• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.21 no.7
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• pp.109-116
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• 2007

The emf of a permanent magnet multi-phase BLAC(Brushless AC) motor is generally a non-sinusoidal or a non-ideal trapezoid wave. So, conventional modeling using a sinusoidal or an ideal trapezoid emf can result in errors to simulate and analyze the properties of a multi-phase BLAC motor. To reduce the modeling error, this paper proposes a phase variable model, which is obtained from a hybrid modeling technique consisting of Finite Element Analysis(FEA) based circuits and equations. Since the phase model parameters including the emf waveform were obtained using FEA, the proposed hybrid modeling technique can be used to implement a simulation model for multi-phase BLAC motors with any emf voltage waveforms. Adequacy of the proposed model was established from the simulation and experimental results for a seven-phase BLAC motor.

• Clinics in Shoulder and Elbow
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• v.18 no.3
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• pp.152-158
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• 2015

Background: Acromioclavicular (AC) stability is maintained through a complex combination of soft-tissue restraints that include coracoclavicular (CC), AC ligament and overlying muscles. Among these structures, the role of the CC ligament has continued to be studied because of its importance on shoulder kinematics, especially after AC injury. This study was designed to determine the geometric change of conoid and trapezoid ligaments and resulting stresses on these ligaments according to various scapular motions. Methods: The scapuloclavicular (SC) complex was isolated from a fresh-frozen cadaver by removing all soft tissues except the AC and CC ligaments. The anatomically aligned SC complex was then scanned with a high-resolution computed tomography scanner into 0.6- mm slices. The Finite element model of the SC complex was obtained and used for calculating the stress on different parts of the CC ligaments with simulated movements of the scapula. Results: Average stress on the conoid ligament during anterior tilt, internal rotation, and scapular protraction was higher, whereas the stress on the trapezoid ligament was more prominent during posterior tilt, external rotation, and retraction. Conclusions: We conclude that CC ligament plays an integral role in regulating horizontal SC motion as well as complex motions indicated by increased stress over the ligament with an incremental scapular position change. The conoid ligament is the key structure restraining scapular protraction that might occur in high-grade AC dislocation. Hence in CC ligament reconstructions involving only single bundle, every attempt must be made to reconstruct conoid part of CC ligament as anatomically as possible.

• Journal of the Korean Society of Costume
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• v.54 no.5
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• pp.109-123
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• 2004

The purpose of this study is to examine features of parts of Jikryung and relations among the features. Results of the study can be described as follows. 1. The short front and long rear of Jikryung was changed into the long front and long rear of the dress in the late 16th century. Kalgit of quasi-square style as double collar was changed into that of common collar in the late 16th century and then into common semi-circle collar in the early 17th century, when double Sup was also changed Into single Sup. Narrow sleeves of Jikryung were replaced by bean chaff-shaped in the late 16th century and then by wide ones in the early period of the next century. The shape of the side hem of Jikryung was changed from rectangle into trapezoid in the early 17th century Triangle-shaped Moo was changed into trapezoid-shaped one in the late 16th century and then again into triangle in the late 17th century 2. Changes in shapes of the parts of Jikryung were made with them correlated. The collar of Jikryung saw change in its form from double to common as its width was reduced. Double Sup was changed into single one and the narrow, short coat string into the long one as Jikryung became a dress needing less adjustment. The sleeves widened as the length of whajang increased. The side hem of Jikryung saw change in its shape from rectangular to trapezoidal one as its position was changed. Trapezoidal Moo was replaced by triangular one as the sleeve of Jikryung was changed in shape. 3. Changes in shapes of the parts of Jikryung influenced the aesthetic beauty of the dress itself In its first period, Jikryung was simple with long, slim silhouettes. In its second period, the dress was rich with increased volume. Finally in its third period, the dress was characterized by the harmony of simpleness and richness.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.418-418
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• 2010

최근 친환경 저전력 차세대 조명소자로 발광다이오드가 각광을 받고 있다. 하지만 종래의 수평형 발광다이오드는 사파이어 기판의 열악한 열전도도 및 전기전도도 특성으로 인하여 효율적인 열방출의 저하가 생기게 되고, 양전극과 음전극의 수평배치에 기인한 심각한 전류쏠림현상 등이 수평형 발광다이오드의 고전력 소자로서의 응용에 걸림돌로 작용하고 있다. 근래에 수평형 발광다이오드의 대안 중 하나로 수직형 발광다이오드에 대한 연구가 활발히 진행되고 있다. 수직형 발광다이오드에서는, 수평형 발광다이오드에서의 전류쏠림현상을 향상시키기 위해 얀전극과 음전극을 수직으로 배치시킨다. 그리고 열전도도 및 전기전도도 특성이 떨어지는 사파이어를 제거하기 위해 LLO(Laser Lift Off)공정이 사용된다. LLO공정으로 인해 수직형 발광다이오드의 구조는 수평형 발광다이오드와 달리 n-GaN이 위로 배치되는 특성을 가진다. 본 연구에서는, 수직형 발광다이오드의 광추출 효율을 증가시키기 위해 SiO2 나노입자를 이용한 GaN 표면요철 형성기술을 개발, 적용 하였다. SiO2 나노입자를 n-GaN상에 단일층으로 분산시키기 위해 PR(PhotoResist), 나노입자, IPA(Isopropyl Alcohol)이 혼합된 용액을 스핀코팅시켰고 그 결과를 SEM으로 확인할 수 있었다. GaN 식각을 위해 SiO2 나노입자를 마스크로 사용하였고, BCl3가스를 사용한 건식식각을 진행하였다. 그 결과 조밀하고 균일한 크기의 Cylinderical Trapezoid 식각 형상이 n-GaN표면에 형성되었음을 SEM으로 확인할 수 있었다. 우리는 표면요철이 없는 발광다이오드와 SiO2 나노입자를 이용한 표면요철이 형성된 발광다이오드의 특성을 비교하였다. 그 결과 표면요철이 있을 때 광출력이 증가함을 확인할 수 있었다. 거기에 더하여 표면요철의 높이가 300nm~1000nm로 변화함에 따른 소자의 특성변화 또한 관찰할 수 있었다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.24 no.11
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• pp.1411-1416
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• 2020

In this paper, we propose a method of extraction analysis of blood flow area on color doppler ultrasonography by using 4-directional contour tracking and K-Means algorithm. In the proposed method, ROI is extracted and a binarization method with maximum contrast as a threshold is applied to the extracted ROI. 4-directional contour algorithm is applied to extract the trapezoid shaped region which has blood flow area of brachial artery from the binarized ROI. K-Means based quantization is then applied to accurately extract the blood flow area of brachial artery from the trapezoid shaped region. In experiment, the proposed method successfully extracts the target area in 28 out of 30 cases (93.3%) with field expert's verification. And comparison analysis of proposed K-Means based blood flow area extraction on 30 color doppler ultrasonography and brachial artery blood flow ultrasonography provided by a specialist yielded a result of 94.27% accuracy on average.

• 제어로봇시스템학회:학술대회논문집
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• 1997.10a
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• pp.807-810
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• 1997

Digital control of robot manipulator employs discrete-time robot models. It is important to explore effective discrete-time robot models and to analyze their properties in control system designs. This paper presents a new type discrete-time robot model. The model is derived by using trapezoid rule to approximate the convolution integral term, then eliminating nonlinear force terms from robot dynamical equations. The new model obtained has very simple structure, and owns the properties of independence to the nonlinear force terms. According to evaluation criteria, three aspects of the model properties: model accuracy, model validity range and model simplicity are examined and compared with commonly used discrete-time robot models. The validity of the proposed model and its advantages to control system designs are verified by simulation results.

• IEIE Transactions on Smart Processing and Computing
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• v.6 no.2
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• pp.85-92
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• 2017

This paper presents a dehazing method based on a fuzzy membership function and variational method. The proposed algorithm consists of three steps: i) estimate transmission through a pixel-based operation using a fuzzy membership function, ii) refine the transmission using an L1-norm-based regularization method, and iii) obtain the result of haze removal based on a hazy image formation model using the refined transmission. In order to prevent color distortion of the sky region seen in conventional methods, we use a trapezoid-type fuzzy membership function. The proposed method acquires high-quality images without halo artifacts and loss of color contrast.

• Proceedings of the KSME Conference
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• 2004.11a
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• pp.720-724
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• 2004

This paper introduces a new type of driving mechanism for rescue robot that has a variable geometry single-track which satisfies the pre-conditions of rescue robot. This mechanism is a symmetric configuration that has dual directions and prepares against overturn. By using transformation, it can reduce the energy consumption in steering and rotating. And also it maximizes the ability to overcome obstacles, like steps. It is designed to make the size of robot compact and to have the low center of gravity in driving on steps. Finally, we optimized the design variables of components determining the shape of reverse-trapezoid frame to enhance the adaptability to 4 phases of climbing steps.

• The Mathematical Education
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• v.52 no.4
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• pp.567-586
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• 2013

The purpose of this study was to introduce the Knowledge Quartet (KQ) framework by which we can analyze teacher knowledge revealed in teaching mathematics. Specifically, this paper addressed how the KQ framework has been developed and employed in the context of research on teacher knowledge. In order to make the framework accessible, this paper analyzed an elementary school teacher's knowledge in teaching her fifth grade students how to figure out the area of a trapezoid using the four dimensions of the KQ (i.e., foundation, transformation, connection, and contingency). This paper is expected to provide mathematics educators with a basis of understanding the nature of teacher knowledge in teaching mathematics and to induce further detailed analyses of teacher knowledge using some dimensions of the KQ framework.

• Journal of the Korean Society of Safety
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• v.14 no.2
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• pp.3-10
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• 1999

Fatigue crack growth rates in commercial plate of high strength Al 7075-T651 were investigated for the T-L direction in air, water and sea water. In this paper the effect of cyclic load wave-form(trapezoid and triangle) on fatigue crack growth rates in air, water and sea water environments were investigated using standard LEFM testing procedures. It was founded that the fatigue crack growth behaviors were not affected by cyclic load wave-forms. In region II (stable crack growth region), the fatigue crack growth behaviors were insensitive to cyclic load wave-forms and were sensitive to environment i.e. fatigue crack growth behaviors were higher in sea water than in air for all cyclic load wave-form. The result of fractographical morphology in air, water and sea water by SEM showed obvious dimple rupture and typical striation in air, but transgranular fracture surface in water and sea water. The values m are not affected by corrosion environments but C are different values.