Influence of electroslag refining on the hot ductility of AISI 4340 steel in torsion

Electroslag refining is a useful remelting process by which clean steels can be produced for sophisticated applications. In this investigation, AISI 4340 steel has been electroslag refined and the improvement in its hot ductility has been assessed using hot torsion tests; electroslag refining has improved the hot ductility considerably. The temperature at which peak ductility is obtained has also increased — from 1473 K in the unrefined steel to 1573 K in ESR steel. Results indicate that it should be possible to subject the ESR ingot to much higher strains per unit operation during industrial hot working processes such as forging, which would result in a considerable saving of power. The improvement in hot ductility in ESR steel has been attributed primarily to the removal of non-metallic inclusions and the reduction in sulphur content. From the apparent activation energy estimated from the hot torsion data, the dynamic recrystallization process is identified as the mechanism controlling the rate of hot deformation.

Magnetic superconductors: Model theories and experimental properties of rare-earth compounds

Superconducting and magnetically long-range ordered states were believed to be mutually exclusive phenomena. The discovery of rare-earth compounds in recent years, which exhibit both superconductivity and magnetic ordering (ferromagnetic, antiferromagnetic or sinusoidal), has led to considerable theoretical and experimental work on such systems. In the present article, we give a review of various theoretical models and important experimental results. In the theoretical sections, we start with the Abrikosov-Gorkov pair breaking theory for dilute alloys and discuss its improvement in the work of Müller-Hartmann and Zittartz. Then, in the context of magnetic superconductors, various microscopic theories that have been advanced are presented. These predict re-entrant behaviour in some systems (ferromagnetic superconductors) and coexistence regions in others (particularly antiferromagnetic superconductors). Following this, phenomenological generalized Ginzburg-Landau theories for two kinds of orders (superconducting and magnetic) are presented. A section dealing with renormalization group analysis of phase diagrams in magnetic superconductors is given. In experimental sections, the properties of each rare-earth compounds (ternary as well as some tetranery) are reviewed. These involve susceptibility, heat capacity, resistivity, upper critical field, neutron scattering and magnetic resonance measurements. The anomalous behaviour of the upper critical field of antiferromagnetic superconductors near the Néel temperature is discussed both in theory sections and experimental section for various systems.

Noncommutative Quantum Field Theories and UV/IR Mixing

Our present-day understanding of fundamental constituents of matter and their interactions is based on the Standard Model of particle physics, which relies on quantum gauge field theories. On the other hand, the large scale dynamical behaviour of spacetime is understood via the general theory of relativity of Einstein. The merging of these two complementary aspects of nature, quantum and gravity, is one of the greatest goals of modern fundamental physics, the achievement of which would help us understand the short-distance structure of spacetime, thus shedding light on the events in the singular states of general relativity, such as black holes and the Big Bang, where our current models of nature break down. The formulation of quantum field theories in noncommutative spacetime is an attempt to realize the idea of nonlocality at short distances, which our present understanding of these different aspects of Nature suggests, and consequently to find testable hints of the underlying quantum behaviour of spacetime. The formulation of noncommutative theories encounters various unprecedented problems, which derive from their peculiar inherent nonlocality. Arguably the most serious of these is the so-called UV/IR mixing, which makes the derivation of observable predictions especially hard by causing new tedious divergencies, to which our previous well-developed renormalization methods for quantum field theories do not apply. In the thesis I review the basic mathematical concepts of noncommutative spacetime, different formulations of quantum field theories in the context, and the theoretical understanding of UV/IR mixing. In particular, I put forward new results to be published, which show that also the theory of quantum electrodynamics in noncommutative spacetime defined via Seiberg-Witten map suffers from UV/IR mixing. Finally, I review some of the most promising ways to overcome the problem. The final solution remains a challenge for the future.

Fracture Behavior of Multidirectional DCB Specimen: Higher-Order Beam Theories

Mathematical models, for the stress analysis of symmetric multidirectional double cantilever beam (DCB) specimen using classical beam theory, first and higher-order shear deformation beam theories, have been developed to determine the Mode I strain energy release rate (SERR) for symmetric multidirectional composites. The SERR has been calculated using the compliance approach. In the present study, both variationally and nonvariationally derived matching conditions have been applied at the crack tip of DCB specimen. For the unidirectional and cross-ply composite DCB specimens, beam models under both plane stress and plane strain conditions in the width direction are applicable with good performance where as for the multidirectional composite DCB specimen, only the beam model under plane strain condition in the width direction appears to be applicable with moderate performance. Among the shear deformation beam theories considered, the performance of higher-order shear deformation beam theory, having quadratic variation for transverse displacement over the thickness, is superior in determining the SERR for multidirectional DCB specimen.

National media regulations in an age of convergent media: Beyond globalisation, neo-liberalism and internet freedom theories

There is a widely held view that the nation-state has become less central to media and communications policy over the last two decades. As Jan van Cuilenberg and Denis McQuail (2003, p. 181) observed in their overview of trends in communications policy-making, 'the old normative media policies have been challenged and policy-makers are searching for a new communications policy paradigm'. There are characteristically five factors put forward as to why the nation-state has become less central to media in the twenty-first century

Theories of moral education and implementation in Indonesia: Re-energizing cultural identity and addressing future challenges

School is regarded as a site of moral training for the younger generation to encounter nation’s future challenges as well as to re-energize nation’s cultural identity. The more competitive global society led by free market trade in terms of ASEAN Economic Community (AEC), requires the school to adapt and change its curriculum more frequently. Like many other countries, Indonesian Ministry of Education and Culture has introduced and nurtured universal values and traditional values respectively through school curriculum reforms to develop students’ ability to participating in global society. This paper will describe classical and contemporary theories related to moral education that have been implemented in Indonesia’s school curriculum and school activities. The theories developed by Durkheim, Alastair MacIntyre, and Basil Bernstein will be discussed. This includes explaining how far the theories have been adopted in Indonesia and how the approaches are currently being used in Indonesian schooling. This paper suggests despite the implementation of those theories in Indonesian schools, the government needs to optimise the operation of those theories to gain significant outcomes.

Conformal invariance and scalar-tensor theories

A new generalisation of Einstein’s theory is proposed which is invariant under conformal mappings. Two scalar fields are introduced in addition to the metric tensor field, so that two special choices of gauge are available for physical interpretation, the ‘Einstein gauge’ and the ‘atomic gauge’. The theory is not unique but contains two adjustable parameters ζ anda. Witha=1 the theory viewed from the atomic gauge is Brans-Dicke theory (ω=−3/2+ζ/4). Any other choice ofa leads to a creation-field theory. In particular the theory given by the choicea=−3 possesses a cosmological solution satisfying Dirac’s ‘large numbers’ hypothesis.

Democratic Legitimacy and the Politics of Rights : A comparative analysis of the conceptual relationship between democracy and rights in contemporary political theories

Democratic Legitimacy and the Politics of Rights is a research in normative political theory, based on comparative analysis of contemporary democratic theories, classified roughly as conventional liberal, deliberative democratic and radical democratic. Its focus is on the conceptual relationship between alternative sources of democratic legitimacy: democratic inclusion and liberal rights. The relationship between rights and democracy is studied through the following questions: are rights to be seen as external constraints to democracy or as objects of democratic decision making processes? Are individual rights threatened by public participation in politics; do constitutionally protected rights limit the inclusiveness of democratic processes? Are liberal values such as individuality, autonomy and liberty; and democratic values such as equality, inclusion and popular sovereignty mutually conflictual or supportive? Analyzing feminist critique of liberal discourse, the dissertation also raises the question about Enlightenment ideals in current political debates: are the universal norms of liberal democracy inherently dependent on the rationalist grand narratives of modernity and incompatible with the ideal of diversity? Part I of the thesis introduces the sources of democratic legitimacy as presented in the alternative democratic models. Part II analyses how the relationship between rights and democracy is theorized in them. Part III contains arguments by feminists and radical democrats against the tenets of universalist liberal democratic models and responds to that critique by partly endorsing, partly rejecting it. The central argument promoted in the thesis is that while the deconstruction of modern rationalism indicates that rights are political constructions as opposed to externally given moral constraints to politics, this insight does not delegitimize the politics of universal rights as an inherent part of democratic institutions. The research indicates that democracy and universal individual rights are mutually interdependent rather than oppositional; and that democracy is more dependent on an unconditional protection of universal individual rights when it is conceived as inclusive, participatory and plural; as opposed to robust majoritarian rule. The central concepts are: liberalism, democracy, legitimacy, deliberation, inclusion, equality, diversity, conflict, public sphere, rights, individualism, universalism and contextuality. The authors discussed are e.g. John Rawls, Jürgen Habermas, Seyla Benhabib, Iris Young, Chantal Mouffe and Stephen Holmes. The research focuses on contemporary political theory, but the more classical work of John S. Mill, Benjamin Constant, Isaiah Berlin and Hannah Arendt is also included.

Interview with Barbara Comber in "Chapter 3 : Critical Literacy" of "Making Literacy Real : Theories and Practices for Learning and Teaching [2nd. Ed.]"

One of the so-called ‘wicked problems’ confronting most nations is poverty, or the unequal distribution of resources. This problem is perennial, but how, where and with which physical, psychological, social and educational effects, and for which students (and their teachers), needs continual scrutiny. Poverty is relative. Entire populations may be poor or groups of people and individuals within nations may be poor. Poverty results from injustice. Not only the un- and under-employed are living in poverty, but also the ‘working poor’. Now we see affluent societies with growing pockets of persistent poverty. While there are those who dispute the statistics on the rise of poverty because different nations use different measures (for example see Biddle, 2013; http://theconversation.com/factcheck-is-poverty-on-the-rise-in-australia-17512), there seems to be little dispute that the gaps between the richest and the poorest are increasing (see http://www.stanford.edu/group/scspi/sotu/SOTU_2014_CPI.pdf)...

Intersoliton forces in weak-coupling quantum field theories

We offer a procedure for evaluating the forces exerted by solitons of weak-coupling field theories on one another. We illustrate the procedure for the kink and the antikink of the two-dimensional φ4 theory. To do this, we construct analytically a static solution of the theory which can be interpreted as a kink and an antikink held a distance R apart. This leads to a definition of the potential energy U(R) for the pair, which is seen to have all the expected features. A corresponding evaluation is also done for U(R) between a soliton and an antisoliton of the sine-Gordon theory. When this U(R) is inserted into a nonrelativistic two-body problem for the pair, it yields a set of bound states and phase shifts. These are found to agree with exact results known for the sine-Gordon field theory in those regions where U(R) is expected to be significant, i.e., when R is large compared to the soliton size. We take this agreement as support that our procedure for defining U(R) yields the correct description of the dynamics of well-separated soliton pairs. An important feature of U(R) is that it seems to give strong intersoliton forces when the coupling constant is small, as distinct from the forces between the ordinary quanta of the theory. We suggest that this is a general feature of a class of theories, and emphasize the possible relevance of this feature to real strongly interacting hadrons.

On walls of marginal stability in N=2 string theories

We study the properties of walls of marginal stability for BPS decays in a class of N = 2 theories. These theories arise in N = 2 string compactifications obtained as freely acting orbifolds of N = 4 theories, such theories include the STU model and the FHSV model. The cross sections of these walls for a generic decay in the axion-dilaton plane reduce to lines or circles. From the continuity properties of walls of marginal stability we show that central charges of BPS states do not vanish in the interior of the moduli space. Given a charge vector of a BPS state corresponding to a large black hole in these theories, we show that all walls of marginal stability intersect at the same point in the lower half of the axion-dilaton plane. We isolate a class of decays whose walls of marginal stability always lie in a region bounded by walls formed by decays to small black holes. This enables us to isolate a region in moduli space for which no decays occur within this class. We then study entropy enigma decays for such models and show that for generic values of the moduli, that is when moduli are of order one compared to the charges, entropy enigma decays do not occur in these models.

On gravitational fields of stars in f(R) gravity theories

Einstein's general relativity is a classical theory of gravitation: it is a postulate on the coupling between the four-dimensional, continuos spacetime and the matter fields in the universe, and it yields their dynamical evolution. It is believed that general relativity must be replaced by a quantum theory of gravity at least at extremely high energies of the early universe and at regions of strong curvature of spacetime, cf. black holes. Various attempts to quantize gravity, including conceptually new models such as string theory, have suggested that modification to general relativity might show up even at lower energy scales. On the other hand, also the late time acceleration of the expansion of the universe, known as the dark energy problem, might originate from new gravitational physics. Thus, although there has been no direct experimental evidence contradicting general relativity so far - on the contrary, it has passed a variety of observational tests - it is a question worth asking, why should the effective theory of gravity be of the exact form of general relativity? If general relativity is modified, how do the predictions of the theory change? Furthermore, how far can we go with the changes before we are face with contradictions with the experiments? Along with the changes, could there be new phenomena, which we could measure to find hints of the form of the quantum theory of gravity? This thesis is on a class of modified gravity theories called f(R) models, and in particular on the effects of changing the theory of gravity on stellar solutions. It is discussed how experimental constraints from the measurements in the Solar System restrict the form of f(R) theories. Moreover, it is shown that models, which do not differ from general relativity at the weak field scale of the Solar System, can produce very different predictions for dense stars like neutron stars. Due to the nature of f(R) models, the role of independent connection of the spacetime is emphasized throughout the thesis.

Quantum Space-Time and Noncommutative Gauge Field Theories

Arguments arising from quantum mechanics and gravitation theory as well as from string theory, indicate that the description of space-time as a continuous manifold is not adequate at very short distances. An important candidate for the description of space-time at such scales is provided by noncommutative space-time where the coordinates are promoted to noncommuting operators. Thus, the study of quantum field theory in noncommutative space-time provides an interesting interface where ordinary field theoretic tools can be used to study the properties of quantum spacetime. The three original publications in this thesis encompass various aspects in the still developing area of noncommutative quantum field theory, ranging from fundamental concepts to model building. One of the key features of noncommutative space-time is the apparent loss of Lorentz invariance that has been addressed in different ways in the literature. One recently developed approach is to eliminate the Lorentz violating effects by integrating over the parameter of noncommutativity. Fundamental properties of such theories are investigated in this thesis. Another issue addressed is model building, which is difficult in the noncommutative setting due to severe restrictions on the possible gauge symmetries imposed by the noncommutativity of the space-time. Possible ways to relieve these restrictions are investigated and applied and a noncommutative version of the Minimal Supersymmetric Standard Model is presented. While putting the results obtained in the three original publications into their proper context, the introductory part of this thesis aims to provide an overview of the present situation in the field.