• Progress in Medical Physics
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• v.4 no.2
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• pp.3-7
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• 1993

In the 7th Steering Committee Meeting held in November 1986 in Suba, Fiji, the steering committee made a decision that the Korea Research Institute of Standards and Science (KRISS) coordinates the program of the regional intercomparison of ionizing radiation measurement. Through mutual communications with the Radiation Laboratory at KRISS, five countries (Australia, China, India, Japan and Malaysia) agreed to participate in the X-ray dosimetry standards intercomparison under the auspices of KRISS.

• Proceedings of the KSME Conference
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• 2001.11b
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• pp.539-544
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• 2001

The holographic measurement techniques can be applied to various industrial fields such as automobile, airplane, construction, electronics, medical, mechanics and physics. The visualization of fluids is very important in aerodynamics, heat transfer and stress analysis. There are classically optical methods such as shadowgraph, schlieren method, and Mach-Zehnder interferometry for visualizing the fluid flow phenomena. But, it is difficult to understand the continuous state of fluids well in those methods. In this study, the real-time holographic interferometer with high-speed camera is applied to the flow visualization. In addition, collimated laser beam and rotating wedge are used for recording and formation of carrier fringes, respectively.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.17 no.1
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• pp.120-125
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• 2008

A flip-chip bonding system using DPSS(Diode Pumped Solid State) Nd:YAG laser(wavelength : 1064nm) which shows a good quality in fine pitch bonding is developed. This laser bonder can transfer beam energy to the solder directly and melt it without any physical contact by scanning a bare chip. By using a laser source to heat up the solder balls directly, it can reduce heat loss and any defects such as bridge with adjacent solder, overheating problems, and chip breakage. Comparing to conventional flip-chip bonders, the bonding time can be shortened drastically. This laser precision micro bonder can be applied to flip-chip bonding with many advantage in comparison with conventional ones.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11a
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• pp.328.2-328
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• 2002

General modeling of a resonant shunting damper has been made Iron piezoelectric sensor/actuator equation. It is found that an additional damping, which is augmented to a system, is generated by the shunt damping effect The transfer function of the tuned electrical absorber is derived for both series and parallel shunt circuit. The governing equations and associated boundary conditions are derived using Hamilton's Principle. The shunt voltage equation is also derived from the charge generated in PZT due to beam vibration. The frequency response function of the obtained mathematical model is compared with that of the tuned eledtrical absorber and experimental work. The vibration amplitude is reduced about 15 dB at targeted second mode frequency.

• Journal of the Earthquake Engineering Society of Korea
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• v.5 no.3
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• pp.79-85
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• 2001

This paper presents an equivalent strut model for seismic design of steel moment connections reinforced with ribs. It is shown from the finite element analysis results that the force transfer mechanism in the rib connections is completely different from that predicted by the classical beam theory and a clear strut action in the ribs does exist. By treating the rib as a strut, an equivalent strut model that could be used as the basis of a practical design procedure is proposed.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.1933-1938
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• 2000

The partial differential equations for a coil spring derived from Timoshenko beam theory and Frenet formulae. Dynamic stiffness matrix of a coil spring composed of a circular wire is assembled by using dispersion relationship, waves and natural frequencies. Natural frequencies are obtained from maxima in the determinant of inverse of a dynamic stiffness matrix with appropriate boundary conditions. The results of the dynamic stiffness method are compared with those of transfer matrix method, finite element method and test.

• Journal of Welding and Joining
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• v.21 no.3
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• pp.30-34
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• 2003

This paper describes the heat distribution characteristics of ASTM A131DH36 high tensile steel for ship structures in 5㎾ $CO_2$ laser welding. In general, high energy of laser beam concentrates on the small area of the weldment instantaneously; therefore, this heat transfer mechanism induces the rapid changes of temperature and mechanical characteristics in laser welds this mechanism. So temperature distribution analysis is important to understand mechanical characteristics of laser welds. Authors have conducted finite element simulation to analyze the heat distribution characteristics in laser welds. The result of simulation has been verified by comparing with the metallurgical experiment result. From the result of this study, we can accurately predict the heat distribution characteristics in laser welds by using numerical simulation.

• Journal of Welding and Joining
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• v.18 no.4
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• pp.76-81
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• 2000

In this research, various heat source equations that have been proposed in previous study were calculated and compared with new model in various laser parameters. This is to treat the problem of predicting, by numerical analysis, the thermo-mechanical behaviors of laser spot welding for thin stainless steel plates. A finite element code, ABAQUS is used for the heat transfer analysis with a three-dimensional plane assumption. Experimental studies if the laser spot welding have also bee conducted to validate the numerical models presented. The results suggest that temperature profiles and weld dimensions are varied according to the heat source of the laser beam. For this reason, it is essential to incorporate an accurate description of the heat source.

• Computers and Concrete
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• v.12 no.1
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• pp.19-36
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• 2013

In the finite element analysis of reinforced concrete structures, discrete representation of the steel reinforcing bars is considered advantageous over smeared representation because of the more realistic modelling of their bond-slip behaviour. However, there is up to now limited research on how to simulate the dowel action of discrete reinforcing bars, which is an important component of shear transfer in cracked concrete structures. Herein, a numerical model for the dowel action of discrete reinforcing bars is developed. It features derivation of the dowel stiffness based on the beam-on-elastic-foundation theory and direct assemblage of the dowel stiffness matrix into the stiffness matrices of adjoining concrete elements. The dowel action model is incorporated in a nonlinear finite element program based on secant stiffness formulation and application to deep beams tested by others demonstrates that the incorporation of dowel action can improve the accuracy of the finite element analysis.

• Journal of Mechanical Science and Technology
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• v.17 no.5
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• pp.668-678
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• 2003

For the purpose to facilitate development of high-speed spindle units (SUs) running on rolling bearings, we have developed a beam element model, algorithms, and software for computer analysis of thermal characteristics of SUs. The thermal model incorporates a model of heat generation in rolling bearings, a model of heat transfer from bearings, and models for estimation of temperature and temperature deformations of SU elements. We have carried out experimental test and made quantitative evaluation of the effect of operation conditions on friction and thermal characteristics of the SUs of grinding and turning machines of typical structures. It is found out that the operation conditions make stronger effect on SU temperatures when rpm increases. A comparison between the results of analysis and experiment proves their good mutual correspondence and allows us to recommend application of the models and software developed for design and research of high-speed SUs running on rolling bearings.