Minimum Approach Distance Research Articles

330kV Live Working Platform Design based on Minimum Approach Distances Analysis via Weighted Digraph

Considering the strict requirements of live working platform in compact substation, a module assembly based structure is put forward. In order to meet the demands of insulation performance, a method of calculating minimum approach distances based on graph theory is proposed, and the feasible regions of structural parameters and flow parameters are obtained, which are finally verified in experiments.

Approximations of Minimum Approach Distance in Electron Mirroring Phenomena

The minimum approaches distance of probing electrons in scanning electron microscope has investigated in accordance to mirror effect phenomenon. The analytical expression for such distance is decomposed using the binomial expansion. With aid of resulted expansion, the distribution of trapped electrons within the sample surface has explored. Results have shown that trapped electron distributes with various forms rather an individual one. The domination of any shape is mainly depend on the minimum approaches distance of probing electrons

AC Flashover Performance of FRP Hot Stick for Live Working in High Altitude Areas

Fiberglass reinforced plastic (FRP) hot sticks are the most common tool used in live working on 10-kV overhead power lines. However, the flashover voltage of hot sticks significantly decreases with increase in altitude. Until now, test data for live working in areas where the altitude exceeds 3000 m have not been available. In this paper, an experimental study on the flashover performance of the FRP hot sticks was carried out in different high-altitude areas. Power frequency discharge tests were performed in Yambajan (4300 m), Lhasa (3600 m), Nyingchi (2900 m), and Wuhan (28 m), respectively. The flashover characteristics in different areas were obtained and analyzed, and a voltage correction method was proposed. Based on these test results, the minimum approach distance of hot stick in high-altitude conditions was determined, and the safety margin was verified. The test results show that for altitudes between 2500 and 4500 m, the hot stick flashover voltage decreases by 7.725% with every 1000 m of altitude increase, and the minimum approach distance of hot stick is 0.6 m (without end fitting) and 0.9 m (with end fitting), and the safety margin is 3.

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

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.

Calculation of safe speed and minimally admissible distance of closing of ships during radar information usage

Exceeding the safe speed and the minimum allowable distance when ships approach each other is considered as one of the main reasons for their collision, especially when using radar information when sailing in reduced visibility or in confined areas. When assigning a safe speed, among other factors, the rules recommend to take into account the state of visibility of the maneuverable capabilities of the ship, especially the distance required to completely stop the ship, as well as the characteristics, efficiency and limitations of radar equipment. But, besides the quality recommendations in the COLREGs, there are no quantitative estimates of the safe speed and excessive convergence of the ships. Each navigator subjectively assigns a safe speed and determines the minimum allowable approach distance for ships. Therefore, the development of a universal method for calculating safe speed and the minimum allowable distance when using radar information is relevant, and the method itself is effective when used on ships, especially when sailing in difficult navigation areas and with limited visibility. The developed method allows to automate the choice of safe speed and eliminate the subjective factor when it is appointed navigator

Flight behavior of targeted fishes depends on variables other than fishing

Behavioral changes due to human predation can affect the functional role of targeted fishes and has implications for ecosystem and fisheries management. Wariness of targeted fishes towards divers, often measured as flight initiation distance (FID), has been shown to increase in areas where spear fishing pressure is higher. Additional research is required to understand how these patterns vary among different species and places. To support such studies, there is a need to explore the relationship of approach starting distance (SD) and other variables that influence measures of fish wariness. We used stereo video to record FID, a new direct measure of minimum approach distance (dMAD), and escape responses of targeted reef fishes in a marine reserve and heavily fished area in Hawai’i. We investigated the role of SD and 15 other variables in influencing FID and dMAD and tested differences between the reserve and fished area. SD explained a large portion of the variability in FID and somewhat less variability in dMAD. FID and dMAD were higher when fishes were travelling (vs feeding), increased with fish body length, and decreased with depth. When including these co-variates in models of FID and dMAD of targeted reef fishes, we found significant differences between study sites for dMAD, though not for FID. We also found differences in escape responses between sites. Based on these results, we recommend using stereo video to conduct measures of dMAD as a complement or alternative to FID, while simultaneously measuring SD and collecting additional data such as escape response. Relative effect sizes of SD and, to a lesser extent, other co-variates were large in comparison to site. Studies that use similar methods and do not control for or incorporate SD may produce biased results with regard to the effects of fishing pressure on flight behavior of targeted fishes.

Human and the beast-Flight and aggressive responses of European bison to human disturbance.

Large mammals are often a source of conflict, and consequently there has been increasing interest in close encounters with them. Knowledge of wildlife responses to human disturbance is crucial for the management of increasing and expanding populations of large animals. We investigated flight initiation distance (FID) and aggressive responses of the European bison–the largest terrestrial mammal of Europe–to human disturbance in the Białowieża Forest (NE Poland). When encountered by humans, bison usually flee. Aggression was observed in only 0.4% of approach attempts. Mean FID was 77±46 m and was influenced by habitat, sex, and supplementary feeding intensity. Females showed greater timidity than males, FID was lower in forest than in open habitats, and supplementary feeding caused a drop in FID. In 84.5% of all documented aggression cases, bison attacks were provoked by humans approaching too close to the bison or by deliberate scaring them. Males were more aggressive than females, and attacked mainly during the rut, while females attacked during the winter and calving. Bison attacked in built-up areas significantly more often than expected. The mean critical distance of attacks was 21±2 m. Most attacks took the form of a short chase preceded by warning signs. Goring was observed in 22.7% of all aggression cases and no fatalities were recorded. Our study shows that bison are not dangerous animals and only manifest aggression in response to prolonged disturbance at close ranges. The education of people and recommendations for minimum approach distances should ensure a low rate of disturbance and safety when encountering large mammals.

Scuba diving and sedentary fish watching: effects of photographer approach on seahorse behavior

ABSTRACTScuba diving tourism represents a growing non-extractive use of the marine environment, being an important income source for coastal communities. However, the activity can cause impacts on benthic sessile organisms by abrading tissues or breaking physical structures. The effects of scuba diving on fishes are less studied and there is no consensus about the impacts caused. We investigated if scuba divers are causing behavioral disruptions on seahorses. Divers using and not using cameras were observed while watching seahorses. We recorded the minimum distance that divers approached, the duration of interaction and physical contacts with seahorses, and the behavioral response of seahorses. Divers using action cameras attached to an extension pole approached the seahorses more closely, causing significantly more behavioral disruptions (escape) and physical contact with them. These repeated behavioral disruptions may negatively impact seahorse habits, such as feeding, reproduction, and resting. To mitigate the potential impacts on seahorses, we recommend the establishment of a minimum approach distance of 36 centimeters, the use of a pre-dive briefing to reinforce low-impact diving techniques, and close supervision by dive leaders to ensure appropriated in-water diver behavior.

Modeling of mixed-solvent electrolyte systems

Models for mixed-solvent strong electrolytes, using an equation of state (EoS) are reviewed in this work. Through the example of ePPC-SAFT (that includes a Born term and ionic association), the meaning and the effect of each contribution to the solvation energy and the mean ionic activity coefficient are investigated. The importance of the dielectric constant is critically reviewed, with a focus on the use of a salt-concentration dependent function. The parameterization is performed using two adjustable parameters for each ion: a minimum approach distance (σMSA) and an association energy (εAB). These two parameters are optimized by fitting experimental activity coefficient and liquid density data, for all alkali halide salts simultaneously, in the range 298 K–423 K. The model is subsequently tested on a large number of available experimental data, including salting out of Methane/Ethane/CO2/H2S. In all cases the deviations in bubble pressures were below 20% AADP. Predictions of vapor-liquid equilibrium of mixed solvent electrolyte systems containing methanol, ethanol are also made where deviations in bubble pressures were found to be below 10% (AADP).

Keeping pace with technology: drones, disturbance and policy deficiency

This paper analyses regulatory responses to rapid intensification of the use of drones/remotely piloted aircraft (RPA) in the context of wildlife protection. Benefits and disadvantages of the technology to wildlife are examined, before three key limitations in policy and law are identified: failure to address wildlife disturbance in RPA regulation; reliance upon insufficiently comprehensive existing wildlife protection legislation to manage disturbance effects; and limited species-specific research on disturbance. A New Zealand case study further reveals an inconsistent regulatory approach struggling to keep pace with innovation, inadequate regulatory capture of environmental effects due to exemption as “aircraft”, and no recognition that specific geographical locations, such as coastal areas, distinguished by recreational pressures and high numbers of threatened species require special consideration. Recommendations include acknowledging the impact on wildlife in policy, gap analysis of legal arrangements for protection from disturbance (including airspace), and adoption of minimum approach distances to threatened species.

Wariness of reef fish to passive diver presence with varying dive gear type across a coral reef depth gradient

Both active and passive human interactions with reef fish communities are increasingly recognized to cause fish behavioural changes. However, few studies have considered how these behavioural adaptations impact standard reef survey techniques, particularly across natural gradients of interest to ecologists and reef managers. Here we measure fish abundance, biomass and minimum approach distance using stereo-video surveys to compare the effects of bubble-producing open-circuit scuba vs near-silent closed-circuit rebreathers. Surveys extended across a shallow to upper-mesophotic gradient on the fringing reefs of Utila, Honduras, to explore how the effects of diver gear choice vary with depth. For most fish families we recorded similar abundances and biomass with the two diving techniques, suggesting that open-circuit transects are generally appropriate for surveying western Atlantic reefs similar to Utila with regular tourist diving but no spearfishing. Despite no overall significant difference in fish abundance or biomass, we identified several fish families (Labridae, Pomacentridae, Scaridae) that allowed closed-circuit rebreather divers to approach more closely than open-circuit divers. In addition, smaller fish generally allowed divers to approach more closely than larger fish, and in most cases divers could approach fish more closely on mesophotic than shallow reefs. Despite these significant differences in approach distances, their magnitude suggest they are unlikely to affect reef fish detectability during normal fish surveys for most families. Our findings highlight the importance of considering variation in fish behavioural adaptations along natural gradients such as depth, which otherwise has the potential to cause biases when surveying by traditional monitoring programmes.

Fish wariness is a more sensitive indicator to changes in fishing pressure than abundance, length or biomass.

Identifying the most sensitive indicators to changes in fishing pressure is important for accurately detecting impacts. Biomass is thought to be more sensitive than abundance and length, while the wariness of fishes is emerging as a new metric. Periodically harvested closures (PHCs) that involve the opening and closing of an area to fishing are the most common form of fisheries management in the western Pacific. The opening of PHCs to fishing provides a unique opportunity to compare the sensitivity of metrics, such as abundance, length, biomass and wariness, to changes in fishing pressure. Diver-operated stereo video (stereo-DOV) provides data on fish behavior (using a proxy for wariness, minimum approach distance) simultaneous to abundance and length estimates. We assessed the impact of PHC protection and harvesting on the abundance, length, biomass, and wariness of target species using stereo-DOVs. This allowed a comparison of the sensitivity of these metrics to changes in fishing pressure across four PHCs in Fiji, where spearfishing and fish drives are common. Before PHCs were opened to fishing they consistently decreased the wariness of targeted species but were less likely to increase abundance, length, or biomass. Pulse harvesting of PHCs resulted in a rapid increase in the wariness of fishes but inconsistent impacts across the other metrics. Our results suggest that fish wariness is the most sensitive indicator of fishing pressure, followed by biomass, length, and abundance. The collection of behavioral data simultaneously with abundance, length, and biomass estimates using stereo-DOVs offers a cost-effective indicator of protection or rapid increases in fishing pressure. Stereo-DOVs can rapidly provide large amounts of behavioral data from monitoring programs historically focused on estimating abundance and length of fishes, which is not feasible with visual methods.

Trophy hunting and perceived risk in closed ecosystems: Flight behaviour of three gregarious African ungulates in a semi-arid tropical savanna

Although being an important conservation tool in Africa, trophy hunting is known to influence risk perception in wildlife species, thus affecting the behaviour and fitness of most targeted species. We studied the effects of trophy hunting on the flight behaviour of impala (Aepyceros melampus), greater kudu (Tragelaphus strepsiceros) and sable (Hippotragus niger) in two closed ecosystems, Cawston Ranch (hunting area) and Stanley and Livingstone Private Game Reserve (tourist area), western Zimbabwe. Using standardized field procedures, we assessed the flight behavioural responses of the three species in two seasons: non-hunting (December–March) and hunting (April–November) between March 2013 and November 2014. We tested the effect of habitat, group size, sex, season, start distance and alert distance on flight initiation distance using linear mixed models. Habitat, group size sex and alert distance did not have any effect on flight initiation distance for the three species. The three species were more alert and displayed longer flight initiation distances in the hunting area compared with the tourist area. Flight initiation distances for the three species were higher during the hunting season for the hunting area and low during the non-hunting season. Flight distances of the three species did not differ between the hunting area and the tourist area. We concluded that trophy hunting increased perceived risk of wild ungulates in closed hunting areas, whereas ungulates in non-hunting areas are less responsive and somehow habituated to human presence. Management plans should include minimum approach distances by tourists as well as establishing seasonal restrictions on special zones to promote species viability. Research aimed at integrating behavioural responses with physiological aspects of target species should be promoted to ensure that managers are able to deal with the behavioural trade-offs of trophy hunting at local and regional scale.

Responses of Australian sea lions, Neophoca cinerea, to anthropogenic activities in the Perth metropolitan area, Western Australia

Abstract Tourist‐based activities, partly due to their rapid increase, have raised concerns regarding the impacts of anthropogenic activity on marine fauna. Documented effects on pinnipeds in proximity to humans include changes in behaviour, site use and potentially higher aggression levels towards people. Effects vary considerably between populations and sites, thus requiring separate assessment of human impacts on activity and energy budgets. Responses of the endangered Australian sea lion, Neophoca cinerea, to human visitation were recorded from November 2013 through April 2014. Exposure levels and response types to anthropogenic activities were assessed at two easily accessible locations with different management schemes, Seal (landing prohibited) and Carnac (landing permitted) islands, Western Australia. Exposure levels were measured as both stimulus type (i.e. ‘People’, ‘Paddlers’, ‘Small’, ‘Medium’, and ‘Large vessels’, ‘Tour vessels’, and ‘Jet skies’), and people (‘Direct’, ‘Attract’, ‘Interact’, ‘View’, ‘Incidental’, ‘Water’, ‘Low‐level’), and vessel activities (‘Interact’, ‘Approach/Follow’, ‘Anchor noise’, ‘Engine noise’, ‘Close to beach’, ‘Moderate/Fast travel’, ‘Slow travel’, ‘Transit’, ‘Drift/At anchor’, ‘Aircraft noise’). Exposure levels varied significantly between the islands in numbers, stimuli type, duration and minimum approach distances. The instantaneous behaviours of ‘Lift head’, ‘Interact’ and ‘Sit’ were the most frequent responses. ‘Aggressive’ and ‘Retreat’ responses, the highest disturbance levels measured, occurred on Carnac approximately once per day, but rarely on Seal Island. ‘Aggressive’ behaviour towards ‘People’ was observed only on Carnac Island and elicited only by ‘People’. ‘People’, ‘Tour vessels’, and scenic ‘Aircrafts’ on both islands as well as ‘Jet skis’ on Carnac Island had the highest probability of triggering responses. Owing to their relatively high visitation at Seal Island, ‘Paddle powered vessels’, followed by ‘Tour vessels’ elicited the highest number of responses, compared with ‘People’, ‘Small’, and ‘Medium vessels’ at Carnac Island. The majority of responses occurred when any stimulus type was at short‐range (≤10 m), and ‘People’ ‘Viewing’ N. cinerea elicited most. Vessels triggered more responses at larger ranges than ‘People’. To limit close‐range access to N. cinerea, one possibility is to close the beach at Carnac Island to human visitation and increase the minimum approach distance by vessels and ‘People’ by installing marker buoys at least 15 m from the shore. © 2016 The Authors. Aquatic Conservation: Marine and Freshwater Ecosystems published by John Wiley & Sons, Ltd.

Calculation of minimum approach distances for tools for live-line working under freezing conditions

IEEE Std. 516-2009 and IEC 61472-2013 present Minimum Approach Distance (MAD) requirements for tools to perform live maintenance safely, provided that the tool has no continuous film of moisture or measurable contamination present on its surface. However, four separate clean FRP hot-stick flashover incidents occurred in Canada under steady-state system conditions at the peak of the voltage negative half-cycle during cold and freezing conditions. This paper investigates IEC and IEEE methods of calculating MAD for tools employed for live working done on the geometry of the Manitoba site incidents at 500-kV. Based on cold fog tests carried out at CIGELE to reproduce these incidents, guidelines for calculating MAD in cold and freezing climate regions are proposed.

The coefficient of normal restitution for the Hertzian contact of two rough spheres colliding in a viscous fluid

We use previous theoretical results for the added mass, history and lubrication forces between two spheres colliding in a fluid with viscosity ν to investigate the effect of viscous dissipation on the coefficient of restitution during contact. We assume that the mechanical interaction is governed by Hertzian mechanical contact of small duration τ and that the minimum approach distance between particles is approximately equal to the height σ of surface micro-asperities. A non-dimensionalization of the equation of motion indicates that the contact dynamics is governed by two parameters – the ratio ϵ of the surface roughness σ and the sphere radius a, and a contact Stokes number defined as Stc=σ2/ντ. An asymptotic solution of the equation of motion in the limit of small ϵ/Stc is used to obtain an explicit expression for the coefficient of restitution during contact and the latter is compared with estimates based on numerical solutions of the non-linear equation of motion.

Database of Bird Flight Initiation Distances to Assist in Estimating Effects from Human Disturbance and Delineating Buffer Areas

AbstractU.S. Fish and Wildlife Service biologists determine effects from disturbance to threatened and endangered bird species, and staffs of federal and state agencies estimate these effects when delineating protective buffers around habitat of bird species of concern on land management areas. These efforts can be informed by the distances at which human activities cause birds to react or move away. To that end, here we present a database of published alert distances (distances at which birds exposed to an approaching human activity exhibit alert behavior), flight initiation distances (distances at which birds exposed to an approaching human activity initiate escape behavior), and minimum approach distances (distances at which humans should be separated from wildlife). The database distinguishes between nesting and nonnesting situations. The nesting database includes 578 alert distances and 2,177 flight initiation distances from 45 studies representing 11 orders, 27 families, and 49 species of birds. The nonnesting database comprises 1,419 alert distances and 34,775 flight initiation distances from 50 studies representing 19 orders, 89 families, and 650 species.

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

We present a framework to elucidate the influence of polydispersity on flow-induced diffusion in active microrheology. A colloidal probe particle is driven through a suspension of hydrodynamically interacting background particles, where the probe may be larger or smaller than the bath particles. The thermodynamic size of the particles may be greater than their hydrodynamic size; the hydrodynamic sizes can be identical with thermodynamic sizes that differ, or vice versa, or a combination of both. The 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. We find that reducing the size of the probe reduces flow-induced diffusion when hydrodynamic interactions are weak but increases flow-induced diffusion when hydrodynamic interactions are strong-regardless of the strength of external forcing. This behavior owes its origins to a rich evolution of the dominance of hydrodynamic and entropic forces with changes in the relative hydrodynamic and thermodynamic sizes of the particles.

Effectiveness of Safe Working Procedure on SMF Exposure Levels and Work Performances in 3 T MRI System Operations

Occupational exposure to static magnetic fields (SMF) is a concern in relation to magnetic resonance imaging (MRI) system operators. Bodily movements inside the stray field around an MRI system induce an electric current inside the body, and this magnetically induced current can cause temporary sensational changes. Although self-motivated motion control near MRI equipment is recommended in order to prevent these effects, a feasible and safe working procedure is required from a health and safety management viewpoint. In this paper, a procedure involving a restricted access area set at a distance of 30 cm from the end of a 3 T MRI system is compared with a protocol in which self-motivated motion control was used (as recommended by the International Commission on Non-Ionizing Protection guidelines). The effects of this safe working procedure on occupational SMF exposure levels and worker performance were evaluated using Hall sensors and a motion capture system. Subjects performed the protocol for head MRI examination both with and without the proposed safe working procedure. The values for maximum field exposure (peak B) were reduced for all subjects using the safe working procedure. The average peak B also decreased by approximately 26%, compared with the results obtained without any restrictions (conventional protocol) ( $p , $t$ -test). Motion analysis of the subjects indicated that the minimum approach distance to the MRI equipment increased due to the adoption of the restricted access area ( $p , $t$ -test), while slight changes were also observed in sojourn time and the differences of the position along the $z$ -axis ( $\Delta z$ , $p , $t$ -test). However, there were no significant differences in the parameters more closely related to worker performance (e.g., distance moved and velocity) when using the protocols with or without the safe working procedure. These results suggest that this simple safe working procedure may be applied to MRI system operation in order to reduce occupational SMF exposure, without noticeable changes in worker performance.

The effects of vessel approaches on the New Zealand fur seal (Arctocephalus forsteri) in the Bay of Plenty, New Zealand

AbstractAnimals that establish new sites near the edge of the species' range may be vulnerable to disturbance as they are low in numbers and are not tied to the sites. Pinniped distributions world‐wide are changing as many species are recolonizing areas of their former ranges and establishing new colonies. Little research is available on the impact that vessel presence may pose on pinnipeds at such sites. This study documents responses of New Zealand fur seals to vessels in the Bay of Plenty, New Zealand, at a recently established breeding colony. Fur seal behavior at the breeding location was recorded in the presence of vessels. GLMM and GAM analyses revealed that fur seal responses varied with month, time of day, duration of vessel exposure, and the distance to the vessel. Age and sex of the seals, and the number of seals present also influenced fur seal response. Fur seals at this site became disturbed when vessels approached to the 10–20 m distance category, and a precautionary minimum approach distance of 50 m has been suggested. This research provides direction for monitoring and minimizing impacts of vessels on fur seals, especially where new sites are being colonized.