scholarly journals A comparison of flood extent modelling approaches through constraining uncertainties on gauge data

2004 ◽  
Vol 8 (6) ◽  
pp. 1141-1152 ◽  
Author(s):  
M. G. F. Werner
Keyword(s):  
Model Calibration ◽  
Calibration Data ◽  
Limited Data ◽  
Calibration Uncertainty ◽  
Reliable Model ◽  
Gauge Data ◽  
The Difference ◽  
Spatial Calibration ◽  
Turbulent Momentum ◽  
2D Model

Abstract. A comparison is made of 1D, 2D and integrated 1D-2D hydraulic models in predicting flood stages in a 17 km reach of the River Saar in Germany. The models perform comparably when calibrated against limited data available from a single gauge in the reach for three low to medium flood events. In validation against a larger event than those used in calibration, extrapolation with the 1D and particularly the integrated 1D-2D model is reliable, if uncertain, while the 2D model is unreliable. The difference stems from the way in which the models deal with flow in the main channel and in the floodplain and with turbulent momentum interchange between the two domains. The importance of using spatial calibration data for testing models giving spatial predictions is shown. Even simple binary (eye-witness) observations on the presence or absence of flooding in establishing a reliable model structure to predict flood extent can be very valuable. Keywords: floods, hydraulic modelling, model calibration, uncertainty analysis

Comparison of two asynchronous QCT methods

2020 ◽  
Vol 24 (4) ◽  
pp. 108-118
Author(s):  
A. V. Petraikin ◽  
A. K. Smorchkova ◽  
N. D. Kudryavtsev ◽  
K. A. Sergunova ◽  
Z. R. Artyukova ◽  
...  
Keyword(s):  
Bone Densitometry ◽  
Pearson Correlation ◽  
Calibration Data ◽  
Mineral Density ◽  
Quantitative Ct ◽  
Short Period ◽  
Potassium Hydrogen ◽  
Patients At Risk ◽  
Ray Density ◽  
The Difference

Rationale. Quantitative CT (QCT) bone densitometry with asynchronous calibration not require a phantom during the scan procedure. Based on calibration data it converts X-ray density in HU to bone mineral density (BMD). Given the large number of CT studies performed on patients at risk of osteoporosis, there is a need for a hands-on method capable of assessing BMD in a short period of time without tailored software or protocols.Goal. To develop a method for QCT bone densitometry using an PHK (PHantom Kalium), to compare the volume BMD measurements with the QCT data with asynchronous calibration provided by software from a reputable developer.Methods. The studies were performed at 64-slice CT unit with body scanning parameters. The BMD was measured using two techniques: 1) QCT with asynchronous calibration using software from a reputable developer; 2) QCT using a PHK phantom (QCT-PHK). For convert the HU to BMD values, we scanned the PHK phantom and calculate correction factor. Phantom contains “vertebrae” filled with potassium hydrogen phosphate in different concentrations. In both methods, the BMD values measured for LI–II, and sometimes for ThXII, LIII.Results. The study enrolled 65 subjects (11 male and 54 female patients); median age 69.0 years. A comparison of the vertebrae BMD measured by QCT and QCT-PHK revealed a significant linear Pearson correlation r = 0.977 (p < 0.05). The Bland–Altman analysis demonstrated a lack of relationship between the difference in measurements and the average BMD and a systematic BMD; bias of +4.50 mg/ml in QCT vs. QCT-PHK. Differences in the division into groups osteoporosis / osteopenia / norm according to the ACR criteria for the two methods were not significant.Conclusion. The developed asynchronous QCT-PHK method measure BMD comparable to the widely used QCT with asynchronous calibration. This method can be used for opportunistic screening for osteoporosis.

scholarly journals Effects of Extracorporeal Membrane Oxygenation Initiation on Oxygenation and Pulmonary Opacities

2021 ◽  
Vol 7 (1) ◽  
pp. 6-13
Author(s):  
Kiran Batra ◽  
Manish Mohanka ◽  
Srinivas Bollineni ◽  
Vaidehi Kaza ◽  
Prabhakar Rajiah ◽  
...  
Keyword(s):  
Extracorporeal Membrane Oxygenation ◽  
P Value ◽  
Limited Data ◽  
Hospital Survival ◽  
Membrane Oxygenation ◽  
Pulmonary Physiology ◽  
Before And After ◽  
Laboratory Variables ◽  
The Difference ◽  
The Impact

Abstract Introduction There is limited data on the impact of extracorporeal membrane oxygenation (ECMO) on pulmonary physiology and imaging in adult patients. The current study sought to evaluate the serial changes in oxygenation and pulmonary opacities after ECMO initiation. Methods Records of patients started on veno-venous, or veno-arterial ECMO were reviewed (n=33; mean (SD): age 50(16) years; Male: Female 20:13). Clinical and laboratory variables before and after ECMO, including daily PaO2 to FiO2 ratio (PFR), were recorded. Daily chest radiographs (CXR) were prospectively appraised in a blinded fashion and scored for the extent and severity of opacities using an objective scoring system. Results ECMO was associated with impaired oxygenation as reflected by the drop in median PFR from 101 (interquartile range, IQR: 63-151) at the initiation of ECMO to a post-ECMO trough of 74 (IQR: 56-98) on post-ECMO day 5. However, the difference was not statistically significant. The appraisal of daily CXR revealed progressively worsening opacities, as reflected by a significant increase in the opacity score (Wilk’s Lambda statistic 7.59, p=0.001). During the post-ECMO period, a >10% increase in the opacity score was recorded in 93.9% of patients. There was a negative association between PFR and opacity scores, with an average one-unit decrease in the PFR corresponding to a +0.010 increase in the opacity score (95% confidence interval: 0.002 to 0.019, p-value=0.0162). The median opacity score on each day after ECMO initiation remained significantly higher than the pre-ECMO score. The most significant increase in the opacity score (9, IQR: -8 to 16) was noted on radiographs between pre-ECMO and forty-eight hours post-ECMO. The severity of deteriorating oxygenation or pulmonary opacities was not associated with hospital survival. Conclusions The use of ECMO is associated with an increase in bilateral opacities and a deterioration in oxygenation that starts early and peaks around 48 hours after ECMO initiation.

Accuracy of Satellite Land Surface Reflectance Determination

1991 ◽  
Vol 30 (7) ◽  
pp. 960-972 ◽  
Author(s):  
O. Arino ◽  
G. Dedieu ◽  
P. Y. Deschamps
Keyword(s):  
Land Surface ◽  
Surface Albedo ◽  
Maximum Error ◽  
Surface Reflectance ◽  
Relative Uncertainty ◽  
Calibration Uncertainty ◽  
Maximum Bias ◽  
Calibration Accuracy ◽  
The Difference

Abstract An accuracy budget of the surface reflectance determination from Meteosat geostationary satellite data is performed. Error analysis allows identification of three main problems: calibration uncertainty of the Meteosat instrument, atmospheric corrections, and surface effects (spectral and directional). Calibration accuracy is 10%, leading to a 10% relative uncertainty on reflectance. Spectral effects of the surface lead to a maximum bias of 0.01 for a vegetated surface as sensed by Meteosat, while directional effects can lead to a bias of 0.035 between two measurements taken at two different sun zenith and azimuth angles at the same view angle over savannas. The maximum error due to the atmosphere is estimated to be of the order of 0.03 in reflectance for a surface reflectance of 0.40 and 0.01 for, a surface reflectance of 0.10. Validation with in situ measurement is within the expected error over savanna. But the difference is still high over the southwest France site of HAPEX-MOBILHY, certainly due to the joint spectral and directional errors. Comparisons with surface albedo maps from literature show the same spatial and spatial evolutions with a better spatial and temporal determination in our results.

scholarly journals 1052 Continuous Blood Pressure Monitoring In Sleep

SLEEP ◽  
2020 ◽  
Vol 43 (Supplement_1) ◽  
pp. A399-A400
Author(s):  
R H Roth ◽  
H Bonner ◽  
J Logan ◽  
M Baruch ◽  
D Calhoun ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Blood Pressure Monitoring ◽  
Decomposition Analysis ◽  
Limited Data ◽  
Cardiovascular Risks ◽  
Nocturnal Hypertension ◽  
Spot Check ◽  
Lack Of Sleep ◽  
Data Points ◽  
The Difference

Abstract Introduction Abnormal nocturnal blood pressure(BP) such as non-dipping or nocturnal hypertension(reverse-dipping) represents a potent marker for cardiovascular risks. Standard cuff-based ambulatory nocturnal BP measurement yields limited data points potentially resulting in imprecise results, especially compared to continuously recorded BP. We hypothesized nocturnal BP based on periodic measurement would be different from true average beat-to-beat based BP. Methods We prospectively enrolled patients undergoing clinically indicated in-lab polysomnography, both CPAP and non-CPAP studies, for sleep apnea evaluation. Nocturnal BP was continuously monitored beat-to-beat by a noninvasive Caretaker™ device, which uses the Pulse Decomposition Analysis(PDA) algorithm. We compared BP recorded at 30-minute intervals with average BP continuously recorded over 30 minutes, both recorded by Caretaker™. We also looked at the differences between recording spot and continuous BP from an awake or sleeping state and BP variability(SD) based on continuously recorded BP. Using first 30 min as a reference, we determined dipping status (dipping: 10-20% reduction, level: 0-10% reduction, riser: any increase) by the two methods. Results A total of 18 patients were recruited(male:11, mean age:52.2). Among a total of 261 periodic BP measurements, 60 (30.0%) were obtained while awake. Mean nocturnal SBP by periodic BP measurement was higher compared with beat-to-beat-derived average BP(135.6mmHg[24.2] vs. 131.5[20.3], p&lt;0.0001). The difference between the two methods remained similar when continuous BP was derived from sleep vs. awake period(4.5mmHg[3.1] vs. 7.7[9.9], p=0.202). BP variability was more pronounced during awake compared with sleep period(6.7mmHg[8.1] versus 3.95[7.5], p=0.047). 8 patients were dippers by spot check measurement, but 11 were dippers by continuous BP. Conclusion Standard ambulatory periodic nocturnal BP recording may not yield true sleep BP patterns due to its spot-check nature and lack of sleep-awake information, which leads to inaccurate dipping measurements. Incorporation of beat-to-beat continuous BP measurement can provide more accurate and meaningful nocturnal BP information. Support N/A

scholarly journals Highly Local Model Calibration with a New GEDI LiDAR Asset on Google Earth Engine Reduces Landsat Forest Height Signal Saturation

2020 ◽  
Vol 12 (17) ◽  
pp. 2840 ◽  
Author(s):  
Sean P. Healey ◽  
Zhiqiang Yang ◽  
Noel Gorelick ◽  
Simon Ilyushchenko
Keyword(s):  
Optical Sensors ◽  
Forest Structure ◽  
Model Calibration ◽  
Google Earth ◽  
Ecosystem Dynamics ◽  
Ecosystem Functions ◽  
Calibration Data ◽  
Local Models ◽  
Google Earth Engine ◽  
Signal Saturation

While Landsat has proved to be effective for monitoring many elements of forest condition and change, the platform has well-documented limitations in measuring forest structure, the vertical distribution of the canopy. This is important because structure determines several key ecosystem functions, including: carbon storage; habitat suitability; and timber volume. Canopy structure is directly measured by LiDAR, and it should be possible to train Landsat structure models at a highly local scale with the dense, global sample of full waveform LiDAR observations collected by NASA’s Global Ecosystem Dynamics Investigation (GEDI). Local models are expected to perform better because: (a) such models may take advantage of localized correlations between structure and canopy surface reflectance; and (b) to the extent that models revert to the mean of the calibration data due to a lack of discrimination, local models will revert to a more representative mean. We tested Landsat-based relative height predictions using a new GEDI asset on Google Earth Engine, described here. Mean prediction error declined by 23% and important prediction biases at the extremes of the range of canopy height dropped as model calibration became more local, minimizing forest structure signal saturation commonly associated with Landsat and other passive optical sensors. Our results suggest that Landsat-based maps of structural variables such as height and biomass may substantially benefit from the kind of local calibration that GEDI’s dense sample of LiDAR data supports.

Velcro Ties in Early Postoperative Pediatric Tracheostomy Care: A Systematic Review and Meta-analysis

2020 ◽  
pp. 019459982096472
Author(s):  
Brent A. Chang ◽  
Joshua Gurberg ◽  
Erin Ware ◽  
Kimberly Luu
Keyword(s):  
Meta Analysis ◽  
Prospective Trial ◽  
Final Analysis ◽  
Cochrane Central Register ◽  
Limited Data ◽  
Cochrane Database ◽  
Central Register ◽  
Significant Difference ◽  
Randomized Prospective Trial ◽  
The Difference

Objective To systematically review the literature to determine the difference in complications between standard twill and Velcro ties following pediatric tracheostomy. Data Sources MEDLINE, Embase, the Cochrane Database of Systematic Reviews, the Cochrane Central Register of Controlled Trials, Web of Science, and CINAHL Plus were searched up to August 2020. Review Methods Two authors independently screened articles for eligibility. Retrospective and prospective studies were included as long as there was a direct comparison between twill and Velcro ties. Quantitative and qualitative analysis was performed. The main outcomes were skin-related complications and accidental decannulation. Results Three studies were included in the final analysis: 1 randomized prospective trial and 2 retrospective studies. There were 238 patients total (137 twill, 101 Velcro). Combined analysis showed skin-related complications in 23% of the Velcro group and 44% of the twill group. Meta-analysis for skin-related complications showed no significant difference when comparing Velcro with standard twill ties (risk ratio, 0.53 [95% CI, 0.24-1.17]; P = .12, n = 238 participants from 3 studies, I2 = 66%). Accidental decannulation rates were overall low and comparable between groups (1.0% of twill, 1.4% of Velcro). Conclusion Based on limited data, skin-related complications were not statistically different between Velcro and twill ties. Accidental decannulation is rare with Velcro and standard twill ties, and both are viable options following pediatric tracheostomy.

Impact of input data uncertainties on urban stormwater model parameters

2009 ◽  
Vol 60 (6) ◽  
pp. 1545-1554 ◽  
Author(s):  
M. Kleidorfer ◽  
A. Deletic ◽  
T. D. Fletcher ◽  
W. Rauch
Keyword(s):  
Input Data ◽  
Flow Parameter ◽  
Data Availability ◽  
Model Parameters ◽  
Calibration Data ◽  
Model Accuracy ◽  
Nitrogen Loads ◽  
Impervious Area ◽  
The Difference ◽  
Type Data

The use of urban drainage models requires careful calibration, where model parameters are selected in order to minimize the difference between measured and simulated results. It has been recognized that often more than one set of calibration parameters can achieve similar model accuracy. A probability distribution of model parameters should therefore be constructed to examine the model's sensitivity to its parameters. With increasing complexity of models, it also becomes important to analyze the model parameter sensitivity while taking into account uncertainties in input and calibration data. In this study a Bayesian approach was used to develop a framework for quantification of impacts of uncertainties in the model inputs on the parameters of a simple integrated stormwater model for calculating runoff, total suspended solids and total nitrogen loads. The framework was applied to two catchments in Australia. It was found that only systematic rainfall errors have a significant impact on flow model parameters. The most sensitive flow parameter was the effective impervious area, which can be calibrated to completely compensate for the input data uncertainties. The pollution model parameters were influenced by both systematic and random rainfall errors. Additionally an impact of circumstances (e.g. catchment type, data availability) has been recognized.

A note on the effect of suckling stimulus on uterine involution, post-partum ovarian activity and fertility in Nili-Ravi buffaloes

1985 ◽  
Vol 41 (1) ◽  
pp. 119-122 ◽  
Author(s):  
R. H. Usmani ◽  
N. Ullah ◽  
S. K. Shah
Keyword(s):  
Post Partum ◽  
Follicular Development ◽  
Reproductive Organs ◽  
Ovarian Activity ◽  
Corpora Lutea ◽  
Limited Data ◽  
Uterine Involution ◽  
Negative Effect ◽  
The Difference ◽  
Larger Sample

ABSTRACTNineteen pluriparous buffaloes of Nili-Ravi breed which calved during the months of October and November 1983 were studied for the effects of sucking stimulus on the uterine involution, post-partum ovarian functions and fertility. On the day of calving, buffaloes were assigned to either a limited-suckling (LS) or non-suckling (NS) group. Changes in reproductive organs were monitored by rectal palpations at weekly intervals. Buffaloes were observed for oestrus twice daily (04.00 and 18.00 h) with the help of a teaser bull, and were artificially inseminated at the first post-partum and each subsequent oestrus. LS buffaloes had a shorter period to uterine involution (20 days) than NS buffaloes (28 days). Intervals to regression of the corpora lutea of pregnancy and to resumption of post-partum follicular development did not differ in the two groups. LS buffaloes had longer intervals to first post-partum oestrus and conception (54 and 88 days respectively) than NS buffaloes (39 and 68 days respectively). However, the difference in services per conception of LS and NS buffaloes was non-significant (2-05 v. 1·62). These limited data reveal that the suckling stimulus has a negative effect on the post-partum resumption of oestrous activity, and that conception is delayed. Further studies are indicated to verify these observations in a larger sample size and during all seasons of the year.

scholarly journals Dynamic calibration uncertainty of three-axis low frequency accelerometers

ACTA IMEKO ◽  
2015 ◽  
Vol 4 (4) ◽  
pp. 75 ◽  
Author(s):  
Giulio D'Emilia ◽  
Antonella Gaspari ◽  
Emanuela Natale
Keyword(s):  
Low Cost ◽  
Low Frequency ◽  
Bias Error ◽  
Dynamic Calibration ◽  
Data Sets ◽  
Calibration Data ◽  
Civil Infrastructures ◽  
Calibration Uncertainty ◽  
The Matrix ◽  
Rotary Device

In this paper a methodology concerning the static and dynamic calibration of three-axis low-cost accelerometers in the (0 to 10) Hz frequency range is described, to be used for evaluation of existing civil infrastructures. <br /> Main and cross sensitivities of the accelerometers have been experimentally estimated by means of the matrix sensitivity concept. <br />The standard deviation of accelerations obtained along all three axes using different calibration data sets in repeatability conditions has been calculated and intended as dynamic calibration uncertainty. <br />The method has been validated by using reference accelerations accurately realized, in order to evaluate the residual bias error. <br />Static and dynamic calibration test benches have been used to realize reference accelerations. In order to create a three-axis acceleration field, a mechanical arm is used in static calibration; a rotary device is used in order to test the accelerometers in dynamic conditions. <br />According to the procedure described in this paper, a great improvement of the low cost accelerometers' metrological characterization could be achieved, especially in dynamic working conditions.

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