Cohesive Behaviours Research Articles

The perceptions of task cohesion in collaborative learning teams

Team cohesion is critical in driving successful outcomes for teams in collaborative learning settings. It shapes team behaviour, fostering shared perceptions, group synchrony and a common goal-oriented approach. This affinity becomes evident in dynamic interactions, offering insights into team behaviour through interaction data analysis. Interpreting interaction data proves complex, hampering our understanding and insights into shared team perceptions and task cohesion development. This paper used temporal motif analysis to examine the changes in team members’ cohesive perceptions and behaviours, including task cohesion, performance outcomes, engagement and group synchrony. Trace data from an online work-integrated learning environment captured learning behaviours, while responses to a questionnaire at different stages of a study program captured task cohesion and cohesive perceptions. The findings reveal teams with strong task cohesion and high performance tend to share similar cohesive perceptions driven by interdependent interactions. Conversely, teams with different cohesion perceptions have lower interaction interdependence and poorer performance. Through analysing team interaction data, this study uncovered key insights to promote positive adjustments aligning team perceptions, enhancing collaborative learning and offering support for improved performance, engagement and synchrony among teams, ultimately benefiting learning outcomes and the cultivation of skills and competencies.

Influence of weight ratio of conductive additive to binder in an electrode on the capacity of Li-ion battery

Changes in the charge and discharge capacity of a lithium-ion battery are investigated by varying the percentage weight composition ratios of conductive additive to polymeric binder in an electrode of a lithium-ion battery. The cathode is made of active material (LiMn2O4), binder (PVDF), and conductive additive (carbon black). To investigate the effect of inactive material composition on battery performance experimentally, the weight percentage of active material in the cathode is fixed at 85 wt% and five different ratios of PVDF/carbon black are assessed by varying conductive additive from 1.5 wt% to 13.5 wt% and binder from 13.5 wt% to 1.5 wt% while fabricating lithium-ion batteries. To study particles' cohesive behaviours between inactive materials in the electrode, various SEM images are taken and analysed for five different compositions of carbon black and PVDF. As a result, the improved battery performance is observed at the ratios of 7.5 wt%-10.5 wt% carbon black and 7.5 wt%-4.5 wt% PVDF.

Discontinuous approaches for nonlinear dynamic analyses of an ancient masonry tower

The aim of this paper is to present the development of discontinuous approaches to simulate the nonlinear dynamic behaviour of the civic clock tower of Rotella, in the province of Ascoli Piceno (Italy). The study involves the use of the Non-Smooth Contact Dynamics method implemented in the LMGC90© code, where sliding motions are governed by Signorini's impenetrability condition and dry-friction Coulomb's law, and the Discrete Element Method with cohesive and tensional behaviours at the joints in the 3DEC© code. The tower was represented using three different geometric models ranged from the most complex one, including the full geometry and multi-leaf masonry walls, to the simplest one, including the single-leaf walls as a simplification of the real masonry. The numerical results highlighted the modes of failure depending on the shape, size and texture of the masonry and the modalities of progressive damage under dynamic actions. Moreover, both numerical approaches have proven to be capable of simulating large displacements and complete block separations, reproducing complex mechanical behaviours and making predictions on the vulnerability assessment of the historical masonry buildings.

How youth are socially engaged in parks: a participatory-approach for understanding youth perceptions and use patterns

Parks are often linked to physical activity for youth provided by park equipment and amenities. Yet, urban green spaces and parks can also afford important opportunities for young people to develop a sense of community, identity and be socially engaged. Spending more time in green spaces can significantly impact the satisfaction and well-being of park users. In this respect, the attractiveness of parks to youth is an important factor to support socially cohesive behaviours. Differences in park preferences and user needs are important, particularly since research often seeks to understand where park users of all ages spend their time and with whom, rather than directly measuring their social network. Hence, parks as sustainable community facilities should promote social interactions among youth, and between youth and adults, which can lead to cohesive behaviours integrated into a social setting. In order for park settings to become favoured by youth, they must afford a range of opportunities for youth activities. This research proposes a youth-friendly participatory-approach that includes a multi-day workshop with youth to explore their social interactions in parks in greater depth. Using drawings, freehand mapping, and discussions using aerial photos of local parks can help us understand how youth use parks, and how they relate to other park users.

Who goes there? Social surveillance as a response to intergroup conflict in a primitive termite

Intergroup conflict has been suggested as a major force shaping the evolution of social behaviour in animal groups. A long-standing hypothesis is that groups at risk of attack by rivals should become more socially cohesive, to increase resilience or protect against future attack. However, it is usually unclear how cohesive behaviours (such as grooming or social contacts) function in intergroup conflict. We performed an experiment in which we exposed young colonies of the dampwood termite, Zootermopsis angusticollis, to a rival colony while preventing physical combat with a permeable barrier. We measured social contacts, allogrooming and trophallaxis before, during and after exposure. Termites showed elevated rates of social contacts during exposure to a rival compared to the pre-exposure phase, but rates returned to pre-exposure levels after colonies were separated for 9 days. There was evidence of a delayed effect of conflict on worker trophallaxis. We suggest that social contacts during intergroup conflict function as a form of social surveillance, to check individual identity and assess colony resource holding potential. Intergroup conflict may increase social cohesion in both the short and the long term, improving the effectiveness of groups in competition.

Modelling mixed mode fracture of mortar joints in masonry buildings

Within the framework of Discrete Element Modelling of masonry structures, a contact law based on Cohesive Zone Model and Coulomb’s law is proposed to describe the fracture behaviour of mortar joints. The contact law is expressed in mixed mode I + II and is based on the cohesive behaviours of pure modes I and II and on the frictional behaviour whose parameters can be estimated from an experimental procedure consisting in two fracture tests. Moreover, it is shown from numerical simulations that the contact law exhibits a load path dependency in agreement with the quasi-brittle behaviour expected for mortar. Finally, a parametric study performed from the simulation of the diagonal compression of a masonry panel shows a good agreement of the obtained load-displacement responses and failure modes compared to experimental results of the literature.

On uniaxial compression and Jenike direct shear testings of cohesive iron ore materials

The flow function of an iron ore material governs its flowability characteristics in material handling chains of the resource industry. A uniaxial compression test is able to obtain a flow function more rapidly compared to the Jenike direct shear test, nevertheless, results often exhibit lower rankings using the former method. This study aims to investigate the fundamental stress states within the test specimen that led to this phenomenon, and to introduce a new uniform density specimen preparation method for a uniaxial compression test in order to achieve comparative flow functions as per the Jenike direct shear test. The minimisation of the wall friction effect and the achievement of the critical state when preparing a uniaxial specimen were explicitly discussed. Experimental investigations on flow functions of a suite of Australian iron ore samples were conducted using both the uniform density uniaxial compression test and the Jenike direct shear test. Results from both methods were indicated to be comparable providing the specimen exhibited cohesive flow behaviours. Additionally, a simple compressibility index, based on the bulk density test of iron ore samples, was derived as a threshold to indicate if a uniform density uniaxial compression test can produce flow functions matching the Jenike direct shear test. The outcome of this research enabled a rapid and reliable flow function testing method for cohesive iron ore materials.

A laser irradiation disc test for fracture testing of refractory fine ceramics

Abstract The critical stress intensity factor, tensile strength and crack stability were analysed for a zirconia refractory by parameter identification based on a laser irradiation test and a finite element simulation. Furthermore, the results for the specific fracture energy were determined for different assumed cohesive behaviours. The tests were carried out on notched discs that were irradiated at their centres. During the tests, temperatures are recorded by a thermo vision camera and the crack propagation by an acoustic emission recorder. Acoustic emission allowed for the determination of the onset of crack initiation (time t 1 ) and unstable crack propagation (time t 2 ). A finite element model representing the geometry of the sample was built to determine the fracture mechanical parameters from t 1 and t 2 . This method is believed to be favourable for rather brittle refractory ceramics, whereas for less brittle materials, a wedge splitting procedure according to Tschegg is considered more favourable.

Modelling of soil–seed contact using the Discrete Element Method (DEM)

It has long been recognised that soil–seed contact is vital to seed germination, as good soil–seed contact promotes water transfer from soil to seed. However, until today, it has not been possible to quantify soil–seed contact, due to the non-homogeneous nature of agricultural soil. This study has made a significant step in advancing the field through modelling the soil–seed regime using the Discrete Element Method (DEM). In the soil–seed model, the seed was simplified as a spherical particle, and agricultural soil was represented by an assembly of completely random individual spherical particles exhibiting cohesive and frictional behaviours. Seed placement was simulated in a fashion similar to the field planting process. Model results showed that the number of active contacts between a seed and soil particles varied from 0 to 33, and the contact area varied from 0 to 41 mm 2 , depending on the size and properties of the seed and soil particles. The greatest contact area was observed when the size ratio of soil to seed is 1.33 or 1.75. Higher soil particle stiffness resulted in a reduced number of contacts and smaller contact area. Simulations of press wheel effects in the model showed that when soil is compacted, both number of contacts and contact area are significantly increased. • The discrete element model developed can simulate seed–soil contact characteristics. • Greatest contact area was for size ratio of soil to seed particle of 1.33 or 1.75. • Soil with lower particle stiffness has better seed–soil contact. • Use of press wheel improves seed–soil contact.

Research on deposition and consolidation behaviour of cohesive sediment with settlement column experiment

The deposition and consolidation behaviour of cohesive sediment is studied with a newly developed integrated settlement column system. This system, which includes graduate (glass) and settlement column (PMMA), has been proved an effective way to study the settlement of sediment suspension with 20∼300 g/L initial concentration. Cohesive sediment deposition and consolidation behaviours are as follows: cohesive sediment settlement can be divided into different stages as the initial free settlement and the consolidation settlement with different sediment interface rate. Cohesive sediment settlement influence factors are mainly the initial concentration and the settlement height, from which, settlement column size effect is determined by three factors as the wall effect, convection effect as well as the flocculation effect. During the final weight consolidation stage, deposited sediment consolidation settlement develops much faster than the excessive pore-pressure dissipation, and the fitted nonlinear consolidation constitutive relationship also can be obtained through deposited sediment layer sampling method. Results from this study indicate that the newly developed integrated settlement column system can effectively simulate the cohesive sediment suspension deposition and consolidation, and the nonlinear consolidation characteristics also can be studied through further experiments.

A discrete element model for soil–sweep interaction in three different soils

Soil–tool interactions are at the centre of many agricultural field operations, including slurry injection. Understanding of soil–tool interaction behaviours (soil cutting forces and soil disturbance) is important for designing high performance injection tools. A discrete element model was developed to simulate a slurry injection tool (a sweep) and its interaction with soil using Particle Flow Code in Three Dimensions (PFC3D). In the model, spherical particles with bonds and viscous damping between particles were used to simulate agricultural soil aggregates and their cohesive behaviours. To serve the model development, the sweep was tested in three different soils (coarse sand, loamy sand, and sandy loam). In the tests, soil cutting forces (draught and vertical forces) and soil disturbance characteristics (soil cross-section disturbance and surface deformation) resulting from the sweep were measured. The measured draught and vertical forces were used in calibrations of the most sensitive model parameter, particle stiffness. The calibrated particle stiffness was 0.75×103Nm−1 for the coarse sand, 2.75×103Nm−1 for the loamy sand, and 6×103Nm−1 for the sandy loam. The calibrated model was validated using the soil disturbance characteristics measured in those three soils. The simulations agreed well with the measurements with relative errors below 10% in most cases.

Group Cohesion without Group Mobilization: The Case of Lesbians, Gays and Bisexuals

Group identities that are chosen, rather than inherited, are often associated with cohesive political attitudes and behaviours. Conventional wisdom holds that this distinctiveness is generated by mobilization through processes such as intra-group contact and acculturation. This article identifies another mechanism that can explain cohesiveness: selection. The characteristics that predict whether an individual selects a group identity may themselves determine political attitudes, and thus may account substantially for the political cohesion of those who share the identity. This mechanism is illustrated with analyses of the causes and consequences of the acquisition of lesbian, gay or bisexual identity. Seldom shared by parents and offspring, gay identity provides a rare opportunity to cleanly identify the selection process and its implications for political cohesion.

On following behaviour as a mechanism for collective movement

During collective movement, animals display a wide variety of mechanisms to maintain cohesion. In some species, individuals rely mainly on following their direct predecessor, thereby forming spectacular processions of individuals in single file. Despite being the simplest case of following behaviour, it is largely absent from the theoretical literature on collective migrations. The objective of this study is to quantify the efficiency of following the predecessor, in terms of ensuring cohesion. The situation we consider is a sequence of individuals facing a bifurcation. The choice between left and right is influenced by the choice of the predecessor. First, we model this situation with a two-state Markov chain with a symmetric transition matrix. Cohesion is quantified as the expected number of individuals on either side, and the expected number of consecutive followers. Although cohesion increases with the probability of following, it remains surprisingly low unless the probability is almost equal to one. Furthermore, cohesion decreases with group size regardless of the probability of following. Then, we generalise our model to situations in which individuals have a preference for one of the two choices (asymmetric transition matrix). For some parameter sets, the tendency to follow each other leads a large fraction of the individuals to the non preferred side. Moreover, this fraction increases with the total population size. Finally, we include the possibility to follow N individuals. This provides the link between our model and other collective migration models. If enough individuals are perceived, the results shift from symmetrical (low cohesion) to asymmetrical (high cohesion) distribution of the individuals. All in all, our results suggest that following the direct predecessor must be complemented with other cohesive behaviours (involving the perception of more individuals or a navigation system) to guarantee its efficiency. We discuss our findings in the context of the different following behaviours covered in the literature.

Dynamics of sand and mud mixtures: A multiprocess-based modelling strategy

Mixed sediments are constituted of cohesive and non-cohesive materials with distinct behaviours that numerical models traditionally manage separately. This paper first introduces a rapid state of the Art in sediment transport modelling in order to point out the specific requirements for process-based models applied to mixed sediments. Based on a preliminary study by Waeles et al. (2007), which showed the validity of the advection approach to compute fine sand transport, a complete modelling strategy is described: it is applied to the suspended transport of sand and mud mixtures, and accounts for consolidation of mixed sediments. Special care is paid to the realistic representation of the structure and density of sand and mud mixtures, and to the segregation in consolidating sediment layers. The model state variables are the different classes of particles, generally classified according to their size, and grouped into categories that are either transported as bedload or in suspension. The bed is described as thin layers characterised by a distribution of these classes. The erosion law for fine sands and for sand and mud mixtures is a function of the excess shear stress calibrated against measurements in a small flume. The transition between cohesive and non-cohesive behaviours is parameterised through a critical mud fraction that depends on the sand grain size: the coarser the sand, the higher the mud content before the sediment becomes cohesive. The consolidation module is based on Gibson equation formulated for each class, and modified to account for segregation. Constitutive relationships are calibrated by means of laboratory settling tests. In the deposition module, new deposits may be managed in different ways (creation of a new layer or integration into the existing surficial layer) depending on the mud fraction and its relative concentration. When deposited material is mixed with the surficial sediment, pores between coarser particles are first filled up with finer particles before increasing the layer thickness. The new modelling frame has first been used to simulate laboratory settling tests with mixed sediments. When the initial mixture density is low, sand particles can settle through the mud and form a dense sandy layer on the bottom. In a second application, the model is used to describe sorting processes when tidal currents re-suspend a sand and mud mixture. A sand layer is then likely to form within the sediment, while the surficial layers are muddier. A dynamic bed armouring process is shown: although sand is easily resuspended, eroded grains in the sand layer settle rapidly, reducing the erosion of underlying sediment. Resulting suspended sediment concentration is strongly reduced, as well as sediment fluxes. The application demonstrates the model ability to simulate layering processes and time-variations of sediment erodibility.

Temporal changes in mother–offspring discrimination in the prairie vole (Microtus ochrogaster)

The objective of this study was to determine if mothers of a group–living rodent that often raise offspring communally exhibit temporal changes in their behaviour towards unrelated offspring. In Experiment 1, we tested the retrieval tendency and huddling behaviour of prairie vole (Microtus ochrogaster) mothers presented with one of their own and one unrelated newborn (1–2 days old). In Experiment 2, we recorded the duration of cohesive and aggressive behaviours by mothers presented with one own or one unrelated newborn (2–4 days old) and later one own or one unrelated weanling (22–24 days old). In both experiments, mothers did not discriminate between own and unrelated newborns. In Experiment 2, mothers treated unrelated newborns the same as their own but were significantly more aggressive towards unrelated weanlings than own weanlings. Mothers were also more likely to behave cohesively with own weanlings than unrelated weanlings. Our results suggest that prairie vole mothers discriminate between unrelated weanlings but not unrelated newborns. Differences in maternal behaviour towards newborn and weanling offspring may result from differences in the costs and benefits of investment in offspring at different ages.

Variations in competitive mechanisms of captive male hamadryas-like baboons in two feeding situations

Experiments were carried out to determine the influence of food distribution (clumped vs dispersed) on processes of competition among seven captive male hamadryas-like baboons. Spatial cohesion, cohesive behaviours that males performed and received from their females, and aggressive and feeding behaviours of the males were collected during 35 min after food supply. Median values and variability of these variables were compared in both the feeding situations. Food distribution influenced both asymmetries in access and the form of competition. When food was clumped, those with less access fed by means of compensatory or alternative strategies (away from the main source and/or by feeding supplants), and they were more aggressive towards other males. When food was dispersed, all individuals could feed simultaneously, males that were more aggressive were those with less cohesive OMUs, despite the fact that cohesive behaviours remained constant. Females appeared to contribute to variation in the OMU's cohesion through their responses to both food distribution and males' competitive ability.

Social organization of Merino sheep of different ages, sex and family structure

Four different groups of Merino sheep were established and social interactions were examined in paddocks which were barren or with trees and other topographic features. Two groups had been established for 2 years. One group consisted of ewes of the same age and the other contained mothers and their unweaned offspring aged 2 and 1 year. Two other groups were established recently: one consisted of sheep of different sexes whose ages ranged from 1 to 5 years and the other group contained ewes of two different age groups. Age effects on cohesive and aggressive behaviours were apparent, with older animals being involved in more fights (usually between themselves), initiating more movements and showing more attention behaviours. In dominance tests the number of fights was significantly higher in the single sex, single age group. In the field, the family group was markedly less responsive in terms of fighting, movement and attention behaviours when compared with the other social groupings. This effect was most obvious in the barren environment. If a behaviour was observed frequently in one member of a family group it normally occurred in the other members of that family. It was twice as likely if the mother of the family initiated a movement that it would be followed by one of her descendants and particularly the younger one. The level of fighting was no different between members of the same family as between members of different families. The evidence for the family group being a socially more complex unit than the other three groups is discussed. The possibility is raised that a socially complex group may be less affected by environmental heterogeneity than groups that were not as well integrated socially.

Social behaviour of the golden-mantled ground squirrel (Spermophilus lateralis)

The social interactions of golden-mantled ground squirrels (Spermophilus lateralis) observed during a 2-year study in the Rocky Mountains of Alberta under natural conditions are described and quantitatively analyzed. Agonistic interactions were common for all age and sex groups, except among littermates before dispersal. Among adults, cohesive and recognitive behaviours were restricted almost exclusively to male–female interactions. For young, cohesive and recognitive behaviours occurred with other young (mainly littermates) and with the mother. This species can be categorized as "asocial" according to G. R. Michener's classification of social organization in ground squirrels.