Weight Distributions of Regular Low-Density Parity-Check Codes over Finite Fields

The average weight distribution of a regular low-density parity-check (LDPC) code ensemble over a finite field is thoroughly analyzed. In particular, a precise asymptotic approximation of the average weight distribution is derived for the small-weight case, and a series of fundamental qualitative properties of the asymptotic growth rate of the average weight distribution are proved. Based on this analysis, a general result, including all previous results as special cases, is established for the minimum distance of individual codes in a regular LDPC code ensemble.Comment: 15 pages, 5 figures, accepted for publication in IEEE Transactions on Information Theory, July 201

Weight Distribution for Non-binary Cluster LDPC Code Ensemble

In this paper, we derive the average weight distributions for the irregular non-binary cluster low-density parity-check (LDPC) code ensembles. Moreover, we give the exponential growth rate of the average weight distribution in the limit of large code length. We show that there exist $(2,d_c)$-regular non-binary cluster LDPC code ensembles whose normalized typical minimum distances are strictly positive.Comment: 12pages, 6 figures, To be presented in ISIT2013, Submitted to IEICE Trans. Fundamental

Assessment of Spring Barley Populations in Comparison to Homogenous Varieties

The necessity to increase genetic diversity in agriculture has been widely discussed during the last decades. Heterogeneous populations is one of the ways to increase genetic diversity in varieties of self-pollinating cereals. The aim of this research was to compare grain yield, its stability, foliar diseases severity and competitiveness against the weeds of spring barley (Hordeum vulgare) populations and homogenous varieties. Field trials consisting of three types of populations (simple, complex and composite cross populations – CCP) containing different levels of diversity and three check varieties were carried out during 2015-2018 under organic and conventional farming systems. No one of the populations had a significantly higher average yield than any of the check varieties. CCP1 showed a tendency to be more productive under organic growing conditions and can be characterized as widely adaptable to various growing conditions with a significantly higher yield as the average overall environments. One of the complex populations showed adaptability to favorable growing conditions and yield insignificantly higher than overall average. Other studied populations can be characterized with wide adaptability and various yield levels. For most of the populations under organic and conventional conditions, a significantly lower net blotch (caused by Pyrenophora teres) severity was observed in comparison with the most susceptible variety; infection with powdery mildew (caused by Blumeria graminis) lower than for check varieties was observed under organic growing conditions, whereas such trend was not observed under conventional conditions. All populations had a significantly lower crop ground cover and slightly lower competiveness against weeds than the variety with the best competitiveness

Adapting lowland rice cultivation to climate change - thermal stress tolerance breeding in the Sahel region of West Africa

The Sahel region of West Africa is characterized by extreme diurnal and seasonal temperature variation subjecting the rice crop to thermal stress at different growth stages. The Africa Rice Center in collaboration with partners is aims to identify rice genotypes and associated traits for use in breeding varieties adapted to the Sahel climate. In one set of field trials established at Ndiaye, Senegal, 244 diverse rice genotypes, including four checks, were sown in February, March, April and July subjecting the rice plants to cold and heat stress at different growth stages. Daily minimum temperatures fell below 20 °C in the months of February and March whilst maximum temperatures regularly rose above 40 °C in April, May and June. The rice crop is thus subjected to cold stress in February and March and to heat stress in April to June. Across the planting dates, total biomass production was highest on average for the February planting date (293.8g/plant) followed by the April planting date (281.0g/plant) and lowest for the July planting date (215.4g/plant). However, spikelet sterility was highest for the April planting date on average relative to other planting dates and lowest for the July planting date. On average plantings in July were earliest (100 days from sowing to maturity) relative to other planting dates whilst plantings in February which corresponded to the sowing date for the dry season crop had the longest crop durations (137 days from sowing to maturity). With regards to crop duration across the planting dates, Chromrong a cold tolerant check from Nepal had the shortest duration across all dates whilst N22 the international heat tolerant check had the longest duration. IR64 an international irrigated lowland check variety and Sahel 108 a local check variety had crop durations generally intermediate between these two checks. Large genotypic variations detected in these traits will be exploited in selecting parents to develop new varieties better adapted to the seasonal Sahelian climate. (Texte intégral

Generation of uncorrelated random scale-free networks

Uncorrelated random scale-free networks are useful null models to check the accuracy an the analytical solutions of dynamical processes defined on complex networks. We propose and analyze a model capable to generate random uncorrelated scale-free networks with no multiple and self-connections. The model is based on the classical configuration model, with an additional restriction on the maximum possible degree of the vertices. We check numerically that the proposed model indeed generates scale-free networks with no two and three vertex correlations, as measured by the average degree of the nearest neighbors and the clustering coefficient of the vertices of degree $k$, respectively

Error Exponents of Low-Density Parity-Check Codes on the Binary Erasure Channel

We introduce a thermodynamic (large deviation) formalism for computing error exponents in error-correcting codes. Within this framework, we apply the heuristic cavity method from statistical mechanics to derive the average and typical error exponents of low-density parity-check (LDPC) codes on the binary erasure channel (BEC) under maximum-likelihood decoding.Comment: 5 pages, 4 figure

Biofouling Effects on the Response of a Wave Measurement Buoy in Deep Water

AbstractThe effects of biofouling on a wave measurement buoy are examined using concurrent data collected with two Datawell Waveriders at Ocean Station P: one heavily biofouled at the end of a 26-month deployment, the other newly deployed and clean. The effects are limited to the high-frequency response of the buoy and are correctly diagnosed with the spectral “check factors” that compare horizontal and vertical displacements. A simple prediction for the progressive change in frequency response during biofouling reproduces the check factors over time. The bulk statistical parameters of significant wave height, peak period, average period, and peak direction are only slightly affected by the biofouling because the contaminated frequencies have very low energy throughout the comparison dataset.</jats:p

On Centroidal Dynamics and Integrability of Average Angular Velocity

In the literature on robotics and multibody dynamics, the concept of average angular velocity has received considerable attention in recent years. We address the question of whether the average angular velocity defines an orientation framethat depends only on the current robot configuration and provide a simple algebraic condition to check whether this holds. In the language of geometric mechanics, this condition corresponds to requiring the flatness of the mechanical connection associated to the robotic system. Here, however, we provide both a reinterpretation and a proof of this result accessible to readers with a background in rigid body kinematics and multibody dynamics but not necessarily acquainted with differential geometry, still providing precise links to the geometric mechanics literature. This should help spreading the algebraic condition beyond the scope of geometric mechanics,contributing to a proper utilization and understanding of the concept of average angular velocity.Comment: 8 pages, accepted for IEEE Robotics and Automation Letters (RA-L