Massive machine type communication(m MTC) is one of the key application scenarios for the fifth generation mobile communication(5 G). Grant-free(GF) transmission can reduce the high signaling overhead in m MTC. Non-or...Massive machine type communication(m MTC) is one of the key application scenarios for the fifth generation mobile communication(5 G). Grant-free(GF) transmission can reduce the high signaling overhead in m MTC. Non-orthogonal multiple access(NMA) can support more users for m MTC than orthogonal frequency division multiple access(OFDMA). Applying GF transmission in NMA system becomes an active topic recently. The in-depth study on applying GF transmission in pattern division multiple access(PDMA), a competitive candidate scheme of NMA, is investigated in this paper. The definition, latency and allocation of resource and transmission mechanism for GF-PDMA are discussed in detail. The link-level and system-level evaluations are provided to verify the analysis. The analysis and simulation results demonstrate that the proposed GF-PDMA has lower latency than grant based PDMA(GB-PDMA), possesses strong scalability to confront collision and provides almost 2.15 times gain over GF-OFDMA in terms of supporting the number of active users in the system.展开更多
Essence of education is to guide. The scene teachers create is like a key to help the students feel the music, and played an active role in the teaching process immeasurably. Through multimedia assisted teaching, the ...Essence of education is to guide. The scene teachers create is like a key to help the students feel the music, and played an active role in the teaching process immeasurably. Through multimedia assisted teaching, the use of a wide range of teaching methods in music teaching, so that the children take the initiative to actively participate in musical activities to develop their musical aesthetic and correct music ability to inspire their interest in learning music, promote classroom further improve the quality of teaching.展开更多
Transonic single-degree-of-freedom(SDOF) flutter and transonic buffet are the typical and complex aeroelastic phenomena in the transonic flow. In this study, transonic aeroelastic issues of an elastic airfoil are inve...Transonic single-degree-of-freedom(SDOF) flutter and transonic buffet are the typical and complex aeroelastic phenomena in the transonic flow. In this study, transonic aeroelastic issues of an elastic airfoil are investigated using Unsteady Reynolds-Averaged Navier-Stokes(URANS) equations. The airfoil is free to vibrate in SDOF of pitching. It is found that, the coupling system may be unstable and SDOF self-excited pitching oscillations occur in pre-buffet flow condition, where the free-stream angle of attack(AOA) is lower than the buffet onset of a stationary airfoil. In the theory of classical aeroelasticity, this unstable phenomenon is defined as flutter. However, this transonic SDOF flutter is closely related to transonic buffet(unstable aerodynamic models) due to the following reasons. Firstly, the SDOF flutter occurs only when the free-stream AOA of the spring suspended airfoil is slightly lower than that of buffet onset, and the ratio of the structural characteristic frequency to the buffet frequency is within a limited range. Secondly, the response characteristics show a high correlation between the SDOF flutter and buffet. A similar "lock-in" phenomenon exists, when the coupling frequency follows the structural characteristic frequency. Finally, there is no sudden change of the response characteristics in the vicinity of buffet onset, that is, the curve of response amplitude with the free-stream AOA is nearly smooth. Therefore, transonic SDOF flutter is often interwoven with transonic buffet and shows some complex characteristics of response, which is different from the traditional flutter.展开更多
This study investigates a particular use of an application of speech recognition technology in the assessment of English proficiency. The use of the application, called Versant English Test, is examined in the context...This study investigates a particular use of an application of speech recognition technology in the assessment of English proficiency. The use of the application, called Versant English Test, is examined in the context of a country where English is not the first language of communication, in order to determine whether or not English as the first language of the country in which the test is taken could have a bearing on the test result. As suggested by Chun（2006）, this study compares the results achieved by test takers in a non-English speaking environment with those obtained by different test takers in an English speaking environment. To be able to decide whether the Versant is more prone to setting-related bias than other English proficiency tests, the Versant test scores are correlated with the TOEFL scores of the test-takers in a non-English speaking setting and the correlation coefficient is then compared with that achieved in an English-speaking environment. The results suggest that the correlation between the Versant and TOEFL in a non-English-speaking environment is not significantly different from that obtained in an English-speaking environment.展开更多
基金supported by National High Technology Research and Development Program of China (863 Program, No. 2015AA01A709)
文摘Massive machine type communication(m MTC) is one of the key application scenarios for the fifth generation mobile communication(5 G). Grant-free(GF) transmission can reduce the high signaling overhead in m MTC. Non-orthogonal multiple access(NMA) can support more users for m MTC than orthogonal frequency division multiple access(OFDMA). Applying GF transmission in NMA system becomes an active topic recently. The in-depth study on applying GF transmission in pattern division multiple access(PDMA), a competitive candidate scheme of NMA, is investigated in this paper. The definition, latency and allocation of resource and transmission mechanism for GF-PDMA are discussed in detail. The link-level and system-level evaluations are provided to verify the analysis. The analysis and simulation results demonstrate that the proposed GF-PDMA has lower latency than grant based PDMA(GB-PDMA), possesses strong scalability to confront collision and provides almost 2.15 times gain over GF-OFDMA in terms of supporting the number of active users in the system.
文摘Essence of education is to guide. The scene teachers create is like a key to help the students feel the music, and played an active role in the teaching process immeasurably. Through multimedia assisted teaching, the use of a wide range of teaching methods in music teaching, so that the children take the initiative to actively participate in musical activities to develop their musical aesthetic and correct music ability to inspire their interest in learning music, promote classroom further improve the quality of teaching.
基金supported by the New Century Program for Excellent Talents of Ministry of Education of China(Grant No.NCET-13-0478)National Natural Science Foundation of China(Grant No.11172237)
文摘Transonic single-degree-of-freedom(SDOF) flutter and transonic buffet are the typical and complex aeroelastic phenomena in the transonic flow. In this study, transonic aeroelastic issues of an elastic airfoil are investigated using Unsteady Reynolds-Averaged Navier-Stokes(URANS) equations. The airfoil is free to vibrate in SDOF of pitching. It is found that, the coupling system may be unstable and SDOF self-excited pitching oscillations occur in pre-buffet flow condition, where the free-stream angle of attack(AOA) is lower than the buffet onset of a stationary airfoil. In the theory of classical aeroelasticity, this unstable phenomenon is defined as flutter. However, this transonic SDOF flutter is closely related to transonic buffet(unstable aerodynamic models) due to the following reasons. Firstly, the SDOF flutter occurs only when the free-stream AOA of the spring suspended airfoil is slightly lower than that of buffet onset, and the ratio of the structural characteristic frequency to the buffet frequency is within a limited range. Secondly, the response characteristics show a high correlation between the SDOF flutter and buffet. A similar "lock-in" phenomenon exists, when the coupling frequency follows the structural characteristic frequency. Finally, there is no sudden change of the response characteristics in the vicinity of buffet onset, that is, the curve of response amplitude with the free-stream AOA is nearly smooth. Therefore, transonic SDOF flutter is often interwoven with transonic buffet and shows some complex characteristics of response, which is different from the traditional flutter.
基金funded by the American University of Sharjah through the university research grant program on a competitive basis
文摘This study investigates a particular use of an application of speech recognition technology in the assessment of English proficiency. The use of the application, called Versant English Test, is examined in the context of a country where English is not the first language of communication, in order to determine whether or not English as the first language of the country in which the test is taken could have a bearing on the test result. As suggested by Chun（2006）, this study compares the results achieved by test takers in a non-English speaking environment with those obtained by different test takers in an English speaking environment. To be able to decide whether the Versant is more prone to setting-related bias than other English proficiency tests, the Versant test scores are correlated with the TOEFL scores of the test-takers in a non-English speaking setting and the correlation coefficient is then compared with that achieved in an English-speaking environment. The results suggest that the correlation between the Versant and TOEFL in a non-English-speaking environment is not significantly different from that obtained in an English-speaking environment.
