• Communications for Statistical Applications and Methods
• /
• v.15 no.1
• /
• pp.65-76
• /
• 2008

Biplots are the multivariate analogue of scatter plots. They approximate the multivariate distribution of a sample in a few dimensions, typically two, and they superimpose on this display representations of the variables on which the samples are measured(Gower and Hand, 1996, Chapter 1). And the relationships between the observations and variables can be easily seen. Thus, biplots are useful for giving a graphical description of the data. However, this method does not give some concise interpretations between variables and observations when the number of observations are large. Therefore, in this study, we will suggest to interpret the biplot analysis by applying the K-means clustering analysis. It shows that the relationships between the clusters and variables can be easily interpreted. So, this method is more useful for giving a graphical description of the data than using raw data.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2005.05b
• /
• pp.614-618
• /
• 2005

수문시계열 분석과 예측은 대부분 ARMA(AutoRegressive Moving Average) 형태의 선형적인 추계학적인 모형을 이용하였으나 자현현상이 복잡해지고 비선형적인 특성을 가짐에 따라 선형적인 해석은 수문시계열의 분석과 예측에 있어서 많은 오류를 내포하고 있다. 이와 같은 문제를 해결하기 위한 시도로 Chaos이론이란 개념이 사용되기 시작하였으며, 수자원분야에서는 1980년대 후반부터 물수지 방정식 및 강우유출에 대한 카오스적 특성분석 등 많은 연구가 진행되었다. 본 연구에서는 영산강유역의 본류를 대표하는 나주지점을 대상으로 2003년 1월 1일 00시부터 2004년 12월 31일 23시까지 17,544개의 시수위 자료에 대하여 해당 년도의 Rating-Curve식을 적용 환산한 유출량자료에 데한 카오스적 특성을 분석하였다. 카오스적 특성을 분석하기에 앞서 원자료에 대하여 이동평균법과 Savitzky-Golay Filter를 적용하여 잡음을 제거하였으며, 1차원의 단일변량의 자료에 대한 상태공간(Phase Space)의 재건을 통하여 비교검토 하였다. 이러한 일련의 과정을 거친 자료에 대하여 상관차원법을 이용하여 영산강 유역의 나주지점의 시유출량 자료에 대한 카오스적 특성을 분석한 결과 저차원의 수렴으로 카오스 특성을 가졌다.

• The Korean Journal of Applied Statistics
• /
• v.24 no.1
• /
• pp.127-136
• /
• 2011

Multiplicative noise model is the one of popular method for masking continuous variables. In this paper, we propose the transformation on the variable to which random noise was multiplied. An advantage of the masking method using proposed transformation is that the masking data users can obtain the unbiased values of mean and variance of original (unmasked) data. We also consider the data utility and correlation structure of variables when we apply the proposed multiplicative noise scheme. To investigate the properties of the method of masking based on multiplicative noise, a simulation study has been conducted using the 2008 Householder Income and Expenditure Survey data.

• Journal of Labour Economics
• /
• v.29 no.1
• /
• pp.99-127
• /
• 2006

This paper examines the effect of the market power of firms in the product market on job creation, job destruction and net job growth. It uses the reconstructed establishment data in the Korean Annual Mining and Manufacturing Survey between 1982 and 2002. This paper shows that job creation has continuously declined since the late 1980s and the decline is common for both market-dominant and competitive firms. The effect of market dominance on job creation is negative, controlling the firm-characteristics variables such as firm size and firm age.

• Journal of Korea Technology Innovation Society
• /
• v.13 no.1
• /
• pp.124-139
• /
• 2010

This study analyzes determinants of innovation in Korea manufacturing industries from 2005 to 2007. In order to do this, we use raw data from 'Korea Innovation Survey 2008: Manufacturing Sector' conducted by STEPI, and also collect financial statement data from Korea Investors Service. As an analytical method for the empirical test, we utilize Probit model. Empirical results show that firm size and market concentration have positive relationship with firm's innovation activities. These support the ‘Schumpeterian hypothesis’. This would be the most distinguished feature of this study compared to previous literatures.Our study also shows that R&D personnel ratio, R&D intensity, and advertising intensity have positive effects on firms' innovation. Thus, we can say that R&D activities and consumer orientation are the main determinants of innovation. However, profit ratio and growth rate do not have any statistically significant effect on firms' innovation.

• Journal of Labour Economics
• /
• v.35 no.3
• /
• pp.83-100
• /
• 2012

This paper estimates the impacts of introducing the 40 hour work week standard in South Korea on actual working hours, wages and employment. We exploit variation in timing of implementing the 40 hour work week standard across industries and establishment size and estimate the causal effects by a triple difference model. Our results show that the 40 hour work week standard decreased actual working hours by about 43 minutes while it increased hourly wage rate by 6.6%. The probability of new hires decreased by about 2.3% points.

• Journal of Korean Library and Information Science Society
• /
• v.31 no.2
• /
• pp.63-91
• /
• 2000

In ths study, I proposed the need for strengthening the information analysis function of research library whch is in charge of knowledge control in a company based on knowledge management. In the operating steps of information management for a company, 1 studed about providmg analyzed dormation at the level of a professional in various forms through intranet within a company after processing and analyzing the collected raw lnformation to make customized lnformation according to the need of each group, rather than passively providing information as required by users. By establishmg the senior decision-making person within the company as the core user in contrast with information s e ~ c e spr ovided in large libraries, ths will give us a new position as lnformation manager, who can accomplish tlie corporate goal. Also, I proposed the details for becoming a pioneer in knowledge management system.

• Water for future
• /
• v.14 no.1
• /
• pp.51-58
• /
• 1981

This study attempts to examine and estabilish a simulation model from the stochastic analysis of daily streamflow. Daily streamflow records obstained at the main gauging stations along the Han, Nakdong and Geum River were used in the analysis. The following results were abtained. From the analysis of time series of streamflow by the correlogram and spectraal density, The serial component of one-year periodicity, serial correlation and irregular or random component were found. The coefficient of determination R2 of multilag model remaine a plateau at log-two, so that second order mu.ltilag model was Known to fit in the simulation of daily streamflow, Consequently, multilag and recised Markov model of the sewnd order give the best results in simulatin of daily streamflow. But the former generally gives better results than the latter. And theoretical markev model is unfit in the simulation of daily series without modification.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2008.05a
• /
• pp.2254-2257
• /
• 2008

홍수와 가뭄, 수질오염 등의 피해에 대한 대책과 보다 효율적인 수자원 관리를 위해서 원자료에 대한 분석이 선행되어야 한다. 따라서 본 연구에서는 나주지점을 대상으로 하여 총유기탄소(Total Organic Carbon: TOC) 자료와 유출량 자료를 수집하였으며, 각 자료에 대하여 상세한 주기성분을 파악하기 위하여 웨이블렛 변환을 적용하였다. 대상지점으로 선정한 나주지점은 전라남도 나주시 나주대교 상류에 위치하고 있으며, 유역면적이 $2,0587.2km^2$이며, 유로 연장은 65.5km이다. 유출량과 수질자료의 주기성 분석을 위해 유기물의 양을 나타내는 수질지표인 TOC와 나주수위관측소에서 관측된 2003년${\sim}$2004년의 시수위자료를 유출량으로 환산한 값을 사용하였으며, 이 자료의 상세한 주기성 파악을 위해 웨이블렛 변환을 사용하였다. 일반적으로 주기성을 파악하기 위하여 푸리에 변환을 사용하지만, 푸리에 변환은 시간정보와 주파수를 동시에 파악할 수 없을 뿐만 아니라, 자료에 불연속성과 고주파수 성분이 포함될 경우 분석이 난이하다. 이러한 푸리에 변환의 단점을 보안한 것이 웨이블렛 변환이며, 푸리에 변환보다 계산속도가 빠르다. 또한 주어진 자료에 대하여 시간과 주파수 영역에서 동시에 파악하는 것이 가능하며, 불규칙한 자료를 평탄하게 함으로서 보다 상세한 주기성을 찾아낼 수 있다. 따라서 본 연구에서 추출한 각 자료의 상세 주기성분들은 향후 수자원 관리를 위한 기초자료로 활용될 수 있을 것으로 기대된다.

• Journal of the Korea Institute of Information Security & Cryptology
• /
• v.23 no.6
• /
• pp.1207-1217
• /
• 2013

This study utilizes raw data from "Research on the actual condition of firms' information security" of KISA (2010) and constructs panel dataset to analyze a causal relationship between information security investment and security breach. Using Difference in Difference estimation method we find the following results. First, while the usual causality that information security investment reduces security breach is not supported, the reverse causality that security breach increases information security investment is well explained. Second, contrary to the conventional wisdom, firms in the finance/insurance business sector show the most significant reverse causality pattern.