248 research outputs found
Efficiency and power of minimally nonlinear irreversible heat engines with broken time-reversal symmetry
We study the minimally nonlinear irreversible heat engines in which the
time-reversal symmetry for the systems may b e broken. The expressions for the
power and the efficiency are derived, in which the effects of the nonlinear
terms due to dissipations are included. We show that, as within the linear
responses, the minimally nonlinear irreversible heat engines enable attainment
of Carnot efficiency at positive power. We also find that the Curzon-Ahlborn
limit imposed on the efficiency at maximum power can be overcomed if the
time-reversal symmetry is broken
Efficiency at maximum power output of an irreversible Carnot-like cycle with internally dissipative friction
We investigate the efficiency at maximum power of an irreversible Carnot
engine performing finite-time cycles between two reservoirs at temperatures
and , taking into account of internally dissipative
friction in two "adiabatic" processes. In the frictionless case, the
efficiencies at maximum power output are retrieved to be situated between
and , with being
the Carnot efficiency. The strong limits of the dissipations in the hot and
cold isothermal processes lead to the result that the efficiency at maximum
power output approaches the values of and
, respectively. When dissipations of two isothermal
and two adiabatic processes are symmetric, respectively, the efficiency at
maximum power output is founded to be bounded between 0 and the Curzon-Ahlborn
(CA) efficiency , and the the CA efficiency is achieved in
the absence of internally dissipative friction
Robust retrieval of material chemical states in X-ray microspectroscopy
X-ray microspectroscopic techniques are essential for studying morphological
and chemical changes in materials, providing high-resolution structural and
spectroscopic information. However, its practical data analysis for reliably
retrieving the chemical states remains a major obstacle to accelerating the
fundamental understanding of materials in many research fields. In this work,
we propose a novel data formulation model for X-ray microspectroscopy and
develop a dedicated unmixing framework to solve this problem, which is robust
to noise and spectral variability. Moreover, this framework is not limited to
the analysis of two-state material chemistry, making it an effective
alternative to conventional and widely-used methods. In addition, an
alternative directional multiplier method with provable convergence is applied
to obtain the solution efficiently. Our framework can accurately identify and
characterize chemical states in complex and heterogeneous samples, even under
challenging conditions such as low signal-to-noise ratios and overlapping
spectral features. Extensive experimental results on simulated and real
datasets demonstrate its effectiveness and reliability.Comment: 12 page
Electro-acupuncture at Jianshi (PC5) and Neiguan (PC6) alters heart rate variability (HRV) in frightened volunteers
No Abstract
Dynamic Loss For Robust Learning
Label noise and class imbalance commonly coexist in real-world data. Previous
works for robust learning, however, usually address either one type of the data
biases and underperform when facing them both. To mitigate this gap, this work
presents a novel meta-learning based dynamic loss that automatically adjusts
the objective functions with the training process to robustly learn a
classifier from long-tailed noisy data. Concretely, our dynamic loss comprises
a label corrector and a margin generator, which respectively correct noisy
labels and generate additive per-class classification margins by perceiving the
underlying data distribution as well as the learning state of the classifier.
Equipped with a new hierarchical sampling strategy that enriches a small amount
of unbiased metadata with diverse and hard samples, the two components in the
dynamic loss are optimized jointly through meta-learning and cultivate the
classifier to well adapt to clean and balanced test data. Extensive experiments
show our method achieves state-of-the-art accuracy on multiple real-world and
synthetic datasets with various types of data biases, including CIFAR-10/100,
Animal-10N, ImageNet-LT, and Webvision. Code will soon be publicly available
A study of Masamichi Royama\u27s definitions of politics and the nation -The period from prewar to postwar-
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