New Special Standards of the Frequency Deviation Unit and the Amplitude Modulation Coefficient Unit

2005 ◽  
Vol 48 (3) ◽  
pp. 260-262
Author(s):  
V. L. Ballo ◽  
V. B. Dobrovol’skii ◽  
A. V. Zen’kovich ◽  
V. A. Rekshinskii
Keyword(s):  
Amplitude Modulation ◽  
Frequency Deviation ◽  
Amplitude Modulation Coefficient ◽  
Modulation Coefficient

Amplitude modulation between multi-scale turbulent motions in high-Reynolds-number atmospheric surface layers

2018 ◽  
Vol 861 ◽  
pp. 585-607 ◽  
Author(s):  
Hongyou Liu ◽  
Guohua Wang ◽  
Xiaojing Zheng
Keyword(s):  
Reynolds Number ◽  
Surface Layer ◽  
Amplitude Modulation ◽  
High Reynolds Number ◽  
Quality Data ◽  
Modulation Effect ◽  
Multi Scale ◽  
Amplitude Modulation Coefficient ◽  
High Reynolds ◽  
Modulation Coefficient

Long-term measurements were performed at the Qingtu Lake Observation Array site to obtain high-Reynolds-number atmospheric surface layer flow data ($Re_{\unicode[STIX]{x1D70F}}\sim O(10^{6})$). Based on the selected high-quality data in the near-neutral surface layer, the amplitude modulation between multi-scale turbulent motions is investigated under various Reynolds number conditions. The results show that the amplitude modulation effect may exist in specific motions rather than at all length scales of motion. The most energetic motions with scales larger than the wavelength of the lower wavenumber peak in the energy spectra play a vital role in the amplitude modulation effect; the small scales shorter than the wavelength of the higher wavenumber peak are strongly modulated, whereas the motions with scales ranging between these two peaks neither contribute significantly to the amplitude modulation effect nor are strongly modulated. Based on these results, a method of decomposing the fluctuating velocity is proposed to accurately estimate the degree of amplitude modulation. The corresponding amplitude modulation coefficient is much larger than that estimated by establishing a nominal cutoff wavelength; moreover, it increases log-linearly with the Reynolds number. An empirical model is proposed to parametrize the variation of the amplitude modulation coefficient with the Reynolds number and the wall-normal distance. This study contributes to a better understanding of the interaction between multi-scale turbulent motions and the results may be used to validate and improve existing numerical models of high-Reynolds-number wall turbulence.

Nonlinear Finite Element Analysis on Statically Indeterminate Prestressed Concrete Beam

2012 ◽  
Vol 482-484 ◽  
pp. 647-650
Author(s):  
Shu Tian Fang ◽  
Ying Zhang ◽  
Wen Zhao Zhong
Keyword(s):  
Finite Element ◽  
Bearing Capacity ◽  
Amplitude Modulation ◽  
Prestressed Concrete ◽  
Concrete Beam ◽  
Bending Moment ◽  
Ultimate Bearing Capacity ◽  
Amplitude Modulation Coefficient ◽  
Modulation Coefficient ◽  
Limiting Value

Embarked from the ductility theory, the bending moment amplitude modulation limiting value ductility expression which satisfies the bearing capacity requirements have been deduced，on the value of the bending moment amplitude modulation coefficient, the influence of the using stage crack width limiting value has been considered, and the suggesting formula of the bending moment amplitude modulation coefficient has been proposed. With the aid of APDL language in the ANSYS, the entire process force analysis to statically indeterminate prestressed concrete beam has been carried on, the finite element computed result and the experiment result has been confirmed, through the example drew correlation curve, confirmed with the experiment, the beam's ultimate bearing capacity has been discussed, and the plastic hinge's formation and the influence of moment redistribution to the ultimate bearing capacity has been analyzed.

scholarly journals Research of metrological capabilities of digital (DDS- and Trueform-) generators

2021 ◽  
pp. 3-9
Author(s):  
Yurii Pavlenko ◽  
Sergii Kirienko ◽  
Valeriy Ogar ◽  
Olena Vаsileva
Keyword(s):  
Amplitude Modulation ◽  
Frequency Modulation ◽  
Nonlinear Distortion ◽  
Modulation Frequency ◽  
Frequency Deviation ◽  
Frequency Noise ◽  
Direct Digital Synthesis ◽  
Modulation Mode ◽  
Nonlinear Distortions ◽  
Digital Synthesis

Abstract One of the fundamental improvements of the measurement standard of frequency deviation of frequency-modulated oscillations was the replacement of analog frequency-modulated generators used in DETU 09-03-95 with digital ones based on the principle of direct digital synthesis (DDS) and its next version of Trueform technology. These generators have wider ranges of frequency deviation and modulation frequencies than analog ones, but nonlinear distortion laws of the frequency modulation are not standardized. The subject of the article is the development of methods and research of these generators and frequency-modulated signals generated by them for nonlinear distortions, accompanying amplitude modulation, frequency noise. Three methods were used in the study: direct measurement; “combination frequencies” and “frequency shift”. The experiment was performed using several measurement methods, which allowed to estimate very small values of nonlinear distortion. Methods were developed and experimental estimations of concomitant amplitude modulation of DDS-generators (in frequency modulation mode), as well as their frequency noise level, were performed. An experimental evaluation of the capabilities of the analog-digital demodulator of the R&S FSL6 spectrum analyzer with the K7 option was performed, its high linearity was shown, its capabilities with respect to the frequency ranges of carrier oscillations and frequency deviation were evaluated. The research results provide a basis for the method of calibration of DDS-generators and demodulator of spectrum analyzers with the K7 option in those ranges where their parameters are not normalized (at direct current up to 8 MHz and F up to 500 kHz).

Synthesis of 16 Quadrature Amplitude Modulation Using Polarization-Multiplexing QPSK Modulator

2011 ◽  
Vol E94-B (7) ◽  
pp. 1809-1814 ◽  
Author(s):  
Isao MOROHASHI ◽  
Takahide SAKAMOTO ◽  
Masaaki SUDO ◽  
Atsushi KANNO ◽  
Akito CHIBA ◽  
...  
Keyword(s):  
Amplitude Modulation ◽  
Quadrature Amplitude Modulation ◽  
Polarization Multiplexing
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