scholarly journals Synoptic-Eddy Feedbacks and Circulation Regime Analysis

2010 ◽  
Vol 138 (11) ◽  
pp. 4026-4034 ◽  
Author(s):  
David M. Straus
Keyword(s):  
Cluster Analysis ◽  
High Frequency ◽  
Low Frequency ◽  
Boreal Winter ◽  
Maximum Covariance Analysis ◽  
The Pacific ◽  
Synoptic Eddies ◽  
Synthetic Datasets ◽  
Definition Of ◽  
Environmental Prediction

Abstract A method to incorporate synoptic eddies into the diagnosis of circulation regimes using cluster analysis is illustrated using boreal winter reanalyses of the National Centers of Environmental Prediction (hereafter observations) over the Pacific–North American region. The motivation is to include the configuration of the high-frequency (periods less than 10 days) transients as well as the low-frequency (periods greater than 10 days) flow explicitly into the definition of the regimes. Principle component analysis is applied to the low-frequency 200-hPa height field, and also to the low-frequency “envelope” modulations of the rms of high-frequency meridional velocity at 200 hPa. A maximum covariance analysis of the height and envelope fields, carried out using the appropriate principal components, defines three modes as explaining most of the covariance. This defines the minimum dimensionality of the space in which to apply k-means cluster analysis to the covariance coefficients. Clusters found using this method agree with results of the previous work. Significance is assessed by comparing cluster analyses with results from synthetic datasets that have the same spectral amplitudes (but random phases) of seasonal means and, separately, intraseasonal fluctuations as do the original observed time series. This procedure ensures that the synthetic series have similar autocovariance structures to the observations. Building on earlier work, the clusters obtained are newly tested to be highly significant without the need for quasi-stationary prefiltering.

Moored Observations of Currents and Water Mass Properties between Talaud and Halmahera Islands at the Entrance of the Indonesian Seas

2021 ◽  
Vol 51 (12) ◽  
pp. 3557-3572
Keyword(s):  
Water Mass ◽  
Low Frequency ◽  
Maximum Velocity ◽  
Boreal Winter ◽  
Indonesian Seas ◽  
Seasonal Movement ◽  
Tropical Water ◽  
The Pacific ◽  
Mass Properties ◽  
Channel Velocity

AbstractThe currents and water mass properties at the Pacific entrance of the Indonesian seas are studied using measurements of three subsurface moorings deployed between the Talaud and Halmahera Islands. The moored current meter data show northeastward mean currents toward the Pacific Ocean in the upper 400 m during the nearly 2-yr mooring period, with the maximum velocity in the northern part of the channel. The mean transport between 60- and 300-m depths is estimated to be 10.1–13.2 Sv (1 Sv ≡ 106 m3 s−1) during 2016–17, when all three moorings have measurements. The variability of the along-channel velocity is dominated by low-frequency signals (periods > 150 days), with northeastward variations in boreal winter and southwestward variations in summer in the superposition of the annual and semiannual harmonics. The current variations evidence the seasonal movement of the Mindanao Current retroflection, which is supported by satellite sea level and ocean color data, showing a cyclonic intrusion into the northern Maluku Sea in boreal winter whereas a leaping path occurs north of the Talaud Islands in summer. During Apri–July, the moored CTDs near 200 m show southwestward currents carrying the salty South Pacific Tropical Water into the Maluku Sea.

scholarly journals Analysis of the ground vibration generated by debris flows and other torrential processes at the Rebaixader monitoring site (Central Pyrenees, Spain)

2014 ◽  
Vol 14 (4) ◽  
pp. 929-943 ◽  
Author(s):  
C. Abancó ◽  
M. Hürlimann ◽  
J. Moya
Keyword(s):  
High Frequency ◽  
Debris Flows ◽  
Low Frequency ◽  
Ground Vibration ◽  
Monitoring Site ◽  
Velocity Signal ◽  
Vibration Sensors ◽  
Definition Of ◽  
Flow Detection ◽  
Central Pyrenees

Abstract. Monitoring of debris flows using ground vibration sensors has increased in the last two decades. However, the correct interpretation of the signals still presents ambiguity. In the Rebaixader monitoring site (Central Pyrenees, Spain) two different ground vibration stations are installed. At the first station the ground velocity signal is transformed into an impulses-per-second signal (low frequency, 1 Hz). The analysis of the data recorded at this station show that the shape of the impulses signal is one of the key parameters to describe the evolution of the event. At the second station the ground velocity signal is directly recorded at high frequency (250 Hz). The results achieved at this station show that the differences in time series and spectral analysis are helpful to describe the temporal evolution of the events. In addition, some general outcomes were obtained: the attenuation of the signal with the distance has been identified as linear to exponential; and the assembly of the geophones to the terrain has an important effect on the amplification of the signal. All these results highlight that the definition of ground vibration thresholds for debris-flow detection or warning purposes is a difficult task; and that influence of site-specific conditions is notable.

scholarly journals What Caused The Increase of Tropical Cyclones In The Western North Pacific During The Period of 2011-2020?

2021 ◽  
Author(s):  
Haili Wang ◽  
Chunzai Wang
Keyword(s):  
Tropical Cyclones ◽  
North Pacific ◽  
High Frequency ◽  
Western North Pacific ◽  
Large Scale ◽  
Low Frequency ◽  
Vertical Wind Shear ◽  
Significant Negative Correlation ◽  
Relative Vorticity ◽  
The Pacific

Abstract Based on satellite era data after 1979, we find that the tropical cyclone (TC) variations in the Western North Pacific (WNP) can be divided into three-periods: a high-frequency period from 1979-1997 (P1), a low-frequency period from 1998-2010 (P2), and a high-frequency period from 2011-2020 (P3). Previous studies have focused on WNP TC activity during P1 and P2. Here we use observational data to study the WNP TC variation and its possible mechanisms during P3. Compared with P2, more TCs during P3 are due to the large-scale atmospheric environmental conditions of positive relative vorticity, negative vertical velocity and weak vertical wind shear. Warmer SST is found during P3, which is favorable for TC genesis. The correlation between the WNP TC frequency and SST shows a significant positive correlation around the equator and a significant negative correlation around 36°N, which is similar to the warm phase of the Pacific Decadal Oscillation (PDO). The correlation coefficient between the PDO and TC frequency is 0.71, significant at 99% confidence level. The results indicate that the increase of the WNP TC frequency during 2011-2020 is associated with the phase transition of the PDO and warmer SST. Therefore, more attention should be given to the warmer SST and PDO phase when predicting WNP TC activity.

scholarly journals RESEARCH OF THE INFLUENCE OF LOW-FREQUENCY AND HIGH-FREQUENCY ACTIONS ON PROCESSING OF TECHNOLOGICAL ENVIRONMENTS

2018 ◽  
Vol 1 ◽  
pp. 73-86
Author(s):  
Ivan Nazarenko ◽  
Oleksandr Luhovskyi ◽  
Iryna Bernyk ◽  
Anatoly Svіdersky
Keyword(s):  
Material Processing ◽  
High Frequency ◽  
Low Frequency ◽  
Viscous Friction ◽  
Technological Parameters ◽  
Acoustic Action ◽  
Technological Environment ◽  
Low Frequencies ◽  
Frictional Forces ◽  
Definition Of

The processing of various vibrational low-frequency and cavitation high-frequency actions by their rheological properties is studied. A mathematical model of the motion of particles of a technological environment is determined taking into account the different nature of the dissipative forces. Two kinds of frictional forces are applied: dry at the first stage of changing the constituents of the mixture and viscous at the second, final stage of compaction of the mixture. The obtained analytical dependencies reveal the physical picture of the behavior of particles and the technological environment as a whole. The key stages of compaction to account for dry and viscous friction between the components of materials are described. It is revealed that processing at low frequencies reduces energy costs. Taking into account in vibroacoustic processes the contribution of higher harmonics greatly accelerates the process of cavitation. This is a fundamentally new result and the idea of the possibility of obtaining an effect for creating new materials. The obtained amplitudes and frequencies of oscillations of both low-frequency and high-frequency modes open a new direction in technologies for improving the quality of material processing. The main modes and parameters of vibrational and acoustic action for effective implementation of material processing processes are determined. The obtained results are applied at definition of rheological and technological parameters at various stages of processing of materials. The basic directions of quality improvement of processing environments are formulated.

Adjective Definitions and the Influence of Word Frequency

2003 ◽  
Vol 46 (5) ◽  
pp. 1061-1076 ◽  
Author(s):  
Sally A. Marinellie ◽  
Cynthia J. Johnson
Keyword(s):  
Young Adults ◽  
Word Frequency ◽  
High Frequency ◽  
Low Frequency ◽  
Semantic Content ◽  
Response Patterns ◽  
Age Group ◽  
Conventional Form ◽  
Syntactic Form ◽  
Definition Of

The present investigation is a study of the development of adjective definitions given by participants in Grades 6 and 10 and by young adults, as well as the influence of word frequency on those definitions. A total of 150 participants (50 per age group) wrote definitions for 6 high-frequency and 6 low-frequency adjectives. Adjective definitions were analyzed for use of semantic content and also grammatical form. Findings indicated that content of adjective definitions generally followed a developmental course from concrete and functional to more abstract. Response patterns of certain categories, such as superordinate, have implications for organization of the mental lexicon and suggest that adjective definitions may be less predictable than definitions of other grammatical categories, such as noun. Although conventional syntactic form was highly used in definitions (i.e., adjectival form for a definition of an adjective), verb form was also highly used. Conventional form may be less useful to characterize adjective definitions than other grammatical classes. Findings suggest that word frequency has a robust influence on adjective definitions and that development progresses differently for high- and low-frequency words.

scholarly journals Roles of Low- and High-Frequency Eddies in the Transitional Process of the Southern Hemisphere Annular Mode

2005 ◽  
Vol 18 (6) ◽  
pp. 782-794 ◽  
Author(s):  
Hideo Shiogama ◽  
Toru Terao ◽  
Hideji Kida ◽  
Tatsuya Iwashima
Keyword(s):  
Pacific Ocean ◽  
Southern Hemisphere ◽  
High Frequency ◽  
Momentum Flux ◽  
Rossby Waves ◽  
Low Frequency ◽  
Wave Activity ◽  
Transitional Process ◽  
The Pacific ◽  
The Pacific Ocean

Abstract The effects of low- and high-frequency eddies (time scales longer and shorter than 10 days, respectively) on the transitional processes of the Southern Hemisphere “Annular Mode” are investigated, based on NCEP–NCAR daily reanalysis data for the period 1979–2001. Special attention is focused on the zonal symmetry/asymmetry and the temporal evolution of the eddy forcing. For the poleward transitional process, the effects of low-frequency eddies precede those of high-frequency eddies in driving the jet transition. Quasi-stationary Rossby waves propagating along the polar jet with wavelengths of 7000 km play an important role. The waves, originally come from the Indian Ocean through the waveguide associated with the polar jet, dissipate equatorward over the eastern Pacific Ocean. This anomalous equatorward dissipation of wave activity induces an anomalous poleward momentum flux, which is responsible for changes in the polar jet over the Pacific Ocean during the beginning stage. Following the low-frequency eddy forcing, momentum forcing anomalies due to the high-frequency eddies rapidly appear. This forcing continues to drive the polar jet poleward over the whole of longitude, while the low-frequency eddies have completed their role of inducing the anomalous poleward momentum flux during the earlier stage. For the equatorward transitional events, the roles of the low-frequency eddy forcing differ from that in the poleward ones. Anomalous equatorward momentum fluxes due to low-frequency eddies appear simultaneously with that due to high-frequency eddies. Quasi-stationary Rossby waves with wavelengths of 7000 km propagate southeastward through the waveguide over the Pacific Ocean. The convergence of their wave activity results in the deceleration of the westerlies over the higher latitudes of the Pacific Ocean. On the other hand, the high-frequency eddy forcing contributes to the equatorward jet drift longitudinally over the whole of the hemisphere.

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.

Real Ear Sound Pressure Levels Developed by Three Portable Stereo System Earphones

1992 ◽  
Vol 1 (4) ◽  
pp. 52-55 ◽  
Author(s):  
Gail L. MacLean ◽  
Andrew Stuart ◽  
Robert Stenstrom
Keyword(s):  
High Frequency ◽  
Sound Pressure ◽  
Low Frequency ◽  
Test System ◽  
Output Frequency ◽  
Frequency Effects ◽  
Adult Men ◽  
Frequency Responses ◽  
Significant Difference ◽  
Sound Pressure Levels

Differences in real ear sound pressure levels (SPLs) with three portable stereo system (PSS) earphones (supraaural [Sony Model MDR-44], semiaural [Sony Model MDR-A15L], and insert [Sony Model MDR-E225]) were investigated. Twelve adult men served as subjects. Frequency response, high frequency average (HFA) output, peak output, peak output frequency, and overall RMS output for each PSS earphone were obtained with a probe tube microphone system (Fonix 6500 Hearing Aid Test System). Results indicated a significant difference in mean RMS outputs with nonsignificant differences in mean HFA outputs, peak outputs, and peak output frequencies among PSS earphones. Differences in mean overall RMS outputs were attributed to differences in low-frequency effects that were observed among the frequency responses of the three PSS earphones. It is suggested that one cannot assume equivalent real ear SPLs, with equivalent inputs, among different styles of PSS earphones.

Evaluation of Special Hearing Aids for Deaf Children

1971 ◽  
Vol 36 (4) ◽  
pp. 527-537 ◽  
Author(s):  
Norman P. Erber
Keyword(s):  
Hearing Aids ◽  
High Frequency ◽  
Hearing Aid ◽  
Low Frequency ◽  
Acoustic Stimulation ◽  
Deaf Children ◽  
Frequency Range ◽  
Frequency Limit ◽  
Unpublished Studies ◽  
Published Research

Two types of special hearing aid have been developed recently to improve the reception of speech by profoundly deaf children. In a different way, each special system provides greater low-frequency acoustic stimulation to deaf ears than does a conventional hearing aid. One of the devices extends the low-frequency limit of amplification; the other shifts high-frequency energy to a lower frequency range. In general, previous evaluations of these special hearing aids have obtained inconsistent or inconclusive results. This paper reviews most of the published research on the use of special hearing aids by deaf children, summarizes several unpublished studies, and suggests a set of guidelines for future evaluations of special and conventional amplification systems.

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