Lossless electroabsorption modulator monolithically rntegrated with a semiconductor optical amplifier and dual-wavegulde spot-size converters

Semiconductor optical amplifier and electroabsorption modulator monolithically integrated with dual-waveguide spot-size converters at the input and output ports is demonstrated by means of selective area growth, quantum-well intermixing, and asymmetric twin waveguide technologies. At the wavelength range of 1550 similar to 1600 nm, lossless operation with extinction ratios of 25-dB dc and 11.8-dB radio frequency and more than 10-GHz 3-dB modulation bandwidth is successfully achieved. The output beam divergence angles of the device in the horizontal and vertical directions are as small as 7.3 degrees x 10.6 degrees, respectively, resulting in 3.0-dB coupling loss with cleaved single-mode optical fiber.

Stabilized and tunable single-frequency erbium-doped fiber ring laser employing external injection locking

A stabilized and tunable single-longitudinal-mode erbium-doped fiber ring laser has been proposed and experimentally demonstrated. The laser is structured by combining the compound cavity with a fiber Fabry-Perot tunable filter. An injection-locking technique has been used to stabilize the wavelength and output power of the laser. One of the longitudinal modes is stimulated by the injected continuous wave so that this mode is able to win the competition to stabilize the system. A minimum output power of 0.6 dBm and a signal-to-noise ratio of over 43 dB within the tuning range of 1527-1562 nm can be achieved with the proposed technique. A wavelength variation of less than 0.01 nm, a power fluctuation of less than 0.02 dB, and a short-term linewidth of about 1.4 kHz have also been obtained.

RBAC与MAC在多级关系数据库中的综合模型

多级安全数据库的安全策略需要各种模型来表达,访问控制模型是其中之一.强制访问控制(MAC)模型保证多级数据库中的信息流动符合系统的安全策略.利用基于角色的访问控制(RBAC)来实现MAC能方便多级安全数据库的权限管理.提出了一种MAC与RBAC的综合模型,定义了多级角色与内部角色的概念,并给出了综合模型中经过修改后的操作,使得系统能自动地完成符合强制访问控制策略的用户权限的管理.该模型方便了管理员的权限管理,适合用户较多,安全层次比较复杂的多级关系数据库系统.最后给出了模型的部分实现机制.

基于本体的发布/订阅系统的数据模型和匹配算法

现有的发布／订阅系统不能根据事件的语义来进行事件与订阅的匹配，且不能支持具有复杂结构（如图状结构）的事件．将语义Web技术引入发布／订阅系统中，提出一种基于本体的发布／订阅系统．该系统采用本体来表示事件的概念模型，采用RDF图来表示事件，采用图模式来表示订阅条件．它能较好地解决现有的发布／订阅系统的上述问题．实验结果表明，该系统具有较高的订阅匹配效率．

Enhanced photocatalytic activity of TiO2 nano-structured thin film with a silver hierarchical configuration

TiO2 sol-gels with various Ag/TiO2 molar ratios from 0 to 0.9% were used to fabricate silver-modified nano-structured TiO2 thin films using a layer-by-layer dip-coating (LLDC) technique. This technique allows obtaining TiO2 nano-structured thin films with a silver hierarchical configuration. The coating of pure TiO2 sol-gel and Ag-modified sol-gel was marked as T and A, respectively. According to the coating order and the nature of the TiO2 sol-gel, four types of the TiO2 thin films were constructed, and marked as AT (bottom layer was Ag modified, surface layer was pure TiO,), TA (bottom layer was pure TiO,, surface layer was Ag modified), TT (pure TiO, thin film) and AA (TiO, thin film was uniformly Ag modified). These thin films were characterized by means of linear sweep voltammetry (LSV), X-ray diffraction (XRD), scanning electron microscopy (SEM), electrochemical impedance spectroscopy and transient photocurrent (I-ph). LSV confirmed the existence of Ago state in the TiO, thin film. SEM and XRD experiments indicated that the sizes of the TiO,, nanoparticles of the resulting films were in the order of TT > AT > TA > AA, suggesting the gradient Ag distribution in the films. The SEM and XRD results also confirmed that Ag had an inhibition effect on the size growth of anatase nanoparticles. Photocatalytic activities of the resulting thin films were also evaluated in the photocatalytic degradation process of methyl orange. The preliminary results demonstrated the sequence of the photocatalytic activity of the resulting films was AT > TA > AA > TT. This suggested that the silver hierarchical configuration can be used to improve the photocatalytic activity of TiO2 thin film.

A double wavelength DFB laser with an identical active area for CWDM

A novel distribute feedback (DFB) laser which gave two different wavelengths under two distinct work conditions was fabricated. The laser consists of two Bragg gratings with different periods corresponding to wavelength spacing of 20 nm in an identical active area. When driving current was injected into one of the different sections separately, two different wavelengths at 1542.4 and 1562.5 nm were realized. The side mode suppression ratio (SMSR) of 45 dB or more both for the two Bragg wavelengths were achieved. The fabricating process of the laser was just the same as that of traditional DFB laser diode. This device can be potentially used in coarse wavelength division multiplexer (CWDM) as a promising light source and the technology idea can be used to enlarge the transmission capacity in metro area network (MAN).

黄土高原陇东盆地朝那红黏土8.1～2.6 Ma的孢粉记录

IEECAS SKLLQG

Prolate and oblate shape coexistence in Pt-188

A standard in-beam gamma-spectroscopy experiment for Pt-188 is performed via the Yb-176(O-18, 6n) reaction at beam energies of 88 and 95 MeV, and the level scheme for (188) Pt is established. Prolate and oblate shape coexistence has been demonstrated to occur in Pt-188 by applying the projected shell model. The rotation alignment of i(13/2) neutrons drives the yrast sequence changing suddenly from prolate to oblate shape at angular momentum 10th, indicating likely a new type of shape phase transition along the yrast line in Pt-188.