Twin disc assessment of wheel/rail adhesion

Loss of adhesion between a railway wheel and the track has implications for both braking and traction. Poor adhesion in braking is a safety issue as it leads to extended stopping distances. In traction, it is a performance issue as it may lead to reduced acceleration which could cause delays. In this work, wheel/rail adhesion was assessed using a twin disc simulation. The effects of a number of contaminants, such as oil, dry and wet leaves and sand were investigated. These have been shown in the past to have significant effect on adhesion, but this has not been well quantified. The results have shown that both oil and water reduce adhesion from the dry condition. Leaves, however, gave the lowest adhesion values, even when dry. The addition of sand, commonly used as a friction enhancer, to leaves, brought adhesion levels back to the levels without leaves present. Adhesion levels recorded, particularly for the wet, dry and oil conditions are in the range seen in field measurements. Relatively severe disc surface damage and subsurface deformation was seen after the addition of sand. Leaves were also seen to cause indents in the disc surfaces. The twin disc approach has been shown to provide a good approach for comparing adhesion levels under a range of wheel/rail contact conditions, with and without contaminants

High Energy Colliders

We consider the high energy advantages, disadvantages and luminosity requirements of hadrons, leptons and photon-photon colliders. Technical problems in obtaining increased energy in each type of machine are presented. The machines relative size are also discussed.Comment: LaTeX, 27 pages, 8 figures (eps, ps). Submitted to the Proceedings of the Princeton's 250th Anniversary Conference on Critical Problems in Physic

High Luminosity Muon Collider Design

Muon Colliders have unique technical and physics advantages and disadvantages when compared with both hadrons and electron machines. They should be regarded as complementary. Parameters are given of a 4 TeV high luminosity muon-muon collider, and of a 0.5 TeV demonstration machine. We discuss the various systems in such muon collider.Comment: LaTeX 5 pages 4 figure

Future Colliders

The high energy physics advantages, disadvantages and luminosity requirements of hadrons, of leptons and photon-photon colliders are considered. Technical arguments for increased energy in each type of machine are presented. Their relative size, and the implications of size on cost are discussed.Comment: LaTeX, 10 pages, 10figure

We Know What You Choose! External Validity of Discrete Choice Models

For over the last thirty years the multinomial logit model has been the standard in choice modeling. Development in econometrics and computational algorithms has led to the increasing tendency to opt for more flexible models able to depict more realistically choice behavior. This study compares three discrete choice models, the standard multinomial logit, the error components logit, and the random parameters logit. Data were obtained from two choice experiments conducted to investigate consumers’ preferences for fresh pears receiving several postharvest treatments. Model comparisons consisted of in-sample and holdout sample evaluations. Results show that product characteristics hence, datasets, influence model performance. We also found that the multinomial logit model outperformed in at least one of three evaluations in both datasets. Overall, findings signal the need for further studies controlling for context and dataset to have more conclusive cues for discrete choice models capabilities.discrete choice models, validation, holdout sample

New strategies for the production of butanol

Fundação para a Ciência e a Tecnologia (FCT

Correction of diffraction effects in confocal raman microspectroscopy

A mathematical approach developed to correct depth profiles of wet-chemically modified polymer films obtained by confocal Raman microscopy is presented which takes into account scattered contributions originated from a diffraction-limited laser focal volume. It is demonstrated that the problem can be described using a linear Fredholm integral equation of the first kind which correlates apparent and true Raman intensities with the depth resolution curve of the instrument. The calculations of the corrected depth profiles show that considerable differences between apparent and corrected depth profiles exist at the surface, especially when profiles with strong concentration gradients are dealt with or an instrument with poor depth resolution is used. Degrees of modification at the surface obtained by calculation of the corrected depth profiles are compared with those measured by FTIR-ATR and show an excellent concordance.</p

Comparison of Stated Choice and In-store Experimental Methods in Predicting Actual Market Behavior for Freshwater Prawn (Macrobrachium rosenbergii) Consumers

The stated choice (SC) and actual revealed pricing/purchase experimental methods were compared for their ability to predict purchasing behavior and willingness-to-pay for freshwater prawns. SC hypothetical bias may be a consequence of difficulties in controlling factors affecting real world situations, small sample sizes and confusion related to the new product.choice experiment, grocery store experiment, new product, purchasing behavior, Consumer/Household Economics,

A Comparison Of Choice Experiments And Actual Grocery Store Behavior: An Empirical Application To Seafood Products

In this paper we compare results from an in-store field experiment and a mail survey choice experiment (CE) to investigate CE’s capacity in predicting grocery store market share. For the comparison, we used three seafood products: freshwater prawns, marine shrimp, and lobster. CE estimates were obtained via four econometric models: the conditional logit, the random parameter logit, the heteroskedastic extreme value, and the multinomial probit. We found that the level of control in the grocery store experiment and the choice of econometric model influenced the capacity of CE to predict grocery store market shares.choice experiment, grocery store, hypothetical bias, Food Consumption/Nutrition/Food Safety, Marketing, C35, Q13,