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Sullivan, Edmund J. "Model‐based towed array processing". Journal of the Acoustical Society of America 101, nr 5 (maj 1997): 3156. http://dx.doi.org/10.1121/1.419142.
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Sullivan, Edmund J., i Geoffrey S. Edelson. "Model‐based broadband towed‐array processing". Journal of the Acoustical Society of America 115, nr 5 (maj 2004): 2577. http://dx.doi.org/10.1121/1.4784220.
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Sullivan, Edmund J., Dieter Brecht i Leif Persson. "Model‐based towed array processor: Experimental results". Journal of the Acoustical Society of America 107, nr 5 (maj 2000): 2890. http://dx.doi.org/10.1121/1.428744.
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Premus, Vincent E., Philip A. Abbot, Vitaly Kmelnitsky, Charles J. Gedney i Ted A. Abbot. "A wave glider-based, towed hydrophone array system for autonomous, real-time, passive acoustic marine mammal monitoring". Journal of the Acoustical Society of America 152, nr 3 (wrzesień 2022): 1814–28. http://dx.doi.org/10.1121/10.0014169.
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An autonomous surface vehicle known as a wave glider, instrumented with a low-power towed hydrophone array and embedded digital signal processor, is demonstrated as a viable low-noise system for the passive acoustic monitoring of marine mammals. Other key design elements include high spatial resolution beamforming on a 32-channel towed hydrophone array, deep array deployment depth, vertical motion isolation, and bandwidth-efficient real-time acoustic data transmission. Using at-sea data collected during a simultaneous deployment of three wave glider-based acoustic detection systems near Stellwagen Bank National Marine Sanctuary in September 2019, the capability of a low-frequency towed hydrophone array to spatially reject noise and to resolve baleen whale vocalizations from anthropogenic acoustic clutter is demonstrated. In particular, mean measured array gain of 15.3 dB at the aperture design frequency results in a post-beamformer signal-to-noise ratio that significantly exceeds that of a single hydrophone. Further, it is shown that with overlapping detections on multiple collaborating systems, precise localization of vocalizing individuals is achievable at long ranges. Last, model predictions showing a 4× detection range, or 16× area coverage, advantage of a 32-channel towed array over a single hydrophone against the North Atlantic right whale upcall are presented for the continental shelf environment south of Martha's Vineyard.
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Zhang, Dapeng, Bowen Zhao i Keqiang Zhu. "Hydrodynamic Response of Ocean-Towed Cable-Array System under Different Munk Moment Coefficients". Sustainability 14, nr 3 (8.02.2022): 1932. http://dx.doi.org/10.3390/su14031932.
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The ocean towing system plays an important role in the ocean development process. The motion of a towed body is closely coupled with the motion of a towing cable. In this paper, the lumped mass method is used to discrete a towing cable into a lumped mass model. At the same time, on the basis of some assumptions, the relationship between the expression of Munk moments in the classical towed body kinematics and the expression of the Munk moments in the hydrodynamic analysis software OrcaFlex is established. Based on the above assumptions and the derivation, combined with the specific parameters of a certain sea state and a certain towing system, the dynamic simulation of the towing system is made by OrcaFlex. By changing the different Munk moment coefficients, the real-time response of the cable tension and the towed underwater body under different Munk moments is achieved. The effects of different Munk moment coefficients on the change of the tension are obtained; the six degrees of freedom of the towed body under the action of different Munk moment coefficients are shown. To obtain the spectral density of the six degrees of freedom of the towed body under the action of different Munk moment coefficients, Fast Fourier Transform is performed on the calculated results of the towed body in the time domain. The results provide a theoretical basis for the optimal design of a cable and towed body.
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Jung, Youngcheol, Woojae Seong, Keunhwa Lee i Seongil Kim. "A Depth-Bistatic Bottom Reverberation Model and Comparison with Data from an Active Triplet Towed Array Experiment". Applied Sciences 10, nr 9 (28.04.2020): 3080. http://dx.doi.org/10.3390/app10093080.
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In this paper, a depth-bistatic bottom reverberation model that employs the ray theory is presented. The model can be applied to an active towed array in the ocean. The reverberation time series are modeled under the depth-bistatic assumption and their Doppler shift is calculated based on the actual source–receiver geometry. This model can handle N × 2D range-dependent bathymetry, the geometry of a triplet array, and the Doppler motion of the source, targets, and receiver. The model predictions are compared with the mid-frequency reverberation data measured by an active triplet towed array during August 2015 in the East Sea, Korea. These data are collected with a variable depth source at mid-frequency and the triplet line array in a deep-water environment. Model predictions of the beam time series and its spectrogram are in good agreement with the measurement. In particular, we discuss the effects of the source and receiver depths on the reverberation in deep water observed in both the measured and modeled results.
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Morten, Jan Petter, Jean-Michael Poudroux i Rune Mittet. "A modeling study of augmenting coarse-grid 3D controlled-source electromagnetics with data from a towed receiver array". GEOPHYSICS 81, nr 1 (1.01.2016): E33—E42. http://dx.doi.org/10.1190/geo2014-0583.1.
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We have considered the simultaneous 3D inversion of controlled-source electromagnetic data from a towed receiver array and a coarse grid of stationary seabed receivers. Our 3D synthetic model demonstrated the sensitivity and effect on imaging of towed and seabed receiver data. The short-offset data from the towed receivers at 1–3 km offset are effective at resolving a shallow resistor at a 400-m burial depth. On the other hand, the data from the stationary seabed receivers have less noise and will resolve the 3D geometry of resistive structures buried at the 1–2 km depths typical of a hydrocarbon reservoir. We have determined how the complementary sensitivity of data from the two receiver types can be used in simultaneous inversion to recover the shallow and deep resistors.
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Hui, Juan, An Bang Zhao, Kun Ping Sun, Shao Juan Wen i Jun Ying Hui. "The Simulation of Tow Ship Noise on Towed Linear Array". Advanced Materials Research 433-440 (styczeń 2012): 2706–11. http://dx.doi.org/10.4028/www.scientific.net/amr.433-440.2706.
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Based on the acoustical properties of the tow ship noise, this paper studies the effect of tow ship noise on the towed linear array sonar system by computer simulation. The tow ship noise which is fairly approximate to the truth tow ship noise is obtained by the typical mathematical mode simulation firstly. Then the near-filed characteristics of the tow ship noise are simulated by using a simplified channel model. Finally, this thesis studies the interference of tow ship noise through beam-forming. The simulation describes acoustic characteristics of the tow ship noise well, and also provides a good theoretical support for the other simulation systems designs.
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Barkley, Yvonne M., Eva-Marie Nosal i Erin M. Oleson. "Model-based localization of deep-diving cetaceans using towed line array acoustic data". Journal of the Acoustical Society of America 150, nr 2 (sierpień 2021): 1120–32. http://dx.doi.org/10.1121/10.0005847.
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Ellis, D. D. "Shallow water reverberation: normal-mode model predictions compared with bistatic towed-array measurements". IEEE Journal of Oceanic Engineering 18, nr 4 (1993): 474–82. http://dx.doi.org/10.1109/48.262297.
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Relano, R.-Jay S., Kate G. Francisco, Ronnie S. Concepcion II, Mike Louie C. Enriquez, Jonah Jahara G. Baun, Adrian Genevie G. Janairo, Ryan Rhay P. Vicerra, Argel A. Bandala i Elmer P. Dadios. "SpeedX: Smart Speed Controller Model of Towed Subterranean Imaging System for Resistivity Data Distortion Reduction Using Computational Intelligence". Journal of Advanced Computational Intelligence and Intelligent Informatics 27, nr 1 (20.01.2023): 3–11. http://dx.doi.org/10.20965/jaciii.2023.p0003.
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Land surveying has been one of the core operations in performing underground imaging. It is known that dynamic and continuous resistivity readings were employed through this technique using the array of capacitive electrodes being towed with a light vehicle. However, the main challenge in doing subsurface surveying is the change in speed of the system when there are inevitable obstacles and sloping road surfaces. To address it, this study will develop prediction models using different computational intelligence such as multigene symbolic regression genetic programming (MSRGP), regression-based decision tree (RTree), and feed forward neural network (FFNN) that will result in a smart speed controller system that can maintain the constant speed of the towed subterranean system. The best performing prediction model will be considered as the SpeedX. The expected output is a correction factor that will signal the speed controller in slow down or inclined plane road environment to maintain a constant speed of 1.6667 m/s for avoidance of data distortion on land surveying. Thus, the MSEs for MSRGP, FFNN, and RTree are 0.00163, 0.00178, and 0.00240, respectively. This results in MSRGP as the best performing model and was considered as the SpeedX model. Other evaluation metrics were employed such as the MAE and R2 which signify the advantage of SpeedX. Furthermore, the comparison between the CI-controlled and uncontrolled towed subterranean imaging trailer system, as well as its advantages clearly highlight the advantage of embedded SpeedX in the system.
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Zhang, Yuhang, Jianbo Ju i Siqing Wang. "Research on the performance of multi-base buoy arrays under the condition of on-called anti-submarine and warship-helicopter cooperation". MATEC Web of Conferences 232 (2018): 04033. http://dx.doi.org/10.1051/matecconf/201823204033.
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In order to improve the performance of traditional on-called Anti-submarine, the method of combining the towed sonar and helicopter deployment with traditional buoy arrays for multi-base searching is proposed. Combining the acoustics principle and the actual movement characteristics of warships and helicopters, model of naval movement and multi-base passive circular buoy arrays,square buoy arrays, and triangle buoy arrays deployed by a helicopter were established. The Monte Carlo method was used to simulate and analyse the effect of the initial distance from the call point, the initial position of the submarine, the speed of the submarine economy, the size parameters of the float array and the number of deployments on the multi-base search performance under each formation. The simulation results show that the search performance of the three multi-base arrays decreases with the increase of the initial distance, the initial position of the submarine, and the speed of the submarine economy; the circular multi-base array has the best search performance, and the appropriate deployment radius and the number of passive buoys to be deployed can be selected according to different search requirements and actual operational conditions. This method is suitable for on-called anti-submarine within a certain distance, and has certain military significance for anti-submarine warfare.
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Sonnemann, Tim, Jan Dettmer, Charles W. Holland i Stan Dosso. "Trans-dimensional Inversion in two spatial dimensions for geoacoustic parameters". Journal of the Acoustical Society of America 152, nr 4 (październik 2022): A185. http://dx.doi.org/10.1121/10.0015972.
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We test a series of model parametrizations to invert a two-dimensional (2-D) seabed transect going from simple fixed-dimensional to more complex trans-dimensional configurations. Inverting spherical-wave reflection coefficient datasets independently as one-dimensional layered models for a 2-D section is less efficient than applying a more parsimonious 2-D parametrization while also carrying out full uncertainty quantification. We approach the problem by proposing different fixed and dynamically inferred parametrization schemes, and discuss implementation, computational cost and resulting accuracy. We demonstrate the application in geoacoustics using a dataset of 1711 source transmissions recorded on a 32-element linear hydrophone array with both source and array towed by an autonomous underwater vehicle along a 12 km transect on the Malta Plateau in the Mediterranean Sea.
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Díaz Charris, Vladimir, i Juan A. Contreras Montes. "Design and development of route planner for Unmanned Surface Vehicles". Ciencia y tecnología de buques 11, nr 21 (15.09.2017): 89. http://dx.doi.org/10.25043/19098642.151.
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This paper describes the development of a route planner for Unmanned Surface Vehicles (USVs) focused on the study of an operational scenario for a specific mission – Anti-Submarine Warfare (ASW). Through the design and implementation of a simulation model, the effect of the different factors that particularly influence ASW is analyzed, such as search pattern, speed and sensor type; dipping sonar or towed array sonar (TAS). By obtaining a measurement of effectiveness, the USV’s response in the deployment of this type of mission can be defined using time to detect the threat in a search area, as parameters to measure the performance.
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Han, Songtong, Xiaoli Rong, Leixiang Bian, Mingyou Zhong i Lining Zhang. "The Application of Magnetometers and Electromagnetic Induction Sensors in UXO Detection". E3S Web of Conferences 131 (2019): 01045. http://dx.doi.org/10.1051/e3sconf/201913101045.
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This paper introduces the physical model of unexploded ordnance (UXO) in the magnetization process and the formula derivation of the magnetic dipole model. The application of magnetometers and electromagnetic induction sensors in the detection of UXO is introduced. The magnetometers introduce the total field measurements technology of the CS optical-pump marine magnetometer and the MagSTAR (Magnetic Scalar Triangulation and Ranging) gradient detection technology. The electromagnetic induction sensors introduce the working theories and the popular product models of Geophex company and Geonics Ltd. The method of detecting UXO by MTADS of United States Naval Research Laboratory (The multisensor towed array detection system) compares the difference between the United States Naval Research Laboratory for target recognition.
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Billings, Stephen, i Laurens Beran. "Optimizing electromagnetic sensors for unexploded ordnance detection". GEOPHYSICS 82, nr 3 (1.05.2017): EN25—EN31. http://dx.doi.org/10.1190/geo2016-0232.1.
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Time-domain electromagnetic (TEM) instruments are the predominant geophysical sensor for detection of buried unexploded ordnance (UXO). Detection surveys commonly use towed TEM sensor arrays to acquire a digital map for target detection. We use a dipolar model to predict a detection threshold for a UXO at a specified clearance depth, given an arbitrary sensor geometry. In general, the minimum target response is obtained for a horizontally oriented target. We find that for multistatic sensors, the minimum response can also depend on the azimuth of the target. By considering the statistics of the target response, we find that the detection threshold can be raised slightly while still ensuring a high probability of detection of UXO at depth. This increase in the detection threshold can have a significant effect on the number of false alarms that need to be interrogated or investigated and hence on the cost of clearance. We also use Monte Carlo simulation to investigate how array geometry and height affect clutter rejection.
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Sonnemann, Tim, Jan Dettmer, Charles W. Holland i Stan Dosso. "High-resolution transdimensional geoacoustic inversion using autonomous underwater vehicle data". Journal of the Acoustical Society of America 152, nr 4 (październik 2022): A146. http://dx.doi.org/10.1121/10.0015845.
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We invert reflection coefficient measurements of muddy sediment layers along a 12-km seabed transect on the Malta Plateau in the Mediterranean Sea using 1711 source transmissions recorded on a 32-element linear hydrophone array with both source and array towed by an autonomous underwater vehicle. Trans-dimensional Bayesian inference using reversible jump Markov chain Monte Carlo sampling is applied to obtain posterior probability densities of the number of homogeneous sediment layers, their depths, and their geoacoustic parameters. The forward sediment acoustics model is based on the grain-shearing model which obeys physical causality and provides correlation between important geoacoustic properties. Each dataset was treated as one-dimensional seabed structure inversion carried out on high performance clusters, and inversion results for multiple data sets were combined to yield a two-dimensional subsurface profile including full uncertainty analysis. Comparisons of inversion results to piston and gravity core estimates show agreement in both geoacoustic parameter values and depths of discontinuities. In the range-dependent model constructed from inverting the entire data set, dipping and terminating layers are observed along the track with high vertical resolution on the order of 10 cm.
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Ellis, Dale D., Jie Yang, John R. Preston i Sean Pecknold. "A Normal Mode Reverberation and Target Echo Model to Interpret Towed Array Data in the Target and Reverberation Experiments". IEEE Journal of Oceanic Engineering 42, nr 2 (kwiecień 2017): 344–61. http://dx.doi.org/10.1109/joe.2017.2674106.
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Schinault, Matthew E., i Purnima Ratilal. "An end-capped lead zirconate titanate broadband hydrophone theoretical calculation and electroacoustic measurement for towed array applications". Journal of the Acoustical Society of America 152, nr 4 (październik 2022): A296. http://dx.doi.org/10.1121/10.0016333.
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Hydrophone transducers for towed array applications require low self-noise, small form factor and a linear frequency response below 50 kHz for general purpose long-range ocean sensing. The design specification for this hydrophone application has several aspects including acoustic sensitivity, frequency response, dissipation factor, and physical size. A comprehensive noise model informs filter design for pre-amplifiers after the piezoelectric element. Theoretical calculation of pressure to voltage conversion is made here by estimating the Free-Field Voltage Sensitivity (FFVS) using methods from R.A. Langevin and G.W. McMahon. Using these methods to achieve the desired design specification, we use two cylindrical ceramics with a split electrode poled in the radial direction with series stacked ceramics using end caps with air backing to increase sensitivity and reduce overall size. An experiment is carried out to measure the resonant modes using a simple impedance measuring circuit which then can be used to estimate FFVS linearity. These results are compared with theoretical calculation for hydrophone response of resonant modes and results from measurement circuit.
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Gagnon, R. "Physical Model Experiments to Assess the Hydrodynamic Interaction Between Floating Glacial Ice Masses and a Transiting Tanker". Journal of Offshore Mechanics and Arctic Engineering 126, nr 4 (1.11.2004): 297–309. http://dx.doi.org/10.1115/1.1835986.
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An array of nine fabricated models comprised of three different shapes, with three model sizes for each shape, has been utilized in tow tank tests to investigate the hydrodynamic interaction between glacial ice masses and a transiting tanker. A generic model tanker was towed past free-floating ice mass models at various speeds and proximities. The ice masses were either spherical, pyramidal or cylindrical in shape. The influence of waves of various periods and wave heights was also investigated. Sway and surge of the ice masses in response to the tanker passage were measured as the primary indicators of the hydrodynamic interactions. Notable among the many observed behaviors was that waves tended to enhance the degree of sway. Also, in the scenarios tested the magnitude of surge speed and sway speed were <10% of the tanker speed, and would therefore not significantly reduce impact speed during collisions. The program results are intended for use primarily in the validation of IOT’s numerical simulations of bergy bit/ship collisions, but can also serve as a validation database for simulation studies by other researchers.
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Kamal, Ashley, i Madeline Miller. "Shallow water acoustic spatial coherence". Journal of the Acoustical Society of America 151, nr 4 (kwiecień 2022): A138. http://dx.doi.org/10.1121/10.0010905.
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The understanding and ability to predict acoustic spatial coherence in dynamic ocean environments is limited, as it depends on many small scale physical processes. Development and validation of theoretical models requires the assessment of coherence in diverse ocean conditions. We compute spatial coherence measures for the SwellEx-96 experiment and evaluate the functional dependence of coherence on frequency in a shallow water environment. The acoustic signals are low-frequency multi-tones (50–400 Hz) transmitted from a ship-towed source and received on horizontal bottom-mounted arrays deployed across the 240-260m isobaths. Following the approach developed by Heaney (2011), coherence measures employed are the “power factor” and “eigenvalue ratio” of the eigenvalues of a cross-spectral density matrix. Advantageously, these methods account for both amplitude and phase, do not require a signal model, and were shown to have low sensitivity to array element position error. We assess whether spatial coherence calculated from the SwellEx-96 data is functionally related to frequency and determine the effect of range on the spatial coherence estimate. Results from this analysis are compared to existing coherence length data estimates and theoretical models.
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Swidinsky, Andrei, i R. Nigel Edwards. "Joint inversion of navigation and resistivity using a fixed transmitter and a towed receiver array: a transient marine CSEM model study". Geophysical Journal International 186, nr 3 (13.07.2011): 987–96. http://dx.doi.org/10.1111/j.1365-246x.2011.05104.x.
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Zhao, Meng, Wenbo Wang, Qunyan Ren, Haiyan Ni, Xu Xiao i Li Ma. "Modified you-only-look-once model for joint source detection and azimuth estimation in a multi-interfering underwater acoustic environment". Journal of the Acoustical Society of America 153, nr 4 (1.04.2023): 2393. http://dx.doi.org/10.1121/10.0017828.
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The you-only-look-once (YOLO) model identifies objects in complex images by framing detection as a regression problem with spatially separated boundaries and class probabilities. Object detection from complex images is somewhat similar to underwater source detection from acoustic data, e.g., time-frequency distributions. Herein, YOLO is modified for joint source detection and azimuth estimation in a multi-interfering underwater acoustic environment. The modified you-only-look-once (M-YOLO) input is a frequency-beam domain (FBD) sample containing the target and multi-interfering spectra at different azimuths, generated from the received data of a towed horizontal line array. M-YOLO processes the whole FBD sample using a single-regression neural network and directly outputs the target-existence probability and spectrum azimuth. Model performance is assessed on both simulated and at-sea data. Simulation results reveal the strong robustness of M-YOLO toward different signal-to-noise ratios and mismatched ocean environments. As tested on the data collected in an actual multi-interfering environment, M-YOLO achieved near-100% target detection and a root mean square error of 0.54° in azimuth estimation.
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Zhu, Chuanqi, Shiliang Fang, Qisong Wu, Liang An, Xinwei Luo i Hongli Cao. "A Time-Frequency Joint Time-Delay Difference Estimation Method for Signal Enhancement in the Distorted towed Hydrophone Array". Remote Sensing 13, nr 22 (15.11.2021): 4586. http://dx.doi.org/10.3390/rs13224586.
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To acquire the enhanced underwater ship-radiated noise signal in the presence of array shape distortion in a passive sonar system, the phase difference of the line-spectrum component in ship-radiated noise is often exploited to estimate the time-delay difference for the beamforming-based signal enhancement. However, the time-delay difference estimation performance drastically degrades with decreases of the signal-to-noise ratio (SNR) of the line-spectrum component. Meanwhile, although the time-delay difference estimation performance of the high-frequency line-spectrum components is generally superior to that of the low-frequency one, the phase difference measurements of the high-frequency line-spectrum component often easily encounter the issue of modulus 2π ambiguity. To address the above issues, a novel time-frequency joint time-delay difference estimation method is proposed in this paper. The proposed method establishes a data-driven hidden Markov model with robustness to phase difference ambiguity by fully exploiting the underlying property of slowly changing the time-delay difference over time. Thus, the phase difference measurements available for time-delay difference estimation are extended from that of low-frequency line-spectrum components in a single frame to that of all detected line-spectrum components in multiple frames. By jointly taking advantage of the phase difference measurements in both time and frequency dimensions, the proposed method can acquire enhanced time-delay difference estimates even in a low SNR case. Both simulation and at-sea experimental results have demonstrated the effectiveness of the proposed method.
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Edwards, R. N. "Two‐dimensional modeling of a towed in‐line electric dipole‐dipole sea‐floor electromagnetic system: The optimum time delay or frequency for target resolution". GEOPHYSICS 53, nr 6 (czerwiec 1988): 846–53. http://dx.doi.org/10.1190/1.1442519.
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Towed in‐line transient electric dipole‐dipole systems are being used to map the electrical conductivity of the sea floor. The characteristic response of a double half‐space model representing conductive seawater and less conductive crustal material to a dipole‐dipole system located at the interface consists of two distinct parts. As time in the transient measurements progresses, two changes in field strength are observed. The first change is caused by the diffusion of the electromagnetic field through the resistive sea floor; the second is caused by diffusion through the seawater. The characteristic times at which the two events occur are measures of sea‐floor and seawater conductivity, respectively. Entirely equivalent responses are observed in a frequency‐domain measurement as frequency is swept from high to low. The simple double half‐space response is modified when the towed array crosses over a conductivity anomaly. I evaluate the magnitude of the anomalous response as a function of delay time and frequency using a two‐dimensional theory and a vertical, plate‐like target. If the ratio of the conductivity of the seawater to that of the sea floor is greater than unity, then an optimum time delay or frequency can be found which maximizes the response. For large conductivity contrasts, the optimum response is greater than the response at late time or zero frequency by a factor of the order of the conductivity ratio.
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Riss, Joëlle, Juan Luis Fernández-Martínez, Colette Sirieix, Ouassima Harmouzi, Antoine Marache i Ali Essahlaoui. "A methodology for converting traditional vertical electrical soundings into 2D resistivity models: Application to the Saïss basin, Morocco". GEOPHYSICS 76, nr 6 (listopad 2011): B225—B236. http://dx.doi.org/10.1190/geo2010-0080.1.
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We demonstrated a simple methodology for the reinterpretation of sets of electrical vertical soundings and the production of 2D resistivity models. The method is applied to the northern central part of the subsiding Saïss basin (Morocco) where a series of vertical electrical soundings (VES) were acquired in 1982 and 1984, using the Schlumberger array with current electrodes semispacings between 3 and 3000 m. We describe a methodology used to estimate and sample apparent resistivities collected from traditional single soundings acquired by using a Schlumberger configuration. We then construct a resistivity pseudosection in a format compatible with a Wenner-Schlumberger array to perform 2D electrical tomography. The methodology takes into account the lateral and vertical spatial correlations shown by the apparent resistivities. The tomographic inversions are performed using a commercial inversion software commonly used in industry. Geostatistical tools are used to quantify the spatial correlation between apparent resistivity data. The result is a series of estimated pseudosections that are inverted to produce 2D resistivity models of the basin along geophysical profiles. We focus our attention on one of these profiles (i.e., one 2D resistivity model). The inverted geoelectrical model allows us to propose a geologic model of the basin. Our methodology allows historical and current data carried out using the Schlumberger configuration, to be rapidly reinterpreted in countries where only low-cost methods, such as VES soundings, can be used due to technology and economic constraints. It can also be applied to cases where continuous or pulled-array continuous vertical soundings method, where a tail of electrodes is towed behind a small vehicle while continuously and simultaneously measuring several electrode configurations, is inoperative due to field conditions (survey length, deep layers, and local environmental conditions).
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Weglein, Arthur B., i Bruce G. Secrest. "Wavelet estimation for a multidimensional acoustic or elastic earth". GEOPHYSICS 55, nr 7 (lipiec 1990): 902–13. http://dx.doi.org/10.1190/1.1442905.
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A new and general wave theoretical wavelet estimation method is derived. Knowing the seismic wavelet is important both for processing seismic data and for modeling the seismic response. To obtain the wavelet, both statistical (e.g., Wiener‐Levinson) and deterministic (matching surface seismic to well‐log data) methods are generally used. In the marine case, a far‐field signature is often obtained with a deep‐towed hydrophone. The statistical methods do not allow obtaining the phase of the wavelet, whereas the deterministic method obviously requires data from a well. The deep‐towed hydrophone requires that the water be deep enough for the hydrophone to be in the far field and in addition that the reflections from the water bottom and structure do not corrupt the measured wavelet. None of the methods address the source array pattern, which is important for amplitude‐versus‐offset (AVO) studies. This paper presents a method of calculating the total wavelet, including the phase and source‐array pattern. When the source locations are specified, the method predicts the source spectrum. When the source is completely unknown (discrete and/or continuously distributed) the method predicts the wavefield due to this source. The method is in principle exact and yet no information about the properties of the earth is required. In addition, the theory allows either an acoustic wavelet (marine) or an elastic wavelet (land), so the wavelet is consistent with the earth model to be used in processing the data. To accomplish this, the method requires a new data collection procedure. It requires that the field and its normal derivative be measured on a surface. The procedure allows the multidimensional earth properties to be arbitrary and acts like a filter to eliminate the scattered energy from the wavelet calculation. The elastic wavelet estimation theory applied in this method may allow a true land wavelet to be obtained. Along with the derivation of the procedure, we present analytic and synthetic examples.
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Hefner, Brian T., Jie Yang i Dajun Tang. "Environmentally constrained modeling of mid-frequency transmission loss and reverberation measured during the Target and Reverberation Experiment 2013". Journal of the Acoustical Society of America 151, nr 4 (kwiecień 2022): A138—A139. http://dx.doi.org/10.1121/10.0010908.
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The goal of the Target and Reverberation Experiment (TREX13) was to make contemporaneous measurements of mid-frequency (1.5–4 kHz) transmission loss and reverberation with extensive environmental measurements so detailed model/data comparison can be achieved and important environmental factors can be identified for different applications. APL-UW collaborated with ARL-Penn State, led by John R. Preston, to deploy the Five Octave Research Array (FORA) on a “clothesline” about 2.1 m above the seafloor. This fixed-source/receiver configuration helped eliminate uncertainties from the motion of a towed array and allow reverberation measurement along a narrow, 7-km-long section of seafloor. The experiment site had a fairly complex spatial distribution of both sediment type and sediment scattering properties and keeping the FORA in a fixed position was instrumental in understanding and modeling the reverberation. While soft sediments make up only 27% of the sediments by area at the site, it is necessary to account for this spatial dependence so that both transmission loss and reverberation can be modeled using a consistent set of environmental inputs. These models and their implications for our understanding of the environmental factors which most impact mid-frequency reverberation will be discussed. [Work supported by the U.S. Office of Naval Research.]
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Li, Nansong, Minghui Zhang i Bo Gao. "Horizontal Correlation of Long-Range Bottom Reverberation in Shallow Sloping Seabed". Journal of Marine Science and Engineering 9, nr 4 (13.04.2021): 414. http://dx.doi.org/10.3390/jmse9040414.
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The performance of active sonar detection systems is seriously affected by the reverberation at the bottom of the waveguide in shallow water. In order to improve the performance of active sonar detection, it is necessary to understand the horizontal correlation of shallow-water bottom reverberation in active towed-array processing technology. However, the current research on the spatial correlation of reverberation is mainly based on vertical correlation, little work has been done on the horizontal correlation characteristics of long-distance seabed reverberation, and there is no support from sea test data. In this paper, the coupled mode reverberation model is applied to the horizontal correlation, and is studied according to the receiving position, time, and frequency. The simulation results show that, for the long-range bottom reverberation, the lateral correlation is greater than the longitudinal correlation in the horizontal space. By introducing the adiabatic mode solution, the mathematical model of horizontal correlation in the range-dependent waveguide with depth is derived. The numerical results show that the influence of the seabed dip angle on the horizontal correlation should be considered and that the horizontal correlation is affected obviously by the propagation effects of the sloped sea floor. Finally, the experimental data processing and analysis are given and verify the correctness of the algorithm.
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Jung, Youngcheol, i Keunhwa Lee. "Observation of the Relationship between Ocean Bathymetry and Acoustic Bearing-Time Record Patterns Acquired during a Reverberation Experiment in the Southwestern Continental Margin of the Ulleung Basin, Korea". Journal of Marine Science and Engineering 9, nr 11 (12.11.2021): 1259. http://dx.doi.org/10.3390/jmse9111259.
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We observed a distinct drop-off region in the bearing-time record of acoustic reverberation data acquired from the south-western continental margin of the Ulleung Basin, East Sea, in the summer of 2015. 3 kHz continuous waves with pulse lengths of 0.1, 0.3, and 1.0 s were used as source pulses, with an R/V Cheonghae vessel towing a variable depth source and a triplet towed array toward the deep sea from shallow water. The observed pattern changed as the R/V Cheonghae moved across the continental slope further into the sea. This pattern arises as a result of the downward-refracted beams in the 1/2 convergence zone interacting with the soft bottom. In addition, the boundary of the drop-off region was modeled with the two-way maximum travel time of the first bottom-reflected rays using the bathymetry model of the General Bathymetric Chart of the Oceans, 2020. Some discrepancies were observed when comparing the modeled curve to the measured results, and the inaccuracy of the bathymetry model on the continental slope could be the main cause of these discrepancies. This pattern could be useful for bathymetry mapping, as well as estimations of source and receiver configurations.
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Amundsen, Lasse, Ørjan Pedersen, Are Osen, Johan O. A. Robertsson i Martin Landrø. "Broadband seismic over/under sources and their designature-deghosting". GEOPHYSICS 82, nr 5 (1.09.2017): P61—P73. http://dx.doi.org/10.1190/geo2016-0512.1.
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The source depth influences the frequency band of seismic data. Due to the source ghost effect, it is advantageous to deploy sources deep to enhance the low-frequency content of seismic data. But, for a given source volume, the bubble period decreases with the source depth, thereby degrading the low-frequency content. At the same time, deep sources reduce the seismic bandwidth. Deploying sources at shallower depths has the opposite effects. A shallow source provides improved high-frequency content at the cost of degraded low-frequency content due to the ghosting effect, whereas the bubble period increases with a lesser source depth, thereby slightly improving the low-frequency content. A solution to the challenge of extending the bandwidth on the low- and high-frequency side is to deploy over/under sources, in which sources are towed at two depths. We have developed a mathematical ghost model for over/under point sources fired in sequential and simultaneous modes, and we have found an inverse model, which on common receiver gathers can jointly perform designature and deghosting of the over/under source measurements. We relate the model for simultaneous mode shooting to recent work on general multidepth level array sources, with previous known solutions. Two numerical examples related to over/under sequential shooting develop the main principles and the viability of the method.
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Lewis, B. T. R., i H. Jung. "Attenuation of refracted seismic waves in young oceanic crust". Bulletin of the Seismological Society of America 79, nr 4 (1.08.1989): 1070–88. http://dx.doi.org/10.1785/bssa0790041070.
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Abstract It is commonly observed in seismic refraction experiments over young oceanic crust that refracted energy is concentrated in the 10 to 15 Hz band, even though the source may have far greater bandwidth. We apply spectral ratio methods to data from a midwater hydrophone array towed 10 km from the Juan de Fuca ridge and confirm that the impulse response of the crust to refracted energy has a peak near 10 Hz. This peak appears to result from a combination of two factors that produce attenuation. One is related to the large velocity gradient in the upper crust caused by crack closure with increasing depth. The other is related to anelastic attenuation, which is probably also related to cracks and voids in the upper crust. At low frequencies (wavelengths greater than or equal to the thickness of the high gradient zone), it is shown that attenuation is dominated by the reflectivity of the upper crust. At high frequencies attenuation is dominated by anelastic effects associated with upper crust Q's of between 10 and 50. The wave propagation is dispersive, causing observable phase shifts in the response function, and Q may be frequency dependent. This model of the propagation explains why refraction data over young oceanic crust have energy concentrated near 10 Hz.
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Hughes, Larry J. "Mapping contaminant-transport structures in karst bedrock with ground-penetrating radar". GEOPHYSICS 74, nr 6 (listopad 2009): B197—B208. http://dx.doi.org/10.1190/1.3223312.
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Ammonium perchlorate, a risk to human health, was used formerly to manufacture rocket fuel at the Naval Weapons Industrial Reserve Plant (NWIRP) McGregor, McLennon County, Texas. Perchlorate exists in several groundwater contaminant plumes, whose geometries were suspected to be influenced by transmissive bedrock structures. To identify these possible contaminant-transport pathways, a towed-array ground-penetrating radar (GPR) system was used to acquire 118 line-km of data across [Formula: see text] of the property. The shallow geology consists of bedrock limestone overlain by [Formula: see text] of clay soil. For the [Formula: see text] antennas used, the conductive clay limits depth penetration to less than [Formula: see text] and yields a [Formula: see text] wavelength, reducing lateral and vertical resolution. Nevertheless, GPR data resolved the top of bedrock in many areas. Linear discontinuities in bedrock were interpreted as weathered fracture zones, and linear areas of signal loss were attributed to deeper clay weathering along fracture zones. GPR-interpreted fractures have orientations corresponding to known lineament and fault trends, appear to control plume geometries, and tend to have higher hydraulic transmissivities. GPR results led to a more complete contaminant-transport model and were used to optimize the positions of monitoring wells needed to define the extent of contamination. This reduced the cost and time required for an environmental investigation at the site. GPR was helpful also in positioning remedial trenches across contaminated structures, resulting in plume containment at the property boundaries.
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Keller, Ray, Lance Davidson, Anna Edlund, Tamira Elul, Max Ezin, David Shook i Paul Skoglund. "Mechanisms of convergence and extension by cell intercalation". Philosophical Transactions of the Royal Society of London. Series B: Biological Sciences 355, nr 1399 (29.07.2000): 897–922. http://dx.doi.org/10.1098/rstb.2000.0626.
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The cells of many embryonic tissues actively narrow in one dimension (convergence) and lengthen in the perpendicular dimension (extension). Convergence and extension are ubiquitous and important tissue movements in metazoan morphogenesis. In vertebrates, the dorsal axial and paraxial mesodermal tissues, the notochordal and somitic mesoderm, converge and extend. In amphibians as well as a number of other organisms where these movements appear, they occur by mediolateral cell intercalation, the rearrangement of cells along the mediolateral axis to produce an array that is narrower in this axis and longer in the anteroposterior axis. In amphibians, mesodermal cell intercalation is driven by bipolar, mediolaterally directed protrusive activity, which appears to exert traction on adjacent cells and pulls the cells between one another. In addition, the notochordal–somitic boundary functions in convergence and extension by ‘capturing’ notochordal cells as they contact the boundary, thus elongating the boundary. The prospective neural tissue also actively converges and extends parallel with the mesoderm. In contrast to the mesoderm, cell intercalation in the neural plate normally occurs by monopolar protrusive activity directed medially, towards the midline notoplate–floor–plate region. In contrast, the notoplate–floor–plate region appears to converge and extend by adhering to and being towed by or perhaps migrating on the underlying notochord. Converging and extending mesoderm stiffens by a factor of three or four and exerts up to 0.6 μN force. Therefore, active, force–producing convergent extension, the mechanism of cell intercalation, requires a mechanism to actively pull cells between one another while maintaining a tissue stiffness sufficient to push with a substantial force. Based on the evidence thus far, a cell–cell traction model of intercalation is described. The essential elements of such a morphogenic machine appear to be (i) bipolar, mediolaterally orientated or monopolar, medially directed protrusive activity; (ii) this protrusive activity results in mediolaterally orientated or medially directed traction of cells on one another; (iii) tractive protrusions are confined to the ends of the cells; (iv) a mechanically stable cell cortex over the bulk of the cell body which serves as a movable substratum for the orientated or directed cell traction. The implications of this model for cell adhesion, regulation of cell motility and cell polarity, and cell and tissue biomechanics are discussed.
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Gray, D. A., B. D. O. Anderson i R. R. Bitmead. "Towed array shape estimation using Kalman filters-theoretical models". IEEE Journal of Oceanic Engineering 18, nr 4 (1993): 543–56. http://dx.doi.org/10.1109/48.262304.
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Wang, Fei, Ke Du, Jingjiang Sun, Fuyun Huang i Zhenghui Xiong. "Shaking Table Array Tests of an Ultra-High-Voltage Cup-Type Transmission Tower-Line System". Shock and Vibration 2019 (11.12.2019): 1–20. http://dx.doi.org/10.1155/2019/2350675.
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Ultra-high-voltage (UHV) cup-type transmission towers supported with long-span transmission lines are unavoidably subjected to the coupling action between the towers and the transmission lines. Therefore, investigating how tower-line coupling affects UHV cup-type transmission towers is important. In this study, three shaking table array tests of an UHV cup-type transmission tower-line system were carried out to investigate the dynamic characteristics of the coupling action between the towers and transmission lines based on the following four comparative models: a single-tower model, a single-tower model with suspended lumped masses, a three-tower-two-line model, and a five-tower-four-line model. The test results demonstrated that the tower-line coupling interaction had a significant effect on the dynamic characteristics and seismic responses, as the suspended conductor line and the suspended lumped mass decreased the frequency of the transmission tower. Under longitudinal ground motion, the model with the suspended lumped mass had the lowest peak acceleration response and the largest peak displacement response. Under the same ground motion, the four models had similar peak strains in the longitudinal direction. Under transverse-the-line ground motion, the model with the suspended lumped mass had the lowest peak acceleration response and the smallest peak responses for displacement and strain in the transverse direction; therefore, this model is inappropriate for the simulation and seismic evaluation of transmission tower-line systems.
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Ma, Lun, Pierre-Luc Delafin, Panagiotis Tsoutsanis, Antonis Antoniadis i Takafumi Nishino. "Blade-Resolved CFD Simulations of a Periodic Array of NREL 5 MW Rotors with and without Towers". Wind 2, nr 1 (14.01.2022): 51–67. http://dx.doi.org/10.3390/wind2010004.
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A fully resolved (FR) NREL 5 MW turbine model is employed in two unsteady Reynolds-averaged Navier–Stokes (URANS) simulations (one with and one without the turbine tower) of a periodic atmospheric boundary layer (ABL) to study the performance of an infinitely large wind farm. The results show that the power reduction due to the tower drag is about 5% under the assumption that the driving force of the ABL is unchanged. Two additional simulations using an actuator disc (AD) model are also conducted. The AD and FR results show nearly identical tower-induced reductions of the wind speed above the wind farm, supporting the argument that the AD model is sufficient to predict the wind farm blockage effect. We also investigate the feasibility of performing delayed-detached-eddy simulations (DDES) using the same FR turbine model and periodic domain setup. The results show complex turbulent flow characteristics within the farm, such as the interaction of large-scale hairpin-like vortices with smaller-scale blade-tip vortices. The computational cost of the DDES required for a given number of rotor revolutions is found to be similar to the corresponding URANS simulation, but the sampling period required to obtain meaningful time-averaged results seems much longer due to the existence of long-timescale fluctuations.
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Zhang, Ya Xin, Qi Gao i Xiao Zi Xu. "The Strength Reliability Analysis at Connecting Region of Cylinder and Skirt of Coke Tower Based on Stochastic Finite Element". Key Engineering Materials 620 (sierpień 2014): 431–36. http://dx.doi.org/10.4028/www.scientific.net/kem.620.431.
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In this paper, Based on the original operating parameters of the Coke tower which works in the PetroChina Dushanzi Petrochemical Corp, and the skirt - tower body support section as the research object, using stochastic finite element method and Monte Carlo method, 60 groups of pressure, temperature are extracted randomly as variables in the original operating parameters curve, the change of the distribution function of temperature and pressure are analysed and established, and 200 groups of random pressure, temperature variable array is produced based on this; The maximum stress in dangerous section corresponding to each array is obtained by using the finite element method, the stress distribution of the probability density function is obtained; The strength reliability analysis of dangerous section is completed by using stress strength interference model and combining with the material intensity distribution function. The analysis results provide the basis for the tower life prediction and predicting repair, and provide a method for reliability analysis of the equipment whose large size is hard to measure and the working environment is hard.
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Lu, Nan-You, Lance Manuel, Patrick Hawbecker i Sukanta Basu. "A Simulation Study on Risks to Wind Turbine Arrays from Thunderstorm Downbursts in Different Atmospheric Stability Conditions". Energies 14, nr 17 (31.08.2021): 5407. http://dx.doi.org/10.3390/en14175407.
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Thunderstorm downbursts have been reported to cause damage or failure to wind turbine arrays. We extend a large-eddy simulation model used in previous work to generate downburst-related inflow fields with a view toward defining correlated wind fields that all turbines in an array would experience together during a downburst. We are also interested in establishing what role contrasting atmospheric stability conditions can play on the structural demands on the turbines. This interest is because the evening transition period, when thunderstorms are most common, is also when there is generally acknowledged time-varying stability in the atmospheric boundary layer. Our results reveal that the structure of a downburst’s ring vortices and dissipation of its outflow play important roles in the separate inflow fields for turbines located at different parts of the array; these effects vary with stability. Interacting with the ambient winds, the outflow of a downburst is found to have greater impacts in an “average” sense on structural loads for turbines farther from the touchdown center in the stable cases. Worst-case analyses show that the largest extreme loads, although somewhat dependent on the specific structural load variable considered, depend on the location of the turbine and on the prevailing atmospheric stability. The results of our calculations show the highest simulated foreaft tower bending moment to be 85.4 MN-m, which occurs at a unit sited in the array farther from touchdown center of the downburst initiated in a stable boundary layer.
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Xue, Zhaoxuan, Xingang Zhang, Jian Hou i Xi Liu. "Optimization Design of Feed Tower for High-frequency Band Multi-beam Antenna on Satellite". Journal of Physics: Conference Series 2383, nr 1 (1.12.2022): 012049. http://dx.doi.org/10.1088/1742-6596/2383/1/012049.
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Aiming at the layout of a certain feed array for multi-beam antenna on satellite, a feed tower design method based on 3D printing technology is proposed. This design method uses aluminum alloy 3D printing to form the main support structure under the premise of avoiding the installation holes and layout positions, and adopts the combination of the main structure of the honeycomb lattice and the local solid structure to reduce the structural quality. The mechanical analysis and optimization of the design model are carried out by combining the actual test data of the mechanical test plate and ANSYS, in which the actual product is tested and verified. The light feed tower can fully meet the requirements of high-frequency multi-beam antenna feed array for high precision and lightweight, which has a certain reference value for the miniaturized design of the antenna.
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Connell, J. R., V. R. Morris i M. E. Hinchee. "Input Turbulence Features at a Megawatt-Size Wind Turbine at Medicine Bow, Wyoming". Journal of Solar Energy Engineering 111, nr 1 (1.02.1989): 62–70. http://dx.doi.org/10.1115/1.3268288.
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In response to recent observations that wind turbulence has a strong effect on wind turbine fatigue life, measurements of turbulent wind velocity profiles have been made at the Medicine Bow, Wyo., WTS-4 wind turbine site. These measurements were taken at seven levels spanning the WTS-4 rotor height on a single meteorological tower 1.75 rotor diameters upstream of the turbine. Concurrent measurements of rotor response were also made. Analysis of the winds at the Medicine Bow site reveals the influence of atmospheric and geographic conditions on what may, at first glance, appear to be a “classic, simple, flat terrain” case. The turbulence data are analyzed to (1) characterize the wind in terms of fixed-point, single-tower properties and (2) model the wind properties as they would be experienced by points on rotating turbine blades. The STRS-2 model, developed by the Pacific Northwest Laboratory, is used to convert single-tower wind characteristics into an estimate of those that would be measured from an array of towers arranged in a crosswind line covering the rotor disk. A response function for the flatwise root bending moment of one of the WTS-4 turbine blades is computed using the turbine data and the STRS-2 data. The STRS-2 model provides a substantially improved correlation with wind turbine blade bending moment over other single-tower estimation methods.
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Rajan, Subramaniam D., G. V. Anand i P. V. Nagesh. "Joint estimation of water column and sediment acoustic properties from broadband towed array data using modal inverse method". Journal of the Acoustical Society of America 120, nr 3 (wrzesień 2006): 1324–34. http://dx.doi.org/10.1121/1.2221558.
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Song, Wenhua, i Pengyu Wang. "High-resolution modal wavenumber estimation in range-dependent shallow water waveguides using vertical line arrays". Journal of the Acoustical Society of America 152, nr 1 (lipiec 2022): 691–705. http://dx.doi.org/10.1121/10.0012187.
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Estimation of modal wavenumbers is important for inference of geoacoustic properties and matched field processing in shallow water waveguides. However, it is challenging in a range-dependent environment, because modal content varies locally in response to changes in the environment. Moreover, the scales of the spatial variations in the waveguide may be on the same order as the range aperture required for resolvability of the individual modes. To this end, high-resolution (HR) wavenumber estimation methods have been widely used. In this paper, the matrix pencil and MUSIC algorithms are generalized to geometry involving a synthetic horizontal aperture (SHA) formed by a towed acoustic source and a fixed full-spanning vertical line array (VLA). The performance of the proposed methods is evaluated by simulated data in a noisy shallow water environment. Numerical results show that, when compared with the previous methods, the proposed methods significantly outperform the previous methods in terms of aperture requirement.
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Debnath, M., C. Santoni, S. Leonardi i G. V. Iungo. "Towards reduced order modelling for predicting the dynamics of coherent vorticity structures within wind turbine wakes". Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 375, nr 2091 (6.03.2017): 20160108. http://dx.doi.org/10.1098/rsta.2016.0108.
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The dynamics of the velocity field resulting from the interaction between the atmospheric boundary layer and a wind turbine array can affect significantly the performance of a wind power plant and the durability of wind turbines. In this work, dynamics in wind turbine wakes and instabilities of helicoidal tip vortices are detected and characterized through modal decomposition techniques. The dataset under examination consists of snapshots of the velocity field obtained from large-eddy simulations (LES) of an isolated wind turbine, for which aerodynamic forcing exerted by the turbine blades on the atmospheric boundary layer is mimicked through the actuator line model. Particular attention is paid to the interaction between the downstream evolution of the helicoidal tip vortices and the alternate vortex shedding from the turbine tower. The LES dataset is interrogated through different modal decomposition techniques, such as proper orthogonal decomposition and dynamic mode decomposition. The dominant wake dynamics are selected for the formulation of a reduced order model, which consists in a linear time-marching algorithm where temporal evolution of flow dynamics is obtained from the previous temporal realization multiplied by a time-invariant operator. This article is part of the themed issue ‘Wind energy in complex terrains’.
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Vitale, Vincenzo. "The Limadou-HEPD Segmented Calorimeter". EPJ Web of Conferences 209 (2019): 01034. http://dx.doi.org/10.1051/epjconf/201920901034.
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The core of the High-Energy Particle Detector (HEPD) on board of the China Seismo-Electromagnetic Satellite (CSES) is a segmented calorimeter, which is composed with an upper tower of plastic scintillator counters and a bottom array of LYSO large crystals. Electrons with energy below 100MeV, protons and light nuclei, below few hundreds ofMeV/nucleon are fully contained within this calorimeter. Mainly the LYSO array (density 7.3 g/cm3, thickness around 29.2 g/cm2) extends the HEPD energy range, allowing those measurements (solar energetic particles, low-energy cosmic rays) which are more related to astroparticle physics topics. Two identical copies of HEPD, and then of its calorimeter, exist: the Flight (FM) and the Qualification (QM) models. While the FM has achieved the orbit on board of the CSES satellite in February 2018, the Qualification Model, is used, at ground, for tests and calibrations. A report on the characterization of this compact particle space detector and on preliminary studies and results, will be given.
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CONWAY, J. S., i C. LOOMIS. "USING AN ANALOG NEURAL NETWORK TO TRIGGER ON TAU LEPTONS AT CDF". International Journal of Modern Physics C 06, nr 04 (sierpień 1995): 549–54. http://dx.doi.org/10.1142/s0129183195000411.
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At the Collider Detector at Fermilab (CDF), we have designed and implemented a trigger for tau leptons using analog neural network electronics. Tau leptons offer a fertile area of research both for standard model tests and for new physics searches. Because the bulk of tau leptons decay into hadrons, it is challenging to distinguish them from ordinary hadron jets. Neural networks are well suited to this type of difficult classification problem. In this case, software simulations show that an efficiency of 15% with a rejection factor of 100 could be obtained. The input to the network is a 5×5×2 array of calorimeter tower energies surrounding the seed tower of a cluster. If the network’s single output exceeds a tunable threshold, the event is passed to the next stage of the trigger. An existing system based on the Intel ETANN (Electrically Trainable Analog Neural Network) chip was used to implement the tau lepton neural network trigger. The performance of the trigger in current CDF data will be presented.
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Chiu, Min-Chie. "Numerical optimization of straight multi-array side-branched mufflers using differential evolution method". Journal of Low Frequency Noise, Vibration and Active Control 37, nr 2 (czerwiec 2018): 313–40. http://dx.doi.org/10.1177/1461348418780019.
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To overcome this noise, traditional reactive as well as dissipative mufflers have been used. However, the allowable backpressure and the extra load acting on the cooling tower are limited. So, in order to efficiently reduce the broad noise under a low-pressure drop and a small dead weight, a straight multi-array resonator muffler without sound absorbing wool is required. Multi-array Helmholtz mufflers with complicated Helmholtz resonators were found to be too expensive in manufacturing costs and can be easily accumulated with duct and water. Therefore, a straight multi-array side-branched muffler with an empty chamber is proposed. Here, to efficiently reduce the broadband noise level, eight kinds of mufflers (muffler A–H) with 1–8 raw chambers internally partitioned with concentric perforated plate will also be introduced. To delineate the best acoustical performance of a space-constrained muffler, a numerical assessment using a four-pole matrix method in conjunction with a differential evolution method is adopted. To verify the availability of the differential evolution optimization, a numerical optimization of mufflers A–H at a pure tone (400 Hz) is exemplified. Before the differential evolution operation in broadband noise elimination can be carried out, the accuracy of the mathematical model has been checked using the experimental data. Consequently, a successful approach in eliminating a broadband noise with a low-pressure drop and a dead load using optimally shaped straight multi-array side-branched mufflers and a differential evolution method within a constrained space has been demonstrated.
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Fierro, Alexandre O., Joanne Simpson, Margaret A. LeMone, Jerry M. Straka i Bradley F. Smull. "On How Hot Towers Fuel the Hadley Cell: An Observational and Modeling Study of Line-Organized Convection in the Equatorial Trough from TOGA COARE". Journal of the Atmospheric Sciences 66, nr 9 (1.09.2009): 2730–46. http://dx.doi.org/10.1175/2009jas3017.1.
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Abstract An airflow trajectory analysis was carried out based on an idealized numerical simulation of the nocturnal 9 February 1993 equatorial oceanic squall line observed over the Tropical Ocean and Global Atmosphere Coupled Ocean–Atmosphere Response Experiment (TOGA COARE) ship array. This simulation employed a nonhydrostatic numerical cloud model, which features a sophisticated 12-class bulk microphysics scheme. A second convective system that developed immediately south of the ship array a few hours later under similar environmental conditions was the subject of intensive airborne quad-Doppler radar observations, allowing observed airflow trajectories to be meaningfully compared to those from the model simulation. The results serve to refine the so-called hot tower hypothesis, which postulated the notion of undiluted ascent of boundary layer air to the high troposphere, which has for the first time been tested through coordinated comparisons with both model output and detailed observations. For parcels originating ahead (north) of the system near or below cloud base in the boundary layer (BL), the model showed that a majority (>62%) of these trajectories were able to surmount the 10-km level in their lifetime, with about 5% exceeding 14-km altitude, which was near the modeled cloud top (15.5 km). These trajectories revealed that during ascent, most air parcels first experienced a quick decrease of equivalent potential temperature (θe) below 5-km MSL as a result of entrainment of lower ambient θe air. Above the freezing level, ascending parcels experienced an increase in θe with height attributable to latent heat release from ice processes consistent with previous hypotheses. Analogous trajectories derived from the evolving observed airflow during the mature stage of the airborne radar–observed system identified far fewer (∼5%) near-BL parcels reaching heights above 10 km than shown by the corresponding simulation. This is attributed to both the idealized nature of the simulation and to the limitations inherent to the radar observations of near-surface convergence in the subcloud layer. This study shows that latent heat released above the freezing level can compensate for buoyancy reduction by mixing at lower levels, thus enabling air originating in the boundary layer to contribute to the maintenance of both local buoyancy and the large-scale Hadley cell despite acknowledged dilution by mixing along updraft trajectories. A tropical “hot tower” should thus be redefined as any deep convective cloud with a base in the boundary layer and reaching near the upper-tropospheric outflow layer.
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Zhu, Xiangqian, Mingqi Sun, Tianhao He, Kaiben Yu, Le Zong i Jin-Hwan Choi. "Study of the Cone-Shaped Drogue for a Deep-Towed Multi-Channel Seismic Survey System Based on Data-Driven Simulations". Journal of Marine Science and Engineering 9, nr 12 (2.12.2021): 1367. http://dx.doi.org/10.3390/jmse9121367.
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A drogue is used to stabilise and straighten seismic arrays so that seismic waves can be well-received. To embed the effect of a cone-shaped drogue into the numerical modelling of the deep-towed seismic survey system, one surrogate model that maps the relationship between the hydrodynamic characteristics of the drogue and towing conditions was obtained based on data-driven simulations. The sample data were obtained by co-simulation of the commercial software RecurDyn and Particleworks, and the modelling parameters were verified by physical experiments. According to the Morison formula, the rotational angle, angular velocity, angular acceleration, towing speed, and towing acceleration of the drogue were selected as the design variables and drag forces and aligning torque were selected as the research objectives. The sample data of more than 8500 sets were obtained from virtual manoeuvres. Subsequently, both polynomial and neural network regression algorithms were used to study these data. Finally, analysis results show that the surrogate model obtained by machine learning has good performance in predicting research objectives. The results also reveal that the neural network regression algorithm is superior to the polynomial regression algorithm, its largest error of mean square is less than 0.8 (N2/N2 mm2), and its R-squared is close to 1.
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Qiu, Dongwei, Tong Wang, Qing Ye, He Huang, Laiyang Wang, Mingxu Duan i Dean Luo. "A Deformation Prediction Approach for Supertall Building Using Sensor Monitoring System". Journal of Sensors 2019 (24.04.2019): 1–12. http://dx.doi.org/10.1155/2019/9283584.
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Using high-precision sensors to monitor and predict the deformation trend of supertall buildings is a hot research topic for a long time. And in terms of deformation trend prediction, the main way to realized deformation trend prediction is the deep learning algorithm, but the accuracy of prediction result needs to be improved. To solve the problem described above, firstly, based on the conditional deep belief network (CDBN) model, the levenberg-marquardt (LM) was used to optimize the CDBN model; the LM-CDBN model has been constructed. Then taking CITIC tower, the tallest building in Beijing as the research object, the real-time monitoring data of the shape acceleration array (SAA) as an example, we used LM-CDBN model to analyse and predict the building deformation. Finally, to verify the accuracy and robustness of LM-CDBN model, the prediction results of the LM-CDBN model are compared with the prediction results of the CDBN model, the extreme learning machine (ELM) model, and the unscented Kalman filter-support vector regression (UKF-SVR) model, and we evaluated the result from three aspects: training error, fitness, and stability of prediction results. The results show that the LM-CDBN model has higher precision and fitting degree in the prediction of deformation trend of supertall buildings. And the MRE, MAE, and RMSE of the LM-CDBN model prediction results are only 0.0060, 0.0023mm, and 0.0031mm, and the prediction result was more in line with the actual deformation trend.