Stress-induced Ageing of Lithium-Ion Batteries

Lithium-ion batteries are well established for use in portable consumer products and are increasingly used in high power electro-mobility and photovoltaic storage applications. In hybrid and plug-in electric vehicles degradation and useful lifetime at standard operation conditions are critical parameters in addition to performance and safety. Here stress-induced ageing of commercially available high power battery cells of the type A123 AHR32113M1 Ultra-B, consisting of a LiFePO4 cathode and a graphite anode have been investigated. A usually accepted capacity loss for electric vehicles of 20% was reached after 8560 stress profiles corresponding to a driving distance of almost 200'000 km. Cycling with a stress profile applying constant power corresponding to the average power and energy of a full stress profile and starting at 60% state of charge showed a much faster capacity loss. Electric impedance measurements show the dependence of the capacity loss and constant phase element at low frequency, indicating Li-ion diffusion blocking in the cathode. Microscopic analysis of anode, separator, and cathode, shows defect formation in bulk material and at interfaces

Connection availability analysis of span-restorable mesh networks

Dual-span failures are the key factor of the system unavailability in a mesh-restorable network with full restorability of single-span failures. Availability analysis based on reliability block diagrams is not suitable to describe failures of mesh-restorable networks with widely distributed and interdependent spare capacities. Therefore, a new concept of restoration-aware connection availability is proposed to facilitate the analysis. Specific models of span-oriented schemes are built and analyzed. By using the proposed computation method and presuming dual-span failures to be the only failure mode, we can exactly calculate the average connection unavailability with an arbitrary allocation rule for spare capacity and no knowledge of any restoration details, or the unavailability of a specific connection with known restoration details. Network performance with respect to connection unavailability, traffic loss, spare capacity consumption, and dual failure restorability is investigated in a case study for an optical span-restorable long-haul networ

Fully Metal-Coated Scanning Near-Field Optical Microscopy Probes with Spiral Corrugations for Superfocusing under Arbitrarily Oriented Linearly Polarised Excitation

We study the effect of a spiral corrugation on the outer surface of a fully metal-coated scanning near-field optical microscopy (SNOM) probe using the finite element method. The introduction of a novel form of asymmetry, devoid of any preferential spatial direction and covering the whole angular range of the originally axisymmetric tip, allows attaining strong field localization for a linearly polarised mode with arbitrary orientation. Compared to previously proposed asymmetric structures which require linearly polarised excitation properly oriented with respect to the asymmetry, such a configuration enables significant simplification in mode injection. In fact, not only is the need for the delicate procedure to generate radially polarised beams overcome, but also the relative alignment between the linearly polarised beam and the tip modification is no longer critica

Assessment of glued timber integrity by limited-angle microfocus X-ray computed tomography

Glued timber products have an extensive range of applications in construction. In this work a Microfocus X-ray Computed Tomography method was developed to inspect gluing defects in timber samples and was applied successfully on experimental data. The bonding plane was segmented into glued and non-glued regions and imaged with 5mm resolution. Moreover, the gap topology between timber lamellas was precisely characterised. Alimited-angle reconstruction with anisotropic frame binning together with a specific glue line readout method efficiently filters out undesired wood structure highlighting the information of the adhesive joint. This method imposes limitations on the size of the specimen in only one dimension. The presence and absence of glue could be detected for glue line thicknesses over 50μm and air gaps larger than 150μm could be characterised. Several information reduction approaches were combined in the reconstruction process to implement the assessment of a 100×100mm2 bonding plane in less than 40

Air-coupled ultrasound as an accurate and reproducible method for bonding assessment of glued timber

Glued timber products are widely used in construction; therefore, it is necessary to develop non-destructive bonding quality assessment methods for long-term structural health monitoring. Air-coupled ultrasound (ACU) inspection is a novel technique, with phenomenal improvements in reproducibility compared to traditional contact ultrasonics, unlimited scanning possibilities, and a high potential for delamination detection in wood products. As part of an ongoing project, glued timber samples of 10mm thickness with artificial glue line defects were inspected. A normal through-transmission set-up with 120kHz transducers allowed for successful and accurate imaging of the geometry of glued and non-glued areas in all inspected objects. The influence of wood heterogeneity and the reproducibility of ACU amplitude measurements were analysed in detail, identifying the main sources of variation. Future work is planned for the inspection of more complex glued timber object

Estimation of affine transformations directly from tomographic projections in two and three dimensions

This paper presents a new approach to estimate two- and three-dimensional affine transformations from tomographic projections. Instead of estimating the deformation from the reconstructed data, we introduce a method which works directly in the projection domain, using parallel and fan beam projection geometries. We show that any affine deformation can be analytically compensated, and we develop an efficient multiscale estimation framework based on the normalized cross correlation. The accuracy of the approach is verified using simulated and experimental data, and we demonstrate that the new method needs less projection angles and has a much lower computational complexity as compared to approaches based on the standard reconstruction technique

Air-coupled ultrasound inspection of glued laminated timber

A novel air-coupled ultrasound (ACU) 120kHz normal transmission system enabled successful imaging of bonding and saw cut defects in multilayered glulam beams up to 280mm in height with a signal-to-noise ratio (SNR) of 40dB. The main wave propagation paths were modeled; quasi-longitudinal and quasi-transverse modes were coupled in each lamella and the sound field was found to be shifted from the insonification axis as a function of the ring angle, leading to interference of wave paths in the receiver and to 15dB amplitude variability in defect-free glulam. The assessment was improved with spatial processing algorithms that profited from the arbitrary scanning resolution and high reproducibility of ACU. Overlapped averaging reduced in-band noise by 15dB, amplitude tracking captured only the first incoming oscillation, thus minimizing diffraction around defect regions, and image normalization compensated 6dB of systematic amplitude variability across the fiber direction. The application of ACU to in situ defect monitoring was demonstrated by using multiparameter difference imaging of measurements of the same sample with and without saw cut defects. The segmentation of the defect geometry was improved significantly and the amplitude variability was reduced by 10dB. Further work is planned to model additional insonification setups and grain and density heterogeneitie

Side effects of angiotensin converting enzyme inhibitor (captopril) in newborns and young infants

Aim: To analyze the side effects of captopril, an angiotensin converting enzyme inhibitor (ACEI) in newborn and young infants. Methods: Retrospective analysis of side effects in 43 patients with congenital heart disease after cardiac surgery treated with captopril for heart failure during a two-year period. Results: Median age of the patients was 26days (range 6-310days), median weight 3.5kg (range 1.9-7.9kg). Initial median dose of captopril was 0.17 mg/kg/day (range 0.05-0.55mg/kg/day), slowly increased over 3-33days to a maximal median dose of 1.86 mg/kg/day (range 0.2-2.3mg/kg/day). All patients were additionally treated with diuretics. Side effects occurred in 17 patients (renal impairment or failure in 6, low blood pressure in 8, and oxygen saturation deficit in 3) requiring cessation or interruption in seven patients with renal impairment/failure (n=4), hypotension (n=1) and aorto-pulmonary shunting with low pulmonary perfusion (n=2). The six children who developed renal impairment or failure did so following a median delay of nine days after reaching the final dose and weighed on average 500g less than the other patients (P=0.046). All side effects were fully reversible. Conclusion: Side effects due to captopril were not dose-related in newborns and infants in this study. However, renal side effects occurred more often in smaller infants. Routine monitoring of infants on ACEI should include renal function tests, blood pressure and transcutaneous oxygen saturation measurement

Assessment of intensity, prevalence and duration of everyday activities in Swiss school children: a cross-sectional analysis of accelerometer and diary data

BACKGROUND: Appropriately measuring habitual physical activity (PA) in children is a major challenge. Questionnaires and accelerometers are the most widely used instruments but both have well-known limitations. The aims of this study were to determine activity type/mode and to quantify intensity and duration of children's everyday PA by combining information of a time activity diary with accelerometer measurements and to assess differences by gender and age. METHODS: School children (n = 189) aged 6/7 years, 9/10 years and 13/14 years wore accelerometers during one week in winter 2004 and one in summer 2005. Simultaneously, they completed a newly developed time-activity diary during 4 days per week recording different activities performed during each 15 min interval. For each specific activity, the mean intensity (accelerometer counts/min), mean duration per day (min/d) and proportion of involved children were calculated using linear regression models. RESULTS: For the full range of activities, boys accumulated more mean counts/min than girls. Adolescents spent more time in high intensity sports activities than younger children (p < 0.001) but this increase was compensated by a reduction in time spent playing vigorously (p = 0.04). In addition, adolescents spent significantly more time in sedentary activities (p < 0.001) and accumulated less counts/min during these activities than younger children (p = 0.007). Among moderate to vigorous activities, children spent most time with vigorous play (43 min/day) and active transportation (56 min/day). CONCLUSION: The combination of accelerometers and time activity diaries provides insight into age and gender related differences in PA. This information is warranted to efficiently guide and evaluate PA promotion