Handwritten Digit Recognition by Spin Waves in a Skyrmion Reservoir

By performing numerical simulations for the handwritten digit recognition task, we demonstrate that a magnetic skyrmion lattice confined in a thin-plate magnet possesses high capability of reservoir computing. We obtain a high recognition rate of more than 88%, higher by about 10% than a baseline taken as the echo state network model. We find that this excellent performance arises from enhanced nonlinearity in the transformation which maps the input data onto an information space with higher dimensions, carried by interferences of spin waves in the skyrmion lattice. Because the skyrmions require only application of static magnetic field instead of nanofabrication for their creation in contrast to other spintronics reservoirs, our result consolidates the high potential of skyrmions for application to reservoir computing devices

Reservoir Computing with Spin Waves in Skyrmion Crystal

Magnetic skyrmions are nanometric spin textures characterized by a quantized topological invariant in magnets and often emerge in a crystallized form called skyrmion crystal in an external magnetic field. We propose that magnets hosting a skyrmion crystal possess high potential for application to reservoir computing, which is one of the most successful information processing techniques inspired by functions of human brains. Our skyrmion-based reservoir exploits precession dynamics of magnetizations, i.e., spin waves, propagating in the skyrmion crystal. Because of complex interferences and slow relaxations of the spin-wave dynamics, the skyrmion spin-wave reservoir attains several important characteristics required for reservoir computing, e.g., the generalization ability, the nonlinearity, and the short-term memory. We investigate these properties by imposing three standard tasks to test the performances of reservoir, i.e., the duration-estimation task, the short-term memory task, and the parity-check task. Through these investigations, we demonstrate that magnetic skyrmion crystals are promising materials for spintronics reservoir devices. Because magnetic skyrmions emerge spontaneously in magnets via self-organization process under application of a static magnetic field, the proposed skyrmion reservoir requires neither advanced nanofabrication nor complicated manufacturing for production in contrast to other previously proposed magnetic reservoirs constructed with fabricated spintronics devices. Our proposal is expected to realize a breakthrough in the research of spintronics reservoirs of high performance.Comment: 16 pages, 12 figure

Supporting effective health and biomedical information retrieval and navigation: A novel facet view interface evaluation

AbstractThere is a need to provide a more effective user interface to facilitate non-domain experts’ health information seeking in authoritative online databases such as MEDLINE. We developed a new topic cluster based information navigation system called SimMed. Instead of offering a list of documents, SimMed presents users with a list of ranked clusters. Topically similar documents are grouped together to provide users with a better overview of the search results and to support exploration of similar literature within a cluster. We conducted an empirical user study to compare SimMed to a traditional document list based search interface. A total of 42 study participants were recruited to use both interfaces for health information exploration search tasks. The results showed that SimMed is more effective in terms of users’ perceived topic knowledge changes and their engagement in user-system interactions. We also developed a new metric to assess users’ efforts to find relevant citations. On average, users need significantly fewer clicks to find relevant information in SimMed than in the baseline system. Comments from study participants indicated that SimMed is more helpful in finding similar citations, providing related medical terms, and presenting better organized search results, particularly when the initial search is unsatisfactory. Findings from the study shed light on future health and biomedical information retrieval system and interface designs

Computational Aspects of Optional P\'{o}lya Tree

Optional P\'{o}lya Tree (OPT) is a flexible non-parametric Bayesian model for density estimation. Despite its merits, the computation for OPT inference is challenging. In this paper we present time complexity analysis for OPT inference and propose two algorithmic improvements. The first improvement, named Limited-Lookahead Optional P\'{o}lya Tree (LL-OPT), aims at greatly accelerate the computation for OPT inference. The second improvement modifies the output of OPT or LL-OPT and produces a continuous piecewise linear density estimate. We demonstrate the performance of these two improvements using simulations

Data-driven and Model-independent Reconstruction of Modified Gravity

In this paper, the modified gravity, which is characterized by the modified factor $\mu$ in the linear matter density perturbation theory, is reconstructed in a completely data-driven and model-independent way via Gaussian process by using currently available cosmic observations, which consist Pantheon+ SNe Ia samples, observed Hubble parameter $H(z)$ and the redshift space distortion $f\sigma_8(z)$ data points. The reconstructed results suggest a time varying $\mu$ at low redshifts. It also implies more complicated modified gravity beyond the simplest general relativity and the Dvali-Gabadadze-Porrati braneworld model is required.Comment: 8 pages, 3 figures, comments welcom

Variations of Endocrine Hormones Concentrations in Tupaia belangeri under Simulated Seasonal Acclimatized: Role of Leptin Sensitivity

Seasonal variations in endocrine hormones concentrations are important for the survival of small mammals during acclimatization. In order to understand the role of leptin sensitivity on other endocrine hormones concentrations, we examined body mass, serum leptin level, serum insulin, tri-iodothyronine (T 3), thyroxine (T4) and thyroid stimulating hormone (TSH) concentrations in Tupaia belangeri under seasonal acclimatized (The simulated temperature and photoperiod in winter: 5°C and SD, 8h:16h Light:Dark; the simulated temperature and photoperiod in summer: 30°C and SD, 16h:8h Light:Dark) for 4 weeks. The results showed that body mass, serum leptin level, serum T3, T4 concentrations and T3/T4 showed significant variation, but serum insulin and TSH concentrations showed no variations between treatment group. There were positive correlation between serum leptin level and insulin, T4 concentrations, and were negative correlation between serum leptin level and body mass, T3 concentrations. However, no correlation was found between serum TSH concentrations and serum leptin level. The present results suggested T. belangeri overcome winter thermogenesis challenges by adjusting body mass and endocrine hormones concentrations. Furthermore, leptin may play an potential role in their body mass regulation in T. belangeri