• 한국통신학회논문지
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• 제35권3C호
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• pp.278-286
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• 2010

DTV의 Full HD급이 보편화되면서 LCD(Liquid Crystal Display)기반 대형화와 고화질 요구가 급속도로 증대되고 있다. 이에 LCD의 잔상효과 제거와 격동적인 화면에서의 고화질 구현을 위해 수신 단에서 후처리 과정으로 움직임 보상 기반 프레임 보간법(MCFI)이 사용되고 있다. 이때 움직임 예측 시 구현의 용이성 때문에 블록정합기법(BMA)이 가장 많이 사용되고 있지만 여러 가지 문제점을 보여주고 있다. 본 논문에서는 움직임 정보의 정확성을 높이고 움직임 예측의 계산량 감소를 위하여 움직임 형태 기반의 움직임 예측 기법을 제안 한다. 움직임 정보의 정확성 향상을 위하여 움직임 형태를 기반으로 움직임 예측을 수행한다. 그리고 계산양 감소를 위하여 움직임 영역에서만 예측을 수행하는데 제안한 방법은 전 영역 움직임 예측기의 평균 25% 계산양만으로 비슷한 성능의 결과를 보여주고 있으며 특히 빠른 움직임 영역에서는 다른 여러 가지 움직임 예측 기법들 보다 우월한 성능을 보여준다.

• 상하수도학회지
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• 제22권1호
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• pp.105-112
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• 2008

Disinfection is a basic and effective microorganism inactivation method and historically contributed a decrease in waterborne diseases. To guarantee the disinfection ability, improving T in CT value is important. Many indexes are used to estimate the hydraulic efficiency, however, these are black-box analysis. Therefore it is need to develope new estimation method. In this study, internal short-circuiting estimation method (ISEM) is developed using CFD and we inquire into the factor which causes increase of $T_{10}/T$ value as LW ratio increases. And the effect of shape on the relation of LW ratio and $T_{10}/T$ is analyzed. As LW ratio increases, internal short-circuiting index (ISI) of influent and effluent zone is rapidly reduced and recirculation and dead zone are reduced in channel zone. Therefore, as the $T_{10}/T$ value converges maximum value, ISI curve is changed from "V" shape to "U" shape and hydraulic efficiency is improved especially in downstream portion of clearwell. The less the shape ratio(width/length of clearwell) is the less the $T_{10}/T$ value is at a same LW ratio because the portion of turning zone increases as shape ration decreases, therefore more boundary separation is generated.

• 비파괴검사학회지
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• 제36권6호
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• pp.460-465
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• 2016

배관 구조물은 긴 길이를 가지며, 일정한 거리에 위치한 고정부에 설치되거나, 지중에 매설된다. 따라서 자중 또는 지반의 움직임으로 변형과 처짐이 발생하기 쉽다. 이러한 배관의 건전성 평가에는 형상 감시 기법이 매우 유용할 수 있다. 광섬유 브래그 격자 센서 (fiber Bragg grating, FBG)는 다중화의 장점이 있어 배관과 같이 긴 길이를 가지는 구조물의 여러 지점에서 변형률 측정에 매우 유용하다. 본 연구에서는 배관의 건전성 평가를 위하여 변형률 기반의 형상추정기법을 제안하였다. 제안된 기법의 유용성을 확인하기 위하여 실험을 통한 검증을 수행하였다. 실험 결과 제안된 FBG를 이용한 형상추정기법이 시험편의 변형에 따라 유사한 형상을 표현할 수 있음을 확인하였다. 또한, 형상추정기법을 통해 도출된 처짐량이 실제 배관에 가해진 처짐과 동일하게 계산됨을 확인하였다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1996년도 한국자동제어학술회의논문집(국내학술편); 포항공과대학교, 포항; 24-26 Oct. 1996
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• pp.792-795
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• 1996

In TIG welding of pipe, back bead size monitoring is important for weld quality assurance. Many researches have been performed on estimation of the back bead size by heat conduction analysis. However numerical conduction model based on many uncertain thermal parameters causes remarkable errors and thermomechanical phenomena in molten pool can not be considered. In this paper, filler wire feeding force in addition to weld current, wire feedrate, torch travel speed and orbital position angle is monitored to estimate back bead size in orbital TIG welding. Monitored welding process variables are fed into an artificial neural network estimator which has been trained with the monitored process variables (input patterns) and actual back bead size (output patterns). Experimental verification of the proposed estimation method was performed. The predicted results are in a good agreement with the actual back bead shape. The results are quite promising in that estimation of invisible back bead shape can be achieved by analyzing the welding parameters without any conventional NDT of welds.

• 한국음향학회지
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• 제19권3호
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• pp.72-76
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• 2000

칼만 필터를 이용한 2차원 견인 배열 (towed may) 형상 추정 기법의 성능을 개선하는 방법을 제안한다. 변위 센서를 이용할 경우, 기존의 칼만 여파기 방법에 의해 추정된 2차원 하이드로폰 수평 좌표는 총 길이가 배열의 길이와 일치하며 등간격 값을 갖게 된다. 이렇게 고정된 수평 좌표를 사용하는 경우 배열의 왜곡 정도가 심화됨에 따라 오차가 증가하게 된다. 이를 개선하기 위해 선형 근사화 방법 또는 스플라인 보간법을 이용하여 발생하는 오차를 줄일 수 있는 방법을 제안하고 컴퓨터 모의 실험을 통해 그 성능을 검증한다.

• 한국정보전자통신기술학회논문지
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• 제15권4호
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• pp.237-242
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• 2022

관제 및 측정 시스템 등에서 고품질 영상을 획득하는 것은 중요한 요소 중 하나이다. 영상 획득 기술 중에서 SFF (Shape from Focus)는 물체를 광축 방향으로 사전에 결정된 스텝 사이즈로 이동시킴으로써 초점 정도가 다른 2D 영상들을 획득함으로써 삼차원 형상을 복원하는 기술이다. SFF를 위해 일정한 스텝 사이즈로 물체를 이동시킬 때 각 스텝에서 광축 방향으로 기계 진동, 즉 지터 노이즈가 발생한다. 본 논문에서는 이 지터 노이즈의 영향을 줄이기 위해 새로운 상태 추정 필터를 설계 및 적용한다. 제안된 방법의 적용을 위해 지터 노이즈와 초점 커브는 가우시안 함수로써 모델링한다. 실험 결과들을 통해 제안된 방법의 효율성을 증명한다.

• Structural Engineering and Mechanics
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• 제88권1호
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• pp.83-94
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• 2023

An accurate and highly efficient inverse element labelled iPCB is developed based on the inverse finite element method (iFEM) for real-time shape estimation of plane-curved structures (such as arch bridges) utilizing onboard strain data. This inverse problem, named shape sensing, is vital for the design of smart structures and structural health monitoring (SHM) procedures. The iPCB formulation is defined based on a least-squares variational principle that employs curved Timoshenko beam theory as its baseline. The accurate strain-displacement relationship considering tension-bending coupling is used to establish theoretical and measured section strains. The displacement fields of the isoparametric element iPCB are interpolated utilizing nonuniform rational B-spline (NURBS) basis functions, enabling exact geometric modelling even with a very coarse mesh density. The present formulation is completely free from membrane and shear locking. Numerical validation examples for different curved structures subjected to different loading conditions have been performed and have demonstrated the excellent prediction capability of iPCBs. The present formulation has also been shown to be practical and robust since relatively accurate predictions can be obtained even omitting the shear deformation contributions and considering polluted strain measures. The current element offers a promising tool for real-time shape estimation of plane-curved structures.

• Structural Engineering and Mechanics
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• 제68권4호
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• pp.399-408
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• 2018

Cable supported structures have been widely used in civil engineering. Cable tension estimation has great importance in cable supported structures' analysis, ranging from design to construction and from inspection to maintenance. Even though the Bernoulli-Euler beam element is commonly used in the traditional finite element method for calculation of frequency and cable tension estimation, many elements must be meshed to achieve accurate results, leading to expensive computation. To improve the accuracy and efficiency, a dynamic finite element method for estimation of cable tension is proposed. In this method, following the dynamic stiffness matrix method, frequency-dependent shape functions are adopted to derive the stiffness and mass matrices of an exact beam element that can be used for natural frequency calculation and cable tension estimation. An iterative algorithm is used for the exact beam element to determine both the exact natural frequencies and the cable tension. Illustrative examples show that, compared with the cable tension estimation method using the conventional beam element, the proposed method has a distinct advantage regarding the accuracy and the computational time.

• Journal of Information Technology Applications and Management
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• 제25권4호
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• pp.115-122
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• 2018

Software reliability has the greatest impact on computer system reliability and software quality. For this software reliability analysis, In this study, we compare and analyze the trends of the properties affecting the reliability according to the shape parameters of Erlang distribution based on the finite fault NHPP. Software failure time data were used to analyze software failure phenomena, the maximum likelihood estimation method was used for parameter estimation. As a result, it can be seen that the intensity function is effective because it shows a tendency to decrease with time when the shape parameters a = 1 and a = 3. However, the pattern of the mean value function showed an underestimation pattern for the true values when the shape parameters a = 1 and a = 2, but it was found to be more efficient when a = 3 because the error width from the true value was small. Also, in the reliability evaluation of the future mission time, the stable and high trend was shown when the shape parameters a = 1 and a = 3, but on the contrary, when a = 2, the reliability decreased with the failure time. Through this study, the property of finite fault NHPP Erlang model according to the change of shape parameter without existing research case was newly analyzed, and new research information that software developers can use as basic guideline was presented.

• Journal of the Korean Data and Information Science Society
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• 제25권3호
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• pp.623-632
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• 2014

We shall consider the estimation for the parameter and the right tail probability in a general exponential distribution. We also shall consider the estimation of the reliability P(X < Y ) and the skewness trends of the density function of the ratio X=(X+Y) for two independent general exponential variables each having different shape parameters and known scale parameter. We then shall consider the estimation of the failure rate average and the hazard function for a general exponential variable having the density function with the unknown shape and known scale parameters, and for a bivariate density induced by the general exponential density.