Light Simplified Cultivation Techniques of Wide Row and Double Ridge with Filming, Fertilizing and Sowing on One for Foxtail Millet

In view of the problems of completely depending on rain, low and unstable yield and complicated planting of dry land foxtail millet, the light simplified cultivation techniques of wide row and double ridge with filming, fertilizing and sowing on one for foxtail millet was formed through the integration of plastic film mulching technology and mechanized production technology by Institute of Millet crops of Hebei Academy of Agriculture and Forestry Sciences, and the techniques were introduced from the key technologies of pre-sowing preparation, sowing, supporting equipment, field management, harvesting, plastic film recycling.

Shaking table test for reinforcement of soil slope with multiple sliding surfaces by reinforced double-row anti-slide piles

Despite the continuous advancements of engineering construction in high-intensity areas,many engineering landslides are still manufactured with huge thrust force,and double-row piles are effective to control such large landslides.In this study,large shaking table test were performed to test and obtain multi-attribute seismic data such as feature image,acceleration,and dynamic soil pressure.Through the feature image processing analysis,the deformation characteristics for the slope reinforced by double-row piles were revealed.By analyzing the acceleration and the dynamic soil pressure time domain,the spatial dynamic response characteristics were revealed.Using Fast Fourier Transform and half-power bandwidth,the damping ratio of acceleration and dynamic soil pressure was obtained.Following that,the Seism Signal was used to calculate the spectral displacement of the accelerations to obtain the regional differences of spectral displacement.The results showed that the overall deformation mechanism of the slope originates from tension failure in the soil mass.The platform at the back of the slope was caused by seismic subsidence,and the peak acceleration ratio was positively correlated with the relative pile heights.The dynamic soil pressure of the front row piles showed an inverted"K"-shaped distribution,but that of the back row piles showed an"S"-shaped distribution.The predominant frequency of acceleration was 2.16 Hz,and the main frequency band was 0.7-6.87 Hz;for dynamic soil pressure,the two parameters became 1.15 Hz and 0.5-6.59 Hz,respectively.In conclusion,dynamic soil pressure was more sensitive to dampening effects than acceleration.Besides,compared to acceleration,dynamic soil pressure exhibited larger loss factors and lower resonance peaks.Finally,back row pile heads were highly sensitive to spectral displacement compared to front row pile heads.These findings may be of reference value for future seismic designs of double-row piles.

Contact Force Distribution and Static Load-carrying Capacity of Large Size Double Row Four-point Contact Ball Bearing

Clearance not only affects the startup torque,rotation precision and stiffness of bearing,but also affects the load distribution,load-carrying capacity and life of bearing.A computational model in which the clearance of bearing is first included is presented for determining the contact force distribution and static load-carrying capacity of a double row four-point contact ball bearing which is subjected to the combined radial,axial and overturning moment loadings.The relation between the negative axial clearance and the contact force distribution is analyzed.The static load-carrying capacity curves are established,and the effects of the changes in negative axial clearance,curvature radius coefficient of raceway groove and initial contact angle on the static load-carrying capacity are analyzed.The results show that,with the increase in the absolute value of negative clearance,the maximum contact load decreases first and then increases.The clearance values in the range of 0.2 mme0 mm have little effect on the static load-carrying capacity of bearing.With the increase in the curvature radius coefficient of raceway groove and the decrease in the initial contact angle,the static load capacity of bearing decreases.

Stem flow of seed-maize under alternate furrow irrigation and double-row ridge planting in an arid region of Northwest China

Maize is widely planted throughout the world and has the highest yield of all the cereal crops. The arid region of North- west China has become the largest base for seed-maize production, but water shortage is the bottleneck for its long-term sustainability. Investigating the transpiration of seed-maize plants will offer valuable information for suitable planting and irrigation strategies in this arid area. In this study, stem flow was measured using a heat balance method under alternate furrow irrigation and double-row ridge planting. Meteorological factors, soil water content （e）, soil temperature （Ts） and leaf area （LA） were also monitored during 2012 and 2013. The diurnal stem flow and seasonal dynamics of maize plants in the zones of south side female parent （SFP）, north side female parent （NFP） and male parent （MP） were investigated. The order of stem flow rate was： SFP〉MP〉NFP. The relationships between stem flow and influential factors during three growth stages at different time scales were analyzed. On an hourly scale, solar radiation （Rs） was the main driving factor of stem flow. The influence of air temperature （Ta） during the maturity stage was significantly higher than in other periods. On a daily scale, Rs was the main driving factor of stem flow during the heading stage. During the filling growth stage, the main driving factor of NFP and MP stem flow was RH and Ts, respectively. However, during the maturity stage, the environ- mental factors had no significant influence on seed-maize stem flow. For different seed-maize plants, the main influential factors were different in each of the three growing seasons. Therefore, we identified them to accurately model the FP and MP stem flow and applied precision irrigation under alternate partial root-zone furrow irrigation to analyze major factors affecting stem flow in different scales.

Double-row repair of rotator cuff tears: Comparing tendon contact area between techniques

BACKGROUND In rotator cuff repair surgery,the double-row technique is widely performed.Studies have shown that with increased contact area and pressure between tendon and bone interface,better healing is promoted.AIM To assess the different suture configurations with the double-row technique and how this influences the contact area of the rotator cuff tendon to bone.METHODS This was a controlled laboratory study where identical tears were created in 24 fresh porcine shoulders over a 1.5 cm×2.5 cm infraspinatus insertion footprint.Double-row repair techniques,with 3 to 4-suture anchors in different configurations(2 medial,2 lateral vs 2 medial,1 lateral vs 1 medial,2 lateral),were employed for three control groups.Each group consisted of eight shoulders with identical repair configurations.Footprint contact areas of the repaired tendon against the tuberosity were determined using pressure sensitive Fujifilm placed between the tendon and tuberosity.RESULTS The mean contact area between tendon and insertion footprint from the imprinted Fujifilm was obtained using computer software.The contact area measured from a standard 4-suture anchor double row repair was 75.1±9.3 mm2,whereas areas obtained for the 2 lateral-1 medial and 2 medial-1 lateral anchor configurations were 72.9±5.2 mm2 and 75.0±4.9 mm2 respectively.No statistical significance was noted between the three groups.CONCLUSION In the technique of double-row repair,using a 3-suture anchor configuration may offer a non-inferior alternative to the standard 4-anchor construct in terms of efficacy.This may also result in overall cost reduction and shorter surgical time.

软土地区基坑前排倾斜双排桩支护现场试验及工作机理

基坑倾斜桩支护大幅提高了无支撑支护结构的适用深度,具有造价低、施工便捷、绿色低碳、变形控制好等特点,然而目前研究多集中在单排倾斜桩,对前排倾斜双排桩支护的试验、理论与应用的研究均较少。针对前排倾斜双排桩支护基坑开展了现场试验,同时采用有限元方法分别从前排斜桩、桩顶连梁及桩间土体作用3个方面深入探究了前排倾斜双排桩支护的工作机理,进一步分析了直斜桩长度和排距对前排倾斜双排桩支护结构受力变形性能的影响。结果表明,相比传统竖直双排桩,前排倾斜双排桩支护结构的支护性能显著提升,前排斜桩主要发挥“斜撑”作用,连梁主要起到将直斜桩及冠梁连接成一个空间刚架的作用,桩间土体能够提高桩土摩阻力,进而有效减小前排倾斜双排桩变形。研究成果有助于前排倾斜双排桩的推广和应用。

气吸双行错置式玉米密植精量排种器设计与试验

针对大豆-玉米复合密植播种模式下传统气吸式排种器单行种盘高转速作业导致充种时间短、气流稳定性差,难以实现高速精量密植播种的问题,设计了一种气吸双行错置式玉米密植精量排种器,阐述了排种器结构与工作原理,对其工作过程及关键部件进行理论分析,构建充种和投种环节的种子力学模型,确定排种盘内外环型孔排布、投种轮、气室等关键结构参数,并开展单、双气道内负压分布、型孔内气流场特性分析,基于DEM-CFD耦合方法对排种器的排种过程进行仿真分析,以作业速度、气室结构和负压为试验因素,充种合格指数、重充指数和漏充指数为评价指标,优选出最优气室结构。通过台架试验开展不同气吸式排种器排种性能对比试验。试验结果表明,在作业速度为5~10 km/h的高速密植工况下,气吸双行错置式密植精量排种器排种合格指数均大于88.7%,且作业速度为10 km/h时,相较于常用单圆环气吸式排种器合格指数提高5.5个百分点,漏播指数降低5.6个百分点;田间试验结果表明,在作业速度为5 km/h下,播种合格指数为95.7%,重播指数为1.6%,漏播指数为2.8%。提出的气吸双行错置式玉米密植精量排种器在高速作业时拥有良好的排种性能,能够满足大豆-玉米高速精量密植播种要求。

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。

关节镜下单排与双排缝合桥技术治疗肩胛下肌腱损伤的临床研究

目的探究关节镜下采用单排与双排缝合桥固定技术治疗肩胛下肌腱损伤的疗效。方法回顾性分析自2018年1月至2020年6月沧州市中心医院采用全关节镜修复治疗的40例肩胛下肌腱损伤患者资料。其中,男23例,女17例;年龄39~70岁,平均(55.25±6.82)岁。依据术中肩胛下肌腱的固定方式分为双排缝合桥固定组(双排组,20例)和单排缝合固定组(单排组,20例)。记录缝合时间、疼痛视觉模拟评分(visual analogue scale,VAS)、美国肩与肘协会评分系统(American Shoulder and Elbow Scoring System,ASES)、洛杉矶加利福尼亚肩关节分级评分(University of California at Los Angeles,UCLA),评估患者术前及术后1年时肩关节功能情况,并应用改良Sugaya分级法评估术后1年肩胛下肌腱愈合和再撕裂情况。结果所有病例获得随访,随访时间12~53个月,平均19.80个月。双排组患者肩胛下肌腱缝合时间多于单排组,差异有统计学意义(P<0.05)。术后1年双排缝合桥固定组的VAS评分[(1.30±0.57)分]、ASES评分[(70.92±5.65)分]、UCLA评分[(26.52±6.88)分]与术前相比明显改善,差异有统计学意义(P<0.05);术后1年单排缝合固定组VAS评分[(1.55±0.69)分]、ASES评分[(70.14±5.46)分]、UCLA评分[(26.89±7.78)分]与术前相比有明显改善,差异有统计学意义(P<0.05)。但术后1年两组间在VAS评分、ASES评分、UCLA评分方面比较,差异均无统计学意义(P>0.05)。根据改良Sugaya分级法,双排组术后1年核磁检查肌腱愈合良好,有1例再撕裂病例,单排组有2例再撕裂病例,两组术后1年肩胛下肌再撕裂情况比较,差异无统计学意义(P>0.05)。结论关节镜下采用单排和双排缝合桥技术修复肩胛下肌腱损伤均可获得满意的临床疗效和较低的再撕裂率。双排缝合固定肩胛下肌腱需要一定的手术技巧,缝合固定时间多于单排缝合方式。

基于SSA-CNN模型的双排开孔圆筒防波堤透射系数预测

双排开孔圆筒防波堤是一种新型环境友好型防波堤,对其消浪特性的研究具有重要工程意义。随着人工智能的发展,基于机器学习技术求解防波堤水动力学问题成了一种新的研究范式。本文提出基于麻雀搜索算法(Sparrow Search Algorithm,SSA)优化卷积神经网络(Convolutional Neural Network,CNN)模型,实现对双排开孔圆筒防波堤透射系数的智能优化预测。结果表明:(1)确定波高、波周期、波长、波速、排间距、开孔率、水深为影响透射系数的关键因子;(2)当SSA-CNN模型的种群数量为10时,对波浪透射系数预测的R2值达到0.9909,平均相对误差相比单一的CNN模型降低了5.07%。研究成果为利用神经网络研究波浪透射问题提供了一种新的优化预测模型。

多冷媒非均质人工冻结壁弹塑性应力分析

【目的】受制冷媒介温度差异以及被冻地层与冻结管距离差异的影响,多冷媒联合双排管冻结壁的非均匀性较为显著,为了合理评价该类冻结壁的安全性,需开展考虑非均质性的多冷媒人工冻结壁弹塑性应力分析。【方法】选取距离1/4管距处的冻结壁作为特征截面,将该截面上的温度分布曲线等效成三段一次函数形式,并将冻结壁视为随温度成线性变化的非均质材料,分别基于4种冻土屈服准则,推导得出多冷媒联合双排管非均质冻结壁弹塑性应力解析表达式。基于该解析表达式,对多冷媒冻结壁的受力特性进行计算,并将该计算结果与均质冻结壁计算得出的结果进行对比。【结果和结论】研究发现:(1)在盐水-二氧化碳联合双排管冻结壁中,径向应力随着相对半径r的增加而上升,环向应力在不同冻结区间(Ⅰ、Ⅱ、Ⅲ)表现出不同的变化趋势。(2)基于均质冻结壁计算理论,弹性极限状态的冻结壁的环向应力最大值出现在冻结壁内侧,弹塑性状态的冻结壁的环向应力最大值出现在弹塑性分界面处,塑性极限状态的冻结壁的环向应力最大值出现在冻结壁最外侧;而基于非均质冻结壁计算理论,冻结壁环向应力最大值始终出现在冻结壁分区界线(r=2)处。(3)在考虑非均质特性后,冻结壁的弹性极限承载力降低1.8%,而塑性极限承载力提高8.1%。在弹塑性状态下,对应相同塑性区相对半径,非均质冻结壁具有更高的承载力,且这种现象随着塑性区相对半径的增大而愈发明显。研究成果对富水地层多冷媒联合冻结帷幕的设计具有重要的参考价值。

肩关节镜下单排缝合与双排缝合治疗肩袖损伤的临床应用比较

目的探讨肩关节镜下单排缝合与双排缝合治疗肩袖损伤的临床应用。方法选取本院2019年7月—2022年6月所治疗的肩袖损伤患者100例,随机分为两组,对照组(50例)行肩关节镜下单排缝合治疗,观察组(50例)行肩关节镜下双排缝合,研究比较其临床应用效果。结果观察组患者治疗后肩关节功能相关指标水平(UCLA分数、Constant分数以及ASES分数)、治疗后肩关节相关(前屈、后伸、外展、内收以及上举)、临床总有效率均显著优于对照组,差异有统计学意义指标活动度(P<0.05)。结论在肩袖损伤治疗过程中采取肩关节镜下双排缝合方式较之单排缝合,其治疗效果更为理想,有利于提升临床治疗效率。

排桩倾斜对双排桩支护结构性状影响分析

依托某双排桩基坑工程实践建立有限元模型,分析前、后排桩倾斜对基坑支护效果的影响,并与现场监测数据进行对比验证。研究结果表明:前排桩倾斜一定的角度,桩身弯矩和轴力增大,前排桩发挥斜撑作用,桩身水平位移及桩顶沉降减小,支护效果提高;随着前排桩倾斜角度的增大,支护效果提升幅度减弱;后排桩倾斜可提高支护效果,不同倾斜角度下,桩身弯矩、轴力、水平位移和桩顶沉降变化幅度不同,但倾斜角度过大导致支护效果减弱;相同排桩倾斜角度下,前排桩倾斜对双排桩支护效果的提升显著优于后排桩倾斜,前排桩倾斜15°时支护效果最优。

基于差分法的双排抗滑桩结构内力计算

为研究有连梁双排抗滑桩快速有效的内力计算模型,在对有连梁双排桩进行受力分析的基础上,将有连梁双排抗滑桩结构简化为在桩顶连系梁零弯矩处断开的2根单桩结构,通过对双排桩受力进行叠加得到前后排桩桩顶连梁传递的弯矩与剪力,基于有限差分法建立了有连梁双排抗滑桩受荷段、嵌固段全桩内力计算模型,进而对有连梁双排抗滑桩桩体内力进行了计算。同时,通过大型室内模型试验内力实测结果对所计算结果进行了对比验证。结果表明:(1)模型试验结果与所建计算模型得到的桩顶位移与桩身弯矩值吻合较好,说明简化计算模型具有一定的适用性;(2)二者的后排桩最大弯矩出现位置略有偏差,计算得到的最大弯矩位置更接近实际桩体破坏位置,进一步验证了全桩内力计算模型的可靠性;(3)所建有限差分计算模型避免了将受荷段与嵌固段利用连续条件进行迭代的复杂运算过程,大大提升了计算效率,为实际工程提供了一种快速高效的有连梁双排桩内力计算方法。

h型双排桩在山地建筑边坡工程中应用

针对山地建筑边坡受用地限制而常用挡墙不太适用的问题,提出了h型双排桩结构形式,其由冠梁、腰梁、盖板、前排桩及后排桩组成。首先,假定h型双排桩的上部山体为滑裂体,采用传递系数法计算剩余下滑力,与双排桩抗滑力进行比较,判断边坡整体稳定性;假定h型双排桩为悬臂二阶柱结构,计算结构变形,判断变形是否满足正常使用要求。其次,依托某边坡工程进行实例论证,该工程竣工已近两年,监测数据表明边坡处于安全稳定可控状态。最后,h型双排桩解决了山地建筑边坡用地受限的难题,双排桩强有力的结构形式提高了悬臂式挡土高度,且双排桩盖板可兼作山地建筑的室外用地使用。

独立分充式大豆双排毛刷高速精量排种器设计与试验

为解决机械式大豆排种器高速播种质量差的问题,设计了一种独立分充式大豆双排毛刷高速精量排种器,采用双排种盘结构增加型孔数量,独立分充避免种群积压互扰,实现高速精量排种作业。通过理论分析,明确了充种、投种性能的影响因素,并确定了型孔与导流槽相关参数。以作业速度、型孔倾角、导流槽倾角为试验因素进行了正交试验,试验结果表明:在大豆株距为8cm、排种器作业速度为9km/h时,较优组合为型孔倾角54°、导流槽倾角39°,此时合格指数为95.5%,漏播指数为2.0%,株距变异系数为13.1%。对比试验结果表明:作业速度为8~12km/h时,独立分充式排种器合格指数比常规毛刷式排种器至少提升1.3个百分点,漏播指数至少减少0.8个百分点,株距变异系数至少减少2个百分点。窄行密植农艺适应性试验结果表明:在作业速度8~12km/h的条件下,独立分充式排种器合格指数达到90.1%,漏播指数不高于4.6%,株距变异系数不大于20.1%,窄行密植种植农艺适应性较高。

基于动态神经网络NARX时间序列的双排桩基坑变形预测

针对目前基于含基本假设或经验公式的传统土力学计算方法,不能有效地反映具有多因素交叉性以及时空性的基坑变形规律,而监测数据时间序列能够真实地表现基坑土体变形的演变,以南宁市亭洪路72号河南水厂住宅小区危旧房改造项目双排桩基坑工程为依托,考虑开挖深度和土体暴露时间这2个因素对监测时间序列的影响,提出一种带有外部输入的非线性自回归(NARX)动态神经网络时间序列模型,多方位预测关键断面重要测点的竖向位移和水平位移。结果表明:预测值和实际监测数据的变化趋势具有较好的一致性,且竖向位移预测值与实际监测值的预测残差小于1.0 mm,水平位移预测残差小于0.3 mm。该模型预测效果良好,同时验证了此模型应用于双排桩基坑变形动态分析的可行性。

堆石体修正Rowe剪胀方程与南水模型

在分析堆石体三轴试验成果的基础上,探讨了堆石体的体积变形特性,提出了形式简洁的堆石体修正Rowe剪胀方程。将所建立的修正Rowe剪胀方程引入到沈珠江院士提出的"南水模型",克服了该模型由于采用体变–轴向应变抛物线假设所带来的一些缺陷。应用堆石体常规三轴试验和典型复杂应力路径三轴试验成果对修正后模型的合理性进行了验证。

双须光电法分梳绒测长仪与手排法的测试结果对比

研制出双须光电法分梳绒测长系统2.0Z版,利用该仪器测试25种分梳山羊绒试样的纤维长度,同时采用GB 18267—2013中的手排法测试上述试样的纤维长度,根据两种测试方法所得结果对比验证2.0Z版测长系统的精确度和稳定性。结果表明,采用手排法测试分梳绒长度时,取样存在样间差异,并且手排法测试样品量少、随机误差高,而双须光电法测试结果稳定。双须光电法分梳绒测长系统2.0 Z版和手排法长度测试的一致性较高,特别是平均长度指标的平均偏倚小于2 mm,相关系数均大于0.8,表明分梳绒测长系统2.0Z版的精确度高。

大跨距双列圆锥滚子轴承热态特性

针对摩擦发热会影响轴承寿命的问题,基于滚动轴承动力学理论,建立了考虑滚子修形的重载特种车辆用大跨距双列圆锥滚子轴承动力学分析模型和精细化轴承功耗数学模型,研究结构、工况参数对轴承摩擦功耗的影响规律,并对滚子与套圈的内滚道、外滚道和大挡边之间的接触温度特性进行分析。研究结果表明:转速、径向载荷增大以及内滚道倾角减小,滚子与挡边、滚道接触区最大温度均增大,且挡边接触区最大温度增大速率较快。轴向载荷增大会使受压侧受载最大滚子与套圈大挡边、滚道接触区最大温度均增大,套圈大挡边接触区最大温度增大速率较快;放松侧温度也增大,但增大速率较慢;倾覆力矩会导致两列滚动体温度产生差异,选择合适的跨距可以减小倾覆力矩对轴承温度的影响。