32,030 research outputs found
Renormalisation group evolution for the effective Hamiltonian with
We discuss the renormalisation group (RG) evolution for the
operators in unquenched QCD with () or, more generally,
() flavors. In particular, we focus on the
specific problem of how to treat the singularities which show up only for
or in the original solution of Buras {\it et al.} for the
RG evolution matrix at next-to-leading order. On top of Buras {\it et al.}'s
original treatment, we use a new method of analytic continuation to obtain the
correct solution in this case. It is free of singularities and can therefore be
used in numerical analysis of data sets calculated in lattice QCD.Comment: 7 pages, minor revisions, to appear in PR
An analytical solution for the elastoplastic response of a continuous fiber composite under uniaxial loading
A continuous fiber composite is modelled by a two-element composite cylinder in order to predict the elastoplastic response of the composite under a monotonically increasing tensile loading parallel to fibers. The fibers and matrix are assumed to be elastic-perfectly plastic materials obeying Hill's and Tresca's yield criteria, respectively. Here, the composite behavior when the fibers yield prior to the matrix is investigated
Structure of logarithmically divergent one-loop lattice Feynman integrals
For logarithmically divergent one-loop lattice Feynman integrals I(p,a),
subject to mild general conditions, we prove the following expected and crucial
structural result: I(p,a) = f(p)log(aM)+g(p)+h(p,M) up to terms which vanish
for lattice spacing a -> 0. Here p denotes collectively the external momenta
and M is a mass scale which may be chosen arbitrarily. The f(p) and h(p,M) are
shown to be universal and coincide with analogous quantities in the
corresponding continuum integral when the latter is regularized either by
momentum cut-off or dimensional regularization. The non-universal term g(p) is
shown to be a homogeneous polynomial in p of the same degree as f(p). This
structure is essential for consistency between renormalized lattice and
continuum formulations of QCD at one loop.Comment: 26 pages (after reformatting using revtex); typos corrected; to
appear in Phys.Rev.
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Integrated Dynamic Facade Control with an Agent-based Architecture for Commercial Buildings
Dynamic façades have significant technical potential to minimize heating, cooling, and lighting energy use and peak electric demand in the perimeter zone of commercial buildings, but the performance of these systems is reliant on being able to balance complex trade-offs between solar control, daylight admission, comfort, and view over the life of the installation. As the context for controllable energy-efficiency technologies grows more complex with the increased use of intermittent renewable energy resources on the grid, it has become increasingly important to look ahead towards more advanced approaches to integrated systems control in order to achieve optimum life-cycle performance at a lower cost. This study examines the feasibility of a model predictive control system for low-cost autonomous dynamic façades. A system architecture designed around lightweight, simple agents is proposed. The architecture accommodates whole building and grid level demands through its modular, hierarchical approach. Automatically-generated models for computing window heat gains, daylight illuminance, and discomfort glare are described. The open source Modelica and JModelica software tools were used to determine the optimum state of control given inputs of window heat gains and lighting loads for a 24-hour optimization horizon. Penalty functions for glare and view/ daylight quality were implemented as constraints. The control system was tested on a low-power controller (1.4 GHz single core with 2 GB of RAM) to evaluate feasibility. The target platform is a low-cost ($35/unit) embedded controller with 1.2 GHz dual-core cpu and 1 GB of RAM. Configuration and commissioning of the curtainwall unit was designed to be largely plug and play with minimal inputs required by the manufacturer through a web-based user interface. An example application was used to demonstrate optimal control of a three-zone electrochromic window for a south-facing zone. The overall approach was deemed to be promising. Further engineering is required to enable scalable, turnkey solutions
Progress on pricing with peering
This paper examines a simple model of how a
provider ISP charges customer ISPs by assuming the provider
ISP wants to maximize its revenue when customer ISPs have
the possibility of setting up peering connections. It is shown that
finding the optimal pricing is NP-complete, and APX-complete.
Customers can respond to price in many ways, including throttling
traffic as well as peering. An algorithm is studied which
obtains a 1/4 approximation for a wide range of customer
responses
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