农家肥撒施机螺旋式撒肥器抛撒性能的试验研究

农家肥撒施机是农家肥施肥机械化作业的重要机具。文中以螺旋式撒肥器为对象,采用试验优化设计的方法,研究了撒肥器的转速、螺旋的螺距和肥料的输送速度对抛撒性能的影响。结果表明:转速为375~400 r/min、螺距340 mm、输送速度12 mm/s能使有效幅宽满足设计要求,不均匀度较小。     

耕作方式对耕层黑土有机碳库储量的短期影响

【目的】探索不同耕作方式对耕层黑土有机碳含量的影响。【方法】以2001年秋在吉林省德惠市中层黑土上进行了3年的田间定位试验小区土壤为研究对象，对免耕、垄作和秋翻3种耕作处理下耕层土壤有机碳的动态变化进行了分析，并采用等深度和等质量土壤碳库储量计算方法，比较了不同耕作处理对耕层土壤有机碳库储量的影响。【结果】不同耕作处理对黑土耕层有机碳的影响无显著性差异，而且免耕处理在短期内没有引起耕层土壤有机碳含量的明显增加，反而有所降低。与2001年试验开始时相比，3年免耕管理使表层0～5 cm土壤有机碳含量仅增加了0.18％，而5～20 cm土层有机碳含量则明显降低。利用等深度（0～30 cm）和等质量（4 040 Mg）土壤碳库储量计算方法对比研究表明，将土壤容重考虑在内的等质量土壤有机碳库储量计算方法可以更准确的反映耕作对土壤有机碳库储量的影响。等质量方法计算表明，3年的免耕试验并没有使耕层土壤有机碳库储量发生明显变化。【结论】在质地粘重和排水不良的土壤上实行免耕，短期内土壤有机碳含量并没有增加。长期效果如何还有待观测。     

差动轮系中的循环功率分析

通过分析典型的差动轮系中齿轮受力与转速的关系,推导出差动轮系中当2个不同构件作主动件时的2种典型工况下,轮系产生循环功率的条件和原因,并采用某液压机械无级变速箱中的双排差动轮系的工作实例进行了分析和验证。研究结果表明,差动轮系中是否产生循环功率取决于2个主动构件的转动方向。该结论可以为采用差动轮系传递动力的系统提供理论参考依据,使系统避免工作在产生循环功率的工况下,提高系统的工作效率。     

轿车电动燃油泵控制原理及其故障检查

分析了轿车电动燃油泵运转的几种控制电路、电动燃油泵转速的几种控制电路;并对电动燃油泵常见故障的检测方法进行了分析。     

木材工业用快速固化酚醛树脂胶的研究进展

从改进酚醛树脂的配方和合成工艺、合成酚醛树脂时添加催化剂或改性剂、调胶时添加固化剂等几个方面,综合叙述了国内外有关提高酚醛树脂固化速度的研究进展,以期为酚醛树脂的应用和研究提供参考。     

The impact of tillage system and herbicides on weed density,diversity and yield of cotton (Gossipium hirsutum L.) and maize (Zea mays L.) under the smallholder sector

The study was carried out to evaluate the impact of tillage system in combination with different herbicides on weed density, diversity, crop growth and yields on 18 farms in Kadoma, Zimbabwe. Experiments were set up as a split plot design with three replications on each farm. Tillage was the main plot (Conservation Tillage (CT), Conventional Tillage (CONV)) and weeding option (hand weeding, cyanazine, atrazine, glyphosate only and mixture of cyanazine + alachlor and atrazine + alachlor) as the sub-plots. Due to the heterogeneous nature of farmers' resource base, the farms were grouped into three farm types: high (Type 1), medium (Type 2) and poorly resourced farmers (Type 3). The hand hoe weeded treatments had 49 percent higher total weed densities in CT relative to CONV, and was statistically similar to the glyphosate treatment. The mixed pre-emergence herbicides reduced the diversity indices by 69 and 70 percent when compared to the hand hoe weeded treatment under CT in cotton and maize, respectively. The effectiveness of all pre-emergence herbicides were not influenced by tillage but were affected by farmers resource endowments with pronounced effect in Farm Type 1. Maximum plant heights of 85 and 238 cm were recorded for mixed pre-emergence herbicides under CT for cotton and maize, respectively. Minimum plant heights of 75 and 217 cm were recorded for the respective hand hoe weeded treatments. The hand hoe weeded treatments resulted in average cotton lint yield of 1497 and 2018 kg ha⁻¹ for maize. The mixed pre-emergence herbicides treatments gave yields of 2138 and 2356 kg ha⁻¹ of cotton and maize, respectively. The higher weed densities in CT under hand weeded treatments underscored the need for other weeding options. Similarly, a mixture of cyanazine + alachlor in cotton and atrazine + alachlor in maize is recommended for suppressing broad and grass weed populations and enhancing yields in CT systems.     

抵御网络流量攻击技术在气象网络中的应用

阐述了流量攻击的作用机制,基于异常流量可能导致局域网运行缓慢,严重的甚至造成局域网瘫痪的情况,以地市级气象网络为例,介绍了局域网流量监控限制的解决方案。同时,介绍了局域网限速的手段在防止流量攻击中的应用,实现对发起攻击的主机自动断开网络链接,对网络病毒实时监控,并提示用户清除病毒。     

桥梁两端交叉口不同控制方式效果的比较

以福清市玉融大桥及两侧桥头交叉口为研究对象,以桥面进口道上的95%排队长度和平均区间速度为交通效益的目标评价指标,应用Synchro和Vissim仿真优化软件对无信号控制、单点优化信号控制和协调优化控制系统进行设计优化及评价.结果表明:采用协调优化控制系统和单点优化信号控制系统后,95%排队长度分别比无信号控制减少了52.00%和49.85%,平均区间速度分别提高了30.78%和7.5%.由此可知,信号协调优化控制系统是比较理想的控制方式.     

N Dynamics under Reduced Tillage

Different methods of tillage are investigated in a field trial in Austria. In those variants where soils are treated with a cultivator respectively a plough in autumn the contents of mineral N (Nmin) in 0-90cm soil depth increased significantly. Therefore the danger of N-leaching or N-losses in autumn or winter is higher in intensively tilled soils (without plant cover) than in soils with minimum tillage (treatment only with rotary driller without any primary treatment before seeding). In this variant Nmin-contents are lower even at the beginning of vegetation due to the plant cover and reduced tillage. At this time the potential of N mineralisation is higher in the minimum tilled plots compared to the more intensively tilled soils due to the accumulation of organic matter. However, despite enhanced potential N availability the N contents of the crops did not increase. The yields don't differ in the investigated tillage systems and N balances are the highest under minimum tillage, therefore a higher N fertilisation in this variant cannot be recommended. An adaptation of N fertilisation according to the lower mineral N contents in spring should be investigated.     

Architecture of stem and branch affects yield formation in short season cotton

The cotton direct seeding after wheat(rape) harvested is under trial and would be the future direction at the Yangtze River Valley region of China. The objective of this study was to quantify the effects of branch and stem architecture on cotton yield and identify the optimal cotton architecture to compensate the yield loss due to the reduction of individual production capacity under high planting density in the direst seeding after wheat harvested cropping system. The characteristics of the stem and branch architecture and the relationships between architecture of the stem and branch with yield formation were studied on eight short season cotton cultivars during 2015 and 2016 cotton growth seasons. Based on the two years results, three cultivars with different architectures of stem and branch were selected to investigate the effect of mepiquat chloride(MC) application on the architecture of the stem and branch, boll retention, and the yield in 2017. Significant differences were observed on plant height, all fruiting nodes to branches ratio(NBR) in the cotton plant, and the curvature of the fruiting branch(CFB) among the studied cultivars. There were three types of stem and fruiting branch structures: Zhong425 with stable and suitable plant height and NBR(about 90 cm and 2.5, respectively), high CFB(more than 10.0), and high boll retention speed and seed cotton yield; Siyang 822 with excessive plant height and NBR, low CFB, and low boll retention speed and seed cotton yield; and other studied cultivars with unstable structure of stem and branch, boll retention speed, and seed cotton yield across years. And MC application could promote the appropriate plant height and NBR and high CFB and thus resulted in high boll retention speed and the yield. The results suggested that the suitable plant height and NBR(about 90 cm and 2.5 respectively), and high CFB(more than 10.0), which was related to both genotype and cultural practice, could promote the higher boll retention speed and seed cotton yield.