Low-Frequency Phase-sensitive Resistivity Measurements, Manitoba (62H,K) and Quebec (21E)

1970 ◽  
Author(s):  
W J Scott
Keyword(s):  
Low Frequency ◽  
Resistivity Measurements ◽  
Phase Sensitive ◽  
Frequency Phase

Squeezing-enhanced fiber Mach-Zehnder interferometer for low-frequency phase measurement

2017 ◽  
Vol 110 (2) ◽  
pp. 021106 ◽  
Author(s):  
Fang Liu ◽  
Yaoyao Zhou ◽  
Juan Yu ◽  
Jiale Guo ◽  
Yang Wu ◽  
...  
Keyword(s):  
Phase Measurement ◽  
Low Frequency ◽  
Zehnder Interferometer ◽  
Frequency Phase ◽  
Mach Zehnder Interferometer

scholarly journals Bioimpedance Vector Patterns Changes in Response to Swimming Training: An Ecological Approach

2020 ◽  
Vol 17 (13) ◽  
pp. 4851 ◽  
Author(s):  
Joana F. Reis ◽  
Catarina N. Matias ◽  
Francesco Campa ◽  
José P. Morgado ◽  
Paulo Franco ◽  
...  
Keyword(s):  
Major Axis ◽  
Training Load ◽  
Single Frequency ◽  
Ecological Approach ◽  
Dry Land ◽  
Competitive Swimming ◽  
Cellular Density ◽  
Joint Interpretation ◽  
Phase Sensitive ◽  
Frequency Phase

Background and aim: Monitoring bioelectric phase angle (PhA) provides important information on the health and the condition of the athlete. Together with the vector length, PhA constitutes the bioimpedance vector analysis (BIVA) patterns, and their joint interpretation exceeds the limits of the evaluation of the PhA alone. The present investigation aimed to monitor changes in the BIVA patterns during a training macrocycle in swimmers, trying to ascertain if these parameters are sensitive to training load changes across a 13-week training period. Methods: Twelve national and international level swimmers (four females; eight males; 20.9 ± 1.9 years; with a competitive swimming background of 11.3 ± 1.8 years; undertaking 16–20 h of pool training and 4–5 h of dry-land training per week and 822.0 ± 59.0 International Swimming Federation (FINA) points) were evaluated for resistance (R) and reactance (Xc) using a single frequency phase sensitive bioimpedance device at the beginning of the macrocycle (M1), just before the beginning of the taper period (M2), and just before the main competition of the macrocycle (M3). At the three-time assessment points, swimmers also performed a 50 m all-out first stroke sprint with track start (T50 m) while time was recorded. Results: The results of the Hotelling T2 test showed a significant vector displacement due to simultaneous R and Xc changes (p < 0.001), where shifting from top to bottom along the major axis of the R-Xc graph from M1 to M2 was observed. From M2 to M3, a vector displacement up and left along the minor axis of the tolerance ellipses resulted in an increase in PhA (p < 0.01). The results suggest a gain in fluid with a decrease in cellular density from M1 to M2 due to decrements in R and Xc. Nevertheless, the reduced training load characterizing taper seemed to allow for an increase in PhA and, most importantly, an increase of Xc, thus demonstrating improved cellular health and physical condition, which was concomitant with a significant increase in the T50 m performance (p < 0.01). Conclusions: PhA, obtained by bioelectrical R and Xc, can be useful in monitoring the condition of swimmers preparing for competition. Monitoring BIVA patterns allows for an ecological approach to the swimmers’ health and condition assessment without resorting to equations to predict the related body composition variables.

Biomaterial Impedance Analyzer Based on Digital Auto Balancing Bridge

2011 ◽  
Vol 291-294 ◽  
pp. 1259-1262
Author(s):  
Nan Li ◽  
Yi Nan Wang ◽  
Hong Shan Nie ◽  
Hong Qi Yu ◽  
Hui Xu
Keyword(s):  
Bridge Circuit ◽  
Design Method ◽  
Circuit Simulation ◽  
Low Frequency ◽  
Operational Amplifiers ◽  
Frequency Synthesis ◽  
Direct Digital Frequency Synthesis ◽  
Impedance Analyzer ◽  
Digital Frequency ◽  
Phase Sensitive

This paper presents the design method of a novel biomaterial impedance analyzer based on digital auto balancing bridge method. The system hardware mainly consists of FPGA, ADC, DACs and operational amplifiers. Many DSP algorithms such as direct digital frequency synthesis (DDS), digital phase sensitive demodulation (DPSD), digital modulation and digital filter are implemented in FPGA to realize the auto balancing function of the bridge circuit. Simulation results show that the system has good performance from low frequency to 10MHz. It is suitable for EIS application in biomaterial analysis.

TIME-RESOLVED STUDY OF PHONON-POLARITONS IN LiTaO3 AT ROOM TEMPERATURE

1993 ◽  
Vol 07 (12) ◽  
pp. 797-811
Author(s):  
S. HUNSCHE ◽  
H.J. BAKKER ◽  
H. KURZ
Keyword(s):  
Room Temperature ◽  
Quantitative Description ◽  
Low Frequency ◽  
Laser Pulses ◽  
Femtosecond Laser Pulses ◽  
Precise Determination ◽  
Time Resolved ◽  
Dispersion Branch ◽  
Phase Sensitive ◽  
Phonon Polaritons

We present a time-resolved study of phonon-polaritons in the ferroelectric LiTaO 3 at room temperature. The coherent generation and phase-sensitive detection of polaritons, using femtosecond Laser pulses, allow precise determination of polariton frequencies and dephasing times. The experimental data clearly show a resonance at 0.95 THz that has not been found in previous IR and Raman studies. The simultaneous coherent excitation of polaritons in the upper and the lower dispersion branch associated with this resonance leads to the observation of phonon-polariton beats, A quantum-mechanical model of the lowest A 1 lattice vibration in LiTaO 3 is developed, which provides a quantitative description of the low-frequency dielectric response, including the polariton dispersion and dephasing. Within this model, the transition at 0.95 THz can be identified as a classically forbidden tunneling resonance.

Field and/or resistivity mapping in MT-VLF and implications for data processing

Geophysics ◽  
1994 ◽  
Vol 59 (11) ◽  
pp. 1695-1712 ◽  
Author(s):  
Roger Guerin ◽  
Alain Tabbagh ◽  
Pierre Andrieux
Keyword(s):  
High Frequency ◽  
Low Frequency ◽  
Test Site ◽  
Horizontal Polarization ◽  
Resistivity Measurements ◽  
Magnetic Components ◽  
Frequency Independent ◽  
Prismatic Bodies ◽  
Lateral Variations ◽  
A Current

The ratio of the horizontal electric and magnetic components of the electromagnetic field generated by a radio transmitter in the very low frequency (VLF) range is used in MT-VLF resistivity mapping to determine the apparent resistivity of the ground. A theoretical calculation of the responses of simple 2-D and 3-D prismatic bodies shows that the measurable lateral variations in both fields are independent, uncoupled, and correspond to frequency‐independent, static variations. It is advantageous therefore to process and map the fields separately. Processing methods used in gravimetry and magnetics are especially appropriate in correcting the apparent anisotropy related to the horizontal polarization of the primary field and in integrating (upward continuation) the high‐frequency spatial variations. The different processes tested on a synthetic case and on data obtained at the Centre de Recherches Géophysiques (CRG) test site showed how to eliminate shallow features and a current channeling conductor to favor the anomaly of a fault. A third example with a hydrogeological application shows the advantages of this method over Wenner direct‐current resistivity measurements.

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