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        • KCI등재

          여드름의 원인 및 관리실태 분석

          박시연,이종헌 대한구강악안면병리학회 2020 대한구강악안면병리학회지 Vol.44 No.1

          The need for skin health care is newly recognized in accordance with the importance and needs of skin care due to harmonious interpersonal relation. In this study, collected 202 questionnaire sheets in Seoul were analyzed by SPSS 18.0 program through data coding and data cleaning, and frequency analysis for general characteristics was done. Heredity, environmental factors and management condition of acne, and the differences according to general characteristics were analyzed by Crosstabs. Mainly, women used skin care shop and their age groups were varied from twenties to fifties. Recognition of skin trouble were compound(42.1%), and significant statistical difference(p<.05), while oily or compound to man and compound or acne skin to woman were observed. First occurrence of acne was generally middle school(33.7%). Facial acne progress areas was cheek(36.1%), forehead(30.7%), chin(28.2%) and neck(5.0%) in descending order, and present state of acne was in progress(60.9%). Etiologic factors were stress(39.1%), pre and post-menstruation(22.8%), environment(20.8%), heredity(17.3%). There was significant statistical difference between gender(p<.01). Treatment places were at dermatologist(45.0%) and special skin care shop(27.2%). The most reliable place for treatment was special skin care shop(44.6%) and dermatologist(42.6%). It suggested that in acne of skin trouble, age groups of customers could be varied among male and female and in order to meet such requirements of customers, high quality service ought to be provided so that acne care could satisfy customers with the differentiated and careful service.

        • KCI등재

          Simulation Study on the Scale Change Test for Autoregressive Models with Heavy-Tailed Innovations

          박시연,이상열 한국데이터정보과학회 2006 한국데이터정보과학회지 Vol.17 No.4

          This paper considers the testing problem for scale changes in autoregressive processes with heavy-tailed innovations. For a test, we propose the CUSUM test statistic based on the trimmed residuals. We perform a simulation study for the mixture normal and Cauchy innovations.

        • KCI등재

          Comparison of time and cost between conventional surgical planning and virtual surgical planning in orthognathic surgery in Korea

          박시연,황대석,송재민,김욱규 대한악안면성형재건외과학회 2019 Maxillofacial Plastic Reconstructive Surgery Vol.41 No.-

          Background: The purpose of this study was to measure the time of the conventional surgical planning (CSP) andvirtual surgical planning (VSP) in orthognathic surgery and to compare them in terms of cost. Material and method: This is a retrospective study of the patients who underwent orthognathic surgery at thePusan National University Dental Hospital from December 2017 to August 2018. All the patients were analyzedthrough both CSP and VSP, and all the surgical stents were fabricated through manual and three-dimensional (3D)printing. The predictor variables were the planning method (CSP vs. VSP) and the surgery type (group I: Le Fort Iosteotomy + bilateral sagittal split osteotomy [LFI+BSSO] or group II: only bilateral sagittal split osteotomy [BSSO]),and the outcomes were the time and cost. The results were analyzed using the paired t test. Results: Thirty patients (12 females, 18 males) met the inclusion criteria, and 17 patients were excluded from thestudy due to missing or incomplete data. There were 20 group I patients (LFI+BSSO regardless of genioplasty) and10 group II patients (BSSO regardless of genioplasty). The average time of CSP for group I was 385 ± 7.8 min, andthat for group II was 195 ± 8.33 min. The time reduction rate of VSP compared with CSP was 62.8% in group I and41.5% in group II. On the other hand, there was no statistically significant cost reduction. Conclusions: The time investment in VSP in this study was significantly smaller than that in CSP, and the differencewas greater in group I than in group II.

        • KCI등재

          Modelling Online Word-of-Mouth Effect on Korean Box-Office Sales Based on Kernel Regression Model

          박시연,김진교 한국데이터정보과학회 2007 한국데이터정보과학회지 Vol.18 No.4

          In this paper, we analyse online word-of-mouth and Korean box-office sales data based on kernel regression method. To do this, we consider the regression model with mixed-data and apply the least square cross-validation method proposed by Li and Racine (2004) to the model. We found the box-office sales can be explained by volume of online word-of-mouth and the characteristics of the movies.

        • KCI등재

          Odontogenic Keratocyst with Calcification in Maxillary Sinus

          박시연,김욱규,유미현,정연화,황대석 대한구강악안면병리학회 2019 대한구강악안면병리학회지 Vol.43 No.2

          Odontogenic keratocyst (OKC), also known as keratocystic odontogenic tumor (KCOT), is an emerging odontogenic tumor originating from the dental lamina. It is an aggressive lesion with a squamous epithelium and a recurrence rate of 15-35%.1 Radiologically, there is a clear, smooth, or shell-like border showing a unilocular or multifocal, polycystic radiographic picture. Hard tissue formation in OKC is a very rare phenomenon and occurs in the form of dystrophic calcification, cartilaginous tissue or dentinoid.2 In this article, we report the case of OKC with calcification. OKC with radiopaque lesion is very rare, these are considered as dystrophic calcification, dentinoid formation, ossification. The incidence of dystrophic calcification in recurrent OKC is low, so it can be inferred that the recurrence rate of OKC with dystrophic calcification is lower than that of conventional OKC.

        • KCI등재

          Modelling KOSPI200 Data Based on GARCH(1,1) Parameter Change Test

          박시연,이상열 한국데이터정보과학회 2007 한국데이터정보과학회지 Vol.18 No.1

          Since the seminal work of Engle (1982), many researchers and practiti oners have developed ARCH-type models to deal with volatility modelling, which, for instance, is crucial to perform the task of derivative pricing, measuring risk, and risk hedging. In this paper, we base the GARCH(1,1) model to analyze the KOSPI200 data, and perform the CUSUM test for detecting parameter changes in the GARCH model. It is shown that the data suffers from a parameter change.

        • KCI등재

          On Goodness-of-fit Tests based on Divergence Measures

          박시연,이상열,이승윤 한국데이터정보과학회 2008 한국데이터정보과학회지 Vol.19 No.1

          In this paper we consider the normality test in autoregressive models. In particular, we propose a class of normality tests based on divergence measures, and evaluate their performance through a simulation study. We demonstrate the test based on the density power divergence measure is robust against outliers.

        • KCI등재

          법인세율 인하에 따른 배당기업의 주주가치 상승효과 분석

          박시연 ( Si Youn Park ), 최문섭 ( Moon Sub Choi ), 최정화 ( Joung Hwa Choi ) 한국세무학회 2013 세무학 연구 Vol.30 No.1

          법인세율의 변동은 기업 활동에 영향을 미쳐 미래 수익과 재무 건전성에 경제·통계적으로 유의미한 영향을 줄 수 있다. 이에 본 연구는 2008년과 2009년에 걸쳐 실시된 국내 법인세율 인하에 따른 한국거래소 유가증권시장 상장 배당기업의 주주가치 상승효과를 사건연구(event study)를 통해 분석하였다. 사건일은 2008년과 2009년 각각 법인세율 인하 개정안 발표일과 의결일로 지정하였다. 분석결과 국회에서 법인세율 인하 개정안 발표 시 배당기업의 누적초과수익률(cumulative abnormal return)이 무배당기업의 그것을 상회했으며, 배당기업 중 배당성향이 높은 고배당기업의 누적초과수익률이 저배당기업의 그것 보다 높게 관찰되었다. 또한 다중회귀분석 결과 법인세율 인하 개정안 발표일 전후 5일([-2, +2]) 및 11일([-5, +5])의 사건구간에서 배당성향과 누적비정상수익률 간에양(+)의 상관관계가 나타났다. 이는 효율적 시장가설에 반하는 이례현상(anomaly)이며, 법인세율 인하가 발표되는 시점에 투자자들이 이를 새롭고 의미 있는 정보로 인지하여 투자 의사결정에 반영했음을 함의한다. 과거 법인세율 인하시 기업의 배당성향 상승을 경험한 투자자들의 행태가 고배당기업과 누적초과수익률 간 유의적인 양(+)의 상관관계에 영향을 주었다는 추론이 가능하다. Corporate tax rate changes are known to wield economically and statistically significant influences on the future revenues and financial conditions of firms through their operation channels. In this regard, we study the shareholder value effects of the Korea Stock Exchange-listed firms due to the 2008 announcement and 2009 enactment of marginal tax rate reduction made by the Government and Assembly of the Republic of Korea. The empirical implications of our event study are as follows: First, the cumulative abnormal return (CAR) of an average dividend-paying company dominates that of a non-dividend cohort. Second, a high-dividend listing, on average, posts a higher CAR than a low-dividend peer. Lastly, controlled for a variety of firm-level factors, the payout ratio positively affects the CAR through 5-day and 11-day event periods around the announcement made in 2008. This is an anomaly that counter-exemplifies the efficient market hypothesis:The traders are deemed to acknowledge a tax rate decrease as new and meaningful information for their amended investment behavior, reminiscent of their past learning experience of a positive correlation between a high-dividend stock and its high announcement return.

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