• 한국항공우주학회지
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• 제33권2호
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• pp.75-83
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• 2005

NASA와 독일 DLR의 Gravity Recovery and Climate Experiment (GRACE)는 편대비행을 하는 두 개의 저궤도 위성을 이용하여 지구중력장을 측정하는 연구이다. 주요 관측 장비는 위성 사이의 거리를 측정하기 위한 초단파 거리측정기와 비중력 가속도를 측정하기 위한 정전기 방식의 3축 가속도계이다. 기본설계 및 허용오차 분석 등에 활용하기 위하여 정밀한 관측기 시뮬레이션 모델을 개발하였는데, 본 논문에서는 이러한 모델링 기법과 이를 적용한 궤도 및 중력장 추정기법에 관해 살펴보았다.

• 한국기계가공학회지
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• 제7권1호
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• pp.53-61
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• 2008

In this research, the layout and geometry of U-type ribs in the part, including significant process conditions, are automatically optimized to reduce part warpage with robustness in consideration. The optimization procedure are based on an iterative redesign methodology integrated with computer aided injection molding simulation, Taguchi's Design of Experiment(DOE), and a direct search-based optimization method. The robustness of a design alternative is efficiently measured by introducing composite noise factor and Taguchi's signal-to-noise ratio. As a solution search methodology, the modified design space reduction method based on orthogonal arrays is employed to exploit an optimal robust design alternative. To illustrate the proposed methodology, a case study is performed on simulation results, where an optimal robust design alternative is obtained with a moderate number of iterations.

• 한국조명전기설비학회:학술대회논문집
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• 한국조명전기설비학회 2009년도 춘계학술대회 논문집
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• pp.17-20
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• 2009

Available daylight in inside offers comfortable view environment, and psychological and physical advantages to people in a room. Architecture design has need of daylight prediction for reflection efficiently daylight. But it is difficult to predict the illuminance values in daylight system. Using various lighting simulation software is easy and simple, but we can find different results under the same conditions. This study compares with illuminance values from simulation (Lightscape 3.2, RELUX 2007, RADIANCE 3.9) and Mock-up experiment with the same space and parameter of daylight (location of space and window, date, time and sky condition).

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2003년도 Proceedings of ACRS 2003 ISRS
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• pp.837-839
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• 2003

Low spatial resolution remote sensing (RS) data (LSRD) are promising in agricultural monitoring activities due to their high temporal resolution, but under such a spatial resolution, mixing in a pixel is a common problem. In this study, a numerical experiment was conducted to explore a mixed pixel problem in agriculture using a combined RSsimulation model SWAP (Soil-Water-Atmosphere -Plant) and a Genetic Algorithm (GA) approach. Results of the experiments showed that it is highly possible to address the mixed pixel problem with LSRD.

• 한국공간구조학회논문집
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• 제13권1호
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• pp.51-57
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• 2013

There can be diverse causes in the destruction of a large space structure by strong wind such as characteristics of construction materials and changes in internal and external wind pressure of the structure. To evaluate the wind pressure of roof against the large space structure, wind pressure experiment is performed. However, in this wind pressure experiment, peak internal pressure coefficient is set according to the opening of the roof in Korea wind code. In this article, it was tried to identify the change of internal pressure coefficient and the characteristics of wind pressure coefficient acting on the roof by two kinds of opening on the side of the structure with Hyperbolic Paraboloid Spatial Structures roof. When analyzing internal pressure coefficient according to roof shape, it was found that minimum (52%) and maximum (30%~80%) overestimation was made comparing to partial opening type proposed in the current wind load. It is judged that evaluation according to the opening rate of the structure should be made to evaluate the internal pressure coefficient according to load.

• 대기
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• 제27권4호
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• pp.499-509
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• 2017

Possible links among cosmic ray, cloud, and climate have scientific uncertainties. The reputed topics have been highly controversial during several decades. A link between the atmospheric ionization by galactic cosmic rays (GCR), which is modulated by solar activities, and global cloud cover was firstly proposed in 1997. Some researchers suggested that the GCR can stimulate the formation of cloud condensation nuclei (CCN) in the atmosphere, and then the higher CCN concentrations may lead to an increase of cloud cover, resulting in a cooling of the Earth's climate, and vise versa. The CLOUD (Cosmic leaving outdoor droplets) experiment was designed to study the effect of GCR on the formation of atmospheric aerosols and clouds under precisely controlled laboratory conditions. A state-of-the-art chamber experiment has greatly advanced our scientific understanding of the aerosol formation in early stage and its nucleation processes if the GCR effect is considered or not. Many studies on the climate-GCR (or space weather) connection including the CLOUD experiment have been carried out during the several decades. Although it may not be easy to clarify the physical connection, the recent scientific approaches such as the laboratory experiments or modeling studies give some implications that the research definitively contributed to reduce the scientific uncertainties of natural and anthropogenic aerosol radiative forcing as well as to better understand the formation processes of fine particulate matters as an important parameter of air quality forecast.

• 조명전기설비학회논문지
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• 제24권1호
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• pp.35-44
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• 2010

주광은 인공광원보다 심리적 안정과 심리적 신체적 건강 측면 등에서 질적으로 우세하며, 작업능률의 향상에 도움을 주는 것으로 알려져 있다. 또한 쾌적한 빛 환경에 대한 재실자들의 요구가 증가하고 있다. 그러나 주광의 양과 질이 항상 일정하지 않아 예측하기가 어렵기 때문에 이러한 주광의 유용성에도 불구하고 건축설계에 주광을 적극적으로 반영하는 경우가 드물다. 본 연구의 목적은 이러한 주광의 성능을 계량화하고 가시화 할 수 있는 다양한 조명시뮬레이션 소프트웨어(Lightscape 3.2, Relux 2007, Radiance 3.9)를 사용함으로 주광을 예측하고, 도출된 결과 값과 Mock-up 실험의 실측값을 비교 분석을 통하여 조명 시뮬레이션 소프트웨어 활용성을 극대화하는 것이다.

• International Journal of Aeronautical and Space Sciences
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• 제18권2호
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• pp.236-244
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• 2017

In this study, the high-velocity impact penetration behavior of $[45/0/-45/90]_{ns}$ carbon/epoxy composite laminates was studied. The considered configuration includes a spherical steel ball impacting clamped circular laminates with various thicknesses and diameters. First, the impact experiment was performed to measure residual velocity and extent of damage. Next, the impact experiment was numerically simulated through finite element analysis using LS-dyna. Three-dimensional solid elements were used to model each ply of the laminates discretely, and progressive material failure was modeled using MAT162. The result indicated that the finite element simulation yielded residual velocities and damage modes well-matched with those obtained from the experiment. It was found that fiber damage was localized near the impactor penetration path, while matrix and delamination damage were much more spread out with the damage mode showing a dependency on the orientation angles and ply locations. The ballistic-limit velocities obtained by fitting the residual velocities increased almost linearly versus the laminate diameter, but the amount of increase was small, showing that the impact energy was absorbed mostly by the localized impact damage and that the influence of the laminate size was not significant at high-velocity impact.

• 한국항공우주학회지
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• 제30권5호
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• pp.56-61
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• 2002

평판 날개의 플러터에 대한 실험적 연구가 수행되었으며, 여러 가지 플러터 해석 방법들을 실험결과와 비교함으로써 검증하였다. 플러터 실험을 위한 날개 모델과 장치들이 아음속 풍동에 설치되었다. 시스템 식렬법을 이용하여 풍동 실험 데이터로부터 플러터 속도를 예측하였다. 날개 모델의 플러터 해석을 위해 MSC/NASTRAN, V-g방법, 근궤적법이 사용되었다. 해석으로 구한 플러터 속도와 실험으로부터 추정된 플러터 속도를 비교하였으며, 그 결과 잘 일치하였다. 본 연구의 날개 모델이 플러터 해석의 벤치마크 모델로 사용될 수 있을 것이다.

• International Journal of Aeronautical and Space Sciences
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• 제4권1호
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• pp.75-87
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• 2003

The primary objective of this study is to demonstrate ground-based experiment for the attitude control of spacecraft. A two-axis rotational simulator with a flexible ann is constructed with on-off air thrusters as actuators. The simulator is also equipped with payload pointing capability by simultaneous thruster and DC servo motor actuation. The azimuth angle is controlled by on-off thruster command while the payload elevation angle is controlled by a servo-motor. A thruster modulation technique PWM(Pulse Width Modulation) employing a time-optimal switching function plus integral error control is proposed. An optical camera is used for the purpose of pointing as well as on-board rate sensor calibration. Attitude control performance based upon the new closed-loop control law is demonstrated by ground experiment. The modified switching function turns out to be effective with improved pointing performance under external disturbance. The rate sensor calibration technique by Kalman Filter algorithm led to reduction of attitude error caused by the bias in the rate sensor output.