Gevrey properties of real planar singularly perturbed systems

By applying geometric techniques to real analytic singularly perturbed vector fields on the plane, we develop a way to give a bound on the Gevrey type of the Taylor development of canard manifolds at degenerate planar turning points. By blowing up the phase space at the turning point, we find asymptotic estimates even when such expansions w.r.t. traditional phase space variables do not exist. The asymptotic estimates are then used to give a sufficient and necessary condition on the existence of (local) canard solutions.     

Developing a hybrid emulsion polymerization system to synthesize Fe3O4/polystyrene latexes with narrow size distribution and high magnetite content

A hybrid emulsion polymerization was formulated for synthesizing Fe₃O₄/polystyrene composite latex. This system, containing binary droplets that are magnetic (Mag)‐droplets with a diameter of 100–200 nm and styrene (St)‐droplets with a diameter of 3–4 μm, was obtained by mixing Mag‐miniemulsion and St‐macroemulsion. With extremely low surfactants concentration (?critical micelle concentration, CMC), the nucleated loci are selectively controlled in the Mag‐droplets, as the result of smaller droplet size and larger surface ratio. Both water‐soluble potassium persulfate (KPS) and oil‐soluble 2,2′‐azobis(2‐isobutyronitrile) was adopted to initiate the polymerization. In the presence of KPS, magnetic polystyrene latices with particles size of 60–200 nm, narrow size distribution, and high magnetite content (86 wt % measured by TGA) were attained successfully. The synthesized magnetic Fe₃O_4/polystyrene latices assembled into well‐ordered hexagonal structure in the surface of a carbon supported copper grid. The influence of various parameters on various aspects of the as‐synthesized Fe₃O₄/polystyrene was investigated in detail: type of initiator on composite morphology, feed ratio of Mag‐miniemulsion and St‐macroemulsion on magnetite content, and hydrophobic agent or amount of surfactant on size and size distribution. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5285–5295, 2007     

非理想信道下Colpitts混沌电路的自适应同步研究

本文研究了Colpitts混沌电路在非理想信道条件下的自适应同步问题。引入自适应控制器对输入到响应部分（response system）的衰变混沌信号进行预处理，来补偿衰落信道对于同步性能的影响。给出了系统的数学模型，对恒定信道衰变和时变信道衰变两种非理想信道条件下的混沌ColpiRs电路的自适应同步进行了数值仿真研究。仿真结果表明，对于恒定或慢变化的时变信道衰变，自适应控制器可以有效的提高Colpitts电路响应部分和驱动部分（Drive system）的同步性能。     

单稳态触发器的结构及其开关级设计原理

根据单稳态触发器定时单元特性,提出了单稳态触发器的一般结构.在此基础上,运用传输电压开关理论进行了CMOS单稳态触发器的开关级设计研究,并具体设计了两个单稳态触发器.设计实例表明文中提出的方法不仅简单、有效,而且具有通用性.     

CMOS电路中抗Latch-up的保护环结构研究

闩锁是CMOS集成电路中的一种寄生效应,这种PNPN结构一旦被触发,从电源到地会产生大电流,导致整个芯片的失效。针对芯片在实际测试中发现的闩锁问题,介绍了闩锁的测试方法,并且利用软件Tsuprem4和Medici模拟整个失效过程,在对2类保护环(多子环/少子环)作用的分析,以及各种保护结构的模拟基础之上,通过对比触发电压和电流,得到一种最优的抗Latch up版图设计方法,通过进一步的流片、测试,解决了芯片中的闩锁失效问题,验证了这种结构的有效性。     

介质的非均匀性对高次谐波影响的研究

讨论了气体介质的非均匀性对飞秒激光高次谐波产生过程的可能影响.计算结果表明,采用喷阀技术所提供的气体介质的密度梯度和气体原子运动速度的影响很小,不会产生实验上可观测的效果.这一结果支持了喷气靶在高次谐波产生中的广泛应用 关键词： 高次谐波 气体介质 各向异性 飞秒激光     

高压电场作用下乙醇-水溶液体系变化红外光谱分析

本文报道了用红外光谱分析电磁场作用下乙醇 水溶液体系变化情况。分析结果表明 :当乙醇溶液受到 2 0kV·cm- 1 的交变电磁场处理 (5 0Hz)时 ,分子之间的氢键缔合先增大后减少 ;高乙醇含量溶液受到同样强度电场较长时间处理时 ,有乙醇发生氧化反应 ,从红外谱中可看到νCO 峰及ν(OH) (H2 O) 峰的出现 ;经处理后的溶液自然放置 7天再测定 ,其红外谱图基本保持不变。文中对各出现变化的峰进行了分析 ,并对其机理进行了推导     

The Properties of Light Pressure Force with High Order in Laser Fields

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高功率微波高斯馈源口面场分析

 用波导本征模展开方法对用于高功率微波发射系统的方角锥高斯馈源口面场进行分析，提出结合馈源远场辐射特性和避免高功率击穿折衷选定相应的高斯模注腰半径，进而确定多个波导模幅值，从而为运用模匹配或耦合波理论设计高斯馈源提供依据。     

THE DESIGNS OF HIGH EFFICIENCY LAUNCHER OF QUASI-OPTICAL MODE CONVERTER FOR HIGH POWER GYROTRONS

A high efficiency launcher of quasi-optical (QO) mode converters for high power gyrotrons have been designed and tested. A helical cut launcher radiates the RF power via its straight cut onto the first phase correcting mirror. The launchers have been optimized for the TE_31.8 mode at 170 GHz and TE_22.6 mode at 110 GHz by numerically optimizing a launcher surface. The helical cut of the launcher has been optimized by taking the taper angle into account. Further more, the amplitude of the surface perturbation have been optimized for improved focusing in order to reduce the diffraction losses at the helical cut. Low power measurement shows a good agreement with the design. High efficiency characteristics of the design have also been calculated on the assumption of frequency downshift due to the thermal expansion of the cavity and stepwise frequency tuning by changing the operating mode. Besides, the possibility of high efficiency launcher for higher mode is discussed, and these results give the prospect to high efficiency long pulse gyrotrons.