• 한국음향학회지
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• 제15권1호
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• pp.17-22
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• 1996

소나 시스템에 주로 사용이 되는 평면 배열형 음향 트랜스듀서는 수중에서 음을 방사하여 빔(beam)을 형성하게 된다. 이러한 빔은 트랜스듀서 진동체에서 발생하는 음향 출력이 공간상에 분포되어 일어난다. 따라서 방사 출력의 산출은 트랜스듀서의 성능 및 효율을 예측하는데 필요하다. 본 논문에서는 무한 배플에 고정된 9개의 음향 진동체를 모델로 선정하였다. 개별 진동체에서의 음향 방사량은 자기방사 및 상호방사의 조합으로 표현이 되며 전기적 등가회로 기법을 이용하여 진동체 상호간의 음향 간섭 영향을 고려하여 평면 배열형 음향 트랜스듀서 진동체의 방사 출력 예측 기법을 제안 하였다.

• Journal of the Optical Society of Korea
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• 제10권1호
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• pp.16-22
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• 2006

Wavefront sensing using a Shack-Hartmann sensor has been widely used for estimating wavefront errors or distortions. The sensor combines the local slopes, which are estimated from the centroids of each lenslet image, to give the overall wavefront reconstruction. It was previously shown that the pupil-plane irradiance profile effects the centroid estimation. Furthermore, a previous study reported that the reconstructed wavefront from a planar wavefront with a Gaussian pupil irradiance profile contains large focus and spherical aberration terms when there is a focus error. However, it has not been reported yet how seriously the pupil irradiance profiles, which can occur in practical applications, effect the sensing errors. This paper considered two cases when the irradiance profiles are not uniform: 1) when the light source is Gaussian and 2) when there is a partial interference due to a double reflection by a beam splitting element. The images formed by a Shack-Hartmann sensor were simulated through fast Fourier transform and were then supposed to be detected by a noiseless CCD camera. The simulations found that sensing errors, due to the Gaussian irradiance profile and the partial interference, were found to be smaller than RMS ${\lambda}/50$ when ${\lambda}$ is $0.6328\;{\mu}m$, which can be ignored in most practical cases where the reference and test beams have the same irradiance profiles.

• 한국태양에너지학회:학술대회논문집
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• 한국태양에너지학회 2011년도 추계학술발표대회 논문집
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• pp.232-235
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• 2011

Radiation data are the best source of information for estimating average incident radiation. Lacking this or data from nearby locations of similar climate, it is possible to use empirical relationships to estimate radiation from days of cloudiness. It is necessary to estimate the regression coefficients in order to predict the daily global radiation on a horizontal surface. There fore many different equations have proposed to evaluate them for certain areas. In this work a new correlation has been made to predict the solar radiation for 16 different areas over Korea by estimating the regression coefficients taking into account cloud cover. Particularly, the straight line regression model proposed shows reliable results for estimating the global radiation on a horizontal surface with monthly average deviation of-0.26 to +0.53% and each station annual average deviation of -1.61 to +1.7% from measured values.

• 전기학회논문지
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• 제58권2호
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• pp.415-421
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• 2009

TOA(time-of-arrival) and TDOA(time-difference-of-arrival) positioning techniques are commonly used in many radio-navigation systems. From the literature, it is known that the position estimate and error covariance matrix of TDOA obtained by GN(Gauss-Newton) method is exactly the same as that of TOA when the error source of the range measurement is only an IID white Gaussian noise. In case of geo-location and indoor positioning, however, multi-path or NLOS(non-line-of-sight) error is frequently appeared in range measurements. Though its occurrence is random, the multipath acts like a bias for a stationary user if it occurs. This paper presents the comparisons of error characteristics between TOA and TDOA positioning in presence of multi-path or NLOS error. It is analytically shown that the position estimate of TDOA is exactly the same as that of TOA even when bias errors are included in range measurements with different magnitudes. By computer simulation, position estimation error and error distribution are analyzed in presence of range bias errors.

• 전기학회논문지
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• 제56권11호
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• pp.2040-2050
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• 2007

In this study, we present a novel method for estimating the information of MU(motor unit) which is the basic element of human muscle by using surface EMG. Some of the method developed in this field could only estimate the numbers of MU that is activated. However, in our study the MU-simulator based on the line source model was designed to estimate the MU information including the numbers of MU and muscle fiber, conduction velocity, MU diameter, fiber diameter, and end plate position. The SMUAP(single motor unit action potential) detector was designed and CMAP(compound muscle action potential) by electrical stimulus was recorded. With these data, the MU-simulator can estimate the MU information by varying muscle paramater settings through MSE(mean square error) method. Our results shows that the proposed method can be comparable with the method of anatomical studies. Moreover, our system can be utilized to build a tool for diagnosis and treatment assessment of neuromuscular patients.

• 전기학회논문지
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• 제56권11호
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• pp.2051-2057
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• 2007

In Oriental medicine, the status of a tongue is the important indicator to diagnose one's health like physiological and clinicopathological changes of inner parts of the body. The method of tongue diagnosis is not only convenient but also non-invasive and widely used in Oriental medicine. However, tongue diagnosis is affected by examination circumstances a lot like a light source, patient's posture and doctor's condition. To develop an automatic tongue diagnosis system for an objective and standardized diagnosis, segmenting a tongue is inevitable but difficult since the colors of a tongue, lips and skin in a mouth are similar. The proposed method includes preprocessing, graph-based over-segmentation, detecting positions with a local minimum over shading, detecting edge with color difference and estimating edge geometry from the probable structure of a tongue, where preprocessing performs down-sampling to reduce computation time, histogram equalization and edge enhancement. A tongue was segmented from a face image with a tongue from a digital tongue diagnosis system by the proposed method. According to three oriental medical doctors' evaluation, it produced the segmented region to include effective information and exclude a non-tongue region. It can be used to make an objective and standardized diagnosis.

• 한국음향학회지
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• 제37권3호
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• pp.139-146
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• 2018

단상태 소나는 음원의 송신시간과 반사파의 수신시간 정보를 이용하여 표적의 위치를 산출한다. 그러나 음원의 송신시간 정보를 수신센서와 공유하지 않는 비동기 양상태 소나 시스템에서는 표적의 위치를 산출하기 위해 수신센서에서 음원의 직접파(direct blast)를 탐지해야한다. 본 논문에서는 직접파에 대한 PRI(Pulse Repetition Interval)와 적응적인 임계치 추정을 통해 직접파 탐지를 수행하는 기법을 제안한다. 모의 신호 및 해상 실험 데이터를 이용하여 제안하는 기법의 성능을 분석하였고 그 결과 강한 배경소음 및 직접파와 유사한 다수의 표적 반사파가 존재하는 환경에서도 강인한 직접파 탐지 성능을 보여주었다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집B
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• pp.618-623
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• 2001

In a practical vibration isolation system, vibration is transmitted from the source to the receiver through several paths such as more than one inter-connected point and multi-degree of freedom at each connection point. Therefore, the major path investigation for vibration transmission among them is often required in a point of view of isolation. For the path analysis of multi-dimensional vibration isolation system, it is useful to employ the concept of vibration power in high frequency range where radiation of noise from the receiver structure is concerned. The idea is simple to understand and formulate but rather complicated to apply in practice. For an accurate estimation of power flow especially over a high frequency range, it is well known in theory that rotational motions should be taken into consideration together with translational motions at inter-connected points. In reality, however, power transmissions related to rotational terms are often neglected mainly due to difficulties in the instrumentation. In this paper, necessary formula and measurable mechanical quantities for vibration power analysis will be reviewed and experimental results with rotational terms included for compressor system in a commercial air conditioner will be shown.

• 전자공학회논문지SC
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• 제49권4호
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• pp.1-9
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• 2012

본 논문은 금속이나 유리와 같이 정반사 특성을 갖는 경면반사체의 3차원 형상 추정을 위한 영상처리에 관한 것으로, 조명계와 CCD 카메라 및 경면반사체로 이루어진 머신비전 시스템의 기하학적 광로분석을 통해 반사체의 형상이 반사광의 광로에 주는 영향을 수식화하고, 이를 반사체의 3차원 형상 추정에 이용하였다. 즉, 공간적으로 분포된 점광원들이 반사체에 정반사되어 취득된 영상에서, 반사체의 형상에 따라 영상에서의 점광원의 상대적 위치가 변화되므로, 이 변화량을 이용하여 3차원 정보를 추정하는 방법을 제시하고, 실험을 통하여 반사체의 3차원 형상의 추정이 가능함을 보인다.

• International Journal of Reliability and Applications
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• 제13권1호
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• pp.19-35
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• 2012

This paper presents an optimum design of step-stress partially accelerated life test (PALT) plan which allows the test condition to be changed from use to accelerated condition on the occurrence of fixed number of failures. Various life distribution models such as exponential, Weibull, log-logistic, Burr type-Xii, etc have been used in the literature to analyze the PALT data. The need of different life distribution models is necessitated as in the presence of a limited source of data as typically occurs with modern devices having high reliability, the use of correct life distribution model helps in preventing the choice of unnecessary and expensive planned replacements. Truncated distributions arise when sample selection is not possible in some sub-region of sample space. In this paper it is assumed that the lifetimes of the items follow Truncated Logistic distribution truncated at point zero since time to failure of an item cannot be negative. Optimum step-stress PALT plan that finds the optimal proportion of units failed at normal use condition is determined by using the D-optimality criterion. The method developed has been explained using a numerical example. Sensitivity analysis and comparative study have also been carried out.