scholarly journals Development of a Drone’s Vibration, Shock, and Atmospheric Profiles

2021 ◽  
Vol 11 (11) ◽  
pp. 5176
Author(s):  
Changfeng Ge ◽  
Kyle Dunno ◽  
Mukul Anand Singh ◽  
Long Yuan ◽  
Li-Xin Lu
Keyword(s):  
Field Data ◽  
Response Spectrum ◽  
Vertical Plane ◽  
Distribution Channel ◽  
Vertical Direction ◽  
Simulation Techniques ◽  
Standards Of Practice ◽  
Technological Advances ◽  
Power Spectral ◽  
G Value

Technological advances in unmanned aerial vehicles (UAVs) have made it possible to employ drone deliveries for packaged products, but currently no standards of practice are available to qualify packaged products traveling through this distribution channel. This research proposes a methodology to collect field data from a UAV to develop simulation techniques for use with package testing equipment. This project utilized data recorders to measure the vibration, shock, and atmospheric field data on two models of the DJI drones. The root mean square G value (Grms), the power spectral density (PSD), maximum G-values and shock response spectrum, and atmospheric data were reported in this study. The study found that the general shape of the PSD profile of the drones differed from the PSD air profiles of the aircraft. The overall recorded Grms levels of the drones were also significantly higher than those of the published air profile of the aircraft. Moreover, the study found that the drone’s in-flight vibration intensities in the horizontal level were consistently higher than those in the vertical direction. The major sources of vibration and shock in both drones’ models originated from the two-propeller rotations. Shocks recorded during the flight reached 14 G, took place in the horizontal plane with the drone accelerating as opposed to the vertical plane where the drone is landing.

scholarly journals Dielectric anisotropy as indicator of crystal orientation fabric in Dome Fuji ice core: method and initial results

2021 ◽  
pp. 1-12
Author(s):  
Tomotaka Saruya ◽  
Shuji Fujita ◽  
Ryo Inoue
Keyword(s):  
Crystal Orientation ◽  
Horizontal Plane ◽  
Ice Core ◽  
Vertical Plane ◽  
Vertical Direction ◽  
Core Sample ◽  
Dielectric Anisotropy ◽  
Principal Axes ◽  
Polycrystalline Ice ◽  
Initial Results

Abstract Polycrystalline ice is known to exhibit macroscopic anisotropy in relative permittivity (ɛ) depending on the crystal orientation fabric (COF). Using a new system designed to measure the tensorial components of ɛ, we investigated the dielectric anisotropy (Δɛ) of a deep ice core sample obtained from Dome Fuji, East Antarctica. This technique permits the continuous nondestructive assessment of the COF in thick ice sections. Measurements of vertical prism sections along the core showed that the Δɛ values in the vertical direction increased with increasing depth, supporting previous findings of c-axis clustering around the vertical direction. Analyses of horizontal disk sections demonstrated that the magnitude of Δɛ in the horizontal plane was 10–15% of that in the vertical plane. In addition, the directions of the principal axes of tensorial ɛ in the horizontal plane corresponded to the long or short axis of the elliptically elongated single-pole maximum COF. The data confirmed that Δɛ in the vertical and horizontal planes adequately indicated the preferred orientations of the c-axes, and that Δɛ can be considered to represent a direct substitute for the normalized COF eigenvalues. This new method could be extremely useful as a means of investigating continuous and depth-dependent variations in COF.

On the Combined Effect of Mean Flow and Acoustic Excitation on Structural Response and Radiation

1997 ◽  
Vol 119 (3) ◽  
pp. 448-456 ◽  
Author(s):  
A. Frendi ◽  
L. Maestrello
Keyword(s):  
Mach Number ◽  
Response Spectrum ◽  
Structural Response ◽  
Harmonic Excitation ◽  
Two Dimensions ◽  
Physical Problem ◽  
Acoustic Excitation ◽  
Mean Flow ◽  
Power Spectral ◽  
The Mean

Numerical experiments in two dimensions are carried out in order to investigate the response of a typical aircraft structure to a mean flow and an acoustic excitation. Two physical problems are considered; one in which the acoustic excitation is applied on one side of the flexible structure and the mean flow is on the other side while in the second problem both the mean flow and acoustic excitation are on the same side. Subsonic and supersonic mean flows are considered together with a random and harmonic acoustic excitation. In the first physical problem and using a random acoustic excitation, the results show that at low excitation levels the response is unaffected by the mean flow Mach number. However, at high excitation levels the structural response is significantly reduced by increasing the Mach number. In particular, both the shift in the frequency response spectrum and the broadening of the peaks are reduced. In the second physical problem, the results show that the response spectrum is dominated by the lower modes (1 and 3) for the subsonic mean flow case and by the higher modes (5 and 7) in the supersonic case. When a harmonic excitation is used, it is found that in the subsonic case the power spectral density of the structural response shows a subharmonic (f/4) while in the supersonic case no subharmonic is obtained.

scholarly journals Flood design recipes vs. reality: can predictions for ungauged basins be trusted?

2014 ◽  
Vol 14 (6) ◽  
pp. 1417-1428 ◽  
Author(s):  
A. Efstratiadis ◽  
A. D. Koussis ◽  
D. Koutsoyiannis ◽  
N. Mamassis
Keyword(s):  
Flood Risk ◽  
Field Data ◽  
Ungauged Basins ◽  
Hydrological Data ◽  
Preliminary Results ◽  
Eu Directive ◽  
Technological Advances ◽  
Quality And Reliability ◽  
Engineering Practices ◽  
Current Engineering

Abstract. Despite the great scientific and technological advances in flood hydrology, everyday engineering practices still follow simplistic approaches that are easy to formally implement in ungauged areas. In general, these "recipes" have been developed many decades ago, based on field data from typically few experimental catchments. However, many of them have been neither updated nor validated across all hydroclimatic and geomorphological conditions. This has an obvious impact on the quality and reliability of hydrological studies, and, consequently, on the safety and cost of the related flood protection works. Preliminary results, based on historical flood data from Cyprus and Greece, indicate that a substantial revision of many aspects of flood engineering procedures is required, including the regionalization formulas as well as the modelling concepts themselves. In order to provide a consistent design framework and to ensure realistic predictions of the flood risk (a key issue of the 2007/60/EU Directive) in ungauged basins, it is necessary to rethink the current engineering practices. In this vein, the collection of reliable hydrological data would be essential for re-evaluating the existing "recipes", taking into account local peculiarities, and for updating the modelling methodologies as needed.

Use of RVT for Computation of In-Structure Response Spectra and Peak Responses and Comparison to Time History and Response Spectrum Analysis

2018 ◽  
Vol 34 (4) ◽  
pp. 1913-1930 ◽  
Author(s):  
Irmela Zentner
Keyword(s):  
Response Spectrum ◽  
Structural Response ◽  
Time History ◽  
Strong Motion ◽  
Response Spectra ◽  
Combination Rules ◽  
Floor Response Spectra ◽  
Power Spectral ◽  
Time Histories ◽  
Definition Of

The random vibration theory offers a framework for the conversion of response spectra into power spectral densities (PSDs) and vice versa. The PSD is a mathematically more suitable quantity for structural dynamics analysis and can be straightforwardly used to compute structural response in the frequency domain. This allows for the computation of in-structure floor response spectra and peak responses by conducting only one structural analysis. In particular, there is no need to select or generate spectrum-compatible time histories to conduct the analysis. Peak response quantities and confidence intervals can be computed without any further simplifications such as currently used in the response spectrum method, where modal combination rules have to be derived. In contrast to many former studies, the Arias intensity-based definition of strong-motion duration is adopted here. This paper shows that, if the same definitions of strong-motion duration and modeling assumptions are used for time history and RVT computations, then the same result can be expected. This is illustrated by application to a simplified model of a reactor building.

scholarly journals Flood design recipes vs. reality: can predictions for ungauged basins be trusted?

2013 ◽  
Vol 1 (6) ◽  
pp. 7387-7416 ◽  
Author(s):  
A. Efstratiadis ◽  
A. D. Koussis ◽  
D. Koutsoyiannis ◽  
N. Mamassis
Keyword(s):  
Field Data ◽  
Ungauged Basins ◽  
Unit Hydrograph ◽  
Hydrological Data ◽  
Eu Directive ◽  
Technological Advances ◽  
Quality And Reliability ◽  
Engineering Practices ◽  
Current Engineering ◽  
Scs Cn

Abstract. Despite the great scientific and technological advances in flood hydrology, everyday engineering practices still follow simplistic approaches, such as the rational formula and the SCS-CN method combined with the unit hydrograph theory that are easy to formally implement in ungauged areas. In general, these "recipes" have been developed many decades ago, based on field data from few experimental catchments. However, many of them have been neither updated nor validated across all hydroclimatic and geomorphological conditions. This has an obvious impact on the quality and reliability of hydrological studies, and, consequently, on the safety and cost of the related flood protection works. Preliminary results, based on historical flood data from Cyprus and Greece, indicate that a substantial revision of many aspects of flood engineering procedures is required, including the regionalization formulas as well as the modelling concepts themselves. In order to provide a consistent design framework and to ensure realistic predictions of the flood risk (a key issue of the 2007/60/EU Directive) in ungauged basins, it is necessary to rethink the current engineering practices. In this vein, the collection of reliable hydrological data would be essential for re-evaluating the existing "recipes", taking into account local peculiarities, and for updating the modelling methodologies as needed.

scholarly journals Optimization of Damage Equivalent Accelerated Test Spectrum Derivation Using Multiple Non-Gaussian Vibration Data

2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Fei Xu ◽  
Kjell Ahlin ◽  
Binyi Wang
Keyword(s):  
Field Data ◽  
Response Spectrum ◽  
Model Parameters ◽  
Modal Parameter ◽  
Accelerated Test ◽  
Dynamic Selection ◽  
Extreme Response ◽  
Non Gaussian ◽  
Selection Of ◽  
Test Spectrum

The response spectra are widely used in the damage assessment of non-Gaussian random vibration environments and the derivation of damage equivalent accelerated test spectrum. The effectiveness of the latter is strongly affected by modal parameter uncertainties, multiple field data processing, and the nonsmooth shape of the derived power spectral density (PSD). Optimization of accelerated test spectrum derivation based on dynamic parameter selection and iterative update of spectrum envelope is presented in this paper. The extreme response spectrum (ERS) envelope of the field data is firstly taken as the limiting spectrum, and the corresponding relationship between damping coefficient, fatigue exponent, and damage equivalent PSD under different test times is constructed to achieve the dynamic selection of uncertain parameters in the response spectrum model. Then, an iterative update model based on the weighted sum of fatigue damage spectrum (FDS) error is presented to reduce the error introduced by the nonsmooth shape of the derived PSD. The case study shows that undertest can be effectively avoided by the dynamic selection of model parameters. The weighted error is reduced from 80.1% to 7.5% after 7 iterations. Particularly, the error is close to 0 within the peak and valley frequency band.

scholarly journals Flight of a Guided Aerial Bomb Along a Vertical Plane in Turbulent Atmosphere

2019 ◽  
Vol 10 (3) ◽  
pp. 19-30
Author(s):  
Konrad STEFAŃSKI ◽  
Marta GRZYB
Keyword(s):  
Turbulent Atmosphere ◽  
Vertical Plane ◽  
Universal Method ◽  
Flight Trajectory ◽  
Proportional Navigation ◽  
The Earth ◽  
Power Spectral ◽  
Atmospheric Disturbances ◽  
Ground Target ◽  
Atmospheric Phenomena

The control of a homing flying object, which a guided aerial bomb (GAB) is, takes place in the earth’s atmosphere, which may feature various atmospheric phenomena that are disturbances to the GAB control. The atmospheric disturbances include air turbulences, wind pockets, and wind gusts. For the purpose of the research discussed in this paper, the atmospheric disturbances were qualified as a stochastic process of power spectral density according to the Dryden model. This paper presents a method of controlling a GAB in motion through a turbulent atmosphere of the earth. The GAB was homed to a moving ground target by the most universal method of proportional navigation. The research discussed in this paper included an analysis of the effect of atmospheric disturbances on the target striking accuracy of a GAB moving along a vertical plane, the GAB flight trajectory, the values of force inputs which controlled the GAB flight, the values of actual attack angles, the values of kinematic transverse overloads, and the control errors input to the guidance controller. The numerical simulations were completed during the research in Matlab/Simulink, and certain results thereof are represented in a graphical format.

scholarly journals Seismic Behaviour of Offshore Steel Jacket Platform Braced in Horizontal and Vertical Planes

2019 ◽  
Vol 8 (12) ◽  
pp. 1947-1953
Keyword(s):  
Seismic Analysis ◽  
Response Spectrum ◽  
Vertical Plane ◽  
Static Method ◽  
Base Shear ◽  
Response Spectrum Method ◽  
Seismic Behaviour ◽  
Jacket Platform ◽  
Spectrum Method ◽  
Time Period

The offshore jacket platforms are primarily installed in the large oceans mainly for drilling the crude oil, carbohydrates and production of electricity. The current studies emphasize on the structural performance of offshore deck jacket platform with different bracing systems. Earthquake analysis has been performed to calculate the seismic responses, with the help of bracings to control the seismic induced vibrations of the jacket platforms. For this study, a jacket platform made up of steel members has been modeled and then analyzed under earthquake and wave loadings. This paper mainly deals to compute and compare the seismic behavior of offshore steel deck platform using SAP 2000 v20 software with bracing in the horizontal plane and bracing in both horizontal and vertical planes. The total number of 8 models has been analyzed in the SAP2000 software with bracing i.e. X, V, Inverted V and K in the vertical plane and bracing i.e. X, V, Inverted V and K in both horizontal and vertical plane. A relative study has been carried out in Time period, deck displacement and base shear. Seismic analysis using linear static, i.e. Equivalent static method (ESA) and linear dynamic, i.e. Response spectrum method (RSA) has been performed. Further deck displacement, time period and base shear are determined by Equivalent static method and Response spectrum method for various types of bracing models in both horizontal and vertical planes. Among the all various types of bracing models, Inverted V bracing in the vertical plane is found to be the optimum model among all other models.

scholarly journals Damage estimation on concrete gravity dams through artificial accelerograms

2018 ◽  
Vol 211 ◽  
pp. 14001
Author(s):  
Enrico Zacchei ◽  
José Luis Molina
Keyword(s):  
Response Curve ◽  
Seismic Analysis ◽  
Response Spectrum ◽  
Damage Index ◽  
Spectral Density Function ◽  
Gravity Dams ◽  
Concrete Gravity Dams ◽  
Power Spectral ◽  
The Time Domain ◽  
Artificial Accelerograms

The aim of this paper is to analyse the damage on gravity dams through artificial earthquakes from two methods. The first procedure defines the performance and the response curve of concrete gravity dams using a harmonic function which establishes linear displacements. The other procedure to obtain the artificial earthquake defines the power spectral density function consistent with the response spectrum. This artificial accelerogram is necessary to quantify the response curve of concrete gravity dams in the time domain. The seismic activity in Spain is not frequent, therefore it is often difficult to select real accelerograms to perform a complete seismic analysis, which makes artificial accelerograms extremely useful. Finally, combining these two procedures, a damage index is determined for assessing the crack’s magnitude. These both efficient and practical procedures are useful to develop further complicated analysis.

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