scholarly journals An Algorithm for Diagnosing Injection Systems of Marine Engines

2018 ◽  
Vol 1 (1) ◽  
pp. 227-233
Author(s):  
Artur Bejger ◽  
Jan Drzewieniecki
Keyword(s):  
Acoustic Emission ◽  
Elastic Waves ◽  
High Frequency ◽  
Injection System ◽  
Low Frequencies ◽  
Marine Engines ◽  
Source Signal ◽  
Working Parameters ◽  
Close Source ◽  
Selection Of

Abstract The article presents the developed methods for diagnosing and analysing signals from injection systems of marine engines. As a source signal, the authors use elastic waves of acoustic emission. The essential fact in the case here considered is that the high frequency of signal from working elements of the injection system comes from a close source directly related to the change of the working parameters of the element (system). Characteristically for elastic waves of acoustic emission, low frequencies (e.g. those from other sources, such as machines in the engine room) are in this case attenuated. Therefore, the proper selection of the method for the analysis allows us accurately diagnose the injection system of a working engine.

scholarly journals Maass, Pavon & Suitner HARMONIC ANALYSIS OF SOCIAL COGNITION

2021 ◽  
Author(s):  
Anne Maass
Keyword(s):  
Social Cognition ◽  
High Frequency ◽  
Personal Characteristics ◽  
Future Research ◽  
Weighted Sum ◽  
Social Stimuli ◽  
Low Frequencies ◽  
High Frequencies ◽  
The Social ◽  
Selection Of

In this paper, we argue that some fundamental concepts and tools of signal processing may beeffectively applied to represent and interpret social cognition processes. From this viewpoint,individuals or, more generally, social stimuli are thought of as a weighted sum of harmonics withdifferent frequencies: Low frequencies represent general categories such as gender, ethnic group,nationality, etc., whereas high frequencies account for personal characteristics. Individuals arethen seen by observers as the output of a filter that emphasizes a certain range of high or lowfrequencies. The selection of the filter depends on the social distance between the observingindividual or group and the person being observed as well as on motivation, cognitive resourcesand cultural background. Enhancing low- or high-frequency harmonics is not on equal footing, thelatter requiring supplementary energy. This mirrors a well-known property of signal processingfilters. More generally, in the light of this correspondence, we show that several established resultsof social cognition admit a natural interpretation and integration in the signal processinglanguage. While the potential of this connection between an area of social psychology and one ofinformation engineering appears considerable (compression, information retrieval, filtering,feedback, feedforward, sampling, aliasing, etc.), in this paper we shall limit ourselves to layingdown what we consider the pillars of this bridge on which future research may be founded.

scholarly journals Earless toads sense low frequencies but miss the high notes

2017 ◽  
Vol 284 (1864) ◽  
pp. 20171670 ◽  
Author(s):  
Molly C. Womack ◽  
Jakob Christensen-Dalsgaard ◽  
Luis A. Coloma ◽  
Juan C. Chaparro ◽  
Kim L. Hoke
Keyword(s):  
High Frequency ◽  
Species Differences ◽  
Low Frequency ◽  
Auditory Brainstem ◽  
Low Frequencies ◽  
Hearing Sensitivity ◽  
Sensory Pathways ◽  
Airborne Sound ◽  
Vibrational Sensitivity ◽  
Species Specific

Sensory losses or reductions are frequently attributed to relaxed selection. However, anuran species have lost tympanic middle ears many times, despite anurans' use of acoustic communication and the benefit of middle ears for hearing airborne sound. Here we determine whether pre-existing alternative sensory pathways enable anurans lacking tympanic middle ears (termed earless anurans) to hear airborne sound as well as eared species or to better sense vibrations in the environment. We used auditory brainstem recordings to compare hearing and vibrational sensitivity among 10 species (six eared, four earless) within the Neotropical true toad family (Bufonidae). We found that species lacking middle ears are less sensitive to high-frequency sounds, however, low-frequency hearing and vibrational sensitivity are equivalent between eared and earless species. Furthermore, extratympanic hearing sensitivity varies among earless species, highlighting potential species differences in extratympanic hearing mechanisms. We argue that ancestral bufonids may have sufficient extratympanic hearing and vibrational sensitivity such that earless lineages tolerated the loss of high frequency hearing sensitivity by adopting species-specific behavioural strategies to detect conspecifics, predators and prey.

Guided Wave Acoustic Emission from Fatigue Crack Growth in Aluminium Plate

2006 ◽  
Vol 13-14 ◽  
pp. 23-28 ◽  
Author(s):  
C.K. Lee ◽  
Jonathan J. Scholey ◽  
Paul D. Wilcox ◽  
M.R. Wisnom ◽  
Michael I. Friswell ◽  
...  
Keyword(s):  
Acoustic Emission ◽  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Elastic Waves ◽  
Fatigue Cracks ◽  
Guided Wave ◽  
Experimental Results ◽  
Multiple Reflections ◽  
Alloy Plate

Acoustic emission (AE) testing is an increasingly popular technique used for nondestructive evaluation (NDE). It has been used to detect and locate defects such as fatigue cracks in real structures. The monitoring of fatigue cracks in plate-like structures is critical for aerospace industries. Much research has been conducted to characterize and provide quantitative understanding of the source of emission on small specimens. It is difficult to extend these results to real structures as most of the experiments are restricted by the geometric effects from the specimens. The aim of this work is to provide a characterization of elastic waves emanating from fatigue cracks in plate-like structures. Fatigue crack growth is initiated in large 6082 T6 aluminium alloy plate specimens subjected to fatigue loading in the laboratory. A large specimen is utilized to eliminate multiple reflections from edges. The signals were recorded using both resonant and nonresonant transducers attached to the surface of the alloy specimens. The distances between the damage feature and sensors are located far enough apart in order to obtain good separation of guided-wave modes. Large numbers of AE signals are detected with active fatigue crack propagation during the experiment. Analysis of experimental results from multiple crack growth events are used to characterize the elastic waves. Experimental results are compared with finite element predictions to examine the mechanism of AE generation at the crack tip.

The Investigation of the Optimization Scheme of the Low-cycle Fatigue Cropping Based on the Acoustic Emission Technique

2021 ◽  
Author(s):  
Yujian Ren ◽  
Jingxiang Li ◽  
Yuanzhe Dong ◽  
Dong Jin ◽  
Shengdun Zhao
Keyword(s):  
Acoustic Emission ◽  
High Frequency ◽  
Control Method ◽  
Low Cycle Fatigue ◽  
Control Strategies ◽  
Low Frequency ◽  
Loading Frequency ◽  
Cycle Fatigue ◽  
Al 6061 ◽  
Whole Process

Abstract High efficiency and good section quality are two main objectives of metal bar cropping. A suitable control method can help to achieve both goals. An investigation of the control method of low-cycle fatigue cropping (LCFC) based on the acoustic emission (AE) technique has been proposed in this study. Ring-down counts and kurtosis are used to monitor the whole process of LCFC. The results showed that kurtosis is more suitable for monitoring the LCFC process and as a critical parameter to optimize the control method than ring-down counts in the noisy factory environment.Moreover, three types of materials are studied in this experiment; by combine with the AE results, macroscopic images and microscopic images of sections, characteristics of various LCFC stages are obtained. The results also indicated reduce the area of the transient fracture zone is the key to improve the section quality. Reducing the load frequency before the unstable crack propagation stage will beneficial to realize the goals. Based on the evaluation of kurtosis, an optimized control method is presented, and two control parameters: transient time T and the critical value of the slope of kurtosis C are determined. For 16Mn, 1045 and Al 6061, the T is 5s, 10s, and 1s, respectively. For 16Mn, 1045, and Al 6061, the C is 100, 300, and 0, respectively. Two parameters, h and S, are used to evaluate the section quality and four control strategies are compared. The results indicate the optimal control methods can improve the section quality effectively. The influence trend of reducing loading frequency is investigated by further comparison. It can be seen as the frequency decreases, the efficiency of the section quality improving decreases. In order to realize the optimal results, different control strategies are adopted for different materials. Strategy 1 (high frequency is 20Hz，high frequency thought the whole process), strategy 2 (high frequency is 20Hz，low frequency is 8.33Hz), and strategy 3 (high frequency is 20Hz，low frequency is 6.67Hz) is suitable for Al 6061, 1045, and 16Mn, respectively.

Проблемы локации источников акустической эмиссии

2021 ◽  
pp. 35-44
Author(s):  
Ю.Г. Матвиенко ◽  
И.Е. Васильев ◽  
Д.В. Чернов ◽  
В.И. Иванов ◽  
С.В. Елизаров
Keyword(s):  
Acoustic Emission ◽  
High Frequency ◽  
Tensile Tests ◽  
Threshold Method ◽  
Near Zone ◽  
Speed Dependence ◽  
Partial Energy ◽  
Base Size ◽  
Frequency Components ◽  
Amplitude Level

The accuracy of the location of acoustic emission (AE) sources in the concentrator zones (central holes 5 mm in diameter) located at a distance of 40 mm from the receiving transducers during tensile tests of steel, aluminum alloy and composite flat specimens with dimensions of 550x50x4 mm was evaluated. Calculated speed dependence of propagation of pulses on the level of their amplitude and the partial energy of the high-frequency components of the spectrum is studied. With the threshold method of signal registration, the error in the location of AE event sources arising in the near zone of the receiving transducers at a distance 𝛥L<0.1 m can significantly exceed 10% relative to the base size (B) of the location area, when B<0.5 m. Moreover, with a decrease in the distance 𝛥L<0.05 m, the level of possible error will increase, reaching 20-30% relative to the basic size of the antenna array, when recording pulses with an amplitude level um<60 dB and a fraction of the energy of high-frequency spectrum components not exceeding 10%.

Frequency-Weighted Variable-Length Controllers Using Anytime Control Strategies

2011 ◽  
Author(s):  
Gundula B. Runge ◽  
Al Ferri ◽  
Bonnie Ferri
Keyword(s):  
Time Scale ◽  
Weighting Function ◽  
Control Strategies ◽  
Low Frequency ◽  
Low Frequencies ◽  
High Frequencies ◽  
Frequency Components ◽  
Computational Resources ◽  
Weighted Variable ◽  
Selection Of

This paper considers an anytime strategy to implement controllers that react to changing computational resources. The anytime controllers developed in this paper are suitable for cases when the time scale of switching is in the order of the task execution time, that is, on the time scale found commonly with sporadically missed deadlines. This paper extends the prior work by developing frequency-weighted anytime controllers. The selection of the weighting function is driven by the expectation of the situations that would require anytime operation. For example, if the anytime operation is due to occasional and isolated missed deadlines, then the weighting on high frequencies should be larger than that for low frequencies. Low frequency components will have a smaller change over one sample time, so failing to update these components for one sample period will have less effect than with the high frequency components. An example will be included that applies the anytime control strategy to a model of a DC motor with deadzone and saturation nonlinearities.

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