A numerical model is presented to investigate the performance of homogeneous charge compression ignition(HCCI) engines fueled with ethanol. Two approaches are studied. On one hand, two-step reaction mechanisms with Ar...A numerical model is presented to investigate the performance of homogeneous charge compression ignition(HCCI) engines fueled with ethanol. Two approaches are studied. On one hand, two-step reaction mechanisms with Arrhenius reaction rates are implemented in combustion chemistry modeling. On the other hand, a reduced mechanism containing important reactions of ethanol involving heat release rate and reaction rates compatible with experimental data is employed. Since controls of combustion phenomenon and ignition timing are the main issues of these engines, the effects of inlet temperature and equivalence ratio as the controlling factors on the operating parameters such as ignition timing, burn duration, in-cylinder temperature and pressure of HCCI engines are explored. The results show that the maximum predicted pressures for thermodynamic model are about 71.3×10~5 Pa and 79.79×10~5 Pa, and for chemical kinetic model, they are about 71.48×10~5 Pa and 78.123×10~5 Pa, fairly comparable with corresponding experimental values of 72×10~5 Pa and 78.7×10~5 Pa. It is observed that increasing the initial temperature advances the ignition timing, decreases the burn duration and increases the peak temperature and pressure. Moreover, the maximum temperature and pressure are associated with richer mixtures.展开更多
Mergers and acquisitions (M&A) are the important methods to quickly acquire external resources, achieve the economies of scale and the economies of scope, improve market share, and expand the scale of enterprise, w...Mergers and acquisitions (M&A) are the important methods to quickly acquire external resources, achieve the economies of scale and the economies of scope, improve market share, and expand the scale of enterprise, while M&A performance is an important index to measure if enterprise M&A is successful. In this paper, the influence of entrepreneurs' political connection on the M&A driving factors and M&A efficiency of the enterprises with different property rights are analyzed using 357 mergers and acquisitions of China' s 189 listed companies in 2005-2011 as samples based on the distinction between political connection and the nature of enterprise property rights. The results show that the political connection plays a very significant positive influence on the M&A performances of the central state-owned enterprises and private enterprises, but exerts a very significant negative influence on the local state-owned enterprises; the intensity of entrepreneurs' political connection also plays a certain influence on enterprise merger and acquisition, and the central political connection and the local political connection are significantly different in the influence on the enterprise M&A performance.展开更多
As a new affective variable in the field of L2 (Second Language) Acquisition, the study of WTC (Willingness to Communicate) has attracted widespread attention since the 1990s, which is not only an effective way to...As a new affective variable in the field of L2 (Second Language) Acquisition, the study of WTC (Willingness to Communicate) has attracted widespread attention since the 1990s, which is not only an effective way to promote language learning but also an important language target itself. Based on the data got from the questionnaire, the present study intends to explore the level, gender difference, correlation with academic .performance, and influencing factors of English majors' WTC inside classroom using both quantitative and qualitative research method. The results reveal that English majors' WTC inside classroom is comparatively high; there is no significant gender difference in English majors' WTC inside classroom, and there is significant positive correlation between WTC inside classroom and academic achievement; furthermore, language capacity, language anxiety, and communicative atmosphere are the main influencing factors展开更多
文摘A numerical model is presented to investigate the performance of homogeneous charge compression ignition(HCCI) engines fueled with ethanol. Two approaches are studied. On one hand, two-step reaction mechanisms with Arrhenius reaction rates are implemented in combustion chemistry modeling. On the other hand, a reduced mechanism containing important reactions of ethanol involving heat release rate and reaction rates compatible with experimental data is employed. Since controls of combustion phenomenon and ignition timing are the main issues of these engines, the effects of inlet temperature and equivalence ratio as the controlling factors on the operating parameters such as ignition timing, burn duration, in-cylinder temperature and pressure of HCCI engines are explored. The results show that the maximum predicted pressures for thermodynamic model are about 71.3×10~5 Pa and 79.79×10~5 Pa, and for chemical kinetic model, they are about 71.48×10~5 Pa and 78.123×10~5 Pa, fairly comparable with corresponding experimental values of 72×10~5 Pa and 78.7×10~5 Pa. It is observed that increasing the initial temperature advances the ignition timing, decreases the burn duration and increases the peak temperature and pressure. Moreover, the maximum temperature and pressure are associated with richer mixtures.
文摘Mergers and acquisitions (M&A) are the important methods to quickly acquire external resources, achieve the economies of scale and the economies of scope, improve market share, and expand the scale of enterprise, while M&A performance is an important index to measure if enterprise M&A is successful. In this paper, the influence of entrepreneurs' political connection on the M&A driving factors and M&A efficiency of the enterprises with different property rights are analyzed using 357 mergers and acquisitions of China' s 189 listed companies in 2005-2011 as samples based on the distinction between political connection and the nature of enterprise property rights. The results show that the political connection plays a very significant positive influence on the M&A performances of the central state-owned enterprises and private enterprises, but exerts a very significant negative influence on the local state-owned enterprises; the intensity of entrepreneurs' political connection also plays a certain influence on enterprise merger and acquisition, and the central political connection and the local political connection are significantly different in the influence on the enterprise M&A performance.
文摘As a new affective variable in the field of L2 (Second Language) Acquisition, the study of WTC (Willingness to Communicate) has attracted widespread attention since the 1990s, which is not only an effective way to promote language learning but also an important language target itself. Based on the data got from the questionnaire, the present study intends to explore the level, gender difference, correlation with academic .performance, and influencing factors of English majors' WTC inside classroom using both quantitative and qualitative research method. The results reveal that English majors' WTC inside classroom is comparatively high; there is no significant gender difference in English majors' WTC inside classroom, and there is significant positive correlation between WTC inside classroom and academic achievement; furthermore, language capacity, language anxiety, and communicative atmosphere are the main influencing factors