聚四氟乙烯和氟化乙丙烯共聚物复合膜的压电性

以多孔PTFE膜为骨架,而以致密（非多孔）FEP膜为储电介质层的孔洞结构复合压电驻极体膜的制备方法.利用正压电效应,测量了复合膜的准静态压电系数d₃₃;研究了压电系数的热稳定性和复合膜中空间电荷的动态特性;并通过介电谐振谱的分析,比较了这类复合膜的准静态和动态压电系数.结果表明：FEP和PTFE复合膜压电驻极体的准静态压电系数d₃₃可以达到300 pC/N.经90℃老化20 h 后的d₃₃仍保持在初 关键词： 压电驻极体 压电性 多孔聚四氟乙烯 致密氟化乙丙烯共聚物     

氟聚合物压电驻极体的压电性及其电荷的动态行为

描述了一种可控微结构的多孔聚合物压电功能膜的制备方法,讨论了采用该工艺制备的聚四氟乙烯(PTFE)和全氟乙丙烯共聚物(FEP)复合膜压电驻极体的压电性能及其热稳定性.通过等温压电系数衰减和短路热刺激放电(TSD)方法,研究了氟聚合物复合膜压电活性热稳定性改善的根源,以及脱阱电荷输运和复合的特性.结果表明,这类氟聚合物压电驻极体膜的准静态压电系数d₃₃可高达2200pC/N;压电系数d₃₃的压强特性在直到20kPa的压强范围内呈现良好的 关键词： 氟聚合物 压电驻极体 热稳定性 电荷动态特性     

人工调控微结构压电驻极体的热稳定性和电荷动态特性

利用表面带有周期性结构的硬质模板,通过冷压工艺将周期结构图案复制到多孔聚四氟乙烯(PTFE)薄膜表面,再经过热黏合工艺与致密氟化乙丙烯共聚物(FEP)薄膜复合,制备出了高度有序的微孔结构复合膜,并用电晕充电的方法对复合膜进行极化处理,最终获得氟聚合物复合膜压电驻极体.借助对这类复合膜压电驻极体介电谐振谱的测量,得到了材料的杨氏模量.并利用等温热老化工艺对它们的压电系数d33的热稳定性进行了考察.最后通过短路热刺激放电谱的测量和分析,讨论了该复合膜在热老化处理后的电荷动态 关键词： 有序结构 压电驻极体 压电性 电荷动态特性     

聚四氟乙烯多孔膜的压电活性及其稳定性

研究了经单向机械拉伸形成的非极性空间电荷型薄膜驻极体聚四氟乙烯(PTFE)多孔膜的压电性.讨论了由PTFE多孔膜和非多孔的聚合物薄膜（PTFE，聚酰亚胺PI，氟化乙丙烯共聚物FEP 和聚三氟氯乙烯PCTFE）组成的双层膜的突出压电活性.初步研究结果指出：在优化的极化条 件下形成的上述双层压电膜以外电极测量的准静态压电d₃₃常数可达186 pC/N， 这个数值与压电陶瓷锆钛酸铅PZT的相应常数接近，而比铁电聚合物聚偏氟乙烯(PVDF)的相 应常数约高出一个数量级.还研究了这类柔性多孔膜 关键词： 聚四氟乙烯多孔膜 压电性 空间电荷驻极体 充电参数 压电活性的热稳定性     

聚四氟乙烯多孔薄膜驻极体的电荷储存稳定性

利用在室温和高温下的栅控恒压电晕充电,常温电晕充电后经不同温度老化处理后的表面电位衰减测量,及开路热刺激放电(ThermallyStimulatedDischarge,TSD)研究了正负充电后PTFE(Polytetrafluoroethylene)多孔薄膜驻极体的电荷储存稳定性.PTFE多孔膜,PTFE非多孔膜(TeflonPTFE)和FEP(TetrafluoroethylenehexafluoropropyleneCopolymer)非多孔膜(TeflonFEP)间的电荷储存稳定性的比较研究也已进行.通过等温退极化程序,对上述三种薄膜驻极体的电荷储存寿命(有效时间常数)τ进行了定量估算.结果指出:在有机驻极体材料中,对正负充电后两种极性驻极体样品的PTFE多孔薄膜驻极体均呈现最优异的电荷储存稳定性,尤其是在高温条件下.通过扫描电镜(SEM)对这种新结构的氟聚合物驻极体材料的突出电荷储存能力和结构根源也已初步讨论. 关键词： 聚四氟乙烯 多孔膜 驻极体 电荷稳定性     

稳定的驻极体的制备

本文以实验资料和新近理论为依据,论述了稳定的驻极体的制备。在常温下工作的驻极体最好用聚四氟乙烯(PTFE)或聚全氟乙丙烯(FEP)制作;而长期在高温环境中(80—90℃)工作的驻极体,最好用聚二氯对苯撑二甲基(PDCPX)制作。稳定的驻极体的制备,不管用什么方法,极化后的热处理对其稳定性是必要的。     

多孔聚四氟乙烯/氟代乙烯丙烯共聚物复合驻极体材料的压电效应研究

采用高温熔融和电晕充电方法制备了由聚四氟乙烯/氟代乙烯丙烯共聚物复合而成的空间电荷驻极体压电膜.借助准静态压电系数测量，研究了制备工艺对复合膜压电活性的影响.根据Kacprzyk等提出的复合驻极体膜的压电模型，结合等温表面电位衰减和压电系数衰减测量结果，讨论了驻极体复合膜系统中的压电性产生机制.结果表明，压电效应的大小不仅取决于俘获在材料中的电荷密度的大小，还与被俘获电荷在材料中的存在形式和分布有关. 关键词： 空间电荷驻极体 压电效应 聚合物复合膜     

电晕充电多孔PTFE/PP复合驻极体过滤材料的电荷存储特性

报道采用电晕充电方法，对用高温熔融粘合工艺制备得到的双向拉伸多孔PTFE与PP复合过滤材料进行驻极体改性，并采用热刺激放电和表面电位测量等方法研究了材料的电荷存储稳定性,根据驻极体相关理论，对实验结果进行了解释. 结果表明，电晕充电的多孔PTFE/熔喷或纺粘PP覆膜材料中，既存在空间电荷又存在极化电荷，复合膜的界面是电荷陷阱的主要来源. 从不同面对复合膜材料进行充电时，材料具有完全不同的电荷存储特性. 由于材料体内空间电荷和极化电荷的极性相反、相互补偿，表面电位测定并不能真正反映材料内部电荷的存储状态. 关键词： 驻极体 电晕充电 聚合物复合膜 热刺激放电     

有序结构氟聚合物压电驻极体的制备和压电性研究

描述了一种有序微孔结构压电聚合物功能膜的制备方法,利用模板的高度有序实现薄膜微孔结构的精确控制.将此制备方法用于氟聚合物压电驻极体薄膜的制备,通过扫描电子显微镜(SEM)对其微观结构的观察表明薄膜具有理想的有序结构.对氟聚合物压电驻极体压电性的研究则是利用正压电效应测量准静态压电系数d₃₃,通过等温衰减和压强依赖性的测量考察其压电性能.结果表明:有序结构氟聚合物压电驻极体的准静态压电系数d₃₃可高达300 pC/N;与无序结构氟聚合物     

聚丙烯压电驻极体膜的压电和声学性能研究

以多孔聚丙烯(PP)膜为原材料, 通过压缩气体膨化工艺和电晕极化方法成功制备出PP压电驻极体膜, 并研究了该功能膜的压电和声学性能. 结果表明PP压电驻极体膜厚度方向和横向的杨氏模量分别为1.4和480 MPa, 因此压电系数d₃₃比d₃₁和d₃₂高2个量级以上, d₃₃是该类压电膜压电效应的主要性能指标, 而 d₃₁和d₃₂可以忽略不计. PP压电驻极体膜的准静态压电系数d₃₃在15-35 kPa的压强范围内具有良好的线性度. 在2-300 Hz的测试频率范围内, 300 Hz 下的d₃₃是2 Hz下的81%, 这主要是由PP膜的杨氏模量随频率增大而增强引起的. 在100 Hz-100 kHz 的音频和超声波频率范围内, PP压电驻极体膜具有平坦的频响曲线; 在1 kHz下其开路电压灵敏度和压电系数d₃₃分别为0.85 mV/Pa和164 pC/N. 关键词： 聚丙烯压电驻极体 压电效应 声学性能     

Guided-Wave Two-Dimensional Acousto-Optic Scanner Using Proton-Exchanged Lithium Niobate Waveguide

Two-dimensional scanning of a 0.6328 mum guided-light beam has been realized using noncolinear acousto-optic (AO) coplanar Bragg diffraction together with colinear AO guided-mode to substrate radiation-mode conversion in a Z-cut Xpropagation LiNbO3 proton-exchanged (PE) waveguide. The two surface acoustic (SAW) waves utilized are at the center frequencies of 500 and 200 MHz, propagating in the Y and X axes, respectively. Two-dimensional scanning of approximately 720 resolvable light beam spots, namely, 18 40 (horizontal vertical) scanning, has been demonstrated using a light beam of 1.0 mm aperture. The total number of resolvable beam spots can be greatly increased from 720 by simply utilizing SAW transducers of larger bandwidth and a light beam of greater aperture. It should also be possible to significantly increase the diffraction efficiency from 3 % by optimizing the parameters of the PE waveguide and the SAWs.     

Hybrid Wavelength and Code Division Multiple Access in Optical Networks

A review of schemes for multiple access in fiber optic networks shows that a hybrid of wavelength and code division multiple access (WCDMA) combines the best features of both. In particular, the hybrid scheme retains the large information carrying capacity of wavelength division multiple access (WDMA) and flexibility of code division multiple access (CDMA). In this paper WDMA, optical CDMA (OCDMA), and WCDMA networks are discussed. In OCDMA networks, concept of incoherent and coherent coding including inverse decoding and matched filter is introduced. The delay performance of both WDMA and WCDMA networks, under the simple suboptimum access protocols based on cyclic search, is computed. It has been shown quantitatively that tuning delay significantly affects the delay performance of both WDMA and WCDMA networks. Futhermore, delay performance of WCDMA networks is always better than the WDMA networks for the same tuning delay, load, and number of users.     

Femtosecond Transform-Limited Pulse Generation by Compensating for the Linear Chirp of SPM Spectra in Dispersion Shifted Fibers

A simple technique of pulse compression, based on the linear chirp compensation of self-phase modulation (SPM) spectra in dispersion shifted fibers, is demonstrated. The optimization procedure is carried out, for a short span of a single-mode fiber, using a parabolic law, which describes the behavior of the squared output pulse width versus the pump peak power in the case of Gaussian pulses. The experimental results give a minimum pulse duration of 233 fs, which is in good agreement with the model. Shorter and coherent pulses, down to 90 fs, have been obtained by inserting an interference filter at the optical output.     

Effect ofγ-radiation on the spectral luminescence characteristics of impure cadmium tungstate crystals

Results of a study of the effect of γ-radiation on the spectral luminescence properties of cadmium tungstate crystals doped with silver, bismuth, and molybdenum cations are presented. Spectral characteristics of the nondnnnoped crystals are briefly described. Absorption and photo and X-ray luminescence spectra of the crystals taken before and after exposure to γ-radiation (5.5·10⁴ Gy) are compared. It is found that the spectral characteristics of the crystals doped with silver, bismuth, and molybdenum cations do not change markedly after the exposure. The relation between the type of impurity-induced defects, individual characteristics of the impurity cations, and the character of the effect of γ-radiation on the spectral luminescence properties of impure crystals is analyzed (preliminarily). Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 1, pp. 55–60, January–February, 1997.     

Research on beamforming method for dual-line array with space mismatch between the two line arrays

The performance of port/starboard discrimination of dual-line array will be seriously degraded when the space between the two line arrays of the dual-line array is mismatched. The directivity function of the delay-sum and delay-subtract beamforming is deduced and the port/starboard discrimination of the delay-sum and delay-subtract beamforming is also studied both under the ideal status and the status under which the space between the two line arrays of the dual-line array is mismatched. Analysis results show the delay-subtract beamforming has better performance of port/starboard discrimination. At last, the sea trial results demonstrate the theoretical results.     

Sorting of bending magnets for the SSRF booster

The Shanghai Synchrotron Radiation Facility(SSRF)booster ring,a full energy injector for the storage ring,is deigned to accelerate the electron beam energy from 150MeV to 3.5GeV that demands high extraction efficiency at the extraction energy with low beam loss rate when electrons are ramping.Closed orbit distortion(COD)caused by bending magnet field uniformity errors which affects the machine performance harmfully could be effectively reduced by bending magnet location sorting.Considering the affections of random errors in measurement,both ideal sorting and realistic sorting are studied based on measured bending magnet field uniformity errors and one reasonable combination of bending magnets which can reduce the horizontal COD by a factor of 5is given as the final installation sequence of the booster bending magnets in this paper.     

Retrieval of ultraviolet skylight radiances and O3 slant column densities from balloon-borne limb spectrometer

With a novel light-weight and absolutely calibrated ultraviolet （UV） spectrometer, UV skylight radiances and O3 slant column densities are measured by balloon-borne limb measurements in Xinjiang area, China. UV skylight radiances measured at the height of 31 km are compared with the results from Modtran in the wavelength range from 290 to 420 nm. O3 slant column densities are derived from radiance spectra in the Huggins bands （320 - 335 nm） using differential optical absorption spectroscopy method. And the parameter exhibits a good correlation with the same value simulated by radiative transfer model （Tracy）. The O3 profile simultaneously measured by an O3 sonde is used as input in Tracy calculations. The O3 sonde is launched on the same balloon.     

Design optimization of highly sensitive LSPR enhanced surface plasmon resonance biosensors with nanoholes

For breaking through the sensitivity limitation of conventional surface plasmon resonance (SPR) biosensors, novel highly sensitive SPR biosensors with Au nanoparticles and nanogratings enhancement have been proposed recently.But in practice, these structures have obvious disadvantages.In this study, a nanohole based sensitivity enhancement SPR biosensor is proposed and the influence of different structural parameters on the performance is investigated by using rigorous coupled wave analysis (RCWA).Electromagnetic field distributions around the nanohole are also given out to directly explain the performance difference for various structural parameters.The results indicate that significant sensitivity increase is associated with localized surface plasmons (LSPs) excitation mediated by nanoholes.Except to outcome the weakness of other LSP based biosensors, larger resonance angle shift, reflectance amplitude, and sharper SPR curves' width are obtained simultaneously under optimized structural parameters.     

Polymer gratings based on photopolymerization for low-order distributed feedback polymer lasers

Novel polymer distributed feedback(DFB)gratings are fabricated based on photopolymerization to reduce lasing threshold of polymer lasers.A photopolymer formulation sensitive to 355-nm ultraviolet(UV)light is proposed for the fabrication of polymer gratings and it can be used to form polymer films by spin-coating process.A very low surface-relief depth ranging from 12.5 to about 1.0 nm has been demonstrated with a refractive-index modulation of about 0.012.The experimental results indicate that such polymer gratings have promising potentials for the fabrication of low-order DFB organic semiconductor lasers.