› Traveling Wave Magnetophoresis
After I enrolled at Duke, I began working with the Magnetic Nanosystems Group to explore the non-linear dynamics of superparamagnetic beads in potential energy landscapes generated through superimposition of a rotating external magnetic field onto a micro-magnet array. Aside from demonstration of intriguing mechanics, systems like this have promising applications to micro-organism sorting and development of high-precision lab-on-a-chip devices.
Here is a
visualization of the system I initially focused on.
By varying the direction of the external field with respect to the substrate magnetization, my objective was to be able to design a system where beads of differing sizes could be driven at varying angles across the substrate, or even lead to orthogonal separation. My simulations confirmed this possibility, though experiments proved more challenging, and require ongoing effort to fully realize this behavior. If implemented, it is a very efficient sorting mechanism for biological cargo in arbitrary quantities.
During my summers, I traveled to Shanghai Jiaotong University, and studied the effect of varying the frequency ratio and phase difference between the horizontal and vertical fields on the dynamics of these magnetic beads. The system in this situation has potential to drive beads of two different sizes into opposite directions, and I used numerical simulations to guide my experimental efforts to realize this important behavior.
An illustration of how phase difference impacts the direction of the beads' motion on the substrate is shown below for various bead sizes. I am currently focusing on experiments with a slightly modified system that would allow even more enhanced control of directionality among different bead sizes.
As a part of my work within the group, I also developed a code that could automatically and robustly tag the locations of colloids within a micrograph.
This code was then utilized in various projects, such as in the study of a simple method to direct the self-assembly of colloids into numerous complex structures, selection among which is governed by two experimental parameters, ferrofluid concentration and number ratio of the two bead types undergoing assembly.
A phase diagram of the rich possibilities that this system allows is shown below:
am currently focusing on new substrate geometries for the same rotating
field setup, and exploring further avenues and applications that this
system can provide.
› Soft Active Materials
I have also worked in the Soft Active Materials Laboratory at Duke on studies relating to real-time observation of electromechanical instability formation in dielectric elastomers.
› Non-Linear Dynamics
Another project I work on (in the Duke University Non-Linear Dynamics Group) is exploring the non-linear dynamics of a rocking block on an oscillating foundation.
› Porous Media and Multiphase Flows
I worked in the Porous Media and Multiphase Flows lab at the Virginia Commonwealth University from
Prior to my research studies, I formulated scripts to generate
computational models of non-woven fibrous media structures for various
CFD codes like GeoDict (Fraunhofer ITWM) and Fluent (ANSYS). My primary
research study was to investigate the sensitivity of numerical
permeability computations to a media's fiber orientation. I discovered
that transverse permeability calculations are independent of planar
fiber orientation, but proportional to deviation of fiber angles from a
planar setup. The results were published in Physics of Fluids.
My structure generation code was utilized by the Porous Media lab
for a study on the impact of fiber orientation on fluid spread in
fibrous sheets, the results of which were published in the International Journal of Heat and Mass Transfer.
A highlight figure from the Phys. Fluids paper, which depicts the
relation between transverse permeability and through-plane fiber angle
deviation (from zero), is shown below. The results were in disagreement
with those presented in a former Phys. Fluids article on a related
› Radiative Heat Transfer
While at the Porous Media lab in VCU, I also did modeling work
relating to heat flow in fibrous materials. This work has extensive
relevance to industrial applications, including the design of household
and spaceship (re-entry) insulation materials. For fibrous materials
with fiber diameter much larger than the wavelength of incoming rays, I
used ray-tracing to accurately model the radiative mode of heat
transfer as a function of various microstructural parameters.The results were published in the International Journal of Heat and Mass Transfer.
An example of a structure generated by my code, frozen at a particular instant through the simulation, is shown below:
› The TinyHPC Cluster and Operating System
TinyHPC is a Class I beowulf high performance computing cluster of the shared memory architecture that I built in the summer following my junior year in high school. It uses MPI for inter-node communication. It has a theoritical peak of 15.6 GFLOPS
The first day I got a cluster running (ParallelKnoppix) is
13. 2008. This version was composed of a
Gateway e3400 Desktop, and two Toshiba Satellite laptops connected by
D-Link DI-524. The next version connected by an Intel Express 330T hub
and having four nodes running PelicanHPC (one Satellite laptop, and
three desktops being from Gateway, Tangent, and eMachines) was created
July 08. 2008. A similar version with six
nodes (the other Toshiba laptop, and another desktop) was finished on
Up till here, these clusters did not do well on the HPL due to their
hetrogeneous nature. As such, I decided to build a homogeneous cluster.
I obtained five Intel 815EGEW motherboads and five Intel Celeron FCPGA2
1.3 GHz processor, as well as 512 Mb RAM sticks, power supplies, and
network cards. The next version was ready by
July 29. 2008.
This version is now the TinyHPC
› Computational Intelligence
I worked in the Compuational Intelligence and Simulation lab at
VCU since about
2008. My work related to neural network based prediction
of corrosion fatigue.
› Shell Access Over Email
A lot of us need access to our home computers, but for one reason or another, cannot transport it everywhere with us. SSH might be an answer to some, but not everyone, mainly due to lack of resources (such as a computer to SSH from!).
Since I am able to email from my cell phone to my computer, I decided to set something up to let me email my computer shell commands that it can execute, while maintain a sensible degree of security that's enough for an average user - of course, this email-terminal setup can never be as secure as SSH as it is now. Anyways, here is the source if anyone wants to use it or play around with it. The code is in Python. It uses LibGMAIL, so you'll have to install that first to make any use out of the application.
› Natural Language Programming
An attempt was made to design and implement a system that
users to program a computer through limited domain natural language
statements, thus extending the ability to interact with machines at a
system level to the relatively novice population. The proposed system
design combines a range of artificial intelligence related techniques,
including natural language parsing, noun phrase chunking, named entity
recognition, and neural network classification to translate raw natural
language statements into a custom backend language that is designed to
make the mapping of natural language parses to it as direct as
possible. The entire system is also unique in its ability to “learn”
from experience, made possible by the use of adaptive neural networks
for the translation phase. As such, the system steadily improves over
time in its ability to understand natural language statements, and
coupled with the fact that it allows the user to program in an
interactive manner, gives highly accurate results. A screenshot of the interface is presented below.
This project was
done over the course of my junior year. It won many
awards at regional and state science competitions, including
recognition from Intel, SAIC, the Army, and the Air Force.