[目的/意义]探讨论文被引频次的影响因素及其关系,有助于在计量评价过程中合理地使用基于被引频次的计量指标。[方法/过程]以Web of Science数据库2000年发表的所有论文为基础,利用Tobit多元回归模型探索作者数、机构数、跨学科性、国...[目的/意义]探讨论文被引频次的影响因素及其关系,有助于在计量评价过程中合理地使用基于被引频次的计量指标。[方法/过程]以Web of Science数据库2000年发表的所有论文为基础,利用Tobit多元回归模型探索作者数、机构数、跨学科性、国内合作、国际合作和参考文献数量6个常见的影响因素对论文被引频次的影响。[结果/结论]研究发现机构数存在明显的多重共线性,因此进一步通过全子集回归分析筛选最佳回归模型。研究结果表明,作者数、机构数、跨学科性、国际合作和参考文献数量对论文被引频次有积极的影响,其中国内合作对被引频次的影响力很微弱,容易受到机构数的干扰,而机构数和参考文献数量是论文特征中影响被引频次最重要的因素。展开更多
Excessive vibrations of railway vehicles induced by dynamic impact loadings have a significant impact on train operating safety and stability;however,due to the complexity and diversity of railway lines and service en...Excessive vibrations of railway vehicles induced by dynamic impact loadings have a significant impact on train operating safety and stability;however,due to the complexity and diversity of railway lines and service environment,they are extremely difficult to eliminate.A comprehensive overview of recent studies on the impact vibration behavior of railway vehicles was given in this paper.First,the sources of impact excitations were categorized in terms of wheel-rail contact irregularity,aerodynamic loads,and longitudinal impulses by train traction/braking.Then the main research approaches of vehicle impact vibration were briefly introduced in theoretical,experimental,and simulation aspects.Also,the impact vibration response characteristics of railway vehicles were categorized and examined in detail to various impact excitation sources.Finally,some attempts of using the railway vehicle vibration to detect track defects and the possible mitigation measures were outlined.展开更多
In deep underground engineering,rock burst and other dynamic disasters are prone to occur due to stress concentration and energy accumulation in surrounding rock.The control of dynamic disasters requires bolts and cab...In deep underground engineering,rock burst and other dynamic disasters are prone to occur due to stress concentration and energy accumulation in surrounding rock.The control of dynamic disasters requires bolts and cables with high strength,high elongation,and high energy-absorbing capacity.Therefore,a constant resistance energy-absorbing(CREA)material is developed.In this study,the dynamic characteristics of the new material are obtained via the drop hammer tests and the Split Hopkinson Pressure Bar(SHPB)tests of the new material and two common bolt(CB)materials widely used in the field.The test results of drop hammer test and SHPB test show that the percentage elongation of CREA material is more than 2.64 and 3.22 times those of the CB material,and the total impact energy acting on CREA material is more than 18.50 and 21.84 times,respectively,indicating that the new material has high elongation and high energy-absorbing capacity.Subsequently,the CREA bolts and cables using the new material are developed,which are applied in roadways with high stress and strong dynamic disturbance.The field monitoring results show that CREA bolts and cables can effectively control the surrounding rock deformation and ensure engineering safety.展开更多
文摘农产品在收获、分级、包装、运输和加工中将发生机械损伤 ,而碰撞是导致机械损伤的主要原因之一。该文以黄花梨为试验对象 ,进行了不同下落高度、不同梨质量和坚实度等对碰撞参数指标如力峰值、到达力峰值时间、碰撞总时间、力峰值 /到达力峰值时间的比值等影响的碰撞特性试验。试验表明 3个试验因子对力峰值 /到达力峰值时间的比值、损伤体积和力峰值的影响大都为显著。碰撞参数指标内部之间的相关性不尽相同。碰撞损伤预测模型可采用 V =β0 +β1 h +β2 m
文摘[目的/意义]探讨论文被引频次的影响因素及其关系,有助于在计量评价过程中合理地使用基于被引频次的计量指标。[方法/过程]以Web of Science数据库2000年发表的所有论文为基础,利用Tobit多元回归模型探索作者数、机构数、跨学科性、国内合作、国际合作和参考文献数量6个常见的影响因素对论文被引频次的影响。[结果/结论]研究发现机构数存在明显的多重共线性,因此进一步通过全子集回归分析筛选最佳回归模型。研究结果表明,作者数、机构数、跨学科性、国际合作和参考文献数量对论文被引频次有积极的影响,其中国内合作对被引频次的影响力很微弱,容易受到机构数的干扰,而机构数和参考文献数量是论文特征中影响被引频次最重要的因素。
基金supported by the National Key Research and Development Program(Grant 2020YFA0710902)the National Natural Science Foundation of China(Grants 11772275,U19A20110)。
文摘Excessive vibrations of railway vehicles induced by dynamic impact loadings have a significant impact on train operating safety and stability;however,due to the complexity and diversity of railway lines and service environment,they are extremely difficult to eliminate.A comprehensive overview of recent studies on the impact vibration behavior of railway vehicles was given in this paper.First,the sources of impact excitations were categorized in terms of wheel-rail contact irregularity,aerodynamic loads,and longitudinal impulses by train traction/braking.Then the main research approaches of vehicle impact vibration were briefly introduced in theoretical,experimental,and simulation aspects.Also,the impact vibration response characteristics of railway vehicles were categorized and examined in detail to various impact excitation sources.Finally,some attempts of using the railway vehicle vibration to detect track defects and the possible mitigation measures were outlined.
基金This work was supported by the National Natural Science Foundation of China(Nos.41941018,52074164,and 42077267);the Natural Science Foundation of Shandong Province,China(Nos.2019SDZY04 and ZR2020JQ23)the Project of Shandong Province Higher Educational Youth Innovation Science and Technology Program,China(No.2019KJG013).
文摘In deep underground engineering,rock burst and other dynamic disasters are prone to occur due to stress concentration and energy accumulation in surrounding rock.The control of dynamic disasters requires bolts and cables with high strength,high elongation,and high energy-absorbing capacity.Therefore,a constant resistance energy-absorbing(CREA)material is developed.In this study,the dynamic characteristics of the new material are obtained via the drop hammer tests and the Split Hopkinson Pressure Bar(SHPB)tests of the new material and two common bolt(CB)materials widely used in the field.The test results of drop hammer test and SHPB test show that the percentage elongation of CREA material is more than 2.64 and 3.22 times those of the CB material,and the total impact energy acting on CREA material is more than 18.50 and 21.84 times,respectively,indicating that the new material has high elongation and high energy-absorbing capacity.Subsequently,the CREA bolts and cables using the new material are developed,which are applied in roadways with high stress and strong dynamic disturbance.The field monitoring results show that CREA bolts and cables can effectively control the surrounding rock deformation and ensure engineering safety.
