• 한국음향학회지
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• 제32권4호
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• pp.287-293
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• 2013

본 논문에서는 20 kHz와 32.5 kHz에 공진 주파수를 갖는 다공진 트랜스듀서를 $3{\times}16$ 배열로 구성하여 파라메트릭 배열 신호를 생성하는 시스템을 제안한다. 배열 트랜스듀서를 구동하기 위해 LM1875증폭기 소자를 이용하여 16채널 다중 증폭기를 제작하였고, 임의의 파형 생성 및 분석을 하기 위해 PXI 시스템과 LabView 8.6을 이용한 시스템이 구축되었다. 구축된 시스템을 이용하여 거리에 따른 음압레벨 변화와 빔 패턴을 측정하여 파라메트릭 현상을 확인하였다. 이론적으로 계산된 차 주파수의 감쇠거리와 회절거리는 각각 15.51 m와 1.9332 m이며, 음압레벨 실험결과 회절거리 이전 근거리 음장에서 차 주파수의 음압이 누적되어 증가되는 현상을 확인 하였다. 실험을 통해 측정된 차 주파수의 빔 패턴은 2개의 1차 주파수가 중첩된 빔 패턴과 유사함을 확인하여 고지향 파라메트릭 신호가 생성됨을 확인하였다.

• 한국치위생학회지
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• 제10권1호
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• pp.197-213
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• 2010

Objectives : This research identified the frequency and satisfaction level of the observation and performance practice during the clinical practice process conducted by dental hygiene students. With the goal of providing base data required for the development and operation of increasingly effective clinical practice program and for the improvement of the existing clinical practice training. Methods : The subjects in this study were 278 students of a university located in Masan. Survey comprised of 49 questions in 10 clinical practice domains was conducted. Results : 1. As for the observation practice by each grade, there was significant difference in oral radiology, pediatric dentistry, periodontology, oral surgery(p<0.05). As for the performance practice executed for each grade, there was significant difference in the oral radiology, preventive dentistry and oral surgery(p<0.05). As for the satisfaction level for each grade, there was significant difference in basic medical service(p<0.05). 2. As for the observation practice by each clinical practice institution, there was significant difference in oral medicine, oral radiology, preventive dentistry, prosthodontics, pediatric dentistry, orthodontics and oral surgery(p<0.05). As for the performance practice executed by each practice institution, there was significant difference in basic medical service, oral medicine, oral radiology, operative dentistry, prosthodontics, orthodontics, oral surgery(p<0.05). As for the satisfaction level by each practice institution, there was significant difference in the oral radiology, preventive dentistry, operative dentistry, prosthodontics, orthodontics, oral surgery(p<0.05). Conclusions : As for the satisfaction level for the clinical practice, basic medical service is the crimary care clinical practice which is most basic and that is executed the most in a dental clinic. Satisfaction level was the highest in the domains where there were extensive observation and practice frequency. By conducting observation and practice frequency in the clinical practice process by each clinical practice domain in a broad and diverse manner, it would be possible to improve the ability of the clinical practice trainees who improve their clinical work execution capability and satisfaction level on the clinical practice.

• 말소리와 음성과학
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• 제7권4호
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• pp.85-92
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• 2015

This study aimed to establish characteristics related to voice and speech through the natural base frequency analysis of esophagus vocalization. In the study, 8 subjects were selected for esophagus vocals, and 10 other subjects were selected for a control group. MDVP(Multi-dimensional Voice Program, Model 4800, USA, 2001), Multi Speech(Model 3700, Kaypantax, USA, 2008) were used as experiment equipment. The speech samples selected for evaluation were vowels and sentences (both declarative and interrogative). For acoustic analysis, the intonation form of fo, jitter, energy, shimmer, HNR, and intonation patterns of the speech sample were measured. The results were as follows: First, the natural intrinsic frequency of extended vowels in the esophagus vocal group was lower than the frequency in the normal vocal group. In particular, the intrinsic frequency difference for high vowel /i/ was much greater than the frequency difference for low vowel /a/. Second, the jitter values of the esophagus vocal group were higher than the control group. In particular, there was a large difference between the jitter values for /a/ and /i/, with the jitter values being highest for /i/. Third, there was no significant difference in vocal strength between the esophagus vocal patient group and the control group. Fourth, the shimmer values of the voices in the esophagus vocal group were higher than shimmer values in the control group. In particular, there was a large difference in shimmer values for low vowel /a/. Fifth, the HNR values of the esophagus vocal group were showed significantly lower than the control group. In particular, the largest difference in HNR values between the two groups was for high vowel /i/. Sixth, the pitch contours of interrogative and declarative sentences of the esophagus vocal patient group showed a different form or only had with small differences compared to the pitch contours of the normal vocal group, thus presenting an inconsistent pattern.

• 융합신호처리학회논문지
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• 제15권3호
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• pp.91-96
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• 2014

두 개의 입력소자에 의한 음원방향 및 분리방법으로서는 연산량이 적고, 음원분리 성능이 높은 주파수 양귀 모델(Frequency Domain Binaural Model : FDBM)이 있다. FDBM은 주파수 영역에서 양귀간 위상차(Interaural Phase Difference : IPD) 및 양귀간 레벨차(Interaural Level Difference : ILD)를 구하여 음향신호가 오는 방향과 음원의 분리처리를 한다. 그러나 실제 환경에서는 반사음의 문제가 되고 있다. 이러한 반사음에 의한 영향을 줄이기 위하여 선행음 효과에 의한 직접음의 음상정위를 모의하여 초기 도착음을 검출하고 직접음이 오는 방향과 음원분리 방법을 제시하였다. 제시한 방법을 이용하여 음원방향 추정 및 분리에 대한 성능을 시뮬레이션으로 검토하였다. 그 결과, 방향추정은 음원이 오는 방향에서 ${\pm}10%$의 범위로 집중되어 음원의 방향과 가까운 값으로 추정되었다, 반사음이 존재하는 경우의 음원분리는 기존의 FDBM에 비하여 코히런스(Coherence), 음성품질 지각평가 PESQ(Perceptual Evaluation of Speech Quality : PESQ)가 높고, 정면에서의 지향특성 감쇠량이 작아 분리의 정도가 개선됨을 나타내었다. 그러나 반사음이 존재하지 않는 경우는 분리 정도가 낮았다.

• 수산해양기술연구
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• 제37권4호
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• pp.313-320
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• 2001

In the presence of incident waves with different frequencies, there are second order sum and difference frequency wane exciting forces due to the nonlinearty of the incident waves. Although the magnitudes of these nonlinear forces are small, they act at sum and difference frequencies away from those of the incident waves. So, the second order sum and difference frequency wane loads occurring close to the natural frequencies of TLPs often give greater contributions to high and low frequency resonant responses. The components of the second order forces which depend on first order quantities have been evaluated using the three dimensional source distribution method. The numerical results of time domain motion analysis for the nonlinear wave exciting forces in regular waves are compared with the numerical ones of frequency domain analysis. The results of comparison confirmed the validity of the proposed approach.

• 음성과학
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• 제11권4호
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• pp.163-171
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• 2004

The primary goal of the present study was to explore more detailed evidence for the influence of aging and gender effects on the capability of Korean healthy, ears to generate DPOAEs. DPOAEs were examined in series of human subjects, with clinically nonnal hearing, ranging in age from 10 to 65 years. All 60 Koreans were divided into 6 age groups. Each age group included 10 participants, 5 females and 5 males. The gender effects on the difference between the absolute amplitude and noise floor value in DPOAEs did not exist. The difference increased as the frequency increased. The aging effects on the difference between the absolute amplitude and noise floor value in DPOAEs did exist. The difference increased as the frequency increased but orderly age effects could not be found. The principle finding was that, when compared between emissions in young and old ears, DPOAEs accurately tracked the systematic deterioration of high-frequency hearing in aging individuals. Such results support the need to reestablish the criterion for interpretation of DPOAEs in the elderly.

• 전기학회논문지P
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• 제62권1호
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• pp.1-5
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• 2013

The aim of this study is to research maximum harvesting energy by the optimal input wave condition. The voltage characteristics of the PZT bimorph were investigated in terms of the sine wave, triangle wave and square wave according to frequency range 0~70Hz. It was found that the square wave compared with a triangular wave or square wave was showed the higher output energy. PZT bimorph was mechanically vibrated by solenoid coil experiments, which revealed two voltage peak mode according to frequency. Maximum voltage at second vibration frequency 28Hz demonstrated that the generated DC voltage was proportional to the tip displacement of the bimorph and the phase difference between the input frequency and bimorph vibration frequency was 90 degree. It was expected that optimized design to harvest a much higher energy level from lower frequency vibrations.

• 반도체디스플레이기술학회지
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• 제4권2호
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• pp.11-14
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• 2005

In plasma processing reactors, it is common practice to control plasma density and ion bombardment energy by manipulating excitation voltage and frequency. In this paper, a dually excited capacitively coupled rf plasma reactor is self-consistently simulated with a three moment model. Effects of phase differences between primary and secondary voltage waves, simultaneously modulated at various combinations of commensurate frequencies, on plasma properties are investigated. The simulation results show that plasma potential and density as well as primary self-dc bias are nearly unaffected by the phase lag between the primary and the secondary voltage waves. The results also show that, with the secondary frequency substantially lower than the primary frequency, secondary self·do bias remains constant regardless of the phase lag. As the secondary frequency approaches to the primary frequency, however, the secondary self-dc bias becomes greatly altered by the phase lag, and so does the ion bombardment energy at the secondary electrode. These results demonstrate that ion bombardment energy can be more carefully controlled through plasma simulation.

• 한국전자파학회논문지
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• 제18권10호
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• pp.1163-1171
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• 2007

본 논문에서는 OPLL의 기술적 구성 요소인 주파수 및 위상 차이 검출기, 루프 여파기, VCO 반도체 레이저의 위상 잡음 설계에 대하여 이론적으로 검토하였으며, 설계 파라미터들을 도출하였다. 계산된 파라미터들로 구현한 설계 및 실험 결과, 주파수 및 위상 검출기는 헤테로다인된 차이 주파수와 1.5 GHz 기준 주파수 사이의 에러 성분을 이론식에 맞게 추출하였으며, 주파수 및 위상 고정 범위는 ${\pm}150MHz$이었다. 본 논문은 헤테로다인 위상 고정 루프 구현에 대한 설계 및 실험 결과를 기술하였다.

• 대한산업공학회지
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• 제30권1호
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• pp.27-35
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• 2004

A study was conducted to investigate an optimal vibration frequency for mobile phones with just noticeable difference(JND). The just noticeable difference, Weber's law, is the minimum amount by which stimulus intensity must be changed in order to produce a noticeable variation in sensory experience. In order to find the optimal vibration frequency, sixteen frequencies ranged from 24Hz to 603Hz were selected. Subjects then wereasked to differentiate a pair of vibration frequencies. For the analysis, the psychometric function to determine the optimal vibration frequency and the logistic regression to validate the determined frequency were used. The results show that the 2nd order polynomial equations were best fitted for the JND psychometric function and the optimal mobile phone vibrations were determined at 140Hz, 151 Hz, and 160Hz. With the ogive-shaped psychometric function developed by the logistic regression, the results of this study was validated that the determined vibration frequencies (140Hz, 151 Hz, and 160Hz) were optimal mobile phone vibration frequencies.