357 research outputs found
Using Patran and Supertab as pre- and postprocessors to COSMIC/NASTRAN
Patran and Supertab are interactive computer graphics pre- and postprocessors that can be used to generate NASTRAN bulk data decks and to visualize results from a NASTRAN analysis. Both of the programs are in use at the Numerical Structural Mechanics Branch of the David Taylor Research Center (DTRC). Various aspects of Patran and Supertab are discussed including: geometry modeling, finite element mesh generation, bulk data deck creation, results translation and visualization, and the user interface. Some advantages and disadvantages of both programs will be pointed out
Animation of finite element models and results
This is not intended as a complete review of computer hardware and software that can be used for animation of finite element models and results, but is instead a demonstration of the benefits of visualization using selected hardware and software. The role of raw computational power, graphics speed, and the use of videotape are discussed
Computer animation of modal and transient vibrations
An interactive computer graphics processor is described that is capable of generating input to animate modal and transient vibrations of finite element models on an interactive graphics system. The results from NASTRAN can be postprocessed such that a three dimensional wire-frame picture, in perspective, of the finite element mesh is drawn on the graphics display. Modal vibrations of any mode shape or transient motions over any range of steps can be animated. The finite element mesh can be color-coded by any component of displacement. Viewing parameters and the rate of vibration of the finite element model can be interactively updated while the structure is vibrating
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Exploring Model-Based Engineering Concepts for Additive Manufacturing
Robust geometry and tolerance representations are needed in additive manufacturing for
precise part specification and interoperability with downstream activities such as manufacturing,
inspection, and long-term archiving. A disconnection exists between process-independent part
geometry and tolerances, and process-dependent information requirements for additive
manufacturing. Existing and emerging standards for part geometry (ASTM AMF, 3MF, ISO
10303 STEP) and tolerances (ASME Y14) contain information related to the additive
manufacturing process. Details of the standards will be discussed, how their use and
improvement can benefit the additive manufacturing process, and their integration into the
model-based engineering paradigm.Mechanical Engineerin
Mobile 3D Visualization for Construction
ABSTRACT: Until recently, visualization of 3D models required computational resources available only on desktop computers in office environments. With the advance of technology, it is now possible to visualize substantial 3D models on mobile handheld computers in the field. This paper discusses some of the current technology, discusses the use of the Virtual Reality Modeling Language on mobile handheld computers, shows several examples of 3D structural steelwork models visualized on a mobile handheld computer, and identifies some of the limitations imposed by current technology
Automating Robot Planning Using Product and Manufacturing Information
AbstractAdvances in sensing, modeling, and control have made it possible to increase the accuracy of robots, and enable them to perform in dynamic environments. Often, performance deficiencies are not evident until late in the development of the manufacturing process, which delays the beginning of production and may cause damage to parts that have already undergone costly manufacturing steps. The goal of this research is to determine if a robot can meet manufacturing requirements, how to optimally plan robot activities, and to monitor robot processes to track performance. To achieve this, representations of product and manufacturing information and robot capabilities should be carried through the design, process planning, production, and analysis phases. Standards for the exchange of this information have been developed, such as ISO 10303 Part 242 for semantic product and manufacturing information and device kinematics, and the Robot Operating System Industrial specification for robot modeling, path planning, and execution. This paper surveys the relevant technologies and standards needed to enable automated deployment of robots in new application areas
A search for thermal gyro-synchrotron emission from hot stellar coronae
We searched for thermal gyro-synchrotron radio emission from a sample of five
radio-loud stars whose X-ray coronae contain a hot ( K) thermal
component. We used the JVLA to measure Stokes I and V/I spectral energy
distributions (SEDs) over the frequency range 15--45 GHz, determining the
best-fitting model parameters using power-law and thermal gyro-synchrotron
emission models. The SEDs of the three chromospherically active binaries
(Algol, UX Arietis, HR 1099) were well-fit by a power-law gyro-synchrotron
model, with no evidence for a thermal component. However, the SEDs of the two
weak-lined T Tauri stars (V410 Tau, HD 283572) had a circularly polarized
enhancement above 30 GHz that was inconsistent with a pure power-law
distribution. These spectra were well-fit by summing the emission from an
extended coronal volume of power-law gyro-synchrotron emission and a smaller
region with thermal plasma and a much stronger magnetic field emitting thermal
gyro-synchrotron radiation. We used Bayesian inference to estimate the physical
plasma parameters of the emission regions (characteristic size, electron
density, temperature, power-law index, and magnetic field strength and
direction) using independently measured radio sizes, X-ray luminosities, and
magnetic field strengths as priors, where available. The derived parameters
were well-constrained but somewhat degenerate. The power-law and thermal
volumes in the pre-main-sequence stars are probably not co-spatial, and we
speculate they may arise from two distinct regions: a tangled-field
magnetosphere where reconnection occurs and a recently discovered axisymmetric
toroidal magnetic field, respectively.Comment: Submitted to MNRAS; 18 pages, 10 figure
Local syzygies of multiplier ideals
In recent years, multiplier ideals have found many applications in local and
global algebraic geometry. Because of their importance, there has been some
interest in the question of which ideals on a smooth complex variety can be
realized as multiplier ideals. Other than integral closure no local
obstructions have been known up to now, and in dimension two it was established
by Favre-Jonsson and Lipman-Watanabe that any integrally closed ideal is
locally a multiplier ideal. We prove the somewhat unexpected result that
multiplier ideals in fact satisfy some rather strong algebraic properties
involving higher syzygies. It follows that in dimensions three and higher,
multiplier ideals are very special among all integrally closed ideals.Comment: 8 page
Managing the Built Environment for Health Promotion and Disease Prevention With Maharishi Vastu Architecture: A Review
Background and objectives: The evolution of healthcare from 18th-century reductionism to 21st-century postgenomic holism has been described in terms of systems medicine, and the impact of the built environment on human health is the focus of investigation and development, leading to the new specialty of evidence-based, therapeutic architecture. The traditional system of VÄstu architectureâa design paradigm for buildings which is proposed to promote mental and physical healthâhas been applied and studied in the West in the last 20 years, and features elements absent from other approaches. This review critically evaluates the theory and research of a well-developed, standardized form of VÄstuâMaharishi VastuÂź architecture (MVA). MVAâs principles include development of the architectâs consciousness, universal recommendations for building orientation, siting, and dimensions; placement of key functions; and occupantsâ head direction when sleeping or performing tasks. The effects of isolated VÄstu elements included in MVA are presented. However, the full value of MVA, documented as a systematic, globally applicable practice, is in the effect of its complete package, and thus this review of MVA includes evaluating the experience of living and working in MVA buildings. Methods: The published medical and health-related literature was systematically surveyed for research on factors related to isolated principles applied in MVA as well as on the complete system. Results: Published research suggests that incorporating MVA principles into buildings correlates with significant improvements in occupantsâ physical and mental health and quality of life: better sleep, greater happiness of children, and the experience of heightened sense of security and reduced stress. The frequency of burglaries, a social determinant of health, also correlates. Potential neurophysiological mechanisms are described. Conclusions: Findings suggest that MVA offers an actionable approach for managing a key social determinant of health by using architectural design as preventive medicine and in public health
Health economic analyses of latent tuberculosis infection screening and preventive treatment among people living with HIV in lower tuberculosis incidence settings: a systematic review [version 2; peer review: 1 approved, 1 approved with reservations]
INTRODUCTION: In lower tuberculosis (TB) incidence countries (<100 cases/100,000/year), screening and preventive treatment (PT) for latent TB infection (LTBI) among people living with HIV (PLWH) is often recommended, yet guidelines advising which groups to prioritise for screening can be contradictory and implementation patchy. Evidence of LTBI screening cost-effectiveness may improve uptake and health outcomes at reasonable cost. METHODS: Our systematic review assessed cost-effectiveness estimates of LTBI screening/PT strategies among PLWH in lower TB incidence countries to identify model-driving inputs and methodological differences. Databases were searched 1980-2020. Studies including health economic evaluation of LTBI screening of PLWH in lower TB incidence countries (<100 cases/100,000/year) were included. RESULTS: Of 2,644 articles screened, nine studies were included. Cost-effectiveness estimates of LTBI screening/PT for PLWH varied widely, with universal screening/PT found highly cost-effective by some studies, while only targeting to high-risk groups (such as those from mid/high TB incidence countries) deemed cost-effective by others. Cost-effectiveness of strategies screening all PLWH from studies published in the past five years varied from US144,929/quality-adjusted life-year gained (2018 prices). Study quality varied, with inconsistent reporting of methods and results limiting comparability of studies. Cost-effectiveness varied markedly by screening guideline, with British HIV Association guidelines more cost-effective than NICE guidelines in the UK. DISCUSSION: Cost-effectiveness studies of LTBI screening/PT for PLWH in lower TB incidence settings are scarce, with large variations in methods and assumptions used, target populations and screening/PT strategies evaluated. The limited evidence suggests LTBI screening/PT may be cost-effective for some PLWH groups but further research is required, particularly on strategies targeting screening/PT to PLWH at higher risk. Standardisation of model descriptions and results reporting could facilitate reliable comparisons between studies, particularly to identify those factors driving the wide disparity between cost-effectiveness estimates. REGISTRATION: PROSPERO CRD42020166338 (18/03/2020)
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