Remote detection of gaseous ammonia using the near infrared transmission properties of polyaniline

Ammonia is a key component of many industrial processes where it is used in very high concentrations. The applications range from high quality steel production and fertiliser manufacture, to the refrigeration of food products and ice ring leisure facilities. Ammonia escapes have been identified as a large and serious problem by both government and industry. Simple and robust ammonia sensors for remote monitoring applications remain an area of continuous interest.

Polyaniline is a conducting polymer used in ‘electronic nose’ instrumentation and has been shown to be electronically sensitive to ammonia. In this paper, we report on the application of electrochemically-prepared polyaniline films for the measurement of gaseous ammonia at 1300 nm. This wavelength corresponds to a region of high optical transmission for optical fibres and is also compatible with telecom devices and technology. A simple and robust measurement system based on a standard telecom 1300 nm LED is described and remote sensing using 100 m of duplex multimode fibre is demonstrated.

Typically, the transmission of the polyaniline films at 1300 nm increases by approximately 1% in response to gaseous ammonia levels of 6 ppm in 50% RH. This represents the lower limit of detection in our study. Although initially the sensors react to the presence of ammonia very fast it takes over several hours for the output to reach the equilibrium. Clearly this is impractical however, it is possible to differentiate between different concentrations of ammonia by taking two readings at fixed intervals. A calibration curve for the sensors was obtained using two readings 15 s apart. The response time of the polyanaline films was found to be insensitive to the humidity variations in the range of 30–70% RH, however, over the 10–90% variation the changes were of the same order of magnitude as those induced by 6 ppm of ammonia.     

Velocity-Guided Tracking of Deformable Contours in Three Dimensional Space

This paper presents a 3D active contour model for boundary detection and tracking of non-rigid objects, which applies stereo vision and motion analysis to the class of energy-minimizing deformable contour models, known as snakes. The proposed contour evolves in three-dimensional space in reaction to a 3D potential function, which is derived by projecting the contour onto the 2D stereo images. The potential function is augmented by a kinetic term, which is related to the velocity field along the contour. This term is used to guide the inter-image contour displacement. The incorporation of inter-frame velocity estimates in the tracking algorithm is especially important for contours which evolve in 3D space, where the added freedom of motion can easily result in loss of tracking. The proposed scheme incorporates local velocity information seamlessly in the snake model, with little computational overhead, and does not require exogenous computation of the optical flow or related quantities in each image. The resulting algorithm is shown to provide good tracking performance with only one iteration per frame, which provides a considerable advantage for real time operation.     

信息论在异常检测中的应用

异常检测能有效地检测出新类型的攻击,但是目前大多数入侵检测使用的异常检测技术都缺乏理论指导,通常是经过反复的实验建立检测模型,这样建立的模型只适用于某些环境,不具有通用性。该文提出了一种可以指导异常检测的理论基础———信息论,介绍了应用在异常检测中的几种信息论的方法,包括熵,条件熵,相对(条件)熵,信息量。利用这些方法可以指导异常模型建立过程和解释模型性能。最后该文还通过举例说明了这种理论的可行性和必要性。     

选频光释光断代初探

介绍了一种新发展起来的光释光测定年龄的技术－选频光释光技术。该技术使用的设备是光释光谱仪－BG1999。一年来该谱仪运行正常，性能稳定；实验结果令人信服。     

Effects of Deposition Temperature on the Properties of Fluorinated Amorphous Carbon Films

Fluorinated amorphous carbon films (a-C:F) were prepared at different temperatures using a microwave electron cyclotron resonance chemical vapor deposition (ECR-CVD) reactor with CHF3 and C2H2 as source gases. Films were annealed at 500℃ in vacuum ambience inorder to investigate the relationship of their thermal stability, optical and electrical propertieswith deposition temperature. Results indicate that the films deposited at high temperature have a less CFx bonding and a more cross-linking structure thus a better thermal stability. They also have a lower bandgap, higher dielectric constant and higher leakage current.     

磁光玻璃费尔德常数的波长依赖性和磁光玻璃光纤电流传感器中存在的问题

介绍了磁光玻璃的费尔德常数与工作波长的关系，对ZF1，ZF6磁光玻璃样品，测试了不同工作波长下的费尔德常数，实验值和理论值基本一致，并指出了误差来源，最后，分析了磁光玻璃应用在磁光玻璃光纤电流传感器中存在的问题。     

光纤瞬态磁场传感器的研究及其应用

为了对超高压变电站的开关瞬态磁场进行有效的测量，该文研制了一套光纤瞬态磁场传感器。采用单匝线圈作为磁场探头，利用光纤作为信号传输通路，解决了强电磁干扰环境内的瞬态磁场测量问题。提出了数字频率均衡方法，满足了变电站开关瞬态磁场测量对传感器的宽频带要求。实验室测试和现场应用表明，该传感器在频带宽度、测量范围、线性度和抗电磁干扰性能等方面，均可满足变电站开关瞬态磁场测量的要求。将该传感器应用于我国某500kV变电站开关操作和电抗器投切操作产生的瞬态磁场测量，取得了满意的结果。     

配电自动化通信系统的设计与实现

通信是配电系统实现综合自动化必不可少的组成部分，是配网调度中心实现对远方终端的数据传输、采集和进行遥控操作的必要手段。文中论述了配电自动化通信系统的功能，并结合德州配电自动化工程的实际情况，提出了配电自动化通信系统的设计要求、层次结构、通信方式及其具体实现方法。     

海底光缆有源探测技术的研究

介绍了海底光缆路由和故障点有源探测的基本原理和方法。着重分析了无铜内导体的海底光缆线路的探测距离和缆内无缝金属管材或供检测用的小直径铜导线导体电阻的关系。最后讨论了增加探测范围的方法。     

光纤在继电保护中的应用

介绍了光纤的基本结构、基本工作原理和特点，以及电力光纤网络的现状，分析了电力光纤网络和电力光缆的发展方向。重点剖析了目前在电力光纤网络中光纤保护的几种基本方式和主要特点，讨论了光纤保护在实际应用中可能遇到的问题及其解决办法。