Spatially Varying Elasticity in Image Registration

2007 ◽  
Vol 46 (03) ◽  
pp. 287-291 ◽  
Author(s):  
A. Franz ◽  
B. Fischer ◽  
S. Kabus
Keyword(s):  
Image Registration ◽  
Elastic Properties ◽  
Displacement Field ◽  
Material Properties ◽  
Real Life ◽  
Two Dimensions ◽  
Image Domain ◽  
Material Parameters ◽  
Registration Scheme ◽  
Spatially Varying

Summary Objectives: In this paper we are concerned with elastic image registration. Usually, elastic approaches assume constant material parameters and result in a smooth displacement field. However, a constant choice has its shortcomings for images with varying elastic properties, like bones and soft tissue. The proposed method allows forspatially varying material properties. Methods: The proposed variational registration scheme is based on a segmentation of the template image. Individual material properties can be assigned to each segmented region. The proposed variable elastic regulariser leads to a displacement field which is adapted to the locally chosen material properties. Results: The capability of this approach is demonstrated by a synthetic and by real-life examples in two dimensions. For all examples the proposed method is compared to a conventional scheme where the material parameters are constants in the entire image domain. Conclusions: A method for non-parametric registration which supports spatially varying elastic properties such as (in)compressibility or Young’s modulus in certain image regions is proposed. It allows for registration results to be more realistic compared to conventional approaches. Also, for a particular structure, an approximated preservation of volume or shape can be achieved.

Modeling the Inflation Response of C57BL/6 Mouse Sclera

2011 ◽  
Author(s):  
Kristin M. Myers ◽  
Thao D. Nguyen
Keyword(s):  
Material Properties ◽  
Soft Tissues ◽  
Ganglion Cells ◽  
The United States ◽  
Small Rodent ◽  
Tissue Samples ◽  
Tissue Microstructure ◽  
Material Parameters ◽  
Meaningful Material

Small rodent models have become increasingly useful to investigate how the mechanical properties of soft tissues may influence disease development. These animal models allow access to aged, diseased, or genetically-altered tissue samples, and through comparisons with wild-type or normal tissue it can be explored how each of these variables influence tissue function. The challenges to deriving meaningful material parameters for these small tissue samples include designing physiologically-relevant mechanical testing protocols and interpreting the experimental load-displacement data in an appropriate constitutive framework to quantify material parameters. This study was motivated by determining the possible role of scleral material properties in the development of glaucomatous damage to the retinal ganglion cells (RGC). Glaucoma is one of the leading causes of blindness in the United States and in the world with an estimate of 60 million people affected by this year [1]. Through exploring mouse models, the overall goal of our work is to determine the role of scleral material properties and scleral tissue microstructure in the pathogenesis of glaucoma.

scholarly journals Dengue, Zika and Chicungunha: The use of a mathematic concept to develop an educational game for helping on fighting important viral diseases

2016 ◽  
Vol 3 (7) ◽  
pp. 127
Author(s):  
T. Dutra ◽  
D.P. Costa ◽  
C.F.S. Barboza ◽  
L. Alves ◽  
H.C. Castro
Keyword(s):  
Real Life ◽  
Computer Game ◽  
Theoretical Concept ◽  
Two Dimensions ◽  
Educational Game ◽  
Main Element ◽  
Viral Diseases ◽  
Mathematical Concepts ◽  
Breeding Sites ◽  
The City

<em>Dengue is the leading cause of viral death worldwide. The vector Aedes aegypti mosquito is also responsible for Zika and Chincungunha transmission, another very compromising viral diseases. As the understanding of the vector life cycle and its habitat is important for preventing and fighting against these diseases, we propose to use a mathematic concept, graphos, and a problem-based situation (the removal of potential breeding sites for mosquitoes in the player city) to design a computational game that may help on spreading information and to stimulate a players proactive virtual and real behavior. Thus this paper describes the design and construction of an educational computer game called "Graphos against mosquitos," based on graphos, a mathematics theoretical concept. We designed the Graphos game using as the main elements: a child, twelve neighborhood blocks, mosquitoes, streets and containers where mosquitoes lay eggs (tires, cans, bottles, plants with water deposits). In the game, the player (Avatar) is the main element that should "walk in" the streets (edges) of the city, removing the potential breeding grounds for mosquitoes in each block (vertices). As this game is based on the mathematics theoretical concept graphos using two dimensions, the city has two distinct vertices that are the beginning and end of it, which discriminate the beginning and end of the game. The player should remove all containers of each street, avoiding mosquitoes growth and passing only one time for each of them. As containers are removed, the player gains points and is prevented to return to the previous street. In this game the removal of all containers that pose risk of becoming mosquito breeding sites, without coming back to the previous street but only forward, is translatable into " graphos language". When finishing the game properly, it opens a final screen where the player is awarded with a medal. On this screen, the player can write his/her name, being invited to act as a "health worker" no longer in virtual form, but in the real life. Through teaching by using computational material ruled by mathematical concepts such as graphos, we hope to stimulate and contribute for fighting and controlling the vector of these serious viral diseases.</em>

scholarly journals A Global Optimization Approach to Solve Multi-Aircraft Routing Problems

2010 ◽  
pp. 237-259
Author(s):  
S.P. Wilson ◽  
M.C. Bartholomew-Biggs ◽  
S.C. Parkhurst
Keyword(s):  
Global Optimization ◽  
Real Life ◽  
Two Dimensions ◽  
Numerical Results ◽  
Solution Technique ◽  
Optimization Approach ◽  
Routing Problem ◽  
Aircraft Routing ◽  
Optimization Calculation ◽  
Multiple Routes

This chapter describes the formulation and solution of a multi-aircraft routing problem which is posed as a global optimization calculation. The chapter extends previous work (involving a single aircraft using two dimensions) which established that the algorithm DIRECT is a suitable solution technique. The present work considers a number of ways of dealing with multiple routes using different problem decompositions. A further enhancement is the introduction of altitude to the problems so that full threedimensional routes can be produced. Illustrative numerical results are presented involving up to three aircraft and including examples which feature routes over real-life terrain data.

Simulation Study of Granular Compaction Dynamics under Vertical Tapping

2007 ◽  
Vol 555 ◽  
pp. 107-112 ◽  
Author(s):  
D. Arsenović ◽  
S.B. Vrhovac ◽  
Z.M. Jakšić ◽  
Lj. Budinski-Petković ◽  
A. Belić
Keyword(s):  
Numerical Simulation ◽  
Molecular Dynamics ◽  
Friction Coefficient ◽  
Simulation Study ◽  
Material Properties ◽  
Two Dimensions ◽  
Second Phase ◽  
Hard Disks ◽  
Compaction Process ◽  
Granular Compaction

We study by numerical simulation the compaction dynamics of frictional hard disks in two dimensions, subjected to vertical shaking. Shaking is modeled by a series of vertical expansions of the disk packing, followed by dynamical recompression of the assembly under the action of gravity. The second phase of the shake cycle is based on an efficient event−driven molecular−dynamics algorithm. We analyze the compaction dynamics for various values of friction coefficient and coefficient of normal restitution. We find that the time evolution of the density is described by ρ(t)=ρ∞ − ρEα[−(t/τ)α], where Eα denotes the Mittag−Leffler function of order 0<α<1. The parameter τ is found to decay with tapping intensity Γ according to a power law τ ∝ Γ−γ , where parameter γ is almost independent of the material properties of grains. Also, an expression for the grain mobility during compaction process has been obtained.

Entrepreneurial learning as an effectual process

2019 ◽  
Vol 26 (6) ◽  
pp. 631-647 ◽  
Author(s):  
Dag Håkon Haneberg
Keyword(s):  
Real Life ◽  
Two Dimensions ◽  
Organisational Learning ◽  
Three Dimensions ◽  
New Venture ◽  
Entrepreneurial Learning ◽  
Content Type ◽  
Process Characteristics ◽  
One Year ◽  
Multiple Actors

Purpose The purpose of this paper is to address how entrepreneurial learning may be understood as an effectual process in the early phase of venture creation. Design/methodology/approach Previous research is used to develop a conceptual frame of reference, which is further developed through a longitudinal qualitative case study of five new venture teams. Conceptualising these teams’ learning as sequences of events over a one-year period provides rich insight from real-life processes. Findings A conceptual model of how entrepreneurial learning may be understood as an effectual process is presented. The interactions and interdependencies between nine process characteristics along three main dimensions in the process, activity, multiple actors and context-dependent, demonstrate how the process tie together as a whole. Research limitations/implications The present paper argues for further cross-fertilisation of entrepreneurial learning and effectuation research and showcases how studies of entrepreneurial learning may contribute to organisational learning in entrepreneurial ventures. The conceptualisation of characteristics and dimensions aims to support future process studies by suggesting a framework for analysing process events in longitudinal studies. Originality/value Previous research has already established how activities are central to entrepreneurial learning and emphasised that what constitutes the two dimensions of multiple actors and context-dependence is important. The present paper contributes to entrepreneurial learning with an enhanced understanding of why and how the three dimensions are important as well as interdependent and mutually interactive. The present paper also contributes to organisational learning by extending the understanding of learning in emerging entrepreneurial organisations.

scholarly journals A design-based approach to support and nurture open educational practices

2017 ◽  
Vol 12 (1) ◽  
pp. 1-20 ◽  
Author(s):  
Shironica P. Karunanayaka ◽  
Som Naidu
Keyword(s):  
Belief Systems ◽  
Real Life ◽  
Two Dimensions ◽  
Educational Resources ◽  
Pedagogical Practices ◽  
Educational Practices ◽  
Process Data ◽  
Instructional Resources ◽  
Content Type ◽  
Open Educational Practices

Purpose A critical attribute of open educational practices (OEP) is the pursuit of open scholarship which comprises the release of educational resources under an open licence scheme that permits no-cost access, use, reuse, adaptation, retention and redistribution to others. The degree of openness in relation to this attribute will depend on the context and culture of the place and the people in it. When left to chance, the adoption and practice of open scholarship by educators is at best sketchy. For optimum impact, a design-based approach is essential. A central focus of such an approach will need to target educators’ belief systems and practices about their scholarship. Any such work will involve researchers collaborating with practitioners in real-life settings to improve educational practices through iterative analysis, design, development and implementation. The purpose of this paper is to report on how the development and use of such a design-based approach, implemented by the Open University of Sri Lanka, impacted the adoption and uptake of open scholarship among teachers in the Sri Lankan school system in terms of changes in their use of instructional resources, pedagogical thinking and pedagogical practices. Design/methodology/approach The study adopted a design-based research (DBR) approach (Reeves, 2006), which involved researchers collaboratively working with practitioners in real-life settings to improve their educational practices along three aspects – instructional resource use, pedagogical perspectives and pedagogical practices. Based on the four stages of the DBR approach – analysis, solution, testing and refinement, and reflection, a professional development intervention programme was designed and implemented to support teachers on the integration of open educational resources (OER) and adoption of OEP in their teaching-learning process. Data collected throughout the process using multiple strategies such as questionnaire surveys, concept mapping, lesson plans, focus group interviews, self-reflections and “stories”, were analyzed using both qualitative and quantitative methods. Findings By the end of the intervention, significant changes were observed in teachers’ use of instructional resources, their pedagogical thinking and pedagogical practices. While resource usage has shifted from no or low usage of OER to reuse, revise, remix and creation of OER, the pedagogical thinking and practices of teachers moved from a content-centric and individualized patterns to more constructivist, context centric and collaborative ways. The diffusion of OEP was prominent along two dimensions – enhancements in the individual practices in innovative OER use as well as collaborative practices of sharing of resources, knowledge and good practices. Practical implications The systematic and flexible methodology adopted based on the DBR approach via a framework designed as a contextualized, process oriented and a self-reflective enquiry has been very useful to support changes in OEP among practitioners over time. Originality/value This iterative process allowed the researchers to function as “designers”, while investigating real-life issues in collaboration with the practitioners through reflective enquiry to further refine innovative practices towards OEP. This provides valuable insights for improved design solutions for future interventions in similar contexts.

scholarly journals Inverse Approach to Evaluate the Tubular Material Parameters Using the Bulging Test

2015 ◽  
Vol 2015 ◽  
pp. 1-9 ◽  
Author(s):  
Yulong Ge ◽  
Xiaoxing Li ◽  
Lihui Lang
Keyword(s):  
Finite Element ◽  
Constitutive Model ◽  
Material Properties ◽  
Hybrid Algorithm ◽  
Material Parameters ◽  
Inverse Approach ◽  
Material Evaluation ◽  
Levenberg Marquardt ◽  
Bulging Test ◽  
Inverse Procedure

Tubular material parameters are required for both part manufactory process planning and finite element simulations. The bulging test is one of the most credible ways to detect the property parameters for tubular material. The inverse approach provides more effective access to the accurate material evaluation than with direct identifications. In this paper, a newly designed set of bulging test tools is introduced. An inverse procedure is adopted to determine the tubular material properties in Krupkowski-Swift constitutive model of material deformation using a hybrid algorithm that combines the differential evolution and Levenberg-Marquardt algorithms. The constitutive model’s parameters obtained from the conventional and inverse methods are compared, and this comparison shows that the inverse approach is able to offer more information with higher reliability and can simplify the test equipment.

Lifetime Assessments of an Old Westinghouse-Design Steam Chest

2012 ◽  
Author(s):  
Sazzadur Rahman ◽  
Waheed Abbasi ◽  
Thomas W. Joyce
Keyword(s):  
Steam Turbine ◽  
Material Properties ◽  
Power Plants ◽  
Real Life ◽  
Cyclic Stress ◽  
Steam Turbines ◽  
Reliable Operation ◽  
Steady State Operation ◽  
Different Temperatures ◽  
Transient Events

Fossil steam turbines were designed for approximately thirty years of reliable operation based on a normal duty cycle. During operation, highly stressed components of steam turbine power plants undergo a change in material properties due to cyclic stress and exposure to different temperatures. Among all the components of a steam turbine, the steam chest is affected the most as it experiences a wide variation of stresses and loads during transient events and steady-state operation. These factors can strongly influence the metallurgical condition and overall reliable life of steam chests. In this paper, Siemens’ overall approach for lifetime assessments will be discussed with a real life example on a 40 year old Westinghouse-design steam chest. The methodology and the findings from the assessment are also discussed.

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