By orthogonal design theory, technological parameters of chrysanthemum-like ZnO particles prepared in a hydrothermal process are optimized. This paper reports a set of technological parameters for growing chrysanthemu...By orthogonal design theory, technological parameters of chrysanthemum-like ZnO particles prepared in a hydrothermal process are optimized. This paper reports a set of technological parameters for growing chrysanthemumlike ZnO particles on a large scale. It investigates the morphologies and crystalline structures of the as-synthesized three-dimensional ZnO particles with a scanning electron microscope, x-ray diffractometer and transmission electron microscope, and the possible growth mechanism on the three-dimensional ZnO particles. The experimental results indicate that the values of ε′ε″ and tan δe gradually increase in the X band with the improvement of the developmental level of chrysanthemum-like ZnO particles, implying that the electromagnetic wave absorbing property depends on the morphologies of three-dimensional ZnO particles.展开更多
This paper investigates the effect of Nb doping on the electronic structure and optical properties of Sr2TiO4 by the first-principles calculation of plane wave ultra-soft pseudo-potential based on density functional t...This paper investigates the effect of Nb doping on the electronic structure and optical properties of Sr2TiO4 by the first-principles calculation of plane wave ultra-soft pseudo-potential based on density functional theory （DFT）.The calculated results reveal that due to the electron doping,the Fermi level shifts into conduction bands（CBs） for Sr2NbxTi1-xO4 with x=0.125 and the system shows n-type degenerate semiconductor features. Sr2TiO4 exhibits optical anisotropy in its main crystal axes,and the c-axis shows the most suitable crystal growth direction for obtaining a wide transparent region.The optical transmittance is higher than 90% in the visible range for Sr2Nb0.125Ti0.875O4.展开更多
Chrysanthemum-like ZnO nanowire clusters with different Sb-doping concentrations were prepared using a hy- drothermal process. The microstructures, morphologies, and dielectric properties of the as-prepared products w...Chrysanthemum-like ZnO nanowire clusters with different Sb-doping concentrations were prepared using a hy- drothermal process. The microstructures, morphologies, and dielectric properties of the as-prepared products were characterized by X-ray diffraction （XRD）, high-resolution transmission electron microscopy （HRTEM）, field emission environment scanning electron microscope （FEESEM）, and microwave vector network analyzer respectively. The results indicate that the as-prepared products are Sb-doped ZnO single crystallines with a hexagonal wurtzite structure, the flower bud saturation degree Fd is obviously different from that of the pure ZnO nanowire clusters, the good dielectric loss property is found in Sb-doped ZnO products with low density, and the dielectric loss tangent tanSe increases with the increase of the Sb-doping concentration in a certain concentration range.展开更多
Adsorption and reaction of CO on two possible terminations of SrTiO3 （100） surface are investigated by the first-principles calculation of plane wave ultrasoft pseudopotentiai based on the density function theory. T...Adsorption and reaction of CO on two possible terminations of SrTiO3 （100） surface are investigated by the first-principles calculation of plane wave ultrasoft pseudopotentiai based on the density function theory. The adsorption energy, Mulliken population analysis, density of states （DOS） and electronic density difference of CO on SrTiO3 （100） surface, which have never been investigated before as far as we know are performed. The calculated results reveal that the Ti-CO orientation is the most stable configuration and the adsorption energy （0.449eV） is quite small. CO molecules adsorb weakly on the SrTiO3 （100） surface, there is predominantly electrostatic attraction between CO and the surface rather than a chemical bonding mechanism.展开更多
Through hydrothermal process, the chrysanthemum-like ZnO particles are prepared with zinc acetate dihydrate （Zn（CH3COO）2·2H2O） and sodium hydroxide （NaOH） used as main resources under the different concentr...Through hydrothermal process, the chrysanthemum-like ZnO particles are prepared with zinc acetate dihydrate （Zn（CH3COO）2·2H2O） and sodium hydroxide （NaOH） used as main resources under the different concentrations of surfactant polyacrylamide （PAM）. The microstructure, morphology and the electromagnetic properties of the as-prepared products are characterized by high-resolution transmission electron microscopy （HRTEM）, field emission environment scanning electron microscope （FEESEM） and microwave vector network analyzer, respectively. The experimental results indicate that the as-prepared products are ZnO single crystalline with hexagona wurtzite structure, that the values of slenderness ratio Ld are different in different PAM concentrations, and that the good magnetic loss property is found in the ZnO products, and the average magnetic loss tangent tan δu increases with PAM concentration increasing, while the dielectric loss tangent tan ~e decreases.展开更多
With widely availed clinically used radionuclides,Cer enkov luminescence imaging(CLI)has become a potential tool in the field of optical molecular imaging.However,the impulse noises introduced by high-energy gamma ray...With widely availed clinically used radionuclides,Cer enkov luminescence imaging(CLI)has become a potential tool in the field of optical molecular imaging.However,the impulse noises introduced by high-energy gamma rays that are generated during the decay of radionuclide reduce the image quality significantly,which affects the acauracy of quantitative analysis,as well as the three dimensional reconstruction.In this work,a novel denoising framework based on fuzzy dlustering and curvat ure driven difusion(CDD)is proposed to remove this kind of impulse noises.To improve the accuracy,the F u1zzy Local Information C-Means algorithm,where spatial information is evolved,is used.We evaluate the per formance of the proposed framework sys-tematically with a series of experiments,and the corresponding results demonstrate a better denoising effect than those from the commonly used median filter method.We hope this work may provide a useful data pre processing tool for CLI and its following studies.展开更多
The effect of La doping on the electronic structure and optical properties of SrTiO3 and Sr2 TiO4 is investigated by the first-principles calculation of plane wave ultrasoft pseudopotential based on the density functi...The effect of La doping on the electronic structure and optical properties of SrTiO3 and Sr2 TiO4 is investigated by the first-principles calculation of plane wave ultrasoft pseudopotential based on the density function theory （DFT）. The calculated results reveal that the electron doping in the case of Sr0.875La0.125 TiO3 and Sr1.875Lao.125TiO4 can be described within the rigid band model. The La^3＋ ions fully acts as electron donors in Sr0.875La0.125 TiO3 and Sr1.875 La0.125 TiO4 systems and the Fermi level shifts further into the conduction bands （CBs） for Sr1.875Lao.125 TiO4 compared to Sr0.875 Lao. 125 TiO3. The two systems exhibit n-type degenerate semiconductor features. At the same time, the density of states （DOS） of the two systems shift towards low energies and the optical band gaps are broadened. The Sr1.875La0.125 TiO4 is highly transparent with the transmittance about 90% in the visible range, which is larger than that of Sr0.875Lao.125 TiO3（85%）. The wide band gap, small transition probability and weak absorption due to the low partial density of states （PDOS） of impurity in the Fermi level result in the optical transparency of the films.展开更多
The effect of In doping on the electronic structure and optical properties of Sr2 TiO4 is investigated by a firstprinciples calculation of plane wave ultrasoft pseudopotentials based on density functional theory. The ...The effect of In doping on the electronic structure and optical properties of Sr2 TiO4 is investigated by a firstprinciples calculation of plane wave ultrasoft pseudopotentials based on density functional theory. The calculated results reveal that corner-shared TiO6 octahedra dominate the main electronic properties of Sr2TiO4 and the covalency of the Ti-O（1） bond in the ab plane is stronger than that of the Ti-O（2） bond along the c-axis. After In doping, there is a little lattice expansion in Sr2In0.125 Ti0.875 O4 and the interaction between the Ti-O bond near the impurity In atom is weakened. The binding energies of Sr2TiO4 and Sr2In0.125Ti0.875O4 estimated from the electronic structure calculations indicate that the crystal structure of Sr2In0.125 Ti0.875 O4 is still stable after doping, but its stability is lower than that of undoped Sr2TiO4. Moreover, the valence bands （VBs） of the Sr2In0.125Ti0.875O4 system consist of O 2p and In 4d states, and the mixing of O 2p and In 4d states makes the top VBs shift significantly to high energies, resulting in visible light absorption. The adsorption of visible light is of practical importance for the application of St2 TiO4 as a photocatalyst.展开更多
The effects of La and Sb doping on the electronic structure and optical properties of SrTiO3 are investigated by first-principles calculation of the plane wave ultra-soft pseudo-potential based on density functional t...The effects of La and Sb doping on the electronic structure and optical properties of SrTiO3 are investigated by first-principles calculation of the plane wave ultra-soft pseudo-potential based on density functional theory. The calculated results reveal that corner-shared TiO6 octahedra dominate the main electronic properties of SrTiO3, and its structural stability can be improved by La doping. The La^3＋ ion fnlly acts as an electron donor in Sr0.875La0.125TiO3 and the Fermi level shifts into the conduction bands （CBs） after La doping. As for SrSb0.125Ti0.87503, there is a distortion near the bottom of the CBs for SrSb0.125Ti0.87503 after Sb doping and an incipient localization of some of the doped electrons trapped in the Ti site, making it impossible to describe the evolution of the density of states （DOS） within the rigid band model. At the same time, the DOSs of the two electron-doped systems shift towards low energies and the optical band gaps are broadened by about 0.4 and 0.6 eV for Sr0.875La0.125TiO3 and SrSb0.125Ti0.87503, respectively. Moreover, the transmittance of SrSb0.125Ti0.87503 is as high as 95% in most of the visible region, which is higher than that of Sr0.875La0.125TiO3（85%）. The wide band gap, the small transition probability and the weak absorption due to the low partial density of states （PDOS） of impurity in the Fermi level result in the significant optical transparency of SrSb0.125Ti0.875O3.展开更多
Chrysanthemum-like ZnO nanowire clusters with different Mn-doping concentrations are prepared by a hydrothermal process. The microstructnre, morphology and electromagnetic properties are characterized by x-ray diffrac...Chrysanthemum-like ZnO nanowire clusters with different Mn-doping concentrations are prepared by a hydrothermal process. The microstructnre, morphology and electromagnetic properties are characterized by x-ray diffractometer high-resolution transmission electron microscopy （HRTEM）, a field emission environment scanning electron microscope （FEESEM） and a microwave vector network analyser respectively. The experimental results indicate that the as- prepared products are Mn-doped ZnO single crystalline with a hexagonal wurtzite structure, that the growth habit changes due to Mn-doping and that a good magnetic loss property is found in the Mn-doped ZnO products, and the average magnetic loss tangent tandm is up to 0.170099 for 3% Mn-doping, while the dielectric loss tangent tande is weakened, owing to the fact that ions Mn2＋ enter the crystal lattice of ZnO.展开更多
Low pressure metalorganic chemical vapour deposition （LP-MOCVD） growth and characteristics of InAsSb on （100） GaSb substrates are investigated. Mirror-like surfaces with a minimum lattice mismatch are obtained. Th...Low pressure metalorganic chemical vapour deposition （LP-MOCVD） growth and characteristics of InAsSb on （100） GaSb substrates are investigated. Mirror-like surfaces with a minimum lattice mismatch are obtained. The samples are studied by photoluminescence spectra, and the output is 3.17μm in wavelength. The surface of InAsSb epilayer shows that its morphological feature is dependent on buffer layer. With an InAs buffer layer used, the best surface is obtained. The InAsSb film shows to be of n-type conduction with an electron concentration of 8.52 × 10^16 cm^-3.展开更多
The steady-state and transient electron transport properties ofβ-(Al_(x)Ga_(1-x))_(2)O_(3)/Ga_(2)O_(3)heterostructures were investigated by Monte Carlo simulation with the classic three-valley model.In particular,the...The steady-state and transient electron transport properties ofβ-(Al_(x)Ga_(1-x))_(2)O_(3)/Ga_(2)O_(3)heterostructures were investigated by Monte Carlo simulation with the classic three-valley model.In particular,the electronic band structures were acquired by first-principles calculations,which could provide precise parameters for calculating the transport properties of the two-dimensional electron gas(2DEG),and the quantization effect was considered in theΓvalley with the five lowest subbands.Wave functions and energy eigenvalues were obtained by iteration of the Schrödinger–Poisson equations to calculate the 2DEG scattering rates with five main scattering mechanisms considered.The simulated low-field electron mobilities agree well with the experimental results,thus confirming the effectiveness of our models.The results show that the room temperature electron mobility of theβ-(Al_(0.188)Ga_(0.812))_(2)O_(3)/Ga_(2)O_(3)heterostructure at 10 k V·cm^(-1)is approximately153.669 cm^(2)·V^(-1)·s^(-1),and polar optical phonon scattering would have a significant impact on the mobility properties at this time.The region of negative differential mobility,overshoot of the transient electron velocity and negative diffusion coefficients are also observed when the electric field increases to the corresponding threshold value or even exceeds it.This work offers significant parameters for theβ-(Al_(x)Ga_(1-x))_(2)O_(3)/Ga_(2)O_(3)heterostructure that may benefit the design of high-performanceβ-(Al_(x)Ga_(1-x))_(2)O_(3)/Ga_(2)O_(3)heterostructure-based devices.展开更多
By orthogonal design theory, technological parameters of the （002）-oriented ZnO film prepared in sol-gel process are optimized. A set of technological parameters for growing highly （002）-oriented ZnO film is obtai...By orthogonal design theory, technological parameters of the （002）-oriented ZnO film prepared in sol-gel process are optimized. A set of technological parameters for growing highly （002）-oriented ZnO film is obtained. As a result, it is proven that the Zn^2＋ concentration is the most important factor to grow a highly （002）-oriented ZnO film. We take an appropriate Zn^2＋ concentration 0.35mol/L for the aimed film, of which photoluminescence property is better than those of the films derived from other Zn^2＋ concentrations precursor solution. The Zn^2＋ concentration either larger or smaller than 0.35 mol/L leads to the （002）-oriented degree decrease of films. By employing an atom force microscope, a hexagonal atom arrangement, which indicates that the film site detected is a ZnO single crystal, is observed in the surface of the highly （002）-oriented film.展开更多
By making use of the density functional theory (DFT) of the first principles and generalized gradient approximation method, the electronic structures and properties of ideal GaN and AlxGa1-xN crystals (x = 0.25, 0.5, ...By making use of the density functional theory (DFT) of the first principles and generalized gradient approximation method, the electronic structures and properties of ideal GaN and AlxGa1-xN crystals (x = 0.25, 0.5, 0.75) have been calculated and analyzed, and the influence of the doping quantity of x on the characteristics of AlxGa1-xN has been studied. The calculation results show that optical band gap of AlxGa1-xN crystal is widened that the Eg of AlxGa1-xN can be adjusted by the x, and the absorption spectrum shifts to high-energy direction with the increase of the x, and then the Fermi energy moves to the top of valence band slightly which leads to that conductivity weakened after mixed with the Al. At the same time, the variation trends of complex dielectric function, absorption spectrum and transitivity have been made clear, and the results show that AlxGa1-xN compounds can achieve the theoretical design of photoelectric performance. In a word, AlxGa1-xN crystals are potential semiconductors with very remarkable photoelectric properties, which can be applied in the development of the diversified GaN devices.展开更多
At present, CuInSe2 (referred to as CIS) semiconductor has become one of the hot points in solar cell field at home and abroad for its excellent performances, such as direct bandgap, high light absorption coefficient,...At present, CuInSe2 (referred to as CIS) semiconductor has become one of the hot points in solar cell field at home and abroad for its excellent performances, such as direct bandgap, high light absorption coefficient, high photoelectric conversion efficiency and long-term stability. In this paper, the CIS bulk materials are prepared by the horizontal Bridgman method with double-heat sources, the crystal structure, microstructure morphology and composition of the samples are analyzed in X-ray diffraction instrument (XRD) and scanning electronic microscope (SEM) with Energy Dispersive X-ray Spectrum (EDX), and surface electrical state and electrical properties of the samples are characterized in X-ray photoelectron spectroscopy (XPS) and four point resistivity test system. The results show that the CIS crystal was grown, and that the conductive performance of the samples is good which display the characteristics of p-type semiconductor. Furthermore, a thin film CIS sample was obtained by argon ion-beam scanning bombardment, and it has high solar energy absorptivity and the bandgap of 0.99 eV analyzed in Ultraviolet-visible Spectrum that is suitable for solar cell. Keywords:展开更多
Advancing aqueous zinc-ion batteries(AZIBs)are significantly challenged by the need to find cathode materials that can provide both high capacity and fast reaction kinetics.Tellurium telluride,a topological insulator,...Advancing aqueous zinc-ion batteries(AZIBs)are significantly challenged by the need to find cathode materials that can provide both high capacity and fast reaction kinetics.Tellurium telluride,a topological insulator,has emerged as a promising cathode candidate for AZIBs,garnering increasing attention.However,the complete understanding of its electrochemical reaction mechanism and its unsatisfactory energy storage performance are major obstacles to the practical use.In this work,we synthesize a bimetallic bismuth-nickel telluride with Te vacancies,defined as Bi_(2)Te_(3-x)/NiTe_(2),which forms a topological insulator/topological Dirac semimetal heterostructure through a hydrothermal approach.The electrochemical reaction mechanism of Bi_(2)Te_(3-x)/NiTe_(2),along with its phase and structural changes are elucidated by using in-situ X-ray diffraction,various electrochemical techniques,and ex-situ characterizations.The influences of Bi_(2)Te_(3-x)/NiTe_(2)on the electronic structure,interracial electron transfer,migration barrier,and ion adsorption energy are investigated by using density functional theory calculations.Our findings reveal that Bi_(2)Te_(3-x)/NiTe_(2)exhibits excellent specific capacity,stable cycling,and superior rate capability as a cathode material for AZIBs.Moreover,further studies demonstrate that Bi_(2)Te_(3-x)/NiTe_(2)maintains exceptional performance at low temperatures of-15 and-5℃,and also retains stability and flexibility when integrated into flexible battery packs.展开更多
Bioluminescent tomography(BLT)is a noninvasive imaging technology that uses optical methods to study physiological and pathological processes at the cellular and molecular levels.It is a powerful tool for early diagno...Bioluminescent tomography(BLT)is a noninvasive imaging technology that uses optical methods to study physiological and pathological processes at the cellular and molecular levels.It is a powerful tool for early diagnosis and treatment of tumors,as well as drug development.However,the simplified optical transmission models and the ill-posed inverse reconstruction limit its wide applications.The development of deep learning has provided new potential for extending the applications of optical BLT.Researchers have introduced various methods such as neural networks and self-attention mechanisms to improve reconstruction accuracy.Despite these efforts,weak energy points around the reconstructed light source center still impact the accuracy of restoration.In this study,we propose a dual-branch network based on a combination of attention mechanism and fully connected layers(FC-AM)to reduce centroid error and improve reconstruction performance.The network architecture consists of a fully connected(FC)subnetwork and an attention mechanism-based dual-branch(AMDB)subnetwork.The FC subnetwork is used to process input data.AMDB subnetwork is used for deep feature extraction,and captures feature information from different perspectives in parallel.Each branch of the AMDB subnetwork is composed of four AM subnets,which extract features through multilayer linear transformations and attention mechanisms.The outputs of the AMDB are combined through feature fusion to produce the final result.Numerical simulations and experimental results demonstrate that the FC-AM network significantly improves BLT reconstruction performance compared to existing methods(KNN_LC and AMLC networks),offering enhanced stability and accuracy.展开更多
Face recognition based on few training samples is a challenging task. In daily applications, sufficient training samples may not be obtained and most of the gained training samples are in various illuminations and pos...Face recognition based on few training samples is a challenging task. In daily applications, sufficient training samples may not be obtained and most of the gained training samples are in various illuminations and poses. Non-sufficient training samples could not effectively express various facial conditions, so the improvement of the face recognition rate under the non-sufficient training samples condition becomes a laborious mission. In our work, the facial pose pre-recognition(FPPR) model and the dualdictionary sparse representation classification(DD-SRC) are proposed for face recognition. The FPPR model is based on the facial geometric characteristic and machine learning, dividing a testing sample into full-face and profile. Different poses in a single dictionary are influenced by each other, which leads to a low face recognition rate. The DD-SRC contains two dictionaries, full-face dictionary and profile dictionary, and is able to reduce the interference. After FPPR, the sample is processed by the DD-SRC to find the most similar one in training samples. The experimental results show the performance of the proposed algorithm on olivetti research laboratory(ORL) and face recognition technology(FERET) databases, and also reflect comparisons with SRC, linear regression classification(LRC), and two-phase test sample sparse representation(TPTSSR).展开更多
Fluorescence imaging techniques represent essential tools in in vitro,preclinical,and clinical studies.In this study,an improved one-step hydrothermal method to synthesize citric acid(CA)modifiedα-NaYbF_(4):2%Er^(3+)...Fluorescence imaging techniques represent essential tools in in vitro,preclinical,and clinical studies.In this study,an improved one-step hydrothermal method to synthesize citric acid(CA)modifiedα-NaYbF_(4):2%Er^(3+)nanocrystals was proposed.The introduction of various doping ions into NaYbF_(4):2%Er^(3+)and the different valence states of the same ions affect both the crystal size and upconversion luminesce nce.There fore,we investigated the upconversion luminesce nce enha ncement of NaYbF_(4):2%Er^(3+)by ion doping and find that the upconversion luminescence intensity of the upconversion nanoparticles(UCNPs)co-doped with 5 mol%Fe^(2+)ions shows the greatest enhancement,especially for red emission at654 nm.Furthermore,HeLa cells incubated with UCNPs allow for imaging with strong red upconversion emission detectio n.Confocal laser scanning microscope(CLSM)fluorescent images of HeLa cells indicate that NaYbF_(4):2%Er/5%Fe^(2+)leads to a clear outline and improves visualization of the cell morphology.In addition,the CA coated NaYbF_(4):2%Er^(3+)/5%Fe^(2+)nanoparticles and NaYbF_(4):2%Er^(3+)/5%Fe^(2+)show low cytotoxicity in HeLa cells.Organ imaging reveals the efficiency of these UCNPs to analyze the lungs,liver,and spleen.Together,these results indicate that the Cit-NaYbF_(4):2%Er^(3+)/5%Fe^(2+)UCNPs are efficient nanoprobes for fluorescence molecular to mography.展开更多
In order to utilize integrated passive technology in printed circuit boards （PCBs）, manufacturing processing for integrated resistors by lamination method was investigated. Integrated resistors fabricated from Ohmeg...In order to utilize integrated passive technology in printed circuit boards （PCBs）, manufacturing processing for integrated resistors by lamination method was investigated. Integrated resistors fabricated from Ohmega technologies in the experiment were 1 408 pieces per panel with four different patterns A, B, C and D and four resistance values of 25, 50, 75 and 100 fL Six panel per batch and four batches were performed totally. The testing was done for 960 pieces of integrated resistors randomly selected with the same size. The value distribution ranges and the relative standard deviation （RSD） show that the scatter degree of the resistance decreases with the resistor size increasing and/or with the resistance increasing. Patterns D with resistance of 75 and 100% for four patterns have the resistance value variances less than 10%. Patterns C and D with resistance of 100 Ω have the manufacturing tolerance less than 10%. The process capabilities are from about 0.6 to 1.6 for the designed testing patterns, which shows that the integrated resistors fabricated have the potential to be used in multilayer PCBs in the future.展开更多
基金supported by the National High Technology Research and Development Program of China (Grant No 2005A000200)the Xi’an Applied Materials Innovation Fund (Grant No XA-AM-200712)the Innovative Experiment Program for Chinese students (Grant No State 200721)
文摘By orthogonal design theory, technological parameters of chrysanthemum-like ZnO particles prepared in a hydrothermal process are optimized. This paper reports a set of technological parameters for growing chrysanthemumlike ZnO particles on a large scale. It investigates the morphologies and crystalline structures of the as-synthesized three-dimensional ZnO particles with a scanning electron microscope, x-ray diffractometer and transmission electron microscope, and the possible growth mechanism on the three-dimensional ZnO particles. The experimental results indicate that the values of ε′ε″ and tan δe gradually increase in the X band with the improvement of the developmental level of chrysanthemum-like ZnO particles, implying that the electromagnetic wave absorbing property depends on the morphologies of three-dimensional ZnO particles.
基金Project supported by the Natural Science Foundation of ShaanXi Province of China (Grant No 2005F06)Northwest University(NWU) Graduate Innovation and Creativity Funds (Grant No 08YZZ47)
文摘This paper investigates the effect of Nb doping on the electronic structure and optical properties of Sr2TiO4 by the first-principles calculation of plane wave ultra-soft pseudo-potential based on density functional theory （DFT）.The calculated results reveal that due to the electron doping,the Fermi level shifts into conduction bands（CBs） for Sr2NbxTi1-xO4 with x=0.125 and the system shows n-type degenerate semiconductor features. Sr2TiO4 exhibits optical anisotropy in its main crystal axes,and the c-axis shows the most suitable crystal growth direction for obtaining a wide transparent region.The optical transmittance is higher than 90% in the visible range for Sr2Nb0.125Ti0.875O4.
基金Project supported by the National Natural Science Foundation of China (Grant No. 60976069)the Natural Science Foundation of Shaanxi Province, China (Grant No. 2010JM6008)the Xi’an Scientific and Technological Project, China (GrantNo. CXY1008)
文摘Chrysanthemum-like ZnO nanowire clusters with different Sb-doping concentrations were prepared using a hy- drothermal process. The microstructures, morphologies, and dielectric properties of the as-prepared products were characterized by X-ray diffraction （XRD）, high-resolution transmission electron microscopy （HRTEM）, field emission environment scanning electron microscope （FEESEM）, and microwave vector network analyzer respectively. The results indicate that the as-prepared products are Sb-doped ZnO single crystallines with a hexagonal wurtzite structure, the flower bud saturation degree Fd is obviously different from that of the pure ZnO nanowire clusters, the good dielectric loss property is found in Sb-doped ZnO products with low density, and the dielectric loss tangent tanSe increases with the increase of the Sb-doping concentration in a certain concentration range.
基金Supported by the Natural Science Foundation of Shaanxi Province under Grant No 2005F06.
文摘Adsorption and reaction of CO on two possible terminations of SrTiO3 （100） surface are investigated by the first-principles calculation of plane wave ultrasoft pseudopotentiai based on the density function theory. The adsorption energy, Mulliken population analysis, density of states （DOS） and electronic density difference of CO on SrTiO3 （100） surface, which have never been investigated before as far as we know are performed. The calculated results reveal that the Ti-CO orientation is the most stable configuration and the adsorption energy （0.449eV） is quite small. CO molecules adsorb weakly on the SrTiO3 （100） surface, there is predominantly electrostatic attraction between CO and the surface rather than a chemical bonding mechanism.
基金Project supported by the National High Technology Research and Development Program of China (Grant No 2005A000200)the Xi’an Applied Materials Innovation Fund, China (Grant No XA-AM-200712)the Innovative Experiment Program for Chinese Students (Grant No State 200721)
文摘Through hydrothermal process, the chrysanthemum-like ZnO particles are prepared with zinc acetate dihydrate （Zn（CH3COO）2·2H2O） and sodium hydroxide （NaOH） used as main resources under the different concentrations of surfactant polyacrylamide （PAM）. The microstructure, morphology and the electromagnetic properties of the as-prepared products are characterized by high-resolution transmission electron microscopy （HRTEM）, field emission environment scanning electron microscope （FEESEM） and microwave vector network analyzer, respectively. The experimental results indicate that the as-prepared products are ZnO single crystalline with hexagona wurtzite structure, that the values of slenderness ratio Ld are different in different PAM concentrations, and that the good magnetic loss property is found in the ZnO products, and the average magnetic loss tangent tan δu increases with PAM concentration increasing, while the dielectric loss tangent tan ~e decreases.
基金the Program of the National Natural Science Foundation of China under Grant Nos.61701403,61601363,11571012,61372046 and 61640418the Natural Science Basic Research Plan in Shaanxi Province of China under Grant Nos.2017JQ6006 and 2017JQ6017.
文摘With widely availed clinically used radionuclides,Cer enkov luminescence imaging(CLI)has become a potential tool in the field of optical molecular imaging.However,the impulse noises introduced by high-energy gamma rays that are generated during the decay of radionuclide reduce the image quality significantly,which affects the acauracy of quantitative analysis,as well as the three dimensional reconstruction.In this work,a novel denoising framework based on fuzzy dlustering and curvat ure driven difusion(CDD)is proposed to remove this kind of impulse noises.To improve the accuracy,the F u1zzy Local Information C-Means algorithm,where spatial information is evolved,is used.We evaluate the per formance of the proposed framework sys-tematically with a series of experiments,and the corresponding results demonstrate a better denoising effect than those from the commonly used median filter method.We hope this work may provide a useful data pre processing tool for CLI and its following studies.
基金Supported by the National Natural Science Foundation of Shaanxi Province under Grant No 2005F06.
文摘The effect of La doping on the electronic structure and optical properties of SrTiO3 and Sr2 TiO4 is investigated by the first-principles calculation of plane wave ultrasoft pseudopotential based on the density function theory （DFT）. The calculated results reveal that the electron doping in the case of Sr0.875La0.125 TiO3 and Sr1.875Lao.125TiO4 can be described within the rigid band model. The La^3＋ ions fully acts as electron donors in Sr0.875La0.125 TiO3 and Sr1.875 La0.125 TiO4 systems and the Fermi level shifts further into the conduction bands （CBs） for Sr1.875Lao.125 TiO4 compared to Sr0.875 Lao. 125 TiO3. The two systems exhibit n-type degenerate semiconductor features. At the same time, the density of states （DOS） of the two systems shift towards low energies and the optical band gaps are broadened. The Sr1.875La0.125 TiO4 is highly transparent with the transmittance about 90% in the visible range, which is larger than that of Sr0.875Lao.125 TiO3（85%）. The wide band gap, small transition probability and weak absorption due to the low partial density of states （PDOS） of impurity in the Fermi level result in the optical transparency of the films.
文摘The effect of In doping on the electronic structure and optical properties of Sr2 TiO4 is investigated by a firstprinciples calculation of plane wave ultrasoft pseudopotentials based on density functional theory. The calculated results reveal that corner-shared TiO6 octahedra dominate the main electronic properties of Sr2TiO4 and the covalency of the Ti-O（1） bond in the ab plane is stronger than that of the Ti-O（2） bond along the c-axis. After In doping, there is a little lattice expansion in Sr2In0.125 Ti0.875 O4 and the interaction between the Ti-O bond near the impurity In atom is weakened. The binding energies of Sr2TiO4 and Sr2In0.125Ti0.875O4 estimated from the electronic structure calculations indicate that the crystal structure of Sr2In0.125 Ti0.875 O4 is still stable after doping, but its stability is lower than that of undoped Sr2TiO4. Moreover, the valence bands （VBs） of the Sr2In0.125Ti0.875O4 system consist of O 2p and In 4d states, and the mixing of O 2p and In 4d states makes the top VBs shift significantly to high energies, resulting in visible light absorption. The adsorption of visible light is of practical importance for the application of St2 TiO4 as a photocatalyst.
基金Project supported by the Northwest University (NWU) Graduate Innovation and Creativity Funds (Grant No. 08YZZ47)the Natural Science Foundation of Shaanxi Province of China (Grant No. 2009JM8013)
文摘The effects of La and Sb doping on the electronic structure and optical properties of SrTiO3 are investigated by first-principles calculation of the plane wave ultra-soft pseudo-potential based on density functional theory. The calculated results reveal that corner-shared TiO6 octahedra dominate the main electronic properties of SrTiO3, and its structural stability can be improved by La doping. The La^3＋ ion fnlly acts as an electron donor in Sr0.875La0.125TiO3 and the Fermi level shifts into the conduction bands （CBs） after La doping. As for SrSb0.125Ti0.87503, there is a distortion near the bottom of the CBs for SrSb0.125Ti0.87503 after Sb doping and an incipient localization of some of the doped electrons trapped in the Ti site, making it impossible to describe the evolution of the density of states （DOS） within the rigid band model. At the same time, the DOSs of the two electron-doped systems shift towards low energies and the optical band gaps are broadened by about 0.4 and 0.6 eV for Sr0.875La0.125TiO3 and SrSb0.125Ti0.87503, respectively. Moreover, the transmittance of SrSb0.125Ti0.87503 is as high as 95% in most of the visible region, which is higher than that of Sr0.875La0.125TiO3（85%）. The wide band gap, the small transition probability and the weak absorption due to the low partial density of states （PDOS） of impurity in the Fermi level result in the significant optical transparency of SrSb0.125Ti0.875O3.
基金supported by the National Natural Science Foundation of China (Grant No. 60976069)the Natural Science Foundation of Shaanxi Province,China (Grant No. 2010JM6008)the Xi’an Scientific and Technological Project,China (Grant No. CXY1008)
文摘Chrysanthemum-like ZnO nanowire clusters with different Mn-doping concentrations are prepared by a hydrothermal process. The microstructnre, morphology and electromagnetic properties are characterized by x-ray diffractometer high-resolution transmission electron microscopy （HRTEM）, a field emission environment scanning electron microscope （FEESEM） and a microwave vector network analyser respectively. The experimental results indicate that the as- prepared products are Mn-doped ZnO single crystalline with a hexagonal wurtzite structure, that the growth habit changes due to Mn-doping and that a good magnetic loss property is found in the Mn-doped ZnO products, and the average magnetic loss tangent tandm is up to 0.170099 for 3% Mn-doping, while the dielectric loss tangent tande is weakened, owing to the fact that ions Mn2＋ enter the crystal lattice of ZnO.
基金Project supported by the National High Technology Research and Development Program of China (Grant No 2005A000200)the West Light Plan of China (Grant No 2005ZD01)the Xi’an Applied Materials Innovation Fund of China (Grant No XA-AM-200613)
文摘Low pressure metalorganic chemical vapour deposition （LP-MOCVD） growth and characteristics of InAsSb on （100） GaSb substrates are investigated. Mirror-like surfaces with a minimum lattice mismatch are obtained. The samples are studied by photoluminescence spectra, and the output is 3.17μm in wavelength. The surface of InAsSb epilayer shows that its morphological feature is dependent on buffer layer. With an InAs buffer layer used, the best surface is obtained. The InAsSb film shows to be of n-type conduction with an electron concentration of 8.52 × 10^16 cm^-3.
基金Project supported by the National Natural Science Foundation of China(Grant No.61474090)the Key Research and Development Program of Shaanxi Province of China(Grant No.2017ZDXM-GY-052)+1 种基金the Fundamental Research Funds for the Central Universities(Grant No.20109205456)the Innovation Fund of Xidian University。
文摘The steady-state and transient electron transport properties ofβ-(Al_(x)Ga_(1-x))_(2)O_(3)/Ga_(2)O_(3)heterostructures were investigated by Monte Carlo simulation with the classic three-valley model.In particular,the electronic band structures were acquired by first-principles calculations,which could provide precise parameters for calculating the transport properties of the two-dimensional electron gas(2DEG),and the quantization effect was considered in theΓvalley with the five lowest subbands.Wave functions and energy eigenvalues were obtained by iteration of the Schrödinger–Poisson equations to calculate the 2DEG scattering rates with five main scattering mechanisms considered.The simulated low-field electron mobilities agree well with the experimental results,thus confirming the effectiveness of our models.The results show that the room temperature electron mobility of theβ-(Al_(0.188)Ga_(0.812))_(2)O_(3)/Ga_(2)O_(3)heterostructure at 10 k V·cm^(-1)is approximately153.669 cm^(2)·V^(-1)·s^(-1),and polar optical phonon scattering would have a significant impact on the mobility properties at this time.The region of negative differential mobility,overshoot of the transient electron velocity and negative diffusion coefficients are also observed when the electric field increases to the corresponding threshold value or even exceeds it.This work offers significant parameters for theβ-(Al_(x)Ga_(1-x))_(2)O_(3)/Ga_(2)O_(3)heterostructure that may benefit the design of high-performanceβ-(Al_(x)Ga_(1-x))_(2)O_(3)/Ga_(2)O_(3)heterostructure-based devices.
基金Supported by the Natural Science Foundation of Shaanxi Province under Grant No 2005F39, and the Applied Materials Innovation Fund of Xi＇an under Grant No AM07012.
文摘By orthogonal design theory, technological parameters of the （002）-oriented ZnO film prepared in sol-gel process are optimized. A set of technological parameters for growing highly （002）-oriented ZnO film is obtained. As a result, it is proven that the Zn^2＋ concentration is the most important factor to grow a highly （002）-oriented ZnO film. We take an appropriate Zn^2＋ concentration 0.35mol/L for the aimed film, of which photoluminescence property is better than those of the films derived from other Zn^2＋ concentrations precursor solution. The Zn^2＋ concentration either larger or smaller than 0.35 mol/L leads to the （002）-oriented degree decrease of films. By employing an atom force microscope, a hexagonal atom arrangement, which indicates that the film site detected is a ZnO single crystal, is observed in the surface of the highly （002）-oriented film.
文摘By making use of the density functional theory (DFT) of the first principles and generalized gradient approximation method, the electronic structures and properties of ideal GaN and AlxGa1-xN crystals (x = 0.25, 0.5, 0.75) have been calculated and analyzed, and the influence of the doping quantity of x on the characteristics of AlxGa1-xN has been studied. The calculation results show that optical band gap of AlxGa1-xN crystal is widened that the Eg of AlxGa1-xN can be adjusted by the x, and the absorption spectrum shifts to high-energy direction with the increase of the x, and then the Fermi energy moves to the top of valence band slightly which leads to that conductivity weakened after mixed with the Al. At the same time, the variation trends of complex dielectric function, absorption spectrum and transitivity have been made clear, and the results show that AlxGa1-xN compounds can achieve the theoretical design of photoelectric performance. In a word, AlxGa1-xN crystals are potential semiconductors with very remarkable photoelectric properties, which can be applied in the development of the diversified GaN devices.
文摘At present, CuInSe2 (referred to as CIS) semiconductor has become one of the hot points in solar cell field at home and abroad for its excellent performances, such as direct bandgap, high light absorption coefficient, high photoelectric conversion efficiency and long-term stability. In this paper, the CIS bulk materials are prepared by the horizontal Bridgman method with double-heat sources, the crystal structure, microstructure morphology and composition of the samples are analyzed in X-ray diffraction instrument (XRD) and scanning electronic microscope (SEM) with Energy Dispersive X-ray Spectrum (EDX), and surface electrical state and electrical properties of the samples are characterized in X-ray photoelectron spectroscopy (XPS) and four point resistivity test system. The results show that the CIS crystal was grown, and that the conductive performance of the samples is good which display the characteristics of p-type semiconductor. Furthermore, a thin film CIS sample was obtained by argon ion-beam scanning bombardment, and it has high solar energy absorptivity and the bandgap of 0.99 eV analyzed in Ultraviolet-visible Spectrum that is suitable for solar cell. Keywords:
基金supported by the National Natural Science Foundation of China(No.52372223)the Science Foundation of Shaanxi Province(No.2023-JC-ZD-03 and 2022GD-TSLD-15)Shaanxi Fundamental Science Research Project for Mathematics and Physics(No.23JSQ005)。
文摘Advancing aqueous zinc-ion batteries(AZIBs)are significantly challenged by the need to find cathode materials that can provide both high capacity and fast reaction kinetics.Tellurium telluride,a topological insulator,has emerged as a promising cathode candidate for AZIBs,garnering increasing attention.However,the complete understanding of its electrochemical reaction mechanism and its unsatisfactory energy storage performance are major obstacles to the practical use.In this work,we synthesize a bimetallic bismuth-nickel telluride with Te vacancies,defined as Bi_(2)Te_(3-x)/NiTe_(2),which forms a topological insulator/topological Dirac semimetal heterostructure through a hydrothermal approach.The electrochemical reaction mechanism of Bi_(2)Te_(3-x)/NiTe_(2),along with its phase and structural changes are elucidated by using in-situ X-ray diffraction,various electrochemical techniques,and ex-situ characterizations.The influences of Bi_(2)Te_(3-x)/NiTe_(2)on the electronic structure,interracial electron transfer,migration barrier,and ion adsorption energy are investigated by using density functional theory calculations.Our findings reveal that Bi_(2)Te_(3-x)/NiTe_(2)exhibits excellent specific capacity,stable cycling,and superior rate capability as a cathode material for AZIBs.Moreover,further studies demonstrate that Bi_(2)Te_(3-x)/NiTe_(2)maintains exceptional performance at low temperatures of-15 and-5℃,and also retains stability and flexibility when integrated into flexible battery packs.
基金supported by the National Natural Science Foundation of China(62101439)the Key Research and Development Program of Shaanxi(2023-YBSF-289).
文摘Bioluminescent tomography(BLT)is a noninvasive imaging technology that uses optical methods to study physiological and pathological processes at the cellular and molecular levels.It is a powerful tool for early diagnosis and treatment of tumors,as well as drug development.However,the simplified optical transmission models and the ill-posed inverse reconstruction limit its wide applications.The development of deep learning has provided new potential for extending the applications of optical BLT.Researchers have introduced various methods such as neural networks and self-attention mechanisms to improve reconstruction accuracy.Despite these efforts,weak energy points around the reconstructed light source center still impact the accuracy of restoration.In this study,we propose a dual-branch network based on a combination of attention mechanism and fully connected layers(FC-AM)to reduce centroid error and improve reconstruction performance.The network architecture consists of a fully connected(FC)subnetwork and an attention mechanism-based dual-branch(AMDB)subnetwork.The FC subnetwork is used to process input data.AMDB subnetwork is used for deep feature extraction,and captures feature information from different perspectives in parallel.Each branch of the AMDB subnetwork is composed of four AM subnets,which extract features through multilayer linear transformations and attention mechanisms.The outputs of the AMDB are combined through feature fusion to produce the final result.Numerical simulations and experimental results demonstrate that the FC-AM network significantly improves BLT reconstruction performance compared to existing methods(KNN_LC and AMLC networks),offering enhanced stability and accuracy.
基金supported by the National Natural Science Foundation of China(6137901061772421)
文摘Face recognition based on few training samples is a challenging task. In daily applications, sufficient training samples may not be obtained and most of the gained training samples are in various illuminations and poses. Non-sufficient training samples could not effectively express various facial conditions, so the improvement of the face recognition rate under the non-sufficient training samples condition becomes a laborious mission. In our work, the facial pose pre-recognition(FPPR) model and the dualdictionary sparse representation classification(DD-SRC) are proposed for face recognition. The FPPR model is based on the facial geometric characteristic and machine learning, dividing a testing sample into full-face and profile. Different poses in a single dictionary are influenced by each other, which leads to a low face recognition rate. The DD-SRC contains two dictionaries, full-face dictionary and profile dictionary, and is able to reduce the interference. After FPPR, the sample is processed by the DD-SRC to find the most similar one in training samples. The experimental results show the performance of the proposed algorithm on olivetti research laboratory(ORL) and face recognition technology(FERET) databases, and also reflect comparisons with SRC, linear regression classification(LRC), and two-phase test sample sparse representation(TPTSSR).
基金Project supported by the Natural Science Basic Research Program of Shaanxi Province(2021JZ-43)the Key Program for International Science and Technology Cooperation Projects of Shaanxi Province(2018KWZ-08)+2 种基金the National Key Research and Development Program of China(2019YFC1520904)the Scientific Research Plan of Shannxi Provincial Education Department,China(18JK0780)Ningxia Natural Fund(2023AAC03338)。
文摘Fluorescence imaging techniques represent essential tools in in vitro,preclinical,and clinical studies.In this study,an improved one-step hydrothermal method to synthesize citric acid(CA)modifiedα-NaYbF_(4):2%Er^(3+)nanocrystals was proposed.The introduction of various doping ions into NaYbF_(4):2%Er^(3+)and the different valence states of the same ions affect both the crystal size and upconversion luminesce nce.There fore,we investigated the upconversion luminesce nce enha ncement of NaYbF_(4):2%Er^(3+)by ion doping and find that the upconversion luminescence intensity of the upconversion nanoparticles(UCNPs)co-doped with 5 mol%Fe^(2+)ions shows the greatest enhancement,especially for red emission at654 nm.Furthermore,HeLa cells incubated with UCNPs allow for imaging with strong red upconversion emission detectio n.Confocal laser scanning microscope(CLSM)fluorescent images of HeLa cells indicate that NaYbF_(4):2%Er/5%Fe^(2+)leads to a clear outline and improves visualization of the cell morphology.In addition,the CA coated NaYbF_(4):2%Er^(3+)/5%Fe^(2+)nanoparticles and NaYbF_(4):2%Er^(3+)/5%Fe^(2+)show low cytotoxicity in HeLa cells.Organ imaging reveals the efficiency of these UCNPs to analyze the lungs,liver,and spleen.Together,these results indicate that the Cit-NaYbF_(4):2%Er^(3+)/5%Fe^(2+)UCNPs are efficient nanoprobes for fluorescence molecular to mography.
基金Project(041010) supported by Start-Up Foundation of Northwest University,ChinaProject(UIT/39) supported by University-Industry Collaboration Program from the Innovation and Technology Fund of Hong Kong,China
文摘In order to utilize integrated passive technology in printed circuit boards （PCBs）, manufacturing processing for integrated resistors by lamination method was investigated. Integrated resistors fabricated from Ohmega technologies in the experiment were 1 408 pieces per panel with four different patterns A, B, C and D and four resistance values of 25, 50, 75 and 100 fL Six panel per batch and four batches were performed totally. The testing was done for 960 pieces of integrated resistors randomly selected with the same size. The value distribution ranges and the relative standard deviation （RSD） show that the scatter degree of the resistance decreases with the resistor size increasing and/or with the resistance increasing. Patterns D with resistance of 75 and 100% for four patterns have the resistance value variances less than 10%. Patterns C and D with resistance of 100 Ω have the manufacturing tolerance less than 10%. The process capabilities are from about 0.6 to 1.6 for the designed testing patterns, which shows that the integrated resistors fabricated have the potential to be used in multilayer PCBs in the future.
