• 한국빅데이터학회지
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• 제6권2호
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• pp.39-49
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• 2021

최근 국가 관측망, 기업 공기 측정기 등을 통해 많고 다양한 기상 데이터가 수집되고 있다. 기계학습 기법을 통해 기상 예측하려는 노력이 곳곳에서 이루어지고 있으며, 국내 미세먼지는 농도가 증가해오고 사람들의 관심이 높아 가장 관심있는 예측 대상 중 하나이다. 본 연구에서는 서울시 전역에 설치된 840여 개실외공기측정기 데이터를 사용하여 PM10·PM2.5 예측 모형을 비교하고자 한다. 5분 뒤 미세먼지 농도 예측을 통해 실시간으로 정보를 제공할 수 있으며, 이는 10분·30분·1시간 뒤 예측 모형 개발에 기반이 될 수 있다. 잡음 제거, 결측치 대체 등의 데이터 전처리를 진행하였고, 시·공간 변수를 고려할 수 있는 파생 변수를 생성하였다. 모형의 매개변수는 반응 표면 방법을 통해 선택하였다. XGBoost, 랜덤포레스트, 딥러닝(Multilayer Perceptron)을 예측 모형으로 사용하여, 미세먼지 농도와 예측값의 차이를 확인하고, 모형 간 성능을 비교하고자 한다.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제50권7호
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• pp.315-322
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• 2001

High speed brushless permanent magnet(PM) machines need a key technology to minimize the iron core losses in stator and the eddy current losses in the retained sleeve and magnets caused by slotting harmonics. Thus, slotless or iron-coreless brushless PM machines have been applied for a very high rotational speed and/or the ripple-free torque. Unfortunately, slotless or coreless PM machines have lower open-circuit field than slotted and/or iron-cored types, which cause to reduce power density. Fortunately, Halbach array can generate the strong magnetic field systems without additional magnetic materials. In this paper, the 4-pole Halbach array is applied to the high speed machine and is compared with the radial magnetized PM array in field system. The iron-/air-cored stator of PM machine is constructed with/without winding slots. Open circuit magnetic fields of each type are presented from the analytical method and finite element method. Consequently, it is confirmed that the Halbach array field system with slotless stator is more suitable to the high speed motor because it has high flux density, sinusoidal flux distribution than others.

• 대한치과기공학회지
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• 제38권2호
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• pp.63-68
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• 2016

Purpose: The purpose of this study was to assess the internal fitness of the PMMA 3-unit bridge that was fabricated with 5-axis milling machine and to verify the clinically allowable values. Methods: For fabrication of the crown bridge in this study, 25-27 abutment teeth were used. The prepare abutment teeth were scanned with a scanner and 3-unit bridge was designed by using design software. Upon the completion of the design, the 3-unit bridge was fabricated by using a PMMA block with 5-axis milling machine. The internal surface of the fabricated 3-unit bridge was scanned by using a scanner and the difference between the 3-unit bridge and the abutment teeth was assessed by merging them together. Results: $RMS{\pm}SD$ values for PRE group, MOL group, and BRI group were $51.2{\pm}18.2$, $44.8{\pm}10.0$, and $52.1{\pm}8.3{\mu}m$, respectively. The mean of the PRE group was bigger than that of the MOL and BRI group; however, statistically significant difference was not found (p>0.05). Conclusion: The PMMA 3-unit bridge that was fabricated with 5-axis milling machine presented stable internal values for each crown and overall internal values were within the range of clinically allowable values.

• 한국산업정보학회논문지
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• 제19권3호
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• pp.49-56
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• 2014

툴 프리세터는 수치제어 공작기계용 공구의 테이퍼부를 기준으로 하여 날끝 치수를 사전에 정렬하기 위한 장치로서 여기에는 접촉과 비접촉, 두 가지 방식이 있다. 광학센서 기반 비접촉 방식은 측정의 유연성과 편리함의 이점을 가지고 있다. 본 논문에서는 선형 스케일러와 머신 비전을 도입한 산업용 툴 프리세터 장비 개발을 다룬다. 측정 전에 대상 공구를 기구부에 고정시키고 광학부를 정렬한다. 공구 영상을 취득한 후 제시된 영상처리 알고리즘은선형 스케일러로부터 광학부의 이동 거리를 조합하여 공구의 정밀한 치수를 계산해낸다. 실험 결과, 본 장비의 정밀도가 ${\pm}20um$ 범위내에 있음을 검증하였다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2011년도 제42회 하계학술대회
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• pp.882-883
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• 2011

This paper deals with comparison on Electromagnetic losses of slotted and slotless high-speed PM Machine for Micro Turbine. Losses are consist of core losses, copper losses and eddy current losses. We are using both analytical method and 2D Finite Element Method for more detailed losses analysis. And then We compare Electromagnetic losses of slotted and slotless PM synchronous machine. This machine has designed of a generator of 800W, 400000rpm and a starter of 400W, 200000rpm.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2015년도 제46회 하계학술대회
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• pp.833-834
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• 2015

For the design of a permanent magnet linear synchronous machine with slotless stator structure, this paper addresses a three-dimensional (3D) analytical approach for consideration of end effects. In contrast, analytical method can derive solutions in substantially shorter times with high reliability. Therefore, we derive accurate analytical solutions to dramatically reduce the time need for analysis. In addition, we performed characteristic analysis of permanent magnet linear synchronous machine (PMSLM) according to PM overhang length.

• Communications for Statistical Applications and Methods
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• 제10권1호
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• pp.225-232
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• 2003

The support vector machine (SVM) is becoming increasingly popular in classification. The import vector machine (IVM) has been introduced for its advantages over SMV. This paper tries to improve the IVM. The proposed method, which is referred to as the polychotomous machine (PM), uses the Newton-Raphson method to find estimates of coefficients, and the Rao and Wald tests, respectively, for addition and deletion of import points. Because the PM basically follows the same addition step and adopts the deletion step, it uses, typically, less import vectors than the IVM without loosing accuracy. Simulated and real data sets are used to illustrate the performance of the proposed method.

• 전기의세계
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• 제21권4호
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• pp.15-21
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• 1972

For the conventional DC machine, the armature MMF is negligible compared with field MMF except when the machine is under heavy load or transient conditions. During the motor starting or reversal, the transient armature current and corresponding MMF effect the flux density of each pole in the machine magnetic circuit. However, the circuit flux density is restored to normal values by the field winding MMF after the transient armature current dies in an electromagnetic DC motor. Permanent magnet servomotor have no field windings about the circuit poles to restore circuit flux density through the demagnetized part of each pole after the transient armature MMF dies, and portions of the magnetic circuit stay permanently demagnetized. Thus the problem of stabilizing a magnet pole piece under the influence of the transient armature current need attentions. This work present the recoil operation of the servomotor with PM poles in conjunctions with the influence of the armature reaction effect. The development of an analytical and quantatative study is presented for predicting the regime of the recoil operation under this condition.

• 한국해양공학회지
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• 제25권2호
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• pp.79-84
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• 2011

The purpose of this study was to investigate the buckling load of filament-wound composite towers for large scale wind-turbines using the finite element method (FEM). To define the material properties, we used both the effective property method and stacking properties method. The effective properties method assumes that a composite consists of one ply. The stacking properties method assumes that a composite consists of several stacked plies. First, a linear buckling analysis of the tower, filament-wound with angles of $[{\pm}60]$, was carried out using the two methods for composite material properties: the stacking method and effective method. An FE analysis was also performed for the composite towers using the filament winding angles of $[{\pm}30]$, $[{\pm}45]$, and $[{\pm}60]$. The FE analysis results using the stacking properties of the composite were in good agreement with the results from the effective properties method. The difference between the FEM results and material properties method was approximately 0~2.3%. Above the angle of $[{\pm}60]$, there was little change in the buckling load.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제49권3호
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• pp.145-151
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• 2000

The topological investigations regarding magnetic circuit geometry and winding form of the transverse flux machine have brought up a variety of constructable arrangements with different features for several types of application[1, 2]. Here with, a novel PM-exited linear motor with inner mover, based on the transverse flux configuration leads to a considerable increase in power density for moving part. In this study we designed PM-exited transverse flux linear motor for ropeless elevator, whose output power density is higher and weight is lighter than conventional linear synchronous motors. When the designed motor in this study is applied to ropeless elevator, it is possible to increase power density more than 400% comparing with PM exited linear synchronous motor. The result of this study can be utilized for ropeless elevator or gearless direct linear moving system with high output[3].