感应耦合等离子体刻蚀在聚合物光波导制作中的应用

提出了利用感应耦合等离子体(ICP)刻蚀技术提高聚合物光波导器件性能的方法,介绍了ICP刻蚀技术的原理和优点。选取聚甲基丙烯酸甲酯-甲基丙烯酸环氧丙酯(P(MMA-GMA))作为波导材料,采用氧气作为刻蚀气体,研究了ICP参数变化对刻蚀效果的影响。介绍了倒脊形光波导的制备过程,采用改变单一工艺参数的方法,分析了刻蚀效果随时间、功率、压强、气体流量等参数的变化,对参数优化后刻蚀得到的凹槽和平板结构进行了表征。实验结果表明:在天线射频功率为300 W,偏置射频功率为30 W,气体压强为0.5 Pa,氧气流速为50 cm³/min的条件下,可获得侧壁陡直、底面平整的P(MMA-GMA)凹槽结构。     

数学教学改革与初等数学现代化中的几个问题

小平同志提出的“教育要面向现代化、面向世界、面向未来”的方针,是我国进行教育数学改革的指导思想。而改革的内容,则主要涉及三个方面:教育体制、教学内容和教学方法,本文试图从一个侧面谈谈数学教学改革和初等数学现代化的问题,也就是如何用现代数学的科学观点去认识、处理初等数学的问题。一.中学数学的双重逻辑结构问题 1.如所周知,数学公理化其完美、奥妙者当首推平面几何,它始自欧几里得而基本上完成于希尔伯特。整个平面几何学象一座辉煌大厦,在少数公理的根基上逻辑地构筑起来,形成了初等几何体系,其思想也逐渐渗透并贯串了代数、三角等学科,这就形成了直到今天我们还在使用的中学数学教材的基本结构,也形成了几百年来人们进行数学思维的三段论式的推理模式。我们的数学教学大纲中所规定的关于能力培     

UNIFORM GROOVE-DEPTH RAC BY USING TRANSDUCER WEIGHTING

A new weighting method,transducer weighting.for the uniform groove-deph RAC is proposed in thispaper.The weighted input and output transducersform a weighting transversal filter In addition,the groove-width weighting,which can be used as an auxiliary is also discussed. By using the new methods,two uniform groove depth RACs have been designed and fabricated,Thesidelobe suppressions achieved are 31 dB and 32 dB.respectively.The results are considered satisfactorybecause the phase compensation by metal strip was not applied.     

测度链上的柯西不等式

研究了测度链上的柯西不等式,给出测度链上柯西不等式的具体形式.此外,还对测度链上的柯西不等式作了推广.     

毛白杨的叶肉原生质体培养再生植株

毛白杨(Populus tomentosa)是我国华北地区特有的一种林木,从毛白杨无菌苗分离得到的叶肉原生质体在改良的KM8p液体培养基中进行浅层培养,7天后开始第一次细胞分裂,1O天时分裂频率可达20％左右,随后形成大量的细胞团和愈伤组织,通过调整培养基中的激素浓度,愈伤组织呈黄绿色并逐渐变得紧密,当这种愈伤组织转到附加玉米素和吲嗓乙酸或者萘乙酸的MS培养基上时,培养4—5周后开始有芽的分化,待芽伸长后从基部切下转到无激素的1/2MS培养基上,即长根形成完整植株。     

Effects of polarization and p-type GaN resistivity on the spectral response of InGaN/GaN multiple quantum well solar cells

Effects of polarization and p-type GaN resistivity on the spectral response of InGaN/GaN multiple quantum well(MQW) solar cells are investigated. It is found that due to the reduction of piezoelectric polarization and the enhancement of tunneling transport of photo-generated carriers in MQWs, the external quantum efficiency(EQE) of the solar cells increases in a low energy spectral range(λ 370 nm) when the barrier thickness value decreases from 15 nm to 7.5 nm. But the EQE decreases abruptly when the barrier thickness value decreases down to 3.75 nm. The reasons for these experimental results are analyzed. We are aware that the reduction of depletion width in MQW region, caused by the high resistivity of the p-type GaN layer may be the main reason for the abnormally low EQE value at long wavelengths(λ 370 nm).     

C,igahertz longitudinal acoustic phonons originating from ultrafast ligand field transitions in hematite thin films

The creation and propagation of longitudinal acoustic phonons （LAPs） in high quality hematite thin films （α-Fe203） epitaxially grown on different substrates （BaTiO3, SrTiO3, and LaAlO3） are investigated using the femtosecond pump- probe technique. Transient reflection measurements （AR/R） indicate the photo-excited electron dynamics, and the initial decay less than 1 ps and the slow decay of -500 ps are attributed to the electron-LO phonon coupling and electron-hole nonradiative recombination, respectively. LAPs in α-Fe2O3 film can be created by ultrafast excitation of the ligand field state, such as the ligand field transitions under 800-nm excitation as well as the ligand to metal charge-transfer with 400- nm excitation. The strain modulations of the sound velocity and the out-of-plane elastic properties are demonstrated in α-Fe2O3 film on different substrates.     

次临界能源堆物理设计进展

聚变-裂变混合能源堆包括聚变中子源和次临界能源堆,主要目标是生产电能。回顾了国内外混合堆的发展历史,给出混合能源堆设计的边界条件和约束条件,说明次临界能源堆以铀锆合金为燃料、水为冷却剂的设计思想。利用输运燃耗耦合程序MCORGS计算了混合能源的燃耗,给出了中子有效增殖因数、能量放大倍数和氚增殖比等物理量随时间的变化。通过分析能谱和重要核素随燃耗时间的变化,说明混合能源堆与核燃料增殖、核废料嬗变混合堆的不同特点。论述了混合堆的热工设计并进行了安全分析。对于燃耗数值模拟程序,通过多家对算,保证其计算结果的可信性。针对次临界能源堆的特点,利用贫铀球壳建立了贫铀聚乙烯装置和贫铀LiH装置,并且专门设计加工了天然铀装置,开展铀裂变率、造钚率、产氚率等中子学积分实验,验证了数值模拟的可靠性。