反铁磁链中Dzyaloshinskii–Moriya机制驱动矢量自旋手征束缚态的研究

Dzyaloshinskii-Moriya(DM)相互作用驱动的矢量自旋手征态,能和声子发生耦合,具备非常丰富的物理现象.本论文以一维反铁磁链中自旋手征-声子耦合模型为基础,研究不同声子环境下,耦合强度对自旋手征动力学演化过程的影响规律.结果表明,对自旋S=1/2的系统,在不同的声子浴(sub-Ohmic(0 1))中,均会在非相干到相干自旋涨落过程中产生无能隙一级相变,其来源是自旋手征束缚态的形成.相变发生的临界自旋-声子耦合强度正比于自旋涨落大小,反比于系统德拜频率.当自旋-声子耦合强度超过其临界值时,自旋手征束缚态的产生将极大地抑制非相干自旋涨落.     

NO在稀有金属钇表面的吸附行为

以往的理论在预测六方结构(HCP)金属的表面能时,计算值与实验值存在较大误差.鉴于此,本文首先用一种较为合理的方法精准地预测了稀有金属钇(Y)(0001)面的表面能,计算值(1.141 J/M²)与实验值(1.125 J/M²)吻合的很好.随后,系统研究了NO小分子在Y(0001)面不同位置(空位、桥位和端位)的吸附行为.结果表明:空位(H1)表现出了良好的吸附能力,吸附能超过了5eV,同时N-O键长伸长量超过了24%,此时,NO分子几乎平行地吸附于Y(0001)表面.所有的吸附位置的N-O分子伸长量范围为0.2?-0.42?.这种伸长量明显超过了NO在其它金属表面时的计算结果.     

Lu-Eu共掺杂Ga2O3的光电性质的第一性原理计算

宽禁带半导体β-Ga₂O₃因为具有优良的物理化学性能而成为研究热点.本文基于DFT(Density Functional Theory)的第一性原理方法,先采用PBE(Perdew-Burke-Ernzerhof)中的GGA(Generalized Gradient Approximation)和GGA+U(Generalized Gradient Approximation-Hubbard U)的方法计算了本征β-Ga₂O₃,Lu掺杂浓度为12.5%的β-Ga₂O₃及Lu-Eu共掺杂浓度为25%的β-Ga₂O₃结构的晶格常数、能带结构和体系总能量.发现采用GGA+U的方法计算的带隙值更接近实验值,于是采用GGA+U的方法计算了本征β-Ga₂O₃,Lu掺杂的β-Ga₂O₃以及Lu-Eu共掺杂的β-Ga₂O...     

Multiscale Weighted Permutation Entropy Analysis of Schizophrenia Magnetoencephalograms

Schizophrenia is a neuropsychiatric disease that affects the nonlinear dynamics of brain activity. The primary objective of this study was to explore the complexity of magnetoencephalograms (MEG) in patients with schizophrenia. We combined a multiscale method and weighted permutation entropy to characterize MEG signals from 19 schizophrenia patients and 16 healthy controls. When the scale was larger than 42, the MEG signals of schizophrenia patients were significantly more complex than those of healthy controls (p<0.004). The difference in complexity between patients with schizophrenia and the controls was strongest in the frontal and occipital areas (p<0.001), and there was almost no difference in the central area. In addition, the results showed that the dynamic range of MEG complexity is wider in healthy individuals than in people with schizophrenia. Overall, the multiscale weighted permutation entropy method reliably quantified the complexity of MEG from schizophrenia patients, contributing to the development of potential magnetoencephalographic biomarkers for schizophrenia.     

基于双积分模拟重构大动态范围CIS系统研究

提出一种采用列共用模拟重构电路和双积分三采样工作时序的CMOS图像传感器(CIS)系统架构,可实现光电响应曲线压缩和像素固定模式噪声(FPN)消除,提高传感器动态范围到83 dB,使成像质量提高.该结构具有与单采样相同的像素阵列,仅增加很小的处理电路.改进的工作时序优化了长积分、短积分和信号处理的时序分配.系统控制由FPGA实现.功能和数模混合仿真验证表明,方案是可行的.     

One‐Pot Synthesis of 2,5‐Furandicarboxylic Acid from 2‐Furoic Acid by a Pd‐catalyzed Bromination–Hydroxycarbonylation Tandem Reaction in Acetate Buffer

The one‐pot synthesis of 2,5‐furandicarboxylic acid from 2‐furoic acid with a yield of 57 % was achieved for the first time using a Pd‐catalyzed bromination‐hydroxycarbonylation tandem reaction in HOAc‐NaOAc buffer. This synthetic protocol shows major improvements compared to previously reported methods, such as using biomass‐based 2‐furoic acid as low‐cost raw material, one‐pot synthesis without isolation of intermediate products, and no need for an acidification procedure. Experiments indicate that the involved Xantphos‐modified Pd‐catalyst and the buffer solution play significant promoting roles for each individual reaction whereas Br₂ (as the brominating reagent) had a negative effect on the second hydroxycarbonylation step, while CO was deleterious for the first bromination step. Hence, in this practical one‐pot synthesis, Br₂ should be consumed in the first bromination step as fully as possible, and CO is introduced after the first bromination step has been completed.     

基于自主管理机制的网格监测系统故障诊断与恢复

为了使网格监测系统能够自主地处理自身的故障、应对复杂多变的网格环境,基于自主组织、管理机制和自主计算技术中的自修复、自愈等思想,R-Net监测系统(RNMS)对监测系统故障的探测、诊断、处理和恢复进行了研究,并把重点放在节点组的故障恢复上.实现了网格监测系统故障诊断与恢复机制,使得监测系统能够无需管理人员的参与、自主地处理一些常见的故障,降低了系统维护的复杂性和成本,增加了系统的易用性和可靠性.     

Dipolar Glass Polymers for Capacitive Energy Storage at Room Temperatures and Elevated Temperatures

Dielectric polymers are the materials of choice for high energy density film capacitors. The increasing demand for advanced electrical systems requires dielectric polymers to operate efficiently under extreme conditions, especially at elevated temperatures. However, the low permittivity and relatively low operating temperature of dielectric polymers limit the high-temperature capacitive energy storage applications.Fortunately, dipolar glass polymers are demonstrated as the preferred materials to...     

Saprophytic Bacillus Accelerates the Release of Effective Components in Agarwood by Degrading Cellulose

The value of Agarwood increases with time due to the gradual release of its major components, but the mechanism behind this remains unclear. Herein we reveal that the potential driving force of this process is the degradation of cellulose in Agarwood by its saprophytic Bacillus subtilis. We selected 10-year-old Agarwood from different places and then isolated the saprophytic bacteria. We confirmed these bacteria from different sources are all Bacillus and confirmed they can degrade cellulose, and the highest cellulase activity reached 0.22 U/mL. By co-cultivation of the bacterium and Agarwood powder, we found that three of the strains could release the effective components of Agarwood, while they had little effect in increasing the same components in living Aquilaria sinensis. Finally, we demonstrated that these saprophytic Bacillus subtilis have similar effects on Zanthoxylum bungeanum Maxim and Dalbergiaod orifera T. Chen, but not on Illicium verum Hook. f, Cinnamomum cassia Presl and Phellodendron chinense Schneid. In conclusion, our experiment revealed that the saprophytic Bacillus release the effective components of Agarwood by degrading cellulose, and we provide a promising way to accelerate this process by using this bacterial agent.     

HSDPA与WiMAX的技术综合比较

本文首先介绍了HSDPA和WiMAX两种技术的特点,然后对其进行了比较,前者技术较为成熟,也容易实现,设备成本相对低廉;后者在数据传输速率和覆盖范围方面具有优势,但升级的成本较高.