39,515 research outputs found
Frequency and voltage partitioning in presence of renewable energy resources for power system (example: North Chile power network)
This paper investigates techniques for frequency and voltage partitioning of power network based on the
graph-theory. These methods divide the power system into distinguished regions to avoid the spread of disturbances
and to minimize the interaction between these regions for frequency and voltage control of power system. In case
of required active and reactive power for improving the performance of the power system, control can be performed
regionally instead of a centralized controller. In this paper, renewable energy sources are connected to the power
network to verify the effect of these sources on the power systems partitioning and performance. The number of
regions is found based on the frequency sensitivity for frequency partitioning and bus voltage for voltage partitioning to disturbances being applied to loads in each region. The methodology is applied to the north part of Chile power
network. The results show the performance and ability of graph frequency and voltage partitioning algorithm to divide
large scale power systems to smaller regions for applying decentralized controllers.Peer ReviewedPostprint (published version
Are galaxy distributions scale invariant? A perspective from dynamical systems theory
Unless there is evidence for fractal scaling with a single exponent over
distances .1 <= r <= 100 h^-1 Mpc then the widely accepted notion of scale
invariance of the correlation integral for .1 <= r <= 10 h^-1 Mpc must be
questioned. The attempt to extract a scaling exponent \nu from the correlation
integral n(r) by plotting log(n(r)) vs. log(r) is unreliable unless the
underlying point set is approximately monofractal. The extraction of a spectrum
of generalized dimensions \nu_q from a plot of the correlation integral
generating function G_n(q) by a similar procedure is probably an indication
that G_n(q) does not scale at all. We explain these assertions after defining
the term multifractal, mutually--inconsistent definitions having been confused
together in the cosmology literature. Part of this confusion is traced to a
misleading speculation made earlier in the dynamical systems theory literature,
while other errors follow from confusing together entirely different
definitions of ``multifractal'' from two different schools of thought. Most
important are serious errors in data analysis that follow from taking for
granted a largest term approximation that is inevitably advertised in the
literature on both fractals and dynamical systems theory.Comment: 39 pages, Latex with 17 eps-files, using epsf.sty and a4wide.sty
(included) <[email protected]
Interconnect research influenced
This article shows that Rent's rule can be viewed as a fundamental law of nature with respect to electronic circuits. As there are many interpretations of the rule, this article will shed some light on the core of Rent's rule and the research that has been built on it
An algorithmic definition of the axial map
The fewest-line axial map, often simply referred to as the 'axial map, is one of the primary tools of space syntax. Its natural language definition has allowed researchers to draw consistent maps that present a concise description of architectural space; it has been established that graph measures obtained from the map are useful for the analysis of pedestrian movement patterns and activities related to such movement: for example, the location of services or of crime. However, the definition has proved difficult to translate into formal language by mathematicians and algorithmic implementers alike. This has meant that space syntax has been criticised for a lack of rigour in the definition of one of its fundamental representations. Here we clarify the original definition of the fewest-line axial map and show that it can be implemented algorithmically. We show that the original definition leads to maps similar to those currently drawn by hand, and we demonstrate that the differences between the two may be accounted for in terms of the detail of the algorithm used. We propose that the analytical power of the axial map in empirical studies derives from the efficient representation of key properties of the spatial configuration that it captures
Flow-Based Network Analysis of the Caenorhabditis elegans Connectome
We exploit flow propagation on the directed neuronal network of the nematode C. elegans to reveal dynamically relevant features of its connectome. We find flow-based groupings of neurons at different levels of granularity, which we relate to functional and anatomical constituents of its nervous system. A systematic in silico evaluation of the full set of single and double neuron ablations is used to identify deletions that induce the most severe disruptions of the multi-resolution flow structure. Such ablations are linked to functionally relevant neurons, and suggest potential candidates for further in vivo investigation. In addition, we use the directional patterns of incoming and outgoing network flows at all scales to identify flow profiles for the neurons in the connectome, without pre-imposing a priori categories. The four flow roles identified are linked to signal propagation motivated by biological input-response scenarios
Reformulating Space Syntax: The Automatic Definition and Generation of Axial Lines and Axial Maps
Space syntax is a technique for measuring the relative accessibility of different locations in a spatial system which has been loosely partitioned into convex spaces.These spaces are approximated by straight lines, called axial lines, and the topological graph associated with their intersection is used to generate indices of distance, called integration, which are then used as proxies for accessibility. The most controversial problem in applying the technique involves the definition of these lines. There is no unique method for their generation, hence different users generate different sets of lines for the same application. In this paper, we explore this problem, arguing that to make progress, there need to be unambiguous, agreed procedures for generating such maps. The methods we suggest for generating such lines depend on defining viewsheds, called isovists, which can be approximated by their maximum diameters,these lengths being used to form axial maps similar to those used in space syntax. We propose a generic algorithm for sorting isovists according to various measures,approximating them by their diameters and using the axial map as a summary of the extent to which isovists overlap (intersect) and are accessible to one another. We examine the fields created by these viewsheds and the statistical properties of the maps created. We demonstrate our techniques for the small French town of Gassin used originally by Hillier and Hanson (1984) to illustrate the theory, exploring different criteria for sorting isovists, and different axial maps generated by changing the scale of resolution. This paper throws up as many problems as it solves but we believe it points the way to firmer foundations for space syntax
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