Studies of the movement of ice through low-pressure waterworks

Abstract Passage of ice through hydraulic structures is a significant and urgent issue for study. When examining this issue, various conditions should be taken into account. Thus, the successful passage of ice through hydraulic structures depends both on ice characteristics, the parameters of the spillway structures, and on the ice movement velocity in front of the spillway. The goals have been formed; the research tasks have been set. As a result, a theoretical solution to determine the bending moments necessary for calculating the fracture of ice floes has been obtained. The proposed analytical solution for determining the bending moments is found based on a system solution of differential equations of a rigid body motion in a fluid. The assumptions made for this case are set out in the article. The resulting dependence makes it possible to determine the bending moments in any section of the ice section and take into account the flow dynamics. A complex of laboratory studies was carried out, aimed at studying the ice movement velocities on the developed and manufactured model of a spillway with a wide threshold, in front of which an auxiliary threshold is installed to create a concentrated fall. The dependence for determining the velocity in the form of a trigonometric function is obtained and converted into a convenient formula. The performed calculations are compared with the field data and satisfactory results are given.

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A Hybrid Tracking System of Full-Body Motion Inside Crowds

Sensors ◽

10.3390/s21062108 ◽

2021 ◽

Vol 21 (6) ◽

pp. 2108

Author(s):

Maik Boltes ◽

Juliane Adrian ◽

Anna-Katharina Raytarowski

Keyword(s):

Motion Tracking ◽

Inertial Sensors ◽

Tracking System ◽

Body Motion ◽

Whole Body ◽

Body Parts ◽

Movement Velocity ◽

Camera System ◽

Pedestrian Dynamics ◽

Full Body

For our understanding of the dynamics inside crowds, reliable empirical data are needed, which could enable increases in safety and comfort for pedestrians and the design of models reflecting the real dynamics. A well-calibrated camera system can extract absolute head position with high accuracy. The inclusion of inertial sensors or even self-contained full-body motion capturing systems allows the relative tracking of invisible people or body parts or capturing the locomotion of the whole body even in dense crowds. The newly introduced hybrid system maps the trajectory of the top of the head coming from a full-body motion tracking system to the head trajectory of a camera system in global space. The fused data enable the analysis of possible correlations of all observables. In this paper we present an experiment of people passing though a bottleneck and show by example the influences of bottleneck width and motivation on the overall movement, velocity, stepping locomotion and rotation of the pelvis. The hybrid tracking system opens up new possibilities for analyzing pedestrian dynamics inside crowds, such as the space requirement while passing through a bottleneck. The system allows linking any body motion to characteristics describing the situation of a person inside a crowd, such as the density or movements of other participants nearby.

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Some Simplified Solutions for Relatively Stiff Beams on Elastic Foundations

Journal of Engineering for Industry ◽

10.1115/1.3667572 ◽

1963 ◽

Vol 85 (1) ◽

pp. 1-4 ◽

Cited By ~ 1

Author(s):

Bernard W. Shaffer

Keyword(s):

Rigid Body ◽

Linear Approximation ◽

Characteristic Parameter ◽

Rigid Body Motion ◽

Body Motion ◽

Approximate Analysis ◽

Bending Moments ◽

Elastic Foundations ◽

Exact Theory ◽

Central Forces

Maximum bending moments, rotations, and deflections of beams resting on elastic foundations and subject to central forces and bending moments are computed on the basis of a linear approximation to the foundation reaction. This reaction is determined from the rigid-body motion of the beam, and is thus statically determinate. The results of these approximate analyses are compared with those obtained from the exact theory in terms of the “characteristic parameter” of the beam, which is a function of the relative stiffnesses of the beam and the foundation. It is shown that the approximate analysis introduces very little error if the beam is stiff as compared to the foundation on which it rests.

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Simulation of Wave Interaction With a Circular Ice Floe

Journal of Offshore Mechanics and Arctic Engineering ◽

10.1115/1.4042096 ◽

2019 ◽

Vol 141 (4) ◽

Cited By ~ 4

Author(s):

Luofeng Huang ◽

Giles Thomas

Keyword(s):

Sea Ice ◽

Numerical Simulations ◽

Wave Interaction ◽

Body Motion ◽

Applied Model ◽

Ice Retreat ◽

Level Ice ◽

Resource Exploration ◽

Ice Floes ◽

Sea Ice Retreat

Global warming is inducing sea ice retreat, which is opening new shipping routes and extending the accessible area for resource exploration. This encourages an increasing research interest in sea ice behavior. With the sea ice melting, level ice is broken up by waves propagated from the open ocean, resulting in an environment where both floating ice floes and waves exist. Such wave–ice interaction can bring significant influences on the potential human activities. This work presents a series of numerical simulations to predict the behavior of a circular ice floe forced by regular waves, with different wavelength and wave amplitude conditions being investigated. The numerical model was validated against experiments, and it revealed good accuracy in predicting the rigid body motion of an ice floe, including some extreme cases that are difficult to model by previous methods. Two specific behaviors were observed during the numerical simulations, namely overwash and scattering. Both behaviors are discussed in detail to analyze their linear/nonlinear effect on the ice floe motion. The applied model could be used to provide valuable estimations for arctic engineering purposes.

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Hydrogen Cyanide Polymers from the Impact of Comet P/Shoemaker-Levy 9 on Jupiter

International Astronomical Union Colloquium ◽

10.1017/s025292110001469x ◽

1997 ◽

Vol 161 ◽

pp. 179-187

Author(s):

Clifford N. Matthews ◽

Rose A. Pesce-Rodriguez ◽

Shirley A. Liebman

Keyword(s):

Amino Acids ◽

Solar System ◽

Hydrogen Cyanide ◽

Nitrogen Heterocycles ◽

Laboratory Studies ◽

Heterogeneous Solids ◽

The Many ◽

Comet Halley ◽

The Impact ◽

By Products

AbstractHydrogen cyanide polymers – heterogeneous solids ranging in color from yellow to orange to brown to black – may be among the organic macromolecules most readily formed within the Solar System. The non-volatile black crust of comet Halley, for example, as well as the extensive orangebrown streaks in the atmosphere of Jupiter, might consist largely of such polymers synthesized from HCN formed by photolysis of methane and ammonia, the color observed depending on the concentration of HCN involved. Laboratory studies of these ubiquitous compounds point to the presence of polyamidine structures synthesized directly from hydrogen cyanide. These would be converted by water to polypeptides which can be further hydrolyzed to α-amino acids. Black polymers and multimers with conjugated ladder structures derived from HCN could also be formed and might well be the source of the many nitrogen heterocycles, adenine included, observed after pyrolysis. The dark brown color arising from the impacts of comet P/Shoemaker-Levy 9 on Jupiter might therefore be mainly caused by the presence of HCN polymers, whether originally present, deposited by the impactor or synthesized directly from HCN. Spectroscopic detection of these predicted macromolecules and their hydrolytic and pyrolytic by-products would strengthen significantly the hypothesis that cyanide polymerization is a preferred pathway for prebiotic and extraterrestrial chemistry.

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Cognitive Aging in a Precision Sport Context

European Psychologist ◽

10.1027/1016-9040.1.3.166 ◽

1996 ◽

Vol 1 (3) ◽

pp. 166-179 ◽

Cited By ~ 6

Author(s):

Bo Molander ◽

Lars Bäckman

Keyword(s):

Older Adult ◽

Cognitive Abilities ◽

Cognitive Aging ◽

Motor Performance ◽

Intervention Programs ◽

Laboratory Studies ◽

High Arousal ◽

Memory And Attention ◽

Age Related ◽

Principal Finding

Highly skilled miniature golf players were examined in a series of field and laboratory studies. The principal finding from these studies is that young and young adult players (range = 15-38 years) score equally well or better in competition than in training whereas older adult players (range = 46-73 years) perform worse in competitive events than under training conditions. It was also found that the impairment in motor performance on the part of the older players is associated with age-related deficits in basic cognitive abilities, such as memory and attention. These results support the hypothesis that older players may be able to compensate for age-related deficits under relaxed conditions, but not under conditions of high arousal. The possibility of improving the performance of the older players in stressful situations by means of various intervention programs is discussed.

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Automation Surprise

Aviation Psychology and Applied Human Factors ◽

10.1027/2192-0923/a000113 ◽

2017 ◽

Vol 7 (1) ◽

pp. 28-41 ◽

Cited By ~ 4

Author(s):

Robert J. de Boer ◽

Karel Hurts

Keyword(s):

Flight Control ◽

Representative Sample ◽

Aviation Safety ◽

Control Mode ◽

Cognitive Errors ◽

Laboratory Studies ◽

Airline Pilots ◽

Flight Operations ◽

Widespread Phenomenon ◽

Few Data

Abstract. Automation surprise (AS) has often been associated with aviation safety incidents. Although numerous laboratory studies have been conducted, few data are available from routine flight operations. A survey among a representative sample of 200 Dutch airline pilots was used to determine the prevalence of AS and the severity of its consequences, and to test some of the factors leading to AS. Results show that AS is a relatively widespread phenomenon that occurs three times per year per pilot on average but rarely has serious consequences. In less than 10% of the AS cases that were reviewed, an undesired aircraft state was induced. Reportable occurrences are estimated to occur only once every 1–3 years per pilot. Factors leading to a higher prevalence of AS include less flying experience, increasing complexity of the flight control mode, and flight duty periods of over 8 hr. It is concluded that AS is a manifestation of system and interface complexity rather than cognitive errors.

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