Acoustic evaluation of the vertical distribution of dwarf ayu Plecoglossus altivelis altivelis in Lake Biwa

SUMMARY: The vertical distribution of dwarf ayu Plecoglossus altivelis altivelis in the pelagic waters of Lake Biwa was evaluated from June to September in 1995–97 from eight acoustic surveys using a quantitative echosounder. In each survey, echoes from a depth range of 3 m to the sea bottom were collected at a station every 2.7 s for 24 h together with measurements of vertical profiles of water temperature and chlorophyll-a. The ayu's echoes were identified using an underwater video camera. The ayu were observed near the maximum chlorophyll-a depth and above the thermocline. Their density was highest at depths of 4–11 m with 2–4 individuals/m ³ and was almost zero below 20 m. Echo signs were recorded as having a frequent duration of more than 1 h at night, whereas were of a shorter duration in the day. The fish stay in the epilimnion during the day without any clear vertical migration, but are distributed more uniformly at night. The advantages of remaining in the epilimnion are discussed in terms of food availability and predator avoidance.     

薄壁封闭环磨削回弹的建模与数值研究

提出了卡环制造过程中磨削回弹的计算模型。根据卡环的精度和啮合力要求,设计了特殊制造工艺。考虑弯曲残余应力,对磨削工序进行力学分析,提出了磨削回弹弯矩、磨削回弹后搭叠长度和啮合力变化的计算模型;开发了卡环制造辅助工艺系统——Shuttle,对卡环磨削工序进行了模拟,并结合实验讨论了磨削前后曲率半径、啮合力和搭叠长度随余量的变化规律。研究表明：随着磨削余量的增加,试样磨削前的啮合力增加,而磨削回弹后的啮合力呈下降趋势;试样磨削前后的搭叠长度均呈下降趋势,并且试样截面惯性矩越大,磨削回弹后试样的搭叠长度下降速度越慢;在各工序阶段,试样的曲率半径有不同程度的增加。     

TritonX-100对月季切花效应的研究

以月季为材料,研究聚乙二醇辛基苯基醚(TritonX-100)预处理缓解水分胁迫对切花的影响.结果表明:体积分数0.01 % TritonX-100预处理1 h能有效缓解短期水分胁迫对月季切花水分代谢的影响,从而使切花瓶插寿命接近正常水平.     

玉米秸秆切割过程的非线性数值模拟与仿真试验

应用Solidworks软件建立玉米秸秆—切割刀片参数化模型,借助LS-DYNA971非线性有限元软件模拟切割刀片切割玉米秸秆的过程。玉米秸秆切割的有限元数值模拟能降低试验成本和缩短试验时间,可视化数值模拟过程可为玉米秸秆收获机械的设计提供理论参考。利用参数化模型特点,通过改变玉米秸秆直径大小、秸秆含水率、切割方式和刀片刀端线速度进行正交仿真试验。结果表明：对切割力来说,含水率对其影响最显著,其它影响依次为：秸秆直径、切割方式、刀片刀端线速度;对切割功耗来说,含水率影响最显著,其次分别为：秸秆直径、刀片刀端线速度、切割方式。经正交综合平衡法分析可知：当刀片刀端线速度为28 m·s^-1,采取滑切方式,玉米秸秆含水率、直径分别为45%、26 mm时为最优。玉米秸秆—切割刀片动力学可视化数值模拟仿真模型的构建和分析, 对玉米秸秆收获机械设计具有重要的参考价值。     

滴水量对新大豆27号根系生长及产量的影响

为揭示滴水量对超高产大豆根系生长的影响规律,设置975 m3·hm-2(W1)、1 575 m3·hm-2(W2)、2175 m3·hm-2(W3)、2 775 m3·hm-2(W4)4种滴水处理,对各处理0~100 cm土层含水量、新大豆27号根系干重、侧根长和产量进行测定分析。结果表明:随着滴水量的增加,0~40 cm土层的含水量增加;0~20 cm土层根干重密度和侧根长密度增幅最大,20~40 cm土层增幅其次;增加生育中后期0~80 cm土层总根干重和总侧根长,鼓粒初期W2、W3、W4处理的根干重分别较W1增加14.2%、30.4%、41.1%,侧根长分别较W1增加17.4%、25.7%、40.3%;提高0~40 cm土层根系活力,增加根系伤流量,提高水分利用效率,W3、W4鼓粒初期0~80 cm土层根干重分别为88.6、95.8 g·m-2,侧根长为432.4~482.9 m·m-2,产量分别为6 082.6 kg·hm-2、6 404.7 kg·hm-2,水分利用效率为1.30左右。新疆伊宁地区大豆的适宜滴水量为2 175~2 775 m3·hm-2。     

浅析灌溉对作物根系及产量的影响

结合文献资料,从作物根系的水平分布、垂直分布、硝态氮运移及产量等几个方面,概述了不同灌溉量和灌溉方式对作物的影响,分析了滴灌、渗灌等微灌技术的应用。最后,针对经济林木生产的实际现状,进行了展望：探索一种成本低、简单易操作、便于推广应用的灌溉措施更具有理论和实践意义。     

Persistence of tebufenozide in aquatic ecosystems under laboratory and field conditions

The persistence and dissipation behaviour of tebufenozide, an ecdysone agonist, were investigated: (1) under laboratory conditions in aquatic models set up in glass aquaria, and (2) under field conditions in in-situ aquatic enclosures deployed in a mixed-wood boreal forest lake. Two models were set up in the laboratory study (Study I), which was conducted at constant conditions of temperature, water pH and photoperiod. In Model I, partitioning of tebufenozide from sediment, treated at a concentration of 1400 μg kg^-1, into untreated water was examined. The results showed that the chemical moved very little from the treated sediment into water. The concentration in sediment and water decreased gradually during the 90-day incubation period. Tebufenozide disappeared faster from the top layer of sediment than from the middle and bottom layers. The half-lives of disappearance were 64 days for the top layer but >90 days for the middle and bottom layers respectively. In Model II, partitioning from water, treated at a concentration of 350 μg litre^-1, into untreated sediment was investigated. The results showed that the chemical moved from treated water into sediment due to adsorption. Little vertical downward movement of the adsorbed residues from the top layer of sediment occurred into layers beneath. The adsorbed residues were also not released readily back into water. The concentration in water and sediment decreased gradually during the 90-day incubation period. The half-life of dissipation from water was 67 days. The field microcosm study (Study II), conducted under fluctuating conditions of temperature, water pH and photoperiod, involved application of tebufenozide onto aquatic enclosures at four concentrations of 0·05, 0·10, 0·26 and 0·5 mg litre^-1. This study also showed that the chemical moved downwards from the applied location and was adsorbed onto sediment. The chemical persisted longer in Study II than in Study I. Tebufenozide, being photo-labile, probably degraded faster after constant exposure to light in Study I than after exposure to fluctuating light in Study II. At 90 days after treatment in Study I, only about 55% of the applied material persisted in the sediment, and there was little accumulation. In Study II, the material not only persisted but also was accumulated in the sediment, since at 92 days post-treatment the residues were about 25 times higher than the applied concentration level. Residues in water also decreased more rapidly in Study I than in Study II, because the concentration at 90 days post-treatment was about 41% of the applied value. In Study II, however, about 65% of the applied chemical persisted in water at 92 days post-treatment. While the long persistence of tebufenozide in both the laboratory and field studies was attributable to its low vapour pressure, low water solubility, high octanol/water partition coefficient etc., the differences in the persistence characteristics observed in the two studies were due to the fluctuating environmental conditions and water pH encountered in the field study, compared with the constant environmental conditions and water pH utilized in the laboratory study. © 1997 SCI.     

立式金属油罐容量检定中的几个问题

针对JJG168-87计量规程在实际使用中的缺陷，对罐壁圈板径向偏差测量位置的确定，油罐充满油品后直径增大值的修正等问题，提出了具体的解决方法。     

基于表型和SRAP 标记的切花菊品种遗传多样性分析

 利用45 个表型性状和SRAP 标记分析56 个切花菊品种的遗传多样性。表型变异分析结果 表明：21 个性状表现出品种内一致性高及品种间特异性强;主成分分析发现,主成分贡献值较大的性状 有花序直径、花序类型和瓣型等花部性状,其次是叶部和茎杆性状,说明所选用的切花菊品种在分类时 应以花部性状为主,叶部和茎杆性状为辅;表型性状基于遗传距离UPGMA 聚类,将56 个切花菊品种分 为平瓣类、匙瓣类、桂瓣类、匙瓣-平瓣类和管瓣类,聚类结果大致按照花径-瓣型-花型分类。14 对 SRAP 引物组合扩增56 个切花菊品种的DNA,共扩增出454 条带,其中多态性带423 条,占扩增带数的 93.17%,多态性含量PIC 值在0.72 ~ 0.89 之间,平均为0.82,说明切花菊品种在分子水平上具有丰富的 遗传多样性。基于SRAP 标记的UPGMA 聚类分析显示：品种间遗传相似系数在0.64 ~ 0.97 之间,将56 个切花菊品种分为平瓣类-匙瓣、桂瓣类和管瓣类,聚类结果大致按照花径-瓣型-花型分类。Mantel 检验相关性系数为0.682,两种聚类结果有相似之处,均能很好体现试验切花菊品种间的遗传关系。     

棉花冠层叶面积的动态模拟

根据试验资料,在系统分析棉花冠层叶面积时空分布规律的基础上,充分考虑叶面积空间垂直分布的异质性,以生育期内累积的每日相对热效应为预报因子,构建了棉花叶面积垂直分布和叶面积指数的动态模拟模型。利用不同年份不同播期的试验资料对模型进行了验证,累积叶面积指数L（z）的模拟结果与1∶1直线之间的R^2和均方根误差分别为0.969和0.257,叶面积指数LAI的模拟结果与1∶1直线之间的R^2和均方根误差分别为0.936和0.305。结果说明模型具有较好的预测性和实用性。模型的模拟结果可作为冠层结构参数,用于冠层辐射传输模型和光合作用模型。