Representation of high frequency Space Shuttle data by ARMA algorithms and random response spectra

1990 ◽  
Author(s):  
P. SPANOS ◽  
L. MUSHUNG
Keyword(s):  
High Frequency ◽  
Space Shuttle ◽  
Response Spectra ◽  
Random Response ◽  
Frequency Space

Spectral Representation of High‐Frequency Space Shuttle Data

1994 ◽  
Vol 7 (3) ◽  
pp. 315-327
Author(s):  
P. D. Spanos ◽  
L. J. Mushung ◽  
D. A. Nelson ◽  
D. A. Hamilton
Keyword(s):  
High Frequency ◽  
Spectral Representation ◽  
Space Shuttle ◽  
Frequency Space

Seismic Qualification by Testing for Electrical and Active Mechanical Equipment to be Installed in Hard-Rock High Frequency Sites

2009 ◽  
Author(s):  
Pei-Ying Chen ◽  
Ching Hang Ng
Keyword(s):  
Ground Motion ◽  
Seismic Design ◽  
High Frequency ◽  
Power Plants ◽  
Hard Rock ◽  
Response Spectra ◽  
Nuclear Industry ◽  
Mechanical Equipment ◽  
Regulatory Requirements ◽  
Structure Response

All electric and active mechanical equipment important to safety must be seismically qualified by either analysis, testing, or a combination of both. The general requirements for seismic qualification of electric and active mechanical equipment in nuclear power plants are delineated in Appendix S to Title 10, Part 50, of the Code of Federal Regulations (10 CFR Part 50), item 52.47(20) of 10 CFR 52.47, and Appendix A to 10 CFR Part 100. The staff at the US Nuclear Regulatory Commission (NRC) has recognized that the Certified Design Ground Motion may be exceeded by the site-specific ground motion. The exceedances are generally in the high-frequency range for the Central and Eastern US sites. For equipment seismic qualification consideration, the exceedances must be addressed at both the ground level and the floor level where the equipment is located. Thus, the in-structure response spectra at some locations may exceed those in-structure response spectra generated by the certified seismic design response spectra. The U.S. nuclear industry and the NRC have initiated activities to address this issue. Two scenarios that revealed themselves during the review activities of the design certification and combined license applications for new reactors will be expounded upon in the paper. In Case I, equipment seismic qualification has been approved for a certified design and equipment is to be installed at a hard-rock high frequency (HRHF) site with certified seismic design response spectra (CSDRS) exceeded by the Ground Motion Response Spectra (GMRS) of the hard-rock site. In Case II, equipment seismic qualification has not been approved for a design certification and there is an application with GMRS exceeding the not-yet-approved CSDRS. In the paper, the staff will begin the discussion with the regulatory requirements for seismic qualification of electric and mechanical equipment. The focus of the paper is to identify the staff concern and illustrate the resolution between the NRC staff and an applicant on the seismic qualification of equipment by testing, in particular for equipment to be installed in hard-rock high frequency sites, to meet the regulatory requirements.

scholarly journals On the Effectiveness of Low Frequency Perturbations

2019 ◽  
Author(s):  
Yash Sharma ◽  
Gavin Weiguang Ding ◽  
Marcus A. Brubaker
Keyword(s):  
High Frequency ◽  
State Of The Art ◽  
Low Frequency ◽  
Human Perception ◽  
Search Space ◽  
Frequency Space ◽  
Performance Improvements ◽  
Frequency Regime ◽  
Frequency Components ◽  
Norm Constraint

Carefully crafted, often imperceptible, adversarial perturbations have been shown to cause state-of-the-art models to yield extremely inaccurate outputs, rendering them unsuitable for safety-critical application domains. In addition, recent work has shown that constraining the attack space to a low frequency regime is particularly effective. Yet, it remains unclear whether this is due to generally constraining the attack search space or specifically removing high frequency components from consideration. By systematically controlling the frequency components of the perturbation, evaluating against the top-placing defense submissions in the NeurIPS 2017 competition, we empirically show that performance improvements in both the white-box and black-box transfer settings are yielded only when low frequency components are preserved. In fact, the defended models based on adversarial training are roughly as vulnerable to low frequency perturbations as undefended models, suggesting that the purported robustness of state-of-the-art ImageNet defenses is reliant upon adversarial perturbations being high frequency in nature. We do find that under L-inf-norm constraint 16/255, the competition distortion bound, low frequency perturbations are indeed perceptible. This questions the use of the L-inf-norm, in particular, as a distortion metric, and, in turn, suggests that explicitly considering the frequency space is promising for learning robust models which better align with human perception.

Static Application of Transient Hydrodynamic Loads on Vessel Internal Structures As a Result of Pulse Jet Mixer Overblow: High-Frequency Load Acoustic Event

2020 ◽  
Author(s):  
Brian Fant ◽  
Rafael Garcilazo ◽  
Robert Blevins
Keyword(s):  
Test Data ◽  
High Frequency ◽  
Response Spectra ◽  
Geometric Constraints ◽  
Analysis Model ◽  
Element Analysis ◽  
Acoustic Event ◽  
Forcing Function ◽  
Internal Structures ◽  
Pulse Jet

Abstract At the Hanford Waste Treatment and Immobilization Plant (WTP), various vessels are designed to be agitated with internal pulse jet mixers (PJMs) in order to provide a means of mixing with no moving parts local to the vessel. PJMs are operated by use of an applied vacuum to draw liquid in followed by motive air to force liquid out (while not completely discharging all the liquid). This continual operation results in mixing of the vessel contents. In off-normal conditions, PJMs may completely discharge resulting in air rapidly injected into the vessel (PJM overblow). An evaluation is complete to determine the statically applied transient acoustic event loads resulting from Pulse Jet Mixer (PJM) overblow on a vessel’s internal submerged structures. The high-frequency acoustic load on internal structures is determined via analysis of overblow hydrophone test data, vessel modal and harmonic analysis, determination of an overblow forcing function through a Fourier analysis of test data compared to modal analysis of the vessel, application of the overblow forcing function in a finite element analysis model with acoustic fluid elements, use of a displacement-response spectra, and Hooke’s Law. Compared to previous analyses, this improved method can account for changes to PJM cavity pressure, PJM nozzle diameter, and more accurately represents the loads because it considers geometric constraints.

The Effects of Discretization Errors on the High Frequency Content of In-Structure Response Spectra

2016 ◽  
Author(s):  
Greg Mertz ◽  
Robert Spears ◽  
Thomas Houston
Keyword(s):  
Ground Motion ◽  
High Frequency ◽  
Time History ◽  
Response Spectra ◽  
Frequency Content ◽  
Time Step ◽  
Structure Response ◽  
Time History Response ◽  
Ground Motion Records ◽  
High Frequency Content

The next generation ground motion prediction equations predict significant high frequency seismic input for rock sites in the Central Eastern United States (CEUS). This high frequency motion is transmitted to basemat supported components and may be transmitted to components supported on elevated slabs. The existing ASCE 4 analysis requirements were initially developed based on seismic motions having lower frequencies, typical of ground motions in the Western United States (WUS). The adequacy of the existing ASCE 4 analysis requirements are examined using high frequency CEUS spectral shapes and the potential error inherent in using the existing approach to computing in structure response spectra is quantified. Modifications to reduce potential error in the existing ASCE 4 criteria are proposed. In structure response spectra are typically generated for a subsystem given the time history response of a building region. The building time history response is based on analyses that use either modal time history superposition, direct integration or complex frequency response analysis of the building and supporting soil. Input to the building analyses consist of either real or synthetic discretized ground motion records. The discretized ground motion records are often based on recorded ground motion seeds and are often limited to a 0.005 second time step. Thus the time step of the seed record often limits the frequency content of the problem. Both the building analyses and in structure response spectra subsystem analysis may interpolate the discretized ground motion records to obtain stable results. This interpolation generates errors that are propagated through the analyses used to calculate in structure response spectra. These errors may result in extraneous high frequency content in the in structure response spectra. Errors are quantified by comparison of time history parameters, Fourier components and in structure response spectra.

The Damage Potential of Eastern North American Earthquakes

1993 ◽  
Vol 64 (2) ◽  
pp. 119-137 ◽  
Author(s):  
Glenn L. Greig ◽  
Gail M. Atkinson
Keyword(s):  
North American ◽  
High Frequency ◽  
High Stress ◽  
Response Spectra ◽  
Elastic Response ◽  
Damage Potential ◽  
Elastic Response Spectra ◽  
Attenuation Models ◽  
Ground Motion Records ◽  
Stress Drops

Abstract We compare the damage potential of three recent eastern North American (ENA) earthquakes (Nahanni, 1985; Saguenay, 1988; and Mont Laurier, 1990) to that of the 1989 Loma Prieta, California earthquake. The Saguenay and Mont Laurier events were noteworthy due to their unusually high stress drops. The comparisons are based on synthetic ground motion records generated by the stochastic method, using source and attenuation models that were derived from actual records for each event. Damage potential is characterized by inelastic strength demand spectra, obtained by analyzing the response of nonlinear oscillators to each record. There is a strong similarity between the inelastic spectra and the more familiar elastic response spectra, although some significant differences are observed. Comparisons between events show that a moderate high-stress ENA earthquake, like Saguenay, can be as damaging to high-frequency structures as a major California earthquake.

On the Fatigue at Very High Frequency — Part I: Theoretical and Variational Formulation

1991 ◽  
Vol 113 (2) ◽  
pp. 205-209 ◽  
Author(s):  
Kong Xiangan ◽  
K. Saanouni ◽  
C. Bathias
Keyword(s):  
High Frequency ◽  
Time Integration ◽  
Classical Problem ◽  
Fatigue Tests ◽  
Evolution Problem ◽  
Very High Frequency ◽  
Thermoelastic Wave ◽  
Frequency Space ◽  
Endurance Tests ◽  
Very High

This first part of our study is concerned with the theoretical and variational formulations of the problem of elastic cyclic loading at very high frequency (or acoustic fatigue). The problem is treated by using the theory of longitudinal thermoelastic wave motion in a finite medium with and without running crack. Two methods are used to formulate the evolution problem: the first one deals with the use of classical time integration schema, and the second uses the Fourier transformation to solve the evolution problem in the frequency space. Comparison of our results with some closed form solutions of some classical problem is presented. In a second paper this method is used to calculate thermo-mechanical fields in specimens used in ultrasonic fatigue tests (endurance tests and crack growth tests).

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