Spin Pumping from a Quantum Dot in the Presence of Decoherence

We study the pumped spin current of an interacting quantum dot tunnel coupled to a single lead in the presence of electron spin resonance （ESR） field. The spin decoherence in the dot is included by the Bffttiker approach. Using the nonequilibrium Green＇s function technique, we show that ESR-induced spin flip can generate finite spin current with no charge transport. Both the Coulomb interaction and spin decoherence decrease the amplitude of spin current. The dependence of pumped spin current on the intensity and frequency of ESR field, and the spin decoherence is discussed.     

Temperature Dependence of Photoluminescence from Single and Ensemble InAs/GaAs Quantum Dots

We investigate the temperature dependence of photoluminescence from single and ensemble InAs/GaAs quantum dots systematically. As temperature increases, the exciton emission peak for single quantum dot shows broadening and redshift. For ensemble quantum dots, however, the exciton emission peak shows narrowing and fast redshift. We use a simple steady-state rate equation model to simulate the experimental data of photoluminescence spectra. It is confirmed that carrier-phonon scattering gives the broadening of the exciton emission peak in single quantum dots while the effects of carrier thermal escape and retrapping play an important role in the narrowing and fast redshift of the exciton emission peak in ensemble quantum dots.     

拖曳线列阵用光纤水听器的研究

报道了光纤水听器用于拖曳线列阵的研究结果。在保证光纤水听器声相位灵敏度的前提下, 优化设计了光纤水听器的结构,降低了光纤水听器的加速度灵敏度36dB。实验测得在20-1600Hz 频段,该光纤水听器的相位灵敏度为-162．7dB,频段内灵敏度的起伏为±0．7dB,加速度灵敏度小于-30dB。     

26Al的加速器质谱测量及其应用

26Al是一个在多个学科都非常有意义的放射性核素。主要介绍了国内外在利用加速器质谱技术测量26Al时所开展的各种测量方法、各自的优缺点和测量灵敏度，并介绍了目前利用^26Al在地球科学、生物医学、核物理以及天体物理等诸多方面的应用研究工作。     

Design and Fabrication of 1.06 μm Resonant-Cavity Enhanced Reflective Modulator with GaInAs/GaAs Quantum Wells

A resonant-cavity enhanced reflective optical modulator is designed and fabricated, with three groups of three highly strained InGaAs/GaAs quantum wells in the cavity, for low voltage and high contrast ratio operation. The quantum wells are positioned in antinodes of the optical standing wave. The modulator is grown in a single growth step in an molecular beam epitaxy system, using GaAs/AlAs distributed Bragg reflectors as both the top and bottom mirrors. Results show that the reflection device has a modulation extinction of 3 dB at -4.5 V bias.     

Magnetic properties of misch-metal partially substituted Nd–Fe–B magnets sintered by dual alloy method

The misch-metal(MM) partially substituted Nd–Fe–B sintered magnets were fabricated by the dual alloy method,and the crystal structure, microstructure, and magnetic properties were analyzed comprehensively. X-ray diffraction(XRD)reveals that the increasing content of the MM has an inconsiderable effect on the crystallographic alignment of the magnets.Grains of the two main phases are uniformly distributed, and slightly deteriorate on the grain boundary. Due to the diffusion between the adjacent grains, the MM substituted Nd–Fe–B magnets contain three types of components with different Ce/La concentrations. Moreover, the first-order reversal curve(FORC) diagram is introduced to analyze the magnetization reversal process, coercivity mechanism, and distribution of reversal field in magnetic samples. The analysis indicates that there are two major reversal components, corresponding to the two different main phases. The domain nucleation and growth are determined to be the leading mechanism in controlling the magnetization reversal processes of the magnets sintered by the dual alloy method.     

基于波长调制技术对强水蒸气干扰下痕量氨气的测量研究

本文采用免标定波长调制光谱技术结合修正算法实现了电厂脱硝过程中高浓度水蒸气干扰下的痕量逃逸氨浓度测量。分析和讨论了背景对实验测量信号的影响,选择信背比较高的四次谐波用于NH_3浓度的反演,并进行了实验验证。对于烟气中高浓度水蒸气的干扰,利用了H_2O强吸收峰位置标定绝对波数及NH_3吸收峰位置,此外本文提出的修正算法结合免标定波长调制算法可以同时实现H_2O和NH3浓度的准确反演,并通过实验验证了算法的正确性。最后将该修正方法应用于电厂逃逸氨浓度测量并获得了较为可靠的结果.     

电场调谐InAs单量子点的发光光谱

采用稳态和时间分辨发光光谱,研究了生长在p-i-n二极管结构内的InAs单量子点发光光谱的电场调谐特性.随着电场强度的增加,观察到量子点中激子发光的Stark 效应.通过选择不同波长的激光线激发量子点样品,发现随着电场强度的增加导致量子点发光强度的减弱,这是由于量子点俘获载流子概率的减小所致,而激子寿命的增加源于电场导致激子的Stark效应. 关键词： InAs单量子点 Stark效应 电子-空穴分离     

釉灰制备原料和工艺对其组成的影响

釉灰是我国古代独特的传统釉用核心原料,其中以景德镇生产的釉灰最具代表性和影响力,正所谓“无灰不成釉”。它不仅成就了景德镇宋元明清的制瓷盛况,而且拥有复杂、严谨且带有一丝“神秘”色彩的制备工艺,其原料选择、工艺原理、釉用机理长期以来一直是中外研究者探究我国古代制瓷“秘诀”的一个重要课题。实验采集了狼萁草等四种典型柴草和两种石灰石,分别进行了煅烧实验,并借助EDXRF和X射线衍射仪(XRD),对各原料灰化后的化学组成及不同煨烧次数所制得釉灰的化学组成和物相组成进行科学表征和对比研究,初步剖析了釉灰制备采用独特的三次煨烧工艺的科学意义。结果表明,狼萁草化学组成中Fe₂O₃和MnO含量分别高达1.41%和1.52%,而P₂O₅含量则为四者中最低的0.54% ,不仅有利于景德镇传统灰釉呈现 “白中泛青”的效果,还有利于提高釉层的透明度,促进景德镇传统釉下青花等彩绘瓷的发色。灰色石灰石不仅CaO含量低于黝黑色石灰石,且MgO含量更是高达35.79%,这正是古代制灰匠偏爱选择黝黑色石灰石的主要原因。此外,研究还发现,随着煨烧次数的增加,不仅釉灰化学组成中的K₂O,P₂O₅,MnO,Fe₂O₃的含量均呈明显递增趋势,且其物相组成中的CaCO₃含量呈递增趋势,而Ca(OH)₂含量则刚好相反,呈下降趋势,这不仅有利于景德镇瓷器呈现“颜如玉”的外观特质,也有利于克服配釉过程中釉浆因含一定量的Ca(OH)₂而引起的“作浓”现象。可见,釉灰制备选用独特的原料及其煨烧工艺,是景德镇古代灰釉独具特色并得以长期发展的技术保障之一。     

基于太赫兹时域光谱技术与PCA-BPN网络的转基因大豆鉴别

基于太赫兹波段内的光谱分析技术以及主成分特性分析与反向前馈神经网络建模,提出了一种转基因大豆鉴别方法.从光谱数据中提取累计方差贡献率达到97.582％的前8种主成分因子,并将其作为输入源导入神经网络模型,通过剔除冗余数据、降低数据维数,所建立的神经网络模型能准确识别校验集.该方法可以实现转基因大豆的快速、无损检测,在农业安全领域有广泛的应用前景.