Evaluation of the agronomic effectiveness of natural and partially acidulated phosphate rocks in several soils using32P isotopic dilution techniques

The agronomic effectiveness of two natural phosphate rocks (PRs) from North Carolina (USA) and Togo and their 50% partially acidulated products (PAPRs) was evaluated in two greenhouse experiments using³²P isotopic dilution techniques, namely L and A_L values.In the first experiment rye grass was grown in a soil from Ghana. While the proportion of P in the plant derived from the P fertilizer (Pdff) ranged on. the average from about 10% for the PRs up to 80% for the PAPRs, the P fertilizer recovery was less than 1% for a 60-day growth period. In the second experiment, average values of P in the maize plants derived from the PAPRs ranged from 35% to 75% in 3 different soils. Both PRs were ineffective with the exception of North Carolina PR in the Seibersdorf soil. The P fertilizer recovery was 0.25% for the North Carolina PR in this soil whereas the recovery values ranged from 1.2% to 1.6% for the PAPRs.Mean values of the relative fertilizer efficiency estimated from the L values of each soil were less than 1% for the PRs whereas the values for the PAPRs which were dependent on soil type ranged from 20% up to 45%. The coefficient of relative effect of partial acidulation, that was calculated from the ratio of A_L values for PR and PAPR in each soil indicated that partial acidulation increased the effectiveness of the natural PRs in all soils under study.This study showed that the use of³²P isotope dilution techniques allows an accurate measurement of the P availability from natural and modified PR products to crops. Another advantage is that quantitative comparison of the P sources under study, PRs and PAPRs in this case, can be made even in soils where there is no response to the applied P sources.     

基于无线传感网络技术在高压开关柜测温中的应用研究

无线传感网络是目前国内外研究的热点课题,并且在结构健康监测中具有广阔应用前景。为了简化传感器铺设的及布线的繁琐,采用Nordic2.4G无线通信技术,高压开关柜中高压侧采用多点组网的方式,即高压侧多路测温系统,对应低压侧一路接收系统。本文方案利用无线收发nRF24L01芯片设计传感节点电路,介绍了系统硬件组成与工作原理,较好实现了温度的实时远程监测。     

尿素和精喹禾灵不同配施对紫苏光合性能和产量的影响

采用随机区组试验设计,研究尿素(0,1,2,4和8g/L)与10.8%精喹禾灵乳油(0,0.8,1.6,2.4和3.2mL/L)不同配施对紫苏光合、叶绿素荧光特性、除草效果和产量的影响.结果表明:精喹禾灵与8g/L尿素配施可显著降低紫苏的光合特性、光系统Ⅱ的实际光化学效率和产量;而精喹禾灵与1~4g/L尿素配施均有高于单用精喹禾灵处理的趋势.A组的Q1N3处理(先施4g/L的尿素再施0.8mL/L的精喹禾灵)效果最佳,能显著提高紫苏在精喹禾灵胁迫下的光合性能,增强紫苏对光破坏的防御机制,增产10.54%.表明精喹禾灵可对紫苏产生胁迫,尿素可缓解其对紫苏的伤害.     

人体腰椎模拟植入椎弓根螺钉的有限元分析

利用三维绘图软件构建人体腰椎L4-L5节段几何模型,并模拟植入椎弓根螺钉.通过UG与Ansys Workbench的无缝接口将所建模型导入后者,对模型赋值并进行有限元分析,得出在人体站立情况下腰椎的应力云图与位移云图.从云图中可看出正常腰椎模型的最大应力出现在L4下关节突附近,值为15.073 MPa;最大位移出现在椎间盘上表面前部,值为0.161 mm.植入椎弓根螺钉的腰椎模型最大应力出现在螺钉的中部,值为38.613 MPa;最大位移出现在第4腰椎上端的前部,值为0.136 mm.结果表明：植入的椎弓根螺钉可缓解椎体的承载负担,并且可使腰椎变形减小.该结论可为同类腰椎固定手术以及脊柱的生物力学分析提供理论参考.     

基于稀疏强特征提取的三维地震数据完备方法

随着复杂储层地震资料特征筛选的机器学习技术的进步,如何有效地对参与地震属性优选和储层反演的地震样本进行采集和分析,成为目前智能地震预测领域的一个研究热点。目前的方法多着重于模型分类算法的改进,在标签的制作和采集方面不仅耗费大量时间进行人工标注,还存在标签不平衡情况下类内可靠性、类间平衡性不强等问题。为此,提出基于稀疏强特征提取的三维地震数据完备方法。首先,基于多数决原则的样本分割(Sample Segmentation Based on Majority Rule, SSMR)寻迹多尺度、多标签三维地震样本,进行采集、自动标注;然后,改进标签洗牌平衡方法(Improved Label Shuffling Balance Method, ILSB),通过“2+1”的样本增广平衡策略进行数据完备处理,改善样本采样不平衡性导致的模型训练偏向性;最后,利用基于最小L₁范数稀疏表示对奇异值分解结果进行强特征提取(Minimum L₁-norm Based Sparse Representation for Feature Extraction, L     

Wear mechanisms of PcBN tools when machining AISI 316L

This paper investigates the machinability of AISI 316L stainless steel without and with NMI treatment, when machined with three different PcBN tool grades: low cBN content (50% vol.), medium (65% vol.) and high (90% vol.). The NMI treatment consisted of resulfurized and Ca-treated steels with two different Si/Al ratio. The tool materials were evaluated in terms of tool life, showing the best performance for the medium cBN content grade. Results showed that the crater wear has a more significant effect on the tool performance than the standard wear criteria of maximum flank wear. The worn tools were examined using scanning electron microscopy (SEM), focused ion beam (FIB) and transmission electron microscopy (TEM). In most cases, the crater exhibited three distinct regions from the edge to the end of the contact zone: the plateau, middle crater, and the upper region. Plateau and crater region displayed tool protective layer (TPL), consisting mostly of Al, Si, Mg and Ca-oxides; and some dimples in the tool from preferential wear of cBN grains. In the upper region of the best performing material, a ~1.5 μm thick TPL of mostly MnCr₂O₄ spinel was found, a result of the transfer of Mn- and Cr-rich oxide NMIs found in this material or oxidation of workpiece material, during the machining process.     

Q235-304L电偶对在Na2S溶液中的电偶腐蚀行为研究

用电化学法和浸泡法研究了Q235-304L电偶对在3种不同浓度的Na2S溶液中的电偶腐蚀行为,用SEM观察试样的表面形貌.结果表明:在3种溶液中Q235钢的阳极过程均为混合控制,而304L的阴阳极过程均为电化学控制;偶接后Q235钢表面阳极金属的溶解过程与阴极过程同时进行,其阳极溶解电流大于电偶电流值;电偶腐蚀效应随阴阳极面积比的增大而增大;随着S2-浓度的升高,电偶对中Q235钢的腐蚀速率减小,电偶腐蚀效应也随之降低.     

纯铝累积叠轧焊高温力学性能与显微组织研究

室温条件下对退火态L2纯铝进行了6道次的累积叠轧焊试验,通过高温拉伸、透射电镜和扫描电镜实验,研究叠轧前后材料在高温拉伸过程中力学性能的变化、组织结构的演变以及拉伸后的断口形貌。结果表明,在高温拉伸过程中,叠轧后材料发生了动态回复,形成的亚晶组织随温度升高而长大;叠轧前后材料的抗拉强度随温度单调递减,延伸率则先升高,达到极值后降低;断口形貌显示,叠轧材料的高温断裂属于韧性断裂。     

电磁动态金属粉末注射成型型坯结构性能的研究

利用自行设计的电磁动态注射机DPII-90，对不锈钢金属粉末316L和粘结剂的混合喂料进行稳态和动态注塑成型实验，研究振动参数对金属粉末和粘结剂混合喂料的均匀化和密实机理的影响。实验结果表明，各动态成型条件下的型坯密度明显大于稳态成型条件下的密度。当振动频率（或振幅）不变时，随着振幅（频率）的增大，型坯密度呈非线性增大，达到最大值后缓慢下降，存在一个最佳值。在频率7Hz-10Hz，振幅50μm～150μm的范围内，注射出的型坯密度较高，密实性好。电镜扫描（SEM）发现，金属粉末与粘结剂的分散均匀和完善程度的变化规律和型坯密度随着振幅（频率）的变化规律基本一致。     

L12型Al3Ti合金室温变形超位错的分解及计算机图像模拟

利用透射电子显微镜和计算机图像模拟技术研究了ＬＩ２型Ａｌ３Ｔｉ合金室温变形的位错核心结构，结果表明：α（１１０）超位错在｛１１１｝面上分解成两个α／３｛１１２｝型超偏位错，其间为超点阵内禀层错。