143 research outputs found
Spatial and time evolution of non linear waves in falling liquid films by the harmonic expansion method with predictor-corrector integration
Falling film flows in vertical or inclined planes, and pipes,
are present in the energy and chemical industry (Chemical
reactors, evaporators, condensers…). The occurrence of waves
in these falling films is of relevance because it enhances the
heat and mass transfer in comparison with a flat film.
Perturbation theory can be applied to the Navier-Stokes
(NS) equations expressing the velocity and the pressure in
terms of an order formal parameter representing the smallness
of the stream wise spatial derivative. Normally good results are
obtained for this kind of problems solving the first order NS
equations.
In the present work we use the integral approach method
and we expand the velocity profile of the falling liquid in a
complete orthogonal set of harmonic functions satisfying the
boundary conditions of the NS problem in first order
approximation of the formal expansion. The present model does
not assume self-similar profile of the velocity and its
convergence to the solution is good with few harmonics.
The problem is discretized by means of a uniform grid.
Then the partial differential equations are integrated over the
length of an arbitrary node. Proceeding in this way we have
obtained a set of coupled ordinary differential equation system
(ODES) for the harmonics of the flow rate and the film
thickness at each grid node The resulting coupled ODES is
integrated by a semi-implicit predictor-corrector method of the
Adams-Moulton type that converges, with one iteration, at each
time step.
The method predicts well the experimental data on the
evolution of the waves with time, the height of the waves, the
wave separation, and the wave profiles for different
experimental conditions. Providing a physical understanding of
the non-linear wave phenomena produced in falling films.Papers presented to the 12th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Costa de Sol, Spain on 11-13 July 2016
Non iterative model for steam condensation in presence of non-condensable gases inside passive containment cooling vertical tubes
Paper presented at the 5th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, South Africa, 1-4 July, 2007.The modelling of condensation in presence of non-condensable gases is of relevance for the design of passive containment cooling condenser of the third generation of Passive Nuclear Power Plants. Fast and accurate methods of predictions for condensation in presence of non-condensable gases are necessary in order to be implemented in the thermal-hydraulic codes without slowing down the computational speed of these codes. In this paper we present a mechanistic model for condensation in presence of non-condensable gases inside vertical tubes. In this model we take into account the influence of the non-condensable gases over the liquid side heat transfer without any iteration to calculate the liquid-steam interfacial temperature. The trick is to perform a set of Taylor expansions for the main physical magnitudes as viscosity, steam mass fraction and so on. We also consider the interfacial shear stress exerted by the steam-non-condensable mixture flow over the condensate layer thickness. The calculation of the condensate layer thickness can be performed with the help of the mass, energy and momentum conservation equations and can be achieved without any iteration following the method of Munoz-Cobo et al [1,2]. The new proposed mechanistic model solves explicitly the real interfacial temperature by means of a cubic or a quartic equation depending on the degree of approximation that has been chosen. Moreover, as the main non-condensable effects can be accounted for in the heat and mass transfer processes, the new model will be more realistic. The model has been validated with the Vierow experimental data, obtaining a total average relative error, for the fourth order equation method model, of 21% with 268 experimental points at different conditionscs201
Production Trends, Collaboration, and Main Topics of the Integrative and Complementary Oncology Research Area: A Bibliometric Analysis
Background: The prevalence of cancer has increased over time worldwide. Nevertheless, the number of deaths has been
reduced during the past 2 decades. Thus, one-third of the cancer patients are users of complementary and alternative
therapies, looking for other types of interventions. The main aim of the present study is to understand the current status of
the research in integrative and complementary oncology. Three different aspects were analyzed: production trends, country
collaboration, and leading research topics. Methods: The dataset was obtained from the documents indexed under the
Integrative and Complementary Medicine category of the Web of Science database from 1976 to 2017. VOSviewer and
SciMAT software were employed to perform the bibliometric analysis. Results: The Journal of Ethnopharmacology, China
Medical University and the People’s Republic of China are the leading producers in the field. Regarding the collaboration,
the United States and China present a close connection. The scientific community is focused on the following topics:
apoptosis, breast cancer, oxidative stress, chemotherapy, and nuclear factor-Kappa-B (NF-Kappa-B). Conclusions: The
present article shows potentially important information that allows understanding of the past, present, and future of
research in integrative and complementary oncology. It is a useful evidence-based framework on which to base future
research actions and academic directions
Comparative Evaluation of Three Automated Systems for DNA Extraction in Conjunction with Three Commercially Available Real-Time PCR Assays for Quantitation of Plasma Cytomegalovirus DNAemia in Allogeneic Stem Cell Transplant Recipientsâ–ż
Limited data are available on the performance of different automated extraction platforms and commercially available quantitative real-time PCR (QRT-PCR) methods for the quantitation of cytomegalovirus (CMV) DNA in plasma. We compared the performance characteristics of the Abbott mSample preparation system DNA kit on the m24 SP instrument (Abbott), the High Pure viral nucleic acid kit on the COBAS AmpliPrep system (Roche), and the EZ1 Virus 2.0 kit on the BioRobot EZ1 extraction platform (Qiagen) coupled with the Abbott CMV PCR kit, the LightCycler CMV Quant kit (Roche), and the Q-CMV complete kit (Nanogen), for both plasma specimens from allogeneic stem cell transplant (Allo-SCT) recipients (n = 42) and the OptiQuant CMV DNA panel (AcroMetrix). The EZ1 system displayed the highest extraction efficiency over a wide range of CMV plasma DNA loads, followed by the m24 and the AmpliPrep methods. The Nanogen PCR assay yielded higher mean CMV plasma DNA values than the Abbott and the Roche PCR assays, regardless of the platform used for DNA extraction. Overall, the effects of the extraction method and the QRT-PCR used on CMV plasma DNA load measurements were less pronounced for specimens with high CMV DNA content (>10,000 copies/ml). The performance characteristics of the extraction methods and QRT-PCR assays evaluated herein for clinical samples were extensible at cell-based standards from AcroMetrix. In conclusion, different automated systems are not equally efficient for CMV DNA extraction from plasma specimens, and the plasma CMV DNA loads measured by commercially available QRT-PCRs can differ significantly. The above findings should be taken into consideration for the establishment of cutoff values for the initiation or cessation of preemptive antiviral therapies and for the interpretation of data from clinical studies in the Allo-SCT setting
Allelic Variation of MYB10 Is the Major Force Controlling Natural Variation in Skin and Flesh Color in Strawberry (Fragaria spp.) Fruit
Independent mutations in the transcription factor MYB10 cause most of the anthocyanin variation observed in diploid woodland strawberry (Fragaria vesca) and octoploid cultivated strawberry (Fragaria x ananassa). The fruits of diploid and octoploid strawberry (Fragaria spp) show substantial natural variation in color due to distinct anthocyanin accumulation and distribution patterns. Anthocyanin biosynthesis is controlled by a clade of R2R3 MYB transcription factors, among which MYB10 is the main activator in strawberry fruit. Here, we show that mutations in MYB10 cause most of the variation in anthocyanin accumulation and distribution observed in diploid woodland strawberry (F. vesca) and octoploid cultivated strawberry (F. xananassa). Using a mapping-by-sequencing approach, we identified a gypsy-transposon in MYB10 that truncates the protein and knocks out anthocyanin biosynthesis in a white-fruited F. vesca ecotype. Two additional loss-of-function mutations in MYB10 were identified among geographically diverse white-fruited F. vesca ecotypes. Genetic and transcriptomic analyses of octoploid Fragaria spp revealed that FaMYB10-2, one of three MYB10 homoeologs identified, regulates anthocyanin biosynthesis in developing fruit. Furthermore, independent mutations in MYB10-2 are the underlying cause of natural variation in fruit skin and flesh color in octoploid strawberry. We identified a CACTA-like transposon (FaEnSpm-2) insertion in the MYB10-2 promoter of red-fleshed accessions that was associated with enhanced expression. Our findings suggest that cis-regulatory elements in FaEnSpm-2 are responsible for enhanced MYB10-2 expression and anthocyanin biosynthesis in strawberry fruit flesh.Peer reviewe
El arabe marroqui
DT / CINDOC - Centro de Informaciòn y Documentaciòn CientìficaSIGLEESSpai
Measuring the online attention of the Rehabilitation Web of Science category: an Altmetrics-based analysis
Social media has changed the way of the scientific output dissemination. Although currently the impact on social media is not considered as a substitute of the traditional metrics, they start to be considered as complementary. These new measures, that quantify the social impact, are known as Altmetrics. In that way, the Rehabilitation research field is composed of different professional areas that have a high impact on the general population well-being. For this reason, it could be interesting to measure the impact on social media and relate it to the scientific impact. Therefore, in the present work, two different analyses were performed based on the papers published in the Rehabilitation Web of Science category in the period 2013-2017: i) a descriptive analysis of the documents, in order to discover the overall impact, the Top 20 journals, and Top 10 papers by mentions and citations; and ii) a statistical analysis based on correlation, to discover the relationships between the different variables. Among our findings, Twitter is the social media in which the production attracts higher social attention. Nevertheless, not all types of documents and journals obtain the same social and scientific recognition
Influence of the spacer location and the direct heating in the single and two phase region on the development of in-phase instabilities of boiling water reactors
The dynamic of boiling flows can be considered as a
complex problem where generally more than one instability
mechanism is present. This problem of two-phase flow
instabilities is found in a big variety of energy and chemical
engineering systems such as the channels of Boiling Water
Reactors (BWR), conventional steam boilers, and phase change
heat exchangers used in the chemical industry. Among the
different instability types, one of the most important for the
nuclear engineering field is the in-phase instability that appears
in boiling water reactors (BWR). In this instability type a
synchronized oscillation of the power and the thermal-hydraulic
variables is produced in all the channels of the reactor. This
paper study the influence of the spacer location and the direct
heating i.e. the heating of the boiling channels by neutron and
gamma rays on the in-phase instabilities BWRs.Papers presented to the 12th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Costa de Sol, Spain on 11-13 July 2016
Comparison of polynomial chaos expansion methods for uncertainty quantification in computational fluid dynamics simulations
Computational Fluid Dynamics (CFD) computer codes have
proven to be a powerful tool in the analysis of all kinds of fluid
systems. However, there is still a lack of practical methods for
determining the uncertainty of their results, as most current techniques
require performing too many simulations to be affordable
in industrial-scale situations. One of the most promising methods
for uncertainty quantification in computational fluid dynamics
is Polynomial Chaos Expansion, a name that includes a variety
of techniques, all based on the same mathematical background:
projecting the system’s response into a basis of orthogonal polynomials.
This paper discusses the main advantages and drawbacks
of three of these techniques, namely random sampling,
Gaussian quadrature and linear regression, in terms of reliability,
ease of use and computational costs. All three techniques were
applied to simulations of the turbulent mixing of two streams of
water inside a Y-shaped channel, and the results compared with
experimental data. Results show that, in this test case, quadrature
method provides more reliable results than the other two
techniques, with a lower computational cost. Due to its robustness
and low number of simulations required, Polynomial Chaos
Expansion via quadrature methods might be suitable for most industrial
CFD simulations.Papers presented to the 12th International Conference on Heat Transfer, Fluid Mechanics and Thermodynamics, Costa de Sol, Spain on 11-13 July 2016
- …