• Journal of Powder Materials
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• v.27 no.2
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• pp.103-110
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• 2020

Aluminum (Al) - based powders have attracted attention as key materials for 3D printing because of their excellent specific mechanical strength, formability, and durability. Although many studies on the fabrication of 3D-printed Al-based alloys have been reported, the influence of the size of raw powder materials on the bulk samples processed by selective laser melting (SLM) has not been fully investigated. In this study, AlSi10Mg powders of 65 ㎛ in average particle size, prepared by a gas atomizing process, are additively manufactured by using an SLM process. AlSi10Mg powders of 45 ㎛ average size are also fabricated into bulk samples in order to compare their properties. The processing parameters of laser power and scan speed are optimized to achieve densified AlSi10Mg alloys. The Vickers hardness value of the bulk sample prepared from 45 ㎛-sized powders is somewhat higher than that of the 65 ㎛m-sized powder. Such differences in hardness are analyzed because the reduction in melt pool size stems from the rapid melting and solidification of small powders, compared to those of coarse powders, during the SLM process. These results show that the size of the powder should be considered in order to achieve optimization of the SLM process.

• Korean Journal of Construction Engineering and Management
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• v.10 no.1
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• pp.136-145
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• 2009

The objective of the Intelligent Excavation System (IES) is to recognize the work environment and produce work plan and automatically control the excavator through integrating sensor and robot technologies. This paper discusses one of the core technologies of IES development project, development of 3D work environment modeling. 3D laser scanner is used for 3-dimensional mathematical model that can be visualized in virtual space in 3D. This paper describes (1) how the most appropriate 3D imaging system has been chosen; (2) the development of user interface and customization of the s/w to control the scanner for IES project; (3) the development of the mobile station for the scanner; (4) and the algorithm for the automatic registration of laser scan segments for IES project. The development system has been tested on the construction field and lessons learned and future development requirements are suggested.

• Proceedings of the Korean Institute Of Construction Engineering and Management
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• 2007.11a
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• pp.977-982
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• 2007

There have been many efforts in automatic object recognition using computing technologies. Especially in the development of automated construction equipment, automatic object recognition is very important issue for the proper equipment maneuvering. 3D laser scanning, which uses (time-of-flight) method to construct the 3-dimensional information, is applied to the civil earth work environment for its high accuracy, quick data collection, and object recognition capability that will be developed by the authors in the future. The 3D earth model is also used as a fundamental information for intelligent earth work task planning. This paper presents the analysis of the 3D laser scanner market and selection of the most optimum 3D scanner for the intelligent earth work planning. As well as the hardware configuration for the automated 3D earth modeling is developed but also the software structure and detailed user interface are designed in this research. In addition, it is presented in this paper that the accuracy comparison test between TotalStation(R) which is a traditional survey tool and ScanStation(R). The accuracy test is done by relative distance measurement using known targets.

• Journal of Technologic Dentistry
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• v.45 no.1
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• pp.1-7
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• 2023

Purpose: To evaluate the marginal and internal fit of metal coping fabricated by a metal three-dimensional (3D) printer that uses selective laser melting (SLM). Methods: An extraoral scanner was used to scan a die of the prepared maxillary right first molar, and the coping was designed using computer-aided design software and saved as an stereo lithography (STL) file. Ten specimens were printed with an SLM-type metal 3D printer (SLM group), and 10 more specimens were fabricated by casting the castable patterns output generated by a digital light processing-type resin 3D printer (casting the 3D printed resin patterns [CRP] group). The fit was measured using the silicon replica technique, and 8 points (A to H) were set per specimen to measure the marginal (points A, H) and internal (points B~G) gaps. The differences among the groups were compared using the Mann-Whitney U-test (α=0.05). Results: The mean of marginal fit in the SLM group was 69.67±18.04 ㎛, while in the CRP group was 117.10±41.95 ㎛. The internal fit of the SLM group was 95.18±41.20 ㎛, and that of the CRP group was 86.35±32 ㎛. As a result of statistical analysis, there was a significant difference in marginal fit between the SLM and CRP groups (p<0.05); however, there was no significant difference in internal fit between the SLM group and the CRP group (p>0.05). Conclusion: The marginal and internal fit of SLM is within the clinically acceptable range, and it seems to be applicable in terms of fit.

• Journal of Korean Tunnelling and Underground Space Association
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• v.12 no.3
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• pp.239-245
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• 2010

The present study is about an efficient extraction of tunnel cross sections from huge point cloud achieved by a terrestrial laser scanner. A method, using a hash-based data structure, is introduced, by which point clouds, potentially composing cross sections, are extracted along a tunnel center line. The center line is estimated by linking points which are drawn in the middle of pseudo cross sections based on the hash-based data structure. Point clouds of a same thickness are extracted at a same interval along the center line. In result, it took less than 3 seconds and 124 MB of memory to extract, out of the 7.5 million points, the point clouds of 1 m interval and 0.1 m thickness. A manual operation, however, was needed to fix the outliers on the center line and to select both start and end points on it.

• The korean journal of orthodontics
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• v.41 no.2
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• pp.76-86
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• 2011

Objective: To investigate whether the accuracy of 3D laser scanning is influenced by the angles and number of scans. Methods: Using a 3D laser scanner, 10 manikins with facial markers were scanned at 7 horizontal angles (front view and at $20^{\circ}$, $45^{\circ}$, and $60^{\circ}$ angles on the right and left sides). Three-dimensional facial images were reconstructed by 6 methods differing in the number and angles of scans, and measurements of these images were compared to the physical measurements from the manikins. Results: The laser scan images were magnified by 0.14 - 0.26%. For images reconstructed by merging 2 scans, excluding the front view; and by merging 3 scans, including the front view and scans obtained at $20^{\circ}$ on both sides; several measurements were significantly different than the physical measurements. However, for images reconstructed by merging 3 scans, including the front view; and 5 scans, including the front view and scans obtained at $20^{\circ}$ and $60^{\circ}$ on both sides; only 1 measurement was significantly different. Conclusions: These results suggest that the number and angle of scans influence the accuracy of 3D laser scanning. A minimum of 3 scans, including the front view and scans obtained at more than $45^{\circ}$ on both sides, should be integrated to obtain accurate 3D facial images.

• Fibers and Polymers
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• v.4 no.2
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• pp.71-76
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• 2003

We evaluated the seam characteristics with finishing, seaming and sealing processes and seam Puckering behavior of the breathable waterproof fabrics with laser scan. There were differences in 99% significant level between the seamed fabric and the sealed fabric. Seam breakage was initiated with the breakage of sewing thread, so the seam strength after seaming was almost uniform. The sewn seam strength and elongation increased with sealing process in all finishing methods. Pucker grade of laminating type was generally much higher than that of the coating type. We confirmed that wave length and amplitude have more important meaning than the number of weave in the breathable waterproof fabrics. The puckering in breathable waterproof fabrics is mainly occurred by inherent and feeding pucker. The former if due to the insertion of sewing thread and the littler is caused by differential feeding when two pieces of fabric are fed into the gap between a press foot and needle plate.

• 한국신재생에너지학회:학술대회논문집
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• 2010.11a
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• pp.44.1-44.1
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• 2010

레이저 가공기술은 공정 적용이 용이하고 응용 분야가 넓어 산업 전반에 걸쳐 널리 사용되고 있다. 특히, 태양전지 제조공정에서는 cutting, grooving, doping, ablation등의 분야에 활발하게 적용되고 있으며 최근에는 다양한 종류의 레이저를 기술을 이용하여 효율 향상과 원가 절감을 위해 많은 기관에서 활발하게 연구를 진행하고 있다. 본 연구에서는 실리콘웨이퍼에 특정 파장의 레이저를 조사하여 실리콘웨이퍼 표면의 용융과 고상화를 통해 구조적, 전기적 특성 변화를 확인하였다. Si wafer의 표면은 레이저 조사 조건에 의해 다결정화 하며 레이저의 power와 frequency, scan speed등을 조절하여 다결정 실리콘 영역의 형성 깊이를 조절 할 수 있다. 다결정화 된 부분의 구조적 특성은 SED과 XRD를 이용하여 측정하였으며, 전기적 특성은 면저항 측정을 통하여 실시하였다. 또한 이러한 특성을 이용하여 태양전지 제조 공정의 적용가능성을 평가하였다.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.151.1-151.1
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• 2016

Complex oxide heterointerfaces have been extensively explored in the past due to the novel phenomenon emerging at such interfaces that differ from their individual bulk counterparts. The integration of a ferromagnetic (FM) material with the superconducting (SC) material leading to proximity effect is one of the commonly studied phenomenon in these heterostructures. In continuation, we have stabilized the FM layer La0.7Ca0.3MnO3 (LCMO) on SC material YBa2Cu3O7-${\delta}$ (YBCO) using pulsed laser deposition technique and explored the structural, magnetic, electrical and magneto-transport properties of this heterostructure. ${\Phi}$-scan measurements confirm the epitaxial nature of LCMO/YBCO heterostructure grown on single crystalline SrTiO3 substrate. The FM transition of LCMO and SC transition of YBCO are observed in the magnetization measurements of the bilayer structure. Through electrical measurements, we understood that the proximity effect leads to lowering of the SC transition of YBCO. The role of interface in the bilayer structure is also realized through electrical transport measurements.

• Restorative Dentistry and Endodontics
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• v.24 no.1
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• pp.129-135
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• 1999

In this review article, in vivo and in vitro wear test methods which measure the wear of tooth and restorative material were discribed. In vivo test, the criteria of each test were reviewed. The merits and limitations were also commented. In vitro tests, three dimensional scanning methods which scan the occlusal tooth surface three dimensionally were described. Profilometer method, Pin on disk method, laser scanner method were reviewed and the limitations of each test were commented. Additionally, the structer of the three dimensional scanner which has been developed in Zurich university and has been reputated as the most accurate one was described. This study was partly supported by 1997 post-doctoral foreign study program.