水流作用下悬跨管道振动的实验研究

为了比较得到水下管道安全悬跨长度的判别条件并验证其合理性。使用弹性力一重力相似理论设计模型实验,管道两端均采用固定约束,管道与水流之间的角度分别为90°、75°、60°、45°和30°,悬跨管长分别为1．00m、0．81m、0．73rn、0．70rn。通过实验比较fn≥10fs、fn≥（0．7）-1．fs、fn=5fs（fn为悬跨管道固有频率;六为水流激振频率）3种条件对悬跨管道振动的判别情况。研究表明,根据fn=5fs,即约化速度K=1的条件,计算得到的临界长度较安全、合理,并由fn=5f条件给出了不同管径、壁厚和流速条件下管道临界长度的规律图,研究结果可为水下悬跨管道的安全评价提供借鉴。（图3,表2,参13）     

狗牙根种质资源的根系分布特征及抗拉强度研究

为比较不同狗牙根种质资源的固土护坡能力,研究了不同狗牙根的根系分布特征及抗拉强度,结果表明:狗牙根的根系集中分布在0～10 cm土层,其根长密度和根重密度随土层深度的增加而减少,C2的根长密度和根重密度均优于C1和C3.3份狗牙根材料的平均根直径均小于1.0 mm,C2的有效根密度最大;狗牙根的根系抗拉强度均随根系直径的增加而减小,3份材料的根系最大抗拉强度的峰值均出现在根系直径小于0.4 mm径级,表明细根的固土护坡能力较粗根好,3份材料中C2的根系平均抗拉强度最大.从3份狗牙根材料中初步筛选出较适宜做护坡的狗牙根为C2.     

基于三维重建的动物体尺获取原型系统

为提高现有动物体尺获取技术的效率和自动化程度,提出双深度摄像头动物实时三维重建系统,进而进行动物体尺获取。基于随机采样一致性算法的圆球标定方法对摄像头外参数进行自动标定,再利用外参数将同步获取的点云数据进行配准达到实时重建,最后采用优化拾取机制后的交互式测量方法得到体尺。选取Xtion PRO作为点云数据采集设备并以猪标本作为重建对象,利用高精度激光扫描仪的重建数据与该系统重建结果进行了对比试验,结果表明圆球标定算法能够全自动快速地获取摄像头外参数,用该参数配准后的数据平均误差在7.50 mm以内,该系统以15帧/s的速度重建猪体全身,获取误差在4%以内的体尺信息,达到农业上动物体尺测量的一般要求,该系统可用于动物体尺测量。     

土壤湿度和机械长度对棉花秸秆分解率的影响

新疆棉花秸秆产量巨大,但是棉花秸秆的木质素和纤维素含量较高,不易被分解,很难作为饲料利用。本文研究了棉花秸秆在不同条件(土壤水分、棉花机械长度)处理下的分解速率。从土壤水分条件来看,棉花秸秆在50%土壤饱和含水量下的分解最为理想,其分解率在100 d后达到54.08%;从棉花秸秆粉碎程度来看,棉花秸秆粉碎越细越有利于其分解,但是3 cm处理100 d后分解率为54.12%,而1 cm处理100 d后分解率只有47.42%,说明棉花秸秆分解需要一定的孔隙度。另外,棉花秸秆分解之后对土壤肥力也有很大影响。此次试验结果可为推广大田试验提供科学依据。     

丝羽乌骨鸡快大型新品系早期生长发育规律及肉用性能的研究

本试验对丝羽乌骨鸡快大型新品系的早期生长发育规律及肉用性能进行了系统的研究。利用Logistic模型确定了快大型新品系丝羽乌骨鸡的生长模型,并以此制定了标准生长曲线。研究结果表明,其生长拐点为:10.5周龄;在14周龄时体重约1.0kg,公、母鸡屠宰率分别达到85.88%、84.12%;胸肌率分别达到17.78%、17.28%;腿肌率分别达到24.38%、22.54%。在14周龄时,为较适合的上市日龄。     

日本沿海捕鳗笼的网目选择性

1995~2000年在东京湾进行的套网法实验,结果表明:网目尺寸为21·0、18·1、15·5、13·6、11·6mm的笼网目选择率在星康吉鳗全长035·50cm、l>32·50cm、l>27·50cm、l>26·50cm、l>24·00cm时,全长选择率几乎接近于1·00,50%选择全长分别为29·80、26·80、23·00、22·00、20·00cm;选择域为3·80、4·30、3·50、3·00、3·00cm。依据AIC理论,套网和实验网的网目接近时,套网的影响显著;Single curve model所得到的主选择性曲线可更好地反映网目选择性。50%选择相对体周长MGc1·11,选择域为0·52。01·60,选择率趋向于1·00。     

Density effects on length at maturity of walleye pollock <Emphasis Type="Italic">Theragra chalcogramma</Emphasis> off the pacific coast of northern Japan in the 1990s

To determine how stock abundance fluctuations of walleye pollock Theragra chalcogramma are related to variations in reproductive characteristics, the length at 50% maturity of the fish sampled off the Pacific coast of northern Japan from 1990 to 1999 was examined. In both sexes, the fish density increased, and the body length of age-3-5 fish decreased, but the condition factor and the age at 50% maturity showed no clear trend during this period. Male length at 50% maturity decreased, while value for females showed no clear trend. In both sexes, significant negative correlations were found between density index (combined age-3-5) and each body length at age-3-5. Significant positive correlations were seen between each body length at age-3-5 and length at 50% maturity in males. Positive correlation between body length at age-5 and length at 50% maturity was significant in females from 1990 to 1999, except for the samples in 1998. We suggest that the fish density might affect the length at maturity in males and possibly also in females.     

三种植被类型植物根系对崇明岛海岸带稳定性的影响

Coastal erosion is currently a major problem along the southern coast of Chongming Island, Shanghai. To enhance the erosion protection ability of coastal shelterbelts, two woody tree species, Taxodium ascendens and Salix babylonica, were planted separately into Phragmites australis + Scirpus mariqueter communities in 2006. Two years later, we investigated whether either of these experiments reduced erosion and increased stability in the native herbaceous plant community. We also examined soil stability and root length density under T. ascendens added, S. babylonica added and native herbaceous vegetation conditions along an intertidal gradient from the soil surface to a depth of 40 cm in each experiment, thus to determine the capacity of T. ascendens and S. babylonica to contribute to shoreline stabilization. Topsoil under the native vegetation had greater stability at the middle and higher intertidal zones because its soil stability index and root length density were significantly higher than in the T. ascendens or S. babylonica planted communities. The effect of T. ascendens on soil stability was not generally better than that of the native vegetation. Only at the 20-30 cm soil depth of the middle intertidal zone and in the 10-20 cm layer of the higher intertidal zone the soil stability index and root length densities under the T. ascendens added condition were significantly higher (P < 0.05) than those of the native vegetation. The S. babylonica planted soil had greater stability in the deeper soil layer than the soil under either the native vegetation or the T. ascendens added condition, and its soil stability index and root length density were significant higher (P < 0.05) than those of other vegetation conditions at the 30-40 cm soil depth for the lower intertidal zone and at the 20-40 cm layer for middle and higher intertidal zones.     

垂直线源灌线源长度对湿润体特性的影响

垂直线源灌可将水分直接输送到果树的根系,减少土面蒸发损失,以提高水分利用效率。通过模拟试验,研究了线源长度对土壤湿润体变化特性的影响。结果表明,不同线源长度土壤表面水平湿润半径、最大水平湿润半径和垂直湿润深度均与入渗时间的平方根呈线性关系,线源长度对土壤表面水平湿润半径和最大水平湿润半径的影响不明显,土壤表面水平湿润半径与最大水平湿润半径的比值和入渗时间的平方根符合线性关系,土壤表面水平湿润半径与垂直湿润深度的比值随入渗时间的增加而增大,随线源长度的增加而减小。这些研究结果可为垂直线源灌技术参数确定提供参考。     

基于微根管技术的玉米根系生长监测

为了研究玉米根系生长规律,该文利用固城农业气象试验站内设置的大型根剖面系统,采用微根管观测法,对试验地上玉米主要生育期的根系生长动态进行定期直接跟踪监测,并以方形整段标本法作为参照标准,对试验数据采用MATLAB软件辅助图像处理和现代统计方法进行分析。结果表明：微根管法与方形整段标本法对得出的根长密度随深度增加呈递减型有较好的一致性,两者相关系数达到0.83以上,通过0.05的显著性检验;由观测数据建立的回归方程能较好地反映土壤中玉米根系生长规律,进一步表明微根管法是一种破坏性较小、可准确定位跟踪植物根系在土壤中生长动态变化的先进技术,对植物根系生长研究有较好的推广应用价值。