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1.
《农业机械学报》2003,(4)
The discipline of Agricultural Mechanization Engineering in Shandong University of Technology is thefirst one in the history of the University with its own superiority and characteristics in the development ofdiscipline and professional training.About 40 0 0 undergraduate students have graduated from the disci-pline,34graduate students have enrolled M.Sc.program and1 1 students have enrolled joint- training Ph Dprogram with other universities in the area of agricultural mechanization engin… 相似文献
2.
《Agricultural Systems》2002,71(1-2):59-73
Feed resources and nutrition constitute the principal technical constraints to ruminant production in Asia. Four main categories of feed resources are potentially available for use in smallholder crop–animal systems. These are pastures (native and improved grasses, herbaceous legumes and multi-purpose trees), crop residues, agro-industrial by-products (AIBPs), and non-conventional feed resources (NCFRs). Priorities for the use of crop residues in terms of nutrient potential and animal species are indicated. Of the technologies developed to improve the nutritive value of crop residues, more attention has been given to chemical treatment of cereal straws than to supplementation. However, a failure to demonstrate cost-effectiveness has discouraged on-farm adoption. The production of fodder from food crop systems and the establishment of multi-purpose trees and shrubs are potentially important for insuring adequate feed supplies for ruminants and improving soil fertility, but there has been limited adoption on small farms to date. Equally, there is significant potential for the more effective use of locally-produced AIBPs and NCFRs, all of which are under-utilised currently. 相似文献
3.
By discretizing the convection terms with AUSM+ up scheme in the rotating coordinate system, a finite volume analysis code based on multi block structured grids was developed indepen dently so as to realize the numerical solving of internal flow fields of turbomachineries. Taking an unshrouded radial impeller with the working fluid of water vapour as the research object, the flow response to the fluctuation of rotational speed was calculated. By comparing the surface pressure profiles and velocity contours calculated by the code and commercial software respectively, the accuracy of flow solver was verified. The analysis of flow response data indicates that, as the wor king condition shifts closer towards the surge boundary, the response of flow parameters such as mass flow and aerodynamic torque will be more nonsynchronous with the fluctuation of rotational speed, and also the influence of density variation on mass flow variation will be smaller. Moreover, the transient variation region of working condition performance will deviate farther away from the steady performance curve as the working condition approaches the surge boundary. Compared to the working conditions with small mass flows, the distribution characteristics of pressure difference load on the blade surface vary little under large mass flow conditions. The reduction of fluctuation amplitude of rotational speed exerts no influence on abating the hysteresis of flow response. 相似文献
4.
《Agricultural Systems》2007,94(1-3):170-190
Farmers within irrigation systems, such as those in Bali, solve complex coordination problems to allocate water and control pests. Lansing and Kremer’s [Lansing, J.S., Kremer, J.N., 1993. Emergent properties of Balinese water temples. American Anthropologist 95(1), 97–114] study of Balinese water temples showed that this coordination problem can be solved by assuming simple local rules for how individual communities make their decisions. Using the original Lansing–Kremer model, the robustness of their insights was analyzed and the ability of agents to self-organize was found to be sensitive to pest dynamics and assumptions of agent decision making. 相似文献
5.
In consideration of the problem that the effect of conduit structure on water hammer has been ignored in the classical theory, the Poisson coupling between the fluid and the pipeline was stu died and a fourteen equation mathematical model of fluid-structure interaction (FSI) was developed in this paper. Then, the transfer matrix method (TMM) was used to calculate the modal frequency, modal shape and frequency response. The results were compared with that in experiment to verify the correctness of the TMM and the results show that the fluid-structure coupling has a greater impact on the modal frequencies than the modal shape. Finally, the influence on the response spectrum of diffe rent damping ratios was studied and the results showed that the natural frequency under different dam ping ratios has changed little but there is a big difference for the pressure spectrum. With the decrease of damping ratio, the damping of the system on frequency spectrum is more and more significant and the dispersion and dissipation is more and more apparent. So the appropriate damping ratio should be selected to minimize the effects of the vibration of the FSI. 相似文献
6.
《Agricultural Water Management》2001,47(2):155-178
The method for verification of numerical solution of water flow towards a drain in homogeneous soil under steady rainfall or steady irrigation recharge is presented in the paper. In 1979, Zaradny and Feddes proved that the accuracy of the numerical result depended, among other things, on the size and pattern of discretization applied. Ibidem, a partly verification of numerical solution was presented. It was based on the Thiem–Dupuit well formula and on the hodograph solutions given by Van Deemter [Van Deemter, J.J., 1950. Versl. Landb. Onderz. 56 (7), 1–67] and Childs [Childs, E.C., 1959. J. Soil Sci. 10 (1), 83–100]. Up till now, there was no full verification of this solution. The proposed method which depends on replacement of the drain by horizontal ‘well’ in a confined aquifer of a constant thickness, the geometry of which in the x–z plane is compatible, in shape and size, with saturated zone in the numerical solution gives the possibility of such verification. For this problem groundwater flow can be described by the Laplace equation. The analytical solutions for the hydraulic head φ and the stream function ψ, specification of boundary conditions for the considered problem and the method of determination of the Fourier series constants are given in the paper. Presented results confirm the correctness of numerical solution given by Zaradny and Feddes [Zaradny, H., Feddes, R., 1979. Agric. Water Manage. 2, 37–53] and they also show that when verification with respect to observed and measured data is impossible, such tests should be performed. 相似文献
7.
《Agricultural Systems》1999,60(2):113-122
The use of numerical optimization techniques on simulation models is a developing field. Many of the available algorithms are not well suited to the types of problems posed by models of agricultural systems. Coming from different historical and developmental backgrounds, both genetic algorithms and evolution strategies have proven to be thorough and efficient methods in identifying the global optimum of such systems. A challenging herd dynamics model is used to test and compare optimizations using binary and real-value genetic algorithms, as well as evolution strategies. All proved successful in identifying the global optimum of this model, but evolution strategies were notably slower in achieving this. As the more successful innovations of each of these methods are being commonly adopted by all, the boundaries between them are becoming less clear-cut. They are effectively merging into one general class of optimization methods now termed evolutionary algorithms. 相似文献
8.
【Objective】This paper studied the spatiotemporal changes in hydro-chemical properties of groundwater in irrigation districts within the Kaidu River basin, as well as the factors that affect these changes.【Method】Groundwater samples were taken in January, March, July and September in 2017 from the irrigation area in the Kaidu river basin. Spatiotemporal change in hydro-chemical properties of the groundwater and its impacting factors were analyzed using statistics, spatial interpolation, and Piper and Gibbs diagram.【Result】①The groundwater quality was generally good, with low TDS and being dominated by HCO-3, Na+, Ca2+ and SO2-4. The mean TDS was high in winter and low in summer, and it was related to the depth of groundwater table. ② Na+, Ca2+ and SO2-4 varied erratically both in time and space. ③The hydro-chemical type of the groundwater in the studied area was HCO-3-SO2-4-Na+-Ca2+, and remained almost unchanged in the four seasons. ④The rock weathering appears to affect the hydro- chemical propertied of the groundwater most. The impact of human activities was mainly in spring, summer and autumn in the oasis and lakeside region, and it was stronger in irrigation season than in non-irrigation season.【Conclusion】Our results suggest that pumping groundwater for irrigation should be rationally managed and the associated change in chemical properties of the groundwater should be monitored; this applies not only to the studied sites but also to regions on the southern slope of the Tianshan Mountain. © 2019 Authors. All rights reserved. 相似文献
9.
Wang L.Li S.Wang Y.Wang X. 《灌溉排水学报》2019,(11):65-73
【Objective】In order to obtain the irrigation infiltration recharge coefficient in the lower reaches of Aksu river and improve the numerical simulation accuracy of groundwater in the study area,the influencing factors of the irrigation infiltration recharge coefficient in this area were analyzed. 【Method】In this paper,field sampling and indoor irrigation experiments were carried out by selecting representative points under different irrigation schemes,vadose zone thickness and soil structure in the lower Aksu area,and numerical simulation of vadose zone flow was carried out in combination with Hydrus-1d. Hydrus-1d model was used to calculate irrigation inflow under this soil structure by changing irrigation schemes and vadose zone thickness. Change of seepage recharge coefficient. On the basis of the calculation results of the model,the relationship between irrigation schedule,aeration zone thickness and irrigation infiltration recharge coefficient is analyzed firstly,and then the main factors affecting irrigation infiltration recharge coefficient in soil structure are analyzed with the method of model calculation and mathematical statistics. 【Result】The results showed that the irrigation infiltration recharge coefficient ranged from 0.320 to 0.474 under drip irrigation and from 0.408 to 0.561 under border irrigation. The irrigation infiltration recharge coefficient varied under different irrigation schemes,while the irrigation infiltration recharge coefficient decreased with the increase of aeration zone thickness. The main factors affecting irrigation infiltration recharge are soil permeability coefficient,soil bulk density and initial soil water content. 【Conclusion】According to indoor experiment combined with numerical model to calculate the irrigation infiltration coefficient under different irrigation system range, it is concluded that the influence factors of irrigation infiltration coefficient of irrigation system, the thickness of the vadose zone and reflects soil permeability coefficient of soil structure, soil quality and soil initial moisture content, volume for the downstream area irrigation infiltration coefficient selection in arid areas and provides the theory basis for further research. © 2019 Journal of Irrigation and Drainage. All rights reserved. 相似文献
10.
《Agricultural Water Management》1987,12(3):207-219
Saline irrigation waters dominant in sodium salts limit the potential yield of agricultural crops directly by affecting physiological functions of plants and/or indirectly by degrading the soil environment. The vital role of calcium in the regulation of ionic relations in plants and in improving the soil physical condition offers the possibility of combating salinity by both physical manipulation of the soil environment and genetic manipulation of the plant.This paper discusses the physiological role of calcium as related to salt tolerance of crops and also its influence on the structural improvement of salt affected soils. Other aspects covered include the availability of soil calcium to plants and a formula to calculate calcium requirements. Future research needs on the use of calcium in irrigating with saline-sodic water are also indicated. 相似文献
11.
Qin J.Lyu M.Deng Z.Gu S.Gao J. 《灌溉排水学报》2019,(7):10-16
[Objective]Soil moisture plays an important role in ecosystem function and hydrological processes. This paper investigated the hieratical distribution of soil moisture at different scales over a maize field.[Method] The studied site was a 50 m×50 m plot at the Experiment Station of Chinese Academy of Agricultural Sciences in Xinxiang, Henan province. We measured soil moisture in 0~100 cm soil from 36 locations at 10 m×10 m and 2 m×2 m scale, respectively.[Result]Geostatistical analysis revealed that the soil moisture was normally distributed and its confidence level at every scale was higher than that of logarithmic normal distribution. The value of the confidence level decreased as the sampling scale increased, and the difference between average soil moisture content at fine scale and moderate scale was smaller than the difference between moderate scale and large scale. In general, the confidence interval, standard deviation and coefficient of variation of the soil moisture increased with sampling scale. At large scale, the semi-variance function increased with lag distance, while at small and moderate scale, the variation function appeared to be independent of the lag distance. To achieve the same confidence level and accuracy in estimating soil moisture, the number of samples needed to be taken from the field increased with sampling scale. We also found that in estimating soil moisture, the number of samples needed to be taken depended on the required accuracy more than on the confidence level.[Conclusion]The probabilistic distribution and statistical characteristics of soil moisture in the field was scale-dependent. In estimating soil moisture, the number of sampled taken from the field needs to consider the scales to which the measured data will be applied. © The Author(s) 2019. 相似文献
12.
【Objective】Soil is heterogenous and its physical and chemical properties vary spatiotemporally. The purpose of this paper is to present the results of an experimental study on the physical and chemical properties of soil in Anabasis salsa in Gobi region at the southeastern edge of Junggar basin.【Method】We measured organic matter, total phosphorus, total nitrogen, electrical conductivity, pH and water content in soil at locations 5 cm and 10 cm from the center of shrubs, and 20 cm from the outer edge of shrubs.【Result】In horizonal direction, there was no significant difference in organic matter, total nitrogen, total phosphorus, electrical conductivity, pH and water content in the 0~50 cm soil at all locations. In vertical direction, the organic matter and total phosphorus in the proximity of the Anabasis salsa decreased monotonically along the soil profile, while the total nitrogen increased first with the depth followed by a decrease. Both electrical conductivity and pH increased with depth, and soil moisture peaked somewhere within the soil profile.【Conclusion】Our results showed that the physical and chemical properties of soil in Anabasis salsa did not show significant change in lateral direction but varied erratically in the vertical direction. © 2019 Authors. All rights reserved. 相似文献
13.
《Agricultural Water Management》2001,51(1):53-78
Intensification of the agricultural sector and the increase in quantity and decrease in quality of municipal and industrial wastewater, in particular during the past decades, resulted in many industrial countries, such as Belgium, in a sharp degradation of surface water and groundwater. To control the current degree of contamination and reduce the environmental impact of the agricultural sector, the Flemish government recently introduced a number of regulations aiming at controlling the use of nitrogen fertilisers. To facilitate the implementation and the control of the new regulations, threshold values of allowable doses of organic and inorganic nitrogen fertilisers, and their spreading in time were made soil independent. As the soil physical, chemical and biological response depends on the geohydrology of the site and the past fertilisation practice, fertiliser standards applied on different soil–crop systems result in different leaching patterns.To assess the effect of the soil on the nitrogen leaching, a number of past experimental field trials were analysed using the WAVE model as modelling tool for the reconstruction of the nitrogen dynamics. As a first step in the study, the historic data of the field experiments were used to calibrate and validate the WAVE model. The deterministic calibration and validation of the WAVE model yielded a set of model parameters for the examined soil–crop–fertiliser practice conditions. The bottlenecks in the calibration were the nitrogen mineralisation parameters and the initialisation and subdivision of the soil organic matter over the different organic pools. The model validation, being the second step in the study, revealed the power of the WAVE model to predict the evolution and transformations of nitrogen in the soil profile and the leaching of nitrate at the bottom of the root zone. In a third step, the WAVE model was used in a scenario-analysis exercise to examine the factors effecting the amount of nitrate leached at the bottom of the root zone. This analysis revealed that the nitrate leached out of the soil profile is controlled by the fertiliser practice, the rainfall depth and its distribution, the soil texture, the soil mineralisation capacity and the past fertilisation practice. 相似文献
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15.
[Objective]Irrigation schedule needs to know the spatiotemporal dynamics of soil moisture in root zone. The objective of this paper is to investigate the feasibility of using matric potential measured at 20 cm below the drip emitter as a proxy for soil moisture in the root zone to schedule irrigation.[Method]The experiment was conducted in a greenhouse and the model plant was tomato. We compared seven matric potential (SMP) thresholds in that whenever the measured soil matric potential dropped below them, drip irrigation was resumed. The values of the SMP thresholds varied from flowering and fruit-setting stage to fruiting stage, and the seven combinations (flowering and fruit-setting stage/fruiting stage) were -15 kPa/-15 kPa (S1), -15 kPa/-30 kPa (S2), -15 kPa/-45 kPa (S3), -25 kPa/-25 kPa (S4), -30 kPa/-15 kPa (S5), -30 kPa/-30 kPa (S6), and -30 kPa/-45 kPa (S7). In each treatment, we measured growth, fruit quality, water consumption and water use efficiency of the tomato.[Result]Stem diameter increased with SMP threshold at both flowering and fruit-setting stage and fruiting stage, whereas the plant height was only responsive to SMP at flowing and fruit-setting stage. The relative chlorophyll content in leaf (SPAD) did not show significant difference between treatments at flowering and fruit-setting stage but inversely increased with the SMP threshold at fruit setting stage. Decreasing the SMP threshold at flowering and fruit-setting stage could reduce the percentage of defective fruits and increase soluble solids content. Yield increased inversely with SMP threshold at fruit setting stage, peaking when SMP was -45 kPa. Lowering the SMP threshold increased irrigation amount and hence water consumption, thereby decreasing water use efficiency. [Conclusion]Our experimental results suggest that setting the SMP at -30 kPa at the flowering and fruit-setting stage and -45 kPa at the fruiting period appears to be optimal to best balance yield, fruit quality, irrigation water use efficiency and water use efficiency for winter-spring tomato grown in solar greenhouse in North China. © The Author(s) 2019. 相似文献
16.
Peter E. Holm Helle Marcussen Anders Dalsgaard 《Irrigation and Drainage Systems》2010,24(1-2):127-142
Non-treated wastewater is used for irrigation of aquatic food production systems in the peri-urban areas of the major cities in Southeast Asia. This paper complement the knowledge on agricultural soil-based crops irrigated with low quality water, by reviewing the research findings on the wastewater-fed aquatic productions with special focus on heavy metals and other potentially toxic elements (PTEs) in the production systems of Hanoi in Vietnam and Phnom Penh in Cambodia. In Hanoi, sediments in the wastewater exposed rivers of Hanoi were reported to be polluted with PTEs, in particular with Cadmium (Cd). The river sediment had a high retention capacity for PTEs which seems to prevent the transport of PTEs to the wastewater-fed production systems. In Phnom Penh, domestic and industrial wastewater is pumped into the Cheung Ek Lake located south of the city. A major part of the water spinach (Ipomoea aquatica Forssk.) consumed in the city is produced in the lake. The concentrations of some PTEs were elevated at the wastewater inlets to the lake compared to concentrations at the lake outlet and at the control site. Water spinach is by far the major vegetable produced in the wastewater-fed systems in Hanoi and Phnom Penh, but did only contain PTEs in concentrations within or slightly above the concentration range observed for water spinach grown in agricultural soil not exposed to wastewater. PTE concentration in fish grown in wastewater-fed systems in Hanoi and Phnom were low. However, mean PTE concentrations in liver and skin of some fish were high. Consumption of muscle tissue from fish produced in wastewater-fed systems in Hanoi and Phnom Penh resulted in an estimated intake of PTEs amounting to less than 9% of the tolerable intake. It was concluded, that the PTE concentrations in fish and water spinach from Hanoi and Cheung Ek Lake in Phnom Penh constituted low food safety risks for consumers. 相似文献
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18.
Wang Y.Dong Y.Jiao L. 《灌溉排水学报》2019,(7):110-115
【Objective】The evapotranspiration of crop depends on many factors and this paper analyzed its sensitivity to various meteorological factors in Ebinur lake oasis.【Method】Monthly ET0 in Ebinur lake oasis was calculated using the Penman-Monteith formula based on meteorological data measured from 1962 to 2016 at four meteorological stations in the region. The sensitivity of ET0 to the highest and lowest temperature, relative humidity, sunshine duration and wind speed was calculated using sensitivity analysis; and the possible existence of any trends in the ET0 was analyzed using the MK trend test. We also calculated the variation of the sensitivity coefficient for each site.【Result】The MK trend test revealed that the evapotranspiration, sunshine duration and wind speed in the region have been in decline, while the highest and lowest temperature and the relative humidity have been in rise. Analysis found that the ET0 was sensitive to meteorological factor in an order of relative humidity > the highest temperature > wind speed > the lowest temperature > sunshine duration. The sensitivity coefficient of ET0 to different meteorological factors varies spatially, with the coefficients for the highest and lowest temperature, wind speed and relative humidity being high at Alashan pass-way in northern Ebinur lake, and low at Wenquan station. Wenquan station had longer sunshine duration than Alashan pass-way.【Conclusion】ET0 is most sensitive to relative humidity in Ebinur lake oasis, and least sensitive to sunshine duration. © 2019 Authors. All rights reserved. 相似文献
19.
Citrus irrigation scheduling is usually based on evapotranspiration (ET) multiplied by a crop coefficient that varies throughout the year. However, ET at 10°C and less has not been investigated. Citrus acclimate to temperatures below 10°C, which affects ET, and therefore may allow irrigation scheduling to be adjusted accordingly. Three separate growth chamber experiments were conducted in complete block design with two temperature treatments and 8-one tree replications with the objective of determining water use of ‘Hamlin’ orange exposed to cold temperatures. The treatments included: full cold-acclimating temperatures, alternating 10 days cold and 3 days warm temperatures, and alternating 10 days warm and 3 days cold temperatures. Although well-watered, trees exposed to temperatures ≤10°C demonstrated lower water use compared to trees held at temperatures that promoted growth. Reduction of water use of cold-treated plants than the controls was 66, 20–57, and 14–28% during full cold-acclimating temperatures, alternating 10 days cold and 3 days warm, and alternating 10 days warm and 3 days cold temperatures, respectively. Reduced water use of cold-treated plants was due to stomatal closure, increased root resistance, and decreased leaf area. Effective irrigation scheduling based on water requirements as they change during cold-acclimating temperatures should save water while providing adequate water for yield and quality. 相似文献
20.
Ali Rahimi Khoob 《Irrigation Science》2008,26(3):253-259
The Penman–Monteith equation (PM) is widely recommended because of its detailed theoretical base. This method is recommended
by FAO as the sole method to calculate reference evapotranspiration (ETo) and for evaluating other methods. However, the detailed climatological data required by the Penman–Monteith equation are
not often available especially in developing nations. Hargreaves equation (HG) has been successfully used in some locations
for estimating ETo where sufficient data were not available to use PM method. The HG equation requires only maximum and minimum air temperature
data that are usually available at most weather stations worldwide. Another method used to estimate ETo is the artificial neural network (ANN). Artificial neural networks (ANNs) are effective tools to model nonlinear systems
and require fewer inputs. The objective of this study was to compare HG and ANN methods for estimating ETo only on the basis of the temperature data. The 12 weather stations selected for this study are located in Khuzestan plain
(southwest of Iran). The HG method mostly underestimated or overestimated ETo obtained by the PM method. The ANN method predicted ETo better than HG method at all sites. 相似文献