• Korean Journal of Computational Design and Engineering
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• v.16 no.4
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• pp.285-291
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• 2011

A pose estimation process from medical images is calculating locations and orientations of objects obtained from Computed Tomography (CT) volume data utilizing X-ray images from two directions. In this process, digitally reconstructed radiograph (DRR) images of spatially transformed objects are generated and compared to X-ray images repeatedly until reasonable transformation matrices of the objects are found. The DRR generation and image comparison take majority of the total time for this pose estimation. In this paper, a fast DRR generation technique based on GPU parallel computing is introduced. A volume ray-casting algorithm is explained with brief vector operations and a parallelization technique of the algorithm using Compute Unified Device Architecture (CUDA) is discussed. This paper also presents the implementation results and time measurements comparing to those from pure-CPU implementation and open source toolkit.

• Transactions of the Korean Society of Automotive Engineers
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• v.25 no.1
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• pp.111-115
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• 2017

This forged piston is proposed with a lighter weight and higher durability than a gravity casting piston for gasoline engines. However, a forged piston is very difficult to develop and mass-produce due to lack of basic technologies such as design, material and forging technique. First, we benchmarked existing forged pistons according to database design parameters. Second, we evaluated two solidification processes, continuous casting and spray forming, to produce heat-resistant alloy billets for forging. The spray forming process gives better mechanical properties at all temperatures, particularly at elevated temperatures except when poor formability is present. We used DEFORM simulation to determine the optimum process condition with billet from spray forming and successfully commercialized it with LF Sonata HEV.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.7 no.2
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• pp.9-14
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• 1998

One of the areas in the continuous casting process that up to this point, has not been definitively instrumented is a method of reliably locating the part of a continuously cast strand that remains liquid for a period after the outer portion has solidified. To solve the problem. Electromagnetic Trandsducers(EMAT) which operate across an air gap without the need for a coupling medium has been developed. The system was designed to employ a through transmission technique which enhanced the signal-to-noise ratio. The Al 75$\times$75mm and 75$\times$100mm simulators with 2, 4, 8, 16, 32 mm hole respectively has been produced in order to verify the developed EMAT system and to measure to liquid core in continuous casting strand. The system developed can be employed for the optimization of torch cutting speed and for the final cut length of the bloom as well as calculation of average bloom temperature.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2004.11a
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• pp.114-121
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• 2004

• Conservation Science in Museum
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• v.23
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• pp.1-16
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• 2020

In this paper, Gilt-bronze Standing Avaolkiteshvara (National Treasure No. 293, M355) excavated at Gyuam-ri in Buyeo was observed with a microscope to identify the production technique applied to it. It was also analyzed with XRF and hard X-ray to identify the composition and the surface treatment techniques and casting method applied. In this statue, Avalokiteshvara is standing upright on a lotus pedestal. The lotus designs on the pedestal and those on the shawl flowing down on both sides of the statue are characteristic of Buddhist statues from the seventh century or later. The use of supports to affix the outer and inner molds and traces of injected cast were observed in the interior of the pedestal. The blisters on the arms and pedestal created during the bronze casting indicate the use of lost-wax casting, which was popularly employed for the production of mid- or small-sized gilt-bronze Buddhist statues in ancient times. The composition analysis identified a copper-tin-lead ternary alloy in the interior of the statue that was conventional used in the sixth and seventh centuries. It is likely that this simple alloy was used to facilitate casting and produce clearer expressions of designs and ornaments on the statue. Mercury (Hg) was detected on the surface of the statue, indicating the use of amalgam-plating with gold (Au) dissolved in mercury. This plating method is a common surface treatment technique used for small gilt-bronze statutes in ancient Korea.

• The Journal of Advanced Prosthodontics
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• v.10 no.1
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• pp.25-31
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• 2018

PURPOSE. The aim of the present study was to record the metal-ceramic bond strength of a feldspathic dental porcelain and a Co-Cr alloy, using the Direct Metal Laser Sintering technique (DMLS) for the fabrication of metal substrates. MATERIALS AND METHODS. Ten metal substrates were fabricated with powder of a dental Co-Cr alloy using DMLS technique (test group) in dimensions according to ISO 9693. Another ten substrates were fabricated with a casing dental Co-Cr alloy using classic casting technique (control group) for comparison. Another three substrates were fabricated using each technique to record the Modulus of Elasticity (E) of the used alloys. All substrates were examined to record external and internal porosity. Feldspathic porcelain was applied on the substrates. Specimens were tested using the three-point bending test. The failure mode was determined using optical and scanning electron microscopy. The statistical analysis was performed using t-test. RESULTS. Substrates prepared using DMLS technique did not show internal porosity as compared to those produced using the casting technique. The E of control and test group was $222{\pm}5.13GPa$ and $227{\pm}3GPa$, respectively. The bond strength was $51.87{\pm}7.50MPa$ for test group and $54.60{\pm}6.20MPa$ for control group. No statistically significant differences between the two groups were recorded. The mode of failure was mainly cohesive for all specimens. CONCLUSION. Specimens produced by the DMLS technique cover the lowest acceptable metal-ceramic bond strength of 25 MPa specified in ISO 9693 and present satisfactory bond strength for clinical use.

• Journal of Korea Foundry Society
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• v.30 no.3
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• pp.100-110
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• 2010

The solidification sequence and formation of intermetallic phase of Fe-rich Al-Si-Cu alloy were investigated by using real-time imaging of synchrotron X-ray radiation. Effects of cooling rate during uni-directional solidification on the resultant solidification behavior was also studied in a specially constructed vacuum chamber in the SPring-8 facility. The series of radiographic images were complementarily analyzed with conventional analysis of OM and SEM/EDX for phase identification. Detailed solidification sequence and formation mechanisms of various phases were discussed based on real-time image analysis. The growth rates of $\alpha$-AlFeMnSi and ${\beta}-Al_5FeSi$ were measured in order to understand the growth behavior of each phase. It is suggested that real-time imaging technique can be a powerful tool for the precise understanding of solidification behavior of various industrial materials.

• Journal of Korea Foundry Society
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• v.27 no.6
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• pp.237-242
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• 2007

To improve the quality of the product and the cost efficiency, the joining of A356 alloy to an Al-18wt%Si alloys has been performed by centrifugal casting. The influence of the mold preheating temperature, the pouring temperature and the rotational velocity of the mold on the microstructures of the shell in the centrifugal casting was investigated using the experimental and simulation methods. In the present study, the cellular automaton (CA) technique and the finite volume method (FVM) were adopted to simulate the evolution of the macro structures and to calculate the temperature profiles, respectively. The evolution of the microstructures was also simulated using a modified cellular automaton (MCA) model. The optimal rotational speed of the mold for obtaining the sound shape of the shell was estimated experimentally to be over 1200 rpm. For the uniform microstructure, the outer shell needs to be cast with higher preheated mold temperature and lower pouring temperature, and the melt was poured at lower temperature in the inner shell. In order to obtain the sound shape of the joining, the different materials were poured simultaneously.

• Journal of Korea Foundry Society
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• v.13 no.3
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• pp.268-275
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• 1993

In gravity die casting, die cooling systems are frequently employed with water cooling to remove the heat of the solidifying metal. Thermal modeling is an important technique in mold design for improving the productivity of the process. Computer simulation system which consists of pre-processor, main solidification simulator and post-processor has been developed for three dimensional solidification analysis of cyclic gravity die casting. The pre-processor is used for mesh generation in a PC system. The modified finite difference method is adopted for the main solidification simulation algorithm during all the casting cycles. The post-processor graphically presents the simulation results. Several experiments in automotive cast piston were carried out. The temperature variations in casting and mold with time are measured experimentally, and the results are compared with calculation results. The effects of cycle number on solidification pattern are also studied. Several experimental results for the prediction of shrinkage defects are compared with calculated results.

• Journal of computational fluids engineering
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• v.2 no.1
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• pp.117-128
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• 1997

Effects of dam and weir on the fluid flow and behavior of inclusions in the continuous casting tundish have been studied using the CFD (Computational Fluid Dynamics) technique. Inclusions affecting the quality of steel products have been considered to be passive: the fluid flow has been obtained for unstaggered grid points defined on body-fitted generalized cuvilinear coordinates with no attention on inclusions, and the spatial propagation of inclusions has been determined by using the flow field data. The result show that the dam and weir direct the flow to the free surface and increase the residence time of inclusions significantly, and thereby that inclusions have much more chance to be floated to the free surface of the tundish where it is eliminated. It is also found that they offer more margin on the geometric design of exit nozzles connected to moulds. This finding is particularly important for twin casting operations where the quality of steel products from the two moulds be kept uniformly.