Different toughening strategies for UV-cured epoxy resins

Owing to their outstanding properties, epoxy resins are widely used in different industries and recently used in novel applications such as semiconductors and lithographic inks. Due to their low fracture toughness, Toughening of epoxy is widely discussed in literature during last decades. Many toughening agents including organic and inorganic materials are used to accomplish this purpose. The objectives of this research are to synthesize and use different toughening agents and study the influence of these modifiers on the mechanical and thermal properties in general and the fracture toughness in particular of the UV-cured cycloaliphatic epoxy resins. Particularly, we desired to improve the fracture toughness of modified epoxies cured via UV light without sacrificing their thermal and other mechanical properties. Polymeric molecules or ceramic nanoparticles have been introduced; (1) Hyperstar polymers based on hyperbranched polyester core with or without hydroxyl reactive groups in their arms (2) reactive core/shell polymeric nanoparticles prepared by seeded emulsion polymerization (3) reactive or nonreactive diblock copolymer prepared via ATRP and based on polyethylene oxide and (4) commercial alumina nanoparticles as inorganic particles. The effect of the addition of these toughening agents on the rate of UV-curing process and glass transition temperature, Tg, have been investigated. Subsequently, the morphology of the facture surfaces has been studied carefully using FE-SEM. The stress intensity factor, KIC, measurements which is an indicator for fracture toughness was evaluated in terms of single-edge-notch three-point-bending (SENB). Cationic UV-curing technique was utilized for the preparation of the modified epoxy composites. Specifically, the cationic photopolymerization of cycloaliphatic epoxy is known to proceed through nucleophilic attack of neutral monomer to oxonium cation, which is active chain end of the polymerization. The UV induced polymerization technique is a solvent free method occurring at room temperature which is eco-friendly. It is indeed a polymerization process used for industrial applications because of the high production rate and the low energy consumption compared to thermal processes. The rapid UV-curing process helps to maintain good dispersion of modified particles avoiding further aggregation that could occur during longer thermal treatment

Delays in IP routers, a Markov model

Delays in routers are an important component of end-to-end delay and therefore have a significant impact on quality of service. While the other component, the propagation time, is easy to predict as the distance divided by the speed of light inside the link, the queueing delays of packets inside routers depend on the current, usually dynamically changing congestion and on the stochastic features of the flows. We use a Markov model taking into account the distribution of the size of packets and self-similarity of incoming flows to investigate their impact on the queueing delays and their dynamics

Patch-based modelling of city-centre bus movement with phase-type distributions

Abstract We propose a methodology for constructing a stochastic performance model of a public transportation network using real-world data. Our main data source consists of Automatic Vehicle Location (AVL) measurements of buses in the Edinburgh region. Although the data has a relatively low frequency, we can use it to parameterise a model in which a bus moves between predefined patches in the city. We fit the probability distributions of the sojourn times in the patches to phase-type distributions using the tool HyperStar. We then translate the output from HyperStar to a model of a complete part of a bus route expressed in the reactive modules language of the PRISM model checker. Finally, we demonstrate how we can use the numerical techniques implemented in PRISM to answer meaningful questions about the performance of the bus network in the context of a case study involving the addition of trams to a busy section of Edinburgh's city centre

Accurate Analysis of Quality Properties of Software with Observation-Based Markov Chain Refinement

We introduce a tool-supported method for the automated refinement of continuous-time Markov chains (CTMCs) used to assess quality properties of component-based software. Existing research focuses on improving the efficiency of CTMC analysis and on identifying new applications for this analysis. As such, ensuring that the analysis is accurate by using CTMCs that closely model the behaviour of the analysed software has received relatively little attention. Our new method addresses this gap by refining the high-level CTMC model of a component-based software system based on observations of the execution times of its components. Our refinement method reduced analysis errors by 77–90.3% for a service-based system implemented using six public web services from three different providers, improving the accuracy of the analysis and significantly reducing the risk of invalid software engineering decisions

Finding Optimal Timetables for Edinburgh Bus Routes

AbstractWe present a novel application of stochastic simulation and model-checking methods to determining whether bus services are fulfilling their service-level agreement to provide on-time departures of buses from stops sufficiently often. We use open data on predicted bus arrival times to parameterise a stochastic model of a particular bus route from Edinburgh city centre out to suburban and rural areas to the south of the city. We validate and then analyse our stochastic model using both simulation and model-checking methods. Finally, we complete an optimisation study on the model and discover a better timetable for the service which would expose the bus service operator to less financial risk of penalties being applied by the regulatory authorities which define standards for bus service, punctuality and reliability

An Analysis Pathway for the Quantitative Evaluation of Public Transport Systems

We consider the problem of evaluating quantitative service-level agreements in public services such as transportation systems. We describe the integration of quantitative analysis tools for data fitting, model generation, simulation, and statistical model-checking, creating an analysis pathway leading from system measurement data to verification results. We apply our pathway to the problem of determining whether public bus systems are delivering an appropriate quality of service as required by regulators. We exercise the pathway on service data obtained from Lothian Buses about the arrival and departure times of their buses on key bus routes through the city of Edinburgh. Although we include only that example in the present paper, our methods are sufficiently general to apply to other transport systems and other cities