Browsing by Author "Huang, CS"

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A neural network approach for structural identification and diagnosis of a building from seismic response data
(2003-02-01)
Huang, CS
;
Hung, SL
;
Wen, CM
;
Tu, TT
;
土木工程學系
This work presents a novel procedure for identifying the dynamic characteristics of a building and diagnosing whether the building has been damaged by earthquakes, using a back-propagation neural network approach. The dynamic characteristics are directly evaluated from the freighting matrices of the neural network trained by observed acceleration responses and input base excitations. Whether the building is damaged under a large earthquake is assessed by comparing the modal parameters and responses for this large earthquake with those for a small earthquake that has not Caused this building any damage. The feasibility of the approach is demonstrated through processing the dynamic responses of a five-storey steel frame. subjected to different strengths of the Kobe earthquake, in shaking table tests. Copyright (C) 2002 John Wiley Sons, Ltd.
A wavelet-based approach to identifying structural modal parameters from seismic response and free vibration data
(2005-11-01)
Huang, CS
;
Hung, SL
;
Lin, CI
;
Su, WC
;
土木工程學系
This work presents the use of a discrete wavelet transform to determine the natural frequencies, damping ratios, and mode shapes of a structure from its free vibration or earthquake response data. The wavelet transform with orthonormal wavelets is applied to the measured acceleration responses of a structural system, and to reconstruct the discrete equations of motion in various wavelet subspaces. The accuracy of this procedure is numerically confirmed; the effects of mother wavelet functions and noise on the ability to accurately estimate the dynamic characteristics are also investigated. The feasibility of the present procedure to elucidate real structures is demonstrated through processing the measured responses of steel frames in shaking table tests and the free vibration responses of a five-span arch bridge with a total length of 440 m.
An analytical solution for in-plane free vibration and stability of loaded elliptic arches
(2003-05-01)
Nieh, KY
;
Huang, CS
;
Tseng, YP
;
土木工程學系
;
Department of Civil Engineering
In-plane free vibration and stability analyses of elliptic arches subjected to a uniformly distributed vertical static loading are performed here. A variational principle is applied to derive the governing equations for free vibration and stability of preloaded arches, considering the effect of the extensibility of the arch centerline but neglecting the effect of shear deformation. Particular attention is given to present a general procedure for combining series solutions with stiffness matrixes to construct an analytical solution for free vibration and stability of loaded arches with varying curvature. The correctness of the proposed solution is verified through a convergence study on the vibration frequencies of a loaded circular arch and by comparing the results with published data. The solution is further applied to investigate the behaviors of clamped or fixed-free elliptic arches. (C) 2003 Elsevier Science Ltd. All rights reserved.
An analytical solution for vibrations of a polarly orthotropic Mindlin sectorial plate with simply supported radial edges
(2004-05-21)
Huang, CS
;
Ho, KH
;
土木工程學系
;
Department of Civil Engineering
This paper presents the first known analytical solution for vibrations of a polarly orthotropic Mindlin sectorial plate with simply supported radial edges. The solution is a series solution constructed using the Frobenius method and exactly satisfies not only the boundary conditions along the radial and circular edges, but also the regularity conditions at the vertex of the radial edges. The moment and shear force singularities at the vertex are exactly considered in the solution. The correctness of the proposed solution is confirmed by comparing non-dimensional frequencies of isotropic plates obtained from the present solution with published data obtained from a closed-form solution. This paper also investigates the effects of elastic and shear moduli on the vibration frequencies of the sectorial plates with free or fix boundary conditions along the circumferential edge. A study is also carried out about the influence of elastic and shear moduli on the moment and shear force singularities at the plate origin (r = 0) for different vertex angles. (C) 2003 Elsevier Ltd. All rights reserved.
Analysis of stress singularities at bi-material corners in Reddy's theory of plate bending
(2006-03-01)
Huang, CS
;
土木工程學系
;
Department of Civil Engineering
The order of stress singularity at a sharp corner of a plate needs to be known before a numerical approach can be taken to determine accurately the stress distribution of a plate with irregular geometry (such as a V-notch) under loading. This work analyzes the order of the stress singularity at a bi-material corner of a thick plate under bending, based on Reddy's third-order shear deformation plate theory. An eigenfunction expansion technique is used to derive the asymptotic displacement field in the vicinity of the sharp corner by solving the equilibrium equations in terms of displacement functions. This paper explicitly shows the first known characteristic equations for determining the order of the stress singularity at the interface corner of a bonded dissimilar isotropic plate. Moreover, the numerical results are given in graphic form for the order of stress singularity at the interface corner in bonded dissimilar isotropic plates and at the vertex of a bi-material wedge with free radial edges. The results presented herein fill some of the gaps in the literature.
Axial load behavior of stiffened concrete-filled steel columns
(2002-09-01)
Huang, CS
;
Yeh, YK
;
Liu, GY
;
Hu, HT
;
Tsai, KC
This study investigates the axial load behavior of concrete-filled steel tubular (CFT) columns with the width-to-thickness ratios between 40 and 150, and proposes an effective stiffening scheme to improve the mechanical properties of square cross-sectional CFT columns. Seventeen specimens were tested to examine the effects of cross-sectional shapes, width-to-thickness ratios, and stiffening arrangements on the ultimate strength, stiffness, and ductility of CFT columns. Moreover, nonlinear finite element analysis was also conducted to investigate cross-sectional axial stress distribution at the ultimate strength. Comparing the measured ultimate strength with estimates by using some current specifications suggested that current specifications may considerably underestimate the ultimate strength of circular CFT columns, particularly for columns with a small width-to-thickness ratio. Results in this study demonstrate that the proposed stiffening scheme can significantly enhance the ultimate strength and ductility of square CFT columns.
Collective excitations in a single-layer carbon nanotube
(1996-06-15)
Lin, MF
;
Chuu, DS
;
Huang, CS
;
Lin, YK
;
Shung, KWK
The inter-pi-band response function of a single-layer carbon nanotube is calculated within the random-phase approximation. Such a cylindrical system exhibits rich inter-pi-band excitations. The decoupled pi plasmons;of different angular momenta (L's) strongly depend on the transferred momenta (q's). Furthermore, they exhibit a dimensionality crossover as the nanotube radius is increased. For small q's and L's, the pi plasmon frequency is similar to 6-8 eV, which is insensitive to the nanotube geometry such as the radius and chiral angle. Comparison with recent experiments is discussed.
Collective excitations in graphite layers
(1997-09-01)
Huang, CS
;
Lin, MF
;
Chuu, DS
;
電子物理學系
;
Department of Electrophysics
The pi-electronic excitations in graphite layers are studied within the self-consistent-field approach. The pi plasmon behaves as an optical plasmon, mainly due to the pi-band characteristics. The excitation spectra and the pi-plasmon frequencies are obviously enhanced by the interlayer Coulomb interactions and increase with the number of graphite layers. (C) 1997 Published by Elsevier Science Ltd.
Corner singularities in bi-material Mindlin plates
(2002-05-01)
Huang, CS
;
土木工程學系
;
Department of Civil Engineering
An eigenfunction expansion solution is first developed to find stress singualrities for bi-material wedges by directly solving the governing equations of the Mindlin plate theory in terms of displacement components. The singularity orders of moments and shear forces at corners are determined from the corresponding asymptotic solutions having the lowest order in r and satisfying the radial boundary conditions and continuity conditions. The present solution is applied to thoroughly examine the singularities occurring at the interface joint of bonded dissimilar isotropic plates and at the vertex of a bi-material wedge with two simply supported radial edges. The corresponding characteristic equations for determining the singularity orders of moments and shear forces are explicitly given. The singularity orders of moment are shown in graphic form as functions of the flexural rigidity ratio and corner angle, while the shear force singularity orders are given as functions of the corner angle and the shear modulus ratio multiplied by the thickness ratio. The order of moment singularity obtained here for bonded dissimilar plates is also compared with that based on the classical plate theory. (C) 2002 Elsevier Science Ltd. All rights reserved.
Corner stress singularities in a high-order plate theory
(2004-08-01)
Huang, CS
;
土木工程學系
;
Department of Civil Engineering
In the context of Lo's high-order plate theory, the present work applies the eigenfunction expansion approach to investigating the Williams-type stress singularities at the vertex of a wedge. The characteristic equations for determining the orders of singularities in stress resultants are separately developed for plates under extension and bending. The characteristic equations of plates under extension differ from those in generalized plane stress cases when the clamped boundary condition is imposed along one of the radial edges around the vertex. For plates under bending, the presented characteristic equations are identical to those of first-order shear deformation plate theory (FSDPT) if the clamping is not involved in boundary conditions along the radial edges of the vertex. The orders of singularities in stress resultants, which vary with the vertex angle, are plotted for various types of boundary conditions. The results are also comprehensively compared with those obtained according to other plate theories such as classical plate theory, FSDPT and Reddy's refined plate theory. (C) 2004 Elsevier Ltd. All rights reserved.
Damage detection of structures using unsupervised fuzzy neural network
(2005)
Wen, CM
;
Hung, SL
;
Huang, CS
;
Jan, JC
;
土木工程學系
This work presents an artificial neural network (ANN) approach for detecting structural damage. An unsupervised neural network which incorporates the fuzzy concept (named the Unsupervised Fuzzy Neural Network, UFN) is adopted to detect localized damage. The structural damage is assumed to take the form of reduced elemental stiffness. The damage site is demonstrated to correlate with the changes in the modal parameters of the structure. Therefore, a feature representing the damage location termed the Damage Localization Feature (DLF) is presented. When the structure experiences damage or change in the structural member, the measured DLF is obtained by analyzing the recorded dynamic responses of the structure. The location of the structural damage then can be identified using the UFN according to the measured DLF information. This study verifies the proposed model using an example involving a five-storey frame building. Both single and multiple damaged sites are considered. The effects of measured noise and the use of incomplete modal data are introduced to inspect the capability of the proposed detection approach.
Effects of Ni thickness and reflow times on interfacial reactions between Ni/Cu under-bump metallization and eutectic Sn-Pb solder in flip-chip technology
(2003-02-01)
Huang, CS
;
Duh, JG
;
Chen, YM
;
Wang, JH
;
材料科學與工程學系
Flip-chip interconnection technology plays a key role in today's electronics packaging. Understanding the interfacial reactions between the solder and under-bump metallization (UBM) is, thus, essential. In this study, different thicknesses of electroplated Ni were used to evaluate the phase transformation between Ni/Cu under-bump metallurgy and eutectic Sn-Pb solder in the 63Sn-37Pb/Ni/Cu/Ti/Si3N4/Si multilayer structure for the flip-chip technology. Interfacial reaction products varied with reflow times. After the first reflow, layered (Ni1-x,Cu-x)(3)Sn-4 was found between solder and Ni. However, there were two interfacial reaction products formed between solders and the UBM after three or more times reflow. The layered (Ni1-xCux)(3)Sn-4 was next to the Ni/Cu UBM. The islandlike (Cu1-y,Ni-y)(6)Sn-5 was formed between (Ni,Cu)(3)Sn-4 and solders. The amounts of (Cu1-y,Ni-y)(6)Sn-5 intermetallic compound (IMC) could be related to the Ni thickness and reflow times. In addition, the influence of Cu contents on phase transformation during reflow was also studied.
Electronic excitations of an electron-gas cylinder bundle
(1998-01-01)
Lin, MF
;
Huang, CS
;
Chuu, DS
;
電子物理學系
;
Department of Electrophysics
We study the dielectric response function of an electron-gas cylinder bundle. The electron-electron interactions among different cylinders are taken into account. The electronic excitations are associated with those of an isolated cylinder. However, a cylinder bundle exhibits the three-dimensional characteristics, but a single cylinder the one-dimensional characteristics. The excitation properties are highly anisotropic. The plasma oscillations perpendicular and parallel to the axial direction quite differs from each other. The ratio between their oscillation frequencies is generally smaller than 1/root 2, which depends on the cylinder radius and the effective mass. (C) 1997 Elsevier Science Ltd.
Electronic excitations of an electron-gas cylinder bundle
(1998-01-01)
Lin, MF
;
Huang, CS
;
Chuu, DS
;
電子物理學系
;
Department of Electrophysics
We study the dielectric response function of an electron-gas cylinder bundle. The electron-electron interactions among different cylinders are taken into account. The electronic excitations are associated with those of an isolated cylinder. However, a cylinder bundle exhibits the three-dimensional characteristics, but a single cylinder the one-dimensional characteristics. The excitation properties are highly anisotropic. The plasma oscillations perpendicular and parallel to the axial direction quite differs from each other. The ratio between their oscillation frequencies is generally smaller than 1/root 2, which depends on the cylinder radius and the effective mass. (C) 1997 Elsevier Science Ltd.
Elementary excitations in cylinder bundles
(1998-07-01)
Huang, CS
;
Lin, MF
;
Chuu, DS
;
電子物理學系
;
Department of Electrophysics
Elementary excitations in a cylinder bundle, which is formed by packing the same hollow tubules into a two-dimensional triangular lattice, are studied. The dielectric response function is calculated within the linear response approximation. The electronic excitations of the cylinder bundle are the superposition of those of all tubules. Due to the intertube Coulomb interactions, their characteristics quite differ from those of an isolated tubule. The plasmon, which corresponds to the coherent oscillations of all carriers, could exhibit a prominent peak in excitation spectrum. The excitation properties strongly depend on the tubular radius, the effective electron mass, and the magnitude and the direction of the momentum transfer (q). At small momentum, there exists a simple relation between excitation properties and polar angles (theta's). Both intensity of excitation spectrum and plasmon frequency decrease as theta increases. The collective plasma oscillations parallel and perpendicular to the tubular axis contrast sharply with each other, which clearly illustrates the anisotropic behavior. The ratio between these two plasmon frequencies is found to be smaller than root 2.
Finite element analysis of CFT columns subjected to an axial compressive force and bending moment in combination
(2005-12-01)
Hu, HT
;
Huang, CS
;
Chen, ZL
;
土木工程學系
;
Department of Civil Engineering
Proper material constitutive models for concrete-filled tube (CFT) columns subjected to an axial compressive force and bending moment in combination are proposed and verified in this paper by using the nonlinear finite element program ABAQUS compared against experimental data. In the numerical analysis, the cross sections of the CFT columns are categorized into three groups, i.e., ones with circular sections, ones with square sections, and ones with square sections stiffened with reinforcing ties. It is shown that the steel tubes can provide a good confining effect on the concrete core when the axial compressive force is large. The confining effect of a square CFT stiffened by reinforcing ties is stronger than that of the same square CFT without stiffening ties but weaker than that of a circular CFT. Nevertheless, when the spacing of reinforcing ties is small, a CFT with a square section might possibly achieve the same confining effect as one with a circular section. (c) 2005 Elsevier Ltd. All rights reserved.
High-performance hydrogenated amorphous-Si TFT for AMLCD and AMOLED applications
(2005-10-01)
Chen, CW
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Chang, TC
;
Liu, PT
;
Lu, HY
;
Wang, KC
A novel technology for manufacturing high-performance hydrogenated amorphous silicon (a-Si:H) thin-film transistors (TFTs) is developed in this letter. In the bottom gate light-shield a-Si:H TFT structure, the side edge of a-Si:H island is capped with extra deposition of heavily phosphorous-doped a-Si layer. Such an ingenuity can effectively eliminate the leakage path between the parasitic contacts of source/drain metal and the sidewall of a-Si:H island edge. In addition, electrical performance of the novel a-Si:H TFT device exhibits superior effective carrier mobility as high as 1.05 cm(2)/Vs, due to the enormous improvement in parasitic resistance. The impressively high performance of the proposed a-Si:H TFT provides the potential to apply foractive matrix liquid crystal display and active matrix organic light-emitting diode technology.
In-plane free vibration and stability of loaded and shear-deformable circular arches
(2003-11-01)
Huang, CS
;
Nieh, KY
;
Yang, MC
;
土木工程學系
;
Department of Civil Engineering
The first known equations governing vibrations of preloaded, shear-deformable circular arches are derived according to a variational principle for dynamic problems concerning an elastic body under equilibrium initial stresses. The equations are three partial differential equations with variable coefficients. The governing equations are solved for arches statically preloaded with a uniformly distributed vertical loading, by obtaining a static, closed-form solution and an analytical dynamic solution from series solutions and dynamic stiffness matrices. Convergence to accurate results is obtained by increasing the number of elements or by increasing both the number of terms in the series solution and the number of terms in the Taylor expansion of the variable coefficients. Graphs of non-dimensional frequencies and buckling loads are presented for preloaded clamped arches. They clarify the effects of opening angle and thickness-to-radius ratio on vibration frequencies and buckling loads. The effects of static deformations on vibration frequencies are also investigated. This work also compares the results obtained from the proposed governing equations with those obtained from the classical theory neglecting shear deformation. (C) 2003 Elsevier Ltd. All rights reserved.
Metallurgical reaction of the Sn-3.5Ag solder and Sn-37Pb solder with Ni/Cu under-bump metallization in a flip-chip package
(2003-12-01)
Huang, CS
;
Duh, JG
;
Chen, YM
;
材料科學與工程學系
;
Department of Materials Science and Engineering
Several international legislations recently banned the use of Pb because of environmental concerns. The eutectic Sn-Ag solder is one of the promising candidates to replace the conventional Sn-Pb solder primarily because of its excellent mechanical properties. In this study, interfacial reaction of the eutectic Sn-Ag and Sn-Pb solders with Ni/Cu under-bump metallization (UBM) was investigated with a joint assembly of solder/Ni/Cu/Ti/Si(3)N(4)/Si multilayer structures. After reflows, only one (Ni,Cu)(3)Sn(4) intermetallic compound (IMC) with faceted and particlelike grain feature was found between the solder and Ni. The thickness and grain size of the IMC increased with reflow times. Another (Cu,Ni)(6)Sn(5) IMC with a rod-type grain formed on (Ni,Cu)(3)Sn(4) in the interface between the Sn-Pb solder and the Ni/Cu UBM after more than three reflow times. The thickness of the (Ni,Cu)(3)Sn(4) layer formed in the Sn-Pb system remained almost identical despite the numbers of reflow; however, the amounts of (Cu,Ni)(6)Sn(5) IMC increased with reflow times. Correlations between the IMC morphologies, Cu diffusion behavior, and IMC transformation in these two solder systems will be investigated with respect to the microstructural evolution between the solders and the Ni/Cu UBM. The morphologies and grain-size distributions of the (Ni,Cu)(3)Sn(4) IMC formed in the initial stage of reflow are crucial for the subsequent phase transformation of the other IMC.
Modal identification of structures from ambient vibration, free vibration, and seismic response data via subspace approach
(2001-12-01)
Huang, CS
;
Lin, HL
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土木工程學系
;
Department of Civil Engineering
This work presents a unified procedure for determining the natural frequencies, modal damping ratios and modal shapes of a structure from its ambient vibration, free vibration and earthquake response data. To evaluate the coefficient matrices of a state-space model, the proposed procedure applies a subspace approach cooperating with an instrumental variable concept. The dynamic characteristics of a structure are determined from the coefficient matrices. The feasibility of the procedure is demonstrated through processing an in situ ambient vibration measurement of a five-storey steel frame, an impulse response measurement of a three-span continuous bridge, and simulated earthquake responses of five-storey steel frames from shaking table tests. The excellent agreement of the results obtained herein with those published previously confirms the feasibility of the present procedure. Copyright (C) 2001 John Wiley & Sons, Ltd.