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위성용 다중대역광학센서의 광학 성능 향상을 위한 자중보상기법
윤도희 한국군사과학기술학회 2024 한국군사과학기술학회지 Vol.27 No.2
This paper discusses a gravity compensation technique designed to reduce wavefront error caused by gravityduring the assembly and alignment of satellite multi-band optical sensor. For this study, the wavefront error causedby gravity was analyzed for the opto-mechanical structure of multi-band optical sensor. Wavefront error, anindicator of optical performance, was computed by using the displacements of optics calculated through structuralanalysis and optical sensitivity calculated through optical analysis. Since the calculated wavefront error caused bygravity exceeded the allocated budget, the gravity compensation technique was required. This compensationtechnique reduces wavefront error effectively by applying the compensation load to the appropriate position of thehousing tube. This method successfully meets the wavefront error budget for all bands. In the future, a gravitycompensation equipment applying this technique will be manufactured and used for assembly and alignment ofmulti-band optical sensor.
윤도희(Do-hee Yoon) 항공우주시스템공학회 2024 항공우주시스템공학회지 Vol.18 No.2
인공위성은 발사체 모델과 연성하중해석을 수행하여 설계를 최종 검증하게 된다. 연성하중해석 결과의 정확도를 높이기 위해서는 유한요소모델 정확도가 매우 중요하며, 이를 위해 모델 보정은 필수적이다. 일반적으로 모델 보정은 재료 물성치와 두께 등을 하나씩 바꿔가며 수행하게 되는데, 이는 매우 많은 시간과 비용이 소요된다. 따라서 본 논문에서는 최적화 기법을 이용하여 탑재체 유한요소모델의 보정작업을 보다 효율적으로 수행하였다. 분산분석을 통해 중요 변수를 선정하고, 크리깅 대체 모델을 이용하여 해석과 최적화에 필요한 시간과 비용을 절감하였다. 본 논문에서 제안한 보정 방법은 진동 시험결과만 있으면 적용할 수 있으며, 수치적인 계산 비용과 소요 시간을 대폭 줄일 수 있다는 점에서 효율성 측면에서 큰 장점이 있다. A satellite is ultimately verified by performing a coupled load analysis with the launch vehicle. To increase the accuracy of the coupled load analysis results, it is important to have good accuracy of the finite element model. Therefore, finite element model correlation is essential. In general, model correlation is performed by changing the material properties and thickness one by one, but this process takes a lot of time and cost. The current paper proposes an efficient model correlation method using optimization. Significant variables were selected through analysis of variance, and the time and cost required for analysis and optimization were reduced by using the Kriging surrogate model. The method proposed in this paper can be applied only with the vibration test results, and it has a great advantage in terms of efficiency in that it can significantly reduce the numerical calculation cost and time required.
Subcutaneous Fat Necrosis of the Newborn Associated with Cardiomyopathy
김태윤,윤도희,김정원,장재현,전정식 대한피부과학회 1997 Annals of Dermatology Vol.9 No.1
Subcutaneous fat necrosis of the newborn is an uncommon disorder characterized by firm subcutaneous plaques and nodules usually appearing shortly after birth. It runs a relatively benign course and may completely resolve in a few months without any recurrence. We report a case of subcutaneous fat necrosis in a 15 day-old male suffering from severe perinatal asphyxia and hypoxic cardiomyopathy, who presented with indurated subcutaneous nodules and plaques on the both shoulders and the back. Histologically the subcutaneous fat showed focal necrosis with needle-shaped clefts, lymphohistiocytic infiltration and foreign body reactions consistent with subcutaneous fat necrosis of the newborn. In our patient, compromised cardiac output due to cardiomyopathy might have aggravated the hypoxic condition and it could be speculated that cardiomyopathy-induced systemic hypoxia gave rise to hypothermia of the skin as a result of peripheral vasoconstriction. This report presents a causal relationship of cardiomyopathy and subcutaneous fat necrosis of the newborn.