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为获取高矿化度土壤水条件下的水力特征参数,并比较不同处理的影响,实验测定淡水、30、100及250g/L土壤水矿化度处理土样脱湿过程的水分特征曲线,并利用RETC软件进行模型参数拟合。结果表明,粉质黏土条件下,van Genuchten-Burdine模型可拟合各不同处理土壤水分特征曲线。各组实测曲线形态显示,在吸力较大阶段,当土壤水吸力增大到一定程度时含水率才发生变化,二者呈多值对应关系。TDS-30处理对应的残余体积含水率θr最大,α、n值最小,非饱和水力传导度K值衰减最快;中等大小孔隙的变化对非饱和水力传导度影响较为显著。研究成果可为深入开展矿化度潜水蒸发数值计算提供支持。 相似文献
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可视化编程技术在发动机外特性曲线绘制中的应用 总被引:1,自引:0,他引:1
通过对汽车发动机外特性的理论分析,在处理汽车发动机外特性曲线时,建立了一种适合处理发动机外特性曲线的三次样条函数拟合的数学模型,在C Builder可视化开发平台上,编制了汽车发动机外特性曲线绘制程序.利用三次样条函数插值法对实验数据进行拟合,实现了发动机外特性曲线绘制的自动化. 相似文献
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在分析ISO10823、DIN8195、ANSIB29.^-1等标准和有关文献的基础上,结合一些国际知名链条公司的功率曲线,探讨了ISO10823功率曲线的建立基础,提出了使用标准时应注意的问题。 相似文献
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以遥感影像为数据源,提取2000,2003和2007年三时相的昌平区土地利用信息,以高程150 m为界限划分为山地生态涵养区和平原经济发展区。分析表明,平原经济发展区土地利用结构变化主要体现为耕地向城矿居用地转化,而山地生态涵养区各组分变化并不明显。应用空间洛伦茨曲线和空间基尼系数分析揭示三时相不同土地用途的分布特征,研究发现水域和城矿居用地的空间分布在三时相最不均匀,集中于平原经济发展区,耕地和林地比较均匀,未利用地分布变化较大。7年之间耕地、林地和水域在向均匀方向发展,城矿居用地先趋于不均匀后转向均匀发展,未利用地恰好相反。 相似文献
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Helena T. Nyman Annemarie T. Kristensen Mads Kjelgaard-Hansen Fintan J. McEvoy 《Veterinary radiology & ultrasound》2005,46(3):243-250
Contrast-enhanced ultrasonography, a new imaging modality in veterinary medicine, can provide data on tissue perfusion. The objective of this study was to use the ultrasonographic contrast agent SonoVue to evaluate various transit time indices in the normal canine liver, to examine the effect of anesthesia on these parameters, and to evaluate the safety of this agent in dogs. The liver of 11 healthy dogs was studied by ultrasound during an intravenous bolus injection of SonoVue. Each dog underwent the examination twice, first with and later without the use of anesthesia. A time-intensity curve was generated from a selected region of interest within the liver from each scanning session. Ratios derived from peak enhancement, time to peak enhancement, up-slope and full-width half-maximum (FWHM) of the curve were calculated from the time-intensity curves, and are reported. There were no statistically significant differences (P > 0.05) in peak enhancement, up-slope and FWHM between dogs that were anesthetized and dogs that were not. Time to peak enhancement, however, was significantly shorter when the dogs were anesthetized than when they were nonanesthetized (P < 0.05). There were no biologically significant changes in clinical laboratory findings. This study indicates that contrast-enhanced ultrasound using SonoVue gives reproducible liver perfusion data, and appears to be a safe and well-tolerated agent for use in dogs. When considering normal values, the use of anesthetic drugs has to be considered. 相似文献
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N. D. Paveley † J. M. Thomas T. B. Vaughan N. D. Havis D. R. Jones 《Plant pathology》2003,52(5):638-647
A function was derived to predict fungicide efficacy when more than one application of a single active ingredient is made to a crop, given parameters describing the dose–response curves of the component single-spray applications. In the function, a second application is considered to act on that proportion of the total pathogen population which was uncontrollable at the time of the first application (represented by the lower asymptote of the dose–response curve for the first treatment), plus any additional part of the population which survived the first application as a result of a finite dose being applied. Data to estimate the single-spray dose–response curve parameters and validate predictions of two-spray programme efficacy were obtained from separate subsets of treatments in four field experiments. A systemic fungicide spray was applied to wheat at a range of doses, at one or both of two times (t1 and t2), in all dose combinations. Observed values of the area under the disease progress curve (AUDPC) for septoria leaf blotch (Mycosphaerella graminicola) were used to construct response surfaces of dose at t1 by dose at t2 for each culm leaf layer. Parameters were estimated from single-spray and zero-dose treatment data only. The model predicted a high proportion (R2 = 71–95%) of the variation in efficacy of the two-spray programmes. AUDPC isobols showed that the dose required at t2 was inversely related to the dose at t1, but the slope of the relationship varied with the relative timings of t1 and t2 in relation to culm leaf emergence. Isobols were curved, so the effective dose – the total dose required to achieve a given level of disease suppression – was lower when administered as two applications. 相似文献
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水分胁迫对常见绿化植物苗木光响应特性的影响 总被引:1,自引:0,他引:1
采用盆栽试验研究正常供水(黎明前小枝水势ψ-0.8MPa)和中度水分胁迫(-2.5MPaψ-3.5MPa)条件下,3种生活型绿化植物苗木光响应特性。结果表明:3种生活型苗木光响应曲线均与非直角双曲线接近;在正常供水条件下,乔木、灌木和攀援植物苗木的最大光合速率(Pnmax)分别为10.44、11.17、16.40μmol·m-2·s-1,表观光合量子效率(AQ,Y)分别为0.066、0.045、0.037,暗呼吸速率(Rd)分别为0.56、1.47、1.51μmol·m-2·s-1,光补偿点(LC,P)分别为17、33、46μmol·m-2·s-1,光饱和点(LS,P)分别为336、358、612μmol·m-2·s-1;土壤水分胁迫能显著降低乔木、灌木和攀援植物苗木的Pnmax、AQ,Y,而对Rd无显著影响,LS,P和LC,P的变化因种类而不同。在土壤水分胁迫条件下,灌木表现出较高的光合活性,其Pnmax、AQ,Y和Rd值均比乔木和攀援植物高,表明灌木苗木对土壤水分的生态适应能力较强。 相似文献