Interpebble contact radius in a comet nucleus

In recent years, the gravitational collapse of pebble clumps in the early Solar System has been regarded as a plausible scenario for the origin of comets. In this context, ``pebbles'' represent mm- to cm-sized dust aggregates composed of (sub)micron-sized dust particles, and the structure of km-sized comets is thought to be an agglomerate of pebbles. The contact radius for pebble-pebble contacts was modelled in an earlier study; however, the pressure dependence of the interpebble contact radius was not considered. Here, we revisit the interpebble contact radius in a comet nucleus. We calculated the interpebble contact radius based on JKR contact theory, and we took into consideration the effect of lithostatic pressure. We found that the interpebble contact radius varies with depth from the surface, and the earlier model underestimated it by one order of magnitude at the centre of the comet nucleus.Comment: 9 pages, 6 figures. Accepted for publication in MNRA

EFFECT OF SHOES AND TIGHTS WITH THE SUPPORT FUNCTION ON SUPPORT LEG DURING RUNNING

The study aimed to clarify the effect of shoes (WS) and tights (BT) with the support function on support leg during running. The subjects, eight female Japanese runners, ran for 1-min periods on a treadmill. Motion, electromyography (EMG), acceleration and angular velocity were recorded. The following results were obtained: 1) there was difference in the pronation angle between support shoes and non-support shoes. 2) There was difference in angle of lower leg in frontal plane between support shoes and non-support shoes. 3) Combination of WS and BT might decrease angle of the foot and shank in frontal plane and stabilize the trunk, but the effect varies depending on subjects

Performance of large scaled tsunami run-up analysis using explicit ISPH method

The tsunami run-up simulation by the particle method at city level needs to huge number of particle at least 1 billion particles. The conventional particle simulation method is not easy to solve these huge problem even on the premise of using supercomputer. Then, a new particle method ’fully explicit Incompressible SPH’ is developed that takes into consideration both calculation efficiency and accuracy. Finally, we demonstrate the future plan how to use our simulation resultes for a practical ’Soft’ disaster mitigation method through the evacuation education with the Virtual Reality(VR) system

Interparticle normal force in highly porous granular matter during compression

We perform a numerical simulation of compression of a highly porous dust aggregate of monodisperse spheres. We find that the average interparticle normal force within the aggregate is inversely proportional to both the filling factor and the average coordination number, and we also derive this relation theoretically. Our findings would be applicable for granular matter of arbitrary structures, as long as the constituent particles are monodisperse spheres.Comment: 9 pages, 7 figures. Accepted for publication in PR

Early SNS-based monitoring system for the COVID-19 outbreak in Japan: a population-level observational study

Background: The World Health Organization declared the novel coronavirus outbreak (COVID-19) to be a pandemic on March 11, 2020. Large-scale monitoring for capturing the current epidemiological situation of COVID-19 in Japan would improve preparation for and prevention of a massive outbreak. Methods: A chatbot-based healthcare system named COOPERA (COvid-19: Operation for Personalized Empowerment to Render smart prevention And care seeking) was developed using the LINE app to evaluate the current Japanese epidemiological situation. LINE users could participate in the system either though a QR code page in the prefecture’s website, or a banner at the top of the LINE app screen. COOPERA asked participants questions regarding personal information, preventive actions, and non-specific symptoms related to COVID-19 and their duration. We calculated daily cross correlation functions between the reported number of infected cases confirmed by PCR and the symptom-positive group captured by COOPERA. Results: We analyzed 206,218 participants from three prefectures reported between March 5 and 30, 2020. The mean (standard deviation) age of participants was 44.2 (13.2). No symptoms were reported by 96.93% of participants, but there was a significantly positive correlation between the reported number of COVID-19 cases and self-reported fevers, suggesting that massive monitoring of fever might help to estimate the scale of the COVID-19 epidemic in real time. Conclusions: COOPERA is the first real-time system being used to monitor trends in COVID-19 in Japan, and provides useful insights to assist political decisions to tackle the epidemic