Hydroelastic stability and wave propagation in fluid-filled channels

In this thesis analytical and numerical methods are used to investigate the stability and propagation of waves in various fluid-filled elastic-walled channels. In Chapter 2 a linear temporal stability analysis is performed for various channel wall configurations, the results of which are compared to determine how different physical effects contribute to the stability. In Chapter 3 a linear spatial stability analysis is performed for flow between linear plates, this is a limiting case of the wall configuration in Chapter 2. Roots of the dispersion relation are found and their stability and direction of propagation determined. Chapters 4 and 5 focus on the propagation of nonlinear waves on liquid sheets between thin infinite elastic plates. Both linear and nonlinear models are used for the elastic plates. One-dimensional time-dependent equations are derived based on a long wavelength approximation. Symmetric and antisymmetric travelling waves are found with the linear plate model and symmetric travelling waves are found for the fully nonlinear case. Numerical simulations are employed to study the evolution in time of initial disturbances and to compare the different models used. Nonlinear effects are found to decrease the travelling wave speed compared with linear models. At sufficiently large amplitude of initial disturbances, higher order temporal oscillations induced by nonlinearity can lead to thickness of the liquid sheet approaching zero. Finally, in Chapter 6, an extension of the model from Chapters 4 and 5 is considered, the elasticities of the two channel walls are allowed to differ. The effect of this difference is determined through a mix of techniques and the limiting case of one wall having no elasticity is discussed

"It's cleaner, definitely": Collaborative Process in Audio Production.

Working from vague client instructions, how do audio producers collaborate to diagnose what specifically is wrong with a piece of music, where the problem is and what to do about it? This paper presents a design ethnography that uncovers some of the ways in which two music producers co-ordinate their understanding of complex representations of pieces of music while working together in a studio. Our analysis shows that audio producers constantly make judgements based on audio and visual evidence while working with complex digital tools, which can lead to ambiguity in assessments of issues. We show how multimodal conduct guides the process of work and that complex media objects are integrated as elements of interaction by the music producers. The findings provide an understanding how people currently collaborate when producing audio, to support the design of better tools and systems for collaborative audio production in the future

Giraffe translocation population viability analysis

Most populations of giraffes have declined in recent decades, leading to the recent IUCN decision to upgrade the species to Vulnerable status, and some subspecies to Endangered. Translocations have been used as a conservation tool to re-introduce giraffes to previously occupied areas or establish new populations, but guidelines for founding populations are lacking. To provide general guidelines for translocation projects regarding feasibility, we simulated various scenarios of translocated giraffe populations to identify viable age and sex distributions of founding populations using population viability analysis (PVA) implemented in Vortex software. We explored the parameter space for demography and the genetic load, examining how variation in founding numbers and sex ratios affected 100 yr probability of population extinction and genetic diversity. We found that even very small numbers of founders (N ≤ 10 females) can appear to be successful in the first decades due to transient positive population growth, but with moderate population growth rate and moderate genetic load, long-term population viability (probability of extinction 95% genetic diversity of the source population in an isolated population, 50 females and 5 males are recommended to compose the founding population. Sensitivity analyses revealed first-year survival and reproductive rate were the simulation parameters with the greatest proportional influence on probability of extinction and genetic diversity. These simulations highlight important considerations for translocation success and data gaps including true genetic load in wild giraffe populations

Overcoming the common pool problem through voluntary cooperation: the rise and fall of a fishery cooperative

We analyze a seldom used, but highly promising form of rights-based management over common pool resources that involves the self-selection of heterogeneous fishermen into sectors. The fishery management regime assigns one portion of an overall catch quota to a voluntary cooperative, with the remainder exploited as a commons by those choosing to fish independently. Data from an Alaska commercial salmon fishery confirm our model's key predictions, that the co-op would facilitate the consolidation of fishing effort, coordination of harvest activities, sharing of information and provision of shared infrastructure. We estimate that the resulting rent gains were at least 25%. A lawsuit filed by two disgruntled independents led to the co-op's demise, an outcome also predicted by our model. Our analysis provides guidance for designing fishery reform that leads to Pareto improvements for fishermen of all skill levels, which suggests a structure that enables reform without losers.

Interaction-induced shift of the cyclotron resonance of graphene using infrared spectroscopy

We report a study of the cyclotron resonance (CR) transitions to and from the unusual $n=0$ Landau level (LL) in monolayer graphene. Unexpectedly, we find the CR transition energy exhibits large (up to 10%) and non-monotonic shifts as a function of the LL filling factor, with the energy being largest at half-filling of the $n=0$ level. The magnitude of these shifts, and their magnetic field dependence, suggests that an interaction-enhanced energy gap opens in the $n=0$ level at high magnetic fields. Such interaction effects normally have limited impact on the CR due to Kohn's theorem [W. Kohn, Phys. Rev. {\bf 123}, 1242 (1961)], which does not apply in graphene as a consequence of the underlying linear band structure.Comment: 4 pages, 4 figures. Version 2, edited for publication. Includes a number of edits for clarity; also added a paragraph contrasting our work w/ previous CR expts. in 2D Si and GaA

Superlattice Magnetophonon Resonances in Strongly Coupled InAs/GaSb Superlattices

We report an experimental study of miniband magnetoconduction in semiconducting InAs/GaSb superlattices. For samples with miniband widths below the longitudinal optical phonon energy we identify a new superlattice magnetophonon resonance (SLMPR) caused by resonant scattering of electrons across the mini-Brillouin zone. This new resonant feature arises directly from the drift velocity characteristics of the superlattice dispersion and total magnetic quantisation of the superlattice Landau level minibands.Comment: 9 pages, 8 figures, submitted to Phys. Rev.

Syntheses, Structures, and Corrosion Inhibition of Various Alkali Metal Carboxylate Complexes

Complexes of the alkali metals Li-Cs with 3-thiophenecarboxylate (3tpc), 2-methyl-3-furoate (2m3fur), 3-furoate (3fur), 4-hydroxycinnamate (4hocin), and 4-hydroxybenzoate (4hob) ions were prepared via neutralisation reactions, and the structures of [Li2(3tpc)2]n (1Li); [K2(3tpc)2]n (1K); [Rb(3tpc)(H2O)]n (1Rb); [Cs{H(3tpc)2}]n (1Cs); [Li2(2m3fur)2(H2O)3] (2Li); [K2(2m3fur)2(H2O)]n (2K); [Li(3fur)]n(3Li); [K(4hocin](H2O)3]n (4K); [Rb{H(4hocin)2}]n.nH2O (4Rb); [Cs(4hocin)(H2O)]n (4Cs); [Li(4hob)]n (5Li); [K(4hob)(H2O)3]n (5K); [Rb(4hob)(H2O)]n (5Rb); and [Cs(4hob)(H2O)]n (5Cs) were determined via X-ray crystallography. Bulk products were also characterised via XPD, IR, and TGA measurements. No sodium derivatives could be obtained as crystallographically suitable single crystals. All were obtained as coordination polymers with a wide variety of carboxylate-binding modes, except for dinuclear 2Li. Under conditions that normally gave coordinated carboxylate ions, the ligation of hydrogen dicarboxylate ions was observed in 1Cs and 4Rb, with short H-bonds and short O…O distances associated with the acidic hydrogen. The alkali-metal carboxylates showed corrosion inhibitor properties inferior to those of the corresponding rare-earth carboxylates

Simplifying ARM concurrency: Multicopy-atomic axiomatic and operational models for ARMv8

ARM has a relaxed memory model, previously specified in informal prose for ARMv7 and ARMv8. Over time, and partly due to work building formal semantics for ARM concurrency, it has become clear that some of the complexity of the model is not justified by the potential benefits. In particular, the model was originally non-multicopy-atomic : writes could become visible to some other threads before becoming visible to all — but this has not been exploited in production implementations, the corresponding potential hardware optimisations are thought to have insufficient benefits in the ARM context, and it gives rise to subtle complications when combined with other ARMv8 features. The ARMv8 architecture has therefore been revised: it now has a multicopy-atomic model. It has also been simplified in other respects, including more straightforward notions of dependency, and the architecture now includes a formal concurrency model. In this paper we detail these changes and discuss their motivation. We define two formal concurrency models: an operational one, simplifying the Flowing model of Flur et al., and the axiomatic model of the revised ARMv8 specification. The models were developed by an academic group and by ARM staff, respectively, and this extended collaboration partly motivated the above changes. We prove the equivalence of the two models. The operational model is integrated into an executable exploration tool with new web interface, demonstrated by exhaustively checking the possible behaviours of a loop-unrolled version of a Linux kernel lock implementation, a previously known bug due to unprevented speculation, and a fixed version.</jats:p

First light for the desert fireball network

Accepted versio