Revising Nitrogen Recommendations for Wheat in Response to the Need for Support of Variable-Rate Nitrogen Application

Sampling studies in North Dakota conducted from 1994 to 2003 showed that variable-rate N application could be practically directed with zone soil sampling. Results from variable-rate N studies using zone soil sampling were often less than rewarding due in part to the use of a whole-field predicted yield-based formula for developing the N recommendation in each zone. Nitrogen rate studies on spring wheat and durum were established in 2005 through 2009 with the objective to reexamine N recommendations and construct a new system if necessary. The results of the study and archived wheat N response data showed that the state should be divided into three separate N response regions. Within each region historic yields from low to high productivity were defined. The gross N rate was determined using the return-to-N concept developed in the US corn-belt states but with additional consideration for wheat protein value The gross N rate is then modified by credits for previous crop, soil test N from zone soil sampling, tillage systems, excessive straw from the previous year, relative susceptibility to nitrate leaching or denitrification. Finally, the user is encouraged to use common sense and consider whether particular fields have characteristics that require more or less N fertilizer than suggested by the recommendation formulas.

New algorithm for variable-rate linear broadcast network coding

To adjust the variance of source rate in linear broadcast networks, global encoding kernels should have corresponding dimensions to instruct the decoding process. The algorithm of constructing such global encoding kernels is to adjust heterogeneous network to possible link failures. Linear algebra, graph theory and group theory are applied to construct one series of global encoding kernels which are applicable to all source rates. The effectiveness and existence of such global encoding kernels are proved. Based on 2 information flow, the algorithm of construction is explicitly given within polynomial time O（｜E｜ ｜T｜.ω^2max）, and the memory complexity of algorithm is O（｜E｜）. Both time and memory complexity of this algorithm proposed can be O（ωmax） less than those of algorithms in related works.

A unified result for variable-rate linear network coding

Fong et al.analyzed variable-rate linear network coding for linear broadcast.However,the authors didn't investigate it for the other three types of linear network codes.In this paper,by simple and clear proofs,it is found that there are similar results for variable-rate linear generic and linear dispersion if the field size is large enough.It means that linear generics and linear dispersions of different dimensions can be implemented on the same network,while each non-source node is required to store only one copy of the local encoding kernel within a session.Moreover,an example is given to show that there isn't a similar result for linear multicast.

Design and Experiment of Slave Computer Control System for Applying Variable-rate Liquid Fertilizer

In order to increase the applying rate of liquid fertilizer and reduce environmental pollution, a slave computer control system for applying variable-rate liquid fertilizer was designed. The system used SMC as core processor and electrically controlled pressure regulator as execution component. The characteristic equation of the system was obtained by using classical control theory. Results indicated that the characteristic equation met the requirements of routh-criterion, which indicated the working process of the system was stable. Performance of the slave computer was verified via bench tests. Results demonstrated that there was no significant influence on the response from interclass error. The fertilization error was less than 0.9, and the fertilization accuracy was larger than 97%. The liquid fertilizer emitted by the fertilizing devices had no significant difference in uniformity, which met the demands of the slave computer control system for applying variable-rate liquid fertilizer.

Assessment of Lubrication Property and Machining Performance of Nanofluid Composite Electrostatic Spraying(NCES)Using Different Types of Vegetable Oils as Base Fluids of External Fluid

The current study of minimum quantity lubrication(MQL)concentrates on its performance improvement.By contrast with nanofluid MQL and electrostatic atomization(EA),the proposed nanofluid composite electrostatic spraying(NCES)can enhance the performance of MQL more comprehensively.However,it is largely influenced by the base fluid of external fluid.In this paper,the lubrication property and machining performance of NCES with different types of vegetable oils(castor,palm,soybean,rapeseed,and LB2000 oil)as the base fluids of external fluid were compared and evaluated by friction and milling tests under different flow ratios of external and internal fluids.The spraying current and electrowetting angle were tested to analyze the influence of vegetable oil type as the base fluid of external fluid on NCES performances.The friction test results show that relative to NCES with other vegetable oils as the base fluids of external fluid,NCES with LB2000 as the base fluid of external fluid reduced the friction coefficient and wear loss by 9.4%-27.7%and 7.6%-26.5%,respectively.The milling test results display that the milling force and milling temperature for NCES with LB2000 as the base fluid of external fluid were 1.4%-13.2%and 3.6%-11.2%lower than those for NCES with other vegetable oils as the base fluids of external fluid,respectively.When LB2000/multi-walled carbon nanotube(MWCNT)water-based nanofluid was used as the external/internal fluid and the flow ratio of external and internal fluids was 2:1,NCES showed the best milling performance.This study provides theoretical and technical support for the selection of the base fluid of NCES external fluid.

Effect of steam spraying on a sintering bed on sinter quality and the emission of flue gas pollutants

The technology for spraying a sintering bed and thus improving sinter quality indicators while reducing the emission of flue gas pollutants has recently become an important research topic.The impacts on sinter quality and emissions when spraying the sintering surface with different amounts and flow rates of steam were investigated in this study.The sinter quality indicators were most effectively improved by spraying 180 g of steam flow continuously at a rate of 0.02 m^(3)/min for 15 min after ignition for 8 min.The optimal effect on emission reduction was obtained by spraying 90 g of steam flow continuously at a rate of 0.01 m^(3)/min for 15 min after ignition for 8 min.

激光复合冷喷涂技术研究进展

冷喷涂是一种基于材料高速撞击产生剧烈塑性变形实现结合的沉积方法,具备加工温度低、沉积效率高、热影响小等优势,已在增材制造、工业关键零部件的修复再制造等领域展现出巨大潜力。冷喷涂复合制造技术是一种新兴技术,其中激光复合冷喷涂是一个重要的方向,近年来得到了越来越多的关注。对激光复合冷喷涂技术研究进展进行回顾和总结,对激光预处理、激光同步复合和激光后处理3种复合方式进行重点阐释。针对每种复合方式,分别从复合原理、复合优势及复合效果3个方面进行总结,对比激光复合冷喷涂技术与单一技术在沉积层微观组织以及性能等方面的差异。通过对激光复合冷喷涂技术最新进展的全面总结和归纳,将为进一步推动激光复合冷喷涂技术的研究和应用提供指导和参考。

基于轻量化PointNet网络的林果园喷雾作业靶标实时识别方法

为了进一步提高喷雾机器人靶标检测的精准性、实时性和应用部署的实用性,该研究提出一种基于轻量化PointNet网络的林果园喷雾作业靶标实时识别方法。首先通过区域提取降采样、地面分割和改进DBSCAN聚类等点云预处理方法提取原始点云中的靶标;然后通过移动最小二乘上采样将靶标点云转化为满足点云识别网络输入要求的点云数据;最终通过在PointNet网络中引入残差模块和改进循环剪枝算法轻量化PointNet网络,完成林果树靶标的实时识别。试验结果表明,在ModelNet40数据集上,轻量化PointNet网络可达89.7%的准确率;在实际苗圃环境的试验中,该研究方法对靶标的识别准确率可达92.49%,同时误识率与拒识率分别为13.4%和6.47%,相较PointNet网络识别准确率提升了4.38个百分点,误识率和拒识率分别降低了7.2和4.07个百分点;轻量化PointNet网络识别准确率仅比PointNet++网络低1.14个百分点,误识率和拒识率分别高了0.9和1.12个百分点。但是轻量化PointNet网络的模型参数量较PointNet网络和PointNet++网络的模型参数量显著减少,仅为PointNet网络的11.5%,PointNet++网络的27.02%;运算量相较PointNet网络、PointNet++网络分别减少13.3和76.79个百分点。该研究提出的轻量化PointNet网络具有较高的实时性、精确性和鲁棒性,能够满足林果园喷雾作业的靶标识别需求,可为林果园喷雾作业靶标实时识别提供参考。

钢纤维喷射砂浆力学性能与流动度多因素正交试验分析

为探究基体因素对钢纤维喷射砂浆力学性能和流动度的影响,基于正交试验方法对砂浆试件进行了力学性能和流动度测试。结果表明:砂胶比(A)对劈裂抗拉强度的影响较大,对7 d抗压强度有一定的影响,对后期抗折强度影响特别显著;钢纤维掺量(B)对劈裂抗拉强度、前期抗折强度和前中期抗压强度的影响分别为特别显著、显著和不显著;速凝剂掺量(C)对7 d前抗压强度、中后期劈裂抗拉强度影响显著;粉煤灰掺量(D)仅对后期抗压强度的影响显著;前述四种因素掺量对流动度的影响均不显著。由层次分析法得到对抗压强度、抗折强度、劈裂抗拉强度和流动度改善效果最佳的配合比分别为A1B3C3D1、A3B3C1D2、A3B3C3D1、A2B1C1D3,由功效系数法得到综合最佳配合比为A2B3C1D2。钢纤维在基体中起桥接与锚固加强的作用,速凝剂在水化过程中消耗大量的Ca(OH)_(2)并生成钙矾石,促使喷射砂浆早期强度迅速提升。

微米级类球形介孔材料用于乙烯聚合催化剂

采用2-(4-氯磺酰苯基)乙基三甲氧基硅烷对类球形介孔材料进行疏水处理,制备了疏水性类球形介孔材料,将其作为载体,通过气流式喷雾干燥技术制备了聚乙烯催化剂。对疏水处理前后的类球形介孔材料进行了XRD、N2吸附-脱附、TEM、SEM表征,考察了气流式喷雾干燥过程中载气流量和浆料浓度对聚乙烯催化剂的影响,并评价了催化剂的乙烯聚合性能。实验结果表明,类球形介孔材料在疏水处理后孔结构和微观结构稳定;最佳喷雾干燥条件为喷雾干燥器进、出风口温度分别为140,105℃,载气流量为30 L/s,浆料浓度为30%(w);在最佳喷雾干燥条件下制备的催化剂用于乙烯聚合时,催化活性为28000 g/g,远高于工业用TS-610硅胶制备的催化剂的活性(9000 g/g),反应得到的聚合物性能也优于TS-610硅胶制备的催化剂得到的聚乙烯粉料。

余热回收喷淋塔喷淋优化研究

针对喷淋塔内烟气偏流影响烟气与下落液滴群热质交换的问题,构建并通过试验验证了喷淋塔内气液流动及余热回收理论模型,基于液滴自调整效应,运用CFD技术模拟研究4种喷淋层布置方式下余热回收喷淋塔的性能,获得了最佳喷淋方案及其喷淋参数。结果表明:与常规单层均匀喷淋方式相比,增设半层喷淋能够有效提升塔内烟气流动均匀性,塔内烟气均匀度由1降至0.3左右,喷淋塔全热交换效率最多可提升20%;半层喷淋最佳布置位置在烟气入口中心线上3 m处;综合考虑余热回收效果和运行成本,最佳喷淋液滴直径为0.6~0.8 mm,最佳水气比为5 kg/kg。构建的喷淋塔内烟气余热回收模型与提出的喷淋优化方法可为其特性分析、工艺优化、参数设计及运行提供理论指导。

连栋温室分段变距喷雾机器人设计与试验

针对国内连栋温室缺乏植保喷雾机、机械走直定位与换轨转向精度低等问题,设计了一种连栋温室分段变距喷雾机器人,在实现无人化喷药的同时提高作业精度。为满足连栋温室机械作业路轨结合、精准切换的要求,提出一种通用型移动底盘,并确定其关键设计参数;为减少底盘上下轨时的偏移量,设计轨上矫正装置,通过分析计算及试验验证,确定其安装余量为4 mm;针对底盘对轨误差大的问题,提出一种二维码融合陀螺仪及光电传感器双向垂直寻迹的路面关键点定位与转向控制方法。设计分段变距喷雾装置,提出一种丝杆滑台驱动的喷杆变距方案,分析校验其驱动参数以满足工作要求;基于滚针轴承设计喷杆辅助防抖装置,减小因喷杆剧烈抖动带来的滑台与喷杆损伤。开发底盘运动及分段变距喷雾控制系统,实现喷雾机器人在连栋温室内的全程自动化作业。最后,对样机进行底盘性能与喷雾效果试验。底盘作业时直线行走与对轨误差平均值分别为4.8、5.8 mm,满足控制精度要求;避障距离为34 cm,满足安全性要求;防抖装置的安装使喷杆行进方向的抖动量从-1°~1.3°降低到±0.4°内,喷头方向的抖动量从±0.5°降低到±0.3°内,防抖效果显著;分段变距喷雾作业后,盛果期番茄叶片正面雾滴沉积量为1.76μL/cm^(2),反面沉积量为0.2μL/cm^(2),雾滴体积中径在100~180μm之间,满足作业要求。

红肉火龙果粉的发泡微波冷冻干燥制备与质量评价

制备浆果粉末产品是延长其货架期的有效手段。为降低干燥过程能耗和保留产品营养成分,该研究以平均含水率(87.03±1.26)%的新鲜红肉火龙果果浆为原料,采用冷冻干燥和喷雾干燥两种方法制备了火龙果粉末。以残余湿含量、色泽和典型生物活性成分甜菜红素、芦丁和总酚保留率为指标对产品质量进行了评价。用质量比为3%(w/w)的分离乳清蛋白和2.5%(w/w)的果胶为添加剂制备了未发泡和发泡2种样品,进行了传统和微波冷冻干燥试验。结果表明,使用石英底盘,在30˚C、20 Pa下,发泡样品比未发泡样品冷冻干燥时间缩短了39.06%;施加1 W微波功率时,未发泡和发泡样品微波冷冻干燥时间比无微波时分别缩短了18.75%和12.82%。用碳化硅底盘替代石英底盘,在30˚C、20 Pa和1 W下,发泡样品微波冷冻干燥时间比未发泡和发泡样品传统无微波冷冻干燥分别缩短了65.62%和43.59%。分别以5.5%(w/w)的分离乳清蛋白和15.6%(w/w)的麦芽糊精为添加剂,进行了喷雾干燥试验。工艺参数为进风温度150˚C、出风温度85˚C、进料速度28 mL/min。冷冻干燥产品的甜菜红素、芦丁和总酚保留率分别在72%、84%和75%以上,而喷雾干燥产品的保留率显著降低。该研究采用的冷冻干燥方法能够大幅缩短干燥时间、提高产品质量,为浆果类粉末产品的制备提供工业解决方案。

镁合金表面热喷涂WC-10Co-4Cr粒子沉积及分布特性

为了探究高速空气燃料热喷涂(activated combustion-high velocity air fuel,AC-HVAF)过程中喷涂粒子撞击基材后的沉积特性。采用AC-HVAF热喷涂技术在AZ80镁合金基体上沉积WC-10Co-4Cr硬质涂层。通过离散沉积实验获得薄层沉积粒子,探讨各种沉积形貌的种类、形成原因、结合机制及射流中粒子的径向和轴向分布。结果表明:在AC-HVAF粒子沉积过程中,嵌入型沉积为主要的沉积形貌,同时包含少量的破碎型与空腔型沉积粒子。在涂层的形成过程中,嵌入型沉积对涂层/基体结合性能起重要作用;空腔型沉积的小颗粒及破碎型沉积的大颗粒是造成沉积效率下降的主要原因。喷涂粒子主要集中在射流中心,越靠近射流边缘,空腔型沉积粒子越多,最终导致AC-HVAF粒子射流呈现出空间分布特征。

加热温度对工业规模CeCl_(3)喷雾焙烧反应器影响的数值模拟

CeO_(2)颗粒由于具有优异的性能,市场对CeO_(2)颗粒的需求逐年增加。为探究使用在氧化铁颗粒工业化生产的Ruthner型喷淋焙烧反应器生产CeO_(2)颗粒的可能性,结合单液滴失重试验,使用ANSYS Fluent软件,分别探究550、650、750和850℃四种不同加热温度对反应器的影响。单液滴失重试验表明,氯化铈和氯化铁、氯化亚铁的热解过程基本一致,使用该型反应器制备CeO_(2)颗粒理论上可行。对小型工业反应器进行等比例建模,研究反应器内部化学反应的具体过程。结果表明,550℃是最合适的温度,对工业生产具有一定指导意义。

单旋翼无人机植保作业系统的研制与实验研究

为了提高植保无人机的工作效率,降低无人机的操作难度,研制了单旋翼无人机植保作业系统。根据植保作业流程,单旋翼无人机植保作业系统实现启动、预热、起飞、飞行、喷洒作业、加药和返航等全过程无人工干预的自动飞行作业。单旋翼无人机植保控制系统包括作业平台、飞行控制、数据链路、地面站系统、系统应用、飞行器管理、用户信息管理、专业知识管理、大数据业务,实现了喷洒区域的精准控制,地面站系统与飞行系统的控制与交互,植保信息的存贮与分析等。通过实验研究表明:单旋翼无人机植保作业系统有效提高了植保工作效率,降低了飞行操作人员的操作难度。

喷淋作用下的深水测试放喷热辐射规律及关键参数

在深水天然气测试过程中,多相混合物会通过地面流程分离、泄压、加热后通过燃烧臂放喷燃烧,现场一般采用喷淋的方式来降低热辐射的影响。为了降低深水放喷测试作业时平台及燃烧臂的热辐射风险隐患,首先采用Thornton模型研究了火焰表面辐射能量、视角系数以及水幕透射率等参数,构建了喷淋作用下放喷火焰的热辐射通量计算模型,并结合现场燃烧放喷下的仿真模型,应用有限元软件分析了放喷喷淋影响下的火焰温度和辐射量变化规律。研究结果表明:(1)喷淋形成的水幕使靠近平台区域的温度和辐射量明显降低,放喷管道附近的辐射量由2 050 W/m^(2)减小到了1 840 W/m^(2);(2)在单个水幕的作用下,水幕吸收了一定的热辐射量,水幕温度从11.85℃上升到约26.85℃;(3)由于平台附近的空气中CO_(2)和H_(2)O含量较低,空气的热辐射吸收系数较小,温度主要受到热对流的影响,空气温度基本保持在26.85~36.15℃之间;(4)不同放喷管径和产量变化下平台附近区域的温度和辐射量变化趋势基本一致,管径减小使得辐射峰值增大。结论认为,该研究成果进一步明确了深水测试放喷不同工况下的热辐射分布,为深水地面放喷热辐射设计分析及安全控制提供了技术支撑。

基于响应曲面法的木材喷涂漆雾扩散角度与均匀度优化

【目的】探究木材喷涂喷头结构参数对喷口流速v_(2)、漆雾扩散角度γ和漆雾均匀性λ的影响,求解喷头最优结构参数,提高木材喷涂效率和喷涂效果。【方法】基于雾滴碰撞、聚集和积累理论初步探究v_(2)、γ和λ的影响因素,将优化参数设为原始喷头的7项关键内部结构参数,包括内壁倒角β、三段管道内壁长度L_(1)至L_(3)和三段管道内壁直径d_(1)至d_(3),利用Design Expert设计7因素3水平3指标的BBD响应曲面试验,探究各结构参数对v_(2)、γ和λ的影响显著性。BBD试验各组结果由3部分仿真获得,采用k-ε模型进行喷头内部流场仿真、KHRT模型进行高压平口雾化仿真。应用Image J测定漆雾扩散角度,通过Python运用“雾滴撒点法”完成对每组雾化仿真结果的均匀性标定,利用多目标优化方法求解喷头最优结构参数,并通过仿真喷涂和实机喷涂验证其喷涂效果。【结果】BBD响应曲面试验结果表明,7项关键内部结构参数对指标的影响十分复杂,但3项指标v_(2)、 γ和λ回归显著(P≤0.000 1),多目标优化下的理论最优漆雾扩散角度为21.28°、最优漆雾均匀性为3.053;最优喷头的喷涂仿真试验结果表明,优化后喷口流速v_(2)由35.8 m·s^(-1)升至107 m·s^(-1),漆雾扩散角度γ由16.74°升至21.09°(与理论相差0.883%),漆雾均匀性λ由3.62升至3.03(λ越小代表越均匀,与理论相差0.751%)。在木材喷涂实机试验中,优化前后木材喷涂试样漆厚标准差由21.71μm降至17.74μm,单面喷涂时间由6.2 s降至5.5 s,单面喷头移动行程由3 255 mm降至2 887 mm。【结论】基于“雾滴撒点法”的漆雾均匀性评判标准以及基于响应曲面法和多目标的喷头结构参数优化方法可对木材喷涂喷头优化设计提供一定参考,对提高木材喷涂漆面均匀性和木材喷涂效率具有一定效果和帮助。

水喷雾对隧道遮挡火灭火性能及顶棚温度的影响

水喷雾系统作为一种有效的火灾扑救设施,被广泛应用于隧道等场所中。本研究基于1:8的缩尺寸双层隧道火灾试验平台(36 m长、单层隧道净高0.58 m),在该模型的下层隧道空间内开展了水喷雾试验,探究了水喷雾系统工作压力、开启时间、喷淋区段和开启组数等因素对火灾控制效果的影响。研究结果表明,水雾与火焰作用过程中火焰强化和燃烧抑制作用共同存在,燃烧抑制作用随着水喷雾压力的增加而增强,喷水压强超过0.30 MPa后燃烧抑制起主导作用;火源熄灭时间随着水喷雾区段的增加而缩短;越早启动水喷雾系统,越能迅速有效地将火场温度控制在较低水平,较晚开启水喷雾,高温汽化产生大量水蒸气,对燃烧产生阻隔作用,减弱火势的增长,同时水喷雾区段作用范围对隧道火灾烟气温度分布具有显著影响。

外源施硒对绿竹生长、光合作用以及硒含量的影响

【目的】为提高绿竹笋的硒含量并改善其品质提供参考。【方法】结合盆栽试验和田间试验,盆栽试验以2年生绿竹盆栽苗为试验材料,田间试验以成林绿竹为试验材料,研究外源施硒对绿竹生长、光合作用和硒含量的影响。用亚硒酸钠(Na_(2)SeO_(3))配制成不同质量浓度(0、100、200、300和400 mg/L)的硒溶液,以叶面喷施方式对绿竹进行喷施处理,盆栽试验每株喷施100 mL(以叶面形成均匀水滴但不滴落为准),田间试验每个处理喷施20 L溶液(为避免不同浓度溶液的交互影响,喷施时由低浓度到高浓度喷施)。测定绿竹生长、光合色素含量以及硒含量指标,探讨不同浓度硒处理对绿竹生长及硒富集的影响。【结果】经100、200和300 mg/L质量浓度硒处理后,绿竹的株高、基径、叶长和叶宽均有不同程度的提高。不同浓度硒处理对绿竹叶片光合色素含量和抗氧化酶活性也有一定程度的影响,主要表现为低促高抑。盆栽试验和田间试验的绿竹各器官硒含量变化趋势表现一致,随着施硒浓度的增加呈线性增加趋势。盆栽试验中,绿竹各器官按照硒含量由大到小排列依次为竹叶、竹鞭、竹枝、竹秆;田间试验中,绿竹各器官按照硒含量由大到小排列依次为竹叶、竹鞭、竹枝、竹秆、竹笋;田间试验中绿竹各器官硒含量低于盆栽试验,随着施硒浓度的增加,绿竹各器官硒含量的增加速率也有所降低。【结论】叶面喷施300 mg/L的亚硒酸钠溶液处理对盆栽和田间绿竹生长、光合作用以及硒富集的效果最好。