• 한국항공우주학회지
• /
• 제30권1호
• /
• pp.56-64
• /
• 2002

본 논문에서는 복합재료 얇은 벽보의 열진동 응답에 대해 연구하였다. 복합재료 얇은 벽보로 모델링한 위성체 유연 구조물은 회전관성과 1차, 2차 와핑. 전단변형의 비고전적 요소를 포함한다. CUS구조물로 모델링한 복합재료 얇은 벽보의 열진동 특성은 적층순서와 섬유강화복합재료의 방향특성인자로부터 기인된 종방향 굽힘과 횡방향 굽힘이 연성과 관련하여 연구되었다. 열에 의한 구조물의 변형과 온도 구배가 연성된 열 진동에 대한 해석이 수행되었다.

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

• 한국항공우주학회지
• /
• 제44권7호
• /
• pp.562-567
• /
• 2016

비행속도와 조건에 따라 최적화된 형상을 갖는 모핑 날개는 작동기 기술, 구조 기계장치 기술, 유연 외피 재료, 제어법칙 기술 등 해결할 문제가 많다. 본 연구에서는 빠른 응답속도를 갖는 모핑 날개를 개발하기 위한 첫 단계로 형상기억합금 선을 작동기와 복원용 비틀림 스프링으로 구동되는 단일 플랩을 갖는 에어포일 설계하고 제작하였다. 제작된 모핑 에어포일의 작동실험을 통해 설계 개념의 타당성을 검증하였다. 실험을 통해 측정한 결과 원활한 작동과 매우 빠른 반응속도를 확인하였다.

• 통합자연과학논문집
• /
• 제2권2호
• /
• pp.55-58
• /
• 2009

A ligand-receptor docking program is an indispensible tool in modern pharmaceutical design. An accurate prediction of small molecular docking pose to a receptor is essential in drug design as well as molecular recognition. An effective docking program requires the ability to locate a correct binding pose in a surprisingly complex conformational space. However, there is an inherent difficulty to predict correct binding pose. The odds are more demanding than finding a needle in a haystack. This mainly comes from the flexibility of both ligand and receptor. Because the searching space to consider is so vast, receptor rigidity has been often applied in docking programs. Even nowadays the receptor may not be considered to be fully flexible although there have been some progress in search algorithm. Improving the efficiency of searching algorithm is still in great demand to explore other applications areas with inherently flexible ligand and/or receptor. In addition to classical search algorithms such as molecular dynamics, Monte Carlo, genetic algorithm and simulated annealing, rather recent algorithms such as tabu search, stochastic tunneling, particle swarm optimizations were also found to be effective. A good search algorithm would require a good balance between exploration and exploitation. It would be a good strategy to combine algorithms already developed. This composite algorithms can be more effective than an individual search algorithms.

• Structural Engineering and Mechanics
• /
• 제55권4호
• /
• pp.719-742
• /
• 2015

This paper dealt the free vibration analysis of thick truncated conical composite sandwich shells with transversely flexible cores and simply supported boundary conditions based on a new improved and enhanced higher order sandwich shell theory. Geometries were used in the present work for the consideration of different radii curvatures of the face sheets and the core was unique. The coupled governing partial differential equations were derived by the Hamilton's principle. The in-plane circumferential and axial stresses of the core were considered in the new enhanced model. The first order shear deformation theory was used for the inner and outer composite face sheets and for the core, a polynomial description of the displacement fields was assumed based on the second Frostig's model. The effects of types of boundary conditions, conical angles, length to radius ratio, core to shell thickness ratio and core radius to shell thickness ratio on the free vibration analysis of truncated conical composite sandwich shells were also studied. Numerical results are presented and compared with the latest results found in literature. Also, the results were validated with those derived by ABAQUS FE code.

• 대한산업공학회지
• /
• 제40권1호
• /
• pp.128-134
• /
• 2014

With the development of Information Communication Technology and a way of solving problems such as productivity improvement, advanced working attitude, greenhouse gas reduction, low birth rate, aged problem, etc., the need of smart work is increasing. Getting out of legacy working types that are limited in time and space, the flexible seat system at a smart work center that supports the smart working environment is proposed. However, the seat choice based on employee's emotional judgement may cause the decline of forming cooperative space and mutual communication because of the scattered seat arrangement between employees. This paper proposed a seat recommendation method for the mutual cooperation at a smart work center. The method is based on a work similarity of employees. A prototype system also implemented to show the feasibility.

• 한국가구학회지
• /
• 제23권4호
• /
• pp.342-354
• /
• 2012

This study aimed at acknowledging characteristics of space usage and suggesting orientation of space planning and furniture designing that meet various residents' demands correlating with residential area, furniture and family members by doing fact finding of volume of the furniture in medium/small sized apartment. The contents of the study are "experience of functional remodeling," "a number of bedrooms correlating with a number of family" and "furniture arrangement of each space and characteristics of space utilization" based on forty six cases. Followings are results of the study. 1) It was acknowledged that the function of space relating to family members largely depends on furniture arrangement correlating with age of children. It is needed that flexible planning of residential area to meets growing children and various family demands. 2) Functional remodeling requires furniture rearrangement attended with the remodeling. Thus, it is required that ideas in more simple and efficient furniture designing and consideration of construction environment embracing that ideas. 3) It can be acknowledged that the most demanding matter to enjoy satisfied and comfortable life in residential area is the matter of storage area. It is also understandable that the matter can be worse by time going by and the change of living pattern. Therefore, it is required that the consideration of enough storage area compatible with its function of the room and the planning of built-in furniture for storage.

• 대한두경부종양학회지
• /
• 제28권2호
• /
• pp.114-117
• /
• 2012

Background and Objectives : To assure the surgical completeness of the gasless endoscopic thyroidectomy via single incision axillary approach using flexible videoscope which provide wide angle and working space, we compared single incision axillary approach and axillo-areolar approach by means of clinical, surgical outcomes. Materials and Methods : From March 2011 to July 2012, 24 patients who had underwent endoscopic thyroidectomy via transaxillary approach were enrolled. Of total, 17 patients underwent single incision axillary approach(group I) and the other 7 underwent axillo-areolar approach(group II). Results : Patient demographics, surgical indications were similar between the two groups. The operating time(group I 144.6min, group II 153.6 min ; p=.29), blood loss(group I : 55.4cc, group II : 35.7cc : p=.64), hospital stay(group I : 4.2days, group II : 4.4 days ; p=.65) were similar in the two groups. Overall, two patients in group I(2/17, 11.8%) experienced postoperative complications, including one hematoma and one seroma. Due to narrow working space, one patient was change to axillo-areolar approach during single incision axillary approach with $30^{\circ}$ rigid endoscope. Conclusion：Single incision axillary approach is safe and effective similar to other endoscopic thyroidectomy methods using flexible videoscope. Different with $30^{\circ}$ rigid endoscope, 10-mm flexible videoscope can put inside the axillary inicision site in different axis with endoscopic instruments. This difference in endoscopic axis help to prevent crash with endoscopic instrument.

• Journal of Astronomy and Space Sciences
• /
• 제15권1호
• /
• pp.209-220
• /
• 1998

The stability problem of steady motion of a rigid body with multi-elastic appendages and multi-liquid-filled cavities, in the presence of no external forces or torque, is considered in this paper. The flexible appendages are modeled as the clamped -free-free-free rectangular plates, or/and as the discrete mass- spring sub-system. The motion of liquid in every single ellipsoidal cavity is modeled as the uniform vortex motion with a finite number of degrees of freedom. Assuming that stationary holonomic constraints imposed on the body allow its rotation about a spatially fixed axis, the equation of motion for such a systematic configuration can be very complex. It consists of a set of ordinary differential equations for the motion of the rigid body, the uniform rotation of the contained liquids, the motion of discrete elastic parts, and a set of partial differential equations for the elastic appendages supplemented by appropriate initial and boundary conditions. In addition, for such a hybrid system, under suitable assumptions, their equations of motion have four types of first integrals, i.e., energy and area, Helmholtz' constancy of liquid - vortexes, and the constant of the Poisson equation of motion. Chetaev's effective method for constructing Liapunov functions in the form of a set of first integrals of the equations of the perturbed motion is employed to investigate the sufficient stability conditions of steady motions of the complete system in the sense of Liapunov, i.e., with respect to the variables determining the motion of the solid body and to some quantities which define integrally the motion of flexible appendages. These sufficient conditions take into account the vortexes of the contained liquids, the vibration of the flexible components, and coupling among the liquid-elasticity solid.

• 한국항공우주학회지
• /
• 제49권3호
• /
• pp.185-195
• /
• 2021

본 연구의 날갯짓 초소형 비행체는 실제 생명체의 날개를 모방하여, 매우 유연한 재질의 캠버날개를 활용한다. 캠버 날개는 생명체와 유사하게 앞전, 시맥, 박막과 같이 특성이 서로 다른 세가지 재질로 구성되어 있고 다양한 방식으로 구속되어 있다. 날개의 유연성을 활용한 수동 회전(passive rotation) 방식은 앞전과 시맥의 재질이 날갯짓 궤적에 매우 큰 영향을 미치는 요소이기 때문에 적절한 유연성을 갖는 재질의 선정이 필수적이다. 이러한 날개의 재질들과 복잡한 형상을 사실적으로 모델링하여 정밀하게 해석할 수 있는 유체-구조 연성해석 프로그램을 개발하고, 날개의 앞전과 시맥의 탄성 계수의 변화에 따른 공력탄성학 효과를 정밀하게 분석하였다. 결과적으로 재료의 탄성 계수 변화만으로도 날개의 비틀림각 궤적을 적절히 발생시킴으로써 날갯짓 비행체의 추력 및 효율을 크게 증가시킬 수 있음을 보였다.