11351 research outputs found
Sort by
Temperature and probe-to-probe variability effects on the performance of capacitance soil moisture sensors in an oxisol
No full textReliable and accurate monitoring of soil water content (θ) across the landscape is indispensable for many water resources applications. Capacitance-based in situ soil water content measuring devices are extensively used despite their sensitivity to soil properties besides water content, e.g., temperature and organic matter content. The main goals of this study were to: (i) examine the effects of temperature, hysteresis of the temperature response, and probe-to-probe variability on the performance of three (5TE, EC-5, and EC-TM) single capacitance sensors (SCS) in a Hawaiian Oxisol; and (ii) develop empirical calibration equations to correct for temperature and improve measurement accuracy. The SCS raw output and thermocouple temperature measurements were recorded at 1-min intervals during heating and cooling cycles between 1 and 45°C. The three SCS and thermocouples were inserted in uniformly packed soils with θ varying from 0 to 0.55 m3 m−3. We used three probes for each SCS, and the entire experiment was replicated with two heating and cooling cycles. Temperature, hysteresis, and the probe-to-probe variability effects were highly significant (p \u3c 0.05) for all three SCS. Estimated θ using soil-specific calibrations at 25°C significantly increased with increasing temperature for all SCS. The 5TE sensor showed increasing temperature sensitivity with increasing water content. However, the EC-5 and EC-TM sensors exhibited a bidirectional response to temperature, with the highest sensitivity at ~0.10 m3 m−3 water content. An empirically derived temperature-dependent calibration equation substantially reduced the variability (\u3e90% reduction in interquartile range) in measured water content due to changing soil temperature. Applying differing temperature corrections for heating and cooling did not improve the calibration any further
Analysis of Groundwater Contaminants Using Aris Dispersion Model
Get PDFThe paper presents the study of dispersion of contaminants in unsteady laminar flow of an incompressible fluid (groundwater) bounded by an upper porous layer and lower impermeable layer with interphase mass transfer. An analytical solution of unsteady advection dispersion based on Aris-Barton method of moments is presented up to the second moment about the mean in axial direction
A Web Application For Studying Collusion Attacks Through Friend Search Engine
No full textA large number of applications have been developed by Online Social Networks (OSNs) to entertain and serve their users, for instance, friend search engine. However, less attention has been paid to the possible privacy breaches against friend search engines. In this paper, we discuss the design and implementation of our web application which is intended to collect real-world attack data for studying such breaches
Healthy Houston Initiative College Of Agriculture And Human Sciences - 2016
Get PDFhttps://digitalcommons.pvamu.edu/pv-magazine/1009/thumbnail.jp
Panther - March 2016 - Vol. XCVI, No. 13
Get PDFhttps://digitalcommons.pvamu.edu/pv-panther-newspapers/1923/thumbnail.jp
Measurement Error Estimation Methods in Survey Methodology
Get PDFOne of the most important topics that are discussed in survey methodology is the accuracy of statistics or survey errors that may occur in the parameters estimation process. In statistical literature, these errors are grouped into two main categories: sampling errors and non-sampling errors. Measurement error is one of the most important non-sampling errors. Since estimating of measurement error is more complex than other types of survey errors, much more research has been done on ways of preventing or dealing with this error. The main problem associated with measurement error is the difficulty to measure or estimate this error in surveys. Various methods can be used for estimating measurement error in surveys, but the most appropriate method in each survey should be adopted according to the method of calculating statistics and the survey conditions. This paper considering some practical experiences in calculating and evaluating surveys results, intends to help statisticians to adopt an appropriate method for estimating measurement error. So to achieve this aim, after reviewing the concept and sources of measurement error, some methods of estimating the error are revised in this paper. Also, the advantages and disadvantages of measurement error estimation methods are discussed and some examples of estimating methods using surveys real data are shown in this paper. It should be noted that if estimating the measurement error with an acceptable accuracy is impossible in practice, it should be ensured based on statistical methods that this error does not have a large value or any increasing trend over time
Approximate Analytical Solution of Boussinesq Equation in Homogeneous Medium with Leaky Base
Get PDFApproximate analytical solutions of Boussinesq equation are widely used for approximation of subsurface seepage flow in confined and unconfined aquifers under varying hydrological conditions. In this paper, we use a 2-dimensional linearized Boussinesq equation to simulate the water table fluctuations in an isotropic aquifer overlying a semi pervious bed under multiple localized recharge and withdrawal. The unconfined aquifer is considered to be in contact with two water bodies of constant water head along opposite cost lines, while the remaining two faces have no flow condition. The mathematical model is solved analytically using finite Fourier sine transform and the application of the results is illustrated with a numerical example. It is observed that the vertical flow through the base of the aquifer is an important factor in the determination of groundwater mound and cone of depression
LRS Bianchi Type-II Cosmological Model with String Bulk Viscous Fluid and Magnetic Field in Barber’s Second Self Creation Theory
Get PDFWe present a solution of LRS Bianchi type-II space-time with string viscous fluid and magnetic field by solving the Barber’s field equations of self-creation theory of gravitation and it is seen that Barber scalar function affects the other physical parameters of the model and contributes a very high matter density, with high particle density at early stage of the universe and also it contributes the negative role of bulk viscous fluid in the evolution. Other geometrical and physical aspects of the model are also studied