scholarly journals High Ripple-Density Resolution for Discriminating Between Rippled and Nonrippled Signals: Effect of Temporal Processing or Combination Products?

2021 ◽  
Vol 25 ◽  
pp. 233121652110101
Author(s):  
Dmitry I. Nechaev ◽  
Olga N. Milekhina ◽  
Marina S. Tomozova ◽  
Alexander Y. Supin
Keyword(s):  
Low Frequency ◽  
Noise Signal ◽  
Density Variation ◽  
Choice Procedure ◽  
Masker Level ◽  
Reference Signals ◽  
Forced Choice Procedure ◽  
The Mean ◽  
Density Resolution

The goal of the study was to investigate the role of combination products in the higher ripple-density resolution estimates obtained by discrimination between a spectrally rippled and a nonrippled noise signal than that obtained by discrimination between two rippled signals. To attain this goal, a noise band was used to mask the frequency band of expected low-frequency combination products. A three-alternative forced-choice procedure with adaptive ripple-density variation was used. The mean background (unmasked) ripple-density resolution was 9.8 ripples/oct for rippled reference signals and 21.8 ripples/oct for nonrippled reference signals. Low-frequency maskers reduced the ripple-density resolution. For masker levels from −10 to 10 dB re. signal, the ripple-density resolution for nonrippled reference signals was approximately twice as high as that for rippled reference signals. At a masker level as high as 20 dB re. signal, the ripple-density resolution decreased in both discrimination tasks. This result leads to the conclusion that low-frequency combination products are not responsible for the task-dependent difference in ripple-density resolution estimates.

Biological Motion Alters Coherent Motion Perception

Perception ◽  
10.1068/p5933 ◽  
2008 ◽  
Vol 37 (12) ◽  
pp. 1783-1789 ◽  
Author(s):  
Kiyoshi Fujimoto ◽  
Akihiro Yagi
Keyword(s):  
Motion Perception ◽  
Biological Motion ◽  
Coherent Motion ◽  
Choice Procedure ◽  
Motion Coherence ◽  
Forced Choice Procedure ◽  
The Mean ◽  
Point Light ◽  
Direction Opposite ◽  
Method Of Constant Stimuli

When a movie presents a person walking, the background appears to move in the direction opposite to the person's gait. This study verified this backscroll illusion by presenting a point-light walker against a background of a random-dot cinematogram (RDC). The RDC consisted of some signal dots moving coherently either leftward or rightward among other noise dots moving randomly. The method of constant stimuli was used to vary the RDC in motion coherence from trial to trial by manipulating the direction and percentage of the signal dots. Six observers judged the perceived direction of coherent motion in a two-alternative forced-choice procedure. Response rates for coherent motion perception in the direction opposite to walking were evaluated as a function of motion coherence. The results showed that the psychometric function shifted toward the direction determined by a bias in the opposite direction to the walker. The mean threshold was about half as high as that in a control condition in which the positions of the point-lights were scrambled to impair the recognition of the walker. The results demonstrate that biological motion noticeably affects the appearance of motion coherence in the background.

scholarly journals Low-Frequency Modulation of Turbulent Diapycnal Mixing by Anticyclonic Eddies Inferred from the HOT Time Series

2013 ◽  
Vol 43 (4) ◽  
pp. 824-835 ◽  
Author(s):  
Zhao Jing ◽  
Lixin Wu
Keyword(s):  
Time Series ◽  
Dissipation Rate ◽  
Low Frequency ◽  
Diapycnal Mixing ◽  
Dissipation Rates ◽  
Low Frequency Variability ◽  
Increasing Trend ◽  
The Mean ◽  
Anticyclonic Eddies

Abstract Profiles of potential density obtained from CTD measurements during the Hawaii Ocean Time series (HOT) program in the vicinity of the island of Oahu, Hawaii, are used to evaluate low-frequency variability of turbulent kinetic dissipation rates based on a finescale parameterization method. A distinct seasonal cycle, as well as an increasing trend of dissipation rates, is found in the upper 300–600 m. The trend is mainly due to the much weaker diapycnal mixing in the first four years of the record, that is, 1988–92. In the upper 300–600 m, enhanced diapycnal mixing is found under anticyclonic eddies with the mean dissipation rate about 53% larger than that under eddy-free conditions. The modulation of dissipation rates by anticyclonic eddies becomes more evident with increasing eddy strength. The role of cyclonic eddies in modulating diapycnal mixing is almost negligible compared with that of anticyclonic eddies. The mean dissipation rate under cyclonic eddies is comparable to that under eddy-free conditions with a difference of less than 10%. Seasonality of the dissipation rates is partly modulated by the seasonal variation of anticyclonic eddies.

Target Duration Effects on Iconic Memory: The Confounding Role of Changing Stimulus Dimensions

1980 ◽  
Vol 32 (2) ◽  
pp. 269-285 ◽  
Author(s):  
Gerald M. Long ◽  
Barbara Sakitt
Keyword(s):  
Task Performance ◽  
Stimulus Duration ◽  
Iconic Memory ◽  
Target Duration ◽  
General Level ◽  
Gap Detection ◽  
Improve Performance ◽  
Choice Procedure ◽  
Forced Choice Procedure

Observers’ accuracy in detecting a narrow spatial gap between two brief, luminous rectangles presented successively was determined within a two-alternative, forced-choice procedure. This successive-field task requires iconic memory, because the information (rectangle position) in the two presentations must be combined for successful gap detection. On this task, the effect of varying the duration of the first rectangle was systematically investigated over several target luminance levels and for several ISI conditions between rectangles. At the long ISI conditions (100 and 300 ms), the effects of increasing stimulus duration was to improve performance. However, at the brief ISI condition (20 ms), increasing stimulus duration initially depressed task performance. It was found that, with practice, this initial performance drop largely disappeared, and the beneficial influence of increasing target duration was again obtained. These results are discussed in terms of (a) a proposed retinal locus for the iconic memory involved and (b), at a more general level, the potentially distracting role of changing stimulus dimensions on a task employing transient stimuli as in the present study.

scholarly journals WAVE OVERTOPPING AT MALECÃ’N TRADICIONAL, LA HABANA, CUBA

2017 ◽  
pp. 24
Author(s):  
Luis Fermin Cordova Lopez ◽  
Daniela Salerno ◽  
Fabio Dentale ◽  
Alessandro Capobianco ◽  
Mariano Buccino
Keyword(s):  
Wave Spectrum ◽  
Low Frequency ◽  
Incoming Wave ◽  
Experimental Campaign ◽  
Frequency Components ◽  
The Mean ◽  
The Government ◽  
The Stability ◽  
The City

With the aim of redesigning the geometry of the Malecòn, a vertical face seawall protecting the northern waterfront of the city of La Habana, a wide experimental campaign was carried out. The latter was performed in the frame of a collaboration between the Government of the isle of Cuba and the CUGRI consortium, an Italian institution which joins the Universities of Salerno and Napoli “Federico II”. The different solutions investigated allowed both to detect the best solution for reducing the overtopping and to assess the role of wave setup and low frequency components of the incoming wave spectrum on the predictions of the mean overtopping rate. The stability of two nearshore structures designed to protect the seawall has also been assessed.

scholarly journals Quantifying the Role of Occurrence Losses in Catastrophe Excess of Loss Reinsurance Pricing

Risks ◽  
2021 ◽  
Vol 9 (3) ◽  
pp. 52
Author(s):  
Shree Khare ◽  
Keven Roy
Keyword(s):  
Order Statistics ◽  
Model Development ◽  
Low Frequency ◽  
Covariance Structure ◽  
Before And After ◽  
The Mean ◽  
Market Practice ◽  
The Impact ◽  
Catastrophe Reinsurance

The aim of this paper is to merge order statistics with natural catastrophe reinsurance pricing to develop new theoretical and practical insights relevant to market practice and model development. We present a novel framework to quantify the role that occurrence losses (order statistics) play in pricing of catastrophe excess of loss (catXL) contracts. Our framework enables one to analytically quantify the contribution of a given occurrence loss to the mean and covariance structure, before and after the application of a catXL contract. We demonstrate the utility of our framework with an application to idealized catastrophe models for a multi-peril and a hurricane-only case. For the multi-peril case, we show precisely how contributions to so-called lower layers are dominated by high frequency perils, whereas higher layers are dominated by low-frequency high severity perils. Our framework enables market practitioners and model developers to assess and understand the impact of altered model assumptions on the role of occurrence losses in catXL pricing.

Achromatic Transparency and the Role of Local Contours

Perception ◽  
10.1068/p3357 ◽  
2002 ◽  
Vol 31 (7) ◽  
pp. 775-790 ◽  
Author(s):  
Reza Kasrai ◽  
Frederick A A Kingdom
Keyword(s):  
Sudden Change ◽  
Forced Choice ◽  
Single Plane ◽  
Choice Procedure ◽  
Background Material ◽  
Forced Choice Procedure ◽  
Pass Through ◽  
Luminance Stimulus ◽  
Flanking Regions

In this paper we investigate the role of contours and junctions in the perception of single-plane achromatic transparency. In order to measure the accuracy with which observers encode transparency, a six-luminance stimulus was employed in which the figural properties could be easily manipulated. Accuracy was measured by requiring subjects to select (either by the method of adjustment or by using a forced-choice procedure) the luminance that best completed a simulated transparent filter. The X junctions in the stimulus were destroyed or perturbed in three experiments. Simple occlusion of the junction (experiment 1), and perturbation of the orientation of the contours of the filter as they pass through the junction (experiment 3) resulted in small but significant reductions in performance. On the other hand, a sudden change in orientation of the background (material) contours (experiment 2) resulted in a small but significant enhancement of overall performance compared with the control stimulus. In the forced-choice task, reversals in the polarity of contours (as defined by the brightness order of flanking regions) around the junction were shown to effect large changes in subjects' accuracy in processing transparency. The overall results show that X and Ψ junctions are indeed salient properties of transparent stimuli. The findings suggest that jagged contours with sudden changes in direction are more likely to be attributed to reflectance (material) changes than to changes due to a transparent filter (or to illumination).

Calculation-and-experimental estimation of the role of the frequency ratio in changing the endurance at two-frequency deformation modes

2019 ◽  
Vol 85 (1(I)) ◽  
pp. 64-71 ◽  
Author(s):  
M. M. Gadenin
Keyword(s):  
High Frequency ◽  
Experimental Studies ◽  
Low Frequency ◽  
Reduction Factor ◽  
Single Frequency ◽  
Cyclic Loads ◽  
Small Ratio ◽  
Harmonic Components ◽  
Deformation Modes

The cycle configuration at two-frequency loading regimes depends on the number of parameters including the absolute values of the frequencies and amplitudes of the low-frequency and high-frequency loads added during this mode, the ratio of their frequencies and amplitudes, as well as the phase shift between these harmonic components, the latter having a significant effect only with a small ratio of frequencies. Presence of such two-frequency regimes or service loading conditions for parts of machines and structures schematized by them can significantly reduce their endurance. Using the results of experimental studies of changes in the endurance of a two-frequency loading of specimens of cyclically stable, cyclically softened and cyclically hardened steels under rigid conditions we have shown that decrease in the endurance under the aforementioned conditions depends on the ratio of frequencies and amplitudes of operation low-frequency low-cycle and high-frequency vibration stresses, and, moreover, the higher the level of the ratios of amplitudes and frequencies of those stacked harmonic processes of loading the greater the effect. It is shown that estimation of such a decrease in the endurance compared to a single frequency loading equal in the total stress (strains) amplitudes can be carried out using an exponential expression coupling those endurances through a parameter (reduction factor) containing the ratio of frequencies and amplitudes of operation cyclic loads and characteristic of the material. The reduction is illustrated by a set of calculation-experimental curves on the corresponding diagrams for each of the considered types of materials and compared with the experimental data.

Long-term dynamics and destruction of marsh vegetation in the Kolokolkova Bay of the Barents Sea

2012 ◽  
pp. 66-77 ◽  
Author(s):  
I. A. Lavrinenko ◽  
O. V. Lavrinenko ◽  
D. V. Dobrynin
Keyword(s):  
Species Composition ◽  
Plant Communities ◽  
Barents Sea ◽  
Mean Value ◽  
Marsh Vegetation ◽  
Composition And Structure ◽  
The Mean ◽  
Species Composition And Structure

The satellite images show that the area of marshes in the Kolokolkova bay was notstable during the period from 1973 up to 2011. Until 2010 it varied from 357 to 636 ha. After a severe storm happened on July 24–25, 2010 the total area of marshes was reduced up to 43–50 ha. The mean value of NDVI for studied marshes, reflecting the green biomass, varied from 0.13 to 0.32 before the storm in 2010, after the storm the NDVI decreased to 0.10, in 2011 — 0.03. A comparative analysis of species composition and structure of plant communities described in 2002 and 2011, allowed to evaluate the vegetation changes of marshes of the different topographic levels. They are fol­lowing: a total destruction of plant communities of the ass. Puccinellietum phryganodis and ass. Caricetum subspathaceae on low and middle marches; increasing role of halophytic species in plant communities of the ass. Caricetum glareosae vic. Calamagrostis deschampsioides subass. typicum on middle marches; some changes in species composition and structure of plant communities of the ass. Caricetum glareosae vic. Calamagrostis deschampsioides subass. festucetosum rubrae on high marches and ass. Parnassio palustris–Salicetum reptantis in transition zone between marches and tundra without changes of their syntaxonomy; a death of moss cover in plant communities of the ass. Caricetum mackenziei var. Warnstorfia exannulata on brackish coastal bogs. The possible reasons of dramatic vegetation dynamics are discussed. The dating of the storm makes it possible to observe the directions and rates of the succession of marches vegetation.

Seasonal trends in the stable isotopic composition of snow and meltwater runoff in a subarctic catchment at Okstindan, Norway

2004 ◽  
Vol 35 (2) ◽  
pp. 119-137 ◽  
Author(s):  
S.D. Gurney ◽  
D.S.L. Lawrence
Keyword(s):  
Isotopic Composition ◽  
Mean Value ◽  
Mean Values ◽  
Stable Isotopic Composition ◽  
Meltwater Runoff ◽  
Stable Isotopic ◽  
The Mean ◽  
The Difference ◽  
Δ18o And Δd

Seasonal variations in the stable isotopic composition of snow and meltwater were investigated in a sub-arctic, mountainous, but non-glacial, catchment at Okstindan in northern Norway based on analyses of δ18O and δD. Samples were collected during four field periods (August 1998; April 1999; June 1999 and August 1999) at three sites lying on an altitudinal transect (740–970 m a.s.l.). Snowpack data display an increase in the mean values of δ18O (increasing from a mean value of −13.51 to −11.49‰ between April and August), as well as a decrease in variability through the melt period. Comparison with a regional meteoric water line indicates that the slope of the δ18O–δD line for the snowpacks decreases over the same period, dropping from 7.49 to approximately 6.2.This change points to the role of evaporation in snowpack ablation and is confirmed by the vertical profile of deuterium excess. Snowpack seepage data, although limited, also suggest reduced values of δD, as might be associated with local evaporation during meltwater generation. In general, meltwaters were depleted in δ18O relative to the source snowpack at the peak of the melt (June), but later in the year (August) the difference between the two was not statistically significant. The diurnal pattern of isotopic composition indicates that the most depleted meltwaters coincide with the peak in temperature and, hence, meltwater production.

scholarly journals Forensic Investigation of Four Monitored Green Infrastructure Inlets

Water ◽  
2021 ◽  
Vol 13 (13) ◽  
pp. 1787
Author(s):  
Leena J. Shevade ◽  
Franco A. Montalto
Keyword(s):  
Measurement Uncertainty ◽  
Green Infrastructure ◽  
Stormwater Management ◽  
Catchment Area ◽  
Low Flow ◽  
Inflow Rate ◽  
Forensic Investigation ◽  
Flow Conditions ◽  
The Mean

Green infrastructure (GI) is viewed as a sustainable approach to stormwater management that is being rapidly implemented, outpacing the ability of researchers to compare the effectiveness of alternate design configurations. This paper investigated inflow data collected at four GI inlets. The performance of these four GI inlets, all of which were engineered with the same inlet lengths and shapes, was evaluated through field monitoring. A forensic interpretation of the observed inlet performance was conducted using conclusions regarding the role of inlet clogging and inflow rate as described in the previously published work. The mean inlet efficiency (meanPE), which represents the percentage of tributary area runoff that enters the inlet was 65% for the Nashville inlet, while at Happyland the NW inlet averaged 30%, the SW inlet 25%, and the SE inlet 10%, considering all recorded events during the monitoring periods. The analysis suggests that inlet clogging was the main reason for lower inlet efficiency at the SW and NW inlets, while for the SE inlet, performance was compromised by a reverse cross slope of the street. Spatial variability of rainfall, measurement uncertainty, uncertain tributary catchment area, and inlet depression characteristics are also correlated with inlet PE. The research suggests that placement of monitoring sensors should consider low flow conditions and a strategy to measure them. Additional research on the role of various maintenance protocols in inlet hydraulics is recommended.

Sign in / Sign up

Export Citation Format

Share Document