111,273 research outputs found

### A connection element for modelling end-plate connections in fire

In this paper a robust 2-noded connection element has been developed for modelling the bolted end-plate connection between a steel beam and column at elevated temperatures. The connection element allows the element nodes to be placed at the reference plane with offset and the non-uniform temperature distributions within the connection. In this model the connection failure due to bending, axial tension, compression and vertical shear are considered. The influence of the axial tensile force of the connected beam on the connection is also taken into account. This model has the advantages of both the previous simple and component-based models. A total of 23 fire tests were used to extensively validate the model. It can be seen that the current model is robust and has a capability to predict the behaviour of a bolted end-plate connection under fire attack with reasonable accuracy. Compared to the tested results the predictions of the current model were mainly on the conservative side. Hence, the model can be used for structural fire engineering design on steel-framed composite buildings. The idea described in this paper can also easily be applied to develop other kinds of connections, such as simple connections, column based connections or hollow section connections, and so on. (c) 2010 Elsevier Ltd. All rights reserved

### Codes Cross-Correlation Impact on S-curve Bias and Data-Pilot Code Pairs Optimization for CBOC Signals

The aim of this paper is to analyze the impact of spreading codes cross-correlation on code tracking performance, and to optimize the data-pilot code pairs of Galileo E1 Open Service (OS) Composite Binary Offset Carrier (CBOC) signals. The distortion of the discriminator function (i.e., S-curve), due to data and pilot spreading codes cross-correlation properties, is evaluated when only the data or pilot components of CBOC signals are tracked, considering the features of the modulation schemes. Analyses show that the S-curve bias also depends on the receiver configuration (e.g., the tracking algorithm and correlator spacing). In this paper, two methods are proposed to optimize the data-pilot code pairs of Galileo E1 OS. The optimization goal is to obtain minimum average S-curve biases when tracking only the pilot components of CBOC signals for the specific correlator spacing. The S-curve biases after optimization processes are analyzed and compared with the un-optimized results. It is shown that the optimized data-pilot code pairs could significantly mitigate the intra-channel (i.e., data and pilot) codes cross-correlation，and then improve the code tracking performance of CBOC signals

### The tensor structure on the representation category of the $\mathcal{W}_p$ triplet algebra

We study the braided monoidal structure that the fusion product induces on
the abelian category $\mathcal{W}_p$-mod, the category of representations of
the triplet $W$-algebra $\mathcal{W}_p$. The $\mathcal{W}_p$-algebras are a
family of vertex operator algebras that form the simplest known examples of
symmetry algebras of logarithmic conformal field theories. We formalise the
methods for computing fusion products, developed by Nahm, Gaberdiel and Kausch,
that are widely used in the physics literature and illustrate a systematic
approach to calculating fusion products in non-semi-simple representation
categories. We apply these methods to the braided monoidal structure of
$\mathcal{W}_p$-mod, previously constructed by Huang, Lepowsky and Zhang, to
prove that this braided monoidal structure is rigid. The rigidity of
$\mathcal{W}_p$-mod allows us to prove explicit formulae for the fusion product
on the set of all simple and all projective $\mathcal{W}_p$-modules, which were
first conjectured by Fuchs, Hwang, Semikhatov and Tipunin; and Gaberdiel and
Runkel.Comment: 58 pages; edit: added references and revisions according to referee
reports. Version to appear on J. Phys.

### Open-closed field algebras

We introduce the notions of open-closed field algebra and open-closed field
algebra over a vertex operator algebra V. In the case that V satisfies certain
finiteness and reductivity conditions, we show that an open-closed field
algebra over V canonically gives an algebra over a \C-extension of the
Swiss-cheese partial operad. We also give a tensor categorical formulation and
categorical constructions of open-closed field algebras over V.Comment: 55 pages, largely revised, an old subsection is deleted, a few
references are adde

### Vertex operator algebras, the Verlinde conjecture and modular tensor categories

Let V be a simple vertex operator algebra satisfying the following
conditions: (i) The homogeneous subspaces of V of weights less than 0 are 0,
the homogeneous subspace of V of weight 0 is spanned by the vacuum and V' is
isomorphic to V as a V-module. (ii) Every weak V-module gradable by nonnegative
integers is completely reducible. (iii) V is C_2-cofinite. We announce a proof
of the Verlinde conjecture for V, that is, of the statement that the matrices
formed by the fusion rules among irreducible V-modules are diagonalized by the
matrix given by the action of the modular transformation \tau\mapsto -1/\tau on
the space of characters of irreducible V-modules. We discuss some consequences
of the Verlinde conjecture, including the Verlinde formula for the fusion
rules, a formula for the matrix given by the action of \tau\mapsto -1/\tau and
the symmetry of this matrix. We also announce a proof of the rigidity and
nondegeneracy property of the braided tensor category structure on the category
of V-modules when V satisfies in addition the condition that irreducible
V-modules not equivalent to V has no nonzero elements of weight 0. In
particular, the category of V-modules has a natural structure of modular tensor
category.Comment: 18 pages. To appear in the Proc. Natl. Acad. Sci. US

### Bootstrap consistency for general semiparametric $M$-estimation

Consider $M$-estimation in a semiparametric model that is characterized by a
Euclidean parameter of interest and an infinite-dimensional nuisance parameter.
As a general purpose approach to statistical inferences, the bootstrap has
found wide applications in semiparametric $M$-estimation and, because of its
simplicity, provides an attractive alternative to the inference approach based
on the asymptotic distribution theory. The purpose of this paper is to provide
theoretical justifications for the use of bootstrap as a semiparametric
inferential tool. We show that, under general conditions, the bootstrap is
asymptotically consistent in estimating the distribution of the $M$-estimate of
Euclidean parameter; that is, the bootstrap distribution asymptotically
imitates the distribution of the $M$-estimate. We also show that the bootstrap
confidence set has the asymptotically correct coverage probability. These
general conclusions hold, in particular, when the nuisance parameter is not
estimable at root-$n$ rate, and apply to a broad class of bootstrap methods
with exchangeable bootstrap weights. This paper provides a first general
theoretical study of the bootstrap in semiparametric models.Comment: Published in at http://dx.doi.org/10.1214/10-AOS809 the Annals of
Statistics (http://www.imstat.org/aos/) by the Institute of Mathematical
Statistics (http://www.imstat.org

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