Damage Detection in Flexible Propeller Beam Structures by Exploiting Impact-Induced Coupled Acceleration Signals

2011 ◽  
Author(s):  
Ioannis T. Georgiou
Keyword(s):  
Data Driven ◽  
Distributed Information ◽  
Modal Expansion ◽  
Shape Difference ◽  
Spatio Temporal ◽  
Temporal Sample ◽  
High Level ◽  
Proper Orthogonal ◽  
Acceleration Signals

A local damage at the tip of a composite propeller is diagnosed by properly comparing its impact-induced free coupled dynamics to that of a pristine wooden propeller of the same size and shape. This is accomplished by creating indirectly via collocated measurements distributed information for the coupled acceleration field of the propellers. The powerful data-driven modal expansion analysis delivered by the Proper Orthogonal Decomposition (POD) Transform reveals that ensembles of impact-induced collocated coupled experimental acceleration signals are underlined by a high level of spatio-temporal coherence. Thus they furnish a valuable spatio-temporal sample of coupled response induced by a point impulse. In view of this fact, a tri-axial sensor was placed on the propeller hub to collect collocated coupled acceleration signals induced via modal hammer nondestructive impacts and thus obtained a reduced order characterization of the coupled free dynamics. This experimental data-driven analysis reveals that the in-plane unit components of the POD modes for both propellers have similar shapes-nearly identical. For the damaged propeller this POD shape-difference is quite pronounced. The shapes of the POD modes are used to compute indices of difference reflecting directly damage. At the first POD energy level, the shape-difference indices of the damaged composite propeller are quite larger than those of the pristine wooden propeller.

Acquirement and Interpretation of Spatially Distributed Impulsive Acceleration Signals in a Flexible Shaft-Propeller System

2012 ◽  
Author(s):  
Ioannis T. Georgiou
Keyword(s):  
Distributed Information ◽  
Spatially Distributed ◽  
Experimental Time Series ◽  
Impulsive Response ◽  
Impulsive Dynamics ◽  
Spatio Temporal ◽  
Pod Analysis ◽  
Proper Orthogonal ◽  
Acceleration Signals

This work reports on the spatio-temporal characterization of collocated ensembles of experimental time series of the impulsive dynamics in a complex flexible structural-machinery system composed of a shaft supporting at its free end a three-bladed boat propeller. A few state-of-the-art piezoelectric accelerometers sample simultaneously the impulsive response of the system as a function of the location of a modal hammer force applied sequentially over a global interrogation curve. The typical ensemble of collocated signals is subject to a systematic coherence analysis by advanced tools based on the theory of Proper Orthogonal Decomposition (POD) transforms. It turns out that three different collocated ensembles of acceleration signals, collected at the blades at symmetric locations, are very coherent and robust as distributed information over the space-time domain. The characteristics of coherence of the collocated databases are studied in depth by presenting a detailed POD analysis at the system and subsystems levels. The main result is the fact that the POD modes of collocated acceleration databases that exploit structural symmetries seem to provide reliable means to detect sharply differences-due to damage and perhaps design fault-in the subsystem impulsive response.

Proper Othrogonal Decomposition of Collocated Signals for Detection of Damage in an Aircraft Propeller

2010 ◽  
Author(s):  
Ioannis Georgiou
Keyword(s):  
Damage Detection ◽  
Orthogonal Decomposition ◽  
Data Driven ◽  
Complex Structures ◽  
Propeller Blade ◽  
Reciprocity Principle ◽  
Backbone Curve ◽  
High Degree ◽  
Proper Orthogonal ◽  
Acceleration Signals

The powerful data-driven analysis furnished by the Proper Orthogonal Decomposition Transform (POD) reveals that ensembles of collocated acceleration signals associated with a sequence of point impulses applied over a backbone curve of a propeller are underlined by a high degree of spatiotemporal coherence, a fact reflecting Maxwell’s reciprocity principle. Thus collocated signals seem to furnish a true spatiotemporal sample of transient response to a point impulse of complex structures such as propellers. In view of this fact, three sensors are placed on an installed propeller to collect collocated signals at the blades and hub for damage detection. Preliminary results indicate that abnormality indicators present in the dominant POD mode of the ensembles of collocated signals are related directly to the presence of damage at the tip of a propeller blade.

Modeling and design of role engineering in development of access control for dynamic information systems

2013 ◽  
Vol 61 (3) ◽  
pp. 569-579 ◽  
Author(s):  
A. Poniszewska-Marańda
Keyword(s):  
Information Systems ◽  
Dynamic Information ◽  
Minimal Set ◽  
Distributed Information ◽  
Heterogeneous Information ◽  
System Protection ◽  
Level Model ◽  
Model Independent ◽  
Role Concept ◽  
High Level

Abstract Nowadays, the growth and complexity of functionalities of current information systems, especially dynamic, distributed and heterogeneous information systems, makes the design and creation of such systems a difficult task and at the same time, strategic for businesses. A very important stage of data protection in an information system is the creation of a high level model, independent of the software, satisfying the needs of system protection and security. The process of role engineering, i.e. the identification of roles and setting up in an organization is a complex task. The paper presents the modeling and design stages in the process of role engineering in the aspect of security schema development for information systems, in particular for dynamic, distributed information systems, based on the role concept and the usage concept. Such a schema is created first of all during the design phase of a system. Two actors should cooperate with each other in this creation process, the application developer and the security administrator, to determine the minimal set of user’s roles in agreement with the security constraints that guarantee the global security coherence of the system.

scholarly journals Fluorescence Fluctuation Spectroscopy enables quantification of potassium channel subunit dynamics and stoichiometry

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Giulia Tedeschi ◽  
Lorenzo Scipioni ◽  
Maria Papanikolaou ◽  
Geoffrey W. Abbott ◽  
Michelle A. Digman
Keyword(s):  
Plasma Membrane ◽  
Protein Diffusion ◽  
Ion Diffusion ◽  
Fluorescence Fluctuation Spectroscopy ◽  
Biophysical Characterization ◽  
Kv Channels ◽  
Subunit Stoichiometry ◽  
Spatio Temporal ◽  
Voltage Sensing Domain

AbstractVoltage-gated potassium (Kv) channels are a family of membrane proteins that facilitate K+ ion diffusion across the plasma membrane, regulating both resting and action potentials. Kv channels comprise four pore-forming α subunits, each with a voltage sensing domain, and they are regulated by interaction with β subunits such as those belonging to the KCNE family. Here we conducted a comprehensive biophysical characterization of stoichiometry and protein diffusion across the plasma membrane of the epithelial KCNQ1-KCNE2 complex, combining total internal reflection fluorescence (TIRF) microscopy and a series of complementary Fluorescence Fluctuation Spectroscopy (FFS) techniques. Using this approach, we found that KCNQ1-KCNE2 has a predominant 4:4 stoichiometry, while non-bound KCNE2 subunits are mostly present as dimers in the plasma membrane. At the same time, we identified unique spatio-temporal diffusion modalities and nano-environment organization for each channel subunit. These findings improve our understanding of KCNQ1-KCNE2 channel function and suggest strategies for elucidating the subunit stoichiometry and forces directing localization and diffusion of ion channel complexes in general.

SPATIO-TEMPORAL CHARACTERIZATION of litter at a touristic sandy beach in south Brazil

2021 ◽  
pp. 116927
Author(s):  
Bruna de Ramos ◽  
Melanie Vianna Alencar ◽  
Fábio Lameiro Rodrigues ◽  
Ana Luzia de Figueiredo Lacerda ◽  
Maíra Carneiro Proietti
Keyword(s):  
Sandy Beach ◽  
Spatio Temporal ◽  
South Brazil
Sign in / Sign up

Export Citation Format

Share Document