Greedy kernel methods for accelerating implicit integrators for parametric ODEs

We present a novel acceleration method for the solution of parametric ODEs by single-step implicit solvers by means of greedy kernel-based surrogate models. In an offline phase, a set of trajectories is precomputed with a high-accuracy ODE solver for a selected set of parameter samples, and used to train a kernel model which predicts the next point in the trajectory as a function of the last one. This model is cheap to evaluate, and it is used in an online phase for new parameter samples to provide a good initialization point for the nonlinear solver of the implicit integrator. The accuracy of the surrogate reflects into a reduction of the number of iterations until convergence of the solver, thus providing an overall speedup of the full simulation. Interestingly, in addition to providing an acceleration, the accuracy of the solution is maintained, since the ODE solver is still used to guarantee the required precision. Although the method can be applied to a large variety of solvers and different ODEs, we will present in details its use with the Implicit Euler method for the solution of the Burgers equation, which results to be a meaningful test case to demonstrate the method's features

Application of the analytic hierarchy process in a comparative analysis of automated information systems

In a scientific study, we investigated decision-making methods, in particular, the methods of expert estimations to solve problems. Reflected the possibility of using the analytic hierarchy process for researching and selection of information systems in accordance with the requirements of the customer. Comparative analysis has been performed on the example of automated library information systems

Excitons and Many-Electron Effects in the Optical Response of Single-Walled Boron Nitride Nanotubes

We report first-principles calculations of the effects of quasiparticle self-energy and electron-hole interaction on the optical properties of single-walled BN nanotubes. Excitonic effects are shown to be even more important in BN nanotubes than in carbon nanotubes. Electron-hole interactions give rise to complexes of bright (and dark) excitons, which qualitatively alter the optical response. Excitons with binding energy larger than 2 eV are found in the (8,0) BN nanotubes. Moreover, unlike the carbon nanotubes, theory predicts that these exciton states are comprised of coherent supposition of transitions from several different subband pairs, giving rise to novel behaviors.Comment: 4 pages, 4 figure

AI in marketing, consumer research and psychology: A systematic literature review and research agenda

This study is the first to provide an integrated view on the body of knowledge of artificial intelligence (AI) published in the marketing, consumer research, and psychology literature. By leveraging a systematic literature review using a data-driven approach and quantitative methodology (including bibliographic coupling), this study provides an overview of the emerging intellectual structure of AI research in the three bodies of literature examined. We identified eight topical clusters: (1) memory and computational logic; (2) decision making and cognitive processes; (3) neural networks; (4) machine learning and linguistic analysis; (5) social media and text mining; (6) social media content analytics; (7) technology acceptance and adoption; and (8) big data and robots. Furthermore, we identified a total of 412 theoretical lenses used in these studies with the most frequently used being: (1) the unified theory of acceptance and use of technology; (2) game theory; (3) theory of mind; (4) theory of planned behavior; (5) computational theories; (6) behavioral reasoning theory; (7) decision theories; and (8) evolutionary theory. Finally, we propose a research agenda to advance the scholarly debate on AI in the three literatures studied with an emphasis on cross-fertilization of theories used across fields, and neglected research topics

Groundwater microflora of the Aptian-Cenomanian deposits at the Igolsko-Talovoe field in Tomsk Region

The authors have studied the microbiological composition of the groundwater of the Aptian-Cenomanian deposits in the territory of the Igolsko-Talovoe field in Tomsk Region. The detected diversity of the physiological groups of bacteria can be a corrosive component for waters used in the reservoir pressure maintenance system. The research findings have allowed making conclusions about the need to study the contribution of all microorganisms inhabiting the waters of the Aptian-Cenomanian deposits to corrosion

Tight--binding description of the quasiparticle dispersion of graphite and few--layer graphene

A universal set of third--nearest neighbour tight--binding (TB) parameters is presented for calculation of the quasiparticle (QP) dispersion of $N$ stacked $sp^2$ graphene layers ($N=1... \infty$) with $AB$ stacking sequence. The QP bands are strongly renormalized by electron--electron interactions which results in a 20% increase of the nearest neighbour in--plane and out--of--plane TB parameters when compared to band structure from density functional theory. With the new set of TB parameters we determine the Fermi surface and evaluate exciton energies, charge carrier plasmon frequencies and the conductivities which are relevant for recent angle--resolved photoemission, optical, electron energy loss and transport measurements. A comparision of these quantitities to experiments yields an excellent agreement. Furthermore we discuss the transition from few layer graphene to graphite and a semimetal to metal transition in a TB framework.Comment: Corresponding author: A. Gr\"uneis Tel.: +49 351 4659 519 e--mail: [email protected]

Racial disparity in educational punishment

There is a growing epidemic of children of color being disproportionately and inappropriately disciplined due to recommendations for exclusionary educational discipline practices such as suspension and expulsion. Throughout the literature, SES, level of ability, gender, and skin color were essential factors in evaluating students’ suspension risk. The most salient of these factors is race. Implicit bias towards darker-skinned students is the main factor for the discipline gap. This literature review explores the causes and rates that middle school and high school students of color are disproportionately recommended for suspension and expulsion and the consequences of racially discriminatory discipline practices. Exclusionary punishment criminalizes youth and leads to worse life outcomes. Expulsion and suspension lead to higher rates of youth crime in the community, and they are contributing factors to the school-to-prison pipeline. As zero-tolerance policies grow more popular for non-criminal offenses in the school setting, the circumstances around the behaviors leading to mandatory suspension and expulsion are no longer considered. Students’ involvement in the school, positive student-teacher relationships, and students’ individuation are critical protective factors in reducing racial bias in discipline. This literature synthesizes and critically analyzes the body of literature in this field. Recommendations for additional research regarding intersectionality between race and gender need to be funded, zero-tolerance policies need to be abolished and school administrators dedicated to positive student outcomes need to be hired

The impact of service robots on customer satisfaction online ratings: The moderating effects of rapport and contextual review factors

Recent research has established a positive relationship between the use of service robots powered by artificial intelligence in hospitality firms and customer satisfaction online ratings, a particularly important form of electronic word of mouth. However, it is not clear if and how this relationship is augmented or diminished by moderating factors. In this study, we examined four potential moderators by using machine learning and natural language processing techniques to analyze 20,166 online reviews of hotels that had implemented service robots. We had four key findings. First, a positive service robot-satisfaction rating relationship was further enhanced by improved customer-service robot rapport during the service encounter. Second, higher customer effort focused on service robots in a review reduced the service robot-satisfaction rating relationship. Third, posting reviews using a mobile device (vs. other devices) showed higher satisfaction ratings. Finally, customers' prior experience in writing online reviews was unrelated to the service robot-satisfaction rating relationship. Taken together, these results suggest that service robots should be designed to be interactive and encourage customers to build rapport, for example, by service robots engaging in conversational flows. Moreover, customers should be nudged to use their mobile devices to post timely reviews on their positive human–robot interactions