小麦多品种混播对条锈病的控制及稳产作用研究

通过对6个不同抗性水平的小麦品种进行不同组合的混播,系统调查了各品种净作和多品种混播田小麦条锈病的病情发展动态。     

Earthworms as seedling predators: Importance of seeds and seedlings for earthworm nutrition

Anecic earthworms have been shown to collect, concentrate and bury seeds in their burrows. Moreover, recent studies suggest that earthworms function as granivores and seedling herbivores thereby directly impacting plant community assembly. However, this has not been proven unequivocally. Further, it remains unclear if earthworms benefit from seed ingestion, i.e., if they assimilate seed carbon. We set up a series of three laboratory experiments in order to test the following hypotheses: (1) anecic earthworms (Lumbricus terrestris L.) not only ingest seeds but also seedlings, (2) ingestion of seedlings is lower than that of seeds due to a ‘size refuge’ of seedlings (i.e., they are too big to be swallowed), and (3) seeds and seedlings contribute to earthworm nutrition. L. terrestris readily consumed legume seedlings in the radicle stage, whereas legume seeds and seedlings in the cotyledon stage, and grass seeds and seedlings in the radicle and cotyledon stage were ingested in similar but lower amounts. Importantly, ingestion of seedlings, in contrast to seeds, was lethal for all plant species. Moreover, earthworm weight change varied with the functional identity and vitality of seeds and natural ¹⁵N signatures in earthworm body tissue underlined the importance of seedlings for earthworm nutrition. The results indicate that the anecic earthworm L. terrestris indeed functions as a granivore and seedling herbivore. The selectivity in seedling ingestion points at the potential of direct earthworm effects on plant community assembly. Further, seeds and seedlings most likely contribute significantly to earthworm nutrition potentially explaining the collection and concentration of seeds by L. terrestris in its middens and burrows; however, the present results call for experiments under more natural conditions.     

Fungal toxins affect the fitness and stable isotope fractionation of Collembola

We investigated the effect of the fungal toxin sterigmatocystin on the fitness and stable isotope fractionation of two Collembola species (Folsomia candida and Heteromurus nitidus) feeding on mixed vs. single diets. Four knock out mutants of Aspergillus nidulans with the sterigmatocystin production blocked at different steps along the biosynthetic pathway were combined in mixed diets with either the high quality fungus Cladosporium cladosporioides or the low quality fungus A. nidulans (wildtype). Using fungi labeled with stable isotopes (¹³C and ¹⁵N) we evaluated the incorporation of carbon and nitrogen from individual fungi. We hypothesised that (i) Collembola fitness decreases with the putative toxicity of the fungi (ii) Collembola benefit from ingestion of mixed diets due to toxin dilution and (iii) fractionation of ¹³C and ¹⁵N is more pronounced in more toxic diets. Mixed diets did not uniformly improve fitness. Toxin dilution, however, played an important role in Collembola fitness. The fractionation of ¹³C and ¹⁵N varied with sterigmatocystin mutant strains, and Collembola species often differed from the expected enrichment per trophic level. The results show that fungal toxin production may affect stable isotope fractionation, presumably by altering consumer excretion rates necessary for detoxification.     

马蹄形无压隧洞恒定渐变流水面线计算的新解析法

对马蹄形无压隧洞的恒定非均匀流沿程水面线进行了深入研究,基于恒定渐变流基本微分方程,通过采用数值分析理论,得到流程S与始、末段水深h1、h2的解析函数,通过该函数可直接计算沿程水面线。该方法比《水工隧洞设计规范》中推荐的分段求和试算法更简单、便捷,特别对水深较敏感段,规范推荐试算法误差较大,并且逐段试算推求水深将导致末端断面水深误差逐步累积,导致误差大,精度下降。最后通过工程实例计算比较得出：新解析法计算成果与规范推荐法（程序）计算成果基本一致,甚至优于规范推荐的分段试算法,完全满足工程实践要求。     

XF(X=H,D,T)的高精度理论研究

运用包括非迭代三激发电子相关耦合簇CCSD(T)方法和Dunning等人使用的相关一致aug-CC-PVxZ(x=D,T,Q,5)自洽基组对XF(X=H,D,T)分子进行了结构优化,优化值然后被插值到CBS极限.结果表明随着x的增大aug-CC-PVxZ系列基组优化的结构逼近实验值,计算频率与实验值最大差距不足1%,最小仅为0.099%,平衡间距最大只有0.8%的差距.通过计算还表明:在结构优化和频率分析时CCSD(T)显示出优秀的特性,但在研究与边界态或解离有关的问题时,CCSD(T)不能给出良好的结果,相反CCSD方法却能给出合理的解离极限.最后我们研究了XF(X=H,D,T)的分子势能函数和光谱常数,理论结果与已知实验值吻合的非常好.首次获得了XF(X=H,D,T)系列分子的ωeye,ωeze,β,γ,He,Fe值.     

影响农户与农民专业合作社稳定关系的因素分析——基于四川参合农户视角

通过对四川省300名参加农民专业合作社农户的问卷调查,运用二元Logistic回归模型分析了影响农户与农民专业合作社保持稳定关系的因素。结果表明,主要影响因素为农户产品通过合作组织销售的份额、受教育程度、合作社服务能力、盈余返还机制等,且各个因素的影响程度不同。基于此,提出了相应的对策建议。     

A study on kinetic characteristics of auto Ignition process of natural gas hydrogen air mixture

Based on GRI Mech 3.0 mechanism, using kinetic model, the auto ignition characteristics of nature gas hydrogen air mixture are studied in different initial conditions under constant pressure. This study focuses on the changes of temperature and component concentrations,ignition delay time and flame propagation speed. The results show that under different initial conditions, with the increase of hydrogen fraction in the mixture, the ignition delay time decreases significantly and flame propagation speed increases significantly. On the other hand, Hydrogen fraction has been found of little influence on flame temperature.     

Dual mode AC DC AC converter for contactless power transfer system

A new type AC DC AC converter which can work in Buck or Boost mode is proposed in order to overcome the deficiencies of the primary circuit of the traditional contactless power transfer system. Through switching this two modes and turning the duty cycles of the switches, not only the resonant current amplitude of the primary resonant current can be controlled to be constant against a wide range variation of input voltage, but also the problems, such as surge current, high cost, complex control etc., caused by the DC filter and DC/DC converter in a traditional CPT system are effectively eliminated. The topology and operation principle of the proposed converter have been analyzed. The corresponding control strategy has been presented and verified by simulation results.     

Thermal time approach to predicting seedling emergence dates of red clover,white clover and lucerne in farm fields

A practical method for predicting seedling emergence dates of red and white clovers, and lucerne is proposed. The germination response at seven different constant temperatures ranging from 5 to 35°C was examined. Germination rate, which is a reciprocal of the duration for 50% germination of seeds, was linearly regressed against temperature to calculate the base temperature and thermal constant of seed germination. The calculated values were 3·9°C and 15·8 degree days for red clover, 4·2°C and 13·6 degree days for white clover, and 2·9°C and 17·7 degree days for lucerne. Using the base temperatures, thermal constants, and the daily mean air temperatures at the study site, the seedling emergence dates of the three forage legumes were predicted. At the same time, in an outdoor pot experiment, seeds of these legumes were sown approximately every 3 weeks and seedling emergence dates were determined. The predicted dates of seedling emergence generally fitted the observed dates. Another prediction was attempted using the base temperatures, thermal constants, and normal daily mean air temperatures recorded over more than 30 years in the study site. This prediction showed that the seedlings of the three forage legumes began to emerge at the beginning of April and could continue to emerge until the beginning of November when their non‐dormant seeds were present in the site, and that when the seeds were sown from mid‐November of one year to late March of the next year, the emergence of seedlings was delayed until the beginning of April.     

基于H桥驱动电路的半导体制冷片恒温控制系统

设计了一种以单片机HT46R47为核心,半导体制冷片为发热制冷体的智能恒温控制系统.通过H桥驱动电路控制半导体制冷片进行加热或制冷,实现了自动恒温控制.