scholarly journals Detection of Bolt Looseness Based on Average Autocorrelation Function

2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Jigang Wu ◽  
Jun Shao ◽  
Gen Zhou ◽  
Deqiang Yang ◽  
Yuan Cheng
Keyword(s):  
Autocorrelation Function ◽  
Time Lag ◽  
Damage Index ◽  
Experimental System ◽  
Theoretical Background ◽  
Bolted Connection ◽  
Original Response ◽  
Displacement Signal ◽  
Low Costs ◽  
Heavy Loads

Bolted connections are widely used in multiple engineering fields including aerospace and mechanical engineering due to their numerous advantages like the ability to bear relatively heavy loads, low costs, easy installation, and implementation. Bolt looseness may lead to costly disasters in industries and some cases of injuries. A new method for bolt looseness detection based on average autocorrelation function is proposed. It does not usually directly extract the looseness damage feature from the original response signal to detect the bolt looseness, but it uses the average autocorrelation function value at time lag T = 0 of the vibration pixel displacement signal to establish the looseness damage index. In terms of structural arrangement of this paper, firstly, the theoretical background of the proposed method is given. Then, an experimental system for bolt looseness detection based on computer vision is designed, and a verification experiment is carried out with the bolted connection plate as the experimental object. The results show that the proposed method can effectively obtain the location of the looseness damage of the bolted connection plate, which provides a new technical reference for the online monitoring of the looseness damage of bolted connection plate.

Structural Health Monitoring Experimental System Implemented in a Turboprop Commercial Aircraft

2007 ◽  
Vol 347 ◽  
pp. 311-317
Author(s):  
Igor Bovio ◽  
Leonardo Lecce
Keyword(s):  
Structural Damage ◽  
Damage Index ◽  
Experimental System ◽  
Experimental Tests ◽  
Processing Technique ◽  
Commercial Aircraft ◽  
Destructive Testing ◽  
Before And After ◽  
Neural Network Algorithm ◽  
Testing Field

The purpose of the paper is to present an innovative application within the Non Destructive Testing field based upon vibration measurements developed by the authors, and already tested for analysing damage of many structural elements. After having tested this application on different test articles in laboratory condition, experimental tests have been executed, in collaboration with the ATR company, on a turboprop ATR-72 aircraft, in order to validate the technique on a real aeronautical structure. The monitoring system have operated an off-line check on the structure, during the aircraft ground operations, as if it were a normal maintenance procedure. The results are reported in the paper. This proposed new method is based upon the acquisition and comparison of the Frequency Response Functions (FRFs) of the monitored structure before and after damage occurs. Structural damage modify the dynamic behaviour of a structure affecting its mass, stiffness and damping, and consequently the FRFs of a damaged structure, when compared with the FRFs of its sound configuration, making the identification, localization and quantification of damage possible. The activities presented in the paper focus mainly on a new FRFs processing technique based upon the determination of a representative “Damage Index” for identifying and analysing damage. Furthermore, a dedicated neural network algorithm has been elaborated to develop an automatic system which recognises positive samples, “healthy” states of the analysed structure, discarding negative ones, “damaged or perturbed” states of the analysed structure. From an architectural standpoint, piezoceramic patches have been used as both actuators and sensors.

Diffusion of Gases in Porous Solids. I. Theoretical Background and Experimental Method

1974 ◽  
Vol 52 (15) ◽  
pp. 2684-2691 ◽  
Author(s):  
K. R. Weller ◽  
N. S. Stenhouse ◽  
Harry Watts
Keyword(s):  
Diffusion Coefficients ◽  
Experimental System ◽  
Theoretical Background ◽  
Porous Solids ◽  
Diffusion Cell ◽  
Improved Method ◽  
Method Of Calculation ◽  
The Past ◽  
Concentration Changes

In the past, some authors have not defined the diffusion coefficient appropriate to their experimental system, consequently, valuable data have been lost. We discuss the various diffusion coefficients referred to all possible frames of reference in relation to the choice of a suitable experimental system for the determination of gaseous diffusion coefficients in porous media. A modified Ney and Armistead type diffusion cell is described with an improved method of calculation of results from continuously monitored concentration changes in the diffusion cell.

scholarly journals ORGANIZATION OF DISTANCE SUBJECT-SUBJECT INTERACTION IN THE COURSE OF FUTURE ENGLISH PHILOLOGISTS TRAINING

2019 ◽  
Vol 71 (3) ◽  
pp. 236
Author(s):  
Svitlana O. Shekhavtsova
Keyword(s):  
Personal Development ◽  
English Language ◽  
Teaching Practice ◽  
Experimental System ◽  
Theoretical Background ◽  
Future Teachers ◽  
Self Reflection ◽  
The Future ◽  
Four Blocks ◽  
The University

The article provides theoretical background and experimental substantiation of the organization of distance subject-subject interaction in the course of future English philologists training. The actual course of subjectness development in students which is directed to vocational and pedagogical activities applies those informational and communicative technologies which would contribute to the personal development of the students as the subjects of vocational and pedagogical activities. It also deals with the the most rational Internet technologies which provide the didactic resources and the ability to implement subject-subject interaction between the teachers and the students. Hence, distance form of interaction has particular advantages, for example: prompt transmission of different amounts of information to any distance and in any form: sound (Podcast), visual (PowerPoint Presentation), text (a report on teaching practice, exercises, portfolio), graphic, etc.; possibility to effectively change the information via the Internet from the workplace; possibility of interactive communication with the help of purposefully created multimedia information and operative feedback etc. The criteria for the subjectness development in the future English language philologists have been identified. It has been found out that the first criterion concerns value-motivational sphere of the personality of the future philologist; the second criterion is the criterion of subjectness, which characterizes self-knowledge and self-education of the future teachers; the third criterion allows to determine the subjectness of the future teachers concerning self-improvement and self-development at the university; the fourth criterion proves the acquisition of subjectness related to self-reflection by the future philologists. The experimental system of the subjectness development in the future English philologists included four blocks, which define the stages of the subjectness development, and which are united by the common goal and contents. In practice, this system was introduced at the stage of the developing experiment, which provided for the development of methodological recommendations for the university teachers on the organization of subject-subject interaction of the future English philologists within the distance specialized course.

An experimental system for analysis of the dynamic sap-flow characteristics in young trees: results of a beech tree

2004 ◽  
Vol 31 (1) ◽  
pp. 83 ◽  
Author(s):  
Kathy Steppe ◽  
Raoul Lemeur
Keyword(s):  
Steady State ◽  
Water Flow ◽  
Sap Flow ◽  
Time Lag ◽  
Vapour Pressure Deficit ◽  
Experimental System ◽  
Rate Of Change ◽  
Good Correspondence ◽  
Internal Water ◽  
Beech Tree

This paper describes an experimental system designed for analysis of the dynamic water flow through young trees, complemented with test results of a 2-year-old beech tree (Fagus sylvatica L.). The system allows automatic and simultaneous measurements of a complex set of plant physiological processes at leaf, branch, stem and root levels [transpiration (E), sap flow (F) and diameter fluctuations (Δd)], in combination with the micrometeorological variables that control these processes [soil and air temperature (Ts and Ta), vapour pressure deficit of the air (D) and photosynthetically active radiation (PAR)]. A 2-d experimental period was used to study the whole-tree water transport dynamics of the young beech tree. Good correspondence between E of the leaves and F in the supporting branch was found. An increased time lag between the F measurements along the hydraulic pathway down towards the root system was observed, indicating the non-steady-state nature of the water flow. The daytime Δd of stem and branch revealed the depletion and the replenishment of internal water reserves. The daily amount of water withdrawn from internal storage was 5% of the total daily transpiration. A good linear relationship was found between the rate of change in internal water storage and the rate of change in stem diameter, having no time lag. We conclude that the data obtained with this system will allow experimental assessment of hydraulic properties in young trees and facilitate calibration of models for non-steady-state conditions of water flow in young trees.

Oscillatory Flow Between Two Hemispheres for Shearing Protein Solution

2015 ◽  
Vol 137 (10) ◽  
Author(s):  
Dejuan Kong ◽  
Anita Penkova ◽  
Satwindar Singh Sadhal
Keyword(s):  
Shear Rate ◽  
Oscillatory Flow ◽  
Molecular Mechanisms ◽  
Outer Boundary ◽  
Experimental System ◽  
Theoretical Background ◽  
Physical Factors ◽  
Protein Solution ◽  
Steady Streaming ◽  
And Control

Protein aggregation, one of the common molecular mechanisms for neurodegenerative diseases, is affected by variety of physical factors, one of which is shear rate of protein solution. This paper provides theoretical background on the shear rate in the experimental system we have proposed to effectively apply and control shear. We carried out the mathematical analysis of the flow field resulted from torsional or transverse oscillation on the outer boundary between two concentric hemispheres by perturbation method. We have obtained analytical solutions for the velocity field, the shear rate, and the flow pattern of steady streaming created by the nonlinear interaction of the oscillatory flow.

level of the shellfish toxicity is still low, but it increases to a higher level and reaches a maximal level after most of the dinoflagellates disappear from the environment. There is always about a 1 week time lag between the peaks of these parameters (Ogata et al. 1982, Sekiguchi et al. 1989). This phenomenon is difficult to explain if the toxins in the dinoflagellates transfer to the shellfish via the food chain. However, it is hard to evaluate the balance of the toxin amount between dinoflagellates and shellfish in a field survey in which samples of shellfish and plankton are collected periodically at a station set in the field, even though the frequency of the sampling is increased. Thus, the nature of the balance of the toxins be­ tween shellfish and dinoflagellates has not been clarified by data from field surveys. Recently, we examined this problem by feeding dinoflagel­ lates to shellfish. As handling of the shellfish during the experiments was found to affect much the feeding behavior of the shellfish (Sekiguchi et al. 2001a), a single specimen of shellfish was reared in a single tank, and the known amount of the cultured cells of dinoflagellate was fed to the shellfish specimen (Sekiguchi et al. 2001b). These experiments showed that shellfish accumulate toxins by ingesting the toxic dinoflagellate, and they release a part of the toxins to the environmental water even while ingesting the dinoflagellate. When the feeding stopped, the shellfish ex­ creted the toxins continuously. The profile of excreted toxins was similar to that accumulated in the shellfish, that is, shellfish release the toxin components non-selectively. Interestingly, the amount of toxins accumulated in the shellfish was not parallel to that of dinoflagellate cells fed to the shellfish (Fig. 8). At the earlier period of the experiment when shellfish were ingesting the cells, the amount of toxins accumulated in the shellfish was often more than that in the dinoflagellates fed to the shellfish. In the later period when the feeding was stopped, the sum of the toxins in the shellfish and rearing water had decreased to a level which was less than that introduced from the dinoflagellates cells, showing that some amount of toxins disappeared from the experimental system. However, this level recovered to the almost same level as that derived from the fed cells of the dinoflagellate, when they were further reared. These facts indicate that a part of the toxins was transformed to an unknown form which could not be detected by chemi­ cal analysis, such as HPLC. The unknown form of the toxins is gradually transformed to toxins again in the shellfish which can be detected by the chemical analysis. The unexpected high level of toxins accumulated in the shellfish, more than the fed amount of toxins, may show that an unknown form of toxins occurs also in the dinoflagellate fed to the shellfish. Thiol compounds of biological origin, such as GSH, are thought to be involved in the formation of the unknown form of toxins. Proteinous thiols such as that with a cystein residue may be involved in the formation of the

2003 ◽  
pp. 343-344
Keyword(s):  
Cultured Cells ◽  
Time Lag ◽  
Experimental System ◽  
Environmental Water ◽  
Single Specimen ◽  
Biological Origin ◽  
Thiol Compounds ◽  
Field Surveys ◽  
Unknown Form ◽  
High Level

HOW TO DETERMINE THE REDUNDANCY OF NOISY CHAOTIC TIME SERIES

1996 ◽  
Vol 06 (01) ◽  
pp. 101-117 ◽  
Author(s):  
WILLFRIED WIENHOLT ◽  
BERNHARD SENDHOFF
Keyword(s):  
Time Series ◽  
Mutual Information ◽  
Time Lag ◽  
Theoretical Background ◽  
Small Data ◽  
Data Sets ◽  
Reliable Determination ◽  
Small Data Sets ◽  
Clear Differentiation

The mutual information and the redundancy are used in the time series analysis as tools to determine the best possible time-lag for successful phase space reconstruction. The known methods exhibit difficulties and inaccuracy when applied to noisy and small data sets. In this paper, we will introduce two methods to make a more reliable determination of the redundancy possible. Firstly, we will modify the Θ-function used in the correlation intergrals and, secondly, we will use the "Neural Gas" algorithm to calculate reference vectors and local radii, which enter the redundancy calculations. A clear differentiation between the redundancy and the mutual information on information theoretical background provides the path along which the new methods can be introduced and applied to the Mackey–Glass and Lorenz systems.

scholarly journals Artefact-removal algorithms for Fourier domain quantum optical coherence tomography

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Sylwia M. Kolenderska ◽  
Maciej Szkulmowski
Keyword(s):  
Optical Coherence Tomography ◽  
Structural Information ◽  
Experimental System ◽  
Theoretical Background ◽  
Fourier Domain ◽  
Optical Coherence ◽  
Joint Spectrum ◽  
Spectrum Detection ◽  
Artefact Removal ◽  
Quantum Optical

AbstractQuantum Optical Coherence Tomography (Q-OCT) is a non-classical equivalent of Optical Coherence Tomography and is able to provide a twofold axial resolution increase and immunity to resolution-degrading dispersion. The main drawback of Q-OCT are artefacts which are additional elements that clutter an A-scan and lead to a complete loss of structural information for multilayered objects. Whereas there are very practical and successful methods for artefact removal in Time-domain Q-OCT, no such scheme has been devised for Fourier-domain Q-OCT (Fd-Q-OCT), although the latter modality—through joint spectrum detection—outputs a lot of useful information on both the system and the imaged object. Here, we propose two algorithms which process a Fd-Q-OCT joint spectrum into an artefact-free A-scan. We present the theoretical background of these algorithms and show their performance on computer-generated data. The limitations of both algorithms with regards to the experimental system and the imaged object are discussed.

Learning Control Method for Robotic Dynamical System

1997 ◽  
Vol 9 (1) ◽  
pp. 57-64
Author(s):  
Tohru Kumagai ◽  
◽  
Mitsuo Wada ◽  
Sadayoshi Mikami ◽  
Ryoichi Hashimoto ◽  
...  
Keyword(s):  
Inverted Pendulum ◽  
Control Method ◽  
Reference Model ◽  
Time Lag ◽  
Experimental System ◽  
Learning Control ◽  
Reference Models ◽  
New Learning ◽  
Output System ◽  
Single Input

We present a new learning control method to control a single input multi output system. In conventional learning controllers using a neural network, it is difficult to treat a multi-output system because of the difficulty in designing reference models. Hence, we propose to divide a complex plant into sub-plants and to use a learning controller for each one. We use our method to the regulation problem of the inverted pendulum that is a oneinput, two-output system. In the simulation and the experimental system, we regulate the inverted pendulum and show the effectiveness of this method. We also show that our learning control system can regulate a system that has a time lag between the input and the output signals. Moreover, we show that a reference model of order lower than the plant order is available.

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