scholarly journals FASS: a turbulence profiler based on a fast, low-noise camera

2020 ◽  
Author(s):  
A Guesalaga ◽  
B Ayancán ◽  
M Sarazin ◽  
R W Wilson ◽  
S Perera ◽  
...  
Keyword(s):  
Power Spectra ◽  
Statistical Processing ◽  
Low Noise ◽  
Optical Turbulence ◽  
Angular Coordinate ◽  
Below Ground ◽  
Ground Distance ◽  
Measurement Campaigns ◽  
Good Agreement ◽  
Reference Functions

Abstract The measurement of the atmospheric optical turbulence with a new scintillation profiler is described and demonstrated. The instrument, FASS (Full Aperture Scintillation Sensor), uses new fast and low-noise detectors to record and process sequences of scintillation images. Statistical processing of these data is based on the calculation of power spectra of intensity in annular pupil zones over the angular coordinate. The angular power spectra are used to measure the optical turbulence intensity of 14 layers located at logarithmically-spaced distances from 0.3 km to 25 km. The reference functions relating turbulence strength to the angular power spectra are computed by numerical simulation. Measurement of the ground-later turbulence and total seeing with FASS is possible when the detector is conjugated to a negative (below ground) distance. Results of measurement campaigns at Paranal are reported, documenting a good agreement of turbulence profiles measured by FASS with two other instruments, SCIDAR and MASS.

Expert survey and analysis of the results

2019 ◽  
Vol 85 (7) ◽  
pp. 73-82
Author(s):  
Vladimir O. Tolcheev
Keyword(s):  
Data Analysis ◽  
Research University ◽  
Statistical Processing ◽  
Educational Process ◽  
Expert Survey ◽  
Educational Modules ◽  
Training Modules ◽  
Engineering Institute ◽  
Good Agreement ◽  
Statistical Criteria

The issues of organizing an expert survey and carrying out statistical processing and analysis of the results are considered. The experts are the fifth-year students undergoing training at the Department of Management and Informatics «Moscow Power Engineering Institute» of the National Research University. The goal of the survey is revealing the disciplines that are most useful for employment in their specialty. We discuss the special features of the survey and a concept of «work in the specialty», with due regard for statistical reliability of the results. Data of written questionnaire gained in 2018 were processed and analyzed using cluster analysis (construction of dendrograms and application of the K-means method) and non-parametric statistical criteria (Friedman and Mann – Whitney – Wilcoxon). Data processing is implemented in the program STATISTICA. The analysis is carried out to reveal significant differences between the educational courses and assess the degree of consistency of the respondents to divide them into clusters that unite the students with similar judgments. Data analysis revealed that experts’ estimates in 2018 are in fairly good agreement with the estimates of previous studies; among the respondents there are three coalitions corresponding to the training modules «Software», «Management Theory», «Data Analysis»; the overall consistency of students in the two groups is very low (and, on the contrary, high in the identified clusters); grades are homogeneous and do not depend on training groups (and employment – unemployment of the respondents). The obtained results allow us to address a number of important questions regarding the ways of improving the educational process, e.g., to optimize yearly course hours for different educational modules.

Numerical Calculation of Pressure Fluctuations in the Volute of a Centrifugal Fan

2005 ◽  
Vol 128 (2) ◽  
pp. 359-369 ◽  
Author(s):  
Rafael Ballesteros-Tajadura ◽  
Sandra Velarde-Suárez ◽  
Juan Pablo Hurtado-Cruz ◽  
Carlos Santolaria-Morros
Keyword(s):  
Fluid Dynamics ◽  
Pressure Fluctuations ◽  
Three Dimensional ◽  
Power Spectra ◽  
Operating Conditions ◽  
Experimental Results ◽  
Time Dependent ◽  
Centrifugal Fan ◽  
Wall Pressure Fluctuations ◽  
Good Agreement

In this work, a numerical model has been applied in order to obtain the wall pressure fluctuations at the volute of an industrial centrifugal fan. The numerical results have been compared to experimental results obtained in the same machine. A three-dimensional numerical simulation of the complete unsteady flow on the whole impeller-volute configuration has been carried out using the computational fluid dynamics code FLUENT®. This code has been employed to calculate the time-dependent pressure both in the impeller and in the volute. In this way, the pressure fluctuations in some locations over the volute wall have been obtained. The power spectra of these fluctuations have been obtained, showing an important peak at the blade passing frequency. The amplitude of this peak presents the highest values near the volute tongue, but the spatial pattern over the volute extension is different depending on the operating conditions. A good agreement has been found between the numerical and the experimental results.

scholarly journals A MULTI-BASELINE 12 GHz ATMOSPHERIC PHASE INTERFEROMETER WITH ONE MICRON PATH LENGTH SENSITIVITY

2012 ◽  
Vol 01 (01) ◽  
pp. 1250002 ◽  
Author(s):  
ROBERT S. KIMBERK ◽  
TODD R. HUNTER ◽  
PATRICK S. LEIKER ◽  
RAYMOND BLUNDELL ◽  
GEORGE U. NYSTROM ◽  
...  
Keyword(s):  
Path Length ◽  
Statistical Data ◽  
Ground Level ◽  
Low Noise ◽  
System Stability ◽  
Primary Data ◽  
Below Ground ◽  
Satellite Dish ◽  
Analog Correlator ◽  
Target Satellite

We have constructed a five station 12 GHz atmospheric phase interferometer (API) for the Submillimeter Array (SMA) located near the summit of Mauna Kea, Hawaii. Operating at the base of unoccupied SMA antenna pads, each station employs a commercial low noise mixing block coupled to a 0.7 m off-axis satellite dish which receives a broadband, white noise-like signal from a geostationary satellite. The signals are processed by an analog correlator to produce the phase delays between all pairs of stations with projected baselines ranging from 33–261 m. Each baseline's amplitude and phase is measured continuously at a rate of 8 kHz, processed, averaged and output at 10 Hz. Further signal processing and data reduction is accomplished with a Linux computer, including the removal of the diurnal motion of the target satellite. The placement of the stations below ground level with an environmental shield combined with the use of low temperature coefficient, buried fiber optic cables provides excellent system stability. The sensitivity in terms of rms path length is 1.3 microns which corresponds to phase deviations of about 1° of phase at the highest operating frequency of the SMA. The two primary data products are: (1) standard deviations of observed phase over various time scales, and (2) phase structure functions. These real-time statistical data measured by the API in the direction of the satellite provide an estimate of the phase front distortion experienced by the concurrent SMA astronomical observations. The API data also play an important role, along with the local opacity measurements and weather predictions, in helping to plan the scheduling of science observations on the telescope.

scholarly journals Optical turbulence and spectral condensate in long fibre lasers

2012 ◽  
Vol 468 (2145) ◽  
pp. 2496-2508 ◽  
Author(s):  
E. G. Turitsyna ◽  
Gregory Falkovich ◽  
Atalla El-Taher ◽  
Xuewen Shu ◽  
Paul Harper ◽  
...  
Keyword(s):  
Numerical Simulations ◽  
Intermediate State ◽  
Experimental Results ◽  
Fibre Laser ◽  
Optical Turbulence ◽  
Fibre Lasers ◽  
Sharp Transition ◽  
Narrow Spectrum ◽  
Good Agreement

We study numerically optical turbulence using the particular example of a recently created, ultra-long fibre laser. For normal fibre dispersion, we observed an intermediate state with an extremely narrow spectrum (condensate), which experiences instability and a sharp transition to a fluctuating regime with a wider spectrum. We demonstrate that the number of modes has an impact on the condensate's lifetime. The smaller the number of modes, the more resistant is the condensate to perturbations. Experimental results show a good agreement with numerical simulations.

Path Loss through Pine Forest around Beach for Wireless Sea Wave Energy Sensor Network

2012 ◽  
Vol 433-440 ◽  
pp. 3954-3958 ◽  
Author(s):  
Supachai Phaiboon ◽  
Supanuch Seesaiprai
Keyword(s):  
Sensor Network ◽  
Wave Energy ◽  
Path Loss ◽  
Low Noise ◽  
Loss Model ◽  
Path Loss Model ◽  
Proposed Model ◽  
Energy Sensor ◽  
Sea Wave ◽  
Good Agreement

This paper presents an empirical path loss model through forest for measuring sea wave energy using 2.4 GHz wireless sensor network (WSN). The empirical path loss model was determined from measurement campaign by using 18 dBm transmitter and the receivers with a low noise amplify. The conventional path loss models for forest environments were carried out such as Weissberger, ITU-R, COST 235 and Torrico models. From the results it is found that the proposed model provides a good agreement and is used for planning WSN.

Analytical Acoustic Power Spectrum Formulations for Rotating Monopole and Dipole Point Sources

2016 ◽  
Vol 138 (2) ◽  
Author(s):  
Yijun Mao ◽  
Chen Xu
Keyword(s):  
Power Spectrum ◽  
Power Spectra ◽  
Expansion Method ◽  
Acoustic Power ◽  
Point Sources ◽  
Harmonic Series ◽  
Dipole Source ◽  
Power Ratio ◽  
Good Agreement ◽  
Series Expansion Method

Analytical acoustic power spectrum formulations for the rotating monopole and dipole point sources are proposed by employing the spherical harmonic series expansion method. Both the analytical acoustic power spectra and the overall acoustic power show a good agreement with the results obtained from other methods. A nondimensional acoustic power ratio (APR) is employed to investigate the effects of the rotational Mach number, the direction of the dipole source, and the number of sources on the acoustic power output.

Low-noise, high-speed detector development for optical turbulence fluctuation measurements for NSTX

2010 ◽  
Vol 81 (10) ◽  
pp. 10D718 ◽  
Author(s):  
N. L. Schoenbeck ◽  
S. D. Ellington ◽  
R. J. Fonck ◽  
K. Jaehnig ◽  
G. R. McKee ◽  
...  
Keyword(s):  
High Speed ◽  
Low Noise ◽  
Optical Turbulence ◽  
Turbulence Fluctuation

S-Z POWER SPECTRA

2008 ◽  
Vol 23 (17n20) ◽  
pp. 1498-1505 ◽  
Author(s):  
YOEL REPHAELI ◽  
SHARON SADEH
Keyword(s):  
Standard Model ◽  
Dark Energy Model ◽  
Density Fluctuation ◽  
Power Spectra ◽  
Observational Evidence ◽  
Clusters Of Galaxies ◽  
The Standard Model ◽  
Non Gaussian ◽  
Cluster Abundance ◽  
Good Agreement

There is some observational evidence for earlier evolution of clusters of galaxies than predicted in the standard ΛCDM model with a Gaussian primordial density fluctuation field, and a low value for the mass variance parameter (σ8). Particularly difficult in this model is the interpretation of possible excess CMB anisotropy on cluster scales as due to the Sunyaev-Zeldovich (S-Z) effect. We have calculated S-Z power spectra in the standard model, and in two alternative models which predict higher cluster abundance - a model with non-Gaussian PDF, and an early dark energy model. As anticipated, the levels of S-Z power in the latter two models are significantly higher than in the standard model, and in good agreement with current measurements of CMB anisotropy at high multipole values. Our results provide a sufficient basis for testing the viability of the three models by future high quality measurements of cluster abundance and the anisotropy induced by the S-Z effect.

Electrophysiological properties of the tongue epithelium of the toad Bufo marinus

2002 ◽  
Vol 205 (13) ◽  
pp. 1943-1952
Author(s):  
Timothy K. Baker ◽  
Karina Rios ◽  
Stanley D. Hillyard
Keyword(s):  
Short Circuit ◽  
Power Spectra ◽  
Short Circuit Current ◽  
Low Noise ◽  
Bufo Marinus ◽  
K Channel ◽  
Fluctuation Analysis ◽  
Lingual Epithelium ◽  
Taste Cells ◽  
Toad Bufo

SUMMARY The dorsal lingual epithelium from the tongue of the toad Bufo marinus was mounted in an Ussing-type chamber, and the short-circuit current (Isc) was measured using a low-noise voltage clamp. With NaCl Ringer bathing the mucosal and serosal surfaces of the isolated tissue, an outwardly directed (mucosa-positive) Isc was measured that averaged -10.71±0.82 μA cm-2 (mean ± S.E.M., N=24) with a resistance of 615±152 Ω cm2 (mean ± S.E.M., N=10). Substitution of chloride with sulfate as the anion produced no significant change in Isc. Fluctuation analysis with either NaCl or Na2SO4 Ringer bathing both sides of the tissue revealed a spontaneous Lorentzian component, suggesting that the Isc was the result of K+ secretion through spontaneously fluctuating channels in the apical membrane of the epithelium. This hypothesis was supported by the reversible inhibition of Isc by Ba2+ added to the mucosal Ringer. Analysis of the kinetics of Ba2+ inhibition of Isc indicates that there might be more than one type of K+ channel carrying the Isc. This hypothesis was supported by power spectra obtained with a serosa-to-mucosa K+gradient, which could be fitted to two Lorentzian components. At present, the K+ secretory current cannot be localized to taste cells or other cells that might be associated with the secretion of saliva or mucus. Nonetheless, the resulting increase in [K+] in fluid bathing the mucosal surface of the tongue could presumably affect the sensitivity of the taste cells. These results contrast with those from the mammalian tongue, in which a mucosa-negative Isc results from amiloride-sensitive Na+ transport.

scholarly journals Imaging systematics and clustering of DESI main targets

2020 ◽  
Vol 496 (2) ◽  
pp. 2262-2291 ◽  
Author(s):  
Ellie Kitanidis ◽  
Martin White ◽  
Yu Feng ◽  
David Schlegel ◽  
Julien Guy ◽  
...  
Keyword(s):  
Power Spectra ◽  
Luminous Red Galaxies ◽  
Cross Correlations ◽  
Emission Line Galaxies ◽  
Using Data ◽  
Red Galaxies ◽  
The Impact ◽  
Stellar Density ◽  
North Galactic ◽  
Good Agreement

ABSTRACT We evaluate the impact of imaging systematics on the clustering of luminous red galaxies (LRG), emission-line galaxies (ELG), and quasars (QSO) targeted for the upcoming Dark Energy Spectroscopic Instrument (DESI) survey. Using Data Release 7 of the DECam Legacy Survey, we study the effects of astrophysical foregrounds, stellar contamination, differences between north galactic cap and south galactic cap measurements, and variations in imaging depth, stellar density, galactic extinction, seeing, airmass, sky brightness, and exposure time before presenting survey masks and weights to mitigate these effects. With our sanitized samples in hand, we conduct a preliminary analysis of the clustering amplitude and evolution of the DESI main targets. From measurements of the angular correlation functions, we determine power law fits $r_0 = 7.78 \pm 0.26\, h^{-1}$Mpc, γ = 1.98 ± 0.02 for LRGs and $r_0 = 5.45 \pm 0.1\, h^{-1}$Mpc, γ = 1.54 ± 0.01 for ELGs. Additionally, from the angular power spectra, we measure the linear biases and model the scale-dependent biases in the weakly non-linear regime. Both sets of clustering measurements show good agreement with survey requirements for LRGs and ELGs, attesting that these samples will enable DESI to achieve precise cosmological constraints. We also present clustering as a function of magnitude, use cross-correlations with external spectroscopy to infer dN/dz and measure clustering as a function of luminosity, and probe higher order clustering statistics through counts-in-cells moments.

Sign in / Sign up

Export Citation Format

Share Document