• Structural Engineering and Mechanics
• /
• 제35권2호
• /
• pp.141-173
• /
• 2010

In this paper a boundary element method is developed for the general flexural-torsional buckling analysis of Timoshenko beams of arbitrarily shaped cross section. The beam is subjected to a compressive centrally applied concentrated axial load together with arbitrarily axial, transverse and torsional distributed loading, while its edges are restrained by the most general linear boundary conditions. The resulting boundary value problem, described by three coupled ordinary differential equations, is solved employing a boundary integral equation approach. All basic equations are formulated with respect to the principal shear axes coordinate system, which does not coincide with the principal bending one in a nonsymmetric cross section. To account for shear deformations, the concept of shear deformation coefficients is used. Six coupled boundary value problems are formulated with respect to the transverse displacements, to the angle of twist, to the primary warping function and to two stress functions and solved using the Analog Equation Method, a BEM based method. Several beams are analysed to illustrate the method and demonstrate its efficiency and wherever possible its accuracy. The range of applicability of the thin-walled theory and the significant influence of the boundary conditions and the shear deformation effect on the buckling load are investigated through examples with great practical interest.

• Interaction and multiscale mechanics
• /
• 제1권1호
• /
• pp.123-142
• /
• 2008

Current methodologies used for the inference of thin film stresses through curvature measurements are strictly restricted to stress and curvature states which are assumed to remain uniform over the entire film/substrate system. These methodologies have recently been extended to non-uniform stress and curvature states for the thin film subject to non-uniform, isotropic misfit strains. In this paper we study the same thin film/substrate system but subject to non-uniform, anisotropic misfit strains. The film stresses and system curvatures are both obtained in terms of the non-uniform, anisotropic misfit strains. For arbitrarily non-uniform, anisotropic misfit strains, it is shown that a direct relation between film stresses and system curvatures cannot be established. However, such a relation exists for uniform or linear anisotropic misfit strains, or for the average film stresses and average system curvatures when the anisotropic misfit strains are arbitrarily non-uniform.

• 한국통신학회논문지
• /
• 제18권8호
• /
• pp.1059-1068
• /
• 1993

임의 모양을 갖는 마이크로스트립 안테나의 해석에 역점을 두었다. 마이크로스트립 안테나의 가장 일반적이고 정확한 해석법은 주파수 영역에서 정의되는 전계적분방정식을 이용하는 것이다. 본 논문에서는 전계적분방정식을 수정한 MPIE(Mixed potential integral equation)를 이용하여 공간영역에서 해를 구하였다. 이 방법은 스칼라와 벡터 포텐셜과 관련된 Green함수를 다층매질 이론에 의해 계산하고 Sommerfeld 적분방정식에 의해 표현한다. 또한 적분방정식은 rooftop 부분기저함수를 이용한 모멘트법을 이용하여 해를 구하였다. 따라서 임의의 모양의 마이로스트립 안테나를 임의의 주파수와 임의의 기판상에서 해석할 수 있다. 구형 마이크로스트립 안테나와 L자형 마이크로스트립 안테나의 수치 결과를 실험치와 비 교하였다.

• 대한전자공학회논문지TC
• /
• 제39권10호
• /
• pp.27-37
• /
• 2002

본 논문에서는 주파수 영역에서 3차원 임의형태의 유전체 산란 해석을 위하여 다양한 결합 적분방정식(combined field integral equation, CFIE)의 구성을 제안한다. 서로 다른 시험 함수의 조합으로 8 가지의 CFIE를 제안하였다. 본 논문의 목적 중의 하나는 제안된 모든 CFIE가 구조물의 내부공진 주파수에서 공진문제를 극복하지 못함을 보이는 것이다. 또한 이 8가지의 CFIE는 네 개의 항으로 구성되는데, 이 중에서 하나를 무시하는 방법으로 16가지의 새로운 CFIE를 제안하였다. 수치 예로서 유전체로부터의 원거리장과 레이다 단면적(radar cross section, RCS) 계산 결과들을 보이며, 제안되는 각 CFIE의 동작 특성을 비교하여 고찰하였다.

• 대한전기학회논문지:전기물성ㆍ응용부문C
• /
• 제51권11호
• /
• pp.551-558
• /
• 2002

A time-domain combined field integral equation (CFIE) is presented to obtain the transient scattering response from arbitrarily shaped three-dimensional conducting bodies. This formulation is based on a linear combination of the time-domain electric field integral equation (EFIE) with the magnetic field integral equation (MFIE). The time derivative of the magnetic vector potential in EFIE is approximated using a central finite difference approximation and the scalar potential is averaged over time. The time-domain CFIE approach produces results that are accurate and stable when solving for transient scattering responses from conducting objects. The incident spectrum of the field may contain frequency components, which correspond to the internal resonance of the structure. For the numerical solution, we consider both the explicit and implicit scheme and use two different kinds of Gaussian pulses, which may contain frequencies corresponding to the internal resonance. Numerical results for the EFIE, MFIE, and CFIE are presented and compared with those obtained from the inverse discrete Fourier transform (IDFT) of the frequency-domain CFIE solution.

• BMB Reports
• /
• 제33권3호
• /
• pp.208-212
• /
• 2000

In order to develop a specific genetic marker for the Korean native cattle (Hanwoo), an arbitrarily-primed polymerase chain reaction (AP-PCR) analysis of 6 different cattle breeds was attempted. Eight different arbitrary primers, each longer than 20-mer nucleotides, were used. In comparison to the AP-PCR patterns, several distinctive DNA bands that are specific for a certain breed were detected. When the primer Kpn-X was employed, a 280bp DNA fragment was found to be specific only for Hanwoo. In an individual analysis of Hanwoo, this AP-PCR marker was observed in 123 head of cattle among the 153 that were tested (80.4%). Nucleotide sequencing revealed that this fragment has a short microsatellite sequence of tandem repeat, $A(G)_{1-2}\;(C)_{1-3}AGAG$. According to the analysis of AP-PCR band patterns, Hanwoo was discovered to be genetically most closely-related with Holstein among the various cattle breeds.

• 대한기계학회논문집A
• /
• 제24권3호
• /
• pp.550-559
• /
• 2000

One of the most important factor to be considered for the analysis of sheet metal forming processes is the tool surface description for arbitrarily- shaped sheet metal parts. In the present study , finite element approach is used to describe the arbitrarily shaped tool surface. In finite element mesh approach, tool surfaces ar, described by finite elements. The finite elements mesh description of the tool surface, which is originally described by CAD data, needs much time and time-consuming graphic operation. The method, however, has been widely used to describe a complex tool surface. In the present study, the contact searching algorithm for the finite element mesh approach is developed based on cell strategy method and sheet surface normal scheme. For the verification purpose, a clover cup drawing, Baden-Baden oilpan problem and a trunk floor drawing were investigated. The computational results based on the finite element approach were compared with the results of available parametric patch approach and experiments.

• 제어로봇시스템학회논문지
• /
• 제14권1호
• /
• pp.54-61
• /
• 2008

This paper proposes a new algorithm for detecting and recognizing overlapped objects among a stack of arbitrarily located objects using a signature representation scheme. The proposed algorithm consists of two processes of detecting overlap of objects and of determining the boundary between overlapping objects. To determine overlap of objects, in the first step, the edge image of object region is extracted and those areas in the object region are considered as the object areas if an area is surrounded by a closed edge. For each object, its signature image is constructed by measuring the distances of those edge points from the center of the object, along the angle axis, which are located at every angle with reference to the center of the object. When an object is not overlapped, its features which consist of the positions and angles of outstanding points in the signature are searched in the database to find its corresponding model. When an object is overlapped, its features are partially matched with those object models among which the best matching model is selected as the corresponding model. The boundary among the overlapping objects is determined by projecting the signature to the original image. The performance of the proposed algorithm has been tested with the task of picking the top or non-overlapped object from a stack of arbitrarily located objects. In the experiment, a recognition rate of 98% has been achieved.

• Investigative Magnetic Resonance Imaging
• /
• 제22권3호
• /
• pp.141-149
• /
• 2018

Purpose: The purpose of this study is to develop a simple method to measure magnetic susceptibility of arbitrarily shaped materials through MR imaging and numerical modeling. Materials and Methods: Our 3D printed phantom consists of a lower compartment filled with a gel (gel part) and an upper compartment for placing a susceptibility object (object part). The $B_0$ maps of the gel with and without the object were reconstructed from phase images obtained in a 3T MRI scanner. Then, their difference was compared with a numerically modeled $B_0$ map based on the geometry of the object, obtained by a separate MRI scan of the object possibly immersed in an MR-visible liquid. The susceptibility of the object was determined by a least-squares fit. Results: A total of 18 solid and liquid samples were tested, with measured susceptibility values in the range of -12.6 to 28.28 ppm. To confirm accuracy of the method, independently obtained reference values were compared with measured susceptibility when possible. The comparison revealed that our method can determine susceptibility within approximately 5%, likely limited by the object shape modeling error. Conclusion: The proposed gel-phantom-based susceptibility measurement may be used to effectively measure magnetic susceptibility of MR-compatible samples with an arbitrary shape, and can enable development of various MR engineering parts as well as test biological tissue specimens.

• 대한임상검사과학회지
• /
• 제36권2호
• /
• pp.89-97
• /
• 2004

Many strains of Staphylococcus aureus were isolated from pus samples from primary, secondary, and tertiary medical institutions and were subjected to an antibiotic sensitivity test. Ciprofloxacin, clindamycin, erythromycin, gentamicin, oxacillin penicillin, tetracycline, trimethoprim/sulfamethoxazole, vancomycin and teicoplanin were used for the antibiotic sensitivity test. The strains showed hightest resistance to penicillin(91%), but all of strains tested were susceptible to vancomycin and teicoplanin. The isolated multi-drug(penicillin-tetracycline-ciprofloxacin-clindamycin-erythromycin- oxacillin-gentamicin) resistant S. aureus were analyzed genotypically using an AP-PCR(Arbitrarily Primed polymerase chain reaction) with an arbitrary 3 primers. Based on the result for genotype analysis, the genotypes identified by S1 primer did not coincide with those of S2 or E2 primers. Genotypes identified by S2 primer did not coincide with those of S1 or E2 primers. Also genotypes identified by the E2 primer did not coincide with those of S1 or S2 primers. Therefore, an analysis of AP-PCR test with multiple primers will provide more sensitive identification. A strain from a secondary medical institution and a strain from a tertiary medical institution which showed the same genotype for S1, S2, and E2 primers are required for further epidemiological study.