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321.
322.
泥炭生化复合肥料田间对比试验 总被引:1,自引:0,他引:1
本文介绍了泥炭生化复合肥料与其它几种肥料的田间对比试验。试验结果表明,泥炭生化复合肥料的肥效优于其它几种肥料,且对农业生产的增产效果显著 相似文献
323.
Gary L. Ketcheson Walter F. Megahan John G. King 《Journal of the American Water Resources Association》1999,35(1):83-98
ABSTRACT: Erosion and sedimentation data from research watersheds in the Silver Creek Study Area in central Idaho were used to test the prediction of logging road erosion using the R1-R4 sediment yield model, and sediment delivery using the “BOISED” sediment yield prediction model. Three small watersheds were instrumented and monitored such that erosion from newly constructed roads and sediment delivery to the mouths of the watersheds could be measured for four years following road construction. The errors for annual surface erosion predictions for the two standard road tests ranged from +31.2 t/ha/yr (+15 percent) to -30.3 t/ha/yr (-63 percent) with an average of zero t/ha/yr and a standard deviation of the differences of 18.7 t/ha/yr. The annual prediction errors for the three watershed scale tests had a greater range from -40.8 t/ha/yr (-70 percent) to +65.3 t/ha/yr (+38 percent) with a mean of -1.9 t/ha/yr and a standard deviation of the differences of 25.2 t/ha/yr. Sediment yields predicted by BOISED (watershed scale tests) were consistently greater (average of 2.5 times) than measured sediment yields. Hillslope sediment delivery coefficients in BOISED appear to be overly conservative to account for average site conditions and road locations, and thus over-predict sediment delivery. Mass erosion predictions from BOISED appear to predict volume well (465 tonnes actual versus 710 tonnes predicted, or a 35 percent difference) over 15 to 20 years, however mass wasting is more episodic than the model predicts. 相似文献
324.
325.
Heavy Metal Toxicity Responses of Two Willow (Salix) Varieties Grown Hydroponically: Development of a Tolerance Screening Test 总被引:1,自引:0,他引:1
The E.U. funded BIORENEW project is investigating bioremediation of industrially degraded land using biomass fuel crops, including willow. One of its goals is to develop a rapid screening test to assess the metal tolerance of large numbers of willow varieties. This should reflect how a plant will respond to heavy metals under various field conditions and in the long term. A preliminary experiment tested two varieties of contrasting ability to thrive in metal-contaminated soils. Trees were exposed to a metal cocktail in three different strengths of background solution. An appropriate strength solution (1/4 strength Hoaglands) was identified for differentiating variety performance, based on its effect on the biomass of plant fractions relative to control fractions. This is a response to heavy metals which can be quantified rapidly and simply. The relative performance of the varieties was comparable to their performance in field studies. This test will be used to assess the tolerance of further varieties. 相似文献
326.
By scoring the chromosome number of developing embryos, we show that the sex ratio bias of the African social spider Stegodyphus dumicola Pocock is the result of an overproduction of female embryos. Only 17% of 585 embryos sexed from 14 egg sacs were male, a
significant departure from a 1:1 sex ratio. We also explored the possibility of direct control of the sex of individual offspring
in this species by examining the variance in the number of males per sac and the spatial distribution of male and female embryos
within the sacs. We postulated that a variance in the number of males per sac lower than binomial (i.e., underdispersed or
precise sex ratios) or a non-random distribution of male embryos within the sacs would suggest direct control of the sex of
individual offspring. We found that the variance in the number of males per sac was indistinguishable from binomial and significantly
larger than expected under exact ratios. Likewise, the spatial distribution of male embryos within three sacs examined was
no more clustered than expected by chance. The sex ratio biasing mechanism in this species, therefore, apparently only allows
control of the mean sex ratio but not of its variance. We present randomization and Monte Carlo methods that can be applied
to test for departures from a random spatial arrangement of male and female embryos in an egg mass and for departures from
binomial or exact ratios when not all members of a clutch have been sexed.
Received: 21 October 1998 / Received in revised form: 23 March 1999 / Accepted: 26 April 1999 相似文献
327.
大型蚤毒理试验应用与研究进展 总被引:3,自引:0,他引:3
大型蚤作为国际公认的标准试验生物 ,其毒理试验被许多国家定为毒性必测项目 ,各国纷纷建立了自己的标准方法 ,因此有着广阔的应用前景。在分析中 ,主要介绍了大型蚤的试验培养技术和国内外对其毒理试验方面的研究概况。 相似文献
328.
329.
下蜀土边坡地震稳定性的大型振动台试验研究(Ⅰ)——模型试验设计 总被引:1,自引:1,他引:0
为研究下蜀土边坡的地震稳定性,选用天然下蜀土,按照Meymand的相似法则,对一坡高为0.5m、宽度为1.05m、坡角为45°的模型边坡进行了几何相似常数为20的1g大型振动台模型试验详细设计。首先,运用数值模拟的方法确定了模型边坡尺寸适当的边界范围,模型边坡地基厚度、坡脚前缘和坡肩后缘长度均取为0.5m;其次,按照确定的模型几何尺寸设计了符合试验要求的模型箱,其内壁净尺寸(长×宽×高)为1500mm×1050mm×1100mm,属刚性模型箱,且不会与模型边坡发生共振;最后,制定了包括加速度和位移在内的数据量测策略,运用拟静力法求得下蜀土边坡平均屈服加速度为0.561g,综合确定了地震动峰值(PGA)按0.1g、0.3g、0.6g和0.9g的顺序逐级加载的原则,并制定了详细的试验步骤,从而可保障试验得到可靠的结果。 相似文献
330.
基于虚拟仪器技术的振动台模型试验98通道动态信号采集系统研制 总被引:3,自引:0,他引:3
土工结构振动台模型试验除了需采集常规的加速度、位移、应变信号外,还需采集模型场地土中振动孔隙水压力、动土压力等信号,由于同步采集的动态信号的多样性和复杂性,一般的振动台信号采集系统难以满足这样的多种动态信号同步采集要求。基于传感器融合技术和虚拟仪器技术,研发了一套适用于多种类型信号输入的动态信号同步采集系统,可实现80通道动态信号、18通道数字信号的同步采集、回放和频谱分析等功能,并具有界面友好、使用维护方便等特点。 相似文献