87 research outputs found
Similarity signature curves for forming periodic orbits in the Lorenz system
In this paper, we systematically investigate the short periodic orbits of the
Lorenz system by the aid of the similarity signature curve, and a novel method
to find the short-period orbits of the Lorenz system is proposed. The
similarity invariants are derived by the equivariant moving frame theory and
then the similarity signature curve occurs along with them. The similarity
signature curve of the Lorenz system presents a more regular behavior than the
original one. By combining the sliding window method, the quasi-periodic orbits
can be detected numerically, all periodic orbits with period in
the Lorenz system are found, and their period lengths and symbol sequences are
calculated
MORE: Measurement and Correlation Based Variational Quantum Circuit for Multi-classification
Quantum computing has shown considerable promise for compute-intensive tasks
in recent years. For instance, classification tasks based on quantum neural
networks (QNN) have garnered significant interest from researchers and have
been evaluated in various scenarios. However, the majority of quantum
classifiers are currently limited to binary classification tasks due to either
constrained quantum computing resources or the need for intensive classical
post-processing. In this paper, we propose an efficient quantum
multi-classifier called MORE, which stands for measurement and correlation
based variational quantum multi-classifier. MORE adopts the same variational
ansatz as binary classifiers while performing multi-classification by fully
utilizing the quantum information of a single readout qubit. To extract the
complete information from the readout qubit, we select three observables that
form the basis of a two-dimensional Hilbert space. We then use the quantum
state tomography technique to reconstruct the readout state from the
measurement results. Afterward, we explore the correlation between classes to
determine the quantum labels for classes using the variational quantum
clustering approach. Next, quantum label-based supervised learning is performed
to identify the mapping between the input data and their corresponding quantum
labels. Finally, the predicted label is determined by its closest quantum label
when using the classifier. We implement this approach using the Qiskit Python
library and evaluate it through extensive experiments on both noise-free and
noisy quantum systems. Our evaluation results demonstrate that MORE, despite
using a simple ansatz and limited quantum resources, achieves advanced
performance.Comment: IEEE International Conference on Quantum Computing and Engineering
(QCE23
Preconditioned Federated Learning
Federated Learning (FL) is a distributed machine learning approach that
enables model training in communication efficient and privacy-preserving
manner. The standard optimization method in FL is Federated Averaging (FedAvg),
which performs multiple local SGD steps between communication rounds. FedAvg
has been considered to lack algorithm adaptivity compared to modern first-order
adaptive optimizations. In this paper, we propose new communication-efficient
FL algortithms based on two adaptive frameworks: local adaptivity (PreFed) and
server-side adaptivity (PreFedOp). Proposed methods adopt adaptivity by using a
novel covariance matrix preconditioner. Theoretically, we provide convergence
guarantees for our algorithms. The empirical experiments show our methods
achieve state-of-the-art performances on both i.i.d. and non-i.i.d. settings.Comment: preprin
A microfluidic study of transient flow states in permeable media using fluorescent particle image velocimetry
Velocity fields in flow in permeable media are of great importance to many subsurface processes such as geologic storage of CO2 , oil and gas extraction, and geothermal systems. Steady-state flow is characterized by velocity fields that do not change significantly over time. The flow field transitions to a new steady state once it experiences a disturbance such as a change in flow rate or in pressure gradient. This transition is often assumed to be instantaneous, which justifies the expression of constitutive relations as functions of instantaneous phase saturations. This work examines the evolution of velocity fields in a surrogate quasi-2D permeable medium using a microfluidic device, a microscopy system, and a high-speed camera. Tracer particles are injected into the medium along with Deionized water. The evolution of the velocity field is examined by tracing these particles in the captured images using the standard high-density particle image velocimetry algorithm founded on cross-correlation. The results suggest that the transition between steady states for an incompressible fluid takes a finite and non-negligible amount of time that is independent of the magnitude of the change in pressure gradient. The existence of transient states and the nature of the response during these states are readily interpreted by the principle of least action where flow gradually establishes an optimal configuration such that energy dissipation is minimized. The findings provide evidence against the applicability of the assumption that flowing phases relax instantaneously to their steady states and, hence, against the accuracy of the classical multiphase extension of Darcy’s law.Cited as: Sun, J., Li, Z., Furtado, F., Aryana, S. A. A microfluidic study of transient flow states in permeable media using fluorescent particle image velocimetry. Capillarity, 2021, 4(4): 76-86, doi: 10.46690/capi.2021.04.0
ExplainCPE: A Free-text Explanation Benchmark of Chinese Pharmacist Examination
As ChatGPT and GPT-4 spearhead the development of Large Language Models
(LLMs), more researchers are investigating their performance across various
tasks. But more research needs to be done on the interpretability capabilities
of LLMs, that is, the ability to generate reasons after an answer has been
given. Existing explanation datasets are mostly English-language general
knowledge questions, which leads to insufficient thematic and linguistic
diversity. To address the language bias and lack of medical resources in
generating rationales QA datasets, we present ExplainCPE (over 7k instances), a
challenging medical benchmark in Simplified Chinese. We analyzed the errors of
ChatGPT and GPT-4, pointing out the limitations of current LLMs in
understanding text and computational reasoning. During the experiment, we also
found that different LLMs have different preferences for in-context learning.
ExplainCPE presents a significant challenge, but its potential for further
investigation is promising, and it can be used to evaluate the ability of a
model to generate explanations. AI safety and trustworthiness need more
attention, and this work makes the first step to explore the medical
interpretability of LLMs.The dataset is available at
https://github.com/HITsz-TMG/ExplainCPE.Comment: EMNLP 2023 Finding
Enterprise social media adoption:Its impact on social capital in work and job satisfaction
Enterprise social media is increasingly being recognized as an important technical tool to achieve more effective management and sustainable development. Limited research has been conducted on workplace satisfaction in the enterprise social media context. To fill this gap, we propose a research model explaininghowemployees' usage of enterprise social media influences job satisfaction from the social capital perspective. Through a survey of 509 respondents, we conceptualize the constructs of enterprise social media use (i.e., work-related use and social-related use), social capital (i.e., bridging social capital and bonding social capital), and job satisfaction. We empirically validate the proposed model. The results largely support the proposed hypotheses. Firstly, both work-related use and social-related use positively impact bridging and bonding social capital. Secondly, bridging and bonding social capital play different roles in job satisfaction. Bonding social capital promotes job satisfaction, while bridging social capital inhibits job satisfaction. Thirdly, work-related use accumulates more bridging social capital, while social-related use is more conducive to the establishment of bonding social capital. Finally, some theoretical and practical implications are discussed.</p
Hydrogels for Oral Tissue Engineering: Challenges and Opportunities
Oral health is crucial to daily life, yet many people worldwide suffer from oral diseases. With the development of oral tissue engineering, there is a growing demand for dental biomaterials. Addressing oral diseases often requires a two-fold approach: fighting bacterial infections and promoting tissue growth. Hydrogels are promising tissue engineering biomaterials that show great potential for oral tissue regeneration and drug delivery. In this review, we present a classification of hydrogels commonly used in dental research, including natural and synthetic hydrogels. Furthermore, recent applications of these hydrogels in endodontic restorations, periodontal tissues, mandibular and oral soft tissue restorations, and related clinical studies are also discussed, including various antimicrobial and tissue growth promotion strategies used in the dental applications of hydrogels. While hydrogels have been increasingly studied in oral tissue engineering, there are still some challenges that need to be addressed for satisfactory clinical outcomes. This paper summarizes the current issues in the abovementioned application areas and discusses possible future developments
Daily MODIS 500 m Reflectance Anisotropy Direct Broadcast (DB) Products for Monitoring Vegetation Phenology Dynamics
Land surface vegetation phenology is an efficient bio-indicator for monitoring ecosystem variation in response to changes in climatic factors. The primary objective of the current article is to examine the utility of the daily MODIS 500 m reflectance anisotropy direct broadcast (DB) product for monitoring the evolution of vegetation phenological trends over selected crop, orchard, and forest regions. Although numerous model-fitted satellite data have been widely used to assess the spatio-temporal distribution of land surface phenological patterns to understand phenological process and phenomena, current efforts to investigate the details of phenological trends, especially for natural phenological variations that occur on short time scales, are less well served by remote sensing challenges and lack of anisotropy correction in satellite data sources. The daily MODIS 500 m reflectance anisotropy product is employed to retrieve daily vegetation indices (VI) of a 1 year period for an almond orchard in California and for a winter wheat field in northeast China, as well as a 2 year period for a deciduous forest region in New Hampshire, USA. Compared with the ground records from these regions, the VI trajectories derived from the cloud-free and atmospherically corrected MODIS Nadir BRDF (bidirectional reflectance distribution function) adjusted reflectance (NBAR) capture not only the detailed footprint and principal attributes of the phenological events (such as flowering and blooming) but also the substantial inter-annual variability. This study demonstrates the utility of the daily 500 m MODIS reflectance anisotropy DB product to provide daily VI for monitoring and detecting changes of the natural vegetation phenology as exemplified by study regions comprising winter wheat, almond trees, and deciduous forest
Daily MODIS 500 m Reflectance Anisotropy Direct Broadcast (DB) Products for Monitoring Vegetation Phenology Dynamics
Land surface vegetation phenology is an efficient bio-indicator for monitoring ecosystem variation in response to changes in climatic factors. The primary objective of the current article is to examine the utility of the daily MODIS 500 m reflectance anisotropy direct broadcast (DB) product for monitoring the evolution of vegetation phenological trends over selected crop, orchard, and forest regions. Although numerous model-fitted satellite data have been widely used to assess the spatio-temporal distribution of land surface phenological patterns to understand phenological process and phenomena, current efforts to investigate the details of phenological trends, especially for natural phenological variations that occur on short time scales, are less well served by remote sensing challenges and lack of anisotropy correction in satellite data sources. The daily MODIS 500 m reflectance anisotropy product is employed to retrieve daily vegetation indices (VI) of a 1 year period for an almond orchard in California and for a winter wheat field in northeast China, as well as a 2 year period for a deciduous forest region in New Hampshire, USA. Compared with the ground records from these regions, the VI trajectories derived from the cloud-free and atmospherically corrected MODIS Nadir BRDF (bidirectional reflectance distribution function) adjusted reflectance (NBAR) capture not only the detailed footprint and principal attributes of the phenological events (such as flowering and blooming) but also the substantial inter-annual variability. This study demonstrates the utility of the daily 500 m MODIS reflectance anisotropy DB product to provide daily VI for monitoring and detecting changes of the natural vegetation phenology as exemplified by study regions comprising winter wheat, almond trees, and deciduous forest
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