A carding machine comprises a main drum fed by a feed system with roughly attenuated and cleaned fibers, a plurality of fixed clothed segments, and opening cylinders or briseurs which feed the said main drum at different points of the main drum. The valve device has a valve chamber. The compounds of the invention are potent inhibitors of proteases, especially trypsin-like serine proteases, such as chymotrypsin, trypsin, thrombin, plasmin and factor Xa. The other generates an analog representation of a cancellation signal that is used to electronically cancel the echo before analog-to-digital conversion of the received signal. The method can efficiently and accurately measure the concentrations of nitric acid, phosphoric acid, and acetic acid contained in the acid mixture of aluminum etchant. The tool set also conceals a pair of small implements such as any two of a knife, a fork or a pair of scissors or a bottle opener or a peeler, which can be taken out from the tool set for use.