Fiber Dispersion and Nonlinearity Influences on Transmissions of AM and FM Data Modulation Signals in Radio-Over-Fiber System

Transmission properties of data amplitude modulation (AM) and frequency modulation (FM) in radio-over-fiber (RoF) system are studied numerically. The influences of fiber dispersion and nonlinearity on different microwave modulation schemes, including double side band (DSB), single side band (SSB) and optical carrier suppression (OCS), are investigated and compared. The power penalties at the base station (BS) and the eye opening penalties of the recovered data at the end users are both calculated and analyzed. Numerical simulation results reveal that the power penalty of FM can be drastically decreased due to the larger modulation depth it can achieve than that of AM. The local spectrum broadening around subcarrier microwave frequency of AM due to fiber nonlinearity can also be eliminated with FM. It is demonstrated for the first time that the eye openings of the FM recovered data can be controlled by its modulation depths and the coding formats. Negative voltage encoding format was used to further decrease the RF frequency thus increase the fluctuation period considering their inverse relationship.

电子级气体N2、H2、O2、Ar、He、HCl、CO2、NH3 28种杂质分析技术及质量监控

于G批量导入至Hzhangdi

Polycrystalline silicon thin films and solar cells prepared by rapid thermal CVD

Polycrystalline silicon (poly-Si) films(similar to 10 mu m) were grown from dichlorosilane by a rapid thermal chemical vapor deposition (RTCVD) technique, with a growth rate up to 100 Angstrom/s at the substrate temperature (T-s) of 1030 degrees C. The average grain size and carrier mobility of the films were found to be dependent on the substrate temperature and material. By using the poly-Si films, the first model pn(+) junction solar cell without anti-reflecting (AR) coating has been prepared on an unpolished heavily phosphorus-doped Si wafer, with an energy conversion efficiency of 4.54% (AM 1.5, 100 mW/cm(2), 1 cm(2)).

Cl2／Ar／BCl3ICP刻蚀对AIGaN的损伤研究

感应耦合等离子体（ICP）刻蚀在AlGaN基紫外探测器台面制作中起着重要作用，初步研究了Cl2／Ar／BCl3ICP刻蚀对A1GaN材料的损伤。运用X射线光电子能谱（XPS）对ICP刻蚀前后的n型Al0.45Ga0．55N表面进行了分析，并对刻蚀后AlGaN材料在N2气中快速热退火进行了研究。结果表明，在N2气中550℃退火3min对材料的电学性能有明显的改善作用。

PHCs污染土壤中植物-AM真菌联合生态效应研究

AM真菌的形成，对共生植物有许多有益的作用。近年来，科学家又将菌根用于修复污染的土壤。对辽河油田和沈抚污水灌区进行了AM菌的调查，结论如下：I)辽河油田和沈抚污水灌区的主要的AM真菌是Glomus mosseae, G. geospora, G. constrictum, Paraglomus occultum，其中优势属为Glomus。因北方冬季的严寒，经过一个冬季，土壤中的抱子密度减少80％以上。在资源调查的基础上，以三叶草、万寿菊和大豆作为供试植物，做盆栽模拟实验，结果为：I )当柴油浓度高达30 000 mg·kg~(-1)时，AM菌仍能侵染菊花，和菊花形成共生体；2）随着油浓度的增加，侵染率先增加，而后降低。3)随着油浓度的增加，叶绿素总量先略微增加，当油浓度高达30 000 mg·kg~(-1)时，叶绿素含量下降；4）随着油浓度的增加和灭菌，植物的营养生长和生殖生长受到抑制，而接AM菌、细菌和固氮菌能缓和这种抑制；5）随着油浓度的增加和AM菌的生育进程，AM菌的接种效应在增强。6）对接菌和不接菌的处理来说，随着油浓度的增加，降解率先增加，5000 mg·kg~(-1)时达到最大，分别为94.280la和93. 16%;然后降解率降低。低浓度时接入AM菌，能促进柴油的降解；而当油浓度高达30000mg·kg~(-1)时，不接AM菌反而降解效果会好些。