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ON GLOBAL STABILITY OF A NONRESIDENT COMPUTER VIRUS MODEL

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Acta Mathematica Scientia 2014年第5期34卷 1427-1445页

作者： Yoshiaki MUROYA Huaixing LI toshikazu kuniya Department of Mathematics Waseda University 3-4-1 Ohkubo Shinjuku-ku Tokyo 169-8555 Japan College of Sciences Tianjin University of Technology Graduate School of Mathematical Sciences University of Tokyo 3-8-1 Komaba Meguro-ku

In this paper, we establish new sufficient conditions for the infected equilibrium of a nonresident computer virus model to be globally asymptotically stable. Our results extend two kind of known results in recent lit... 详细信息

关键词： nonresident computer virus model permanence global asymptotic stability Lyapunov function

GLOBAL STABILITY OF EXTENDED MULTI-GROUP SIR EPIDEMIC MODELS WITH PATCHES THROUGH MIGRATION AND CROSS PATCH INFECTION

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Acta Mathematica Scientia 2013年第2期33卷 341-361页

作者： Yoshiaki MUROYA Yoichi ENATSU toshikazu kuniya Department of Mathematics Waseda University3-4-1OhkuboShinjuku-kuTokyo 169-8555Japan Graduate School of Fundamental Sciences and Engineering Waseda University3-4-1OhkuboShinjuku-kuTokyo 169-8555Japan Graduate School of Mathematical Sciences University of Tokyo3-8-1KomabaMeguro-kuTokyo 153-8914Japan

In this article, we establish the global stability of an endemic equilibrium of multi-group SIR epidemic models, which have not only an exchange of individuals between patches through migration but also cross patch in... 详细信息

关键词： multi-group SIR epidemic model patch global asymptotic stability Lyapunovfunction

Evaluation of the effect of the state of emergency for the first wave of COVID-19 in Japan

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Infectious Disease Modelling 2020年第1期5卷 580-587页

作者： toshikazu kuniya Graduate School of System Informatics Kobe University1-1 Rokkodai-choNada-kuKobe657-8501Japan

In this paper,we evaluate the effect of the state of emergency for the first wave of COVID-19 in Japan,2020 from the viewpoint of mathematical *** Japan,it was announced during the period of the state of emergency from April 7 to May 25,2020 that the 80%reduction of the contact rate is needed to control the *** numerical simulation,we show that the reduction rate seems to have reached up to 86%.Moreover,we estimate the control reproduction number R c during the period of the state of emergency as R c?0:36(95%CI,0.34e0.39),and show that the effective reproduction number R e after the lifting of the state of emergency could be greater than *** result suggests us that the second wave of COVID-19 in Japan could possibly occur if any effective intervention will not be taken again.

关键词： COVID-19 SEIR epidemic model Basic reproduction number State of emergency

Seismic assessment of two multi-tiered pagodas damaged by the 2015 Nepal earthquake

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Earthquake Engineering and Engineering Vibration 2021年第2期20卷 453-469页

作者： Yohei Endo toshikazu Hanazato Department of Architecture Shinshu University4-17-1 WakasatoNagano 380-8553Japan Department of Architecture Mie University1577 Kurimamachiya-chōTsuMie 514-8507MieJapan

A seismic assessment of two multi-tier pagodas by numerical analysis is presented *** Changu Narayan temple and the Kumbeshwar temple in Nepal are used as the case *** pagodas are built of brick masonry in earthen mortar,with timber columns and *** Changu Narayan temple is a two-tier pagoda,and was seriously damaged during the 2015 Gorkha *** Kumbeshwar temple is a five-tier pagoda,and its top-tier collapsed due to the Gorkha earthquake.A seismic assessment was carried out using finite element(FE)*** FE models were prepared,and dynamic identification tests and penetrometer tests were *** analysis and nonlinear dynamic analysis were performed as part of the seismic *** main shock of the 2015 Gorkha earthquake was considered as the input *** behavior between the two pagodas was compared with the collapse mechanisms and damage patterns observed in the actual *** comparison suggested common structural features of multi-tier *** study is dedicated to providing a better understanding of the seismic behavior of multi-tier pagoda-type structures and provides suggestions for their effective analysis.

关键词： masonry multi-tier pagoda seismic assessment nonlinear dynamic analysis FEM analysis

An international expert consensus of management of recurrent hepatocellular carcinoma: a viewpoint

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Hepatobiliary Surgery and Nutrition 2020年第3期9卷 394-396页

作者： kuniya Tanaka Yuki Takahashi Tetsuji Wakabayashi Department of Gastroenterological and General Surgery Showa University Fujigaoka HospitalYokohamaJapan

We read with great interest the article titled "Multidisciplinary management of recurrent and metastatic hepatocellular carcinoma after resection: an international expert consensus" (1) published in Hepato Biliary Sur... 详细信息

关键词： Surgery hepatocellular carcinoma

Tandem planet formation for solar system-like planetary systems

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Geoscience Frontiers 2017年第2期8卷 223-231页

作者： Yusuke Imaeda toshikazu Ebisuzaki RIKEN 2-1Hirosawa351-0198Japan

We present a new united theory of planet formation,which includes magneto-rotational instability（MRl） and porous aggregation of solid particles in a consistent *** show that the ＂tandem planet formation＂ regime is likely to result in solar system-like planetary *** the tandem planet formation regime,planetesimals form at two distinct sites：the outer and inner edges of the MRl suppressed *** former is likely to be the source of the outer gas giants,and the latter is the source for the inner volatile-free rocky *** study spans disks with a various range of accretion rates,and we find that tandem planet formation can occur for M = 10^7.3- 10^-6.9Myr^-*** rocky planets form between 0.4-2 AU,while the icy planets form between 6-30 All;no planets form in 2-6 AU region for any accretion *** is consistent with the gap in the solid component distribution in the solar system,which has only a relatively small Mars and a very small amount of material in the main asteroid belt from 2-6 *** tandem regime is consistent with the idea that the Earth was initially formed as a completely volatile-free *** and other volatile elements came later through the accretion of icy material by occasional inward scattering from the outer *** between reductive minerals,such as schreibersite（Fe-jP）,and water are essential to supply energy and nutrients for primitive life on Earth.

关键词： Accretion disk Planet formation Magneto-rotational instability Origin of life

The origin of high eccentricity planets:The dispersed planet formation regime for weakly magnetized disks

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Geoscience Frontiers 2017年第2期8卷 233-245页

作者： Yusuke Imaeda toshikazu Ebisuzaki RIKEN 2-1Hirosawa351-0198Japan

In the tandem planet formation regime,planets form at two distinct sites where solid particles are densely accumulated due to the on/off state of the magnetorotational instability（MRI）.We found that tandem planet formation can reproduce the solid component distribution of the Solar System and tends to produce a smaller number of large planets through continuous pebble flow into the planet formation *** the present paper,we investigate the dependence of tandem planet formation on the vertical magnetic field of the protoplanetary *** calculated two cases of BZ 3.4 × 10^-3 G and BZ = 3.4 × 10^-5 G at 100 AU as well as the canonical case of BZ = 3.4 × 10^-4 *** found that tandem planet formation holds up well in the case of the strong magnetic field（BZ 3.4 × 10^-3 G）.On the other hand,in the case of a weak magnetic field（BZ= 3.4 × 10^-5 G） at 100 AU,a new regime of planetary growth is realized：the planets grow independently at different places in the dispersed area of the MRl-suppressed region of r-8-30 AU at a lower accretion rate of M 〈 10^-7.4M⊙yr^-*** call this the ＂dispersed planet formation＂ *** may lead to a system with a larger number of smaller planets that gain high eccentricity through mutual collisions.

关键词： Accretion disk Planet formation Magnetorotational instability

Single planet formation regime in the high-ionization environment:Possible origin of hot Jupiters and super-Earths

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Geoscience Frontiers 2018年第4期9卷 1023-1031页

作者： Yusuke Imaeda toshikazu Ebisuzaki RIKEN

We studied the particle growth in a protoplanetary disk in a high-ionization environment and found that icy planet formation is inactive for a disk with an ionization rate 100 times higher than that of the present Solar System. In particular, in the case of M 〈 10^（-7.4）M_☉yr^（-1）, only rocky planet formation occurs. In such a case, all the solid materials in the disk drift inward, eventually reach the inner MRI front,and accumulate there. They form a dense, thin sub-disk of solid particles, which undergoes gravitational instability to form rocky planetesimals. The planetesimals rapidly grow into a planet through pebble accretion. Consequently, rocky planets tend to be much larger than planets formed through other regimes（tandem planet formation regime and dispersed planet formation regime）, in which icy planet formation actively takes place. These rocky planets may evolve into hot Jupiters if they grow fast enough to the critical core mass of the runaway gas accretion before the dispersal of the disk gas, or they may evolve into super-Earths if the gas dispersed sufficiently early.

关键词： Accretion disk Planet formation Magneto-rotational instability Galactic cosmic rays Hot Jupiter Super-Earth

Population synthesis of planet formation using a torque formula with dynamic effects

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Geoscience Frontiers 2017年第2期8卷 215-222页

作者： Takanori Sasaki toshikazu Ebisuzaki Department of Astronomy Kyoto University RIKEN

Population synthesis studies into planet formation have suggested that distributions consistent with observations can only be reproduced if the actual Type Ⅰ migration timescale is at least an order of magnitude longer than that deduced from linear *** past studies considered the effect of the Type I migration of protoplanetary embryos,in most cases they used a conventional formula based on static torques in isothermal disks,and employed a reduction factor to account for uncertainty in the mechanism ***,in addition to static torques,a migrating planet experiences dynamic torques that are proportional to the migration *** dynamic torques can impact on planet migration and predicted planetary *** this study,we derived a new torque formula for Type Ⅰ migration by taking into account dynamic *** formula was used to perform population synthesis simulations with and without the effect of dynamic *** many cases,inward migration was slowed significantly by the dynamic *** the static torque case,gas giant formation was effectively suppressed by Type I migration;however,when dynamic effects were considered,a substantial fraction of cores survived and grew into gas giants.

关键词： Planetary formation Population synthesis Type Ⅰ migration