• Journal of Biosystems Engineering
• /
• 제22권1호
• /
• pp.41-48
• /
• 1997

A nondestructive quality inspection technique using acoustic impulse response method was studied to investigate the feasibility of egg shell inspection. An experimental system was built to generate impact force, to measure the response signal and to analyze the frequency spectrum. This system includes an impulse generating unit, an egg holding seat, a microphone with preamplifier, and a digital oscilloscope connected to Personal Computer by RS-232C interface. The factors such as impulse generating method, egg holding method, and sensor location were evaluated by analyzing the power spectrum density of the measured signal. The results obtained are summarized as follows : 1. From the sampled eggs, the proper conditions for detecting damaged eggs were found as followings; ceramic for the impact ball material, rubber for egg seat material, 20 degrees for an impact angle of pendulum, 10mm for the distance between egg and sensor, the sharp side for impacting part, and 180 degrees for the location of sensor. 2. Examination of the Fourier transformed analysis in beth normal and damaged eggs revealed that those factors such as the resonant frequency, a number of peak frequencies and the magnitude of power spectrum were important to detect damaged eggs.

• International journal of advanced smart convergence
• /
• 제4권2호
• /
• pp.138-144
• /
• 2015

Digital filters are extensively used in the world of communication. In order to design a digital finite impulse response (FIR) filter that satisfies all the required conditions is challenging. In this paper, design techniques of digital low pass FIR filters using Rectangular window method, Hamming window, Hanning window, and Optimal Parks McClellan method are presented. The stability, number of components required and filter coefficients are demonstrated for different design techniques. It is demonstrated that filter design using hamming window is comparatively better than rectangular and hanning window though the components required for all of the windowing technique are same, hamming shows higher stability. The stability is shown with the help of magnitude and phase spectrum of each window. Simulation is carried out using MATLAB and comparisons are made entirely based on the output of the simulation.

• 대한기계학회논문집A
• /
• 제25권11호
• /
• pp.1802-1812
• /
• 2001

The theoretical method is developed to investigate the effects of ring stiffeners on free vibration characteristics and transient response for the ring stiffened composite cylindrical shells subjected to the impulse pressure Loading. In the theoretical procedure, the Love's thin shell theory combined with the discrete stiffener theory to consider the ring stiffening effect is adopted to formulate the theoretical model. The concentric or eccentric ring stiffeners are laminated with composite and have the uniform rectangular cross section. The modal analysis technique is used to develop the analytical solutions of the transient problem. The analysis is based on an expansion of the loads, displacements in the double Fourier series that satisfy the boundary conditions. The effect of stiffener's eccentricity, number, size, and position on transient response of the shells is examined. The results are verified by comparison with FEM results.

• 한국자동차공학회논문집
• /
• 제6권3호
• /
• pp.169-176
• /
• 1998

A method for the dynamic analysis of multibody systems undertaking impulsive force is introduced in this paper. A partial velocity matrix based on Kane's method is introduced to reduce the number of equations to be solved. Only minimum number of equations of motion can be obtained by using the partial velocity matrix. This reduces the computational effort significantly to obtain the dynamic response of the system. At the very moment of the impulse, instead of using the numerical integrator to solve the equations of motion, the impulse and momentum principle is used to obtain the dynamic response. The impulse as wall as the reaction force acting on the kinematic joints can easily calculated too.

• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2001년도 추계학술대회논문집 II
• /
• pp.586-591
• /
• 2001

Dynamic analysis using impulse responses is formulated to estimate effect of slider rail shape on dynamic responses. Impulse responses are obtained on numerical nonlinear model including rigid motion of slider and fluid motion of air bearing under the slider. Dynamic characteristics of slider motion are evaluated by utilizing the decay ratio of impulse responses and modal frequencies from frequency response functions. The dynamic characteristics of the developed NFR(Near Field Recording) slider are checked by comparing those of HDD sider(Nutcracker). Also, sensitivities of slider position conditions and rotation speed on the dynamic characteristics are investigated. The researches show that the utilized method is a good indicator of designing the better slider.

• 지구물리와물리탐사
• /
• 제16권1호
• /
• pp.45-52
• /
• 2013

본 연구에서는 판상 구조물의 비파괴시험을 위한 충격응답시험기 및 운용 소프트웨어를 개발하였으며, 콘크리트 또는 아스팔트로 포장된 인도에서 충격응답 자료 취득 시험을 실시하였다. 현장 자료 취득 시험에서 개발된 시스템은 안정적으로 신속하게 충격응답반응을 측정하였다. 현장 시험 결과, 포장재 특성에 따라 동적강성, 평균운동성 등의 절대 값이 크게 변화 하였다. 또한 일부 구간에서는 포장재 또는 하부 지반의 변화를 반영하는 것으로 판단되는 값의 변화가 측정되었다. 본 연구를 통해 만들어진 시스템은 판상구조물의 상태에 대한 정보를 쉽고 빠르게 획득할 수 있을 것으로 판단된다. 본 연구에서 개발된 장비를 이용하여 조사 대상물에 대한 2차원 측정과 모니터링을 한다면, 구조물의 유지 보수에 유용한 정보를 얻을 수 있을 것으로 기대된다.

• 대한전기학회:학술대회논문집
• /
• 대한전기학회 1987년도 전기.전자공학 학술대회 논문집(II)
• /
• pp.1252-1255
• /
• 1987

In this paper an approach for the analysis of the transient field response of radially symmetric transducer due to a wideband ultrasonic pulse is presented, which is based on a development of Green's function and applies the linear system theory to obtain an analytic expression for the impulse response of an annulus with a planar or spherical geometry. For the focused annular array, the impulse responses of the indivisual annuli are convolved with the delayed excitation pulse, and then summed to obtain the resultant response of the array. This process is very effective in the study of the various focusing abilities of the annular array. For illustration, the field distribution of a five element annular array is treated in detail for several focusing system.

• 제어로봇시스템학회:학술대회논문집
• /
• 제어로봇시스템학회 1992년도 한국자동제어학술회의논문집(국제학술편); KOEX, Seoul; 19-21 Oct. 1992
• /
• pp.164-169
• /
• 1992

Classical methods for estimating transfer function models have not always been successful. A statistic approach to the identification of transfer function models which is corrupted by disturbances or noise is presented. The estimated impulse response is obtained from the autocorrelation function and cross correlation function between the measured input and output. Several data analysis tools such as R- , S- and GPAC array for the estimated impulse response give us pretty clear information on the order of transfer function models.

• 한국지반환경공학회 논문집
• /
• 제12권4호
• /
• pp.53-63
• /
• 2011

동적 지진해석 수행 시 적절한 입력지진파를 선정 생성하는 것은 매우 중요하다. 현재 국내에서는 일반적으로 국외에서 계측된 강진 기록이나 인공지진파가 입력지진파로 사용된다. 계측지진기록은 지진파의 고유성질인 시간에 따라서 주파수 특성이 변이하는 비정상(Non-Stationary) 특성을 가지고 있지만 설계 응답스펙트럼과는 일치하지 않으며 주파수영역에서 생성된 인공지진파는 설계 응답스펙트럼과는 일치하지만 정상(Stationary) 특성을 가지고 있는 단점이 있다. 본 연구에서는 계측기록의 Non-stationary 특성을 보존하되 동시에 설계 응답스펙트럼에 상응하는 지진파를 생성하였다. 적용된 기법은 Impulse 함수를 이용하여 시간영역에서 지진기록을 목표 스펙트럼에 상응하도록 보정하는 알고리즘이다. 적용 결과, 시간영역 변화 알고리즘은 성공적으로 계측 지진기록을 설계 응답스펙트럼와 일치하도록 조정할 수 있으며 원 지진기록의 Non-stationary 특성을 보존하는 것으로 나타났다. 나아가 계측 지진기록과 보정된 지진기록을 적용한 비선형 지반응답해석을 수행한 결과, 보정된 지진파를 이용한 결과가 보다 합리적인 것으로 나타났다. 본 연구에서 변환된 지진기록은 기존 기록의 문제점을 보완하는 진보된 입력지진파인 것으로 나타났으며 추후 지진해석 시 이를 준용하는 것이 합리적일 것으로 판단된다.

• Journal of Korea Trade
• /
• 제23권5호
• /
• pp.87-101
• /
• 2019

Purpose - This paper examines the effectiveness of the foreign exchange risk insurance system in the promotion of SME exports in Korea. The purpose of this study is to analyze the short-term and long-term responses of SME exports to foreign exchange risk insurance support policies. Based on these empirical studies, we would like to present some operational improvements to the operation of the foreign exchange risk insurance system. Design/methodology - In order to analyze the effect of exchange risk insurance on the exports of SMEs, a VAR model consisting of foreign exchange risk insurance underwriting values, export relative price, and domestic demand pressure, including export volume, was established. The study began with tests of the stationarity of time series data. The unit root tests showed that all concerned variables were non-stationary. Accordingly, the results of the cointegration test showed that the tested variables are not cointegrated. Finally, an impulse response function and variance decomposition analysis were conducted to analyze the impulse of foreign exchange risk insurance on exports of SMEs. Findings - As a result of estimating the VAR (1) model, foreign exchange risk insurance was found to be significant at a 1% significance level for SME' export promotion. In the impulse response analysis, SMEs' export response to the impulse of foreign exchange risk insurance showed that exports gradually increased until the third quarter, and then slowed down. However, the impulse did not disappear, and appeared continuously. Originality/value - This study analyzed the effect of foreign exchange insurance on exports of SMEs by applying the VAR model. In particular, this study is the first to analyze the short-term and long-term effects of foreign exchange risk insurance on exports of SMEs. The empirical evidence in the current study have a policy implication for the policy authority to support and promote the foreign exchange risk insurance in the effect of exchange rate volatility on Korea' export SMEs.