Effects of Continuous Nitrogen Application on Grain Yield and Nitrogen Uptake and Utilization in Winter Wheat-Summer Maize Rotation System

[Objective] This study aimed to achieve high yield and stable yield of win- ter wheat-summer maize rotation system and provide basis for rational application of nitrogen fertilizer. [Method] Effects of continuous nitrogen application on grain yield, economic profit, nitrogen uptake and utilization efficiency, and soil inorganic nitrogen accumulation in winter wheat-summer maize rotation system were investigated. [Re- sult] Nitrogen application could significantly increase the y（eld of the winter wheat- summer maize rotation system, which increased by 17.76%-30.32% and 22.24%- 46.63% in two rotation cycles, respectively. The yield of the winter wheat-summer maize rotation system was the maximum in two rotation cycles with nitrogen appli- cation amount of 660.0 kg/hm2, which reached respectively 23 391.19 and 23 444.35 kg/hm2, the yield and economic benefit were the highest, the nitrogen fertilizer use efficiency was 22.2% and 30.7%, the agronomic efficiency was 8.3 and 11.3 kg/kg. However, the nitrogen fertilizer use efficiency and agronomic efficiency between ni- trogen application amount of 540.0 and 660.0 kg/hm2 showed no significant differ- ence. After two rotation cycles, inorganic nitrogen accumulation in 0-40 cm soil with nitrogen application amount of 540.0 kg/hm2 was almost equal to that before experi- ment. [Conclusion] Under the experimental conditions, comprehensively considering the grain yield, economic profit, nitrogen fertilizer efficiency and soil inorganic nitro- gen balance, the optimal nitrogen application amount was 625.3-660.0 kg/hm2 in high-yield winter wheat-summer maize rotation system.

Fate of ^(15)N-Labeled Urea Under a Winter Wheat-Summer Maize Rotation on the North China Plain

A field experiment was conducted to investigate the fate of ^15N-labeled urea and its residual effect under the winter wheat （Triticum aestivum L.） and summer maize （Zea mays L.） rotation system on the North China Plain. Compared to a conventional application rate of 360 kg N ha^-1 （N360）, a reduced rate of 120 kg N ha^-1 （N120） led to a significant increase （P 〈 0.05） in wheat yield and no significant differences were found for maize. However, in the 0-100 cm soil profile at harvest, compared with N360, N120 led to significant decreases （P 〈 0.05） of percent residual N and percent unaccounted-for N, which possibly reflected losses from the managed system. Of the residual fertilizer N in the soil profile, 25.6%-44.7% and 20.7%-38.2% for N120 and N360, respectively, were in the organic N pool, whereas 0.3%-3.0% and 11.2%-24.4%, correspondingly, were in the nitrate pool, indicating a higher potential for leaching loss associated with application at the conventional rate. Recovery of residual N in the soil profile by succeeding crops was less than 7.5% of the applied N. For N120, total soil N balance was negative; however, there was still considerable mineral N （NH4^＋-N and NO3^--N） in the soil profile after harvest. Therefore, N120 could be considered ngronomically acceptable in the short run, but for long-term sustainability, the N rate should be recommended based on a soil mineral N test and a plant tissue nitrate test to maintain the soil fertility.

The adjusting mining technology of combining fully mechanized with individual prop,rotating,hilt,irregular form,and double unit face on thin coal seam of Tianchen Mine

Analyzed the situations and characteristics of thin coal seam mining and its mining technologies,and introduced the mining innovation technology used by Tianchen Coal Mine of Zhaozhuang Coal Company of China.This innovation technology combined the fully mechanized mining with individual props,and the working face of mining is over length,irregular form and double units.The rotational adjusting mining technology on thin coal seam is also practiced in this new mining technology.The detail technologies,such as outlays of working face and ways,mining methods,equipments of cutting,transporting and sporting,have been introduced.So that,using the synthetic and creative mining tech- nologies,Tianchen Coal Mine solves the mining problems of thin coal seam successfully.

Effects of multiple shapes for steady flow with transformer oil+Fe_(3)O_(4)+TiO_(2) between two stretchable rotating disks

In this study,we examine the effects of various shapes of nanoparticles in a steady flow of hybrid nanofluids between two stretchable rotating disks.The steady flow of hybrid nanofluids with transformer oil as the base fluid and Fe_(3)O_(4)+TiO_(2)as the hybrid nanofluid is considered.Several shapes of Fe_(3)O_(4)+TiO_(2)hybrid nanofluids,including sphere,brick,blade,cylinder,and platelet,are studied.Every shape exists in the same volume of a nanoparticle.The leading equations(partial differential equations(PDEs))are transformed to the nonlinear ordinary differential equations(ODEs)with the help of similarity transformations.The system of equations takes the form of ODEs depending on the boundary conditions,whose solutions are computed numerically by the bvp4c MATLAB solver.The outputs are compared with the previous findings,and an intriguing pattern is discovered,such that the tangential velocity is increased for the rotation parameter,while it is decreased by the stretching values because of the lower disk.For the reaction rate parameter,the concentration boundary layer becomes shorter,and the activation energy component increases the rate at which mass transfers come to the higher disk but have the opposite effect on the bottom disk.The ranges of various parameters taken into account are Pr=6.2,Re=2,M=1.0,φ_(1)=φ_(2)=0.03,K=0.5,S=-0.1,Br=0.3,Sc=2.0,α_(1)=0.2,γ=0.1,E_(n)=2.0,and q=1.0,and the rotation factor K is within the range of 0 to 1.

Nonlinear modes in rotating double well potential with parity–time symmetry

We investigate the nonlinear modes in a rotating double well potential with 79T symmetry. Focus on the existence and stability of the nonlinear PT modes in this system, we found that five types of PT modes can stably exist by given certain parameter settings. The multistable area between these modes are studied numerically and the bistable and tristable areas are delimited. With different input trial wavefunctions, five types of solitary wave modes are identified. We found that the rotating of the potential can significantly affect the power flow of the fundamental harmonic mode, whose effect is absent for the other modes.

Dynamic analysis of rotating flexible disk subjected to double slider loading systems

Rotating disk subjected to stationary slider loading system is a very common mechanical structure. This paper investigates the multibody dynamics of a rotating flexible annular thin disk subjected to double slider loading systems. Along the rotating disk radial and circumferential directions, two stationary slider loading systems are distributed. System dynamic model is solved by Galerkin＇s method, and then natural frequency, dynamic stability and mode shape are determined with a quadratic eigenvalue problem. Effects of the distributing positions and interaction mechanism of the double slider loading systems on natural frequency, dynamic stability and mode shape are discussed and investigated.

Numerical Simulation of Double Diffusive Mixed Convection in a Horizontal Annulus with Finned Inner Cylinder

The present work relates to a numerical investigation of double diffusive mixed convection around a horizontal annulus with a finned inner cylinder.The solutal and thermal buoyancy forces are sustained by maintaining the inner and outer cylinders at uniform temperatures and concentrations.Buoyancy effects are also considered,with the Boussinesq approximation.The forced convection effect is induced by the outer cylinder rotating with an angular velocity(ω)in an anti-clockwise direction.The studies are made for various combinations of dimensionless numbers;buoyancy ratio number(N),Lewis number(Le),Richardson number(Ri)and Grashof number(Gr).The isotherms,isoconcentrations and streamlines as well as both average and local Nusselt and Sherwood numbers were studied.A finite volume scheme is adopted to solve the transport equations for continuity,momentum,energy and mass transfer.The results indicate that the use of fins on the inner cylinder with outer cylinder rotation,significantly improves the heat and mass transfer in the annulus.

Soil physical properties,nutrients,and crop yield with two-year tillage rotations under a winter wheat-summer maize double cropping system

Winter wheat and summer maize were planted from 2015-2017 to study the effects of different rotational tillage patterns on soil physicochemical properties,crop yield,water content,and fertilizer utilization.The tillage treatments were designed as wheat subsoiling-maize no tillage(WS-MN),wheat rotary tillage-maize subsoiling(WR-MS),wheat subsoiling-maize subsoiling(WS-MS),and conventional wheat rotary tillage-maize no tillage(WR-MN)as a control.Among the four treatments,WS-MN and WR-MS were single-season subsoiling treatments,and WS-MS was a two-season subsoiling treatment.The average soil bulk density decreased by 7.6%in the single-and double-season subsoiling groups compared to the WR-MN group,and the total porosity and noncapillary porosity increased by 10.7%and 12.2%,respectively.Single-or double-season subsoiling treatment was not conducive to water storage in the 0-20 cm soil layer but increased the water content of the 20-140 cm soil layer,and the average soil water content of the 0-140 cm layer was increased by 11.6%in the two-growing season treatment groups compared with the WR-MN group.In WS-MS and WS-MN groups compared with the WR-MN group,the soil ammonium nitrogen content was increased by an average of 18.6%in 0-20 cm soil and 16.8%in 20-100 cm soil;soil nitrate-nitrogen content was decreased by 13.5%in 0-100 cm soil;total organic carbon and microbial carbon contents in the 15-30 cm soil were increased by 18.1%and 12.7%,respectively;and soil urease,catalase,and alkaline phosphatase activities were increased by 46.1%,15.2%,and 23.1%,respectively.Annual crop yield and water use efficiency increased by 8.9%and 15.0%,respectively,in both the single-and double-season subsoiling treatment groups.This study demonstrated the advantages of subsoiling tillage and suggested that it is suitable for crop cultivation in the Haihe Plain,China.

肩关节镜下双排缝合桥技术治疗老年肩袖损伤46例

目的 探讨肩关节镜下双排缝合桥修复手术对老年肩袖损伤病人疼痛、手臂与肩部功能障碍(DASH)评分及再撕裂发生率的影响。方法 回顾性分析2018年8月至2020年2月阜阳市第二人民医院收治的89例老年肩袖损伤病人的临床资料,依照手术方法的不同划分成对照组(肩关节镜下单排铆钉固定)、治疗组(肩关节镜下双排缝合桥修复手术),分别为43例、46例。于术前、术后1年采用视觉模拟评分法(VAS)评定患肩疼痛度,采用手臂与肩部功能障碍(DASH)评分量表评定肩关节功能,测量患肩关节前屈、外展活动度,并统计两组1年内再撕裂发生率。通过logistic回归分析确定病人术后再撕裂发生的影响因素。结果 术后1年两组不同撕裂程度病人VAS、DASH评分及患肩关节前屈、外展活动度与同组术前相比均明显改善(均P<0.05),术后两组轻度撕裂病人上述指标改善情况比较差异无统计学意义(均P>0.05),而治疗组中、重度撕裂病人上述指标改善情况均明显较对照组优(均P<0.05);治疗组再撕裂发生率4.35%明显较对照组的23.26%低(P<0.05);年龄、手术方式是病人术后再撕裂发生的影响因素(均P<0.05)。结论 对老年肩袖损伤病人实施肩关节镜下双排缝合桥修复手术,可有效改善患肩疼痛及功能,显著降低再撕裂发生率。

数控机床旋转轴多自由度静/热误差同步测量与建模

针对现有的数控机床旋转轴误差测量与建模方法仅考虑多自由度静态几何误差或单自由度热误差单独作用的影响,未考虑几何误差和热误差耦合影响的问题,提出了一种基于球杆仪的数控机床旋转轴多自由度静/热误差同步测量与建模方法。首先基于齐次坐标变换建立球杆仪杆长变化模型,再基于该模型使用非齐次线性方程组建立静/热误差辨识模型;其次设计了适应多自由度静/热误差同步测量的球杆仪安装模式以缩短测量时间,减少热逸散对测量结果的影响;再次基于卷积长短期记忆神经网络(CNN-LSTM)建立旋转轴多自由度静/热误差预测模型;最后在数控蜗杆砂轮磨齿机的C轴上进行误差测量实验,对多种转速下的旋转轴多自由度误差进行快速辨识,并通过CNN-LSTM静/热误差预测模型对多自由度误差和球杆仪杆长变化进行预测,以验证所建模型的准确性。

基于改性粉煤灰材料的双滤筒VOCs吸附装置开发

针对挥发性有机物(VOCs)污染,基于改性粉煤灰材料的理化性质设计了一种新型VOCs高效吸附装置。采用改性粉煤灰为吸附剂,其成本低廉且再生操作简单;内外双滤桶设计大大增加了被处理气体和吸附剂的接触面积;旋转上升的气流设计使气压分配均匀,避免沟流的出现,减小死层厚度,提高吸附剂的利用率;设有再生装置,吸附剂可与滤筒整体更换,避免散料运输时造成二次污染。本装置贴近工业生产气体处理实际,是一种可实现VOCs高效捕集及回收、吸附剂反复利用的VOCs处理新工艺。

水平井尾管完井与钻井一体化设计控制技术

针对水平井尾管导向钻井技术存在的钻机旋转系统负载大、地面扭矩传动效率低、使用与维护成本高等问题,提出了水平井双管柱尾管差速旋转钻进新方法,揭示了相应的技术原理,设计了双管柱差速旋转传动、复合旋转导向及悬挂器等井下专用工具,优化了相关工艺流程;提出了导向钻具组合工具面控制方法,建立了水平井双管柱尾管差速旋转钻进延伸极限计算模型。结果表明:水平井双管柱尾管差速旋转钻进技术配备常规随钻测量仪器和螺杆钻具,通过调节钻柱转速可以控制导向钻具组合的工具面,实现了水平井双管柱尾管差速旋转导向钻进;基于鄂尔多斯盆地东缘深部煤层气水平井工程案例计算水平井双管柱钻进延伸极限,与常规尾管钻井方式相比,采用双管柱尾管差速旋转钻进方式显著增大了水平井延伸极限,为水平井尾管完井与钻井一体化设计控制提供了参考。

计及风力发电机转速安全约束的DFIG一次调频模型预测控制策略

针对传统方法控制双馈感应发电机(DFIG)的调频效果过于依赖参数整定的问题,该文提出了一种基于模型预测控制(MPC),计及转速安全约束的风力发电机参与一次调频控制策略。该方法结合风力发电机动力学模型与频率响应模型建立预测模型,通过线性回归方法变参考值将风力发电机转速的稳定性纳入考虑。相较于虚拟惯性控制等方法将系统频率偏差与转子动能直接关联,该文方法通过建立全新的预测模型,实时统筹考虑整个系统的状态信息,无需反复调整参数,在考虑转速安全性的同时兼顾全局性能。最后,通过实际算例分析验证了该文调频策略的有效性以及相对现有方法的优越性。

串列联动双圆柱流致摆振试验研究

提出了串列联动双圆柱流致摆振理念,构建了摆振运动方程,分析了受力与运动规律,建立了摆振试验装置,并基于室内试验探究了串列联动双圆柱流致摆振特性,研究旨在为流致振动发电设备设计提供参考。研究表明:串列联动双圆柱摆振响应表现为涡激振动规律;间距比对摆振振幅和锁定区间影响较大,当间距比为4时振幅最小且响应中出现“再增长区”,当间距比为6时振幅最大,当间距比为8时锁定区间最大;系统刚度对摆振响应趋势影响不大,但不同刚度下摆振达到的最大振幅差异明显,该试验最大弧长比A^(*)为0.98,出现在1 400 N/m刚度工况。

广义椭偏仪双补偿器任意比例旋转控制系统

针对目前广义椭偏仪双旋转补偿器控制旋转比例单一的问题,提出一套基于STM32单片机与步进电机的广义椭偏仪双补偿器任意比例旋转控制系统。该系统采用STM32F1单片机进行编程控制两个步进电机旋转的基础速度、速度比、旋转光学周期数,并通过LabVIEW软件进行编程,获得与之配套的上位机控制系统,完成双补偿器的任意比例旋转控制。通过搭建的广义椭偏实验系统采集双补偿器不同转速比下对空气样本测量的图像,并将其中转速比为5∶3的数据采集结果与理论空气样本波形进行归一化处理。结果显示,实际空气穆勒矩阵与理论穆勒矩阵元素的最大误差为0.014,平均误差为0.004 3,验证了该系统具有较高的可靠性与测量精度。

双支点对转轴承腔两相流动及换热特性的数值研究

为探究双支点对转轴承腔两相流动及换热特性,利用耦合的CLSVOF两相流方法开展数值研究,对比高低压轴同转、对转形式下的轴承腔流动及换热特征,重点探讨对转条件下,高低压轴转速及双侧供油流量对轴承腔壁面油气分布特征与换热特性的影响。结果表明:不同转向下轴承腔壁面油膜形成过程类似,滑油在壁面以油滴、油矢、油带形式分布;同转形式下壁面流线旋向相同,对转形式下壁面流线旋向则相反,对转提高了轴承腔壁面剪切力及湍流强度,平均换热系数相对提升了16.47%;对转转速越大或转速比越高时,壁面滑油体积分数增大而油膜厚度降低,油膜流速平均增加72.95%,双侧供油量或供油流量比越大时,壁面滑油体积分数与油膜厚度均上升,油膜流速平均增加31.02%;增加转速与供油流量均可提高壁面热流密度,增大换热系数,采用双支点对转形式布局能够一定程度提高轴承腔换热性能,有利于保障发动机的安全可靠运转。

自制旋转机械故障模拟试验台的转子振动特性研究

采用软件仿真与实验分析相结合的方法,研究自制旋转机械故障模拟试验台转子的振动特性。使用Solidworks软件对转子进行三维实体建模,并在Altair Hyper Mesh软件中划分网格,导入到ANSYS Workbench软件进行后处理分析。首先通过静力学分析获得双盘转子变形与应力分布情况;考虑陀螺效应的影响,通过模态分析获取固有频率及振型云图;生成Campbell图,分析转子在设定转速区间内振动分量的变化特征;通过谐响应分析获取特定频域内的动态响应。最后进行实验模态分析,并与仿真结果进行对比,从而验证有限元模型的准确性。研究表明:转轴轴肩位置处存在一定程度的应力集中;临界转速远大于工作转速,可有效避免共振;该结构动刚度良好符合设计要求。在工程问题中,常根据整机的简化动力学模型自行搭建试验台进行研究,研究成果可为该类型转子的振动特性分析提供参考,并为旋转机械故障的模拟实验起到了一定的指导作用。

基于异步旋转磁极的TC4薄板双面磁粒研磨工艺研究

目的为提升传统磁粒研磨TC4薄板的加工效率,改善表面形貌,设计了相对磁极产生相对转速差的双面磁粒研磨装置。方法基于两侧相对磁极的异步旋转,使两侧磁极产生相对转速差,进行磁性磨粒的受力和运动分析,对材料去除量进行计算分析。利用Maxwell软件,对不同的相对转速差进行磁场的模拟仿真,进而使用设计的双面磁粒研磨加工装置,对TC4薄板的双面进行研磨。最后,使用粗糙度仪和超景深3D电子显微镜,对研磨前后的工件表面进行观察分析。结果对于磁极的同步旋转,即当两侧磁极转速为500 r/min时,正面表面粗糙度Ra的平均值从0.47μm下降至0.2μm,下降幅度为57%,反面表面粗糙度Ra的平均值从0.46μm下降至0.21μm,下降幅度为54%。对于磁极异步旋转,即磁极Ⅰ转速为500r/min、磁极Ⅱ转速为600 r/min时,正面表面粗糙度Ra的平均值从0.47μm下降至0.1μm,下降幅度为78%,反面表面粗糙度Ra的平均值从0.48μm下降至0.1μm,下降幅度为79%,正面最大高度差的平均值从62.5μm下降至10.4μm,下降幅度为83%,反面最大高度差的平均值从63.2μm下降至10.3μm,下降幅度为84%,材料去除效率最高,表面质量得到有效改善。结论采用异步旋转双面磁粒研磨的方式,可以有效促进磁性磨粒的翻滚运动,加速切削刃的更新。该装置加工时能够产生相对较高的磁感应强度,磁场梯度变化适中,有利于提升表面质量,修复工件表面的缺陷,大幅度提升了研磨的效率。

双转台五轴数控机床旋转轴位置无关几何误差辨识

针对双转台五轴数控机床旋转轴几何误差辨识精度问题,提出一种在机床坐标系下的旋转轴位置无关几何误差(PIGEs)辨识模型。建立了刀具球与工件球在机床坐标系下的实际初始坐标,通过逆矩阵得到工件球在所测轴的实际初始位置,基于4种测量模式建立了包含球杆仪安装误差与旋转轴PIGEs的杆长变化量数学模型。仿真分析了PIGEs对测量模式的影响,结果表明刀具球在两旋转轴轴线交点位置时,平行度误差不影响球杆仪杆长变化量。最后,通过实验辨识出旋转轴8项PIGEs,并对旋转轴PIGEs的4项位置误差进行补偿。实验结果表明,补偿后的位置误差最大绝对值由203.5μm减小至5.1μm,所提出的辨识模型可以有效提高五轴机床精度。

同向双螺旋排肥器优化设计与试验

针对传统排肥器存在施肥不均而造成肥料利用率低问题,设计了一种双排肥轮结构的同向双螺旋排肥器,通过理论分析确定排肥器的理论排肥量及影响排肥均匀性的参数,以排肥轮螺距、中心距、叶片高度为试验因素,以排肥均匀性波动系数和轴向平均速度为试验指标,进行三因素三水平Box-Behnken试验。结果显示:排肥轮螺距对排肥均匀性波动系数影响极显著,排肥轮中心距、叶片高度对排肥均匀性波动系数影响显著,排肥轮螺距、中心距、叶片高度对轴向平均速度影响极显著,在排肥轮中心距为48 mm、螺距32.5~33.2 mm、叶片高度13.5~14.7 mm时,排肥均匀性波动系数≤10%、肥料轴向平均速度≥30 mm/s,排肥器作业性能最佳。在最优参数组合下排肥均匀性波动系数台架试验与仿真试验相对误差为1.47%、单圈排肥量台架试验与仿真试验相对误差为1.96%,台架试验与仿真试验吻合较好。在不同转速下同向双螺旋排肥器较单螺旋排肥器排肥均匀性波动系数平均降低64.21%、单圈排肥量平均提升72.16%,优化后的同向双螺旋排肥器排肥均匀性好且排肥流量大。