Hydrodynamic Assessment of a Biofouled Wave Buoy in Coastal Zone

2020 ◽  
Author(s):  
Hafizul Islam ◽  
Ricardo M. Campos ◽  
Tobias R. S. Ferreira ◽  
C. Guedes Soares
Keyword(s):  
High Frequency ◽  
Measurement Accuracy ◽  
Historical Data ◽  
Vertical Motion ◽  
Guanabara Bay ◽  
Coastal Zones ◽  
Hydrodynamic Impact ◽  
Biological Growth ◽  
Hydrodynamic Response ◽  
The Difference

Abstract Accumulation of biological growth or biofouling can significantly influence the measurement accuracy of a buoy, unless it is cleaned on frequent intervals. This paper addresses the hydrodynamic impact of biofouling on met-ocean buoys moored in coastal zones. The analyses are mostly based on a Brazilian Navy buoy on the coast of Rio de Janeiro – Brazil. After only four months moored in the warm waters of the Guanabara Bay, the same buoy gained 25% in weight due to fouling, with additional important modifications on the shape and drag below the waterline. Initially, historical data measured by the buoy was analyzed to observe changes in its response over time. A motion response factor (lateral motion/vertical motion) was calculated from the data that showed a significant impact of biofouling for particular wave conditions. Next, OpenFOAM is used to perform RANS simulations for the buoy, at three different wave scenarios, in both clean and fouled condition to observe the difference in hydrodynamic response. The results indicated that the response amplitude operator varies notably for low and high-frequency cases between cleaned and fouled buoy. Our paper suggests that standard guidelines related to buoy cleaning intervals for biofouling and uncertainty applied in their measured readings may not be equal for all conditions. Buoys placed near the coast with warmer waters are more prone to biofouling and might have higher uncertainty in their measured data.

Comparison of In-the-Ear and Over-the-Ear Hearing Aid Fittings

1986 ◽  
Vol 51 (4) ◽  
pp. 362-369 ◽  
Author(s):  
Donna M. Risberg ◽  
Robyn M. Cox
Keyword(s):  
Hearing Aids ◽  
High Frequency ◽  
Comparative Evaluation ◽  
Speech Intelligibility ◽  
Hearing Aid ◽  
Hearing Aid Fitting ◽  
The Difference ◽  
Functional Gain ◽  
The Relationship

A custom in-the-ear (ITE) hearing aid fitting was compared to two over-the-ear (OTE) hearing aid fittings for each of 9 subjects with mild to moderately severe hearing losses. Speech intelligibility via the three instruments was compared using the Speech Intelligibility Rating (SIR) test. The relationship between functional gain and coupler gain was compared for the ITE and the higher rated OTE instruments. The difference in input received at the microphone locations of the two types of hearing aids was measured for 10 different subjects and compared to the functional gain data. It was concluded that (a) for persons with mild to moderately severe hearing losses, appropriately adjusted custom ITE fittings typically yield speech intelligibility that is equal to the better OTE fitting identified in a comparative evaluation; and (b) gain prescriptions for ITE hearing aids should be adjusted to account for the high-frequency emphasis associated with in-the-concha microphone placement.

scholarly journals Hyperfine structure in the arc spectrum of cæsium and nuclear rotation

1928 ◽  
Vol 121 (787) ◽  
pp. 432-447 ◽  
Keyword(s):  
Hyperfine Structure ◽  
Nuclear Spin ◽  
High Frequency ◽  
Principal Series ◽  
Very High Frequency ◽  
Nuclear Rotation ◽  
Higher Temperature ◽  
The Difference ◽  
Mechanical Moment ◽  
Very High

The arc spectrum of cæsium was investigated with the object of finding whether any of its lines possessed hyperfine structure, resulting from a nuclear magnetic moment, due to a quantised nuclear spin. The lines belonging to the principal series should, owing to the greater degree of penetration of the electron in the (1 s or 6 1 ) orbit, and the correspondingly greater interaction, show the greatest effect. The lines of the principal series are very easily broadened if the vapour pressure of the metal becomes high, so that great care had to be used in obtaining the spectrum of cæsium at a sufficiently low temperature. The most satisfactory method of excitation was found to be the application by means of external electrodes of a very high frequency alternating current to a tube filled with helium at about 2 mm. pressure containing a small quantity of cæsium. The tube required slight heating to bring out the cæsium lines; without this the helium spectrum was very much stronger than the metallic spectrum. At a very low vapour pressures of cæsium the discharge was blue in colour. Under these conditions the lines of the principal series showed no broadening greater than that due to thermal agitation, but at a slightly higher temperature the colour of the discharge became purple and the lines broadened. The lines belonging to the principal series were found to be very close doublets with very nearly constant frequencies differences. A theory is worked out which explains the origin of these doublets, assuming a nuclear spin of one half quantum; by correlating the difference in the separation of the hyperfine structure doublets in the 1 s — m 2 p 3/2 lines and the 1 s — m 2 p 1/2 lines, it is shown that a ratio of the magnetic to the mechanical moment of the nucleus about twice as great as the corresponding ratio for the electron would account for the observed frequency differences. The spectral notation used throughout is that of Hund. The results are compared with those found for the hyperfine structure of some of the bismuth lines by Back and Goudsmid, and are found to be in satisfactory agreement. A selection principle is found which applies both to the bismuth and the cæsium spectrum.

High-frequency seismic noise as a function of depth

1991 ◽  
Vol 81 (4) ◽  
pp. 1101-1114
Author(s):  
Jerry A. Carter ◽  
Noel Barstow ◽  
Paul W. Pomeroy ◽  
Eric P. Chael ◽  
Patrick J. Leahy
Keyword(s):  
New York ◽  
High Frequency ◽  
Seismic Noise ◽  
Low Frequency ◽  
Time Variability ◽  
Orthogonal Components ◽  
The Difference ◽  
Frequency Coherence ◽  
Cultural Noise ◽  
Natural Wind

Abstract Evidence is presented supporting the view that high-frequency seismic noise decreases with increased depth. Noise amplitudes are higher near the free surface where surface-wave noise, cultural noise, and natural (wind-induced) noise predominate. Data were gathered at a hard-rock site in the northwestern Adirondack lowlands of northern New York. Between 15- and 40-Hz noise levels at this site are more than 10 dB less at 945-m depth than they are at the surface, and from 40 to 100 Hz the difference is more than 20 dB. In addition, time variability of the spectra is shown to be greater at the surface than at either 335- or 945-m depths. Part of the difference between the surface and subsurface noise variability may be related to wind-induced noise. Coherency measurements between orthogonal components of motion show high-frequency seismic noise is more highly organized at the surface than it is at depth. Coherency measurements between the same component of motion at different vertical offsets show a strong low-frequency coherence at least up to 945-m vertical offsets. As the vertical offset decreases, the frequency band of high coherence increases.

scholarly journals The IG- file use to Gauge the Apical Diameter in Endodontics: An In Vitro Study

2018 ◽  
Vol 12 (1) ◽  
pp. 638-646 ◽  
Author(s):  
Massimo Amato ◽  
Alfredo Iandolo ◽  
Giuseppe Pantaleo ◽  
Dina Abtellatif ◽  
Michele Simeone ◽  
...  
Keyword(s):  
Measurement Accuracy ◽  
Reference Value ◽  
In Vitro Study ◽  
Vitro Study ◽  
Root Canals ◽  
New Instrument ◽  
Clinician Experience ◽  
Incorrect Measurement ◽  
The Difference

Aim: The aim of this study was to evaluate the efficacy of the IG-file, a new instrument designed for apical diameter gauging. Materials and Methods: After shaping with F1 Universal Protaper, 60 roots were randomly divided into two groups and assigned to two operators, One Expert in Endodontics (EO) and One Unexpert (UO). In each sample, after canal curvatures have been detected, the apical diameters were measured with the IG-file and the K-NiTi. The results were compared with the reference value obtained by retrograde apical gauging. The data were statistically analyzed. Results: Among 60 samples, 10% of errors were recorded when the IG-files were used; in the K-NiTi group the incorrect measurements were 70%. In both groups (expert and unexpert) the IG-file measurements were more accurate than the K-NiTi (90 vs 33 and 90 vs 26,7). The differences were statistically significant. In curved canals, the difference between measurement rates performed with both instruments was statistically significant (85,7% IG-file vs 28,6% K-NiTi) as well as for the samples without curvatures (92,3% IG file vs 30,8% NiTi file). In root canals without curvatures overestimation errors in K-NiTi file group are more frequent than underestimation errors. This difference was statistically significant. Conclusion: A proper gauging of the apical diameter has a key role in endodontic therapy; an incorrect measurement can lead to clinical failures. This “in vitro” study highlights that IG-file improves measurement accuracy independently from clinician experience. Furthermore, in curved canals, the IG-file is more accurate than K-NiTi.

scholarly journals PENENTUAN INVESTASI BERDASARKAN TINGKAT RISIKO PADA SAHAM SYARIAH, REKSADANA SYARIAH, DAN EMAS PERIODE 2011-2015

2019 ◽  
Vol 5 (6) ◽  
pp. 486
Author(s):  
Ayu Fitri ◽  
Dina Fitrisia Septiarini
Keyword(s):  
Mutual Fund ◽  
Historical Data ◽  
Stock Exchange ◽  
Secondary Data ◽  
Gold Price ◽  
Quantitative Approach ◽  
Purposive Sampling ◽  
Significant Difference ◽  
The Difference

The purpose of this study was to determine the difference of rate of risk on islamic stock, islamic mutual fund, and gold period 2011-2015. It uses quantitative approach by using Kruskal Wallis test. The sample collecting method used purposive sampling. This study was used secondary data that was collected from official websites of Indonesia Stock Exchange, PT BNP Paribas, and Price Gold. Data used was historical data from JII index, NAV per unit BNP Paribas Pesona Syariah, and gold price. The result Kruskal-Wallis test show that there was significant difference of rate of risk on islamic stock, islamic mutual fund, and gold. But, when used Mann-Whitney next test show that there was no significant difference on Islamic stock. The result of this study proved that islamic stock was more best than gold and islamic mutual fund

Nonword repetition and levels of abstraction in phonological knowledge

2006 ◽  
Vol 27 (4) ◽  
pp. 577-581 ◽  
Author(s):  
Benjamin Munson
Keyword(s):  
High Frequency ◽  
Low Frequency ◽  
Nonword Repetition ◽  
Chronological Age ◽  
Frequency Effect ◽  
Vocabulary Size ◽  
Levels Of Abstraction ◽  
Opposite Pattern ◽  
The Difference ◽  
Restriction Of Range

Susan Gathercole's Keynote Article (2006) is an impressive summary of the literature on nonword repetition and its relationship to word learning and vocabulary size. When considering research by Mary Beckman, Jan Edwards, and myself, Gathercole speculates that our finding of a stronger relationship between vocabulary measures and repetition accuracy for low-frequency sequences than for high-frequency sequences is due to differences in the range of the two measures. In our work on diphone repetition (e.g., Edwards, Beckman, & Munson, 2004; Munson, Edwards, & Beckman, 2005) we tried to increase the range in our dependent measures by coding errors on a finer grained scale than simple correct/incorrect scoring would allow. Moreover, restriction of range does not appear to be the driving factor in the relationship between vocabulary size and the difference between high- and low-frequency sequence repetition accuracy (what we call the frequency effect) in at least one of our studies (Munson et al., 2005). When the children with the 50 lowest mean accuracy scores for high-frequency sequences were examined, vocabulary size accounted for 10.5% of the variance in the frequency effect beyond what was accounted for by chronological age. When the 50 children with the highest mean accuracy scores for high-frequency sequences were examined (a group in which the range of high-frequency accuracy scores was more compressed, arguably reflecting ceiling effects), an estimate of vocabulary size accounted for only 6.9% of the frequency effect beyond chronological age. The associated β coefficient was significant only at the α<0.08 level. This is the opposite pattern than Gathercole's argument would predict.

scholarly journals Research on Improvement of the Combination Method for Conflicting Evidence Based on Historical Data

Symmetry ◽  
2020 ◽  
Vol 12 (5) ◽  
pp. 762
Author(s):  
Shuai Yuan ◽  
Honglei Wang
Keyword(s):  
Decision Rule ◽  
Historical Data ◽  
Evidence Theory ◽  
Weighted Average ◽  
Combination Method ◽  
Final Decision ◽  
Evidence Based ◽  
Combination Methods ◽  
Conflicting Evidence ◽  
The Difference

In a multi-sensor system, due to the difference of performance of sensors and the environment in which the sensor collects evidence, evidence collected will be highly conflicting, which leads to the failure of D-S evidence theory. The current research on combination methods of conflicting evidence focuses on eliminating the problem of "Zadeh paradox" brought by conflicting evidence, but do not distinguish the evidence from different sources effectively. In this paper, the credibility of each piece of evidence to be combined is weighted based on historical data, and the modified evidence is obtained by weighted average. Then the final result is obtained by combining the modified evidence using D-S evidence theory, and the improved decision rule is used for the final decision. After the decision, the system updates and stores the historical data based on actual results. The improved decision rule can solve the problem that the system cannot make a decision when there are two or more propositions corresponding to the maximum support in the final combination result. This method satisfies commutative law and associative law, so it has the symmetry that can meet the needs of the combination of time-domain evidence. Numerical examples show that the combination method of conflict evidence based on historical data can not only solve the problem of “Zadeh paradox”, but also obtain more reasonable results.

DIFFERENCE FREQUENCY HARMONIC ION HEATING

1967 ◽  
Vol 45 (5) ◽  
pp. 1771-1781 ◽  
Author(s):  
C. R. James ◽  
W. B. Thompson
Keyword(s):  
High Frequency ◽  
Collision Frequency ◽  
Difference Frequency ◽  
Fourth Power ◽  
Heating Process ◽  
Ion Heating ◽  
Frequency Signal ◽  
Transverse Waves ◽  
The Difference ◽  
Frequency Harmonic

The heating of a magnetized hot diffuse plasma using the difference frequency signal generated from two high-frequency (35 GHz) transverse waves is examined. The plasma is described by the cold plasma model and a series expansion of harmonics is used to obtain a solution to the equations. It is shown that the energy absorbed by the ions can be made inversely proportional to the collision frequency and the fourth power of the driven frequency and proportional to the fourth power of the driven electric field intensity. An investigation of the sensitivity of the heating process to fluctuations in frequency, density, and d-c. magnetic field is carried out.

Dissociating early and late visual processing via the Ebbinghaus illusion

2016 ◽  
Vol 33 ◽  
Author(s):  
FILIPP SCHMIDT ◽  
ANDREAS WEBER ◽  
ANKE HABERKAMP
Keyword(s):  
Visual Processing ◽  
High Frequency ◽  
Time Course ◽  
Temporal Dynamics ◽  
Low Frequency ◽  
Response Speed ◽  
Ebbinghaus Illusion ◽  
Priming Effects ◽  
Parvocellular Pathway ◽  
The Difference

AbstractVisual perception is not instantaneous; the perceptual representation of our environment builds up over time. This can strongly affect our responses to visual stimuli. Here, we study the temporal dynamics of visual processing by analyzing the time course of priming effects induced by the well-known Ebbinghaus illusion. In slower responses, Ebbinghaus primes produce effects in accordance with their perceptual appearance. However, in fast responses, these effects are reversed. We argue that this dissociation originates from the difference between early feedforward-mediated gist of the scene processing and later feedback-mediated more elaborate processing. Indeed, our findings are well explained by the differences between low-frequency representations mediated by the fast magnocellular pathway and high-frequency representations mediated by the slower parvocellular pathway. Our results demonstrate the potentially dramatic effect of response speed on the perception of visual illusions specifically and on our actions in response to objects in our visual environment generally.

Heterogeneity of mean alveolar pressure during high-frequency oscillations

1987 ◽  
Vol 62 (1) ◽  
pp. 223-228 ◽  
Author(s):  
J. L. Allen ◽  
I. D. Frantz ◽  
J. J. Fredberg
Keyword(s):  
High Frequency ◽  
Flow Distribution ◽  
Transpulmonary Pressure ◽  
Alveolar Pressure ◽  
Regional Heterogeneity ◽  
Regional Flow ◽  
High Frequency Oscillations ◽  
Dynamic Head ◽  
Mean Pressure ◽  
The Difference

Mean alveolar pressure may exceed mean airway pressure during high-frequency oscillations (HFO). To assess the magnitude of this effect and its regional heterogeneity, we studied six excised dog lungs during HFO [frequency (f) 2–32 Hz; tidal volume (VT) 5–80 ml] at transpulmonary pressures (PL) of 6, 10, and 25 cmH2O. We measured mean pressure at the airway opening (Pao), trachea (Ptr), and four alveolar locations (PA) using alveolar capsules. Pao was measured at the oscillator pump, wherein the peak dynamic head was less than 0.2 cmH2O. Since the dynamic head was negligible here, and since these were excised lungs, Pao thus represented true applied transpulmonary pressure. Ptr increasingly underestimated Pao as f and VT increased, with Pao - Ptr approaching 8 cmH2O. PA (averaged over all locations) and Pao were nearly equal at all PL's, f's, and VT's, except at PL of 6, f 32 Hz, and VT 80 ml, where (PA - Pao) was 3 cmH2O. Remarkably, mean pressure in the base exceeded that in the apex increasingly as f and VT increased, the difference approaching 3 cmH2O at high f and VT. We conclude that, although global alveolar overdistension assessed by PA - Pao is small during HFO under these conditions, larger regional heterogeneity in PA's exists that may be a consequence of airway branching angle asymmetry and/or regional flow distribution.

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