• Proceedings of the IEEK Conference
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• 2003.07a
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• pp.3-6
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• 2003

본 논문에서는 다중 경로 페이딩 하에서 동작하는 동기식 DS-CDMA 시스템에서 특별히 근거리 또는 실내 수신의 경우에 발생할 수 있는 짧은 시간 내에 밀집된 다중 경로 성분을 구분해 낼 수 있는 견고한 지연 추정 알고리즘을 제안한다. Sliding correlator 출력에 대한 시평균 상관 행렬을 고유치 분석을 통하여 eigenvector로 분해한 다음 관찰 영역은 신호 부분 영역과 잡음 부분 영역으로 분리할 수 있다. 제안하는 알고리즘에서는 단순한 기존의 sliding correlator 나 잡음공간 만으로의 projection 을 통한 MUSIC-type 알고리즘보다 성능이 월등히 뛰어난 ML (Maximum likelihood) 방식을 소개한다. 이 방식은 기존의 방식보다 복잡도는 약간 증가하지만 지연 측정 성능은 탁월하게 증가하는 것을 보여준다.

• Journal of the Korean Operations Research and Management Science Society
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• v.14 no.2
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• pp.1-18
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• 1989

콘태이너 선박은 출발항과 종착항의 두항구 사이를 잇는 지정된 항로를 오가면서 항로의 중도에 있는 각 항구에 기항하여 화물을 상.하역하는 형태로 각 항구 사이의 화물운송을 수행한다. 이때 이윤을 최대화 하기 위해서 선박을 어느 항구에 기항하고, 또 기항하는 항구에서는 얼마만큼의 화물을 항.하역할 것인지를 적절하게 결정해야 한다. 이러한 콘테이너 선박 운항경로 문제를 모형화 하고, 0-1 혼합정수 계획법을 이용한 수리모형을 제시한 후, 최소비용 흐름문제와 분지한계 기법을 이용한 최적해법을 제시하였다. 본 논문에서는 제시한 해법에서는 먼저, 기항하기로 한 항구의 집합에 따라 부분문제를 정의한다. 또한 분해된 부분문제에서 추가로 기항할 항구들에 대한 운항구간의 적제 한계와 운항비용을 완화시킨 문제를 정의하고, 그것을 다시 최소비용흐름문제를 이용하여 풀어서 상한값ㄹ 구한다. 이와 같은 방법으로 각 부분문제의 하한값과 하한값을 계신히여, 그것을 이용하여 분지를 절단하고, 또한 상한값이 높은 부분문제를 우선적으로 선택하여 분지합으로써 최적해를 구한다.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.10
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• pp.120-129
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• 2003

For successful establishment of the roughing CAM system based on reverse engineering, it is necessary to develop the measurement method for generation of roughing path from a physical footwear model. In this study, the development of the roughing path measurement system is presented. It consists of 3 CCD cameras, image acquisition board and the roughing path measurement algorithm. The 3 CCD cameras capture images of the sidewall and the bottom of the footwear and, from two images, the outer and inner lines are extracted using image-processing algorithm. The roughing path measurement algorithm generates the roughing path which is reflected on the change of resolution according to the distance between the CCD camera and the measured point. The experimental results show that the developed system can measure the roughing path within the allowable roughing error range.

• 한국유가공학회:학술대회논문집
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• 2003.11a
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• pp.61-74
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• 2003

담즙산은 cholesterol의 대사산물로 체내에서 cholesterol을 제거하는 주경로로서, 체내 cholesterol 대사를 조절하는 중요한 수단이다. 최근에 복합담즙산 분해활력이 높은 L. acidophilus에 의한 혈중 cholesterol 저하효과에 관한 많은 연구들이 보고되고 있으며, 이것은 복합담즙산의 분해로 생성되는 유리 담즙산의 분 배출 증가와 장내 cholesterol 흡수에 필요한 복합 micelle 형성의 방해에 의한 것으로 알려져 있다. 즉, 유리 담즙산은 장내에서 복합담즙산보다 용해성이 낮아서 흡수되지 않고 분으로 배출되기 쉬워, 간에서는 분으로 배출된 양만큼의 부족한 복합담즙산을 보충하기 위해 cholesterol을 이용하여 새로운 복합담즙산을 생성하기 때문에 결국은 체내의 혈중cholesterol 수준을 감소시키는 것으로 생각된다. 또한 담즙으로 분비되는 복합담즙산은 소장내에서 cholesterol의 용해 흡수에 도움을 주지만 유리 담즙산은 cholesterol 용해성이 낮기 때문에, 장내 cholesterol 흡수에 영향을 미치는 것으로 생각된다.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.42 no.1
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• pp.29-37
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• 2005

One of the principal disadvantages of multicarrier modulation technique is the sensitivity to the frequency offset introduced by Doppler shift. This frequency offset introduces inter-carrier interference (ICI) among the multiplicity of carriers in the multicarrier modulated signal. However, Doppler spread induced by temporal channel variations can Provide another means for diversity. In this paper, we propose a modified multicarrier code division multiple access (CDMA) system to exploit Doppler diversity as well as multipath diversity. The key work of our framework is a canonical time-frequency-based decomposition of the mobile wireless channel into series of independent fading channel. The decomposition naturally leads to a time-frequency generalization of the Rake receiver that exploits both multipath and Doppler diversity.

• The Journal of the Korea institute of electronic communication sciences
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• v.15 no.2
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• pp.327-334
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• 2020

In this paper, an automatic cruise system of unmanned boat was developed for surveying water depth in reservoir using accurate location information. Using global satellite navigation system(GNSS) data in real time, this unmanned system, combined with an echo sounder, can simultaneously collect location information and depth information on the reservoir. This automatic navigation system allows the automatic route generation program to automatically generate a cruise route according to the input conditions for grid sizes of 5m, 10m and 20m, and automatically controls the cruise route with high positional accuracy. The developed system was tested to verify the applicability of the selected Yonggok(Geoncheon) reservoir as a test reservoir located in Suncheon, Jeollanam-do.

• Journal of the Korean Chemical Society
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• v.32 no.3
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• pp.267-275
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• 1988

Fine powders of amorphous $Al_2O_3,\;SiO_2,\;Al_2O_3-SiO_2$ system were prepared by hydrolysis of solutions containing alkoxides, aluminium tri-isopropoxide and silicon tetra-ethoxide. High purity ultrafine ${\beta}-sialon$ powders were prepared by the carbothermal reduction-nitridation of amorphous $Al_2O_3-SiO_2$ powders mixed with carbon black as a reducing agent. In the hydrolysis step the effect of the factors such as pH, reaction temperature and amount of water on the conversion rate of alkoxides to oxides was investigated. In the carbothermal reduction-nitridation the reaction path was assumed by the analysis of intermediates formed in the process of ${\beta}-sialon$ synthesis and the reaction kinetics of ${\beta}-sialon$ formation was considered.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.26 no.11B
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• pp.1546-1555
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• 2001

Conventionally, in a CDMA system analysis, we assume only a single path within one chip duration. But, in this paper, we assume various number of multipaths within one chip duration according to spreading bandwidth in fixed channel model. Thus we take into account of the effects of autocorrelation and relative phases among multipath components within one chip duration according to different bandwidth, and analyze fading effects. And we derive the pdf of output signal. Then, we derive the average error probability versus the number of users from derived pdf. We use a Maximal Ratio Combining (MRC) RAKE receiver under the JTC channel model which is one of the popular realistic wideband channel models. And we employ hybrid FDMA/CDMA systems to compare the performance of W-CBMA system for the same occupied total bandwidth. Then, we compare and analyze them for different bandwidth based on the number of users as a parameter. From the simulation results for different bandwidth, better performance can be obtained for wider bandwidth system where more resolvable multipath components are available.

• Journal of Soil and Groundwater Environment
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• v.11 no.1
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• pp.1-6
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• 2006

The analysis of functional population and its dynamics on the environment is essential for understanding bioremediation in environment. Here, we report a method for oligonucleotide microarray for the monitoring of aliphatic and aromatic degradative genes. This microarray contained 15 unique and group-specific probes which were based on 100 known genes involved pathways in biodegradation. Hybridization specificity tests with pure cultures, strain Pseudomonas aeruginosa KCTC 1636 indicated that the designed probes on the arrays appeared to be specific to their corresponding target genes. It was found that the presence of 8 genes encoding alkane, naphthalene, biphenyl, pyrene (PAH ring-hydroxylating) degradation pathway could be detected in oil contaminated soil sample. Therefore, the findings of this study strongly suggest that oligonucleotide microarray is an effective diagnostic tool for evaluating biodegradation capability in oil contaminated subsurface environment.

• Applied Chemistry for Engineering
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• v.10 no.3
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• pp.388-393
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• 1999

Polyurethane foams are polymeric material with repeating groups of urethane and urea. When these are heated with ethylene glycol and K acetate catalyst at $200^{\circ}C$, the transesterification of them leads to soluble products. The mechanisms of the reaction were investigated from the molecular weight and the component distributions of the products by GPC and IR analysis. The degradation of the urethane groups was faster than that of urea groups in transesterification reaction. K acetate catalyst accelerated the rate of the transesterification because it had a high ionization tendency. Each reaction, using K or Sr acetate as a catalyst, progressed in the same reaction path but yielded different compositions in products because of the difference of the reaction rate.