Experimental Study of Jet Noise Characteristics of Series Connected Nozzles

2005 ◽  
Author(s):  
Qiang Xu
Keyword(s):  
Frequency Spectrum ◽  
Frequency Band ◽  
Low Frequency ◽  
Jet Noise ◽  
Steel Tube ◽  
The Other ◽  
Chamber Pressure ◽  
Band Frequency ◽  
Noise Characteristics ◽  
Frequency Peak

Put abstract text here. A serial of experiments were conducted to study the noise radiated from a series connected nozzle pair. The experiment results are presented in this paper. This nozzle pair consists of two nozzles, one is called source nozzle, and the other is a secondary nozzle. In these experiments, the structure of source nozzle was fixed while that of secondary nozzle was changeable. The source nozzle is mounted on a pressure chamber which is connected to an air compressor. A steel tube is fixed at the tail of source nozzle. The secondary nozzle is connected to the other end of the tube. Throat size of secondary nozzle is larger then that of source nozzle. 15 types of nozzles with different expansion ratio, length of expand segment, and throat structure were used as the secondary nozzle. Jet noise pressure of these nozzle pairs was measured by 40AF Free Field Microphone. The frequency spectrum of jet noise from source nozzle with steel tube under different chamber pressures was calculated. The pressure range is from 0.1 to 1.2 MPa. This result is compared with those spectrums of nozzle pair with different secondary nozzle under different chamber pressures. The trend of peak frequency shifts for different nozzle pair and different chamber pressure is presented in this paper. The secondary nozzles make frequency peak shift from the source nozzle, especially in low frequency band. Different structure of secondary nozzle has different influence on the frequency characteristics of jet noise. Length of expand segment has greater influence on low frequency peak than other two factors. Joint time-frequency analysis is also used in analyze the change of frequency spectrum during throat size decreased under fixed chamber pressure and various spectrograms are also presented. In low frequency band, frequency peak remains during the change of source nozzle throat size. But in higher frequency band, the frequency peak shifts from low frequency to higher ones as the throat size decreases.

Computer Restoration of 2D Medical Diagnostic Signals with Noise Frequency Spectrum

1970 ◽  
Vol 111 (5) ◽  
pp. 133-136
Author(s):  
M. Nikolova ◽  
Tz. Dimitrova
Keyword(s):  
Mathematical Method ◽  
Frequency Spectrum ◽  
Frequency Band ◽  
Low Frequency ◽  
Experimental Results ◽  
Medical Diagnostic ◽  
Noise Frequency ◽  
Influence Of Noise

An application of mathematical method of Aisenberg for restoration of low frequency medical diagnostic signals after influence of noise is described in the paper. The restoration of frequency spectrum of medical diagnostic signals has been done after preliminary analyses of frequency spectrum of signals with noise and disposition of frequency band of noise in the frequency band of information signals. Some experimental results obtained on the base of application of Aisenberg's method for restoration of medical diagnostic signals are described in the paper. Ill. 9, bibl. 8 (in English; abstracts in English and Lithuanian).http://dx.doi.org/10.5755/j01.eee.111.5.374

scholarly journals An Approach to 1/f Noise Detection Based on Adaptive T-ATFPF Algorithm

CONVERTER ◽  
2021 ◽  
pp. 407-418
Author(s):  
Jie Wu, Xiaojuan Chen, Zhaohua Zhang
Keyword(s):  
White Noise ◽  
Thermal Noise ◽  
Low Frequency ◽  
Window Length ◽  
Time Frequency ◽  
Noise Characteristics ◽  
Small Window ◽  
Frequency Peak ◽  
Variable Window ◽  
Conventional Algorithm

The generation of 1/f noise is closely related to the quality defects of IGBT devices. In the process of detecting IGBT single tube noise, thermal noise and shot noise show obvious white noise characteristics in the low frequency band, which are detected under the background of strong white noise 1/f noise can characterize the performance of IGBT devices. Therefore, on the basis of the Time-Frequency Peak Filtering (TFPF) algorithm, a two-dimensional time-domain adaptive T-ATFPF algorithm is proposed, and the adaptive segmentation is realized by means of the confidence interval crossing criterion based on Chebyshev’s inequality. Variable window length,use a small window length to process the signal section, which retains more detailed information of the effective signal.Use a larger window length to process the buffer section to ensure a smooth transition.Use the large window length to process the noise section, which more effectively suppresses randomness for noise, apply T-ATFPF to artificial synthesis model and actual model. Experimental results indicate that compared with the conventional algorithm, the improved method can better recover 1/f noise, and the ratio of signal to noise is greatly improved by about 1.3dB.

Comparison of various techniques used to estimate spontaneous baroreflex sensitivity (the EuroBaVar study)

2004 ◽  
Vol 286 (1) ◽  
pp. R226-R231 ◽  
Author(s):  
Dominique Laude ◽  
Jean-Luc Elghozi ◽  
Arlette Girard ◽  
Elisabeth Bellard ◽  
Malika Bouhaddi ◽  
...  
Keyword(s):  
Spectral Analysis ◽  
Frequency Band ◽  
Baroreflex Sensitivity ◽  
Low Frequency ◽  
The Other ◽  
Data Sets ◽  
Noninvasive Blood Pressure ◽  
Sequence Method ◽  
Baroreflex Failure ◽  
Spontaneous Baroreflex

This study compared spontaneous baroreflex sensitivity (BRS) estimates obtained from an identical set of data by 11 European centers using different methods and procedures. Noninvasive blood pressure (BP) and ECG recordings were obtained in 21 subjects, including 2 subjects with established baroreflex failure. Twenty-one estimates of BRS were obtained by methods including the two main techniques of BRS estimates, i.e., the spectral analysis (11 procedures) and the sequence method (7 procedures) but also one trigonometric regressive spectral analysis method (TRS), one exogenous model with autoregressive input method (X-AR), and one Z method. With subjects in a supine position, BRS estimates obtained with calculations of α-coefficient or gain of the transfer function in both the low-frequency band or high-frequency band, TRS, and sequence methods gave strongly related results. Conversely, weighted gain, X-AR, and Z exhibited lower agreement with all the other techniques. In addition, the use of mean BP instead of systolic BP in the sequence method decreased the relationships with the other estimates. Some procedures were unable to provide results when BRS estimates were expected to be very low in data sets (in patients with established baroreflex failure). The failure to provide BRS values was due to setting of algorithmic parameters too strictly. The discrepancies between procedures show that the choice of parameters and data handling should be considered before BRS estimation. These data are available on the web site ( http://www.cbi.polimi.it/glossary/eurobavar.html ) to allow the comparison of new techniques with this set of results.

scholarly journals A Literature Review of Bimodal Fitting

2020 ◽  
Vol 16 (4) ◽  
pp. 265-275
Author(s):  
Junghwa Bahng ◽  
Soo Hee Oh
Keyword(s):  
Cochlear Implant ◽  
Frequency Band ◽  
Hearing Aid ◽  
Low Frequency ◽  
Balance Test ◽  
Band Frequency ◽  
Hearing Aid Fitting ◽  
Fitting Procedures ◽  
Band Adjustment ◽  
Bimodal Hearing

Although there are quite a few bimodal cochlear implant users, bimodal fitting guidelines were not fully developed. Bimodal fitting optimization is one of the factors that contribute to successful bimodal outcomes. The purpose of this study is to investigate recent literatures related to bimodal fitting to establish evidence based bimodal fitting guidelines. Three databases including Google Scholar, PubMed publisher, and PLOS One were searched to review bimodal fitting literatures. A total of 599,604 articles were identified by using ten bimodal relevant keywords at the initial stage. Then, we included 192 articles with abstract review, inclusion and exclusion criteria and removals of duplicates. Lastly, two authors reviewed full texts and identified a total of 19 bimodal fitting articles. Results were categorized into type of bimodal intervention, procedures, and outcomes. Bimodal fitting procedures, test materials, and questionnaires were also summarized. A total of 18 articles consist of bimodal hearing aid fitting covering hearing aid fitting formula, gain adjustment, loudness balance, frequency band, frequency lowering technology, and overall bimodal fitting guidelines. Only one article includes bimodal cochlear implant fitting with low frequency band adjustment. Several factors including real-ear measurement, loudness balance test, frequency band selection considering cochlear dead region, and subjective questionnaires are considered to optimize bimodal hearing aid fitting. Bimodal fitting guidelines considering several relevant factors will optimize bimodal fitting and improve bimodal benefits.

ANALYSIS OF NOISE CHARACTERISTICS OF GaAs TUNNEL DIODES

2013 ◽  
Vol 12 (03) ◽  
pp. 1350014 ◽  
Author(s):  
VILIUS PALENSKIS ◽  
JONAS MATUKAS ◽  
JUOZAS VYŠNIAUSKAS ◽  
SANDRA PRALGAUSKAITĖ ◽  
HADAS SHTRIKMAN ◽  
...  
Keyword(s):  
White Noise ◽  
Shot Noise ◽  
Thermal Noise ◽  
Low Frequency ◽  
The Other ◽  
Frequency Noise ◽  
Tunnel Diodes ◽  
Low Frequency Noise ◽  
Noise Characteristics

An analysis and investigation of noises of GaAs tunnel diodes, which abrupt p+-n+ profile was obtained by using amphoteric nature of silicon, were performed. The main scope of this work was to verify the concepts of the explanation of white noise characteristics on the ground of shot noise and on the ground of the Gupta theorem of thermal noise in resistive elements. The other scope was to investigate the peculiarities of low frequency noise in p+-n+ junctions formed by using amphoteric silicon nature.

Contact Current Density Analysis Inside Human Body in Low-Frequency Band Using Geometric Multi-Grid Solver

2020 ◽  
Vol E103.C (11) ◽  
pp. 588-596
Author(s):  
Masamune NOMURA ◽  
Yuki NAKAMURA ◽  
Hiroo TARAO ◽  
Amane TAKEI
Keyword(s):  
Frequency Band ◽  
Current Density ◽  
Human Body ◽  
Low Frequency ◽  
Density Analysis

Investigation of Low-Frequency Noise Characteristics in Gated Schottky Diodes

2021 ◽  
Vol 42 (3) ◽  
pp. 442-445
Author(s):  
Dongseok Kwon ◽  
Wonjun Shin ◽  
Jong-Ho Bae ◽  
Suhwan Lim ◽  
Byung-Gook Park ◽  
...  
Keyword(s):  
Schottky Diodes ◽  
Low Frequency ◽  
Frequency Noise ◽  
Low Frequency Noise ◽  
Noise Characteristics

scholarly journals Nucleotide Variation at theCHALCONE ISOMERASELocus inArabidopsis thaliana

Genetics ◽  
2000 ◽  
Vol 155 (2) ◽  
pp. 863-872 ◽  
Author(s):  
Helmi Kuittinen ◽  
Montserrat Aguadé
Keyword(s):  
Nucleotide Diversity ◽  
Direct Relationship ◽  
Selective Sweep ◽  
Balancing Selection ◽  
Neutral Theory ◽  
Low Frequency ◽  
The Other ◽  
Nucleotide Variation ◽  
Rapid Population Growth ◽  
History Of

AbstractAn ~1.9-kb region encompassing the CHI gene, which encodes chalcone isomerase, was sequenced in 24 worldwide ecotypes of Arabidopsis thaliana (L.) Heynh. and in 1 ecotype of A. lyrata ssp. petraea. There was no evidence for dimorphism at the CHI region. A minimum of three recombination events was inferred in the history of the sampled ecotypes of the highly selfing A. thaliana. The estimated nucleotide diversity (θTOTAL = 0.004, θSIL = 0.005) was on the lower part of the range of the corresponding estimates for other gene regions. The skewness of the frequency spectrum toward an excess of low-frequency polymorphisms, together with the bell-shaped distribution of pairwise nucleotide differences at CHI, suggests that A. thaliana has recently experienced a rapid population growth. Although this pattern could also be explained by a recent selective sweep at the studied region, results from the other studied loci and from an AFLP survey seem to support the expansion hypothesis. Comparison of silent polymorphism and divergence at the CHI region and at the Adh1 and ChiA revealed in some cases a significant deviation of the direct relationship predicted by the neutral theory, which would be compatible with balancing selection acting at the latter regions.

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