62 research outputs found
MECHANISTIC STUDIES OF HOMOGENEOUS GOLD(Ⅰ)-CATALYZED HYDROAMINATION OF ALKENYL AMIDES
No full textHydroamination is a facile and atom-economical process that can afford amines or iminesby direct addition of a nitrogen atom and a hydrogen atom on a multiple bond, without
leaving groups produced. Throughout the past few decades, while it has been attracting
much attention and witnessing many achievements and much progress, yet its
development and application have been restrained by some weaknesses, including but not
limited to: a high temperature occasionally required, the typical need of high catalyst
loading comparative to other metal complexes, the demand of geminal substitution on the
carbon chains of some reactants (i.e. Thorpe-Ingold effect), low turnover rates, and a
tendency to form adducts with silver co-catalyst. The essential reason for such
decelerated development is the electronic repulsion between the nucleophilic nitrogen
atom and the electron-rich multiple bond, which under normal conditions tends to
distance the two reacting species and to forbid the reaction. Additionally, alkynes seem to
have higher reactivity than do alkenes, and intermolecular hydroamination reactions are
slower or more difficult to happen than intramolecular ones. With an aim to optimize the
conditions, the author also made efforts to investigate some specific hydroamination
reactions
Multi-Modalities in Mobile Technology for Assisted Learning Performance in Higher Education in China
No full textMobile technology, especially mobile learning, has long been an emerging and thriving field, and remains a main theme in mobile learning applications and systems. The extensive utilization of mobile learning has prompted the invention of many mobile applications. As a result of rapid advances in application technologies, various learning applications can combine different media or multi-modalities, such as video, audio, images, animated graphics, and text, to create multimedia learning resources that engage learners. However, the most favorable modalities in different learning applications that assist performance are worth exploring. This study employed mixed methods to investigate the current multi-modality situation in learning application utilization among 300 university students in China, where a rapid educational technology revolution is occurring. The findings revealed that the verbal modality (M = 3.99, S*D = 0.79) and the writing modality (M = 3.99, S*D = 0.75) in the learning applications were less enjoyable and less effective at enhancing learning performance. In exam-based or function-based apps, all five modalities in this research were considered important, especially the visual and aural modes. The results of this study also revealed that a majority of university learners were satisfied with the multi-modalities in different types of applications, except for game-based apps, that assist their learning performance (56.7%, M = 3.87, S*D = 0.79), which contrasts with the results of several related studies. Overall, college users perceived that multi-modalities were effective in helping them to complete tasks, and all modalities in current applications satisfied most of the users’ needs to assist their learning performance. In the end, the findings indicated a positive and strong linear relationship [r = 0.766, p < 0.05] between multi-modalities and assisted learning performance with the help of more capable (knowledgeable) others with the use of mobile applications
Adopting strategies of mobile technology for assisted learning performance in higher education in China
No full textMobile technology, particularly mobile-assisted learning, has long been a rapidly growing and dynamic field. A prominent focus within this domain is the development and implementation of mobile learning applications and systems. The widespread adoption of mobile learning has led to the emergence of numerous applications, granting higher education students increased autonomy in leveraging mobile devices to support their academic performance. However, the abundance of available options has made the strategic selection and effective use of appropriate applications a pressing issue. This study employed a mixed-methods approach to investigate strategies for adopting mobile learning applications in Chinese higher education institutions—a context in which limited research has been conducted despite the ongoing technological transformation in mainland China. The findings revealed that academic major significantly influenced students’ learning performance supported by mobile applications, primarily due to differing academic demands [F(11, 289) = 1.788, p = .056, η² = 0.064]. Learners’ positive perceptions of mobile learning applications were found to be crucial to their assisted learning outcomes. Moreover, most students acknowledged the necessity of receiving guidance when selecting learning applications. Among the various forms of support examined, teacher recommendations were particularly valued. However, both in-class and out-of-class support remained insufficient. While online searches and social media offer some assistance, there is a strong preference among students for direct guidance from instructors. Furthermore, existing mobile learning applications do not fully meet the diverse needs of all learners. To address these challenges, this study proposes an eight-stage adoption strategy aimed at enhancing university students’ learning performance through more effective use of mobile applications
Cortical entrainment to hierarchical contextual rhythms recomposes dynamic attending in visual perception
No full textTemporal regularity is ubiquitous and essential to guiding attention and coordinating behavior within a dynamic environment. Previous researchers have modeled attention as an internal rhythm that may entrain to first-order regularity from rhythmic events to prioritize information selection at specific time points. Using the attentional blink paradigm, here we show that higherorder regularity based on rhythmic organization of contextual features (pitch, color, or motion) may serve as a temporal frame to recompose the dynamic profile of visual temporal attention. Critically, such attentional reframing effect is well predicted by cortical entrainment to the higher-order contextual structure at the delta band as well as its coupling with the stimulus-driven alpha power. These results suggest that the human brain involuntarily exploits multiscale regularities in rhythmic contexts to recompose dynamic attending in visual perception, and highlight neural entrainment as a central mechanism for optimizing our conscious experience of the world in the time dimension
Temporal integration by multi-level regularities fosters the emergence of dynamic conscious experience
No full textThe relationship between integration and awareness is central to contemporary theories and research on consciousness. Here, we investigated whether and how information integration over time, by incorporating the underlying regularities, contributes to our awareness of the dynamic world. Using binocular rivalry, we demonstrated that structured visual streams, constituted by shape, motion, or idiom sequences containing perceptual- or semantic-level regularities, predominated over their nonstructured but otherwise matched counterparts in the competition for visual awareness. Despite the apparent resemblance, a substantial dissociation of the observed rivalry advantages emerged between perceptual- and semantic-level regularities. These effects stem from nonconscious and conscious temporal integration processes, respectively, with the former but not the latter being vulnerable to perturbations in the spatiotemporal integration window. These findings corroborate the essential role of structure-guided information integration in visual awareness and highlight a multi-level mechanism where temporal integration by perceptually and semantically defined regularities fosters the emergence of continuous conscious experience.
How information integration contributes to the generation of consciousness in a dynamic environment remains unclear. In binocular rivalry, structured visual streams with perceptual- and semantic-level regularities dominate visual awareness over their non-structured counterparts. Such advantages stem from non-conscious and conscious temporal integration, respectively, and exhibit different tolerance to spatiotemporal perturbations within the integration window, revealing a multi-level mechanism whereby structure-guided temporal integration fosters the emergence of continuous conscious experience. # imag
V-Engine Engineering Analytical Powertrain Ford Motor Company Publishing Corresponding Author
No full textThe long computational time required in constructing optimal designs for computer experiments has limited their uses in practice. In this paper, a new algorithm for constructing optimal experimental designs is developed. There are two major developments involved in this work. One is on developing an efficient global optimal search algorithm, named as enhanced stochastic evolutionary (ESE) algorithm. The other is on developing efficient methods for evaluating optimality criteria. The proposed algorithm is compared to existing techniques and found to be much more efficient in terms of the computation time, the number of exchanges needed for generating new designs, and the achieved optimality criteria. The algorithm is also very flexible to construct various classes of optimal designs to retain certain desired structural properties. Key words: optimal design, computer experiments, stochastic evolutionary algorith
Fourier Analysis of Neural Distinguishers
No full textRecent studies have consistently demonstrated the significant potential of deep learning for distinguishing attacks in cryptanalysis. A considerable body of research has focused on progressively improving the accuracy of these methods across various block ciphers. However, to date, there is still little theoretical understanding of why these approaches succeed. Furthermore, a notable deficiency lies in their interpretability; specifically, researchers are unable to discern the features learned by the machine learning algorithms in a human-understandable form. To a certain extent, this limitation impedes further research into the security of block ciphers and extension attacks. Motivated by this gap, we propose a method based on the Goldreich- Levin algorithm to analyze and interpret what black-box distinguishers learn. With this approach, we reinterpret some established advanced neural distinguishers in terms of Fourier representation. Specifically, it is able to resolve the previous neural distinguisher in several Fourier terms. Notably, we identify a new distinguisher technique from neural networks, which can be considered as a generalization of the Differential-Linear (DL) distinguishers. Moreover, we demonstrate that the neural network not only learned the optimal DL distinguishers found using the existing MILP/MIQCP model, but also discovered even superior ones. Finally, we discuss how to determine the weights of Fourier representation using a statistical method
A simple and economical method of gas chromatography-mass spectrometry to determine the presence of 6 pesticides in human plasma and its clinical application in patients with acute poisoning
No full textCement sheath integrity analysis of underground gas storage well based on elastoplastic theory
No full textPharmacokinetics and bioequivalence study of tetramethylpyrazine phosphate tablets after single-dose administration in healthy Chinese male subjects
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