Development of an expert system based on fuzzy logic as support for heat pipes design

Heat pipe design and selection require specialist knowledge due to numerous possible combinations and restrictions that should be considered. The general objective of this work is to design a Specialist System that assists future engineers in material and working fluid selection for a suitable heat pipe application, based on the technical operating requirements. The methodology consisted of a qualitative perspective through interviews with two specialist engineers in the heat pipes area. The resulting information from the interviews was organized into a library, working as a source for the specialist system. In addition, several books from the literature completed the information in the library. Based on the operating conditions and the provided library, the program recommends suitable materials and working fluids and the necessity of porous media for the application, like a consult with a heat pipe specialist. The new expert system can be a tool for researchers and engineers in heat pipe design as passive control systems, providing more suitable solutions for each application

FMECA and FTA analysis applied to the manufacturing process of pulsating heat pipes

Pulsating heat pipes (PHPs) offer significant advantages for the thermal control of electronic components due to their simple manufacturing and high heat transfer rates. The reliability of PHPs has traditionally been assessed through long-life testing, but detailed reliability analyses from an equipment perspective are limited. The study of PHP reliability is essential due to its application and operational conditions. For instance, in aerospace applications these devices operate under severe conditions, and maintenance or replacement is impossible during operation, making them critical components in system functionality. The reliability analysis of PHPs focuses on the manufacturing process, considering future operating conditions. Although preliminary PHP testing will be conducted on Earth, laboratory conditions are less stringent due to the difficulty of replicating launch acceleration and space conditions for long-term testing under microgravity. This study presents an FMECA (Failure Modes, Effects, and Criticality Analysis) of the pulsating heat pipe manufacturing process, breaking down the production of each component. The results indicate that the most critical point is concentrated in the assembly of these components, leading to a higher incidence of welding failures. It recommends further work to improve welding and analyze mechanical stresses within the heat pipe

Performance evaluation of a parabolic cylinder collector applying the Monte Carlo ray tracing method

The purpose of this article is to evaluate the performance of a prototype parabolic trough collector for three proposed scenarios, where geometric designs with optical characteristics are tested according to the appropriate technological paradigm; low cost of maintenance and implementation, intensive local labor, materials and resources of the implementation area. The device was developed by the Energy, Automation and Control Systems Research Group GISEAC of the Unidades Tecnológicas de Santander for low-cost water heating; using materials and labor for its fabrication easily available locally. Monte Carlo ray tracing methodology was applied using the open-access software SolTrace and Tonatiuh. To select the geometric scenario to be simulated, the edge angle and the width of the primary reflection system of the device were varied. The results obtained showed that the aperture of the parabola has a direct impact on the drop in the concentration ratio (CR) percentage value and the performance of the prototype

Characterization in vitro and in vivo of a pandemic H1N1 influenza virus from a fatal case

Pandemic 2009 H1N1 (pH1N1) influenza viruses caused mild symptoms in most infected patients. However, a greater rate of severe disease was observed in healthy young adults and children without co-morbid conditions. Here we tested whether influenza strains displaying differential virulence could be present among circulating pH1N1 viruses. The biological properties and the genotype of viruses isolated from a patient showing mild disease (M) or from a fatal case (F), both without known co-morbid conditions were compared in vitro and in vivo. The F virus presented faster growth kinetics and stronger induction of cytokines than M virus in human alveolar lung epithelial cells. In the murine model in vivo, the F virus showed a stronger morbidity and mortality than M virus. Remarkably, a higher proportion of mice presenting infectious virus in the hearts, was found in F virus-infected animals. Altogether, the data indicate that strains of pH1N1 virus with enhanced pathogenicity circulated during the 2009 pandemic. In addition, examination of chemokine receptor 5 (CCR5) genotype, recently reported as involved in severe influenza virus disease, revealed that the F virus-infected patient was homozygous for the deleted form of CCR5 receptor (CCR5Δ32).Funding Statement: This work was supported by Instituto de Salud Carlos III (Programa especial de investigación sobre la gripe pándemica GR09/0023, GR09/0040, GR09/0039) and Ciber de Enfermedades Respiratorias. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.S

Large expert-curated database for benchmarking document similarity detection in biomedical literature search

Document recommendation systems for locating relevant literature have mostly relied on methods developed a decade ago. This is largely due to the lack of a large offline gold-standard benchmark of relevant documents that cover a variety of research fields such that newly developed literature search techniques can be compared, improved and translated into practice. To overcome this bottleneck, we have established the RElevant LIterature SearcH consortium consisting of more than 1500 scientists from 84 countries, who have collectively annotated the relevance of over 180 000 PubMed-listed articles with regard to their respective seed (input) article/s. The majority of annotations were contributed by highly experienced, original authors of the seed articles. The collected data cover 76% of all unique PubMed Medical Subject Headings descriptors. No systematic biases were observed across different experience levels, research fields or time spent on annotations. More importantly, annotations of the same document pairs contributed by different scientists were highly concordant. We further show that the three representative baseline methods used to generate recommended articles for evaluation (Okapi Best Matching 25, Term Frequency-Inverse Document Frequency and PubMed Related Articles) had similar overall performances. Additionally, we found that these methods each tend to produce distinct collections of recommended articles, suggesting that a hybrid method may be required to completely capture all relevant articles. The established database server located at https://relishdb.ict.griffith.edu.au is freely available for the downloading of annotation data and the blind testing of new methods. We expect that this benchmark will be useful for stimulating the development of new powerful techniques for title and title/abstract-based search engines for relevant articles in biomedical research.Peer reviewe

Effect of angiotensin-converting enzyme inhibitor and angiotensin receptor blocker initiation on organ support-free days in patients hospitalized with COVID-19

IMPORTANCE Overactivation of the renin-angiotensin system (RAS) may contribute to poor clinical outcomes in patients with COVID-19. Objective To determine whether angiotensin-converting enzyme (ACE) inhibitor or angiotensin receptor blocker (ARB) initiation improves outcomes in patients hospitalized for COVID-19. DESIGN, SETTING, AND PARTICIPANTS In an ongoing, adaptive platform randomized clinical trial, 721 critically ill and 58 non–critically ill hospitalized adults were randomized to receive an RAS inhibitor or control between March 16, 2021, and February 25, 2022, at 69 sites in 7 countries (final follow-up on June 1, 2022). INTERVENTIONS Patients were randomized to receive open-label initiation of an ACE inhibitor (n = 257), ARB (n = 248), ARB in combination with DMX-200 (a chemokine receptor-2 inhibitor; n = 10), or no RAS inhibitor (control; n = 264) for up to 10 days. MAIN OUTCOMES AND MEASURES The primary outcome was organ support–free days, a composite of hospital survival and days alive without cardiovascular or respiratory organ support through 21 days. The primary analysis was a bayesian cumulative logistic model. Odds ratios (ORs) greater than 1 represent improved outcomes. RESULTS On February 25, 2022, enrollment was discontinued due to safety concerns. Among 679 critically ill patients with available primary outcome data, the median age was 56 years and 239 participants (35.2%) were women. Median (IQR) organ support–free days among critically ill patients was 10 (–1 to 16) in the ACE inhibitor group (n = 231), 8 (–1 to 17) in the ARB group (n = 217), and 12 (0 to 17) in the control group (n = 231) (median adjusted odds ratios of 0.77 [95% bayesian credible interval, 0.58-1.06] for improvement for ACE inhibitor and 0.76 [95% credible interval, 0.56-1.05] for ARB compared with control). The posterior probabilities that ACE inhibitors and ARBs worsened organ support–free days compared with control were 94.9% and 95.4%, respectively. Hospital survival occurred in 166 of 231 critically ill participants (71.9%) in the ACE inhibitor group, 152 of 217 (70.0%) in the ARB group, and 182 of 231 (78.8%) in the control group (posterior probabilities that ACE inhibitor and ARB worsened hospital survival compared with control were 95.3% and 98.1%, respectively). CONCLUSIONS AND RELEVANCE In this trial, among critically ill adults with COVID-19, initiation of an ACE inhibitor or ARB did not improve, and likely worsened, clinical outcomes. TRIAL REGISTRATION ClinicalTrials.gov Identifier: NCT0273570

Fabricação e análise estrutural, morfológica e termo hidráulica de um trocador de calor tipo circuito impresso

Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico, Programa de Pós-Graduação em Engenharia Mecânica, Florianópolis, 2020.Os trocadores de calor tipo circuito impresso (em inglês, Printed Circuit Heat Exchanger ? PCHE), são uma variação de trocadores de calor compactos e sua fabricação se constitui de dois principais processos: o ataque fotoquímico para a usinagem dos canais e a união por difusão para a solda do núcleo. Esta pesquisa foi dividida em três principais etapas. A primeira consistiu em buscar fornecedores nacionais capacitados para realizar a usinagem de canais via ataque fotoquímico, bem como fabricar três placas com canais de diferentes dimensões (semicircular com raio de 1,2 mm, semicircular com raio de 2,4 mm e canais passantes) em chapas com 3 mm de espessura em aço inoxidável AISI 316L e analisar o resultado obtidos a fim de se identificar as limitações do fabricante e verificar a viabilidade de se fabricar um trocador de calor tipo circuito impresso nacionalmente. A segunda etapa consistiu em fabricar um PCHE de canais semicirculares com raio de 2,4 mm, retos e em escoamento cruzado, com núcleo de dimensões externas 173x173x113 mm. A terceira etapa consistiu em realizar os testes experimentais para a análise termo hidráulica do dispositivo utilizando água no ramal frio e ar no ramal quente, bem como analisar seu desempenho termo hidráulico e comparar com um modelo matemático da literatura. Os testes foram realizados no limite da bancada disponível, com Reynolds de 835 a 2793 no ramal quente e de 511 a 2081 no ramal frio. Como principais resultados obtidos, tem-se que após uma pesquisa de mercado foi encontrado até o presente momento apenas um fornecedor nacional com condições de fabricar as peças na espessura de chapa, material e profundidade dos canais desejada. Ainda assim, o PCHE testado foi fabricado nos limites do processo. As peças fabricadas apresentaram alguns micro-alvéolos observados através do microscópio óptico e do microscópio eletrônico de varredura, e alguns defeitos visíveis a olho nu na região que seria a interface de união das peças. Os resultados obtidos nos ensaios de tração foram levemente inferiores aos ensaios realizados pelo grupo na união de placas de 3 mm sem canais, porém, muito similares. O mesmo foi observado qualitativamente ao avaliar a interface de união por metalografia. A área final dos canais foi em média 9% inferior ao esperado no ramal quente e 5% no ramal frio. O trocador de calor testado não apresentou vazamentos aparentes. Nos testes experimentais, o ar foi o fluido limitante nas trocas térmicas, devido à baixa capacidade térmica. O máximo calor trocado foi de 4kW, e o maior valor de Nusselt no ramal quente, calculado a partir do fator j de Colburn, foi de aproximadamente 10. A queda de pressão atingiu 674Pa no ramal quente e a 926Pa no ramal frio. Para o cálculo do fator de atrito experimental, foi proposto um coeficiente de distribuição de velocidade para canais semicirculares, a partir de dados da literatura.Abstract: Printed Circuit Heat Exchangers (PCHE) are compact heat exchangers and their fabrication consists of two principal process: photochemical machining, to make the channels, and diffusion bonding, to join the stacked plates. This research work aims to assess the fabrication and thermal performance of PCHEs, taking into account the availability of national machining suppliers and the manufacturing technology. The first step of this research consists in finding Brazilian companies able to manufacture appropriate channels for actual engineering equipment. Stainless steel 316L flat plates of 3 mm thickness produced, with different geometry channels (semicircular channels, one with 1.2 mm depth, other with 2.4 mm depth and the last with thorough channels). The second step aims to fabricate an actual cross current PCHE, with straight semicircular channels of 2.4 mm depth. In the last step, experimental tests were carried out to analyze the thermo-hydraulic performance of the heat exchange and to compare the results with mathematical models from the literature. Flow regime was limited by the experimental setup, with a Reynolds number at laminar and transition regime (from 835 to 2793) in the hot side and at laminar regime and beginning of transition regime (from 511 to 2081) in the cold side. As main results, it was found in this period of time only one national company has the necessary know how to fabricate the parts on the desired specifications and, in this case, the PCHE was fabricated close to the limits of the company's production. Fabricated plates presented larger diameter pits that were observed with optical and scanning electron microscopes; besides, some defects were detected also on the interface surface by a visual inspection. For both tensile tests and metallography, the results shown that the channel cross section areas were somewhat smaller than expected: about 9% and 5% lower for the hot and cold side respectively. The heat exchanger tested was free of apparent leakage. In the experimental tests the air flow limited the heat exchange capacity of the device, with a maximum heat of 4kW. Pressure drop reached 674Pa in the hot side and 927Pa in the cold side. Finally, to calculate the Fanning friction factor, a velocity distribution coefficient developed for a semicircular channel, was proposed based on literature data