11351 research outputs found
Sort by
Potential impact of climate change on irrigation water requirements for some major crops in the northern high plains of Texas
No full textFuture irrigation water requirements (IWRs) for different crops will be affected by the variation of rainfall and evapotranspiration that are projected to be impacted by future climate change. Thus, there is a need to investigate the potential impact of climate change and increasing climate extremes on the sustainability of agricultural production systems. The main goal of this study is to analyze the potential impact of climate change on IWRs for four major crops (corn, cotton, sorghum and winter wheat) in the Northern High Plains of Texas (NHPT). Specific objectives are to (i) generate and analyze projected daily climate data based on different Global Climate Models (GCMs) and (ii) assess the potential impact of climate change on IWRs and other water balance components of four major crops. Daily gridded climate data from the National Center for Environmental Prediction (NCEP) Climate Forecast System Reanalysis (CFSR) for the 1981 to 2010 period were used to represent observed historical daily climate data. We applied the statistical downscaling model Long Ashton Research Station Weather Generator (LARS-WG) to generate projected daily climate data at each grid cell (approximately 38 × 38 km) within the study region. The climate data for three future periods, that is, the 2020s, 2050s, and 2090s, were generated using outputs from 15 GCMs under three emission scenarios (B1, A1B, and A2). The hydrologic parameters of the major soil types in the study region were derived from the Soil Survey Geographic Database (SSURGO). Irrigation water requirements and major water budget components for all grid cells were calculated using the Irrigation Management System (IManSys) model based on crop specific growth parameters, site-specific soil hydrological properties, irrigation system efficiency, and long-term daily climate data (current and future climate scenarios). Monthly temperature and reference evapotranspiration were projected to increase; however, annual precipitation was expected to decrease in the future projection periods. Thus, gross irrigation requirements (GIRs) of all four crops, with an irrigation system efficiency of 75%, were assumed to increase (2.08-3.77% in the 2020s, 6.23-9.25% in 2055s and 6.81-19.52% in 2090s), threatening the possibility of serious groundwater depletion and long-term sustainable agriculture in this region. Further work is needed to predict crop yield responses to potential climate change scenarios for these different future periods
Optimum turf grass irrigation requirements and corresponding water- energy-CO2 Nexus across Harris County, Texas
No full textHarris County is one of the most populated counties in the United States. About 30% of domestic water use in the U.S. is for outdoor activities, especially landscape irrigation and gardening. Optimum landscape and garden irrigation contributes to substantial water and energy savings and a substantial reduction of CO2 emissions into the atmosphere. Thus, the objectives of this work are to (i) calculate site-specific turf grass irrigation water requirements across Harris County and (ii) calculate CO2 emission reductions and water and energy savings across the county if optimum turf grass irrigation is adopted. The Irrigation Management System was used with site-specific soil hydrological data, turf crop water uptake parameters (root distribution and crop coefficient), and long-term daily rainfall and reference evapotranspiration to calculate irrigation water demand across Harris County. The Irrigation Management System outputs include irrigation requirements, runoff, and drainage below the root system. Savings in turf irrigation requirements and energy and their corresponding reduction in CO2 emission were calculated. Irrigation water requirements decreased moving across the county from its north-west to its south-east corners. However, the opposite happened for the runoff and excess drainage below the rootzone. The main reason for this variability is the combined effect of rainfall, reference evapotranspiration, and soil types. Based on the result, if the average annual irrigation water use across the county is 25 mm higher than the optimum level, this will result in 10.45 million m3 of water losses (equivalent water use for 30,561 single families), 4413 MWh excess energy use, and the emission of 2599 metric tons of CO2
Optimal Inequalities for Submanifolds of an Indefinite Space Form
Get PDFOptimal inequalities involving the scalar curvature, the mean curvature vector and the second fundamental form for pseudo Riemannian submanifolds are proved and the equality cases of these inequalities are discussed. These results are studied for submanifolds of various indefinite contact space forms
Analysis of M[X1],M[X2]/G1,G2/1 retrial queueing system with priority services, working breakdown, collision, Bernoulli vacation, immediate feedback, starting failure and repair
Get PDFThis paper considers an M[X1] , M[X2] /G1,G2/1 general retrial queueing system with priority services. Two types of customers from different classes arrive at the system in different independent compound Poisson processes. The server follows the non-pre-emptive priority rule subject to working breakdown, Bernoulli vacation, starting failure, immediate feedback, collision and repair. After completing each service, the server may go for a vacation or remain idle in the system. The priority customers who find the server busy are queued in the system. If a low-priority customer finds the server busy, he is routed to orbit that attempts to get the service. The system may become defective at any point of time while in operation. However, when the system becomes defective, instead of stopping service completely, the service is continued to the interrupted customer only at a slower rate. Using the supplementary variable technique, the joint distribution of the server state and the number of customers in the queue are derived. Finally, some performance measures are obtained
Transient analysis of a Markovian Single Vacation Feedback Queue with an Interrupted Closedown Time and Control of Admission During Vacation
Get PDFThis paper analyzes the transient behavior of an M/M/1 queueing model with single vacation, feedback, interrupted closedown time and control of admission during vacation. The time-dependent system size probabilities for the proposed model are obtained using generating function in the closed form. Further, the system performance measures like mean and variance of system size are also obtained for the time-dependent case. Finally, numerical illustrations are presented to understand the effect for various system parameters
Unified Ball Convergence of Inexact Methods For Finding Zeros with Multiplicity
Get PDFWe present an extended ball convergence of inexact methods for approximating a zero of a nonlinear equation with multiplicity m; where m is a natural number. Many popular methods are special cases of the inexact method
Spectral tau-Jacobi algorithm for space fractional advection-dispersion problem
Get PDFIn this paper, we use the shifted Jacobi polynomials to approximate the solution of the space fractional advection-dispersion. The method is based on the Jacobi operational matrices of fractional derivative and integration. A double shifted Jacobi expansion is used as an approximating polynomial. We apply this method to solve linear and nonlinear term FDEs by using initial and boundary conditions
A Simulation Study on the Size and Power Properties of Some Ridge Regression Tests
Get PDFRidge regression techniques have been extensively used to solve the multicollinearity problem for both linear and non-linear regression models since its inception. This paper studied different ridge regression t-type tests of the individual coefficients of a linear regression model. A simulation study has been conducted to evaluate the performance of the proposed tests with respect to their sizes and powers under different settings of the linear regression model. Our simulation results demonstrated that most of the proposed tests have sizes close to the 5% nominal level and all tests except tAKS, tkM2 and tkM9 have considerable gain in powers over the ordinary OLS t-type test. It is also observed that some of the proposed test statistics are performing better than the HK and HKB tests which are proposed some authors
Non-Standard Finite Difference Schemes for Investigating Stability of a Mathematical Model of Virus Therapy for Cancer
Get PDFIn this paper, a special case of finite difference method called non-standard finite difference (NSFD) method was studied to compute the numerical solutions of the nonlinear mathematical model of the interaction between tumor cells and oncolytic viruses. The global stability of the equilibrium points of the discrete model is investigated by using the Lyapunov stability theorem. Some conditions were gained for the local asymptotical stability of the equilibrium points of the system. Finally, numerical simulations are carried out to illustrate the main theoretical results. The discrete system is dynamically consistent with its continuous model, it preserves essential properties, such as positivity, boundedness of the solution, stability properties of the equilibrium points
Bifurcation Analysis for Prey-Predator Model with Holling Type III Functional Response Incorporating Prey Refuge
Get PDFIn this paper, we carried out the bifurcation analysis for a Lotka-Volterra prey-predator model with Holling type III functional response incorporating prey refuge protecting a constant proportion of the preys. We study the local bifurcation considering the refuge constant as a parameter. From the center manifold equation, we establish a transcritical bifurcation for the boundary equilibrium. In addition, we prove the occurrence of Hopf bifurcation for the homogeneous equilibrium. Moreover, we give the radius and period of the unique limit cycle for our syste