Optimisation of pyrolysis parameters for CF composites with respect to mechanical properties of recovered fibers

The aerospace/aeronautics, energy and automotive industries are the primary users of advanced polymer composites in structural components. Increasing number of those components are reaching End of Life and will be disposed in landfills, which is currently the most common option worldwide. However, environmental concerns and consequent demands from society drives industries to search for ways to repurpose decommissioned composite structures. The most beneficial would be to reuse composites and/or their constituents after the service life. Thermal recycling is a method to recover costly fibers and lower the environmental impact. The objective of this work is to optimize conditions of pyrolysis of carbon fiber (CF) composite aiming to recover reinforcement with highest mechanical properties. The specimens for this study were cut (15x30x3mm) from epoxy/CF laminate with randomly oriented fiber. To identify the best conditions, the pyrolysis is performed at different thermal cycles under various environments with mass loss monitored throughout the experiments. The conditions of the reference experiment are based on data from literature (550C for 30 min under nitrogen atmosphere, with oxidation in air for 60 min, see Fig. 1). Additionally, pyrolysis was performed under different temperatures and environments: variation of temperature on first stage, dipping specimens in hot furnace instead of gradual heating, changing conditions of oxidation. In order to select pyrolysis process with most optimal conditions the surface of the recovered fibres is investigated by means of optical microscopy and scanning electron microscopy. The mechanical properties of fibers are evaluated and compared to virgin fibers

The effects of Stefan flow on the flow surrounding two closely spaced particles

The aim of the work was to study the effects of neighboring particles with uniform Stefan flow in particle–fluid flows. Particle-resolved numerical simulations were carried out for particles emitting a uniform Stefan flow into the bulk fluid. The bulk fluid was uniform and isothermal. The Stefan flow volume emitted from the two particles is equal, such that it represents idealized conditions of reacting particles. Particles were located in tandem arrangement and particle distances were varied between 1.1 and 10 particle diameters (1.1≤L/D≤10). Three particle Reynolds numbers were considered during the simulations (Re=2.3,7 and 14), which is similar to our previous studies. Three Stefan flow velocities were also considered during simulations to represent inward, outward, and no Stefan flow. The drag coefficient of the particles without Stefan flow showed that the results fit with previous studies on neighbor particle effects. When the particle distance is greater than 2.5 diameters (L/D>2.5), the effects of Stefan flow and neighboring particles are independent of each other. I.e. an outward Stefan flow decreases the drag coefficient (CD) while an inward Stefan flow increases it and the upstream particle experience a higher CD than the downstream particle. When L/D≤2.5, the effect of Stefan flow is dominant, such that equal and opposite pressure forces act on the particles, resulting in a repelling force between the two neighboring particles. The pressure force showed a large increase compared to the viscous force at these distances. The effect of Stefan flow is weakened at higher Reynolds numbers. A model was developed for the calculation of the drag coefficient. The model, which reproduce the results from the numerical simulations presented above, is a product of independent models that describe the effects of both neighboring particles and two distinguished effects of the Stefan flow. © 2023 The Author(s)The effects of Stefan flow on the flow surrounding two closely spaced particlespublishedVersio

Impurity-induced stabilization of solitons in arrays of parametrically driven nonlinear oscillators

Chains of parametrically driven, damped pendula are known to support soliton-like clusters of in-phase motion which become unstable and seed spatiotemporal chaos for sufficiently large driving amplitudes. We show that the pinning of the soliton on a "long" impurity (a longer pendulum) expands dramatically its stability region whereas "short" defects simply repel solitons producing effective partition of the chain. We also show that defects may spontaneously nucleate solitons.Comment: 4 pages in RevTeX; 7 figures in ps forma

Integrable semi-discretization of the coupled nonlinear Schr\"{o}dinger equations

A system of semi-discrete coupled nonlinear Schr\"{o}dinger equations is studied. To show the complete integrability of the model with multiple components, we extend the discrete version of the inverse scattering method for the single-component discrete nonlinear Schr\"{o}dinger equation proposed by Ablowitz and Ladik. By means of the extension, the initial-value problem of the model is solved. Further, the integrals of motion and the soliton solutions are constructed within the framework of the extension of the inverse scattering method.Comment: 27 pages, LaTeX2e (IOP style

Propagation of non-linear circularly polarised Alfven waves in a homogeneous medium

We study the evolution of non-linear circularly polarised Alfven waves by solving numerically the time-dependent equations of magnetohydrodynamics (MHD) in one dimension. We examine the behaviour of the waves and find that different physical mechanisms are relevant in different ranges of beta. In a low beta plasma the wave may undergo a parametric decay. This is because the wave excites a density enhancement that travels slower than the wave itself and thus interacts with the wave. When beta is greater or equal to one the density enhancement does not interact with the wave and no decay takes place, instead the Alfven wave is reflected against the density enhancement. The reflection zone propagates with the speed 1/n of the Alfven speed. Because of that the magnetic flux is conserved which results in an amplification of the oscillating magnetic field by a factor 1/n. We find that n depends on beta, and that in particular it is less or equal to one for values of beta ~ 1 and is greater or equal to one for beta >> 1. We discuss the relevance of these mechanisms to the acceleration of the solar wind, and the triggering of MHD turbulence in the polar wind region. In particular these simulations can explain the presence of inward propagating Alfven waves in the solar corona

Clinical presentation, demographics and outcome of Tuberculosis (TB) in a low incidence area: a 4-year study in Geneva, Switzerland

<p>Abstract</p> <p>Background</p> <p>The incidence of tuberculosis (TB) in developed countries has decreased since the 1990s, reflecting worldwide efforts to identify and treat TB according to WHO recommendations. However TB remains an important public health problem in industrialized countries with a high proportion of cases occurring among subjects originating from high prevalence countries. The aim of this study was to describe clinical and social characteristics of patients with TB and their outcome in a low incidence area with a high immigration rate.</p> <p>Methods</p> <p>Four-year retrospective study based on a computerized database and subsequent review of medical records of all patients with TB followed at the outpatient section of the Division of Pulmonary Diseases, Geneva University Hospital, Switzerland.</p> <p>Results</p> <p>252 patients (84% foreigners, 25% asylum seekers) aged 38 ± 19 yrs were studied (11% co-infected with HIV). TB was intrapulmonary (TBP) in 158 cases (63%), extrapulmonary (TBE) in 137 (54%), and both in 43 cases (17%). TBP was smear (S)+/culture (C)+ in 59%, S-/C+ in 37%, S-/C- in 4%. Smoking was significantly associated with cavitary disease.</p> <p>Time from onset of symptoms to diagnosis was 2.1 ± 3.1 months. Initially, 10% were asymptomatic; 35% had no general symptoms. Despite systematic sputum analysis (induced or spontaneous), TBP was confirmed only by bronchoscopy in 38 subjects (24% of TBP). Side effects requiring changes in treatment occurred in 38 cases (11%).</p> <p>Treatment was completed in 210 (83%) patients. In 42 cases, follow up was unsuccessful; causes were: failure (n = 2; 0.8%), defaulters (n = 8; 3%), transfer out (n = 28; 11%) and death (n = 4; 1.6%). Relapse rate was 0.24 per 100 patient-years. Considering S+ TBP only, success rate was 87%.</p> <p>Conclusion</p> <p>TB in our area is predominantly a disease of young foreign-born subjects. Smoking appears as a possible risk factor for cavitary TBP. Time to diagnosis remains long. Compliance to treatment is satisfactory. Success rate for S+ TBP is within WHO objectives.</p

Regeneration limit of classical Shannon capacity

Since Shannon derived the seminal formula for the capacity of the additive linear white Gaussian noise channel, it has commonly been interpreted as the ultimate limit of error-free information transmission rate. However, the capacity above the corresponding linear channel limit can be achieved when noise is suppressed using nonlinear elements; that is, the regenerative function not available in linear systems. Regeneration is a fundamental concept that extends from biology to optical communications. All-optical regeneration of coherent signal has attracted particular attention. Surprisingly, the quantitative impact of regeneration on the Shannon capacity has remained unstudied. Here we propose a new method of designing regenerative transmission systems with capacity that is higher than the corresponding linear channel, and illustrate it by proposing application of the Fourier transform for efficient regeneration of multilevel multidimensional signals. The regenerative Shannon limit -the upper bound of regeneration efficiency -is derived

Is there loss or qualitative changes in the expression of thyroid peroxidase protein in thyroid epithelial cancer?

There is disagreement concerning the expression of thyroid peroxidase (TPO) in thyroid cancer, some studies finding qualitative as well as quantitative differences compared to normal tissue. To investigate TPO protein expression and its antigenic properties, TPO was captured from a solubilizate of thyroid microsomes by a panel of murine anti-TPO monoclonal antibodies and detected with a panel of anti-human TPO IgGκ Fab. TPO protein expression in 30 samples of malignant thyroid tissue was compared with TPO from adjacent normal tissues. Virtual absence of TPO expression was observed in 8 cases. In the remaining 22 malignant thyroid tumours the TPO protein level varied considerably from normal to nearly absent when compared to normal thyroid tissue or tissues from patients with Graves' disease (range less than 0.5 to more than 12.5 μg mg−1 of protein). When expressed TPO displayed similar epitopes, to that of TPO from Graves' disease tissue. The results obtained by the TPO capturing method were confirmed by SDS-PAGE and Western blot analysis with both microsomes and their solubilizates. The present results show that in about two-thirds of differentiated thyroid carcinomas, TPO protein is expressed, albeit to a more variable extent than normal; when present, TPO in malignant tissues is immunologically normal. © 2001 Cancer Research Campaignhttp://www.bjcancer.co