171 research outputs found
Statistical Self-Similar Properties of Complex Networks
It has been shown that many complex networks shared distinctive features,
which differ in many ways from the random and the regular networks. Although
these features capture important characteristics of complex networks, their
applicability depends on the type of networks. To unravel ubiquitous
characteristics that complex networks may have in common, we adopt the
clustering coefficient as the probability measure, and present a systematic
analysis of various types of complex networks from the perspective of
statistical self-similarity. We find that the probability distribution of the
clustering coefficient is best characterized by the multifractal; moreover, the
support of the measure had a fractal dimension. These two features enable us to
describe complex networks in a unified way; at the same time, offer unforeseen
possibilities to comprehend complex networks.Comment: 11 pages, 4 figure
Interaction of particles with a cavitation bubble near a solid wall
Hard particle erosion and cavitation damage are two main wear problems that
can affect the internal components of hydraulic machinery such as hydraulic
turbines or pumps. If both problems synergistically act together, the damage
can be more severe and result in high maintenance costs. In this work, a study
of the interaction of hard particles and cavitation bubbles is developed to
understand their interactive behavior. Experimental tests and numerical
simulations using computational fluid dynamics (CFD) were performed.
Experimentally, a cavitation bubble was generated with an electric spark near a
solid surface, and its interaction with hard particles of different sizes and
materials was observed using a high-speed camera. A simplified analytical
approach was developed to model the behavior of the particles near the bubble
interface during its collapse. Computationally, we simulated an air bubble that
grew and collapsed near a solid wall while interacting with one particle near
the bubble interface. Several simulations with different conditions were made
and validated with the experimental data. The experimental data obtained from
particles above the bubble were consistent with the numerical results and
analytical study. The particle size, density and position of the particle with
respect to the bubble interface strongly affected the maximum velocity of the
particles
Experiments and theory of selective assembly using topography and ultrasonically-induced fluid forces
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2007.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Includes bibliographical references (leaves 127-129).A site-selective self-assembly technique called templated assembly by selective removal (TASR) is introduced and demonstrated. A theory is created to describe its operation, and its correspondence with experiments is shown. In the experiments, the topography of the template is modified to match the shapes of micron-sized microsphere components at the locations where the components are intended to assemble; then the components and template are coated with a hydrophobic layer. The substrate and components are then placed in a fluid environment for the assembly process, and megahertz frequency ultrasound is applied to the fluidic bath to selectively remove components from undesired sites. Experiments successfully demonstrated highly selective assembly of the microcomponents with the diameters in the range from 1.6[mu]m to 0.4[mu]m into the shapematched holes in the template. Based on the understanding of hydrophobic interfacial energy and the flow fields created by ultrasound, a theory was proposed to describe the mechanism of component removal and was carefully verified with additional experiments. In the present work, scalability and repeatability of the present approach were also addressed and experimentally investigated. Additionally, component circulation was qualitatively assessed in association with near-boundary acoustic streaming flow, and its contribution to the present assembly process is discussed.by Sunghwan Jung.Ph.D
Growing crack analyses using nodal release technique
Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1995.Includes bibliographical references (leaves 78-80).by Sunghwan Jung.M.S
Surface Waves on a Semi-toroidal Water Ring
We study the dynamics of surface waves on a semi-toroidal ring of water that
is excited by vertical vibration. We create this specific fluid volume by
patterning a glass plate with a hydrophobic coating, which confines the fluid
to a precise geometric region. To excite the system, the supporting plate is
vibrated up and down, thus accelerating and decelerating the fluid ring along
its toroidal axis. When the driving acceleration is sufficiently high, the
surface develops a standing wave, and at yet larger accelerations, a traveling
wave emerges. We also explore frequency dependencies and other geometric shapes
of confinement
- …