Evaluation of Thermal Degradation of 2.25Cr-1Mo Steel by High Frequency Ultrasonic Attenuation Measurement

2005 ◽  
Vol 475-479 ◽  
pp. 257-260 ◽  
Author(s):  
Jai Won Byeon ◽  
C.S. Kim ◽  
S.I. Kwun ◽  
S.J. Hong
Keyword(s):  
Attenuation Coefficient ◽  
High Frequency ◽  
Ultrasonic Attenuation ◽  
Attenuation Coefficients ◽  
Low Frequencies ◽  
High Frequencies ◽  
Noticeable Increase ◽  
Mean Size ◽  
Longitudinal Ultrasonic Wave ◽  
Degradation Time

It was attempted to assess nondestructively the degree of isothermal degradation of 2.25Cr-1Mo steel by using high frequency longitudinal ultrasonic wave. Microstructural parameter (mean size of carbides), mechanical property (Vickers hardness) and ultrasonic attenuation coefficient were measured for the 2.25Cr-1Mo steel isothermally degraded at 630°C for up to 4800 hours in order to find the correlation among these parameters. The ultrasonic attenuation coefficients at high frequencies (over 35MHz) were observed to increase rapidly in the initial 1000 hours of degradation time and then slowly thereafter, while the ones at low frequencies showed no noticeable increase. Ultrasonic attenuation at high frequencies increased as a function of mean size of carbides. Ultrasonic attenuation coefficient was found to have a linear correlation with the hardness, and suggested accordingly as a potential nondestructive evaluation parameter for assessing the mechanical strength reduction of the isothermally degraded 2.25Cr-1Mo steel.

scholarly journals The Estimation of Hydrometeor Profiles from Wideband Microwave Observations

2000 ◽  
Vol 39 (10) ◽  
pp. 1645-1656 ◽  
Author(s):  
Gail M. Skofronick-Jackson ◽  
James R. Wang
Keyword(s):  
High Frequency ◽  
Cloud Water ◽  
Tropical Ocean ◽  
Low Frequencies ◽  
High Frequencies ◽  
Atmospheric Research ◽  
Brightness Temperatures ◽  
Microphysical Properties ◽  
Ice Microphysics ◽  
Updraft Region

Abstract Profiles of the microphysical properties of clouds and rain cells are essential in many areas of atmospheric research and operational meteorology. To enhance the understanding of the nonlinear and underconstrained relationships between cloud and hydrometeor microphysical profiles and passive microwave brightness temperatures, estimations of cloud profiles for an anvil region, a convective region, and an updraft region of an oceanic squall were performed. The estimations relied on comparisons between radiative transfer calculations of incrementally estimated microphysical profiles and concurrent dual-altitude wideband brightness temperatures from the 22 February 1993 flight during the Tropical Ocean and Global Atmosphere Coupled Ocean–Atmosphere Response Experiment. The wideband observations (10–220 GHz) are necessary for estimating cloud profiles reaching up to 20 km. The low frequencies enhance the rain and cloud water profiles, and the high frequencies are required to detail the higher-altitude ice microphysics. A microphysical profile was estimated for each of the three regions of the storm. Each of the three estimated profiles produced calculated brightness temperatures within ∼10 K of the observations. A majority of the total iterative adjustments were to the estimated profile’s frozen hydrometeor characteristics and were necessary to match the high-frequency calculations with the observations. This requirement indicates a need to validate cloud-resolving models using high frequencies. Some difficulties matching the 37-GHz observation channels on the DC-8 and ER-2 aircraft with the calculations simulated at the two aircraft heights (∼11 km and 20 km, respectively) were noted, and potential causes were presented.

scholarly journals Novel Negative Capacitance and Conductance in All Temperatures and Voltages of Au/CNTs/n-Si/Al at Low and High Frequencies

2021 ◽  
Author(s):  
A. Ashery ◽  
Samia Gad ◽  
A. E.H. Gaballah ◽  
G. M. Turky
Keyword(s):  
Carbon Nanotube ◽  
High Frequency ◽  
Series Resistance ◽  
Negative Capacitance ◽  
Donor Concentration ◽  
Low Frequencies ◽  
High Frequencies ◽  
Depletion Width ◽  
Density Surface ◽  
P Type

Abstract The structure of carbon nanotube CNTs functioning as p-type material deposited over n-type silicon to produce heterojunction of Au/CNTs/n-Si/Al is presented in this study.This work explored the capacitance and conductance at various frequencies, temperatures, and voltages, the novelty here is that negative capacitance and conductance were observed at high frequencies in all temperatures and voltages, whereas capacitance appeared at both high and low frequencies, such as (2x107,1x107,1x102,10) Hz. At high-frequency f = 2x107 Hz, the capacitance raises while the conductance decreases; at all temperatures and voltages, the capacitance and conductance exhibit the same behavior at particular frequencies such as 1x106,1x105,1x104,1x103Hz, however their behavior differs at 2x107,1x107, 1x102 and 10Hz. Investigating the reverse square capacitance with voltage yielded the energy fermi (Ef), density surface of states (Nss), depletion width (Wd), barrier height, series resistance, and donor concentration (Nd)

GPS collars are more efficient when collecting high-frequency data

2016 ◽  
Vol 38 (2) ◽  
pp. 237 ◽  
Author(s):  
H. W. McGregor ◽  
S. M. Legge ◽  
M. E. Jones ◽  
C. N. Johnson
Keyword(s):  
High Frequency ◽  
Pivotal Role ◽  
High Frequency Data ◽  
Frequency Data ◽  
Low Frequencies ◽  
High Frequencies ◽  
Gps Collars

Selecting an appropriate fix schedule has a pivotal role when using GPS collars. On the basis of deployments of GPS collars on 35 cats, we report on an often overlooked consideration: that GPS units are more efficient collecting data at high frequencies (15 min between fixes in this study) than low frequencies (>2 h between fixes).

A theory of compressional wave attenuation in noncohesive sediments

Geophysics ◽  
1985 ◽  
Vol 50 (8) ◽  
pp. 1311-1317 ◽  
Author(s):  
C. McCann ◽  
D. M. McCann
Keyword(s):  
Wave Attenuation ◽  
Compressional Wave ◽  
Solid Particles ◽  
Biot’S Theory ◽  
Attenuation Coefficients ◽  
Low Frequencies ◽  
Biot's Theory ◽  
Compressional Waves ◽  
High Frequencies ◽  
Water Saturated

Published reviews indicate that attenuation coefficients of compressional waves in noncohesive, water‐saturated sediments vary linearly with frequency. Biot’s theory, which accounts for attenuation in terms of the viscous interaction between the solid particles and pore fluid, predicts in its presently published form variation proportional to [Formula: see text] at low frequencies and [Formula: see text] at high frequencies. A modification of Biot’s theory which incorporates a distribution of pore sizes is presented and shown to give excellent agreement with new and published attenuation data in the frequency range 10 kHz to 2.25 MHz. In particular, a linear variation of attenuation with frequency is predicted in that range.

Prediction of Propeller Cavitation Noise From Model Tests and Its Comparison With Full Scale Data

1985 ◽  
Vol 107 (1) ◽  
pp. 112-119 ◽  
Author(s):  
G. Bark
Keyword(s):  
High Frequency ◽  
Full Scale ◽  
Cavitation Noise ◽  
Low Frequencies ◽  
High Frequencies ◽  
Analysis Methods ◽  
Test Parameters ◽  
Cavitation Tunnel ◽  
Simple Scaling ◽  
Scale Data

This paper deals with the prediction of propeller cavitation noise from model experiments in a cavitation tunnel. The purpose was to investigate the validity of a simple scaling formula for high frequency cavitation noise, and to get information about the influence of test parameters and analysis methods. The results indicate that the scaling formula normally used at low frequencies can, as a first approximation, be used also at high frequencies. Concerning analysis methods it is demonstrated that the noise signals in model and full scale may have different statistical properties, implying that the simple root-mean-square value of the model signal is not always a sufficient basis for prediction of full scale noise.

scholarly journals Physics Augmented U-Net: A High-Frequency Aware Generative Prior for Microscopy

2021 ◽  
Author(s):  
Jathurshan Pradeepkumar ◽  
Mithunjha Anandakumar ◽  
Vinith Kugathasan ◽  
Andrew Seeber ◽  
Dushan N Wadduwage
Keyword(s):  
High Frequency ◽  
Forward Model ◽  
The Other ◽  
Structured Illumination ◽  
Structured Illumination Microscopy ◽  
Experimental Conditions ◽  
Low Frequencies ◽  
High Frequencies ◽  
Proposed Model ◽  
Microscopy Images

A key challenge in optical microscopy is to image fast at high-resolution. To address this problem, we propose "Physics Augmented U-Net", which combines deep learning and structured illumination microscopy (SIM). In SIM, the structured illumination aliases out-of-band high-frequencies to the passband of the microscope; thus SIM captures some high-frequencies even when the image is sampled at low-resolution. To utilize these features, we propose a three-element method: 1) a modified U-Net model, 2) a physics-based forward model of SIM 3) an inference algorithm combining the two models. The modified U-Net architecture is similar to the seminal work, but the bottleneck is modified by concatenating two latent vectors, one encoding low-frequencies (LFLV), and the other encoding high-frequencies (HFLV). LFLV is learned by U-Net contracting path, and HFLV is learned by a second encoding path. In the inference mode, the high-frequency encoder is removed; HFLV is then optimized to fit the measured microscopy images to the output of the forward model for the generated image by the U-Net. We validated our method on two different datasets under different experimental conditions. Since a latent vector is optimized instead of a 2D image, the inference mode is less computationally complex. The proposed model is also more stable compared to other generative prior-based methods. Finally, as the forward model is independent of the U-Net, Physics Augmented U-Net can enhance resolution on any variation of SIM without further retraining.

Low frequency damping and ultrasonic attenuation in Ti3Sn-based alloys

1994 ◽  
Vol 9 (6) ◽  
pp. 1441-1448 ◽  
Author(s):  
Catherine R. Wong ◽  
Robert L. Fleischer
Keyword(s):  
High Temperature ◽  
Room Temperature ◽  
Ultrasonic Attenuation ◽  
Low Frequency ◽  
Basic Mechanism ◽  
Low Frequencies ◽  
High Frequencies ◽  
Young’S Moduli ◽  
High Temperature Alloys ◽  
Damping Behavior

Studies of high-temperature alloys in the Ti-Sn system based on the intermetallic compound Ti3Sn have identified alloys that damp strongly both at low frequencies (0.1 to 10 Hz) and high frequencies (5 to 20 MHz). The low frequency damping behavior shows loss factors as high as 0.04 at room temperature and Young's moduli that rise with temperature from 40 °C to 100 °C for two alloys. Although the basic mechanism or mechanisms of energy dissipation are presently unknown, the alloys are notable for unusual shapes of microhardness indentations. The deformations imply that large reversible strains can occur at temperatures from 23 °C to 1150 °C.

Permeability and borehole Stoneley waves: Comparison between experiment and theory

Geophysics ◽  
1989 ◽  
Vol 54 (1) ◽  
pp. 66-75 ◽  
Author(s):  
Kenneth W. Winkler ◽  
Hsui‐Lin Liu ◽  
David Linton Johnson
Keyword(s):  
High Frequency ◽  
Low Frequency ◽  
Theoretical Models ◽  
Oil Field ◽  
Stoneley Wave ◽  
Biot Theory ◽  
Frequency Dependent ◽  
Low Frequencies ◽  
High Frequencies ◽  
Theoretical Predictions

We performed laboratory experiments to evaluate theoretical models of borehole. Stoneley wave propagation in permeable materials. A Berea sandstone and synthetic samples made of cemented glass beads were saturated with silicone oils. We measured both velocity and attenuation over a frequency band from 10 kHz to 90 kHz. Our theoretical modeling incorporated Biot theory and Deresiewicz‐Skalak boundary conditions into a cylindrical geometry and included frequency‐dependent permeability. By varying the viscosity of the saturating pore fluid, we were able to study both low‐frequency and high‐frequency regions of Biot theory, as well as the intermediate transition zone. In both low‐frequency and high‐frequency regions of the theory, we obtained excellent agreement between experimental observations and theoretical predictions. Velocity and attenuation (1/Q) are frequency‐dependent, especially at low frequencies. Also at low frequencies, velocity decreases and attenuation increases with increasing fluid mobility (permeability/viscosity). More complicated behavior is observed at high frequencies. These results support recent observations from the oil field suggesting that Stoneley wave velocity and attenuation may be indicative of formation permeability.

scholarly journals Maass, Pavon & Suitner HARMONIC ANALYSIS OF SOCIAL COGNITION

2021 ◽  
Author(s):  
Anne Maass
Keyword(s):  
Social Cognition ◽  
High Frequency ◽  
Personal Characteristics ◽  
Future Research ◽  
Weighted Sum ◽  
Social Stimuli ◽  
Low Frequencies ◽  
High Frequencies ◽  
The Social ◽  
Selection Of

In this paper, we argue that some fundamental concepts and tools of signal processing may beeffectively applied to represent and interpret social cognition processes. From this viewpoint,individuals or, more generally, social stimuli are thought of as a weighted sum of harmonics withdifferent frequencies: Low frequencies represent general categories such as gender, ethnic group,nationality, etc., whereas high frequencies account for personal characteristics. Individuals arethen seen by observers as the output of a filter that emphasizes a certain range of high or lowfrequencies. The selection of the filter depends on the social distance between the observingindividual or group and the person being observed as well as on motivation, cognitive resourcesand cultural background. Enhancing low- or high-frequency harmonics is not on equal footing, thelatter requiring supplementary energy. This mirrors a well-known property of signal processingfilters. More generally, in the light of this correspondence, we show that several established resultsof social cognition admit a natural interpretation and integration in the signal processinglanguage. While the potential of this connection between an area of social psychology and one ofinformation engineering appears considerable (compression, information retrieval, filtering,feedback, feedforward, sampling, aliasing, etc.), in this paper we shall limit ourselves to layingdown what we consider the pillars of this bridge on which future research may be founded.

scholarly journals High Frequency Performance of Piezoelectric Diaphragms for Impedance-Based SHM Applications

2020 ◽  
Vol 2 (1) ◽  
pp. 16
Author(s):  
Guilherme Rezende ◽  
Fabricio Baptista
Keyword(s):  
High Frequency ◽  
Structural Damage ◽  
Low Cost ◽  
Low Frequency ◽  
Experimental Tests ◽  
Piezoelectric Transducers ◽  
Low Frequencies ◽  
High Frequencies ◽  
Electromechanical Impedance ◽  
Damage Indices

Piezoelectric transducers are used in a wide variety of applications, including damage detection in structural health monitoring (SHM) applications. Among the various methods for detecting structural damage, the electromechanical impedance (EMI) method is one of the most investigated in recent years. In this method, the transducer is typically excited with low frequency signals up to 500 kHz. However, recent studies have indicated the use of higher frequencies, usually above 1 MHz, for the detection of some types of damage and the monitoring of some structures’ characteristics that are not possible at low frequencies. Therefore, this study investigates the performance of low-cost piezoelectric diaphragms excited with high frequency signals for SHM applications based on the EMI method. Piezoelectric diaphragms have recently been reported in the literature as alternative transducers for the EMI method and, therefore, investigating the performance of these transducers at high frequencies is a relevant subject. Experimental tests were carried out with piezoelectric diaphragms attached to two aluminum bars, obtaining the impedance signatures from diaphragms excited with low and high frequency signals. The analysis was performed using the real part of the impedance signatures and two basic damage indices, one based on the Euclidean norm and the other on the correlation coefficient. The experimental results indicate that piezoelectric diaphragms are usable for the detection of structural damage at high frequencies, although the sensitivity decreases.

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