214 research outputs found
Analysis of the Brownian Motion by Elementary School Students
To stimulate the intellectual curiosity of elementary school students, we
conducted a workshop in distance education aimed at exploring the microscopic
world inside a cell. In this workshop, elementary school students motivated to
learn more on the subject of science analyzed movies of the Brownian motion of
micrometer-sized particles suspended in water, using an open-source software,
Tracker. These students then performed two-dimensional(2D)-random walk
experiments using a dice game sheet to examine the physical mechanism of
Brownian motion. After the workshop, we conducted a questionnaire-based survey.
Many participants answered that the contents were difficult but interesting,
suggesting that our workshop was very efficient to stimulate the curiosity of
motivated students.Comment: 16 pages, 10 figures, the following article has been submitted to The
Physics Teache
Shaping Graphene: An Alternative Approach
With experimentation on graphene (an atomic layer of graphite) becoming more and more common it is imperative that we have the capability to shape the material beyond the random manner in which it is deposited by mechanical exfoliation. This capability would be invaluable not only for the interesting electronic and optical properties that can be obtained, but also potentially for characterizing the mechanical resonators that we have been able to fabricate here at Pomona College by suspending few-layer graphene sheets over trenches in SiO2. We propose novel methods for etching graphene that should allow us to shape the material when used in conjunction with our e-beam lithography capabilities
Crumbling Crystals: On the Dissolution Mechanism of NaCl in Water
Life on Earth depends upon the dissolution of ionic salts in water,
particularly NaCl. However, an atomistic scale understanding of the process
remains elusive. Simulations lend themselves conveniently to studying
dissolution since they provide the spatio-temporal resolution that can be
difficult to obtain experimentally. Nevertheless, the complexity of various
inter- and intra-molecular interactions require careful treatment and long time
scale simulations, both of which are typically hindered by computational
expense. Here, we use advances in machine learning potential methodology to
resolve for the first time at an ab initio level of theory the dissolution
mechanism of NaCl in water. The picture that emerges is that of a steady
ion-wise unwrapping of the crystal preceding its rapid disintegration,
reminiscent of crumbling. The onset of crumbling can be explained by a strong
increase in the ratio of the surface to volume of the crystal. Overall,
dissolution is comprised of a series of highly dynamical microscopic
sub-processes, resulting in an inherently stochastic mechanism. These atomistic
level insights now pave the way for a general understanding of dissolution
mechanisms in other crystals, and the methodology is primed for more complex
systems of recent interest such as water/salt interfaces under flow and salt
crystals under confinement
Mapping Structural Heterogeneity at the Nanoscale with Scanning Nano-structure Electron Microscopy (SNEM)
Here we explore the use of scanning electron diffraction coupled with
electron atomic pair distribution function analysis (ePDF) to understand the
local order as a function of position in a complex multicomponent system, a hot
rolled, Ni-encapsulated, ZrCuNiAl bulk metallic
glass (BMG), with a spatial resolution of 3 nm. We show that it is possible to
gain insight into the chemistry and chemical clustering/ordering tendency in
different regions of the sample, including in the vicinity of nano-scale
crystallites that are identified from virtual dark field images and in heavily
deformed regions at the edge of the BMG. In addition to simpler analysis,
unsupervised machine learning was used to extract partial PDFs from the
material, modeled as a quasi-binary alloy, and map them in space. These maps
allowed key insights not only into the local average composition, as validated
by EELS, but also a unique insight into chemical short-range ordering
tendencies in different regions of the sample during formation. The experiments
are straightforward and rapid and, unlike spectroscopic measurements, don't
require energy filters on the instrument. We spatially map different quantities
of interest (QoI's), defined as scalars that can be computed directly from
positions and widths of ePDF peaks or parameters refined from fits to the
patterns. We developed a flexible and rapid data reduction and analysis
software framework that allows experimenters to rapidly explore images of the
sample on the basis of different QoI's. The power and flexibility of this
approach are explored and described in detail. Because of the fact that we are
getting spatially resolved images of the nanoscale structure obtained from
ePDFs we call this approach scanning nano-structure electron microscopy (SNEM),
and we believe that it will be powerful and useful extension of current 4D-STEM
methods
Understanding Soft Errors in Uncore Components
The effects of soft errors in processor cores have been widely studied.
However, little has been published about soft errors in uncore components, such
as memory subsystem and I/O controllers, of a System-on-a-Chip (SoC). In this
work, we study how soft errors in uncore components affect system-level
behaviors. We have created a new mixed-mode simulation platform that combines
simulators at two different levels of abstraction, and achieves 20,000x speedup
over RTL-only simulation. Using this platform, we present the first study of
the system-level impact of soft errors inside various uncore components of a
large-scale, multi-core SoC using the industrial-grade, open-source OpenSPARC
T2 SoC design. Our results show that soft errors in uncore components can
significantly impact system-level reliability. We also demonstrate that uncore
soft errors can create major challenges for traditional system-level checkpoint
recovery techniques. To overcome such recovery challenges, we present a new
replay recovery technique for uncore components belonging to the memory
subsystem. For the L2 cache controller and the DRAM controller components of
OpenSPARC T2, our new technique reduces the probability that an application run
fails to produce correct results due to soft errors by more than 100x with
3.32% and 6.09% chip-level area and power impact, respectively.Comment: to be published in Proceedings of the 52nd Annual Design Automation
Conferenc
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Scalable Manufacturing of Superhydrophobic Micro- and Nanostructured Condensation Accelerating and Droplet Shedding Surfaces for Air Conditioning Performance Enhancement
One solution currently being explored for reducing the condensation effects of water inside the evaporator coil of an air conditioning system is the use of textured surface morphologies on the evaporator fins that may enable water droplets to both condense and shed more quickly. While multiple pattern scales and geometries have been characterized on metal substrates, including posts, pillars, post arrays, reentrant structures, micro/nano hierarchical patterns, and microchannels, there is a dearth of research associated with microdome patterns, the significance being that nature’s most famous superhydrophobic, water-shedding surface, the lotus leaf, utilizes these features. Here, aluminum surfaces have been fabricated with varying micropillar and microdome structures and a hydrothermally grown nanoporous layer of zinc oxide to create a hierarchical morphology that is reminiscent of the lotus leaf geometry. Micropillar and microdome array structures with comparable feature sizes and areal densities were fabricated, and their static and dynamic water contact angles were characterized in order to understand the influence of microstructural geometry on water-shedding performance. These hierarchical surfaces were further characterized in dynamic condensing conditions using a custom-designed wind tunnel setup to simulate an air conditioning inlet environment. Video footage was recorded, and an image analysis algorithm was developed and applied in order to compare surface performance. The entire zinc oxide nanostructure synthesis process was then scaled and applied to a full-scale cooling coil for later evaluation in a simulated building testbed. The results of all surface characterization methods and condensation tests, the wind tunnel test bed design, the image analysis algorithm development, and the scaling process are reported
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