Yi Hong-Xia

The Research of the Semantic Search Engine Based on the Ontology

In order to solve the problems of the low query precision and the shortness in understanding users query intention that occur in traditional search engine, a framework of semantic search engine based on ontology is brought forwards. It need to extract information after the information crawled by the spider, and an algorithm of information extraction based on ontology is proposed. By using semantic reasoning which based on ontology, it helps the search engine to understand users query intention. A prototype of search engine is developed by using of lucene, and the search result is better than that of common search engine.

Magnetic focusing of electron beams with Gaussian current distribution

The non-laminar electron beams having an originally Gaussian current distribution is measured at IECAS, and the electron trajectories without and with RF signal are calculated using BWI code in the presence uniform magnetic and PPM focusing.

Design of slow wave structures for an X-band broadband TWT

In this paper, the design of slow wave structures for an X-band broadband TWT with suppression of backward-wave using the helix pitch step method is present. An optimized design of a high-power X-band broadband TWT with improved BWO suppression and forward-wave saturated output power is presented.

Research on radiator for space traveling wave tube

Heat radiator for space traveling wave tube has been analyzed using ANSYS, and has been produced. The heat vacuum test shows that the experiment data agrees well with the simulated one.

Development of a Ku-band 150W space TWT

This paper reports the design, simulation work and test results of a 150W Ku-band continuous wave space Traveling Wave Tube (TWT), which is fulfilled at the Institute of Electronics, Chinese Academy of Sciences. The double-anode gun, helix pitch-tapering slow wave structure, non-axisymmetric four-stage depressed collector and radiation-cooled radiator are used in this TWT. The test results indicate that in the case of saturated drive, the TWT can get a power of more than 154W, an efficiency of more than 62%, a phase shift less than 46.6 degree, and AM/PM factor less than 4.3deg/dB with the beam transmission rate of more than 98.5% in the operation band of 12.25-12.75-GHz. The environment testing was performed and the results show that the configuration design of this TWT is satisfied for a satellite mechanics environment and the heat dissipation design is satisfied for an airborne environment.

A study on fundamental theory for spread launch model of electrons

This paper presents a study on the mechanism of electronic emission by constructing electronic spread launching model and solving Poisson equation analytically between two planar plane. The results show that electron beam introduces periodic and non-periodic perturbation to primary vacuum potential. The overall effect of periodic perturbation can be ignored because of symmetry but non-periodic perturbation is dependent on initial condition intensively, especially emitting velocitys direction. When the launch angle varies from 0 degree to 90 degree, four perturbation peaks take on and beside them electron beam has no impact on vacuum potential, which provide a theoretical explanation for MICHELLEs nine-particle launch model.

The derivation of space-charge-limited current between concentric sphere

In high-power microwave diode design, the space-charge-limited current is important because of its relation to the diode impedance, and the formation of the virtual cathode. Although the Langmuir-Blodgett law, as a numerical solution, is helpful, a simple functional expression would be more convenient for practical research and the divergence of the series for large Rc/Ra would be avoided. First principle has been applied to derivate two-dimensional space-charge-limited current for planar plane capacitor and coaxial cylinders and its reliability has been examined adequately. This paper obtained the functional expression of space-charge-limited current for concentric sphere, the space-charge factor in this expression is got by comparison with classical Langmuir flow between concentric sphere.