Experimental Characterization of Synchronous Vibrations of Blades

2011 ◽  
Author(s):  
Juan C. Jauregui ◽  
Mihir Sen ◽  
Carlos S. Lopez-Cajun
Keyword(s):  
Weak Interactions ◽  
Low Frequency ◽  
Turbine Rotor ◽  
Time Intervals ◽  
Low Frequency Vibration ◽  
Time Period ◽  
Manufacturing Errors ◽  
Blade Tip ◽  
Medium Time

Blades in a turbine rotor synchronize their individual vibrations after a certain period of time. Each blade has a slightly different natural frequency due to manufacturing errors, and it responds individually to external excitations. Nevertheless, after a period of time the blades synchronize and vibrate at the same frequency due to weak interactions between them. In this work, experiments are reported that identify blade synchronization. Individual blade vibrations were measured simultaneously under different conditions. Measurements were made with accelerometers attached to the tip of each blade which were very light in comparison with the mass of the blade. The blades were first excited by an impact force and the natural frequencies were identified. Then, the blades were excited by airflow and individual blade-tip vibrations were recorded at several subsequent time intervals. Synchronization is analyzed through the correlation between the time responses of every blade. The correlation was calculated at each of these intervals and the results were plotted in maps. It was found that the synchronization evolves as a function of time; it is high after a medium time period and reduced at longer time periods. Thus blade synchronization presents a long wave variation that could be a source of a very low frequency vibration. It was also possible to say that synchronization is dominated by the structure of the rotor.

Dynamic Response of Normal and Osteoporotic Trabecular Bone by Vibration Analysis

2005 ◽  
Author(s):  
Wafa Tawackoli ◽  
Gemunu Gunaratne ◽  
Fazle Hussain ◽  
Michael Liebschner
Keyword(s):  
Treatment Efficacy ◽  
Low Frequency ◽  
Osteoporotic Fractures ◽  
Vibrational Modes ◽  
Response Signal ◽  
Noninvasive Sensors ◽  
Low Frequency Vibration ◽  
The Us ◽  
Monitoring Treatment

Osteoporosis afflicts about 200 million people worldwide; and osteoporotic fractures are in the millions annually in the US alone and cost tens of billions of dollars [1]. Characterization of bone quality in osteoporotic patients is important with respect to monitoring treatment efficacy, though currently quite limited. While some technical hurdles in developing a noninvasive diagnostic tool using low frequency vibration have been overcome, changes in the frequency response signal of bone have not been investigated at the various bone organizational levels. Our principal hypothesis is that the vibrational modes of bone tissue change significantly with the deterioration of bone micro-architecture and that these modes can be captured by noninvasive sensors.

A review of spectral analysis for low-frequency transient vibrations

2020 ◽  
pp. 146134842094200
Author(s):  
Chin-Tsun Chen ◽  
Luh-Maan Chang ◽  
Chin-Hsiung Loh
Keyword(s):  
Spectral Analysis ◽  
High Speed ◽  
Vibration Isolation ◽  
Measurement Data ◽  
Low Frequency ◽  
Vibration Signal ◽  
Spectral Amplitude ◽  
High Tech ◽  
Low Frequency Vibration ◽  
Time Period

The precision tools equipped with active vibration isolation platform in high-tech facilities are sensitive to low-frequency vibration. Currently, there are neither standards nor rules to select the time period of vibration data for conducting the spectral analysis of low-frequency vibration, and none of the analyses can be used to compare and discuss the differences of spectral amplitude generated by the selection of different time periods. Therefore, to estimate the amplitude of low-frequency vibration, the spectral analysis at low-frequency range is crucial. This paper is to elaborate the spectral analysis procedures on various band widths by using zero-padding on the vibration signal in low-frequency band. The mechanism not only facilitates to obtain more reliable result but also to lay a common base for comparison from different user. Finally, the in situ measurement data, including high-speed train-induced low-frequency vibration, are used to exemplify the length of time period affects the results of spectral analysis, either on narrowband or one-third octave band analysis.

A Study on the Fine Structure of the Lateral Line Organ of the Sea Eel

1973 ◽  
Vol 31 ◽  
pp. 648-649
Author(s):  
K. Hama
Keyword(s):  
Fine Structure ◽  
Electron Microscope ◽  
Lateral Line ◽  
Low Frequency ◽  
Sensory Cells ◽  
Apical Surface ◽  
Voltage Electron ◽  
Sensory Epithelia ◽  
Low Frequency Vibration ◽  
Transmission Electron

The lateral line organs of the sea eel consist of canal and pit organs which are different in function. The former is a low frequency vibration detector whereas the latter functions as an ion receptor as well as a mechano receptor.The fine structure of the sensory epithelia of both organs were studied by means of ordinary transmission electron microscope, high voltage electron microscope and of surface scanning electron microscope.The sensory cells of the canal organ are polarized in front-caudal direction and those of the pit organ are polarized in dorso-ventral direction. The sensory epithelia of both organs have thinner surface coats compared to the surrounding ordinary epithelial cells, which have very thick fuzzy coatings on the apical surface.

Gelatin and Glycerine-Based Bioadhesive Vaginal Hydrogel

2020 ◽  
Vol 17 (4) ◽  
pp. 303-311
Author(s):  
Roberta Cassano ◽  
Federica Curcio ◽  
Delia Mandracchia ◽  
Adriana Trapani ◽  
Sonia Trombino
Keyword(s):  
Differential Scanning Calorimetry ◽  
Inflammatory Process ◽  
Vaginal Mucosa ◽  
Vaginal Infection ◽  
Scanning Calorimetry ◽  
Time Intervals ◽  
Site Specific ◽  
Release Studies ◽  
Hiv Seropositive

Aim: The work’s aim was the preparation and characterization of a hydrogel based on gelatin and glycerine, useful for site-specific release of benzydamine, an anti-inflammatory drug, able to attenuate the inflammatory process typical of the vaginal infection. Objective: The obtained hydrogel has been characterized by Electronic Scanning Microscopy (SEM) and Differential Scanning Calorimetry (DSC). In addition, due to the precursor properties, the hydrogel exhibits a relevant mucoadhesive activity. Methods: The swelling degree was evaluated at two different pHs and at defined time intervals. In particular, phosphate buffers were used at pH 6.6, in order to mimic the typical conditions of infectious diseases at the vaginal level, particularly for HIV-seropositive pregnant women, and pH 4.6, to simulate the physiological environment. Results: The obtained results revealed that the hydrogel swells up well at both pHs. Conclusion: Release studies conducted at both pathological and physiological pHs have shown that benzydamine is released at the level of the vaginal mucosa in a slow and gradual manner. These data support the hypothesis of the hydrogel use for the site-specific release of benzydamine in the vaginal mucosa.

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