A DEM study of silo discharge of a cohesive solid

Bulk handling of powders and granular solids is common in many industries and often gives rise to handling difficulties especially when the material exhibits complex cohesive behaviour. For example, high storage stresses in a silo can lead to high cohesive strength of the stored solid, which may in turn cause blockages such as ratholing or arching near the outlet during discharge. This paper presents a Discrete Element Method study of discharge of a granular solid with varying levels of cohesion from a flat-bottomed silo. The DEM simulations were conducted using the commercial EDEM code with a recently developed DEM contact model for cohesive solids implemented through an API. The contact model is based on an elasto-plastic contact with adhesion and uses hysteretic non-linear loading and unloading paths to model the elastic-plastic contact deformation. The adhesion parameter is a function of the maximum contact overlap. The model has been shown to be able to predict the stress history dependent behaviour depicted by a flow function of the material. The effects of cohesion on the discharge rate and flow pattern in the silo are investigated. The predicted discharge rates are compared for the varying levels of cohesion and the effect of adhesion is evaluated. The ability of the contact model to qualitatively predict the phenomena that are present in the discharge of a silo has been shown with the salient feature of mixed flow from a flat bottomed hopper identified in the simulation.

Characterisation of the performance of sustainable grout containing bentonite for geotechnical applications

The grouts used in sealing or backfilling boreholes should ideally be selected to be compatible with the insitu field instruments installed in the borehole and also be engineered to match closely the geotechnical properties of the parent soils. A stable grout can be made using cement with various proportions of bentonite. The grout stability is very important during both the liquid and set conditions. The liquid grout fluidity should be as viscous as possible to avoid segregation, yet fluid enough to be easily pumpable and fill voids and over-break in the borehole. This paper investigates the effect of bentonite on the fresh and rheological properties of cement-based grouts in order to develop a stable grout to be used in these geotechnical situations. These properties were evaluated by the mini-slump flow, marsh cone flow time, Lombardi plate cohesion meter, static bleeding, yield stress and plastic viscosity values. Additionally, the compressive strength at 3 days, 7 days and 28 days were also investigated. The key parameters investigated were the dosages of bentonite and water-to-binder ratio (W/B). Test results showed that the dosage of bentonite had a significant effect on the fluidity, rheological properties and compressive strength of grout. The increase in the dosage of bentonite led to increasing the values of flow time, plate cohesion meter, yield stress and plastic viscosity, and reducing the mini-slump results, the static bleeding and the compressive strength at 3 days, 7 days and 28 days. Conversely, the increase in W/B led to decreasing the values of flow time, plate cohesion meter, yield stress, and plastic viscosity and the compressive strength, while increasing the mini-slump results and bleeding. Some recommendations for suitable mix proportions for use in soil boreholes are made.

Parades, Flags, Carnivals and Riots: Public Space, Contestation and Transformation in Northern Ireland

This paper explores one of the defining aspects of politics and identity in Northern Ireland: the control and utilization of public space, particularly urban public space. Ethnopolitical conflict consistently reveals itself through contestation over public space. The role of ritual events is important in the development of political identity and group cohesion. The symbolic landscape will be constructed through displays of identity by dominant groups and their ability to control that landscape by inhibiting displays by other groups. This will reveal itself through frequent contests over rituals and symbols. This paper looks at the role of ritual events in civic spaces in Belfast but particularly asks what role they might play in conflict transformation. The 1998 agreement offered political structures that provided for shared power after 30 years of violent conflict. At the same time, there was an increase in contestation over public space as political groups within the previously marginalized Catholic community demanded recognition within the public sphere and a rebalancing of the public space through changes to the previously dominant Protestant and Unionist expression of identity. The paper concludes by suggesting that in “shared space” a new civic identity that spans the political and ethnic divisions has started to develop in Belfast and that this might evolve despite an increased residential division throughout the urban area.

Explaining voting behaviour on free votes: Solely a matter of preference?

While studies examining free votes find MPs’ preferences influence their voting behaviour, most studies also show MPs tend to divide along party lines even after the whips have been withdrawn. Recent work offers a possible alternative explanation for this finding: this sustained party cohesion represents the impact of MPs’ party identification similar to party identification effects in the electorate. This argument is tested using a series of free votes on same-sex relations. Even after controlling for preferences using several direct measures, party continues to shape voting behaviour. Although indirect, this provides evidence in favour of the party-asidentification argument. 

Interpretations of national identity in post-conflict Northern Ireland: A comparison of different school settings

It is generally accepted that education has a significant role to play in anysociety transitioning from conflict to a more peaceful dispensation. Indeed,some have argued that the education system potentially represents the singlemost effective agent of social change with the capacity to bridge ethnicdivision in conflict affected countries. Despite the potential, educationalpolicy-makers grapple with the dilemma as to precisely how school systemscan best facilitate this agenda. This paper thus attempts to shed lightupon the dilemma by exploring pupil identity and associated intergroupattitudes across various school types in Northern Ireland. Five schools wereselected for the study with each one representing a particular sector withinthe Northern Irish education system (maintained grammar, maintainedsecondary, controlled grammar, controlled secondary, integrated). This led toa total sample size of 265 pupils. The main findings show that children acrossseparate Catholic, separate Protestant and mixed Catholic and Protestanteducational contexts construct and interpret identity differently. At thesame time, our data suggest that no one school setting has supremacy inpromoting social cohesion. The implications of these findings are discussed.

Measuring healthcare integration: Operationalization of a framework for a systems evaluation of palliative care structures, processes, and outcomes

BACKGROUND: Healthcare integration is a priority in many countries, yet there remains little direction on how to systematically evaluate this construct to inform further development. The examination of community-based palliative care networks provides an ideal opportunity for the advancement of integration measures, in consideration of how fundamental provider cohesion is to effective care at end of life.

AIM: This article presents a variable-oriented analysis from a theory-based case study of a palliative care network to help bridge the knowledge gap in integration measurement.

DESIGN: Data from a mixed-methods case study were mapped to a conceptual framework for evaluating integrated palliative care and a visual array depicting the extent of key factors in the represented palliative care network was formulated.

SETTING/PARTICIPANTS: The study included data from 21 palliative care network administrators, 86 healthcare professionals, and 111 family caregivers, all from an established palliative care network in Ontario, Canada.

RESULTS: The framework used to guide this research proved useful in assessing qualities of integration and functioning in the palliative care network. The resulting visual array of elements illustrates that while this network performed relatively well at the multiple levels considered, room for improvement exists, particularly in terms of interventions that could facilitate the sharing of information.

CONCLUSION: This study, along with the other evaluative examples mentioned, represents important initial attempts at empirically and comprehensively examining network-integrated palliative care and healthcare integration in general.