Physical and Numerical Difficulties in Computer Modelling of Pellet-Cladding Contact Problems for Burned-Up Fuel

The importance of fuel reliability is growing due to the deregulated electricity market and the demands on operability and availability to the electricity grid of nuclear units. Under these conditions of fuel exploitation, the problems of PCMI (Pellet-Cladding Mechanical Interaction) are very important from the point of view of fuel rod integrity and reliability. Severe loading is thermophysically and mechanically expressed as a greater probability of cladding failure especially during power maneuvering. We have to be able to make a realistic prediction of safety margins, which is very difficult by using computer simulation methods. NRI (Nuclear Research Institute) has recently been engaged in developing 2D and 3D FEM (Finite Element Method) based models dealing with this problem. The latest effort in this field has been to validate 2D r-z models developed in the COSMOS/M system against calculations using the FEMAXI-V code. This paper presents a preliminary comparison between classical FEM based integral code calculations and new models that are still under development. The problem has not been definitely solved. The presented data is of a preliminary nature, and several difficult problems remain to be solved.

Quantitative Algebras and a Classification of Metric Monads

Quantitative algebras are $\Sigma$-algebras acting on metric spaces, where operations are nonexpanding. We prove that for finitary signatures $\Sigma$ there is a bijective correspondence between varieties of quantitative algebras and strongly finitary monads on the category $\mathsf{Met}$ of metric spaces. For uncountable cardinals $\lambda$ there is an analogous bijection between varieties of $\lambda$-ary quantitative algebras and strongly $\lambda$-accessible monads. Moreover, we present a bijective correspondence between $\lambda$-varieties of $\Sigma$-algebras as introduced by Mardare, Panangaden and Plotkin and enriched, surjections-preserving $\lambda$-accesible monads on $\mathsf{Met}$. Finally, a bijective correspondence between generalized $\lambda$-ary varieties and enriched $\lambda$-accessible monads on $\mathsf{Met}$ in general is presented

Measurement of Heat Transfer Coefficients in an Agitated Vessel with Tube Baffles

Cooling or heating an agitated liquid is a very common operation in many industrial processes. A classic approach is to transfer the necessary heat through the vessel jacket. Another option, frequently used in the chemical and biochemical industries is to use the heat transfer area of vertical tube baffles. In large equipment, e.g. fermentor, the jacket surface is often not sufficient for large heat transfer requirements and tube baffles can help in such cases. It is then important to know the values of the heat transfer coefficients between the baffles and the agitated liquid. This paper presents the results of heat transfer measurements using the transient method when the agitated liquid is periodically heated and cooled by hot and cold water running through tube baffles. Solving the unsteady enthalpy balance, it is possible to determine the heat transfer coefficient. Our results are summarized by the Nusselt number correlations, which describe the dependency on the Reynolds number, and they are compared with other measurements obtained by a steady-state method

Different Sensitivity to Isoprenalin in Mice of Two Strains and Its Changes with Age

. Parameters of locomotor activity of mice of two strains (conventional male [CBA x C57BL] 10 Fi mice and Conventional random breed male ICR mice) are reported together with their per cent mortality after administration of isoprenaIin (ISO) at 400 mg • kg-i, 700 mg . kg-i and 750 mg/kg body mass in mice aged 3 months and at 400 mg . kg-i body mass in animals aged 5 months. Age-dependent changes in body mass and myocardial mass were assessed. It is concluded that mice of the two strains differed in their sensitivity to ISO. The o:served higher resistance of (CBA x C57BL/I0) Fl mice to ISO toxicity can be related to their higher locomotor activity and lower I::ody mass. Isoprenalin, mice, myocardium, staircase test The sensitivity to isoprenalin (ISO) is conditioned by a number of factors the quality of which varies from species to species (Venault et aI. 1986). Of particular importance is the cardiotoxic effect of ISO inducing myocardial lesions of coagulative myocytolysis (COAM) type with subsequent development of necroses In conventional male (CBA x C57BL/I0) Fi mice no significant biochemical or morphological myocardial changes have been found after administration of ISO in doses of 10 to 100 mg. kg-I body mass which are used routinely in rats (Fleckenstein et aI. 1977; Materials and Methods The experimental animals were 60 conventional male (CBA x C57BL/I0) Fl mice (breeding colony of Institute of Biophysics, Czechoslovak Academy of Sciences, Bmo) aged 3 months and having 33.3 ± 1.8 g in body mass and 50 conventional random breed male ICR mice (breeding colony of VELAZ, Prague, Czechoslovakia) aged 3 months and having 37.4 ± 3.0 g in body mass. One week before the experiment the mice were transferred to the laboratory and kept ther

Diagnostics of Various Phenomena in LV Devices Under Real Switching Conditions

The article deals with issues to be tackled when performing experiments with low voltage devices under real switching conditions and subsequently discusses various phenomena in an experimental device. The first part describes optimum setting of diagnostic equipment - mainly for optical diagnostic methods. The second part describes some phenomena encountered during switching process under real switching conditions - arc roots movement (cathode and anode spots). These phenomena are not only important for experimental study itself but also form necessary input data for numerical models and their validation

Zamyšlení nad cestou ke škole budoucnosti

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Універсітэт. - № 11 (2114)

PERMON makes use of theoretical results in quadratic programming algorithms and domain decomposition methods. It is built on top of the PETSc framework for numerical computations. This paper describes its fundamental packages and shows their applications. We focus here on contact problems of mechanics decomposed by means of a FETI-type non-overlapping domain decomposition method. These problems lead to inequality constrained quadratic programming problems that can be solved by our PermonQP package.11510

Permutation Entropy and Signal Energy Increase the Accuracy of Neuropathic Change Detection in Needle EMG

Background and Objective. Needle electromyography can be used to detect the number of changes and morphological changes in motor unit potentials of patients with axonal neuropathy. General mathematical methods of pattern recognition and signal analysis were applied to recognize neuropathic changes. This study validates the possibility of extending and refining turns-amplitude analysis using permutation entropy and signal energy. Methods. In this study, we examined needle electromyography in 40 neuropathic individuals and 40 controls. The number of turns, amplitude between turns, signal energy, and “permutation entropy” were used as features for support vector machine classification. Results. The obtained results proved the superior classification performance of the combinations of all of the above-mentioned features compared to the combinations of fewer features. The lowest accuracy from the tested combinations of features had peak-ratio analysis. Conclusion. Using the combination of permutation entropy with signal energy, number of turns and mean amplitude in SVM classification can be used to refine the diagnosis of polyneuropathies examined by needle electromyography

Heat Transfer at the Bottom of a Cylindrical Vessel Impinged by a Swirling Flow from an Impeller in a Draft Tube

Heat transfer at the bottom of a cylindrical vessel impinged by a flow with tangential velocity component generated by an axial-flow impeller in a draft tube was measured using the electrodiffusion experimental method. Local values of the Nusselt numbers along the radial coordinate of the heat transfer surface and corresponding mean values are presented for relatively small distances of the draft tube from the impinged surface (0.25 ≤ h / d ≤ 1). Such small distances are typical for mixing of liquids, which ensures good homogenization and increases the intensity of heat and mass transfer in many industrial operations. Results are compared with literature data for unconfined impinging jets with no tangential velocity components. The additional tangential velocity component generated by the rotating impeller significantly influences the hydrodynamics of the impinging jet and decreases the heat transfer intensity in the case of small distances from the impinged surface. A correlation describing the mean Nusselt number at the vessel bottom is proposed. It can be used in a design of a real industrial piece of equipment with heat transfer situated at the bottom. This work is licensed under a Creative Commons Attribution 4.0 International License