Gradient dynamics model for drops spreading on polymer brushes

When a liquid drop spreads on an adaptive substrate the latter changes its properties what may result in an intricate coupled dynamics of drop and substrate. Here we present a generic mesoscale hydrodynamic model for such processes that is written as a gradient dynamics on an underlying energy functional. We specify the model details for the example of a drop spreading on a dry polymer brush. There, liquid absorption into the brush results in swelling of the brush causing changes in the brush topography and wettability. The liquid may also advance within the brush via diffusion (or wicking) resulting in coupled drop and brush dynamics. The specific model accounts for coupled spreading, absorption and wicking dynamics when the underlying energy functional incorporates capillarity, wettability and brush energy. After employing a simple version of such a model to numerically simulate a droplet spreading on a swelling brush we conclude with a discussion of possible model extensions

Analytic real-time analysis and timed automata: a hybrid methodology for the performance analysis of embedded real-time systems

This paper presents a compositional and hybrid approach for the performance analysis of distributed real-time systems. The developed methodology abstracts system components by either flow-oriented and purely analytic descriptions or by state-based models in the form of timed automata. The interaction among the heterogeneous components is modeled by streams of discrete events. In total this yields a hybrid framework for the compositional analysis of embedded systems. It supplements contemporary techniques for the following reasons: (a) state space explosion as intrinsic to formal verification is limited to the level of isolated components; (b) computed performance metrics such as buffer sizes, delays and utilization rates are not overly pessimistic, because coarse-grained analytic models are used only for components that conform to the stateless model of computation. For demonstrating the usefulness of the presented ideas, a corresponding tool-chain has been implemented. It is used to investigate the performance of a two-staged computing system, where one stage exhibits state-dependent behavior that is only coarsely coverable by a purely analytic and stateless component abstraction. Finally, experiments are performed to ascertain the scalability and the accuracy of the proposed approac

Towards a UTP semantics for modelica

We describe our work on a UTP semantics for the dynamic systems modelling language Modelica. This is a language for modelling a system’s continuous behaviour using a combination of differential algebraic equations and an event-handling system. We develop a novel UTP theory of hybrid relations, inspired by Hybrid CSP and Duration Calculus, that is purely relational and provides uniform handling of continuous and discrete variables. This theory is mechanised in our Isabelle implementation of the UTP, Isabelle/UTP, with which we verify some algebraic properties. Finally, we show how a subset of Modelica models can be given semantics using our theory. When combined with the wealth of existing UTP theories for discrete system modelling, our work enables a sound approach to heterogeneous semantics for Cyber-Physical systems by leveraging the theory linking facilities of the UTP

The Pressing Need to Raise the Status of the Teaching Profession: The Launch Story of the Teachers of Australia Social Media Campaign

This paper presents the start-up methodology for a project that leverages the opportunities that social media affords to give teachers voice and agency. In response to negative press about teachers in mainstream media, coupled with research that shows that teachers are working hard to meet student academic and wellbeing needs, the researchers employed the assertive technologies of social media and started a campaign to promote the work of pre-service and in-service teachers. The paper presents the theorising behind the start-up methodology for the social media campaign and outlines a response to an identified opportunity. It argues that social media provides new opportunities for professional connectedness, story sharing and collegial support

Performance Evaluation of Components Using a Granularity-based Interface Between Real-Time Calculus and Timed Automata

To analyze complex and heterogeneous real-time embedded systems, recent works have proposed interface techniques between real-time calculus (RTC) and timed automata (TA), in order to take advantage of the strengths of each technique for analyzing various components. But the time to analyze a state-based component modeled by TA may be prohibitively high, due to the state space explosion problem. In this paper, we propose a framework of granularity-based interfacing to speed up the analysis of a TA modeled component. First, we abstract fine models to work with event streams at coarse granularity. We perform analysis of the component at multiple coarse granularities and then based on RTC theory, we derive lower and upper bounds on arrival patterns of the fine output streams using the causality closure algorithm. Our framework can help to achieve tradeoffs between precision and analysis time.Comment: QAPL 201

Influence of different abstractions on the performance analysis of distributed hard real-time systems

System level performance analysis plays a fundamental role in the design process of hard real-time embedded systems. Several different approaches have been presented so far to address the problem of accurate performance analysis of distributed embedded systems in early design stages. The existing formal analysis methods are based on essentially different concepts of abstraction. However, the influence of these different models on the accuracy of the system analysis is widely unknown, as a direct comparison of performance analysis methods has not been considered so far. We define a set of benchmarks aimed at the evaluation of performance analysis techniques for distributed systems. We apply different analysis methods to the benchmarks and compare the results obtained in terms of accuracy and analysis times, highlighting the specific effects of the various abstractions. We also point out several pitfalls for the analysis accuracy of single approaches and investigate the reasons for pessimistic performance prediction

Evaluation of the Efficiency of an Elevated Temperature Proton Exchange Membrane Water Electrolysis System

In recent years, a significant interest has been growing in elevated temperature (ET) electrolytes for proton exchange membrane water electrolysis (PEMWE). In this study, the energy and exergy analysis developed for PEMWE has been extended to evaluate the performance of ET-PEMWE, with the model aiming to utilise the energy in the most efficient manner and also take into account potential heat losses. The latter is particularly important considering that heat losses become more pronounced with higher temperature differences. The model shows that the stack operates in autothermic mode over a considerable range of current density. Thus heating inputs to the stack and feed water become progressively unnecessary as polarization losses make up for these heating requirements. This also allows surplus heat to be utilised for secondary applications. The exergy efficiency for ET has been calculated to surpass that for low temperature (LT), with the maximum improvement reaching 3.8% points. Taking into account exergy favours higher temperature differences - a benefit which outweighs the fact that a greater quantity of thermal power is recovered in the LT system (due to higher polarization losses). This finding also shows the suitability of adopting exergy efficiency as the performance indicator for PEMWE systems. © 2021 The Author(s). Published on behalf of The Electrochemical Society by IOP Publishing Limited

Pattern Formation in Slot-Die Coating

We experimentally study the occurrence of pattern formation during the slot-die coating of low-viscosity nearly Newtonian liquids onto Polyethylenterephthalat (PET)-substrates. In particular, it is demonstrated that with increase of the coating speed a homogeneous coating becomes unstable with respect to periodic stripe patterns. Thereby, depending on the liquid viscosity, the stripes can be oriented parallel or perpendicular with respect to the coating direction. Mixed states do also occur. The spatial period of perpendicular [parallel] stripes increases [decrease] with the coating speed. The dependence of the effect on various control parameters of slot-die coating is investigated. Finally, a simple theoretical model based on the hydrodynamics of thin films of partially wetting liquids is analysed. Comparing the results to the experiments, conclusions are drawn regarding the acting instability and pattern formation mechanisms.Comment: 24 pages, 10 figure

Understanding the activity transport nexus in water and CO2_{2} electrolysis: State of the art, challenges and perspectives

This article reviews the challenge of expanding the current research focus on water and CO2 electrolysis from catalyst-related insights towards achieving complete understanding of the activity transport nexus within full electrolysis cells. The challenge arises from the complex interaction of a multitude of phenomena taking place at different scales that span several orders of magnitude. An overview of current research on materials and components, experiments and simulations are provided. As well as obvious differences, there are similar principles and phenomena within water and CO$_{2}$ electrolysis technologies, which are extracted. Against this background, a perspective on required future research within the individual fields, and the need for a multidisciplinary research approach across natural, materials and engineering sciences to tackle the activity transport nexus is presented

Soluble Fluoridobromates as Well‐Behaved Strong Fluorination Reagents

We present a facile synthesis of the soluble fluoridobromates [NEt3Me][BrF4] and [NEt3Me][Br2F7] via fluorination of the corresponding bromide salts in acetonitrile, propionitrile or bromine. We structurally characterized the [BrF2]– anion, an intermediate during the synthesis, for the first time. Additionally, the dissolution of noble metals to form the corresponding halometallates as well as the application of [NEt3Me][BrF4] as a fluorination agent for disulfides to form pentafluorosulfanyls was studied