Abstract:In this paper, first the operating principles of a non-isolated universal bidirectional DC-DC converter are studied and analyzed. The presented power converter is capable of operating in all power transferring directions in buck/boost modes. Zero voltage switching can be achieved for all the power switches through proper modulation strategy design, therefore, the presented converter can achieve high efficiency. To further improve the efficiency, the relationship between the phase-shift angle and the overall system efficiency is analyzed in detail, an adaptive phase-shift (APS) control method which determines the phase-shift value between gating signals according to the load level is then proposed. As the modulation strategy is a software-based solution, there is no requirement for additional circuits, therefore, it can be implemented easily and instability and noise susceptibility problems can be reduced. To validate the correctness and the effectiveness of the proposed method, a 300 W prototyping circuit is implemented and tested. A low cost dsPIC33FJ16GS502 digital signal controller is adopted in this paper to realize the power flow control, DC-bus voltage regulation and APS control. According to the experimental results, a 12.2% efficiency improvement at light load and 4.0% efficiency improvement at half load can be achieved.

No abstract

No abstract

In the previous complexity measurement models of manufacturing system (MS), all the resources in enterprise were taken into account, so the result is that the models required large amount of information, which makes the model difficult to expand in practice. As the manufacturing system efficiency is determined by key resources. Only improving the key resources production efficiency can the MS efficiency be improved. So the manufacturing system complexity has to been measured based on the key resources firstly. The Optimized Production Technology is applied to the complexity measurement of MS and a new complexity measurement was proposed. With the information entropy, a static complexity measurement model and a dynamic model are built based on key resources. A case was used to verify the feasibility of the developed model. The advantages and shortcomings of the manufacturing system's complexity measurement were deduced based on key resources at last.

Automatic measurement systems play an important role in various applications of the industry. It is effective in reducing the cost, time consumption of researches and developments, and increasing the product qualities. Web-based teaching tools and materials can provide a dramatic benefit to teaching and learning. Therefore, a web-based integrated measurement system which automatically measure and identify those inherent characteristics of electromagnetic devices is proposed in this paper for students to learn the idea of automatic measurement platform and its applications. A programmable devices test bench, a web-based distance laboratory and a user interactive e-learning platform comprise the presented system. The programmable devices test bench can be reconfigured by the student via a webbased interface to construct various drive circuits and devices under test. The internet accessible distance laboratory permits the instructors and students to remotely conduct experiments over the Internet. The integrated interactive material can assist to the educational environment of the course and can be executed on any modern personal computer without additional hardware. Key features of the proposed teaching aids and materials include flexibility, efficient programming interface, provision for distance waveform measurements and asynchronous learning.Index Terms -Automatic measurement system, E-learning platform, Interactive interface, Teaching aids and materials.

In order to simulate the rupture process of Cartridge Case, material failure constitutive model is researched. Johnson-Cook plasticity model is given as an analytical function of equivalent plastic strain, strain rate, stress triaxiality. Johnson-Cook plasticity model and Johnson-Cook Damage initiation criterion are used to describe the plastic deformation and fracture of case for the pressure of power gas. Using the implementation of this stress-displacement and characteristic length, problem of the relationship between fracture energy and the characteristic length in finite element model is solved. Finally, the simulated model which includes barrel, case, bolt and locking rigidity spring is built. Comparing the fracture shape and position in simulated test and physical experiment, the results are very similar. It proves that the rupture process of Cartridge Case can be simulated by the constitutive model which is introduced in this paper.

No abstract