Quantitative Analyse

Ohne Zusammenfassung     

A Balian–Low Theorem for Subspaces

We extend the Balian–Low theorem to Gabor subspaces of \(L^2({\mathbb {R}})\) by involving the concept of additional time–frequency shift invariance. We prove that if a Gabor system on a lattice of rational density is a Riesz sequence generating a subspace which is invariant under an additional time–frequency shift, then its generator cannot decay fast simultaneously in time and frequency.

     

Finite mixture of regression models for censored data based on scale mixtures of normal distributions

Advances in Data Analysis and Classification - In statistical analysis, particularly in econometrics, the finite mixture of regression models based on the normality assumption is routinely used to...     

The challenges in reliable determination of degradation rates and lifetime in polymer electrolyte membrane fuel cells

The durability of polymer electrolyte membrane fuel cells (PEMFCs) needs to be further improved to cope with application requirements and economic competitiveness. This article highlights the challenges in the reliable determination of degradation rates and lifetime. The reliable evaluation of performance degradation rates is fundamental to quantify and benchmark durability and to allow comparisons between PEMFC durability tests performed using different materials or in different laboratories. The use of efficient recovery procedures enables the discrimination of reversible and irreversible voltage losses and facilitates the understanding of recovery mechanisms. In the end, recent contributions about lifetime diagnoses and prediction are presented, which are promising to be implemented in PEMFC applications.     

Heat treatment as a key factor for enhancing the photodegradation performance of hydrothermally-treated sol–gel TiO2–SiO2 nanocomposites

Journal of Sol-Gel Science and Technology - Most studies related to the synthesis of TiO2–SiO2 composites for photocatalytic applications did not systematically evaluate the textural and...