• 제목/요약/키워드: Difference-in-Differences Method

검색결과 2,181건 처리시간 0.03초

인터넷과 슬라이드를 이용한 경관평가방법의 비교 (A Comparison of Landscape Evaluation between the Internet and Slide Method)

  • 허준
    • 한국조경학회지
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    • 제29권5호
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    • pp.20-27
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    • 2001
  • The purpose of this study is to investigate and compare the validity and the reliability of the visual simulation method using the internet. For this. the evaluation of the artificial and natural landscape through the medium of color slides are compared with the internet survey. Data is analysed through the comparison of t-test between the two media by landscape type, and spatial image is analysed by factor analysis algorithm. Principle component analysis using Varimax Method is applied for extraction and factor rotation respectively. The results of this study can be summarized as follows; There are no statistical differences between the two methods with artificial and natural landscape in the total data that included second tests. Factors covering the spatial image are found to be \`aesthetic\`, \`spatial shape\`, and \`familiarity\`. Total variance is obtained as 66.4%. There are no statistical differences between the two methods in 2/3 of the cases. In the case of far view of artificial landscape, the results of the t-test show that the two methods are exactly the same. Especially in the case of the artificial far landscape shows no difference of all factors between two methods. There are no differences between first and second tests of the same media and the same landscape type. And it shows the reliability of this method. These results suggest that the probability that the internet can be used as a medium of landscape evaluation and gathering information on anyone\`s landscape image. Simulation techniques with the internet survey method should be further developed for practical application.

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프로젝트 진도 측정 방법의 비교와 적용에 관한 연구 (A Study on the Comparison and Application of the Methods of Measuring Projects'Progress)

  • 민택기;송창용
    • 산업경영시스템학회지
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    • 제36권3호
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    • pp.87-94
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    • 2013
  • The progress that becomes a basis for measuring the outcome of project is a core of project control. Follow-up corrective actions are determined depending on the degree of their differences. The methods of measuring the project progress have been developed though a variety of research and many were verified through the cases. Among such methods, this study selected Start/Finish method and Fixed Formula method. In order to check the limitations of the progress utilized in the two methods, the study compared their progresses to the progress of Percentage Complete method and analyzed the differences shown in their actual applications. Through this, it suggested the forms and scale of the projects appropriate to the application of Fixed Formula method. As for the research progress method, the study first generated a number of virtual project schedules for the establishment of an analysis model. These project schedules were varied in a way that they had different project periods and the number of different activities. The study also generated numerous project schedules for difference test. After establishing a virtual schedule plan by the scale of projects, it measured their progresses by period, analyzed the differences and repeated this procedure to obtain the results.

주간에 두 타워로부터 관측된 에디 공분산 자료의 확률 오차의 추정 (Estimation of the Random Error of Eddy Covariance Data from Two Towers during Daytime)

  • 임희정;이영희;조창범;김규랑;김백조
    • 대기
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    • 제26권3호
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    • pp.483-492
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    • 2016
  • We have examined the random error of eddy covariance (EC) measurements on the basis of two-tower approach during daytime. Two EC towers were placed on the grassland with different vegetation density near Gumi-weir. We calculated the random error using three different methods. The first method (M1) is two-tower method suggested by Hollinger and Richardson (2005) where random error is based on differences between simultaneous flux measurements from two towers in very similar environmental conditions. The second one (M2) is suggested by Kessomkiat et al. (2013), which is extended procedure to estimate random error of EC data for two towers in more heterogeneous environmental conditions. They removed systematic flux difference due to the energy balance deficit and evaporative fraction difference between two sites before determining the random error of fluxes using M1 method. Here, we introduce the third method (M3) where we additionally removed systematic flux difference due to available energy difference between two sites. Compared to M1 and M2 methods, application of M3 method results in more symmetric random error distribution. The magnitude of estimated random error is smallest when using M3 method because application of M3 method results in the least systematic flux difference between two sites among three methods. An empirical formula of random error is developed as a function of flux magnitude, wind speed and measurement height for use in single tower sites near Nakdong River. This study suggests that correcting available energy difference between two sites is also required for calculating the random error of EC data from two towers at heterogeneous site where vegetation density is low.

하이힐이 요부 및 천골경사각에 미치는 영향 (Effect of High heel on Lumbar and sacral curve)

  • 이태식;송민영;김미소
    • 대한물리치료과학회지
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    • 제18권4호
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    • pp.73-79
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    • 2011
  • Purpose : This study is to know how position change in high-heels affects sacral tilt angle. 15 healthy women aged 21.87(standard deviation=3.54) were tested. Method : Lumbar and sacral tilt angle was measured by radiography barefooted, and after 15 mins of application time, they were measured in the same way in high-heels. Result : There was not notable difference in lumbar lordosis, lumbosacral angle, and sacral tilt angle. However, there was differences in change degree, which was measured by estimation data of [post-pre)/pre]${\times}$100. Conclusion : There was no notable difference in lumbar lordosis, lumbosacral angle, and sacral tilt angle, but as there were differences in change degree, research about how women's lumbar change when heel height increases is needed.

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디지츨 영상의 복사 방지를 위한 적응 워터마킹 방법 (An Adaptive Watermarking Method for Copy Protectionof Digital Images)

  • 김덕령;박성한
    • 전자공학회논문지S
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    • 제35S권4호
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    • pp.85-95
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    • 1998
  • In this paper, a new watermarking method for a copy protectionof images is proposed. The proposed method adaptively embeds a watermark in the frequency domain of images using human visual system model. For this purpose, the Just Noticeable Differences(JNDs) of each frequency coeffeicient value of a luminance plane is first found using Watson and Solomon's visual system model. An invisible maximum watermark value with is different in every position according to the characteristics of images is determined usig JND and Minkowski metric. A low frequency domain is divided into two sets based on a PN-sequence to protect thewatermark from the attack. The watermarks are added to one set of coefficients and detecting a watermark, the difference between the mean values of absolute coefficient values of both sets is calculated. The embedded watermark is tested using statistical hypothesis based on test static dertermined by the ean difference. To demonstrate the perfromance of the proposed method, the new watermarking method is applied to a high frequency image and low frequency images. Experimenatal results show the watermark is invisible and robust to JPEGlossy compression and noise.

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뇌졸중 환자의 일반적 특성에 따른 정서인식의 차이 (Emotional Recognition According to General Characteristics of Stroke Patients)

  • 박성호;김민호
    • 대한통합의학회지
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    • 제3권1호
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    • pp.63-69
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    • 2015
  • Purpose: The purpose of this study was to investigate the differences in emotion recognition according to general characteristics of stroke patients. Method: The subjects consisted of 38 stroke patients receiving rehabilitation at S Hospital in Busan. Used the eMETT program to assess emotional cognition. Result: The age and duration of disease showed statistically significant differences in emotion recognition ability score, the gender and lesion showed a statistically significant difference in some emotion(p<.05). Conclusion: The results of this study it can be seen that the difference in emotion recognition ability in accordance with the general characteristics of the stroke. There will be a variety of future research related to standardized research or interventions targeted at stroke patients and normal controls to be carried out.

Analysis of the influence of panel characteristics on odor measurement based on the air dilution olfactory method in Korea

  • Kim, Sun-Tae;Lee, Seokjun;Yim, Bongbeen
    • Environmental Engineering Research
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    • 제24권1호
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    • pp.91-98
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    • 2019
  • This study was to objectify differences in the results of odor testing according to the characteristics of panel members that participate in air dilution olfactory method (ADOM) testing. When differences in the results of olfactory testing were reviewed in relation to characteristics of the panelists, the result of entire panels for the site boundary Proficiency Testing Materials (PTMs) showed no difference according to panelist sex, age, smoking status, and past participation in ADOM tests. As for the outlet PTMs, distinct differences appeared in relation to the smoking status and age of panelists. The frequency distribution for all the panelists (Dev($D/T_{total}$)) showed a form similar to a normal distribution, so it is thought to be more appropriate for the review of effect of panelist characteristics on the result of air dilution olfactory tests. In addition, the ADOM testing method implemented as the standard method for odor compounds in Korea (Dev($D/T_3$)) will have to be implemented along with a concurrent assessment, for the purpose of identifying the effect of panelist characteristics on administrative dispositions against malodors.

Korean E-commerce Platform's Dashboard Style Decision Support System

  • 염경민;박재상;유병준
    • 한국벤처창업학회:학술대회논문집
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    • 한국벤처창업학회 2021년도 추계학술대회
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    • pp.113-117
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    • 2021
  • Due to the recent COVID-19 pandemic, SMEs are forced to converge themselves into online business to cope with the rapidly changing business environment. However, due to various difficulties of becoming an online business, most SMEs choose to use services provided by the online sales platform. These platforms offer valuable support such as DSS in return for the high amount of commission fee. We analyze a novel data set from Naver Corporation's 'Smart Store' platform with the quasi-experimental method (propensity score matching technique combined with the difference in differences analysis) to analyze DSS usage and SME's performance empirically. Our results suggest that DSS usage leads to an increase in SME's sales performance in means of sales frequency and sales amount. Additionally, we have found weak support that DSS usage enables SMEs to attract customers better than those not using DSS.

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가정생활주기에 따른 가계의 저축행태 분석 -대구시 주부를 중심으로- (A Study on the household Savings Behavior According to Family Life Cycle)

  • Cho, hee keum
    • 가정과삶의질연구
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    • 제2권1호
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    • pp.57-66
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    • 1984
  • This study examines differences in the household saving show significant differences according to the specific stage of family life cycle. 337 housewives in Taegu were interviewed by questionnaire. Analysing method employed are frequency, percentage and Chisquare test. Findings are as follows; 1) The average ratios of household saving show significant differences according to the specific stage of family life cycle. 2) Purposed of household savings had significant differences at each stage of the family life cycle. 3) Selections of financial goods did not have significant differences according to the sage of family life cycle . 4) Selections of financial goods had significant difference according to the purposed of household savings.

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외식업체 종사원의 서비스 지향성 요인에 관한 차이 분석 (An Analysis of the Differences in Foodservice Industry Employees Service Orientation Factor)

  • 김기영;민계홍
    • 한국조리학회지
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    • 제13권1호
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    • pp.166-178
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    • 2007
  • A review of literature relating to the research topic and a survey method have been implemented in order to analyze effects of service orientation. For data analysis, a reliability analysis was performed to test the reliability of the construct and a series of an exploratory factor analysis was used for the validity test. The findings of the study were as follows: Classified into sex, service leadership factor and service skill factor showed meaningful difference between groups. Classified with age, service training factor, service leadership factor, service standardization factor, service technology factor, and service compensation factor showed meaningful difference between groups. Classified with scholarship, service compensation factor showed meaningful difference. Classified into working year, employees' discretion factor showed meaningful difference. Classified into work department, service training factor and employees' right factor showed meaningful difference. In addition, classified into monthly average incomes, employees' discretion factor showed meaningful difference.

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