Broadband dielectric characterization of piezoelectric poly(vinylidene fluoride)thin films between 278 K and 308 K

This work describes the dielectric properties of piezoelectric poly(vinylidene fluoride) (PVDF) thin films in the frequency and temperature ranges relevant for usual applications. We measured the isothermal dielectric relaxation spectra of commercial piezoelectric PVDF thin films between 10 Hz to 10 MHz, at several temperatures from 278 K to 308 K. Measurements were made for samples in mechanically free and clamped conditions, in the direction of the poling field (perpendicular to the film). We found that the imaginary part of the dielectric relaxation spectra of free and clamped PVDF samples is dominated by a peak, above 100 kHz, that can be characterized by a Havriliak-Negami function. The characteristic time follows an Arrhenius dependence on temperature. Moreover, the spectra of the free PVDF samples show two additional peaks at low frequencies which are associated with mechanical relaxation processes. Our results are important for the characterization of piezoelectric PVDF, particularly after the stretching and poling processes in thin films, and for the design and characterization of a broad range of ultrasonic transducers.     

盐诱导金纳米粒子自组装和沉降制备具有宽波段吸收特性的黑金

通过向金溶胶中加入无机盐诱导金纳米粒子自组装,并自然沉降金纳米粒子组装体得到黑金薄膜.研究结果表明,该黑金薄膜在400~1600 nm的宽带范围内表现出很强的吸收能力（>80%）,在400~800 nm的可见范围内能达到94%,表现出高光热转换能力和宽波段的高表面增强拉曼散射（SERS）活性.     

遗传算法在优化设计宽频微带天线中的应用

将遗传算法与FDTD法结合优化设计出了一种宽频微带天线.文中简要讨论了遗传算法的操作过程,并介绍了减少遗传算法与FDTD法结合优化微带天线计算量的方法.与初始矩形微带天线相比,优化后天线的阻抗带宽增加了三倍多.     

How to successfully promote ICT usage: A comparative analysis of Denmark and Japan

The paper presents a comparative analysis of two advanced ICT nations, Japan and Denmark. While Japan is very advanced with respect to its telecommunications infrastructure, Denmark has come further than Japan regarding the use of ICT infrastructures. This paper compares Denmark, a leader in ICT usage, and Japan, which lags in that regard, analyzes differences in institutions, technologies, and services offered, and examines factors contributing to the success of Denmark in promoting ICT usage from a Japanese perspective. Strong governmental leadership, and common techno-infrastructure such as personal ID and digital signature that serve different systems, and user-orientation of service design are the characteristics of Danish efforts absent in Japan.     

基于VBS实现BRAS在线用户数的自动提取

【】介绍了利用SecureCRT工具和VBScript脚本语言,开发实现了BRAS设备上在线用户数的自动生成,并通过批处理和任务计划程序设计完成了定时自动运行,有效提高了工作效率和数据准确性。     

Signal losses in pesticide analysis using the broadband isolation waveform in a commercial quadrupole ion trap to accomplish precursor ion isolation in tandem mass spectrometry

Signal losses due to precursor ion isolation in a quadrupole-ion-trap mass spectrometer were studied using selected pesticides as model compounds. These signal losses originate from isolations of ion populations employing the broadband isolation (bbiso) waveform used in the Varian quadrupole ion-trap precursor ion isolation protocol. Signal losses were found to be ‘precursor ion structure’ dependent upon isolation using the bbiso. The effect of the bbiso waveform on the ionic structure and nature of substituents on the precursor ion was investigated. Isolation of old electron radical molecular ions of the type [M^+?] showed remarkable signal losses compared with isolation of fragment ions derived from the same compounds. The impact of the bbiso waveform on the response of the instrument using mass spectrometry/mass spectrometry and the bbiso waveform was also examined. The response of the instrument as related to the calculated Instrument Detection Limits was observed to parallel ion population losses.     

Molecular Dynamics in 1- and 2-D Confinement as Studied for the Case of Poly(Cis-1,4-Isoprene)

Broadband Dielectric Spectroscopy (BDS) is used to probe the molecular dynamics of Type A polymer, poly(cis-1,4-isoprene), when confined in the 1-dimensional (1D) exploring space of thin layers and the 2-dimensional (2D) constraining geometry of unidirectional anodic aluminum oxide (AAO) nanopores. For both cases, it was observed that the structural relaxation remains bulk-like in its mean relaxation rate, although the distribution of its relaxation times is broadened in 2D confinement. Furthermore, the fluctuation of the end-to-end vector is interrupted, with the 1D case being relatively less pronounced. By this clear-cut comparison, it is demonstrated that the effects of confinement on molecular dynamics depend, inter alia, on the dimensionality of the restricting space.     

Fabrication of PbS nanocrystal-sensitized ultrafine TiO2 nanotubes for efficient and unusual broadband-light-driven hydrogen production

It is highly desired to maximize the use of solar light by developing broadband-light-responsive H₂ production system in the field of photocatalysis. Herein, a novel PbS/(Pt–TiO₂) nanocomposite with efficient and unusual broadband-light-driven H₂ production feature is constructed by using infrared-bandgap PbS nanocrystals as sensitizer of Pt-loaded ultrafine anatase TiO₂ nanotubes (Pt–TiO₂). After optimizing the component ratio, the resultant PbS/(Pt–TiO₂) nanocomposite delivers a H₂ production activity of 813 and 186 μmol h^?1 under ultraviolet (UV)-visible (Vis)-near-infrared (NIR) and Vis-NIR light irradiation, respectively. Moreover, an apparent quantum yield of 38.6%, 26.2%, 2.43%, 3.21%, 2.17%, 0.36%, 0.11% and 0.01% can be attained from the PbS/(Pt–TiO₂) nanocomposite illuminated at 350, 420, 550, 700, 760, 850, 950 and 1064 nm monochromatic light, respectively. The intimate interfacial contacts in the PbS nanocrystals decorated ultrafine TiO₂ nanotubes, which serve as the support and electron acceptor of PbS nanocrystals, can effectively promote the photoexcited hot electrons transferring from PbS nanocrystals to TiO₂ nanotubes before the thermalization losses, and thus causing the efficient Vis-NIR-light-responsive H₂ production activity of the PbS/(Pt–TiO₂) nanocomposite. These results provide an intriguing application of infrared-bandgap materials to exploit the low-energy photons of the solar light for constructing efficient and unusual broadband-responsive H₂ production system.     

新颖的双通道输出高功率掺铒光纤宽带光源

在分析L波段放大自发辐射(ASE)谱产生原理的基础上,设计出一种新颖的双级结构掺铒光纤ASE宽带光源,该光源可在两个端口分别输出高功率的C波段和L波段的ASE谱.设计将C波段ASE谱注入到掺铒光纤中作为L波段ASE谱的二次抽运源,使得L波段ASE谱功率得到了有效提高.优化光源结构参量后从两个端口分别获得了12.97 dBm和12.81 dBm的C波段和L波段ASE宽带谱.将两个输出端口组合得到了功率为15.9 dBm,泵浦转换效率达到21.6%的C+L波段超宽带ASE光源.     

具有高机械强度的掺Er3+∶TeO2-Nb2O5玻璃的光谱性质研究

熔制了掺铒碲铌玻璃样品(100-XTeO2-XNb2O5(X=5,10,15,20 mol%),测试了其密度、折射率、转变温度、析晶温度、维氏机械强度、吸收光谱、荧光光谱、荧光寿命等参量。利用Judd-Ofelt和McCumber理论分别计算了铒离子强度参量Ωt (t=2, 4, 6)和受激发射截面σemi的大小,研究了掺铒碲铌玻璃样品光谱参量对Nb2O5成分的依赖性,并与典型的碲锌钠玻璃（75TeO2-20ZnO-5Na2O）在热学、机械强度、光谱性质和放大品行四个方面进行了比较.