Stability of the stochastic heat equation in L1([0,1])L^1([0,1])

We consider the white-noise driven stochastic heat equation on $[0,\infty)\times[0,1]$ with Lipschitz-continuous drift and diffusion coefficients $b$ and $\sigma$. We derive an inequality for the $L^1([0,1])$-norm of the difference between two solutions. Using some martingale arguments, we show that this inequality provides some {\it a priori} estimates on solutions. This allows us to prove the strong existence and (partial) uniqueness of weak solutions when the initial condition belongs only to $L^1([0,1])$, and the stability of the solution with respect to this initial condition. We also obtain, under some conditions, some results concerning the large time behavior of solutions: uniqueness of the possible invariant distribution and asymptotic confluence of solutions

Measurement of thermal conductance of silicon nanowires at low temperature

We have performed thermal conductance measurements on individual single crystalline silicon suspended nanowires. The nanowires (130 nm thick and 200 nm wide) are fabricated by e-beam lithography and suspended between two separated pads on Silicon On Insulator (SOI) substrate. We measure the thermal conductance of the phonon wave guide by the 3 method. The cross-section of the nanowire approaches the dominant phonon wavelength in silicon which is of the order of 100 nm at 1K. Above 1.3K the conductance behaves as T3, but a deviation is measured at the lowest temperature which can be attributed to the reduced geometry

Absolute continuity for some one-dimensional processes

We introduce an elementary method for proving the absolute continuity of the time marginals of one-dimensional processes. It is based on a comparison between the Fourier transform of such time marginals with those of the one-step Euler approximation of the underlying process. We obtain some absolute continuity results for stochastic differential equations with H\"{o}lder continuous coefficients. Furthermore, we allow such coefficients to be random and to depend on the whole path of the solution. We also show how it can be extended to some stochastic partial differential equations and to some L\'{e}vy-driven stochastic differential equations. In the cases under study, the Malliavin calculus cannot be used, because the solution in generally not Malliavin differentiable.Comment: Published in at http://dx.doi.org/10.3150/09-BEJ215 the Bernoulli (http://isi.cbs.nl/bernoulli/) by the International Statistical Institute/Bernoulli Society (http://isi.cbs.nl/BS/bshome.htm

Internal friction in advanced Fe-Al intermetallics

We have measured the internal friction and the dynamic modulus of an Fe–38 at.% Al alloy using a forced torsion pendulum working between 10−3 and 10 Hz. The measurements have been carried out as a function of temperature (from room temperature to 1200 K) and as a function of frequency. Two peaks have been observed in the internal friction spectra, at about 780 and 1100 K, which are largely superposed in the intermediate temperature range. Both peaks and the corresponding modulus defect shift in temperature with the oscillation frequency, and can be attributed to relaxation mechanisms. Previous results in the literature seem to indicate that the low temperature peak is the Zener relaxation of Al atoms. The activation energy of the high-temperature peak, referred to as P1 peak because it has not been studied previously, has been determined to be Hact = 2.87 eV, from the results of measurements at different temperatures and frequencies. We discuss the possible mechanisms, which could be responsible of this P1 peak, and suggest that it could be attributed to the intrinsic movements of left angle bracket1 0 0right-pointing angle bracket perfect dislocations over the Peierls barrier by kink pair formation in the B2 ordered FeAl

A Vector Approach to Cryptography Implementation

International audienceThe current deployment of Digital Right Management (DRM) schemes to distribute protected contents and rights is leading the way to massive use of sophisticated embedded cryptographic applications. Embedded microprocessors have been equipped with bulky and power-consuming co-processors designed to suit particular data sizes. However, flexible cryptographic platforms are more desirable than devices dedicated to a particular cryptographic algorithm as the increasing cost of fabrication chips favors large volume production. This paper proposes a novel approach to embedded cryptography whereby we propose a vector-based general purpose machine capable of implementing a range of cryptographic algorithms. We show that vector processing ideas can be used to perform cryptography in an e±cient manner which we believe is appropriate for high performance, flexible and power efficient embedded systems

Hardware-Software Codesign of a Vector Co-processor for Public Key Cryptography

International audienceUntil now, most cryptography implementations on parallel architectures have focused on adapting the software to SIMD architectures initially meant for media applications. In this paper, we review some of the most significant contributions in this area. We then propose a vector architecture to efficiently implement long precision modular multiplications. Having such a data level parallel hardware provides a circuit whose decode and schedule units are at least of the same complexity as those of a scalar processor. The excess transistors are mainly found in the data path. Moreover, the vector approach gives a very modular architecture where resources can be easily redefined. We built a functional simulator onto which we performed a quantitative analysis to study how the resizing of those resources affects the performance of the modular multiplication operation. Hence we not only propose a vector architecture for our Public Key cryptographic operations but also show how we can analyze the impact of design choices on performance. The proposed architecture is also flexible in the sense that the software running on it would offer room for the implementation of counter-measures against side-channel or fault attacks

EMU and France

This article examines the loss of sovereignty that the transition to the Union implies for France in Economic and Monetary Union. In the first part, it reviews several episodes of French monetary history, and illustrates the constraints that today limit the margin of manoeuvre of France in terms of economic policy. France retains only a very limited and purely formal margin of manoeuvre, both in terms of monetary policy and the use of the exchange rate. A second section examines the interactions between different exchange rate regimes - flexible rates, stable but adjustable rates, fixed rates - and the markets for goods, labor and capital. The next section examines adjustment within an Economic and Monetary Union. The article concludes with an examination of the options open to France in the nineties. It shows that a devaluation policy would be extremely costly, and that maintaining the option to devalue significantly reduces the room for manoeuvre of fiscal policy. To restore this margin of manouvre, France should, on the one hand, make the Bank of France independent and responsible for the stability of the value of the currency and, on the other hand, propose to Germany and other countries for a strong currency of the Community to set the exchange rate of their currencies definitively and without fluctuation, in order to further guarantee the financial stability required for the use of any instrument of economic policy. This solution would also have the advantage of accelerating the transition to EMU and showing the movement