Modelling the settling of suspended sediments for concentrations close to the gelling concentration

This paper deals with the sedimentation of highly concentrated sediment suspensions (cohesive as well as non-cohesive) and the beginning of the consolidation of cohesive sediments. Based on a comparison of existing empirical formulas and experimental data, the particle Reynolds number was shown to be of importance for the behaviour of particularly non-cohesive sediments. In addition it plays a role in determining whether one or two interfaces develop during the sedimentation phase. In the case of cohesive sediments, the estimation of the gelling concentration, although difficult, seems to be fundamental. Some suggestions on the estimation of the permeability coefficient and total settling function are then given in order to improve the modelling of the sedimentation and consolidation behaviour for concentrations close to the gelling concentration

Retours d'expérience d'Asie et Europe pour le développement de systèmes de transparence pour le transport solide dans des projets de barrage hydro-électrique

HydroAsia, Vietiane, LAO, 01-/03/2016 - 03/03/2016International audienceSediment trapping in reservoirs is a serious concern for dam operators as it usually induces a series of adverse impacts upstream, within and downstream impoundments. Many strategies can be applied in order to avoid sediment continuity disruption. Such challenge is all the more important in mountainous and tropical basins that sediment-laden flows are particularly intense there. Among possible strategies, drawdown routing aims at minimizing sediment deposition while drawdown flushing is favored to recover storage volume. However, those options require designing suitable gate arrangement and operation rules, so as to achieve in particular following objectives: (1) recover natural-like flow conditions in the reservoir as soon as high flows and flood events are experienced in the basin, (2) allow a wide range of sediments extending from silt to gravel to pass as much as possible through the dam and (3) regulate if necessary solid fluxes released from the reservoir according to eco-friendly flushing principles. Through several examples taken in Japan and France on the Mimikawa and Rhône River basins respectively, the purpose of this communication is to present a series of case studies for which such successful strategies have been applied either from the very beginning of the design stage of the project or after several years of operation in the frame of retrofitting operations. Experience shows that many factors have to be taken into account to design appropriate operation rules and optimize the vertical distribution of hydraulic facilities contributing to pass sediment-laden flows. Those are in particular the catchment size, the stream slope, the hydrological and sediment regimes of the river, the possible existence of upstream reservoirs, the relative importance of each sediment transportation process at reservoir inlet, the different issues at stake along the stream, the range of target-particles to be passed through the dam as well as the dam height. Concerning that latter criterion in particular, suggestions resulting from proved feedbacks are proposed so as to specify, according to the dam height, the possible needs for including bottom outlets, low level outlets and/or surface spillways

Deep Learning Causal Attributions of Breast Cancer

In this paper, a deep learning-based approach is applied to high dimensional, high-volume, and high-sparsity medical data to identify critical casual attributions that might affect the survival of a breast cancer patient. The Surveillance Epidemiology and End Results (SEER) breast cancer data is explored in this study. The SEER data set contains accumulated patient-level and treatment-level information, such as cancer site, cancer stage, treatment received, and cause of death. Restricted Boltzmann machines (RBMs) are proposed for dimensionality reduction in the analysis. RBM is a popular paradigm of deep learning networks and can be used to extract features from a given data set and transform data in a non-linear manner into a lower dimensional space for further modelling. In this study, a group of RBMs has been trained to sequentially transform the original data into a very low dimensional space, and then the k-means clustering is conducted in this space. Furthermore, the results obtained about the cluster membership of the data samples are mapped back to the original sample space for interpretation and insight creation. The analysis has demonstrated that essential features relating to breast cancer survival can be effectively extracted and brought forward into a much lower dimensional space formed by RBMs

On the estimation of the bed-material transport and budget along a river segment: application to the Middle Loire River, France

Sediment load and budgets are a fundamental component of the process-based hydromorphological framework developed by the REFORM project, and are needed to accurately assess the current condition of a river, its sensitivity to change, and its likely future evolutionary trajectory. This paper presents an evaluation of three different methods for estimating both bedload sediment transport and bed-material budget within river channels, using the Middle Loire River as a case study. The first method is based on the stream power concept and does not need any hydraulic calculations. It yields estimates of the sediment transport in the same order of magnitude as measurements but poor results for the bed-material budget in terms of magnitude and tendency. For the second method, hydraulic parameters are computed using the Manning–Strickler equation (or a 1D hydraulic model for steady flow). It provides useful indicators for understanding river dynamics but does not yield significant improvements compared to the first method. The third method uses 1D numerical software for water flow and river bed evolution. It yields the most accurate results for both sediment transport and bed evolution but requires more data and overall more work to construct the model. Guidance is provided on the amount of data required, the competence needed to build the models, and the predictive capability of each of the methods

Validation of gyrokinetic modelling of light impurity transport including rotation in ASDEX Upgrade

Upgraded spectroscopic hardware and an improved impurity concentration calculation allow accurate determination of boron density in the ASDEX Upgrade tokamak. A database of boron measurements is compared to quasilinear and nonlinear gyrokinetic simulations including Coriolis and centrifugal rotational effects over a range of H-mode plasma regimes. The peaking of the measured boron profiles shows a strong anti-correlation with the plasma rotation gradient, via a relationship explained and reproduced by the theory. It is demonstrated that the rotodiffusive impurity flux driven by the rotation gradient is required for the modelling to reproduce the hollow boron profiles at higher rotation gradients. The nonlinear simulations validate the quasilinear approach, and, with the addition of perpendicular flow shear, demonstrate that each symmetry breaking mechanism that causes momentum transport also couples to rotodiffusion. At lower rotation gradients, the parallel compressive convection is required to match the most peaked boron profiles. The sensitivities of both datasets to possible errors is investigated, and quantitative agreement is found within the estimated uncertainties. The approach used can be considered a template for mitigating uncertainty in quantitative comparisons between simulation and experiment.Comment: 19 pages, 11 figures, accepted in Nuclear Fusio

Indirect measurement of poloidal rotation using inboard–outboard asymmetry of toroidal rotation and comparison with neoclassical predictions

An alternative experimental spectroscopic measurement of poloidal plasma rotation in toroidally confined plasmas is proven effective in the TCV tokamak. Charge exchange recombination measurements of the toroidal rotation profile over the full mid-plane plasma diameter are used to infer the complete bi-dimensional flow structure of the intrinsic C6+ impurity, which includes its poloidal component. For divergence free flows, the difference between the toroidal rotation frequency ft = ut/R at the inboard and outboard locations on the same flux surface is proportional to the poloidal rotation. This indirect measurement provides increased accuracy as the measured quantity ft,in − ft,out ≈ 4qup/Raxis (q is the local safety factor) is larger than the intrinsic uncertainties of a direct spectroscopic measurement of poloidal velocity. The method is applied in a variety of TCV ohmic and electron cyclotron heated L-mode plasmas in the banana-plateau collisionality regime (0.2 < ν∗ii < 2.4). In the radial range of normalized poloidal flux ρψ < 0.8, an impurity poloidal velocity of up = 0.5–2.5 kms−1 is observed, always in the electron diamagnetic drift direction. The measurements are compared with neoclassical calculations and they agree in magnitude and sign to within <1 kms−1

A multi-scale hierarchical framework for developing understanding of river behaviour to support river management

The work leading to this paper was funded through the European Union’s FP7 programme under Grant Agreement No. 282656 (REFORM). The framework methodology was developed within the context of Deliverable D2.1 of the REFORM programme, and all partners who contributed to the development of the four parts of this deliverable are included in the author list of this paper. More details on the REFORM framework can be obtained from part 1 of Deliverable D2.1 (Gurnell et al. 2014), which is downloadable from http://​www.​reformrivers.​eu/​results/​deliverables