174,927 research outputs found
Holografia digital complexa utilizando um interferômetro shearing
No full textTese (doutorado) - Universidade Federal de Santa Catarina, Centro Tecnológico. Programa de Pós-Graduação em Engenharia Mecânica.A evolução das câmeras CCD e sistemas de processamento de imagens viabilizaram o desenvolvimento da holografia digital. O filme fotográfico pôde ser substituído por sensores CCD de elevada resolução, capazes de registrar os complexos padrões de interferência. A reconstrução do holograma é efetuada inteiramente de forma digital, sendo possível registrar com precisão pequenos campos de deslocamentos e deformações. Na holografia clássica, assim como na holografia digital e na holografia digital complexa um fator limitante que inviabiliza medições em campo é a elevada sensibilidade às perturbações externas do arranjo holográfico. É fundamental que o arranjo seja isolado de perturbações externas, o que torna a prática destas medições restrita a um ambiente de laboratório. A nova configuração proposta neste trabalho utiliza um interferômetro "shearing" para produzir uma onda de referência implícita. A informação de intensidade e a informação de fase são utilizadas para a reconstrução da frente de onda. O holograma resultante deste processo está sendo denominado "holograma digital complexo". Este trabalho apresenta em detalhes o princípio da nova configuração. Diferentes algoritmos foram criados e testados para o cálculo do "holograma digital complexo". Experimentos monitorados foram realizados e demonstram a viabilidade da técnica para futuras aplicações para a medição de deslocamentos
Enhanced heterogeneous nucleation on oxides in Al alloys by intensive melt shearing
No full textThis thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.Aluminium alloys, including both foundry and wrought alloys, have been extensively used for light-weight structural and functional applications. A grain refined as-cast microstructure is generally highly desirable for either subsequent processing ability or mechanical properties of the finished components. In this thesis, the grain refined microstructures in Al alloys have been achieved by intensive melt shearing using the melt conditioning by advanced shearing technology (MCAST) without deliberate grain refiner additions. Such grain refinement has been attributed to the enhanced heterogeneous nucleation on the dispersed oxide particles. It has been established that the naturally occurring oxides in molten Al alloys normally have a good crystallographic match with the a-Al phase, indicating the high potency of oxide particles as the nucleation sites of the a-Al phase. The governing factors for these oxide particles to be effective grain refiners in Al alloys have been proposed, including the achievement of good wetting between oxide particles and liquid aluminium, a sufficient number density and uniform spatial distribution of the dispersed oxide particles, and near equilibrium kinetic conditions in liquid alloys. In the present study, near equilibrium kinetic conditions can be achieved by intensive melt shearing using a twin screw mechanism, which has been confirmed by the observed equilibrium a-AlFeSi phase in a cast Al alloy and the transformation from g- to a-Al2O3 at 740±20oC under intensive shearing. For different alloy systems, depending on the alloy system, and melting conditions, due to the particular types of oxide formed and its crystallographic and chemical characteristics, the nucleation site of the nucleated phase is different. Specifically, MgAl2O4 relative to MgO, and a-Al2O3 relative to g-Al2O3, have higher potency as heterogeneous nucleation sites of a-Al phase in Al alloys. In future, the modification of the crystallographic match, and of the other surface characteristics related to the interfacial energy between the specific oxides and nucleated phase by trace alloying addition through segregation to the interface between oxides and nucleated phases combined with physical melt processing (such as intensive shearing in the present study) should be investigated in more detail.This study was funded by the EPSRC and Norton Aluminium Limited, UK
Multi-tow shearing mechanism for high-speed manufacturing of variable angle tow composites
No full textAn innovative tow steering technique using shear deformation characteristics of the dry tow material has been developed to minimize the process-induced defects by changing the most fundamental way of handling tow materials of all conventional AFP techniques, and was named as ‘CTS (Continuous Tow Shearing)’. The objective of this research was to improve the productivity of the CTS process by using the stitched unidirectional non-crimped fabric (NCF) with multiple carbon tows rather than a single carbon tow and eliminating the in-situ impregnation process with slow process speed. A prototype of the CTS head module with a wide feed mechanism for the NCF and the resin film was developed and installed on a prepreg cutting machine for process validation
Governing Security: The Age of Diversity
No full textThe ratios of private security to state police range from two or three to one in places like Canada and the US to about five or six to one in places like South Africa. In Canada the police, perhaps more than elsewhere, have been prepared to face the police crisis directly and openly. One of the engagements that developed at the Montreal conference was between Ian Blair and the senior executives of several very large private security agencies. Private security sometimes exists within nodal assemblages that link them closely to state agencies. The idea of the regulatory state is both a descriptive and an explanatory idea at the same time as it is a normative idea. It is used to argue that states have been, and should be, shifting their governing focus from being providers to being the primary auspice of governance. Diversity affects the providers but not the auspices of governance.No Full Tex
Privatisation, Pluralisation and the Globalisation of Policing
No full textPolice, as a formal institution, operate as a part of a three way relationship with the community and the state. In this research paper, Philip Stenning and Clifford Shearing explore how changes in both the community and the state may reshape both the institution of the police and the role of policing. This paper extends the conversation from our previous 2013 publication ‘Public Private Policing’ which was based on a forum held at the AIPM in the same year.No Full Tex
Insurance and climate change
No full textThis chapter uses a desktop study to examine the insurance industry’s potential as a ‘fulcrum institution’ that can influence others to prevent and address environmental harms from climate change. As this chapter demonstrates, given insurance’s central economic role, the relationship between insurers and climate change is complicated and conflicted. After the discussion of insurers as shapers of climate risk (the first section of the chapter), this chapter explains how (in the second section) insurers are strongly implicated in creating climate change and attendant climate risk in the period since industrialisation through facilitating the accelerating fossil-fuel-based economic development and growth that causes climate change; this is the dominant dimension in insurers’ relationship with climate change. In the third section of this chapter, the authors review insurers’ responses over the past decade to increasing climate risk. Responses have been largely adaptive and aimed at increasing insurers’ capacity to accommodate the climate risks faced by their policyholders. Some responses have been ‘weakly mitigative’, meaning that they provide for some mitigation, but on a very limited scale, and largely as side effects of initiatives unrelated to climate change. In marked contrast, a very limited number of recent ‘divest and decline’ actions by insurance industry actors can be described as ‘strongly mitigative’, as described in the fourth section. The fifth section concludes the chapter with some remarks on the prospects for further strong mitigation action from insurers on climate change and their role as governors of security beyond the state
Measurements of Shearing Property of High N Alloy Steel at Super High Strain Rates
No full textIn order to obtain the dynamic shearing property of high N alloy steel, the plugging test was
performed by using the improved Hopkinson pressure bar system. As dynamic shearing strengths, the
dynamic shearing energies during plugging process of two type high N alloy steels were determined
from the shearing constitutive relationship at different super high strain rates. According to the theory
of dislocation dynamics in Seeger equation, a dynamic shearing damage constitutive relationship was
established and the different parameters of this material were determined by using the curve fitting
method. The measured results indicated that the dynamic shearing property of high N alloy steel could
be obtained effectively by the improved Hopkinson pressure bar system, and the effects of strain rate
could be simulated by dynamic shearing damage constitutive relationship
Effect of pre-shearing on the steady and dynamic rheological properties of mud sediments
No full textMud sediments can exhibit a complex rheological behaviour particularly a thixotropic character or structural recovery after breakup due to the presence of organic matter/biopolymer. Such biopolymers can lead towards the development of flocculated structures having multiple length scales which are sensitive to shearing rate and history. In this study, the extent and rate of structural recovery of mud sediments was studied by measuring the storage modulus as a function of time using small amplitude oscillatory tests after a destructive steady shearing. This linear viscoelastic response of the sediments was further investigated as a function of several parameters including pre-shear rate, pre-shear time, measuring geometry, mud density and organic matter content. The equilibrium storage modulus (G∞ ') and the characteristic time (tr) for the structural recovery of the sediment matrix were estimated by fitting the experimental data to a stretched exponential function. The normalized storage modulus, G'/G0 ' (i.e., structural parameter) was used to relate it with the yield stresses of mud sediments. The results showed that the recovery of structure after shearing was instantaneous (tr being of the order of seconds), however, the extent of recovery was highly dependent on the studied parameters. The extent of recovery was higher for the samples with lower density and lower organic matter content. The effect of the shearing time on tr and G∞ ' was almost negligible, which implies that the destruction of the structure was achieved within seconds. Using vane geometry, the extent of recovery was higher than using Couette geometry which is linked with the distribution of shear stresses within the cell for each geometry. Yield stresses showed a strong dependency on structural parameter, until it reaches very small values. At low values of structural parameter, the yield stresses were constant as the structural recovery was even faster than the time required to perform the amplitude sweep tests. This study provides an extensive knowledge about the structural recovery in mud sediments under different shearing conditions which can be useful for sediment management.Rivers, Ports, Waterways and Dredging EngineeringEnvironmental Fluid Mechanic
Criminology and the Anthropocene
No full textThe Anthropocene signals a new age in our earth’s history, a human age, where we are revealed as a powerful force shaping planetary systems. What might criminology be in the Anthropocene? What does the Anthropocene suggest for future theory and practice of criminology? This book seeks to contribute to this research agenda by examining, contrasting and interrogating different vantage points, aspects and thinking within criminology.
Bringing together a range of multidisciplinary chapters at the cutting edge of thinking and environmental rethinking in criminology, this book explores a mix of key intractable problems of the Anthropocene, including climate change and overexploitation of natural resources that cause environmental insecurities; crime and corruption; related human insecurity and fortressed spaces; and the rise of new risks and social harms.
Of interest to scholars in the fields of criminology, sociology and environmental studies, this book provides readers with a basis for analysing the challenges of, and possible approaches to, the Anthropocene at all levels (local, national, regional and international) and discusses the future(s) of criminology for improving social policies and practice
Application of an Ultrafine Shearing Method for the Extraction of C-Phycocyanin from Spirulina platensis
No full textCell disruption is an important step during the extraction of C-phycocyanin from Spirulina platensis. An ultrafine shearing method is introduced and combined with soaking and ultrasonication to disrupt the cell walls of S. platensis efficiently and economically. Five kinds of cell disruption method, including soaking, ultrasonication, freezing-thawing, soaking-ultrafine shearing and soaking-ultrafine shearing-ultrasonication were applied to break the cell walls of S. platensis. The effectiveness of cell breaking was evaluated based on the yield of the C-phycocyanin. The results show that the maximum C-phycocyanin yield was 9.02%, achieved by the soaking-ultrafine shearing-ultrasonication method, followed by soaking (8.43%), soaking-ultrafine shearing (8.89%), freezing and thawing (8.34%), and soaking-ultrasonication (8.62%). The soaking-ultrafine shearing-ultrasonication method is a novel technique for breaking the cell walls of S. platensis for the extraction of C-phycocyanin
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