Abstract: A cationic copolymer represented by the following formula (I) has a viscosity average molecular weight in a range from 2 million to 10 million. In the cationic copolymer, the mole fractions of three structural units corresponding to three monomers are as follows: x being in a range from 0.01 to 20%, y being in a range from 0 to 15%, and z=1?x?y. When used in the construction of leaking stoppage in an oil well, a cationic chemical lost circulation additive prepared with the cationic copolymer is mixed with an anionic drilling fluid in a section of the wellbore where lost circulation occurs. Then neutral reaction and cross linking reaction occur, so that the viscosity of the resulting mixture rapidly increases to form a space grid structure. This blocks off the leakage path, and thus effects on efficient leaking stoppage in a short time period.

Abstract: A cationic copolymer represented by the following formula (I) has a viscosity average molecular weight in a range from 2 million to 10 million. In the cationic copolymer, the mole fractions of three structural units corresponding to three monomers are as follows: x being in a range from 0.01 to 20%, y being in a range from 0 to 15%, and z=1?x?y. When used in the construction of leaking stoppage in an oil well, a cationic chemical lost circulation additive prepared with the cationic copolymer is mixed with an anionic drilling fluid in a section of the wellbore where lost circulation occurs. Then neutral reaction and cross linking reaction occur, so that the viscosity of the resulting mixture rapidly increases to form a space grid structure. This blocks off the leakage path, and thus effects on efficient leaking stoppage in a short time period.

Abstract: A wind turbine blade has a suction side shell member and a pressure side shell member. The shell members are joined along a leading and trailing edge from a root to a tip of the blade and defining an internal cavity of the blade. A pressure sensor is configured on at least one of the suction or pressure side shell members. The pressure sensor further includes a body mounted to an inner surface of the respective shell member within the internal cavity. A sensing element has a first side exposed to external air pressure through a passage in the respective shell member, and an opposite second side exposed to a reference pressure. Control circuitry within the body generates a variable output signal as a function of a pressure differential between the external air pressure and reference pressure experienced by the sensing element.

Abstract: A wind turbine tower includes an induction brazed joint coupling a first wind tower section and a second wind tower section.