A real-time monitoring approach for bivariate event data

Early detection of changes in the frequency of events is an important task in many fields, such as disease surveillance, monitoring of high-quality processes, reliability monitoring, and public health. This article focuses on detecting changes in multivariate event data by monitoring the time-between-events (TBE). Existing multivariate TBE charts are limited because they only signal after an event occurred for each of the individual processes. This results in delays (i.e., long time-to-signal), especially when we are interested in detecting a change in one or a few processes with different rates. We propose a bivariate TBE chart, which can signal in real-time. We derive analytical expressions for the control limits and average time-to-signal performance, conduct a performance evaluation and compare our chart to an existing method. Our findings showed that our method is an effective approach for monitoring bivariate TBE data and has better detection ability than the existing method under transient shifts and is more generally applicable. A significant benefit of our method is that it signals in real-time and that the control limits are based on analytical expressions. The proposed method is implemented on two real-life datasets from reliability and health surveillance.     

Removal of low-concentration benzene in indoor air with plasma-MnO2 catalysis system

Non-thermal plasma (NTP) and combined plasma-MnO₂ catalytic (CPMC) air cleaners were tested for removal of low-concentration benzene in air. Both air cleaners were made of stainless steel needle matrix plate and used DC corona discharger. The effects of discharge power and relative humidity (RH) on benzene removal efficiency were investigated in a closed chamber. The intermediate products produced in purification processes were analyzed using gas chromatography-mass spectrometer (GC-MS). The concentrations of discharge byproducts and CO₂ selectivity produced in both processes were also compared. It was found that the benzene removal efficiency increased with discharge power in both systems; With the increase of RH in air, benzene removal efficiency firstly increased and then decreased in NTP while it gradually decreased in CPMC. For a fixed discharge power of 9 W and RH of 20% in CPMC, the conversion of benzene increased from 82.9% to 89.6%, the CO₂ selectivity increased from 38% to 80%, the concentration of O₃ decreased from 25.3 ppm to 1.3 ppm, and NO₂ formation decreased from 234 ppm to 25.7 ppm, compared with NTP.     

大速差射流型双一次风通道通用煤粉主燃烧器

本文介绍了一种新型煤粉主燃烧器－双一次风通道通用煤粉主燃烧器。它既保留了大速差射流燃烧技术的优点，又彻底克服了燃烧器内容易局部结焦的缺点，从而由辅助燃烧器（或预燃室）发展成为主燃烧器。具有煤种适应性广，低负荷运行范围大，煤粉着火点位置可控等优点。     

利用超声雾化器制作冷风机

利用超声雾化器制作的冷风机,具有水雾颗粒更细,更容易进行交换,在单位时间内能获得更多汽化热,使冷风机降温效率更高的优点。     

CCD在光学镀膜宽带膜厚监控系统中的应用研究

讨论了 CCD的主要特性及对宽带膜厚监控系统的影响 ,介绍了典型的 CCD数据采集系统。建立了一套基于 CCD的宽带膜厚监控系统 ,并对该系统进行了光谱标定及光谱补偿 ,给出了提高信噪比及减小非线性影响的处理方法。     

三维荧光光谱技术在水监测中的应用

应用荧光光谱技术分析水中污染物的含量具有灵敏度高、检测速度快等优点,三维荧光光谱技术可以提供在普通的荧光光谱中所得不到的信息,此技术可以用于多组分同时测量。讨论了如何运用三维荧光光谱技术分析水中污染物的成分,计算其含量,并给出了有效的荧光光谱特征数据库建立、多组分分析和浓度反演的数学模型。     

基于M-Z干涉仪原理的光纤超声检测

提出了一种基于M_Z(Mach_Zehnder)干涉仪原理的光纤超声检测技术和U形结构的光纤传感器。讨论了光纤传感器与超声波之间的相互作用关系。对传感器的灵敏度与传感光纤的有效长度、U形结构的个数之间的关系进行了理论分析,实验结果和理论分析结果是一致的。通过比较超声波在三种不同入射方式下探测器的输出电压可知,该结构的光纤传感器在声信号垂直入射时由探测器探测到的信号最强,即传感器有很强的方向性,适合于对声表面波的定向检测。     

激光诱导荧光探测水体中溶解有机物浓度

用Nd∶YAG激光器的三倍频355 nm光作为激发光源,根据激光诱导荧光(LIF)方法激发并探测污染水体的荧光光谱.通过对荧光光谱的分析处理研究归一化荧光强度,即450 nm处水中溶解有机物(DOM)峰与405 nm处水的拉曼峰的比值,反演溶解有机物浓度.用商品腐殖酸和去离子水配置成已知浓度的溶液代替标准DOM溶液进行标定,得到回归方程.结果证明,DOM的归一化荧光强度与水体中DOM浓度有较好的线性关系,因此LIF方法是对大面积水域水质进行动态遥测的较理想方法.     

光锥与TDI-CCD耦合监控中测试目标的一种实现方法

为了给光锥与时间延迟积分电荷耦合器件耦合监控装置提供有效的被测运动条纹,分析了传统推扫成像实验装置的不足之处,设计了电子显示目标滚屏运动装置.采用光学相机对印刷条纹静止成像,并用TDI-CCD数字相机对监视器屏幕上的运动条纹动态成像.实验结果表明,该方案解决了高分辨率的鉴别率图样无法在监视器或投影仪上精确显示的困难.与传统的实验室模拟装置相比,该方案提高了鉴别率条纹的运动稳定性,减小了条纹运动速率与TDI-CCD扫描行频间的失配误差,不仅能够对耦合过程实施监控,而且还能用于耦合系统的像质评价.     

Explorations and Expectations of Equidistribution Adaptations for Nonlinear Quenching Problems

Finite difference computations that involve spatial adaptation commonly employ an equidistribution principle. In these cases, a new mesh is constructed such that a given monitor function is equidistributed in some sense. Typical choices of the monitor function involve the solution or one of its many derivatives. This straightforward concept has proven to be extremely effective and practical. However, selections of core monitoring functions are often challenging and crucial to the computational success. This paper concerns six different designs of the monitoring function that targets a highly nonlinear partial differential equation that exhibits both quenching-type and degeneracy singularities. While the first four monitoring strategies are within the so-called primitive regime, the rest belong to a later category of the modified type, which requires the priori knowledge of certain important quenching solution characteristics. Simulated examples are given to illustrate our study and conclusions.