• International Journal of Fuzzy Logic and Intelligent Systems
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• 제16권4호
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• pp.276-280
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• 2016

A fixed rate speech coder based on the filter bank and the non-uniform sampling technique is proposed. The non-uniform sampling is achieved by the detection of inflection points (IPs). A speech block is band passed by the filter bank, and the subband signals are processed by the IP detector, and the detected IP patterns are compared with entries of the IP database. For each subband signal, the address of the closest member of the database and the energy of the IP pattern are transmitted through channel. In the receiver, the decoder recovers the subband signals using the received addresses and the energy information, and reconstructs the speech via the filter bank summation. As results, the coder shows fixed data rate contrary to the existing speech coders based on the non-uniform sampling. Through computer simulation, the usefulness of the proposed technique is confirmed. The signal-to-noise ratio (SNR) performance of the proposed method is comparable to that of the uniform sampled pulse code modulation (PCM) below 20 kbps data rate.

• 대한의용생체공학회:의공학회지
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• 제16권3호
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• pp.279-288
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• 1995

Ultrasonic Doppler systems for the purpose of estimating blood flow velocity, blood flow volume, and flow imaging are commonly used due to advantages of non-invasive and real time observation. Specially, the technical developments of color flow mapping (2-D Doppler) systems have made a relatively rapid progress. However, the 2-D Doppler systems have several problems, such as the range ambiguity, low signal to noise ratio, and slow frame rate. The slow frame rate problem is resolved by using the spatial average which is a method to acquire more data samples for mean frequency estimation. In this paper, spatial average method using the 2nd order sampling instead of quadrature sampling is proposed. The experimental results show that the proposed methods have good performance and easy application to the color flow mapping system.

• 대한전자공학회논문지
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• 제16권6호
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• pp.22-30
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• 1979

새로운 구조의 양전자 전산 단층 촬영기(Positron Computerized Tomography)를 제안하고 그 시스템의 성능을 컴퓨터로 예측하였다. 이 새로운 구조의 시스템은 sampling 간격을 임의로 할 수 있기 때문에 기존의 시스템에 비해서 보다 높은 분해능의 단층 영상을 얻을 수 있다. 컴퓨터 시뮬레이션으로 이 시스템에 어떠한 artifact가 생기나 살펴 보았고 Poisson noiserk 더해졌을 때의 영상을 비교함으로써 이 시스템이 기존의 시스템보다 나은 영상을 얻을 수 있음을 확인하였다.

• Journal of Mechanical Science and Technology
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• 제17권12호
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• pp.1986-1993
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• 2003

The spatially resolved spray volume fractions from both line-of-sight data of direct measuring cells and a laser diffraction particle analyzer (LDPA) are tomographically reconstructed by the Convolution Fourier transformation, respectively. Asymmetric sprays generated from a twin-hole injector are tested with 12 equiangular projections of measurements. For each projection angle, a line-of-sight integrated injection rate was measured using a direct sampling method and also a liquid volume fraction from a set of line-of-sight Fraunhofer diffraction measurements was measured using a light extinction method. Interpolated data between the projection angles effectively increase the number of projections, significantly enhancing the signal-to-noise level in the reconstructed data. The reconstructed volume fractions from the direct sampling cells were used as reference data for evaluating the accuracy of the volume fractions from the LDPA.

• 전자공학회논문지B
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• 제31B권9호
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• pp.142-149
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• 1994

Hangul is expressed by the basic elements, twenty-four characters. Because these characters are composed of a circle and lines, Hough transform(HT), which has a powerful performance on the noise in extracting lines, is introduced. Many difficulties often occur when the original HT is used to extract strokes and it's direction, position and length from handwritten Hangul characters. Original HT has eight direction selected as samples in the transformed image should be calculated for these eight directions. In this paper, the generalized sampling rule is suggested. According to the rule, those directions which are possible to a line are the only thing to be calculated. The experoment result turned out to be higher than the method that Chen suggested in sampling rate. Anogher experiment result is done on the 1800 handwritten Hangul characters that 10 persons wrote. By feature extracting the oritinal HT and sampling HT. And as a result of six type classification, the suggested method came out higher than original HT.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2009년도 추계학술대회 논문집
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• pp.113-118
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• 2009

A designer regards the vibration system as a linear system. However, in real world, nonlinearity of a vibration system should exist caused by various factors like manufacturing conditions or uncertain material properties. So, properties of a spring and a damper which are consisting the vibration system have statistical distribution. Therefore, a designer needs to analyze the statistical nonlinearity in a vibration system. In this paper, $1^{st}$ Taylor series expansion method and univariate dimension reduction method apply to a performance measure of nonlinear vibration system, and compare each result. And then, merits and demerits of each method are discussed. For apply more actual problem, a performance measure population is estimated based on design variable samples like properties of spring or damper.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2000년도 ITC-CSCC -2
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• pp.1080-1083
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• 2000

In this paper, we show that a variation in sampling rate give rise to system performance degradation and propose a method to effectively reduce the error. We first capture the variation as a first order autoregressive (AR) model and project it as an additional sensor measurement noise. By considering that the sensor measurements include correlated noise, we perform a decorrelation process and then apply a standard Kalman filter (SKF) to estimate the target-state. As a result of the two-step procedure, we achieve a significant reduction in the target state estimation error.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2004년도 추계학술대회논문집
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• pp.685-688
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• 2004

This paper addresses the study on developing the angular vibration calibration system which requires the highly accurate measurement technique of the amplitude and period of an oscillating angular motion. Two developed models for the low and high frequency ranges are introduced and their main features are also compared. In addition to the angular vibration exciters, a new measurement method, referred to the 'equi-angle sampling method', is proposed and its theoretical backgrounds are introduced. The proposed method is shown to provide much less measurement uncertainty, compared the fringe counting method. Experimental results demonstrate what amount of angular vibration amplitude measurement uncertainty is improved by suing the proposed equi-angle sampling method.

• 한국정보통신학회논문지
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• 제8권1호
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• pp.34-40
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• 2004

본 논문에서는 X-band용 저위상잡음을 갖는 위상고정 유전체 공진 발진기를 설계 및 제작하였다. 위상고정 유전체 공진 발진기의 루프대역 내의 위상잡음을 개선하기 위해서 샘플링위상비교기(Sampling Phase Detector)를 사용하여 전압제어 유전체 공진 발진기를 고안정의 기준주파수에 위상 고정시켰으며 루프대역 밖의 위상잡음을 개선하기 위해서 고임피던스 변환기를 이용한 낮은 위상잡음의 전압제어 발진기를 설계하였다. 제작된 위상고정 유전체 공진 발진기는 51.67㏈c의 고조파 억압특성을 가지고 있으며 공급전력은 1.95W 이하를 필요로 한다. 위상잡음은 상온에서 -107.17㏈c/Hz $\circleda$10KHz와 -113.0㏈c/Hz $\circleda$100KHz의 우수한 특성을 나타내었으며 출력전력은 $-20 ∼ +70^{\circ}C$의 온도 범위에서 13.0㏈m${\pm}$0.33㏈의 안정된 특성을 나타내었다.

• 대한전자공학회논문지TC
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• 제42권5호
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• pp.13-22
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• 2005

OFDM(orthogonal frequency division multiplexing) 변조를 이용한 WLAN(wireless local area network) 시스템은 고속 무선 데이터 통신을 위한 대표적 수단으로 전송률의 향상을 위해 활발히 연구되고 있다. 본 논문에서는 WLAN의 정확한 채널 등화와 샘플링 클럭 추적을 위하여 비터비 복호기 출력을 이용한 등화 및 샘플링 클럭 추적 알고리듬을 제안한다. 이 알고리듬은 파일럿 신호를 이용하여 대략의 클럭 주파수 복원과 채널등화를 수행한 후 비터비 복호기의 출력을 다시 부호화하여 등화 및 샘플링 클럭의 추적에 이용하는 알고리듬이다. 제안한 알고리듬의 우수성을 ETSI WLAN 채널 환경에서 컴퓨터 모의실험을 통하여 보였다.