A three-dimensional cyclic symmetry finite element model of titanium-matrix composites（TMCs） ring was developed to investigate the stress distribution and burst failure. The effects of fiber volume fractions, reinfo...A three-dimensional cyclic symmetry finite element model of titanium-matrix composites（TMCs） ring was developed to investigate the stress distribution and burst failure. The effects of fiber volume fractions, reinforced areas, thermal residual stresses and two different temperatures on stress distribution were studied. The burst speed was obtained through analyzing the hoop tensile stresses under a series of rotating speeds. The results indicate that at the two different temperatures, the influences of fiber volume fractions and reinforced areas on stress level and distribution are different. Some proposals are provided for the structure design of the TMCs ring. With regard to thermal residual stresses, a larger reinforced area is an advisable choice for design of the ring at higher temperature.展开更多
Based on deformation and failure characteristics of the second belt conveyor roadway at level II of Zhuxianzhuang coal mine, laboratory experiments, numerical calculation and field test were adopted to analyze the com...Based on deformation and failure characteristics of the second belt conveyor roadway at level II of Zhuxianzhuang coal mine, laboratory experiments, numerical calculation and field test were adopted to analyze the composition and microstructure of mudstone, the law of mudstone hydration and its strength weakening induced by water, the characteristics of surrounding rock deformation and failure under the action of confined water. Results showed that montmorillonite clay minerals accounted for as much as 76% of mudstone, with a large number of pores existing in the microstructure. Besides, as the molecular structure of montmorillonite changed, mudstone microstructure damage occurred with the macroscopic manifestation of its theological instability. Weakening degree of confined water on residual strength of mudstone was almost 50%. The instability mechanism of soft rock roadway caused by high confined water is that surrounding rock circulates the process of ＂fracture-seepage-mud ding-closed＂ twice, which weakens its strength and leads to roadway instability. A combined support technology, namely the, ＂high-toughness sealing layer ＋ hollow grouting cables ＋ full-length anchoring bolts with deep borehole＂ was proposed. Based on field observation, the soft rock roadway was controlled effectively, which also verified the effectiveness of new control technology for surrounding rock.展开更多
To reduce the nitrate leaching risk after potato （Solanum tuberosum L.） harvest and improve nitrogen fertilizer-use efficiency, a potato-cabbage double cropping system （DCS） was established at Hetao, North China, ...To reduce the nitrate leaching risk after potato （Solanum tuberosum L.） harvest and improve nitrogen fertilizer-use efficiency, a potato-cabbage double cropping system （DCS） was established at Hetao, North China, an arid area with irrigated land. A two-year field experiment demonstrated that planting early-maturing potato cultivar under plastic mulch shortened its growth period by 14 d and allowed a second crop of cabbage to scavenge the soil residual NO^--N to a depth of 160 cm, substantially reducing the risk of nitrate leaching into groundwater. The yearly total N uptake in DCS was about 110 kg ha-1 more than that in the conventional cropping system （CCS）, i.e., mono potato planting. This accounted for apparent nitrogen recovery （ANR） improvement of 16.90%-26.57% in the DCS as compared to that in the CCS for both years. As a result, the soil residual NO3-N in the 0-160 cm soil profile in the DCS was lower than that in the CCS. The solar energy-use efficiency and soil-use efficiency were also substantially increased with DCS.展开更多
基金Projects(51071122,51271147,51201134)supported by the National Natural Science Foundation of ChinaProject(3102014JCQ01023)supported by the Fundamental Research Funds for the Central UniversitiesProject(115-QP-2014)supported by the Research Fund of the State Key Laboratory of Solidification Processing in Northwestern Polytechnical University,China
文摘A three-dimensional cyclic symmetry finite element model of titanium-matrix composites（TMCs） ring was developed to investigate the stress distribution and burst failure. The effects of fiber volume fractions, reinforced areas, thermal residual stresses and two different temperatures on stress distribution were studied. The burst speed was obtained through analyzing the hoop tensile stresses under a series of rotating speeds. The results indicate that at the two different temperatures, the influences of fiber volume fractions and reinforced areas on stress level and distribution are different. Some proposals are provided for the structure design of the TMCs ring. With regard to thermal residual stresses, a larger reinforced area is an advisable choice for design of the ring at higher temperature.
基金the Natural Science Foundation of Jiangsu Province(No.BK20141130)the Fundamental Research Funds for the Central Universities(No.2014QNB27)
文摘Based on deformation and failure characteristics of the second belt conveyor roadway at level II of Zhuxianzhuang coal mine, laboratory experiments, numerical calculation and field test were adopted to analyze the composition and microstructure of mudstone, the law of mudstone hydration and its strength weakening induced by water, the characteristics of surrounding rock deformation and failure under the action of confined water. Results showed that montmorillonite clay minerals accounted for as much as 76% of mudstone, with a large number of pores existing in the microstructure. Besides, as the molecular structure of montmorillonite changed, mudstone microstructure damage occurred with the macroscopic manifestation of its theological instability. Weakening degree of confined water on residual strength of mudstone was almost 50%. The instability mechanism of soft rock roadway caused by high confined water is that surrounding rock circulates the process of ＂fracture-seepage-mud ding-closed＂ twice, which weakens its strength and leads to roadway instability. A combined support technology, namely the, ＂high-toughness sealing layer ＋ hollow grouting cables ＋ full-length anchoring bolts with deep borehole＂ was proposed. Based on field observation, the soft rock roadway was controlled effectively, which also verified the effectiveness of new control technology for surrounding rock.
基金Supported by the Inner Mongolia Agricultural University Innovation Team Foundation for Potato,China (No.NDPYTD2010-5)the Ministry of Agriculture Special Industry Foundation of China (No. 201103003)the Hong Kong Research Grants Council of China (No. HKBU 262809)
文摘To reduce the nitrate leaching risk after potato （Solanum tuberosum L.） harvest and improve nitrogen fertilizer-use efficiency, a potato-cabbage double cropping system （DCS） was established at Hetao, North China, an arid area with irrigated land. A two-year field experiment demonstrated that planting early-maturing potato cultivar under plastic mulch shortened its growth period by 14 d and allowed a second crop of cabbage to scavenge the soil residual NO^--N to a depth of 160 cm, substantially reducing the risk of nitrate leaching into groundwater. The yearly total N uptake in DCS was about 110 kg ha-1 more than that in the conventional cropping system （CCS）, i.e., mono potato planting. This accounted for apparent nitrogen recovery （ANR） improvement of 16.90%-26.57% in the DCS as compared to that in the CCS for both years. As a result, the soil residual NO3-N in the 0-160 cm soil profile in the DCS was lower than that in the CCS. The solar energy-use efficiency and soil-use efficiency were also substantially increased with DCS.
