Connecting dispersion models and wall temperature prediction for laminar and turbulent flows in channels

In a former paper, Drouin et al. (2010) proposed a model for dispersion phenomena in heated channels that works for both laminar and turbulent regimes. This model, derived according to the double averaging procedure, leads to satisfactory predictions of mean temperature. In order to derive dispersion coefficients, the so called ‘‘closure problem’’ was solved, which gave us access to the temperature deviation at sub filter scale. We now propose to capitalize on this useful information in order to connect dispersion modeling to wall temperature prediction. As a first step, we use the temperature deviation modeling in order to connect wall to mean temperatures within the asymptotic limit of well established pipe flows. Since temperature in wall vicinity is mostly controlled by boundary conditions, it might evolve according to different time and length scales than averaged temperature. Hence, this asymptotic limit provides poor prediction of wall temperature when flow conditions encounter fast transients and stiff heat flux gradients. To overcome this limitation we derive a transport equation for temperature deviation. The resulting two-temperature model is then compared with fine scale simulations used as reference results. Wall temperature predictions are found to be in good agreement for various Prandtl and Reynolds numbers, from laminar to fully turbulent regimes and improvement with respect to classical models is noticeable

Football Matches: the Effects on Crime

The heavy police presence at football matches in England has reduced hooliganism in the stadium - but at what cost in terms of both policying budgets and under-protected places elsewhere in the neighbourhood? Olivier Marie examines the multiple effects of football matches on crime.Football, police, crime

Police and Thieves in the Stadium: Measuring the (Multiple)Effects of Football Matches on Crime

During large sporting events criminal behaviour may be affected via three main channels: (i) fan concentration, (ii) self incapacitation, and (iii) police displacement. In this paper I exploit information on football (soccer) matches for nine London teams linked to detailed recorded crime data at the area level to empirically estimate these different effects. My findings show that only property crime significantly increases in the communities hosting football matches but that they experience no changes in violent offences. These results are robust to controlling for a large number of game type and outcome characteristics. There is no evidence of temporal displacement of criminal activity. Our conceptual model suggests that the away game attendance effect on crime is due to voluntary incapacitation of potential offenders. I argue that the police displacement effect of hosting a match increases property crime by 7 percentage point for every extra 10,000 supporters.Football, police, crime

Police and Thieves in the Stadium: Measuring the (Multiple) Effects of Football Matches on Crime

During large sporting events criminal behaviour may be affected via three main channels: (i) fan concentration, (ii) self incapacitation, and (iii) police displacement. In this paper I exploit information on football (soccer) matches for nine London teams linked to detailed recorded crime data at the area level to empirically estimate these different effects. My findings show that only property crime significantly increases in the communities hosting football matches but that they experience no changes in violent offences. These results are robust to controlling for a large number of game type and outcome characteristics. There is no evidence of temporal displacement of criminal activity. Our conceptual model suggests that the away game attendance effect on crime is due to voluntary incapacitation of potential offenders. I argue that the police displacement effect of hosting a match increases property crime by 7 percentage point for every extra 10,000 supporters.public economics ;

Crime and police resources: the street crime initiative

In this paper we look at links between police resources and crime in a different way to the existing economics of crime work. To do so we focus on a policy intervention - the Street Crime Initiative - that was introduced in England and Wales in 2002. This allocated additional resources to some police force areas to combat street crime, whereas other forces did not receive any additional funding. Estimates derived from several empirical strategies show that robberies did fall significantly in SCI police forces relative to non-SCI forces after the initiative was introduced. Moreover, the policy seems to have been a cost effective one. There is some heterogeneity in this positive net social benefit across different SCI police forces, suggesting that some police forces may have made better use of the extra resources than others. Overall, we reach the conclusion that increased police resources do in fact lead to lower crime, at least in the context of the SCI programme we study

Bimodalities : a survey of experimental data and models

Bimodal distributions of some chosen variables measured in nuclear collisions were recently proposed as a non ambiguous signature of a first order phase transition in nuclei. This section presents a compilation of both theoretical and experimental studies on bimodalities performed so far, in relation with the liquid-gas phase transition in nuclear matter.Comment: 12 pages, 18 figures, 1 table Appeared in European Physics Journal A as part of the Topical Volume "Dynamics and Thermodynamics with Nuclear Degrees of Freedom

Rheological behaviour and spectroscopic investigations of cerium-modified AlO(OH)colloidal suspensions

The rheological behaviour of aqueous suspensions of boehmite (AlO(OH)) modified with different Ce-salts (Ce(NO3)3, CeCl3, Ce(CH3COO)3 and Ce2(SO4)3) was investigated at a fixed Ce/Al molar ratio (0.05). Freshly prepared boehmite suspensions were near-Newtonian and time-independent. A shear-sensitive thixotropic network developed when Ce-salts with monovalent anions were introduced in the nanoparticle sols. The extent of particle aggregation dramatically increased with ageing for Ce(NO3)3 and CeCl3 whereas an equilibrium value was reached with Ce(CH3COO)3. The addition of Ce2(SO4)3 with divalent anions involved no thixotropy but rather a sudden phase separation. The combined data set of IRTF and DRIFT spectra indicated that free View the MathML source anions of peptized boehmite adsorb on the nanoparticle surface by H-bond. The introduction of Ce-salts in the boehmite sol led to the coordination between Ce3+ ions and View the MathML source anions adsorbed on boehmite i.e. to [Ce(NO3)4(H2O)x]− complex. Such coordination led to a thixotropic behaviour which was lower with Ce(NO3)3 compared to CeCl3 and Ce(CH3COO)3. In contrast, Ce2(SO4)3 formed insoluble complexes with dissolved aluminium species. The formation of H-bonded surface nitrate complexes was found to play a decisive role on the particle–particle interactions and consequently on the rheological behaviour of the sols

Crime and Police Resources: The Street Crime Initiative

In this paper we look at links between police resources and crime in a different way to the existing economics of crime work. To do so we focus on a policy intervention - the Street Crime Initiative - that was introduced in England and Wales in 2002. This allocated additional resources to some police force areas to combat street crime, whereas other forces did not receive any additional funding. Estimates derived from several empirical strategies show that robberies did fall significantly in SCI police forces relative to non-SCI forces after the initiative was introduced. Moreover, the policy seems to have been a cost effective one. There is some heterogeneity in this positive net social benefit across different SCI police forces, suggesting that some police forces may have made better use of the extra resources than others. Overall, we reach the conclusion that increased police resources do in fact lead to lower crime, at least in the context of the SCI programme we study.Street crime, Police resources, Cost effectiveness

Continuity of the asymptotic shape of the supercritical contact process

We prove the continuity of the shape governing the asymptotic growth of the supercritical contact process in Z^d , with respect to the infection parameter. The proof is valid in any dimension d $\ge$ 1