scholarly journals Measurement of the quality factor of a new low-frequency differential accelerometer for testing the equivalence principle

2014 ◽  
Vol 85 (1) ◽  
pp. 014502 ◽  
Author(s):  
V. Iafolla ◽  
C. Lefevre ◽  
E. Fiorenza ◽  
F. Santoli ◽  
S. Nozzoli ◽  
...  
Keyword(s):  
Quality Factor ◽  
Equivalence Principle ◽  
Low Frequency

scholarly journals Realization of SIMO biquad filters and quadrature sinusoidal oscillators using OTRAs

2021 ◽  
Author(s):  
Garima Garima ◽  
◽  
Pragati Kumar ◽  
Data Ram Bhaskar ◽  
◽  
...  
Keyword(s):  
Quality Factor ◽  
Experimental Validation ◽  
Low Frequency ◽  
Spice Simulation ◽  
Sinusoidal Oscillators ◽  
Input Multiple Output ◽  
Condition Of Oscillation ◽  
Single Input ◽  
Simulation Results ◽  
Quality Factor Q

In this communication, two single-input multiple-output (SIMO) type biquad filters employing operational transresistance amplifiers (OTRAs) have been presented. Various parameters of the proposed filter circuits viz. pole frequency (ɷ), pole quality factor (Q) and the gain are independently controllable. The proposed filter configurations can also be converted into low frequency oscillators with fully uncoupled control of condition of oscillation and frequency of oscillation with quadrature output voltages. The active and passive sensitivities of the proposed circuits have been found to be small. SPICE simulation results and experimental validation of the proposed circuits employing OTRAs realized with AD844 type CFOAs have also been presented.

scholarly journals Magnetic Pendulum Arrays for Efficient ULF Transmission

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Srinivas Prasad M N ◽  
Rustu Umut Tok ◽  
Foad Fereidoony ◽  
Yuanxun Ethan Wang ◽  
Rui Zhu ◽  
...  
Keyword(s):  
Quality Factor ◽  
Free Space ◽  
Low Frequency ◽  
Transmission Efficiency ◽  
Experimental Results ◽  
Proof Of Concept ◽  
Electrically Small Antennas ◽  
Fundamental Limits ◽  
Small Antennas ◽  
Order Of Magnitude

Abstract The frequencies lying between 300 Hz to 3 kHz have been designated as Ultra Low Frequency (ULF) with corresponding wavelengths from 1000 Km to 100 Km. Although ULF has very low bandwidth it is very reliable, penetrating and difficult to jam which makes it a great choice for communication in underwater and underground environments. Small and portable ULF antennas within a diameter of 1 meter would operate under an electrical length on the order of 10−4 to 10−6 wavelengths in free space, making them very inefficient because of fundamental limits on radiation from electrically small antennas. To overcome this problem, Mechanical Antennas or ‘Mechtennas’ for Ultra Low Frequency Communications have been proposed recently. For efficient generation of ULF radiation, we propose a portable electromechanical system called a Magnetic Pendulum Array (MPA). A proof of concept demonstration of the system at 1.03 kHz is presented. The theory and experimental results demonstrate that such a system can achieve a significantly higher quality factor than conventional coils and thus order of magnitude higher transmission efficiency. The concept can be easily scaled to the ULF range of frequencies.

NOISE CHARACTERISTICS OF 340 nm AND 280 nmGaN-BASED LIGHT EMITTING DIODES

2004 ◽  
Vol 14 (03) ◽  
pp. 702-707
Author(s):  
SHAYLA SAWYER ◽  
SERGEY L. RUMYANTSEV ◽  
NEZIH PALA ◽  
MICHAEL S. SHUR ◽  
YURIY BILENKO ◽  
...  
Keyword(s):  
Light Intensity ◽  
Quality Factor ◽  
Light Emitting Diodes ◽  
Low Frequency ◽  
Low Frequencies ◽  
Light Emitting ◽  
Visible Wavelength ◽  
Noise Characteristics ◽  
Uv Leds ◽  
Halogen Lamps

Low frequency fluctuations in light intensity of 340 nm and 280 nm GaN -based light emitting diodes (LEDs) are compared with noise properties of other commercially available UV and visible wavelength LEDs and halogen lamps. At low frequencies, LEDs can exhibit lower levels of noise than halogen lamps. An LED noise quality factor β is estimated for the UV LEDs.

Theoretical and practical aspects of absorption in the application of in‐seam seismic coal exploration

Geophysics ◽  
1982 ◽  
Vol 47 (12) ◽  
pp. 1645-1656 ◽  
Author(s):  
Th. Krey ◽  
H. Arnetzl ◽  
M. Knecht
Keyword(s):  
Quality Factor ◽  
Seismic Waves ◽  
Guided Waves ◽  
Country Rock ◽  
Low Frequency ◽  
Quality Factors ◽  
Ruhr Area ◽  
Phase Signal ◽  
Quality Factor Q

During the last two decades, the detection of coal seam discontinuities by seismic waves guided by the seam has become a special branch of exploration seismics in Europe. Waves consisting purely of SH motion (so‐called waves of Love type) are of special interest, and the rather high frequencies of the Airy phase, in thin seams, are most important because they present very high reflectivity at seam interruptions. Absorption increases with frequency in most layers, and therefore attenuates the high Airy‐phase frequencies more severely than the earlier low‐frequency part of the guided waves. Another fact additionally impairs the Airy‐phase signal: the quality factor Q is much lower in coal than in the schists and sandstones of the Carboniferous country rock. Unfortunately, most of the energy of the Airy phase is transferred by the coal, whereas the lower frequencies have their main energy conveyed by the country rock above and below the seam. In order to allow a better understanding of the influence of absorption on Love‐type seam waves, several simplified computations were carried out for the fundamental mode of a seam typical for the northwest‐German Ruhr area. The assumptions are as follows: The quality factors [Formula: see text] for coal and [Formula: see text] for the country rock do not depend upon frequency; higher powers of [Formula: see text] and [Formula: see text] can be neglected; and the distance from the source is large enough to allow the two‐dimensional plane‐wave case to be considered. The mathematics resulting from these assumptions and adequate data processing of transmission records provides the possibility to determine the quality factor [Formula: see text] of coal in‐situ, although the thickness of the seam may be much smaller than the wavelengths involved. [Formula: see text] may become of interest for practical mining problems.

Low-Frequency Acoustic Sweep Monitoring of Bone Integrity and Osteoporosis

1999 ◽  
Vol 121 (4) ◽  
pp. 423-431 ◽  
Author(s):  
S. D. Panteliou ◽  
H. Abbasi-Jahromi ◽  
A. D. Dimarogonas ◽  
W. Kohrt ◽  
R. Civitelli
Keyword(s):  
Quality Factor ◽  
Animal Studies ◽  
Structural Integrity ◽  
Low Frequency ◽  
Temperature Changes ◽  
Healthy Control ◽  
Linear Correlations ◽  
Production Of Entropy

We developed a noninvasive method to evaluate bone structural integrity. It is based on the measurement of the dynamic characteristics of the bone using sweeping sound excitation in the range of acoustic frequencies. The Quality Factor (a measure of material damping) has been used as an indicator of the tendency of the bone to fracture. Results of animal studies have supported this hypothesis since linear correlations were observed between bone density, quality factor, and impact strength. A vibration excitation in the form of an acoustic sweep signal is applied to a bone to measure the quality factor. Rat bones were tested, obtained from animals with osteoporosis age-dependent (tested in vitro) or ovariectomy-induced (tested in vivo), and compared with bones of healthy (control) rats. The change in damping was, on average, equal or greater to the change in density. Moreover, excellent correlation of the quality factor was obtained with bone fracture energy measured with an impact test. During a vibration cycle, the changing strain results in temperature changes due to the reciprocity of temperature and strain. Nonreversible conduction of heat due to the unequal temperature change results in entropy production that is enhanced due to the stress concentration about the voids associated with bone porosity. Damping is a measure of the production of entropy. Its measure, the quality factor, represents a potentially useful tool for monitoring bone integrity, which is deteriorating in diseases characterized by disruption of the trabecular architecture, such as osteoporosis. A computational model yielded results that are in good correlation with the experimental results.

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