• Proceedings of the Korean Society For Composite Materials Conference
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• 2002.05a
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• pp.181-183
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• 2002

The accurate permeability for preform is critical to model and design the impregnation of fluid resin in the composite manufacturing process. In this study, the in-plane and transverse permeability for a woven fabric are predicted numerically through the coupled flow model which combines microscopic with macroscopic flow. The microscopic and macroscopic flow which are flows within the micro-unit and macro-unit cell, respectively, are calculated by using 3-D CVFEM(control volume finite element method). To avoid checker-board pressure field and improve the efficiency on numerical computation, A new interpolation function for velocity is proposed on the basis of analytic solutions. The permeability of plain woven fabric is measured through unidirectional flow experiment and compared with the permeability calculated numerically. Based on the good agreement of the results, the relationships between the permeability and the structures of preform such as the fiber volume fraction and stacking effect can be understood. The reverse and the simple stacking are taken in account. Unlike past literatures, this study is based on more realistic unit cell and the improved prediction of permeability can be achieved. It is observed that in-plane flow is more dominant than transverse flow in the real flow through preform and the stacking effect of multi-layered preform is negligible. Consequently, the proposed coupled flow model can be applied to modeling of real composite materials processing.

• Journal of the Korean Institute of Telematics and Electronics
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• v.25 no.7
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• pp.767-773
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• 1988

We have proposed a new simple and easy method for the observation of OSF growth and shrinkage. This method is to observe the behavior of OSF in thedamaged region during oxidation as well as annealing process after introducing mechanical damage on the silicon surface by pressure-controllable indentor. The effect of SiO2 layer on the shrinkage of pregrown OSF generated by the proposed method has been investigated using the samples with or without SiO2 layer. From the experimental data, we suggest a model for the shrinkage of OSF, which is based on the recombinaiton mechanism between silicon interstitial and vacancy at the Si-SiO2 interface.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.36 no.1
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• pp.9-18
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• 2023

Predicting the compressive strength of high-performance concrete (HPC) is challenging because of the use of additional cementitious materials; thus, the development of improved predictive models is essential. The purpose of this study was to develop an HPC compressive-strength prediction model using an ensemble machine-learning method of combined bagging and stacking techniques. The result is a new ensemble technique that integrates the existing ensemble methods of bagging and stacking to solve the problems of a single machine-learning model and improve the prediction performance of the model. The nonlinear regression, support vector machine, artificial neural network, and Gaussian process regression approaches were used as single machine-learning methods and bagging and stacking techniques as ensemble machine-learning methods. As a result, the model of the proposed method showed improved accuracy results compared with single machine-learning models, an individual bagging technique model, and a stacking technique model. This was confirmed through a comparison of four representative performance indicators, verifying the effectiveness of the method.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.66 no.2
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• pp.447-452
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• 2017

The stator phase winding of a linear pulse motor, which is a new type of linear motor, is comprised of two phases and is structurally characterized by a stacking method in which the winding of one phase is laid on top of the winding of another phase. Such a structural characteristic induces a difference in the flux linkage resulting from the flux of each stator phase winding in the same condition. The difference in the induced flux linkage acts as a kind of thrust ripple component in terms of the generated thrust. Thus, in order to maintain consistent thrust force, a method is required to solve the problem caused by the structural singularity. Hence, in this study, we present a technique for reducing the thrust force ripple generated by the stacking of the stator phase windings of a linear pulse motor through the generation of a compensating current reference value of the current controller in order to keep the torque constant. The proposed compensating algorithm is validated by simulations and experimental results.

• Journal of the Korean Association of Geographic Information Studies
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• v.19 no.2
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• pp.98-106
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• 2016

Remote sensing is an efficient technology for observing and monitoring the land surfaces inaccessible to humans. This research proposes a methodology for improving the accuracy of the land cover classification using the Landsat-8 operational land imager(OLI) image. The proposed methodology consists of the following steps. First, the normalized difference vegetation index(NDVI) and normalized difference water index(NDWI) images are generated from the given Landsat-8 OLI image. Then, a new image is generated by adding both NDVI and NDWI images to the original Landsat-8 OLI image using the layer-stacking method. Finally, the maximum likelihood classification(MLC), and support vector machine(SVM) methods are separately applied to the original Landsat-8 OLI image and new image to identify the five classes namely water, forest, cropland, bare soil, and artificial structure. The comparison of the results shows that the utilization of the layer-stacking method improves the accuracy of the land cover classification by 8% for the MLC method and by 1.6% for the SVM method. This research proposes a methodology for improving the accuracy of the land cover classification by using the layer-stacking method.

• Journal of the Microelectronics and Packaging Society
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• v.23 no.3
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• pp.1-6
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• 2016

The Internet of Things (IoT) is a new technology paradigm demanding one packaged system of various semiconductor and MEMS devices. Therefore, the development of electronic packaging technology with very high connectivity is essential for successful IoT applications. This paper discusses both fan-out wafer level packaging (FOWLP) and 3D stacking technologies to achieve the integrattion of heterogeneous devices for IoT. FOWLP has great advantages of high I/O density, high integration, and design flexibility, but ultra-fine pitch redistribution layer (RDL) and molding processes still remain as main challenges to resolve. 3D stacking is an emerging technology solving conventional packaging limits such as size, performance, cost, and scalability. Among various 3D stacking sequences wafer level via after bonding method will provide the highest connectivity with low cost. In addition substrates with ultra-thin thickness, ultra-fine pitch line/space, and low cost are required to improve system performance. The key substrate technologies are embedded trace, passive, and active substrates or ultra-thin coreless substrates.

• Korean Institute of Interior Design Journal
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• v.13 no.3
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• pp.145-152
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• 2004

The European architects including MVRDV, Rem Koolhaas, Van Berkel, and Zaha Hadid tend to use the their own design strategy based on the objective data. This Architectural design method leads to make new paradigm of contemporary architecture. For the purpose of the understanding a part of new architecture paradigm I will analyze the case of Villa VPRO designed by MVRDV. At the result, I can draw the following conclusions. First, through collecting and analyzing data, drawing design concept and planning the space program, they decided on the design strategies of Villa VPRO. They designed the space volume having 42.4m$\times$42.4m floors and infiltrated environmental elements to solve the problems about deep space. Second, Villa VPRO was constructed by 'creative space-making system: a series of floors much like a geological formation, the continuous floors interconnected by spatial means, the precision bombardments of snake-like holes, open elevations, the stacking spaces. Third, Villa VPRO produced the spectacle space effect the various formation of continuous floors make a lot of difference space types in this building. Also they lead to move naturally and give event space. A numbers of holes and openness make it possible to provide friendly environment with combining light and air with views of the surrounding and transparency. And using the method of stacking many types of space make the differences in height.

• BMB Reports
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• v.38 no.6
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• pp.763-765
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• 2005

A new simplified procedure for identifying human plasmin was developed using a DTT copolymerized agarose stacking gel (ASG) system. Agarose (1%) was used for the stacking gel because DTT inhibits the polymerization of acrylamide. Human plasmin showed the lowest activity at pH 9.0. There was a similar catalytically active pattern observed under acidic conditions (pH 3.0) to that observed under alkaline conditions (pH 10.0 or 11.0). Using the ASG system, the primary structure of the heavy chain could be established at pH 3.0. This protein was found to consist of three fragments, 45 kDa, 23 kDa, and 13 kDa. These results showed that the heavy chain has a similar structure to the autolysed plasmin (Wu et al., 1987b) but there is a different start amino acid sequence of the N-termini.

• Transactions of the Korean Society of Machine Tool Engineers
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• v.16 no.6
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• pp.79-85
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• 2007

The modem industry age began when the conveyer system was introduced by Ford to produce model "T". The conveyer system is designed to optimize and maximize mass production of a specific item. Nowadays, however, accommodating to individual tastes has become an important factor in selection of products. Thus, rather than the mass production of one item, producing fewer but a wide variety of goods became important. To give flexibility and elasticity to the conveyer system, a new method of transportation where it is possible to choose a specific item is necessary. Therefore mall quantity and high-volume mass production was decrescent and small quantity batch production was expanded. In this paper, we developed multiple crate stacking and picking system to give flexibility to the conveyer system. First, we verified the conceptually designed system through manufacture. Second, we solved the problems that would happen on the actual field using pneumatic system. Finally, we optimized the system through FEM technique. This system works with stability and fast speed and can improve work efficiency which would minimize the losses resulting from too much dependence on manual labor.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.18 no.12
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• pp.1124-1128
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• 2005

New piezoelectric actuator design, which can reduce the number of the stacking layer without lowering the piezoelectric displacement, is suggested in this work. Each layer of the new designed multilayer actuator has the same electrode pattern as the cross-sectioned layer of the existing multilayer actuator has. The piezoelectric displacement was calculated by Finite-Element Method (FEM) analysis. The maximum piezoelectric displacement of the new-designed actuator with 13 layers was calculated to be almost same value (55.9 ${\mu}m$) as that of the existing actuator with 25 layers(60.1 ${\mu}m$).