Статті в журналах: "Frequency ratio measurement"

1

Lu, Yun-Chih, Chi-Hung Wu, and Yi-Jan Emery Chen. "A 65 nm CMOS Statistical Frequency Ratio Calculator for Frequency Measurement." IEEE Transactions on Industrial Electronics 68, no. 4 (April 2021): 3558–66. http://dx.doi.org/10.1109/tie.2020.2977536.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

2

Wei, Zhou, Xuan Zong-Qiang, Yu Jian-Guo, Wang Hai, Zhou Hui, and Li Zhi-Qi. "A Novel Frequency Measurement Method Suitable for a Large Frequency Ratio Condition." Chinese Physics Letters 21, no. 5 (May 2004): 786–88. http://dx.doi.org/10.1088/0256-307x/21/5/006.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

3

JONES, M. J., S. D. MOTTRAM, E. S. LIN, and G. SMITH. "MEASUREMENT OF ENTRAINMENT RATIO DURING HIGH FREQUENCY JET VENTILATION." British Journal of Anaesthesia 65, no. 2 (August 1990): 197–203. http://dx.doi.org/10.1093/bja/65.2.197.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

4

Zhou, Feng, Min Lei, Xiao Dong Yin, and Shu Han Zhang. "Measure Characteristic of UHV Power Frequency Voltage Ratio Standard." Advanced Materials Research 354-355 (October 2011): 1210–15. http://dx.doi.org/10.4028/www.scientific.net/amr.354-355.1210.

Повний текст джерела

Анотація:

In order to meet the urgent needs of voltage measurement traceability and transfer in the construction of ultra-high voltage power grid, 1000kV series standard voltage transformer is developed as the standard instrument, and then its measurement characteristics is tested. According to the theory and construction of the series power frequency voltage ratio standard, semi-insulating transformer voltage summation is proposed to make the voltage ratio measurement of SSTV whose accuracy can reach the 0.02 level trace to the source of national power frequency ratio standard of 500kV successfully. The compatibility is better than compared to traditional voltage coefficient measuring method.

Стилі APA, Harvard, Vancouver, ISO та ін.

5

Akamatsu, Daisuke, Masami Yasuda, Hajime Inaba, Kazumoto Hosaka, Takehiko Tanabe, Atsushi Onae, and Feng-Lei Hong. "Frequency ratio measurement of ^171Yb and ^87Sr optical lattice clocks." Optics Express 22, no. 7 (March 27, 2014): 7898. http://dx.doi.org/10.1364/oe.22.007898.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

6

Yang, Yuxuan, Yang Xu, Tian Guan, Lixuan Shi, Jinyu Li, Dongmei Li, Yonghong He, Xiangnan Wang, Zhangyan Li, and Yanhong Ji. "Spectrum Intensity Ratio Detection for Frequency Domain Weak Measurement System." IEEE Photonics Journal 12, no. 4 (August 2020): 1–12. http://dx.doi.org/10.1109/jphot.2019.2942718.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

7

Baranov, Pavel F., Valeriy N. Borikov, and Edvard I. Tsimbalist. "Instrument for Measurement of Transfer Ratio Voltage Transformers." Applied Mechanics and Materials 799-800 (October 2015): 1325–29. http://dx.doi.org/10.4028/www.scientific.net/amm.799-800.1325.

Повний текст джерела

Анотація:

The paper presents the instrument for measurement of transfer ratio voltage transformers in the frequency range. The instrument distinctive feature is measuring of small differential signal of the voltages with sensitivity 2 nV against the background of large common-mode signal. The instrument features, its technical and metrological parameters are also considered.

Стилі APA, Harvard, Vancouver, ISO та ін.

8

KATO, Rina, Kanna YAMADA, Yuki MISHINA, and Takeshi KANDA. "Measurement of equivalent ratio in rocket engine high frequency vibration model." Proceedings of Mechanical Engineering Congress, Japan 2021 (2021): J191–04. http://dx.doi.org/10.1299/jsmemecj.2021.j191-04.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

9

Yue, Chang Xi, Enrico Mohns, Feng Zhou, Min Lei, Shu Han Zhang, and Qiong Xiang. "A Complex Voltage Ratio Measurement System for the Audio Frequency Range." Applied Mechanics and Materials 239-240 (December 2012): 278–82. http://dx.doi.org/10.4028/www.scientific.net/amm.239-240.278.

Повний текст джерела

Анотація:

This paper describes the setup of a complex voltage ratio measurement system for the audio frequency range. A wideband two-channel digitizer and a differential analogue channel switching front-end are used as the heart of the system. The complex error, frequency response characteristics and short term stability of the system are tested in this paper. The errors range from 1×10-7at 50 Hz to 10×10-6at 200 kHz in ratio 1:1 test with 6 V input voltages. And errors are below ±8×10-7and ±0.06 μrad in ratio 1:1 test with a 4V power line (50 Hz) input voltage over 64 hours. The test results and comparisons between with and without channel exchange mode confirm the remarkable improvement regarding the suppression of the static mismatch errors of the digitizer and show the usefulness of the system at 50 Hz too.

Стилі APA, Harvard, Vancouver, ISO та ін.

10

Akamatsu, Daisuke, Masami Yasuda, Hajime Inaba, Kazumoto Hosaka, Takehiko Tanabe, Atsushi Onae, and Feng-Lei Hong. "Errata: Frequency ratio measurement of ^171Yb and ^87Sr optical lattice clocks." Optics Express 22, no. 26 (December 19, 2014): 32199. http://dx.doi.org/10.1364/oe.22.032199.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

11

Muggli, P., M. Q. Tran, and T. M. Tran. "Velocity ratio measurement using the frequency of the gyro backward wave." Physics of Fluids B: Plasma Physics 3, no. 6 (June 1991): 1315–18. http://dx.doi.org/10.1063/1.859825.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

12

Dingding, Zhao, and Cai Ping. "Permanent Calibration in High Frequency Ratio (>0.3) Dynamic Unbalance Measurement." Procedia Engineering 29 (2012): 4278–81. http://dx.doi.org/10.1016/j.proeng.2012.01.657.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

13

Swanson, David C. "Precision spectral peak frequency measurement using a window leakage ratio function." Mechanical Systems and Signal Processing 54-55 (March 2015): 1–15. http://dx.doi.org/10.1016/j.ymssp.2014.08.017.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

14

Lesovoi, Sergey, and Mariia Globa. "Measurement of Siberian Radioheliograph cable delays." Solar-Terrestrial Physics 7, no. 4 (December 20, 2021): 93–97. http://dx.doi.org/10.12737/stp-74202110.

Повний текст джерела

Анотація:

To achieve the maximum dynamic range of solar radio images obtained using aperture synthesis in relatively wide frequency bands 0.1−0.5 % of the operating frequency, it is necessary to compensate the signal propagation delays in the antenna receive path before calculating visibility functions (hereinafter visibilities). When visibilities are corrected without delay compensation, the signal-to-noise ratio decreases due to residual phase slopes in the receiving system bandwidth. In addition to enhancing dynamic range, preliminary compensation for delays simplifies real-time imaging — no antenna gain calibration is required to get a first approximation image. The requirements for the accuracy of antenna placement are also reduced — in contrast to the measurement of the phase visibility error, the measurement of the delay is actually not so critical to the antenna position errors that are larger than the operating wavelength. The instantaneous frequency band of the Siberian Radioheliograph, which determines the minimum step for measuring the phase slope, and hence the accuracy of determining the delay, is 10 MHz. At the speed of light in an optical fiber of ~0.7c, a step of 10 MHz makes it possible to unambiguously measure the difference between electrical lengths of cables up to 20 m and to correct antenna positions by radio observations, even if the error in the position of the antennas exceeds the operating wavelength. Correction of the band phase slopes during the observation time adapts the radio telescope to the temperature drift of delays and decreases antenna gain phase spread. This, in turn, leads to more stable solutions to systems of equations containing antenna gains as unknowns.

Стилі APA, Harvard, Vancouver, ISO та ін.

15

Al-Ameri, S., A. A. Alawady, M. F. M. Yousof, H. Ahmad, Ali A. Salem, and M. A. Talib. "Frequency response analysis for transformer tap changer damage detection." International Journal of Power Electronics and Drive Systems (IJPEDS) 11, no. 1 (March 1, 2020): 350. http://dx.doi.org/10.11591/ijpeds.v11.i1.pp350-358.

Повний текст джерела

Анотація:

Frequency response analysis (FRA) method has been proven to detect the transformer winding damage. However, there is no practical study which investigates the damages on transformer tap changer even though it has a high failure rate. Hence, this paper investigates normal and faulty transformer tap changer using FRA. The FRA measurements conducted using four different test configurations. Also, normal tap changer, pitting and coking tap changer contact were investigated. In addition to FRA measurement, winding resistance measurement has been conducted. The transformer turn ratio measurement also conducted to identify the taps positions. This study results significant to understand the effect of pitting and coking tap changer on the transformer frequency response. The results showed that pitting has a slight influence on the frequency response. However, coking shows a huge variation in low-frequency response. This effect observed during the winding resistance measurement.

Стилі APA, Harvard, Vancouver, ISO та ін.

16

Křen, Petr. "Laser frequency counting and frequency modulation width measurement from a fft signal." Metrology and Measurement Systems 19, no. 3 (October 1, 2012): 565–72. http://dx.doi.org/10.2478/v10178-012-0049-0.

Повний текст джерела

Анотація:

Abstract A new method of optical frequency beat counting based on fast Fourier transform (FFT) analysis is described. Signals with a worse signal-to-noise ratio can be counted correctly comparing to the conventional counting method of detecting each period separately. The systematic error of FFT counting below 10 Hz is demonstrated and can be decreased. Additionally the modulation width of a frequency-stabilized laser with high frequency modulation index can be simultaneously measured during a carrier frequency measurement against an optical frequency synthesizer or other laser.

Стилі APA, Harvard, Vancouver, ISO та ін.

17

Le, Minda, V. Chandrasekar, and Sounak Biswas. "Evaluation and Validation of GPM Dual-Frequency Classification Module after Launch." Journal of Atmospheric and Oceanic Technology 33, no. 12 (December 2016): 2699–716. http://dx.doi.org/10.1175/jtech-d-15-0253.1.

Повний текст джерела

Анотація:

AbstractThe Dual-Frequency Precipitation Radar (DPR) on board the Global Precipitation Measurement (GPM) Core Observatory has reflectivity measurements at two different frequencies: Ku and Ka bands. The dual-frequency ratio from the measurements has been used to perform rain type classification and microphysics retrieval in the current DPR level 2 algorithm. The dual-frequency classification module is a new module in the GPM level 2 algorithm. The module performs rain type classification and melting region detection using the vertical profile of the dual-frequency ratio. This paper presents an evaluation of the performance of the GPM dual-frequency classification module after launch. The evaluation process includes a comparison between the dual-frequency classification results and the TRMM legacy single-frequency results, as well as validation with ground radars.

Стилі APA, Harvard, Vancouver, ISO та ін.

18

Rouleau, Lucie, Isadora Ruas Henriques, and Jean-François Deü. "Influence of the Poisson's ratio on the efficiency of viscoelastic damping treatments." INTER-NOISE and NOISE-CON Congress and Conference Proceedings 263, no. 3 (August 1, 2021): 3790–94. http://dx.doi.org/10.3397/in-2021-2521.

Повний текст джерела

Анотація:

An efficient way of mitigating noise and vibration is to embed viscoelastic patches into the host structure. Viscoelastic properties are of significant importance in determining the performance of the passive damping treatment. The behaviour of homogeneous isotropic materials is described by two elastic constants (generally the Young modulus and the Poisson ratio, or the shear and bulk moduli), which are frequency- and temperature-dependent in the case of viscoelastic materials. In practice, the Poisson's ratio is often considered as independent of temperature and frequency. One goal of this work is to numerically evaluate the validity of this assumption and its limitations (frequency range, thickness of the viscoelastic layer). To this end, a thermo-mechanical characterization of a viscoelastic material is carried out by dynamic measurements of the complex shear and bulk moduli, allowing the indirect measurement of the frequency- and temperature-dependent Poisson's ratio. Moreover, the measurements of the Poisson's ratio (direct or indirect) can lead to considerable uncertainties. For instance, large discrepancies have been observed when characterizing the Poisson's ratio of polymer foams. Another goal of this work is to investigate the influence of those uncertainties on the dynamic response of a damped structure.

Стилі APA, Harvard, Vancouver, ISO та ін.

19

Liu, Yang, Jigou Liu, and Ralph Kennel. "Frequency Measurement Method of Signals with Low Signal-to-Noise-Ratio Using Cross-Correlation." Machines 9, no. 6 (June 18, 2021): 123. http://dx.doi.org/10.3390/machines9060123.

Повний текст джерела

Анотація:

Precise frequency measurement plays an essential role in many industrial and robotic systems. However, different effects in the application’s environment cause signal noises, which make frequency measurement more difficult. In small signals or rough environments, even negative Signal-to-Noise Ratios (SNRs) are possible. Thus, frequency measuring methods, which are suited for low SNR signals, are in great demand. While denoising methods such as autocorrelation do not suffice for small signal with low SNR, frequency measurement methods such as Fast-Fourier Transformation or Continuous Wavelet Transformation suffer from Heisenberg’s uncertainty principle, which makes simultaneous high frequency and time resolutions impossible. In this paper, the cross-correlation spectrum is presented as a new frequency measuring method. It can be used in any frequency domain, and provides greater denoising than autocorrelation. Furthermore, frequency and time resolutions are independent from one another, and can be set separately by the user. In simulations, it achieves an average deviation of less than 0.1% on sinusoidal signals with a SNR of −10 dB and a signal length of 1000 data points. When applied to “self-mixing”-interferometry signals, the method can reach a normalized root-mean square error of 0.2% with the aid of an estimation method and an averaging algorithm. Therefore, further research of the method is recommended.

Стилі APA, Harvard, Vancouver, ISO та ін.

20

Chen, Shu-Jung, and Yung-Chuan Wu. "Active Thermoelectric Vacuum Sensor Based on Frequency Modulation." Micromachines 11, no. 1 (December 21, 2019): 15. http://dx.doi.org/10.3390/mi11010015.

Повний текст джерела

Анотація:

This paper introduces a thermoelectric-type sensor with a built-in heater as an alternative approach to the measurement of vacuum pressure based on frequency modulation. The proposed sensor is fabricated using the TSMC (Taiwan Semiconductor Manufacturing Company, Hsinchu, Taiwan) 0.35 μm complementary metal-oxide-semiconductor-microelectro-mechanical systems (CMOS–MEMS) process with thermocouples positioned central-symmetrically. The proposed frequency modulation technique involves locking the sensor output signal at a given frequency using a phase-lock-loop (PLL) amplifier to increase the signal-to-noise ratio (SNR) and thereby enhance the sensitivity of vacuum measurements. An improved first harmonic signal detection based on asymmetrical applied heating gives a precise measurement. Following calibration, the output voltage is in good agreement with the calibration values, resulting in an error of 0.25% under pressures between 0.1–10 Torr.

Стилі APA, Harvard, Vancouver, ISO та ін.

21

Khan, Zahid, Giovanni Cascante, and M. Hesham El Naggar. "Measurement of dynamic properties of stiff specimens using ultrasonic waves." Canadian Geotechnical Journal 48, no. 1 (January 2011): 1–15. http://dx.doi.org/10.1139/t10-040.

Повний текст джерела

Анотація:

The measurement of low-strain properties (wave velocity and damping ratio) of geomaterials is affected by equipment-generated delays, coupling of transducers, and wave reflections. This study presents a new technique to measure ultrasonic properties of stiff specimens accurately. Compressional-wave velocities in cylindrical rods of different lengths and materials were measured using different ultrasonic equipment. The error induced by different equipment was below 1% after the measurements were corrected by the equipment time delay. Shear-wave velocities of different materials were measured using ultrasonic transducers (frequency < 1 MHz) and a resonant column device (frequency < 200 Hz). The difference in shear-wave velocities was less than 4%, and the measured values are in agreement with published results for all tested materials. A new methodology based on the first two reflections of the main pulse has been developed to measure the damping ratio of stiff specimens using ultrasonic equipment. The ultrasonic measurements of the damping ratio compare well with resonant column results. A more reliable determination of the dynamic Poisson’s ratio of a cemented sand was achieved using corrected ultrasonic-wave velocities.

Стилі APA, Harvard, Vancouver, ISO та ін.

22

Nazemosadat, Elham, Sergi García, and Ivana Gasulla. "Heterogeneous multicore fiber-based microwave frequency measurement." Optics Express 30, no. 15 (July 11, 2022): 26886. http://dx.doi.org/10.1364/oe.463152.

Повний текст джерела

Анотація:

A novel microwave frequency measurement scheme using a heterogeneous multicore fiber (MCF) is experimentally demonstrated. The inherently different relative group delays among the cores of a heterogeneous 7-core MCF are used to realize two individual 2-tap microwave filters with different free spectral ranges (FSRs). The ratio of the frequency response traces of these two filters is used to establish an amplitude comparison function (ACF). Furthermore, by varying the operational wavelength, the relative group delays between the cores and consequently the FSRs of the filters are tuned and different ACF curves are obtained. The complementary information provided by these different ACFs allows us to estimate the unknown frequency with an improved accuracy, over a broad measurement range. In our experiments, a measurement error of ±71 MHz is achieved over a frequency range of 0.5-40 GHz. The proposed scheme offers flexibility and compactness, thanks to the parallelism provided by the MCF.

Стилі APA, Harvard, Vancouver, ISO та ін.

23

Kawanishi, Tetsuya. "Precise Optical Modulation and Its Application to Optoelectronic Device Measurement." Photonics 8, no. 5 (May 11, 2021): 160. http://dx.doi.org/10.3390/photonics8050160.

Повний текст джерела

Анотація:

Optoelectronic devices which play important roles in high-speed optical fiber networks can offer effective measurement methods for optoelectronic devices including optical modulators and photodetectors. Precise optical signal modulation is required for measurement applications. This paper focuses on high-speed and precise optical modulation devices and their application to device measurement. Optical modulators using electro-optic effect offers precise control of lightwaves for wideband signals. As examples, this paper describes frequency response measurement of photodetectors using high-precision amplitude modulation and wavelength domain measurement of optical filters using fast optical frequency sweep. Precise and high-speed modulation can be achieved by active trimming which compensates device structure imbalance due to fabrication error, where preciseness can be described by on-off extinction ratio. A Mach-Zehnder modulator with sub Mach-Zehnder interferometors can offer high extinction-ratio optical intensity modulation, which can be used for precise optoelectronic frequency response measurement. Precise modulation would be also useful for multi-level modulation schemes. To investigate impact of finite extinction ratio on optical modulation, duobinary modulation with small signal operation was demonstrated. For optical frequency domain analysis, single sideband modulation, which shifts optical frequency, can be used for generation of stimulus signals. Rapid measurement of optical filters was performed by using an optical sweeper consisting of an integrated Mach-Zehnder modulator for optical frequency control and an arbitrary waveform generator for generation of a source frequency chirp signal.

Стилі APA, Harvard, Vancouver, ISO та ін.

24

Inagaki, Keizo, Tetsuya Kawanishi, and Masayuki Izutsu. "Optoelectronic frequency response measurement of photodiodes by using high-extinction ratio optical modulator." IEICE Electronics Express 9, no. 4 (2012): 220–26. http://dx.doi.org/10.1587/elex.9.220.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

25

Hisai, Yusuke, Daisuke Akamatsu, Takumi Kobayashi, Kazumoto Hosaka, Hajime Inaba, Feng-Lei Hong, and Masami Yasuda. "Improved frequency ratio measurement with 87Sr and 171Yb optical lattice clocks at NMIJ." Metrologia 58, no. 1 (January 8, 2021): 015008. http://dx.doi.org/10.1088/1681-7575/abc104.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

26

Jalaly, I. "Measurement of signal/noise ratio as function of frequency in voice communication system." Electronics Letters 25, no. 25 (1989): 1741. http://dx.doi.org/10.1049/el:19891164.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

27

Li, Chaoyang, Dapeng Wang, Zeming Li, Xin Li, Toshiyuki Kawaharamura, and Mamoru Furuta. "Stoichiometry Control of ZnO Thin Film by Adjusting Working Gas Ratio during Radio Frequency Magnetron Sputtering." Journal of Materials 2013 (February 28, 2013): 1–6. http://dx.doi.org/10.1155/2013/547271.

Повний текст джерела

Анотація:

ZnO thin films were deposited on quartz glasses by a radio frequency (rf) magnetron sputtering. The mechanism for stoichiometry in the ZnO thin films was investigated by adjusting Ar/O2 working gas ratio during deposition. The optical emission spectroscopy (OES) in situ measurement revealed the kinetics species variation during rf plasma deposition process. It was found that the intensity of the excited atomic oxygen (O*) was increased with the oxygen ratio increasing, resulting in enhancing the oxidization effect during ZnO film fabrication. On the contrary, the intensities of atomic zinc emission were gradually decreased, resulting in the zinc ratio in the film were decreased with the oxygen ratio increasing. Therefore, it is possible to control the stoichiometry of ZnO film by simply adjusting the working gas ambient in the rf plasma deposition. The structural and optical properties of ZnO thin films were investigated as well.

Стилі APA, Harvard, Vancouver, ISO та ін.

28

Fan, Sichen, Jun Ruan, Dandan Liu, Xinliang Wang, Fan Yang, Yong Guan, Hui Zhang, Junru Shi, Yang Bai, and Shougang Zhang. "Phase Variation Measurement in Mach–Zehnder Interferometric Switch." Measurement Science Review 21, no. 6 (October 26, 2021): 180–84. http://dx.doi.org/10.2478/msr-2021-0024.

Повний текст джерела

Анотація:

Abstract Phase variations of the interrogation field lead to frequency shifts in Ramsey-type atomic clocks. This paper reports the development of a 300 MHz Mach–Zehnder (MZ) switch that effectively suppresses phase-transient effects. Similar to MZ interferometers, this radio-frequency (RF) MZ switch comprises two arms that are power- and phase-matched with each other. By inserting a PIN diode RF switch in one arm, the other arm remains undisturbed, freeing it of the phase transient. Trigger phase fluctuation measurements are implemented by using a lock-in amplifier to extract the in-phase and quadrature (I/Q) demodulation data. The results show that the extinction ratio of the RF MZ switch phase fluctuations is <5 μrad, which is significantly lower than that of a PIN (50 μrad). When applied to a cesium fountain clock, the RF MZ switch produces a frequency shift better than 1.73 × 10−16.

Стилі APA, Harvard, Vancouver, ISO та ін.

29

Wang, Peng, Chang Jia Yan, Tong Niu, Xue Fang, Zhi Peng Jin, and Bo Shi Guan. "Frequency Meter with Equal Precision Based FPGA + MCU." Applied Mechanics and Materials 614 (September 2014): 308–11. http://dx.doi.org/10.4028/www.scientific.net/amm.614.308.

Повний текст джерела

Анотація:

Aiming at such disadvantages of traditional frequency measurement technology as low precision and small measurement range, the combination of FPGA and MCU is applied in this paper to realize equal precision frequency measurement. The system makes full use of advantages FPGA, which has high speed and multi-I/O port, and MCU which has good man-machine interface and flexible control function. By controlling the time of enable signal allowed frequency measurement equal to integer cycles of measured signal, the frequency measurement accuracy can keep constant in the whole measurement range. The frequency measurement range of meter is 0.1 Hz~ 50 MHz, and the accuracy of frequency measurement is 10-6 Hz. In addition to measuring frequency, the system also can detect the period, pulse width and duty ratio. The simulation and experimental results show that the frequency meter has such advantages as compact structure, small volume, high reliability and precision and wide frequency measurement range.

Стилі APA, Harvard, Vancouver, ISO та ін.

30

Shevkun, Sergii, Maryna Dobroliubova, and Evhen Lapko. "Evaluation of measurement uncertainty when calibrating power analyzers of high-frequency signals in coaxial paths." Ukrainian Metrological Journal, no. 2 (June 30, 2022): 40–46. http://dx.doi.org/10.24027/2306-7039.2.2022.263889.

Повний текст джерела

Анотація:

Implementation of modern requirements for the quality and stability of radio communications, including the required data rate in industrial and atmospheric jamming, is impossible without accurate measurements of signal power at the output of transmitting devices in the transmitter-antenna section. Such measurements are performed using power analyzers that measure both incident and reflected waves. These parameters allow calculating the standing wave ratio, which makes it possible to ensure optimal coordination of the transmitter with antenna, the required power modes and the efficiency of the transmitter as a whole. The paper presents main results of the research on the evaluation of measurement uncertainty when calibrating of the analyzers of the throughput power of high-frequency signals in coaxial paths. The structural scheme and equations (model) of measurements, and features of calculating uncertainty budget are described. The basic principles for obtaining continuous calibration results in the whole range of measurements are revealed. An example of presenting calibration results in graphical form is given. The content of quantitative and qualitative indicators of corrections that must be taken into account during calibration to achieve the highest accuracy of measurements is revealed. It is expedient to use practical results of researches on calibration of throughput power meters in many areas connected with telecommunications and transmission of radio signals.

Стилі APA, Harvard, Vancouver, ISO та ін.

31

Feng, Cheng, Stefan Preussler, Jaffar Emad Kadum, and Thomas Schneider. "Measurement Accuracy Enhancement via Radio Frequency Filtering in Distributed Brillouin Sensing." Sensors 19, no. 13 (June 28, 2019): 2878. http://dx.doi.org/10.3390/s19132878.

Повний текст джерела

Анотація:

In this article, we demonstrate the noise reduction and signal to noise ratio (SNR) enhancement in Brillouin optical time-domain analyzers (BOTDA). The results show that, although the main noise contribution comes from the Brillouin interaction itself, a simple low pass filtering on the detected radio frequency (RF) signal reduces remarkably the noise level of the BOTDA traces. The corresponding SNR enhancement depends on the employed cut-off frequency of the low pass filter. Due to the enhancement of the SNR, a mitigation of the standard deviation error of the Brillouin frequency shift (BFS) has been demonstrated. However, RF filters with low cut-off frequency could lead to distortions on the trace signals and therefore detection errors on a non-uniform BFS. The trade-off between the noise reduction and the signal distortion as well as an optimal cut-off frequency are discussed in detail.

Стилі APA, Harvard, Vancouver, ISO та ін.

32

Elhajj, Mireille, and Washington Ochieng. "Impact of New GPS Signals on Positioning Accuracy for Urban Bus Operations." Journal of Navigation 73, no. 6 (June 15, 2020): 1284–305. http://dx.doi.org/10.1017/s0373463320000272.

Повний текст джерела

Анотація:

This paper analyses for the first time the impact of new GPS signals on positioning accuracy for dynamic urban applications, taking bus operations as an example. The performance assessment addresses both code measurement precision and positioning accuracy. The former is based on signal-to-noise ratio and estimation of multipath and noise by a combination of code and carrier phase measurements. The impact on positioning accuracy is derived by comparing the performance achievable with the conventional single frequency GPS only positioning both relative to reference trajectories from the integration of carrier phase measurements with data from a high grade inertial measurement unit. The results show that L5 code measurements have the highest precision, followed by L1 C/A and L2C. In the positioning domain, there is a significant improvement in two-dimensional and three-dimensional accuracy from dual frequency code measurements over the single frequency measurements, of 39% and 48% respectively, enabling more bus operation services to be supported.

Стилі APA, Harvard, Vancouver, ISO та ін.

33

Lee, Joonsung, Yizhuang Song, Narae Choi, Sungmin Cho, Jin Keun Seo, and Dong-Hyun Kim. "Noninvasive Measurement of Conductivity Anisotropy at Larmor Frequency Using MRI." Computational and Mathematical Methods in Medicine 2013 (2013): 1–12. http://dx.doi.org/10.1155/2013/421619.

Повний текст джерела

Анотація:

Anisotropic electrical properties can be found in biological tissues such as muscles and nerves. Conductivity tensor is a simplified model to express the effective electrical anisotropic information and depends on the imaging resolution. The determination of the conductivity tensor should be based on Ohm's law. In other words, the measurement of partial information of current density and the electric fields should be made. Since the direct measurements of the electric field and the current density are difficult, we use MRI to measure their partial information such as B1 map; it measures circulating current density and circulating electric field. In this work, the ratio of the two circulating fields, termed circulating admittivity, is proposed as measures of the conductivity anisotropy at Larmor frequency. Given eigenvectors of the conductivity tensor, quantitative measurement of the eigenvalues can be achieved from circulating admittivity for special tissue models. Without eigenvectors, qualitative information of anisotropy still can be acquired from circulating admittivity. The limitation of the circulating admittivity is that at least two components of the magnetic fields should be measured to capture anisotropic information.

Стилі APA, Harvard, Vancouver, ISO та ін.

34

Fattah, Elrangga Ibrahim. "Microzonation of Cisarua District Using Horizontal Vertical Spectral Ratio." Jurnal Ilmu dan Inovasi Fisika 5, no. 2 (August 9, 2021): 88–94. http://dx.doi.org/10.24198/jiif.v5i2.31533.

Повний текст джерела

Анотація:

The Bandung region is part of the framework of the Indonesian tectonic system, namely the tectonic plate meeting zone, where the Indo Autralia plate is infiltrated under the Eurasian plate in a convergent manner. The subduction process produces an effect in the form of an active fault geological structure in the Bandung area. One of these active faults is the Lembang Fault, which has a length of ± 29 kilometers and a shear acceleration of 3 to 5.5 millimeters per year. The microtremor measurement method is a passive geophysical method that utilizes natural subsurface vibrations so that it can provide dominant frequency data and amplification factors for soil layers. Based on the results of seismic susceptibility research using microtremor measurements using the HVSR method in the Lembang Fault zone in Cisarua Sub-District, it can be seen that the distribution of the dominant frequency values tends to be influenced by lithology and topography. In the research area, it is known to have a dominant frequency value that varies due to the different types of lithological units. In general, the dominant frequency ranges from 1-3 Hz because it is dominated by tuff sand and tuff pumice, and areas composed of volcanic breccias have a dominant frequency value between 3-6 Hz. Meanwhile, the amplification factor value will be influenced by rock deformation and weathering. The area that has a very high amplification factor value is in the southeast of the study area with an A0 value greater than 5. This indicates that the area is composed of a layer of thick and not dense tuff sand

Стилі APA, Harvard, Vancouver, ISO та ін.

35

Kim, Hyojung, Jongwoo Park, Junehwan Kim, Nara Lee, Gaeun Lee, Soonkon Kim, Pyungho Choi, Dohyun Beak, Jangkun Song, and Byoungdeog Choi. "Leakage Current Analysis Method for Metal Insulator Semiconductor Capacitors Through Low-Frequency Noise Measurement." Journal of Nanoscience and Nanotechnology 21, no. 3 (March 1, 2021): 1966–70. http://dx.doi.org/10.1166/jnn.2021.18901.

Повний текст джерела

Анотація:

Use of thinner oxides to improve the operating speed of a complementary metal-oxidesemiconductor (CMOS) device causes serious gate leakage problems. Leakage current of the dielectric analysis method has I–V, C–V, and charge pumping, but the procedure is very complicated. In this premier work, we analyzed the leakage current of metal insulator semiconductor (MIS) capacitors with different initiators through low-frequency noise (LFN) measurement with simplicity and high sensitivity. The LFN measurement results show a correlation between power spectral density (SIG) and gate leakage current (IG). MIS capacitors of hafnium zirconium silicate (HZS, (HfZrO4)1-x (SiO2)x) were used for the experiments with varying SiO2 ratio (x = 0, 0.1, 0.2) of hafnium zirconium oxide (HZO, HfZrO4). As the SiO2 ratio increased, the leakage current decreased according to J–V measurement. Further, the C–V measurement confirmed that the oxide-trapped charge (Not) increased with increasing SiO2 ratio. Finally, the LFN measurement method revealed that the cause of leakage current reduction was trap density reduction of the insulator.

Стилі APA, Harvard, Vancouver, ISO та ін.

36

Sun, Yong Ming, and Hang Sun. "Impact Analysis of the Flexural Rigidity on the Frequency and Tension of the Stay Cable." Key Engineering Materials 540 (January 2013): 153–63. http://dx.doi.org/10.4028/www.scientific.net/kem.540.153.

Повний текст джерела

Анотація:

Research and practice show that frequency method is still the most practical and accurate method among all kinds of cable force measurements. Based on the classical string vibration theory, the finite element model of stay cable was created, and a method of iteratively computing stay cable balance curve considering with flexural rigidity was proposed. How dose the flexural rigidity affects the balance curve of stay cable was discussed, and the changing curves of the distance-to-sagging ratio following the pull-to-bend ratio were plotted, which indicated the bigger flexural rigidity, the smaller sagging. 25 pairs cable modality of Xichang cable stayed bridge were accurately analyzed, mode crossover was testified by finite element method, changing curves of frequency and mode shape following the cable force were separately plotted, and changing rule was induced, practical cable force computing method was given. Frequency difference is suitable to judge the rank of actual measurement frequency, and the second frequency is recommended to compute cable force. Engineering instance analysis testified, the method of practical cable force measurement could rule out errors by mode crossover, and be applied to cable with any lengths and any force.

Стилі APA, Harvard, Vancouver, ISO та ін.

37

Atkishkin, Sergey F. "MODEL OF INSTANTANEOUS FREQUENCY MEASUREMENT RECEIVER WITH PRELIMINARY FREQUENCY MULTIPLICATION AND AUXILIARY CHANNEL BASED ON NONLINEAR SCATTERING PARAMETERS." T-Comm 15, no. 3 (2021): 40–49. http://dx.doi.org/10.36724/2072-8735-2021-15-3-40-49.

Повний текст джерела

Анотація:

The article deals with instantaneous frequency measurement (IFM) receiver model. Proposed receiver exploits preliminary frequency multiplication of input signal and auxiliary microwave detector channel. Article goal is investigation of microwave transfer coefficient irregularity compensation method. Another goal is investigation and reduction of measurement error sources. Research goals are reached by mathematical model construction and it further investigation. Mathematical model is based on the nonlinear large signal scattering parameters. Model demonstrates that preliminary frequency multiplication allows reduction of required group delay time of delay line. It is showed that measurement result affected by transfer coefficient irregularity, transfer coefficient instability of receiver chain elements and multiply reflected from irregularities waves. Auxiliary measurement channel and measurement function in the form of voltage ratio at basic channel detector and auxiliary channel detector provide a way to reduce influence of input signal amplitude, instabilities and irregularities of transfer coefficient on the frequency measurement result. It is showed that full reduction of aforementioned factors prevented by parasitic harmonics and multiply reflected waves. Required suppression level of parasitic harmonic are presented. Obtained results can find applications in sphere of electronic warfare and measurement theory and techniques.

Стилі APA, Harvard, Vancouver, ISO та ін.

38

Zhou, Xinhua, Tian Gao, Eugene S. Takle, Xiaojie Zhen, Andrew E. Suyker, Tala Awada, Jane Okalebo, and Jiaojun Zhu. "Air temperature equation derived from sonic temperature and water vapor mixing ratio for turbulent airflow sampled through closed-path eddy-covariance flux systems." Atmospheric Measurement Techniques 15, no. 1 (January 5, 2022): 95–115. http://dx.doi.org/10.5194/amt-15-95-2022.

Повний текст джерела

Анотація:

Abstract. Air temperature (T) plays a fundamental role in many aspects of the flux exchanges between the atmosphere and ecosystems. Additionally, knowing where (in relation to other essential measurements) and at what frequency T must be measured is critical to accurately describing such exchanges. In closed-path eddy-covariance (CPEC) flux systems, T can be computed from the sonic temperature (Ts) and water vapor mixing ratio that are measured by the fast-response sensors of a three-dimensional sonic anemometer and infrared CO2–H2O analyzer, respectively. T is then computed by use of either T=Ts1+0.51q-1, where q is specific humidity, or T=Ts1+0.32e/P-1, where e is water vapor pressure and P is atmospheric pressure. Converting q and e/P into the same water vapor mixing ratio analytically reveals the difference between these two equations. This difference in a CPEC system could reach ±0.18 K, bringing an uncertainty into the accuracy of T from both equations and raising the question of which equation is better. To clarify the uncertainty and to answer this question, the derivation of T equations in terms of Ts and H2O-related variables is thoroughly studied. The two equations above were developed with approximations; therefore, neither of their accuracies was evaluated, nor was the question answered. Based on first principles, this study derives the T equation in terms of Ts and the water vapor molar mixing ratio (χH2O) without any assumption and approximation. Thus, this equation inherently lacks error, and the accuracy in T from this equation (equation-computed T) depends solely on the measurement accuracies of Ts and χH2O. Based on current specifications for Ts and χH2O in the CPEC300 series, and given their maximized measurement uncertainties, the accuracy in equation-computed T is specified within ±1.01 K. This accuracy uncertainty is propagated mainly (±1.00 K) from the uncertainty in Ts measurements and a little (±0.02 K) from the uncertainty in χH2O measurements. An improvement in measurement technologies, particularly for Ts, would be a key to narrowing this accuracy range. Under normal sensor and weather conditions, the specified accuracy range is overestimated, and actual accuracy is better. Equation-computed T has a frequency response equivalent to high-frequency Ts and is insensitive to solar contamination during measurements. Synchronized at a temporal scale of the measurement frequency and matched at a spatial scale of measurement volume with all aerodynamic and thermodynamic variables, this T has advanced merits in boundary-layer meteorology and applied meteorology.

Стилі APA, Harvard, Vancouver, ISO та ін.

39

Clary, Jean, Louis-Philippe Nadeau, and Cédric Chavanne. "The Effect of Measurement Limitations on High-Frequency Radar-Derived Spectral Energy Fluxes." Journal of Atmospheric and Oceanic Technology 36, no. 11 (November 2019): 2139–52. http://dx.doi.org/10.1175/jtech-d-18-0237.1.

Повний текст джерела

Анотація:

AbstractThe ocean’s inverse cascade of energy from small to large scales has been confirmed from satellite altimetry for scales larger than 100 km. However, measurements of the direct energy cascade to smaller scales have remained difficult to obtain. Here, the possibility of estimating these energy transfers to smaller scales from observations by high-frequency radars is investigated using numerical simulations. Synthetic measurements are first extracted from a quasigeostrophic simulation of freely decaying turbulence for which the reference energy flux is characterized by the transition from positive to negative values. Fluxes obtained from synthetic data are compared to this reference flux in order to assess the robustness to various measurement limitations. The geometry of the observational domain (nonperiodicity, domain size, and aspect ratio) affects mostly large scales, while the spatial resolution of the instruments affects mostly small scales. In contrast, measurement noise and missing data affect both large and small scales. Despite resulting in significant biases in the amplitude of the fluxes, the transition scale between the positive and negative fluxes is relatively robust to measurement limitations. These results are also confirmed using a simulation from a primitive-equations model in a realistic coastal geometry.

Стилі APA, Harvard, Vancouver, ISO та ін.

40

Lesovoi, Sergey, and Mariia Globa. "Measurement of Siberian Radioheliograph cable delays." Solnechno-Zemnaya Fizika 7, no. 4 (December 20, 2021): 99–103. http://dx.doi.org/10.12737/szf-74202110.

Повний текст джерела

Анотація:

To achieve the maximum dynamic range of solar radio images obtained using aperture synthesis in relatively wide frequency bands 0.1−0.5 % of the operating frequency, it is necessary to compensate the signal propagation delays in the antenna receive path before calculating visibility functions (hereinafter visibilities). When visibilities are corrected without delay compensation, the signal-to-noise ratio decreases due to residual phase slopes in the receiving system bandwidth. In addition to enhancing dynamic range, preliminary compensation for delays simplifies real-time imaging — no antenna gain calibration is required to get a first approximation image. The requirements for the accuracy of antenna placement are also reduced — in contrast to the measurement of the phase visibility error, the measurement of the delay is actually not so critical to the antenna position errors that are larger than the operating wavelength. The instantaneous frequency band of the Siberian Radioheliograph, which determines the minimum step for measuring the phase slope, and hence the accuracy of determining the delay, is 10 MHz. At the speed of light in an optical fiber of ~0.7c, a step of 10 MHz makes it possible to unambiguously measure the difference between electrical lengths of cables up to 20 m and to correct antenna positions by radio observations, even if the error in the position of the antennas exceeds the operating wavelength. Correction of the band phase slopes during the observation time adapts the radio telescope to the temperature drift of delays and decreases antenna gain phase spread. This, in turn, leads to more stable solutions to systems of equations containing antenna gains as unknowns.

Стилі APA, Harvard, Vancouver, ISO та ін.

41

Vu, Thanh Tung, Hong Hai Hoang, Toan Thang Vu, and Ngoc Tam Bui. "A Displacement Measuring Interferometer Based on a Frequency-Locked Laser Diode with High Modulation Frequency." Applied Sciences 10, no. 8 (April 13, 2020): 2693. http://dx.doi.org/10.3390/app10082693.

Повний текст джерела

Анотація:

Laser interferometers can achieve a nanometer-order uncertainty of measurements when their frequencies are locked to the reference frequencies of the atom or molecule transitions. There are three types of displacement-measuring interferometers: homodyne, heterodyne, and frequency modulation (FM) interferometers. Among these types of interferometer, the FM interferometer has many advantageous features. The interference signal is a series of time-dependent harmonics of modulation frequency, so the phase shift can be detected accurately using the synchronous detection method. Moreover, the FM interferometer is the most suitable for combination with a frequency-locked laser because both require frequency modulation. In previous research, low modulation frequencies at some tens of kHz have been used to lock the frequency of laser diodes (LDs). The low modulation frequency for the laser source means that the maximum measurement speed of the FM interferometers is limited. This paper proposes a novel contribution regarding the application of a high-frequency modulation for an LD to improve both the frequency stability of the laser source and the measurement speed of the FM interferometer. The frequency of the LD was locked to an I2 hyperfine component at 1 MHz modulation frequency. A high bandwidth lock-in amplifier was utilized to detect the saturated absorption signals of the I2 hyperfine structure and induce the signal to lock the frequency of the LD. The locked LD was then used for an FM displacement measuring interferometer. Moreover, a suitable modulation amplitude that affected the signal-to-noise ratio of both the I2 absorption signal and the harmonic intensity of the interference signal was determined. In order to verify the measurement resolution of the proposed interferometer, the displacement induced by a piezo electric actuator was concurrently measured by the interferometer and a capacitive sensor. The difference of the displacement results was less than 20 nm. To evaluate the measurement speed, the interferometer was used to measure the axial error of a high-speed spindle at 500 rpm. The main conclusion of this study is that a stable displacement interferometer with high accuracy and a high measurement speed can be achieved using an LD frequency locked to an I2 hyperfine transition at a high modulation frequency.

Стилі APA, Harvard, Vancouver, ISO та ін.

42

Bratchenko, H. D., М. O. Koptielov, H. H. Smahliuk, and M. A. Martynov. "ACCURACY ESTIMATION OF MEASURING THE INSTANTANEOUS FREQUENCIES AND PHASES OF COMPONENTS OF THE MULTICOMPONENT NON-STATIONARY SIGNAL." Key title: Zbìrnik naukovih pracʹ Odesʹkoï deržavnoï akademìï tehnìčnogo regulûvannâ ta âkostì, no. 2(19) (2021): 48–62. http://dx.doi.org/10.32684/2412-5288-2021-2-19-48-62.

Повний текст джерела

Анотація:

Measurements of instantaneous frequencies and phases of non-stationary components of the multicomponent signals are actual in processing medical, radar, sonar, seismic, vibration, and speech signals. When we measure the parameters of multi-component non-stationary signals, it is a need to measure the instantaneous frequency and current phase of several non-stationary frequency-modulated signal components. In this article, estimates of the measurement accuracy of the specified parameters of the non-stationary signal components were obtained using the method of simulation modeling. Measurement methods based on the short-time Fourier transform and the proposed method with local adaptive matching filtering of signal components in the frequency domain in the time-sliding observation window were studied. Adjustment of matched filters is performed separately for each component of the signal, returning to the time domain and taking into account the filter settings in the previous time window. The simulation method is used for the signal model consisting of three components. The first two components are the frequency modulated harmonic ones and the last is harmonic with constant frequency. The amplitudes of components and additive Gaussian noise variance were variated to study the influence of signal-to-noise ratio on the accuracy of measurements. Estimates of the experimental standard deviation of instantaneous frequencies and current phase measurements were obtained by comparing them with their known dependencies. The frequency laws of non-stationary signal components were chosen to be harmonic, which also allowed us to evaluate the influence of the nonlinearity of the instantaneous frequency change on the measurement accuracy. The results of differential phase measurements between two measurement channels are obtained to illustrate the quality of such ones for multi-component non-stationary signals situations. The results of this study may be useful for the development of imaging methods in inverse synthetic aperture radars (ISAR) and interferometric ISAR.

Стилі APA, Harvard, Vancouver, ISO та ін.

43

Yang Yi, 杨奕, 孙青 Sun Qing, 邓玉强 Deng Yuqiang, 冯美琦 Feng Meiqi, and 赵昆 Zhao Kun. "Study on Beat Signal with High Signal-to-Noise Ratio in Terahertz Frequency Measurement." Chinese Journal of Lasers 44, no. 6 (2017): 0604006. http://dx.doi.org/10.3788/cjl201744.0604006.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

44

Ochiai, Hirokazu, and Yutaka Kaneda. "Impulse response measurement with constant signal-to-noise ratio over a wide frequency range." Acoustical Science and Technology 32, no. 2 (2011): 76–78. http://dx.doi.org/10.1250/ast.32.76.

Повний текст джерела

Стилі APA, Harvard, Vancouver, ISO та ін.

45

Hou, Pei Guo, Xiang Zheng Xiao, and Zhong Dong Wang. "Research on Measurement Method of Oil-Water Interface Based on Oscillation Frequency." Advanced Materials Research 317-319 (August 2011): 1026–30. http://dx.doi.org/10.4028/www.scientific.net/amr.317-319.1026.

Повний текст джерела

Анотація:

At the view of the present situation of the oil-water interface measurement, all sorts of measurement method can not eliminate the interference of temperature and hang oil. In order to control water ratio of purification oil at the output, simple interface detector cannot have satisfy the actual needs. A key contribution of this paper is to propose a solution based on a new type of sensor head and a test of new solution to the problem of capacitive sensing at high water ratio. A LC oscillation circuits is used to detect the variation of capacitance, overcoming the influence of the hang oil and the temperature.

Стилі APA, Harvard, Vancouver, ISO та ін.

46

Ishii, Shoken, Kohei Mizutani, Philippe Baron, Hironori Iwai, Ryoko Oda, Toshikazu Itabe, Hirotake Fukuoka та ін. "Partial CO2 Column-Averaged Dry-Air Mixing Ratio from Measurements by Coherent 2-μm Differential Absorption and Wind Lidar with Laser Frequency Offset Locking". Journal of Atmospheric and Oceanic Technology 29, № 9 (1 вересня 2012): 1169–81. http://dx.doi.org/10.1175/jtech-d-11-00180.1.

Повний текст джерела

Анотація:

Abstract A coherent 2-μm differential absorption and wind lidar (Co2DiaWiL) with a 2-μm single-frequency Q-switched laser with laser frequency offset locking was used for long-range CO2 measurement. The frequency stabilization of the single-frequency λ on pulsed laser was 1.0 MHz. Experimental horizontal CO2 measurement over a column range of 2.6–5.6 km and 900 shot pairs (1-min integration time) was conducted on 22 October 2009 to examine the detection sensitivity of the Co2DiaWiL. The achieved precision was less than 2.1%. The root-mean-square of the differences between the 30-min CO2 averages measured by the Co2DiaWiL and a ground-based in situ instrument was 0.9% (3.5 ppm). Experimental vertical CO2 measurements were conducted in February 2010 and January and February 2011. The partial CO2 column-averaged dry-air mixing ratios (XCO2) for an altitude between 0.4 and 1.0 km in 2010 and 2011 were 403.2 ± 4.2 and 405.6 ± 3.4 ppm, respectively. In the paper, the Co2DiaWiL results were well validated carefully against those of the airborne in situ instrument; they agreed well within the margin of error. The values of XCO2 measured in presence of cirrus clouds near the tropopause (hard target cases) show a difference of less than 4.1 ppm with the airborne measurements performed on 14 February 2010. This result demonstrates the capability of the Co2DiaWiL to measure XCO2 within a precision better than 1%.

Стилі APA, Harvard, Vancouver, ISO та ін.

47

Armstrong, M. A., M. Ravasio, W. G. Versteijlen, D. J. Verschuur, A. V. Metrikine, and K. N. van Dalen. "Seismic inversion of soil damping and stiffness using multichannel analysis of surface wave measurements in the marine environment." Geophysical Journal International 221, no. 2 (February 14, 2020): 1439–49. http://dx.doi.org/10.1093/gji/ggaa080.

Повний текст джерела

Анотація:

SUMMARY Determination of soil material damping is known to be difficult and uncertain, especially in the offshore environment. Using an advanced inversion methodology based on multichannel spectral analysis, Scholte and Love wave measurements are used to characterize subsea soil from a North Sea site. After normalization, a determinant-based objective function is used in a genetic algorithm optimization to estimate the soil shear modulus. The inverted shear-modulus profile is comparable to previously published results for the same data, although a higher degree of certainty is achieved in the near-surface layers. The half-power bandwidth method is used for extracting the attenuation curve from the measurements and efficient reference data points are chosen based on wavelet compression. The material-damping ratio inversion is performed using a modified stochastic optimization algorithm. Accounting for measurement errors, the material-damping ratio profile is retrieved from the fundamental-mode Scholte wave with a high degree of certainty. Furthermore, a method is proposed for identifying the frequency dependence of the material-damping ratio from in situ measurements. No evidence for frequency dependence is found and the small-strain soil material-damping ratio at this site can be said to be frequency independent for the measured conditions.

Стилі APA, Harvard, Vancouver, ISO та ін.

48

Gao, Cui Yun, Ming Liu, Wen Jing Li, and Ru Han. "Study of High Precision Frequency Measurement Method of Power System Based on DSP." Advanced Materials Research 403-408 (November 2011): 3030–34. http://dx.doi.org/10.4028/www.scientific.net/amr.403-408.3030.

Повний текст джерела

Анотація:

In the power systems, frequency is an important parameter for harmonic analysis. This paper proposes a modified high precision zero-crossing detection method. The high frequency noise will affect the power system’s frequency measurement, FIR processing is used for the power signal. Simulation shows that after effective De-noising or when the signal-to-noise ratio (SNR) is higher, the method can reach the precision of 0.01Hz and meet the requirements of frequency measurement precision.

Стилі APA, Harvard, Vancouver, ISO та ін.

49

Cheon, Song-I., Soon-Jae Kweon, Youngin Kim, Jimin Koo, Sohmyung Ha, and Minkyu Je. "An Impedance Readout IC with Ratio-Based Measurement Techniques for Electrical Impedance Spectroscopy." Sensors 22, no. 4 (February 17, 2022): 1563. http://dx.doi.org/10.3390/s22041563.

Повний текст джерела

Анотація:

This paper presents an error-tolerant and power-efficient impedance measurement scheme for bioimpedance acquisition. The proposed architecture measures the magnitude and the real part of the target complex impedance, unlike other impedance measurement architectures measuring either the real/imaginary components or the magnitude and phase. The phase information of the target impedance is obtained by using the ratio between the magnitude and the real components. This can allow for avoiding direct phase measurements, which require fast, power-hungry circuit blocks. A reference resistor is connected in series with the target impedance to compensate for the errors caused by the delay in the sinusoidal signal generator and the amplifier at the front. Moreover, an additional magnitude measurement path is connected to the reference resistor to cancel out the nonlinearity of the proposed system and enhance the settling speed of the low-pass filter by a ratio-based detection. Thanks to this ratio-based detection, the accuracy is enhanced by 30%, and the settling time is improved by 87.7% compared to the conventional single-path detection. The proposed integrated circuit consumes only 513 μW for a wide frequency range of 10 Hz to 1 MHz, with the maximum magnitude and phase errors of 0.3% and 2.1°, respectively.

Стилі APA, Harvard, Vancouver, ISO та ін.

50

Shin, Myoungin, Wooyoung Hong, Keunhwa Lee, and Youngmin Choo. "Frequency Analysis of Acoustic Data Using Multiple-Measurement Sparse Bayesian Learning." Sensors 21, no. 17 (August 30, 2021): 5827. http://dx.doi.org/10.3390/s21175827.

Повний текст джерела

Анотація:

Passive sonar systems are used to detect the acoustic signals that are radiated from marine objects (e.g., surface ships, submarines, etc.), and an accurate estimation of the frequency components is crucial to the target detection. In this paper, we introduce sparse Bayesian learning (SBL) for the frequency analysis after the corresponding linear system is established. Many algorithms, such as fast Fourier transform (FFT), estimate signal parameters via rotational invariance techniques (ESPRIT), and multiple signal classification (RMUSIC) has been proposed for frequency detection. However, these algorithms have limitations of low estimation resolution by insufficient signal length (FFT), required knowledge of the signal frequency component number, and performance degradation at low signal to noise ratio (ESPRIT and RMUSIC). The SBL, which reconstructs a sparse solution from the linear system using the Bayesian framework, has an advantage in frequency detection owing to high resolution from the solution sparsity. Furthermore, in order to improve the robustness of the SBL-based frequency analysis, we exploit multiple measurements over time and space domains that share common frequency components. We compare the estimation results from FFT, ESPRIT, RMUSIC, and SBL using synthetic data, which displays the superior performance of the SBL that has lower estimation errors with a higher recovery ratio. We also apply the SBL to the in-situ data with other schemes and the frequency components from the SBL are revealed as the most effective. In particular, the SBL estimation is remarkably enhanced by the multiple measurements from both space and time domains owing to remaining consistent signal frequency components while diminishing random noise frequency components.

Стилі APA, Harvard, Vancouver, ISO та ін.

Статті в журналах з теми "Frequency ratio measurement"

Оформте джерело за APA, MLA, Chicago, Harvard та іншими стилями