灯泵染料激光器增强预燃泵浦系统的研究

闪光灯泵浦染料激光器结构简单且能得到很高的泵浦能量。但由于灯的脉冲上升时间较长,要避免染料分子能级系际交叉的影响,提高器件转换效率,往往要对三重态采用化学猝灭或机械猝灭。这些方法有利有弊,且不易推广。我们选择了另外的途径解决这一问题。在没有采用化学猝灭,机械猝灭作用亦较差的情况下,研究了新型的增强预燃泵浦技术及系统,取得了明显的效果:使用若丹明6G激光染料,宽带激光输出能量大于140mJ,激光脉冲半宽度不大于0.3μs,峰值功率大于400kW,放电回路用火花开关,重复频率高于20次/s。泵浦系统中用上增强预燃泵浦技术,激光输出能量最大能提高六倍多。     

准分子激光泵浦的皮秒染料激光器

利用准分子激光泵浦猝灭式染料激光器，获得了３０ｐｓ的可调谐染料激光脉冲输出。     

二极管激光器泵浦全固态可调谐染料激光器

新型激光染料Pyrronlethene567具有较高的荧光量子产额（），较低的三重态吸收（三重态猝灭系数，较宽的波长调谐范围（550～580nm连续可调）及良好的化学稳定性．以固态溶胶凝胶（Sol－Gel）材料为基质，将通常在液体状态下工作的激光染料固化，可以很好地保持染料活性，并实现染料激光器的小型化和固态化，具有一定的应用前景．染料激光器一般以氙灯、氩离子激光器等为泵浦源，装置庞大、激光转换效率低、引起的热效应显著．二极管泵浦激光器（DPL）是一种小型化的新型激光器件，采用二极管激光器作为泵浦源，具有转换效率高、寿命长、…     

ps单脉冲超强度的产生和返回放大

我们发展了一种新的猝灭技术——调制猝灭,利用延迟后的部分泵浦光的相干场,经过适当的空间相移,叠加到分布反馈染料激光器(DFDL)的原泵浦区,适时地消除DFDL中泵浦强度的轴向周期性调制,从而使分布反馈振荡自行终止。应用这一办法,在泵浦强度远高于阈值的情况下,可以方便而可靠地获得单个的ps脉冲输出。由于猝灭后的激活染料仍然处于高度     

乙酸溶液荧光猝灭的机理研究

从理论上对紫外光激励乙酸产生荧光及荧光猝灭机理分别进行了分析研究.结果表明,乙酸溶液在253.7nm紫外光照射下可以发出明显的荧光,而且随着溶液浓度的变化产生了荧光猝灭的现象.分析认为,荧光猝灭的主要原因是动态猝灭过程-由最低激发单重态(n,π)转入三重态(π,π)所致,并对淬灭常数进行了计算.研究乙酸本体荧光特性及荧光猝灭机理可为其作为猝灭剂、溶剂、催化剂和食品添加剂时其它分子荧光光谱的研究提供参考.     

染料放大器的ASE和飞秒脉冲放大

分析了染料放大器(DLA)的放大的自发辐射(ASE)的分布、上能级以及三重态粒子数分布。用数学方法模拟计算了泵浦作用时非饱和情形下染料分子的储能和飞秒脉冲的放大。我们认为,设计一个染料放大器必须考虑三重态积累对分子储能的影响。用调Q倍频Nd∶YAG脉冲同步泵浦染料二级放大器放大飞秒脉冲,得到的第一、二级放大倍数分别为1000和60,对于第一级放大,计算结果与实验结果基本相符。     

泵浦染料激光器的壁消融闪光灯

消融灯与普通的脉冲氙灯相比,不但亮度大,稳定性好,而且还具有结构简单,制做容易,灯内气压可调等优点.这种灯可以产生微秒量级的光脉冲.用它作为染料激光器的泵源,可以避免染料分子三重态的猝灭效应,得到较高的转换效率.     

染料激光器(中)

二、猝灭作用有机染料激光器中作为活性介质的染料分子受到泵浦光源的照射后,电子吸收了被激发到能量较高的激发态,是否一定能够产生激光呢?毛主席教导我们:“世界上的事情是复杂的,是由各方面的因素决定的.看问题要从各方面去看,不能只从单方面看.”在染料激光器中,除了和荧光作用相应的受激辐射过程之外,尚有一些和光发射相竞争的无辐射过程,而这些过程足以降低荧光效率,甚至猝灭激光.主要的有两种来源,一种是来自有机分子的二聚物;另一种是来自有机分子的三重态,尤其是后者,对染料激光器运转的影响极大,所以我们着重从染料分子的能谱结构来分析它们的作用,并找出解决的办法.现在先讨论二聚物的作用.     

闪光灯泵浦脉冲染料激光器的新进展

本文介绍了用于治癌的闪光灯泵浦染料激光器研制工作中所取得的技术突破: 1.采用国产奇通红染料的效果良好,达到并超过了进口染料的水平。该染料是天津染料研究所应本课题的需要而研制的。 2.找出了染料三重态猝灭剂环辛四烯的使用方法,使器件效率明显提高,达50%左右,因而大大降低了脉冲氙灯的使用条件,提高灯及器件的寿命。 3.改善了耦合效率,由一般的50%提高到80%以上,使经光纤输出的平均功率达到1W以上。     

掺染料聚合物光纤放大器的瞬态增益性能分析

文章使用速率方程的方法,给出了一个能够描述掺有机染料聚合物光纤放大器增益性 能的模型,考虑了染料三重态能级对速率方程的影响,得到了放大器的瞬态增益特性。结果表明在7kW泵浦功率下,信号可以获得27dB的增益。     

Bringing the fiber to the home

The issues involved in replacing copper telephone lines by fiber all the way to the subscriber's home are examined. The advantages of deploying single-mode fiber in the trunk and local-loop feeder networks are enumerated. The biggest problem namely, how to power the electronics in the absence of copper wire, is discussed. The need to allow a graceful upgrade to capture future opportunities for broadband revenue is emphasized, and potential broadband services are described. Predictions are made regarding the ISDN network of the future     

Multiregime character of the nonlinear precession of the second-order magnetization under the conditions for the orientational transition

The forced nonlinear precession of the magnetization vector in the normally magnetized magnetic plate is considered under the conditions for the orientational transition. The time dependences and precession patterns of the oscillations of magnetization are presented. Five regimes of precession are revealed: small-amplitude circular precession, precession of the equilibrium position without encircling of center, undamped precession of equilibrium position with encircling of center, damped precession of equilibrium position with encircling of center, and full-scale circular precession. The transitions between the regimes are studied using the 3D model of potential. The domains of the regimes of precession are determined on the plane decay parameter-ac field amplitude. It is demonstrated that a variation in the amplitude of the ac field leads to the stepwise dynamic orientational transition from the fourth regime to the fifth regime. The recommendations for the practical applications are worked out using the results.     

Approximations for the probability in the tails of the binomial distribution (Corresp.)

Upper and lower bounds for the probability in the tails of a binomial distribution are investigated. New bounds are obtained which are computationally simple and, in the case of the lower bound, significantly better than previously known bounds.     

受控源“电阻性”和“有源性”的研究

首先对受控源的电阻性和有源性进行了分析,然后比较完整系统地讨论了受控源的双重特性在线性时不变含受控源网络中的作用,并通过实例说明了受控源的双重特性在电路等效变换以及叠加定理中的具体的应用。     

On the Numerical Inversion of the Schwarz-Christoffel Conformal Transformation

Considering the numerical optimization approach for the inversion of the Schwarz-Christoffel conformal transformation formula, some improvements in integration procedures and some topics in optimization methods are discussed. Predictor-corrector techniques are introduced in order to map internal lines after the polygonal boundary is transformed these are applied to the dielectric interface in inhomogeneous line cross sections, allowing conformal transformation of quasi-TEM structures by purely numerical methods. Some examples of computations are presented, and some results are compared to known analytical calculations.     

片式元件与钢球自动分离机的设计

为了解决片式元件滚镀电极后将元件与电镀辅助钢球分离的问题,分析了各种分离原理与方法中存在的问题,确定了斜面振动分离技术,并开展了相应分离机的设计理论的探讨,给出了振动分选机构、上料机构和角度调整机构设计思想以及系统的电器控制方法与选型技术等,获得了一台能够满足元件生产需要的分选机.     

On the theory of the electrocardiogram

The biophysical basis for understanding the electrocardiogram is set forth. Bioelectric sources arise from electrical activity in the heart at the cellular level. The relation of these sources, which can be formally represented as impressed currents, to potentials involves solution of the volume conductor problem. This solution is based on Green's theorem. Sources are related to the transmembrane action potential through a bidomain model of heart muscle. Microscopic and macroscopic aspects of the bidomain model are developed. Various transformations of the source are considered, including multipoles, multiple dipoles, and replacement of the volume distribution with distributions on the heart surface. Time integrals of the waveform are related to excitation time and action potential duration. The theoretical results form the basis of a computer model of the electrocardiogram that relates skin potentials to the spatial and temporal distribution of action potentials in the heart     

高频地波雷达中电离层杂波的自适应抑制

首先分析了高频地波雷达中电离层杂波的类型，并给出了电离层杂波的仿真结果。在此基础上，给出了利用相参旁瓣对消滤波器对电离层杂波进行自适应抑制的方法。利用辅助天线输出中的干扰成分，自适应的调整其加权系数，最大程度的估计出主天线输出中的干扰。然后在主天线的输出中减去这个估计出的干扰。最后，对现有的相参旁瓣对消滤波器进行改进，并且给出了改进的相参旁瓣对消滤波器的抑制结果。     

Large-Scale Waves in the Thermosphere Observed by the AE-C Satellite

Atmosphere Explorer C (AE-C) data are analyzed to study wavelike perturbations in the thermosphere at an altitude of about 260 km. The data were measured during one orbit on January 20, 1975. The examples shown are typical of many other orbits of both satellites AE-C and AE-E. Four geophysical parameters are analyzed: nitrogen and oxygen densities, electron density, and ion temperature, as measured by three different instruments. The data are processed by normalizing them to their average values and extracting their trends. Their fluctuations are obtained by passing the normalized detrended data through a high-pass filter. Strong periodicities are apparent that persist throughout the records, regardless of filter cutoff frequency. Fluctuations are compared by computing cross correlation functions. Spectra are obtained using the MEM and FFT procedures. It is demonstrated, for the first time, that relationships between ion variations and neutral variations are coherent over a wide range of scale sizes over global distances. It is also inferred from plane wave modeling studies and from the persistent periodicities over global distances that a quasi-stationary wave structure is present in the thermosphere that may slowly dissipate and be regenerated by auroral region sources. Large-scale structures are found in all four parameters with horizontal scale sizes ranging from about 400 to about 4000 km. The spectra for all parameters contain peaks at wavelength that are confirmed by the periods of the fluctuations, and decrease with decreasing wavelength with a power law type of variation.     

推动政府上网工程 促进信息化发展

介绍了政府上网的目标,进展情况,阐述了政府上 网重在应用并提出了应注重的问题。