14,730 research outputs found
STEP/XML based macro data representation for parametric CAD model exchange
There is tremendous need in collaborative design today for the integration of heterogeneous CAx systems. This general practice has serious shortcomings like design discontinuity, limited parallelisation, loss of information, and conversion errors. To overcome these shortcomings, macro-parametric approach (MPA), which is a history-based method of parametric CAD model exchange, has been proposed. The macro-parametric approach is a way to achieve compatible CAD model exchange amongst a variety of mutually incompatible CAD systems. CAD models can be exchanged in the form of a macro file that comprises a sequence of modeling commands. A standard macro file that contains a set of event-driven commands can transfer the designer intent such as parameters, features and constraints. Currently, STEP (STandard for the Exchange of Product model data) as an international standard (ISO-10303, Industrial automation systems and integration - Product data representation and exchange) for the computer-interpretable representation and the exchange of product model data is widely used. STEP is becoming the 'lingua franca' in the area of modelling and exchanging product data. One remaining problem of the using STEP as a neutral format is that it does not retain parametric information such as the designer intent but only the pure boundary representation (B-rep) of the CAD model. The B-rep model without parametric information presents difficulties for engineering changes and it may also lead to an unexpected distortion of shape. This research aims to investigate an exchange method that uses STEP/XML (extensible mark-up) technology to express a set of standard modeling commands extracted from CAD models created by Autodesk InventorTM, to enable the same CAD models are readable and shareable with other CAD application systems
A Systematic Review of Strong Gravitational Lens Modeling Software
Despite expanding research activity in gravitational lens modeling, there is
no particular software which is considered a standard. Much of the
gravitational lens modeling software is written by individual investigators for
their own use. Some gravitational lens modeling software is freely available
for download but is widely variable with regard to ease of use and quality of
documentation. This review of 13 software packages was undertaken to provide a
single source of information. Gravitational lens models are classified as
parametric models or non-parametric models, and can be further divided into
research and educational software. Software used in research includes the
GRAVLENS package (with both gravlens and lensmodel), Lenstool, LensPerfect,
glafic, PixeLens, SimpLens, Lensview, and GRALE. In this review, GravLensHD,
G-Lens, Gravitational Lensing, lens and MOWGLI are categorized as educational
programs that are useful for demonstrating various aspects of lensing. Each of
the 13 software packages is reviewed with regard to software features
(installation, documentation, files provided, etc.) and lensing features (type
of model, input data, output data, etc.) as well as a brief review of studies
where they have been used. Recent studies have demonstrated the utility of
strong gravitational lensing data for mass mapping, and suggest increased use
of these techniques in the future. Coupled with the advent of greatly improved
imaging, new approaches to modeling of strong gravitational lens systems are
needed. This is the first systematic review of strong gravitational lens
modeling software, providing investigators with a starting point for future
software development to further advance gravitational lens modeling research
Cost-effectiveness analysis in R using a multi-state modelling survival analysis framework: a tutorial
This tutorial provides a step-by-step guide to performing cost-effectiveness analysis using a multi-state modelling approach. Alongside the tutorial we provide easy-to-use functions in the statistics package R. We argue this multi-state modelling approach using a package such as R has advantages over approaches where models are built in a spreadsheet package. In particular, using a syntax-based approach means there is a written record of what was done and the calculations are transparent. Reproducing the analysis is straightforward as the syntax just needs to be run again. The approach can be thought of as an alternative way to build a Markov decision analytic model, which also has the option to use a state-arrival extended approach if the Markov property does not hold. In the state-arrival extended multi-state model a covariate that represents patients’ history is included allowing the Markov property to be tested. We illustrate the building of multi-state survival models, making predictions from the models and assessing fits. We then proceed to perform a cost-effectiveness analysis including deterministic and probabilistic sensitivity analyses. Finally, we show how to create two common methods of visualising the results, namely cost-effectiveness planes and cost-effectiveness acceptability curves. The analysis is implemented entirely within R. It is based on adaptions to functions in the existing R package mstate, to accommodate parametric multi-state modelling which facilitates extrapolation of survival curves
MatchIt: Nonparametric Preprocessing for Parametric Causal Inference
MatchIt implements the suggestions of Ho, Imai, King, and Stuart (2007) for improving parametric statistical models by preprocessing data with nonparametric matching methods. MatchIt implements a wide range of sophisticated matching methods, making it possible to greatly reduce the dependence of causal inferences on hard-to-justify, but commonly made, statistical modeling assumptions. The software also easily fits into existing research practices since, after preprocessing data with MatchIt, researchers can use whatever parametric model they would have used without MatchIt, but produce inferences with substantially more robustness and less sensitivity to modeling assumptions. MatchIt is an R program, and also works seamlessly with Zelig.
Digitally interpreting traditional folk crafts
The cultural heritage preservation requires that objects persist throughout time to continue to communicate an intended meaning. The necessity of computer-based preservation and interpretation of traditional folk crafts is validated by the decreasing number of masters, fading technologies, and crafts losing economic ground. We present a long-term applied research project on the development of a mathematical basis, software tools, and technology for application of desktop or personal fabrication using compact, cheap, and environmentally friendly fabrication devices, including '3D printers', in traditional crafts. We illustrate the properties of this new modeling and fabrication system using several case studies involving the digital capture of traditional objects and craft patterns, which we also reuse in modern designs. The test application areas for the development are traditional crafts from different cultural backgrounds, namely Japanese lacquer ware and Norwegian carvings. Our project includes modeling existing artifacts, Web presentations of the models, automation of the models fabrication, and the experimental manufacturing of new designs and forms
A Project Based Approach to Statistics and Data Science
In an increasingly data-driven world, facility with statistics is more
important than ever for our students. At institutions without a statistician,
it often falls to the mathematics faculty to teach statistics courses. This
paper presents a model that a mathematician asked to teach statistics can
follow. This model entails connecting with faculty from numerous departments on
campus to develop a list of topics, building a repository of real-world
datasets from these faculty, and creating projects where students interface
with these datasets to write lab reports aimed at consumers of statistics in
other disciplines. The end result is students who are well prepared for
interdisciplinary research, who are accustomed to coping with the
idiosyncrasies of real data, and who have sharpened their technical writing and
speaking skills
Parametric Modeling of Machine Tools
The chapter deals with the problems of machine tool computer-aided design (CAD) based on the methods and means of parameterization for the main components of metal-cutting machine and equipment in the CAD “APM WinMachine” environment. The models and algorithms of parametric modeling for the configurations of machine tool milling and multioperational type by the criteria of maximum rigidity and minimum reduced load on the front spindle support are developed. The express procedure for generating the transverse layout of the main drive in the multivariate design mode has been implemented
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