• 반도체디스플레이기술학회지
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• 제8권1호
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• pp.43-48
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• 2009

We have examined the problem of the number of quad-tree blocks that an n-dimensional rectangle will be decomposed into on the average. the contribution of this paper are both practical and theoretical. In this paper, we develops the overlapping multi-scale models and the region quad-tree models which is useful in computer graphics animation, image processing, pattern recognition and also for modeling three dimensional objects. These models, which represent something of a conceptual departure from other models developed for multi-scale framework were developed with the specific interest of producing smooth estimates.

• International Journal of Aeronautical and Space Sciences
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• 제18권1호
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• pp.70-81
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• 2017

Various components of an engine nozzle are modeled as flexible multi-body components that are operated under high temperature and pressure. In this paper, in order to predict complex behavior of an engine nozzle, thermo-fluid-flexible multi-body dynamics coupled analysis framework was developed. Temperature and pressure on the nozzle wall were obtained by the steady-state flow analysis for a two-dimensional nozzle. The pressure and temperature-dependent material properties were delivered to the flexible multi-body dynamics analysis. Then the deflection and strain distribution for a nozzle configuration was obtained. Heat conduction and thermal analyses were done using MSC.NASTRAN. The present framework was validated for a simple nozzle configuration by using a one-way coupled analysis. A two-way coupled analysis was also performed for the simple nozzle with an arbitrary joint clearance, and an asymmetric flow was observed. Finally, the total strain result for a realistic nozzle configuration was obtained using the one-way and two-way coupled analyses.

• Advances in aircraft and spacecraft science
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• 제10권3호
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• pp.245-256
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• 2023

In order to improve aerodynamic performance of multi-stage axial flow turbines used in aircraft engines, a one-dimensional aerodynamic design and optimization framework is constructed. In the method, flow path is generated by solving mass continuation and energy conservation with loss computed by the Craig & Cox model; Also real gas properties has been taken into consideration. To obtain an optimal result, a multi-objective genetic algorithm is used to optimize the efficiencies and determine values of various design variables; Final design can be selected from obtained Pareto optimal solution sets. A three-stage axial turbine is used to verify the effectiveness of the developed optimization framework, and designs are checked by three-dimensional CFD simulation. Results show that the aerodynamic performance of the optimized turbine has been significantly improved at design point, with the total-to-total efficiency increased by 1.17% and the total-to-static efficiency increased by 1.48%. As for the off-design performance, the optimized one is improved at all working points except those at small mass flow.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년도 학술대회
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• pp.378-385
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• 2008

The present paper deals with the accurate and robust limiting procedure for the multi-dimensional flow analysis on unstructured meshes. The multi-dimensional limiting process (MLP) which was successfully proposed on structured grid system is extended to unstructured meshes. Based on MUSCL-type framework on unstructured meshes, the new slope limiter is devised to satisfy the MLP condition, which is quite effective to regulate the unwanted oscillations, especially on multiple dimensions. Considering the neighborhood based on the vertex of the cell, as well as the edge, this limiting strategy captures the multi-dimensional flow features very accurately with the proper stencils. From the various numerical results, these desirable characteristics of the proposed limiting strategy are clearly shown.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2008년 추계학술대회논문집
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• pp.378-385
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• 2008

The present paper deals with the accurate and robust limiting procedure for the multi-dimensional flow analysis on unstructured meshes. The multi-dimensional limiting process (MLP) which was successfully proposed on structured grid system is extended to unstructured meshes. Based on MUSCL-type framework on unstructured meshes, the new slope limiter is devised to satisfy the MLP condition, which is quite effective to regulate the unwanted oscillations, especially on multiple dimensions. Considering the neighborhood based on the vertex of the cell, as well as the edge, this limiting strategy captures the multi-dimensional flow features very accurately with the proper stencils. From the various numerical results, these desirable characteristics of the proposed limiting strategy are clearly shown.

• 디지털융복합연구
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• 제15권10호
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• pp.243-251
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• 2017

효과적인 데이터 분석 및 활용을 위해서는 빅 데이터를 내부 데이터와 유연하게 연계할 수 있는 방안이 필요하다. 빅 데이터 분석 정보를 내부 정보시스템과 연계시키기 위한 방안으로서 본 연구는 다차원 이벤트 온톨리지를 제시하였다. 이를 위해서 먼저 빅 데이터 분석 정보를 이벤트 모형을 사용하여 온톨리지로 표현하고, 다차원 데이터베이스 또한 OWL-DL 온톨리지로 변환하여 표현하였다. 다차원 이벤트 온톨리지에서 빅 데이터 분석정보들은 차원 계층구조를 통하여 다차원 데이터베이스에 저장된 모든 개체들에게 공유되는데, 본 연구에서는 이를 이벤트의 하향공유, 상향 공유 및 복합 이벤트 공유로 구분한다. 이들 정보공유 유형별로 빅 데이터 분석 정보의 공유 및 활용 방안들을 제시하였으며, Protege를 사용하여 시험적으로 구현하였다. 본 연구는 외부의 빅 데이터 분석 정보를 내부의 다차원 데이터베이스와 연계하는 방안을 실험적으로 제시하였다는 점에서 의의를 가진다고 할 수 있다.

• 지역연구
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• 제14권1호
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• pp.21-45
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• 1998

Urban quality of life(QOL) is recently considered as the important determinant of inter-urban migration and industrial location chice. However, there is little concensus in the method of measurement of QOL. This study provides an theoretical framework of the measurement of QOL. This study provides an theoretical framework of the measurement of QOL, and developes a new method, a multi-year$\cdot$mulit-dimensional distance index model. Based on the theoretical framework and the method, the QOLs of 74 urban areas in Korea are measured, and the determinants of the QOL and the changes of the QOL between two years of 1993 and 1995 are analyzed. The results of the analysis are as follows: 1) The interurban differences of the QOL tens to be interban differences of the QOL tend to be intensified over time. 2) The OQLs of the cities in the Capital Region are relatively deteriorated. 3) The conditions of education$\cdot$Culture$\cdot$leisure life determiner over 65% of the QOL of the Korean cities.

• 한국콘텐츠학회논문지
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• 제12권4호
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• pp.76-85
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• 2012

오피니언마이닝 기법은 대량의 고개리뷰들에 나타나는 핵심개체 또는 속성들에 대하여 고객들이 느끼는 긍정 또는 부정의 정도를 계산할 수 있지만, 그 분석능력이 단순하다는 한계가 있다. 본 논문에서는 온라인 고객리뷰들에 대하여 다차원적으로 분석할 수 있는 기법을 제안하였다. 기존의 OLAP기법을 텍스트 데이터형에 적용할 수 있도록 수정하였다. 다차원 분석모델은 명사축과 형용사축, 문서축으로 구성되는 3차원 공간 개념을 4개의 관계형 테이블로 실체화 한 것이다. 다차원 분석모델은 기존의 오피니언마이닝, 정보요약, 클러스터링 알고리즘들을 융합할 수 있는 새로운 틀이라는 점에서 그 가치가 있다. 본 논문에서 제안한 다차원 분석모델과 알고리즘들을 실제로 구현하여 온라인 고객리뷰에 대한 복잡한 분석을 수행할 수 있음을 확인하였다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제4권2호
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• pp.154-173
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• 2010

Database outsourcing is unavoidable in the near future. In the scenario of data stream outsourcing, the data owner continuously publishes the latest data and associated authentication information through a service provider. Clients may register queries to the service provider and verify the result's correctness, utilizing the additional authentication information. Research on On-line Stream Analytics (OLSA) is motivated by extending the data cube technology for higher multi-level abstraction on the low-level-abstracted data streams. Existing work on OLSA fails to consider the issue of database outsourcing, while previous work on stream authentication does not support OLSA. To close this gap and solve the problem of OLSA query authentication while outsourcing data streams, we propose MDAHRB and MDAHB, two multi-dimensional authentication approaches. They are based on the general data model for OLSA, the stream cube. First, we improve the data structure of the H-tree, which is used to store the stream cube. Then, we design and implement two authentication schemes based on the improved H-trees, the HRB- and HB-trees, in accordance with the main stream query authentication framework for database outsourcing. Along with a cost models analysis, consistent with state-of-the-art cost metrics, an experimental evaluation is performed on a real data set. It exhibits that both MDAHRB and MDAHB are feasible for authenticating OLSA queries, while MDAHRB is more scalable.

• 한국산업정보학회논문지
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• 제18권6호
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• pp.71-82
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• 2013

최근 공공서비스의 효율성과 효과성이 중요 이슈로 나타나면서, 성과관리시스템에 대한 연구가 활발히 이루어지고 있다. 공공서비스 성과관리시스템 관련 연구는 효율성만을 평가하거나 설문조사를 기반으로 한 정성적 평가에 의존하고 있다. 그러나 공공서비스는 상당히 광범위하고 복잡하기 때문에 종합적인 관점이 요구된다. 공공서비스의 사회성, 공익성, 공공성 등의 다양한 측면을 고려하고, 사업의 올바른 방향성을 제시할 수 있는 성과관리시스템의 도입이 시급한 실정이다. 따라서 본 연구에서는 공공서비스를 다면적으로 평가할 수 있는 성과관리시스템의 새로운 프레임워크를 제시하고, 이를 실제 공공서비스 평가에 적용하였다. 정량평가, DEA(Data Envelopment Analysis) 평가와 더불어 전문가의 정성평가를 더하여 다면적 관점에서 공공서비스를 평가하기 위한 프레임워크를 제시하였다. 마지막으로 본 연구에서 제시된 연구 프레임워크를 C시의 공공서비스에 적용하여, 프레임워크의 실행가능성과 유용성 검증하였다.