{HEAD ~ The presence} of {TAIL ~ some gases} such as air or an inert gas, or a vacuum, in the porous insulation material reduces the overall dielectric constant of the insulation material, thereby effectively reducing the capacitance of the structure 
{ HEAD ~ The presence } of { TAIL ~ some gases } such as air or an inert gas , or a vacuum , in the porous insulation material reduces the overall dielectric constant of the insulation material , thereby effectively reducing the capacitance of the structure
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