In this paper a study for the selection of an NPE (nonylphenol ethoxylates)—free cocktail is discussed in order to be used for our routine liquid scintillation counting measurements. The NPE are ...added in the REACH (Registration, Evaluation, Authorization and Restriction of Chemicals)—list of amendments to Annex XIV, as chemicals which can’t be used anymore (Commission Regulation (EU) 2017/999). Nine NPE-free cocktails were bought from different producers and investigated with respect to the homogeneity, background level and influence on counting efficiency for different radionuclides. Several sample matrices were considered for direct measurement of
3
H and
14
C. Based on this study we could select the best cocktail which fulfills our requirements for routine analyses.
Aims. From light curve and radar data we know the spin axis of only 43 near-Earth asteroids. In this paper we attempt to constrain the spin axis obliquity distribution of near-Earth asteroids by ...leveraging the Yarkovsky effect and its dependence on an asteroid’s obliquity. Methods. By modeling the physical parameters driving the Yarkovsky effect, we solve an inverse problem where we test different simple parametric obliquity distributions. Each distribution results in a predicted Yarkovsky effect distribution that we compare with a χ2 test to a dataset of 125 Yarkovsky estimates. Results. We find different obliquity distributions that are statistically satisfactory. In particular, among the considered models, the best-fit solution is a quadratic function, which only depends on two parameters, favors extreme obliquities consistent with the expected outcomes from the YORP effect, has a 2:1 ratio between retrograde and direct rotators, which is in agreement with theoretical predictions, and is statistically consistent with the distribution of known spin axes of near-Earth asteroids.
The evaluation of the on-ground casualty risk assessments due to a controlled or uncontrolled re-entry is highly sensitive to the accurate prediction of fragmentation events during an atmospheric ...re-entry. The main objective of this study is an investigation into the use of peridynamics (PD) to improve the analysis of fragmentation during atmospheric re-entry with respect to currently adopted semi-empirical approaches. The high temperatures characterising such scenarios may substantially impact fragmentation, which requires appropriate modelling of the damage process within the PD method. The damage models in PD require experimentally determined fracture mechanical properties that are unavailable as a function of temperature. This work proposes a numerical methodology to estimate the PD damage parameters changes with temperature to enable the study of fragmentation during atmospheric re-entry. Initially, tensile-testing simulation experiments are performed in peridynamics to calibrate material parameters for steel and aluminium alloys as a function of temperature. Then, a parametric study is carried out to evaluate the temperature-dependent damage model parameters for the same materials. The applicability of the proposed methodology is showcased using a re-entry test case scenario.
The gas turbine used in marine propulsion for increased efficiency and safety and with a very good power / weight ratio, have a control system that provides alarm, monitoring and control functions, ...including over-speed protection. The paper presents the inclusion of redundancy in the control of the gas turbine so that it works under optimum operating conditions under any regime. The authors' contribution consisted in the elaboration of control schemes so as to ensure a redundancy of the gas turbine control in case the main control module fails. The analysis of the gas turbine construction led to the elaboration of the hardware structure of the system, based on the doubling of the fuel and speed controls as well as of the related transducers by the gas turbine manufacturer. This redundancy is ensured by the introduction of an additional control module that ensures minimal functionality until the status of the main module is restored. The operation of the two modules, the basic one and the redundant one, are ensured on the basis of software, designed by the authors of the paper. The implemented program also limits the size of the variation, keeping the turbines in a correct operating mode.
This study compares different approaches for the quantification of the massic activity of 36Cl in graphite samples. All approaches consisted of a combustion step in combination with a trapping ...solution to collect the volatile elements. Two different resins were used to separate 36Cl from the matrix (CL resin and PS resin). Liquid scintillation counting (LSC), scintillation counting (SC) and tandem inductively coupled plasma mass spectrometry (ICP-MS/MS) were used to quantify 36Cl activity. The chemical yield in all approaches was determined by means of ion chromatography (IC). In addition, the methods were applied to a real activated graphite sample.
•Determination of 36Cl in graphite samples from decommissioning scenarios.•Pyrolysis used for graphite sample combustion.•Two different resins used to separate chlorine from the sample matrix: CL resin and TK-TcScint resin.•Two different techniques used to measure 36Cl activity: scintillation counting and ICP-MS/MS.•36Cl determined in real activated graphite samples by using different approaches.
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