延胡索不同水分条件下盆栽试验

摘要：对盆栽延胡索进行不同水分条件的试验,测量其蒸腾耗水量,研究延胡索在生育各时期中的耗水特征以及水分条件与产量的关系,为陕南延胡索规范化种植的合理灌溉提供理论依据。研究表明：延胡索的耗水量在全生育期内有两个高峰期,分别为12月和3~4月。不同的水分处理对延胡索产量有一定影响,水分不足会抑制延胡索地上部分生长,减少地下部分物质积累量。     

盐溶液浸泡养护固化土的耐久性分析

基于改善固化土养护环境的思路,提出了用硅酸钠、硫酸钠和氢氧化钠的混合溶液以及饱和石灰水养护固化土,以期达到提高固化土的耐久性,延长固化土使用寿命的目的。通过无侧限抗压强度试验、干湿循环试验、冻融循环试验以及扫描电子显微镜试验对两种盐溶液养护进行了对比研究。试验结果表明,硅酸钠、硫酸钠和氢氧化钠的混合溶液养护与饱和石灰水养护均可提高固化土的强度、抗干湿循环以及抗冻融循环的耐久性;硅酸钠、硫酸钠和氢氧化钠的混合溶液养护对强度和耐久性的提高优于饱和石灰水养护;微观结构分析表明,两种溶液养护固化土生成了较多致密的凝胶物质,增加了黏聚力,降低了孔隙率,减少了大孔隙。     

造林工程施工信息ER模型设计

造林工程施工信息具有明显的时间和空间特征。属性、空间和时间是造林工程施 工信息数 据必须具备的3要素。造林工程施工信息数据库的主要实体有造林地基本信息、造林地作 业设计 信息、造林地施工信息、造林地检查验收信息和造林工程质量信息。应用ER模型能够简 单、清晰 地表示造林工程施工信息数据库实体与实体之间的关系。     

The Effects of Urbanization on the Siting and Expansion of Livestock Facilities in Illinois Under Proposed Legislation: A Spatial Analysis

Across the country, setback restrictions that require livestock facilities to be located away from neighboring residences and populated areas are making the siting or expansion of operations a growing challenge for livestock producers. In this study, Geographic Information Systems (GIS) technology was utilized to examine the impact of increasingly restrictive legislation on the availability of land for the siting or expansion of confined livestock operations. Georeferenced data from two southern Illinois counties were analyzed to quantify the effects of a proposed amendment to the Illinois Livestock Management Facilities Act that would increase the setback distances required between confined livestock operations and populated areas. The results of this study demonstrate that increases in setback distances can greatly reduce the availability of rural land for the siting of livestock facilities, even in rural counties with low population densities. In Franklin County, Illinois, a proposed 3.2-km setback distance would remove 70% of rural land from availability for livestock facilities siting. This loss would be experienced even though only 4.2% of the county is urbanized. Results also suggest that the land-use impacts from siting legislation may be reduced when urban development is clustered rather than scattered across the landscape.     

离心式消防泵内流特性

为了研究离心式消防泵外特性、内流特性及空化特性,基于RNG k-ε湍流模型对某一比转数为24.7的离心式消防泵不同工况下的内部非定常流动进行数值模拟.结果表明:在关死点工况下,离心泵消防泵叶轮内部产生大量的失速旋涡,尤其在叶轮出口位置出现面积较大且极高湍动能的涡核分布,严重影响流道的通流能力,且造成较大的能量损失;随着流量增大,流道内的旋涡逐渐消失,流场趋于稳定,涡核分布基本保持稳定且对称;随着流量持续增大,离心式消防泵轴向力逐渐增大,在极小流量和极大流量工况下的轴向力波动相对较强;随着流量增大,径向力逐渐降低,且不同工况下径向力的矢量分布均呈现六齿形分布;随着流量的增大,离心式消防泵扬程特性曲线受空化的影响更加明显,随扬程曲线开始下降时的NPSHR也逐渐增大,但下降速度相对较慢.     

紫果黑蕊猕猴桃营养品质变化及其相关性分析

为更好地促进高品质彩色猕猴桃的选育和开发,本研究以秦岭地区野生的紫果型黒蕊猕猴桃为材料,在果实成熟过程中采集不同果色时期（绿色、浅紫色、紫色和深紫色）的猕猴桃果实,对其营养成分（可溶性固形物、可溶性糖、可滴定酸、Vc和花青素）含量进行分析,探寻果实营养品质变化规律。结果发现,紫果黑蕊猕猴桃果实随着成熟,果色由绿色逐渐变为深紫色,其可溶性固形物、可溶性糖、花青素含量逐渐增加,各时期含量差异显著且两两间分别呈极显著正相关;可滴定酸和Vc含量逐渐降低,两者含量呈极显著负相关,但与可溶性固形物、可溶性糖、花青素含量分别呈显著负相关。结果表明,该紫果黒蕊猕猴桃果实成熟度越高,紫色特征越明显,可溶性固形物和可溶性糖含量越高,可滴定酸含量越低,但同时Vc含量也越低。     

Effects of codend circumference and twine diameter on selection in south-eastern Australian fish trawls

Two experiments, done in a south-eastern Australian trawl fishery targeting school whiting (Sillago flindersi: Sillaginidae), examined the relative efficiencies and selectivities of five codends and extension sections made from double-twine, 90-mm (inside stretched length) mesh netting. All extension sections were made from 3-mm diameter twine and were 100 meshes long and 100 meshes in circumference, while the codends were 25 meshes in length. The first experiment tested three codends made from 4-mm diameter twine: one with a circumference of 100 meshes and two of 200-mesh circumference, with one of the latter incorporating two cross-sectional joins in its extension piece. The second experiment compared two 200-mesh circumference codends, one constructed from 3-mm diameter twine and the other from 5-mm diameter twine. The codends were alternately fished with a small-meshed control. The results showed a general trend of reduced selection by the 200-mesh circumference and thicker twined codends, and especially by the industry-preferred 200-mesh circumference codend constructed from 5-mm diameter twine. Experiment 1 found that the 100-mesh codend caught significantly fewer school whiting, retained catch and total catch than did the two 200-mesh codends, and the 200-mesh codend with the modified extension section caught significantly fewer school whiting and retained catch than did the 200-mesh codend with the straight extension. In the second experiment, the 200-mesh 5-mm twine codend caught significantly more total and retained catch, school whiting, and longspine flathead (Platycephalus longispinis: Platycephalidae) than did the 200-mesh 3-mm twine codend. Across all codends, the smallest lengths at 50% probability of retention (L₅₀) were estimated for longspine flathead, redfish (Centroberyx affinis: Berycidae) and longfin gurnard (Lepidotrigla argus: Triglidae) in the 5-mm 200-mesh codend. The limited size range of school whiting resulted in unreliable estimation of selectivity in the 200-mesh 5-mm twine codend, but this design was the only one that retained a substantial proportion of individuals below the minimum marketable length (15 cm fork length). While the 200-mesh 5-mm twine codend retained commercial quantities of school whiting, it seems far from optimal. It is suggested that a more efficient design comprising possibly smaller, square-shaped meshes should be developed and used in conjunction with temporal, spatial and catch restrictions.     

多叶羽扇豆种子成熟度和烫种对发芽的影响

为提高多叶羽扇豆种子的吸涨率和发芽率,对不同成熟度和烫种对种子发芽的影响进行了研究。结果表明:新收绿籽1 d吸涨率、发芽率和发芽势最高,分别达100%、96%和96%;烫种可以提高种子1 d吸涨率,烫种时间对种籽发芽的影响是烫种1 min,发芽率和发芽势最高,达72%和62%,随着烫种时间的增加,发芽率和发芽势逐渐下降。     

两级星型五分支传动静态均载分析

为分析两级星型五分支传动系统的均载问题,根据该系统构成功率流动闭环的特点,推导扭转角变形协调条件,结合力矩平衡条件,运用当量啮合误差理论,建立静态条件下的均载力学分析模型,求解得到均载系数,分析制造误差、安装误差、构件浮动对均载特性的影响。结果表明：太阳轮、内齿圈、星轮的误差单独影响均载特性时,内齿圈的误差影响最大,各构件制造误差影响的均载系数随时间做周期变化;太阳轮基于花键间隙浮动和内齿圈径向浮动,改善了均载特性,通过试验验证了理论分析的正确性。