Page 7 - CEGE Magazine Fall 2024

YUAN LI CONT...
using image processing technology
on both the macro- and micro-scales.
Once we understand the interaction
between algal cells and clay particles, we
can propose a comprehensive method
to guide the use of clay to mitigate
cyanobacterial blooms.
Clay-algae flocculation is a promising
method to remove HABs in aquatic
ecosystems. Many HAB-generating
species, such as M. aeruginosa, produce
toxins and harm the environment,
human health, and the economy.
Natural clays, such as bentonite and
kaolinite, have been applied to mitigate
HABs. By forming large aggregates
in the water column, the flocculation
of algal cells and clay particles can
remove toxins and cells. In Judy Yang’s
lab, we are investigating the effect of
laponite, a synthetic, biodegradable, and
commercially available smectite clay, on
removing HAB cells. We compare its cell
removal efficiencies with bentonite and
kaolinite through clay-algae flocculation
experiments. Our results show that
laponite is more efficient in removing
M. aeruginosa cells compared with
bentonite and kaolinite. Specifically,
we have shown that to remove 80%
of M. aeruginosa cells from the water
column, 0.1 g/L of laponite (clay mass
to the total volume) is needed, which
is much smaller than the required 2
g/L of kaolinite and 4 g/L of bentonite.
We demonstrated that the superior
performance of laponite clay occurs
because its particle size is smaller
compared to bentonite and kaolinite,
which leads to a higher encounter rate
between cells and clay particles. We also
examined the influence of cell density
on cell removal efficiency. We used this
research to demonstrate that laponite
can efficiently remove harmful algal cells
from Powderhorn Lake.
In collaboration with Prof. Guzina and Dr.
Marc Bonnet from the École nationale
supérieure de techniques avancées
(ENSTA), France, I recently completed a
project on the wave-based viscoelastic
imaging of rock specimens. This imaging
is similar to an MRI or ultrasound used in
medical elastography to detect cancerous
tumors. The immediate application of
this work is to monitor the mechanical
transformations in rock subjected to
reactive flow. The work is supported as
part of the Center on Geo-processes
in Mineral Carbon Storage (GMCS), an
Energy Frontier Research Center funded
by the US Department of Energy, at the
University of Minnesota.
The overall objective of the GMCS is to
understand and develop the science
and engineering needed to store CO2
permanently in the subsurface by way of
mineralization, which is the safest way to
reduce net-CO2 emissions. Mafic and
ultramafic rocks like basalt and peridotite
are found abundantly both onshore and
offshore. These rocks interact with injected
carbon causing it to mineralize into a solid
form. Understanding the interaction of
carbon with mafic rock can help facilitate
development of technologies that improve
mineralized carbon storage.
Mineralization does have challenges.
It is often self-limiting, as pores clog
and reduce permeability. Alternatively,
rock can also fracture and increase
permeability through crystallization in pore
spaces. A better understanding of these
mechanisms is required to fully utilize
the potential of this process. Our work
aims to non-intrusively characterize the
mechanical fingerprint of these processes
using waves.
In a second exciting project, Prof.
Guzina and I work with Dr. Shixu Meng
from Virginia Tech to study how waves
can be manipulated through various
metamaterials. Metamaterials are used
for a range of purposes, including energy
harvesting, vibration isolation, sensing,
communication, and cloaking, to name
just a few. Typically, devices would be
analyzed and designed using physical or
numerical simulations, which are often
costly and restrict the designers’ ability
to optimize their design. We propose a
semi-analytical method that significantly
reduces computational costs, enabling
us to explore a vast design space and
optimally design metamaterial devices for
specific tasks.
  The ASCE Engineering Mechanics Institute (EMI) conference was a
wonderful networking experience. It was nice meeting people from
around the world with a wide range of expertise. ASCE EMI is a wonderful
platform to share ideas related to my research on 2D rainbow traps,
which has applications in various areas including energy harvesting,
cloaking, and vibration isolation. This was my first conference; there was
so much to learn, especially communication and presentation skills. 
Prasanna Salasiya, Geomechanics
Advised by Bojan Guzina
Received a travel grant funded by Charles
and Marlys Nelson
University of Minnesota College of Science and Engineering | DEPARTMENT OF CIVIL, ENVIRONMENTAL, AND GEO- ENGINEERING 7