红外图像的一种Type-Ⅱ模糊增强算法

提出了一种基于Type-Ⅱ模糊集的红外图像增强算法,该算法首先根据像素的邻域相关性对图像进行预处理,然后以Ostu分割阈值为基础,构造了红外图像的Type-Ⅱ模糊特征平面;然后,采用不同的变换规则对图像进行模糊增强,并将结果进行融合;最后,通过Type reduction和去模糊化操作得到增强后的输出图像。对几幅典型的红外图像的增强实验表明,提出的方法能够有效地提高红外图像的对比度。

基于完备循环差集的大围长Type-Ⅱ QC-LDPC码的构造

针对当前type-Ⅱ准循环低密度奇偶校验(quasi-cyclic low-density parity-check,QC-LDPC)码的校验矩阵中存在权重为2的循环矩阵(weight-2circulant matrices,W2CM)导致Tanner图更容易产生短环,从而影响迭代译码收敛性的问题,基于完备循环差集(cyclic difference sets,CDS)提出了一种围长为8的type-ⅡQC-LDPC码的新颖构造方法。该方法构造的校验矩阵由权重为0的零矩阵、权重为1的循环置换矩阵和W2CM组成,保留了type-ⅡQC-LDPC码的具有更高最小距离上界的优点,改善了码的纠错性能;且Tanner图中无4、6环的出现,译码时具有较快的收敛速度。仿真结果表明:所构造的围长为8的type-ⅡQC-LDPC码在加性高斯白噪声信道下采用和积算法迭代译码时具有较好的纠错性能且无错误平层现象。

基于完备循环差集的type-Ⅱ QC-LDPC码的构造

针对当前type-Ⅱ的准循环低密度奇偶校验(quasi-cyclic low-density parity check,QC-LDPC)码中仅含有权重为2的循环置换矩阵而引入短环,导致迭代译码性能下降的问题,基于完备循环差集给出了近似双对角结构的type-ⅡQC-LDPC码的设计方法,该方法构造的奇偶校验矩阵由零矩阵,权重为1的循环单位阵和权重为2的循环矩阵组成,不但围长至少为8,而且还保留了type-ⅡQC-LDPC码具有更高最小距离上界的优点,从而使译码时可快速收敛。仿真结果表明:构造的type-ⅡQC-LDPC码在加性高斯白噪声(additive white Gauss noise,AWGN)信道下,采用和积(sum-product algorithm,SPA)译码时,码字无明显的错误平层且具有良好的纠错性能。

Type-Ⅱ型中红外发光二极管及激光器的进展情况

目前,中红外器件的应用已越来越广泛。为了更好地了解此类器件的结构和发展状况,本文结合国外在此方向上所取得的结果,对这类器件的结构设计做了比较详细的介绍。这些器件已能在218K温度下连续工作,其功率达到了500mW,78K时的阈值电流密度为31A/cm^2,特征温度也达到了103K。

Statistical Analysis for the Birnbaum-Saunders Fatigue Life Distribution under Type-Ⅱ Bilateral Censoring and Multiply Type-II Censoring

In present paper, we obtain the inverse moment estimations of parameters of the Birnbaum-Saunders fatigue life distribution based on Type-Ⅱ bilateral censored samples and multiply Type-Ⅱ censored sample. In this paper, we also get the interval estimations of the scale parameters.

Statistical Analysis for the Birnbaum-Saunders Fatigue Life Distribution under Multiply Type-ⅡCensoring

In present paper, we derive the quasi-least squares estimation(QLSE) and approximate maximum likelihood estimation(AMLE) for the Birnbaum-Saunders fatigue life distribution under multiply Type-Ⅱcensoring. Furthermore, we get the variance and covariance of the approximate maximum likelihood estimation.

Different effect of NiMnCo or FeNiCo on the growth of type-Ⅱa large diamonds with Ti/Cu as nitrogen getter

In order to synthesize high-quality type-Ⅱa large diamond, the selection of catalyst is very important, in addition to the nitrogen getter. In this paper, type-IIa large diamonds are grown under high pressure and high temperature（HPHT） by using the temperature gradient method（TGM）, with adopting Ti/Cu as the nitrogen getter in Ni70Mn25Co5（abbreviated as NiMnCo） or Fe（55）Ni（29）Co（16）（abbreviated FeNiCo） catalyst. The values of nitrogen concentration（Nc） in both synthesized high-quality diamonds are less than 1 ppm, when Ti/Cu（1.6 wt%） is added in the FeNiCo or Ti/Cu（1.8 wt%） is added in the NiMnCo. The difference in solubility of nitrogen between both catalysts at HPHT is the basic reason for the different effect of Ti/Cu on eliminating nitrogen. The nitrogen-removal efficiency of Ti/Cu in the NiMnCo catalyst is less than in the FeNiCo catalyst. Additionally, a high-quality type-Ⅱa large diamond size of 5.0 mm is obtained by reducing the growth rate and keeping the nitrogen concentration of the diamond to be less than 1 ppm, when Ti/Cu（1.6 wt%） is added in the FeNiCo catalyst.

Interface effect on superlattice quality and optical properties of InAs/GaSb type-Ⅱ superlattices grown by molecular beam epitaxy

We systematically investigate the influence of InSb interface(IF)engineering on the crystal quality and optical properties of strain-balanced InAs/GaSb type-Ⅱsuperlattices(T2SLs).The type-Ⅱsuperlattice structure is 120 periods InAs(8 ML)/GaSb(6 ML)with different thicknesses of InSb interface grown by molecular beam epitaxy(MBE).The highresolution x-ray diffraction(XRD)curves display sharp satellite peaks,and the narrow full width at half maximum(FWHM)of the 0th is only 30-39 arcsec.From high-resolution cross-sectional transmission electron microscopy(HRTEM)characterization,the InSb heterointerfaces and the clear spatial separation between the InAs and GaSb layers can be more intuitively distinguished.As the InSb interface thickness increases,the compressive strain increases,and the surface“bright spots”appear to be more apparent from the atomic force microscopy(AFM)results.Also,photoluminescence(PL)measurements verify that,with the increase in the strain,the bandgap of the superlattice narrows.By optimizing the InSb interface,a high-quality crystal with a well-defined surface and interface is obtained with a PL wavelength of 4.78μm,which can be used for mid-wave infrared(MWIR)detection.

Type-Ⅱ Core/Shell Nanowire Heterostructures and Their Photovoltaic Applications

Nanowire-based photovoltaic devices have the advantages over planar devices in light absorption and charge transport and collection.Recently,a new strategy relying on type-Ⅱ band alignment has been proposed to facilitate efficient charge separation in core/shell nanowire solar cells.This paper reviews the type-Ⅱ heterojunction solar cells based on core/shell nanowire arrays,and specifically focuses on the progress of theoretical design and fabrication of type-Ⅱ Zn O/Zn Se core/shell nanowire-based solar cells.A strong photoresponse associated with the type-Ⅱ interfacial transition exhibits a threshold of 1.6 e V,which demonstrates the feasibility and great potential for exploring all-inorganic versions of type-Ⅱ heterojunction solar cells using wide bandgap semiconductors.Future prospects in this area are also outlooked.

2D/2D type-Ⅱ Cu2ZnSnS4/Bi2WO6 heterojunctions to promote visible-light-driven photo-Fenton catalytic activity

In this work,a set of novel Cu2ZnSnS4/Bi2WO6(CZTS/BWO)two-dimensional(2 D)/two-dimensional(2 D)type-Ⅱheterojunctions with different CZTS weight ratios(1%,2%,and 5%)were successfully synthesized via a brief secondary solvothermal process.The successful formation of the heterojunctions was affirmed by characterization methods such as X-ray photoelectron spectroscopy and high-resolution transmission electron microscopy.The photocatalytic activity results showed that the prepared CZTS/BWO heterojunctions had excellent photocatalytic behaviors for organic degradation,especially when the mass fraction of CZTS with respect to BWO in the composite was 2%.Moreover,the addition of hydrogen peroxide(H2O2)could further improve the dye and antibiotic degradation efficiencies.The reinforced photocatalytic and photo-Fenton degradation performance were primarily attributable to the introduction of BWO,which afforded increased active sites,expanded the solar spectral response range,and accelerated the cycle of Cu(Ⅱ)/Cu(Ⅰ);after four cycling times,its catalytic activity did not decrease significantly.In addition,reasonable hypotheses of the photocatalytic and photo-Fenton catalytic mechanisms were formulated.This study is expected to provide a visual approach for designing a novel photo-Fenton catalyst to jointly utilize the photocatalytic and Fenton activities,which can be better applied to the purification of residual organics in wastewater.

Very long wavelength infrared focal plane arrays with 50% cutoff wavelength based on type-Ⅱ In As/GaSb superlattice

A very long wavelength infrared（VLWIR） focal plane array based on In As/Ga Sb type-Ⅱ super-lattices is demonstrated on a Ga Sb substrate. A hetero-structure photodiode was grown with a 50% cut-off wavelength of 15.2 μm, at 77 K.A 320×256 VLWIR focal plane array with this design was fabricated and characterized. The peak quantum efficiency without an antireflective coating was 25.74% at the reverse bias voltage of-20 mV, yielding a peak specific detectivity of 5.89×10^10cm·Hz^1/2·W^-1. The operability and the uniformity of response were 89% and 83.17%. The noise-equivalent temperature difference at 65 K exhibited a minimum at 21.4 mK, corresponding to an average value of 56.3 mK.

原位构筑Type-Ⅱ型异质结MgSnOH6/SnO2及其光催化降解罗丹明B的研究

本文采用一锅法水热制备Type-Ⅱ型光催化复合材料MgSn(OH)6/SnO2,并将其用于降解罗丹明B溶液的研究。通过粉末X射线多晶衍射和傅里叶红外反射光谱进行结构表征。研究结果表明,原料MgCl2·6H2O/SnCl4·5H2O=4/6 mmol时,具有最优的光催化降解效果,其降解率在60 min达到99%,光催化降解行为满足赝一级动力学模型,速率常数为0.076 min^-1。光催化活性自由基捕获实验发现,羟基自由基(·OH),超氧自由基(·O2^-)和空穴(h^+)均为主要的氧化活性物种。此外,我们还采用光电化学测量研究了其光催化机理。光催化活性的增强是由于在MgSn(OH)6和SnO2之间形成了Type-II型异质结,加速了光生电子和空穴的有效分离。循环实验表明MSOH-SO-50样品具有良好的光催化降解和结构稳定性。本文的研究为探索新型、高效的半导体光催化剂提供了重要的研究指导。

A statistical inference for generalized Rayleigh model under Type-Ⅱ progressive censoring with binomial removals

This paper considers the parameters and reliability characteristics estimation problem of the generalized Rayleigh distribution under progressively Type-Ⅱ censoring with random removals,that is,the number of units removed at each failure time follows the binomial distribution.The maximum likelihood estimation and the Bayesian estimation are derived.In the meanwhile,through a great quantity of Monte Carlo simulation experiments we have studied different hyperparameters as well as symmetric and asymmetric loss functions in the Bayesian estimation procedure.A real industrial case is presented to justify and illustrate the proposed methods.We also investigate the expected experimentation time and discuss the influence of the parameters on the termination point to complete the censoring test.

Experimental method to explore the adaptation degree of type-Ⅱand all-solid-state Z-scheme heterojunction structures in the same degradation system

TiO2 nanoparticles were prepared using the hydrothermal method and modified with CgN to syn-thesize a Type-Ⅱheterojunction semiconductor photocatalyst,TiO2-C;Na.In addition,a carbon layerwas coated onto the TiO2 nanoparticles and the obtained material was uniformly covered on thesurface of CaNa to form an all-solid-state Z-scheme semiconductor photocatalyst,TiO2-C-C3N4,Through characterization by XRD,XPS,SEM,TEM,BET,photoelectrochemical experiments,UV-visible diffuse reflection,and PL spectroscopy,the charge transfer mechanism and band gappositions for the composite photocatalysts were analyzed.The Type-Ⅱand all-solid-state Z-schemeheterojunction structures were compared.By combining microscopic internal mechanisms withmacroscopic experimental phenomena,the relationship between performance and structure wasverified.Experimental methods were used to explore the adaptation degree of different photocata-lytic mechanisms using the same degradation system.This study highlights effective photocatalystdesign to meet the requirements for specific degradation conditions.

Improvement of TE-polarized emission in type-Ⅱ InAlN–AlGaN/AlGaN quantum well

The optical properties of the type-Ⅱ lineup InxAl1-xN-Al0.59Ga0.41N/Al0.74Ga0.26N quantum well(QW) structures with different In contents are investigated by using the six-by-six K-P method.The type-Ⅱ lineup structures exhibit the larger product of Fermi-Dirac distribution functions of electron fc^n and hole(1-fv^Um) and the approximately equal transverse electric(TE) polarization optical matrix elements(|Mx|^2) for the c1-v1 transition.As a result, the peak intensity in the TE polarization spontaneous emission spectrum is improved by 47.45%-53.84% as compared to that of the conventional AlGaN QW structure.In addition, the type-Ⅱ QW structure with x^0.17 has the largest TE mode peak intensity in the investigated In-content range of 0.13-0.23.It can be attributed to the combined effect of |Mx|^2 and fc^n(1-fv^Um) for the c1-v1, c1-v2, and c1-v3 transitions.

一种基于TYPE-Ⅱ跟踪型RDC算法的电路设计

为提高电机控制DSP电路集成规模,将旋变数字转换电路进行IP化,提供电机轴位置反馈信息,对电机控制算法中Type-Ⅱ型跟踪环路的算法进行深入分析,并论证Type-Ⅱ型跟踪环路计算位置和速度的原理、实现旋变数字转换(RDC)工作的过程。针对分析的算法提出可IP化的RDC模块结构,使用精确查表结构实现正余弦信号转换、利用乘法器与滤波器组合达到解调效果。在实验室使用硬件描述语言实现电路并验证电路功能,使此算法更加具体清晰,在DSP电路集成中具有一定优势。

Growth of high material quality InAs/GaSb type-Ⅱ superlattice for long-wavelength infrared range by molecular beam epitaxy

By optimizing theⅤ/Ⅲbeam-equivalent pressure ratio,a high-quality InAs/GaSb type-Ⅱsuperlattice material for the long-wavelength infrared(LWIR)range is achieved by molecular beam epitaxy(MBE).High-resolution x-ray diffraction(HRXRD),atomic force microscopy(AFM),and Fourier transform infrared(FTIR)spectrometer are used to characterize the material growth quality.The results show that the full width at half maximum(FWHM)of the superlattice zero-order diffraction peak,the mismatching of the superlattice zero-order diffraction peak between the substrate diffraction peaks,and the surface roughness get the best results when the beam-equivalent pressure(BEP)ratio reaches the optimal value,which are 28 arcsec,13 arcsec,and 1.63?,respectively.The intensity of the zero-order diffraction peak is strongest at the optimal value.The relative spectral response of the LWIR detector shows that it exhibits a 100%cut-off wavelength of 12.6μm at 77 K.High-quality epitaxial materials have laid a good foundation for preparing high-performance LWIR detector.

Realization of low-energy type-Ⅱ Dirac fermions in(Ir_(1-x)Pt_x)Te_2 superconductors

Topological Dirac semimetals(DSMs) present a kind of topologically nontrivial quantum state of matter, which has massless Dirac fermions in the bulk and topologically protected states on certain surfaces. In superconducting DSMs, the effects of their nontrivial topology on superconducting pairing could realize topological superconductivity in the bulk or on the surface. As superconducting pairing takes place at the Fermi level E_F, to make the effects possible, the Dirac points should lie in the vicinity of E_F so that the topological electronic states can participate in the superconducting paring. Here,we show using angle-resolved photoelectron spectroscopy that in a series of(Ir_(1-x)Pt_x)Te_2 compounds, the type-Ⅱ Dirac points reside around E_F in the superconducting region, in which the bulk superconductivity has a maximum T_c of ～ 3 K.The realization of the coexistence of bulk superconductivity and low-energy Dirac fermions in(Ir_(1-x)Pt_x)Te_2 paves the way for studying the effects of the nontrivial topology in DSMs on the superconducting state.

Magnetic impurity in hybrid and type-Ⅱ nodal line semimetals

We study the Kondo screening of a spin-1/2 magnetic impurity in the hybrid nodal line semimetals(NLSMs) and the type-Ⅱ NLSMs by using the variational method. We mainly study the binding energy and the spin–spin correlation between magnetic impurity and conduction electrons. We find that in both the hybrid and type-Ⅱ cases, the density of states(DOS) is always finite, so the impurity and the conduction electrons always form bound states, and the bound state is more easily formed when the DOS is large. Meanwhile, due to the unique dispersion relation and the spin–orbit couplings in the NLSMs, the spatial spin–spin correlation components show very interesting features. Most saliently, various components of the spatial spin–spin correlation function decay with 1/r^(2) in the hybrid NLSMs, while they follow 1/r^(3) decay in the type-Ⅱ NLSMs. This property is mainly caused by the special band structures in the NLSMs, and it can work as a fingerprint to distinguish the two types of NLSMs.

Strain compensated type Ⅱ superlattices grown by molecular beam epitaxy

We investigate a strain compensation method for the growth of complex interband cascade laser structures. For thick In As/Al Sb superlattice clad layers, the sublayer thicknesses were adjusted so that the tensile strain energy in the In As sublayer was equal to the compressive strain energy in the Al Sb sublayer. For the four-constituent active region, as the compressive strain in the Ga0.65In0.35Sb alloy layer was large, a tensile strain was incorporated in the chirped In As/Al Sb superlattice region for strain compensation to the Ga0.65In0.35Sb alloy. A laser structure of thickness 6 μm was grown on the Ga Sb substrate by molecular beam epitaxy. The wafer exhibited good surface morphology and high crystalline quality.