In near-infrared spectroscopy,the traditional feature band extraction method has certain limitations.Therefore,a band extraction method named the three-step extraction method was proposed.This method combines characte...In near-infrared spectroscopy,the traditional feature band extraction method has certain limitations.Therefore,a band extraction method named the three-step extraction method was proposed.This method combines characteristic absorption bands and correlation coefficients to select characteristic bands corresponding to various spectral forms and then uses stepwise regression to eliminate meaningless variables.Partial least squares regression(PLSR)and extreme learning machine(ELM)models were used to verify the effect of the band extraction method.Results show that the differential transformation of the spectrum can effectively improve the correlation between the spectrum and nickel(Ni)content.Most correlation coefficients were above 0.7 and approximately 20%higher than those of other transformation methods.The model effect established by the feature variable selection method based on comprehensive spectral transformation is only slightly affected by the spectral transformation form.Infive types of spectral transformation,the RPD values of the proposed method were all within the same level.The RPD values of the PLSR model were concentrated between 1.6 and 1.8,and those of the ELM model were between 2.5 and2.9,indicating that this method is beneficial for extracting more complete spectral features.The combination of the three-step extraction method and ELM algorithm can effectively retain important bands associated with the Ni content of the soil.The model based on the spectral band selected by the three-step extraction method has better prediction ability than the other models.The ELM model of the first-order differential transformation has the best prediction accuracy(RP^2=0.923,RPD=3.634).The research results provide some technical support for monitoring heavy metal content spectrum in local soils.展开更多
Distribution of localized damage in shear band can’ t be predicted theoretically based on classical elastoplastic theory. The average damage variable in shear band was considered to be a non-local variable. Based on ...Distribution of localized damage in shear band can’ t be predicted theoretically based on classical elastoplastic theory. The average damage variable in shear band was considered to be a non-local variable. Based on non-local theory, an analytical expression for the localized damage in strain-softening region of shear band in the process of shear band propagation was presented using boundary condition and symmetry of local damage variable, etc. The results show that dynamic shear softening modulus, dynamic shear strength and shear elastic modulus influence the distribution of the localized damage in shear band. Internal length of ductile metal only governs the thickness of shear band. In the strain-softening region of shear band, the local damage variable along shear band’s tangential and normal directions is non-linear and highly non-uniform. The non-uniformities in the normal and tangential directions of shear band stem from the interactions and interplaying among microstructures and the non-uniform distribution of shear stress, respectively. At the tail of the strain-softening region, the maximum value of local damage variable reaches 1. This means that material at this position fractures completely. At the tip of shear band and upper as well as lower boundaries, no damage occurs. Local damage variable increases as dynamic shear softening modulus decreases or shear elastic modulus increases, leading to difficulty in identification or detection of damage for less ductile metal material at higher strain rates.展开更多
Solar-blind ultraviolet （UV） band-pass filter has significant value in many scientific, commercial, and military appli- cations, in which the detection of weak UV signal against a strong background of solar radiatio...Solar-blind ultraviolet （UV） band-pass filter has significant value in many scientific, commercial, and military appli- cations, in which the detection of weak UV signal against a strong background of solar radiation is required. In this work, a solar-blind filter is designed based on the concept of ＂transparent metal＂. The filter consisting of Al/SiO2 multilayers could exhibit a high transmission in the solar-blind wavelength region and a wide stopband extending from near-ultraviolet to infrared wavelength range. The central wavelength, bandwidth, Q factor, and rejection ratio of the passband are numerically studied as a function of individual layer thickness and multilayer period.展开更多
The occurrence of both band-like and atom-like Auger spectra involving valence band electron of d-transition metals is discussed based on the two-step model of the Auger electron emission, i.e.an initial core-hole is ...The occurrence of both band-like and atom-like Auger spectra involving valence band electron of d-transition metals is discussed based on the two-step model of the Auger electron emission, i.e.an initial core-hole is first generated and the Auger transition occurs between the core-hole andthe valence states, The occupied vaIence states relax to screen the core-hole which results in a redistribution of the valence electrons, The electronic states concerned by the Auger transitionare calculated by the FLAPW method. There is a clear relation between band-like and atom-like features of the spectra and the different responses of these metals to the existence of a core-hole.展开更多
A theoretical model of flatband voltage （VFB） of metal/high-k/Si02/Si stack is proposed based on band alignment of entire gate stack, i.e., the VFB is obtained by simultaneously considering band alignments of metal/...A theoretical model of flatband voltage （VFB） of metal/high-k/Si02/Si stack is proposed based on band alignment of entire gate stack, i.e., the VFB is obtained by simultaneously considering band alignments of metal/high-k, high-k/SiO2 and SiO2/Si interfaces, and their interactions. Then the VFB of TiN/HfO2/SiO2/Si stack is experimentally obtained and theoretically investigated by this model. The theoretical calculations are in good agreement with the experimental results. Furthermore, both positive VFB shift of TiN/HfO2/SiO2/Si stack and Fermi level pinning are successfully interpreted and attributed to the dielectric contact induced gap states at TiN/HfO2 and HfO2/SiO2 interfaces.展开更多
Large-area in-situ synthesized TiB2(TiB, Fe2B)—Fe metal-ceramic composite coating has been fabricated on medium carbon steel by laser cladding with the optimal laser parameters and overlapping coefficient. The bondin...Large-area in-situ synthesized TiB2(TiB, Fe2B)—Fe metal-ceramic composite coating has been fabricated on medium carbon steel by laser cladding with the optimal laser parameters and overlapping coefficient. The bonding interfaces between the cladding layer and the matrix and among different tracks are excellent. Microanalysis on the cladding layer shows that the morphology is a little different from each other and the element distribution and the mechanical properties are unanimous in each track while the mechanical property of the cladding layer shows a gradual change from the surface to the matrix. The in-situ separating out thin ceramic phases in the coating contribute to the improving of its properties greatly.展开更多
The coexistent phenomenon of deformed and transformed adiabatic shear bands(ASBs) of ductile metal was analyzed using the JOHNSON-COOK model and gradient-dependent plasticity(GDP).The effects of melting point,density,...The coexistent phenomenon of deformed and transformed adiabatic shear bands(ASBs) of ductile metal was analyzed using the JOHNSON-COOK model and gradient-dependent plasticity(GDP).The effects of melting point,density,heat capacity and work to heat conversion factor were investigated.Higher work to heat conversion factor,lower density,lower heat capacity and higher melting point lead to wider transformed ASB and higher local plastic shear deformation between deformed and transformed ASBs.Higher work to heat conversion factor,lower density,lower heat capacity and lower melting point cause higher local plastic shear deformation in the deformed ASB.Three reasons for the scatter in experimental data on the ASB width were pointed out and the advantages of the work were discussed.If the transformed ASB width is used to back-calculate the internal length parameter in the GDP,undoubtedly,the parameter will be extremely underestimated.展开更多
This paper has theoretically studied the characteristic frequencies of band structures in two-dimensional metallic- dielectric photonic crystals. It is demonstrated that a large filling fraction benefits the existence...This paper has theoretically studied the characteristic frequencies of band structures in two-dimensional metallic- dielectric photonic crystals. It is demonstrated that a large filling fraction benefits the existence of absolute photonic band gap, while a smaller filling fraction benefits an absolute negative refraction band. In addition, it also finds that the relation between the cut-off frequency of E-polarized wave and the filling fraction exceeding 10% is content with a linear increasing function, whose coefficients are exponential to the normalized lattice constant. These investigations have significant implications for tuning the operational frequencies to desired applications and manufacturing photonic crystals.展开更多
In metal-gate/high-k stacks adopted by the 45 nm technology node, the fiat-band voltage （Vfb） shift remains one of the most critical challenges, particularly the flat-band voltage roll-off （Vfb roll-off） phenomeno...In metal-gate/high-k stacks adopted by the 45 nm technology node, the fiat-band voltage （Vfb） shift remains one of the most critical challenges, particularly the flat-band voltage roll-off （Vfb roll-off） phenomenon in p-channel metal- oxide-semiconductor （pMOS） devices with an ultrathin oxide layer. In this paper, recent progress on the investigation of the Vfb shift and the origin of the Vfb roll-off in the metal-gate/high-k pMOS stacks are reviewed. Methods that can alleviate the Vfb shift phenomenon are summarized and the future research trend is described.展开更多
The electronic band stucturec of crystalline Na2KC60, Na2RbC40 and Na2CsC60 are examined using the three-dimensional crystal orbital method. Our calculation results reveal that ground states of all these three alkali-...The electronic band stucturec of crystalline Na2KC60, Na2RbC40 and Na2CsC60 are examined using the three-dimensional crystal orbital method. Our calculation results reveal that ground states of all these three alkali-metal doped fullerides from a metalic conducting phase with a rather narrow molecular crystal-like band stucture and a high density of state near the fermi-level, which indicate a very high Tc for this newly found molecular superconductors. A monotonic relationship is found between our calculated band dispersion ,Fermi-level density of state, and the experimental transition temperature Tc, which is in exceuentt agreemet with the prediction of the BCS model.展开更多
Narrow gap welding has merits of lower residual stress and distortion, and superior mechanical properties of joints. A major problem of this process is the lack of fusion in sidewalls, hence many methods of weaving ar...Narrow gap welding has merits of lower residual stress and distortion, and superior mechanical properties of joints. A major problem of this process is the lack of fusion in sidewalls, hence many methods of weaving arc have been developed to increase heating effect of arc to the sidewalls. In this work, a new approach Without weaving arc is attempted to ensure the penetration of sidewall, and ultra-narrow gap welding with the gap of less than 5 mm was executed successfully. In this approach, the width of gap is decreased further, so that the sidewalls are made within range of arc heating to obtain the enough heat. In order to prevent the arc from being attracted by sidewall and going up along the sidewalls, two pieces of flux bands consisting of the specified aggregates are adhered to the sidewalls to constrain the arc. In addition, when flux band being heated by the arc, slag and gases are formed to shield the arc and the weld pool. This technique was tested on the welding experiment of pipeline steel with thickness of 20 mm. The involved welding parameters were obtained, that is, the width of gap is 4 mm, the welding current 250 A, and the heat input 0. 5 kJ/mm, the width of heat-affected zone is 1 -2 mm.展开更多
The electronic density of states and band structures of doped and un-doped anatase TiO2 were studied by the Linearized Augmented Plane Wave method based on the density functional theory. The calculation shows that the...The electronic density of states and band structures of doped and un-doped anatase TiO2 were studied by the Linearized Augmented Plane Wave method based on the density functional theory. The calculation shows that the band structures of TiO2 crystals doped with transition metal atoms become narrower. Interesting, an excursion towards high energy level with increasing atomic number in the same element period could be observed after doping with transition metal atoms.展开更多
基金supported jointly by the National Key Research Program of China (Nos. 2016YFC0502102, 2016YFC0502300)‘‘Western light’’ talent training plan (Class A)+5 种基金Chinese academy of science and technology services network program (No. KFJ-STS-ZDTP-036)international cooperation agency international partnership program (Nos. 132852KYSB20170029, 2014-3)Guizhou high-level innovative talent training program ‘‘ten’’ level talents program (No. 2016-5648)United fund of karst science research center (No. U1612441)International cooperation research projects of the national natural science fund committee (Nos. 41571130074, 41571130042)Science and Technology Plan of Guizhou Province of China (No. 2017–2966)
文摘In near-infrared spectroscopy,the traditional feature band extraction method has certain limitations.Therefore,a band extraction method named the three-step extraction method was proposed.This method combines characteristic absorption bands and correlation coefficients to select characteristic bands corresponding to various spectral forms and then uses stepwise regression to eliminate meaningless variables.Partial least squares regression(PLSR)and extreme learning machine(ELM)models were used to verify the effect of the band extraction method.Results show that the differential transformation of the spectrum can effectively improve the correlation between the spectrum and nickel(Ni)content.Most correlation coefficients were above 0.7 and approximately 20%higher than those of other transformation methods.The model effect established by the feature variable selection method based on comprehensive spectral transformation is only slightly affected by the spectral transformation form.Infive types of spectral transformation,the RPD values of the proposed method were all within the same level.The RPD values of the PLSR model were concentrated between 1.6 and 1.8,and those of the ELM model were between 2.5 and2.9,indicating that this method is beneficial for extracting more complete spectral features.The combination of the three-step extraction method and ELM algorithm can effectively retain important bands associated with the Ni content of the soil.The model based on the spectral band selected by the three-step extraction method has better prediction ability than the other models.The ELM model of the first-order differential transformation has the best prediction accuracy(RP^2=0.923,RPD=3.634).The research results provide some technical support for monitoring heavy metal content spectrum in local soils.
基金Project(2004F052) supported by the Educational Department of Liaoning Province, China
文摘Distribution of localized damage in shear band can’ t be predicted theoretically based on classical elastoplastic theory. The average damage variable in shear band was considered to be a non-local variable. Based on non-local theory, an analytical expression for the localized damage in strain-softening region of shear band in the process of shear band propagation was presented using boundary condition and symmetry of local damage variable, etc. The results show that dynamic shear softening modulus, dynamic shear strength and shear elastic modulus influence the distribution of the localized damage in shear band. Internal length of ductile metal only governs the thickness of shear band. In the strain-softening region of shear band, the local damage variable along shear band’s tangential and normal directions is non-linear and highly non-uniform. The non-uniformities in the normal and tangential directions of shear band stem from the interactions and interplaying among microstructures and the non-uniform distribution of shear stress, respectively. At the tail of the strain-softening region, the maximum value of local damage variable reaches 1. This means that material at this position fractures completely. At the tip of shear band and upper as well as lower boundaries, no damage occurs. Local damage variable increases as dynamic shear softening modulus decreases or shear elastic modulus increases, leading to difficulty in identification or detection of damage for less ductile metal material at higher strain rates.
基金supported by the National Basic Research Program of China(Grant Nos.2010CB327504,2011CB922100,and 2011CB301900)the National NaturalScience Foundation of China(Grant Nos.60936004 and 11104130)+1 种基金the Natural Science Foundation of Jiangsu Province,China(Grant Nos.BK2011556 andBK2011050)the Priority Academic Program Development of Jiangsu Higher Education Institutions,China
文摘Solar-blind ultraviolet （UV） band-pass filter has significant value in many scientific, commercial, and military appli- cations, in which the detection of weak UV signal against a strong background of solar radiation is required. In this work, a solar-blind filter is designed based on the concept of ＂transparent metal＂. The filter consisting of Al/SiO2 multilayers could exhibit a high transmission in the solar-blind wavelength region and a wide stopband extending from near-ultraviolet to infrared wavelength range. The central wavelength, bandwidth, Q factor, and rejection ratio of the passband are numerically studied as a function of individual layer thickness and multilayer period.
文摘The occurrence of both band-like and atom-like Auger spectra involving valence band electron of d-transition metals is discussed based on the two-step model of the Auger electron emission, i.e.an initial core-hole is first generated and the Auger transition occurs between the core-hole andthe valence states, The occupied vaIence states relax to screen the core-hole which results in a redistribution of the valence electrons, The electronic states concerned by the Auger transitionare calculated by the FLAPW method. There is a clear relation between band-like and atom-like features of the spectra and the different responses of these metals to the existence of a core-hole.
基金supported by the National Natural Science of China(Grant Nos.61176091 and 50932001)
文摘A theoretical model of flatband voltage （VFB） of metal/high-k/Si02/Si stack is proposed based on band alignment of entire gate stack, i.e., the VFB is obtained by simultaneously considering band alignments of metal/high-k, high-k/SiO2 and SiO2/Si interfaces, and their interactions. Then the VFB of TiN/HfO2/SiO2/Si stack is experimentally obtained and theoretically investigated by this model. The theoretical calculations are in good agreement with the experimental results. Furthermore, both positive VFB shift of TiN/HfO2/SiO2/Si stack and Fermi level pinning are successfully interpreted and attributed to the dielectric contact induced gap states at TiN/HfO2 and HfO2/SiO2 interfaces.
文摘Large-area in-situ synthesized TiB2(TiB, Fe2B)—Fe metal-ceramic composite coating has been fabricated on medium carbon steel by laser cladding with the optimal laser parameters and overlapping coefficient. The bonding interfaces between the cladding layer and the matrix and among different tracks are excellent. Microanalysis on the cladding layer shows that the morphology is a little different from each other and the element distribution and the mechanical properties are unanimous in each track while the mechanical property of the cladding layer shows a gradual change from the surface to the matrix. The in-situ separating out thin ceramic phases in the coating contribute to the improving of its properties greatly.
基金Project(2004F052) supported by the Educational Department of Liaoning Province, China
文摘The coexistent phenomenon of deformed and transformed adiabatic shear bands(ASBs) of ductile metal was analyzed using the JOHNSON-COOK model and gradient-dependent plasticity(GDP).The effects of melting point,density,heat capacity and work to heat conversion factor were investigated.Higher work to heat conversion factor,lower density,lower heat capacity and higher melting point lead to wider transformed ASB and higher local plastic shear deformation between deformed and transformed ASBs.Higher work to heat conversion factor,lower density,lower heat capacity and lower melting point cause higher local plastic shear deformation in the deformed ASB.Three reasons for the scatter in experimental data on the ASB width were pointed out and the advantages of the work were discussed.If the transformed ASB width is used to back-calculate the internal length parameter in the GDP,undoubtedly,the parameter will be extremely underestimated.
基金Project supported by the National 973 （Grant No 2004CB719804） and the National Natural Science Foundation of China.
文摘This paper has theoretically studied the characteristic frequencies of band structures in two-dimensional metallic- dielectric photonic crystals. It is demonstrated that a large filling fraction benefits the existence of absolute photonic band gap, while a smaller filling fraction benefits an absolute negative refraction band. In addition, it also finds that the relation between the cut-off frequency of E-polarized wave and the filling fraction exceeding 10% is content with a linear increasing function, whose coefficients are exponential to the normalized lattice constant. These investigations have significant implications for tuning the operational frequencies to desired applications and manufacturing photonic crystals.
基金Project supported by the National Natural Science Foundation of China (Grants Nos.50802005 and 11074020)the Program for New Century Excellent Talents in University,China (Grant No.NCET-08-0029)+1 种基金the Ph.D.Program Foundation of Ministry of Education of China (Grant No.200800061055)the Hong Kong Research Grants Council General Research Funds,China (Grant No.CityU112608)
文摘In metal-gate/high-k stacks adopted by the 45 nm technology node, the fiat-band voltage （Vfb） shift remains one of the most critical challenges, particularly the flat-band voltage roll-off （Vfb roll-off） phenomenon in p-channel metal- oxide-semiconductor （pMOS） devices with an ultrathin oxide layer. In this paper, recent progress on the investigation of the Vfb shift and the origin of the Vfb roll-off in the metal-gate/high-k pMOS stacks are reviewed. Methods that can alleviate the Vfb shift phenomenon are summarized and the future research trend is described.
文摘The electronic band stucturec of crystalline Na2KC60, Na2RbC40 and Na2CsC60 are examined using the three-dimensional crystal orbital method. Our calculation results reveal that ground states of all these three alkali-metal doped fullerides from a metalic conducting phase with a rather narrow molecular crystal-like band stucture and a high density of state near the fermi-level, which indicate a very high Tc for this newly found molecular superconductors. A monotonic relationship is found between our calculated band dispersion ,Fermi-level density of state, and the experimental transition temperature Tc, which is in exceuentt agreemet with the prediction of the BCS model.
文摘Narrow gap welding has merits of lower residual stress and distortion, and superior mechanical properties of joints. A major problem of this process is the lack of fusion in sidewalls, hence many methods of weaving arc have been developed to increase heating effect of arc to the sidewalls. In this work, a new approach Without weaving arc is attempted to ensure the penetration of sidewall, and ultra-narrow gap welding with the gap of less than 5 mm was executed successfully. In this approach, the width of gap is decreased further, so that the sidewalls are made within range of arc heating to obtain the enough heat. In order to prevent the arc from being attracted by sidewall and going up along the sidewalls, two pieces of flux bands consisting of the specified aggregates are adhered to the sidewalls to constrain the arc. In addition, when flux band being heated by the arc, slag and gases are formed to shield the arc and the weld pool. This technique was tested on the welding experiment of pipeline steel with thickness of 20 mm. The involved welding parameters were obtained, that is, the width of gap is 4 mm, the welding current 250 A, and the heat input 0. 5 kJ/mm, the width of heat-affected zone is 1 -2 mm.
文摘The electronic density of states and band structures of doped and un-doped anatase TiO2 were studied by the Linearized Augmented Plane Wave method based on the density functional theory. The calculation shows that the band structures of TiO2 crystals doped with transition metal atoms become narrower. Interesting, an excursion towards high energy level with increasing atomic number in the same element period could be observed after doping with transition metal atoms.
