基于离散元法的旋耕过程土壤运动行为分析

土壤与耕作部件间的相互作用规律是设计和选用土壤耕作部件的基础。研究土壤和耕作部件间的相互作用规律就是要研究耕作部件对土壤产生的作用和它们之间的作用力,首先必须探讨耕作部件工作时土壤运动规律和施加于土壤的作用力。为此本文建立基于离散元方法的旋耕工作模型;对比分析实验与仿真的土壤位移:在土槽实验中采用示踪块方法测量土壤位移,仿真中通过追踪表层土壤颗粒的运动获得仿真位移;利用实验和仿真数据对土壤位移和运动机理进行分析。结果表明:土壤水平和侧向位移都随着转速增加呈现增加的趋势;土壤的水平运动位移总是大于同转速下的侧向位移。浅层土壤颗粒的运动位移最大,中层土壤次之,深层土壤最小。较深位置的土壤,距离旋转中心越近的土壤颗粒水平位移和侧向位移越大。在旋耕刀切土范围内的土壤,有向相反方向运动趋势的浅、中、深层颗粒比例分别为26.2%、72.1%、48.4%。在水平力作用下,大部分土壤颗粒随着旋耕刀切土有向后运动的行为;土壤在开始时刻的侧向受力和侧向运动方向,由颗粒的侧向位置是否偏离侧切刃轴线决定,位于侧切刃轴线左侧的颗粒,则其侧向力向左,反之亦然;土壤在垂直方向先随着刀具入土向下运动,然后滑出刀刃边界被抛起。本文建立的仿真模型得到的土壤水平位移和侧向位移与相应实验值的误差为24.9%和15.3%。本文运用离散元法进行旋耕过程中土壤宏观和细观运动行为的分析,有助于理解旋耕刀与土壤的相互作用机理,为旋耕机械的设计与优化提供理论依据。

小麦茎秆力学性能的国内外研究

小麦是我国主要粮食经济作物。本文对其茎秆的拉伸、剪切、弯曲、压缩等力学性能的研究进展进行了简要回顾,对现有研究存在的不足进行了简要分析。国内外的相关研究均忽略了小麦茎秆上鞘的存在对小麦茎秆力学性能的影响,鲜有文献分析小麦茎秆的力学性质与机具的相互作用。将小麦茎秆力学性能与现有的仿真分析技术结合,将有利于小麦茎秆力学性能的发挥及农业机械的设计与优化。

液氨预处理工艺对五节芒酶解糖化效果的影响

为提高五节芒可发酵单糖的产量,采用液氨对其进行预处理。选用预处理温度T、五节芒含水率M、驻留时间t和液氨用量比k为变量因素,在试验范围内T（70～170℃）、M（20%～200%）、t（5～30 min）、k（0.5～5.0）通过对各因素的不同取值,分析上述因素对五节芒酶解效果的影响。结果表明：在T=130℃、M=80%、t=10 min、k=2.0的条件下预处理,五节芒72 h的葡聚糖和木聚糖酶解率分别为72.1%和82.5%,即100 g干基原材料可获得可发酵单糖55.8 g,是未经预处理样品酶解率的3.65倍。因此,液氨预处理能够有效促进五节芒的酶解单糖转化率。

植保无人飞机作业参数对田外除草靶标区内外雾滴沉积规律的影响

雾滴大小、气象条件和施药装备的作业参数对雾滴的覆盖范围、靶标的吸附性能有影响。无人飞机(UAV)是目前有助于高效喷雾的现代施药技术装备。然而作业参数对靶标区和脱靶区的影响依然尚待确定。开展了田间试验并运用沉积扫描软件测定了在田外除草中不同飞行高度(2 m和3 m)和飞行速度(2 m/s和3 m/s)下雾滴的沉积量、覆盖密度、覆盖率和雾滴直径。结果表明,当无人飞机在处理T_(1)中以2 m/s速度、2 m高度飞行时,靶标区域平均沉积量最高,为2.29μL/cm^(2),飞行航线中央0点位置的覆盖率达到36.19%。处理T_(1)、T_(2)、T_(3)和T_(4)在飞行航线中央的雾滴谱相对宽度分别为0.70、1.01、1.03、1.05。处理T_(1)体积中值直径(VMD,也即D_(v0.5))最大,为448.75μm;而处理T_(4)的D_(v0.5)最小,为238.95μm。单旋翼无人飞机在脱靶区的沉积量几乎可以忽略不计。本研究为无人飞机运营商、农民和生产企业提供了参考,从而优化航空植保技术在除草上的应用。

Effects of droplet size and spray interval on root-to-shoot ratio,photosynthesis efficiency,and nutritional quality of aeroponically grown butter head lettuce

The proper selection of the atomizer(droplet size)and nutrient solution spray interval is one of the most important factors to be investigated in aeroponics system for sustainable agriculture.The aim of this study was to research the effects of four aeroponics atomizing nozzles(one air-assisted;A_(1),two air-less;A_(2) and A_(3),and one ultrasonic fogger;A_(4))with droplet sizes of 11.24μm,26.35μm,17.38μm,and 4.89μm,respectively,four spray intervals(15 min(I_(1)),30 min(I_(2)),45 min(I_(3))and 60 min(I_(4)))at a 5 min of constant spray time by atomizing the Hoagland’s nutrient solution on growth,root-to-shoot ratio,photosynthesis characteristics,pigments,and nutritional quality of the aeroponically grown lettuce.The experimental results demonstrated that in A_(1) atomizer and I_(2) interval,the growth,photosynthesis efficiency,chlorophyll,carotenoids,and nutritional values of the lettuce were significantly higher compared to that grown in A_(2) and A_(3) atomizers at all spray intervals.The shoot developments were more constrained than root,prominent to the alteration of root-to-shoot ratio(fresh and dry)in the influence of different droplet sizes and spray intervals.Moreover,the plants did not grow well in A_(4) atomizer associated with proposed spray intervals.The results disclosed that there was an obvious interaction between droplet sizes(atomizers)and spray intervals for growth,the ratio of root to shoot,photosynthesis efficiency,pigments,and nutritional quality of the aeroponically grown lettuce.This research study increases the awareness of the proper droplet size(atomizer)and the regulation of nutrient solution spray interval for leafy vegetables grown in an aeroponics system.

Mechanical strength of wheat grain varieties influenced by moisture content and loading rate

Mechanical shear resistance of wheat grain is a significant concern for the designers and researchers related to the design of threshing,handling and processing machinery of the field crops.The grain mechanical properties directly affect the machine geometry and its operational parameters.The present study was carried out to determine the shear resistance of five wheat varieties(Locally names;TD-02,Sindhu-1105,Benazir,China and SKD-118)influenced by moisture content(16.7%,18.7%and 19.5%)and loading rate(3 mm/s,6 mm/s and 9 mm/s).However,some physio-dimensional properties(length,width,thickness,slenderness ratio,surface area and sphericity)were obtained at different moisture contents.The results showed that the shear resistance reduced by increasing the moisture content and loading rate.The average shear resistance decreased from 10.45 N to 3.74 N for 3-9 mm/s loading rate at moisture content of 16.7%to 19.5%.Thus,the maximum correlation(r=0.905)of shear resistance obtained at 16.7%,whereas minimum correlation(r=0.692)obtained at 19.5%.The shear resistance of wheat grain was highly significant(p<0.05)at 9 mm/s for 19.5%.Shear resistance decreased with an increase in the moisture content in the grain whereas deformation is increasing with the increase of moisture content.However,the maximum bulk density of wheat grain obtained at 19.5%for SKD-118,while the minimum obtained at 16.7%for TD-02.It is recommended that the design and modification of wheat grain processing equipment should be executed on the physio-mechanical properties of grain varieties.

Effects of different irrigation frequencies and incorporation of rice straw on yield and water productivity of wheat crop

The current rapid increase in irrigation water consumption is considered unsustainable and threatens the world food production.Therefore,it is mandatory to promote modern techniques and to manage existing conventional irrigation methods.The present study was attempted to determine the effects of different irrigation frequencies and rice straw incorporation rates on yield and water productivity of the wheat crop.The experiment was arranged with randomize complete block design involving nine treatments(RS 0 I 7,RS 0 I 15,RS 0 I 22,RS 1 I 7,RS 1 I 15,RS 1 I 22,RS 2 I 7,RS 2 I 15 and RS 2 I 22)under three replications.Results exposed that the incorporation of rice straw with different irrigation frequencies significantly improved physico-chemical properties of soil.Moreover,soil bulk density,infiltration rate,pH,electrical conductivity significantly decreased and soil porosity significantly increased under all treatments.Furthermore,maximum crop yield and crop water productivity of 7706.4 kg/hm 2 and 1.92 kg/m 3 respectively were found under RS 1 I 15 treatment.Based on experimental results it can be concluded that irrigation frequency and incorporation of rice straw had significant effects on the physico-chemical properties of soil,total grain yield and water productivity of the wheat crop.However,this study suggested that the wheat crop yield and water productivity could be increased by incorporating 1 t/hm 2 rice straw with 15 d of irrigation frequency.

Predicting 3D forces of disc tool and soil disturbance area using fuzzy logic model under sensor based soil-bin

A knowledge-based fuzzy logic model was developed on experimental data and used to predict the draft,side and vertical forces and soil disturbance area by disc tillage tool operation.The laboratory research work was conducted to evaluate the performance of the disc tool at three working speeds(1.25 m/s,1.98 m/s and 2.47 m/s,respectively)and depths(0-5 cm,5-10 cm and 10-15 cm,respectively)on paddy soil under soil-bin environment.Further,draft(Fx),side(Fz)and vertical(Fy)forces of disc and soil disturbance area were assessed and predicted towards working speeds and depths.A fuzzy prediction model with two input variables(speed and depth)and four output variables was developed and the Mamdani inference approach was used.Draft,side and vertical forces of disc and soil disturbance area were positively responded 0.97,0.95 and 0.84 and 0.99,respectively.The prediction results showed a close relationship between measured and predicted data.Similarly,the measured and predicted results revealed that the draft,side,vertical forces,and soil disturbance area slightly increased,while increasing the speed and depth of the disc tool.Furthermore,disc forces and soil disturbed area were highly significant(p<0.05)for higher speed towards depth.It was concluded that the fuzzy model may be introduced for predicting the disc forces and soil disturbance area during the disc tillage tool operation with high accuracy.

Discrete element method simulation of disc type furrow openers in paddy soil

For granular materials,discrete element modeling is one of the best computer tools to simulate their behavior and interactions.A field experiment was carried out to evaluate the performance of disc furrow openers in paddy soil.Discrete element simulation was done to develop a 3D DEM model for notched,toothed and double disc furrow openers using EDEM software.Hertz Mindlin contact model with bonding was applied for simulation to fulfill the obligations of the soil moisture and bonding between the cohesive particles.Simulated and field experimental data were compared to determine the applicability in the different working conditions.The results of the simulation validated the applicability of the Hertz-Mindlin contact model with bonding to simulate the no till paddy soil using an extremely narrow tillage tool.The calibrated value of normal and shear stiffness was 5×10^(7)N/m,and the calibrated value of bond normal and shear strength was 3×10^(7)Pa.The relative error(-1.7%to 20.6%)for the double disc furrow opener was lower as compared with that notch typed(29.2%to 44.4%)and toothed type(31.5%to 45.9%)furrow openers.

Overview of the aeroponic agriculture-An emerging technology for global food security

Traditionally,crops are cultivated in soil-based open field systems.Seasonality,environmental degradation,urbanization,and food security issues have replaced open-field systems with modern plant production systems.Soilless culture is one of the modern plant production systems,which involves much higher use of available resources.The presented study provides information about currently accessible soilless systems and discussed the aeroponic system.Compared to other soilless systems,aeroponic reduce water usage through continuous water circulation.However,the aeroponic is not entirely implemented among local farmers,and very few farmers have adopted the system due to the lack of research and technical information available in the literature.Therefore,this study was planned to provide information about the development and maintenance tasks required for practicing the aeroponic system.This study could provide knowledge to the researchers,farmers,and those people interested in practicing the aeroponic system.

Influences of moisture content and compressive loading speed on the mechanical properties of maize grain orientations

Determination of the mechanical properties(rupture force,deformation,hardness,and toughness)of maize grain could be a significant concern for designing the harvester,thresher,and handling,processing,and storage equipment.Thus,the present research was conducted to assess the vertical and lateral rupture force,deformation,hardness,and toughness of maize grain(Beijing Denong,Lianchuang,Suyu 20,Liyu 88 and Suyu 29)influenced by different moisture contents(11.2%,17.5%,and 21.3%)and compressive loading speeds(5,10,15,20,and 25 mm/min,respectively).Besides,the mean length,width,thickness,geometric mean diameter,equivalent diameter,arithmetic diameter,sphericity,grain volume,surface area,and aspect ratio of the selected varieties were measured.The results showed that the highest length,width,thickness and sphericity,grain volume,surface area,and aspect ratio were obtained at moisture of 21.3%,whereas the lowest was at 11.2%.Moreover,it was observed that as increasing the loading speed from 5 to 25 mm/min,the vertical and lateral rupture forces decreased.However,as increasing moisture contents from 11.2%to 21.3%,the vertical and lateral rupture forces,hardness,and toughness decreased noticeably.Furthermore,the maximum correlation(R2=0.9957)between rupture force and loading speed was found for Liyu 88 at moisture of 17.5%and minimum correlation(R2=0.7002)was found for Suyu 29 at moisture of 11.2%.Moreover,the highest lateral and vertical rupture force was noticed(p<0.05)at a loading speed of 5 mm/min.Based on the experimentally obtained results,it was concluded that the properties of maize grain evaluated were relevant to the design of planter,harvesters,thrashers,and processing machine.

Effects of soil mechanical properties on the height and tractive performance of rubber grouser at different moisture contents

Rubber tracked vehicles are commonly used on agricultural machinery that perform agricultural operations such as rice harvesting in soft paddy fields with low bearing capacity.Research was carried out to assess the influence of soil moisture content and mechanical properties on the tractive performance of a rubber grouser with three heights(45 mm,55 mm,60 mm).The direct shear test and penetration test were used in this study,which was based on a semi-empirical approach of determining tractive parameters.Direct shear tests were used to measure soil shear strength parameters such as cohesion,adhesion,internal and exterior friction angles.The results of the penetration test were used to determine tractive parameters such as soil thrust,running resistance,and traction,for the penetration test,a device was designed and developed.The experimental results revealed that soil cohesion and adhesion increased linearly with increasing soil moisture content,however adhesion dropped after 30.7%.Similarly,the soil thrust initially increased till 21.5%then decreased.Furthermore,running resistance had a decreasing trend over soil moisture content whereas maximum traction achieved for 45 mm grouser height at 21.5%moisture content.It was concluded that a rubber grouser with 45 mm height had better traction rather than 55 mm and 60 mm,it can be suitably used for designing a track system for a crawler vehicle(e.g.,harvester)leading to its greater adoption among the farmers.

Sowing uniformity of bed-type pneumatic maize planter at various seedbed preparation levels and machine travel speeds

Precision planters are important machines in the regime of modern technological agriculture.Field conditions,seed metering system and machine operating parameters affect the pneumatic planter performance.The pneumatic planter was evaluated to determine the effect of three tillage levels(L1,L2,and L3)and four travel speeds(S1,S2,S3 and S4).The sowing uniformity of the planter was observed with respect to the horizontal distribution of seeds within a row and described by using the precision index(Ip),the multiple index(Imult),the miss-seeding index(Imiss)and the quality of feed index(Iqf).The results revealed that the tillage levels(L)and travel speed(S)had a significant effect(p<0.05)on dependent variables.The maximum Imiss(22.12%)was observed at L1 and S4 whereas the maximum Imult was observed at L1 and S1.The mean values of missing-,multi-,quality-feed and precision indices were 5.14%,5.833%,89.03%and 17.85%at L3,respectively.The mean values of multi-index 17.59%,14.44%,12.40%and 10.18%,quality feed index 74.07%,75.92%,75.74%and 74.07%and precision indices 21.47%,23.26%,25.51%and 28.53%were at S1,S2,S3 and S4,respectively.The study showed that maize could be seeding within an acceptable precise range by bed-type pneumatic planter subjected to the proper seedbed preparation level.

Comparing kernel damage of different threshing components using high-speed cameras

Grain damage research has been a focus of many experts in the agriculture machinery industry.A threshing test-bed was developed to investigate the movement and influence of different threshing and separating units on maize grains.The damage to maize grains was analyzed with a high-speed camera to observe the movement and damage received by the maize grains.The results showed that the threshing and separating effects of the perforated concave plate were obviously lower than that of the round steel concave plate,the threshing effects of the rigid rasp bar and polyurethane rasp bar were similar,and the damage ratio of the polyurethane rasp bar was relatively low.It also indicated that moisture content has a significant effect on the damage ratio and damage type of maize grains.The different threshing component types used in this study had an obvious effect on the degree of damage to high moisture content maize grains and the damage to high-moisture kernels during threshing could be further identified.The results can provide a reference for the design of threshing and separating devices in the maize combine harvesting machinery.