Cooling Diffusion

Figure 23. The Rofin Sinar Diffusion cooled DC-series CO2 slab laser with output power up to 3500 W [60],...

CVD diamond windows are now being used in commercial high power CO2 lasers. An example is the Rofin Sinar Diffusion-cooled CO2 slab laser with an output power of 3500 W [48] shown in Fig. 23. In this laser, the CVD diamond window is used to seal the slab cavity, as shown schematically in Fig. 24. 

According to the proposed classification, the classes from the first group of adhesives can be distinguished by the way in which the polymer is returned to a solid state (evaporation of the solvent, water diffusion, cooling) we therefore talk about Adhesives Implemented via a Physical Process (AIPPs). In the second group, the distinction tends to be according to the way in which the polymerization or cross-linking process occurs, and we talk about Adhesives Implemented via a Chemical Process (AICPs) (O Fig. 14.1). 

Equation (16) indicates that the decay constant a is a linear function of the buckling B. Careful experiments, however, indicate a slightly nonlinear relationship between a and B. This is explained as being due to diffusion cooling, the preferential leakage of neutrons of higher energy from the medium. 

If condensation requires gas stream cooling of more than 40—50°C, the rate of heat transfer may appreciably exceed the rate of mass transfer and a condensate fog may form. Fog seldom occurs in direct-contact condensers because of the close proximity of the bulk of the gas to the cold-Hquid droplets. When fog formation is unavoidable, it may be removed with a high efficiency mist collector designed for 0.5—5-p.m droplets. Collectors using Brownian diffusion are usually quite economical. If atmospheric condensation and a visible plume are to be avoided, the condenser must cool the gas sufftciendy to preclude further condensation in the atmosphere. 

A number of chemiluminescent reactions have been studied by producing key reactants through pulsed electric discharge, by microwave dissociation, or by observing the reactions of atoms and free radicals produced in the inner cone of a laminar flame as they diffuse into the flame s cool outer cone (182,183). These are either combination reactions or atom-transfer reactions involving transfer of chlorine (184) or oxygen atoms (181,185—187), the latter giving excited oxides. 

Fig. 4. Diffusion bonding process (a) apply metal foil and cut to shape, (b) lay up desired pHes, (c) vacuum encapsulate and heat to fabrication temperature, (d) apply pressure and hold for consoHdation cycle, and (e) cool, remove, and clean part.

Stmctures that form as a function of temperature and time on cooling for a steel of a given composition are usually represented graphically by continuous-cooling and isothermal-transformation diagrams. Another constituent that sometimes forms at temperatures below that for peadite is bainite, which consists of ferrite and Fe C, but in a less well-defined arrangement than peadite. There is not sufficient temperature and time for carbon atoms to diffuse long distances, and a rather poody defined acicular or feathery stmcture results. 

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