A novel grid generation method based on multi-resolution data fusion for 2D shallow water models

This paper discusses the ability of the two-dimensional (2D) shallow water equations to model meandering flows in shallow rectangular reservoirs. Four meandering flows of various shallowness were modeled using an academic flow model that includes a depth-averaged k-ϵ model accounting for the horizontal and vertical turbulent length-scales. Different roughness heights were considered for modeling the bottom friction. A proper orthogonal decomposition (POD) was applied to the simulation results to extract the behavior of the main structures responsible for the meandering flow. The same POD analysis was also performed for the reference experimental flow fields, obtained by large-scale particle image velocimetry. The first two POD modes obtained from the numerical simulations assuming a smooth bottom are in good agreement with the experimental modes in terms of energy, as well as temporal and spatial variations, whatever the shallowness. In contrast, the remaining simulated modes are not well rendered. The effect of an increased roughness height in the simulations is finally discussed. It leads to an improved reproduction of the first two modes and of the following modes, except when significant viscous effects govern in the flow.

Modular Multilevel Converter (MMC) is a mainstream technology in the field of flexible DC transmission engineering. The establishment of electromagnetic transient simulation model of MMC is the basis for theoretical research and engineering application. The Thévenin’s equivalent-based electromagnetic transient model of MMC has high simulation accuracy and less simulation time, which is widely used in the simulation system of MMC with high level number. However, the model is difficult to simulate the internal electromagnetic transient process of the submodule, such as the inability to effectively measure the current stress of the IGBT and the continuity diode when testing and analyzing the equivalent experimental stress, as well as the inability to simulate and analyze the internal faults of the submodule. In order to solve this problem, this paper proposes a highly accurate and efficient electromagnetic transient simulation model of MMC converter based on PSCAD/EMTDC. Specifically, the internal sub-modules of the MMC model are divided into two categories: special sub-modules and general sub-modules. For the special sub-modules, the detailed models are established respectively; for the general sub-modules, the Thévenin’s equivalent model is established. The model has high simulation speed and accuracy, while the interface is generalized and preserves the station-level and valve-level control strategies. The simulation is carried out by PSCAD/ EMTDC, and the experimental results verify the correctness and effectiveness of the proposed modeling method.

Analysis of two sources of variability of basin outflow hydrographs computed with the 2D shallow water model Iber: Digital Terrain Model and unstructured mesh size

This paper present a novel logic-timing simulator that includes the degradation delay model (DDM) called HALOTIS. DDM obtains high accuracy in glitches treatment and it has been included in HALOTIS simulation engine. Also, it is possible to estimate switching activity using it, and the results show a high accuracy in simulations when these are compared to HSPICE.

A depth-averaged two-dimensional (2D) numerical model for unsteady flow and nonuniform sediment transport in open channels is established using the finite volume method on a nonstaggered, curvilinear grid. The 2D shallow water equations are solved by the SIMPLE(C) algorithms with the Rhie and Chow’s momentum interpolation technique. The proposed sediment transport model adopts a nonequilibrium approach for nonuniform total-load sediment transport. The bed load and suspended load are calculated separately or jointly according to sediment transport mode. The sediment transport capacity is determined by four formulas which are capable of accounting for the hiding and exposure effects among different size classes. An empirical formula is proposed to consider the effects of the gravity on the sediment transport capacity and the bed-load movement direction in channels with steep slopes. Flow and sediment transport are simulated in a decoupled manner, but the sediment module adopts a coupling procedure for the computations of sediment transport, bed change, and bed material sorting. The model has been tested against several experimental and field cases, showing good agreement between the simulated results and measured data.

Trauma is a global burden. Emergency medical services (EMS) provide care for individuals who have serious injuries or suffered a major trauma. This paper provides a comprehensive overview of telemedicine applications in prehospital trauma care. We conducted a systematic review according to PRISMA guidelines. We identified articles by electronic database search (PubMed, EMBASE, the Cochrane Library, CINAHL, SpringerLink, LIVIVO, DARE, IEEE Xplore, Google Scholar and ScienceDirect) using keywords related to prehospital settings, ambulance, telemedicine and trauma. Search terms and inclusion criteria were specified a priori by the PICOS template and revised throughout a configurative approach iteratively, to outline the complexity and variety of different telemedical concepts. A final sample of 15 records was systematically selected. Most interventions were piloted and/or evaluated in Germany for trauma victims in prehospital settings. Six studies were simulated scenarios. Telemedical assistance (TMA) via real-time telemetry systems (RTS), enabling video and audio conferencing between EMS by tele-emergency physicians (TEP) were associated with a higher treatment quality and a shorter time-to-treatment in invasive procedures. By initiating in-hospital preparations based on telemedical prehospital notification (TPN), loss of information during the clinical handover was reduced and in-hospital protocols were activated with high accuracy. Remotely guided ultrasound (Tele-Ultrasound) by TEP showed an overall high diagnostic accuracy in simulations. Technical solutions were reliable, seemed practical and auspicious. The review indicates that TMA and TPN are accompanying telemedical concepts in out-of-hospital trauma care. Well-designed populated studies are needed to fully assess the effect of telemedicine in acute trauma care. Therefore, evidence regarding the effectiveness of telemedicine in prehospital setting for trauma patients is still limited.

To evaluate the accuracy of virtual simulation, which is less time-consuming than physical simulation, with the new laser system Dorado CT4 in 96 prostate cancer patients. Virtual simulation was based on a spiral scan with 8 mm reconstruction index and 8 mm slice thickness in 64 patients (group A), and 3 mm reconstruction index and 3 mm slice thickness in 32 patients (group B). Both groups were evaluated for impact on maximum difference (Deltamax) regarding the isocenters obtained from virtual simulation versus those obtained from physical simulation. In the entire cohort, mean differences were as follows: Deltamax 5.7 +/- 3.5 mm, Deltax (left/right) 2.8 +/- 2.9 mm, Deltay (anterior/posterior) 4.5 +/- 3.8 mm, and Deltaz (cranial/caudal) 2.1 +/- 2.2 mm. In group A, mean values were Deltamax 6.2 +/- 3.8 mm, Deltax 2.9 +/- 3.1 mm, Deltay 4.9 +/- 4.2 mm, and Deltaz 2.3 +/- 2.3 mm. In group B, mean values were Deltamax 4.8 +/- 2.8 mm, Deltax 2.7 +/- 2.7 mm, Deltay 3.7 +/- 2.7 mm, and Deltaz 1.7 +/- 2.0 mm. Time of radiotherapy (primary vs. salvage RT) and radiation regimen (external-beam radiotherapy [EBRT] vs. high-dose-rate brachytherapy [HDR-BT] plus EBRT) had no significant impact on Deltamax. Virtual simulation with the new laser system Dorado CT4 was very precise for both primary and salvage RT in the treatment of prostate cancer patients. High precision was achieved for both EBRT and HDR-BT plus EBRT. Virtual simulation should be performed with a planning CT with 3 mm reconstruction index and 3 mm slice thickness for high accuracy.

Dam break is one of the most dangerous disasters, which cause a large mass of water from the reservoir is suddenly released to the downstream. Although dam break events are still rare, the occurrences can cause severe damage to the downstream area, especially if the downstream is an urban area. Urban flood due to dam break has a different characteristic compared to the flood in nature. Modeling the flood is good way to learn the urban flood characteristic. Therefore, further studies are needed to develop an urban dam break model. Numerical modeling is one of the most effective methods to simulate the flood. In numerical modeling, buildings can be modeled with 3 approaches, as a wall boundary, as an area with high manning value, and as a contour. This paper discusses about two-dimensional flow of a dam break which flows through a sloping channel and single building, particularly comparing 3 approaches to modeled the building. The case is based on laboratory experiment of previous study. The model was developed with 2D Shallow Water Equations (SWE) which are based on the conservation of mass and momentum derived from Navier Stokes equation. The equations then discretized using Mac-Cormack numerical scheme. Numerical filter is used to reduce the numerical instability or oscillation in the model. The numerical model results are then compared to the experimental result from previous study. The accuracy of the numerical model was checked using Root Mean Square Error (RMSE) to determine the best methods to modeled the building. The results indicate that modeling the building as a wall boundary have the best results with lowest RMSE value and also shown the closest comparison of water level compared to the experimental results. By conducting this study, it is hoped to assist the urban dam break modeling in the future.

Efficient Semi-Analytical Simulation for Heston Model

In this paper, a family of high-order linearly implicit exponential integrators conservative schemes is constructed for solving the multi-dimensional nonlinear fractional Schrödinger equation. By virtue of the Lawson transformation and the generalized scalar auxiliary variable approach, the equation is first reformulated to an exponential equivalent system with a modified energy. Then, we construct a semi-discrete conservative scheme by using the Fourier pseudo-spectral method to discretize the exponential system in space direction. After that, linearly implicit energy-preserving schemes which have high accuracy are given by applying the Runge–Kutta method to approximate the semi-discrete system in temporal direction and using the extrapolation method to the nonlinear term. As expected, the constructed schemes can preserve the energy exactly and implement efficiently with a large time step. Numerical examples confirm the constructed schemes have high accuracy, energy-preserving, and effectiveness in long-time simulation.

According to Principle of New Information Priority in grey theory, giving the new information larger weight in modeling can improve the effectiveness of gray model. For the GM (1, 1)model has very small samples, and the high overall simulation accuracy does not necessarily guarantee high prediction accuracy, we put forward weighted least square method to estimate parameters in GM (1, 1) model. Focusing on improving the simulation accuracy of new information, focusing on grasping the latest development' law of things, and aiming at improving the prediction accuracy by giving residual sum of squares of new information larger weight. Finally, we use an example to verify the practicality and reliability of the model.

Flood nowcasting at detailed, fine spatiotemporal scales is crucial for the deployment of reliable warning systems, especially in built-up environments where the majority of socio-economic activity is concentrated. These environments are also characterized by significant complexities that require sufficient detail, up to street level. The derivation of flood maps for early warning systems can be organized via three main pillars: a) nowcasting of rainfall at high spatiotemporal resolution, typically obtained from weather radars; b) deployment of physics-based mechanistic simulators, typically based on 2D Shallow Water Equations; c) utilization of High-Performance Computing (HPC) facilities to handle the associated significant computational effort and make practically feasible the computational process. However, even with such infrastructure, there are still limitations mainly arising from: a) model errors, either related with the epistemic or the deep uncertainty of real-world randomness; b) the required simulation time which can still be prohibitive for the development of operational nowcasting tools, especially for large case study areas. The first limitation is addressed through impact-based approaches, in which uncertainties are compensated through the translation of the natural variables derived by the model (i.e. water depths and flow velocities) into classified hazard zones. With respect to the second limitation, surrogate modelling, and particularly the relevant Machine Learning (ML) techniques, promises a potential remedy to the high computational burden, since it enables the development of fast emulators based on the results derived by the mechanistic (accurate, yet slow) simulators. However, the high spatiotemporal variability of flood-related variables, as exhibited in detailed scales increases significantly the dimensionality of the problem, hampering the application of such techniques in real-world operational conditions. To address this, herein we explore the use of dimensionality-reduction techniques such as, Single Value Decomposition (SVD) and Principal Component Analysis (PCA), which are widely employed, for similar purposes, in the domain of data science. The feasibility of such methods is investigated via impact-based flood maps derived by a detailed mechanistic simulator in real-world conditions.

Shallow wake patterns are investigated by numerical method based on the solutions of two-dimensional (2D) shallow water equations and three-dimensional (3D) Reynolds-Averaged Navier-Stokes (RANS) equations with the implicit scheme on collocated mesh in the FVM framework. The analysis are made on vorticity contour distribution, transverse velocity (uy) variation with time, Strouhal number (St) and time-averaged longitudinal velocity (ux) to verify the characteristics of shallow wakes behind cylinder. We compare the numerical results with Chen’s experiment very well and show the capability and difference of 2D model and 3D model in modeling shallow wake structure. The results show that the 2D model predicts the vortex street (VS) wake well, yet the 3D model is fit for the steady bubble (SB) wake. The 2D model performs more accurately when VS wake transforms to unsteady bubble (UB) wake, while the 3D model is better when UB wake transforms to SB wake.

Balancing Source Terms and Flux Gradients in High-Resolution Godunov Methods: The Quasi-Steady Wave-Propagation Algorithm

Land use simulations are critical in predicting the impact of land use change (LUC) on the Earth. Various assumptions and policies influence land use structure and are a key factor in decisions made by policymakers. Meanwhile, the spatial autocorrelation effect between land use types has rarely been considered in existing land use spatial simulation models, and the simulation accuracy needs to be further improved. Thus, in this study, the driving mechanisms of LUC are analyzed. The quantity demand and spatial distribution of land use are predicted under natural development (ND), economic development (ED), ecological protection (EP), and sustainability development (SD) scenarios in Zhengzhou based on the coupled Multi-Objective Programming (MOP) model and the Patch-generating Land Use Simulation model (PLUS) considering Spatial Autocorrelation (PLUS-SA). We conclude the following. (1) The land use type in Zhengzhou was mainly cultivated land, and 83.85% of the land for urban expansion was cultivated land from 2000 to 2020. The reduction in forest from 2010 to 2020 was less than that from 2000 to 2010 due to the implementation of the policy in which farmland is transformed back into forests. (2) The accuracy of PLUS-SA was better than that of the traditional PLUS and Future Land Use Simulation (FLUS) models, and its Kappa coefficient, overall accuracy, and FOM were 0.91, 0.95, and 0.29, respectively. (3) Natural factors (temperature, precipitation, and DEM) contributed significantly to the expansion of cultivated land, and the increase in forest, grass, and construction land was greatly affected by socioeconomic factors (population, GDP, and proximity to town). (4) The land use structure will be more in line with the current requirements for sustainable urban development in the SD scenario, and the economic and ecological benefits will increase by 0.75 × 104 billion CNY and 1.71 billion CNY, respectively, in 2035 compared with those in 2020. The PLUS-SA model we proposed had higher simulation accuracy in Zhengzhou Compared with the traditional PLUS and FLUS models, and our research framework can provide a basis for decision-makers to formulate sustainable land use development policies to achieve high-quality and sustainable urban development.