• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.05a
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• pp.311-315
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• 2002

The coupled finite/boundary element method is used in numerical analysis for acoustic radiation from the vibration of rectangular composite plate which is simply supported. This analysis is validated using the Wallace equation for an isotropic plate. Active control of sound fields has been carried out using 3 pairs of piezoelectric sensor/actuator and a pair of viscoelastic material by passive constrained layer damping treatment. The results show that the optimal placement of piezoelectric sensor/actuator and VE patch is required to control the sound fields from a vibrating composite plate.

• Tunnel and Underground Space
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• v.5 no.2
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• pp.123-133
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• 1995

A two dimensional visco-plastic finite element model capable of handling the multistep excavaton was developed for investigating the effect of excavation-support sequences on the behaviour of underground openings in the jointed rock mass. Ubiquitous joint pattern was considered in the model and joint properties in each set were assumed to be identical. Passive, fully-grouted rockbolts were considered in the model. Visco-plastic deformations of joints and rockbolts were assumed to be governed by Mohr-Coulomb and von Mises yield criteria, respectively. With the ability of removing elements, the model can von Mises yield criteria, respectively. With the ability of removing elements, the model can simulate the multi-step excavation-support sequences. The reliability of the model to the stability analysis for the underground excavation in practice was checked by simulating the behavior of underground crude oil storage caverns under construction.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2012.10a
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• pp.102-107
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• 2012

In this study, the design procedure of hybrid active mount by an electro-magnetic actuator is proposed to reduce the transmitted force from naval shipboard equipment to ship hull structure. The hybrid type mount which is composed of a passive rubber element and an electro-magnetic actuator is introduced and, through the vibration measurement for the objective pump system, the required force of the actuator is computed and discussed in detail. The initial designs were supposed for three types, one is moving coil type actuator and the others are moving permanent magnet type actuators. Based on the initial design concept, the final designs considering shock resistance and interference with mover and stator are proposed and examined.

• International Journal of Aeronautical and Space Sciences
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• v.12 no.4
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• pp.331-345
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• 2011

In this paper, a visco-hysteretic vibration absorber (VA) is proposed to increase the flutter speed of an airfoil and enhance damping in the pre- and post-flutter regimes. The passive system consists of a parallel arrangement of a dashpot and a rateindependent hysteretic element, represented by the Bouc-Wen differential model. The equations of motion are obtained and various tools of linear and nonlinear dynamics are employed to study the effects of the visco-hysteretic VA in the pre- and postflutter ranges.

• Journal of the Korean Home Economics Association
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• v.33 no.2
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• pp.113-127
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• 1995

The purpose of this study was to examine the children's adjustment according to the their problems and problem solving pattern in single mother. The data of this study were abtained from 186 children of single-mother. For analysis of data, Factor analysis, t-test, One-way ANOVA, pearson's correlation, Multiple regression were used The results are as follows; 1. The children's problem are composed seven factors that are house life, emotion, school life, peer-relationships, academic achievement, finicial, future life. The family structural variables to have relationship with the children's problem are age, sex, father's absence reason, SES, mother postering attitude. 2. The mean value of children's problem solving pattern such as seeking religion support and passive appraisal was highest. The children's problem solving pattern were affected by mother's fostering attitude. 3. The inadequacy among children in single-mother was related to mother fostering attitude after father's loss, children's problem and children's problem solving pattern that emphasizes the interdependence of each element in this children's adjustment network.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.52 no.10
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• pp.487-491
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• 2003

The low-cost, simple structured micropump which is actuated by piezoelectric-discs, is fabricated with polydimethylsiloxane (PDMS) and the performances of the micropump, such as pump rate and backpressure, are characterized. The PDMS micropump with diffusers instead of passive check valves as a flow-rectifying element was fabricated. The deflection of glass diaphragm measured by atomic force microscope (AFM) is about 0.4$\mu\textrm{m}$ when applying a 150V square wave voltage at 300Hz across a 300${\mu}\ell$ thick piezoelectric disc. While the square wave driving voltage is applied to the piezoelectric disc of the actuator, the flow rate is measured by fluid displacement variation of the outlet tube. The flow rate of micropump increases with enhancing the applied voltage due to the increase of diaphragm deflection. The flow rate and the backpressure of the micropump with diffusers are about 32.9${\mu}\ell$/min and 173Pa respectively for the above mentioned deflection conditions.

• Nuclear Engineering and Technology
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• v.50 no.1
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• pp.80-87
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• 2018

Consideration is given to the possibility to use changes in buoyancy as a negative reactivity feedback mechanism during temperature transients in heavy liquid metal fast reactors. It is shown that by the proper use of heavy pellets in the fuel elements, fuel rods could be endowed with a passive self-ejection mechanism and then with a negative feedback. A first estimate of the feasibility of the mechanism is calculated by using a simplified geometry and model. If in addition, a neutron poison pellet is introduced at the bottom of the fuel, then when the fuel element is displaced upward by buoyancy force, the reactivity will be reduced not only by disassembly of the core but also by introducing the neutron poison from the bottom. The use of induced buoyancy opens up the possibility of introducing greater amounts of actinides into the core, as well as providing a palliative solution to the problem of positive coolant temperature reactivity coefficients that could be featured by the heavy liquid metal fast reactors.

• Proceedings of the KIPE Conference
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• 2008.06a
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• pp.28-30
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• 2008

This paper proposes soft switching boost converter operating in zero current switching(ZCS) mode for photovoltaic and fuel cell power generation. The proposed topology is capable of reducing the size, and capability of passive element by using soft switching, and it allows for reduction of IGBT switching losses, for the increased of switching frequency. A detail mode analysis of operating in presented. We present the converter topology, principle of operation and simulation results obtained from the PSIM simulator. The performance of the proposed technique in evaluation on 1kW(380V,2.6A) experimental prototype circuit operating at 30kHz.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.1043-1044
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• 2006

Compositional dependence of corrosion behavior of rapidly solidified Mg-rich Mg-Zn-Y alloys in NaCl aqueous solution has been investigated. Mg-Zn-Y ternary alloys containing small amounts of Zn exhibited low corrosion rate, although the $Mg_{98}Y_2$ (at. %) binary alloy showed severe corrosion with violet evolution of hydrogen. The alloy with highest corrosion-resistance was $Mg_{97.25}Zn_{0.75_Y_2$, its corrosion rate was about 1 mm year-1 in 0.17 M (1.0 wt. %) NaCl solution. $Mg_{97.25}Zn_{0.75}Y_2$ alloy exhibited passive region in anodic polarization curves when immersed in NaCl solution. Rapidly solidification and small amount of Zn addition may bring about an increase in electrochemical homogeneity of Mg-Zn-Y alloys, resulting in enhancement of corrosion resistance.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.322-322
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• 2008

Low-temperature co-fired ceramics (LTCC) have turned out to be very promising technology in accordance with the rapid developments in semiconductor technology. The demands for compact electrical assemblies, smaller power loss as well as high signal density can be fulfilled by LTCC. And for the multi-layered ceramic devices with embedded passive components such as high dielectric constant decoupling capacitor, LTCC materials require the several conditions to avoid delamination and internal cracks. For the present study, diopside-based glass is chosen as the LTCC substrate material in view of its high coefficient of thermal expansion (CTE). From the experimental resultsn the influence of each element on the CTE change can be revealed.