• 농업과학연구
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• 제32권1호
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• pp.29-42
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• 2005

본 연구에서는 청과물 포장설계 시 중요한 자료가 되는 참외의 공진 주파수 및 정점가속도 등과 같은 진동특성을 분석하기 위하여 실험 장치를 구성하고 진동시험장치의 제어 및 계측을 위한 컴퓨터 프로그램을 개발하였다. 이를 이용하여 참외의 진동 특성을 측정하였으며 이들과 참외의 기본적인 물성 값인 질량, 체적 및 장 단축과의 관계를 구명하였던 주요 연구결과를 요약하면 다음과 같다. 1. 참외의 진동특성을 분석할 수 있는 실험 장치를 구성하였으며, 장치의 제어와 계측을 위한 컴퓨터 프로그램을 개발하였다. 2. 공시 참외의 공진 진동수는 약물결 50.8~72.6 Hz 범위로 나타났으며, 점점 가속도는 약1.24~1.92G-rms범위로 나타났다. 3. 참외의 공진 주파수 및 정점 가속도는 참외의 질량, 체적 및 장 단축이 증가함에 따라 감소 하였으며 참외의 질량과 공진 주파수 및 정점 가속도와의 상관관계가 가장 높게 나타났다. 4. 참외의 공진주파수 및 정점가속도를 추정할수 있는 회귀모형을 참외의 질량 및 장 단축을 독립변수로 하여 개발하였으며 회귀모형을 평가한 결과 참외의 질량과 장 단축을 측정하면 참외의 공진 주파수와 정점 가속도를 추정할 수 있을 것으로 판단되었다.

• International journal of advanced smart convergence
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• 제6권2호
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• pp.59-64
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• 2017

There are three sorts of voices of female vocalists: soprano, mezzo-soprano, and contralto according to the transliteration. Among them, the soprano has the highest vocal range. Since the voice is generated through the human vocal tract based on the voice generation model, it is greatly influenced by the vocal tract. The structure of vocal organs differs from person to person, and the formants characteristic of vocalization differ accordingly. The formant characteristic refers to a characteristic in which a specific frequency band appears distinctly due to resonance occurring in each vocal tract in the vocal process. Formant characteristics include personality that occurs in the throat, jaw, lips, and teeth, as well as phonological properties of phonemes. The first formant is the throat, the second formant is the jaw, the third formant and the fourth formant are caused by the resonance phenomenon in the lips and the teeth. Among them, pronunciation is influenced not only by phonological information but also by jaws, lips and teeth. When the mouth is small or the jaw is stiff when pronouncing, pronunciation becomes unclear. Therefore, the higher the accuracy of the pronunciation characteristics, the more clearly the formant characteristics appear in the grammar spectrum. However, many soprano singers can not open their mouths because their jaws, lips, teeth, and facial muscles are rigid to maintain high tones when singing, which makes the pronunciation unclear and thus the formant characteristics become unclear. In this paper, in order to confirm the accuracy of the pronunciation characteristics of soprano singers, the experimental group was selected as the soprano singers A, B, C, D, E of Korea and analyzed the grammar spectrum and conducted the MOS test for pronunciation recognition. As a result, soprano singer B showed a clear recognition from F1 to F5 and MOS test result showed the highest recognition rate with 4.6 points. Soprano singers A, C, and D appear from F1 to F3, but it was difficult to find formants above 2kHz. Finally, the soprano singer E had difficulty in finding the formant as a whole, and MOS test showed the lowest recognition rate at 2.1 points. Therefore, we confirmed that the soprano singer B, which exhibits the most distinct formant characteristics in the grammar spectrum, has the best pronunciation accuracy.

• 한국터널지하공간학회 논문집
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• 제11권1호
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• pp.71-83
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• 2009

숏크리트는 터널에서 적용되는 요요한 주지보재이다. 숏크리트의 품질평가는 터널의 안전한 시공과 효과적인 운영을 위한 핵심 요소이다. 숏크리트가 암반에 적절히 타설되었다 하더라도, 막장 및 벤치부에서의 발파, 수축, 지반의 변형 등으로 인해 숏크리트 균열발생 및 배면공동 등의 문제를 야기한다. 본 논문에서는 비파괴 시험인 충격 반항 기법(Impact-Echo) 및 지하레이다 탐사(GPR)를 이용하여 경임에 타설된 숏크리트 배면의 접착상태를 평가하고자 하였다. 기존의 수치해석 연구에 대한 검증과 더불어 현장 적용성에 대한 검토를 위해 실험적 연구를 수행하였다. 숏크리트의 접착상태는 완전 접착, 접착력 상실 및 공동 조건으로 구분할 수 있다. 실내 실대형 시험체에 이 세 가지 숏크리트 접착상태를 조사하였다. 충격반향시험으로부터 획득된 신호는 시간영역, 주파수 영역, 및 시간-주파수 영역에서 각각 분석되었다. 능동적 신호 처리 기법인 Short-Time Fourier Transform(STFT)을 이용하여 숏크리트 배면의 접착상태를 효과적으로 예측할 수 있었으며, 그 결과는 기존의 수치해석 연구로부터 획득한 신호특성과 잘 부합하였다. 숏크리트 배면의 접착상태가 불량할수록 다음과 같은 특징들을 나타낸다. 즉, 주파수 영역에서 자기스펙트럼밀도가 커지며, 기하학적 감쇠비는 감소하고, 시간-주파수 영역에서 윤곽선은 시간축에 평행한 형상을 나타내며, 숏크리트 두께가 얇을수록 그 공진시간이 길어진다. 또한 본 연구에서 제시한 상관계수를 이용하여 숏크리트의 접착상태를 정량적으로 평가할 수 있다. 본 연구 결과를 바탕으로 숏크리트의 접착상태를 평가할 수 있는 평가 기법 및 평가 기준을 제안하였다.

• 대한치과보철학회지
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• 제46권6호
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• pp.628-633
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• 2008

STATEMENT OF PROBLEM: The application of a simple, clinically applicable noninvasive test to assess implant stability are considered highly desirable. So far there is still a controversy about correlation of various tests and implant stability. PURPOSE: In order to assess implant stability, the development of a new method is critical. It's possible to assess implant stability by calculating energy and angular momentum during implant installation. The purpose of this study is to evaluate the correlation of energy and implant stability. MATERIAL AND METHODS: Twenty three implants were installed in two different types of pig bone. Type I bone was retrieved from the distal aspect of the rib, with more cortical bone. Type II bone came from a more proximal region with less cortical components and a higher content of bone marrow and spongeous trabeculae. Insertion torque, removal torque, ISQ values and angular momentum and energy were measured. Pearson Correlation test was done to analyze the relation between RFA, maximum insertion torque, mean insertion torque, bone type, energy and removal torque. RESULTS: Type I bone showed higher removal torque than type II bone. Energy value was significantly correlated with maximum insertion torque and mean insertion torque. RFA values were related with insertion torques but the significance was lower than Energy value. CONCLUSION: Within the limitation of this study energy values were considered clinically predictable method to measure the implant stability.

• Maxillofacial Plastic and Reconstructive Surgery
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• 제32권2호
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• pp.107-111
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• 2010

Purpose: The aim of this study is to compare the stability between Mg-incorporated implant, TiUnite and Machined implant. Materials and Methods: Premolars of 3 Mini pigs (24 months) were extracted. After 2 months later, total 27 fixtures of implants (9 of each design : Machined/ TiUnite/ Mg-incorporated) were inserted into the mandible of 3 mini-pig. Implant stability was estimated by RFA in installation to 2, 4 & 6 weeks. Statistical analysis of RFA values was performed with time and between groups using repeated measure ANOVA and turkey's multiple comparison test. Results: In analyzing the mean value for the observation periods, three types of implants yielded a slight decrease in RFA mean value after 2 week, followed by increase at 4-6 weeks. Mg incorporated oxidized implants demonstrated significantly higher RFA mean values at 6 weeks comparing other groups. The difference of RFA value with time and between groups was statistically significant. Conclusion: We concluded that Mg implants may reduce failure rates of clinical implants In the early period of bone healing and Mg implants may shorten the bone healing time from surgery to functional loading.

• Advances in aircraft and spacecraft science
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• 제4권6호
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• pp.613-637
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• 2017

The development systems for the Structural Health Monitoring has attracted considerable interest from several engineering fields during the last decades and more specifically in the aerospace one. In fact, the introduction of those systems could allow the transition of the maintenance strategy from a scheduled basis to a condition-based approach providing cost benefits for the companies. The research presented in this paper consists of a definition and next comparison of four methods applied to numerical measurements for the extraction of damage features. The first method is based on the determination of the Structural Intensity field at the on-resonance condition in order to acquire information about the dissipation of vibrational energy throughout the structure. The Damage Quantification Indicator and the Average Integrated Global Amplitude Criterion methods need the evaluation of the Frequency Response Function for a healthy plate and a damaged one. The main difference between these two parameters is their mathematical definition and therefore the accuracy of the scalar values provided as output. The fourth and last method is based on the Mode-shape Curvature, a FRF-based technique which requires the application of particular finite-difference schemes for the derivation of the curvature of the plate. All the methods have been assessed for several damage conditions (the shape, the extension and the intensity of the damage) on two test plates: an isotropic (steel) plate and a 4-plies composite plate.

• 전기학회논문지
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• 제65권9호
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• pp.1571-1576
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• 2016

A Tesla coil is an electrical resonant transformer circuit invented by Nikola Tesla in 1891. It is used to produce high-voltage, low-current, high frequency alternating-current electricity. Tesla coil can generate a long streamer with several million volts of electricity as a high voltage device. It is basically consists of a voltage transformer, high voltage capacitor, spark gap, primary coil, secondary coil and toroid. It is difficult to appear in the output size of the streamer is controlled by the spark gap. The general decision method of the length of streamer is to display the electric output in accordance with the design specifications in initial development plan. Design specifications and the electric output is determined by the application of facilities. In this paper the spark gap is replaced with periodic switching semiconductor device to control output voltage easily in order to apply overvoltage protective circuit due to a secondary coil and a performance test. In these days, their main use is for entertainment and educational displays of the museum, although small coils are still used as leak detectors for high vacuum systems.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회A
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• pp.1231-1236
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• 2007

This study presents the static and dynamic actuating performances of a bending piezoelectric actuator with a thin sandwiched PZT plate under a static load. The stored elastic energy within the actuators which occurs during a curing process is obtained through a flexural bending test. An actuating performance is evaluated in terms of an actuating displacement at the simply supported condition. The results reveal that an actuator that consists of a top layer having a high elastic modulus and a low coefficient of thermal expansion exhibits a better performance than the rest of actuators due to the formation of the large stored elastic energy within the actuator system. When actuators are excited at the alternating current voltage, the effect of PZT ceramic softening results in a slight reduction in the resonance frequency of each actuator as the applied electric field increases. It is thus suggested that the static and dynamic actuating characteristics of bending piezoelectric actuators with a thin sandwiched PZT plate should be simultaneously considered in controlling their performances.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 제36회 하계학술대회 논문집 A
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• pp.93-95
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• 2005

Coupling capacitor voltage transformers (CCVT) are widely used in high voltage power systems to obtain standard low voltage signal for protective relaying and measuring instruments. To obtain high accuracy, capacitances and inductances are tuned to the power system frequency, making a parallel resonant circuit. When no fault occurs, no distortion of the secondary voltage is generated. However, when a fault occurs, harmonics generated break the resonance between capacitances and inductance, which generates the distortion of the secondary voltage. This paper proposes an algorithm for compensating the secondary voltage of the CCVT. With the values of the secondary voltage of the CCVT, the secondary currents, the primary currents and the voltages across the capacitors and inductor are calculated. Test results indicate that the proposed algorithm can compensate the distorted secondary voltage of the CCVT, and is irrespective of the fault distance, the fault inception angle and the burden.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2006년도 제37회 하계학술대회 논문집 A
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• pp.266-267
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• 2006

A coupling capacitor voltage transformer (CCVT) is used in extra high voltage and ultra high voltage transmission systems to obtain the standard low voltage signal for protection and measurement. To obtain the high accuracy at the power system frequency, a tuning reactor is connected between a capacitor and a voltage transformer (VT). Thus, no distortion of the secondary voltage is generated when no fault occurs. However, when a fault occurs, the secondary voltage of the CCVT has some errors due to the transient components resulting from the fault. This paper proposes an algorithm for compensating the secondary voltage of the CCVT in the time domain. With the values of the secondary voltage of the CCVT, the secondary and the primary currents are obtained; then the voltage across the capacitor and the tuning reactoris calculated and then added to the measured secondary voltage. The proposed algorithm includes the effect of the non-linear characteristic of the VT and the influence of the ferro-resonance suppression circuit. Test results indicate that the algorithm can successfully compensate the distorted secondary voltage of the CCVT irrespective of the fault distance, the fault inception angle and the fault impedance.