Abstract: A high temperature resistant polyimide film and its preparation method. The present invention relates to a polyimide film and its preparation method and solves the problems of honeycomb's and skin panel's core adhesive—polyimide film with insufficient heat resistance, no climbing of bonding core structure and adhesive fillet formation. The high temperature resistant polyimide film is made by polyimide solution, inorganic filler modifier and interface coupling agent by the steps of: under specific temperature and stirring conditions, adding inorganic filler modifier and interface coupling agent to polyimide solution, stirring to obtain the adhesive agent; filtering and degassing the adhesive agent, casting to a stainless steel drum with carrier cloth and release paper to obtain a self-supporting film; then heating and annealing to obtain the final polyimide film. The present invention is applied to high temperature resistant polyimide film and its preparation method.

Abstract: A self-inspection method for a hydraulic control turning system of a generator rotor includes: establishing a length dimension relationship table among a plurality of hydraulic cylinders of the hydraulic control turning system; selecting a reference hydraulic cylinder, and acquiring a reference length dimension when the reference hydraulic cylinder is located at a target working position, the target working position is a position at which a turning pin corresponding to the reference hydraulic cylinder is inserted into an adapted hole; and performing a function inspection of a motion execution module in sequence by the plurality of the hydraulic cylinders, based on the reference length dimension and the length dimension relationship table.

Abstract: A system for controlling a generator rotor locking pin, comprising a fixed locking pin and a rotor formed with a locking hole, and further comprising a detection reference component synchronously rotating with the rotor and formed with a detection hole, the detection hole radially corresponding to the locking hole; an optical quantity detection component fixed with respect to the rotor; and a control component configured to output a first control instruction to a rotor driving component according to a position signal of the detection hole obtained by the optical quantity detection component. The detection hole is used as an object to be detected, so that the circumferential relative position relationship of the locking hole with respect to the locking pin can be accurately determined, to output the first control instruction to the rotor driving component, thereby accurately centering the locking pin and the locking hole along with the rotation of the rotor.

Abstract: The present invention discloses a method for preparing 2,3,3,3-tetrafluoropropene using methylmagnesium chloride, comprising the following steps: 1) preparing 1,1,2-trifluoropropene (CH3CF?CF2); 2) preparing 1,1,1,2,2-pentafluoropane (CF3CF2CH3); 3) preparing 2,3,3,3-tetrafluoropropene (CF3CF?CH2). In the present invention, using a Grignard reagent, namely methylmagnesium chloride, and tetrafluoroethylene as starting raw materials, 2,3,3,3-tetrafluoropropene is prepared by three steps of nucleophilic addition-elimination, fluorine addition, and dehydrofluorination in sequence. The process flow is relatively short, and the product yield is high.

Abstract: The present invention discloses a method for preparing 2,3,3,3-tetrafluoropropene using methylmagnesium chloride, comprising the following steps: 1) preparing 1,1,2-trifluoropropene (CH3CF?CF2); 2) preparing 1,1,1,2,2-pentafluoropane (CF3CF2CH3); 3) preparing 2,3,3,3-tetrafluoropropene (CF3CF?CH2). In the present invention, using a Grignard reagent, namely methylmagnesium chloride, and tetrafluoroethylene as starting raw materials, 2,3,3,3-tetrafluoropropene is prepared by three steps of nucleophilic addition-elimination, fluorine addition, and dehydrofluorination in sequence. The process flow is relatively short, and the product yield is high.

Abstract: A cycloheptane derivative as represented by formula (I), and preparation method and use thereof; the compound has photostability and thermostability, wide nematic phase and liquid crystalline state temperature range, and good low-temperature intersolubility, and particularly has low rotary viscosity ?1 and good dielectric anisotropy (??>0).

Abstract: A cycloheptane derivative as represented by formula (I), and preparation method and use thereof; the compound has photostability and thermostability, wide nematic phase and liquid crystalline state temperature range, and good low-temperature intersolubility, and particularly has low rotary viscosity ?1 and good dielectric anisotropy (??>0).