각막 난시가 토릭소프트콘택트렌즈 착용으로 인한 축 회전 변화에 미치는 영향

조창권(Chang Kwon Cho),서우현(Woo Hyun Seo),김소라(So Ra Kim),박미정(Mijung Park) 한국안광학회 2019 한국안광학회지 Vol.24 No.2

Purpose: In this study, the changing pattern of axial rotation was investigated when the gaze direction and wearing time changed after wearing toric soft contact lenses according to the wearers’ corneal astigmatism. Methods: Toric soft contact lenses with double thin zone design were placed on 85 eyes having with-the-rule astigmatism. The changes in the axial direction and degree of rotation according to the gaze direction were respectively measured after 15 min and 6 h of wearing the lens. We further analyzed the difference of the axial rotation according to corneal astigmatism. Results: On fixing the eyes on 9 gaze directions while wearing the toric soft lenses, the lenses were mostly rotated to the temporal direction, and the rotation to the temporal direction was greater with the wearing time. A higher change in the degree of rotation was observed in the low corneal astigmatism group when analyzing the rotational change based on 5° rotation according to the wearers’ corneal astigmatism in the primary gaze direction. However, the change in the degree of rotation in the middle and high astigmatism group was rarely observed. Conclusions: From these results, it was found that the rotational pattern of the toric soft lenses varied by the lens wearers’ corneal astigmatism. Furthermore, the degree and direction of rotation were different according to the wearing time in each gaze direction. Therefore, it is suggested that the precise fitting guideline for toric soft lenses should be applied for the low astigmatism group having a large degree of lens rotation.

민족정체성 유지행동이 심리적 웰빙과 직무만족에 미치는 영향: 미얀마와 베트남 노동자를 대상으로

조창권 ( Chang Kwon Cho ),이금희 ( Jinxi Michelle Li ) 아시아.유럽미래학회 2016 유라시아연구 Vol.13 No.3

The increased number of foreigners in Korea (now more than 1.8 million) has necessitated understanding, analyzing and interpreting the immigration issues in order to solve the foreign workers` social problems. This paper aims to investigate how the behavior aspects of ethnic identity (using home-country media, maintaining religious traditions, hanging around with homeland people) influence psychological well-being and job satisfaction. In addition, the paper aims to provide practical guidelines for social welfare organizations and enterprises which support and recruit them. The sample of our respondents was 146 foreign workers (90 Myanmar workers and 56 Vietnamese workers) in Korea. We used SPSS 21.0 for statistical analysis. The results are as follows: using home-country media and maintaining religious traditions significantly influence both psychological well-being and job satisfaction. Furthermore, psychological well-being was found to mediate the relationship between home-country media and job satisfaction as well as between religious traditions and job satisfaction. This study highlighted and demonstrated the importance of maintaining heritage culture in Korean multicultural policies. Integration has been considered as the most desirable acculturation strategy, but Korean multicultural policies have predominantly emphasized the assimilation aspect of integration only and have neglected another dimension of integration, which is maintaining heritage culture. Therefore, multicultural policies in Korea should help foreigners maintain their own home culture as well as help them adjusted to Korean culture. To do this, Korean government and other relevant agencies such as social services need to help foreigners easily access to home country media, help them connect to the relevant religious groups to maintain their own religious tradition, and establish social or cyber communities for the members from their own home countries.

효과적으로 미로를 찾기 위한 적응적 체인로봇

조창권 ( Chang-kwon Cho ),우균 ( Gyun Woo ) 한국정보처리학회 2011 한국정보처리학회 학술대회논문집 Vol.18 No.1

체인로봇은 단일 로봇보다 강인성 측면에서 유리하기 때문에 무인탐사 환경에 적합하다. 체인로봇을 관리하기 위해서는 선두 로봇을 선정하고 군집을 관리하는 방법이 사용된다. 본 논문에서는 군집로봇의 효과적인 미로 탐색을 위해 체인로봇 그룹의 순위를 미로 환경에 맞게 적응적으로 순위를 재지정하는 방법인 적응적 체인로봇 알고리즘을 제안한다. 그리고 체인 알고리즘을 적용한 경우와 적응적 체인 알고리즘을 적용한 경우로 나누어 2차원 맵을 탐색하는 실험을 수행하였다. 군집로봇이 맵을 이동하는 과정에서 선두 로봇이 동작 불능 상태가 되는 경우가 발생할 수도 있다. 이때 체인로봇을 적응적으로 순위를 재지정하는 방법을 사용하였다. 본 논문에서 제시한 방법을 시뮬레이션 환경에서 실험하였는데 실험 결과에 따르면 100%의 성공률을 얻을 수 있었다.

PBUG: 모바일 로봇 쌍을 위한 버그 알고리즘

조창권 ( Chang-kwon Cho ),우균 ( Gyun Woo ) 한국정보처리학회 2012 한국정보처리학회 학술대회논문집 Vol.19 No.1

논문은 한 대의 모바일 로봇의 모션 계획 알고리즘인 Bug1과 Bug2를 개선한 알고리즘을 제안한다. 장애물이 있는 환경에서 목표지점까지 도달하기 위한 경로 계획 알고리즘으로 Bug1과 Bug2가 제안되었지만, 이 두 알고리즘은 모두 장애물 형태에 따라 탐사 시간이 오래 걸릴 수 있다는 단점이 있다. Bug2 알고리즘은 Bug1 알고리즘을 개선한 형태로 제안되었지만 심지어 극적적인 경우에는 무한 루프에 빠진다는 단점이 있다. 이 논문에서는 이러한 단점을 해결하기 위해 한 쌍의 모바일 로봇을 이용한 병렬 탐색 PBug1, PBug2 알고리즘을 제안한다. 제안된 PBug1과 PBug2 알고리즘은 각각 Bug1과 Bug2의 속도를 보장하며 일반적으로 빠른 탐사시간을 보인다. 특히 PBug2 알고리즘은 Bug2와 달리 무한루프에 빠지는 경우가 없다. 제안된 알고리즘의 성능을 평가하기 위해 PBug1, PBug2 알고리즘을 구현하여 Bug1, Bug2 알고리즘과 비교하였다. 실험결과 PBug1 알고리즘은 Bug1 알고리즘보다 탐사 시간이 64.9%로 감소하였고 PBug2 알고리즘은 Bug1 알고리즘과 비슷한 탐사 시간을 보였다.

온도 변화의 반복이 소프트콘택트렌즈 파라미터에 미치는 영향

조창권(Chang Kwon Cho),송태환(Tae Hwan Song),이세은(Se Eun Lee),김소라(So Ra Kim),박미정(Mijung Park) 한국안광학회 2018 한국안광학회지 Vol.23 No.3

Purpose: The present study was conducted to investigate the changes in parameters of soft contact lenses caused by repeat exposure to various temperatures during distribution or storage. Methods: Intact 4 soft contact lenses made of different materials with or without wetting agent were placed for 4 hours at .20, 20, 50, and 80℃, and then stabilized at room temperature for additional 20 hours, respectively. This procedure was repeated 1, 3, and 5 time(s), and then refractive power, diameter, base curve, water content, thickness, visible light transmittance, UV transmittance and oxygen permeability of each lens were measured. Results: Although there were differences in degree in all four types of soft contact lenses, statistically significant changes in lens parameters were observed at .20℃ and 80℃. The overall diameter, water content, base curve and central thickness were increased or decreased in all lenses regardless of temperatures; however, the refractive power showed different pattern of increase/decrease at low and high temperatures indicating that the degree and pattern of change varied according to the lens parameters. Also, the changing pattern of parameters was different at low temperature and high temperature depending on the ionicity of soft lens, the presence of wetting agent, and the presence of silicone hydrogel material. Conclusions: From the results, the soft lens parameters were revealed to change by exposure to low- or high-temperature environment that may happened during distribution. Since these changes may cause problems with vision correction or comfort, it is necessary to prepare the standard for temperature during lens distribution and pay attention to it.

유통시 노출 가능한 온도에서의 써클콘택트렌즈 표면 및 파라미터 변화

송태환(Tae Hwan Song),조창권(Chang Kwon Cho),이세은(Se Eun Lee),김소라(So Ra Kim),박미정(Mijung Park) 한국안광학회 2019 한국안광학회지 Vol.24 No.1

Purpose: In the present study, changes in the surface and parameters of circle contact lenses (cosmetic colored contact lenses, hereafter referred to as circle lenses) used for cosmetic purposes were investigated when the lenses were exposed to various changes of temperature during their distribution. Methods: Three types of sealed circle lenses were respectively placed at temperatures of −20, 20, 50, and 80°C for 4 hours, and subsequently stabilized for 20 hours; this procedure was repeated once, 3 times, and 5 times. Changes in the pigmentation pattern and parameters of the lenses were then measured. Results: The change of parameters was observed in all of the etafilcon A circle lenses made by using the sandwich method, and hilafilcon B and methafilcon A lenses with pigmentation on their surfaces; however, the degree of change caused by the different temperatures was different according to the type of circle lens. There were some cases in which a statistically significant change in each parameter was noted for each circle lens, and there were also parameters that exceeded the range of standard error stipulated by Ministry of Food and Drug Safety. The cracks of the pigmentation pattern and small holes were observed in a circle lens with the dye on its surface at −20°C, and the large or small aggregation of dye was observed at −80°C. Conclusions: In the present study, changes in the parameters and pigmentation pattern of circle lenses were found at different temperature conditions during distribution. These changes can cause problems related to vision and comfort. Thus, it is suggested that the establishment of the temperature standard for distributing lenses, and further evaluation of the stability against heat that may occur during the pigmentation process are necessary.

군집로봇 간의 충돌 회피를 위한 시뮬레이션

조창권 ( Chang-kwon ),우균 ( Cho Gyun Woo ) 한국정보처리학회 2010 한국정보처리학회 학술대회논문집 Vol.17 No.2

군집로봇은 어떤 작업을 수행하기 위해 여러 로봇이 함께 움직이게 된다. 이렇게 여러 로봇이 함께 작업을 수행하다 보면 로봇 간의 충돌을 피해야 할 경우가 발생한다. 각 로봇은 주어진 환경을 인식하고 모델링하며 로봇들 간에 충돌을 피하여 주어진 임무를 효과적으로 이행할 수 있게 하는 것이 이 연구의 핵심이다. 로봇 간 충돌을 효과적으로 해결하기 위해 충돌 전 다양한 위치와 다양한 방법으로 충돌을 피할 수 있도록 했다. 따라서 이 논문에서는 카메라 센서와 위치정보 통신을 이용한 방법을 통해 군집로봇간의 충돌 회피에 대해 연구하였다.

통신해양기상위성 해양탑재체 신뢰성 예측

최재동(Jae-Dong Choi),조창권(Chang-Kwon Cho),강금실(Gum-Sil Kang) 한국항공우주연구원 2006 항공우주기술 Vol.5 No.1

본 연구에서는 해양탑재체의 고장모드 영향분석 및 신뢰성 예측결과가 제시되었다. 해양탑재체는 한반도 해역을 약 500m 급의 공간분해능을 갖는 8개 가시광선 대역 채널을 통해 관측한다. 해양탑재체를 구성하는 서브 구성품들의 안정성과 신뢰성 확보를 위해 부품별 고장검출영향분석이 수행되었다. 또한 기능 고장이 시스템과 위성체에 미치는 영향에 대해 분석되었다. 시스템의 복잡성을 설명하기 위하여 다른 관측위성에 사용된 유사 부품들을 통해 신뢰성 예측결과가 제시되었다. This paper presents Failure Mode Effect Analysis (FMEA) and Reliability Expectation at GOCI system level. The function of Gael payload is to acquire data in 8 visible spectral bands with a spatial resolution of about 500 m over the Korean sea. For stability and reliability of the subsystems making up the GOCI, a functional FMEA is performed and each functional failure is studied in terms of functional effect on the system. The reliability performances are expected through the similar equipments used on other earth observation spacecrafts in order to take into account the complexity of the considered item.

노즐 탭과 노즐 내부 낮은 돌출부가 초음속 제트유동장에 미치는 영향에 관한 연구

진원진(Won-Jin Jin),조창권(Chang-Kwon Cho),이열(Yeon Lee),윤웅섭(Woong-Sun Yoon) 한국항공우주학회 2002 韓國航空宇宙學會誌 Vol.30 No.5