多孔介质中的双稳热对流

对矩形横截面多孔介质中热对流的复杂分岔行为──二次分岔进行研究．使用Ｌｉａｐｕｎｏｖ－Ｓｃｈｍｉｄｔ约化并充分利用问题本身的对称性，研究了于最低的两个不同临界Ｒａｙｌｅｉｇｈ数处从平凡的静态传热解产生的热对流主分岔解之间的相互作用；揭示了主分岔解的二次分岔并给出了主分岔解及二次分岔解的渐近展开．稳定性分析表明从第二临界Ｒａｙｌｅｉｇｈ数产生的主分岔解经二次分岔后由不稳定变得稳定，从而与由最小临界Ｒａｙｌｅｉｇｈ数产生的主分岔解组成双稳定热对流．文中理论分析可较恰当地解释已有的数值模拟结果．     

适合自主探究式学习的光纤传感器组合演示装置

介绍了自行研制的光纤传感器组合演示装置,探索建立基于现代教育理念的演示实验教学模式,阐述该类演示装置在整个专业课程体系中的地位和作用.     

Ⅱ-Ⅵ族碲化物体单晶低温光致发光谱研究

采用熔体法生长Ⅱ-Ⅵ族碲化物体单晶时,不同的生长条件及热经历过程会导致生长态晶体材料中,占主导的点缺陷类型存在较大的差异,进而影响了晶体的物理性能及器件的使用。低温光致发光(PL)谱作为一种无损检测方法,可以用于研究不同条件下生长的Ⅱ-Ⅵ族碲化物体单晶中的点缺陷和杂质的能级状态。对比富Te条件下生长的未掺杂ZnTe和CdTe晶体在8.6 K下的PL谱可以发现,电阻率较低的p型ZnTe晶体,其PL谱中,电子到中性受主复合发光峰(e, A0)强度高于施主-受主对复合发光峰(DAP),而高电阻率阻n型CdTe晶体则刚好相反,这可能是由于生长速率及降温过程的热经历不同导致占主导的本征点缺陷类型不同造成的。按化学计量比生长的未掺杂CdZnTe晶体,其PL谱中自由激子发光峰(D0, X)占主导,而(e, A0)峰强度高于DAP峰,变温PL谱测试表明当温度高于15 K时,(e, A0)峰与DAP峰逐渐叠加在一起。In掺杂导致在富Te条件下生长的CdZnTe晶体的PL谱中产生明显的A中心复合发光峰,与导带的能量差约为0.15 eV,主要与In补偿Cd空位形成的复合体[In+_CdV2-_Cd]-有关,且其强度与In掺杂元素的含量成正比。     

移动加热器法生长CZT晶体的成分及缺陷均匀性研究

采用移动加热器法,成功生长出尺寸为φ55 mm×70 mm的CdZnTe晶体.采用电子探针、光致发光谱等方法,测试了晶体径向的成分和缺陷分布,并与垂直布里奇曼法生长的同成分CdZnTe晶体进行了对比分析.结果表明,移动加热器法生长的CdZnTe晶体沿径向的成分和缺陷分布均匀,均优于垂直布里奇曼法生长的晶体.     

ACRT-Te溶剂法生长的ZnTe∶Cr晶体的光谱性能

采用改进的ACRT-Te溶剂法制备了ZnTe∶ Cr晶体,并对晶体的光谱特性进行了表征.紫外-可见-近红外透过光谱分析表明,晶体在800 nm和1790 nm处出现了与Cr2+有关的强吸收,并在570 ～ 750 nm范围内存在与Zn空位有关的吸收.低温光致发光(PL)谱分析表明,晶体在530 nm附近和595 ～ 630 nm之间出现近带边(NBE)发射和自激活(SA)发射.进一步分析表明,NBE发射由受主束缚激子(A1,X)峰、电子-受主对(e,A)峰和施主-受主对(DAP)发光峰组成.利用Arrhenius公式对变温PL谱上的NBE峰进行拟合,得出样品在低温(＜50 K)和高温(＞50 K)时的热猝灭激活能分别为3.87 meV和59.53 meV.红外荧光谱分析表明,ZnTe∶ Cr晶体的室温荧光发射带为2～2.6 μm,荧光寿命为1.0 ×10-6s.     

有限时宽序列的Semi-Blind反褶积——Ⅱ.非线性问题

本文继文献[1]进一步研究Semi-Blind反褶积的非线性问题。在Z变换域中,通过利用多项式方程根与系数的关系,得到了若干定理,表明对于某些x(n),y(n)序列,仅需已知x(n),y(n)头尾共两个采样点,由z(n)便可以唯一地确定全部x(n),y(n)。文中就几种已知条件,给出了由z(n)可以唯一确定的x(n),y(n)信号类应满足的充要条件。此外,还给出了一种非线性Semi-Blind反褶积的实现方法及计算机实验结果。     

A new model analysis of the third harmonic voltage in inductive measurement for critical current density of superconducting films

The critical current density J c is one of the most important parameters of high temperature superconducting films in superconducting applications,such as superconducting filter and superconducting Josephson devices.This paper presents a new model to describe inhomogeneous current distribution throughout the thickness of superconducting films applying magnetic field by solving the differential equation derived from Maxwell equation and the second London equation.Using this model,it accurately calculates the inductive third-harmonic voltage when the film applying magnetic field with the inductive measurement for J c.The theoretic curve is consistent with the experimental results about measuring superconducting film,especially when the third-harmonic voltage just exceeds zero.The J c value of superconducting films determined by the inductive method is also compared with results measured by four-probe transport method.The agreements between inductive method and transport method are very good.     

b→cτ■ decay in supersymmetry with R-parity violation

In past years,several hints of lepton flavor universality(LFU)violation have emerged from the b→ct■,and b→sl~+l-data.More recently,the Belle Collaboration has reported the first measurement of the D* longitudinal polarization fraction in the B→D*τV decay.Motivated by this intriguing result,along with the recent measurements of RJ/Ψand τ polarization,we present the study of b→ct■ decays in supersymmetry(SUSY)with R-parity violation(RPV).We consider B→D(*)t■,Bc→ηct■,Bc→J/ψt■ and ∧b→∧ct■ modes and focus on the branching ratios,LFU ratios,forward-backward asymmetries,polarizations of daughter hadrons,and the τ lepton.The RPV SUSY was capable of explaining the RD(*) anomalies at the 2σ level,after taking into account various flavor constraints.In the allowed parameter space,the differential branching fractions and LFU ratios are largely enhanced by the SUSY effects,especially in the large dilepton invariant mass region.Moreover,a lower bound B(B~+→K~+vv)7.37×10~(-6) is obtained.These observables could provide testable signatures at the high-luminosity LHC and SuperKEKB,and correlate with direct searches for SUSY.     

Distinctive distribution of defects in CdZnTe:In ingots and their effects on the photoelectric properties

Photoelectric properties of CdZnTe:In samples with distinctive defect distributions are investigated using various techniques. Samples cut from the head(T04) and tail(W02) regions of a crystal ingot show distinct differences in Te inclusion distribution. Obvious difference is not observed in Fourier transform infrared(FTIR) spectra, UV–Vis–NIR transmittance spectra, and Ⅰ–Ⅴ measurements. However, carrier mobility of the tip sample is higher than that of the tail according to the laser beam induced current(LBIC) measurements. Low temperature photoluminescence(PL) measurement presents sharp emission peaks of D~0 X and A~0 X, and relatively large peak of D~0 X(or A~0 X)/D_(complexfor) T04, indicating a better crystalline quality. Thermally stimulated current(TSC) spectrum shows higher density of shallow point defects, i.e.,Cd vacancies, In_(Cd)~+, etc., in W02 sample, which could be responsible for the deterioration of electron mobility.