133 research outputs found
Exact closed-form expressions for the complete RTM correction
No full textWe present exact, closed-form expressions for the complete RTM correction and the harmonic correction to disturbing potential, gravity disturbance, gravity anomaly, and height anomaly. They need to be applied in quasi-geoid modelling whenever data points are buried inside the masses after residual terrain model (RTM) reduction and analytically downward-continued functionals of the disturbing potential at the original locations of the data points are required. Compared to recent work of the authors published in this journal, no Taylor series enter the expressions and numerical instabilities of the harmonic downward continuation from the RTM surface to the Earth’s surface are avoided as are inaccuracies in the free-air upward continuation from the Earth’s surface to the RTM surface caused by a lack of precise information about higher-order derivatives of the disturbing potential. The new expressions can easily be implemented in any existing RTM software package and do not require additional computational resources. For two test areas located in western Norway and the Auvergne in France, we compute the complete RTM correction and the harmonic correction to the afore-mentioned functionals of the disturbing potential. Overall, all harmonic corrections are non-negative with maximum values of 1.54 m 2/ s 2, 263.0 μ Gal, 263.9 μ Gal, and 15.7 m (Norway) and 1.55 m 2/ s 2, 263.3 μ Gal, 263.3 μ Gal, and 15.8 cm (Auvergne) for disturbing potential, gravity disturbance, gravity anomaly, and height anomaly, respectively. The medians are 0.02 m 2/ s 2, 33.6 μ Gal, 33.7 μ Gal, and 0.3 cm (Norway) and 0.01 m 2/ s 2, 19.2 μ Gal, 19.2 μ Gal, and 0.1 cm (Auvergne). We also show that the nth Taylor polynomials used in the recent work of the authors published in this journal may have large remainders depending on the topography in the vicinity of the evaluation point no matter how n is chosen. Finally, we show that the commonly used expression for the harmonic correction to gravity anomaly introduced in 1981 is almost exact, though it was derived along a completely different line of reasoning. The errors do not exceed 49 μ Gal in both test areas. Moreover, the errors have a negligible impact on the computed height anomalies in one-centimetre quasi-geoid modelling, as the mean error does not exceed a few μ Gal in both test areas.Physical and Space Geodes
The RTM harmonic correction revisited
No full textIn this paper, we derive improved expressions for the harmonic correction to gravity and, for the first time, expressions for the harmonic correction to potential and height anomaly. They need to be applied at stations buried inside the masses to transform internal values into harmonically downward continued values, which are then input to local quasi-geoid modelling using least-squares collocation or least-squares techniques in combination with the remove-compute-restore approach. Harmonic corrections to potential and height anomaly were assumed to be negligible so far resulting in yet unknown quasi-geoid model errors. The improved expressions for the harmonic correction to gravity, and the new expressions for the harmonic correction to potential and height anomaly are used to quantify the approximation errors of the commonly used harmonic correction to gravity and to quantify the magnitude of the harmonic correction to potential and height anomaly. This is done for two test areas with different topographic regimes. One comprises parts of Norway and the North Atlantic where the presence of deep, long, and narrow fjords suggest extreme values for the harmonic correction to potential and height anomaly and corresponding large errors of the commonly used approximation of the harmonic correction to gravity. The other one is located in the Auvergne test area with a moderate topography comprising both flat and hilly areas and therefore may be representative for many areas around the world. For both test areas, two RTM surfaces with different smoothness are computed simulating the use of a medium-resolution and an ultra-high-resolution reference gravity field, respectively. We show that the errors of the commonly used harmonic correction to gravity may be as large as the harmonic correction itself and attain peak values in areas of strong topographic variations of about 100 mGal. Moreover, we show that this correction may introduce long-wavelength biases in the computed quasi-geoid model. Furthermore, we show that the harmonic correction to height anomaly can attain values on the order of a decimetre at some points. Overall, however, the harmonic correction to height anomaly needs to be applied only in areas of strong topographic variations. In flat or hilly areas, it is mostly smaller than one centimetre. Finally, we show that the harmonic corrections increase with increasing smoothness of the RTM surface, which suggests to use a RTM surface with a spatial resolution comparable to the finest scales which can be resolved by the data rather than depending on the resolution of the global geopotential model used to reduce the data.Physical and Space Geodes
The Prediction of Multi-scale Voids and Their Mechanical Effect on Thick Composite Structures Manufactured by RTM
No full textThick composite laminates can be used in aerospace and automotive industry replacing metals for weight saving.Increasing the thickness can bring more defects, like voids.This master thesis focuses on the multi-scale voids prediction and their mechanical effect simulation of thick composite laminates manufacturing by \ac{RTM}.It could be potentially used in safe design of thick composite components.The main objective of the thesis work is to analyze the effect of multi-scale voids caused by the filling process on mechanical properties of thick composite laminates. First is using PAM-RTM to simulate the locations of voids and their percentage.Then, the material properties of each \ac{MVE} with different micro and macro voids are evaluated by Digimat at micro and meso scales.After that, the macro-scale material properties of the thick laminates are simulated in ABAQUS.%This simulation process is reliable after verifying with the results of a literature.The simulation processes are verified by using the parameters from the literature and then comparing with the published results.The simulation from PAM-RTM indicates the average void percentage of the whole laminate reduces with the increasing injection pressure or permeabilities.The total void volume increases with an increasing laminate thickness but the average void volume does not change with the changing thickness.The result of this thesis suggests that the effect of multi-scale voids on material properties (i.e., Young's modulus, Poisson's ratio, and Shear modulus) does not change due to an increasing thickness.The writing presents the actions taken in order to achieve the objective of the research successfully.Aerospace Engineerin
RTM user's guide
No full textRTM is a FORTRAN '77 computer code which simulates the infiltration of textile reinforcements and the kinetics of thermosetting polymer resin systems. The computer code is based on the process simulation model developed by the author. The compaction of dry, woven textile composites is simulated to describe the increase in fiber volume fraction with increasing compaction pressure. Infiltration is assumed to follow D'Arcy's law for Newtonian viscous fluids. The chemical changes which occur in the resin during processing are simulated with a thermo-kinetics model. The computer code is discussed on the basis of the required input data, output files and some comments on how to interpret the results. An example problem is solved and a complete listing is included
RTM: Interactive estimation tool for modelling real-time wind speed
No full text
Abstract
Renewable energy sources have been become important in the whole world along with the rapid depletion of energy
resources. Potential of the wind energy, one of the most important renewable energy sources, in any region can be estimated
using the statistical methods. For modelling, various distributions were used the wind speed data in the related modelling
literature. Moreover, in the literature, fitting these distributions was performed via static data. Distributions must be
dynamically adapted as the wind speed changes over time. The Real- Time Modelling (RTM) tool is proposed to determine
the most appropriate distribution of real-time wind speed in this study. The developed RTM tool for modelling real-time wind
speed model can determine the best distribution according to some evaluation criteria. This study show that the developed
RTM tool work effectively and efficiently in the real-time wind speed data.
Editor: H. Kemal İlter, Ankara Yıldırım Beyazıt University, Turkey
Received: August 19, 2018, Accepted: October 18, 2018, Published: November 10, 2018
Copyright: © 2018 IMISC Özsoy et al. This is an open-access article distributed under the terms of the Creative Commons
Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author
and source are credited.
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Time and distribution: a model of ape biogeography
No full textWe use data from 20 chimpanzee, bonobo and gorilla study sites to develop an African great ape time budgets model to predict the animals' capacity to survive in a range of habitats across sub-Saharan Africa. The model uses body mass and climatic data to predict the time animals must allocate to key activities (feeding, moving, resting and social interaction), and then uses these to assess the limiting group size that could be sustained in a particular habitat. The model is robust against changes in minimum cut-off values, and predicts the current biogeographic distributions of the two African ape species remarkably well. Predicted group sizes for Pan and Gorilla are close to observed averages. The model also indicates that moving time plays a crucial role for both Pan and Gorilla site presence: i.e. at sites where they are absent it is primarily moving time that is increased as compared to other time budget variables. Finally, the model demonstrates that Pan and Gorilla distributions and group sizes can be accurately modelled by simply modifying the body mass variable, indicating that both share a similar underlying ecological bauplan
Detection of Hidden Cracks in Concrete Structures Using Reverse Time Migration of Ultrasonic Echo Data
No full textUltrasonic echo measurements are widely used in the field of non-destructive testing (NDT). In civil engineering, concrete structures are evaluated by this technique. Currently, Synthetic Aperture Focusing Technique (SAFT), a group of migration algorithms, is state of the art in ultrasonic data processing. Reverse Time Migration (RTM), recently introduced to NDT, shows significant improvements in mapping complex structures, like vertical steps. Modelling a concrete test specimen, synthetic experiments confirm that RTM can be used to map notches and crack-like structures in concrete. With introducing heterogeneous synthetic models, the influence of the migration velocity of RTM was investigated. Furthermore experiments on real concrete structures were conducted. Thereby ultrasonic echo data is acquired on a test specimen with a known vertical notch. A commercial ultrasonic tomograph and a scanner system, developed at BAM, are used. The data from both systems is processed using SAFT and compared to results of RTM of the scanner data. Results from the SAFT migration do not reveal any information about the vertical notch, other than an indication of the lateral position. Data migrated using RTM shows the side wall of the notch and affirms its potential for such purposes. Processing the data from the commercial ultrasonic device using RTM does not show any improvements compared to the initial SAFT result. The fixed aperture of the device is not suitable for RTM. An additional measurement is performed on a second specimen using the scanner system. The specimen shows several fine cracks of which only outcrops at the sides are visible. Results of RTM indicate mapped signatures from those cracks. Their lateral positions along the specimen as well as an estimate about the crack height can be determined within the final images. This study thereby introduces the applicability of RTM for detecting cracks within concrete structures.Civil Engineering and GeosciencesGeoscience & EngineeringIDEA Leagu
Modular RT-Motion USB
No full textDuring the course of this thesis, RTM-USB (Real Time Motion on Universal Serial Bus) has grown from a single board motor controller to a motion control platform. The original RTM-USB board, containing a CPU and two motor drivers, has been extended (hardware wise) with a network/bus interface which makes it easy to expand the hardware functionality of the platform. Research has been undertaken in order to see which hardware extensions would be interesting for implementation on this platform. In order to demonstrate the usability of the proposed modular concept a few extension modules are implemented in hardware and the software needed to connect these extension modules to the original RTM-USB board has been written. Additionally, FPGA applications for motion control have been studied. In parallel with this thesis there was a parallel activity, which made the original RTM-USB software more extendable. Both projects and the original RTM-USB hardware and software, compose the new RTM-USB platform.Computer EngineeringComputer EngineeringElectrical Engineering, Mathematics and Computer Scienc
Evaluation of sensor technologies for on-line raw material characterization in “Reiche Zeche” underground mine - outcomes of RTM implementation
No full textThe increasing advances in sensor technology have resulted in greater availability of sensor data for a wide range of applications. One such application is raw material characterization in mining operations. Sensor technologies operate over certain range of the electromagnetic spectrum and provide information on several aspects of material properties. The sensitivity and the material properties the instrument detects and measures varies from sensor to sensor. The purpose of this study was to synthesize and evaluate the use of sensor technologies for characterization of a polymetallic sulphide deposit in “Reiche Zeche” underground mine. This paper discusses the material characterization methodology using sensor technologies, demonstrates how it fits within the Real-Time Mining (RTM) framework, identifies the interface for both software and hardware requirements and defines the gaps and limitations of application of sensors. It provides a brief overview of the use of sensor and data fusion for material characterization to convey a high-level context in raw material characterization. The sensor technologies considered in this study include RGB imaging, visible–near infrared (VNIR), short wave infrared (SWIR), mid-wave infrared (MWIR), long-wave infrared (LWIR) and Raman spectroscopy.The required information from sensor data in mining operations is not limited to grade control applications. Information on co-occurring minerals or elements are also important for definition of requirements in mineral processing, to identify indirect proxies of elements/minerals of interest, to understand the formation of minerals, to define requirements for blasting parameters, to improve safety and to define requirements for environmental monitoring of toxic material. In view of these points, there is a need for combinations of sensors to achieve a near complete description of material composition and properties. The methodological approaches developed for information extraction from each sensor data and fused data are presented. This includes both direct mineral fingerprinting and indirect proxies using spectral data. The efficient sensor data processing methods and the acquired results from the use of individual sensor and the fused data are summarized. Overall, the acquired results from the use of each sensor technology and the data fusion approach significantly contributed to an improvement of data quality and illustrate the efficiency of use of sensors in the mining industry. However, some of the observed limitations include lack of system robustness, a need for test case specific mineral libraries, the need for development of an integrated principled tool for efficient data collection, processing and knowledge generation. Going forward, automated material characterization is possible with robust system design (exemplified by portable and ruggedized system) and efficient software (test case specific mineral libraries) that can be developed using a combined sensor signal.Resource Engineerin
A Runtime Testability Metric for Dynamic High-Availability Component-based Systems
No full textRuntime testing is emerging as the solution for the integration and assessment of highly dynamic, high availability software systems where traditional development-time integration testing cannot be performed. A prerequisite for runtime testing is the knowledge about to which extent the system can be tested safely while it is operational, i.e., the system’s runtime testability. This article evaluates Runtime Testability Metric (RTM), a cost-based metric for estimating runtime testability. It is used to assist system engineers in directing the implementation of remedial measures, by providing an action plan which considers the trade-off between testability and cost. We perform a theoretical and empirical validation of RTM, showing that RTM is indeed a valid, and reasonably accurate measurement with ratio scale. Two testability case studies are performed on two different component-based systems, assessing RTM’s ability to identify runtime testability problems.Software Computer TechnologyElectrical Engineering, Mathematics and Computer Scienc
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