The so-called 'negative difference effect'(NDE) was often defined by the increasing rate of hydrogen evolution from magnesium(Mg) surface under anodic polarization.In this work,a series of electrochemical test...The so-called 'negative difference effect'(NDE) was often defined by the increasing rate of hydrogen evolution from magnesium(Mg) surface under anodic polarization.In this work,a series of electrochemical tests and microstructure observations were performed to provide an evidence that the NDE of Mg-Li alloys can be retarded by increasing lithium content.Potentiostatic,galvanostatic and potentiodynamic polarization experiments using Mg-xLi(x=4,7.5 and 14 wt%) alloys electrodes indicated that Mg-4 Li alloy maintained the enhancing NDE prior to anodic dissolution as that of conventional Mg alloys.However,the emergence of β-Li phase weakened the NDE of duplex Mg-7.5 Li alloy at a low anodic current density,but it was still enhanced apparently after a high applied anodic value(more than 2 mA/cm^2).The surface observations,including the plane and cross-sectional morphologies,confirmed that the cracked surface film derived from the anodic dissolution resulted in the catalytic activity of NDE for Mg-4 Li and Mg-7.5 Li alloys.Furthermore,the NDE of Mg-14 Li alloy was suppressed obviously after a prior applied anodic polarization,which was attributed to the persistent and integrated surface film which endured a higher level of applied anodic potential and current.展开更多
According to the revised Cailikefu＇s rolling shear force formula, motion path equation of spatial seven-bar path was built, and a mechanical model, with the new structural feature of negative offset, was thus success...According to the revised Cailikefu＇s rolling shear force formula, motion path equation of spatial seven-bar path was built, and a mechanical model, with the new structural feature of negative offset, was thus successfully established for 2 800 mm heavy shear of some iron and steel company. Shear and bar forces of steel plate, before and after the adoption of negative offset structure, were analyzed, as well as horizontal force component of mechanism that influences pure rolling shear and back-wall push force that keeps blade clearance. It was found that the back-wall push force keeps large even at the time that the maximum rolling shear was obtained; meanwhile, back-wall push force is the most approximate to side forces when 60--100 mm of offset was adopted. Both theoretical results and onsite shear quality show that the negative offset plays an important role in ensuring the stability of pure rolling shear and keeping blade clearance constant.展开更多
We study property T for an action α of a discrete group Γ on a unital C~*-algebra A. Our main results improve some well-known results about property T for groups. Moreover, we introduce Hilbert A-module property T a...We study property T for an action α of a discrete group Γ on a unital C~*-algebra A. Our main results improve some well-known results about property T for groups. Moreover, we introduce Hilbert A-module property T and show that the action α has property T if and only if the reduced crossed product ■has Hilbert A-module property T.展开更多
The Ti/Y modified CuO-based negative temperature coefficient （NTC） thermistors, Cu0.988-2yY0.008TiyO （TYCO; y-- 0.01, 0.015, 0.03, 0.05 and 0.07）, were synthesized through a wet-chemical method followed by a tradi...The Ti/Y modified CuO-based negative temperature coefficient （NTC） thermistors, Cu0.988-2yY0.008TiyO （TYCO; y-- 0.01, 0.015, 0.03, 0.05 and 0.07）, were synthesized through a wet-chemical method followed by a traditional ceramic sintering technology. The related phase component and electrical properties were investigated. XRD results show that the TYCO ceramics have a monoclinic structure as that of CuO crystal. The TYCO ceramics can be obtained at the sintering temperature 970℃-990℃, and display the typical NTC characteristic. The NTC thermal-sensitive constants of TYCO thermistors can be adjusted from 1112 to 3700 K by changing the amount of Ti in the TYCO ceramics. The analysis of complex impedance spectra revealed that both the bulk effect and grain boundary effect contribute to the electrical behavior and the NTC effect. Both the band conduction and electron-hopping models are proposed for the conduction mechanisms in the TYCO thermistors.展开更多
A novel material of ZrMnMo3012 with negative thermal expansion is presented. The phase transition temperature and coemcient of thermal expansion （CTE） are investigated by temperature-dependent x-ray diffraction and ...A novel material of ZrMnMo3012 with negative thermal expansion is presented. The phase transition temperature and coemcient of thermal expansion （CTE） are investigated by temperature-dependent x-ray diffraction and Raman spectra. It is shown that ZrMnMo3012 adopts monoclinic structure with space group P21/a （No. 14） from 298 to 358K and transforms to orthorhombic with space group Pnma （No. 62） above 363K. The linear CTE obtained from the results of XRD refinement is -2.80 × 10-6 K-1 from 363 to 873 K. The CTE of the bulk cylinder ceramic measured by a thermal dilatometer is -4.7× 10-6 K-1 from 373 to 773K approximatively.展开更多
基金supported financially by the National Key Research and Development Program of China (Nos. 2017YFB0702001 and 2016YFB0301105)the National Natural Science Foundation of China Projects (Nos. 51901047,51871211 and51701129)+5 种基金the Doctor Startup Fund of Natural Science Foundation Program of Liaoning Province (No. 2019-BS-200)the Strategic New Industry Development Special Foundation of Shenzhen (No. JCYJ20170306141749970)the Funds of International Joint Laboratory for Light Alloys, the Liaoning Bai Qian Wan Talents Programthe Domain Foundation of Equipment Advance Research of 13th Five-year Plan (No. 61409220118)the Innovation Fund of Institute of Metal Research (IMR), Chinese Academy of Sciences (CAS)the National Basic Research Program of China (No. 2013CB632205)。
文摘The so-called 'negative difference effect'(NDE) was often defined by the increasing rate of hydrogen evolution from magnesium(Mg) surface under anodic polarization.In this work,a series of electrochemical tests and microstructure observations were performed to provide an evidence that the NDE of Mg-Li alloys can be retarded by increasing lithium content.Potentiostatic,galvanostatic and potentiodynamic polarization experiments using Mg-xLi(x=4,7.5 and 14 wt%) alloys electrodes indicated that Mg-4 Li alloy maintained the enhancing NDE prior to anodic dissolution as that of conventional Mg alloys.However,the emergence of β-Li phase weakened the NDE of duplex Mg-7.5 Li alloy at a low anodic current density,but it was still enhanced apparently after a high applied anodic value(more than 2 mA/cm^2).The surface observations,including the plane and cross-sectional morphologies,confirmed that the cracked surface film derived from the anodic dissolution resulted in the catalytic activity of NDE for Mg-4 Li and Mg-7.5 Li alloys.Furthermore,the NDE of Mg-14 Li alloy was suppressed obviously after a prior applied anodic polarization,which was attributed to the persistent and integrated surface film which endured a higher level of applied anodic potential and current.
基金Item Sponsored by National Natural Science Foundation of China (50575155)National Tenth-Five Key Technologies Research and Development Program(ZZ01-13A-03-03-04)Shanxi Provincial Key Technologies Research and Development Program of China (2006031174)
文摘According to the revised Cailikefu＇s rolling shear force formula, motion path equation of spatial seven-bar path was built, and a mechanical model, with the new structural feature of negative offset, was thus successfully established for 2 800 mm heavy shear of some iron and steel company. Shear and bar forces of steel plate, before and after the adoption of negative offset structure, were analyzed, as well as horizontal force component of mechanism that influences pure rolling shear and back-wall push force that keeps blade clearance. It was found that the back-wall push force keeps large even at the time that the maximum rolling shear was obtained; meanwhile, back-wall push force is the most approximate to side forces when 60--100 mm of offset was adopted. Both theoretical results and onsite shear quality show that the negative offset plays an important role in ensuring the stability of pure rolling shear and keeping blade clearance constant.
基金Supported by the National Natural Science Foundation of China(Grant Nos.11871303,11671133 and 11701327)Natural Science Foundation of Shandong Province(Grant No.ZR2019MA039)+1 种基金the China Postdoctoral Science Foundation(Grant No.2018M642633)a Project of Shandong Province Higher Educational Science and Technology Program(Grant No.J18KA238)
文摘We study property T for an action α of a discrete group Γ on a unital C~*-algebra A. Our main results improve some well-known results about property T for groups. Moreover, we introduce Hilbert A-module property T and show that the action α has property T if and only if the reduced crossed product ■has Hilbert A-module property T.
文摘The Ti/Y modified CuO-based negative temperature coefficient （NTC） thermistors, Cu0.988-2yY0.008TiyO （TYCO; y-- 0.01, 0.015, 0.03, 0.05 and 0.07）, were synthesized through a wet-chemical method followed by a traditional ceramic sintering technology. The related phase component and electrical properties were investigated. XRD results show that the TYCO ceramics have a monoclinic structure as that of CuO crystal. The TYCO ceramics can be obtained at the sintering temperature 970℃-990℃, and display the typical NTC characteristic. The NTC thermal-sensitive constants of TYCO thermistors can be adjusted from 1112 to 3700 K by changing the amount of Ti in the TYCO ceramics. The analysis of complex impedance spectra revealed that both the bulk effect and grain boundary effect contribute to the electrical behavior and the NTC effect. Both the band conduction and electron-hopping models are proposed for the conduction mechanisms in the TYCO thermistors.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11574276,51503185 and 51302249the Doctoral Fund of the Ministry of Education of China under Grant No 20114101110003
文摘A novel material of ZrMnMo3012 with negative thermal expansion is presented. The phase transition temperature and coemcient of thermal expansion （CTE） are investigated by temperature-dependent x-ray diffraction and Raman spectra. It is shown that ZrMnMo3012 adopts monoclinic structure with space group P21/a （No. 14） from 298 to 358K and transforms to orthorhombic with space group Pnma （No. 62） above 363K. The linear CTE obtained from the results of XRD refinement is -2.80 × 10-6 K-1 from 363 to 873 K. The CTE of the bulk cylinder ceramic measured by a thermal dilatometer is -4.7× 10-6 K-1 from 373 to 773K approximatively.
