• Proceedings of the Korea Water Resources Association Conference
• /
• 2021.06a
• /
• pp.397-397
• /
• 2021

본 연구의 목적은 비매개변수적 리샘플링 기법을 이용하여 농업용 저수지 유입 설계홍수량의 구간을 추정하는 기법을 제안하는 데 있다. 본 연구는 설계홍수량을 점 추정하여 안전계수(safety factor)를 적용하는 기존 방법에 대한 대안을 제시하고자 한다. 설계홍수량의 구간 추정을 수행하기 위해 부트스트랩 기법(bootstrap technique)을 사용하였다. 부트스트랩 기법을 이용하여 95% 신뢰수준에 해당하는 신뢰구간을 추정하였다. 본 연구의 공간적인 범위는 남한의 30개 농업용 저수지이며, 시간적인 범위는 과거 기간(2015s: 1986-2015)과 미래기간(2040s: 2011-2040, 2070s: 2041-2070, 2100s: 2071-2100)을 설정하였다. 본 연구에서는 200년 빈도, 24시간 지속기간을 대표적인 결과로 선정하여 분석하였다. 빈도분석은 GEV 분포를 사용하였고, L-moment 방법을 이용하여 매개변수를 추정하였다. 설계홍수량은 HEC-1 모형을 이용하여 산정하였다. 최종적으로 설계홍수량 구간 추정한 결과를 기존의 점 추정한 뒤 안전계수를 적용한 기존 방법과 비교하였다. 97.5th BCa percentile 기준으로 상대적인 변화를 비교해보면, 미래로 갈수록 구간 추정으로 산정한 설계홍수량이 점차 증가하는 것으로 도출되었다. 한강 및 금강 유역에 위치한 농업용 저수지의 설계홍수량이 낙동강 유역에 비해 상대적으로 큰 변화를 보여주었다. 몇몇 농업용 저수지에 대해서 2040s 기간에 다소 감소하기도 하였으나 2070s 기간 이후에 다시 증가하는 결과를 보여주었다. 낙동강 유역의 위치는 농업용 저수지의 설계홍수량은 미래로 갈수록 크게 증가하지 않는 경향을 보여주었다. 본 연구는 설계홍수량을 추정하는 데 있어 결정론적인 방법에서 더 나아가 자료의 통계적인 특성을 고려하여 구간 추정을 수행하는 방법론을 제공할 수 있을 것으로 사료된다.

• Annals of Hepato-Biliary-Pancreatic Surgery
• /
• v.27 no.1
• /
• pp.40-48
• /
• 2023

Backgrounds/Aims: Timing of resection for synchronous colorectal liver metastasis (CRLM) has been debated for decades. The aim of the present study was to assess the feasibility of simultaneous resection of CRLM in terms of major complications and develop a prediction model for safe resections. Methods: A retrospective single-center study of synchronous, resectable CRLM, operated between 2013 and 2021 was conducted. Upper limit of 95% confidence interval (CI) of major complications (≥ grade IIIA) was set at 40% as the safety threshold. Logistic regression was used to determine predictors of morbidity. Prediction model was internally validated by bootstrap estimates, Harrell's C-index, and correlation of predicted and observed estimates. Results: Ninety-two patients were operated. Of them, 41.3% had rectal cancers. Major hepatectomy (≥ 4 segments) was performed for 25 patients (27.2%). Major complications occurred in 20 patients (21.7%, 95% CI: 13.8%-31.5%). Predictors of complications were the presence of comorbidities and major hepatectomy (area under the ROC curve: 0.692). Unacceptable level of morbidity (≥ 40%) was encountered in patients with comorbidities who underwent major hepatectomy. Conclusions: Simultaneous bowel and CRLM resection appear to be safe. However, caution should be exercised when combining major liver resections with bowel resection in patients with comorbid conditions.

• ALGAE
• /
• v.39 no.2
• /
• pp.97-108
• /
• 2024

The Ralfsiaceae family, part of the Ralfsiales order and consisting of crustose brown algae, includes five genera: Analipus, Endoplura, Fissipedicella, Heteroralfsia, and Ralfsia. In this study, a novel crustose genus named Ramipedicella gen. nov. is introduced within the Ralfsiaceae based on molecular and morphological analyses. Phylogenetic analyses using both concatenated dataset (rbcL + COI-5P genes) and rbcL indicate that the crustose brown algae that we collected from Korea and Russia form a unique grouping within the Ralfsiaceae. This grouping is strongly supported by both bootstrap analysis and Bayesian posterior probabilities. The genetic differences in the rbcL and COI-5P sequences between Ramipedicella and other genera within Ralfsiaceae range from 6.7 to 9.3% for rbcL and from 15.5 to 20.8% for COI-5P. Ramipedicella is characterized by crustose thalli having new crusts growing on top of old ones with a hypothallial basal layer and erect perithallial filaments, long cells with width-to-length ratio of 1 : 1-16, single chloroplast per cell, plurangia with one to several sterile cells, one to several unangia produced from unicellular stalks or from the lateral-basal region to the paraphyses, and unangia arising sequencially in irregularly branched specialized filaments. Ramipedicella, the recently identified genus, comprises two distinct species. Ramipedicella miniloba, the type species, is distinguished by crusts with small lobes, numerous hair tufts, plurangia terminated by 1-4 sterile cells, and large oblong unangia. Ramipedicella longicellularis is identified by generally smooth crusts, absence of phaeophycean hairs, plurangia terminated by 1-2 apical sterile cells, and smaller mostly oblanceolate unangia.

• Journal of Intelligence and Information Systems
• /
• v.19 no.2
• /
• pp.39-54
• /
• 2013

Recent explosive increase of electronic commerce provides many advantageous purchase opportunities to customers. In this situation, customers who do not have enough knowledge about their purchases, may accept product recommendations. Product recommender systems automatically reflect user's preference and provide recommendation list to the users. Thus, product recommender system in online shopping store has been known as one of the most popular tools for one-to-one marketing. However, recommender systems which do not properly reflect user's preference cause user's disappointment and waste of time. In this study, we propose a novel recommender system which uses data mining and multi-model ensemble techniques to enhance the recommendation performance through reflecting the precise user's preference. The research data is collected from the real-world online shopping store, which deals products from famous art galleries and museums in Korea. The data initially contain 5759 transaction data, but finally remain 3167 transaction data after deletion of null data. In this study, we transform the categorical variables into dummy variables and exclude outlier data. The proposed model consists of two steps. The first step predicts customers who have high likelihood to purchase products in the online shopping store. In this step, we first use logistic regression, decision trees, and artificial neural networks to predict customers who have high likelihood to purchase products in each product group. We perform above data mining techniques using SAS E-Miner software. In this study, we partition datasets into two sets as modeling and validation sets for the logistic regression and decision trees. We also partition datasets into three sets as training, test, and validation sets for the artificial neural network model. The validation dataset is equal for the all experiments. Then we composite the results of each predictor using the multi-model ensemble techniques such as bagging and bumping. Bagging is the abbreviation of "Bootstrap Aggregation" and it composite outputs from several machine learning techniques for raising the performance and stability of prediction or classification. This technique is special form of the averaging method. Bumping is the abbreviation of "Bootstrap Umbrella of Model Parameter," and it only considers the model which has the lowest error value. The results show that bumping outperforms bagging and the other predictors except for "Poster" product group. For the "Poster" product group, artificial neural network model performs better than the other models. In the second step, we use the market basket analysis to extract association rules for co-purchased products. We can extract thirty one association rules according to values of Lift, Support, and Confidence measure. We set the minimum transaction frequency to support associations as 5%, maximum number of items in an association as 4, and minimum confidence for rule generation as 10%. This study also excludes the extracted association rules below 1 of lift value. We finally get fifteen association rules by excluding duplicate rules. Among the fifteen association rules, eleven rules contain association between products in "Office Supplies" product group, one rules include the association between "Office Supplies" and "Fashion" product groups, and other three rules contain association between "Office Supplies" and "Home Decoration" product groups. Finally, the proposed product recommender systems provides list of recommendations to the proper customers. We test the usability of the proposed system by using prototype and real-world transaction and profile data. For this end, we construct the prototype system by using the ASP, Java Script and Microsoft Access. In addition, we survey about user satisfaction for the recommended product list from the proposed system and the randomly selected product lists. The participants for the survey are 173 persons who use MSN Messenger, Daum Caf$\acute{e}$, and P2P services. We evaluate the user satisfaction using five-scale Likert measure. This study also performs "Paired Sample T-test" for the results of the survey. The results show that the proposed model outperforms the random selection model with 1% statistical significance level. It means that the users satisfied the recommended product list significantly. The results also show that the proposed system may be useful in real-world online shopping store.

• The Korean Journal of Malacology
• /
• v.29 no.4
• /
• pp.335-341
• /
• 2013

The seven mitochondrial DNA regions (ND2, ND5, ND4, ND4L, ND6, ND1 and 12SrRNA) of Haliotis discus hannai were examined to estimate the availability as a genetic marker for the study of population genetic. The region with the highest genetic variation was ND4 (Haplotype diversity = 1.0000, Nucleotide diversity = 0.0108). On the other hand, ND2 and ND1 regions have significantly appeared genetic divergence between clusters (divergence of 90% and 87%). Also, pairwise $F_{ST}$ between clusters within ND2 and ND1 regions showed high values; 0.4061 (P = 0.0000), 0.4805 (P = 0.0000) respectively. Therefore we can infer that it is the most efficient and accurate way to analyze the region of ND4 with the highest variation in addition to the regions of ND2 and ND1, which formed clusters with high bootstrap value, for study of population genetic structure in this species.

• Korean Journal of Social Welfare
• /
• v.67 no.1
• /
• pp.263-288
• /
• 2015

This study is to research the mediating effects of optimism and quality of relationship which interpersonal traumatic experience influences posttraumatic growth. It focuss on verifying the impact of interpersonal traumatic experience to optimism and quality of relationship and the influence of optimism and quality of relationship to posttraumatic growth. And also it is to verify dual mediating effect between optimism and quality of relationship. Data for this study were collected through the use of a survey instrument completed by 405 interpersonal traumatic experience, 30-60 age group. Collected data were analysed by AMOS program, Structure Equation Model(SEM) was implemented to verify the mediating effect between optimism and quality of relationship. Finally, Phantom Variable was utilized for verification of indirect influence of a multi mediating effects. The findings of this study were as follows, First, the result shows that the higher level interpersonal traumatic experience, the higher posttraumatic growth they have. Second, it shows that optimism and quality of relationship have partial mediating effect between interpersonal traumatic experience and posttraumatic growth. Third, it was analyzed that optimism and quality of relationship had double mediating effect. Based on these findings, the research discussion reinforced the importance of intervene with its optimism and quality of relationship in the site of those who experience interpersonal trauma. Theological, political and practical implications of this study are as follows. First, it has a series of significance in terms of that this study confirmed its influence considering the quality of relationship from interpersonal experience among relevant factors of traumatic accident, optimism among individual factors, quality of relationship among environmental factors based on 'the crisis of life and the theory of individual growth'. econd, even though optimism and quality of relationship were proved as major predictors for posttraumatic growth of those who experience interpersonal traumatic, psychological support center for traumatic experience is not operated systematically in Korea. Third, this study implies that it should intervene mainly with its optimism and quality of relationship in the site of those who experience interpersonal trauma such as any abuses including sexual abuse, bullying, and divorce.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.41 no.11
• /
• pp.1364-1373
• /
• 2016

Ultra High Definition Television (UHDTV) has attracted much attention as one of next generation broadcasting services. For the commercialization of UHD broadcasting service, standardization groups including the DVB (Digital Video Broadcasting) and the ATSC (Advanced Television Systems Committee) have decided to adopt the Orthogonal Frequency Division Multiplexing (OFDM) for signal transmission. However, when the carrier frequency is not properly synchronized at the receiver, inter-symbol interference (ISI) and inter-carrier interference (ICI) may occur. In order to avoid performance degradation resulting from ISI or ICI, receivers should synchronize the carrier frequency by using preambles and pilot symbols. However, there only few published literature dealing with the frequency offset estimation methods regarding the next generation terrestrial broadcasting. In this respect, this paper proposes a method to estimate timing and fractional frequency offset for the ATSC 3.0 system by using a preamble bootstrap symbol. The proposed detector can detect the fractional frequency offset by adding a complex conjugate product on the conventional estimator where only timing offset can be estimated.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.21 no.11
• /
• pp.340-348
• /
• 2020

This study was conducted to find the mediating effect of self-leadership in the relationship between academic self-efficacy and college-life satisfaction of Chinese students majoring in beauty. Surveys were answered by 400 Chinese students from July to August 2019 and analyzed as follows. We used the SPSS22.0 program and Process macro for SPSS to analyze the frequency, descriptive statistics, correlation analysis, and bootstrap method. The results of the analysis showed a positive correlation among the college-life satisfaction, self-leadership, and academic self-efficacy of Chinese students, and self-leadership acted as a partially mediating variable between academic self-efficacy and college-life satisfaction. Therefore, it was found that a higher college-life satisfaction and self-leadership resulted in a higher academic self-efficacy. Based on these results, in order to alleviate the problems of college life maladjustment and low learning efficiency of Chinese students majoring in beauty, the development of self-leadership education programs is becoming more important. This must be emphasized in the Edu-Tech era due to the need for customized education programs for international students amidst the COVID-19 pandemic.

• The Korean Journal of Quaternary Research
• /
• v.13 no.1
• /
• pp.25-33
• /
• 1999

The relationships between climate (monthly precipitation and temperatures) and tree-ring growth of Korean fir (Abies koreana) growing at subalpine (1,600∼l,700m) zone on the south slope, Joong-Bong and the north slope, Changgun-Bong in the Cheonwang-bong area in Chiri mountains in the southern Korea were analyzed. Two cores from each of 10∼12 trees were extracted. The relationship between tree-ring(standardized) chronologies and climate was analyzed by the response-function method. Climate variables could explain 45.9∼53.8% of total variance in the chronologies. The precipitation response function of Korean fir were similar at both sites in overall ; positive for March∼May and August, and negative for February and July. The south-slope fir of Joong-Bong possessed higher negative temperature response function for February and August than north-slope one. The positive response function for April temperature was significant for both sites. In contrary to other subalpine species (e.g., Pinus koraiensis and Taxus cuspidata) in South Korea, whose growths are positively correlated with temperature in most seasons, the growths of Korean fir trees in Mt. Chiri appeared to be mainly limited by the moisture regime of spring prior to the cambial growth and early growing season.

• Asian Pacific Journal of Cancer Prevention
• /
• v.15 no.16
• /
• pp.6811-6817
• /
• 2014

Background: Breast cancer risk prediction models are widely used in clinical practice. They should be useful in identifying high risk women for screening in limited-resource countries. However, previous models showed poor performance in derived and validated settings. Therefore, we aimed to develop and validate a breast cancer risk prediction model for Thai women. Materials and Methods: This cross-sectional study consisted of derived and validation phases. Data collected at Ramathibodi and other two hospitals were used for deriving and externally validating models, respectively. Multiple logistic regression was applied to construct the model. Calibration and discrimination performances were assessed using the observed/expected ratio and concordance statistic (C-statistic), respectively. A bootstrap with 200 repetitions was applied for internal validation. Results: Age, menopausal status, body mass index, and use of oral contraceptives were significantly associated with breast cancer and were included in the model. Observed/expected ratio and C-statistic were 1.00 (95% CI: 0.82, 1.21) and 0.651 (95% CI: 0.595, 0.707), respectively. Internal validation showed good performance with a bias of 0.010 (95% CI: 0.002, 0.018) and C-statistic of 0.646(95% CI: 0.642, 0.650). The observed/expected ratio and C-statistic from external validation were 0.97 (95% CI: 0.68, 1.35) and 0.609 (95% CI: 0.511, 0.706), respectively. Risk scores were created and was stratified as low (0-0.86), low-intermediate (0.87-1.14), intermediate-high (1.15-1.52), and high-risk (1.53-3.40) groups. Conclusions: A Thai breast cancer risk prediction model was created with good calibration and fair discrimination performance. Risk stratification should aid to prioritize high risk women to receive an organized breast cancer screening program in Thailand and other limited-resource countries.