针对数字移动无线电(Digital Mobile Radio,DMR)系统大区制组网存在的局限性,对比了DMR进行多基站组网时异频网络和同频网络两种模式的特点,指出了同频多基站组网的优势和关键技术。通过对同频网络固有的差拍衰落和码间干扰等自干扰问...针对数字移动无线电(Digital Mobile Radio,DMR)系统大区制组网存在的局限性,对比了DMR进行多基站组网时异频网络和同频网络两种模式的特点,指出了同频多基站组网的优势和关键技术。通过对同频网络固有的差拍衰落和码间干扰等自干扰问题的分析和研究,根据DMR的基本参数进行了理论计算,提出了减少和消除差拍衰落的方法和措施,并就工程应用中相干区的设计问题给出了相干区的设计原则和建议。展开更多
An anhydride monomer containing ether oxide bridge, 7-oxa-bicyclo[2,2,1]hept-5-ene-2,3-dicarboxylic anhydride （ONA）, was successfully synthesized by Diels-Alder reaction of furan and maleic anhydride. The ONA was al...An anhydride monomer containing ether oxide bridge, 7-oxa-bicyclo[2,2,1]hept-5-ene-2,3-dicarboxylic anhydride （ONA）, was successfully synthesized by Diels-Alder reaction of furan and maleic anhydride. The ONA was also studied as an end-cap for the polymerization of monomer reactant （PMR） type polyimides. Three molecular weight levels of the ONA end-capped PMR resins were evaluated. The effects of process conditions of these novel PMR resins on thermal and mechanical properties were investigated. It was demonstrated that the imidized prepolymers using the end-cap have good processability, and the cured polyimide specimens exhibited good thermal stability. The initial decomposition temperature, Td （ca. 580℃） and glass transition temperature, Tg （330℃） of the novel resin （PI-20）, prepared trader optimum process conditions, compare favorably with the Td （ca. 620℃） and Tg （ca. 348℃） of the state-of-the-art resin （PI＇-20）, respectively.展开更多
文摘针对数字移动无线电(Digital Mobile Radio,DMR)系统大区制组网存在的局限性,对比了DMR进行多基站组网时异频网络和同频网络两种模式的特点,指出了同频多基站组网的优势和关键技术。通过对同频网络固有的差拍衰落和码间干扰等自干扰问题的分析和研究,根据DMR的基本参数进行了理论计算,提出了减少和消除差拍衰落的方法和措施,并就工程应用中相干区的设计问题给出了相干区的设计原则和建议。
基金financially supported by the Research Foundation of State Key Laboratory of Applied Organic Chemistry
文摘An anhydride monomer containing ether oxide bridge, 7-oxa-bicyclo[2,2,1]hept-5-ene-2,3-dicarboxylic anhydride （ONA）, was successfully synthesized by Diels-Alder reaction of furan and maleic anhydride. The ONA was also studied as an end-cap for the polymerization of monomer reactant （PMR） type polyimides. Three molecular weight levels of the ONA end-capped PMR resins were evaluated. The effects of process conditions of these novel PMR resins on thermal and mechanical properties were investigated. It was demonstrated that the imidized prepolymers using the end-cap have good processability, and the cured polyimide specimens exhibited good thermal stability. The initial decomposition temperature, Td （ca. 580℃） and glass transition temperature, Tg （330℃） of the novel resin （PI-20）, prepared trader optimum process conditions, compare favorably with the Td （ca. 620℃） and Tg （ca. 348℃） of the state-of-the-art resin （PI＇-20）, respectively.
