Existence and uniqueness of elastic-plastic interfaces

A systematic discussion of the existence and uniqueness of spherically symmetric (Part I), and cylindrically symmetric (Part II), elastic-plastic interfaces is presented using non-linear constitutive laws. The work generalises results obtained by various authors, using both linear and non linear constitutive laws. An established local expansion procedure, together with matching across the curves of discontinuity which may exist in an appropriate space-time plane, provide explicit relations for the rate of change of the yield function in terms of given initial distributions, for a complete set of interface speeds. The validity conditions for each of the possible types of motion are used to give sets of inequalities satisfied by the initial distributions. It is shown that the inequalities constituting the set of validity conditions for each particular motion are consistent and exclusive, and hence that each motion exists and is unique.     

Consumer neuroscience: an overview of an emerging discipline with implications for consumer policy

In recent years, interest in the integration and application of neuroscientific theories, concepts, findings and methods to the research discipline of consumer behavior has been increasing. The sub-discipline of consumer neuroscience that has resulted from that interest belongs to the innovative approach of neuroeconomics. Consumer neuroscience investigates problems of consumption and marketing through methods and findings from neuroscience. Conventional research in consumer behavior and marketing necessarily looked at the human organism as being a “black box??which cannot be assessed directly, or physiologically. This was a time when research mainly used theoretical constructs to interpret these bodily processes and resulting behavior. More recently, however, modern techniques and methods in neuroscience have facilitated a far more direct look into the “black box??of the organism as the basis for the sub-discipline of consumer neuroscience. Consumer neuroscience, therefore, can significantly benefit research in the field of consumer behavior, particularly in the attempt to better understand human behavior in decision-making processes. Although consumer neuroscience is a fledgling discipline, it constitutes a complementing advancement toward more comprehensive testing and expansion of theory. Against this background, the primary goal of the paper is to provide an overview of methods, findings, and implications of selected studies in consumer neuroscience. Furthermore, we integrate aspects of consumer policy and neuroethics, discussing the possible implications of these insights for consumer protection.     

Examination of heat transfer correlations and a model for flow boiling of R134a in small diameter tubes

Analysis of various existing correlations including a three-zone evaporation model is made using a comparison with recent experimental results obtained in this study. Flow boiling heat transfer experiments were conducted with two stainless steel tubes of internal diameter 4.26 mm and 2.01 mm. The working fluid was R134a and parameters were varied in the range: mass flux 100–500 kg/m²s; pressure 8–12 bar; quality up to 0.9; heat flux 13–150 kW/m². The local heat transfer coefficient was independent of vapour quality when this was less than about 40–50% in the 4.26 mm tube and 20–30% in the 2.01 mm tube. Local transient dryout was deduced when the quality was above these values. Furthermore, at high heat flux values the heat transfer coefficient decreased with vapour quality for the entire quality range indicating early occurrence of dryout.Existing correlations, which are based on large tube boiling processes, do not predict the present small diameter data to a satisfactory degree. A better agreement is observed with the recent, state-of-the-art, three-zone evaporation model. However, the model does not predict the effect of diameter and the partial dryout. Nevertheless, the observation suggests that the flow pattern based modelling approach performs at least as well as empirical correlations that are based on macroscale modelling. Aspects of the model that need further consideration are also proposed in this study.     

Spatio-temporal analysis of nucleate pool boiling: identification of nucleation sites using non-orthogonal empirical functions

The analysis of spatio-temporal data and the physical understanding of the systems generating them are often limited by the available techniques. These limitations are especially evident in nucleate boiling. This paper investigates the analysis of a sequence of temperature fields obtained from a pool nucleate boiling experiment. Spatio-temporal data for the wall temperature in pool nucleate boiling of water on a thin, horizontal, stainless steel plate were obtained by liquid crystal thermography and high speed video recording. A previous analysis provided examples of the thermal conditions for activation of individual nucleation sites, for the heat transfer mechanisms during bubble growth and for the consequent interactions between adjacent sites. Principal component analysis (PCA) is shown to provide a reconstruction of the temperature fields that is accurate in the root mean square sense but which obscures information about the underlying physics, such as positions of the nucleation sites. In contrast, a new approach using non-orthogonal empirical functions (NEFs) encodes the relevant physical constraints (e.g., each NEF has a radially symmetrical form as suggested by the pattern of cooling during bubble growth). NEFs provide an efficient identification of the positions of active sites in successive frames; they are better suited to the analysis of non-stationary dynamics than PCA and allow for information compression.     

What do consumers know about the economy?

This research investigates Minimal Economic Knowledge (MEK) of consumers in Germany—that is, basic economic knowledge needed for understanding and successfully participating in the economy. First we develop a scale for measuring MEK in four economic domains: finance, labour economics, consumption, and public economics, testing for three kinds of knowledge within each domain, namely facts, concepts, and causal relationships. Second, we conduct an empirical study to test MEK level and influence of demographic drivers in a representative sample of German adult consumers (N = 1,314), with a mean result of only 59.4 points (of 100), indicating a considerable lack of even minimal economic knowledge. And third, using a subsample, we study factors that result in differences in the level of MEK showing among others that the choice of “sensationalist” versus “serious” news sources, both on television and in newspapers, is associated with a loss of about 10 MEK points, while, surprisingly, participating in an economics course did not enhance minimal economic knowledge. The article closes with a discussion of implications for consumer policy-making.     

Flow Boiling in Rectangular Microchannels: 1-D Modeling of the Influence of Inlet Resistance on Flow Reversal

Pressure changes caused by the growth of confined bubbles during flow boiling in mini-/microchannels lead to transient flow reversal in the presence of inlet (upstream) compressibility. A one-dimensional (1-D) model is presented to study the effect of inlet resistance on maximum flow reversal distance, local pressure fluctuations for different initial upstream compressible volumes, channel dimension, locations of nucleation site, heat flux, and initial channel velocity for water and FC-72 at atmospheric pressure and R134a at 800 kPa. The two upstream compressibility models considered are condensable vapor in a subcooled boiling region and trapped noncondensable gas.     

Flow boiling in a 1.1 mm tube with R134a: Experimental results and comparison with model

A detailed comparison of flow boiling heat transfer results in a stainless steel tube of 1.1 mm internal diameter with results of a three-zone flow model are presented in this paper. The working fluid is R134a. Other parameters were varied in the range: mass flux 100–600 kg/m² s; heat flux 16–150 kW/m² and pressure 6–12 bar.The experimental results demonstrate that the heat transfer coefficient increases with heat flux and system pressure, but does not change with vapour quality when the quality is less than about 50% for low heat and mass flux values. The effect of mass flux is observed to be insignificant. For vapour quality values greater than 50% and at high heat flux values, the heat transfer coefficient does not depend on heat flux and decreases with vapour quality. This could be caused by dryout. The three-zone evaporation model predicts the experimental results fairly well, especially at relatively low pressure. However, the dryout region observed at high quality is highly over-predicted by the model. The sensitivity of the performance of the model to the three optimised parameters (confined bubble frequency, initial film thickness and end film thickness) and some preliminary investigation relating the critical film thickness for dryout to measured tube roughness are also discussed.