• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.35 no.1
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• pp.80-85
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• 2022

ZnO-based transparent conductive films have been widely studied to achieve high performance optoelectronic devices such as next generation flexible and transparent display systems. In order to achieve a transparent flexible ZnO-based device, a low temperature growth technique using a flexible polymer substrate is required. In this work, high quality flexible ZnO films were grown on colorless polyimide substrate using atomic layer deposition (ALD). Transparent ZnO films grown from 80 to 200℃ were fabricated with a metal-semiconductor-metal structure photodetectors (PDs). As the growth temperature of ZnO film increases, the photocurrent of UV PDs increases, while the sensitivity of that decreases. In addition, it is found that the response times of the PDs become shorter as the growth temperature increases. Based on these results, we suggest that high-quality ZnO film can be grown below 200℃ in an atomic layer deposition system, and can be applied to transparent and flexible UV PDs with very fast response time and high photocurrent.

• Journal of Korean Tunnelling and Underground Space Association
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• v.10 no.4
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• pp.371-382
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• 2008

The objective of this study is to develop the laboratory testing method for evaluating the loading capacity of lattice girder used for support in tunnel structure. 3-point flexible strength test and 4-point flexible strength test were performed on three types of lattice girder, such as $LG-50{\times}20{\times}30$, $LG-70{\times}20{\times}30$, and $LG-95{\times}22{\times}32$, mainly used in Korea. Two types of loading position for each flexible strength test were used to analyze the behavior of load-deformation. The loading distribution in the lattice girder was analyzed by means of strains measured by strain gauges attached on chords and diagonal bars. In 3-point flexible strength test, the difference of the average of maximum flexible strength according to loading position had the range from 10% to 33%. In 4-point flexible strength test, the average of maximum flexible strength according to loading position was almost no difference. The difference between the average of maximum flexible strengths obtained from 3-point and 4-point flexible strength tests was from 13.56 to 31.55%. The load applied on the lattice girder was concentrated to the main chord in 3-point flexible strength test. The load applied on the lattice girder in 4-point flexible strength test was distributed to three chords and diagonal bars.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2012.10a
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• pp.449-450
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• 2012

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2010.11a
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• pp.273-274
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• 2010

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.8 no.4
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• pp.274-286
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• 1996

Two-dimensional flexible body analysis (hydroelasticity theory) is adopted to a very large floating structure that may be multimodule and extend in the longitudinal direction. The boundary-element method (BEM) and Green function method(GFM) are used to obtain the hydrodynamic coefficients. The structure is considered to be a flexible beam responding to waves in the vertical direction and a consistent formulation for the hydrostatic stiffness is derived. The resulting coupled equations of motion are solved directly. Two designs of the module connectors are considered: a rotationally-flexible hinge connector, and a rotationally-rigid connector Numerical examples are presented to an integrated system of semi-submersibles. The analysis provides basic motions and section forces, which are useful to develop an understanding of the fundamental modes of displacement and force amplitudes for which multi-module VLFSs must be designed. The results show that while the hinge connectors result in greater motion, the rigid connectors increase substantially the sectional moments.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.25 no.3
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• pp.339-347
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• 2014

In this paper, the authors present a new design for a broad-band metamaterial(MTM) absorber that utilizes flexible substrate. The proposed MTM unit cell is constructed by a electric-inducive-capacitive(ELC) resonator and a cut-wire on the same side of the flexible polyimide substrate. To reduce the radar cross section at frequencies other than the targeted frequency bands, the metallic pattern layer of the proposed structure is placed facing toward the incident wave propagation direction. A prototype absorber was fabricated with a planar array of $33{\times}45$ unit cells. Our experiments showed that the proposed absorber exhibits a peak absorption rate of 92 % and 93 % at 9.06 GHz and 15.0 GHz, respectively, and 75 % of the full-width at half-maximum(FWHM) bandwidth is achieved. The proposed backplane-less MTM structure can be used for a broad-band microwave absorber and irregular surface applications.

• Journal of Mechanical Science and Technology
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• v.16 no.7
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• pp.896-901
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• 2002

This paper presents a nonlinear modeling method for dynamic analysis of flexible structures undergoing overall motions that employs the mode approximation method. This method, different from the naive nonlinear method that approximates only Cartesian deformation variables, approximates not only deformation variables but also strain variables. Geometric constraint relations between the strain variables and the deformation variables are introduced and incorporated into the formulation. Two numerical examples are solved and the reliability and the accuracy of the proposed formulation are examined through the numerical study.

• 제어로봇시스템학회:학술대회논문집
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• 1997.10a
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• pp.280-284
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• 1997

In this paper, Nonlinear VSS control based on bang-bang control concept is derived under the assumption that the control input is bounded. We try to derive control algorithm which has almost same performance as the time optimal control. We focus this control scheme on the real implementation of DC motor position controller of flexible link, i.e. we obtain the switching curves from the real data of DC motor system operating under the full maximum and minimum applied voltages. State space is separated into several regions and we set different switching surfaces in each region to reduce chattering problem. The efficiency of the proposed controller is compared with PID controller and it is shown that the controller converges fast than PID controller without chattering. The hybrid controller scheme is also proposed not only to control the position of hub but also to reduce the vibration of end tip of flexible link.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.400.2-400.2
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• 2016

Dye-sensitized solar cells (DSSCs) have been widely investigated as a next generation solar cell because of their simple structure and low manufacturing cost. To realize a commercially competitive technology of DSSCs, it is imperative to employ a technique to prepare nanocrystlline thin film on the flexible organic substrate, aiming at increasing the flexibility and reducing the weight as well as the overall device thickness of DSSCs. The key operation of glass-to-plastic substrates conversion is to prepare mesoporous TiO2 thin film at low temperature with a high surface area for dye adsorption and a high degree of crystallinity for fast transport of electrons. However, the electron transport in the TiO2 film synthesized at low temperature is very poor. So, in this study, TiO2 films synthesized at high temperature were transferred on the selective substrate. We fabricated DSSCs at low temperature using this method. So, we confirmed that the performance of DSSCs using TiO2 films synthesized at high temperature was improved.

• Journal of the Korean Society for Precision Engineering
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• v.9 no.2
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• pp.81-91
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• 1992

A control methodology for suppressing the elastodynamic responses of high-speed flexible linkage mechanisms is presented by adopting the concept of smart structures featuring piezoelectric films. The dynamic modeling of the proposed mechanism is accomplished by employing a finite element formulation which accounts for dynamic motion in both inertial and elastic coordinates. The dynamics of piezoelectric actuators and sensors bonded on the original flexible structure are developed for one-dimensional beam in conjunction with the modal analysis. The linear optimal controller which consists of a feedback control law and a Luenberger observer is employed. Numerical simulation is performed to evaluate the improvement of elastodynamic responses.