Condensed-Matter and Materials Physics The Science of the World Around Us (2007) / Chapter Skim
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5 What Happens Far from Equilibrium and Why?
5 What Happens Far from Equilibrium and Why?
Pages 91-110
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From page 91... ...
The Importance of Far-From-Equilibrium Phenomena We live in a world of evolving structures and patterns. When energy is continually supplied to systems with many interacting constituents, the outcome generally differs strikingly from the unchanging state that characterizes equilibrium.
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From page 92... ...
Instead, it arises across the entire spectrum of condensed-matter and materials physics in a host of problems of fundamental interest. Far-from equilibrium phenomena also benefit and plague us in technology and in everyday life.
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From page 93... ...
Far-from-equilibrium physics is connected intimately to both fundamental scientific challenges and cutting-edge materials processing. And, far-from-equilibrium physics underlies a wide range of phenomena outside the traditional boundaries of CMMP, including earthquakes, hurricanes, galaxy formation, and consciousness.
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From page 94... ...
This focus led to the spectacular success of CMMP in realizing that the enormous variety of equilibrium phase transitions can be understood in terms of a few classes of behavior. This history motivates CMMP researchers to search for similar organizing principles in the even vaster array of far-from-equilibrium phenomena.
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From page 95... ...
One way to keep a system from its natural state of rest and to push it into the far-from-equilibrium regime involves continual and sufficiently strong forcing. For example, the energy that continually strikes Earth from the Sun gives rise to far-from-equilibrium behavior ranging from chaotic weather patterns to the stag gering diversity of life.
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From page 96... ...
SOURCES: (Left) Savannah River National Laboratory, Department of Energy.
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From page 97... ...
Since these materials cannot relax to equilib rium, they typically retain a memory of the preparation or processing conditions, a key for many technological innovations such as molded plastic parts and shape memory polymers. Transitions from far-from-equilibrium glassy states to near equilibrium crystalline states are the basis for chalcogenide glass optical disks and phase-change memory devices.
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From page 98... ...
For example, in North America, new plants designed for processing granular materials initially operate at only about 50 to 60 percent of design capacity, while those designed for the handling of liquids immediately operate at nearly full efficiency. Investment in this area of CMMP would not only raise the level of fundamental understanding needed for innovative solutions to pervasive industrial problems but would also increase the pool of scientifically trained people who can contribute to the understanding of materials-processing industries.
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From page 99... ...
from-equilibrium conditions is that small differences in the physical or chemical properties of neighboring regions in a material can be amplified; in equilibrium, diffusion tends to smooth out such differences. This property can be exploited to aggregate inorganic components, such as metallic, magnetic, or semiconducting particles, on selective polymer domains.
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From page 100... ...
Models such as the Lorenz model and other climate models include only a few degrees of free dom, yet successfully capture qualitatively many features of Earth's climate. Similar approaches are used to gain insight into the origin of Earth's magnetic field, mantle convection, Jupiter's red spot, and the cycle of solar flares.
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From page 101... ...
to flutter ing (right) motion, visualized by imaging fluid flow around a filament tied to a post (circle at the top)
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From page 102... ...
Theoretical techniques used in CMMP to study equi librium critical phase transitions, such as the renormalization group, can be useful here. These techniques are designed to understand how physics at small length scales or timescales affects behavior at somewhat larger length scales or timescales, a b FIGURE 5.7 Far-from-equilibrium behavior often involves processes interacting over a large range of length scales and timescales, leading to characteristic patterns such as the ones observed in the fracture of a glass (left)
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From page 103... ...
The focus here is on turbulence, which is one of the most common far-from e quilibrium phenomena in the environment and in industrial processes. Turbu lence produces complex flow structures that modify the transport of momentum, mass, and heat, thereby creating a wide variety of both wanted and unwanted effects: a means for rapid mixing of reagents in industrial processes but also parasitic drag in pipe flow and, on a larger scale, catastrophic weather patterns such as hurricanes.
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From page 104... ...
Extensions of this approach have demonstrated how the unique behavior in the vicinity of a singularity can be used to achieve unprecedented levels of processing control, which can be used, for example, to uniformly encapsulate live cells prior to transplantation (Figure 5.8, right panel)
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From page 105... ...
For example, cars are now designed with complicated internal networks involving many components, backup mechanisms, and adaptive feedback loops to ensure reliable operation under a wide range of environmental conditions. Likewise, biological networks, such as those that enable white blood cells to pursue invading bacteria, have evolved to be insensitive to biochemical changes in their components.
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From page 106... ...
Similar avalanches occur in granular materials, as in landslides or mud slides, or during earthquakes (Figure 5.10)
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From page 107... ...
For certain classes of driven dissipative systems -- such as sheared glasses, foams, or fluidized granular materials such as vibrated or gas fl uidized granular beds -- there is evidence that the notion of an effective tempera ture can be useful in predicting behavior. Important CMMP issues are to elucidate the conditions under which effective temperatures provide a reasonable description and to determine the extent of the analogy to ordinary temperature.
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From page 108... ...
Because the relaxation time exceeds any measurable timescale as the glassy state is approached, a glass by definition is a system far from equilibrium. Similar glassy states are found not only in ordinary liquids but in many elec tronic systems in the presence of disorder, including interacting electron spin sys tems (spin glasses)
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From page 109... ...
Because the jammed state is out of equilibrium, even the most basic questions about any jamming transition remain intensely controversial. Is there a true thermodynamic transition, at which the relaxation time diverges?
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From page 110... ...
Currently, research on far-from-equilibrium phenomena is fragmented into small subfields. These are typically divided along the types of materials or specific phenomena studied -- for example, fracture in solids or turbulence in fluids.
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