주파수-파수 스펙트럼과 라돈변환을 이용한 희소 배열 기반 방위추정 기법 연구

최용화,김동현,김재수,Choi, Yong Hwa,Kim, Dong Hyeon,Kim, J.S. 한국음향학회 2019 한국음향학회지 Vol.38 No.2

When an array receives a signal with a frequency higher than the design frequency, there is an ambiguity in beamforming due to spatial aliasing. In order to overcome this problem, Abadi proposed frequency-difference beamforming. However, there is a constraint that the minimum frequency bandwidth is required according to the value of the difference frequency. In this paper, we propose a method to find the direction of the target signal with spatial aliasing based on the frequency-wavenumber spectrum combined with Radon transform. The proposed method can estimate the direction of the target without ambiguities when the signal has nonnegligible bandwidth. We tested the algorithm by simulating a broadband signal and verified the results with the frequency-difference beamforming method using SAVEX15 (Shallow Water Acoustic Variability EXperiment 2015)'s shrimp noise data.

양지꽃(Potentilla fragarioides) 지상부의 항산화물질

최용화,김명조,이행순,윤봉식,호창서,곽상수,Choi, Yong-Hwa,Kim, Myong-Jo,Lee, Haeng-Soon,Yun, Bong-Sik,Hu, Changxu,Kwak, Sang-Soo 한국생약학회 1998 생약학회지 Vol.29 No.2

Six antioxidative compounds in the aerial parts of Potentilla fragarioides were isolated by a bioassay guided purification using a DPPH free radical. They were identified as (+)-catechin, isoquercitrin, quercitrin, $quercetin-3-O-{\beta}-D-glucopyranosyl-{\beta}-D-xylopyranoside$, caffeic acid, and 4-O-caffeoyl-L-threonic acid on the basis of $^{1}H$ and $^{13}C-NMR$ and MS data. The DPPH radical scavenging activity of five compounds $(RC_{50}:\;7.5{\sim}10.5\;{\mu}g)$ except for quercitrin $(16\;{\mu}g)$ was more effective than those of ${\alpha}-tocopherol$ $(12\;{\mu}g)$ and BHA $(14\;{\mu}g)$.

해당화(Rosa rugosa) 잎의 항산화물질

최용화,김명조,이행순,호창서,곽상수,Choi, Yong-Hwa,Kim, Myong-Jo,Lee, Heang-Soon,Hu, Chang-Xu,Kwak, Sang-Soo 한국생약학회 1997 생약학회지 Vol.28 No.4

To search for useful antioxidants from plant materials, we investigated the antioxidative activity in the methanol extracts of 30 Chinese medicinal plants using DPPH method. The highest activity $(RC_{50}:\;12\;{\mu}g)$ was showed in the methanol extract of Rosa rugosa, followed by Potentilla fruticosa $(14\;{\mu}g)$, P. fragarioides $(16\;{\mu}g)$. And Geum aleppicum $(18\;{\mu}g)$. From the leaves of R. rugosa, two antioxidative compounds were isolated by a bioassay guided purification and identified as isoquercitrin and ${\beta}-glucogallin$ on the basis of $^1H-,\;^{13}C-\;NMR$, and FAB-MS data. ${\beta}-Glucogallin$ is the first report in this plant. The DPPH radical scavenging activity of ${\beta}-glucogallin\;(RC_{50}:\;8.5\;{\mu}g)$ was more effective than those of ${\alpha}-tocopherol\;(12\;{\mu}g)$ and BHA $(14\;{\mu}g)$.

[환경]Imidazole계 살균제 Prochloraz의 토양 중 잔류량과 반감기분석

최용화(Yong Hwa Choi),한성수(Seong Soo Han),김일광(Il Kwang Kim) 한국분석과학회 2002 분석과학 Vol.15 No.1

자산가치주 투자에 효과적인 트레이딩 기법의 개발

최용화(Yong-Hwa Choi),주복규(Bok-Gyu Joo) 한국정보기술학회 2014 한국정보기술학회논문지 Vol.12 No.1

Recently, stock market trends is that growth stock is popular and asset stock is not. Therefore, asset value stocks have low volume and under-valued. In this paper, we developed a system trading technique for asset value stocks using RSI(Relative Strength Index) Index. Our strategy is that we catch the point when a stock price is going down under its real-value for psychological reasons using RSI index, then automatically execute buy or sell with the help of TRIX index. We applied our technique to a popular trading system with large historical data and validated its effectiveness. The proposed technique will provide individual investors to get stable profits for asset-value stocks.

장수풍뎅이 유충 추출물이 사염화탄소에 의한 마우스의 간 손상에 미치는 영향

최용화(Yong Hwa Choi),이기열(Kiyeol Lee),양경미(Kyung Mi Yang),정윤미(Yun Mi Jeong),서정숙(Jung Sook Seo) 한국식품영양과학회 2006 한국식품영양과학회지 Vol.35 No.10

This study was conducted to investigate the effect of methanol extract of Allomyrina dichotoma larva (MEAL) on carbon tetrachloride (CCl4)-induced hepatotoxicity in mice. ICR mice were divided into 5 groups [Vehicle control, CCl4 (10 μg/g) alone, CCl4 plus a low dose (50 μg/g) of MEAL, CCl4 plus a high dose (100 μg/g) of MEAL]. Silymarin (2 μg/g) was used as the reference in the experiment. Administration of MEAL tended to decrease the serum alanine transaminase (ALT) activity induced by CCl4 treatment in mice. Hepatic concentration of thiobarbituric acid-reactive substances (TBARS) in a high-dose group of diet decreased to the level of silymarin-treated group. Hepatic activity of glutathione S-transferase in MEAL-treated group was lower than that of CCl4-treated group. Serum concentration of bilirubin was significantly increased by CCl4 treatment, but MEAL or silymarin recovered the level. These results suggest that MEAL may exert the protective effect against CCl4-induced hepatotoxicity in mice. However, more intensive studies would be needed to elucidate the protective mechanism of the beetle on hepatotoxicity of mice.

비목나무(Lindera erythrocarpa) 잎으로부터 항진균성 활성물질의 분리

최용화 ( Yong Hwa Choi ),권순열 ( Sun Youl Kwon ),김진호 ( Jin Ho Kim ),백남인 ( Nam In Baek ),최경자 ( Gyung Ja Choi ),조광연 ( Kwang Yun Cho ),이병무 ( Byung Moo Lee ) 한국응용생명화학회 2003 Applied Biological Chemistry (Appl Biol Chem) Vol.46 No.2

Methanol extract obtained from Lindera erythrocarpa leaves was successively fractionated with n-hexane, ethylacetate, n-butanol, and H_2O. From ethylacetate fraction, an active fraction was isolated through repeated silica gel colunm chromatography and recrystallization, and was identified as a stereoisomer complex of methyllucidone by MS and NMR analyses. The complex showed 85% antifungal activity at 50 μg/ml against the disease wheat leaf rust.

수평 및 수직 T형 분지관을 통한 냉매의 이상유동 분배 특성

최용화(Yong Hwa Choi),조금남(Keumnam Cho) 대한설비공학회 2001 대한설비공학회 학술발표대회논문집 Vol.2001 No.-

Antifungal Activity of Streptomyces pad anus isolate TH04 against Monilinia fructicola, Brown rot Fungus on Stone-fruits

임태헌,최용화,이동운,한상섭,차병진,Lim, Tae-Heon,Choi, Yong-Hwa,Lee, Dong-Woon,Han, Sang-Sub,Cha, Byeong-Jin The Korean Society of Pesticide Science 2008 농약과학회지 Vol.12 No.3

The Streptomyces padanus isolate TH04, isolated from mummified peaches, showed strong antifungal activity to Monilinia fructicola. The inhibition activity of the isolate TH04 to mycelial growth and spore germination at 1% concentration of sub-antifungal powder made from culture suspension (CS) was ranged from 79.8% to 81.0% and from 73.9% to 75.8% to M. fructicola four strains, respectively. In the test of antifungal activity in mixed culture of the isolate and M. fructicola, inhibition rate was 7.5%, 86.8% and 94.0% in 0.01, 0.1, and 1% concentration of CS containing bacterial cell of the isolate, respectively. On apples (cultivar; Fuji), the control values of the isolate TH04 crude filtrates (0.1 and 1%) were 85.9% and 100%, respectively. The results suggest that the isolate TH04 indicate development possibility as biocontrol agent of brown rot caused by M. fructicola with the study on delivery method and fermentation condition to produce an antifungal compound.

수박 과실썩음병 병원균(Acidovorax avenae subsp. citrulli)에 대한 식물유래 항균 활성물질 탐색

노진택,최용화,Noh, Jin-Taek,Choi, Yong-Hwa 한국유기농업학회 2015 한국유기농업학회지 Vol.23 No.1

133 Species of medicinal plants were used for the development of natural agrichemicals with anti-microbial activity against Acidovorax avenae subsp. citrulli, a pathogen of bacterial fruit blotch in watermelon. The MeOH-extracts of these medicinal plants were examined for anti-microbial activity by bioassay. The MeOH-extract of Citrus unshiu Markovich had the strongest antibacterial activity against Acidovorax avenae subsp. citrulli. To identify anti-microbial compounds from Citrus unshiu Markovich, solvent-fractionation was used. The fraction of hexane, which showing the highest value of anti-microbial activity, was analyzed by GC-MS. Each mass spectra, corresponding to each peak of chromatogram, was compared to mass database of Wiley library. As a result, d-Limonene, ${\gamma}$-terpinene, ${\beta}$-linalool, terpineol, palmitic acid, 9,12-octadecadienoic acid, Linolenic acid, and stigmasterol were identified. Among them, d-Limonene, ${\gamma}$-terpinene, ${\beta}$-linalool, and terpineol confirmed to be shown the anti-microbial activity by bioassay. Especially, d-Limonene and ${\gamma}$-terpinene found to have strong activity. In conclusion, we thought d-limonene and ${\gamma}$-terpinene from Citrus unshiu Markovich. Latin, had anti-microbial activity against Acidovorax avenae subsp. citrulli and could be candidates for the control agents for the control of bacterial fruit blotch in watermelon.