• 한국소음진동공학회논문집
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• 제16권12호
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• pp.1192-1200
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• 2006

Viscoelastic damping materials are widely used to reduce noise and vibration because of its low cost and easy implementation, for examples, on the body structure of passenger cars, air planes, electric appliances and ships. To design the damped structures, the material property such as elastic modulus and loss factor is essential information. The four-parameter fractional derivative model well describes the dynamic characteristics of the viscoelastic damping materials with respect to both frequency and temperature. However, the identification procedure of the four-parameter is very time-consuming one. In this study a new identification procedure of the four-parameters is proposed by using an FE model and a gradient-based numerical search algorithm. The identification procedure goes two sequential steps to make measured frequency response functions(FRF) coincident with simulated FRFs: the first one is a peak alignment step and the second one is an amplitude adjustment step. A numerical example shows that the proposed method is useful in identifying the viscoelastic material parameters of fractional derivative model.

• 한국통신학회논문지
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• 제24권9A호
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• pp.1329-1338
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• 1999

본 논문에서, LMS 알고리즘의 수렴 속도를 향상시키기 위한 효율적인 신호간섭 제어기법을 제안한다. 수신 데이터를 재활용하여 심볼 시간 주기에 계수들을 곱함으로써 적응되는 제안된 알고리즘의 수렴특성이 수렴 속도의 향상을 이론적으로 증명하기 위해 분석한다. 스텝-크기 매개변수 $\mu$가 증가됨에 따라 알고리즘의 수렴 속도가 제어된다. 또한, 스텝-크기 매개변수 $\mu$의 증가는 실험적으로 계산된 학습 곡선에서 분산을 감소시키는 효과를 갖는다. 고유치 확산을 증가시킴에 따라 적응 등화기의 수렴속도를 천천히 제어하고 평균 자승 에러의 안정-상태 값을 증가시키는 효과를 나타내며 데이터-재사용 LMS 기술이 수렴속도를 (B+1)배만큼 증가시켜 필터 알고리즘에서 신호간섭제어의 우수성을 입증한다.

• 한국광학회지
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• 제8권3호
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• pp.250-253
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• 1997

광선로에 존재하는 분산의 영향은 외부 변조기에서 일어나는 Chirp현상과 비선형 현상인 SPM에 따라서 달라지게 된다. SPM의 영향은 신호 파워에 따라 달라지게 되고, 외부 변조하에서의 Chirp은 외부 변조기의 변조 조건에 따라 달라진다. 따라서 광통신 시스템에서는 분산과 SPM, 그리고 처핑 현상을 적절히 이용하여 수신 감도 저하를 최소화할 수 있게 된다. 주어진 광통신 시스템의 광신호 세기 분포 하에서 SPM과 외부 변조기 Chirp을 고려하여 신호 펄스폭의 변화를 Split Step Fourier 방법을 이용하여 수치해석하였으며, 400 km 전송을 목표로 한 경우 수신 감도 저하를 최소화하는 최저의 Chirp인자 값을 얻을 수 있었다. 또한 실제 전송 실험을 통하여 계산 결과와 비교하였다.

• PNF and Movement
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• 제6권2호
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• pp.19-30
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• 2008

Purpose : This study was performed for find out temporal spatial parameter of the gait according to age. Method : Four groups of healthy people were allocated randomly in this study : group I(little child, 15), group II(child, 18) and group III(young people, 17), group(elder people, 16). This study was performed from 01 December to 31 December in 2007. Results : The results were as follows : 1. The swing phase was the longest group II, group IV was the shortest. Each groups, there was significant difference in swing phase(p<.05). 2. The stance phase was the longest group IV, group II was the shortest. Each groups, there was significant difference in stance phase(p<.05). 3. The single support time was the longest group II, group IV was the shortest. Each groups, there was significant difference in single support time(p<.05). 4. The double support time was the longest group IV, group II was the shortest. Each groups, there was significant difference in double support time(p<.05). 5. The gait velocity was the fastest group II, group I was the slowest. Each groups, there was significant difference in gait velocity(p<.05). 6. The toe in/out was very increased group IV, group I was very decreased. Each groups, there was significant difference in toe in/out(p<.05). 7. The cadence was the highest group I, group IV was the lowest. Each groups, there was significant difference in cadence(p<.05). 8. The step length was the longest group III, group I was the shortest. Each groups, there was significant difference in step length(p<.05). 9. The step length asymmetry ratio was the highest group IV, group III was the lowest. Each groups, there was no significant difference in step length asymmetry ratio(p>.05). 10. The single support time asymmetry ratio was the highest group I, group IV was the lowest. Each groups, there was no significant difference in single support time asymmetry ratio (p>.05). 11. The FAP was the highest group III, group I was the lowest. Each groups, there was significant difference in FAP(p<.05).

• 지질공학
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• 제20권2호
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• pp.203-212
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• 2010

본 연구는 연구지역의 수리상수를 추정하여 오염된 지하수의 정화공법 설계에 효과적으로 사용하는데 목적이 있다. 이를 위하여 수행된 수리시험은 순간수위변화시험, 단공양수시험 및 단계양수시험이다. 순간수위변화시험은 대표적인 Bouwer and Rice 직선법과 C-B-P 특성곡선법(type curve)으로 해석하였다. Bouwer and Rice법으로 해석한 평균 수리전도도 값은 $4.48{\times}10^{-3}cm/sec$ 이며 중앙값은 $1.16{\times}10^{-3}cm/sec$이다. C-B-P법으로 구한 평균 수리전도도 값은 $2.37{\times}10^{-3}cm/sec$이며 중앙값은 $7.09{\times}10^{-4}cm/sec$이다. 두 해석 결과 연구지역의 하부가 화강암으로 이루어져 있어 대체로 투수성이 낮아 Bouwer and Rice법으로 해석한 수리전도도가 높게 나타난다. 단공양수시험은 GW7, GW12 및 MW9 관정에서 수행하였으며 여러 종류의 특성곡선법을 적용하여 해석하였다. GW7 관정은 GW12 및 MW9 관정보다 수리전도도 및 투수량 계수가 낮으며 이는 기반암의 파쇄대 및 절리의 여부와 관련된 것으로 판단된다. 단계양수시험은 KDPW1 및 KDPW2 관정에서 수행하였으며 해석방법에 따라 수리상수 값의 차이가 나타나지만 매우 미미하며 본 연구에서 해석한 수리상수 값은 오염지하수 정화설계에 있어 적절히 활용될 것으로 판단된다.

• 한국자동차공학회논문집
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• 제23권1호
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• pp.56-64
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• 2015

This study presents a model-based gain scheduling strategy for PI-based EGR controllers. The air-to-fuel ratio is used as an indirect measurement of the EGR rate. In order to cope with the nonlinearity and parameter varying characteristics of the EGR system, we proposed a static gain model of the EGR system using a new scheduling parameter. With the 810 steady-state measurements, the static gain model achieved 0.94 of R-squared value. Based on the static gain of the EGR system, the PI gains were robustly designed using quantitative feedback theory. Consequently, the gains of the PI controller are scheduled according to the static gain parameter of the EGR path in runtime. The proposed model-based gain scheduling strategy was validated through various operating conditions of engine experiments such as setpoint step responses and disturbance rejections.

• Steel and Composite Structures
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• 제31권5호
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• pp.469-488
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• 2019

We in this paper study nonlinear bending of a functionally graded porous nanobeam subjected to multiple physical load based on the nonlocal strain gradient theory. For more reasonable analysis of nanobeams made of porous functionally graded magneto-thermo-electro-elastic materials (PFGMTEEMs), both constituent materials and the porosity appear gradient distribution in the present expression of effective material properties, which is much more suitable to the actual compared with the conventional expression of effective material properties. Besides the displacement function regarding physical neutral surface is introduced to analyze mechanical behaviors of beams made of FGMs. Then we derive nonlinear governing equations of PFGMTEEMs beams using the principle of Hamilton. To obtain analytical solutions, a two-step perturbation method is developed in nonuniform electric field and magnetic field, and then we use it to solve nonlinear equations. Finally, the analytical solutions are utilized to perform a parametric analysis, where the effect of various physical parameters on static bending deformation of nanobeams are studied in detail, such as the nonlocal parameter, strain gradient parameter, the ratio of nonlocal parameter to strain gradient parameter, porosity volume fraction, material volume fraction index, temperature, initial magnetic potentials and external electric potentials.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2007년도 춘계학술대회 논문집
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• pp.332-335
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• 2007

The superplastic forming (SPF) has been widely used in the automotive and aerospace industry because it has great advantages to produce very light and strong components. Finite element method (FEM) is used to model the process of superplastic forming/diffusion bonding (SPF/DB), to predict the pressure-time curve and to analyze the process parameter. In this study, process design of SPF/DB is carried out a 3-sheet sandwich part. SPF/DB process with pressure control was analyzed by using finite element method. For obtaining proper shape, step-by-step pressurization is proposed. The first step of SPD/DB process is obtained by applying of pressure in patches. From the next step it applied pressure to all regions (between inner sheets, between inner and face sheets). By using the proposed pressurization scheme, deficit in part shape is found to be eliminated.

• IEIE Transactions on Smart Processing and Computing
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• 제1권2호
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• pp.78-87
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• 2012

In this paper, we address the tracking problem caused by camera motion and rolling shutter effects associated with CMOS sensors in consumer handheld cameras, such as mobile cameras, digital cameras, and digital camcorders. A modified particle filtering method is proposed for simultaneously tracking objects and compensating for the effects of camera motion. The proposed method uses an elastic registration algorithm (ER) that considers the global affine motion as well as the brightness and contrast between images, assuming that camera motion results in an affine transform of the image between two successive frames. By assuming that the camera motion is modeled globally by an affine transform, only the global affine model instead of the local model was considered. Only the brightness parameter was used in intensity variation. The contrast parameters used in the original ER algorithm were ignored because the change in illumination is small enough between temporally adjacent frames. The proposed particle filtering consists of the following four steps: (i) prediction step, (ii) compensating prediction state error based on camera motion estimation, (iii) update step and (iv) re-sampling step. A larger number of particles are needed when camera motion generates a prediction state error of an object at the prediction step. The proposed method robustly tracks the object of interest by compensating for the prediction state error using the affine motion model estimated from ER. Experimental results show that the proposed method outperforms the conventional particle filter, and can track moving objects robustly in consumer handheld imaging devices.

• 대한의용생체공학회:학술대회논문집
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• 대한의용생체공학회 1998년도 추계학술대회
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• pp.201-202
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• 1998

In this paper we suggested an automated method for detecting and counting rapid eye movement(REM) using EOG during sleep. This method is formulated by two step fuzzy logic. At first step, the velocity and the distance of single channel eye movement are used for the fuzzy input to get the possibility of being REM at each EOG. At second step, the two possibility values of both EOG from the first step and the correlation coefficient of both eye movements are used for the fuzzy logic input, and the output is the final possibility of being Rapid Eye Movement. We applied this algorithm to the normal and narcoleptic sleep data and compared the difference. We found the possibility that the count of REM can be a parameter that has significant physiological meanings.