• 한국구조물진단유지관리공학회 논문집
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• 제14권2호
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• pp.184-192
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• 2010

철근콘크리트 구조물의 사용성을 검토할 때 처짐은 가장 중요한 사항 중 하나이며, 철근콘크리트 휨 부재의 처짐은 일반적으로 유효 단면2차모멘트의 개념을 적용하여 구해진다. 그러나 이미 사용중인 철근콘크리트 보에서 정확한 사용하중을 알기 어려운 경우에는 기존의 방법으로 처짐을 계산하는 것이 쉽지 않다. 따라서, 이 연구에서는 철근콘크리트 보에서 균열과 처짐은 상호 밀접한 관련이 있다는 사실을 바탕으로 작용하는 하중의 크기에 무관하게 철근 콘크리트 보 부재의 균열 상태로부터 처짐을 쉽게 산정할 수 있는 방법을 제안하고자 하였다. 균열폭의 합, 평균변형률 및 곡률 등의 관계를 이용하여 처짐식을 제안하였으며, 수정계수를 적용하여 보다 정확한 처짐식을 제안하고자 하였다. 이 제안식을 사용할 경우, 철근콘크리트 보에 작용하는 하중 크기에 무관하게 균열을 측정함으로써 처짐 추정치를 얻을 수 있으며, 유효 단면 2차 모멘트 값을 산출하여 처짐을 산정하는 기존의 방법에 비해 비교적 간단하게 처짐을 산출 할 수 있다.

• 대한의용생체공학회:의공학회지
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• 제30권1호
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• pp.10-17
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• 2009

Accurate electroencephalography (EEG) forward calculation is of importance for the accurate estimation of neuronal electrical sources. Conventional studies concerning the EEG forward problems have investigated various factors influencing the forward solution accuracy, e.g. tissue conductivity values in head compartments, anisotropic conductivity distribution of a head model, tessellation patterns of boundary element models, the number of elements used for boundary/finite element method (BEM/FEM), and so on. In the present paper, we investigated the influence of modeling errors in the boundary element volume conductor models upon the accuracy of the EEG forward solutions. From our simulation results, we could confirm that accurate construction of boundary element models is one of the key factors in obtaining accurate EEG forward solutions from BEM. Among three boundaries (scalp, outer skull, and inner skull boundary), the solution errors originated from the modeling error in the scalp boundary were most significant. We found that the nonuniform error distribution on the scalp surface is closely related to the electrode configuration and the error distributions on the outer and inner skull boundaries have statistically meaningful similarity to the curvature distributions of the boundary surfaces. Our simulation results also demonstrated that the accumulation of small modeling errors could lead to considerable errors in the EEG source localization. It is expected that our finding can be a useful reference in generating boundary element head models.

• 한국정밀공학회지
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• 제19권6호
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• pp.43-50
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• 2002

In the design of structure, the forces acting on tai structure are key parameter fur noise and vibration control. However, in the complex structure, the forces at the injection point on the structure cannot be measured directly. So, it is necessary to find out Indirect force evaluation method. In this paper, forces have been measured with In-situ vibration responses and system information. And, three existing techniques of indirect force measurement, vita. direct inverse. principal component analysis and regularization have been compared. This paper shows that multi-vibration responses are essential for talc precise estimation of the forces. To check these conditions, rotary compressor is adopted as test sample, because it is very difficult to measure the injection forces from internal excitation to shell. It alas also been obtained that relatively higher force is transmitted through three welding paths to the compressor shell. It shows a good agreement between direct and indirect force evaluation with curvature shell and plate.

• 한국정밀공학회지
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• 제23권6호
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• pp.119-127
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• 2006

A non-destructive time domain approach to examine structural damage using parameterized partial differential equations and Galerkin approximation techniques is presented. The time domain analysis for damage detection is independent of modal parameters and analytical models unlike frequency domain methods which generally rely on analytical models. The time history of the vibration response of the structure was used to identify the presence of damage. Damage in a structure causes changes in the physical coefficients of mass density, elastic modulus and damping coefficients. This is a part of our ongoing effort on the general problem of modeling and parameter estimation for internal damping mechanisms in a composite beam. Namely, in detecting damage through time-domain or frequency-domain data from smart sensors, the common damages are changed in modal properties such as natural frequencies, mode shapes, and mode shape curvature. This paper examines the use of beam-like structures with piezoceramic sensors and actuators to perform identification of those physical parameters, and detect the damage. Experimental results are presented from tests on cantilevered composite beams damaged at different locations and different dimensions. It is demonstrated that the method can sense the presence of damage and obtain the position of a damage.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2001년도 유체기계 연구개발 발표회 논문집
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• pp.37-42
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• 2001

A computerized axial flow fan design system is developed with the capabilities for predicting the aerodynamic performance and the noise characteristics of fan. In the present study, the basic fan blading design is made by combining vortex distribution scheme with camber line design, airfoil selection, blade thickness distribution and stacking of blade elements. With the designed fan blade geometry, the through-flow field and the performance of fan are analyzed by using the streamline curvature computing scheme with spanwise total pressure loss and flow deviation models. Fan noise is assumed to be generated due to the pressure fluctuation induced by wake vortices of fan blades and to radiate as dipole distribution. The vortex-induced fluctuating pressure on blade surface is calculated by combining thin airfoil theory and the predicted flow field data. The predicted performances, sound pressure level and noise directivity patterns of fan by the present method are favorably compared with the test data of actual fans. Furthermore, the present method is shown to be very useful in designing the blade geometry of new fan and optimizing design variables of the fan to achieve higher efficiency and lower noise level.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1997년도 추계학술대회 논문집
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• pp.286-289
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• 1997

In the design of structure the forces acting on the structure are important parameter for noise and vibration control. However, in the complex structure, the forces at the injection pomt on the structure cannot be measured directly. Thus it is necessary to find out indirect force evaluation method. In thls paper forces have been measured with in-situ vibration responses and system information. Three existing techniques of indirect force measurement, viz. direct inverse, principal component analysis and regularization have been compared. It has been shown that multi-vibration responses are essential for the precise estimation of the forces. To satisfy those cond~tions, Rotary compressor is adopted as test sample, because it is very difficult to measurc the injection forces from internal excitat~on to shell. It has also been obtained that relatively higher force IS transmitted through three welding paths to the compressor shell. It shows a good agreement between direct and indirect force evaluation wlth curvature shell and plate and is investigated the possibility of force evaluation of rotary compressor as a complex structure.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1997년도 추계학술대회 논문집
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• pp.564-567
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• 1997

In the design of structure the forces acting on the structure are important parameter for noise and vibration control. However, in the complex structure, the forces at the injection point on the structure cannot be measured directly. Thus it is necessary to find out indirect force evaluation method. In this paper forces have been measured with in-situ vibration responses and system information. Three existing techniques of indirect force measurement, viz. direct inverse, principal component analysis and regularization have been compared. It has been shown that multi-vibration responses are essential for the precise estimation of the forces. To satisfy those conditions, Rotary compressor is adopted as test sample, because it is very difficult to measure the injection forces from internal excitation to shell. It has also been obtained that relatively higher force is transmitted though three welding paths to the compressor shell. It shows a good agreement between direct and indirect force evaluation with curvature shell and plate and is investigated the possibility of force evaluation of rotary compressor as a complex structure.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2011년도 춘계학술대회 논문집
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• pp.389-394
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• 2011

Existing FPS(Friction Pendulum System) is isolation system which is possible to isolate structures by pendulum characteristic from ground vibration. Structural natural frequency could be decided by designing the radius of curvature of FPS. Thus, response vibration could be reduced by changing natural frequency of structures from FPS. But effective periods of recorded seismic wave were various and estimation of earthquake characteristic could be difficult. If effective periods of seismic wave correspond to natural frequency of structures with FPS, resonance can be occurred. Therefore, CFPBS(Cone-type Friction Pendulum Bearing System) was developed for controlling the response acceleration and displacement by the slope of friction surfaces. Structural natural frequency with CFPBS can be changed according to position of ball on the friction surface which was designed cone-type. Therefore, Divergence of response could be controlled by CFPBS which had constantly changing natural frequency with low modal participation factor in wide-range. In this study, Seismic performance of CFPBS was evaluated by numerical analysis and shaking table test.

• 한국측량학회지
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• 제22권4호
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• pp.391-400
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• 2004

철도 곡선부는 열차 운행속도에 중요한 영향을 미친다. 이 곡선부에서 완화곡선 길이는 곡선구간의 선형 적합성을 평가하는데 주요 요인 중 하나가 되며, 이 값은 주행속도와 캔트값에 의해 결정 되어진다. 본 연구에서는 장항선을 대상으로 완화곡선 길이를 확보하기 위한 평가를 실시한 결과 곡선구간의 약 2/3이 연장에 필요한 구간으로 밝혀졌으며, 완화곡선 연장방법을 적용함에 있어 곡선중점의 변경은 없고 곡선반경을 변화시켜 연장하는 방법이 선로중심선에서의 최대 이동량 및 곡선반경 편차를 최소화시킬 수 있으며, 또한 전면적인 선형개량이 어려울 경우 선형 적합성 및 속도향상에 효과적일 것이다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1987년도 전기.전자공학 학술대회 논문집(I)
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• pp.311-315
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• 1987

In this paper an efficient algorithm to estimate the volume and surface area and the reconstruction algorithm for 3-dimensional graphics are presented. The graph theory is used to estimate the optimal quantitative factors. To improve the computing efficiency, the algorithm to get proper contour points is performed by applying several tolerances. The search and the given arc cost is limited according to the change of curvature of the cross-sectional contour. For mathematical model, these algorithms for volume estimation based on polyhedral approximation are applied to the selected optimal surface. The results show that the values of the volume and surface area for tolerances 1.0005, 1.001 and 1.002 approximate to values for tolerances 1.000 resulting in small errors. The reconstructed three-dimensional images are sparse and consist of larger triangular tiles between two cross sections as tolerance is increasing.