Four-channel Model Research Articles

Sequence recommendation using multi-level self-attention network with gated spiking neural P systems

Sequence recommendation is used to predict the user's next potentially interesting items and behaviors. It not only focuses on the user's independent interaction behavior, but also considers the user's historical behavior sequence. However, sequence recommendation still faces some challenges: the existing models still have shortcomings in addressing long-term dependencies and fully utilizing contextual information in sequence recommendation. To address these challenges, we propose a four-channel model based on a multi-level self-attention network with gated spiking neural P (GSNP) systems, termed SR-MAG model. The four channels are divided into two groups, and each group is composed of an attention channel and an GSNP attention channel. Moreover, they process long-term sequences and short-term sequences respectively to obtain long-term or short-term attention channel features. These features are then passed through a self-attention network to effectively extract user context information. The proposed SR-MAG model is tested on three real datasets and compared with 10 baseline methods. Experimental results demonstrate the effectiveness of the proposed SR-MAG model in sequence recommendation tasks.

Multichannel hyperspherical model for Efimov physics with van der Waals interactions controlled by a Feshbach resonance

Here we present a four-channel model that incorporates a magnetically tunable Feshbach resonance in a system of three atoms that interact via pairwise van der Waals interactions. Our method is designed to model recent experiments where the tunability of the scattering length has been used to study three-body Efimov states, which appear in the limit of a diverging two-body scattering length. Using this model, we calculate three-body adiabatic and effective potential curves and study how the strength (or width) of the Feshbach resonance affects the three-body potential that is connected to the Efimov effect. We find that the position of the repulsive barrier, which has been used to explain the so-called van der Waals universality in broad resonances, is slightly shifted as the narrow resonance limit is approached and that this shift is correlated to the appearance of two avoided crossings in the adiabatic energy landscape. More importantly, the attractive well is markedly shifted upward in energy and is extremely shallow for the narrowest resonance. We argue that this behavior is connected to the breakdown of van der Waals universality for weak (narrow) resonances.

User roles for emergency management in social media: Understanding actors' behavior during the 2018 Majorca Island flash floods

Social media assemble multiple users' interactions across singular events. Authorities need to navigate this diversity to effectively communicate and promote collaborative strategies. During emergency situations, discerning “who is there” is even more important for authorities, as this tracing process can save lives reaching the appropriate targets. This article contributes to this problem during emergency situations by proposing a user role taxonomy. We argue that focusing on functional behaviors could bypass the complexity of defining audiences during critical events. We test our framework using data from the 2018 flash floods in Sant Llorenç, Majorca island (Spain). Results show a diverse set of audience roles that emerge during crisis and post-crisis stages. We also identify the inclination of actors to represent certain roles and not others. Our findings contribute to understand crisis development models, and also crisis coordination configurations, such as the four-channel model or the network coordination perspective. Practical implications for public managers vary from improving coordination to influence audience's behavior during crises.

Flow and business simulation games: A typology of students

In the context of management training business simulation games are increasingly emerging as pedagogical tools for motivating and engaging players actively in the learning experience. Business simulation games provide opportunities for students to enter the flow state. However, few studies have applied flow theory in this specific context. Using data from a two-wave longitudinal study with a sample of 430 students who played a business simulation game, this research draws on the four-channel model of flow to identify subgroups of students based on their levels of skill and challenge and to analyse the evolution of their optimal experience of flow. In addition, it explores whether students in flow achieve higher learning outcomes; in particular, students’ perceived learning, satisfaction and skills development.

Investigation of rotating mode behavior in BWR out-of-phase limit cycle oscillations – Part 1: Reduced order model

Previous neutronic/thermal-hydraulic (TH) coupled numerical simulations using full-core TRACE/PARCS and SIMULATE-3K BWR models have shown evidence of a specific “rotating mode” behavior (steady rotation of the symmetry line, i.e. constant phase shift of approximately 90° between the first two azimuthal modes) in out-of-phase limit cycle oscillations, regardless of initial conditions and even if the first two azimuthal modes have different natural frequencies. This suggests a nonlinear coupling between these modes; otherwise, the phase shift between these modes would change at a constant rate during the limit cycle. The goal of the present work is to gain further insights on the rotating mode behavior using a simplified mathematical model which contains all of the important physics for this application while providing sufficient flexibility and simplicity to allow for in-depth understanding of the underlying phenomena. This was accomplished using a multi-channel, multi-modal reduced-order model, using a modification of the fixed pressure drop boundary condition to simulate channel coupling via the inlet and outlet plena, in order to destabilize the out-of-phase mode over the in-phase mode. Examination of the time-dependent solution of the nonlinear system showed a clear preference for rotating mode behavior in the four-channel model under stand-alone TH conditions and for conditions with weak neutronic feedback. When neutronic feedback was strengthened (i.e., larger reactivity feedback coefficients), the side-to-side mode (stationary symmetry line) was favored instead. Additional analyses using higher-fidelity numerical modeling, as well as a physical explanation for the rotating behavior seen in both sets of analyses, will be provided in a companion paper (“Part 2”).

Discriminative and affective touch: sensing and feeling.

The multimodal properties of the human somatosensory system continue to be unravelled. There is mounting evidence that one of these submodalities-touch-has another dimension, providing not only its well-recognized discriminative input to the brain, but also an affective input. It has long been recognized that touch plays an important role in many forms of social communication and a number of theories have been proposed to explain observations and beliefs about the "power of touch." Here, we propose that a class of low-threshold mechanosensitive C fibers that innervate the hairy skin represent the neurobiological substrate for the affective and rewarding properties of touch.

Challenges to the four-channel model of flow: Primary assumption of flow support the moderate challenging control channel

Flow theory postulates that the psychological state of flow emerging when one engages in activities where skill level and challenge are both high, results in ‘optimal’ subjective experiences relative to other psychological states, and is intrinsically motivated. The experience sampling method was used on a sample of college students to compare daily activities associated with flow (high skill, high challenge) to the psychological state of control (high skill, moderate challenge) in relation to the subjective experiences of enjoyment, happiness, intrinsic motivation, and cognitive involvement. Contrary to flow theory, enjoyment, happiness, and intrinsic motivation were characteristic of activities associated with being in ‘control,’ as opposed to flow. Flow activities were associated with being cognitively involved in the task at hand. We believe such theoretically important findings have been masked when using the original four-channel model of flow, but are clarified with use of the revised experience fluctuation model.

Understanding the Dynamics of Emergency Communication: Propositions for a Four-Channel Model

Emergency management efforts rely strongly on the clarity, coordination and efficiency of communication among emergency responders, disaster preparedness experts, emergency response agencies, the public, and other stakeholders. Though emergency communications systems have been researched, the research has often not taken into account the impacts of social networks, mass media, and new internet based technology. This research investigates the role of social networking (the public as participants) in the mechanisms of emergency communication. A model of communication (a four-channel model) is proposed to represent emergency communication interactions via internet tools, cell phones and social networks; and to relate these dynamics with prior research.

Communications orales – Recherche fondamentale/recherche clinique

Previous neutronic/thermal-hydraulic (TH) coupled numerical simulations using full-core TRACE/PARCS and SIMULATE-3K BWR models have shown evidence of a specific “rotating mode” behavior (steady rotation of the symmetry line, i.e. constant phase shift of approximately 90° between the first two azimuthal modes) in out-of-phase limit cycle oscillations, regardless of initial conditions and even if the first two azimuthal modes have different natural frequencies. This suggests a nonlinear coupling between these modes; otherwise, the phase shift between these modes would change at a constant rate during the limit cycle. The goal of the present work is to gain further insights on the rotating mode behavior using a simplified mathematical model which contains all of the important physics for this application while providing sufficient flexibility and simplicity to allow for in-depth understanding of the underlying phenomena. This was accomplished using a multi-channel, multi-modal reduced-order model, using a modification of the fixed pressure drop boundary condition to simulate channel coupling via the inlet and outlet plena, in order to destabilize the out-of-phase mode over the in-phase mode. Examination of the time-dependent solution of the nonlinear system showed a clear preference for rotating mode behavior in the four-channel model under stand-alone TH conditions and for conditions with weak neutronic feedback. When neutronic feedback was strengthened (i.e., larger reactivity feedback coefficients), the side-to-side mode (stationary symmetry line) was favored instead. Additional analyses using higher-fidelity numerical modeling, as well as a physical explanation for the rotating behavior seen in both sets of analyses, will be provided in a companion paper (“Part 2”).

The elusive experience of ‘flow’: Qualitative and quantitative indicators

In this investigation mixed methods were used to examine flow within the context of a writing task. Forty-four secondary students aged between 15 and 18 years completed a computer-based writing task requiring them to examine information and then write on one of two topical issues. We examined the level of agreement between end-of-task ratings based on two approaches to measuring flow, the four-channel model ratio of challenge and skill, and a classification based on ratings of absorption, timelessness and effort. Flow groups that emerged were significantly associated but not entirely consistent. A range of additional data sources concerning students’ on-task experiences illustrated different patterns of task engagement. The variability between indicators suggests that flow cannot be reliably identified through any narrow set of measures. Just as the flow experience is complex so a range of indicators is needed to identify when and how students experience flow in their learning.

New concept of the first wall to reduce MHD pressure drop

Numerical analysis of MHD flow in rectangular channel is performed to evaluate the performance of remountable first wall with liquid blanket like Li or Flibe, where fabrication and maintenance of the system become extremely simplified. Four-channel model is used to calculate the MHD pressure drop in variously coated channels. The effect of crack existence in the coated layer of flow channel on the MHD pressure drop is also evaluated for real usage. The numerical results indicate that some amount of crack existence is allowable, which shows possibility to apply the first wall concept to future fusion reactor design.

Some characteristics of tactile channels

The four information-processing channels of glabrous skin have distinct tuning characteristics which appear to be determined in the periphery at the level of sensory receptors and their afferent nerve fibers. The four-channel model [J Acoust Soc Am 84 (1988) 1680] has been updated to include measurement over a wider frequency range of tuning of the P and NP I channels, psychophysically determined by forward-masking and adaptation tuning curve methods. In addition to differences in their tuning, the P and NP channels differ in the following ways: (1) the P channel, but not NP channels, has been found to be capable of temporal summation, which operates by neural integration; (2) the capacity for spatial summation is also an exclusive property of the P channel; (3) sensitivity declines with age at a greater rate in the P channel than in the NP channels; (4) the masking or adaptation of a channel has no effect on the sensitivity of the other channels, although the channels interact in the summation of the perceived magnitudes of stimuli presented to separate channels.

The frequency selectivity of information-processing channels in the tactile sensory system

The frequency selectivity of the P, NP I, and NP II channels of the four-channel model of mechanoreception for glabrous skin was measured psychophysically by an adaptation tuning curve procedure. The results substantially extend the frequency range over which the frequency selectivity of these channels is known and further confirm the hypothesis that the input stage of each of these channels consists of specific sensory nerve fibers and associated receptors. Specifically, the frequency characteristics of Pacinian nerve fibers, rapidly adapting (RA) nerve fibers, and slowly adapting Type II (SA II) nerve fibers were found to be the peripheral neurophysiological correlates of the P, NP I, and NP II channels, respectively. The finding that the tuning characteristic for a test stimulus of 250 Hz delivered through a small (0.008 cm2) contactor depended dramatically on the duration of the test stimulus whereas the detection threshold did not, provides new evidence in support of the hypothesis that separate NP II and P channels exist.

A reexamination of the folding mechanism of dihydrofolate reductase from Escherichia coli: Verification and refinement of a four-channel model

The mechanism of folding of dihydrofolate reductase from Escherichia coli was reinvestigated by studying the unfolding and refolding kinetics using absorbance and fluorescence spectroscopies. The original kinetic model proposed that folding involved a series of native, intermediate, and unfolded forms which interconverted through four independent channels linked by slow cis/trans isomerization reactions at Xaa-Pro peptide bonds [Touchette, N. A., Perry, K. M., & Matthews, C. R. (1986) Biochemistry 25, 5445]. Recently, alternative sequential models have been proposed [Frieden, C. (1990) Proc. Natl. Acad. Sci. U.S.A. 87, 4413; Kuwajima et al. (1991) Biochemistry 30, 7693] which challenge the original proposal. Stopped-flow studies of the intrinsic tryptophan fluorescence demonstrated the presence of three (and tentatively four) kinetic phases in unfolding which correlated well with four phases previously observed in refolding experiments. By monitoring the binding of the inhibitor methotrexate during folding at varying relative concentrations of inhibitor to protein, it was found that the selective loss of the slow-folding phases at substoichiometric levels could only be explained by a four-channel folding model. Double-jump experiments (native-->unfolded-->native) showed that the four refolding channels are populated within 20 s at 15 degrees C and are not likely to be due to proline isomerization. Reverse double-jump experiments (unfolded-->native-->unfolded) demonstrated that interconversions between native conformers are more rapid than originally proposed. Interestingly, the majority of the protein folds through a channel to a native conformer that is minimally populated at equilibrium. This implies that although the folding of dihydrofolate reductase is ultimately under thermodynamic control, kinetic factors contribute to the transient populations of native species during folding.

Spatial integration characteristics in motion detection and direction identification

Spatial integration characteristics were assessed with drifting gratings for both detection and direction-identification contrast thresholds. Thresholds were measured while stimulus width, length or both were varied. It was found that: (1) the shape of the size/sensitivity functions changes with spatial, but not with temporal, frequency; (2) direction-identification thresholds diverge from the detection thresholds below 1 cycle but can be reliably measured for stimulus widths as small as 0.1275 cycles; (3) the integration characteristics are slightly anisotropic for the identification but not for the detection process, and (4) the two-dimensional spatial integration cannot be directly predicted from its one-dimensional characteristics. Width/sensitivity detection functions are well fitted by predictions of Wilson and Bergen's four-channel model. Predictions from a temporal covariance model provide a poor fit to the identification data. It is argued that classes of detection and direction-identification models must involve identical nonlinearities prior to their respective thresholds. It is concluded that the hypothesis according to which both performances are determined by the same spatial integration stage cannot be rejected.

Models for unambiguousE-vector navigation in the bee

Models for unambiguousE-vector navigation in the bee