For a misfit dislocation,the balance equations satisfied by the displacement fields are modified,and an extra term proportional to the second-order derivative appears in the resulting misfit equation compared with the...For a misfit dislocation,the balance equations satisfied by the displacement fields are modified,and an extra term proportional to the second-order derivative appears in the resulting misfit equation compared with the equation derived by Yao et al.This second-order derivative describes the lattice discreteness effect that arises from the surface effect.The core structure of a misfit dislocation and the change in interfacial spacing that it induces are investigated theoretically in the framework of an improved Peierls-Nabarro equation in which the effect of discreteness is fully taken into account.As an application,the structure of the misfit dislocation for a honeycomb structure in a two-dimensional heterostructure is presented.展开更多
A theoretical model was suggested which describes the generation of the misfit dislocation dipole in the system of the viscoelastic matrix containing a circular stiff nanoscale inhomogeneity.The critical condition of ...A theoretical model was suggested which describes the generation of the misfit dislocation dipole in the system of the viscoelastic matrix containing a circular stiff nanoscale inhomogeneity.The critical condition of misfit dislocation dipole and the solution of equilibrium position were given.The influence of the ratio of shear modulus,the misfit strain and viscosity on the equilibrium of the dislocation and critical parameter of inhomogeneity was investigated.The result shows that the equilibrium position de increases with the increase of the ratio of original shear modulus and the effect decreases with the increase of viscosity of matrix.Along with the increase of viscosity of matrix,de first increases and then decreases and possesses maximum value when t=0.3τ and tends to a stable value when t≥1.0τ.Along with the increase of viscosity of matrix,Rc first decreases and then increases and possesses minimum value when t=0.3τ and tends to a stable value when t≥1.0τ.展开更多
Reflection full-waveform inversion （RFWI） updates the low- and high- wavenumber components, and yields more accurate initial models compared with conventional full-waveform inversion （FWI）. However, there is stron...Reflection full-waveform inversion （RFWI） updates the low- and high- wavenumber components, and yields more accurate initial models compared with conventional full-waveform inversion （FWI）. However, there is strong nonlinearity in conventional RFWI because of the lack of low-frequency data and the complexity of the amplitude. The separation of phase and amplitude information makes RFWI more linear. Traditional phase-calculation methods face severe phase wrapping. To solve this problem, we propose a modified phase-calculation method that uses the phase-envelope data to obtain the pseudo phase information. Then, we establish a pseudophase-information-based objective function for RFWI, with the corresponding source and gradient terms. Numerical tests verify that the proposed calculation method using the phase-envelope data guarantees the stability and accuracy of the phase information and the convergence of the objective function. The application on a portion of the Sigsbee2A model and comparison with inversion results of the improved RFWI and conventional FWI methods verify that the pseudophase-based RFWI produces a highly accurate and efficient velocity model. Moreover, the proposed method is robust to noise and high frequency.展开更多
LiMn_(y)Fe_(1-y)PO_(4) is considered a promising cathode material for next-generation lithium-ion batteries(LIBs) due to its high energy density and low cost. Its energy density degradation is often ascribed to the ca...LiMn_(y)Fe_(1-y)PO_(4) is considered a promising cathode material for next-generation lithium-ion batteries(LIBs) due to its high energy density and low cost. Its energy density degradation is often ascribed to the capacity loss during cycling. However, in this study, we find that the energy density degradation mainly roots in voltage decay. We have synthesized a series of LiMn_(y)Fe_(1-y)PO_(4) /C(0.5 ≤ y ≤ 0.8) and find this voltage decay is correlated with the Mn content. A high amount Mn leads to a heavier voltage decay.In-situ X-ray diffraction(XRD) and high-resolution transmission electron microscopy(HRTEM) reveal the nature of this effect, which show a mismatch along the b-axis of-2.68%(charge) and +3.4%(discharge), a volume misfit of-4.41%(charge) and +4.54%(discharge) between Li_(x)Mn_(y)Fe_(1-y)PO_(4) and Mn_(y)Fe_(1-y)PO_(4) during phase transitions. The resultant misfit strains during Li+insertion compared to extraction result in structural degradations, such as amorphization and impurity(Mn F3) accumulation after cycling. The voltage decay can be alleviated by kinetic relaxations and recovered by a wild reannealing. This work demonstrates effective strategies to improve the energy density and cycling performance of LiMn_(y)Fe_(1-y)PO_(4) /C,providing good references for other LIB cathodes, such as the Li-rich cathodes.展开更多
The effect of H impurity on the misfit dislocation in Ni-based single-crystal superalloy is investigated using the molecular dynamic simulation. It includes the site preferences of H impurity in single crystals Ni and...The effect of H impurity on the misfit dislocation in Ni-based single-crystal superalloy is investigated using the molecular dynamic simulation. It includes the site preferences of H impurity in single crystals Ni and Ni3Al, the interaction between H impurity and the misfit dislocation and the effect of H impurity on the moving misfit dislocation. The calculated energies and simulation results show that the misfit dislocation attracts H impurity which is located at the γ/γ′ interface and Ni3Al and H impurity on the glide plane can obstruct the glide of misfit dislocation, which is beneficial to improving the mechanical properties of Ni based superalloys.展开更多
The interfacial binding covalent bond density (CBD) and the local environmental total bond order (LTBO) of the Ni/Ni3Alinterface with different lattice misfits (δ) were calculated by using first-principles discrete v...The interfacial binding covalent bond density (CBD) and the local environmental total bond order (LTBO) of the Ni/Ni3Alinterface with different lattice misfits (δ) were calculated by using first-principles discrete variation Xα method. It was foundthat the effects of lattice misfits on the electronic structures of incoherent Ni/Ni3Al interface were very obvious. On one hand,less than -0.6% negative lattice misfit can promote the binding strength of γ/γ′ interface. On the other hand, the totalbonding strength of γ/γ′ interface decreases with increasing δ. Therefore, the magnitude and sign of lattice misfit must becarefully controlled for balancing the high temperature creep strength of Ni-base single crystal superalloy and the structuralstability of γ/γ′interface when one designs a new Ni-base single crystal superalloy.展开更多
Current methodologies used for the inference of thin film stress through curvature measurements are strictly restricted to stress and curvature states which are assumed to remain uniform over the entire film/substrate...Current methodologies used for the inference of thin film stress through curvature measurements are strictly restricted to stress and curvature states which are assumed to remain uniform over the entire film/substrate system. By considering a circular thin film/substrate system subject to non-uniform, but axisymmetric misfit strain distributions in the thin film, we derived relations between the film stresses and the misfit strain, and between the plate system＇s curvatures and the misfit strain. These relations feature a “local” part which involves a direct dependence of the stress or curvature components on the misfit strain at the same point, and a “non-local” part which reflects the effect of misfit strain of other points on the location of scrutiny. Most notably, we also derived relations between the polar components of the film stress and those of system curvatures which allow for the experimental inference of such stresses from full-field curvature measurements in the presence of arbitrary radial non-uniformities. These relations also feature a “non-local” dependence on curvatures making a full-field measurement a necessity. Finally, it is shown that the interfacial shear tractions between the film and the substrate are proportional to the radial gradients of the first curvature invariant and can also be inferred experimentally.展开更多
The misfit layer compound(SnS)_(1.2)(TiS_(2))_(2)is a promising low-cost thermoelectric material because of its low thermal conductivity derived from the superlattice-like structure.However,the strong covalent bonds w...The misfit layer compound(SnS)_(1.2)(TiS_(2))_(2)is a promising low-cost thermoelectric material because of its low thermal conductivity derived from the superlattice-like structure.However,the strong covalent bonds within each constituent layer highly localize the electrons thereby it is highly challenging to optimize the power factor by doping or alloying.Here,we show that Bi doping at the Sn site markedly breaks the covalent bonds networks and highly delocalizes the electrons.This results in a high charge carrier concentration and enhanced power factor throughout the whole temperature range.It is highly remarkable that Bi doping also significantly reduces the thermal conductivity by suppressing the heat conduction carried by phonons,indicating that it independently modulates phonon and charge transport properties.These effects collectively give rise to a maximum ZT of 0.3 at 720 K.In addition,we apply the single Kane band model and the Debye–Callaway model to clarify the electron and phonon transport mechanisms in the misfit layer compound(SnS)_(1.2)(TiS_(2))_(2).展开更多
Technical development oriented on the detailed seismic imaging and velocity model building coupled with rapid increase of the computing power available nowadays make it possible to process large volumes of seismic dat...Technical development oriented on the detailed seismic imaging and velocity model building coupled with rapid increase of the computing power available nowadays make it possible to process large volumes of seismic data using numerically intensive approaches based the wavefield propagation.展开更多
The classical elastic impedance （EI） inversion method, however, is based on the L2-norm misfit function and considerably sensitive to outliers, assuming the noise of the seismic data to be the Guassian-distribution....The classical elastic impedance （EI） inversion method, however, is based on the L2-norm misfit function and considerably sensitive to outliers, assuming the noise of the seismic data to be the Guassian-distribution. So we have developed a more robust elastic impedance inversion based on the Ll-norm misfit function, and the noise is assumed to be non-Gaussian. Meanwhile, some regularization methods including the sparse constraint regularization and elastic impedance point constraint regularization are incorporated to improve the ill-posed characteristics of the seismic inversion problem. Firstly, we create the Ll-norm misfit objective function of pre-stack inversion problem based on the Bayesian scheme within the sparse constraint regularization and elastic impedance point constraint regularization. And then, we obtain more robust elastic impedances of different angles which are less sensitive to outliers in seismic data by using the IRLS strategy. Finally, we extract the P-wave and S-wave velocity and density by using the more stable parameter extraction method. Tests on synthetic data show that the P-wave and S-wave velocity and density parameters are still estimated reasonable with moderate noise. A test on the real data set shows that compared to the results of the classical elastic impedance inversion method, the estimated results using the proposed method can get better lateral continuity and more distinct show of the gas, verifying the feasibility and stability of the method.展开更多
Rhodium oxides, including a misfitlayered structure with alternate stacking of a rock salttype layer and a hexagonal RhO2 layer, are expected to have good thermoelectric properties. Among them, the thermoelectric prop...Rhodium oxides, including a misfitlayered structure with alternate stacking of a rock salttype layer and a hexagonal RhO2 layer, are expected to have good thermoelectric properties. Among them, the thermoelectric properties (electrical conductivity (σ), Seebeck coefficient (S), Figure of merit (ZT) and calculated thermal conductivity (κ) by S, σ, ZT, and absolute temperature (T)) of bismuth-based rhodium oxides ((Bi1-x,Pbx) 2Sr2Rh2Oy, x = 0 and 0.02, hereafter BSR and BPSR, respectively) were investigated. In comparison with Bi2Sr2Co2Oy (BSC) at 700°C, S and κ enhanced (increased S, 110 (BSR) and 105 μV K-1 (BPSR) from 85 μV K-1 (BSC) and decreased κ, 0.32 (BSR) and 0.50 W m-1 K-1 (BPSR) from 1.75 W m-1 K-1 (BSC)), whereas σ decreased (15 (BSR) and 31 S cm-1 (BPSR) from 70 S cm-1 (BSC)). BPSR reached the highest ZT value of 0.067 at 700°C, compared to those of 0.056 (BSR) and 0.027 (BSC).展开更多
The microstructural characteristic of the misfit-layered compound PbTiS3 has been studied with transmission electron microscopy. All the incommensurate modulation-induced satellite spots and main diffraction spots of ...The microstructural characteristic of the misfit-layered compound PbTiS3 has been studied with transmission electron microscopy. All the incommensurate modulation-induced satellite spots and main diffraction spots of basic sublattices can be indexed systematically with a superspace group method. Finally, the relationship between the electronic transport properties and the crystal structure is discussed.展开更多
The critical misfit of epitaxial growth metallic thin films f_c was thermodynamically considered. It is found that there exists a competition between the energy of the misfit dislocation of film and non-coherent inter...The critical misfit of epitaxial growth metallic thin films f_c was thermodynamically considered. It is found that there exists a competition between the energy of the misfit dislocation of film and non-coherent interface energy of film-substrate. Equilibrium between these energies was present at a critical atomic misfit f_c. When the atomic misfit is larger than the critical value, epitaxial growth does not occur. The critical misfit of the epitaxial growth thin films can be predicted. The results show that f_c is proportional to the non-coherent interface energy of the film-substrate, and inversely proportional to the elastic modulus and the thickness of the film.展开更多
The crystallography and morphology of precipitates in different systems were rationalized based on the optimum matching conditions. The interfaces that obey these conditions were conveniently identified in reciprocal ...The crystallography and morphology of precipitates in different systems were rationalized based on the optimum matching conditions. The interfaces that obey these conditions were conveniently identified in reciprocal space,in terms of three △g's parallelism rules. The theoretic basis of the O-lattice and CSL/DSC theory for these rules was provided briefly. Examples of small lattice misfit system(a Ti alloy),and large lattice misfit systems(Al and Mg alloys) were presented. The effect of lattice parameters on the orientation relationship and morphology was also discussed.展开更多
The structural property of GaSb epilayers grown on semi-insulator GaAs （001） substrate by metalorganic chemical vapor deposition （MOCVD） using Triethylgallium （TEGa） and trimethylantimony （TMSb）, was investiga...The structural property of GaSb epilayers grown on semi-insulator GaAs （001） substrate by metalorganic chemical vapor deposition （MOCVD） using Triethylgallium （TEGa） and trimethylantimony （TMSb）, was investigated by variation of the Sb：Ga （V/Ill） ratio. An optimum V/Ill ratio of 1.4 was determined in our growth conditions. Using transmission electron microscopy （TEM）, we found that there was an interracial misfit dislocations （IMF） growth mode in our experiment, in which the large misfit strain between epilayer and substrate is relaxed by periodic 90 deg. IMF array at the hetero-epitaxial interface. The rms roughness of a 300 nm-thick GaSb layer is only 2.7 nm in a 10μm×10μm scan from atomic force microscopy （AFM） result. The best hole density and mobility of 300 nm GaSb epilayer are 5.27xi06 cm-3（1.20×106） and 553 cm2-V-l.s-1 （2340） at RT （77 K） from Hall measurement, respectively. These results indicate that the IMF growth mode can be used in MOCVD epitaxial technology similar to molecular beam epitaxy （MBE） technology to produce the thinner GaSb layer with low density of dislocations and other defects on GaAs substrate for the application of devices.展开更多
A conventional X-ray difFractometer has been used to determine the -y/y＇ lattice misfit and γ＇ volume fraction for a Ru-containing nickel-based single crystal superalloy at room temperature. The rocking curve was u...A conventional X-ray difFractometer has been used to determine the -y/y＇ lattice misfit and γ＇ volume fraction for a Ru-containing nickel-based single crystal superalloy at room temperature. The rocking curve was used to characterize the distribution of subgrains. The diffraction peaks obtained by w-20 scan were used to determine the γ/γ＇ lattice misfit and γ＇ volume fraction. A three peaks fitting model was proposed. The peak fitting results are in good agreement with the model. The X-ray diffraction results indicate that the nickel-based single crystal superalloy was not a perfect monocrystalline material, which is comprised of many subgrains; and each subgrain also consists of large numbers of mosaic structures. In addition, two anomalous reflection phenomena were found during the experiment and discussed with respect to their occurrence and impact on the measurement. The experimental results show that the γ/γ＇ lattice misfit and ~/r volume fraction will be various at the different regions of its dendritic microstructure. The average γ/γ＇ lattice misfit and γ＇ volume fraction of the experimental alloy are approximately-0.2% and 70%, respectively. Furthermore, the γ＇ volume fraction calculated by atom microprobe （AP） data is also basically consistent with the experimental results.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant No.11874093).
文摘For a misfit dislocation,the balance equations satisfied by the displacement fields are modified,and an extra term proportional to the second-order derivative appears in the resulting misfit equation compared with the equation derived by Yao et al.This second-order derivative describes the lattice discreteness effect that arises from the surface effect.The core structure of a misfit dislocation and the change in interfacial spacing that it induces are investigated theoretically in the framework of an improved Peierls-Nabarro equation in which the effect of discreteness is fully taken into account.As an application,the structure of the misfit dislocation for a honeycomb structure in a two-dimensional heterostructure is presented.
基金Project(10472030) supported by the National Natural Science Foundation of China
文摘A theoretical model was suggested which describes the generation of the misfit dislocation dipole in the system of the viscoelastic matrix containing a circular stiff nanoscale inhomogeneity.The critical condition of misfit dislocation dipole and the solution of equilibrium position were given.The influence of the ratio of shear modulus,the misfit strain and viscosity on the equilibrium of the dislocation and critical parameter of inhomogeneity was investigated.The result shows that the equilibrium position de increases with the increase of the ratio of original shear modulus and the effect decreases with the increase of viscosity of matrix.Along with the increase of viscosity of matrix,de first increases and then decreases and possesses maximum value when t=0.3τ and tends to a stable value when t≥1.0τ.Along with the increase of viscosity of matrix,Rc first decreases and then increases and possesses minimum value when t=0.3τ and tends to a stable value when t≥1.0τ.
基金jointly supported by the NSF(Nos.41104069 and 41274124)the National 973 Project(No.2014CB239006)+1 种基金National Oil and Gas Project(Nos.2016ZX05014001and 2016ZX05002)the Tai Shan Science Foundation for The Excellent Youth Scholars
文摘Reflection full-waveform inversion （RFWI） updates the low- and high- wavenumber components, and yields more accurate initial models compared with conventional full-waveform inversion （FWI）. However, there is strong nonlinearity in conventional RFWI because of the lack of low-frequency data and the complexity of the amplitude. The separation of phase and amplitude information makes RFWI more linear. Traditional phase-calculation methods face severe phase wrapping. To solve this problem, we propose a modified phase-calculation method that uses the phase-envelope data to obtain the pseudo phase information. Then, we establish a pseudophase-information-based objective function for RFWI, with the corresponding source and gradient terms. Numerical tests verify that the proposed calculation method using the phase-envelope data guarantees the stability and accuracy of the phase information and the convergence of the objective function. The application on a portion of the Sigsbee2A model and comparison with inversion results of the improved RFWI and conventional FWI methods verify that the pseudophase-based RFWI produces a highly accurate and efficient velocity model. Moreover, the proposed method is robust to noise and high frequency.
基金supported by the 21C Innovation Laboratory,Contemporary Amperex Technology Ltd. by project No. 21C-OP-202103the National Natural Science Foundation of China(52072061)。
文摘LiMn_(y)Fe_(1-y)PO_(4) is considered a promising cathode material for next-generation lithium-ion batteries(LIBs) due to its high energy density and low cost. Its energy density degradation is often ascribed to the capacity loss during cycling. However, in this study, we find that the energy density degradation mainly roots in voltage decay. We have synthesized a series of LiMn_(y)Fe_(1-y)PO_(4) /C(0.5 ≤ y ≤ 0.8) and find this voltage decay is correlated with the Mn content. A high amount Mn leads to a heavier voltage decay.In-situ X-ray diffraction(XRD) and high-resolution transmission electron microscopy(HRTEM) reveal the nature of this effect, which show a mismatch along the b-axis of-2.68%(charge) and +3.4%(discharge), a volume misfit of-4.41%(charge) and +4.54%(discharge) between Li_(x)Mn_(y)Fe_(1-y)PO_(4) and Mn_(y)Fe_(1-y)PO_(4) during phase transitions. The resultant misfit strains during Li+insertion compared to extraction result in structural degradations, such as amorphization and impurity(Mn F3) accumulation after cycling. The voltage decay can be alleviated by kinetic relaxations and recovered by a wild reannealing. This work demonstrates effective strategies to improve the energy density and cycling performance of LiMn_(y)Fe_(1-y)PO_(4) /C,providing good references for other LIB cathodes, such as the Li-rich cathodes.
基金supported by the National Basic Research Program of China (Grant No.2011CB606402)the National Natural Science Foundation of China (Grant No.51071091)
文摘The effect of H impurity on the misfit dislocation in Ni-based single-crystal superalloy is investigated using the molecular dynamic simulation. It includes the site preferences of H impurity in single crystals Ni and Ni3Al, the interaction between H impurity and the misfit dislocation and the effect of H impurity on the moving misfit dislocation. The calculated energies and simulation results show that the misfit dislocation attracts H impurity which is located at the γ/γ′ interface and Ni3Al and H impurity on the glide plane can obstruct the glide of misfit dislocation, which is beneficial to improving the mechanical properties of Ni based superalloys.
文摘The interfacial binding covalent bond density (CBD) and the local environmental total bond order (LTBO) of the Ni/Ni3Alinterface with different lattice misfits (δ) were calculated by using first-principles discrete variation Xα method. It was foundthat the effects of lattice misfits on the electronic structures of incoherent Ni/Ni3Al interface were very obvious. On one hand,less than -0.6% negative lattice misfit can promote the binding strength of γ/γ′ interface. On the other hand, the totalbonding strength of γ/γ′ interface decreases with increasing δ. Therefore, the magnitude and sign of lattice misfit must becarefully controlled for balancing the high temperature creep strength of Ni-base single crystal superalloy and the structuralstability of γ/γ′interface when one designs a new Ni-base single crystal superalloy.
文摘Current methodologies used for the inference of thin film stress through curvature measurements are strictly restricted to stress and curvature states which are assumed to remain uniform over the entire film/substrate system. By considering a circular thin film/substrate system subject to non-uniform, but axisymmetric misfit strain distributions in the thin film, we derived relations between the film stresses and the misfit strain, and between the plate system＇s curvatures and the misfit strain. These relations feature a “local” part which involves a direct dependence of the stress or curvature components on the misfit strain at the same point, and a “non-local” part which reflects the effect of misfit strain of other points on the location of scrutiny. Most notably, we also derived relations between the polar components of the film stress and those of system curvatures which allow for the experimental inference of such stresses from full-field curvature measurements in the presence of arbitrary radial non-uniformities. These relations also feature a “non-local” dependence on curvatures making a full-field measurement a necessity. Finally, it is shown that the interfacial shear tractions between the film and the substrate are proportional to the radial gradients of the first curvature invariant and can also be inferred experimentally.
基金financially supported by the National Key Research and Development Program of China(Grant No.2018YFA0702100)the Joint Funds of the National Natural Science Foundation of China+1 种基金the Chinese Academy of Sciences’Large-Scale Scientific Facility(Grant No.U1932106)the Sichuan University Innovation Research Program of China(Grant No.2020SCUNL112)。
文摘The misfit layer compound(SnS)_(1.2)(TiS_(2))_(2)is a promising low-cost thermoelectric material because of its low thermal conductivity derived from the superlattice-like structure.However,the strong covalent bonds within each constituent layer highly localize the electrons thereby it is highly challenging to optimize the power factor by doping or alloying.Here,we show that Bi doping at the Sn site markedly breaks the covalent bonds networks and highly delocalizes the electrons.This results in a high charge carrier concentration and enhanced power factor throughout the whole temperature range.It is highly remarkable that Bi doping also significantly reduces the thermal conductivity by suppressing the heat conduction carried by phonons,indicating that it independently modulates phonon and charge transport properties.These effects collectively give rise to a maximum ZT of 0.3 at 720 K.In addition,we apply the single Kane band model and the Debye–Callaway model to clarify the electron and phonon transport mechanisms in the misfit layer compound(SnS)_(1.2)(TiS_(2))_(2).
基金by the SEISCOPE consortium(http://seiscope2.osug.fr),sponsored by AKERBP,CGG,CHEVRON,EQUINOR,EXXON-MOBIL,JGI,SHELL,SINOPEC,SISPROBE,and TOTALthe Polish National Science Center,(Grant No.2019/33/B/ST10/01014)
文摘Technical development oriented on the detailed seismic imaging and velocity model building coupled with rapid increase of the computing power available nowadays make it possible to process large volumes of seismic data using numerically intensive approaches based the wavefield propagation.
基金Projects(U1562215,41674130,41404088)supported by the National Natural Science Foundation of ChinaProjects(2013CB228604,2014CB239201)supported by the National Basic Research Program of China+1 种基金Projects(2016ZX05027004-001,2016ZX05002006-009)supported by the National Oil and Gas Major Projects of ChinaProject(15CX08002A)supported by the Fundamental Research Funds for the Central Universities,China
文摘The classical elastic impedance （EI） inversion method, however, is based on the L2-norm misfit function and considerably sensitive to outliers, assuming the noise of the seismic data to be the Guassian-distribution. So we have developed a more robust elastic impedance inversion based on the Ll-norm misfit function, and the noise is assumed to be non-Gaussian. Meanwhile, some regularization methods including the sparse constraint regularization and elastic impedance point constraint regularization are incorporated to improve the ill-posed characteristics of the seismic inversion problem. Firstly, we create the Ll-norm misfit objective function of pre-stack inversion problem based on the Bayesian scheme within the sparse constraint regularization and elastic impedance point constraint regularization. And then, we obtain more robust elastic impedances of different angles which are less sensitive to outliers in seismic data by using the IRLS strategy. Finally, we extract the P-wave and S-wave velocity and density by using the more stable parameter extraction method. Tests on synthetic data show that the P-wave and S-wave velocity and density parameters are still estimated reasonable with moderate noise. A test on the real data set shows that compared to the results of the classical elastic impedance inversion method, the estimated results using the proposed method can get better lateral continuity and more distinct show of the gas, verifying the feasibility and stability of the method.
文摘Rhodium oxides, including a misfitlayered structure with alternate stacking of a rock salttype layer and a hexagonal RhO2 layer, are expected to have good thermoelectric properties. Among them, the thermoelectric properties (electrical conductivity (σ), Seebeck coefficient (S), Figure of merit (ZT) and calculated thermal conductivity (κ) by S, σ, ZT, and absolute temperature (T)) of bismuth-based rhodium oxides ((Bi1-x,Pbx) 2Sr2Rh2Oy, x = 0 and 0.02, hereafter BSR and BPSR, respectively) were investigated. In comparison with Bi2Sr2Co2Oy (BSC) at 700°C, S and κ enhanced (increased S, 110 (BSR) and 105 μV K-1 (BPSR) from 85 μV K-1 (BSC) and decreased κ, 0.32 (BSR) and 0.50 W m-1 K-1 (BPSR) from 1.75 W m-1 K-1 (BSC)), whereas σ decreased (15 (BSR) and 31 S cm-1 (BPSR) from 70 S cm-1 (BSC)). BPSR reached the highest ZT value of 0.067 at 700°C, compared to those of 0.056 (BSR) and 0.027 (BSC).
基金Project supported by the National Basic Research Program of China(Grant No.2012CB932302)the National Natural Science Foundation of China(Grant No.50921091)the Specific Funding of the Discipline and Graduate Education Project of Beijing Municipal Commission of Education,China
文摘The microstructural characteristic of the misfit-layered compound PbTiS3 has been studied with transmission electron microscopy. All the incommensurate modulation-induced satellite spots and main diffraction spots of basic sublattices can be indexed systematically with a superspace group method. Finally, the relationship between the electronic transport properties and the crystal structure is discussed.
基金Project(2004CB619301) supported by the National Key Fundamental Research and Development Program of China Pro ject(50025101) supported by the National Natural Science Foundation of China
文摘The critical misfit of epitaxial growth metallic thin films f_c was thermodynamically considered. It is found that there exists a competition between the energy of the misfit dislocation of film and non-coherent interface energy of film-substrate. Equilibrium between these energies was present at a critical atomic misfit f_c. When the atomic misfit is larger than the critical value, epitaxial growth does not occur. The critical misfit of the epitaxial growth thin films can be predicted. The results show that f_c is proportional to the non-coherent interface energy of the film-substrate, and inversely proportional to the elastic modulus and the thickness of the film.
基金Projects(59871021, 50271035, 50471012) supported by the National Natural Science Foundation of China.
文摘The crystallography and morphology of precipitates in different systems were rationalized based on the optimum matching conditions. The interfaces that obey these conditions were conveniently identified in reciprocal space,in terms of three △g's parallelism rules. The theoretic basis of the O-lattice and CSL/DSC theory for these rules was provided briefly. Examples of small lattice misfit system(a Ti alloy),and large lattice misfit systems(Al and Mg alloys) were presented. The effect of lattice parameters on the orientation relationship and morphology was also discussed.
基金supported by the National Natural Science Foundation of China(Grant Nos.51071038and60576007)Program for New Century Excellent Talents in University(NCET-09-0265)the Sichuan Province Science Foundation for Youths(No.2010JQ0002)
文摘The structural property of GaSb epilayers grown on semi-insulator GaAs （001） substrate by metalorganic chemical vapor deposition （MOCVD） using Triethylgallium （TEGa） and trimethylantimony （TMSb）, was investigated by variation of the Sb：Ga （V/Ill） ratio. An optimum V/Ill ratio of 1.4 was determined in our growth conditions. Using transmission electron microscopy （TEM）, we found that there was an interracial misfit dislocations （IMF） growth mode in our experiment, in which the large misfit strain between epilayer and substrate is relaxed by periodic 90 deg. IMF array at the hetero-epitaxial interface. The rms roughness of a 300 nm-thick GaSb layer is only 2.7 nm in a 10μm×10μm scan from atomic force microscopy （AFM） result. The best hole density and mobility of 300 nm GaSb epilayer are 5.27xi06 cm-3（1.20×106） and 553 cm2-V-l.s-1 （2340） at RT （77 K） from Hall measurement, respectively. These results indicate that the IMF growth mode can be used in MOCVD epitaxial technology similar to molecular beam epitaxy （MBE） technology to produce the thinner GaSb layer with low density of dislocations and other defects on GaAs substrate for the application of devices.
基金supported by the National Basic Research Program (973 Program) of China under grant No. 2010CB631200the National Natural Science Foundation of China (NSFC) under grant No.50931004
文摘A conventional X-ray difFractometer has been used to determine the -y/y＇ lattice misfit and γ＇ volume fraction for a Ru-containing nickel-based single crystal superalloy at room temperature. The rocking curve was used to characterize the distribution of subgrains. The diffraction peaks obtained by w-20 scan were used to determine the γ/γ＇ lattice misfit and γ＇ volume fraction. A three peaks fitting model was proposed. The peak fitting results are in good agreement with the model. The X-ray diffraction results indicate that the nickel-based single crystal superalloy was not a perfect monocrystalline material, which is comprised of many subgrains; and each subgrain also consists of large numbers of mosaic structures. In addition, two anomalous reflection phenomena were found during the experiment and discussed with respect to their occurrence and impact on the measurement. The experimental results show that the γ/γ＇ lattice misfit and ~/r volume fraction will be various at the different regions of its dendritic microstructure. The average γ/γ＇ lattice misfit and γ＇ volume fraction of the experimental alloy are approximately-0.2% and 70%, respectively. Furthermore, the γ＇ volume fraction calculated by atom microprobe （AP） data is also basically consistent with the experimental results.
