Abstract: Proposed is a method of manufacturing a carbon precursor fiber for a gas diffusion layer having excellent tensile properties (e.g., strength and modulus) by controlling the cross-sectional shape of carbon fiber. The method includes preparing a polyacrylonitrile-based copolymer, preparing spinning products by spinning a spinning solution containing the polyacrylonitrile-based copolymer in a coagulation bath, and obtaining a carbon precursor fiber by drawing the spinning products through heat treatment. The coagulation bath includes an amount of about 60% to 90% by volume of methanol and an amount of about 10% to 40% by volume of dimethylformamide based on the total volume of the coagulation bath.

Abstract: An apparatus for measuring the strength of concrete using a surface wave velocity including an ultrasonic transmission and reception probe is provided. The apparatus is configured to include a surface wave velocity measurement device including an ultrasonic transmission probe and an ultrasonic reception probe. Further, a method of constructing the slip form of a concrete column member is provided. The method is capable of reducing the construction period by raising a concrete form rapidly and safely using a method of determining the slip-up time of the slip form based on the strength of concrete measured by the apparatus.

Abstract: An apparatus for measuring the strength of concrete using a surface wave velocity including an ultrasonic transmission and reception probe is provided. The apparatus is configured to include a surface wave velocity measurement device including an ultrasonic transmission probe and an ultrasonic reception probe. Further, a method of constructing the slip form of a concrete column member is provided. The method is capable of reducing the construction period by raising a concrete form rapidly and safely using a method of determining the slip-up time of the slip form based on the strength of concrete measured by the apparatus.