Spectroscopic determination of leaf water content using continuous wavelet analysis

The gravimetric water content (GWC, %), a commonly used measure of leaf water content, describes the ratio of water to dry matter for each individual leaf. To date, the relationship between spectral reflectance and GWC in leaves is poorly understood due to the confounding effects of unpredictably varying water and dry matter ratios on spectral response. Few studies have attempted to estimate GWC from leaf reflectance spectra, particularly for a variety of species. This paper investigates the spectroscopic estimation of leaf GWC using continuous wavelet analysis applied to the reflectance spectra (350-2500 nm) of 265 leaf samples from 47 species observed in tropical forests of Panama. A continuous wavelet transform was performed on each of the reflectance spectra to generate a wavelet power scalogram compiled as a function of wavelength and scale. Linear relationships were built between wavelet power and GWC expressed as a function of dry mass (LWC_D) and fresh mass (LWC_F) in order to identify wavelet features (coefficients) that are most sensitive to changes in GWC. The derived wavelet features were then compared to three established spectral indices used to estimate GWC across a wide range of species.Eight wavelet features observed between 1300 and 2500 nm provided strong correlations with LWC_D, though correlations between spectral indices and leaf GWC were poor. In particular, two features captured amplitude variations in the broad shape of the reflectance spectra and three features captured variations in the shape and depth of dry matter (e.g., protein, lignin, cellulose) absorptions centered near 1730 and 2100 nm. The eight wavelet features used to predict LWC_D and LWC_F were not significantly different; however, predictive models used to determine LWC_D and LWC_F differed. The most accurate estimates of LWC_D and LWC_F obtained from a single wavelet feature showed root mean square errors (RMSEs) of 28.34% (R² = 0.62) and 4.86% (R² = 0.69), respectively. Models using a combination of features resulted in a noticeable improvement predicting LWC_D and LWC_F with RMSEs of 26.04% (R² = 0.71) and 4.34% (R² = 0.75), respectively. These results provide new insights into the role of dry matter absorption features in the shortwave infrared (SWIR) spectral region for the accurate spectral estimation of LWC_D and LWC_F. This emerging spectral analytical approach can be applied to other complex datasets including a broad range of species, and may be adapted to estimate basic leaf biochemical elements such as nitrogen, chlorophyll, cellulose, and lignin.     

Functionalized poly (vinyl alcohol) polymer as chemodosimeter material for the colorimetric sensing of cyanide in pure water

New poly (vinyl alcohol) (PVA) derivative containing pendant chemoselective functionality is prepared for the cyanide detection in pure water. Particularly, incorporation of the chemodosimeter 4 on PVA is performed by direct coupling of the hydroxyl group of the dye 4 and PVA hydroxyl groups via ethereal linkage using di-bromoalkane as a cross-linking agent. The chemosensory capacity of the polymeric material for the colorimetric sensing of cyanide in water is based on the reactivity of this anion toward the chemodosimeter, and its water solubility is given by PVA moiety. The chemodosimeter is developed on the basis of the trifluoroacetyl group as electrophile receptor of the cyanide anions. The final water soluble functionalized polymer presents a sensible selectivity toward cyanide anions in pure water.     

Applying content analysis for investigating the reporting of water issues

This article presents a content analysis approach for contextualizing the reporting of water and water-related issues. The intent of our approach is to enable an understanding of how important environmental topics such as water-related issues are presented to the public, and thus potentially influencing public perceptions on the issues. Multiple statistical and analytical methods are integrated in order to analyze online newspapers articles to evaluate the context, regionalism and relevance of the reporting of water issues. Using 10 online newspapers from Nebraska, USA, the content analysis approach revealed that water is most often reported in the state in the context of agriculture, while other topics such as water quality and habitat are less frequently discussed. Second, there is a lack of spatial dependency in the reporting of water across Nebraska as newspapers in close proximity to one another do not demonstrate similar reporting. Finally, the reporting of water in some newspapers is noticeably linked to local daily water quantity observations. These results suggest that, although the topic of water as an environmental issue may be vitally important across a region, the context of how water issues are reported is driven by local issues and, in some cases, relevant physical processes. Results show that there is a relative lack of coverage on major water and environmental issues except when issues are of immediate public concern. We discuss how these results could be used by resource managers to interpret media content and the public’s understanding of important environmental topics.     

采用电容传感器的型砂含水率检测仪

介绍一种采用电容传感器的型砂含水率检测仪,它采用微电容测量技术对信号进行检测,并通过单片机对数据进行处理和控制,测量准确度高于1%,既可作为便携式仪表使用,也可用在生产线上实现混砂加水的自动控制,具有使用方便、测量速度快、性能稳定、控制可靠等优点。     

智能PID算法在液位控制系统中的应用

针对自己开发的液位控制系统参数难以调整的问题,本文提出了一种智能PID的液位控制方法。智能PID控制算法是在常规PID控制算法的基础上,根据前人和专家的经验以及操作人员的实际经验,针对具有大滞后、时变、非线性系统对象而提出的控制算法。该算法是分段进行调节的,它既有较好的快速性,又有迟滞(死区)控制的稳定性和抗干扰能力。实验结果表明:这种控制方法不仅简单、精度高,而且具有一定的实用价值。     

Application of mesh-adaptation for pollutant transport by water flow

An adaptive finite volume method is proposed for the numerical solution of pollutant transport by water flows. The shallow water equations with eddy viscosity, bottom friction forces and wind shear stresses are used for modelling the water flow whereas, a transport-diffusion equation is used for modelling the advection and dispersion of pollutant concentration. The adaptive finite volume method uses simple centred-type discretization for the source terms, can handle complex topography using unstructured grids and satisfies the conservation property. The adaptation criteria are based on monitoring the pollutant concentration in the computational domain during its dispersion process. The emphasis in this paper is on the application of the proposed method for numerical simulation of pollution dispersion in the Strait of Gibraltar. Results are presented using different tidal conditions and wind-induced flow fields in the Strait.     

A dielectric-based combined horizontal sensor for on-the-go measurement of soil water content and mechanical resistance

Precision agriculture is drawing widespread attention and increasing interest in the use of on-the-go sensors to extract soil and plant information. This new trend is evident from an increased number of (tillage) studies concerning the development of sensors for measuring physical soil properties. In this study, a new dielectric-based horizontal sensor was designed and stationary calibrated in pots for measurement of volumetric soil water content. Subsequently, the sensor was combined with a load cell and installed on a tine with thickness of 25 mm, and its dynamic performance was assessed. The load cell behind the tine measures horizontal soil mechanical resistance. In order to evaluate the on-the-go performance of this combined sensor, two experiments were carried out in a soil bin, with the purpose of (i) measuring soil water content along a transect of longitudinally variable water contents, (ii) investigating the difference in horizontal resistance force measured by either the combined (horizontal force and water content) or a single sensor (horizontal force only). The stationary calibration results showed that quadratic equations with coefficients of determination (R²) of 0.989 and 0.918 could be fitted to the data points obtained from measurements in soil bulk densities of 1.5 and 1.2 g cm⁻³, respectively. The results of the soil bin experiments indicated that the response of the dielectric sensor to soil water content variations was reasonable, but that the output voltage of the sensor should be amplified for a better sensitivity and resolution. The presented combined sensor can provide useful information on soil physical properties towards site specific applications in soils.     

Estimation of vegetation water content and photosynthetic tissue area from spectral reflectance: a comparison of indices based on liquid water and chlorophyll absorption features

Because of the high water content of vegetation, water absorption features dominate spectral reflectance of vegetation in the near-infrared region of the spectrum. In comparison to indices based on chlorophyll absorption features (such as the normalized difference vegetation index (NDVI)), indices based on the water absorption bands are expected to “see” more deeply into thick canopies and have a preferential sensitivity to thin as opposed to thick tissues. These predictions are based on the much lower absorption coefficients for water in the short wavelength water bands as compared to chlorophyll. Thus, the water bands may have advantages over NDVI for remote sensing of photosynthetic tissues. Previous studies have primarily related water band indices (WI) to leaf area index (LAI). Here we expand the definition of photosynthetic tissues to include thin green stems and fruits and measure a wide range of species to determine the influence of variable tissue morphologies and canopy structures on these relationships. As expected, indices based on reflectance in the water absorption bands in the near infrared were best correlated with the water content of thin tissues (less than 0.5-cm thickness). The choice of wavelength for a water index was much more important for thick than for thin canopies, and the best wavelengths were those where water absorptance was weak to moderate. We identified three wavelength regions (950-970, 1150-1260 and 1520-1540 nm) that produced the best overall correlations with water content. Comparison of these wavelength regions with the atmospheric “windows” where water vapor absorption is minimal suggests that the 1150-1260 and 1520-1540 nm regions would be the best wavelengths for satellite remote sensing of water content. We also developed and tested a new Canopy Structure Index (CSI) that combines the low absorptance water bands with the simple ratio vegetation index (SR) to produce an index with a wider range of sensitivity to photosynthetic tissue area at all canopy thicknesses. CSI was better than either WI or SR alone for prediction of total area of photosynthetic tissues. However, SR was best for prediction of leaf area when other green tissues were excluded. All of these relationships showed good generality across a wide range of species and functional types.     

Preservice elementary teachers as information and communication technology designers: an instructional systems design model based on an expanded view of pedagogical content knowledge

Abstract This study discusses the evolution of an instructional systems design (ISD) model that is based on an expanded view of Shulman's concept of pedagogical content knowledge (PCK). An initial model was evaluated in the first iteration of a design experiment, and then it was changed and assessed in two other iterations that followed. The proposed ISD model can be used in educational technology courses, elementary teacher education method courses, and teacher professional development courses to develop information and communication technology (ICT)-related PCK. ICT-related PCK comprises a body of knowledge that educators need to be able to teach with ICT. Evidence from the present study, with preservice elementary teachers, indicates that the evolved model was effective in developing some aspects of ICT-related PCK. Based on the results of the study, more systematic efforts are needed to engage preservice teachers in technology-rich design activities, so that they can adequately develop all aspects of ICT-related PCK. Finally, this study provides baseline data that can be used for comparison purposes in future studies that may be conducted to further validate or modify the suggested ISD model.     

Participatory Framework for Assessment and Improvement of Tools (ParFAIT): Increasing the impact and relevance of water management decision support research

This paper proposes the Participatory Framework for Assessment and Improvement of Tools (ParFAIT) as a way to address low uptake of Water Resources Systems Optimization (WRSO) tools. ParFAIT is a transdisciplinary process conducted in five stages, two of which are participatory modeling (PM) exercises. Herein we describe the framework, introduce our candidate tool- Multiobjective Evolutionary Algorithm (MOEA)-assisted optimization, and present the results of our first PM workshop. MOEA-assisted optimization has been put forth as a planning and decision making aid for utilities facing a large number of decisions and highly uncertain futures. The PM workshop, designed to solicit input on a tool testbed, was held in February 2015 with representatives from six Front Range, Colorado, water utilities. Our results include an expanded characterization of the decision making landscape, feedback on water utility decisions and performance goals commonly employed in WRSO studies, and new questions that warrant future investigation by researchers.     

Effects of woody elements on simulated canopy reflectance: Implications for forest chlorophyll content retrieval

An important bio-indicator of actual plant health status, the foliar content of chlorophyll a and b (Cab), can be estimated using imaging spectroscopy. For forest canopies, however, the relationship between the spectral response and leaf chemistry is confounded by factors such as background (e.g. understory), canopy structure, and the presence of non-photosynthetic vegetation (NPV, e.g. woody elements)—particularly the appreciable amounts of standing and fallen dead wood found in older forests. We present a sensitivity analysis for the estimation of chlorophyll content in woody coniferous canopies using radiative transfer modeling, and use the modeled top-of-canopy reflectance data to analyze the contribution of woody elements, leaf area index (LAI), and crown cover (CC) to the retrieval of foliar Cab content. The radiative transfer model used comprises two linked submodels: one at leaf level (PROSPECT) and one at canopy level (FLIGHT). This generated bidirectional reflectance data according to the band settings of the Compact High Resolution Imaging Spectrometer (CHRIS) from which chlorophyll indices were calculated. Most of the chlorophyll indices outperformed single wavelengths in predicting Cab content at canopy level, with best results obtained by the Maccioni index ([R₇₈₀ − R₇₁₀] / [R₇₈₀ − R₆₈₀]). We demonstrate the performance of this index with respect to structural information on three distinct coniferous forest types (young, early mature and old-growth stands). The modeling results suggest that the spectral variation due to variation in canopy chlorophyll content is best captured for stands with medium dense canopies. However, the strength of the up-scaled Cab signal weakens with increasing crown NPV scattering elements, especially when crown cover exceeds 30%. LAI exerts the least perturbations. We conclude that the spectral influence of woody elements is an important variable that should be considered in radiative transfer approaches when retrieving foliar pigment estimates in heterogeneous stands, particularly if the stands are partly defoliated or long-lived.     

Phthalocyanines as sensitive coatings for QCM sensors: Comparison of gas and liquid sensing properties

The quartz crystal microbalance (QCM) was used to investigate the liquid sensing properties of a set of phthalocyanines (Pcs) which were systematically varied by attaching the substituent 2,2,3,3-tetrafluoropropyloxy to different positions and by introducing a central metal ion (i.e. Ni²⁺, Zn²⁺, and Cu²⁺). The responses to low concentrations of organic compounds such as hydrocarbons and chlorocarbons dissolved in water were recorded. The materials were very sensitive to the tested compounds with detection limits in the lower parts-per-million range and they exhibited a good sensing performance as the sensors have been working fully reversibly and reliably over long periods of time. Besides, the influence of substitution pattern and choice of central metal ion on the liquid sensing properties of Pcs were studied for the first time. The results show that the responses differ notably from each other depending on the modifications made to the Pc. Finally, it is demonstrated that the gas and liquid sensing responses of the materials are highly correlated and can be linked to each other with the help of a basic physical model.     

Spectral sensing of foliar water conditions in two co-occurring conifer species: Pinus edulis and Juniperus monosperma

Many fundamental ecosystem properties and dynamics are determined by plant water stress, particularly in dryland ecosystems where water is usually limiting. Indeed, under severe drought, plant water stress and associated insect infestations can produce landscape-scale mortality. Despite the fundamental importance of plant water stress in determining properties and dynamics at ecosystem and landscape scales, approaches for remotely sensing plant water stress are largely lacking, particularly for conifers. We evaluated the remotely sensed detection of foliar drought stress in two conifer species, Pinus edulis and Juniperus monosperma, which are co-dominants of extensive-juniper woodlands in North America, the first of which experienced extensive mortality in association with a recent drought. Needle spectra were made on these species in the field using an integrating sphere and portable spectrometer. Two indices of foliar water condition, plant water content (% of dry mass) and plant water potential, were compared to five spectral analyses: continuum removal of the 970 and 1200 nm water absorption features, the Normalized Difference Water Index (NDWI), the Normalized Difference Vegetation Index (NDVI), and the red edge wavelength position. For P. edulis, plant water content was significantly correlated with four of the five indices: NDVI (R²=0.71) and NDWI (R²=0.68) which exhibited stronger relationships than 970 nm continuum removal (R²=0.57) or red edge position (R²=0.45). All five indices were significantly correlated with P. edulis water content when trees undergoing mortality were included in analyses (R²=0.60-0.93). Although the correlations were weaker than for plant water content, plant water potential was significantly correlated with NDWI (R²=0.49), 970 nm (R²=0.44), NDVI (R²=0.35), and red edge (R²=0.34); again all five indices had significant relationships when trees undergoing mortality were included (R²=0.51-0.86). The relationships were weaker for J. monosperma: water content was significantly related to 970 nm (R²=0.50) and 1200 nm (R²=0.37) continuums and NDVI (R²=0.33), while water potential was related only to 1200 nm (R²=0.40). Our results demonstrate a critical link between plant physiological characteristics tied to water stress and associated spectral signatures for two extensive co-occurring conifer species.     

Implementation of an object oriented data model in an information system for water catchment management: Java JDO and Db4o Object Database

Object-oriented technologies are playing increasingly important roles in every level of software application for water resource management and modelling, except for data management levels where the relational logic is still the uncontested choice of information system developers despite the object–relational impedance mismatch. In this paper, we would like to present our experience concerning two different technologies for developing the object-oriented data management layer in information systems for water resources management: (i) the Java solution to obtain transparent persistence, the Java Data Object (JDO) technology; (ii) a purer object solution with a light open source Object Database, Db4o. The process for implementing the two technologies in a Java-based hydro-information system is described, and the two different solutions were analysed and compared.     

Indices for the evaluation of neural network performance as classifier: Application to structural elucidation in infrared spectroscopy

An application of Artificial Neural Networks (ANN) to the substructure detection, from infrared spectra, of organic compounds is described. Several ANNs have already been implemented for this purpose, and show promising initial results; however, many problems remain to be resolved. We wished to train ANNs to assist in a decision support system using several spectroscopic methods to elucidate the structure of unknown molecules. To optimise the ANN with respect to spectral feature extraction, network architecture, training regime and threshold determination, we have investigated several indices for use in the evaluation of network performance. Since much published work on ANN application in this field present performance indices that are poorly defined or of limited use, we recommend that the basic results be reported so that readers may calculate indices to suit their own particular needs. These basic quantities are identified and a set of derived indices recommended.     

SODA: A new method of in-scene atmospheric water vapor estimation and post-flight spectral recalibration for hyperspectral sensors: Application to the HyMap sensor at two locations

A new method of estimating per-pixel atmospheric column water vapor (ACWV) and potential differences in the reported band center wavelengths of the HyMap sensor has been developed. The new method uses variations of a second order derivative algorithm (SODA) to assess the impact of atmospheric residual features on calculated surface reflectance spectra after atmospheric compensation. The SODA method provides an alternative to the current band ratio techniques of ACWV estimation and also allows the same form of algorithm to be used for the estimation of possible band shifts. A comparison of in-situ measured surface reflectance at two field sites in Western Australia demonstrates improvement in the resulting spectra when post-flight updates are made to the reported HyMap band center wavelengths and applied during the atmospheric compensation process. The same SODA methodology was varied to estimate the ACWV on a per-pixel basis and found to significantly reduce the appearance of the underlying surface structure on the resulting ACWV images as well as improve the overall accuracy of the estimation. The ACWV estimated from the HyMap imagery at the two field sites was found to agree with in-situ atmospheric ACWV measurements to within 2% and represented a two fold increase in accuracy over a 3 band ratio Continuum Interpolated Band Ratio (CIBR) technique of ACWV estimation.