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Computer-aided Design (computer-aided + design)
Selected AbstractsSpatial Information: Classification and Applications in Building DesignCOMPUTER-AIDED CIVIL AND INFRASTRUCTURE ENGINEERING, Issue 4 2002Tang-Hung Nguyen Physical properties of building components are usually represented in building data models by their three-dimensional geometry and topology,also called spatial information. While geometric data of building components can be manipulated and managed by a computer-aided design (CAD) interface, their spatial relations (or topological information) are conventionally represented in a manual fashion into data models. The manual data representation, however, is inherently a complex and challenging task due to the wide variety of spatial relationships. Thus, topological information should be classified and modeled in such a way that the required spatial data for a particular design task can be automatically retrieved. This paper attempts to identify and classify various topological information commonly used in building design and construction into more specific categories (e.g., adjacency, connection, containment, separation, and intersection) to support automatic deduction of the spatial information in a computer-based building design system. The paper also discusses typical applications of the topological relations to different design activities. Finally, the development of deduction algorithms and the proposed building design system are briefly described. [source] Load-bearing capacity of all-ceramic three-unit fixed partial dentures with different computer-aided design (CAD)/computer-aided manufacturing (CAM) fabricated framework materialsEUROPEAN JOURNAL OF ORAL SCIENCES, Issue 4 2008Florian Beuer The purpose of this in vitro study was to compare the load-bearing capacity of posterior three-unit fixed dental prostheses (FDP) produced with three different all-ceramic framework materials: glass-infiltrated alumina (ICA), glass-infiltrated alumina strengthened with zirconia (ICZ), and yttria-stabilized polycrystalline zirconia (YZ). Additionally, the influence on aging of mechanical cyclic fatigue loading and thermal cycling in water were evaluated. A total of 20 frameworks each were fabricated from ICA, ICZ, and YZ by a computer-aided design (CAD)/computer-aided manufacturing (CAM) system. The framework designs were identical for all specimens. All frameworks were veneered with porcelain and cemented with glass,ionomer. Prior to fracture testing, 10 FDP of each experimental group were subjected to thermal and mechanical cycling. Additionally, fractographic analysis was performed. Statistical analysis showed that FDP made from YZ had significantly higher load to failure, whereas no difference was found between the other two materials. Aging did not have a significant effect on the fracture load. [source] A general framework for evaluating nonlinearity, noise and dynamic range in continuous-time OTA-C filters for computer-aided design and optimizationINTERNATIONAL JOURNAL OF CIRCUIT THEORY AND APPLICATIONS, Issue 4 2007S. Koziel Abstract Efficient procedures for evaluating nonlinear distortion and noise valid for any OTA-C filter of arbitrary order are developed based on matrix description of a general OTA-C filter model. Since those procedures use OTA macromodels, they allow us to obtain the results significantly faster than transistor-level simulation. On the other hand, the general OTA-C filter model allows us to apply matrix transforms that manipulate (rescale) filter element values and/or change topology without changing its transfer function. Due to this, the proposed procedures can be used in direct optimization of OTA-C filters with respect to important characteristics such as noise performance, THD, IM3, DR or SNR. As an example, a simple optimization procedure using equivalence transformations is discussed. An application example of the proposed approach to optimal block sequencing and gain distribution of 8th order cascade Butterworth filter is given. Accuracy of the theoretical tools has been verified by comparing to transistor-level simulation results and to experimental results. Copyright © 2006 John Wiley & Sons, Ltd. [source] CAD of evanescent-mode bandpass filters based on the short ridged waveguide sectionsINTERNATIONAL JOURNAL OF RF AND MICROWAVE COMPUTER-AIDED ENGINEERING, Issue 6 2001Anatoly Kirilenko Abstract The paper presents the internal details of a developed full-wave algorithm for the computer-aided design of evanescent-mode bandpass filters formed by single- or double-short ridged waveguide sections. New filter configurations with an enlarged cross section of filter housing and nonconventional notch-strip-notch elements providing improved stopband performance are given special considerations. Additional input,output transformers built on rectangular waveguide sections are used in designing broadband filters. Characteristics of one of the designed filters are verified by measured data. © 2001 John Wiley & Sons, Inc. Int J RF and Microwave CAE 11: 354,365, 2001 [source] Biofunctional rapid prototyping for tissue-engineering applications: 3D bioplotting versus 3D printing,JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 3 2004Andreas Pfister Abstract Two important rapid-prototyping technologies (3D Printing and 3D Bioplotting) were compared with respect to the computer-aided design and free-form fabrication of biodegradable polyurethane scaffolds meeting the demands of tissue-engineering applications. Aliphatic polyurethanes were based on lysine ethyl ester diisocyanate and isophorone diisocyanate. Layer-by-layer construction of the scaffolds was performed by 3D Printing, that is, bonding together starch particles followed by infiltration and partial crosslinking of starch with lysine ethyl ester diisocyanate. Alternatively, the 3D Bioplotting process permitted three-dimensional dispensing and reactive processing of oligoetherurethanes derived from isophorone diisocyanate, oligoethylene oxide, and glycerol. The scaffolds were characterized with X-ray microtomography, scanning electron microscopy, and mechanical testing. Osteoblast-like cells were seeded on such scaffolds to demonstrate their potential in tissue engineering. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 624,638, 2004 [source] Thoracoscopic cell sheet transplantation with a novel deviceJOURNAL OF TISSUE ENGINEERING AND REGENERATIVE MEDICINE, Issue 4 2009Masanori Maeda Abstract Regenerative medicine with transplantable cell sheets fabricated on temperature-responsive culture surfaces has been successfully achieved in clinical applications, including skin and cornea treatment. Previously, we reported that transplantation of fibroblast cell sheets to wounded lung had big advantages for sealing intraoperative air leaks compared with conventional materials. Here, we report a novel device for minimally invasive transplantation of cell sheets in endoscopic surgery, such as video-assisted thoracoscopic surgery (VATS). The novel device was designed with a computer-aided design (CAD) system, and the three-dimensional (3D) data were transferred to a 3D printer. With this rapid prototyping system, the cell sheet transplantation device was fabricated using a commercially available photopolymer approved for clinical use. Square cell sheets (24 × 24 mm) were successfully transplanted onto wound sites of porcine lung placed in a human body model, with the device inserted through a 12 mm port. Such a device would enable less invasive transplantation of cell sheets onto a wide variety of internal organs. Copyright © 2009 John Wiley & Sons, Ltd. [source] New and accurate synthesis formulas for open supported coplanar waveguidesMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 2 2010S. Kaya Abstract In this article, new and accurate synthesis formulas to compute the physical dimensions of open supported coplanar waveguides (OS-CPWs) are presented. The synthesis formulas are obtained with the use of differential evolution (DE) and particle swarm optimization (PSO) algorithms. They are useful for the computer-aided design of OS-CPWs. The average percentage errors of the synthesis formulas obtained by using DE and PSO algorithms are computed to be 1.26% and 1.67%, respectively, for 4560 OS-CPW samples having different electrical parameters and physical dimensions, as compared with the results of quasi-static analysis. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 262,269, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24908 [source] Kirschning and Jansen computer-aided design formulae for the analysis of parallel coupled linesMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 10 2009J. A. Brandão Faria Abstract Among the many computer-aided design (CAD) formulae used for the calculation of the wave parameters of coupled microstrip lines where fringing field effects occur, the Kirschning and Jansen equations are the most utilized ones, not only because of their high accuracy, but also because of their wide range of application. Here, we show that, despite the aforementioned advantages, such equations may lack physical meaning. We prove, for the first time, that the utilization of these widespread CAD equations can lead to positive valued mutual capacitances, an unacceptable result from the viewpoint of electromagnetic theory. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2466,2470, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24659 [source] New and accurate synthesis formulas for multilayer homogeneous coupling structureMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 10 2007Kerim Guney Abstract New, accurate closed-form formulas for the synthesis of multilayer homogeneous coupling structure (MHCS) are presented. They are obtained by using a differential evolution algorithm (DEA), and are useful for the computer-aided design (CAD) of MHCS. The average percentage error is found to be 0.38% for 1825 MHCS samples having different electrical parameters and physical dimensions, as compared with the results of the quasi-static analysis. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 2486,2489, 2007; Published online in Wiley InterScience (www.interscience.wiley.com) DOI 10.1002/mop.22743 [source] Innovation alignment and project network dynamics: An integrative model for changePROJECT MANAGEMENT JOURNAL, Issue 3 2007John E. Taylor Abstract Innovation research has predominantly focused on hierarchically organized firms competing within single markets. Recently, however, researchers have debated over whether the increasing use of project networks within and across industries promotes or stifles innovation. This paper discusses a model based on crossnational diffusion data from three technological innovations in three-dimensional computer-aided design (3D CAD) and related implementation data from 82 firms. From the data we induce a set of constructs that form the basis of a two-stage model for understanding innovation in project networks. In the first stage of the model the alignment of an innovation to the existing allocation of work in a project network is ascertained. In the second stage, the implementation success and diffusion outcomes for innovations misaligned with the allocation of work are governed by the relational stability, accrual of interests, boundary permeability, and existence of an agent for project network change. In developing this integrative, two-stage model we resolve the contradiction in the academic literature regarding the degree to which project network dynamics can promote or stifle innovation. [source] Measurements of Tooth Movements in Relation to Single-Implant Restorations during 16 Years: A Case ReportCLINICAL IMPLANT DENTISTRY AND RELATED RESEARCH, Issue 4 2005Torsten Jemt LSD ABSTRACT Background: Osseointegrated implants behave as ankylotic abutments, and their positions are not affected by dentofacial changes. Purpose: To measure changes in occlusion in relation to single implants in one patient after more than 15 years in function. Materials and Methods: One 25-year-old female was treated with two single implants in the upper central incisor and bicuspid area after trauma. Study casts made prior to treatment (1987) and after 16 years in function (2004) were scanned by means of an optical scanner. Using the palate as the reference, the models were placed in the same coordinate system and analyzed and compared in a computer-aided design (CAD) program. The results of the measurements of the casts were also compared with clinical photographs taken at the time of treatment (1988), after 9 years (1997), and after 16 years (2004) in function. Results: The clinical photographs showed obvious signs of implant infraposition after 9 years. New crowns were made in the incisor region after 15 years (2002), but signs of infraposition were again present at the final examination (2004). Measurements of the casts indicated small tooth movements with a pattern of slight eruption of upper teeth combined with a palatal inclination, mesial drift, and lingual inclination and crowding of the lower anterior teeth. The small measured vertical eruption of the teeth was less than the observed clinical infraposition of the implant crowns, indicating that the vertical position of the palatal may have changed in relation to the implants as well. Conclusion: Obvious dentofacial changes may take place in adult patients. Teeth may adjust for this, and no major problems may arise in the dentate patient. However, because the positions of implants are not affected by dentofacial changes, other patterns of clinical problems can be seen when implant patients present with these changes. The character and frequency of these dentofacial changes that may compromise implant treatment in the long term are not yet known. [source] | |||||||||||||