6,624 research outputs found

    Essays on Panel Data Prediction Models

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    Forward-looking analysis is valuable for policymakers as they need eïŹ€ective strategies to mitigate imminent risks and potential challenges. Panel data sets contain time series information over a number of cross-sectional units and are known to have superior predictive abilities in comparison to time series only models. This PhD thesis develops novel panel data methods to contribute to the advancement of short-term forecasting and nowcasting of macroeconomic and environmental variables. The two most important highlights of this thesis are the use of cross-sectional dependence in panel data forecasting and to allow for timely predictions and ‘nowcasts’.Although panel data models have been found to provide better predictions in many empirical scenarios, forecasting applications so far have not included cross-sectional dependence. On the other hand, cross-sectional dependence is well-recognised in large panels and has been explicitly modelled in previous causal studies. A substantial portion of this thesis is devoted to developing cross-sectional dependence in panel models suited to diverse empirical scenarios. The second important aspect of this work is to integrate the asynchronous release schedules of data within and across panel units into the panel models. Most of the thesis emphasises the pseudo-real-time predictions with eïŹ€orts to estimate the model on the data that has been released at the time of predictions, thus trying to replicate the realistic circumstances of delayed data releases.Linear, quantile and non-linear panel models are developed to predict a range of targets both in terms of their meaning and method of measurement. Linear models include panel mixed-frequency vector-autoregression and bridge equation set-ups which predict GDP growth, inïŹ‚ation and CO2 emissions. Panel quantile regressions and latent variable discrete choice models predict growth-at-risk and extreme episodes of cross-border capital ïŹ‚ows, respectively. The datasets include both international cross-country panels as well as regional subnational panels. Depending on the nature of the model and the prediction targets, diïŹ€erent precision criteria evaluate the accuracy of the models in out-of-sample settings. The generated predictions beat respective standard benchmarks in a more timely fashion

    Tipping Points and Early Warning Signals in the Climate-Carbon System

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    This is a thesis about tipping points and early warning signals. The tipping points investigated are related to various components of the climate-carbon system. In contrast, the work on early warning signals has more generic applications, however in this thesis they are analysed in the context of the climate-carbon system. The thesis begins with an introduction to the climate-carbon system as well as a discussion of tipping points in the Earth system. Then a more mathematical summary of tipping points and early warning signals is given. An investigation into the ‘compost bomb’ is undertaken, in which the spatial structure of soils is accounted for. It is found that a hot summer could cause a compost bomb. The effect of biogeochemical heating on the stability of the global carbon cycle is investigated and it is found to play only a small role. The potential for instabilities in the climate-carbon cycle is further investigated when the dynamic behaviour of the ocean carbon cycle is accounted for. It is found that some CMIP6 models may be close to having an unstable carbon cycle. Spatial early warning signals are investigated in the context of more rapidly forced systems. It is found that spatial early warning signals perform better when the system is rapidly forced compared with time series based early warning signals. The typical assumptions about white noise made when using early warning signals are also studied. It is found that time correlated noise may mask the early warning signal. It is shown that a spectral analysis can avoid this problem.European Commissio

    Modeling and MR-thermometry for adaptive hyperthermia in cervical Cancer

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    LIPIcs, Volume 251, ITCS 2023, Complete Volume

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    LIPIcs, Volume 251, ITCS 2023, Complete Volum

    Doubly Robust Estimators with Weak Overlap

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    In this paper, we derive a new class of doubly robust estimators for treatment effect estimands that is also robust against weak covariate overlap. Our proposed estimator relies on trimming observations with extreme propensity scores and uses a bias correction device for trimming bias. Our framework accommodates many research designs, such as unconfoundedness, local treatment effects, and difference-in-differences. Simulation exercises illustrate that our proposed tools indeed have attractive finite sample properties, which are aligned with our theoretical asymptotic results

    Proceedings of SIRM 2023 - The 15th European Conference on Rotordynamics

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    It was our great honor and pleasure to host the SIRM Conference after 2003 and 2011 for the third time in Darmstadt. Rotordynamics covers a huge variety of different applications and challenges which are all in the scope of this conference. The conference was opened with a keynote lecture given by Rainer Nordmann, one of the three founders of SIRM “Schwingungen in rotierenden Maschinen”. In total 53 papers passed our strict review process and were presented. This impressively shows that rotordynamics is relevant as ever. These contributions cover a very wide spectrum of session topics: fluid bearings and seals; air foil bearings; magnetic bearings; rotor blade interaction; rotor fluid interactions; unbalance and balancing; vibrations in turbomachines; vibration control; instability; electrical machines; monitoring, identification and diagnosis; advanced numerical tools and nonlinearities as well as general rotordynamics. The international character of the conference has been significantly enhanced by the Scientific Board since the 14th SIRM resulting on one hand in an expanded Scientific Committee which meanwhile consists of 31 members from 13 different European countries and on the other hand in the new name “European Conference on Rotordynamics”. This new international profile has also been emphasized by participants of the 15th SIRM coming from 17 different countries out of three continents. We experienced a vital discussion and dialogue between industry and academia at the conference where roughly one third of the papers were presented by industry and two thirds by academia being an excellent basis to follow a bidirectional transfer what we call xchange at Technical University of Darmstadt. At this point we also want to give our special thanks to the eleven industry sponsors for their great support of the conference. On behalf of the Darmstadt Local Committee I welcome you to read the papers of the 15th SIRM giving you further insight into the topics and presentations

    The UN-Intended Effects of Risky Mandates

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    In May 1948, the United Nations launched its first peacekeeping mission named the United Nations Truce Supervision Organization (UNTSO). Since this first mission, the United Nations has launched over 70 peacekeeping missions in regions such as Europe, Latin America, Asia, and Africa (Bellamy and Williams, 2015). The overarching goal of the United Nations, and the Security Council as the organ responsible for authorizing peacekeeping missions, is to protect international peace (United Nations, 1945a). However, the means of achieving international peace differs across missions. One source of variation concerning the means of achieving peace is found in peacekeeping mission mandates. While these mandates are determined on a case-by-case basis (United Nations Secretariat, 2008), scholars and policymakers find that mandates are becoming increasingly risky regarding peacekeeper physical security due to the surge in mandates that authorize the use of force (Howard and Dayal, 2018). Furthermore, the conflict environment has made mandate implementation increasingly dangerous, as seen by the overall increase in peacekeeper fatalities (Henke, 2019). The rise in the number of peacekeeping missions, increased peacekeeper fatalities, and the frequent authorization of risky mandates risk leads to the question, how does mandate risk affect peacekeeping mission outcomes? I argue that missions with high-risk mandates and dangerous conflict environments generate sub-optimal mission outcomes, specifically, fewer troop contributions from troop-contributing states, smaller troop deployments in the host state, and shorter force commander tenures. The dissertation is organized in the following way. In Chapter 1, I motivate the dissertation using qualitative and quantitative evidence to create the empirical puzzle. In Chapter 2, I explain the literature on the foundational and modern questions of peacekeeping research. With this information, I then introduce the three literatures I intend to address in the dissertation, which are troop contributions, local troop deployments, and force commander tenure, that concludes with the gaps my work fills. Chapter 3 contains a brief discussion on the mission creation process that ranges from initial authorization to putting “boots on the ground” in the mission host state. Following the background knowledge, I develop three chapters with unique theoretical arguments and empirical models to determine the effect of mission mandates on various outcomes. Chapter 4 introduces the concept and measure of mandate risk employed through the remainder of the dissertation. From this explanation, I argue that higher levels of mandate risk and conflict environment danger increase the perceived costs of troop contributions, leading to reduced troop contribution levels. In Chapter 5, I generate the force commander’s dilemma to demonstrate that mandate risk and conflict danger are associated with small troop deployments in the host state and the conclusion that the reducing effect of mandates deteriorates after a significant amount of time. I argue in Chapter 6 that risky mandates and dangerous conflict conditions should reduce force commander tenures, but empirical models do not provide evidence in support of the argument. Last, I summarize each chapter’s conclusions, ramifications for the peacekeeping literature, policy implications, and directions for future work in Chapter 7
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