Abstract: The present disclosure belongs to the technical field of PVC foam co-extruded sheets, and particularly relates to a wide low-temperature impact-resistant and bending-resistant PVC foam co-extruded sheet and a preparation method thereof. The PVC foam co-extruded sheet of the present disclosure includes a core layer and a skin layer. Raw materials of the core layer include PVC resin powder, a silicon-acrylic composite low-temperature toughening and reinforcing agent, a filler, a foaming regulator I, a white foaming agent, a calcium-zinc stabilizer, a cold-resistant plasticizer, stearic acid, polyethylene wax, and oxidized polyethylene wax.

Abstract: An impact-resistant balanced hydro-cylinder with pressure relief and buffering protection comprises a cylinder body (11), a piston (13), a piston rod (14), and a first valve core (21) and a second valve core (51) slidable relative to the cylinder body (11). A closed first gas cavity (22) and a closed second gas cavity (52) are respectively formed between the two valve cores and inner walls of two opposite ends of the cylinder body (11). A closed first oil cavity (32) and a closed second oil cavity (42) are respectively formed between the two valve cores and two end faces of the piston (13). A through hole (33) for the first oil cavity and a through hole (43) for the second oil cavity are respectively provided in the positions on the cylinder body (11) corresponding to the first oil cavity (32) and the second oil cavity (42).

Abstract: An automatic fire-extinguishing system and method for a cable tunnel. The system includes an inspection robot, a positioning robot, and guide rails fixed on an inner top of the tunnel, where the inspection robot and the positioning robot are connected to the guide rails respectively, and the positioning robot is arranged in a groove of the inspection robot and able to be moved by the inspection robot along the guide rails; and the positioning robot is able to independently enter and exit an inner space of the inspection robot along the guide rails, and the positioning robot is configured to control a built-in fire-extinguishing mechanism to extinguish fire at a position with a preset distance from a fire source. Both fire-fighting medium docking and fire extinguishing are realized; a quick access to a battery is realized and fire-extinguishing inspection efficiency of a cable tunnel is improved.

Abstract: Disclosed is a method for producing series of phase change wax products, comprising: refining a Fischer-Tropsch synthesis wax raw material via a hydrogenation reaction to obtain a refined Fischer-Tropsch wax; and subjecting the refined Fischer-Tropsch wax to reduced pressure distillation to separate continuous fractions with a distillation range of 5° C.-30° C. by continuously increasing the operation temperature so as to obtain series of phase change wax products, wherein the pressure for the reduced pressure distillation is 0-1000 pa, the operation temperature at the top of the column is 120° C.-260° C., and the phase change enthalpy value of the series of phase change wax products is ?170 J/g. According to the method, phase change wax products of various grades with melting points from 5° C. to 80° C. can be separated and produced from the refined Fischer-Tropsch wax. The products have concentrated carbon numbers and relatively high enthalpy values.