This study aimed to analyze the absorption, utilization and transfer char- acteristics of nitrogen in high-yield winter wheat （Triticum aestivum） cultivars at dif- ferent sowing dates, so as to determine the optimum...This study aimed to analyze the absorption, utilization and transfer char- acteristics of nitrogen in high-yield winter wheat （Triticum aestivum） cultivars at dif- ferent sowing dates, so as to determine the optimum sowing dates for different high-yield wheat cultivars. A field experiment was conducted in the Shajiang black soil of Anhui Province with Jimai 22, Wanrnai 52 and Zhoumai 22, and the effects of early sowing （October 3）, optimum sowing （October 12） and late sowing （October 30） on wheat plant N content and accumulation, pre-and post-anthesis N accumula- tion （NA） of total plant, nitrogen remobUization to grain （NR）, N remobilization effi- ciency （NRE）, contribution of N remobilized to grain （NRC）, grain yield, N use effi- ciency （NUE） and N harvest index （NHI） of different wheat cultivar were investigat- ed. The results showed that sowing date had an impact on N content, absorption and utilization in wheat plants at various growth stages. The NA, NR and NRC of aboveground vegetative organs of wheat before anthesis were higher than those af- ter anthesis. Under the condition of late sowing, the grain N accumulation mainly depended on the N absorption by vegetative organs before anthesis. Under the conditions of optimum and early sowing, the absorbed N after anthesis accounted for a large proportion in grain N accumulation. The N uptake intensity and relative cumulative rate differed greatly among different growth stages and different-genotype wheat cultivars, and the pre-anthesis NA, pre-anthesis NR, pre-anthesis NRE, post- anthesis N assimilation amount and post-anthesis NRC showed significant differ- ences among different wheat cultivars. The grain yields of different wheat cultivars under the early and optimum sowing were all higher than those under the late sowing. The NHI and grain N accumulation were highest under the optimum sow- ing, and the latter significantly decreased with the delay of sowing dates. In con- trast, the NUE was highest under the late sowing, reaching 35.95%-41.32%. It indi- cated that under the condition of late sowing, most of the nitrogen was not ab- sorbed by wheat, but the use efficiency of the absorbed nitrogen significantly in- creased. In overall, the three high-yield wheat cultivars were all suitable for early and optimum sowing. Under the condition of late sowing, the yield of Zhoumai 22 showed the smallest differences with those under early and optimum sowing, and its NUE was significantly improved. Therefore, among the three high-yield wheat culti- vars, Zhoumai 22 was most suitable for late sowing.展开更多
In order to clean production of chromium compounds, it is a critical process to remove aluminates and utilize aluminum compounds from artificial chromate alkali solutions. The effects of Na2 Cr O4 on the neutralizatio...In order to clean production of chromium compounds, it is a critical process to remove aluminates and utilize aluminum compounds from artificial chromate alkali solutions. The effects of Na2 Cr O4 on the neutralization curve, Al（OH）3 precipitation efficiency and induction period of bayerite were investigated. The results indicate that the neutralization curve of the artificial chromate alkali solutions shows three distinct regions and its induction period is longer than that of pure sodium aluminate solutions at the same aluminum concentration. And the decreased temperature and volume fraction of CO2 enhance the particle size of bayerite β-Al（OH）3. Bayerite composed of agglomerates of rods and cone frustums was obtained from alkali metal chromate solutions with 28.5% CO2（volume fraction） at temperatures ranging from 50 °C to 70 °C. Coarse bayerite with particle size（d50） from 24.2 μm to 29.3 μm extremely has few impurities, which is suitable for comprehensive utilization.展开更多
A nonlinear explicit dynamic finite element formulation based on the generalized beam theory(GBT)is proposed and developed to simulate the dynamic responses of prismatic thin-walled steel members under transverse impu...A nonlinear explicit dynamic finite element formulation based on the generalized beam theory(GBT)is proposed and developed to simulate the dynamic responses of prismatic thin-walled steel members under transverse impulsive loads.Considering the rate strengthening and thermal softening effects on member impact behavior,a modified Cowper-Symonds model for constructional steels is utilized.The element displacement field is built upon the superposition of GBT cross-section deformation modes,so arbitrary deformations such as cross-section distortions,local buckling and warping shear can all be involved by the proposed model.The amplitude function of each cross-section deformation mode is approximated by the cubic non-uniform B-spline basis functions.The Kirchhoff s thin-plate assumption is utilized in the construction of the bending related displacements.The Green-Lagrange strain tensor and the second Piola-Kirchhoff(PK2)stress tensor are employed to measure deformations and stresses at any material point,where stresses are assumed to be in plane-stress state.In order to verify the effectiveness of the proposed GBT model,three numerical cases involving impulsive loading of the thin-walled parts are given.The GBT results are compared with those of the Ls-Dyna shell finite element.It is shown that the proposed model and the shell finite element analysis has equivalent accuracy in displacement and stress.Moreover,the proposed model is much more computationally efficient and structurally clearer than the shell finite elements.展开更多
In the distribution family with common support and the one side truncated distribution family, Bickle, I. A. Ibragimov and R. Z. Hasminskii proved two important convolution theorems. As to the two-side truncated case,...In the distribution family with common support and the one side truncated distribution family, Bickle, I. A. Ibragimov and R. Z. Hasminskii proved two important convolution theorems. As to the two-side truncated case, we also proved a convolution theorem, which plays an extraordinary role in the efficiency theory. In this paper, we will study another kind of two-side truncated distribution family, and prove a convolution result with normal form. On the basis of this convolution result, a new kind of efficiency concept is given; meanwhile, we will show that MLE is an efficient estimate in this distribution family.展开更多
基金Supported by National Key Technology Research and Development Program(2012BAD04B09,2013BAD07B08)
文摘This study aimed to analyze the absorption, utilization and transfer char- acteristics of nitrogen in high-yield winter wheat （Triticum aestivum） cultivars at dif- ferent sowing dates, so as to determine the optimum sowing dates for different high-yield wheat cultivars. A field experiment was conducted in the Shajiang black soil of Anhui Province with Jimai 22, Wanrnai 52 and Zhoumai 22, and the effects of early sowing （October 3）, optimum sowing （October 12） and late sowing （October 30） on wheat plant N content and accumulation, pre-and post-anthesis N accumula- tion （NA） of total plant, nitrogen remobUization to grain （NR）, N remobilization effi- ciency （NRE）, contribution of N remobilized to grain （NRC）, grain yield, N use effi- ciency （NUE） and N harvest index （NHI） of different wheat cultivar were investigat- ed. The results showed that sowing date had an impact on N content, absorption and utilization in wheat plants at various growth stages. The NA, NR and NRC of aboveground vegetative organs of wheat before anthesis were higher than those af- ter anthesis. Under the condition of late sowing, the grain N accumulation mainly depended on the N absorption by vegetative organs before anthesis. Under the conditions of optimum and early sowing, the absorbed N after anthesis accounted for a large proportion in grain N accumulation. The N uptake intensity and relative cumulative rate differed greatly among different growth stages and different-genotype wheat cultivars, and the pre-anthesis NA, pre-anthesis NR, pre-anthesis NRE, post- anthesis N assimilation amount and post-anthesis NRC showed significant differ- ences among different wheat cultivars. The grain yields of different wheat cultivars under the early and optimum sowing were all higher than those under the late sowing. The NHI and grain N accumulation were highest under the optimum sow- ing, and the latter significantly decreased with the delay of sowing dates. In con- trast, the NUE was highest under the late sowing, reaching 35.95%-41.32%. It indi- cated that under the condition of late sowing, most of the nitrogen was not ab- sorbed by wheat, but the use efficiency of the absorbed nitrogen significantly in- creased. In overall, the three high-yield wheat cultivars were all suitable for early and optimum sowing. Under the condition of late sowing, the yield of Zhoumai 22 showed the smallest differences with those under early and optimum sowing, and its NUE was significantly improved. Therefore, among the three high-yield wheat culti- vars, Zhoumai 22 was most suitable for late sowing.
基金Project(51125018)supported by the National Science Found for Distinguished Young Scholars of ChinaProject(2011BAC06B07)supported by the National Key Technologies R&D Program of China+2 种基金Project(2011AA060704)supported by the National Hi-tech Research and Development Program of ChinaProjects(51204153,21106167)supported by the National Natural Science Foundation of ChinaProjects(2012M510552,2013T60175)supported by Financial Grant from the China Postdoctoral Science Foundation
文摘In order to clean production of chromium compounds, it is a critical process to remove aluminates and utilize aluminum compounds from artificial chromate alkali solutions. The effects of Na2 Cr O4 on the neutralization curve, Al（OH）3 precipitation efficiency and induction period of bayerite were investigated. The results indicate that the neutralization curve of the artificial chromate alkali solutions shows three distinct regions and its induction period is longer than that of pure sodium aluminate solutions at the same aluminum concentration. And the decreased temperature and volume fraction of CO2 enhance the particle size of bayerite β-Al（OH）3. Bayerite composed of agglomerates of rods and cone frustums was obtained from alkali metal chromate solutions with 28.5% CO2（volume fraction） at temperatures ranging from 50 °C to 70 °C. Coarse bayerite with particle size（d50） from 24.2 μm to 29.3 μm extremely has few impurities, which is suitable for comprehensive utilization.
基金The National Natural Science Foundation of China(No.51078229)the Specialized Research Fund for the Doctoral Program of Higher Education(o.20100073110008)
文摘A nonlinear explicit dynamic finite element formulation based on the generalized beam theory(GBT)is proposed and developed to simulate the dynamic responses of prismatic thin-walled steel members under transverse impulsive loads.Considering the rate strengthening and thermal softening effects on member impact behavior,a modified Cowper-Symonds model for constructional steels is utilized.The element displacement field is built upon the superposition of GBT cross-section deformation modes,so arbitrary deformations such as cross-section distortions,local buckling and warping shear can all be involved by the proposed model.The amplitude function of each cross-section deformation mode is approximated by the cubic non-uniform B-spline basis functions.The Kirchhoff s thin-plate assumption is utilized in the construction of the bending related displacements.The Green-Lagrange strain tensor and the second Piola-Kirchhoff(PK2)stress tensor are employed to measure deformations and stresses at any material point,where stresses are assumed to be in plane-stress state.In order to verify the effectiveness of the proposed GBT model,three numerical cases involving impulsive loading of the thin-walled parts are given.The GBT results are compared with those of the Ls-Dyna shell finite element.It is shown that the proposed model and the shell finite element analysis has equivalent accuracy in displacement and stress.Moreover,the proposed model is much more computationally efficient and structurally clearer than the shell finite elements.
基金This research is supported by Youth Science Foundation of Beijing Normal University.
文摘In the distribution family with common support and the one side truncated distribution family, Bickle, I. A. Ibragimov and R. Z. Hasminskii proved two important convolution theorems. As to the two-side truncated case, we also proved a convolution theorem, which plays an extraordinary role in the efficiency theory. In this paper, we will study another kind of two-side truncated distribution family, and prove a convolution result with normal form. On the basis of this convolution result, a new kind of efficiency concept is given; meanwhile, we will show that MLE is an efficient estimate in this distribution family.
