小波域基于MFA_ICA检测的数字图像水印算法

基于MFA_ICA（Independent Component Analysis based on Mean Field Approximation）理论提出了一种数字图像水印算法。该算法利用MFA_ICA进行水印和原始图像的估计,并用估计出的独立分量检测水印是否存在。与传统线性相关检测器相比,该算法消除了原始载体的干扰,检测性能明显提高。重要的是,不仅通过仿真实验证明了该算法较强抵抗JPEG压缩、剪切和白噪声等攻击的能力,而且从理论上也给出了严格的证明。     

STUDY ON NEW PASSIVE SCALAR FLUX MODEL WITH DIFFUSIVITY OF COMPLEX NUMBER

The turbulent passive scalar fluxes were studied by separately considering the contributions of small-eddy motions and large-eddy ones.Explicit algebraic approximation was achieved for both small-eddy and large-eddy scalar fluxes.Especially, the large-eddy scalar flux was modelled with complex diffusivity.The singular difficulties in usual algebraic scalar models, do not occur any more in this model.In addition, this new model provides a new way to reasonably describe the negative transport phenomena appearing in asymmetric turbulent flows.     

神经网络算法在南水北调冰期输水中的应用

通过分析南水北调沿线气候和气温特点,用LevenbergMarquart算法改进传统BP神经网络算法进行气温稳定转负日期的预报。把该模型应用到南水北调沿线新乡、安阳、邢台和石家庄2003—2006年气温稳定转负日期预报中,取得良好效果。立冬日作为气温转负日期统计的基准点,提高了预报精度,说明中国传统二十四节气对于冰情预报及其它同气温和气候相关的预报有重要的参考价值。     

电力系统稳定器在喜河水电站的应用研究

针对喜河水电站水轮发电机励磁控制系统中的励磁调节器产生负阻尼转矩可能导致电力系统低频振荡的问题,采用电力系统稳定器(PSS)以抑制低频振荡。建立了喜河水电站3号水轮机组的PSS模型,通过模型参数测试结果与仿真结果的比较,验证了参数的准确性,并进行了现场试验研究。结果表明,该机组PSS能够有效地抑制系统低频振荡,对本机振荡有良好的正阻尼作用。     

一种负温度系数SrTiO3基陶瓷材料的研制

通过适量的Bi3+、Pb2+的掺杂改性和CuO助熔剂的助烧,SrTiO3可在1 300℃以下烧结,获得的瓷料之εr高于2 500,tanδ小于0.05%,容量温度变化率在–40℃大于25.2%,在85℃小于–25.2%,该瓷料满足N4700温度系数要求,是容量–温度特性呈线性变化的高性能负温度系数陶瓷材料。     

负压差对固体进料系统压力分布和气固两相流动规律的影响

A series of experiments on a solid feed system was performed to investigate the effects of negative pressure gradient on the gas-solid flow pattern and hydrodynamic characteristics. Based on the non-fluidized gas-solid two phase flow and particulate mechanics in the standpipe, a method for predicting the pressure of the air passing through the recycle chamber and the pressure drop through the loop seal slit in these systems is also presented. The predicted pressure profile along the negative pressure gradient from the proposed model exhibits a good agreement with the experimental data. The experimental data show that the gas flow in the standpipe is always upward in the negative pressure gradients, while the direction of gas cannot be changed by the drag force. The solid flow rate, the materiel bed height in the recycle chamber (Hf), the pressure drop across the slit (△Pg） decrease with an increasing negative pressure gradient. At a given negative pressure gradient, the superficial gas velocity through the recycle chamber of the loop seal does not affect the pressure drop in standpipe. It increases with an increasing negative pressure gradient.     

Quantum effect of cooling down the environment temperature of mesoscopic LC circuit

We examine the quantum effect of cooling down the environment temperature of mesoscopic LC circuit, and find that the ground state of the circuit is no longer in the thermo vacuum state, but in a negative binomial state. We calculate energy of the circuit in this new state, which increases with the cooling of the environment.     

Electrical oscillation generation with current-induced resistivity switching in VO2 micro-channel devices

We report large amplitude modulation waveforms as large as ~ 10 V using vanadium dioxide micro-channel devices operating under current-controlled conditions. The self-sustained electrical oscillations were generated by controlling the applied current in the negative differential resistance region of the investigated devices. An appropriate value of internal capacitance was achieved as parasitic capacitance in the device structure to stabilize the electrical oscillations. This eliminates the need of an external pulsed source or any external passive component connected to the micro-channel devices. Amplitude and frequency of the oscillation were tuned by illuminating the device micro-channel with an external laser. An equivalent circuit model was developed to simulate the waveforms. A good agreement between experiment and simulation was verified.     

Low-energy electron elastic scattering cross sections for excited Au and Pt atoms

Electron elastic total cross sections (TCSs) and differential cross sections (DCSs) in both impact energy and scattering angle for the excited Au and Pt atoms are calculated in the electron impact energy range 0 ? E ? 4.0 eV. The cross sections are found to be characterized by very sharp long-lived resonances whose positions are identified with the binding energies of the excited anions formed during the collisions. The recent novel Regge-pole methodology wherein is embedded through the Mulholland formula the electron-electron correlations is used together with a Thomas-Fermi type potential incorporating the crucial core-polarization interaction for the calculations of the TCSs. The DCSs are evaluated using a partial wave expansion. The Ramsauer-Townsend minima, the shape resonances and the binding energies of the excited Au⁻ and Pt⁻ anions are extracted from the cross sections, while the critical minima are determined from the DCSs.     

Episodes of thoron exposure due to consumer products claiminghealth benefits of negative ions

In May 2018,the primetime news casted a shocking report saying that radon concentration on a certain model of bed mattress found to be as high as 2 200 Bq/m³.After a humble,the Nuclear Safety and Security Commission(NSSC) of Korea confirmed that significant amount of thoron gas is emanated from several mattress models marketed by a company claiming beneficial health effects of negative ions.Laboratory analysis showed that some internal fabric sheets of those mattresses contain high co...