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The super-efficiency data envelopment analysis model is innovative in evaluating the performance of crude oil prices’ volatility forecasting models. This multidimensional ranking, which takes account of multiple criteria, gives rise to a unified decision as to which model performs best. However, the rankings are unreliable because some efficiency scores are infeasible solutions in nature. What’s more, the desirability of indexes is worth discussing so as to avoid incorrect rankings. Hence, herein we introduce four models, which address the issue of undesirable characteristics of indexes and infeasibility of the super efficiency models. The empirical results reveal that the new rankings are more robust and quite different from the existing results.

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Compared with traditional learning methods, Educational virtual community has the incomparable advantage of knowledge diffusion with high efficiency and wide range. It is conductive to the knowledge acquisition and innovation of learners, and it provides a platform for learners to change their roles from the passive recipient of information to the main participant of knowledge acquisition. Based on the interactions between users' personal, technical and organizational characteristics, a modified technology acceptance model was presented in this paper to explain the willingness and behavior of knowledge sharing in EVC in order to propose and validate the effects of perceived usefulness, perceived ease of use, and psychological ownership on the willingness and behavior of knowledge sharing. In this research, the methods of interviewing and questionnaires with 40 questions included have adopted and 334 members from 32 educational virtual communities were surveyed. Based on the 326 valid samples, the hypothesis of research be tested with software SPSS 22.0 by structural equation model. Empirical research found that: Perceived usefulness and perceived ease of use has remarkable positive impact on knowledge sharing willingness, and perceived usefulness with greater function can significantly promote perceived ease of use; psychological ownership can affect not only the knowledge sharing behavior through the knowledge sharing willingness, but also the behavior directly; the knowledge sharing willingness plays a fully mediating role between perceived usefulness and knowledge sharing behavior, while there exist the significant mediating effects between perceived ease of use and knowledge sharing behavior, and between psychological ownership and knowledge sharing behavior. Based on the conclusion of this research, the interactions between different factors should be taken into account in order to advance the willingness and behavior of knowledge sharing among EVC members and the perceived usefulness, perceived ease of use and psychological ownership level of community members should be proactively promoted.

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