Boiling Liquid Expanding Vapor Explosion of liquid hydrogen

This thesis focuses on the modelling of liquid hydrogen Boiling Liquid Expanding Vapor Explosions (BLEVEs). This terminology identifies a catastrophic release of this unconventional fuel following the loss of its containment. The present work aims to enhance the knowledge on the consequences of such explosions, using the data collected from crucial experiments to validate the simulations. The consequence analysis of the "SH2IFT Project" and the ”Bursting Tank Scenario” experimental BLEVEs is carried out simulating the explosions to verify the reliability of the implemented physical models. To complete the modeling of the catastrophic rupture of liquid hydrogen (LH2) tanks, the combustion process is taken into account to describe the aftermath of the simulated accidents in terms of overpressure and impulse. Furthermore, it is also discussed the possible involvement of the endothermic reaction of the hydrogen para-isomer converting into its ortho-isomer form. In this way, a further validation and confrontation between the models currently used for conventional liquid fuels like propane and liquefied petroleum gas (LPG) is possible, adopting and adapting them to the specific case of a liquid hydrogen catastrophic release. So, it is possible to consider this thesis as divided in three major steps: the first one is the analysis of the physical explosions with the proposed models, the second one is the adaptation of such models to take hydrogen combustion into consideration and the third and last one is an analysis of the para-ortho reaction which may follow the explosion. At the end, a confrontation between the experimental data and the proposed calculations is carried out, underlining the aspects which still require further studies, experiments and documentation

Search for high mass resonances decaying to Higgs pairs in the bbbb final state with the CMS experiment at the LHC

The discovery of the Higgs boson at the LHC in 2012 represents a major step in our understanding of fundamental interactions. Moreover, the newly-discovered particle can be seen as a promising "tool" to look for new phenomena. Specifically, this thesis focuses on high mass resonances decaying to Higgs pairs. The search presented in this thesis aims to be as much as possible model inde- pendent. Nevertheless, the results can be interpreted within several New Physics models. Among those, two possible scenarios are the Randall-Sundrum Radion and massive KK-Graviton productions in Warped Extra Dimensions. Other well motivated scenarios featuring a heavy CP-even scalar decaying to Higgs pairs are the Next-to-Minimal Supersymmetric Standard Model and the Twin Higgs model. The analysis target is a narrow di-Higgs resonance with both Higgs bosons decaying to b quarks, in the highest possible mass range detectable at the LHC (above ∼ 1 TeV). Despite the large QCD multi-jet background, the b ̄ bb ̄ b final state has showed the best sensitivity overall for resonance masses 400 GeV in the LHC Run1 searches, but no evidence of signal. A high mass resonance is expected to produce two energetic Higgs bosons, so that the b quarks produced from their decay are collimated along the direction of motion. As a consequence, the hadronization products of a pair of narrowly separated b quarks can be reconstructed as a single large jet. Boosted Higgs bosons decaying to b-quark pairs can be distinguished from the QCD multi-jet background exploiting the jet substructure and through a dedicated b-tagging algorithm. The transition region between the aforementioned boosted topology and the resolved topology, where four unmerged b-jets are reconstructed, has been studied for the first time in this thesis and it is addressed matching one large Higgs jet to a pair of unmerged b-jets. The analysis has been carried out on 2.7/fb of proton-proton collision data recorded by the CMS experiment at the LHC at a center of mass energy of 13 TeV during 2015. The benchmark signal process used to design the analysis strategy is the spin-2 Bulk Graviton with negligible natural width. A data-driven estimation of the background, which minimizes systematic uncertainties that might arise from poorly-understood QCD multi-jet backgrounds in the simulation, has been employed. As no signal evidence has been detected, upper limits on the production cross section of the benchmark resonance in the mass range 600-3000 GeV are presented. The event reconstruction addressing the transition region has been found to improve the sensitivity of ∼15-20%

A DNN for CMS track classification and selection

The upgrade of the track classification and selection step of the CMS tracking to a Deep Neural Network is presented. The CMS tracking follows an iterative approach: tracks are reconstructed in multiple passes starting from the ones that are easiest to find and moving to the ones with more complex characteristics (lower transverse momentum, high displacement). The track classification comes into play at the end of each iteration. A classifier using a multivariate analysis is applied after each iteration and several selection criteria are defined. If a track meets the high purity requirement, its hits are removed from the hit collection, thus simplifying the later iterations, and making the track classification an integral part of the reconstruction process. Tracks passing loose selections are also saved for physics analysis usage. The CMS experiment improved the track classification starting from a parametric selection used in Run 1, moving to a Boosted Decision Tree in Run 2, and finally to a Deep Neural Network in Run 3. An overview of the Deep Neural Network training and current performance is shown

Fragments Generated During Liquid Hydrogen Tank Explosions

Liquid hydrogen (LH2) may be employed to transport large quantities of pure hydrogen or be stored onboard of ships, airplanes and trains fuelled by hydrogen, thanks to its high density compared to gaseous compressed hydrogen. LH2 is a cryogenic fluid with an extremely low boiling point (-253°C at atmospheric pressure) that must be stored in double-walled vacuum insulated tanks to limit the boil-off formation. There is limited knowledge on the consequences of LH2 tanks catastrophic rupture. In fact, the yield of the consequences of an LH2 tank explosion (pressure wave, fragments and fireball) depend on many parameters such as tank dimension, filling degree, and tank internal conditions (temperature and pressure) prior the rupture. Only two accidents provoked by the rupture of an LH2 tank occurred in the past and a couple of experimental campaigns focussed on this type of accident scenario were carried out for LH2. The aim of this study is to analyse one of the LH2 tank explosion consequences namely the fragments. The longest horizontal and vertical ranges of the fragments thrown away from the blast wave are estimated together with the spatial distribution around the tank. Theoretical models are adopted in this work and validated with the experimental results. The proposed models can aid the risk analysis of LH2 storage technologies and provide critical insights to plan a prevention and mitigation strategy and improve the safety of hydrogen applications

Modelling of Fireballs Generated After the Catastrophic Rupture of Hydrogen Tanks

The interest towards hydrogen skyrocketed in the last years. Thanks to its potential as an energy carrier, hydrogen will be soon handled in public and densely populated areas. Therefore, accurate models are necessary to predict the consequences of unwanted scenarios. These new models should be employed in the consequence analysis, a phase of risk assessment, and thus aid the selection, implementation, and optimization of effective risk-reducing measures. This will increase safety of hydrogen technologies and therefore favour their deployment on a larger scale. Hydrogen is known to be an extremely flammable gas with a low radiation flame compared to hydrocarbons. However, luminous fireballs were generated after the rupture of both compressed gaseous and liquid hydrogen tanks in many experiments. Moreover, it was demonstrated that conventional empirical correlations, initially developed for hydrocarbon fuels, underestimate both dimension and duration of hydrogen fireballs recorded during small-scale tests (Ustolin and Paltrinieri, 2020). The aim of this study is to obtain an analysis of hydrogen fireballs to provide new critical insights for consequence analysis. A comparison among different correlations is conducted when predicting fireball characteristics during the simulation of past experiments where both gaseous and liquid hydrogen tanks were intentionally destroyed. All the models employed in this study are compared with the experimental results for validation purposes. Specific models designed for hydrogen can support the design of hydrogen systems and increasing their safety and promote their future distribution

How resistant are levodopa-resistant axial symptoms? Response of freezing, posture and voice to increasing levodopa intestinal infusion rates in Parkinson's disease

Treatment of freezing of gait (FoG) and other Parkinson's disease (PD) axial symptoms is challenging. Systematic assessments of axial symptoms at progressively increasing levodopa doses are lacking. We sought to analyze the resistance to high levodopa doses of FoG, posture, speech, and altered gait features presenting in daily-ON therapeutic condition

Generalizing mkFit and its Application to HL-LHC

mkFit is an implementation of the Kalman filter-based track reconstruction algorithm that exploits both thread- and data-level parallelism. In the past few years the project transitioned from the R&D phase to deployment in the Run-3 offline workflow of the CMS experiment. The CMS tracking performs a series of iterations, targeting reconstruction of tracks of increasing difficulty after removing hits associated to tracks found in previous iterations. mkFit has been adopted for several of the tracking iterations, which contribute to the majority of reconstructed tracks. When tested in the standard conditions for production jobs, speedups in track pattern recognition are on average of the order of 3.5x for the iterations where it is used (3-7x depending on the iteration). Multiple factors contribute to the observed speedups, including vectorization and a lightweight geometry description, as well as improved memory management and single precision. Efficient vectorization is achieved with both the icc and the gcc (default in CMSSW) compilers and relies on a dedicated library for small matrix operations, Matriplex, which has recently been released in a public repository. While the mkFit geometry description already featured levels of abstraction from the actual Phase-1 CMS tracker, several components of the implementations were still tied to that specific geometry. We have further generalized the geometry description and the configuration of the run-time parameters, in order to enable support for the Phase-2 upgraded tracker geometry for the HL-LHC and potentially other detector configurations. The implementation strategy and high-level code changes required for the HL-LHC geometry are presented. Speedups in track building from mkFit imply that track fitting becomes a comparably time consuming step of the tracking chain

Riesgos y oportunidades asociados a la conservación de los polinizadores y a la gestión de los servicios de polinización en América Latina

Se realizó una revisión sobre el estado de conservación de los polinizadores y la polinización en América Latina (LA). Se presentan pautas para mejorar las oportunidades de conservación, considerando las amenazas a los polinizadores y las perspectivas desde el conocimiento tradicional y local. El análisis indica que diversas amenazas (e.g., agricultura a gran escala, deforestación, uso excesivo de agroquímicos) están vinculadas con la disminución de polinizadores, afectando la reproducción de las plantas nativas y los rendimientos de muchos cultivos. LA alberga la mayor diversidad de abejas en todo el mundo y una gran diversidad de polinizadores vertebrados (e.g., colibríes, aves de percha nectarívoras, murciélagos nectarívoros y otros mamíferos). Se proporcionan recomendaciones para proteger los polinizadores nativos y mejorar los servicios de polinización, las que podrían ser consideradas por los tomadores de decisiones y así promover la conservación biocultural. Por ejemplo, desarrollar instrumentos legales, políticas e incentivos para ayudar a los agricultores a mantener los hábitats naturales, para reemplazar o reducir el uso de agroquímicos y para promover las prácticas agroecológicas; perfeccionar las reglamentaciones sobre aplicación de agroquímicos para minimizar la exposición de los polinizadores a insecticidas y herbicidas; mejorar la comunicación pública del conocimiento sobre los polinizadores y la polinización para incentivar un cambio en las prácticas agrícolas hegemónicas y los patrones de consumo actuales; considerar otras éticas ambientales de las minorías étnicas para enfatizar la necesidad de promover una relación sostenible entre producción de alimentos y biodiversidad. Se necesita urgentemente una visión más amplia que combine las dimensiones sociales, ecológicas y culturales para una mejor toma de decisiones. Esta perspectiva socio-agroecológica holística es importante para conservar y gestionar los polinizadores a diferentes escalas espaciales y temporales, y para poder integrar los servicios de polinización con enfoques de gestión del territorio favorables a los polinizadores y con sistemas agrícolas diversificados.The conservation status of pollinators and pollination in Latin America (LA) is reviewed. The knowledge regarding native and managed pollinators (e.g., honeybee and stingless bees) and pollination services was synthetized, and the guidelines to improve the opportunities for conservation are provided, considering the threats to pollinators and the perspectives from traditional and local knowledge. The analysis indicates that diverse threats (e.g., large-scale agriculture, deforestation, overuse of agrochemicals) are linked with pollination and pollinator decline, which affect the reproduction of most native plants and the yields of many crops. LA harbours the highest bee diversity worldwide, with 26% of the total recorded species, and it is a biodiversity hotspot of vertebrate pollinators, including hummingbirds, perching birds, nectarivorous bats and other mammal pollinators. Specific recommendations to conserve native pollinators and to improve pollination services are provided, which could be considered by stakeholders and governments aiming to elaborate biocultural conservation. For example, introducing policies and legal responses for incentives to help farmers maintain natural habitats and forests, to replace or reduce agrochemicals and to improve diversified crop production with agroecological practices; refining agrochemical regulations to minimize the exposure of pollinators to insecticides and herbicides; improving knowledge and education on pollinators and pollination gives societies worldwide the opportunity to change current hegemonic agricultural practices and consumption patterns; integrating different land ethical views of ethnic minorities on a sustainable relationship between production and biodiversity. A wider view combining social, ecological, cultural dimensions may support better decision making. This holistic socio-agroecological perspective is urgently needed to conserve and manage pollinators at different spatial and temporal scales, and to integrate pollination services, pollinator-friendly habitat management approaches and diversified farming systems.Fil: Galetto, Leonardo. Universidad Nacional de Córdoba - CONICET. Instituto Multidisciplinario de Biología Vegetal (IMBIV)Fil: Aizen, Marcelo Adrian. Universidad Nacional del Comahue - CONICET. Instituto de Investigaciones en Biodiversidad y Medioambiente (INIBIOMA)Fil: del Coro Arizmendi, María. Universidad Nacional Autónoma de México, Tlalnepantla, MéxicoFil: Magalhães Freitas, Breno. Universidade Federal do Ceará - Departamento de Zootecnia - Setor de Abelhas, Fortaleza, BrazilFil: Garibaldi, Lucas Alejandro. Universidad Nacional de Río Negro - CONICET. Instituto de Investigaciones en Recursos Naturales, Agroecología y Desarrollo Rural (IRNAD)Fil: Giannini, Tereza Cristina. Instituto Tecnológico Vale Desenvolvimento Sustentavel, Belem, BrazilFil: Lopes, Ariadna Valentina. Universidade Federal de Pernambuco - Departamento de Botánica, Recife, BrazilFil: Espírito Santo, Maria do. Universidade Estadual de Montes Claros - Departamento de Biologia Geral (CCBS), MG, BrasilFil: Nates Parra, Guiomar. Universidad Nacional de Colombia, Bogotá DC, ColombiaFil: Motta Maués, Márcia. Embrapa Amazônia Oriental - Laboratório de Entomologia, Belém, Pará, BrazilFil: Rodríguez, Jaime I.. Museo Nacional de Historia Natural de Bolivia, La Paz, BoliviaFil: Quezada Euán, José Javier Guadalupe. Universidad Autónoma de Yucatán - Departamento de Apicultura Tropical, Mérida, México (FMVZ)Fil: Viana, Blandina Felipe. Universidade Federal da Bahia, Salvador, Bahia, BrazilFil: Imperatriz Fonseca, Vera Lucia. Instituto Tecnológico Vale Desenvolvimento Sustentavel, Belem, Para, BrazilFil: Vandame, Rémy. El Colegio de la Frontera Sur, San Cristóbal de las Casas, Chiapas, Méxic

Novel 3D Pixel Sensors for the Upgrade of the ATLAS Inner Tracker

The ATLAS experiment will undergo a full replacement of its inner detector to face the challenges posed by the High Luminosity upgrade of the Large Hadron Collider (HL-LHC). The new Inner Tracker (ITk) will have to deal with extreme particle fluences. Due to its superior radiation hardness the 3D silicon sensor technology has been chosen to instrument the innermost pixel layer of ITk, which is the most exposed to radiation damage. Three foundries (CNM, FBK, and SINTEF), have developed and fabricated novel 3D pixel sensors to meet the specifications of the new ITk pixel detector. These are produced in a single-side technology on either Silicon On Insulator (SOI) or Silicon on Silicon (Si-on-Si) bonded wafers by etching both n- and p-type columns from the same side. With respect to previous generations of 3D sensors they feature thinner active substrates and smaller pixel cells of 50 × 50 and 25 × 100 µm2. This paper reviews the main design and technological issues of these novel 3D sensors, and presents their characterization before and after exposure to large radiation doses close to the one expected for the innermost layer of ITk. The performance of pixel modules, where the sensors are interconnected to the recently developed RD53A chip prototype for HL-LHC, has been investigated in the laboratory and at beam tests. The results of these measurements demonstrate the excellent radiation hardness of this new generation of 3D pixel sensors that enabled the project to proceed with the pre-production for the ITk tracker.publishedVersio