• Korean Journal of Computational Design and Engineering
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• v.10 no.6
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• pp.444-454
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• 2005

Recently, the requirements of multi-resolution models of a solid model, which represent an object at multiple levels of feature detail, are increasing for engineering tasks such as analysis, network-based collaborative design, and virtual prototyping and manufacturing. The research on this area has focused on several topics: topological frameworks for representing multi-resolution solid models, criteria for the level of detail (LOD), and generation of valid models after rearrangement of features. As a solution to the feature rearrangement problem, the new concept of the effective zone of a feature is introduced in the former part of the paper. In this paper, we propose a feature-based non-manifold modeling system to provide multi-resolution models of a feature-based solid or non-manifold model on the basis of the effective feature zones. To facilitate the implementation, we introduce the class of the multi-resolution feature whose attributes contain all necessary information to build a multi-resolution solid model and extract LOD models from it. In addition, two methods are introduced to accelerate the extraction of LOD models from the multi-resolution modeling database: the one is using an NMT model, known as a merged set, to represent multi-resolution models, and the other is storing differences between adjacent LOD models to accelerate the transition to the other LOD. We also suggest the volume of the feature, regardless of feature type, as a criterion for the LOD. This criterion can be used in a wide range of applications, since there is no distinction between additive and subtractive features unlike the previous method.

• Spatial Information Research
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• v.14 no.3 s.38
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• pp.321-334
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• 2006

3D spatial data are of increasing interest in landscape analysis, urban planning and map services based on Web, because of its reality. But the amount of 3D spatial data are very large in comparison with 2D spatial data. Therefore it is necessary to have a efficient methods to transfer and visualize 3D spatial data. The concept of Level of Detail in Computer Graphics is effective. This paper briefly presents two LOD data models of data transmission based on the spatial data model of international standards. First, it is separated LOD model that gives a LOD level to object. Second is Selective LOD model that gives a LOD level to object's element. We compared the efficiency of 3D data transmission based on two LOD model.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2009.04a
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• pp.356-359
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• 2009

본 연구에서는 교량의 정보를 효율적으로 관리하고 활용할 수 있는 3차원 형상기반 표준정보모델을, 현실 세계와 유사한 3차원 가상공간에 표현함으로써 실제 공간에 대해 보다 정확한 분석을 수행 할 수 있도록 교량정보모델과 3차원 지리정보체계를 연계하는 방안을 제시하였다. 교량의 표준정보모델은 기존에 개발된 STEP 기반의 교량정보모델을 활용하였으며, 3차원 지리정보체계는 지리정보상에 3차원 도시객체를 표현하기 위한 표준데이터모델인 CityGML를 활용하였다. 교량정보모델을 GIS와 연계하기 위한 핵심 요소인 교량구조물의 형상표현 LOD(Level of Detail)는 CityGML의 가이드라인을 준용하여 교량구조물에 적합하도록 새롭게 구성하였다. 즉, 빌딩구조물 위주로 정의되어진 기존의 CityGML의 한계점을 극복하기 위해, 총 5단계의 교량구조물의 LOD를 작성하여 각 단계별로 지리정보 상에 교량 형상을 표현할 수 있도록 LOD를 정의하였다. 또한, 두 모델을 소프트웨어적으로 연계하기 위하여 기존의 STEP 기반 교량정보모델을 활용하여, GIS의 정보로 변환하기 위한 소프트웨어 아키텍처를 구성하였다.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.7
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• pp.22-34
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• 2020

Three-dimensional (3D) computer-aided design (CAD) models require different levels of detail (LODs) depending on their purpose. Therefore, it is beneficial to automatically simplify 3D CAD assembly models to meet the desired LOD. Feature-based 3D CAD assembly models typically have the lowest and highest feasible limits of LOD during simplification. In order to help users obtain a feasible simplification result, we propose a method to simplify feature-based 3D CAD assembly models by determining the lowest and highest limits of LOD. The proposed method is verified through experiments using a simplification prototype implemented as a plug-in type module on Siemens NX.

• Korean Journal of Construction Engineering and Management
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• v.20 no.6
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• pp.89-97
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• 2019

Recently, BIM has been actively introduced in construction projects. In particular, the introduction of BIM in cost estimating process is expected to improve the accuracy and efficiency of the cost estimate. However, the quantity calculation and BoQ documents preparation process still require manual work. Although the BIM model may support quantification process, it is still problematic that the level of detail of the model must be very detailed to meet the items in BoQ. To address this, it is necessary to analyse the LOD criteria and to analyze the extent to which quantity can be computed according to the level of detail in the BIM model. For the analysis of LOD-based work items, the work item grades were divided into A,B, and C. In this study, the ratio and cost of each item that can be calculated at the LOD level in the detailed design phase are reviewed for each type of work, and the method for improving the quantity calculation using BIM is proposed. In the LOD 300 stage(Detailed design stage), the largest number of items in the class B, the major improvement class, are window and glass work. In addition, the most expensive type of work was analyzed by reinforced concrete work. In the future, it is necessary to suggest appropriate improvement way for items with high item ratios and items with high cost ratios. The results of this study are expected to be used as a BIM-based cost estimation or as basic data for improving the current BoQ system.

• Journal of the Korean Society for Library and Information Science
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• v.51 no.3
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• pp.163-188
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• 2017

This study aims to propose disaster safety information service model based on LOD for effective management and dissemination of the information. To achieve the aim of this study, current state of disaster safety information was analyzed through online search and face-to-face interviews, and then the information was divided into 6 types. Finally, this study proposed specific process of building disaster safety information LOD service with considerations reflecting the information characteristics. The process for building LOD was based on Guidelines for Building Linked Data written by National Information Society Agency. Especially, ontology concept model was defined by using standard lexical resources and modeling tools based on 6 types of disaster safety information, and classes and properties were proposed. The results of this study will make disaster safety information more useful for common people.

• Journal of the Korea Convergence Society
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• v.11 no.10
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• pp.89-96
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• 2020

Linked Data allows structured data to be published in a standard way that datasets from various domains can be interlinked. With the rapid evolution of Linked Open Data(LOD), researchers are exploiting it to solve particular problems such as semantic similarity assessment. In this paper, we propose a method, on top of the basic concept of Linked Data Semantic Distance (LDSD), for calculating the Linked Data semantic distance between resources that can be used in the LOD-based recommender system. The semantic distance measurement model proposed in this paper is based on a similarity measurement that combines the LOD-based semantic distance and a new link weight using TF-IDF, which is well known in the field of information retrieval. In order to verify the effectiveness of this paper's approach, performance was evaluated in the context of an LOD-based recommendation system using mixed data of DBpedia and MovieLens. Experimental results show that the proposed method shows higher accuracy compared to other similar methods. In addition, it contributed to the improvement of the accuracy of the recommender system by expanding the range of semantic distance calculation.

• Journal of the Korean Society for information Management
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• v.32 no.1
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• pp.109-134
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• 2015

In the Korean wave 3.0 age, it is needed to prepare how to globalize and hold Korean culture through development of various Korean wave culture contents from existing contents focused on media. The goal of this study is to establish the foundation for developing the various Korean wave culture contents as linking information about other culture contents as well as food culture by extending Korean culture contents service based on LOD. For this purpose, this study established and assorted the concept of food culture through the literature review and case study and analyzed the applicability of the services of food culture contents based on LOD. Futhermore, this study provides the basis on extension of Korean wave culture service and suggests the process of implementation of food culture LOD and service model.

• Journal of the Korea Society of Computer and Information
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• v.22 no.6
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• pp.57-68
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• 2017

The Linked Open Data(LOD) cloud is quickly becoming one of the largest collections of interlinked datasets and the de facto standard for publishing, sharing and connecting pieces of data on the Web. Data publishers from diverse domains publish their data using Resource Description Framework(RDF) data model and provide SPARQL endpoints to enable querying their data, which enables creating a global, distributed and interconnected dataspace on the LOD cloud. Although it is possible to extract structured data as query results by using SPARQL, users have very poor in analysis and visualization of RDF data from SPARQL query results. Therefore, to tackle this issue, based on Formal Concept Analysis, we propose a novel approach for analyzing and visualizing useful information from the LOD cloud. The RDF data analysis and visualization technique proposed in this paper can be utilized in the field of semantic web data mining by extracting and analyzing the information and knowledge inherent in LOD and supporting classification and visualization.

• International Journal of CAD/CAM
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• v.8 no.1
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• pp.37-40
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• 2009

Based on the study of Digital Elevation Simplification Model and fractal theory, this paper put forward a new method to simulate complex terrain. That use simplified DEM data to construct terrain frame based on the quad tree at first, and then use fractal to generate the details of every node of the tree. In the process of construction, the LOD theory is used to simplify the terrain and get its typical data. According to the change of view position and direction, the paper gives a new way to judge the visibility of the surface patch. Experimental results show that this algorithm is simple, efficient and supports the real time dynamic simulation of terrain model.