In this paper, based on a new type of censoring scheme called an adaptive type-II progressive censoring scheme introduce by Ng et al. [1], Naval Research Logistics is considered. Based on this type of censoring the ma...In this paper, based on a new type of censoring scheme called an adaptive type-II progressive censoring scheme introduce by Ng et al. [1], Naval Research Logistics is considered. Based on this type of censoring the maximum likelihood estimation (MLE), Bayes estimation, and parametric bootstrap method are used for estimating the unknown parameters. Also, we propose to apply Markov chain Monte Carlo (MCMC) technique to carry out a Bayesian estimation procedure and in turn calculate the credible intervals. Point estimation and confidence intervals based on maximum likelihood and bootstrap method are also proposed. The approximate Bayes estimators obtained under the assumptions of non-informative priors, are compared with the maximum likelihood estimators. Numerical examples using real data set are presented to illustrate the methods of inference developed here. Finally, the maximum likelihood, bootstrap and the different Bayes estimates are compared via a Monte Carlo simulation study.展开更多
InAs/GaSb type-II superlattce (T2SL) photodetector structures at the MWIR regime were grown by molecular beam epitaxy. The growth temperature and group-V soaking times were optimized with respect to interface and tran...InAs/GaSb type-II superlattce (T2SL) photodetector structures at the MWIR regime were grown by molecular beam epitaxy. The growth temperature and group-V soaking times were optimized with respect to interface and transport quality. Novel strain compensation schemes with insertion of InSb layers were proposed and tested to be efficient to tune the overall strain between tensile and compressive without degradation of interface and optical quality. The effect of the proposed methods is modeled by analytic functions.? Band structure calculations were also carried out for the proposed T2SL structures to assist optimizing sample designs. Single pixel photodiodes with a low dark current were demonstrated.展开更多
In this paper,we propose a new extension of the traditional Rayleigh distribution called the modified Kies Rayleigh distribution.The new distribution contains one scale and one shape parameter and its hazard rate func...In this paper,we propose a new extension of the traditional Rayleigh distribution called the modified Kies Rayleigh distribution.The new distribution contains one scale and one shape parameter and its hazard rate function can be increasing and bathtub-shaped.Some mathematical properties of the new distribution are derived including quantiles and moments.The parameters of modified Kies Rayleigh distribution are estimated based on progressively Type-II censored data.For this purpose,we consider two estimation methods,namely maximum likelihood and maximum product of spacing estimation methods.To compare the efficiency of the proposed estimators,a simulation study is carried out.To show the applicability of the new model as well as the estimation methods,one real data for failure times of software is analyzed.Based on the empirical parts,we can conclude that the proposed model can be considered as a good model in the field of life testing and reliability analysis compared with other competing models.展开更多
In this paper, the effect of magnetic nanoparticles on the mechanical properties of a type-II superconductor is investigated both theoretically and numerically. Magnetic part of the pinning force associated with the i...In this paper, the effect of magnetic nanoparticles on the mechanical properties of a type-II superconductor is investigated both theoretically and numerically. Magnetic part of the pinning force associated with the interaction between a finite-size spheroidal magnetic inclusion and an Abrikosov vortex is calculated in the London approximation. It is found that the size and shape of magnetic nanoparticles result in different enhancements of vortex pinning in large-k type-II superconductors. Meanwhile, the screening current induced by a magnetic spheroid suffer the action of Lorentz force, which will lead to prestress in the superconductor, so further numerical calculations are needed to explore the interaction between the spheroidal magnetic particle and superconductor. The distribution of displacement, stress and strain in the superconductor are finally obtained. It is shown that different sizes and shapes of nanoparticles also can change the distributions of these quantities.展开更多
In this paper, we present an investigation of type-II ＇W＇ quantum wells for the InAs/Ga1-xInxSb/A1Sb family, where ＇W＇ denotes the conduction profile of the material. We focus our attention on using the eight-band...In this paper, we present an investigation of type-II ＇W＇ quantum wells for the InAs/Ga1-xInxSb/A1Sb family, where ＇W＇ denotes the conduction profile of the material. We focus our attention on using the eight-band k. p model to calculate the band structures within the framework of finite element method. For the sake of clarity, the simulation in this paper is simplified and based on only one period--A1Sb/InAs/Ga1-xInxSb/InAs/A1Sb. The obtained numerical results include the energy levels and wavefunctions of carriers. We discuss the variations of the electronic properties by changing several important parameters, such as the thickness of either InAs or Cal_xInxSb layer and the alloy composition in Ga1-xInxSb separately. In the last part, in order to compare the eight-band k·p model, we recalculate the conduction bands of the ＇W＇ structure using the one-band k·p model and then discuss the difference between the two results, showing that conduction bands are strongly coupled with valence bands in the narrow band gap structure. The in-plane energy dispersions, which illustrate the suppression of the Auger recombination process, are also obtained.展开更多
Light-harvesters with long-lived excited states are desired for efficient solar energy conversion systems. Many solar-to-fuel conversion reactions, such as H2 evolution and CO2 reduction, require multiple sequential e...Light-harvesters with long-lived excited states are desired for efficient solar energy conversion systems. Many solar-to-fuel conversion reactions, such as H2 evolution and CO2 reduction, require multiple sequential electron transfer processes, which leads to a complicated situation that excited states involves not only excitons （electron-hole pairs） but also multi-excitons and charged excitons. While long-lived excitons can be obtained in various systems （e.g., semiconductor nanocrystals）, multi-excitons and charged excitons are typically shorted-lived due to nonradiative Auger recombination pathways whereby the recombination energy of an exciton is quickly transferred to the third carrier on a few to hundreds of picoseconds timescale. In this work, we report a study of excitons, trions （an exciton plus an additional charge）, and biexcitons in CdSe/CdTe colloidal quantum wells or nanoplatelets. The type- II band alignment effectively separates electrons and holes in space, leading to a single exciton lifetime of 340 ns which is -2 order of magnitudes longer than that in plane CdSe nanoplatelets. More importantly, the electron-hole separation also dramatically slows down Auger decay, giving rise to a trion lifetime of 70 ns and a biexciton lifetime of 11 ns, among the longest values ever reported for colloidal nanocrystals. The long-lived exciton, trion, and biexciton states, combined with the intrinsically strong light-absorption capability of two-dimensional systems, enable the CdSe/CdTe type-II nanoplatelets as promising light harvesters for efficient solar-to-fuel conversion reactions.展开更多
An inverse problemin practical scientific investigations is the process of computing unknown parameters from a set of observations where the observations are only recorded indirectly,such as monitoring and controlling...An inverse problemin practical scientific investigations is the process of computing unknown parameters from a set of observations where the observations are only recorded indirectly,such as monitoring and controlling quality in industrial process control.Linear regression can be thought of as linear inverse problems.In other words,the procedure of unknown estimation parameters can be expressed as an inverse problem.However,maximum likelihood provides an unstable solution,and the problembecomes more complicated if unknown parameters are estimated from different samples.Hence,researchers search for better estimates.We study two joint censoring schemes for lifetime products in industrial process monitoring.In practice,this type of data can be collected in fields such as the medical industry and industrial engineering.In this study,statistical inference for the Chen lifetime products is considered and analyzed to estimate underlying parameters.Maximum likelihood and Bayes’rule are both studied for model parameters.The asymptotic distribution of maximumlikelihood estimators and the empirical distributions obtained withMarkov chainMonte Carlo algorithms are utilized to build the interval estimators.Theoretical results using tables and figures are adopted through simulation studies and verified in an analysis of the lifetime data.We briefly describe the performance of developed methods.展开更多
A new extended exponential lifetime model called Harris extended-exponential(HEE)distribution for data modelling with increasing and decreasing hazard rate shapes has been considered.In the reliability context,researc...A new extended exponential lifetime model called Harris extended-exponential(HEE)distribution for data modelling with increasing and decreasing hazard rate shapes has been considered.In the reliability context,researchers prefer to use censoring plans to collect data in order to achieve a compromise between total test time and/or test sample size.So,this study considers both maximum likelihood and Bayesian estimates of the Harris extended-exponential distribution parameters and some of its reliability indices using a progressive Type-II censoring strategy.Under the premise of independent gamma priors,the Bayesian estimation is created using the squared-error and general entropy loss functions.Due to the challenging form of the joint posterior distribution,to evaluate the Bayes estimates,samples from the full conditional distributions are generated using Markov Chain Monte Carlo techniques.For each unknown parameter,the highest posterior density credible intervals and asymptotic confidence intervals are also determined.Through a simulated study,the usefulness of the various suggested strategies is assessed.The optimal progressive censoring plans are also shown,and various optimality criteria are investigated.Two actual data sets,taken from engineering and veterinary medicine areas,are analyzed to show how the offered point and interval estimators can be used in practice and to verify that the proposed model furnishes a good fit than other lifetimemodels:alpha power exponential,generalized-exponential,Nadarajah-Haghighi,Weibull,Lomax,gamma and exponential distributions.Numerical evaluations revealed that in the presence of progressively Type-II censored data,the Bayes estimation method against the squared-error(symmetric)loss is advised for getting the point and interval estimates of the HEE distribution.展开更多
The main purpose of this paper is to obtain the inference of parameters of heterogeneous population represented by finite mixture of two Pareto (MTP) distributions of the second kind. The constant-partially accelerate...The main purpose of this paper is to obtain the inference of parameters of heterogeneous population represented by finite mixture of two Pareto (MTP) distributions of the second kind. The constant-partially accelerated life tests are applied based on progressively type-II censored samples. The maximum likelihood estimates (MLEs) for the considered parameters are obtained by solving the likelihood equations of the model parameters numerically. The Bayes estimators are obtained by using Markov chain Monte Carlo algorithm under the balanced squared error loss function. Based on Monte Carlo simulation, Bayes estimators are compared with their corresponding maximum likelihood estimators. The two-sample prediction technique is considered to derive Bayesian prediction bounds for future order statistics based on progressively type-II censored informative samples obtained from constant-partially accelerated life testing models. The informative and future samples are assumed to be obtained from the same population. The coverage probabilities and the average interval lengths of the confidence intervals are computed via a Monte Carlo simulation to investigate the procedure of the prediction intervals. Analysis of a simulated data set has also been presented for illustrative purposes. Finally, comparisons are made between Bayesian and maximum likelihood estimators via a Monte Carlo simulation study.展开更多
Band structure analysis holds significant importance for understanding the optoelectronic characteristics of semiconductor structures and exploring their potential applications in practice. For quantum well structures...Band structure analysis holds significant importance for understanding the optoelectronic characteristics of semiconductor structures and exploring their potential applications in practice. For quantum well structures, the energy of carriers in the well splits into discrete energy levels due to the confinement of barriers in the growth direction. However, the discrete energy levels obtained at a fixed wave vector cannot accurately reflect the actual energy band structure. In this work, the band structure of the type-II quantum wells is reanalyzed. When the wave vectors of the entire Brillouin region(corresponding to the growth direction) are taken into account, the quantized energy levels of the carriers in the well are replaced by subbands with certain energy distributions. This new understanding of the energy bands of low-dimensional structures not only helps us to have a deeper cognition of the structure, but also may overturn many viewpoints in traditional band theories and serve as supplementary to the band theory of low-dimensional systems.展开更多
In this paper, an interpolating method for bivariate cubic splines with C2-join on type-II triangular at a rectangular domain is given, and the approximation degree, inter- polating existence and uniqueness of the cub...In this paper, an interpolating method for bivariate cubic splines with C2-join on type-II triangular at a rectangular domain is given, and the approximation degree, inter- polating existence and uniqueness of the cubic splines are studied.展开更多
Field equations in the presence of perfect fluid distribution are obtained in a scalar tensor theory of gravitation proposed by Brans and Dicke[1] with the aid of Bianchi type-II, VIII & IX metrics. Exact prefect ...Field equations in the presence of perfect fluid distribution are obtained in a scalar tensor theory of gravitation proposed by Brans and Dicke[1] with the aid of Bianchi type-II, VIII & IX metrics. Exact prefect fluid Bianchi type- IX cosmological model is presented since other models doesn’t exist in Brans-Dicke scalar tensor theory of gravitation. Some physical properties of the model are also discussed.展开更多
We present a theoretical study on the terahertz (THz) optoelectronic properties of long-period InAs/GaSb type-II super lattices (SLs). The eight-band k·p model is used to calculate the electronic structures of su...We present a theoretical study on the terahertz (THz) optoelectronic properties of long-period InAs/GaSb type-II super lattices (SLs). The eight-band k·p model is used to calculate the electronic structures of such SLs and on the basis of band structures, the Boltzmann equation approach is employed to calculate the optical absorption coefficients for the corresponding SL systems. It is found that long-period InAs/GaSb type-II SLs have a considerable absorption in the THz bandwidth. By examining the dependence of THz absorption coefficient on the InAs/GaSb layer widths, we demonstrate that with a proper choice of InAs/GaSb layer widths, an optimized THz absorption can be achieved. This study is pertinent to the potential application of InAs/GaSb type-II SLs as THz photo detectors.展开更多
Blue emissive quantum dots are key materials in emerging light-emitting technologies for display applications.Herein,we report the synthesis of ZnSeTe/CdZnSe-based type-II core–shell quantum dots with a low Cd conten...Blue emissive quantum dots are key materials in emerging light-emitting technologies for display applications.Herein,we report the synthesis of ZnSeTe/CdZnSe-based type-II core–shell quantum dots with a low Cd content of less than 2.5%.By modifying the Cd content of the CdZnSe shell,photoluminescence emission can be tuned from 430 to 510 nm with a full width at half maximum of less than 26 nm.Transient absorption spectra illustrate the charge transfer between the conduction band of ZnSeTe and the conduction band of CdZnSe,as well as the recombination between the valence band of ZnSeTe and the conduction band of CdZnSe.By subsequent growth of ZnSe and ZnS shells,the resulting quantum dots achieved a photoluminescence quantum yield of 95%.We further demonstrate a blue quantum dot light-emitting diode with an emission peak at 467 nm,showing a maximum external quantum efficiency of 5%,a maximum luminance of 10,376 cd·m^(-2),and an extrapolated T95 lifetime of 4.7 h.展开更多
An edge soliton is a localized bound state that arises from the balance between diffraction broadening and nonlinearity-induced self-focusing.It typically resides either at the edge or at the domain wall of a lattice ...An edge soliton is a localized bound state that arises from the balance between diffraction broadening and nonlinearity-induced self-focusing.It typically resides either at the edge or at the domain wall of a lattice system.To the best of our knowledge,most reported edge solitons have been observed in conservative Hermitian systems;whether stable edge solitons can exist in non-Hermitian systems remains an open question.In this work,we utilize a photonic lattice that naturally exhibits type-II Dirac cones and introduce a domain wall by carefully configuring gains and losses at the three sites within each unit cell.Surprisingly,edge states localized at the domain wall can exhibit entirely real propagation constants.Building on these edge states,we demonstrate the existence of edge solitons that can propagate stably over distances significantly exceeding those in the experimental settings adopted in this study.Although these solitons eventually couple with the bulk states and ultimately collapse,they exhibit remarkable resilience.Our findings establish that a domain wall supporting loss-resistant edge solitons,which can also evade the skin effect,is achievable in non-Hermitian systems.This discovery holds promising potential for the development of compact functional optical devices.展开更多
文摘In this paper, based on a new type of censoring scheme called an adaptive type-II progressive censoring scheme introduce by Ng et al. [1], Naval Research Logistics is considered. Based on this type of censoring the maximum likelihood estimation (MLE), Bayes estimation, and parametric bootstrap method are used for estimating the unknown parameters. Also, we propose to apply Markov chain Monte Carlo (MCMC) technique to carry out a Bayesian estimation procedure and in turn calculate the credible intervals. Point estimation and confidence intervals based on maximum likelihood and bootstrap method are also proposed. The approximate Bayes estimators obtained under the assumptions of non-informative priors, are compared with the maximum likelihood estimators. Numerical examples using real data set are presented to illustrate the methods of inference developed here. Finally, the maximum likelihood, bootstrap and the different Bayes estimates are compared via a Monte Carlo simulation study.
文摘InAs/GaSb type-II superlattce (T2SL) photodetector structures at the MWIR regime were grown by molecular beam epitaxy. The growth temperature and group-V soaking times were optimized with respect to interface and transport quality. Novel strain compensation schemes with insertion of InSb layers were proposed and tested to be efficient to tune the overall strain between tensile and compressive without degradation of interface and optical quality. The effect of the proposed methods is modeled by analytic functions.? Band structure calculations were also carried out for the proposed T2SL structures to assist optimizing sample designs. Single pixel photodiodes with a low dark current were demonstrated.
基金the Deanship Scientific Research(DSR)King Abdulaziz University,Jeddah under Grant No.(G:337-130-1441).
文摘In this paper,we propose a new extension of the traditional Rayleigh distribution called the modified Kies Rayleigh distribution.The new distribution contains one scale and one shape parameter and its hazard rate function can be increasing and bathtub-shaped.Some mathematical properties of the new distribution are derived including quantiles and moments.The parameters of modified Kies Rayleigh distribution are estimated based on progressively Type-II censored data.For this purpose,we consider two estimation methods,namely maximum likelihood and maximum product of spacing estimation methods.To compare the efficiency of the proposed estimators,a simulation study is carried out.To show the applicability of the new model as well as the estimation methods,one real data for failure times of software is analyzed.Based on the empirical parts,we can conclude that the proposed model can be considered as a good model in the field of life testing and reliability analysis compared with other competing models.
基金supported by the National Natural Science Foundation of China(Nos.11032006 and 11121202)
文摘In this paper, the effect of magnetic nanoparticles on the mechanical properties of a type-II superconductor is investigated both theoretically and numerically. Magnetic part of the pinning force associated with the interaction between a finite-size spheroidal magnetic inclusion and an Abrikosov vortex is calculated in the London approximation. It is found that the size and shape of magnetic nanoparticles result in different enhancements of vortex pinning in large-k type-II superconductors. Meanwhile, the screening current induced by a magnetic spheroid suffer the action of Lorentz force, which will lead to prestress in the superconductor, so further numerical calculations are needed to explore the interaction between the spheroidal magnetic particle and superconductor. The distribution of displacement, stress and strain in the superconductor are finally obtained. It is shown that different sizes and shapes of nanoparticles also can change the distributions of these quantities.
基金supported by the National Natural Science Foundation of China (Grant No. 60636030)
文摘In this paper, we present an investigation of type-II ＇W＇ quantum wells for the InAs/Ga1-xInxSb/A1Sb family, where ＇W＇ denotes the conduction profile of the material. We focus our attention on using the eight-band k. p model to calculate the band structures within the framework of finite element method. For the sake of clarity, the simulation in this paper is simplified and based on only one period--A1Sb/InAs/Ga1-xInxSb/InAs/A1Sb. The obtained numerical results include the energy levels and wavefunctions of carriers. We discuss the variations of the electronic properties by changing several important parameters, such as the thickness of either InAs or Cal_xInxSb layer and the alloy composition in Ga1-xInxSb separately. In the last part, in order to compare the eight-band k·p model, we recalculate the conduction bands of the ＇W＇ structure using the one-band k·p model and then discuss the difference between the two results, showing that conduction bands are strongly coupled with valence bands in the narrow band gap structure. The in-plane energy dispersions, which illustrate the suppression of the Auger recombination process, are also obtained.
文摘Light-harvesters with long-lived excited states are desired for efficient solar energy conversion systems. Many solar-to-fuel conversion reactions, such as H2 evolution and CO2 reduction, require multiple sequential electron transfer processes, which leads to a complicated situation that excited states involves not only excitons （electron-hole pairs） but also multi-excitons and charged excitons. While long-lived excitons can be obtained in various systems （e.g., semiconductor nanocrystals）, multi-excitons and charged excitons are typically shorted-lived due to nonradiative Auger recombination pathways whereby the recombination energy of an exciton is quickly transferred to the third carrier on a few to hundreds of picoseconds timescale. In this work, we report a study of excitons, trions （an exciton plus an additional charge）, and biexcitons in CdSe/CdTe colloidal quantum wells or nanoplatelets. The type- II band alignment effectively separates electrons and holes in space, leading to a single exciton lifetime of 340 ns which is -2 order of magnitudes longer than that in plane CdSe nanoplatelets. More importantly, the electron-hole separation also dramatically slows down Auger decay, giving rise to a trion lifetime of 70 ns and a biexciton lifetime of 11 ns, among the longest values ever reported for colloidal nanocrystals. The long-lived exciton, trion, and biexciton states, combined with the intrinsically strong light-absorption capability of two-dimensional systems, enable the CdSe/CdTe type-II nanoplatelets as promising light harvesters for efficient solar-to-fuel conversion reactions.
基金Let Pub(www.letpub.com)for its linguistic assistance during the preparation of this manuscript.This study was funded by Taif University Researchers Supporting Project number(TURSP-2020/279),Taif University,Taif,Saudi Arabia.
文摘An inverse problemin practical scientific investigations is the process of computing unknown parameters from a set of observations where the observations are only recorded indirectly,such as monitoring and controlling quality in industrial process control.Linear regression can be thought of as linear inverse problems.In other words,the procedure of unknown estimation parameters can be expressed as an inverse problem.However,maximum likelihood provides an unstable solution,and the problembecomes more complicated if unknown parameters are estimated from different samples.Hence,researchers search for better estimates.We study two joint censoring schemes for lifetime products in industrial process monitoring.In practice,this type of data can be collected in fields such as the medical industry and industrial engineering.In this study,statistical inference for the Chen lifetime products is considered and analyzed to estimate underlying parameters.Maximum likelihood and Bayes’rule are both studied for model parameters.The asymptotic distribution of maximumlikelihood estimators and the empirical distributions obtained withMarkov chainMonte Carlo algorithms are utilized to build the interval estimators.Theoretical results using tables and figures are adopted through simulation studies and verified in an analysis of the lifetime data.We briefly describe the performance of developed methods.
基金This research was funded by Princess Nourah bint Abdulrahman University Researchers Supporting Project Number(PNURSP2023R175),Princess Nourah bint Abdulrahman University,Riyadh,Saudi Arabia.
文摘A new extended exponential lifetime model called Harris extended-exponential(HEE)distribution for data modelling with increasing and decreasing hazard rate shapes has been considered.In the reliability context,researchers prefer to use censoring plans to collect data in order to achieve a compromise between total test time and/or test sample size.So,this study considers both maximum likelihood and Bayesian estimates of the Harris extended-exponential distribution parameters and some of its reliability indices using a progressive Type-II censoring strategy.Under the premise of independent gamma priors,the Bayesian estimation is created using the squared-error and general entropy loss functions.Due to the challenging form of the joint posterior distribution,to evaluate the Bayes estimates,samples from the full conditional distributions are generated using Markov Chain Monte Carlo techniques.For each unknown parameter,the highest posterior density credible intervals and asymptotic confidence intervals are also determined.Through a simulated study,the usefulness of the various suggested strategies is assessed.The optimal progressive censoring plans are also shown,and various optimality criteria are investigated.Two actual data sets,taken from engineering and veterinary medicine areas,are analyzed to show how the offered point and interval estimators can be used in practice and to verify that the proposed model furnishes a good fit than other lifetimemodels:alpha power exponential,generalized-exponential,Nadarajah-Haghighi,Weibull,Lomax,gamma and exponential distributions.Numerical evaluations revealed that in the presence of progressively Type-II censored data,the Bayes estimation method against the squared-error(symmetric)loss is advised for getting the point and interval estimates of the HEE distribution.
文摘The main purpose of this paper is to obtain the inference of parameters of heterogeneous population represented by finite mixture of two Pareto (MTP) distributions of the second kind. The constant-partially accelerated life tests are applied based on progressively type-II censored samples. The maximum likelihood estimates (MLEs) for the considered parameters are obtained by solving the likelihood equations of the model parameters numerically. The Bayes estimators are obtained by using Markov chain Monte Carlo algorithm under the balanced squared error loss function. Based on Monte Carlo simulation, Bayes estimators are compared with their corresponding maximum likelihood estimators. The two-sample prediction technique is considered to derive Bayesian prediction bounds for future order statistics based on progressively type-II censored informative samples obtained from constant-partially accelerated life testing models. The informative and future samples are assumed to be obtained from the same population. The coverage probabilities and the average interval lengths of the confidence intervals are computed via a Monte Carlo simulation to investigate the procedure of the prediction intervals. Analysis of a simulated data set has also been presented for illustrative purposes. Finally, comparisons are made between Bayesian and maximum likelihood estimators via a Monte Carlo simulation study.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 61991441 and 62004218)the Strategic Priority Research Program of Chinese Academy of Sciences (Grant No. XDB01000000)Youth Innovation Promotion Association Chinese Academy of Sciences (Grant No. 2021005)。
文摘Band structure analysis holds significant importance for understanding the optoelectronic characteristics of semiconductor structures and exploring their potential applications in practice. For quantum well structures, the energy of carriers in the well splits into discrete energy levels due to the confinement of barriers in the growth direction. However, the discrete energy levels obtained at a fixed wave vector cannot accurately reflect the actual energy band structure. In this work, the band structure of the type-II quantum wells is reanalyzed. When the wave vectors of the entire Brillouin region(corresponding to the growth direction) are taken into account, the quantized energy levels of the carriers in the well are replaced by subbands with certain energy distributions. This new understanding of the energy bands of low-dimensional structures not only helps us to have a deeper cognition of the structure, but also may overturn many viewpoints in traditional band theories and serve as supplementary to the band theory of low-dimensional systems.
文摘In this paper, an interpolating method for bivariate cubic splines with C2-join on type-II triangular at a rectangular domain is given, and the approximation degree, inter- polating existence and uniqueness of the cubic splines are studied.
文摘Field equations in the presence of perfect fluid distribution are obtained in a scalar tensor theory of gravitation proposed by Brans and Dicke[1] with the aid of Bianchi type-II, VIII & IX metrics. Exact prefect fluid Bianchi type- IX cosmological model is presented since other models doesn’t exist in Brans-Dicke scalar tensor theory of gravitation. Some physical properties of the model are also discussed.
文摘We present a theoretical study on the terahertz (THz) optoelectronic properties of long-period InAs/GaSb type-II super lattices (SLs). The eight-band k·p model is used to calculate the electronic structures of such SLs and on the basis of band structures, the Boltzmann equation approach is employed to calculate the optical absorption coefficients for the corresponding SL systems. It is found that long-period InAs/GaSb type-II SLs have a considerable absorption in the THz bandwidth. By examining the dependence of THz absorption coefficient on the InAs/GaSb layer widths, we demonstrate that with a proper choice of InAs/GaSb layer widths, an optimized THz absorption can be achieved. This study is pertinent to the potential application of InAs/GaSb type-II SLs as THz photo detectors.
基金the National Natural Science Foundation of China(Nos.U23A20683,52403291)Natural Science Foundation of Beijing Municipality(No.Z210018)China Postdoctoral Science Foundation(No.2024M764129).
文摘Blue emissive quantum dots are key materials in emerging light-emitting technologies for display applications.Herein,we report the synthesis of ZnSeTe/CdZnSe-based type-II core–shell quantum dots with a low Cd content of less than 2.5%.By modifying the Cd content of the CdZnSe shell,photoluminescence emission can be tuned from 430 to 510 nm with a full width at half maximum of less than 26 nm.Transient absorption spectra illustrate the charge transfer between the conduction band of ZnSeTe and the conduction band of CdZnSe,as well as the recombination between the valence band of ZnSeTe and the conduction band of CdZnSe.By subsequent growth of ZnSe and ZnS shells,the resulting quantum dots achieved a photoluminescence quantum yield of 95%.We further demonstrate a blue quantum dot light-emitting diode with an emission peak at 467 nm,showing a maximum external quantum efficiency of 5%,a maximum luminance of 10,376 cd·m^(-2),and an extrapolated T95 lifetime of 4.7 h.
基金supported by the Natural Science Basic Research Program of Shaanxi Province,China(No.2024JC-JCQN-06)the National Natural Science Foundation of China(No.12474337).
文摘An edge soliton is a localized bound state that arises from the balance between diffraction broadening and nonlinearity-induced self-focusing.It typically resides either at the edge or at the domain wall of a lattice system.To the best of our knowledge,most reported edge solitons have been observed in conservative Hermitian systems;whether stable edge solitons can exist in non-Hermitian systems remains an open question.In this work,we utilize a photonic lattice that naturally exhibits type-II Dirac cones and introduce a domain wall by carefully configuring gains and losses at the three sites within each unit cell.Surprisingly,edge states localized at the domain wall can exhibit entirely real propagation constants.Building on these edge states,we demonstrate the existence of edge solitons that can propagate stably over distances significantly exceeding those in the experimental settings adopted in this study.Although these solitons eventually couple with the bulk states and ultimately collapse,they exhibit remarkable resilience.Our findings establish that a domain wall supporting loss-resistant edge solitons,which can also evade the skin effect,is achievable in non-Hermitian systems.This discovery holds promising potential for the development of compact functional optical devices.
