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11.
针对硬态切削条件下的切削力控制问题,建立了控制模型,使用MATLAB/SIMULINK设计了PID/PD控制器,对径向力的控制效果进行了仿真。结果表明:通过调节进给量能够有效地控制径向切削力变化,同时,能够较好地控制刀具的磨损速率。 相似文献
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- 1. Microhabitat preferences of freshwater mussels and associated substrate characteristics were investigated across a range of geomorphic reaches in the Hawkesbury–Nepean River, Australia.
- 2. The structure of substratum patches available was strongly influenced by geomorphic reach type. In each reach type, mussel distribution was most frequently correlated with coarse sand and a roughness element characteristic for that reach. Roughness elements such as boulders and cobbles create a flow refuge and were linked with mussel size.
- 3. Small mussels tended to be associated with boulder‐stabilized habitats and medium sized mussels with cobble habitats. Large mussels rarely co‐occurred with any particular roughness element. Individual species were strongly linked to geomorphic reach type. This association may be due to species' differences in ability to colonize available microhabitat types.
- 4. The highly tolerant Velesunio ambiguus dominated shale reaches, characterized by fine sediments and human impacts. In contrast, Hyridella depressa dominated in gorges, utilizing small flow refuges among boulders, while H. australis were present in low densities across a range of substrate conditions.
- 5. The persistence of multispecies assemblages in mussel beds throughout the Hawkesbury–Nepean River implies similar niche utilization among species. Partitioning of habitats across species on the basis of size suggests some degree of habitat selection, or differential survival. At the local scale, microhabitat characteristics influenced the size distribution and densities of mussel assemblages. Continuing declines in mussel densities are likely to result from ongoing channel modification and increased siltation resulting from changes to riparian vegetation.
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油菜机械移栽载苗基质块力学与生物学特性分析 总被引:1,自引:3,他引:1
为保证油菜载苗基质块具有良好的机械移栽适应性和幼苗生长质量,该文针对油菜机械移栽过程中载苗基质易出现破损导致取送苗失效问题,以正方体油菜载苗基质块为研究对象,对载苗基质块力学特性和生物学特性进行研究,开展以基质成分配比(蚯蚓粪:黄棕壤∶蛭石混合体积比为1∶2∶1、1∶1∶1和2∶1∶1)、基质压实度(基质与穴孔体积比为1.0、1.2和1.4)、硼硒营养液浓度(0.24%、0.27%和0.30%)为因素的正交试验。结果表明:基质成分配比和基质压实度对油菜载苗基质块力学特性影响分别为极显著和显著;基质成分配比及基质压实度对幼苗壮苗指数影响极显著,硼硒营养液浓度对其影响显著;基质成分配比和基质压实度均对基质包裹度及根系健壮度影响极显著,硼硒营养液浓度对基质包裹度及根系健壮度影响显著。采用综合评分法得出基质成分配比为1∶1∶1、基质压实度为1.2、硼硒营养液浓度为0.30%时油菜载苗基质块力学特性及幼苗生长质量较优。对上述因素组合所育油菜载苗基质块进行台架试验可知:在移栽机横向推苗速度20 mm/s,同步输送带速度30 mm/s,取苗频率40株/min试验条件下,基质损失率为2.57%、送取苗成功率为90.93%,满足机械移栽需求。 相似文献
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对南方红豆杉扦插苗和实生苗光合生理特性比较研究结果表明,南方红豆杉扦插苗叶重、叶绿素a和b、叶绿素总量、CO2补偿点及净光合速率、硝酸还原酶活性均小于相应树龄实生苗。 相似文献
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不同处理对四季秋海棠扦插生根的影响研究 总被引:10,自引:1,他引:10
以四季秋海棠为材料,进行扦插生根研究。试验结果表明:不同季节、不同基质、不同植物生长调节剂对四季秋海棠扦插生根有很大的影响,其中秋季扦插,以河沙做基质,以30mg/LNAA、30mg/LIAA或50mg/LIBA处理的插条生根效果较好。 相似文献
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Summary We studied the effect of three successive cuttings on N uptake and fixation and N distribution in Leucaena leucocephala. Two isolines, uninoculated or inoculated with three different Rhizobium strains, were grown for 36 weeks and cut every 12 weeks. The soil was labelled with 50 ppm KNO3 enriched with 10 atom % 15N excess soon after the first cutting. Except for the atom % 15N excess in branches of K28 at the second cutting, both the L. leucocephala isolines showed similar patterns of total N, fixed N2, and N from fertilizer distribution in different parts of the plant at each cutting. The Rhizobium strain did not influence the partitioning of 15N among the different plant parts. Significant differences in 15N enrichment occurred in different parts. Live nodules of both isolines showed the lowest atom % 15N excess values (0.087), followed by leaves (0.492), branches (0.552), stems (0.591), and roots (0.857). The roots contained about 60% of the total plant N and about 70% of the total N derived from fertilizer over the successive cuttings. The total N2 fixed in the roots was about 60% of that fixed in the whole plant, while the shoots contained only 20% of the fixed N2. We conclude that N reserves in roots and nodules constitute another N source that must be taken into account when estimating fixed N2 or the N balance after pruning or cutting plants. 15N enrichment declined up to about fivefold in the reference and the N2-fixing plants over 24 weeks following the 15N application. The proportion and the amounts of N derived from fertilizer decreased, while the amount derived from N2 fixation increased with time although its proportion remained constant. 相似文献