• Journal of Industrial Technology
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• v.19
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• pp.227-233
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• 1999

Simple equations which can predict "exact" values of the natural frequency of vibration for the special orthotropic laminates are presented. Many laminates with certain orientations have decreasing values of $B_{16}$ and $B_{26}$ as the number of plies increases. Such laminates, with $D_{16}=D_{26}{\rightarrow}0$, including the laminates with anti-symmetric configurations can be solved by the same equation for the special orthotropic laminates. If the quasi-isotropic constants are used, the equations for the isotropic plates can be used. Use of some coefficients cab produce "exact" value for laminates with such configurations. Natural frequencies of the plate with varying aspect ratios is presented.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2003.11a
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• pp.54-58
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• 2003

In this study, the solution of Gel'fand-Levitan-Marchenko integral equation in the inverse scattering problem is efficiently solved for arbitrarily specified spectra pattern which are reflected from the restricted potential. The procedure is based on the successive approach without iterations. This method lessens the truncation errors which plague conventional design schemes using specific windows for reflection coefficients. It is shown that the method is adequate for the synthesis of the continuously varying one-dimensional potential of the nonuniformly distributed dielectric constants.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.66 no.1
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• pp.27-32
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• 2017

This paper presents a Daubechies wavelet-based fault detection method for fault identification in transmission lines. After the Daubechies wavelet coefficients are calculated, the proposed algorithm has been implemented difference equation using C language. We have modeled a 154kV transmission line using the ATPDraw software and have acquired test data. In order to evaluate effects of DC offset, simulations carried out while varying an inception angle of the voltage $0^{\circ}$, $45^{\circ}$, $90^{\circ}$. For performance evaluation, fault distance was varied. As we can see from the off-line simulation, the proposed algorithm shows rapid and accurate fault detection. Also we can see the proposed algorithm is not affected by the fault inception angle change.

• International Journal of Aeronautical and Space Sciences
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• v.6 no.2
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• pp.46-55
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• 2005

A rocket-powered vehicle is designed conceptually which uses an engine running on methane and oxygen and delivering 10 tons of thrust. The aerodynamic coefficients of the vehicle are taken to be those of the Japan's HOPE-X, and the weight of this vehicle is estimated using a method developed by NASA. The resulting vehicle will be about 9 meters long, 5.8 meters in wing span, weigh about 2 tons empty, carry a maximum of 5.6 tons of propellant, and endure a g-load of 4.5. The craft will be able to carry five passengers, in addition to a pilot, and fly for space tourism between a northern and a southern airport with a maximum g-load varying from 3g to 4g depending on the route flown.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.11
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• pp.1010-1013
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• 2006

Hydrogenated Diamond-like carbon (DLC) films were Prepared by the radio frequency plasma enhanced chemical vapor deposition (RF PECVD) method on silicon substrates using methane $(CH_4)$ and hydrogen $(H_2)$ gas for the application to solid lubricant of MEMS devices. We have checked the influence of varying RF power on tribological properties of DLC film. We have checked their performance as two kinds of method such as FFM (Friction Force Microscope) and BOD (Ball-on Disk) measurement. The friction coefficients and the contact number of cycles to steady state decreased as the increase of RF power with FFM and BOD measurement, respectively.

• Wind and Structures
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• v.7 no.1
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• pp.41-54
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• 2004

An analysis refinement of the Messina Strait suspension bridge project has been recently required, concerning mainly the yaw angle effects on the multi-box deck section aerodynamics and the vortex shedding at low reduced velocities $V^*$. In particular the possible interaction of the axial flow with the large cross beams has been investigated. An original test rig has been designed at this purpose allowing for both forced motion and free motion aero elastic tests, varying the average angle of attack ${\alpha}$ and the deck yaw angle ${\beta}$. The hydraulic driven test rig allowed for both dynamic and stationary tests so that both the stationary coefficients and the flutter derivatives have been evaluated for each yaw angle. Specific free motion tests, taking advantage from the aeroelastic features of the section model, allowed also the study of the vortex shedding induced phenomena.

• Wind and Structures
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• v.15 no.2
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• pp.177-188
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• 2012

The meteorological events that cause most strong winds in Brazil are extra-tropical cyclones, downbursts and tornadoes. However, one hurricane formed off the coastline of southern Brazil in 2005, a tropical storm formed in 2010 and there are predictions that others may form again. Events such as those described in the paper and which have occurred before 1987, generate data for the wind map presented in the Brazilian wind loading code NBR-6123. This wind map presents the reference wind speeds based on 3-second gust wind speed at 10 m height in open terrain, with 50-year return period, varying from 30 m/s (north half of country) to 50 m/s (extreme south). There is not a separation of the type of climatological event which generated each registered velocity. Therefore, a thunderstorm (TS), an extra-tropical pressure system (EPS) or even a tropical cyclone (TC) are treated the same and its resulting velocities absorbed without differentiation. Since the flow fields generated by each type of meteorological event may be distinct, the indiscriminate combination of the highest wind velocities with aerodynamic coefficients from boundary layer wind tunnels may lead to erroneous loading in buildings.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2007.04a
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• pp.21-26
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• 2007

This paper presents an impedance-based structural health monitoring (SHM) technique considering temperature effects. The temperature variation results in a significant impedance variation, particularly both horizontal and vertical shifts in the frequency domain, which may lead to erroneous diagnostic results of real structures. A new damage detection strategy has been proposed based on the correlation coefficient (CC) between the reference impedance data and a concurrent impedance data with an effective frequency shift which is defined as the shift causing the maximum correlation. The proposed technique was applied to a lab-sized steel truss bridge member under the temperature varying environment. From an experimental study, it has been demonstrated that a narrow cut inflicted artificially to the steel structure was successfully detected using the proposed SHM strategy.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.34D no.6
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• pp.50-57
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• 1997

TiO$_{2}$ tin films have been grown by MOCVD and their cahracteristics of crystallization and microstructures ahve been invetigated. Envelope mehtods are applied to the analysis of the transmission spectra to obtain the optical constants such as refractive indices and extinction coefficients for the TiO$_{2}$ thin films. The envelope methods are proved to be accurate by simulatin gthe transmission spectra. TiO$_{2}$ thin films start to crystallize at 350.deg.C and then crystallize fully into anatase phase at 400.deg.C or higher temperatures. Activation energies are obtained by plotting the deposition rate with varying the substrate temperature. It is 17.8 kcal/mol for the reaction limited regions. The refractive index and the extinction coefficient of the TiO$_{2}$ thin film at .gamma.=632.8 nm increases from 2.19 to 2.32 and decreases from 0.021 to 0.007, respectively, as the substrate temperature increases from 400 to 600.deg. C.

• Proceedings of the KIEE Conference
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• 2007.10a
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• pp.433-434
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• 2007

In this paper, active control of noise in a HVAC duct is considered. Most adaptive control filters have used FIR structures based on filtered-x LMS algorithms. But, the IIR structures are more desirable for the active control of duct noise in order to remove the poles introduced by the acoustic feedback and presented an algorithm to adjust the coefficients of an IIR filter using the recursive least mean square (RLMS) algorithm. A smoothed LMS algorithm is proposed to improve a convergent speed of filter parameters when the noise is wide band and power of input is time varying. And computer simulations have performed to show the effectiveness of the proposed algorithm.