A novel forming method of nickel based super-alloy thin-walled part with variable diameter sections was proposed by using inner and outer pressure with the visco-elasto-plastic pressure-carrying medium at room tempera...A novel forming method of nickel based super-alloy thin-walled part with variable diameter sections was proposed by using inner and outer pressure with the visco-elasto-plastic pressure-carrying medium at room temperature,and the principle of the method was provided.Experiments and FE simulations were carried out to analyze the deformation characteristics for the part with larger variable diameter ratio(35%).The results show that visco-elasto-plastic pressure-carrying medium can meet the requirements of the room-temperature deformation condition for nickel based super-alloy sheet.The inner and outer pressure forming with the visco-elasto-plastic pressure-carrying medium can meet the requirements of dimensional accuracy for the thin-walled part with variable diameter sections.The thinning of wall-thickness is less than 4%.This method provides a new approach for near-net shape forming of nickel based super-alloy thin-walled parts with variable diameter sections.展开更多
Active control of the local environment of the cold atmospheric plasma(CAP) jet is of great importance in actual applications since the CAP operates in an open atmosphere with the inevitable entrainment of the surroun...Active control of the local environment of the cold atmospheric plasma(CAP) jet is of great importance in actual applications since the CAP operates in an open atmosphere with the inevitable entrainment of the surrounding cold air. In this paper, the solid shielding effects of the cylindrical quartz tubes with different inner diameters on the characteristics of the CAP jets driven by a radio-frequency(RF) power supply are studied experimentally. The experimental results show that the total length of the shielded plasma jet can be increased significantly by an appropriate combination of the quartz tube inner diameter and that of the plasma generator nozzle exit with other parameters being unchanged. This phenomenon may be qualitatively attributed to the loss of diffusion of the charged particles in the radial direction under different inner diameters of the quartz tubes. Compared with the plasma free jet, the plasma shielding jet is produced with optimized parameters including longer plasma jet length, higher concentrations of chemically reactive species, higher rotational, vibrational, and electron excitation temperatures when the inner diameters of the solid shielding tube and the generator nozzle exit are the same. A maximum plasma jet length of 52.0 cm is obtained in contrast to that of 5.0 cm of the plasma free jet in this study. The experimental results indicate that the solid shielding effect provides a new method for the active control of the local environment of the RF-CAP jet operating in an open atmosphere.展开更多
Long steel piles with large diameters have been more widely used in the field of ocean engineering. Owing to the pile with a large diameter, soil plug development during pile driving has great influences on pile drive...Long steel piles with large diameters have been more widely used in the field of ocean engineering. Owing to the pile with a large diameter, soil plug development during pile driving has great influences on pile driveability and bearing capacity. The response of soil plug developed inside the open-ended pipe pile during the dynamic condition of pile-driving is different from the response under the static condition of loading during service. This paper addresses the former aspect. A numerical procedure for soil plug effect prediction and pile driveabihty analysis is proposed and described. By taking into consideration of the pile dimension effect on side and tip resistance, this approach introduces a dimensional coefficient to the conventional static eqnihbrium equations for the plug differential unit and proposes an improved static equity method for the plug effect prediction. At the same time, this approach introduces a simplified model by use of one-dimensional stress wave equation to simulate the interaction between soil plug and pile inner wall. The proposed approach has been applied in practical engineering analyses. Results show that the calculated plug effect and pile driveabihty based on the proposed approach agree well with the observed data.展开更多
Nickel-based superalloys are widely employed in modern aircraft engines because of their excellent material characteristics, particularly in the fabrication of film cooling holes. However, the high machining requireme...Nickel-based superalloys are widely employed in modern aircraft engines because of their excellent material characteristics, particularly in the fabrication of film cooling holes. However, the high machining requirement of a large number of film cooling holes can be extremely challenging. The hybrid machining technique of tube electrode high-speed electrochemical discharge drilling (TEHECDD) has been considered as a promising method for the production of film cooling holes. Compared with any single machining process, this hybrid technique requires the removal of more complex machining by-products, including debris produced in the electrical discharge machining process and hydroxide and bubbles generated in the electrochemical machining process. These by-products significantly affect the machining efficiency and surface quality of the machined products. In this study, tube electrodes in different inner diameters are designed and fabricated, and the effects of inner diameter on the machining efficiency and surface quality of TEHECDD are investigated. The results show that larger inner diameters could effectively improve the flushing condition and facilitate the removal of machining by-products. Therefore, higher material removal efficiency, surface quality, and electrode wear rate could be achieved by increasing the inner diameter of the tube electrode. (C) 2015 The Authors. Production and hosting by Elsevier Ltd. on behalf of Chinese Society of Aeronautics and Astronautics.展开更多
目的:分析超声检测下腔静脉(IVC)和锁骨下静脉(SCV)内径变异在预测全麻诱导后低血压(PIH)中的价值。方法:回顾性选取2021年5月—2023年5月在咸宁市第一人民医院行全麻手术的204例患者作为研究对象,根据是否发生PIH将其分为研究组(发生PI...目的:分析超声检测下腔静脉(IVC)和锁骨下静脉(SCV)内径变异在预测全麻诱导后低血压(PIH)中的价值。方法:回顾性选取2021年5月—2023年5月在咸宁市第一人民医院行全麻手术的204例患者作为研究对象,根据是否发生PIH将其分为研究组(发生PIH,86例)和对照组(未发生PIH,118例)。对两组患者的基础资料、麻醉诱导前血压、麻醉诱导药物用量进行对比。比较IVC内径的最大值(IVCmax)和最小值(IVCmin)、SCV内径的最大值(SCVmax)和最小值(SCVmin),并计算IVC塌陷指数(IVCCI)和SCV塌陷指数(SCVCI)。采用受试者工作特征(ROC)曲线分析IVC、SCV内径及变异对全麻PIH的预测价值。结果:两组基础资料、麻醉诱导前血压指标和麻醉诱导药物用量比较,差异均无统计学意义(P>0.05)。研究组IVCmax、IVCmin、SCVmax、SCVmin水平均低于对照组,IVCCI、SCVCI水平均高于对照组,差异均有统计学意义(P<0.05)。受试者操作特征(ROC)曲线分析结果显示,麻醉诱导前IVCmax、IVCmin、SCVmax、SCVmin、IVCCI、SCVCI水平预测PIH的ROC曲线下面积(area under curve,AUC)分别为0.674、0.675、0.618、0.707、0.895、0.905,其中,SCVCI的AUC和cut-off值下的敏感度均为最高,分别为0.905、65.12%。结论:全麻PIH患者可表现为IVC和SCV内径缩小及IVCCI、SCVCI等内径变异指标的增高,采用血管超声技术检测上述变异指标可辅助预测PIH风险。展开更多
文摘A novel forming method of nickel based super-alloy thin-walled part with variable diameter sections was proposed by using inner and outer pressure with the visco-elasto-plastic pressure-carrying medium at room temperature,and the principle of the method was provided.Experiments and FE simulations were carried out to analyze the deformation characteristics for the part with larger variable diameter ratio(35%).The results show that visco-elasto-plastic pressure-carrying medium can meet the requirements of the room-temperature deformation condition for nickel based super-alloy sheet.The inner and outer pressure forming with the visco-elasto-plastic pressure-carrying medium can meet the requirements of dimensional accuracy for the thin-walled part with variable diameter sections.The thinning of wall-thickness is less than 4%.This method provides a new approach for near-net shape forming of nickel based super-alloy thin-walled parts with variable diameter sections.
基金supported by National Natural Science Foundation of China (Nos. 11475103, 21627812, 51578309)the National Key Research and Development Program of China (No. 2016YFD0102106)the Tsinghua University Initiative Scientific Program (No. 20161080108)
文摘Active control of the local environment of the cold atmospheric plasma(CAP) jet is of great importance in actual applications since the CAP operates in an open atmosphere with the inevitable entrainment of the surrounding cold air. In this paper, the solid shielding effects of the cylindrical quartz tubes with different inner diameters on the characteristics of the CAP jets driven by a radio-frequency(RF) power supply are studied experimentally. The experimental results show that the total length of the shielded plasma jet can be increased significantly by an appropriate combination of the quartz tube inner diameter and that of the plasma generator nozzle exit with other parameters being unchanged. This phenomenon may be qualitatively attributed to the loss of diffusion of the charged particles in the radial direction under different inner diameters of the quartz tubes. Compared with the plasma free jet, the plasma shielding jet is produced with optimized parameters including longer plasma jet length, higher concentrations of chemically reactive species, higher rotational, vibrational, and electron excitation temperatures when the inner diameters of the solid shielding tube and the generator nozzle exit are the same. A maximum plasma jet length of 52.0 cm is obtained in contrast to that of 5.0 cm of the plasma free jet in this study. The experimental results indicate that the solid shielding effect provides a new method for the active control of the local environment of the RF-CAP jet operating in an open atmosphere.
基金supported by the National Natural Science Foundation of China (Grant No.50309009)the National High Technology Research and Development Program of China(863 Program,Grant No.2004AA616100)
文摘Long steel piles with large diameters have been more widely used in the field of ocean engineering. Owing to the pile with a large diameter, soil plug development during pile driving has great influences on pile driveability and bearing capacity. The response of soil plug developed inside the open-ended pipe pile during the dynamic condition of pile-driving is different from the response under the static condition of loading during service. This paper addresses the former aspect. A numerical procedure for soil plug effect prediction and pile driveabihty analysis is proposed and described. By taking into consideration of the pile dimension effect on side and tip resistance, this approach introduces a dimensional coefficient to the conventional static eqnihbrium equations for the plug differential unit and proposes an improved static equity method for the plug effect prediction. At the same time, this approach introduces a simplified model by use of one-dimensional stress wave equation to simulate the interaction between soil plug and pile inner wall. The proposed approach has been applied in practical engineering analyses. Results show that the calculated plug effect and pile driveabihty based on the proposed approach agree well with the observed data.
基金the financial support provided by the National Natural Science Foundation of China (No. 51475237)the National High-Tech Research and Development Program of China (No. 2013AA040101)+1 种基金the Program for New Century Excellent Talents in University (No. NCET-12-0627) of Chinathe Funding of Jiangsu Innovation Program for Graduate Education (No. KYLX_0232) of China
文摘Nickel-based superalloys are widely employed in modern aircraft engines because of their excellent material characteristics, particularly in the fabrication of film cooling holes. However, the high machining requirement of a large number of film cooling holes can be extremely challenging. The hybrid machining technique of tube electrode high-speed electrochemical discharge drilling (TEHECDD) has been considered as a promising method for the production of film cooling holes. Compared with any single machining process, this hybrid technique requires the removal of more complex machining by-products, including debris produced in the electrical discharge machining process and hydroxide and bubbles generated in the electrochemical machining process. These by-products significantly affect the machining efficiency and surface quality of the machined products. In this study, tube electrodes in different inner diameters are designed and fabricated, and the effects of inner diameter on the machining efficiency and surface quality of TEHECDD are investigated. The results show that larger inner diameters could effectively improve the flushing condition and facilitate the removal of machining by-products. Therefore, higher material removal efficiency, surface quality, and electrode wear rate could be achieved by increasing the inner diameter of the tube electrode. (C) 2015 The Authors. Production and hosting by Elsevier Ltd. on behalf of Chinese Society of Aeronautics and Astronautics.
文摘目的:分析超声检测下腔静脉(IVC)和锁骨下静脉(SCV)内径变异在预测全麻诱导后低血压(PIH)中的价值。方法:回顾性选取2021年5月—2023年5月在咸宁市第一人民医院行全麻手术的204例患者作为研究对象,根据是否发生PIH将其分为研究组(发生PIH,86例)和对照组(未发生PIH,118例)。对两组患者的基础资料、麻醉诱导前血压、麻醉诱导药物用量进行对比。比较IVC内径的最大值(IVCmax)和最小值(IVCmin)、SCV内径的最大值(SCVmax)和最小值(SCVmin),并计算IVC塌陷指数(IVCCI)和SCV塌陷指数(SCVCI)。采用受试者工作特征(ROC)曲线分析IVC、SCV内径及变异对全麻PIH的预测价值。结果:两组基础资料、麻醉诱导前血压指标和麻醉诱导药物用量比较,差异均无统计学意义(P>0.05)。研究组IVCmax、IVCmin、SCVmax、SCVmin水平均低于对照组,IVCCI、SCVCI水平均高于对照组,差异均有统计学意义(P<0.05)。受试者操作特征(ROC)曲线分析结果显示,麻醉诱导前IVCmax、IVCmin、SCVmax、SCVmin、IVCCI、SCVCI水平预测PIH的ROC曲线下面积(area under curve,AUC)分别为0.674、0.675、0.618、0.707、0.895、0.905,其中,SCVCI的AUC和cut-off值下的敏感度均为最高,分别为0.905、65.12%。结论:全麻PIH患者可表现为IVC和SCV内径缩小及IVCCI、SCVCI等内径变异指标的增高,采用血管超声技术检测上述变异指标可辅助预测PIH风险。
