多共振分量融合CNN的行星齿轮箱故障诊断

针对行星齿轮箱中各部件所激起的振动成分混叠、早期故障特征经常被较强的各级齿轮谐波成分以及环境噪声所湮没的问题,提出一种多共振分量融合卷积神经网络(multi-resonance component fusion based convolutional neural network,简称MRCF-CNN)的行星齿轮箱故障诊断方法。首先,对振动信号进行共振稀疏分解,得到包含齿轮谐波成分的高共振分量和可能包含轴承故障冲击成分的低共振分量;其次,构建多共振分量融合卷积神经网络,将得到的高、低共振分量和原始振动信号进行自适应的特征级融合,通过有监督的方式训练模型并进行行星齿轮箱故障诊断。对行星齿轮箱实验数据的分析结果表明,该方法能够有效分类行星齿轮箱中滚动轴承和齿轮的故障,成功对行星齿轮箱故障进行诊断,同时能够进一步增强卷积神经网络对振动信号所蕴含的故障信息的辨识能力。

部分时滞诱发Watts-Strogatz小世界神经元网络产生随机多共振

已有研究显示时滞可诱发神经元网络产生随机多共振,但它们主要讨论了神经元间的耦合都存在时滞的情形.然而实际中,有些神经元间的信息传递是瞬时的或时滞很小可以忽略的,即神经元网络中只有部分神经元间的耦合具有时滞,简称部分时滞(若神经元网络内共有l条耦合边,其中有l1条耦合边是具有时滞的,而剩余的耦合边的时滞为零,则我们称这类时滞为部分时滞).本文以Watts-Strogatz小世界神经元网络为研究对象,主要讨论部分时滞对该神经元网络系统响应强度的影响.研究结果指出,系统响应强度随部分时滞的增加呈现多峰的变化态势,即部分时滞可诱发随机多共振现象;而且使系统响应强度达到最优水平的部分时滞的取值区间随随机时滞边概率的增加渐渐变窄,当随机时滞边概率足够大时,系统响应强度只有在时滞位于外界信号周期的整数倍附近才会达到最优.此外,我们还分析了随机连边概率和神经元网络中边的总数对部分时滞诱发的随机多共振现象的影响.结果显示,部分时滞诱发的随机多共振现象对随机连边概率具有一定的鲁棒性,而神经元网络中边的总数对部分时滞诱发的随机多共振的影响则较大.

基于多共振热活化延迟荧光材料与器件的研究进展

多共振热活化延迟荧光(multi-resonance thermally activated delayed fluorescence,MR-TADF)材料,已成为有机发光二极管中引人注目的发射体。MR-TADF材料通常表现出非常窄的发射带、高的光致发光量子产率、小的ΔE_(ST)值以及高的化学和热力学稳定性,这些特性使其被用于制备性能优异的蓝光TADF有机发光二极管。总结主要的MR-TADF化合物及其衍生物,重点对分子结构和器件性能进行了讨论。该综述对本领域的发展提供依据,具有一定的理论指导意义。

噪声诱使模块化神经元网络产生随机多共振现象

首先,研究了噪声在多模块神经元网络中诱导的随机多共振现象.随机多共振现象是指存在不同的噪声强度,系统在这些噪声强度下对阈下信号的响应达到局部最优.其次,以FitzHugh-Nagumo神经元构成的模块化神经元网络为研究对象,通过数值模拟发现,神经元网络的系统响应随着噪声强度的增加多次达到局部最优,即产生随机多共振现象.同时,通过分析神经元网络平均膜电位的时序图,发现噪声通过诱导神经元网络在一个周期内产生多次发放进而诱导多次共振.最后,我们分析了两个子网络中加入不同强度的噪声时,噪声诱导神经元网络中的随机多共振现象.结果显示,当两个子网络加入不同强度的噪声时,随机多共振现象也会产生.

具有随机黏性阻尼的分数维线性振荡器中的随机多共振

分数阶微积分具有对历史状态的动态记忆特性和路径依赖性等优良特性,因此实际中许多系统,特别是那些具有记忆的动力学过程,用分数阶模型比通常使用的整数阶模型更加合适。在分数阶系统的研究中,采用Gamma函数的记忆核函数是采用Mittag-Leffler函数的记忆核函数的一个特例,而后者更具一般性,特别是其中包含系统特征记忆时间,可以在复杂无序的非均匀环境中描述介质分子对系统运动产生的记忆效应。因此采用Mittag-Leffler函数的分数维导数可以从特征记忆时间和分数维数两个维度更好地刻画系统的性能。该文研究了具有随机黏性阻尼的分数维线性振荡器中的随机多共振现象,分数维振荡器的系统记忆核采用Mittag-Leffler函数。基于线性系统理论,利用Mittag-Leffler函数和分数维导数的性质,推导出系统输出幅度(SPA)的解析表达式。在SPA与分数振荡器记忆时间的关系曲线上发现了随机多共振现象。在SPA与噪声扁平率和黏性阻尼系数的关系曲线上,出现了随机共振效应。SPA随着系统特征频率、驱动信号频率以及噪声相关时间的变化而非单调变化。

多共振热激活延迟荧光过程的理论研究

本工作借助第一性原理和动力学演化,系统地研究了四个叔丁基-咔唑及吩噻嗪取代的硼-氮化合物(BCz-BN、2PTZ-BN、Cz-PTZ-BN和2Cz-PTZ-BN)的多共振热激活延迟荧光的高效发光机制.结果表明上述分子T_(1)与T_(2)间的内转换速率远大于其它辐射与非辐射速率,同时T_(2)到S_(1)的反向系间窜越速率也高于T_(1)到S_(1)的反向系间窜越速率,因此其多共振热激活延迟荧光过程应遵循T_(1)→T_(2)→S_(1)→S_(0)的路径.进一步动力学演化表明,T_(1)与T_(2)之间的内转换主要发生在演化初期,随着时间的推移,能量逐渐由T_(2)向S_(1)转移,并最终在S_(1)完成荧光发射.上述研究揭示了多共振延迟荧光的微观本质,为未来设计及合成新的多共振热激活延迟荧光分子提供了理论依据.

一种曲面背衬的宽带超声换能器

利用多共振原理设计一种圆形宽带超声换能器。它以通常的平板圆形压电晶片作为换能器振子,加上曲面背衬使整个系统达到多共振状态。实验表明,这种设计的尝试是成功的,其电阻抗曲线的共振峰明显被抑制,带宽增加了一倍以上。

Pore structure and liquid flow velocity distribution in water-saturated porous media probed by MRI

Magnetic resonance imaging （MRI） was used to probe the structure and flow velocity within the interparticle space of a packed bed of agar beads under water-saturated condition. The images of the velocity field at three different flow rates were obtained. To determine the pore-parameter of the porous media, the internal structure of the bed was also obtained using image processing technique. The results show that the porosity of the sample is 31.28% and the fitting curve for the distribution of pore equivalent diameter follows Gaussian distribution. The velocity profiles do shift as the flow rate varies and the solution flow through the void space is not a homogeneous flow in any pores. The velocity distributions within the pore are roughly parabolic with the local maximum being near the center. About half of the velocity components are in the class of 0-1 cm/s. The frequency of lower velocity components is lower at higher flow rate, but to higher velocity components, it is just the opposite.

Nuclear magnetic resonance T_2 spectrum:multifractal characteristics and pore structure evaluation

Pore structure characteristics are important to oil and gas exploration in complex low-permeability reservoirs. Using multifractal theory and nuclear magnetic resonance （NMR）, we studied the pore structure of low-permeability sandstone rocks from the 4th Member （Es4） of the Shahejie Formation in the south slope of the Dongying Sag. We used the existing pore structure data from petrophysics, core slices, and mercury injection tests to classify the pore structure into three categories and five subcategories. Then, the T2 spectra of samples with different pore structures were interpolated, and the one- and three-dimensional fractal dimensions and the multifractal spectrum were obtained. Parameters a （intensity of singularity） andf（a） （density of distribution） were extracted from the multifractal spectra. The differences in the three fractal dimensions suggest that the pore structure types correlate with a andf（a）. The results calculated based on the multifractal spectrum is consistent with that of the core slices and mercury injection. Finally, the proposed method was applied to an actual logging profile to evaluate the pore structure of low-permeability sandstone reservoirs.

Delamination Damage Detection in Laminated Composite by LDR-Based Multi-frequency Method

Local defected resonance(LDR)is a recently-developed non-destructive testing method,which identifies damage by detecting the vibrational response of the structural surface under the wideband ultrasonic excitation. The concept of LDR is studied and applied for damage imaging of delamination in composite laminates. Aiming at the problem of poor anti-noise ability and inaccurate damage identification in traditional detection process,an LDR-based multi-frequency method is proposed. Experimental results show that the proposed method can realize the localization and imaging of delamination damage in composite materials.

Measurement of Photoionization Cross Sections of the Excited States of Titanium

Resonance-enhanced multiphoton ionization of the titanium atoms has been investigated in the 293 321 nm wavelength. We couple a laser-ablated metal target into a molecular beam to produce free atoms. Ions produced from photoionization of the neutral atoms are monitored by a home-built time-of-flight mass spectrometer. Photoionization cross sections of the excited states of Ti I were deduced from the dependence of the ion signal intensity on the laser intensity for photon energies close to the ionization threshold. The values obtained range from 0.2 Mb to 6.0 Mb. No significant isotope-dependence was found from measurements of the photoionization cross sections of ^46Ti, ^47Ti, and ^48Ti.

Measurement of Two Phase Flow in Porous Medium Using High-resolution Magnetic Resonance Imaging

Measurement of two phase flow in porous medium for sequestration was carried out using high-resolution magnetic resonance imaging (MRI) technique. The porous medium was a packed bed of glass beads. Spin echo multi sequence was used to measure the distribution of CO2 and water in the porous medium. The intensity images show that the fluid distribution is non-uniform due to its viscosity and pore structure of porous medium. The velocity distribution of fluids is calculated from the saturation of water and porosity of porous medium. The experimental results show that fluid velocities vary with time and position. The capillary dispersion rate donated the effects of capillary, which was largest at water saturations of 0.45. The displacement process is different between in BZ-02 and BZ-2. The final water residual saturation depends on permeability and porosity.

Multi-Resonant-Activation for a System Only Driven by Multi-State Noise

We consider the escape of the particles multi-state noise. It is shown that, the noise can make over fluctuating potential barrier for a system only driven by a the particles escape over the fluctuating potential barrier in some circumstances; but in other circumstances, it can not. If the noise can make the particle escape over the fluctuating potential barrier, the mean first passage time （MFPT） can display the phenomenon of multi-resonant-activation. For this phenomenon, there are two kinds of resonant activation to appear. One is resonant activation for the MFPTs as the function of the flipping rates of the fluctuating potential barrier; the other is that for the MFPTs as the functions of the transition rates of the multi-state noise.

Transferring Multi-Dimensional Quantum States and Preparing Quantum Networks in Cavity QED

In this paper we propose a scheme for transferring quantum states and preparing quantum networks. Compared with the previous schemes, this scheme is more efficient, since three or four-dimensional quantum states can be transferred with a single step and information interchange of three-dimensional quantum states can be realized, which is a significant improvement. It is based on the resonant interaction of a three-mode cavity field with an atom. As a consequence, the interaction time is shortened greatly. Furthermore, we give some discussions about the feasibility of the scheme.

DOBUTAMINE MAGNETIC RESONANCE IMAGING PREDICTS CONTRACTILE RESERVE OF CHRONICALLY DYSFUNCTIONAL MYOCARDIUM: COMPARISON WITH FLUORINE-18 FLUORODEOXYGLUCOSE POSITRON EMISSION TOMOGRAPHY

This study sought to investigate whether low dose dobutamine MRI can detect residual myocardial viability in patients with chronic myocardial infarction and left ventricular dysfunction. Methods. Eleven patients with chronic myocardial infarction and left ventricular dysfunction were employed for identification of viable myocardium by cine MRI during dobutamine infusion. All patients underwent coronary angiography and left ventriculography, 18 FDG PET, MRI at rest and stress.The systolic wall thickening measured at rest and during stress was compared with the results of 18 FDG PET, respectively. Results. A significant difference of either dobutamine induced systolic wall thickening (SWth stress ) or dobutamine induced contractile reserve (ΔSWth= SWth stress - SWth rest ) was present between viable and scar regions (1 0±0 3 versus -0 3 ±0 1, P<0 01; 1 0±0 3 versus -0 2±0 2, P<0 01). Conclusions. Dobutamine induced contractile reserve can be predicted in the regions of akinesia or dyskinesia at rest when systolic wall thickening was 1 0 mm during dobutamine stimulation.

Multidisciplinary imaging of liver hydatidosis

Liver hydatidosis is a parasitic endemic disease affecting extensive areas in our planet, a significant stigma within medicine to manage because of its incidence, possible complications, and diagnostic involvements. The diagnosis of liver hydatidosis should be as fast as possible because of the relevant complications that may arise with disease progression, involving multiple organs and neighboring structures causing disruption, migration, contamination. The aim of this essay is to illustrate the role of imaging as ultrasonography （US）, multi detector row computed tomography, and magnetic resonance imaging （MRI） in the evaluation of liver hydatidosis： the diagnosis, the assessment of extension, the identification of possible complications and the monitoring the response to therapy. US is the screening method of choice. Computed tomography （CT） is indi-cated in cases in which US is inadequate and has high sensitivity and specificity for calcified hydatid cysts. Magnetic resonance is the best imaging procedure to demonstrate a cystic component and to show a biliary tree involvement. Diagnostic tests such as CT and MRI are mandatory in liver hydatidosis because they allow thorough knowledge regarding lesion size, location, and relations to intrahepatic vascular and biliary structures, providing useful information for effective treatment and decrease in post-operative morbidity. Hydatid disease is classified into four types on the basis of their radiologic appearance.

Hyperperfusion of Multiple Sclerosis Plaques Characterized by 3D FSE Arterial Spin Labelling

MULTIPLE sclerosis （MS） is a common inflammatory demyelinating disorder of central nervous system, and the disease burder could be well evaluated by conven-tional magnetic resonance imaging （MRI）,1 including T2-weighted, fluid-attenuatd inversion recovery, and postcontrast Tl-weighted sequences. 2 We investigated the perfusion state of MS plaques using brain perfusion imaging in a 12-year-old boy with MS.

Neurological Manifestations of Takayasu Arteritis

Objective To investigate the clinical neurological manifestations of Takayasu arteritis (TA). Methods A retrospective study was conducted with 63 consecutive TA cases admitted to Peking Union Medical College Hospital from January 2009 to May 2010. All the patients fulfilled the diagnostic criteria of TA by the American College of Rheumatology. Among the 63 TA patients, 27 with neurological manifestations were included in the present study. All the patients were evaluated using standardized neurological examination, sonography, computed tomography (CT) angiography, and cerebral CT or magnetic resonance imaging. Results Dizziness and visual disturbance were the most common symptoms, which occurred in 20 (74.1%) and 16 (59.3%) patients respectively. Another common symptom was headache, observed in 15 (55.6%) patients. Six (22.2%) patients had suffered from ischemic stroke; 7 (25.9%) patients had epileptic seizures. Two (7.4%) patients were diagnosed as reversible posterior encephalopathy syndrome (RPES) based on typical clinical and imaging manifestations. Conclusions Neurological manifestations are common symptoms in TA patients in the chronic phase, including dizziness, visual disturbance, headache, ischemic stroke, seizures, and some unusual ones such as RPES. We suggested RPES be included into the differential diagnosis of acute neurological changes in TA.

UV Photodissociation Dynamics of Nitric Acid： The Hydroxyl Elimination Channel

Sliced velocity mapping ion imaging technique was employed to investigate the dynamics of the hydroxyl elimination channel in the photodissociaiton of nitric acid in the ultraviolet region. The OH product was detected by （2＋1） resonance enhanced multiphoton ionization via the D^2∑^- electronic state. The total kinetic energy spectra of the OH＋NO2 channel from the photolysis of HONO2 show that both ：NO2（X2A1） and NO2（A2B2） channels are present, suggesting that both 1^1A″ and 2^1A″ excited electronic states of HONO2 are involved in the excitation. The parallel angular distributions suggest that the dissociation of the nitric acid is a fast process in comparison with the rotational period of the HNO3 molecule. The anisotropy parameter β for the hydroxyl elimination channel is found to be dependent on the OH product rotational state as well as the photolysis energy.

Synthesis and Structure of Chromium Complexes with New Tetradentate Schiff Base N202-Type Ligand

In this research two chromium（II][） and （VI） complexes of tetradentate Schiff bases have been prepared by condensing of salicylaldehyde with 4-methyl 1,2-phenylenediamine. Schiff base complexes of chromium（Ill） have been employed to design and synthesize polynuclear complexes. So they have played an important role in molecular magnetism. Synthesized complexes were characterized by elemental analysis, IR, molar conductivity and NMR. The free ligands were alsc characterized by 1H, 13C NMR spectra. The 13C NMR and IR spectra of free ligand and the complexes are compared and discussed.