Insecticide, in Food Matrices Using Terahertz Time-Domain Spectroscopy

Baek, Seung Hyun,Kang, Ju Hee,Hwang, Yeun Hee,Ok, Kang Min,Kwak, Kyungwon,Chun, Hyang Sook Springer-Verlag 2016 Journal of infrared, millimeter and terahertz wave Vol.37 No.5

<P>The aim of this study was to investigate the feasibility of detecting methomyl, a carbamate insecticide, in food matrices (wheat and rice flours) using terahertz time-domain spectroscopy (THz-TDS). In the frequency range 0.1-3 THz, the characteristic THz absorption peaks of methomyl at room temperature were detected at 1 (33.4 cm(-1)), 1.64 (54.7 cm(-1)), and 1.89 (63.0 cm(-1)) THz. For detailed spectral analysis, the vibrational frequency and intensity of methomyl were calculated using solid-state density functional theory to mimic molecular interactions in the solid state. Qualitatively, the simulated spectrum was in good agreement with the experimental spectrum. Analysis of the individual absorption modes revealed that all of the features in the THz spectrum of methomyl were mainly generated from intermolecular vibrations. The peak appearing at 1 THz (33.4 cm(-1)) was then selected and tested for its suitability as a fingerprint for detecting methomyl in food matrices. Its absorbance was dose-dependently distinguishable from that of wheat and rice flours. The calibration curve of methomyl had a regression coefficient of > 0.974 and a detection limit of < 3.74 %. Accuracy and precision expressed as recovery and relative standard deviation in interday repeatability were in the ranges 78.0-96.5 and 2.83-4.98 %, respectively. Our results suggest that THz-TDS can be used for the rapid detection of methomyl in foods, but its sensitivity needs to be improved.</P>

Practical error concealment strategy for video streaming adopting scalable video coding

Chun-Su Park,Hyeong-Min Nam,Seung-Won Jung,Seung-Jin Baek,Sung-Jea Ko IEEE 2009 IEEE transactions on consumer electronics Vol.55 No.3

<P>The scalable video coding (SVC) standard adopts four post-processing error concealment (EC) methods as a non-normative tool in order to conceal a lost picture in transmission. In this paper, we first introduce an error tracking model with which the concealment error and propagation error can be estimated. Then, we analyze the four EC methods using the error tracking model. Until now, there have been few studies on how to conceal SVC bitstream corrupted by burst errors. Based on the results of the error analysis, we propose a selection-based EC strategy to conceal burst errors for SVC bitstream. In the proposed strategy, one of the four EC methods is adaptively selected such that the visual degradation is minimized for each lost picture. The experimental results show that the proposed EC strategy can improve the EC performance without increasing the computational complexity. Moreover, the proposed strategy does not require any modification of the conventional SVC codec since it utilizes only the EC methods adopted in the standard.</P>

Biological Activity of Water Extract from Atractylodes macrocephala

Chun Ju Yeon,Lee Hyun Ok,Baek Seung Hwa The Physiological Society of Korean Medicine and T 2004 동의생리병리학회지 Vol.18 No.2

The effects of water extract from Atractylodes macrocephala Koidz on biological activity were investigated. The crude water extract of A. macrocephala inhibited the growth of the dermatophytic fungus Trichophyton mentagrophytes ATCC 28185, (3 mm inhibition zone at 300 ㎍/disc). However, it did not show growth inhibition activity against Sreptococcus mutans JC-2 (MIC >1,000 ㎍/mL). This extract was cytotoxic to P388 murine leukaemia cells ATCC CCL 46 P388D1, (IC/sub 50/ 62.24 ㎍/mL at 150 ㎍/disc). These results suggest that water extract of A. macrocephala possesses antitumoral, and antimicrobial activities.

Reduced restenosis and enhanced re-endothelialization of functional biodegradable vascular scaffolds by everolimus and magnesium hydroxide

Baek Seung-Woon,Kim Da-Seul,Song Duck Hyun,Kim Han Byul,Lee Semi,김준혁,Lee Jun-Kyu,Hong Young Joon,Park Chun Gwon,Han Dong Keun 한국생체재료학회 2023 생체재료학회지 Vol.27 No.00

Coronary artery disease is a cardiovascular disease with a high mortality and mortality rate in modern society. Vascular stent insertion to restore blood flow is essential to treat this disease. A fully biodegradable vascular scaffold (BVS) is a vascular poly (L-lactic acid) (PLLA) stent that is receiving growing interest as this is biodegradable in the body and does not require secondary removal surgery. However, acidic byproducts composed of PLLA produced during the biodegradation of the BVS can induce an inflammatory response. Magnesium hydroxide, a basic inorganic particle, neutralizes the acidic byproducts of PLLA. In this study, we investigated using a BVS coated with everolimus and surface-modified magnesium hydroxide that suppresses smooth muscle cell proliferation and protects endothelial cells, respectively. The various characteristics of the functional stent were evaluated using in vitro and in vivo analyses. The BVS was successfully prepared with evenly coated everolimus and surface-modified magnesium hydroxide. A neutral pH value was maintained by magnesium hydroxide during degradation, and everolimus was released for one month. The coated BVS effectively inhibited protein adsorption and platelet adhesion, demonstrating excellent blood compatibility. In vitro analysis showed that BVS protects endothelial cells with magnesium hydroxide and selectively inhibits smooth muscle cell proliferation via everolimus treatment. The functional BVS was inserted into porcine coronary arteries for 28 days, and the results demonstrated that the restenosis and inflammation greatly decreased and re-endothelialization was enhanced as compared to others.This study provides new insights into the design of drug-incorporated BVS stent for coronary artery disease.