• Journal of Power Electronics
• /
• 제14권1호
• /
• pp.165-174
• /
• 2014

The cascaded H-Bridge Dynamic Voltage Restorer (DVR) is used for protecting high voltage and large capacity loads from voltage sags. The LC filter in the DVR is needed to eliminate switching ripples, which also provides an accurate tracking feature in a certain frequency range. Therefore, the parameter optimization of the LC filter is especially important. In this paper, the value range functions for the inductance and capacitance in LC filters are discussed. Then, parameter variations under different conditions of voltage sags and power factors are analyzed. In addition, an optimized design method is also proposed with the consideration of multiple impact factors. A detailed optimization procedure is presented, and its validity is demonstrated by simulation and experimental results. Both results show that the proposed method can improve the LC filter design for a cascaded H-Bridge DVR and enhance the performance of the whole system.

• 제어로봇시스템학회논문지
• /
• 제17권1호
• /
• pp.22-30
• /
• 2011

Plane detection is very important information for mission-critical of robot in 3D environment. A representative method of plane detection is Hough-transformation. Hough-transformation is robust to noise and makes the accurate plane detection possible. But it demands excessive memory and takes too much processing time. Iterative randomized Hough-transformation has been proposed to overcome these shortcomings. This method doesn't vote all data. It votes only one value of the randomly selected data into the Hough parameter space. This value calculated the value of the parameter of the shape that we want to extract. In Hough parameters space, it is possible to detect accurate plane through detection of repetitive maximum value. A common problem in these methods is that it requires too much computational cost and large number of memory space to find the distribution of mixed multiple planes in parameter space. In this paper, we detect multiple planes only via data sampling using Self Organizing Map method. It does not use conventional methods that include transforming to Hough parameter space, voting and repetitive plane extraction. And it improves the reliability of plane detection through division area searching and planarity evaluation. The proposed method is more accurate and faster than the conventional methods which is demonstrated the experiments in various conditions.

• 대한전자공학회논문지SP
• /
• 제40권6호
• /
• pp.61-70
• /
• 2003

본 논문에서는 SMV와 G.723.1 음성부호화기를 위한 파라미터 직접 변환 방식의 상호부호화 알고리듬을 제안한다. 상호부호화를 위하여 부가적인 복호화, 부호화 과정을 거쳐야하는 Tandem 방식과 달리 제안된 방식에서는 양 음성부호화기가 음성을 부호화하는데 공통적으로 사용되는 파라미터들을 직접 변환한다. 제안된 알고리듬은 파라미터 복호화, LSP 변환, 피치 지연 변환, 여기신호 변환 그리고 비트율 결정으로 이루어진다. 제안된 알고리듬을 다양한 방법으로 평가해 본 결과 계산량과 지연시간을 줄이면서 tandem 방식과 동등한 수준의 음질을 구현함을 확인할 수 있었다.

• Journal of the Korean Statistical Society
• /
• 제21권1호
• /
• pp.35-46
• /
• 1992

On Box-Cox transformation, one or few responses are influential on transformation parameter estimator. To detect influential observatins, several diagnostics (Cook and Wang 1983, Hinkley and Wang 1988, Lawrance 1988, Tsai and Wu 1990) have been suggested. We compare these diagnostics and denote the necessity of multiple cases deletion which is important especially when the masking effect is present. Also, analytic expression of Tsai and Wu's diagnostic is given. We suggest a computationally feasible and useful algorithm based on the basic building blocks, and present descriptive examples using artificial data.

• 한국음향학회지
• /
• 제23권5호
• /
• pp.400-409
• /
• 2004

본 논문에서는 임의의 화자가 발성한 음성을 다른 화자가 발성한 음성처럼 들리도록 변환하는 음성 변환 알고리즘을 제안하였다. 개인이 지니고 있는 음성의 특성을 변환하기 위해 성도 전달 함수의 특성을 변환 변수로 사용하였으며, 기존의 기법과 비교하여 목표 화자의 음성과 주관적, 객관적으로 더욱 유사한 변환음을 얻기 위한 새로운 방법을 제안하였다. 성도 전달 함수의 변환은 전체 특징 벡터 공간을 분류 한 뒤, 각 구획에 대한 선형 변환식을 통해 구현된다. 특징 변수로서 LPC 켑스트럼을 사용하였으며, 벡터 공간의 분류와 선형 변환식의 추정을 동시에 최적화시키는 분류-변환 알고리즘이 새로이 제안되었다. 제안된 음성 변환 기법의 성능을 평가하기 위해 3명의 남성 화자와 1명의 여성 화자로부터 수집된 약 150개의 문장을 사용하여 변환 규칙을 생성하였으며, 이를 동일한 화자가 발성한 다른 150개의 문장에 대해 적용하여 객관적인 성능 평가와 주관적 청취 테스트를 수행하였다.

• 한국측량학회지
• /
• 제15권1호
• /
• pp.29-39
• /
• 1997

최근 LIS/GIS측량과 지적조사 등의 분야에서는 위성측위시스템(GPS릿 활용이 보편화됨에 따라 지역측지계에서 지구중심좌표계로 변환하기 위한 국가변환요소를 필요로 하고 있다. 이 논문에서는 벳셀타원체 기준의 한국측지좌표와 WGS84좌표간의 변환요소를 가중변수에 의한 최소제곱해법에 따라 결정하였다. 국가기준점망의 31개 측점에 대한 GPS관측으로부터 결정된 지심3차원좌표의 GPS성과와 실용성과 또는 정밀1차성과간의 기준계 변환요소는 표준편차 1미터 이내이며 벳셀지오이드고를 고려할 때 GPS기선해석을 위한 초기좌표결정과 중축척지도의 변환과 LIS/GIS 데이터베이스의 수정에 이용할 수 있는 것으로 분석되었다.

• 품질경영학회지
• /
• 제21권1호
• /
• pp.96-107
• /
• 1993

In parameter design Taguchi analyzed a statistic which he called signal-to-noise(SN) ratio by using the experimental design technique. However he gave no justification for using SN ratios in the optimization procedure of parameter design. In this paper we discuss the validity of such SN ratios as proper statistics to be analyzed in parameter design. Moreover, using the real empirical data we examine the appropriateness of SN ratios, and we explain how transformation technique can be applied in parameter design as an alternative method of analysis.

• Communications for Statistical Applications and Methods
• /
• 제8권2호
• /
• pp.357-366
• /
• 2001

The present paper develops a method to check the propriety of link functions for binary data. In order to parameterize a certain type of goodness of the link, a family of link functions indexed by a shape parameter is proposed. I first investigate the maximum likelihood estimation of the shape parameter as well as regression parameters and then derive their large sample behaviors of the estimators. A score test is considered to evaluate the goodness of the current link function. For illustration, I employ two families of power transformations, the modulus transformation by John and Draper (1980) and the extended power transformation by Yeo and Johnson (2000), which are appropriate to detect symmetric and asymmetric inadequacy of the selected link function. respectively.

• 조명전기설비학회논문지
• /
• 제26권1호
• /
• pp.29-37
• /
• 2012

A simple and effective dead time compensation scheme for a PWM inverter-fed permanent magnet synchronous motor (PMSM) drive using the model reference adaptive control (MRAC) and coordinate transformation is presented. The basic concept is to first transform a time-varying disturbance caused by the dead time and inverter nonlinearity into unknown constant or slowly-varying one by the coordinate transformation, and then use the MRAC design technique to estimate this parameter in the stationary reference frame. Since the MRAC scheme is a suitable way of estimating such a parameter, the control performance can be significantly improved as compared with the conventional observer-based method tracking time-varying parameters. In the proposed scheme, the disturbance voltage caused by the dead time is effectively estimated and compensated by on-line basis without any additional circuits nor existing disadvantages as in the conventional methods. The asymptotic stability is proved and the effectiveness of the proposed scheme is verified.

• Journal of the Korean Physical Society
• /
• 제73권9호
• /
• pp.1303-1309
• /
• 2018

In the present paper, we study the entropy analysis of boundary layer flow over a slender stretching sheet under the action of a non uniform magnetic field that is acting perpendicular to the flow direction. The effects of viscous dissipation and Joule heating are included in the energy equation. Using similarity transformation technique the momentum and thermal boundary layer equations to a system of nonlinear differential equations. Numerical solutions are obtained using the shooting and fourth-order Runge-Kutta method. The expressions for the entropy generation number and Bejan number are also obtained using a suggested similarity transformation. The main objective of this article is to investigate the effects of different governing parameters such as the magnetic parameter ($M^2$), Prandtl number (Pr), Eckert number (Ec), velocity index parameter (m), wall thickness parameter (${\alpha}$), temperature difference parameter (${\Omega}$), entropy generation number (Ns) and Bejan number (Be). All these effects are portrayed graphically and discussed in detail. The analysis reveals that entropy generation reduces with decreasing wall thickness parameter and increasing temperature difference between the stretching sheet and the fluid outside the boundary layer. The viscous and magnetic irreversibilities are dominant in the vicinity of the stretching surface.