University of Luxembourg

About: University of Luxembourg is a education organization based out in Luxembourg, Luxembourg. It is known for research contribution in the topics: Context (language use) & Computer science. The organization has 4744 authors who have published 22175 publications receiving 381824 citations.

A Sparse Bayesian Approach to the Identification of Nonlinear State-Space Systems

Abstract: This technical note considers the identification of nonlinear discrete-time systems with additive process noise but without measurement noise. In particular, we propose a method and its associated algorithm to identify the system nonlinear functional forms and their associated parameters from a limited number of time-series data points. For this, we cast this identification problem as a sparse linear regression problem and take a Bayesian viewpoint to solve it. As such, this approach typically leads to nonconvex optimizations. We propose a convexification procedure relying on an efficient iterative re-weighted $\ell_{1}$ -minimization algorithm that uses general sparsity inducing priors on the parameters of the system and marginal likelihood maximisation. Using this approach, we also show how convex constraints on the parameters can be easily added to the proposed iterative re-weighted $\ell_{1}$ -minimization algorithm. In the supplementary material available online (arXiv:1408.3549), we illustrate the effectiveness of the proposed identification method on two classical systems in biology and physics, namely, a genetic repressilator network and a large scale network of interconnected Kuramoto oscillators.

Breast-feeding and childhood-onset type 1 diabetes: A pooled analysis of individual participant data from 43 observational studies

Abstract: OBJECTIVE To investigate if there is a reduced risk of type 1 diabetes in children breastfed or exclusively breastfed by performing a pooled analysis with adjustment for recognized confounders. RESEARCH DESIGN AND METHODS Relevant studies were identified from literature searches using MEDLINE, Web of Science, and EMBASE. Authors of relevant studies were asked to provide individual participant data or conduct prespecified analyses. Meta-analysis techniques were used to combine odds ratios (ORs) and investigate heterogeneity between studies. RESULTS Data were available from 43 studies including 9,874 patients with type 1 diabetes. Overall, there was a reduction in the risk of diabetes after exclusive breast-feeding for >2 weeks (20 studies; OR = 0.75, 95% CI 0.64–0.88), the association after exclusive breast-feeding for >3 months was weaker (30 studies; OR = 0.87, 95% CI 0.75–1.00), and no association was observed after (nonexclusive) breast-feeding for >2 weeks (28 studies; OR = 0.93, 95% CI 0.81–1.07) or >3 months (29 studies; OR = 0.88, 95% CI 0.78–1.00). These associations were all subject to marked heterogeneity (I 2 = 58, 76, 54, and 68%, respectively). In studies with lower risk of bias, the reduced risk after exclusive breast-feeding for >2 weeks remained (12 studies; OR = 0.86, 95% CI 0.75–0.99), and heterogeneity was reduced (I 2 = 0%). Adjustments for potential confounders altered these estimates very little. CONCLUSION The pooled analysis suggests weak protective associations between exclusive breast-feeding and type 1 diabetes risk. However, these findings are difficult to interpret because of the marked variation in effect and possible biases (particularly recall bias) inherent in the included studies.

A generic method for secure Sbox implementation

Abstract: Cryptographic algorithms embedded in low resource devices are vulnerable to side channel attacks. Since their introduction in 1996, the effectiveness of these attacks has been highly improved and many countermeasures have been invalidated. It was especially true for countermeasures whose security was based on heuristics and experiments. Consequently, there is not only a need for designing new and various countermeasures, but it is also necessary to prove the security of the new proposals in formal models. In this paper we provide a simple method for securing the software implementation of functions called SBoxes that are widely used in symmetric cryptosystems. The main advantage of the proposed solution is that it does not require any RAM allocation. We analyze its efficiency and we compare it with other well-known countermeasures. Moreover, we use a recently introduced proof-of-security framework to demonstrate the resistance of our countermeasure from the viewpoint of Differential Power Analysis. Finally, we apply our method to protect the AES implementation and we show that the performances are suitable for practical implementations.

Comparing Immigration Policies: An Overview from the IMPALA Database

Abstract: This paper introduces a method and preliminary findings from a database that systematically measures the character and stringency of immigration policies. Based on the selection of that data for nine countries between 1999 and 2008, we challenge the idea that any one country is systematically the most or least restrictive toward admissions. The data also reveal trends toward more complex and, often, more restrictive regulation since the 1990s, as well as differential treatment of groups, such as lower requirements for highly skilled than low-skilled labor migrants. These patterns illustrate the IMPALA data and methods but are also of intrinsic importance to understanding immigration regulation.