Study on the influence of conductive defects of composite insulators on live-line working approach distance

2021 ◽  
Author(s):  
L. Xinglie ◽  
F. Yuqun ◽  
P. Yong ◽  
Q. Weinan
Keyword(s):  
Approach Distance

DART and LICIACUBE: Documenting Kinetic Impact

2021 ◽  
Author(s):  
Andrew Cheng ◽  
Elizabetta Dotto ◽  
Eugene Fahnestock ◽  
Vincenzo Della Corte ◽  
Nancy Chabot ◽  
...  
Keyword(s):  
Time Delay ◽  
Velocity Distribution ◽  
Physical Properties ◽  
Optical Depth ◽  
Depth Profiles ◽  
Full Characterization ◽  
Approach Distance ◽  
Impact Ejecta ◽  
The Impact

<p>The NASA Double Asteroid Redirection Test (DART) mission will demonstrate asteroid deflection by a kinetic impactor. DART will impact Dimorphos, the secondary member of the (65803) Didymos system, in late September to early October, 2022 in order to change the binary orbit period. DART will carry a 6U CubeSat called LICIACube, contributed by the Italian Space Agency, to document the DART impact and to observe the impact ejecta. LICIACube will be released by DART 10 days prior to Didymos encounter, and LICIACube will fly by Dimorphos at closest approach distance of about 51 km and with a closest approach time delay of about 167 s after the DART impact. LICIACube will observe the structure and evolution of the DART impact ejecta plume and will obtain images of the surfaces of both bodies at best ground sampling about 1.4 m per pixel. LICIACube imaging importantly includes the non-impact hemisphere of the target body, the side not imaged by DART.</p> <p> </p> <p>The LICIACube flyby trajectory, notably the closest approach distance and the time delay of closest approach, are designed to optimize the study of ejecta plume evolution without exposing the satellite to impact hazard. LICIACube imaging will determine the direction of the ejecta plume and the ejection angles, and will further help to determine the ejecta momentum transfer efficiency <em>β</em>. The ejecta plume structure, as it evolves over time, is determined by the amount of ejecta that has reached a given altitude at a given time. The LICIACube plume images enable characterization of the ejecta mass versus velocity distribution, which is strongly dependent on target properties like strength and porosity and is therefore a powerful diagnostic of the DART impact, complementary to measurements of the DART impact crater by the ESA Hera mission which will arrive at Didymos in 2026. Hera will measure crater radius and crater volume to determine the total volume of ejecta, which together with a ejecta mass-velocity distribution gives a full characterization of the DART impact.</p> <p> </p> <p>Models of the ejecta plume evolution as imaged by LICIACube show how LICIACube images can discriminate between different target physical properties (mainly strength and porosity), thereby allowing inferences of the magnitude of the ejecta momentum. Measured ejecta plume optical depth profiles can distinguish between gravity-controlled and strength-controlled impact cases and help determine target physical properties. LICIACube ejecta plume images further provide information on the direction of the ejecta momentum as well as the magnitude, requiring full 2-D simulations of the plume images. We will present new simulation model optical depth profiles across the plume at arbitrary positions.</p> <p><br />We thank NASA for support of the DART project at JHU/APL, under Contract # NNN06AA01C, Task Order # NNN15AA05T. The Italian LICIACube team acknowledges financial support from Agenzia Spaziale Italiana (ASI, contract No. 2019-31-HH.0 CUP<br />F84I190012600).</p>

scholarly journals Behavioral responses of Australian fur seals to boat approaches at a breeding colony

2018 ◽  
Vol 31 ◽  
pp. 35-52 ◽  
Author(s):  
Julia J. Back ◽  
Andrew J. Hoskins ◽  
Roger Kirkwood ◽  
John P.Y. Arnould
Keyword(s):  
Time Of Day ◽  
Species Variation ◽  
Strong Response ◽  
Approach Distance ◽  
Fur Seals ◽  
Increase Energy Expenditure ◽  
Fur Seal ◽  
Steep Decline ◽  
Breeding Seasons ◽  
Resting Behavior

In Australia, a multi-million-dollar industry is based on viewing the Australian fur seal (Arctocephaluspusillusdoriferus), predominantly through boat visits to breeding colonies. Regulation of boat approaches varies by site and no systematic investigations have been performed to inform management guidelines. To investigate possible effects of disturbance, experimental boat approaches were made to a colony at Kanowna Island in northern Bass Strait and seal responses were monitored using instantaneous scan sampling. Colony attendance (individuals remaining ashore) was found to be influenced by approach distance and time of day, but was not affected by environmental variables or season, whereas onshore resting behavior was influenced by approach distance, time of day, ambient temperature and wind direction. Onshore resting behavior decreased following experimental boat approaches to 75 m, but changes in abundance of individuals ashore were not observed at this distance. In contrast, approaches to 25 m elicited a strong response, with a steep decline in the number of individuals ashore. This response was strongest when approaches occurred in the morning, with a decline of approximately 47% of individuals, compared to a decline of 21% during afternoon approaches. With regard to onshore resting behavior, afternoon approaches to 75 m led to minimal response. The remaining three combinations of approach distance and time of day had a similar pattern of reductions in the proportion of individuals engaging in onshore resting behavior. The strongest response was again seen during approaches to 25 m conducted in the morning. These behavior changes suggest that unrestricted boat-based ecotourism at Australian fur seal colonies has the potential to increase energy expenditure and reduce the number of seals ashore. Increasing minimum approach distances to ≥75 m and/or restricting visits to afternoons may minimize these impacts at Kanowna Island during the post-molt and non-breeding seasons. As several studies have demonstrated considerable intra-species variation in seal responses to boat approaches, research at other colonies is needed before these findings can be generalized to the remainder of the Australian fur seal population.

scholarly journals Approaching birds with drones: first experiments and ethical guidelines

2015 ◽  
Vol 11 (2) ◽  
pp. 20140754 ◽  
Author(s):  
Elisabeth Vas ◽  
Amélie Lescroël ◽  
Olivier Duriez ◽  
Guillaume Boguszewski ◽  
David Grémillet
Keyword(s):  
Best Practices ◽  
Unmanned Aerial Vehicles ◽  
Ecological Research ◽  
Ethical Guidelines ◽  
Wetland Area ◽  
Physiological Indicators ◽  
Approach Distance ◽  
Aerial Vehicles ◽  
Approach Speed ◽  
The Impact

Unmanned aerial vehicles, commonly called drones, are being increasingly used in ecological research, in particular to approach sensitive wildlife in inaccessible areas. Impact studies leading to recommendations for best practices are urgently needed. We tested the impact of drone colour, speed and flight angle on the behavioural responses of mallards Anas platyrhynchos in a semi-captive situation, and of wild flamingos ( Phoenicopterus roseus ) and common greenshanks ( Tringa nebularia ) in a wetland area. We performed 204 approach flights with a quadricopter drone, and during 80% of those we could approach unaffected birds to within 4 m. Approach speed, drone colour and repeated flights had no measurable impact on bird behaviour, yet they reacted more to drones approaching vertically. We recommend launching drones farther than 100 m from the birds and adjusting approach distance according to species. Our study is a first step towards a sound use of drones for wildlife research. Further studies should assess the impacts of different drones on other taxa, and monitor physiological indicators of stress in animals exposed to drones according to group sizes and reproductive status.

scholarly journals Approximations of Minimum Approach Distance in Electron Mirroring Phenomena

2019 ◽  
Vol 571 ◽  
pp. 012126
Author(s):  
Hassan N. Al-Obaidi ◽  
Imad H. Khaleel ◽  
Ali S. Mahdi
Keyword(s):  
Approach Distance

The impact of probe size on measurements of diffusion in active microrheology

Lab on a Chip ◽  
2016 ◽  
Vol 16 (16) ◽  
pp. 3114-3129 ◽  
Author(s):  
Nicholas J. Hoh ◽  
Roseanna N. Zia
Keyword(s):  
Hydrodynamic Size ◽  
Diffusive Behavior ◽  
Approach Distance ◽  
Probe Size ◽  
The Impact

A framework to study the influence of polydispersity on flow-induced diffusion in active microrheology is presented. It is found that diffusive behavior is set entirely and dually by the proximity with which two particles can approach one another, and by the extent to which this minimum approach distance is occupied by the hydrodynamic size of the forced particle.

Risk factors affecting escape behavior by the desert iguana, Dipsosaurus dorsalis: speed and directness of predator approach, degree of cover, direction of turning by a predator, and temperature

2003 ◽  
Vol 81 (6) ◽  
pp. 979-984 ◽  
Author(s):  
W E Cooper Jr.
Keyword(s):  
Risk Factors ◽  
Body Temperature ◽  
Escape Behavior ◽  
Primary Response ◽  
Single Individual ◽  
Factors Affecting ◽  
Escape Theory ◽  
Approach Distance ◽  
Dipsosaurus Dorsalis ◽  
Air Temperatures

Escape from predators by desert iguanas (Dipsosaurus dorsalis) conforms to predictions of optimal escape theory based on risk. I simulated an approaching predator to study risk factors. The primary response variable was approach distance (= flight-initiation distance), i.e., the distance between predator and prey when the prey initiates escape. In additional studies, I recorded whether lizards permitted me to approach close enough to noose them (an indicator of wariness) and the method of escape. Approach distance was greater when the predator approached rapidly than slowly and directly than indirectly, and when the predator turned toward the lizard rather than away. It was greater in open than in more densely covered habitats, which may reflect greater risk due to conspicuousness and (or) a greater distance to refuge. Early in the day at lower air temperatures, desert iguanas permitted a closer approach before initiating escape. While basking after emergence from burrows, lizards escaped into burrows; later in the day they fled. Lizards that fled had high body temperatures; a single individual captured immediately after entering a burrow had a lower body temperature. Lizards presumably enter burrows when low body temperature limits the running speed, but burrow use is costly because attainment of the activity temperature is delayed because of time elapsed and the temperature decrease in burrows.

Escape behavior by prey blocked from entering the nearest refuge

1999 ◽  
Vol 77 (4) ◽  
pp. 671-674 ◽  
Author(s):  
William E Cooper, Jr.
Keyword(s):  
Escape Behavior ◽  
Free Access ◽  
Flight Initiation Distance ◽  
Approach Distance ◽  
Increase Risk ◽  
Time Required ◽  
Optimal Approach ◽  
Flight Initiation

Current models of optimal antipredation behavior do not apply to prey blocked by a predator from access to the primary refuge because the predator is closer than the optimal approach distance and flight toward the refuge would increase risk. If other alternative refuges are available, the prey should flee toward the best alternative one. I studied the effect of an approaching human simulated predator interposed between prey and refuge on the use of alternative refuges and on flight-initiation distance in the keeled earless lizard, Holbrookia propinqua. When the predator approached on a line between a lizard and its closest refuge, the lizard invariably fled to or toward an alternative refuge. Lizards were significantly more likely to use alternative refuges than lizards approached on a line connecting the closest refuge, prey, and predator, but with the lizard between the predator and the refuge. Flight-initiation distance was significantly greater for lizards having free access to the closest refuge than for those blocked from it, perhaps because of the time required to assess the new risk posed by blockage of the closest refuge, to select the best alternative refuge, or to wait for the predator to commit to a closing pattern before choosing the best flight option.

Numerical Contact Analysis of Transversely Isotropic Coatings: A Cylinder Within a Circumferential Groove

2000 ◽  
Vol 123 (2) ◽  
pp. 436-440 ◽  
Author(s):  
Clint Morrow, ◽  
Michael Lovell, ◽  
Zhi Deng
Keyword(s):  
Finite Element ◽  
Normal Load ◽  
Transversely Isotropic ◽  
Element Model ◽  
Contact Length ◽  
Operating Conditions ◽  
Circumferential Groove ◽  
Approach Distance ◽  
Dimensional Finite Element ◽  
Coating Parameter

The contact characteristics of transversely isotropic coatings are investigated for a cylinder within a circumferential groove using a two-dimensional finite element model. With the model, contact behavior is evaluated at more than 400 operating conditions by varying coating material, coating thickness, normal load, and cylinder/groove radii. Based on the finite element results, numerical expressions are derived for the maximum surface pressure, contact length, and approach distance as a function of a transversely isotropic coating parameter, ζ. The importance of these expressions, as related to design and the selection of materials for reducing wear in contacting surfaces, is subsequently discussed.

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