During cantilever cast in construction of high-pier and large-span continuous rigid frame bridges, structural stability in the longest cantilevered stage is very important. Based on a practical design case of a large-...During cantilever cast in construction of high-pier and large-span continuous rigid frame bridges, structural stability in the longest cantilevered stage is very important. Based on a practical design case of a large-span continuous rigid frame bridge in Wuhan, the longest span stability coefficient is calculated with linear-buckling and nonlinear-buckling methods, respectively. The influences of both geometrical nonlinearity and the dual nonlinearity of material and geometry are considered. Numerical results indicate that the nonlinear solution is necessary to stability analysis because linear buckling loads are much higher than those of nonlinear buckling. Thus, the edge fiber yield criterion is more convenient and faster than ultimate loading criterion when estimating nonlinear stability of structure, and can be used easily in the initial engineering design.展开更多
Over the last decade,various Fe-Ni alloys have been developed at Baosteel using the EAF-AOD-LFVD-CC route. This paper first reveals the main cause of defects in Fe-Ni alloys,including surface edge cracks on hot-rollin...Over the last decade,various Fe-Ni alloys have been developed at Baosteel using the EAF-AOD-LFVD-CC route. This paper first reveals the main cause of defects in Fe-Ni alloys,including surface edge cracks on hot-rolling strips and slivers on cold-rolling strips of Fe-36% Ni alloy. Then,the material properties and in-situ solidification behavior w ere experimentally investigated. The gas content and average diameter of the inclusions in Fe-36% Ni alloy that occur along the EAF-AOD-LF-VD-CC route w ere also investigated via potentiostatic electrolysis using a non-aqueous organic electrolytic. Furthermore,the heat transfer and solidification in a continuous casting mold w ere predicted based on an inverse heat transfer model using the measured mold temperature. Experimental results show that the gas content,w hich is < 0. 001 5% in a continuous casting slab,and the average diameter of the inclusions both decrease during the metallurgical EAF-AOD-LF-VD-CC process. The average diameter of the inclusions in a continuous casting slab is ～ 18 μm,w hich tends to induce slivers during subsequent cold-rolling process. Experimental in-situ solidification results show that the mushy zone betw een the liquidus and solidus of Fe-Ni alloy is much narrow er than that of plain carbon steel. Stresses are generated during continuous casting,primarily due to the thermal contraction of a few percentage points,and any strain applied to the steel w ithin this temperature region w ill cause cracks to propagate outw ard from the solidification front betw een the dendrites. Numerical simulation results illustrate that heat flux and shell thickness are uneven across the w idth of the mold,particularly the shell thickness close to the edge of the slab surface in the fixed face is 6-mm thinner than that at the slab center. Based on these results,the incidence of surface defects in Fe-Ni alloy can be greatly reduced by the adjustment and optimization of its refining and continuous casting process.展开更多
Focusing on the extending length restriction of the completion screen pipe resistance running into ultra-short radius horizontal well,this paper proposed technology of hydraulic drive completion tubular string running...Focusing on the extending length restriction of the completion screen pipe resistance running into ultra-short radius horizontal well,this paper proposed technology of hydraulic drive completion tubular string running into ultra-short radius horizontal well.Innovative hydraulic drive tools and string structure are designed,which are composed of guide tubing,hydraulic drive tubing and non-metallic completion screen pipe from inside to outside.A novel mechanical-hydraulic coupling model is established.Based on the wellbore structure of an ultra-short radius horizontal well for deep coalbed methane,the numerical calculations of force and hydraulic load on tubular strings were accomplished by the mechanical-hydraulic coupling model.The results show that the extending length of completion tubular string with the hydraulic drive is 17 times that of conventional completion technology under the same conditions.The multi-factor orthogonal design is adopted to analyze the numerical calculations,and the results show that the extending length of the completion tubular string is mainly affected by the completion tubular string structure and the friction coefficient between the non-metallic composite continuous screen pipe and the wellbore.Two series of hydraulic drive completion tubular string structures suitable for ultra-short radius horizontal wells under different conditions are optimized,with the extending limits of 381 m and 655 m,respectively.These researches will provide theoretical guidance for design and control of hydraulic drive non-metallic composite continuous completion screen pipe running into ultra-short radius horizontal wells.展开更多
为探讨单向倒刺线连续缝合与可吸收线连续锁边缝合在全膝关节置换术加速康复中的临床应用效果,回顾性分析2020年3月—2022年6月邯郸市中心医院行初次全膝关节置换手术的106例患者,分为对照组(52例)和观察组(54例)。对照组采用可吸收线...为探讨单向倒刺线连续缝合与可吸收线连续锁边缝合在全膝关节置换术加速康复中的临床应用效果,回顾性分析2020年3月—2022年6月邯郸市中心医院行初次全膝关节置换手术的106例患者,分为对照组(52例)和观察组(54例)。对照组采用可吸收线连续锁边缝合切口,观察组采用单向倒刺线连续缝合切口。比较两组缝合时间、手术时间、失血量和术后住院时间、膝关节活动度(range of motion,ROM)、膝关节功能以及并发症差异。结果表明:观察组缝合时间短于对照组(P<0.05),皮下瘀斑、针刺伤发生率低于对照组(P<0.05)。观察组手术时间、平均失血量和平均住院时间、术后7 d美国纽约特种外科医院评分(hospital for special surgery knee score,HSS)、Rasmussen评分、膝关节ROM、切口红肿、切口感染、切口延迟愈合发生率与对照组比较差异无统计学意义(P>0.05)。可见单向倒刺线连续缝合可缩短缝合时间,降低术后皮下瘀斑和针刺伤发生率,有利于患者术后功能的恢复,缩短住院时间,在全膝关节置换术加速康复中具有一定优势。展开更多
基金The National Natural Science Foundation of China (No.50608036)
文摘During cantilever cast in construction of high-pier and large-span continuous rigid frame bridges, structural stability in the longest cantilevered stage is very important. Based on a practical design case of a large-span continuous rigid frame bridge in Wuhan, the longest span stability coefficient is calculated with linear-buckling and nonlinear-buckling methods, respectively. The influences of both geometrical nonlinearity and the dual nonlinearity of material and geometry are considered. Numerical results indicate that the nonlinear solution is necessary to stability analysis because linear buckling loads are much higher than those of nonlinear buckling. Thus, the edge fiber yield criterion is more convenient and faster than ultimate loading criterion when estimating nonlinear stability of structure, and can be used easily in the initial engineering design.
文摘Over the last decade,various Fe-Ni alloys have been developed at Baosteel using the EAF-AOD-LFVD-CC route. This paper first reveals the main cause of defects in Fe-Ni alloys,including surface edge cracks on hot-rolling strips and slivers on cold-rolling strips of Fe-36% Ni alloy. Then,the material properties and in-situ solidification behavior w ere experimentally investigated. The gas content and average diameter of the inclusions in Fe-36% Ni alloy that occur along the EAF-AOD-LF-VD-CC route w ere also investigated via potentiostatic electrolysis using a non-aqueous organic electrolytic. Furthermore,the heat transfer and solidification in a continuous casting mold w ere predicted based on an inverse heat transfer model using the measured mold temperature. Experimental results show that the gas content,w hich is < 0. 001 5% in a continuous casting slab,and the average diameter of the inclusions both decrease during the metallurgical EAF-AOD-LF-VD-CC process. The average diameter of the inclusions in a continuous casting slab is ～ 18 μm,w hich tends to induce slivers during subsequent cold-rolling process. Experimental in-situ solidification results show that the mushy zone betw een the liquidus and solidus of Fe-Ni alloy is much narrow er than that of plain carbon steel. Stresses are generated during continuous casting,primarily due to the thermal contraction of a few percentage points,and any strain applied to the steel w ithin this temperature region w ill cause cracks to propagate outw ard from the solidification front betw een the dendrites. Numerical simulation results illustrate that heat flux and shell thickness are uneven across the w idth of the mold,particularly the shell thickness close to the edge of the slab surface in the fixed face is 6-mm thinner than that at the slab center. Based on these results,the incidence of surface defects in Fe-Ni alloy can be greatly reduced by the adjustment and optimization of its refining and continuous casting process.
基金Supported by the Innovative Research Group Project of China National Natural Science Foundation(51821092)Key Project of China National Natural Science Foundation(U1762214).
文摘Focusing on the extending length restriction of the completion screen pipe resistance running into ultra-short radius horizontal well,this paper proposed technology of hydraulic drive completion tubular string running into ultra-short radius horizontal well.Innovative hydraulic drive tools and string structure are designed,which are composed of guide tubing,hydraulic drive tubing and non-metallic completion screen pipe from inside to outside.A novel mechanical-hydraulic coupling model is established.Based on the wellbore structure of an ultra-short radius horizontal well for deep coalbed methane,the numerical calculations of force and hydraulic load on tubular strings were accomplished by the mechanical-hydraulic coupling model.The results show that the extending length of completion tubular string with the hydraulic drive is 17 times that of conventional completion technology under the same conditions.The multi-factor orthogonal design is adopted to analyze the numerical calculations,and the results show that the extending length of the completion tubular string is mainly affected by the completion tubular string structure and the friction coefficient between the non-metallic composite continuous screen pipe and the wellbore.Two series of hydraulic drive completion tubular string structures suitable for ultra-short radius horizontal wells under different conditions are optimized,with the extending limits of 381 m and 655 m,respectively.These researches will provide theoretical guidance for design and control of hydraulic drive non-metallic composite continuous completion screen pipe running into ultra-short radius horizontal wells.
文摘为探讨单向倒刺线连续缝合与可吸收线连续锁边缝合在全膝关节置换术加速康复中的临床应用效果,回顾性分析2020年3月—2022年6月邯郸市中心医院行初次全膝关节置换手术的106例患者,分为对照组(52例)和观察组(54例)。对照组采用可吸收线连续锁边缝合切口,观察组采用单向倒刺线连续缝合切口。比较两组缝合时间、手术时间、失血量和术后住院时间、膝关节活动度(range of motion,ROM)、膝关节功能以及并发症差异。结果表明:观察组缝合时间短于对照组(P<0.05),皮下瘀斑、针刺伤发生率低于对照组(P<0.05)。观察组手术时间、平均失血量和平均住院时间、术后7 d美国纽约特种外科医院评分(hospital for special surgery knee score,HSS)、Rasmussen评分、膝关节ROM、切口红肿、切口感染、切口延迟愈合发生率与对照组比较差异无统计学意义(P>0.05)。可见单向倒刺线连续缝合可缩短缝合时间,降低术后皮下瘀斑和针刺伤发生率,有利于患者术后功能的恢复,缩短住院时间,在全膝关节置换术加速康复中具有一定优势。
