Controller synthesis for dynamic hierarchical real-time plants using timed automata

We use timed I/O automata based timed games to synthesize task-level reconfiguration services for cost-effective fault tolerance in a case study. The case study shows that state-space explosion is a severe problem for timed games. By applying suitable abstractions, we dramatically improve the scalability. However, timed I/O automata do not facilitate algorithmic abstraction generation techniques. The case study motivates the development of timed process automata to improve modeling and analysis for controller synthesis of time-critical plants which can be hierarchical and dynamic. The model offers two essential features for industrial systems: (i) compositional modeling with reusable designs for different contexts, and (ii) state-space reduction technique. Timed process automata model dynamic networks of continuous-time communicating plant processes which can activate other plant processes. We show how to establish safety and reachability properties of timed process automata by reduction to solving timed games. To mitigate the state-space explosion problem, an algorithmic state-space reduction technique using compositional reasoning and aggressive abstractions is also proposed. In this article, we demonstrate the theoretical framework of timed process automata and the effectiveness of the proposed state-space reduction technique by extending the case study.     

Language-specific model checking of UML-RT models

Model-driven development (MDD) deals with complexities of modern software development by using models. Their verification is one of the opportunities of MDD, since it can be performed in the early stages of the development. The prevailing trend in verification of MDD models has been to translate them to an input language of one of the existing tools, most notably model checkers. Such an approach has advantages; for instance, we can use tools that achieved a higher level of maturity, including SPIN, NuSMV and Java PathFinder. However, the input languages of model checkers are typically not compatible with MDD models, which can make the translations very complex and difficult to maintain. Moreover, it is more difficult to take advantage of specific features of the structure and semantics of models to, e.g., speed up analysis. In this paper, we depart from the translational trend and present more direct and dedicated approach. We use an MDD language, namely UML-RT (used in IBM Rational Software Architect RealTime Edition), and we introduce a verification method built around its main features such as hierarchical structures, action code and asynchronous communication. In our method we use a formalization tailored to UML-RT models. This enables very easy transformation of models, but also reduces the necessary translations of verification results and directly supports the most important features of UML-RT. The proposed method includes an on-the-fly model checking algorithm based on the original CTL labeling. This algorithm is further optimized to include lazy composition. In the paper, we present all necessary components of the checking algorithms. Additionally, we also show the results of experiments with our implementation using several UML-RT models and CTL formulas. The experiments provide some evidence of the viability of a language-specific analysis of MDD models and of the effectiveness of our optimizations in certain cases.     

Ideas in the Workplace: A New Approach Towards Organizing the Fuzzy Front End of the Innovation Process

This article pinpoints requirements for organizing the fuzzy front end of the innovation process. The author derived the conditions for computer‐aided idea management from benchmarking the fuzzy front ends of several German and European companies and proposes differentiating between general and company‐specific requirements for organizing the fuzzy front end. It is suggested that structuring the fuzzy front end involves low financial investment but highly sensitive and transparent leadership. Using specific properties of ideas in the workplace as springboards, considerations on further new requirements for successful idea management are developed. Placing a particular emphasis on the interface between the idea owner and the idea‐adoption system, an ‘idea types’ model is developed, which defines four different extreme types of employees and their inclinations to solve problems. An extended set of requirements for managing ideas in the workplace as a useful instrument in creation and implementation of idea‐pipelines in companies and in checking software programmes for idea management or the early stages of new product development programmes is presented.     

Industrially-styled room-temperature pulsed laser deposition of titanium-based coatings

Titanium-based compounds are widely used as coating materials for mechanical, tribological, electrical, optical, catalytic, sensoric, micro-electronical applications due to their exceptionally physical and chemical properties. Recently, the trend of using temperature-sensitive materials like polymers and tool steels with the highest hardness demands new low-temperature coating techniques for protective surface finishing as well as for surface functionalization, but up to now there is lack of industrially scaled vacuum coating techniques at temperatures below 50 °C. An alternative for overcoming this problem is the pulsed laser deposition (PLD) technique, which was up-scaled for industrial demands at Laser Center Leoben of JOANNEUM RESEARCH Forschungsgesellschaft mbH.The current paper summarizes the application of the industrially-scaled PLD technique on the deposition of the presently most important Ti-based coatings: metallic titanium, titanium nitride (TiN), titanium oxide (TiO₂) and titanium carbonitride (TiCN). PLD coating allows, even at room temperature, the formation of film structures of Zone-T type of Thornton's structure zone model, both on substrates aligned normal and parallel to the incident vapor flux. The high-energetic deposition conditions are revealed by the occurrence of (2 2 0) textures for the fcc TiN-based films. The dense grown structure affects advantageously the tribological behavior—generally, low wear rates and (for TiCN) very low friction coefficients were found. For TiO₂ coatings, growing as a mixture of β-TiO₂ and amorphous phases, the easily reproducible change of deposition parameters in the room-temperature PLD allows large differences in the optical transmission and electrical resistance.     

Implied Open-circuit Voltage Imaging via a Single Bandpass Filter Method—Its First Application in Perovskite Solar Cells

A novel, camera-based method for direct implied open-circuit voltage (iV_OC) imaging via the use of a single bandpass filter (s-BPF) is developed for large-area photovoltaic solar cells and precursors. The photoluminescence (PL) emission is imaged using a narrow BPF with centre energy inside the high-energy tail of the PL emission, utilising the close-to-unity and nearly constant absorptivity of typical photovoltaic devices in this energy range. As a result, the exact value of the sample's absorptivity within the BPF transmission band is not required. The use of an s-BPF enables a fully contactless approach to calibrate the absolute PL photon flux for spectrally integrated detectors, including cameras. The method eliminates the need for knowledge of the imaging system spectral response. Through an appropriate choice of the BPF centre energy, a range of absorber compositions or a single absorber with different surface morphologies, such as planar and textured, can be imaged, all without the need for additional detection optics. The feasibility of this s-BPF method is first validated. The relative error in iV_OC is determined to be ≤1.5%. The method is then demonstrated on device stacks with two different perovskite compositions commonly used in single-junction and monolithic tandem solar cells.     

Effects of accessible website design on nondisabled users: age and device as moderating factors

This study examined how implementing recommendations from Web accessibility guidelines affects nondisabled people in different age groups using different technical devices. While recent research showed positive effects of implementing such recommendations for nondisabled users, it remains unclear whether such effects would apply to different age groups and kind of devices. A 2 × 2 × 2 design was employed with website accessibility (high accessibility vs. very low accessibility), age (younger adults vs. older adults) and type of device (laptop vs. tablet) as independent variables. 110 nondisabled participants took part in a usability test, in which performance and satisfaction were measured as dependent variables. The results showed that higher accessibility increased task completion rate, task completion time and satisfaction ratings of nondisabled users. While user age did not have any effects, users showed faster task completion time under high accessibility when using a tablet rather than a laptop. The findings confirmed previous findings, which showed benefits of accessible websites for nondisabled users. These beneficial effects may now be generalised to a wide age range and across different devices.

Practitioner Summary: This work is relevant to the design of websites since it emphasises the need to consider the characteristics of different user groups. Accessible website design (aimed at users with disabilities) leads to benefits for nondisabled users across different ages. These findings provide further encouragement for practitioners to apply WCAG 2.0.     

Properties of BaxSr1−x TiO3 films grown by rf magnetron sputtering on sapphire with an SrTiO3 sublayer

Results are presented of experiments to deposit barium strontium titanate films on an r-cut sapphire substrate with a strontium titanate sublayer. It is shown that the use of a strontium titanate sublayer can ensure that the dielectric properties of barium strontium titanate films have a weak temperature dependence over a wide temperature range. Moreover, the parameters of the films are consistent with those required to fabricate microwave microelectronics devices. Pis’ma Zh. Tekh. Fiz. 25, 1–5 (July 26, 1999)     

Production of Functionally Graded Materials from Electrochemically Modified Carbon Preforms

A new process based on carbon as a precursor material has been applied successfully to the production of graded Al₂O₃/Al composites. For this purpose, distinct porosity gradients were introduced into carbon materials via anodic oxidation. The graded structure of the carbon preforms was replicated using two subsequent infiltration steps to yield fully dense Al₂O₃/Al functionally graded materials with an interpenetrating network microstructure and a continuous variation of metal content.     

Nanoporous Plasmonic Metamaterials

We review different routes for the generation of nanoporous metallic foams and films exhibiting well‐defined pore size and short‐range order. Dealloying and templating allows the generation of both 2D and 3D structures that promise a plasmonic response determined by material constituents and porosity. Viewed in the context of metamaterials, the ease of fabrication of samples covering macroscopic dimensions is highly promising, and suggests more in‐depth investigations of the plasmonic and photonic properties of this material system for photonic applications.