• 한국산학기술학회논문지
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• 제12권5호
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• pp.2203-2208
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• 2011

턱관절의 물리치료를 통한 훈련으로 모음 조음에 관여하는 구강 공명강을 증가시켜, 턱관절의 정상적인 발성패턴을 유지하도록 하여 턱관절장애 환자의 모음의 음향학적 특성 변화를 보고자 하였다. 연구 대상은 턱관절장애로 진단 받은 3명의 20~30대 성인 남자를 대상으로 하였다. 실험방법은 대상자간 중다기초선 설계를 이용하여 기초선 단계, 치료 단계, 유지 단계로 진행하였다. 치료는 한 회기를 30분으로 하여 주 3회 실시하였고 3회기를 한 평가단위로 5회의 중간평가를 실시하였다. 평가방법은 Praat 음성 분석프로그램을 이용하여 /ㅏ/ 모음의 연장 발성에 대한 제 1포먼트 주파수(F1), 제 2포먼트 주파수(F2) 그리고 기본주파수(F0)를 분석하였다. 물리치료를 통한 훈련 프로그램을 실시한 결과 턱관절장애 환자의 제 1포먼트 주파수(F1), 제 2포먼트 주파수(F2) 그리고 기본주파수(F0)는 치료 전 보다 증가하는 변화를 보였고, 이는 모음의 개구도와 관계된 제 1 포먼트 주파수(F1) 뿐만 아니라 모음의 전후설, 성대의 움직임과 관련이 있는 제 2포먼트 주파수(F2) 그리고 기본주파수(F0)의 변화도 함께 보임으로써 턱관절과 모음 및 음성 산출의 연관성을 보여주었다.

• Structural Engineering and Mechanics
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• 제72권6호
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• pp.747-762
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• 2019

Based on the ball-screw mechanism, a tuned viscous mass damper (TVMD) has been proposed, which has functions of amplifying physical mass of the system and frequency tuning. Considering the sensitivity of a single TVMD's effectiveness to frequency mistuning like that of the conventional tuned mass damper (TMD) and according to the concept of the conventional multiple tuned mass damper (MTMD), in the present paper, multiple tuned mass viscous dampers (MTVMD) consisting of many tuned mass dampers (TVMD) with a uniform distribution of natural frequencies are considered for attenuating undesirable vibration of a structure. The MTVMD is manufactured by keeping the stiffness and damping constant and varying the mass associated with the lead of the ball-screw type inerter element in the damper. The structure is represented by its mode-generalized system in a specific vibration mode controlled using the mode reduced-order method. Modal properties and fundamental characteristics of the MTVMD-structure system are investigated analytically with the parameters, i.e., the frequency band, the average damping ratio, the tuning frequency ratio, the total number of TVMD and the total mass ratio. It is found that there exists an optimum set of the parameters that makes the frequency response curve of the structure flattened with smaller amplitudes in a wider input frequency range. The effectiveness and robustness of the MTVMD are also discussed in comparison with those of the usual single TVMD (STVMD) and the results shows that the MTVMD is more effective and robust with the same level of total mass.

• 한국전자파학회논문지
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• 제24권1호
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• pp.82-90
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• 2013

본 논문에서는 고주파 회로 모델링을 이용하여 전기자동차의 모터 구동 시스템으로부터 방출되는 전도성 전자파 노이즈를 시스템-레벨에서 분석하였다. 관련 전도 방출의 주요 원인은 모터 구동 시스템에서 사용하는 펄스폭 변조방식의 스위칭 동작에 기인하며, 이러한 전도 방출은 공통-임피던스 결합 및 유도성 결합을 통해 AM/FM 주파수 대역에서의 무선주파수 간섭을 유발한다. 이러한 문제를 분석하기 위해 모터 구동 시스템을 구성하고 있는 IGBT와 고압 커패시터, 인버터, 모터 및 고전압 케이블과 버스 바에 대한 기본 회로는 물론, 각 부분에서 존재하는 기생 성분 및 비선형 특성을 해석하여 모터 구동 시스템 전체를 포함한 시스템-레벨의 고주파 등가회로 모델을 제안하였다. 이러한 모델을 이용한 모터 구동시스템의 전도 방출 특성을 시뮬레이션하고, 측정하였으며, 비교적 큰 해석구조임에도 불구하고 두 결과가 비교적 잘 일치함을 확인하였다. 향후 이러한 접근방법이 전기자동차의 전자파 적합성 설계에 효과적으로 사용될 수 있을 것으로 기대한다.

• 한국정보통신학회논문지
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• 제15권2호
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• pp.307-314
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• 2011

인지통신(cognitive radio)과 같이 가변 스펙트럼 할당이 필요한 시스템을 위한 새로운 전치왜곡기를 제안한다. 본 논문에서 고려하는 시스템 모델에서 신호는 한 순간에는 작은 대역폭을 차지하지만 그 중심 주파수가 시간에 따라 변화할 수 있는 상황을 가정한다. 이러한 시나리오에서는 전력 증폭기 출력 단에 위치하는 종단 필터로는 전력증폭기에 의한 하모닉을 제거하지 못하는 상황이 발생할 수 있다. 제안된 전치왜곡기는 기본 주파수 (${\omega}_0$) 신호의 비선형 왜곡을 선형화할 뿐만 아니라, $2{\omega}_0$, $3{\omega}_0$, ...에서 발생하는 하모닉도 동시에 제거한다. 제안된 전치왜곡기는 ${\omega}_0$ 주파수의 정수배에 대응하는 여러 개의 전치왜곡기가 결합된 구조를 가지고 있다. 기본 주파수 ${\omega}_0$에 해당하는 전치왜곡기는 기본 주파수 신호의 선형화를 담당하며, 나머지 주파수에 대응하는 전치왜곡기는 하모닉을 제거하는 역할을 담당한다. 제안된 전치왜곡기에서 필요한 변수는 최소 평균 자승 에러 알고리즘에 의해 동시에 계산되며, 모의실험 결과에 따르면 제안된 방법을 이용하면 기본 주파수의 스펙트럼에 발생하는 스펙트럼 왜곡이 20dB 감소하며, 2차 및 3차 하모닉도 기본 신호의 전력대비 약 -70dB로 작아지는 것을 확인할 수 있다.

• International Journal of Fluid Machinery and Systems
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• 제10권2호
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• pp.119-137
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• 2017

Although the stall stagnation phenomena have often been experienced in site and also analytically in numerical experiments in surges in systems of compressors and flow paths, the fundamental causes have not been identified yet. In order to clarify the situations, behaviours of infinitesimal disturbance waves superposed on a main flow were studied in a simplified one-dimensional flow model. A ratio of the amplifying rate of the system instability to the characteristic slope of the compressor element was surveyed as the instability enhancement factor. Numerical calculations have shown the following tendency of the factor. In the situation where both the sectional area ratio and the length ratio of the delivery flow-path to the suction duct are sufficiently large, the enhancement factors are greater in magnitude, which means occurrence of ordinary deep surges. However, in the situation where the area ratio and/or the length ratio is relatively smaller, the enhancement factor tends to lessen significantly, which situation tends to suppress deep surges for the same value of the characteristic slope. It could result in the stall stagnation condition. In the domain of area ratio vs. length ratio of the delivery duct to the suction duct, contour-lines of the enhancement factor behave qualitatively similar to those of the stall stagnation boundaries of a fan analytically obtained, suggesting that a certain range of the enhancement factor values could specify the stagnation occurrence. The significant decreases in the factors are observed to accompany appearances of phase lags and travelling waves in the wave motions, which macroscopically suggests breaking down of the complete surge actions of filling and emptying of the air in the delivery duct. The strength of the action is deeply related with acoustic interferences and is evaluated in terms of the volume-modified reduced resonance frequency proposed by the author. These observations have shown the fundamental cause and the sequence of the stall stagnation in principle.

• 한국GIS학회:학술대회논문집
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• 한국GIS학회 2008년도 공동추계학술대회
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• pp.297-302
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• 2008

The positioning technology for a moving object is an important and essential component of ubiquitous computing environment and applications, for which Radio Frequency Identification(RFID) has been considered as a core technology. RFID-based positioning system calculates the position of moving object based on k-nearest neighbor(k-nn) algorithm using detected k-tags which have known coordinates and kcan be determined according to the detection range of RFID system. In this paper, RFID-based positioning system determines the position of moving object not using weight factor which depends on received signal strength but assuming that tags within the detection range always operate and have same weight value. Because the latter system is much more economical than the former one. The geometries of tags were determined with considerations in huge buildings like office buildings, shopping malls and warehouses, so they were determined as the line in I-Dimensional space, the square in 2-Dimensional space. In 1-Dimensional space, the optimal detection range is determined as 125% of the tag spacing distance through the analytical and numerical approach. Here, the analytical approach means a mathematical proof and the numerical approach means a simulation using matlab. But the analytical approach is very difficult in 2-Dimensional space, so through the numerical approach, the optimal detection range is determined as 134% of the tag spacing distance in 2-Dimensional space. This result can be used as a fundamental study for designing RFID-based positioning system.

• 한국GIS학회:학술대회논문집
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• 한국GIS학회 2008년도 공동추계학술대회
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• pp.270-271
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• 2008

The positioning technology for a moving object is an important and essential component of ubiquitous communication computing environment and applications, for which Radio Frequency IDentification Identification(RFID) is has been considered as also a core technology for ubiquitous wireless communication. RFID-based positioning system calculates the position of moving object based on k-nearest neighbor(k-nn) algorithm using detected k-tags which have known coordinates and k can be determined according to the detection range of RFID system. In this paper, RFID-based positioning system determines the position of moving object not using weight factor which depends on received signal strength but assuming that tags within the detection range always operate and have same weight value. Because the latter system is much more economical than the former one. The geometries of tags were determined with considerations in huge buildings like office buildings, shopping malls and warehouses, so they were determined as the line in 1-Dimensional space, the square in 2-Dimensional space and the cubic in 3-Dimensional space. In 1-Dimensional space, the optimal detection range is determined as 125% of the tag spacing distance through the analytical and numerical approach. Here, the analytical approach means a mathematical proof and the numerical approach means a simulation using matlab. But the analytical approach is very difficult in 2- and 3-Dimensional space, so through the numerical approach, the optimal detection range is determined as 134% of the tag spacing distance in 2-Dimensional space and 143% of the tag spacing distance in 3-Dimensional space. This result can be used as a fundamental study for designing RFID-based positioning system.

• 말소리와 음성과학
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• 제7권4호
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• pp.77-83
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• 2015

Voice complication without the laryngeal nerve injury can occur after thyroidectomy. The purpose of this study is to investigate voice changes according to extent of thyroidectomy with acoustic analysis. Thirty-five female patients with papillary thyroid carcinoma took voice evaluation at before and 1 month, and 3 months after thyroidectomy. Acoustic analysis parameters were speaking fundamental frequency(SFF), min $F_0$, max $F_0$, dynamic range $F_0$, jitter, shimmer, noise-to-harmonic ratio(NHR), and Cepstral prominence peak(CPP). Repeated-measured analysis of variance was applied. Time-related voice changes showed significant differences in all parameters except NHR. At 1 month after surgery, voice quality was worse and pitch was decreasing, but voice quality and pitch were improving at 3-month follow-up. Voice changes according to the extent of surgery were in SFF, max $F_0$, and dynamic range $F_0$. Time by surgery-related voice change existed only in min $F_0$. The result showed that the severity of voice complication depended on the extend of thyroidectomy which had a negative impact on $F_0$-related parameters. The deterioration of voice quality at 1 month after thyroidectomy may be affected by the loss of thyroid hormone in the blood. The descent of $F_0$-related parameters may be impacted by laryngeal fixation of surgical site adhesion.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2007년도 하계종합학술대회 논문집
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• pp.159-160
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• 2007

Two analog predsitorters (PDs) using the mixing operation are proposed to compensate for the memory effects of the power amplifier and then significantly cancel IM3 components with the independent control of IM3 terms. In the first PD, IM3 terms are generated by using mixing operation of low frequency terms. In the second PD, the double mixing operation of the fundamental components is used. For a two-tone signal with 20-MHz tone spacing, the notable IM3 suppression is achieved over a whole output power range.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2001년도 추계 학술발표회 논문집 Proceedings of EESK Conference-Fall 2001
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• pp.75-82
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• 2001

A dynamic interaction analysis of an adjacent surface fecundation on a layered half-space is performed in the frequency domain. A semi-analytical approach is employed to reduce the integration range of the wavenumber in the surface fundamental solution for a layered half-space in boundary element (BE) formulations. The present study then adopts a combined boundary and finite element method to analyze the dynamic behavior of a system of flexible surface foundations on an elastic homogeneous and layered half-space. Numerical examples are presented to demonstrate the accuracy of the developed method. The examples show the feasibility of an extended application fur the complicated dynamic interaction of foundations on layered media.