3D B-Rep meshing for real-time data-based geometric parametric analysis

This paper presents an effective framework to automatically construct 3D quadrilateral meshes of complicated geometry and arbitrary topology adapted for parametric studies. The input is a triangulation of the solid 3D model’s boundary provided from B-Rep CAD models or scanned geometry. The triangulated mesh is decomposed into a set of cuboids in two steps: pants decomposition and cuboid decomposition. This workflow includes an integration of a geometry-feature-aware pants-to-cuboids decomposition algorithm. This set of cuboids perfectly replicates the input surface topology. Using aligned global parameterization, patches are re-positioned on the surface in a way to achieve low overall distortion, and alignment to principal curvature directions and sharp features. Based on the cuboid decomposition and global parameterization, a 3D quadrilateral mesh is extracted. For different parametric instances with the same topology but different geometries, the MEG-IsoQuad method allows to have the same representation: isotopological meshes holding the same connectivity where each point on a mesh has an analogous one into all other meshes. Faithful 3D numerical charts of parametric geometries are then built using standard data-based techniques. Geometries are then evaluated in real-time. The efficiency and the robustness of the proposed approach are illustrated through a few parametric examples.

Implementation of the RCIP scheme and its performance for 1-D age computations in ice-sheet models

Ice-sheet age computations are formulated using an Eulerian advection equation, and there are many schemes that can be used to solve them numerically. Typically, these differ in numerical characteristics such as stability, accuracy, and diffusivity. Furthermore, although various methods have been presented for ice-sheet age computations, the constrained interpolation profile method and its variants have not been examined in this context. The present study introduces one of its variants, a rational function-based constrained interpolation profile (RCIP) scheme, to one-dimensional ice age computation and demonstrates its performance levels via comparisons with those obtained from first- and second-order upwind schemes. Our results show that the RCIP scheme preserves the pattern of input surface mass balance histories in terms of the vertical profile of internal annual layer thickness better than the other schemes.

The Karakoram Predicament

<p>The anomalous behaviour of Karakoram Glaciers (Hewitt, 2005) in the backdrop of a warming planet has been a decade long debate baffling climatologists worldwide. While a lot of effort has been given to understand this behaviour, very little has been explored with respect to the factors that favour glaciation rates. A fundamental approach to glacial mass budget calculation involves a simplistic assessment of accumulation and melt. Analysis of meteorological datasets over the last 40 years yields conflicting scenarios. On one hand, we have observed a significant negative trend in winter rainfall and snowfall amount coupled with increasing surface temperatures and vertical mixing of atmospheric vapour. On the other hand, parameters that reflect the bulk of a cryospheric reservoir such as snow depth, dry snow/wet snow percentages show stable to increasing trend. Between lower moisture input and potential ablation rates, the steady-state nature of Karakoram glaciers have emulated optimism in the works of climatologists worldwide. In this study, we have tried to formulate an ‘accumulation index’ as a function of moisture input, surface temperature and atmospheric vertical circulation. Precipitation trends are negative yet periodic which suffices a positive accumulation rate. At the same time, local factors such as debris field and wet snow cover area help preserve the accumulated bulk of a given winter through the upcoming warm summers. However, in a potentially warming planet, accumulation rates aren't proportional to ambient temperature. Studies show that the mass balance turns sharply negative at temperatures above -10 °C due to accelerated ablation which overcompensates accumulation. This makes the Karakoram phenomenon a function of global meteorology rather than local factors i.e. debris cover, vorticity, etc. Therefore, we suggest that the Karakoram Glaciers aren’t behaving anomalously, but lagging in phase with central and eastern Himalayan glaciated regions.</p>

Implementation of RCIP scheme and its performance for 1D age computations in ice-sheet models

Ice sheet age computations are formulated using an Eulerian advection equation, and there are many schemes that can be used to solve them numerically. Typically, these differ in numerical characteristics such as stability, accuracy, and diffusivity. Furthermore, although various methods have been presented for ice sheet age computations, the constrained interpolation profile method and its variants have not been examined in this context. The present study introduces one of its variants, a rational function-based constrained interpolation profile scheme (RCIP) to one-dimensional ice age computation, and demonstrates its performance levels via comparisons with those obtained from first- and second-order upwind schemes. Our results show that the RCIP scheme preserves the pattern of input surface mass balance histories, in terms of the vertical profile of internal annual layer thickness, better than the other schemes.

Validity and informativity enhancement of ultrasonic testing of cast parts of railway rolling stock

Introduction. Due to the process reasons, the structure of cast parts of the railway rolling stock (RRS) often has embedded flaws that affect drastically their strength. The degree of impact depends on many factors including the shape and location of defects in the product. The shape of the defect has the greatest effect under alternating loads. This often refers to dynamically loaded parts of the RRS underframe. The defect oriented perpendicularly to the direction of tensile loads reduces the component life to the maximum. To identify embedded flaws, the parts are subjected to ultrasonic testing by the classical pulse-echo technique. However, such methods require increased validity and informativity. For example, they do not provide the determination of the type and orientation of the defect. Materials and Methods. Features, advantages and disadvantages of the classical pulse-echo technique of the ultrasonic non-destructive testing, which is based on the registration of the following echo signals, are considered: sent; reflected from the opposite surface (bottom) of the object; reflected from the defect (if any). The pulse arrival time is proportional to the thickness of the part. If there is a defect, this time is proportional to the distance from the pulse input surface to the defect. This method can determine the presence of a defect, but it cannot determine its type. Research Results. To determine the shape of a defect, a dualfrequency defectometry method is proposed. Its principle, algorithm and implemented analytical dependencies are described. When an echo signal from a defect is detected in the monitoring object, the amplitudes of the bottom signals and the amplitudes of the echo signals from the defect are measured at the ultrasonic wave frequencies of 2.5 MHz and 5.0 MHz. The defect shape factor is calculated from the analytical dependence; and the type of defect is determined. It can be volume (pores, shells, non-metallic inclusions) or planar (cracks, segregations, etc.). Discussion and Conclusions. A dual-frequency defectometry method to determine the type of defect under the manual ultrasonic testing of the RRS cast parts is proposed in the paper. For an express automated use of the proposed method, the software product NDTRT-07.04-L is developed, and its operation algorithm is described. The application of the technique can increase the validity and informativity of the test results

Geoinformation modeling of potential productivity in agricultural landscapes for the formation of sustainable land use

The work is devoted to geoinformation modeling of potential and really possible yield of leading agricultural crops in the agricultural landscapes of the Simferopol region of the Republic of Crimea. The study area is characterized by high agricultural development, complicated physical and geographical location and insufficient moisture. Algorithm for geoinformation modeling of potential and really possible crop yields by the amount of arrival of photosynthetically active radiation for each point of input surface is considered. The resulting cartogram of averaged values deviation of potential and really possible yields from actual for leading agricultural crops can be used in the development of scientifically based recommendations for transformation of agricultural lands in complicated physical and geographical conditions.

A geometry-dependent surface Lambertian-equivalent reflectivity product for UV–Vis retrievals – Part 1: Evaluation over land surfaces using measurements from OMI at 466 nm

The anisotropy of the Earth's surface reflection has implications for satellite-based retrieval algorithms that utilize climatological surface reflectivity databases that do not depend upon the observation geometry. This is the case for most of the current ultraviolet and visible (UV–Vis) cloud, aerosol, and trace-gas algorithms. The illumination–observation dependence of surface reflection is described by the bidirectional reflectance distribution function (BRDF). To account for the BRDF effect, we use the concept of geometry-dependent surface Lambertian-equivalent reflectivity (GLER), which is derived from the top-of-atmosphere (TOA) radiance computed with Rayleigh scattering and surface BRDF for the exact geometry of a satellite-based pixel. We present details on the implementation of land and water surface BRDF models, and we evaluate our GLER product over land surfaces using observed Sun-normalized radiances at 466 nm. The input surface BRDF parameters for computing TOA radiance are derived from Moderate Resolution Imaging Spectroradiometer (MODIS) satellite observations. The observed TOA radiance for comparison is from the Ozone Monitoring Instrument (OMI). The comparison shows good agreement between observed and calculated OMI reflectivity in 2006 in typical geographical regions, with correlation coefficients greater than 0.8 for some regions. Seasonal variations of clear-sky OMI reflectivity (i.e., with minimum clouds and aerosols) closely follow those computed using MODIS-derived GLER over land. GLER also captures the cross-track dependence of OMI-derived LER, though the latter is slightly higher than the former presumably owing to residual cloud and aerosol (nonabsorbing) contamination, particularly over dark surfaces (heavily vegetated regions such as mixed forest, croplands, and grasslands). Calibration differences between OMI and MODIS may also be responsible for some of this bias. The standard OMI climatological surface reflectivity database predicts higher radiances than GLER and OMI observations with different seasonal variation over most regions and does not have any angular-dependent variation. Overall, our evaluation demonstrates that the GLER product adequately accounts for surface BRDF effects while at the same time simplifying the surface BRDF implementation within the existing OMI retrieval infrastructure; use of our GLER product requires changes only to the input surface reflectivity database.

Peak Flows and Stormwater Networks Design—Current and Future Management of Urban Surface Watersheds

Stormwater urban drainage systems are typically designed in open channel flow. Pipe sewers must have enough capacity to transport maximum design flows for a given frequency of the project rainfall. The classic rational method or related procedures that are based on rational approaches are still currently used to a great extent, particularly for small urban drainage basins, and the pipes are frequently designed in uniform steady flow. Numerical integration of Saint-Venant equations for one-dimensional gradually varied unsteady flow allows the computation of waves’ progression along the pipes for given input surface hydrographs. This paper presents a comprehensive, systematic, simple, and original comparison between the peak flows that are achieved through simulation in unsteady flow using an implicit complete dynamic model, developed in the Laboratory of Hydraulics, Water Resources and Environment of Coimbra University, and those that are obtained with the classic rational method along urban drainage networks. Boundary conditions and some approximations typically considered in the methodologies are analyzed in detail. Classic rational approaches may underestimate the peak and design flows. Practical recommendations for the system design phase when rational approaches are used are also proposed. The need for indispensable requirements for suitable urbanization rules, intelligent management of surface runoff in urban basins, and control measures for the reduction of peak flows entering existing networks is confirmed and reinforced.