Search

APDCDM（双极性占空比复用）是降低DCDM（占空比复用）信号幅值级数的一种有效方法。为了进一步降低APDCDM信号的幅值级数,提出了基于信号替换原理的I-APDCDM（改进型双极性占空比复用）技术。分析了I-APDCDM中信号替换的工作原理及电路实现方法,采用Optisystem和MATLAB联合仿真技术设计了I-APDCDM光纤传输系统,分析了改进后系统的传输距离和调制器的消光比对I-APDCDM信号的影响规律。仿真结果表明,I-APDCDM将APDCDM复用信号的幅值级数降低了1级,每比特复用信号的平均能量降低了A2 Ts/24,有效地提高了系统的性能。

提出了一种60GHz毫米波、UWB（超宽带）信号和基带信号混合传输的光纤通信系统。在中心站采用10GHz RF（射频）信号驱动两个并行PM（相位调制器）产生三阶边带,在基站通过PD（光检测器）拍频生成6倍频的60GHz毫米波;利用高斯电脉冲驱动双极型MZM（马赫-曾德调制器）生成二阶UWB信号;UWB信号和基带信号通过偏振复用调制在同一光载波上。仿真结果表明,2.5Gbit/s的信号经20km单模光纤传输后,眼图清晰;生成的UWB信号中心频率为5.5GHz,相对带宽达到98%,符合FCC（美国联邦通信委员会）标准。

为产生全光域UWB（超宽带）一阶和二阶信号,降低光载UWB系统成本,提出了一种基于偏振调制同时光生一阶和二阶UWB信号的方法。将两路极性相反的高斯脉冲信号通过PolM（偏振调制器）相位调制到偏振态正交的两个光载波上,利用PMF（保偏光纤）引入适当的群延时,生成一阶UWB信号。通过PC（偏振控制器）控制输入光信号与PMF主轴所成的角度,产生一对极性相反的一阶UWB信号,并对其中一路进行适当的延时,合成后即可生成二阶UWB信号。所得一阶UWB信号的中心频率为5.36GHz,-10dB绝对带宽为8.96GHz,相对带宽为167%;二阶UWB信号的中心频率为5.83GHz,-10dB绝对带宽为7.36GHz,相对带宽为126%,均满足FCC（美国联邦通信委员会）标准。分析了偏振调制中时延对生成的UWB信号性能的影响。结果表明,当偏振调制中引入的时延τ=TFWHM时,生成的二阶UWB信号更符合FCC要求。

[Objective] Tt is important to investigate the relationship between soil water and each environmental factor in the deep profile after vegetation change in the Loess Plateau and to identify the main controlling factors for the comprehensive regulation of soil water. Methods] Soil samples were collected from farmland, grassland and the 15 m depth of the habitation of salix psammophila and Populus in Dingbian County, northern Shaanxi. The soil samples were analysed using traditional statistics and wavelet coherence analysis. Results] The order of magnitude of soil water content and storage in ()一15 m was farmland〉grassland a salix psam m op hila '> pop la r, with water deficit of 81 0 mm, 1 375 mm, 1 371 mm and 1 7 62 m m, respectively. Based on wavelet coherence analysis of control factors, soil electrical conductivity (EC) was found to be the single dominant factor explaining water transport, and the area of positive correlation between EC and soil water was found throughout the scales. The two-factor combinations that combined effect of farmland are EC and sand, and magnetic susceptibility and sand for the lands grown salix psammophila and poplar. The two-factor combinations enhanced the degree of coherence mainly at large scales. Conclusion] Deep soil water is more influenced by soil properties, but plant root conditions can seriously perturb the relationship between water and soil properties. [ABSTRACT FROM AUTHOR]

Copyright of Acta Scientiarum Naturalium Universitatis Sunyatseni / Zhongshan Daxue Xuebao is the property of Sun-Yat-Sen University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Chinese Journal of Applied Ecology / Yingyong Shengtai Xuebao is the property of Chinese Journal of Applied Ecology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Chinese Journal of Applied Ecology / Yingyong Shengtai Xuebao is the property of Chinese Journal of Applied Ecology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Forest Engineering is the property of Forest Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Chinese Journal of Diabetes Mellitus is the property of Chinese Journal of Diabetes Mellitus and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

[Objectives] With rice variety 'Nipponbare' serving as genetic transformation materials, functions of stomatal regulation channel OsKAT3 was studied by RNAi techniques. [Methods] Based on the sequence alignment between the OsKAT3 and KAT-like channels among the Arabidopsis and rice, a specific fragment of the C terminal was chosen for constructing OsKAT3 RNAi expression vector. The primer was designed and the restriction site was inserted, and the OsKAT3 was used as a template for RNAi-OsKAT3 cis-and trans-fragments of PCR amplification. The PCR amplification fragments were connected to the pMD19-T vectors and sequenced after bacterial colony PCR confirmation. The sequencing results showed that RNAi-OsKAT3 cis-and trans-fragments were correctly connected to the pMD19-T vectors. Then the RNAi-OsKAT3 cis-and trans-fragments were digested by restriction enzyme Sac I/Spe I and BamH I/Kpn I, respectively, and connected to the plasmid pTCK303 with a hairpin structure. PCR and double digestion verification showed that constructed pTCK303-OsKAT3(RNAi-OsKAT3) structural integrity was then transformed into rice by Agrobacterium-mediated methods. [Results] Positive recombinant plants were confirmed by PCR with a universal primer pair designed according to the flank sequence of multiple clone site in pTCK303, indicating that the specific cis- and trans-fragments were successfully integrated into the genome of the regeneration rice. Further real-time PCR results also confirmed that the expression of OsKAT3 in the RNAi transgenic plants was successfully suppressed. [Conclusions] The expression of OsKAT3 was suppressed by RNAi technology in the T0 generation RNAi transgenic rice plants, providing a vital foundation for follow-up studies of the function of the OsKAT3. [ABSTRACT FROM AUTHOR]