Selection of a Realistic Viscous Vortex Tangential Velocity Profile for Computer Simulation of Vortex-Structure Interaction

Structure loading by vortices is a relevant phenomenon in numerous fields of engineering significance. Computer modelling is a powerful tool that can be used to study the loading produced on structures by impacting vortices. Realistic simulation of vortex-loading of structures necessitates the use of a realistic vortex tangential velocity profile (TVP). The present study compiles measured TVPs from various types of experimentally-produced vortices as well as real-world tornado and hurricane vortices. The measured TVPs are compared with commonly-used, analytical TVPs. Analytical TVPs that realistically represent the range of measured TVPs are identified and selected for use in future computer simulation studies

Process Chain for Numerical Simulation of IMLS

Additive layer manufacturing methods imply, among other advantages, extensive flexibility concerning their ability to realize mass customization. Despite various efforts towards process enhancement, numerous deficiencies concerning part distortion or residual stresses are still observable. The present work deals with the definition of an efficient process chain for numerical simulation of indirect metal laser sintering (IMLS), in order to improve dimensional accuracy. The underlying method is based on investigations of dilatometric behavior of iron based powder, which is integrated into reaction kinetic models and coupled with a finite element analysis (FEA). Thus, singular process steps, e. g. solid phase sintering, phase transformations or infiltration, are numerically modelled with adequate accuracy. Referring to thermomechanical simulation, possibilities for pre-scaling of part geometries are presented.Mechanical Engineerin

Responsibility Effects in Decision Making under Risk

We systematically explore decision situations in which a decision maker bears responsibility for somebody else's outcomes as well as for her own in situations of payoff equality. In the gain domain we confirm the intuition that being responsible for somebody else's payoffs increases risk aversion. This is however not attributable to a 'cautious shift' as often thought. Indeed, looking at risk attitudes in the loss domain, we find an increase in risk seeking under responsibility. This raises issues about the nature of various decision biases under risk, and to what extent changed behavior under responsibility may depend on a social norm of caution in situations of responsibility versus naive corrections from perceived biases. To further explore this issue, we designed a second experiment to explore risk-taking behavior for gain prospects offering very small or very large probabilities of winning. For large probabilities, we find increased risk aversion, thus confirming our earlier finding. For small probabilities however, we find an increase of risk seeking under conditions of responsibility. The latter finding thus discredits hypotheses of a social rule dictating caution under responsibility, and can be explained through flexible self-correction models predicting an accentuation of the fourfold pattern of risk attitudes predicted by prospect theory. An additional accountability mechanism does not change risk behavior, except for mixed prospects, in which it reduces loss aversion. This indicates that loss aversion is of a fundamentally different nature than probability weighting or utility curvature. Implications for debiasing are discussed

Responsibility Effects in Decision Making under Risk

We systematically explore decision situations in which a decision maker bears responsibility for somebody else's outcomes as well as for her own in situations of payoff equality. In the gain domain we confirm the intuition that being responsible for somebody else's payoffs increases risk aversion. This is however not attributable to a 'cautious shift' as often thought. Indeed, looking at risk attitudes in the loss domain, we find an increase in risk seeking under responsibility. This raises issues about the nature of various decision biases under risk, and to what extent changed behavior under responsibility may depend on a social norm of caution in situations of responsibility versus naive corrections from perceived biases. To further explore this issue, we designed a second experiment to explore risk-taking behavior for gain prospects offering very small or very large probabilities of winning. For large probabilities, we find increased risk aversion, thus confirming our earlier finding. For small probabilities however, we find an increase of risk seeking under conditions of responsibility. The latter finding thus discredits hypotheses of a social rule dictating caution under responsibility, and can be explained through flexible self-correction models predicting an accentuation of the fourfold pattern of risk attitudes predicted by prospect theory. An additional accountability mechanism does not change risk behavior, except for mixed prospects, in which it reduces loss aversion. This indicates that loss aversion is of a fundamentally different nature than probability weighting or utility curvature. Implications for debiasing are discussed.risk attitude; other-regarding preferences; prospect theory; agency; social norms

Hydrogen Flare Stack Diffusion Flames - Low and High Flow Instabilities, Burning Rates, Dilution Limits, Temperatures, and Wind Effects

Combustion characteristics and safety factors for hydrogen diffusion flames in flare stack operation

1420 MHz Continuum Absorption Towards Extragalactic Sources in the Galactic Plane

We present a 21-cm emission-absorption study towards extragalactic sources in the Canadian Galactic Plane Survey (CGPS). We have analyzed HI spectra towards 437 sources with S > 150 mJy, giving us a source density of 0.6 sources per square degree at arcminute resolution. We present the results of a first analysis of the HI temperatures, densities, and feature statistics. Particular emphasis is placed on 5 features with observed spin temperatures below 40 K. We find most spin temperatures in the range from 40 K to 300 K. A simple HI two-component model constrains the bulk of the cold component to temperatures (T_c) between 40 K and 100 K. T_c peaks in the Perseus arm region and clearly drops off with Galactocentric radius, R, beyond that. The HI density follows this trend, ranging from a local value of 0.4 cm^{-3} to less than 0.1 cm^{-3} at R = 20 kpc. We find that HI emission alone on average traces about 75% of the total HI column density, as compared to the total inferred by the emission and absorption. Comparing the neutral hydrogen absorption to CO emission no correlation is found in general, but all strong CO emission is accompanied by a visible HI spectral feature. Finally, the number of spectral HI absorption features per kpc drop off exponentially with increasing R.Comment: 13 pages, 13 figures, Accepted for March 2004 Ap

An Annotated Checklist and Key to Hermit Crabs of Tampa Bay, Florida, and Surrounding Waters

Fourteen species of hermit crabs, belonging to 5 genera, were identified from 35 stations in Tampa Bay and adjacent continental shelf waters. Ninety-two samples were taken from the intertidal zone to 15 m with a variety of gear including dip nets, trawls, dredges, and hand collections using SCUBA. Pagurus maclaughlinae, Pagurus longicarpus, and Pagurus pollicaris were distributed throughout the bay. These species were often sympatric, and were commonly found in seagrass beds, sandy substrates, and sand/mud substrates, respectively. Clibanarius vittatus, Pagurus gymnodactylus, and Pagurus stimpsoni inhabited the higher salinity waters of the bay entrance. Paguristes sp., Paguristes hummi, Pagurus impressus and Petrochirus diogenes were collected from the lower bay to offshore on hard substrates and sand. Paguristes puncticeps, Paguristes sericeus and Pagurus carolinensis were collected only offshore on hard substrates. The latter species is reported from the Gulf of Mexico for the first time. Isocheles wurdemanni appears to be restricted to high energy beaches. An illustrated key as well as information on distribution, reproductive biology, taxonomic problems, symbionts, and coloration are presented

Oscillatory instabilities during formic acid oxidation on Pt(100), Pt(110) and Pt(111) under potentiostatic control. II. Model calculations

A kinetic model is developed for the electrocatalytic oxidation of formic acid on Pt under potentiostatic control. The model development proceeds stepwise via a simple model of the electrocatalytic CO oxidation. The full model consists of four coupled, nonlinear ordinary differential equations. The scanned and stationary current/outer potential (I/U) behavior, stationary current oscillations, two-parameter bifurcation diagrams and stirring effects are simulated using realistic model parameters. The numerical findings are found to be consistent with the experimental results given by Strasser et al. The model reproduces period-1 as well as mixed-mode oscillations. Furthermore, a mechanistic analysis of the model was performed: two suboscillators are identified whose characteristics allow a plausible interpretation of the observed dynamics. After a classification of the suboscillators into previously described categories, an attempt is made to identify the minimal mechanistic requirements for electrochemical current oscillations

An Annotated Checklist and Key to Hermit Crabs of Tampa Bay, Florida, and Surrounding Waters

Fourteen species of hermit crabs, belonging to 5 genera, were identified from 35 stations in Tampa Bay and adjacent continental shelf waters. Ninety-two samples were taken from the intertidal zone to 15 m with a variety of gear including dip nets, trawls, dredges, and hand collections using SCUBA. Pagurus maclaughlinae, Pagurus longicarpus, and Pagurus pollicaris were distributed throughout the bay. These species were often sympatric, and were commonly found in seagrass beds, sandy substrates, and sand/mud substrates, respectively. Clibanarius vittatus, Pagurus gymnodactylus, and Pagurus stimpsoni inhabited the higher salinity waters of the bay entrance. Paguristes sp., Paguristes hummi, Pagurus impressus and Petrochirus diogenes were collected from the lower bay to offshore on hard substrates and sand. Paguristes puncticeps, Paguristes sericeus and Pagurus carolinensis were collected only offshore on hard substrates. The latter species is reported from the Gulf of Mexico for the first time. Isocheles wurdemanni appears to be restricted to high energy beaches. An illustrated key as well as information on distribution, reproductive biology, taxonomic problems, symbionts, and coloration are presented