A sub-Riemannian curvature-dimension inequality, volume doubling property and the Poincar\'e inequality

Let $\mathbb{M}$ be a smooth connected manifold endowed with a smooth measure $\mu$ and a smooth locally subelliptic diffusion operator $L$ satisfying $L1=0$, and which is symmetric with respect to $\mu$. We show that if $L$ satisfies, with a non negative curvature parameter, the generalized curvature inequality introduced by the first and third named authors in \cite{BG}, then the following properties hold: 1 The volume doubling property; 2 The Poincar\'e inequality; 3 The parabolic Harnack inequality. The key ingredient is the study of dimensional reverse log-Sobolev inequalities for the heat semigroup and corresponding non-linear reverse Harnack type inequalities. Our results apply in particular to all Sasakian manifolds whose horizontal Webster-Tanaka-Ricci curvature is non negative, all Carnot groups with step two, and to wide subclasses of principal bundles over Riemannian manifolds whose Ricci curvature is non negative

A localization and updating strategy of large finite element models in structural dynamics

The purpose of this paper is to evaluate the application of the error of constitutive law method to the updating of large FE models of space structures using FRF experimental results. First, we briefly recall the theoretical basis of this method in modal and frequency approaches. Then, the notion of visibility is introduced to improve the modelling of localization error and the quality of modal updating, for low frequencies. Finally we propose a global strategy and discuss the results we obtained on satellite JASON2

Semi-parametric estimation of shifts

We observe a large number of functions differing from each other only by a translation parameter. While the main pattern is unknown, we propose to estimate the shift parameters using $M$-estimators. Fourier transform enables to transform this statistical problem into a semi-parametric framework. We study the convergence of the estimator and provide its asymptotic behavior. Moreover, we use the method in the applied case of velocity curve forecasting.Comment: Published in at http://dx.doi.org/10.1214/07-EJS026 the Electronic Journal of Statistics (http://www.i-journals.org/ejs/) by the Institute of Mathematical Statistics (http://www.imstat.org

Estimation error for blind Gaussian time series prediction

We tackle the issue of the blind prediction of a Gaussian time series. For this, we construct a projection operator build by plugging an empirical covariance estimation into a Schur complement decomposition of the projector. This operator is then used to compute the predictor. Rates of convergence of the estimates are given

Biofilms in porous media: development of macroscopic transport equations via volume averaging with closure for local mass equilibrium conditions

In this work, we upscale a pore-scale description of mass transport in a porous medium containing biofilm to develop the relevant Darcy-scale equations. We begin with the pore-scale descriptions of mass transport, interphase mass transfer, and biologically-mediated reactions; these processes are then upscaled using the method of volume averaging to obtain the macroscale mass balance equations. We focus on the case of local mass equilibrium conditions where the averaged concentrations in the fluid and biological phases can be assumed to be proportional and for which a one-equation macroscopic model may be developed. We predict the effective dispersion tensor by a closure scheme that is solved for the cases of both simple and complex unit cells. The domain of validity of the approach is clearly identified, both theoretically and numerically, and unitless groupings indicating the domain of validity are reported

The Paris Residential Market: Driving Factors and Market Behaviour 1973-2001

In this paper we investigate the driving factors associated with the Paris apartment market. We explore a database of nearly 230 000 transactions for residential properties in the Paris area over the 1973 – 2001 period. We develop a factorial model that may capture the systematic link between residential prices and a set of predefined economic variables or a linear combination of these economic variables. We assume that capital growth rates in real estate are related to the variables we defined in the last paragraph. We measure this link which underlines the ‘true path’ of the real estate market: in that way we can develop an index as a function of many other indices. The methodology we develop, based on a multifactor approach to apartment price movements in the long run, has two main advantages over traditional indices. Firstly, we are able to identify the main driving factors for the Paris residential market. And secondly, the factors thus derived can be used to generate a “factor model” useful in comparison to existing capital growth indices and that provides valuable intuition for forecasting residential prices.Real estate indexes; Repeat sales; Risk factors

Which Capital Growth Index for the Paris Residential Market?

In this paper we address the issue of measuring price performance for the Paris residential market. Our main focus is on choosing the appropiate index or indices capable of efficiently capturing capital growth, capital risk, and identifying the main risk factors inherent in this specific market.We identifying three existing indices but show that they may not be completely appropriate to address our main goals. We therefore construct two complementary repeat sales indices: a Case & Shiller (1987) Weighted Repeat sales (WRS) index and a Factorial index using the Baroni, Barthélémy & Mokhrane (2001) approach. We use the CD-BIEN database that contains more than 220 000 repeta sales transactions for residential properties in Paris area covering the period 1983-2001 period.We estimate these two indices for the Paris and close surrounding area and compare them to different existing indices: (I) the square metre index provides by the Chambre des Notaires de Paris and INSEE, (II) the IDP indices, (III) the listed real estate index. OUR conclusions yield interesting implications concerning real estate risk and suggest the construction of jointly using the repeat sales and the factorial approachesReal estate indexes; valuation-based index; repaet sales; risk factors

Optimal holding period In Real Estate Portfolio

This paper considers the use of simulated cash flows to determine the optimal holding period in real estate portfolio to maximize its present value. The traditional DCF approach with an estimation of the resale value through a growth rate of the future cash flow does not let appear this optimum. However, if the terminal value is calculated from the trend of a diffusion process of the price, an optimum may appear under certain conditions. Finally we consider the sensitivity of the optimal holding period to the different parameters involved in the cash flow estimations. This methodology may be applied in commercial valuation and enables to get an optimal holding period for a given portfolio.valuation, DCF, optimal holding period, commercial property