Abstract: A method for preparing (S)-nicotine by reduction includes conducting a reduction process on an alkene compound as shown in Formula I and/or an iminium cation compound as shown in Formula II, thereby producing (S)-nicotine. The method is simple, safe, reliable, and yields both high purity and high quantities of (S)-nicotine production.

Abstract: A screw compressor slide valve with gas pulsation attenuation function includes valve walls and internal through holes. A screw compressor includes the screw compressor slide valve. A part of exhausted gas of the screw compressor is directly discharged from an exhaust port to an exhaust chamber to form a main exhaust flow channel; another part of the exhausted gas is discharged from the exhaust port into the exhaust chamber after being delayed by the internal through holes, which forms a branched exhaust flow channel. Since the branched exhaust flow channel is longer than the main exhaust flow channel, when the gas pulsation in the branched exhaust flow channel lags behind that in the main exhaust flow channel by 180-degree in phase, two gas pulsations in the two flow channels are offset due to opposite gas pulsation phases, which attenuates the gas pulsation, thereby suppressing induced vibration and noise.

Abstract: Provided is a steam jet multifunctional aircraft deicing vehicle with steam jet, includes a vehicle body, where a steam generating assembly is arranged in the vehicle body, and the steam generating assembly is connected with a steam conveying assembly. A moving assembly is rotatably connected above the vehicle body, and the moving assembly is rotatably connected with an execution assembly. The execution assembly includes a first spray head assembly and a second spray head assembly. The steam conveying assembly includes a first supercharger and a second supercharger arranged side by side, where an air outlet end of the first supercharger is communicated with one end of a first air outlet pipe, and an other end of the first air outlet pipe is communicated with spray heads of the second spray head assembly through a first air pipeline.

Abstract: The present disclosure discloses a pre-roll advertisement playing method, a terminal, and a video server, and relates to the field of multimedia technologies. The method includes: after detecting a play operation of an offline video, determining a current network connection status of a terminal; when the terminal is in a first connection state, determining, among multiple pre-roll advertisements obtained by the terminal, a specified pre-roll advertisement corresponding to the offline video; and playing the specified pre-roll advertisement in a process of playing the offline video. When playing an offline video in a non-WiFi connection state, the terminal may additionally play a pre-roll advertisement. Therefore, an audience range of the pre-roll advertisement is expanded, and an application range is relatively wide.

Abstract: The present disclosure discloses a pre-roll advertisement playing method, a terminal, and a video server, and relates to the field of multimedia technologies. The method includes: after detecting a play operation of an offline video, determining a current network connection status of a terminal; when the terminal is in a first connection state, determining, among multiple pre-roll advertisements obtained by the terminal, a specified pre-roll advertisement corresponding to the offline video; and playing the specified pre-roll advertisement in a process of playing the offline video. When playing an offline video in a non-WiFi connection state, the terminal may additionally play a pre-roll advertisement. Therefore, an audience range of the pre-roll advertisement is expanded, and an application range is relatively wide.