有色冶金用大功率整流设备的设计和发展趋势

介绍有色金属冶金过程中使用的大功率整流设备的基本要求。比较大功率整流设备电联结型式。讨论整流设备的效率和功率因数 ,特征谐波电流和非特征谐波电流。

大型铝电解整流机组方案确定

叙述了电解负荷对供电的技术要求及大型整流机组的类型 ,分析了整流机组的一次电压、机组数量、机组额定电流、直流额定电压以及整流相数的确定方法 ,并利用具体实例 ,阐述其在工程设计中的适用性。

10万t/a离子膜烧碱整流装置技术方案和运行总结

介绍了10万t/a离子膜烧碱整流装置的谐波计算和脉波数选择,电压等级和电容补偿的确定,同相逆并联和非同相逆并联的比较,整流装置的组成和运行经验。

城市轨道交通整流与谐波抑制

城市轨道交通的快速发展改变了人们的出行方式,但同时造成供电系统的谐波污染却是不可忽视的。24脉波整流系统作为城市轨道交通牵引供电最重要的设备,有效的减少了直流侧电压波动、网侧电压畸变和低次谐波电流含量。然而非线性电力电子器件的接入必然会对供电系统带来谐波污染,虽然低次谐波成分减少了,但对于地铁供电可靠性要求较高的用电场合,谐波仍然是其安全运行的潜在威胁。有源电力滤波器的出现解决了这一问题,利用自换相变流技术,能够对电力系统中的无功和谐波进行综合补偿,对无功从容性到感性的连续调节,也可对系统中的谐波进行动态补偿,且体积小,不会造成谐振,从而得到了广泛的研究。

Decomposition of the Unsteady Wave Patterns for Bessho form Translating-Pulsating Source Green Function

In order to interpret the physical feature of Bessho form translating-pulsating source Green function, the phase function is extracted from the integral representation and stationary-phase analysis is carried out in this paper. The complex characteristics of the integral variable and segmentation of the integral intervals are discussed in m complex plane. In θ space, the interval [-π/2+φ,-π/2+φ-iε] is dominant in the near-field flow, and there is a one-to-one correspondence between the real intervals in m space and the unsteady wave patterns in far field. If 4τ>1(τ is the Brard number), there are three kinds of propagation wave patterns such as ring-fan wave pattern, fan wave pattern and inner V wave pattern, and if 0<4τ<1, a ring wave pattern, an outer V and inner V wave pattern are presented in far field. The ring-fan or ring wave pattern corresponds to the interval [-π+α,-π/2+φ] for integral terms about k2, and the fan or outer V wave pattern and inner V wave pattern correspond to [-π+α,-π/2) and(-π/2,-π/2+φ] respectively for terms about k1. Numerical result shows that it is beneficial to decompose the unsteady wave patterns under the condition of τ≠0 by converting the integral variable θ to m. In addition, the constant-phase curve equations are derived when the source is performing only pulsating or translating.

Effects of Pulse Ultrasound on Adsorption of Geniposide on Resin 1300 in a Fixed Bed

The effects of pulse ultrasound with different pulse parameters on the breakthrough curves of Geniposide on Resin 1300 were studied. The mass transfer model describing the adsorption process was constructed. Adsorption capability and the overall mass-transfer coefficient were obtained by fitting the constructed mass-transfer model and the experimental data. The effects of pulse ultrasound on adsorption of Geniposide on Resin1300 in a fixed bed were studied and compared. Amount of Geniposide adsorbed on Resin 1300 in the presence of ultrasound is lower than that in the absence of ultrasound, but the mass-transfer rate with ultrasonic irradiation is higher than that without ultrasound. Furthermore, mass transfer rate is enhanced by pulse modulation. In the conditions studied, the adsorption equilibrium constant decreases with increasing ultrasonic power, while the overall mass-transfer co-efficient increases. With increasing pulse duty ratio, adsorption equilibrium constant decreases initially, reaches a minimum when pulse duty ratio is 0.5, and then increases. On the contrary, the overall mass-transfer coefficient in-creases initially and reaches a maximum when pulse ratio is 0.5, and then decreases. Effects of pulse period on ad-sorption equilibrium and mass transfer rate reached the peak at pulse period of 28.6 ms.

AN ITERATIVE ALGORITHM FOR OPTIMAL DESIGN OF NON-FREQUENCY-SELECTIVE FIR DIGITAL FILTERS

This paper proposes a novel iterative algorithm for optimal design of non-frequency-selective Finite Impulse Response(FIR) digital filters based on the windowing method.Different from the traditional optimization concept of adjusting the window or the filter order in the windowing design of an FIR digital filter,the key idea of the algorithm is minimizing the approximation error by succes-sively modifying the design result through an iterative procedure under the condition of a fixed window length.In the iterative procedure,the known deviation of the designed frequency response in each iteration from the ideal frequency response is used as a reference for the next iteration.Because the approximation error can be specified variably,the algorithm is applicable for the design of FIR digital filters with different technical requirements in the frequency domain.A design example is employed to illustrate the efficiency of the algorithm.

Pulsed digital micro-holography of femto-second order by double-wavelength recording

Double-wavelength recording used in a pulsed digital micro-holographic system to record ultra-fast processing of the order of femto-second is reported for the first time, where a BBO crystal is used to generate harmonic wave of the incident laser wave, and both of the basic and the frequency doubled waves are time-delayed and introduced to a Michelson＇s interferometer to record two sub-holograms with different spatial frequencies on a single frame of a CCD. In the experiment, an ultrafast dynamic process of air ionization induced by a single femto-second laser pulse is recorded with holography by this system, and both of intensity and phase difference images digitally reconstructed are obtained through Fourier transformation and digital faltering, which show clearly the dynamic process of formation and propagation of the plasma, with a time resolution of the order of femto-second.

Four optimal design approaches of high-order finite-impulse response filters based on neural network

Four optimal approaches of high-order finite-impulse response(FIR) digital filters were developed for designing four types filters using neural network algorithms. The solutions were presented as parallel algorithms to approximate the desired frequency response specification. Therefore, these methods avoid matrix inversion, and make a fast calculation of the filter’s coefficients possible. The convergence theorems of these proposed algorithms were presented and proved to illustrate them stable, and the implementation of these methods was described together with some design guidelines. The simulation results show that the ripples of the designed FIR filters are significantly little in the pass-band and stop-band, and the proposed algorithms are of fast convergence.

Focusing of Spherical Nonlinear Pulses for Nonlinear Wave Equations Ⅲ. Subcritical Case

This paper studied spherical pulses of solutions of the system of semilinear wav e equations with the pulses focusing at a point in three space variables. It is shown that there is no nonlinear effect at leading terms of pulses, when the ini tial data is subcritical.

FPGA-based High-precision Measurement Algorithm for the Ultrasonic Echo Time of Flight

Based on the evaluation of advantages and disadvantages of high-precision digital time interval measuring algorithms, and combined with the principle of the typical time-difference ultrasonic flow measurement, the requirements for the measurement of echo time of flight put forward by the ultrasonic flow measurement are analyzed. A new high-precision time interval measurement algorithm is presented, which combines the pulse counting method with the phase delay interpolation. The pulse counting method is used to ensure a large dynamic measuring range, and a double-edge triggering counter is designed to improve the accuracy and reduce the counting quantization error. The phase delay interpolation is used to reduce the quantization error of pulse counting for further improving the time measurement resolution. Test data show that the systexn for the measurement of the ultrasonic echo time of flight based on this algorithm and implemented on an Field Programmable Gate Army（FleA） needs a relatively short time for measurement, and has a measurement error of less than 105 ps.

High-Speed Numeral Filter in Impulse Voltage Measurement

Since the CPU of embed system has some limitation in operating speed, a new filter was put forward which implemented mountain template convolution by performing rectangle template convolution two times. It can obtain time and frequency localization with computational complexity greatly reduced. This algorithm was applied to lightning waveforms (include chopped waveforms) parameter calculation. It simplifies the computation and the results pretreated by this algorithm are in accord with IEC1083-2 completely. It was applied in embed system successfully. Its capability in frequency restraining was researched. The validity of the algorithm was proved in theory when processing lightning waves. The standard sources and the processing results are consistent completely.

Statistical analysis of pressure fluctuations during unsteady flow for low-specific-speed centrifugal pumps

A three-dimensional transient numerical simulation was conducted to study the pressure fluctuations in low-specific-speed centrifugal pumps. The characteristics of the inner flow were investigated using the SST k-ω turbulence model. The distributions of pressure fluctuations in the impeller and the volute were recorded, and the pressure fluctuation intensity was analyzed comprehensively, at the design condition, using statistical methods. The results show that the pressure fluctuation intensity increases along the impeller streamline from the leading edge to the trailing edge. In the impeller passage, the intensity near the shroud is much higher than that near the hub at thc inlet. However, the intensity at the middle passage is almost equal to the intensity at the outlet. The pressure fluctuation intensity is the highest at the trailing edge on the pressure side and near the tongue because of the rotor-stator interaction. The distribution of pressure fluctuation intensity is symmetrical in the axial cross sections of the volute channel. However, this intensity decreases with increasing radial distance. Hence, the pressure fluctuation intensity can be reduced by modifying the geometry of the leading edge in the impeller and the tongue in the volute.

Modulation by anti-oketsu formulations in Kampo medicine of human arterial stiffness

Objective:In traditional herbal medicine(Kampo medicine in Japan),'sho'is diagnosed by the traditional assessments of clinical conditions.Among a variety of the shos,there is an'oketsu'syndrome,which is a stagnation and disturbance of microcirculation.The prompt effects of four anti-oketsu formulations in Kampo medicine on cardiovascular functions were compared in oketsu and non-oketsu persons.Methods:The arterial pulse wave from radial artery is formed by the combination with ejection and reflection pulses.An augmentation index(AI),a ration of the ejection and reflection pulses,indicates a degree of arteriosclerosis.For both seventy-six students with oketsu and thirty-seven students with non-oketsu,Kampo formulations overcoming oketsu of Tokishakuyakusan(TS,Dang-Gui-Shao-Yao-San),Kamishoyosan(KS,Jia-Wei-Xiao-Yao-San),Keisibukuryogan(KB,Gui-Zhi-Fu-Ling-Wan)and Tokakujokito(TJ,Tao-He-Cheng-Qi-Tang)were taken once,and then,the cardiovascular functions including blood pressure,heart rate,central arterial blood pressure(CBP)and AI were examined for 60 min.Results:At 40-60 min after an intake,these formulations decreased the AI almost by 6-18%(n=76),by 18.3±3.1%(P<0.01,n=15)with TJ.Simultaneously,the CBP was reduced by 9.0±1.8%(P<0.05,n=23)with KS and by 9.1±2.0%(P<0.05,n=15)with TJ.On the other hands,non-oketsu group had less or no effect by any kinds of the formulations.Conclusion:The anti-oketsu formulations can exert the ameliorative action for oketsu persons via decreasing AI and CBP.

Numerical Evaluation of Longitudinal Motions of Wigley Hulls Advancing in Waves by Using Bessho Form Translating-Pulsating Source Green's Function

In the framework of 3D potential flow theory, Bessho form translating-pulsating source Green's function in frequency domain is chosen as the integral kernel in this study and hybrid source-and-dipole distribution model of the boundary element method is applied to directly solve the velocity potential for advancing ship in regular waves. Numerical characteristics of the Green function show that the contribution of local-flow components to velocity potential is concentrated at the nearby source point area and the wave component dominates the magnitude of velocity potential in the far field. Two kinds of mathematical models, with or without local-flow components taken into account, are adopted to numerically calculate the longitudinal motions of Wigley hulls, which demonstrates the applicability of translating-pulsating source Green's function method for various ship forms. In addition, the mesh analysis of discrete surface is carried out from the perspective of ship-form characteristics. The study shows that the longitudinal motion results by the simplified model are somewhat greater than the experimental data in the resonant zone, and the model can be used as an effective tool to predict ship seakeeping properties. However, translating-pulsating source Green function method is only appropriate for the qualitative analysis of motion response in waves if the ship geometrical shape fails to satisfy the slender-body assumption.

Numerical Simulation of Microwave Pulse Coupling into the Rectangular Cavity with Aperture Arrays

In this paper,the finite-difference time-domain(FDTD)algorithm is employed to simulate microwave pulse coupling into the rectangular cavity with aperture arrays.In the case in which the long-side of the slot in aperture arrays is perpendicular to the incident electrical field,and the electrical distribution of each center of slot in the aperture arrays in the process of microwave pulse coupling into the rectangular cavity with aperture arrays is analyzed in detail. We find that the effect of field enhancement of the slot in the middle of all the slots which distribute in the direction parallel to the incident electrical field is minimum and increases in turn from the middle to both sides symmetrically. We also find that the effect of field enhancement of the slot in the middle of all the slots which distribute in the direction perpendicular to the incident electrical field is maximum and decreases in turn from the middle to both sides symmetrically.In the same time,we investigate the factors that influence the effect of field enhancement of the center of each slot and the coupling electrical distribution in the cavity,including the number of slots and the spacing between slots.

浅谈中盐红四方35KV整流变压器抑制谐波的方法和原理

整流设备采用三相桥式可控整流装置，利用A、B两台ZHSSPT-11831／36型整流变压器将交流电网电压变换成整流装置所需要的电压，并通过提高整流脉波数来抑制谐波．满足变压器网侧和阀侧的运行要求。现分析整流变压器抑制谐波的方法和原理。

Association between non-alcoholic fatty liver disease and arterial stiffness in the non-obese, non-hypertensive, and non-diabetic young and middle-aged Chinese population

Background and objective： Non-alcoholic fatty liver disease（NAFLD） is associated with arterial stiffness in the general population. Age, obesity, hypertension, and diabetics are risk factors for arterial stiffness. In this study, we aimed to investigate the association between NAFLD and arterial stiffness as measured by brachial-ankle pulse wave velocity（baPWV） in the non-obese, non-hypertensive, and non-diabetic young and middle-aged Chinese population. Methods： A cross-sectional study with 1296 non-obese, non-hypertensive, and non-diabetic young and middle-aged（20–65 years） subjects undergoing routine medical check-ups in the International Health Care Center of the Second Affiliated Hospital of School of Medicine of Zhejiang University was carried out. Fatty liver was diagnosed by ultrasonography, and baPWV was measured using an automatic waveform analyzer. The subjects were classified into two groups according to the presence of NAFLD, and divided into a further two groups according to their baPWV. Results： The overall incidence of NAFLD was 19.0%, and NAFLD patients had a significantly higher level of baPWV than the controls（（1321±158） cm/s vs.（1244±154） cm/s; P〈0.001）. The incidence of NAFLD was clearly higher in the increased baPWV group than in the normal baPWV group（29.3% vs. 16.9%; P〈0.001）, and the incidence increased in line with the increase of baPWV quartiles in the normal range as well as with the severity of arterial stiffness（both P for trend 〈0.001）. Multiple linear logistic regression analysis showed that the presence of NAFLD was positively and independently associated with baPWV. Conclusions： Our results suggest that the presence of NAFLD is associated with arterial stiffness as measured by baPWV in the non-obese, non-hypertensive, and non-diabetic young and middle-aged Chinese population.

Implementing single-scale wavelet transform processor with magnetostatic surface wave device

When the envelope of the conducting strips for the input transducer of magnetostatic surface wave(MSSW) device is designed according to the wavelet-function envelope,the impulse-response function of the input transducer for MSSW device is equal to the wavelet function,so that single-scale wavelet-transform processor of MSSW type is fabricated.First,according to the envelope function of the wavelet,the length function of the conducting strips is defined,then,the lengths of the conducting strips can be calculated from the length function of the conducting strips,finally,the input transducer can be designed according to the lengths and widths for the conducting strips.The compensation method of the insertion loss for single-scale wavelet trans-form processor of MSSW type is also given in the paper.When the output end of single-scale wavelet transform processor of MSSW type is connected to the amplifier,its insertion loss can be compensated.

Effect of Exit Geometry of Tail Pipe on the Performance of Pulse Jet Engines

In this paper,the effect of geometries of tube open end on the shock,compression and expansion wavespropagating in the tube was investigated numerically and experimentally.One of them is a conventional straightshock tube with an open end.The other has a divergent tail tube at the exit.Applying a divergent tail tube(flaretube)to an open end shock tube,the period of one-cycle process could be shortened and the pressure behind theexpansion wave produced at the exit of the shock tube could be lowered much more below the atmosphericpressure than that produced in the straight tube.The results suggested that the intake air into the engine wassignificantly increased by applying a flare tube instead of a straight tube.