• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.30 no.4
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• pp.84-91
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• 2002

Thrust vector characteristics of jet vanes installed in a shroud are very unique and much more complicated than those of the jet vane acting without any shroud by the fact of additional physical phenomena. The fluid dynamic interferences induced by jet vanes and shroud as well as jet vane's aerodynamic performance are investigated to characterize thrust vector control by semi-empirical model, three dimensional numerical analysis including real complex geometry, and ground firing test of real motors.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2004.10a
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• pp.451-458
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• 2004

The caisson-type breakwaters have been widely used in the area of harbor construction. Because of the importance of the breakwaters, structural health monitoring in the breakwaters by using appropriate methods is of great needs. In this study, a caisson-type breakwater that has fatigue cracks due to wave-impact is investigated. First, a signal-based structural health monitoring method is proposed for the breakwaters structures. Excitation and sensor systems are designed on finite element model and monitoring categories are also selected. Structural health monitoring was realized by using measured dynamic response signals and analyzed information.

• Smart Structures and Systems
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• v.14 no.4
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• pp.501-516
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• 2014

The rocking pier system (RPS) allows the columns to rock on beam or foundation surfaces during the attacks of a strong earthquake. Literatures have proved that seismic energy dissipated by the RPS through the column impact is limited. To enhance the energy dissipation capacity of a RPS bridge substructure, frictional hinge dampers (FHDs) were installed and evaluated by shaking table tests. The supplemental FHDs consist of two brass plates sandwiched by three steel plates. The strategy of self-centering design is to isolate the seismic energy by RPS at the columns and then dissipate the energy by FHDs at the bridge deck. Component tests of FHD were first conducted to verify the friction coefficient and dynamic characteristic of the FHDs. In total, 32 shaking table tests were conducted to investigate parameters such as wave forms of the earthquake (El Centro 1940 and Kobe 1995) and normal forces applied on the friction dampers. An analytical model was also proposed to compare with the tested damping of the bridge sub-structure with or without FHDs.

• Advances in nano research
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• v.1 no.1
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• pp.13-27
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• 2013

Carbon nanotube characterized by additional inductive effect as compared with the traditional conductors like copper wires of the same size. Consequently, carbon nanotubes have high characteristic impedance and slow wave propagation in comparison with traditional conductors. Due to these characteristics, carbon nanotubes can be used as antenna. In view of this, we describe and review the present research progress on carbon nanotube antennas. We present different analysis models and results which are developed to investigate the characteristics of CNT antennas. Then we conclude by summarizing the characteristics of CNT antennas and specifying the operating frequency limit.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2001.09a
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• pp.139-146
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• 2001

The seismic safety analysis were performed for the center-core rockfill dam(CCRD) The static and pseudo-static FEM analysis using seismic coefficient Method, and dynamic FEM analysis using Hachinohe earthquake wave(0.12g) were used for the seismic safety of CCRD. The results of seismic analysis were that the factor of safety of down slope was 1.5, horizontal displacement is about 14.3cm, and vertical displacement is 3.3cm at dam creast. The model dam did not show any seismic stability problems for 0.12g. And much more research is still necessary in seismic safety of CCRD.

• Water for future
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• v.18 no.3
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• pp.265-270
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• 1985

The prediction of a design-flood hydrograph at a particular site on a river may be based on the derivation of discharge or stage hydrograph at an upstream section, togeater with a method to route this hydrograph along the rest of river. On the other hand, flood routing methods provide a useful tool for the analysis of flooding in all but the smaller catchment, and these methods are largely stored into hydrological method and hydraulic method. Although the Muskingum Method as a hydrological method ignores dynamic effects on the flood wave, Muskingum-Cunge Method based on hydraulic method is possible to improve the method so that it gives a good approximation to the solution of the linear convective-diffusion equation. This is made on the basis of the finite diffeience equation for the Muskingum Method. In the study, the outflows predicted by Muskingum-Cunge Method are campared with the observed outflows of the Pyung Chang River.

• Water for future
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• v.18 no.1
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• pp.67-73
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• 1985

Tidal propagation in the Keum River has been routinely handled by numerical integration of the long fravity wave equation by Dronkers. The dynamic equations include non-linear terms thereby reproducing the shallow water tides. The model was used to compute tidal distribution of the Kum River for aveage spring, mean, neap tidal conditions and further utilised to investigate the waterlevel response within tidal reaches by combined tide and flood discharge effects. The objective of this initial study is to investigate the tidal dynamics of the lower reaches of the Keum River under the condition of before-cross-channel barrage construction.

• Journal of Communications and Networks
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• v.16 no.5
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• pp.534-547
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• 2014

Large-scale failures resulting from natural disasters or intentional attacks are now causing serious concerns for communication network infrastructure, as the impact of large-scale network connection disruptions may cause significant costs for service providers and subscribers. In this paper, we propose a new framework for the analysis and prevention of network service disruptions in large-scale failure scenarios. We build dynamic deterministic and probabilistic models to capture the impact of regional failures as they evolve with time. A probabilistic failure model is proposed based on wave energy behaviour. Then, we develop a novel approach for preventive protection of the network in such probabilistic large-scale failure scenarios. We show that our method significantly improves uninterrupted delivery of data in the network and reduces service disruption times in large-scale regional failure scenarios.

• Journal of Powder Materials
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• v.24 no.1
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• pp.17-23
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• 2017

In this study, a finite element analysis approach is proposed to predict the fluid-structure interaction behavior of active materials for lithium-ion batteries (LIBs), which are mainly composed of graphite powder. The porous matrix of graphite powder saturated with fluid electrolyte is considered a representative volume element (RVE) model. Three different RVE models are proposed to consider the uncertainty of the powder shape and the porosity. P-wave modulus from RVE solutions are analyzed based on the microstructure and the interaction between the fluid and the graphite powder matrix. From the results, it is found that the large surface area of the active material results in low mechanical properties of LIB, which leads to poor structural durability when subjected to dynamic loads. The results obtained in this study provide useful information for predicting the mechanical safety of a battery pack.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.11a
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• pp.226-233
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• 2003

There are many researches going on to develop the information storage devices using Blue-ray disc and DVD as a demand for high-density information storage devices is highly increasing. This high-density information storage device requires a short-wave laser and objective lens of high numerical aperture set in fer its operation. And, that brings out rapid decrease of tilt tolerance. Therefore, it is necessary that an actuator should control tilt motions to get a stable signal. In this paper, a new mathematical form of 3-D.O.F coupled model is formulated and magnetic circuit in constraints is most effectively designed with the use of the moving coil type actuator in higher sensitivity. Further, this paper presents a tilt coil whose rotational center point is put on that of the lens through the variation of tilt coil and proposes a 3-axis actuator with high sensitivity improved in its dynamic property through its structure analysis.