VictorJuiz/thesis huggingface dataset:
Automating inference for non–standard models

Probabilistic models enable us to infer the underlying relationships within data and make decisions based on this information. Certain models are more commonly used not because they are more appropriate to imitate a particular system, but because they are simple enough to analyze given the current computational resources and available inference algorithms. However, there are a broad range of non-standard models that we could use to describe real-world tasks better; they may have complex dependency structures, variables following non-common distributions, and/or a stochastic number of variables. But we typically avoid using them as these features substantially complicate the inference procedure such that many conventional inference algorithms would fail when dealing with these models.
To alleviate the computational concerns of data scientists or domain experts and free them to develop non-standard, complex models as needed, more sophisticated inference methods need to be more easily accessible. Additionally, because it is usually difﬁcult to extract helpful information of non-standard models ahead of inference, like where the modes might be, such inference techniques should be expected to work reasonably well without too much such information. In an ideal world, domain experts would be able to specify any model of interest, and no longer need to worry about the technical details of inference algorithms or how to implement them. Moreover, these algorithms are provided as generic engines and can be used to reason the models in an automated manner. Achieving so is the ambitious, long-term goal of the emerging ﬁeld called probabilistic programming.
The aim of this thesis is to make inroads to this ultimate goal: we develop and automate advanced inference methods that are applicable for a broad range of non-standard probabilistic models. In particular, we introduce a novel class of adaptive inference algorithms which can be implemented in a black-box manner. They are especially useful for the models with multiple, separated modes where many off-the-shelf options struggle. Furthermore, we investigate both a restricted class of probabilistic programming systems (PPSs) that impose strong constraints on the model class to ensure inference efﬁciency, and universal PPSs which are designed around the long-term goal and aim to support any possible model but substantially complicate the inference procedures. For the former, we propose a principled way to extend them to incorporate a broader range of models and inference engines that are not supported before. For the latter, we develop a general framework to handle one class of the most challenging models where the support of a model can be stochastic.

Keywords: Non–Standard Statistical Models
Probabilistic Programming
Bayesian Inference
Advisor: Rainforth, T
Staton, S
Teh, YW
Yang, H
Essays in private equity

This dissertation presents three empirical analyses on private equity (PE) investments. The first chapter, The accuracy of net asset values in private equity: Evidence from the secondary market, examines pricing in the secondary market for PE fund stakes. The average transaction occurs at a discount, which is commonly attributed to compensation for liquidity provision. As a quarter of bids come in at a par or a premium, this cannot be the full explanation. I document that cross-sectional variation in discounts predicts future fund returns. The second chapter explores The dynamics of pay-for-performance sensitivity in private equity funds arising from carried interest. As carried interest is conditional on beating a hurdle rate, pay-for-performance sensitivity is increasing in fund performance, and increasingly so as the fund matures. I document that within-fund variation in pay-for-performance sensitivity is positively related to growth in portfolio companies acquired in buyouts. The effect is stronger when the importance of the direct component is high relative to the indirect component of pay for performance. To rule out confounding factors, I utilize public market movements to generate exogenous variation in the measure. My findings provide evidence of the importance of incentives for value creation. The third chapter, Managerial ownership and operational improvements in buyouts, investigates the relevance of CEO ownership stakes in companies acquired in buyouts. I find that post-buyout CEO equity ownership stakes are positively associated with profitability improvements. Consistent with an effect of incentives, the results are stronger when the ownership stake increases, and are driven entirely by the subsample in which the CEO is retained. Taken together, these three studies contribute to the growing body of work on private equity investments and the impact of private equity ownership on companies acquired in buyouts. They open the door to further theoretical and empirical research in the field.

Keywords: Private Equity
Leveraged Buyouts
Incentives
Advisor: Phalippou, L
Jenkinson, T
Sumatran mesocarnivores: small-medium sized wild felids of the Kerinci Seblat landscape

The study of mesopredators, their guilds, and conservation has had little attention in the tropics of Southeast Asia. A particularly interesting group, from the point of view of their ecological community and because of their generally threatened status, is the Felidae. This thesis reports an intensive camera-trapping study of small-medium sized wild felids in the Kerinci Seblat landscape in west-central Sumatra. Samples were drawn from seven study areas across a diversity of habitats occupied by clouded leopard, golden cat, marbled cat, leopard cat, and their prey. The papers comprising this thesis report on the ecology, behaviour, population status and trends, core areas and habitat connectivity of this predator- prey community, and prioritizing conservation in a multi-species management approach. Specifically, this thesis has five main results: (i) revealed spatial and temporal interactions between clouded leopard, golden cat, and their respective prey through performing Bayesian two species occupancy modelling and temporal overlap analyses; (ii) estimated population densities of clouded leopard, in the context of human activities, by implementing Bayesian Spatially Explicit Capture Recapture (SECR) and identified and quantified illegal human activities detected by camera traps; (iii) estimated occupancy states as an indicator of clouded leopard and golden cat population dynamics from consecutive surveys in 2009-11 and 2014-16 and anthropogenic pressures from deforestation in the surrounding areas; and (iv) identified high priority areas within and outside protected area networks through estimating multi-species habitat use and least cost path and kernel density estimate analyses for defining core areas and corridor networks. Integrating these four research themes, this thesis contributes to absent information on the felid mesocarnivores of Sumatra, and offers analytical methodologies for assessing their ecology, behaviour, conservation, and management that can be applied throughout the tropics.

Keywords: core area
corridor
Bayesian SECR
marbled cat
Asiatic golden cat
Bayesian occupancy
Sumatran clouded leopard
UNICOR
Sumatra
Kerinci Seblat
temporal overlap
leopard cat
least cost path
Single Season Single Species Occupancy
Advisor: Macdonald, D
Understanding the formation and evolution of asteroids through analysis of carbonaceous chondrites

The transport and evolution of volatiles (e.g. water, organics) during the formation of the inner terrestrial planets of our Solar System is relatively poorly constrained. A number of dynamical mechanisms have been proposed that transport volatile rich material from the outer Solar System (i.e. from beyond the snow-line, currently 5 AU), and primitive, volatile-rich asteroids may provide clues as to these processes. Observations demonstrate that these asteroids have similar infrared spectra to CI, CM and CY carbonaceous chondrite meteorites. Thus, by studying the composition and alteration histories of these families of meteorites it can potentially provide insights into the physical processes that occurred or are occurring on these asteroids.
In this thesis I link trends in the spectra of both aqueously altered and aqueously and thermally altered CI, CM and CY chondrites with meteorite mineralogy. I demonstrate how these trends may be applied to remote asteroid spectra to examine their surface mineralogy and processing history. I describe how trends in the near- (NIR) and mid-infrared (MIR) spectra of aqueously altered meteorites can reflect the phyllosilicate composition and therefore degree of aqueous alteration. I also report that trends in aqueously and thermally altered meteorite NIR and MIR spectra reflect a combination of phyllosilicate and olivine compositions and abundances. Furthermore, I describe and assess differences between the MIR reflectance spectra typically collected in laboratories, and emissivity spectra acquired under asteroid environmental conditions that more accurately replicate the spectral flux received when observing a remote airless body. I then use the spectra collected to aid in the interpretation of spectra of a range of potentially volatile-rich objects including NEOs visited by Hayabusa2 and OSIRIS-REx, main-belt asteroids and Jupiter Trojans. The spectra will also be a valuable aid in analysis of future remote telescopic observations of and spacecraft missions to small bodies.

Keywords: Asteroids
Spectroscopy
Meteorites
Advisor: Donaldson Hanna, K
Russell, S
King, A
Bowles, N
Modelling removal of sulphur dioxide from flue gas in purification devices

Many chemical filters contain reactive components where harmful substances are removed or transformed. In this thesis, we consider the problem of removal of sulphur dioxide from flue gas using filters made from a porous catalytic medium. This is inspired by a filter, designed by W. L. Gore and Associates, Inc., which converts gaseous sulphur dioxide into liquid sulphuric acid via a chemical reaction that occurs on the surface of microscopic catalytic pellets. During the device operation, the liquid sulphuric acid accumulates within the filter and reduces its efficiency. We derive a series of mathematical models that explore various aspects of this problem and ultimately serve to predict the performance of the device. We begin by considering a fundamental fluid dynamics problem of spreading of a thin film under surface tension with liquid injection due to the chemical reaction. We then formulate a microscale model for the gas and liquid transport within the porous filter material and, separately, present a radially symmetric model for a single catalytic pellet, which we use to estimate the unknown reaction rate constant based on real observations. Although we do not explicitly account for the porous scaffold of the filter, the model set-up is appropriate for the case of hydrophobic material. We move on to upscale the microscale equations to a set of device-scale equations using homogenisation techniques. We obtain numerical solutions and asymptotic predictions for various limits that compare well, and also explore the effect of changing the system parameters, such as the gas speed, on the effective cleansing of flue gas. In addition, we develop a model for two neighbouring pellets, one of which is completely submerged by sulphuric acid, which is useful to understand the long-term behaviour of the system once a continuous layer of liquid forms near the surface of the filter sheets. We also study a simplified problem where the filter is made from hydrophilic material and identify the key differences in the resulting liquid transport. Finally, we present a model for the hygroscopy of sulphuric acid, which helps evaluate the effect of water absorption on the liquid growth within the filter. All the models we develop retain generality and can be applied to other physical and industrial processes.

Keywords: sulphur dioxide
asymptotic analysis
filtration
homogenisation
porous media
fluid dynamics
Advisor: Breward, C
Griffiths, I
Venkateshwaran, V
Schwendeman, D
Beuscher, U
Improving acquisition speed and efficiency of advanced arterial spin labelling MRI

Magnetic resonance imaging (MRI) is a notoriously slow imaging method compared with other imaging modalities, for example computed tomography. It can, however, produce contrasts and attain biophysical information that is unattainable by other methods and is thus a valuable clinical tool.
In recent years, image acquisition times have been reduced through image reconstruction methods that require less data than traditional methods. In this thesis, these kinds of methods are used and extended upon for improved acquisition speed of an MRI method that is particularly slow due to requiring multiple encoded acquisitions to produce a single composite image: arterial spin labelling (ASL).
In conventional ASL, two encodings are used; one with "labelled" blood and one without "labelling", such that subtracting one from the other gives an image of just the blood signal. Angiography can be used to visualise blood flow through the arteries, and perfusion imaging to assess oxygen and nutrient supply to the tissue. Some advanced ASL methods require even more encodings that can be decoded to reveal more information about the cerebral haemodynamics. An example of such an advanced ASL method is vessel-encoded ASL, which allows for generation of separate images of blood originating from different arteries.
In this thesis, modern MRI sampling and reconstruction methods are optimised for vessel-encoded ASL and other ASL variants, with the aim of bringing these modalities towards clinically feasible scan times, which would eventually allow for more information-rich assessments of the cerebrovasculature and the perfusion state of the brain in, for example, patients suffering from stroke, dementia, and arteriovenous malformations.
By careful joint consideration of the multi-dimensional data, the data acquisition, and the reconstruction, very high acceleration factors can be achieved. This is demonstrated, first for vessel-encoded ASL angiography in 2D and 3D, then in similar advanced ASL methods (time-encoded ASL angiography, and combined angiography and perfusion imaging). A new radial sampling scheme is also presented and assessed on ASL angiographic data, that could have impact on imaging methods beyond ASL, in particular other dynamic MRI modalities.

Keywords: Imaging
ASL
Non-linear image reconstruction
Compressed sensing
Image reconstruction
Accelerated imaging
MRI
Advisor: Okell, T
Chiew, M
Jezzard, P
Quasi-phase-matched high-harmonic generation in gas-filled hollow-core photonic crystal fibre

High-order harmonic generation (HHG) provides a promising tabletop source of coherent short wavelength radiation. However, the low generation efficiency limits the mean photon flux of HHG sources when driven with low average power, kHz repetition rate lasers. The HHG flux could be increased by employing MHz repetition rate driving lasers. However, the low pulse energy necessitates tight focusing, which limits the effective interaction volume. Generating harmonics in a gas-filled photonic crystal fiber (PCF) mitigates this problem, but for both free focus and PCF targets, the HHG conversion efficiency is optimized at technologically challenging multi-bar gas pressures. In this thesis, HHG is performed with µJ-level driving pulses in hollow-core PCFs. Dramatic 160-fold enhancement of the HHG flux through a novel, time-multiplexed multi-modal quasi-phasematching technique is observed at low gas-pressures. Non-phase-matched generation of high-harmonic photon energies up to 61.6 eV with continuous spectral tunability made possible by controlled ionization-induced blue-shifting of the driving laser is presented and fully phase-matched HHG in an argon-filled PCF is explored.
Synthesized, multi-colour ultrashort pulses of light open the door to a new class of interesting experiments in atomic, molecular and optical science. Characterization of these pulses is not possible using established pulse characterization techniques, if the spectrum of the synthesized pulse exhibits extended intensity nulls, since the relative spectral phase of different spectral regions cannot be determined. In this thesis, a spectral-gap-immune pulse characterization technique is demonstrated. Two mutually coherent ultrafast pulses are derived from a Ti:Sapphire laser. An extended spectral gap is introduced into the spectrum of one pulse using an amplitude-only pulse shaper. The pulse is then spectrally sheared and subsequently interfered with the other uncharacterised pulse. By using the MICE technique, the spectral intensities and phases of the two fields are retrieved from a series of interferograms. The experimental results presented in this thesis show that SPICE is capable of reconstructing the spectral phase across an extended spectral gap enabling temporal characterization of multi-colour light pulses.

Keywords: Photonic-Crystal-Fibre
HHG
Advisor: Walmsley, I
Hooker, S
Political development in Kuwait : continuity and change in an Arab independent Gulf state

This thesis is primarily concerned with political development in Kuwait since the 1961 Treaty with Britain. It provides a substantial historical introduction in the first two chapters and then examines the drafting of a constitution and the creation of a legislative assembly, the composition and work of the assembly and its committees, relations with the government, and the impact of the assembly on its powers. It discusses the suspension of the National Assembly in 1976 and the elections to the new Assembly of 1981. The argument of the thesis is that in spite of the impact of oil wealth (whose impact on government and society is discussed) political behaviour in Kuwait can only be understood in the context of the continuity of development from the earliest days, particularly in the position of the ruling family within Kuwaiti society, the tradition of shūrā (consultation)and the degree of practical independence which were established before 1961 and have been modified but not abandoned since then. It has therefore been the intention of this thesis to avoid the general preoccupations of 'political modernization', and to examine political development in Kuwait in terms of the existing relations among the main social groups comprising Kuwaiti society. It is thus an examination of how a merchant-city-state has been transformed into a modern constitutional monarchy, and the way in which its main social groups have continued to operate within a new constitutional framework.

Keywords: government
politics
development
change
Political
continuity
state
Gulf
Arab
Kuwait
independent
Slaughter or sacrifice? : the religious rhetoric of blood sacrifice in the British and German armies, 1914-1919

In 1914 the language of sacrifice and redemption was everywhere. This thesis compares the responses of English Anglican and German Protestant military chaplains to the Great War (1914-1918). Instead of reconstructing their relationship with combatants, it reconstructs their mental worlds. Examining their diaries, sermons, letters, articles, and meditations,it traces their religious ideals of redemption through blood. It argues that chaplains on both sides of the front shared a moral language of redemptive sacrifice,articulating different permutations of the same idea. That moral language initially comprehended the war as an episode of salvation, correcting a crisis of modernity through sacred violence. War was interpreted as the culmination of the ‘social question,’the climax of the churches’ quest for community, social cohesion, the healing of class antagonism, the reclamation of the sacred. They proclaimed the war as a sacrament, a rite of purification that would purge modernity of its disorders, restore morality and renew piety. They commonly presumed a fallen, hedonistic and profane industrialised world, its social cohesion threatened by godless materialism, and its need for redemption. By blood the dead would purchase a cleansed, uplifted and redeemed society. Witnessing catastrophic bloodshed, the central moral problem for most chaplains was not high casualties alone. It was the threat that mass death would not morally and spiritually transform their societies. As the conflict escalated into attrition and stalemate, chaplains’ increasingly doubted whether war could be intrinsically redemptive, redefining the ideal as a duty of civilians to repay their blood-debt to the dead and justify the sacrifices of their compatriots. Because chaplains were implicated in mass death by virtue of their office,the ideal of redemption through war became more an obligation than perception, an ideal that must be pursued lest the sacrifices of soldier-martyrs be cheapened. Divergences and nuanced differences emerged that distinguished Anglican and Protestant perceptions of the moral and spiritual impact of the war. Intraconfessional divergences emerged, in England over the relationship with French Catholic iconography and patri-passionism, in Germany over the meaning of defeat and the legitimacy of the new political order it replaced the Wilhelmine constitution. However, the common moral language of redemptive sacrifice outweighs the confessional and national differences in their responses to mechanised slaughter.

Keywords: Britain
War
rhetoric
slaughter
World
army
history
blood
British
religious
Germany
German
sacrifice
armies
Advisor: Stargardt, N
Muslim politics in the Indo-Pakistan sub-continent, 1858-1916

The decline of Muslim power in India became complete with the abolition of the sovereignty of the King of Delhi after the 1857 Mutiny. In the succeeding years far reaching changes took place in the economic and political condition of the Muslims. As is explained by Hunter in his Indian Musalmans, owing to the unfavourable educational and administrative policy of the Government, within fourteen years of the Mutiny the number of Muslims in Government departments and in respectable professions in Bengal had decreased to a negligible proportion. Conditions in other parts of the country were almost as depressing as in Bengal.
The impoverishment of the Muslims had not wholly resulted from the events following the Mutiny. In fact, it had continued side by side with the decline of their power in India.
The first reaction to this development appeared in the form of the Faraizi and the Wahhabi movements of the early nineteenth century. The Wahhabi movement, started by Sayyid Ahmad Barelvi, aimed at the re-establishment of Muslim rule in India by resorting to a holy war first against the Sikhs and after that against the British. He started the Jihad against the Sikhsin 1826 on the North-West Frontier and continued it with some success till 1831 when he was killed in a battle at Balakot. His followers appear to have remained active on the Frontier till the 1860s.
The most influential Muslim in the post-Mutiny period was Sayyid Ahmad Khan. He believed that the Muslim regeneration in India was possible only after the establishment of cordial relations between them and their rulers. Both by his pen and word he endeavoured to prove that the Muslims were not disloyal to British rule. His efforts helped a great deal in bringing about a reconciliation between the Muslims and the British.

Keywords: political
politics
Islam
Muslim
sub-continent
activity
Indo-Pakistan
India
state