scholarly journals Recrystallization and damage of ice in winter sports

2017 ◽  
Vol 375 (2086) ◽  
pp. 20150353 ◽  
Author(s):  
Alexandra Seymour-Pierce ◽  
Ben Lishman ◽  
Peter Sammonds
Keyword(s):  
Energy Dissipation ◽  
Total Energy ◽  
Polarized Light ◽  
Experimental Results ◽  
Winter Sports ◽  
Thin Sections ◽  
Winter Sport ◽  
Show Evidence ◽  
Earthquake Faults ◽  
Total Energy Dissipation

Ice samples, after sliding against a steel runner, show evidence of recrystallization and microcracking under the runner, as well as macroscopic cracking throughout the ice. The experiments that produced these ice samples are designed to be analogous to sliding in the winter sport of skeleton. Changes in the ice fabric are shown using thick and thin sections under both diffuse and polarized light. Ice drag is estimated as 40–50% of total energy dissipation in a skeleton run. The experimental results are compared with visual inspections of skeleton tracks, and to similar behaviour in rocks during sliding on earthquake faults. The results presented may be useful to athletes and designers of winter sports equipment. This article is part of the themed issue ‘Microdynamics of ice’.

Use of a stacked drop manhole for energy dissipation: a case study in Edmonton, Alberta

2009 ◽  
Vol 36 (6) ◽  
pp. 1037-1050 ◽  
Author(s):  
G. Adriana Camino ◽  
David Z. Zhu ◽  
Nallamuthu Rajaratnam ◽  
Manas Shome
Keyword(s):  
Energy Dissipation ◽  
Total Energy ◽  
Laboratory Investigation ◽  
Flow Regimes ◽  
Flow Patterns ◽  
The Other ◽  
Inflow Conditions ◽  
Water Depths ◽  
Total Energy Dissipation

This paper reports on a laboratory investigation into the performance of a novel stacked drop manhole design where two identical rectangular manholes are stacked one beside the other but at different heights so that there is a drop in elevation from one to the other. The focus of the study was to estimate the energy dissipation that occurs in such stacked manholes during diverse inflow conditions. Flow regimes inside the structure were identified and the effectiveness of the design was assessed under variable inflow conditions. Total energy dissipation in the stacked manhole was found to range from about 50% to 90%, and the contribution of each manhole chamber to the overall energy dissipation was assessed. A relationship between water depths in the manhole chambers and the corresponding outflow conditions was established. In addition, an analysis of the flow patterns and flow regimes highlighted the relevant parameters involved in the mechanisms of energy dissipation.

scholarly journals Estimating Energy Dissipation Rate from Breaking Waves Using Polarimetric SAR Images

Sensors ◽  
2020 ◽  
Vol 20 (22) ◽  
pp. 6540
Author(s):  
Rafael D. Viana ◽  
João A. Lorenzzetti ◽  
Jonas T. Carvalho ◽  
Ferdinando Nunziata
Keyword(s):  
Energy Dissipation ◽  
Total Energy ◽  
Dissipation Rate ◽  
Temporal Distribution ◽  
Wave Model ◽  
Breaking Waves ◽  
Fast Response ◽  
Energy Dissipation Rate ◽  
Sar Data ◽  
Total Energy Dissipation

The total energy dissipation rate on the ocean surface, ϵt (W m−2), provides a first-order estimation of the kinetic energy input rate at the ocean–atmosphere interface. Studies on the spatial and temporal distribution of the energy dissipation rate are important for the improvement of climate and wave models. Traditional oceanographic research normally uses remote measurements (airborne and platforms sensors) and in situ data acquisition to estimate ϵt; however, those methods cover small areas over time and are difficult to reproduce especially in the open oceans. Satellite remote sensing has proven the potential to estimate some parameters related to breaking waves on a synoptic scale, including the energy dissipation rate. In this paper, we use polarimetric Synthetic Aperture Radar (SAR) data to estimate ϵt under different wind and sea conditions. The used methodology consisted of decomposing the backscatter SAR return in terms of two contributions: a polarized contribution, associated with the fast response of the local wind (Bragg backscattering), and a non-polarized (NP) contribution, associated with wave breaking (Non-Bragg backscattering). Wind and wave parameters were estimated from the NP contribution and used to calculate ϵt from a parametric model dependent of these parameters. The results were analyzed using wave model outputs (WAVEWATCH III) and previous measurements documented in the literature. For the prevailing wind seas conditions, the ϵt estimated from pol-SAR data showed good agreement with dissipation associated with breaking waves when compared to numerical simulations. Under prevailing swell conditions, the total energy dissipation rate was higher than expected. The methodology adopted proved to be satisfactory to estimate the total energy dissipation rate for light to moderate wind conditions (winds below 10 m s−1), an environmental condition for which the current SAR polarimetric methods do not estimate ϵt properly.

Effect of Roughness on Frictional Energy Dissipation in Presliding Contacts

2015 ◽  
Vol 138 (1) ◽  
Author(s):  
Deepak B. Patil ◽  
Melih Eriten
Keyword(s):  
Energy Dissipation ◽  
Total Energy ◽  
Rough Surface ◽  
Power Law ◽  
Roughness Parameters ◽  
Frictional Energy ◽  
Real Area Of Contact ◽  
Frictional Energy Dissipation ◽  
Total Energy Dissipation ◽  
Real Area

A finite element model (FEM) is used to investigate the effect of roughness on the frictional energy dissipation for an elastic contact subjected to simultaneous normal and tangential oscillations. Frictional energy losses are correlated against the maximum tangential load as a power-law where the exponents show the degree of nonlinearity. Individual asperity is shown to undergo similar stick–slip cycles during a loading period. Taller asperities are found to contribute significantly to the total energy dissipation and dominate the trends in the total energy dissipation. The authors' observations for spherical contacts are extended to the rough surface contact, which shows that power-law exponent depends on stick durations individual asperity contacts experience. A theoretical model for energy dissipation is then validated with the FEM, for both spherical and rough surface contacts. The model is used to study the influence of roughness parameters (asperity density, height distribution, and fractal dimension) on magnitude of energy dissipation and power-law exponents. Roughness parameters do not influence the power-law exponents. For a phase difference of π/2 between normal and tangential oscillations, the frictional energy dissipation shows quadratic dependence on the tangential fluctuation amplitude, irrespective of the roughness parameters. The magnitude of energy dissipation is governed by the real area of contact and, hence, depends on the surface roughness parameters. Larger real area of contact results in more energy under similar loading conditions.

States of minimum dissipation in magnetohydrodynamics: a review

1996 ◽  
Vol 56 (3) ◽  
pp. 531-551 ◽  
Author(s):  
Lee Phillips
Keyword(s):  
Fluid Dynamics ◽  
Energy Dissipation ◽  
Boundary Conditions ◽  
Total Energy ◽  
Recent Literature ◽  
Steady States ◽  
Current State ◽  
State Of Research ◽  
Total Energy Dissipation

The hypothesis that the steady, or statistically steady, states of a magnetofluid can be predicted by minimizing the integral of the total energy dissipation is discussed in relation to theorems in fluid dynamics. A survey is made of the recent literature wherein the hypothesis is used to predict magnetofluid behaviour and some related work. A detailed discussion of boundary conditions is provided, and we close with a brief summary of the current state of research.

A perturbative approach to the backflow dynamics of nematic defects

2011 ◽  
Vol 23 (1) ◽  
pp. 181-200 ◽  
Author(s):  
PAOLO BISCARI ◽  
TIMOTHY J. SLUCKIN
Keyword(s):  
Liquid Crystal ◽  
Energy Dissipation ◽  
Velocity Field ◽  
Total Energy ◽  
Asymptotic Theory ◽  
Perturbative Expansion ◽  
Perturbative Approach ◽  
Director Dynamics ◽  
Charged Defects ◽  
Total Energy Dissipation

We present an asymptotic theory that includes in a perturbative expansion the coupling effects between the director dynamics and the velocity field in a nematic liquid crystal. Backflow effects are most significant in the presence of defect motion, since in this case the presence of a velocity field may strongly reduce the total energy dissipation and thus increase the defect velocity. As an example, we illustrate how backflow influences the speeds of opposite-charged defects.

scholarly journals An Investigation of Differences in Lower Extremity Biomechanics During Single-Leg Landing From Height Using Bionic Shoes and Normal Shoes

2021 ◽  
Vol 9 ◽  
Author(s):  
Datao Xu ◽  
Huiyu Zhou ◽  
Julien S. Baker ◽  
Bíró István ◽  
Yaodong Gu
Keyword(s):  
Energy Dissipation ◽  
Total Energy ◽  
Lower Limb ◽  
Sagittal Plane ◽  
Reaction Force ◽  
Frontal Plane ◽  
Flexion Angle ◽  
Initial Contact ◽  
Lower Limb Injury ◽  
Total Energy Dissipation

Bionic shoes utilizing an actual foot shape sole structure can alter lower limb’s biomechanics, which may help in the development of specific training or rehabilitation programs. The purpose of this study was to investigate the biomechanical differences in the lower limb during a single-leg landing task using bionic shoes (BS) and normal shoes (NS). Fifteen healthy male subjects participated in this study, sagittal, and frontal plane data were collected during the landing phase (drop landing from 35 cm platform). Our study showed that BS depicted a significantly greater minimum knee flexion angle at initial contact (p = 0.000), a significantly greater minimum (initial contact) hip flexion angle at initial contact (p = 0.009), a significantly smaller sagittal plane total energy dissipation (p = 0.028), a significantly smaller frontal plane total energy dissipation (p = 0.008), a significantly smaller lower limb total energy dissipation (p = 0.017) than NS during the landing phase. SPM analysis revealed that BS depicted a significantly smaller knee joint vertical reaction force during the 13.8–19.8% landing phase (p = 0.01), a significantly smaller anterior tibia shear force during the 14.2–17.5% landing phase (p = 0.024) than NS. BS appears to change lower limb kinematics at initial contact and then readjust the landing strategies for joint work and joint reaction force, thereby reducing the risk of lower limb skeletal muscle injury. BS have great potential for future development and application uses, which may help athletes to reduce lower limb injury risk.

scholarly journals An Evolution Based on Various Energy Strategies

Entropy ◽  
2021 ◽  
Vol 23 (3) ◽  
pp. 317
Author(s):  
Alexander O. Gusev ◽  
Leonid M. Martyushev
Keyword(s):  
Energy Dissipation ◽  
Total Energy ◽  
Entropy Production ◽  
Basic Principles ◽  
Specific Strategy ◽  
Interesting Connection ◽  
Simulation Results ◽  
Energy Strategies ◽  
Selection Of ◽  
Total Energy Dissipation

The simplest model of the evolution of agents with different energy strategies is considered. The model is based on the most general thermodynamic ideas and includes the procedures for selection, inheritance, and variability. The problem of finding a universal strategy (principle) as a selection of possible competing strategies is solved. It is shown that when there is non-equilibrium between the medium and agents, a direction in the evolution of agents arises, but at the same time, depending on the conditions of the evolution, different strategies can be successful. However, for this case, the simulation results reveal that in the presence of significant competition of agents, the strategy that has the maximum total energy dissipation of agents arising as a result of evolution turns out to be successful. Thus, it is not the specific strategy that is universal, but the maximization of dissipation. This result discovers an interesting connection between the basic principles of Darwin–Wallace evolution and the maximum entropy production principle.

Sport Injury and Illness: Surveillance of Tropical Country Athletes during the 1st Winter Children of Asia Games

2020 ◽  
Vol 103 (11) ◽  
pp. 1116-1120
Keyword(s):  
Sports Participation ◽  
Upper Respiratory Tract ◽  
Tropical Country ◽  
Winter Sports ◽  
Winter Sport ◽  
Observational Prospective Cohort Study ◽  
Competition Period ◽  
Cross Country Skiing ◽  
Associated Risk Factors ◽  
Type Of Injury

Background: The systematic surveillance of injuries and illness in young athletes is important to reduce the loss of training and competition time and enable continuing sports participation. However, the risk and incidence of injury and illness in tropical country athletes competing in winter sports remains unclear. Objective: To identify the incidence, severity, and causes of injuries and illness in the Thailand National Youth Team during the 10-day First Winter Children of Asia Games. Materials and Methods: In the present observational prospective cohort study, the authors used the International Olympic Committee (IOC) injury and illness surveillance system for multisport events. The injuries and illnesses of 18 Thailand athletes were collected daily by the team physician over a 10-day competition period. Results: Eight injuries and nine illnesses were reported, equating to 44.4% of the athletes sustaining at least one injury and 50% at least one illness, an incidence rate of 2.6 injuries and 7.3 illnesses per 100 athletes, respectively. The risk of sustaining an injury was highest during cross country skiing while the most common type of injury was a sprain. The upper respiratory tract was the site most affected by illness with females reporting a greater illness rate. Conclusion: The presented data constitute the basis for future analyses of injury and illness associated risk factors in winter sports, which are essential to develop and implement effective preventative strategies in tropical winter sport athletes. Keywords: Surveillance, Injury and illness, Winter sport

scholarly journals Experimental/Numerical Evaluation of Steel Trapezoidal Corrugated Infill Panels with an Opening

2021 ◽  
Vol 11 (7) ◽  
pp. 3275
Author(s):  
Majid Yaseri Gilvaee ◽  
Massood Mofid
Keyword(s):  
Energy Dissipation ◽  
Ultimate Strength ◽  
Steel Plate ◽  
Shear Walls ◽  
Experimental Results ◽  
Structural Performance ◽  
Initial Stiffness ◽  
Infill Panels ◽  
Energy Dissipation Capacity ◽  
Ductility Ratio

This paper investigates the influence of an opening in the infill steel plate on the behavior of steel trapezoidal corrugated infill panels. Two specimens of steel trapezoidal corrugated shear walls were constructed and tested under cyclic loading. One specimen had a single rectangular opening, while the other one had two rectangular openings. In addition, the percentage of opening in both specimens was 18%. The initial stiffness, ultimate strength, ductility ratio and energy dissipation capacity of the two tested specimens are compared to a specimen without opening. The experimental results indicate that the existence of an opening has the greatest effect on the initial stiffness of the corrugated steel infill panels. In addition, the experimental results reveal that the structural performance of the specimen with two openings is improved in some areas compared to the specimen with one opening. To that end, the energy dissipation capacity of the specimen with two openings is obtained larger than the specimen with one opening. Furthermore, a number of numerical analyses were performed. The numerical results show that with increasing the thickness of the infill plate or using stiffeners around the opening, the ultimate strength of a corrugated steel infill panel with an opening can be equal to or even more than the ultimate strength of that panel without an opening.

Comparing the Seismic Performance of Beam-Column Joints with and without SFRC when Subjected to Cyclic Loading

2012 ◽  
Vol 626 ◽  
pp. 85-89 ◽  
Author(s):  
Kay Dora Abdul Ghani ◽  
Nor Hayati Hamid
Keyword(s):  
Energy Dissipation ◽  
Cyclic Loading ◽  
Seismic Performance ◽  
Experimental Work ◽  
Concrete Beam ◽  
Steel Fiber ◽  
Precast Concrete ◽  
Experimental Results ◽  
Column Joint ◽  
Initial Cracks

The experimental work on two full-scale precast concrete beam-column corner joints with corbels was carried out and their seismic performance was examined. The first specimen was constructed without steel fiber, while second specimen was constructed by mixed up steel fiber with concrete and placed it at the corbels area. The specimen were tested under reversible lateral cyclic loading up to ±1.5% drift. The experimental results showed that for the first specimen, the cracks start to occur at +0.5% drifts with spalling of concrete and major cracks were observed at corbel while for the second specimen, the initial cracks were observed at +0.75% with no damage at corbel. In this study, it can be concluded that precast beam-column joint without steel fiber has better ductility and stiffness than precast beam-column joint with steel fiber. However, precast beam-column joint with steel fiber has better energy dissipation and fewer cracks at corbel as compared to precast beam-column joint without steel fiber.

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