Concentration Fluctuation Spectra in Turbulent Slurry Pipeline Flow

1989 ◽  
Vol 111 (3) ◽  
pp. 317-323 ◽  
Author(s):  
R. J. Sumner ◽  
C. A. Shook ◽  
M. C. Roco
Keyword(s):  
Cross Section ◽  
Electrical Resistance ◽  
High Frequency ◽  
Particle Diameter ◽  
Low Frequency ◽  
Frequency Spectra ◽  
Concentration Time ◽  
Solids Concentration ◽  
Slurry Flows ◽  
Effective Domain

Using probes responding to changes of slurry electrical resistance with concentration, time spectra of longitudinal concentration fluctuations in turbulent slurry flows have been measured. The sensors, with an effective domain approximately 1 mm in diameter, showed the spectra to be relatively insensitive to location within the pipe cross section. High frequency spectra were found to be relatively insensitive to slurry concentration and particle diameter. Low frequency spectra showed fluctuation amplitudes which increased with solids concentration.

Two-week normobaric intermittent hypoxia exposures enhance oxyhemoglobin equilibrium and cardiac responses during hypoxemia

2014 ◽  
Vol 307 (6) ◽  
pp. R721-R730 ◽  
Author(s):  
Peizhen Zhang ◽  
H. Fred Downey ◽  
Shande Chen ◽  
Xiangrong Shi
Keyword(s):  
High Frequency ◽  
Respiratory Function ◽  
Intermittent Hypoxia ◽  
Low Frequency ◽  
Frequency Spectra ◽  
Rightward Shift ◽  
Cardiac Responses ◽  
Arterial Blood ◽  
Equilibrium Response ◽  
End Tidal

Intermittent hypoxia (IH) is extensively applied to challenge cardiovascular and respiratory function, and to induce physiological acclimatization. The purpose of this study was to test the hypothesis that oxyhemoglobin equilibrium and tachycardiac responses during hypoxemia were enhanced after 14-day IH exposures. Normobaric-poikilocapnic hypoxia was induced with inhalation of 10% O2 for 5–6 min interspersed with 4 min recovery on eight nonsmokers. Heart rate (HR), arterial O2 saturation (SaO2), and end-tidal O2 (PetO2) were continuously monitored during cyclic normoxia and hypoxia. These variables were compared during the first and fifth hypoxic bouts between day 1 and day 14. There was a rightward shift in the oxyhemoglobin equilibrium response following 14-day IH exposures, as indicated by the greater PetO2 (an index of arterial Po2) at 50% of SaO2 on day 14 compared with day 1 [33.9 ± 1.5 vs. 28.2 ± 1.3 mmHg ( P = 0.005) during the first hypoxic bout and 39.4 ± 2.4 vs. 31.4 ± 1.5 mmHg ( P = 0.006) during the fifth hypoxic bout] and by the augmented gains of ΔSaO2/ΔPetO2 (i.e., deoxygenation) during PetO2 from 65 to 40 mmHg in the first (1.12 ± 0.08 vs. 0.80 ± 0.02%/mmHg, P = 0.001) and the fifth (1.76 ± 0.31 vs. 1.05 ± 0.06%/mmHg, P = 0.024) hypoxic bouts. Repetitive IH exposures attenuated ( P = 0.049) the tachycardiac response to hypoxia while significantly enhancing normoxic R-R interval variability in low-frequency and high-frequency spectra without changes in arterial blood pressure at rest or during hypoxia. We conclude that 14-day IH exposures enhance arterial O2 delivery and improve vagal control of HR during hypoxic hypoxemia.

scholarly journals Effects of Multiconstituent Tides on a Subterranean Estuary With Fixed-Head Inland Boundary

2021 ◽  
Vol 8 ◽  
Author(s):  
Xiayang Yu ◽  
Pei Xin ◽  
Chengji Shen ◽  
Ling Li
Keyword(s):  
Coastal Aquifers ◽  
Functional Data ◽  
High Frequency ◽  
Submarine Groundwater Discharge ◽  
Low Frequency ◽  
Freshwater Input ◽  
Frequency Spectra ◽  
Subterranean Estuary ◽  
Unconfined Aquifers ◽  
Tidal Constituents

While tides of multiple constituents are common in coastal areas, their effects on submarine groundwater discharge (SGD) and salinity distributions in unconfined coastal aquifers are rarely examined, with the exception of a recent study that explored such effects on unconfined aquifers with fixed inland freshwater input. For a large proportion of the global coastline, the inland areas of coastal aquifers are topography-limited and controlled by constant heads. Based on numerical simulations, this article examines the variation of SGD and salinity distributions in coastal unconfined aquifers with fixed-head inland boundaries at different distances from the shoreline (i.e., 50, 100, 150, and 200 m). The results showed that the fluctuation intensity of freshwater input was enhanced as the inland aquifer extent decreased, e.g., the range of tide-induced fluctuations in freshwater input increased by around 5 times as the inland aquifer extent decreased from 200 to 50 m. The frequency spectra of the fluctuations of SGD and salinity distributions showed that the coastal aquifer of a shorter inland aquifer extent smoothed out fewer high-frequency tidal constituents but enhanced interaction among different tidal constituents. The interaction among tidal constituents generated new low-frequency signals in the freshwater input and salinity distributions. Regressions based on functional data analysis demonstrated that the inland freshwater input and salinity distributions at any given moment were related to the antecedent (previous) tidal conditions weighted using the probability density function of the Gamma distribution. The influence of the antecedent tidal conditions depended on the inland aquifer extent.

scholarly journals How well are FREQUENCY SENSITIVITIES OF grasshopper ears tuned to species-specific song spectra?

1996 ◽  
Vol 199 (7) ◽  
pp. 1631-1642
Author(s):  
J Meyer ◽  
N Elsner
Keyword(s):  
High Frequency ◽  
Broad Band ◽  
Low Frequency ◽  
Attachment Site ◽  
The Body ◽  
Frequency Range ◽  
Frequency Spectra ◽  
Interspecific Differences ◽  
Tympanal Membrane ◽  
Species Specific

Grasshoppers of 20 acridid species were examined using spectral analysis, laser vibrometry and electrophysiology to determine whether the song spectra, the best frequencies of tympanal-membrane vibrations and the threshold curves of the tympanal nerves are adapted to one another. The songs of almost all species have a relatively broad-band maximum in the region between 20 and 40 kHz and a narrower peak between 5 and 15 kHz. There are clear interspecific differences in the latter, which are not correlated with the length of the body or of the elytra. At the site of attachment of the low-frequency receptors (a-cells), the tympanal membrane oscillates with maximal amplitude in the region from 5 to 10 kHz. At the attachment site of the high-frequency receptors (d-cells), there is also a maximum in this region as well as another around 15-20 kHz. The tympanal nerve is most sensitive to tones between 5 and 10 kHz, with another sensitivity maximum between 25 and 35 kHz. The species may differ from one another in the position of the low-frequency peaks of the membrane oscillation, of the nerve activity and of the song spectra. No correlation was found between the characteristic frequency of the membrane oscillation and the area of the tympanal membrane. Within a given species, the frequency for maximal oscillation of the membrane at the attachment site of the low-frequency receptors and the frequency for maximal sensitivity of the tympanal nerve are in most cases very close to the low-frequency peak in the song spectrum. In the high-frequency range, the situation is different: here, the position of the peak in the song spectrum is not correlated with the membrane oscillation maximum at the attachment site of the high-frequency receptors, although there is a correlation between the song spectrum and the sensitivity of the tympanal nerve. On the whole, therefore, hearing in acridid grasshoppers is quite well adjusted to the frequency spectra of the songs, partly because the tympanal membrane acts as a frequency filter in the low-frequency range.

Energy Transfer From High-to Low-Frequency Modes in a Flexible Structure via Modulation

1994 ◽  
Vol 116 (2) ◽  
pp. 203-207 ◽  
Author(s):  
S. A. Nayfeh ◽  
A. H. Nayfeh
Keyword(s):  
Cross Section ◽  
High Frequency ◽  
Natural Frequencies ◽  
Circular Cross Section ◽  
Low Frequency ◽  
Cantilever Beams ◽  
Axially Symmetric ◽  
Internal Resonances ◽  
Planar Motions ◽  
High Frequency Modes

An experimental study of the response of axially-symmetric (i.e., circular cross-section) cantilever beams to planar external excitations is presented. Because of the axial symmetry, one-to-one internal resonances occur at each natural frequency. These resonances cause the planar motions to lose stability and nonplanar (whirling) motions are observed. Under certain conditions, periodically-and chaotically-modulated motions may occur. In addition, when the beam is excited near one of its high natural frequencies, large first-mode responses accompanied by slow modulations of the amplitudes and phases of high-frequency modes are observed. This interaction between high-and low-frequency modes may be extremely dangerous because the amplitudes of the responses of the low-frequency modes can be very large compared with those of the directly excited high-frequency modes.

scholarly journals Uneven distribution of Y-chromosome haplogroups in the regional populations of ukrainians

2018 ◽  
Vol 23 ◽  
pp. 232-237
Author(s):  
O. M. Utevska ◽  
L. A. Atramentova
Keyword(s):  
Y Chromosome ◽  
Frequency Distribution ◽  
High Frequency ◽  
Gene Pool ◽  
Low Frequency ◽  
Snp Markers ◽  
Uneven Distribution ◽  
Haplogroup Frequency ◽  
Frequency Spectra

Aim. The aim was to compare the frequency spectra of Y chro mosome haplogroups among Ukrainians from different regions, identify atypical populations and determine their characteristics. Methods. A sample of Ukrainians (n = 1141) from 12 regions of Ukraine was investigated. DNA samples were genotyped by the SNP markers of the Y chromosome. The frequencies of Y chromosome haplogroups for the regions were compared using the χ2 and F tests. Results. Differences between regions in the haplogroup frequency distribution were determined, atypical populations were detected, and the features of their Y-chromosome spectrum were studied. Conclusions. Lviv and Rivne samples were the closest to frequencies of Y-chromosome haplogroups averaged for Ukraine. The highest specificity was found in samples from Khmelnitska (R-M198(×M458) high frequency, R-M458 low frequency), Zaporozhska (E-M78 absence) and Chernigov (R-M458 high frequency, R-M198(×M458) low frequency) regions. Keywords: Y-chromosome, haplogroup, Ukrainians, gene pool.

Scaling Behavior Of Dynamic Permeability In Porous Media

1988 ◽  
Vol 137 ◽  
Author(s):  
Ping Sheng ◽  
Min-Yao Zhou ◽  
E. Charlaix ◽  
A. Kushnick ◽  
J. P. Stokes
Keyword(s):  
Cross Section ◽  
High Frequency ◽  
Low Frequency ◽  
Universal Function ◽  
The Other ◽  
Formation Factor ◽  
Geometric Information ◽  
Cross Sectional ◽  
Dynamic Permeability ◽  
Dimensionless Function

AbstractWe show that the scaling of the dynamic permeability κ(ω) by its static value κ0 and the frequency ω by a characteristic frequency ω0 particular to the medium results in a dimensionless function , with , which is dominated by the geometry of the throat regions in a porous medium. If the pore cross sectional area S varies slowly near the throat, i.e. dS/dz ≃ 0 where z is the distance normal to the cross section, then is an approximate universal function independent of microstructures. When scaling holds, the dynamic permeability κ(ω) is shown to contain only two pieces of geometric information, and the knowledge of either the low-frequency or the high-frequency asymptotic constants of κ(ω) would enable one to deduce the other missing parameters. In particular, since the high-frequency asymptotic parameters of κ(ω) can be related to the electrical formation factor and the volume-to-surface ratio, the static permeability value κ0 may be directly deduced from such non-permeability measurements.

scholarly journals Динамика магнитных скирмионов в наноточках

2018 ◽  
Vol 60 (6) ◽  
pp. 1135
Author(s):  
З.В. Гареева ◽  
К.Ю. Гуслиенко
Keyword(s):  
Ultrathin Films ◽  
High Frequency ◽  
Linear Array ◽  
Linear Chain ◽  
Low Frequency ◽  
Characteristic Difference ◽  
Frequency Spectra ◽  
High Frequency Excitation ◽  
Frequency Excitation ◽  
Magnetic Skyrmions

AbstractBloch and Neel magnetic skyrmions have been studied in systems of confined geometry (nanodots, a linear array of nanodots). The spectra of low- and high-frequency excitation modes of a skyrmion state have been calculated. It has been shown that skyrmion spectrum asymmetry, namely, the characteristic difference between the frequencies of the azimuthal modes of the azimuthal skyrmion modes rotating clockwise and counterclockwise, is associated with asymmetry in the magnetization profiles of high-frequency spin waves propagating on the background of a skyrmion state in a nanodot. The low-frequency spectrum contains the only gyrotropic mode localized near the center of a nanodot. The gyrotropic frequency depends on the material parameters of a nanodot and the size of a skyrmion. The eigenfrequency of the gyrotropic mode of an isolated skyrmion in a nanodot in ultrathin films ( L ~ 1 nm) does not depend on the internal structure of a skyrmion and is the same for Bloch and Neel skyrmions. The interaction of skyrmions, in particular, in a linear chain of nanodots with the ground skyrmion state, leads to distinctions in low-frequency spectra. The structure of a skyrmion (of Bloch or Neel type) is exhibited as a shift of dispersion curves and a difference between the frequencies of ferromagnetic resonance in a system of interacting skyrmions.

Incidence of Internal Decay in American Elms (Ulmus americana) Under Regular Fungicide Injection to Manage Dutch Elm Disease

2020 ◽  
Vol 46 (1) ◽  
pp. 1-11
Author(s):  
Nicholas Brazee ◽  
Robert Marra
Keyword(s):  
Cross Section ◽  
Electrical Resistance ◽  
Low Frequency ◽  
Dutch Elm Disease ◽  
Chi Square ◽  
Ulmus Americana ◽  
Lower Trunk ◽  
Decay Class ◽  
The Cross ◽  
Chi Square Analysis

Fungicide injection is regularly performed to prevent and manage Dutch elm disease (DED) of American elm (Ulmus americana). In an effort to better understand the effects of long-term fungicide injection on tree health, sonic tomography (SoT) and electrical-resistance tomography (ERT) were used to nondestructively determine the incidence and severity of internal decay in the lower trunk of American elms in suburban and urban settings. Overall, 253 sonic and electrical-resistance tomograms were generated from 210 American elms. Sampled trees were partitioned into two fungicide injection groups: (1) regular injection; and (2) irregular injection or no known history of injection. Among all American elms, the incidence of internal decay in the lower trunk was 30% (63/210) with a mean percent decay, as determined by SoT, of 39%. Based on Chi-square analysis, there were no significant differences in the frequency of elms with decay by injection history (P = 0.799). Mean percent decay was significantly different by dbh class (P = 0.005) and while linear regression demonstrated a positive correlation between percent decay and dbh, most of the variability went unexplained (R2 = 0.182). For elms with decay, there was a significantly higher frequency of trees in the lowest decay class (< 25% of the cross section) compared to the highest decay class (> 75% of the cross section). The results suggest that the wounding associated with regular fungicide injection does not increase the likelihood of internal decay and that American elms exhibit a low frequency and severity of internal decay.

Simulations of high-resolution images of amorphous silicon films

1986 ◽  
Vol 44 ◽  
pp. 544-545
Author(s):  
G. Y. Fan ◽  
J. M. Cowley
Keyword(s):  
Electron Microscope ◽  
High Frequency ◽  
Fourier Transformation ◽  
Amorphous Materials ◽  
Low Frequency ◽  
Chromatic Aberration ◽  
Structure Information ◽  
Frequency Components ◽  
High Resolution Images ◽  
Spatial Frequency Spectrum

It is well known that the structure information on the specimen is not always faithfully transferred through the electron microscope. Firstly, the spatial frequency spectrum is modulated by the transfer function (TF) at the focal plane. Secondly, the spectrum suffers high frequency cut-off by the aperture (or effectively damping terms such as chromatic aberration). While these do not have essential effect on imaging crystal periodicity as long as the low order Bragg spots are inside the aperture, although the contrast may be reversed, they may change the appearance of images of amorphous materials completely. Because the spectrum of amorphous materials is continuous, modulation of it emphasizes some components while weakening others. Especially the cut-off of high frequency components, which contribute to amorphous image just as strongly as low frequency components can have a fundamental effect. This can be illustrated through computer simulation. Imaging of a whitenoise object with an electron microscope without TF limitation gives Fig. 1a, which is obtained by Fourier transformation of a constant amplitude combined with random phases generated by computer.

SEM image sharpness analysis

1996 ◽  
Vol 54 ◽  
pp. 142-143
Author(s):  
M. T. Postek ◽  
A. E. Vladar
Keyword(s):  
High Frequency ◽  
Low Frequency ◽  
Quantitative Information ◽  
Primary Electron ◽  
Image Sharpness ◽  
Critical Dimensions ◽  
Sem Image ◽  
Frequency Changes ◽  
Electron Microscopes ◽  
Scanning Electron

Fully automated or semi-automated scanning electron microscopes (SEM) are now commonly used in semiconductor production and other forms of manufacturing. The industry requires that an automated instrument must be routinely capable of 5 nm resolution (or better) at 1.0 kV accelerating voltage for the measurement of nominal 0.25-0.35 micrometer semiconductor critical dimensions. Testing and proving that the instrument is performing at this level on a day-by-day basis is an industry need and concern which has been the object of a study at NIST and the fundamentals and results are discussed in this paper.In scanning electron microscopy, two of the most important instrument parameters are the size and shape of the primary electron beam and any image taken in a scanning electron microscope is the result of the sample and electron probe interaction. The low frequency changes in the video signal, collected from the sample, contains information about the larger features and the high frequency changes carry information of finer details. The sharper the image, the larger the number of high frequency components making up that image. Fast Fourier Transform (FFT) analysis of an SEM image can be employed to provide qualitiative and ultimately quantitative information regarding the SEM image quality.

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