Breaking Dense Structures: Proving Stability of Densely Structured Hybrid Systems

Abstraction and refinement is widely used in software development. Such techniques are valuable since they allow to handle even more complex systems. One key point is the ability to decompose a large system into subsystems, analyze those subsystems and deduce properties of the larger system. As cyber-physical systems tend to become more and more complex, such techniques become more appealing. In 2009, Oehlerking and Theel presented a (de-)composition technique for hybrid systems. This technique is graph-based and constructs a Lyapunov function for hybrid systems having a complex discrete state space. The technique consists of (1) decomposing the underlying graph of the hybrid system into subgraphs, (2) computing multiple local Lyapunov functions for the subgraphs, and finally (3) composing the local Lyapunov functions into a piecewise Lyapunov function. A Lyapunov function can serve multiple purposes, e.g., it certifies stability or termination of a system or allows to construct invariant sets, which in turn may be used to certify safety and security. In this paper, we propose an improvement to the decomposing technique, which relaxes the graph structure before applying the decomposition technique. Our relaxation significantly reduces the connectivity of the graph by exploiting super-dense switching. The relaxation makes the decomposition technique more efficient on one hand and on the other allows to decompose a wider range of graph structures.Comment: In Proceedings ESSS 2015, arXiv:1506.0325

A Parametric Sound Object Model for Sound Texture Synthesis

This thesis deals with the analysis and synthesis of sound textures based on parametric sound objects. An overview is provided about the acoustic and perceptual principles of textural acoustic scenes, and technical challenges for analysis and synthesis are considered. Four essential processing steps for sound texture analysis are identifi ed, and existing sound texture systems are reviewed, using the four-step model as a guideline. A theoretical framework for analysis and synthesis is proposed. A parametric sound object synthesis (PSOS) model is introduced, which is able to describe individual recorded sounds through a fi xed set of parameters. The model, which applies to harmonic and noisy sounds, is an extension of spectral modeling and uses spline curves to approximate spectral envelopes, as well as the evolution of parameters over time. In contrast to standard spectral modeling techniques, this representation uses the concept of objects instead of concatenated frames, and it provides a direct mapping between sounds of diff erent length. Methods for automatic and manual conversion are shown. An evaluation is presented in which the ability of the model to encode a wide range of di fferent sounds has been examined. Although there are aspects of sounds that the model cannot accurately capture, such as polyphony and certain types of fast modulation, the results indicate that high quality synthesis can be achieved for many different acoustic phenomena, including instruments and animal vocalizations. In contrast to many other forms of sound encoding, the parametric model facilitates various techniques of machine learning and intelligent processing, including sound clustering and principal component analysis. Strengths and weaknesses of the proposed method are reviewed, and possibilities for future development are discussed

Who shares and who doesn't? Results of the UK Sharing Economy Consumer Survey 2017

The survey, which was conducted in July 2017, captures 1220 responses, and is based on a representative sample of UK population based on gender, income level, education level, and place of residence in the UK. It was structured to ask questions about informants’ current usage of, opinions about, and future intentions to use the following sharing categories: places to stay (e.g. Airbnb, Beds on Board), rides (e.g. Uber, Liftshare), rental cars (e.g. Easycar, Zipcar), parking (e.g. JustPark, Your Parking Space), services (e.g. Parcelly, TaskRabbit), meals (e.g. MealSharing, Eatwith), pre-owned goods (e.g. eBay, Gumtree) and funding (e.g. Justgiving, Crowdcube)

Introduction to the Minitrack on Advances in Trust, Identity, and Trusted Systems in Technology-Mediated Environments

Within the 52nd Hawaiian International Conference on System Sciences (HICSS), we organize for the third time a minitrack on Trust, Identity, and Trusted Systems in Technology-mediated Environments. Trust is a pervasive concern not just with new technologies but also with established technologies as they become more complex and interdependent. Through five papers and an open discussion, the minitrack will discuss and debate when and to what degree trust matters, in what form(s), and with which consequences in the context of existing and emerging hardware and software technologies, e.g., biometric technologies, cryptocurrencies, artificial intelligence, peer-to-peer networked platforms, and autonomous vehicles

Homeownership, mortgages, and unemployment

According to Oswald’s thesis, homeownership increases unemployment. Empirical research on micro-data has indeed confirmed that unemployed homeowners are less inclined to change their residential location and accept a new job elsewhere. However, it is also repeatedly found that unemployed homeowners tend to find a job more easily than otherwise comparable tenants. This paper aims to make a new contribution to the scientific debate on Oswald’s thesis by addressing the risk attitudes of job seekers. We show that decreasing absolute risk aversion implies that the exit rate from unemployment is increasing in housing costs, in the context of a standard job search model. Therefore, the higher costs associated with leveraged homeownership may be the driving force of homeowners’ observed labor market performance. We test this prediction on the basis of Dutch data on individual unemployment spells. Contrary to our hypothesis, we do not find evidence that a higher mortgage is associated with higher exit rates from unemployment. Rather, our findings support earlier micro-econometric results that homeownership tends to accelerate a successful job search

Persistence or Convergence? The East-West Tax Morale Gap in Germany

This paper studies differences in tax morale attitudes between East and West Germany using multiple recent data sets. Contrary to previous 1990s evidence, but in line with recent studies on an east-west mentality gap, we find a persistent higher tax morale in East Germany and no indication of convergence over time. Distinguishing between region of living and birth and periods of within-country migration reveals that the East Germans who stayed determine the results and that migration vanishes differences. Regional economic heterogeneity of tax revenue transfers cannot explain the results. We find a framing effect on the tax morale gap with questions phrasing tax paying as the duty of a good citizen. This result suggests no gap of tax morale with moral reasoning related to the social order and citizenry