A new Architecture for High Speed, Low Latency NB-LDPC Check Node Processing

International audience—Non-binary low-density parity-check codes have superior communications performance compared to their binary counterparts. However, to be an option for future standards, efficient hardware architectures must be developed. State-of-the-art decoding algorithms lead to architectures suffering from low throughput and high latency. The check node function accounts for the largest part of the decoders overall complexity. In this paper a new hardware aware check node algorithm and its architecture is proposed. It has state-of-the-art communications performance while reducing the decoding complexity. The presented architecture has a 14 times higher area efficiency, increases the energy efficiency by factor 2.5 and reduces the latency by factor of 3.5 compared to a state-of-the-art architecture

Statistical mechanics of ecological systems: Neutral theory and beyond

The simplest theories often have much merit and many limitations, and, in this vein, the value of neutral theory (NT) of biodiversity has been the subject of much debate over the past 15 years. NT was proposed at the turn of the century by Stephen Hubbell to explain several patterns observed in the organization of ecosystems. Among ecologists, it had a polarizing effect: There were a few ecologists who were enthusiastic, and there were a larger number who firmly opposed it. Physicists and mathematicians, instead, welcomed the theory with excitement. Indeed, NT spawned several theoretical studies that attempted to explain empirical data and predicted trends of quantities that had not yet been studied. While there are a few reviews of NT oriented toward ecologists, the goal here is to review the quantitative aspects of NT and its extensions for physicists who are interested in learning what NT is, what its successes are, and what important problems remain unresolved. Furthermore, this review could also be of interest to theoretical ecologists because many potentially interesting results are buried in the vast NT literature. It is proposed to make these more accessible by extracting them and presenting them in a logical fashion. The focus of this review is broader than NT: new, more recent approaches for studying ecological systems and how one might introduce realistic non-neutral models are also discussed

Size, Timing, and Landscape Impacts of Glacial Lake Outburst Floods in the Channeled Scabland of Eastern Washington, USA

Extreme floods have dramatically altered landscapes on Earth and Mars through bedrock erosion, sediment deposition, and canyon formation. The Channeled Scabland of the Columbia Plateau in eastern Washington, USA, is perhaps the most striking example of such a landscape, where outburst floods from an ice-dammed glacial Lake Missoula eroded immense canyons and transported large volumes of sediment during the late Pleistocene. Despite advances in numerical modeling and geochemical exposure dating methods, it has remained a challenge to untangle the complex interactions between floodwater, bedrock, and glacial ice to link the size of a flood with its impact on the landscape. When the landscape experiences erosion in response to multiple extreme floods, erosional and depositional features represent a discrete flood or phase of flooding, when topography and other initial conditions may have differed substantially from their modern configuration. This discrepancy limits the accuracy with which the hydraulics of prior catastrophic floods can be assessed using geologic evidence indicating the extent of flooding. An improved understanding of how extreme floods erode bedrock, and how to account for this erosion when interpreting the landforms left behind by extreme floods, is therefore necessary. In this dissertation, I re-evaluate discharges of extreme floods after accounting for the topographic change due to flood-induced erosion, and evaluate these discharges in the context of geologic evidence. I first compare the discharges necessary to inundate mapped high-water marks assuming various configurations of ice and bedrock representative of different phases of the formation of Grand Coulee, the largest canyon in the Channeled Scabland. I find that only 15–20% of the discharge that reaches the high-water marks in the present-day topography is needed to inundate the same high-water marks when the topography is reconstructed to a partially incised state, yet these smaller discharges produce sufficient shear stress to erode bedrock and permit canyon incision. I then extended the analysis to include three flood channels, applying a novel method that extrapolates the long profiles of hanging tributaries to reconstruct the pre-flood topography that floods first encountered and to quantify the degree of erosion for each channel. Similarly, I find that discharges 20–40% of those necessary to inundate high-water marks on the modern topography do so on the reconstructed topography. These smaller discharges could transport the volume of rock eroded from their respective canyons in approximately 7–18 floods, consistent with depositional evidence limited to high-energy floods. These floods constitute about 20% of the approximately 100 total floods from glacial Lake Missoula. Finally, I investigate the timing of floods through the major flood-modified pathways across the Columbia Plateau, using cosmogenic nuclide exposure dating, to determine the rate and timing of incision and place canyon formation in the context of the broader history of flooding in this landscape. I find that the two largest canyons in the Channeled Scabland eroded rapidly over the course of a single glaciation. Together, these results suggest that discharge estimates which rely on the modern topography of flood-carved canyons produce substantial overestimates. However, when the erosion produced by extreme floods is understood and accounted for, canyon geometry can reveal a wealth of information about the floods that carved them

Inequalities involving hypergeometric and related functions

Abstract An inequality is being proved which is connected to cost-effective numerical density estimation of the hyper-gamma probability distribution. The left-hand side of the inequality is a combination of two in the third parameter distinct versions of the hypergeometric function at the point one. All three parameters are functions of the distribution’s terminal shape. The first and second are equal. The distinct third parameters of the two hypergeometric functions depend on terminal and initial shape. The other side of the inequality is determined by the quotient of two infinite series, which are related to the first derivatives with respect to terminal shape of the hypergeometric functions which appear in its left-hand side