基于AutoCAD的圆柱齿轮计算机辅助设计系统的研究

为了实现圆柱齿轮的设计计算与绘图的自动化，文章提出了应用VISUALC 编程与AutoCAD结合的方案，制定了开发目标与开发环境，确定了系统的数据结构，实现了圆柱齿轮的参数化自动设计与自动绘图，参数自动检测和自动纠错，     

山地拖拉机变速箱齿轮的模态优化

针对山地轻型拖拉机变速箱工作中常遇到的振动严重、无法模态优化等问题,确定了模态优化目标,基于序列二次规划法,利用Mat Lab对该变速箱齿轮进行模态优化,并应用ANSYS对优化模型进行模态分析。分析表明,优化后的变速箱齿轮模型具有更高的低阶固有频率,验证了模态优化的正确性。本研究对优化山地拖拉机变速箱的齿轮模态及降低振动提供了有效方法。     

Equine cervical intervertebral disc degeneration is associated with location and MRI features

Morphology of the equine cervical intervertebral disc is different from that in humans and small companion animals and published imaging data are scarcely available. The objectives of this exploratory, methods comparison study were (a) to describe MRI features of macroscopically nondegenerated and degenerated intervertebral discs (b) to test associations between spinal location and macroscopic degeneration or MRI‐detected annular protrusion and between MRI‐detected annular protrusion and macroscopic degeneration, and (c) to define MRI sequences for characterizing equine cervical intervertebral disc degeneration. Ex vivo MRI of intervertebral discs was performed in 11 horses with clinical signs related to the cervical region prior to macroscopic assessment. Mixed‐effect logistic regression modeling included spinal location, MRI‐detected annular protrusion, and presence of macroscopic degeneration with “horse” as random effect. Odds ratio and 95% confidence interval were determined. Reduced signal intensity in proton density turbo SE represented intervertebral disc degeneration. Signal voids due to presence of gas and/or hemorrhage were seen in gradient echo sequences. Presence of macroscopic intervertebral disc degeneration was significantly associated with spinal location with odds being higher in the caudal (C5 to T1) versus cranial (C2 to C5) part of the cervical vertebral column. Intervertebral discs with MRI‐detected annular protrusion grades 2‐4 did have higher odds than with grade 1 to have macroscopic degeneration. It was concluded that MRI findings corresponded well with gross macroscopic data. Magnetic resonance imaging of the equine cervical intervertebral disc seems to be a promising technique, but its potential clinical value for live horses needs to be explored further in a larger and more diverse population of horses.     

基于HYDRUS模型的华北平原小麦种植区水盐运移模拟

土壤中水分和盐分是影响作物生长的两个关键因素,揭示水盐运移机制对阐明作物利用土壤水过程具有重要意义。本研究以华北平原典型农田——中国科学院禹城综合试验站为试验地,基于试验站内冬小麦种植地的长期土壤水分观测数据及室内土柱试验,应用HYDRUS-1D模型分别阐明土壤水分及盐分变化规律及分布特征,探究影响水盐运移的驱动因素,并评价HYDRUS-1D模型对研究区水盐运移模拟的适用性。水分运移模拟结果表明:浅层土壤水分运移模拟因受外界因素的剧烈影响而较深层土壤产生更大的误差,10cm、20 cm、30 cm、40 cm和60 cm处水分运移模拟结果的均方根误差分别为0.0348 cm~3·cm~(-3)、0.0179 cm~3·cm~(-3)、0.0179cm~3·cm~(-3)、0.0122cm~3·cm~(-3)和0.0053cm~3·cm~(-3);水分运移模拟的纳什效率系数平均值为0.826,变异系数为0.0560,表明模拟结果与实测土壤水分变化过程一致性较好。土柱试验结果显示:灌水8 L,入渗12 h、24 h、40 h、45 h和48 h后,各时刻土壤盐分含量在垂向上整体呈现先增大后减少的分布规律,均方根误差分别为0.181 g·kg~(-1)、0.131 g·kg~(-1)、0.120 g·kg~(-1)、0.034 g·kg~(-1)和0.027 g·kg~(-1),平均误差的平均值为0.174 g·kg~(-1)。受蒸发、耕作、根系等影响,理化性质变异性较大导致浅层土壤盐分运移模拟值与实测值偏差增大,纳什效率系数的变异系数达9.71。灌水8 L、16 L、24 L,入渗48 h后分别在土壤23 cm、26 cm、29 cm处出现盐分含量峰值,表明增加灌水量可加强盐分淋洗效果。此研究可为深入探究华北平原冬小麦土壤水盐运移规律、优化农田水资源管理、提高水资源利用效率提供一定理论基础。     

伴随阴离子对马铃薯种植冲击土中钾素固持与淋溶的影响

A column study was carried out to assess the influence of accompanying anions on potassium (K) leaching at potato growing sites with different soil textures (sandy loam and clay loam) in northwestern India. Potassium was applied in the top 15 cm layer of soil column at 30 and 60 mg K kg^-1 through different sources having different accompanying anions (Cl^-, SO₄^2-, NO₃^- and H₂PO₄^-). Maximum K was retained in the top 0--15 cm layer with a sharp decrease in K content occurring in 15--30 cm layer of the soil column. The trend was similar for both levels of applied K as well as frequency of leaching and soil type. The decrease of K content in soil column after four leaching events was maximum in case of Khanaura sandy loam, while only minor decrease was observed in Hundowal clay loam when K was applied at 60 mg K kg^-1, indicating higher potential of clay rich soil to adsorb K. In general, the K leaching in presence of the accompanying anions followed the order of SO₄^2- ≤ H₂PO₄^2- < NO₃^- = Cl^-. Highest 1 mol L^-1 CH3COONH4-extractable K was retained when K was applied along with SO42- and H2PO4- anions, and the least was retained when accompanying anion was Cl^-1. The influence of anions was more pronounced in the light textured soil and at high amounts of K application. Higher levels of K application resulted in higher losses of K, especially in sandy loam soil as observed from the leachate concentration. Among the different K sources, the maximum amount of K leaching was noticed in the soil column amended with KCl. After four leachings, the maximum amount of K leached out was 6.40 mg L^-1 in Hundowal clay loam and 9.29 mg L^-1 in Khanaura sandy loam at 60 mg K kg^-1 of soil application through KCl. These concentrations were lower than the recommended guideline of the World Health Organisation (12.00 mg L^-1).     

高效液相色谱法测定糖肽酮萜素中低聚糖的含量

采用高效液相色谱法（HPLC），分离柱选用ODS色谱柱，以纯水为洗脱液，用示差折光检测。测定了饲料添加剂和功能食品中低聚糖的含量，即蔗糖、水苏糖和棉子糖。本法具有流动相价廉、无污染、快速简便和稳定性好的特点，色谱柱使用寿命长。     

离散测量齿形误差随机过程的统计分析

通过对 5组齿形误差的实际测量数据所进行的统计分析 ,得出了其测量过程是一种非平稳随机过程的结论 ,而且由此发现综合齿形误差中存在有递增的系统误差 ,并初步分析了其产生的原因 .还用最小二乘原理建立了齿形误差均值的拟合直线函数和精度较高的谐波函数模型 .     

电加载变速箱试验台温度检测系统

该系统以单片机为核心,包括信号采集与变送、A/D转换、显示与报警以及串行通信等模块。     

齿顶曲线误差对非圆齿轮副重合度的影响

以非圆齿轮插齿加工为例，分析了利用渐开线圆柱插齿刀加工非圆齿轮时齿顶曲线误差对非圆齿轮重合度的影响，为严格控制非圆齿轮副的重合度提供了理论保证。     

渐开线圆柱齿轮的优化设计

本文应用正交表对渐开线圆柱齿轮进行优化设计,结果表明,这种方法能较好地将设计公式中的各因素进行均衡塔配,有利于选取最优的方案、经验证证明,用此法设计的齿轮传动平稳,性能好,结构紧凑。经济性好。它不仅减少了计算上的麻烦,而且能简便地确定出各因素的最佳数值。