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Antioxidant Compounds from Distylium racemosum Leaves
Park, Youngki,Lee, Wi Young,Ahn, Jin Kwon,Lee, Hak-Ju,Chin, Hwi Seung,Kwon, Young Jin 한국목재공학회 2003 목재공학 Vol.31 No.6
The leaves of D. racemosum showed strong DPPH (1,l-diphenyl-2-picrylhydrazyl) radical scavenging activity and the order of the radical scavenging activity against DPPH radical is ethyl acetate (EtOAc) fraction>crude extracts>residue fraction>hexane fraction>ether fraction, under the experimental conditions.Since EtOAc fraction has highest antioxidative activity among these fractions, the isolation was performed from the EtOAc fraction of the leaves of D. racemosum and four phenolic compounds were isolated and identified as follows: methyl gallate, kaempferol, quercetin and quercitrin. The free radical scavenging activities of these compounds were 79.9%, 9.31%, 93.6% and 66.7% at 10 ㎍/㎖, respectively. The IC_(50) of compound 1, compound 2, compound 3 and compound 4 were 6.1, 4.1, 3.6 and 6.5 ㎍/㎖, respectively.These compounds have higher antioxidative activity compared with reference compounds, ascorbic acid (IC_(50) = 9.6 ㎍/㎖).
YoungKi Park(박영기),Omar A. El Sawy,Taeho Hong(홍태호) 한국경영학회 2020 Korea Business Review Vol.24 No.신년 특별호
본 연구에서는 기업이 실시간 기업(Real-Time Enterprise: RTE)로의 디지털 트랜스포메이션을 통해 디지털 비즈니스 세상에서 기회와 위협으로 나타나는 중요한 비즈니스 이벤트를 성공적으로 감지하고 관리할 수 있다는 것을 설명하는데 있다. 본 연구에서는 RTE 능력을 중요한 비즈니스 이벤트에 시기적절하게 감지하고 반응할 수 있는 조직의 능력으로 정의한다. 더 나아가서, 센스메이킹과 실행 능력을 RTE 능력의 두 축으로 설정하고, 비즈니스 인텔리전스와 통신지원을 디지털 트렌스포메이션을 통한 RTE로 도달하는 두 개의 중요한 기술로 정의한다. 다양한 산업에서 총 96개 기업을 대상으로 191개의 설문조사 자료를 사용하여 비즈니스 인텔리전스와 통신지원기술이 RTE 능력과 기업 성과를 달성하는데 있어서 각기 다르게 역할을 하고 있음을 실증분석을 통해 제시하였다. 정보기술은 빠르게 변화하는 환경에서 RTE 능력을 확장하여 간접적으로 기업이 경쟁우위를 달성할 수 있게 할 수 있음을 본 연구에서 제시하였다. 느린 환경에서는 RTE능력이 기업 성과를 높이지 않는 것으로 분석되었으며, 재설정된 자원과 구조에 대한 잦은 대처는 오히려 경쟁우위를 감퇴시기는 것으로 분석되었다. This study aims to explain digital transformation of firms to real-time enterprises (RTE) that can successfully sense and manage important business events that appear as opportunities and threats in the digitized business world. We define RTE capabilities as the organizational ability to sense and act to important business events in a timely manner. Furthermore, we define sensemaking and acting capability as two dimensions of RTE capabilities and business intelligence and communication support as two key information technologies for digital transformation into RTE. Using 191 survey responses from 96 firms in diverse industries, we find that the different roles of BI and communication support technologies in achieving high RTE capabilities and firm performance across different environmental velocities. IT enables firms to achieve competitive advantage indirectly by enhancing RTE capabilities in fast environments. In slow environments, RTE capabilities appear not to enhance performance, but instead frequent actions to reconfigure resources and structures seem to deteriorate competitive advantage.
A novel algorithm for scalable <i>k</i>-nearest neighbour graph construction
Park, Youngki,Hwang, Heasoo,Lee, Sang-goo SAGE Publications 2016 JOURNAL OF INFORMATION SCIENCE Vol.42 No.2
<P>Finding the k-nearest neighbours of every node in a dataset is one of the most important data operations with wide application in various areas such as recommendation and information retrieval. However, a major challenge is that the execution time of existing approaches grows rapidly as the number of nodes or dimensions increases. In this paper, we present greedy filtering, an efficient and scalable algorithm for finding an approximate k-nearest neighbour graph. It selects a fixed number of nodes as candidates for every node by filtering out node pairs that do not have any matching dimensions with large values. Greedy filtering achieves consistent approximation accuracy across nodes in linear execution time. We also present a faster version of greedy filtering that uses inverted indices on the node prefixes. Through theoretical analysis, we show that greedy filtering is effective for datasets whose features have Zipfian distribution, a characteristic observed in majority of large datasets. We also conduct extensive comparative experiments against (a) three state-of-the-art algorithms, and (b) three algorithms in related research domains. Our experimental results show that greedy filtering consistently outperforms other algorithms in various types of high-dimensional datasets.</P>
기능성 교잡종 다래 신품종의 영양성분 및 유용성분 분석
Youngki Park,Jae Hee Kim,Sea Hyun Kim 한국약용작물학회 2017 한국약용작물학술대회 발표집 Vol.2017 No.05
Background : In order to develop new cultivar of hybrid kiwifruit with cold tolerance, high useful components and high quality fruit, we have been crossed ‘Hayward’ (Actinidia deliciosa) with A. arguta. The new hybrid kiwifruit cultivars were 'DM', 'HO', and 'JW'. Actinidia arguta, called hardy kiwifruit, has an edible smooth skin and contains high amounts of sugar and vitamin C. It is native to north China, Korea, and Japan. A. deliciosa are known as kiwifruit and originated in Southwest China. The fruit of A. deliciosa appreciated for its sweet, slightly acidic flesh and high nutritional value, especially due its high content in vitamin C like A. arguta. The cultivar ‘Hayward’ of A. deliciosa occupies the majority of the world kiwifruit cultivated surface, and is the cultivar commercially produced in Korea. However, the kiwifruit producing areas are limited to warm climates region, it can be cultivated in the southern parts of Korea. In our research, several hybrids have been developed to enhance cold tolerance by crossing ‘Hayward’ with domestic species. Methods and Results : In our research, several hybrids have been developed to enhance cold tolerance by crossing ‘Hayward’ with domestic species. Freeze dried the fruit of hybrid kiwifruit was finely ground, extracted twice with methanol (MeOH). The crude extracts of the fruit was analyzed with HPLC for vitamin C and β-carotene analysis. Conclusion : Moisture and carbohydrate contents of hardy kiwi fruit in this study varied from 81.40 - 83.57% and 14.63 - 16.90 g/100 g, respectively. Among new cultivars, JW had higher fat(0.17 g/100 g) and protein(1.33 g/100 g) contents than others. The highest vitamin C and β-carotene content of hardy kiwi fruit were 120.70 ㎎/ 100 g, 0.14 ㎎/kg, respectively in DM.
A Study on a Real Inversion Formula for the Laplace Transformation
Park, Youngki 연세대학교 대학원 1982 延世論叢 Vol.19 No.1
이 논문의 중요한 결과는 다음과 같이 요약된다. (1) 함수 h(s)=h(ξ+iη)는 ζ>0에 대하여 해석적 이고, ξ→0일때 거의 모든 부분에서 Lp(-∞,∞)(1<P≤2) 에 속하는 경계함수를 갖고, ξ>0에 대하여 Cauchy적분 *****(p273) 로 표시된다. h(iη)가 임의의 Lq(-∞,∞) (1<q≤2)에서 Fourieer변환을 가지면, *****(p273) 인 Laplace적분 h(s)= *****로 표시된다. (2) 위의 결과에서 s,t가 real인 경우에 L2(0,∞)에 속하는 φ(t)는 실측을 따라서 h(s)의 값으로 부터 다음과 같이 얻어진다. *****(p273)