基于石英增强光声光谱技术的开放光路气体传感系统研究

针对传统石英增强光声光谱系统存在体积大、实时性差,无法实现在狭小空间中探测等缺点,提出一种基于光纤引导方式的开放光路石英增强光声光谱传感系统。系统用光纤将激光引导至石英音叉两叉指中央,以实现对狭小空间中痕量气体的探测。搭建了实验系统,开展了对常温常压下空气中水蒸气含量的探测来验证该系统的探测灵敏度及可靠性。得到其归一化噪声系数为7.15e-7cm^(-1)?W/Hz^(1/2)。实验结果表明,该系统的探测灵敏度是传统石英增强光声光谱系统的5倍。该系统体积小、实时性强,无需样本取样,适用于开放环境中对痕量气体的检测。     

Modeling the impact of spectral sensor configurations on the FLD retrieval accuracy of sun-induced chlorophyll fluorescence

Chlorophyll fluorescence is related to photosynthesis and can serve as a remote sensing proxy for estimating photosynthetic energy conversion and carbon uptake. Recent advances in sensor technology allow remote measurements of the sun-induced chlorophyll fluorescence signal (Fs) at leaf and canopy scale. The commonly used Fraunhofer Line Depth (FLD) principle exploits spectrally narrow atmospheric oxygen absorption bands and relates Fs to the difference of the absorption feature depth of a fluorescensing and a non-fluorescensing surface. However, due to the nature of these narrow bands, Fs retrieval results depend not only on vegetation species type or environmental conditions, but also on instrument technology and processing algorithms. Thus, an evaluation of all influencing factors and their separate quantification is required to further improve Fs retrieval and to allow a reproducible interpretation of Fs signals.Here we present a modeling study that isolates and quantifies the impacts of sensor characteristics, such as spectral sampling interval (SSI), spectral resolution (SR), signal to noise ratio (SNR), and spectral shift (SS) on the accuracy of Fs measurements in the oxygen A band centered at 760 nm (O₂-A). Modeled high resolution radiance spectra associated with known Fs were spectrally resampled, taking into consideration the various sensor properties. Fs was retrieved using the three most common FLD retrieval methods, namely the original FLD method (sFLD), the modified FLD (3FLD) and the improved FLD (iFLD). The analysis investigates parameter ranges, which are representative for field and airborne instruments currently used in Fs research (e.g., ASD FieldSpec, OceanOptics HR, AirFLEX, AISA, APEX, CASI, and MERIS).Our results show that the most important parameter affecting the retrieval accuracy is SNR, SR accounts for ≤ 40% of the error, the SSI for ≤ 12%, and SS for ≤ 7% of the error. A trade-off study revealed that high SR can partly compensate for low SNR. There is a strong interrelation between all parameters and the impact of specific parameters can compensate or amplify the influence of others. Hence, the combination of all parameters must be considered by the evaluation of sensors and their potential for Fs retrieval. In general, the standard FLD method strongly overestimates Fs, while 3FLD and iFLD provide a more accurate estimation of Fs. We conclude that technical sensor specifications and the retrieval methods cause a significant variability in retrieved Fs signals. Results are intended to be one relevant component of the total uncertainty budget of Fs retrieval and have to be considered in the interpretation of retrieved Fs signals.     

Closed loop identification and control loop reconfiguration: an industrial case study

The results of a joint university–industry collaborative project for control loop reconfiguration using closed loop experimental data from a fuel gas pressure control system are described in this paper. The fuel gas pressure was being regulated using a butane stream. For economic reasons, it was necessary to switch control to the ethane stream. Previous attempts at effecting this changeover had proved unsuccessful. In this study, a powerful system identification technique namely Canonical Variate Analysis (CVA) was employed to obtain the empirical plant models. A PI controller was then designed using the direct synthesis method. Acceptable closed loop behavior was obtained with little online tuning.     

一种适用于构件系统的软件抗衰技术框架

近年来,软件抗衰技术已被证实是解决软件衰老问题的有效途径。本文针对构件系统特点,将Micro-Reboot思想引入到软件抗衰技术中,也即将单个构件作为抗衰技术中检测和措施的对象,一方面使得每个构件能够长时间保持在良好状态,从而提高整个体系的性能,另一方面引入Request—Retry机制,提高系统的可用性。本文基于J2EE构件模型开发出一种新的软件抗衰技术框架,相关理论已成果并在江苏省科技攻关项目“城域网海量视听信息实时点播系统”中应用。     

Identification and control of open-loop unstable processes by relay methods

This paper describes a reliable automatic PID tuning method for open-loop unstable processes. Identification with low order models is performed by means of two relay tests, one with an additional delay, which does not require a priori knowledge about the process, with the only necessary condition being that the process be gain stabilisable. This paper provides an overview of the method, states conditions that need to be satisfied for its successful implementation, and demonstrates its application on a number of examples.     

围术期麻醉深度的模糊控制

针对手术过程中麻醉深度的控制问题,提出了一种PID参数自整定模糊控制策略。应用这种方法对麻醉过程中平均动脉血压的控制进行了计算机仿真研究,获得了良好的仿真结果。理论分析和仿真结果证明了此方法的准确性和可靠性,为围术期麻醉深度的控制提供了一种新方法。。     

竹红菌乙素对人红细胞膜蛋白荧光猝灭机理的研究

本文利用人红细胞膜蛋白内源荧光(主要指色氨酸),经加入不同的竹红菌乙素之后,引起了荧光猝灭现象,根据荧光猝灭原理分别从吸收光谱,荧光光谱,稳态变温实验和瞬态荧光等技术分析了上述的猝灭过程,实验证明:该猝灭是以动态碰撞过程为主要作用机理,据此作者提出了乙素可以用于生物膜体系的蛋白质荧光猝灭剂的理由。     

具有温度补偿的FBG电流传感器研究

采用双光纤Bragg光栅(FBG)和2种不同的解调方法实现对基于电磁力的FBG电流传感的温度补偿,对2种解调方法进行比较。实验结果表明:采用光谱分析仪(OSA)进行波长解调,测量范围为0.35～2.5 A,灵敏度为0.93 nm/A;采用滤波调谐进行光强解调,测量范围为0.30～0.70 A,灵敏度可达到9.6 nW/mA。     

时滞系统模糊整定PID控制的仿真研究

文中引入1／1pade级数逼近纯滞后环节，根据两步法设计内模控制器。由等效式可以看出，单位反馈控制器可以由带滤波器的PID控制器文现，内模调节即转化成为PID控制器的参数整定。采用模糊自调整控制方案整定PID参数，同时结合针对时滞系统的模糊控制规则和一般二维模糊控制器的通用规则，设计模糊控制器，充分利用模糊控制、内模控制、PID控制的优点。将所设计的系统应用于具有大时滞、大惯性特点的电厂主汽温控制系统检验其性能，仿真试验证明了这一方法具有很好的鲁棒性、控制精度和抗干扰能力。