针对正交码移键控(code shift keying,CSK)误比特率(bit error rate,BER)性能下降和非正交码索引调制(non-orthogonal-code index modulation,N-CIM)未能充分利用扩频码自相关性的不足,提出一种非正交CSK和码索引调制(non-orthogonal-CS...针对正交码移键控(code shift keying,CSK)误比特率(bit error rate,BER)性能下降和非正交码索引调制(non-orthogonal-code index modulation,N-CIM)未能充分利用扩频码自相关性的不足,提出一种非正交CSK和码索引调制(non-orthogonal-CSK-code index modulation,N-CSK-CIM)算法。发送端信息比特分为调制比特和扩频码映射比特;调制比特用来进行符号调制,映射比特映射为扩频码的索引和码相位索引。首先根据调制比特进行符号调制,然后利用映射比特映射的扩频码索引选择同一原始扩频码,并根据码相位索引进行码移键控产生新的扩频码,调制后的符号实部与虚部分别用这一新的扩频码进行扩频。仿真结果表明,在加性高斯白噪声(additive white Gaussian noise,AWGN)信道和瑞利衰落信道中,相同信噪比时,N-CSK-CIM算法的BER性能优于N-CIM算法和正交CSK算法。展开更多
The hydrophobic silica aerogel （SiO2 aerogel） was prepared by/n situ polymerization sol-gel method and ethanol supercritical drying, with tetraethoxysilane （TEOS） as silica source, phenyltriethoxysilane （PTES） a...The hydrophobic silica aerogel （SiO2 aerogel） was prepared by/n situ polymerization sol-gel method and ethanol supercritical drying, with tetraethoxysilane （TEOS） as silica source, phenyltriethoxysilane （PTES） as modifier, ethanol as solvent and ammonia as catalyst. The effects of n（PTES）/n（TOES） were investigated on gel time, structure, and hydrophobicity. The SiO2 aerogel was measured by Fourier transform infrared spectroscopy （FT-IR） and scanning electron microscopy （SEM）. The effects of n（PTES）/n（TOES） were also studied on adsorption property of pentane, hexane, heptane, octane, benzene, toluene, o-xylenc, nitromethane, nitroethane, and nitrobenzene. The adsorption intensity of SiO2 aerogel was compared with that of activated carbon. The results show, with the increasing ofn（PTES）/n（TOES）, the surface area, pore volume, and pore size of SiO2 aerogel decreased, gel time and hydrophobicity increased, and the contact angle could be 154° with n（PTES）/n（TOES）=0.7. The adsorption intensity of SiO2 aerogel with n（PTES）/n（TOES）=0.5 was bigger than that of activated carbon with an average 5.84 times of 10 organic liquid. The adsorption intensity of aerogel with n（PTES）/n（TOES） =0.1 was the best one in all samples with the average 8.33 times compared with that of activated carbon.展开更多
文摘针对正交码移键控(code shift keying,CSK)误比特率(bit error rate,BER)性能下降和非正交码索引调制(non-orthogonal-code index modulation,N-CIM)未能充分利用扩频码自相关性的不足,提出一种非正交CSK和码索引调制(non-orthogonal-CSK-code index modulation,N-CSK-CIM)算法。发送端信息比特分为调制比特和扩频码映射比特;调制比特用来进行符号调制,映射比特映射为扩频码的索引和码相位索引。首先根据调制比特进行符号调制,然后利用映射比特映射的扩频码索引选择同一原始扩频码,并根据码相位索引进行码移键控产生新的扩频码,调制后的符号实部与虚部分别用这一新的扩频码进行扩频。仿真结果表明,在加性高斯白噪声(additive white Gaussian noise,AWGN)信道和瑞利衰落信道中,相同信噪比时,N-CSK-CIM算法的BER性能优于N-CIM算法和正交CSK算法。
基金Funded by the National Natural Science Foundation of China(No.10976013)the Science Project of Ministry of Housing and Urban-Rural Development(No.2011-K7-16)the State Key Laboratory of Materials Oriented Chemical Engineering(No.KL11-09)
文摘The hydrophobic silica aerogel （SiO2 aerogel） was prepared by/n situ polymerization sol-gel method and ethanol supercritical drying, with tetraethoxysilane （TEOS） as silica source, phenyltriethoxysilane （PTES） as modifier, ethanol as solvent and ammonia as catalyst. The effects of n（PTES）/n（TOES） were investigated on gel time, structure, and hydrophobicity. The SiO2 aerogel was measured by Fourier transform infrared spectroscopy （FT-IR） and scanning electron microscopy （SEM）. The effects of n（PTES）/n（TOES） were also studied on adsorption property of pentane, hexane, heptane, octane, benzene, toluene, o-xylenc, nitromethane, nitroethane, and nitrobenzene. The adsorption intensity of SiO2 aerogel was compared with that of activated carbon. The results show, with the increasing ofn（PTES）/n（TOES）, the surface area, pore volume, and pore size of SiO2 aerogel decreased, gel time and hydrophobicity increased, and the contact angle could be 154° with n（PTES）/n（TOES）=0.7. The adsorption intensity of SiO2 aerogel with n（PTES）/n（TOES）=0.5 was bigger than that of activated carbon with an average 5.84 times of 10 organic liquid. The adsorption intensity of aerogel with n（PTES）/n（TOES） =0.1 was the best one in all samples with the average 8.33 times compared with that of activated carbon.
