Time operator in QFT with Virasoro constraints

Time operator is studied on the basis of field quantization, where the difficulty stemming from Pauli?s theorem is circumvented by borrowing ideas from the covariant quantization of the bosonic string, i.e., one can remove the negative energy states by imposing Virasoro constraints. Applying the index theorem, one can show that in a different subspace of a Fock space, there is a different self-adjoint time operator. However, the self-adjoint time operator in the maximal subspace of the Fock space can also represent the self-adjoint time operator in the other subspaces, such that it can be taken as the single, universal time operator. Furthermore, a new insight on Pauli?s theorem is presented.     

Calculation on the CO2 influences on the structure,stability of (MgO)m (m = 1–6) clusters

ABSTRACT

The concentration of carbon dioxide (CO₂) has a significant influence on the morphology of thermal decomposition products of magnesite. So, structures, stabilities and adsorption mechanisms of (MgO)_m (m?=?1–6) clusters by one or two CO₂ molecules were calculated by the GGA-PW91 method. The results show that the stability of the considered clusters is (MgO)_m(CO₂)₂ clusters > (MgO)_m(CO₂) clusters > (MgO)_m clusters by the average binding energy. Certain low-lying isomers of (MgO)_m(CO₂) and (MgO)_m(CO₂)₂ clusters which have an isolated O atom are deviating from the cluster center which possess higher kinetic activity. (MgO)_m clusters prefer to adsorb a CO₂ molecule, while (MgO)₃(CO₂) clusters prefer to adsorb a CO₂ molecule rather than the neighbors. Magnesite is difficult to transit to (MgCO₃)₂ clusters at room temperature. However, magnesite will spontaneously transit to (MgO)₂ clusters and further transit to MgO crystal which need to adsorb more energy at 700?K.     

ONOO-活性氧的荧光光谱分析进展

系统介绍了ONOO^-活性氧的化学性质，并对其参与的主要化学反应进行了分类和总结．同时，比较了近年来用于ONOO^-检测的方法，并重点论述了荧光光谱分析方法尤其是酶催化动力学荧光分析法在检测ONOO^-活性氧方面的优势和最新的研究进展．     

Polarimetric-Spectral-Sensitive Compressed Ultrafast Photography Enables Real-Time Intensity Visualization of Time-Varying Polarized Ultrafast Laser Pulses

Ultrafast laser pulses with complex spatiotemporal and polarization couplings have shown great application prospects in coherent control, particle acceleration, molecular dynamics excitation, and chiral or anisotropic detection. It is very important to observe the polarization-coupled ultrafast laser pulses for characterizing the performance of laser source and understanding the laser-matter interaction, but there is currently no detection technique that can completely characterize them, including the spatio-, spectral-, and polarimetric-temporal information. In this work, a polarimetric-spectral-sensitive has been compressed ultrafast photography (PS-CUP) to realize the real-time intensity visualization of time-varying polarized (TP) ultrafast laser pulses. PS-CUP can not only distinguish the polarization state of a TP pulse, but also realize the spatio-, spectral- and polarimetric-temporal measurement. To demonstrate the ability of polarization resolving detection, PS-CUP is used to successfully distinguish between the sinistral and dextral TP pulses and measure the angle and degree of linear polarization of a dextral TP pulse, respectively, and the experimental results are highly consistent with theoretical simulations. Owing to the unprecedented multidimensional detection ability, PS-CUP is prospected to provide a powerful tool for the diagnosis of various complex ultrafast laser pulses and the detection of ultrafast chiral optics.     

非PLL相位平均型参考线原型验证

射频相位参考线是粒子加速器的重要组成部分之一,为射频低电平控制系统(LLRF)、束流诊断系统、定时系统等提供稳定的相位锁定参考信号。为减少远距离传输过程中由环境温度变化导致的射频传输线中的射频相位漂移,多个加速器装置中已经采用射频相位参考线提供射频相位参考,这些相位参考的实现方案主要是基于恒温控制和基于光纤锁相。与这些方案相比,采用相位平均方法不仅可以保持长距离节点之间的相位稳定,而且更易于现场安装与维护。现有的带有锁相环(PLL)的终端短路方式实现相位平均参考线的方案仍有一些节点数量限制等方面的不足,本文对相位平均参考线结构进行了去除PLL的简化设计并进行了验证,以期增加更多的相位分配节点以及降低对射频器件参数的要求。对非PLL的单端输入终端短路相位平均方案与两端输入各节点间互为参考的相位平均方案分别进行了实验测试,结果表明两者的相位RMS精度可以达到0.1°~0.3°。并对不同的相位平均实现方案中相位不稳定的产生原因进行了分析,结果表明,除环境温度外,同轴线缆材质、合成相位与幅度的不平衡合成等也是重要影响因素。     

用于SCA ASIC测试的数字读出模块设计

高速开关电容阵列(SCA)具有高速采样、低功耗的特点,基于SCA的高速波形数字化是目前高精度时间测量的一个重要研究方向。为此,我们开展SCA芯片的研究,目前已设计完成原型ASIC设计,并正在进行后续版本的改进设计。为便于未来多版本ASIC的测试和评估,需设计具有一定通用性的数字读出模块,本论文工作主要介绍此模块的设计工作以及相应的数据读出软件。数字读出模块基于FPGA实现对待测ASIC的控制、配置及数据读出,采用DDR3片外存储芯片,使用USB3.0等接口进行数据传输;上位机软件基于Python3.7设计,实现了数据采集与波形绘制等功能。目前已使用设计完成的数字读出模块对第2版SCA ASIC进行了初步的测试,测试结果表明,此读出模块工作正常,且SCA芯片输出结果符合预期。     

非定常Navier-Stokes方程基于两重网格离散的有限元并行算法

基于两重网格离散和区域分解技巧,提出三种求解非定常Navier-Stokes方程的有限元并行算法.算法的基本思想是在每一时间迭代步,在粗网格上采用Oseen迭代法求解非线性问题,在细网格上分别并行求解Oseen、Newton、Stokes线性问题以校正粗网格解.对于空间变量采用有限元离散,时间变量采用向后Euler格式离散.数值实验验证了算法的有效性.     

基于三维荧光光谱法和PARAFAC对多环芳烃定性定量分析

三维荧光光谱法在研究多环芳烃(PAHs)类物质的荧光信息时起到了重要作用。多环芳烃类物质具有致癌性,难降解性,多由尾气排放,垃圾焚烧产生,危害着人类健康及环境,因此人们不断探索对多环芳烃检测的方法。实验选取多环芳烃中的苊和萘作为检测物质,利用FLS920荧光光谱仪,为避免荧光光谱仪本身产生的瑞利散射影响,设置起始的发射波长滞后激发波长40 nm,设置扫描的激发波长(λex)范围为:200~370 nm,发射波长(λem)范围为:240~390 nm,对多环芳烃进行荧光扫描获取荧光数据,采用三维荧光光谱技术结合平行因子算法对混合溶液中的苊和萘进行定性定量分析。实验选用的苊和萘均购于阿拉丁试剂官网,配制浓度为10 mg·L-1的一级储备液,再将一级储备液稀释,得到苊和萘浓度为0.5,1,1.5,2,2.5,3,3.5,4和4.5 mg·L-1的二级储备液,并将苊和萘进行混合。在进行光谱分析前需要对苊和萘的光谱进行预处理,采用空白扣除法扣除拉曼散射的影响,并采用集合经验模态分解(EEMD)消除干扰噪声。实验测得苊存在两个波峰,位于λex=298 nm,λem=324/338 nm处,萘存在一个波峰,位于λex=280 nm,λem=322 nm处。选用的PARAFAC算法对组分数的的选择很敏感,因此采用核一致诊断法预估组分数,估计值2和3的核一致值都在60%以上,分别对混合样品进行了2因子和3因子的PARAFAC分解,将分解后得到的激发发射光谱数据和各组分浓度数据进行归一化处理,并绘制光谱图,与归一化处理后的真实的激发发射光谱图和各组分浓度图进行对比。同时将PARAFAC得到的混合样本的预测浓度,通过计算回收率(R)和均方根误差(RMSEP)来判定定量分析的准确度。选择2因子时,各混合样品中苊和萘拟合度为95.7%和96.7%,平均回收率分别为101.8%和98.9%,均方根误差分别为0.0187和0.0316;选择3因子时,各混合样品中苊和萘拟合度为95.3%和95.8%,平均回收率分别为97%和102.5%,均方根误差分别为0.033和0.116,由三项指标可得选用2因子进行定性定量分析的效果明显好于选用3因子。分析实验结果表明,基于三维荧光光谱法和PARAFAC算法对混合样品进行定性定量分析,能够有效的判定混合样品的类别,同时能够成功的预测出混合样品的浓度。     

基于多通道盲识别的自适应光学图像事后处理

为实时恢复天文或空间目标的湍流退化成像,提出一种适应大气湍流动态变化的多通道自适应光学图像恢复方法.以自适应光学校正后不同时刻的目标成像作为多个通道,建立求解系统点扩散函数的线性方程,根据解出的点扩散函数利用超拉普拉斯算法,求解待观测目标的估计值.结果表明:不同时刻的点扩散函数之间存在互质关系,满足多通道盲识别的理论要求.利用建立的线性方程求解出的点扩散函数与原点扩散函数的均方误差在10^-30~10^-27量级,采用超拉普拉斯算法恢复出的目标成像与原始目标之间的均方误差在10^-5~10^-4量级.本文研究为湍流退化图像的实时恢复提供了理论基础.     

Design of diamond-shape photonic crystal fiber polarization filter based on surface plasma resonance effect

A novel plasmonic polarization filter based on the diamond-shape photonic crystal fiber(PCF) is proposed. The resonant coupling characteristics of the PCF polarization filter are investigated by the full-vector finite-element method. By optimizing the geometric parameters of the PCF, when the fiber length is 5 mm, the polarization filter has a bandwidth of 990 nm and an extinction ratio(ER) of lower than -20 dB. Moreover, a single wavelength polarization filter can also be achieved, along with an ER of -279.78 dB at wavelength 1.55 μm. It is believed that the proposed PCF polarization filter will be very useful in laser and optical communication systems.