• Journal of radiological science and technology
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• v.46 no.5
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• pp.427-433
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• 2023

This study aimed to quantitatively compare the diameters measured directly from the coronal plane or sagittal plane of 2D digital subtraction angiography (DSA) and the cross-sectional area-converted diameters calculated from contrast-enhanced MR (CE-MR) imaging. A retrospective analysis was conducted on 20 patients who underwent both 2D DSA and CE-MR imaging. Firstly, the venous diameters of the superior sagittal sinus (SSS) and transverse sinus (TS) were directly measured from 2D DSA. Subsequently, the axial planes for SSS diameter and the sagittal plane for TS in CE-MR imaging were utilized to calculate cross-sectional area-based converted diameters. The numerical values obtained from 2D DSA and CE-MR imaging were compared pairwise at each location. For SSS, the diameter measured by 2D DSA was 27% larger than the conversion-based diameter from CE-MR imaging (9.8±1.4 mm vs. 7.1±1.3 mm, P<0.05). Similarly, for the right TS, the difference was 16% (8.8±3.2 mm vs. 7.4±2.0 mm, P<0.05), and for the left TS, the difference was 22% (8.4±2.8 mm vs. 6.6±1.3 mm, P<0.05). In conclusion, the diameter measured directly in conventional 2D DSA may be larger than the diameter converted based on the cross-sectional area. Therefore, when selecting the size of the stent, it is crucial to make precise determinations while keeping this fact in mind.

• The Proceedings of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.9 no.2
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• pp.146-146
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• 1995

본 논문은 유도전동기의 운전조작시에 발생되는 자계변화특성에 대하여 기술하였다. 본 측정시스템은 자기적분형 자계센서, 증폭기, 능동형 적분기로 이루어졌으며, 교정실험에 대한 측정계의 주파수대역과 감도는 각각 20[Hz]∼0.234[mV/μT]이다. 유도전동기의 기동과 정상운전중에 발생하는 자계성분을 측정하였으며, 고조파 성분을 고속 푸리에 변환기법으로 분석하였다. 유도전동기의 직입기동시에는 단일성 펄스자계가 강하게 발생하였으며, 이의 피크치는 정상상태의 값보다 5배이상 크게 나타났다. 이러한 긴 과도시간과 강한 자계의 세기는 전동기의 큰 인덕턴스와 동특성에 기인된다. 유도전동기의 정상운전시에는 유도전동기의 극수에 의존하는 기본파에 대한 분조파의 자계성분이 관측되었다. 또한, 자계의 분조파 성분은 전동기의 토크 변동으로 불균일한 회전토크로 인해 생기는 맥동전류와 전압플리커에 의해서 발생하는 것으로 생각된다. 인버터구동형 유도전동기에서는 직입기동에 비하여 많은 고조파 성분이 발생되고 있었으며, 특히 전동기의 구동주파수가 낮을수록 맥동토크에 의한 전류변화로 고조파 성분은 더욱 증가하였다.

• Proceedings of the KIPE Conference
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• 2012.11a
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• pp.231-232
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• 2012

본 논문에서는 회전자 인버터 내장형 동기 전동기에 고주파 신호 주입 센서리스 알고리즘을 적용하는 방법을 제안한다. 고주파 신호주입 센서리스는 자기적인 돌극성을 활용하여 자속축을 찾기 때문에, 자기적인 돌극성이 뚜렷하지 않은 회전자 인버터 내장형 동기 전동기에서는 이를 적용할 수 없는 문제가 존재 한다. 이를 해결하기 위해 회전자 인버터를 이용하여 가상의 돌극성을 생성하고, 이 가상의 돌극성을 이용한 고주파 신호주입 센서리스 알고리즘을 제안한다. 제안된 방법은 실험을 통하여 검증되었으며, 추가적인 손실이나 하드웨어 없이 센서리스 운전이 가능함을 확인하였다.

• The Transactions of the Korean Institute of Power Electronics
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• v.3 no.3
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• pp.263-272
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• 1998

This paper presents the new control strategy that can minimizes the torque ripple by considering the magnetic nonlinearity and phase torque averlapping intervals, and describes the whole SRM drive system using proposed control method implemented by DSP(Digital Signal Processor). To do this, inductance and torque are, at first, measured according to the variation of rotor position angle while current is kept constant at predetermined several values. From these measured values, the entire inductance and torque for any current and rotor position are inferred by using neural network. And the waveform of the reference phase torque is determined for the torque ripple to be minimized considering the torque overlap between phases. The controller is designed for the actual torque obtained by the inferred torque look-up table using measured current and rotor position angle to track the predetermined reference phase torque by delta modulation technique. To perform a real time processing and ensure the reliability of the controller, DSP is implemented.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11b
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• pp.816-821
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• 2002

It is getting more important that energy efficiency and manufacturing cost of the electric motor in appliance. The SRM has been alternative choice. But acoustic noise and harshness in this motor was widely known. So this paper had been studied on the noise reduction of a SRM in air conditioner. This works include some parameters regarding to blown noise sources like a reluctance torque ripple, air gap eccentricity, Especially, it was focused on dynamic characteristics of the system based on mechanical viewpoint. It came to successful results. Besides, this gave us a validity of phase excitation in experimental measurements.

• The Science & Technology
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• v.33 no.8 s.375
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• pp.16-17
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• 2000

뉴욕증권거래소의 객장은 집어던지는 매매전표, 주문하는 거래인의 함성 그리고 미친듯이 두드리는 컴퓨터 건반 소리로 온통 난장판같다. 그러나 이런 소란 속에서 객장부 수석차장 안 앨런은 마치 딴 세상에서 살고 있는 것처럼 조용히 자기 일에만 몰두하고 있다. 강철-유리로 격리된 작은 방에서 그녀는 소음과 번쩍이는 게시판의 숫자에는 개의치 않고 모든 거래현황을 컴퓨터모델로 보여 주는 1.8m ×1.2m 크기의 납작한 디스플레이패널에 정신을 집중하고 있다. 앨런은 최근 신설한 이 '뉴욕증시 가상거래객장'에서 마우스를 움직여 특정한 주식이나 주식집단의 시세와 거래량의 실시나 변화를 나타내는 아이콘을 찍으면 궁금한 가격변동이나 거래패턴을 그 자리에서 알 수 있다. '가상거래객장'의 울긋불긋한 그래픽과 심벌들을 통해 그녀는 거래소의 '맥동'을 언제든지 모니터할 수 있다.

• The Transactions of the Korean Institute of Power Electronics
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• v.3 no.1
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• pp.46-52
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• 1998

This paper describes a current-shaping method for the production of constant torque of SRM under the nonlinear magnetic saturation condition. A current detection technique in the inductance increasing region and an approximation technique for modeling of nonlinear inductance profile are adopted. In the proposed system, a single switching angle control and voltage control is used to shape the current waveform for the generation of flat torque at any given load condition. Finally the validity of the proposed method was verified using a constructed 3HP 6/4 SRM.

• The Proceedings of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.9 no.2
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• pp.58-67
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• 1995

The paper describes the variation of magnetic fields caused by the operation of induction motors. The measuring system consists of the self-integrating magnetic field sensor, amplifier, and active integrator. From the calibration experiments, the frequency bandwidth of the magnetic field measuring system ranges from 20[Hz] to 300[kHz] and sensitivity is 0.234(mV/$\mu\textrm{T}$]. The magnetic fields generated under steady state and starting operations of duction motor are recorded by the proposed measuring system, and the fast Fourier transformation(FFT) of the measured data is performed to analyze the harmonic components. A single pulsed magnetic field is strongly caused by direct starting the induction motor, and its peak value is greater than 5 times as compared with the steady state value. The long transient duration and high intensity originates from the large inductance and dynamic characteristic of the induction motor, During the steady state operation of induction motor, subharmonics of magnetic field components, which depend on the pole number of induction motor, are observed. The lower order power-line harmonics can be inferred from the voltage flicker and current ripple which are derived from the torque fluctuation of induction motor. In the case of the induction motor drived by inverter, the harmonics of magnetic field are much more than those caused by direct starting method and are found generally to increase with decreasing the driving frequency.