• 한국소음진동공학회:학술대회논문집
• /
• 한국소음진동공학회 2007년도 춘계학술대회논문집
• /
• pp.489-493
• /
• 2007

Mmulti-domain noise analysis method using Power Flow Boundary Element Method(PFBEM) has been developed successfully. Some applications are introduced. several examples. PFBEM is a numerical analysis method formulated by applying Boundary Element Method(BEM) to Power Flow Analysis(PFA). PFBEM is very powerful in predicting noise level in medium-to-high frequency ranges. However there are restrictions in analyzing the coupled structures and multi-media. In this paper, an analysis method for multi-domain acoustic problems in the diverse acoustic fields is suggested. And the developed method is applied to the car interior and exterior multi-domain noise analysis.

• 한국세라믹학회지
• /
• 제32권3호
• /
• pp.359-365
• /
• 1995

The grain boundary effect on the ionic conductivity was investigated using a.c. admittance analysis in (Bi2O3)0.715(CaO)0.285 oxygen-ion conducting solid electrolyte. As a separated arc representing grain boundary polarization was not observed in the admittance plane, bulk conductivity was measrued for samples with various grain sizes in the temperature range from 48$0^{\circ}C$ to 72$0^{\circ}C$ and the conductivity distribution between grain interior and grain boundary was determined by the reported analytical methods. In the above temperature range, grain boundary worked as a high conductive path instead of blocking layer and ionic conduction through grain boundary was significant. The activation energy for conduction through grain and grain boundary was 78 and 106 kJ/mol, respectively.

• Structural Engineering and Mechanics
• /
• 제22권1호
• /
• pp.1-16
• /
• 2006

This paper presents a virtual boundary element-equivalent collocation method (VBEM) for the plane magnetoelectroelastic solids, which is based on the fundamental solutions of the plane magnetoelectroelastic solids and the basic idea of the virtual boundary element method for elasticity. Besides all the advantages of the conventional boundary element method (BEM) over domain discretization methods, this method avoids the computation of singular integral on the boundary by introducing the virtual boundary. In the end, several numerical examples are performed to demonstrate the performance of this method, and the results show that they agree well with the exact solutions. So the method is one of the efficient numerical methods used to analyze megnatoelectroelastic solids.

• 한국자동차공학회논문집
• /
• 제8권6호
• /
• pp.230-237
• /
• 2000

The wheel bearing in vehicles has been improved to unit module by joining a bearing to a hub in order to achieve weight reduction and easy assembly. Currently, the contact force between a raceway and balls of a bearing is applied as the external force in order to analyse the structure of the unit type bearings. In this paper, simplified boundary conditions are discussed for structure analysis of wheel bearing unit. From the procedure, the contact conditions of balls and race in wheel bearing unit are considered as equivalent non-linear spring elements. The end node of a spring element is constrained in displacement. And the external force of boundary conditions is applied at the contact point between tire and road. For the evaluation of this analysis, its results for the force of spring elements are compared with contact forces of calculated results. and also maximum equivalent stresses of analysis are compared with results of test at the flange of inner ring. The analysis results with proposed boundary conditions are more accurate than results from analysis which is generally used.

• 한국지진공학회논문집
• /
• 제19권1호
• /
• pp.37-43
• /
• 2015

This paper presents a detailed procedure for a nonlinear soil-structure interaction of a seismically isolated NPP(Nuclear Power Plant) structure using the boundary reaction method (BRM). The BRM offers a two-step method as follows: (1) the calculation of boundary reaction forces in the frequency domain on an interface of linear and nonlinear regions, (2) solving the wave radiation problem subjected to the boundary reaction forces in the time domain. For the purpose of calculating the boundary reaction forces at the base of the isolator, the KIESSI-3D program is employed in this study to solve soil-foundation interaction problem subjected to vertically incident seismic waves. Wave radiation analysis is also employed, in which the nonlinear structure and the linear soil region are modeled by finite elements and energy absorbing elements on the outer model boundary using a general purpose nonlinear FE program. In this study, the MIDAS/Civil program is employed for modeling the wave radiation problem. In order to absorb the outgoing elastic waves to the unbounded soil region, spring and viscous-damper elements are used at the outer FE boundary. The BRM technique utilizing KIESSI-3D and MIDAS/Civil programs is verified using a linear soil-structure analysis problem. Finally the method is applied to nonlinear seismic analysis of a base-isolated NPP structure. The results show that BRM can effectively be applied to nonlinear soil-structure interaction problems.

• 소성∙가공
• /
• 제8권4호
• /
• pp.384-392
• /
• 1999

In metal forming, there are problems with recurrent geometric characteristics without explicitly prescibed boundary conditions. In such problems, so-called recurrent boundary conditions must be introduced. In this paper, as a practical application of the proposed method, the precision cold forging of a helical gear has been simulated by a three-dimensional rigid-plastic finite element method and compared with the experiment. The application of recurrent boundary conditions to helical gear forging analysis is proved to be effective and valid. the elastic stress analysis of the die for helical gear forging has been calculated by using the nodal force at the final stage obtained from the rigid-plastic finite element analysis. In order to obtain more precise gear products, the elastic analysis of the die after release of punch and the elastic spring-back analysis of product after ejection have been performed, and the final dimension of the computational product has been in good agreement with that of the experimental product.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제7권11호
• /
• pp.2804-2823
• /
• 2013

Wireless sensor network (WSN) is a promising technology for monitoring physical phenomena at fine-grained spatial and temporal resolution. However, the typical approach of sending each sensed measurement out of the network for detailed spatial analysis of transient physical phenomena may not be an efficient or scalable solution. This paper focuses on in-network physical phenomena detection schemes, particularly the distributed computation of the boundary of physical phenomena (i.e. event), to support energy efficient spatial analysis in wireless sensor networks. In-network processing approach reduces the amount of network traffic and thus achieves network scalability and lifetime longevity. This study investigates the recent advances in distributed event detection based on in-network processing and includes a concise comparison of various existing schemes. These boundary detection schemes identify not only those sensor nodes that lie on the boundary of the physical phenomena but also the interior nodes. This constitutes an event geometry which is a basic building block of many spatial queries. In this paper, we introduce the challenges and opportunities for research in the field of in-network distributed event geometry boundary detection as well as illustrate the current status of research in this field. We also present new areas where the event geometry boundary detection can be of significant importance.

• 한국전산구조공학회논문집
• /
• 제18권3호
• /
• pp.255-263
• /
• 2005

본 논문에서는 다양한 문제들의 형상 설계 민감도 해석에 대한 효율적인 경계기반 기법을 제시하였다 우선 문제에서 정의된 일반적인 함수들에 대한 연속체 형태의 식에 근거하여, 경계 적분 형태의 해석적 민감도 식을 유도하였다. 이 식은 다양한 형상 설계 문제들의 경사를 계산하는데 편리하게 사용할 수 있다. 그리고 경계법은 형상 변분 벡터가 전체 도메인이 아닌 경계에서만 요구된다는 장점이 있는데, 여기서 경계 형상 변분은 형상 함수의 복잡한 해석적 미분 대신 형상을 미소 증분시킴으로써 편리하게 계산할 수 있다. 제시한 방법의 효율성을 보이기 위해 포텐셜 유동 문제와 필렛(fillet)에서의 응력 집중 문제에 이를 적용하였다.

• 전산구조공학
• /
• 제9권4호
• /
• pp.127-134
• /
• 1996

본 논문은 경계요소법에 의한 콘크리트의 진행성 파괴해석에 관한 연구이다. 콘크리트의 파괴진행해석을 위하여 경계요소법에 의한 변위 및 표면력 경계 적분방정식으로부터 균열을 포함한 연속체의 균열 경계적분 방정식을 정식화하였다. 콘크리트의 균열진행을 해석하기 위하여 균열 선단에서의 파괴진행영역을 Dugdale-Barenblatt형 모델을 사용하여 모델링하였고 균열진행영역의 인장연화상태를 선형으로 가정하여 모델링하였다. 정식화된 경계적분방정식에 의한 콘크리트 보와 여러가지 하중상태에 있는 인장시편에 대한 진행성 파괴해석을 실시하였으며 해석치와 실험치의 비교로부터 경계요소법에 의한 진행성 파괴해석방법은 최대하중 및 최대하중 이후의 거동을 포함한 콘크리트 구조물의 비선형 거동을 잘 예측함을 보여주고 있다 .

• 대한조선학회논문집
• /
• 제34권4호
• /
• pp.53-60
• /
• 1997

비선형 자유표면파 현상은 여러 가지 수치해법에 의하여 연구되고 있으나 이들 중에서 경계요소법이 가장 유망한 것으로 알려져 있다. 그러나, 경제요소법에 의한 수치과정에 해결해야 할 몇가지 문제점들이 남아있는 것도 주지의 사실이다. 본 논문에서는 경계요소해석에 의한 비선형 자유표면파의 수치해석과정을 보다 정확하고 신속하게 처리하기 위하여, 요소적분의 수치적분과 선형계에 대한 반복해법 등을 심도있게 논의하였다. 그리고 해석해가 있는 경우에 대하여, 개발된 경계요소법의 우수성을 확인하였다.