The numerical modelling of 2D shallow flows in complex geometries involving transient flow and movable boundaries has been a challenge for researchers in recent years. There is a wide range of ...physical situations of environmental interest, such as flow in open channels and rivers, tsunami and flood modelling, that can be mathematically represented by first-order non-linear systems of partial differential equations, whose derivation involves an assumption of the shallow water type. Shallow water models may include more sophisticated terms when applied to cases of not pure water floods, such as mud/debris floods, produced by landslides. Mud/debris floods are unsteady flow phenomena in which the flow changes rapidly, and the properties of the moving fluid mixture include stop and go mechanisms. The present work reports on a numerical model able to solve the 2D shallow water equations even including bed load transport over erodible bed in realistic situations involving transient flow and movable flow boundaries. The novelty is that it offers accurate and stable results in realistic problems since an appropriate discretization of the governing equations is performed. Furthermore, the present work is focused on the importance of the computational cost. Usually, the main drawback is the high computational effort required for obtaining accurate numerical solutions due to the high number of cells involved in realistic cases. However, the proposed model is able to reduce computer times by orders of magnitude making 2D applications competitive and practical for operational flood prediction. Moreover our results show that high performance code development can take advantage of general purpose and inexpensive Graphical Processing Units, allowing to run almost 100 times faster than old generation codes in some cases.
Oocyte maturation is a long process during which oocytes acquire their intrinsic ability to support the subsequent stages of development in a stepwise manner, ultimately reaching activation of the ...embryonic genome. This process involves complex and distinct, although linked, events of nuclear and cytoplasmic maturation. Nuclear maturation mainly involves chromosomal segregation, whereas cytoplasmic maturation involves organelle reorganization and storage of mRNAs, proteins and transcription factors that act in the overall maturation process, fertilization and early embryogenesis. Thus, for didactic purposes, we subdivided cytoplasmic maturation into: (1) organelle redistribution, (2) cytoskeleton dynamics, and (3) molecular maturation. Ultrastructural analysis has shown that mitochondria, ribosomes, endoplasmic reticulum, cortical granules and the Golgi complex assume different positions during the transition from the germinal vesicle stage to metaphase II. The cytoskeletal microfilaments and microtubules present in the cytoplasm promote these movements and act on chromosome segregation. Molecular maturation consists of transcription, storage and processing of maternal mRNA, which is stored in a stable, inactive form until translational recruitment. Polyadenylation is the main mechanism that initiates protein translation and consists of the addition of adenosine residues to the 3′ terminal portion of mRNA. Cell cycle regulators, proteins, cytoplasmic maturation markers and components of the enzymatic antioxidant system are mainly transcribed during this stage. Thus, the objective of this review is to focus on the cytoplasmic maturation process by analyzing the modifications in this compartment during the acquisition of meiotic competence for development.
An equilibrium needs to be established by the cellular and acellular components of the ovarian follicle if developmental competence is to be acquired by the oocyte. Both cumulus cells (CCs) and ...follicular fluid (FF) are critical determinants for oocyte quality. Understanding how CCs and FF influence oocyte quality in the presence of deleterious systemic or pelvic conditions may impact clinical decisions in the course of managing infertility. Given that the functional integrities of FF and CCs are susceptible to concurrent pathological conditions, it is important to understand how pathophysiological factors influence natural fertility and the outcomes of pregnancy arising from the use of assisted reproduction technologies (ARTs). Accordingly, this review discusses the roles of CCs and FF in ensuring oocyte competence and present new insights on pathological conditions that may interfere with oocyte quality by altering the intrafollicular environment.
•POD-based ROMs are constructed to approximate the solution of transport equations.•A novel coordinate transformation strategy allows to extrapolate solutions in time.•The model is validated using ...advection-dominated problems.•The model is extended to 2D using Radon transform.
The use of reduced-order models (ROMs) for the numerical approximation of the solution of partial differential equations is a topic of current interest, being motivated by the high computational efficiency of ROMs when compared to full-order models (FOMs). To construct a ROM to approximate the solution of transport equations, the use of the proper orthogonal decomposition (POD) method is a common choice. POD-based ROMs rely on the snapshot method, which consists in the off-line computation of a set of values corresponding to the solution up to the training time by means of the FOM. Then, the ROM is constructed and solved, up to the training time. When considering parabolic equations, the method is able to compute the solution beyond the training time. However, when considering hyperbolic problems, POD-based ROMs fail when computing the solution beyond the training time, this being one of the strongest limitations of POD-based ROMs. In this work, a strategy in the framework of POD-based ROMs to predict solutions in time is introduced. This method, called CT-ROM, is based on a coordinate transformation and allows to compute the solution of advection-dominated problems beyond the training time. The performance of this strategy is assessed using a variety of test cases, showing promising results in all of them. The extension of the CT-ROM to higher spatial dimensions by means of the Radon transform is also presented. The results obtained are encouraging and motivate the application of this idea to more complex problems.
•A sophisticated fully 2D model accelerated with GPU is presented.•Details of the numerical scheme and the acceleration technique are given.•The necessity of these numerical fixes in real cases is ...demosntrated.•The model is applied to a large stretch of the Ebro River.•The results are compared with field measurements.
The challenge of finding a compromise between computational time and level of accuracy and robustness has traditionally expanded the use simplified models rather than full two-dimensional (2D) models for flood simulation. This work presents a GPU accelerated 2D shallow water model for the simulation of flood events in real time. In particular, an explicit first-order finite volume scheme is detailed to control the numerical instabilities that are likely to appear when used in complex topography. The model is first validated with the benchmark test case of the Toce River (Italy) and numerical fixes are demonstrated to be necessary. The model is next applied to reproduce real events in a reach of the Ebro River (Spain) in order to compare simulation results with field data. The second case deals with a large domain (744 km2) and long flood duration (up to 20 days) allowing an analysis of the performance and speed-up achieved by different GPU devices. The high values of fit between observed and simulated results as well as the computational times achieved are encouraging to propose the use of the model as forecasting system.
The electronic nose is a non-invasive technology suitable for the analysis of edible oils. One of the practical applications in the olive oil industry is the classification of virgin oils based on ...their sensory characteristics. Notwithstanding that this technology, at this stage, cannot realistically replace the currently used methods, it is fruitful for a preliminary analysis of the oil quality. This work makes use of this technology to develop a methodology for the detection of the threshold by which an extra-virgin olive oil (EVOO) drops into the virgin olive oil (VOO) category. With this aim, two features were studied: the level of fruitiness level and the type of defect. The results showed a greater influence of the level of fruitiness than the type of defect in the determination of the detection threshold. Furthermore, three of the sensors (S2, S7 and S9) of the commercial e-nose PEN3 were identified as the most discriminating in the classification between EVOO and VOO oils.
The three-dimensional organization of biomolecules important for the functioning of all living systems can be determined by cryo-electron tomography imaging under native biological contexts. ...Cryo-electron tomography is continually expanding and evolving, and the development of new methods that use the latest technology for sample thinning is enabling the visualization of ever larger and more complex biological systems, allowing imaging across scales. Quantitative cryo-electron tomography possesses the capability of visualizing the impact of molecular and environmental perturbations in subcellular structure and function to understand fundamental biological processes. This review provides an overview of current hardware and software developments that allow quantitative cryo-electron tomography studies and their limitations and how overcoming them may allow us to unleash the full power of cryo-electron tomography.
In this work approximate augmented Riemann solvers are formulated providing appropriate numerical schemes for mathematical models of granular flow on irregular steep slopes. Fluxes and source terms ...are discretized to ensure steady state configurations including correct modeling of start/stop flow conditions, both in a global and a local system of coordinates. The weak solutions presented involve the effect of bed slope in pressure distribution and frictional effects by means of the adequate gravity acceleration components. The numerical solvers proposed are first tested against 1D cases with exact solution and then their results are compared with experimental data in order to check the suitability of the mathematical models described in this work. Comparisons between results provided when using global and local system of coordinates are presented. The obtained results point out that both the global and the local system of coordinates can be used to predict faithfully the overall behavior of the phenomena considered in this work.
AbstractA study of the efficiency of a zero-inertia model (ZI) for two-dimensional (2D) overland flow simulation is presented in this work. An upwind numerical scheme is used for the spatial ...discretization in the frame of finite-volume methods and an implicit formulation is chosen to avoid numerical instability. The scheme is applied in both structured and unstructured meshes, focusing in the latter ones due to their good adaptability. The ZI equation has a nonlinear character; hence, a linearization is required in the implicit procedure. This is carried out by means of Picard iterations method as a previous step to the system matrix resolution, characteristic of implicit techniques. The BiConjugate Gradient Stabilized (BiCGStab) method combined with sparse storage strategies is selected for the system resolution. A dual-threshold incomplete lower upper factorization (ILUT) is chosen as matrix preconditioner. Computational efficiency of the implicit temporal discretization for ZI model is explored under both steady and unsteady flow conditions by comparing the CPU times against the explicit version of the same model.
In this work, an implicit method for solving 2D hyperbolic systems of equations is presented, focusing on the application to the 2D shallow water equations. It is based on the first order Roe’s ...scheme, in the framework of finite volume methods. A conservative linearization is done for the flux terms, leading to a non-structured matrix for unstructured meshes thus requiring iterative methods for solving the system. The validation is done by comparing numerical and exact solutions in both unsteady and steady cases. In order to test the applicability of the implicit scheme to real world situations, a laboratory scale tsunami simulation is carried out and compared to the experimental data. The implicit schemes have the advantage of the unconditional stability, but a quality loss in the transient solution can appear for high CFL numbers. The properties of the scheme are well suited for the simulation of unsteady shallow water flows over irregular topography using all kind of meshes.
•We use a 2D implicit surface flow model based on shallow water equations.•A robust wet/dry treatment is implemented.•The scheme is validated by means of exact solutions and experimental data.•CFL numbers up to 300 are reached.•The efficiency of the implicit scheme is explored.
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