18,889 research outputs found
Convertible Codes: New Class of Codes for Efficient Conversion of Coded Data in Distributed Storage
Erasure codes are typically used in large-scale distributed storage systems to provide durability of data in the face of failures. In this setting, a set of k blocks to be stored is encoded using an [n, k] code to generate n blocks that are then stored on different storage nodes. A recent work by Kadekodi et al. [Kadekodi et al., 2019] shows that the failure rate of storage devices vary significantly over time, and that changing the rate of the code (via a change in the parameters n and k) in response to such variations provides significant reduction in storage space requirement. However, the resource overhead of realizing such a change in the code rate on already encoded data in traditional codes is prohibitively high.
Motivated by this application, in this work we first present a new framework to formalize the notion of code conversion - the process of converting data encoded with an [n^I, k^I] code into data encoded with an [n^F, k^F] code while maintaining desired decodability properties, such as the maximum-distance-separable (MDS) property. We then introduce convertible codes, a new class of code pairs that allow for code conversions in a resource-efficient manner. For an important parameter regime (which we call the merge regime) along with the widely used linearity and MDS decodability constraint, we prove tight bounds on the number of nodes accessed during code conversion. In particular, our achievability result is an explicit construction of MDS convertible codes that are optimal for all parameter values in the merge regime albeit with a high field size. We then present explicit low-field-size constructions of optimal MDS convertible codes for a broad range of parameters in the merge regime. Our results thus show that it is indeed possible to achieve code conversions with significantly lesser resources as compared to the default approach of re-encoding
Greenhouse Gas Inventory in the Forestry Sector
Among the components in the inventory of greenhouse gas sources and sinks, forestry and land use are the most complex. This paper summarizes the necessary data on land use. Analysis indicates a change in the inventory/sinks done by the Philippine Forestry and Land Use Change.land use planning, natural resources and environment, forestry sector, land management
Greenhouse Gas Inventory in the Forestry Sector
Among the components in the inventory of greenhouse gas sources and sinks, forestry and land use are the most complex. This paper summarizes the necessary data on land use. Analysis indicates a change in the inventory/sinks done by the Philippine Forestry and Land Use Change.land use planning, natural resources and environment, forestry sector, land management
Endosperm sterol phenotype and germination in wheat
Free and conjugated sterols of endosperm, coats, scutellum, coleoptile and roots have been analysed at different germination stages in two wheat cultivars with different endosperm sterol phenotypes. It seems that sterol metabolism of the developing tissues, namely coleoptile and roots, is not affected by the sterol conjugation profile of the endosperm. Enough sterol is present in the mature embryo to supply the germinating axis during the observation period (144 hr at 16°). The data suggest that sterol is transferred from scutellum to coleoptile and roots during germinatio
Disorder-induced mechanism for positive exchange bias fields
We propose a mechanism to explain the phenomenon of positive exchange bias on
magnetic bilayered systems. The mechanism is based on the formation of a domain
wall at a disordered interface during field cooling (FC) which induces a
symmetry breaking of the antiferromagnet, without relying on any ad hoc
assumption about the coupling between the ferromagnetic (FM) and
antiferromagnetic (AFM) layers. The domain wall is a result of the disorder at
the interface between FM and AFM, which reduces the effective anisotropy in the
region. We show that the proposed mechanism explains several known experimental
facts within a single theoretical framework. This result is supported by Monte
Carlo simulations on a microscopic Heisenberg model, by micromagnetic
calculations at zero temperature and by mean field analysis of an effective
Ising like phenomenological model.Comment: 5 pages, 4 figure
Interferometric evanescent wave excitation of nano-antenna for ultra-sensitive displacement and phase metrology
We propose a method for ultra-sensitive displacement and phase metrology
based on the interferometric evanescent wave excitation of nano-antennas. We
show that with a proper choice of nano-antenna, tiny displacements or relative
phase variations can be converted into sensitive scattering direction changes
in the Fourier -space. These changes stem from the strong position
dependence of the imaginary Poynting vector orientation within interfering
evanescent waves. Using strongly-evanescent standing waves, high sensitivity is
achieved in the nano-antenna's zero scattering direction, which varies linearly
with displacement over a long range. With weakly-evanescent wave interference,
even higher sensitivity to tiny displacement or phase changes can be reached
around chosen location. The high sensitivity of the proposed method can form
the basis for many applications
Multivectorial strategy to interpret a resistive behaviour of loads in smart buildings
In Smart buildings, electric loads are affected by an
important distortion in the current and voltage waveforms,
caused by the increasing proliferation of non linear electronic
devices. This paper presents an approach on non sinusoidal
power theory based on Geometric Algebra that clearly improves
traditional methods in the optimization of apparent power and
power factor compensation. An example is included that
demonstrates the superiority of this approach compared with
traditional methods.Universidad de Málaga. Campus de Excelencia Internacional AndalucĂa Tech
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