Design and Analysis of Efficient Parallel Bayesian Model Comparison Algorithms

Bayesian model comparison provides a rational and consistent method for applying logic and probability to the problem of evaluating models. Model comparison requires numerical techniques that are usually very time consuming to run. This dissertation proposes extensions to several existing numerical model comparison techniques, including nested sampling and thermodynamic integration, that incorporate parallel algorithm design to achieve significant speed-ups. Serial computer performance gains have sloin recent years, and most processing speed improvements are seen in the area of parallel architectures. This work discusses the design, theoretical analysis, and empirical analysis of these algorithms, focusing on the performance of these algorithms with respect to accuracy and run time. Many disciplines in science and engineering make use of existing model comparison techniques. This work aims to save investigators in these disciplines time, and potentially attract those who may have been put off by time complexity concerns, by developing a general approach to model comparison that takes full advantage of modern parallel computing platforms

Cycling stability of a hybrid activated carbon//poly(3- methylthiophene) supercapacitor with N-butyl-Nmethylpyrrolidinium bis(trifluoromethanesulfonyl)imide ionic liquid as electrolyte

A long cycle-life, high-voltage supercapacitor featuring an activated carbon//poly(3-methylthiophene) hybrid configuration with N-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide ionic liquid, a solvent-free green electrolyte, was developed. The cyclability of a laboratory scale cell with electrode mass loading sized for practical uses was tested at 60 °C over 16,000 galvanostatic charge–discharge cycles at 10 mA cm−2 in the 1.5 and 3.6 V voltage range. The reported average and maximum specific energy and power, specific capacitance and capacity, equivalent series resistance and coulombic efficiency over cycling demonstrate the long-term viability of this ionic liquid as green electrolyte for high-voltage hybrid supercapacitors

TI-Stan: Model comparison using thermodynamic integration and HMC

© 2019 by the authors. We present a novel implementation of the adaptively annealed thermodynamic integration technique using Hamiltonian Monte Carlo (HMC). Thermodynamic integration with importance sampling and adaptive annealing is an especially useful method for estimating model evidence for problems that use physics-based mathematical models. Because it is based on importance sampling, this method requires an efficient way to refresh the ensemble of samples. Existing successful implementations use binary slice sampling on the Hilbert curve to accomplish this task. This implementation works well if the model has few parameters or if it can be broken into separate parts with identical parameter priors that can be refreshed separately. However, for models that are not separable and have many parameters, a different method for refreshing the samples is needed. HMC, in the form of the MC-Stan package, is effective for jointly refreshing the ensemble under a high-dimensional model. MC-Stan uses automatic differentiation to compute the gradients of the likelihood that HMC requires in about the same amount of time as it computes the likelihood function itself, easing the programming burden compared to implementations of HMC that require explicitly specified gradient functions. We present a description of the overall TI-Stan procedure and results for representative example problems

Shopping arcade in Central Square, Cambridge, Mass.

Thesis (M. Arch.)--Massachusetts Institute of Technology, Dept. of Architecture, 1976.Includes bibliographical references (leaves 45-48).M.Arch

An assessment of the sensitivity of a low pressure time projection chamber to the direction of WIMP-induced nuclear recoils/

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2013.Cataloged from PDF version of thesis.Includes bibliographical references (pages 207-219).Direct directional detection of dark matter could provide an unambiguous observation of dark matter due to the predicted directional anisotropy of dark matter particles in the galactic reference frame. The Dark Matter Time Projection Chamber (DMTPC) collaboration develops TPCs with optical readout whose goal is the detection of the sense and direction of nuclear recoils generated by dark matter interactions with carbon and fluorine atoms in low pressure CF 4 gas, from which the direction of the incident dark matter particle can be inferred. The TPC contains a mesh based amplification stage that facilitates the two-dimensional imaging of nuclear recoil tracks using CCD cameras. Reconstructing the direction of recoils has been a subject of intensive R&D over the past several years, culminating in the design and construction of a current generation detector, the "4-shooter." The 4-shooter is prototyping several new detector techniques for a larger (1 m3 ) detector. The third dimension of recoils will be reconstructed in this detector using PMTs and the timing of induced charge signals in the detector amplification region. The 4-shooter's performance has being studied extensively on the surface of the Earth at MIT using alpha particles, low energy neutrons, and X-rays. This thesis reports on surface commissioning data taken with the 4-shooter.by Shawn Wesley Henderson.Ph.D

Tetra­kis(acetonitrile-κN)lithium hexa­fluoridophosphate acetonitrile monosolvate

In the title compound, [Li(CH3CN)4]PF6·CH3CN, the asymmetric unit consists of three independent tetra­hedral [Li(CH3CN)4]+ cations, three uncoordinated PF6 − anions and three uncoordinated CH3CN solvent mol­ecules. The three anions are disordered over two sites through a rotation along one of the F—P—F axes. The relative occupancies of the two sites for the F atoms are 0.643 (16):0.357 (16), 0.677 (10):0.323 (10) and 0.723 (13):0.277 (13). The crystal used was a racemic twin, with approximately equal twin components

SOCIAL SERVICES IN CAPE TOWN: AN ANALYSIS USING THE POLITICAL ETHICS OF CARE

At the time of South Africa’s transition to a constitutional democracy in 1994 the African National Congress (ANC) government inherited a deeply divided racially-based social welfare service system. Accordingly, the first priority of the newly elected government was to develop social policies to address the inequalities resulting from the apartheid period and to redirect resources to previously disadvantaged groups, especially black South Africans, since the white community had been the main beneficiaries of specialised professional services and institutional care (Bozalek, 1999; Follentine, 2004; Orner, 2003; Sevenhuijsen, Bozalek, Gouws & Minnaar-McDonald, 2003a; Republic of South Africa, 1997). The ANC’s election manifesto, its Reconstruction and Development (RDP) policy, had committed the government to a number of strategies to meet people’s basic needs and to alleviate poverty and inequality, among them were employment creation; a living wage for all citizens; the democratisation of state structures; housing provision; and land redistribution (Republic of South Africa, 1994). The Constitution reinforced these commitments in its recognition of socio-economic rights, including the rights to adequate housing, health care, food, water, education and social security. The Human Rights Commission and other independent bodies, such as the Gender Commission, were set up by the Constitution to monitor human rights violations. There were expectations that social services would deliver on the social and economic rights outlined in the South African Constitution (1996) within the available resource constraints (Republic of South Africa, 2006)

Poly[[(acetonitrile)­lithium(I)]-μ3-tetra­fluoridoborato]

The structure of the title compound, [Li(BF4)(CH3CN)]n, consists of a layered arrangement parallel to (100) in which the Li+ cations are coordinated by three F atoms from three tetra­fluoridoborate (BF4 −) anions and an N atom from an acetonitrile mol­ecule. The BF4 − anion is coordinated to three different Li+ cations though three F atoms. The structure can be described as being built from vertex-shared BF4 and LiF3(NCCH3) tetra­hedra. These tetra­hedra reside around a crystallographic inversion center and form 8-membered rings

Proof Repair Infrastructure for Supervised Models: Building a Large Proof Repair Dataset

We report on our efforts building a new, large proof-repair dataset and benchmark suite for the Coq proof assistant. The dataset is made up of Git commits from open-source projects with old and new versions of definitions and proofs aligned across commits. Building this dataset has been a significant undertaking, highlighting a number of challenges and gaps in existing infrastructure. We discuss these challenges and gaps, and we provide recommendations for how the proof assistant community can address them. Our hope is to make it easier to build datasets and benchmark suites so that machine-learning tools for proofs will move to target the tasks that matter most and do so equitably across proof assistants

Lithium bis­(2-methyl­lactato)borate monohydrate

The title compound {systematic name: poly[[aqua­lithium]-μ-3,3,8,8-tetra­methyl-1,4,6,9-tetra­oxa-5λ4-borataspiro­[4.4]nonane-2,7-dione]}, [Li(C8H12BO6)(H2O)]n (LiBMLB), forms a 12-membered macrocycle, which lies across a crystallographic inversion center. The lithium cations are pseudo-tetra­hedrally coordinated by three methyl­lactate ligands and a water mol­ecule. The asymmetric units couple across crystallographic inversion centers, forming the 12-membered macrocycles. These macrocycles, in turn, cross-link through the Li+ cations, forming an infinite polymeric structure in two dimensions parallel to (101)