Calorimetric consequences of thermal softening in Johnson–Cook’s model

At high loading rates, the development of adiabatic shear bands in metals is conventionally attributed to the strong interactions induced by viscoplastic dissipation within the bands and thermal softening effects. The rheological equation proposed by Johnson and Cook takes both viscoplastic hardening and thermal softening into account. The present paper reviews and includes this equation into a thermodynamic framework in order to analyse the energy impacts of thermal softening. Indeed this latter implies the existence of a ther-momechanical coupling source, probably non-negligible and which must be considered when estimating temperature variations induced by shear band development

Resource modalities in game semantics

The description of resources in game semantics has never achieved the simplicity and precision of linear logic, because of a misleading conception: the belief that linear logic is more primitive than game semantics. We advocate instead the contrary: that game semantics is conceptually more primitive than linear logic. Starting from this revised point of view, we design a categorical model of resources in game semantics, and construct an arena game model where the usual notion of bracketing is extended to multi- bracketing in order to capture various resource policies: linear, affine and exponential

Minimax adaptive tests for the Functional Linear model

We introduce two novel procedures to test the nullity of the slope function in the functional linear model with real output. The test statistics combine multiple testing ideas and random projections of the input data through functional Principal Component Analysis. Interestingly, the procedures are completely data-driven and do not require any prior knowledge on the smoothness of the slope nor on the smoothness of the covariate functions. The levels and powers against local alternatives are assessed in a nonasymptotic setting. This allows us to prove that these procedures are minimax adaptive (up to an unavoidable \log\log n multiplicative term) to the unknown regularity of the slope. As a side result, the minimax separation distances of the slope are derived for a large range of regularity classes. A numerical study illustrates these theoretical results

An Empirical Analysis of Foreign Exchange Reserves in Emerging Asia

Over the past few years, the ability of the United States to finance its current account deficit has been facilitated by massive purchases of U.S. Treasury bonds and agency securities by Asian central banks. In this process, Asian central banks have accumulated large stockpiles of U.S.-dollar foreign exchange reserves. How far is the current level of reserves from that predicted by the standard macroeconomic determinants? The authors answer this question by using Pedroni's (1999) panel cointegration tests as the basis for the estimation of a long-run reserve-demand function in a panel of eight Asian emerging-market economies. This is a key innovation relative to the existing research on international reserves modelling: although the data are typically I(1), the literature ignores this fact and makes statistical inference based on unadjusted standard errors. While the authors find evidence of a positive structural break in the demand for international reserves by Asian central banks in the aftermath of the financial crisis of 1997-98, their results indicate that the actual level of reserves accumulated in 2003-04 was still in excess relative to that predicted by the model. Therefore, as long as historical relationships hold, a slowdown in the rate of accumulation of reserves is likely. This poses negative risks for the U.S. dollar. However, both the substantial capital losses that Asian central banks would incur if they were to drastically change their holding policy and the evidence that the currency composition of reserves evolves only gradually mitigate the risks of a rapid depreciation of the U.S. dollar triggered by Asian central banks.Econometric and statistical methods; International topics; Financial stability

Search Frictions in Physical Capital Markets as a Propagation Mechanism

We build a Dynamic General Equilibrium model with search frictions for the allocation of physical capital and investigate its implications for the business cycle. While the model is in principle capable of generating substantial internal propagation to small exogenous shocks, the quantitative effects are modest once we calibrate the model to fit firm-level capital flows. We then extend the model with credit market frictions that lead to countercyclical default and countercyclical risk premia as in the data. Countercyclical default directly affects capital reallocation and has important general equilibrium income effects on labor supply. Yet, for calibrations in line with observed consumption dynamics, we find that even in this extended model, search frictions in physical capital markets play only a small role for business cycle fluctuations.Capital allocation frictions, search and matching, credit frictions, business cycles, dynamic general equilibrium

Employee ownership as a signal of management quality

The employees' decision to become shareholder of the company they work for can be a consequence of employers' matching contribution in company stock. From a behavioral perspective, employees would regard these contributions as an implicit investment advice made by their employer. This paper adopts another viewpoint. Since employee ownership can be used as an entrenchment mechanism, we suggest that employer's matching policy can be considered as an imperfect signal of management quality. This paper suggests that employee ownership can be used by managers to compensate their management skills to the market. It recommends that employee ownership policy should not be influenced by the managers.Employee ownership ; corporate governance ; management entrenchment

MUSE: The Bank of Canada's New Projection Model of the U.S. Economy

Staff projections provided for the Bank of Canada's monetary policy decision process take into account the integration of Canada's very open economy within the global economy, as well as its close real and financial linkages with the United States. To provide inputs for this projection, the Bank has developed several models, including MUSE, NEUQ (the New European Quarterly Model), and BoC-GEM (Bank of Canada Global Economy Model), to analyze and forecast economic developments in the rest of the world. The authors focus on MUSE, the model currently used to describe interaction among the principal U.S. economic variables, including gross domestic product, inflation, interest rates, and the exchange rate. Brief descriptions are also provided of NEUQ and BoC-GEM.

New Internal Stress Driven on-Chip Micromachines for Extracting Mechanical Properties of Thin Films

A new concept of micromachines has been developed for measuring the mechanical properties of thin metallic films. The actuator is a beam undergoing large internal stresses built up during the deposition process. Al thin films are deposited partly on the actuator beam and on the substrate. By etching the structure, the actuator contracts and pulls the Al film. Full stress strain curves can be generated by designing a set of micromachines with various actuator lengths. In the present study, the displacements have been measured by scanning electronic microscopy. The stress is derived from simple continuum mechanics relationships. The tensile properties of Al films of various thicknesses have been tested. A marked increase of the strength with decreasing film thickness is observed.Comment: Submitted on behalf of TIMA Editions (http://irevues.inist.fr/tima-editions