scholarly journals Stochastic cycle selection in active flow networks

2016 ◽  
Vol 113 (29) ◽  
pp. 8200-8205 ◽  
Author(s):  
Francis G. Woodhouse ◽  
Aden Forrow ◽  
Joanna B. Fawcett ◽  
Jörn Dunkel
Keyword(s):  
Broad Class ◽  
Generic Model ◽  
Rate Theory ◽  
Flow Networks ◽  
Complex Flow ◽  
Slime Molds ◽  
Arterial Blood ◽  
Wide Range ◽  
Theoretical And Numerical Analysis ◽  
Active Flow

Active biological flow networks pervade nature and span a wide range of scales, from arterial blood vessels and bronchial mucus transport in humans to bacterial flow through porous media or plasmodial shuttle streaming in slime molds. Despite their ubiquity, little is known about the self-organization principles that govern flow statistics in such nonequilibrium networks. Here we connect concepts from lattice field theory, graph theory, and transition rate theory to understand how topology controls dynamics in a generic model for actively driven flow on a network. Our combined theoretical and numerical analysis identifies symmetry-based rules that make it possible to classify and predict the selection statistics of complex flow cycles from the network topology. The conceptual framework developed here is applicable to a broad class of biological and nonbiological far-from-equilibrium networks, including actively controlled information flows, and establishes a correspondence between active flow networks and generalized ice-type models.

On LES Methods Applied to Seal Geometries

2012 ◽  
Author(s):  
James Tyacke ◽  
Richard Jefferson-Loveday ◽  
Paul Tucker
Keyword(s):  
Maximum Error ◽  
Labyrinth Seal ◽  
Navier Stokes ◽  
Final Solution ◽  
Complex Flow ◽  
Eddy Simulation ◽  
Wide Range ◽  
Large Eddy ◽  
Rans Models ◽  
Flow Through

Nine Large Eddy Simulation (LES) methods are used to simulate flow through two labyrinth seal geometries and are compared with a wide range of Reynolds-Averaged Navier-Stokes (RANS) solutions. These involve one-equation, two-equation and Reynolds Stress RANS models. Also applied are linear and nonlinear pure LES models, hybrid RANS-Numerical-LES (RANS-NLES) and Numerical-LES (NLES). RANS is found to have a maximum error and a scatter of 20%. A similar level of scatter is also found among the same turbulence model implemented in different codes. In a design context, this makes RANS unusable as a final solution. Results show that LES and RANS-NLES is capable of accurately predicting flow behaviour of two seals with a scatter of less than 5%. The complex flow physics gives rise to both laminar and turbulent zones making most LES models inappropriate. Nonetheless, this is found to have minimal tangible results impact. In accord with experimental observations, the ability of LES to find multiple solutions due to solution non-uniqueness is also observed.

DIGITALIS TOLERANCE IN YOUNG PUPPIES

PEDIATRICS ◽  
1970 ◽  
Vol 46 (5) ◽  
pp. 730-736
Author(s):  
Katherine H. Halloran ◽  
Steven C. Schimpff ◽  
Jean G. Nicolas ◽  
Norman S. Talner
Keyword(s):  
Blood Gases ◽  
Acid Base Balance ◽  
Acid Base ◽  
Littermate Control ◽  
Premature Ventricular Contractions ◽  
Toxic Dose ◽  
Arterial Blood ◽  
Wide Range ◽  
Base Balance ◽  
The Mean

Tolerance to acetyl strophanthidin, a rapid-acting cardiac aglycone, was determined in 28 anesthetized mongrel puppies, ages 16 to 56 days, and compared to tolerance in 16 littermate puppies in whom acute hypercapnic acidemia was produced. The tolerance was also compared to that of four adult mongrel dogs. The toxic dose was defined as the intravenous amount required to produce four consecutive premature ventricular contractions. A marked variation in the toxic dose was found in the 28 control puppies (range 83 to 353 µg/kg, mean 169 µg/kg) which could not be correlated with age, arterial blood gases or pH, serum potassium or sodium, arterial pressure, or heart rate. The toxic dose was significantly greater in the puppies than in the adult dogs, in whom the mean toxic dose was 64 µg/kg (range 50 to 89 µg/kg). A significant increase in tolerance was also observed in the puppies with hypercapnic acidemia (mean toxic dose 220 µg/kg, range 93 to 375 µg/kg) in comparison to tolerance in the control puppies and despite the wide range of tolerance, each of the puppies with hypercapnic acidemia showed greater tolerance than its littermate control puppy. Assessment of the clinical implications of these findings will require study of the effects of alterations in acid-base balance on the inotropic effect of acetyl strophanthidin in addition to the toxic electrophysiologic effects.

Three-Dimensional Sloshing of Water on Decks

1988 ◽  
Vol 25 (04) ◽  
pp. 253-261
Author(s):  
Michael S. Pantazopoulos
Keyword(s):  
Hyperbolic Equations ◽  
Equations Of Motion ◽  
Three Dimensional ◽  
Nonlinear Hyperbolic Equations ◽  
Complex Flow ◽  
Random Choice ◽  
Three Dimensional Flow ◽  
Random Choice Method ◽  
Wide Range ◽  
Choice Method

A methodology is proposed to solve the problem of the three-dimensional flow of water sloshing on the deck of a vessel, and to calculate the resulting forces and moments at the center of gravity. The Eulerian equations of motion of the water particle for incompressible inviscid shallow water flow are formulated with respect to a system attached to the oscillating vessel. The system of the nonlinear hyperbolic equations of motion is solved numerically using Glimm's method (random-choice method). Complex flow patterns consisting of oblique bores and "swirling" motions of the water on deck were revealed, for a vessel oscillating in roll and pitch motions, for a wide range of excitation frequencies. Large accumulation of water occurs at the corners while parts of the deck become dry. Significant rolling moments due to sloshing are exerted on the vessel. These must be taken into account when the dynamic response of the vessel is studied.

scholarly journals Mobile Serious Game Design using User Experience: Modeling of Software Product Line Variability

2019 ◽  
Vol 14 (23) ◽  
pp. 55
Author(s):  
Chaimae Meftah ◽  
Asmaâ Retbi ◽  
Samir Bennani ◽  
Mohamed Khalidi Idrissi
Keyword(s):  
User Experience ◽  
Game Design ◽  
Software Product Line ◽  
Product Line ◽  
Feature Model ◽  
Generic Model ◽  
Learner Engagement ◽  
New Approach ◽  
Wide Range ◽  
Software Product

In recent years, gamification has emerged as a new approach to increasing learner engagement. It covers a very wide range of games with very different purposes and with many fields of application. However, most of the gamification solutions proposed do not adopt the same modeling approach and little attention has been paid to mobile serious games (MSG) belonging to different pedagogical contexts. In order to overcome these difficulties, we have developed in this paper a generic model based on the Software Product Line (SPL) approach to manage the common and variable points of the MSG product set. We have also focused on the User eXperience (UX) concept to study the aspects that most affect the player’s experience in the context of MSGs. These aspects have been modeled in the form of features in the SPL Feature Model. MSG designers can use the model proposed during the development process, both to manage variability and to create an effective and fun learning environment.

Neonatal intestinal oxygen consumption during arterial hypoxemia

1983 ◽  
Vol 244 (3) ◽  
pp. G278-G283
Author(s):  
D. I. Edelstone ◽  
D. R. Lattanzi ◽  
M. E. Paulone ◽  
I. R. Holzman
Keyword(s):  
Intestinal Tract ◽  
Concentration Difference ◽  
Fick Principle ◽  
Arterial Blood ◽  
Wide Range ◽  
O2 Extraction ◽  
Neonatal Lambs ◽  
O2 Supply ◽  
Oxygen Requirements ◽  
O2 Delivery

In 12 chronically catheterized neonatal lambs, we determined intestinal tract blood flow (Qi) and O2 consumption (VO2i) at O2 contents of arterial blood (CaO2) ranging from 15.3 to 3.2 ml O2/dl blood. We measured Qi with the radioactive microsphere technique and computed intestinal O2 delivery (DO2i), VO2i, and O2 extraction (VO2i/DO2i) using the Fick principle. In lambs breathing air, mean Qi = 214 ml X min-1 X 100 g intestine-1, DO2i = 27.0 ml O2 X min-1 X 100 g-1, O2 extraction = 21%, and VO2i = 5.6 ml O2 Xmin-1 X 100 g-1. During reductions in CaO2, Qi and DO2i decreased. Intestinal O2 extraction increased sufficiently, however, so that VO2i was maintained over the range of CaO2 from 15.3 to about 6.5 ml O2/dl blood. VO2i was independent of Qi at Qi greater than 160 ml X min-1 X 100 g-1. When CaO2 was reduced below values of 6.5 ml O2/dl blood, corresponding to Qi less than 160 ml X min-1 X 100 g-1, VO2i fell in association with increases in the H+ concentration difference between mesenteric venous and arterial blood. These data indicate that the intestinal tract of the neonatal lamb can meet its oxygen requirements when O2 supply varies over a wide range. When O2 availability reaches a critically low level, intestinal anaerobic metabolism develops as the O2 supply to the neonatal intestinal tract becomes inadequate for the O2 demand.

scholarly journals ETHOS – an effective parametrization and classification for structure formation: the non-linear regime at z ≳ 5

2020 ◽  
Vol 498 (3) ◽  
pp. 3403-3419
Author(s):  
Sebastian Bohr ◽  
Jesús Zavala ◽  
Francis-Yan Cyr-Racine ◽  
Mark Vogelsberger ◽  
Torsten Bringmann ◽  
...  
Keyword(s):  
Power Spectrum ◽  
Structure Formation ◽  
Parameter Space ◽  
Broad Class ◽  
High Redshift ◽  
Acoustic Oscillations ◽  
Effective Parameters ◽  
Matter Power Spectrum ◽  
Wide Range ◽  
Non Linear

ABSTRACT We propose two effective parameters that fully characterize galactic-scale structure formation at high redshifts (z ≳ 5) for a variety of dark matter (DM) models that have a primordial cutoff in the matter power spectrum. Our description is within the recently proposed ETHOS framework and includes standard thermal warm DM (WDM) and models with dark acoustic oscillations (DAOs). To define and explore this parameter space, we use high-redshift zoom-in simulations that cover a wide range of non-linear scales from those where DM should behave as CDM (k ∼ 10 h Mpc−1), down to those characterized by the onset of galaxy formation (k ∼ 500 h Mpc−1). We show that the two physically motivated parameters hpeak and kpeak, the amplitude and scale of the first DAO peak, respectively, are sufficient to parametrize the linear matter power spectrum and classify the DM models as belonging to effective non-linear structure formation regions. These are defined by their relative departure from cold DM (kpeak → ∞) and WDM (hpeak = 0) according to the non-linear matter power spectrum and halo mass function. We identify a region where the DAOs still leave a distinct signature from WDM down to z = 5, while a large part of the DAO parameter space is shown to be degenerate with WDM. Our framework can then be used to seamlessly connect a broad class of particle DM models to their structure formation properties at high redshift without the need of additional N-body simulations.

Quantification of O2 consumption and arterial pressure as independent determinants of coronary flow

1987 ◽  
Vol 252 (3) ◽  
pp. H545-H553 ◽  
Author(s):  
I. Vergroesen ◽  
M. I. Noble ◽  
P. A. Wieringa ◽  
J. A. Spaan
Keyword(s):  
Coronary Artery ◽  
Arterial Pressure ◽  
Coronary Flow ◽  
Left Main Coronary Artery ◽  
External Pressure ◽  
Arterial Blood Flow ◽  
O2 Consumption ◽  
Left Main ◽  
Arterial Blood ◽  
Wide Range

The steady-state relationship between coronary arterial blood flow (CBF) and both myocardial O2 consumption (MVO2) and coronary arterial pressure (P) was explored in anesthetized dogs and goats. Both species were subjected to constant pressure perfusion of the left main coronary artery by an external pressure-controlling circuit. In addition a group of goats was studied with normal aortic perfusion using an occluder around the left main coronary artery to vary coronary arterial pressure. The statistical analysis revealed that despite the direct effect of P on MVO2 (the Gregg effect) the effects of both variables on CBF were independent and linear over a wide range of P and MVO2 so that multiple regression analysis with a linear equation (CBF = a X P + b X MVO2 + c) gave an excellent fit which was not improved by the introduction of an addition interactive term b3MVO2 X P. The mean correlation coefficient for all animals was greater than 0.9. From these data we conclude that any factor regulating coronary arterial flow would be influenced by both MVO2 and perfusion pressure in an independent way. This study characterizes the stationary behavior of local coronary flow control. Hence, it specifies quantitatively the relations to be predicted by hypotheses aiming to explain this control mechanism.

The performance of a centrifugal compressor with a tandem impeller in off-design conditions

2019 ◽  
Vol 234 (2) ◽  
pp. 156-172 ◽  
Author(s):  
Ziliang Li ◽  
Xingen Lu ◽  
Ge Han ◽  
Yanfeng Zhang ◽  
Shengfeng Zhao ◽  
...  
Keyword(s):  
Centrifugal Compressor ◽  
Performance Enhancement ◽  
Pressure Ratio ◽  
Operating Conditions ◽  
Complex Flow ◽  
Maximum Enhancement ◽  
Operating Range ◽  
Wide Range ◽  
Compressor Performance ◽  
Low Efficiency

Centrifugal compressors often suffer relatively low efficiency and a terrible operating range particularly due to the complex flow structure and intense impeller/diffuser interaction. Numerous studies have focused on improving the centrifugal compressor performance using many innovative ideas, such as the tandem impeller, which has become increasingly attractive due to its ability to achieve the flow control with no additional air supply configurations and control costs in compressor. However, few studies that attempted to the investigation of tandem impeller have been published until now and the results are always contradictory. To explore the potential of the tandem impeller to enhance the compressor performance and the underlying mechanism of the flow phenomena in the tandem impellers, this paper numerically investigated a high-pressure-ratio centrifugal compressor with several tandem impellers at off-design operating speeds. The results encouragingly demonstrate that the tandem impeller can achieve a performance enhancement over a wide range of operating conditions. Approximately 1.8% maximum enhancement in isentropic efficiency and 5.0% maximum enhancement in operating range are achieved with the inducer/exducer circumferential displacement of [Formula: see text] = 25% and 50%, respectively. The observed stage performance gain of the tandem impellers decreases when the operating speed increases due to the increased inducer shock, increased wake losses, and deteriorated tandem impeller discharge flow uniformity. In addition, the tandem impeller can extend the impeller operating range particularly at low rotation speeds, which is found to be a result from the suppression of the low-momentum fluid radial movement. The results also indicate that the maximum flux capacity of the tandem impeller decreases due to the restriction of the inducer airfoil Kutta–Joukowsky condition.

Acute and chronic pulmonary vasoconstriction after left lung autotransplantation in conscious dogs

1992 ◽  
Vol 73 (2) ◽  
pp. 603-609 ◽  
Author(s):  
P. A. Murray ◽  
R. S. Stuart ◽  
C. D. Fraser ◽  
D. M. Fehr ◽  
B. B. Chen ◽  
...  
Keyword(s):  
Left Lung ◽  
Blood Gases ◽  
Conscious Dogs ◽  
Specific Effects ◽  
Vascular Regulation ◽  
Post Surgery ◽  
Pulmonary Vasoconstriction ◽  
Arterial Blood ◽  
Pulmonary Arterial ◽  
Active Flow

We investigated the acute and chronic effects of left lung autotransplantation (LLA) on the left pulmonary vascular pressure-flow (LP/Q) relationship in conscious dogs. Continuous LP/Q plots were generated in chronically instrumented conscious dogs 2 days, 2 wk, 1 mo, and 2 mo after LLA. Identically instrumented normal conscious dogs were studied at equal time points post-surgery. LLA had little or no effect on baseline systemic hemodynamics or blood gases. In contrast, compared with normal conscious dogs, striking active flow-independent pulmonary vasoconstriction was observed 2 days post-LLA. The slope of the LP/Q relationship was increased from a normal value of 0.275 +/- 0.021 to 0.699 +/- 0.137 mmHg.ml-1.min-1.kg-1 2 days post-LLA. Pulmonary vasoconstriction of similar magnitude was also observed on a chronic basis at 2 wk, 1 mo, and even 2 mo post-LLA. Pulmonary vasoconstriction post-LLA was not due to fixed resistance at the left pulmonary arterial or venous anastomotic sites. Finally, systemic arterial blood gases were unchanged when total pulmonary blood flow was directed to exclusively perfuse the transplanted left lung. Thus, LLA results in both acute and chronic pulmonary vasoconstriction in conscious dogs. LLA should serve as a useful stable experimental model to assess the specific effects of surgical transplantation on pulmonary vascular regulation.

scholarly journals Augmentative Modelling: A Template for Populus spp. Stand Biomass in Eurasia Region

2020 ◽  
Vol 24 (5) ◽  
pp. 827-832
Author(s):  
Andreevich Usoltsev Vladimir ◽  
Omid Reza Shobairi Seyed ◽  
Stepanovich Tsepordey Ivan ◽  
Petrovich Chasovskikh Viktor
Keyword(s):  
Additive Model ◽  
Component Composition ◽  
Generic Model ◽  
Total Biomass ◽  
Biological Productivity ◽  
Local Conditions ◽  
Component Structure ◽  
Allometric Models ◽  
Wide Range ◽  
Populus Spp

Today, estimating of biological productivity or carbon-depositing ability of forests is going on the global level, and its increase is one of the major factors of climate stabilization. In recent years, two trends in the harmonization of allometric models of tree biomass have been developing. The  first of them is related to ensuring the additivity of the biomass component composition, and the second one – to the search for the so-called generic model applicable to a wide range of environmental conditions. However, all "generic" models give significant biases in their application in local conditions. In our modeling, we adhere to the principle of biomass additivity, split "generic" model into regional variants by introducing dummy variables, and build the model at the transcontinental level for the first time. When using the unique in terms of the volume of database on the level of stand of the genus Populus spp. in a number of 212 sample plots, the trans-Eurasian additive allometric models of biomass of standsfor Eurasian Populus forests are developed, and thereby the combined problem of model additivity and generality is solved. The additive model of forest biomass of Populus is harmonized in two ways: it eliminated the internal contradictions of the component and the total biomass equations, and in addition, it takes into account regional differences of forest stands not only on total, aboveground and underground biomass, but also on its component structure, i.e. it reflects the regional peculiarities of the component structure of biomass. Keywords: genus Populus spp., biomass of forests, allometric models, sample plots, biological productivity

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