Based on the surveys and the statistic data during 1980-2003, the variation character of grain yield per unit area in Northeast China and its main factors have been discussed by the methods of statistics and grey corr...Based on the surveys and the statistic data during 1980-2003, the variation character of grain yield per unit area in Northeast China and its main factors have been discussed by the methods of statistics and grey correlation analysis. The results show that: 1) the grain yield per unit area has been taking on an increasing trend in the recent 20 years. It increased from 2519.80kg/ha in 1980 to 4216.11kg/ha in 2003, with an increasing rate of 67.32%; 2) the variation of grain yield per unit area is considerably prominent and its range is also very great, with the maximal increase rate of 42.59% and maximal decrease rate of 21.13%, respectively, which are far above the whole Chinese average level; 3) the variation of main crops' yield per unit area is remarkable, which takes on the character that the yield of corn is much higher than that of soybean and rice; and 4) the grey correlation analysis shows that the most important factors impacting the variation of grain yield per unit area are the total power of agricultural machinery, the consumption of chemical fertilizer and effective irrigated area. However, the influence of natural disaster and income level should not be ignored. Effective ways to improve grain yield per unit area are to construct farmland improvement groundwork, reclaim the middle- and low-yield farmland, etc.展开更多
In Haigh Westergaard stress space linear combination of twin shear stress and Tresca yield functions is called the mean yield （MY） criterion. The mathematical relationship of the criterion and its plastic work rate ...In Haigh Westergaard stress space linear combination of twin shear stress and Tresca yield functions is called the mean yield （MY） criterion. The mathematical relationship of the criterion and its plastic work rate done per unit volume were derived. A generalized worked example of slab forging was analyzed by the criterion and its corresponding plastic work rate done per unit volume. Then, the precision of the solution was compared with those by Mises and Twin shear stress yield criterions, respectively. It turned out that the calculated results by MY criterion were in good agreement with those by Mises criterion.展开更多
Based on the combination test of various distances between ridges or plants, the influences of corresponding cultivation techniques on the per unit area yield of a variety of sweet potatoes Xushu 22 in Xianning City w...Based on the combination test of various distances between ridges or plants, the influences of corresponding cultivation techniques on the per unit area yield of a variety of sweet potatoes Xushu 22 in Xianning City were analyzed. The results show that different distances between ridges or plants had significant effects on the per unit area yield of Xushu 22; when the distances between ridges and plants for Xushu 22 planted in the city were 80 and 21 cm respectively, the per u- nit area yield of Xushu 22 was the highest, up to 48 340.7 kg/hm2.展开更多
The maximum yield growth range of wheat yield per unit in China is analyzed from three aspects including photosynthesis production potential of wheat,the changing trend of per unit wheat in the previous years and pote...The maximum yield growth range of wheat yield per unit in China is analyzed from three aspects including photosynthesis production potential of wheat,the changing trend of per unit wheat in the previous years and potential of distribution area agricultural crops.In the paper,the potential of using light,the external potential of historical yield evolution tend and AEZ (agricultural ecological zone) are applied to calculate the per unit yield potential of Chinese wheat.The results assume that the maximum growth range of per unit yield in different stages was different:before 1991,the growth range was 10%;before 1996,the growth range was 9%;before 2000,the growth range was 8%.Any variety of wheat and planting technology higher than the above growth range can only be promoted in restricted area and has the statistical error.The results are of reference significance to Chinese wheat production.展开更多
The spike-grain structure and yield data of winter wheat observed at 10 winter wheat observation stations in Jiangsu agrometeorological observation stations in the China Meteorological Observation Network were used to...The spike-grain structure and yield data of winter wheat observed at 10 winter wheat observation stations in Jiangsu agrometeorological observation stations in the China Meteorological Observation Network were used to design the assessment model and evaluation criteria of the effects of climate change on spikegrain structure and yield of winter wheat. The linear regression method was used to determine the parameters of the assessment model,and the climate fact extrapolation method was used to determine future climate change scenarios. The effects of climate change on spike-grain structure and yield of winter wheat in Jiangsu Province were calculated and analyzed finally. The results showed that with the climate change,the meteorological conditions during the growth and development of winter wheat changed,which caused the number of effective spikes to decrease,and the number of grains per spike and thousand-grain weight to increase,and this new type of spike-grain structure combination was beneficial to the increase of the unit yield of winter wheat. The variations of meteorological elements caused by climate change during winter wheat growth and development had different effects on spike-grain structure at different growth stages. The spike-grain structure had an "increasing-decreasing" periodic variation with the growth period overall,with a period of one to three stages. The relationship between winter wheat growth and development and meteorological conditions can be adjusted in real time through stress-resistant cultivation techniques to achieve the high-yield and high-quality cultivation target of winter wheat production.展开更多
基金Under the auspices of the National Natural Science Foundation of China (No. 40601027)
文摘Based on the surveys and the statistic data during 1980-2003, the variation character of grain yield per unit area in Northeast China and its main factors have been discussed by the methods of statistics and grey correlation analysis. The results show that: 1) the grain yield per unit area has been taking on an increasing trend in the recent 20 years. It increased from 2519.80kg/ha in 1980 to 4216.11kg/ha in 2003, with an increasing rate of 67.32%; 2) the variation of grain yield per unit area is considerably prominent and its range is also very great, with the maximal increase rate of 42.59% and maximal decrease rate of 21.13%, respectively, which are far above the whole Chinese average level; 3) the variation of main crops' yield per unit area is remarkable, which takes on the character that the yield of corn is much higher than that of soybean and rice; and 4) the grey correlation analysis shows that the most important factors impacting the variation of grain yield per unit area are the total power of agricultural machinery, the consumption of chemical fertilizer and effective irrigated area. However, the influence of natural disaster and income level should not be ignored. Effective ways to improve grain yield per unit area are to construct farmland improvement groundwork, reclaim the middle- and low-yield farmland, etc.
基金This research was supported by the National Natural Sci—ence Foundation of China(Grant No.50474015)
文摘In Haigh Westergaard stress space linear combination of twin shear stress and Tresca yield functions is called the mean yield （MY） criterion. The mathematical relationship of the criterion and its plastic work rate done per unit volume were derived. A generalized worked example of slab forging was analyzed by the criterion and its corresponding plastic work rate done per unit volume. Then, the precision of the solution was compared with those by Mises and Twin shear stress yield criterions, respectively. It turned out that the calculated results by MY criterion were in good agreement with those by Mises criterion.
基金Supported by National Technical System of Sweet Potato Industry of China~~
文摘Based on the combination test of various distances between ridges or plants, the influences of corresponding cultivation techniques on the per unit area yield of a variety of sweet potatoes Xushu 22 in Xianning City were analyzed. The results show that different distances between ridges or plants had significant effects on the per unit area yield of Xushu 22; when the distances between ridges and plants for Xushu 22 planted in the city were 80 and 21 cm respectively, the per u- nit area yield of Xushu 22 was the highest, up to 48 340.7 kg/hm2.
基金Supported by the Special Fund Project for Governors in Guizhou Province [2010(131)]
文摘The maximum yield growth range of wheat yield per unit in China is analyzed from three aspects including photosynthesis production potential of wheat,the changing trend of per unit wheat in the previous years and potential of distribution area agricultural crops.In the paper,the potential of using light,the external potential of historical yield evolution tend and AEZ (agricultural ecological zone) are applied to calculate the per unit yield potential of Chinese wheat.The results assume that the maximum growth range of per unit yield in different stages was different:before 1991,the growth range was 10%;before 1996,the growth range was 9%;before 2000,the growth range was 8%.Any variety of wheat and planting technology higher than the above growth range can only be promoted in restricted area and has the statistical error.The results are of reference significance to Chinese wheat production.
基金Supported by 2016 Key Business Project of Jiangsu Meteorological Bureau(20161122)
文摘The spike-grain structure and yield data of winter wheat observed at 10 winter wheat observation stations in Jiangsu agrometeorological observation stations in the China Meteorological Observation Network were used to design the assessment model and evaluation criteria of the effects of climate change on spikegrain structure and yield of winter wheat. The linear regression method was used to determine the parameters of the assessment model,and the climate fact extrapolation method was used to determine future climate change scenarios. The effects of climate change on spike-grain structure and yield of winter wheat in Jiangsu Province were calculated and analyzed finally. The results showed that with the climate change,the meteorological conditions during the growth and development of winter wheat changed,which caused the number of effective spikes to decrease,and the number of grains per spike and thousand-grain weight to increase,and this new type of spike-grain structure combination was beneficial to the increase of the unit yield of winter wheat. The variations of meteorological elements caused by climate change during winter wheat growth and development had different effects on spike-grain structure at different growth stages. The spike-grain structure had an "increasing-decreasing" periodic variation with the growth period overall,with a period of one to three stages. The relationship between winter wheat growth and development and meteorological conditions can be adjusted in real time through stress-resistant cultivation techniques to achieve the high-yield and high-quality cultivation target of winter wheat production.
