Improved Spring Vegetation Phenology Calculation Method Using a Coupled Model and Anomalous Point Detection

High temporal resolution remote sensing satellite data can be used to collect vegetation phenology observations over regional and global scales. Logistic and polynomial functions are the most widely used methods for fitting time series normalized difference vegetation index (NDVI) derived from the Moderate Resolution Imaging Spectroradiometer (MODIS). Furthermore, the maximum in the curvature of the fitted curve is usually considered as the spring green-up date. However, the existing green-up date calculation methods have low accuracy for sparse vegetation. This paper proposes an improved green-up date calculation method using a coupled model and anomalous point detection (CMAPD). This model is based on a combination of logistic and polynomial functions, which is used to fit time series vegetation index. Anomalous values were identified using the nearest neighbor algorithm, and these values were corrected by the combination of growing degree-days (GDD) and land use type. Then, the trends and spatial patterns of green-up date was analyzed in the Sanjiangyuan area. The results show that the coupled model fit the time series data better than a single logistic or polynomial function. Besides, the anomalous point detection method properly controlled the green-up date within the local threshold, and could reflect green-up date more accurately. In addition, a weak statistically significant advance trend for average vegetation green-up date was observed from 2000 to 2016. However, in 10.4% of the study area, the the green-up date has significant advanced. Regression analysis showed that the green-up date is correlated to elevation: the green-up date is clearly later at higher elevations.

Quality indices of groundwater for agricultural use in the Soconusco, Chiapas, Mexico

In Soconusco, Chiapas, in spite of the high availability of surface water, it is resorting to the use of groundwater. Knowledge about the quality of surface or groundwater used to irrigate crops in that region is low. This paper aims to contribute to the knowledge of the quality of groundwater for agricultural use through the characterization of the spatial variability. Assuming a random spatial distribution of 45 samples which were collected in situ were determined: acidity and alkalinity (pH), electrical conductivity (EC), Total Dissolved Solids (TDS), cations and anions and trace elements; in addition to the agricultural index: Sodium Adsorption Ratio (SAR), Residual Sodium Carbonate (RSC), Soluble Sodium Percentage (SSP), Sodium Percentage (% Na), Kelly Ratio (KR), Magnesium Adsorption Ratio (MAR), Permeability Index (PI), Effective Salinity (ES), Salinity Potential (SP) and Osmotic Potential (OP). In general, SSP, % Na, KR, PI are low, there is only one anomalous point (9) with high values at W of the study area. Similarly, PS, ES, Cl, Na and SAR are low except point 16 and conversely, RSC and pH are high, except at this point located in the center of the study area. The results allow us to infer that the water in that aquifer presents no problems or sodicity toxic ions. In 27 sites sampled values above 250 µmhos/cm were found at 25°C, classified as medium to high risk of salinity, unsuitable for agricultural use. Analysis of the combined effect of the presence of sodium (SAR) and salinity (EC or TDS) shows that 27 of analyzing sites have restricted water medium at very high for use in irrigation.

Application and Research of Geologic Radar in Groundwater Disease of Tunnel Engineering Inspection

In order to diagnose the disease degree of operation tunnels and to estimate tunnel's security condition, this paper analyzes the causes of bugs existing behind the tunnel lining, expounds the theory and method of making non-destructive test on tunnel lining quality by using Geological Radar. By processing and analyzing field data, the following functions can be performed, such as detecting the thickness of concrete lining accurately, determining the distribution position and quantities of rebar and grid steel, searching existed cavity and uncompacted area behind the lining especially lining arch top. We also apply the method of morphology to the extraction of liner image feature. We get the liner boundary line and waterlogging area more intuitively by wavelet analysis, and find the anomalous point in the liner. It has been proved that Geologic Radar is a feasible method to inspect the structure of tunnel concrete lining. A dopting hole-drilling method to make verifications with detecting results of geological radar, the results of the two kinds of methods have not big difference.

Anomalous Change of the Viscosity and the Structure of Sn Melt with Temperature

On the basis of measuring the viscosity of Sn melt and referring to analysis of high temperature XRD, the change of viscosity and structure for Sn melt with temperature were carried out. The results show that there is discontinuous change of viscosity for Sn melt with the temperature. The state of Sn melt are divided into high, middle and low-temperature region according to the change of viscosity, and there is an anomalous point of viscosity change between different temperature region. There is a correlation between the viscosity change of and the structure change of Sn melt. The coordination number and correlation radius, and the fluid cluster size of Sn melt decrease with the increase of temperature, so that the viscosity of Sn melt decrease. But there is an anomalous change in the vicinity 673 K and 1073 K, it results in discontinuous change in viscosity of Sn melt.

Resistivity-Temperature Feature of Ga36.5Sb63.5 Melt

In the present work, the resistivity of Ga36.5Sb63.5 alloy during cooling process was studied by the method of DC Four electrodes . The result of the experiment showed that there is an anomalous point at 710°C－735°C on the resistivity-temperature curve of Ga36.5Sb63.5 melt. At the same time, The relevance of the resistivity and the liquid structure of the alloy was analyzed. The physical properties of Ga36.5Sb63.5 alloy melt was discussed.