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Copyright of Journal of Irrigation & Drainage is the property of Journal of Irrigation & Drainage Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Anhui Agricultural Sciences is the property of Journal of Anhui Agricultural Sciences Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Irrigation & Drainage is the property of Journal of Irrigation & Drainage Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Dew formation and its influence on soil water content are an important basis for next-level quantification of water cycling and eco-hydrological processes. To reveal the dew formation process, over a consecutive 3-year period, we monitored meteorological parameters and soil water content in the top layer at 30-minute recording intervals in the Central Ningxia Province arid belt. The dew amount was measured using a leaf wetness sensor. Annual dew yield in this region reached 56.41 mm, 75% of which occurred from June to October. Maximum monthly and maximum daily dew were 13.40 mm and 0.80 mm, respectively, and mainly occurred in the early morning from 03:00 to 08:00 am. Meteorological parameters responsible for dew formation were: air temperature between 0—24.4 ℃, relative humidity between 50%—100%, wind speed between 0.16—1.74 m/s, and wind direction between 30—60 degrees and 270—330 degrees. There was a very significant and highly correlated linear and inverse relationship between relative humidity and the difference between air temperature and dewpoint. When the difference was < 3 ℃ and the corresponding humidity > 80%, dew formation was much more likely. When daily dew reached 0.6 mm, 0.7 mm and 0.8 mm, soil water storage in the top 5cm soil increased by 0.10 mm, 0.20 mm and 0.25 mm, respectively. Annual dewfall was 13.5% of the rainfall, and the annual frequency of dew occurrence was 126 days (35%), indicating that dew is a significant water source for local water and ecosystem cycling. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Irrigation & Drainage is the property of Journal of Irrigation & Drainage Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

An ecological irrigation district has emerged as the modern management with healthy ecosystems in precision agriculture. A health assessment of irrigation districts has been one of the most important operations for the decision-making on agricultural water management and pollution. In this study, a novel health evaluation was made on the ecological irrigation district using multisource data. A study area was selected as a part of the Yellow River basin, located at Helan County in Ningxia, China. A knowledge mapping was also applied to systematically sort out the index systems of comprehensive evaluation on the irrigation districts using a VOSviewer platform. The key indicators were then screened with a high co-occurrence frequency. An indicator system was constructed for the comprehensive evaluation of the ecological irrigation districts. Five categories of the primary indicators were divided in the indicator system, including the ecological environment (B1), the modernization of water transmission and distribution (B2), and the modernization of field engineering (B3), the modernization of production and management (B4), and production efficiency (B5). There was also 18 second-grade indicators in total. All indicators were classified into one to four levels of health. With the support of GIS, these indicators were quantified by combining the remote sensing data (LandSat8, MODIS) with research statistics and field trial data. The weight of each indicator was confirmed through Analytic Hierarchy Process (AHP). The evaluation data was divided by the scale of townships, where each administrative division was used as an evaluation unit. Finally, a fuzzy evaluation model was used to implement the comprehensive evaluation on the health level of the ecological irrigation district in the study area. The results show that there were large differences in the indicator B1 among the evaluation units, especially from the indicator of watershed area (C13) and the indicator of water quality in the main drainage ditches (C14), indicating a higher weight. At the same time, the degree of aridity (vegetation index VSWI) (C16) indicated a great potential to save water in the study area. Therefore, it was still encouraged to develop water-saving irrigation. More importantly, there were small differences in the indicators of B2, B3, B4, and B5 among the evaluation units, indicating the consistent upgrading of irrigation districts. Consequently, the highest value of health level (0.81) was found in Nanliangtaizi and Jingxing Farm, whereas, the lowest value was in Hongguang Town (0.69), where all evaluation units were in the range of health level 3 to 2. In addition, 0.325 of the irrigation districts were presented at the first level of health, whereas, 0.272 of the irrigation districts were at the second level, indicating an excellent operating condition. This study can provide a strong reference to efficiently construct the ecological irrigation districts in Northwest China. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Irrigation & Drainage is the property of Journal of Irrigation & Drainage Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Reverse Osmosis (RO) is one of the most advanced and effective membrane separation treatments in desalination. Forward Osmosis (FO) is also one type of membrane separation that can spontaneously draw the water from the RO concentrated water. However, the regeneration of draw solution requires much energy in the FO system. A Fertilizer-Drawn Forward Osmosis (FDFO) process is thus selected to reduce the energy consumption for the draw solution, where the fertilizer solution was used as the draw solution. The RO concentrated water is continuously concentrated, while the fertilizer draw solution is continuously diluted in the process of FDFO. The diluted fertilizer draw solution can widely be expected for the agricultural irrigation without regeneration. In this study, the influence factors of the forward water and reverse salt flux in the FO process were determined under the different type, concentration, and temperature of draw solution, as well as the concentration of feed solution. KCl, KNO3, NaNO3, NH4HCO3, (NH4)2SO4, and NH4Cl were selected as the draw solutions for the single factor comparison tests of FDFO. The results show that the forward water fluxes and reverse salt fluxes differed greatly with different kinds of draw solutions. The forward water fluxes of draw solutions were ranked in the order of KCl > NH4Cl > NaNO3 > NH4HCO3 > (NH4) 2SO4 > KNO3. The reverse salt flux was NaNO3 > NH4HCO3 > KNO3 > KCl > NH4Cl > (NH4)2SO4. The forward water flux of KCl and NH4Cl was the largest, while the reverse salt flux was smaller. Therefore, KCl and NH4Cl were more suitable for a single fertilizer draw solution. A FO test was carried out under the different concentration and temperature of KCl draw solution. The results showed that the forward water flux of KCl draw solution at 2 mol/L was 3.56 times than that of 0.5 mol/L, and the forward water flux of KCl draw solution at 55℃ was about twice than that of 25℃. Therefore, the forward water flux increased significantly, with the increase of the concentration and temperature of draw solution. However, there was no increase in the forward water flux and the reverse salt flux, when the concentration of draw solution increased exponentially. Additionally, the increased multiple of forward water and reverse salt flux was less than the draw solution concentration. Another FO test was also carried out under the various concentration and temperature of NaNO3 draw solution. The results showed that the reverse salt flux increased by 2.94 times, when the concentration of NaNO3 draw solution increased from 0.5 to 2 mol/L, while, the reverse salt flux increased by 1.64 times, when the temperature of NaNO3 draw solution increased from 25 to 55℃. Therefore, the reverse salt flux increased, with the increase of the concentration and temperature of draw solution. Furthermore, the temperature increased exponentially, so did the forward water flux. Since the RO concentrated and deionized water were selected as the feed solution in the FO experiment, it was found that the higher concentration of feed solution, but the smaller forward water flux. [ABSTRACT FROM AUTHOR]

The FAO-56 Penman-Monteith estimates that the ET0 method is widely used, but multiple meteorological data are required for calculation. Developing an alternative method that can provide accurate or at least close to the FAO-56 Penman-Monteith ET0 estimate is one of the research hotspots in the field with as little meteorological data as possible. In this paper, combined with Canonical Correlation Analysis (CCA) and k nearest neighbor algorithm (k-NN), the potential evapotranspiration calculation method (CCA-k-NN) of self-optimizing nearest neighbor algorithm is proposed, and the potential evapotranspiration is realized by using less meteorological data. Estimate. The core idea is to use the CCA algorithm to find the meteorological data most relevant to the potential evapotranspiration, to realize the dimensionality reduction of the meteorological data when the ET0 is estimated later, and then use the k-NN algorithm to estimate the ET0. The Northwest China region was selected as a use case. The regional meteorological data were divided into training dataset, verification dataset and test dataset from time and space scales. The ET0 was estimated by the method in the three types of datasets respectively, and the FAO-56 Penman-Monteith as a reference, evaluated the estimation accuracy and applicability of the CCA-k-NN method. The results show that the CCA-k-NN method has a high correlation with the FAO-56 Penman-Monteith (correlation coefficient greater than 0.9), and has good estimation accuracy. The root mean square error and Mean Absolute Error are both less than 1 mm·d-1. On the spatial scale, the Nash-Sutcliffe coefficient of efficiency is greater than 0.5, and the Nash-Sutcliffe coefficient of efficiency on the time scale is greater than 0.8, the CCA-k-NN method is applicable at both space and time scales. At the same time, compared with other alternative methods, the algorithm has low time complexity O(n), which can effectively reduce the time cost when calculating large amounts of data. The FAO-56 Penman-Monteith estimates that the ET0 method is widely used, but multiple meteorological data are required for calculation. Developing an alternative method that can provide accurate or at least close to the FAO-56 Penman-Monteith ET0 estimate is one of the research hotspots in the field with as little meteorological data as possible. In this paper, combined with Canonical Correlation Analysis (CCA) and k nearest neighbor algorithm (k-NN), the potential evapotranspiration calculation method (CCA-k-NN) of self-optimizing nearest neighbor algorithm is proposed, and the potential evapotranspiration is realized by using less meteorological data. Estimate. The core idea is to use the CCA algorithm to find the meteorological data most relevant to the potential evapotranspiration, to realize the dimensionality reduction of the meteorological data when the ET0 is estimated later, and then use the k-NN algorithm to estimate the ET0. The Northwest China region was selected as a use case. The regional meteorological data were divided into training dataset, verification dataset and test dataset from time and space scales. The ET0 was estimated by the method in the three types of datasets respectively, and the FAO-56 Penman-Monteith as a reference, evaluated the estimation accuracy and applicability of the CCA-k-NN method. The results show that the CCA-k-NN method has a high correlation with the FAO-56 Penman-Monteith (correlation coefficient greater than 0.9), and has good estimation accuracy. The root mean square error and Mean Absolute Error are both less than 1 mm·d-1. [ABSTRACT FROM AUTHOR]

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Drainage & Irrigation Machinery Engineering / Paiguan Jixie Gongcheng Xuebao is the property of Editorial Department of Drainage & Irrigation Machinery Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In order to solve the problems of zero discharge of reverse osmosis (RO) brine, the coupling matching of solar collector and membrane distillation, the cooling water reduction and phase change heat recovery in the steam condensation process of membrane distillation system, the RO brine desalination system by solar vacuum membrane distillation in cold area was designed and verified in the test. The system consists of RO concentrated tank, membrane distillation module, solar collector, condensing unit, circulation pump, vacuum pump, fresh water tank, and so on. The condensing devices are self-made stainless steel heat exchange coil placed in the RO freshwater pool and geothermal coil placed in the underground of the greenhouse. The components of the system are designed in detail, and the self-made condensing device is the focus in the design. The system is placed in a greenhouse in Xinrong Village, Helan County, Yinchuan City, Ningxia. The front end of the system is an RO system for greenhouse irrigation. Since RO concentrated water cannot be discharged, it is further diluted by vacuum membrane distillation. In order to reduce energy consumption, the RO concentrated water treated by membrane distillation is heated by a solar collector. The fresh water vapor produced by membrane distillation is cooled by the stainless steel heat exchange coil in the RO fresh water tank and the greenhouse geothermal coil, which solves the problem of cooling water reduction in the steam condensation process of the membrane distillation system, and realizes phase change heat recovery and heats the greenhouse. Through measuring the relevant parameters of each component of the system, the solar collector effect, the RO brine desalination effect of the vacuum membrane distillation, the condensation effect of the condensing device and the heating effect of the greenhouse crop were tested and analyzed. The tests show that under the test conditions, the selected collector area can basically meet the heat requirement of membrane distillation for the whole year, the length of the stainless steel heat-dissipating coil designed in the greenhouse fresh-water tank can meet the steam condensation requirement, and the geothermal coils laid in 30-40 cm depth below the surface can meet condensation requirements and greenhouse heating requirements. The amount of freshwater produced by membrane distillation increases with the increase of the inlet temperature of the RO brine on feeding side and the vacuum pressure on the permeate side. When the inlet temperature of the RO brine on feeding side is 80 °C and the vacuum pressure of permeate side is -0.080 MPa, the water production is 37.62 L/h. When the operating time of the vacuum membrane distillation system reaches 240 h, the membrane fouling increases and the water production decreases. When the hollow fiber membrane is cleaned, the water production after washing is increased by nearly 1.5 times compared with that before washing. It has been verified by experiments that the RO concentrated water desalination system by solar vacuum membrane distillation in cold area can basically meet the requirements for use. This study has important significance for reducing the energy consumption of membrane distillation system, realizing the zero discharge of RO brine, and reducing the concentration of brine in the environment. [ABSTRACT FROM AUTHOR]

In order to explore the law of stress-strain for the U-shaped steel mold prefabricated concrete channel, numerical simulation was carried out under different thickness, longitudinal stiffener and transverse stiffeners with D60 U-shaped steel mold as research object by ADINA software that used for different thickness, different longitudinal stiffener numerical simulation of different ribs and transverse stiffeners of steel mold. The results indicate that the displacement of the steel mold on the straight linear segments is the maximum, the arc segments come second and the straight line connecting segments and arc segments connecting segment are the minimum. Stress in a straight line connecting segment and arcs connecting segment of steel model are the maximum, the straight linear segment and arc segments are lesser and the degree of influence of the thickness of the steel mold is larger than the number of longitudinal stiffener and the degree of influence of the number of longitudinal stiffener is larger than the number of transverse stiffener of steel model. Within the allowable deformation range, the appropriate thickness of the prefabricated concrete lining steel mold channel is 8 mm-10 mm and the appropriate number of longitudinal stiffeners is 3 to 4 and the appropriate number of transverse stiffeners is 2 (1 transverse stiffener for each straight linear segment and arc segment). [ABSTRACT FROM AUTHOR]

Studies on growth and development dynamics of watermelon in gravel-mulched field are helpful in improving utilization efficiency of nutrient, reducing influence of ageing gravel-mulched field on watermelon growth and development and scientifically regulating and controlling watermelon growth and development. This article took into consideration of soil moisture, nutrient, temperature and illumination and established watermelon growth and development dynamic model and leaf area index (LAI) model of watermelon in gravel-mulched field. In 2006, a field experiment was performed in Yinxi Group, Hongquanzi Village, Zhongwei City, Ningxia (37°0'N, 105°12'E). In 2009, two different barrel experiments were conducted under rain shelter. Since the development dynamic model was built based on experience and previous published results. Data from the field and barrel experiments were used to validate the model. The LAI model was established by logistic model, a regression model. The model establishment was based on the results from one barrel experiment in 2009 and the model validation was based on those from the other barrel experiment in 2009. All the experiment simulated dry year, normal year and wet year with volumetric soil moisture of 11-20, 13-24 and 16-27 cm3/cm3, respectively. In the field experiment, organic fertilizer was 150 kg/hm2 for all types of years. In the barrel experiment for LAI model establishment, organic fertilizer was 0, 600, 1 200 and 1 800 kg/hm2. In the barrel experiment for LAI model validation, in addition to application amount above, organic fertilizer amount expanded to 1 560 kg/hm2 and urea was also used with different amount of 48, 61.5 and 33 kg/hm2. The experiment was under drip irrigation under film mulching. Model evaluation was based on root mean square of error(RMSE), normalized RMSE (nRMSE), and correlation coefficient (r). The results showed that: 1) the growth and development dynamic model had the RMSE of 0.95 and 1.78 d, nRMSE of 9.6% and 5.45, and r about 1. It suggested that the model was reliable in simulating growth and development dynamics of watermelon in gravel-mulched field; 2) the LAI model had RMSE of 0.00074-0.0033 d, nRMSE of 0.34%-2.3%, and r of 0.98 under all the type of year. The simulation results of the logistic model were consistent with the measured values and it could fit well the peaks of LAI curves. The LAI model had high accuracy of simulation of watermelon LAI in gravel-mulched field. The models here could be used for understanding watermelon growth dynamics in gravel-mulched field, and provide technical support for improving the utilization efficiency of water and fertilizer, and regulating and controlling watermelon growth process effectively. [ABSTRACT FROM AUTHOR]

Gravel-mulched field is typical in Northwest of China for watermelon production. Few studies are on dry matter and yield models establishment of watermelon in gravel-mulched field, which is good for prediction of watermelon growth and yield. This study aimed to establish the dry matter and yield models for watermelon in gravel-mulched field based on photosynthesis and water-N coupling. Two experiments were designed in 2009. One was for photosynthesis-based dry matter model validation (Exp. 1) and the other was for water-N coupling model validation (Exp. 2). The experiments were conducted under a rain shelter in order to simulate different types of rainfall years.The experimental site was located in Hongquanzi Village, Zhongwei City of Ningxia (37°56′N, 105°15′E). The soil and gravel were taken from 0-40 cm depth of a typical 2-a gravel-mulched field. Based on experience and previous published papers, volumetric soil moistures of 11%-20%, 13%-24% and 16%-27% simulated dry, normal and wet years, respectively. The organic fertilizer application rate was designed at 4 levels at 0, 600, 1200 and 1800 kg/hm2. In Exp.2, five levels of organic fertilizer application rate were 600, 750, 1 200, 1 560 and 1 800 kg/hm2 and 5 levels of urea at 24, 33, 48, 61.5, 72 kg/hm2. All the experiment was conducted in barrels. A photosynthesis-based dry matter accumulation model of watermelon was established based on daily total photosynthetic assimilation amount calculated with Gauss integration method. The dry matter and yield models were also established using multiple regression method. The models were evaluated by indexes of correlation coefficient (r), root mean square of error (RMSE), and normalized RMSE (nRMSE). The results showed that: 1) the photosynthesis-based dry matter model had RMSE of 22.5 kg/hm2, nRMSE of 14.5% and r of 0.893, which indicate that the model was reliable in watermelon dry matter accumulation simulation; 2) Water-N coupling model of watermelon dry matter had low accuracy (R2=0.30) for ET≥150.2-513.8 mm and available N≥172.1-241.7 kg/hm2, and the accuracy became higher (R2=0.78, P<0.01) for ET≥213-513.8 mm and available N≥172.1-226.9 kg/hm2. The water-N coupling model of watermelon economic yield also had higher accuracy (R2=0.88, P<0.01) for ET≥213-513.8 mm and available N≥172.1-226.9 kg/hm2. Meanwhile, the water-N coupling model of watermelon dry matter and economic yield had low RMSE (25.2 and 668 kg/hm2) and nRMSE (15.4% and 14.1%), which indicated the water-N coupling model was reliable in dry matter and yield simulation of watermelon for ET≥150.2-513.8 mm and available N≥172.1-241.7 kg/hm2. The models here could be used for dry matter and yield prediction of watermelon in gravel-mulched field and provide useful tool for improving the utilization efficiency of water and fertilizer. [ABSTRACT FROM AUTHOR]