• Bulletin of the Korean Chemical Society
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• 제34권11호
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• pp.3335-3339
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• 2013

Boron-doped ZnO (BZO) nanorods were grown on quartz substrates using hydrothermal synthesis, and the temperature-dependence of their photoluminescence (PL) was measured in order to investigate the origins of their PL properties. In the UV range, near-band-edge emission (NBE) was observed from 3.1 to 3.4 eV; this was attributed to various transitions including recombination of free excitons and their longitudinal optical (LO) phonon replicas, and donor-acceptor pair (DAP) recombination, depending on the local lattice configuration and the presence of defects. At a temperature of 12 K, the NBE produces seven peaks at 3.386, 3.368, 3.337, 3.296, 3.258, 3.184, and 3.106 eV. These peaks are, respectively, assigned to free excitons (FX), neutral-donor bound excitons ($D^{\circ}X$), and the first LO phonon replicas of $D^{\circ}X$, DAP, DAP-1LO, DAP-2LO, and DAP-3LO. The peak position of the FX and DAP were also fitted to Varshni's empirical formula for the variation in the band gap energy with temperature. The activation energy of FX was about ~70 meV, while that of DAP was about ~38 meV. We also discuss the low temperature PL near 2.251 eV, related to structural defects.

• 한국항공운항학회지
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• 제16권3호
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• pp.50-57
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• 2008

This paper analyse the economic inducement effects of aviation industry using Input-Output Model. For measuring economic inducement effects of aviation industry on korean economy, this paper divides air transport industry as two - manufacturing industry and service industry. we also use Input-Output Table of year 1990 through 2003 from Bank of Korea. Empirical results tells that aviation manufacturing industry have high product inducement effects to national economy although its low value-added coefficient such as 0.486 for aviation manufacturing industry and 0.447 for aviation service industry. public R&D doesn't have much effect to each of aviation industries.

• 한국기계가공학회지
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• 제15권5호
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• pp.86-92
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• 2016

In this study, we used a polymer deposition system, based on fused deposition modeling, to fabricate the 3D scaffold and then fabricated micro-pores on a 3D scaffold using a salt leaching method. Materials included polycaprolactone (PCL) and sodium chloride (NaCl). The 3D porous scaffolds were fabricated according to blending ratio such as PCL (70 wt%)/NaCl (30 wt%) and PCL (50 wt%)/NaCl (50 wt%). The 3D porous scaffolds were observed by scanning electron microscopy. The results showed that 3D porous scaffolds had a deposition width of $500{\mu}m$, contained a pore size of $500{\mu}m$ and below $100{\mu}m$. To evaluate the 3D porous scaffolds for bone tissue engineering, we carried out the cell proliferation experiment using a CCK-8 and a mechanical strength test using a universal testing machine. In summary, the 3D porous scaffold was found to be suitable for cancellous bone of human in accordance with the result of in-vitro cell proliferation and mechanical strength. Thus, a 3D porous scaffold could be a promising approach for effective bone regeneration.

• 한국기계가공학회지
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• 제21권4호
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• pp.100-106
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• 2022

Topology optimization is applied for the optimal design of various products to ensure weight reduction and productivity improvement. Reducing the weight of the mold while maintaining its rigidity can ensure shortening of the production cycle, stabilization of the mold temperature, and reduction of mold material costs. In this study, a topology optimization technique was applied to the optimal design of the injection mold, and a topology-optimized model of the mold was obtained. First, the injection mold for the square specimens was modeled. Subsequently, a structural analysis was performed by implementing a load condition generated during the injection molding process. Topology optimization was performed based on the structural analysis results, and the models of the initial and topology-optimized designs were manufactured at 1/4 magnification using a 3D printer. Consequently, compared with the existing model, the weight of the topology-optimized model decreased by 9.8%, and the manufacturing time decreased by 7.61%.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 춘계학술대회 논문집
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• pp.982-986
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• 2005

Digital Manufacturing is a technology to facilitate effective product developments and agile productions by digital environments representing the physical and logical schema and the behavior of real manufacturing system including manufacturing resources, processes and products. A digital virtual factory as a well-designed and integrated environment is essential for successful applications of this technology. In this research, we constructed a sophisticated digital virtual factory by measuring and 3-D CAD modeling using parametric methods. Specific parameters of each objects were decided by object-oriented schema of the digital factory. It is expected that this method is very useful for constructions of a digital factory, and helps to manage diverse information and re-use 3D models.

• 한국생산제조학회지
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• 제20권4호
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• pp.458-463
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• 2011

A CHS(Container Handling System) is a system to load and to unload ISO 2000 or ISO 4000 standard containers which is widely used for various industrial transport purpose. A new light type of CHS is introduced in this paper, in order to reduce weight of cargos and to give the convenience in cargo loading and unloading without additional lifting equipments. The structural models of this system are created to assemble the smooth integration of system and to interface the each composing units with the specification of truck chassis to be mounted. These models are applied to find the suitable design parameters under the condition of force restrictions of each units. Finally, the stability of this system are investigated by analyzing the dynamic simulation using Visual NASTRAN 4D, and it could be recommend the good design parameters for the manufacturing purpose.

• 한국기계가공학회지
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• 제20권3호
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• pp.122-128
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• 2021

Machining operations require removal of chips to keep the coolant clean and fresh throughout the operation time. In this study, microchip removal equipment was developed using AutoCAD and CATIA programs for 3D modeling and 2D draft. In addition, the flow analysis and electromagnetic field analysis of the equipment were performed using the COMSOL Multiphysics program. The flow design of the coolant oil tank was realized on the basis of fluid analysis results. Further, on the basis of magnetic density analysis, a conveyer was designed for effectively removing metal microchips in the tank by using arrays of neodymium permanent magnets.

• Smart Structures and Systems
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• 제29권6호
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• pp.767-775
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• 2022

Metal additive manufacturing (AM), also known as metal three-dimensional (3D) printing, produces 3D metal products by repeatedly adding and solidifying metal materials layer by layer. During the metal AM process, products experience repeated local melting and cooling using a laser or electron beam, resulting in product defects, such as warpage, cracks, and internal pores. Such defects adversely affect the final product. This paper proposes the in situ monitoring-based warpage prediction of metal AM products with experimental feature extraction. The temperature profile of the metal AM substrate during the process was experimentally collected. Time-domain features were extracted from the temperature profile, and their relationships to the warpage mechanism were investigated. The standard deviation showed a significant linear correlation with warpage. The findings from this study are expected to contribute to optimizing process parameters for metal AM warpage reduction.

• 대한치과보철학회지
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• 제59권3호
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• pp.370-378
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• 2021

목적: 본 연구의 목적은 CAD-CAM 방식으로 제작한 RPD framework의 제조 과정 및 제작 방법에 따른 적합도를 문헌 고찰을 통해 평가하는 것이다. 재료 및 방법: 다음의 PICO (patient, intervention, comparison, and outcome) 질문과 관련한 특정 키워드를 이용하여 PubMed 데이터베이스 상에서 포괄적인 문헌 검색을 시행하였다: "제조 과정 및 제작 방식에 따라 디지털 RPD framework의 정확도에 차이가 있는가?" 결과: 총 7개의 문헌이 선택되었으며, 이 중 두 문헌에서 구강스캔과 모형스캔을 이용한 디지털 RPD framework의 정확도에 관하여 비교하였으나, 일관된 결과를 얻지 못하였다. 제작 방식에 따른 비교 문헌에서는 적층 가공 또는 절삭 가공을 통해 제작된 RPD framework 모두 임상적으로 허용가능한 수준의 정확도를 보였으며, PEEK (Polyetheretherketone) milling RPD framework가 전통적 주조방식으로 제작하거나 3D 프린팅으로 제작한 RPD framework보다 높은 적합도를 보였다. Milling RPD framework에서는 direct 방식으로 제작한 경우에 indirect 방식의 경우보다 우수한 적합도가 관찰되었으나, 3D 프린팅 RPD framework에서는 indirect 방식으로 제작한 경우에 더 높은 적합도를 보였다. 결론: CAD-CAM 기술을 이용하여 제작된 디지털 RPD framework는 제조 과정이나 방식에 관계없이 임상적으로 허용되는 수준의 정확도를 보였다. 구강스캔 또는 모형스캔의 디지털 인상 채득 방법에 따라서는 일관된 결과가 보고되지 않았으며, 추후 연구가 필요하다.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 1998년도 춘계학술대회 논문집
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• pp.227-232
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• 1998

We developed a Off-Line Graphic Simulator which can simulate a robot model in 3D graphics space in Windows 95 version. 4 axes SCARA robot was adopted as an objective model. Forward kinematics, inverse kinematics and robot dynamics modeling were included in the developed program. The interface between users and the off-line program system in the Windows 95's graphic user interface environment was also studied. The developing language is Microsoft Visual C++. Graphic libraries, OpenGL, by Silicon Graphics, Inc. were utilized for 3D graphics.