453 research outputs found
Phase transition of the El Niño–Southern Oscillation: A stationary SST mode
ABSTRACT A stationary SST mode is proposed to understand the physical mechanisms responsible for the phase transition of the El Niño-Southern Oscillation. This stationary SST mode differs from the original delayed oscillator mode and the slow SST mode in the sense that it considers both balanced and unbalanced thermocline depth variations and does not take into account the zonal propagation of SST. Within this mode, the Walker circulation acts as a positive feedback mechanism to amplify and maintain an existing interannual SST anomaly, whereas the Hadley circulation acts as a negative feedback mechanism that dismisses the original anomaly and causes the phase shift from a warm (cold) to a cold (warm) episode. The key to the cause of interannual oscillations in the stationary SST mode lies in the zonal-mean thermocline depth variation that is not in equilibrium with the winds. Because of the nonequilibrium, this part of the thermocline depth anomaly tends to have a phase lag with the wind (or SST) anomaly and therefore holds a key for the interannual oscillation. The zonally asymmetric part of the thermocline depth anomaly, on the other hand, is always in Sverdrup balance with the winds. Such a phase relationship agrees well with observations and with GCM simulations. The stationary SST mode strongly depends on the basin width, on the air-sea coupling strength, and on the seasonal-cycle basic state. For a reasonable parameter regime, it depicts an interannual oscillation with a period of 2-7 years. This stationary SST mode is also season dependent: it has a maximum growth rate during the later part of the year and a negative growth rate during the northern spring, which may explain the occurrence of the mature phases of the El Niño in the northern winter and a rapid drop of the lagged correlation of the Southern Oscillation index in the boreal spring
Matching Exemplar as Next Sentence Prediction (MeNSP): Zero-shot Prompt Learning for Automatic Scoring in Science Education
Developing models to automatically score students' written responses to
science problems is critical for science education. However, collecting and
labeling sufficient student responses for training models is time and
cost-consuming. Recent studies suggest that pre-trained language models (PLMs)
can be adapted to downstream tasks without fine-tuning with prompts. However,
no research has employed such a prompt approach in science education. As
student responses are presented with natural language, aligning the scoring
procedure as the next sentence prediction task using prompts can skip the
costly fine-tuning stage. In this study, we developed a zero-shot approach to
automatically score student responses via Matching Exemplars as Next Sentence
Prediction (MeNSP). This approach employs no training samples. We first apply
MeNSP in scoring three assessment tasks of scientific argumentation and found
machine-human scoring agreements, Cohen's Kappa ranges from 0.30 to 0.57, and
F1 score ranges from 0.54 to 0.81. To improve the performance, we extend our
research to the few-shots setting, either randomly selecting labeled student
responses or manually constructing responses to fine-tune the models. We find
that one task's performance is improved with more samples, Cohen's Kappa from
0.30 to 0.38, and F1 score from 0.54 to 0.59; for the two others, scoring
performance is not improved. We also find that randomly selected few-shots
perform better than the human expert-crafted approach. This study suggests that
MeNSP can yield referable automatic scoring for student responses while
significantly reducing the cost of model training. This method can benefit
low-stakes classroom assessment practices in science education. Future research
should further explore the applicability of the MeNSP in different types of
assessment tasks in science education and improve the model performance.Comment: 10+3 page
Electromagnetic Nondestructive Evaluation of Wire Insulation and Models of Insulation Material Properties
Polymers have been widely used as wiring electrical insulation materials in space/air-craft. The dielectric properties of insulation polymers can change over time, however, due to various aging processes such as exposure to heat, humidity and mechanical stress. Therefore, the study of polymers used in electrical insulation of wiring is important to the aerospace industry due to potential loss of life and aircraft in the event of an electrical fire caused by breakdown of wiring insulation. Part of this research is focused on studying the mechanisms of various environmental aging process of the polymers used in electrical wiring insulation and the ways in which their dielectric properties change as the material is subject to the aging processes. The other part of the project is to determine the feasibility of a new capacitive nondestructive testing method to indicate degradation in the wiring insulation, by measuring its permittivity
Analysis of Linear Receivers in a Target SINR Game for Wireless Cognitive Networks
Abstract-Signal to Interference plus Noise Ratio (SINR) is a key parameter for every user in a wireless network. Different users with heterogeneous QoS requirements have different target SINR requirements. In cognitive radio (CR) networks, secondary users try to access the available spectrum in order to make successful transmissions. However, without proper regulation, they may transmit at their maximum power to achieve the highest possible SINR, which can be even worse than the current wasteful static spectrum utilization. A target SINR game (TSG) is a powerful tool to regulate each secondary user's behavior, provide them with decent SINRs (i.e. close to their target SINRs) and simultaneously limit the interference they cause to primary users and other secondary users. The goal of this paper is to analyze the performance of the Matched Filter (MF) receiver and the linear MMSE receiver (LMMSE) in a TSG. As expected, the LMMSE shows several advantages in performance over the MF
MedEdit: Model Editing for Medical Question Answering with External Knowledge Bases
Large Language Models (LLMs), although powerful in general domains, often
perform poorly on domain-specific tasks like medical question answering (QA).
Moreover, they tend to function as "black-boxes," making it challenging to
modify their behavior. Addressing this, our study delves into model editing
utilizing in-context learning, aiming to improve LLM responses without the need
for fine-tuning or retraining. Specifically, we propose a comprehensive
retrieval strategy to extract medical facts from an external knowledge base,
and then we incorporate them into the query prompt for the LLM. Focusing on
medical QA using the MedQA-SMILE dataset, we evaluate the impact of different
retrieval models and the number of facts provided to the LLM. Notably, our
edited Vicuna model exhibited an accuracy improvement from 44.46% to 48.54%.
This work underscores the potential of model editing to enhance LLM
performance, offering a practical approach to mitigate the challenges of
black-box LLMs.Comment: 6 page
Unidirectional Photonic Reflector Using a Defective Atomic Lattice
Based on the broken spatial symmetry, we propose a novel scheme for
engineering a unidirectional photonic reflector using a one-dimensional atomic
lattice with defective cells that have been specifically designed to be vacant.
By trapping three-level atoms and driving them into the regime of
electromagnetically induced transparency, and through the skillful design of
the number and position of vacant cells in the lattice, numerical simulations
demonstrate that a broad and high unidirectional reflection region can be
realized within EIT window. This proposed unidirectional reflector scheme
provides a new platform for achieving optical nonreciprocity and has potential
applications for designing optical circuits and devices of nonreciprocity at
extremely low energy levels
Exploring the Influence of Information Entropy Change in Learning Systems
In this work, we explore the influence of entropy change in deep learning
systems by adding noise to the inputs/latent features. The applications in this
paper focus on deep learning tasks within computer vision, but the proposed
theory can be further applied to other fields. Noise is conventionally viewed
as a harmful perturbation in various deep learning architectures, such as
convolutional neural networks (CNNs) and vision transformers (ViTs), as well as
different learning tasks like image classification and transfer learning.
However, this paper aims to rethink whether the conventional proposition always
holds. We demonstrate that specific noise can boost the performance of various
deep architectures under certain conditions. We theoretically prove the
enhancement gained from positive noise by reducing the task complexity defined
by information entropy and experimentally show the significant performance gain
in large image datasets, such as the ImageNet. Herein, we use the information
entropy to define the complexity of the task. We categorize the noise into two
types, positive noise (PN) and harmful noise (HN), based on whether the noise
can help reduce the complexity of the task. Extensive experiments of CNNs and
ViTs have shown performance improvements by proactively injecting positive
noise, where we achieved an unprecedented top 1 accuracy of over 95% on
ImageNet. Both theoretical analysis and empirical evidence have confirmed that
the presence of positive noise can benefit the learning process, while the
traditionally perceived harmful noise indeed impairs deep learning models. The
different roles of noise offer new explanations for deep models on specific
tasks and provide a new paradigm for improving model performance. Moreover, it
reminds us that we can influence the performance of learning systems via
information entropy change.Comment: Information Entropy, CNN, Transforme
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