757 research outputs found

    Semi-Implicit Variational Inference via Score Matching

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    Semi-implicit variational inference (SIVI) greatly enriches the expressiveness of variational families by considering implicit variational distributions defined in a hierarchical manner. However, due to the intractable densities of variational distributions, current SIVI approaches often use surrogate evidence lower bounds (ELBOs) or employ expensive inner-loop MCMC runs for unbiased ELBOs for training. In this paper, we propose SIVI-SM, a new method for SIVI based on an alternative training objective via score matching. Leveraging the hierarchical structure of semi-implicit variational families, the score matching objective allows a minimax formulation where the intractable variational densities can be naturally handled with denoising score matching. We show that SIVI-SM closely matches the accuracy of MCMC and outperforms ELBO-based SIVI methods in a variety of Bayesian inference tasks.Comment: 17 pages, 8 figures; ICLR 202

    The Plastics Collection Reference Packet

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    This reference packet is an informational tool to support further research into the history of plastics—whether interested in companies, individuals within the plastics industry\u27s history, historical plastics materials, essays, and more. All content featured within this packet was previously published on the former plastics.syr.edu website as part of a Syracuse University Libraries and Special Collections Research Center (SCRC) partnership established in 2007 with the Plastics Pioneers Association (PPA)—an association of plastics industry professionals interested in preserving the plastics industry\u27s past

    The impact of foreign aid on investment, growth and the exchange rate in West Africa

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    Since the last two to three decades, the economic performance of the African countries has been the focus of global attention. While other developing countries that share similar characteristics are beginning to emerge, Africa is yet to 'take off'. At the regional level, the North and Southern regions have made some progress but West Africa in spite of its deep integration has barely managed to outperform the East and Central regions. This thesis focuses on the investigation of the relationship between foreign aid and economic performance in West Africa. Using annual data from 1975 to 2005, it examines the impact of foreign aid on private investment, growth, the real effective exchange rate, as well as the nature of the relationship between external debt, private investment and growth in Nigeria. The first of the main findings of the thesis is that the impact of foreign aid on private investment and growth in West Africa depends on the type of aid. Also, the effect of aid uncertainty on private investment cannot be attributed to aggregate aid, as multilateral aid does not appear to be volatile. Second, the thesis by splitting aid into multilateral and bilateral components, addresses a major issue in the aid-growth debate - the bi-directional causation between aid and growth. Third, based on two recent pooled estimation techniques - the pooled mean group estimator (PMG) and the dynamic fixed effects (DFE), the thesis examined the effect of foreign aid inflows on the real exchange rate - the so-called 'Dutch Disease' hypothesis, relying mainly on the floating aspect of the real effective exchange rate. Finally, using the ARDF approach, we find that official debt of around 40 percent of GDP is not inimical to growth for Nigeria

    Portfolio Allocation and Optimization with Carbon Offsets: Is it Worth the While?

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    We explore whether the integration of carbon offsets into investment portfolios improves perfor-mance. Our results show that investment strategies that include such offsets achieve higher Sharpe Ratios than the diversified benchmark portfolios. The efficient frontier of optimal portfolio choices is shifted upwards as a result of including compliance and voluntary carbon offsets in the portfolio. Our results also show that while diversified portfolios may benefit from carbon offsets integration, voluntary carbon offsets are significantly more sensitive to exogenous shocks than compliance carbon allowances. All these results are novel and may encourage investors to invest in such sustainable asset classes

    Factors influencing successful reconstruction of tympanic membrane perforations : a systematic review and meta-analysis

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    Based on a systematic review and meta-analysis, our study aimed to provide information about the factors that influence the success of tympanic membrane reconstruction.Our systematic search was conducted on November 24, 2021, using the CENTRAL, Embase, and MEDLINE databases. Observational studies with a minimum of 12 months of follow-up on type I tympanoplasty or myringoplasty were included, while non-English articles, patients with cholesteatoma or specific inflammatory diseases, and ossiculoplasty cases were excluded. The protocol was registered on PROSPERO (registration number: CRD42021289240) and PRISMA reporting guideline was used. Risk of bias was evaluated with the QUIPS tool. A random effect model was used in the analyses. Primary outcome was the rate of closed tympanic cavities.After duplicate removal, 9454 articles were found, of which 39 cohort studies were included. Results of four analyses showed significant effects: age (OR: 0.62, CI 0.50; 0.78, p value: 0.0002), size of the perforation (OR: 0.52, CI 0.29; 0.94, p value: 0.033), opposite ear condition (OR: 0.32, CI 0.12; 0.85, p value: 0.028), and the surgeon's experience (OR: 0.42, CI 0.26; 0.67, p value: 0.005), while prior adenoid surgery, smoking, the site of the perforation, and discharge of the ear did not. Four factors: etiology, Eustachian tube function, concomitant allergic rhinitis, and duration of the ear discharge were analyzed qualitatively.The age of the patient, the size of the perforation, the opposite ear status, and the surgeon's experience have a significant effect on the success of tympanic membrane reconstruction. Further comprehensive studies are needed to analyze the interactions between the factors.Not applicable

    Crime and criminal justice : criminological research in the 2nd decade at the Max Planck Institute in Freiburg

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    Advanced Techniques and Efficiency Assessment of Mechanical Processing

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    Mechanical processing is just one step in the value chain of metal production, but to some exten,t it determines an effectiveness of separation through suitable preparation of the raw material for beneficiation processes through production of required particle sze composition and useful mineral liberation. The issue is mostly related to techniques of comminution and size classification, but it also concerns methods of gravity separation, as well as modeling and optimization. Technological and economic assessment supplements the issue

    Essays on Energy Portfolio Management

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    Diese englischsprachige Dissertation behandelt ausgewählte Fragen zum Thema Portfoliomanagement in Energiemärkten. Im Kontext der modernen Portfoliotheorie werden theoretische Verteilungsannahmen untersucht, die einen optimalen Mittelwert-Varianz-Ansatz implizieren. Der Bereich zu Energiemärkten befasst sich einerseits mit Kurzfristprognosen von Day-Ahead-Preisen auf dem Strommarkt. Andererseits werden auf dem Erdgasmarkt die von komplexen Energiederivaten impliziten Volatilitäten analysiert. Einige interessante Beiträge, die diese Dissertation liefert, sind beispielsweise (i) die Erkenntnis, dass sich der Mittelwert-Varianz-Ansatz zur Bestimmung eines optimalen Portfolios von Vermögensgegenständen auch im Falle einer schiefen Renditeverteilung theoretisch rechtfertigen lässt, (ii) eine umfangreiche Vergleichsstudie mit verschiedenen Ansätzen zur Reduktion der Komplexität von multivariaten Strompreisprognosen und (iii) die Entwicklung eines theoretischen Rahmens und effizienten Algorithmus zur Übersetzung von Preisen für Swing-Optionen in implizite Volatilitäten
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