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基于瑞利散射强度谱动态扩展的大量程分布式光纤传感系统
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作者 陈家豪 刘庆文 +1 位作者 常晏铭 何祖源 《光学学报》 EI CAS CSCD 北大核心 2024年第11期251-257,共7页
基于背向瑞利散射和啁啾脉冲的光纤分布式声传感器实现了动态信号的高性能测量,但其过小的量程限制了准静态信号的测量能力。为此,本文提出了一种基于瑞利频谱解调法的频谱扩展算法,利用光纤受到应变时瑞利散射强度谱发生频移的特点,在... 基于背向瑞利散射和啁啾脉冲的光纤分布式声传感器实现了动态信号的高性能测量,但其过小的量程限制了准静态信号的测量能力。为此,本文提出了一种基于瑞利频谱解调法的频谱扩展算法,利用光纤受到应变时瑞利散射强度谱发生频移的特点,在应变测量过程中动态扩展分布式光纤传感系统的参考频谱频率范围以提高测量量程。在实验中,利用扫频范围为1 GHz的啁啾脉冲,实现了198με应变信号的测量,测量量程相较于无扩展算法时扩大了65倍。 展开更多
关键词 分布式光纤 瑞利散射 传感量程 互相关 频谱扩展
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Fuzzy Neural Network Model of 4-CBA Concentration for Industrial Purified Terephthalic Acid Oxidation Process 被引量:7
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作者 刘瑞兰 苏宏业 +3 位作者 牟盛静 贾涛 陈渭泉 褚健 《Chinese Journal of Chemical Engineering》 SCIE EI CAS CSCD 2004年第2期234-239,共6页
A fuzzy neural network (FNN) model is developed to predict the 4-CBA concentration of the oxidation unit in purified terephthalic acid process. Several technologies are used to deal with the process data before modeli... A fuzzy neural network (FNN) model is developed to predict the 4-CBA concentration of the oxidation unit in purified terephthalic acid process. Several technologies are used to deal with the process data before modeling.First,a set of preliminary input variables is selected according to prior knowledge and experience. Secondly,a method based on the maximum correlation coefficient is proposed to detect the dead time between the process variables and response variables. Finally, the fuzzy curve method is used to reduce the unimportant input variables.The simulation results based on industrial data show that the relative error range of the FNN model is narrower than that of the American Oil Company (AMOCO) model. Furthermore, the FNN model can predict the trend of the 4-CBA concentration more accurately. 展开更多
关键词 purified terephthalic acid 4-carboxybenzaldchydc fuzzy neural network soft sensor input variables selection fuzzy curve dead time detection
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Temporal Patterns in Symptoms of Nitrogen Deficiency as Revealed by Remote Sensing of Corn Canopy 被引量:1
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作者 J. ZHANG A. M. BLACKMER +2 位作者 P. M. KYVERYGA M. J. GLADY T. M. BLACKMER 《Pedosphere》 SCIE CAS CSCD 2010年第1期15-22,共8页
To evaluate the temporal patterns of N deficiencies in corn and assess the ability of remote sensing to diagnose N deficiencies during the vegetative growth of corn, three field-scale experiments were conducted with v... To evaluate the temporal patterns of N deficiencies in corn and assess the ability of remote sensing to diagnose N deficiencies during the vegetative growth of corn, three field-scale experiments were conducted with various rates (56, 112, and 168 kg N ha-1 ), timing (early and late applications) and placement (injected into soil and dribbled on soil surface) of N fertilization in a split-plot design. Relationships between canopy reflectance during the growing season and yield data at the end of growing season were studied for different treatments. Results showed significant variation in both grain yields and canopy reflectance among the three cornfields. The N fertilization made in early June resulted in low canopy reflectance in early July, but the differences disappeared as the season progressed. The effect of N rates on canopy reflectance was not significant in early July but it gradually became detectable in mid-July and thereafter. The fertilizer placement had a significant effect on grain yields only in one field but not on canopy reflectance in all three fields. These observations suggest that the deficiency of N developed under field conditions is a dynamic phenomenon, which adds complexity for accurately defining "N deficiency" and effectively developing management strategies for in-season correction. Remote sensing throughout the season helps collect information about important interactions that have not been given enough attention in the past. 展开更多
关键词 canopy reflectance fertilizer placement TIMING yield response
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Outlining a stepwise,multi-parameter debris flow monitoring and warning system:an example of application in Aizi Valley,China 被引量:1
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作者 CHEN Ning-sheng Javed Iqbal TANO LI +5 位作者 HU Gui-sheng WANG Feng-niang YANG Cheng-lin DING Hai-tao HE Na WANG Tao 《Journal of Mountain Science》 SCIE CSCD 2016年第9期1527-1543,共17页
In recent years, the increasing frequency of debris flow demands enhanced effectiveness and efficiency of warning systems. Effective warning systems are essential not only from an economic point of view but are also c... In recent years, the increasing frequency of debris flow demands enhanced effectiveness and efficiency of warning systems. Effective warning systems are essential not only from an economic point of view but are also considered as a frontline approach to alleviate hazards. Currently, the key issues are the imbalance between the limited lifespan of equipment, the relatively long period between the recurrences of such hazards, and the wide range of critical rainfall that trigger these disasters. This paper attempts to provide a stepwise multi-parameter debris flow warning system after taking into account the shortcomings observed in other warning systems. The whole system is divided into five stages. Differentwarning levels can be issued based on the critical rainfall thresholds. Monitoring starts when early warning is issued and it continues with debris flow near warning, triggering warning, movement warning and hazard warning stages. For early warning, historical archives of earthquake and drought are used to choose a debris flow-susceptible site for further monitoring. Secondly, weather forecasts provide an alert of possible near warning. Hazardous precipitation, model calculation and debris flow initiation tests, pore pressure sensors and water content sensors are combined to check the critical rainfall and to publically announce a triggering warning. In the final two stages, equipment such as rainfall gauges, flow stage sensors, vibration sensors, low sound sensors and infrasound meters are used to assess movement processes and issue hazardwarnings. In addition to these warnings, communitybased knowledge and information is also obtained and discussed in detail. The proposed stepwise, multiparameter debris flow monitoring and warning system has been applied in Aizi valley China which continuously monitors the debris flow activities. 展开更多
关键词 Debris Flow Monitoring system Warning system Aizi Valley Rainfall threshold
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Design and Implementation of Image Acquisition System Based on STM32
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作者 QIN Wei YU Chaogang 《International English Education Research》 2017年第2期64-66,共3页
In order to solve the difficulty of reading inconvenience in the measurement process of digital track gauge, a kind of image data acquisition system with low cost and stable performance is designed. The system uses th... In order to solve the difficulty of reading inconvenience in the measurement process of digital track gauge, a kind of image data acquisition system with low cost and stable performance is designed. The system uses the Cortex-M4 as the core of the STM32F407ZGT6 as the control core, the use of OV2640 as an image sensor to collect images, and the collection of image files stored in the SD card for subsequent image processing to achieve the goal of rail adjustment to lay the foundation. The experimental results show that the image acquisition is stable and refiable and the collected images are clear and meet the design requirements. 展开更多
关键词 STM32F407 OV2640 Image acquisition
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Dynamic Crowd Loading Test on Tibetan Ancient Structures
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作者 Na Yang Ting Guo 《Journal of Civil Engineering and Architecture》 2010年第5期15-21,共7页
The field test of a typical Tibetan ancient structure instrumented with displacement and acceleration transducers was conducted to measure time histories due to crowd walking and running. The test case is introduced f... The field test of a typical Tibetan ancient structure instrumented with displacement and acceleration transducers was conducted to measure time histories due to crowd walking and running. The test case is introduced firstly. The displacement time histories are then used to analyze the dynamic property such as fundamental frequency of vertical vibration and damping ratio of the test structure, and the acceleration time histories are applied to evaluate the floor vibration serviceability. The floor interaction and comparison of human walking and running are also discussed. Some valuable conclusions are given. 展开更多
关键词 Tibetan ancient structure field test dynamic property crowd walking and running floor vibration serviceability.
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Experimental and Theoretical Analysis of an Optical Current Sensor for High Power Systems 被引量:2
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作者 A. C. S. BRIGIDA I. M. NASCIMENTO +4 位作者 S. MENDONCA J. C. W. A. COSTA M. A. G. MARTINEZ, J. M. BAPTISTA,P. A. S. JORGE J. C. W. A. COSTA, M. A. G. MARTINEZ, J. M. BAPTISTA J. M. BAPTISTA P.A.S. JORGE 《Photonic Sensors》 SCIE EI CAS 2013年第1期26-34,共9页
A magneto-optical sensor, using a dual quadrature polarimetfic processing scheme, was evaluated for current metering and protection applications in high voltage lines. Sensor calibration and resolution were obtained i... A magneto-optical sensor, using a dual quadrature polarimetfic processing scheme, was evaluated for current metering and protection applications in high voltage lines. Sensor calibration and resolution were obtained in different operational conditions using illumination in the 1550-nm band. Results obtained indicated the feasibility of interrogating such sensor via the optical ground wire (OPGW) link installed in standard high power grids. The polarimetric bulk optical current sensor also was theoretically studied, and the effects of different sources of error considering practical deployment were evaluated. In particular, the interference from external magnetic fields in a tree-phase system was analyzed. 展开更多
关键词 Fiber optic optical current sensor linear birefringence Faraday effect tree-phase system
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Implementation of Interrogation Systems for Fiber Bragg Grating Sensors 被引量:1
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作者 Benjamin VARGHESE P. Dinesh KUMAR R. Mittu RAJU K. N. MADHUSOODANAN 《Photonic Sensors》 SCIE EI CAS 2013年第3期283-288,共6页
The development of two simple methods for wavelength-optical intensity modulation techniques for fiber Bragg grating (FBG) sensors is presented. The performance is evaluated by measuring the strain and temperature. ... The development of two simple methods for wavelength-optical intensity modulation techniques for fiber Bragg grating (FBG) sensors is presented. The performance is evaluated by measuring the strain and temperature. The first method consists of a narrow band source, an optical circulator, an FBG; and a power meter. The source and Bragg reflected signal from the FBG need to be matched to get linear results with good power levels. The source spectral power levels are very critical in this study. The power reflected from a matched reference FBG is fed into the measuring FBG in the second method. Since the FBGs are matched, the entire power is reflected back initially. During the measurement, the change in the measurand causes the reflected power from the sensing FBG to vary. A costly high resolution spectrum analyzer is required only during the characterization of the FBG and source. The performances of two interrogators are compared by measuring the strain and temperature. In the second method, the strain measurements can be made insensitive to the temperature variation by selecting a source with a flat spectrum at the measurement range. Highlights of these methods are the portability, cost effectiveness and better resolution. 展开更多
关键词 Fiber Bragg grating INTERROGATOR reflected power strain and temperature measurement
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