• 한국분무공학회지
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• 제23권1호
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• pp.1-8
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• 2018

In this study, the effects of variation in cam phasing and valve lift of exhaust valves by using Cam-in-Cam system on combustion and emission characteristics for diesel engine were investigated under GT-POWER simulation environment. This paper showed analytic result of combustion characteristics and diesel exhaust valve's control with GT-Power 1-D detail model. As a result, it was found that volumetric efficiency and IMEP were decreased as the exhaust valve opening and closing timing is advanced due to its internal EGR effects. Also, it was found that NOx emission were decreased as EVC timing was retarded. These show that the retarding the exhaust valve closing and opening while keeping the duration at constant can be effective for controlling AFR and mixing rate in diffusion combustion of diesel engine.

• 한국정밀공학회지
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• 제13권3호
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• pp.150-157
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• 1996

In this paper, to develop a smart CAD/CAM system for systematically performing from the 3-D solid shape design of products to the CNC cutting operation of products by a machining center, a B-Rep solid modeler is realized based on the half edge data structure. Because the B-Rep solid modeler has the various capabilities related to the solid definition functions such as the creation operation of primitives and the translational and rotational sweep operation, the solid manipulation functions such as the split operation and the Boolean set operation, and the solid inversion function for effectively using the data structure, the 3-D solid shape of products can be easily designed and constructed. Also, besides the automatic generation of CNC code, the B-Rep solid modeler can be used as a powerful tool for realizing the automatic generation of finite elements, the interfer- ence check between solids, the structural design of machine tools and robots and so on.

• Journal of Periodontal and Implant Science
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• 제41권6호
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• pp.293-301
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• 2011

Purpose: We have previously reported that tetra-cell adhesion molecule (T-CAM) markedly enhanced the differentiation of osteoblast-like cells grown on anorganic bone mineral (ABM). T-CAM comprises recombinant peptides containing the Arg- Gly-Asp (RGD) sequence in the tenth type III domain, Pro-His-Ser-Arg-Asn (PHSRN) sequence in the ninth type III domain of fibronectin (FN), and the Glu-Pro-Asp-Ilu-Met (EPDIM) and Tyr-His (YH) sequence in the fourth fas-1 domain of ${\beta}$ig-h3. Therefore, the purpose of this study was to evaluate the cellular activity of osteoblast-like cells and the new bone formation on ABM coated with T-CAM, while comparing the results with those of synthetic cell binding peptide (PepGen P-15). Methods: To analyze the cell viability, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay was performed, andto analyze gene expression, northernblot was performed. Mineral nodule formations were evaluated using alizarin red stain. The new bone formations of each group were evaluated using histologic observation and histomorphometrc analysis. Results: Expression of alkaline phosphatase mRNA was similar in all groups on days 10 and 20. The highest expression of osteopontin mRNA was observed in the group cultured with ABM/P-15, followed by those with ABM/T-CAM and ABM on days 20 and 30. Little difference was seen in the level of expression of collagen type I mRNA on the ABM, ABM/T-CAM, and ABM/P-15 cultured on day 20. There were similar growth and proliferation patterns for the ABM/T-CAM and ABM/P-15. The halo of red stain consistent with $Ca^{2+}$ deposition was wider and denser around ABM/T-CAM and ABM/P-15 particles than around the ABM particles. The ABM/T-CAM group seemed to have bone forming bioactivity similar to that of ABM/P-15. A complete bony bridge was seen in two thirds of the defects in the ABM/T-CAM and ABM/P-15 groups. Conclusions: ABM/T-CAM, which seemed to have bone forming bioactivity similar to ABM/P-15, was considered to serve as effective tissue-engineered bone graft material.

• 대한치과보철학회지
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• 제42권2호
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• pp.142-153
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• 2004

Statement of problem: Increasing demand of esthetic restorations made lots of kinds of ceramic materials. Among them, zirconia has been being focused by many dentists. But, mechanical properties of zirconia were still unclear. Purpose : The purposes of this study were to analyze the flexural strength of various zirconia ceramics which had been currently used for clinic i.e., In-Ceram Zirconia(Vita Zahnfabrik, Bad $S\"{a}ckingen$, Germany), Celay Zirconia(Vita Zahnfabrik, Bad $S\"{a}ckingen$, Germany) and CAD/CAM Zirconia (Adens Zi-Ceram. Seoul , Korea). Material and methods: The four point bending test(ASTM Cl161) was used to measure the flexural strength of a specimen before and after circular heat treatment and fatigue loading. Results : 1. The average value of flexural strengths of CAD/CAM Zirconia, Celay Zirconia, In-Ceram Zirconia in dry condition were 806.5 MPa, 669.9 MPa, 605.6 MPa, respectively. There was a statistically significant difference in strength among the types (P<0.05). 2. After thermocycling, the average flexural strengths of CAD/CAM Zirconia, Celay Zirconia, In-Ceram Zirconia were 791.2 MPa, 604.2 MPa, 605.4 MPa, respectively. CAD/CAM Zirconia showed statistically significant higher strength(P<0.05). The others showed no significant difference after thermocycling(P>0.05). 3. After fatigue loading in wet condition. the average flexural strengths of CAD/CAM Zirconia, Celay Zirconia, In-Ceram Zirconia were 806.0 MPa, 674.9 MPa, 601.7 MPa, respectively. There was a significant difference in strength among the types(P<0.05). 4. There was no statistically significant difference in strength of the specimens according to experimental methods except for before and after thermocycling in Celay Zirconia(P>0.05). Conclusion: Besides high esthetic quality, zirconia had sufficiently high mechanical strength.

• The Journal of Advanced Prosthodontics
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• 제14권5호
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• pp.273-284
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• 2022

PURPOSE. Computer-aided design and manufacturing (CAD-CAM) of implant abutments has been shown to result in surface contamination from site-specific milling and fabrication processes. If not removed, these contaminants can have a potentially adverse effect and may trigger inflammatory responses of the peri-implant tissues. The aim of the present study was to evaluate the bacterial disinfection and cleaning efficacy of ultrasonic reprocessing in approved disinfectants to reduce the microbial load of CAD-CAM abutments. MATERIALS AND METHODS. Four different types of custom implant abutments (total N = 32) with eight specimens in each test group (type I to IV) were CAD-CAM manufactured. In two separate contamination experiments, specimens were contaminated with heparinized sheep blood alone and with heparinized sheep blood and the test bacterium Enterococcus faecium. Abutments in the test group were processed according to a three-stage ultrasonic protocol and assessed qualitatively and quantitatively by determination of residual protein. Ultrasonicated specimens contaminated with sheep blood and E. faecium were additionally eluted and the dilutions were incubated on agar plates for seven days. The determined bacterial counts were expressed as colony-forming units (CFU). RESULTS. Ultrasonic reprocessing resulted in a substantial decrease in residual bacterial protein to less than 80 ㎍ and a reduction in microbiota of more than 7 log levels of CFU for all abutment types, exceeding the effect required for disinfection. CONCLUSION. A three-stage ultrasonic cleaning and disinfection protocol results in effective bacterial decontamination. The procedure is reproducible and complies with the standardized reprocessing and disinfection specifications for one- or two-piece CAD-CAM implant abutments.

• 대한조선학회논문집
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• 제32권4호
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• pp.9-18
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• 1995

국내에서 사용되고 있는 CAD/CAM 시스템들은 모두 도입한 제품들로, 그 구조가 폐쇄형으로 되어있기 때문에, 원천기술을 갖고있지 못한 후발 개발자들은 그 내부구조를 파악하기 어렵다. 근래에 정보기술분야에서 개방형 구조를 갖는 시스템들이 등장하여 좋은 기회를 제공하고 있다. 이 글에서는 개방형 구조를 갖는 형상모델러를 개발하기 위하여 그 시스템설계를 수행한 내용을 소개한다. 기존의 유사한 형상모델러들을 조사분석하여, 새로운 시스템이 갖추어야하는 기능들을 파악하였으며, 공학설계의 전 과정을 형상모델러가 유연하게 지원하기 위하여 복합다양체를 지원하는 자료구조를 갖는 것이 필요하다고 판단하였다. 이를 토대로 개방형 구조를 갖는 형상모델러의 골격에 대한 기준모델이 제안되었다. 이러한 기준모델과 자료구조, 그리고 공통의 개발환경은 시스템 개발을 위한 여러 사람의 참여와, 업무분담, 그리고 분담개발된 요소기능들의 통합을 지원하는 유효한 수단이 될 것이다.

• 한국CDE학회논문집
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• 제10권4호
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• pp.254-261
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• 2005

The purpose of this research is to develop a method for cutting non-circular holes on a bent thick plate. Generally in order to cut the holes on the large plates, a special-purpose 5-axis machine is needed. However, such a machine is unavailable in most of the machine shops. This paper provides a description of such a method that utilizes a general-purpose 5-axis water-jet machine in place of the special-purpose machine: First, the bent piece is transformed into a flat plate, where the shape of the holes is reconstructed by considering deformation during bending. Then, after a 5-axis NC data is generated, the holes on the flat plate are cut using the 5-axis water-jet machine. The final step is to return to its, original shape by bending the plate with its newly-cut holes. The proposed methodology is implemented as a dedicated system by customizing a commercial CAD/CAM system. Some illustrations are provided throughout the paper in order to show the validity of the proposed methods and the developed system.

• Journal of Multimedia Information System
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• 제2권3호
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• pp.255-262
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• 2015

The modern manufacturing systems and technologies produce products that are more accurate day by day. This can be reached mainly by improvement the manufacturing process with at the same time restricting more and more the quality specifications and reducing the uncertainty in part. The main objective an industry becomes to lower the part's variability, since the less variability - the better is product. One of the part of this task is measuring the object's uncertainty. The main purpose of this study is to understand the application of bootstrap method for uncertainty evaluation. Bootstrap method is a collection of sample re-use techniques designed to estimate standard errors and confidence intervals. In the case study a surface of an automobile engine block - (Top view side) is measured by Coordinate Measuring Machine (CMM) and analyzed for uncertainty using Geometric Least Squares in complex with bootstrap method. The designed experiment is composed by three similar measurements (the same features in unique reference system), but with different points (5, 10, 20) concentration at each level. Then each cloud of points was independently analyzed by means of non-linear Least Squares, after estimated results have been reported. A MatLAB software tool used to generate new samples using bootstrap function. The results of the designed experiment are summarized and show that the bootstrap method provides the possibility to evaluate the uncertainty without repeating the Coordinate Measuring Machine (CMM) measurements many times, i.e. potentially can reduce the measuring time.

• 대한기계학회논문집A
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• 제21권12호
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• pp.2134-2145
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• 1997

We present a framework of an intelligent design system for embodiment design of machine tools which can support efficiently and systematically the machine design by utilizing design knowledge such as objects(part), know-how, public, evaluation, and procedures. The design knowledge of machining center has been accumulated through interview with design experts of machine tool companies. The processes of embodiment design of machining center are established and represented by the IDEF0 model from the field surveys. We also introduce a hybrid knowledge representation so that the system can easily deal with various and complicated design knowledge. The intelligent design system is being developed on the basis of object-oriented programming, and all parts of a design object, machining center, are also classified by the object-oriented modeling.

• 한국방송∙미디어공학회:학술대회논문집
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• 한국방송∙미디어공학회 2016년도 하계학술대회
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• pp.260-263
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• 2016

Recently high dynamic range imaging technique is hot issue in computer graphic area. We present a progressive tone mapping algorithm, which is based on weighted least squares optimization framework. Our approach combines weighted leastsquaresfiltering with iCAM06, for showing more perceptual high dynamic range images in conventional display, while avoiding visual halo artifacts. We decompose high dynamic range image into base layer and detail layer. The base layer has large scale variation, it is obtained by using weighted least squares filtering, and then the base layer incorporates iCAM06 model. Then, adaptive compression on the base layer according to human visual system. Only the base layer reduces contrast, and preserving detail. The resultshows more perceptual color appearance and preserve fine detail, while avoiding common artifacts.