• Journal of the Korean institute of surface engineering
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• v.49 no.4
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• pp.368-375
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• 2016

MoN-Cu thin films were prepared to achieve appropriate properties of high hardness and low friction coefficient, which could be applied to automobile engine parts for reducing energy consumption as well as solving wear problems. Composite thin films of MoN-Cu have been deposited by various processes using multiple targets such as Mo and Cu. However, those deposition with multiple targets revealed demerits such as difficulties in exact control of composition and homogeneous deposition. This study is aiming for suggesting an appropriate process to solve those problems. A single alloying target of Mo-Cu (10 at%) was prepared by powder metallurgy methods of mechanical alloying (MA) and spar plasma sintering (SPS). Thin film of MoN-Cu was then deposited by magnetron sputtering using the single alloying target of Mo-Cu (10 at%). Properties of the resulting MoN-Cu thin film were examined and compared to those of MoN-Cu thin films prepared with double targets of Mo and Cu.

• Transactions on Control, Automation and Systems Engineering
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• v.4 no.1
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• pp.84-91
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• 2002

A new composite control method for a carriage balancing single inverted pendulum system is proposed and applied to swing up the pendulum and to stabilize it under the state constraint. The target inverted pendulum system has an extremely limited length of the cart(below 16cm). The proposed swing-up controller comprises a sliding mode control algorithm and an optimal control algorithm based on two regions: the region near the inverted unstable equilibrium position and the rest of the state space including the downward stable equilibrium position. The sliding mode controller uses a switching control action to converge along the specified path(hyperplane) derived from energy equation from a state around the path to desired state(standing position). An optimal control method is also used to guarantee the stability at unstable equilibrium position. Compared with the reported controllers, it is simpler and easier to implement. Experimental results are given to show the effectiveness of this controller.

• Journal of the Korean Society for Heat Treatment
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• v.26 no.2
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• pp.66-71
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• 2013

The purpose of this study is to prepare a high-strength Fiberglass Reinforced Metal (FRM). Aluminum covering over carbon fibers (CF) was made to increase their wettability to molten aluminum. A cylindrical sputtering apparatus was used for the covering. One tow of carbon fibers was placed along the central axis of the cylindrical target. Aluminum was uniformly coated around the carbon fiber tow. But in case of CF without sizing treatment, aluminum spread into the inside of the tow. Preforms of carbon fiber/aluminum composite were made by impregnating carbon fiber with molten aluminum. Contact angle of molten aluminum to the aluminum-coated carbon fiber was about $30^{\circ}$. The fractured section of preform was observed by SEM, which showed that molten aluminum wetted the outer part of the tow well but had not penetrated into the center, and that adhesion between CF and aluminum matrix was in good condition.

• Computers and Concrete
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• v.6 no.2
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• pp.95-108
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• 2009

In the current research, a displacement-based seismic design scheme to retrofit reinforced concrete columns using FRP composite materials has been proposed. An accurate prediction for the nonlinear flexural analysis of FRP jacketed concrete members has been presented under multiaxial constitutive laws of concrete and composite materials. Through modification of the displacement coefficient method (DCM) and the direct displacement-based design method (DDM) of reinforced concrete structures, two algorithms for a performance-based seismic retrofit design of reinforced concrete columns with a FRP jacket have been newly introduced. From applications to retrofit design it is known that two methods are easy to apply in retrofit design and the DCM procedure underestimates the target displacement to compare with the DDM procedure.

• Journal of Aerospace System Engineering
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• v.1 no.1
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• pp.36-44
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• 2007

This study was performed on preliminary structural design of a small scale WIG craft which has been developed as a next generation high speed maritime transportation system in Korea. A composite structure design using the foam-sandwich for main wing and tail fins and the honeycomb sandwich and skin-stringer-ring frame for fuselage was applied for weight reduction as well as structural stability. A commercial FEM code, NASTRAN for was utilized to confirm the structural safety for the reiterate design modifications to meet design requirements including the target weight. Each main wing was jointed with the fuselage by eight high strength insert bolts for easy assembling and disassembling as well as for assuring the required 20 years service life. For control surface structural design, the channel type spar, the foam sandwich skin and the lug joint were adopted.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.424-429
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• 2008

Aircraft flutter analysis model consists of dynamic FE model and aerodynamic model. Dynamic FE model is composed of stiffness and mass model, and is used for the prediction of normal mode characteristics of the structure. Since aircraft flutter analysis is normally performed in the modal domain, dynamic FE model shall be constructed to describe the modal characteristics of the structure with sufficient accuracy. In this study, dynamic FE modeling method was described using full airframe FE model and structural and system weight data for aircraft flutter analysis. In addition, full airframe dynamic FE model for composite small aircraft was constituted for normal mode and flutter analysis, and the mass modeling results were compared with the target weight data to validate the mass modeling method proposed. Finally, full airframe flutter analysis of composite small aircraft was performed with the dynamic FE model and the aerodynamic model composed.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.68 no.1
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• pp.145-152
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• 2019

A composite guidance scheme is proposed for air-to-ground anti-tank missiles launched from an airborne platform. Long-range anti-tank missiles usually use a fiber optic line (FOL) for the datalink between an operator and the missile to obtain real-time target information and to command the missile. Also, impact angle control is used to maximize the warhead effectiveness, but it should be carefully implemented due to interference between the launch platform and the FOL. Thus, the proposed guidance scheme takes into account both impact angle and FOL constraints. Under system lag and acceleration limits, a selection method of guidance gains and calculation logic of the maximum achievable impact angle are proposed for a guideline of practical implementation. The performance of the proposed guidance scheme is investigated by nonlinear simulations with various engagement conditions.

• Steel and Composite Structures
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• v.47 no.4
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• pp.513-521
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• 2023

The goal of this work is to create a new and improved GWO (Grey Wolf Optimizer), the so-called Robot GWO (RGWO), for dynamic and static target tracking involving multiple robots in unknown environmental conditions. From applying ourselves with the Gray Wolf Optimization Algorithm (GWO) and how it works, as the name suggests, it is a nature-inspired metaheuristic based on the behavior of wolf packs. Like other nature-inspired metaheuristics such as genetic algorithms and firefly algorithms, we explore the search space to find the optimal solution. The results also show that the improved optimal control method can provide superior power characteristics even when operating conditions and design parameters are changed.

• Journal of Korea Water Resources Association
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• v.51 no.7
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• pp.543-554
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• 2018

A methodology has been presented for evaluating the partial safety factors on the sliding failure mode of vertical caissons of composite breakwaters and for determining the cross sections of those by Level I reliability-based design method. Especially, a mathematical model has been suggested for the sake of a consistency of code format as well as convenience of application in practical design, for which the uncertainties associated with buoyancy and its own weight can be taken into account straightforwardly. Furthermore, design criteria equation has been derived by considering accurately the effect of uplift pressure, so that the cross sections of caissons can be assessed which must be safe against the sliding failure. It has been found that cross sections estimated from partial safety factors proposed in this paper are in very good agreement with the results of Level II AFDA and Level III MCS under the same target probability of failure. However, partial safety factors of the Technical Standards and Commentaries for Port and Harbour Facilities in Japan and Coastal Engineering Manual in USA tend to estimate much bigger or smaller cross sections in comparison to the present results. Finally, many reliability re-analyses have been performed in order to conform whether the stability level of cross section estimated by Level I reliability-based design method is satisfied with the target probability of failure of partial safety factors or not.

• Journal of the Korea institute for structural maintenance and inspection
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• v.10 no.4
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• pp.145-154
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• 2006

This paper presents a method to enhance the load carrying capacity for a two-span continuous steel-concrete composite beam strengthened with external tendons. The tendon is placed at the bottom of steel beam where the positive bending moment occurs. This results in the reduction of the negative bending moment as well as the positive bending moment. This paper describes the procedure to determine the number of tendon and the initial tendon force for the target rating factor in the rating factor equation. An example beam is given to demonstrate the proposed procedure, and it validity is confirmed.