The effect of artificial defects on the compressive properties of hollow sphere cellular aluminium (HSCA)

Hollow sphere cellular aluminium (HSCA) samples were fabricated by bonding together two kinds of single aluminium hollow spheres with the same outside diameter of 4 mm but different wall thicknesses of 0.1 mm and 0.3 mm, in which the hollow spheres with the thinner sphere wall thickness were used as artificial defects. Four types of HSCA samples with the same relative density but various distributions of artificial defects were prepared by simple cubic packing. For comparing, HSCA sample without defective hollow spheres inside was also prepared. The effects of the distribution of the artificial defects on the deformation behaviours and mechanical properties were investigated by compressive tests. Results indicated that the nominal stress - nominal strain curve and the deformation behavior of the HSCA samples varied with the distribution of the artificial defects in spite of the same relative density. It is therefore suggested that the deformation behavior and mechanical property of cellular materials were also significantly affected by the distribution of defects. In particular, the plateau stress of the HSCA samples increased with the decrease in number of contact points between the normal hollow spheres and the defective hollow spheres in the loading direction during deformation.

Compressive properties and energy absorption of hollow sphere aluminium

Manufactured cellular aluminums have been developed for a wide range of automotive applications where weight savings, improved safety, crashworthiness and comfort are required. The plateau deformation behavior of cellular aluminums under compressive loading makes this new class of lightweight materials suitable for energy absorption and comes close to ideal impact absorbers. In the present study, aluminum hollow hemispheres were firstly processed by pressing. Hollow sphere aluminum samples with a body-centered cubic (BCC) packing were then fabricated by bonding together single hollow spheres, which were prepared by adhering together hollow hemispheres. Hollow sphere aluminum samples with various kinds of sphere wall thicknesses of 0.1 mm, 0.3 mm and 0.5 mm but the same outside diameter of 4 mm were investigated by compressive tests. The effects of the sphere wall thickness on the mechanical properties and energy absorption characteristics were investigated.

Processing and mechanical properties of hollow sphere aluminum foams

Hollow sphere metallic foams are a new class of cellular material that possesses the attractive advantages of uniform cell size distribution and regular cell shape. These result in more predictable physical and mechanical properties than those of cellular materials with a random cell size distribution and irregular cell shapes. In the present study, single aluminum hollow spheres with three kinds of sphere wall thickness as 0.1 mm, 0.3 mm and 0.5 mm were processed by a new pressing method. Hollow sphere aluminum foam samples were prepared by bonding together single hollow spheres with simple cubic packing (SC) and body-centered cubic packing (BCC). Compressive tests were carried out to evaluate the deformation behaviors and mechanical properties of the hollow sphere aluminum foams. Effects of the sphere wall thickness and packing style on the mechanical properties were investigated.

Audiences and public : when cultural engagement matters for the public sphere

Audiences and Publics: When Cultural Engagement Matters for the Public Sphere, edited by Sonia Livingstone, is reviewed.

Reinvigorating the public sphere : the role of voluntary associations

This thesis examines the key question: can voluntary associations enhance democracy? It tests critical claims made by Habermas and others that voluntary associations have the potential to reinvigorate a public sphere in a state of atrophy. The thesis outlines the major theoretical arguments pertaining to these areas and then presents the results of empirical work within voluntary organisations. Specifically the thesis: Critically examines the concept of the public sphere, being a sphere between the state and civil society and investigates why theorists have advocated voluntary associations, claimed to be the core institutions of civil society, as sites where democratic ideals can be secured; Goes on to examine the concept of civil society and reviews the recent literature that has attempted to define and analyse the role of voluntary associations in contemporary society; Tests empirically the normative ideals that have been advocated on behalf of voluntary associations through the presentation of data obtained using qualitative methodology. The analysis of the data collected during interviews with key employees and members of six voluntary associations in Melbourne, Australia allows for a more informed knowledge regarding the key concepts and themes of the thesis. The thesis ends by directly addressing the following points: whether or not the public sphere is in a state of atrophy; the particular nature of voluntary associations contemporary engagement in the public sphere; and whether voluntary associations can indeed, be sites where democracy can be enhanced and democratic ideals be secured. It is concluded that voluntary associations operate within Habermasian public spheres, counterspheres, and postmodern public spheres and that unitary notions of the public sphere, such as those Habermas proposes, do not adequately explain voluntary associations engagement in the public sphere. Accordingly, it is concluded that voluntary associations have the potential to invigorate public spheres, though not in ways that many theorists writing on the subject suggest.

The streets of Iraq : protests, the public sphere and democracy

Since the invasion of Iraq by Coalition forces in 2003, much attention has been paid to the violence ravaging Iraq’s streets, so much so that they have become synonymous with bloodshed and chaos. This paper begins by countering this prominent view with a brief outline of some of the more positive scenes that have played out on Iraq’s streets, including the successful elections of 2005 and 2009. The bulk of the paper builds on this discussion to detail the various protest movements that have emerged across Iraq since 2003, including those organised by Shia clerics, minority movements, women’s organisations and Iraqi worker unions. This paper concludes by arguing that the willingness of normal Iraqi citizens to exercise their democratic right to protest indicates the degree to which democratic ideals are taking hold in Iraq and represents a fundamental step towards a more peaceful and inclusive future.

Read all about it : the free press, the public sphere and democracy in Iraq

Despite a wealth of recent research which has detailed the impact that new media outlets and technologies have had on the Middle East’s nascent public sphere and its role in promoting democracy, there has been little investigation into the re-emergence of the free press in Iraq following the toppling of Saddam Hussein in 2003 and the corresponding end to his tight control over the nation’s media sector. This paper begins by reviewing Iraq’s long relationship with the written word and its corresponding public sphere. It traces the introduction of the printing press to Iraq by the Ottomans and details those periods when the Iraqi press was truly free, fostering the emergence of a civil society and democratic reforms (such as under the Young Turks, the early Hashemite era and following the Second World War). It also examines those periods when the Iraqi media was most restricted and did little else than praise the regime at hand (such as under Ottoman rule and most recently under the Ba†th regime, especially under Saddam Hussein). Following on, this article reviews the developments since the fall of Saddam Hussein and, despite the extensive interference in Iraq’s media sector from governmental entities both outside and inside Iraq, it concludes by arguing that these papers have been central to the re-emergence of an Iraqi public sphere which has openly debated and discussed the issues pertinent to post-Saddam Iraq.

The coming republic : citizenship and the public sphere in post-colonial Australia

The 'coming republic' (Home, 1992) is a reference point in a public discourse about Australian citizenship and national identity. An analysis of this debate raises questions about the degree to which the mass media, as the site of a contemporary public sphere, facilitates democratic change and promotes or demotes the various interests competing for scarce speaking positions. This paper uses the Australian experience to question the ideologies that support the media as marketplace, and suggests the need for an alternative to liberal-democratic and pluralist approaches to theorising the public sphere.