A major motivation for this work is to investigate a method of computer simulation for compensating fixed pattern noise of the infrared focal plane arrays. A mathematical model of the output signal of focal plane arra...A major motivation for this work is to investigate a method of computer simulation for compensating fixed pattern noise of the infrared focal plane arrays. A mathematical model of the output signal of focal plane array was established; a compensating algorithm utilizing reference source was derived and simulating programs were designed. The images of compensating process verify the influence of nonuniformity of responsibility and offset on fixed pattern noise. The result show that simulating method of investigating compensation technology for focal plane arrays is feasible, the generated images and methods can be used to the study of image recognition.展开更多
A spurious effect of blowing noise is sometimes detected on fans working at high flow rate, showing a large hump around 4000 Hz on the acoustic spectra. A Tollmien-Shlichtling （TS） effect is suspected, and several c...A spurious effect of blowing noise is sometimes detected on fans working at high flow rate, showing a large hump around 4000 Hz on the acoustic spectra. A Tollmien-Shlichtling （TS） effect is suspected, and several compressible LES are made on aerodynamic profiles to detect and investigate this phenomenon. Vortex shedding is observed at the trailing edge, triggering some density fluctuations when a thin boundary layer exists on the profile upper side. Acoustic waves with length equivalent to the chord are observed. A profile modification is proposed with a camber brought closer to the leading edge. This shape tested on a prototyped fan confirms the weakening of the TS effect.展开更多
文摘A major motivation for this work is to investigate a method of computer simulation for compensating fixed pattern noise of the infrared focal plane arrays. A mathematical model of the output signal of focal plane array was established; a compensating algorithm utilizing reference source was derived and simulating programs were designed. The images of compensating process verify the influence of nonuniformity of responsibility and offset on fixed pattern noise. The result show that simulating method of investigating compensation technology for focal plane arrays is feasible, the generated images and methods can be used to the study of image recognition.
文摘A spurious effect of blowing noise is sometimes detected on fans working at high flow rate, showing a large hump around 4000 Hz on the acoustic spectra. A Tollmien-Shlichtling （TS） effect is suspected, and several compressible LES are made on aerodynamic profiles to detect and investigate this phenomenon. Vortex shedding is observed at the trailing edge, triggering some density fluctuations when a thin boundary layer exists on the profile upper side. Acoustic waves with length equivalent to the chord are observed. A profile modification is proposed with a camber brought closer to the leading edge. This shape tested on a prototyped fan confirms the weakening of the TS effect.
