Fatigue properties of multifunctional metal‐ and carbon‐fibre‐reinforced polymers and intrinsic capabilities for damage monitoring

Carbon‐fibre‐reinforced polymers (CFRP) structures offer enhanced lightweight potential in comparison with monolithic metallic concepts. Brittle failure behaviour and the insufficient level of electrical conductivity limit the lightweight potential of composites. One promising new approach to solve these issues is the additional integration of metal fibres. Structural components are subjected to cyclic loads during their lifetime. Therefore, the present study focuses on the influence of additional steel fibre reinforcement on the fatigue behaviour of CFRP laminates. Magnetic properties are determined because of the deformation‐induced phase transformation of the chosen austenitic steel fibres, which are also applied as intrinsic damage sensors. Interrupted fatigue tests are carried out accompanied by scanning electron microscopy to obtain differences in failure mechanisms. Beside a detailed overview of the steel fibre influence on the fatigue properties of conventional CFRP structures, the functional evidence of a new method for nondestructive testing by a magnet inductive measuring device is shown.     

End-groups in poly(methyl methacrylate) and polystyrene prepared by radical polymerization in the presence of derivatives of stilbene

Polymers of methyl methacrylate and styrene have been prepared in the presence of low concentrations of various para-derivatives of stilbene, using ¹³C-benzoyl peroxide as the source of the initiating radicals. Examination of the ¹³C-NMR signals due to benzoate end-groups showed that in each case a high proportion of the initiator fragments was attached to a stilbene unit. The results indicate that each of the stilbenes has very high reactivity towards the benzoyloxy radical, depending upon the nature of the substituent. Radical polymerization involving benzoyl peroxide and a stilbene provides a method for the preparation of polymers with special end-groups.     

Estimation of BIST Resources During High-Level Synthesis

Lower bound estimations of functional resources at various stages of high-level synthesis have been developed to guide synthesis algorithms toward optimal solutions. In this paper we present lower bounds on the number of test resources (i.e., registers that generate pseudo-random test patterns and/or compress test responses) required to test a synthesized data path using built-in self-test (BIST). The bounds on different types of test resources are proved to be individually achievable and experiments show that in most cases the bounds can be achieved simultaneously and with minimum number of functional registers. Efficient ways of computing the lower bounds are developed. The estimations are performed on scheduled data flow graphs with a given module assignment and provide a practical way of selecting or modifying module assignments and schedules such that the resulting synthesized data path requires a small number of BIST resources to test itself.     

31P NMR spectroscopy detects metabolic abnormalities in asymptomatic patients with hypertrophic cardiomyopathy

BACKGROUND: Hypertrophic cardiomyopathy (HCM) often causes sudden, unexpected death in adolescents and young adults. Alterations in myocardial metabolism are considered to be causes for contractile dysfunction. We examined the question of whether metabolic abnormalities antedate the manifestation of symptoms in patients with HCM. METHODS AND RESULTS: Proton-decoupled 31P NMR spectroscopy of the anterior left ventricular wall of the heart of 14 young, asymptomatic patients with HCM was performed with a 1.5-T whole-body imager. Spectra of the phosphate metabolites were compared with those of normal control subjects. The patients exhibited a significantly reduced (P<0.02) ratio of phosphocreatine (PCr) to ATP of 1.98+/-0.37 (mean+/-SD), compared with 2.46+/-0.53 obtained in 11 normal control subjects. In addition, the group of patients with severe hypertrophy of the interventricular septum (n=8) showed a significantly increased (P<0.05) Pi-to-PCr ratio, with a Pi x 100/PCr of 20.0+/-8.3 versus 9.7+/-7.2 in control subjects. Both abnormalities are similar to those found in ischemic myocardium. This view is also supported by a significantly increased (P<0.01) phosphomonoester (PME)-to-PCr ratio, with a PME x 100/PCr of 20.7+/-11.2 compared with 8.4+/-6.7 in control subjects, indicating altered glucose metabolism. CONCLUSIONS: 31P NMR spectroscopy detects alterations of myocardial metabolism in asymptomatic patients with HCM. These alterations may contribute to the understanding of the pathophysiology and natural history of the disease.     

A fast and robust hybrid method for block‐structured mesh deformation with emphasis on FSI‐LES applications

The present work introduces an efficient technique for the deformation of block‐structured grids occurring in simulations of fluid–structure interaction (FSI) problems relying on large‐eddy simulation (LES). The proposed hybrid approach combines the advantages of the inverse distance weighting (IDW) interpolation with the simplicity and low computational effort of transfinite interpolation (TFI), while preserving the mesh quality in boundary layers. It is an improvement over the state‐of‐the‐art currently in use. To reach this objective, in a first step, three elementary mesh deformation methods (TFI, IDW, and radial basis functions) are investigated based on several test cases of different complexities analyzing not only their capabilities but also their computational costs. That not only allows to point out the advantages of each method but also demonstrates their drawbacks. Based on these specific properties of the different methods, a hybrid methodology is suggested that splits the entire grid deformation into two steps: first, the movement of the block‐boundaries of the block‐structured grid and second, the deformation of each block of the grid. Both steps rely on different methodologies, which allows to work out the most appropriate method for each step leading to a reasonable compromise between the grid quality achieved and the computational effort required. Finally, a hybrid IDW‐TFI methodology is suggested that best fits to the specific requirements of coupled FSI‐LES applications. This hybrid procedure is then applied to a real‐life FSI‐LES case. Copyright © 2016 John Wiley & Sons, Ltd.     

SiGeSn Ternaries for Efficient Group IV Heterostructure Light Emitters

SiGeSn ternaries are grown on Ge‐buffered Si wafers incorporating Si or Sn contents of up to 15 at%. The ternaries exhibit layer thicknesses up to 600 nm, while maintaining a high crystalline quality. Tuning of stoichiometry and strain, as shown by means of absorption measurements, allows bandgap engineering in the short‐wave infrared range of up to about 2.6 µm. Temperature‐dependent photoluminescence experiments indicate ternaries near the indirect‐to‐direct bandgap transition, proving their potential for ternary‐based light emitters in the aforementioned optical range. The ternaries' layer relaxation is also monitored to explore their use as strain‐relaxed buffers, since they are of interest not only for light emitting diodes investigated in this paper but also for many other optoelectronic and electronic applications. In particular, the authors have epitaxially grown a GeSn/SiGeSn multiquantum well heterostructure, which employs SiGeSn as barrier material to efficiently confine carriers in GeSn wells. Strong room temperature light emission from fabricated light emitting diodes proves the high potential of this heterostructure approach.     

A formal nethod (a networked formal method)

A year-long trial has seen a large lightweight verification problem treated by an ad hoc distributed network of identical solvers. The trialled problem is the semantic analysis of the C code in the Linux kernel to exclude a common deadlock possibility. The aim of the programme behind the experiment is to develop a viable loosely coupled distributed formal method which a community of interested part-time helpers on the net can lend their computing cycles to as they will, or send their own verification problems to for solving.