Search

We present a novel approach to represent ecological systems using reaction networks, and show how a particular framework called chemical organization theory (COT) sheds new light on the longstanding complexity-stability debate. Namely, COT provides a novel conceptual landscape plenty of analytic tools to explore the interplay between structure and stability of ecological systems. Given a large set of species and their interactions, COT identifies, in a computationally feasible way, each and every sub-collection of species that is closed and self-maintaining. These sub-collections, called organizations, correspond to the groups of species that can survive together (co-exist) in the long-term. Thus, the set of organizations contains all the stable regimes that can possibly happen in the dynamics of the ecological system. From here, we propose to conceive the notion of stability from the properties of the organizations, and thus apply the vast knowledge on the stability of reaction networks to the complexity-stability debate. As an example of the potential of COT to introduce new mathematical tools, we show that the set of organizations can be equipped with suitable joint and meet operators, and that for certain ecological systems the organizational structure is a non-boolean lattice, providing in this way an unexpected connection between logico-algebraic structures, popular in the foundations of quantum theory, and ecology., Author(s): Tomas Veloz [sup.1] [sup.2] [sup.3] Author Affiliations: (1) grid.8767.e, 0000 0001 2290 8069, Center Leo Apostel for Interdisciplinary Studies, Vrije Universiteit Brussel, , Brussels, Belgium (2) Instituto de Filosofía [...]

In this article, synchronization of two different fractional-order memristor-based chaotic systems is considered. To achieve synchronization, an active control technique is used. The main proof is concerned with the problem of synchronization of memristor-based Lorenz systems with memristor-based Chua's circuits. Numerical simulations of fractional-order memristorbased chaotic systems are performed by using the Caputo version and a predictor-corrector algorithm for fractional-order differential equations, which is a generalization of the Adams-Bashforth-Moulton method. From the simulations, it will be verified that the proposed control method is effective in achieving synchronization. PACS Nos.: 05.45.Xt, 05.45.Gg. Nous etudions ici la synchronisation de deux differents systemes chaotiques bases sur des memristances d'ordre fractionnaire. Pour reussir la synchronisation, nous utilisons une technique de controle actif. La preuve principale concerne la synchronisation de systemes de Lorentz bases sur memristances avec des circuits de Chua bases sur memristances. Les simulations numeriques des systemes bases sur memristances d'ordre fractionnaire sont faites a l'aide de la version de Caputo et d'un algorithme de prediction-correction pour des equations differentielles d'ordre fractionnaire, qui est une generalisation de la methode de Adams-Bashforth-Moulton. A partir des simulations, nous verifions que la methode de controle proposee est efficace pour reussir la synchronisation. [Traduit par la Redaction], 1. Introduction Fractional-order calculus is an area of mathematics that deals with derivatives and integrals from noninteger orders, and was introduced in the early 17th century. In the last few [...]

Proof at the nexus of pure mathematics and algorithms puts 'quantum weirdness' on a whole new level. Proof at the nexus of pure mathematics and algorithms puts 'quantum weirdness' on a whole new level., Author(s): Davide Castelvecchi Author Affiliations: How 'spooky' is quantum physics? The answer could be incalculable Quantum entanglement is at the centre of a mathematical proof. Credit: Victor De Schwanberg/Science Photo [...]

In this paper we describe how adaptive planning emerges from a tradition of blueprint planning, and analyze how different forms of planning are related to the implementation of innovative urban projects. We use two concepts from complexity sciences to discuss adaptive planning versus blueprint planning, namely the concept of contingency and the concept of (dissipative) self-organization. In our paper we demonstrate that the apparent dichotomy between blueprint planning and adaptive planning might not be as strict as often assumed. Our case study Water Square Rotterdam reveals how adaptive planning can coincide with elements of blueprint planning, shaped by so-called 'situational responsive leadership', with attention for context and complexity. Based on our case study, we argue that situational responsive leadership, with a mixture of adaptive and traditional project planning elements, improves successful implementation of innovative urban projects., Introduction Recent years have seen a rise in literature and empirical studies on urban and metropolitan governance (for instance Kreukels et al., 2003; Heinelt & Kubler, 2005; Feiock, 2004). This [...]

The Interstate 80 (I-80) Corridor System Master Plan (CSMP) study brought diverse stakeholders from California, Nevada, Utah, and Wyoming together for an in-depth dialogue. The collaborative was convened by the Nevada Department of Transportation with the intent to generate an ongoing enduring structure. Interactions were facilitated using virtual means such as conference calls. This assessment reviews the stakeholders' activities through the first two years in terms of complexity and collaboration. Collaboration assessment used the lens of diversity, interdependence, and authentic dialogue theory based collaboration which is detailed. Complexity assessment employed agents, interactions, nonlinearity, systems and robustness, and adaptations characteristics previously identified by collaborative practitioners. Still emerging theory suggested each assessment be done independently and compared. The results revealed a collaborative presence within the stakeholder network and less telling complexity structure. Results enforced the notion that complexity properties require more time to identify particularly in virtual environments., Introduction Complexity and collaboration represent two emerging areas of study in public administration theory. Complexity originated in the study of scientific phenomena (Morgol, 2005). Collaboration emerged from a pragmatic movement [...]

Urban planning projects are planned and organized through arrangements between actors. These arrangements are institutional interventions: they intervene in the institutional landscape as existing organizational boundaries are (temporarily) redrawn. Such boundary decisions are intended to simplify complexity. However, these boundary decisions also produce new complexities as new boundary issues arise. Our contribution investigates these boundary issues by studying and comparing three urban planning projects in the Rotterdam urban system (the Netherlands). The analysis shows that the boundary issues are often underestimated and that coping strategies are required to deal with them. Because boundary issues pose serious threats to the success or even survival of projects, management should invest in increasing the capacity to deal with (often unexpected) boundary issues., Introduction The management and organization of urban planning projects is accompanied by institutional interventions to deal with the complexity of the projects. Institutional interventions are materialized organizational arrangements between the [...]

Complexity and administrative learning In addition to addressing citizen interests, the demands placed on public administration include coordinating interests among public agencies with differential jurisdictional authorities and working with private [...]

Within the world of social entrepreneurship, there has been a focus on scaling programs to meet the needs of more and more people. This scaling effort has only had a [...]

How well equipped are we to deal with the real world and its opportunities, threats and demands? As children we are brought up on stories which tend to end 'happily [...]

This teaching note presents 7 basic ideas that are drawn from complexity theory. These ideas are designed to help students appreciate and work with the complex systems that they often face in practice. Although complexity theory may be presented using mathematical language not easily accessible to non-mathematicians, it also may be presented by using everyday language and easy-to-understand examples. This note offers a straightforward presentation of basic concepts that help students to recognize, appreciate, and work with the complexity of situations faced in practice settings., HELPING STUDENTS TO understand the relationships among individuals and the systems with which they interact is central to social work education. Social work's understanding of systems has evolved over time, [...]

Evidence-based practice (EBP) has emerged as an alternative to traditional social work practice and has ignited a new round in the decades-old debate about the relationship between knowledge and practice in the field. This article identifies several limitations inherent in the EBP perspective and argues that it would be unfortunate if EBP were to become the new paradigm for social work practice and education. It also presents a new perspective for social work called design-based practice (DBP), which is based on the work of Herbert Simon and Mary Parker Follett, and compares this perspective with EBP and authority-based practice. DBP rests on the belief that knowledge is derived from experience and interactions between practitioners and clients and that professional practice should be primarily concerned with 'how things ought to be.' KEY WORDS: complexity; design; knowledge; social work practice, The relationship between knowledge and practice in the field of social work has continued to spark debate among scholars and practitioners (Gomory, 1997). Many have argued that only knowledge derived [...]

I THE IMPROVABILITY THESIS and The Issue Of 'Natural Evil.' The claim that this is the best possible world may seem to be absurd because so much appears to be [...]