• 한국강구조학회 논문집
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• 제10권2호통권35호
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• pp.221-232
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• 1998

본 연구에서는 지진 등과 같이 소성변형의 범위가 큰 Low-Cycle-Fatigue 범주에서 구조물의 응력변동을 중심으로 사용되는 기존의 피로곡선인 S-N선도 보다 실질적으로 간단하게 측정하여 분석할 수 있는 소성회전각에 의한 피로곡선을 제시하였다. 이는 소성힌지가 생성되는 곳의 소성변형율과 구조물의 소성회전각이 서로 정비례를 이루는 상관관계임을 입증하여, 실험을 통하여 밝혀진 소성변형율의 피로곡선의 기울기와 소성회전각의 기울기가 서로 같은 값을 가짐을 보여 주었다. 이론은 Manson과 Coffin의 변형을 피로곡선을 도입하였고, 실험은 ECCS 주관하에 실시하였으며, 수치해석을 통하여 소성힌지 부위의 위치와 정확한 소성변형율을 산정할 수 있었다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 학술대회 논문집 정보 및 제어부문
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• pp.46-48
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• 2004

This paper presents a simple method of rotational and translational motion estimation for digital image stabilization. The scheme first computes the rotation center by taking least squares of selected local velocity vectors, and the rotational angle is found from special subset of motion vectors. And then translational motion can be estimated by the relation among movement of rotation center, rotation angle and translation movement. To show the effectiveness of our approach, the synthetic images are evaluated, resulting in better performance.

• Wind and Structures
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• 제38권5호
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• pp.341-354
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• 2024

This paper presents a theoretical method to deal with the aerodynamic performance and pitch optimization of the horizontal axis wind turbine blades at low wind speeds. By considering a blade element, the functional relationship among the angle of attack, pitch angle, rotational speed of the blade, and wind speed is derived in consideration of a quasi-steady aerodynamic model, and aerodynamic loads on the blade element are then obtained. The torque and torque coefficient of the blade are derived by using integration. A polynomial approximation is applied to functions of the lift and drag coefficients for the symmetric and asymmetric airfoils respectively, where specific expressions of aerodynamic loads as functions of the angle of attack (which is a function of pitch angle) are obtained. The pitch optimization problem is investigated by considering the maximum value problem of the instantaneous torque of a blade as a function of pitch angle. Dynamic pitch laws for HAWT blades with either symmetric or asymmetric airfoils are derived. Influences of parameters including inflow ratio, rotational speed, azimuth, and wind speed on torque coefficient and optimal pith angle are discussed.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 추계학술대회 논문집
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• pp.176-180
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• 2002

All types of VLM-s process include the linear heat cutting of EPS foam to generate a layer with 3D shape. The dimensional accuracy and part quality of the cut part are dependent on the thermal characteristics in the EPS foam. The thermal characteristics are determined by operating parameters such as an effective heat input and cutting angle. The objective of this study is to investigate into the influence of cutting angle on the kerfwidth and the melted length of the cut part using the numerical analysis and the experiments in generally sloped cutting with two cutting angles. In order to estimate an accurate temperature field, the transient thermal analysis using moving coordinate system, the fully conformed mesh and the heat flux model with two cutting angles is carried out. From the results of the analysis and the experiments, it has been found that the influence of the rotational angle about x-axis in which the rotational axis is normal with hotwire cutting direction is appreciably negligible in comparison with that of the rotational angle about y-axis.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1995년도 하계학술대회 논문집 B
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• pp.849-851
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• 1995

Magnetic heads on vcr drum are adjusted for protrusion, rotational angle, setting angle between two symmetrically positioned heads and height difference. Developed adjustment system covered assembly spec., namely ${\pm}2{\mu}m$ and ${\pm}30{\mu}m$ in rotational angle by using the image processing to determine head positions and S/W algorithm to compensate mechanical errors.

• 대한족부족관절학회지
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• 제18권3호
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• pp.119-123
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• 2014

Purpose: This study was designed to evaluate the clinical efficacy of temporary K-wire fixation in F-plate fixation for displaced intra-articular calcaneal fractures. Materials and Methods: Two groups (group 1 with F-plate fixation only and group 2 with temporary K-wire fixation and F-plate fixation) of patients were included in this study. The temporary K-wire was removed six weeks after the operation. Each group consisted of 33 cases. Rotational axis angles were measured radiographically and the foot and ankle outcome score (FAOS) was used for clinical assessment. Results: In group 1, the mean rotational axis angle was reduced from $27^{\circ}$ preoperatively to $5.59^{\circ}$ postoperatively and the angle at last follow-up was $9.94^{\circ}$. There was an increase in angle of $4.35^{\circ}$ between postoperative and the last follow-up measurement. In group 2, the mean rotational axis angle was reduced from $21.2^{\circ}$ preoperatively to $4.39^{\circ}$ postoperatively and the angle at last follow-up was $5.91^{\circ}$. There was an increase in angle of $1.52^{\circ}$ between postoperative and the last follow-up measurement. Significant difference in the changes of rotational axis angle was observed between the two groups. However, no significant difference in FAOS was observed between the two groups. Conclusion: Temporary K-wire fixation can prevent reduction loss when treating displaced intra-articular calcaneal fractures with an F-plate.

• 한국자기학회지
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• 제10권4호
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• pp.178-182
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• 2000

본연구에서는 서로 직교하는 yoke 장치와 4-채널 과도기록장치를 사용하여 회전하는 자기장을 발생시키고, 회전자화에 의한 자기적 손실을 측정할 수 있는 측정시스템을 구성하였다. 개발된 측정장치를 사용하여 무방향규소강의 회전자화에 의한 자기적특성을 측정하였으며, 회전자화에 의한 손실의 측정에서 자기유도성분의 측정방향과 자화력성분의 측정방향이 일치하지 않아, 시계방향 및 반시계방향으로 측정한 값이 차이를 나타내었다. 그러나 시계방향 및 반시계방향으로 측정한 회전자화에 의한 손실값의 평균은 일정함을 알 수 있었으며, 이를 이용할 경우 회전자화의 폭정오차를 줄일 수 있었다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1997년도 추계학술대회 논문집
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• pp.883-886
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• 1997

In all Rapid Prototyping (RP) processes, a CAD solid model is sliced ito thin layers of uniform, but not necessarily constant, thickness in the building direction. Each cross-sectional layer is successively deposited and, at the same tim, bonded onto the previous layer; the stacked layers form a physical part of the model. The objective of this study is to develop a methode for calculating the rotational angle(θ/sub x/, θ/sub y/) of the linear hotwire cutting system in the three-dimensional space for the Variable Lamination Manufacturing process using expandable polystyrene foam sheet (VLM-S). In order to examine the applicability of the developed method to VLM-S, various three-dimensional shapes, such s a screw, an extruded cross, and a figure of Sonokong, were made using the data obtaiend from the method.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2003년도 ICCAS
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• pp.231-236
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• 2003

This paper presents a simple approach on the rotational motion estimation and correction for the roll stabilization of the sight system. The algorithm first computes the rotational center from the selected local velocity vectors of related pixels by least square methods. And then, rotational angle is found from the special subset of the motion vector. Finally, motion correction is performed by the nearest neighbor interpolation technique. In order to show the performance of the algorithm, the evaluation for the synthetic and real image was performed. The test results show good performance compared with previous approach.

• 드라이브 ㆍ 컨트롤
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• 제13권4호
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• pp.59-67
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• 2016

This paper proposes a model-prediction-based collision-avoidance algorithm for excavators for which the recursive-least-squares (RLS) estimation of the excavator's rotational inertia is used. To estimate the rotational inertia of the excavator, the RLS estimation with multiple forgetting and two updating rules for the nominal parameter and the forgetting factors was conducted based on the excavator-swing dynamics. The average value of the estimated rotational inertia that is for the minimizing effects of the estimation error was computed using the recursive-average method with forgetting. Based on the swing dynamics, the computed average of the rotational inertia, the damping coefficient for braking, and the excavator's braking angle were predicted, and the predicted braking angle was compared with the detected-object angle for a safety evaluation. The safety level defined in this study consists of the three levels safe, warning, and emergency braking. The analytical rotational-inertia-based performance evaluation of the designed estimation algorithm was conducted using a typical working scenario. The results of the safety evaluation show that the predictive safety-evaluation algorithm of the proposed model can evaluate the safety level of the excavator during its operation.