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Conference on advanced sensor systems and applications ii

作者： Wu, KH Yan, K Huang, ZH Wang, RR Hangzhou Dianzi Univ Sch Automat Hangzhou 310018 Peoples R China

ISBN: (纸本)081945589X

Air pollution monitoring is an important aspect of environmental protection. The pollutants to be detected are usually more than one in air or smoke monitoring. Researching new techniques that can meet the demand of detecting the pollutants at the same time is important and necessary. The paper researched the method of detecting multi-parameters in one optical fiber gas sensing system. The system used multi-wavelength and time division multiplex technique to detect the concentration of SO2 and NO2 simultaneously based on gas' spectra absorption principle. The light differential absorption formula was deduced. The two strong and weak absorbing wavelengths were chosen as signal and reference relatively. To every gas, optical coupler and narrow-band optical filters were used to generate signal and reference light from a high brightness LED. The central wavelength of filters is identical to the strong or weak absorption wavelength respectively. The multi-channel signals were switched to one light beam using a 4x1 optical switch controlled by computer in designed time sequence. The output light after absorbing by gas was coupled on a high sensitivity PIN detector. To achieve high detecting sensitivity, the light source was modulated by a pulse signal. The power and temperature control circuits were also used to stabilize the output power and wavelength of light source. After differential absorption process, the concentration of different gas can be deduced in one set of common optical and electrical sensing system.

关键词： optical fiber sensor gas sensor multi-parameters measurement environmental monitoring

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Fiber thermometer based on the cross detection of the fluorescence lifetime of Cr³⁺:YAG crystal fiber and Plank's blackbody radiation from cryogenic up to 1400°C

Fiber thermometer based on the cross detection of the fluore...

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Conference on advanced sensor systems and applications ii

作者： Ye, LH Qiu, YQ Shen, YH He, SL Zhejiang Univ State Key Lab Modern Opt Instrumentat Ctr Opt & Electromagnet Res Hangzhou 310027 Peoples R China

ISBN: (纸本)081945589X

A fiber thermometer using the cross detection of the fluorescence lifetime and blackbody radiation was presented to measure temperature from -10 degrees C up to 1400 degrees C. Using a long pure YAG crystal fiber as the seed and a 0.1 at. % Cr2O3-doped Y3Al5O12 sintered powder rod as the source rod, a YAG fiber thermal probe with Cr3+-ions doped end was grown by laser heated pedestal growth method. A blackbody cavity was constructed by sintered a thin ceramic layer around the Cr3+: YAG fiber end. A phase-locked detection scheme was used for the fluorescence lifetime detection. The fluorescence characteristics of the Cr3+-ions doped YAG was analyzed in a temperature range from -10 degrees C up to 500 degrees C. From 350 degrees C to 1400 degrees C the blackbody radiation signal in a narrow waveband were detected. Because the fluorescence lifetime was intensity independent, it should have the long-term stability and would not change if the fiber connectors of the probes were realigned. So the fluorescence lifetime based temperature measurement could be used to recalibrate that based on the blackbody radiation detection. Preliminary experimental results showed that the system could achieve a resolution much better than 1 degrees C over the whole temperature range from -10 degrees C to 1400 degrees C.

关键词： Cr3+: YAG crystal fiber fluorescence decay time blackbody radiation temperature sensor

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Energy-conserving data placement and asynchronous multicast in wireless sensor networks 03

Energy-conserving data placement and asynchronous multicast ...

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1st International Conference on Mobile systems, applications and Services

作者： Bhattacharya, S Kim, H Prabh, S Abdelzaher, T Univ Virginia Dept Comp Sci Charlottesville VA 22904 USA

ISBN: (纸本)1931971099

In recent years, large distributed sensor networks have emerged as a new fast-growing application domain for wireless computing. In this paper, we present a distributed application-layer service for data placement and asynchronous multicast whose purpose is power conservation. Since the dominant traffic in a sensor network is that of data retrieval, (i) caching mutable data at locations that minimize the sum of request and update traffic, and (ii) asynchronously multicasting updates from sensors to observers can significantly reduce the total number of packet transmissions in the network. Our simulation results show that our service subsequently reduces network energy consumption while maintaining the desired data consistency semantics.

关键词： Multicasting

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Shape memory alloys: Properties and engineering applications

Shape memory alloys: Properties and engineering applications

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Conference on Smart Materials, Structures and systems

作者： Krishnan, RV Bhaumik, SK Natl Aeronaut Lab Div Mat Sci Bangalore 560017 Karnataka India

ISBN: (纸本)0819448680

Shape memory alloys (SMAs) are a promising class of advanced materials with interesting properties, which make them suitable for a variety of engineering applications. The uses of SMAs in engineering applications have extended year by year. SMAs are being used in a number of industrial applications such as aerospace, automotive, biomaterial, chemical-sensor, construction, electronics, metal forming, storage and retrieval of information, optics etc. This paper highlights some of these engineering applications of SMAs. This also includes the recent research on the possible use of SMAs in smart structures. The important properties of SMAs that provide the impetus for using these materials in innovative applications are (i) shape memory effect, (ii) pseudoelasticity and (iii) high damping capacity. For a better appreciation, some of the basic principles and properties related to the unique behaviour of this class of materials are also discussed.

关键词： shape memory alloys properties applications

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Performance analysis of a stellar-inertial system for spacecraft autonomous attitude determination based on MEMS and CMOS technology

Performance analysis of a stellar-inertial system for spacec...

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54th International Astronautical Congress of the International Astronautical Federation (IAF), the International Academy of Astronautics and the International Institute of Space Law

作者： Accardo, D. Rufino, G. Grassi, M. Department of Space Science and Engineering L.G. Napolitano University of Naples Federico II Naples Italy

This paper deals with the performance analysis and preliminary design of an integrated system for autonomous attitude state determination of spacecrafts based on the fusion of MEMS (Micro-Electro-Mechanical-System) gyros with an advanced CMOS-based star sensor. In the integration scheme the star sensor is used as aiding sensor. sensor data fusion is performed by means of Kalman filtering, following a detailed analysis of star trackers and gyros measurement errors. As a consequence, the integrated system performances are estimated by covariance propagation. In particular, the steady state error covariance for different inertial and stellar sensor typologies and aiding sensor update intervals is numerically analysed, in order to evaluate different sensor configurations considering the performances of sensors available in the market. Analysis results will help in selecting the star sensor data rate and the updating frequency to be used for the inertial sensor aiding. The study is performed considering the following sensor physical parameters: gyros drift rate, resolution and bias stability;star sensor sensitivity, detection limit, field-of-view and instantaneous field of view;star catalogue size and coverage. The above parameters are modelled with reference to state-of-art MEMS gyros and MOS and CMOS-based star sensors. Results show that stellar-inertial sensors for coarse/medium (0.01°) and high (<0.001°) attitude accuracy applications can be obtained by integrating, respectively, MEMS silicon vibrating gyros with CMOS-based star sensor and fyber optic gyros with MOS-based star sensors. Finally, preliminary analysis also shows that integrated systems with mass of about 2 kg and power consumption lower than 15 W can be realised, that are adequate for microsatellite applications. Copyright © 2003 by the International Astronautical Federation. All rights reserved.

关键词： Spacecraft

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Nonlinear observer designs for fuel cell power systems

Nonlinear observer designs for fuel cell power systems

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作者： Gorgun, Haluk Rensselaer Polytechnic Institute

学位级别：Ph.D.

A fuel cell is an electrochemical device that combines hydrogen and oxygen, with the aid of electro-catalysts, to produce electricity. A fuel cell consists of a negatively charged anode, a positively charged cathode and an electrolyte, which transports protons or ions. A low temperature fuel cell has an electrical potential of about 0.7 Volt when generating a current density of 300–500 mA/cm2. Practical fuel cell power systems will require a combination of several cells in series (a stack) to satisfy the voltage requirements of specific applications. Fuel cells are suitable for a potentially wide variety of applications, from stationary power generation in the range of hundreds of megawatts to portable electronics in the range of a couple of watts. Efficient operation of a fuel cell system requires advanced feedback control designs. Reliable measurements from the system are necessary to implement such designs. However, most of the commercially available sensors do not operate properly in the reformate and humidified gas streams in fuel cell systems. sensors working varying degrees of success are too big and costly, and sensors that are potentially low cost are not reliable or do not have the required life time [28]. Observer designs would eliminate sensor needs for measurements, and make feedback control implementable. Since the fuel cell system dynamics are highly nonlinear, observer design is not an easy task. In this study we aim to develop nonlinear observer design methods applicable to fuel cell systems. In part I of the thesis we design an observer to estimate the hydrogen partial pressure in the anode channel. We treat inlet partial pressure as an unknown slowly varying parameter and develop an adaptive observer that employs a nonlinear voltage injection term. However in this design Fuel Processing System (FPS) dynamics are not modelled, and their effect on the anode dynamics are treated as plant uncertainty. In part ii of the thesis we study the FPS dynamics

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Processing of polymer composites: an optical fibre-based sensor system for on-line amine monitoring

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COMPOSITES PART A-APPLIED SCIENCE AND MANUFACTURING 2001年第11期32卷 1561-1572页

作者： Liu, T Fernando, GF Cranfield Univ Royal Mil Coll Sci Dept Syst Engn Swindon SN6 8LA Wilts England

advanced fibre reinforced composites used for primary and secondary load-bearing applications are generally made with multi-component resin systems. The thermal. mechanical and chemical properties of the composites are strongly influenced by the cure state of the resin which is itself influenced by the degree of mixing of the various components in the resin and their stoichiometric ratio. This paper reports on the development of an optical fibre sensor system as part of a clean filament winding process. The function of the sensor system is for monitoring: (i) the amine concentration and (ii) the extent of mixing in an amine/epoxy based thermoset. Differential scanning calorimetry was used to assess the influence of mixing efficiency on the enthalpy of the cure reaction. (C) 2001 Elsevier Science Ltd. All rights reserved.

关键词： resins filament winding static mixer

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The new method of historical sensor data integration using neural networks

The new method of historical sensor data integration using n...

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1st International Workshop on Intelligent Data Acquisition and advanced Computing systems

作者： Turchenko, V Kochan, V Sachenko, A Laopoulos, T Ternopil Acad Natl Econ Lab Automated Syst & Networks UA-46004 Ternopol Ukraine

ISBN: (纸本)078037164X

The main feature of neural network using for accuracy improvement of physical quantities (for example, temperature, humidity, pressure etc.) measurement by data acquisition systems is insufficient volume of input data for predicting neural network training at an initial exploitation period of sensors. The authors have proposed the technique of data volume increasing for predicting neural network training using (i) additional approximating neural network;(ii) method of "historical" data integration (fusion). In this paper we have proposed the advanced method of "historical" data integration and presented simulation results on mathematical models of sensor drift using single-layer perceptron.

关键词： historical sensor data integration (fusion) sensor drift prediction accuracy improvement intelligent systems

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advanced Photonic sensors and applications ii Conference

作者： John, MS Murukeshan, VM Asundi, A Nanyang Technol Univ Sch Mech & Prod Engn Singapore 639798 Singapore

ISBN: (纸本)0819443263

Dynamic analysis of structures and machines provide valuable information on the performance and reliability of structures. In this paper, we present the development of a Fiber Optic Polarimetric sensor (FOPS(C)) for dynamic and impact loading. The sensor monitors the change in the state of polarization of the light beam traversing the fiber under dynamic loading. The dynamic response of three different sensing optical fibers - high birefringence (bow-tie) fiber, low birefringence fiber and an ordinary communication grade single mode fiber are evaluated. The studies were carried out by embedding the optical fibers in a glass fiber reinforced plastic (GFRP) specimen and the performances of the three different systems were compared.

关键词： Fiber Optic Polarimetric sensor smart structures dynamic analysis composite materials

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An overview of the posters presented at Watermatex 2000. ii. sensor/monitoring, control and decision support systems

An overview of the posters presented at Watermatex 2000. II....

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5th IWA International Symposium on systems Analysis and Computing in Water Quality Management

作者： Volcke, EIP Clement, L Van de Steene, M Vanrolleghem, PA State Univ Ghent BIOMATH B-9000 Ghent Belgium

This paper gives an overview of the poster sessions on sensor/monitoring, control and decision support systems, as they have been presented during the Watermatex 2000 conference. The COST benchmark for the comparison of different control strategies has been analysed. Two different teams have performed research on the control of sewers to decrease combined sewer overflows. Extended methods for gauge monitoring accuracy are proposed. The use of adaptive controllers for improving control performance under varying process conditions is demonstrated in two applications. More advanced techniques for monitoring and control are also discussed. applications are situated in the field of fault detection and control. Three posters on decision support systems have presented the methodology and architecture of specific applications. Rewarded posters are mentioned and have been selected for full paper publication in this issue of Wat. Sci. Tech.

关键词： control sensors monitoring decision support systems

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