Survivability of Deterministic Dynamical Systems

The notion of a part of phase space containing desired (or allowed) states of a dynamical system is important in a wide range of complex systems research. It has been called the safe operating space, the viability kernel or the sunny region. In this paper we define the notion of survivability: Given a random initial condition, what is the likelihood that the transient behaviour of a deterministic system does not leave a region of desirable states. We demonstrate the utility of this novel stability measure by considering models from climate science, neuronal networks and power grids. We also show that a semi-analytic lower bound for the survivability of linear systems allows a numerically very efficient survivability analysis in realistic models of power grids. Our numerical and semi-analytic work underlines that the type of stability measured by survivability is not captured by common asymptotic stability measures.Comment: 21 pages, 6 figure

Survivability : A Unifiying Concept for the Transient Resilience of Deterministic Dynamical Systems

16 pagesNon peer reviewedPreprin

Software Engineering I: Teaching Challenges

The term software engineering can be traced to the late 1960s in response to large-scale, software development problems. Since then it has evolved as a discipline, both within industry and the academy. There have been distinct educational successes: “Standard practice” has matured (and found its way into more textbooks),the ACM and IEEE Computer Society have published curriculum guidelines, computer science programs commonly offer at least one software engineering course, and software engineering degrees (undergraduate or graduate) are more common. However, software engineering still presents a challenge. The term itself has become contorted by companies (and society in general); software has become far more diverse (along with the environments in which software engineers work); industrial software processes are not easily replicated in the classroom; what students are expected to know (once they are employed) has expanded significantly; software tools change rapidly (affecting student expectations); and the discipline involves far more than “good program-ming” (or a large programming project). This talk describes these challenges – and suggestions for dealing with them – in light of my 30 years teaching software engineering in a university

Ancillary health effects of climate mitigation scenarios as drivers of policy uptake: a review of air quality, transportation and diet co-benefits modeling studies

Background: Significant mitigation efforts beyond the Nationally Determined Commitments (NDCs) coming out of the 2015 Paris Climate Agreement are required to avoid warming of 2 °C above pre-industrial temperatures. Health co-benefits represent selected near term, positive consequences of climate policies that can offset mitigation costs in the short term before the beneficial impacts of those policies on the magnitude of climate change are evident. The diversity of approaches to modeling mitigation options and their health effects inhibits meta-analyses and syntheses of results useful in policy-making. Methods/Design: We evaluated the range of methods and choices in modeling health co-benefits of climate mitigation to identify opportunities for increased consistency and collaboration that could better inform policy-making. We reviewed studies quantifying the health co-benefits of climate change mitigation related to air quality, transportation, and diet published since the 2009 Lancet Commission 'Managing the health effects of climate change' through January 2017. We documented approaches, methods, scenarios, health-related exposures, and health outcomes. Results/Synthesis: Forty-two studies met the inclusion criteria. Air quality, transportation, and diet scenarios ranged from specific policy proposals to hypothetical scenarios, and from global recommendations to stakeholder-informed local guidance. Geographic and temporal scope as well as validity of scenarios determined policy relevance. More recent studies tended to use more sophisticated methods to address complexity in the relevant policy system. Discussion: Most studies indicated significant, nearer term, local ancillary health benefits providing impetus for policy uptake and net cost savings. However, studies were more suited to describing the interaction of climate policy and health and the magnitude of potential outcomes than to providing specific accurate estimates of health co-benefits. Modeling the health co-benefits of climate policy provides policy-relevant information when the scenarios are reasonable, relevant, and thorough, and the model adequately addresses complexity. Greater consistency in selected modeling choices across the health co-benefits of climate mitigation research would facilitate evaluation of mitigation options particularly as they apply to the NDCs and promote policy uptake

Development of a biodegradable microstent for minimally invasive treatment of Fallopian tube occlusions

Obstructions of the Fallopian tube represent one of the most common reasons for an unfulfilled desire to have children. Microstent technology opens up new therapeutic possibilities to restore the natural lumen of the Fallopian tube within a single treatment. Within the current work we developed a self-expandable biodegradable microstent for gynecological applications. Based on a novel microstent design, prototypes were manufactured from poly-L-lactide tubing by means of fs-laser cutting. Microstent prototypes were characterized morphologically by means of scanning electron microscopy and biaxial laser scanning. As manufactured, a microstents outside diameter of about 2.3 mm and a strut thickness/width of about 114 µm/103 µm was measured. Mechanical characterization of microstents included bending as well as crimping and release behavior. After crimping to a minimum diameter of 0.8 mm and consecutive release, a microstent recovery to a diameter of 1.8 mm was found. Therefore, proof-of-concept for the self-expandable microstent could be successfully provided. © 2020 by Walter de Gruyter Berlin/Boston 2020

A systematic study on Pt based, subnanometer-sized alloy cluster catalysts for alkane dehydrogenation: effects of intermetallic interaction

Platinum-based bimetallic nanoparticles are analyzed by the application of density functional theory to a series of tetrahedral Pt3X cluster models, with element X taken from the P-block, preferably group 14, or from the D-block around group 10. Almost identical cluster geometries allow a systematic investigation of electronic effects induced by different elements X. Choosing the propane-to-propene conversion as the desired dehydrogenation reaction, we provide estimates for the activity and selectivity of the various catalysts based on transition state theory. No significant Brønsted-Evans-Polanyi-relation could be found for the given reaction. A new descriptor, derived from an energy decomposition analysis, captures the effect of element X on the rate-determining step of the first hydrogen abstraction. Higher activities than obtained for pure Pt4 clusters are predicted for Pt alloys containing Ir, Sn, Ge and Si, with Pt3Ir showing particularly high selectivity

Complex systems.

The “extension” of the self is a dominant theme in McLuhan’s (1911-1980) Understanding Media, in which “all technologies are extensions of our physical being”. His discussion of “extension of consciousness” via “electric technology” was prophetic, whereby “the entire business of man becomes learning and knowing” and “all forms of wealth result from the movement of information”. The net result is a “total field of inclusive awareness” where we are both aware and affected by things outside of us -- as part of a large, complex, system. In Technology & Justice, Grant (1918-1988) wrote that “... modern technology is not simply an extension of human making ... but is a new account of what it is to know and to make in which both activities are changed ...”, where “... technology is the pervasive mode of being in our political and social lives”. In other words, technology has permeated the whole of society. This too can be regarded as a large, complex system. Both writers recognized that technology simplifies this complex system to conform to its assumptions and goals. Consequently, the system often behaves badly. “Even specialist learning in higher education proceeds by ignoring interrelationships; for such complex awareness slows down the achieving of expertness” (McLuhan). And “… technology … tends to pare down the actual novelness of our situation, so that we are not allowed to contemplate that situation for what it is” (Grant). In other words, the messy (often, human) elements are simplified to fit the assumptions and goals of organizational structure, terminology, or methods. Unfortunately, neither writer addresses how to deal with this oversimplification. Nassim Taleb (b 1960) suggests that a complex system should be seen for what it is (volatile and random) and not what we often imagine it to be (stable and deterministic). In particular, he advocates making decisions (and building systems) that are antifragile, i.e, capable of benefiting from random events, errors, and volatility. He also warns against cause-effect predictions with complex systems, recognizing that “… the notion of cause itself is suspect; it is either nearly impossible to detect or not really defined.” The presentation will sketch some concepts from Taleb for problems described by McLuhan and Grant

Toward an Integrated Tool Environment for Static Analysis of UML Class and Sequence Models

There is a need for more rigorous analysis techniques that developers can use for verifying the critical properties in UML models. The UML-based Specification Environment (USE) tool supports verification of invariants, preconditions, and postconditions specified in the Object Constraint Language (OCL). Due to its animation and analysis power, it is useful when checking critical non-functional properties such as security policies. However, the USE requires one to specify a model using its own textual language and does not allow one to import any model specification files created by other UML modeling tools. Hence, you would create a model with OCL constraints using a modeling tool such as the IBM Rational Software Architect (RSA) and then use the USE for the model verification. This approach, however, requires a manual transformation between two different specification formats, which diminishes advantage of using tools for model-level verification. In this paper, we describe our own implementation of a specification transformation engine based on the Model-Driven Architecture (MDA) framework. Our approach currently supports automatic tool-level transformations to USE from UML modeling tools built on the Eclipse-based Modeling Framework (EMF)