講師：Ram Adar (School of Physics and Astronomy, Tel Aviv University, Israel)
題目： Bjerrum pairs in ionic solutions: a Poisson-Boltzmann approach
要旨：
Ionic solutions are often regarded as fully dissociated ions dispersed
in a polar solvent. While this picture holds for dilute solutions, at
higher ionic concentrations, oppositely charged ions can associate into
dimers, referred to as Bjerrum pairs. We consider the formation of such
pairs within the nonlinear Poisson-Boltzmann framework, and investigate
their effects on bulk properties of electrolytes. Our findings show that
pairs can reduce the magnitude of the dielectric decrement of ionic
solutions as the ionic concentration increases. We describe the effect
of pairs on the Debye screening length, and relate our results to recent
surface-force experiments.
講師：Subhadeep Roy (Earthquake Research Institute, University of Tokyo)
題目： Fracture in Different Scales: A Statistical Mechanical Approach
要旨：
Fracture is a complex phenomenon involving large span of time and
length scales, starting from atomic scale or laboratory scale to
geological scale like earthquake. A failure process can take place
showing precursory rupture events, or catastrophically without showing
such precursor. Also the rupture events might show correlation among
themselves or might happen in a random manner. So the important question
is: What are the physical criteria that govern the mode of failure?
In statistical mechanics, disorder systems and systems out of
equilibrium are extensively studied in the last decade. So it will be
interesting to study fracture in statistical mechanical point of view.
The talk deals with the implementation of two main factors, disorder
and stress release range, that guides failure process. A a statistical
model namely Fiber Bundle Model is used to study the effect of above
two parameters on the failure process, starting from laboratory scale
to earthquake.
