Optical parameters and absorption studies of UV‐irradiated azo dye‐doped PMMA films

PMMA and PMMA films doped with different contents of azo dye have been made by using the casting technique. The absorption spectral analysis showed that the doped films have two absorption bands attributed to the π‐π* and n‐π* transition of chromophore groups. These bands disappear upon UV‐irradiation, suggesting that the studied system undergoes a photo degradation process. The absorption coefficient and optical energy gap (E_g) have been obtained from the absorption edge in the 200–900 nm range. It was found that E_g decreases with increasing doping levels, whereas it increases with increasing irradiation time. The width of the tail of localized states in the band gap (ΔE) was evaluated using the Urbach edge method. Some optical parameters were determined from the reflection and transmission spectra in the spectral range of 200–2500 nm. The dependence of the refractive index on irradiation time and doping level have been discussed. It was found that the photo‐induced refractive index changes are very large. These changes suggest the applicability of the studied system in optical devices. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Liquid penetration length of heptamethylnonane and trimethylpentane under unsteady in-cylinder conditions

While strategies employing early or late direct-injection of fuel can improve emissions, they also can lead to impingement of liquid-phase fuel on the piston and/or cylinder wall due to low in-cylinder temperatures and densities during the injection event. Previous work has shown that liquid-phase fuel films formed in this way can lead to pronounced degradations in efficiency and emissions. To avoid these problems, a quantitative understanding of fuel-property effects on the liquid penetration length is needed, and this understanding must include conditions where in-cylinder thermodynamic conditions and the injection rate vary with time. This work reports liquid penetration lengths measured in an optical engine under such time-varying conditions. Diagnostics included laser light scattering for measurement of the liquid length and conventional pressure-data acquisition for heat-release analysis. Unsteady liquid penetration was characterized for different injection timings, injection pressures, intake-manifold pressures, and fuel volatilities to gain an understanding of the relative importance of these factors. Fuel volatility was studied by using two fuels, 2,2,4,4,6,8,8-heptamethylnonane (HMN) and 2,2,4-trimethylpentane (TMP), which have very different volatility characteristics. Measured liquid lengths changed as in-cylinder conditions changed, with increasing temperature and density during the compression stroke causing a decrease in liquid length, and decreasing temperature and density during the expansion stroke causing an increase in liquid length. Intake-manifold pressure and fuel volatility were found to be primary factors governing liquid length. Heat loss from the charge gas to the engine and local charge cooling due to fuel vaporization were found to have a secondary influence on liquid length. Injection pressure was found to have little effect.     

石英光纤表面金属化的研究概况

石英光纤表面金属化有多种方法可以实现,化学镀的方法明显优于其他方法。本文主要介绍了国内外石英光纤表面金属化的研究概况,对用化学镀以及电镀的方法对光纤表面进行金属化的光纤表面预处理过程、化学镀镀液组成、电镀的镀液组成及镀覆条件作了详细论述。     

2.5Gb/s 0.35μm CMOS单片集成光接收机电路设计与实现

采用0.35μm CMOS工艺设计并实现了单片集成光接收机电路.该芯片能将光电检测器检测到的速率为2.5Gb/s的信号进行放大,进行时钟恢复、数据判决,并通过一到四路分接输出四路速率为622Mb/s的信号.恢复出的经过四分频的时钟抖动以及最后分接输出的四路数据抖动的均方值分别为1.9ps和13ps.芯片在标准的5V电源电压下,功耗为2.05W,整个芯片面积为1600μm×870μm.     

基于FPGA的喷绘机高速光纤通信系统设计与实现

为解决喷绘机打印数据实时传输问题,将以现场可编程门阵列(FPGA)和串行解串器为基础的高速光纤通信技术应用到打印数据的通讯中。系统中FPGA用于实现通讯数据的存取、8B/10B编解码和CRC校验的功能;串行解串器实现了并/串和串/并转换及锁相功能;光收发一体模块实现了电光转换和光电转换。该光纤通信系统在喷绘机上进行了实际打印试验,应用结果表明系统在300 Mbps通信带宽下能够稳定传输,在120小时的连续测试过程中没有出现打图错误现象。实现了高可靠性、长距离、高速数据传输的功能。     

一种宽范围测速系统的设计

针对光电编码器的宽范围测速系统存在低速振动测速不准和高速巨量中断导致实时性欠佳的问题,采用抗振动M/T测速方法结合可预置N分频器,低频时采用脉冲电平逻辑滤波,清除干扰,保证测速的准确性,高频时采用分频计数,降低处理器中断处理的次数,提高测速系统运行的效率,从硬件和软件两个方面较好地解决了这个问题,并据此研制以32位嵌入式处理器(LPC2114)为控制器的宽范围测速系统,同时给出系统的硬件和软件设计方案。研究结果表明该设计方法是有效的。     

Modulation Depth Based on Frequency-shift Characteristic of LiNbO3 Waveguide Electro-optic Intensity Modulator

The modulation depth,defined according to practical mod-ulation results,which changes with the microwave power and its fre-quency,is significant for systems utilizing the frequency-shift charac-teristic of the LiNbO3 waveguide Electro-Optic Intensity Modulator (EOIM).By analyzing the impedance mismatch between the micro-wave source and the EOIM,the effective voltage applied to the RF port of the EOIM is deprived frcm the microwave power and its fre-quency.Associating with analyses of the phase velocity mismatch be-tween the microwave and the optical wave,the theoretical modulation depth has been obtained,which is verified by experimental results.We provide a method to choose the appropriate modulation depth to optimize the desired sideband through proper transmission bias far the system based an the frequency-shift characteristic of the EOIM.     

数字化变电站与常规变电站建设差异

随着IEC61850标准、智能化开关、光电式电流,电压互感器、一次设备状态在线检测等技术的成熟和应用,国家电网公司已将数字化变电站建设纳入规划并重点发展。数字化变电站的推广应用将彻底改变传统变电站的建设模式。通过对数字化变电站与常规变电站的类比,较为详尽的剖析了数字化变电站的相关新型技术。     

基于TL16C554A串口扩展在光纤变电站通信管理单元中的应用

简单介绍了35 kV光纤变电站的通信系统,阐述了在该通信系统的基础上利用TL16C554A对CPU进行的串口扩展,并给出了硬件电路及接口程序。     

海底光缆锚害的有限元分析

船锚造成的海缆故障非常普遍,船锚的钩挂是造成海底光缆故障的主要原因,对海底光缆的锚害研究迫在眉睫。首先建立了船锚钩挂海缆的有限元模型,进行了船锚钩挂海缆的仿真,然后通过分析海缆受到船锚钩挂后的变形和应变,研究了海缆各组成部分抗船锚钩挂的能力、船锚损害海底光缆的机理以及海缆结构与抗船锚钩之间的关系,得出了相关的结论。