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Results for “dissipative systems”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS1994

Evolution of wave function in a dissipative system

For a dissipative system with Ohmic friction, we obtain a simple and exact solution for the wave function of the system plus the bath. It is described by the direct product in two independent Hilbert space. One of them is described by an effective Hamiltonian, the other represents the effect of the bath, i.e., the Brownian motion, thus clarifying the structure of the wave function of the system whose energy is dissipated by its interaction with the bath. No path integral technology is needed in this treatment. The derivation of the Weisskopf-Wigner line width theory follows easily.

Yu, Li-Hua↗
DOE OSTI2020

Heat dissipation systems with hygroscopic working fluid

A heat dissipation system apparatus and method of operation using hygroscopic working fluid for use in a wide variety of environments for absorbed water in the hygroscopic working fluid to be released to minimize water consumption in the heat dissipation system apparatus for effective cooling in environments having little available water for use in cooling systems. The system comprises a low-volatility, hygroscopic working fluid to reject thermal energy directly to ambient air. The low-volatility and hygroscopic nature of the working fluid prevents complete evaporation of the fluid and a net consumption of water for cooling, and direct-contact heat exchange allows for the creation of large interfacial surface areas for effective heat transfer. Specific methods of operation prevent the crystallization of the desiccant from the hygrosopic working fluid under various environmental conditions.

42 ENGINEERING↗
DOE OSTI2023

Heat dissipation systems with hygroscopic working fluid

A heat dissipation system apparatus and method of operation using hygroscopic working fluid for use in a wide variety of environments for absorbed water in the hygroscopic working fluid to be released to minimize water consumption in the heat dissipation system apparatus for effective cooling in environments having little available water for use in cooling systems. The system comprises a low-volatility, hygroscopic working fluid to reject thermal energy directly to ambient air. The low-volatility and hygroscopic nature of the working fluid prevents complete evaporation of the fluid and a net consumption of water for cooling, and direct-contact heat exchange allows for the creation of large interfacial surface areas for effective heat transfer. Specific methods of operation prevent the crystallization of the desiccant from the hygrosopic working fluid under various environmental conditions.

Martin, Christopher L.↗
NASA NTRS1971

Dissipative systems

The abstract theory presented shows how the theory of dissipative systems of ordinary differential equations can be extended to include a wide class of functional and partial differential equations. Since the basic hypotheses are all in terms of boundedness, finding sufficient conditions in terms of Liapunov functions was not difficult. Work is being undertaken to solve some nontrivial examples to illustrate how the theory can applied.

Lasalle, J. P.↗
NASA NTRS1972

Dissipative systems.

A theory is presented that shows how the concept of dissipative systems of ordinary differential equations can be extended to include a broad class of functional and partial differential equations, such as retarded functional differential equations and parabolic partial differential equations. Since the basic hypotheses are all in terms of boundedness, finding sufficient conditions in terms of Liapunov functions would not be too difficult.

Lasalle, J. P.↗
DOE OSTI2020

Heat dissipation systems with hygroscopic working fluid

In various embodiments, the present invention relates to heat dissipation systems including a hygroscopic working fluid and methods of using the same. In various embodiments, the present invention provides a method for heat dissipation using a hygroscopic working fluid. The method can include transferring thermal energy from a heated process fluid to the hygroscopic working fluid in a process heat exchanger, to form a cooled process fluid. The method can include condensing liquid from a feed gas on a heat transfer surface of a feed gas heat exchanger in contact with the cooled process fluid, to form a cooled feed gas, the heated process fluid, and a condensate. The method can include dissipating thermal energy from the hygroscopic working fluid to a cooling gas composition with a fluid-air contactor. The method can include transferring moisture between the hygroscopic working fluid and the cooling gas composition with the fluid-air contactor. The method can include adding at least part of the condensate to the hygroscopic working fluid.

Martin, Christopher Lee↗
NASA NTRS1993

Solar flares and avalanches in driven dissipative systems

The contention of Lu and Hamilton (1991) that the energy release process in solar flares can be understood as avalanches of many small reconnection events is further developed. The dynamics of the complex magnetized plasma of solar active regions is modeled with a simple driven dissipative system, consisting of a vector field with local instabilities that cause rapid diffusion of the field. It is argued that the avalanches in this model are analogous to solar flares. The distributions of avalanches in this model are compared with the solar flare frequency distributions obtained from ISEE 3/ICE satellite observations. Quantitative agreement is found with the energy, peak luminosity, and duration distributions over four orders of magnitude in flare energy, from the largest flares down to the completeness limit of the observations. It is predicted that the power-law solar flare frequency distributions will be found to continue downward with the same logarithmic slopes to an energy of about 3 x 10 exp 25 ergs and duration of about 0.3 s, with deviations from power-law behavior below these values.

Lu, Edward T.↗
DOE OSTI2021

Singularities in nearly uniform one-dimensional condensates due to quantum diffusion

Dissipative systems often exhibit wavelength-dependent loss rates. One prominent example is Rydberg polaritons formed by electromagnetically induced transparency, which have long been a leading candidate for studying the physics of interacting photons and also hold promise as a platform for quantum information. In this system, dissipation is in the form of quantum diffusion, i.e., proportional to k 2 (k being the wavevector) and vanishing at long wavelengths as k→0. Here, we show that one-dimensional condensates subject to this type of loss are unstable to long-wavelength density fluctuations in an unusual manner: after a prolonged period in which the condensate appears to relax to a uniform state, local depleted regions quickly form and spread ballistically throughout the system. We connect this behavior to the leading-order equation for the nearly uniform condensate—a dispersive analog to the Kardar-Parisi-Zhang equation—which develops singularities in finite time. Furthermore, we show that the wavefronts of the depleted regions are described by purely dissipative solitons within a pair of hydrodynamic equations, with no counterpart in lossless condensates. We close by discussing conditions under which such singularities and the resulting solitons can be physically realized.

74 ATOMIC AND MOLECULAR PHYSICS↗
NASA NTRS1993

Dissipative control of energy flow in interconnected systems

Dissipative energy flow controllers are designed for interconnected modal subsystems. Active feedback controllers for vibration suppression are then viewed as either an additional subsystem or a dissipative coupling. These controllers, which are designed by the LQG positive real control approach, maximize energy flow from a specified modal subsystem.

Kishimoto, Y.↗
NASA NTRS1985

Lorentz-covariant dissipative Lagrangian systems

The concept of dissipative Hamiltonian system is converted to Lorentz-covariant form, with evolution generated jointly by two scalar functionals, the Lagrangian action and the global entropy. A bracket formulation yields the local covariant laws of energy-momentum conservation and of entropy production. The formalism is illustrated by a derivation of the covariant Landau kinetic equation.

Kaufman, A. N.↗