The combined effects of isothermal annealing and pre-compression on the mechanical properties of Cu36Zr48Al8Ag8 bulk metallic glass （BMG） were investigated. The as-cast specimens were first annealed at 743 K for 10 ...The combined effects of isothermal annealing and pre-compression on the mechanical properties of Cu36Zr48Al8Ag8 bulk metallic glass （BMG） were investigated. The as-cast specimens were first annealed at 743 K for 10 min, and then pre-compressed under 800 MPa for 1, 3, 5 and 10 h, respectively. The results indicated that annealing resulted in the formation of nanocrystals with a diameter of -10 nm in the amorphous matrix and a drastic decrease of the free volume, leading to complete loss of the plasticity of the BMG. Applying pre-compression under a stress of 800 MPa for a proper duration （5 h） resumed part of the lost free volume in the BMG matrix and therefore partially recovered the plasticity. A very long period of pre-compression （10 h） decreased the free volume again, which was caused by the excessive crystal growth.展开更多
In the present work the electronic density of states of liquid,viz.,Zintli alloys,have been studied only at the composition of their maximum resistivity to have an elementary idea about the behaviors of the alloys wit...In the present work the electronic density of states of liquid,viz.,Zintli alloys,have been studied only at the composition of their maximum resistivity to have an elementary idea about the behaviors of the alloys with respect to nearly free electron behavior.The study reveals that the anomalous electronic behavior of liquid Li-Pb,Na-Pb,Li-Sn,and Na-Sn can be attributed to the preferential ordering of unlike atoms.展开更多
The influence of free-end torsion on compressive behavior of an extruded AZ31 rod at various temperatures was studied.Pre-torsion generates a high density of dislocations and a large number of{1012}twins in the matrix...The influence of free-end torsion on compressive behavior of an extruded AZ31 rod at various temperatures was studied.Pre-torsion generates a high density of dislocations and a large number of{1012}twins in the matrix,which can largely enhance the compressive yield strength at RT and 100℃.However,with increasing temperature,hardening effect via pre-torsion gradually decreases.When the compressive temperature reaches 300℃,pre-torsion reduces the compressive yield strength.Moreover,initial dislocations and twins via torsion help to refine the sub-structure and accelerate the continuous dynamic recrystallization during compression at 200℃.Thus,twisted sample exhibits more rapid flow softening behavior than the as-extruded sample at 200℃.When compressed at 300℃,the twins and dislocations via torsion were largely eliminated during the holding time,and the discontinuous dynamic recrystallization was enhanced.It is found that the compression curves of twisted sample and as-extruded sample tended to be coincident at 300℃.Related mechanisms were discussed in detail.展开更多
Since the 2008 international financial crisis, international political and economic disorder has become obvious. Major reasons are the decline of US-led Western developed economies' global influence; US and other ...Since the 2008 international financial crisis, international political and economic disorder has become obvious. Major reasons are the decline of US-led Western developed economies' global influence; US and other Western countries inaction or ineffective actions; power diffusion allowing non-state actors to intervene; a global governance short of needed rules; and mainstream economic theory's overemphasis on market roles. International disorder is a long-term process posing a potential threat to China's national interests. The situation challenges China to create an international economic and trade order, thereby shaping itself as prophet of global free trade, shaper of international economic and trade rules, and trendsetter for globalization.展开更多
A Smith-Purcell （SP） free electron laser （FEL） ,composed of a metallic diffraction flat grating,an open cylindrical mirror cavity and a relativistic sheet electron beam with moderate energy, is presented. The char...A Smith-Purcell （SP） free electron laser （FEL） ,composed of a metallic diffraction flat grating,an open cylindrical mirror cavity and a relativistic sheet electron beam with moderate energy, is presented. The characteristics of this device are studied by theoretical analysis,experimental measurements and particle-in-cell （PIO） simulation method. Results indicate that the coherent radiation with an output peak power up to 50 MW at millimeter wavelengths can be generated by using relativistic electron beam of moderate energy.展开更多
Ashcroft＇s local empty core （EMC） model pseudopotential in the second-order perturbation theory is used to study the electron dispersion relation, the Fermi energy, and deviation in the Fermi energy from free elect...Ashcroft＇s local empty core （EMC） model pseudopotential in the second-order perturbation theory is used to study the electron dispersion relation, the Fermi energy, and deviation in the Fermi energy from free electron value for the liquid alkali metals and their equiatomic binary alloys for the first time. In the present computation, the use of pseudo-alloy-atom model （PAA） is proposed and found successful. The influence of the six different forms of the local field correction functions proposed by Hartree （H）, Vashishta Singwi （VS）, Taylor （T）, lehimaru-Utsumi （IU）, Farid et al. （F）, and Sarkar et al. （S） on the aforesaid electronic properties is examined explicitly, which reflects the varying effects of screening. The depth of the negative hump in the electron dispersion of liquid alkalis decreases in the order Li --→ K, except for Rb and Cs, it increases. The results of alloys are in predictive nature.展开更多
A novel continuum robot for colonoscopy is presented.The aim is to develop a robot for colonoscopywhich can provide the same functions as conventional colonoscope,but much less pain and discomfort forpatient.In contra...A novel continuum robot for colonoscopy is presented.The aim is to develop a robot for colonoscopywhich can provide the same functions as conventional colonoscope,but much less pain and discomfort forpatient.In contrast to traditional rigid-link robot,the robot features a continuous backbone with nojoints.The continuum robot is 300 mm in total length and 12 mm in diameter that is less than the averagediameter of human colon(20 mm).The robot has a total of 4 DOF(degrees of freedom)and is actuatedremotely by 6 hybrid step motors through super-elastic NiTi wires.Its shape can be changed with highdexterity,therefore ensuring its adaptability to the tortuous shape of human colon.The mechanical struc-ture,kinematics and DSP-based control system are discussed; prototype experiments are carried out tovalidate the kinematics model and to show the motion performances.展开更多
In this paper we report the rebuilding of liquid metal experimental loop （LMEL） to avoid loop danger in running. In the new loop, We have eliminated the hidden trouble of the inherent safety in the former loop, obta...In this paper we report the rebuilding of liquid metal experimental loop （LMEL） to avoid loop danger in running. In the new loop, We have eliminated the hidden trouble of the inherent safety in the former loop, obtained more stable magnetic field region, upgraded the reliability of the data acquisition and processing. New LMEL can provide the more extensive experiments on MHD effects and their thermal-hydraulics on the liquid metal divertor and the liquid metal blanket.展开更多
Liquid metal free surface flows （films, jets and droplets） are considered as diverter/ limiter system and first wall in fusion reactor, but the knowledge Of liquid metal free surface under a non-uniform magnetic fie...Liquid metal free surface flows （films, jets and droplets） are considered as diverter/ limiter system and first wall in fusion reactor, but the knowledge Of liquid metal free surface under a non-uniform magnetic field is very limited. In this article, the stability of a jet flow under a gradient magnetic field is investigated, and its MHD effects are the top concern. Based on numerical simulation and experimental results, a simplified model is developed to analyze the MHD effects of the jet flow and to explain the reason why it can keep stable under a strong non-uniform magnetic field.展开更多
1,3‐Dienes are a class of easily accessible and versatile feedstock chemicals that can participate in a wide range of reactions to facilitate the synthesis of various valuable allylic compounds.In the past decades,ra...1,3‐Dienes are a class of easily accessible and versatile feedstock chemicals that can participate in a wide range of reactions to facilitate the synthesis of various valuable allylic compounds.In the past decades,radical methodology has emerged as a powerful tool for organic synthesis by virtue of the fact that diverse highly reactive radical species can usually be generated under mild,neutral and controlled conditions,and allow for rapid generation of molecular complexity.In this review,we critically illustrate the recent advances in the field of radical‐mediated transformations of 1,3‐dienes based on the different radical precursors and working modes.Wherever possible,particular emphasis is also put on the related mechanistic studies and synthetic applications.展开更多
The liquid metal free surface innovation concept have been considered as liquid metal devices of divertor/limiter and tile of first wall in fusion device because it can withstand over 50 MW·m^2 heating load, is e...The liquid metal free surface innovation concept have been considered as liquid metal devices of divertor/limiter and tile of first wall in fusion device because it can withstand over 50 MW·m^2 heating load, is easily renewed by circulation and many overcome neutron irradiation damage life time limit. There are three types of free surface in the innovation concept as film, curtain （jets or drops） and capillary. The free surface jet is played a more attention at present. But it is no so clear and only a few available data that their magneto-hydrodynamics （MHD） instabilities, interaction with plasma and exclusion of the particles （ions, Alpha particles and so on） from liquid metal, in despite of many liquid metal free surface facilities built and operated especially in US in last two years. Recently, some primary results are carried out at LMEL facility at Southwestern Institute of Physics.展开更多
The paper aims to investigate the current account imbalances in the context of an overview of macroeconomic fundamentals after the liberalization process in Turkey. Two main questions discussed here are： （1） What i...The paper aims to investigate the current account imbalances in the context of an overview of macroeconomic fundamentals after the liberalization process in Turkey. Two main questions discussed here are： （1） What is the link between liberalization and current account imbalances; （2） What kind of mechanisms ensured this link to become a vicious circle. The period after 1989, Turkey was characterized by significant fluctuations in macroeconomic activity by the implementation of liberalization policies. Once financial liberalization is adopted, Turkey faced with a new challenge： large current account deficits. On the other hand, foreign capital inflows aggravated a lending boom. Because of excessive risk taken by banks, interest rates began to rise. As mentioned above, the paper studies Turkey＇s liberalization process with a number of indicators that point to a fragility of the external balance： unhealthy structure of financial sector, particularly banking sector, large fiscal imbalances, low savings and investment rates, unstable GDP growth. Domestic structural features combining with macroeconomic policy stance and political factors are examined as well展开更多
Prior researches focus mainly on the relationship between governance structure and earnings quality. Unlike the previous researches, this study attempts to empirically examine the role of surplus free cash flow （SFCF...Prior researches focus mainly on the relationship between governance structure and earnings quality. Unlike the previous researches, this study attempts to empirically examine the role of surplus free cash flow （SFCF） as a moderator in the relationship with the new requirements of Malaysian code on corporate governance （MCCG）. By using the estimated generalized least square （EGLS） upon a sample of Malaysian firms, the results show that firms with an independent chairman experience persistent earnings numbers. The results also demonstrate that the current earnings of finns with small boards and independent audit committee members are more likely to persist in the future, when SFCF is high. However, in contradiction to the authors＇ expectation is the significant, but negative and interactive effect of current earnings and audit committee competence on earnings persistence. The findings, though disappointing, suggest investors to consider both the governance structure and free cash flow （FCF） agency problem when evaluating the sustainability of firms＇ earnings. They also call for more independent directors, effective meetings, and more competent audit committee members.展开更多
基金Projects(51328101,51301142)supported by the National Natural Science Foundation of ChinaProject(2015JJ2206)supported by Hunan Provincial Natural Science Foundation of China
文摘The combined effects of isothermal annealing and pre-compression on the mechanical properties of Cu36Zr48Al8Ag8 bulk metallic glass （BMG） were investigated. The as-cast specimens were first annealed at 743 K for 10 min, and then pre-compressed under 800 MPa for 1, 3, 5 and 10 h, respectively. The results indicated that annealing resulted in the formation of nanocrystals with a diameter of -10 nm in the amorphous matrix and a drastic decrease of the free volume, leading to complete loss of the plasticity of the BMG. Applying pre-compression under a stress of 800 MPa for a proper duration （5 h） resumed part of the lost free volume in the BMG matrix and therefore partially recovered the plasticity. A very long period of pre-compression （10 h） decreased the free volume again, which was caused by the excessive crystal growth.
文摘In the present work the electronic density of states of liquid,viz.,Zintli alloys,have been studied only at the composition of their maximum resistivity to have an elementary idea about the behaviors of the alloys with respect to nearly free electron behavior.The study reveals that the anomalous electronic behavior of liquid Li-Pb,Na-Pb,Li-Sn,and Na-Sn can be attributed to the preferential ordering of unlike atoms.
基金the National Natural Science Foundation of China(No.51601154)Southwest University Undergraduate Innovation Project(No.zsm2021026).
文摘The influence of free-end torsion on compressive behavior of an extruded AZ31 rod at various temperatures was studied.Pre-torsion generates a high density of dislocations and a large number of{1012}twins in the matrix,which can largely enhance the compressive yield strength at RT and 100℃.However,with increasing temperature,hardening effect via pre-torsion gradually decreases.When the compressive temperature reaches 300℃,pre-torsion reduces the compressive yield strength.Moreover,initial dislocations and twins via torsion help to refine the sub-structure and accelerate the continuous dynamic recrystallization during compression at 200℃.Thus,twisted sample exhibits more rapid flow softening behavior than the as-extruded sample at 200℃.When compressed at 300℃,the twins and dislocations via torsion were largely eliminated during the holding time,and the discontinuous dynamic recrystallization was enhanced.It is found that the compression curves of twisted sample and as-extruded sample tended to be coincident at 300℃.Related mechanisms were discussed in detail.
文摘Since the 2008 international financial crisis, international political and economic disorder has become obvious. Major reasons are the decline of US-led Western developed economies' global influence; US and other Western countries inaction or ineffective actions; power diffusion allowing non-state actors to intervene; a global governance short of needed rules; and mainstream economic theory's overemphasis on market roles. International disorder is a long-term process posing a potential threat to China's national interests. The situation challenges China to create an international economic and trade order, thereby shaping itself as prophet of global free trade, shaper of international economic and trade rules, and trendsetter for globalization.
文摘A Smith-Purcell （SP） free electron laser （FEL） ,composed of a metallic diffraction flat grating,an open cylindrical mirror cavity and a relativistic sheet electron beam with moderate energy, is presented. The characteristics of this device are studied by theoretical analysis,experimental measurements and particle-in-cell （PIO） simulation method. Results indicate that the coherent radiation with an output peak power up to 50 MW at millimeter wavelengths can be generated by using relativistic electron beam of moderate energy.
文摘Ashcroft＇s local empty core （EMC） model pseudopotential in the second-order perturbation theory is used to study the electron dispersion relation, the Fermi energy, and deviation in the Fermi energy from free electron value for the liquid alkali metals and their equiatomic binary alloys for the first time. In the present computation, the use of pseudo-alloy-atom model （PAA） is proposed and found successful. The influence of the six different forms of the local field correction functions proposed by Hartree （H）, Vashishta Singwi （VS）, Taylor （T）, lehimaru-Utsumi （IU）, Farid et al. （F）, and Sarkar et al. （S） on the aforesaid electronic properties is examined explicitly, which reflects the varying effects of screening. The depth of the negative hump in the electron dispersion of liquid alkalis decreases in the order Li --→ K, except for Rb and Cs, it increases. The results of alloys are in predictive nature.
基金Supported by the High Technology Research Development Programme of China (No. 2007AA042105)the Program for Changjiang Scholars and Innovative Research Team in University (IRT0423)
文摘A novel continuum robot for colonoscopy is presented.The aim is to develop a robot for colonoscopywhich can provide the same functions as conventional colonoscope,but much less pain and discomfort forpatient.In contrast to traditional rigid-link robot,the robot features a continuous backbone with nojoints.The continuum robot is 300 mm in total length and 12 mm in diameter that is less than the averagediameter of human colon(20 mm).The robot has a total of 4 DOF(degrees of freedom)and is actuatedremotely by 6 hybrid step motors through super-elastic NiTi wires.Its shape can be changed with highdexterity,therefore ensuring its adaptability to the tortuous shape of human colon.The mechanical struc-ture,kinematics and DSP-based control system are discussed; prototype experiments are carried out tovalidate the kinematics model and to show the motion performances.
文摘In this paper we report the rebuilding of liquid metal experimental loop （LMEL） to avoid loop danger in running. In the new loop, We have eliminated the hidden trouble of the inherent safety in the former loop, obtained more stable magnetic field region, upgraded the reliability of the data acquisition and processing. New LMEL can provide the more extensive experiments on MHD effects and their thermal-hydraulics on the liquid metal divertor and the liquid metal blanket.
基金Supported by National Natural Science Foundation of China（B10275019）
文摘Liquid metal free surface flows （films, jets and droplets） are considered as diverter/ limiter system and first wall in fusion reactor, but the knowledge Of liquid metal free surface under a non-uniform magnetic field is very limited. In this article, the stability of a jet flow under a gradient magnetic field is investigated, and its MHD effects are the top concern. Based on numerical simulation and experimental results, a simplified model is developed to analyze the MHD effects of the jet flow and to explain the reason why it can keep stable under a strong non-uniform magnetic field.
文摘1,3‐Dienes are a class of easily accessible and versatile feedstock chemicals that can participate in a wide range of reactions to facilitate the synthesis of various valuable allylic compounds.In the past decades,radical methodology has emerged as a powerful tool for organic synthesis by virtue of the fact that diverse highly reactive radical species can usually be generated under mild,neutral and controlled conditions,and allow for rapid generation of molecular complexity.In this review,we critically illustrate the recent advances in the field of radical‐mediated transformations of 1,3‐dienes based on the different radical precursors and working modes.Wherever possible,particular emphasis is also put on the related mechanistic studies and synthetic applications.
文摘The liquid metal free surface innovation concept have been considered as liquid metal devices of divertor/limiter and tile of first wall in fusion device because it can withstand over 50 MW·m^2 heating load, is easily renewed by circulation and many overcome neutron irradiation damage life time limit. There are three types of free surface in the innovation concept as film, curtain （jets or drops） and capillary. The free surface jet is played a more attention at present. But it is no so clear and only a few available data that their magneto-hydrodynamics （MHD） instabilities, interaction with plasma and exclusion of the particles （ions, Alpha particles and so on） from liquid metal, in despite of many liquid metal free surface facilities built and operated especially in US in last two years. Recently, some primary results are carried out at LMEL facility at Southwestern Institute of Physics.
文摘The paper aims to investigate the current account imbalances in the context of an overview of macroeconomic fundamentals after the liberalization process in Turkey. Two main questions discussed here are： （1） What is the link between liberalization and current account imbalances; （2） What kind of mechanisms ensured this link to become a vicious circle. The period after 1989, Turkey was characterized by significant fluctuations in macroeconomic activity by the implementation of liberalization policies. Once financial liberalization is adopted, Turkey faced with a new challenge： large current account deficits. On the other hand, foreign capital inflows aggravated a lending boom. Because of excessive risk taken by banks, interest rates began to rise. As mentioned above, the paper studies Turkey＇s liberalization process with a number of indicators that point to a fragility of the external balance： unhealthy structure of financial sector, particularly banking sector, large fiscal imbalances, low savings and investment rates, unstable GDP growth. Domestic structural features combining with macroeconomic policy stance and political factors are examined as well
文摘Prior researches focus mainly on the relationship between governance structure and earnings quality. Unlike the previous researches, this study attempts to empirically examine the role of surplus free cash flow （SFCF） as a moderator in the relationship with the new requirements of Malaysian code on corporate governance （MCCG）. By using the estimated generalized least square （EGLS） upon a sample of Malaysian firms, the results show that firms with an independent chairman experience persistent earnings numbers. The results also demonstrate that the current earnings of finns with small boards and independent audit committee members are more likely to persist in the future, when SFCF is high. However, in contradiction to the authors＇ expectation is the significant, but negative and interactive effect of current earnings and audit committee competence on earnings persistence. The findings, though disappointing, suggest investors to consider both the governance structure and free cash flow （FCF） agency problem when evaluating the sustainability of firms＇ earnings. They also call for more independent directors, effective meetings, and more competent audit committee members.
