212 research outputs found
On upper bounds on the smallest size of a saturating set in a projective plane
In a projective plane (not necessarily Desarguesian) of order
a point subset is saturating (or dense) if any point of is collinear with two points in. Using probabilistic methods, the
following upper bound on the smallest size of a saturating set in
is proved: \begin{equation*} s(2,q)\leq 2\sqrt{(q+1)\ln
(q+1)}+2\thicksim 2\sqrt{q\ln q}. \end{equation*} We also show that for any
constant a random point set of size in with is a saturating
set with probability greater than Our probabilistic
approach is also applied to multiple saturating sets. A point set is -saturating if for every point of the number of secants of through is at least , counted with
multiplicity. The multiplicity of a secant is computed as
The following upper bound on the smallest
size of a -saturating set in is proved:
\begin{equation*} s_{\mu }(2,q)\leq 2(\mu +1)\sqrt{(q+1)\ln (q+1)}+2\thicksim
2(\mu +1)\sqrt{ q\ln q}\,\text{ for }\,2\leq \mu \leq \sqrt{q}. \end{equation*}
By using inductive constructions, upper bounds on the smallest size of a
saturating set (as well as on a -saturating set) in the projective
space are obtained.
All the results are also stated in terms of linear covering codes.Comment: 15 pages, 24 references, misprints are corrected, Sections 3-5 and
some references are adde
Towards Traditional Carbon Fillers: Biochar-Based Reinforced Plastic
The global market of carbon-reinforced plastic represents one of the largest economic platforms. This sector is dominated by carbon black (CB) produced from traditional oil industry. Recently, high technological fillers such as carbon fibres or nanostructured carbon (i.e. carbon nanotubes, graphene, graphene oxide) fillers have tried to exploit their potential but without economic success. So, in this chapter we are going to analyse the use of an unconventional carbon filler called biochar. Biochar is the solid residue of pyrolysis and can be a solid and sustainable replacement for traditional and expensive fillers. In this chapter, we will provide overview of the last advancement in the use of biochar as filler for the production of reinforced plastics
Introducing the Novel Mixed Gaussian-Lorentzian Lineshape in the Analysis of the Raman Signal of Biochar
In this research, an innovative procedure is proposed to elaborate Raman spectra obtained
from nanostructured and disordered solids. As a challenging case study, biochar, a bio-derived
carbon based material, was selected. The complex structure of biochar (i.e., channeled surface,
inorganic content) represents a serious challenge for Raman characterization. As widely reported,
the Raman spectra are closely linked to thermal treatments of carbon material. The individual
contributions to the Raman spectra are difficult to identify due to the numerous peaks that
contribute to the spectra. To tackle this problem, we propose a brand new approach based on the
introduction, on sound theoretical grounds, of a mixed Gaussian-–Lorentzian lineshape. As per the
experimental part, biochar samples were carbonized in an inert atmosphere at various temperatures
and their respective spectra were successfully decomposed using the new lineshape. The evolution
of the structure with carbonization temperature was investigated by Raman and XRD analysis. The
results of the two techniques fairly well agree. Compared to other approaches commonly reported
in the literature this method (i) gives a sounder basis to the lineshape used in disordered materials,
and (ii) appears to reduce the number of components, leading to an easier understanding of their
origin
- …