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a b s t r a c tThis paper investigates the behaviour of subgroups in crowd dynamics by means of filming and observation. An existing crowd modelling program, CrowdDMX, based on a discrete element model (DEM) has been modified on the basis of observations made in this paper and literature. Each person is represented as three overlapping circles and motion is modelled in a Newtonian manner. It incorporates psychological forces as well as physical forces in a 2D time-stepping environment. The DEM model was modified to include realistic subgroup behaviour, representing people in the crowd desiring to stay together (families, friends, etc.). Subgroup psychological forces were incorporated. The previous model only simulated individuals moving independently, which was unrealistic in some situations as shown by the observation and filming part of the study. The revised program models subgroups realistically including the tendency to avoid subgroup division in cases of contra-flow.

The way an object is released by the passer to a partner is fundamental for the success of the handover and for the experienced fluency and quality of the interaction. Nonetheless, although its apparent simplicity, object handover involves a complex combination of predictive and reactive control mechanisms that were not fully investigated so far. Here, we show that passers use visual-feedback based anticipatory control to trigger the beginning of the release, to launch the appropriate motor program, and adapt such predictions to different speeds of the receiver’s reaching out movements. In particular, the passer starts releasing the object in synchrony with the collision with the receiver, regardless of the receiver’s speed, but the passer’s speed of grip force release is correlated with receiver speed. When visual feedback is removed, the beginning of the passer’s release is delayed proportionally with the receiver’s reaching out speed; however, the correlation between the passer’s peak rate of change of grip force is maintained. In a second study with 11 participants receiving an object from a robotic hand programmed to release following stereotypical biomimetic profiles, we found that handovers are experienced as more fluent when they exhibit more reactive release behaviours, shorter release durations, and shorter handover durations. The outcomes from the two studies contribute understanding of the roles of sensory input in the strategy that empower humans to perform smooth and safe handovers, and they suggest methods for programming controllers that would enable artificial hands to hand over objects with humans in an easy, natural and efficient way.

We explore a surprising phenomenon in which an obstruction accelerates, rather than decelerates, a moving flexible object. It has been claimed that the right kind of discrete chain falling onto a table falls faster than a free-falling body. We confirm and quantify this effect, reveal its complicated dependence on angle of incidence, and identify multiple operative mechanisms. Prior theories for direct impact onto flat surfaces, which involve a single constitutive parameter, match our data well if we account for a characteristic delay length that must impinge before the onset of excess acceleration. Our measurements provide a robust determination of this parameter. This supports the possibility of modeling such discrete structures as continuous bodies with a complicated constitutive law of impact that includes angle of incidence as an input.

Seeds are the crucial input in agriculture as most of the world food crops are grown from seeds and they are circulated at large scale in international trade. However, many plant pathogens can be seed transmitted, and seed distribution is an extremely capable way of introducing plant pathogens into fresh areas as well as a means of endurance of the pathogen between growing seasons. In past decades, chemicals are widely used for seed treatment as a potent approach towards disease control; however, rising concern about their negative impact on the environment and human health minimizes their use and promotes biological control for plant pathogens. Biopriming is a currently popular approach of seed treatment which includes inoculation of seed with beneficial microorganisms (biological aspect) and seed hydration (physiological aspect) to protect the seed from various seed-and soilborne diseases. Biopriming treatment is able to incite changes in plant characteristics and facilitate uniform seed germination and growth associated with microorganism inoculation. Seed priming and osmo-priming are commonly being used in many horticultural crops to amplify the growth and uniformity of germination. However, it may be used alone or in combination with biocontrol agents to advance the rate of seed emergence and minimize soilborne diseases. On the other hand, some biocontrol agents are used as seed dressers and are able to colonize the rhizosphere, helping seeds to resist various abiotic stresses