Estimation of evapotranspiration by the Food and Agricultural Organization of the United Nations (FAO) Penman–Monteith temperature (PMT) and Hargreaves–Samani (HS) models under temporal and spatial criteria – a case study in Duero basin (Spain)

The evapotranspiration-based scheduling method is the most common method for irrigation programming in agriculture. There is no doubt that the estimation of the reference evapotranspiration (ETo) is a key factor in irrigated agriculture. However, the high cost and maintenance of agrometeorological stations and high number of sensors required to estimate it make it non-plausible, especially in rural areas. For this reason, the estimation of ETo using air temperature, in places where wind speed, solar radiation and air humidity data are not readily available, is particularly attractive. A daily data record of 49 stations distributed over Duero basin (Spain), for the period 2000–2018, was used for estimation of ETo based on seven models against Penman–Monteith (PM) FAO 56 (FAO – Food and Agricultural Organization of the United Nations) from a temporal (annual or seasonal) and spatial perspective. Two Hargreaves–Samani (HS) models, with and without calibration, and five Penman–Monteith temperature (PMT) models were used in this study. The results show that the models' performance changes considerably, depending on whether the scale is annual or seasonal. The performance of the seven models was acceptable from an annual perspective (R2>0.91, NSE > 0.88, MAE < 0.52 and RMSE < 0.69 mm d−1; NSE – Nash–Sutcliffe model efficiency; MAE – mean absolute error; RMSE – root-mean-square error). For winter, no model showed good performance. In the rest of the seasons, the models with the best performance were the following three models: PMTCUH (Penman–Monteith temperature with calibration of Hargreaves empirical coefficient – kRS, average monthly value of wind speed, and average monthly value of maximum and minimum relative humidity), HSC (Hargreaves–Samani with calibration of kRS) and PMTOUH (Penman–Monteith temperature without calibration of kRS, average monthly value of wind speed and average monthly value of maximum and minimum relative humidity). The HSC model presents a calibration of the Hargreaves empirical coefficient (kRS). In the PMTCUH model, kRS was calibrated and average monthly values were used for wind speed and maximum and minimum relative humidity. Finally, the PMTOUH model is like the PMTCUH model except that kRS was not calibrated. These results are very useful for adopting appropriate measures for efficient water management, especially in the intensive agriculture in semi-arid zones, under the limitation of agrometeorological data.

PERBANDINGAN NILAI PERCEPATAN TANAH MAKSIMUM BERDASARKAN MODIFIKASI KONSTANTA ATENUASI DAN DATA ACCELEROGRAPH TAHUN 2008-2016 PADA STASIUN BMKG LAMPUNG

Peak ground acceleration is one of the parameters used in estimating the extent of breakdown caused by earthquake shocks. In the present study, the determination of an attenuation empirical formula PGA (Peak Ground Acceleration) based on the attenuation equation Lin and Wu (2010). Data used in the study of seismic event data by period year 2008-2012. Through the calculation of regression analysis, then obtained the function attenuation of peak ground acceleration in Lampung region at each station accelerograph.At the LWLI accelerograph station obtained the value of the empirical coefficient of the distance of earthquake -2.351, the empirical coefficient of earthquake magnitude 0,574, and the constant 2,430. At the KASI accelerograph station obtained the value of the empirical coefficient of the distance of earthquake -2.522, the empirical coefficient of earthquake magnitude 0.654, and the constant 2.182. At the BLSI accelerograph station obtained the value of the empirical coefficient from the distance of earthquake -3.224, the empirical coefficient of earthquake magnitude 0.651, and constant 4,092. At the KLI accelerograph station obtained the value of the empirical coefficient from the distance of earthquake -2.746, the empirical coefficient of earthquake magnitude 0.751, and the constant 2.053.Result of correlation test verification, chart relation between distance and magnitude earthquakes, ratio PGA contour maps, as well as a ratio between the value of PGA models with the observation of accelerograph year 2013-2016 show that the acceleration attenuation function of the obtained soil is relatively good. Based on PGA attenuation contour map model at an event the earthquake on 28th May 2011, PGA great value be found in the Liwa region with a PGA score of 10-20 gal and its seismic intensity value is V-VI MMI. It happens because of the source the earthquake is in the western sea of Liwa.

Development of mathematical model and computer program for primary design of transonic axial compressor

The mathematical model underlying the program for calculating and designing axial compressors is presented. The process of calculating the pressure loss in the elements of the axial compressor stage flow path is described. The loss coefficient consists of losses on the limiting surfaces, secondary losses and profile losses. The effect of roughness on the pressure loss is taken into account by introducing the corresponding empirical coefficient. An algorithm for calculating the blades and vanes angles of the impeller and the guide apparatus is presented by calculating the incidence angle and the lag angle of the flow. The flow lag angle is the sum of the lag angle of the flow on the profile and the lag angle due to viscous flow on the limiting surfaces

Mathematical model of the 9th version Universal modeling method: features and results of identification

The Universal modeling method is a complex of computer programs for calculating the characteristics and optimal design of centrifugal compressors based on mathematical models of efficiency and head. Practical experience allows improving the mathematical models that underlie the Method. Determining the non-incidence inlet in a blade cascade is an important part of calculating the compressor gasdynamic characteristics. In the 8th version of the Universal modeling method, a formula is used to calculate the direction of the critical stream line, containing an empirical coefficient X. The practice of application has shown that the value of the empirical coefficient changes the amount of losses in the impeller in off-design flow rates. A new scheme for modeling velocity diagrams is proposed. It is made for the stage operation mode corresponding to the zero incidence angle. The successful use of the model for the impeller made it possible to extend it to the vane diffuser and return channel. Several other improvements are made too. A new mathematical model is developed for calculating the flow parameters in the exit nozzles of centrifugal compressor stage. The mathematical model for calculating the flow parameters in the vaneless diffusers is modernized. The applicability boundary of the new model is expanded to a range of diffusers of low consumption stages with a relative width of up to 0,006. The resulting mathematical model is identified by the test results of two family model stages and plant tests of industrial compressors

Vibration Reliability Evaluation of Main Fan Spindle Bearings

Based on an analysis of failure causes, the axial force is the main reason why spindle bearings vibrate abnormally and cause frequent failures of the main fans in mines. In this paper, the probability density function of the spindle bearing vibration was established through the bootstrap maximum entropy method, the Lagrangian multiplier and the empirical coefficient were introduced, and models of the upper- and lower-bound functions of the probability density and the true value function of the failure probability were established. The true value function and interval estimation values of vibration reliability were obtained on the basis of maximum entropy. The analysis results showed that the estimation true values of vibration decreased with an increase in the empirical coefficient. When the empirical coefficient was less than 0.1, the estimated true value decreased sharply. When the empirical coefficient was greater than 0.1, the vibration value decreased linearly with the empirical coefficient. When the empirical coefficient was 0.1, the estimated true value was 0.85 mm/s2, which is consistent with the change in the actual vibration value. Therefore, when the main fan is fault predicted, the vibration value should be 0.85 mm/s2 as the basis for judgment and then the theoretical basis for the fault diagnosis of the spindle bearing are provided.

An Introduction to the Hyperspace of Hargreaves-Samani Reference Evapotranspiration

Climate change has been shown to directly influence evapotranspiration, which is one of the crucial watershed processes. The common approach to its calculation is via mathematical equations, such as 1985 Hargreaves-Samani (HS85). It computes reference evapotranspiration (ETo) through three climatic variables and one constant: RA (extra-terrestrial radiation), TC (mean temperature), TR (temperature range) and KR (empirical coefficient). To make HS85 more accurate, one of its authors proposed an equation for KR as a function of TR in 2000 (HS00). Both models are 4D and their internal behaviours are difficult to understand, hence, the data driven applications prevalent among experts and managers. In this study, we introduce an innovative research by trying to respond to two questions. What are the relationships between TC and TR? What are the internal patterns of HS hyperspace (4D domain) and the changes in ETo possibilities of the two models? In the proposed approach, thresholds for the four variables are utilized to cover majority of the agroclimatic situations in the world and the hyperspace is discretized with more than 50,000 calculation nodes. The ETo results show that under various climatic conditions, the behaviour of HS is nonlinear (more for HS00) leading to an increased uncertainty particularly for data driven applications. TC and TR show patterns useful for regions with less data.

AJUSTE DA EQUAÇÃO DE HARGREAVES E SAMANI A PARTIR DE DADOS LISIMÉTRICOS PARA O MUNICÍPIO DE JUAZEIRO-BA

AJUSTE DA EQUAÇÃO DE HARGREAVES E SAMANI A PARTIR DE DADOS LISIMÉTRICOS PARA O MUNICÍPIO DE JUAZEIRO-BA EDGO JACKSON PINTO SANTIAGO¹; VINÍCIUS EVANGELISTA ALVES OLIVEIRA²; RODRIGO RAFAEL DA SILVA³; IRIS SANTANA GONÇALVES4 E GERTRUDES MACÁRIO DE OLIVEIRA5 1 Mestrando, PPHI, Depto de Tecnologia e Ciências Sociais, UNEB, Juazeiro, BA. Av. Edgard Chastinet, SN, São Geraldo, 48900-000, Juazeiro, BA. Fone (74)36117248. Email: [email protected] Mestrando, PPHI, Depto de Tecnologia e Ciências Sociais, UNEB, Juazeiro, BA.3 Bolsista PIBIC, Graduando Eng. Agronômica, Depto de Tecnologia e Ciências Sociais, UNEB, Juazeiro, BA.4 Bolsista FAPESB, Graduanda Eng. Agronômica, Depto de Tecnologia e Ciências Sociais, UNEB, Juazeiro, BA.5 Doutora, Professora, Depto de Tecnologia e Ciências Sociais, UNEB, Juazeiro, BA. 1 RESUMO O conhecimento preciso da evapotranspiração é fundamental para um manejo eficiente da irrigação; e para medida direta da mesma, são utilizados tanques lisimétricos. Entretanto, diante da dificuldade de instalação e operação desses instrumentos, recorre-se a estimativas, e entre os métodos de estimativas, destacam-se os métodos empíricos, difundidos e largamente utilizados por sua simplicidade. O objetivo deste trabalho foi calibrar a equação de Hargreaves e Samani, como base em dados lisimétricos. Foram utilizados dados diários de evapotranspiração da grama e temperatura do ar referente ao período de 2007 a 2015. O ajuste dos coeficientes empíricos da equação de Hargreaves e Samani foi realizado por meio de regressão linear. Para análise comparativa foi utilizado coeficiente de desempenho (c) proposto por Camargo e Sentelhas. Obteve-se para os parâmetros α e β os respectivos valores: 0,0018 e 0,38; valores inferiores aos parâmetros originais. A utilização da equação de Hargreaves e Samani parametrizada com base em dados lisimétricos apresentou desempenho ruim para as condições climáticas de Juazeiro, BA. PALAVRAS-CHAVE: evapotranspiração; temperatura; manejo da irrigação. SANTIAGO, E. J. P.; OLIVEIRA, V. E. A.; SILVA, R. R. da; GONÇALVES, I. S.; OLIVEIRA, G. M. deADJUSTING THE HARGREAVES AND SAMANI EQUATION TO THE LYSIMETER DATA FROM THE JUAZEIRO-BAHIA MUNICIPALITY 2 ABSTRACT The precise knowledge of evapotranspiration is essential for the efficient irrigation management; and for the direct measurement thereof, lysimeter tanks are used. However, given the difficulty involving the installation and operation of these instruments, the Group uses estimates and different methods for estimating the stand-empirical methods, disseminated and widely used for its simplicity. The objective of this study was to calibrate the Hargreaves & Samani equation, based on lysimeter data. We used daily data of evapotranspiration of grass and air temperature related to the period from 2007 to 2015. The adjustment of the empirical coefficient of the Hargreaves & Samani equation was performed by linear regression. For a comparative analysis, the coefficient of performance ''c'' proposed by Camargo & Sentelhas was utilized. The respective values were obtained for parameters α and β: 0.0018 to 0.38, which are lower values than the original parameters. Using the Hargreaves & Samani parameterized equation based on lysimeter data showed a poor performance for the climatic conditions of Juazeiro, BA. Keywords: evapotranspiration; Temperature; irrigation management.

On the influence of overconsolidation effect on the compressibility assessment of subsoil by means of CPTU and DMT

The paper contains the analysis of the influence of overconsolidation effect on the values of constrained moduli, assumed by means of two most popular in situ advanced tests. The tested soils included two geological formations: normally consolidated tills of the Pomeranian phase and overconsolidated tills of the Posnanian phase. The overconsolidation ratio (OCR) was derived from CPTU, DMT and oedometric tests. The tests revealed that for the assessment of changes in constrained modulus in the subsoil with CPTU and DMT, the formulas determining the relationship between cone resistance, DMT results and constrained moduli requires empirical coefficient different for soils of varied genesis.

Determining the susceptibility of soils materials to erosion by rain-impacted flows

Conceptually, rain has a capacity to cause erosion (rainfall erosivity) and soils have a susceptibility to erosion by rainfall (soil erodibility) but no absolute measure of rainfall erosivity exists. Consequently, soil erodibility is nothing more than an empirical coefficient in the relationship between an index of rainfall erosivity and soil loss. Erosion by rain-impacted flow is influenced by the size, velocity and impact frequency of the raindrops but also flow depth and velocity. Experiments with artificial rainfall falling on sloping surfaces in the field usually do not enable flow depth and velocity to be well measured or controlled. Also, sprays produce artificial rainfall where the spatial uniformity in rainfall intensity, drop size and frequency is often less than desirable. Artificial rainfall produced by pendant drop formers can produce rainfall that has better spatial uniformity. Equipment for controlling flow depth and velocity over eroding surfaces has been developed and used to calibrate the effect of flow depth on the discharge of sediment by rain-impacted flow using artificial rainfall having a uniform drop-size distribution under laboratory conditions. Once calibrated, laboratory experiments can be conducted to rank soils according to their susceptibility to erosion under the flows impacted by the artificial rainfall under conditions where the erosive stress applied to the eroding surface is well controlled.