Interpretation of Coastal HF Radar–Derived Surface Currents with High-Resolution Drifter Data

2007 ◽  
Vol 24 (4) ◽  
pp. 666-680 ◽  
Author(s):  
Carter Ohlmann ◽  
Peter White ◽  
Libe Washburn ◽  
Brian Emery ◽  
Eric Terrill ◽  
...  
Keyword(s):  
San Diego ◽  
Surface Current ◽  
Hf Radar ◽  
Absolute Difference ◽  
Time And Space ◽  
Santa Barbara ◽  
Mean Absolute Difference ◽  
The Difference ◽  
Surface Drifters ◽  
Good Agreement

Abstract Dense arrays of surface drifters are used to quantify the flow field on time and space scales over which high-frequency (HF) radar observations are measured. Up to 13 drifters were repetitively deployed off the Santa Barbara and San Diego coasts on 7 days during 18 months. Each day a regularly spaced grid overlaid on a 1-km2 (San Diego) or 4-km2 (Santa Barbara) square, located where HF radar radial data are nearly orthogonal, was seeded with drifters. As drifters moved from the square, they were retrieved and replaced to maintain a spatially uniform distribution of observations within the sampling area during the day. This sampling scheme resulted in up to 56 velocity observations distributed over the time (1 h) and space (1 and 4 km2) scales implicit in typical surface current maps from HF radar. Root-mean-square (RMS) differences between HF radar radial velocities obtained using measured antenna patterns, and average drifter velocities, are mostly 3–5 cm s−1. Smaller RMS differences compared with past validation studies that employ current meters are due to drifter resolution of subgrid-scale velocity variance included in time and space average HF radar fields. Roughly 5 cm s−1 can be attributed to sampling on disparate time and space scales. Despite generally good agreement, differences can change dramatically with time. In one instance, the difference increases from near zero to more than 20 cm s−1 within 2 h. The RMS difference and bias (mean absolute difference) for that day exceed 7 and 12 cm s−1, respectively.

Performance Evaluation of Different Cost Functions in Motion Vector Estimation

2014 ◽  
Vol 5 (1) ◽  
pp. 45-65 ◽  
Author(s):  
Suvojit Acharjee ◽  
Sayan Chakraborty ◽  
Wahiba Ben Abdessalem Karaa ◽  
Ahmad Taher Azar ◽  
Nilanjan Dey
Keyword(s):  
Video Compression ◽  
Motion Vector ◽  
Video Data ◽  
Cost Functions ◽  
Absolute Difference ◽  
Surveillance Video ◽  
Mean Absolute Difference ◽  
Vector Estimation ◽  
The Difference ◽  
Temporal Redundancy

Video is an important medium in terms of information sharing in this present era. The tremendous growth of video use can be seen in the traditional multimedia application as well as in many other applications like medical videos, surveillance video etc. Raw video data is usually large in size, which demands for video compression. In different video compressing schemes, motion vector is a very important step to remove the temporal redundancy. A frame is first divided into small blocks and then motion vector for each block is computed. The difference between two blocks is evaluated by different cost functions (i.e. mean absolute difference (MAD), mean square error (MSE) etc).In this paper the performance of different cost functions was evaluated and also the most suitable cost function for motion vector estimation was found.

Patient-Specific 3-D Magnetic Resonance Imaging–Based Dynamic Simulation of Hip Impingement and Range of Motion Can Replace 3-D Computed Tomography–Based Simulation for Patients With Femoroacetabular Impingement: Implications for Planning Open Hip Preservation Surgery and Hip Arthroscopy

2019 ◽  
Vol 47 (12) ◽  
pp. 2966-2977 ◽  
Author(s):  
Till D. Lerch ◽  
Celia Degonda ◽  
Florian Schmaranzer ◽  
Inga Todorski ◽  
Jennifer Cullmann-Bastian ◽  
...  
Keyword(s):  
Arthroscopic Surgery ◽  
3D Models ◽  
Absolute Difference ◽  
Patient Specific ◽  
Slice Thickness ◽  
Childbearing Age ◽  
Mean Absolute Difference ◽  
Hip Impingement ◽  
The Difference ◽  
Ct And Mri

Background: Femoroacetabular impingement (FAI) is a complex 3-dimensional (3D) hip abnormality that can cause hip pain and osteoarthritis in young and active patients of childbearing age. Imaging is static and based on 2-dimensional radiographs or computed tomography (CT) scans. Recently, CT-based 3D impingement simulation was introduced for patient-specific assessments of hip deformities, whereas magnetic resonance imaging (MRI) offers a radiation-free alternative for surgical planning before hip arthroscopic surgery. Purpose: To (1) investigate the difference between 3D models of the hip, (2) correlate the location of hip impingement and range of motion (ROM), and (3) correlate diagnostic parameters while comparing CT- and MRI-based osseous 3D models of the hip in symptomatic patients with FAI. Study Design: Cohort study (Diagnosis); Level of evidence, 2. Methods: The authors performed an institutional review board–approved comparative and retrospective study of 31 hips in 26 symptomatic patients with FAI. We compared CT- and MRI-based osseous 3D models of the hip in the same patients. 3D CT scans (slice thickness, 1 mm) of the entire pelvis and the distal femoral condyles were obtained. Preoperative MRI of the hip was performed including an axial-oblique T1 VIBE sequence (slice thickness, 1 mm) and 2 axial anisotropic (1.2 × 1.2 × 1 mm) T1 VIBE Dixon sequences of the entire pelvis and the distal femoral condyles. Threshold-based semiautomatic reconstruction of 3D models was performed using commercial software. CT- and MRI-based 3D models were compared with specifically developed software. Results: (1) The difference between MRI- and CT-based 3D models was less than 1 mm for the proximal femur and the acetabulum (median surface distance, 0.4 ± 0.1 mm and 0.4 ± 0.2 mm, respectively). (2) The correlation for ROM values was excellent ( r = 0.99, P < .001) between CT and MRI. The mean absolute difference for flexion and extension was 1.9°± 1.5° and 2.6°± 1.9°, respectively. The location of impingement did not differ between CT- and MRI-based 3D ROM analysis in all 12 of 12 acetabular and 11 of 12 femoral clock-face positions. (3) The correlation for 6 diagnostic parameters was excellent ( r = 0.98, P < .001) between CT and MRI. The mean absolute difference for inclination and anteversion was 2.0°± 1.8° and 1.0°± 0.8°, respectively. Conclusion: Patient-specific and radiation-free MRI-based dynamic 3D simulation of hip impingement and ROM can replace CT-based 3D simulation for patients with FAI of childbearing age. On the basis of these excellent results, we intend to change our clinical practice, and we will use MRI-based 3D models for future clinical practice instead of CT-based 3D models. This allows radiation-free and patient-specific preoperative 3D impingement simulation for surgical planning and simulation of open hip preservation surgery and hip arthroscopic surgery.

scholarly journals P1559 3D echocardiography improves the agreement between left ventricular and right ventricular stroke volumes in healthy individuals

2020 ◽  
Vol 21 (Supplement_1) ◽  
Author(s):  
A P Pilalidou ◽  
V K Kantartzi ◽  
C A Adamopoulos ◽  
L Z Zitiridou ◽  
M D Dimtsa ◽  
...  
Keyword(s):  
Healthy Subjects ◽  
Left Ventricular ◽  
Absolute Difference ◽  
P Value ◽  
Healthy Individuals ◽  
Mean Absolute Difference ◽  
Mean Values ◽  
Intracardiac Shunt ◽  
The Mean ◽  
The Difference

Abstract Funding Acknowledgements None Background/Introduction: Calculation of the LV and RV stroke volumes (SV) with the volumetric method can be useful for assessment of valvular regurgitant volumes and intracardiac shunt ratios. However, this method often yields significant differences between the estimated LV and RV SV even in healthy subjects. We hypothesized that this discrepancy can be largely due to the assumption of LV and RV outflow tract circularity which forms the basis of 2D derived areas. Purpose To assess if the use of 3D transoesophageal (TOE) derived LVOT and RVOT areas can improve the agreement between LV and RV stroke volumes using the volumetric approach in healthy subjects with no valvular abnormality or intracardiac shunt. Methods We studied 20 patients (9 Males, age: 51 ± 19 y) submitted to TOE for various reasons, who had normal cardiac anatomy and function and good quality 3D TOE LVOT and RVOT data. Two dimensional TOE measurements of the LVOT and RVOT diameters were made in a zoomed mid oesophageal long axis and short axis view respectively; using these measurements 2D TOE LVOT and RVOT derived areas were calculated assuming circularity. In a similar way, we calculated the 2D LVOT and RVOT areas using data from transthoracic echo (TTE) for each patient. Offline analysis of the 3D TOE data allowed direct planimetry of the LVOT and RVOT areas devoid of any geometric assumptions. Finally, calculation of the 2D TTE, 2D TOE and 3D TOE LV and RV stroke volumes were performed for each patient based on the acquired data. The difference between LV and RV stroke volume (which theoretically should be around zero) for each technique and for each patient was also calculated. Results The mean LV and RV SV for the whole cohort, did not differ significantly within each method: 2D-TTE. However, the mean absolute difference between LV and RV stoke volumes for each technique was significantly lower with the use of 3D TOE compared to both 2D TTE and 2D TOE. Mean values and dispersion of absolute differences for each method are shown in Figure 1. Conclusions Compared to 2D, use of direct 3D TOE RVOT and LVOT planimetry yielded significantly less difference between RV and LV stroke volumes in healthy individuals. This finding can have potential clinical implications for more accurate assessment of valvular regurgitant volumes or intracardiac shunts. The mean absolute difference LV-RV Absolute mean defference between LV and RV 95%ΔΕ F(2.38) p-value TTE 2D 18,65 ± 11,72 (13,2-24,1) 8.63 0.001 TOE 2D 13,45 ± 12,44 (7,6-19.3) 8.63 0.001 TOE 3D 6,45 ± 3,62 (4,8-8,1) 8.63 0.001 Abstract P1559 Figure. Bland Altaman Analysis

Abstract P154: Results From A Randomized Trial Of Different Rest Times Before Initiating BP Measurements

Hypertension ◽  
2020 ◽  
Vol 76 (Suppl_1) ◽  
Author(s):  
Tammy M Brady ◽  
Junichi Ishigami ◽  
Edgar R Miller ◽  
Kunihiro Matsushita ◽  
Lawrence J Appel ◽  
...  
Keyword(s):  
Rest Period ◽  
Wait Time ◽  
Community Dwelling ◽  
Absolute Difference ◽  
Resource Constrained ◽  
Mean Absolute Difference ◽  
Rest Periods ◽  
The Difference ◽  
Mean Differences ◽  
Design And Methods

Background: BP measurement guidelines recommend ≥5 min of rest before initiation of readings; this wait time is challenging to implement, especially in resource-constrained settings. Objective: Compare the effects of resting 0 or 2 min vs. 5 min on BP. Design and methods: RCT of community-dwelling adults, 18-80yrs. Participants had 4 sets of BP measurements (Omron HEM 970XL). In a cross-over design, the order of rest for the 1 st 3 sets [0min, 2min, 5min 1 ] was random. The 4 th set was always a 2nd 5min rest period (5min 2 ) to estimate repeatability. Mean BP for each rest period, mean absolute difference between each participant’s mean BP after 5min 1 and the other rest periods were determined. To determine if resting 0min and/or 2min was non-inferior to 5min 1 , we calculated the difference of differences, with ≤ ±2 mmHg considered non-inferior. Analyses were for the population overall and stratified by SBP ≥ vs. < 140mmHg. Results: N=113, mean age 55yrs, 36% male (n=41), 74% AA (n=84), 28% SBP > 140mmHg (n=32). Overall, mean 5min 1 BP was 128/75 and 5min 2 BP was 127/76 (p=NS), similar to mean BP at 2min and 0min (127/74 for both). The absolute difference of differences between 2min and 5min 1 SBP for the population overall was > ±2 mmHg, but for those with SBP <140, resting 2min and 0min BP was ≤ ±2 mmHg (Table). Conclusion: In this RCT, mean differences in BP by rest period were small. BPs obtained after shorter rest periods were non-inferior than those obtained after 5min when SBP <140. This suggests shorter rest times, even 0 min, may be reasonable for screening when the initial SBP is <140. These findings could improve the efficiency of hypertension screening, especially in resource-constrained settings.

Explaining the magnetism of gold

2017 ◽  
Author(s):  
Robson de Farias
Keyword(s):  
Gas Phase ◽  
Computational Study ◽  
Formation Enthalpy ◽  
Gold Atom ◽  
Orbital Energy ◽  
Knudsen Effusion ◽  
Energy Diagram ◽  
Unpaired Electrons ◽  
The Difference ◽  
Good Agreement

<p>In the present work, a computational study is performed in order to clarify the possible magnetic nature of gold. For such purpose, gas phase Au<sub>2</sub> (zero charge) is modelled, in order to calculate its gas phase formation enthalpy. The calculated values were compared with the experimental value obtained by means of Knudsen effusion mass spectrometric studies [5]. Based on the obtained formation enthalpy values for Au<sub>2</sub>, the compound with two unpaired electrons is the most probable one. The calculated ionization energy of modelled Au<sub>2</sub> with two unpaired electrons is 8.94 eV and with zero unpaired electrons, 11.42 eV. The difference (11.42-8.94 = 2.48 eV = 239.29 kJmol<sup>-1</sup>), is in very good agreement with the experimental value of 226.2 ± 0.5 kJmol<sup>-1</sup> to the Au-Au bond<sup>7</sup>. So, as expected, in the specie with none unpaired electrons, the two 6s<sup>1</sup> (one of each gold atom) are paired, forming a chemical bond with bond order 1. On the other hand, in Au<sub>2</sub> with two unpaired electrons, the s-d hybridization prevails, because the relativistic contributions. A molecular orbital energy diagram for gas phase Au<sub>2</sub> is proposed, explaining its paramagnetism (and, by extension, the paramagnetism of gold clusters and nanoparticles).</p>

Effect of leakage and blockage on the acoustic behavior of particle filters

2019 ◽  
Vol 67 (6) ◽  
pp. 483-492
Author(s):  
Seonghyeon Baek ◽  
Iljae Lee
Keyword(s):  
Transfer Matrix ◽  
Particle Filters ◽  
Acoustic Analysis ◽  
Transmission Loss ◽  
One Dimensional ◽  
Filter System ◽  
The Difference ◽  
The One ◽  
Analytical Approaches ◽  
Good Agreement

The effects of leakage and blockage on the acoustic performance of particle filters have been examined by using one-dimensional acoustic analysis and experimental methods. First, the transfer matrix of a filter system connected to inlet and outlet pipes with conical sections is measured using a two-load method. Then, the transfer matrix of a particle filter only is extracted from the experiments by applying inverse matrices of the conical sections. In the analytical approaches, the one-dimensional acoustic model for the leakage between the filter and the housing is developed. The predicted transmission loss shows a good agreement with the experimental results. Compared to the baseline, the leakage between the filter and housing increases transmission loss at a certain frequency and its harmonics. In addition, the transmission loss for the system with a partially blocked filter is measured. The blockage of the filter also increases the transmission loss at higher frequencies. For the simplicity of experiments to identify the leakage and blockage, the reflection coefficients at the inlet of the filter system have been measured using two different downstream conditions: open pipe and highly absorptive terminations. The experiments show that with highly absorptive terminations, it is easier to see the difference between the baseline and the defects.

scholarly journals Mask-R$$^{2}$$CNN: a distance-field regression version of Mask-RCNN for fetal-head delineation in ultrasound images

2021 ◽  
Author(s):  
Sara Moccia ◽  
Maria Chiara Fiorentino ◽  
Emanuele Frontoni
Keyword(s):  
Fetal Growth ◽  
A Priori ◽  
Absolute Difference ◽  
Ultrasound Images ◽  
Fetal Head ◽  
Mean Absolute Difference ◽  
Distance Field ◽  
Feature Pyramid ◽  
End To End ◽  
Ablation Study

Abstract Background and objectives Fetal head-circumference (HC) measurement from ultrasound (US) images provides useful hints for assessing fetal growth. Such measurement is performed manually during the actual clinical practice, posing issues relevant to intra- and inter-clinician variability. This work presents a fully automatic, deep-learning-based approach to HC delineation, which we named Mask-R$$^{2}$$ 2 CNN. It advances our previous work in the field and performs HC distance-field regression in an end-to-end fashion, without requiring a priori HC localization nor any postprocessing for outlier removal. Methods Mask-R$$^{2}$$ 2 CNN follows the Mask-RCNN architecture, with a backbone inspired by feature-pyramid networks, a region-proposal network and the ROI align. The Mask-RCNN segmentation head is here modified to regress the HC distance field. Results Mask-R$$^{2}$$ 2 CNN was tested on the HC18 Challenge dataset, which consists of 999 training and 335 testing images. With a comprehensive ablation study, we showed that Mask-R$$^{2}$$ 2 CNN achieved a mean absolute difference of 1.95 mm (standard deviation $$=\pm 1.92$$ = ± 1.92  mm), outperforming other approaches in the literature. Conclusions With this work, we proposed an end-to-end model for HC distance-field regression. With our experimental results, we showed that Mask-R$$^{2}$$ 2 CNN may be an effective support for clinicians for assessing fetal growth.

Eve Kosofsky Sedgwick and the difference geography makes

2021 ◽  
Vol 11 (1) ◽  
pp. 117-121 ◽  
Author(s):  
David K Seitz
Keyword(s):  
Time And Space ◽  
Textual Practice ◽  
Reparative Reading ◽  
The Difference ◽  
The U.S ◽  
Eve Kosofsky Sedgwick

Ruez and Cockayne point out that queer theorist Eve Sedgwick’s reflections on paranoid and reparative readings accompanying one another came directly out of her queer political as well as textual practice in the U.S. Wrongly dismissed as mundane, this crucial contextualizing work is something geographers do especially well. Indeed, understanding the context for Sedgwick’s theories of paranoid and reparative reading is vital as we reflect on how her concepts travel across time and space.

scholarly journals Gap Filling of the CALYPSO HF Radar Sea Surface Current Data through Past Measurements and Satellite Wind Observations

2016 ◽  
Vol 2016 ◽  
pp. 1-9 ◽  
Author(s):  
Adam Gauci ◽  
Aldo Drago ◽  
John Abela
Keyword(s):  
Oil Spills ◽  
Surface Current ◽  
Radar Data ◽  
Current Data ◽  
Hf Radar ◽  
Sea Surface ◽  
Machine Learning Techniques ◽  
Learning Techniques ◽  
Spatial Coverage ◽  
Essential Components

High frequency (HF) radar installations are becoming essential components of operational real-time marine monitoring systems. The underlying technology is being further enhanced to fully exploit the potential of mapping sea surface currents and wave fields over wide areas with high spatial and temporal resolution, even in adverse meteo-marine conditions. Data applications are opening to many different sectors, reaching out beyond research and monitoring, targeting downstream services in support to key national and regional stakeholders. In the CALYPSO project, the HF radar system composed of CODAR SeaSonde stations installed in the Malta Channel is specifically serving to assist in the response against marine oil spills and to support search and rescue at sea. One key drawback concerns the sporadic inconsistency in the spatial coverage of radar data which is dictated by the sea state as well as by interference from unknown sources that may be competing with transmissions in the same frequency band. This work investigates the use of Machine Learning techniques to fill in missing data in a high resolution grid. Past radar data and wind vectors obtained from satellites are used to predict missing information and provide a more consistent dataset.

Sign in / Sign up

Export Citation Format

Share Document