Hydraulic geometry and resistance to flow in headwater streams in the Northwest Territories, Canada

2012 ◽  
Vol 39 (12) ◽  
pp. 1252-1263 ◽  
Author(s):  
Abul Basar M. Baki ◽  
David Z. Zhu ◽  
Gregory Courtice
Keyword(s):  
Northwest Territories ◽  
Headwater Streams ◽  
Dominant Role ◽  
Hydraulic Geometry ◽  
Power Functions ◽  
Mean Velocity ◽  
Mean Values ◽  
Mean Width ◽  
The Mean

Hydraulic geometry and resistance to flow of headwater streams in the Northwest Territories of Canada are presented in this paper. Power functions describe at-a-station hydraulic geometry relationships very well, where positive exponents of width, depth, and velocity have mean values of 0.14, 0.17, and 0.65, respectively. These values were found to be lower, much lower, and higher than corresponding mean values of width, depth, and velocity exponents found in the literature. The mean velocity exponent is greater than mean width and depth exponents combined, demonstrating the dominant role of velocity in accommodating varying discharge in all streams evaluated in this study. Darcy–Weisbach resistance factor (f) and Manning’s n individually vary over three orders of magnitude, 1.0–267 and 0.085–1.37, respectively. Despite large ranges, hydraulic relations are described effectively through power equations and Keulegan function curves fitted for each section.

Seasonal trends in the stable isotopic composition of snow and meltwater runoff in a subarctic catchment at Okstindan, Norway

2004 ◽  
Vol 35 (2) ◽  
pp. 119-137 ◽  
Author(s):  
S.D. Gurney ◽  
D.S.L. Lawrence
Keyword(s):  
Isotopic Composition ◽  
Mean Value ◽  
Mean Values ◽  
Stable Isotopic Composition ◽  
Meltwater Runoff ◽  
Stable Isotopic ◽  
The Mean ◽  
The Difference ◽  
Δ18o And Δd

Seasonal variations in the stable isotopic composition of snow and meltwater were investigated in a sub-arctic, mountainous, but non-glacial, catchment at Okstindan in northern Norway based on analyses of δ18O and δD. Samples were collected during four field periods (August 1998; April 1999; June 1999 and August 1999) at three sites lying on an altitudinal transect (740–970 m a.s.l.). Snowpack data display an increase in the mean values of δ18O (increasing from a mean value of −13.51 to −11.49‰ between April and August), as well as a decrease in variability through the melt period. Comparison with a regional meteoric water line indicates that the slope of the δ18O–δD line for the snowpacks decreases over the same period, dropping from 7.49 to approximately 6.2.This change points to the role of evaporation in snowpack ablation and is confirmed by the vertical profile of deuterium excess. Snowpack seepage data, although limited, also suggest reduced values of δD, as might be associated with local evaporation during meltwater generation. In general, meltwaters were depleted in δ18O relative to the source snowpack at the peak of the melt (June), but later in the year (August) the difference between the two was not statistically significant. The diurnal pattern of isotopic composition indicates that the most depleted meltwaters coincide with the peak in temperature and, hence, meltwater production.

Role of Plaque Morphology in Altering the Flow Characteristics in Diseased Coronary Artery

2012 ◽  
Author(s):  
Carlos Moreno ◽  
Kiran Bhaganagar
Keyword(s):  
Coronary Artery ◽  
Nonlinear Response ◽  
Flow Characteristics ◽  
Proximal Region ◽  
Patient Specific ◽  
Plaque Morphology ◽  
Mean Velocity ◽  
Peak Location ◽  
The Mean

Patient specific simulations of a single patient based on an accurate representation of the plaque in a diseased coronary artery with 35% stenosis are performed to understand the effect of inlet forcing frequency and amplitude on the wall shear stress (WSS). Numerical simulations are performed with unsteady flow conditions in a laminar regime. The results have revealed that at low amplitudes, WSS is insensitive to forcing frequency and is it in phase with Q. The maximum WSS is observed at the proximal region of the stenosis, and WSS has highest negative values at the peak location of the stenosis. For higher pulsatile amplitude (a > 1.0), WSS exhibits a strong sensitivity with forcing frequencies. At higher forcing frequency the WSS exhibits nonlinear response to the inlet forcing frequency. Furthermore, significant differences in the mean velocity profile are observed during maximum and minimum volumetric flow rates.

Achieving comparable perfusion results across vendors. The next step in standardizing stroke care: a technical report

2019 ◽  
Vol 11 (12) ◽  
pp. 1257-1260 ◽  
Author(s):  
Girish Bathla ◽  
Kaustubh Limaye ◽  
Bruno Policeni ◽  
Ernst Klotz ◽  
Markus Juergens ◽  
...  
Keyword(s):  
Ct Perfusion ◽  
Stroke Care ◽  
Vessel Occlusion ◽  
Mean Values ◽  
Technical Report ◽  
Significant Difference ◽  
Wilcoxon Paired Test ◽  
The Mean ◽  
Core Infarct

BackgroundThe role of mechanical thrombectomy in acute ischemic stroke (AIS) has been further expanded by recent trials which relied on the results of CT perfusion (CTP) imaging. However, CTP parameters for ischemia and infarct can vary significantly across different vendors.MethodsWe compared the outcomes of the Siemens CTP software against the clinically validated RAPID software in 45 consecutive patients with suspected AIS. Both perfusion softwares initially processed images using vendor defined parameters for hypoperfusion and non-viable tissue. The software thresholds on the Siemens software were decrementally altered to see if concordant results between softwares could be attained.ResultsAt baseline settings, the mean values for core infarct and hypoperfusion were different (mean of 30/69 mL, respectively, for RAPID and 49/77 mL for Siemens). However, reducing the threshold values for the later software showed a concordance of values at a relative cerebral blood flow <20%, with resulting core infarct and hypoperfusion volumes at 31/69 mL, respectively, for the Siemens software. A Wilcoxon paired test showed no significant difference between the calculated core infarct and hypoperfusion values, both for the entire population as well as for the subgroup of patients with large vessel occlusion.ConclusionEquivalent CTP results between vendor softwares may be attainable by altering the thresholds for hypoperfused and non-viable tissue, despite differences in acquisition techniques, post-processing, and scanners.

Sand bars in tidal channels. Part 1. Free bars

2001 ◽  
Vol 440 ◽  
pp. 49-74 ◽  
Author(s):  
G. SEMINARA ◽  
M. TUBINO
Keyword(s):  
Three Dimensional ◽  
Basic Mechanism ◽  
Critical Value ◽  
Suspended Load ◽  
Tidal Channels ◽  
Three Dimensional Model ◽  
Mean Values ◽  
Depth Ratio ◽  
Mean Width ◽  
The Mean

We investigate the basic mechanism whereby bars form in tidal channels or estuaries. The channel is assumed to be long enough to allow neglect of the effects of end conditions on the process of bar formation. In this respect, the object of the present analysis differs from that of Schuttelaars & de Swart (1999) who considered bars of length scaling with the finite length of the tidal channel. The channel bottom is assumed to be cohesionless and consisting of uniform sediments. Bars are shown to arise from a mechanism of instability of the erodible bed subject to the propagation of a tidal wave. Sediment is assumed to be transported both as bedload and as suspended load. A fully three-dimensional model is employed both for the hydrodynamics and for sediment transport. At the leading order of approximation considered, the effects of channel convergence, local inertia and Coriolis forces on bar instability are shown to be negligible. Unlike fluvial free bars, in the absence of mean currents tidal free bars are found to be non-migrating features (in the mean). Instability arises for large enough values of the mean width to depth ratio of the channel, for given mean values of the Shields parameter and of the relative channel roughness. The role of suspended load is such as to stabilize bars in the large-wavenumber range and destabilize them for small wavenumbers. Hence, for large values of the mean Shields stress, it turns out that the first critical mode (the alternate bar mode) is characterized by a very small value of the critical width to depth ratio. Furthermore, the order-m mode being characterized by a critical value of the width to depth ratio equal to m times the critical value for the first mode, it follows that for large values of the mean Shields stress several unstable modes are simultaneously excited for relatively low values of the aspect ratio. This suggests that the actual bar pattern observed in nature may arise from an interesting nonlinear competition among different unstable modes.

scholarly journals Benzodiazepine premedication in general anaesthesia: a clinical comparative study

2019 ◽  
Vol 6 (2) ◽  
pp. 45
Author(s):  
Babita Lahkar ◽  
Kalpajit Dutta
Keyword(s):  
Blood Pressure ◽  
Body Weight ◽  
General Anaesthesia ◽  
Physical Status ◽  
Mean Values ◽  
Prolonged Sedation ◽  
Grade Ii ◽  
Delayed Recovery ◽  
The Mean

<p class="abstract"><strong>Background:</strong> The main aims of pre-anaesthetic medication are anxiolysis, analgesia, anti-emesis and reducing perioperative patient risk. Producing a state of amnesia for pre and post-operative events is desired by all. This study has been undertaken to evaluate the role of three of the benzodiazepines i.e. diazepam, lorazepam and midazolam during general anaesthesia, in providing anxiolysis, sedation and amnesia.</p><p class="abstract"><strong>Methods:</strong> The study included patients with ASA grade I and ASA grade II physical status of both sexes, age ranging between 18-60 years. Patients were divided into three groups of thirty patients each, every group receiving intramuscular injections of diazepam 0.1 mg/kg body weight, lorazepam 0.07 mg/kg body weight and midazolam 0.08 mg/kg body weight respectively; 45 minutes prior to induction of general anaesthesia. Anxiety assessment before premedication along with assessment of sedation after premedication was done.</p><p class="abstract"><strong>Results:</strong> Before premedication the mean values of pulse rate, blood pressure and respiratory rate were not significantly different among the three groups (p&gt;0.05). Maximum changes in these parameters were observed with Midazolam followed by lorazepam and diazepam. The dose of thiopentone used as inducing agent was also lowered significantly in case of midazolam (p&lt;0.05). One patient in midazolam group showed respiratory depression whereas four patients receiving lorazepam and diazepam showed delayed recovery and prolonged sedation, but the effects were self-limiting.</p><p class="abstract"><strong>Conclusions: </strong>Midazolam offers the maximum advantage in allaying anxiety and providing excellent sedation and amnesia during general anaesthesia and proves to be the most suitable premedicant before general anaesthesia.</p>

scholarly journals Boundary-layer evolution over long wind farms

2021 ◽  
Vol 925 ◽  
Author(s):  
Antonio Segalini ◽  
Marco Chericoni
Keyword(s):  
Boundary Layer ◽  
Kinetic Energy ◽  
Wind Farms ◽  
Internal Boundary Layer ◽  
Internal Boundary ◽  
Inertial Subrange ◽  
Mean Velocity ◽  
Free Stream Turbulence ◽  
The Mean

The structure of the internal boundary layer above long wind farms is investigated experimentally. The transfer of kinetic energy from the region above the farm is dominated by the turbulent flux of momentum together with the displacement of kinetic energy operated by the mean vertical velocity: these two have comparable magnitude along the farm opposite to the infinite-farm case. The integration of the energy equation in the vertical highlighted the key role of the energy flux, and how that is balanced by the growth of the internal boundary layer in terms of energy thickness with a small role of the dissipation. The mean velocity profiles seem to follow a universal structure in terms of velocity deficit, while the Reynolds stress does not follow the same scaling structure. Finally, a spectral analysis along the farm identified the leading dynamics determining the turbulent activity: while behind the first row the signature of the tip vortices is dominant, already after the second row their coherency is lost and a single broadband peak, associated with wake meandering, is present until the end of the farm. The streamwise velocity peak is associated with a nearly constant Strouhal number weakly dependent on the farm layout and free stream turbulence condition. A reasonable agreement of the velocity spectra is observed when the latter are normalised by the velocity variance and integral time scale: nevertheless the spectra show clear anisotropy at the large scales and even the small scales remain anisotropic in the inertial subrange.

scholarly journals The Role of Forcing and Eddy Viscosity Variation on the Log-Layer Mismatch Observed in Wall-Modeled Large-Eddy Simulations

2018 ◽  
Vol 141 (5) ◽  
Author(s):  
Rey DeLeon ◽  
Inanc Senocak
Keyword(s):  
Flow Rate ◽  
Eddy Viscosity ◽  
Degree Of Freedom ◽  
Channel Flows ◽  
Momentum Balance ◽  
Mean Velocity ◽  
Turbulent Channel Flows ◽  
The Mean ◽  
Viscosity Variation

We investigate the role of eddy viscosity variation and the effect of zonal enforcement of the mass flow rate on the log-layer mismatch problem observed in turbulent channel flows. An analysis of the mean momentum balance shows that it lacks a degree-of-freedom (DOF) when eddy viscosity is large, and the mean velocity conforms to an incorrect profile. Zonal enforcement of the target flow rate introduces an additional degree-of-freedom to the mean momentum balance, similar to an external stochastic forcing term, leading to a significant reduction in the log-layer mismatch. We simulate turbulent channel flows at friction Reynolds numbers of 2000 and 5200 on coarse meshes that do not resolve the viscous sublayer. The second-order turbulence statistics agree well with the direct numerical simulation benchmark data when results are normalized by the velocity scale extracted from the filtered velocity field. Zonal enforcement of the flow rate also led to significant improvements in skin friction coefficients.

scholarly journals Ternary vowel length in Shilluk

Phonology ◽  
2019 ◽  
Vol 36 (1) ◽  
pp. 91-125
Author(s):  
Bert Remijsen ◽  
Otto Gwado Ayoker ◽  
Signe Jørgensen
Keyword(s):  
Fundamental Frequency ◽  
The Other ◽  
Supporting Evidence ◽  
Vowel Duration ◽  
Vowel Quality ◽  
Vowel Length ◽  
Mean Values ◽  
Acoustic Study ◽  
The Mean

Ternary or three-level vowel length is typologically rare, and supporting evidence is limited. This paper presents the results of an investigation into the hypothesised case of this configuration in Shilluk. We first describe the role of vowel length in Shilluk phonology and morphology, and then report on an acoustic study in which minimal sets for vowel length (short, long, overlong) are measured for vowel duration, coda duration, vowel quality and fundamental frequency. Short, long and overlong vowels differ significantly and substantially in terms of vowel duration: 96% of the items can be classified successfully for vowel length on the basis of this measurement alone. Of the other measurements, only vowel quality is significant, and this effect is considerably smaller. The mean values for vowel duration – 68, 111 and 150 ms for short, long and overlong vowels respectively – are similar to those reported for ternary vowel length in Dinka.

scholarly journals Social Support And Job Satisfaction Among Academicians: A Comparison Between Public And Private University In Malaysia

2019 ◽  
Vol 8 (5C) ◽  
pp. 449-456
Keyword(s):  
Social Support ◽  
Job Satisfaction ◽  
Positive Impact ◽  
Private University ◽  
Public And Private ◽  
Mean Values ◽  
The Mean ◽  
University Level ◽  
High Level

The role of social support at workplace become one of the most important variables that can give impact on employee’s attitude. Closely related to employee’s performance, many studies have confirmed the role of social support in enhancing employee’s job satisfaction. The aims of this research is two-folds. First, to investigate the differences and second to compare the effect of social support on job satisfaction among academicians in Malaysia. Overall, a total of 420 samples were obtained, wherein 210 participants withdrawn from each setting. Data was collected using self-administrated questionnaire, and analyzed using SPSS version 22. The finding suggested that social support levels (i.e. supervisor support and co-worker support) are higher among academicians in private university. Level of job satisfaction, otherwise is higher among public university. Overall, the mean values indicated high level of social support and job satisfaction among academicians in both university. Analysis of t-Test revealed that there is no significant differences in terms of social support, however the significant being observed in terms of job satisfaction between academicians in Malaysia public and private university. This study also ascertained the positive impact of social support on job satisfaction to both samples. Implication of this study includes empirical contribution and deliberation on social support and job satisfaction. Suggestion from this study includes improving social support to enhance overall academicians’ job satisfaction.

scholarly journals Social Integration and Psychological Wellbeing in a Sample of the Swedish-speaking Minority of Western Finland

2020 ◽  
Vol 9 ◽  
pp. 364-376
Author(s):  
Ingrida Grigaitytė ◽  
Karin Österman ◽  
Kaj Björkqvist
Keyword(s):  
Social Integration ◽  
Sex Difference ◽  
Social Relations ◽  
Psychological Health ◽  
Psychological Wellbeing ◽  
Social Benefits ◽  
Mean Values ◽  
The Mean ◽  
Anxiety Depression

The role of social integration in determining subjective psychological wellbeing in a sample of Swedish-speaking Finns in Ostrobothnia was investigated. A questionnaire was completed by 298 respondents (208 females, 90 males). The mean age was 32.7 years (SD 13.4) for females and 28.9 years (SD 13.4) for males. The age span was between 16 and 90 years. The questionnaire consisted of four scales measuring social integration. Females scored significantly higher on access to social benefits, positive social relations, and trust in the Finnish judiciary system. No sex difference was found for satisfaction with the neighbourhood. The mean values were overall high for both females and males. Respondents over 30 years of age reported significantly more positive social relations and more satisfaction with the neighbourhood compared to respondents under the age of 30. Respondents belonging to a group with high scores of social integration scored significantly lower on anxiety, depression, and somatisation. Conclusively, social integration can be regarded as a resource for psychological health.

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