Fluence rate effects on irradiation embrittlement of model alloys

The Reactor Pressure Vessel (RPV) material of Nuclear Power Plants (NPP) is exposed to neutron irradiation during its operation. Such exposure generally induces degradation of the mechanical and physical properties of the materials: e.g. an increase of the ductile to brittle transition temperature (DBTT) and a decrease of the upper shelf impact energy.At a given irradiation temperature, dose and neutron spectrum, the sensitivity of materials to neutron irradiation depends on their chemical composition. In particular, elements like phosphorus, P, copper, Cu, and nickel, Ni play a key role in RPV steels.The effect of fluence rate on irradiation embrittlement of RPV materials is also a key issue for the correct interpretation of accelerated data and surveillance data in view of reactor pressure vessel life assessment of nuclear reactors. Much effort was done in the last decades to tackle such issues and quite contradictory results have been obtained.Model alloys can successfully be used to study embrittlement mechanisms and the effect of fluence rate. A parametric study of the response to neutron irradiation of 32 different model alloys with systematic variation of elements (Ni from 0.004 to ∼2 wt%, P from 0.001 to 0.039 wt%, Cu from 0.005 to ∼1 wt%) was completed by some members of the European Network AMES. The irradiation of the 32 model alloys took place in the LYRA rig at the High Flux Reactor (HFR) of the Joint Research Centre, Petten, The Netherlands.Some model alloys were also irradiated in commercial reactors, namely in Rovno Nuclear Power Plant (NPP), Ukraine, and Kola NPP in Russia. Data available on these model alloys are presented and analysed in this paper, proving to be very important for the study of fluence rate effect.     

Uncertainty analysis of thermal damage to living biological tissues by laser irradiation based on a generalized duel-phase lag model

The effects of uncertainties of laser exposure time, phase lag times, blood perfusion coefficient, scattering coefficient, and diffuse reflectance of light on the thermal damage of living biological tissue by laser irradiation are investigated using a sample-based stochastic model. The variabilities of input and output parameters are quantified using the coefficient of variance (COV) and interquartile range (IQR), respectively. The IQR analysis concluded that phase lag times for temperature gradient and heat flux, laser exposure time, and blood perfusion rate have more significant influences on the maximum temperature and maximum thermal damage of the living biological tissue induced by laser irradiation than the diffuse reflectance of light and scattering coefficient.     

Improving hydrogen storage properties of magnesium based alloys by equal channel angular pressing

Equal channel angular pressing was applied to a commercial magnesium alloy ZK60 in order to improve its hydrogen storage properties. The microstructure refinement and increase in the density of crystal lattice defects caused by equal channel angular pressing increase hydrogen desorption pressure, change the slope of the pressure plateau in pressure-composition isotherms, decrease the pressure hysteresis, and accelerate the hydrogen desorption kinetics. It is argued that a proper design of the defect structure of materials is a key element in the search for economically viable and environmentally acceptable solutions for mobile hydrogen storage based on metal hydrides.     

Diffuse solar irradiation model evaluation in the North Mediterranean Belt area

The performance of daily and hourly diffuse horizontal solar irradiation models and correlations is examined using an assembled data set of multivariate meteorological time series from countries in the North Mediterranean Belt area. The correlations reviewed use only daily global, hourly global or daily diffuse irradiation as input, for the daily or hourly time scale. The best overall performance was presented by the Frutos correlation for the estimation of the daily diffuse radiation by an adapted version of the Liu and Jordan correlation for the mean daily diffuse radiation profile, and by the Hollands and Crha model for estimation of hourly diffuse values from the corresponding global values. The results show that the best correlation for each site varies. Two empirical piecewise correlations were also developed by the authors with the help of the data bank available, yielding models that showed even better fits to the data. The results show some seasonal and location dependence.     

Environmental evaluation of introducing electric vehicles using a dynamic traffic-flow model

A dynamic traffic-flow model (DTFM) is used in this study to evaluate the effectiveness of introducing electric vehicles (EVs) into the total traffic system as one of the alternative fuel vehicles. This model simulates congested and non-congested traffic flow caused by changes in the traffic demand. An environmental evaluation is carried out on the basis that all vehicles are substituted for EVs. Calculated results indicate that by introducing EVs, the NO_x emissions and the CO₂ emissions can be reduced by approximately 25.7 and 14.4% respectively. If battery performance of EVs is improved further, emissions can be further reduced by 39.6% (NO_x) and 27.8% (CO₂). Since emissions from heavy-duty vehicles are greater than other vehicles, the following measures have to be taken for these vehicles to significantly improve their impact upon the overall environment: (1) improvement in fuel efficiency and reductions of NO_x in exhaust gas, (2) traffic demand management, such as modal shift.     

Thermal damage and ablation behavior of graphene induced by ultrafast laser irradiation

Ultrafast laser-induced damage and ablation of graphene is the one of the most critical parts of precise nanopatterning of graphene by using laser ablation. In this article, we have studied the local damage and ablation behavior of monolayer graphene irradiated by femtosecond single pulse laser using molecular dynamics simulation. A theoretical model of phonon-dominated absorption of laser energy is proposed to describe the interaction between graphene and femtosecond single pulse laser. The simulation results based on this model are quantitatively consistent with experimental and theoretical ones. Furthermore, the effects of laser fluences on the atomic ablation behavior and nanogroove generation are investigated. The results show that the relationship between depth of the induced ablation and laser fluence follows a logarithmic function instead of a simple linear relationship. These results will be useful in providing guidance in femtosecond laser processing of graphene.     

A preliminary evaluation of financial incentives for renewable energy technologies in India

The Government of India has been providing various financial incentives including capital subsidy, interest subsidy and depreciation related income tax benefits with the objective of promoting development and dissemination of renewable energy technologies in the country. These financial incentives have, however, changed from time to time in their type, magnitude, scope and even geographical coverage. In some cases, the state governments have also been providing additional incentives. It is therefore, necessary to undertake a detailed evaluation and comparison of different financial incentives provided for dissemination of renewable energy technologies in India (provided in the past as well as the existing incentives) to facilitate a comprehensive grasp of these measures for future planning. An attempt in this direction has been made in this paper. Simple mathematical expressions have been derived to facilitate comparison among some of the commonly provided financial incentives. Results of some exemplifying calculations for three solar energy systems have been presented and briefly discussed. Copyright © 2004 John Wiley & Sons, Ltd.     

A study on properties of yttrium-stabilized zirconia thin films fabricated by different deposition techniques

This paper investigates the micro-structural, chemical and crystalline properties of yttrium-stabilized zirconia (YSZ) thin films by using pulsed laser deposition (PLD), atomic layer deposition (ALD) and sputter. Atomic ratio of Y:Zr of YSZ thin films fabricated by three different deposition methods was adjustable. ALD YSZ with smaller grains has high density compared to PLD YSZ and sputter YSZ. On the other hand, the low crystallinity of ALD YSZ can be supplemented by annealing process. From these experimental results, ALD YSZ thin film has the characteristics that satisfy requirements for using an electrolyte of thin film solid oxide fuel cells.     

Development of energy model based on total daily irradiation and maximum ambient temperature

To predict the energy produced by photovoltaic modules under certain meteorological conditions, an energy model can be used. Existing energy models need parameters that are not always available. In this study, an energy model based on regression analysis of total daily irradiation and maximum daily ambient temperature is developed. This model is able to predict daily module energy based on these two parameters only. The data used in this study were collected over a 15-month period at the University of Port Elizabeth (UPE), South Africa. The developed model was first compared to two existing energy models using data collected over the month of October 1998. Its validity was then evaluated over the entire 15-month period using seasonal regression coefficients. An application of the model to predict module energy output is illustrated by using data collected at the South African Weather Bureau (SAWB), Port Elizabeth (PE) station. The predicted energy is then compared to the energy measured at UPE. Results obtained show that the developed model is valid and a good predictor of module energy.     

Evidence for chromium stabilisation of irradiation damage in RPV weld metals

A study using some available high-quality data from German surveillance and research programmes has been carried out in order to provide evidence on the prediction capabilities of a semi-mechanistic model for changes in ductile to brittle transition temperature. The model was developed and tuned originally on model alloys and later proved to be suitable also for WWER and other materials. This study demonstrates that the model can predict very well all the results obtained on low nickel–manganese weld metals and that the corrections required for high nickel–manganese weld metals are consistent with those found for model alloys.     

Performance evaluation of hydrogen production based on off-peak electric energy of the nuclear power plant

The article investigates the efficiency of commercial hydrogen production by water electrolysis on the base of NPP excess energy with its additional purification higher than 99.9999%, considering its transport. The competitive high purity hydrogen release price has been determined as compared to the market price. Besides, the use of high duty electrolysis plants has been suggested. Moreover, the advantages of water electrolysis cyclic operation while consuming electric energy from NPP as compared to the continuous mode have been presented in the paper.     

Numerical simulation model for the preliminary design of hybrid electric city bus power train with polymer electrolyte fuel cell

A hybrid power train, consisting of a Polymer Electrolyte Fuel Cell (PEFC) system and batteries, which feeds an electric motor for city bus propulsion, can be dimensioned ad hoc respect to the performed route, avoiding his oversizing in the greater energy rationalization optic.     

Thermomechanics of damage and fatigue by a phase field model

In this paper, we present an isothermal model for describing damage and fatigue by the use of the Ginzburg–Landau (G–L) equation. Fatigue produces progressive damage, which is related with a variation of the internal structure of the material. The G–L equation studies the evolution of the order parameter, which describes the constitutive arrangement of the system and, in this framework, the evolution of damage. The thermodynamic coherence of the model is proved. In the last part of the work, we extend the results of the paper to a nonisothermal system, where fatigue contains thermal effects, which increase the damage of materials.     

A semi-empirical model for electric defrosting of a cylindrical coil cooler

Frost growth on cooling surfaces held at subfreezing temperatures has been shown to cause degradation of the heat transfer performance of the cooler. Despite the initial increase in the heat transfer rate due to the temporary increase in the heat transfer area, periodic frost removal is necessary. This paper presents a model for defrosting a cylindrical coil cooler employing the electric defrosting method. © 1998 John Wiley & Sons, Ltd.     

A new energy efficiency evaluation solution for ethylene cracking furnace based on integrated TOPSIS-DEA model

Ethylene-cracking furnace has the highest energy consumption of all the devices used in the ethylene industry. The accurate energy-efficiency evaluation of an ethylene-cracking furnace is therefore of great significance for energy saving and productivity gain in ethylene production. Traditionally, a data envelopment analysis (DEA) model has been used to evaluate the energy efficiency. However, ethylene-cracking furnace also involves a multi-index and multiworking-condition energy-efficiency evaluation problem that results from there being multiple material flows, multiple energy flows, and multiple production loads. Therefore, this paper proposes a new energy efficiency evaluation solution for an ethylene-cracking furnace that is based on the integrated technique for order preference by similarity to ideal solution (TOPSIS)-DEA model. First, from the perspective of material and energy flows, an energy-efficiency vector (EEV) is designed and integrated into the DEA model to meet the demand for multi-index evaluation. Second, to eliminate interference of changes in working condition on energy efficiency, double virtual energy-efficiency benchmarks (DVEEBs) are built using the relationship between EEV, operating conditions, and nonoperational factors, based on the established cracking model. Finally, the rearranged values of the EEV is solved by the TOPSIS method and then evaluated by the DEA model. The actual numerical results show that the proposed solution can support energy-efficiency evaluation of an ethylene-cracking furnace subject to the multiple indexes and multiple working conditions. Specifically, the interference of changes in the working condition on the evaluation results can be reduced greatly which ensures the accuracy and objectivity of the energy-efficiency evaluation results.     

A new model to describe absorption kinetics of Mg-based hydrogen storage alloys

Based on Chou model and unreacted-core model, a new mixed rate controlling kinetic model has been derived in this paper to investigate the adsorption reaction time t for Mg-based hydrogen storage materials as a function of temperature T, particle radius R₀ and reaction fraction ζ. This new model could be predigested into individual single step and mixed two-connection step equations. The characters of this new model have also been discussed. Moreover, the new model is successfully applied for a real case and results indicate that this new model works very well and could reasonably deal with complex kinetics mechanism.     

Nonlinear analysis of dual-phase lag bio-heat model in living tissues induced by laser irradiation

Abstract

This paper provides a method for determining a numerical solution of the thermal damage of living tissues using a nonlinear dual phase lag model. Due to the nonlinearity of the basic equations, the finite element approach is adopted to solve such problems. The numerical outcomes obtained by the finite element technique are also compared with the existing experimental study to verify the accuracy of the numerical calculations. Based on the formulation of Arrhenius, the thermal damages to the tissues are estimated by the denatured protein range. Numerical results for temperatures are presented graphically. Also, the comparisons between the numerical outcomes and the existing experimental data show that the present mathematical models are effective tools to evaluate the bioheat transfer in a spherical living tissue.