Vysokoškolské ústavy / University Centreshttp://hdl.handle.net/10084/141812019-03-22T08:29:18Z2019-03-22T08:29:18ZDomain knowledge specification for energy tuningKumaraswamy, MadhuraChowdhury, AnamikaGerndt, MichaelBendifallah, ZakariaBouizi, OthmanLocans, UldisŘíha, LubomírVysocký, OndřejBeseda, MartinZapletal, Janhttp://hdl.handle.net/10084/1342452019-03-19T10:19:25Z2019-01-01T00:00:00ZDomain knowledge specification for energy tuning
Kumaraswamy, Madhura; Chowdhury, Anamika; Gerndt, Michael; Bendifallah, Zakaria; Bouizi, Othman; Locans, Uldis; Říha, Lubomír; Vysocký, Ondřej; Beseda, Martin; Zapletal, Jan
To overcome the challenges of energy consumption of HPC systems, the European Union Horizon 2020 READEX (Runtime Exploitation of Application Dynamism for Energy-efficient Exascale computing) project uses an online auto-tuning approach to improve energy efficiency of HPC applications. The READEX methodology pre-computes optimal system configurations at design-time, such as the CPU frequency, for instances of program regions and switches at runtime to the configuration given in the tuning model when the region is executed. READEX goes beyond previous approaches by exploiting dynamic changes of a region's characteristics by leveraging region and characteristic specific system configurations. While the tool suite supports an automatic approach, specifying domain knowledge such as the structure and characteristics of the application and application tuning parameters can significantly help to create a more refined tuning model. This paper presents the means available for an application expert to provide domain knowledge and presents tuning results for some benchmarks.
2019-01-01T00:00:00ZAccurate and efficient explicit approximations of the Colebrook flow friction equation based on the Wright omega-functionBrkić, DejanPraks, Pavelhttp://hdl.handle.net/10084/1342142019-03-14T10:25:28Z2019-01-01T00:00:00ZAccurate and efficient explicit approximations of the Colebrook flow friction equation based on the Wright omega-function
Brkić, Dejan; Praks, Pavel
The Colebrook equation is a popular model for estimating friction loss coefficients in water and gas pipes. The model is implicit in the unknown flow friction factor, f. To date, the captured flow friction factor, f, can be extracted from the logarithmic form analytically only in the term of the Lambert W-function. The purpose of this study is to find an accurate and computationally efficient solution based on the shifted Lambert W-function also known as the Wright omega-function. The Wright omega-function is more suitable because it overcomes the problem with the overflow error by switching the fast growing term, y = W (e(x)), of the Lambert W-function to series expansions that further can be easily evaluated in computers without causing overflow run-time errors. Although the Colebrook equation transformed through the Lambert W-function is identical to the original expression in terms of accuracy, a further evaluation of the Lambert W-function can be only approximate. Very accurate explicit approximations of the Colebrook equation that contain only one or two logarithms are shown. The final result is an accurate explicit approximation of the Colebrook equation with a relative error of no more than 0.0096%. The presented approximations are in a form suitable for everyday engineering use, and are both accurate and computationally efficient.
2019-01-01T00:00:00ZTi and Zn content in moss shoots after exposure to TiO2 and ZnO nanoparticles: Biomonitoring possibilitiesMotyka, OldřichChlebíková, LucieMamulová Kutláková, KateřinaSeidlerová, Janahttp://hdl.handle.net/10084/1342122019-03-19T11:26:50Z2019-01-01T00:00:00ZTi and Zn content in moss shoots after exposure to TiO2 and ZnO nanoparticles: Biomonitoring possibilities
Motyka, Oldřich; Chlebíková, Lucie; Mamulová Kutláková, Kateřina; Seidlerová, Jana
To assess the uptake of nanoparticles by moss shoots and the possibility of biomonitoring the moss of nanoparticle pollution, two moss species frequently used in biomonitoring surveys [Hylocomium splendens (Hedw.) Schimp. and Pleurozium schreberi (Brid.) Mitt.] were repeatedly exposed to known concentrations of either nano-TiO2 or nano-ZnO suspensions. The interspecies differences were assessed by exposing both the species to 1gL(-1) nano-ZnO suspension, H. splendens samples were also exposed to either 0.1gL(-1) or 1gL(-1) suspension of nano TiO2. The exposed samples were analysed for Zn or Ti content using Inductively Coupled Plasma-Atomic Emission Spectroscopy. Both species showed a similar accumulation pattern, H. splendens being a slightly better accumulator. The washing suggests that Ti successfully penetrated the interior of the gametophyte. Since the relationship between the exposure and accumulation is linear, moss biomonitoring is, hereby, considered to be a viable, novel technique in nanoparticle pollution assessment.
2019-01-01T00:00:00ZStronger and more failure-resistant with three-dimensional serrated bimetal interfacesKong, X. F.Beyerlein, Irene J.Liu, Z. R.Yao, B. N.Legut, DominikGermann, Timothy ClarkZhang, Ruifenghttp://hdl.handle.net/10084/1341922019-03-12T10:33:30Z2019-01-01T00:00:00ZStronger and more failure-resistant with three-dimensional serrated bimetal interfaces
Kong, X. F.; Beyerlein, Irene J.; Liu, Z. R.; Yao, B. N.; Legut, Dominik; Germann, Timothy Clark; Zhang, Ruifeng
Low-energy structures of bimetal interfaces commonly occur in nature, yet higher energy forms, made by deviations in the interface plane, are also likely. While these variants may occur less frequently, they can still play an important role in the response of the material under deformation, by acting as preferential sites for defect formation and boundary motion. Here, using atomic-scale simulation and interface defect theory and considering two bimetal systems, Cu/Ag and Cu/Nb, we show that high-energy interfaces can achieve a local, low-energy state by forming atomic-scale serrations and that the predicted size and location of the serrations are consistent with experimental observation. For several distinct strain states, we reveal that interfaces with atomic-scale serrations bear both higher barriers for dislocation nucleation and higher resistances to interfacial shear compared to their planar interface variants. This desirable combination is not a characteristic of the more commonly studied low-energy interfaces, which typically possess a high nucleation barrier and low sliding resistance. We explain, through an analysis of the misfit dislocation structure, that the serrations alter the number of dislocations emitted, change the favorable slip systems, and alleviate the stress concentrations generated by misfit dislocations. An interface engineering strategy is then proposed for designing atomically serrated interfaces to improve mechanical strength and hinder localization and creep of metallic nanomaterials.
2019-01-01T00:00:00Z