Abstract:In order to study the hydrofoil cavitation characteristics in the process of accelerated flow, detached eddy simulation (DES) and homogeneous cavitation model were employed to simulate the unsteady flow around NACA66 model at attack angle of 5.8°. The cavitation number was 0.99 and the corresponding Reynolds number was 8×105. The characteristics of cavitation evolution and flow field structure were obtained in the case of two different accelerations (a1=5m/s2， a2=2.5m/s2). Different numerical simulation results were obtained by studying different accelerations. Cavitation was first born in the leading edge of the hydrofoil, and grew after a period of time and finally separated. Then the cavitation in the leading edge was reduced and the cavitation at the tail of the hydrofoil was increased and backward spread until rupture. Cavitation was first generated at around 0.6 times of total acceleration time and finished a cycle at about 1.12 times of total acceleration time. Oscillation ranges of the lift coefficient became large and the range of the drag coefficient was small with the increase of acceleration. Using small acceleration, the cavitation developed more slowly. The simulation results obtained by DES turbulence model were more close to the experimental values than those obtained by homogeneous cavitation model. The research results can provide reference basis for cavitation characteristics study of hydraulic mechanical startup process.

Abstract:The hump characteristic is one of the detrimental characteristics of axial flow pump. If the pump runs in the hump region, some unsteady flows will occur, such as stall, backflow, cavitation and so on, which will reduce the pump performance. In order to analyze the hump characteristics, numerical method based on the RANS equations and SST k—ω turbulence model was used to simulate the instability flows in the axial flow pump with and without inlet guide vane. The hexahedral meshing scheme was used for the whole computational domain, particularly with O-grid around blades. The characteristics of swirling backflow vortex were firstly investigated. The influences of different distances between inlet guide vane and impeller blade on the swirling backflow vortices and the pressure fluctuations were studied. The effects of variable angles of inlet guide vane on pump performance were also discussed. The results showed that the predicted results were in good agreement with the experimental data. When the flow rate decreased, the backflow region was extended upstream. During the development of the backflow, the swirling vortices occurred in the shear layer between the swirling backflow and the main flow, which caused a lot of low frequency pressure fluctuations and consumed energies, leading to pump head decrease and hump characteristic. The swirling backflow vortices can be broken by inlet guide vane, resulting in decrease of amplitudes of low frequency pressure fluctuations and increase of pump head due to less energy consumed by the swirling vortices. Thus, the hump characteristic of axial flow pump can be improved by inlet guide vane. With the reduction of the distance between inlet guide vane and impeller blade, pump head was increased continuously. In addition, pump head was increased at negative angle of inlet guide vane, while it decreased at positive angle of inlet guide vane, which was resulted from the prewhirl regulation.

Abstract:Fish-friendly designs were done on a traditional pump which was effective for reducing fish mortality during passage through the pumping station. However, optimization designs which were good for fishfriendliness had disadvantageous effect on pump cavitation performance. With the aim of improving the cavitation performance of fish-friendly axial-flow pump, a commercial computational fluid dynamic software ANSYS CFX, which showed a fair agreement with the experimental results, was used to predict the cavitation performance. The predicted NPSHr,3% of original pump was increased from about 3.5m to 9m after fish-friendly designs were done, which was unacceptable for pump running. Therefore, the inner flow field characteristics were numerically analyzed and the result indicated that there was vortex generated next to the hub and the inlet angle of attack was unsuitable, which was the primary reason for cavitation inception. The vortex formation mechanism was discussed and the airfoil section near the hub was redesigned to restrain the vortex generation. Furthermore, the design parameters of other airfoil sections were corrected to make streamlines smooth and fit the profile of blades. The optimization and numerical simulation results showed that the flow field was stable and flow transition around the head of airfoil section was smooth without velocity increment. The streamlines near the blade suction side fit the surface and there was no vortex generated. By reducing the inlet pressure, the predicted NPSHr,3% value of optimized fishfriendly axialflow pump was reduced to about 3m, which was absolutely enough for pump running. The research result provided a complete design method for fish-friendliness and optimization of hydrodynamic performance for axial-flow pump.

Abstract:Insufficient understanding of complex flow feature in pipe-type centrifugal pump is a major problem encountered under the design condition. The inlet distorted flow of the pump duct was described, and the tornado-type vortex formation, propagation and its trigging cavitation bubble for the high noise were explained．The description and explanation were based on numerical simulations by RANS model and experiments．The mechanisms dictating the inlet distortion, including the curved duct flow, flatplate flow and secondary vortex impacts on the incidence angle and boundary layer separation, were studied systematically. Particular attention was devoted to the notable influence of the limiting streamlines on the suction surface and pressure changes at the casing. The primary analysis identified a focus separation vortex route to the Q criterion. Like the tornado, the separation vortex had a vortex leg on the blade suction surface, and it was linked to a low pressure bubble locating ahead of the rotor. In detail, the tornado-type vortex was caused by separation at the leading edge due to high incidence. The separation gave rise to shedding of vortex from the suction surface, and consequent formation of vortex moving ahead of the rotor with the reverse flow. Moreover, another tornado-type vortex was captured standing on mid-part of the suction surface and attaching to the corner close to the shroud, due tp breakdown of former tornado-type vortex, disturbance of adjacent blade and rotation motion. Furthermore, the inlet distortion was the major factor for the complex flow in the pump. By cavitation simulation, the former tornado-type vortex and its inducing cavitation could explain the high noise under the design condition.

Abstract:The disc friction loss and axial force calculation of centrifugal pump and flow characteristics of balance cavity liquid are closely related. At operating points of 0.8Qsp, Qsp and 1.2Qsp, numerical calculation results and experimental results were basically consistent on performance of pump and flow characteristics of balance cavity. Distribution of velocity field was researched in the balance cavity. The distribution curve of dimensionless circumferential velocity component and dimensionless radial velocity component were drawn along the axial direction at different angles and radiuses of balance cavity to analyze the flow characteristics and calculate the disc friction loss in the balance cavity area. The results showed that flow core and turbulent boundary layer existed in the balance cavity liquid. The main flow characteristics were circumferential shear flow and radial differential pressure flow. The dimensionless circumferential velocity component of flow core decreased with the increase of radius, the dimensionless radical velocity component was approximately zero, while turbulent boundary layer liquid was greatly influenced by leakage flow, which was asymmetric under the same flow condition. The radical leakage flow in the sealing back-ring and the axial leakage flow in the balance hole of the impeller played an important part in the flow of radical velocity component at the turbulence boundary layer and circumferential velocity component at the balance holes area. The rotational angular velocity of balance cavity liquid at the same angle and radius increased with the increase of flow. The disk friction loss in the balance cavity decreased with the increase of the flow. Theoretical formula of disc friction loss did not consider the effect of variable flow conditions on pump. The theoretical results were greater than the experimental results and the numerical calculation results.

Abstract:A kind of subsection following steering control strategy and steering wheel input-based electronic control system were proposed to improve the steering maneuverability and security of the hydrostatic-mechanical driving crawler chassis. According to the steering analysis results of the crawler chassis under skid condition, the theoretical steering track was obtained, and it was segmented by mechanical drive axle responding time. Actual steering track followed theoretical steering track by controlling barking-clutch performance in every subsection period according to vehicle direction angle and position tolerances defined in control strategy. The evaluation system of the strategy was established, and the steering relative errors, relative steering radius ratio, executing frequency were selected as evaluation indexes. Algorithm stimulation and real vehicle test with steering electronic controller by adopting this strategy were also carried out. The stimulation results obtained by Matlab showed that the relative error of steering radius was between 5.9% and 10%, and the average frequency of actuator working was from 2.5Hz to 6.6Hz. The real vehicle test results showed that the electronic steering control system and control strategy had well steering performance, and it could meet various steering needs with stable process, and eliminate the destruction to soil and crops via decreasing the pivot steering slipping.

Abstract:Researches on drainage water reuse and its application in the irrigation district have great significance. In addition to safeguarding future food supply, drainage water reuse also raises the application efficiency of irrigation water and fertilizer, and protects the water environment. Basic theory and key technology of drainage water reuse at home and abroad were summarized, including the related study results of basic theory, several engineering modes for drainage water reuse, and management measures to alleviate the negative effects resulting from irrigation with drainage water. Through a systematic-analysis of the existing research results, it was pointed out that drainage water reuse had great potential in China, and it had great significance for water-saving and pollution abatement. The amount of research works about nitrogen and phosphorus in the drainage water was greater than those of salt and other components at present, and reuse engineering mode and irrigation management measures were the key factors affecting recycling effect. In the end, a study was put forward on the changing laws of drainage water quality and quantity, selection of optimal reuse mode, the best comprehensive management measures, evaluation for environment effect and research on risk analysis. These will be major themes of researches on drainage water reuse in the irrigation district in the future.

Abstract:In order to solve the environmental pollution caused by field plastic film residue and explore the effects of different cropping patterns under liquid film mulching on soil moisture and maize growth, the experiment with four planting patterns treatments, including flat planting without mulching (CK), flat planting with liquid film mulching (YM1), ridgefurrow planting with liquid film mulching over ridge only (YM2) and ridge-furrow planting with liquid film mulching over ridges (YM3), were carried out in 2013 and 2014. The results showed that the change of soil moisture under different treatments was basically the same, which presented waving trend as rose firstly and then reduced with the increment of days after sowing. The soil water storages under YM1, YM2, YM3 treatments were significantly increased by 1.23%, 4.29%, 4.79%, respectively, compared with that under CK when the former period precipitation reached 16.1mm, but there was no significant difference among four treatments in soil water storage after rainfall during latter period. The average water storages under YM1, YM2, YM3 treatments were increased by 2.74%, 2.87%, 9.79% and the water consumptions were decreased by 1.26%, 2.03%, 8.17%, respectively, compared with those under CK, with significant difference only existed between YM3 and CK. Compared with CK, the yields of all mulching treatments were 1.88%, 11.32%, 21.96% higher, the average water use efficiencies were improved by 3.17%, 13.51% and 32.67%, respectively, and the yield increment and water use efficiency enhancement effects of YM2 and YM3 were significantly higher than those of CK. In conclusion, YM3 treatment was the best among all treatments in yield increase and water saving, and it could provide theoretical basis for the utilization of liquid film.

Abstract:The effect of interaction of biochar and fertilizer (IBF) on nutrients of red soil, yield of mustard and fertilizer utilization rate was investigated. IBF experiments were conducted, the treatments included RFC treatment (both biochar and fertilizer were applied), RF treatment (only fertilizer applied) and control treatment CK (no biochar and fertilizer applied). The fertilizer application dosages were 100%, 85%, 70%, 55% of the regular fertilizer application quantity, which were correspondingly denoted as RFC0, RFC1, RFC2, RFC3 of RFC treatment and RF0, RF1, RF2, RF3 of RF treatment, respectively. The results showed that the nitrogen utilization rate of RFC3 was higher than those of other treatments. The nitrogen utilization rate, yield of mustard and the soil organic matter content of RFC treatments were averagely increased by 161.42%, 79.28% and 241.42% compared with those of RF treatments, respectively. The alkali-hydrolyzable nitrogen and available phosphorus contents of RFC3 were higher than those of RF0. Additionally, IBF planting pattern promoted mustard to adsorb and accumulate N, P, K effectively. In conclusion, biochar played an important role in nutrients adsorption and enrichment for mustard growth. The mechanism of yield increment and soil fertility enhancement could be explained that the IBF planting pattern brought the comprehensive amendment effect in the red soil and provided mustard with sufficient nutrients by biochar’s adsorption and fixation for nutrients, which made fertilizer and nitrogen fertilizer utilization rate increase significantly, although the application amount of fertilizer was very low in the experiment.

Abstract:Influence of soil salinity on crops is a very complicated process. Planting crops on saline-alkali lands have become one of important restricts in sustainable agricultural development. Xinjiang, locating in the arid region of Northwest China, is encountering serious soil salinization. Wheat is the most commonly grown cereal crop in Xinjiang. Wheat cultivation in saline-alkali lands based on drip irrigation has become the key of agricultural development in Xinjiang. However, the changes of photosynthetic characteristics of wheat under drip irrigation with soil salt content are still not clear, and the salt-tolerance indexes such as salt-tolerance critical value and salt-tolerance limit are unknown in this region. Therefore, it is necessary to explore effects of soil salt content on photosynthetic characteristics and yield component of spring wheat under drip irrigation, comprehend the photosynthesis restriction mechanism of spring wheat as well as the correlation between its yield and soil salt content, and determine salt-tolerance indexes. The pot experiment was carried out in the test site of Key Laboratory of Modern Water-saving Irrigation Corp of Shihezi University from March to October, 2015. Five treatments were set, including growing wheat in non-saline soil, mild saline soil, moderate saline soil, strong saline soil and saline soil, respectively, and each treatment had three replicates. Soil salt contents of the five treatments were 2.0g/kg (CK), 5.0g/kg (T1), 9.0g/kg (T2), 16.5g/kg (T3) and 24.5g/kg (T4). Each plot adopted the same irrigation and fertilization management independently. Dripper flow for drip irrigation was controlled at about 1.8L/h. The irrigation amount for each time was 44mm and totally 11 irrigations were given during the growth period. Photosynthetic characteristics of spring wheat at elongation stage (May 20th), heading stage (May 28th) and milk-ripe stage (June 11th) were tested by using the CI—340 portable photosynthesis system (USA). Test items included environmental indexes (photosynthetically active radiation, air temperature and CO2 concentration in air) and photosynthetic physiological indexes (net photosynthetic rate, transpiration rate, stomatal conductance and intercellular CO2 concentration). Stomatal limitation and non-stomatal limitation values of leaf photosynthesis were calculated according to the recorded data. Meanwhile, changes of spring wheat yield and soil salt content were observed. Salt-tolerance indexes were calculated through linear regression analysis. Results showed that soil salt content significantly affected photosynthetic physiological indexes of spring wheat under drip irrigation. Coexistence of stomatal and non-stomatal factors inhibited leaf photosynthesis of spring wheat. Reduction of net photosynthetic rate under low soil salt content was mainly caused by stomatal factors, while its reduction under high soil salt content was mainly caused by non-stomatal factors. Salt-tolerance critical value and salt-tolerance limit of spring wheat (0~40cm) in Xinjiang under drip irrigation were 6.46g/kg and 30.72g/kg, respectively. When soil salt content was controlled lower than 9.63g/kg, the relative yield of spring wheat under drip irrigation could be generally higher than 90%. It was concluded that spring wheat was suitable to be grown with drip irrigation in non-saline and mild saline soils. The results could provide theoretical supports for field management and high-efficient production of spring wheat using drip irrigation in saline-alkali soils in Xinjiang.

Abstract:Three microporous clay ceramics with uniform microstructure, adequate flexure strength of 11~23MPa, the same pore size about 4.2~4.6μm and different open porosities of 37%, 44% and 51% were fabricated from the powder blend of clay and slag by sintering. The microporous ceramics were machined into circular specimens, and then microporous ceramic irrigation emitters were assembled by installing the circular microporous ceramic specimens in plastic casings. By testing the hydraulic performance of the irrigation emitters, the effects of thickness and open porosity of microporous ceramic specimens and water head in irrigation pipeline on flow rate of irrigation emitters were discussed in detail, and then the relationships among flow rate of irrigation emitters, thickness and open porosity of microporous ceramic specimens as well as the water head in irrigation pipeline were fitted. According to the testing results, the flow rate of irrigation emitters was proportional to the water head in irrigation pipeline, and the linear relationship was not affected by thickness and open porosity of microporous clay ceramics. The thickness and open porosity of the microporous ceramic specimens had great effect on the flow rate of irrigation emitters. As the thickness of microporous ceramic specimens was increased, the flow rate of irrigation emitters was decreased gradually. Due to the power function relationship between the hydraulic conductivity and open porosity of microporous ceramics, the flow rate of irrigation emitters was increased exponentially with the increase of open porosity of microporous ceramics. As demonstrated from the result in this work, the microporus clay ceramics are promising for manufacturing irrigation pitchers and units for water seepage and filtration.

Abstract:Soil-root composites exsit in the degenerated grasslands with high compaction level. In order to break the soil-root composites effectively by mechanical means, the mechanical characteristics of soil-root composites were studied. The physical characteristics of soil-root composites were analyzed, including the compaction, bulk density, moisture content, porosity and root content. Shear strength, unconfined compressive strength and resilience modulus were measured and analyzed, and the influence factors were discussed, which were the bulk density, moisture and root contents. An orthogonal experiment was conducted to evaluate the effects of influence factors on the mechanical properties. The experiment results indicated that the composites in degenerated grassland aggravated soil compaction and gathered roots to distribute in shallow soil layer. The shear strength, unconfined compressive strength and resilience modulus varied with the change of bulk density, moisture content and root content, the interaction effects existed among these factors. The bulk density and moisture content showed significant influences on the internal friction angle (P<0.05). The cohesion and unconfined compressive strength were significantly influenced by moisture content (P<0.05). The shear and unconfined compressive strengths were strengthened as a result of the existence of root system, while its influence on resilience modulus was different. The composites were prone to be broken by mechanical means at high moisture content.

Abstract:Two-year (2012—2013 and 2013—2014) field experiments were conducted to determine the appropriate supplemental irrigation amount of winter oilseed rape (Brassica napus L.) at stem elongation stage with the ridge and furrow rain harvesting cultivation. Four treatments, including T1, T2, T3 (with supplemental irrigation amounts of 0, 60, 120mm under ridge and furrow rain harvesting cultivation, respectively) and CK (with supplemental irrigation amount of 120mm under flat planting cultivation) were set up to evaluate the effects of different supplemental irrigation amounts on soil moisture content at 0~30cm and 30~100cm soil depths, aboveground dry matter, taproot growth parameters, lateral root density, yield components and water use efficiency (WUE) of winter oilseed rape. The results showed that soil moisture contents at 0~30cm soil depth of T2 and T3 at different periods were obviously higher than those of T1 and CK. Aboveground dry matter at flowering stage and pod stage, taproot diameter and dry weight, lateral root density at 0~10cm and 10~20cm soil depths at pod stage of T2 and T3 were significantly higher than those of T1 and CK, and no significant differences were found between T2 and T3. Compared with T1 and CK, seed yields of T2 and T3 in two years were increased by 50.99%, 58.15% and 53.89%, 61.19%, respectively, and WUE of T2 and T3 in two years were improved by 37.28%, 25.98% and 92.77%, 76.90%, respectively. T3 achieved the highest yield in both years, the average yield, crop evapotranspiration (ET) and WUE of which were 3235kg/hm2, 368mm, 0.89kg/m3, respectively. While the highest WUE with average value of 0.96kg/m3 was determined in T2, with average yield of 3089kg/hm2 and average ET of 322mm. Therefore, compared with T3, T2 could save irrigation amount by 60mm, increase WUE by 8.97%, and the yield was just reduced by 4.74%. From the perspective of saving water and increasing yield, T2 was recommended as an appropriate irrigation schedule and cultivation pattern for winter oilseed rape at stem elongation stage.

Abstract:The effects of regulated deficit irrigation (RDI) on growth of roots and shoots of cotton plants were experimentally investigated during the growing seasons of 2013 and 2014 in pot-grown cotton (Gossypium hirsutum L. cv. Meimian 99B) under rainproof shelter condition in Huang-Huai-Hai Region of China, aiming at offering theoretical basis for the establishment of RDI model for water-saving, high yield, high quality and efficiency of cotton crops. A two-factor randomize-block design was applied. The first factor was different growth stages of water deficit, including seedling stage (I), budding stage (II), flowering and boll-setting stages (III) and boll-opening stage (IV). Another factor was different degrees of water deficit, which were three levels controlled by soil relative water content, including light deficit (L), moderate deficit (M) and severe deficit (S) at stages of I to IV, corresponding soil relative water content were controlled at 60%~65% FC (Field capacity), 50%~55% FC and 40%~45% FC, respectively. Totally 12 water deficit treatments with six replicates were designed and applied. Additionally, an appropriate irrigation treatment (with soil relative water content controlled at 60%~70% FC at seedling stage, 60%~70% FC at budding stage, 70%~80% FC at flowering and boll-setting stages and 60%~70% FC at boll-opening stage) during the whole growing season was designed as control (CK) with 24 replicates. Root system parameters, such as root dry weight, root weight density and total shoot dry matter weight were measured synchronously in all treatments during water stress period and after re-watering, respectively. The results indicated that there were differences in effects of RDI on growth of roots and shoots in cotton due to both phenological stages and degrees of water deficit. Although water deficit didn’t change the original trend of root growth in cotton, the growth rate of root was promoted. The growth of root was promoted significantly during moderate water deficit (50%~60% FC) at some growing stages, and there was a ‘super-compensation effect’ in root growth or the effect on delaying senescence of root after re-watering, and a higher ratio of root to shoot (R/S) was still retained at later stage of cotton growth. Therefore, it was indicated that moderate water deficit was suitable irrigation treatment for coordinating the relation of root and shoot growth of cotton. The results suggested that RDI should be adopted as an effective approach in regulating the growth of root and shoot in cotton plants.

Abstract:Through indoor single-line interference infiltration of clean water film hole irrigation and four different clay and sand grades of single-line interference infiltration of muddy water film hole irrigation tests under the same condition, the influence of single-line interference infiltration characteristics of muddy water film hole irrigation under different clay and sand grades was studied, the relationships between single-line interference infiltration of muddy water film hole infiltration volume, single-line interference time, wetting front movement distance and different clay and sand grades were established, the cumulative infiltration volume model and free surface and interference surface wetting front movement distance models for single-line interference infiltration of muddy water film hole per unit area under different clay and sand grades were put forward, and the infiltration reduction feature and influent law of single-line interference infiltration of muddy water film hole irrigation with different clay and sand grades under the relatively same condition of clean water single-line interference infiltration of film hole irrigation were revealed. The results showed that the single-line interference infiltration of muddy water film hole infiltration per unit area of the cumulative infiltration volume was gradually decreased with the increase of physical clay content d0.01 (particle content with diameters less than 0.01mm), the infiltration coefficient K was decreased with the increase of d0.01, and infiltration index α was increased with the increase of d0.01. In the same infiltration time, the vertical and horizontal wetting front movement distances for free surface and interference surface were gradually decreased and the infiltration reduction rate were gradually increased with the increase of physical clay content d0.01.

Abstract:In China, there are large challenges for agricultural drainage system because of frequent flood and shortage of cultivated land, and new requirements are put forward to agricultural drainage system. Improved subsurface drainage was proposed which had characteristics of less cultivated land occupied, more environment friendly and larger drainage discharges than those of conventional subsurface drainage. Based on soil column experiment, the performance and mechanism of the improved subsurface drainage were analyzed under conditions of soil saturation and stable ponding surface water, which considered different soil textures, outflow conditions and ponding depths. Furthermore, a theoretical formula of improved subsurface drainage discharge was given. The results indicated that the drainage capability of the improved subsurface drainage was increased significantly. The drainage discharge equaled to 2~3 times of that of conventional subsurface drainage when filter width was varied from 2cm to 6cm under the experimental conditions. Drainage capability was increased with the increase of filter width, but the increased value was decreased gradually. In addition, the performance of improved subsurface drainage was going to be more obvious with the increase of gap between hydraulic conductivities of soil and filter. Compared the theoretical values with experimental ones, it was shown that the proposed theoretical formula was reasonable and feasible. The research results can provide technological support for the application of improved subsurface drainage. Meanwhile, the research will be beneficial to enrich theory and technology of agriculture drainage, which has important practical significance to ensure food safety and promote sustainable development of irrigated area.

Abstract:The study is aimed to identify the law of how soil property and peanut growth respond to soil and water conservation (SWC) tillage in order to provide a scientific basis for preventing soil erosion, improving soil fertility and increasing peanut yield in red soil sloping land. The impacts of three types of SWC tillage practices, namely vetiver grass hedgerows (VH), straw mulching (SM) and vetiver grass hedgerows plus straw mulching (VH+SM), on soil property and peanut yield were examined and compared with conventional tillage (CT) through a long-term located experiment in sloping land of red soil. Results showed that after five years of the experiment, VH+SM and SM treatments could still promote the growth of stem, leaf, root and fruit of its in peanut flowering and podding periods, and created significant peanut yield increments of 460.65kg/hm2 and 761.11kg/hm2 with increasing rates of 6.19% and 20.32%, respectively, compared with CT. Although VH treatment had no obvious influence on promoting peanut growth and yield, its effect on reducing erosion was remarkable, and thus its comprehensive benefit were still better than that of CT. The three SWC tillage practices all improved the chemical properties of soil to some extent compared with CT. Among them, VH+SM treatment exhibited the best performance, and increased the soil organic matter, total nitrogen and available phosphorus contents by 36.81%, 64.03%, and 43.50%, respectively. Under VH+SM tillage practice, the soil microaggregate (with diameter less than 2μm) content and the total amount of main microbial population were significantly higher than those under CT, indicating that soil physical structure and microbial activity were improved. Hence, the SWC tillage practices were fit for sustainable agricultural development in arid sloping land of red soil in South China. Especially, the combination mode of vetiver grass hedgerows plus straw mulching had outstanding effect on improving soil quality and crop yield.

Abstract:Two-year (2012—2014) field experiment was conducted to promote rainfall utilization efficiency and reduce agricultural pollution caused by plastic film in arid and semi-arid regions of China. A total of five treatments (CK: traditional flat planting with no mulching;M1: ridge-furrow planting with plastic film mulching over ridge;M2: ridge-furrow planting with plastic film mulching over ridge till jointing stage;M3: ridge-furrow planting with biodegradable film mulching over ridge;M4: ridge-furrow planting with liquid film mulching over ridge) were chosen to investigate the effects of different mulching patterns on farmland soil environment, including soil moisture, soil temperature and soil nutrient. In addition, accumulation of shoot dry mass, growth progress, yield, water use efficiency and partial fertilizer productivity of winter wheat were compared among treatments. The results showed that plastic film mulching (M1), biodegradable film mulching (M3) and plastic film mulching till jointing stage (M2) had significant effects on soil conservation, however, liquid film mulching (M4) was inferior in moisture keeping than those of M1, M2 and M3 treatments. Soil nutrient content was decreased after two experimental years in all treatments. Taking soil organic matter content for example, M2 and M3 had higher soil organic matter contents than those of the other treatments and M1 got the lowest soil organic matter content of the five treatments. This meant that mulching with plastic film for a long time would result in rapid decomposition of soil organic matter. Compared with CK, the mulching treatments could remarkably increase soil temperature at early and middle periods, consequently accelerated seedling rate, jointing rate and the accumulation of shoot dry mass, and thus promoted yield, water use efficiency and partial fertilizer productivity of winter wheat. Among the four mulching treatments, M2 and M3 could increase wheat yield, water use efficiency and partial fertilizer productivity to a great extent. Compared with CK, M2 and M3 averagely increased yield by 25.93% and 25.24%, increased water use efficiency by 27.86% and 27.44% and increased partial fertilizer productivity by 25.94% and 25.23% in two years, respectively. And there was no significant difference between them. In conclusion, M2 and M3 were appropriate mulching patterns with less agricultural pollution for winter wheat cultivation in Guanzhong Region, Shaanxi Province.

Abstract:A two-year (2011—2012 and 2013—2014) field experiment was carried out at Yuzhou City of Henan Province, China. The experiment data were used to calibrate and validate the RZWQM (Root zone water quality model) model for its simulation of soil water distributions, above ground biomass and wheat yield under different tillage treatments (conventional tillage, no-tillage and subsoil tillage). The calibrated RZWQM model was then used to simulate the dynamics of soil water storage in the 0~100cm soil layer, crop water consumption, water balance and water use efficiency when conventional tillage was transformed to four types of conservation tillage patterns, including no-tillage, no-tillage with straw mulching, subsoil, and subsoil with straw mulching. The root mean square errors of soil water content were 0.009~0.025cm3/cm3 for model calibration and 0.005~0.054cm3/cm3 for model validation, respectively. Simulation results showed that the RZWQM model was able to simulate the dynamics of soil water content when tillage method was transformed from conventional tillage to the four conservation tillage patterns. Wheat yield was the highest for transformation of conventional tillage to no-tillage, and the water use efficiency could reach 19.3kg/（hm2·mm）. Therefore, no-tillage was the best conservation tillage method for soil moisture conservation among the four conservation tillage patterns.

Abstract:In order to reduce the effect of reservoir operation on river ecological system and solve the ecological problems of Nilki reservoir, an effective ecological scheduling scheme was developed combined with the hydrological variation diagnosis system． Firstly, the hydrological time series was analyzed by hydrological diagnosis method to determine the time node of different human disturbances. Meanwhile, considering the icebound season characteristics in Northeast China, the natural ecological, poor natural and current runoff processes under the mixed time scale were calculated. Secondly, the Nilki reservoir ecological scheduling model restrained by multiple ecological runoff process was established aiming at maximizing the power generation capacity. Finally, according to the water balance equation, the initial population was generated by normalized method to restrict the variables to the same perception radius, and the scheduling process under five kinds of constraints was optimized by firefly algorithm. The results showed that the original river ecological system was not protected effectively under the existed dispatching rules, water was not reasonably used in wet year. Considering the hydrological variation of the ecological scheduling, a low ecological assurance level scheduling scheme was provided for decision-makers by reducing ecological objectives in dry year to reduce the damage to the river ecosystem. The contradiction between hydropower generation and ecological objectives was more obvious in dry season, and it was effectively alleviated in wet season. Therefore, decision-makers need to make scientific decisions in different periods.

Abstract:Spatio-temporal variation of crop water requirement and net irrigation requirement can provide theoretical basis for irrigation scheduling in different areas. The research was based on ground meteorological data from four national meteorological sites and crop coefficient at different growth stages of tobacco in the middle of Yunnan Province. The reference crop evapotranspiration, net irrigation requirement and net irrigation requirement index in the middle of Yunnan Province within 58 years (1956—2013) were calculated using the Penman—Monteith equation recommended by Food and Agriculture Organization in 1998. The water demand variation characteristics of tobacco during the growing season were analyzed. The spatial analysis of water demand, net irrigation requirement and net irrigation requirement index of tobacco was done by using the ordinary Kringing method of GIS. The results showed that as the change of tobacco’s growing season, its net irrigation requirement index was gradually decreased. And the years with net irrigation requirement index which was larger than zero could be accounted for about 54% in the middle of Yunnan Province. It was indicated that tobacco needed artificial irrigation in normal years. The most positive and negative correlation factors for net irrigation requirement of tobacco was precipitation. Besides, the reference crop evapotranspiration, net irrigation requirement and net irrigation requirement index increased with latitude in the middle of Yunnan Province.

Abstract:Making full use of the air temperature, precipitation, normalized difference vegetation index (NDVI) data during 2000 to 2012, the variation of climate and vegetation in Horqin sandy land, as well as the response relationship between vegetation and climate factors were analyzed by qualitative and quantitative methods. The results showed that the vegetation in the region deteriorated gradually from east to west, the area of vegetation growth deteriorated accounted for 28.56% of the research area, and the vegetation growth of the remained area showed ameliorated trend. Perennial vegetation grew well with NDVI, while the precipitation increased faintly and the temperature variation trend was not obvious. The vegetation growth was influenced greatly by 2~3 months accumulated precipitation, the temperature of the month and average temperature of 2~3 months. The vegetation growth was promoted by the following factors, including precipitation increment, temperature rising during April to November, the lowest temperature increment in April compared with inter-annual variation of April to August, as well as the highest or the average temperature decrease from June to August. When NDVI was 0.03~0.33, the vegetation growth was influenced obviously by temperature, when NDVI was 0.33~0.43, it was influenced obviously by precipitation, when NDVI was 0.43~0.62, it was influenced by both temperature and precipitation, however, when NDVI was 0.53~0.62, it was inhibited by the rising temperature. NDVI responded to the changes of precipitation or temperature or combined action of precipitation and temperature in different response ranges, which might overlap.

Abstract:According to FAOSTAT 2014, the production of potato is huge in China, which was almost 96.1363Mt/a, accounting for 24.97% of global production, but subsequently lots of potato stem leaves were produced and had not been effectively utilized. At the same time, the corn straw is also a kind of huge reserve of rural biomass energy, of which the production was about 44Mt/a. The potato planting area in China reached 5.647Mhm2. Southwest mountainous area, northwest area, Inner Mongolia and northeast area are the main planting areas of potatoes, of which the cultivated area approximately accounted for 62% of total potato planting area in China. Thus, large-scale biogas project in these areas can be built by using potato stem leaf as a kind of raw material for anaerobic digestion, which is an efficient path for potato stem leaf recycling. Therefore, based on the early single factor experiment, the parameters optimization of anaerobic digestion process which used potato stem leaf mixed with corn straw as raw material was studied. The quadratic regression orthogonal rotational combination design was used to determine the influences of material concentration, carbon and nitrogen ratio and inoculum quality percentage on mesophilic anaerobic digestion of potato stem leaf mixed with corn straw. Through the research, the quadratic regression model was optimized and decreasedimension was analyzed by the software of Design-Expert. The results showed that the optimum conditions were confirmed as material concentration of 9.87%, carbon and nitrogen ratio of 18.73 and inoculum quality percentage of 20.82%. The predicted TS gas production was 54.55mL/g. In addition, the primary sequence of effect of three factors was inoculum quality percentage, material concentration and carbon and nitrogen ratio. Furthermore, the reciprocal action between inoculum quality percentage and material concentration was obvious. During the verification test, the relative error of TS gas production between model calculation value and experimental value was below 5%. The variance analysis was not significant, and the model matched well with the experiment results.

Abstract:Corn stover is a major agricultural waste, it is abundantly available across China, and its annual production was about 200 million tons in recent years. However, there were limited reports on hydrothermal carbonization of corn stover in the past few years. Thus, corn stover was chosen as the precursor for hydrothermal conversation of the present work. To explore the hydrothermal carbonization process of corn stover and chemical, energetic properties of hydrochar, corn stover was hydrothermally treated at different reaction temperatures from 180℃ to 290℃ for 8h. The results showed that with the increase of reaction temperature, the hydrochar yield was reduced from 71% at 180℃ to 36% at 290℃, and the carbon content of hydrochars was increased from 44.86% of feedstock to 72.36% at 290℃. Simultaneously, when the reaction temperature was increased, the oxygen content of hydrochars was obviously decreased, which was reduced from 44.2% of feedstock to 15.36% at 290℃, thus energy density of hydrochars was clearly increased. When the reaction temperature was up to 290℃, the hydrochar exhibited coal-like oxygen/carbon and hydrogen/carbon atomic ratios, and the higher heating value reached 29.79MJ/kg. Compared with the feedstock, functional group of hydrochars was decreased when the reaction temperature was enhanced. However, the characteristic peaks of C=C, C=O and aromatic functional group in Fourier transform infrared (FTIR) spectra were strengthened. The thermal stability of hydrochars was also increased in thermogravimetry (TG) analysis. Elemental components and FTIR analyses suggested that corn stover during hydrothermal carbonization mainly underwent dehydration and decarboxylation reactions when the operating temperature was below 230℃, however, the process was governed primarily by condensation polymerization and aromatization when the temperature was above 230℃.

Abstract:The electronic tongue has better stability and repeatability than sensory evaluation and it also has the advantages of easy-operated and faster detection speed relative to traditional equipments. At present, the research of electronic tongue is mainly focused on sensor development, and the research on system integration and automation is rare. Thus, a voltammetric electronic tongue was designed, which can automatically adjust the temperature of sample, feed into sample, clean the electrode and detect sample. It included the upper computer, control module, electrode, signal acquisition module, automatic sampling module, thermostatic bath module and display module, etc. The control interface was based on LabVIEW. The upper computer sent commands to control module to drive the automatic sampling module, thermostatic bath module and other modules through the serial port. Signal acquisition module connected the upper computer through USB cable. It contained a three electrodes system, and the signal curve of the sample was obtained by pulse voltammetry. The test results showed that all the modules were stable and reliable and the temperature control accuracy of the sample was (25±1)℃. The area between the signal curve and the X axis was used as the signal characteristic value. The drift of signal characteristic values of 20d was below 5.6%. The characteristic value was affected significantly by the sample temperature. When the sample temperature departure was ±5℃, the error of the characteristic value was 36%. Under the control of temperature bath (25±1)℃, the error of the characteristic value was 5.8%, which indicated that the temperature control can effectively improve the accuracy of electronic tongue detection result. In the detection application，the electronic tongue can distinguish among four different kinds of beer, milk, water and different grades of tea with the principal component analysis (PCA).

Abstract:In order to solve the problem of identification moldy core of apples from the surface, a quick and non-destructive detection method was proposed based on visible/near infrared transmission energy spectroscopy. Visible/near infrared transmission energy spectra of 200 apples were collected in the wavelength range of 200 ~ 1100nm. Totally 140 samples were used for the calibration set, and 60 samples for the validation set. Smoothing method and multiple scattering correction were used to preprocess the original spectra. Totally 12 characteristic wavelengths and 9 principal components were selected by successive projections algorithm (SPA) and principal component analysis (PCA), respectively. Partial least squares discriminant analysis, error back propagation artificial neural networks, and support vector machine (SVM) measurement model were established based on SPA and PCA, respectively. The results showed that the best model was PCA—SVM, and its recognition accuracy rate reached 99.3% for the calibration set and 96.7% for the validation set. The models established based on SPA and PCA were much simpler than those based on full spectra, since the numbers of input variable of them were only about 0.99% and 0.74% of that of full spectra, respectively. The results showed that the method was available and had high identification accuracy. Meanwhile, the results would provide theoretical basis for the research and development of on-line detection of internal quality in apples and portable moldy core apple detector.

Abstract:To study the influence of different processing sequences of acid and osmotic pressure on the inactivation of Salmonella enteritis, a statistical model was used to simulate the inactivation of Salmonella enteritis with different initial inoculations under the optimal processing conditions. The experimental results demonstrated that the sequence of 15% NaCl stress applied firstly and then pH value of 4.5 stress treatment made the number of Salmonella enteritis reduce faster than the reverse sequence or single stress or double stresses used simultaneously at 25℃ in 10h. Moreover, the simulation results indicated that the variability of inactivation time was reduced gradually with the increase of initial inoculation when the inactivation rate of Salmonella enteritis reached 0.9864 and 0.9939, respectively, at all stages of the optimal processing conditions. In addition, the D value by the deterministic inactivation model was a single constant value for a large number of bacteria. However, the fitted D value showed high variability for a small group of bacteria due to the variability of the individual cells, and the D value could be described by the probability distribution. Consequently, the research of different processing sequences of acid and osmotic stress could provide reference of controlling pathogens for food industry production, and the applied statistical modeling method would help to understand the inactivation from the perspective of individual cells as well as to improve the accuracy of risk assessment.

Abstract:Biospeckle is one of the low-cost, portable and online screening tools for optical non-destructive testing technologies, and it shows potential for application to agricultural products quality prediction. Sensory evaluation, texture profile analysis (TPA) and Warner—Bratzler (W—B) shear force were applied to analyze the texture characteristics of beef tenderloin, the correlation between different measuring methods was investigated, and the prediction model of biospeckle for texture characteristics was established. Since the significant difference between tenderloin and shin, it seems not possible to predict their texture characteristics with a same model. Two methods, including slope/bias (S/B) correction method and Kennard—Stone (K—S) typical samples adding method were used to improve the tenderloin prediction model. Compared with the effect of two modified methods, the more accurate and convenient method was chosen to make the model transfer to shin fast. The results showed that the hardness and chewiness of sensory evaluation and TPA had high positive correlation, the determination coefficient (R2) reached 0.98 and 0.90, respectively, and R2 between W—B shear force and hardness of TPA reached 0.95, which proved the reliability of the three texture characteristics measurement methods. The values of R2 for predicting the texture characteristics of hardness, chewiness and W—B shear force with biospeckle activity were 0.83, 0.77 and 0.69, respectively. The results of improvement for the loin model were as follows: as improved with S/B correction method, the root mean square error (RMSE) was 26.65, bias factor (Bf) and accuracy factor (Af) were 1.08 and 1.15, respectively. While the effect of modified with K—S adding method of typical samples was better than that of S/B correction method, and when the adding number of samples was 12, the RMSE was 13.21, Bf and Af values were 1.07 and 1.02, respectively. In conclusion, K—S typical samples adding method could reduce the differences between the different parts, improve the goodness-of-fit of predictive shin model, and produce better effect than S/B correction method.

Abstract:Dielectric barrier discharge (DBD) is hot focus of the discharge technology at present, which owns some advantages, such as simplicity, low cost, easy operation, low-energy consumption, extensive usages and so on. When the DBD reactor worked with two electrodes, the non-thermal plasma (NTP) was ignited by Ar, He, N2, O2 or their mixtures as working gas, which could produce a large amount of X-ray, free radicals, ions, excited atoms and other highly active substances. Hence, the NTP is capable of providing sufficient energy for many chemical reactions. Although the NTP technique could be employed to the nearly whole agricultural production chain from the environment to products, the applications of DBD in agricultural field were just at the beginning step so far. According to the recent references, the detailed conditions of DBD application in agricultural breeding, sterilization, processing and storage, mechanization and engineering, environmental protection, and agro-food quality and safety were introduced. For breeding, DBD could be applied to microbial mutation and seed quality treatment;for the processing of agricultural product, DBD could be employed to sterilization, washing, starch modification, fruit and vegetable storage via ethylene degradation, and so on;for equipment, DBD could be used as a core unit for the ozone generator;for environment protection, DBD could be utilized to degrade microbes, pesticide and veterinary residues, persistent organic pollutants and others in water and soil, and particle matter (PM), total hydrocarbon (THC), NOx, etc. in tail gas from machines;for analytical instrumentation, DBD usually served as an ionization source for mass spectrometry, and an atomizer and excitation unit for atomic spectrometry. In addition, in order to improve the modern agriculture development and protect human’s health and safety, the critical characterization and problems, and the future development for the DBD techniques in agricultural fields mentioned above were analyzed and discussed.

Abstract:In order to find the method of auto detecting body temperature in pig’s cultivation, the homemade thermal infrared imager was used to acquire the infrared thermograms of pigs. The imager was loaded on the arm of the auto-inspection trolley with the camera lens toward pigs, so it can clearly collect the images of pig ear roots. When the thermograms were collected, they were firstly transformed by HSV colorspace into the S-layer images. Furthermore, the morphological closing operation was used for binary image denoising. Finally, adapted Otsu was applied to ear roots detection of piglets, finishing pigs and pregnant pigs separately. The objective function was selected, because it was simple to find a grayscale to maximize η with the minimum computation at the same time. The results showed that the method can be perfectly used to analyze images with complete ear roots for piglets, finishing pigs and pregnant pigs. When the method was applied to those images with incomplete ear roots, the detection rates were 23% for piglets, 25% for finishing pigs and 33% for pregnant pigs.The method cannot be used to analyze images without any ear roots of pigs. The method was applied to the auto-inspection system which can help to find the high temperature pigs in the cultivation. When the abnormal pigs were found, the auto inspection trolley would alert, and then stopped inspecting and began to spray.

Abstract:To explore the visual acuity reaction effect of Locusta migratoria responding to LED light signal, clear the photosensitive response factor and the biological light inducing parameters of Locusta migratoria phototaxis regulated by light, the spectral representation of Locusta migratoria visual reaction stimulated by LED light source was investigated with AvaSpec fiber-optic spectrometer system. On this basis, the degree of Locusta migratoria phototactic response and reaction regulated by spectral light was certificated comparatively through utilizing the investigated device of Locusta migratoria phototactic response to spectral illumination. The results showed that the visual reaction was represented to 380nm, 402nm, 540nm and 602nm glimmer characteristics when Locusta migratoria visual system accepted to absorb 365nm, 400nm, 520nm, and 610nm light photons, and spectral illumination was enhanced, the visual spectral transmission peak amplitude was increased to take on the reaction characteristics of time-varying effect, which originated from the difference of photophysicochemical reactions and light-sensing deconstruction effect of the visual system absorbing different spectral photons, and the visual sensitivity degree of responding to different spectral light stimulation was manifested by visual spectrum peak misregistration and visual spectrum emission amplitude. Moreover, timevarying intensity of Locusta migratoria visual photosensitivity regulation to violet light was the optimal, the following was orange light, and green light was the worst, the visual photosensitivity regulation capacity for orange light was the optimal, the following was green light, and violet light was the worst. Simultaneously, the superior photosensitive aggregating speed for UV light, the better photosensitive aggregating degree for violet light and the better phototactic effect for orange light showed that the phototactic photosensitivity activity, phototactic degree and the phototactic effect were positively correlated with visual stimulation intensity, tim-varying intensity of visual photosensitivity regulation and visual photosensitivity regulation capacity, respectively, and the photosensitive time effectiveness of the visual reaction intensity affected the behavioral selection effect and visual photosensitivity activity effect. Then, based on the stronger stimulating effect of UV light, the better time effectiveness sensitivity of orange light and the stronger photosensitive regulation intensity of violet light, Locusta migratoria phototactic effect can be improved by stimulating time regulation with the combination of UV, violet and orange light. Research results provided theoretical support for the study of trapping mechanical equipment of Locusta migratoria induced by light.

Abstract:Development and layout of the reserved cultivated land resources directly affects the sustainable utilization of land resources and protection of ecological environment. Based on the results of the second round survey of reserved cultivated land resources and targeted at the special environment in Tibet, an exploitation suitability evaluation model of reserved cultivatable land resources in Tibet was presented based on the natural and social benefits. Taking the township level administrative region in Tibet as a unit, clustering variables included each township comprehensive suitability index, continuously concentrated index and yield potential index of reserved cultivatable land resources. Considering the spatial neighbor relationship, the spatial “K” luster analysis was used by tree edge removal (SKATER) algorithm based on graph theory. The cluster analysis was used to determine the exploitation combination of reserved cultivated land resources in Tibet. The results showed that the exploitation suitability of reserved cultivated land resources included three grades, which were the most suitability area, the medium suitability area and the barely suitability area. The area of them accounts for 27.98%, 49.09% and 22.93% of total area of the study area, respectively. According to the model of exploitation combination, the townships with reserved cultivated land resources were divided into three groups as the recently major development area, medium-term moderate development area and long-term development area, which maintained neighbor relationships between the objects, as well as the integrity of the district territories. Furthermore, the results provided reference for the development partition of reserved cultivated land resources for local governments, and it also provided scientific basis for agricultural economy.

Abstract:Data assimilation (DA) provides a way for effective combination of model simulation and observation, and improves accuracy of winter wheat yield estimation. Among various DA methods, the particle filter (PF) is not constrained by the conditions of linear models and Gaussian error distribution, and receives more attention and application of DA. Currently, most researchers adopt single remotely sensed data source and single variable assimilation strategy, which cannot accurately reflect the interactive process among radiation, temperature and water, and limit the performance of data assimilation systems. To improve accuracy of winter wheat yield estimation, a particle filter algorithm was proposed, which was based on a sequential important sampling procedure of assimilating leaf area index (LAI) and vegetation temperature condition index (VTCI) retrieved from MODIS data into the CERES—Wheat model (Crop environment resource synthesis for wheat) to estimate winter wheat yield from 2008 to 2014 in Guanzhong Plain, Shaanxi, China. In order to determine effects of the assimilated variables on winter wheat yield estimation under different management practices, eight typical rainfed farming sites and four irrigation sites were selected, and the assimilated LAI or VTCI or both of them were used to establish winter wheat yield estimation models. The results showed that the assimilated LAI had good temporal and spatial continuity, and the sharp changing points of seasonal LAI were decreased after applying the particle filter assimilation algorithm. The peak and seasonal trend of the assimilated LAI were basically in agreements with those of the remotely sensed LAI, and the problem of low values of MODIS—LAI was solved to a certain degree after assimilation. The seasonal change of assimilated VTCI was in good agreement with those of both the remotely sensed VTCI and the simulated VTCI, and the assimilated VTCI was a good index for indicating crop water stress of winter wheat. These results suggested that the assimilation of LAI and VTCI might be preferable when the study areas were vulnerable to water stress. At the rainfed farming sites, the determination coefficient of the yield estimation model with assimilated LAI and VTCI was the highest as 0.531 (P<0.001), and the determination coefficients of the yield estimation models with assimilated LAI or VTCI were 0.428 and 0.475, respectively, which were both at the significance level of P<0.001. However, at the irrigation sites the determination coefficient of the yield estimation model with assimilated LAI was the highest as 0.539 (P<0.001), the coefficient of the yield estimation model with assimilated LAI and VTCI was 0.457 (P<0.01), and the coefficient of the yield estimation model with assimilated VTCI was the lowest as 0.243 (P<0.10). In conclusion, the LAI and crop water stress were the important factors that affected winter wheat yield in rainfed farming areas, while the LAI became the important factor in irrigation areas. The study could provide a reference for crop yield estimation by using data assimilation algorithms which combined multi-source remotely sensed variables with crop growth model.

Abstract:Moisture content is a major index in the healthy growth of crops. It is beneficial to water and fertilizer management when the crop moisture content is detected timely. The dielectric properties (relative dielectric constant ε′ and dielectric loss factor ε″) of 280 pieces of corn leaves with different moisture contents were measured with a self-made clamping capacitor and an LCR measuring instrument at 36 discrete frequencies over the frequency range of 0.06~200kHz and the moisture content of the corn leaves were measured by drying weight method. To obtain the moisture content of corn leaves, linear regression methods (the combination of SWR and MLR) and nonlinear regression methods (SPA and SVR) were used to establish models to get the relationship between the moisture content and dielectric parameters (ε′, ε″ and the combination of ε′ and ε″), and the leave one out cross validation (LOOCV) was used to select the best models. The results showed that contrasted with the linear regression method, the nonlinear regression method had better predictive ability. The highest coefficient of determination (0.804) and the lowest root mean square error (0.0176) were obtained by using the nonlinear regression model with the variable in the combination of ε′ and ε″, which simplified the model with variables reduced from 72 to 10 and eliminated the overlap variables, and the complexity of the model was decreased effectively. The study indicated that it was feasible to detect the corn leaf moisture content non-destructively, and the results provided a credible method for rapid non-destructive detection of physiology information in crops.

Abstract:Since the sequence data of water temperature in industrialized Litopenaeus vannamei breeding is somehow non-linear, unsteady, and such problems like lower precision in the predicting results, low robustness will appear when utilizing the traditional single item predicting method, a combined non-linear prediction model based on empirical mode decomposition (EMD), phase space reconstruction and extreme learning machine (ELM) was proposed. In modeling, the EMD method was adopted to decompose the original time sequence data of water temperature in industrialized Litopenaeus vannamei breeding into a series of intrinsic mode function (IMF), and reconstruct the phase space of each component, set models of ELM training in phase space, predict each IMF sequence, and then combine and reconstruct the predicted values of each component to get the predicted value of original water temperature sequence. EMD—ELM was tested and compared with other algorithms by applying it to predict water temperature in industrialized Litopenaeus vannamei breeding pond of Zhanjiang City. The experimental results showed that the proposed combination prediction model of EMD—ELM had better prediction effect than the standard extreme learning machine (ELM), least squares support vector regression (LSSVR) and BP neural network methods. And the relative mean absolute percentage error (MAPE), root mean square error (RMSE) and mean absolute error (MAE) between the EMD—ELM and standard LSSVR models were 62.82%、45.62% and 42.77%, respectively, under the same experimental conditions. The relative MAPE, RMSE and MAE between the EMD—ELM and standard ELM models were 34.44%、28.94% and 25.37%, respectively. The relative MAPE, RMSE and MAE between the EMD—ELM and BPNN models were 77.0%、60.83% and 54.77%, respectively. It was obvious that the EMD—ELM had high forecast accuracy and generalization ability. The research results provided a new effective technical support for water temperature management and control in the industrialized cultivation of Litopenaeus vannamei.

Abstract:To explore the effect of water treatment and the influencing factors by using the electrochemical oxidation process in industrial recirculating aquaculture system, the research was conducted under the best condition with temperature of 25℃, current density of 40A/m2 and flow rate of 300mL/min, which was obtained by the former study. With different initial concentrations of ammonia nitrogen, suspended solid of simulated aquaculture water and actual aquaculture water of tilapia from the recirculating aquaculture lab of Zhejiang University, the removal rate of ammonia nitrogen was explored by using electrochemical process combined with UV irradiation. It demonstrated that the effect of using electrochemical process combined with UV irradiation was much better than that of single use of electrochemical process. Therefore, under initial concentrations of ammonia nitrogen at 4mg/L, 7mg/L and 10mg/L of simulated aquaculture water, the removal rates of ammonia nitrogen were increased by 45.0% （p<0.05), 36.0% （p<0.05) and 20.0%（p<0.05), respectively. The initial concentration of ammonia nitrogen、the suspended solid in the aquaculture water and the actual aquaculture water had important effects on removal efficiency of ammonia nitrogen, with the increase of initial concentration of ammonia nitrogen and concentration of suspended solid, the removal efficiency was reduced and the spending time was prolonged. For example, the treatment of different simulated aquaculture water with suspended solid of 100mg/L, 150mg/L, 200mg/L, the removal rate of ammonia nitrogen was decreased with the increase of SS, compared with the simulated aquaculture water only containing ammonia nitrogen, the removal rates of ammonia nitrogen were decreased by 51.7% （p<0.05), 65.5% （p<0.05) and 72.4%（p<0.05), respectively. When dealing with actual aquaculture water, although the system had great effects on the removal of ammonia nitrogen (the efficiency was 97.8%), nitrate nitrogen (the efficiency was 96.9%) and suspended solid (the efficiency was 92.1%), the removal rate of ammonia nitrogen was decreased and the time spent was prolonged.

Abstract:To improve ride comfort and stability of vehicle, a kind of semi-active suspension with double pole magnetorheological damper was designed. Based on the analyses of mechanical model for magnetorheological damper, an improved polynomial model of magnetorheological damper was proposed and a dynamic model of semiactive suspension system with magnetorheological damper was established. The physical prototype for magnetorheological damper was made and the mechanical property tests of the magnetorheological damper were completed. The curves of damping forcedisplacement and damping force-speed were acquired. By using the test results, the model parameters were identified and the improved polynomial mechanical model of the magnetorheological damper was verified. Considering the timedelay impact on the suspension system, the critical time-delay for the magnetorheological suspension was calculated. Smith forecasting compensation control strategy was used and the timedelay fuzzy controller of semi-active suspension with magnetorheological damper was designed. The simulations of time-delay compensation control were carried out by Matlab software. And the test bench systems for semiactive suspension were developed. Then, the tests of the semi-active suspension with magnetorheological damper were done. The simulation and experimental results showed that the magnetorheological damper had good energy dissipation effect, good controllability and the maximum of vibration attenuation function. The improved polynomial mechanical model of the magnetorheological damper was correct. Compared with the passive suspension, sprung mass accelerations for magnetorheological semi-active suspension were dropped by about 30%. The damping effect of the developed semi-active suspension was obvious.

Abstract:The research objective was to propose an analytic model to investigate the transient dynamic behavior of a tracked vehicle powertrain. Firstly, by considering the engine torque harmonics, gear backlash, friction coefficient and other nonlinear factors, lumped-mass component models as diesel engine, torque converter with lockup clutch, wet clutch, spur gear pair and vehicle were developed and then incorporated to an integral model. Then, a gear shift process that induces nonlinear dynamic behaviors, including clonk, gear contact loss and clutch stick-slip judder was simulated with the initial and boundary conditions for the shift process carefully set. Transient dynamic behaviors and the mechanism of dynamic behaviors occurred during the gear shift process were discussed. Finally, time-frequency analysis of output torque was conducted by wavelet transform. The instants of the occurrences of transient dynamic behavior were identified by time-frequency analysis and the corresponding frequency components were examined. The clutch torque pulse with a steep gradient due to the transition between slip and stick was an impact source in the system, and the results also indicated that the gear contact and reverse impact (114Hz) significantly impacted the output torque, the clutch stick-slip judder (1500~5000Hz) also affected the output torque but the high-frequency vibrations (higher than 5kHz) had little influence on it. The wavelet transform based time-frequency frequency analysis can be used to diagnose NVH issues of vehicle powertrain. Also, the system parameters of the powertrain can be optimized to obtain good NVH characteristics by using the simulation method proposed in the article.

Abstract:Through analyzing requirements of injection control of high pressure common rail diesel engine, the air intake system had obvious hysteresis in the changing speed. And this kind of hysteretic performance was represented that the increment of the intake-air could not obviously keep pace with the increment of the injection. Thus, the designed correction algorithm of main injection quantity for changing speed could newly modify the original main injection fuel quantity, and obtain the reasonable air-fuel ratio and optimize the combustion process. For the fluctuation of common rail pressure was caused by the multiple injection, the fuel correction algorithm of multiple injection for common rail pressure fluctuation could pre-rectify the fuel injection pulse width and improve the injection accuracy, which were realized by using the ASCET modeling software tools of ETAS company and the independently developed ECU circuit board. After calibration experiment of the engine on YN33CR high pressure common rail diesel engine, such as starting and idling condition test, main injection quantity correction test of changing speed, fuel correction test of multiple injection for rail pressure fluctuation, constant torque and increasing speed mode test, constant speed and increasing torque mode test, the results showed that the fuel injection control strategies achieved the expected results and it can effectively improve the injection control.

Abstract:The urea selective catalytic reduction (Urea—SCR) system has been widely used in the aftertreatment system of diesel engine, in which the injection quantity of urea is selected as the control input. By the precise control of the ammonia coverage rate, the poisonous NOx can be converted to the environmentally friendly N2 and H2O. As Urea—SCR system has nonlinear characteristics and disturbance is difficult to model, a two degree of freedom control system consisting of a feedforward controller and an H∞ feedback controller was developed. Firstly, the Urea—SCR system model was deduced based on the principle of chemical reaction kinetics. Secondly, the feedforward controller was designed based on the differential flatness method. The flatness output was chose as ammonia coverage rate, then the system state, control input were expressed by flatness output and its finite order derivatives, based on this, the feedforward control input was obtained. Thirdly, the Taylor expansion of the Urea—SCR system model was carried out at the equilibrium point of the feedforward control input, the un-modeling dynamics of urea and parameter uncertainties were considered as the amplitude-bounded disturbance input. The feedback control controller which satisfied the H∞ performance index was designed to accurately control the ammonia coverage rate. Finally, the tracking performance and robustness were verified by the simulation results with the engine dynamics simulation software enDYNA under FTP75 test cycle.

Abstract:Low energy efficiency is a significant problem for the hydraulic excavator. To save energy, the independent metering system is a promising alternative to the conventional valve control system by decoupling the meter-in and meter-out orifices. An independent metering control excavator system is a complex hydraulic-mechanical coupling system. In order to build precious simulation model, it is required to identify each component parameter, including the coupling links between hydraulic and mechanical systems. The nonlinear mathematical models of the system were firstly established. The hydraulic model considered both laminar flow and turbulent flow was used to accurately capture the flow-pressure characteristics. The model parameters were estimated according to measurements. The frictions of actuators were also identified by kinetic equations combined with the least square method. In order to increase the accuracy and speed of parameter identifications, the processes of identifications were transformed to a nonlinear optimization subject and a NLPQL multi-objective optimization algorithm was applied to seek the optimal values of property parameters. Based on the mathematical models, a lumped parametric coupling model was presented. Compared with the co-simulation model in the state of the art, the proposed model was implemented in a parametric platform, conducing to improve simulation efficiency because it had the advantages of short computation time and easy to modify mechanical parameters in terms of operating conditions. Finally, experiments were done to compare with the simulation model. The deviation of static pressures in cylinders between simulated and experimental results was less than 0.2MPa, and that of dynamic velocities was about 4%~6.5%. Besides, the results of independent pressure and velocity close-loop control verified that the presented model had enough computation accuracy to provide a reference for researching the control strategy.

Abstract:A new path planning method was proposed for an excavator to finish the autonomous mining, which was aimed to make the trajectory smooth and continuous, and decrease vibration impact strength. According to the proposed method, the path in working space will be reasonably segmented, so that the calculation of the amount of calculation will be reduced as far as possible in order to ensure that the path deviation of the path planning result is not affected by the task completion, and the trajectory planning of each segment was computed respectively by using interpolation polynomial with variable order. A certain type of single bucket hydraulic excavator was taken as the research object. First of all, the mining path was separated into five segments which employed interpolation polynomial with high order of 3—3—5—3—3 successively in trajectory planning. The simulation was achieved by Matlab software. The result showed that the three curves for joint angle, angular velocity and angular acceleration were smooth and continuous, but some acceleration values in some segments exceeded the acceleration constraint. In order to improve the dynamics performance of the excavator’s working mechanism, the segments having odd values were computed afresh with modified trajectory polynomial of which the highest order was calculated in terms of the acceleration constraint. New curve which figured by the piecewise polynomial with variable order showed that the new trajectory planning could be of use for the stable and continuous operation in autonomous mining.

Abstract:A multi-objective evolutionary algorithm cooperated with decomposition mechanism and opposition-based learning model was proposed for solving complex multi-objective optimization problems. Under the framework of multi-objective evolutionary algorithm based on decomposition, the opposition-based learning model was introduced into the algorithm. The model improved the algorithm’s exploitation. During the evolution process, the opposition-based learning model facilitated the local optimization and the differential evolution strategy enhanced the global research for the new algorithm. The opposition-based learning strategy and differential evolution were in coordination to balance its exploration and exploitation. The benchmark LZ09 series of internationally recognized with complicated Pareto sets were adopted to verify its effectiveness. The proposed multi-objective evolutionary algorithm based on opposition-based learning model was compared with MOEA/D based on DE (MOEA/D—DE), the third evolution step of generalized differential evolution (GDE3), fast and elitist multi-objective genetic algorithm (NSGA—II) and improving strength Pareto evolutionary algorithm (SPEA2), the results showed that the proposed algorithm can obtain Pareto fronts with good convergence, diversity and wild coverage. In order to analyze the algorithm to solve the problem of performance constraints, the proposed algorithm was applied to solve the multi-objective optimization design of speed reducer. The results showed that the Pareto front obtained by the algorithm was uniform, which demonstrated its good performance in solving practical problem with constraints and engineering effectiveness.

Abstract:In order to improve the response and vibration suppression abilities of stabilized platform servo system, a novel vibration suppression strategy was proposed by using an integration of fractional-order improved disturbance observer (FIDOB) based on adaptive grey predictive controller (AGPC) in stabilized platform system. A method of system modeling output module was established based on GM(1,1) power module and an adaptive adjust module was designed. The predicted error and actual error were combined together to form an integrate error, according to the values of the actual control system error and the predicted error, the prediction step and predicted error weight were adjusted to improve the response ability of system and decrease the influence of predicted error on the system output. The fractional-order improved DOB was established, and the robust stability was derived in detail. FIDOB was used to obtain disturbance estimate and generate compensation signal, and as the order of Q-filter was expanded to realnumber domain, FIDOB had a wide range to select a suitable tradeoff between robustness and vibration suppression. Finally, numerical simulation results illustrated that the method can suppress external disturbances and measurement noise well, and it can also improve the response ability of system. The proposed control strategy was simple in control-law derivation, and its effectiveness was validated by numerical simulations. In numerical simulation experiments, with the interference of friction and measurement noise, the tracking error of stabilized platform system was no more than 0.1rad/s. In the static and dynamic experiments, the regulating time of the stabilized platform was decreased by 0.258s, and the stable precision was increased by 1.5°~2.5°.

Abstract:A parallel robot with compliant joints was formed by compliant joint substituted for the traditional joints between the driving rods and the connecting rods in a 3—RRR planar parallel robot. Based on the dynamics models of the parallel robot with compliant joints and the traditional-joint parallel robot, the trajectories of the moving platform and the angles change of driving rods were solved theoretically and compared with each other, and the results showed that both of theoretical calculation curves were very close, but there were high-frequency low-amplitude vibrations in the parallel robot with compliant joints and the maximum relative difference of trajectories of moving platform and of the angles change of driving rods were 1.02% and 1.6%, respectively. At the same time, the maximum driving torques of both robots were compared, and the result was that the maximum driving torques of the parallel robot with compliant joints were less than that of the conventional-joint parallel robot. Simultaneously, the trajectories tracking experiments of the parallel robot with compliant joints and the traditional-joint parallel robot were made respectively, which were compared with the ideal circular path, the result showed that the two experimental trajectories changed both basically consistent, but the magnitudes were different. The two experimental trajectories were compared with each other, and the relative difference was 3.91%. The theoretical and experimental studies proved that it was feasible and effective that the traditional joints were substituted by compliant joints in the parallel robot, which laid foundation for further study of parallel robot with compliant joints.

Abstract:Multi-loop coupled mechanism is a new kind of complicated mechanism which has been used in bio-robot, aviation, refuge and other areas. However, it is deficient in theoretical study. The most basic understanding for a new mechanism is to realize its mobility. Multi-loop coupled mechanism， i.e., serial-parallel hybrid mechanism, is different from the general parallel mechanism， and the former is coupled with each other among the branch chains．Therefore, the analysis of topology structure characteristic of multi-loop coupled mechanism is much more complex．Using the topological structure synthesis theory for parallel mechanism based on POC set and SOC unit ( POC method, for short)，the two classic multi-loop coupled mechanisms, symmetrical and asymmetrical ones, were analyzed. The correct degree of freedom and coupling degree could be calculated only if “coupling-number” was subtracted correspondingly by number of degree of freedom (DOF) and constrain degree when using the corresponding DOF formula and constrain formula．The coupling-number meant the coinciding number for over three branch chains, which was similar to the multiple-kinematic joint in the planar linkages. The result demonstrated that POC method can effectively analyze the multi-loop coupled mechanisms, and its physical and geometrical meanings were clear and the operation was simple and easy to understand. The structure of the multi-loop coupled mechanisms was seemingly complex，but its coupling degree was relatively low compared with 6-SPS Stewart-Gough platform with coupling degree of 3, and the kinematics and dynamic analyses were not complex．Therefore，the multi-loop coupled mechanisms have potential application value, and the application background still needs to be explored.

Abstract:Dielectric electroactive polymer (DEAP) cylindrical actuators have a simple structure and strong capability to output large displacements and forces. Analysis of its structural parameters forms the basis for its design optimization and proper operation of DEAP actuators. Through geometric modeling of the actuator, the impact of axial elongation and diameter-thickness ratio on the deformation of each layer was analyzed. Based on the failure mode analysis, the influence of actuator structure parameters of pre-stretch, winding number of the DEAP film, spring parameters, etc. on its performance was obtained. Results showed that small diameter-thickness ratio and large winding layers would change the film thickness difference significantly in each layer when the actuator was elongated. According to the structural features of cylindrical actuators, the main factors affecting the allowable scope of work were the failure modes of electric breakdown of DEAP film, the loss of actuating force of the compression spring, and extreme deformations. The actuators performed better when the pre-stretch was increased and the pre-stretch ratio in circumference was larger than that in axial. No significant effect was observed on the output performance by increasing the layer-number. Reducing the stiffness and length of the spring can increase the axial stretch ratio of the actuator, and it had variable impact on the axial displacement changes. Meanwhile, the calculated force difference should be prevented from exceeding the preloaded force of the spring.

Abstract:The magnetorheological (MR) valve is a smart control mechanism using the magnetorheologcial fluid as the working fluid. The advantages of regulating pressure drop and fast response time make the valve have a promising application prospects in the hydraulic servo system, and the MR valve can also be used as a bypass valve to control the MR damper, which can be applied to the different types of vibration attenuating system. The change of pressure drop of MR valve considering radial and annular fluid flow paths was outlined through theory analysis, numerical simulation and experimental verification. The magnetized resistance gaps of both MR valves were constrained within a width of 2.5mm and a length of 80mm. The mathematical models of pressure drop of both MR valves were derived separately. The finite element modelling was carried out using ANSYS/Emag software to investigate the distribution of magnetic flux density and dynamic yield stress, and the analytical pressure drop was also obtained, the maximum theoretical pressure drops for the radial and annular type MR valves are 1930kPa and 982kPa respectively. Furthermore, a test rig was set up to test the pressure drop under different applied direct currents and different load cases, the maximum experimental pressure dropts for the radial and annular type MR valves are 950kPa and 660kPa, respectively. The simulation and experimental results showed that the pressure drop of the radial type MR valve was superior to that of annular type MR valve under the same geometry conditions and the same electromagnetic parameters. The results can provide a new guideline for design of other types MR valve.

Abstract:In order to improve the machining accuracy of CNC machine tool and promote manufacturing industry upgrade development, a CNC machine tool spindle optimization design expert system was studied. On the basis of the rich CNC machine tool spindle design experience in current, mechanical dynamics, optimization method and fuzzy logic theory, a spindle transmission type fuzzy optimum seeking method was developed. Taking the dynamic and static performance of CNC machine tool spindle as optimization goals, and adopting the sensitivity analysis to choose the design variables, a mathematic model of the spindle structural multi-objective optimization design was established. A gradual optimization algorithm was put forward to solve the optimization model, and a new kind of spindle structural optimization design method was obtained. Through integrating the “spindle transmission type fuzzy optimum seeking method” with the “spindle structural optimization design method”, the CNC machine tool spindle optimization design expert system was developed. Taking the multi-objective optimization design for a precision CNC machine tool spindle as application case, the optimization design results were compared with the actual situation and the experimental results, which verified the feasibility of the CNC machine tool spindle optimization design expert system.

Abstract:For the geometric error elements of three-axis CNC machining center which greatly affect the machining precision, the spatial geometric error fields were analyzed, and the universe simulation software of error fields was developed. Firstly, error elements were analyzed based on multi-body theory;the spatial geometric error fields of machining center were modeled according to the topological structure of the machining center. It can be seen that the models of spatial geometric error fields were closely relative to the types and the positions of axes in the working piece chain and tool chain of the machining center. The models were different for machine centers with different topological structures. Then, the simulation software of error fields for universe three-axis CNC machining centers was developed due to the modeling process using Visual Studio platform in order to conveniently analyze the different machining centers. The software can realize the visualization of error fields and generate the compensated machining code based on the nominal code. It can give help for the structural design and error compensation of machining centers. Finally, the simulation software was applied to Carver800T vertical machining center. The error fields of this center were analyzed with all measured geometric error data to obtain the error distribution curve and the whole error fields of the machine tool. The compensated machining code was also obtained based on the nominal code of workpiece and the error fields of this machine center. It provided basis for the precision improvement and error compensation of machining center.

Abstract:The piston chamber has compression and expansion in closed volume when it is separated from the process of discharge and suction, which caused cavitations and pressure overshoot or undershoot. In addition, the noise problem caused by flow ripple and pressure pulsation may occur. Therefore, a new valve plate was designed to solve those problems. First of all, the mathematical model of flow characteristic was established to analyze the mechanism of the noise in axial piston pump. Then, the new structure of the valve plate was designed and the structure parameter of triangle notch was optimized. According to the design of valve plate structure, the equation of pressure characteristic in transition region was established. Thereafter, the new valve plate was capable to reduce the pressure pulsation, which was validated by theoretical calculation. Finally, the simulation model of piston pump was developed based on AMEsim to analyze the effects of the new valve plate on flow rate and pressure. Moreover, the simulation model was verified accurately based on the comparison of experiment and simulation results. The flow pulsation rate was calculated in the simulation model with original valve plate and new valve plate under the same working condition. The results showed that the flow pulsation rates with the new valve plate and original valve plate were about 11.47% and 18.22%, respectively, and the flow pulsation rate with the new valve plate was decreased by 6.75% compared with the original one. As a consequence, the results showed that the new valve plate can effectively reduce the fluid borne noise in the axial piston pump. The simulation model can be used in the design of new products, which can lower the cost.

Abstract:Iron-gallium (Galfenol) alloys are new classes of magnetostrictive material which have moderate strain under very low magnetic field intensity, low hysteresis, and high tensile strength. These unique mechanical properties and superior magnetic attributes motivate the use of Galfenol in various actuation and sensing applications. Galfenol systems are usually operated in dynamic magnetic field environment, in which the influence of dynamic loss cannot be neglected. When Galfenol is applied to dynamic magnetic field, the power losses are separated into hysteresis loss, classical eddy current loss and anomalous (or excess) loss. Based on static energy-averaged hysteresis model of Galfenol, the dynamic hysteresis strain and magnetization model considering eddy current losses and excess losses of ferromagnetic material under dynamic magnetic field was proposed. Static strain and magnetic field were measured using testing system of Galfenol magnetic properties. The results showed that the calculation results were in good agreements with experimental results. Relationships between strain and dynamic magnetic field under different frequencies of 〈100〉 oriented polycrystalline Fe83Ga17 were measured. The frequencies were 1Hz, 10Hz, 20Hz, 40Hz, 60Hz, 100Hz, 200Hz and 300Hz. The results of experiments and calculation agreed well when frequencies were below 200Hz, and when frequencies were higher than 200Hz, the results of experiments and calculation had deviations. The model can be used in dynamic application of Galfenol alloy under low frequency such as actuators and vibrators.