The presence of 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 {HEAD ~ the capacitance} of {TAIL ~ the structure} 
The presence of 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 { HEAD ~ the capacitance } of { TAIL ~ the structure }
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