Bulk polymerizations of styrene (St) were carried out in the presence of three reversible addition fragmentation chain transfer (RAFT) agents benzyl dithiobenzoate (BDB), cumyl dithiobenzoate(CDB), and 1-phenylethyl d...Bulk polymerizations of styrene (St) were carried out in the presence of three reversible addition fragmentation chain transfer (RAFT) agents benzyl dithiobenzoate (BDB), cumyl dithiobenzoate(CDB), and 1-phenylethyl dithiobenzoate (PEDB) under low ratio of RAFT agent to initiator. The kinetic model was developed to predict polymerization rate, which indicates that the RAFT polymerization of St is a first-order reaction. In the range of experimental conversions, the plots of -ln(1-x) against time t are approximately linear (x is monomer conversion). The kinetic study reveals the existence of strong rate retardation in RAFT polymerization of styrene. A coefficient K_r is defined to estimate the rate retardation in the RAFT system considering the assumption that the retardation in polymerization rate is mainly attributed to slow fragmentation of the intermediate radicals. K_r relates to the structure of RAFT agents as well as the concentrations of RAFT agent and azobis isobutyronitrile (AIBN). For a certain RAFT agent, the value of K_r is enhanced by the increase in the initial concentration of RAFT agent and the higher ratio of RAFT to AIBN. With the same recipe for different RAFT agents, the increasing trend for the values of K_r is BDB<PEDB<CDB.展开更多
The photon transport properties in one-dimensional coupled-resonator waveguide embedded with a quantum dot molecule are investigated. The calculations reveal that one can control the photon transport by using a gate e...The photon transport properties in one-dimensional coupled-resonator waveguide embedded with a quantum dot molecule are investigated. The calculations reveal that one can control the photon transport by using a gate electric field. The phase shift and group velocity delay of the transmitted single photon are discussed. This research may be found applications in integrated optoelectronic devices and solid quantum devices.展开更多
In the present paper the attention is focused on the effect of small cavities inside in-line tube banks on acoustic resonance which occurred in the two-dimensional model of boiler. We measured the sound pressure level...In the present paper the attention is focused on the effect of small cavities inside in-line tube banks on acoustic resonance which occurred in the two-dimensional model of boiler. We measured the sound pressure level, the amplitude and the phase delay of acoustic pressures and the gap velocity. As a result, we found many peak frequencies of sound pressure level with different Strouhal numbers, mainly about S1=0.15, 0.26 and 0.52. The variation of SPL for S,=0.26, 0.52 components in the tube banks with cavities was the same as the result of no cavities. The existence of cavities inside in-line tube banks caused the resonance of St=0.15. And the acoustic resonance of the first mode in the transverse direction was generated if the small cavities existed inside the tube banks. This resonance was not generated from the tube banks of no cavities. The resonance onset velocity in the transverse mode was fairly slower than that of no cavities. It was easy to generate acoustic resonance when there were small cavities inside in-line tube banks.展开更多
文摘Bulk polymerizations of styrene (St) were carried out in the presence of three reversible addition fragmentation chain transfer (RAFT) agents benzyl dithiobenzoate (BDB), cumyl dithiobenzoate(CDB), and 1-phenylethyl dithiobenzoate (PEDB) under low ratio of RAFT agent to initiator. The kinetic model was developed to predict polymerization rate, which indicates that the RAFT polymerization of St is a first-order reaction. In the range of experimental conversions, the plots of -ln(1-x) against time t are approximately linear (x is monomer conversion). The kinetic study reveals the existence of strong rate retardation in RAFT polymerization of styrene. A coefficient K_r is defined to estimate the rate retardation in the RAFT system considering the assumption that the retardation in polymerization rate is mainly attributed to slow fragmentation of the intermediate radicals. K_r relates to the structure of RAFT agents as well as the concentrations of RAFT agent and azobis isobutyronitrile (AIBN). For a certain RAFT agent, the value of K_r is enhanced by the increase in the initial concentration of RAFT agent and the higher ratio of RAFT to AIBN. With the same recipe for different RAFT agents, the increasing trend for the values of K_r is BDB<PEDB<CDB.
基金Supported by the National Natural Science Foundation of China under Grant Nos. 11004001 and 11105001the Key Project of Chinese Ministry of Education under Grant No. 212076the Anhui Provincial Natural Science Foundation under Grant No. 1208085QA09
文摘The photon transport properties in one-dimensional coupled-resonator waveguide embedded with a quantum dot molecule are investigated. The calculations reveal that one can control the photon transport by using a gate electric field. The phase shift and group velocity delay of the transmitted single photon are discussed. This research may be found applications in integrated optoelectronic devices and solid quantum devices.
基金supported by Grant-in-Aid for Scientific Research (C) from Japan Society for the Promotion of Science
文摘In the present paper the attention is focused on the effect of small cavities inside in-line tube banks on acoustic resonance which occurred in the two-dimensional model of boiler. We measured the sound pressure level, the amplitude and the phase delay of acoustic pressures and the gap velocity. As a result, we found many peak frequencies of sound pressure level with different Strouhal numbers, mainly about S1=0.15, 0.26 and 0.52. The variation of SPL for S,=0.26, 0.52 components in the tube banks with cavities was the same as the result of no cavities. The existence of cavities inside in-line tube banks caused the resonance of St=0.15. And the acoustic resonance of the first mode in the transverse direction was generated if the small cavities existed inside the tube banks. This resonance was not generated from the tube banks of no cavities. The resonance onset velocity in the transverse mode was fairly slower than that of no cavities. It was easy to generate acoustic resonance when there were small cavities inside in-line tube banks.
