セミナーのお知らせ
[MATセミナー開催のお知らせ]
 開催日時：
 2020年3月25日(水) 13:00〜15:00
 開催場所:
 横浜研究所情報技術棟5階508 MATシアター
 使用言語:
 英語
 講演者:
 堀 宗朗
 タイトル:
 Looking for good coordinate system
 概要:

I am expecting the presence of a good coordinate system in which most efficient numerical analysis is made for a physical problem such as a wave equation of solid continuum. The use of principal directions for a secondorder symmetric tensor is a clue of finding one if an orthogonal curvilinear coordinate system is formed. Several trials of finding a good coordinate system are explained.
以降の講演予定
決まり次第掲載いたします
[MATセミナー開催のお知らせ]
 開催日時：
 2020年3月12日(木) 13:00〜15:00
 開催場所:
 横浜研究所情報技術棟5階508 MATシアター
 使用言語:
 英語
 講演者:
 下林 俊典
 タイトル:
 Nucleation energy landscape of membraneless organelles
 概要:

This is the report of oneandahalf year oversea dispatch research in Princeton University. Cells organize intracellular biochemical materials through compartmentalization into various organelles. In general, it has been considered that such compartmentalization requires a lipid bilayer membrane; however, the cell can also compartmentalize the materials without a lipid membrane via liquidliquid phase separation (LLPS).
The membraneless organelles repeat to form or dissolve in response to the endo/exogenous change of system parameters (ex. concentration, temperature and etc). In this seminar, I will talk about our recent efforts to prove the nucleation energy landscape of membraneless organelles in living cells.
[MATセミナー開催のお知らせ]
 開催日時：
 2020年3月11日(水) 13:00〜15:00
 開催場所:
 横浜研究所情報技術棟5階508 MATシアター
 使用言語:
 英語
 講演者:
 Gen Li
 タイトル:
 Novel Mathematical and physical models reveal mechanisms behind complex phenomena in biology
 概要:

In this presentation, the speaker would like to introduce several ongoing studies during the last 6 months on biomechanics, based on novel mathematical and physical models.
[Study 1: On the actuation mechanism of fish swimming] We developed a dedicated experimentalnumerical inverse dynamics approach to calculate the lateral bending moment distributions for a largeamplitude undulatory swimmer that moves freely in 3D space. Our analysis on fish larvae shows that the actuation patterns are not only relatively simple but also strikingly similar.
[Study 2: On an effective approach to test drug effect on fish] The use of zebrafish larvae has aroused wide interest in the medical field. To quantify the influence of drugs on zebrafish larvae swimming behaviors and energetics, we have developed a novel methodology to exploit intravital changes based on observed zebrafish locomotion. The approach has potential to evaluate the influence of drugs on the aquatic animal’s behavior changes and thus support the development of new analgesic and neuroactive drugs.
[Study 3: On the fluid dynamics of a carnivorous plant] The aquatic bladderwort captures zooplankton in mechanically triggered underwater traps. With characteristic dimensions less than 1 mm, the trapping structures are among the smallest known to capture prey by suction—a mechanism that is not effective in the creepingflow regime. To understand what makes suction feeding possible on the small scale of bladderwort traps, we characterized their suction flows experimentally and mathematically.
[Study 4: On the physical mechanism of burstandcoast swimming of fish] This study addresses the physical mechanism of intermittent swimming by considering the burstandcoast regime of fish swimming at different speeds. We show that fish modulate a unique intrinsic cycle to sustain the demanded speed by modifying the bursting to coasting ratio while maintaining the duration of the cycle constant. Numerical simulations suggest that the chosen kinematics correspond to energetically optimized gaits.
[MATセミナー開催のお知らせ]
 開催日時：
 2020年3月4日(水) 13:00〜15:00
 開催場所:
 横浜研究所情報技術棟5階508 MATシアター
 使用言語:
 英語
 講演者:
 Ettore Barbieri
 タイトル:
 Formation and Disruption of Conductive Networks in Pyroresistive Polymer Composites
 概要:

Pyroresistive composites combine the insulating properties of polymers with the conductive ability of a second phase, such as metallic particles. At standard temperatures, the whole material conducts electricity. Upon heating, the polymer expands, and the conductive networks of particles break down, rendering the composite effectively an insulator. Flexible and controllable selfregulating heating devices use these materials. Applications include healthcare appliances, soft robotics, artificial skins and wearable electronics.
Several essential questions arise in the manufacturing of these materials. In this talk, I will address three in particular: at which temperature the composite stops conducting? What is the critical volume fraction of particles for conduction? Does the diameter of the particles influence the disruption of the network? To answer these questions, I will use computer simulations based on thermomechanics, graph theory, percolation theory, random adsorption algorithms and the DLVO theory for colloids.
[MATセミナー開催のお知らせ]
 開催日時：
 2020年2月26日(水) 13:00〜15:00
 開催場所:
 横浜研究所情報技術棟5階508 MATシアター
 使用言語:
 英語
 講演者:
 大島 逸平
 タイトル:
 Transversal Oscillation of an airblasted liquid sheet
 概要:

The atomization phenomenon of an airblasted liquid sheet, which is widely used for many applications, is not clear because of its complicated multiscale and multiphase characteristics. The transversal oscillation induced by the surrounding air flows affects the spray characteristics such as spray angle and droplet diameter. Therefore, it is required to understand the transversal oscillation phenomenon of the liquid sheet and predicting transversal oscillation characteristics.
In this presentation, I will introduce the visualization result obtained by a highspeed camera and the proposed new prediction model for the transversal wavelength of the liquid sheet based on the spanwise oscillation mechanism.
[MATセミナー開催のお知らせ]
 開催日時：
 2020年2月12日(水) 13:00〜15:00
 開催場所:
 横浜研究所情報技術棟5階508 MATシアター
 使用言語:
 英語
 講演者:
 桑野 修
 タイトル:
 Direct observation of flash temperature at frictional interface of synthetic quartz crystal during highvelocity sliding
 概要:

Recent experiments conducted at sub‐seismic to seismic sliding velocities (mm/s to m/s) show the dramatic weakening in the friction coefficient for a wide variety of rock types due to mechanochemical effects by frictional heating. Consequently, several weakening mechanisms have been proposed depending on the type of rock specimens. Some of them are based on the sample observation and analysis after experiments. Direct observation of frictional contacts during an experiment is indisputable to constrain an elementary process at frictional contacts during slip. To measure the temperature distribution of frictional contact directly, we conducted the insitu observation of frictional interface of synthetic quartz crystal using a highspeed camera. I'll talk about our recent experiments to obtain thermal images of a frictional interface.
[MATセミナー開催のお知らせ]
 開催日時：
 2020年2月5日(水) 13:00〜15:00
 開催場所:
 横浜研究所情報技術棟5階508 MATシアター
 使用言語:
 英語
 講演者:
 細野 七月
 タイトル:
 Smoothed Particle Hydrodynamics simulations on FP16
 概要:

The smoothed particle hydrodynamics (SPH) is one of the most widely accepted numerical hydrodynamic schemes.
One serious disadvantage to SPH is its computational cost.
Hence, it is common to apply highperformance computing techniques to SPH.
Lately, the socalled "AIspecific" processors have been hitting the market.
An AIspecific processor is typically a peripheral device to CPU which has many coprocessors which support arithmetic operations of halfprecision floating point numbers (FP16) to reduce the costs for data transfer and arithmetic operations.
Hence, FP16 can also be attractive for scientific computing.
However, FP16 would make simulation accuracy worse, which can be a severe problem for scientific computing whose accuracy is of paramount importance.
Hence, the effectiveness of FP16 to scientific computing should be determined by the balance between reduction of timetosolution and exacerbation of simulation quality.
However, there are almost no studies for SPH which survey the effect of precision on simulation accuracy.
In this work, we aimed at surveying the relationship between timetosolution and simulation accuracy to determine whether FP16 is useful to SPH.
We carried out a test problem, 2D Couette flow with SPH and measured the accuracy and wallclock time by changing precision for floating point numbers.
As a result, we found that the terminal accuracy does not depend on the precision.
[MATセミナー開催のお知らせ]
 開催日時：
 2020年1月29日(水) 13:00〜14:30
 開催場所:
 横浜研究所情報技術棟5階508 MATシアター
 使用言語:
 英語
 講演者:
 野村 瞬
 タイトル:
 Exposing test of concrete specimens in the deep sea
 概要:
 The recent research elucidated that the deep sea has a lot of potential to develop the natural resources of the oceanic energy. Additionally, there are lot of demand to monitor the ocean bottom dynamics to manage the submarine disasters. To increase resource productivity and/or improve monitoring accuracy, the submarine infrastructure with enough stability in long term is essential matter. To overcome potential issues, concrete material is preferential candidate, since it is cheap but presents sufficient stiffness. However, to utilize the concrete material in the deep sea, there are problematic since there are no data over 200 m depth of the sea. In this talk I explain the outline of exposing test in deep sea started from 2018.8. Then the material properties which was recovered from 3500 m depth in 2019.9 are briefly introduced.
[MATセミナー開催のお知らせ]
 開催日時：
 2020年1月22日(水) 15:30〜17:00
 開催場所:
 横浜研究所情報技術棟5階508 MATシアター
 使用言語:
 英語
 講演者:
 西浦 泰介
 タイトル:
 Introduction of my industrial collaborative research
 概要:

Now, I have 8 collaborative projects with outside JAMSTEC in addition to 5 projects collaborated with other JAMSTEC group. There are so many projects, but completed projects are not so many because the working time assigned to one project has less than one month in simple calculation. Although almost all projects are ongoing, I will briefly introduce the overview of each project focused on the industrial collaboration. After that, I will pick up one project among those projects and explain the details in this seminar.
[MATセミナー開催のお知らせ]
 開催日時：
 2020年1月8日(水) 13:00〜15:00
 開催場所:
 横浜研究所情報技術棟5階508 MATシアター
 使用言語:
 英語
 講演者:
 合原 一究
 タイトル:
 Interaction Mechanisms Quantified from Empirical Data (A Case Study on Frog Choruses)
 概要:

Interaction mechanism in the acoustic communication of actual frogs is investigated by combining mathematical modeling and empirical data. Here we use a mathematical model (a phase oscillator model) to describe the deterministic and stochastic features of frog choruses in which male frogs attempt to avoid call overlaps with each other due to acoustic interaction.
The mathematical model with a general interaction term is identified by a Bayesian approach from multiple audio recordings on the choruses of male Japanese tree frogs. Then, we quantify the magnitude of attention paid among the male frogs from the identified model.
In this presentation, I briefly introduce our empirical and theoretical studies on frog choruses, and then explain the details in the model identification from empirical data.