• Structural Engineering and Mechanics
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• v.34 no.4
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• pp.449-474
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• 2010

A smart hollow cylinder consisting of a host functionally graded elastic core layer and two surface homogeneous piezoelectric layers is presented in this paper. The bonding between the layers can be perfect or imperfect, depending on the parameters taken in the general linear spring-layer interface model. The effect of such weak interfaces on free vibration and steady-state response is then investigated. Piezoelectric layers at inner and outer surfaces are polarized axially or radially and act as a sensor and an actuator respectively. For a simply supported condition, the state equations with non-constant coefficients are obtained directly from the formulations of elasticity/piezoelasticity. An approximate laminated model is then introduced for the sake of solving the state equations conveniently. It is further assumed that the hollow cylinder is embedded in an elastic medium and is simultaneously filled with compressible fluid. The interaction between the structure and its surrounding media is taken into account. Numerical examples are finally given with discussions on the effect of some related parameters.

• Electrical & Electronic Materials
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• v.11 no.10
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• pp.24-31
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• 1998

Interfacial effect in polymetric composites have been studied extensively. This report deals mainly with the effects of interfacial space charge and interface structure. A model for the dynamic process of interfacial space charge accumulation is proposed. The new model might interpret some interface phenomena which is difficult to be explained in terms of traditional Maxwell-Wagner theory. An interface structure is also presented, by which the importance of surface treatment of glass Fiber for improving the properties of FRP could be well understood.

• Journal of the Korean Institute of Intelligent Systems
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• v.16 no.2
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• pp.144-149
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• 2006

This paper deals with a balanced model reduction for uncertain nonlinear systems via T-S fuzzy approach. We define a generalized controllability/observability gramian and obtain a balanced state space model using generalized gramians which can be obtained from solutions of linear matrix inequalities. We present a balanced model reduction scheme by truncating not only state variables but also uncertain elements. An upper bound of the model reduction error will also be suggested. In order to demonstrate the efficacy of our method, a numerical example will be presented.

• Proceedings of the Korea Water Resources Association Conference
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• 2002.05a
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• pp.27-40
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• 2002

Developed at Colorado State University, CASC2D-SED is a physically-based model simulating the hydrologic response of a watershed to a distributed rainfall field. The time-dependent processes include: precipitation, interception, infiltration, surface runoff and channel routing, upland erosion, transport and sedimentation. CASC2D-SED is applied to Goodwin Creek, Mississippi. The watershed covers 21 $\textrm{km}^2$ and has been extensively monitored both at the outlet and at several internal locations by the ARS-NSL at Oxford, MS. The model has been calibrated and validated using rainfall data from 16 meteorological stations,6 stream gaging stations and 6 sediment gaging stations. Sediment erosion/deposition rates by size fraction are predicted both in space and time. Geovisualization, a powerful data exploration technique based on GIS technology, is used to analyze and display the dynamic output time series generated by the CASC2D-SED model.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11b
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• pp.134-139
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• 2002

This paper presents a servo design method for high track-density hard disk drives, in which the plant time delay, mainly due to the processor computation time, is taken into account. The key idea behind the proposed design method is to incorporate the delay model into the output equation of the state-space representation for the plant model; thereby, the delay is accounted for by a standard state observer in a natural manner, with simplified state equations as compared to those for conventional methods. The results from practical application confirm that the proposed method is quite effective in realizing a high-bandwidth servo system in hard disk drives.

• Proceedings of the KSR Conference
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• 2011.10a
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• pp.2609-2614
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• 2011

A proportional integral derivative (PID) controller is designed and applied to a magnetic levitation conveyor system to control the levitation gap length of the electromagnet constantly. The PID gain parameters are optimized by response surface methods (RSM). The controller is verified with the state-space model of electromagnetic suspension by MATLAB/SIMULINK program. And, the controller and the state-space model are also verified experimentally. Simulation and experimental results shows the effectiveness of the PID gain tuning by RSM as compared with the classical PID tuning.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.2
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• pp.195-201
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• 2001

An inverse heat conduction problem(IHCP) arises when unknown heat fluxes and whole temperature field are to be found with temperature measurements of a few points. In this paper, observers are proposed as solution algorithm for the IHCP. A 1-dimensional heat transfer problem is modeled with modal analysis and state space equations. Position of the heat source is estimated through test heat inputs and the autocorrelation among a few of temperature data. The modified Bass-Gura method is used to design a state observer to estimate the intensity of heat source and the whole temperature field of a 1-dimensional body. To verify the reliability of this estimator, analytic solutions obtained from the proposed method are compared.

• Journal of Electrical Engineering and Technology
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• v.11 no.1
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• pp.9-19
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• 2016

Accurate models of the characteristics of typical inverse-time overcurrent (OC) protective devices play an important role in the protective coordination schemes. This paper presents a novel approach to determine the OC protective device parameters. The approach is based on the Eigensystem Realization Algorithm which generates a state space model to fit the characteristics of OC protective devices. Instead of the conventional characteristic curves, the dynamic state space model gives a more exact fit of the OC protective device characteristics. This paper demonstrates the feasibility of decomposing the characteristic curve into smooth components and oscillation components. 19 characteristic curves from 13 typical and 6 non-typical OC protective devices are chosen for curve-fitting. The numbers of fitting components required are determined by the maximum absolute values of errors for the fitted equation. All fitted equations are replaced by a versatile equation for the characteristics of OC protective devices which represents the characteristic model of a novel flexible OC relay, which in turn may be applied to improve the OC coordination problems in the sub-transmission and distribution systems.

• Journal of Information Processing Systems
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• v.7 no.4
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• pp.635-652
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• 2011

In ubiquitous environments, many applications need to process data with time and space dimensions. Because of this, there is growing attention not only on gathering spatiotemporal data in ubiquitous environments, but also on processing such data in databases. In order to obtain the full benefits from spatiotemporal data, we need a data model that naturally expresses the properties of spatiotemporal data. In this paper, we introduce three spatiotemporal data models extended from temporal data models. The main goal of this paper is to determine which data model is less complex in the spatiotemporal context. To this end, we compare their query languages in the complexity aspect because the complexity of a query language is tightly coupled with its underlying data model. Throughout our investigations, we show that it is important to intertwine space and time dimensions and keep one-to-one correspondence between an object in the real world and a tuple in a database in order to naturally express queries in ubiquitous applications.

• Proceedings of The Korean Society of Agricultural and Forest Meteorology Conference
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• 2003.09a
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• pp.50-53
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• 2003

Models have been developed to estimate leaf wetness duration (LWD) using conventional weather observations, e.g., air temperature, water vapor pressure, and wind speed, which are relatively invariant over space (Pedro and Gillespie, 1982; Gleason et al., 1994; Francl and Panigrahi, 1997).(omitted)