• Journal of Mechanical Science and Technology
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• v.16 no.1
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• pp.1-12
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• 2002

In this study, a passive suppression scheme for nonlinear flutter problem of composite panel, which is believed to be more reliable than the active control methods in practical operations, is proposed. This scheme utilizes a piezoelectric inductor-resistor series shunt circuit. The finite element equations of motion for an electromechanically coupled system is derived by applying the Hamilton\\`s principle. The aerodynamic theory adopted for the present study is based on the quasi-steady piston theory, and von-barman nonlinear strain-displacement relation is also applied. The passive suppression results for nonlinear panel flutter are obtained in the time domain using the Newmark-$\beta$ method. To achieve the best damping effect, optimal shape and location of fille piezoceramic (PZT) patches are determined by using genetic algorithms. The effects of passive suppression are investigated by employing in turn one shunt circuit and two independent shunt circuits. Feasibility studies show that two independent inductor-resistor shunt circuits suppresses flutter more effectively than a single shunt circuit. The results clearly demonstrate that the passive damping scheme that uses piezoelectric shunt circuit can effectively attenuate the flutter.

• Journal of Power System Engineering
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• v.20 no.3
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• pp.17-21
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• 2016

The corrosion behavior of aluminum alloys in the $H_2SO_4$ solution was investigated based on potentiodynamic techniques. Electrochemical properties, such as corrosion potential($E_c$), passive potential($E_p$), corrosion current density($I_c$), corrosion rate(mpy), of Al-Mg-Si, Al-Cu-Si and Al-Si alloys were characterized at room temperature. Passive aluminum oxide film, which including $Al_2(SO_4)_3$ and $3Al_2O_34SO_38H_2O$, were uniformly formed on the surface via the reaction of Al with $SO{_3}^{2-}$ or $SO{_4}^{2-}$ ions in the $H_2SO_4$ solution and the dependence of the corrosion behavior on the alloying element was discussed. The selective leaching of alloy element increased with increasing Cu content in the aluminum alloys.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.8 no.2
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• pp.27-35
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• 2012

Five zero energy house models developed in Korea for the purpose of the energy performance were compared and analyzed in the study. The standard passive house model applying common technology and efficient energy performance elements was proposed. Standard passive house 5 models have been developed commonly aiming at 100% energy saving, applying high-performance and high-efficiency exterior thermal insulation, using 3 low-e coated window system, and targeting average 0.65 ACH to enhance privacy. Energy recovery ventilators and dry and cold radiant heating floor has been partially applied. Eco-design techniques such as the awning device, heat insulating door, using natural light have been used. Solar and geothermal systems as the application of renewable energy technologies have been commonly applied. And fuel cells were applied to a partial model. The standard model based on common technical elements and average performance of each element and obtained from five model analysis has been proposed in the study.

• Ocean and Polar Research
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• v.42 no.4
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• pp.293-301
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• 2020

Blades of tidal stream turbines have to sustain many different loads during operation in the underwater environment, so securing their structural safety is a key issue. In this study, we focused on periodic loads due to wave orbital motion and propose a load reduction method with a blade design. The flap of an airplane wing is a well-known structure designed to increase lift, and it can also change the load distribution on the wing through deflection. For this reason, we adopted a passive flap structure for the load reduction and investigated its effectiveness by an analytical method based on the blade element moment theory. Flap torsional stiffness required for the design of the passive flap can be obtained by calculating the flap moment based on the analytic method. Comparison between a flapped and a fixed blade showed the effect of the flap on load reduction in a high amplitude wave condition.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2005.11a
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• pp.63-64
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• 2005

This paper proposed a miniaturization passive element employing the multiple microstrip line. As a result of this method, we realized the transmission line miniaturized. The applying structure designed and evaluated a power divider on GaAS MMIC circuit. It draws a plan in a center Frequency as the observation could do good characteristic.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.37 no.5
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• pp.801-813
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• 2017

Passive force acting on the kicker block used to support a raker is different dependent on soil's type. The passive force incorporating a factor of safety is considered for design of the retaining wall. However, an actual passive force developing on the kicker block is overestimated and it may lead to an unsafe design. In this study, the actual passive forces acting on the kicker block in soil ground are evaluated using 3-D Finite Element Program, PLAXIS. Soft and weathered soils are selected as a soil ground. The relation curves between horizontal displacement and actual passive force of the kicker block for each soil ground are obtained through numerical analyses. From the curves, the actual passive forces are determined as a yielding point, which are about 55.5% and 66% of Rankine's passive forces in soft and weathered soils, respectively.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2005.11a
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• pp.17-22
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• 2005

This paper presents a improvement equivalent circuit model for Miniaturized LTCC bandpass filter with two transmission zeros using feed-back capacitor. The bandpass filter equivalent circuit is evaluated by parallel network analysis. Besides, the filter is modeled by proposed passive element modeling algorithm in previous work. Compared to the equivalent circuit of established paper that is configured by excepted capacitance between ground plate and signal plate, this model can include that. The result, the LTCC bandpass filter reduce layers and the size is more smaller.

• International Journal of Automotive Technology
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• v.6 no.6
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• pp.607-613
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• 2005

In this study, a simplified approach to modeling the dynamic characteristics of passive constrained layer damping treatments in finite element models is presented. The basic concept is to represent multi-layered composite structures using an equivalent single layer. The equivalent properties are obtained by using the RKU (Ross, Kerwin and Ungar) equations. Comparisons are given between results obtained by the dynamic analysis of the simple models implemented in MSC/NASTRAN and by test measurements. Surface damping treatments are applied to automotive panels as well as simple structures. Using the proposed equivalent modeling technique, higher computational efficiency for the damped composite structures has been obtained.

• Smart Structures and Systems
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• v.2 no.4
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• pp.305-312
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• 2006

In the case of hospital buildings, where seismic design requirements are very high, existing structuresand especially those attacked by past earthquakes, appear, often, unable to fulfil the necessary safety prerequisites. In this paper, the retrofitting of hospital buildings is investigated, using alternative methods of repair and strengthening. Analysis of an existing hospital building in Patras, Greece, is performed. The load-bearing system is a reinforced concrete system. Two solutions are proposed: strengthening using concrete jackets around column and beam elements and application of viscoelastic dampers for the increase of the stability of the structure. Adequate finite element models are constructed for each case and conclusions are drawn on the efficiency of each rehabilitation method.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.29 no.7
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• pp.22-27
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• 2015

In this paper, the problem of voltage unbalancing in series-connected multiple electric double-layer capacitors(EDLCs) is studied. Good understanding of this problem is required in order to increase reliability and stability of an energy storage system comprising EDLCs. Existing methods to settle voltage unbalancing cannot mitigate the problem enough for each cell, since most method have been applied to each module. For equalizing between cells, Zener diode which is one of passive method have been well examined in literature. However, Zener have well not used in balancing due to heating problem. In addition, It is difficult to choose Zener diode fitted rating voltage of EDLC, because of its internal resistance. Thus, we proposed passive balancing using Zener diode by analyzing parasitic element of Zener and EDLC. To experimentally confirm the balancing effect, we compared in two occasions which are with and without passive. As a result, proposed passive balancing circuit mitigated unbalanced voltage gap between EDLCs.