11 research outputs found
3D Transient simulations of bubbly flow in an asymmetrically aerated flat bubble column
No full textNumerical simulations of a meandering bubble plume in a rectangular flat geometry, the so-called Becker case, ha,ve been obtained using the CFD package Fluent 4.5. The simulations are based on a full two-fluid model including two turbulence models: the k-? model and RNG k-? model. As the interfacial forces between the two phases, the drag force, virtual mass and lift forces have been taken into account. All simulations are transient and performed on twodimensional and three-dimensional grids. Different timesteps and gridsizes are used. Three different outlet conditions are explored. Using no turbulence model in the 2D case results in chaotic gridsize dependent solutions. Including a turbulence model leads to a single liquid circulation cell. The turbulent viscosity is high damping out all oscillations. In case of 3D simulations, the flow becomes transient. Using the lift forces leads to solutions contradictory to experiments. Results with both turbulence models are quite comparable to experiments, although they differ signiflcantly from eachother. The oscillation obtained with k-? has a period of 39 s (41 s in experiments) compared to 27 s with the RNG k-?. The k-? model reproduce a better dispersion effect. The results obtained with RNG k-? exhibit a more chaotic behaviour. However, after refining the grid, the fiow fields of both models change drastically. The outlet boundary condition has an important impact on the dynamic behaviour in the domain.Kramers Laboratorium voor Fysische TechnologieApplied Science
De organisatiewijzer: Een handleiding voor beleggers bij het opstarten en inrichten van een transformatieproces van kantoorgebouwen
No full textMet als bijlage: A0 poster. De vastgoedmarkt kampt regelmatig met een discrepantie tussen vraag en aanbod. In Nederland staat momenteel een groot aantal gebouwen leeg. Kantoren worden niet meer gevuld, mensen ontkerkelijken waardoor er kerken leegkomen, industri gebouwen komen leeg te staan, omdat de industrie verplaatst naar een betere locatie of het buitenland. Doordat onze samenleving op vele punten aan verandering onderhevig is, zullen veel van deze gebouwen de komende jaren structureel leeg blijven. Om deze langdurige structurele leegstand van kantoren tegen te gaan zal voor een deel van deze kantoorpanden een oplossing of een andere bestemming moeten worden gezocht. Transformatie van deze leegstaande kantoren naar een andere, beter passende functie kan zowel een belangrijke bijdrage leveren in het oplossen van de structurele leegstand alsmede in de schreeuwende vraag naar huisvesting. Ondanks dat het mes op deze manier aan twee kanten kan snijden, wordt deze vorm van bouwen niet altijd als re optie meegenomen. De begrippen transformatie en herbestemming zijn de afgelopen tijd steeds meer in de belangstelling komen te staan. Dit heeft als gevolg dat er reeds het nodige op het gebied van transformatie is onderzocht. Echter opvallend is dat ondanks de methoden en technieken die voor hand zijn, transformatie nog maar op kleine schaal wordt toegepast. Met name beleggers houden zich stil op deze markt, terwijl juist zij een belangrijke rol kunnen spelen in het bevorderen van de transformatieopgave. Deze groep krijgt namelijk steeds vaker te horen dat zij een onrendabel kantoorpand in de portefeuille hebben. Zij zijn dan ook de groep die de komende jaren de problemen van de structurele leegstand zullen gaan ondervinden. Om de transformatieopgave in Nederland te bevorderen, richt dit rapport zich dus op deze belangrijkste groep, namelijk de beleggers. Om deze groep te motiveren en enthousiast te maken voor transformatie is het belangrijk dat bepaalde risicos en onzekerheden bij voorbaat worden aangetrokken of weggezet. Met het kiezen van een juiste projectorganisatie- en contractvorm worden vastleggingen gedaan. Op deze manier worden de kansen en bedreigingen ingebed en mogelijk bij een marktpartij ondergebracht. Hierdoor is het voor een belegger toegankelijker te participeren in een transformatieproject. OPdat we de transformatieopgave op een hoger niveau kunnen brengen!Architectur
Meting en interpretatie van de overloopverliezen bij het baggeren van zand met een sleephopperzuiger
No full textTijdens het zuigen van zand met een sleephopperzuiger wordt doorgeladen nadat het overvloeiniveau is bereikt en zal het gezogen debiet via de overvloeikoker overboord verdwijnen. Met dit mengseldebiet zal ook vaste stof overboord verdwijnen. De hoeveelheid vaste stof die overboord verdwijnt wordt het overloopverlies genoemd. De verhouding tussen de hoeveelheid vaste stof die overboord verdwijnt en de ingebrachte hoeveelheid vaste stof wordt het relatief overloopverlies genoemd. De omvang van het overloopverlies is van een groot aantal factoren afhankelijk, zoals bijvoorbeeld grondeigenschappen (korrelverdeling), laadcondities (debiet en concentratie)' methode van inbrengen etc. Er is onderzoek gedaan naar de verschillende invloedsfactoren op het laadproces en er zijn verschillende methoden ontwikkeld om het overloopverlies aan boord te registreren. Deze methoden zijn in de praktijk onder verschillende omstandigheden aan boord van de sleephopperzuiger 'X' beproefd. Uit het onderzoek naar de verschillende invloedsfactoren blijkt dat aan boord regeling van het debiet de beste methode is om het overloopverlies te verminderen. In bepaalde gevallen kan bij verlaging van het debiet zelfs de beladingssnelheid toenemen doordat de stroomsnelheid van het mengsel daalt en de verblijftijd stijgt. Op deze manier kan aan boord met het debiet het beladingsproces beinvloed worden en kan het laadproces geoptimaliseerd worden. Met behulp van een permanente registratie van de overloopverliezen kan beter bepaald worden of het zinvol is om het debiet te verlagen of helemaal te stoppen met laden. Het is afhankelijk van de cyc!ustijd of dit ook economisch zinvol is.Hydraulic EngineeringCivil Engineering and Geoscience
Studying protein unfolding and translocation by the protease FtsH with optical tweezers
No full textThe protease FtsH is a membrane anchored protease that degrades misfolded (membrane) proteins. To study the mechanism behind unfolding and translocation with optical tweezers, the protease had to be purified. However, full-length FtsH has hardly been studied as solubilizing this membrane anchored protease is challenging. Our group (Dr. V. Carvalho and Dr. I. Prabudiansyah) managed to solubilize a thermophilic variant that is found in Aquifex aeolicus. Creating new challenges as it is only active at high temperatures, and optical tweezers usually perform measurements at room temperature. We constructed a new technique to heat the optical tweezers sample to high temperatures (70 ◦C) and developed a new method to locally determine the temperature. With this heating system an attempt was made to study the mechanisms of FtsH, but unfortunately no successful unfolding and degradation patterns were obtained.BN/Marie-Eve Aubin-Tam La
Evaluating urban stormwater drainage using GIS and RS techniques : a case study in Dhaka, Bangladesh
No full textA method is described, integrating Geographical Information System (GIS) functions, remotely sensed images and hydrologic data, to assess the impact of urbanisation on stormwater runoff and drainage. A sample area is selected in the western part of Dhaka City. First, the urbanization trend of Dhaka was assessed, using multitemporal aerial photographs and satellite images. By combining a spaceborne panchromatic image, the digital terrain model (DTM) and reported hydrological data, an assessment was made of the areal extent of the inundations by stormwater runoff within a specific urban drainage area. The DTM was then modified to accommodate expected urbanization trends and conditions. An assessment was then made of the areal spreading and inundation by the floodwaters, illustrating the impacts of future urbanization on urban storm water drainage
Hierarchical Integration of Model Predictive and Fuzzy Logic Control for Combined Coverage and Target-Oriented Search-and-Rescue via Robots with Imperfect Sensors
No full textSearch-and-rescue (SaR) in unknown environments is a crucial task with life-threatening risks. SaR requires precise, optimal, and fast decisions to be made. Robots are promising candidates expected to execute various SaR tasks autonomously. While humans use heuristics to effectively deal with uncertainties of SaR, optimisation of multiple objectives (e.g., the mission time, the area covered, the number of victims detected), in the presence of physical and control constraints, is a mathematical challenge that requires machine computations. Thus including both human-inspired and mathematical capabilities in decision making of SaR robots is highly desired. However, developing control approaches that exhibit both capabilities has been significantly ignored in literature. Moreover, coordinating the decisions of the robots in large-scale SaR missions with affordable computation costs is an open challenge. Finally, in real-life, due to defects (e.g., in the sensors of the robots) or environmental factors (e.g., smoke) data perceived by SaR robots may be prone to uncertainties. We introduce a hierarchical multi-agent control architecture that simultaneously provides the following advantages: exploiting non-homogeneous and imperfect perception capabilities of SaR robots; improving the global performance as it is provided by centralised controllers; computational efficiency and robustness to failure of the central controller as offered by decentralised control methods. The integrated structure of the proposed control framework allows to combine human-inspired and mathematical decision making methods, via respectively fuzzy logic and model predictive control, in a coordinated and computationally efficient way. Our results for various computer-based simulations show that while the area coverage with the proposed control approach is comparable to existing heuristic methods that are particularly developed for coverage-oriented SaR, our approach has a significantly better performance regarding locating the trapped victims. Furthermore, with comparable computation times, the proposed control approach successfully avoids conflicts that may appear in non-cooperative control methods. In summary, the proposed multi-agent control system is capable of combining coverage-oriented and target-oriented SaR in a balanced and coordinated way.</p
Deriving inherent optical properties and associated inversion-uncertainties in the Dutch Lakes
No full textRemote sensing of water quality in inland waters requires reliable retrieval algorithms, accurate atmospheric correction and consistent method for uncertainty estimation. In this paper, the GSM semi-analytical inversion model is modified for inland waters to derive inherent optical properties (IOPs) and their spectral dependencies from air and space borne data. The modified model was validated using two data sets from the Veluwe and the Vecht Dutch lakes. For the Veluwe lakes, the model was able to derive a linear relationship between measured concentrations and estimated IOPs with <i>R</i><sup>2</sup> values above 0.7 for chlorophyll-<i>a</i> (Chl-<i>a</i>) and up to 0.9 for suspended particulate matters (SPM). In the Vecht lakes, the modified model derived accurate values of IOPs. The <i>R</i><sup>2</sup> values were 0.89 for Chl-<i>a</i> and up to 0.95 for SPM. The RMSE values were 0.93 mg m<sup>&minus;3</sup> and 0.56 g m<sup>&minus;3</sup> for Chl-<i>a</i> and SPM respectively. Finally, the IOPs of the Veluwe lakes are derived from multi-spectral, ocean color and hyperspectral airborne data. Inversion-uncertainties of the derived IOPs were also estimated using a standard nonlinear regression technique. The study shows that inversion-uncertainties of remote sensing derived IOPs are proportional to water turbidity
Genetic evidence and host immune response in persons reinfected with SARS-CoV-2, Brazil
No full textWe thank Carmen Beatriz Wagner and Giacoia Gripp for assessments related to the Biosafety Level 3 facility and Marco Alberto Medeiros for assessments related to the sequencing platform. We thank Gonzalo Bello, Dumith Chequer Bou-Habib, Willian Provance, and Fabiano Thompson for insightful discussions. We greatly appreciated the MGI, a partner in the implementation of next-generation sequencing through collaborations with Oswaldo Cruz Foundation, especially for challenging samples of COVID-19.
Author contributions: F.A.B. and P.T.B. conducted clinical surveillance. N.F.R. and F.A.B. enrolled patients in the study. N.F.R., C.Q.S., D.R., I.G.A., V.C.S. performed immunologic assessments. N.F.R., A.P.D.S., M.C.S., F.B.S., M.A.F., J.G., H.J., and H.T. performed sequencing. A.P.D.S., M.C.S., and D.A.T were responsible for bioinformatics. F.A.B., P.T.B., C.M.M., T.M.L.S. handled study coordination. N.F.R., P.T.B., A.MV., and T.M.L.S. prepared and revised the manuscript. All authors revised and approved the manuscript.Mostra que uma primeira exposição à Covid-19 em casos brandos ou assintomáticos pode não produzir resposta imunológica e que a pessoa pode se reinfectar, inclusive, com a mesma variante. A segunda infecção pode provocar sintomas mais fortes do que a primeira. Os dados mostram que para a parcela da população que tem a doença na forma branda (em que não é necessária a hospitalização) isso não significa que fique imune ou que uma reinfecção evolua de forma benigna. O estudo indica ainda que a reinfecção pode ser mais frequente do que se supõe.The dynamics underlying severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) reinfection remain poorly understood. We identified a small cluster of patients in Brazil who experienced 2 episodes of coronavirus disease (COVID-19) in March and late May 2020. In the first episode, patients manifested an enhanced innate response compared with healthy persons, but neutralizing humoral immunity was not fully achieved. The second episode was associated with different SARS-CoV-2 strains, higher viral loads, and clinical symptoms. Our finding that persons with mild COVID-19 may have controlled SARS-CoV-2 replication without developing detectable humoral immunity suggests that reinfection is more frequent than supposed, but this hypothesis is not well documented
The Impact Of Diagnostic Criteria For Neuromyelitis Optica In Patients With Ms: A 10-year Follow-up Of The South Atlantic Project
No full textBackground: It is recognized that there is a particular geographic and ethnic distribution of neuromyelitis optica (NMO) among Caucasian and non-Caucasian populations. Objective: To review the diagnoses of patients whom were enrolled in the South Atlantic Project, a Brazilian multiple sclerosis (MS) survey performed from 1995-1998, and to identify NMO and MS case frequencies. Methods: We reviewed the data from a 10-year follow-up of MS patients. To apply the current diagnostic criteria, the neurologists were asked to collect clinical and laboratory data from the medical records of study patients treated from 1999-2009. Results: The spectrum of inflammatory demyelinating disease in 322 patients (67% white; 33% African-Brazilian) was: 49 (15%) with NMO; 14 (4%) with NMO syndromes; 10 (3%) with acute disseminated encephalomyelitis (ADEM); one isolated tumefactive brain lesion; 249 (77%) with MS (151 with relapsing-remitting MS (RRMS), 70 with secondary progressive MS (SPMS) and 27 with primary progressive MS (PPMS)). Disability was more severe in NMO and PPMS. One-third of the NMO patients had died. Conclusions: The frequency of NMO was 6.8% in São Paulo and 20.5% in Rio de Janeiro, and mainly seen in persons of African descent, which strengthens the hypothesis of there being an ethnic association of this disease. 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