Use of the smart technology for water quality control: feedback from large-scale experimentation

The main purpose of drinking water network is to ensure safe quality of water to users. However, accidental contamination and malicious attacks in water networks can degrade the water quality. Such critical events threat the human health and lead to harmful diseases. Water utilities are concerned by the control of water quality. Since conventional methods based on laboratory analyses require several days, online control technology presents good opportunity to rapid detection of any water contamination. Devices based on smart technology have been developed for real-time control of the water quality. However, the use of these devices is recent and yet requires investigations. This paper presents feedback of the use of the smart technology in a large-scale experimentation conducted at the campus of Lille University within the European project “SmartWater4Europe”. Two devices are used: S::CAN, which measures various parameters such as Conductivity and Turbidity and EventLab, which measures the variation of the refractive index. This paper presents the implementation of these devices, data storage and management as well as analysis of recorded data.     

沉管隧道渗漏水红外自主检测技术

针对港珠澳大桥沉管隧道内行车道及排烟道可能产生的渗漏水病害现象,采用搭载于巡检机器人的红外热成像阵列,进行图像识别。红外热成像阵列能够应对大视场、远测距、高分辨率的工作场景;图像处理算法包含预处理、图像分割、轮廓检测及决策判断等步骤,同时,当满足气象条件及轮廓内像素灰度阈值时,视为可能存在渗漏病害区域。研究结果可实现沉管隧道内主要设施巡检覆盖率达90以上,最小渗漏检测面积01m×01m的技术指标,并开展实验室测试及天津中试场地实验验证指标及检测系统有效性。     

单一平面电容式漏水检测传感器的研究

针对北方地区冬季暖气管道漏水可能导致的大型设备机房或重要仪器损坏的问题,提出了一种用于管道漏水检测的单一平面电容式传感器的设计方案。该装置利用平面电容原理,检测水滴落在平面电容上时引起的电容变化,采用微电容测量电路将电容转换成频率,然后通过单片机处理后计算出电容值,通过和预先设定的阈值电容的比较来判断平板上是否漏水。经实际试验,该方案实施的平面电容式漏水检测传感器应用于管道漏水检测具有结构简单、成本便宜、性能可靠的特点。     

蒸汽炉非接触式水盒水位检测技术应用

传统蒸汽炉水盒采用浮标式进行水位测量,容易污染水位,而且无法实现多档水位的准确检测。文章提出一种非接触式多档水盒水位检测技术。在详细的电容水位测量理论基础上,通过在蒸汽炉水盒外壁安装电容水位检测模块,使用变频斜率的水位判断算法,实现了蒸汽炉水盒多档水位测量。采用DOE方法设置水位判断阈值,大大提高水位判断的一致性与准确性。实验结果表明,本技术可实现蒸汽炉水盒多档水位的精准测量。DOE的水位阈值设置方法可有效兼容水盒安装误差和水温差异,提高水位检测的一致性与可靠性。     

基于McBSP的漏水检测系统应用研究

简要介绍了漏水检测系统的工作流程,该系统要能够接收并处理A/D转换后的数据,具有无线传输数据的功能.选用DSP作为漏水检测的核心处理芯片,TI公司的TMS320VC5402提供两个McBSP,通过适当的寄存器设置,将其中一个McBSP配置成SPI接口主控设备与A/D转换模块相连;由于McBSP是同步串口,而无线通信模块XBee为异步串口,采用过采样的方法将McBSP软件配置成UART.该设计很好地满足了设计要求,充分利用了资源,软硬件实现简单.     

基于声波技术的管道泄漏检测与定位系统的研究

天然气管道漏点在线实时泄漏监测与定位系统的研究与应用,使得泄漏能够被及时发现并确定泄漏点的位置,从而降低因天然气泄漏造成的经济损失,同时对提高天然气输送管线的自动化管理水平有着深远的意义。通过对国内外各种管道泄漏检测技术的研究和分析比较,采用声波检测方法应用于输气管道的泄漏检测策略,在信号处理方面采用虚拟仪器软件设计了天然气管线声波泄漏实时监测定位系统,对泄漏声波信号进行波形实时显示、数字滤波、相关运算以及泄漏点定位等操作,实现了管线泄漏检测的自动化。     

基于BIM技术的大型钢结构建筑可靠性检测方法研究

针对现有大型钢结构建筑可靠性检测方法执行效率低、检测精度低等问题,设计基于BIM技术的大型钢结构建筑可靠性检测方法。首先以大型建筑钢结构为研究对象,运用BIM技术建立合理的建筑钢结构的功能函数用于描述极限状态,以极限状态方程为约束条件构建大型钢结构建筑可靠性分析约束优化模型。其次使用曾广乘子法将约束优化模型转变为无约束优化模型,使用模拟退火算法对该模型进行求解。最后模拟大型建筑钢结构形变状态设计对比实验,实验结果表明与同类检测方法相比,应用基于BIM技术的大型钢结构建筑可靠性检测方法后,检测精度提升97.77%以上,有效缓解了检测效率低下情况。     

Fault detection and identification for reliable large-scale computing

In the letter, the analysis of a new technique for fault-tolerant computing is presented. This technique is applicable to systems with a large number of modules which require the simultaneous and reliable execution of multiple jobs.     

一种改进的支路漏电流检测方案

直流系统(例如220vdc输出电源系统)支路绝缘下降检测系统中,其使用的漏电流传感器基本都属于闭环式传感器,该传感器有个弊端:一旦现场出现传感器失效的话,更换特别困难。本文提出了一种新的改进方案,具体思路如下:因为高导磁环线圈损坏的概率非常低,绝大部分传感器故障都是其基本电路(运放,方波电路等)的失效导致,采用高导磁环形线圈和基本电路分离措施,把基本电路放置下级采集设备中,万一出现故障,也仅需替换下级采集设备即可,该方案大大减少了支路传感器损坏概率,回避了传感器在线更换困难的难题,与此同时,该改进方案还简化系统接线、降低产品成本。     

Generalized feedback detection for spatial multiplexing multi-antenna systems

We present a unified detection framework for spatial multiplexing multiple-input multiple-output (MIMO) systems by generalizing Heller's classical feedback decoding algorithm for convolutional codes. The resulting generalized feedback detector (GFD) is characterized by three parameters: window size, step size and branch factor. Many existing MIMO detectors are turned out to be special cases of the GFD. Moreover, different parameter choices can provide various performance-complexity tradeoffs. The connection between MIMO detectors and tree search algorithms is also established. To reduce redundant computations in the GFD, a shared computation technique is proposed by using a tree data structure. Using a union bound based analysis of the symbol error rates, the diversity order and signal-to-noise ratio (SNR) gain are derived analytically as functions of the three parameters; for example, the diversity order of the GFD varies between 1 and N. The complexity of the GFD varies between those of the maximum-likelihood (ML) detector and the zero-forcing decision feedback detector (ZF-DFD). Extensive computer simulation results are also provided.     

Decision feedback multiuser detection: a systematic approach

A systematic approach to decision feedback multiuser detection is introduced for the joint detection of symbols of K simultaneously transmitting users of a synchronous correlated waveform multiple-access (CWMA) channel with Gaussian noise. A new performance criterion called symmetric energy is defined which is a low-noise indicator of the joint error rate that at least one user is detected erroneously. Even the best linear detectors can perform poorly in terms of symmetric energy compared to the maximum-likelihood detector. A general class of decision feedback detectors (DFDs) is defined with O(K) implementational complexity per user. The symmetric energy of arbitrary DFD and bounds on their asymptotic effective energy (AEE) performance are obtained along with an exact bit-error rate and AEE analysis for the decorrelating DFD. The optimum DFD that maximizes symmetric energy is obtained. Each one of the K! optimum, decorrelating, and conventional DFDs, that correspond to the K! orders in which the users can be detected, are shown to outperform the linear optimum, decorrelating, and conventional detectors, respectively, in terms of symmetric energy. Moreover, algorithms are obtained for determining the choice of order of detection for the three DFDs which guarantee that they uniformly (user-wise) outperform their linear counterparts. In addition to optimality in symmetric energy, it is also shown that under certain conditions, the optimum DFD achieves the AEE performance of the exponentially complex maximum-likelihood detector for all users simultaneously. None of the results of this paper make the perfect feedback assumption. The implications of our work on power control for multiuser detection are also discussed     

Signal design for sequential detection systems with feedback

We consider a coherent white Gaussian channel, through which one of two signals is sent to a receiver which operates as a sequential detector. A noiseless delayless feedback link is assumed, which continuously informs the transmitter of the state of the receivers uncertainty concerning which signal was sent, and which also synchronizes the transmitter when the receiver has reached a decision. The transmitter, in turn, uses the output of the feedback link to modify its transmission so as to hasten the receiver's decision. The following problem is posed: Given average- and peak-power constraints on the transmitter and a prescribed error probability for the receiver, what signal waveforms should the transmitter use in order to minimize the average transmission time, and how should it utilize the fedback values of the receiver's uncertainty to modify these waveforms while transmission is in progress? We give partial solutions to these questions. In particular, we have shown that if the peak-to-average power ratio is allowed to be sufficiently large, substantial improvement of performance may be achieved through the use of uncertainty feedback.     

Edge leakage control in platinum-silicide Schottky-barrier diodesused for infrared detection

Platinum silicide (PtSi) on p-silicon Schottky-barrier focal plane arrays (FPAs) are strong candidates for infrared (IR) detection up to a wavelength of about 5 μm. However, an inherently low quantum efficiency (about 1% at 4 μm) makes it important to maximize the fill factor or the area of the array that is IR-sensitive. Current designs use an n^- guard ring around the PtSi diodes to suppress edge leakage. This is effective, but the guard-ring overlap can significantly reduce the sensitive area of the diode. An aluminium plate that is already used as a photon reflector above the diode in current designs can be positively biased as a field plate to create a surface depletion layer around the diode periphery. This produces leakage current suppression equivalent to the guard ring without giving up IR-sensitive diode area     

反激式开关电源控制芯片中的高精度原边反馈技术

本文提出了一种用于反激式开关电源控制芯片的高精度原边反馈技术,可以自动追踪原边辅助绕组电压的膝电压位置,得到高精度的反馈电压并将其进行模数转换输出反馈量VFB,控制芯片中的数字补偿模块根据VFB的值调节开关管的导通时间,最终实现输出电压的精确调制。本文提出的反馈技术采用csmc0.18 m工艺实现,验证结果显示本设计可以很好的检测到膝电压,实现了精确的原边反馈。     

Fractionally spaced decision feedback joint detection for multitoneCDMA systems

We consider a fractionally spaced decision feedback joint detector (FS-DFJD) for multitone code division multiple access (CDMA) systems. We first derive the structure of the receiver for an minimum mean-squared error (MMSE) criterion. Then we investigate the bit-error rate (BER) performance achieved by this detector for binary phase-shift keying (BPSK) modulation in steady-state conditions. We consider an asynchronous scenario where the signal of each user propagates over a two-path channel. The resistance of the detector against timing errors is studied, and the resistance against a near-far scenario is also demonstrated     

机载大规模复杂系统软件开发技术研究

针对综合模块化航空电子系统中机载软件规模、复杂度大幅上升的趋势,对传统机载软件研制方法不能满足机载大规模复杂软件研制的问题进行了分析。针对机载综合化大规模软件,为解决软件的可信性、确定性、健壮性和连续性,提出"需求管理、模型开发、仿真验证、产品复用、工具支撑、过程管理"为核心的软件开发方法。经过国产机载嵌入式操作系统等机载大规模软件研制实践,可有效提高软件研制质量。该方法对同等软件的研制具有极强的参考价值。     

Adaptive ordering for imperfect successive decision feedback multiuser detection

A method for selecting the order in which the users are detected in communication systems employing adaptive successive decision feedback multiuser detection is proposed. Systems employing channel coding without the assumption of perfect decision feedback are analyzed. The method is based on the mean squared error (MSE) measurements during a training period for each user. The analysis' shows that the method delivers BER performance improvement relative to other previously proposed ordering methods.     

PON:好技术不等于好市场

光纤通信现已经渗入网络的各个层面,从广域网、城域网一直到局域网;从传送层、汇聚层、接入层一直到用户驻地网。但同时,“最后一公里”的接入仍是骨干网与城域网的“瓶颈”,大容量、高速率的宽带接入系统成为解决这一问题的有效方法。目前常用的宽带接入技术——数字用户线(DSL)和电缆调制解调器(CM)利用原本是为电话或有线电视设计的基础设施来传输数据,自然不是最佳的选择,而理论上可以有“无限”接入带宽的光纤接入方式     

采用液滴分析技术定量检测水中溶解氧的研究

在原有光纤-电容传感器的基础上,引入了光纤溶解氧(DO)传感器,在保持液滴分析仪原有结构的情况下,可同时获得水质的定性和定量信息。基于液滴分析技术(DAT)对水中30种不同浓度的DO含量进行了检测。实验结果表明,基于DTA,采用光纤DO传感器检测液体的DO含量是有效的。在考虑温度影响时,二次多项式拟合模型效果最佳,系统的灵敏度可达0.1mg/L,最大相对误差为2.38%。     

基于图像边缘检测的证书防伪技术

证书防伪是人们越来越关注的社会问题,盗版作假日益影响着大家的生活。文中提出了一种基于可信第三方的非嵌入式认证水印的证书防伪技术方案。该方案通过Canny边缘检测技术对经过DWT变换过的图像进行边缘检测,来获取图像的边缘属性,并利用该属性生成含有水印信息的认证码。传统水印算法需要修改载体图像内容,会损害图像数据,但非嵌入式认证水印则避免了对图像数据的破坏,保证了载体图像的质量。无需提取水印,与其他证书防伪技术相比更方便,实验结果表明该方案具有可行性和有效性。