Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “computational design”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 1,369 records · Page 76Linked to original sources
PubMed2006

A three-dimensional evaluation of a laser scanner and a touch-probe scanner.

STATEMENT OF PROBLEM: The fit of a dental restoration depends on quality throughout the entire manufacturing process. There is difficulty in assessing the surface topography of an object with a complex form, such as teeth, since there is no exact reference form. PURPOSE: The purpose of this study was to determine the repeatability and relative accuracy of 2 dental surface digitization devices. A computer-aided design (CAD) technique was used for evaluation to calculate and present the deviations 3-dimensionally. MATERIAL AND METHODS: Ten dies of teeth prepared for complete crowns were fabricated in presintered yttria-stabilized tetragonal zirconia (Y-TZP). The surfaces were digitized 3 times each with an optical or mechanical digitizer. The number of points in the point clouds from each reading were calculated and used as the CAD reference model (CRM). Alignments were performed by registration software that works by minimizing a distance criterion. In color-difference maps, the distribution of the discrepancies between the surfaces in the CRM and the 3-dimensional surface models was identified and located. RESULTS: The repeatability of both scanners was within 10 microm, based on SD and absolute mean values. The qualitative evaluation resulted in an even distribution of the deviations in the optical digitizer, whereas the dominating part of the surfaces in the mechanical digitizer showed no deviations. The relative accuracy of the 2 surface digitization devices was within +/- 6 microm, based on median values. CONCLUSION: The repeatability of the optical digitizer was comparable with the mechanical digitization device, and the relative accuracy was similar.

Computer-Aided Design↗
PubMedDate not supplied

Validation by school nurses of the Nursing Intervention Classification for computer software.

Validation of standardized nursing language for use by specialty nurses is important for the design of computer software. The purposes of this study were to validate the usefulness of the 433 interventions in the Nursing Intervention Classification (NIC) for school nurses and to identify interventions that could be omitted from computer software for school nurses. A school nursing listserv, SCHLRN-L, was used to recruit volunteers. Ninety-three volunteers from the listserv also recruited 26 school nurses who were not members of the listserv. The total sample was 102 school nurses from 25 states and other areas, 76 listserv volunteers, and 26 others. E-mail was used to send and receive the survey forms to portions of the sample. A majority of interventions (n = 241; 56%) were selected as used by more than 50% of the sample. Of these, 53 direct care interventions were selected as used by more than 80% of the sample. Fifty interventions were not used by 100% of the sample. E-mail was a useful means to obtain a national sample and collect data.

Classification↗
PubMedDate not supplied

Wavelet-based multiresolution analysis of irregular surface meshes.

This paper extends Lounsbery's multiresolution analysis wavelet-based theory for triangular 3D meshes, which can only be applied to regularly subdivided meshes and thus involves a remeshing of the existing 3D data. Based on a new irregular subdivision scheme, the proposed algorithm can be applied directly to irregular meshes, which can be very interesting when one wants to keep the connectivity and geometry of the processed mesh completely unchanged. This is very convenient in CAD (Computer-Assisted Design), when the mesh has attributes such as texture and color information, or when the 3D mesh is used for simulations, and where a different connectivity could lead to simulation errors. The algorithm faces an inverse problem for which a solution is proposed. For each level of resolution, the simplification is processed in order to keep the mesh as regular as possible. In addition, a geometric criterion is used to keep the geometry of the approximations as close as possible to the original mesh. Several examples on various reference meshes are shown to prove the efficiency of our proposal.

Algorithms↗
PubMed1996

Use of computational fluid dynamics in the design of surgical procedures: application to the study of competitive flows in cavo-pulmonary connections.

Computational fluid dynamic methods based on a finite-element technique were applied to the study of (1) competition of flows in the inferior and superior venae cavae in total cavopulmonary connection, and (2) competition between flow in the superior vena cava and forward flow from a stenosed pulmonary artery in bidirectional cavopulmonary anastomosis. Models corresponding to various degrees of offsetting and shape of the inferior vena caval anastomosis were simulated to evaluate energy dissipation and flow distribution between the two lungs. A minimal energy loss with optimal flow distribution between the two lungs was obtained by enlarging the inferior vena caval anastomosis toward the right pulmonary artery. This modified technique of total cavopulmonary connection is described. A computational model of the operation was developed in an attempt to understand the mechanisms of postoperative failure. In tight pulmonary artery stenosis (75%), the pulsatile forward flow is primarily directed to the left pulmonary artery, with little influence on superior vena caval pressure and the right pulmonary artery. Pulsatile forward flows corresponding to 15%, 30%, 45%, and 60% of the systemic artery output increased the mean pulmonary artery and superior vena caval pressures by 1, 1.7, 2.4, and 3.6 mm Hg, respectively. Although the modeling studies were not able to determine the cause of postoperative failure, they emphasize the impact of local geometry on flow dynamics. More simulations are required for further investigation of the problem.

Anastomosis, Surgical↗
PubMed2004

Flat or curved pericardial aortic valve cusps: a finite element study.

BACKGROUND AND AIM OF THE STUDY: The finite element method (FEM) has frequently been used to investigate the behavior of the aortic valve, but studies on the performance and behavior of free-hand autologous pericardial aortic valves reconstructed using specially designed valve molds have not been performed. The study aim was to demonstrate the effectiveness of a three-dimensional (3-D) cusp of the authors' design (H-Mold) versus a two-dimensional (2-D) (flat) cusp using a FEM to compare stress distribution and leaflet contact properties. METHODS: Solid models of the aortic root and valve cusps were constructed using a computer-aided design package. All models had different free edge lengths and surface areas, but a constant leaflet attachment length corresponding to a 19 mm annulus diameter. A static pressure of 80 mmHg was applied to all models. RESULTS: The maximum von Mises stress value in the H-Mold at the cusp commissure was 34.5% lower than the stress value in the flat leaflet, while the contact area in the H-Mold leaflet was 85.7% greater than that of the flat leaflet. The length of leaflet free edge greatly influenced maximum von Mises stress intensity at the commissures, and the contact area between leaflets was mainly affected by the geometric shape of the leaflet and its surface area. CONCLUSION: 3-D leaflet geometry was found positively to influence leaflet stress distribution and coaptation. This geometry should have a significant impact on the reliability and long-term durability of pericardial aortic valve reconstruction.

Aortic Valve↗
PubMedDate not supplied

Integration of laser surface digitizing with CAD/CAM techniques for developing facial prostheses. Part 2: Development of molding techniques for casting prosthetic parts.

PURPOSE: This article presents a novel manufacturing approach that integrates laser surface digitizing/scanning and computer-aided design and manufacturing (CAD/CAM) to achieve automated fabrication of spatially and anatomically accurate extraoral facial prostheses. MATERIALS AND METHODS: Contrary to the approach in part 1 for fabricating positive replicas of prostheses, the approaches presented here are focused on designing and producing negative molds of the final prostheses using CAD, rapid prototyping, and rapid tooling techniques. The molds were applied directly to cast the final prostheses, thereby eliminating conventional flasking and investing procedures. RESULTS: Three different facial prostheses were produced to evaluate the proposed approach for prosthesis production. The advantages of this alternative manufacturing approach over the approach presented in part 1 and conventional techniques are discussed. The limitations encountered with the integrated manufacturing system are highlighted. CONCLUSION: With the new techniques, reduced patient discomfort, minimal dependence on the artistic skills of the prosthetist, and short turnaround times for prosthesis production can be expected.

Biocompatible Materials↗
PubMed1998

The significance of rota representation in the design of rotas.

Shift scheduling is based on some representation of shift schedules. The number of different representations currently used is high, and one might expect small practical differences between these representations. However, an analysis of several prominent representations revealed strong differences regarding possible outcomes of the scheduling process and the effort needed for their assessment. Limitations of some representations do not only concern specific rota design issues, such as different staffing levels or different workhours, but also rather simple and straightforward rotas. Furthermore, there is no single representation that is strictly and unequivocally better than the others. Most representations simplify the development of some rotas, while they make it very difficult or even impossible to develop others. Therefore, both designers and the computer systems used for design should use and support several representations and therefore allow smooth transitions between them. In addition knowledge about rota construction techniques should be maintained, as it may ease assessment dramatically.

Computer Simulation↗
PubMed2002

Assessment of facial tissue expansion with three-dimensional digitizer scanning.

This article reports a three-dimensional (3D) digital color scanning system used in the measurement of facial soft tissue expansion. This system consists of digital scanning equipment, software for stereolithographical (STL) forms and nonuniform rational B-spline (NURBS) surfaces, and a computer-aided design program. Accurate data for the area of scar excision and the expanded cervicofacial flap were obtained by using this measuring system in a young patient with scar contracture of the face. This technique can accurately model the reconstruction and make plastic surgery planning a truly interactive procedure.

Adolescent↗
PubMed1991

Clinical trial of a computer-aided system for orthopaedic shoe upper design.

A trial has been conducted to produce the uppers for orthopaedic shoes using an existing commercial computer-aided design system. The aims of the trial were to confirm that a CAD system developed for the volume shoe trade (Shoemaster from Clarks Shoes) could be used for the upper design of orthopaedic shoes and to assess the contribution of professional shoe design on cosmesis and acceptability of these shoes. A small number of adult diabetic patients and children with foot deformities were selected, all of who had previously been prescribed and issued with special shoes. The existing lasts for these patients were digitised, and new styles developed on the CAD system over a 3D image of the last. Pattern pieces were cut automatically and the uppers closed. Lasting was done as normal at the two collaborating orthopaedic companies and the shoes supplied to the patients. The CAD system proved successful in coping with orthopaedic last shapes and shoe requirements. Professional design produced fashionable and cosmetically-pleasing styles within the constraints imposed by the underlying medical conditions.

Adolescent↗
PubMed2005

A technique to produce a mirror-image wax pattern of an ear using rapid prototyping technology.

This article describes the use of computer-aided techniques to produce a wax pattern of a missing ear. A 3-dimensional (3-D) computer model of a conventional cast from a patient was obtained using an optical surface capture device (scanner). The 3-D computer model was inverted, using computer-aided design software. A physical thermoplastic (wax) pattern of the inverted 3-D cast was produced using a rapid prototyping (RP) machine.

Computer Simulation↗
PubMedDate not supplied

A CAD/CAM technique for fabricating facial prostheses: a preliminary report.

A computer-aided designing and manufacturing (CAD/CAM) technique for clinical fabrication of facial prostheses was developed. Laser surface scanning was applied to acquire three-dimensional imaging data of the patient's facial defect. The three-dimensional imaging data was then transferred to a CAD/CAM interactive program for image processing, which then mathematically designed and produced a model for fabrication of the facial prosthesis. This CAD/CAM technique has the potential to simplify the procedure and decrease the laboratory work required compared to that required for the conventional plaster-cast method. This new technique also provides a novel approach to the fabrication of prostheses for the reconstruction of facial defects. Two alternative three-dimensional modeling processes, laser lithographic modeling and numerically controlled milling modeling, were integrated in this study. The possibilities and current limitations of the techniques are also discussed.

Computer-Aided Design↗
PubMed2005

A novel method for in vivo knee prosthesis wear measurement.

Wear remains an important cause of failure in knee replacement. Of the current methods of early performance assessment or prediction, simulators have been un-physiological, single X-ray film analyses remain limited by accuracy and retrieval and survival methods have a prohibitive time scale. An accurate method is needed to allow a timely assessment of polyethylene component wear in vivo, when a new design is introduced, in order to predict likely outcome. We present a new method for measuring wear in vivo that we believe will allow this prediction of long-term wear. X-ray film pairs were taken of implanted prosthetic metal components. When the X-ray system was calibrated, projections of the appropriate Computer Aided Design (CAD) model could be matched to the shapes on the scanned X-ray films to find component positions. Interpenetration of the metal femoral component into the polyethylene component could then be established and represents our estimate of "wear". This method was used to measure in vivo prosthesis wear to an accuracy of 0.11 mm.

Arthroplasty, Replacement, Knee↗
PubMed2000

Assessment, re-design and evaluation of changes to the driver's cab in a suburban electric train.

A new type of electric train, called the Tangara, began replacing older trains on the Sydney city and suburban network in 1990. Shortly afterwards, some of the train drivers began reporting pain in the arms while driving the new train. The Ergonomics Unit of Worksafe Australia was then engaged to identify and assess ergonomic problems in the driver's cab. This process included direct observation of drivers at work, distribution of a self-administered questionnaire to all drivers, and analysis of anthropometric problems using a computer-aided design package. The analysis of 193 completed questionnaires and the problems shown by the design study were used in developing an improved design. A mock-up of the modified cab was made and tried out by 134 drivers whose comments led to further changes. The modified design was applied to new production, and existing cabs were modified during major maintenance. By 1996, 96% of the driver's cabs were to the new design. An evaluation of the new design was undertaken using written questionnaires, which were completed by 227 drivers. The results were strongly in favour of the new design, showing the effectiveness of the ergonomic modifications.

Computer-Aided Design↗
PubMed2006

In silico protein design: fitting sequence onto structure.

In the last 10 yr, efforts have begun to combine the goals and approaches of computational molecular design and protein sequence analysis to provide tools for the rational mutagenesis and functional modification of proteins. These approaches use analysis of the three-dimensional structure of a protein to guide the selection of appropriate amino acid sequences to create desired properties or functions. The convergence of low-cost, high-speed computers, a tremendous increase in protein structure information, and a growing understanding of the forces that control protein structure has resulted in dramatic advances in the ability to control protein function and structure and to create the first truly artificial proteins. Various academic software packages have been developed for in silico protein design. The methods for selecting the protein structure, defining the portion to be designed, and choosing the input parameters for the software are described in this chapter.

Amino Acid Sequence↗
PubMed1982

Anatomical localization schemes for use in positron computed tomography using a specially designed headholder.

A headholder system is described for use in the correlation of images obtained with positron computed tomography (PCT) and other neuroradiological imaging modalities. Methods are described for defining brain anatomy from PCT images by the use of projection schemes from tomographic data. Cross-correlation of images between positron CT and standard lateral skull films, X-ray computed tomography (XCT), and two-dimensional rectilinear positron images are discussed. Such methods allow for improved reproducibility of head positioning and more precise cortical localization necessary in studies of normal brain function as well as in neuropathological conditions.

Brain↗
PubMed2000

Interventions for the primary prevention of work-related carpal tunnel syndrome.

OBJECTIVE: To evaluate interventions for the primary prevention of work-related carpal tunnel syndrome (CTS). SELECTION CRITERIA: Studies had to include an engineering, administrative, personal, or multiple component intervention applied to a working or working-age population. All study designs that included comparison data were considered. Outcome measures included the incidence, symptoms, or risk factors for CTS, or a work-related musculoskeletal disorder of the upper extremity that included CTS in the definition. RESULTS: Twenty-four studies met our inclusion criteria. Engineering interventions included alternative keyboards, computer mouse designs and wrist supports, keyboard support systems, and tool redesign. Personal interventions included ergonomics training, splint wearing, electromyographic biofeedback, and on-the-job exercise programs. Multiple component interventions (e.g., ergonomic programs) included workstation redesign, establishment of an ergonomics task force, job rotation, ergonomics training, and restricted duty provisions. Multiple component programs were associated with reduced incidence rates of CTS, but the results are inconclusive because they did not adequately control for potential confounders. Several engineering interventions positively influenced risk factors associated with CTS, but the evaluations did not measure disease incidence. None of the personal interventions alone was associated with significant changes in symptoms or risk factors. All of the studies had important methodologic limitations that may affect the validity of the results. CONCLUSIONS: While results from several studies suggest that multiple component ergonomics programs, alternative keyboard supports, and mouse and tool redesign may be beneficial, none of the studies conclusively demonstrates that the interventions would result in the primary prevention of carpal tunnel syndrome in a working population. Given the societal impact of CTS, the growing number of commercial remedies, and their lack of demonstrated effec- tiveness, the need for more rigorous and long-term evaluation of interventions is clear. Fund- ing for intervention research should prioritize randomized controlled trials that include: (1) adequate sample size, (2) adjustment for relevant confounding variables, (3) isolation of speci- fic program elements, and (4) measurement of long-term primary outcomes such as the inci- dence of CTS, and secondary outcomes such as employment status and cost.

Carpal Tunnel Syndrome↗
PubMed2005

Design of recombinant stem cell factor-macrophage colony stimulating factor fusion proteins and their biological activity in vitro.

Stem cell factor (SCF) and macrophage colony stimulating factor (M-CSF) can act in synergistic way to promote the growth of mononuclear phagocytes. SCF-M-CSF fusion proteins were designed on the computer using the Homology and Biopolymer modules of the software packages InsightII. Several existing crystal structures were used as templates to generate models of the complexes of receptor with fusion protein. The structure rationality of the fusion protein incorporated a series of flexible linker peptide was analyzed on InsightII system. Then, a suitable peptide GGGGSGGGGSGG was chosen for the fusion protein. Two recombinant SCF-M-CSF fusion proteins were generated by construction of a plasmid in which the coding regions of human SCF (1-165aa) and M-CSF (1-149aa) cDNA were connected by this linker peptide coding sequence followed by subsequent expression in insect cell. The results of Western blot and activity analysis showed that these two recombinant fusion proteins existed as a dimer with a molecular weight of approximately 84 KD under non-reducing conditions and a monomer of approximately 42 KD at reducing condition. The results of cell proliferation assays showed that each fusion protein induced a dose-dependent proliferative response. At equimolar concentration, SCF/M-CSF was about 20 times more potent than the standard monomeric SCF in stimulating TF-1 cell line growth, while M-CSF/SCF was 10 times of monomeric SCF. No activity difference of M-CSF/SCF or SCF/M-CSF to M-CSF (at same molar) was found in stimulating the HL-60 cell linear growth. The synergistic effect of SCF and M-CSF moieties in the fusion proteins was demonstrated by the result of clonogenic assay performed with human bone mononuclear, in which both SCF/M-CSF and M-CSF/SCF induced much higher number of CFU-M than equimolar amount of SCF or M-CSF or that of two cytokines mixture.

Animals↗