[Objective] The paper was to study and modify non-limiting water range （NLWR） of soil. [Method] The water content when total soil water potential was -0.3 MPa or soil mechanical resistance was 0.85 MPa was selected ...[Objective] The paper was to study and modify non-limiting water range （NLWR） of soil. [Method] The water content when total soil water potential was -0.3 MPa or soil mechanical resistance was 0.85 MPa was selected as the lower limit of NLWR to replace the original water content of permanent wilting point or the water content under soil mechanical resistance of 2.0 MPa. NLWR could be calculated us-ing the minimum value of upper limit minus the maximum value of lower limit. [Re-sult] Compared with original NLWR or least limiting water range （LLWR）, the modi-fied NLWR had more practical significance. When Db〉Db-thr, soil physical properties hindered the growth of crops, so the soil should be improved; when Db〉Db-thr, soil physical properties hindered the growth of crops, so-the soil should be improved; wtlen Db〈Db-thr, as long as the soil water content is within NLWR, soil physical properties had no effect on crop growth. NLWR at this time could be used as the basis for irrigation man- agement in farmland. [Conclusion] The study provides theoretical support and scientific basis for relevant researches about evolution rule and regulatory mechanisms of soil physical quality, relationship between soil physical quality and crop growth and yield, water-fertilizer-salt management of soil.展开更多
In this study,the effect of welding parameters on the microstructure and mechanical properties of the dissimilar resistance spot welded DP1000–QP1180 joints was investigated.Heat affected zone(HAZ)width of QP1180 sid...In this study,the effect of welding parameters on the microstructure and mechanical properties of the dissimilar resistance spot welded DP1000–QP1180 joints was investigated.Heat affected zone(HAZ)width of QP1180 side was smaller than that of DP1000 side.HAZ width and indentation depth increased with increasing welding current and welding time.The nugget size increased with increasing welding current whereas it increased at lower currents and decreased at higher currents with increasing welding time.The lowest hardness was on the DP1000 side.On the QP1180 side,the center of HAZ had the peak hardness.With increasing welding current,hardness values throughout the weld zone decreased and the tensile shear load increased.At lower welding currents,the welding time did not affect the tensile shear load.Tensile elongation decreased with the increase of welding time,whereas there is no relationship between the welding current and elongation.The spot-welded joints having higher strength exhibited a more ductile fracture characteristic.展开更多
基金Supported by National Natural Science Foundation of China(41161037,31371582)~~
文摘[Objective] The paper was to study and modify non-limiting water range （NLWR） of soil. [Method] The water content when total soil water potential was -0.3 MPa or soil mechanical resistance was 0.85 MPa was selected as the lower limit of NLWR to replace the original water content of permanent wilting point or the water content under soil mechanical resistance of 2.0 MPa. NLWR could be calculated us-ing the minimum value of upper limit minus the maximum value of lower limit. [Re-sult] Compared with original NLWR or least limiting water range （LLWR）, the modi-fied NLWR had more practical significance. When Db〉Db-thr, soil physical properties hindered the growth of crops, so the soil should be improved; when Db〉Db-thr, soil physical properties hindered the growth of crops, so-the soil should be improved; wtlen Db〈Db-thr, as long as the soil water content is within NLWR, soil physical properties had no effect on crop growth. NLWR at this time could be used as the basis for irrigation man- agement in farmland. [Conclusion] The study provides theoretical support and scientific basis for relevant researches about evolution rule and regulatory mechanisms of soil physical quality, relationship between soil physical quality and crop growth and yield, water-fertilizer-salt management of soil.
基金Project supported by Beycelik Gestamp Inc.,Turkey
文摘In this study,the effect of welding parameters on the microstructure and mechanical properties of the dissimilar resistance spot welded DP1000–QP1180 joints was investigated.Heat affected zone(HAZ)width of QP1180 side was smaller than that of DP1000 side.HAZ width and indentation depth increased with increasing welding current and welding time.The nugget size increased with increasing welding current whereas it increased at lower currents and decreased at higher currents with increasing welding time.The lowest hardness was on the DP1000 side.On the QP1180 side,the center of HAZ had the peak hardness.With increasing welding current,hardness values throughout the weld zone decreased and the tensile shear load increased.At lower welding currents,the welding time did not affect the tensile shear load.Tensile elongation decreased with the increase of welding time,whereas there is no relationship between the welding current and elongation.The spot-welded joints having higher strength exhibited a more ductile fracture characteristic.
