Polarization properties of elliptical core non-hexagonal symmetry polymer photonic crystal fibre

In this paper, polarization properties and propagation characteristics of polymer photonic crystal fibres with elliptical core and non-hexagonal symmetry structure are investigated by using the full vectorial plane wave method. The results how that the birefringence of the fibreis induced by asymmetries of both the cladding and the core. Moreover, by adjusting the non-symmetrical ratio factor of cladding eta from 0.4 to 1 in step 0.1, we find the optimized design parameters f the fibre with high birefringence and limited polarization mode dispersion, operating in a single mode regime at an appropriate wavelength range. The range of wavelength approaches the visible and near-infrared which is consistent with the communication windows of polymer optical fibres.

Generation of 207-femtosecond pulses from a ytterbium figure-of-eight fibre laser

We report the generation of 207-fs pulses with 1.2mW average power at 1036 nm directly from a passively mode-locked Yb-doped fibre laser with a nonlinear optical loop mirror for mode-locking and pairs of diffraction gratings for intracavity dispersion compensation. These results imply a 4-fold reduction in pulse duration over previously reported figure-of-eight cavity passively mode-locked Yb-doped fibre lasers. Stable pulse trains are produced at the fundamental repetition rate of the resonator, 24.0MHz. On the other hand, this laser offers a cleaner spectrum and greater stability and is completely self-starting.

Broadly tunable SOA-based active mode-locked fibre ring laser by forward injection optical pulse

We present a broadly tunable active mode- locked. bre ring laser based on a semiconductor optical ampli. er ( SOA), with forward injection optical pulses. The laser can generate pulse sequence with pulsewidth about 12 ps and high output power up to 8.56dBm at 2.5 GHz stably. Incorporated with a wavelength- tunable optical bandpass. lter, the pulse laser can operate with a broad wavelength tunable span up to 37nm with almost constant pulsewidth. A detailed experimental analysis is also carried out to investigate the relationship between the power of the internal cavity and the pulsewidth of the output pulse sequence. The experimental con. guration of the pulse laser is very simple and easy to setup with no polarization- sensitive components.

Casting preforms for microstructured polymer optical fibre fabrication

A monolithic structured polymer preform was formed by in-situ chemical polymerization of high-purity MMA monomer in a home-made mould. The conditions for fabrication of the preforms were optimized and the preform was drawn to microstructured polymer optical fibre. The optical properties of the resultant elliptical-core fibre were measured. This technique provides advantages over alternative preform fabrication methods such as drilling and capillary stacking, which are less suitable for mass production. (c) 2006 Optical Society of America.

Sol-gel matrix modified microstructured optical fibre towards a fluoride sensitive optical probe

In this article, we report an optical fluoride probe based on microstructured polymer optical fibers (MPOFs) which is modified with morin-Al complex doped silica gel film. This probe is fabricated by sol-gel fluxion coating process. Sol solution doped with morin-Al is directly inhaled into array holes of MPOF and then forms morin-Al-gel matrix film in them. The sensing probe shows different fluorescence intensity to different fluoride ion concentrations in the aqueous solution. The range of response is 550 mmol/L, under the condition of pH 4.6. Crown Copyright (C) 2009 Published by Elsevier B.V. All rights reserved.

A four-phase confocal elliptical cylinder model for predicting the effective thermal conductivity of coated fibre composites

A four-phase confocal elliptical cylinder model is proposed from which a generalised self-consistent method is developed for predicting the thermal conductivity of coated fibre reinforced composites. The method can account for the influence of the fibre section shape ratio on conductivity, and the physical reasonableness of the model is demonstrated by using the fibre distribution function. An exact solution is obtained for thermal conductivity by applying conformal mapping and Laurent series expansion techniques of the analytic function. The solution to the three-phase confocal elliptical model, which simulates composites with idealised fibre-matrix interfaces, is arrived at as the degenerated case. A comparison with other available micromechanics methods, Hashin and Shtrikman's bounds and experimental data shows that the present method provides convergent and reasonable results for a full range of variations in fibre section shapes and for a complete spectrum of the fibre volume fraction. Numerical results show the dependence of the effective conductivities of composites on the aspect ratio of coated fibres and demonstrate that a coating is effective in enhancing the thermal transport property of a composite. The present solutions are helpful to analysis and design of composites.

Post-steam-treatment of Mo/HZSM-5 catalysts: An alternative and effective approach for enhancing their catalytic performances of methane dehydroaromatization

Post-steam-treatment is a facile and effective method for improving the catalytic performances of Mo/HZSM-5 catalysts in methane dehydroaromatization under nonoxidative conditions. The treatment can enhance the stability of the catalyst and also give a higher methane conversion and a higher yield of light aromatics, as well as a decrease in the formation rate of carbonaceous deposits. (27)Al, (29)Si, and (1)H multinuclear magic angle spinning nuclear magnetic resonance, X-ray photoelectron spectroscopy, X-ray diffraction, X-ray fluorescence spectroscopy, and thermogravimetric analysis measurements as well as catalytic reaction evaluations were employed to conduct comparative studies on the properties of the catalysts before and after the post-steam-treatment. The results revealed that the number of free Bronsted acid sites per unit cell decreased, while more Mo species migrated into the HZSM-5 channels for the 6Mo/HZSM-5 catalysts after the post-steam-treatment. In addition, the average pore diameter was also larger for the post-steam-treated catalysts, and this was advantageous for mass transport of the reaction products. However, a severe post-steam-treatment, i.e., with longer treating time, of the 6Mo/HZSM-5 catalyst will lead to the formation of the Al(2)(MoO(4))(3) phases, which is detrimental to the reaction.

Towards manipulation of post-biosynthetic events in secondary metabolism of plant cell cultures

Plant cell cultures have been suggested as a feasible technology for the production of a myriad of plant-derived metabolites. However, commercial application of plant cell culture has met limited success with only a handful of metabolites produced at the pilot- and commercial-scales. To improve the production of secondary metabolites in plant cell cultures, efforts have been devoted predominantly to the optimization of biosynthetic pathways by both process and genetic engineering approaches. Given that secondary metabolism includes-the synthesis. metabolism and catabolism of endogenous compounds by the specialized proteins, this review intends to draw attention to the manipulation and optimization of post-biosynthetic events that follow the formation of core metabolite structures in biosynthetic pathways. These post-biosynthetic events-the chemical and enzymatic modifications, transport, storage/secretion and catabolism/degradation have been largely unexplored in the past. Potential areas are identified where further research is needed to answer fundamental questions that have implications for advanced bioprocess design. Anthocyanin production by plant cell cultures is used as a case study for this discussion, as it presents a good example of compounds for which there are extensive research publications but still no commercial bioprocess. It is perceived that research on post-biosynthetic processes may lead to future opportunities for significant advances in commercial plant cell cultures. (C) 2002 Elsevier Science Inc. All rights reserved.

一种Post-WIMP界面：PGIS的实现

随着计算机应用从桌面环境扩展到移动环境，计算机用户从专业化走向大 众化，传统的 WIMP界面的缺点逐渐体现出来。笔式用户界面作为 Post-WIMP 界面的一种重要形式，具有自然、和谐的交互特性，成为当前研究的热点之一。 针对这一方向，本文对笔式用户界面范式展开了研究。首先，本文阐述了一种 新的基于笔交互的界面范式 PGIS，定义了纸、小工具等交互组件，以及各种组 件的显示形态及交互形式。然后，实现了 PGIS 界面，包括交互对象的管理、 显示等内容。最后，详细介绍了 PGIS 界面的使用过程，并用一个应用实例加 以验证。为了支持上层应用程序的可移植性和可维护性，PGIS界面的使用采用 了模型驱动构架的开发思想。目前，我们基于 PGIS 界面开发了几款优秀的笔 式交互软件，如幼儿教学系统、便签本系统、篮球战术板系统等。这些系统完 全满足用户对笔交互应用程序的需求，目前可在 Linux 系统、Windows 系统等 多种系统上运行。PGIS界面范式的可行性也因此得到了很好的验证。 本文的主要内容有以下几点： 1. 阐述了一种 Post-WIMP范畴下的新的界面范式：PGIS。 本文在对Post-WIMP界面做了充分地理解和分析的基础上，阐述了一种新 的界面范式：PGIS。这是一种基于笔交互的界面范式，文中对该范式的纸笔隐 喻方式、所包含的内容、各交互组件的表现形式、以及各组件间的静态及动态 关系做出了详细的描述。 2. 实现了PGIS界面。 为了验证PGIS界面范式的可行性，并直接支持基于 PGIS范式的应用程序 开发，本文详细介绍了PGIS界面的实现细节，其中包括PGIS界面中所包含的 元素、PGIS界面中交互对象的显示、交互对象的管理、以及交互对象对基本原 语的转换和响应。 3. 介绍了 PGIS界面的使用过程。 整个使用过程采用模型驱动架构的思想，引入对以下三个子模块的调用： 与平台相关的底层核心库和 PGIS 引擎、与平台无关的场景设计工具。这三个 子模块决定了上层应用程序的可移植性和可维护性。另外，场景设计工具提供 了代码自动生成的功能，大幅度缩短了应用程序的开发周期。 4. 实现了一个基于 PGIS界面的幼儿教学系统。 为了说明 PGIS界面的使用流程，本文设计并实现了一个基于PGIS界面的 幼儿教学系统。在开发过程中，大部分工作在场景设计工具中快速完成，小部 分工具集中在数据管理库、场景任务库的开发上。该系统的评估结果很好地验 证了 PGIS界面范式的可行性。

Enhancement of stability of polymer light-emitting diodes by post annealing

We investigate the effect of thermal annealing before and after cathode deposition on the stability of polymer light-emitting diodes (PLEDs) based on green fluorescent polyfluorene derivative. The annealed PLEDs exhibit improved charge transport and red-shift emission compared to the as-fabricated device. The stability of the PLEDs is largely enhanced by post-annealing before and after Ca deposition, which is attributed to the enhanced charge transport and the intimate contact between the cathode and the emissive layer.