Application of wavelet transform to detection of ferro-resonance

The ferro resonance caused by an electromagnetic potential transformer is a frequently occurring internal overvoltage in the power distribution network, and it threatens the safe operation of the network. Fast and accurate detection is the prerequisite for suppression and elimination of ferro resonance. Wavelet transform provides a powerful tool for analysis of nonstationary signals. This paper applies wavelet transform to detect ferro resonance. Analysis results show that it makes extraction of failure information accurate, and fast algorithm makes detection real time.

Value of CA19-9, CA125 and CEA combined magnetic resonance imaging in the diagnosis of pancreatic cancer

Objective:To study the value of CA19-9, CA125 and CEA combined magnetic resonance imaging (MRI) in the diagnosis of pancreatic cancer, and to provide a reference for clinical diagnosis and treatment.Methods:A total of 110 cases of pancreatic cancer admitted to our hospital from November 2015 to November 2017 were selected as the observation group, and another 80 normal pancreas organizers who participated in the physical examination in the same period were selected as the control group. The change of magnetic resonance scanning parameters and serum CA19-9, CA125 and CEA detection were compared between the two groups of subjects at the same time, contrast scan and serum magnetic resonance detection of CA19-9, CA125 and CEA positive rate, and to evaluate the four alone and in combination with the diagnosis of pancreatic cancer specificity, sensitivity, negative predictive value and positive predictive value.Results:The T1WI of the observation group was low or slightly low signal, T2WI was slightly high signal, and the tumor of fat suppression sequence was low signal, which was in line with the typical characteristics of pancreatic cancer. The serum levels of CA19-9, CA125 and CEA in the observation group were significantly higher than those in the control group, and the difference was statistically significant. Compared with the two groups, the positive rates of MRI and serum CA19-9, CA125 and CEA in the observation group were higher than those in the control group, and the difference was statistically significant. The sensitivity and accuracy of MRI scan combined with three serological markers were higher than those of single detection. The specificity was between four.Conclusion: CA19-9, CA125 and CEA combined magnetic resonance imaging (MRI) have good sensitivity and accuracy in diagnosis of pancreatic cancer, but their specificity is common, which should be used for reference.

7.0T nuclear magnetic resonance evaluation of the amyloid beta(1–40) animal model of Alzheimer's disease: comparison of cytology verification

3.0T magnetic resonance spectroscopic imaging brain function in Alzheimer＇s disease. However, is a commonly used method in the research ot the role of 7.0T high-field magnetic resonance spectroscopic imaging in brain function of Alzheimer＇s disease remains unclear. In this study, 7.0T magnetic resonance spectroscopy showed that in the hippocampus of Alzheimer＇s disease rats, the N-acetylaspartate wave crest was reduced, and the creatine and choline wave crest was elevated. This finding was further supported by hematoxylin-eosin staining, which showed a loss of hippocampal neurons and more glial cells. Moreover, electron microscopy showed neuronal shrinkage and mitochondrial rupture, and scanning electron microscopy revealed small size hippocampal synaptic vesicles, incomplete synaptic structure, and reduced number. Overall, the results revealed that 7.0T high-field nuclear magnetic resonance spectroscopy detected the lesions and functional changes in hippocampal neurons of Alzheimer＇s disease rats in vivo, allowing the possibility for assessing the success rate and grading of the amyloid beta （1-40） animal model of Alzheimer＇s disease.

Low noise,continuous-wave single-frequency 1.5-μm laser generated by a singly resonant optical parametric oscillator

We report a low noise continuous-wave （CW） single-frequency 1.5-μm laser source obtained by a singly resonant optical parametric oscillator （SRO） based on periodically poled lithium niobate （PPLN）. The SRO was pumped by a CW single-frequency Nd：YVO4 laser at 1.06μm. The 1.02 W of CW single-frequency signal laser at 1.5 μm was obtained at pump power of 6 W. At the output power of around 0.75 W, the power stability was better than ±l.5% and no mode-hopping was observed in 30 min and frequency stability was better than 8.5 MHz in 1 min. The signal wavelength could be tuned from 1.57 to 1.59 μm by varying the PPLN temperature. The 1.5-μm laser exhibits low noise characteristics, the intensity noise of the laser reaches the shot noise limit （SNL） at an analysis frequency of 4 MHz and the phase noise is less than 1 dB above the SNL at analysis frequencies above 10 MHz.

Magnetic and microwave properties of glass-coated amorphous ferromagnetic microwires

Glass-coated amorphous FeCuNbSiB microwires were prepared by Taylor-Ulitovsky technique. X-ray diffractometry and scanning electron microscopy were used to investigate the microstructure and morphology of the glass-coated microwires respectively. The vibrating sample magnetometer and vector network analyzer were used to study the magnetostatic and microwave properties of glass-coated microwires. The experimental results show that the effective anisotropy of an array of 150 microwires of 10 mm in length is large than that of one microwire of 10 mm in diameter and an array of 150 microwires of 1 mm in diameter. The natural ferromagnetic resonance takes place as the microwave magnetic component is perpendicular to the microwires axis, and the electric dipole resonance takes place as the microwire is long or the short microwire concentration is moderate. The natural ferromagnetic resonance shifts to higher frequency with the larger microwire concentration. The electric dipole resonance is governed by the microwires length and concentration. The glass-coated FeCuNbSiB microwires can be used to design EMI filters and microwave absorbing materials.

Inhibition of Notch 1 signaling in the subacute stage after stroke promotes striatal astrocyte-derived neurogenesis

Inhibition of Notch1 signaling has been shown to promote astrocyte-derived neurogenesis after stroke.To investigate the regulatory role of Notch1 signaling in this process,in this study,we used a rat model of stroke based on middle cerebral artery occlusion and assessed the behavior of reactive astrocytes post-stroke.We used theγ-secretase inhibitor N-[N-(3,5-diuorophenacetyl)-1-alanyl]-S-phenylglycine t-butylester(DAPT)to block Notch1 signaling at 1,4,and 7 days after injury.Our results showed that only administration of DAPT at 4 days after stroke promoted astrocyte-derived neurogenesis,as manifested by recovery of white matter fiber bundle integrity on magnetic resonance imaging,which is consistent with recovery of neurologic function.These findings suggest that inhibition of Notch1 signaling at the subacute stage post-stroke mediates neural repair by promoting astrocyte-derived neurogenesis.

κ-卡拉胶比例对明胶凝胶体系凝胶特性、水分分布及微观结构的影响

论文采用质地剖面(texture profile analysis,TPA)/穿刺分析、低场核磁场共振(low-field nuclear magnetic resonance,LF-NMR)、计算机断层扫描技术(computed tomography,CT)和流变仪研究了κ-卡拉胶的比例对明胶凝胶的凝胶强度、质构特性、水分分布、动态黏弹性和微观结构的影响,并分析了几者之间的相关性。结果表明:随κ-卡拉胶比例的增加,混合凝胶体系的凝胶强度、硬度、咀嚼性、胶凝温度及熔化温度相对增大,弹性及内聚性降低,黏性和回复性先下降后上升;凝胶网络结构趋向于致密、均匀;结合水比例(S_(21))下降,不易流动水比例(S_(22))相对增加,且当体系中κ-卡拉胶的比例逐渐增加至50%时,单组份弛豫时间(T_(2W))及不易流动水的弛豫时间(T_(22))的减小较为明显,而结合水的弛豫时间(T21)变化相对较小;相关性分析表明,凝胶强度、硬度、咀嚼性与S_(21)负相关,与S_(22)、T21正相关。弹性与S_(21)、T_(22)和T_(2W)正相关,与S_(22)负相关。内聚性与T_(22)和T_(2W)正相关。研究可为明胶-κ-卡拉胶复配胶在食品中的应用提供理论支持。

Nonlinear study of the dynamic behavior of a string-beam coupled system under combined excitations

In this paper,the nonlinear dynamic behavior of a string-beam coupled system subjected to external,parametric and tuned excitations is presented.The governing equations of motion are obtained for the nonlinear transverse vibrations of the string-beam coupled system which are described by a set of ordinary differential equations with two degrees of freedom.The case of 1：1 internal resonance between the modes of the beam and string,and the primary and combined resonance for the beam is considered.The method of multiple scales is utilized to analyze the nonlinear responses of the string-beam coupled system and obtain approximate solutions up to and including the second-order approximations.All resonance cases are extracted and investigated.Stability of the system is studied using frequency response equations and the phase-plane method.Numerical solutions are carried out and the results are presented graphically and discussed.The effects of the different parameters on both response and stability of the system are investigated.The reported results are compared to the available published work.

Coupled extension and thickness-twist vibrations of lateral field excited AT-cut quartz plates

In this paper, the coupled extension and thickness- twist vibrations are studied for AT-cut quartz plates under Lateral Field Excitation （LFE） with variations along the x1- direction. Mindlin＇s two-dimensional equations are used for anisotropic crystal plates. Both free and electrically forced vibrations are considered. Important vibration characteristics are obtained, including dispersion relations, frequency spectra, and motional capacitances. It is shown that, to avoid the effects of the couplings between extension and thickness-twist vibrations, a series of discrete values of the length/thickness ratio of the crystal plate need to be excluded. The results are of fundamental significance for the design of LFE resonators and sensors.

Nonlinear dynamic response of beam and its application in nanomechanical resonator

Nonlinear dynamic response of nanomechanical resonator is of very important characteristics in its application. Two categories of the tension-dominant and curvaturedominant nonlinearities are analyzed. The dynamic nonlinearity of four beam structures of nanomechanical resonator is quantitatively studied via a dimensional analysis approach. The dimensional analysis shows that for the nanomechanical resonator of tension-dominant nonlinearity, its dynamic nonlinearity decreases monotonically with increasing axial loading and increases monotonically with the increasing aspect ratio of length to thickness; the dynamic nonlinearity can only result in the hardening effects. However, for the nanomechanical resonator of the curvature-dominant nonlinearity, its dynamic nonlinearity is only dependent on axial loading. Compared with the tension-dominant nonlinearity, the curvature-dominant nonlinearity increases monotonically with increasing axial loading; its dynamic nonlinearity

非线性铁磁谐振无线电能传输拓扑结构

针对负载和耦合系数均有可能大范围变化的实际工况,提出一种新型的基于铁磁谐振的非线性无线电能传输拓扑结构。首先,使用杜芬方程和相量分析法对工作原理进行定性分析;其次,使用有限元电路仿真软件对上述原理进行数值验证计算;最后,搭建了功率可达566 W、效率可达93.5%的非线性拓扑无线电能传输系统原型。实验结果表明,在次级稳压输出200 V的条件下,提出的非线性LCC-LCC拓扑能够适应耦合系数从0.1变化到0.5、负载电阻从72Ω到无穷大的大范围变化,具有出色的抗偏移能力和负载稳定性。所提拓扑原理新颖、结构简单,具备一定的工程应用潜力。

Ciliated hepatic foregut cyst with high intra-cystic carbohydrate antigen 19-9 level

A ciliated hepatic foregut cyst (CHFC) is a rare foregut developmental malformation usually diagnosed in adulthood. Five percent of reported cases of CHFC transform into squamous cell carcinoma. We report the presentation, evaluation, and surgical management of a symptomatic 45-year-old male found to have a 6.2 cm CHFC. Contrast tomography-guided fine-needle aspiration demonstrated columnar, ciliated epithelium consistent with the histologic diagnosis of CHFC. The intracystic levels of carbohydrate antigen (CA) 19-9 and carcinoembryonic antigen (CEA) were extremely high (978118 U/mL and 973 μg/L, respectively). Histologically, the wall of the cyst showed characteristic pseudopapillae lined with a ciliated stratified columnar epithelium, underlying smooth muscle, an outer fibrous layer and no atypia. Immunohistochemistry for CA19-9 and CEA was positive. This is the first case report of a CHFC in which levels of CA 19-9 and CEA were measured. Our findings suggest that a large sized multilocular cyst and elevated cyst CA19-9 and CEA levels do not exclude a CHFC from consideration in the diagnosis. CHFCs should be included in the differential diagnosis of hepatic lesions. Accurate diagnosis of a CHFC is necessary given its potential for malignant transformation, and surgical excision is recommended.

JSZG-抗铁磁谐振三相电压互感器的原理和使用

论述了抗铁磁谐振电压互感器的原理，指明它同时具有不易激发和不易维持谐振的机理，理论和运行经验都表明，只要全部采用本抗谐电压互感器，就不需要再装消谐设备。同时指出安装试验时应特别注意的事项。

“附加共鸣”技术的理论与实践

“附加共鸣”技术是20世纪法国作曲家奥利维埃·梅西安的一种音乐语言技巧,它是一种基于音乐音响的作曲技术,是一种“人为地增加音响共鸣”的技术,它的运用极大地丰富了音乐作品的音响色彩。文章以“附加共鸣”技术作为研究对象,试图梳理和总结其基本理论,对影响该技术的音乐要素进行详细展开。

配电网PT铁磁谐振的机理分析

利用相模变换理论,建立配电网发生绝缘放电时的故障分析模型,运用时变相量的分析方法分析配电网PT发生铁磁谐振的原因,并建立非线性并联铁磁谐振模型,分析电网发生铁磁谐振的机理.配电网的铁磁谐振分为两种类型,即暂态谐振和稳态谐振,发生暂态谐振的主要原因是由于扰动发生时,电网对地等效电容被迅速充电,导致电容储存的电能对PT放电导致暂态谐振.稳态谐振的发生机理则是由于PT铁磁非线性导致系统存在多个稳定运行点,当扰动较大时,将使得配电网电压运行点从正常的状态转移到谐振的稳定运行状态,能否激发稳态谐振取决于扰动量的大小.利用胜利油田6 kV系统作为仿真对象,仿真结果表明,上述理论是正确的,对解决配电网PT烧毁事故具有指导意义.

配电网电压互感器铁磁谐振的特点与抑制

从电磁式电压互感器铁芯饱和引起的铁磁谐振的机理出发,介绍了铁磁谐振的特点与危害,重点对抑制铁磁谐振的常见实用方法作了分析,并得出了结论:对10kV中性点绝缘系统,采用在PT一次侧中性点串接电阻型消谐器是比较成功的,其结构简单,安装方便;35kV系统由于一般出线较长,增装消弧线圈是有效的,对系统的安全运行十分有利。

速饱和型阻尼器对 CVT 铁磁谐振抑制特性的研究

通过对速饱和型阻尼器特性的分析，指出了安装有这种阻尼器的ＣＶＴ（电容式电压互感器）在工作电压偏低时阻尼其内部铁磁谐振方面存在的问题，并给出了解决这一问题的方法。

电力互感器对同步相量测量的影响

电力互感器作为连接一次系统和同步相量测量单元(phasor measurement units,PMUs)的必要设备,是PMU能否准确获取一次系统信息的重要环节,其传变精度和动态特性直接影响PMU相量测量的精度。首先总结了电力系统动态现象所对应的动态信号模型,包括故障引起的非周期分量、幅值突变和系统振荡;分析了电力系统在发生以上动态过程时电力互感器对相量测量的影响;并侧重分析了电容式电压互感器的铁磁谐振和瞬变响应问题以及电流互感器的饱和问题,以此来观察电力互感器在不同动态情况下对相量测量结果的影响。

中性点不接地电网单相接地时电压互感器损坏机理

中性点不接地电网中电压互感器异常损坏随电网发展呈上升趋势。为提出有效的工程防范措施以抑制该趋势,研究了这种异常损坏的机理。采用电网输电线路对地电容与电压互感器电感的并联模型替代已有的电网电容与电压互感器电感的串联模型,对电网发生间歇性单相接地时电压互感器内部的暂态过程进行了分析。由仿真计算、动模实验以及工程实验可得,在这一暂态过程中,电压互感器铁芯将进入深度饱和区,产生很大的暂态过电流。结果说明工作于中性点不接地电网中的电磁型电压互感器可能因暂态过电流导致热破坏,因此应按间歇性单相接地进行热稳定性校验。

35kV母线CVT高压侧熔断器异常爆裂原因及解决方案研究

为了解决甘肃天水电网35kV侧母线CVT在电力电容器合闸时,其高压侧熔断器发生异常爆裂的事故,通过对电力电容器合闸过电压的Matlab仿真分析,得到了引起该事故的原因。电力电容器合闸过程产生的过电压激发CVT中间变压器铁芯饱和,进而引发CVT内部非线性电感和电容铁磁谐振,产生谐振过电流,使熔断器发生爆裂。针对这一原因,文中从限制电力电容器合闸过电压和对CVT消谐两个方面提出了解决方案。仿真验证这些方案具有可行性。