In this paper, we analyze a multiscale operator splitting method for solving systems of ordinary differential equations such as those that result upon space discretization of a reactiondiffusion ...equation. Our goal is to analyze and accurately estimate the error of the numerical solution, including the effects of any instabilities that can result from multiscale operator splitting. We present both an a priori error analysis and a new type of hybrid a priori-a posteriori error analysis for an operator splitting discontinuous Galerkin finite element method. Both analyses clearly distinguish between the effects of the operator splitting and the discretization of each component of the decomposed problem. The hybrid analysis has the form of a computable a posteriori leading order expression and a provably higher order a priori expression. The hybrid analysis takes into account the fact that the adjoint problems for the original problem and a multiscale operator splitting discretization differ in significant ways. In particular, this provides the means to monitor global instabilities that can arise from operator splitting.
In this study we present numerical experiments of time integration methods applied to systems of reaction–diffusion equations. Our main interest is in evaluating the relative accuracy and asymptotic ...order of accuracy of the methods on problems which exhibit an approximate balance between the competing component time scales. Nearly balanced systems can produce a significant coupling of the physical mechanisms and introduce a slow dynamical time scale of interest. These problems provide a challenging test for this evaluation and tend to reveal subtle differences between the various methods. The methods we consider include first- and second-order semi-implicit, fully implicit, and operator-splitting techniques. The test problems include a prototype propagating nonlinear reaction–diffusion wave, a non-equilibrium radiation–diffusion system, a Brusselator chemical dynamics system and a blow-up example. In this evaluation we demonstrate a “split personality” for the operator-splitting methods that we consider. While operator-splitting methods often obtain very good accuracy, they can also manifest a serious degradation in accuracy due to stability problems.
In this paper numerical results are reviewed D.L. Ropp, J.N. Shadid, C.C. Ober, Studies of the accuracy of time integration methods for reaction-diffusion equations, J. Comput. Phys. 194 (2) (2004) ...544–574 that demonstrate that common second-order operator-splitting methods can exhibit instabilities when integrating the Brusselator equations out to moderate times of about seven periods of oscillation. These instabilities are manifested as high wave number spatial errors. In this paper, we further analyze this problem, and present a theorem for stability of operator-splitting methods applied to linear reaction-diffusion equations with indefinite reaction terms which controls both low and high wave number instabilities. A corollary shows that if L-stable methods are used for the diffusion term the high wave number instability will be controlled more easily. In the absence of L-stability, an additional time step condition that suppresses the high wave number modes appears to guarantee convergence at the asymptotic order for the operator-splitting method. Numerical results for a model problem confirm this theory, and results for the Brusselator problem agree as well.
The interaction of an idealized easterly wave with an orographic feature representing the Sierra Madre of Mexico and a large-scale, meridionally sheared zonal flow representing the ITCZ in the ...eastern North Pacific is examined through numerical integration of the shallow water equations on an equatorial beta-plane channel. The model simulations show that as a wave approaches the orography from the east, the relative vorticity in the lee increases due to the wave being modified by the orography. This relative vorticity maximum increases the northward advection of the ITCZ in the lee of the mountain that occurs due to the influence of the mountain anticyclone. The result of this interaction is the development of a localized region of enhanced cyclonic vorticity that moves parallel to the contours of the model orography. There is a minimal increase in the amplitude of the vorticity occuring during interactions between the wave and orography, ITCZ and orography, and wave and ITCZ. The position of the incident wave upstream of the orography at the time that the disturbance in the lee begins to develop and the subsequent motion of the leeside vorticity maximum are in agreement with an observed case of eastern Pacific tropical cyclogenesis, which is also presented.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Objective: This study compared learning and skill transfer among university aviation students using interactive Augmented Reality (AR) technology versus traditional paper-based instruction. While ...similar AR use and research in university education exists, this study piloted a comparative method assessing knowledge retention and transfer.
Background: AR technology is a popular tool used in technical education. But learner behaviors observed like game play and exploration during this study could impact future learning strategy design as AR use increases.
Method: 36 university undergraduate students enrolled in a university aeronautical engineering technology program were divided into AR and paper-based groups and compared on first-time task execution times for starting an aircraft auxiliary power unit (APU). A two-sample Kolmogorov-Smirnov test comparing times for task completion was used.
Results: Learner task times using AR were consistently faster, replicating similar AR studies, compared to learners using paper-based. However, AR test subjects also took longer interacting with the technology, including gaming-style "play" and exploration of the digital twin AR flight deck environment. This is believed to enhance learner innovation, knowledge retention and transfer, warranting further study.
Conclusion: AR users had significantly reduced task execution times. Pre-task "gamification and play" were also observed among the AR users, which could impact how educators and the industry assess and leverage learning strategies when using AR for job task training.
Celotno besedilo
Dostopno za:
BFBNIB, DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Several fundamental requirements must be met so that NMR-based metabolomics and the related technique of metabonomics can be formally adopted into environmental monitoring and chemical risk ...assessment. Here we report an intercomparison exercise which has evaluated the effectiveness of 1H NMR metabolomics to generate comparable data sets from environmentally derived samples. It focuses on laboratory practice that follows sample collection and metabolite extraction, specifically the final stages of sample preparation, NMR data collection (500, 600, and 800 MHz), data processing, and multivariate analysis. Seven laboratories have participated from the U.S.A., Canada, U.K., and Australia, generating a total of ten data sets. Phase 1 comprised the analysis of synthetic metabolite mixtures, while Phase 2 investigated European flounder (Platichthys flesus) liver extracts from clean and contaminated sites. Overall, the comparability of data sets from the participating laboratories was good. Principal components analyses (PCA) of the individual data sets yielded ten highly similar scores plots for the synthetic mixtures, with a comparable result for the liver extracts. Furthermore, the same metabolic biomarkers that discriminated fish from clean and contaminated sites were discovered by all the laboratories. PCA of the combined data sets showed excellent clustering of the multiple analyses. These results demonstrate that NMR-based metabolomics can generate data that are sufficiently comparable between laboratories to support its continued evaluation for regulatory environmental studies.
When performing daily maintenance and repair tasks, technicians require access to a variety of technical diagrams. As technicians trace components and diagrams from page‐to‐page, within and across ...manuals, the contextual information of the components they are analyzing can easily be lost. To overcome these issues, we have developed a Schematic Diagram Visualization System (SDViz) designed for maintaining and highlighting contextual information in technical documents, such as schematic and wiring diagrams. Our system incorporates various features to aid in the navigation and diagnosis of faults, as well as maintaining contextual information when tracing components/connections through multiple diagrams. System features include highlighting relationships between components and connectors, diagram annotation tools, the animation of flow through the system, a novel contextual blending method, and a variety of traditional focus+context visualization techniques. We have evaluated the usefulness of our system through a qualitative user study in which subjects utilized our system in diagnosing faults during a standard aircraft maintenance exercise.
Demand is high for graduates entering the professional aviation and aerospace workforce with resilience competencies like adversity persistence, contextual awareness, being self-directed and ...autonomous, handling change, and ability to establish peer relationships. Research shows resilience competencies are particularly emphasized as essential companions to technical skills among workers in these high-consequence industries, and are viewed as critical predictors and determinants of early career success. However, literature also suggests a growing gap in adequate resilience competency preparation and transfer from academic into professional settings. It is essential for both educator and learner therefore to more precisely identify and engage specific resilience skills. This cross-sectional study examined attitudes and practice of key resilience skills of students in university/collegiate aviation programs during problem-based coursework. A five-point Likert survey instrument was used to evaluate participant levels of agreement and self-reported levels of engagement in resilience behaviors. Exploratory Analysis compared participant data against a resilience competency model developed for this study. These factors include: Adversity Persistence, Contextual Awareness, Self-Directed/Autonomy, Change Management, and Social/Peer Relational Connectivity. A refined resilience competency model emerged from the data that will be used to develop a more effective approach to teaching and applied learning strategies for the practice and transfer of essential resilience competencies into the industry. This is essential in order to meet required performance levels of safety, reliability and other grand challenges facing the future aviation and aerospace workforce. The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.
The automated and robust identification of metabolites in a complex biological sample remains one of the greatest challenges in metabolomics. In our experiments, HSQC carbon–proton correlation NMR ...data with a model that takes intensity information into account improves upon the identification of metabolites that was achieved using COSY proton–proton correlation NMR data with the binary model of Y. Xi, J.S. de Ropp, M.R. Viant, D.L. Woodruff, P. Yu, Metabolomics, 2 (2006) 221–233. In addition, using intensity information results in easier-to-interpret “grey areas” for cases where it is not clear if the compound might be present. We report on highly successful experiments that identify compounds in chemically defined mixtures as well as in biological samples, and compare our two-dimensional HSQC analyses against quantification of metabolites in the corresponding one-dimensional proton NMR spectra. We show that our approach successfully employs a fully automated algorithm for identifying the presence or absence of predefined compounds (held within a library) in biological HSQC spectra, and in addition calculates upper bounds on the compound intensities.
PDF
