Articoli di riviste: "Boundary conditions calibration"

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Herold, Judith, Eric Lemont, Stuart Bettington e Edward Couriel. "CHALLENGES OF BOUNDARY CONDITIONS IN OPEN OCEAN MODELS". Coastal Engineering Proceedings, n. 36v (28 dicembre 2020): 52. http://dx.doi.org/10.9753/icce.v36v.waves.52.

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The development and calibration of coastal numerical models to support engineering design and environmental impact studies is a challenging process and one that requires professional judgement and continual assessment of all aspects of the model makeup. Fundamental to the integrity of the model are appropriate boundary conditions and quality observational data for calibration. Open ocean boundary conditions are typically the most complex and important aspect of a model build. They represent the influence of dynamics occurring beyond the model extent, bridging large-scale dynamics to the small-scale processes in the model. This study discusses the challenges of open ocean boundaries and how we utilised data to achieve an effective model.Recorded Presentation from the vICCE (YouTube Link): https://youtu.be/evL7f_17wZg

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Hwang, B.-W., C.-M. Suh e S.-H. Kim. "Finite element analysis of calibration factors for the modified incremental strain method". Journal of Strain Analysis for Engineering Design 38, n. 1 (1 gennaio 2003): 45–51. http://dx.doi.org/10.1243/030932403762671881.

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To modify the incremental strain method used to evaluate non-uniform residual stress, a finite element analysis (FEA) of the reference model used to describe a hole-drilling test was conducted. The calibration factors for the x and y directions were obtained from the analysis and then their differences were compared under various loading conditions. A hole-drilling test using a steel plate as the reference specimen was introduced, and under the pure bending load, strain relaxation was measured at each hole-drilling step to determine the calibration factors. Although the calibration factors in the x and y directions varied with the boundary conditions used in the FEA, their differences were reduced to zero for all depths when the prescribed loads as the boundary conditions in the x and y directions became the same. In addition, it was analytically and experimentally confirmed that the calibration factors did not vary with the direction. Accordingly, by making the calibration factors equal in the x and y directions in the modified equation for the incremental strain method, no singularity is produced in the stress calculations.

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Campbell, D. S., M. Gundappa e T. E. Diller. "Design and Calibration of a Local Heat-Flux Measurement System for Unsteady Flows". Journal of Heat Transfer 111, n. 2 (1 maggio 1989): 552–57. http://dx.doi.org/10.1115/1.3250713.

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A local heat–flux measurement system was built, calibrated, and tested for use in unsteady flows. The system was designed to maintain constant-wall-temperature boundary conditions. The measuring element is a thin-film heat flux gage made by sputter-coating gold onto a substrate. A constant-temperature anemometer is used to maintain the thin-film gage at a specified temperature under fluctuating conditions. A separate temperature control system maintains the surrounding boundary at the gage temperature. The system was calibrated for both steady and unsteady flows using a specially designed calibrator for local heat flux gages. The steady calibration was done with predominantly convective heat transfer. The unsteady calibration was achieved by adding oscillating radiant energy to the surface. Consequently, quantitative results can be obtained for both the mean and fluctuating components of the heat transfer. The frequency response was good to over 90 Hz. Sample results are presented of the unsteady heat transfer over a circular cylinder caused by natural vortex shedding at 70 to 80 Hz.

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Monfre, Stephen L., e Steven D. Brown. "Quantitative Fourier-Domain Analysis. Part II: Determination of Boundary Conditions". Applied Spectroscopy 46, n. 11 (novembre 1992): 1711–18. http://dx.doi.org/10.1366/0003702924926943.

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A new approach for determining the boundary conditions of a Fourier-domain data set prior to performing quantitative multicomponent analysis has been developed. Processing boundary conditions were determined by calculating the condition number of the calibration matrix which contains the models used to describe the chemical system being studied. Once the boundary conditions for the Fourier-domain data set were determined, the Kalman filter was used to estimate the concentration of individual components in a multicomponent sample. Synthetic data were first analyzed to determine both the feasibility of the data-analysis method and the effect that background variations would have on the concentration estimates. Raw interferograms of multicomponent samples, collected with the use of Fourier transform infrared (FT-IR) spectroscopy, were also analyzed. Validation samples were analyzed to verify the chosen boundary conditions.

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Ahmadi, M. M., P. M. Byrne e R. G. Campanella. "Cone tip resistance in sand: modeling, verification, and applications". Canadian Geotechnical Journal 42, n. 4 (1 agosto 2005): 977–93. http://dx.doi.org/10.1139/t05-030.

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A numerical modeling procedure is presented to evaluate cone tip resistance in sand. The procedure involves a moving boundary simulating cone penetration. The soil is modeled as a MohrCoulomb elasticplastic material with stress-dependent parameters. The procedure is verified by comparing predicted numerical values of cone tip resistance with published experimental measurements from calibration chamber tests. The selected database consists of 59 calibration chamber tests on Ticino sand with different relative densities, overconsolidation ratios, stresses, and boundary conditions. Several applications of the modeling procedure are also presented. The computer program FLAC is used to carry out the analysis.Key words: cone tip resistance, numerical modeling, sand, calibration chamber, Mohr-Coulomb, in situ horizontal stress.

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Sivelle, Vianney, Philippe Renard e David Labat. "Coupling SKS and SWMM to Solve the Inverse Problem Based on Artificial Tracer Tests in Karstic Aquifers". Water 12, n. 4 (16 aprile 2020): 1139. http://dx.doi.org/10.3390/w12041139.

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Artificial tracer tests constitute one of the most powerful tools to investigate solute transport in conduit-dominated karstic aquifers. One can retrieve information about the internal structure of the aquifer directly by a careful analysis of the residence time distribution (RTD). Moreover, recent studies have shown the strong dependence of solute transport in karstic aquifers on boundary conditions. Information from artificial tracer tests leads us to propose a hypothesis about the internal structure of the aquifers and the effect of the boundary conditions (mainly high or low water level). So, a multi-tracer test calibration of a model appeared to be more consistent in identifying the effects of changes to the boundary conditions and to take into consideration their effects on solute transport. In this study, we proposed to run the inverse problem based on artificial tracer tests with a numerical procedure composed of the following three main steps: (1) conduit network geometries were simulated using a pseudo-genetic algorithm; (2) the hypothesis about boundary conditions was imposed in the simulated conduit networks; and (3) flow and solute transport were simulated. Then, using a trial-and-error procedure, the simulated RTDs were compared to the observed RTD on a large range of simulations, allowing identification of the conduit geometries and boundary conditions that better honor the field data. This constitutes a new approach to better constrain inverse problems using a multi-tracer test calibration including transient flow.

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Kacem, Ahmed, Hervé Laurent e Sandrine Thuillier. "Influence of experimental boundary conditions on the calibration of a ductile fracture criterion". Engineering Fracture Mechanics 248 (maggio 2021): 107686. http://dx.doi.org/10.1016/j.engfracmech.2021.107686.

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Baldi, Antonio. "Far-Field Boundary Conditions for Calculation of Hole-Drilling Residual Stress Calibration Coefficients". Experimental Mechanics 57, n. 4 (7 novembre 2016): 659–64. http://dx.doi.org/10.1007/s11340-016-0235-1.

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Han, Liya, Long Yu e Xusheng Zhu. "A Novel Method for Pose and Position Calibration of Laser Displacement Sensors". Sensors 23, n. 4 (4 febbraio 2023): 1762. http://dx.doi.org/10.3390/s23041762.

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Laser displacement sensors are widely used in the aviation industry for the purpose of surface normal measurements. The measurement of a surface normal depends on prior knowledge of the poses and positions of the sensors, which are obtained through calibration. This paper introduces a new parameter to the traditional calibration procedure, to reduce the calibration error, and explores the factors affecting calibration using the Monte Carlo method. In the experiment, the normal measurement error of the probe consisted of four sensors after calibration was less than 0.1∘, which satisfied the established requirements. This paper indicates the boundary conditions for a successful calibration and validates the proposed method, which provides a new method for the pose and position calibration of laser displacement sensors and other similar sensors.

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FURSENKO, Antanas. "Precizinių rastrų formavimo sistemos juostos poslinkio matavimo junginio skaičiuojamieji tyrimai / Analytical research of displacement measuring unit of the precise raster-forming systems". Mokslas - Lietuvos ateitis 9, n. 6 (29 dicembre 2017): 597–601. http://dx.doi.org/10.3846/mla.2017.1092.

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The precision raster-forming systems creation and development must be based on research in the specific work environment. In not ideal metrological conditions the precision raster-forming system allows to achieve high accuracy of the calibration, when used dynamic calibration method.The paper analyzes the possibility of analytical modeling of one main part (steel tape displacement measuring unit) of precise raster forming systems. In the work, a linear mechanical model of steel tape was applied to the load. The work described the equation, which describes the steel tape deformation model under loads with boundary conditions.

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Annunziato, Mario, e Hanno Gottschalk. "CALIBRATION OF LÉVY PROCESSES USING OPTIMAL CONTROL OF KOLMOGOROV EQUATIONS WITH PERIODIC BOUNDARY CONDITIONS". Mathematical Modelling and Analysis 23, n. 3 (14 giugno 2018): 390–413. http://dx.doi.org/10.3846/mma.2018.024.

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We present an optimal control approach to the problem of model calibration for Lévy processes based on an non-parametric estimation procedure of the measure. The optimization problem is related to the maximum likelihood theory of sieves [25] and is formulated with the Fokker-Planck-Kolmogorov approach [3, 4]. We use a generic spline discretization of the Lévy jump measure and select an adequate size of the spline basis using the Akaike Information Criterion (AIC) [12]. The first order necessary optimality conditions are derived based on the Lagrange multiplier technique in a functional space. The resulting Partial Integral-Differential Equations (PIDE) are discretized, numerically solved using a scheme composed of Chang-Cooper, BDF2 and direct quadrature methods, jointly to a non-linear conjugate gradient method. For the numerical solver of the Kolmogorov's forward equation we prove conditions for non-negativity and stability in the L1 norm of the discrete solution.

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Chang, Ze, Hongzhi Zhang, Erik Schlangen e Branko Šavija. "Lattice Fracture Model for Concrete Fracture Revisited: Calibration and Validation". Applied Sciences 10, n. 14 (14 luglio 2020): 4822. http://dx.doi.org/10.3390/app10144822.

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The lattice fracture model is a discrete model that can simulate the fracture process of cementitious materials. In this work, the Delft lattice fracture model is reviewed and utilized for fracture analysis. First, a systematic calibration procedure that relies on the combination of two uniaxial tensile tests is proposed to determine the input parameters of lattice elements—tensile strength, compressive strength and elastic modulus. The procedure is then validated by simulating concrete fracture under complex loading and boundary conditions: Uniaxial compression, three-point bending, tensile splitting, and double-edge-notch beam shear. Simulation results are compared to experimental findings in all cases. The focus of this publication is therefore not only on summarizing existing knowledge and showing the capabilities of the lattice fracture model; but also to fill in an important gap in the field of lattice modeling of concrete fracture; namely, to provide a recommendation for a systematic model calibration using experimental data. Through this research, numerical analyses are performed to fully understand the failure mechanisms of cementitious materials under various loading and boundary conditions. While the model presented herein does not aim to completely reproduce the load-displacement curves, and due to its simplicity results in relatively brittle post-peak behavior, possible solutions for this issue are also discussed in this work.

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Li, Yao, Peifeng Su e Zhe Wang. "Improved Boundary Conditions for a 3D DEM Simple Shear Model". Advances in Civil Engineering 2020 (28 giugno 2020): 1–9. http://dx.doi.org/10.1155/2020/5420793.

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In this study, a 3D simple shear model using DEM is built based on the boundary condition of an NGI-type bidirectional simple shear apparatus. Stack of rings used as lateral constraints in a bidirectional simple shear test is modelled by layers of clumps which is possible to be moved by particles; different contact types and parameters are used to model the sand-loading caps, sand-latex membrane, and sand-sand contacts. A simple shear test using the bidirectional simple shear apparatus is performed for the calibration of the 3D DEM simple shear model. By analyzing the simulation results, the following can be concluded. (1) Rings generated by clumps can provide an accurate boundary condition, effective in computation since no contact force is needed for a clump. (2) In the simulation, the orientation of average contact force changed dramatically during shear. It is in the vertical direction (90°) before shear and changes to 45° at 40% shear strain. No shear band is observed which is consistent with the test, and particles move uniformly. (3) In the simulation, the degree of noncoaxiality is the greatest at the beginning of shear, and it is decreased during shear. However, the degree of noncoaxiality is still large at 20% shear strain where there is a 10° difference between the rotation angle of principal stress and principal strain increment.

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Karban, Pavel, David Pánek, František Mach e Ivo Doležel. "Calibration of numerical models based on advanced optimization and penalization techniques". Journal of Electrical Engineering 68, n. 5 (1 settembre 2017): 396–400. http://dx.doi.org/10.1515/jee-2017-0073.

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Abstract A new approach to estimation of unknown material parameters and boundary conditions of physical models was developed. The approach is based on processing measured data by advanced optimization techniques connected with penalization. The data are supposed to be in the form of random variables with normal probability distributions. Several examples were calculated proving the strength of the proposed algorithm.

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Kenja, Krishna, Sandeep Madireddy e Kumar Vemaganti. "Calibration of hyperelastic constitutive models: the role of boundary conditions, search algorithms, and experimental variability". Biomechanics and Modeling in Mechanobiology 19, n. 5 (5 marzo 2020): 1935–52. http://dx.doi.org/10.1007/s10237-020-01318-3.

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Kozelkov, Andrey, Andrey Kurkin, Dmitry Utkin, Elena Tyatyushkina, Vadim Kurulin e Dmitry Strelets. "Application of Non-Reflective Boundary Conditions in Three-Dimensional Numerical Simulations of Free-Surface Flow Problems". Geosciences 12, n. 11 (21 novembre 2022): 427. http://dx.doi.org/10.3390/geosciences12110427.

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This paper considers the issue of using non-reflective boundaries for surface wave simulations within the framework of three-dimensional Navier–Stokes equations. We distinguish a wave damping approach among the known implementations of non-reflective boundary conditions in surface wave simulations. The approach employs a sponge boundary layer to dampen incident waves. In this paper, we describe implementations of this approach on unstructured meshes. We also present the calibration of free parameters, the values of which control wave damping efficiency and the amplitude of reflected waves. Comparison of the results obtained at different types of distribution for the free parameter was conducted. The implemented wave damping approach was tested by simulating a solitary wave propagating in a water tank. We demonstrate the use of damping non-reflective boundary conditions for the case of a wave traveling across the surface of a real body of water near Sakhalin Island while considering its bathymetry.

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Kubair, Dhirendra V., Maxwell Pinz, Kaitlin Kollins, Craig Przybyla e Somnath Ghosh. "Role of exterior statistics-based boundary conditions for property-based statistically equivalent representative volume elements of polydispersed elastic composites". Journal of Composite Materials 52, n. 21 (22 febbraio 2018): 2919–28. http://dx.doi.org/10.1177/0021998318758498.

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The property-based statistically equivalent RVE or P-SERVE has been introduced in the literature as the smallest microstructural volume element in non-uniform microstructures that has effective material properties equivalent to those of the entire microstructure. An important consideration is the application of appropriate boundary conditions for optimal property-based statistically equivalent representative volume element domains. The exterior statistics-based boundary conditions have been developed, accounting for the statistics of fiber distributions and interactions in the domain exterior to the property-based statistically equivalent representative volume element. This paper is intended to validate the efficacy of the exterior statistics-based boundary condition-based property-based statistically equivalent representative volume elements for evaluating homogenized stiffnesses of a unidirectional polymer matrix composite with a polydispersed microstructure characterized by nonuniform dispersion of carbon fibers of varying sizes in an epoxy matrix. Experimental tests and microstructural characterization of the polymer matrix composite are conducted for calibration and validation of the model. Statistically equivalent microstructural volume elements are constructed from experimental micrographs for direct numerical simulations. The performance of the property-based statistically equivalent representative volume element with exterior statistics-based boundary conditions is compared with other boundary conditions, as well as with the statistical volume elements. The tests clearly show the significant advantages of the exterior statistics-based boundary conditions in terms of accuracy of the homogenized stiffness and efficiency.

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Krysmon, Sascha, Johannes Claßen, Stefan Pischinger, Georgi Trendafilov, Marc Düzgün e Frank Dorscheidt. "RDE Calibration—Evaluating Fundamentals of Clustering Approaches to Support the Calibration Process". Vehicles 5, n. 2 (30 marzo 2023): 404–23. http://dx.doi.org/10.3390/vehicles5020023.

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The topics of climate change and pollutant emission reduction are dominating societal discussions in many areas. In automotive development, with the introduction of real driving emissions (RDE) testing and the upcoming EU7 legislation, there are endless boundary conditions and potential scenarios that need to be evaluated. In terms of vehicle calibration, this is leading to a strong focus on alternative approaches such as virtual calibration. Due to the flexibility of virtual test environments and the variety of RDE scenarios, the amount of data collected is rapidly increasing. Supporting the calibration engineers in using the available data and identifying relevant information and test scenarios requires efficient approaches to data analysis. This paper therefore discusses the potential of data clustering to support this process. Using a previously developed approach for event detection in emission calibration, a methodology for the automatic categorization of events is presented. Approaches to clustering algorithms (hierarchical, partitioning, and density-based) are discussed and applied to data of interest. Their suitability for different signals is investigated exemplarily, and the relevant inputs are analyzed for their usability in calibration procedures. It is shown which clustering approaches have the potential to be implemented in the vehicle calibration process to provide added value to data evaluation by calibration engineers.

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Pratama, Munawir Bintang, Vengatesan Venugopal, Harman Ajiwibowo, Juventus Welly Ginting e Franto Novico. "Modelling Tidal Flow Hydrodynamics of Sunda Strait, Indonesia". ILMU KELAUTAN: Indonesian Journal of Marine Sciences 25, n. 4 (14 novembre 2020): 165–72. http://dx.doi.org/10.14710/ik.ijms.25.4.165-172.

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In the past years, Indonesian people put more attention to Sunda Strait located between Java and Sumatra Islands, one of the busiest straits occupied with residential, recreational, fisheries, transportation, industrial and mining activities. Previous works on numerical modelling of tidal flow hydrodynamics of the Sunda Strait have resulted in good agreement against field data; however, the calibration of the models used was not described in detail. This paper presents the process of setting up the model, extensive calibration, validation and prediction of tidal currents for the Sunda Strait. A two-dimensional tidal-driven model is constructed using Delft3D, an open-source developed by Deltares. Four different bathymetry datasets, four different boundary condition configurations, and various bed roughness values are used, and their suitability in predicting tidal water level and current are investigated. It is found that changing the bathymetry and boundary conditions improve the model validation significantly. GEBCO_2019 bathymetry dataset outperforms the Batnas, even though it has a coarser resolution. For boundary conditions, the combination of water level and current velocity results in a better validation compares to using water level or current velocity only. However, the bed roughness shows an insignificant influence in predicting tidal conditions. The averaged current velocity is lower at the Southern than the Northern side of the strait due to a larger cross-section, consequence of deeper water. High tidal currents of magnitude around 2 m.s-1 are seen at the bottleneck of the strait.

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Ilg, C., C. Liebold, V. Sreenivasa, A. Haufe, C. Karadogan e M. Liewald. "Displacement based Simulation and Material Calibration based on Digital Image Correlation Part II - Application". IOP Conference Series: Materials Science and Engineering 1284, n. 1 (1 giugno 2023): 012056. http://dx.doi.org/10.1088/1757-899x/1284/1/012056.

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Abstract An alternative approach to calibrate material models is proposed. The entire displacement field of a specimen measured with a DIC system was converted into boundary conditions by the Envyo® mapping software. These boundary conditions were imposed on all nodes in the corresponding LS-DYNA® simulation model. In this way a digital twin of the specimen geometry and the experimental kinematics was obtained. Considering the local stress equilibrium over the entire specimen and the equilibrium of global force integrated over many hypothetical cross sections, LS-OPT® was used to iteratively determine the isotropic model parameters of the tested material. A new tensile specimen geometry is introduced to get the most out of a single test. The findings suggest that, at present, convergence in iterative parameter optimization cannot be attained without prior filtering and smoothing of the DIC input data in time and space, despite the utilization of the chosen material model.

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Zevri, Asril, Adam Pamudji Rahardjo e Djoko Legono. "A PROPOSED TECHNIQUE FOR IMPROVING THE ACCURACY OF TIDAL MODELING OF RIVER NETWORKS CONNECTING TO THE DADAHUP IRRIGATION AREA". ASEAN Engineering Journal 13, n. 3 (30 agosto 2023): 99–106. http://dx.doi.org/10.11113/aej.v13.19393.

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Optimizing the operational management of tidal irrigation networks is a significant factor in the reactivation program of the swamp irrigation areas in Central Kalimantan Province. Appropriate water level and flow rate control in a tidal environment would provide a better solution for this effort. Monitoring water parameters and hydraulic modeling is an intelligent technique for evaluating irrigation canals' gate system operations. This paper focuses on providing more accurate hydraulic modeling that requires proper boundary conditions and calibration of the canal roughness coefficient. This study aims to obtain a more precise downstream boundary condition data calibration method with an appropriate river cross-sectional roughness coefficient value to improve the overall hydraulic modeling accuracy of the river network connecting to the Dadahup Irrigation Area. The hydraulic modeling utilized the HEC-RAS Software, where input data preparation used geometric data derived from the National Geospatial Agency's DEM in the form of river channel network chain, cross-section, and long-section data. Boundary condition data evaluation compared and selected data generated from references and the Tides Application Software. The results show that the tide prediction from the Tides Application Software provides the slightest difference between the predicted tide and the measured ones. The river network's channel roughness coefficient calibration utilized the generated boundary condition tide and simultaneously measured water level data at several locations. The results show that the most minor Root Mean Squared Error (RMSE) of the Manning roughness coefficient differences of the river channel network can reach 0.04 with a minimum RMSE value of 0.027.

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Schünemann, Christoph, David Schiela e Regine Ortlepp. "Guidelines to Calibrate a Multi-Residential Building Simulation Model Addressing Overheating Evaluation and Residents’ Influence". Buildings 11, n. 6 (5 giugno 2021): 242. http://dx.doi.org/10.3390/buildings11060242.

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Can building performance simulation reproduce measured summertime indoor conditions of a multi-residential building in good conformity? This question is answered by calibrating simulated to monitored room temperatures of several rooms of a multi-residential building for an entire summer in two process steps. First, we did a calibration for several days without the residents being present to validate the building physics of the 3D simulation model. Second, the simulations were calibrated for the entire summer period, including the residents’ impact on evolving room temperature and overheating. As a result, a high degree of conformity between simulation and measurement could be achieved for all monitored rooms. The credibility of our results was secured by a detailed sensitivity analysis under varying meteorological conditions, shading situations, and window ventilation or room use in the simulation model. For top floor dwellings, a high overheating intensity was evoked by a combination of insufficient use of night-time window ventilation and non-heat-adapted residential behavior in combination with high solar gains and low heat storage capacities. Finally, the overall findings were merged into a process guideline to describe how a step-by-step calibration of residential building simulation models can be done. This guideline is intended to be a starting point for future discussions about the validity of the simplified boundary conditions which are often used in present-day standard overheating assessment.

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Harizi, Khaled, Mohamed Reda Menani, Nabil Chabour e Sofiane Labar. "Initial assessment of the groundwater flow and budget using Geographic Information System, MODFLOW-2005 and the FREEWAT modeling tool in Bouteldja coastal aquifer (Northern East of Algeria)". Acque Sotterranee - Italian Journal of Groundwater 10, n. 3 (29 settembre 2021): 41–51. http://dx.doi.org/10.7343/as-2021-511.

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The Bouteldja coastal aquifer is one of the most important groundwater resources in North eastern of Algeria. The region is under a sub-humid climate with an average rainfall of 600-880 mm/y. The unconfined aquifer is constituted of Quaternary sands formations. The hydrogeological characteristics were determined based on previous reports. A very important inflow recharges the sandy aquifer in the Southeastern boundary, in relation to a fault network system linking the aquifer and the Obeira Lake area. Another inflow is observed at the Southern boundary in relation to the exchanges with the alluvial aquifer of Bouteldja. The purpose of the present study is to provide an initial assessment of the groundwater flow and water budget of this aquifer. To achieve this goal, a one-layer groundwater flow numerical model was developed using the MODFLOW-2005 code and the FREEWAT software, using the available data. The model was run in steady state conditions. Calibration was achieved using the piezometric measurements of May 2018 as calibration target. After several trials of manual calibrations, the model successfully simulated the groundwater flows directions and heads. Calibration efforts lead to an acceptable concordance (for the purpose of this study) between the estimated and calculated hydraulic conductivity and piezometric heads, except at the Eastern border. The analyses of the simulated inflow budget shows that aside the rainfall infiltration, exchanges with surface water bodies, the adjoining alluvial aquifer and the fault system provide a relevant amount of water. This significant recharge needs additional investigations. This numerical modeling exercise using MODFLOW, the FREEWAT software and GIS reached the objective of a preliminary description of the groundwater flow and it represents an acceptable starting point for more thorough hydrodynamic characterization of the Bouteldja coastal aquifer.

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Kowalska, Magdalena. "Influence of Loading History and Boundary Conditions on Parameters of Soil Constitutive Models". Studia Geotechnica et Mechanica 34, n. 1 (1 marzo 2012): 15–33. http://dx.doi.org/10.1515/sgem-2017-0020.

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Abstract Parameters of soil constitutive models are not constant. This mainly concerns the strain parameters such as K, G or Eoed modules. What influences their values is not only soil type, structure and consistency, but also the history of stress and strain states. So, it is the question of the current state but also of what happened to the subsoil in the past (regarding geological and anthropological activity) and what impact would have the planned soil–structure interaction. This paper presents an overview of the literature showing how much the soil constitutive model parameters depend on loading and boundary conditions of a particular geotechnical problem. Model calibration methods are shortly described with special attention paid to the author’s “Loading Path Method”, which allows estimation of optimum parameter values of any soil constitutive model. An example of the use of this method to estimate strain parameters E and ν of Coulomb–Mohr elasticperfectly plastic model is given.

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MORA, MARIA GIOVANNA. "LOCAL CALIBRATIONS FOR MINIMIZERS OF THE MUMFORD–SHAH FUNCTIONAL WITH A TRIPLE JUNCTION". Communications in Contemporary Mathematics 04, n. 02 (maggio 2002): 297–326. http://dx.doi.org/10.1142/s0219199702000646.

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We prove that, if u is a function satisfying all Euler conditions for the Mumford–Shah functional and the discontinuity set of u is given by three line segments meeting at the origin with equal angles, then there exists a neighbourhood U of the origin such that u is a minimizer of the Mumford–Shah functional on U with respect to its own boundary conditions on ∂U. The proof is obtained by using the calibration method.

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Riveiro, B., G. Cubreiro, B. Conde, M. Cabaleiro, R. Lindenbergh, M. Soilán e J. C. Caamaño. "AUTOMATED CALIBRATION OF FEM MODELS USING LIDAR POINT CLOUDS". ISPRS - International Archives of the Photogrammetry, Remote Sensing and Spatial Information Sciences XLII-2 (30 maggio 2018): 969–74. http://dx.doi.org/10.5194/isprs-archives-xlii-2-969-2018.

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In present work it is pretended to estimate elastic parameters of beams through the combined use of precision geomatic techniques (laser scanning) and structural behaviour simulation tools. The study has two aims, on the one hand, to develop an algorithm able to interpret automatically point clouds acquired by laser scanning systems of beams subjected to different load situations on experimental tests; and on the other hand, to minimize differences between deformation values given by simulation tools and those measured by laser scanning. In this way we will proceed to identify elastic parameters and boundary conditions of structural element so that surface stresses can be estimated more easily.

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Itu, Lucian, Dominik Neumann, Viorel Mihalef, Felix Meister, Martin Kramer, Mehmet Gulsun, Marcus Kelm, Titus Kühne e Puneet Sharma. "Non-invasive assessment of patient-specific aortic haemodynamics from four-dimensional flow MRI data". Interface Focus 8, n. 1 (15 dicembre 2017): 20170006. http://dx.doi.org/10.1098/rsfs.2017.0006.

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We introduce a parameter estimation framework for automatically and robustly personalizing aortic haemodynamic computations from four-dimensional magnetic resonance imaging data. The framework is based on a reduced-order multiscale fluid–structure interaction blood flow model, and on two calibration procedures. First, Windkessel parameters of the outlet boundary conditions are personalized by solving a system of nonlinear equations. Second, the regional mechanical wall properties of the aorta are personalized by employing a nonlinear least-squares minimization method. The two calibration procedures are run sequentially and iteratively until both procedures have converged. The parameter estimation framework was successfully evaluated on 15 datasets from patients with aortic valve disease. On average, only 1.27 ± 0.96 and 7.07 ± 1.44 iterations were required to personalize the outlet boundary conditions and the regional mechanical wall properties, respectively. Overall, the computational model was in close agreement with the clinical measurements used as objectives (pressures, flow rates, cross-sectional areas), with a maximum error of less than 1%. Given its level of automation, robustness and the short execution time (6.2 ± 1.2 min on a standard hardware configuration), the framework is potentially well suited for a clinical setting.

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Chiominto, Luciano, Emanuela Natale, Giulio D’Emilia, Sante Alessandro Grieco, Andrea Prato, Alessio Facello e Alessandro Schiavi. "Responsiveness and Precision of Digital IMUs under Linear and Curvilinear Motion Conditions for Local Navigation and Positioning in Advanced Smart Mobility". Micromachines 15, n. 6 (30 maggio 2024): 727. http://dx.doi.org/10.3390/mi15060727.

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Abstract: Sensors based on MEMS technology, in particular Inertial Measurement Units (IMUs), when installed on vehicles, provide a real-time full estimation of vehicles’ state vector (e.g., position, velocity, yaw angle, angular rate, acceleration), which is required for the planning and control of cars’ trajectories, as well as managing the in-car local navigation and positioning tasks. Moreover, data provided by the IMUs, integrated with the data of multiple inputs from other sensing systems (such as Lidar, cameras, and GPS) within the vehicle, and with the surrounding information exchanged in real time (vehicle to vehicle, vehicle to infrastructure, or vehicle to other entities), can be exploited to actualize the full implementation of “smart mobility” on a large scale. On the other hand, “smart mobility” (which is expected to improve road safety, reduce traffic congestion and environmental burden, and enhance the sustainability of mobility as a whole), to be safe and functional on a large scale, should be supported by highly accurate and trustworthy technologies based on precise and reliable sensors and systems. It is known that the accuracy and precision of data supplied by appropriately in-lab-calibrated IMUs (with respect to the primary or secondary standard in order to provide traceability to the International System of Units) allow guaranteeing high quality, reliable information managed by processing systems, since they are reproducible, repeatable, and traceable. In this work, the effective responsiveness and the related precision of digital IMUs, under sinusoidal linear and curvilinear motion conditions at 5 Hz, 10 Hz, and 20 Hz, are investigated on the basis of metrological approaches in laboratory standard conditions only. As a first step, in-lab calibrations allow one to reduce the variables of uncontrolled boundary conditions (e.g., occurring in vehicles in on-site tests) in order to identify the IMUs’ sensitivity in a stable and reproducible environment. For this purpose, a new calibration system, based on an oscillating rotating table was developed to reproduce the dynamic conditions of use in the field, and the results are compared with calibration data obtained on linear calibration benches.

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Ateeq-Ur-Rehman, Sardar, Minh Bui, Shabeh Hasson e Peter Rutschmann. "An Innovative Approach to Minimizing Uncertainty in Sediment Load Boundary Conditions for Modelling Sedimentation in Reservoirs". Water 10, n. 10 (10 ottobre 2018): 1411. http://dx.doi.org/10.3390/w10101411.

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A number of significant investigations have advanced our understanding of the parameters influencing reservoir sedimentation. However, a reliable modelling of sediment deposits and delta formation in reservoirs is still a challenging problem due to many uncertainties in the modelling process. Modelling performance can be improved by adjusting the uncertainty caused by sediment load boundary conditions. In our study, we diminished the uncertainty factor by setting more precise sediment load boundary conditions reconstructed using wavelet artificial neural networks for a morphodynamic model. The model was calibrated for hydrodynamics using a backward error propagation method. The proposed approach was applied to the Tarbela Reservoir located on the Indus River, in northern Pakistan. The results showed that the hydrodynamic calibration with coefficient of determination (R2) = 0.969 and Nash–Sutcliffe Efficiency (NSE) = 0.966 also facilitated good calibration in morphodynamic calculations with R2 = 0.97 and NSE = 0.96. The model was validated for the sediment deposits in the reservoir with R2 = 0.96 and NSE = 0.95. Due to desynchronization between the glacier melts and monsoon rain caused by warmer climate and subsequent decrease of 17% in sediment supply to the Tarbela dam, our modelling results showed a slight decrease in the sediment delta for the near future (until 2030). Based on the results, we conclude that our overall state-of-the-art modelling offers a significant improvement in computational time and accuracy, and could be used to estimate hydrodynamic and morphodynamic parameters more precisely for different events and poorly gauged rivers elsewhere in the world. The modelling concept could also be used for predicting sedimentation in the reservoirs under sediment load variability scenarios.

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Tscheikner-Gratl, Franz, Peter Zeisl, Carolina Kinzel, Johannes Leimgruber, Thomas Ertl, Wolfgang Rauch e Manfred Kleidorfer. "Lost in calibration: why people still do not calibrate their models, and why they still should – a case study from urban drainage modelling". Water Science and Technology 74, n. 10 (3 settembre 2016): 2337–48. http://dx.doi.org/10.2166/wst.2016.395.

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From a scientific point of view, it is unquestioned that numerical models for technical systems need to be calibrated. However, in sufficiently calibrated models are still used in engineering practice. Case studies in the scientific literature that deal with urban water management are mostly large cities, while little attention is paid to the differing boundary conditions of smaller municipalities. Consequently, the aim of this paper is to discuss the calibration of a hydrodynamic model of a small municipality (15,000 inhabitants). To represent the spatial distribution of precipitation, three distributed rain gauges were used for model calibration. To show the uncertainties imminent to the calibration process, 17 scenarios, differing in assumptions for calibration, were distinguished. To compare the impact of the different calibration scenarios on actual design values, design rainfall events were applied. The comparison of the model results using the different typical design storm events from all the surrounding data points showed substantial differences for the assessment of the sewers regarding urban flooding, emphasizing the necessity of uncertainty analysis for hydrodynamic models. Furthermore, model calibration is of the utmost importance, because uncalibrated models tend to overestimate flooding volume and therefore result in larger diameters and retention volumes.

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31

Boikov, Aleksei, Roman Savelev, Vladimir Payor e Alexander Potapov. "Universal Approach for DEM Parameters Calibration of Bulk Materials". Symmetry 13, n. 6 (18 giugno 2021): 1088. http://dx.doi.org/10.3390/sym13061088.

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DEM parameters calibration is the most important step in preparing a DEM model. At the same time, the lack of a universal approach to DEM parameters calibration complicates this process. The paper presents the author’s approach to creating a universal calibration approach based on the physical meaning of the friction coefficients and conducting symmetrical experiments at full scale and in a simulation, as well as the implementation of the approach in the form of a physical test rig. Several experiments were carried out to determine the DEM parameters of six material–boundary pairs. The resulting parameters were adjusted using a refinement experiment. The results confirmed the adequacy of the developed approach, as well as its applicability in various conditions. The limitations of both the approach itself and its specific implementation in the form of a test rig were identified.

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32

Mu, Guozhen, e Qiongying Lyu. "Analysis of Turbulent Boundary Layer Jet Flow Pattern of TPS Standard Nozzle". Journal of Physics: Conference Series 2228, n. 1 (1 marzo 2022): 012039. http://dx.doi.org/10.1088/1742-6596/2228/1/012039.

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Abstract The design of the standard nozzle affects the air mass flow calibration accuracy of TPS. The relationship between the outlet diameter and the jet flow pattern is studied by performing jet simulation simulation on the three outlet size standard nozzles under the same boundary conditions. Through the simulation results, it can be seen that the outlet diameter under a single variable determines the value and range of the jet Mach number, which will cause a huge change in the mixing zone of the turbulent boundary layer, which directly affects the turbulent kinetic energy and has a linear relationship with the mass flow rate.

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Zacchei, Enrico, e Caio Gorla Nogueira. "Calibration of boundary conditions correlated to the diffusivity of chloride ions: An accurate study for random diffusivity". Cement and Concrete Composites 126 (febbraio 2022): 104346. http://dx.doi.org/10.1016/j.cemconcomp.2021.104346.

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34

Tian, Yu, Jun Zhang, Zongjin Ren, Wei Liu, Zhenyuan Jia e Qingbing Chang. "A novel calibration method based on Kirchhoff theory for piezoelectric dynamometer". Sensor Review 38, n. 2 (19 marzo 2018): 137–45. http://dx.doi.org/10.1108/sr-05-2017-0074.

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Purpose This paper aims to improve calibration and force measurement accuracy of multi-sensors’ piezoelectric dynamometer used in thrust measurement of rocket/air vehicle engine. Design/methodology/approach This paper presents a mapping solution method of sensors’ outputs based on the Kirchhoff thin plate theory, builds force-deformation differential equations with specific boundary conditions, uses finite difference (FD) method to solve the equations and analyzes outputs in offset loading forces in four-sensor square layout in main direction. The resultant force deviations calculated by the Kirchhoff theory are optimized with sequence quadratic program (SQP) method, and a calibration method of multiple loading points (MLP) based on the Kirchhoff theory is presented. Experiments of static calibration and verification are complemented to contrast the novel and single loading point (SLP) calibration method. Findings Experiments of static calibration and its verification show that at a loading force of 5,000N, the average resultant force deviations with MLP is 17.87N (0.35% FS) compared with single loading point method 26.45N (0.53% FS), improving calibration and measurement precision. Originality value A novel calibration method with MLP is presented. Force distributions of multiple sensors of main direction in piezoelectric dynamometer with offset loading force are solved with the Kirchhoff theory. The resultant force deviations calculated by Kirchhoff theory are optimized with the SQP method.

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35

Santanello, Joseph A., Sujay V. Kumar, Christa D. Peters-Lidard, Ken Harrison e Shujia Zhou. "Impact of Land Model Calibration on Coupled Land–Atmosphere Prediction". Journal of Hydrometeorology 14, n. 5 (1 ottobre 2013): 1373–400. http://dx.doi.org/10.1175/jhm-d-12-0127.1.

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Abstract Land–atmosphere (LA) interactions play a critical role in determining the diurnal evolution of both planetary boundary layer (PBL) and land surface heat and moisture budgets, as well as controlling feedbacks with clouds and precipitation that lead to the persistence of dry and wet regimes. In this study, the authors examine the impact of improved specification of land surface states, anomalies, and fluxes on coupled Weather Research and Forecasting Model (WRF) forecasts during the summers of extreme dry (2006) and wet (2007) land surface conditions in the U.S. southern Great Plains. The improved land initialization and surface flux parameterizations are obtained through calibration of the Noah land surface model using the new optimization and uncertainty estimation subsystems in NASA's Land Information System (LIS-OPT/LIS-UE). The impact of the calibration on the 1) spinup of the land surface used as initial conditions and 2) the simulated heat and moisture states and fluxes of the coupled WRF simulations is then assessed. In addition, the sensitivity of this approach to the period of calibration (dry, wet, or average) is investigated. Results show that the offline calibration is successful in providing improved initial conditions and land surface physics for the coupled simulations and in turn leads to systematic improvements in land–PBL fluxes and near-surface temperature and humidity forecasts. Impacts are larger during dry regimes, but calibration during either primarily wet or dry periods leads to improvements in coupled simulations due to the reduction in land surface model bias. Overall, these results provide guidance on the questions of what, how, and when to calibrate land surface models for coupled model prediction.

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36

Kuzmanovic, Vladan, Ljubodrag Savic e John Stefanakos. "Long-term thermal two- and three-dimensional analysis of roller compacted concrete dams supported by monitoring verification". Canadian Journal of Civil Engineering 37, n. 4 (aprile 2010): 600–610. http://dx.doi.org/10.1139/l10-004.

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This paper presents two-dimensional (2D) and three-dimensional (3D) numerical models for unsteady phased thermal analysis of RCC dams. The time evolution of a thermal field has been modeled using the actual dam shape, RCC technology and the adequate description of material properties. Model calibration and verification has been done based on the field investigations of the Platanovryssi dam, the highest RCC dam in Europe. The results of a long-term thermal analysis, with actual initial and boundary conditions, have shown a good agreement with the observed temperatures. The influence of relevant parameters on the thermal field of RCC dams has been analyzed. It is concluded that the 2D model is appropriate for the thermal phased analysis, and that the boundary conditions and the mixture properties are the most influential on the RCC dam thermal behavior.

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37

Li, Yujian, Yixin Geng e Liang Mao. "Calibration method for Manning's roughness coefficient for a river flume model". Water Supply 20, n. 8 (6 ottobre 2020): 3597–603. http://dx.doi.org/10.2166/ws.2020.235.

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Abstract This paper takes the Tarim River as an example to study the selection of Manning's roughness coefficient (n) in numerical simulation and presents a new method for calibrating Manning's roughness coefficient of a flume model. The measured topographic data and hydraulic data obtained from the flume experiments are taken as the initial boundary conditions in flow simulation, and n value for a flume model of the Qiman reach of Tarim River is calibrated by using a CCHE2D model. The consistency between the simulated water surface and the measured water surface with different n value is compared by using the error analysis method. Manning's n value for a flume model which meets the minimum error requirements is determined. The relative error between n value obtained by the empirical method and n value obtained by the numerical simulation method is analyzed. The result shows that the calibration method of n value for a flume model by using the CCHE2D model and error analysis presented in this paper is feasible and reliable.

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38

Tönsmann, Max, Fabian Kröhl, Philipp Cavadini, Philip Scharfer e Wilhelm Schabel. "Calibration Routine for Quantitative Three-Dimensional Flow Field Measurements in Drying Polymer Solutions Subject to Marangoni Convection". Colloids and Interfaces 3, n. 1 (15 marzo 2019): 39. http://dx.doi.org/10.3390/colloids3010039.

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Surface-tension induced flows may have a significant impact on the surface topography of thin films or small printed structures derived from polymer solution processing. Despite a century of research on Marangoni convection, the community lacks quantitative experimental flow field data, especially from within drying solutions. We utilize multifocal micro particle tracking velocimetry (µPTV) to obtain these data and show a calibration routine based on point spread function (PSF) simulations as well as experimental data. The results account for a varying sample refractive index, beneficial cover-glass correction collar settings as well as a multifocal lens system. Finally, the calibration procedure is utilized exemplarily to reconstruct a three-dimensional, transient flow field within a poly(vinyl acetate)-methanol solution dried with inhomogeneous boundary conditions.

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Euzenat, F., L. A. Baiza Martinez, W. Yu, P. Maheshwari e M. Pallud. "Wake structure analysis of a wind turbine under various atmospheric flow conditions and its application for mid-fidelity calibration". Journal of Physics: Conference Series 2767, n. 9 (1 giugno 2024): 092029. http://dx.doi.org/10.1088/1742-6596/2767/9/092029.

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Abstract A coupled Actuator Line Method (ALM) Large Eddy Simulation (LES) is used to simulate the wake structure of an isolated wind turbine. The wake centre position, boundary, and dynamics downstream of the wind turbine is determined under different atmospheric flow conditions, including neutral, stable, and unstable stratification. The wake centre lateral displacement and autocorrelation are seen to be affected by the atmospheric flow conditions. Finally, the instantaneous wake structure is then used as reference to improve the accuracy of mid-fidelity approach.

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40

Henrichs, M., A. Welker e M. Uhl. "Modelling of biofilters for ammonium reduction in combined sewer overflow". Water Science and Technology 60, n. 3 (1 luglio 2009): 825–31. http://dx.doi.org/10.2166/wst.2009.397.

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Biofiltration has proved to be a useful system to treat combined sewer overflow (CSO). The study presented uses numerical simulation to detect the critical operating conditions of the filter. The multi-component reactive transport module CW2D was used for the simulation study. Single-event simulations of lab-scale-column experiments with varying boundary conditions regarding the throttle outflow rate were carried out. For the calibration of the CW2D model measurement results of four experiments in two lab-scale columns were used. The model was validated by simulating four events of two further columns filled with the same filter material. These columns were operating with higher throttle outflow rates than the columns used for calibration. For ammonium (NH4-N) a good fit between measured and simulated data could be achieved. However, the comparison of simulated and measured effluent concentrations of nitrate (NO3-N) showed that there is a need for further investigations mainly due to the uncertainties in the degradation process during dry periods between the loadings.

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41

Audet, Lise, Sophie Duchesne e Nomessi Kokutse. "A regionalized river water quality model calibration method based on watershed physical characteristics: application to the Cau River in Vietnam". Revue des sciences de l’eau 31, n. 3 (10 dicembre 2018): 251–69. http://dx.doi.org/10.7202/1054306ar.

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A methodology is proposed for the calibration of river water quality models on large watersheds, in the absence of intensive measurements for water quality and quantity. This methodology is based on: 1) the use of the results from a hydrological model to provide the required hydrological variables to the water quality model; 2) five assumptions for the definition of initial and boundary conditions; 3) a three-step regionalized calibration method, in which the specific characteristics of the different subwatersheds are taken into account and 4) the adjustment of some parameters in order to reproduce processes that are not explicitly represented in the model. The regionalized calibration method relies on a comprehensive study of the land use and characteristics on each subwatershed and the definition of different sets of parameters values in distinct regions. Application to the Cau River, in Vietnam, with QUAL-GIBSI, an adaptation of the QUAL2E model, showed that: i) calibration and validation results were significantly improved by applying regionalized calibration as compared to an initial calibration for which a single set of parameters values was used for the whole simulated river stretch and ii) use of a hydrological model to provide discharge at various points in the watershed allowed to overcome the lack of detailed measurements of discharge at locations other than the watershed outlet.

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Gaiolini, Mattia, Nicolò Colombani, Gianluigi Busico, Fabrizio Rama e Micòl Mastrocicco. "Impact of Boundary Conditions Dynamics on Groundwater Budget in the Campania Region (Italy)". Water 14, n. 16 (9 agosto 2022): 2462. http://dx.doi.org/10.3390/w14162462.

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Groundwater budgets and fluxes are affected by human activities and climate change. Numerical models are cost-effective tools to investigate the different components of the hydrologic cycle. In this study, a groundwater flow model of the unconfined aquifers of the Campania region (Italy) has been developed and calibrated in Processing Modflow 11, resulting in an accurate assessment of groundwater fluxes and their trends over fifteen years (2000–2015). The model was implemented using a high-resolution grid to capture small hydrogeological features such as wells and rivers and informed by time variable datasets used as boundary conditions (i.e., river and sea levels, aquifer recharge, evapotranspiration, and discharge from adjacent systems). Good calibration and validation performances were achieved for piezometric heads (R2 = 0.958). A set of scenarios was developed using constant boundary conditions (i.e., constant sea-level BC, uniform extinction depth BC), and the outputs were compared, quantitively assessing differences in groundwater fluxes. Simulations pointed out that using time series to inform boundary conditions in the model does not always result in a significant change in the computed fluxes. Overall, non-uniform extinction depth was the most influential condition, while both rivers and sea level conditions barely affected groundwater budgets. In addition, results highlighted the need for an accurate estimation of spatiotemporal variations of both recharge and evapotranspiration, due to their strong seasonal variability and their massive contribution to the hydrogeological cycle. Finally, a marked increase of evapotranspiration fluxes controlled by interannual variability of precipitation and atmospheric temperatures has been quantified over the modelled period.

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Salaris, M., S. Cassisi, R. P. Schiavon e A. Pietrinferni. "Effective temperatures of red giants in the APOKASC catalogue and the mixing length calibration in stellar models". Astronomy & Astrophysics 612 (aprile 2018): A68. http://dx.doi.org/10.1051/0004-6361/201732340.

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Abstract (sommario):

Red giants in the updated APOGEE-Kepler catalogue, with estimates of mass, chemical composition, surface gravity and effective temperature, have recently challenged stellar models computed under the standard assumption of solar calibrated mixing length. In this work, we critically reanalyse this sample of red giants, adopting our own stellar model calculations. Contrary to previous results, we find that the disagreement between the Teff scale of red giants and models with solar calibrated mixing length disappears when considering our models and the APOGEE-Kepler stars with scaled solar metal distribution. However, a discrepancy shows up when α-enhanced stars are included in the sample. We have found that assuming mass, chemical composition and effective temperature scale of the APOGEE-Kepler catalogue, stellar models generally underpredict the change of temperature of red giants caused by α-element enhancements at fixed [Fe/H]. A second important conclusion is that the choice of the outer boundary conditions employed in model calculations is critical. Effective temperature differences (metallicity dependent) between models with solar calibrated mixing length and observations appear for some choices of the boundary conditions, but this is not a general result.

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Absi, Rafik, Hitoshi Tanaka, Loreline Kerlidou e Alicia André. "EDDY VISCOSITY PROFILES FOR WAVE BOUNDARY LAYERS: VALIDATION AND CALIBRATION BY A k-ω MODEL". Coastal Engineering Proceedings 1, n. 33 (14 dicembre 2012): 63. http://dx.doi.org/10.9753/icce.v33.waves.63.

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Eddy viscosity in wave boundary layers is a key parameter in coastal engineering. Two analytical eddy viscosity profiles present a particular interest for practical applications: the parabolic-uniform profile (Myrhaug 1982, van Rijn 1993, Liu and Sato 2006) and the exponential-linear profile (Gelfenbaum and Smith 1986, Beach and Sternberg 1988, Hsu and Jan 1998, Absi 2010). The aim of our study is to assess and validate these two profiles by: (1) investigation of eddy viscosity in steady fully developed plane channel flow; (2) comparisons with numerical results of the two equation baseline (BSL) k-ω model (Menter 1994, Suntoyo and Tanaka 2009). Our study shows that these two profiles are able to describe the eddy viscosity distribution in the wave bottom boundary layer but for different wave conditions given by the parameter am/ks, where am is the wave orbital amplitude and ks the equivalent roughness. The exponential-linear profile is adequate for am/ks

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Meshkovsky, Vitaly, Anatoly Sdobnikov, Sergey Churilin e Yuri Kisanov. "Numerical investigations of shape of the reflecting surface made of knitted mesh fabric being pulled on the curvilinear frame". EPJ Web of Conferences 221 (2019): 01031. http://dx.doi.org/10.1051/epjconf/201922101031.

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This paper presents the surface shaping numerical investigations results of truss space constructions mesh reflectors, such as antennas and calibration and adjustment satellites. Shape-generating structure of mentioned constructions adds up to set of triangular facets, made in the form of spatio-curvilinear bar frames, bearing reflecting knitted mesh fabric pulled on it. This work proposes the algorithm of calculation of step-by-step reflecting mesh pulling on the bearing frame’s bars process, using finite elements method. Numerical execution of the developed algorithm involves for resolving the linear elasticity theory first-type boundary value problem, which implies integration of elastic body equilibrium equations without taking into account mass forces when kinematic boundary conditions are given. Analyzing when having done numerical calculations, it's possible to determine what grade obtained shapes of reflecting surfaces are precise with, and to find possible for developing variants of the antenna structure, which would allow to obtain the reflector surface shape with required accuracy by using flexible cables as a part of shape-generating structure. Comparing results of numerical investigations with experimental data received using full-scaled model of spherical calibration and adjustment satellite shows satisfactory qualitative and quantitative matching of both results.

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Langston, L. S., e R. G. Kasper. "Analysis of an Electromagnetic Boundary Layer Probe for Low Magnetic Reynolds Number Flows". Journal of Fluids Engineering 115, n. 4 (1 dicembre 1993): 726–31. http://dx.doi.org/10.1115/1.2910205.

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Electromagnetic (EM) flow meters are used to measure volume flow rates of electrically conductive fluids (e.g., low magnetic Reynolds number flows of seawater, milk, etc.) in pipe flows. The possibility of using a modified form of EM flow meter to nonobtrusively measure boundary-layer flow characteristics is analytically investigated in this paper. The device, named an electromagnetic boundary layer (EBL) probe, would have a velocity integral-dependent voltage induced between parallel wall-mounted electrodes, as a conductive fluid flows over a dielectric wall and through the probe’s magnetic field. The Shercliff-Bevir integral equation, taken from EM flow meter theory and design, is used as the basis of the analytical model for predicting EBL probe voltage outputs, given a specified probe geometry and boundary layer flow conditions. Predictions are made of the effective range of the nonobtrusive EBL probe in terms of electrode dimensions, the magnetic field size and strength, and boundary layer velocity profile and thickness. The analysis gives expected voltage calibration curves and shows that an array of paired electrodes would be a beneficial feature for probe design. A key result is that the EBL probe becomes a displacement thickness meter, if operated under certain conditions. That is, the output voltage was found to be directly proportional to the boundary layer displacement thickness, δ1, for a given free stream velocity.

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Medina-Cetina, Zenon, Ahran Song, Yichuan Zhu, Alma Rosa Pineda-Contreras e Amy Rechenmacher. "Global and Local Deformation Effects of Dry Vacuum-Consolidated Triaxial Compression Tests on Sand Specimens: Making a Database Available for the Calibration and Development of Forward Models". Materials 15, n. 4 (18 febbraio 2022): 1528. http://dx.doi.org/10.3390/ma15041528.

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Abstract (sommario):

A comprehensive experimental database containing results of a series of dry vacuum-consolidated triaxial compression tests was populated. The tests were performed on sand specimens and conducted under similar experimental conditions, in which specimens’ boundary deformation was captured using a three-dimensional digital image correlation analysis (3D-DIC). The use of a standard triaxial device along with the 3D-DIC technology allowed the specimens’ global and local boundary displacement fields to be computed from start to end of the compression phase. By repeating each test under the same experimental conditions and building the specimens using the same type of sand, the boundary deformation patterns could be identified, and the statistics associated with both global and local displacement fields could be assessed. Making this experimental database available to others should serve to calibrate as well as develop new forward models to account for effects associated with the specimens’ local displacements and material heterogeneity and include statistics to represent a specimen’s random response. Moreover, this work will serve as a basis for the statistical characterization of spatio-temporal boundary localization effects used to develop stochastic models and machine-learning models, and simulate virtual triaxial tests.

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Zanchi, Barbara, Matteo Zucchi e Alessio Radice. "On the Relationship between Experimental and Numerical Modelling of Gravel-Bed Channel Aggradation". Hydrology 6, n. 1 (15 gennaio 2019): 9. http://dx.doi.org/10.3390/hydrology6010009.

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This communication explores the use of numerical modelling to simulate the hydro-morphologic response of a laboratory flume subject to sediment overloading. The numerical model calibration was performed by introducing a multiplicative factor in the Meyer–Peter and Müller transport formula, in order to achieve a correspondence with the bed and water profiles recorded during a test carried out under a subcritical flow regime. The model was validated using a second subcritical test, and then run to simulate an experiment during which morphological changes made the water regime switch from subcritical to supercritical. The “relationship” between physical and numerical modelling was explored in terms of how the boundary conditions for the two approaches had to be set. Results showed that, even though the first two experiments were reproduced well, the third one could not be modeled adequately. This was explained considering that, after the switch of the flow regime, some of the boundary conditions posed into the numerical model turned out to be misplaced, while others were lacking. The numerical modelling of hydro-morphologic processes where the flow regime is trans-critical in time requires particular care in the position of the boundary conditions, accounting for the instant at which the water regime changes.

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Nitschke-Pagel, Thomas, Klaus Dilger e Hamdollah Eslami-Chalandar. "Determination of Residual Stresses in Welded Structural Steels with Help of Micromagnetic Measurements". Materials Science Forum 681 (marzo 2011): 194–201. http://dx.doi.org/10.4028/www.scientific.net/msf.681.194.

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Abstract (sommario):

The micromagnetic measurement method is a fast and easy to handle alternative for the determination of residual stresses in steel welds. The accuracy is lower in comparison to diffraction techniques but it can be applied faster and under rough conditions however connected with a lower accuracy. Experimental results of investigations with different steel welds show that the method requires an external calibration and the consideration of particular boundary conditions as well as certain limitations must be accepted. Then the method is a good alternative or more a complementary measurement methods which helps to reduce the effort for the analysis of residual stresses in welded components.

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Caprioli, M., L. Delombaerde, M. De Saint-Hubert, L. de Freitas Nascimento, S. S. Galvez Febles, K. Himschoot, B. van der Heyden et al. "Fading correction for calibration of a novel 2D OSL-film dosimeter". Journal of Physics: Conference Series 2630, n. 1 (1 novembre 2023): 012029. http://dx.doi.org/10.1088/1742-6596/2630/1/012029.

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Abstract (sommario):

Abstract A new film dosimeter based on optically stimulated luminescence (OSL) was calibrated for high-resolution 2D dosimetry in the context of radiotherapy patient-specific quality assurance (PSQA). The OSL-film signal is linear with the dose and decays with time, in a process called fading. Two models were proposed to characterize the fading: (1) a linear model independent from the delivery and of practical use thanks to the straightforward signal-to-dose conversion, and (2) a delivery-dependent model, to investigate whether a more simplified model may be sufficient to accurately determine the fading independently from the specific-irradiation conditions. The models were used in a nonlinear regression over an experimental dataset acquired with a 6MV photon beam in standard calibration settings. Both models were accurate and showed an adjusted-R 2 of 0.98 (1) and 0.99 (2). The residual analysis on both models allowed to define the minimum scanning time to have a discrepancies between the models <1%. Under this condition the OSL fading can be assumed independent on the irradiation parameters. As a consequence, within these boundary conditions, the linear model can be used for the OSL-film calibration.

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