Numerical investigation into the failure of a micropile retaining wall

The paper presents a numerical investigation on the failure of a micropile wall that collapsed while excavating the adjacent ground. The main objectives are: to estimate the strength parameters of the ground; to perform a sensitivity analysis on the back slope height and to obtain the shape and position of the failure surface. Because of uncertainty of the original strength parameters, a simplified backanalysis using a range of cohesion/friction pairs has been used to estimate the most realistic strength parameters. The analysis shows that failure occurred because overestimation of strength and underestimation of loads.Peer ReviewedPostprint (author's final draft

Cotton manufacturers as bankers: the textile trade and credit in spain, 1840-1913

[cat] La historiografia ha assenyalat que en el segle XIX el crèdit que els fabricants cotoners catalans oferien als seus clients era de caràcter informal i, per tant, impossible de ser transferit al sistema bancari. Això hauria tingut un efecte negatiu en la rendibilitat de les empreses cotoneres. A partir de l’anàlisi de diversos arxius empresarials, així com de fonts judicials i notarials, aquest treball confirma aquesta descripció dels fets però proposa una interpretació més optimista. Els fabricants feien de banquers dels seus clients perquè eren els millor situats per a exercir aquesta funció. Havien construït una bona estructura d’informació, gestionaven eficientment el risc creditici i obtenien beneficis d’aquesta activitat.[eng] Historians claim that in the nineteenth century Catalan cotton manufacturers were giving informal credit to their clients, and were therefore unable to transfer this credit to the banking system. Such circumstances would have had a detrimental effect on the profitability of the cotton firms. Based on an analysis of the archives of several firms, as well as judicial and notary sources, we can confirm this state of affairs, but present a more optimistic interpretation of the system. Manufacturers were, in fact, acting as their customers’ bankers because they were in the best position to perform this function. They built up a good information structure, managed the credit risk efficiently and earned money from this activity

Increasing optimism and demand uncertainty

By allowing the initial prior over market size to be a mixture of distributions, this paper extends the model of irreversible investment under uncertainty proposed by Rob (1991). We find that capacity expansion fuels investors' optimism. It is shown in the paper that the crash is always preceded by a boom when the initial prior is a mixture of exponential distributions.Learning Investment Uncertainty

The Wrong Kind of Transparency

In a model of career concerns for experts, when is the principal hurt from observing more information about her agent? This paper introduces a distinction between information on the consequence of the agent's action and information directly on the agent's action. It is the latter kind that can hurt the principal by engendering conformism, which worsens both discipline and sorting. The paper identifies a necessary and sufficient condition on the agent signal structure under which transparency on action is detrimental to the principal. The paper also shows the existence of complementarities between transparency on action and transparency on consequence. The results are used to interpret existing disclosure policies in politics, corporate governance, and delegated portfolio management.Transparency, career concerns, expert agents.

Shear mixing in stellar radiative zones I. Effect of thermal diffusion and chemical stratification

Turbulent transport of chemical elements in radiative zones of stars is considered in current stellar evolution codes thanks to phenomenologically derived diffusion coefficients. Recent local numerical simulations (Prat & Ligni\`eres 2013, A&A, 551, L3) suggest that the coefficient for radial turbulent diffusion due to radial differential rotation satisfies $D_{\rm t}\simeq0.058\kappa/Ri$, in qualitative agreement with Zahn's model. However, this model does not apply when differential rotation is strong with respect to stable thermal stratification or when chemical stratification has a significant dynamical effect, a situation encountered at the outer boundary of nuclear-burning convective cores. We extend our numerical study to consider the effects of chemical stratification and of strong shear, and compare the results with prescriptions used in stellar evolution codes. We performed local, direct numerical simulations of stably stratified, homogeneous, sheared turbulence in the Boussinesq approximation. The regime of high thermal diffusivities, typical of stellar radiative zones, is reached thanks to the so-called small-P\'eclet-number approximation, which is an asymptotic development of the Boussinesq equations in this regime. The dependence of the diffusion coefficient on chemical stratification was explored in this approximation. Maeder's extension of Zahn's model in the strong-shear regime is not supported by our results, which are better described by a model found in the geophysical literature. As regards the effect of chemical stratification, our quantitative estimate of the diffusion coefficient as a function of the mean gradient of mean molecular weight leads to the formula $D_{\rm t}\simeq 0.45\kappa(0.12-Ri_\mu)/Ri$, which is compatible in the weak-shear regime with the model of Maeder & Meynet (1996, A&A, 313, 140).Comment: 10 pages, 9 figures, accepted in A&

Campaign Advertising and Voter Welfare

This paper investigates the role of campaign advertising and the opportunity of legal restrictions on it. An electoral race is modeled as a signalling game with three classes of players: a continuum of voters, two candidates, and one interest group. The group has non-verifiable insider information on the candidates' valence and, on the basis of this information, offers a contribution to each candidate in exchange for a favorable policy position. Candidates spend the contributions they receive on non-directly informative advertising. This paper shows that: (1) A separating equilibrium exists in which the group contributes to a candidate only if the insider information about that candidate is positive; (2) Although voters are fully rational, a ban on campaign advertising can be welfare-improving; and (3) Split contributions may arise in equilibrium (and should be prohibited).Elections;campaign contributions;advertising;voter welfare;split contributions