• 한국정밀공학회지
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• 제24권6호
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• pp.131-137
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• 2007

In metal casting process, it is very difficult to predict the form accuracy of cast part and reduce repeatability error. In this study, the variations of form accuracy were measured in the process of metal cast prototyping, where RP part is manufactured from CAD model in the first, and then, wax part is cast in the vacuum environment using the RP part as master model, and finally metal prototype is cast using ceramic mold and the wax part as pattern. To investigate the variations of form accuracy, the averages and standard deviations of error distribution of the parts measured by 3D scanner were compared. It was observed that the biggest shrinkage is generated during the extraction of wax part in the second step and the biggest deterioration of form accuracy is generated during the metal part casting in the last step.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2000년도 추계학술대회 논문집
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• pp.330-333
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• 2000

Dimensional accuracy and surface quality are very important in rapid prototyping especially when the models are used for the production of tools. This paper presents the development of benchmarking part to investigate dimensional accuracy and surface finish. A new test part is designed to perform benchmarking of major rapid prototyping processes such as selective laser sintering, laminated object manufacturing, stereolithography apparatus, and fused deposition modeling. The test part design includes basic manufacturing features such as holes, walls, squares, cylinder and etc. In addition, the small features are included in order to evaluate the fine details that can be manufactured by a specific RP process. The CMM program that automatically measures different features in the test part is also developed. The evaluation of accuracy as well as surface roughness are discussed for major rapid prototyping processes.

• 한국정밀공학회지
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• 제19권3호
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• pp.152-159
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• 2002

SLA (Stereolithography Apparatus) it a process used to rapidly produce polymer components directly from a computer representation of the part. Though SLA is being recognized as an innovative technology, it still cannot be used to fully practical application since it lacks of dimensional accuracy compared to conventional process. If the shrinkage were perfectly uniform and no distortion took place, excellent part accuracy could still be achieved through and appropriate scaling factor when generating the build file. However, in certain geometries involving intersecting thick and thin sections, nonuniform retrain shrinkage becomes the engine of part distortion. In order to improve the part accuracy of SLA, this paper evaluates how largely each parameter of SLA contributes to the part accuracy and estimates the optimal set of parameter which minimizes the dimension error of the test part, "Slab (100mm$\times$100mm$\times$2mm)"and "scale bar"part. Three control parameters such as critical exposure, generation depth and fill cure depth are used.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1995년도 추계학술대회 논문집
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• pp.907-910
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• 1995

Though SLA(Stereolithography Apparatus) is being recognized as an innovative technology, it still can not be used to fully practical applications since it lacks of dimensional accuracy compared to conventional processes. In SLA, the accuracy of cured part depends upon the set of process parmeters. In order to improve the accuracy of SLA, this paper quantitatively evaluates how largely each process parameter of SLA contributes to the part accuracy and estimates the optimal set of process parameter which minimizes the dimensional errors of the test part, "letter-H" part. For this purpose, we use ANOVA(analysis of variance) and S/N(signal-to-noise)ratio of Taguchi method.hi method.

• 한국생산제조학회지
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• 제9권1호
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• pp.68-74
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• 2000

The STL file format is an approximation of 3-D model with triangular facets. STL is a standard input file format of Rapid Prototyping(RP) equipment In computer graphics a circle has been approximated with an inscribed polygon which causes an error between the real and approximated circles. In this study an intersecting polygon has been used to approximate the circle and applied to produce more accurate RP part. The newly proposed method shows it's excellence in part accuracy.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 1997년도 춘계학술대회 논문집
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• pp.150-155
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• 1997

Rapid Prototyping(RP) is the technique which is used to make prototypes or functional parts directly using the 3-D solid data. Before building the prototype, several processes such as transfering 3D data from CAD system(STL) determination of build-direction, adding support structure and slicing are required. Among the above processes. determination of build-direction is the target of this study. The build direction is determined by many factors according to the objective of the user, like part accuracy, number of support structure, build time, amount of trapped volume, etc, But it is not easy to determine the build-direction because there are many factors and some factors have dependent properties with one another. So, in this study the part accuracy, the number of support structures and build time are considered as the main factor to determine the optimal build-direction. To determine the optimal build-direction for increasing part accuracy, sum of projected area which caused stairstepping effect was considered. The less the projected area is the better part accuracy is About the optimal build-direction to minimize the amount of support structure, sum of projected area of facets that require support structures was considered. About the build time, we considered the minimum height of part we intended. About the build time, we considered the minimun height of part we intended to make.

• 대한임베디드공학회논문지
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• 제17권4호
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• pp.199-208
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• 2022

Korean is an agglutinative language, and one or more morphemes are combined to form a single word. Part-of-speech tagging method separates each morpheme from a word and attaches a part-of-speech tag. In this study, we propose a new Korean part-of-speech tagging method based on the Head-Tail tokenization technique that divides a word into a lexical morpheme part and a grammatical morpheme part without decomposing compound words. In this method, the Head-Tail is divided by the syllable boundary without restoring irregular deformation or abbreviated syllables. Korean part-of-speech tagger was implemented using the Head-Tail tokenization and deep learning technique. In order to solve the problem that a large number of complex tags are generated due to the segmented tags and the tagging accuracy is low, we reduced the number of tags to a complex tag composed of large classification tags, and as a result, we improved the tagging accuracy. The performance of the Head-Tail part-of-speech tagger was experimented by using BERT, syllable bigram, and subword bigram embedding, and both syllable bigram and subword bigram embedding showed improvement in performance compared to general BERT. Part-of-speech tagging was performed by integrating the Head-Tail tokenization model and the simplified part-of-speech tagging model, achieving 98.99% word unit accuracy and 99.08% token unit accuracy. As a result of the experiment, it was found that the performance of part-of-speech tagging improved when the maximum token length was limited to twice the number of words.

• 한국정밀공학회지
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• 제13권4호
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• pp.163-173
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• 1996

Stereolithography is a process used to rapidly produce polymer components directly form a computer representation of the part. There are several considerations to be made for the efficient use of the process. Especially, the build-up orientation of part critically affects the part accuracy, total build time and the volume of support structures. The purpose of tis study is to determine the optimal build-up part orientation for the SLA process with improving part accuracy, and minimizing total build time and the volume of support structures. The forst factor is related to the area of surfaces whioch have staircase protrusions after solidification, the second factor is related to the total number of layers, and the third factor is related to the area of the surfaces which need to be supported with support structures. An algorithm is developed to calculate the staircase area, quantifying the process errors by the volume of materials supposed to be removed or added to the part, and the optimal layer thickness for the SLA system which can handle the variable layer thickness. So the optima l part orientation is determined based on the user's selections of primary criter- ion and the optimal thickness of layers is calculated at any part orientations.

• 전산구조공학
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• 제7권3호
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• pp.153-166
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• 1994

구조물의 손상예측정확도를 모델불확실성의 함수로 산정하는 방법론이 제시되었다. 먼저, 구조물의 손상발생위치과 크기를 결정할 수 있는 알고리즘의 요약되고 모델불확실성과 손상발견정확도를 측정하는 방법들이 제시되었다. 다음으로, 실존구조물의 손상발견정확도에 미치는 모델불확실성의 영향을 산정하는 방법론이 제시되었다. 마지막으로, 한개의 진동모드가 측정된 Plate-Girder교량을 사용하여 이같은 산정방법론의 적합성이 예증되었다.

• 품질경영학회지
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• 제42권3호
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• pp.301-310
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• 2014

Purpose: The purpose of this study is to improve a mechanism of expendable bathythermograph measurement by balancing wire resistances between plus wire part and minus wire part and by removing effects of sea water resistance between XBT(Expendable Bathythermograph) and temperature recorder. Methods: The problems are exactly found out through the analysis of XBT and temperature recorder circuit. A process of XBT manufacturing that balances wire resistances between plus wire part and minus wire part is added. Results: The results of this study are as follows; the complicated test process such as temperature accuracy test with a cistern is substituted with a simple process of XBT manufacturing such as balancing wire resistances between plus wire part and minus wire part. Then, the temperature accuracy tolerance of XBT is improved up to ${\pm}0.1^{\circ}C$. Conclusion: Consequently, balancing wire resistances and removing effects of sea water resistance improve temperature accuracy of XBT and reduce expensive and harassing process of XBT manufacturing.