Texte remanié de: Th. doct.--Nijmegen, Pays-Bas--Radboud Universiteit Nijmegen, 2005. / Contient un résumé en hollandais (p. 491-495). Bibliogr. p. 439-489.

University of Macau / Faculty of Arts and Humanities. / Department of English

Digitized by Kansas Correctional Industries / Department: Architecture.

We have studied precipitate growth and coarsening in ternary alloys using two different phase held models. The first one is a ternary extension of the classical Cahn-Hilliard (C-H) model in which both the phases are characterized using conserved held variables i.e. composition (cB; cC ); mobility matrix and gradient energy efficient are the other input parameters in this model. In the second model, each phase is treated as separate, and phase identify cation is through a (non-conserved) phase held variable ; we have used a grand potential-based (GP) formulation, due to Plapp [1], Choudhury and Nestler [2], where interfacial energy and interface width, as well as free energy and diffusivity matrix for the relevant phases are the input parameters. The first model i.e. the Cahn-Hilliard (C-H) type model is conceptually simple. The model for ternary is a straight forward extension of the binary. The grand potential (GP) formulation has the advantage of being able to incorporate thermodynamic database like Thermocalc in it. We present below a summary of the findings of our research on (a) precipitate growth, precipitate coarsening, and (c) a critical comparison between results from phase held simulations and those from experiments on an Ni-Al-Mo alloy Precipitate growth In our study of precipitate growth in ternary alloys, we end that when both the solute elements have the same diffusivity, precipitate growth behaviour in ternary alloys is identical to that binary alloys; specifically, we recover the temporal power law r2 = kgt relating the particle radius to time, and the growth kg depends only on supersaturation (i.e., equilibrium volume fraction of the precipitate phase), and is independent of the slope of the tie line. However, when one solute element, (say, C) di uses slower than the other (i.e. (DCC =DBB) < 1,(where DBB, DCC are intertie suavities’ in the lab frame of reference), the ux of C at the interface is smaller than that of species B, causing the precipitate to become depleted in C and enriched in B; this process continues until the growth phase enters a scaling regime where we recover the temporal law for growth: r2 = kgt. In this regime, the tie line selected by the precipitate and matrix interfacial compositions is different from the thermodynamic tie line containing the alloy, a result first reported by Coates [3]. After validating our phase held model quantitatively through a critical comparison with Coates' theory of tie line selection, we have characterized the growth behaviour: specifically, we end that growth kg drops with decreasing value of DCC ; the magnitude of this drop is stronger for alloys which (a) are on higher-C tie lines (i.e., the slope of the tie line is higher), and (b) have smaller precipitate volume fractions. Precipitate coarsening In our simulations, we end that precipitate coarsening does indeed enter a scaling regime where the temporal power law r3 = kt (which relates the average precipitate radius r to (b) time t) is valid; the coarsening rate k depends, as expected, not only on precipitate volume fraction, but also on the slope of the tie line and diffusivity ratio (DCC =DBB). (c) (d) When the solutes have equal diffusivity (i.e., (DCC =DBB) = 1), the coarsening behaviour is essentially the same as that in a binary alloy. However, when solute C (say) is the slower di using species, the coarsening rate k drops, with a deeper drop in alloys on higher-C tie lines. Both these conclusions are similar to those from our study of precipitate growth. (e) (f) However, there is a crucial difference between precipitate growth and coarsening in ternary alloys: The suppression in coarsening rate (for DCC < DBB) in ternary alloys is accompanied by another e ect: larger (and growing) precipitates are richer in the faster di using species B, while the smaller and shrinking precipitates are richer in the slower di using C. In other words, during coarsening in ternary alloys, the tie line selected by precipitate and matrix interfacial components depends on precipitate size; during growth, however, the scaling regime is characterized by the same tie line, independent of precipitate size. (g) (h) (i) Critical comparison between theory and experiment (j) (k) (l) We have used the grand potential based phase held model [1] [2] to study coarsening in Ni-Al-Mo alloys. This model has the advantage of ease with which we can incorporate the thermodynamic and kinetic data on real alloys. (m) (n) A comparison of coarsening rate from our 3D simulations with the experimentally observed rate reveals that diffusivity of the faster di using species (which, in Ni-Al-Mo alloys, is aluminium) from our simulations is within an order of magnitude from the experimental value. However the dominant term in the (@ =@c) matrix is underestimated by 2 to 3 orders of magnitude (compared to its value computed from CALPHAD-based thermodynamic data).

This thesis aims to identify and explain how, through the consumption of the wireless as a modern consumer durable, modernism was brought to society. To understand this process, the study will map how social change during the period responded to wider intellectual and aesthetic currents and trends but was driven by emergent commercial, cultural and political economies of a newly mediated society. Furthermore, it seeks to establish that this happened not as a result of social engineering through model housing schemes but as a result of consumer-led demand. This investigation considers how, as part of that newly mediated social environment, the wireless developed following its arrival on the domestic market without having adopted a single stylistic form. It addresses how that form, both stylistically and technically, evolved over a relatively short period to address the economic and cultural requirements and expectations of a new electrically powered domestic entertainment technology. In so doing, a discourse will be established considering these expectations and requirements related to how the wireless in Britain adopted and adapted the Modernist design idiom. It will further consider how the language of Modernism was propagated as the accepted version of what a radio could or should look like, so developing the modernist paradigm in a broader sense. To gain an appreciation of this it is necessary to understand the contemporary public conception of what the modern was in a more general sense. To decipher this public perception of modernity the project aims to extrapolate that public conception through examining other popular forms and products. Although this suggests that Radio was not alone in adopting the language of the moderne, as a product it is notable for its widespread commercial success and as such can be identified as a significant carrier of the coded message of what was modern. Design historians such as Yagou and Forty have attempted to incorporate radio into various strands of historical perception but the typologies they have devised to describe and understand wireless fall short in addressing the relationship between modernity and the wireless and instead see the wireless in terms of being an independent consumer product, a quasi-scientific instrument or else a furnishing form, rather than creating categories which accommodate the wireless and its position as a design type in its own right. To overcome this shortcoming a strand of this thesis seeks to argue that the wireless was itself a proto-modernist device during the early years of market expansion. That device then developed along a natural stylistic course embracing contemporary decorative ideas. By assessing the response of radio manufacturers to the socio-economic conditions of their market, this study has highlighted how through producing a product which addressed contemporary ideas of glamour, ease of use and functionality, the wireless entered a wide range of homes during the 1920s and 1930s. For the public, the immediate appeal of the wireless was that it provided access to the international experience of listening in while simultaneously it provided a template for the consumer to base their understanding of the modern World, both in its mediated form and stylistic appearance. This thesis seeks to demonstrate that during the period 1925 to 1939, the wireless established itself as an unashamedly modern device which appealed to a broad socio economic cross section of the public. By consuming the wireless, the British public accepted a significant technological and stylistic aspect of modernity into their homes. This was achieved despite the privations of the era because of the perceived desirability of wireless broadcasts and the perception of listening in as a popular leisure activity. As a result of that consumer demand, the British public was given access to a range of stylistic versions of modernity through the design of radio cabinetry. These modern styles were readily consumed throughout the social spectrum in preference to historicist alternatives. This demonstrates that the wireless was instrumental in introducing the modernist aesthetic to the British domestic environment.

In my graduation thesis I first of all shortly mentioned frequency–selection filters and their utilisations. However, the base point of this project was to acquaint with different types of signal flow diagrams with whom I should design and analyse frequency-selection filtres with conventional and also innovative active components. As the first I created signal flow diagrams for both voltage and current conveyors. These modern active components are well known today and enable the construction of circuits with better properties than circuits with traditional differentiating amplifiers with voltage feedback. Thereinafter I made signal flow diagrams for OTA component. Transconductancal amplifiers are well known active components used in various areas of analog signal processing. OTA amplifier is in fact the current source controlled by voltage difference, which is characterised by gm transconductance. Ulterior components were IOZ and IZN models of voltage amplifier with voltage gain A. The last component was COA amplifier. It is a current operational amplifier. COA model is fully dual component to VOA, which is classical voltage amplifier. In my project I used filters with two OTA components. This filter offers functions like low-pass filter, band-pass filter, high-pass filter, band-stop filter and two-phase network. Following this I used circuits with two GCC conveyors. These offer band-pass filter, low-pass filter, high-pass filter, band-stop filter and two-phase network. Ultimately I designed filters with COA components, which offer three transmission functions simultaneously (DP, PP and HP). Analysis of these filters was made with a help of PSpice computer programme.

This thesis focuses on a transformational but disregarded period in New Zealand’s twentieth century history, the era from the arrival of the Marines in 1942 to the arrival of Rock Around the Clock in 1956. It examines one of the chief agents in this metamorphosis: the impact of American culture. During this era the crucial conduits of that culture were movies, music and comics. The aims of my thesis are threefold: to explore how New Zealanders responded to this cultural trinity, determine the key features of their reactions and assess their significance. The perceived modernity and alterity of Hollywood movies, musical genres such as swing, and the content and presentation of American comics and ‘pulps’, became the sources of heated debate during the midcentury. Many New Zealanders admired what they perceived as the exuberance, variety and style of such American media. They also applauded the willingness of the cultural triptych to appropriate visual, textual and musical forms and styles without respect for the traditional classifications of cultural merit. Such perceived standards were based on the privileged judgements of cultural arbiters drawn from members of New Zealand’s educational and civic elites. Key figures within these elites insisted that American culture was ‘low’, inferior and commodified, threatening the dominance of a sacrosanct, traditional ‘high’culture. Many of them also maintained that these American cultural imports endangered both the traditionally British nature of our cultural heritage, and New Zealand’s distinctively ‘British’ identity. Many of these complaints enfolded deeper objections to American movies, music and literary forms exemplified by comics and pulps. Significant intellectual and civic figures portrayed these cultural modes as pernicious and malignant, because they were allegedly the product of malignant African-American, Jewish and capitalist sources, which threatened to poison the cultural and social values of New Zealanders, especially the young. In order to justify such attitudes, these influential cultural guardians portrayed the general public as an essentially immature, susceptible, unthinking and puritanical mass. Accordingly, this public, supposedly ignorant of the dangers posed by American culture, required the intervention and protection of members of this elite. Responses to these potent expressions of American culture provide focal points which both illuminate and reflect wider social, political and ideological controversies within midcentury New Zealand. Not only were these reactions part of a process of comprehension and negotiation of new aesthetic styles and media modes. They also represent an arena of public and intellectual contention whose significance has been neglected or under-valued. New Zealanders’ attitudes towards the new cinematic, literary and musical elements of American culture occurred within a rich and revealing socio-political and ideological context. When we comment on that culture we reveal significant features of our own national and cultural selves.