• 전기학회논문지
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• 제58권10호
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• pp.1930-1935
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• 2009

This paper deals with the torque ripple reduction of permanent magnet synchronous motor using harmonic current injection. Torque ripple of electric motor reduces system stability and performances, therefore efforts to reduce torque ripple are exerted in the design process. Torque ripple can be reduced by appropriate pole/slot combination, skew of rotor or stator, design of magnetic circuit, etc. In addition, torque ripple can be also reduced by input voltage and current, and many researches have been conducted to reduce torque ripple for six-step drive. Torque ripple reduction for current vector controlled permanent magnet synchronous motor also have been conducted and verified by investigating back emf wave form. Torque ripple reduction in this paper started from getting torque profile according to input current and electrical angle calculated by FEA, then instantaneous currents at each electrical angles for constant torque are calculated and applied to experiments. Therefore, 0% of torque ripple can be obtained theoretically with harmonic current injection. In order to maximize the effect of torque ripple reduction, a BLDC motor having high harmonic component of back emf is chosen. With sinusoidal current drive, over 100% of torque ripple is obtained initially, then 0.5 % of torque ripple is obtained by FEA using harmonic current injection. The effect is verified by experiment and the presented method can be effectively applicable to Electric Power Steering(EPS).

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• 제41권4호
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• pp.190-193
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• 2015

Objectives: A mesiodens appears most commonly as a supernumerary tooth impacted in the anterior maxilla. The purpose of this study is analyze mesiodens clinically. Materials and Methods: Gender, crown form, direction of impaction, relation to permanent incisors, and chief complaints of patients with extracted mesiodens were analyzed. Results: Patients were analyzed for motivation to visit the hospital; 85.4% of the patients were referred from other hospitals. Mesiodens was more common in males than in females (3.7:1), and 70.1% of patients had only one mesiodens, while 29.6% had two mesiodenses. Of the mesiodenses, 61.4% were of the aconical form, and the most common direction was upward (62.4%), followed by the normal position (26.0%) and the horizontal position (11.6%). The mesiodenses caused orthodontic problems with the permanent incisors in 46.3% of cases. Mesiodens associated with dentigerous cyst was rarely observed in our patient group. Conclusion: Mesiodens is more common in males than in females and often affects the permanent incisors. Thus, careful clinical and radiological evaluations of mesiodenses are important.

• 대한치과보철학회지
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• 제43권4호
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• pp.511-518
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• 2005

Purpose: The purpose of this study is to find the effect of rare earth magnet's magnetic field of to the osteoblast around the implant by the means of observation number, and distribution around the implant which is connected to the permanent magnet but not, counted and compared by the number of cells attached to the surface of the implant. Material and method: The permanent magnets, made in the healing cap form, were connected to the implant future, and placed on the culture plate, The osteoblast-like cell: MC3T3-E1 were used for cell culture. As the control group, the implant were connected to normal healing cap, and cultured in the same conditions. 48 hours later, using inverted microscope, the number and distribution of osteoblast around the implant were observed, and 72 hours later, the number of the cells attached to the implant were counted. Results: As a result, the implant connected to the permanent magnet had proved to have a more concentrated cell distribution rate than the control group. The implant connected to the permanent magnet, neck area : which has about 10 gauss magnetic force, had more cells than apex area. The implant connected to the permanent magnet had proven to attach to the osteoblast more productively than control group's implant. Conclusions: This research showed that the magnetic field of the permanent magnet affected the distribution and growth rate of the osteoblast around the implant. In order to support this study, it also had need to monitor the progress of the permanent magnet specifically shown on the neck area, which has10 gauss magnetic force. So after additional research on the distribution and attachment of the cells, and further more, on bone formation, it will be concluded that the clinical applications ,such as immediate loading of implant treatment are possible.

• Maxillofacial Plastic and Reconstructive Surgery
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• 제33권1호
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• pp.83-88
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• 2011

The goal of this treatment is the surgical-orthodontic eruption of impacted permanent teeth associated with a large dentigerous cyst in a preadolescent patient. Although enucleation of the entire cyst and the extraction of impacted teeth are common treatments, missing permanent teeth cause several problems in young patients. In this report, an 11-year-old female visited with the chief complaint of a large radiolucent lesion from the mandibular anterior area to the left mandibular posterior area. The permanent left canine and premolars were displaced toward the mandibular inferior border area. The extraction of infected deciduous teeth and marsupialization were performed. After 4 months, orthodontic buttons for forced eruption were applied to the impacted permanent teeth. The teeth emerged into the oral cavity 3 months after the orthodontic treatment. Although the root form was abnormal, there were no other pathogenic signs. The alveolar bone had a normal trabecular pattern and the teeth appeared to be well maintained at postoperative 24 months.

• 한국콘텐츠학회논문지
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• 제21권3호
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• pp.88-102
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• 2021

본 연구는 박물관 건축의 작품 중 특별 전시의 기능을 제외한 상설전시가 주를 이루는 박물관을 중심으로 하였다. 사례연구를 통해 나타난 정형, 비정형, 세그먼트, 사선형의 형태를 기준으로 하여, 164건의 작품사례에 적용한 결과 건축형태를 비정형, 정형, 반정형, 세그먼트, 사선형, 선형으로 재분류 하고, 박물관 건축 형태와 중심 공간과의 상관성의 유무를 유추함으로써 비정형 건축형태와 중심공간과의 관계가 성립하는가를 도출하고자 다음과 같이 내용을 정리하였다. 전체적으로 대부분 비정형박물관건축형태와 일치하는 중심공간의 비정형 형태로서 92.7% 분포도를 나타났다. 결과적으로 전반적으로 박물관 비정형 건축형태가 다수 나타났으며 정형보다는 비정형 건축형태에 있어서 중심공간과의 상관성이 성립되는 것으로서 향후 박물관 건축형태는 비정형이 지속적으로 발전 할 것으로 추정되고 중심 공간 실내건축 설계는 건축형태와의 상관성을 고려하여 설계를 지향하는 기초적 근거자료로서 제시하고자 한다.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2011년도 정기총회 및 추계학술대회 논문집
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• pp.428-435
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• 2011

In general, thickness of the sublayers under track is designed based on concept of vertical soil reaction value or vertical stiffness. However, this design method cannot take consideration into soil-track interaction under repetitive load, traffic condition and velocity of the train. Furthermore, the reinforced roadbed soils experience complex behavior that cannot be explained by conventional stress-strain relation expressed as soil reaction value k. The reinforced roadbed soils also can produce cumulative permanent deformation under repetitive load caused by train. Therefore new design method for the sublayers under track must be developed that can consider both elastic modulus and permanent deformation. In this study, a new design concept, a rule-of-thumb, is proposed as the form of design monograph that is developed using elastic multi-layer and finite element programs by analyzing stress and deformation in the sublayers with changing the thickness and elastic modulus of the sublayers and also using data obtained from repetitive triaxial test. This new design concept can be applied to design of the reinforced roadbed before developing full version of design methodology that can consider MGT, axial load and the material properties of the layers. The new design monograph allows the user to design the thickness of the reinforced roadbed based on permanent deformation, elastic modulus and MGT.

• 제어로봇시스템학회논문지
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• 제21권9호
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• pp.801-806
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• 2015

In this paper, we propose cascade-form velocity controller for a permanent magnet synchronous motor (PMSM). The proposed controller consists of a sliding-mode controller (SMC) for the inner current control loop and a model-predictive controller (MPC) for the outer velocity control loop. With SMC, we can ensure that the current tracking error always converges to zero in finite time. The SMC is designed to track the desired currents. Additionally, with MPC, we can obtain the optimal velocity control input which minimizes the cost function. Constraint conditions for input and input variation are included in the MPC design. The simulation results are included to validate the performance of the proposed controller.

• International Journal of Control, Automation, and Systems
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• 제2권3호
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• pp.279-288
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• 2004

This paper presents a novel design for a tubular linear brushless permanent-magnet motor. In this design, the magnets in the moving part are oriented in an NS-NS―SN-SN fashion which leads to higher magnetic force near the like-pole region. An analytical methodology to calculate the motor force and to size the actuator was developed. The linear motor is operated in conjunction with a position sensor, three power amplifiers, and a controller to form a complete solution for controlled precision actuation. Real-time digital controllers enhanced the dynamic performance of the motor, and gain scheduling reduced the effects of a nonlinear dead band. In its current state, the motor has a rise time of 30 ms, a settling time of 60 ms, and 25% overshoot to a 5-mm step command. The motor has a maximum speed of 1.5 m/s and acceleration up to 10 g. It has a 10-cm travel range and 26-N maximum pull-out force. The compact size of the motor suggests it could be used in robotic applications requiring moderate force and precision, such as robotic-gripper positioning or actuation. The moving part of the motor can extend significantly beyond its fixed support base. This reaching ability makes it useful in applications requiring a small, direct-drive actuator, which is required to extend into a spatially constrained environment.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제53권4호
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• pp.229-236
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• 2004

In this paper, the effect of permanent magnet overhang structure on the characteristics in Brushless DC motor has analyzed quantitatively. We classified the overhang structure as symmetric and asymmetric. 3D equivalent magnetic circuit network (EMCN) method which uses the permeance as the distributive variable is used for the efficient analysis of magnetic field. The overhang effect which increases the linkage flux at the stator is verified by comparison between overhang and no overhang structure. In addition, it is known that no load back electro motive force (EMF) is also increased due to the overhang effect. In case of asymmetric overhang structure, the ratio effect of the upper to lower overhang length on the magnetic forces is analyzed. Form the analysis results, the variation of the asymmetric overhang ratio has a significant effect on the axial magnetic force except the radial and tangential magnetic forces. The validity of the analysis results is also clarified by comparison between calculated results and measured ones such as back EMF and cogging torque.

• 한국측량학회:학술대회논문집
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• 한국측량학회 2004년도 추계학술발표회 논문집
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• pp.65-71
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• 2004

The Development of GPS practical using and systematic fixing for GPS Quality Control System on On-Line. Developed the program that can prove GPS quality about GPS permanent observation stations or user GPS data in server client system environment of Web-Based objectively Developed Save-module of graph display of analysis result data and reporter form. Developed the program for making an estimate of GPS satellite information in server client system environment of Web-Based. Designed that the Display can be possible and store estimate result can expresses the form such as Sky Plot, DOPs, Satellite Elevation, satellite number cf predict-time and then the result can be preserved for report form.