• Journal of the Korean Magnetics Society
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• v.26 no.2
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• pp.67-69
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• 2016

Recently, cost of rare-earth magnets has been raised, because rare-earth magnets are monopolized and the export is also regulated in China. For this reason, the induction motor is operated without the rare-earth magnets. The efficient development of induction motor is more important for economical scheme. A torque of the induction motor is computed and the correlation between dimension and resistance of the squirrel cage rotor is investigated. Also, the correlation between leakage reactance and torque was analyzed with respect to the same dimension of rotor with different shapes. Therefore, this paper proposes the method of improvement for squirrel cage rotor.

• The Proceedings of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.10 no.2
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• pp.71-77
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• 1996

The end-ring may contribute a significant influence to the performance of machine. The induced currents flow through the bars of a cage rotor and complete their closed paths by passing around the end-ring. This dissertation is to describe a method for calculating end-ring resistance of squirrel cage rotor, based on 3-D finite element method(A-$\Phi$). The resistance under consideration of skin effect is calculated by using Joule's loss equation.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.7
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• pp.347-352
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• 2019

This study focused on improving the cast quality of small-sized induction motor rotors during the die casting process. A new rotor core cast model was proposed based on previous research results and parametric studies. Numerical analyses using 3-dimensional half models were performed to evaluate the filling patterns of aluminum molten metals into a mold and on-site experiment performed to verify the newly proposed cast model. The following were obtained from numerical filling analyses and experimental results. First, molten metals started to fill the lower end ring, then moved on to fill the core slot and upper end ring and finally stopped to fill at the rotor core slot. Second, significant circulation of molten metals was not observed on the lower end ring, resulting in fewer defects at the section of the lower end ring from the experimental results. Third, the new shape of a rotor core cast was effective in producing rotors with sound cast quality, and reducing the end ring cast defect area by approximately 70 %.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.10
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• pp.115-120
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• 2018

This study examined the cast quality of small-sized induction motor rotors during the die casting process. Numerical analyses with 3-dimensional half models were performed to investigate the filling patterns of aluminum molten metals into a mold after high-speed injections. The following were obtained from numerical analyses and experimental results. First, molten metals started to fill the lower end ring, then moved horizontally to fill the core slot and upper end ring, and finally stopped to fill the rotor core slot. Second, circulation of molten metals occurred at the lower end ring, resulting considerable porosity at the section of lower end ring from the experimental results. Third, further work for obtaining sound quality of rotor core cast is required to develop a new shape of the rotor core cast or improve the die casting conditions.

• Proceedings of the KIEE Conference
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• 2015.07a
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• pp.748-749
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• 2015

본 논문에서는 권선사양에 따른 10kW급 동 다이캐스팅 고속 유도전동기의 전자기적 특성과 전기기기의 진동을 발생시키는 고정자 치의 가진력을 분석하였다. 회전자 모델과 코일의 점적률은 일정하게 유지하면서 턴 수, 코일단면적, 고정자 슬롯의 형상을 변경하였다. 이에 따라 1, 2차 측 저항과 누설리액턴스 성분이 변화함을 확인하였고, 저항과 누설리액턴스 성분의 변화가 유도전동기의 토크, 자속밀도, 효율 특성 및 고정자 치의 가진력에 미치는 영향에 대해 분석하였다.

• Progress in Medical Physics
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• v.26 no.1
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• pp.18-27
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• 2015

Since a Compton camera has high detection sensitivity due to electronic collimation and a good energy resolution, it is a potential imaging system for nuclear medicine. In this study, we investigated the feasibility of a Compton camera for multi-tracer imaging and proposed a rotating Compton camera to satisfy Orlov's condition for 3D imaging. Two software phantoms of 140 and 511 keV radiation sources were used for Monte-Carlo simulation and then the simulation data were reconstructed by listmode ordered subset expectation maximization to evaluate the capability of multi-tracer imaging in a Compton camera. And the Compton camera rotating around the object was proposed and tested with different rotation angle steps for improving the limited coverage of the fixed conventional Compton camera over the field-of-view in terms of histogram of angles in spherical coordinates. The simulation data showed the separate 140 and 511 keV images from simultaneous multi-tracer detection in both 2D and 3D imaging and the number of valid projection lines on the conical surfaces was inversely proportional to the decrease of rotation angle. Considering computation load and proper number of projection lines on the conical surface, the rotation angle of 30 degree was sufficient for 3D imaging of the Compton camera in terms of 26 min of computation time and 5 million of detected event number and the increased detection time can be solved with multiple Compton camera system. The Compton camera proposed in this study can be effective system for multi-tracer imaging and is a potential system for development of various disease diagnosis and therapy approaches.

• Journal of the Korean Chemical Society
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• v.22 no.6
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• pp.380-385
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• 1978

Adsorption isotherms of o-xylene on Spheron 6, a graphitized carbon black, are obtained at various temperatures using a quartz beam microbalance. BET plots are made to estimate the molecular area of o-xylene from these isotherms. On Spheron 6, the molecular area of o-xylene (m.p $-25^{\circ}C$) remains constant until the temperature is increased up to $-15^{\circ}C$, but increases abruptly between $-15^{\circ}C$ and $-14^{\circ}C$, and then again remains constant thereafter. These results are interpreted as implying that the adsorbed o-xylene molecules are flatly localized on Spheron 6 with compact packing below $-15^{\circ}C$ while they gain a rotational degree of freedom around the benzene ring at the higher temperature.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.3A
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• pp.457-464
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• 2006

Fiber-reinforced composite materials due to their high specific strength, high stiffness and light weight are becoming increasingly used in many engineering industry, especially in the aerospace, marin and civil, etc. In this paper, the buckling load and mode shapes of composite laminates with elliptical cross-section including transverse shear deformations are analyzed. For solving this problems, a versatile flat shell element has been developed by combining a membrane element with drilling degree-of-freedom and a plate bending element. Also, an improved shell element has been established by the combined use of the addition of enhanced assumed strain and the substitute shear strain fields. The combined influence of shell geometry and elliptical cross-sectional parameter, fiber angle, and lay-up on the buckling loads of elliptical cylinder is examined. The critical buckling loads and mode shapes analyzed here may serve as a benchmark for future investigations.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.45 no.6
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• pp.27-37
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• 2008

Applications of 3D data increase with advancement of multimedia technique and contents, and it is necessary to manage and to retrieve for 3D data efficiently. In this paper, we propose a new method using the sliced shape which extracts efficiently a feature description for shape-based retrieval of 3D models. Since the feature descriptor of 3D model should be invariant to translation, rotation and scale for its model, normalization of models requires for 3D model retrieval system. This paper uses principal component analysis(PCA) method in order to normalize all the models. The proposed algorithm finds a direction of each axis by the PCA and creates orthogonal n planes in each axis. These planes are orthogonalized with each axis, and are used to extract sliced shape image. Sliced shape image is the 2D plane created by intersecting at between 3D model and these planes. The proposed feature descriptor is a distribution of Euclidean distances from center point of sliced shape image to its outline. A performed evaluation is used for average of the normalize modified retrieval rank(ANMRR) with a standard evaluation from MPEG-7. In our experimental results, we demonstrate that the proposed method is an efficient 3D model retrieval.

• Proceedings of the Korea Information Processing Society Conference
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• 2019.10a
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• pp.538-539
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• 2019

타워크레인은 조선, 건설 등 산업 현장에서 중량물 운반 운전을 위한 도구로 사람이 수동 작업으로 대부분 수행된다. 이러한 타워크레인 운전 훈련 과정은 훈련 실습자에게 장시간 교육하기에 비효율적 뿐 아니라 위험한 작업이므로 최근에는 가상 훈련 시뮬레이션을 통해 이루어 지고 있다. 이러한 가상 타워크레인 시뮬레이션을 구현하기 위해서는 기후환경, 중량물, 줄걸이와 같은 외부적 요인도 중요하지만 타워크레인의 운반 중량물과 직접적으로 연결이되는 로프를 정밀하게 표현하는 것이 중요하다. 하지만, 현재 개발된 대다수의 로프는 단면이 원통형을 띄고 있어 물리적인 요인이 작용하였을 때, 회전축이나 물리적인 형태를 가늠하기가 어렵다. 그러므로, 가상의 타워크레인 시뮬레이션 로프를 실제 타워크레인 슬링벨트와 유사한 면의 형태를 가지고 구축하여 실 환경과 유사한 환경에서 숙련된 타워크레인 시뮬레이션을 훈련하기 위한 로프 시뮬레이션이 필요하다. 따라서, 본 논문에서는 로프 시뮬레이션이 실제와 동일한 형태의 슬링벨트를 제공할 뿐만 아니라 로프의 면 형태 구현하고, 물리시뮬레이션을 통해 로프의 사실적인 움직임을 나타낼 수 있는 가상현실(VR) 기반 훈련 로프 시뮬레이션을 제시한다.