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.

Some Comparative Statics Of Entry In Markets With Demand Complementarities

서대교,신종협,조재린 한양대학교 경제연구소 2012 JOURNAL OF ECONOMIC RESEARCH Vol.17 No.3

This paper develops a two-market Cournot model with complementary demands to investigate comparative statics associated with symmetric and asymmetric entry. Notably, while market prices are decreasing with the number of market rivals, asymmetric entry actually causes prices to rise in the adjacent, complementary market. In addition, the price-decreasing effects of symmetric entry are attenuated with strong cross-price effects.

보험산업 글로벌화를 위한 정책적 지원방안

서대교,오영수,김영진 보험연구원 2009 조사보고서 Vol.2009 No.7

다층 퍼셉트론 기반 고해상도 위성영상의 상대 방사보정

서대교,어양담 한국측량학회 2018 한국측량학회지 Vol.36 No.6

In order to obtain consistent change detection result for multi-temporal satellite images, preprocessing must be performed. In particular, the preprocessing related to the spectral values can be performed by the radiometric normalization, and relative radiometric normalization is generally utilized. However, most relative radiometric normalization methods assume a linear relationship between the two images, and nonlinear spectral characteristics such as phenological differences are not considered. Therefore, this study proposes a relative radiometric normalization which assumes nonlinear relationships that can perform compositive normalization of radiometric and phenological characteristics. The proposed method selects the subject and reference images, and then extracts the radiometric control set samples through the no-change method. In addition, spectral indexes as well as pixel values are extracted in order to consider sufficient information, and modeling of nonlinear relationships is performed through multilayer perceptron. Finally, the proposed method is compared with the conventional relative radiometric normalization methods, which shows that the proposed method is visually and quantitatively superior. 다중시기의 위성상에 대해 일관성 있는 변화탐지 결과를 획득하기 위해서는 전처리 과정이 필수적으로 이루 어져야 한다. 특히, 분광값과 관련된 전처리 과정은 방사보정으로 수행될 수 있으며, 일반적으로 상대 방사보정이 활용되고 있다. 하지만, 대부분의 상대 방사보정은 두 상간의 관계를 선형으로 가정하며, 생태학적 차이와 같은 비선형적인 분광특성은 고려되지 않는다. 따라서, 본 연구에서는 방사 및 생태학적 특성에 대한 복합적인 보정을 수 행할 수 있는 비선형적인 관계를 가정한 상대 방사보정을 제안하다. 제안된 방법은 입력상 및 참조상을 선정 하고, no-change method를 통해 radiometric control set samples를 추출하다. 또한, 충분한 정보를 고려하기 위 하여 화소값뿐만 아니라 분광지수들이 추출되었고, 비선형적인 관계의 모델링은 다층 퍼셉트론을 통해 수행되었 다. 최종적으로 기존의 상대 방사보정기법과 비교 분석을 수행하고, 시각적 및 정략적으로 평가한 결과 제안된 방 법이 기존의 상대 방사보정보다 우수한 것을 확인하다.

확률적 프론티어 모형을 이용한 인도 생명보험시장의 효율성 및 생산성 분석

서대교 한국외국어대학교 인도연구소 2019 남아시아연구 Vol.24 No.4

Using the stochastic frontier analysis, this paper investigates the efficiency and productivity of Indian life insurance companies during the period 2012-2016. The empirical results show that technical efficiency decreases with time, but technical progress does not. The contribution of technical progress to their productivity appears to be greater than that of technical efficiency. As a consequence, the improvements in productivity have been speed up with time. The empirical result of productivity of individual firms show that India First is the most productivity in the sample. The India First accomplished substantial productivity by bancassurance, selling insurance products through affiliated banks. On the other hand, the LIC with the largest assets in the Indian life insurance industry was ranked 11th in terms of productivity. Therefore, it is not obvious that the size of a firm would affect its productivity. 본 연구는 FY2012부터 FY2016까지 인도 생명보험회사를 대상으로 확률적 프론티어 모형을 이용하여 인도 생명보험 산업의 효율성 및 생산성 추정을 실시하였다. 실증분석 결과 생명보험산업의 기술효율성 수준이 기간의 흐름에 따라 낮아지지만 기술진보 수준은 개선되고 있다. 그러나 생산성 개선에 대한 공헌도는 기술진보의 개선이 더 큼에 따라 전체적인 생산성 개선 정도는 기간의 흐름에 따라 개선되는 추이를 보이고 있다. 개별 보험회사의 생산성 변화 추이를 분석한 결과 India First가 제일 우수한 것으로 밝혀졌다. India First는 방카슈랑스를 전문으로 판매하는 보험회사로서 은행 접근이 용이해진 고객들을 대상으로 영업활동을 한 점이 생산성 개선의 요인으로 들 수 있다. 한편 자산규모가 가장 큰 LIC의 경우 생산성 개선 효과가 전체 대상 샘플 중 11위를 차지하여 규모가 생산성 개선에 미치는 영향은 명확하지 않은 것으로 나타났다.

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.

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.

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.

薄板의 加工性에 미치는 異方性에 관한 硏究(Ⅰ)

徐大敎,金東哲,禹鎬吉 충남대학교 공업교육연구소 1981 論文集 Vol.4 No.1

This study is concerned with the anisotropy which affects the workability of several different sheet metals. To do this, authors studied the earing through the deep drawing process, using the results which were obtained by studying the effect of the anisotropy of sheet metal in tensile yielding. The results through this study are as follows; 1) The corresponding maximum errors of the theoretical and experimental results in steel, brass, and aluminum plates in tensile yielding are 16%, 6%, and 5% respectively. 2) The earing of steel, brass and copper plates whose thickness are 0.62㎜ are two or three times as high as those of corresponding plates whose thickness are 0.34㎜. 3) The assumption of costa is satisfied in steel plate, but it is not satisfied in brass plate. It is hoped that the results of this study will be made reference to other works of sheet metal.

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.