Relaxational polarization and diffuse phase transitions of LA-substituted Pb (Zr,Ti)O3-ceramics

Dielectric properties of (Pb,La)Zr0.55Ti0.45O3 ceramics have been investigated as functions of temperature and frequency. The dielectric constant as a function of temperature can be represented over a considerable temperature interval by a quadratic law of the type: ε−1=ε−1max + C(T−TC')2. The permittivity versus temperature curves are strongly broadened around TC' (where is at a maximum) and the dielectric behaviour is at least partly of a relaxational nature. Interpretation of the dielectric behaviour (broadening, frequency dependence, quadratic law) seems possible by assuming a distribution of local Curie temperatures; the standard deviation of which can be correlated with the La concentration

The electric field-induced antiferroelectric to ferroelectric phase transition in some (Pb,La)Zr0.55Ti0.45O3 ceramics

Lanthanum substituted lead zirconate-titanate (PLZT) ceramics of composition 11.1/55/45 have been studied by measuring high electric field properties. Dc bias, dielectric and P-E hysteresis loop measurements have been employed to construct an E (electric field) versus T (temperature) phase diagram. At lower temperatures and small electric fields an antiferroelectric phase with tetragonal symmetry has been found. Applying high electric fields gives rise to a field-induced phase transition from the antiferroelectric to the ferroelectric state, however, without X-ray detectable change in crystal symmetry

A new engineering approach to predict the long-term hydrostatic strength of unplasticized poly(vinyl chloride) pipes

Extruded polymer pipes are qualified using pressurized pipe tests. With these tests the long-term hydrostatic strength is determined by subjecting the pipes to an internal pressure, while measuring the time-to-failure. Although these tests can be accelerated (at higher temperatures), they remain time consuming and require a spacious experimental setup. To circumvent this costly method a model based approach is proposed by which the long-term hydrostatic strength is predicted. Using short term measurements, the input parameters for this approach can be determined. In this engineering approach the effects of physical aging are included. The approach is capable to quantitatively predict the (long-term) failure time of pipe sections under internal pressure

Heart rate variability does not discriminate between different levels of haemodynamic responsiveness during surgical anaesthesia†

Background Hypnotic depth but not haemodynamic responsiveness is measured with EEG-based monitors. In this study we compared heart rate variability (HRV) in unstimulated patients and stimulation-induced HRV at different levels of anaesthesia. Methods A total of 95 ASA I or II patients were randomly assigned to five groups (Group 1: BIS 45(5), remifentanil 1 ng ml−1; Group 2: BIS 45(5), remifentanil 2 ng ml−1; Group 3: BIS 45(5), remifentanil 4 ng ml−1; Group 4: BIS 30(5), remifentanil 2 ng ml−1; Group 5: BIS 60(5), remifentanil 2 ng ml−1). A time- and frequency-domain analysis of the RR interval (RRI) from the electrocardiogram was performed. HRV before induction, before and after a 5 s tetanic stimulus of the ulnar nerve, and before and after tracheal intubation was compared between groups, between stimuli, and between responders to intubation [systolic arterial pressure (SAP) increase >20 mm Hg, a maximal heart rate (HR) after intubation >90 min−1 or both] and non-responders (anova). Results Induction of anaesthesia significantly lowered HR and HRV. Mean RRI before stimulation was higher in G3 than in G1, G2, and G4 (P < 0.001), whereas the other HRV parameters were similar. Intubation induced a greater HRV response than tetanic stimulation. The mean RRI after intubation was lower in G3 compared with the other groups and the sd of the RRI after tetanic stimulation was lower in G3 compared with G5. Otherwise, unstimulated HRV and stimulation-induced HRV were similar in responders and non-responders. Conclusion HRV parameters discriminate between awake and general anaesthesia, are different after tracheal intubation and a 5 s ulnar nerve stimulation, but do not discriminate between different levels of haemodynamic responsiveness during surgical anaesthesi

Finding robust investments for the Dutch gas distribution infrastructure in 2050 by a scenario study

In the changing Dutch energy market, the ageing gas distribution grid needs investments. There is, however, a large uncertainty regarding certain aspects that affect the future role of this gas distribution grid, such as the eventual share of biomethane in the gas mix, whether power-to-gas will take-off and the expected lifetime of the grid. Hence, it is currently unclear what investments need to be made for the gas distribution infrastructure in order to cope with future changes. To find out how the future may unfold for the Dutch gas distribution infrastructure in 2050, four scenarios have been developed. Two key forces – a key force is a factor that has a large impact on the gas distribution grid but great uncertainty exists regarding its outcome – were chosen, namely “perceived energy resource scarcity” and “willingness and ability to reduce greenhouse gas emissions”. Each scenario sketches the future Dutch gas infrastructure by defining, among others, the extent to which biomass will be used to produce biomethane, whether fossil fuel is allowed to be burned locally, and what types of gas will flow through the gas grid. With these scenarios at our disposal, in the next research step, we will establish the impact of the scenarios on the gas distribution grid – i.e. what the layout will be and the corresponding costs – and the accompanying biomethane infrastructure. For this, 3 typical locations were chosen: a rural region, an urban region, and an intermediate region. Through a multi-objective optimization – with maximizing net present value, maximizing biomethane production, and maximizing CO2 emission reduction as objectives – the possible layout of the gas distribution grid and the biomethane infrastructure will be determined for each region. The study’s aim is to find similarities in investments among the different layouts, to come to robust investments for the gas distribution infrastructure