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关键词： Fracture resistance   Mechanical properties   Multilayered zirconia   Translucency   Y-TZP  

摘要： This study evaluated fracture resistance of monolithic fixed dental prostheses (FDPs) fabricated using different placement strategies of various connector designs in multilayered zirconia disc. Monolithic FDPs were placed in translucent and dentin layers of multilayered zirconia disc and fabricated with V-shaped and U-shaped connector designs gained by sharp and blunt millings. The FDPs were cemented on abutment models made of polymer material, underwent thermal cycles, and loaded to fracture using the universal testing machine. Fracture loads and modes were analyzed using two-way ANOVA, Tukey's post hoc test, and Fisher exact test (p <= 0.05). The chosen placement strategy and connector designs gained by different milling procedures in computer-aided design/ computer-aided manufacturing technology affect fracture resistance of monolithic FDPs made of multilayered zirconia materials. Placing the connector in translucent layer rather than dentin layer of multilayered zirconia disc and using sharp milling significantly reduces fracture resistance of monolithic multilayered zirconia FDPs.

关键词： binaries   eclipsing stars   fundamental parameters stars   individ- ual   DT Cam stars   rotation techniques   photometric  

摘要： In this study we analyzed TESS data of detached eccentric binary system DT Cam and we obtained the first physical parameters of the components. We found that the out-of-eclipse variation of the system shows a small amplitude periodic feature. Most of the frequencies obtained are related with the orbital variation except one, for which the period was determined as <^>x0.605 days. The masses and radii of the primary and secondary components were calculated as M1 = 1.793M0, M2 = 1.414M0, R1 = 1.355R0, and R2 = 1.522R0, respectively. Considering the physical properties of the primary component we concluded that it is a rotational variable. We found that the massive component is smaller than the low-mass component. It seems that the secondary component is a pre-main sequence star, which is important for the understanding of stellar structure and evolution.

关键词： 机械工程  

ISBN: (纸本)9787030798138

摘要： 本书旨在整合机械制图和CAD知识，以中望CAD、中望3D软件系统为操作平台，选择涵盖不同领域和应用场景的实例，每个实例都配有详细的CAD操作指南和操作流程，通过图文并茂的内容呈现方式，为读者提供直观的学习资料，使其能够逐步掌握CAD机械设计的技能。本书采用活页式设计，方便读者根据需要灵活选择学习内容。本书适用于应用型高校、职业院校、技工院校机械类相关专业学生，也可作为工程技术人员进行机械设计的工具书，还可作为培训机构和高校相关专业教师开展CAD教学和培训的参考用书。

关键词： Additive manufacturing   CAD/CAM   3D printing   Digital complete denture   Milling  

摘要： This study aims to assess the dimensional accuracy of complete denture bases fabricated from different CAD/CAM technologies and a conventional method, including milling (CNC), PolyJet (PJ), laser sintering (SLS), digital light processing (DLP), and injection molding (IM). It also examines the influence of the removal of technology-specific connectors or support structures when present. Denture base surfaces were digitized using a laboratory scanner, and virtual measurement points were calculated with tetrahedral reference geometries. Defined distances were measured in all spatial directions and compared to design data (p<0.05), revealing significant differences in sagittal (p=0.004), transversal (p<0.001), and vertical (p<0.001) dimensions. Connector removal had no significant impact for CNC but significantly affected DLP. All technologies yielded clinically acceptable results, with CNC milling demonstrating the best overall outcome.

关键词： Design automation   CADCAM   History   Software packages   Product development  

关键词： PICN   polymer-infiltrated ceramic-network   RCB   resin composite blocks   acidic media   microhardness   flexural strength   elastic modulus  

摘要： This study aimed to investigate the effect of acidic media storage (gastric acid and Coca-Cola) on the mechanical properties of CAD/CAM materials. Three types of materials were tested: a polymer-infiltrated ceramic network (PICN) (Vita Enamic (En), VITA Zahnfabrik, Germany), a resin composite block (RCB) (Cerasmart (Cs), GC Corp, Japan), and a conventional resin-based composite (Gradia direct (Gr), GC Corp, Japan), which was used as a control. Beam-shaped specimens of each material, with dimensions of 16 mm x 4 mm x 1.5 mm, were prepared (90 in total). The specimens were divided into subgroups (10 each) and stored for 96 h in either gastric acid, Coca-Cola, or distilled water. Flexural strength and elastic modulus were evaluated using a three-point flexural strength test with acoustic emission (AE) monitoring. Vickers microhardness was measured before and after storage in gastric acid and Coca-Cola. Data were statistically analysed using two-way and one-way ANOVA, the Tukey's post hoc, and independent t-test at a significance level of 0.05. The results showed that Cs and En maintained their flexural strength and elastic modulus after acidic media exposure, while Gr experienced a significant decrease in flexural strength following gastric acid storage (p < 0.01). Initial crack detection was not possible using the AE system, impacting the determination of flexural strength. Exposure to acidic media decreased all materials' microhardness, with Gr showing the most notable reduction (p < 0.0001). Gastric acid had a greater impact on the microhardness of all tested materials compared to Coca-Cola (p < 0.0001). In conclusion, storage in erosive media did not notably affect the flexural strength or elastic modulus of CAD/CAM composites but it did affect hardness. CAD/CAM composite blocks demonstrated superior mechanical properties compared to the conventional composite.

关键词： Triple-vessel coronary artery disease   Surgical revascularization   Operative technique   BIMA T-Graft   Two-inflow   Functional mitral valve regurgitation   MACCE  

摘要： Objective The effect of one-inflow and two-inflow coronary surgical revascularization techniques inclosing skeletonized double mammary artery (BIMA) as T-graft on outcome is studied. Methods Early ad mid-term outcome of complete BIMA revascularization (C-T-BIMA) versus left-sided BIMA with right-sided aorto-coronary bypass (L-T-BIMA + R-CABG) is quantified and analyzed by multivariate logistic regression, Cox-regression, and Kaplan-Meier analysis in a series of 204 consecutive patients treated for triple-vessel coronary disease (3v-CAD). Results The L-T-BIMA + R-CABG technique (n = 104) enables higher number of total (4.02 +/- 0.87 vs. 3.71 +/- 0.69, p = 0.015) and right-sided (1.21 +/- 0.43 vs. 1.02 +/- 0.32, p = 0.001) coronary anastomoses, improves total bypass flow (125.88 +/- 92.41 vs. 82.50 +/- 49.26 ml, p < 0.0001) and bypass flow/anastomosis (31.83 +/- 23.9 vs.22.77 +/- 14.23, p = 0.001), and enhances completeness of revascularization (84% vs.69%, p = 0.014) compared to C-T-BIMA strategy (n = 100), respectively. Although the incidence of MACCE was comparable in the two groups (8% vs.1.2%, p = 0.055), the progression of functional mitral regurgitation (FMR) was significantly lower after L-T-BIMA + R-CABG, then after C-T-BIMA (47% vs.64%, p = 0.017). The use of C-T-BIMA-technique (HR = 4.2, p = 0.01) and preoperative RCA occlusion (HR = 3.006, p = 0.023) predicted FMR progression, whereas L-T-Graft + R-CABG technique protected against it (X-2 = 14.04, p < 0.0001) independent of the anatomic and clinical complexity (Syntax score I: HR = 16.2, p = 0.156, Syntax score II: HR = 1.901, p = 0.751), of early- (0.96% vs.2%, p = 0.617) and mid-term mortality (5.8% vs.4%, p = 0.748) when compared to C-T-BIMA, respectively. Conclusions The two-inflow coronary revascularization by L-T-BIMA + R-CABG better protects against FMR progression without increasing MACCE and mortality. Older patients with RCA occlusion and reduced LV-EF benefit most from the two-inflow L-T-BIMA +

关键词： Product variant design   Product families   Product modelling   Design integration   Systematic approach   CAD   Design automation   Detailed Design Model (DDM)   Multiple-variant Adaptive Redesign Method (M-ARM)  

摘要： Companies with established product families can meet emerging market needs by extending their product families over time, that is, by introducing new product variants sequentially. Starting points for each new design can be generated by integrating design solutions from existing products in the same family. This article introduces an automated systematic approach to derive all possible ways of combining existing designs to produce a new variant with a desired new combination of functionality, based on algorithmic analysis of product models. The approach considers the functions in existing products and how they are realised in specific CAD parts and the geometric features defining them. By automatically generating and evaluating all the options, the new approach helps identify the most efficient way to combine existing parts and features from a product family to generate a new product variant with distinct functionality. The approach has been applied to product families of mechanical and mechatronic consumer products. It was evaluated by manually implementing the automatically-generated redesign instructions in CAD for several product variants, which built confidence in the approach's accuracy and performance. From the evaluation, opportunities for further work are suggested.

关键词： Companies   Software engineering   Pressure vessels   Design automation   Mechanical engineering   Industries   Concrete   Market research   CADCAM   Product design   Product development  

摘要： Covering Tom Lazear's 60 years in the CAD and software marketing industry, this first-hand account details his time with Fluor Corporation and three CAD companies-T&W Systems (later Versacad), Computervision, and Archway Systems. After a 20-year career at Fluor, where he was an early developer and user of CAD technology, Lazear founded the CAD software company T&W Systems, which produced and marketed VersaCAD, an early microcomputer-based CAD product that was later acquired by Prime/Computervision. After managing the Computervision business for a several years, he started the company Archway Systems, which evolved into a value-added reseller for CAD software products produced by Bentley Systems and Intergraph.