Detached eddy simulation of unsteady turbulent flows in the draft tube of a bulb turbine

Les aspirateurs de turbines hydrauliques jouent un rôle crucial dans l’extraction de l’énergie disponible. Dans ce projet, les écoulements dans l’aspirateur d’une turbine de basse chute ont été simulés à l’aide de différents modèles de turbulence dont le modèle DDES, un hybride LES/RANS, qui permet de résoudre une partie du spectre turbulent. Déterminer des conditions aux limites pour ce modèle à l’entrée de l’aspirateur est un défi. Des profils d’entrée 1D axisymétriques et 2D instationnaires tenant compte des sillages et vortex induits par les aubes de la roue ont notamment été testés. Une fluctuation artificielle a également été imposée, afin d’imiter la turbulence qui existe juste après la roue. Les simulations ont été effectuées pour deux configurations d’aspirateur du projet BulbT. Pour la deuxième, plusieurs comparaisons avec des données expérimentales ont été faites pour deux conditions d’opération, à charge partielle et dans la zone de baisse rapide du rendement après le point de meilleur rendement. Cela a permis d’évaluer l’efficacité et les lacunes de la modélisation turbulente et des conditions limites à travers leurs effets sur les quantités globales et locales. Les résultats ont montrés que les structures tourbillonnaires et sillages sortant de la roue sont adéquatement résolus par les simulations DDES de l’aspirateur, en appliquant les profils instationnaires bidimensionnels et un schéma de faible dissipation pour le terme convectif. En outre, les effets de la turbulence artificielle à l’entrée de l’aspirateur ont été explorés à l’aide de l’estimation de l’intermittence du décollement, de corrélations en deux points, du spectre d’énergie et du concept de structures cohérentes lagrangiennes. Ces analyses ont montré que les détails de la dynamique de l’écoulement et de la séparation sont modifiés, ainsi que les patrons des lignes de transport à divers endroits de l’aspirateur. Cependant, les quantités globales comme le coefficient de récupération de l’aspirateur ne sont pas influencées par ces spécificités locales.

Primary prevention of neural tube defects: data from the portuguese national registry of congenital anomalies (RENAC)

Background: In Portugal folic acid supplementation is recommended to start at least 2-3 months before conception for primary prevention of Neural Tube Defects. The aim of this study was to evaluate, within gestations with at least one congenital anomaly, possible association between maternal socio-demographic factors and the use of folic acid. Methods: Using data from the Portuguese national registry of congenital anomalies, for the 2004-2013 period, the association between folic acid use during pregnancy and maternal characteristics was studied using the chi-square test. Results: Considering all reported cases with congenital anomaly, the use of folic acid before conception was reported by 12.7% (n = 1233) of the women; 47.8% (n = 4623) started supplementation during the 1st trimester, 7% (n = 680) did not take folic acid and 32.5% (3143) of the records had no information on folic acid use. Women with professions that require higher academic differentiation started the use of supplements before pregnancy (p <0.001); women under 19 years old and with Arab ethnicity (p <0.001) did not take folic acid. Mothers with a previous pregnancy reported less use of folic acid (11.5% versus 14.7%) than mothers without a previous pregnancy (p <0.001). Conclusions: The results suggest some degree of association between maternal characteristics and use of folic acid. To increase the consumption of folic acid before pregnancy new measures are need to promote this primary prevention, among couples and health professionals. This study highlights some maternal characteristics and subgroups of mothers for who the measures should be reinforced.

Heat transfer rates for cross flow of water through a tube bank at high Reynolds numbers.

Mode of access: Internet.

Primary fallopian tube carcinoma: review of MR imaging findings

Objectives To review the epidemiological and clinical features of primary fallopian tube carcinoma (PFTC), and to illustrate the spectrum of MRI findings, with pathological confirmation. Methods This article reviews the relevant literature on the epidemiological, clinical, and imaging features of primary fallopian tube carcinoma, with pathological confirmation, using illustrations from the authors’ teaching files. Results Primary fallopian tube carcinoma came under focus over the last few years due to its possible role on the pathogenesis of high-grade serous epithelial ovarian and peritoneal cancers. Typical symptoms, together with the presence of some of the most characteristic MRI signs, such as a Bsausage-shaped^ pelvic mass, hydrosalpinx, and hydrometra, may signal the presence of primary fallopian cancer, and allow the radiologist to report it as a differential diagnosis. Conclusions Primary fallopian tube carcinoma has a constellation of clinical symptoms and magnetic resonance imaging features, which may be diagnostic. Although these findings are not present together in the majority of cases, radiologists who are aware of them may include the diagnosis of primary fallopian tube cancer in their report more frequently and with more confidence. Teaching Points • PFTC may be more frequent than previously thought • PFTC has specific clinical and MRI characteristics • Knowledge of typical PFTC signs enables its inclusion in the differential diagnosis • PFTC is currently staged under the 2013 FIGO system • PFTC is staged collectively with ovarian and peritoneal neoplasms

Aerosol transport in a bifurcating tube at cyclic flow

Branching tube flow is a common feature of many fields of science and technology, and occurs both in animate and inanimate systems [1]. The transport of aerosol particles is of particular importance in industrial flow networks but also for the respiratory tree [2]. In this analysis a 3-D numerical study is performed to investigate transport and deposition of aerosol particles in branching tubes. Bifurcation tubes designed according to Hess-Murray law [3] but with different branching angles are analyzed. This study covers cyclic flow conditions at frequencies of 0.25 Hz, 0.50 Hz and 0.75 Hz, Stokes numbers ranging between 0.03 and 0.25, and Reynolds numbers up to 3000.

Direct determination of Cu, Cd, Ni and Pb in aquatic humic substances by graphite furnace atomic absorption spectrometry

A method has been developed for the direct determination of Cu, Cd, Ni and Pb in aquatic humic substances (AHS) by graphite furnace atomic absorption spectrometry. AHS were isolated from water samples rich in organic matter, collected in the Brazilian Ecological Parks. All analytical curves presented good linear correlation coefficient. The limits of detection and quantification were in the ranges 2.5-16.7 mu g g(-1) and 8.5-50.0 mu g g(-1), respectively. The accuracy was determined using recovery tests, and for all analytes recovery percentages ranged from 93 - 98 %, with a relative standard deviation less than 4 %. The results indicated that the proposed method is a suitable alternative for the direct determination of metals in AHS.

Membrana de alumina anódica: comportamento da microestrutura e estudo das propriedades ópticas após tratamento térmico

Thin commercial aluminum electrolytic and passed through reactions was obtained with anodic alumina membranes nanopores. These materials have applications in areas recognized electronic, biomedical, chemical and biological weapons, especially in obtaining nanostructures using these membranes as a substrate or template for processing nanowires, nanodots and nanofibers for applications noble. Previous studies showed that the membranes that have undergone heat treatment temperature to 1300° C underwent changes in morphology, crystal structure and optical properties. This aim, this thesis, a study of the heat treatment of porous anodic alumina membranes, in order to obtain and to characterize the behavior changes structures during the crystallization process of the membranes, at temperatures ranging between 300 and 1700° C. It was therefore necessary to mount a system formed by a tubular furnace resistive alumina tube and controlled environment, applying flux with special blend of Ag-87% and 13% N2, in which argon had the role of carrying out the oxygen nitrogen system and induce the closing of the pores during the densification of the membrane. The duration of heat treatment ranged from 60 to 15 minutes, at temperatures from 300 to 1700° C respectively. With the heat treatment occurred: a drastic reduction of porosity, grain growth and increased translucency of the membrane. For the characterization of the membranes were analyzed properties: Physical - thermogravimetric, X-ray diffraction, BET surface area; morphological - SEM, EDS through compositional and, optical absorbance, and transmittance in the UV-VIS, and FTIR. The results using the SEM showed that crystallization has occurred, densification and significant changes in membrane structure, as well as obtaining microtube, the BET analysis showed a decrease in specific surface area of the membranes has to 44.381 m2.g-1 to less than 1.8 m2.g-1 and in the analysis of transmittance and absorbance was found a value of 16.5% in the range of 800 nm, characteristic of the near infrared and FTIR have confirmed the molecular groups of the material. Thus, one can say that the membranes were mixed characteristics and properties which qualify for use in gas filtration system, as well as applications in the range of optical wavelength of the infra-red, and as a substrate of nanomaterials. This requires the continuation and deepening of additional study

Development of methods for the determination of cadmium and thallium in oil shale by-products with graphite furnace atomic absorption spectrometry using direct analysis.

2014

Reliability of graphite furnace atomic absorption spectrometry as alternative method for trace analysis of arsenic in natural medicinal products

Purpose: To evaluate the comparative efficiency of graphite furnace atomic absorption spectrometry (GFAAS) and hydride generation atomic absorption spectrometry (HGAAS) for trace analysis of arsenic (As) in natural herbal products (NHPs). Method: Arsenic analysis in natural herbal products and standard reference material was conducted using atomic absorption spectrometry (AAS), namely, hydride generation AAS (HGAAS) and graphite furnace (GFAAS). The samples were digested with HNO3–H2O2 in a ratio of 4:1 using microwaveassisted acid digestion. The methods were validated with the aid of the standard reference material 1515 Apple Leaves (SRM) from NIST Results: Mean recovery of three different samples of NHPs, using HGAAS and GFAAS, ranged from 89.3 - 91.4 %, and 91.7 - 93.0 %, respectively. The difference between the two methods was insignificant. A (P= 0.5), B (P=0.4) and C (P=0.88) Relative standard deviation (RSD) RSD, i.e., precision was 2.5 - 6.5 % and 2.3 - 6.7 % using HGAAS and GFAAS techniques, respectively. Recovery of arsenic in SRM was 98 and 102 % by GFAAS and HGAAS, respectively. Conclusion: GFAAS demonstrates acceptable levels of precision and accuracy. Both techniques possess comparable accuracy and repeatability. Thus, the two methods are recommended as an alternative approach for trace analysis of arsenic in natural herbal products.

Development and validation of a computationally efficient pseudo 3D model for planar SOFC integrated with a heating furnace

Efficient numerical models facilitate the study and design of solid oxide fuel cells (SOFCs), stacks, and systems. Whilst the accuracy and reliability of the computed results are usually sought by researchers, the corresponding modelling complexities could result in practical difficulties regarding the implementation flexibility and computational costs. The main objective of this article is to adapt a simple but viable numerical tool for evaluation of our experimental rig. Accordingly, a model for a multi-layer SOFC surrounded by a constant temperature furnace is presented, trained and validated against experimental data. The model consists of a four-layer structure including stand, two interconnects, and PEN (Positive electrode-Electrolyte-Negative electrode); each being approximated by a lumped parameter model. The heating process through the surrounding chamber is also considered. We used a set of V-I characteristics data for parameter adjustment followed by model verification against two independent sets of data. The model results show a good agreement with practical data, offering a significant improvement compared to reduced models in which the impact of external heat loss is neglected. Furthermore, thermal analysis for adiabatic and non-adiabatic process is carried out to capture the thermal behaviour of a single cell followed by a polarisation loss assessment. Finally, model-based design of experiment is demonstrated for a case study.

Finite element modeling of tube deformation during cold pilgering

A three-dimensional finite element model of cold pilgering of stainless steel tubes is developed in this paper. The objective is to use the model to increase the understanding of forces and deformations in the process. The focus is on the influence of vertical displacements of the roll stand and axial displacements of the mandrel and tube. Therefore, the rigid tools and the tube are supported with elastic springs. Additionally, the influences of friction coefficients in the tube/mandrel and tube/roll interfaces are examined. A sensitivity study is performed to investigate the influences of these parameters on the strain path and the roll separation force. The results show the importance of accounting for the displacements of the tube and rigid tools on the roll separation force and the accumulative plastic strain.

Lawful withdrawal: The video

When should a person who has a heart attack not be resuscitated? When should a patient no longer be kept alive on a ventilator, or be provided with food and water by a tube? When should a person not be given a blood transfusion they need to stay alive? The answers to these questions depend on a number of factors including the mental or physical condition of the patient and any wishes they have expressed prior to losing the ability to make this decision, as well as the requirements of good medical practice. This video is a record of a public lecture held on 7 July 2004 by the Faculty of Law at the Queensland University of Technology, in association with the Faculty of Health, the Centre for Palliative Care Research and Education, and Palliative Care Queensland.

Cyclic strain disrupts endothelial network formation on Matrigel

Most forms of tissue healing depend critically on revascularisation. In soft tissues and in vitro, mechanical stimuli have been shown to promote vessel-forming activity. However, in bone defects, increased interfragmentary motion impairs vascular regeneration. Because these effects seem contradictory, we aimed to determine whether a range of mechanical stimuli exists in which angiogenesis is favoured. A series of cyclic strain magnitudes were applied to a Matrigel-based “tube formation” assay and the total lengths of networks formed by human microvascular endothelial cells measured at 24 h. Network lengths were reduced at all strain levels, compared to unstretched controls. However, the levels of pro-angiogenic matrix metalloproteases-2 and -9 in the corresponding conditioned media were unchanged by strain, and vascular endothelial growth factor was uniformly elevated in stretched conditions. By repeating the assay with the addition of conditioned media from mesenchymal stem cells cultivated in similar conditions, paracrine stimuli were shown to increase network lengths, but not to alter the negative effect of cyclic stretching. Together, these results demonstrate that directly applied periodic strains can inhibit endothelial organisation in vitro, and suggest that this may be due to physical disruption rather than biochemical modulation. Most importantly, the results indicate that the straining of endothelial cells and their assembly into vascular-like structures must be studied simultaneously to adequately characterise the mechanical influence on vessel formation.