A Comparison of Information Passing Strategies in System Level Modeling

Frameworks for modeling the communication and coordination of subsystem stakeholders are valuable for the synthesis of large engineering systems. However, these frameworks can be resource intensive and challenging to implement. This paper compares three frameworks, Multidisciplinary Design Optimization (MDO), traditional Game Theory, and a Modified Game Theoretic approach on the form and flow of information passed between subsystems. This paper considers the impact of “complete” information sharing by determining the effect of merging subsystems. Comparisons are made of convergence time and robustness in a case study of the design of a satellite. Results comparing MDO in two- and three-player scenarios indicate that, when the information passed between subsystems is sufficiently linear, the two scenarios converge in statistically indifferent number of iterations, but additional “complete” information does reduce variability in the number of iterations. The Modified Game Theoretic approach converges to a smaller region of the Pareto set compared to MDO, but does so without a system facilitator. Finally, a traditional Game Theoretic approach converges to a limit cycle rather than a fixed point for the given initial design. There may also be a region of attraction for convergence for a traditional Game Theoretic approach.National Science Foundation (U.S.) (Award DMI-0547629

Reducing error and measurement time in impedance spectroscopy using model based optimal experimental design

In this work we introduce several novel tools for the reduction of errors in parameters estimated with electrochemical impedance spectroscopy experiments. An optimization strategy is developed that minimizes an estimate of the errors on the parameters while bounding the experimental time. The approach is also used to reduce experimental time while keeping a bound on the parameter errors. This feature is particularly critical in systems changing significantly within the experimental time. The paper uses a fuel cell electrode model to test this methodology and presents a real time algorithm for coupling experiment with the parameter estimation and experimental optimization

755 Rat engineered heart tissue is a novel in vitro model to evaluate cardiomyocyte proliferation and fibroblast activation after injury

Abstract Aims Adult mammals, including humans, fail to regenerate the majority of the lost cardiomyocytes (CMs) that are replaced with scar tissue after injury. This lack of regenerative response is due to the loss of proliferative capacity of adult CMs which in mice occurs 7 days after birth. An in vitro model that recapitulates these changes has not been developed yet. Using rat engineered heart tissues (rEHTs) we have developed a custom-made cryoinjury system to test the hypothesis that maturation of CMs in EHTs regulates the proliferative response of CMs after injury. Methods rEHT were generated using neonatal rat heart cells. A discrete lesion was produced on the mid-section of mature (Day 18) and immature (Day 6) EHTs using a custom-made system based on liquid nitrogen and a 23G needle and medium was supplemented with EdU for 48 h. Results Cryoinjury in mature EHTs produces a localized injury, preserving their residual contractile activity that does not recover over time. We observed a significant increase of EdU+CMs post injury (6.3 ± 1.9% vs. 10.1 ± 1.6%) without significant changes in Ki67+ and pH3+ CMs suggesting that cryoinjury in mature rEHTs induces DNA synthesis but not CM proliferation. Injury in mature EHTs induced also significant proliferation and activation of fibroblasts with collagen deposition. Interestingly, cryoinjury performed in immature EHTs stimulated a significant proliferative response in CMs Conclusions Similar to adult rodents, we show that cryoinjury induces DNA synthesis in CMs without proliferative response and contractile recovery. On the other hand, cryoinjury in immature EHTs leads to CMs proliferation. Moreover, mature EHT fibroblast response to injury retraces the activation progression of cardiac fibroblast after infarction characterized by proliferation, increase of activation markers, increase of collagen deposition suggesting EHTs as a novel model to investigate the biology of cardiac regeneration upon injury

An information-passing strategy for achieving Pareto optimality in the design of complex systems

Abstract As engineering systems grow in complexity, it becomes more challenging to achieve system-level designs that effectively balance the trade-offs among subsystems. Lewis and others have developed a well-known, traditional game-theoretic approach for formally modeling complex systems that can locate a Nash equilibrium design with a minimum of information sharing in the form of a point design. This paper builds on Lewis' work by proposing algorithms that are capable of converging to Pareto-optimal system-level designs by increasing cooperation among subsystems through additional passed information. This paper investigates several forms for this additional passed information, including both quadratic and eigen-based formulations. Such forms offer guidance to designers on how they should change parameter values to better suit the overall system by providing information on directionality and curvature. Strategies for representing passed information are examined in three case studies of 2-and 3-player scenarios that cover a range of system complexity. Depending on the scenario, findings suggest that passing more information generally leads to convergence to a Pareto-optimal set. However, more iterations may be required to reach the Pareto set than if using a traditional gametheoretic approach

foreword proceedings of the 3rd international electronic conference on sensors and applications

This issue of Proceedings gathers the papers presented at the 3rd International Electronic Conference on Sensors and Applications (ECSA-3), held online on 15–30 November 2016 through the sciforum.net platform developed by MDPI. The annual ECSA conference was initiated in 2014 on an online basis only, to allow the participation from all over the world with no concerns of travel and related expenditures. This type of conference looks particularly appropriate and useful because research concerned with sensors is rapidly growing, and a platform for rapid and direct exchanges about the latest research findings can provide a further burst in the development of novel ideas

Surface reaction and transport in mixed conductors with electrochemically-active surfaces: a 2-D numerical study of ceria

A two-dimensional, small-bias model has been developed for describing transport through a mixed ionic and electronic conductor (MIEC) with electrochemically-active surfaces, a system of particular relevance to solid oxide fuel cells. Utilizing the h-adaptive finite-element method, we solve the electrochemical potential and flux for both ionic and electronic species in the MIEC, taking the transport properties of Sm)(0.15)Ce_(0.85)O_(1.925_ δ) (SDC15). In addition to the ionic flux that flows between the two sides of the cell, there are two types of electronic fluxes: (1) cross-plane current that flows in the same general direction as the ionic current, and (2) in-plane current that flows between the catalytically-active MIEC surface and the metal current collectors. From an evaluation of these fluxes, the macroscopic interfacial resistance is decomposed into an electrochemical reaction resistance and an electron diffusion-drift resistance, the latter associated with the in-plane electronic current. Analysis of the experimental data for the interfacial resistance for hydrogen electro-oxidation on SDC15 having either Pt or Au current collectors (W. Lai and S. M. Haile, J. Am. Ceram. Soc., 2005, 88, 2979–2997; W. C. Chueh, W. Lai and S. M. Haile, Solid State Ionics, 2008, 179, 1036–1041) indicates that surface reaction rather than electron migration is the overall rate-limiting step, and suggests furthermore that the surface reaction rate, which has not been directly measured in the literature, scales with p_(O2)^(-1/4). The penetration depth for the in-plane electronic current is estimated at 0.6 mm for the experimental conditions of interest to SDC15, and is found to attain a value as high as 4 mm within the broader range of computational conditions

Effects of emissions caps on the costs and feasibility of low-carbon hydrogen in the European ammonia industry

The European ammonia industry emits 36 million tons of carbon dioxide annually, primarily from steam methane reforming (SMR) hydrogen production. These emissions can be mitigated by producing hydrogen via water electrolysis using dedicated renewables with grid backup. This study investigates the impact of decarbonization targets for hydrogen synthesis on the economic viability and technical feasibility of retrofitting existing European ammonia plants for on-site, semi-islanded electrolytic hydrogen production. Results show that electrolytic hydrogen cuts emissions, on average, by 85% (36%-100% based on grid price and carbon intensity), even without enforcing emission limits. However, an optimal lifespan average well-to-gate emission cap of 1 kg carbon dioxide equivalent (CO2e)/kg H2 leads to a 95% reduction (92%-100%) while maintaining cost-competitiveness with SMR in renewable-rich regions (mean levelized cost of hydrogen (LCOH) of 4.1 euro/kg H2). Conversely, a 100% emissions reduction target dramatically increases costs (mean LCOH: 6.3 euro/kg H2) and land area for renewables installations, likely hindering the transition to electrolytic hydrogen in regions with poor renewables and limited land. Increasing plant flexibility effectively reduces costs, particularly in off-grid plants (mean reduction: 32%). This work guides policymakers in defining cost-effective decarbonization targets and identifying region-based strategies to support an electrolytic hydrogen-fed ammonia industry