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변곡점 및 단구간 에너지평가에 의한 음성의 천이구간 특징분석
최일홍,장승관,차태호,최웅세,김창석 한국음성과학회 1998 음성과학 Vol.3 No.-
In this paper, I would like to propose a dividing method by estimating the inflection points and the average magnitude energy in speech signals. The method proposed in this paper gave not only a satisfactory solution for the problems on dividing method by zero-crossing rate, but could estimate the feature of the transient period after dividing the starting point and transient period in speech signals before steady state. In the results of the experiment carried out with monosyllable speech, it ws found that even through speech samples indicated in D.C. level, the staring and ending point of the speech signals were exactly divided by the method. In addition to the results, I could compare with the features, such as the length of transient period, the short term energy, the frequency characteristics, in each speech signal. Keywords: inflection points, speech signal, transient period, short-term energy
음성인식을 위한 복합형잡음제거필터와 최적특징추출에 관한 연구
차태호,장승관,최웅세,최일홍,김창석 한국음성과학회 1998 음성과학 Vol.4 No.2
In this paper, a novel method of noise reduction of speech based on a complex adaptive noise canceler and method of optimal feature extraction are proposed. this complex adaptive noise canceler needs simply the noise detection, and LMS algorithm used to calculate the adaptive filter coefficient. The method of optimal feature extraction requires the variance of noise. The experimental results have shown that the proposed method effectively reduced noise in noisy speech. Optimal feature extraction has shown similar characteristics in noise-free speech. Keywords : adaptive noise canceler, feature extraction, LMS algorithm
Inconel 718 상향 엔드밀링시 절삭력에 미치는 공구형상오차
이영문,양승한,장승일,백승기,김선일 한국공작기계학회 2002 한국공작기계학회 춘계학술대회논문집 Vol.2002 No.-
In end milling process, the undeformed chip section area and cutting forces vary periodically with phase change of the tool. However, the real undeformed chip section area deviates from the geometrically ideal one owing to cutter runout and tool shape error. In this study, a method of estimating the real undeformed chip section area which reflects cutter runout and tool shape error was presented during up-end milling of Inconel 718 using measured cutting forces. The specific cutting resistance, K_(r) and K_(t) are defined as the radial and tangential cutting forces divided by the modified chip section area. Both of K_(r) and K_(t) values become smaller as the helix angle increases from 30° to 40°. Whereas they become larger as the helix angle increases from 40° to 50°. On the other hand, the K_(r) and K_(t) values show a tendency to decrease with increase of the modified chip section area and this tendency becomes distinct with smaller helix angle.
Inconel 718 하향 엔드밀링시 절삭력에 미치는 공구형상오차
이영문,양승한,장승일,백승기,이동식 한국공작기계학회 2002 한국공작기계학회 춘계학술대회논문집 Vol.2002 No.-
In end milling process, the undeformed chip section area and cutting forces vary periodically with phase change of the tool. However, the real undeformed chip section area deviates from the geometrically ideal one owing to cutter runout and tool shape error. In this study, a method of estimating the real undeformed chip section area which reflects cutter runout and tool shape error was presented during down end-milling of Inconel 718 using measure cutting forces. Contrary to the up-end milling the value of radial specific cutting resistance, K_(r) becomes larger as the helix angle increases from 30° to 40° and it shows almost same value at 50°. The value of tangential specific cutting resistance, K_(t) becomes larger as the helix angle increases same as in up-end milling, the K_(r) and K_(t) values show a tendency to decrease with increase of the modified chip section area and this tendency is distinct with helix angle 40°.