电激励连续波HF/DF激光器放电参数的优化

放电管作为电激励连续波HF/DF激光器的F原子发生器,在整个激光器系统中占有重要地位。目前流行采用的是高压直流电源加镇流电阻的放电模式,典型电参数为接近10kV高电压、百毫安量级的低电流。传统理论和实验结果均认为:放电管F原子产率与放电管注入功率成正比,从而激光器输出功率也应与之成正比。引入不同阻值的镇流电阻,发现对于相同的注入功率,低电压、大电流模式比高电压、小电流模式更容易获得高的功率输出。     

中继系统中基于折中因子的功率分配方案

中继网络中,在总功率有限的条件下,如何对各个节点之间的功率进行合理分配,从而提高系统的总体性能,是一个关键问题.文章在DF中继网络中,提出了衡量系统性能的折中因子,并以最大化折中因子为优化目的,在系统总功率受限制的条件下,建立了优化模型.通过对优化模型的求解,得到了优化功率分配方案.仿真结果证明了此方法的有效性.     

Bounded sets structure of CpX and quasi‐(DF)‐spaces

For wide classes of locally convex spaces, in particular, for the space $C_p(X)$ of continuous real‐valued functions on a Tychonoff space X equipped with the pointwise topology, we characterize the existence of a fundamental bounded resolution (i.e., an increasing family of bounded sets indexed by the irrationals which swallows the bounded sets). These facts together with some results from Grothendieck's theory of $(DF)$‐spaces have led us to introduce quasi‐ $(DF)$‐spaces, a class of locally convex spaces containing $(DF)$‐spaces that preserves subspaces, countable direct sums and countable products. Regular $(LM)$‐spaces as well as their strong duals are quasi‐ $(DF)$‐spaces. Hence the space of distributions $D^{\prime }(\mathrm{\Omega })$ provides a concrete example of a quasi‐ $(DF)$‐space not being a $(DF)$‐space. We show that $C_p(X)$ has a fundamental bounded resolution if and only if $C_p(X)$ is a quasi‐ $(DF)$‐space if and only if the strong dual of $C_p(X)$ is a quasi‐ $(DF)$‐space if and only if X is countable. If X is metrizable, then $C_k(X)$ is a quasi‐ $(DF)$‐space if and only if X is a σ‐compact Polish space.     

非链式HF/DF激光器的研究进展

HF/DF激光器是中红外波段能提供最高能量输出的激光光源,也是中红外波段应用非常广泛的相干光源。本文介绍了近几年国内外关于非链式HF/DF激光器的研究进展及其成果应用,分析了非链式HF/DF激光器在应用方面的优缺点,总结了实现非链式HF/DF激光输出的关键技术和存在的问题,指出了该技术的未来发展方向。     

＂Amano＂ lipase DF-catalyzed efficient synthesis of 2,2＇-arylmethylene dicyclohexane-1,3-dione derivatives in anhydrous media

A simple and efficient method was developed for the synthesis of 2.2＇-arylmethylene dicyclohexane-1,3- dione derivatives via the Knoevenagel-Michael cascade reactions of aromatic aldehydes and 1,3-cyclic diketones catalyzed by ＂Amano＂ lipase DF, which expands the application field of enzyme catalytic promiscuity. This protocol provides several advantages over the traditional chemical synthesis, such as simple work-up procedure, high yields Cup to 94%） and environmental friendliness.     

High Resolution Crossed Beams Scattering Study of the F＋HD→DF＋H Reaction

Crossed beams scattering study was carried out on the F＋HD→DF＋H reaction using high- resolution H-atom Rydberg tagging time-of-flight technique. Vibrational state-resolved differential cross sections were measured, with partial rotational state resolution, at eight collision energies in the range of 2.51-5.60 kJ/mol. Experimental results indicated that the product angular distributions are predominantly backward scattered. As the collision energy increases, the backward scattered peak becomes broader gradually. Dependence of product vibration branching ratios on the collision energy was also determined. The experimental results show that the DF products are highly inverted in the vibrational state distribution and the DF （v＇=3） product is the most populated state. Furthermore, the DF （v＇=l） product has also been observed at collision energy above 3.97 kJ/mol.     

解码前传半双工中继信道下协作LDPC码设计

为逼近解码前传半双工中继信道容量,该文提出一种协作LDPC编码结构及度分布优化方法。与双层删除LDPC码不同,该结构将中继校验比特视为协作LDPC码的一部分,目的端利用从信源和中继接收的消息进行联合译码获得信源信息。为了分析协作LDPC码性能,拓展传统外信息转移(EXIT)图,推导了基于消息错误概率的双层EXIT图噪声门限分析方法。在此基础上,提出了协作LDPC码度分布优化方法,采用差分进化算法搜索了一组具有最大噪声门限的协作LDPC码。实验仿真证明,与双层删除LDPC码相比,协作LDPC码的性能得到了不同程度的改善。     

Performance analysis of cooperative spatial multiplexing networks with AF/DF relaying and linear receiver over Rayleigh fading channels

Cooperative spatial multiplexing (CSM) system has played an important role in wireless networks by offering a substantial improvement in multiplexing gain compared with its cooperative diversity counterpart. However, there is a limited number of research works that consider the performance of CSM systems. As such, in this paper, we have derived exact performance of CSM with amplify‐and‐forward and decode‐and‐forward relays in terms of outage capacity and ergodic capacity. We have shown that CSM systems yield a unity diversity order regardless of the number of antennas at the destination and the number of relays in the networks, which is the direct result of diversity and multiplexing gain trade‐off. Our analytical expressions are corroborated by Monte‐Carlo simulations. Copyright © 2013 John Wiley & Sons, Ltd.     

DF协作中继网络基于买者/卖者博弈的中继选择和功率分配策略

该文针对采用解码-转发(DF)协议的协作中继网络,提出了一种基于买者-卖者博弈的中继选择和功率分配策略,通过将用户建模为买者,可以以最大效用为标准选择最优中继和确定最佳的购买功率;将中继建模为卖者,可通过先市场后利润的功率价格调整策略获得最大的利润。分析了两者博弈达到平衡的条件并进行了仿真,结果验证了纳什均衡点的存在并表明,该策略计算量少,收敛速度快,实用性强,在兼顾用户和中继节点的利益的同时可以有效提高用户的传输速率,扩大基站的覆盖范围,提高功率利用效率。     

激光器窗口的旋转效应

通过数值计算比较研究了静止、同心旋转、偏心旋转三种模式下高能激光器窗口工作过程中温度场和应力场的特征及其演变规律。研究表明，旋转式激光器窗口不但可使温度场和应力场轴对称化，且可降低最高温升、最大拉应力和最大剪应力；一定偏心距的偏心旋转可以起到消去拉应力、减小剪切应力的作用，从而使激光器窗口的抗激光损伤的能力有较大幅度的提高。