Performance evaluation of a two-dimensional lattice Boltzmann solver using CUDA and PGAS UPC based parallelisation

The Unified Parallel C (UPC) language from the Partitioned Global Address Space (PGAS) family unifies the advantages of shared and local memory spaces and offers a relatively straightforward code parallelisation with the Central Processing Unit (CPU). In contrast, the Computer Unified Device Architecture (CUDA) development kit gives a tool to make use of the Graphics Processing Unit (GPU). We provide a detailed comparison between these novel techniques through the parallelisation of a two-dimensional lattice Boltzmann method based fluid flow solver. Our comparison between the CUDA and UPC parallelisation takes into account the required conceptual effort, the performance gain, and the limitations of the approaches from the application oriented developers’ point of view. We demonstrated that UPC led to competitive efficiency with the local memory implementation. However, the performance of the shared memory code fell behind our expectations, and we concluded that the investigated UPC compilers could not efficiently treat the shared memory space. The CUDA implementation proved to be more complex compared to the UPC approach mainly because of the complicated memory structure of the graphics card which also makes GPUs suitable for the parallelisation of the lattice Boltzmann method

On the friction drag reduction mechanism of streamwise wall fluctuations

Understanding how to decrease the friction drag exerted by a fluid on a solid surface is becoming increasingly important to address key societal challenges, such as decreasing the carbon footprint of transport. Well-established techniques are not yet available for friction drag reduction. Direct numerical simulation results obtained by Józsa et al. (2019) previously indicated that a passive compliant wall can decrease friction drag by sustaining the drag reduction mechanism of an active control strategy. The proposed compliant wall is driven by wall shear stress fluctuations and responds with streamwise wall velocity fluctuations. The present study aims to clarify the underlying physical mechanism enabling the drag reduction of these active and passive control techniques. Analysis of turbulence statistics and flow fields reveals that both compliant wall and active control amplify streamwise velocity streaks in the viscous sublayer. By doing so, these control methods counteract dominant spanwise vorticity fluctuations in the near-wall region. The lowered vorticity fluctuations lead to an overall weakening of vortical structures which then mitigates momentum transfer and results in lower friction drag. These results might underpin the further development and practical implementation of these control strategies

Traces of Carnian volcanic activity in the Transdanubian 1 Range, Hungary

The South Alpine–Dinaridic realm was affected by igneous activity in the Middle Triassic; the marine carbonate platforms and the adjacent basins contain highly variable intrusivevolcanic assemblages. We studied the petrography and determined the zircon U–Pb ages of the Triassic volcanic products in the Transdanubian Range. The geochemical features and thus the geodynamic context of the magmatism is badly known, as the rocks experienced variable chemical alteration. The exact duration of the igneous activity is also poorly constrained, as the geochronological data of the former studies were obtained mostly by the weathering-sensitive K–Ar and Rb–Sr methods and thus some data even being younger than the age of the stratigraphic cover. The presence of andesite dikes and of pebbles and cobbles (< 20cm) of basalt, andesite, rhyolite and of rhyolitic tuff in the Triassic carbonate platform deposits indicate that within the Transdanubian Range formed a volcanic complex in Triassic. The major mineralogical and geochemical features of the Transdanubian igneous suite is similar to the Triassic formations in the Southern Alps. However, dissimilar zircon composition excludes the immediate relationship of the zircon-bearing silicic formations in the two tectonic units. New U–Pb ages show that the beginning of the volcanic activity is probably coeval with the eruption of the widespread "pietra verde" trachytic tuffs in the Upper Anisian–Ladinian successions, but the majority of the ages is younger than those ash layers. The new age constraints give a bench-mark for the termination of the volcanic activity in Carnian time in the Transdanubian Range

MRI-based parameter inference for cerebral perfusion modelling in health and ischaemic stroke

Cerebral perfusion modelling is a promising tool to predict the impact of acute ischaemic stroke treatments on the spatial distribution of cerebral blood flow (CBF) in the human brain. To estimate treatment efficacy based on CBF, perfusion simulations need to become suitable for group-level investigations and thus account for physiological variability between individuals. However, computational perfusion modelling to date has been restricted to a few patient-specific cases. This study set out to establish automated parameter inference for perfusion modelling based on neuroimaging data and thus enable CBF simulations of groups. Magnetic resonance imaging (MRI) data from 75 healthy senior adults were utilised. Brain geometries were computed from healthy reference subjects’ T1-weighted MRI. Haemodynamic model parameters were determined from spatial CBF maps measured by arterial spin labelling (ASL) perfusion MRI. Thereafter, perfusion simulations were conducted in 75 healthy cases followed by 150 acute ischaemic stroke cases representing an occlusion and CBF cessation in the left and right middle cerebral arteries. The anatomical fitness of the brain geometries was evaluated by comparing the simulated grey (GM) and white matter (WM) volumes to measurements in healthy reference subjects. Strong positive correlations were found in both tissue types (GM: Pearson’s r 0.74, P<0.001; WM: Pearson’s r 0.84, P<0.001). Haemodynamic parameter tuning was verified by comparing the total volumetric blood flow rate to the brain in healthy reference subjects and simulations (Pearson’s r 0.89, P<0.001). In acute ischaemic stroke cases, the simulated infarct volume using a perfusion-based estimate was 197±25 ml. Computational predictions were in agreement with anatomical and haemodynamic values from the literature concerning T1-weighted, T2-weighted, and phase-contrast MRI measurements in healthy scenarios and acute ischaemic stroke cases. The acute stroke simulations did not capture small infarcts (left tail of the distribution), which could be explained by neglected compensatory mechanisms, e.g. collaterals. The proposed parameter inference method provides a foundation for group-level CBF simulations and for in silico clinical stroke trials which could assist in medical device and drug development.European Union funding: 77707

The Budaörs-1 well revisited: contributions to the Triassic stratigraphy, sedimentology, and magmatism of the southwestern part of the Buda Hills

The 1,200-m-deep Budaörs-1 borehole provided important data for our understanding of the stratigraphy and tectonic setting of the southern part of the Buda Hills. Although previous reports contained valid observations and interpretations, a number of open questions remained. The importance of this borehole and the unsolved problems motivated us to revisit the archived core. The new studies confirmed the existing stratigraphic assignment for the upper dolomite unit (Budaörs Dolomite Formation) as the dasycladalean alga flora proved its late Anisian to Ladinian age assignment. An andesite dike was intersected within the Budaörs Dolomite. U–Pb age determination performed on zircon crystals revealed a Carnian age (~233 Ma), and settled the long-lasting dispute on the age of this dike, proving the existence of a Carnian volcanic activity in this area after the deposition of the Budaörs Dolomite. Palynostratigraphic studies provided evidence for a late Carnian to early Norian age of the upper part of the lower unit (Mátyáshegy Formation). This result verified an earlier assumption and reinforced the significance of the tectonic contact between the upper unit (Budaörs Formation) and the lower unit (Mátyáshegy Formation). Based on structural observations and construction of cross sections, two alternative models are presented for the structural style and kinematics of the contact zone between the Budaörs and Mátyáshegy Formations. Model A suggests a Cretaceous age for the juxtaposition, along an E–W striking sinistral transpressional fault. In contrast, model B postulates dextral transpression and an Eocene age for the deformation. The latter one is better supported by the scattered dip data; however, both scenarios are considered in this paper as possible models

Comparison of the Genetic Structure of Invasive Bigheaded Carp (Hypophthalmichthys spp.) Populations in Central-European Lacustrine and Riverine Habitats

SIMPLE SUMMARY: Bigheaded carps (bighead carp and silver carp) originated in Southeast and East Asia, and their hybrids were stocked for economic reasons to Hungarian natural waters such as Lake Balaton for decades, while the Tisza River was populated by escaped individuals with farm origins. The presence of these alien species and their hybrids in Hungarian natural water bodies may pose significant ecological risks (connected with their phytoplankton and zooplankton consumption). To be able to deal with the ecological risks and to understand the potential of invasiveness of these species, one must have information on the population-level genetic structures of these alien fish stocks. Ten microsatellite DNA markers and one mitochondrial marker were used to address these questions. The results showed that the two stocks are genetically different; the lake population was genetically more diverse and consisted of hybrid and silver carp individuals, while the river population contained only silver carps. The mitochondrial sequences found in the two populations originated from the Yangtze River. Based on the different genetic structures of the stocks, one can assume that bigheaded carps do not reproduce in Lake Balaton, while the Tisza River stock represents significant reproductive potential and may become invasive in this river. ABSTRACT: Bigheaded carps (bighead carp, Hypophthalmichthys molitrix, and silver carp, Hypophthalmichthys nobilis) and their hybrids play an important ecological and economic role in their original habitat, while their introduced stocks may pose serious ecological risks. To address questions about the persistence and invasiveness of these fish, we need to better understand their population structures. The genetic structures of bigheaded carp populations inhabiting Lake Balaton and the Tisza River were examined with ten microsatellite markers and a mitochondrial DNA marker (COI). The Lake Balaton stock showed higher genetic diversity compared with the Tisza River stock. Based on hierarchical clustering, the Tisza population was characterized only by only silver carps, while the Balaton stock included hybrid and silver carp individuals. All COI haplotypes originated from the Yangtze River. Based on the high genomic and mitochondrial diversity, along with the significant deviation from H–W equilibrium and the lack of evidence of bottleneck effect, it can be assumed that bigheaded carps do not reproduce in Lake Balaton. The present stock in Balaton may have originated from repeated introductions and escapes from the surrounding fishponds. The Tisza stock consists solely of silver carp individuals. This stock appears to have significant reproductive potential and may become invasive if environmental factors change due to climate change

Általános nyelvészeti tanulmányok XXIX. - Kísérletes nyelvészet

Ez a kötet kísérletes nyelvészeti tanulmányokat tartalmaz, azaz olyan kutatások eredményeit ismerteti, amelyek egy tág értelemben vett „laboratóriumban" végzett kísérletek eredményein alapulnak. A kötet koncepciója szerint mind a legmodernebb technikai eszközrendszerekkel felszerelt kísérleti laboratóriumi struktúra, mind valamilyen speciális terep (óvoda, iskola, rehabilitációs intézet), mind pedig az internet, például a Facebook is szolgálhat kísérlet lefuttatásának kereteként. A nyelvészetben alkalmazott kísérletek módszertana természetesen követi a tudományos kísérletek általános paradigmáját és megőrzi annak lényeges jegyét: hogy megismételhető, objektív legyen. Amíg számos interdiszciplináris területen, így például a neurolingvisztikában és a pszicholingvisztikában, a tudományos kísérleteket a 19. század óta alkalmazzák, addig az olyan nyelvészeti témákban, mint a nyelvtan készítése, a nyelvleírás, viszonylag újabb fejlemény a kísérletes módszertan alkalmazása. Ezt sok minden motiválta, többek között a kurrens nyelvészeti modellek, elméletek és variánsaik versengései és ennek kapcsán olyan objektív bizonyítékok keresése, amelyek csak kísérleti helyzetekben állíthatók elő. Kötetünk tanulmányait négy tematikus egység szerint csoportosítottuk: 1. Nyelvleírási kérdések, 2. Nyelvelsajátítás, 3. A mesterségesnyelvtan-elsajátítási paradigma alkalmazásai, 4. Nyelvi zavarok. A szerzők között nemcsak a terület jelentős ismertségű személyiségei, hanem külföldről korábban hazatért, vagy más országokban dolgozó és az itthoniakkal szoros kapcsolatokat fenntartó, sőt Magyarországon működő külföldi kutatók is megtalálhatók, példázva a magyarországi nyelvészet nemzetközi beágyazottságát. Nyolc tanulmány esetében a szerzők mellékeltek a kísérleteik hátteréhez, például az adatbázisokhoz, vagy a keretként szolgáló kutatási projekthez és kutatócsoporthoz elvezető internetes linkeket, melyeket QR-kódok formájában adunk meg. A QR-kódok okostelefonnal azonnal aktív linkekre fordíthatók