Processes for producing formic acid from a carbohydrate-containing material include hydrolyzing a carbohydrate-containing material in the presence of a mineral acid to form an intermediate hydrolysate comprising one or more sugars, and hydrolyzing the intermediate hydrolysate to form a hydrolysate product including formic acid. A feed is arranged between the main and sub reflectors and capable of illuminating, first, the sub-reflector and, through it, the main reflector to form plane wave front. Next, the coating film is removed, and a new growth layer is epitaxially grown on the initial growth layer. The press-fit portion includes a interference fit mechanism that comprises a complementary protrusion and recess. Each group of consecutive switching cycles has at least a predetermined minimum of two or more switching cycles.