Inbound Journey Research Articles

Visual route following for tiny autonomous robots.

Navigation is an essential capability for autonomous robots. In particular, visual navigation has been a major research topic in robotics because cameras are lightweight, power-efficient sensors that provide rich information on the environment. However, the main challenge of visual navigation is that it requires substantial computational power and memory for visual processing and storage of the results. As of yet, this has precluded its use on small, extremely resource-constrained robots such as lightweight drones. Inspired by the parsimony of natural intelligence, we propose an insect-inspired approach toward visual navigation that is specifically aimed at extremely resource-restricted robots. It is a route-following approach in which a robot's outbound trajectory is stored as a collection of highly compressed panoramic images together with their spatial relationships as measured with odometry. During the inbound journey, the robot uses a combination of odometry and visual homing to return to the stored locations, with visual homing preventing the buildup of odometric drift. A main advancement of the proposed strategy is that the number of stored compressed images is minimized by spacing them apart as far as the accuracy of odometry allows. To demonstrate the suitability for small systems, we implemented the strategy on a tiny 56-gram drone. The drone could successfully follow routes up to 100 meters with a trajectory representation that consumed less than 20 bytes per meter. The presented method forms a substantial step toward the autonomous visual navigation of tiny robots, facilitating their more widespread application.

Door-in-door-out times for patients with large vessel occlusion ischaemic stroke being transferred for endovascular thrombectomy: a Victorian state-wide study

BackgroundTime to reperfusion is an important predictor of outcome in ischaemic stroke from large vessel occlusion (LVO). For patients requiring endovascular thrombectomy (EVT), the transfer times from peripheral hospitals in...

Role of the pheromone for navigation in the group foraging ant, Veromessor pergandei.

Navigation is comprised of a variety of strategies which rely on multiple external cues to shape a navigator's behavioral output. Here, we explored in the ant Veromessor pergandei, the interactions between the information provided by the pheromone trail and the home vector guided by the celestial compass. We found that a cross sensory interaction between the pheromone cue and the path integrator underlies correct orientation during the inbound journey. The celestial compass provides directional information, while the presence of the trail pheromone acts as a critical context cue, triggering distinct behaviors (vector orientation, search, and backtracking). While exposed to the pheromone, foragers orient to the vector direction regardless of vector state, while in the pheromone's absence, the current remaining vector determines the forager's navigational behavior. This interaction also occurs in foragers with no remaining path integrator, relying on the activation of a celestial compass-based memory of the previous trip. Such cue interactions maximize the foragers' return to the nest and inhibit movement off the pheromone trail. Finally, our manipulations continuously rotated foragers away from their desired heading, yet foragers were proficient at counteracting these changes, steering to maintain a correct compass heading even at rotational speeds of ~ 40°/s.

Airline choice model for an international round-trip flight considering outbound and return flight schedules

This paper quantified the impact of outbound and return flight schedule preferences on airline choice for international trips. Several studies have used airline choice data to identify preferences and trade-offs of different air carrier service attributes, such as travel time, fare and flight schedule. However, estimation of the effect return flight schedules have on airline choice for an international round-trip flight has not yet been studied in detail. Therefore, this study introduces attributes related to return flight characteristics and round-trip flight schedule interaction into the airline choice models, which have not previously been reported in the literature. We developed a stated preference survey that includes round-trip fares based on flight schedule combinations and the number of days prior to departure fares was purchased. We applied modelling techniques using a set of stated preference data. A mixed logit model was tested for the presence of heterogeneity in passengers' preferences. Our results indicated that models with attributes related to return flight and its interaction with outbound flight attributes have a superior fit compared with models only based on attributes reported in the literature review. The model found shows that airfare, travel time, arrival preference schedule in the outward journey, departure preference in the return journey and the schedule combination of round-trip flight are significantly affecting passenger choice behaviour in international round-trip flights. Sensitivity analysis of airline service characteristics and their marketing implications are conducted. The analysis reports seven policies with the greatest impact on each airline choice probabilities. It shows that by reducing travel time and airfare and by adopting an afternoon and night schedule preference for outbound and return flight, respectively, the highest probability on airline choice would be reached. This research contributes to the current literature by enhancing the understanding of how passengers choose airlines, considering both outbound and inbound journey characteristics. Thus, this study provides an analytical tool designed to provide a better understanding of international round-trip flight demand determinants and support carrier decisions.

Polarized light use in the nocturnal bull ant, Myrmecia midas.

Solitary foraging ants have a navigational toolkit, which includes the use of both terrestrial and celestial visual cues, allowing individuals to successfully pilot between food sources and their nest. One such celestial cue is the polarization pattern in the overhead sky. Here, we explore the use of polarized light during outbound and inbound journeys and with different home vectors in the nocturnal bull ant, Myrmecia midas. We tested foragers on both portions of the foraging trip by rotating the overhead polarization pattern by ±45°. Both outbound and inbound foragers responded to the polarized light change, but the extent to which they responded to the rotation varied. Outbound ants, both close to and further from the nest, compensated for the change in the overhead e-vector by about half of the manipulation, suggesting that outbound ants choose a compromise heading between the celestial and terrestrial compass cues. However, ants returning home compensated for the change in the e-vector by about half of the manipulation when the remaining home vector was short (1−2 m) and by more than half of the manipulation when the remaining vector was long (more than 4 m). We report these findings and discuss why weighting on polarization cues change in different contexts.

GPS tracking reveals rafting behaviour of Northern Gannets (Morus bassanus): implications for foraging ecology and conservation

Capsule Three quarters of tracked Northern Gannets (Morus bassanus) at Grassholm gathered in rafts around the colony, concentrated within a recently designated at-sea Special Protection Area (SPA), but rafting was not correlated with foraging effort.Aims To investigate the incidence, distribution and foraging implications of Northern Gannet rafting behaviour in waters adjacent to a large colony.Methods Using bird-borne global positioning system (GPS) loggers we reconstructed at-sea movement and used a speed filter to identify rafting behaviour within 10 km of the colony. We mapped the spatial distribution of rafting events from 160 breeding individuals over 5 years, and investigated the relationship between foraging effort (trip duration and total distance travelled) and the presence/absence of rafting.Results On average, 74% of tracked birds engaged in rafting. Of the 381 foraging trips analysed, rafting was recorded on 237 (62%). Birds were more likely to raft on outbound (224 trips, 59%), than inbound journeys (38 trips, 10%). Presence/absence of rafting did not correlate significantly with foraging trip distance or duration nor with duration of nest attendance. The majority of rafting was concentrated in a 2-km radius around the colony within a recently designated seaward SPA extension. Birds showed low individual repeatability in rafting, although there was lower variation within, than among, individuals.Conclusion Our results show that rafting is important for breeding gannets on Grassholm, and a recently designated at-sea SPA encapsulates the core distribution of rafting. Rafting did not appear to be correlated with foraging behaviour. Given the dearth of literature on rafting and the wealth of GPS tracking data for seabirds, we suggest that similar research be conducted elsewhere to further elucidate the ecological and applied significance of this behaviour.

Anticipated ambiguity prolongs the present: Evidence of a return trip effect.

Every event that can occupy a span of time can also warp how long that duration feels. No shortage of factors configures such duration estimates, yet they remain largely confined to events experienced in the present moment. Might future events similarly impact duration? The present investigation leverages a phenomenological return trip effect, which documents subjectively longer outbound journeys relative to identical inbound journeys, to inform this question. Through this lens, the focal event (that which will transpire at the destination) can be decoupled from the focal duration (the span of time between the present moment and arrival at that destination). Four studies document a consistent effect in which ambiguity awaiting at a future event (occurring at the destination) expands the subjective magnitude of present durations (the travel time to the destination). Duration judgments thus appear sensitive to an increasingly broad scope of factors, informing models of temporal cognition. (PsycINFO Database Record

A Bivariate Multinomial Probit Model for Trip Scheduling: Bayesian Analysis of the Work Tour

As tour-based methods for activity and travel participation patterns replace trip-based methods, time-of-day (TOD) choice modeling remains problematic. In practice, most travel demand model systems handle tour scheduling via joint-choice multinomial logit (MNL) models, which suffer from the well-known independence of irrelevant alternatives assumption. This paper introduces a random utility maximization model of tour scheduling called the bivariate multinomial probit. This specification enables correlations across TOD alternatives, both outbound and return (on a tour) and over time slots (in a day). The model is estimated in a Bayesian setting on work-tour data from the San Francisco Bay Area with 30-minute time slots at most times of day (for both outbound and inbound journeys). Empirical results suggest that a variety of individual, household, and tour characteristics have reasonable effects on scheduling behavior. For instance, older persons typically pursue work tours at earlier times of day, part-time workers pursue their work tours later, and those with additional activities and tours tend to arrive slightly later and leave much earlier than those undertaking only a single tour, everything else constant. The model outperforms a comparable MNL, while offering reasonable implications under a variety of road-tolling scenarios.

Load affects human odometry for travelled distance but not straight-line distance

In a simple homing task with human participants, we disassociated the outbound distance travelled from the straight-line distance between home and target. Prior to the outbound journey, which involved a detour, participants were given one of two instructions concerning the inbound journey, which did not involve a detour: to walk the distance travelled or to walk to home. The inbound journey under each intention, made with eyes closed at a self-selected pace, was the measure of the perceived distance. We conducted two experiments that differed in whether or not the detour and target were visible during the outbound journey. In both experiments, we manipulated the load carried in the outbound journey (0% or 20% body weight) and the speed (fast or slow) of the outbound journey. The outcome of both experiments was that, indifferent to speed, participants perceived the distance travelled with load to be longer than that travelled without load, but perceived home's straight-line distance from target to be the same for both load conditions. Perceptions of travel distance and straight-line distance seem to be based on different information kinds and to refer to different animal–environment relations. In identifying neural mechanisms supportive of navigation, straight-line distance versus travelled distance may prove to be a productive distinction.

How flexible is the systematic search behaviour of desert ants?

Foraging desert ants, Cataglyphis fortis , rely on path integration for navigation. If the path integrator has not led them to the exact position of the point of departure, the nest entrance, they start a systematic search for the nest. Previous studies have shown that the longer the preceding outbound run has been the less confidence an ant has in its path integrator. This lower confidence is expressed by wider search loops. In this study, we investigated whether additional cues influence the systematic search patterns of desert ants. We captured ants that were trained to a feeder, either at different points during their inbound journeys or when they were about to enter the nest. They were then transferred to an unfamiliar test area, within which their paths were recorded. Most of the ants captured along their inbound path reeled off the remaining part of their runs and then commenced their nest search, whereas those captured at the nest entrance started searching for the nest entrance immediately. The latter group of ants had far narrower search patterns than ants that were captured during their inbound runs, irrespective of search path length (20, 40 or 50 m). This indicates that the ants' systematic search behaviour is more flexible than assumed hitherto. We compare the results with two previous studies and discuss different potential cues that ants could use to adapt their search patterns.

Homing in the wolf spider Lycosa tarantula (Araneae, Lycosidae): the role of active locomotion and visual landmarks

Previous studies on the homing of the wolf spider Lycosa tarantula have shown that it is carried out by path integration. Animals using this mechanism must measure the distance walked and the angles turned. This study aims to understand if wolf spider L. tarantula is able to estimate the walked distance in an outward path. As this information is more likely obtained by proprioceptive mechanisms, active or passive displacements have been performed. An active locomotion was found essential to estimate distances. During passive locomotion, spiders searched for their burrows near the release point while when displaced actively the inbound journey was longer than the outbound one. The possible use of visual landmarks near the burrow was also tested as a cue to complete the inbound journey. Our results did not show that L. tarantula used these visual landmarks to find the burrow. L. tarantula seems to use only proprioceptive information obtained during the outbound path to estimate the distance traveled.

Ant Navigation: One-Way Routes Rather Than Maps

In recent years, there has been an upsurge of interest and debate about whether social insects-central-place foragers such as bees and ants-acquire and use cognitive maps, which enable the animal to steer novel courses between familiar sites . Especially in honey bees, it has been claimed that these insects indeed possess such "general landscape memories" and use them in a "map-like" way . Here, we address this question in Australian desert ants, Melophorus bagoti, which forage within cluttered environments full of nearby and more distant landmarks. Within these environments, the ants establish landmark-based idiosyncratic routes from the nest to their feeding sites and select different one-way routes for their outbound and inbound journeys. Various types of displacement experiments show that inbound ants when hitting their inbound routes at any particular place immediately channel in and follow these routes until they reach the nest, but that they behave as though lost when hitting their habitual outbound routes. Hence, familiar landmarks are not decoupled from the context within which they have been acquired and are not knitted together in a more general and potentially map-like way. They instruct the ants when to do what rather than provide them with map-like information about their position in space.

Orientation ofPolyergus rufescens(Hymenoptera, Formicidae) during slave-making raids

We investigated the factors involved in the orientation of raiders of the European Amazon ant,Polyergus rufescensand how these factors are used by raiders during the different phases of slave-making expeditions. Ants at the head of the raiding column did not follow previously deposited chemical trails but oriented by celestial cues. Raiders in the middle of the column used celestial factors but were also strongly affected by the recruiting activity of the ants that preceded them. During the return trip, raiders used both chemical and celestial cues. The latter allowed the ants to assume the correct home direction while following the chemical trail. Perception of the ultraviolet band of the light spectrum was of crucial importance for the orientation of the raiders, during both the outbound and inbound journeys. This supports the hypothesis thatP.rufescensworkers, like other ants, perceive the pattern of polarized skylight in the ultraviolet range.

Three-dimensional particle anisotropies in and near the plasma sheet of Jupiter observed by the EPAC experiment onboard the Ulysses spacecraft

During its inbound journey into Jupiter's magnetosphere, Ulysses had several encounters with the Jovian plasma sheet near the magnetic equator, which were related with intensity maxima in the energetic particles. We show for the first time anisotropies in three dimensions of three ion species (protons, helium and oxygen) in the energy range 0.24 < E < 0.77 [MeV/nucleon]. The data, obtained with the Energetic Particle Composition Experiment (EPAC) onboard Ulysses have been analysed by using spherical harmonics in three dimensions. We show that the first-order anisotropies of ions in or near the plasma sheet are strongest in a plane parallel to the ecliptic plane and more or less azimuthal with respect to the rotation of Jupiter. We show that the first-order anisotropy amplitude is larger for helium and oxygen ions than for protons in nearly the same energy per nucleon range. We find flow velocities for helium ions which are not consistent with corotation, but are larger by a factor of 2 in and near the Jovian plasma sheet on the dayside magnetosphere. In contrast for protons we observe nearly corotation. Far from the plasma sheet, at high magnetic latitudes, the flow velocities are less than corotation for protons, as well as for helium and oxygen. The azimuthal particle anisotropies are explained by intensity gradients perpendicular to the centre of the plasma sheet, by E × B particle drifts, and by nonadiabatic orbits of the particles near the Jovian plasma sheet. All of the three phenomena act in the same azimuthal direction, perpendicular to the mainly radial magnetic field direction. Each of them can be estimated, but their individual effects cannot be distinguished from each other. In addition, we find a radial component of the anisotropy which apparently is stronger for protons than for heavier ions. This radial anisotropy component is interpreted as a result of the radial outward displacement of ions in an azimuthally swept back magnetic field.

Energetic particle, plasma and magnetic field signatures of a poloidal pulsation in Jupiter's magnetosphere

During its February 1992 inbound journey into Jupiter's magnetosphere, Ulysses made several near-encounters with (and actual traversals of) the Jovian magnetodisk. In at least one such event (investigated here) the anticipated variations in energetic particle fluxes, plasma density, magnetic field intensity, and magnetic field direction at the planetary rotation period were further modulated (strongly and quasi-periodically) at a higher frequency, as if the magnetodisk and magnetic-equatorial surface were “flapping” relative to the position of the spacecraft. This additional modulation occurred around 14: 00–19: 00 U.T. on 7 February (Day 38) 1992, with Ulysses at a nominal (dipolar) magnetic latitude ≈ 11°–22° and at a zenocentric distance r ≈ 18–22 R j. The quasi-period 2π/Ω revealed by autocorrelation analysis of the energetic-proton data (and confirmed by visual examination of plotted data from the various instruments) was about 6.8 ks (≈1.9 h). Oscillations in energetic particle fluxes and plasma density were typically 180° out-of-phase with those in magnetic field intensity. The 6.8 ks period is consistent with oscillation of the magnetic shell of radius r ≈ 21 R j at the second poloidal harmonic, which is the mode that would correspond to a “flapping” of the magnetodisk and (more generally) of the magnetic-equatorial surface.