• Proceedings of the KSR Conference
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• 2009.05a
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• pp.552-559
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• 2009

Most damage identification methods for structural health monitoring developed to date utilize modal domain responses which require postprocessing and inevitably contain errors in transforming the domain of responses. In this paper, the feasibility of a damage identification method based on dynamics responses from moving loads is experimentally verified. The experiment is performed via applying periodic and non-periodic moving loads to a steel beam and acceleration and displacement responses of the beam is measured. The moving loads is applied using steel balls and the damage of a structure is simulated by saw-cutting the beam. The damage identification results using the measured responses show that the moving load response based damage identification method successfully identify all damages in the beam.

• Wind and Structures
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• v.18 no.1
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• pp.21-35
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• 2014

The latest developments in topology optimization are integrated with Computational Fluid Dynamics (CFD) for the conceptual design of building structures. The wind load on a building is simulated using CFD, and the structural response of the building is obtained from finite element analysis under the wind load obtained. Multiple wind directions are simulated within a single fluid domain by simply expanding the simulation domain. The bi-directional evolutionary structural optimization (BESO) algorithm with a scheme of material interpolation is extended for an automatic building topology optimization considering multiple wind loading cases. The proposed approach is demonstrated by a series of examples of optimum topology design of perimeter bracing systems of high-rise building structures.

• Journal of the Semiconductor & Display Technology
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• v.1 no.1
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• pp.1-7
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• 2002

Modem technology depends on the reliability of extremely high precision equipments. In the production of semiconductor wafer, optical and electron microscopes, ion-beam, laser device must maintain their alignments within a sub-micrometer. This equipment requires a vibration free environment to provide its proper function. Therefore, this high technology equipments require very strict environmental vibration criteria because it is used as basic data for the design of building structure and structural dynamics of equipment. In this paper, the new approach is proposed to investigate the mismatch problem of time and frequency domain for vibration criteria of sensitive equipment. The proposed approach is based on a vibration measurement data and a relative transfer function which can be obtained by experiment or analysis.

• Structural Engineering and Mechanics
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• v.33 no.4
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• pp.391-406
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• 2009

Viscoelastic materials store as well as dissipate energy to the thermal domain under deformation. Two efficient modelling techniques reported in literature use coupled (thermo-mechanical) ATF (Augmenting Thermodynamic Fields) displacements and ADF (Anelastic Displacement Fields) displacements, to represent the constitutive relationship in time domain by using certain viscoelastic parameters. Viscoelastic parameters are first extracted from the storage modulus and loss factor normally reported in hand books with the help of Genetic Algorithm and then constitutive relationships are used to obtain the equations of motion of the continuum after discretizing it with finite beam elements. The equations of motion are solved to get the frequency response function and modal damping ratio. The process may be applied to study the dynamic behaviour of composite beams and rotors comprising of several viscoelastic layers. Dynamic behaviour of a composite beam, formed by concentric layers of steel and aluminium is studied as an example.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.10 no.16
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• pp.39-51
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• 1987

This paper deals with the case analysis of second order processes under sampled-data. Proportional Integral-Derivative(PID) control, and development of Decision Support Systems(DSS) for such processes. In this paper three techniques were described for identifying the dynamics of closed loop stable processes. The first, called pulse testing is a frequency-domain method, which yields the frequency response diagram of an open loop process. The second is a time-domain method which yields the gain and time constants of the process model. The third technique is based on step response and gives the parameters of PID controllers. The development of DSS design programs consisting of above three techniques will provide very powerful tools in the microcomputer based process control.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2001.11b
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• pp.1376-1383
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• 2001

Modem technology depends on the reliability of extremely high technology equipments. In the production of semiconductor wafer, optical and electron microscopes, ion-beam, laser device must maintain their alignments within a sub-micrometer. This equipment requires a vibration free environment to provide its proper function. Especially, lithography and inspection devices, which have sub-nanometer class high accuracy and resolution, have come to necessity for producing more improved giga and tera class semiconductor wafers. This high technology equipments require very strict environmental vibration standard, vibration criteria, in proportion to the accuracy of the manufacturing, inspecting devices. The vibration criteria of high sensitive equipment should be represented in the form of 'exactness' and 'accuracy', because this is used as basic data for the design of building structure and structural dynamics of equipment. This paper deals with the properties of time and frequency domain in order to obtain more improved vibration criteria for high sensitive equipment.

• Structural Engineering and Mechanics
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• v.3 no.3
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• pp.273-287
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• 1995

Stochastic response of systems to random excitation can be estimated by direct integration methods in the time domain such as the stochastic central difference method (SCDM). In this paper, the SCDM is applied to compute the variance and covariance in response of linear and nonlinear structures subjected to random excitation. The accuracy of the SCDM is assessed using two-DOF systems with both deterministic and random material properties excited by white noise. For the former case, closed-form solutions can be obtained. Numerical results also are presented for a simply supported geometrically nonlinear beam. The stiffness of this beam is modeled as a random field, and the beam is idealized by the stochastic finite element method. A perturbation technique is applied to formulate the equations of motion of the system, and the dynamic structural response statistics are obtained in a time domain analysis. The effect of variations in structural parameters and the numerical stability of the SCDM also are examined.

• Earthquakes and Structures
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• v.2 no.4
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• pp.323-336
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• 2011

The problem of reconstruction of complete building response from a limited number of response measurements is considered. The response at the intermediate degrees of freedom is reconstructed by using piecewise cubic Hermite polynomial interpolation in time domain. The piecewise cubic Hermite polynomial interpolation is preferred over the spline interpolation due to its trend preserving character. It has been shown that factorization of response data in variable separable form via singular value decomposition can be used to derive the complete set of normal modes of the structural system. The time domain principal components can be used to derive empirical transfer functions from which the natural frequencies of the structural system can be identified by peak-picking technique. A reduced-rank approximation for the system flexibility matrix can be readily constructed from the identified mass-orthonormal mode shapes and natural frequencies.

• BMB Reports
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• v.51 no.12
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• pp.609-610
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• 2018

Glycosylation is one form of protein modification and plays a key role in protein stability, function, signaling regulation and even cancer. NleB and SseK are bacterial effector proteins and possess glycosyltransferase activity, even though they have different substrate preferences. NleB/SseKs transfer the GlcNAc sugar to an arginine residue of host proteins, leading to reduced $NF-{\kappa}B-dependent$ responses. By combining X-ray crystallography, NMR, molecular dynamics, enzyme kinetic assays and in vivo experiments, we demonstrated that a conserved HEN (His-Glu-Asn) motif in the active site plays a key role in enzyme catalysis and virulence. The lid-domain regulates the opening and closing of the active site and the HLH domain determines the substrate specificity. Our findings provide evidence for the enzymatic mechanism by which arginine can be glycosylated by SseK/NleB enzymes.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• v.26 no.4
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• pp.333-342
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• 2022

In this paper, we perform a direct comparison study of real experimental data for domain rearrangement and the Cahn-Hilliard (CH) equation on the dynamics of morphological evolution. To validate a mathematical model for physical phenomena, we take initial conditions from experimental images by using an image segmentation technique. The image segmentation algorithm is based on the Mumford-Shah functional and the Allen-Cahn (AC) equation. The segmented phase-field profile is similar to the solution of the CH equation, that is, it has hyperbolic tangent profile across interfacial transition region. We use unconditionally stable schemes to solve the governing equations. As a test problem, we take domain rearrangement of lipid bilayers. Numerical results demonstrate that comparison of the evolutions with experimental data is a good benchmark test for validating a mathematical model.