Deep Drawing에 미치는 펀치의 形狀半徑의 影響

徐大敎,閔宅基 충남대학교 공업교육연구소 1978 論文集 Vol.1 No.2

Compared to other metal-processes, deep drawing is extremely complex because it has many variable factors and each of them affects the process. In 1950's Chung & Swift and in 1970's Berry & Pope made some remarkable researches for cup-forming, but there are still many unsolved problems. This paper explains clearly some uncertain problems for the effects of punch profile radius.

인도 생명보험시장의 효율성 분석

서대교 한국산업경제학회 2017 한국산업경제학회 정기학술발표대회 논문집 Vol.2017 No.12

Merger Efficiencies in the U.S. Telecommunications Industry

서대교 한국산업경제학회 2013 산업경제연구 Vol.26 No.1

This paper investigates whether productivity growth has increased among ILECs that have merged since the 1996 Telecommunications Act and whether the merged firms performed better than firms that did not merge in terms of productivity growth over the years 1996-2005. The productivity growth measures are obtained from a Malmquist index during pre-merger and post-merger periods. The empirical results provide some evidence of a positive merger effect, although this effect diminishes over time. In addition, this paper finds that non-merged firms underperform in terms of average productivity growth.

박강판 의 변형도 에 따른 Lankford값 의 변화 에 대한 실험적 연구

서대교,김동원 대한기계학회 1984 대한기계학회논문집 Vol.8 No.5

본 연구에서는 예변형된 재료에 있어서의 R값의 변형도 의존성을 고찰하기 위 하여 Rimmed 강판에 대하여 2축인장변형을 예변형으로 준 다음 다시 단축인장시험을 수행하여 R치의 변형도 의존성을 검토 하였다. 아울러 Gotoh의 이론식의 타당성을 실험 결과와 비교하여 검토하였다. The dependence of Lankford's value of rimmed steel sheets on plastic strain in investigated in this paper. It is shown that Gotoh's theory predicts the Lankford's value satisfactorily, if suitable material constants are adopted. In addition the strain dependence of Lankford's value in the balanced biaxially-prestrained steel sheets is studied experimentally.

용접된 판재의 성형 가공시의 용접선 이동에 관한 고찰 ( Weld-Line Dislocation Investigations for the Deep Drawing Process of Welded Sheet )

서대교,김헌영,최유호,허영무 대한기계학회 1998 대한기계학회 춘추학술대회 Vol.- No.-

동태패널모형을 이용한 인도관광수요 결정요인 분석

서대교 한국산업경제학회 2020 산업경제연구 Vol.33 No.4

본 연구는 2004년부터 2017년까지 48개국을 대상으로 인도 관광수요에 영향을 미치는 요인에 대하여 동태적 패널모형을 이용하여 실증분석 하였다. 분석결과 인도 방문객의 1인당 실질 GDP와 영연방 더미는 통계적으로 유의한 양(+)의 부호를 가지며 교통비와 상대가격은 통계적으로 유의한 음(-)의 부호를 가지는 것으로 나타났다. 환율은 통계적으로 유의하지 않은 것으로 밝혀졌다. 한편 인도 방문객의 시차변수에 대한 추정계수는 통계적으로 유의한 양(+)의 부호를 가지는 것으로 나타났다. 이를 종합해보면 인도 방문 광관객의 실질 소득 증가와 방문객의 국적이 영연방국가에 속할 경우 인도의 관광수요에 긍정적인 영향을 끼치는 것으로 나타났다. 반면 여행교통비의 증가와 인도내의 여행 경비의 증가는 인도의 관광수요에 부정적인 영향을 끼치는 것으로 나타났다. 또한 실증분석 결과 관광습관가설을 지지하는 것으로 나타나 질적인 서비스 수준의 향상이 인도 관광수요에 긍정적인 영향을 미치는 것으로 밝혀졌다. This study empirically analyzes the factors influencing the tourism demand for India from 48 countries over the period 2004-2017 by using the Dynamic Panel Model. The results showed that the per capita real GDP and the Commonwealth dummy of visitors to India had statistically significant effects with a positive sign, while the transportation cost and relative prices had statistically significant effects with a negative sign. Foreign Exchange rates were found to be insignificant. On the other hand, the estimated coefficients for lag variables of tourists were found to be positive signs. The increase in real income of visitors to India and the nationality of visitors have positive effects on tourism demand for India. On the other hand, the increases in transportation cost and in travel expenses in India have negative effects on tourism demand for India. In addition, the empirical analysis shows that it supports the Tourism Habit Persistence Hypothesis. Improvements in quality service levels have been found to have positive impacts on tourism demand for India.

COSMO-SkyMed 2 Image Color Mapping Using Random Forest Regression

서대교,김용현,어양담,박완용 한국측량학회 2017 한국측량학회지 Vol.35 No.4

SAR (Synthetic aperture radar) images are less affected by the weather compared to optical images and can be obtained at any time of the day. Therefore, SAR images are being actively utilized for military applications and natural disasters. However, because SAR data are in grayscale, it is difficult to perform visual analysis and to decipher details. In this study, we propose a color mapping method using RF (random forest) regression for enhancing the visual decipherability of SAR images. COSMO-SkyMed 2 and WorldView-3 images were obtained for the same area and RF regression was used to establish color configurations for performing color mapping. The results were compared with image fusion, a traditional color mapping method. The UIQI (universal image quality index), the SSIM (structural similarity) index, and CC (correlation coefficients) were used to evaluate the image quality. The color-mapped image based on the RF regression had a significantly higher quality than the images derived from the other methods. From the experimental result, the use of color mapping based on the RF regression for SAR images was confirmed.

The Study of Korea’s Export Demand Function by Using the Bounds Testing Approach

서대교,강신재 한국산업경제학회 2016 산업경제연구 Vol.29 No.1

The purpose of this study is to investigate whether a long-run relationship exists among time series variables and to find short-run elasticities by using an error correction model if cointegration exists in variables. Therefore, this study estimates the demand function of the Korean exports by using bounds testing approach and then compare income elasticity with price elasticity to see which factor has a greater impact on changes to Korea’s exports. We find that the short-run income elasticities are larger than price elasticities. This implies that the change of Korea’s exports in the short-run is more sensitive than the changes in foreign income (industrial production) compared with that of the price (exchange rate). Korea’s exports in the short-run may have a higher export performance on income than that of price (exchange rate). We also find that joining the OECD members in 1995 and the IT bubble in the world economy in 2001 affect Korea’s export demand.

Study on the Export Competitiveness of China and Korea in the U.S. Market

서대교,강신재 한국산업경제학회 2016 산업경제연구 Vol.29 No.4

The main purpose of this paper is to estimate the degree of competition between Korea’s and China’s exports in the U.S. market by using elasticity of substitution in a simple demand model. The results are as follows: first, Korea has a dominant market share of only goods group code 27 in commodity groups over that of China; otherwise, China’s market shares are dominant over those of Korea for other export sections. Second, most estimates of the elasticity of substitution between the exports of both countries are small (inelastic). However, 61, 62 and 85 commodity groups’ substitute elasticities are large (elastic) and competitive in the U.S. market compared with those of China.

Analysis of Image Preprocessing Effects in a Landsat Image Simulation

서대교,어양담,백근우 대한토목학회 2020 KSCE JOURNAL OF CIVIL ENGINEERING Vol.24 No.7

Optical remote sensing has limitations in obtaining images due to weather and environmental effects, so these limitations must be overcome to produce time-series image data. As an alternative to this, research are being conducted to simulate images at a specific time for which a specific image is needed. The purpose of this study is to improve the results of this process by preprocessing the input images of a multiple linear regression model alongside other remote sensing image simulation methods. Specifically, the input images, which are applied to a multi-linear regression equation, are preprocessed for phenological and radiometric normalization by a random forest regression model. The experimental results show that the proposed method is superior to the conventional methods both visually and quantitatively.