6,847 research outputs found
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
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