Macroeconomics of Credit and Labor Markets Imperfections.

Credit market imperfections influence the labor market and aggregate economic activity. In turn, macroeconomic factors have an impact on the credit sector. To assess these effects in a tractable general-equilibrium framework, we introduce endogenous search frictions, in the spirit of Peter Diamond (1990), in both credit and labor markets. We demonstrate that credit frictions amplify macroeconomic volatility through a financial accelerator. The magnitude of this general-equilibrium accelerator is proportional to the credit gap, defined as the deviation of actual output from its perfect credit market level. We explore various extensions, notably endogenous wages.

Concavity analysis of the tangent method

The tangent method has recently been devised by Colomo and Sportiello (arXiv:1605.01388 [math-ph]) as an efficient way to determine the shape of arctic curves. Largely conjectural, it has been tested successfully in a variety of models. However no proof and no general geometric insight have been given so far, either to show its validity or to allow for an understanding of why the method actually works. In this paper, we propose a universal framework which accounts for the tangency part of the tangent method, whenever a formulation in terms of directed lattice paths is available. Our analysis shows that the key factor responsible for the tangency property is the concavity of the entropy (also called the Lagrangean function) of long random lattice paths. We extend the proof of the tangency to $q$-deformed paths.Comment: published version, 22 page

The Optimal Path of the Chinese Renminbi

This paper provides evidence on the consistency of the determination of the Chinese real effective exchange rate (REER) over time. Especially, we validate coin- tegration between the REER and a set of fundamentals using recent developments in model selection. Error correction model (ECM) path dependence in model se- lection is addressed by using the General-To-Specific (GETS) approach enabling us to obtain empirically constant and encompassing ECM. As inference in finite sam- ples is commonly of concern, statistics' distributional properties for cointegration tests are estimated by Monte Carlo simulations. The final specification of the model is compatible with the natural real exchange rate of Stein (1994). We study the implications of our findings in terms of foreign exchange policy.Exchange Rate, Equilibrium value, GETS, Global Imbalances

The effect of quenching and defects size on the HCF behaviour of Boron steel

This work investigates the effect of natural and artificial surface defects and quenching on the fatigue strength of a Boron steel (22MnB5). A vast experimental campaign has been undertaken to study the high cycle fatigue behaviour and more specifically the fatigue damage mechanisms observed in quenched and untreated materials, under different loading conditions and with differents artificial defects sizes (from 25 μm to 370 μm radius). In order to test the sheet metal in shear an original test apparatus is used. The critical defect size is determined to be 100 ± 50 μm. This critical size does not appear to depend on the loading type or the microstructure of the material (i.e. ferritic–perlitic or martensitic). However, for large defects, the quenched material is more sensitive to the defect size than the untreated material. For a defect size range of 100–300 μm the slope of the Kitagawa–Takahashi diagram is approximately −1/3 and −1/6 for the quenched and untreated materials respectively. A probabilistic approach that leads naturally to a probabilistic Kitagawa type diagram is developed. This methodology can be used to explain the relationship between the influence of the heat treatment and the defect size on the fatigue behaviour of this steel

Simulation of a finishing operation : milling of a turbine blade and influence of damping

Milling is used to create very complex geometries and thin parts, such as turbine blades. Irreversible geometric defects may appear during finishing operations when a high surface quality is expected. Relative vibrations between the tool and the workpiece must be as small as possible, while tool/workpiece interactions can be highly non-linear. A general virtual machining approach is presented and illustrated. It takes into account the relative motion and vibrations of the tool and the workpiece. Both deformations of the tool and the workpiece are taken into account. This allows predictive simulations in the time domain. As an example the effect of damping on the behavior during machining of one of the 56 blades of a turbine disk is analysed in order to illustrate the approach potential