How to Shape Noise Spectra for Continuous System Simulation

Noise for continuous-time system simulation is relevant for many applications, where time-domain results are required. Simulating such noise raises the need to consistently shape the frequency content of the signal. However, the methods for this task are not obvious and often state space implementations of form filters are approximated. In this paper, we address the problem with a new method relying on directly using the specified power spectral density for a convolution filter. For the example of railway track irregularities, we explain how to derive the required filters, implement them in the open-source Noise library, and verify the results. The new method produces correct results, is very simple to use, and enables new features for time simulation of physical systems

Robust Performance Analysis for Gust Loads Computation

In the design process of modern aircraft, a comprehensive analysis of worst case structural gust loads is imperative. Because this analysis requires to consider millions of cases, the examination is extremely time consuming. To solve this problem, a new approach based on robust performance analysis is introduced: the worst case energy-to-peak gain is used to efficiently determine worst case loads of nominal, uncertain, and linear parameter varying gust loads models

How to Shape Noise Spectra for Continuous System Simulation

Abstract Noise for continuous-time system simulation is relevant for many applications, where time-domain results are required. Simulating such noise raises the need to consistently shape the frequency content of the signal. However, the methods for this task are not obvious and often form filters are approximated by state space implementations. In this paper, we address the problem with a new method relying on directly using the specified power spectral density for a convolution filter. For the example of railway track irregularities, we explain how to derive the required filters, implement them in the open-source Noise library, and verify the results. The new method produces correct results, is very simple to use, and enables new features for time simulation of physical systems

ACBD5 and VAPB mediate membrane associations between peroxisomes and the ER

This is the final version of the article. Available from the publisher via the DOI in this record.Peroxisomes (POs) and the endoplasmic reticulum (ER) cooperate in cellular lipid metabolism and form tight structural associations, which were first observed in ultrastructural studies decades ago. PO–ER associations have been suggested to impact on a diverse number of physiological processes, including lipid metabolism, phospholipid exchange, metabolite transport, signaling, and PO biogenesis. Despite their fundamental importance to cell metabolism, the mechanisms by which regions of the ER become tethered to POs are unknown, in particular in mammalian cells. Here, we identify the PO membrane protein acyl-coenzyme A–binding domain protein 5 (ACBD5) as a binding partner for the resident ER protein vesicle-associated membrane protein-associated protein B (VAPB). We show that ACBD5–VAPB interaction regulates PO–ER associations. Moreover, we demonstrate that loss of PO–ER association perturbs PO membrane expansion and increases PO movement. Our findings reveal the first molecular mechanism for establishing PO–ER associations in mammalian cells and report a new function for ACBD5 in PO–ER tethering.This work was supported by grants from the Biotechnology and Biological Sciences Research Council (BB/K006231/1 and BB/ N01541X/1 to M. Schrader). J. Metz and M. Schrader are supported by a Wellcome Trust Institutional Strategic Support Award (WT097835MF and WT105618MA) and L.F. Godinho by a fellowship from Fundação para a Ciência e a Tecnologia, Portugal (SFRH/ BPD/90084/2012). M. Schrader and A.S. Azadi are supported by Marie Curie Initial Training Network action PerFuMe (316723). M. Islinger is supported by MEAMEDMA Anschubförderung, Medical Faculty Mannheim, University of Heidelberg

Robust Performance Analysis Applied to Gust Loads Computation

This paper demonstrates how the robust performance analysis framework can be used to determine worst case loads of flexible aircraft due to 1-cos gusts. This framework is a part of control theory and is used to characterize a system by input-output norms: e.g. the induced L2-L∞ norm represents the worst case energy-to-peak gain. Two very efficient ways to compute this norm are presented. Based on the physical interpretation of this norm, an aircraft model is weighted such that the induced L2-L∞ norm of the weighted system represents a close but guaranteed upper bound for 1-cos gusts and similar excitations. The analysis results are compared to simulations. Since the energy-to-peak gain can be computed in a very efficient way for LTI models, the norm is used to quickly obtain an upper bound for loads and to identify critical flight conditions. In a second example, the analysis is additionally performed on an uncertain mod

How to shape noise spectra for continuous system simulation

Noise for continuous-time system simulation is relevant for many applications, whenever time domain results are required. Simulating such noise raises the need to consistently shape the frequency content of the signal. However, the methods for this task are not obvious and form filters are often used as approximate state space implementations. In this article, we address the problem with a new method which relies on directly using the specified power spectral density for a convolution filter. For the example of railway track irregularities, we explain how to derive the required filters, implement them in the open-source AdvancedNoise library, and verify the results. The new method produces correct results, is very simple to use, and enables new features for time simulation of physical systems

Robust Performance Analysis: a Review of Techniques for Dealing with Infinite Dimensional LMIs

This paper compares three techniques for dealing with infinite dimensional linear matrix inequalities (LMIs) for robust performance analysis: the gridding based approximation, the polytopic relaxation and the linear fractional representation based relaxation. The latter draws on the Full Block S-Procedure with different types of multipliers. All three techniques are applied in two benchmark studies at the example of an aeroelastic system. The studies are backed up by results from the Robust Control Toolbox for Matlab