197 research outputs found
GRINN: A Physics-Informed Neural Network for solving hydrodynamic systems in the presence of self-gravity
Modeling self-gravitating gas flows is essential to answering many
fundamental questions in astrophysics. This spans many topics including
planet-forming disks, star-forming clouds, galaxy formation, and the
development of large-scale structures in the Universe. However, the nonlinear
interaction between gravity and fluid dynamics offers a formidable challenge to
solving the resulting time-dependent partial differential equations (PDEs) in
three dimensions (3D). By leveraging the universal approximation capabilities
of a neural network within a mesh-free framework, physics informed neural
networks (PINNs) offer a new way of addressing this challenge. We introduce the
gravity-informed neural network (GRINN), a PINN-based code, to simulate 3D
self-gravitating hydrodynamic systems. Here, we specifically study
gravitational instability and wave propagation in an isothermal gas. Our
results match a linear analytic solution to within 1\% in the linear regime and
a conventional grid code solution to within 5\% as the disturbance grows into
the nonlinear regime. We find that the computation time of the GRINN does not
scale with the number of dimensions. This is in contrast to the scaling of the
grid-based code for the hydrodynamic and self-gravity calculations as the
number of dimensions is increased. Our results show that the GRINN computation
time is longer than the grid code in one- and two- dimensional calculations but
is an order of magnitude lesser than the grid code in 3D with similar accuracy.
Physics-informed neural networks like GRINN thus show promise for advancing our
ability to model 3D astrophysical flows
An assessment of technology forecasting: Revisiting earlier analyses on dye-sensitized solar cells (DSSCs)
© 2018 Elsevier Inc. The increasingly uncertain dynamics of technological change pose special challenges to traditional technology forecasting tools, which facilitates future-oriented technology analysis (FTA) tools to support the policy processes in the fields of science, technology & innovation (ST&I) and the management of technology (MOT), rather than merely forecasting incremental advances via analyses of continuous trends. Dye-sensitized solar cells are a promising third-generation photovoltaic technology that can add functionality and lower costs to enhance the value proposition of solar power generation in the early years of the 21st century. Through a series of technological forecasting studies analyzing the R&D patterns and trends in Dye-sensitized solar cells technology over the past several years, we have come to realize that validating previous forecasts is useful for improving ST&I policy processes. Yet, rarely do we revisit forecasts or projections to ascertain how well they fared. Moreover, few studies pay much attention to assessing FTA techniques. In this paper, we compare recent technology activities with previous forecasts to reveal the influencing factors that led to differences between past predictions and actual performance. Beyond our main aim of checking accuracy, in this paper we also wish to gain some sense of how valid those studies were and whether they proved useful to others in some ways
Optimising the use of new data streams for making epidemiological inferences in veterinary epidemiology : a thesis presented in partial fulfilment of the requirements for the degree of PhD in Veterinary Epidemiology at Massey University, Manawatu, New Zealand
Many âbig dataâ streams have recently become available in animal health
disciplines. While these data may be able to provide valuable epidemiological
information, researchers are at risk of making erroneous inferences if
limitations in these data are overlooked. This thesis focused on understanding
the better use of two data streamsâlivestock movement records and genetic
sequence data.
The first study analysed national dairy cattle movement data in New
Zealand to explore whether regionalisation of the country based on bovine
tuberculosis risk influenced trade decisions. The results suggested that the
observed livestock movement patterns could be explained by the majority of,
but not all, farmers avoiding purchasing cattle from high disease risk areas.
The second study took an alternative approachâqualitative interviewsâto
understanding farmersâ livestock purchasing practices. This study suggested
that farmers are not necessarily concerned with disease status of source
farms and that it may be the reliance on stock agents to facilitate trade that
creates the observed livestock movement patterns in New Zealand. The
findings from this study also implied that various demographic and
production characteristics of animals may influence farmersâ livestock selling
practices, which were quantitatively verified in the third study analysing
livestock movement data and animal production data. These studies not only
showed that analyses based solely on âbig dataâ can be misleading but also
provided useful information necessary to predict future livestock movement
patterns. The final study evaluated the performance of various genetic
sequence sampling strategies in making phylodynamic inferences. We showed
that using all available genetic samples can be not only computationally
expensive, but also may lead to erroneous inferences. The results also
suggested that strategies for sampling genetic sequences for phylodynamic
analyses may need to be tailored based on epidemiological characteristics of
each epidemic
Research on key techniques of flexible workflow based approach to supporting dynamic engineering design process
Error on title page - correct year of award is 2015 not 2013.Engineering design process (EDP) is a highly dynamic and creative process, and the capability in managing an EDP is considered as a major differentiating factor between competing enterprises. The most important prerequisite to establish an engineering design process excellence is a proper management of all the design process activities and the associated information. The most important impact in recent years on the EDP and on the activities of designers has come from computer-based data processing. Workflow, the automation of a business processes in whole or part, is a useful tool for modelling and managing a business process which can be reprensented by a workflow model (computerized process definition). By considering the dynamic characteristics of EDP, an EDP management system must be flexible enough to support the creative and dynamic EDP. After the introduction of engineering design process and its new trend, as well as flexible workflow technology, reviews of both engineering design process and its supporting flexible workflow technology shows that there is a need for a holistic framework to automate and coordinate design activities in the creative and dynamic EDP, and the flexible workflow technology should also be improved comprehensively in flexibility and intelligence in order to support better engineering design management. By introducing the relations between the EDP and flexible workflow, a virtual workflow and an autonomic flexible workflow built upon autonomic computing is investigated, and an innovative engineering design process management framework based on multi-autonomic objects flexible workflow is proposed. For the flexible workflow modelling in the framework, a dynamic instance-based flexible workflow modelling method is proposed for multi-autonomic objects flexible workflow. In order to improve the intelligence of flexible workflow, after examining the principle of flexible workflow intelligence in flexible workflow, a new flexible workflow autonomic object intelligence algorithm based on both extended Mamdani fuzzy reasoning and neural network is proposed, weighted fuzzy reasoning algorithm, as well as precise and fuzzy hybrid knowledge reasoning algorithm is designed; a bionic flexible workflow adaptation algorithm is proposed to improve the intelligence of autonomic object flexible workflow further. According to the characteristic of EDP, such as cross-enterprises and geographical distribution, and in order to realize the flexible execution of distributed flexible workflow engine, a distributed flexible workflow engine architecture based on web service is proposed and a flexible workflow model description method based on extended WSDL (Web Service Description Language) and BPEL4WS (Business Process Execution Language for Web Services) is proposed. A flexible workflow prototype system supporting engineering design process is implemented according to the proposed EDP management framework in Microsoft VS.Net 2005 environment. The framework is demonstrated by the application in an EDP of a MTO company, and it shows that the proposed framework can support the creative and dynamic process in an efficient way. Finally, the strengths and weakness of the framework as well as the prototype system is discussed based on the results of the evaluation, and the proposed areas of future work are given.Engineering design process (EDP) is a highly dynamic and creative process, and the capability in managing an EDP is considered as a major differentiating factor between competing enterprises. The most important prerequisite to establish an engineering design process excellence is a proper management of all the design process activities and the associated information. The most important impact in recent years on the EDP and on the activities of designers has come from computer-based data processing. Workflow, the automation of a business processes in whole or part, is a useful tool for modelling and managing a business process which can be reprensented by a workflow model (computerized process definition). By considering the dynamic characteristics of EDP, an EDP management system must be flexible enough to support the creative and dynamic EDP. After the introduction of engineering design process and its new trend, as well as flexible workflow technology, reviews of both engineering design process and its supporting flexible workflow technology shows that there is a need for a holistic framework to automate and coordinate design activities in the creative and dynamic EDP, and the flexible workflow technology should also be improved comprehensively in flexibility and intelligence in order to support better engineering design management. By introducing the relations between the EDP and flexible workflow, a virtual workflow and an autonomic flexible workflow built upon autonomic computing is investigated, and an innovative engineering design process management framework based on multi-autonomic objects flexible workflow is proposed. For the flexible workflow modelling in the framework, a dynamic instance-based flexible workflow modelling method is proposed for multi-autonomic objects flexible workflow. In order to improve the intelligence of flexible workflow, after examining the principle of flexible workflow intelligence in flexible workflow, a new flexible workflow autonomic object intelligence algorithm based on both extended Mamdani fuzzy reasoning and neural network is proposed, weighted fuzzy reasoning algorithm, as well as precise and fuzzy hybrid knowledge reasoning algorithm is designed; a bionic flexible workflow adaptation algorithm is proposed to improve the intelligence of autonomic object flexible workflow further. According to the characteristic of EDP, such as cross-enterprises and geographical distribution, and in order to realize the flexible execution of distributed flexible workflow engine, a distributed flexible workflow engine architecture based on web service is proposed and a flexible workflow model description method based on extended WSDL (Web Service Description Language) and BPEL4WS (Business Process Execution Language for Web Services) is proposed. A flexible workflow prototype system supporting engineering design process is implemented according to the proposed EDP management framework in Microsoft VS.Net 2005 environment. The framework is demonstrated by the application in an EDP of a MTO company, and it shows that the proposed framework can support the creative and dynamic process in an efficient way. Finally, the strengths and weakness of the framework as well as the prototype system is discussed based on the results of the evaluation, and the proposed areas of future work are given
3-D Modelling of Biological Systems for Biomimetics
With the advanced development of computer-based enabling technologies,
many engineering, medical, biology, chemistry, physics and food
science etc have developed to the unprecedented levels, which lead to
many research and development interests in various multi-discipline
areas. Among them, biomimetics is one of the most promising and
attractive branches of study. Biomimetics is a branch of study that
uses biological systems as a model to develop synthetic systems. To
learn from nature, one of the fundamental issues is to understand
the natural systems such animals, insects, plants and human beings
etc. The geometrical characterisation and representation of natural
systems is an important fundamental work for biomimetics research.
3D modeling plays a key role in the geometrical characterisation and
representation, especially in computer graphical visualization. This
chapter firstly presents the typical procedure of 3D modelling methods
and then reviews the previous work of 3D geometrical modelling
techniques and systems developed for industrial, medical and animation
applications. Especially the chapter discusses the problems associated
with the existing techniques and systems when they are applied to 3D
modelling of biological systems. In addition, the chapter also presents
two case studies of authorsâ own work. Based upon the discussions, the
chapter proposes some areas of research interests in 3D modelling of
biological systems and for Biomimetics
Modeling, Simulation and Data Processing for Additive Manufacturing
Additive manufacturing (AM) or, more commonly, 3D printing is one of the fundamental elements of Industry 4.0. and the fourth industrial revolution. It has shown its potential example in the medical, automotive, aerospace, and spare part sectors. Personal manufacturing, complex and optimized parts, short series manufacturing and local on-demand manufacturing are some of the current benefits. Businesses based on AM have experienced double-digit growth in recent years. Accordingly, we have witnessed considerable efforts in developing processes and materials in terms of speed, costs, and availability. These open up new applications and business case possibilities all the time, which were not previously in existence. Most research has focused on material and AM process development or effort to utilize existing materials and processes for industrial applications. However, improving the understanding and simulation of materials and AM process and understanding the effect of different steps in the AM workflow can increase the performance even more. The best way of benefit of AM is to understand all the steps related to thatâfrom the design and simulation to additive manufacturing and post-processing ending the actual application.The objective of this Special Issue was to provide a forum for researchers and practitioners to exchange their latest achievements and identify critical issues and challenges for future investigations on âModeling, Simulation and Data Processing for Additive Manufacturingâ. The Special Issue consists of 10 original full-length articles on the topic
Modeling and Simulation in Engineering
This book provides an open platform to establish and share knowledge developed by scholars, scientists, and engineers from all over the world, about various applications of the modeling and simulation in the design process of products, in various engineering fields. The book consists of 12 chapters arranged in two sections (3D Modeling and Virtual Prototyping), reflecting the multidimensionality of applications related to modeling and simulation. Some of the most recent modeling and simulation techniques, as well as some of the most accurate and sophisticated software in treating complex systems, are applied. All the original contributions in this book are jointed by the basic principle of a successful modeling and simulation process: as complex as necessary, and as simple as possible. The idea is to manipulate the simplifying assumptions in a way that reduces the complexity of the model (in order to make a real-time simulation), but without altering the precision of the results
Automating assessment of human embryo images and time-lapse sequences for IVF treatment
As the number of couples using In Vitro Fertilization (IVF) treatment to give birth increases, so too does the need for robust tools to assist embryologists in selecting the highest quality embryos for implantation. Quality scores assigned to embryonic structures are critical markers for predicting implantation potential of human blastocyst-stage embryos. Timing at which embryos reach certain cell and development stages in vitro also provides valuable information about their development progress and potential to become a positive pregnancy. The current workflow of grading blastocysts by visual assessment is susceptible to subjectivity between embryologists. Visually verifying when embryo cell stage increases is tedious and confirming onset of later development stages is also prone to subjective assessment. This thesis proposes methods to automate embryo image and time-lapse sequence assessment to provide objective evaluation of blastocyst structure quality, cell counting, and timing of development stages
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