A pool experiment was carried out to study the effects of different nitrogen applicationstrategies (rates and stages of nitrogen application) on yield and forage nutritivequality of Zea mexicana cultivated in summer, ...A pool experiment was carried out to study the effects of different nitrogen applicationstrategies (rates and stages of nitrogen application) on yield and forage nutritivequality of Zea mexicana cultivated in summer, 2002. In the whole growing stage, its stemwas clipped three times at the height of 25cm when it was 110cm high (H1, H2 and H3 standfor the first, second and third harvest stage, respectively). Six indexes includingcrude protein (CP), ether extract (EE), nitrogen free extract (NFE), acid detergentfiber (ADF), crude ash (CA), and general energy (GE) were employed to evaluate the foragenutritive value. The results showed that the content of CP and EE increased but thecontent of CA and ADF decreased under the two nitrogen rates (High-rate N, 600kgha-1;Mid-rate N, 300kgha-1). The fresh and dry harvest biomass of the whole plants on H1 andthose of the leaves on H2 were also improved. But the stalks on H2 and the whole plantson H3 were affected mainly by dressing nitrogen fertilizer. The yield of CP and EE, CA,NFE, and GE was mainly affected by nitrogen rates. The ADF yield increased was due to theincrement of the fresh and dry harvest biomass. Nitrogen applied as base fertilizer forsummer Zea mexicana can be harvested a higher biomass and improve the forage nutritivequality.展开更多
The effect of cooling rate on structure and properties of wear-resistant low chromium cast iron after 40% hot deformation was investigated by metallographic and scanning electron microscope. The results show that the ...The effect of cooling rate on structure and properties of wear-resistant low chromium cast iron after 40% hot deformation was investigated by metallographic and scanning electron microscope. The results show that the cooling rate is closely related to the structure and properties, and for the cast iron, the best comprehensive mechanical properties were obtained by forced air cooling with a cooling rate as about 7 ℃/s. The reason and regularity for the change of mechanical properties were analyzed.展开更多
Fracture occurred in wiper arm. Through the macro and micro analysis of the wiper arm fracture, chemical composition analysis, metallographic structure analysis, hardness analysis, macrostructure analysis, SEM analysi...Fracture occurred in wiper arm. Through the macro and micro analysis of the wiper arm fracture, chemical composition analysis, metallographic structure analysis, hardness analysis, macrostructure analysis, SEM analysis and so on, the cause of fracture of wiper arm were analyzed. The results show that the high hardness and the large residual stress are the main reasons for the cracking of the wiper arm due to the coincidence between the steel pipe forming weld and the wiper arm forming weld, and the improvement measures are proposed.展开更多
基金financially supported by the National Natural Science Foundation of China(30100108)the National Key Technologies R&D Program in Tenth Five Plan by the Ministry of Science and Technology,China(2002BA51A13).
文摘A pool experiment was carried out to study the effects of different nitrogen applicationstrategies (rates and stages of nitrogen application) on yield and forage nutritivequality of Zea mexicana cultivated in summer, 2002. In the whole growing stage, its stemwas clipped three times at the height of 25cm when it was 110cm high (H1, H2 and H3 standfor the first, second and third harvest stage, respectively). Six indexes includingcrude protein (CP), ether extract (EE), nitrogen free extract (NFE), acid detergentfiber (ADF), crude ash (CA), and general energy (GE) were employed to evaluate the foragenutritive value. The results showed that the content of CP and EE increased but thecontent of CA and ADF decreased under the two nitrogen rates (High-rate N, 600kgha-1;Mid-rate N, 300kgha-1). The fresh and dry harvest biomass of the whole plants on H1 andthose of the leaves on H2 were also improved. But the stalks on H2 and the whole plantson H3 were affected mainly by dressing nitrogen fertilizer. The yield of CP and EE, CA,NFE, and GE was mainly affected by nitrogen rates. The ADF yield increased was due to theincrement of the fresh and dry harvest biomass. Nitrogen applied as base fertilizer forsummer Zea mexicana can be harvested a higher biomass and improve the forage nutritivequality.
文摘The effect of cooling rate on structure and properties of wear-resistant low chromium cast iron after 40% hot deformation was investigated by metallographic and scanning electron microscope. The results show that the cooling rate is closely related to the structure and properties, and for the cast iron, the best comprehensive mechanical properties were obtained by forced air cooling with a cooling rate as about 7 ℃/s. The reason and regularity for the change of mechanical properties were analyzed.
文摘Fracture occurred in wiper arm. Through the macro and micro analysis of the wiper arm fracture, chemical composition analysis, metallographic structure analysis, hardness analysis, macrostructure analysis, SEM analysis and so on, the cause of fracture of wiper arm were analyzed. The results show that the high hardness and the large residual stress are the main reasons for the cracking of the wiper arm due to the coincidence between the steel pipe forming weld and the wiper arm forming weld, and the improvement measures are proposed.
