Dissipative structures thermal mechanisms

All bodies traveling in a fluid experience dynamic heating, the magnitude of which depends upon the body characteristics and the environmental parameters. Modern supersonic aircraft, for example, experience appreciable heating. This incident flux is accommodated by the use of an insulated metallic structure, which provides a near balance between the incident thermal pulse and the heat dissipated by surface radiation. Hence, only a small amount of heat has to be absorbed by mechanisms other than radiation. 

Oscillating phenomena and hysteresis behaviour (bi-, multistability) are the most important phenomena in systems far from thermal equilibrium, excluding spatial structures (patterns, travelling waves). Examples of both types of temporal structures can be found in all disciplines where nonlinear dynamics play a significant role. In biophysics it appears that dissipation provides a general mechanism and may also account for the functional... 

With re-entry vehicles and spaceplanes, the material resistance to extremes of temperature becomes a matter of major concern. When spacecraft dive into the Earth s atmosphere, aerodynamic surfaces are exposed to high thermal and mechanical loads maximum heat fluxes of the order of MW/nr, dynamic pressure, shear stress, acoustic vibrations and material degradation put the vehicles structures to a hard test. Payload and passenger survival is committed to the efficiency of the thermal protection system (TPS) which has to maintain the internal temperature within appropriate limits through various energy dissipating mechanisms. 

Carbon Nanotube and Carbon Nanofiber Nanocomposites. The discovery of single-wall carbon nanotubes (SWNT) has renewed focus on composites with SWNT, multiwalled carbon nanotube (MWNT) and carbon nanofiber (CNF) reinforcements, together referred to as ID Nanocarbon composites (39). These constituents offer promise for new lightweight materials with incredible mechanical, electrical, and thermal properties. ID Nanocarbon materials are envisioned as multifunctional materials, eg single materials used for structures as well as electrical and/or thermal conductors. One example is electronics in a space satellite that need to be lightweight and mechanically supported, have the excess heat dissipated, and be protected from electromagnetic interference (EMI). Other examples are structures that are also batteries and structures that store hydrogen for fuel cells. 

Molded boards are made with resins containing fillers to improve thermal and mechanical properties. The resins are molded into a die or cavity to form the desired shape, including three-dimensional features. The board is metaUzed using conventional seeding and plating techniques. Alternatively, three-dimensional prefabricated films can also be transfer molded and further processed to form structures with finer dimensions. With proper selection of filler materials and epoxy compounds or by molding metal cores, the molded boards can be CTE tailored with enhanced thermal dissipation properties (Seraphim et al, 1989). 

When the PCB is thermally saturated and the component temperatures are still too high to be tolerated at the maximum obtainable system air velocity, other means of conducting heat from the PCB to even larger area system structures are required. The chassis of the system is often the largest surface area structure in the system, is exposed to the ambient air, and often makes a good sink for heat that cannot be dissipated by the PCB alone. Mechanisms to conduct heat into the chassis include chassis screws, gap fillers, connectors, and side rails. Sometimes, radio frequency (RF) shields that are appropriately connected to components can provide additional heat sinking. 

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