• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.03a
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• pp.69-74
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• 2004

In scramjet engines with sidewall compression inlet, it is well known that a non-uniform flow appears since a separated region is generated near the flow centerline on the body side. The separated region is caused by shock-boundary layer interaction and likely to cause un-start phenomena since the flow in the separated region is subsonic and acts as a communication path between the isolator and the combustor. In the present study, the non-uniform flow characteristics in the scramjet inlet-isolator region are numerically studied in detail. Effect of flow suction from body sidewall surface on the non-uniform flow field numerically examined to clarify the flow mechanism to suppress the un-start transition.

• Structural Engineering and Mechanics
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• v.8 no.3
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• pp.299-310
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• 1999

One problem with base isolators of the sliding type is that their dynamic responses are nonlinear, which cannot be solved in an easy manner, as distinction must be made between the sliding and non-sliding phases. The lack of a simple method for analyzing structures installed with base isolators is one of the obstacles encountered in application of these devices. As an initial effort toward simplification of the analysis procedure for base-isolated structures, an approach will be proposed in this paper for computing the equivalent damping for the resilient-friction base isolators (R-FBI), based on the condition that the sum of the least squares of errors of the linearized response with reference to the original nonlinear one is a minimum. With the aid of equivalent damping, the original nonlinear system can be replaced by a linear one, which can then be solved by methods readily available. In this paper, equivalent damping curves are established for all ranges of the parameters that characterize the R-FBI for some design spectra.

• Smart Structures and Systems
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• v.11 no.4
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• pp.387-410
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• 2013

This paper deals with the damage assessment for isolators of base-isolated building systems considering the torsion-coupling (TC) effect by establishing damage indices. The damage indices can indicate the reduction in lateral stiffness of the isolator story as explicit formulas in terms of modal parameters. In addition, the damage location, expressed in terms of the estimated damage index and eccentricities before and after damage, is also presented. Numerical analysis shows that the proposed algorithms are applicable for general base-isolated multi-story TC buildings. A procedure from the analysis of seismic response to the implementation of damage indices is demonstrated by using a numerical case. A system identification technique is employed to extract modal parameters from seismic responses of a building. Results show that the proposed indices are capable of detecting the occurrence of damage and preliminarily estimating the location of damaged isolator.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2006.05a
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• pp.615-618
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• 2006

The broadband power detector for direct- onversion Six-port output circuit was designed and implementaed in this paper. The power detector should linearly operated to produce the linear amplitude and phase signal fer input RF signal in required broadband. So, the power detector should be designed under conditions of matching circuit with low VSWR. The designed power detectors, which were implemented in L-band with 50 ohm matching and Ku-band with matching circuit and isolator, respectively, were evaluated in the performances.

• Journal of the Korean Society for Precision Engineering
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• v.17 no.1
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• pp.21-26
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• 2000

This paper describes a positioning system for ultra-precision that will be utilized in semiconductor manufacturing field and precision machinery. This system is composed with laser scale unit with 10nm resolution, ball screw with LM guide, brushless DC servo motor, vibration isolator and is equipped in chamber for continuous measuring environment. The dynamic of table, the problem of servo control and the traceability for micro step motion are described. These data will be applied for getting more stable system with 50nm resolution.

• Journal of the Korean Society of Industry Convergence
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• v.4 no.2
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• pp.167-175
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• 2001

In this study, a general perturbation method is presented to reanalysis dynamic response of base-isolated systems. The perturbation is expanded to general order and which provide the formulation of perturbed solutions. in which eigensolutions of non-modified system are treated as unperturbed solutions. The accuracy of present method is tested using a 2-DOF system with isolator, where the stiffness and damping coefficients of isolator are changed, respectively, The reanalyzed eigensolutions and response using perturbed solutions are successfully approached to exact ones after just first perturbation. Supposing the practical criterion as ${\pm}5%$ error, the modification range of -50%~30% from original system can be allowed for the first order perturbation. Using higher order solutions, the applicable range will be wide.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2003.03a
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• pp.85-92
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• 2003

Hysteretic behaviors of a seismic isolator are identified by using the regularized output error estimator (OEE) based on the secant stiffness model. A proper regularity condition of tangent stiffness for the current OEE is proposed considering the regularity condition of Duhem hysteretic operator. The proposed regularity condition is defined by 12-norm of the tangent stiffness with respect to time. The secant stiffness model for the OEE is obtained by approximating the tangent stiffness under the proposed regularity condition by the secant stiffness at each time step. A least square method is employed to minimize the difference between the calculated response and measured response for the OEE. The regularity condition of the secant stiffness is utilized to alleviate ill-posedness of the OEE and to yield numerically stable solutions through the regularization technique. An optimal regularization factor determined by geometric mean scheme (GMS) is used to yield appropriate regularization effects on the OEE.

• Proceedings of the Korean Magnestics Society Conference
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• 2004.12a
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• pp.191-192
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• 2004

• Proceedings of the Korean Magnestics Society Conference
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• 2004.12a
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• pp.189-190
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• 2004

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2010.10a
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• pp.252-253
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• 2010