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Página 1 dos resultados de 20101 itens digitais encontrados em 0.004 segundos

- IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC
- Elsevier; Amsterdam
- Oxford University Press
- Cold Spring Harbor Laboratory Press
- Nature Publishing Group
- World Bank, Washington, DC
- Springer US
- Murcia: Escuela de Turismo
- BioMed Central
- Corporation des bibliothécaires professionels du Québec (CBPQ) www.cbpq.ca
- Massachusetts Institute of Technology
- Universidade Cornell
- Universidade de Delaware
- Mais Publicadores...

Resultados filtrados por Publicador: Universidade Cornell

## ‣ Accessible Capacity of Secondary Users

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Português

Relevância na Pesquisa
250.05318%

A new problem formulation is presented for the Gaussian interference channels
(GIFC) with two pairs of users, which are distinguished as primary users and
secondary users, respectively. The primary users employ a pair of encoder and
decoder that were originally designed to satisfy a given error performance
requirement under the assumption that no interference exists from other users.
In the scenario when the secondary users attempt to access the same medium, we
are interested in the maximum transmission rate (defined as {\em accessible
capacity}) at which secondary users can communicate reliably without affecting
the error performance requirement by the primary users under the constraint
that the primary encoder (not the decoder) is kept unchanged. By modeling the
primary encoder as a generalized trellis code (GTC), we are then able to treat
the secondary link and the cross link from the secondary transmitter to the
primary receiver as finite state channels (FSCs). Based on this, upper and
lower bounds on the accessible capacity are derived. The impact of the error
performance requirement by the primary users on the accessible capacity is
analyzed by using the concept of interference margin. In the case of
non-trivial interference margin...

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## ‣ Colimits of accessible categories

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 04/10/2011
Português

Relevância na Pesquisa
248.43855%

We show that any directed colimit of acessible categories and accessible full
embeddings is accessible and, assuming the existence of arbitrarily large
strongly compact cardinals, any directed colimit of acessible categories and
accessible embeddings is accessible.

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## ‣ Local properties of accessible injective operator ideals

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Publicado em 23/04/1996
Português

Relevância na Pesquisa
248.43855%

In addition to Pisier's counterexample of a non-accessible maximal Banach
ideal, we will give a large class of maximal Banach ideals which {\it{are
accessible}}. The first step is implied by the observation that a "good
behaviour" of trace duality, which is canonically induced by conjugate
operator ideals can be extended to adjoint Banach ideals, if and only if these
adjoint ideals satisfy an accessibility condition (theorem 3.1). This
observation leads in a natural way to a characterization of accessible
injective Banach ideals, where we also recognize the appearance of the ideal
of {\it{absolutely summing operators}} (prop. 4.1). By the famous
{\it{Grothendieck inequality}}, every operator from $L_1$ to a Hilbert space
is absolutely summing, and therefore our search for such ideals will be
directed towards Hilbert space factorization - via an operator version of
Grothendieck's inequality (lemma 4.2). As a consequence,we obtain a class of
injective ideals, which are "quasi-accessible", and with the help of
{\it{tensor stability}}, we improve the corresponding norm inequalities, to
get accessibility (theorem 4.1 and 4.2). In the last chapter of this paper we
give applications, which are implied by a non-trivial link of the above
mentioned considerations to normed products of operator ideals.

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## ‣ On the existence of accessible paths in various models of fitness landscapes

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Português

Relevância na Pesquisa
250.05318%

We present rigorous mathematical analyses of a number of well-known
mathematical models for genetic mutations. In these models, the genome is
represented by a vertex of the $n$-dimensional binary hypercube, for some $n$,
a mutation involves the flipping of a single bit, and each vertex is assigned a
real number, called its fitness, according to some rules. Our main concern is
with the issue of existence of (selectively) accessible paths; that is,
monotonic paths in the hypercube along which fitness is always increasing. Our
main results resolve open questions about three such models, which in the
biophysics literature are known as house of cards (HoC), constrained house of
cards (CHoC) and rough Mount Fuji (RMF). We prove that the probability of there
being at least one accessible path from the all-zeroes node $\mathbf {v}^0$ to
the all-ones node $\mathbf {v}^1$ tends respectively to 0, 1 and 1, as $n$
tends to infinity. A crucial idea is the introduction of a generalization of
the CHoC model, in which the fitness of $\mathbf {v}^0$ is set to some
$\alpha=\alpha_n\in[0,1]$. We prove that there is a very sharp threshold at
$\alpha_n=\frac{\ln n}{n}$ for the existence of accessible paths from $\mathbf
{v}^0$ to $\mathbf {v}^1$. As a corollary we prove significant concentration...

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## ‣ Effect of hydrogel particle additives on water-accessible pore structure of sandy soils: A custom pressure plate apparatus and capillary bundle model

Fonte: Universidade Cornell
Publicador: Universidade Cornell

Tipo: Artigo de Revista Científica

Português

Relevância na Pesquisa
250.05318%

To probe the effects of hydrogel particle additives on the water-accessible
pore structure of sandy soils, we introduce a custom pressure plate method in
which the volume of water expelled from a wet granular packing is measured as a
function of applied pressure. Using a capillary bundle model, we show that the
differential change in retained water per pressure increment is directly
related to the cumulative cross-sectional area distribution $f(r)$ of the
water-accessible pores with radii less than $r$. This is validated by
measurements of water expelled from a model sandy soil composed of 2 mm
diameter glass beads. In particular, the expelled water is found to depend
dramatically on sample height and that analysis using the capillary bundle
model gives the same pore size distribution for all samples. The distribution
is found to be approximately log-normal, and the total cross-sectional area
fraction of the accessible pore space is found to be $f_0=0.34$. We then report
on how the pore distribution and total water-accessible area fraction are
affected by superabsorbent hydrogel particle additives, uniformly mixed into a
fixed-height sample at varying concentrations. Under both fixed volume and free
swelling conditions, the total area fraction of water-accessible pore space in
a packing decreases exponentially as the gel concentration increases. The size
distribution of the pores is significantly modified by the swollen hydrogel
particles...

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