冶金因素对纯镍铸铁焊条抗热裂性能影响

研究了钛、铌，钛，钼，硅和钇镁硅铁合金对纯镍铸铁焊条抗热裂性能的影响，试验结果表明，钛，铌，钴，钇和镁在焊缝中的含量有一最佳值，综合利用这些合金元素，可显著改善纯镍铸铁焊条的抗热裂性能，其熔敷金属的机械性能可符合铁素体球墨铸铁（ＱＴ４００－１５）的要求。     

铸造热锻模具钢表面复合强化

研究了Al-C-Ti、Fe-C-Ti、Fe-Al-C-Ti体系热爆反应形成的组织和结构,并结合传统的铸造工艺在铸造模具钢表面形成颗粒增强复合层.研究结果表明：20% Fe-10% Al-C-Ti是较理想的复合体系,其热爆温度低于30% Fe-C-Ti体系,在1 200 ℃热爆反应可充分进行,获得颗粒尺寸为1～2 μm的TiC和少量FeAl.铸造过程中热爆形成的表层增强颗粒与钢发生相互扩散,实现了较好的融合,复合层的厚度达4 mm,硬度得到提高,并呈梯度分布.     

Effect of diet on cast production by the megascolecid earthworm Amynthas alexandri in laboratory culture

Feeding and casting activity of Amynthas alexandri fed on corn, wheat leaves, and mixed grasses were monitored in laboratory cultures. Casts were produced on the surface and sides of the containers. Food consumption varied from 36.5 to 69 mg g^–1 live worm day^–1. Cast production ranged from 3.95 to 5.9 mg g^–1 live worm day^–1. The C:N ratio in casts in laboratory cultures (11.17) and in field samples (8.84) was consistently lower than the corresponding ratio in the parent soil (13.19 and 10.54, respectively). This was probably due to mineralization of plant-derived organic material during passage through earthworms with consequent low C:N ratios.     

Surface cast production by the earthworm Aporrectodea nocturna in a pre-alpine meadow in Switzerland

Field and laboratory experiments were carried out to describe the effects of Aporrectodea nocturna on soil characteristics in a pre-alpine meadow and to support the development of a model of cast production. In the prealpine meadow, increased cast production, first observed about 20 years ago around a newly planted hedge, was recorded to a distance of maximal 170 m from the hedge. Numbers of A. nocturna between 130 and 165 m from the hedge decreased from 164 to 16 individuals m^-2. In the same area cast production steadily decreased from about 1.5 kg m^-2 week^-1 to nil, the plant community structure changed and the microbial biomass decreased, but the root biomass and the moisture content did not change. Laboratory experiments demonstrated that high cast production was not a specific feature of the A. nocturna population nor of the soil in the meadow. Diapause of A. nocturna was terminated in the laboratory during September. A model of cast production potential by the earthworm A. nocturna was established using laboratory determinations of the relationships with body weight, temperature, and water potential. The model was shown to predict cast production in the field given the assumption that the water potential was 0 MPa. According to the model, 81% of surface cast production was by juveniles, and 19% by adults of A. nocturna.     

Comparative analysis of Andiodrilus pachoensis casts in forests and pastures of South-Eastern Amazon (Brazil)

Soil ecosystem engineers produce biogenic structures (casts, mounds, galleries) that strongly affect soil processes. A comparative analysis of the physical characteristics of the casts produced by the earthworm Andiodrilus pachoensis was carried out in four pastures sowed with Brachiaria brizantha and four primary forests on the deforestation front of the Amazonian forest. In both systems, we recorded surface cast density and spatial patterns as well as surface cast physical properties. Cast and vegetation distributions were mapped within plots of sizes ranging from 25 to 50 m², and cast production was monitored during 2 months. Cast spatial distribution varied greatly among plots and across spatial scales ranging from regular at small spatial scales (0–20 cm) to clumped for larger distance ranges (>80 cm). Cast density was not significantly correlated with grass tuft density and their production was independent from the presence of grass tufts in pastures or litter quantity in forests. Although bulk soil properties (pH, C content, structural stability, etc) differed between pastures and forests, cast physical properties did not differ significantly among the studied ecosystem.     

A RESEARCH OF THE INFLUNCE OF RARE-EARTH ELEMENT ON THE THERMAL FATIGUE BEHAVIOR OF CAST IRON

It is known that cylinder heads, exhaust manifoids, ingot molds, etc. are often failed resulting from thermal fatigue. For this reason, the influence of RE on the thermal fatigue behavior of cast iron was studied by measn of a thermal fatigue test unit with completely constrained strain developed by ourselves. The test results shown that RE can improve the thermal fatigue resistance of cast iron greatly when residual RE contents surpass a critical value. This value is 0.04-0.045% for light Rare-Earth, and 0.045-0.05%; for heavy Rare-Earth. Further more, the relationship between RE and the thermophysical and mechanical properties of cast iron which have influence on thermal fatigue resisteance was also discussed.     

最终传动箱体工艺及模具设计

介绍了如何对最终传动箱体零件进行铸造工艺分析,确定铸造工艺方案,合理地选择分型面、分芯面、收缩率、机械加工余量等工艺参数,同时对浇注系统运用大孔出流理论进行了计算,最终使该铸件满足机械加工要求,获得了合格的零件。     

兰州大尾羊心脏冠状循环血管宏观解剖观察

选取五个不同年龄和性别的兰州大尾羊的心脏,分别采用20%的ABS丙酮溶液进行血管灌注,以红色染料的溶液灌注动脉而用蓝色染料的液体来灌注静脉。结果表明,兰州大尾羊的动脉血液是由起源于主动脉的左冠状动脉和右冠状动脉供应的,左冠状动脉比较粗大。     

Burrowing ability of the earthworm Aporrectodea longa limited by soil compaction and water potential

Summary Adult earthworms (Aporrectodea longa) were maintained for 199 days in soil columns (h=30 cm; ø=10 cm) where the water potential ranged from -7 to-65 kPa and compaction from 50 to 350 kPa. The weight of casts on the soil surface was measured at the end of two periods of activity (spring and autumn). Cast production increased with bulk density, but the activity of earthworms was limited both by the mechanical strength of the soil and by decreasing water potential. The results obtained in the laboratory conditions of this study were consistent with field observations on casting and burrowing activities. The effects of water potential and soil compaction on these activities were estimated.