An elasto-plastic fracture mechanics based model for assessment of hydride embrittlement in zircaloy cladding tubes

This paper describes a finite element based fracture mechanics model to assess how hydrides affect the integrity of zircaloy cladding tubes. The hydrides are assumed to fracture at a low load whereas the propagation of the fractured hydrides in the matrix material and failure of the tube is controlled by non-linear fracture mechanics and plastic collapse of the ligaments between the hydrides. The paper quantifies the relative importance of hydride geometrical parameters such as size, orientation and location of individual hydrides and interaction between adjacent hydrides. The paper also presents analyses for some different and representative multi-hydride configurations. The model is adaptable to general and complex crack configurations and can therefore be used to assess realistic hydride configurations. The mechanism of cladding failure is by plastic collapse of ligaments between interacting fractured hydrides. The results show that the integrity can be drastically reduced when several radial hydrides form continuous patterns.     

Process Scheduling Procedure for a Class of Real-Time Comuter Systems

The paper presents the results of the performance evaluation study for a class of real-time computer systems intended for industrial process applications. The developed measures will improve the response time of the system, under the condition of high data arrival rates, where task context switching time and associated overhead are highly exhibited. A discretionary dynamic scheduling and selection discipline is synthesized, producing the minimum global expected waiting time in the system, under the given conditions.     

Carcinogenic properties of silicon carbide whiskers

In experiments with intrapleural injections of silicon carbide whiskers (20 mg X 3, with one month interval) to random-inbred rats their carcinogenic activity close to that of chrysotile B UICC has been established. The pleural mesotheliomas were induced in 47.7 and 34.1% of rats, respectively.     

Selbstbestimmung und Selbstverständnis – Themenschwerpunkte im Umgang mit der Patientenverfügung

Ohne Zusammenfassung     

FEM investigation and thermo-mechanic tests of the new solid tungsten divertor tile for ASDEX Upgrade

A new solid tungsten divertor for the fusion experiment ASDEX Upgrade is under construction at present. A new divertor tile design has been developed to improve the thermal performance of the current divertor made of tungsten coated fine grain graphite. Compared to thin tungsten coatings, divertor tiles made of massive tungsten allow to extend the operational range and to study the plasma material interaction of tungsten in more detail. The improved design for the solid tungsten divertor was tested on different full scale prototypes with a hydrogen ion beam. The influence of a possible material degradation due to thermal cracking or recrystallization can be studied. Furthermore, intensive Finite Element Method (FEM) numerical analysis with the respective test parameters has been performed. The elastic–plastic calculation was applied to analyze thermal stress and the observed elastic and plastic deformation during the heat loading. Additionally, the knowledge gained by the tests and especially by the numerical analysis has been used to optimize the shape of the divertor tiles and the accompanying divertor support structure.This paper discusses the main results of the high heat flux tests and their numerical simulations. In addition, results from some special structural mechanic analysis by means of FEM tools are presented. Finally, first results from the numerical lifecycle analysis of the current tungsten tiles will be reported.     

Photoluminescence of hydrophilic silicon nanocrystals in aqueous solutions

Stable aqueous solutions of undecylenic-acid-grafted silicon nanocrystals (Si-nc) were prepared. The time evolution of the photoluminescence properties of these hydrophilic silicon nanocrystals has been followed on different timescales (hours and days). On a short timescale (hours), Si-nc tend to agglomerate while the PL lineshape and intensity are stable. Agglomeration can be reduced by using suitable surfactants. On a long timescale (days), oxidation of Si-nc occurs even in the presence of surfactants. These two observations render Si-nc very useful as a labeling agent for biosensing.     

Ellipsometric study of thermally induced redistribution and crystallization of Ge in Ge:SiO2 mixture layers

Mixture layers of Ge:SiO₂ of 40:60 mol% respectively, have been prepared by co-sputtering. The thermally induced change of optical properties of the layers was studied by variable angle spectroscopic ellipsometry. The mixture was modelled as an unknown material with optical constants described by multiple oscillators. The optical parameters determined from ellipsometric measurements can be well correlated with structural changes in the mixture. The results indicate that Ge in the mixture deposited or annealed up to 600 °C is in an amorphous state and it redistributes with increase of temperature, changing refractive index through the layer. The crystallization starts between 600 and 650 °C, at first next to the substrate. Crystallites size grows with temperature. Results were compared with findings of grazing incidence wide angle X-ray scattering measurements and a good agreement was found. Ellipsometry has been shown to be an appropriate non-invasive technique for characterization of this kind of layers.     

Addition of Synthetic Biomaterials to Deproteinized Bovine Bone Mineral (DBBM) for Bone Augmentation—A Preclinical In Vivo Study

(1) Aim: To investigate the effect of synthetic bone substitutes, α-tricalcium phosphate (α-TCP) or bi-layered biphasic calcium-phosphate (BBCP) combined with deproteinized bovine bone mineral (DBBM), on bone formation. (2) Methods: Thirty critical size defects were randomly treated with the following five different treatment modalities: (1) negative control (NC, empty), (2) DBBM, (3) α-TCP + DBBM (1:1), (4) BBCP 3%HA/97%α-TCP + DBBM (1:1), and (5) BBCP 6%HA/94%α-TCP + DBBM (1:1). The samples, at four weeks post-surgery, were investigated by micro-CT and histological analysis. (3) Results: A similar level of new bone formation was demonstrated in the DBBM with α-TCP bone substitute groups when compared to the negative control by histomorphometry. DBBM alone showed significantly lower new bone area than the negative control (p = 0.0252). In contrast to DBBM, the micro-CT analysis revealed resorption of the α-TCP + DBBM, BBCP 3%HA/97%α-TCP + DBBM and BBCP 6%HA/94%α-TCP + DBBM, as evidenced by a decrease of material density (p = 0.0083, p = 0.0050 and p = 0.0191, respectively), without changing their volume. (4) Conclusions: New bone formation was evident in all defects augmented with biomaterials, proving the osteoconductive properties of the tested material combinations. There was little impact of the HA coating degree on α-TCP in bone augmentation potential and material resorption for four weeks when mixed with DBBM.     

Determination of As(III) and As(V) in oilseeds by chronopotentiometric stripping analysis: development of a method

Chronopotentiometric stripping analysis (CSA) was used for selective determination of As(III) and As(V) in different oilseeds. After the optimization of experimental parameters an appropriate procedure for sample pretreatment was developed. A detection limit of 2 microg/dm3 for As(III) was obtained with an electrolysis time of 600 s. This method was used for arsenic determination in sunflower, pumpkin, and flax seed, as well as for soy flakes and almond.