Primary Resonance Behavior of Expanded Polymer Cushion Material Under Low-Intensity Harmonic Excitations

The demand to lower costs and reduce the amount of packaging materials utilized in a packaged-product system has placed increased importance on the development of tools to model the behavior of packaging systems. In this dissertation, the free and forced vibration response of a nonlinear, distributed-parameter model of a viscoelastic rod with an applied tip-mass is used to investigate the response of expanded polymer cushion materials to low-intensity harmonic excitations. The rod and tip-mass represent an idealized packaged product system. A nonlinear model is developed from constitutive relations. A classical Maxwell-Weichert model, represented via a Prony series, is used to model the viscoelastic behavior. The model parameters are experimentally identified through the use of static and quasi-static test results. Three different solution techniques are applied, free and forced vibration solutions derived, and used to study the behavior of an idealized packaging system containing Nova Chemicals\u27 Arcel foam. Each solution is validated against experimental results. The first part of this work focuses on the study of the system response linearized about a static equilibrium position. The exact solution to the free and forced vibration problem is considered first, followed by the development of a reduced-order model (ROM). It is observed that, although three Prony series terms are deemed sufficient to fit the static test data, convergence of the dynamic response and study of the storage and loss moduli necessitate the use of additional Prony series terms. Comparison of the ROM solution with that of the exact solution are used to determine the number of modal equations needed for the ROM to accurately capture the steady-state dynamic behavior of the packaging system. It is also shown that both models are able to predict the modal frequencies and the primary resonance response at low acceleration levels with reasonable accuracy given the non-homogeneity and density variation observed in the specimens. Higher acceleration inputs result in softening nonlinear responses highlighting the need for a solution to the nonlinear elastic model. It is concluded that, although proven in its ability to absorb high frequency inputs (impact and shock), Arcel is not an ideal material for energy dissipation at lower frequencies, especially close to the first modal frequency of the mass/rod system. The second part of the dissertation covers solution of the nonlinear model. The governing partial differential equation is discretized into a single-mode nonlinear ordinary differential equation (ODE). Solution of the nonlinear ODE is analytically approximated using the method of multiple scales. Results show that the single-mode analytical solution is capable of capturing the nonlinear bending behavior missed by the linearized model. It is also shown that limitations due to the system identification data collection method affect the ability of the model to capture the degree of nonlinearity present at lower strain levels. While this limitation has no observable effect on the linearized system response, nonlinear modeling can benefit from further work done in the low strain characterization of expanded polymer foam

Efficient parameter search for qualitative models of regulatory networks using symbolic model checking

Investigating the relation between the structure and behavior of complex biological networks often involves posing the following two questions: Is a hypothesized structure of a regulatory network consistent with the observed behavior? And can a proposed structure generate a desired behavior? Answering these questions presupposes that we are able to test the compatibility of network structure and behavior. We cast these questions into a parameter search problem for qualitative models of regulatory networks, in particular piecewise-affine differential equation models. We develop a method based on symbolic model checking that avoids enumerating all possible parametrizations, and show that this method performs well on real biological problems, using the IRMA synthetic network and benchmark experimental data sets. We test the consistency between the IRMA network structure and the time-series data, and search for parameter modifications that would improve the robustness of the external control of the system behavior

Individual and Contextual Factors Associated with Low Childhood Immunisation Coverage in Sub-Saharan Africa: A Multilevel Analysis

Background: In 2010, more than six million children in sub-Saharan Africa did not receive the full series of three doses of the diphtheria-tetanus-pertussis vaccine by one year of age. An evidence-based approach to addressing this burden of un-immunised children requires accurate knowledge of the underlying factors. We therefore developed and tested a model of childhood immunisation that includes individual, community and country-level characteristics. Method and Findings: We conducted multilevel logistic regression analysis of Demographic and Health Survey data for 27,094 children aged 12–23 months, nested within 8,546 communities from 24 countries in sub-Saharan Africa. According to the intra-country and intra-community correlation coefficient implied by the estimated intercept component variance, 21% and 32% of the variance in unimmunised children were attributable to country- and community-level factors respectively. Children born to mothers (OR 1.35, 95%CI 1.18 to 1.53) and fathers (OR 1.13, 95%CI 1.12 to 1.40) with no formal education were more likely to be unimmunised than those born to parents with secondary or higher education. Children from the poorest households were 36% more likely to be unimmunised than counterparts from the richest households. Maternal access to media significantly reduced the odds of children being unimmunised (OR 0.94, 95%CI 0.94 to 0.99). Mothers with health seeking behaviours were less likely to have unimmunised children (OR 0.56, 95%CI 0.54 to 0.58). However, children from urban areas (OR 1.12, 95% CI 1.01 to 1.23), communities with high illiteracy rates (OR 1.13, 95% CI 1.05 to 1.23), and countries with high fertility rates (OR 4.43, 95% CI 1.04 to 18.92) were more likely to be unimmunised. Conclusion: We found that individual and contextual factors were associated with childhood immunisation, suggesting that public health programmes designed to improve coverage of childhood immunisation should address people, and the communities and societies in which they live

Flexible Working and Performance: A Systematic Review of the Evidence for a Business Case

Interest in the outcomes of flexible working arrangements dates from the mid 1970s, when researchers attempted to assess the impact of flexitime on worker performance. This paper reviews the literature on the link between flexible working arrangements and performance related outcomes. Taken together, the evidence fails to demonstrate a business case for the use of flexible working arrangements. This paper attempts to explain the findings by analysing the theoretical and methodological perspectives adopted, as well as the measurements and designs used. In doing so, gaps in this vast and disparate literature are identified and a research agenda is developed

2018 Research & Innovation Day Program

A one day showcase of applied research, social innovation, scholarship projects and activities.https://first.fanshawec.ca/cri_cripublications/1005/thumbnail.jp

Design, optimization and control in systems and synthetic biology

How good is our understanding of the way cells treat information and make decisions? To what extend our current understanding enables us to reprogram and control the way cells behave? In this manuscript I describe several approaches developed for the computational analysis of the dynamics of biological networks. In particular I present work done on (i) the analysis of large gene networks with partial information on parameter values, (ii) the use of specification languages to express observations or desired properties in an abstract manner and efficiently search for parameters satisfying these properties, and (iii) recent efforts to use models to drive gene expression in real-time at the cellular level

Cells driven by computers: long-term model predictive control of gene expression in yeast (keynote talk)

International audienceReal-time control has been recently applied to drive actual intracellular processes with unprecedented accuracy. Here we introduce the motivations for the development of these approaches and then present a platform for the real-time control of gene expression in yeast cells. We conclude by surveying related works and discussing possible future directions