• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.625-628
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• 2008

This study is performed to evaluate the carbonation resistance by measuring carbonation penetration depth and diffusion equivalent air layer thickness for 3 types of repair materials and 2 types of surface protection materials. Diffusion equivalent air layer thickness($S_D$) is thickness of a static air layer that possesses, under the same conditions, the same carbon dioxide permeability as the coating in accordance BS EN 1062-6. There is a significant advantage that continuous test is possible because it does not destroy the specimen. From experiment results, it is concluded that determination of carbon dioxide permeability is effective to evaluate for surface coating materials.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.8 no.6
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• pp.1250-1256
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• 2004

The movement of continuously changing positions should be stored and indexed for querying current and past positions. A simple extension of the original R-tree to add time as another dimension, called 3D R-tree, does not handle current position queries and does not address the problem of low space utilization due to high overlap of index nodes. In this paper, 1 propose the dynamic splitting policy for improving the 3D R-tree in order to improve space utilization of split nodes. 1 also extend the original 3D R-tree by introducing a new tagged index structure for being able to query the current and past positions of moving objects. 1 found out that my extension of the original R-tree, called the tagged dynamic 3DR-tree, outperforms both the 3D R-tree and 75-tree when querying current and past position.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2015.10a
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• pp.397-400
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• 2015

In this paper a solar energy harvesting system with low-cost MPPT control for low duty-cycled sensor nodes is proposed. The targeted applications are environment, structure monitoring sensor nodes that are not required successively to operate, and MPPT(Maximum Power point Tracking) control using simple circuits is low-cost differently than existing MPPT control. The proposed MPPT control is implemented using linear relationship between the open-circuit voltage of a solar cell. The designed MPPT circuit traces the maximum power point by sampling periodically the open circuit voltage of the solar cell and delivers the maximum available power to the load. The proposed circuit is designed in 0.35um CMOS process. The designed chip area is $975um{\times}1025um$ including pads. Measured results show that the designed system can track the MPP voltage by sampling periodically the open circuit voltage of solar cell.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.12C
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• pp.1186-1192
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• 2005

In this paper, we propose a novel channel estimation method based on pilot channel in a frequency interleaved multicarrier code division multiple access (MC-CDMA). Using the chip interleaving (CI) technique in the frequency domain make it possible to achieve higher frequency diversity gain than the system with conventional symbol interleaving. However, in CI-MC-CDMA systems, a pilot channel-based channel estimation (PCCE) cannot be applied because the orthogonality between pilot symbols and the data symbol is not maintained. The proposed method alters the system structure in order to maintain orthogonality between data and pilot channels over two consecutive subcarriers. Therefore, it can obtain accurate channel state information (CSI) in CI-MC-CDMA.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.23 no.8
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• pp.2042-2051
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• 1998

VBR compressed, pre-recorded video is known to exhibit significant, multiple time-scale bit rate variability. To reduce the variability and burstiness of the aggregated transmission rate as low as possible, in this paper, we present an adaptive bandwidth smoothing algorithm, that can be effectively applicalble for VoD services over a shared-medium channel. For these environments where many clients are connected to a single server, by introducing the conventional MVBA(minimum variability bandwidth allocation) algorithm and controlling adaptively the conventional MVBA(minimum variability bandwidth asllocation) algorithm and controlling adaptively the aggregated transmission rate whenever a new clients request is arrived at the server side, the proposed algorithm effectively reduces the burstiness and variability of the aggregated transmission rate. Through computer experiments, it is shown that the proposed method perporms better than the convertional non-aggregated bandwidth smoothing schemes in terms of the peak rate, standard deviation, number of rate changes for the aggregated traffic.

• The KIPS Transactions:PartA
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• v.11A no.2
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• pp.109-114
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• 2004

This paper presents a high-speed bit-parallel systolic divider for computing modular division A($\chi$)/B($\chi$) mod G($\chi$) in finite fields GF$(2^m)$. The presented divider is based on the binary GCD algorithm and verified through FPGA implementation. The proposed architecture produces division results at a rate of one every 1 clock cycles after an initial delay of 5m-2. Analysis shows that the proposed divider provides a significant reduction in both chip area and computational delay time compared to previously proposed systolic dividers with the same I/O format. In addition, since the proposed architecture does not restrict the choice of irreducible polynomials and has regularity and modularity, it provides a high flexibility and Scalability with respect to the field size m. Therefore, the proposed divider is well suited to VLSI implementation.

• KSBB Journal
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• v.8 no.4
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• pp.313-319
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• 1993

Methyl fructoside was synthesized from sucrose and methanol using an immobilized invertase. The enzyme was covalently bound by glutaraldehyde on porous silica coated with polyethyleneimine to give loading capacity of 120mg of invertase per one gram of dry porous silica and effective activity of 100U per one milligram of bound invertase. Polyethyleneimine coating imparted a hydrophillic character, good activity retention and high loading capacity to the surface of porous silica as well as hydrophillic microenviroment in the vicinity of bound invertase. The immobilized enzyme was formed into an alginate-enclosed silica bead to have enough activity for methyl fructoside synthesis from aqueous methanol-sucrose solution. Using the alginate-enclosed biocatalyst the yield of methyl fructoside was obtained as high as 55.9% from aqueous 30% (v/v) methanol and 0.291mo1/l sucrose with 2U/ml activity at $25^{\circ}C$, pH 4.8.

• Journal of Digital Convergence
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• v.11 no.11
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• pp.409-414
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• 2013

Naive Bayesian classifiers are a powerful and well-known type of classifiers that can be easily induced from a dataset of sample cases. However, the strong conditional independence assumptions can sometimes lead to weak classification performance. Normally, naive Bayesian classifiers use Gaussian distributions to handle continuous attributes and to represent the likelihood of the features conditioned on the classes. The probability density of attributes, however, is not always well fitted by a Gaussian distribution. Another eminent type of classifier is the neuro-fuzzy classifier, which can learn fuzzy rules and fuzzy sets using supervised learning. Since there are specific structural similarities between a neuro-fuzzy classifier and a naive Bayesian classifier, the purpose of this study is to apply learning distribution graphs constructed by a neuro-fuzzy network to naive Bayesian classifiers. We compare the Gaussian distribution graphs with the fuzzy distribution graphs for the naive Bayesian classifier. We applied these two types of distribution graphs to classify leukemia and colon DNA microarray data sets. The results demonstrate that a naive Bayesian classifier with fuzzy distribution graphs is more reliable than that with Gaussian distribution graphs.

• Journal of the Society of Naval Architects of Korea
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• v.29 no.4
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• pp.227-233
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• 1992

To study the large displacement and large rotation problems, geometrically nonlinear formulation of eccentric degenerated beam element has been developed, where the restrictions of infinitesimal rotation increments are removed and the incremental equations are derived using the Taylor series expansion of the displacement function at time t+dt. The geometrically nonlinear analyses are carried out for the cases of cantilever, square frame, shallow arch and 45-degree bend beam and all of them are compared with each of the other results published. The element developed in the present research can be efficiently utilized for analysis of the nonlinear behaviours of structures when displacements and rotations are large.

• Proceedings of the Korea Association of Crystal Growth Conference
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• 1996.06b
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• pp.29-53
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• 1996

다공성 실리카 게 분말은 저밀도, 고비표면적의 특성을 가지며 물리적, 화학적 성질이 우수하여 필름의 점착방지제, 페인트의 소광제, 맥주의 흡착제, 촉매의 담지체등 산업전반에 걸쳐 여러용도로 사용되고 있다. 이러한 다공성 실리카 겔 분말은 고상법, 기상법, 액상법등으로 제조할 수 있으며, 이 중에서 sodium silicate를 원료로 하는 액상공정은 다공성의 제어가 용이하고, 공정이 간단하며, 고순도의 균질한 실리카를 얻을 수 있는 방법으로 많이 사용되고 있다. 본 연구에서는 액상법(sol-gel method)를 사용하여 점착방지제, 소광제 등으로 사용되는 다공성 실리카 겔 미분말의 개발에 초점을 두어 연구하였다. 그리고, 겔 분말의 다공성 제어를 위하여 공정 각 단계에서의 겔 내부의 구조의 변화에 대한 연구와 함께 수화겔의 숙성이 기공특성에 미치는 영향, 건조조건의 기공특성에 대한 영향 등을 살펴보았다. 다공성 실리카 겔 미분말은 다음과 같은 공정에 의해 제조되었다. sodium silicate를 황산과 반응시켜 겔화하고 추가의 황산을 투입하여 미반응분의 Na를 제거한 후 pH 7이상의 알카리 영역에서 숙성하여 다공성을 지닌 실리카 수화겔을 제조하였다. 수화겔의 탈수, 세척, 건조 공정을 거쳐 건조겔을 제조하고, 1-20$\mu\textrm{m}$의 크기로 분쇄하여 최종 제품을 얻을 수 있었다. 최종 다공성 실리카 겔 분말은 비표면적 200-700$m^2$/g, 기공부피 0.5-2.5cc/g, 평균 입경 3-5$\mu\textrm{m}$, 백색도 95% 이상의 물성을 보였다. sodium silicate와 황산의 겔화 반응에 의해 생성된 수화겔은 수 nm크기의 일차입자들의 연속적인 network로이루어져 있으며, 일차입자크기가 너무 작기 때문에 내부의 기공들은 별로 존재하지 않는 상태이다. 2차 주가황산 투입에 의해 미반응의 알카리 이온들을 중화, 제거시킬 수 있으며, 겔의 다공성을 좌우하는 숙성단계에서 숙성 pH, 온도, 시간등의 인자에 의해 수화겔의 기공특성을 제어할 수 있다. pH 7이상에서 실리카의 용해도가 크고, 용해도의 입자크기 의존성이 크므로, 일자입자는 Ostwald-ripening에 의해 계속 성장할 수 있으며, 이때, 입자의 성장은 숙성 온도와 시간에 의존한다. 탈수, 세척공정에 의해 가용성 염인 Na2SO4를 제거하고, 건조조건을 변화시킴으로써 기공부피를 증가시키는 것이 가능하였으며, Fast drying을 사용하여 점착방지제에 적합한 기공부피를 갖는 실리카 건조겔을 제조할 수 있었다.