Vehicular ad hoc networks （VANETs） that use the IEEE 802.11p communication standard face a number of challenges, not least when it comes to safety messages on the VANET control channel （CCH） where short delay time...Vehicular ad hoc networks （VANETs） that use the IEEE 802.11p communication standard face a number of challenges, not least when it comes to safety messages on the VANET control channel （CCH） where short delay times and reliable delivery are of pri- mary importance. In this paper we propose a vehicular machine-to-machine （VM2M） overlay network that uses Long Term Evolu- tion （LTE） physical random access channel （PRACH） to emulate VANET CCH. The overlay network uses dedicated preambles to separate vehicular traffic from regular LTE traffic and a cartier sense multiple access with collision avoidance （CSMA-CA） layer similar to the one used in IEEE 802.15.4 to avoid the four step handshake and the overhead it incurs. The performance of the pro- posed overlay is evaluated under a wide range of PRACH parameters which conform to the scenarios with high vehicle velocities and large distances between roadside units （RSUs） that may be encountered in rural areas and on highways.展开更多
From the roots of Sanguisorba alpina, a new triterpenoid was isolated and identified as 2-isobutyryloxy-19α, 25-dihydroxyursa-1, 12-dien-28-oic acid by means of spectral methods, named as aipinic acid.
Phytochemical investigation of the roots of Ligularia nelumbifolia afforded three new sinapyl alcohol derivatives together with two other novel constituents.Their structures were elucidated by high field 1D and 2D NMR...Phytochemical investigation of the roots of Ligularia nelumbifolia afforded three new sinapyl alcohol derivatives together with two other novel constituents.Their structures were elucidated by high field 1D and 2D NMR techniques and chemical transformations.展开更多
Phenylurea reacted with dichlorophenylphosphine and aldehydes or ketones by Mannich-type reaction in anhydrous benzene to give five-mem- bered phosphorous heterocyclic compounds.However.derivatives of α-ureidoalkylph...Phenylurea reacted with dichlorophenylphosphine and aldehydes or ketones by Mannich-type reaction in anhydrous benzene to give five-mem- bered phosphorous heterocyclic compounds.However.derivatives of α-ureidoalkylphosphonic acids were obtained as the reaction performed in glacial acetic acid.展开更多
Ointment-like poly(ortho esters) were synthesized from the reaction of 3,9-bis (methylene)-2,4,8,10-tetraoxaspiro[5.5]undecane with PEG-400,N,N-bis(2-hydroxyethyl)-n-hexadecylamine and N,N-bis(2-hydroxyethyl) palmitam...Ointment-like poly(ortho esters) were synthesized from the reaction of 3,9-bis (methylene)-2,4,8,10-tetraoxaspiro[5.5]undecane with PEG-400,N,N-bis(2-hydroxyethyl)-n-hexadecylamine and N,N-bis(2-hydroxyethyl) palmitamide respectively. The influence of the catalyst on the intrinsic viscosity of polymers was also studied.展开更多
文摘Vehicular ad hoc networks （VANETs） that use the IEEE 802.11p communication standard face a number of challenges, not least when it comes to safety messages on the VANET control channel （CCH） where short delay times and reliable delivery are of pri- mary importance. In this paper we propose a vehicular machine-to-machine （VM2M） overlay network that uses Long Term Evolu- tion （LTE） physical random access channel （PRACH） to emulate VANET CCH. The overlay network uses dedicated preambles to separate vehicular traffic from regular LTE traffic and a cartier sense multiple access with collision avoidance （CSMA-CA） layer similar to the one used in IEEE 802.15.4 to avoid the four step handshake and the overhead it incurs. The performance of the pro- posed overlay is evaluated under a wide range of PRACH parameters which conform to the scenarios with high vehicle velocities and large distances between roadside units （RSUs） that may be encountered in rural areas and on highways.
基金This work was supported by the National Natural Science Foundation of China.
文摘 From the roots of Sanguisorba alpina, a new triterpenoid was isolated and identified as 2-isobutyryloxy-19α, 25-dihydroxyursa-1, 12-dien-28-oic acid by means of spectral methods, named as aipinic acid.
基金①This work was supported by the National Natural Science Foundation of China and the doctoral programmc from State Education Commission of China.
文摘Phytochemical investigation of the roots of Ligularia nelumbifolia afforded three new sinapyl alcohol derivatives together with two other novel constituents.Their structures were elucidated by high field 1D and 2D NMR techniques and chemical transformations.
基金the National Natural Science Foundation of People's Republic of China:
文摘Phenylurea reacted with dichlorophenylphosphine and aldehydes or ketones by Mannich-type reaction in anhydrous benzene to give five-mem- bered phosphorous heterocyclic compounds.However.derivatives of α-ureidoalkylphosphonic acids were obtained as the reaction performed in glacial acetic acid.
文摘Ointment-like poly(ortho esters) were synthesized from the reaction of 3,9-bis (methylene)-2,4,8,10-tetraoxaspiro[5.5]undecane with PEG-400,N,N-bis(2-hydroxyethyl)-n-hexadecylamine and N,N-bis(2-hydroxyethyl) palmitamide respectively. The influence of the catalyst on the intrinsic viscosity of polymers was also studied.
