具有汇聚特性的场发射电子源的模拟研究

提出了一种具有汇聚特性的新型场发射阴极结构,利用有限元方法模拟计算了此种阴极结构在不同参数条件下的电场分布、电子轨迹,考察了不同参数对电子汇聚效果的影响,给出了此种场发射阴极的栅极-阴极间距、栅极宽度、阳极电压、栅极电压等基本参数对汇聚效果的影响.模拟计算结果表明,电子束的汇聚程度随着栅极-阴极间距的增大而增大,随着栅极宽度的增大而减小;电子束的汇聚程度与阳极电压、栅极电压参数密切相关,并存在最优参数.     

高稳定度CPM飞秒激光特性的研究

利用最优化动力学参数的方法,获得了高稳定度的CPM飞秒激光器运转特性。激光器输出平均脉宽43fs,中心波长624nm,平均功率20mW,脉宽不稳定度±3.3％,频率不稳定度小于10~(-6)。     

Solvent extraction of La（III） with 2-ethylhexyl phosphoric acid-2-ethylhexyl ester （EHEHPA） by membrane dispersion micro-extractor

The conventional rare earth solvent extraction equipments have many problems such as long mixing time, low processing capacity, large factory area occupation, high energy consumption and so on. In order to solve the problems, many types of equipments were brought out. In this work, studies were carried out on the La（III） extraction process with 2-ethylhexyl phosphoric acid-2-ethylhexyl ester （EHEHPA） by membrane dispersion micro-extractor. Equilibrium studies showed that the initial aqueous pH value 4.15 with the saponification rate 40%was the optimal operation condition. The effects of membrane dispersion micro-extractor operational conditions such as dispersion mode, bulk flow rate and organic phase flow rate on the extraction efficiency were studied. The results showed that when the organic solution was the dispersed phase, the extraction efficiency was higher than that of others. Increasing bulk flow ratio could enhance the extraction efficiency greatly. When the ratio of organic phase flow rate to that of aque-ous phase was 80：80, the extraction efficiency was over 95%. The effect of stripping phase acidity on the La（III） recovery was studied. The results showed that when the stripping phase pH was 2.0, organic phase flow rate to stripping phase flow rate was 20：80;the re-covery efficiency of La（III） can reach 82%.     

单模光纤传输参数的一种综合测试方法

介绍一种对匹配型单模光纤的传输参数（色散，模场直径，截止波长，非线性截面积等）进行综合测量的方法，它是通过实测的光纤径向折射率分布曲线，经过数据处理和理论计算，最终得到的所需的几何参数和传输参数，作者研究的新的数据处理方法提供了较高的测量准确度，采用这种方法得到了结果和用仪表实测的数据进行比较，其中零色散波长λ０误差小于±２ｎｍ，模场直径误差小于±０．２μｍ。     

Master Diagnostic Curve for Dispersion Coefficient of Soils

A master diagnostic curve (MDC) method is proposed for identifying the dispersion coefficient from observed breakthrough curve in soil–column experiments. The method uses matching of diagnostically plotted points to the MDC. Accurate identification of the dispersion coefficient is possible with a parallel shift of only one axis. Another advantage of the method is that the MDC is an invariant curve and once prepared, can be used for different data sets characterized by high Péclet number. The new method is simple, does not require large computations as in conventional least-squares approach, and yields a quick and accurate estimate of the dispersion coefficient. The new method does not require an initial guess for the dispersion coefficient. It can also yield a value of the dispersion coefficient from a single observed concentration. Although subjectivity is involved in matching, there is a transparent visual realization of the reliability of the estimated dispersion coefficient, and the points with substantial errors. The new method has several advantages over the least-squares approach and is suited for an advanced study on the subject. An estimate of the dispersion coefficient obtained using the new method is as good as obtained using a good optimization method.     

沿射线路径的波动方程延拓吸收与衰减补偿方法

地层的吸收与衰减效应使地震波的振幅被衰减，相位被改变。在地震资料处理流程中，反褶积处理假设地震信号是平稳的，即地震子波的波形不随时间变化（或变化较小），这时用地震道自相关函数代替子波自相关函数才比较可靠；而地震成像也要求炮集与炮集之间、道与道之间的地震波能量一致，否则成像结果不保幅，因此必须对地震波进行吸收与衰减补偿。但是，对地震波吸收与衰减的补偿通常是针对自激自收单道记录的。事实上，地层对地震波的吸收与衰减是沿着波的传播路径发生的，因此，补偿应该与叠前深度偏移成像一样在反向波传播过程中进行。为此，提出了一种沿射线路径波动方程延拓的吸收与衰减补偿（Q值）方法。其基本原理是：用非递归波场延拓代替递归波场延拓，用等效Q值代替分层Q值，用平面波传播思想实现对叠前数据沿波传播路径的吸收与衰减（Q值）补偿。这种方法适合于局部水平层状介质假设的情况。数值试验表明该方法是有效的，补偿后子波波形的一致性得到了改善，衰减的振幅得到了恢复。     

厄米-高斯型短脉冲在光纤中传输的理论研究

从含高阶色散的非线性薛定谔方程出发 ,用矩法研究了厄米 高斯型短脉冲在光纤中的传输 ,获得了脉冲各参量在光纤中演化的耦合微分方程组 ,再利用龙格 库塔法得到此微分方程组的解 ,并与数值模拟进行了比较 ,两者吻合较好。     

利用后置补偿法对10-Gbit/s长距离波分复用光纤传输系统进行色散均衡

通过系统仿真,对以常规单模光纤和色散补偿光纤(SMF+DCF)组成的16×10-Gb/s WDM色散补偿系统进行了分析,调制器啁啾为0,激光器静态线宽为5MHz.结果表明:(1)对于数百公里的传输距离,以DCF进行在线补偿就可以使各个信息达到较好的色散补偿效果(16×10-Gb/s,400km,眼图代价差别小于0.5dB);(2)由于SPM在SMF光纤中对脉冲的压缩效应,每一信道应保持略微偏正的残留色散量;(3)对于上千公里的传输距离,仅以DCF进行在线补偿无法同时均衡所有信道的色散(16×10-Gb/s, 1200km,眼图代价差别大于0.85dB).为此,本文以SMF或DCF在系统接收端再次对各信道逐个进行色散补偿(后置色散补偿),达到了良好的效果(16×10-Gb/s, 1200km, 眼图代价差别小于0.3dB).     

单分散性微米级微球的合成EI

研究了苯乙烯在乙醇/水介质中,以聚电解质聚丙烯酸为分散剂,偶氮二异丁腈为引发剂的分散聚合行为。考察了溶剂体系、分散剂用量、单体浓度、引发剂种类和用量、反应温度及时间诸因素对聚合反应及产物的影响。通过改变各种反应条件,采用分散聚合法,成功地合成出平均粒径2.1μm的单分散聚苯乙烯微球。     

Preparation of Core-shell Structured Particles and Their Nucleation in Polyester： Ⅰ. Preparation of Monodisperse SiO2／PS Core-shell Composite Particles

To enhance the nucleation and crystallization properties of polyester (e.g., polyethylene terephthalate, PET),core-shell structured particles are used to improve these properties by controlling the inorganic dispersion properties in the polymers. In the paper, monodisperse particles of silica/polystyrene (PS) are prepared with both dispersion and emulsion polymerization techniques. The monodisperse silicon dioxide particles are first prepared with the seed growth method and modified by the coupling agents. Silica is properly modified with KH-570, and its size deviation is 3.0% or so. The modified silica then reacts with the mixture of ethanol, water medium, and monomer of styrene under dispersion polymerization. Results show that the dispersion polymerization technique is more suitable for monodisperse core-shell SiO2/PS particles than that of the emulsion. The morphology and molecular structure of the core-shell particles are investigated with the transmission electron microscope (TEM), and fourier transform infra-red spectroscopy (FTIR). The results show that the modified silica particles are successfully encapsulated with polystyrene. The average number of silica particles encapsulated into each polystyrene sphere decreases when the size of silica particles increases from 50 nm to 600 nm, and will approach one when the silica is greater than 380nm in size. The mass ratio for silica/PS particles in emulsion polymerization is 4.7/1,lower than that of 6.8/1 for dispersion polymerization, which is the first reported optimized data for preparing the similar monodisperse composite particles. Thus, the PS shell in the former is thinner than that in the latter.