The double ended guillotine break leading to density-driven air ingress has been identified as a low probability yet high consequence event for Very High Temperature Reactor (VHTR). The lower plenum of the VHTR contains the core support structure and is composed of graphite. During an air ingress event, oxidation of the graphite structure under high temperature conditions in an oxygen containing environment could degrade the integrity of the core support structure. Following this large break, air from the reactor containment will begin to enter the lower plenum via two mechanisms: diffusion or density driven stratified flow. The large difference in time scales between the mechanisms leads to the need to perform high fidelity experimental studies to investigate the dominant the air ingress mechanism. A scaled test facility has been designed and built that allows the acquisition of velocity measurements during stratification after a pipe break. A non-intrusive optical measurement technique provides full-field velocity measurements profiles of the two species Particle Image Velocimetry (PIV). The data allow a more developed understanding of the fundamental flow features, the development of improved models, and possible mitigation strategies in such a scenario.Two brine-water experiments were conducted with different break locations. Flow fronts were analyzed and findings concluded that the flow has a constant speed through the pipe after the initial lock exchange. The time in which the flow enters the lower plenum is an important factor because it provides the window of opportunity for mitigation strategies in an actual reactor scenario. For both cases the flow of the heavier density liquid (simulating air ingress from the reactor containment) from the pipe enters the reactor vessel in under 6 seconds. The diffusion velocity and heavy flow front of the stratified flow layer were compared for the SF6/He gas case. It is seen that the diffusion plays less of a role as the transport mechanism in comparison to the density-driven stratified flow since the velocity of the diffusion is two orders of magnitude smaller than the velocity of the stratified flow mechanism. This is the reason for the need for density-driven stratified flow investigations following a LOCA. These investigations provided high-quality data for CFD validation in order for these models to depict the basic phenomena occurring in an air ingress scenario.

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This thesis investigates the use of houndedness. claims for credibility and the exploitation o\' reflexive accounting within know ledge w ork. The current literature t'rom the sociology of scientific knowledge is used to contextualize this investigation, which constructs the thesis' central problem as a concern with the way boundary maintaining and boundary breaking activities contribute to the distribution of science and technology into its wider context. Two distinct and apparentK contrasting knowledge cultures are used to explore this problem; the social studies of technology (SST-1) is constituted as an academic knowledge culture and stratified systems theory (SST-2) is constituted as a consultancy culture. Ethnographic investigation and a variety of textual forms are used to address each of these cultures and the relationship between them. The constituted distinction is used as a further resource for investigating the problem. Chapters one to three provide the "introduction', 'aims' and "methodology' and exemplify boundedness, credibility and reflexivity in the culture of SST-1. Chapters four to six provide the "data' chapters of the thesis and exemplify boundedness, credibility and reflexivity in the culture of SST-2. This investigation identifies the concepts of unlocatability. conscription of members at the margins, and flexible and locked boundedness as key features of SST-2. In the final chapter, this thesis claims the apparent contrast between SST-1 and SST-2 is unsustainable as they can both be constructed as "working" via the variable 'incorporation' of "entities' (people, roles, locations, artefacts, ideas) into "conscripting organisms'. However, the boundaries constructed for the production of this thesis allow us to establish SST-1 and SST-2 as similar in using conscription and distinct in the focus of conscription. SST-1 is constituted as conscripting at the core and SST-2 is constituted as conscripting at the margins.

[Abstract]: Mobile Games are becoming very popular. Players play games under various conditions and so we need protocols which can adapt. However, unlike the desktop, there are many issues with that of mobile communication. This dissertation proposes a stratified protocol to be implemented in order to solve these communication problems more effectively. The protocol itself dynamically adapts to the changing bandwidth capacity of the network. The term stratified means that the payload in the protocol packets is subdivided into different categories, or strata, of data which are handled differently dependingon network conditions. Such a protocol needs to be responsible as it must make decisions which do notworsen the problem of network congestion when it arises.An experiment was conducted with a view to determining whether it is important to address difficulties with technical quality of communication. This experiment showedthat gaming satisfaction of players does depend on technical quality of communication and that the way in which this dependence on technical quality is exhibited depends upon the particular gaming genre. This dependence on genre and the fact that different games make use of communication services differently suggests that stratification of communication protocols could be useful.

Thesis (Ph. D.)--University of Washington, 1989. / Vita. Includes bibliographical references (leaves [182]-185).

Thesis (Ph.D.) - University of St Andrews, May 2007.

Thesis (Ph. D.)--University of Washington, 1999. / Vita. Includes bibliographical references (p. 87-92).

Thesis (Sc. D.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering, 1983. / Supervised by William D. Grant. Includes bibliographical references (leaves 201-205).