21 research outputs found
PDF modelling and particle-turbulence interaction of turbulent spray flames
No full textTurbulent spray flames can be found in many applications, such as Diesel engines, rocket engines and power plants. The many practical applications are a motivation to investigate the physical phenomena occurring in turbulent spray flames in detail in order to be able to understand, predict and optimise them. Turbulent spray flames are a two-phase flow system consisting of a turbulent reacting continuum phase and a dispersed liquid phase contained in the continuum phase. In this thesis the interaction between these two phases is being studied, and specifically the effects of vaporisation and the effects of the presence of droplets on the turbulence characteristics of the continuum phase (the two-way coupling effect). The main goal of the research described in this thesis is to develop and evaluate stochastic Lagrangian models for turbulent spray flames that are characterised by significant or dominant two-way coupling effects. In the first part of the thesis, isolated droplet vaporisation models are studied and several models are evaluated. The problem of droplet interaction is briefly explained using some simple simulations and general theoretical ideas and the concept of group combustion is introduced. In the second part of the thesis the hybrid Lagrangian-Lagrangian method is presented. The continuum phase is described by the transport equation for the joint mass density function (MDF) of velocity and composition, which is solved indirectly using a Monte Carlo particle method where Langevin type equations are solved. This method is augmented by a finite volume method where the mean Eulerian transport equations for momentum, Reynolds stresses and turbulence dissipation are solved, making it a hybrid approach for the continuum phase. The dispersed phase is described solely by the droplet MDF which is also solved using a Monte Carlo method. A novel modification of the turbulence model for the pressure rate of strain in the Eulerian transport equation for the Reynolds stresses is presented that takes into account the effect of the presence of particles and the effect of mass transfer. The models in the Langevin equation in the Lagrangian formulation are then modified in order to be consistent with the p ressure rate of strain model in the Eulerian formulation. The modification of the diffusion term in the Langevin equation implies a modification of Kolmogorov's hypothesis regarding the first order Lagrangian structure function. An investigation of the transport equation for the scalar dissipation rate shows that Lagrangian mixing models are affected by liquid particle vaporisation. Other theoretical developments are the extension of the Generalised Gradient diffusion model and the Daly Harlow model for the triple correlations and an exact expression for the effect of mass transfer on the turbulence dissipation. In the third part of this thesis the results of numerical simulations of two test cases are presented. In the first test case an Eulerian-Lagrangian approach was used and the influence of the modification of the model for the pressure rate of strain by the presence of particles is investigated for an axially symmetric non-burning turbulent dispersed spray and compared with experimental data. Small improvements in turbulence quantities over the conventional turbulence and two-way coupling model are noticed when the novel modification of the pressure rate of strain is being used. In the second test case, simulations of an axially symmetric turbulent spray flame are performed to illustrate the performance of the complete hybrid method proposed in this thesis. A good agreement with experimental data was found using the hybrid method. In the mass transfer controlled spray flame studied in this thesis, taking into account the reduction of the drag coefficient and the heat and mass transfer coefficient due to mass transfer turned out to be crucial to the performance of the method.Applied Science
Comparing the impacts of geometry level of detail in computational wind engineering with on-site urban measurements
No full textUrbanization has led to more than half of the world’s population living in cities. The design of sustainable and resilient urban environments is becoming increasingly critical to optimize the well-being of their inhabitants and the planet. One of the major challenges in achieving this is the complex wind flow patterns in densely built-up areas, which require accurate prediction and analysis to effectively harness the potential benefits of wind flow, such as natural ventilation and wind power generation. However, the unique features of urban landscapes, such as high-rise buildings, narrow streets, and irregular building shapes, make the analysis of wind flow within urban canopies complicated.In recent years, Computational Fluid Dynamics (CFD) has become a vital tool for studying wind flow in urban areas. Still, the complex geometries of buildings can lead to challenges, including recirculation, reattachment, intense turbulence, and dead zones. Moreover, vegetation plays a crucial role in controlling wind flow in dense areas by acting as a physical barrier, significantly reducing the wind speed and alter the wind flow direction. Additionally, generating geometry for computa-tional fluid dynamics (CFD) simulation in complex urban environments is a chal-lenging and time-consuming process.Hence, for this thesis, the City4CFD software will be used to automatically recon-struct a 3D model of Stanford University at LoD1.2, which will significantly reduce the time and effort required to generate the complex geometry necessary for com-putational fluid dynamics (CFD) simulations in urban environments. The results will be compared to those obtained from an already manually reconstructed model at LoD2.1 and real-world measurements conducted within the area of interest. This will allow me to determine the differences introduced by different level of detail.The research will address several sub-questions, such as the steps needed to auto-matically reconstruct a 3D city model, the potential improvements in simulation accuracy by increasing LoD, and the impact of complex geometries on wind flow. The results of the thesis indicated that a more complex geometry Level of Detail (LoD) can enhance the accuracy of simulations by providing a more precise de-piction of wind flow patterns. In other words, a higher LoD geometry, such as LoD2.1, can more accurately predict wind patterns in urban environments based on real-world measurements. The study observed that the LoD2.1 model, which in-corporates more complex features, generated simulation outcomes that were closer to the measurements compared to the less detailed LoD1.2 model.Geomatic
Evaluation of a modified reynolds stress model for turbulent dispersed two-phase flows including two-way coupling
No full textApplied Science
Informal teacher communities enhancing the professional development of medical teachers: a qualitative study
No full textInformal teacher communities enhancing the professional development of medical teachers a qualitative study van Lankveld, T.; Schoonenboom, J.I.; Kusurkar, R.; Beishuizen, J.J.; Croiset, G.; Volman, M.L.L. Published in: BMC Medical Education DOI: 10.1186/s12909-016-0632-2 Link to publication Citation for published version (APA): van Lankveld, T., Schoonenboom, J., Kusurkar, R., Beishuizen, J., Croiset, G., & Volman, M. (2016). Informal teacher communities enhancing the professional development of medical teachers: a qualitative study. BMC Medical Education, General rights It is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), other than for strictly personal, individual use, unless the work is under an open content license (like Creative Commons). Disclaimer/Complaints regulations If you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask the Library: https://uba.uva.nl/en/contact, or a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. You will be contacted as soon as possible. Download date: 29 Jun 2019 R E S E A R C H A R T I C L E Open Access Informal teacher communities enhancing the professional development of medical teachers: a qualitative study Abstract Background: Informal peer learning is a particularly powerful form of learning for medical teachers, although it does not always occur automatically in the departments of medical schools. In this article, the authors explore the role of teacher communities in enhancing informal peer learning among undergraduate medical teachers. Teacher communities are groups of teachers who voluntarily gather on a regular basis to develop and share knowledge. Outside of medical education, these informal teacher communities have proved to be an effective means of enhancing peer learning of academic teachers. The processes underlying this outcome are, however, not known. This study therefore aims to explore the processes that make informal teacher communities effective in supporting peer learning of teachers. Methods: A qualitative study was performed at a Dutch medical school, where a student-centred undergraduate curriculum had recently been introduced. As part of this curriculum, tutors are segregated into separate specialty areas and thus have only limited opportunities for informal learning with other tutors. The authors followed two informal teacher communities aimed at supporting these tutors. They observed the interactions within the teacher communities and held semi-structured interviews with ten of the participants. The observation notes and interview data were analysed using thematic analysis. Results: The informal teacher communities allowed the tutors to engage in a dialogue with colleagues and share questions, solutions, and interpretations. The teacher communities also provided opportunities to explicate tacit expertise, which helped the tutors to develop an idea of their role and form a frame of reference for their own experiences. Furthermore, the communities enhanced the tutors' sense of belonging. The tutors felt more secure in their role and they felt valued by the organisation due to the teacher communities. Conclusions: This study shows that informal teacher communities not only support the professional development of tutors, but also validate and strengthen their identity as teachers. They seem to provide a dialogical space where informal intercollegiate learning is stimulated, stories are shared, tacit knowledge is made explicit, concerns are shared, and teacher identity is nurtured
Systolic time intervals vs invasive predictors of fluid responsiveness after coronary artery bypass surgery(dagger)
No full textOBJECTIVES: Haemodynamic parameters for predicting fluid responsiveness in intensive care patients are invasive, technically challenging or not universally applicable. We compared the initial systolic time interval (ISTI), a non-invasive measure of the time interval between the electrical and mechanical activities of the heart measured by impedance cardiography, with invasively measured haemodynamic parameters in predicting fluid responsiveness after cardiac surgery. METHODS: Thirty-two clinically hypovolemic patients admitted to the intensive care unit after coronary artery bypass surgery received 500 ml of gelatine solution in two volume loading steps of 250 ml at an infusion rate of 1000 ml/h. Haemodynamic and biochemical measurements were done at baseline and 15 min after each volume loading step with continuous recording of the impedance cardiogram and electrocardiogram. RESULTS: Forty-four percentage (n = 14) of patients showed a stroke volume (SV) index increase >10%. ISTI predicted fluid responsiveness with an optimum threshold of >153 ms (P = 0.023) and a sensitivity of 71% and specificity of 78%. The predictive values of ISTI did not differ from those of arterial pressure or SV at baseline. A decrease of ISTI of =8.3 ms predicted fluid responsiveness with the highest positive predictive value (88%, P = 0.004) among the variables, and absence thereof virtually excluded fluid responsiveness (specificity 94%). CONCLUSIONS: Non-invasively measured ISTI is able to predict and monitor fluid responsiveness after cardiac surgery non-inferiorly to invasively measured haemodynamic indices. © The Author 2013. Published by Oxford University Press on behalf of the European Association for Cardio-Thoracic Surgery. All rights reserved
Globaal ontwerp van een offshore installatie voor totale behandeling van een aardolie/aardgas stroom
No full textDocument uit de collectie Chemische ProcestechnologieDelftChemTechApplied Science
Free serum cortisol during the postoperative acute phase response determined by equilibrium dialysis liquid chromatography-tandem mass spectrometry
No full textIn severely ill patients low concentrations of the corticosteroid binding globulin are typically found; the aim of this study was to quantify directly free bioactive cortisol concentrations in the sera of postoperative cardiosurgical patients. Serum samples of 12 consecutive patients undergoing aortocoronary bypass surgery taken preoperatively and on the postoperative days 1 to 4 were analyzed. Total serum cortisol was quantified using liquid chromatographytandem mass spectrometry with an online sample extraction system and trideuterated cortisol as the internal standard, and free serum cortisol was measured after overnight equilibrium dialysis. Whereas on the first postoperative day, the median total serum cortisol concentration was approximately twofold increased compared to preoperative samples (preoperatively, 245 nmol/l (interquartile range (IQR) 203293 nmol/l); first postoperative day, 512 nmol/l (IQR 410611 nmol/l)), median dialyzable free cortisol concentration was almost sevenfold increased (preoperatively, 14.2 nmol/l (IQR 10.920.7 nmol/l); first postoperative day, 98.3 nmol/l (IQR 81.3134 nmol/l)). On the fourth postoperative day, median free cortisol was still significantly increased compared to baseline sampling (p < 0.05), whereas median total cortisol was not. A median of 5.7% (IQR 5.47.0%) of total cortisol was found as free cortisol on the preoperative day, 21.2% (IQR 18.9 23.5%) on the first postoperative day and 10.5% (IQR 9.814.0%) on the fourth postoperative day. It is concluded that during the postoperative period the freeto bound ratio of cortisol is highly variable and that during the acute phase response direct quantification of free bioactive cortisol concentrations seems to be biologically more appropriate than the measurement of total cortisol concentrations
AS INTERAÇÕES EM PRÁTICAS DE REVISÃO E DE REESCRITA TEXTUAIS REALIZADAS POR MEIO DO MODELO DE ROTAÇÃO POR ESTAÇÕES NO ENSINO MÉDIO INTEGRADO
No full textThis thesis concerns the interaction between students as well as between them and the teacher in practices of revision and rewriting of Enem argumentative essays, carried out through active methodologies. The work is the result of qualitative and interpretivist research, affiliated with Applied Linguistics (Moita Lopes, 1994, 2006) and methodologically carried out through assumptions of the conception of action research (Thiollent, 2011). The thesis defended is that the participation of the students in revision and rewriting activities, in groups, organized based on an active methodology related to blended learning, the station rotation model, together with the teacher’s actions throughout the educational practice, contributes to the development of the autonomy of these pupils as revisers of their own texts. Thus, the main goal of the study is to understand how the interactions of integrated high school students between each other and with the teacher, during their participation in collective revision and rewriting activities guided by the station rotation model can develop the autonomy of the pupils as revisers of their own text production. The specific goals are: i) to analyze the contribution of scaffolding present in the interactions between the students as well as between them and the teacher, during the revision and rewriting activities carried out collectively, to the development of the students as text revisers; and ii) to analyze which aspects of the group discussions are reflected in the students’ text production when they need to revise and rewrite their own texts without the help of an external reader. The main theoretical base for the research is: the enunciative-discursive view of language (Bakhtin, 2015, 2016; Volóchinov, 2017, 2019); the understanding of writing as work (Fiad; Mayrink-Sabinson, 1994 [1991]); Vigotski’s studies (2001, 2007) on interaction, collaboration and internalization, as well as those of Van de Pol, Volman and Beishuizen (2010) about scaffolding. The data were generated from a teaching project about the Enem essay conducted by the author of this work, in the Federal Institute of Mato Grosso do Sul (IFMS) – campus Coxim, in 2023, through recording of interactions, questionnaires, interviews, materials written by students and by the researcher as well as field notes. The contribution of the research relies on the fact that it allows for the expansion of understanding, development and improvement of the work with collective and collaborative text revision and rewriting through active methodologies, consisting of a contribution to teacher training. The results show that both the interactions between the students and between them and the educator contributed to the development of participants as revisers of their own texts. This was due to the fact that the students progressively internalized knowledge and practices that are important to revise and to rewrite, starting from situations in which they received more external collaboration to those in which this support decreased. In addition, the research highlights the teacher’s acting as an essential factor to students’ development of autonomy in the revision and rewriting of their texts.Esta tese trata da interação entre os estudantes e da deles com o professor nas práticas de revisão e de reescrita de textos dissertativo-argumentativos do Enem, realizadas por meio de metodologias ativas. O trabalho resulta de uma pesquisa de natureza qualitativa, de cunho interpretativista, filiada à Linguística Aplicada (Moita Lopes, 1994, 2006) e desenvolvida metodologicamente a partir de princípios da concepção de pesquisa-ação (Thiollent, 2011). A tese defendida é a de que a participação dos estudantes em atividades de revisão e de reescrita, em grupos, organizadas a partir de uma metodologia ativa ligada à educação híbrida, o modelo de rotação por estações, em conjunto com as ações realizadas pelo docente ao longo da atividade educativa, contribui para o desenvolvimento da autonomia desses discentes enquanto revisores de seus próprios textos. Assim, o objetivo geral do estudo é compreender como as interações dos estudantes de ensino médio integrado, entre si e com o docente, durante a participação em atividades de revisão e reescrita coletivas pautadas pelo modelo de rotação por estações pode desenvolver a autonomia desses aprendizes como revisores de suas próprias produções textuais. Os objetivos específicos são: i) analisar a contribuição dos andaimes presentes nas interações entre os estudantes e nas deles com o docente, durante as atividades de revisão e reescrita realizadas coletivamente, para o desenvolvimento dos educandos enquanto revisores de textos; e ii) analisar quais aspectos das discussões em grupo aparecem refletidos na produção textual dos estudantes quando eles precisam revisar e reescrever seus próprios textos sem o auxílio de um leitor externo. As principais bases teóricas em que se apoia o trabalho são: o entendimento enunciativo-discursivo da linguagem (Bakhtin, 2015, 2016; Volóchinov, 2017, 2019); a compreensão da escrita como trabalho (Fiad; Mayrink-Sabinson, 1994 [1991]); os estudos de Vigotski (2001, 2007) sobre interação, colaboração e internalização, bem como os de Van de Pol, Volman e Beishuizen (2010) acerca da andaimagem. Os dados foram gerados a partir de um projeto de ensino sobre a redação do Enem, conduzido pelo autor deste trabalho, no Instituto Federal de Mato Grosso do Sul (IFMS) – câmpus Coxim, em 2023, por meio de gravações das interações em áudio, questionários, entrevistas, materiais escritos pelos discentes e pelo pesquisador, bem como anotações de campo. A contribuição do estudo está no fato de que ele permite ampliar a compreensão, o desenvolvimento e o aprimoramento do trabalho com revisão e reescrita textuais coletivas e colaborativas por meio de metodologias ativas, consistindo em um aporte para a formação de professores. Os resultados indicam que tanto as interações estabelecidas entre os estudantes quanto as deles com o educador contribuíram para o desenvolvimento dos educandos enquanto revisores de seus próprios textos. Isso se deu pelo fato de que os participantes internalizaram progressivamente saberes e práticas importantes para revisar e reescrever, partindo de situações em que recebiam mais colaboração externa para outras em que esse suporte diminuía. Ademais, a investigação evidencia a atuação do professor como fator essencial para o desenvolvimento da autonomia dos discentes na revisão e na reescrita de seus textos
Disfunção cardíaca na sepse experimental avaliada em coração isolado e perfundido de camundongo
No full textDissertação (mestrado) - Universidade Federal de Santa Catarina, Centro de Ciências Biológicas, Programa de Pós-Graduação em Farmacologia, Florianópolis, 2010A síndrome da resposta inflamatória sistêmica (SIRS), quando associada a uma infecção pode evoluir para sepse e choque séptico, que são importantes causas de morte nas UTIs. Em geral, a morte é causada por um colapso cardiovascular e hipotensão refratária, que aparecem logo no início da sepse. A disfunção vascular é mais estudada e compreendida que a disfunção cardíaca, contudo a última é reconhecida como um importante mediador da disfunção de múltiplos órgãos na sepse. O objetivo do presente trabalho foi caracterizar a disfunção cardíaca na sepse experimental induzida pela ligadura e perfuração do ceco (CLP) em camundongos, utilizando a metodologia de coração isolado e perfundido (preparação de Langendorff), e também, avaliar a participação do óxido nítrico nesse processo. Os parâmetros cardíacos avaliados foram: Tensão sistólica e diastólica, +dT/dt (velocidade de contração), -dT/dt (velocidade de relaxamento), AUC (área sob a curva), pressão de perfusão das coronárias e frequência cardíaca. Observamos que durante a sepse severa (índice de mortalidade de 100% quarenta e oito horas após a CLP) o perfil de atividade apresentado pelos corações sépticos, apesar de variado, mostra que a sepse causa importantes alterações na funcionalidade cardíaca. O parâmetro tensão sistólica, três horas após os animais serem submetidos à CLP, mostrou que 38% dos corações apresentaram valores superiores aos apresentados pelos corações controle (e por isso denominados de suprafuncionais), 12% apresentaram valores inferiores (subfuncionais) e 50% apresentaram valores semelhantes aos apresentados pelos corações controle (normofuncionais). Seis horas após a CLP o subgrupo suprafuncional correspondeu a apenas 21% do total de corações avaliados, enquanto o subgrupo subfuncional correspondeu a 29%. Doze horas após a CLP o subgrupo normofuncional foi o mais numeroso, correspondendo a 77% do total de corações avaliados. Por fim, vinte e quatro horas após a CLP houve um aumento substancial no número de corações subfuncionais, representando 40% dos corações avaliados. Perfil semelhante foi encontrado em relação aos parâmetros velocidade de contração, velocidade de relaxamento e AUC. Quando estimulados com isoprenalina para avaliação da capacidade contrátil e capacidade cronotrópica positiva, os corações dos animais submetidos à CLP vinte e quatro horas antes apresentaram importante redução no funcionamento das células auto-rítmicas do nodo sino-atrial, alterações no sistema de condução dos estímulos e ainda, o sistema contrátil destes corações encontrou-se parcialmente reduzido. Tanto os corações suprafuncionais avaliados três horas após a CLP quanto os corações suprafuncionais avaliados vinte e quatro horas após, apresentaram tensão sistólica superior à apresentada pelos corações controle em resposta à isoprenalina. A resposta cronotrópica e inotrópica positiva dos demais corações avaliados (subfuncionais três horas após a CLP, normofuncionais três e vinte e quatro horas após a CLP) foi semelhante à resposta apresentada pelos corações controle, sugerindo que a atividade beta-adrenérgica, atividade contrátil e o aspecto elétrico da frequência cardíaca estão preservados nestes corações. Observamos ainda que os níveis plasmáticos de NOx encontram-se elevados a partir de três horas após o procedimento cirúrgico, permanecendo assim até pelo menos quarenta e oito horas após a CLP. A infusão de um inibidor não-seletivo das enzimas NOS (L-NAME) não alterou a atividade basal dos corações controle e dos corações sépticos avaliados vinte e quatro horas após a CLP. Por outro lado, quando estimulados com isoprenalina, os corações controle infundidos com L-NAME apresentaram resposta cronotrópica e inotrópica positiva inferior à apresentada pelos corações controle que receberam apenas Krebs. Os corações sépticos que receberam L-NAME quando estimulados com isoprenalina apresentaram resposta concentração-dependente à isoprenalina, tanto no parâmetro tensão sistólica quanto no parâmetro frequência cardíaca, efeito este que não foi observado nos corações sépticos que receberam apenas Krebs. O substrato L-arginina não é um fator limitante para a produção de óxido nítrico, visto que não foram observadas diferenças em corações controle e corações sépticos avaliados vinte e quatro horas após a CLP e que tiveram arginina adicionada à solução de perfusão. Assim, nosso trabalho mostra que ocorrem importantes alterações cardíacas durante a sepse, as quais acometem tanto a maquinaria contrátil quanto as células auto-rítmicas, tendo início logo nas primeiras horas de instalação do quadro e perdurando até horários mais tardios. Demonstramos ainda, que o óxido nítrico parece estar envolvido nas alterações observadas
Large health disparities in cardiovascular death in men and women, by ethnicity and socioeconomic status in an urban based population cohort
No full textBackground: Socioeconomic status and ethnicity are not incorporated as predictors in country-level cardiovascular risk charts on mainland Europe. The aim of this study was to quantify the sex-specific cardiovascular death rates stratified by ethnicity and socioeconomic factors in an urban population in a universal healthcare system. Methods: Age-standardized death rates (ASDR) were estimated in a dynamic population, aged 45–75 in the city of The Hague, the Netherlands, over the period 2007–2018, using data of Statistics Netherlands. Results were stratified by sex, ethnicity (country of birth) and socioeconomic status (prosperity) and compared with a European cut-off for high-risk countries (ASDR men 225/100,000 and women 175/100,000). Findings: In total, 3073 CVD deaths occurred during 1·76 million person years follow-up. Estimated ASDRs (selected countries of birth) ranged from 126 (95%CI 89–174) in Moroccan men to 379 (95%CI 272–518) in Antillean men, and from 86 (95%CI 50–138) in Moroccan women to 170 (95%CI 142–202) in Surinamese women. ASDRs in the highest and lowest prosperity quintiles were 94 (95%CI 90–98) and 343 (95%CI 334–351) for men, and 43 (95%CI 41–46) and 140 (95%CI 135–145), for women, respectively. Interpretation: In a diverse urban population, large health disparities in cardiovascular ASDRs exists across ethnic and socioeconomic subgroups. Identifying these high-risk subgroups followed by targeted preventive efforts, might provide a basis for improving cardiovascular health equity within communities. Instead of classifying countries as high-risk or low-risk, a shift towards focusing on these subgroups within countries might be needed. Funding: Leiden University Medical Center and Leiden Universit
