The effect of task complexity on the human learning function

This experimental study analysed the effects of the complexity (entropy) of a repetitive tusk on the human looming function for the task. The results from 20 subjects revealed that the task entropy had a significant influence on the relationship between the performance (cycle time) and practice (the number of repetitions or cycle number). The model parameters for this relationship were found to be significantly and linearly related to the task entropy, the nominal rate of which varied within the maximum range of 0·9·to 6.1 bits/s     

Energy efficiency investments in Kraft pulp mills given uncertain climate policy

Energy efficiency measures in pulp mills can potentially reduce the consumption of biofuel, which can instead be exported and used elsewhere. In this paper a methodology is proposed for analysing the robustness of energy efficiency investments in Kraft pulp mills or other industrial process plants equipped with biofuelled combined heat and power units, given uncertain future climate policy. The outlook for biofuel and electricity prices is a key factor for deciding if energy efficiency measures are cost competitive. CO ₂ emission charges resulting from climate policy are internalized and thus included in electricity and biofuel prices. The proposed methodology includes a price-setting model for biofuel that assumes a constant price ratio between biofuel and electricity in the Nordic countries. Thirteen energy efficiency retrofit measures are analysed for an existing Swedish Kraft pulp mill. Special attention is paid to heat-integrated evaporation using excess process heat. Four possible energy market development paths are considered that reflect different climate policies. Pulp mill energy efficiency investments considered are shown to be robust with respect to uncertain climate policy. Copyright © 2006 John Wiley & Sons, Ltd.     

The geography of science in 12 European countries: a NUTS2-level analysis

Scientometrics - Europe has a long history as a global center of scientific research, but not all European regions are alike. Regions such as Île de France and the corridor that stretches from...     

Low frequency dielectric spectroscopy of bitumen binders as an indicator of adhesion potential to quartz aggregates using Portland cement

The purpose of this investigation was to interpret the bitumen-aggregate adhesion based on the dielectric spectroscopic response of individual material components utilizing their dielectric constants, refractive indices and average tangent of the dielectric loss angle (average loss tangent). Dielectric spectroscopy of bitumen binders at room temperature was performed in the frequency range of 0.01–1000 Hz. Dielectric spectroscopy is an experimental method for characterizing the dielectric permittivity of a material as a function of frequency. Adhesion data has been determined using the Rolling bottle method. The results show that the magnitude of the average tangent of the dielectric loss angle (average loss tangent) depends on bitumen type. The average loss tangent in the frequency range 0.01–1 Hz is introduced as a potential indicator for predicting polarizability and, thereby, adhesion potential of bitumen binders to quartz aggregates when using Portland cement. In order to obtain acceptable adhesion of 70/100 penetration grade bitumen binders and quartz aggregates when using Portland cement, it is suggested that the binder have an average tan δ > 0.035 in the frequency range 0.01–1 Hz.     

Dynamic start-up optimization of a plate reactor with uncertainties

In this paper, start-up of a plate reactor with an exothermic reaction is considered. Dynamic optimization is used to obtain start-up trajectories, while a feedback control system is designed for on-line control. The problem is challenging, since the process model is highly nonlinear, and subject to uncertainty. Limited bandwidth of the feedback control system requires that the optimization gives optimal solutions with low sensitivity to uncertainty. Special attention is given to the problem of formulating an optimal control problem based on physical insight to reduce the sensitivity of the solution, thus increasing the overall robustness of the closed loop system. The resulting solutions are evaluated in Monte Carlo simulations. The study shows that introducing concentration constraints on the injected chemical in combination with high frequency penalties on the control signals lead to less sensitive optimal solutions, thus yielding a more robust start-up. Automatic computer tools that greatly simplifies the task of formulating complex dynamic optimization problems have been used to obtain the start-up trajectories and are briefly presented.