A simple method which is suitable for determining with reasonable precision the parameters of gas flow system has been proposed. An inverse boundary-value problem is considered. The model of gas flow ...with the Danckwert’s boundary conditions in a real measurement system has been analyzed and solved. The tracer technique was applied to determine axial dispersion coefficient of gas phase and Pèclet number. These parameters are commonly used to characterize the flow behavior of fluids. Axial dispersion coefficients were estimated by comparing model solution with recorded TCD signal (an inverse problem as a method for model parameter estimation) employing the Laplace transform technique. The Gaver-Stehfest algorithm for the solution of the mathematical model has been applied. The proposed model of gas show a good agreement with the experimental data. The obtained results show that under operation conditions in the studied system the flow behaviour is neither plug flow nor perfect mixing. The described method is very fast in both experimental and computational part. Simple and errorless derivation of sophisticated model formulas has been possible by application of the Computer Algebra System-type program. The program also simplifies computations. Mathematical manipulations and computations were performed using program Maple®.
Backgrounds from long-lived radon decay products are often problematic for low-energy neutrino and rare-event experiments. These isotopes, specifically
210
Pb
,
210
Bi
, and
210
Po
, easily plate out ...onto surfaces exposed to radon-loaded air. The alpha emitter
210
Po
is particularly dangerous for detectors searching for weakly-interacting dark matter particles. Neutrons produced via (
α
, n) reactions in detector materials are, in some cases, a residual background that can limit the sensitivity of the experiment. An effective solution is to reduce the
222
Rn
activity in the air in contact with detector components during fabrication, assembly, commissioning, and operation. We present the design, construction, calibration procedures and performance of an electrostatic radon detector made to monitor two radon-suppressed clean rooms built for the DARKSIDE-50 experiment. A dedicated data acquisition system immune to harsh operating conditions of the radon monitor is also described. A record detection limit for
222
Rn
specific activity in air achieved by the device is
0.05
mBqm
-
3
(STP). The radon concentration of different air samples collected from the two DARKSIDE-50 clean rooms measured with the electrostatic detector is presented.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Numerical simulations of the KOBO extrusion process are presented in this paper. The coupled thermomechanical Eulerian-Lagrangian approach was applied for the three-dimensional finite element model. ...The dynamic explicit Euler forward method was used in numerical calculations. The elastic-plastic Chaboche model assuming isotropic and kinematic hardening under variable temperature conditions was applied to describe the behaviour of the material under cyclic loading. In numerical computations Chaboche material model implemented in commercial software, as well as the proprietary one written as FORTRAN procedure were tested. The numerical results present the stress and strain distributions in the extruded material, as well as an increase of temperature due to the plastic work and friction. The shape of plastic strain zones was verified experimentally. The approach presented in the paper is a promising numerical tool to simulate the KOBO process.
The FEM simulations of the ECAP including real conditions of the process – the friction between the metal extruded and the die walls, as well as, the channels rounding, were done here in two scales – ...macro- and micro-. The macroscopic analyses were done for isotopic material with a non-linear hardening using the UMAT user material procedure. The pure Lagrangian approach was applied here. The stress, strains and their increments, as well as, the deformation gradient tensor were recorded for selected finite elements in each calculation step. The displacements obtained in the macroscopic FEM analysis are then used as the kinematic input for the polycrystalline structure. The dislocation slip was included as the source of the plastic deformation here for the face-centered cubic structure. The results obtained with the use of the crystal plasticity show the heterogeneous distribution of stress and strain within the material associated with the grains anisotropy. The results in both micro- and macro- scales are coincident. The FEM analyses show the potential of the application of the crystal plasticity approach for solving elastic-plastic problems including the material forming processes.
Abstract Objectives The electroencephalographic signal is largely exposed to external disturbances. Therefore, an important element of its processing is its thorough cleaning. Methods One of the ...common methods of signal improvement is the independent component analysis (ICA). However, it is a computationally expensive algorithm, hence methods are needed to decrease its execution time. One of the ICA algorithms (fastICA) and parallel computing on the CPU and GPU was used to reduce the algorithm execution time. Results This paper presents the results of study on the implementation of fastICA, which uses some multi-core architecture and the GPU computation capabilities. Conclusions The use of such a hybrid approach shortens the execution time of the algorithm.
We present new constraints on sub-GeV dark-matter particles scattering off electrons based on 6780.0 kg d of data collected with the DarkSide-50 dual-phase argon time projection chamber. This ...analysis uses electroluminescence signals due to ionized electrons extracted from the liquid argon target. The detector has a very high trigger probability for these signals, allowing for an analysis threshold of three extracted electrons, or approximately 0.05 keVee. We calculate the expected recoil spectra for dark matter-electron scattering in argon and, under the assumption of momentum-independent scattering, improve upon existing limits from XENON10 for dark-matter particles with masses between 30 and 100 MeV/c^{2}.
Kynurenic acid (KYNA), a secondary product of the kynurenine pathway of tryptophan degradation, known mainly as an endogenous neuroprotectant, shows also immunotropic properties. Some quantities of ...KYNA are present in food and are effectively absorbed in the gastrointestinal tract. Since the spleen is an important target of dietary immunomodulators, the aim of the study was to determine the effect of exogenous KYNA on murine splenocytes. Splenocytes isolated from adult BALB/c mice were used in the study. Firstly, the effect of increasing KYNA concentrations (0-5 mM) on the viability, and proliferative and cytokine response (interleukin 1β IL-1β, IL-6, IL-10, tumor necrosis factor α TNF-α) of murine splenocytes under in vitro conditions was determined. Then, proliferative and cytokine responses were determined in cells derived from animals receiving kynurenic acid in drinking water at concentrations of 2.5, 25, or 250 mg/l for 7-14 days. Cytokine levels were measured using commercial immunoassay (ELISA) kits, and cell viability and proliferation was determined with MTT reduction assay. Exogenous KYNA was characterised by a low level of cytotoxicity towards murine splenocytes, and was well tolerated by the animals receiving it in drinking water. As expected, it exhibited anti-inflammatory action towards the activated splenocytes, under both in vitro and ex vivo conditions. Surprisingly, however, KYNA itself influenced the activity of resting, non-stimulated cells, exerting an immunostimulant effect in vitro, and an immunosuppressive effect under ex vivo conditions. The obtained results indicate not only anti-inflammatory, but also more complex, immunomodulating properties of KYNA, which require more detailed investigation.
The Event-Related Potentials were investigated on a group of 70 participants using the dense array electroencephalographic amplifier with photogrammetry geodesic station. The source localisation was ...computed for each participant. The activity of brodmann areas (BAs) involved in the brain cortical activity of each participant was measured. Then the mean electric charge flowing through particular areas was calculated. The five different machine learning tools (logistic regression, boosted decision tree, Bayes point machine, classic neural network and averaged perceptron classifier) from the Azure ecosystem were trained, and their accuracy was tested in the task of distinguishing standard and target responses in the experiment. The efficiency of each tool was compared, and it was found out that the best tool was logistic regression and the boosted decision tree in our task. Such an approach can be useful in eliminating somatosensory responses in experimental psychology or even in establishing new communication protocols with mildly mentally disabled subjects.
Ion beam induced defect processes in wide bandgap compound semiconductors are rather complex because of the formation of different types of defects and their transformations. In this paper, we report ...results of the study on the mechanism of defect formation, migration and agglomeration in 300 keV Ar-ion bombarded ZnO single crystals. RBS/c analysis performed with the use of the unique McChasy code allowed determination of depth distributions for different defect types separately. Complementary HRXRD analysis was applied to study lattice deformation due to ion bombardment. It has been observed that migration of simple defects and their agglomeration lead to the formation of two types of dislocation loops: basal loops located at the depth corresponding to the range of incident Ar ions and prismatic loops located beyond the ion range. The stress induced by defects in the bombarded layer has been identified as the driving force for defect migration and loop formation. As soon as the critical stress is attained bombarded layer undergoes plastic deformation resulting in the formation of a dense dislocation tangle.
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