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Abstract  

The emission of uranium oxides from overheated nuclear fuels proceeds as a function of time, depending mainly on temperature, oxygen potential of the amosphere in contact, and structure and composition of the fuel matrix itself. This time dependent emission results in variation of the U-concentration in the released aerosol. The subsequent annealing (maturation) reactions acting on the aerosol particles are greatly affected by the emission sequence of the different elements. The maturation phase strongly influences the properties of particles dispersed in the environment: e.g. the rate of leaching of the particles is particularly sensitive to their chemical history.

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Aerobic wastewater treatment requires extensive aeration, which primary function is to provide oxygen to the biomass responsible for degradation of wastewater constituents. Besides the effective oxygen transfer efficiency aeration is responsible for fluid flow created by bubbles. In this research bubbles were released from plate diffusers and the impact on mixing were analyzed. Various aeration flow rates and initial bubble sizes were calculated. Residence time distributions in each scenario were compared applying numerical tracer study. Outcome of the calculations is that the aeration reduces the theoretical residence time significantly and therefore the traditional sizing methods needs to be revisit in wastewater treatment.

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It is assumed that there is a group of unrelated individuals taken at random from a large population which is exposed to the same time-continuous threat of dying. Accumulated loss of each player increases as the game goes on until at least one participant volunteers to take some extra risk on its own. The risk is taken by a volunteer in order to stop the threat may or may not depend on the time of volunteering. This situation can be modeled as an n-player War of Attrition, which ends when one of the players volunteers. We called this sort of generalization, ieThe (n-player) volunteer dilemmalr. Indeed, a two-player volunteer dilemma is equivalent to the original War of Attrition. It was further assumed that both the risk for the volunteer and the in- tensity of the risk of waiting are time dependent according to some integrable function, this instead of being con- stants as assumed in the original War of Attrition model of Maynard Smith. Necessary and sufficient conditions for a strategy to be a Nash strategy are given. This strategy is characterized by a time-intensity of volunteering. In the stationary case the Nash strategy is proven to be ESS.

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Abstract  

The relative activities of the members of the principal radioactive families, with respect to the initial activities of chosen parents were calculated for a wide range of time intervals. Tables and graphs that are useful for radiochemistry, source standardization and chronology are presented.

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In our paper we investigate the unbiased movement of the unicellular eukaryotic ciliate Tetrahymena Pyriformis. We use a time-delayed version of the previously known model to describe the specific movement of this species. With the help of semi-discretization, we state analytic results for the model.

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Abstract  

The method described in this paper is based on the fact that the distribution of the periods betwen two signals following one other is affected by the dead-time of the detector. The simple electronic circuit designed can be linked to the output of the pre-amplifier.

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Abstract  

The asymptotic behaviour of the temperature decay constants in Fourier's series is shown to be a powerful tool for a simplification of the latter, which may considerably save computing time, simplify the alternative series obtained from the Laplace transformation, thus, solve, at least in principle, the convergence problem of both standard series and lift the problem of matching both ones.

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Abstract  

One of the most recent developments in equipment for high and/or varying count rates, as encountered in the gamma-ray spectrometry needed for INAA via short-lived radionuclides, is the advent of EG&G Ortec's DSPECplus. This all-in-one apparatus provides digital signal processing and zero-dead-time counting. One such DSPEC unit was tested at IRI with respect to performance as a function of count rate. Optimum parameter settings for different applications were established. It is concluded that this spectrometer allows for measurements with count rates up to at least 105 cps with an accuracy of a few percent (depending on the calibration approach), a peak position stability of 5.10-3%. and a peak width stability of 5%. It is also concluded that the normal spectrum provides a good estimate for the uncertainties in the zero-dead-time spectrum acquired with this spectrometer.

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Temperature-programmed desorption (TPD) of water was applied to characterize short-time dealuminated HZSM-5 zeolites. Using a regularization method, distribution functions of the effective desorption energy of water were calculated. The results clearly show that during dealumination a new adsorption site is formed which can be attributed to non-framework or transient aluminium species. The highest concentration of these sites was observed for a dealumination time of 25-30 min. NO adsorption studies support this result. Furthermore, it could be concluded that the heterogeneity and the average acid strength of the remaining Si-OH-Al groups of the dealuminated samples do not change compared to the Si-OH-Al groups of the parent HZSM-5 zeolite.

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Abstract  

The time resolved dependences of xenon fluorescence in the ultraviolet region were observed. The formation rate constant k2=1.65·10–39 cm6·s–1, as well as the lifetime of Xe 2 ** excimers equal to 8.1 ns have been found in agreement with earlier reports. The present evaluation, however, gave the lifetime of the Xe 2 ** precursors 6=100–200 ns, i.e. much shorter than reported by MILLET et al.

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