A Hyperspectral Bidirectional Reflectance Model for Land Surface

A hyperspectral bidirectional reflectance (HSBR) model for land surface has been developed in this work. The HSBR model includes a very diverse land surface bidirectional reflectance distribution function (BRDF) database with ~40,000 spectra. The BRDF database is saved as Ross-Li parameters, which can generate hyperspectral reflectance spectra at different sensor and solar observation geometries. The HSBR model also provides an improved method for generating hyperspectral surface reflectance using multiband satellite measurements. It is shown that the land surface reflective spectrum can be easily simulated using BRDF parameters or reflectance at few preselected wavelengths. The HSBR model is validated using the U.S. Geological Survey (USGS) vegetation database and the AVIRIS reflectance product. The simulated reflective spectra fit the measurements very well with standard deviations normally smaller than 0.01 in the unit of reflectivity. The HSBR model could be used to significantly improve the quality of the reflectance products of satellite and airborne sensors. It also plays important role for intercalibration among space-based instruments and other land surface related applications.

Новый метод дистанционного обнаружения утечек воды из трубопроводов

Рассмотрена возможность разработки нового метода дистанционного обнаружения утечек воды из трубопроводов. Для выработки рекомендаций по оптимальной реализации высотного (самолетного или спутникового) зондирования с целью обнаружения утечек воды из трубопроводов проанализированы основные физические процессы, влияющие на результаты обнаружения утечек воды методом дистанционного зондирования. Показана необходимость учета следующих физических воздействий: зависимость отражательного спектра почвы от ее влажности зависимость оптической плотности атмосферного аэрозоля (AOD) от относительной влажности (RH) инверсная взаимосвязь между температурой и влажностью воздуха зависимость отраженного сигнала почвы от температуры из-за сушки почвы. Предложен новый метод обнаружения утечек из трубопровода, предусматривающий повторную проходку трассы водопровода и сравнение полученных спектрометрических результатов с учетом влияния температуры воздуха на влажность почвы и степень увлажненности атмосферного аэрозоля.The possibility of developing a new method for remote detection of water leaks in pipelines is considered. To develop the recommendations on the optimal implementation of altitude (aircraft or satellite) sounding in order to detect water leaks in pipelines, the main physical processes that affect the results of detecting water leaks by remote sensing are analyzed. The need for taking into account the following physical effects is shown: the dependence of the reflective spectrum of the soil on its moisture content the dependence of the optical density of atmospheric aerosol (AOD) on the relative humidity (RH) inverse relationship between the air temperature and humidity temperature dependence of the reflected signal of the soil due to soil drying. A new method for detecting leaks in pipelines is proposed that involves re-driving the water pipeline route and comparing the obtained spectrometric results taking into account the influence of the air temperature on the soil moisture and the degree of the atmospheric aerosol humidity.

Temperature Effect on Fiber Optical Sensors for Dry Cast Storage Health Monitoring

The increasing number, size, and complexity of nuclear facilities deployed worldwide are increasing the need to maintain readiness and develop innovative sensing materials to monitor important to safety structures (ITS). Assessing and supporting next generation nuclear materials management and safeguards for future U.S. fuel cycles with minimum human intervention is of paramount importance. Technologies for the diagnosis and prognosis of a nuclear system, such as dry cast storage system (DCSS), can improve verification of the health of the structure that can eventually reduce the likelihood of inadvertently failure of a component. In the past decades, an extensive sensor technology development has been used for structural health monitoring (SHM). Fiber optical sensors have emerged as one of the major SHM technologies developed particularly for temperature and strain measurements. However, the fiber optical sensors and sensing system has not been developed with adequate solutions and guideline for DCSS applications. This paper presents an experimental study of temperature effect on fiber Bragg grating (FBG) sensors. The reflective spectrum of FBG sensors on the structure was measured with a tunable laser source. The shift of FBG reflective spectrum reflected the thermal expansion on the structure. The shift of the spectrum due to the temperature effect was correlated to the temperature changes. In addition, the FBG sensing methodology including high frequency guided ultrasonic waves (GUW) under different temperatures were also performed to check the performance of high frequency, small strain sensing. The potential of FBG sensors for DCSS applications was explored. The paper ends with conclusions and suggestions for further work.

Indicators of Professional Development in Texts Written by Prospective Teachers

The writing of narratives is a frequently used educational tool in teacher education. This activity has several aims, such as bridging the gap between theory and practice, transforming experience into knowledge, and fostering consciousness and reflexivity among prospective teachers. We consider that the writing of narratives, framed with some guidelines, represents a mean to build professional knowledge. To get a better insight into the processes involved in the writing of narratives, this article examines the cognitive and discursive mechanisms that underlie professional development. We rely on indicators of professional development observed through a psycholinguistic analysis of narrative texts. This type of text analysis is anchored in a Vygotskian perspective, according to which language; thinking and action are interdependent in the constitution of an individual’s system of mental representations. In this article, we present an educational artifact for narrative writing, a grid for the analysis of discourses in the context of teacher education (the Analysis of Discourses About Professional Apprenticeship grid), our methodological framework and some results. The use of this grid is illustrated with examples of the prospective teachers’ narratives and questionings. Finally, we suggest that professional knowledge results from the convergence between enunciative undertakings, regulations of action, and conceptions and reflective spectrum. This convergence determines the strength of professional knowledge built. Moreover, the texts that have been analyzed reveal the fundamental questionings the trainee teachers have when faced with the task of textualizing their professional knowledge as well as the meaning they give to their activity.

The Application of Wavelet Denoise in Sampled Grating Comb Filter

This paper based on the theoretical basis of sampled fiber grating, using transfer matrix method to analyze sampled fiber grating. By changing the parameters of sampled fiber grating and simulating its reflective spectrum. Four optical comb filters based on sampled grating were designed. Then the wavelet de-noising principle was introduced. In order to optimize designing of sampling grating comb filter, a filtering analysis and denoising method by using wavelet analysis to denoise was proposed. Finally, the automatic one-dimensional denoising was used with db6 wavelet. It not only denoise reflective spectrum noise, but also play a certain inhibition in the side-lobe interference the signal received. The smooth reflective spectrum can be got after denoising.

Study on Tunable Filtering Characteristic of 1-D Defect Photonic Crystal Based on Surface Wave Resonance

A optical biosensor used in index dynamic detection has been proposed combining the tunable filtering characteristics of defect photonic crystal with the surface wave resonance principle. The sensing model of the biosensing chip based on defect photonic crystal has been established based on rigid coupled wave method, which obtained the relationship between the change of resonant angle for reflective spectrum and the variation of refractive index for biomolecule detected. Using the photonic crystal with the defect layer in place of the metal film in the surface plasma resonance (SPR) sensor, repeatedly total reflection would take place in the defect layer, which would increase the senstivity of the measurement system.