14,027 research outputs found
On the Performance Prediction of BLAS-based Tensor Contractions
Tensor operations are surging as the computational building blocks for a
variety of scientific simulations and the development of high-performance
kernels for such operations is known to be a challenging task. While for
operations on one- and two-dimensional tensors there exist standardized
interfaces and highly-optimized libraries (BLAS), for higher dimensional
tensors neither standards nor highly-tuned implementations exist yet. In this
paper, we consider contractions between two tensors of arbitrary dimensionality
and take on the challenge of generating high-performance implementations by
resorting to sequences of BLAS kernels. The approach consists in breaking the
contraction down into operations that only involve matrices or vectors. Since
in general there are many alternative ways of decomposing a contraction, we are
able to methodically derive a large family of algorithms. The main contribution
of this paper is a systematic methodology to accurately identify the fastest
algorithms in the bunch, without executing them. The goal is instead
accomplished with the help of a set of cache-aware micro-benchmarks for the
underlying BLAS kernels. The predictions we construct from such benchmarks
allow us to reliably single out the best-performing algorithms in a tiny
fraction of the time taken by the direct execution of the algorithms.Comment: Submitted to PMBS1
Historical data as a baseline for conservation: reconstructing long-term faunal extinction dynamics in Late Imperial–modern China
Extinction events typically represent extended processes of decline that cannot be reconstructed using short-term studies. Long-term archives are necessary to determine past baselines and the extent of human-caused biodiversity change, but the capacity of historical datasets to provide predictive power for conservation must be assessed within a robust analytical framework. Local Chinese gazetteers represent a >400-year country-level dataset containing abundant information on past environmental conditions and include extensive records of gibbons, which have a restricted present-day distribution but formerly occurred across much of China. Gibbons show pre-twentieth century range contraction, with significant fragmentation by the mid-eighteenth century and population loss escalating in the late nineteenth century. Isolated gibbon populations persisted for ~40 years before local extinction. Populations persisted for longer at higher elevations, and disappeared earlier from northern and eastern regions, with the biogeography of population loss consistent with the contagion model of range collapse in response to human demographic expansion spreading directionally across China. The long-term Chinese historical record can track extinction events and human interactions with the environment across much longer timescales than are usually addressed in ecology, contributing novel baselines for conservation and an increased understanding of extinction dynamics and species vulnerability or resilience to human pressures
Наукова спадщина О.О. Русова в контексті актуальних проблем української етнології
У лютому виповнилося 160 років з дня народження відомого вченого, етнографа, статистика та громадського діяча Олександра Русова.This article is devoted to the famous scholar, ethnographer, civil activist Oleksandr Rusov. All his work was concentrated on the study of Ukrainian folk, their history, life style and language. Among his most prominent works was the foundation of the statistics as the scholarly discipline and its use for the ethnographical studies. Special attention deserves his work “The Statistics of the Ukrainian Population of the European Russia”. His data on Ukrainian and Russian population in various regions at different historical times are very valuable for the contemporary scholars. He actively participated in Ukrainian cultural life: he was the organizer of the first Ukrainian plays on Kyiv stages, the editor of Prague edition of “Kobzar”, and participated in different social and cultural organizations
Controlling Nanowire Growth by Light.
Individual Au catalyst nanoparticles are used for selective laser-induced chemical vapor deposition of single germanium nanowires. Dark-field scattering reveals in real time the optical signatures of all key constituent growth processes. Growth is initially triggered by plasmonic absorption in the Au catalyst, while once nucleated the growing Ge nanowire supports magnetic and electric resonances that then dominate the laser interactions. This spectroscopic understanding allows real-time laser feedback that is crucial toward realizing the full potential of controlling nanomaterial growth by light.We acknowledge financial support from EPSRC Grant EP/G060649/1, EP/L027151/1, EP/G037221/1, EPSRC NanoDTC, and ERC Grant LINASS 320503. S.H. acknowledges funding from ERC Grant InsituNANO 279342.This is the author accepted manuscript. The final version is available from ACS via http://dx.doi.org/10.1021/acs.nanolett.5b0295
Palaeohydrology of the Mulhouse Basin: are fluid inclusions in halite tracers of past seawater composition?
Brine reactions processes were the most important factors controlling the major-ion evolution in the Oligocene, Mulhouse Basin (France) evaporite basin. The combined
analysis of fluid inclusions in primary textures in halite by Cryo-SEM-EDS with sulfate-δ34S, δ18O and 87Sr/86Sr isotope
ratios reveals hydrothermal inputs and recycling of Permian evaporites, particularly during advanced stages of evaporation in the Salt IV member which ended with sylvite formation. The lower part of the Salt IV evolved from an originally
marine input. Sulfate-δ34S shows Oligocene marine-like signatures at the base of the member (Fig.1). However, enriched sulfate-δ18O reveals the importance of re-oxidation
processes. As evaporation progressed other non-marine or marine-modified inputs from neighbouring basins became more important. This is demonstrated by an increase in K
concentrations in brine inclusions, Br in halite and variations in sulfate isotopes trends and 87Sr/86Sr ratios. The recycling of
previously precipitated evaporites was increasingly important with evaporation. Therefore, regardless of the apparent marine
sequence (gypsum, halite, potassic salts), the existence of diverse inputs and the consequent chemical changes to the brine preclude the use of trapped brine inclusions in direct reconstruction of Oligocene seawater chemistry.European Association for Geochemistry; Geochemical Societ
Seasonal Training-Load Quantification in Elite English Premier League Soccer Players
Purpose: To quantify the seasonal training load completed by professional soccer players of the English Premier League. Methods: Thirty players were sampled (using GPS, heart rate, and rating of perceived exertion [RPE]) during the daily training sessions of the 2011–12 preseason and in-season period. Preseason data were analyzed across 6 × 1-wk microcycles. In-season data were analyzed across 6 × 6-wk mesocycle blocks and 3 × 1-wk microcycles at start, midpoint, and end-time points. Data were also analyzed with respect to number of days before a match. Results: Typical daily training load (ie, total distance, high-speed distance, percent maximal heart rate [%HRmax], RPE load) did not differ during each week of the preseason phase. However, daily total distance covered was 1304 (95% CI 434–2174) m greater in the 1st mesocycle than in the 6th. %HRmax values were also greater (3.3%, 1.3–5.4%) in the 3rd mesocycle than in the first. Furthermore, training load was lower on the day before match (MD-1) than 2 (MD-2) to 5 (MD-5) d before a match, although no difference was apparent between these latter time points. Conclusions: The authors provide the 1st report of seasonal training load in elite soccer players and observed that periodization of training load was typically confined to MD-1 (regardless of mesocycle), whereas no differences were apparent during MD-2 to MD-5. Future studies should evaluate whether this loading and periodization are facilitative of optimal training adaptations and match-day performance
Practical approach on frail older patients attended for acute heart failure
Acute heart failure (AHF) is a multi-organ dysfunction syndrome. In addition to known cardiac dysfunction, non-cardiac comorbidity, frailty and disability are independent risk factors of mortality, morbidity, cognitive and functional decline, and risk of institutionalization. Frailty, a treatable and potential reversible syndrome very common in older patients with AHF, increases the risk of disability and other adverse health outcomes. This position paper highlights the need to identify frailty in order to improve prognosis, the risk-benefits of invasive diagnostic and therapeutic procedures, and the definition of older-person-centered and integrated care plans
Energy and angular momentum balance in wall-bounded superfluid turbulence
A superfluid in the absence of the viscous normal component should be the
best realization of an ideal inviscid Euler fluid. As expressed by d'Alembert's
famous paradox, an ideal fluid does not exert drag on bodies past which it
flows, or in other words, it does not exchange momentum with them. Also, the
flow of an ideal fluid does not dissipate kinetic energy. We study
experimentally whether these properties apply to the flow of superfluid 3He-B
in a rotating cylinder at low temperatures. It is found that ideal behavior is
broken by quantum turbulence, which leads to substantial energy dissipation, as
observed also earlier. Here we show that remarkably, nearly ideal behavior is
preserved with respect to the angular-momentum exchange between the superfluid
and its container, i.e., the drag almost disappears in the zero-temperature
limit. This mismatch between energy and angular-momentum transfer results in a
new physical situation where the proper description of wall-bounded quantum
turbulence requires two effective friction parameters, one for energy
dissipation and another for momentum coupling, which become substantially
different at very low temperatures.Comment: 7 pages, 3 figure
Comparison of Wheel-Rail Contact Modelling in Multibody System Online Simulation
The wheel-rail contact modelling is always an interesting topic in rail vehicle system dynamics simulation. Many contact models have been developed for different purposes, and each model has its own pros and cons for different applications. In multibody system (MBS) simulation of rail vehicles, the efficiency and accuracy of the wheel-rail contact model are of importance. It is the aim of this paper to compare in MBS online simulation one classical approach (Hertz theory+FASTSIM), one approximated non-Hertzian approach and the ‘exact’ solver CONTACT and show the influences of the contact modelling on the results of vehicle dynamics simulations
Structural phase transition in IrTe: A combined study of optical spectroscopy and band structure calculations
IrPtTe is an interesting system showing competing phenomenon
between structural instability and superconductivity. Due to the large atomic
numbers of Ir and Te, the spin-orbital coupling is expected to be strong in the
system which may lead to nonconventional superconductivity. We grew single
crystal samples of this system and investigated their electronic properties. In
particular, we performed optical spectroscopic measurements, in combination
with density function calculations, on the undoped compound IrTe in an
effort to elucidate the origin of the structural phase transition at 280 K. The
measurement revealed a dramatic reconstruction of band structure and a
significant reduction of conducting carriers below the phase transition. We
elaborate that the transition is not driven by the density wave type
instability but caused by the crystal field effect which further
splits/separates the energy levels of Te (p, p) and Te p bands.Comment: 16 pages, 5 figure
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