scholarly journals The determination of Schumann resonance mode frequencies using iterative procedure of complex demodulation

2013 ◽  
Vol 43 (4) ◽  
pp. 305-326 ◽  
Author(s):  
Adriena Ondrášková ◽  
Sebastian Ševčík
Keyword(s):  
Low Frequency ◽  
Peak Frequency ◽  
Precise Determination ◽  
Primary Sources ◽  
Frequency Noise ◽  
Schumann Resonance ◽  
Complex Demodulation ◽  
Vertical Electric Field ◽  
Short Signal

Abstract The more precise determination of instantaneous peak frequency of Schumann resonance (SR) modes, especially based on relatively short signal sequences, seems to be important for detailed analysis of SR modal frequencies variations. Contrary to commonly used method of obtaining modal frequencies by Lorentzian fitting of DFT spectra, the attempt was made to employ the complex demodulation method in iterated form. The results for SR signals contaminated with low-frequency noise and hum in various degree as well as the comparison with standard method are presented. Real signals of vertical electric field component picked up at the Astronomical and Geophysical Observatory of Comenius University at Modra, Slovakia, were the primary sources.

scholarly journals The iterative complex demodulation applied on short and long Schumann resonance measured sequences

2014 ◽  
Vol 44 (4) ◽  
pp. 313-328 ◽  
Author(s):  
Adriena Ondrášková ◽  
Sebastián Ševčík
Keyword(s):  
Solar Cycle ◽  
Precise Determination ◽  
Schumann Resonance ◽  
Modal Frequency ◽  
Complex Demodulation ◽  
Function Fitting ◽  
Cycle Maximum ◽  
Short Signal ◽  
Frequency Variations

Abstract The precise determination of instantaneous frequency of Schumann resonance (SR) modes, with the possibility of application to relatively short signal sequences, seems to be important for detailed analysis of SR modal frequency variations. Contrary to commonly used method of obtaining modal frequencies by the Lorentz function fitting of DFT spectra, we employ the complex demodulation (CD) method in iterated form. Results of iterated CD method applied on short and long measured sequences are compared. Results for SR signals as well as the comparison with Lorentz function fitting are presented. Decrease of frequencies of all first four SR modes from the solar cycle maximum to solar cycle minimum has been found using also the CD method.

scholarly journals Superluminal Motion in CTA 102

1989 ◽  
Vol 134 ◽  
pp. 529-530
Author(s):  
Ann E. Wehrle
Keyword(s):  
Flux Density ◽  
High Speed ◽  
Low Frequency ◽  
Precise Determination ◽  
Flux Variation ◽  
Low Frequencies ◽  
Superluminal Motion ◽  
Low Frequency Variability ◽  
Expansion Speed

Sholomitskii (1965) discovered that the flux density of the quasar CTA 102 varies at low frequencies on a timescale of a few months. Low-frequency variability can be explained by “superluminal flux variation” (Romney et al. 1984): If the intrinsic brightness of a component moving in a relativistically beamed source varies by only a few percent, the observer sees its flux density change by a much larger factor δ3-α when the optically thin blob moves almost directly toward the observer. Such a relativistically beamed source is likely to exhibit superluminal motion if studied with sufficient resolution and sensitivity. Superluminal motion in CTA 102 was discovered by Bååth (1987) who concluded on the basis of maps made at three epochs at a frequency of 932 MHz that two components were separating at a rate of 0.65 milliarcseconds (mas) per year. Using a redshift z = 1.037 and H0 = 100 km s−1 Mpc−1, q0 = 0.5, this expansion speed corresponds to (18 ± 4)h−1c. The extraordinarily high speed led us to make VLBI images of the source at a higher frequency in order to increase the resolution and make a more precise determination of the speed.

Required Data Collection Times for Steady and Quasi-steady Experiments

2017 ◽  
Author(s):  
Robert F. Roddy ◽  
David E. Hess
Keyword(s):  
High Frequency ◽  
Low Frequency ◽  
Frequency Noise ◽  
Surface Ship ◽  
System A ◽  
Low Pass ◽  
Collection Period ◽  
Almost All ◽  
Low Pass Filters

One of the requirements in performing steady or quasi-steady experiments is the determination of adequate collection times so that the data will not be biased due to low frequency energy in the data stream. Since virtually all steady experiments run at DTMB have low pass filters in line with the signal conditioning, high frequency noise is not a consideration in determining the required collection times. At both EMB and DTMB almost all of the surface ship drag measurements were made using gravity type balances until about 1970. These balances used both springs and dampers to modify the natural frequency of the system so that a good average model drag could be determined in a 5-6 sec collection period. Submarine model experiments began using block gages to measure drag beginning in the late 1950's. For these experiments crude methods were used to damp the output data but, to the author’s knowledge, no methods were ever put into place that was analogous to the springs and damper system. A method for determining the required collection times for any steady or quasi-steady experiment is presented along with sample cases showing the necessity for, and the utility of, using such a method.

scholarly journals Spring peepers Pseudacris crucifer modify their call structure in response to noise

2014 ◽  
Vol 60 (4) ◽  
pp. 438-448 ◽  
Author(s):  
Dalal E. L. Hanna ◽  
David R. Wilson ◽  
Gabriel Blouin-Demers ◽  
Daniel J. Mennill
Keyword(s):  
Low Frequency ◽  
Peak Frequency ◽  
Advertisement Call ◽  
Artificial Noise ◽  
Frequency Noise ◽  
Call Rate ◽  
Advertisement Calls ◽  
Call Structure ◽  
Acoustic Interference ◽  
Pseudacris Crucifer

Abstract Acoustic interference can impede effective communication that is important for survival and reproduction of animals. In response to acoustic interference, some animals can improve signalling efficacy by altering the structure of their signals. In this study, we played artificial noise to 46 male spring peepers Pseudacris crucifer, on their breeding grounds, and tested whether the noise affected the duration, call rate, and peak frequency of their advertisement calls. We used two experimental noise treatments that masked either the high- or low-frequency components of an average advertisement call; this allowed us to evaluate whether frogs adaptively shift the peak frequency of their calls away from both types of interference. Our playback treatments caused spring peepers to produce shorter calls, and the high-frequency noise treatment caused them to lower the frequency of their calls immediately after the noise ceased. Call rate did not change in response to playback. Consistent with previous studies, ambient temperature was inversely related to call duration and positively related to call rate. We conclude that noise affects the structure of spring peeper advertisement calls, and that spring peepers therefore have a mechanism for altering signal structure in response to noise. Future studies should test if other types of noise, such as biotic or anthropogenic noise, have similar effects on call structure, and if the observed changes to call structure enhance or impair communication in noisy environments [Current Zoology 60 (4): 438–448, 2014].

PRECLINICAL AND CLINICAL STUDY OF EXTRACELLULAR DNA IN CANCER AND OTHER DISEASES ASSOCIATED WITH APOPTOSIS DISORDER

2018 ◽  
Vol 64 (3) ◽  
pp. 435-439
Author(s):  
Irina Vasileva ◽  
Viktor Bespalov
Keyword(s):  
Chronic Obstructive Pulmonary Disease ◽  
Malignant Tumors ◽  
Low Frequency ◽  
Prostatic Hyperplasia ◽  
Extracellular Dna ◽  
Chronic Obstructive ◽  
Frequency Noise ◽  
Obstructive Pulmonary Disease ◽  
Oncological Diseases

Oncological diseases at all stages of carcinogenesis are accompanied by violation of apoptosis processes. Drug and radiotherapy activates the apoptosis of tumor cells. This study presents the results of extracellular DNA changes after exposure to ionizing radiation and low-frequency noise are presented, administration of vitamins; in animals with benign prostatic hyperplasia, with ovarian cancer; in clinical studies in patients with chronic obstructive pulmonary disease, and in acute disorders of cerebral circulation. The possibilities of determination of extracellular DNA for the evaluation of the action of carcinogens, the complex diagnosis of precancerous diseases, the progression of precancerous diseases and malignant tumors are considered.

Determination of a Low Frequency Noise Source's Parameters by a Space Intensity Sensor

1993 ◽  
Vol 12 (1) ◽  
pp. 25-29
Author(s):  
A.N. Ivannikov ◽  
V.I. Pavlov ◽  
S.V. Holodova
Keyword(s):  
Experimental Data ◽  
Experimental Investigation ◽  
Low Frequency ◽  
Frequency Noise ◽  
Acoustic Sensor ◽  
Low Frequency Noise ◽  
Source Power ◽  
First Results ◽  
Basic Equations

The aim of this paper is to present the basic equations and the first results of an experimental investigation using the space intensity sensor. We offer a multi-element acoustic sensor that gives the opportunity to find the source's parameters (distance between the observer and the source, direction to the source, power of its radiation, its multipole type). It is very important for the diagnosis of natural low frequency sources. The results of the measurements of the sound multipole source's parameters are presented. The test's experimental data correspond well to the real controlled parameters.

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