Since the classical stability cannot deal with the behavior of closed-loop silicon carbide (SiC) MOSFET gate drive during switching transients, a finite-time stability analysis method is proposed and demonstrated. First, a small-signal SiC MOSFET model including the nonlinearity of parameters is employed to derivation the state equations of the drive circuit. Then a determination procedure of nonlinear parameters is illustrated. Finally, the behavior of the drive circuit during switching transients is evaluated using Davari's method. Different circuit designs are analyzed using the proposed method and analysis results are confirmed by experiments.
Electron density is one of the important parameters of plasma. In the aerospace field, the density distribution of plasma on the surface of an aircraft will have an important effect on it. In this field, the current research mostly stays in the laboratory stage or static electron density diagnosis stage, and there is still a certain distance from the actual application. This study is based on the traditional Langmuir probe theory and follows the assumptions of the Langmuir probe theory to make a qualitative analysis of its voltammetric characteristics. Based on the above analysis, a single flush-probe was designed, and a method for diagnosing electron density for low pressure was proposed. It was verified by experiments that the method can accurately obtain parameters of plasma such as electron density in the low pressure range, which can provide a certain reference for future electronic density diagnosis in the aerospace.
A new type of photolithography tool has been developed, addressing the specific needs of MCM manufacture. It is based on scanning projection exposure. It can expose panels at variable sizes up to 500 mm by 600 mm (typical laminate size), with an optical resolution of less than 5 /spl mu/m and an overlay accuracy of 2 /spl mu/m (typical thin film design rules). With the exposure being a mask projection, mask damage and subsequent yield problems are generally avoided.< >
Aerial image segmentation algorithms are used in many scenarios such as traffic warning, road assistance, terrain mapping and military reconnaissance. It has been widely applied in both military and civilian applications. A lot of researches on target detection and recognition technology in aerial images have been carried out. In addition, technologies such as computer vision and machine learning have been introduced. Compared with the research on image segmentation algorithms, there are relatively few studies on evaluation method segmentation algorithms. In view of the above situation, the evaluation method of aerial image segmentation is established, and the performance of comprehensive evaluation of the medhod for image segmentation algorithms is verified. Specifically, it includes similarity index, misidentification similarity index and distance index. Selecting image data sources with different degrees of complexity are selected in order to verify the effectiveness of the above image segmentation evaluation method. The results show that the evaluation indicators prove that the algorithms can achieve effective target segmentation to a certain extent. The segmentation accuracy rate is above 95%. In view of the accuracy and effectiveness of the aerial image segmentation algorithm, it is expected to be further applied in the field of aerial images.
With the continuous development of aerial photography technology, its imaging quality is higher and higher, and the post-processing technology requirements for aerial images are getting higher and higher. Aerial image target recognition technology has been a hot research content in recent years. This technology relies on computer vision and image processing algorithm. But aerial images have certain particularities, including long shooting distances, complex image backgrounds, and variable target angles. The above factors can easily lead to indistinguishability between the target boundary and the background information of the aerial images. In order to solve that problem, a smooth edge feature information recognition method for aerial images is proposed. The energy fitting term related to the gray value inside and outside the curve is introduced, with that the method can get rid of the dependence of the detection operator as the stopping function of the curve evolution. In order to prevent the algorithm from falling into a local optimal solution in the iterative process, the Dirac function with a non-zero value in the domain is adopted. With synthetic and natural images, the effectiveness and accuracy of the method is verified. The robustness of the algorithm will be verified in the future researches by the acquired aerial image data set.
Traditional weapon systems and near-space vehicles may face severe intra-atmospheric or extra-atmospheric nuclear explosion environments during combat flight. Nuclear explosions can produce large-scale and comprehensive destructive effects, which bring great challenges to the performance and survival of weapon systems. In the nearby space of tens of kilometers, due to the gradual thinning of the air, the ray particles can travel a considerable distance. Considering the above situation, the neutron radiation penetration rate of the specified material by modeling the aircraft structural material and particle source is given in this research. According to the simulation analysis, the neutron ray penetration rate has nothing to do with the number of neutrons when the thickness of the aircraft structural material remains unchanged. In conclusion, a basis for the subsequent assessment of the neutron radiation environment inside the aircraft is proposed, which can provide guidance for the damage assessment of electronic equipment and the design of anti-nuclear reinforcement.
A new type of photolithography tool has been developed, addressing the specific needs of MCM manufacture. It is based on scanning projection exposure. It can expose panels at variable sizes up to 500 mm by 600 mm (typical laminate size), with an optical resolution of less than 5 gm and an overlay accuracy of 2 /spl mu/m (typical thin film design rules). With the exposure being a mask projection, mask damage and subsequent yield problems are generally avoided.
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