Is nuclear economical in comparison to renewables?

The European Union is divided on the issue of electricity production. While there is consensus that generation technologies need to be low on greenhouse gas emissions, the question of whether to use renewables or nuclear to meet this power demand is highly controversial. Both options still require financial support and this is not going to change in the near future. This raises the question of where public money should be invested in order to achieve greater economic efficiency: into support for renewable energies (RE) or support for nuclear power plants?This paper sets out to answer this question. The detailed model-based prospective scenario assessment performed in this study provides the basis for estimating future cost developments. After discussing the existing support schemes for renewables, the paper compares these with a nuclear model. The comparison is conducted exemplarily for the United Kingdom (UK) at a country level and for the EU 28 overall. The recent state aid case for the construction of the Hinkley Point nuclear power plant (NPP) in the UK serves as the model for the nuclear option.     

A novel coupled biokinetic-equilibrium model to capture oyster metal bioaccumulation in a contaminated estuary (Sydney estuary,Australia)

Enriched concentrations of metal contaminants have been reported in surficial sediments and tissues of aquatic organisms in Sydney estuary, New South Wales, Australia. Dietary ingestion of contaminated, suspended sediments is potentially a major route of metal exposure to the filter-feeder Saccostrea glomerata. A dynamically coupled biokinetic-equilibrium bioaccumulation model was developed to explore sediment-oyster-metal uptake interactions. The biokinetic component simulated the sediment dynamics and oyster uptake and loss kinetics while the ion equilibrium model accounted for the metal speciation reactions. Results of a laboratory-based mesocosm experiment as well as data from the literature were used to parameterise the model. The model demonstrated a good fit of the experimental data and indicated that dissolved and particulate organic matter were important determinants of metal bioavailability to this species. The model served also as a unique tool to formulate testable hypotheses and help to better explain the bioaccumulation patterns observed from the experiment.     

Thermal error modelling of a gantry-type 5-axis machine tool using a Grey Neural Network Model

This paper presents a new modelling methodology for compensation of the thermal errors on a gantry-type 5-axis CNC machine tool. The method uses a “Grey Neural Network Model with Convolution Integral” (GNNMCI(1, N)), which makes full use of the similarities and complementarity between Grey system models and artificial neural networks (ANNs) to overcome the disadvantage of applying either model in isolation. A Particle Swarm Optimisation (PSO) algorithm is also employed to optimise the proposed Grey neural network. The size of the data pairs is crucial when the generation of data is a costly affair, since the machine downtime necessary to acquire the data is often considered prohibitive. Under such circumstances, optimisation of the number of data pairs used for training is of prime concern for calibrating a physical model or training a black-box model. A Grey Accumulated Generating Operation (AGO), which is a basis of the Grey system theory, is used to transform the original data to a monotonic series of data, which has less randomness than the original series of data. The choice of inputs to the thermal model is a non-trivial decision which is ultimately a compromise between the ability to obtain data that sufficiently correlates with the thermal distortion and the cost of implementation of the necessary feedback sensors. In this study, temperature measurement at key locations was supplemented by direct distortion measurement at accessible locations. This form of data fusion simplifies the modelling process, enhances the accuracy of the system and reduces the overall number of inputs to the model, since otherwise a much larger number of thermal sensors would be required to cover the entire structure. The Z-axis heating test, C-axis heating test, and the combined (helical) movement are considered in this work. The compensation values, calculated by the GNNMCI(1, N) model were sent to the controller for live error compensation. Test results show that a 85% reduction in thermal errors was achieved after compensation.     

Mathematical modelling of abrasive waterjet footprints for arbitrarily moving jets: Part I—single straight paths

It is notoriously well-known that abrasive waterjet milling (AWJM) is difficult to perform controlled-depth owing to variable geometries of the footprints that depends not only on jet energy and the exposure time upon the workpiece, but also on the orientation of the jet relative to the target surface. An attempt is made to develop a model that can be generally applied to different machine system and to predict individual jet footprints that are one of the key steps for controlled-depth AWJM. To address this, the paper breaks new ground in geometrical modelling of AWJM with the benefit of having few variables for predicting the footprints obtained under the following conditions: (i) any time exposures (i.e. V_f, jet feed speeds); (ii) jet orientations (θ) relative to the target surface; (iii) arbitrarily moving straight jet-paths (β). These conditions reflect the real industrial conditions under which the process is run. The geometrical model results in a non-linear partial differential equation, a method to evaluate the material specific erosion rate from the characteristics of a shallow trench obtained experimentally using high jet feed speeds. Under these conditions, the governing equations can be linearised and solved analytically.The model validation for full profile of trenches generated at various tilt angles (θ=70-90°), jet feed rates (V_f=500-1000 mm/min) and jet path directions (β=0-270°) indicates that a high degree of accuracy (mean of the residuals R_M<3% and root-mean-square error of residuals R_RMS<6%) has been achieved. This innovative footprint modelling approach has the key advantage of being independent of the properties of the workpiece material and/or machine setup, since it calibrates the specific etching rate. By considering any orientation of the jet plume vector relative to the target surface, this approach becomes a powerful tool for the development of advanced jet path strategies to enable AWJM of complex geometries.     

One-photon processes of latent image formation in silver halides

Abstract

A new one-photon process for latent image formation in silver halides is proposed. The model is an extension of the theoretical concepts of Gurney-Mott, Hamilton and Lowe. Hamilton proposed a four-photon mechanism for the photochemical formation of Ag₄ latent image centres. Subsequently, Lowe developed a two-photon mechanism, which includes hole trapping by Ag₂ reduction centres. Mitchell proposed a two-photon mechanism based on the presence of electron trapping Ag₂ centres that act as sublatent image centres. One-photon latent image formation was proposed which relied on gold-containing electron-trapping centres; however, these mechanisms were considered to be fogging mechanisms. From the concepts of the previous mechanisms, a one-photon latent image mechanism is proposed that does not result in fog. This one-photon process is based on the presence of both electron and hole-trapping Ag₂ centres on the same crystal before exposure. Both photoelectron and photohole, which arc formed by light absorption, participate in this mechanism. The required electron-hole energy separation is estimated to be about 1.4 eV and is thus well above the thermal energy at room temperature (about 0.03 eV). Experimental evidence for one-photon processes in silver halide systems supports the proposed one-photon mechanism for Ag₄ latent image formation.     

Optimisation of the fuelling of hydrogen vehicles using cascade systems and ejectors

The present study investigates the replacement of expansion valves, used in the cascade system of hydrogen fuelling stations, by a series of ejectors. The major advantage of using ejectors is to recover part of the kinetic energy lost during the expansion of a high-pressure primary flow, in order to entrain a lower pressure secondary flow; thus resulting in a more efficient fuelling.Firstly, a quasi-steady 1-D simulation model of the ejector was calibrated using computational fluid dynamics in terms of the main geometry and pressure conditions.Secondly, the quasi-steady 1-D model of the ejector was used in a dynamic model of the hydrogen fuelling station, in order to investigate the influence of its geometry on the transient fuelling performances. Different fuelling scenarios were explored with varying number of buffer tanks in the cascade system of the fuelling station, and different initial pressures in the vehicle's tank. The results show that the replacement of the expansion valve by an ejector may reduce the energy consumption for hydrogen compression by up to 6.5% using two buffer tanks in the cascade system. On the other hand, increasing the number of buffer tanks reduces the energy savings as the driving pressure ratio decreases.     

Foot landmarking for footwear customization

As consumers are becoming increasingly selective of what they wear on their feet, manufacturers are experiencing problems developing and fitting the right footwear. Literature suggests that shoes with a shape similar to feet may be comfortable because they attempt to maintain the feet in a neutral posture. The objective of this paper is to develop a metric to quantify mismatches between feet and lasts and also to be able to generate the two-dimensional outline of the foot using the minimum number of landmarks. Fifty Hong Kong Chinese were participants in the experiment. In addition to subject weight, height, foot length and foot width, the left foot outlines were drawn and 18 landmarks were marked on each of the two-dimensional foot outlines. A step-wise procedure was used to reduce the chosen 18 landmarks to eight, such that the mean absolute negative error (an indicator of ‘tightness’) between the foot outline and the modelled curve was 1.3 mm. These eight landmarks seem to show an improvement over those proposed by other researchers, thus showing the importance of choosing the right landmarks for modelling the foot. The positive and negative absolute errors were on average 1.8 mm and 1.3 mm respectively. Moreover, the mean errors for the toe region and for the rest of the foot were 1.7 mm and 1.6 mm respectively. The results indicate that the foot outline, an important component for footwear functionality and fitting, may be modelled using eight critical landmarks.     

A generalised model for cheese mass loss determination during ripening

A generalised mechanistic model describing cheese mass loss during ripening in controlled conditions is proposed. It is based on two main processes occurring in the cheese rind: respiratory activity of the microbial consortia and water evaporation. The generalisation is based on (i) two different cheesemaking methods and cheese sizes (Camembert, a soft cheese and Saint-Nectaire, a pressed non-cooked cheese), (ii) several trials performed at ranging controlled ripening temperatures (7-16 °C) and relative humidities (88-98%) and (iii) different ripening room sizes and air flow patterns. Some hypothesis underlying this generalisation are discussed. The model fits the experimental data accurately: the absolute mean error is lower than 11% of the experimental cheese mass loss. The two main factors governing the water transfer rate are the ripening room relative humidity and the cheese surface water activity. Their impact on the model accuracy is about 40% and 20%, respectively.     

Experimental evaluation of plowing and scratch hardness of aqueous two-component polyurethane (2K-PUR) coatings on glass and polycarbonate

Scratch resistance of aqueous two-component (2K-PUR) polyurethane coatings deposited on glass and polycarbonate was investigated by constant mode scratch tests. Penetration and residual depths as well as scratch widths were experimentally evaluated. A first analytical model was applied to estimate plowing and scratch hardness of the polyurethane coatings according to contact pressure and load rate and the corresponding 3D maps were drawn out. The experimental findings allowed mapping the scratch response the polyurethane coatings came through varying the applied load, load rate and substrate compliance, thus establishing the basis for the development of useful tools for failure prediction of the investigated coating systems in a broad range of operational conditions.     

Re-print of: FDTD simulation of microwave heating of variable feed

Microwave heating inside a cavity is not uniform and depends on various factors such as: cavity geometry, properties of treated material and frequency. In most applications of microwave (MW) heating there is only a small variation in the nature of the feed. At present, the assessment of uniformity of heating is possible only for the case of batch processing cavities. Therefore, it is desirable to have a parameter that will quantify uniformity of heating for continuously operated (non-batch) applicators. This paper has given an account of and the reasons for the widespread use of a new smoothness parameter (SP). This parameter is also compared to the already available parameter (designed for batch processes) through Finite-difference time-domain (FDTD) simulations.Assuming a uniform load, it was demonstrated that heating time and applied microwave power have only a small influence on the proposed uniformity parameter. Simulations of heating were carried out using a variable feed inside two microwave applicators with different uniformity parameters. The results are presented in this paper.