“边界工作”是研究新闻从业者如何通过特定的话语策略来维护自身职业地位与合法性的经典理论框架。然而,ChatGPT和Sora等技术的开发应用表明生成式人工智能已具备多模态内容生产能力,套用“边界工作”理论中的扩张(expansion)、驱逐(ex...“边界工作”是研究新闻从业者如何通过特定的话语策略来维护自身职业地位与合法性的经典理论框架。然而,ChatGPT和Sora等技术的开发应用表明生成式人工智能已具备多模态内容生产能力,套用“边界工作”理论中的扩张(expansion)、驱逐(expulsion)和自主性保护(protection of autonomy)三条阐释维度已不足以说明生成式人工智能参与新闻生产的种种实践进路。受布尔迪厄“场域”理论启发,哥伦比亚大学教授伊亚尔(Gil Eyal)提出基于关系视角的“边界域”(Boundary zone)理论。本文认为,新闻“边界域”为毗邻新闻业的其他社会场域中的行动者提供了活动的机会空间,技术行动者和职业行动者获得平等的实践身份,新的社会场域由此得以诞生。媒体主导的新闻场域和科技公司主导的技术场域之间的“边界域”成为未来新闻实践的主体网络。展开更多
To examine the influence of grain boundary engineering(GBE)on the work hardening behavior,the tensile tests were carried out on the non-GBE and GBE AL6XN super-austenitic stainless steel(ASS)samples with a comparable ...To examine the influence of grain boundary engineering(GBE)on the work hardening behavior,the tensile tests were carried out on the non-GBE and GBE AL6XN super-austenitic stainless steel(ASS)samples with a comparable grain size at two strain rates of 10^(-2)s^(-1)and 10^(-4)s^(-1).The evolution of deformation microstructures was revealed by transmission electron microscopy(TEM)and quasi-in situ electron backscatter diffraction(EBSD)observations.The results show that the influence of GBE on the mechanical properties of AL6XN super-ASS is mainly manifested in the change of work hardening behavior.At the early stage of plastic deformation,GBE samples show a slightly lowered work hardening rate,since the special grain boundaries(SBs)of a high fraction induce a higher dislocation free path and a weaker back stress;however,with increasing plastic deformation amount,the work hardening rate of GBE samples gradually surpasses that of non-GBE samples due to the better capacity of maintainable work hardening that is profited from the inhibited dislocation annihilation by SBs.In a word,the enhanced capacity of sustained work hardening effectively postpones the appearance of necking point and thus efficaciously ameliorates the ductility of GBE samples under the premise of little changes in yield strength and ultimate tensile strength.展开更多
This experiment used a parallel array of hot wire probes to simultaneously measure the temperature and velocity fields in the non-isothermal turbulent boundary layer of a rotating straight channel. The Reynolds number...This experiment used a parallel array of hot wire probes to simultaneously measure the temperature and velocity fields in the non-isothermal turbulent boundary layer of a rotating straight channel. The Reynolds numbers are 15,000 and 25,000, respectively. The rotation numbers are 0, 0.07, 0.14, 0.21 and 0.28, respectively. The purpose of this study is to calculate the turbulent Prandtl number in a rotating non-isothermal turbulent boundary layer. Due to the difficulty in measuring local turbulent Prandtl numbers, this study focuses on the average turbulent Prandtl numbers in the logarithmic region instead. Under static conditions, this value is taken as 0.9 normally. This research finds that rotation conditions can affect the turbulent Prandtl number by affecting the properties of velocity and temperature boundary layers. The change range of the turbulent Prandtl number is roughly 0.6–1.1. The influence of the leading side is greater than that of the trailing side, especially at high rotation numbers. This can provide validation and guidance for numerical simulation. Other information within the turbulent boundary layer is also discussed. It is hoped that this study would enhance our understanding of the mechanism of turbulent flow in the turbulent layer at rotating conditions.展开更多
文摘“边界工作”是研究新闻从业者如何通过特定的话语策略来维护自身职业地位与合法性的经典理论框架。然而,ChatGPT和Sora等技术的开发应用表明生成式人工智能已具备多模态内容生产能力,套用“边界工作”理论中的扩张(expansion)、驱逐(expulsion)和自主性保护(protection of autonomy)三条阐释维度已不足以说明生成式人工智能参与新闻生产的种种实践进路。受布尔迪厄“场域”理论启发,哥伦比亚大学教授伊亚尔(Gil Eyal)提出基于关系视角的“边界域”(Boundary zone)理论。本文认为,新闻“边界域”为毗邻新闻业的其他社会场域中的行动者提供了活动的机会空间,技术行动者和职业行动者获得平等的实践身份,新的社会场域由此得以诞生。媒体主导的新闻场域和科技公司主导的技术场域之间的“边界域”成为未来新闻实践的主体网络。
基金financially supported by the National Natural Science Foundation of China(NSFC)under Grant Nos.51871048 and 52171108。
文摘To examine the influence of grain boundary engineering(GBE)on the work hardening behavior,the tensile tests were carried out on the non-GBE and GBE AL6XN super-austenitic stainless steel(ASS)samples with a comparable grain size at two strain rates of 10^(-2)s^(-1)and 10^(-4)s^(-1).The evolution of deformation microstructures was revealed by transmission electron microscopy(TEM)and quasi-in situ electron backscatter diffraction(EBSD)observations.The results show that the influence of GBE on the mechanical properties of AL6XN super-ASS is mainly manifested in the change of work hardening behavior.At the early stage of plastic deformation,GBE samples show a slightly lowered work hardening rate,since the special grain boundaries(SBs)of a high fraction induce a higher dislocation free path and a weaker back stress;however,with increasing plastic deformation amount,the work hardening rate of GBE samples gradually surpasses that of non-GBE samples due to the better capacity of maintainable work hardening that is profited from the inhibited dislocation annihilation by SBs.In a word,the enhanced capacity of sustained work hardening effectively postpones the appearance of necking point and thus efficaciously ameliorates the ductility of GBE samples under the premise of little changes in yield strength and ultimate tensile strength.
基金the National Natural Science Foundation of China(No.51906008,No.51822602)National Science and Technology Major Project(2017-Ⅲ-0003-0027)the Fundamental Research Funds for the Central Universities(No.YWF-20-BJ-J-822).
文摘This experiment used a parallel array of hot wire probes to simultaneously measure the temperature and velocity fields in the non-isothermal turbulent boundary layer of a rotating straight channel. The Reynolds numbers are 15,000 and 25,000, respectively. The rotation numbers are 0, 0.07, 0.14, 0.21 and 0.28, respectively. The purpose of this study is to calculate the turbulent Prandtl number in a rotating non-isothermal turbulent boundary layer. Due to the difficulty in measuring local turbulent Prandtl numbers, this study focuses on the average turbulent Prandtl numbers in the logarithmic region instead. Under static conditions, this value is taken as 0.9 normally. This research finds that rotation conditions can affect the turbulent Prandtl number by affecting the properties of velocity and temperature boundary layers. The change range of the turbulent Prandtl number is roughly 0.6–1.1. The influence of the leading side is greater than that of the trailing side, especially at high rotation numbers. This can provide validation and guidance for numerical simulation. Other information within the turbulent boundary layer is also discussed. It is hoped that this study would enhance our understanding of the mechanism of turbulent flow in the turbulent layer at rotating conditions.
