大中型输配水渠道工程系统优化设计     

程吉林 《扬州大学学报(农业与生命科学版)》1992,(4)

提出了大中型输配水渠道工程系统优化设计的定量定性混合系统动态规划模型。模型以计算分析期内总支出费用最小为目标函数,各渠段纵坡和定性规划方案为系统变量,渠道不冲不淤流速、水头损失、投资等为约束条件。克服了目前优化方法中不能综合考虑各渠段断面设计参数、配套建筑物设计参数和位置、渠道断面形状、衬砌方式优化的缺陷,为大中型输配水渠道工作系统优化提出了一个新的方法。  相似文献   

Structure—activity relationships of organotin biocides and Ceratocystis ulmi     

George Eng  Stephen P. Coddington  Laura L. Stockton  Alexander D. W. Acholonu 《Pest management science》1989,26(2):117-121

The effect of organotin compounds on the growth of Ceratocystis ulmi, the causative agent of Dutch elm disease, was studied in shake culture. Triphenyltin, (C₆H₅)₃SnX, tricyclohexyltin, (C₆H₁₁)₃SnX, and tributyltin, (C₄H₉)₃SnX, compounds were all effective in the inhibition of C. ulmi in vitro. The anionic group, X, did not play a major role in the inhibitory activities of these compounds, suggesting that the species involved in the inhibition is R₃Sn⁺ or the hydrated cation.  相似文献   

Assay-guided fractionation study of alpha-amylase inhibitors from Garcinia mangostana pericarp     

Loo AE  Huang D 《Journal of agricultural and food chemistry》2007,55(24):9805-9810

Alpha-amylase inhibitor (alpha-AI) activity of Garcinia mangostana, commonly known as mangosteen, pericarp extracts was studied by assay guided fractionations from lipophilic to hydrophilic using combined solvent extraction and Amberlite XAD2 adsorption chromatography. Neither the lipophilic, xanthone containing fraction, nor the highly polar fraction, which has no affinity on Amberlite XAD2, showed any alpha-AI. The fraction that shows very high inhibitory activity contains primarily polyphenols and can be adsorbed on Amberlite XAD2. The IC50 of 5.4 microg/mL of this fraction is comparable to that of acarbose, a prescribed alpha-AI used in the control of type II diabetes, at 5.2 microg/mL. Total phenolic content (TPC) of each fraction was measured and the TPC has no correlation with the alpha-AI activity. The lipophilic fraction contains mainly xanthones as revealed by HPLC-MS analysis. Colorimetric analysis coupled with UV-vis and IR spectroscopic analysis demonstrated that the fractions with high alpha-AI activity are primarily oligomeric proanthocyanidins (OPCs) with little gallate moiety. There is also evidence to show that the alpha-AI by these OPCs is not purely by nonspecific protein complexation. Both tannic acid and G. mangostana OPCs precipitate BSA equally well but G. mangostana OPCs are 56 times more effective in inhibiting alpha-amylase.  相似文献   

Sources and inheritance of resistance to stemphylium leaf spot of lettuce     

D. Netzer  D. Globerson  CH. Weintal  R. Elyassi 《Euphytica》1985,34(2):393-396

Summary None of the tested cultivars of lettuce was found resistant to Stemphylium leaf spot, a common disease in Israel. Within a Lactuca saligna population collected in wild lettuce in Israel, resistance was traced. Interspecific crosses of L. saligna x L. sativa were made and the mode of inheritance of resistance to this disease was studied. Resistance is apparently controlled by two genes: one dominant (Sm₁) and one recessive (sm₂).Contribution No. 1176-E 1984 series, from the ARO.  相似文献   

水泵进水口临界淹没深度试验力学准则的研究     

王林锁 《扬州大学学报(农业与生命科学版)》1991,(3)

对影响进水口旋涡运动的主要因素进行了理论分析,研究了旋涡型式和Fr数的关系,确定了临界淹没深度试验所要求的力学准则,首次提出新的特征参数,得出了相应的临界淹没深度的计算公式。  相似文献   

棉苗营养钵移栽打穴机构优化设计     

殷珍荣  张凤举 《扬州大学学报(农业与生命科学版)》1992,(4)

棉苗营养钵移栽打穴机系多杆组合机构,通过优化设计,在主体的曲柄摇杆机构的连杆上,正确地确定了安装打穴筒的方位,且在摇杆与动点M_1之间联接一个空间机构,使打穴筒在切土工作行程同时,绕自身轴线转动,以利切土。通过电视屏幕与模型调试,使打穴筒在近穴底反转,以利断土。通过技术鉴定的机型在生产中较受棉农欢迎。  相似文献   

Structure of the hydrated alpha-Al(2)O(3) (0001) surface     

Eng PJ  Trainor TP  Brown GE  Waychunas GA  Newville M  Sutton SR  Rivers ML 《Science (New York, N.Y.)》2000,288(5468):1029-1033

The physical and chemical properties of the hydrated alpha-Al(2)O(3) (0001) surface are important for understanding the reactivity of natural and synthetic aluminum-containing oxides. The structure of this surface was determined in the presence of water vapor at 300 kelvin by crystal truncation rod diffraction at a third-generation synchrotron x-ray source. The fully hydrated surface is oxygen terminated, with a 53% contracted double Al layer directly below. The structure is an intermediate between alpha-Al(2)O(3) and gamma-Al(OH)(3), a fully hydroxylated form of alumina. A semiordered oxygen layer about 2.3 angstroms above the terminal oxygen layer is interpreted as adsorbed water. The clean alpha-Al(2)O(3) (0001) surface, in contrast, is Al terminated and significantly relaxed relative to the bulk structure. These differences explain the different reactivities of the clean and hydroxylated surfaces.  相似文献   

GM（1,1）模型在农机发展预测中的应用     

毕文平  苏尚华 《河北农业大学学报》1992,15(3):81-86

本文应用灰色系统理论及专家调控方法,对廊坊市1988～1995年农机化发展进行了预测,预测结果:历史拟合误差平均为4.74％;小误差概率均接近或等于1,对社会经济时间数列方差比小于0.35,并针对预测结果与目前农机现状提出了六点发展衣机化的措施与建议。  相似文献   

异步电机效率测试误差的分析计算     

赵龙章  孙贵根 《扬州大学学报(农业与生命科学版)》1992,(1)

用间接测量法分析了异步电动机效率测试的随机误差规律,研究了效率测试误差区域的计算方法,并作了实测计算例证。  相似文献   

6TD—280型脱水多用机研制过程中脱水机理分析     

张福 《内蒙古农业大学学报(自然科学版)》1988,(2)

本文着重讲述了,在6TD—280型脱水多用机研制过程中,对于小型立式脱水机的脱水机理,进行了分析和探讨。对于“爬升法”,“离心法”及“旋转抛分法”用于马铃薯淀粉浆液的浓缩和脱水,进行了详细的论述,并且为采用“旋转抛”分法设计小型立式脱水机,提供了一个初步设计计算的依据。  相似文献