Energy conserving schemes for the simulation of musical instrument contact dynamics

Collisions are an innate part of the function of many musical instruments. Due to the nonlinear nature of contact forces, special care has to be taken in the construction of numerical schemes for simulation and sound synthesis. Finite difference schemes and other time-stepping algorithms used for musical instrument modelling purposes are normally arrived at by discretising a Newtonian description of the system. However because impact forces are non-analytic functions of the phase space variables, algorithm stability can rarely be established this way. This paper presents a systematic approach to deriving energy conserving schemes for frictionless impact modelling. The proposed numerical formulations follow from discretising Hamilton׳s equations of motion, generally leading to an implicit system of nonlinear equations that can be solved with Newton׳s method. The approach is first outlined for point mass collisions and then extended to distributed settings, such as vibrating strings and beams colliding with rigid obstacles. Stability and other relevant properties of the proposed approach are discussed and further demonstrated with simulation examples. The methodology is exemplified through a case study on tanpura string vibration, with the results confirming the main findings of previous studies on the role of the bridge in sound generation with this type of string instrument.

The Landscape of Differences: Contact and Segregation in the Everyday Encounters

The article examines everyday life in Northern Ireland’s segregated communities and focus on a neglected empirical dimension of ethnic and social segregation developed within the socio-spatial relations between people and their built environment. It shows how the everyday urban encounters are reproduced through negotiating differences and the ways in which living in divided communities lead to social inequality and imbalanced use of space. The article employed qualitative research methods with individuals and community groups from the Fountain estate, a small Protestant enclave in Derry/Londonderry. Their stories were replete with cases of injustice and insights into the daily struggles that have generally occurred within theories of contact and social segregation as a whole. In fact, people in the Fountain presented their own intertextual references on what was more significant for them as a matter of routine survival and belonging, which allowed them to be more constructive about themselves. While segregation has persisted for multiple decades; time is believed to be the factor most likely to change it, as it is hoped that the younger generation will provide lasting change to Northern Ireland and eventual peace between currently segregated communities.

On Irish sticklebacks: morphological diversification in a secondary contact zone

Question: How parallel is adaptive evolution when it occurs from different genetic backgrounds?
Background: Divergent evolutionary lineages of several post-glacial fish species including the threespine stickleback are found together in Ireland.
Goals: To investigate the morphological diversity of stickleback populations in Ireland and assess whether morphology evolved in parallel between evolutionary lineages.
Methods: We sampled stickleback from lake, river, and coastal habitats across Ireland. Microsatellite and mitochondrial DNA data revealed evolutionary history. Geometric morphometrics and linear trait measurements characterized morphology. We used a multivariate approach to quantify parallel and non-parallel divergence within and between lineages.
Results: Repeated evolution of similar morphologies in similar habitats occurred across Ireland, concordant with patterns observed elsewhere in the stickleback distribution. A strong pattern of habitat-specific morphology existed even among divergent lineages. Furthermore, a strong signal of shared morphological divergence occurred along a marine–freshwater axis. Evidently, deterministic natural selection played a more important role in driving freshwater adaptation than independent evolutionary history.

‘Plugging the Gap’: Shared Education and the promotion of community relations through schools in Northern Ireland

Although there is no consensus amongst educationalists as to the role schools play as drivers of hostilities in divided societies, there is broad agreement that they can facilitate more positive intergroup relations. In Northern Ireland the promotion of school based inter-group contact has been offered as a means through which this can happen. Until 2007, the approach was twofold, reflected on the one hand in short-term contact opportunities for pupils in predominantly Catholic and Protestant schools, and on the other, in support for integrated schools which educate Catholics and Protestants together. In 2007 the Shared Education Programme was introduced to ‘bridge the gap’ between short-term opportunities for contact, and ‘full immersion’ integrated schools. Informed by contact theory, shared education offers curriculum based interaction between pupils attending all school types, aimed at promoting the type of contact likely to reduce negative social attitudes and ultimately contribute to social harmony. In this paper, we examine the impact of shared education thus far. Our analysis suggests that whilst shared education is generally effective in promoting positive assessments of other group members, there is a danger that programme impact may be inhibited by the foregrounding of educational over reconciliation priorities. Appreciating that the downplaying reconciliation objectives may have been necessary when the programme was established in order to maximize recruitment to it, we argue that if the full potential of shared education is to be realized, moving forward, it is important for schools to engage with issues of group differences.

Effect of contact pressure on fretting fatigue behavior of Ti-1023

With a new test facility, we have investigated fretting fatigue properties of Ti-1023 titanium alloy at different contact pressure. Both fatigue fracture and fretting scar were analyzed by scanning electron microscopy (SEM). Moreover, the depth of crack initiation area in fatigue fracture has been analyzed quantitatively, to investigate the relationship between the depth of crack initiation area and the fretting fatigue strength. The changing trends of the depth of crack initiation area and fretting fatigue strength with the increase of contact pressure show obvious opposite correlations. The depth of crack initiation area increases rapidly with the increase of contact pressure at low contact pressure (smaller than 10 MPa), and the fretting fatigue strength drops rapidly. At the contact pressure of 10–45 MPa, both the depth of crack initiation area and the fretting fatigue strength do not vary significantly. Contact pressure influences fatigue strength through influencing the initiation of fatigue crack. The main damage patterns are fatigue flake and plow.

Young People’s Offending Careers and Criminal Justice Contact: A Case for Social Justice

This article draws on an analysis of young people’s offending careers. The research was initiated against a backdrop of changing discourse around youth justice in Ireland with a shift towards prevention of offending and diversion from the criminal justice system. Locating crime and criminal justice contact within a biographical context indicated that participants’ offending, and lives generally, was bound up in marginalized transitions to adulthood, and embedded within social and economic environments characterized by high deprivation. The findings support a further shift in focus towards addressing social injustice as a necessary prerequisite to tackle the origins of youth offending.

‘A picture of who we are as a family’: conceptualizing post-adoption contact as practices of family display

Social work has a central role in negotiating and supporting birth family contact following adoption from care. This paper argues that family display (Finch) offers a useful conceptual resource for understanding relationships in the adoptive kinship network as they are enacted through contact. It reports on an interpretative phenomenological analysis of adoptive parents' accounts of open adoption from care that revealed direct and indirect contact to be contexts in which they and birth relatives performed family display practices: communicating the meaning of their respective relationships with the adopted child and seeking recognition that this was a legitimate family relationship. The analysis explores how family display was performed, and the impact of validating or invalidating responses. It aims to illuminate these social and interpretive processes involved in adoptive kinship in order to inform social work support for contact. The findings suggest that successful contact may be promoted by helping adoptive and birth relatives validate the legitimacy of the other's kin connection with the child, and through arrangements that facilitate family-like interactions.

Joining together or pushing apart? Building relations and exploring difference through shared education in Northern Ireland

In divided societies, the promotion of cross-cultural contact through the education system has been central to efforts to improve intergroup relations. This approach is informed by an understanding of the contact hypothesis, which suggests that positive contact with a member of a different group should contribute to improvements in attitudes towards the group as a whole. While a substantial body of research provides support for contact theory, critics have argued that its emphasis on harmonious encounters can result in the neglect of group differences and associated issues of conflict and discrimination during contact. The research discussed in this article explores this tension with reference to two shared education projects in Northern Ireland. Research data, gathered primarily through interviews with pupils, confirms that divisive issues are rarely addressed during contact and explores several influences on this: the nature of pupils’ relationships, the programme structure, and the prevailing social norms of avoidance.