• ETRI Journal
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• v.34 no.5
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• pp.706-712
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• 2012

In previous work, novel maskless bumping and no-flow underfill technologies for three-dimensional (3D) integrated circuit (IC) integration were developed. The bumping material, solder bump maker (SBM) composed of resin and solder powder, is designed to form low-volume solder bumps on a through silicon via (TSV) chip for the 3D IC integration through the conventional reflow process. To obtain the optimized volume of solder bumps using the SBM, the effect of the volumetric mixing ratio of resin and solder powder is studied in this paper. A no-flow underfill material named "fluxing underfill" is proposed for a simplified stacking process for the 3D IC integration. It can remove the oxide layer on solder bumps like flux and play a role of an underfill after the stacking process. The bumping process and the stacking process using the SBM and the fluxing underfill, respectively, for the TSV chips are carefully designed so that two-tier stacked TSV chips are sucessfully stacked.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.13 no.8
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• pp.718-723
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• 2000

The critical characteristics of Bi-2223 HTS tapes made by PIT method are influenced by the heat treatment and the mechanical processing. In this study firstly we investigated the influence o rolling reduction rate in mechanical process for improving Jc of HTS tapes. As a result the optimized rolling reduction rate that we obtained was 10%-50% and 30%-30% (1st-2nd). And then we fabricated the stacking type HTS tapes that made of the multi-filamentary tapes with various length(3, 5, 10cm) and with various number of stacking (1, 5, 10 layer). Measuring the critical current and observing the structure of grain we concluded that the stacking type tapes will be able to operate more stably by adding the number of stacking tapes. And we could expect that by minimizing the gap between Ag-sheath of tapes mechanical strength of stacking HTS tapes is enhanced and current in tapes will flow more stably.

• The Journal of Society for e-Business Studies
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• v.25 no.3
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• pp.1-13
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• 2020

Machine learning refers to a model generation technique that can solve specific problems from the generalization process for given data. In order to generate a high performance model, high quality training data and learning algorithms for generalization process should be prepared. As one way of improving the performance of model to be learned, the Ensemble technique generates multiple models rather than a single model, which includes bagging, boosting, and stacking learning techniques. This paper proposes a new Ensemble technique with multiple stacking that outperforms the conventional stacking technique. The learning structure of multiple stacking ensemble technique is similar to the structure of deep learning, in which each layer is composed of a combination of stacking models, and the number of layers get increased so as to minimize the misclassification rate of each layer. Through experiments using four types of datasets, we have showed that the proposed method outperforms the exiting ones.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.10a
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• pp.739-742
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• 2014

In the process of MLCC manufacturing, MLCC stacking process is the key process of making high quality MLCC. Since MLCC is small components, the entire process of MLCC stacking process is minute and sensitive to micro errors. To prevent micro error, we suggest condition-based monitoring which quantifies error based on feature extraction and quantifying error method. As results, it has been shown that the suggested algorithm has effectiveness of condition based monitoring of MLCC stacker.

• Computers and Concrete
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• v.32 no.5
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• pp.513-525
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• 2023

Recently, research on predicting the behavior of reinforced concrete (RC) columns using machine learning methods has been actively conducted. However, most studies have focused on predicting the ultimate strength of RC columns using a regression algorithm. Therefore, this study develops a successive machine learning process for predicting multiple nonlinear behaviors of rectangular RC columns. This process consists of three stages: single machine learning, bagging ensemble, and stacking ensemble. In the case of strength prediction, sufficient prediction accuracy is confirmed even in the first stage. In the case of displacement, although sufficient accuracy is not achieved in the first and second stages, the stacking ensemble model in the third stage performs better than the machine learning models in the first and second stages. In addition, the performance of the final prediction models is verified by comparing the backbone curves and hysteresis loops obtained from predicted outputs with actual experimental data.

• Communications for Statistical Applications and Methods
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• v.28 no.3
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• pp.217-232
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• 2021

The Korea film industry has matured and the number of movie-watching per capita has reached the highest level in the world. Since then, movie industry growth rate is decreasing and even the total sales of movies per year slightly decreased in 2018. The number of moviegoers is the first factor of sales in movie industry and also an important factor influencing additional sales. Thus it is important to predict the number of movie audiences. In this study, we predict the cumulative number of audiences of films using stacking, an ensemble method. Stacking is a kind of ensemble method that combines all the algorithms used in the prediction. We use box office data from Korea Film Council and web comment data from Daum Movie (www.movie.daum.net). This paper describes the process of collecting and preprocessing of explanatory variables and explains regression models used in stacking. Final stacking model outperforms in the prediction of test set in terms of RMSE.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2012.10a
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• pp.467-468
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• 2012

• Journal of Welding and Joining
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• v.24 no.2
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• pp.64-70
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• 2006

The 3-dimensional (3D) chip stacking technology is a leading technology to realize a high density and high performance system in package (SiP). There are several kinds of methods for chip stacking, but the stacking and interconnection through Cu filled through-hole via is considered to be one of the most advanced stacking technologies. Therefore, we studied the optimum process of through-hole via formation and Cu filling process for Si wafer stacking. Through-hole via was formed with DRIE (Deep Reactive ion Etching) and Cu filling was realized with the electroplating method. The optimized conditions for the via formation were RE coil power of 200 W, etch/passivation cycle time of 6.5 : 6 s and SF6 : C4F8 gas flow rate of 260 : 100 sccm. The reverse pulsed current of 1.5 A/dm2 was the most favorable condition for the Cu electroplating in the via. The Cu filled Si wafer was chemically and mechanically polished (CMP) for the following flip chip bumping technology.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.10 no.1
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• pp.38-46
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• 2011

A study was performed to investigate the dynamic behaviors of fiber-reinforced composite materials subjected to transversely low-velocity impact. For this purpose, the simulation of modified beam finite element based on higher order beam theory for two(isotropic and anisotropic) materials is carried out according to the changes of material property, stacking sequence, geometric dimension and impact velocity of steel ball, etc. Main composite materials for simulation are composed of $[0^{\circ}/90^{\circ}/0^{\circ}/-90^{\circ}/0^{\circ}]_{2s}$, $[0^{\circ}/90^{\circ}/0^{\circ}/-90^{\circ}/0^{\circ}]_s$ and $[0^{\circ}/45^{\circ}/0^{\circ}/-45^{\circ}/0^{\circ}]_{2s}$, $[0^{\circ}/45^{\circ}/0^{\circ}/-45^{\circ}/0^{\circ}]_s$ stacking sequences. The effectiveness of this simulation for qualitative and quantitative evaluations in composite materials subjected to foreign object impact was established.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2000.04a
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• pp.618-623
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• 2000

In order to increase the porductivity of electrical parts, manufacturing processes using progressive dies have been widely used in the industry. Motor cores have been fabricated using progressive stacking die with the lamination procedure for better electro-magnetic property. for the proper design of a process, a prediction of the process is required to obtain many design parameters. In this work, rigid-plastic finite element analysis is carried out in order to simulate the lamination this work, rigid-plastic finite element analysis is carried out in order to simulate the lamination process of the motor core. The effects of the embossing depth and the amount of deviation are investigated and compared with experiments. The forming process can then be predicted successfully from the results of analyses, which enables to design appropriately the die and the process.