scholarly journals Dynamics of a Radially Rotating Beam With Impact, Part 2: Experimental and Simulation Results

1990 ◽  
Vol 112 (1) ◽  
pp. 71-77 ◽  
Author(s):  
A. S. Yigit ◽  
A. G. Ulsoy ◽  
R. A. Scott
Keyword(s):  
Computational Model ◽  
Excellent Agreement ◽  
Balance Model ◽  
Momentum Balance ◽  
Rotating Beam ◽  
Elastic Links ◽  
Wide Range ◽  
Sensitivity Studies ◽  
Simulation Results ◽  
Parameter Values

A theoretical and computational model to study the dynamics of a radially rotating beam with impact were presented in Part 1. In this paper the experimental results are presented and they are compared with simulations using the momentum balance model described in Part 1. Excellent agreement was found between the experiments and simulation. Sensitivity studies were employed to show that the model is applicable for a fairly wide range of parameter values. Thus, the momentum balance method has been demonstrated to be capable of accurately predicting the dynamics of systems which consist of rigid and elastic links undergoing impact.

Dynamics of a Radially Rotating Beam With Impact, Part 1: Theoretical and Computational Model

1990 ◽  
Vol 112 (1) ◽  
pp. 65-70 ◽  
Author(s):  
A. S. Yigit ◽  
A. G. Ulsoy ◽  
R. A. Scott
Keyword(s):  
Rigid Body ◽  
Computational Model ◽  
Computational Algorithm ◽  
Coefficient Of Restitution ◽  
Experimental Results ◽  
Body Motion ◽  
Momentum Balance ◽  
Rotating Beam ◽  
Before And After ◽  
Simulation Results

A model is presented for the dynamics of a radially rotating beam with impact. The model uses a momentum balance method and a coefficient of restitution, and enables one to predict the rigid body motion as well as the elastic motion before and after impact. A computational algorithm is also developed to implement the model. In Part 2 simulation results will be compared with experimental results to investigate the validity of the model.

scholarly journals Modelling Global Ice and Climate Changes Through the Ice Ages

1990 ◽  
Vol 14 ◽  
pp. 23-27 ◽  
Author(s):  
W.F. Budd ◽  
P. Rayner
Keyword(s):  
Sea Ice ◽  
Ice Sheets ◽  
Ice Cover ◽  
Balance Model ◽  
Annual Variations ◽  
Sensitivity Tests ◽  
Mixed Layer Ocean ◽  
Wide Range ◽  
Sensitivity Studies ◽  
Snow And Ice

A global energy balance model has been developed which includes an interactive mixed layer ocean, sea ice, and snow and ice cover on the land. A full annual cycle is included and the model provides a close simulation to the variation of surface temperature through the year over land and over ocean as a function of latitude. The present annual variations of sea ice and snow on the ground are also well simulated. The model has been used for a wide range of sensitivity tests which include variations of the solar constant, surface albedos, and the effects of feed-back, or absence of feed-back, in the reponse of the snow and ice cover. Studies have been made of the model’s response to the long term variations in the Earth’s Orbital characteristics such as changes in the perihelion, the obliquity and the eccentricity as well as various combined changes. Independent sensitivity studies of the response of the model to the presence of the large ice sheets in the northern hemisphere have also been carried out. A series of model runs have been performed to study climatic changes around the globe from 160 000 years Β.P. (Before Present) to the present. An examination is made of the impacts of the orbital changes alone, as well as with the feed-back from the large ice sheets.

scholarly journals Modelling Global Ice and Climate Changes Through the Ice Ages

1990 ◽  
Vol 14 ◽  
pp. 23-27
Author(s):  
W.F. Budd ◽  
P. Rayner
Keyword(s):  
Sea Ice ◽  
Ice Sheets ◽  
Ice Cover ◽  
Balance Model ◽  
Annual Variations ◽  
Sensitivity Tests ◽  
Mixed Layer Ocean ◽  
Wide Range ◽  
Sensitivity Studies ◽  
Snow And Ice

A global energy balance model has been developed which includes an interactive mixed layer ocean, sea ice, and snow and ice cover on the land. A full annual cycle is included and the model provides a close simulation to the variation of surface temperature through the year over land and over ocean as a function of latitude. The present annual variations of sea ice and snow on the ground are also well simulated. The model has been used for a wide range of sensitivity tests which include variations of the solar constant, surface albedos, and the effects of feed-back, or absence of feed-back, in the reponse of the snow and ice cover.Studies have been made of the model’s response to the long term variations in the Earth’s Orbital characteristics such as changes in the perihelion, the obliquity and the eccentricity as well as various combined changes. Independent sensitivity studies of the response of the model to the presence of the large ice sheets in the northern hemisphere have also been carried out. A series of model runs have been performed to study climatic changes around the globe from 160 000 years Β.P. (Before Present) to the present. An examination is made of the impacts of the orbital changes alone, as well as with the feed-back from the large ice sheets.

scholarly journals β-Lactoglobulin Adsorption Layers at the Water/Air Surface: 5. Adsorption Isotherm and Equation of State Revisited, Impact of pH

2021 ◽  
Vol 5 (1) ◽  
pp. 14
Author(s):  
Georgi G. Gochev ◽  
Volodymyr I. Kovalchuk ◽  
Eugene V. Aksenenko ◽  
Valentin B. Fainerman ◽  
Reinhard Miller
Keyword(s):  
Theoretical Description ◽  
Fluid Interfaces ◽  
Interfacial Behavior ◽  
Current State ◽  
Air Interface ◽  
Direct Measurements ◽  
Wide Range ◽  
Dilational Viscoelasticity ◽  
Parameter Values ◽  
Β Lactoglobulin

The theoretical description of the adsorption of proteins at liquid/fluid interfaces suffers from the inapplicability of classical formalisms, which soundly calls for the development of more complicated adsorption models. A Frumkin-type thermodynamic 2-d solution model that accounts for nonidealities of interface enthalpy and entropy was proposed about two decades ago and has been continuously developed in the course of comparisons with experimental data. In a previous paper we investigated the adsorption of the globular protein β-lactoglobulin at the water/air interface and used such a model to analyze the experimental isotherms of the surface pressure, Π(c), and the frequency-, f-, dependent surface dilational viscoelasticity modulus, E(c)f, in a wide range of protein concentrations, c, and at pH 7. However, the best fit between theory and experiment proposed in that paper appeared incompatible with new data on the surface excess, Γ, obtained from direct measurements with neutron reflectometry. Therefore, in this work, the same model is simultaneously applied to a larger set of experimental dependences, e.g., Π(c), Γ(c), E(Π)f, etc., with E-values measured strictly in the linear viscoelasticity regime. Despite this ambitious complication, a best global fit was elaborated using a single set of parameter values, which well describes all experimental dependencies, thus corroborating the validity of the chosen thermodynamic model. Furthermore, we applied the model in the same manner to experimental results obtained at pH 3 and pH 5 in order to explain the well-pronounced effect of pH on the interfacial behavior of β-lactoglobulin. The results revealed that the propensity of β-lactoglobulin globules to unfold upon adsorption and stretch at the interface decreases in the order pH 3 > pH 7 > pH 5, i.e., with decreasing protein net charge. Finally, we discuss advantages and limitations in the current state of the model.

scholarly journals Design and Evaluation of Large-Scale IoT-Enabled Healthcare Architecture

2021 ◽  
Vol 11 (8) ◽  
pp. 3623
Author(s):  
Omar Said ◽  
Amr Tolba
Keyword(s):  
Packet Loss ◽  
Large Scale ◽  
Performance Metrics ◽  
Medical System ◽  
Healthcare Data ◽  
High Altitude Platforms ◽  
Wide Range ◽  
Simulation Results ◽  
Healthcare Architecture ◽  
The Internet Of Things

Employment of the Internet of Things (IoT) technology in the healthcare field can contribute to recruiting heterogeneous medical devices and creating smart cooperation between them. This cooperation leads to an increase in the efficiency of the entire medical system, thus accelerating the diagnosis and curing of patients, in general, and rescuing critical cases in particular. In this paper, a large-scale IoT-enabled healthcare architecture is proposed. To achieve a wide range of communication between healthcare devices, not only are Internet coverage tools utilized but also satellites and high-altitude platforms (HAPs). In addition, the clustering idea is applied in the proposed architecture to facilitate its management. Moreover, healthcare data are prioritized into several levels of importance. Finally, NS3 is used to measure the performance of the proposed IoT-enabled healthcare architecture. The performance metrics are delay, energy consumption, packet loss, coverage tool usage, throughput, percentage of served users, and percentage of each exchanged data type. The simulation results demonstrate that the proposed IoT-enabled healthcare architecture outperforms the traditional healthcare architecture.

scholarly journals A New Statistic for Detecting Genetic Differentiation

Genetics ◽  
2000 ◽  
Vol 155 (4) ◽  
pp. 2011-2014 ◽  
Author(s):  
Richard R Hudson
Keyword(s):  
Genetic Differentiation ◽  
Dna Sequences ◽  
Genetic Data ◽  
Island Model ◽  
Wide Range ◽  
Infinite Sites Model ◽  
Parameter Values

Abstract A new statistic for detecting genetic differentiation of subpopulations is described. The statistic can be calculated when genetic data are collected on individuals sampled from two or more localities. It is assumed that haplotypic data are obtained, either in the form of DNA sequences or data on many tightly linked markers. Using a symmetric island model, and assuming an infinite-sites model of mutation, it is found that the new statistic is as powerful or more powerful than previously proposed statistics for a wide range of parameter values.

Nitrification in bulk water and biofilms of algae wastewater stabilization ponds

2007 ◽  
Vol 55 (11) ◽  
pp. 93-101 ◽  
Author(s):  
M.A. Babu ◽  
M.M. Mushi ◽  
N.P. van der Steen ◽  
C.M. Hooijmans ◽  
H.J. Gijzen
Keyword(s):  
Model Equation ◽  
Bulk Water ◽  
Balance Model ◽  
Nitrification Rate ◽  
Relative Contribution ◽  
Activity Test ◽  
Stabilization Ponds ◽  
Wide Range ◽  
Water Columns ◽  
Wastewater Stabilization Ponds

Nitrogen removal in wastewater stabilization ponds is poorly understood and effluent monitoring data show a wide range of differences in ammonium. For effluent discharge into the environment, low levels of nitrogen are recommended. Nitrification is limiting in facultative wastewater stabilization ponds. The reason why nitrification is considered to be limiting is attributed to low growth rate and wash out of the nitrifiers. Therefore to maintain a population, attached growth is required. The aim of this research is to study the relative contribution of bulk water and biofilms with respect to nitrification. The hypothesis is that nitrification can be enhanced in stabilization ponds by increasing the surface area for nitrifier attachment. In order to achieve this, transparent pond reactors representing water columns in algae WSP have been used. To discriminate between bulk and biofilm activity, 5-day batch activity tests were carried out with bulk water and biofilm sampled. The observed value for Rnitrbulk was 2.7 × 10−1 mg-N L−1 d−1 and for Rbiofilm was 1,495 mg-N m−2 d −1. During the 5 days of experiment with the biofilm, ammonia reduction was rapid on the first day. Therefore, a short-term biofilm activity test was performed to confirm this rapid decrease. Results revealed a nitrification rate, Rbiofilm, of 2,125 mg-N m−2 d−1 for the first 5 hours of the test, which is higher than the 1,495 mg-N m−2 d−1, observed on the first day of the 7-day biofilm activity test. Rbiofilm and Rnitrbulk values obtained in the batch activity tests were used as parameters in a mass balance model equation. The model was calibrated by adjusting the fraction of the pond volume and biofilm area that is active (i.e. aerobic). When assuming a depth of 0.08 m active upper layer, the model could describe well the measured effluent values for the pond reactors. The calibrated model was validated by predicting effluent Kjeldahl nitrogen of algae ponds in Palestine and Colombia. The model equation predicted well the effluent concentrations of ponds in Palestine.

Motion of slender bodies in unsteady Stokes flow

2011 ◽  
Vol 688 ◽  
pp. 66-87 ◽  
Author(s):  
Efrath Barta
Keyword(s):  
Stokes Flow ◽  
Slenderness Ratio ◽  
Creeping Flow ◽  
Slender Body Theory ◽  
Wide Range ◽  
Unsteady Stokes Flow ◽  
Slender Bodies ◽  
Set Up ◽  
Micro Organisms ◽  
Parameter Values

AbstractThe flow regime in the vicinity of oscillatory slender bodies, either an isolated one or a row of many bodies, immersed in viscous fluid (i.e. under creeping flow conditions) is studied. Applying the slender-body theory by distributing proper singularities on the bodies’ major axes yields reasonably accurate and easily computed solutions. The effect of the oscillations is revealed by comparisons with known Stokes flow solutions and is found to be most significant for motion along the normal direction. Streamline patterns associated with motion of a single body are characterized by formation and evolution of eddies. The motion of adjacent bodies results, with a reduction or an increase of the drag force exerted by each body depending on the direction of motion and the specific geometrical set-up. This dependence is demonstrated by parametric results for frequency of oscillations, number of bodies, their slenderness ratio and the spacing between them. Our method, being valid for a wide range of parameter values and for densely packed arrays of rods, enables simulation of realistic flapping of bristled wings of some tiny insects and of locomotion of flagella and ciliated micro-organisms, and might serve as an efficient tool in the design of minuscule vehicles. Its potency is demonstrated by a solution for the flapping of thrips.

Convective and turbulent motions in non-precipitating Cu. Part 1: Method of separation of convective and turbulent motions

2021 ◽  
Author(s):  
Mark Pinsky ◽  
Eshkol Eytan ◽  
Ilan Koren ◽  
Orit Altaratz ◽  
Alexander Khain
Keyword(s):  
Velocity Field ◽  
Vertical Velocity ◽  
Isotropic Turbulence ◽  
Convective Velocity ◽  
Cloud Dynamics ◽  
Wide Range ◽  
Homogeneous And Isotropic Turbulence ◽  
Microphysical Processes ◽  
Bin Microphysics ◽  
Parameter Values

AbstractAtmospheric motions in clouds and cloud surrounding have a wide range of scales, from several kilometers to centimeters. These motions have different impacts on cloud dynamics and microphysics. Larger-scale motions (hereafter referred to as convective motions) are responsible for mass transport over distances comparable with cloud scale, while motions of smaller scales (hereafter referred to as turbulent motions) are stochastic and responsible for mixing and cloud dilution. This distinction substantially simplifies the analysis of dynamic and microphysical processes in clouds. The present research is Part 1 of the study aimed at describing the method for separating the motion scale into a convective component and a turbulent component. An idealized flow is constructed, which is a sum of an initially prescribed field of the convective velocity with updrafts in the cloud core and downdrafts outside the core, and a stochastic turbulent velocity field obeying the turbulent properties, including the -5/3 law and the 2/3 structure function law. A wavelet method is developed allowing separation of the velocity field into the convective and turbulent components, with parameter values being in a good agreement with those prescribed initially. The efficiency of the method is demonstrated by an example of a vertical velocity field of a cumulus cloud simulated using SAM with bin-microphysics and resolution of 10 m. It is shown that vertical velocity in clouds indeed can be represented as a sum of convective velocity (forming zone of cloud updrafts and subsiding shell) and a stochastic velocity obeying laws of homogeneous and isotropic turbulence.

Numerical simulations of wet snow avalanches: interplay between cohesion and friction

2021 ◽  
Author(s):  
Guillaume Chambon ◽  
Thierry Faug ◽  
Mohamed Naaim
Keyword(s):  
Numerical Simulations ◽  
Flow Regimes ◽  
Liquid Water Content ◽  
Snow Avalanches ◽  
Shallow Flow ◽  
Distinctive Features ◽  
Wide Range ◽  
Wet Snow ◽  
Sensitivity Studies ◽  
Avalanche Flow

<p>Wet snow avalanches present distinctive features such as unusual trajectories, peculiar deposit shapes, and a rheological behavior displaying a combination of granular and pasty features depending on the actual snow liquid water content. Complex transitions between dry (cold) and wet (hot) flow regimes can also occur during a single avalanche flow. In an attempt to account for this complexity, we report on numerical simulations of avalanches using a frictional-cohesive rheology implemented in a depth-averaged shallow-flow model. Through extensive sensitivity studies on synthetic and real topographies, we show that cohesion plays a key role to enrich the physics of the simulated flows, and to represent realistic avalanche behaviors. First, when coupled to a proper treatment of the yielding criterion, cohesion provides a way to define objective stopping criteria for the flow, independently of the issues incurred by artificial diffusion of the numerical scheme. Second, and more importantly, the interplay between cohesion and friction gives raise to a variety of nontrivial physical effects affecting the dynamics of the avalanches and the morphology of the deposits. The relative weights of frictional and cohesive contributions to the overall stress are investigated as a function of space and time during the propagation, and related to the formation of specific features such as lateral levées, hydraulic jumps, etc. This study represents a first step towards robust avalanches simulations, spanning the wide range of possible flow regimes, through shallow-flow approaches. Future improvements involving more refined cohesion parameterizations will be discussed.</p>

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