利用KTP晶体实现1.08μmNd：YAP激光器锁模

本文描述了利用ＫＴＰ晶体和腔的基波输出镜构成非线性镜实现１．０８μｍＮｄ：ＹＡＰ激光器的被动锁模。实验表明，这种新的锁模技术比用染料作可饱和吸收体的被动锁模技术有很多突出的优点，具有很大的发展潜力。实验测得锁模时基波１．０８μｍ输出２．４ｍＪ，二次谐波０．５４μｍ输出０．５ｍＪ（同样条件下的静态输出为２．５ｍＪ），基波脉冲的平均脉宽为４０ｐｓ。     

LD泵浦Nd：BGO晶体的自调Q激光器

首次实现了ＬＫ泵浦Ｎｄ∶ＢＧＯ固体激光器的１．０６４μｍ的激光输出，泵浦阈值功率为２５ｍＷ，在连续运转状态下得到最大为４０ｍＷ的ＴＥＭ００模输出，光－光效率为１３．３％，根据法拉第磁光效庆理论，了ＬＤ泵浦Ｎｄ∶ＢＧＯ自调Ｑ激光器的各种参数，并研制成该激光器，在该器件中，作为损耗调制元件的磁光调制器就是绕有线圈的Ｎｄ∶ＢＧＯ晶体本身，实验在重复率为１ＫＨｚ的条件下得到了ＦＷＨＭ为１００ｎｓ的稳定脉冲     

基于增广Lagrange函数的RQP方法

Recursive quadratic programming is a family of techniques developd by Bartholomew-Biggs and other authors for solving nonlinear programming problems.This paperdescribes a new method for constrained optimization which obtains its search di-rections from a quadratic programming subproblem based on the well-known aug-mented Lagrangian function.It avoids the penalty parameter to tend to infinity.We employ the Fletcher‘s exact penalty function as a merit function and the use of an approximate directional derivative of the function that avoids the need toevaluate the second order derivatives of the problem functions.We prove that thealgorithm possesses global and superlinear convergence properties.At the sametime, numerical results are reported.     

GM(1,1)的周期修正模型及其在泉水流量预测中的应用

本文阐述了 GM( 1 ,1 )的残差周期修正模型 ,并将它应用于山西神头泉的流量预测中 ,建立了神头泉流量的 GM( 1 ,1 )周期修正模型 ,对其流量进行了预测 ,为神头泉域岩溶水资源开发利用和保护提供了科学依据     

A globally convergent algorithm for the Euclidean multiplicity location problem

The Euclidean single facility location problem (ESFL) and the Euclidean multiplicity location problem (EMFL) are two special nonsmooth convex programming problems which have attracted a large literature. For the ESFL problem, there are algorithms which converge both globally and quadratically. For the EMFL problem, there are some quadratically convergent algorithms, but for global convergence, they all need nontrivial assumptions on the problem.In this paper, we present an algorithm for EMFL. With no assumption on the problem, it is proved that from any initial point, this algorithm generates a sequence of points which converges to the closed convex set of optimal solutions of EMFL.This research is supported in part by the Air Force Office of Scientific Research Grant AFOSR-87-0127, the National Science Foundation Grant DCR-8420935 and University of Minnesota Graduate School Doctoral Dissertation Fellowship awarded to G.L. Xue.     

线型聚能装药的理论研究

本文提出了一端起爆的线型聚能装药射流形成的不定常理论模型。根据这一模型,当金属罩在爆轰波作用下的运动速度为已知时,则不论此速度是否是时间或初始位置的函数,都能得到射流形成时的速度,质量和位置等参数。 按照本文模型,Defourneaux.M.的定常射流形成定常模型是一个简单的特例。我们利用本文的模型对等厚度装药的情况进行了计算,并与实验结果比较,两者符合良好。同时计算结果表明,考虑射流形成的不定常因素,可以较好地解释射流头部的质量堆积和射流内部的反向速度梯度等实验现象。本文的模型可以为线型聚能切割索的设计提供较为准确的理论指导。     

核壳结构硒化镉/硫化镉/巯基乙酸量子点载流子输运特性

采用水溶液法合成了巯基乙酸(TGA) 包覆的CdSe 量子点. 通过X 射线粉末衍射和高分辨透射显微镜检测结果证实, 合成得到闪锌矿结构CdSe 量子点. 能谱图和傅里叶变换红外光谱图结果说明, 在核CdSe 纳米粒子表面与配体TGA 之间有CdS 壳层结构形成. 利用样品表面光电压(SPV) 谱, 指认CdSe 量子点精细能带结构以及各自对应的激发态特征: 475 nm (2.61 eV) 和400 nm (3.1 eV) 两个波长处的SPV 响应峰分别与CdSe 核和CdS 壳层带-带隙跃迁相对应; 370 nm (3.35 eV) 附近SPV 响应峰可能与TGA 中羰基与巯基或羧基之间发生的n →π^* 跃迁有关. 场诱导表面光电压谱结果证实, 合成的CdSe 量子点具有明显的N 型表面光伏特性, 而上述n→π^* 跃迁则具有P 型表面光伏特性. 荧光光谱谱线均匀增宽以及SPV 响应峰位蓝移, 说明样品具有明显的量子尺寸效应. 结合不同pH 值下合成的CdSe 量子点的SPV 谱和表面光声谱发现, SPV 响应强度与表面光声光谱信号强度变化趋势恰好相反. 上述样品表面光伏效应表明, CdSe 量子点表面和相界面处的精细电子结构以及光生载流子的输运特性均与量子点的尺寸大小存在某种内在联系. 关键词： 硒化镉量子点 光生载流子 表面光电压谱 表面光声光谱     

Temperature dependent exchange bias effect in polycrystalline BiFeO3/FM (FM = NiFe, Co) bilayers

Extensive studies on the temperature (T) dependent exchange bias effect were carried out in polycrystalline BiFeO₃(BFO)/NiFe and BFO/Co bilayers. In contrast to single-crystalline BFO/ferromagnet (FM) bilayers, sharp increase of the exchange bias field (H _E ) below 50 K were clearly observed in both of these two bilayers. However, when T is higher than 50 K, H _E increases with T and decreases further when T is larger than 230 K (for BFO/NiFe) or 200 K (for BFO/Co), which is similar to those reported in single-crystalline BFO/FM bilayers. After the exploration of magnetic field cooling, the temperature dependent exchange bias can be explained considering two contributions from both the interfacial spin-glass-like frustrated spins and the polycrystalline grains in the BFO layer. Moreover, obvious exchange bias training effect can be observed at both 5 K and room temperature and the corresponding results can be well fitted based on a recently proposed theoretical model taking into account the energy dissipation of the AFM layer.     

脉冲激发三能级体系半导体量子点的单光子发射效率

研究了脉冲激发下单个半导体量子点中单光子发射的统计特性.在旋转波近似条件下，由系统粒子数演化主方程并结合量子回归理论推导了二阶相关函数的运动方程，利用此方程讨论了二阶相关函数随输入脉冲面积的关系.在窄脉冲宽度的脉冲激发下，单光子的发射概率p和效率η都随着强度的增强而产生振荡.研究表明，采用窄脉冲宽度，当输入脉冲面积在π附近时可以得到较高的单光子发射效率. 关键词： 半导体量子点 单光子发射 三能级系统     

基于圆环形薄壁截面梁的光纤光栅传感研究

提出将圆环形薄壁截面梁应用于光纤光栅传感，用一个光栅实现了对温度与应力的同时区分测量；对圆环形薄壁截面梁的应变进行了理论与实验分析，结果表明圆环形薄壁截面梁各点应变与该点角度的二倍呈余弦变化关系. 关键词： 光纤光栅传感 圆环形薄壁截面梁 啁啾