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This article shows an experimental method to summarize the effect of transformer inrush currents on a digital overcurrent relay. The effect of these currents on instantaneous and definite-time overcurrent functions is shown by simple time-current curves. In the case of inverse-time overcurrent functions, an equivalent current is obtained for each test point, from the operation time and the curve equation. Limit-curves in the time-current graph, which summarize the way to avoid the operation of inverse-time overcurrent functions for transformer inrush currents, are found for each type of inverse curve. Three different cases for waveshapes of transformer inrush currents were injected into a commercial relay in order to assess their effect on phase and ground overcurrent functions. Instantaneous and definite-time functions, and seven types of inverse-time functions were tested. For the sake of simplicity, the effect of transformer inrush currents on inverse-time overcurrent functions can be grouped for each case of waveshape. A brief theoretical description of some factors that influence the dynamic behavior of overcurrent functions is also included.

In membrane bioreactors applied to wastewater treatment, fouling is typically a complex function of sludge characteristics. A pilot-scale tertiary submerged membrane bioreactor (tMBR) was continuously operated for over 200 days to assess the effect of biomass physiological state and environmental stress on process performance. Sludge characteristics were evaluated in terms of suspended solid concentration (MLSS and MLVSS), apparent viscosity, bioflocculation state, filterability, bioactivity, biopolymeric clusters (BPCs) and soluble microbial products. During the initial period of the tMBR start-up, when MLSS was below 3000 mg/L, the biomass was found to be very sensitive to environmental stress by sudden oxygen increase or organic shock loading, resulting in temporary biomass deflocculation and BPC release, and consequently, severe induced membrane fouling. However, at higher MLSS values, low stable biomass growth (0.04 ± 0.002 kg MLVSS/kg COD) was measured, regardless of organic overloading shocks or feeding failures. This period was also characterised by low bioactivity, BPC content and membrane fouling. Statistical analysis showed that BPCs have an important role when compared with other sludge properties as indicators of its fouling potential.

Abstract The Ria de Muros is a large coastal embayment on the north-western coast of Spain in which the peak tidal currents exceed 2 m/s. It is therefore a promising site for tidal stream power. The key point when assessing this resource is the accurate estimation of the tidal currents. In this work a finite difference numerical model is used for this purpose. The model solves the vertically integrated Navier–Stokes hydrodynamics and transport equations. It is validated with in situ velocity measurements performed by means of an acoustic Doppler current profiler (ADCP). Thereafter the tidal flow velocities and the corresponding power densities are computed. The largest values are found in a section of the inner ria, in which two points are selected for a detailed assessment of the resource. The model is then run to compute the tidal stream and the corresponding power density at these points during a 14-day period, so as to cover the spring–neap cycle. The power density curve thus obtained is numerically integrated to compute the annual energy output that can be obtained by a tidal stream power plant at each location.

A multichip module component manufacturing process combining multilayer polyimide and multilayer low-temperature cofired ceramic structures, using the latter as the encapsulation support, is described. A first characterization of the results is also reported. The procedures described make it possible to integrate resistances in thin/thick-film technology. >

AbstractThis paper presents a method for estimating recombination parameters in the volume and surface of solar cell precursors throughout the manufacturing process, taking into account several effects that are generally neglected. The technique is based on the comprehensive reconstruction of the effective lifetime assuming a set of fundamental parameters and its comparison to the experimental data obtained from the photoconductance measured under uniform generation in quasi‐steady state conditions. The analysis starts from the semianalytical solution of the minority carrier profiles in the structures under test. This analysis overcomes the usual flat profile approximation and presents important advantages. It allows the asymmetry presented by the solar cell precursors to be taken into account and deals with a wide range of surface conditions: emitters, bare silicon or dielectric passivations. The model also accounts for the effect of the electric field in the volume, and implements several phenomena that are sometimes neglected but are relevant when measuring industrial solar cells precursors: the injection dependence of mobilities and recombination lifetimes, the presence of non‐recombinant traps and the Depletion Region Modulation effect. The estimation technique requires uniform generation, which greatly facilitates the calculation of the carrier profiles and allows for a simple method for the auto calibration of the light absorption. Copyright © 2006 John Wiley & Sons, Ltd.

Technical and economic developments in battery and fast-charging technologies could soon make fuel cell electric vehicles, which run on hydrogen, superfluous in road transport

Abstract A new physical model to calculate the fluid-dynamic behaviour and energy conversion in turbocharger turbines for internal-combustion (I.C.) engines is presented. The model has been developed to be used as a boundary condition in wave action models. The model uses data from the turbine characteristic curves and it is based on the idealization of the turbine by simple elements: ideal nozzles and an intermediate volume. Two typical turbine types are discussed here: a single entry turbine and a twin entry turbine. In order to validate the model, a comparison between calculated and measured engine running variables related to the turbine behaviour is presented.

Abstract Wave trends have been shown to be relevant to energy generation in various areas of the world. Accordingly, this article describes the impact of wave trends on the design of oscillating water column wave energy converters. First, wave trends across the North-East Atlantic Ocean are analysed based on the ERA5 reanalysis. In addition, an empirical model that provides the capture width of an oscillating water column is employed, identifying an approximately linear relationship between the average wavelength and the optimal width of the chamber. Thus, combining wave trends and the empirical model, the optimal size of the chamber is found to vary significantly between different geographical locations and over the four decades between 1979 and 2018. Differences between the original geometry and the geometry optimised considering wave trends, reach up to 15% in some locations. As a consequence, oscillating water column chambers designed based on past available resources rather than the resource corresponding to the time when the device is to be deployed are demonstrated to be inefficient, with a significant difference in the optimal width and absorbed energy of the chamber. Accounting for changes in resource availability over time may assist in cost optimisation of unconventional renewable energy technologies.

Dietary change presents an opportunity to meet the dual challenges of non-communicable diseases and the effects of climate change in China. Based on a food survey and reviewed data sets, we linked nutrient composition and carbon footprint data by aggregating 1950 types of foods into 28 groups. Nine dietary scenarios for both men and women were modeled based on the current diet and latest National Program for Food and Nutrition. Linear uncertainty optimization was used to produce diets meeting the Chinese Dietary Reference Intakes for adults aged 18-50years while minimizing carbon footprints. The theoretical optimal diet reduced daily footprints by 46%, but this diet was unrealistic due to limited food diversity. Constrained by acceptability, the optimal diet reduced the daily carbon footprints by 7-28%, from 3495 to 2517-3252g CO2e, for men and by 5-26%, from 3075 to 2280-2917g CO2e, for women. Dietary changes for adults are capable of benefiting China in terms of the considerable footprint reduction of 53-222Mt.CO2eyear-1, when magnified based on the Chinese population, which is the largest worldwide. Seven of eight scenarios showed that reductions in meat consumption resulted in greater reductions in greenhouse gas emissions. However, dramatic reductions in meat consumption may produce smaller reductions in emissions, as the consumption of other ingredients increases to compensate for the nutrients in meat. A trade-off between poultry and other meats (beef, pork, and lamb) is usually observed, and rice, which is a popular food in China, was the largest contributor to carbon footprint reductions. Our findings suggest that changing diets for climate change mitigation and human health is possible in China, though the per capital mitigation potential is slight lower than that in developed economies of France, Spain, Sweden, and New Zealand.