Thermal-hydraulic and aerosol containment phenomena modelling in ASTEC severe accident computer code

Transients in containment systems of different scales (Phebus.FP containment, KAEVER vessel, Battelle Model Containment, LACE vessel and VVER-1000 nuclear power plant containment) involving thermal-hydraulic phenomena and aerosol behaviour, were simulated with the computer integral code ASTEC. The results of the simulations in the first four facilities were compared with experimental results, whereas the results of the simulated accident in the VVER-1000 containment were compared to results obtained with the MELCOR code. The main purpose of the simulations was the validation of the CPA module of the ASTEC code. The calculated results support the applicability of the code for predicting in-containment thermal-hydraulic and aerosol phenomena during a severe accident in a nuclear power plant.     

Influence of stretching ratio and salt concentration on the porosity of polypropylene films containing sodium chloride particles

The incorporation of salt in a polymer matrix could potentially achieve a humidity‐regulating film system of high porosity for packaging applications. In this study, sodium chloride (NaCl) powder was used as a model substance for humidity‐regulating fillers in polypropylene films. A polypropylene homopolymer was extrusion‐blended with NaCl at concentrations of 0.03, 0.06, 0.12, and 0.24 g NaCl·g film^–1. Films were produced and were subsequently oriented mono and biaxially. At stretching ratios (SRs) of between 2 and 25 a porosity of 20% v/v to 50% v/v was achieved. The porosity positively correlated with the SR. An empirical model based on ellipsoids that approximated the correlation between the SR and the porosity was developed. This correlation offers a basis for further studies on other salt‐polymer systems that have undergone differing orientation processes. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013     

Spray-flame synthesis of La(Fe,Co)O3 nano-perovskites from metal nitrates

Nano-sized perovskites were synthesized in a spray flame from nitrate precursors dissolved in ethanol and in ethanol/2-ethylhexanoic acid (2-EHA) mixtures. Experiments with ethanol led to a broad particle-size distribution and to the formation of undesired phases such as La₂CoO₄, La₂O₃, and Co₃O₄. The addition of 2-EHA can initiate micro explosions of the burning droplets and has been systematically investigated toward the formation of single-phase, high-surface-area LaCoO₃ and LaFeO₃ with a narrow size distribution. To investigate the effect of 2-EHA, temperature-dependent changes of the chemical composition of the precursor solutions were analyzed with ATR-FTIR between 23 and 70°C. In all cases, the formation of esters was identified while in the solutions containing iron, additional formation of carboxylates was observed. The synthesized materials were characterized by BET SSA, XRD, SAED and EDX-TEM and their catalytic activity was analyzed, reaching 50% CO conversion at temperatures below 160 and 300°C for LaCoO₃ and LaFeO₃, respectively.     

Coextrusion of Mg–Al macro composites

In this study extrusion experiments were carried out in order to investigate and develop the coextrusion process for light weight magnesium–aluminum macro composites. Seamless tubes were extruded using hybrid billets combining EN AW-6060 tubes as coating material and various Mg-alloys (ZM21, AZ31, AS11, AM10, AM30 and AM50) as core material. Further AZ31/EN AW-6060 rods were produced to investigate the influence of the die angle and different combining techniques of Mg-core and Al-sleeve on the diffusion layer formation. Additionally the effect of mechanically interlocked fittings and a Zn-foil as interlayer material on the coextrusion process and products were examined. For characterization of the compound's shear strength push-out tests were performed.     

Synergized poly(lactic acid)–hydroxyapatite composites: Biocompatibility study

In vitro biocompatibility of impact modified composites produced from poly(lactic acid) (PLA) and hydroxyapatite (HA) is reported in this study. Surface modification was previously used to facilitate the dispersion of HA in PLA, whereas impact property of the PLA-HA composites was deliberately enhanced as it was necessary. Herein, osteoblast cell culture assay was used to assess the possible effects of HA surface modification and impact modification on the cell behavior in physiological media. Furthermore, antimicrobial properties of the HA were assessed. Evidence of HA modification was confirmed through elemental and spectroscopic analysis. Incorporation of HA offered better cell attachment and proliferation to the PLA matrix, with significant increase in the cell viability (%). Also, modification of HA did not present obvious cytotoxicity to the PLA-HA composite. Conversely, incorporation of impact modifier slowed down the rate of cell proliferation on the composite surface but facilitates increased wettability. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47400.     

Fast and Accurate Thickness Determination of Unknown Materials using Terahertz Time Domain Spectroscopy

We present a fast and accurate time domain based algorithm which extracts simultaneously the thickness and refractive index of highly transparent samples from terahertz time domain spectroscopy data. The utilized transfer function considers the Fabry-Perot oscillations of the sample and enables to analyze data with multiple reflections. The algorithm can also be applied to signals corrupted by vapor absorption lines. Since the data extraction takes only fractions of a second, this computation method is well suited for real-time monitoring of industrial processes. We show that the accuracy of the new algorithm is comparable to that of sophisticated, highly accurate and time consumptive frequency domain algorithms.     

Modelling the effects of environmental conditions on wind turbine failures

Operation and maintenance is one of the main cost drivers of modern wind farms and has become an emerging field of research over the past years. Understanding the failure behaviour of wind turbines (WTs) can significantly enhance operation and maintenance processes and is essential for developing reliability and strategic maintenance models. Previous research has shown that especially the environmental conditions, to which the turbines are exposed to, affect their reliability drastically. This paper compares several advanced modelling techniques and proposes a novel approach to model WT system and component failures based on the site‐specific weather conditions. Furthermore, to avoid common problems in failure modelling, procedures for variable selection and complexity reduction are discussed and incorporated. This is applied to a big failure database comprised of 11 wind farms and 383 turbines. The results show that the model performs very well in several situations such as modelling general WT failures as well as failures of specific components. The latter is exemplified using gearbox failures.