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81.
蒋月评 《湖南农业大学学报(自然科学版)》1999,26(4)
研究了4 种高维 Mobius 群的初等子群定义之间的关系⒚得到了高维 Mobius 群是初等群的充要条件;在离散的条件下,给出了这种初等子群的结构性定理⒚ 相似文献
82.
提出了一套完整的衡量水泵企业集团的经营业绩、管理水平和经济效益指标体系,以及运用这些指标的方法,并用了一个实例来进一步说明。 相似文献
83.
大型地下洞室群的施工通风问题是保证安全、加快施工进度的关键。传统的施工通风设计无法掌控真实通风效果,导致资源浪费。基于流体力学理论的地下洞室群施工通风三维数值模拟,能定量分析大型洞室、关键节点或通风洞(井)等的通风效果,为通风方案的设计和优化提供依据。 相似文献
84.
企业制度层文化和精神层文化是饲料企业文化的重要组成部分,两者对饲料企业行为层文化和物质层文化具有决定性作用。兼容性是企业制度层文化与精神层文化关系研究中首先要解决的关键问题。文中在对这个问题分析的基础上,进一步使用系统论的方法研究了饲料企业精神层文化与企业制度层文化在兼容情况下与不兼容情况下的关系,并针对处于企业制度层文化和企业精神层文化不兼容状态中的饲料企业,提出了相应的对策建议。 相似文献
85.
Sub-group formation and the adoption of the alternate wetting and drying irrigation method for rice in China 总被引:1,自引:0,他引:1
Using group-level and household-level data collected in 2006-2007 in two districts in Hubei Province of China, we investigate social capital and water source variables and assess the factors influencing the formation of a sub-group, which is a sub-set of the original water user group (WUG). We use a probit model and regression analysis to examine the impact of sub-group formation on the adoption of alternate wetting and drying (AWD). Results show that when social capital is strong, farmers tend not to form sub-groups because strong social capital can prevent overuse of water. However, when social capital in a group is weak, farmers need to avoid overuse of water by forming a sub-group. Therefore, if farmers in the group of weak social capital are physically constrained and thus fail to form a sub-group, overuse of water is more likely. Such failure occurs when the existence of many water sources physically prevents farmers from forming a sub-group. We also found that when social capital is strong, farmers adopt the AWD practice even without forming a sub-group. 相似文献
86.
87.
The addition of genistein, a plant-to-bacteria signal molecule, to Bradyrhizobium japonicum cells prior to use as inocula has been shown to increase nodule number and promote soybean N2 fixation at low root zone temperatures. Previous greenhouse and field experiments involving only two cultivars have indicated that soybean [ Glycine max (L.) Merr.] cultivars can vary in their response to genistein application. The objective of this study was to evaluate a range of soybean cultivars for response to genistein application under short-season cool-spring Canadian conditions. A 2-year field study was conducted in 1997 and 1998 with a range of soybean cultivars recommended for Quebec. The 11 cultivars tested represented a range of yield potentials and maturity groups. They were inoculated with genistein-preincubated B. japonicum inocula or regular inocula, applied into the furrow at the time of planting. The results of these experiments indicated that neither maturity nor yield was correlated with increases in nodulation, biomass, and plant total nitrogen content resulting from genistein treatment and that all maturity groups responded to genistein application in essentially the same way. Thus, response of soybean cultivars to genistein addition is regulated by genotype characteristics other than maturity or yield level. 相似文献
88.
土-结构动力相互作用分析的子结构法中,土-结构系统运动方程的刚度矩阵和阻尼矩阵与频率相关。工程中通常采用系统的基本频率来计算地基的动力阻抗以简化运动方程的求解。对于土-桩-结构系统,本文提出一种时域中的精确解法来考察这种近似解法的有效性。 相似文献
89.
不同原料生物炭对铵态氮的吸附性能研究 总被引:7,自引:3,他引:4
为探讨不同原料生物炭对铵态氮吸附量及吸附机制,以花生壳、玉米秆、杨木屑和竹屑为原料,在500℃下充N_2保护热解制备生物炭,通过电镜扫面图(SEM)与傅立叶红外光谱图(FTIR)表征NH_4~+-N在生物炭表面的吸附特征,结合批量平衡吸附试验,对比研究不同原料生物炭对NH_4~+-N的吸附性能。结果表明:吸附后生物炭表面附着颗粒或粉末物质,孔隙被填充,表面变得较为平坦。四种生物炭表面分布的-OH、-C=O、-C-O,以及花生壳生物炭与玉米秆生物炭表面的-CH_3、-CH_2、-O-参与了吸附;Langmuir方程可以较好地拟合四种生物炭对NH_4~+-N的等温吸附;吸附均在50 min内达到平衡,伪二级动力学方程均可以较好地描述生物炭对NH_4~+-N的动力学吸附过程;在溶液pH=7.00条件下,初始浓度为800 mg·L~(-1)的体系中,四种生物炭对NH_4~+-N的最大吸附量为9.5~15 mg·g~(-1),吸附能力大小为花生壳生物炭玉米秆生物炭竹屑生物炭杨木屑生物炭。研究表明,生物炭表面含氧官能团对吸附NH_4~+-N起到决定性作用,吸附为单分子层吸附,且由快速反应所控制,四种生物炭中吸附性最好的是花生壳生物炭。 相似文献
90.
Multilocus PCR assay reveals high diversity of vegetative compatibility types in populations of Cryphonectria parasitica in Croatia 下载免费PDF全文
The ascomycete fungus Cryphonectria parasitica, causal agent of chestnut blight, is probably one of the best known invasive fungal pathogens in forests of Europe and North America. Mycovirus that reduces virulence of C. parasitica can be used as a biocontrol agent of the chestnut blight. However, anastomosis‐mediated virus transmission is limited by a vegetative (in)compatibility (vc) system involving at least six known diallelic vic genetic loci. This study looked at vegetative compatibility (vc) diversity in two populations of C. parasitica in Croatia. For that purpose, a PCR assay was validated and implemented using already known/published and newly designed primers for amplification of six known vic loci. The vc genotypes determined by PCR for 158 C. parasitica isolates investigated in this study were in complete agreement with the vc genotypes determined by pairwise co‐culturing of the same isolates, revealing the specificity and accuracy of the PCR‐based molecular vic genotyping assay. Twenty‐six unique vc genotypes were found among 158 isolates, and 19 vc types per population, which makes Croatian C. parasitica populations among the most diverse in Europe regarding the number of vc types and genetic diversity. Low values of multilocus linkage disequilibrium suggest sexual reproduction as a major contributor to high C. parasitica genetic diversity in studied populations. 相似文献