Research Achievements by Yuko Hatano (Updated on October 15, 2021)
My specialty is to make new mathematical models to the real data collected
from various environments, such as the atmosphere or the hydrosphere.
I always try to construct a universal model, taking advantage of the portability of mathematics.
It is not the state-of-the-art math, but mostly undergraduate level.
Still, with that level of math, we can do many things useful to our society.
More specifically, I have worked on mathematical modeling of spread of nuclear contaminants,
since my background is nuclear engineering.
Accidental emissions of radionuclides give information on how substances
in the nature will migrate, regardless of where they are; in the atmosphere,
or in a lake. It is indispensable to predict the migration quantitatively.
1. One of my most important contributions is to quantitatively describe, over a decade, the
spread of radioactive pollutants in the air around the Chernobyl
power plant. Based on my mathematical model, I derived a formula in 1997
https://www.sciencedirect.com/science/article/pii/S1352231097005116.
It gives the decrease of the airborne concentration of a specific radionuclide(such as
Cs-134,137, Ce-144, Ru-106) in the form as
t^{-4/3}exp(-λt),
where λ is a constant and t is the days elasped after the accident.
My formula well reproduces the data measured in both Chernobyl
and Fukushima.
Some groups of researchers have also tested my formula and proved its validity
[Magnoni, 2012; Matsumura et al., 2018; Kitayama et al., 2016; Ochiai et al., 2016].
Moreover, using the formula, we may estimate the date that a contamination occurred.
Suppose someone discovered a polluted site, not knowing who or
when the contamination happened. We can estimate an approximate date when
the pollution occurred, if we start measuring the airborne concentration after the discovery.
The formula diverges at t=0,
so that we make a plot of concentration versus the date of measurement.
The time at which the vertical axis diverges to infinity should be t=0,
i.e., the date when the contamination happened.
(Hatano and Hatano, 2003).
It may also be applicable to non-radioactive, general pollutants.
For the achievement of the Chernobyl analysis,
I got the Young Investigator Award in 1999.
After the Fukushima accident, I had interviews with major newspaper companies
(Aasahi webronza).
My research has been referred to in the newspapers
(Sankei, Mainichi, Akahata, Nikkan Kogyo).
Besides my appointment at Graduate School of Systems and Information Engineering,
I have a concurrent post at CRiED (Center for Research in Isotopes and
Environmental Dynamics, University of Tsukuba) since the accident.
It is one of the leading teams in Japan that measure and collect
the data of radionuclides in Fukushima.
The special feature of my formula is its range of application;
it is applicable to the time range from one year to a hundred and the spatial range
from one kilometer to a hundred. The ranges of my study span the typical
human lifetime and the typical evacuation area of a nuclear accident,
I hope an immediate use for the society.
2. Another contribution of mine is a mathematical model of permeation
of pollutants in water through porous media, such as crushed rocks and sands.
I took this model from transport of electron in a metal with impurities.
Although the model was originally considered in a microscopic scale, the model fit surprisingly well the experimental data of the concentration profile of the pollutants at the outlet of a tube filled with crushed granite. This is another incident that shows the universality of mathematical models.
This study in 1998 https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1029/98WR00214 is now
cited in papers of the field of inverse problem in mathematics as a standard reference.
According to Google Scholar Citations, the citation is still growing.
3. Long-term change of the Cs-137 concentration in Lake Onuma (赤城大沼) after the Fukushima accident.
https://www.nature.com/articles/s41598-021-99667-1?proof=tNature
The model used here is the same one as in 2 (above, porous media).
University of Tsukuba, OCW