• 대한의용생체공학회:의공학회지
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• 제28권4호
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• pp.471-476
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• 2007

Various active microwave imaging techniques have been developed for cancer detection for past several decades. Both the microwave tomography and the UWB radar techniques, constituting functional microwave imaging systems, use the electrical property contrast between normal tissues and malignancies to detect the latter in an early development stage. Even though promising simulation results have been reported, the understanding of the functional microwave imaging diagnostics has been relied heavily on the complicated numerical results. We present a computationally efficient and physically instructive analytical electromagnetic wave channel models developed for functional microwave imaging system in order to detect especially the breast tumors as early as possible. The channel model covers the propagation factors that have been examined in the previous 2-D models, such as the radial spreading, path loss, partial reflection and transmission of the backscattered electromagnetic waves from the tumor cell. The effects of the system noise and the noise from the inhomogeneity of the tissue to the reconstruction algorithm are modeled as well. The characteristics of the reconstructed images of the tumor using the proposed model are compared with those from the confocal microwave imaging.

• Steel and Composite Structures
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• 제33권6호
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• pp.877-889
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• 2019

The developments of double skin composite (DSC) walls with novel enhanced C-channel connectors (DSCW-EC) were reported. Followed axial compression tests on prototype walls were carried to evaluate structural performances of this novel DSC composite structures. The testing program consists of five specimens and focused on the layout of the novel enhanced C-channel (EC) connectors, which include the web direction of C-channels, steel-faceplate thickness, vertical and horizontal spacing of C-channels. Crushing in concrete core and buckling of steel faceplate were two main observed failed modes from the compression tests. However, elastic or plastic buckling of the steel faceplate varies with designed parameters in different specimens. The influences of those investigated parameters on axial compressive behaviors of DSCW-ECs were analyzed and discussed. Recommendations on the layout of novel EC connectors were then given based on these test results and discussions. This paper also developed analytical models for predictions on ultimate compressive resistance of DSCW-ECs. Validation against the reported test results show that the developed theoretical models predict well the ultimate compressive resistance of DSCW-ECs.

• 인터넷정보학회논문지
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• 제5권1호
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• pp.41-49
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• 2004

다단상호연결네트윅의 성능평가시 실제적인 환경을 고려하기 위하여는 비균일 트래픽이 존재할 때 및 복수버퍼를 가질 때의 성능평가가 필수적이나 기존의 비균일트래픽하에서의 연구는 입력버퍼의 경우보다 상대적으로 모델링이 쉬운 출력버퍼를 가지고 있을 때를 고려한다든가 블럭킹 상태를 고려하지 못한다든, 단일버퍼만 고려한다든가 하는 결점을 가지고 있다. 따라서 본 논문에서는 입력버퍼를 가진 밴연형 다단상호연결네트윅이 비균일트래픽하에서 모델링하고 성능평가를 하는데 특히 다중의 입력버퍼를 가졌을 경우를 해석적으로 모델링하고 그 모델로부터의 결과와 시뮬레이션으로부터의 결과를 비교하여 구해진 모델의 우수성을 입증한다.

• Steel and Composite Structures
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• 제19권5호
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• pp.1145-1165
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• 2015

A behavior model for screw connections is developed to provide a better representation of the nonlinear response of thin steel plate shear walls (TSPSWs) with infill plates attached to the boundary frame members via self-drilling screws. This analytical representation is based on the load-bearing deformation relationship between the infill plate and the screw threads. The model can be easily implemented in strip models of TSPSWs where the tension field action of the infill plates is represented by a series of parallel discrete tension-only strips. Previously reported experimental results from tests of two different TSPSWs are used to provide experimental validation of the modeling approach. The beam-to-column connection behavior was also included in the analyses using a four parameter rotational spring model that was calibrated to a test of an identical frame as used for the TSPSW specimens but without the infill plates. The complete TSPSW models consisting of strips representing the infill plates, zero length elements representing the load-bearing deformation response of the screw connection at each end of the strips and the four parameter spring model at each beam-to-column connection are shown to have good agreement with the experimental results. The resulting models should enable design and analysis of TSPSWs for both new construction and retrofit of existing buildings.

• International Journal of Naval Architecture and Ocean Engineering
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• 제6권4호
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• pp.1182-1196
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• 2014

In problems of global hydroelastic ship response in severe seas including the whipping problem, we need to know the hydrodynamic forces acting on the ship hull during almost arbitrary ship motions. In terms of ship sections, some of them can enter water but others exit from water. Computations of nonlinear free surface flows, pressure distributions and hydrodynamic forces in parallel with the computations of the ship motions including elastic vibrations of the ship hull are time consuming and are suitable only for research purposes but not for practical calculations. In this paper, it is shown that the slamming forces can be decomposed in two components within three semi-analytical models of water entry. Only heave motion is considered. The first component is proportional to the entry speed squared and the second one to the body acceleration. The coefficients in these two components are functions of the penetration depth only and can be precomputed for given shape of the body. During the exit stage the hydrodynamic force is proportional to the acceleration of the body and independent of the body shape for bodies with small deadrise angles.

• 인터넷정보학회논문지
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• 제4권5호
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• pp.43-49
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• 2003

밴연형 구조는 다단상호연결네트웍 중에서도 여러 변형 구조가 파생이 된 매우 중요하고 광범위하게 사용되는 구조이다. 이러한 구조를 위한 기존의 성능평가 연구는 주로 입력트래픽이 균일할 때를 가정한 것이어서 실제적이지 못하다. 비균일트래픽하에서의 기존의 연구도 입력버퍼의 경우보다 상대적으로 모델링이 쉬운 출력버퍼를 가지고 있을 때를 고려한다든가 블럭킹 상태를 고려하지 못한다든가 하는 결점을 가지고 있다. 본 논문에서는 입력버퍼를 가진 밴연형 다단상호연결네트웍이 비균일트래픽하에서 원하는 성능목표치를 만족시킬 수 있는지를 알아보기 위하여 해석적 모델을 개발하고 그 모델로부터의 결과와 시뮬레이션으로부터의 결과를 비교하여 구해진 모델의 우수성을 입증하였다.

• Advances in materials Research
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• 제9권1호
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• pp.63-98
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• 2020

The novelty of this paper is the use of a simple higher order shear and normal deformation theory for bending and free vibration analysis of functionally graded material (FGM) beams on two-parameter elastic foundation. To this aim, a new shear strain shape function is considered. Moreover, the proposed theory considers a novel displacement field which includes undetermined integral terms and contains fewer unknowns with taking into account the effects of both transverse shear and thickness stretching. Different patterns of porosity distributions (including even and uneven distribution patterns, and the logarithmic-uneven pattern) are considered. In addition, the effect of different micromechanical models on the bending and free vibration response of these beams is studied. Various micromechanical models are used to evaluate the mechanical characteristics of the FG beams for which properties vary continuously across the thickness according to a simple power law. Hamilton's principle is used to derive the governing equations of motion. Navier type analytical solutions are obtained for the bending and vibration problems. Numerical results are obtained to investigate the effects of power-law index, length-to-thickness ratio, foundation parameter, the volume fraction of porosity and micromechanical models on the displacements, stresses, and frequencies.

• 국제강구조저널
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• 제18권4호
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• pp.1325-1335
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• 2018

This study dealt with investigating the seismic performance of the smart and shape memory alloy (SMA) and magnets plus rubber-spring (MRS) dampers and their effects on the seismic resistance of multiple-span simply supported bridges. The rubber springs in the MRS dampers were pre-compressed. For this aim, a set of experimental works was performed together with developing nonlinear analytical models to investigate dynamic responses of the bridges subjected to earthquakes. Fragility analysis and probabilistic assessment were conducted to assess the seismic performance for the overall bridge system. Fragility curves were then generated for each model and were compared with those of as-built. Results showed dampers could increase the seismic capacity of bridges. Furthermore, from system fragility curves, use of damper models reduced the seismic vulnerability in comparison to the as-built bridge model. Although the SMA damper showed the best seismic performance, the MRS damper was the most appropriate one for the bridge in that the combination of magnetic friction and pre-compressed rubber springs was cheaper than the shape memory alloy, and had the similar capability of the damper.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2000년도 추계 학술발표회 논문집 Proceedings of EESK Conference-Fall 2000
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• pp.233-238
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• 2000

The purpose of this study is to outline the analysis procedure for evaluating the performance of moment resisting steel frames. For this purpose, three ordinary moment resisting frames are designed in compliance to UBC 1994. The evaluation is performed by nonlinear static procedures using two analytical models. Only one analytical model using panel element can reflect the panel zone deformation explicitly. The limit values in FEMA 273 are used as guidelines of predicted demand parameters by which the performance of OMRFs may be assessed.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 가을 학술발표회 논문집
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• pp.885-890
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• 2001

For the shear strength prediction of reinforced concrete beams, this paper considered the bending moment effect. Experimental results of the thirty-seven reinforced concrete beams were compared with analytical results by the FA-STM, TATM and TATM considered bending moment effect. While Ratios of test results to analytical results by using the truss models does not considered the bending moment effect decreased as shear span ratio increased, those by using the proposed method considered that were almost constant regardless of the increase of the shear span ratio. Predicted results obtained from proposed method agreed well with the experimental results.