Ar-N₂-O₂기체 분위기에서 RF 스퍼터링에 의한 TiO₂박막의 물성

우충하,김경찬 啓明大學校 自然科學硏究所 2007 自然科學硏究論集 Vol.25 No.2

Predicting Debt Default of P2P Loan Borrowers Using Self-Organizing Map

Seung Hyun Kim,Dong Won Lee,Bong Ju Jeong,Kyong Joo Oh 계명대학교 자연과학연구소 2019 Quantitative Bio-Science Vol.38 No.1

P2P loans-a typical example of modern financial markets combining finance and technology-have been growing over time in terms of their size and speed. In Korea, the market size of P2P loans is not large, and cases of delinquency are relatively few. However, in the U.S., several studies have predicted loan overdue in the P2P loan market, which is a developed financial market. Many studies had previously predicted the possibility of delinquency in these P2P loans by building a single model through artificial intelligence methodologies. However, this study used a methodology based on artificial intelligence and the self-organizing map, which finds a cluster of data on similar customers, and confirms that its predictive power is greater than that of the delinquency prediction method relying on only artificial intelligence. This study aimed to conduct empirical research on borrowers’ past dues in 2015 by randomizing customer data from Lending Club.

Sensory Evaluation of Kwamaegi Produced Using Different Treatments

Joung Ae Kim 계명대학교 자연과학연구소 2019 Quantitative Bio-Science Vol.38 No.1

Kwamaegi is a traditional Korean seafood dish made from the flesh of Pacific saury, Cololabis Saira. It is mostly produced in the Pohang area. As it is a recognized healthy food containing the omega-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), its rate of consumption is increasing every year. The purpose of this research was to conduct the sensory evaluation for Kwamaegi produced using four different processing methods and to examine the consumer satisfaction level for specific parts of Kwamaegi. A questionnaire survey was conducted among 30 ordinary citizens from the Pohang area. The results showed that Kwamaegi produced by drying on a bamboo blind was the most preferred dish. Overall, the body part of Kwamaegi was most preferred. Satisfaction analysis indicated that the significant factors which affected the satisfaction level were the processing method and the body part of Kwamaegi which was consumed. It also showed that our artificial drying method was appropriate. Thus, processing methods need to be consistently monitored and improved to increase the taste of Kwamaegi.

Anti-proliferative Activity of 3,5-Diaminoindazole Analogues

Jongwon Park,Jinho Lee 계명대학교 자연과학연구소 2019 Quantitative Bio-Science Vol.38 No.1

Cancer is the second leading cause of death worldwide. Small-molecule anticancer agents with tolerable safety profiles have been developed to improve survival rates. Indazole analogues have received considerable attention due to their anticancer properties. A series of N3-acyl-N5-pyrimidinyl-3,5-diaminoindazoles were synthesized and their antiproliferative activities were evaluated in Caki, A549, HepG2, AMC-HN4, and SNU484 human cancer cell lines. Cellular selectivity of 3,5-diaminoindazole with a modified structure of the N5-pyrimidinyl substituent was studied. While both compounds 9a and 9b showed a high selectivity for the HepG2 cell line, compound 9b had a higher selectivity than 9a, with an IC50«0.1 μM.

Dickey-Fuller Test for an Extended MA Model

Cheolyong Park,Jeongcheol Ha,Tae Yoon Kim,Sun-Young Hwang,Heesoo Lee 계명대학교 자연과학연구소 2019 Quantitative Bio-Science Vol.38 No.1

The AR(1) model Xt=ρXt-1+ϵt with iid error ϵt has been used extensively for the inference of the stochastic process Xt where its key parameter ρ plays an essential role. In particular, the Dickey-Fuller test (DF test) has been extensively used for testing random walk model (or ρ=1) in the literatures. However, it is well known that the DF test is subject to serious size distortion when errors are correlated. This study proposes the use of an extended MA(∞) model Xt=∑<SUP>∞</SUP>(i=0) bi ϵt-i for a more precise inference of Xt by the DF test. We develop and investigate a new persistency parameter b∞=limj→∞ bj from the extended MA(∞) model. It is shown that the DF test serves well for testing the MA(∞) model with the new persistency parameter b∞. Our approach critically addresses the size distortion issues in the literatures.

Polyphenol, Flavonoid and Tannin Variation in Puer Tea Extracts

Mu-Seog Choe,Chan-Ho Jung,Jung-Hwan Park,Woong-Kyu Yoon,Byung-Tae Min,Min Yoo 계명대학교 자연과학연구소 2019 Quantitative Bio-Science Vol.38 No.1

Puer tea, known for its anti-inflammatory, antioxidant, and weight-loss activities, is made by drying and fermenting bamboolike plant leaves, produced in the Yunnan area of China. During storage, tannins are oxidized, so that the bitter taste disappears, while the fragrance is maintained. Puer tea has recently been recognized as a functional food as its health benefits have gained interest. We investigated how its total polyphenol, flavonoid, and tannin contents change according to extraction time, extraction frequency, and at different time intervals after extraction. The contents of polyphenols, flavonoids, and tannins increased with longer extraction times. Additional extractions led to a decrease in total polyphenol content, but it was maintained to some extent after a certain number of extractions. This is presumably due to the presence of the lipid-soluble or insoluble polyphenols, after the initial extraction of the water-soluble ones. The total flavonoid and tannin content showed a slight decrease with the increasing number of extractions, which remained, however, within the experimental error range. This experiment showed that the total polyphenol level decreased by 26% compared to the first and second extract upon additional extractions of the puer tea, and by 67% 10 times after extraction. The results of this study indicate that the functional beverage mixed with puer tea and lactic acid bacteria exerts a strong synergistic effect.

A Study of the Convertible Bond Index and the Investment Performance Using Rough Set

Sung Yeop Lee,Jun Hyuk Yang,Bong Ju Jeong,Kyong Joo Oh 계명대학교 자연과학연구소 2019 Quantitative Bio-Science Vol.38 No.1

Among mezzanine securities, convertible bonds are the most frequently issued products in the domestic and foreign security markets. However, the mezzanine market in Korea is developed mainly as a private placement market, which is difficult for individual investors to approach. Related products have been released recently, but the minimum subscription is high, and with no published convertible bond index, this type of investment is difficult to evaluate and its performance hard to measure. In this study, we confirm that the characteristics of the convertible bond index as an investment product are similar to those of the stock price index, using correlation and chaos analyses (e.g., Hurst exponent analysis), correlation dimension analysis, and maximum Lyapunov exponent analysis based on the global convertible bond index. At the same time, we establish an investment strategy based on the rough set theory and find that the convertible bond index, unlike the stock index, has a defensive tendency in the downside market. This research contributes to the development of the convertible bond index in the domestic market and the design of financial products based on this index.

Multivariate Bias Correction for Climate Simulation Data, with Application to Precipitation Extremes in Korea

Juyoung Hong,Tae Yoon Kim,Jeong-Soo Park 계명대학교 자연과학연구소 2019 Quantitative Bio-Science Vol.38 No.2

Much of knowledge on future climate change depends on projections from the simulation codes with global circulation models (GCMs) and regional climate models (RCMs). But even state-of-art simulation codes still have a rather coarse resolution and and are substantially biased compared to real-world climate. In an attempt to remove systematic biases between simulation model output and real observations, a variety of statistical bias correction (BC) methods has been developed. The methods are classified to univariate and multivariate ones. This study reviews these techniques with more emphasis on recently advanced multivariate methods. These includes delta change approach, quantile mapping, quantile delta mapping, empirical copula bias correction, multivariate quantile delta mapping and multivariate stochastic BC with optimal transport function. An application of multivariate BC method to annual daily extreme rainfall in Korea peninsula is presented. We applied an ensemble prediction with generalized extreme value distribution (GEVD) to the data obtained as simulated by the coupled model intercomparison project phase six (CMIP6) models. Simulation data under three RCP (Representative Concentration Pathway) scenarios, namely RCP 2.6, RCP 4.5 and RCP 8.5, are employed. The 20-year and 50-year return levels and return periods relative to the reference years (1973-2014) are estimated for two future periods, namely period 1 (2021-2050) and period 2 (2061-2099).

A Study on the Correlation between the Urban Heat Island Phenomenon and High Concentrations of Ozone in Daegu

Eun-Ji An,Hae-Dong Kim 계명대학교 자연과학연구소 2019 Quantitative Bio-Science Vol.38 No.2

Recently, the summertime’s extremely high temperature phenomenon, caused by climate change, and urban heat islands have become a serious social problem. Urban areas have low albedo and huge thermal capacity, creating high temperatures and long-lasting characteristics. According to many studies, temperature increases in large cities is due to urban heat islands rather than global warming. We studied the distribution of air temperature using the high density urban climate observation network data of Daegu (2016-2018). From the distribution of monthly averaged air temperatures, we concluded that air temperatures at the center of Daegu were higher than in the suburbs. At the elementary school near the center of Daegu, the daily minimum air temperature is more than or equal to 25°C, and the daily maximum air temperature is more than or equal to 35°C. We also investigated the effects of urban heat islands on the deterioration of the city̓s air quality. It was concluded that the air pollution level in the city center increased because the suburban wind blew into the city overnight when the urban heat island’s intensity was strong, causing air pollution to be transported and stagnant.

Properties of Saltine Crackers : Effect of the Addition of Doenjang and Makgeolli

Joo Hyun Kim,Bong Kyung Koh 계명대학교 자연과학연구소 2019 Quantitative Bio-Science Vol.38 No.1

In this study, we aimed to evaluate the effect of doenjang and makgeolli addition on the properties of saltine crackers. Saltine crackers of two types were prepared by adding Korean traditional fermented foods doenjang and makgeolli that made up a final amount of 10% of the weight of wheat flour and substituted an equal quantity of formula water, respectively. The saltiness of the doenjang added crackers (DCs) was adjusted to match that of control crackers (CCs). The peak and hot paste viscosities of the makgeolli added crackers (MCs) were significantly lower than those of CCs. However, there was no significant difference in the RVA viscosities between DCs and CCs. Fermented doughs of DCs and MCs were lighter and had a lower pH after sheeting and molding when compared to that of CCs. There was no significant difference in the length of baked crackers; however, DCs and MCs were thinner than CCs. The moisture content of DCs was over 7%, which is suboptimal for a cracker. The DCs showed significantly lower scores in terms of crispy texture and savory taste, whereas scored highest in off-flavor upon sensory evaluation. MCs showed the highest score in terms of hardness and scored relatively high in crispness; they did not show significant difference in terms of off-flavor, savory taste, or aftertaste when compared to CCs. From these results, we concluded that the addition of doenjang at 10% of wheat flour weight enhanced fermentation; however, it did not impart desirable qualities, such as moisture content, textural properties, and flavor, to crackers. By contrast, the addition of makgeolli instead of formula water improved saltine cracker fermentation, moisture content, texture properties, and flavor.