集成L2TP和IPSec技术构建安全的远程接入虚拟专用网

目前远程接入VPN主要基于L2TP协议实现,但是L2TP隧道传输协议本身没有为通信提供任何形式的安全保护,因此这种结构的VPN存在着安全隐患.为了解决这个问题,在研究远程接入VPN特点和功能基础上,利用IPSec协议为L2TP协议提供安全保护,提出了集成L2TP和IPSec构建安全的远程接入VPN方案.     

Subwavelength-diameter silica wires for low-loss optical wave guiding

Silica waveguides with diameters larger than the wavelength of transmitted light are widely used in optical communications, sensors and other applications. Minimizing the width of the waveguides is desirable for photonic device applications, but the fabrication of low-loss optical waveguides with subwavelength diameters remains challenging because of strict requirements on surface roughness and diameter uniformity. Here we report the fabrication of subwavelength-diameter silica 'wires' for use as low-loss optical waveguides within the visible to near-infrared spectral range. We use a two-step drawing process to fabricate long free-standing silica wires with diameters down to 50 nm that show surface smoothness at the atomic level together with uniformity of diameter. Light can be launched into these wires by optical evanescent coupling. The wires allow single-mode operation, and have an optical loss of less than 0.1 dB mm(-1). We believe that these wires provide promising building blocks for future microphotonic devices with subwavelength-width structures.     

Involvement of Ca<Superscript>2+</Superscript>/CaM in the signal transduction of acetylcholine regulating stomatal movement

It has been known that the neurotransmitter acetylcholine (ACh) also exists in plants and is able to regulate the movement of stomata.In another aspect,Ca^2 /CaM as the second messengers have a critical role of signal transduction in stomatal guard-cell,Here we showed that Ca^2 /CaM were also involved in the ACh regulated stomatal movement,In the medium containing Ca^2 ,the Ca^2 channel blockers (NIF and Ver)and CaM inhibitors (TFP and W7 ) could neutralize the ACh induced stomatal opening,however,they are ineffective in the medium containing K^ ,Those results indicated that Ca^2 /CaM were involved in the signal transduction pathway of ACh regulating stomatal movement.     

The effects of microfilament and microtubule inhibitors and periodic electrical impulses on phloem transport in pea seedling

In phloem transport, whether protoplasmic activity participates in assisting sap flow in sieve element-companion cell complcx hils long been in debate. The prcsent investigation assumcd microfilament (MF) and microtubule (MT), the two constituents of the protoplasmic cytoskeleton, as motive force, and employed germinating pea seedling suspended in moist chamber as experinental material: thc seed being the source; the elongating root, the sink.¹⁴C-labeled sucrose was added to the seed as indicator. The amount of sap transported from source to sink was measured by the increase in root elongation. The transport phloem was within the cylinder of the peclcd root in thc middle. The exposed cylinder was treated with MF inhibitor (cytochalasin B), or microtubule inhibitor (amiphosmethyl). Results showed that the sap influx into the elongating root. and the¹⁴C activity as well, was reduced by abut one half in treatrrrent with cytochaliisin B, and much less by amiphos-methyl treatment. Similar effect was shown in clcctrical impulse Ireatnimt, which scems to disrupt the MF and MT configuration.     

Point defects in active layers of TFEL devices based on ZnS

Point defects in the active layer of a layered optimization thin film electroluminescent device of ZnS; Er³⁺ were studied. The results indicate that besides Er³⁺ substituting for Zn²⁺ as luminescent centers, the dominant point defects are sulfur vacancies, zinc vacancies, shallow donors and deep acceptors. Their influence on electroluminescence is discussed.     

BaFX:Eu(X:Cl,Br)中电子陷阱的研究

X线影像板需要近红外光激励．掺入Ca2＋,S2＋,Mg2＋后,用650～700um光激励BaFX：Eu2＋,可以更为灵敏．用正电子湮没寿命谱,电子顺磁共振谱,加热发光谱和光激励发光谱,研究了X射线辐照后BaFx：Eu（X：CI,Br）电子陷阱的性质、状态、密度和转换．     

变参数土层的动力特性和地震反应分析

应用模态摄动原理和一维剪切波动方程，建立了变参数土层自振特性的简捷计算方法。，从而为计算各类变参数地震反应提供了一个有效的计算手段。这一方法不仅适用于分层均匀土层，也适用于土介质物理特性沿深度不均匀变化的土层。这种变化规律既可用解析函数表示，也可采用列表函数     

面向对象的全真动态I—D图的研究

采用面向对象的程序设计方法，在ＷＩＮＤＯＷＳ环境下成功地实现地全真动态Ｉ－Ｄ图的显示与应用，完全取代传统的Ｉ－Ｄ图作业方式，为暖通空调工程师和设计人员提供了极为方便的分析计算工具。     

有源滤波器直流侧电压闭环控制的稳定性研究

分析了三相系统中无功电流和谐波电流瞬时功率的性质。从有源电力滤波器交直流侧瞬时功率平衡方程的角度出发，推导了关于小信号扰动的近似等效的数学模型，获得了在此例控制和比例积分控制下的稳定性判据。最后用计算机仿真验证了理论分析的正确性。     

（诱导）磁场对大蒜生长影响的试验研究

研究磁肥（磁性微粒）产生的诱导磁场对大蒜母体营养物质转移过程的影响表明：磁场可加速蒜籽萌发和蒜籽生长，磁肥产生的磁场强度和类型不同其增产效果也有明显的差异。