Impulsive fluid forcing and water strider locomotion

2007 ◽  
Vol 573 ◽  
pp. 211-236 ◽  
Author(s):  
OLIVER BÜHLER
Keyword(s):  
Compressible Flows ◽  
Laboratory Experiments ◽  
Water Strider ◽  
Global Response ◽  
Weakly Compressible ◽  
Momentum Budget ◽  
Horizontal Momentum ◽  
Wave Emission ◽  
Localized Forcing ◽  
Recent Laboratory

This paper presents a study of the global response of a fluid to impulsive and localized forcing; it has been motivated by the recent laboratory experiments on the locomotion of water-walking insects reported in Hu, Chan & Bush (Nature, vol. 424, 2003, p. 663). These insects create both waves and vortices by their rapid leg strokes and it has been a matter of some debate whether either form of motion predominates in the momentum budget. The main result of this paper is to argue that generically both waves and vortices are significant, and that in linear theory they take up the horizontal momentum with share 1/3 and 2/3, respectively.This generic result, which depends only on the impulsive and localized nature of the forcing, is established using the classical linear impulse theory, with adaptations to weakly compressible flows and flows with a free surface. Additional general comments on experimental techniques for momentum measurement and on the wave emission are given and then the theory is applied in detail to water-walking insects.Owing to its generality, this kind of result and the methods used to derive it should be applicable to a wider range of wave–vortex problems in the biolocomotion of water-walking animals and elsewhere.

scholarly journals Social Tipping Interventions Can Promote the Diffusion or Decay of Sustainable Consumption Norms in the Field. Evidence from a Quasi-Experimental Intervention Study

2021 ◽  
Vol 13 (6) ◽  
pp. 3529
Author(s):  
Joël Berger
Keyword(s):  
Laboratory Experiments ◽  
Sustainable Consumption ◽  
Environmentally Sustainable ◽  
Carbon Neutrality ◽  
Consumption Decisions ◽  
Policy Tool ◽  
Field Evidence ◽  
Current Prevalence ◽  
Quasi Experimental ◽  
Recent Laboratory

The diffusion of environmentally sustainable consumption patterns is crucial for reaching net carbon neutrality. As a promising policy tool for reaching this goal, scholars have put forward social tipping interventions (SOTIs). “Social tipping” refers to the phenomenon that a small initial change in a parameter of a social system can create abrupt, nonlinear change via self-reinforcing feedback. If this reduces the burden on the environment, it is of potential interest for environmental policy. SOTIs are attempts to create social tipping intentionally. SOTIs produce rapid norm changes in laboratory experiments. However, little is known about the potential of SOTIs in the field. This research reports on a field intervention promoting the consumption of hot beverages in reusable mugs instead of one-way cups, conducted at Swiss university cafeterias (N = 162,523 consumption decisions). Two SOTIs involved an appeal promoting sustainable consumption with regular feedback about the current prevalence of sustainable consumption. Two control treatments involved either the same appeal without feedback or no intervention. This research offers three key findings. First, SOTIs involving regular normative feedback can transform sustainable consumption from a minority behavior into a social norm within weeks. Second, tipping points in real-world environmental dilemmas may exceed the values found in recent laboratory experiments (≥50% vs. ≥25%). Third, SOTIs can also promote the decay of sustainable consumption. By implication, the risk-free use of SOTIs requires deeper insights into the boundary conditions of these dynamics.

scholarly journals Upper Extremity Biomechanics and Gender: The Effects of Modern Computing Technologies

2018 ◽  
Vol 62 (1) ◽  
pp. 967-971
Author(s):  
Sarah M. Coppola ◽  
Jack.T Dennerlein
Keyword(s):  
Upper Extremity ◽  
Laboratory Experiments ◽  
Female Gender ◽  
Mobile Technologies ◽  
Activity Performance ◽  
Repetitive Injury ◽  
Technical Specifications ◽  
And Gender ◽  
Forearm Muscle ◽  
Recent Laboratory

Mobile computing devices are often designed with a one-size-fits-all approach, and consumers purchase devices based off of technical specifications rather than whether the devices fit them. Female gender is associated with higher risks of upper extremity repetitive injury, which may be caused by the generally smaller anthropometry of women (Cote, 2011; Won, Johnson, Punnett, & Dennerlein, 2009). This paper explores two mobile technologies’ effects on forearm muscle activity, performance, and self-reported experience within each gender for two recent laboratory experiments. A typing study with four short travel keyboards showed that female participants are more affected by different key switch designs than male participants. A touchscreen thumb swiping study revealed that male and female participants were similarly affected by tablet size, swipe location, and swipe direction. These results demonstrate the need to include both genders in usability testing for mobile technology and to consider individual differences when designing technologies.

Judgment Based Marketing Decision Models: Problems and Possible Solutions

1981 ◽  
Vol 45 (4) ◽  
pp. 13-23 ◽  
Author(s):  
Dipankar Chakravarti ◽  
Andrew Mitchell ◽  
Richard Staelin
Keyword(s):  
Decision Making ◽  
Comparative Analysis ◽  
Laboratory Experiments ◽  
Field Studies ◽  
Decision Models ◽  
Future Research ◽  
Marketing Decision ◽  
Recent Laboratory

This paper presents a comparative analysis of the findings of two field studies and three recent laboratory experiments that assessed the efficacy of judgment based models in aiding marketing decision making. This analysis indicates factors that may affect the effectiveness of these models. The implications of the findings for users of judgment based marketing decision models as well as model builders are discussed, and suggestions are made for future research to improve the models’ effectiveness.

scholarly journals Lattice Boltzmann model for weakly compressible flows

2020 ◽  
Vol 101 (1) ◽  
Author(s):  
Praveen Kumar Kolluru ◽  
Mohammad Atif ◽  
Manjusha Namburi ◽  
Santosh Ansumali
Keyword(s):  
Lattice Boltzmann ◽  
Compressible Flows ◽  
Lattice Boltzmann Model ◽  
Weakly Compressible ◽  
Boltzmann Model

Non neutral Plasmas in the Laboratory and Astrophysics

1985 ◽  
Vol 6 (2) ◽  
pp. 127-129 ◽  
Author(s):  
F. Curtis Michel
Keyword(s):  
Neutron Star ◽  
Laboratory Experiments ◽  
Light Cylinder ◽  
Rotator Model ◽  
Recent Laboratory ◽  
The Way

AbstractRecent laboratory experiments have confirmed theoretical expectations that the aligned rotator model (Goldreich and Julian 1969) does not function in the way originally expected, if at all. These experiments confirm that the nonneutral (completely charge-separated) plasma is isolated into finite regions, which in the case of the magnetosphere about an aligned rotator means in general that there is no plasma from the neutron star to be found at the light-cylinder. Hence the interesting pulsar-like properties originally postulated no longer follow.

scholarly journals Improved δ-SPH Scheme with Automatic and Adaptive Numerical Dissipation

Water ◽  
2020 ◽  
Vol 12 (10) ◽  
pp. 2858 ◽  
Author(s):  
Abdelkader Krimi ◽  
Luis Ramírez ◽  
Sofiane Khelladi ◽  
Fermín Navarrina ◽  
Michael Deligant ◽  
...  
Keyword(s):  
Kinetic Energy ◽  
Smoothed Particle Hydrodynamics ◽  
Numerical Scheme ◽  
Compressible Flows ◽  
Adaptive Method ◽  
Numerical Dissipation ◽  
Numerical Examples ◽  
Weakly Compressible ◽  
Particle Hydrodynamics ◽  
Smoothed Particle

In this work we present a δ-Smoothed Particle Hydrodynamics (SPH) scheme for weakly compressible flows with automatic adaptive numerical dissipation. The resulting scheme is a meshless self-adaptive method, in which the introduced artificial dissipation is designed to increase the dissipation in zones where the flow is under-resolved by the numerical scheme, and to decrease it where dissipation is not required. The accuracy and robustness of the proposed methodology is tested by solving several numerical examples. Using the proposed scheme, we are able to recover the theoretical decay of kinetic energy, even where the flow is under-resolved in very coarse particle discretizations. Moreover, compared with the original δ-SPH scheme, the proposed method reduces the number of problem-dependent parameters.

scholarly journals Investigation of a potential HCHO measurement artifact from ISOPOOH

2016 ◽  
Vol 9 (9) ◽  
pp. 4561-4568 ◽  
Author(s):  
Jason M. St. Clair ◽  
Jean C. Rivera-Rios ◽  
John D. Crounse ◽  
Eric Praske ◽  
Michelle J. Kim ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Laboratory Experiments ◽  
First Generation ◽  
Atmospheric Composition ◽  
Previous Exposure ◽  
Methyl Vinyl ◽  
Isoprene Oxidation ◽  
Measurement Artifact ◽  
Recent Laboratory

Abstract. Recent laboratory experiments have shown that a first generation isoprene oxidation product, ISOPOOH, can decompose to methyl vinyl ketone (MVK) and methacrolein (MACR) on instrument surfaces, leading to overestimates of MVK and MACR concentrations. Formaldehyde (HCHO) was suggested as a decomposition co-product, raising concern that in situ HCHO measurements may also be affected by an ISOPOOH interference. The HCHO measurement artifact from ISOPOOH for the NASA In Situ Airborne Formaldehyde instrument (ISAF) was investigated for the two major ISOPOOH isomers, (1,2)-ISOPOOH and (4,3)-ISOPOOH, under dry and humid conditions. The dry conversion of ISOPOOH to HCHO was 3 ± 2 % and 6 ± 4 % for (1,2)-ISOPOOH and (4,3)-ISOPOOH, respectively. Under humid (relative humidity of 40–60 %) conditions, conversion to HCHO was 6 ± 4 % for (1,2)-ISOPOOH and 10 ± 5 % for (4,3)-ISOPOOH. The measurement artifact caused by conversion of ISOPOOH to HCHO in the ISAF instrument was estimated for data obtained on the 6 September 2013 flight of the Studies of Emissions and Atmospheric Composition, Clouds and Climate Coupling by Regional Surveys (SEAC4RS) campaign. Prompt ISOPOOH conversion to HCHO was the source of < 4 % of the observed HCHO, including in the high-isoprene boundary layer. Time-delayed conversion, where previous exposure to ISOPOOH affects measured HCHO later in the flight, was conservatively estimated to be < 10 % of observed HCHO, and is significant only when high ISOPOOH sampling periods immediately precede periods of low HCHO.

scholarly journals One conceivable mechanism of UV-light induced SO<sub>2</sub> Oxidation to H<sub>2</sub>SO<sub>4</sub>

2010 ◽  
Vol 10 (6) ◽  
pp. 3141-3145 ◽  
Author(s):  
A. Sorokin
Keyword(s):  
Uv Irradiation ◽  
Laboratory Experiments ◽  
Uv Light ◽  
Radical Mechanism ◽  
Oh Radical ◽  
Additional Source ◽  
So2 Oxidation ◽  
Conceivable Mechanism ◽  
Excited Oxygen ◽  
Recent Laboratory

Abstract. The electron-excited chemistry of sulfur dioxide oxidation induced by UV irradiation of air with trace O3 and SO2 is considered. The importance of this mechanism is evaluated based on recent laboratory experiments on SO2 oxidation in a laminar tube with air induced by UV irradiation. Results show that under respective conditions the route of SO2 oxidation involving electron excited oxygen molecules may present an additional source of gaseous H2SO4 production to known OH-radical mechanism.

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