Based on the laboratory calibration before launch of CBERS-02 IRMSS thermal infrared channel, the onboard blackbody calibration, the radiometric cross- calibration against TERRA MODIS corresponding channel and the in-...Based on the laboratory calibration before launch of CBERS-02 IRMSS thermal infrared channel, the onboard blackbody calibration, the radiometric cross- calibration against TERRA MODIS corresponding channel and the in-flight field calibration at Lake Qinghai: water surface radiometric calibration test site of China on Aug. 17, 2004 are carried out in this research. When making onboard blackbody calibration of CBERS-02 IRMSS, it is necessary to understand inside structures and light path in IRMSS camera and receive and process calibration blackbody signals at normal and high temperatures. Onboard blackbody calibration results of each detector are very important to relative radiometric calibration of images processing and absolute radiometric calibration of each detector. In-flight field calibration mainly contains field experiments, obtaining synchronous images, spectrum marching and MODTRAN radiative transmi- ssion computation. Radiometric cross-calibration of CBERS-02 IRMSS thermal band against TERRA MODIS selected 6 times synchronous images of two sensors passing through Lake Qinghai and Lake Taihu from August to December, 2004 to compute the cross calibration data. Combining the in-flight field calibration and radiometric cross calibration data, the absolute radiometric calibration coefficients are calculated by the linear regression method. This new calibration model can obviously control the radiometric calibration uncertainties aroused by the single point method used in the in-flight calibration of CBERS-02 IRMSS, this kind of sensors cannot receive the cosmic background radiation. In this research, the radiometric calibration coefficients obtained through the linear regression model are 8.53 (gain, unit: DN/W m?2sr?1μm?1) and 44.92 (offset, unit: DN).展开更多
The ring-banded spherulite is a special morphology of polymer crystals and has attracted considerable attention over recent decades. In this study, a new phase field model with polymer characteristics is established t...The ring-banded spherulite is a special morphology of polymer crystals and has attracted considerable attention over recent decades. In this study, a new phase field model with polymer characteristics is established to investigate the emergence and formation mechanism of the ring-banded spherulites of crystalline polymers. The model consists of a nonconserved phase field representing the phase transition and a temperature field describing the diffusion of the released latent heat. The corresponding model parameters can be obtained from experimentally accessible material parameters.Two-dimensional calculations are carried out for the ring-banded spherulitic growth of polyethylene film under a series of crystallization temperatures. The results of these calculations demonstrate that the formation of ring-banded spherulites can be triggered by the self-generated thermal field. Moreover, some temperature-dependent characteristics of the ring-banded spherulites observed in experiments are reproduced by simulations, which may help to study the effects of crystallization temperature on the ring-banded structures.展开更多
Thick film of Polystyrene (PS)/CdS semiconducting optical nanocomposite has been synthesized by dispersing nanofiller particles of CdS in PS matrix. The nanostructure of the CdS particles has been ascertained through ...Thick film of Polystyrene (PS)/CdS semiconducting optical nanocomposite has been synthesized by dispersing nanofiller particles of CdS in PS matrix. The nanostructure of the CdS particles has been ascertained through X-ray Diffraction (XRD) and Transmission Electron Microscopy (TEM). Small angle x-ray scattering analysis has been performed in order to ascertain nanocomposite character of the PS/CdS sample. Scanning Electron Microscopy (SEM) analyses of these samples have been carried out to establish the surface morphology. Optical Absorption Spectroscopy is used to measure the energy band gap of PS/CdS nanocomposite by using Tauc relation whereas Transient Plane Source Technique is used for the determination of thermal conductivity of the prepared samples. The phase transition temperature and elastic response of the prepared samples have been ascertained through Dynamic Mechanical Analyzer (DMA). This study reveals that the thermal conductivity, Young’s modulus and the toughness of the material are greatly influenced by the existence of interfacial energetic interaction between dispersed CdS nanofiller particles and matrix of PS.展开更多
Dynamic compression tests were carried out to investigate dynamic mechanical behavior and adiabatic shear bands in ultrafine grained(UFG)pure zirconium prepared by equal channel angular pressing(ECAP)and rotary swayin...Dynamic compression tests were carried out to investigate dynamic mechanical behavior and adiabatic shear bands in ultrafine grained(UFG)pure zirconium prepared by equal channel angular pressing(ECAP)and rotary swaying.The cylindrical specimens were deformed dynamically on the split Hopkinson pressure bar(SHPB)at different strain rates of 800 to 4000s^-1 at room temperature.The temperature distribution of the shear bands was estimated on the basis of temperature rise of uniform plastic deformation stage and thermal diffusion effect.The results show that the true stress-true strain curves of UFG pure zirconium are concave upward trend of strain in range of 0.02-0.16 due to the effects of strain hardening,strain rate hardening and thermal softening.The formation of the adiabatic shear bands is the main reason of UFG pure zirconium failure.A large number of micro-voids are observed in the adiabatic shear bands,and the macroscopic cracks develop from the micro-voids coalescence.The fracture surface of UFG pure zirconium exhibits quasi cleavage fracture with the characteristic features of shear dimples and river pattern.The highest temperature within the shear bands of UFG pure zirconium is about 592 K.展开更多
The oxidative polycondensation reaction conditions of 4-m-tolylazomethinephenol （4-TAMP） in the presence of air O2 and NaOCl as oxidants were studied in an aqueous alkaline medium between 50 and 90℃. The structures...The oxidative polycondensation reaction conditions of 4-m-tolylazomethinephenol （4-TAMP） in the presence of air O2 and NaOCl as oxidants were studied in an aqueous alkaline medium between 50 and 90℃. The structures of the obtained monomer and oligomer were confirmed by FT-IR, UV-Vis, ^1H- and ^13C-NMR and elemental analysis techniques. The physical characterization was made by TG-DTA, size exclusion chromatography （SEC） and solubility tests. At the optimum reaction conditions, the yield of oligo-4-m-tolylazomethinephenol （O-4-TAMP） was found to be 62.50% （for air O2 oxidant） and 90.0% （for NaOCl oxidant）, respectively. According to the SEC analysis, the number-average molecular weight （Mn）, weight-average molecular weight （Mw） and polydispersity index （PDI） values of O-4-TAMP were found to be 2310, 2610 g tool 1 and 1. 13, respectively, using air O2, and 1390, 1710 g mol^-1 and 1.23, using NaOCl, respectively. According to TG-DTA analyses, O-4-TAMP was more stable than 4-TAMP against thermal decomposition. The weight losses of 4-TAMP and O-4-TAMP were found to be 68% and 58% at 1000℃. Electrical conductivity of the O-4-TAMP was measured, showing that the polymer is a typical semiconductor. Electrochemically, the highest occupied molecular orbital （HOMO）, the lowest unoccupied molecular orbital （LUMO） and electrochemical energy gaps （E＇g） for 4-TAMP are -5.96, -3.22 and 2.74 eV, respectively. The HOMO, LUMO and （E＇g） for O-4-TAMP are -5.78, -3.44 and 2.34 eV, respectively. According to UV-Vis measurements, optical band gaps （Eg） of 4-TAMP and O-4-TAMP were found to be 3.45 and 3. 1 0 eV, respectively.展开更多
In this work, we investigate strain effects induced by the deposition of gate dielectrics on the valence band structures in Si （110） nanowire via the simulation of strain distribution and the calculation of a genera...In this work, we investigate strain effects induced by the deposition of gate dielectrics on the valence band structures in Si （110） nanowire via the simulation of strain distribution and the calculation of a generalized 6 × 6k .p strained valence band. The nanowire is surrounded by the gate dielectric. Our simulation indicates that the strain of the amorphous SiO2 insulator is negligible without considering temperature factors. On the other hand, the thermal residual strain in a nanowire with amorphous SiO2 insulator which has negligible lattice misfit strain pushes the valence subbands upwards by chemical vapour deposition and downwards by thermal oxidation treatment. In contrast with the strain of the amorphous SiO2 insulator, the strain of the HfO2 gate insulator in Si （110） nanowire pushes the valence subbands upwards remarkably. The thermal residual strain by HfO2 insulator contributes to the up-shifting tendency. Our simulation results for valence band shifting and warping in Si nanowires can provide useful guidance for further nanowire device design.展开更多
P-type ZnO is crucial for the realization of ZnO-based homojunction ultraviolet optoelectronic devices. The problem associated with the preparation of stable p-type ZnO with high hole density still hinders device appl...P-type ZnO is crucial for the realization of ZnO-based homojunction ultraviolet optoelectronic devices. The problem associated with the preparation of stable p-type ZnO with high hole density still hinders device applications. In this paper,we introduce an alternative route to stabilizing N in the oxidation process, the thermal stability of p-ZnO is significantly improved. Finally, we discuss the limitations of the alternative doping method and provide some prospective outlook of the method.展开更多
The solidified microstructure of a Ni-Cu-Si cast alloy has been investigated, and a kind of banding structure was observed. The results showed that, the banding structure was composed of coarser particles which were N...The solidified microstructure of a Ni-Cu-Si cast alloy has been investigated, and a kind of banding structure was observed. The results showed that, the banding structure was composed of coarser particles which were Ni3Si type of precipitates and similar to the fine particles precipitate uniformly distributed within matrix of Ni solid solution, in both crystal structure and composition. The formation of bandings was resulted from cast thermal stress and dislocation walls. It was found that the cracks propagated along these bandings in tensile test. The banding structure can be depressed by reducing the cast thermal stress, which can improve the tensile ductility.展开更多
The analysis of the density of states for electrons in single quantum well, the conduction band nonparabolicity take is account. It is shown that the degree of conduction band nonparabolicity pronounces depending on t...The analysis of the density of states for electrons in single quantum well, the conduction band nonparabolicity take is account. It is shown that the degree of conduction band nonparabolicity pronounces depending on the energy density of states. With increasing temperature, a step change in the density of states smoothes and at high temperatures is completely blurred. Nonparabolicity dispersion law manifests itself in a wide range of temperatures. Calculations are carried out for the example of the quantum wells in InAs and InSb.展开更多
An original theoretical model for describing the low-temperature thermal conductivity in systems with a region of forbidden values （a gap） in the phonon spectrum is proposed. The model is based on new experimental r...An original theoretical model for describing the low-temperature thermal conductivity in systems with a region of forbidden values （a gap） in the phonon spectrum is proposed. The model is based on new experimental results on the temperature dependence of the phonon diffusion coefficient in nanoceramics and dielectric glasses which showed a similar anomalous behavior of the diffusion coefficient in these systems that may be described under the assumption of a gap in the phonon spectrum. In this paper, the role of the gap in low-temperature behavior of the thermal conductivity, ~＇（T）, is analyzed. The plateau in the temperature dependence of the thermal conductivity is shown to correlate with the position and the width of the gap. The temperature dependence of thermal conductivity of such systems when changing the scat- tering parameters related to various mechanisms is studied. It is found that the umklapp process （U-processes） involving low-frequency short-wavelength phonons below the gap forms the behavior of the temperature dependence of thermal con- ductivity in the plateau region. A comparison of the calculated and experimental results shows considerable possibilities of the model in describing the low-temperature thermal conductivity in glass-like systems.展开更多
文摘Based on the laboratory calibration before launch of CBERS-02 IRMSS thermal infrared channel, the onboard blackbody calibration, the radiometric cross- calibration against TERRA MODIS corresponding channel and the in-flight field calibration at Lake Qinghai: water surface radiometric calibration test site of China on Aug. 17, 2004 are carried out in this research. When making onboard blackbody calibration of CBERS-02 IRMSS, it is necessary to understand inside structures and light path in IRMSS camera and receive and process calibration blackbody signals at normal and high temperatures. Onboard blackbody calibration results of each detector are very important to relative radiometric calibration of images processing and absolute radiometric calibration of each detector. In-flight field calibration mainly contains field experiments, obtaining synchronous images, spectrum marching and MODTRAN radiative transmi- ssion computation. Radiometric cross-calibration of CBERS-02 IRMSS thermal band against TERRA MODIS selected 6 times synchronous images of two sensors passing through Lake Qinghai and Lake Taihu from August to December, 2004 to compute the cross calibration data. Combining the in-flight field calibration and radiometric cross calibration data, the absolute radiometric calibration coefficients are calculated by the linear regression method. This new calibration model can obviously control the radiometric calibration uncertainties aroused by the single point method used in the in-flight calibration of CBERS-02 IRMSS, this kind of sensors cannot receive the cosmic background radiation. In this research, the radiometric calibration coefficients obtained through the linear regression model are 8.53 (gain, unit: DN/W m?2sr?1μm?1) and 44.92 (offset, unit: DN).
基金Project supported by the National Key Basic Research Program of China(Grant No.2012CB025903)the National Natural Science Foundation of China(Grant No.11402210)+1 种基金the Northwestern Polytechnical University Foundation for Fundamental Research(Grant No.JCY20130141)the Ministry of Education Fund for Doctoral Students Newcomer Awards of China
文摘The ring-banded spherulite is a special morphology of polymer crystals and has attracted considerable attention over recent decades. In this study, a new phase field model with polymer characteristics is established to investigate the emergence and formation mechanism of the ring-banded spherulites of crystalline polymers. The model consists of a nonconserved phase field representing the phase transition and a temperature field describing the diffusion of the released latent heat. The corresponding model parameters can be obtained from experimentally accessible material parameters.Two-dimensional calculations are carried out for the ring-banded spherulitic growth of polyethylene film under a series of crystallization temperatures. The results of these calculations demonstrate that the formation of ring-banded spherulites can be triggered by the self-generated thermal field. Moreover, some temperature-dependent characteristics of the ring-banded spherulites observed in experiments are reproduced by simulations, which may help to study the effects of crystallization temperature on the ring-banded structures.
文摘Thick film of Polystyrene (PS)/CdS semiconducting optical nanocomposite has been synthesized by dispersing nanofiller particles of CdS in PS matrix. The nanostructure of the CdS particles has been ascertained through X-ray Diffraction (XRD) and Transmission Electron Microscopy (TEM). Small angle x-ray scattering analysis has been performed in order to ascertain nanocomposite character of the PS/CdS sample. Scanning Electron Microscopy (SEM) analyses of these samples have been carried out to establish the surface morphology. Optical Absorption Spectroscopy is used to measure the energy band gap of PS/CdS nanocomposite by using Tauc relation whereas Transient Plane Source Technique is used for the determination of thermal conductivity of the prepared samples. The phase transition temperature and elastic response of the prepared samples have been ascertained through Dynamic Mechanical Analyzer (DMA). This study reveals that the thermal conductivity, Young’s modulus and the toughness of the material are greatly influenced by the existence of interfacial energetic interaction between dispersed CdS nanofiller particles and matrix of PS.
基金Funded by National Natural Science Foundation of China(No.51474170)Natural Science Foundation of Shaanxi Province(No.2016JQ5026)Foundation of Liaoning Province Educational Committee(No.2017LNQN14).
文摘Dynamic compression tests were carried out to investigate dynamic mechanical behavior and adiabatic shear bands in ultrafine grained(UFG)pure zirconium prepared by equal channel angular pressing(ECAP)and rotary swaying.The cylindrical specimens were deformed dynamically on the split Hopkinson pressure bar(SHPB)at different strain rates of 800 to 4000s^-1 at room temperature.The temperature distribution of the shear bands was estimated on the basis of temperature rise of uniform plastic deformation stage and thermal diffusion effect.The results show that the true stress-true strain curves of UFG pure zirconium are concave upward trend of strain in range of 0.02-0.16 due to the effects of strain hardening,strain rate hardening and thermal softening.The formation of the adiabatic shear bands is the main reason of UFG pure zirconium failure.A large number of micro-voids are observed in the adiabatic shear bands,and the macroscopic cracks develop from the micro-voids coalescence.The fracture surface of UFG pure zirconium exhibits quasi cleavage fracture with the characteristic features of shear dimples and river pattern.The highest temperature within the shear bands of UFG pure zirconium is about 592 K.
基金This work was supported by TUBITAK and DPT Grants Commission for a research grant (No. TBAG-2451 (104T062)).
文摘The oxidative polycondensation reaction conditions of 4-m-tolylazomethinephenol （4-TAMP） in the presence of air O2 and NaOCl as oxidants were studied in an aqueous alkaline medium between 50 and 90℃. The structures of the obtained monomer and oligomer were confirmed by FT-IR, UV-Vis, ^1H- and ^13C-NMR and elemental analysis techniques. The physical characterization was made by TG-DTA, size exclusion chromatography （SEC） and solubility tests. At the optimum reaction conditions, the yield of oligo-4-m-tolylazomethinephenol （O-4-TAMP） was found to be 62.50% （for air O2 oxidant） and 90.0% （for NaOCl oxidant）, respectively. According to the SEC analysis, the number-average molecular weight （Mn）, weight-average molecular weight （Mw） and polydispersity index （PDI） values of O-4-TAMP were found to be 2310, 2610 g tool 1 and 1. 13, respectively, using air O2, and 1390, 1710 g mol^-1 and 1.23, using NaOCl, respectively. According to TG-DTA analyses, O-4-TAMP was more stable than 4-TAMP against thermal decomposition. The weight losses of 4-TAMP and O-4-TAMP were found to be 68% and 58% at 1000℃. Electrical conductivity of the O-4-TAMP was measured, showing that the polymer is a typical semiconductor. Electrochemically, the highest occupied molecular orbital （HOMO）, the lowest unoccupied molecular orbital （LUMO） and electrochemical energy gaps （E＇g） for 4-TAMP are -5.96, -3.22 and 2.74 eV, respectively. The HOMO, LUMO and （E＇g） for O-4-TAMP are -5.78, -3.44 and 2.34 eV, respectively. According to UV-Vis measurements, optical band gaps （Eg） of 4-TAMP and O-4-TAMP were found to be 3.45 and 3. 1 0 eV, respectively.
基金Project supported by the National Basic Research Program of China (Grant No. 2006CB302705)the Foundation for Key Program of Ministry of Education, China (Grant No. 107003)
文摘In this work, we investigate strain effects induced by the deposition of gate dielectrics on the valence band structures in Si （110） nanowire via the simulation of strain distribution and the calculation of a generalized 6 × 6k .p strained valence band. The nanowire is surrounded by the gate dielectric. Our simulation indicates that the strain of the amorphous SiO2 insulator is negligible without considering temperature factors. On the other hand, the thermal residual strain in a nanowire with amorphous SiO2 insulator which has negligible lattice misfit strain pushes the valence subbands upwards by chemical vapour deposition and downwards by thermal oxidation treatment. In contrast with the strain of the amorphous SiO2 insulator, the strain of the HfO2 gate insulator in Si （110） nanowire pushes the valence subbands upwards remarkably. The thermal residual strain by HfO2 insulator contributes to the up-shifting tendency. Our simulation results for valence band shifting and warping in Si nanowires can provide useful guidance for further nanowire device design.
基金Project supported by the National Natural Science Foundation of China(Grant No.11474076)
文摘P-type ZnO is crucial for the realization of ZnO-based homojunction ultraviolet optoelectronic devices. The problem associated with the preparation of stable p-type ZnO with high hole density still hinders device applications. In this paper,we introduce an alternative route to stabilizing N in the oxidation process, the thermal stability of p-ZnO is significantly improved. Finally, we discuss the limitations of the alternative doping method and provide some prospective outlook of the method.
文摘The solidified microstructure of a Ni-Cu-Si cast alloy has been investigated, and a kind of banding structure was observed. The results showed that, the banding structure was composed of coarser particles which were Ni3Si type of precipitates and similar to the fine particles precipitate uniformly distributed within matrix of Ni solid solution, in both crystal structure and composition. The formation of bandings was resulted from cast thermal stress and dislocation walls. It was found that the cracks propagated along these bandings in tensile test. The banding structure can be depressed by reducing the cast thermal stress, which can improve the tensile ductility.
文摘The analysis of the density of states for electrons in single quantum well, the conduction band nonparabolicity take is account. It is shown that the degree of conduction band nonparabolicity pronounces depending on the energy density of states. With increasing temperature, a step change in the density of states smoothes and at high temperatures is completely blurred. Nonparabolicity dispersion law manifests itself in a wide range of temperatures. Calculations are carried out for the example of the quantum wells in InAs and InSb.
基金the National Natural Science Foundation of China(Nos.51704209,U1810208,U1810122)the Central Government Guided Local Science and Technology Development Projects,China(No.YDZJSX2021A010)+5 种基金the Projects of International Cooperation in Shanxi Province,China(Nos.201803D421086,201903D421076)Shanxi Province Patent Promotion Implementation Fund,China(No.20200718)the Technological Innovation Programs of Higher Education Institutions in Shanxi Province,China(No.201802034)Shanxi Province Scientific Facilities and Instruments Shared Service Platform of Magnesium-based Materials Electric Impulse Aided Forming,China(No.201805D141005)Science and Technology Major Project of Shanxi Province,China(Nos.20191102008,20191102007,20181101008)Yantai High-end Talent Introduction“Double Hundred Plan”,China(2021)。
基金Project supported by the Ural Branch of the Russian Academy of Sciences,Russia(Grant No.18-2-2-12)the Russian Foundation for Basic Research,Russia(Grant Nos.16-07-00529 and 18-07-00191)the Financing Program,Russia(Grant No.AAAA-A16-116021010082-8)
文摘An original theoretical model for describing the low-temperature thermal conductivity in systems with a region of forbidden values （a gap） in the phonon spectrum is proposed. The model is based on new experimental results on the temperature dependence of the phonon diffusion coefficient in nanoceramics and dielectric glasses which showed a similar anomalous behavior of the diffusion coefficient in these systems that may be described under the assumption of a gap in the phonon spectrum. In this paper, the role of the gap in low-temperature behavior of the thermal conductivity, ~＇（T）, is analyzed. The plateau in the temperature dependence of the thermal conductivity is shown to correlate with the position and the width of the gap. The temperature dependence of thermal conductivity of such systems when changing the scat- tering parameters related to various mechanisms is studied. It is found that the umklapp process （U-processes） involving low-frequency short-wavelength phonons below the gap forms the behavior of the temperature dependence of thermal con- ductivity in the plateau region. A comparison of the calculated and experimental results shows considerable possibilities of the model in describing the low-temperature thermal conductivity in glass-like systems.
