229 research outputs found
Heavy quark fragmentation functions at next-to-leading perturbative QCD
It is well-known that the dominant mechanism to produce hadronic bound states
with large transverse momentum is fragmentation. This mechanism is described by
the fragmentation functions (FFs) which are the universal and
process-independent functions. Here, we review the perturbative FFs formalism
as an appropriate tool for studying these hadronization processes and detail
the extension of this formalism at next-to-leading order (NLO). Using the
Suzuki's model, we calculate the perturbative QCD FF for a heavy quark to
fragment into a S-wave heavy meson at NLO. As an example, we study the LO and
NLO FFs for a charm quark to split into the S-wave -meson and compare our
analytic results both with experimental data and well-known phenomenological
models
Optimal performance of voltage-probe quantum heat engines
The thermoelectric performance at a given output power of a voltage-probe
heat engine, exposed to an external magnetic field, is investigated in linear
irreversible thermodynamics. For the model, asymmetric parameter, general
figures of merit and efficiency at a given output power are analytically
derived. Results show a trade-off between efficiency and output power, and we
recognize optimum-efficiency values at a given output power are enhanced
compared to a B\"uttiker-probe heat engine due to the presence of a
characteristic parameter, namely . Moreover, similar to a B\"uttiker-probe
heat engine, the universal bounds on the efficiency are obtained, and the
efficiency at a given output power can exceed the Curzon-Ahlborn limit. These
findings have practical implications for the optimization of realistic heat
engines and refrigerators. By controlling the values of the asymmetric
parameter, the figures of merit, and , it may be possible to design more
efficient and powerful thermoelectric devices.Comment: 14 pages including 6 multi-panel figure
A Hybrid End-to-End Spatio-Temporal Attention Neural Network with Graph-Smooth Signals for EEG Emotion Recognition
Recently, physiological data such as electroencephalography (EEG) signals
have attracted significant attention in affective computing. In this context,
the main goal is to design an automated model that can assess emotional states.
Lately, deep neural networks have shown promising performance in emotion
recognition tasks. However, designing a deep architecture that can extract
practical information from raw data is still a challenge. Here, we introduce a
deep neural network that acquires interpretable physiological representations
by a hybrid structure of spatio-temporal encoding and recurrent attention
network blocks. Furthermore, a preprocessing step is applied to the raw data
using graph signal processing tools to perform graph smoothing in the spatial
domain. We demonstrate that our proposed architecture exceeds state-of-the-art
results for emotion classification on the publicly available DEAP dataset. To
explore the generality of the learned model, we also evaluate the performance
of our architecture towards transfer learning (TL) by transferring the model
parameters from a specific source to other target domains. Using DEAP as the
source dataset, we demonstrate the effectiveness of our model in performing
cross-modality TL and improving emotion classification accuracy on DREAMER and
the Emotional English Word (EEWD) datasets, which involve EEG-based emotion
classification tasks with different stimuli
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