Abstract:THz wave technology has a broad application prospect in the fields of biomedical, material science, astronomy and military communication. The operation principles of several vacuum electronic devices which can generate THz wave are presented. The bottleneck problems met with in their development are described. The superiorities for using vacuum electronic devices to generate THz wave are derived. The current research and application status of the THz vacuum electronic devices at home and abroad is presented and the prospects of THz wave generation technologies of vacuum electronic devices are given.

Abstract:The change of solvent-induced infrared spectra has been widely used in the spectroscopic study of solute-solvent interaction. The solvent effect of infrared spectra is presented. The theoretical and experimental research progress of influence of solvent effect on infrared spectra at home and abroad in recent years is summarized. It is of reference value to the further study of the solvent effect of infrared spectra.

Abstract:Simulation of infrared scenes against cold background is the key technology for the hardware-in-the-loop simulation test of a space target detection system. However, it is somewhat difficult to simulate the cold background in space with the existing technologies. A system for testing the radiation characteristics of an infrared target against cold background is established by using a high and low temperature chamber. The images of an infrared target obtained at different background temperatures are studied. Finally, the relation between the infrared target image and the background radiation is obtained. The experimental result shows that for a blackbody target with a certain temperature, the images received by the detector when the background temperature varies in a certain range have few changes. The same law can be obtained at both focal plane and defocusing plane. This conclusion is of reference value to the hardware-in-the-loop simulation of infrared scenes at lower background temperatures.

Abstract:The characteristics of long-wavelength infrared background radiation from upper atmosphere are the important research topics for target recognition and infrared radiation characteristic measurement. According to the NRLMSIS-00 empirical atmosphere model, the influence of the temperature and gas concentration of upper atmosphere on infrared radiation is analyzed. By using SHARC, the upper atmospheric radiance code, the upper atmospheric background radiation in different observation positions and different atmospheric modes is calculated numerically and analyzed theoretically in the waveband from 6 μm to 15 μm. The result shows that the long-wavelength infrared radiation of upper atmosphere can be attenuated with the increase of limb tangent height, can be enhanced with the increase of observation zenith angle and can be attenuated with the increase of solar zenith angle. The aurora and twilight are of importance to the enhancement of the upper atmospheric long-wavelength infrared radiation and the upper atmospheric long-wavelength infrared radiation can be varied with the change of latitude and season. This analysis is of reference value to the space target sensing and infrared remote sensing.

Abstract:As the main supporting structure for a space visible camera, the truss is critical for ensuring the mechanical performance of the camera body. To improve the stiffness and stability of the space camera body, the design of a truss structure is studied. The basic structure of a truss, the influence factors of mechanical property of poles and the influence of pole length and angle on the camera body are presented. The features of both Δ shape and X shape truss structures are analyzed. By selecting reasonable quantity and distribution form for poles, the mechanical properties of the camera truss are ensured. Then, the mechanical properties of the camera body are verified. The result shows that this design can ensure the truss structure to obtain good mechanical properties. So, it meets the design requirements of the camera body.

Abstract:Using a mid-infrared CO₂ laser in terahertz difference frequency generation (THz-DFG) is an effective method for improving conversion efficiency and output power. According to the three-wave interaction of difference frequency, the AgGaS₂ crystal is analyzed theoretically. The angle tunable curves of difference-frequency-generated THz wave under both oeo-type and oee-type phase matching conditions are simulated numerically. The walk-off angle and acceptable parameter of light wave in the crystal are calculated. In addition, the effective nonlinear coefficient and theoretical power conversion efficiency of the crystal are taken into account. The research result shows that the AgGaS₂ crystal is suitable for widely tunable THz-DFG with a CO₂ laser.

Abstract:By incorporating class-invariant prior information into the object function of a Support Vector Machine (SVM) algorithm, a SVM infrared spectroscopic qualitative analysis algorithm based on drift constraint is proposed. Because the algorithm simulates the drift term of infrared spectrum into a low order polynomial and requires the normal vector of the decision surface to be perpendicular to the drift direction, the classifier can remove the effect of sample drift. The influence of band selection and regularization parameters on classification accuracy is described in detail and the classification results of different SVM algorithms are compared. The experimental result shows that compared with the standard SVM algorithm and other similar algorithms, the DCSVM algorithm has a higher classification accuracy.

Abstract:By using an infrared temperature measurement technology and combining conduction with convection, a method to reversely calculate the solidification temperature of a casting part according to its surface temperature measured in the casting process is proposed. It is verified that the method can give a more accurate quantitative detection result from the surface temperature of the casting part in its casting process. The actual test result shows that this method is feasible. In addition, it can reversely calculate the surface temperature of different casting parts during casting by writing a simple program and inputting the specific parameters of different parts. So, this method can be used in the production of casting.