无人值守变电站电力设备音频监测及故障诊断系统

针对智能变电站的无人值守需求及现有故障诊断系统的不足,提出一种电力设备音频监测及故障诊断系统。根据变电站电力设备音频信号信噪比较低的特点,采用具有强鲁棒性的梅尔频率倒谱系数作为判断音频信号异常的特征参数,在此基础上根据音频特征构成多样本观测序列,并采用隐马尔科夫模型进行故障诊断,通过对比对数似然估计概率的输出值确定故障类型。该方法具有实时性较强的优势,也避免了现有故障诊断方法要求较大样本容量的缺陷。实验结果表明,该故障诊断系统具有较高的识别率和鲁棒性。     

Single photon and nonlocality

In a paper by Home and Agarwal [1], it is claimed that quantum nonlocality can be revealed in a simple interferometry experiment using only single particles. A critical analysis of the concept of hidden variable used by the authors of [1] shows that the reasoning is not correct.      

基于HMM的机载设备状态健康评估方法研究

针对机载设备的状态健康评估问题,采用隐马尔科夫模型(HMM)对其进行性能退化程度的评估。首先引入状态条件概率矢量对HMM进行不确定性改进,并推导了其表达式;其次以状态条件概率比值为基础,给出了机载设备状态等级量化分值的计算方法,并据此设计了机载设备状态健康评估流程。最后以飞机发动机温控放大器为例进行仿真验证,结果表明上述方法能够给出直观、准确的状态评估结果。     

Large payload quantum steganography based on cavity quantum electrodynamics

A large payload quantum steganography protocol based on cavity quantum electrodynamics (QED) is presented in this paper, which effectively uses the evolutionary law of atoms in cavity QED. The protocol builds up a hidden channel to transmit secret messages using entanglement swapping between one GHZ state and one Bell state in cavity QED together with the Hadamard operation. The quantum steganography protocol is insensitive to cavity decay and the thermal field. The capacity, imperceptibility and security against eavesdropping are analyzed in detail in the protocol. It turns out that the protocol not only has good imperceptibility but also possesses good security against eavesdropping. In addition, its capacity for a hidden channel achieves five bits, larger than most of the previous quantum steganography protocols.     

Dosimetric characterization of the Exradin W1 plastic scintillator detector through comparison with an in-house developed scintillator system

New commercial dosimetry systems need careful characterization and can benefit from the comparison with similar, in-house developed solutions. A comparison between such two dosimetry systems, both based on fibre-coupled organic plastic scintillator detectors, is presented. One system is the Exradin W1, fully commercialized by Standard Imaging, while the other system is the non-commercial ME40 system, developed by DTU Nutech with the aim of fundamental dosimetric research. Both systems employ plastic scintillator detectors that can be considered similar in design, calibrated using the same method, but differing primarily in the signal detection hardware. The two systems were compared with respect to essential dosimetric properties, with the purpose of testing their performance under conditions less well discussed in the literature. A Farmer ionization chamber was used as the primary reference of the comparison. The study demonstrated that the Cerenkov light ratio calibration coefficient of both systems was not constant, but changed systematically with photon beam quality to a maximum difference of 1.1%. Calibration with respect to stem effect correction should therefore be performed for every investigated beam quality when using plastic scintillator detectors. Both systems were found to be dose rate independent, even for the highest instantaneous dose rate evaluated (1.5 mGy per pulse). Low-dose measurements revealed large uncertainties for both systems, although the ME40 system handled short beam deliveries under reference conditions with accuracy and precision within 0.4%. Changes in response due to field size dependence were investigated and found to be as large as 3.3% for the W1 and 5.4% for the ME40, biasing output factor measurements in large fields. Great caution is therefore advised if using either system for measurements in large fields or under circumstances where the fibre irradiation geometry is unfavourable. Measurements of reference dose to water yielded differences up to 1.5% when compared with the Farmer ionization chamber for all investigated beam qualities.     

Prequantum Classical Statistical Field Theory: Complex Representation, Hamilton-Schrödinger Equation, and Interpretation of Stationary States

We develop a prequantum classical statistical model in that the role of hidden variables is played by classical (vector) fields. We call this model Prequantum Classical Statistical Field Theory (PCSFT). The correspondence between classical and quantum quantities is asymptotic, so we call our approach asymptotic dequantization. We construct the complex representation of PCSFT. In particular, the conventional Schrödinger equation is obtained as the complex representation of the system of Hamilton equations on the infinite-dimensional phase space. In this note we pay the main attention to interpretation of so called pure quantum states (wave functions) in PCSFT, especially stationary states. We show, see Theorem 2, that pure states of QM can be considered as labels for Gaussian measures concentrated on one dimensional complex subspaces of phase space that are invariant with respect to the Schrödinger dynamics. “A quantum system in a stationary state ψ” in PCSFT is nothing else than a Gaussian ensemble of classical fields (fluctuations of the vacuum field of a very small magnitude) which is not changed in the process of Schrödinger's evolution. We interpret in this way the problem of stability of hydrogen atom. One of unexpected consequences of PCSFT is the infinite dimension of physical space on the prequantum scale.     

Relaxation dynamics and fragility during liquid–glass transitions of poly(propylene glycol)s

The acoustic and thermal properties of the liquid–glass transitions of propylene glycol and its oligomers, poly (propylene glycol)s, were studied by temperature modulated DSC and Brillouin scattering. The fragility indices were determined from Angell plots using the observed modulation frequency dependence of the complex heat capacity. The variation in the glass transition temperatures is discussed on the basis of the free volume theory. The relaxation time of the structural relaxation obeys the Vogel–Fulcher law, and its high frequency end is in good agreement with the result of the dielectric measurement in the literature. The correlation between the observed thermal expansion coefficients and the glass transition temperature is discussed based on the free volume theory. The sound velocity and attenuation were accurately determined as a function of the temperature by Brillouin scattering by combination with the refractive index measurement. The relaxation dynamics were discussed by considering the relaxation from segmental motions. All of these physical properties were discussed based on the third-order anharmonicity and the Grüneisen parameter.     

Nuclear axial currents from scale-chiral effective field theory

By incorporating hidden scale symmetry and hidden local symmetry in the nuclear effective field theory,combined with the double soft-pion theorem, we predict that the Gamow-Teller operator coming from the space component of the axial current should remain unaffected by the QCD vacuum change caused by the baryonic density,whereas the first forbidden beta transition operator coming from the time component should be strongly enhanced.While the latter has been confirmed for some time, the former was given support by a powerful recent ab initio quantum Monte Carlo calculation for light nuclei, which also confirmed the old?chiral filter hypothesis." Formulated in terms of the Fermi-liquid fixed point structure of strong-coupled nuclear interactions, we offer an extremely simple resolution to the long-standing puzzle of the?quenched g A," g_A~(eff) ≈1 [1], found in nuclear Gamow-Teller beta transitions, giant Gamow-Teller resonances, and double beta decays.     

基于归一化割的主题划分算法研究

为了保证抽取信息的全面性,主题划分成了不可或缺的工作。借助同义词词林,从词语的语义角度计算文本中各个段落间的相似度,建立段落文本关系图。基于文本关系图对归一化割分割准则中权值矩阵的构建做出调整,使之更能体现出段落间的相似程度,并使用该准则对文本进行主题划分。结果表明,该方法无论是对连续段落还是跨段落表达同一主题的主题划分均较为有效。