A global renewable energy system: A modelling exercise in ETSAP/TIAM

This paper aims to test the ETSAP²-TIAM global energy system model and to try out how far it can go towards a global 100% renewable energy system with the existing model database. This will show where limits in global resources are met and where limits in the data fed to the model until now are met.     

A renewable energy scenario for Aalborg Municipality based on low-temperature geothermal heat, wind power and biomass

Aalborg Municipality, Denmark, wishes to investigate the possibilities of becoming independent of fossil fuels. This article describes a scenario for supplying Aalborg Municipality’s energy needs through a combination of low-temperature geothermal heat, wind power and biomass. Of particular focus in the scenario is how low-temperature geothermal heat may be utilised in district heating (DH) systems. The analyses show that it is possible to cover Aalborg Municipality’s energy needs through the use of locally available sources in combination with significant electricity savings, heat savings, reductions in industrial fuel use and savings and fuel-substitutions in the transport sector. With biomass resources being finite, the two marginal energy resources in Aalborg are geothermal heat and wind power. If geothermal heat is utilised more, wind power may be limited and vice versa. The system still relies on neighbouring areas as an electricity buffer though.     

Catalytic oxidation of butane to maleic anhydride enhanced yields in the presence of CO2 in the reactor feed

The addition of CO₂ to the reaction mixture for the oxidation of butane over a VPO catalyst gives rise to significantly improved yields of maleic anhydride.     

Network survivability modeling

Critical services in a telecommunication network should be continuously provided even when undesirable events like sabotage, natural disasters, or network failures happen. It is essential to provide virtual connections between peering nodes with certain performance guarantees such as minimum throughput, maximum delay or loss. The design, construction and management of virtual connections, network infrastructures and service platforms aim at meeting such requirements.In this paper we consider the network’s ability to survive major and minor failures in network infrastructure and service platforms that are caused by undesired events that might be external or internal. Survive means that the services provided comply with the requirement also in presence of failures. The network survivability is quantified as defined by the ANSI T1A1.2 committee which is the transient performance from the instant an undesirable event occurs until steady state with an acceptable performance level is attained.The assessment of the survivability of a network with virtual connections exposed to link or node failures is addressed in this paper. We have developed both simulation and analytic models to cross-validate our assumptions. In order to avoid state space explosion while addressing large networks we decompose our models first in space by studying the nodes independently and then in time by decoupling our analytic performance and recovery models which gives us a closed form solution. The modeling approaches are applied to both small and real-sized network examples. Three different scenarios have been defined, including single link failure, hurricane disaster, and instabilities in a large block of the system (transient common failure).The results show very good correspondence between the transient loss and delay performance in our simulations and in the analytic approximations.     

Modelling and experimental validation of thin-film effects in thermopile-based microscale calorimeters

Calorimeters can be miniaturized to the point where they can be integrated into platforms such as micro-total analysis systems (μTAS) or lab-on-chip. Models of microscale calorimeters currently fail to account for variations of material properties known to be present in thin films. This study attempts to address this deficiency. Resistivity and absolute Seebeck coefficient of gold and nickel thin films were found to vary linearly with the inverse of film thickness in the submicron range. Thin-film thermopiles composed of gold and nickel were fabricated and their resistance and sensitivity were measured. Our results show that thin-film effects can introduce a 15% decrease in sensitivity (temperature-to-voltage conversion ratio) and a 30% decrease in resolution (smallest resolvable temperature difference). Introducing material properties variation with film thickness into models of thermopile performance resulted in improved estimates. Modelling results suggest that grain boundary scattering is a strong contributor to the observed film-thickness-related change of resistivity and Seebeck coefficient. These observations have implications for improving the design and fabrication of thermopile-based, and other microfabricated, microscale calorimeters.     

Modelling and estimation of wafer yields and defect densities from microelectronics test structure data

Test structures are being used widely in microchip manufacturing in order to extract yield information for VLSI circuits manufactured in the same technology. We present and discuss a statistical method used for predicting full scale wafer yields, based on an ‘outlier detection’ principle applied to scaled test structure electrical and visual data. A case study, based on data from a joint ALCATEL ESPACE/INTELSAT research project, illustrates a successful application of this methodology.     

Wood preparation, storage, and drying

The research cooperation in this activity has shown a fundamentally different attitude between the participating scientists in the scientific line of procedure considered.

One group proceeds pragmatically. The group has the opinion that drying progress in big chip stacks is determined by so many intercorrelated factors that it is practically impossible to work out mathematical models of the drying progress. Therefore, the group conducts full scale field trials.

Contrary to this attitude a more scientific line of procedure is maintained by other scientists. This line of procedure tries to establish the natural laws which determine drying of comminuted wood fuels. This is done by mathematical modelling and controlled laboratory experiments.

Both types of experiment are described in this paper.     

On the analysis of field failure data for repairable systems

Reliability assessments of repairable (electronic) equipment are often based on failure data recorded under field conditions. The main objective in the analyses is to provide information that can be used in improving the reliability through design changes. For this purpose it is of particular interest to be able to locate ‘trouble-makers’, i.e. components that are particular likely to fail. In the present context, reliability is measured in terms of the mean cumulative number of failures as a function of time. This function may be considered for the system as a whole, or for stratified data. The stratification is obtained by sorting data according to different factors, such as component positions, production series, etc. The mean cumulative number of failures can then be estimated either nonparametrically as an average of the observed failures, or parametrically, if a certain model for the lifetimes of the components involved is assumed. As an example we here consider a simple component lifetime model based on the assumption that components are ‘drawn’ randomly from a heterogeneous population, where a small proportion of the components are weak (with a small mean lifetime), and the remaining are standard components (with a large mean lifetime). This model enables formulation of an analytical expression for the mean cumulative number of failures. In both the nonparametric and the parametric case the uncertainty of the estimation may be assessed by computing a confidence interval for the estimated values (a confidence band for the estimated time functions). The determination of confidence bands provides a basis for assessing the significance of the factors underlying the stratification. The methods are illustrated through an industrial case study using field failure data.     

Quantitative recovery of volatiles from fats and oils by combined high vacuum degassing and thin film molecular distillation

An apparatus is described which in one unit combines conventional high vacuum degassing on cold finger with falling film molecular distillation. The upper part of the cold finger is for the collection of the most volatile substances, while the lower part is for the condensing of substances which are molecular distilled from a wiped falling film. All the connections in the glass apparatus are made from Teflon or Viton-O-rings, and the turning of the rotor in the molecular distillation part is carried out by means of a magnetic coupling. In this way, the risk for contamination is reduced greatly. As all volatile substances after the treatment of the oil are on the same cold finger, the collection can be made by a high vacuum distillation into a small glass chilled with liquid nitrogen. In the bp range of 40–450 C, the apparatus gives recoveries of volatiles in or below the ppm range between 71–114% with coefficients of variance between 5–23%. The recoveries are found with internal standards added before treatment of the oil. Below 70 C, the recoveries drop to some extent. The volatiles are substances with different kinds of functional groups, e.g. hydrocarbons, aldehydes, ketones, acids, esters, lactones, and sulfur containing substances.     

A New Transducer for Local Load Measurements of Friction and Roll Pressure in Cold Flat Rolling

The only way to establish the true rolling pressure and the true friction condition in cold rolling is to conduct measurements in the roll bite. A new transducer design is therefore proposed, in order to overcome problems in previous measurements in the past 70 years. The new idea is to increase the contact surface of the transducer, to be larger than the arc of contact. This is in contrast to the smaller and smaller contact pin design that has been prevailing. The measurements were conducted during cold dry rolling of both copper strips and stainless steel strips in a pilot mill. The recordings were selected from a steady state with no disturbance from the material flow. The transducer was able to simultaneously measure both the normal pressure and the friction stress. An estimation of the coefficient of friction was accordingly performed. The new transducer works very well, it was seen to be robust and able to avoid signal disturbance. The pressure and friction stress distribution results was as expected by the authors and showed good reproducibility, together with a proven agreement between recorded and simulated signals.