過去の先進国際セミナー
| 開催日 | 2018/2/19 (月) |
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| 時間帯 | 13:00～ |
| 講師 | Dr. Jürgen Müller (Associate Professor, Algebra and Number Theory, Wuppertal University, Germany) |
| 講演題目 | On numbers and secrets |
| 要旨 | Data security has become a most important issue: How can information be protected from unauthorised access? And how can mathematical number theory be utilised to achieve this? The aim of this talk is to introduce a few of the (simpler) ideas playing a role here. |
| 会場 | 理学部 2号館 209 |
| 開催日 | 2017/7/21 (金) |
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| 時間帯 | 18:30～20:00 |
| 講師 | Dr. Ipek Tuvay (Assistant Professor of Mathematics, Mimar Sinan Fine Arts University, Turkey) |
| 講演題目 | Fusion systems and Scott modules |
| 要旨 | In the modular representation theory of finite groups there is an important notion called "a Scott module" after L.L.Scott. This is an indecomposable kG-module which has a G-stable k-basis and it has the trivial kG-module in its socle, where G is a finite group, k is an algebraically closed field of prime characteristic p, and kG is the group algebra of G over k. In this lecture we will be discussing (so-called) fusion systems and the Scott modules for kind of particular but interesting cases. 参考文献: 1. J.L.Alperin. Local representation theory. Cambridge University Press, 1986. 2. H.Nagao and Y.Tsushima. Representations of Finite Groups. Academic Press, 1989. |
| 会場 | 理学部 2号館 208 |
| 開催日 | 2016/4/28 (木） |
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| 時間帯 | 16:10-17:40 |
| 講師 | Dr. Carlo Requião da Cunha (Assistant Professor of Physics, Univ. Federal do Rio Grande do Sul, Brazil) |
| 講演題目 | Nanostructuring Oxide Semiconductors for Solar Cell Applications |
| 要旨 | According to the American Energy Information Administration (EIA), the global demand for energy is expected to grow 56 % by 2040. Nonetheless, 80 % of the world energy is expected to keep coming from fossil fuels. These are pollutant sources that not only increase an ongoing problematic global warming but are also often extracted from regions of high political instabilities. One possible candidate that can remedy this problem is the solar cell. These are semiconductor devices that use a nearly inexhaustible and green energy supply. Nevertheless, the detailed balance maximum efficiency for solar cells is limited to approximately 46 %. In our group we have been investigating both theoretically [*1][*2] and experimentally[*3][*4] nanostructured materials that might be able to circumvent this limit with multiple carrier generation. Our main effort is on the preparation and characterization of oxide semiconductors by low-cost processes such as the low-temperature sol-gel chemistry. In this seminar, the thermodynamics of P-N solar cells will be discussed and then some theoretical results from Monte Carlo simulations on gel structures will be shown. Our results suggest that there is a disorder threshold that separates fracton and phonon states. Moreover, the nanoparticles that compose the gel structure can be tuned to form either Zipf scale-free or Poisson networks depending on the synthesis temperature and concentration of precursors. Experimentally, we have been synthesizing monolithic high-surface area tin oxide and tungsten trioxide aerogels by a sol-gel technique.[*3} A full characterization with SEM/TEM, BET/BJH, XRD, UV/Vis, FTIR, PL, PIXE and Thermogravimetry was performed. Our results indicate that the sol-gel synthesis inadvertently produces materials with oxygen deficiency. These defects produces a Burstein-Moss shift in oxide semiconductors, which is readily detectable by optical spectroscopy and severly changes its electrical properties.[*4] Along this seminar all techniques will be thoroughly discussed and experimental results will be compared to theoretical models. [*1] E. L. da Rocha and C. R. da Cunha, Chaos, Solitons & Fractals 44 (2011) 241. [*2] R. V. Morales, C. R. da Cunha and C. R. Rambo, Physica A 406 (2014) 131. [*3] C. R. da Cunha, G. H. Toffolo, C. E. I. dos Santos and R. P. Pezzi, J. Non-Cryst. Sol. 380 (2013) 48. [*4] C. R. da Cunha, F. D. da Silva and R. Morales, MRS Proc. 1731 (2015). |
| 会場 | 自然科学系総合研究棟2 マルチメディア講義室 |
| 開催日 | 2016/1/13 (水） |
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| 時間帯 | 19:30～21:00 |
| 講師 | Dr. Kevin Nute (Professor of Architecture, University of Oregon, USA) |
| 講演題目 | The Wilderness in the Metropolis Natural Change in Urban Buildings 都市のウィルダネス 都市建築の中の自然変動 |
| 要旨 | Over the past three decades the human benefits of contact with nature have been widely documented, but most building occupants do not have immediate access to natural outdoor spaces, particularly in large cities. This illustrated talk showed how the movements of the weather can be used to bring both nature and sensory stimulation to the occupants of urban buildings while also raising awareness of under-utilized sustainable practices. 自然との触れ合いによる我々への恩恵は、過去30年間にわたって立証されてきた。しかしほとんどの建物の住人、特に大都市に暮らしている人々は野外の自然空間へ直接にアクセスすることができない。その講演では、スライドを用いて、サステイナブルな自然とパッシブ活用の認識が高まる中、天気の動きがいかに自然と知覚・刺激両方を都市建築の使用者へもたらすかを明らかにしていた。 |
| 会場 | 工学部15号棟110番講義室 |
| 開催日 | 2015/2/20 (金） |
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| 時間帯 | 12:50～14:20 |
| 講師 | Dr. Nan Zhang (Simon Fraser University, Canada) |
| 講演題目 | Structure-property relationship in piezoelectric materials |
| 要旨 | Piezoelectricity exists in varies types of materials such as solid ceramics, single crystals as well as biological matters, and these materials are extensively found in sensors, actuators and transducers for commercial, scientific and daily-life uses. One of the most popular family displaying piezoelectric properties belongs to the class of crystal structure called the perovskite, which has the basic chemical formula ABX3, where A and B are cations and X is an anion, usually oxygen. The fundamental structure is cubic, with the anions forming a corner-linked array of octahedra. The A cation occupies the space between the octahedra while the B cation is at the centre of the octahedra. Although the aristotype of this material is highly symmetrical, with temperature change, pressure change or chemical modification, it is easily distorted into a lower symmetry. The structural modifications are usually very subtle, but they have significant effects on the properties of the material. The structural phase transitions induced by temperature, pressure or chemical composition are believed to be highly related to the piezoelectric performance of the crystals and therefore become the core subject in both fundamental study to clarify the origin of some materials’ high property and the application study to manufacture devices ready to use in all kinds of environments. Among the large variety of the perovskites piezoelectric crystals, the solid solution of lead zirconate and lead tinanate (PbZr1-xTixO3, PZT) and the solid solution of lead magnesium niobate and lead tinanate ((1-x)[PbMg1/3Nb2/3O3]-x[PbTiO3], PMN-PT) have displayed the most excellent piezoelectric properties. It is commonly believed to be attributed to the formation of morphotropic phase boundary or region. Considering the toxicity of the large amount of lead used in both PZT and PMN-PT, there are also considerable efforts all over the world trying to find lead-free materials to replace PZT / PMN-PT in the near future. Success of the finding is based on the similarity of the lead-free candidates with the original high-performed peizoelectrics as well as the correct fundamental understanding of the general property-structure relationship from the material science point of view. In this talk, some fundamental knowledge of the crystal symmetry as well as the effects of the structural change on the materials’ property will be explained. Certain materials will be discussed as the examples of the experimental techniques and the analytical methods to study this subject. Finally, the future in the scientific and application aspects for piezoelectrics studies will be summarized in the hope of an inspiration for students especially the future scientists. |
| 会場 | 先進科学センター会議室（理学部2号館2階） |
| 開催日 | 2013/8/19 (月) |
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| 時間帯 | 11:00-12:00 |
| 講師 | Dr. Vinai Norasakkunkit （Assistant Professor,Gonzaga University, USA） |
| 講演題目 | When Society Changes Faster than Culture: Youth and the "Dark Side" of Globalization in Post-Industrial Japan |
| 要旨 | Dr. Vinai Norasakkunkit examines how Japanese youth are being marginalized in their own society by focusing on the psychological consequences of cultural practices at the institutional level, especially in the labor market, not keeping up with social structural changes and globalization trends. Specifically Dr. Norasakkunkit argues that Japanese youth bear the brunt of the cost of institutional resistance to globalization pressures. He further experimentally examines some of the psychological consequences of being marginalized in this way, including shifting values and shifting motivational processes. This research is the culmination of Dr. Norasakkunkit’s work in experimental cultural psychology and some theoretical work at the intersection of psychology and sociology. This research examines what is happening in postindustrial Japan as an example of some of the challenges related to social structural changes due to globalization pressures. |
| 会場 | 工学系総合研究棟2階第2会議室 |
| 開催日 | 2012/6/19 (火） |
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| 時間帯 | 17:30- |
| 講師 | Dr. Renate Wackerbauer （Associate Professor, University of Alaska Fairbanks, USA） |
| 講演題目 | Reversibility of Arctic sea ice retreat - a conceptual multi-scale modeling approach. |
| 要旨 | Arctic summer sea ice has retreated at increased rates over the past decade. Large modeling efforts are undertaken to predict the future of Arctic sea ice, since it profoundly influences the future of a warming climate and life on earth. Global circulation models (GCMs) are currently the primary tool used to project climate over the next century. However, the complexity of highly parameterized GCMs makes it very difficult to assess feedback processes in climate without the concurrent use of conceptual models. We have developed a lattice-type thermodynamic complex systems model for the ice-albedo feedback that includes the basic physics of ice-water phase transition, a nonlinear diffusive energy transport in a possibly heterogeneous ice-ocean layer, and spatiotemporal atmospheric and oceanic drives. We show that reversibility of Arctic sea ice retreat strongly depends on the albedo parameterization and on the spatial scale of the model. |
| 会場 | 先進科学センター会議室（理学部2号館2階） |
| 開催日 | 2012/6/13 (水） |
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| 時間帯 | 18：00-20：00 |
| 講師 | Prof. Thomas Thiis （ノルウェイ生命科学大学 数理工学科 教授） |
| 講演題目 | Climate, buildings and infrastructure |
| 会場 | 自然科学系総合研究棟2階マルチメディア講義室 |
| 開催日 | 2012/2/28 (火） |
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| 時間帯 | 13:30-15:00 |
| 講師 | Dr. Robert Eder (Karlsruhe Institute of Technology, Germany) |
| 講演題目 | The Variational Cluster Approximation |
| 要旨 | A main challenge in present solid state theory is the description of strongly correlated electron systems. Among the schemes proposed for the solution of this problem there are also variational principles for the electronic self-energy. In the present talk one of the schemes, the variational cluster approximation will be explained. This relies on the numerical generalization of trial self-energies by exact diagonalization of small clusters. As an application, the spin state transition in LaCoO_3 will be discussed. |
| 会場 | 先進科学センター会議室（理学部2号館2階） |
| 開催日 | 2012/2/20 (月) |
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| 時間帯 | 16:10-17:40 |
| 講師 | Dr.Ranjit Biswas (Associate Professor, S.N.Bose National Centre for Basic Sciences) |
| 講演題目 | Reaction Rate and Solvation Dynamics in Neat Solvents, Electrolyte Solutions and Ionic Liquids:Similarity and Differences |
| 会場 | 自然科学2号棟8階共通ゼミ室 |