Otimização do comportamento dinâmico-acústico de ventiladores de bombas de calor

The aim of this investigation is the aeroacoustic analysis of the boundary layer separation noise and trailing edge noise in a heat pump axial fan, using Computational Fluid Dynamics (CFD), Fluid Fluid Structure Interaction (FSI) and Computational Aeroacoustics (CAA). The Broadband Noise Source (BNS) model and Transition SST turbulence model, implemented in Fluent 19.0, were used to study the boundary layer noise component of the three noise reduction features in steady-state and transient simulations. The objectives of this study were divided into two main parts: the analysis and optimization of golf ball dimples to control the the boundary layer separation on fan blade and the study regarding the application of two features from the "silent" flight of the owl on the fan, the finlets and the flexible trailing edge. The parametric optimization on dimples showed a 15,1% shift in boundary layer separation. This optimized pattern when applied to the suction side of the fan blade shifting the boundary layer separation which promotes the inhibition of the vortex generated at the junction of the blade with the hub resulting in a reduction of up to 0,8 dB under normal fan operating conditions. It was also found that dimples have a greater influence on operating conditions under an airflow less than 1500 m3/h, showing a shift in the stall resulting in an increase of the fan efficiency by 1,9% and a decrease in the boundary layer noise of 2,9 dB. On the second part of the work it was found that a fan with finlets presented a reduction of 0,3 dB at 300 rpm, although the results showed an increase in noise and a decrease in efficiency for higher rpm than those for which the finlets were optimized. The study of an flexible trailing edge showed a decrease in the thickness of the turbulence generated by the boundary layer. This, due to the downward movement of the flexible trailing edge that decreases the pressure mismatch between the suction surface and the pressure surface and the decrease of the angle of attack caused by its upward movement. Experimental measurements of an dimpled fan prototype, conducted in a hemi-anechoic chamber showed noise improvements in the order of 0,5 dB(A), the results suggested that for lower velocities than 380 rpm an increase in the fan efficiency is expected. Lastly, an attempt was made to induce stall in the fan through the obstruction of the heat pump evaporator. This investigation identified that for an airflow of 1700 m3/h at 535 rpm the original fan enters in a light stall condition while the dimpled fan prototype maintains its normal operating conditions, resulting in a reduction of 0,9 dB(A).O objetivo deste trabalho de investigação consistiu na análise do ruído aeroacústico emitido pelo ventilador aplicado às unidades exteriores das bombas de calor, recorrendo a Computational Fluid Dynamics (CFD), Fluid Fluid Structure Interaction (FSI) e Computational Aeroacoustics (CAA). O modelo acústico Broadband Noise Source (BNS) e o modelo de turbulência Transition SST, implementados no código comercial Fluent 19.0 foram utilizados para avaliar diferentes técnicas de redução do ruído emitido pela separação da camada limite e pelo bordo de fuga. Os objetivos deste estudo estão divididos em duas componentes: a análise e otimização de cavidades inspiradas nas bolas de golf para o atraso da separação da camada limite na pá do ventilador e o estudo da implementação de duas características do voo "silencioso" das corujas no ventilador, o bordo de fuga alhetado e o bordo de fuga flexível. Os resultados da otimização paramétrica das cavidades das bolas de golf mostram um atraso na separação da camada limite de 15,1%. Este padrão otimizado quando aplicado no lado de sucção da pá do ventilador atrasa a separação da camada limite o que promove a inibição do vortex gerado entre a pá e o centro do ventilador resultando numa redução de até 0,8 dB em condições normais de funcionamento do ventilador. As cavidades das bolas de golf mostram ter uma maior influência para condições de operação com um fluxo de ar inferior a 1500 m3/h, mostrando atrasar o fenômeno de stall, aumentado a eficiência do ventilador em 1,9% e diminuíndo o ruído aerodinâmico em 2,9 dB em comparação com o modelo original. Na segunda parte da tese foi descoberto que um bordo de fuga alhetado revela uma redução de ruído de 0,3 dB a 300 rotações por minuto, sendo que se verifica perda de eficiência e aumento do ruído do ventilador para rotações por minuto superiores aos quais as alhetas foram geometricamente otimizadas. O estudo da utilização de um bordo de fuga flexível mostrou a diminuição da espessura da turbulência gerada pela camada limite através do movimento descende do bordo de fuga flexível que diminui a diferença de pressão entre a superfície de sucção e a superfície pressão e a diminuição do ângulo de ataque com o seu movimento ascendente. Medições experimentais realizados numa câmara semi-anecóica do protótipo do ventilador com cavidades inspiradas nas bolas de golf mostraram melhorias na ordem de 0,5 dB(A) para diferentes rotações por minuto e sugerem um aumento da eficiência para rotações por minuto inferiores a 380. Por fim foi feita a tentativa de induzir um escoamento totalmente separado no ventilador através da obstrução do evaporador da bomba de calor, este estudo identificou que que para um fluxo de ar de 1700 m3/h a 535 rotações por minuto o ventilador original entra em condição de separação total sendo que o protótipo do ventilador com cavidades inspiradas nas bolas de golf mantem condições de funcionamento normais, resultando numa redução de 0,9 dB(A).Mestrado em Engenharia Mecânic

Pervasive gaps in Amazonian ecological research

Biodiversity loss is one of the main challenges of our time,1,2 and attempts to address it require a clear un derstanding of how ecological communities respond to environmental change across time and space.3,4 While the increasing availability of global databases on ecological communities has advanced our knowledge of biodiversity sensitivity to environmental changes,5–7 vast areas of the tropics remain understudied.8–11 In the American tropics, Amazonia stands out as the world’s most diverse rainforest and the primary source of Neotropical biodiversity,12 but it remains among the least known forests in America and is often underrepre sented in biodiversity databases.13–15 To worsen this situation, human-induced modifications16,17 may elim inate pieces of the Amazon’s biodiversity puzzle before we can use them to understand how ecological com munities are responding. To increase generalization and applicability of biodiversity knowledge,18,19 it is thus crucial to reduce biases in ecological research, particularly in regions projected to face the most pronounced environmental changes. We integrate ecological community metadata of 7,694 sampling sites for multiple or ganism groups in a machine learning model framework to map the research probability across the Brazilian Amazonia, while identifying the region’s vulnerability to environmental change. 15%–18% of the most ne glected areas in ecological research are expected to experience severe climate or land use changes by 2050. This means that unless we take immediate action, we will not be able to establish their current status, much less monitor how it is changing and what is being lostinfo:eu-repo/semantics/publishedVersio

Search for dark matter produced in association with bottom or top quarks in √s = 13 TeV pp collisions with the ATLAS detector

A search for weakly interacting massive particle dark matter produced in association with bottom or top quarks is presented. Final states containing third-generation quarks and miss- ing transverse momentum are considered. The analysis uses 36.1 fb−1 of proton–proton collision data recorded by the ATLAS experiment at √s = 13 TeV in 2015 and 2016. No significant excess of events above the estimated backgrounds is observed. The results are in- terpreted in the framework of simplified models of spin-0 dark-matter mediators. For colour- neutral spin-0 mediators produced in association with top quarks and decaying into a pair of dark-matter particles, mediator masses below 50 GeV are excluded assuming a dark-matter candidate mass of 1 GeV and unitary couplings. For scalar and pseudoscalar mediators produced in association with bottom quarks, the search sets limits on the production cross- section of 300 times the predicted rate for mediators with masses between 10 and 50 GeV and assuming a dark-matter mass of 1 GeV and unitary coupling. Constraints on colour- charged scalar simplified models are also presented. Assuming a dark-matter particle mass of 35 GeV, mediator particles with mass below 1.1 TeV are excluded for couplings yielding a dark-matter relic density consistent with measurements

Pervasive gaps in Amazonian ecological research

Biodiversity loss is one of the main challenges of our time,1,2 and attempts to address it require a clear understanding of how ecological communities respond to environmental change across time and space.3,4 While the increasing availability of global databases on ecological communities has advanced our knowledge of biodiversity sensitivity to environmental changes,5,6,7 vast areas of the tropics remain understudied.8,9,10,11 In the American tropics, Amazonia stands out as the world's most diverse rainforest and the primary source of Neotropical biodiversity,12 but it remains among the least known forests in America and is often underrepresented in biodiversity databases.13,14,15 To worsen this situation, human-induced modifications16,17 may eliminate pieces of the Amazon's biodiversity puzzle before we can use them to understand how ecological communities are responding. To increase generalization and applicability of biodiversity knowledge,18,19 it is thus crucial to reduce biases in ecological research, particularly in regions projected to face the most pronounced environmental changes. We integrate ecological community metadata of 7,694 sampling sites for multiple organism groups in a machine learning model framework to map the research probability across the Brazilian Amazonia, while identifying the region's vulnerability to environmental change. 15%–18% of the most neglected areas in ecological research are expected to experience severe climate or land use changes by 2050. This means that unless we take immediate action, we will not be able to establish their current status, much less monitor how it is changing and what is being lost

Characterisation of microbial attack on archaeological bone

As part of an EU funded project to investigate the factors influencing bone preservation in the archaeological record, more than 250 bones from 41 archaeological sites in five countries spanning four climatic regions were studied for diagenetic alteration. Sites were selected to cover a range of environmental conditions and archaeological contexts. Microscopic and physical (mercury intrusion porosimetry) analyses of these bones revealed that the majority (68%) had suffered microbial attack. Furthermore, significant differences were found between animal and human bone in both the state of preservation and the type of microbial attack present. These differences in preservation might result from differences in early taphonomy of the bones. © 2003 Elsevier Science Ltd. All rights reserved

Global variation in postoperative mortality and complications after cancer surgery: a multicentre, prospective cohort study in 82 countries

© 2021 The Author(s). Published by Elsevier Ltd. This is an Open Access article under the CC BY-NC-ND 4.0 licenseBackground: 80% of individuals with cancer will require a surgical procedure, yet little comparative data exist on early outcomes in low-income and middle-income countries (LMICs). We compared postoperative outcomes in breast, colorectal, and gastric cancer surgery in hospitals worldwide, focusing on the effect of disease stage and complications on postoperative mortality. Methods: This was a multicentre, international prospective cohort study of consecutive adult patients undergoing surgery for primary breast, colorectal, or gastric cancer requiring a skin incision done under general or neuraxial anaesthesia. The primary outcome was death or major complication within 30 days of surgery. Multilevel logistic regression determined relationships within three-level nested models of patients within hospitals and countries. Hospital-level infrastructure effects were explored with three-way mediation analyses. This study was registered with ClinicalTrials.gov, NCT03471494. Findings: Between April 1, 2018, and Jan 31, 2019, we enrolled 15 958 patients from 428 hospitals in 82 countries (high income 9106 patients, 31 countries; upper-middle income 2721 patients, 23 countries; or lower-middle income 4131 patients, 28 countries). Patients in LMICs presented with more advanced disease compared with patients in high-income countries. 30-day mortality was higher for gastric cancer in low-income or lower-middle-income countries (adjusted odds ratio 3·72, 95% CI 1·70–8·16) and for colorectal cancer in low-income or lower-middle-income countries (4·59, 2·39–8·80) and upper-middle-income countries (2·06, 1·11–3·83). No difference in 30-day mortality was seen in breast cancer. The proportion of patients who died after a major complication was greatest in low-income or lower-middle-income countries (6·15, 3·26–11·59) and upper-middle-income countries (3·89, 2·08–7·29). Postoperative death after complications was partly explained by patient factors (60%) and partly by hospital or country (40%). The absence of consistently available postoperative care facilities was associated with seven to 10 more deaths per 100 major complications in LMICs. Cancer stage alone explained little of the early variation in mortality or postoperative complications. Interpretation: Higher levels of mortality after cancer surgery in LMICs was not fully explained by later presentation of disease. The capacity to rescue patients from surgical complications is a tangible opportunity for meaningful intervention. Early death after cancer surgery might be reduced by policies focusing on strengthening perioperative care systems to detect and intervene in common complications. Funding: National Institute for Health Research Global Health Research Unit

Effects of hospital facilities on patient outcomes after cancer surgery: an international, prospective, observational study

© 2022 The Author(s). Published by Elsevier Ltd. This is an Open Access article under the CC BY 4.0 licenseBackground: Early death after cancer surgery is higher in low-income and middle-income countries (LMICs) compared with in high-income countries, yet the impact of facility characteristics on early postoperative outcomes is unknown. The aim of this study was to examine the association between hospital infrastructure, resource availability, and processes on early outcomes after cancer surgery worldwide. Methods: A multimethods analysis was performed as part of the GlobalSurg 3 study—a multicentre, international, prospective cohort study of patients who had surgery for breast, colorectal, or gastric cancer. The primary outcomes were 30-day mortality and 30-day major complication rates. Potentially beneficial hospital facilities were identified by variable selection to select those associated with 30-day mortality. Adjusted outcomes were determined using generalised estimating equations to account for patient characteristics and country-income group, with population stratification by hospital. Findings: Between April 1, 2018, and April 23, 2019, facility-level data were collected for 9685 patients across 238 hospitals in 66 countries (91 hospitals in 20 high-income countries; 57 hospitals in 19 upper-middle-income countries; and 90 hospitals in 27 low-income to lower-middle-income countries). The availability of five hospital facilities was inversely associated with mortality: ultrasound, CT scanner, critical care unit, opioid analgesia, and oncologist. After adjustment for case-mix and country income group, hospitals with three or fewer of these facilities (62 hospitals, 1294 patients) had higher mortality compared with those with four or five (adjusted odds ratio [OR] 3·85 [95% CI 2·58–5·75]; p<0·0001), with excess mortality predominantly explained by a limited capacity to rescue following the development of major complications (63·0% vs 82·7%; OR 0·35 [0·23–0·53]; p<0·0001). Across LMICs, improvements in hospital facilities would prevent one to three deaths for every 100 patients undergoing surgery for cancer. Interpretation: Hospitals with higher levels of infrastructure and resources have better outcomes after cancer surgery, independent of country income. Without urgent strengthening of hospital infrastructure and resources, the reductions in cancer-associated mortality associated with improved access will not be realised. Funding: National Institute for Health and Care Research

Search for direct top squark pair production in final states with two leptons in s=13\sqrt{s} = 13 TeV pppp collisions with the ATLAS detector

International audienceThe results of a search for direct pair production of top squarks in events with two opposite-charge leptons (electrons or muons) are reported, using $36.1~\hbox {fb}^{-1}$ of integrated luminosity from proton–proton collisions at $\sqrt{s}=13$ TeV collected by the ATLAS detector at the Large Hadron Collider. To cover a range of mass differences between the top squark $\tilde{t}$ and lighter supersymmetric particles, four possible decay modes of the top squark are targeted with dedicated selections: the decay $\tilde{t} \rightarrow b \tilde{\chi }_{1}^{\pm }$ into a b-quark and the lightest chargino with $\tilde{\chi }_{1}^{\pm } \rightarrow W \tilde{\chi }_{1}^{0}$ , the decay $\tilde{t} \rightarrow t \tilde{\chi }_{1}^{0}$ into an on-shell top quark and the lightest neutralino, the three-body decay $\tilde{t} \rightarrow b W \tilde{\chi }_{1}^{0}$ and the four-body decay $\tilde{t} \rightarrow b \ell \nu \tilde{\chi }_{1}^{0}$ . No significant excess of events is observed above the Standard Model background for any selection, and limits on top squarks are set as a function of the $\tilde{t}$ and $\tilde{\chi }_{1}^{0}$ masses. The results exclude at 95% confidence level $\tilde{t}$ masses up to about 720 GeV, extending the exclusion region of supersymmetric parameter space covered by previous searches

Searches for the ZγZ\gamma decay mode of the Higgs boson and for new high-mass resonances in pppp collisions at s=13\sqrt{s} = 13 TeV with the ATLAS detector

International audienceThis article presents searches for the Zγ decay of the Higgs boson and for narrow high-mass resonances decaying to Zγ, exploiting Z boson decays to pairs of electrons or muons. The data analysis uses 36.1 fb$^{−1}$ of pp collisions at $\sqrt{s}=13$ recorded by the ATLAS detector at the CERN Large Hadron Collider. The data are found to be consistent with the expected Standard Model background. The observed (expected — assuming Standard Model pp → H → Zγ production and decay) upper limit on the production cross section times the branching ratio for pp → H → Zγ is 6.6. (5.2) times the Standard Model prediction at the 95% confidence level for a Higgs boson mass of 125.09 GeV. In addition, upper limits are set on the production cross section times the branching ratio as a function of the mass of a narrow resonance between 250 GeV and 2.4 TeV, assuming spin-0 resonances produced via gluon-gluon fusion, and spin-2 resonances produced via gluon-gluon or quark-antiquark initial states. For high-mass spin-0 resonances, the observed (expected) limits vary between 88 fb (61 fb) and 2.8 fb (2.7 fb) for the mass range from 250 GeV to 2.4 TeV at the 95% confidence level