• 전기전자학회논문지
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• 제19권1호
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• pp.87-93
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• 2015

본 논문에서는 디지털 패스가 없는 연산증폭기 공유 기법을 이용한 $145{\mu}W$, 87dB SNR을 갖는 저전력 3차 Sigma-Delta 변조기를 제안한다. 기존 구조는 아날로그와 디지털 패스를 사용한 구조로 첫 번째 적분기의 계수가 작다는 단점을 지연된 피드포워드 패스를 추가하여 개선하였다. 제안한 구조는 디지털 패스를 제거하여 첫 번째 적분기의 계수를 크게 하였고 연상증폭기 공유 기법을 이용하여 전력소모가 기준 구조보다 적다. 전원전압 1.8V, 신호대역폭 20KHz, 샘플링 주파수 2.8224MHz 조건에서 $0.18{\mu}m$ CMOS 공정을 이용하여 제안한 구조의 시뮬레이션한 결과, SNR(Signal to Noise Ratio)은 87dB, 전력소비는 $145{\mu}W$이다.

• 한국정보통신학회:학술대회논문집
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• 한국해양정보통신학회 2007년도 추계종합학술대회
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• pp.180-184
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• 2007

최대 토크를 발휘하도록 정현파형 연구자석형 동기전동기를 구동하기 위해서는 회전자 절대위치에 동기화된 120도 위상차를 갖는 3상 정현파 전류 입력이 고정자 코일에 요구된다. 그러므로 회전자 절대위치 검출이 필연적이다. 그리고 고정자 자계와 회전자 자계 사이의 90도 위상 관계가 정류 동작에 의해 유지 되야 한다. 정류를 위한 절대 위치 검출은 일반적으로 모터 축에 부착된 엔코더 출력 신호의 분석에 의해 이루어진다. 본 연구는 현대의 엔코더 시스템을 부착한 모터의 절대위치를 검출 할 수 있는 신호처리 논리회로 설계를 목적으로 하며, 고정자 코일에 정현파 전류 입력을 만들어주기 위한 삼상 기준파형을 발생시킨다.

• 한국정보통신학회논문지
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• 제15권5호
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• pp.1018-1024
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• 2011

최대 토크를 발휘하도록 정현파형 영구자석형 동기전동기를 구동하기 위해서는 회전자 절대위치에 동기화된 120도 위상차를 갖는 3상 정현파 전류 입력이 고정자 코일에 요구된다. 그러므로 회전자 절대위치 검출이 필연적이다. 그리고 고정자 자계와 회전자 자계 사이의 90도 위상 관계가 정류 동작에 의해 유지되어야 한다. 정류를 위한 절대 위치 검출은 일반적으로 모터 축에 부착된 엔코더 출력 신호의 분석에 의해 이루어진다. 본 연구는 현대의 엔코더 시스템을 부착한 모터의 절대위치를 검출 할 수 있는 신호처리 논리회로 설계를 목적으로 하며, 고정자 코일에 정현파 전류 입력을 만들어주기 위한 삼상 기준파형을 발생시킨다.

• Korean Journal of Radiology
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• 제22권10호
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• pp.1708-1718
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• 2021

Objective: The purpose of this study was to evaluate the magnetic resonance (MR) characteristics and applicability of new, uniform, extremely small iron-based nanoparticles (ESIONs) with 3-4-nm iron cores using contrast-enhanced magnetic resonance angiography (MRA). Materials and Methods: Seven types of ESIONs were used in phantom and animal experiments with 1.5T, 3T, and 4.7T scanners. The MR characteristics of the ESIONs were evaluated via phantom experiments. With the ESIONs selected by the phantom experiments, animal experiments were performed on eight rabbits. In the animal experiments, the in vivo kinetics and enhancement effect of the ESIONs were evaluated using half-diluted and non-diluted ESIONs. The between-group differences were assessed using a linear mixed model. A commercially available gadolinium-based contrast agent (GBCA) was used as a control. Results: All ESIONs showed a good T1 shortening effect and were applicable for MRA at 1.5T and 3T. The relaxivity ratio of the ESIONs increased with increasing magnetic field strength. In the animal experiments, the ESIONs showed peak signal intensity on the first-pass images and persistent vascular enhancement until 90 minutes. On the 1-week follow-up images, the ESIONs were nearly washed out from the vascular structures and organs. The peak signal intensity on the first-pass images showed no significant difference between the non-diluted ESIONs with 3-mm iron cores and GBCA (p = 1.000). On the 10-minutes post-contrast images, the non-diluted ESIONs showed a significantly higher signal intensity than did the GBCA (p < 0.001). Conclusion: In the phantom experiments, the ESIONs with 3-4-nm iron oxide cores showed a good T1 shortening effect at 1.5T and 3T. In the animal experiments, the ESIONs with 3-nm iron cores showed comparable enhancement on the first-pass images and superior enhancement effect on the delayed images compared to the commercially available GBCA at 3T.

• Imaging Science in Dentistry
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• 제34권1호
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• pp.49-54
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• 2004

Primary intraosseous carcinoma (PIOC) is a rare odontogenic carcinoma defined as a squamous cell carcinoma arising within a jaw having no initial connection with the oral mucosa, and presumably developing from residues of the odontogenic epithelium. A 56-year-old patient who complained of delayed healing after extraction of upper left central incisor visited our department. The conventional radiographs showed a bony destructive lesion with ill-defined margin and moth-eaten appearance. On the computed tomographic images, the lesion perforated the labial cortex of alveloar bone, elevated the left nasal floor superiorly, and perforated partially both nasal floor. The magnetic resonance images showed low signal intensity at T2 and Tl weighted images at the area and adjacent soft tissue. Histologically, there were irregular epithelial islands with cell atypia, nuclear hyperchromatism, pleomorphism, atypical mitosis. The final diagnosis was PIOC.

• ETRI Journal
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• 제21권2호
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• pp.9-21
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• 1999

In this paper, to enhance the performance of ${\pi}$/4-DQPSK (${\pi}$/4-differential quadrature phase shift keying), the scheme using nonredundant multiple error correction is proposed and investigated. This scheme for the differential detection of ${\pi}$/4-DQPSK uses the signal output which is delayed for more than two time slots as the parity check bit and applies it to nonredundant multiple error correction. The proposed system was used for studying the performance of ${\pi}$/4-DQPSK with Nonredundant Error Correction (NEC) in additive white Gaussian noise (AWGN) and Nakagami fade modeled mobile communication channel, and it was observed that the performance increased as the error correction capability increased.

• 한국멀티미디어학회논문지
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• 제8권3호
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• pp.328-335
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• 2005

본 논문에서는 혼합된 입력음성신호들을 분리하기 위해 마이크로폰 어레이를 이용한 주파수영역 ICA 블라인드 음원분리 방법을 제안한다. 음성신호가 지연 혼합되어 입력되더라도 신호와 잡음을 분리하기 위한 분리행렬이 최적해로 수렴할 수 있도록 입력신호의 상호상관도를 이용하여 지연 혼합의 초기 지연값을 결정하는 방법을 제안한다. 그리고 계산량을 줄이기 위하여 주파수영역 블라인드 음원분리 알고리즘을 채용한다. 본 논문에서 제안하는 블라인드 음원분리 방법의 성능을 컴퓨터시뮬레이션을 통하여 확인한다.

• Journal of Power Electronics
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• 제9권5호
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• pp.718-725
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• 2009

To get instantaneous reference data in a single power system with vector space phasors, the instantaneous load current is adopted as a phase and another new signal, which is delayed through filtering by the phase-delay property of a low-pass filter, is used as the secondary phase. Because the two-phases have a different phase, the instantaneous value of the harmonic current can be obtained without a time-delay in calculation. The reference voltage is created by multiplying the coefficient k by the compensation current using the rotating reference frame synchronized with the source-frequency. To verify the validity of the proposed control method, experiments are carried out on a prototype of the single-phase hybrid active power filter system.

• Journal of Electrical Engineering and Technology
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• 제3권1호
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• pp.94-100
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• 2008

This paper presents a new control method of single-phase active power filter (APF) for the compensation of harmonic current components in nonlinear loads. To facilitate the possibility of complex calculation for harmonic current detection of the single phase, a single-phase system that has two phases was constructed by including an imaginary second-phase giving time delay to the load current. The imaginary phase, which lagged the load current T/4 (Here T is the fundamental cycle) is used in the conventional method. But in this proposed method, the new signal as the second phase is delayed by the filter. Because this control method is applied to a single-phase system, an instantaneous calculation was developed by using the rotating reference frames synchronized to source-frequency rather than by applying instantaneous reactive power theory that uses the conventional fixed reference frames. The control scheme of single-phase APF for the current source with R-L loads is applied to a laboratory prototype to verify the proposed control method.

• 전기학회논문지P
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• 제62권3호
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• pp.111-116
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• 2013

Noise problem that occurs on the road is raising a lot of problems in the economic, social and environmental aspects. The objective of this paper is to propose ANC(active noise cancellation)-based road traffic noise reduction algorithm-model which can reduce noise by generating frequency opposed to noise sources to improve and complement the problem that existing physical form of a noise barrier. In this paper, we measured the noise characteristic from collection of two difference car noise also ANC simulation has been performed by using road traffic noises input. In order to compare the control performance, we performed noise reduction simulation of ANC by filtered-X LMS algorithm and delayed control signal injection. As a result of this simulation, we confirmed that convergence performance and noise decrease effect to the filtered-X LMS algorithm by inputting the road traffic noise.