Limit load instabilities in structural elements

Este trabajo analiza distintas inestabilidades en estructuras formadas por distintos materiales. En particular, se capturan y se modelan las inestabilidades usando el método de Riks. Inicialmente, se analiza la bifurcación en depósitos cilíndricos formados por material anisótropo sometidos a carga axial y presión interna. El análisis de bifurcación y post-bifurcación asociados con cilindros de pared gruesa se formula para un material incompresible reforzado con dos fibras que son mecánicamente equivalentes y están dispuestas simétricamente. Consideramos dos casos en la naturaleza de la anisotropía: (i) Fibras refuerzo que tienen una influencia particular sobre la respuesta a cortante del material y (ii) Fibras refuerzo que influyen sólo si la fibra cambia de longitud con la deformación. Se analiza la propagación de las inestabilidades. En concreto, se diferencia en el abultamiento (bulging) entre la propagación axial y la propagación radial de la inestabilidad. Distintos modelos sufren una u otra propagación. Por último, distintas inestabilidades asociadas al mecanismo de ablandamiento del material (material softening) en contraposición al de endurecimiento (hardening) en una estructura (viga) de a: hormigón y b: hormigón reforzado son modeladas utilizando una metodología paralela a la desarrollada en el análisis de inestabilidades en tubos sometidos a presión interna. This present work deals with the instability of structures made of various materials. It captures and models different types of instabilities using numerical analysis. Firstly, we consider bifurcation for anisotropic cylindrical shells subject to axial loading and internal pressure. Analysis of bifurcation and post bifurcation of inflated hyperelastic thick-walled cylinder is formulated using a numerical procedure based on the modified Riks method for an incompressible material with two preferred directions which are mechanically equivalent and are symmetrically disposed. Secondly, bulging/necking motion in doubly fiber-reinforced incompressible nonlinearly elastic cylindrical shells is captured and we consider two cases for the nature of the anisotropy: (i) reinforcing models that have a particular influence on the shear response of the material and (ii) reinforcing models that depend only on the stretch in the fiber direction. The different instability motions are considered. Axial propagation of the bulging instability mode in thin-walled cylinders under inflation is analyzed. We present the analytical solution for this particular motion as well as for radial expansion during bulging evolution. For illustration, cylinders that are made of either isotropic incompressible non-linearly elastic materials or doubly fiber reinforced incompressible non-linearly elastic materials are considered. Finally, strain-softening constitutive models are considered to analyze two concrete structures: a reinforced concrete beam and an unreinforced notch beam. The bifurcation point is captured using the Riks method used previously to analyze bifurcation of a pressurized cylinder.

Correlation between carotid bifurcation calcium burden on non-enhanced CT and percentage stenosis, as confirmed by digital subtraction angiography

Objectives: Previous evidence supports a direct relationship between the calcium burden (volume) on post-contrast CT with the percent internal carotid artery (ICA) stenosis at the carotid bifurcation. We sought to further investigate this relationship by comparing non-enhanced CT (NECT) and digital subtraction angiography (DSA). Methods: 50 patients (aged 41-82 years) were retrospectively identified who had undergone cervical NECT and DSA. A 64-multidetector array CT (MDCT) scanner was utilised and the images reviewed using preset window widths/levels (30/300) optimised to calcium, with the volumes measured via three-dimensional reconstructive software. Stenosis measurements were performed on DSA and luminal diameter stenoses >40% were considered "significant". Volume thresholds of 0.01, 0.03, 0.06, 0.09 and 0.12 cm(3) were utilised and Pearson's correlation coefficient (r) was calculated to correlate the calcium volume with percent stenosis. Results: Of 100 carotid bifurcations, 88 were available and of these 7 were significantly stenotic. The NECT calcium volume moderately correlated with percent stenosis on DSA r=0.53 (p<0.01). A moderate-strong correlation was found between the square root of calcium volume on NECT with percent stenosis on DSA (r=0.60, p<0.01). Via a receiver operating characteristic curve, 0.06 cm(3) was determined to be the best threshold (sensitivity 100%, specificity 90.1%, negative predictive value 100% and positive predictive value 46.7%) for detecting significant stenoses. Conclusion: This preliminary investigation confirms a correlation between carotid bifurcation calcium volume and percent ICA stenosis and is promising for the optimal threshold for stenosis detection. Future studies could utilise calcium volumes to create a "score" that could predict high grade stenosis.

Clinical outcomes after zotarolimus and everolimus drug eluting stent implantation in coronary artery bifurcation lesions: insights from the RESOLUTE All Comers Trial

OBJECTIVE We investigated clinical outcomes after treatment of coronary bifurcation lesions with second generation drug eluting stents (DES). DESIGN Post hoc analysis of a randomised, multicentre, non-inferiority trial. SETTING Multicentre study. PATIENTS All comers study with minimal exclusion criteria. INTERVENTIONS Patients were treated with either zotarolimus or everolimus eluting stents. The patient population was divided according to treatment of bifurcation or non-bifurcation lesions and clinical outcomes were compared between groups. MAIN OUTCOMES MEASURES Clinical outcomes within 2-year follow-up. RESULTS A total of 2265 patients were included in the present analysis. Two-year follow-up data were available in 2223 patients: 1838 patients in the non-bifurcation group and 385 patients in the bifurcation group. At 2-year follow-up the bifurcation and the non-bifurcation lesion groups showed no significant differences in terms of cardiac death (2.3 vs 2.1, p=0.273), target lesion failure (9.7% vs 13.8%, p=0.255), major adverse cardiac events (11.5% vs 15.1%, p=0.305), target lesion revascularisation (4.7% vs 6.0%, p=0.569), and definite or probable stent thrombosis (1.6% vs 1.8%, p=0.419). CONCLUSIONS The use of second generation DES for the treatment of coronary bifurcation lesions was associated with similar long term mortality and clinical outcomes compared with non-bifurcation lesions.

The Coming of Post-reflexive Society: Commodification and Language in Digital Capitalism

Language is a unique aspect of human communication because it can be used to discuss itself in its own terms. For this reason, human societies potentially have superior capacities of co-ordination, reflexive self-correction, and innovation than other animal, physical or cybernetic systems. However, this analysis also reveals that language is interconnected with the economically and technologically mediated social sphere and hence is vulnerable to abstraction, objectification, reification, and therefore ideology – all of which are antithetical to its reflexive function, whilst paradoxically being a fundamental part of it. In particular, in capitalism, language is increasingly commodified within the social domains created and affected by ubiquitous communication technologies. The advent of the so-called ‘knowledge economy’ implicates exchangeable forms of thought (language) as the fundamental commodities of this emerging system. The historical point at which a ‘knowledge economy’ emerges, then, is the critical point at which thought itself becomes a commodified ‘thing’, and language becomes its “objective” means of exchange. However, the processes by which such commodification and objectification occurs obscures the unique social relations within which these language commodities are produced. The latest economic phase of capitalism – the knowledge economy – and the obfuscating trajectory which accompanies it, we argue, is destroying the reflexive capacity of language particularly through the process of commodification. This can be seen in that the language practices that have emerged in conjunction with digital technologies are increasingly non-reflexive and therefore less capable of self-critical, conscious change.

Vaughan, Suzi and Armstrong, Wendy (2009) Threads of tension. In: Vaughan, Suzi and Schmidt, Christine Margaret, (eds.) Five Fashion Musings. Post Pressed, Brisbane, Qld, pp. 9-15.

five:fashion musings is an upcoming 2009 publicaton to celebrate the fashion discipline's five-year milestone at the Queensland Unviesity of Technology. it represents a body of work by fashion practitioners, aceademic and educators commissioned to explore their research in fashion theory, practice and pedogogy through five key themes.

A new measure to quantify chest wall deformity in scoliosis patients : does rib hump measurement correlate with anterior chest wall deformity post surgery?

The primary aims of scoliosis surgery are to halt the progression of the deformity, and to reduce its severity (cosmesis). Currently, deformity correction is measured in terms of posterior parameters (Cobb angles and rib hump), even though the cosmetic concern for most patients is anterior chest wall deformity. In this study, we propose a new measure for assessing anterior chest wall deformity and examine the correlation between rib hump and the new measure. 22 sets of CT scans were retrieved from the QUT/Mater Paediatric Spinal Research Database. The Image J software (NIH) was used to manipulate formatted CT scans into 3-dimensional anterior chest wall reconstructions. A ‘chest wall angle’ was then measured in relation to the first sacral vertebral body. The chest wall angle was found to be a reliable tool in the analysis of chest wall deformity. No correlation was found between the new measure and rib hump angle. Since rib hump has been shown to correlate with vertebral rotation on CT, this suggests that there maybe no correlation between anterior and posterior deformity measures. While most surgical procedures will adequately address the coronal imbalance & posterior rib hump elements of scoliosis, they do not reliably alter the anterior chest wall shape. This implies that anterior chest wall deformity is to a large degree an intrinsic deformity, not directly related to vertebral rotation.

Concerning the house museum and the picturesque landscape in the work of Sir John Soane : with raw hints for post-heritage museum space

The picturesque aesthetic in the work of Sir John Soane, architect and collector, resonates in the major work of his very personal practice – the development of his house museum, now the Soane Museum in Lincoln’s Inn Fields in London. Soane was actively involved with the debates, practices and proponents of picturesque and classical practices in architecture and landscape and his lectures reveal these influences in the making of The Soane, which was built to contain and present diverse collections of classical and contemporary art and architecture alongside scavenged curiosities. The Soane Museum has been described as a picturesque landscape, where a pictorial style, together with a carefully defined itinerary, has resulted in the ‘apotheosis of the Picturesque interior’. Soane also experimented with making mock ruinscapes within gardens, which led him to construct faux architectures alluding to archaeological practices based upon the ruin and the fragment. These ideas framed the making of interior landscapes expressed through spatial juxtapositions of room and corridor furnished with the collected object that characterise The Soane Museum. This paper is a personal journey through the Museum which describes and then reviews aspects of Soane’s work in the context of contemporary theories on ‘new’ museology. It describes the underpinning picturesque practices that Soane employed to exceed the boundaries between interior and exterior landscapes and the collection. It then applies particular picturesque principles drawn from visiting The Soane to a speculative project for a house/landscape museum for the Oratunga historic property in outback South Australia, where the often, normalising effects of conservation practices are reviewed using minimal architectural intervention through a celebration of ruinous states.

Making visible the coding process : Using qualitative data software in a post-structural study

Qualitative research methods require transparency to ensure the ‘trustworthiness’ of the data analysis. The intricate processes of organizing, coding and analyzing the data are often rendered invisible in the presentation of the research findings, which requires a ‘leap of faith’ for the reader. Computer assisted data analysis software can be used to make the research process more transparent, without sacrificing rich, interpretive analysis by the researcher. This article describes in detail how one software package was used in a poststructural study to link and code multiple forms of data to four research questions for fine-grained analysis. This description will be useful for researchers seeking to use qualitative data analysis software as an analytic tool.