효율적인 표면 검색을 위한 광섬유 공초점 간섭 현미경의 주사범위 제한 방식

김대찬,이승걸 한국물리학회 2003 새물리 Vol.46 No.5

We have developed a fiber-optic confocal scanning interference microscope by using a fiber with an index-mismatched end. The microscope uses the beam reflected at the end face of the fiber as reference beam. In order to reduce the vertical scanning time, were restricted the measurement distance to the period of oscillation of the interference axial response curve. In this configuration, surface profiles were measured by using the phase difference corresponding to the topography of the sample, unlike the extended focus image method. Thus, samples could be measured precisely even with an objective lens of extremely low numerical aperture or with a relatively broad axial response curve in the near-infrared region. 굴절률 정합을 하지 않은 광섬유 종단에서의 반사광을 기준광속으로 활용하는 간단한 구조의 광섬유 공초점 간섭현미경을 제작하였으며, 종방향 주사시간을 단축하기 위하여 주사범위를 interference axial response curve의 진동주기에 해당하는 거리로 제한하였다. 이때, 표면 높낮이 정보는 종래의 extended focus image와 달리 시료 표면의 높낮이에 대응하는 위상차를 측정하는 방식이 되므로 낮은 NA의 대물렌즈를 사용하거나 광원 파장이 긴 경우와 같이 axial response curve가 넓은 경우에도 시료 표면 높낮이를 정밀하게 측정할 수 있게 된다.

공간회귀분석을 활용한 지방정부의 인구경쟁력 결정요인 분석

김대찬,이수창 대한지방자치학회 2019 한국지방자치연구 Vol.21 No.2

본 연구는 인구 유입을 그간 단순히 한 지역에서 다른 지역으로 인구가 이동하는 정책 적 의지가 약한 개념에서 벗어나, 지방정부가 인구를 적극적으로 유치하기 위해 다른 지 역에 비해 경쟁력을 강화하는 역동적이고 정책 지향적인 개념인 인구경쟁력이라는 용어 를 사용하여 이의 결정요인을 실증적으로 검정하고자 한다. 이를 위해 지역의 공간적 특 성을 토대로 지방정부의 인구경쟁력에 영향을 미치는 12개 요인을 가정하고 229개 시군 구를 대상으로 2010년부터 2017년까지 수집된 자료를 활용하여 공간회귀분석을 실시하였 다. 본 연구는 전통적 회귀분석모형(OLS), 공간시차모형(SLM), 공간오차모형(SEM)의 3 가지 모형을 적용하여 공간자료의 특성이 제대로 반영될 수 있도록 하였다. 분석결과, OLS모형과 SLM모형보다는 SEM모형이 더 적합한 것으로 나타났다. SEM모형에 따르 면, 고용률, 대중교통 차량 수, 고령화, 소득세, 범죄 발생 건수가 지역의 인구경쟁력에 영향을 미치는 요인으로 확인되었다. This study is to identify the determinants of population competitiveness of local governments. It assumes 12 determinants of population competitiveness from spatial characteristics of regions and collects data from 229 cities from 2010 to 2017. The study conducts spatial regression analysis on open source software R and GeoDa applying ordinary least square, spatial lag model, and spatial error model to the analytical model in order to reflect the characteristics of spatial data. As a result, it shows that the spatial error model is higher in the fit of a model than ordinary least square and spatial lag model in comparison with R2-value. It also represents that employment, movement convenience, high income, aging, and crime occurrence have an influence on net migration. The study finally tries to draw an implication from the analytical results based on an explanation for the difference between regions with population growth and ones with population decrease.

Analysis of Prognostic Factors Affecting Admission in Acute Alcohol-intoxicated Patients with Traumatic Brain Injury Visiting Emergency Room

김대찬,강구현,김원희,장용수,최현영,하진근,이병국,김오현,류지호,조규종,조영석,강보승,김호중,이정훈,최한주,염석란,최인근 대한응급의학회 2017 大韓應急醫學會誌 Vol.28 No.6

Purpose: This study analyzed the prognostic factors affecting admission in acute alcohol-intoxicated traumatic brain injury (TBI) patients visiting the emergency room. Methods: A multicenter, retrospective observational study was conducted on 821 acute alcohol-intoxicated adult trauma patients, who visited 10 university hospital emergency centers from April to November 2016. The primary outcome was hospital admission. The secondary outcome was in-hospital mortality. Results: One hundred sixty-eight patients diagnosed with acute alcohol-intoxicated TBI were analyzed. The increase in blood alcohol concentration was associated significantly with a mild decrease in admission (adjusted odds ratio, 0.993; 95% confidence interval, 0.989 to 0.998; p=0.01). Moderate to severe TBI patients showed a significant increase in admission compared to mild TBI patients (adjusted odds ratio, 12.449; 95% confidence interval, 3.316 to 46.743; p<0.001). Conclusion: This study showed that the admission was inversely correlated with the blood alcohol concentration and is correlated directly with the increase in the severity in TBI. Therefore, emergency physicians may be required to identify the severity of TBI rapidly and accurately in acute alcohol-intoxicated trauma patients visiting the emergency room.

광섬유 공초점 간섭 현미경과 위상 변위법을 결합한 표면 검색

김대찬,이승걸 한국광학회 1999 한국광학회지 Vol.10 No.3

단일모드 광섬유와 결합기를 이용하여 간결한 구조의 광섬유 공초점 간섭 현미경을 구성하였으며, 위상 변위법을 응용한 표면 검색 방법을 제안하여 통신용의 반도체 레이저와 같이 비교적 긴 파장의 광원과, 낮은 NA의 대물렌즈를 사용하더라도 정밀한 시료 표면 검색이 가능함을 보였다. 이때 시료 표면의 높낮이는 시료로부터 반사된 빛의 위상으로부터 결정되며, 종래의 공초점 현미경에 비하여 주사시간을 크게 단축할 수 있었다. 끝으로 종래의 방법에 비해 제안된 방법은 시료의 반사율 변화에 덜 민감함을 확인할 수 있었다. The fiber-optical confocal scanning interference microscope with a simple configuration was constructed with a 4-port fiber-optic coupler, and the new method based on the phase shifting method was proposed for surface profiling by the system. In the method, the height of a specimen was determined from the phase of confocal beam. It was verified experimentally that the method was applicable to even the confocal interference microscope with a long-wavelength source and a low NA objective, and that the scanning time could be drastically reduced compared with the conventional method. Finally, it was found that our method is less sensitive to the variation of surface reflectivity than the conventional method.

Measurement of the Internal Structure of an Optical Waveguide Embedded in a Flexible Optical Circuit Board by Enhancing the Signal Contrast of a Confocal Microscope

이원준,김대찬,이승걸,오범환,박세근,이일항 한국광학회 2011 Current Optics and Photonics Vol.15 No.1

In this study, the internal structure of an optical waveguide embedded in a flexible optical circuit board is observed with a confocal microscope. In order to increase the light reflection from an internal material interface with a very small index difference, and thus enhance the signal contrast, a theta microscopy scheme has been integrated into a conventional confocal microscope, and a high NA oil-immersion lens has been used. The interface reflectivity is increased from roughly 0.0015% to 0.025% by the proposed method, and the internal structure can thus be successfully measured.

Decision Tree Analysis for Prediction Model of Poverty of The Older Population in South Korea

이수창,김대찬 국제문화기술진흥원 2022 International Journal of Advanced Culture Technolo Vol.10 No.2

This study aims to investigate factors that affect elderly poverty based on a comprehensive and universal perspective, suggesting some alternatives for improving the poverty rate of the elderly. The comprehensive and universal approach to the poverty of the aged that this study attempts can give a better understanding of the elderly poverty beyond the contribution of the existing literature, with the research model including individual, family, labor, and income factors as the causes of old-age poverty from the comprehensive and universal perspective on the causes of poverty of the elderly. In addition, the study attempts to input variants of variables into the equation for the causes of elderly poverty by using panel data from the 8th Korean Retirement and Income Study. This study employs decision tree analysis to determine the cause of the poverty of the elderly using CHAID. The decision tree analysis shows that the most vital variable affecting elderly poverty is making income. For the poor elderly without earned income, public pensions, educational careers, and residential areas influence elderly poverty, but for the poor elderly with earned income, wage earners and gender are variables that affect poverty. This study suggests some alternatives to improve the poverty rate of the aged. The government should create a better working environment such as senior re-employment for old people to be able to participate in economic activities, improve public pension or social security for workers with unfavorable conditions for public security of old age, and give companies that create employment of the aged diverse incentives.

인구통계학적 구조 변화와 범죄 감소 간의 관계에 있어서 인구 감소의 조절 효과 검증

이수창,김대찬 국제문화기술진흥원 2023 The Journal of the Convergence on Culture Technolo Vol.9 No.3

This study aims to empirically verify the moderating effect of population drop on the relationship between demographic changes and crime decline in local cities facing population decline in Korea. The study employs changes in the population of young adults, men, elderly, foreign residents, and population movement as factors of demographic changes, including types of the city as a control variable in the research model. The rate of change in population drop is used as a moderator variable and the rate of change in crime decline as a dependent variable. Data are collected from 155 cities with declining populations from 2010 to 2022 through KOSIS, the National Statistics Portal, and information disclosure requests. Data collected are analyzed using moderated regression analysis. In the first and second stages of the analysis, they show that changes in the population of young adults, population movement, foreign people, population drop, and the type of city affect the change in crime. Moderated regression analysis shows that only the interaction terms among changes in the population of young adults, changes in population movement, and changes in the population of foreigners and the population drop affects change in crime significantly. 본 연구는 인구 감소로 인한 지역의 인구통계학적 구조 변화와 범죄 발생 간의 영향 관계에 있어서 인구 감소의 조절효과를 실증적으로 검증하고자 하였다. 이를 위해 인구통계학적 구조 변화를 구성하는 요인으로 청년층 인구의 변화, 남성 인구의 변화, 노인 인구의 변화, 외국인 인구의 변화, 인구이동의 변화를 선정하였으며, 통제변수로 도시의 유형을 연구모형에 투입하였다. 조절변수로는 인구 감소율을 그리고 종속변수로는 범죄 발생 변화율을 각각 활용하였다. 본 연구는 2010년부터 2022년까지 인구가 감소한 155개 지역을 대상으로 자료를 수집하였다. 자료는 KOSIS 국가통계포털과 정보공개 신청을 통해 수집되었으며, 수집된 자료는 조절회귀분석에 의해 분석되었다. 청년층 인구 변화율, 남성 인구 변화율, 노인 인구 변화율, 외국인 인구 변화율, 인구이동 변화율, 인구감소율, 그리고 통제변수인 지역의 유형을 독립변수로 투입한 1단계와 2단계 분석에서 청년층 인구 변화율, 외국인 인구 변화율, 인구이동 변화율, 인구감소율, 그리고 지역의 유형이 범죄 발생 변화율에 유의미한 영향을 미치는 것으로 나타났다. 인구 감소의 조절효과를 검증하기 위해 조절회귀분석을 실시한 결과, 청년층 인구 변화율, 인구이동 변화율, 그리고 외국인 인구 변화율과 인구 감소율의 상호작용항이 통계학적으로 유의미한 것으로 나타났다.

LED 광원 크기에 따른 자유 형상 렌즈의 조명 성능 변화와 공차 특성

양재석,김대찬,오범환,박세근,유일현,이승걸,Yang, Jae-Suk,Kim, Dae-Chan,O, Beom-Hoan,Park, Se-Geun,You, Il Hyun,Lee, Seung Gol 한국광학회 2013 한국광학회지 Vol.24 No.1

본 논문에서는 점광원을 기준으로 설계된 자유 형상 렌즈(freeform lens)의 조명 성능과 LED 광원 크기와의 관계 및 공차 특성을 살펴보았다. 비교를 위해 발산 조명 모델(divergent illumination model)을 적용한 두 가지 렌즈와 중첩 조명 모델(overlapped illumination model)을 적용한 한가지 렌즈를 설계하였다. LED 광원이 커짐에 따라 평균 조도에 비해 조도 균일도가 상대적으로 크게 감소하였으며, 정렬 오차에 의한 성능 저하는 거의 발생하지 않았다. 하지만 LED 광원의 방출 특성 변화는 LED 광원 크기에 관계없이 조명 성능에 영향을 미치는 것으로 확인하였다. 발산 조명 모델로 설계된 렌즈가 전반적으로 우수한 성능을 보였지만, LED 방출 특성 변화에 대해서는 중첩 조명 모델로 설계된 렌즈의 성능이 상대적으로 적게 변화함을 알 수 있었다. In this paper, the illumination performances of three freeform lenses optimally designed for a point source were investigated for several LEDs with different source sizes, and also the tolerance characteristics of the lenses were analyzed. For comparison, two lenses with different sizes were designed with a divergent illumination model, and the last one was done with an overlapped illumination model. As the LED source size increased, the illuminance uniformity decreased more strongly, and the influence of a source misalignment on illumination performance became insignificant. However, the variation of LED radiation characteristics had strong effect on the illumination performance, irrespective of LED source size. Even though the lens based on a divergent illumination model showed superior performance compared to the lens based on an overlapped illumination model, the latter was less sensitive to the variation of LED radiation characteristics.

Relationship between Change of Demographic Composition and Crime : Comparing Areas with Growth in Population to Areas with Decline

이수창,김대찬 국제문화기술진흥원 2022 International Journal of Advanced Culture Technolo Vol.10 No.3

This study is to investigate that population change as a result of the decline in population has a correlation with a decrease in crime, with the change in the demographic composition by comparing with two models: model with growth in population and one with the decline in population. We collected demographic data for all cities in Korea from the 2010 Census to 2020 offered by the Korean Statistical Information Service, with crime data comprising serious reported crime events from the Korean Nation Police Agency through requesting data related to the total number of crimes at the same as the period of demographic data. This study can identify the impacts of demographic changes as a result of population change on crime change through a comparative analysis between areas with population growth and ones with population decline. We can confirm that there are differences in determinants of crime between areas with population increase and one with population decrease from the analysis of the impact of demographic change as a result of population change on crime change.

대면적 COB-type LED 패키지를 포함한 LED 램프의 좁은 광속각 구현을 위한 2차 광학계 최적 설계

김봉준,김대찬,오범환,박세근,김봉호,이승걸,Kim, Bongjun,Kim, Dae-Chan,O, Beom-Hwan,Park, Se-Geun,Kim, Bongho,Lee, Seung Gol 한국광학회 2014 한국광학회지 Vol.25 No.2

본 논문에서는 직경이 14.5 mm인 대면적 COB-type LED 패키지를 사용하면서도 15도 이내의 좁은 광속각을 구현하기 위해, 광학계 크기를 축소하고 동시에 satellite ring 발생을 억제할 수 있는 이중 반사경 구조를 고안하여 조명광학계용 2차 광학계를 최적 설계하였다. 최적 설계를 위해 광원 크기와 제 1 반사경의 광속각 관계를 이용하였고, satellite ring 발생을 억제하기 위한 제 2 반사경의 최적 위치 및 크기를 고려하였다. 그 결과 대체 상용 제품의 크기 제한을 만족하며 80%의 광속 효율을 달성할 수 있었다. In this paper secondary optics for an LED lamp with a narrow beam angle of $15^{\circ}$ were optimized by using a two-reflector system, to reduce both its size and the occurrence of satellite rings. The conic constant and the curvature of the primary reflector were determined by considering the relation of the source size to the beam angle, and the optimal position and radius of the secondary reflector were found for reducing the occurrence of satellite rings. Luminous flux efficiency was about 80%.