• Journal of the Institute of Electronics Engineers of Korea SC
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• v.49 no.3
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• pp.75-81
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• 2012

In this paper, an efficient means to estimate the dispersion characteristics of active FSS (or ESS) is presented. We numerically investigate the effective permittivity and the transmission coefficient of 2D metal-fiber composites using linear-lumped impedance loading. We modify the GEC method which is applied to 2D fiber composite material with arbitrary fiber orientation. We show that by varying the impedance value it is possible to control the resonance frequency of the array as well as the bandwidth.

• Environmental Sciences Bulletin of The Korean Environmental Sciences Society
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• v.4 no.3
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• pp.165-171
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• 2000

Experiments were carried out to measure variations in the oxidation potential and current density using the polarization curves of polycarbonate. The results were then examined to identify the influences affecting the oxidation potential related to various conditions, such as temperature, pH, and oxydase(citrate and lipase). The lines representing the active anodic and cathodic dissolution shifted only slightly in the potential direction relative to temperature, pH, and the effect of the enzyme. The Tafel slope for the anodic and cathodic dissolution was determined such that the reversibility polarization was indicated as being effected by various conditions. The slope of the polarization curves describing the active-to-passive transition region shifted noticeably in their direction. Also, by varying the conditions, the optimum conditions for the most ready transform were identified, including temperature, pH, oxidation rate, and resistance of oxidation potential. The critical oxidation sensitivity(I(sub)r/I(sub)f) of the anodic current density peak and maximum passive current density was also determined, which is used in measuring the critical corrosion sensitivity of a polycarbonate.

• 제어로봇시스템학회:학술대회논문집
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• 2001.10a
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• pp.178.4-178
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• 2001

In this paper a self-tuning gain-scheduled skyhook control for semi-active suspension systems is investigated. The dynamic characteristics of a continuously variable damper including electro-hydraulic pressure control valves is analyzed. A 2-d.o.f. time-varying quarter-car model that permits variations in sprung mass and suspension spring coefficient is considered. The self-tuning skyhook control algorithm proposed in this paper requires only the measurement of body acceleration. The absolute velocity of the sprung mass and the relative velocity of the suspension deflection are estimated by using integral filters. The skyhook gains are gain-scheduled in such a way that the body acceleration and the dynamic tire force are optimized. An ECU prototype ...

• Journal of Advanced Marine Engineering and Technology
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• v.28 no.3
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• pp.538-550
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• 2004

The convection heat transfer coefficients on the top surface of a large liquid petroleum liquid injection(LPLi) engine piston with the oil gallery are analyzed by solving an inverse thermal conduction problem. The heat transfer coefficients are numerically found so that the difference between analyzed temperatures from the finite element method and measured temperatures is minimized. Using the resulting heat transfer coefficients as the boundary condition, temperature of a large LPLi engine piston is analyzed. With varying cooling water temperature, temperature, stress, and thermal expansion of the piston are analyzed and evaluated.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2005.11a
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• pp.178-179
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• 2005

Numerical and experimental investigation of incompressible turbulent flow and heat transfer through square channels with varying number of ribbed walls were conducted to determined pressure drop and heat transfer. The CFX solver used for the computation. The rough walls have a $45^0$ inclined square rib. Uniform heat flux is maintained on whole inner heat transfer channel area. The numerical results agreed well with experimental data that obtained for 7600$D_h$) of 0.0667. The results show that values of local heat transfer coefficient and friction factor increase with an increasing number of ribbed walls.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.21 no.5
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• pp.747-754
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• 2012

A solar power generator is usually installed outdoors and it is exposed to extreme environments such as snow weight and wind loading. The solar tracker structure should be designed to have sufficient stiffness and strength against such loads. In this paper, simulations are performed by varying the parameters such as wind directions, wind speeds and the pose of the solar panel to evaluate the effects of extreme wind on solar tracker. As the effects of wind load, maximum displacement and maximum equivalent stress in the solar tracker are calculated. Finite element stress analysis is carried out by using the pressure distribution that is obtained by prior wind load analysis due to the flow around the solar tracker. The stress analysis of solar tracker to check and/or improve structural robustness provides some useful instructions for structural design or revision of solar tracker.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 1989.10a
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• pp.25-28
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• 1989

Live load data in domestic office buildings have been collected in a systematic manner. Based on surveyed data, equivalent uniformly distributed load intensities, which produce the same load effect as the actual spatially varying live load, have been obtained for various structural members(such as slab, beam, column, etc.). Influence surface method has been employed to compute load effects under real live load, inclucing beam moment, slab moment as well as axial force and moments in column. The results have been examined to find probabilistic characteristics and relationship between influence area and load intensity(or coefficient of variation). The results were also compared with other survey results and found to be reasonable.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.2 no.3
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• pp.155-165
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• 1990

The purpose of this research is to study the characteristics of heat exchanger using heat pipe under various working conditions by a finite element analysis and experiment. The results are as follows. 1) In this study, h = $Max^B$ is used for the convective heat transfer coefficient and A = 2.761 and B = 0.701 $Mmax^{(-0.0626)}$ were obtained as the results of experiment. 2) For several different working conditions, (Q/Qb) is predicted by varying the values of L/Lt and Re/Rc. The maximum value of (Q/Qb) is achieved when Re/Rc = 1 and Le/Lc = 0.5. 3) The comparison between calculated value and experimental data showed agreement within 5% error. Therefore the method may be used to predict the performance of heat exchanger using heat pipe for similar geometric conditions. 4) For Re/Re/Rc of 0.2-0.3, the minimum thermal resistance exists when Le/Lt is 0.4-0.65.

• Journal of the Korean Institute of Telematics and Electronics
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• v.24 no.4
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• pp.719-726
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• 1987

In this paper, an adaptive IIR (infinite impulse response) notch filter of lattice type is constructed and its adaptation algorithm is proposed for the detection and retrieval of a sine wave signal embedded in noise. A modified method which adapts only one coefficient of the filter is also suggested. All these methods adapt the coefficients while keepting the poles of the filter inside the unit circle on z-plane, and thus they satisfy the condition on the stability of the IIR filter after it has converged. To investigate the convergence characteristics of these methods such as convergence speed and output S/N ratio, intensive computer simulation has been performed by varying the frequency of the sine wave and the input S/N ratio. And the results of the simulation have been compared to those of Rao and Kung's which shows relatively fast convergence speed. The methods proposed here, especially the second one. shows faster convergence speed and higher output S/N ratio than the Rao and Kung's.

• East Asian mathematical journal
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• v.32 no.5
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• pp.659-675
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• 2016

In this paper, we study the generalized Kirchhoff type equation in the presence of past and finite history $$\large u_{tt}-M(x,t,{\tau},\;{\parallel}{\nabla}u(t){\parallel}^2){\Delta}u+{\normalsize\displaystyle\smashmargin{2}{\int\nolimits_0}^t}\;h(t-{\tau})div[a(x){\nabla}u({\tau})]d{\tau}\\\hspace{25}-{\normalsize\displaystyle\smashmargin{2}{\int\nolimits_{-{\infty}}}^t}\;k(t-{\tau}){\Delta}u(x,t)d{\tau}+{\mid}u{\mid}^{\gamma}u+{\mu}_1u_t(x,t)+{\mu}_2u_t(x,t-s(t))=0.$$ Under the smallness condition with respect to Kirchhoff coefficient and the relaxation function and other assumptions, we prove the expoential decay rate of the Kirchhoff type energy.