Estimating Demand with Varied Levels of Aggregation.

The response of consumer demand to prices, income, and other characteristics is important for a range of policy issues. Naturally, the level of detail for which consumer behaviour can be estimated depends on the level of disaggregation of the available data. However, it is often the case that the available data is differently aggregated in different time periods, with the information available in later time periods usually being more detailed. The applied researcher is thus faced with choosing between detail, in which case the more highly aggregated data is ignored; or duration, in which case the data must be aggregated up to the "lowest common denominator". This paper develops a specification/estimation technique that exploits the entire information content of a variably-aggregated data set.Singular demand systems, Linear expenditure system, Almost ideal demand system, Missing data.

The Benefit Function Approach to Modeling Price-Dependent Demand Systems: An Application of Duality Theory

In this article we advocate more extensive use of the benefit function in specifying price-dependent or inverse demand models. In particular, we demonstrate how duality theory may be used to establish the inter-relationships between the Marshallian (or Hicksian) inverse demands and Luenberger's adjusted price functions, allowing estimable inverse demands to be derived directly from a benefit function. We also make use of a numerical inversion estimation method to rectify the "unobservability of utility problem" encountered in the empirical analysis of these inverse demands. To illustrate the usefulness of the proposed methods, we estimate two systems of inverse demands for Japanese quarterly fish consumption. Results generally indicate that the proposed methods are promising and operationally feasible so that we have opened up a wider range of empirical inverse demand specifications that can be subjected to tight theoretical restrictions.Benefit Functions; Duality Theory; Numerical Inversion Estimation Method

Application of Gr/PMR-15 to commercial aircraft

Following from early experience with polyimides on the SST program and Shuttle aft flap studies the Boeing Company is now working on collaborative programs with its principal nacelle suppliers to pursue the development of Gr/PMR-15 nacelle components. Two programs are currently in effect. The first program is directed specifically towards the flight test and service evaluation at the earliest possible date of a 747 nacelle core cowl structure. The second program seeks to firmly establish the producibility and cost of a 757 thrust reverser C duct in a production environment. The near term objectives of these programs include: (1) the comparison of estimated cost and weight of Gr/PMR-15 versus metal structure, (2) the engine test of representative composite structure, (3) the preliminary design and analysis of the C duct structure, and (4) the preparation of cost data and time schedules for the development and producibility program. In addition to powerplant structure, the propulsion ducting system has shown to be a strong candidate for Gr/PMR-15 application. Currently, the Boeing 747 Organization is evaluating the use of PMR-15 matrix composites to replace nearly 800 lbs of titanium ducting per airplane

Does Associative Memory Play a Role in Solving Physics Problems?

This is the final version of the article. Available from the publisher via the link in this record.Previous research has found that people frequently provide incorrect predictions about the path of moving objects when given an idealised physics problem to solve. The aim of this research was to explore whether these incorrect predictions are due to the application of an incorrect naïve physics theory, whether incorrect perceptions generated from past experiences lead to misconceptions of how moving objects behave, or whether it is a combination of both. Thirty-one participants volunteered to take part in the experiment which followed a two (experience congruent/incongruent with naïve physics theory) by two (carried versus free-moving object) within-subject design. The dependent variable was participant response (straight down or curved forwards). Results of the study revealed that participants provided answers both consistent and inconsistent with the naïve physics theory. This suggests that responses were primarily elicited through the retrieval of associatively-mediated memories of similar scenarios - some of which contain perceptual illusions. Possible methodological limitations and alternative theoretical explanations are discussed, along with practical and theoretical implications for education and learning

Naïve Physics - the wrong theory?

PublishedCopyright © 2013 Cognitive Science SocietyIn this paper we examine the idea of a "naïve physics" in humans solving physics problems. This invokes the idea that people have a theory of motion in their heads that is non- Newtonian, and hence leads to systematic errors on these problems. We are able to show that, by selecting our problems carefully, it is possible to obtain answers that are consistent with this naïve physics and inconsistent with it; suggesting that it is not used to solve these problems but sometimes offered as post-hoc justification for the answers given. We offer evidence that the answers given owe more to past experience than any theory, and that a theory that postulates extrapolation on the basis of associative memory can give a good account of our results

Effect of homogenisation conditions on recrystallisation in the Al-Mg-Mn alloy AA5454

The purpose of the present work is to understand the microstructure development and, particularly, to control the progress of recrystallisation in hot strip in the Al-Mg-Mn alloy AA 5454, which is typically used for the manufacture of structural automotive components. The chemical composition, together with the thermomechanical processing history of this material, has a strong influence on the microstructure of the product and the resulting properties as it is supplied to the customer. Electrical conductivity measurements, thermal analysis and electron microscopy have been carried out to characterise the evolution of precipitation state at various stages in the processing route. The conditions of the homogenisation heat treatment have been varied, and the effect on subsequent recrystallisation after hot rolling has been evaluated in both the as cast and rough rolled condition by optical microscopy techniques. Results indicate that the conditions of homogenisation heat treatment and roughing rolling are critical for the generation of a suitable recrystallised microstructure in AA 5454 hot strip. A new two stage homogenisation practice has been developed to expedite post-rolling recrystallisation in this alloy

Thyroxine treatment in patients with symptoms of hypothyroidism but thyroid function tests within the reference range: randomised double blind placebo controlled crossover trial

OBJECTIVES: To determine whether thyroxine treatment is effective in patients with symptoms of hypothyroidism but with thyroid function tests within the reference range, and to investigate the effect of thyroxine treatment on psychological and physical wellbeing in healthy participants. DESIGN: Randomised double blind placebo controlled crossover trial. SETTING: Outpatient clinic in a general hospital. Participants: 25 patients with symptoms of hypothyroidism who had thyroid function tests within the reference range, and 19 controls. Methods: Participants were given thyroxine 100 microgram or placebo to take once a day for 12 weeks. Washout period was six weeks. They were then given the other to take once a day for 12 weeks. All participants were assessed physiologically and psychologically at baseline and on completion of each phase. MAIN OUTCOME MEASURES: Thyroid function tests, measures of cognitive function and of psychological and physical wellbeing. RESULTS: 22 patients and 19 healthy controls completed the study. At baseline, patients' scores on 9 out of 15 psychological measures were impaired when compared with controls. Patients showed a significantly greater response to placebo than controls in 3 out of 15 psychological measures. Healthy participants had significantly lower scores for vitality when taking thyroxine compared to placebo (mean (SD) 60 (17) v 73 (16), P<0.01). However, patients' scores from psychological tests when taking thyroxine were no different from those when taking placebo except for a poorer performance on one visual reproduction test when taking thyroxine. Serum concentrations of free thyroxine increased and those of thyroid stimulating hormone decreased in patients and controls while they were taking thyroxine, confirming compliance with treatment. Although serum concentrations of free triiodothyronine increased in patients and controls taking thyroxine, the difference between the response to placebo and to thyroxine was significant only in the controls. CONCLUSIONS: Thyroxine was no more effective than placebo in improving cognitive function and psychological wellbeing in patients with symptoms of hypothyroidism but thyroid function tests within the reference range. Thyroxine did not improve cognitive function and psychological wellbeing in healthy participants

Categorisation and perceptual Learning: Why tDCS to Left DLPFC Enhances Generalisation.

In Associative Learning and Cognition, Homage to Prof. N.J. Mackintosh. Editors: Trobalon JB, Chamizo VD. Barcelona 10 Sep 2016This is the author accepted manuscript. The final version is available from University of Barcelona via the link in this record.In the 27 years that have passed since the McLaren, Kaye and Mackintosh (MKM) model of perceptual learning was first proposed, it has undergone considerable theoretical development and been subject to extensive empirical test. But we would argue that the basic principles of the theory remain as valid today as they were in 1989. One of these principles was that salience modulation of stimulus representations based on prediction error was a key component of latent inhibition and perceptual learning. It was this modification of what was otherwise a fairly basic adaptation of the model for categorisation proposed by McCleland and Rumelhart (M&R) that transformed a system that would exhibit enhanced generalisation as category learning progressed, into one that would instead offer an improved capacity for discrimination between exemplars as a consequence of experience with the category. This modification has only been tested indirectly up until now, by looking at the predictions that flow from it and then comparing them to animal and human discrimination following stimulus pre-exposure. In this chapter we test this principle more directly, by using tDCS to disrupt the modulation of salience by prediction error, and show that when this is done, people exhibit the enhanced generalisation predicted by the standard M&R model. We conclude that our results provide further support for the MKM approach to stimulus representation