• 대한수학회논문집
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• 제34권2호
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• pp.565-572
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• 2019

In this paper, we consider a Korteweg-de Vries equation in noncylindrical domain. This work is devoted to prove existence and uniqueness of global solutions employing Faedo-Galerkin's approximation and transformation of the noncylindrical domain with moving boundary into cylindrical one. Moreover, we estimate the exponential decay of solutions in the asymptotically cylindrical domain.

• 대한수학회지
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• 제59권2호
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• pp.279-298
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• 2022

In this paper, the existence and uniqueness for the global solution of neutral stochastic functional differential equation is investigated under the locally Lipschitz condition and the contractive condition. The implicit iterative methodology and the Lyapunov-Razumikhin theorem are used. The stability analysis for such equations is also applied. One numerical example is provided to illustrate the effectiveness of the theoretical results obtained.

• 로봇학회논문지
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• 제2권1호
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• pp.29-39
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• 2007

We present an implementation of particle filter algorithm for global localization and kidnap recovery of mobile robot. Firstly, we propose an algorithm for efficient particle initialization using sonar line features. And then, the average likelihood and entropy of normalized weights are used as a quality measure of pose estimation. Finally, we propose an active kidnap recovery by adding new particle set. New and independent particle set can be initialized by monitoring two quality measures. Added particle set can re-estimate the pose of kidnapped robot. Experimental results demonstrate the capability of our global localization and kidnap recovery algorithm.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2015년도 제46회 하계학술대회
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• pp.1383-1384
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• 2015

In this paper, a dynamics model embedded navigation filter is newly suggested for underwater autonomous systems without position or attitude aid. In order to ensure the observability on the INS errors, the hydrodynamics of the underwater vehicle is incorporated with the INS attitude error. This approach allows us to estimate and compensate the INS errors in spite of using external velocity sensor. Through the simulation, the performance and effectiveness of the proposed scheme are demonstrated.

• 대한전자공학회논문지
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• 제22권3호
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• pp.60-67
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• 1985

본 논문에서는 VLSI layout CAD에 있어서의 새로운 그로발 라우팅(global routing) 기법을 제안하고 이에 관하여 논하였다. 종래의 그로발 라우터에서는 핀의 위치를 모두 셀의 중앙에 두었기 때문에 신호선의 채널 사용량을 정확히 산출할 수 없었다. 그 결과 디테일드 라우팅 (detailed routing)시 배선량 overflow가 발생하여 100% 결선을 저해하는 많은 요인을 내포하고 있었다. 본 논문에서는 이러한 문제점을 모두 보완하기 위하여 핀순서를 고려한 새로운 방법의 그로발 라우팅 알고리즘을 제안하였다. 이 알고리즘을 사용하여 그로발 라우터를 실현하고, 계산기상의 실험 결과를 통하여 제안한 알고리즘의 유용성을 보였다.

• Journal of Korea Trade
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• 제26권4호
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• pp.1-22
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• 2022

Purpose - This paper empirically investigates the effect of a rise in the global value chain (GVC) on the industry-level efficiency of resource allocation (based on plant-level inefficiency measures) in Korea, with a focus on various channels through which a rise in the GVC can increase competition among firms and thus induce resources to be allocated more efficiently across firms. Design/methodology - We empirically investigate the relationship between the industry-specific importance of GVC and the industry-level allocative inefficiency that is measured as the dispersion of the plant-level marginal revenue of capital (MRK) as in Hsieh and Klenow's (2009) influential model. We compute MRK dispersion for industries sorted by various characteristics that are closely related to firm/industry sensitivity to the GVC. In other words, we compute the average industry-level MRK dispersion for industries sorted by industry-specific importance of GVC and compute the difference between the two groups of industries (higher vs. lower than the median GVC); we also calculate the difference between industries sorted by industry-specific export (import) intensity. This is our difference-in-difference estimate of the MRK dispersion associated with the GVC for the export (import)-intensive industry versus the non-export (non-import)-intensive industry. This difference-in-difference estimate of the MRK dispersion conditional vs. unconditional on firm-level productivity is then calculated further (triple-difference estimate). Findings - A rise in GVC is associated with a decrease in the MRK dispersion in the export-intensive industry compared to the non-export-intensive industry. The same is true for industries that rely heavily on imports versus those that do not (i.e., import intensive vs. non-intensive). Furthermore, the reduction in the MRK dispersion in the export-intensive industry associated with an increase in the GVC is disproportionately greater for high-productivity firms. In contrast, the negative relationship between GVC and MRK dispersion in the import-intensive industry is disproportionately smaller for high-productivity firms. Originality/value - Existing studies focus on the relationship between GVC and aggregate output, exports, and imports at the country level. We investigate detailed firm/industry-level mechanisms that determine the relationship between GVC, trade, and productivity. Using the plant-level data in South Korea, we investigate how GVC is related to the cross-firm MRK dispersion, an important measure of allocative inefficiency, based on Hsieh and Klenow's (2009) influential economic theory. This is the first study to provide plant-level evidence of how GVC affects MRK dispersion. Furthermore, we examine how the relationship between GVC and MRK-dispersion varies across export intensity, import intensity, and firm-level productivity, providing insight into how GVC can affect firms' exposure to competition in the global market differently depending on market conditions and thus generate trade-related productivity gains.

• 대한기계학회논문집A
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• 제29권5호
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• pp.754-761
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• 2005

The 40\% of wall thickness criterion which has been used as a plugging rule of steam generator tubes is applicable only to a single cracked tube. In the previous studies performed by authors, several global failure prediction models were introduced to estimate the failure loads of steam generator tubes containing two adjacent parallel axial through-wall cracks. These models were applied for thin plates with two parallel cracks and the COD base model was selected as the optimum one. The objective of this study is to verify the applicability of the proposed optimum global failure prediction model for real steam generator tubes with two parallel axial through-wall cracks. For the sake of this, a series of plastic collapse tests and finite element analyses have been carried out fur the steam generator tubes with two machined parallel axial through-wall cracks. Thereby, it was proven that the proposed optimum failure prediction model can be used as the best one to estimate the failure load quite well. Also, interaction effects between two adjacent cracks were assessed through additional finite element analyses to investigate the effect on the global failure behavior.

• 대한교통학회지
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• 제26권5호
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• pp.41-49
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• 2008

세계화를 통해 글로벌 공급사슬은 더욱 복잡해지고, 고객들은 모든 물류서비스를 통합적으로 제공받을 수 있는 기업에 대한 의존도가 높아짐에 따라 고객들은 물류 기업에 대해서 가격뿐만 아니라 운영적인 측면에서 높은 효율성을 요구하고 있다. 이에 본 연구에서는 자료포락분석(Data Envelopment Analysis)을 중심으로 전세계 물류산업의 효율성의 추이와 비효율성에 영향을 미치는 요소들에 대한 연구를 진행하였다. 그 결과를 요약하면, 5개년간 세계의 물류산업의 효율성은 높아지는 추세를 보이고 있었으며, 비효율성은 규모에 의한 비효율성보다는 순수기술효율성에 의해 나타난 비효율성에 의해서 나타나고 있었다. 비효율성에 영향을 미치는 외부적인 요소를 살펴보면, 우선 세계화는 비효율성에 영향을 주고 있다. 세계화의 요소 중에서는 경제적인 요소보다는 전반적인 세계화 정도가 더 영향을 미쳤으며, 인프라와 관련되어서는 인력, 금융적 지원, 기반 등 소프트웨어적 측면의 영향력이 더 유의했으며 법제도적인 측면에서는 집행의 투명성, 법제도의 효과가 유의하게 영향을 미치는 것을 밝혀냈다.

• 대한전자공학회논문지SP
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• 제47권2호
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• pp.77-85
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• 2010

온라인 지문 인식 시스템에서는 주변 환경, 사용자의 지문 상태 및 입력 방법에 따라 다양한 품질의 지문이 입력된다. 따라서 지문 인식 시스템의 성능을 향상시키기 위해서는, 입력된 지문 영상을 이용하여 본인과 타인간의 변별력을 높이는 연구뿐만 아니라 다양한 품질의 지문 영상들 중에서 품질이 좋은 지문 영상을 선택하여 이를 인식에 사용하는 연구도 병행이 되어야 한다. 하지만 대부분의 기존 연구에서는 지문의 지역적인 품질만을 측정하였기 때문에 한 장의 지문영상의 품질에 대한 예측은 거의 이루어지지 않았다. 따라서 본 논문에서는 획득된 지문 영상의 품질을 판단하기 위해서 지역적인 지문 품질 측정과 이를 통한 전역적 지문 품질 측정 방볍을 제안하였다. 지역적인 지문 품질 평가에서는 각 지문 블록에서 그레디언트(Gradient)의 확률 밀도 함수(Probability Density Function)의 형태를 측정하여 블록 별 품질 값을 예측하였고, 이를 기반으로 전역적인 품질 평가에서는 신경망(Neural network)올 사용하여 지문 영상 전체를 평가함으로써 입력된 영상의 사용 여부를 판단하였다. FVC2002 데이터베이스를 사용하여 실험한 결과, 제안한 전역적 방법을 사용하였을 때 NFIQ(NIST Fingerprint Image Quality)의 방법보다 정합 예측 성능이 높게 나타난 것올 확인할 수 있었다.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2015년도 학술발표회
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• pp.467-467
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• 2015

Sustainable water resource management requires the assessment of hydrological variability in response to climate fluctuations and anthropogenic activities. Determining quantitative estimates of water balance and total basin discharge are of utmost importance to understand the variations within a basin. Hard-to-reach areas with few infrastructures, coupled with lengthy administrative procedures makes in-situ data collection and water management processes very difficult and unreliable. In this study, the hydrological behavior of Lake Chad whose extent, extreme climatic and environmental conditions make it difficult to collect field observations was examined. During a 10 year period [January 2003 to December 2013], dataset from space-borne and global hydrological models observations were analyzed. Terrestial water storage (TWS) data retrieved from Gravity Recovery and Climate Experiment (GRACE), lake level variations from Satellite altimetry, water fluxes and soil moisture from Global Land Data Assimilation System (GLDAS) were used for this study. Furthermore, we combined altimetry lake volume with TWS over the lake drainage basin to estimate groundwater and soil moisture variations. This will be validated with groundwater estimates from WaterGAP Global Hydrology Model (WGHM) outputs. TWS showed similar variation patterns Lake water level as expected. The TWS in the basin area is governed by the lake's surface water. As expected, rainfall from GLDAS precedes GRACE TWS with a phase lag of about 1 month. Estimates of groundwater and soil moisture content volume changes derived by combining altimetric Lake Volume with TWS over the drainage basin are ongoing. Results obtained shall be compared with WaterGap Hydrology Model (WGHM) groundwater estimate outputs.