GaAsN/GaAs量子阱在1 MeV电子束辐照下的退化规律

为研究GaAsN/GaAs量子阱在电子束辐照下的退化规律与机制,对GaAsN/GaAs量子阱进行了不同注量(1×10¹⁵,1×10¹⁶ e/cm²)1 MeV电子束辐照和辐照后不同温度退火(650,750,850℃)试验,并结合Mulassis仿真和GaAs能带模型图对其分析讨论。结果表明,随着电子注量的增加,GaAsN/GaAs量子阱光学性能急剧降低,注量为1×10¹⁵ e/cm²和1×10¹⁶ e/cm²的电子束辐照后,GaAsN/GaAs量子阱PL强度分别衰减为初始值的85%和29%。GaAsN/GaAs量子阱电子辐照后650℃退火5 min,样品PL强度恢复到初始值,材料带隙没有发生变化。GaAsN/GaAs量子阱辐照后750℃和850℃各退火5 min后,样品PL强度随退火温度的升高不断减小,同时N原子外扩散使得样品带隙发生约4 nm蓝移。退火温度升高没有造成带隙更大的蓝移,这是由于进一步的温度升高产生了新的N—As间隙缺陷...     

钛氧化物结构及其拉曼光谱表征

采用密度泛函理论(DFT),对几种钛的氧化物晶体结构进行了几何构型优化,得到了与X-ray晶体衍射实验结果相一致的结构参数。在优化几何构型基础上进行了分子振动模的分析和计算,钛氧化物均采用数字化基组和局域密度近似,并选择vwn对局域交换相关能量参数化,使用自旋非限制函数。同时,测定了钛的氧化物(TiO, Ti₂O₃,Ti₃O₅,锐钛矿型TiO₂和金红石型TiO₂)几种晶体的拉曼光谱,并分别解释了相关的拉曼活性振动模。结果表明：计算的频率与实验结果比较一致,理论计算频率可以指导实验谱图谱峰位置的归属分析。通过钛的一系列氧化物的常温拉曼光谱分析, 得知不同氧化物有不同特征峰,有利于含钛氧化物材料类型的诊断,为沟通结构和性能的相互关系奠定基础。     

Cu取代对水滑石前驱物及其衍生氧化物性能的影响

恒定二价与三价阳离子比为3,采用共沉淀法制备不同Cu含量的系列水滑石前驱物,经过焙烧形成复合氧化物(CuO质量分数为0、5%、10%、15%、20%、30%、40% )材料.采用X射线衍射(XRD)、热重分析(TGA)、差示扫描量热(DSC)、程序升温还原(TPR)、傅立叶红外光谱分析(FTIR)等表征手段研究了Cu、Mg含量对材料前驱物和衍生复合氧化物物化性能的影响.结果表明,在CuO≤30%范围内可以形成结构完整的水滑石前驱物, CuO>40%时出现Cu(OH)2 杂相; CuO≤20% (质量分数)时,经高温焙烧可得到的均匀的复合氧化物,CuO>20%时出现CuO偏析.Cu、Mg含量对材料的热稳定性能有显著的影响,焙烧温度和组成决定了材料的还原性能.     

基于Er3+：YAlO3/TiO2的可见光催化降解室内甲醛

为使TiO2能够在可见光下发挥其于紫外激发的高光催化活性降解室内甲醛,采用水热处理法将TiO2与掺杂稀土离子Er3+的上转换发光剂Er3+∶YAlO3结合,制备具有可见光响应的Er3+∶YAlO3/TiO2光催化剂,并对其进行了表征分析。结果表明,TiO2以锐钛矿为主,且Er3+∶YAlO3可有效地将可见光上转换至可激发TiO2的紫外光。在箱式反应器中进行光催化降解气态甲醛,研究了甲醛初始浓度与催化剂用量对甲醛降解效率的影响。结果表明,该光催化反应的假一级反应速率常数( kapp )与甲醛初始浓度成正相关,而随催化剂用量的增加先升高后降低。当甲醛初始浓度为0.058 mg/m3、催化剂用量为0.1224 g/L时,kapp最大为3.65×10-3 min-1。该反应符合Langmuir-Hinshelwood模型,反应速率常数为5×10-8 mg/( L·min)。     

V-Bi复合氧化物的合成和光谱研究

本文采用凝胶溶胶法和微波制备法合成了Ｋ－Ｂｉ复合氧化物,用ＦＴＩＲ,ＮＩＲ ＦＴ－Ｒａｍａｎ和ＸＲＤ对其进行研究。     

Mo-Fe-Bi复合氧化物的制备和光谱研究

本文采用溶胶方法和沉淀方法制备Ｍｏ－Ｆｅ－Ｂｉ复合氧化物,用ＦＴＩＲ、ＮＩＲ ＦＴ－Ｒａｍａｎ和ＸＲＤ对其进行研究。     

Influence of Intrinsic Decoherence on Entanglement in Two-Qubit Quantum Heisenberg XYZ Chain

Taking the intrinsic decoherence effect into account, we investigate the time evolution of entanglement for two-qubit XYZ Heisenberg model in an external uniform magnetic field. Concurrence, the measurement of entanglement,is calculated. We show how the intrinsic decoherence modifies the time evolution of the entanglement and find that at short-time case, concurrence is oscillating as increasing magnetic field, which implies that entanglement may be enhanced or weakened in some time regions.     

Influence of Intrinsic Decoherence on Entanglement in Two-Qubit Quantum Heisenberg XYZ Chain

Taking the intrinsic decoherence effect into account, we investigate the time evolution of entanglement for two-qubit XYZ Heisenberg model in an external uniform magnetic field. Concurrence, the measurement of entanglement,is calculated. We show how the intrinsic decoherence modifies the time evolution of the entanglement and find that at short-time case, concurrence is oscillating as increasing magnetic field, which implies that entanglement may be enhanced or weakened in some time regions.     

基于扣除法的电吸收调制器本征特性分析方法

基于电吸收调制器的工作原理和等效电路模型对调制器的高频响应特性进行分析,提出了一种采用频率响应扣除法提取有源区本征响应的仿真新方法.该方法能简单地去掉封装网络、夹具及光探测仪器等带来的影响,用该方法得到了待测lnGaAs/InAIAs材料电吸收调制器准确的的高频本征响应特性.     

多光谱真温快速反演方法

材料的未知发射率是辐射测温的一大障碍,它导致了无法依靠单组测量数据获得材料的真实温度,人们只能通过假定材料发射率模型来计算出材料的亮度温度等非真实温度.基于这样的背景,Gardner J等科学家们提出了多光谱测温法并不断完善其理论,如今多光谱测温广泛应用于高温和超高温测量、高温目标的热性能测量、真实温度动态测量等.20...     

Fast frictionless expansion of an optical lattice

We investigate fast frictionless expansion of an optical lattice with dynamically variable spacing (accordion lattice). We design an expansion trajectory that yields a final state identical to the initial state up to an irrelevant phase factor. We discuss the effect of additional force and nonlinear interaction on the fast frictionless expansion.     

On Time Scales of Intrinsic Oscillations in the Climate System

Proxy temperature data records featuring local time series, regional averages from areas all around the globe, as well as global averages, are analyzed using the Slow Feature Analysis (SFA) method. As explained in the paper, SFA is much more effective than the traditional Fourier analysis in identifying slow-varying (low-frequency) signals in data sets of a limited length. We find the existence of a striking gap from ~1000 to about ~20,000 years, which separates intrinsic climatic oscillations with periods ranging from ~60 years to ~1000 years, from the longer time-scale periodicities (20,000 year+) involving external forcing associated with Milankovitch cycles. The absence of natural oscillations with periods within the gap is consistent with cumulative evidence based on past data analyses, as well as with earlier theoretical and modeling studies.     

热阴极径向温度非均匀性对本征发射度的影响

从热发射理论出发,推导了非均匀发射阴极的均方根本征发射度的一般计算形式。针对一种最常见的温度径向分布近似模型,给出了均方根发射度随温度非均匀性变化趋势的理论数值解。基于有限差分法粒子仿真技术统计了热阴极的本征发射度,仿真结果与理论解一致,验证了非均匀发射热阴极本征均方根发射度一般形式的正确性。结果表明,径向温度非均匀性引起均方根发射度显著变化,非均匀系数为10%时引起均方根发射度下降约15%。本文建立的理论形式和仿真方法可以有效评估束流品质控制目标和工程热设计之间的依赖关系,以指导高效费比的工程设计。     

Effect of the Spin Fluctuations on the Carrier Thermal Conductivity in High-Tc Oxides

A theory of the carrier thermal conductivity for electron antiferromagnetic spin fluctuation scattering has been developed and on this basis the experimental results of high-T_c oxides have been interpreted. Our theoretical analysis fits the experimental results excellently and suggests that the antiferromagnetic spin fluctuations affect the carrier thermal conductivity in high-T_c oxides.     

基于色氨酸本征荧光测量的生物气溶胶检测技术研究

生物气溶胶与环境质量和人类健康密切相关。基于光学测量的气溶胶检测技术具有快速、无损和灵敏的优点,是目前的研究主流。而对检测系统的标定技术及其评价方法尚无国家标准可依。基于本征荧光测量技术,研制完成了一套针对包括病毒气溶胶在内的生物气溶胶检测装置。并在此基础上,以色氨酸气溶胶作为被检物,提出了一种生物气溶胶检测与标定方法。实验结果表明,研制的检测装置对色氨酸气溶胶具良好的线性响应特性,线性相关系数R2≥0.99,灵敏度达到4000L-1。证明了通过测量气溶胶中色氨酸含量检测生物气溶胶技术的可行性与可靠性。还探讨了利用多通道本征荧光检测技术实现对生物粒子种类进行预判别的可行性。     

A Volatility Estimator of Stock Market Indices Based on the Intrinsic Entropy Model

Grasping the historical volatility of stock market indices and accurately estimating are two of the major focuses of those involved in the financial securities industry and derivative instruments pricing. This paper presents the results of employing the intrinsic entropy model as a substitute for estimating the volatility of stock market indices. Diverging from the widely used volatility models that take into account only the elements related to the traded prices, namely the open, high, low, and close prices of a trading day (OHLC), the intrinsic entropy model takes into account the traded volumes during the considered time frame as well. We adjust the intraday intrinsic entropy model that we introduced earlier for exchange-traded securities in order to connect daily OHLC prices with the ratio of the corresponding daily volume to the overall volume traded in the considered period. The intrinsic entropy model conceptualizes this ratio as entropic probability or market credence assigned to the corresponding price level. The intrinsic entropy is computed using historical daily data for traded market indices (S&P 500, Dow 30, NYSE Composite, NASDAQ Composite, Nikkei 225, and Hang Seng Index). We compare the results produced by the intrinsic entropy model with the volatility estimates obtained for the same data sets using widely employed industry volatility estimators. The intrinsic entropy model proves to consistently deliver reliable estimates for various time frames while showing peculiarly high values for the coefficient of variation, with the estimates falling in a significantly lower interval range compared with those provided by the other advanced volatility estimators.     

Effect of Intrinsic Decoherence of Milburn＇s Model on Entanglement of Two-Qutrit States

We analyze the time evolution of entanglement of two-qutrit system within the framework of Milburn's model of intrinsic decoherence. The entanglement evolution relies not only on the parameters of system, but also on the concrete states either pure or mixed. The linear entropy used to measure the extent to which the intrinsic decoherence affects quantum states is evaluated.     

Effect of Intrinsic Decoherence on Nonclassical Effects of the Nondegenerate Bimodal Multiquanta JCM

We study the nondegenerate multiquanta Jaynes-Cummings model governed by Milburn equation. This models the decoherence of a quantum system as it evolves through intrinsic mechanisms beyond conventional quantum mechanics governed by the Schrödinger equation. We find an exact solution of this equation and apply it to investigate the effects of the intrinsic decoherence on nonclassical effects of the system, such as collapses and revivals of the population inversion and squeezing of the radiation field, for the resonant and the off-resonant cases when the particle (atom or trapped ion) is taken to be prepared initially in a coherent superposition state.     

Time-resolved luminescence of complex wide-gap oxide crystals under inner-shell excitation

In order to investigate the soft X-ray energy transformation in oxide detectors the optical spectra of several wide-gap oxide crystals were analyzed. The time-resolved luminescence (2.5–10.5 eV) and luminescence excitation spectra (50–200 and 500–630 eV) as well as decay kinetics of luminescence at 10 and 295 K were recorded using the synchrotron radiation from BW3 channel (HASYLAB, DESY). Several analogous features were discovered in the excitation spectra of both intrinsic self-trapped exciton luminescence and recombination luminescence for BeO, BeAl₂O₄, Be₂SiO₄ and AlPO₄ crystals under inner-shell excitation. Simultaneously, the excitation of Ce³⁺-luminescence in scintillating Be₂La₂O₅-Ce crystals significantly differs.