• 대한전자공학회논문지TC
• /
• 제45권10호
• /
• pp.49-58
• /
• 2008

본고 및 연구를 통하여 JEM(Jet Engine Modulation)의 특성 및 기본원리를 파악하며, 실제 항공기 중 저속항공기의 RCS 및 JEM을 측정하는 것이 목적이다. 측정시에는 원하지 않는 여러 오차들이 발생하게 되는데 여러 오차를 제거하기 위해 교정(Calibration)방법을 사용하게 되는데 본고에서는 IACT(Isolated Antenna Calibration Technique)방법을 사용하였다. 측정은 옥외(Outdoor)에서 이루어졌으며 항공기는 공군에서 운용하고 있는 T-103을 표적으로 측정하였다. T-103에 대한 JEM스펙트럼을 추출하며 고정된 표적에 대한 주파수 특성과 도플러에 의한 변화를 판단하는 것이다. 주파수는 일반적인 공대공 항공기에서 운용되는 X밴드를 사용하여 측정하였으며 공대공 항공기에서 저속항공기를 식별하는데 있어 측정을 통하여 분석하였다.

• 대한기계학회논문집A
• /
• 제22권3호
• /
• pp.483-492
• /
• 1998

An inverse analysis been applied to obtain the flow stress of the material. In this method, a ring-shaped specimen is compressed between two flat tools. This procedure employs, as the object function of inverse analysis, the balance of measured loads and reaction forces calculated by using rigid-plastic finite element method. The balance is explicit scalar function of flow stress which is a function of some unknown constants. For minimizing the balance, Newton-Raphon scheme is used. The friction factor, m, between flat tools and the specimen is determined by using friction area-divided method. The proposed method allows an accurate identification by avoiding the usual assumptions made in order to convert experimental measures into stress-strain relation. In this paper, the proposed method is numerically tested. A commercial pure aluminum was selected, as an example, to apply the method and the results are compared with stress-strain relation obtained by experiments.

• 방송공학회논문지
• /
• 제16권4호
• /
• pp.614-623
• /
• 2011

본 논문에서는 방송용 증강현실 시스템을 위한 실시간 카메라 추적 알고리듬을 제안한다. SURF(speeded up robust features) 알고리듬을 이용하여 추적을 초기화하며, 안정적인 실시간 카메라 추적을 위해 다층(multi-scale) 구조를 사용한다. 미리 알려져 있지 않고 시간에 따라 변하는 조명 환경에서의 특징 추적을 위해 정규상호상관도(normalized cross correlation, NCC)를 사용한다. 방송제작에는 줌 렌즈를 장착한 카메라가 사용되기 때문에 카메라의 초점거리를 온라인으로 추정할 필요가 있다. 카메라의 회전과 이동으로 이루어진 외부 포즈(pose) 변수와 함께 내부 변수인 초점거리를 목적함수에 포함시켜 함께 최적화한다. 실험결과는 제안한 온라인 카메라 보정 기법에 의해 카메라의 초점거리가 정확히 구해지는 것을 보여준다.

• 대한한방내과학회지
• /
• 제28권4호
• /
• pp.769-778
• /
• 2007

Background & Object : Postprandial epigastric fullness is one of common symptoms in functional dyspepsia, but its pathophysiological mechanism has still been unknown. In this study, its association between postprandial epigastric fullness and pyloric valve disturbance was studied through analysis of bowel sounds and electrogastrography. Methods : Bowel sounds and electrogastrography were recorded together for fasting 15 min and postprandial 40 min. Parameters of bowel soundincluding motility index, sound to sound interval, standard deviation of sound to sound interval, sounds per minute, % of bowel sound, sound length, intensity, dominant frequency of sounds, and postprandial / fasting ratio of dominant frequency of sounds were analyzed with a specialized program. By electrogastrography, regularity of slow waves and power ratio were obtained. Results : Significances of bowel sounds appeared in motility index (p=0.046), dominant frequency of fasting (p=0.048), postprandial (p=0.003), and the ratio of postprandial/fasting (p=0.000); those of EGG parameters were shown in postprandial regularity of slow waves (p=0.006) and power ratio (p=0.011). Conclusion : Pyloric valve disturbance was a cause of postprandial epigastric fullness in patients with functional dyspepsia. Analysis of bowel sound might be useful in diagnosing its existence.

• 조명전기설비학회논문지
• /
• 제18권2호
• /
• pp.23-28
• /
• 2004

전기 임피던스 단층촬영법(electrical impedance tomography, EIT)은 미지의 내부 저항률 분포를 갖는 물체 주위에 특수하게 제작된 전극을 여러 개 배치하고 적절하게 설계된 전류를 주입하여 이에 따른 인가전압을 물체 경계에서 측정한 후 이를 근거로 EIT의 영상복원 알고리즘에서 물체 내부의 미지의 저항률 분포를 재구성하는 기술이다. 전기 임피던스 단층촬영법의 영상복원 과정은 비선형 방정식으로 기술되며, 그 해석적인 해를 구하기가 매우 어려우므로 수치적인 방법으로 근사해를 구한다. 본 논문에서는 EIT 영상복원 방법으로 동시 인자변환 확률적 근사화(simultaneous perturbation stochastic approximation, SPSA) 방법을 제안한다. SPSA 방법을 이용한 EIT 영상복원의 성능을 컴퓨터시뮬레이션을 통해 살펴보고 기존의 mNR 방법에 의해 얻어진 결과와 비교 분석하도록 한다.

• 한국정밀공학회지
• /
• 제18권9호
• /
• pp.61-70
• /
• 2001

This paper introduces a new digitization method with sensor fusion for shape measurement in reverse engineering. Digitization can be classified into contact and non-contact type according to the measurement devices. Important thing in digitization is speed and accuracy. The former is excellent in speed and the latter is good for accuracy. Sensor fusion in digitization intends to incorporate the merits of both types so that the system can be automatized. Firstly, non-contact sensor with vision system acquires coarse 3D point data rapidly. This process is needed to identify and loco]ice the object located at unknown position on the table. Secondly, accurate 3D point data can be automatically obtained using scanning probe based on the previously measured coarse 3D point data. In the research, a great number of measuring points of equi-distance were instructed along the line acquired by the vision system. Finally, the digitized 3D point data are approximated to the rational B-spline surface equation, and the free-formed surface information can be transferred to a commercial CAD/CAM system via IGES translation in order to machine the modeled geometric shape.

• 제어로봇시스템학회:학술대회논문집
• /
• 제어로봇시스템학회 1989년도 한국자동제어학술회의논문집; Seoul, Korea; 27-28 Oct. 1989
• /
• pp.781-785
• /
• 1989

In the field of control technology, too, it is about time that the students should free themseleves from the paradigm of Newtonian mechanics. Otherwise, they might fail to grasp the essence of control. Now, let us consider the essence of control. Control consists of manipulating a particular object, matter, energy of environment on the basis of certain medium information. (measurement data, force, etc.) So, we shall look into the methods of manipulation. Here, we consider natural control, constraining control, and hybrid control as basic methods of manipulation. In this paper, we would like to put forward the daring proposal that it's called a Holon-type hybrid control system. It is intended to control a plat with complicated or unknown characteristics where a conventional control theory is not easy to apply. A prototype system has been developed and applied to a real plant. The control system is a multi-layer system. Each layer includes different control input. The important features of the system are as follows: 1) Each layer behaves autonomously and also cooperates with each other to optimize the whole plant. 2) The controller optimizes a plant without mathematical models when these models are not easy to obtain.

• 한국정밀공학회:학술대회논문집
• /
• 한국정밀공학회 2003년도 춘계학술대회 논문집
• /
• pp.490-493
• /
• 2003

This paper describes the development of a small 6-axis force/moment sensor for robot's finger, which measures forces Fx. Fy, Fz, and moments Mx, My, Mz simultaneously. In order to safely grasp an unknown object using the robot's gripper, and accurately perceive the position of it in the gripper, it should measure the force in the gripping direction, the force in the gravity direction and the moments each direction. and perform the control using the measured forces and moments. Thus, the robot's gripper should be composed of 6-axis force/moment sensor that can measure forces Fx, Fy, Fz, and moments Mx, My. Mz simultaneously. In this paper, the small 6-axis force/moment sensor for measuring forces Fx, Fy, Fz, and moments Mx, My, Mz simultaneously was newly modeled using several parallel-plate beams, designed, and fabricated. The characteristic test of made sensor was performed, and the result shows that interference errors or the developed sensor are less than 3%. Thus, the developed small 6-axis force/moment sensor may be used for robot's gripper.

• 전기전자학회논문지
• /
• 제4권2호
• /
• pp.249-256
• /
• 2000

전기 임피던스 단층촬영에서는, 각기 다른 주입 전류패턴에 의해 유기된 경계면의 전압 값을 이용하여 다양한 복원 알고리즘에 의해 물체의 내부 저항률(전도율) 분포를 추정한다. 본 논문에서는, 부가적인 사전 정보를 soft 제약조건으로 비용함수에 추가하고, 비용함수의 가중행렬을 지수적으로 가중된 최소자승법에 근거하여 선택하는 수정된 조정 Newton-Raphson(mNR) 법을 제안한다. 32채널에 대한 컴퓨터 시뮬레이션 결과, 제안된 방법은 기존의 조정 mNR 법에 비해 계산부담은 약간 증가하지만 복원성능이 개선됨을 보인다.

• 제어로봇시스템학회논문지
• /
• 제9권1호
• /
• pp.50-56
• /
• 2003

In electrical impedance tomography(EIT), various image reconstruction algorithms have been used in order to compute the internal resistivity distribution of the unknown object with its electric potential data at the boundary. Mathematically the EIT image reconstruction algorithm is a nonlinear ill-posed inverse problem. This paper presents a new combined method based on genetic algorithm(GA) and modified Newton-Raphson(mNR) algorithm via two-step approach for the solution of the static EIT inverse problem. In the first step, each mesh is classified into three mesh groups: target, background, and temporary groups. The mNR algorithm can be used to determine the region of group. In the second step, the values of these resistivities are determined using genetic algorithm. Computer simulations with the 32 channels synthetic data show that the spatial resolution of reconstructed images by the proposed scheme is improved compared to that of the mNR algorithm at the expense of increased computational burden.