• Korean Journal of Radiology
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• 제19권6호
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• pp.1007-1020
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• 2018

Objective: To compare the diagnostic performance of cardiovascular magnetic resonance (CMR) myocardial perfusion at 1.5- and 3-tesla (T) for detecting significant coronary artery disease (CAD), with invasive coronary angiography (ICA) as the reference method. Materials and Methods: We prospectively enrolled 281 patients (age $62.4{\pm}8.3$ years, 193 men) with suspected or known CAD who had undergone 1.5T or 3T CMR and ICA. Two independent radiologists interpreted perfusion defects. With ICA as the reference standard, the diagnostic performance of 1.5T and 3T CMR for identifying significant CAD (${\geq}50%$ diameter reduction of the left main and ${\geq}70%$ diameter reduction of other epicardial arteries) was determined. Results: No differences were observed in baseline characteristics or prevalence of CAD and old myocardial infarction (MI) using 1.5T (n = 135) or 3T (n = 146) systems. Sensitivity, specificity, positive and negative predictive values, and area under the receiver operating characteristic curve (AUC) for detecting significant CAD were similar between the 1.5T (84%, 64%, 74%, 76%, and 0.75 per patient and 68%, 83%, 66%, 84%, and 0.76 per vessel) and 3T (80%, 71%, 71%, 80%, and 0.76 per patient and 75%, 86%, 64%, 91%, and 0.81 per vessel) systems. In patients with multi-vessel CAD without old MI, the sensitivity, specificity, and AUC with 3T were greater than those with 1.5T on a per-vessel basis (71% vs. 36%, 92% vs. 69%, and 0.82 vs. 0.53, respectively). Conclusion: 3T CMR has similar diagnostic performance to 1.5T CMR in detecting significant CAD, except for higher diagnostic performance in patients with multi-vessel CAD without old MI.

• 디자인학연구
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• 제17권1호
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• pp.241-252
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• 2004

CAD는 이미 디자인 분야에서도 중요하게 사용되는 도구로 동시 공학적 프로세스 상에서 전통적인 디자인 방법은 점점 사라져 가고 있다. 하지만, 리버스 엔지니어링(Reverse Engineering) 방식의 CAD 도구는 디자이너들의 작업을 위해 사용하는 도구로는 아직 많은 문제점들을 가지고 있다. 특히 디자인 프로세스 초기 단계의 직관적인 작업의 특성으로 인해 디자이너들이 기존의 CAD 도구들을 이 단계에서 적용하기는 거의 불가능하다. 최근 이러한 정성적인 문제들에 대해 구체적으로 접근하려는 연구들이 소프트웨어 뿐 아니라 하드웨어적 측면에서도 이루어지고 있다. 이 글에서는 디자인 프로세스 상에서 사용되는 기존의 3D CAD 도구의 문제점들과 최근 연구되고 있는 새로운 인터페이스 접근 방법들에 대해 알아보았다. 또한 디자이너들을 위한 CAD 개발을 위한 가이드라인을 제시하고 이를 통해 유비쿼터스 컴퓨팅 환경에서 효율적으로 사용할 수 있는 디자인 도구를 개발하기 위한 방안을 제시하였다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회A
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• pp.672-677
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• 2007

Recently, the new finite element method which uses NURBS as shape functions was proposed. It is very promising because it can directly use CAD data to describe geometry and discretize problem domain. In this case, CAE models are not approximated but represent exact geometry. So, it can contribute to more accurate results. In addition, it can greatly reduce CAE costs in that simulation models don't have to be made up independently. But in spite of these advantages, the method using NURBS have also some disadvantages. NURBS surface cannot be refined locally. T-splines are recently developed surface modeling technique. A T-spline surface is a NURBS surface with T-junctions and is defined by a control grid called T-mesh. The T-junctions enable T-spline surfaces to be refined locally. That is, it is possible to add a single control point to a T-spline control grid without propagating an entire row or column of control points and without altering the surface. In this research, the finite element analysis using T-splines is studied. In this analysis, CAD data are used directly for engineering analysis. Some problems with complex geometry are solved. And the results will be compared with ones of conventional FEM.

• Structural Engineering and Mechanics
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• 제30권2호
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• pp.225-245
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• 2008

T-splines are recently proposed mathematical tools for geometric modeling, which are generalizations of B-splines. Local refinement can be performed effectively using T-splines while it is not the case when B-splines or NURBS are used. Using T-splines, patches with unmatched boundaries can be combined easily without special techniques. In the present study, an analysis framework using T-splines is proposed. In this framework, T-splines are used both for description of geometries and for approximation of solution spaces. This analysis framework can be a basis of a CAD/CAE integrated approach. In this approach, CAD models are directly imported as the analysis models without additional finite element modeling. Some numerical examples are presented to illustrate the effectiveness of the current analysis framework.

• BMB Reports
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• 제36권2호
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• pp.237-242
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• 2003

Hepatic lipase is a key enzyme that is involved in HDL-C metabolism. The goal of this study was to find out the frequency of the hepatic lipase C514T polymorphism, and evaluate its relationship with plasma HDL-C levels and coronary artery disease (CAD) in Koreans. Two hundred and twenty four subjects with no previous history of lipid-lowering therapy, 118 patients with significant CAD, and 106 controls were examined with respect to their genotypes, lipid profiles, and other risk factors for CAD. The frequency of the -514T allele was 0.37 in men and 0.35 in women, which were higher than the frequency that was reported in Caucasians, but lower than the frequency that was reported in African-Americans. The -514T allele was associated with significantly higher HDL-C levels in women. After controlling for age, gender, BMI, DM, and smoking, the non-CC genotype was significantly associated with HDL-C levels, and explained 6% of the HDL-C variation in this study. When the genotypes-distribution was compared between the CAD and non-CAD patients, the hepatic lipase C-514T polymorphism was not associated with the presence of CAD. Koreans have a higher frequency of the hepatic lipase gene 514T allele than Caucasians, and the -514T allele is associated with higher plasma HDL-C levels in Korean women, and perhaps non-smoking men. However, our data does not suggest an association between the polymorphism and an increased risk of CAD.

• 대한기계학회논문집A
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• 제33권2호
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• pp.127-134
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• 2009

T-splines are recently proposed geometric modeling tools. A T-spline surface is a NURBS surface with T-junctions and is defined by a control grid called T-mesh. Local refinement can be performed very easily for T-splines while it is limited for B-splines or NURBS. Using T-splines, patches with unmatched boundaries can be combined easily without special technique. In this study, the analysis methodology using T-splines is proposed. In this methodology, T-splines are used both for description of geometries and for approximation of solution spaces. Two-dimensional linear elastic and dynamic problems will be solved by employing the proposed T-spline finite element method, and the effectiveness of the current analysis methodology will be verified.

• 대한치과교정학회지
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• 제50권6호
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• pp.373-382
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• 2020

Objective: To compare computer-aided design and computer-aided manufacturing (CAD/CAM) customized nitinol retainers with standard stainless-steel fixed retainers over a 12-month study period. Methods: This randomized controlled trial (RCT) was conducted on 62 patients randomly allocated to a control group that received stainless-steel retainers or a test group that received customized CAD/CAM nickel-titanium retainers. Four time points were defined: retainer placement (T0) and 1-month (T1), 6-month (T2), and 12-month (T3) follow-up appointments. At each time point, Little's irregularity index (LII) (primary endpoint) and dental stability measurements such as intercanine width were recorded in addition to assessment of periodontal parameters. Radiological measurements such as the incisor mandibular plane angle (IMPA) were recorded at T0 and T3. Failure events (wire integrity or debonding) were assessed at each time point. Results: From T0 to T3, LII and other dental measurements showed no significant differences between the two groups. The data for periodontal parameters remained stable over the study period, except for the gingival index, which was slightly, but significantly, higher in the test group at T3 (p = 0.039). The IMPA angle showed no intergroup difference. The two groups showed no significant difference in debonding events. Conclusions: This RCT conducted over a 12-month period demonstrated no significant difference between customized CAD/CAM nickel-titanium lingual retainers and standard stainless-steel lingual retainers in terms of dental anterior stability and retainer survival. Both retainers eventually appeared to be equally effective in maintaining periodontal health.

• 대한치과기공학회지
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• 제38권4호
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• pp.365-380
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• 2016

Purpose: The purpose of this study was to ascertain the need to reform curriculums for digital experts in a way that include the practical and educational aspects of dental labs by determining why educational reforms are needed to comply with changes in dental technology business that are brought by the applications of digital scanning and what changes are being actually brought by the use of CAD/CAM. Methods: This study analyzed the need of education and practice in relation to CAD/CAM by using the independent sample t-test and One-way ANOVA. in accordance with the participants demographic characteristics and job-related variables and factors related to CAD/CAM, and provided only some of the analysis results that were found statistically significant. Concerning the need of education and practice in relation to CAD/CAM, the study also used the independent sample t-test to measure difference in the perception of that need within each of the three groups, or those of job performance, job efficiency and knowledge gain at the signficance level of ${\alpha}=.05$. Results: Dental technologists surveyed here were perceiving that the use of CAD/CAM would bring changes in their job performance, job efficiency and knowledge gain. They were expecting that the biggest changes would be made in work climate and product quality as sub-areas of job performance. However, they said that in terms of job efficiency, the use of CAD/CAM would change job contribution, job satisfaction and job efficiency, but not lead to staffing. These results suggest that more special programs for CAD/CAM education are needed to bring up CAD/CAM experts who are more specialized. Conclusion: Among 13 skills related to CAD/CAM, what is most needed to be educated to dental technologists was "molding the occlusal surface" (M=4.19), followed by "designing the 3-D work" (M=4.17), "final shape modification" (M=4.16), "molding the border" (M=4.15) and "checking the fit of prothesis" (M=4.14) in order.

• The Journal of Advanced Prosthodontics
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• 제14권1호
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• pp.56-62
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• 2022

PURPOSE. The aim of this study was to investigate shade changes in fully- and pre-crystalized CAD-CAM lithium disilicate crowns after the required and additional firing processes. MATERIALS AND METHODS. One hundred and five crowns of shade A1 with high translucency were milled out of CAD-CAM lithium disilicate blocks and categorized as follows (n = 15): (1) restorations fabricated from Straumann n!ce with no additional sintering process; (2) restorations fabricated from Straumann n!ce with one additional sintering process; (3) restorations fabricated from Straumann n!ce with two additional sintering processes; (4) restorations fabricated from Amber Mill with one sintering process; (5) restorations fabricated from Amber Mill with two sintering processes; (6) restorations fabricated from IPS e.max CAD with one sintering process; (7) restorations fabricated from IPS e.max CAD with two sintering processes. All restorations were evaluated with a color imaging spectrophotometer. RESULTS. All restorations presented some color alteration from the original shade both after a single and after two firing processes. CONCLUSION. The required and additional sintering processes for restorations fabricated with chairside CAD-CAM lithium disilicate blocks cause an alteration of the original shade selected. Shade A1 high translucency restorations tend to change to a more yellowish B1 shade after a sintering process.

• 복식
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• 제41권
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• pp.23-47
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• 1998

Ornaments is a province of the fashion. It usually express noble metals and jewel's adorn-ment as the symbol of status and riches for a long time. The ornament design of Jewels drawing project and a product by computer are increased development and as exertion as a realization of automation. Through the use of CAD software(Auto CAD R 13 & Jewel CAD) \circled1 A design development of the jewels in industrial society \circled2 A metals art & design on the dress and it's ornaments - Study about application of principle(liberal curve, arrangement of repeated form, gradual unity, rhythmical harmony) Although Auto CAD don't various expression of Jewels than a Jewel CAD, formative.scientific.funtional development of geometrical form is free. That is (to say), geometrical form is given much weigh in the general CAD, but Jewel CAD made concentrate software on the jewels design for the expression of liberal form. The CAD/CAM software for jewellery program is composed of main menu, icons, hotkeys. Changing form is derived from a definite point, curve elements of a drawing. \circled1 3-Dimensional \circled2 Easy and flexible \circled3 Bulit-in and self created library \circled4 From simple wire frame to full color images. As a CAD can practice all the creation activity effectively, from Design & Drafting Software to Rendering generally can present precise results. A point of view of the connection the scientist and art, this practicableness of CAD have a lot of possiblity of development. That will do much for the related fields of industry. Consequently, subjective intension of a creator & humanity with value plays role in practical application of the design.