With the pedagogical reformation of College English,the syllabus of College English Test Band 4 has been revised with the purpose of putting emphasis on listening tests so that it can have the positive washback effect...With the pedagogical reformation of College English,the syllabus of College English Test Band 4 has been revised with the purpose of putting emphasis on listening tests so that it can have the positive washback effect on ELT.While language testing is a crucial means to measure the effectiveness of foreign language teaching and learning,this paper will analyze the old and new format of CET Band 4 to see if the new one will promote the development of listening ability and whether it produces the positive washback effect on ELT.展开更多
Numerical investigations of the ＇banding＇ microstructure formation during solidification of Ti-6Al-4 V alloy in the centrifugal casting are conducted using a multi-scale model, which combines the finite difference m...Numerical investigations of the ＇banding＇ microstructure formation during solidification of Ti-6Al-4 V alloy in the centrifugal casting are conducted using a multi-scale model, which combines the finite difference method （FDM） at the macroscale with a cellular automaton （CA） model at the microscale. The macro model is used to simulate the fluid flow and heat transfer throughout the casting. The micro model is used to predict the nucleation and growth of microstructures. With the proposed model, numerical simulations are performed to study the influences of the nucleation density, mould rotation speed, and casting size upon the ＇banding＇ microstructure formation. It is noted that changing the nucleation density has a minor effect on the microstructure formation. The rotation speed promotes the formation of ＇banding＇ microstructure, which is more noticeable for larger size castings. The ＇major mechanism responsible for this ＇banding＇ phenomenon is the spatial variation in cooling rates created by centrifugal force.展开更多
Accurate and elegant diction is undoubtedly an important criterion for the evaluation of a good article. In College English Band 4/6 Writing, it is vital that the candidates attach great importance to the meticulous c...Accurate and elegant diction is undoubtedly an important criterion for the evaluation of a good article. In College English Band 4/6 Writing, it is vital that the candidates attach great importance to the meticulous choice of words, using the advanced and precise vocabulary to replace the primary and general ones. This paper highlights the significance of diamond words in the upgrading of literal and artistic flavor of an article, which directly affects the final grading of the writing. While summarizing and analyzing the problems of candidates in word manipulation and selection in writing, the author offers solution and strategy on how to upgrade the insipid and dull words by means of synonymous substitution and transformation with an aim to enhance the impressiveness and readability of the essay, and ultimately improve band 4/6 writing performance展开更多
The relevance-adaptation theory can be said to be a combination of relevance theory and adaptation theory.It is a kind of cognition of context.Generally speaking,cognition context is a kind of mental cognition,which b...The relevance-adaptation theory can be said to be a combination of relevance theory and adaptation theory.It is a kind of cognition of context.Generally speaking,cognition context is a kind of mental cognition,which belongs to a form of mental structure recognition,relating to the knowledge,understanding and relevance of discourse information in this context.This article mainly elaborates the operation mechanism of relevance and adaptation theory and the comparison of relevance of College English Test Band 4 and 6.This can be used as a reference for relevant academic staff.展开更多
Superior ballistic performance and the lightweight character of Ti alloys are considered as main reasons for their use in armour applications against a broad spectrum of ballistic threats,e.g.bullet,fragment or blast ...Superior ballistic performance and the lightweight character of Ti alloys are considered as main reasons for their use in armour applications against a broad spectrum of ballistic threats,e.g.bullet,fragment or blast impact.Because dynamic loading caused by typical penetrators is characterized by high strain rates,only specific test methods allow a closer investigation of the respective material behaviour.In the present study,quasi-static and dynamic compression tests as well as ballistic tests were conducted on a twophase a+βalloy Ti-6Al-4V(in m%)manufactured by hot-rolling.Post-deformation heat treatments,influencing microstructure and mechanical properties were applied in order to compare three different microstructural configurations:as-rolled,mill-annealed and bimodal.While,on the one hand,ballistic tests were employed for the determination of the ballistic limit velocity v_(50),compression tests,on the other hand,delivered essential input parameters for the application of the Johnson-Cook constitutive model in a finite element simulation of the impact event.The comparison of experimental results to simulation results was supplemented by means of microstructural characterization of tested samples with the focus set on the prevalently observed deformation and damage mechanisms,as for example adiabatic shearing.展开更多
The dynamic fracture behaviors of Ti-6Al-4V alloy at high strain rate loading were investigated systemically through Taylor impact test, over the range of impact velocities from 145 m/s to 306 m/s. The critical impact...The dynamic fracture behaviors of Ti-6Al-4V alloy at high strain rate loading were investigated systemically through Taylor impact test, over the range of impact velocities from 145 m/s to 306 m/s. The critical impact velocity of fracture ranges from 217 m/s to 236 m/s. Smooth surfaces and ductile dimple areas were observed on the fracture surfaces. As the impact velocity reached 260 m/s, the serious melting regions were also observed on the fracture surfaces. Self-organization of cracks emerges when the impact velocity reaches 260 m/s, while some special cracks whose ＂tips＂ are not sharp but arc and smooth, and without any evidence of deformation or adiabatic shear band were also observed on the impact end surfaces. Examination of the sections of these special cracks reveals that the cracks expand along the two maximum shear stress directions respectively, and finally intersect as a tridimensional ＂stagger ridge＂ structure.展开更多
The paper introduces relevance theory and explores the application of relevance theory to CET-4 listening comprehension teaching, especially the teaching of CET-4 listening comprehension in the first section whose tes...The paper introduces relevance theory and explores the application of relevance theory to CET-4 listening comprehension teaching, especially the teaching of CET-4 listening comprehension in the first section whose test format is multiple choice question, simplified as MCQ.展开更多
Ultra-narrow-band phosphors have gained widespread applications in lighting and displays to enhance brightness and improve color saturation.Typical phosphor designs employ UCr_(4)C_(4)-type compounds and designing new...Ultra-narrow-band phosphors have gained widespread applications in lighting and displays to enhance brightness and improve color saturation.Typical phosphor designs employ UCr_(4)C_(4)-type compounds and designing new narrow-band phosphors with high color purity is a major challenge.Here,we explored a Eu^(2+)-doped Ba_(5)GeO_(4)Br_(6)phosphor,showing a narrow-band blue emission(λ_(em)=436 nm) excitation at the near-ultraviolet light with a full width at half maximum of 30.7 nm and high color purity of 96.6%.In addition,attractive cathodoluminescence characteristics were systematically analyzed by varying filament current(30-70 mA) and accelerating voltage(3-7 eV).Robust anti-degradation behavior and color point stability under continuous electron beam bombardment were confirmed.Given its excellent performance in photoluminescence and cathodoluminescence,application in wide color gamut displays appears promising.Using commercial phosphors β-SiAlON:Eu^(2+)and K_(2)SiF6:Mn^(4+)as green and red light co nverte rs respectively,and the title phosphor as the blue light converters,the fabricated w-LED exhibits a wide color gamut of 82% NTSC.展开更多
文摘With the pedagogical reformation of College English,the syllabus of College English Test Band 4 has been revised with the purpose of putting emphasis on listening tests so that it can have the positive washback effect on ELT.While language testing is a crucial means to measure the effectiveness of foreign language teaching and learning,this paper will analyze the old and new format of CET Band 4 to see if the new one will promote the development of listening ability and whether it produces the positive washback effect on ELT.
基金the Science and Technology Department of Hei Longjiang Province (No.GC05A209)the Science and Technology Department of Harbin (No.2005AA5CG046) for financial support.
文摘Numerical investigations of the ＇banding＇ microstructure formation during solidification of Ti-6Al-4 V alloy in the centrifugal casting are conducted using a multi-scale model, which combines the finite difference method （FDM） at the macroscale with a cellular automaton （CA） model at the microscale. The macro model is used to simulate the fluid flow and heat transfer throughout the casting. The micro model is used to predict the nucleation and growth of microstructures. With the proposed model, numerical simulations are performed to study the influences of the nucleation density, mould rotation speed, and casting size upon the ＇banding＇ microstructure formation. It is noted that changing the nucleation density has a minor effect on the microstructure formation. The rotation speed promotes the formation of ＇banding＇ microstructure, which is more noticeable for larger size castings. The ＇major mechanism responsible for this ＇banding＇ phenomenon is the spatial variation in cooling rates created by centrifugal force.
文摘Accurate and elegant diction is undoubtedly an important criterion for the evaluation of a good article. In College English Band 4/6 Writing, it is vital that the candidates attach great importance to the meticulous choice of words, using the advanced and precise vocabulary to replace the primary and general ones. This paper highlights the significance of diamond words in the upgrading of literal and artistic flavor of an article, which directly affects the final grading of the writing. While summarizing and analyzing the problems of candidates in word manipulation and selection in writing, the author offers solution and strategy on how to upgrade the insipid and dull words by means of synonymous substitution and transformation with an aim to enhance the impressiveness and readability of the essay, and ultimately improve band 4/6 writing performance
文摘The relevance-adaptation theory can be said to be a combination of relevance theory and adaptation theory.It is a kind of cognition of context.Generally speaking,cognition context is a kind of mental cognition,which belongs to a form of mental structure recognition,relating to the knowledge,understanding and relevance of discourse information in this context.This article mainly elaborates the operation mechanism of relevance and adaptation theory and the comparison of relevance of College English Test Band 4 and 6.This can be used as a reference for relevant academic staff.
文摘Superior ballistic performance and the lightweight character of Ti alloys are considered as main reasons for their use in armour applications against a broad spectrum of ballistic threats,e.g.bullet,fragment or blast impact.Because dynamic loading caused by typical penetrators is characterized by high strain rates,only specific test methods allow a closer investigation of the respective material behaviour.In the present study,quasi-static and dynamic compression tests as well as ballistic tests were conducted on a twophase a+βalloy Ti-6Al-4V(in m%)manufactured by hot-rolling.Post-deformation heat treatments,influencing microstructure and mechanical properties were applied in order to compare three different microstructural configurations:as-rolled,mill-annealed and bimodal.While,on the one hand,ballistic tests were employed for the determination of the ballistic limit velocity v_(50),compression tests,on the other hand,delivered essential input parameters for the application of the Johnson-Cook constitutive model in a finite element simulation of the impact event.The comparison of experimental results to simulation results was supplemented by means of microstructural characterization of tested samples with the focus set on the prevalently observed deformation and damage mechanisms,as for example adiabatic shearing.
基金Project (51001014) supported by the Young Scientists Fund of the National Natural Science Foundation of China
文摘The dynamic fracture behaviors of Ti-6Al-4V alloy at high strain rate loading were investigated systemically through Taylor impact test, over the range of impact velocities from 145 m/s to 306 m/s. The critical impact velocity of fracture ranges from 217 m/s to 236 m/s. Smooth surfaces and ductile dimple areas were observed on the fracture surfaces. As the impact velocity reached 260 m/s, the serious melting regions were also observed on the fracture surfaces. Self-organization of cracks emerges when the impact velocity reaches 260 m/s, while some special cracks whose ＂tips＂ are not sharp but arc and smooth, and without any evidence of deformation or adiabatic shear band were also observed on the impact end surfaces. Examination of the sections of these special cracks reveals that the cracks expand along the two maximum shear stress directions respectively, and finally intersect as a tridimensional ＂stagger ridge＂ structure.
文摘The paper introduces relevance theory and explores the application of relevance theory to CET-4 listening comprehension teaching, especially the teaching of CET-4 listening comprehension in the first section whose test format is multiple choice question, simplified as MCQ.
基金Project supported by the Natural Science Foundation of Shaanxi Provincial Department of Education,China (21JK0708)the Key Laboratory for Special Function Materials and Structure Design of the Ministry of the Education of Lanzhou University,China (lzujbky-2021-kb06)。
文摘Ultra-narrow-band phosphors have gained widespread applications in lighting and displays to enhance brightness and improve color saturation.Typical phosphor designs employ UCr_(4)C_(4)-type compounds and designing new narrow-band phosphors with high color purity is a major challenge.Here,we explored a Eu^(2+)-doped Ba_(5)GeO_(4)Br_(6)phosphor,showing a narrow-band blue emission(λ_(em)=436 nm) excitation at the near-ultraviolet light with a full width at half maximum of 30.7 nm and high color purity of 96.6%.In addition,attractive cathodoluminescence characteristics were systematically analyzed by varying filament current(30-70 mA) and accelerating voltage(3-7 eV).Robust anti-degradation behavior and color point stability under continuous electron beam bombardment were confirmed.Given its excellent performance in photoluminescence and cathodoluminescence,application in wide color gamut displays appears promising.Using commercial phosphors β-SiAlON:Eu^(2+)and K_(2)SiF6:Mn^(4+)as green and red light co nverte rs respectively,and the title phosphor as the blue light converters,the fabricated w-LED exhibits a wide color gamut of 82% NTSC.
