520 research outputs found
Parallel Computers and Complex Systems
We present an overview of the state of the art and future trends in high performance parallel and distributed computing, and discuss techniques for using such computers in the simulation of complex problems in computational science. The use of high performance parallel computers can help improve our understanding of complex systems, and the converse is also true --- we can apply techniques used for the study of complex systems to improve our understanding of parallel computing. We consider parallel computing as the mapping of one complex system --- typically a model of the world --- into another complex system --- the parallel computer. We study static, dynamic, spatial and temporal properties of both the complex systems and the map between them. The result is a better understanding of which computer architectures are good for which problems, and of software structure, automatic partitioning of data, and the performance of parallel machines
The C parameter distribution in e+e- annihilation
We study perturbative and non-perturbative aspects of the distribution of the
C parameter in e+e- annihilation using renormalon techniques. We perform an
exact calculation of the characteristic function, corresponding to the C
parameter differential cross section for a single off-shell gluon. We then
concentrate on the two-jet region, derive the Borel representation of the
Sudakov exponent in the large-beta_0 limit and compare the result to that of
the thrust T. Analysing the exponent, we distinguish two ingredients: the jet
function, depending on Q^2C, summarizing the effects of collinear radiation,
and a function describing soft emission at large angles, with momenta of order
QC. The former is the same as for the thrust upon scaling C by 1/6, whereas the
latter is different. We verify that the rescaled C distribution coincides with
that of 1-T to next-to-leading logarithmic accuracy, as predicted by Catani and
Webber, and demonstrate that this relation breaks down beyond this order owing
to soft radiation at large angles. The pattern of power corrections is also
similar to that of the thrust: corrections appear as odd powers of Lambda/(QC).
Based on the size of the renormalon ambiguity, however, the shape function is
different: subleading power corrections for the C distribution appear to be
significantly smaller than those for the thrust.Comment: 24 pages, Latex (using JHEP3.cls), 1 postscript figur
Calibration of Plastic Phoswich Detectors for Charged Particle Detection
The response of an array of plastic phoswich detectors to ions of has been measured from =12 to 72 MeV. The detector response has been
parameterized by a three parameter fit which includes both quenching and high
energy delta-ray effects. The fits have a mean variation of with
respect to the data.Comment: 17 pages, 5 figure
Adaptive workflow nets for grid computing
Existing grid applications commonly use workflows for the orchestration of grid services. Existing workflow models however suffer from the lack of adaptivity. In this paper we define Adaptive Grid Workflow nets (AGWF nets) appropriate for modeling grid workflows and allowing changes in the process structure as a response to triggering events/exceptions. Moreover, a recursion is allowed, which makes the model especially appropriate for a number of grid applications. We show that soundness can be verified for AGWF nets
Scaling Rule for Nonperturbative Radiation in a Class of Event Shapes
We discuss nonperturbative radiation for a recently introduced class of
infrared safe event shape weights, which describe the narrow-jet limit.
Starting from next-to-leading logarithmic (NLL) resummation, we derive an
approximate scaling rule that relates the nonperturbative shape functions for
these weights to the shape function for the thrust. We argue that the scaling
reflects the boost invariance implicit in NLL resummation, and discuss its
limitations. In the absence of data analysis for the new event shapes, we
compare these predictions to the output of the event generator PYTHIA.Comment: 23 pages, 3 figures, uses JHEP3.cls (included); v2 - version to
appear in JHE
Solution and bulk properties of branched polyvinyl acetates IV--Melt viscosity
The melt viscosities of some randomly branched and some comb shaped branched polyvinyl acetate fractions were compared to the viscosities of linear polymer over a range of molecular weights. The melt viscosity of the branched polymer was usually higher than that of linear polymer of the same weight average molecular weight. The extent of this increase was related to the molecular weight of the branches but no correlation could be found which included the number of branches per molecule. This unusual behaviour is believed to be due to the fact that the length of the branches in the polymers of this study was above the critical chain length for polyvinyl acetate which made it possible for the branches to be engaged in intermolecular chain entanglements.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/32168/1/0000223.pd
Beyond nudges: Tools of a choice architecture
The way a choice is presented influences what a decision-maker chooses. This paper outlines the tools available to choice architects, that is anyone who present people with choices. We divide these tools into two categories: those used in structuring the choice task and those used in describing the choice options. Tools for structuring the choice task address the idea of what to present to decision-makers, and tools for describing the choice options address the idea of how to present it. We discuss implementation issues in using choice architecture tools, including individual differences and errors in evaluation of choice outcomes. Finally, this paper presents a few applications that illustrate the positive effect choice architecture can have on real- world decisions
Взаємозв’язок великих кондратьєвських циклів розвитку економіки і системних світових конфліктів
Однією з найважливіших проблем, що постала перед сучасною наукою у зв’язку із стрімким розгортанням глобальної економічної кризи, загостренням світових конфліктів, є вироблення науково обґрунтованих «метричних» експрес прогнозів розвитку суспільства на ближчу і далеку перспективу
Event Shape/Energy Flow Correlations
We introduce a set of correlations between energy flow and event shapes that
are sensitive to the flow of color at short distances in jet events. These
correlations are formulated for a general set of event shapes, which includes
jet broadening and thrust as special cases. We illustrate the method for
electron-positron annihilation dijet events, and calculate the correlation at
leading logarithm in the energy flow and at next-to-leading-logarithm in the
event shape.Comment: 43 pages, eight eps figures; minor changes, references adde
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