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Fukaya, C., M. Watanabe, K. Sumi, T. Otaka, K. Shijo, T. Nagaoka, K. Kobayashi, H. Oshima, T. Yamamoto y Y. Katayama. "S28-3 D-wave monitoring in brain tumor surgery". Clinical Neurophysiology 121 (octubre de 2010): S44. http://dx.doi.org/10.1016/s1388-2457(10)60183-6.
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Ghadirpour, Reza, Davide Nasi, Corrado Iaccarino, Antonio Romano, Luisa Motti, Rossella Sabadini, Franco Valzania y Franco Servadei. "Intraoperative neurophysiological monitoring for intradural extramedullary spinal tumors: predictive value and relevance of D-wave amplitude on surgical outcome during a 10-year experience". Journal of Neurosurgery: Spine 30, n.º 2 (febrero de 2019): 259–67. http://dx.doi.org/10.3171/2018.7.spine18278.
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OBJECTIVEThe purpose of this study was to evaluate the technical feasibility, accuracy, and relevance on surgical outcome of D-wave monitoring combined with somatosensory evoked potentials (SSEPs) and motor evoked potentials (MEPs) during resection of intradural extramedullary (IDEM) spinal tumors.METHODSClinical and intraoperative neurophysiological monitoring (IONM) data obtained in 108 consecutive patients who underwent surgery for IDEM tumors at the Institute for Scientific and Care Research “ASMN” of Reggio Emilia, Italy, were prospectively entered into a database and retrospectively analyzed. The IONM included SSEPs, MEPs, and—whenever possible—D-waves. All patients were evaluated using the modified McCormick Scale at admission and at 3, 6, and 12 months of follow-up .RESULTSA total of 108 patients were included in this study. A monitorable D-wave was achieved in 71 of the 77 patients harboring cervical and thoracic IDEM tumors (92.2%). Recording of D-waves in IDEM tumors was significantly associated only with a preoperative deeply compromised neurological status evaluated using the modified McCormick Scale (p = 0.04). Overall, significant IONM changes were registered in 14 (12.96%) of 108 patients and 9 of these patients (8.33%) had permanent loss of at least one of the 3 evoked potentials. In 7 patients (6.48%), the presence of an s18278 caudal D-wave was predictive of a favorable long-term motor outcome even when the MEPs and/or SSEPs were lost during IDEM tumor resection. However, in 2 cases (1.85%) the D-wave permanently decreased by approximately 50%, and surgery was definitively abandoned to prevent permanent paraplegia. Cumulatively, SSEP, MEP, and D-wave monitoring significantly predicted postoperative deficits (p = 0.0001; AUC = 0.905), with a sensitivity of 85.7% and a specificity of 97%. Comparing the area under the receiver operating characteristic curves of these tests, D-waves appeared to have a significantly greater predictive value than MEPs and especially SSEPs alone (0.992 vs 0.798 vs 0.653; p = 0.023 and p < 0.001, respectively). On multiple logistic regression, the independent risk factors associated with significant IONM changes in the entire population were age older than 65 years and an anterolateral location of the tumor (p < 0.0001).CONCLUSIONSD-wave monitoring was feasible in all patients without severe preoperative motor deficits. D-waves demonstrated a statistically significant higher ability to predict postoperative deficits compared with SSEPs and MEPs alone and allowed us to proceed with IDEM tumor resection, even in cases of SSEP and/or MEP loss. Patients older than 65 years and with anterolateral IDEM tumors can benefit most from the use of IONM.
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Fujiki, Minoru, Yoshie Furukawa, Tohru Kamida, Mitsuhiro Anan, Ryo Inoue, Tatsuya Abe y Hidenori Kobayashi. "Intraoperative corticomuscular motor evoked potentials for evaluation of motor function: a comparison with corticospinal D and I waves". Journal of Neurosurgery 104, n.º 1 (enero de 2006): 85–92. http://dx.doi.org/10.3171/jns.2006.104.1.85.
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Object The goal of this study was to compare motor evoked potentials recorded from muscles (muscle MEPs or corticomuscular MEPs) with corticospinal MEPs recorded from the cervical epidural space (spinal MEPs or corticospinal MEPs) to assess their efficacy in the intraoperative monitoring of motor function. Methods Muscle and spinal MEPs were simultaneously recorded during surgery in 80 patients harboring brain tumors. Each case was assigned to one of four groups according to final changes in the MEPs: 1) Group A, in which there was an increased amplitude in the muscle MEP with an increased I3 wave amplitude (12 cases); 2) Group B, in which there was no significant change in the MEP (43 cases); 3) Group C, in which there was a decreased muscle MEP amplitude (< 35% of the control) with a decreased I wave amplitude but an unchanged D wave (15 cases); or 4) Group D, in which there was an absent muscle MEP with a decreased D wave amplitude (10 cases). In patients in Group A, the increase in the amplitude of the muscle MEP (range of increase 128–280%, mean increase 188.75 ± 48.79%) was well correlated with the increase in the I3 wave in corticospinal MEPs. Most of these patterns were observed in patients harboring meningiomas (10 [83.3%] of 12 cases). Patients in Group B displayed no changes in muscle and corticospinal MEPs and no signs of postoperative neurological deterioration. Patients in Group C showed a substantial decrease in the amplitude of the muscle MEP (range of decrease 5.3–34.8% based on the control waveform, mean change 21.81 ± 10.93%) without deterioration in the corticospinal D wave, and exhibited severe immediate postoperative motor dysfunction. This indicates dysfunction of the cortical gray matter, including the motor cortices, which are supposed to generate I waves. Patients in Group D exhibited decreases in the corticospinal D wave (range of decrease 21.5–55%, mean decrease 39.75 ± 11.45%) and an immediate cessation of the muscle MEP as well as severe permanent motor paresis. Conclusions These results indicate that, during surgery, monitoring of corticomuscular MEPs (which are related to I waves) is a much more sensitive method for the detection of immediate motor cortical damage than monitoring of corticospinal MEPs (D wave).
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Mordret, Aurélien, Roméo Courbis, Florent Brenguier, Małgorzata Chmiel, Stéphane Garambois, Shujuan Mao, Pierre Boué et al. "Noise-based ballistic wave passive seismic monitoring – Part 2: surface waves". Geophysical Journal International 221, n.º 1 (18 de febrero de 2020): 692–705. http://dx.doi.org/10.1093/gji/ggaa016.
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SUMMARY We develop a new method to monitor and locate seismic velocity changes in the subsurface using seismic noise interferometry. Contrary to most ambient noise monitoring techniques, we use the ballistic Rayleigh waves computed from 30 d records on a dense nodal array located above the Groningen gas field (the Netherlands), instead of their coda waves. We infer the daily relative phase velocity dispersion changes as a function of frequency and propagation distance with a cross-wavelet transform processing. Assuming a 1-D velocity change within the medium, the induced ballistic Rayleigh wave phase shift exhibits a linear trend as a function of the propagation distance. Measuring this trend for the fundamental mode and the first overtone of the Rayleigh waves for frequencies between 0.5 and 1.1 Hz enables us to invert for shear wave daily velocity changes in the first 1.5 km of the subsurface. The observed deep velocity changes (±1.5 per cent) are difficult to interpret given the environmental factors information available. Most of the observed shallow changes seem associated with effective pressure variations. We observe a reduction of shear wave velocity (–0.2 per cent) at the time of a large rain event accompanied by a strong decrease in atmospheric pressure loading, followed by a migration at depth of the velocity decrease. Combined with P-wave velocity changes observations from a companion paper, we interpret the changes as caused by the diffusion of effective pressure variations at depth. As a new method, noise-based ballistic wave passive monitoring could be used on several dynamic (hydro-)geological targets and in particular, it could be used to estimate hydrological parameters such as the hydraulic conductivity and diffusivity.
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Knafo, William. "COVID-19: Monitoring the propagation of the first waves of the pandemic". 4open 3 (2020): 5. http://dx.doi.org/10.1051/fopen/2020005.
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Introduction: A phenomenological approach is proposed to monitor the propagation of the first waves of the COVID-19 pandemic. Method: A large set of data collected during the first months of 2020 is compiled into a series of semi-logarithmic plots, for a selection of 32 countries from the five continents. Results: Three regimes are identified in the propagation of an epidemic wave: a pre-epidemic regime 1, an exponential-growth regime 2, and a resorption regime 3. A two-parameters scaling of the first-wave death variation reported in China is used to fit the first-wave data reported in other countries. Comparison is made between the propagation of the pandemic in different countries, which are classified into four groups, from Group A where the pandemic first waves were contained efficiently, to Group D where the pandemic first waves widely spread. All Asian countries considered here, where fast and efficient measures have been applied, are in Group A. Group D is composed of Western-European countries and the United States of America (USA), where late decisions and confused political communication (pandemic seriousness, protection masks, herd immunity, etc.) led to a large number of deaths. Discussion: The threat of resurging epidemic waves following a lift of lockdown measures is discussed. The results obtained in Asian countries from group A, as Hong Kong and South Korea, are highlighted, and the measures taken there are presented as examples that other countries may follow.
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He, Wen, Changsong Zheng, Shenhai Li, Wenfang Shi y Kui Zhao. "Strength Development Monitoring of Cemented Paste Backfill Using Guided Waves". Sensors 21, n.º 24 (20 de diciembre de 2021): 8499. http://dx.doi.org/10.3390/s21248499.
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The strength of cemented paste backfill (CPB) directly affects mining safety and progress. At present, in-situ backfill strength is obtained by conducting uniaxial compression tests on backfill core samples. At the same time, it is time-consuming, and the integrity of samples cannot be guaranteed. Therefore guided wave technique as a nondestructive inspection method is proposed for the strength development monitoring of cemented paste backfill. In this paper, the acoustic parameters of guided wave propagation in the different cement-tailings ratios (1:4, 1:8) and different curing times (within 42 d) of CPBs were measured. Combined with the uniaxial compression strength of CPB, relationships between CPB strength and the guided wave acoustic parameters were established. Results indicate that with the increase of backfill curing time, the guided wave velocity decreases sharply at first; on the contrary, attenuation of guided waves increases dramatically. Finally, both velocity and attenuation tend to be stable. When the CPB strength increases with curing time, guided wave velocity shows an exponentially decreasing trend, while the guided wave attenuation shows an exponentially increasing trend with the increase of the CPB strength. Based on the relationship curves between CPB strength and guided wave velocity and attenuation, the guided wave technique in monitoring the strength development of CPB proves feasible.
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Barzilai, Ori, Zvi Lidar, Shlomi Constantini, Khalil Salame, Yifat Bitan-Talmor y Akiva Korn. "Continuous mapping of the corticospinal tracts in intramedullary spinal cord tumor surgery using an electrified ultrasonic aspirator". Journal of Neurosurgery: Spine 27, n.º 2 (agosto de 2017): 161–68. http://dx.doi.org/10.3171/2016.12.spine16985.
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Intramedullary spinal cord tumors (IMSCTs) represent a rare entity, accounting for 4%–10% of all central nervous system tumors. Microsurgical resection of IMSCTs is currently considered the primary treatment modality. Intraoperative neurophysiological monitoring (IONM) has been shown to aid in maximizing tumor resection and minimizing neurological morbidity, consequently improving patient outcome. The gold standard for IONM to date is multimodality monitoring, consisting of both somatosensory evoked potentials, as well as muscle-based transcranial electric motor evoked potentials (tcMEPs). Monitoring of tcMEPs is optimal when combining transcranial electrically stimulated muscle tcMEPs with D-wave monitoring. Despite continuous monitoring of these modalities, when classic monitoring techniques are used, there can be an inherent delay in time between actual structural or vascular-based injury to the corticospinal tracts (CSTs) and its revelation. Often, tcMEP stimulation is precluded by the surgeon’s preference that the patient not twitch, especially at the most crucial times during resection. In addition, D-wave monitoring may require a few seconds of averaging until updating, and can be somewhat indiscriminate to laterality. Therefore, a method that will provide immediate information regarding the vulnerability of the CSTs is still needed.The authors performed a retrospective series review of resection of IMSCTs using the tip of an ultrasonic aspirator for continuous proximity mapping of the motor fibers within the spinal cord, along with classic muscle-based tcMEP and D-wave monitoring.The authors present their preliminary experience with 6 patients who underwent resection of an IMSCT using the tip of an ultrasonic aspirator for continuous proximity mapping of the motor fibers within the spinal cord, together with classic muscle-based tcMEP and D-wave monitoring. This fusion of technologies can potentially assist in optimizing resection while preserving neurological function in these challenging surgeries.
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Kalgutkar, AkshayPrakash y Sauvik Banerjee. "Semi-Analytical Finite Element Method for the Analysis of Guided Wave Dispersion in the Pre-stressed Composite Plates". Proceedings of the 12th Structural Engineering Convention, SEC 2022: Themes 1-2 1, n.º 1 (19 de diciembre de 2022): 1413–21. http://dx.doi.org/10.38208/acp.v1.671.
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Ultrasonic guided wave techniques offer an accurate and efficient procedure for damage monitoring in the structures. To develop reliable damage monitoring systems, it is essential to have a thorough understanding of the quantitative nature of ultrasonic guided waves that can be transmitted in composite laminates. In the present paper, the Semi-Analytical Finite Element (SAFE) method is employed due to its efficiency in the treatment of wave propagation problems involving complex materials and geometry. SAFE method is considered for the analysis of dispersion behaviour of guided waves in composite laminates by accounting the effect of in-plane load. The present study considers an infinite width plate such that the cross-section of the waveguide is modelled using 3 noded isoparametric 1-D elements representing the thickness of the plate. Equation of motion is formulated by using Hamilton’s equation. Finally, various parametric studies are carried out. The study includes analysing the effect of wave velocity in the plate subjected to applied in-plane load, and understanding the effect of dispersion characteristics on the direction of propagation (slowness curve). The study shows that at the lower frequency thickness product, the group velocity of the wave increases with the increase in the applied tensile load and vice-versa.
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Sun, Ya Jie, Yong Hong Zhang, Cheng Shan Qian, Zi Jia Zhang y Qi Wang. "3-D Imaging Based Ultrasonic Phased Array Theory for Composite Structure Damage Identification". Applied Mechanics and Materials 389 (agosto de 2013): 881–86. http://dx.doi.org/10.4028/www.scientific.net/amm.389.881.
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The Lamb wave phased array theory is utilized to analysis the damage scattered signals to identify the structure defect. The damage scattered signals are gotten by comparing the health signals with the damage signals. Phased array theory based structural health monitoring can scan the structure in a certain range of 0°~180° by controlling the time delay of the excitation signals and the response signals. The processed signals in monitoring direction is shown on 3-D imaging to express the damage location in the structure. The method is verified by the experiment on the composite structure and the result shows that the Lamb wave phased array method can detect the damage in the composite structure and the 3-D image clearly displays the structure damage location.
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Luo, Bin, Whitney Trainor-Guitton, Ebru Bozdağ, Lisa LaFlame, Steve Cole y Martin Karrenbach. "Horizontally orthogonal distributed acoustic sensing array for earthquake- and ambient-noise-based multichannel analysis of surface waves". Geophysical Journal International 222, n.º 3 (16 de junio de 2020): 2147–61. http://dx.doi.org/10.1093/gji/ggaa293.
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SUMMARY A 2-D orthogonal distributed acoustic sensing (DAS) array designed for seismic experiments was buried horizontally beneath the Kafadar Commons Geophysical Laboratory on the Colorado School of Mines campus at Golden, Colorado. The DAS system using straight fibre-optic cables is a cost-efficient technology that enables dense seismic array deployment for long-term seismic monitoring, favouring both earthquake-based and ambient-noise-based surface wave analysis for subsurface characterization. In our study, the horizontally orthogonal DAS array records ambient noise data for a period of about two months from November 2018 to January 2019. During this time, the array also detected seismic signals from an ML3.6 earthquake at Glenwood Springs, Colorado, which exhibit opposite signal polarities in the orthogonal DAS section recordings. We derive the transformation matrix for DAS strain measurements in horizontally orthogonal cables to retrieve both Rayleigh and Love wave dispersion information from the single-component DAS signals using the 2-D multichannel analysis of surface waves method. In addition, ambient noise interferometry is applied to long-term DAS noise recordings. Our theoretical derivation demonstrates that Rayleigh and Love wave Green's functions are coupled in the noise cross-correlation functions (NCFs) of DAS receiver pairs. Stacking NCFs over the horizontally orthogonal DAS array can constructively recover the radial Rayleigh wave component but destructively suppress the Love wave component. The multimodal Monte Carlo inversion of the earthquake-based Rayleigh wave and Love wave dispersion measurements and the noise-based Rayleigh wave measurement reveals a 1-D layered structure that agrees qualitatively with geological surveys of the site. Our study demonstrates that although straight fibre-optic cables lack broadside sensitivity, using appropriate DAS array configuration and seismic array methods can extend the seismic acquisition ability of DAS and enable its application to a broad range of scenarios.
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Wulff, Angelika‐M y Svein Mjaaland. "Seismic monitoring of fluid fronts: An experimental study". GEOPHYSICS 67, n.º 1 (enero de 2002): 221–29. http://dx.doi.org/10.1190/1.1451622.
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Seismic signatures of time‐dependent reservoir processes, necessary for the interpretation of 4‐D seismic data, are still insufficiently described. This experiment was designed to monitor fluid‐front movements and saturation changes and to identify the related seismic signatures. Ultrasonic P‐ and S‐wave transmission and reflection measurements were used to monitor the waterflooding of a porous sandstone. The sandstone was flooded in steps by filling a tank in which the room‐dry cubic (50‐cm side) block of rock was placed. Waterflooding caused the velocity, amplitude, and frequency of the transmitted waves to diminish significantly; however, the changes were reversible by drying. The maximum reduction of the velocities was 7% and 12% for P‐ and S‐waves, respectively. The velocity and amplitude behavior can be explained by the Biot‐Gassmann's theory, local fluid flow, and grain‐surface effects. The correct interpretation of seismic signatures of fluid processes in reservoirs thus involves a knowledge of rock physical relations and attenuation mechanisms. Even at small saturations, reflections from the block bottom were strongly attenuated, but those from the upgoing water front could be monitored. The latter reflections were best observed in differential seismic traces, confirming that seismic monitoring can observe moving fronts directly.
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Iyer, Srikrishna, Leo Zhao, Manoj Prabhakar Mohan, Joe Jimeno, Mohammed Yakoob Siyal, Arokiaswami Alphones y Muhammad Faeyz Karim. "mm-Wave Radar-Based Vital Signs Monitoring and Arrhythmia Detection Using Machine Learning". Sensors 22, n.º 9 (19 de abril de 2022): 3106. http://dx.doi.org/10.3390/s22093106.
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A non-contact, non-invasive monitoring system to measure and estimate the heart and breathing rate of humans using a frequency-modulated continuous wave (FMCW) mm-wave radar at 77 GHz is presented. A novel diagnostic system is proposed which extracts heartbeat phase signals from the FMCW radar (reconstructed using Fourier series analysis) to test a three-layer artificial neural network model to predict the presence of arrhythmia in individuals. The effect of person orientation, distance of measurement and movement was analyzed with respect to a reference device based on statistical measures that include number of outliers, mean, mean squared error (MSE), mean absolute error (MAE), median absolute error (medAE), skewness, standard deviation (SD) and R-squared values. The individual oriented in front of the radar outperformed almost all other orientations for most distances with an expected d = 90 cm and d = 120 cm. Furthermore, it was found that the heart rate that was measured while walking and the breathing rate which was measured for a motionless individual generated results with the lowest SD and MSE. An artificial neural network (ANN) was trained using the MIT-BIH database with a training accuracy of 93.9 % and an R2 value = 0.876. The diagnostic tool was tested on 15 subjects and achieved a mean test accuracy of 75%.
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Zhang, Guangdong, Xiongbing Li, Shuzeng Zhang y Tribikram Kundu. "Sideband peak count-index technique for monitoring multiple cracks in plate structures using ordinary state-based peri-ultrasound theory". Journal of the Acoustical Society of America 152, n.º 5 (noviembre de 2022): 3035–48. http://dx.doi.org/10.1121/10.0015242.
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This work presents a peri-ultrasound theory based on ordinary state-based peridynamics for modeling elastic waves propagating in three-dimensional (3-D) plate structures and interacting with multiple cracks. A recently developed nonlinear ultrasonic technique called sideband peak count-index (or SPC-I) is adopted for monitoring one or more cracks with thickness values equal to 0 mm (crack-free), 1, 2, and 4 mm. Three separate scenarios—one crack, two cracks, and four cracks in 3-D plate structures—are investigated. These cracks can be classified as thin and thick cracks depending on the horizon size, which is mentioned in peri-ultrasound theory. Computed results for all three cases show larger SPC-I values for thin cracks than for thick cracks and the case of no cracks. This observation is in line with the previously reported results in the literature and proves that the state-based peri-ultrasound theory can capture the expected nonlinear response of elastic waves interacting with multiple cracks without changing the cracks' surface locations artificially, and this is always needed in most of the other numerical methods. The proposed state-based peri-ultrasound theory is more flexible and reliable for solving 3-D problems, and the out-of-plane wave field can be obtained for engineering analysis.
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GOTO, Shintaro y Kiyonori IISAWA. "Study on the Monitoring of 2-D Wave Parameter Using Simulated Image of Marine Radar." Journal of the Japan society of photogrammetry and remote sensing 34, n.º 2 (1995): 36–44. http://dx.doi.org/10.4287/jsprs.34.2_36.
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Raghavan, Ajay y Carlos E. S. Cesnik. "3-D Elasticity-Based Modeling of Anisotropic Piezocomposite Transducers for Guided Wave Structural Health Monitoring". Journal of Vibration and Acoustics 129, n.º 6 (8 de febrero de 2007): 739–51. http://dx.doi.org/10.1115/1.2748776.
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Anisotropic piezocomposite transducers (APTs), such as macro fiber composites and active fiber composites, have great potential to be used as structurally integrated transducers for guided-wave (GW) structural health monitoring. Their main advantages over conventional monolithic piezoceramic wafer transducers are mechanical flexibility, curved surface conformability, power efficiency, their ability to excite focused GW fields, and their unidirectional sensing capability as a GW sensor. In this paper, models are developed to describe excitation of GW fields by APTs in isotropic structures. The configurations explored are plane Lamb-wave fields in beams with rectangular cross-section, axisymmetric GW fields in cylinders, and 3-D GW fields in plates. The dynamics of the substrate and transducer are assumed uncoupled. The actuator is modeled as causing shear traction at the edges of the actuator’s active area along the fiber direction. The sensor is modeled as sensing the average extensional strain over the active area along the fiber direction. The work is unique in that the formulation is based on 3-D elasticity, and no reduced-order structural assumptions are used. This is crucial to model multimodal GW propagation, especially at high frequencies. A formulation is also proposed to model the behavior of APTs as GW sensors. Finally, results from experimental tests to examine the validity of the models are discussed and the possible sources of error are examined in detail.
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Ulkatan, S., M. Neuwirth, F. Bitan, C. Minardi, A. Kokoszka y V. Deletis. "Monitoring of scoliosis surgery with epidurally recorded motor evoked potentials (D wave) revealed false results". Clinical Neurophysiology 117, n.º 9 (septiembre de 2006): 2093–101. http://dx.doi.org/10.1016/j.clinph.2006.05.021.
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Markosian, Christopher, Catherine A. Mazzola y Luke D. Tomycz. "Gross Total Resection of Pediatric Cervical Intramedullary Ependymoma with D-Wave Monitoring: A Case Report". SN Comprehensive Clinical Medicine 2, n.º 12 (2 de noviembre de 2020): 2973–75. http://dx.doi.org/10.1007/s42399-020-00618-0.
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MINOWA, MASAHIRO, EVGENY A. PODOLSKIY, SHIN SUGIYAMA, DAIKI SAKAKIBARA y PEDRO SKVARCA. "Glacier calving observed with time-lapse imagery and tsunami waves at Glaciar Perito Moreno, Patagonia". Journal of Glaciology 64, n.º 245 (12 de abril de 2018): 362–76. http://dx.doi.org/10.1017/jog.2018.28.
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ABSTRACTCalving plays a key role in the recent rapid retreat of glaciers around the world. However, many processes related to calving are poorly understood since direct observations are scarce and challenging to obtain. When calving occurs at a glacier front, surface-water waves arise over the ocean or a lake in front of glaciers. To study calving processes from these surface waves, we performed field observations at Glaciar Perito Moreno, Patagonia. We synchronized time-lapse photography and surface waves record to confirm that glacier calving produces distinct waves compared with local noise. A total of 1074 calving events were observed over the course of 39 d. During austral summer, calving occurred twice more frequently than in spring. The cumulative distribution of calving-interevent time interval followed exponential model, implying random occurrence of events in time. We further investigated wave properties and found that source-to-sensor distance can be estimated from wave dispersion within ~20% error. We also found that waves produced by different calving types showed similar spectra in the same frequency range between 0.05–0.2 Hz, and that the amplitude of surface waves increased with the size of calving. This study demonstrates the potential of surface-wave monitoring for understanding calving processes.
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van Kempen, Tim A., Filippo Oggionni y Richard M. van Hees. "Monitoring the Tropospheric Monitoring Instrument (TROPOMI) short-wave infrared (SWIR) module instrument stability using desert sites". Atmospheric Measurement Techniques 14, n.º 10 (20 de octubre de 2021): 6711–22. http://dx.doi.org/10.5194/amt-14-6711-2021.
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Abstract. Since its launch in 2017, Tropospheric Monitoring Instrument (TROPOMI) on S-5P has provided very high quality data using daily global coverage for a number of key atmospheric trace gases. Over its first 1000 d in operation, the short-wave infrared (SWIR) module has been very stable, and the continuously monitored calibration has remained of high quality. This calibration relies on a combination of extensive pre-launch and post-launch measurements, complemented by regular monitoring of internal light sources and background measurements. In this paper we present a method and results for independent validation of the SWIR module calibration and instrument stability by examining the signal stability of a sample of 23 pseudo-invariant calibration desert sites. The data covers over 2 years of operational data. With a Lambertian surface assumption, the results show that the SWIR module has little to no instrument degradation down to an accuracy of about 0.3 % yr−1, validating results obtained from the internal calibration suite. The method presented here will be used as ongoing validation of the SWIR calibration.
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Earp, S., A. Curtis, X. Zhang y F. Hansteen. "Probabilistic neural network tomography across Grane field (North Sea) from surface wave dispersion data". Geophysical Journal International 223, n.º 3 (8 de agosto de 2020): 1741–57. http://dx.doi.org/10.1093/gji/ggaa328.
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SUMMARY Surface wave tomography uses measured dispersion properties of surface waves to infer the spatial distribution of subsurface properties such as shear wave velocities. These properties can be estimated vertically below any geographical location at which surface wave dispersion data are available. As the inversion is significantly non-linear, Monte Carlo methods are often used to invert dispersion curves for shear wave velocity profiles with depth to give a probabilistic solution. Such methods provide uncertainty information but are computationally expensive. Neural network (NN) based inversion provides a more efficient way to obtain probabilistic solutions when those solutions are required beneath many geographical locations. Unlike Monte Carlo methods, once a network has been trained it can be applied rapidly to perform any number of inversions. We train a class of NNs called mixture density networks (MDNs), to invert dispersion curves for shear wave velocity models and their non-linearized uncertainty. MDNs are able to produce fully probabilistic solutions in the form of weighted sums of multivariate analytic kernels such as Gaussians, and we show that including data uncertainties as additional inputs to the MDN gives substantially more reliable velocity estimates when data contains significant noise. The networks were applied to data from the Grane field in the Norwegian North sea to produce shear wave velocity maps at several depth levels. Post-training we obtained probabilistic velocity profiles with depth beneath 26 772 locations to produce a 3-D velocity model in 21 s on a standard desktop computer. This method is therefore ideally suited for rapid, repeated 3-D subsurface imaging and monitoring.
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Rasgado-Moreno, Carlos-Omar, Marek Rist, Raul Land y Madis Ratassepp. "Acoustic Forward Model for Guided Wave Propagation and Scattering in a Pipe Bend". Sensors 22, n.º 2 (9 de enero de 2022): 486. http://dx.doi.org/10.3390/s22020486.
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The sections of pipe bends are hot spots for wall thinning due to accelerated corrosion by fluid flow. Conventionally, the thickness of a bend wall is evaluated by local point-by-point ultrasonic measurement, which is slow and costly. Guided wave tomography is an attractive method that enables the monitoring of a whole bend area by processing the waves excited and received by transducer arrays. The main challenge associated with the tomography of the bend is the development of an appropriate forward model, which should simply and efficiently handle the wave propagation in a complex bend model. In this study, we developed a two-dimensional (2D) acoustic forward model to replace the complex three-dimensional (3D) bend domain with a rectangular domain that is made artificially anisotropic by using Thomsen parameters. Thomsen parameters allow the consideration of the directional dependence of the velocity of the wave in the model. Good agreement was found between predictions and experiments performed on a 220 mm diameter (d) pipe with 1.5d bend radius, including the wave-field focusing effect and the steering effect of scattered wave-fields from defects.
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Steinmann, René, Céline Hadziioannou y Eric Larose. "Effect of centimetric freezing of the near subsurface on Rayleigh and Love wave velocity in ambient seismic noise correlations". Geophysical Journal International 224, n.º 1 (28 de agosto de 2020): 626–36. http://dx.doi.org/10.1093/gji/ggaa406.
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SUMMARY About a decade ago, noise-based monitoring became a key tool in seismology. One of the tools is passive image interferometry (PII), which uses noise correlation functions (NCF) to retrieve seismic velocity variations. Most studies apply PII to vertical components recording oceanic low-frequent ambient noise ( < 1 Hz). In this work, PII is applied to high-frequent urban ambient noise ( > 1 Hz) on three three-component sensors. With environmental sensors inside the subsurface and in the air, we are able to connect observed velocity variations with environmental parameters. Temperatures below 0 °C correlate well with strong shear wave velocity increases. The temperature sensors inside the ground suggest that a frozen layer of less than 5 cm thickness causes apparent velocity increases above 2 % , depending on the channel pair. The observations indicate that the different velocity variation retrieved from the different channel pairs are due to different surface wave responses inherent in the channel pairs. With dispersion curve modelling in a 1-D medium we can verify that surfaces waves of several tens of metres wavelength experience a velocity increase of several percent due to a centimetres thick frozen layer. Moreover, the model verifies that Love waves show larger velocity increases than Rayleigh waves. The findings of this study provide new insights for monitoring with PII. A few days with temperature below 0 °C can already mask other potential targets (e.g. faults or storage sites). Here, we suggest to use vertical components, which is less sensitive to the frozen layer at the surface. If the target is the seasonal freezing, like in permafrost studies, we suggest to use three-component sensors in order to retrieve the Love wave response. This opens the possibility to study other small-scale processes at the shallow subsurface with surface wave responses.
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Antkowiak, L., M. Putz, R. Sordyl, S. Pokora y M. Mandera. "Intramedullary spinal cord tumors in children: the relevance of motor evoked potentials and D-wave monitoring". Brain and Spine 2 (2022): 101574. http://dx.doi.org/10.1016/j.bas.2022.101574.
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Thompson, Ian. "Virtual hull monitoring of a naval vessel using hindcast data and reconstructed 2-D wave spectra". Marine Structures 71 (mayo de 2020): 102730. http://dx.doi.org/10.1016/j.marstruc.2020.102730.
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Bao, Yu, Yong Wang, Guangxiao Deng y Qinghui Mao. "Elastic wave pre-stack reverse-time migration based on the second-order P- and S-wave decoupling equation". Journal of Geophysics and Engineering 19, n.º 5 (octubre de 2022): 1221–34. http://dx.doi.org/10.1093/jge/gxac078.
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Abstract The problems of large computation, large storage and low-frequency noises have been the key factors limiting the development of elastic wave pre-stack reverse-time migration (RTM). Most research has centered on the wave equation of first-order velocity stress and using Helmholtz separation to get pure primary and secondary waves. However, the cost is enormous and the amplitude and phase of wavefields will be changed. So, we use the second-order P- and S-wave decoupling equations to construct seismic wavefields that reduce the number of variables, and the storage space required for boundary wavefields is reduced by ∼78%. Then we bring the boundary-saving approach into our study during the wavefield extrapolation process so that we can reconstruct the source wavefields completely. Finally, for the wave equations of second-order displacement used in this study, the Poynting vector expressed by the traditional method was not applicable. Therefore, we derived the formula of the energy flux density vector represented by displacements and used it in directional traveling wave decomposition to suppress low-frequency noise in the imaging profile. Subsequently, based on the inner product imaging conditions, the RTM of the 2-D salt dome model was calculated. The results illustrate the effectiveness and practicability of the proposed solution.
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Barthwal, Himanshu, Frank J. Calixto y Mirko van der Baan. "3-D attenuation tomography from microseismicity in a mine". Geophysical Journal International 219, n.º 3 (30 de agosto de 2019): 1805–17. http://dx.doi.org/10.1093/gji/ggz396.
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SUMMARY We perform 3-D attenuation tomography using microseismic data recorded during an underground mine development. The whole path attenuation parameter t* is obtained by least-squares inversion of P-wave amplitude spectra of the events recorded by 7 monitoring wells each containing 4 3C geophones. The corner frequencies obtained during P-wave spectral inversion of the 488 identified events range from 140 to 220 Hz which are typical for microseismic events with a negative moment magnitude of around –1. The quality factor Q obtained from tomographic inversion varies between 9 and 72 with the event cluster location characterized by a low Q value of 10. Two high Q regions of 30–72 are located at depths of 0.45 and 0.5 km, one between 0–0.15 km east and 0.3–0.5 km north which correlate with the high-grade ore deposit, and another centred around 0.45 km east and 0.25 km north. The high (-low) Q values, in general, correlates with the high (-low) velocities present in the velocity tomography model. A joint interpretation of seismic attenuation and velocity models reveals the heterogeneity present in the mine which aids in delineating the ore body using seismic waves in addition to other measurements such as gravity inversion and direct sampling from drillholes.
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Tura, Ali, James Simmons, Sima Daneshvar, Matthew Copley y Joseph Stitt. "Improving reservoir characterization and time-lapse seismic through joint inversion of PP- and PS-wave seismic data". Interpretation 10, n.º 2 (14 de marzo de 2022): T341—T350. http://dx.doi.org/10.1190/int-2021-0167.1.
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Using synthetic and field data examples, we find that joint prestack amplitude variation with angle (AVA) inversion of PP- and PS-wave data can significantly improve estimation of P-impedance, S-impedance, and density. For reservoir characterization, improvements in these parameters can better identify reservoir rock and fluid properties. For reservoir monitoring, time-lapse (4D) changes in P-impedance, S-impedance, and density can lead to inversion of saturation and pressure changes. We see that in the joint inversion, 4D S-impedance is better estimated and not coupled to 4D P-impedance. These claims are first demonstrated on synthetic data, and then shown on an onshore unconventional play from Colorado and offshore 4-D-4C data set from the North Sea. Joint inversion of PP- and PS-wave data requires a higher level of care compared with PP-waves because the two wave modes need to be acquired, processed, and merged properly. This has diminished the use of converted waves in the past. However, modern acquisition and processing on land and offshore data make this technology quantitatively more accurate and realizable. As such, we also provide best practices for a successful project. We indicate that joint inversion can lead to a larger chance of success in placing exploration and development wells.
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Zhang, Xiao Hui y Xi Ling Zhao. "A Design of Pulse-Wave Data Collection System". Applied Mechanics and Materials 127 (octubre de 2011): 48–52. http://dx.doi.org/10.4028/www.scientific.net/amm.127.48.
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In this paper, a newly design of pulse-wave data collection system continuously and non-invasion by using the means of clip-on transmission oxygen sensor for getting information of pulse-wave, using the wave can calculate a number of important parameters of blood, it may solve the problem of real-time, continuous and dynamic blood flow monitoring in clinic, This design use sensor to get photoelectric volume pulse wave then the signal through amplification and filter circuit ,after then it is sent to A / D converter and DSP. The powerful instruction functions and fast processing speed DSP makes this design can quickly and easily detect the pulse wave signal. This design not only used for clinical care, but also can be used for community or family health care on detection of cardiovascular blood flow. This design can make the telemedicine care ture by DSP and the PC communication, It provides a simple and easy method to monitor the pulse-wave signal .
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Deora, Harsh. "Resection of Cervical Intramedullary Ependymoma Under D-Wave and SSEP/MEP Monitoring without the Use of Coagulation". Neurology India 70, n.º 6 (2022): 2354. http://dx.doi.org/10.4103/0028-3886.364079.
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Noszczyk-Nowak, Agnieszka. "QTc Dispersion and T-Wave Alternans as Predictors of Mortality in Dogs with Dilated Cardiomyopathy and Ventricular Tachycardia in Holter Monitoring. a Retrospective Study". Bulletin of the Veterinary Institute in Pulawy 56, n.º 2 (1 de junio de 2012): 189–92. http://dx.doi.org/10.2478/v10213-012-0034-0.
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Abstract The study presents a comparison of the results received from dogs with dilated cardiomyopathy (DCM) that died during the first 30 d of observation and from dogs with DCM that survived the first 30 d after the ECG. No differences were noted in the duration of QT or QTc in healthy dogs and dogs with DCM. QTcd was significantly higher in dogs with DCM and in dogs with DCM, which did not survive over 30 d of observation and dogs with DCM that died after the 30th d of observation. The presence of T-wave alternans (TWA) was more frequently observed in dogs with DCM (85% of the dogs) that died in less than 30 d during the observation. QTcd and TWA seem to be a useful non-invasive diagnostic tool to anticipate the risk of cardiac death in dogs with DCM.
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Voinova, Marina V. "On Mass Loading and Dissipation Measured with Acoustic Wave Sensors: A Review". Journal of Sensors 2009 (2009): 1–13. http://dx.doi.org/10.1155/2009/943125.
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We summarize current trends in the analysis of physical properties (surface mass density, viscosity, elasticity, friction, and charge) of various thin films measured with a solid-state sensor oscillating in a gaseous or liquid environment. We cover three different types of mechanically oscillating sensors: the quartz crystal microbalance with dissipation (QCM-D) monitoring, surface acoustic wave (SAW), resonators and magnetoelastic sensors (MESs). The fourth class of novel acoustic wave (AW) mass sensors, namely thin-film bulk acoustic resonators (TFBARs) on vibrating membranes is discussed in brief. The paper contains a survey of theoretical results and practical applications of the sensors and includes a comprehensive bibliography.
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Gaeta, Maria Gabriella, Achilleas G. Samaras, Ivan Federico, Renata Archetti, Francesco Maicu y Giuliano Lorenzetti. "A coupled wave–3-D hydrodynamics model of the Taranto Sea (Italy): a multiple-nesting approach". Natural Hazards and Earth System Sciences 16, n.º 9 (6 de septiembre de 2016): 2071–83. http://dx.doi.org/10.5194/nhess-16-2071-2016.
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Abstract. The present work describes an operational strategy for the development of a multiscale modeling system, based on a multiple-nesting approach and open-source numerical models. The strategy was applied and validated for the Gulf of Taranto in southern Italy, scaling large-scale oceanographic model results to high-resolution coupled wave–3-D hydrodynamics simulations for the area of Mar Grande in the Taranto Sea. The spatial and temporal high-resolution simulations were performed using the open-source TELEMAC suite, forced by wind data from the COSMO-ME database, boundary wave spectra from the RON buoy at Crotone and results from the Southern Adriatic Northern Ionian coastal Forecasting System (SANIFS) regarding sea levels and current fields. Model validation was carried out using data collected in the Mar Grande basin from a fixed monitoring station and during an oceanographic campaign in October 2014. The overall agreement between measurements and model results in terms of waves, sea levels, surface currents, circulation patterns and vertical velocity profiles is deemed to be satisfactory, and the methodology followed in the process can constitute a useful tool for both research and operational applications in the same field and as support of decisions for management and design of infrastructures.
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Hu, Xiong Wei, Xin Feng y Jing Zhou. "Damage Identification of Cracked Pipes Based on Reflection Characteristics of Guided Waves". Applied Mechanics and Materials 94-96 (septiembre de 2011): 623–26. http://dx.doi.org/10.4028/www.scientific.net/amm.94-96.623.
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A methodology of damage identification for the circumferentially cracked pipe is presented by using the quantitative relationship between crack size and reflection characteristics of guided waves. Firstly, the reflection characteristics and mode conversion behavior were theoretically studied by the 3-D finite element (FE) analysis. It is found that the reflection coefficients (RCs) of longitudinal L(0,2) and F(1,3) modes quantitatively is related to the circumferential length and radial depth of the crack. Then we present a novel method to quantitatively identify the crack. The feasibility of the proposed method was numerically investigated. The method only requires the longitudinal excitation mode of guided wave in the pipe, which shows the good potential for real application or in-situ damage monitoring. Introduction
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Shuck, Edward L., Thomas L. Davis y Robert D. Benson. "Multicomponent 3-D characterization of a coalbed methane reservoir". GEOPHYSICS 61, n.º 2 (marzo de 1996): 315–30. http://dx.doi.org/10.1190/1.1443961.
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Methane is produced from fractured coalbed reservoirs at Cedar Hill Field in the San Juan Basin. Fracturing and local stress are critical to production because of the absence of matrix permeability in the coals. Knowledge of the direction of open fractures, the degree of fracturing, reservoir pressure, and compartmentalization is required to understand the flow of fluids through the reservoir. A multicomponent 3-D seismic survey was acquired to aid in coalbed methane reservoir characterization. Coalbed reservoir heterogeneities, including isolated pressure cells, zones of increased fracture density, and variable fracture directions, have been interpreted through the analysis of the multicomponent data and integration with petrophysical and reservoir engineering studies. Strike‐slip faults, which compartmentalize the reservoir, have been identified by structural interpretation of the 3-D P‐wave seismic data. These faults form boundaries for pressure cells that have been identified by P‐wave reflection amplitude anomalies. The analysis of polarizations, traveltimes, and reflection amplitudes from the shear‐wave seismic data has allowed the identification of zones of variable fracture direction and fracture density. There is good agreement between stresses inferred from the structural interpretation and those indicated by the shear‐wave polarizations. Reflection amplitudes have been calibrated to seismic velocities and reservoir pressures through the use of petrophysical data taken from core samples. New methods have been developed for the statistical analysis of prestack shear‐wave polarizations, poststack polarizations, and the accurate determination of traveltime anisotropy. The prestack polarization analysis method allows for rapid and efficient determination of a dominant polarization direction. Shear‐wave anisotropy has been quantified over the reservoir zone using both traveltime and thin‐bed reflection response with excellent agreement between the two methods. Crack densities computed from the anisotropy show two regions of high crack density, one coinciding with a sealed overpressured cell and the other in the region of the Hamilton ♯3 well. This indicates the potential for monitoring production of coalbed methane reservoirs using multicomponent seismology.
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Lee, Sang-Jun, Junkee Rhie, Seongryong Kim, Tae-Seob Kang y Chang Soo Cho. "1-D velocity model for the North Korean Peninsula from Rayleigh wave dispersion of ambient noise cross-correlations". Journal of Seismology 24, n.º 1 (16 de noviembre de 2019): 121–31. http://dx.doi.org/10.1007/s10950-019-09891-6.
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AbstractMonitoring seismic activity in the north Korean Peninsula (NKP) is important not only for understanding the characteristics of tectonic earthquakes but also for monitoring anthropogenic seismic events. To more effectively investigate seismic properties, reliable seismic velocity models are essential. However, the seismic velocity structures of the region have not been well constrained due to a lack of available seismic data. This study presents 1-D velocity models for both the inland and offshore (western East Sea) of the NKP. We constrained the models based on the results of a Bayesian inversion process using Rayleigh wave dispersion data, which were measured from ambient noise cross-correlations between stations in the southern Korean Peninsula and northeast China. The proposed models were evaluated by performing full moment tensor inversion for the 2013 Democratic People’s Republic of Korea (DPRK) nuclear test. Using the composite model consisting of both inland and offshore models resulted in consistently higher goodness of fit to observed waveforms than previous models. This indicates that seismic monitoring can be improved by using the proposed models, which resolve propagation effects along different paths in the NKP region.
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FUJII, Masami, Sadahiro NOMURA, Hirochika IMOTO, Hironobu TANAKA, Takayuki OKU, Tetsu KUROKAWA, Kei HARADA et al. "The Usefulness of the Intraoperative Monitoring of the Motor Evoked Potential (MEP) with D-wave in Aneurysm Surgery". Surgery for Cerebral Stroke 36, n.º 5 (2008): 373–79. http://dx.doi.org/10.2335/scs.36.373.
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Zhang, Tuo, Christoph Sens-Schönfelder y Ludovic Margerin. "Sensitivity kernels for static and dynamic tomography of scattering and absorbing media with elastic waves: a probabilistic approach". Geophysical Journal International 225, n.º 3 (4 de febrero de 2021): 1824–53. http://dx.doi.org/10.1093/gji/ggab048.
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SUMMARY Scattered seismic coda waves are frequently used to characterize small scale medium heterogeneities, intrinsic attenuation or temporal changes of wave velocity. Spatial variability of these properties raises questions about the spatial sensitivity of seismic coda waves. Especially the continuous monitoring of medium perturbations using ambient seismic noise led to a demand for approaches to image perturbations observed with coda waves. An efficient approach to localize spatial and temporal variations of medium properties is to invert the observations from different source–receiver combinations and different lapse times in the coda for the location of the perturbations. For such an inversion, it is key to calculate the coda-wave sensitivity kernels which describe the connection between observations and the perturbation. Most discussions of sensitivity kernels use the acoustic approximation in a spatially uniform medium and often assume wave propagation in the diffusion regime. We model 2-D multiple non-isotropic scattering in a random elastic medium with spatially variable heterogeneity and attenuation using the radiative transfer equations which we solve with the Monte Carlo method. Recording of the specific energy density of the wavefield that contains the complete information about the energy density at a given position, time and propagation direction allows us to calculate sensitivity kernels according to rigorous theoretical derivations. The practical calculation of the kernels involves the solution of the adjoint radiative transport equations. We investigate sensitivity kernels that describe the relationships between changes of the model in P- and S-wave velocity, P- and S-wave attenuation and the strength of fluctuation on the one hand and seismogram envelope, traveltime changes and waveform decorrelation as observables on the other hand. These sensitivity kernels reflect the effect of the spatial variations of medium properties on the wavefield and constitute the first step in the development of a tomographic inversion approach for the distribution of small-scale heterogeneity based on scattered waves.
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Correia, Emilia, Luis Tiago Medeiros Raunheitte, José Valentin Bageston y Dino Enrico D'Amico. "Characterization of gravity waves in the lower ionosphere using very low frequency observations at Comandante Ferraz Brazilian Antarctic Station". Annales Geophysicae 38, n.º 2 (24 de marzo de 2020): 385–94. http://dx.doi.org/10.5194/angeo-38-385-2020.
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Abstract. The goal of this work is to investigate the gravity wave (GW) characteristics in the low ionosphere using very low frequency (VLF) radio signals. The spatial modulations produced by the GWs affect the conditions of the electron density at reflection height of the VLF signals, which produce fluctuations of the electrical conductivity in the D region that can be detected as variations in the amplitude and phase of VLF narrowband signals. The analysis considered the VLF signal transmitted from the US Cutler, Maine (NAA) station that was received at Comandante Ferraz Brazilian Antarctic Station (EACF, 62.1∘ S, 58.4∘ W), with its great circle path crossing the Drake Passage longitudinally. The wave periods of the GWs detected in the low ionosphere are obtained using the wavelet analysis applied to the VLF amplitude. Here the VLF technique was used as a new aspect for monitoring GW activity. It was validated comparing the wave period and duration properties of one GW event observed simultaneously with a co-located airglow all-sky imager both operating at EACF. The statistical analysis of the seasonal variation of the wave periods detected using VLF technique for 2007 showed that the GW events occurred all observed days, with the waves with a period between 5 and 10 min dominating during night hours from May to September, while during daytime hours the waves with a period between 0 and 5 min are predominant the whole year and dominate all days from November to April. These results show that VLF technique is a powerful tool to obtain the wave period and duration of GW events in the low ionosphere, with the advantage of being independent of sky conditions, and it can be used during the whole day and year-round.
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YAMAMOTO, Takamitsu, Yoichi KATAYAMA, Takafumi NAGAOKA, Kazutaka KOBAYASHI y Chikashi FUKAYA. "Intraoperative Monitoring of the Corticospinal Motor Evoked Potential (D-wave): Clinical Index for Postoperative Motor Function and Functional Recovery". Neurologia medico-chirurgica 44, n.º 4 (2004): 170–82. http://dx.doi.org/10.2176/nmc.44.170.
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Chen, Mingtong, Hao Qiu y Faxin Li. "SH Guided Wave Tomography for Structural Health Monitoring Based on Antiparallel Thickness-Shear (d15) Piezoelectric Transducers". IEEE Sensors Journal 21, n.º 24 (15 de diciembre de 2021): 27385–92. http://dx.doi.org/10.1109/jsen.2021.3127005.
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Yao, Shouguang, Xinyu Huang, Linglong Zhang, Huiyi Mao y Xiaofei Sun. "Analysis and Prediction of Flow-Induced Vibration of Convection Pipe for 200 t/h D Type Gas Boiler". Axioms 11, n.º 4 (5 de abril de 2022): 163. http://dx.doi.org/10.3390/axioms11040163.
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This paper is aimed at the analysis and prediction of the fluid-induced vibration phenomenon in the convection tube bundle area caused by Karman vortex street shedding in the background of a 200 t/h large-capacity D-type gas boiler. Based on the numerical simulation of flue heat state flow field and fast Fourier transform, the lift coefficient curve of different monitoring areas and the corresponding Karman vortex street shedding frequency are obtained. The accuracy of the analysis model is validated by comparing Karman vortex shedding frequency with acoustic equipment standing wave frequency. In order to meet the design requirements of the 200 t/h D-type gas boiler for reliable and stable operation, the vibration characteristics and variation rules of a convection tube bundle in a D-type boiler under different working conditions are predicted.
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Sala, Francesco, Giorgio Palandri, Elisabetta Basso, Paola Lanteri, Vedran Deletis, Franco Faccioli y Albino Bricolo. "Motor Evoked Potential Monitoring Improves Outcome after Surgery for Intramedullary Spinal Cord Tumors: A Historical Control Study". Neurosurgery 58, n.º 6 (1 de junio de 2006): 1129–43. http://dx.doi.org/10.1227/01.neu.0000215948.97195.58.
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Abstract OBJECTIVE: The value of intraoperative neurophysiological monitoring (INM) during intramedullary spinal cord tumor surgery remains debated. This historical control study tests the hypothesis that INM monitoring improves neurological outcome. METHODS: In 50 patients operated on after September 2000, we monitored somatosensory evoked potentials and transcranially elicited epidural (D-wave) and muscle motor evoked potentials (INM group). The historical control group consisted of 50 patients selected from among 301 patients who underwent intramedullary spinal cord tumor surgery, previously operated on by the same team without INM. Matching by preoperative neurological status (McCormick scale), histological findings, tumor location, and extent of removal were blind to outcome. A more than 50% somatosensory evoked potential amplitude decrement influenced only myelotomy. Muscle motor evoked potential disappearance modified surgery, but more than 50% D-wave amplitude decrement was the major indication to stop surgery. The postoperative to preoperative McCormick grade variation at discharge and at a follow-up of at least 3 months was compared between the two groups (Student's t tests). RESULTS: Follow-up McCormick grade variation in the INM group (mean, +0.28) was significantly better (P = 0.0016) than that of the historical control group (mean, –0.16). At discharge, there was a trend (P = 0.1224) toward better McCormick grade variation in the INM group (mean, –0.26) than in the historical control group (mean, –0.5). CONCLUSION: The applied motor evoked potential methods seem to improve long-term motor outcome significantly. Early motor outcome is similar because of transient motor deficits in the INM group, which can be predicted at the end of surgery by the neurophysiological profile of patients.
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Béres, Szabolcs, Lőrinc Holczer y László Hejjel. "On the Minimal Adequate Sampling Frequency of the Photoplethysmogram for Pulse Rate Monitoring and Heart Rate Variability Analysis in Mobile and Wearable Technology". Measurement Science Review 19, n.º 5 (1 de octubre de 2019): 232–40. http://dx.doi.org/10.2478/msr-2019-0030.
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Abstract Recently there has been great interest in photoplethysmogram signal processing. However, its minimally necessary sampling frequency for accurate heart rate variability parameters is ambiguous. In the present paper frequency-modulated 1.067 Hz cosine wave modelled the variable PPG in silico. The five-minute-long, 1 ms resolution master-signals were decimated (D) at 2-500 ms, then cubic spline interpolated (I) back to 1 ms resolution. The mean pulse rate, standard deviation, root mean square of successive pulse rate differences (RMSSD), and spectral components were computed by Varian 2.3 and compared to the master-series via relative accuracy error. Also Poincaré-plot morphology was assessed. Mean pulse rate is accurate down to 303 ms (D) and 400 ms (I). In low-variability series standard deviation required at least 5 ms (D) and 100 ms (I). RMSSD needed 10 ms (D), and 303 ms (I) in normal, whereas 2 ms (D) and 100 ms (I) in low- variability series. In the frequency domain 5 ms (D) and 100 ms (I) are required. 2 ms (D) and 100 ms (I) preserved the Poincaré-plot morphology. The minimal sampling frequency of PPG for accurate HRV analysis is higher than expected from the signal bandwidth and sampling theorem. Interpolation improves accuracy. The ratio of sampling error and expected variability should be considered besides the inherent sensitivity of the given parameter, the interpolation technique, and the pulse rate detection method.
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Duan, Chenglong, David Lumley y Hejun Zhu. "Estimation of micro-earthquake source locations based on full adjoint P and S wavefield imaging". Geophysical Journal International 226, n.º 3 (3 de junio de 2021): 2116–44. http://dx.doi.org/10.1093/gji/ggab203.
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SUMMARY Locating micro-earthquakes with high resolution and accuracy is a challenge for traveltime inversion, which has uncertainty on the order of a Fresnel zone (many wavelengths). We develop a wave-equation imaging method to increase resolution and reduce location errors to less than a wavelength, but requires very densely deployed receiver arrays with wide aperture and considerable computational cost. Instead of using acoustic data or direct P wave arrivals only, we use elastic multicomponent data and present a new method that uses the full P and S adjoint wavefields to image the microseismic source locations. We separate the P and S waves from the data, and extrapolate the P and S wavefields of each receiver subarray by solving the P and S adjoint wave equations in parallel. We formulate three source imaging conditions by multiplying over subarrays the adjoint P wavefield (IP), S wavefield (IS) and cross-correlated P and S wavefields (IPS). We perform numerical experiments on the highly realistic SEG SEAM4D reservoir model using surface acquisition array geometries. Results for 2-D and 3-D microseismic source estimations show clean images without noisy artefacts at shallow depths. In particular, IPS provides the highest resolution source location image, while IP is limited by the P wavelength and IS is influenced by small coda artefacts. The major-axis alignment and resolution of the source location image are determined by the hypocentral location with respect to the receiver array and illumination-angle coverage, respectively. We discuss the impacts of S-wave attenuation and frequency bandwidth on the source location images. Noise tests indicate that the imaging results are relatively insensitive to ambient noise, as is observed for the surface monitoring data. Using smoothed velocity models, the imaging results are similar to the results using the true realistically heterogeneous velocity model. The 90 per cent confidence ellipse of the source location due to Gaussian-distributed velocity errors shows a larger depth error as the source becomes deeper, while the horizontal error does not change as much.
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Gresil, Matthieu y Victor Giurgiutiu. "Time-Domain Hybrid Global-Local Prediction of Guided Waves Interaction with Damage". Key Engineering Materials 558 (junio de 2013): 116–27. http://dx.doi.org/10.4028/www.scientific.net/kem.558.116.
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This paper presents a hybrid finite element and analytical method to predict the 1-D guided wave propagation interaction with damage for nondestructive evaluation (NDE) and structural health monitoring (SHM) application. The finite element mesh is used to describe the region around the damage (defects or flaws). In contrast to other hybrid models developed elsewhere, the interaction between Lamb waves and defects is computed in the time domain using the explicit solver of the commercial finite element method (FEM) software ABAQUS. Analytical methods can perform efficient modeling of wave propagation but are limited to simple geometries. Realistic structures with complicated geometries are usually modeled with the FEM. However, to obtain an accurate wave propagation solution at ultrasonic frequencies is computationally intensive and may become prohibitive for realistic structures. In response to today's complex cases not covered by the simulation tools available, we aim to develop an efficient and accessible tool for SHM applications. This tool will be based on a hybrid coupling between analytical solutions and time domain numerical codes. Lamb wave interaction with a notch is investigated by using this method, and the results obtained are with respect to transmission, reflection and mode conversion. Because of the symmetric mode shape, S0 is more sensitive to the shallow notch than A0. By making use of the fact that the reflection increases with increase in notch depth and mode conversion are maximized when the notch is around half through the thickness of the plate, the reflection and conversion coefficients can be used to characterize the depth of the notch.
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Wilcox, Paul D., C. K. Lee, Jonathan J. Scholey, Michael I. Friswell, M. R. Wisnom y B. W. Drinkwater. "Progress Towards a Forward Model of the Complete Acoustic Emission Process". Advanced Materials Research 13-14 (febrero de 2006): 69–76. http://dx.doi.org/10.4028/www.scientific.net/amr.13-14.69.
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Acoustic emission (AE) techniques have obvious attractions for structural health monitoring (SHM) due to their extreme sensitivity and low sensor density requirement. A factor preventing the adoption of AE monitoring techniques in certain industrial sectors is the lack of a quantitative deterministic model of the AE process. In this paper, the development of a modular AE model is described that can be used to predict the received time-domain waveform at a sensor as a result of an AE event elsewhere in the structure. The model is based around guided waves since this is how AE signals propagate in many structures of interest. Separate modules within the model describe (a) the radiation pattern of guided wave modes at the source, (b) the propagation and attenuation of guided waves through the structure, (c) the interaction of guided waves with structural features and (d) the detection of guided waves with a transducer of finite spatial aperture and frequency response. The model is implemented in the frequency domain with each element formulated as a transfer function. Analytic solutions are used where possible; however, by virtue of its modular architecture it is straightforward to include numerical data obtained either experimentally or through finite element analysis (FEA) at any stage in the model. The paper will also show how the model can used, for example, to produce probability of detection (POD) data for an AE testing configuration.
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Li, Zhi, Tian Jin, Yongpeng Dai y Yongkun Song. "Through-Wall Multi-Subject Localization and Vital Signs Monitoring Using UWB MIMO Imaging Radar". Remote Sensing 13, n.º 15 (23 de julio de 2021): 2905. http://dx.doi.org/10.3390/rs13152905.
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Radar-based non-contact vital signs monitoring has great value in through-wall detection applications. This paper presents the theoretical and experimental study of through-wall respiration and heartbeat pattern extraction from multiple subjects. To detect the vital signs of multiple subjects, we employ a low-frequency ultra-wideband (UWB) multiple-input multiple-output (MIMO) imaging radar and derive the relationship between radar images and vibrations caused by human cardiopulmonary movements. The derivation indicates that MIMO radar imaging with the stepped-frequency continuous-wave (SFCW) improves the signal-to-noise ratio (SNR) critically by the factor of radar channel number times frequency number compared with continuous-wave (CW) Doppler radars. We also apply the three-dimensional (3-D) higher-order cumulant (HOC) to locate multiple subjects and extract the phase sequence of the radar images as the vital signs signal. To monitor the cardiopulmonary activities, we further exploit the VMD algorithm with a proposed grouping criterion to adaptively separate the respiration and heartbeat patterns. A series of experiments have validated the localization and detection of multiple subjects behind a wall. The VMD algorithm is suitable for separating the weaker heartbeat pattern from the stronger respiration pattern by the grouping criterion. Moreover, the continuous monitoring of heart rate (HR) by the MIMO radar in real scenarios shows a strong consistency with the reference electrocardiogram (ECG).
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Rindraharisaona, Elisa J., Guilhem Barruol, Emmanuel Cordier, Fabrice R. Fontaine y Alicia Gonzalez. "Cyclone Signatures in the South-West Indian Ocean from Two Decades of Microseismic Noise". Atmosphere 12, n.º 4 (13 de abril de 2021): 488. http://dx.doi.org/10.3390/atmos12040488.
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Tropical Cyclones (TC) represent the most destructive natural disaster affecting the islands in the South-West Indian Ocean (SWIO) each year. Monitoring ocean activity is therefore of primary importance to secure lands, infrastructures and peoples, but the little number of oceanographic instruments makes it challenging, particularly in real time. Long-term seismological records provide a way to decipher and quantify the past cyclonic activity by analyzing microseisms, seismic waves generated by the ocean activity and propagating through the solid Earth. In the present study, we analyze this microseismic noise generated by cyclones that develop in the SWIO basin between 1999 and 2020, using broadband seismic stations in La Réunion. The power spectral density (PSD), together with the root mean square (RMS) analyses of continuous seismic data recorded by the permanent Geoscope RER seismic station, indicate the intensification of the microseismic noise amplitude in proportion to the cyclone intensity. Thus, we establish a relationship between the cyclone intensity and the PSD of the Secondary Microseisms (SM) in frequency band ∼0.14 to 0.25 Hz (4 to 7 s period). The Pearson coefficient between the observed and estimated TC intensity are >0.8 in the presence of a cyclone with mean wind speeds >75 km/h and with a seismic station distance-to-storm center D < 3000 km. A polarization analysis in the time and frequency domains allows the retrieval of the backazimuth of the SM sources during isolated cyclone events and well-polarized signal, i.e., CpH > 0.6. We also analyzed the RMS of the Primary Microseisms (PM frequency between ∼0.05 and 0.1 Hz, i.e., for 10 to 20 s period) for cyclones passing nearby La Réunion (D < 500 km), using the available temporary and permanent broadband seismic stations. We also found high correlation coefficients (>0.8) between the PM amplitude and the local wave height issued from the global hindcast model demonstrating that the PM amplitude can be used as a robust proxy to perform a real-time wave-height monitoring in the neighboring ocean. Transfer functions are calculated for several cyclones to infer wave height from the seismic noise amplitude recorded on land. From the analysis of two decades of data, our results suggest that it is possible to quantify the past ocean activity for as long as continuous seismic archives are available, emphasizing microseismic noise as a key observable for quantifying and understanding the climate change.
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Sun, Zhigang, Bruno Rocha, Kuo-Ting Wu y Nezih Mrad. "A Methodological Review of Piezoelectric Based Acoustic Wave Generation and Detection Techniques for Structural Health Monitoring". International Journal of Aerospace Engineering 2013 (2013): 1–22. http://dx.doi.org/10.1155/2013/928627.
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Piezoelectric transducers have a long history of applications in nondestructive evaluation of material and structure integrity owing to their ability of transforming mechanical energy to electrical energy and vice versa. As condition based maintenance has emerged as a valuable approach to enhancing continued aircraft airworthiness while reducing the life cycle cost, its enabling structural health monitoring (SHM) technologies capable of providing on-demand diagnosis of the structure without interrupting the aircraft operation are attracting increasing R&D efforts. Piezoelectric transducers play an essential role in these endeavors. This paper is set forth to review a variety of ingenious ways in which piezoelectric transducers are used in today’s SHM technologies as a means of generation and/or detection of diagnostic acoustic waves.
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Ružić, Ž., V. Vujnović, K. Pavlovski, H. Božić, J. R. Percy, A. Attard, P. Harmanec, J. Horn, P. Koubský y K. Juza. "Activity of the Be star 28 Cygni: 1985–1991". Symposium - International Astronomical Union 162 (1994): 102–3. http://dx.doi.org/10.1017/s0074180900214629.
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28 Cyg (V1624 Cyg, HD 191610, HR 7708; B2e, v sin i = 310 km s-1) has been the target of several observational projects, and in 1988 of a large international campaign. This attention was inspired by several photometric studies and especially by the 1985 nearly simultaneous optical and UV spectroscopic monitoring by Peters & Penrod (1988). They found that the line-profile variations were controlled by two frequencies, 1.45 c/d, and 7.43 c/d, which they identified with sectorial pulsations of modes l = 2, m = +2 and l = 10, m = +10. Rapid changes (0.5 to 1 hr) of the CIV wind profile were found; its equivalent width appeared to correlate with the phase of the l = 2 mode. Pavlovski & Ružić (1990) - who independently analysed Hvar 1985 UBV photometry of 28 Cyg - found periodic light variations with a double-wave light curve and a frequency of 1.54 c/d. However – because of the residual scatter around the mean light–curve – the authors tentatively suggested possible multiperiodicity (1.54, 1.33, and 0.95 c/d).