Convolutional Goppa Codes

We define Convolutional Goppa Codes over algebraic curves and construct their corresponding dual codes. Examples over the projective line and over elliptic curves are described, obtaining in particular some Maximum-Distance Separable (MDS) convolutional codes.Comment: 8 pages, submitted to IEEE Trans. Inform. Theor

Extinction calculations of multi-sphere polycrystalline graphitic clusters - A comparison with the 2175 AA peak and between a rigorous solution and discrete-dipole approximations

Certain dust particles in space are expected to appear as clusters of individual grains. The morphology of these clusters could be fractal or compact. In this paper we study the light scattering by compact and fractal polycrystalline graphitic clusters consisting of touching identical spheres. We compare three general methods for computing the extinction of the clusters in the wavelength range 0.1 - 100 micron, namely, a rigorous solution (Gerardy & Ausloos 1982) and two different discrete-dipole approximation methods -- MarCODES (Markel 1998) and DDSCAT (Draine & Flatau 1994). We consider clusters of N = 4, 7, 8, 27,32, 49, 108 and 343 particles of radii either 10 nm or 50 nm, arranged in three different geometries: open fractal (dimension D = 1.77), simple cubic and face-centred cubic. The rigorous solution shows that the extinction of the fractal clusters, with N < 50 and particle radii 10 nm, displays a peak within 2% of the location of the observed interstellar extinction peak at ~4.6 inverse micron; the smaller the cluster, the closer its peak gets to this value. By contrast, the peak in the extinction of the more compact clusters lie more than 4% from 4.6 inverse micron. At short wavelengths (0.1 - 0.5 micron), all the methods show that fractal clusters have markedly different extinction from those of non-fractal clusters. At wavelengths > 5 micron, the rigorous solution indicates that the extinction from fractal and compact clusters are of the same order of magnitude. It was only possible to compute fully converged results of the rigorous solution for the smaller clusters, due to computational limitations, however, we find that both discrete-dipole approximation methods overestimate the computed extinction of the smaller fractal clusters.Comment: Corrections added in accordance with suggestions by the referee. 12 pages, 12 figures. Accepted for publication in Astronomy & Astrophysic

Energy Evaluation of the Use of an Absorption Heat Pump in Water Distillation Process

It is impossible to transform the whole energy into useful work. It is impossible to increase the processes of cultivation of foods without water. It is impossible to separate all ions and minerals from water. Most of the real processes are thermodynamically irreversible. Calculations may indicate the fraction of efficiency of a thermal process. All the above mentioned facts have led to some proposals of cycles that exchange energy in order to produce a useful effect for the society. The key sustainable related parts are: to obtain water free of minerals or ions by distillation process. In this chapter, thermodynamic cycles will be explained for distillation using thermodynamic cycles of thermal machines called absorption heat pumps (AHPs). Distillation process offers to the AHPs an opportunity to diminish the consumptions of fossil fuels. The AHPs are able to work with 2% of mechanical energy to carry out a sustainable distillation process. Most of the energy of an absorption heat pump operation is thermal energy. The operation of the AHPs are defined with the coefficient of performance (COP); the variations of this parameter are shown as function of the different scenarios to obtain sustainable distilled water

Mechanical properties of zeolitic metal-organic frameworks: Mechanically flexible topologies and stabilization against structural collapse

We report the low elastic modulus of a zeolitic MOF, along with stabilization against structural collapse by filling with solvent.This is the author-accepted manuscript. It is under embargo for 12 months after publication. The final version of this article is published by RSC in CrystEngComm and can be found here: http://dx.doi.org/10.1039/c4ce02145