A method for sensorless on-line vibration monitoring of inductionmachines

This paper proposes a method for the sensorless online vibration monitoring of induction machines based on the relationship between the current harmonics in the machine and their related vibration harmonics. Initially, the vibration monitoring system records two baseline measurements of current and vibration with the machine operating under normal conditions. The baseline data is then evaluated to determine the critical frequencies to monitor online. Once these frequencies are determined, the baseline vibration measurement is simply used to scale the current harmonic signal to an estimated vibration level. Based on theoretical analysis, simulation results and the experimental results shown here, a linear relationship between the current harmonics and vibration level can be assumed. The results of two experiments on a three-phase 230 V 10 hp induction motor operating under no load are discussed and show the feasibility of this method for sensorless online vibration monitoring     

An advanced computer code for single-tuned harmonic filter design

The objective of this paper is to present a novel approach for limiting harmonic and improving reactive compensation for industrial power systems using single-tuned filters. The unique feature of the developed power distribution model is that it incorporates both the filter capacity and resonant point as design parameters. The model also considers the detuning effects due to temperature and frequency variations, as well as manufacturing tolerances. The proposed approach was implemented as a PC-based computer code, and it was integrated with a user-friendly graphical user interface. The developed analysis tool was employed to solve the harmonic problems of several industrial plants, and the results all showed great improvements after using this computer tool     

一种适于大型水轮发电机磁场计算前处理的新方法

本文在采用微分法生成四边形网格的基础上,实现了大型水轮发电机有限元计算用的三角单元自动生成。在前处理技术中,提出了采用电机定子线圈轮换数进行源区加电流的新方法。     

Vibration measurement by the time-averaged electronic speckle pattern interferometry methods

Three different image-processing methods based on the time-averaged technique were compared by the electronic speckle pattern interferometry (ESPI) technique for vibration measurement. The three methods are the video-signal-addition method, the video-signal-subtraction method, and the amplitude-fluctuation method. Also, errors introduced by using the zero-order Bessel function directly into the analysis of the fringe pattern were investigated. The video-signal-addition method has been the most generally used ESPI technique for vibration measurement. However, without additional image and/or signal-processing procedures, the fringe pattern obtained directly by the video-signal-addition method is rather difficult to observe. The reason for poor visibility of the experimentally obtained fringe pattern with this method is explained. To increase the fringe pattern's visibility without additional image and/or signal processes, we tried two video-signal-subtraction methods. One of the two methods is the video-signal-subtraction method that has normally been used in the static applications. The other method, called the amplitude-fluctuation method, and its associated theory are reported here.     

Experimental study of the geometric group-delay dispersion in graded-index media

We use the highly sensitive method of spatially coherent white-light interferometry to measure the geometric group-delay dispersion in graded-index media. Our measurements confirm previous analyses that the geometric dispersion produced by off-axis beam propagation is anomalous (negative), hence may be used to eliminate the ubiquitous positive dispersion in optical systems. Fabrication of large index-gradient waveguides optimal for dispersion compensation is discussed.     

Real-time optical image subtraction and edge enhancement using ferroelectric liquid-crystal devices based on speckle modulation

We carried out real-time optical image subtraction and edge enhancement based on a speckle modulation technique by using ferroelectric liquid-crystal polarization switches and a ferroelectric liquid-crystal spatial light modulator. A ferroelectric liquid-crystal spatial light modulator is employed as a real-time and multiple-exposure optical device, and successful results are obtained from three-exposure images modulated by speckles. Thus, image subtraction and edge enhancement are realized in real time. The whole operation is performed within several milliseconds with modest operating conditions. Because the spatial light modulator has a high resolution of greater than 100 line pairs/mm and can store fine speckle patterns, the image qualities we obtained are quite satisfactory.     

NMR study of quaternary superconductor RM2B2C (R = Y,La, Th,and M = Ni,Pd, Pt)

¹⁹⁵Pt-,¹³⁹La- and¹¹B-NMR have been investigated in quaternary RM₂B₂C (R=Y, La, Th and M=Ni, Pd, Pt). The electric quadrupole frequency of¹³⁹La changes more than 5 times in magnitude from M=Ni to Pt, indicating that the hybridization of La-5d and d-electrons of M-element changes largely. The analysis of¹¹B and¹³⁹La spectra shows also the large change of the magnetic anisotropy with R and M element, i.e., _{II c}>_{II ab} in LaNi₂B₂C, but _{II c}>_{II ab} YNi₂B₂C.The data of T₁T and K of¹⁹⁵Pt and¹¹B are consistent with the band effects and with no evidence of strong antiferromagnetic correlation effects.     

Calculations of fracture criteria by classical mechanics I — Pellini's Duplex Rule

In a previous paper we presented a relaxation method to compute the elastic strain concentration of a crack. It was also shown, based on this method and in conjunction with the Rule of Sliding, that the plastic strain concentration curve can be calculated. In the current paper, we present the calculations of static load fracture using the relaxation method that we have previously proposed and the fracture criterion, f, of the second strength theory. Our results are in good agreement with those predicted by Pellini's Duplex Rule. We thus provide a theoretical basis for the Fracture Arrest Diagram of Pellini.     

The interactions between In-Sn solders and an electroless Ni-P deposit upon heat treatment

The interactions between In-Sn solders and an electroless Ni-P deposit within the multilayer combinations comprised of In-Sn/electroless Ni-P/Al were investigated with the aid of heat treatments at various temperatures and durations. The main reaction product was identified with X-ray diffractometry (XRD) as In₃Ni₂ regardless of the In-contents of the In-Sn solders. The formation of this In₃Ni₂ compound occurred through the diffusion of Ni towards the In-Sn solder. The intermetallic compound layer achieved its maximum thickness within 100 h upon heat treatment at 60 C; the thickness of the compound layer did not increase upon extending heat treatment. Sn tended to dissolve in the In₃Ni₂ compound.     

Infective endocarditis complicated with rapidly progressive glomerulonephritis: a case report

Despite a general national decline in criminal activities in the 1990s, juvenile criminal offenses continue to increase, (including violent, property, and delinquency acts). In addition increased numbers of children are being held in juvenile jails. It is all but impossible for pediatric health providers to think that "their patients" and "their practices" are immune from the epidemic of crime that affects and is caused by "just kids."