• Transactions of the Korean Society of Mechanical Engineers A
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• v.36 no.5
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• pp.579-590
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• 2012

Weight reduction of a railway axle, which is one of heaviest parts in an urban railway vehicle, is discussed in this paper. A wheelset of a railway vehicle is very important with regard to railway safety, and its structural strength should always be considered when attempting to reduce the railway axle weight. In this work, the weight of the axles of a trailer bogie and a motor bogie of the Korean EMU was reduced by replacing solid axles with hollow axles. On the basis of the EN standard for railway axle design, the strength of existing solid axles was analyzed and the required bore size of a hollow axle was determined. It is shown that the weight of the concurrent axle of the Korean EMU can be reduced by up to 20% with a very small decrease in the structural strength. Finite element analyses were also carried out to verify the design result for lightweight hollow axles.

• Journal of the Korean Society for Railway
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• v.13 no.3
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• pp.271-277
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• 2010

In this paper, a numerical model for a Kevlar/Epoxy and Carbon-Kevlar/Epoxy tube used as an energy absorbing component has been developed and then results have been verified through experiment. The 2D shell element and Chang-Chang failure criterion of LS-DYNA that is commercial explicit FE code was used. Mechanical material properties for the model were obtained by material testing in advance. The numerical results were compared with quasi-static test results under axial compressive loading at 10mm/min. From the results, in the case of the Kevlar/Epoxy tube, load-crushed displacement curves were very close to the experiments and SEA (specific energy absorption) shows a good agreement with experimental one within less than 6%. However, the Carbon-Kevlar/Epoxy tube shows some differences with the experimental results.

• Korean Journal of Optics and Photonics
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• v.4 no.4
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• pp.420-427
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• 1993

Dielectric thin film mirrors are embedded in multimode and single-mode fibers by a fusion splicing technique. The fibers with $45{\circ}$ angled embedded mirrors serve as ultra-compact directional couplers with low excess optical loss of 0.2 dB for multimode and 0.5 dB for single mode at 1.3 ${\mu}m$ and excellent mechanical properties. The reflectance is wavelength dependent and strongly polarization depencient. Far-field scans of the reflected output power measured with a white-light source show a pattern which is almost circularly symmetric with aspect ratio of 1.09 at 5% of the peak power. The splitting ratio in a multimode coupler measured with a diode laser source is much less dependent on input coupling conditions than in conventional fused biconical-taper couplers, indicating that these couplers are less susceptible to modal noise occuring in optical fiber communication systems. Spectral properties of multilayer internal mirrors normal to the fiber axis have been investigated experimentally, and a matrix analysis has been used to explain the results.

• Aerospace Engineering and Technology
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• v.1 no.1
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• pp.163-172
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• 2002

The turbine system composed of a nozzle and a rotor is used to drive turbopumps while gas passes through the nozzle, potential energy is converted to kinematic energy, which forces the rotor blades to spin. In this study, an aerodynamic design of a turbine system is investigated using compressible fluid dynamic theories with some pre-determined design requirements (i.e.,pressure ratio, rotational speed, required power etc.) obtained from a liquid rocket engine (L.R.E.) system design. For simplicity of a turbine system, impulse-type rotor blades for open type L.R.E. have been chosen. Usually, the open-type turbine system requires low mass flow rate compared to the close-type system. In this study, a partial admission nozzle is adopted to maximize the efficiency of the close-type turbine system. A design methodology of the a turbine system has been introduced. Especially, a partial admission nozzle has been designed by means of simple empirical correlations between efficiency and configuration of the nozzle. Finally, a turbine system design for a 10 ton thrust level of L.R.E is presented.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.41 no.8
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• pp.505-510
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• 2017

This paper presents a low-cost robotic device for shoulder rehabilitation, which is capable of treating various shoulder disabilities. A 3-DOF passive shoulder joint tracking module was designed to allow for translational motion of the shoulder joint center during arm swing, which is essential for natural shoulder movement. The weight of the user's arm and the device were compensated for by springs, to enable gravity-free shoulder motion. In order to reduce the device's cost, only one actuator was used, which can be aligned with the user's shoulder joint in various orientations. The device is capable of implementing five representative shoulder motions, including flexion/extension, abduction/adduction, horizontal abd/adduction, internal/external rotation, and oblique raise. The proposed low-cost shoulder rehabilitation robot is expected to provide effective rehabilitation for patients with various shoulder impairments.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.2
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• pp.129-136
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• 2014

Target-tracking systems are important for carrying out effective surveillance missions using mobile surveillance robots. In this paper, we propose a target-tracking algorithm using camera image data for a three-axis mobile surveillance robot and carry out an actual hardware test for verifying the proposed algorithm. The heading direction vector of a camera system is deduced from the position error between the viewfinder center and the object center in a camera image. The position error is obtained using the CAMShift(Continuously Adaptive Mean Shift) algorithm, an image processing technique. The performance test of an actual three-axis mobile surveillance robot was carried out for verifying the proposed target-tracking algorithm in a real environment.

• Journal of Korea Society of Industrial Information Systems
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• v.24 no.1
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• pp.39-44
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• 2019

A high-temperature superconducting(HTS) generators have been actively studied because of its advantages of weight, size, and efficiency. A large-scale superconducting wind power generator becomes a very low-speed high-torque rotating machine. In these machines, high electromagnetic force and torque are important issued. Two generators connected in series on one shaft design are one of the solution to overcome the high torque problem. In this paper, the authors design and analyze a 15 MW class HTS generator. The 15 MW HTS generator is confirmed in terms of magnetic field distribution and torque performance using a 3D finite element method. As a result, the designed generators generates less torque than a conventional generator. The designed 15 MW superconducting generator will be effectively utilized in the construction of the large-scale wind power generation system.

• Journal of the Microelectronics and Packaging Society
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• v.31 no.2
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• pp.36-44
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• 2024

Copper electrodeposition technology is essential for producing copper films and interconnects in the microelectronics industries including semiconductor packaging, semiconductors and secondary battery, and there are extensive efforts to control the microstructure of these films and interconnects. In this study, we investigated the influence of crystallographic orientation on the local plastic deformation of copper films for secondary batteries deformed by uniaxial tensile load. Crystallographic orientation maps of two electrodeposited copper films with different textures were measured using an electron backscatter diffraction (EBSD) system and then used as initial conditions for crystal plasticity finite element analysis to predict the local plastic deformation behavior within the films during uniaxial tension deformation. Through these processes, the changes of the local plastic deformation behavior and texture of the films were traced according to the tensile strain, and the crystal orientations leading to the inhomogeneous plastic deformation were identified.

• Journal of the Korea institute for structural maintenance and inspection
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• v.27 no.4
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• pp.23-32
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• 2023

The seismic performance of buried PE pipes is reported to be favorable due to their exceptional elongation capacity at break. Although a seismic performance evaluation procedure based on the response displacement method has been summarized in Korea for fusion-bonded PE pipes, there is currently no procedure available for mechanically jointed PE pipes. This article aims to present a seismic performance evaluation procedure based on the response displacement method specifically designed for mechanically jointed PE pipes in Korea. When employing the mechanical joining method for PE pipes, it is recommended to adhere to the evaluation procedure established for segment-type pipes. This involves assessing the stress induced by the pipe, the expansion and contraction strain of the joint, and the bending angle of the pipe joint. Furthermore, the coefficient of inhomogeneity of the soil, which is necessary for estimating the axial strain of the ground, is introduced. Additionally, a computation method for determining lateral displacement and reconsolidation settlement in soil susceptible to liquefaction is proposed. As a result of the sensitivity analysis considering the typical soil condition in Korea, the mechanically jointed PE pipe with a certain quality was shown to have good structural seismic safety when soil liquefaction was not considered. This procedure serves as a valuable tool for seismic design and evaluating the seismic performance of mechanically joined buried PE pipes, which are primarily utilized for connecting small-diameter pipes.

• Composites Research
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• v.35 no.5
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• pp.303-308
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• 2022

PIC (Piecewise Integrated Composite) is a new concept for designing a composite structure with mosaically assigning various types of stacking sequences in order to improve mechanical properties of laminated composites. Also, machine learning is a sub-category of artificial intelligence, that refers to the process by which computers develop the ability to continuously learn from and make predictions based on data, then make adjustments without further programming. In the present study, the tapered box beam type PIC robot arm for carrying and transferring wide and thin LCD display was designed based on the machine learning in order to increase structural stiffness. Essential training data were collected from the reference elements, which were intentionally designated elements among finite element models, during preliminary FE analysis. Additionally, triaxiality values for each finite element were obtained for judging the dominant external loading type, such as tensile, compressive or shear. Training and evaluating machine learning model were conducted using the training data and loading types of elements were predicted in case the level accuracy was fulfilled. Three types of stacking sequences, which were to be known as robust toward specific loading types, were mosaically assigned to the PIC robot arm. Henceforth, the bending type FE analysis was carried out and its result claimed that the PIC robot arm showed increased stiffness compared to conventional uni-stacking sequence type composite robot arm.