132 research outputs found
Integrated methods and scenario development for urban groundwater management and protection during tunnel road construction: a case study of urban hydrogeology in the city of Basel, Switzerland
In the northwestern area of Basel, Switzerland, a tunnel highway connects the French highway A35 (Mulhouse-Basel) with the Swiss A2 (Basel-Gotthard-Milano). The subsurface highway construction was associated with significant impacts on the urban groundwater system. Parts of this area were formerly contaminated by industrial wastes, and groundwater resources are extensively used by industry. During some construction phases, considerable groundwater drawdown was necessary, leading to major changes in the groundwater flow regime. Sufficient groundwater supply for industrial users and possible groundwater pollution due to interactions with contaminated areas had to be taken into account. A groundwater management system is presented, comprising extensive groundwater monitoring, high-resolution numerical groundwater modeling, and the development and evaluation of different scenarios. This integrated approach facilitated the evaluation of the sum of impacts, and their interaction in time and space with changing hydrological boundary conditions. For all project phases, changes of the groundwater system had to be evaluated in terms of the various goals and requirements. Although the results of this study are case-specific, the overall conceptual approach and methodologies applied may be directly transferred to other urban area
Self-organized criticality as an absorbing-state phase transition
We explore the connection between self-organized criticality and phase
transitions in models with absorbing states. Sandpile models are found to
exhibit criticality only when a pair of relevant parameters - dissipation
epsilon and driving field h - are set to their critical values. The critical
values of epsilon and h are both equal to zero. The first is due to the absence
of saturation (no bound on energy) in the sandpile model, while the second
result is common to other absorbing-state transitions. The original definition
of the sandpile model places it at the point (epsilon=0, h=0+): it is critical
by definition. We argue power-law avalanche distributions are a general feature
of models with infinitely many absorbing configurations, when they are subject
to slow driving at the critical point. Our assertions are supported by
simulations of the sandpile at epsilon=h=0 and fixed energy density (no drive,
periodic boundaries), and of the slowly-driven pair contact process. We
formulate a field theory for the sandpile model, in which the order parameter
is coupled to a conserved energy density, which plays the role of an effective
creation rate.Comment: 19 pages, 9 figure
Criticality of compact and noncompact quantum dissipative models in dimensions
Using large-scale Monte Carlo computations, we study two versions of a
-symmetric model with Ohmic bond dissipation. In one of these
versions, the variables are restricted to the interval , while the
domain is unrestricted in the other version. The compact model features a
completely ordered phase with a broken symmetry and a disordered phase,
separated by a critical line. The noncompact model features three phases. In
addition to the two phases exhibited by the compact model, there is also an
intermediate phase with isotropic quasi-long-range order. We calculate the
dynamical critical exponent along the critical lines of both models to see
if the compactness of the variable is relevant to the critical scaling between
space and imaginary time. There appears to be no difference between the two
models in that respect, and we find for the single phase transition
in the compact model as well as for both transitions in the noncompact model
User participation in watershed management and research:
Many watershed development projects around the world have performed poorly because they failed to take into account the needs, constraints, and practices of local people. Participatory watershed management—in which users help to define problems, set priorities, select technologies and policies, and monitor and evaluate impacts—is expected to improve performance. User participation in watershed management raises new questions for watershed research, including how to design appropriate mechanisms for organizing stakeholders and facilitating collective action. Management of a complex system such as a watershed may also require user participation in the research process itself. An increasing number of watershed research projects are already participatory, however challenges remain to institutionalizing user participation in both watershed management and research.
How self-organized criticality works: A unified mean-field picture
We present a unified mean-field theory, based on the single site
approximation to the master-equation, for stochastic self-organized critical
models. In particular, we analyze in detail the properties of sandpile and
forest-fire (FF) models. In analogy with other non-equilibrium critical
phenomena, we identify the order parameter with the density of ``active'' sites
and the control parameters with the driving rates. Depending on the values of
the control parameters, the system is shown to reach a subcritical (absorbing)
or super-critical (active) stationary state. Criticality is analyzed in terms
of the singularities of the zero-field susceptibility. In the limit of
vanishing control parameters, the stationary state displays scaling
characteristic of self-organized criticality (SOC). We show that this limit
corresponds to the breakdown of space-time locality in the dynamical rules of
the models. We define a complete set of critical exponents, describing the
scaling of order parameter, response functions, susceptibility and correlation
length in the subcritical and supercritical states. In the subcritical state,
the response of the system to small perturbations takes place in avalanches. We
analyze their scaling behavior in relation with branching processes. In
sandpile models because of conservation laws, a critical exponents subset
displays mean-field values ( and ) in any dimensions. We
treat bulk and boundary dissipation and introduce a new critical exponent
relating dissipation and finite size effects. We present numerical simulations
that confirm our results. In the case of the forest-fire model, our approach
can distinguish between different regimes (SOC-FF and deterministic FF) studied
in the literature and determine the full spectrum of critical exponents.Comment: 21 RevTex pages, 3 figures, submitted to Phys. Rev.
Redefining managerial effectiveness in a multilevel organization : a structurationist account
Many organization theories consist of an interpretation frame and an idea about the ideal equilibrium state. This article explains how the equilibrium concept is used in four organization theories: the theories of Fayol, Mintzberg, Morgan, and Volberda. Equilibrium can be defined as balance, fit or requisite variety. Equilibrium is related to observables dependent on the definition of organization as work organization, formal organization or artifact organization. Equilibrium can be explicitly related to performance in the theory used, enabling cross-sectional research. The discussed theories can be mapped on a state space model in a way that clarifies the equilibrium concept, namely a mu-space (Fayol and Morgan), or a gamma-space (Mintzberg and Volberda). 1 Prof.dr. Henk W.M. Gazendam is professor of Information Systems in the Public Sector at the Faculty of Public Administration at Twente University and associate professor of Information Strategy at the Faculty of Management and Organization at Groningen University (P.O.Box 800, NL-9700-AV Groningen, The Netherlands, tel +31-50-3637078, email [email protected]). 2 Contribution to the Computational and Mathematical Organization Theory Workshop, May 3 and 4, 1996, Washington Hilton & Towers. 3 The author wishes to thank Vincent Homburg for his valuable comments.
25 Years of Self-Organized Criticality: Numerical Detection Methods
The detection and characterization of self-organized criticality (SOC), in
both real and simulated data, has undergone many significant revisions over the
past 25 years. The explosive advances in the many numerical methods available
for detecting, discriminating, and ultimately testing, SOC have played a
critical role in developing our understanding of how systems experience and
exhibit SOC. In this article, methods of detecting SOC are reviewed; from
correlations to complexity to critical quantities. A description of the basic
autocorrelation method leads into a detailed analysis of application-oriented
methods developed in the last 25 years. In the second half of this manuscript
space-based, time-based and spatial-temporal methods are reviewed and the
prevalence of power laws in nature is described, with an emphasis on event
detection and characterization. The search for numerical methods to clearly and
unambiguously detect SOC in data often leads us outside the comfort zone of our
own disciplines - the answers to these questions are often obtained by studying
the advances made in other fields of study. In addition, numerical detection
methods often provide the optimum link between simulations and experiments in
scientific research. We seek to explore this boundary where the rubber meets
the road, to review this expanding field of research of numerical detection of
SOC systems over the past 25 years, and to iterate forwards so as to provide
some foresight and guidance into developing breakthroughs in this subject over
the next quarter of a century.Comment: Space Science Review series on SO
History, Egyptology, and the Bible: An Interdisciplinary Case Study from a Biblical Foundation
This is a case study that follows the principles developed in the first conference paper presented in the Biblical Foundations for Faith and Learning Conference (Cancun, 2011) and specifically applies these principles to a problem in the narrow field of History, Egyptology, and the Bible. Due to political and ideological reasons the field of Egyptology has been largely isolated from biblical studies and the history of Canaan and Israel. In recent years, minimalist biblical scholars have challenged the long-held consensus that the peoples, places, and polities of Canaan and Israel existed in the second millennium. The biblical references to these entities have been re-dated to the sixth-third centuries BC, hundreds of years after the setting presented by the biblical writers. This paper will address these assumptions and provide new evidence from Egyptology that supports the geographical setting presented in the Bible during the second millennium BC. The conclusions are based on a book that will be completed this year, entitled, The Name Equation: Asiatic Peoples, Places, and Polities during the Egyptian New Kingdom. Its goal is to draw together the biblical, archaeological, and Egyptological data together for an interdisciplinary approach to the problem from a biblical foundation
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