• 한국음향학회지
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• 제39권2호
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• pp.87-97
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• 2020

본 논문에서는 공기 중 광대역 초음파 방사용 압전 박막 기반 초소형 초음파 트랜스듀서(piezoelectric Micro-machined Ultrasonic Transducer, pMUT)의 설계 연구가 진행되었다. 하나의 트랜스듀서로 광대역을 달성하는 방법 중 하나는 다공진 시스템으로 설계하는 것이다. 새로운 pMUT은 박막 구조의 앞면과 뒷면에 적절한 음향 구조를 추가하여 다공진 시스템을 구현하도록 설계되었다. 박막 앞쪽은 도파관 구조로 모델링된 방사 파트로, 박막 뒷쪽은 음향 공동으로 모델링된 패키징 파트로 이루어져있다. 박막 파트, 방사 파트, 패키징 파트로 구성된 새로운 pMUT은 집중 변수 모델로 설계되었으며, 최종적으로 유한요소해석으로 검증되었다. 최종 설계된 pMUT은 102 kHz ~ 132 kHz (-3 dB)의 주파수 대역을 달성하였다.

• 정보교육학회논문지
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• 제20권4호
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• pp.323-332
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• 2016

로봇의 발음인식과 진단 그리고 발음빠르기는 로봇보조언어교육의 가장 중요한 상호작용이다. 이 연구는 한국인 초등 영어 학습자를 위하여 음율적 오류를 수정함으로써 원어민과 같은 억양을 산출하기 위한 로봇음성합성기의 효과성을 측정하기 위한 것이다. 이를 위해 초등 4학년 영어학습자들의 F0 범위값과 발화 속도라는 음성음향적 변수를 측정하여 분석하였고, 그 결과를 정규 영어교육의 시작하지 않은 1학년 학습자와 비교하였다. 로봇음성합성기를 활용한 언어학습에서 두 집단은 F0값보다 발화속도 변인에 반응하였다.

• 대한전자공학회논문지TC
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• 제48권1호
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• pp.25-31
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• 2011

소나 시스템은 항해와 해양 탐사, 수중 통신 등에 사용되며 정확성과 신뢰성을 향상시키기 위해 다양한 통계적 신호처리 기법들이 사용되고 있다. 수중에서의 다중 경로 특성은 검파 및 통신을 수행하는데 있어 열악한 환경을 제공한다. 파라메트릭 어레이 트랜스듀서의 고 지향성을 이용하면 다중 경로의 영향이 최소화될 뿐만 아니라, 파라메트릭 배열에 적합한 최적 검파기법을 사용하면 통산 성능이 향상된다. 본 논문에서는 on-off keying 통신 산호 검파를 위해 최대우도법(Maximum likelihood method)을 사용하였으며, LabVIEW 기반으로 파라메트릭 배열 트랜스듀서를 사용한 소나 시스템을 구현하여 시스템의 성능을 검증하였다. 또한, 다양한 트랜스듀서의 특성을 반영할 수 있는 GUI 소프트웨어도 설계 및 구현되어 다양한 소나 시스템의 성능 평가의 용이성을 증가시켰다. 본 논문에서 제안된 시스템은 실험실내에서의 다양한 모의실험이 가능하여 실제 해양 장비의 개발에 소요되는 비용과 시간을 감소시키는데 기여할 것으로 기대된다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2012년도 춘계학술대회 논문집
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• pp.447-452
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• 2012

Among the various elements affecting a customer's evaluation of automobile quality, buzz, squeak and rattle (BSR) are considered to be major factors. In most vehicle manufacturers, the BSR problems are solved by find-fix method with the vehicle road test, mainly due to various excitation sources, complex generation mechanism and subjective response. The aim of this paper is to develop the integrated experimental method to systematically tackle the BSR problems in early stage of the vehicle development cycle by resolving these difficulties. To achieve this aim, the developed experimental method ought to include the following requirements: to find and fix the BSR problem for modules instead of a full vehicle in order to tackle the problem in the early stage of the vehicle development cycle; to develop the exciter system including the zig and road-input-signal reproducing algorithm; to automatically localize the source region of BSR; to develop sound quality index that can be used to assess the subjective responses to BSR. Also, the BSR sound quality indexes based on the Zwicker's sound quality parameters using a multiple regression analysis. The four sound metrics from Zwicker's sound quality parameter are computed for the signals recorded for eight BSR noise source regions localized by using the acoustic-field visualized results. Then, the jury test of BSR noise are performed for participants. On a basis of the computed sound metrics and jury test result, sound quality index is developed to represent the harsh of BSR noise. It is expected that the developed BSR detection system and sound quality indexes can be used to reduce the automotive interior BSR noise in terms of subjective levels as well as objective levels.

• 한국전문물리치료학회지
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• 제15권3호
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• pp.35-43
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• 2008

The purpose of this study was to compare spatio-temporal parameters during walking between patients with idiopathic Parkinson's disease and a control group matched for age, height, and weight. Thirty-three subjects were included in this study. Fifteen normal subjects (age, $63.3{\pm}5.8$ yrs; height, $164.1{\pm}8.7$ cm; weight, $60.7{\pm}17.5$ kg) and eighteen patients (age, $64.0{\pm}7.7$ yrs; height, $164.7{\pm}7.3$ cm; weight, $63.6{\pm}7.7$ kg) participated in the study. The Vicon 512 Motion analysis system was used for gait analysis in each group during walking, with and without an obstacle. The measured spatio-temporal parameters were cadence, walking speed, stride time, step time, single limb support time, double limb support time, stride length, and step length. Results in stride length and step length, when walking without an obstacle, showed a significantly greater decrease in the patient group compared to the control group. During walking with an obstacle, the patient group showed a significantly greater decrease in the step length as compared to the control group. For the control group, there were significant decreases in parameters of cadence and walking speed and increases in parameters of stride time, step time, and single limb support time when walking with an obstacle. The patient group had lower cadence and walking speed and higher stride time, step time, and single limb support time during walking with an obstacle than in walking without an obstacle. These results suggest that patients with Parkinson's disease who walk over an obstacle can decrease cadence, stride length, and step length. Further study is needed, performed with more obstacles and combined with other external cues, such as visual or acoustic guides.

• 대한기계학회논문집A
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• 제38권4호
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• pp.459-468
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• 2014

공명기의 공명주파수를 계산할 수 있는 전통적인 공식의 정확도를 높이기 위한 추가 관계식을 수치적인 방법으로 얻는다. 그 전통적인 공식은 단순함 때문에 산업계에서 널리 사용되고 있지만, 덕트 소음 저감용 공명기의 공동과 목에 대한 정보를 충분히 제공하지 못한다. 그러므로, 산업 현장에서는 그 공식이 갖는 형상의 불확실성 때문에 실제 공명기 설계에 많은 어려움을 겪고 있다. 이 단점을 극복하기 위해서, 본 연구에서는 수치 계산 결과를 이용하여 추가 근사식을 유도하고자 한다. 이를 위해, 목과 공동의 형상 계수를 정의하고, 공명기의 투과 손실 곡선 상의 피크 주파수와 계산식의 공명 주파수가 일치해야 한다는 조건을 사용하여 형상 계수들 사이의 관계식을 유도하였다. 유도된 관계식의 유효성을 수치적인 방법과 실험적인 방법으로 검증하였다.

• 대한후두음성언어의학회지
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• 제28권2호
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• pp.84-88
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• 2017

Background and Objectives : The purpose of this study was to compare the usefulness of Cepstral peak prominence (CPP) with parameter of Multiple Dimensional Voice Program (MDVP) in evaluating unilateral vocal fold paraylsis patients with subjective voice impairment. Materials and Methods : From July 2014 to August 2016, 37 patients with unilateral vocal fold paralysis who had been diagnosed with unilateral vocal fold paralysis and had received two or more voice tests before and after the diagnosis were evaluated for maximum phonation time (MPT), MDVP and CPP. Respectively. Voice tests were performed with short vowel /a/ and paragraph reading. Results : The CPP-a (CPP with vowel /a/) and CPP-s (CPP with paragraph reading) of the Cepstrum were statistically negatively correlated with G, R, B, and A before the voice therapy. Jitter, Shimmer, and NHR of MDVP were positively correlated with G, R, B. Jitter, Shimmer, and NHR of the MDVP were significantly correlated with the Cepstrum index. G, B, A and CPP-a and CPP-s showed a statistically significant negative correlation and a somewhat higher correlation coefficient between 0.5 and 0.78. On the other hand, in MDVP index, there was a positive correlation with G and B only with Jitter of 0.4. Conclusion : CPP can be an important evaluation tool in the evaluation of speech in the unilateral vocal cord paralysis when speech energy changes or the cycle is not constant during speech.

• 대한후두음성언어의학회지
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• 제16권2호
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• pp.158-164
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• 2005

Melody intonation therepy (MIT) is to improve the linguistic aspects of the verbal utterance for aphasic patients utilizing the intact right brain. It is applied to the aphasic patients with good comprehension, poor fluency, and little available speech are thought to be ideal candidates. The purpose of the study was to investigate the effects of Korean Melody intonation therapy (kMIT) in patients with non-fluent aphasia. Five male non-fluent aphasic patients were participated in this study. Average ages were 49.9 years old. Each therapy took 45-50minutes once a week for six months. Aphasic Screen lest (RISS) was used to assess language parameter such as Auditory comprehension, oral expression, reading, writing and calculation ability before and after kMIT. Mean of Length Utterance, verbal intelligibility and articulation disorder were assessed also. Computerized Speech Lab was used to assess the acoustic characteristics of aphasic patients before and after kMIT. The results are as follows : 1) Auditory comprehension, oral expression, reading, writing and calculation ability of the subjects increased after UH'. However, only oral expression showed significant difference (p<0.05). 2) Mean of Length Utterance of five patients generally increased after Un. 3) After kMIT, verbal intelligibility increased and showed significant difference (p<0.05). 4) Misarticulation rate generally decreased after m. 5) Voice Onset Time of the alveolar lenis /t/ and velar lenis /k/ gradually decreased after kMIT. 6) However, intonation pattern were increased gradually in yes'no question after kMIT.

• 대한기계학회논문집B
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• 제32권5호
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• pp.342-350
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• 2008

The effects of combustion instability on flow structure and flame dynamics with the inlet configurations in a model gas turbine combustor were investigated using large eddy simulation (LES). A G-equation flamelet model was employed to simulate the unsteady flame behaviors. As a result of mean flow field, the change of divergent half angle($\alpha$) at combustor inlet results in variations in the size and shape of the central toroidal recirculation (CTRZ) as well as the flame length by changing corner recirculation zone (CRZ). The case of ${\alpha}=45^{\circ}$ show smaller size and upstream location of CTRZ than those of $90^{\circ}$ and $30^{\circ}$ by the development of higher swirl velocity. The flame length in the case of ${\alpha}=45^{\circ}$ is shorter than other cases, while the case of ${\alpha}=30^{\circ}$ yields the longest flame length due to the decrease of effective reactive area with the absence of CRZ. Through the analysis of pressure fluctuation, it was identified that the case of ${\alpha}=45^{\circ}$ shows the largest damping effect of pressure oscillation in all configurations and brings in the noise reduction of 2.97dB, compared to that of ${\alpha}=30^{\circ}$ having the largest pressure oscillation. These reasons were discussed in detail through the analysis of unsteady phenomena related to recirculation zone and flame surface. Finally the effects of flame-acoustic interaction were evaluated using local Rayleigh parameter.

• 전력전자학회논문지
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• 제10권4호
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• pp.313-322
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• 2005

본 논문은 복공진 인버터를 적용한 250[W] 메탈핼라이드램프를 구동하기 위한 고역률 전자식 안정기를 설계하고 구현하였다. 제안된 전자식 안정기는 역률 개선 회로기능을 갖는 부스트 능동 PFC 회로와 하프 브리지 복공진형 인버터로 구분된 2개의 전력처리단으로 구성되어 있다. 회로 기본동작원리 및 회로 해석은 무차원화 파라미터를 도입하여 범용성을 부여하여 도식적으로 나타내었다. 음향공명을 제거하기 위해 타이머 IC와 구동 IC로 구성된 간단한 주파수 제어기를 구현하였다. 실험을 통해 복공진 인버터를 적용한 고역률 메탈핼라이드램프용 전자식 안정기가 안정적으로 동작함을 확인하였다