• 대한의용생체공학회:의공학회지
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• 제14권2호
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• pp.125-136
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• 1993

The study of Cochlear biomechanics is to clearly define three biomechanical principles of the Cochlea : Activity, Nonlinearity and Feedback. In this article, the Cochlea is linearly and actively modelled in one dimensional time domain. The sharp tunning of the Basilar Membrane displacement is shown when the amplifying activity of hair cells is added to the model. The amplified energy of the travelling displacement wave is emitted throughout the Cochlear fluid, so that the model becomes unstable. A new technique is introduced to reduce strong echos fro the Helicotrema. It makes the model less unstable. Both pure and click tones are used as input stimuli onto the ear durm. When the model is normal, the click response of the model shows that the backward emission of the amplified fluid pressure has mainly the echos from the Helicotrema. However, when the linear and active model is assumed to be abnormal, that is, some of hair cells are damaged not to produce the active process, the effect of the hair cell damage is resulted in the Oto-acoustic emission. The frequency response of the abnormally emitted sound pressure shows that the Oto-acoustic emission has the information about the characteristic frequency of the damaged hair cell. The main aim of this paper is to demonstrate the active biomechanics of the Chchlea in the time domain.

• 융합신호처리학회 학술대회논문집
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• 한국신호처리시스템학회 2000년도 하계종합학술대회논문집
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• pp.269-272
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• 2000

It is need to develop and apply a human pulse diagnosis system providing a quantitative and automatic analysis in the the oriental medicine. In order to analyze quantitatively the characteristic of pulsation, each of points had to be recognized accurately notifying the existence and the position of feature point in the wave form. And getting the period of human pulse. Thus, in this paper, it is proposed the preprocessing method of human pulse and the detection method of period by Wavelet Transformation. The human pulse is seprated from each band through Wavelet Transformation and feature points can be recognized through over the fact, and then the parameter of proposed Mac-Jin parameter is measured. Commonly, Human pulse signal has often various noises which are baseline drift, high frequency noise and so on. So it is significant to remove that noises. Thus, in this paper, the one period of human pulse is deciede and the feature points are detected after doing the preprocessing by wavelet transformation. As a result, it could be confirmed that this method is effective as a real program for the auto-diagnosis of human pulse.

• Bulletin of the Korean Chemical Society
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• 제19권5호
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• pp.527-530
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• 1998

This paper presents the electrochemistry and molecular orbital (MO) picture of a series of conformationally-restricted thioxantone derivatives. A series of $C_2-substituted$ thioxanthones were examined to probe the electronic influence of the substituent on the electrooxidation and electroreduction sites (i.e., on the electron densities at the 10-and 9-positions), respectively. In the presence of "electrophoric" groups such as C=O and S, characteristic electrochemical reduction and oxidation responses are observed. The electrochemical reaction was diffusion-controlled, because the $I_p/{\upsilon}^{1/2}$ ratio was constant for the anodic and cathodic wave of thioxantone derivatives. These substituent effects are presented in terms of correlations of oxidation (or reduction) potentials with the highest occupied molecular orbital (HOMO), or lowest unoccupied molecular orbital (LUMO) energies, respectively. There is good correlation between energies of the HOMO vs. $E_{pa}^{(+)}$ and energies of the LUMO vs. $E_{pc}^{(-)}$. Frontier Molecular Orbital (FMO) is changed by the functional group of thioxanthones. FMO energy level was offered us the information about the electron transfer direction, and the coefficient of FMO was offered the information about the electron transfer position. Sulfur atom has an important effect on oxidation potential, $E_{pa}^{(+)}$ and the carbonyl carbon has an important effect on reduction potential, $E_{pc}^{(-)}$. Therefore we were appreciated that the contribution of sulfur atom for the $E_{pa}^{(+)}$ and HOMO energies is larger than the contribution of carbonyl group for the $E_{pc}^{(-)}$ and LUMO energies.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2011년도 제36회 춘계학술대회논문집
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• pp.211-214
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• 2011

본 연구에서는, step을 적용한 추력 노즐 내부 유동장의 횡력 특성을 조사하기 위하여 수치해석적 연구를 수행하였다. 비정상, 축대칭, 압축성 N-S 방정식을 유한 체적법으로 이산화 하였으며, SST k-${\omega}$ 난류모델을 적용하였다. 엔진 정지과정을 모사하기 위하여, NPR은 100~10로 변화시켜 계산 하였다. 본 연구의 결과로 박리점 및 마하디스크 위치는 구동 압력비에 크게 의존하며, 또한 step의 적용이 횡력 특성에 지대한 영향을 미칠 수 있음을 알았다.

• 한국공간구조학회논문집
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• 제19권2호
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• pp.101-108
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• 2019

In this paper, the characteristic of intrinsic mode function(IMF) and its orthogonalization of ensemble empirical mode decomposition(EEMD), which is often used in the analysis of the non-linear or non-stationary signal, has been studied. In the decomposition process, the orthogonal IMF of EEMD was obtained by applying the Gram-Schmidt(G-S) orthogonalization method, and was compared with the IMF of orthogonal EMD(OEMD). Two signals for comparison analysis are adopted as the analytical test function and El Centro seismic wave. These target signals were compared by calculating the index of orthogonality(IO) and the spectral energy of the IMF. As a result of the analysis, an IMF with a high IO was obtained by GSO method, and the orthogonal EEMD using white noise was decomposed into orthogonal IMF with energy closer to the original signal than conventional OEMD.

• 센서학회지
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• 제27권6호
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• pp.421-426
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• 2018

To develop a piezoelectric inkjet printhead for high-resolution and high-speed printing, we studied the characteristics of an inkjet printhead by analyzing the major design parameters. An analytical model for the inkjet printhead was established, and numerical analysis of the coupled first-order differential equation for the defined state variables was performed using state equations. To design the dimension of the inkjet printhead with a driving frequency of 100 kHz, the characteristics of the flow rate and discharge pressure of the nozzle were analyzed with respect to design variables of the flow chamber, effective sound wave velocity, driving voltage, and voltage waveform. It was predicted that the change in the height of the flow chamber does not significantly affect the Helmholtz resonance frequency and discharge speed of the nozzle. From the analysis of change in flow chamber width, it is observed that as the width of the flow chamber increases, the ejection speed greatly increases and the Helmholtz resonance frequency decreases considerably, thereby substantially affecting the performance of the inkjet printhead.

• 한국정보통신학회:학술대회논문집
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• 한국정보통신학회 2016년도 추계학술대회
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• pp.703-705
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• 2016

본 논문에서는 광대역 특성을 갖는 이동통신 RF 모듈의 수동 혼변조 왜곡신호를 측정할 수 있는 시스템을 개발하였다. 광대역 특성을 나타내기 위하여 RF 수신단에서 저 잡음 특성과 광대역 특성을 만족하는 수신기를 설계하였으며 RF 수신 단에서 넓은 동적영역(high dynamic range)을 나타내도록 하였다. 설계된 수동 혼변조 왜곡 측정시스템에서 FPGA/DSP를 적용하여 측정된 PIMD신호를 PC에 기록하도록 프로그램 하였다. 650MHz-2700MHz 까지 가변하여 제3차 혼변조 왜곡신호를 측정하여 최고 -138dB를 나타내었다.

• Advances in aircraft and spacecraft science
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• 제6권3호
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• pp.225-238
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• 2019

A spike attached to a blunt nosed body significantly alters its flow field and influences the aerodynamic coefficients at hypersonic speed. The basic body is an axisymmetric, with a hemisphere nose followed by a cylindrical portion. Five different types of spikes, namely, conical aerospike, hemisphere aerospike, flat-face aerospike, hemisphere aerodisk and flat-face aerodisk are attached to the basic body in order to assess the aerodynamic characteristic. The spiked blunt body without the aerospike or aerodisk has been set to be a basic model. The coefficients of drag, lift and pitching moment were measured with and without blunt spike body for the length-to-diameter ratio (L/D) of 0.5, 1.0, 1.5 and 2.0, at Mach 6 and angle of attack up to 8 degrees using a strain gauge balance. The measured forces and moment data are employed to determine the relative performance of the aerodynamic with respect to the basic model. A maximum of 77 percent drag reduction was achieved with hemisphere aerospike of L/D = 2.0. The comparison of aerodynamic coefficients between the basic model and the spiked blunt body reveals that the aerodynamic drag and pitching moment coefficients decrease with increasing the L/D ratio and angle of attack but the lift coefficient has increasing characteristics.

• Advances in concrete construction
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• 제13권3호
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• pp.223-231
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• 2022

The problem is formulated by applying the Kirchhoff's conception for shell theory. The longitudinal modal displacement functions are assessed by characteristic beam ones meet clamped-clamped end conditions applied at the shell edges. The fundamental natural frequency of rotating functionally graded cylindrical shells of different parameter versus ratios of length-to-diameter and height-to-diameter for a wide range has been reported and investigated through the study with fractions laws. The frequency first increases and gain maximum value with the increase of circumferential wave mode. By increasing different value of height-to-radius ratio, the resulting backward and forward frequencies increase and frequencies decrease on increasing height-to-radius ratio. Moreover, on increasing the rotating speed, the backward frequencies increases and forward frequencies decreases. The trigonometric frequencies are lower than that of exponential and polynomial frequencies. Stability of a cylindrical shell depends highly on these aspects of material. More the shell material sustains a load due to physical situations, the more the shell is stable. Any predicted fatigue due to burden of vibrations is evaded by estimating their dynamical aspects.

• 한국군사과학기술학회지
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• 제27권5호
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• pp.558-566
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• 2024

This study proposes method for enhancing the performance of previously developed or produced weapon systems without developing new detection equipment by using Phase Gradient Metasurfaces(PGMS). Metasurface has been studied and utilized a lot to improve the detection performance of inorganic systems, but its utilization is low due to its narrow bandwidth and complex structure. To address some of these limitations, dual-band power focusing PGMS is proposed. Its frequency independent unit cell characteristic enables creating metasurface that concentrates signals in dual-band. The designed PGMS was validated through near-field and far-field measurement, confirming signal concentration at the specified focal length and improved gain in the dual bands.