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AICS Cafe

AICS Cafe is a place where the researchers in AICS can frankly discuss about their researches beyond their own disciplinary wall in order to collaborate with each other. We plan to have it twice a month regularly. We welcome all people including the promotion office and administration division of K computer in AICS.

  • Purpose : In order to promote the research collaboration beyond each of existing research disciplines, this seminar provides the discussion field for exchanging information, understanding neighboring researchers, and collaboration between each other.
  • Place: Workshop room (6th floor) at AICS
  • Lang : presentation in Japanese or English, the slide in English
  • Etc.: Please give your presentations clearly to researchers in other fields. Please do not hesitate to ask a question to the speakers.

The 83rd AICS Cafe
Date and Time: Thu. Jan. 21, 2016, 14:00-15:30
Place: Workshop room (6th floor) at AICS

Rescheduled from January 7
(This session will start at 14:00 on Thursday !)


Title: Numerical challenge to sunspot 11-year cycle
Speaker: Hideyuki Hotta (Assistant Professor, Chiba University; invited by Particle Simulator Research Team)

Presentation Language: Japanese
Presentation Material: Japanese

Abstract: Detail

The sun is a magnetized star. We can frequently observe sunspot, i.e., strong magnetic region, on the solar surface. The magnetic field is thought to be generated in the solar interior by dynamo action of turbulent ionized plasma. The number of sunspot has a long-standing big mystery, i.e., 11-year cycle. We have not understood what makes this beautiful cycle. The key is the turbulent thermal convection in the solar convection zone. The turbulence, however, is nonlinear and complicated, and investigations by numerical calculation have important roles. Since we had problems on using large supercomputers and increasing resolution, we newly adopt a method so called, the Reduced Speed of Sound Technique (RSST) which can solve our previous problems. Using this method we have significantly improved our understanding of turbulent flow and magnetic field in the solar interior. In the talk, one example, the small-scale effect for constructing the large-scale magnetic field is shown.
 

Profile: Detail

Hideyuki Hotta invented a method which can efficiently use large computers even for the solar convection zone with changing an equation of the problem, while he was still a graduate student at the department of Earth and Planetary Science, The University of Tokyo. Then he reproduce the near surface shear layer which was a long standing problem in the solar physics using the K computer for the first time. After he got PhD at March 2014, he stayed High Altitude Observatory, USA as a JSPS fellow. He studied generation mechanisms of magnetic field in the solar interior and revealed that there is significantly stronger magnetic field than previously expected. From July 2015, he has moved to Chiba university as a tenure track assistant professor and continues studying the solar interior with using large computers.

The 82nd AICS Cafe (Progress Report*)
Date and Time: Thu. Jan. 14, 2016, 15:00-16:00
Place: Workshop room (6th floor) at AICS

(This session will be held on Thursday!)
Title: Understanding and improving predictability of precipitation
Speaker: Shigenori Otsuka (Data Assimilation Research Team)

Presentation Language: Japanese
Presentation Material: English

* This AICS Cafe is a special AICS Cafe, which is an occasion for postdoctoral researchers in their 4th year to report their research activities after joining AICS. Attendance of broad audience including PI, is kindly appreciated.

Abstract: Detail

Precipitation forecast is important for our daily life. However, predictability of atmospheric motion has intrinsic limitations due to the chaotic nature of the dynamics. We investigate the predictability limits of convective precipitation by extracting the growing modes using the breeding method. To improve practical predictability, we developed an adaptive multi-model ensemble Kalman filter algorithm and a space-time extrapolation system with data assimilation. In this presentation, we will demonstrate the performance with synthetic and real observations.

The 81st AICS Cafe
Date and Time: Thu. Dec. 17, 2015, 15:00-16:00
Place: Workshop room (6th floor) at AICS

(This session will be held on Thursday!)
Title: Eclipse PTP, Docker and software development for the K computer
Speaker: Peter Bryzgalov (HPC Usability Research Team)

Presentation Language: Japanese
Presentation Material: English

Abstract: Detail

How can I understand a program structure? How can I detect performance issues with my MPI application? Is it possible to make program refactoring easy? How do I setup development environment? How can I use existing git repository?
These are some of the topics I plan to address in my talk. I shall demonstrate how Eclipse PTP IDE can be used to speed up many aspects of parallel program development cycle. I shall show how Docker can be used for an easy setup of development environment for parallel applications that can be built and run on the K computer.
Presentation will be available at: http://www.slideshare.net/PeterBryzgalov/aics-cafe2

The 80th AICS Cafe (Progress Report*)
Date and Time: Tue. Dec. 1, 2015, 15:00-16:00
Place: Workshop room (6th floor) at AICS

(This session will be held on Tuesday!)

Title: Asian summer monsoon and development of SCALE-LES
Speaker: Tsuyoshi Yamaura (Computational Climate Science Research Team)

Presentation Language: Japanese
Presentation Material: English

* This AICS Cafe is a special AICS Cafe, which is an occasion for postdoctoral researchers in their 4th year to report their research activities after joining AICS. Attendance of broad audience including PI, is kindly appreciated.

Abstract: Detail

Asian monsoon is a planetary-scale climate system driven by differences in heat capacity between the Asian Continent and its surrounding ocean. In boreal summer, a large-scale thermal low system appears on the Asian Continent, leading to change wind direction from ocean to the continent; note that wind direction is from the continent to ocean in boreal winter. Corresponding to this change in the wind direction, rainy season begins in most region in Asia, e.g., the rainy season is known as Baiu in Japan in early summer. For improvement of the prediction of the summer precipitation in Japan, and for prediction of the precipitation change in the future climate, our research team develop a Large Eddy Simulation model (SCALE-LES). This talk introduces a series of studies related to the Asian summer monsoon. At the same time, the treatment of lower boundary condition in the SCALE-LES, which is a crucial issue of our studies, is discussed.

The 79th AICS Cafe
Date and Time: Wed. Oct. 7, 2015, 15:00-16:00
Place: Workshop room (6th floor) at AICS
 
(This session will be held on Wednesday!)

Title: An Introduction to Control of K computer's power consumption

Speaker: Toshiyuki Tsukamoto (Deputy Division Director, Operations and Computer Technologies Division / Team Head, Facility Operations and Development Team)

Presentation Language: Japanese
Presentation Material: Japanese

Abstract: Detail

The K computer facilities have many features not found at other supercomputer sites. These include an expansive and pillar-free computer-room, power supply system that consists of a co-generation system (CGS) and a high-speed current-limiting circuit breaker without uninterruptible power supply (UPS), distribution boards installed not on computer-room walls but under a raised floor, extremely quiet and high-efficiency air conditioners, and water-cooling system for CPUs featuring precise temperature control. To ensure stable working of K computer and its peripherals, the facility operations and development team (FODT) of the operations and computer technologies division, RIKEN AICS is responsible for operation and enhancement of the facilities. Furthermore, FODT conducts research on the advanced management and operations of AICS’ facilities. One of the most serious problems is rapid and substantial increase in electricity prices since 2011. Therefore, we investigate the most suitable driving conditions for AICS facilities to achieve effective cost reduction. Another problem is increased power consumption by AICS. The use of electricity by AICS is strictly limited by a contract between AICS and the local electric supply company. However, recently, the facility’s power consumption exceeded the contract limit. This matter is important because the company requires us to accept a raise in the upper/lower power limit, which amounts to an increase in electricity cost. To prevent this problem, we have investigated a method to control K computer’s power consumption by using emergency job stopping together with the system operations and development team and the software development team of operations and computer technologies division, RIKEN AICS.

The 78th AICS Cafe (Progress Report*)
Date and Time: Fri. Sep. 25, 2015, 15:00-16:00
Place: Workshop room (6th floor) at AICS


Title: A framework of data integration processing for urban disaster simulations
Speaker: Hideyuki O-Tani (Computational Disaster Mitigation and Reduction Research Unit)
* This AICS Cafe is a special AICS Cafe, which is an occasion for postdoctoral researchers in their 4th year to report their research activities after joining AICS. Attendance of broad audience including PI, is kindly appreciated.

Abstract: Detail

In order to make reliable estimations of urban disasters, such as seismic damage of structures and tsunami inundation, we need the detailed urban models for the target city. The models may include the information about all individual buildings and the underground data.
However, the quantity and quality of available single raw sources for them are limited and fragmented. Thus we need to make the detailed information pre-processing and integrating the heterogeneous raw sources, including administrative data, 3D building shapes, and a set of borehole data. The key issue is how to automate the model construction avoiding manual work.
This talk introduces some challenges in urban simulation modeling, and proposes a framework of data integration processing. The framework can automate some intermediate data conversions required in the processing.

The 77th AICS Cafe (Progress Report*)
Date and Time: Thu. Sep. 10, 2015, 15:00-16:00
Place: Workshop room (6th floor) at AICS

Rescheduled from July 17

Title: Development of massively parallel algorithm and code for molecular electronic structure calculations on peta-scale supercomputers
Speaker: Michio Katouda (Computational Molecular Science Research Team)
* This AICS Cafe is a special AICS Cafe, which is an occasion for postdoctoral researchers in their 4th year to report their research activities after joining AICS. Attendance of broad audience including PI, is kindly appreciated.

Abstract: Detail

Massively parallel computing in the field of theoretical and computational molecular science becomes more important year by year to utilize massively parallel supercomputers to perform the first-principle electronic structure calculations on large-size and complicated molecular systems. Our research team has been developed the novel molecular science software NTChem [1] for the massively parallel computing of electronic structures on the petascale supercomputer such as the K computer. NTChem involves the novel development of theory and algorithm, which make possible through the collaborative use of the K computer across the fields of computational science and computer science. In this talk, I introduce my works about the development of massively parallel algorithms and its implementations into NTChem. We present the overview of the massively parallel algorithm and its implementation of (1) the Hartree-Fock and density functional theory (DFT) self-consistent field calculations [1], (2) the time-dependent DFT excited-state calculation [1], and (3) the resolution of identity second-order Møller–Plesset perturbation (RI-MP2) calculations for energy [3, 4] and energy gradient, respectively.

References:
[1] Nakajima, T.; Katouda, M.; Kamiya, M.; Nakatsuka, Y. Int. J. Quantum Chem. 2015, 115, 349–359. doi: 10.1002/qua.24860.
[2] http://labs.aics.riken.jp/nakajimat_top/ntchem_e.html
[3] Katouda, M.; Nakajima, T. J. Chem. Theory Comput. 2013, 9, 5373–5380. doi: 10.1021/ct400795v.
[4] Katouda, M.; Nakajima, T.; Nagase S. Proceedings of JSST 2012, 2012, 338–343.

The 76th AICS Cafe
Date and Time: Fri. Sep. 4, 2015, 15:00-16:00
Place: Workshop room (6th floor) at AICS


Title: An introduction to computational social science and frameworks for parameter-space explorations
Speaker: Yohsuke Murase (Discrete Event Simulation Research Team)

Abstract: Detail

The abundance of digital data due to the rapid development of ICT has generated entirely new, multidisciplinary approaches in social sciences, in which network theory and computational science play a considerable role both in terms of data analysis and modeling. Nowadays this field is known as computational social science and it has attracted a lot of attention.
In the first half of my talk, I will give a brief overview of computational social science and then introduce our recent researches on modeling social relationships[1,2]. In order to understand the underlying social activities, we propose microscopic models and compare the properties of the generated networks with the empirical observations.
In the latter half, I will introduce two kinds of frameworks for parameter-space explorations which is being developed by our team[3]. One of the most fundamental difficulties of social simulations is that the models for social phenomena are not established well as those for natural sciences. It is also difficult to determine the initial condition or boundary condition even if big data are available since they are usually incomplete. Thus, for social simulation, it is more important to capture the global property of phase space rather than simulating a specific event precisely. To overcome these difficulties, we are developing frameworks which enables us to explore parameter space more efficiently.

References:
[1] Y. Murase et al., "Multilayer weighted social network model", Phys. Rev. E, 90, 052810 (2014) doi: 10.1103/PhysRevE.90.052810
[2] Y. Murase et al., "Modeling the role of relationship fading and breakup in social network formation”, PLoS ONE 10(7) e0133005 (2015) doi: 10.1371/journal.pone.0133005
[3] https://github.com/crest-cassia/oacis
      Y. Murase et al., "A tool for parameter-space exploration", Physics Procedia 57, 73 (2014) doi: 10.1016/j.phpro.2014.08.134

The 75th AICS Cafe (Progress Report*)
Date and Time: Thu. Jul. 30, 2015, 15:00-16:00
Place: Workshop room (6th floor) at AICS


Title: Stability analysis of soil liquefaction for rational prediction of earthquake induced ground failure
Speaker: Jian CHEN (Computational Disaster Mitigation and Reduction Research Unit)
* This AICS Cafe is a special AICS Cafe, which is an occasion for postdoctoral researchers in their 4th year to report their research activities after joining AICS. Attendance of broad audience including PI, is kindly appreciated.

Abstract: Detail

Liquefaction refers to a sudden change in ground behaviour from solid-like to fluid-like. Induced by strong ground motion of an earthquake, soil happens to lose its strength and to start to flow, causing damages to structures on or under the liquefied ground.
Coupling between soil particles and pore waters is a key mechanism of liquefaction. Based on continuum mechanics, governing equations of soil displacement and pore water pressure are derived. Transition from a stable to an unstable solution of the governing equations is regarded as a source of liquefaction initiation. Stability analysis of the solution thus facilitates better numerical treatment of the initiation and development of liquefaction.
We carry out the stability analysis linearizing the governing equations. It is shown that dilatancy (shear deformation inducing volume change) changes the stability of plane waves of soil displacement and pore water pressure; the wave becomes unstable when the dilatancy ratio exceeds a certain critical value [1]. We further carry out numerical analysis that uses K computer for a spherical wave, developing a finite element method based on the particle discretization scheme that is suitable to compute soil particle detachment. It is shown that an unstable solution is captured; the dilatancy effect triggers and the detaching effect spatially expands the unstable solutions [2].
The loss of stability has been overlooked in the numerical analysis of liquefaction. For more rational prediction, therefore, it is necessary to develop a code which accounts for the stability. A finite element analysis that solves this problem is being developed.

References:
[1]. J. Chen, H. O-tani and M. Hori, On Mathematical Stability Analysis of Liquefaction Considering Soil-Water Coupling, Journal of Japan Society of Civil Engineers, vol.70, No.2, I_641-I_648, 2014. doi: 10.2208/jscejam.70.I_641
[2]. J. Chen, H. O-tani and M. Hori, Stability analysis of soil liquefaction using a finite element method based on particle discretization scheme, Computers and Geotechnics, vol. 67, 64–72, 2015. doi: 10.1016/j.compgeo.2015.02.008

The 74th AICS Cafe
Date and Time: Fri. Jul. 3, 2015, 15:00-16:00
Place: Workshop room (6th floor) at AICS
 

Title: An introduction of cloud-aerosol interaction, cloud microphysical model
Speaker: Yousuke Sato (Computational Climate Science Research Team)

Abstract: Detail

Aerosol, which is tiny particle in the atmosphere, affects the microphysical and radiative properties of cloud particles. This effect is called “cloud-aerosol interaction”, which is one of the most uncertain factors for climate predictions. Cloud microphysical model and aerosol transport model, which are parts of component in atmospheric numerical simulation code, have been developed and used to understand the cloud-aerosol interaction. In my talk, I first introduce the cloud-aerosol interaction, the cloud microphysical model, and the aerosol transport model. After that I will introduce several examples about how to use the cloud microphysical model and aerosol transport model for understanding the cloud-aerosol interaction.