性本爱丘山——读丘山诗集《交流电》

春暖花开的季节,早莺争暖树,新燕啄春泥。此时,邱建国(笔名丘山)兄的诗集《交流电》(当代世界出版社,2023)出版了。很快收到他的签名赠书,甚是高兴,忙不迭地读起来了。我非诗人,不写诗,但偶尔读读诗,附庸一下风雅。因为心中也老念叨人们常说的一句:生活不仅有眼前的苟且,还有诗和远方。远方无法常去,但诗可常读。

Design and verification of an improved experimental platform for stray current in urban rail transit

With the rapid development of urban rail transit,there have been an urgent problem of excessive stray current.Because the stray current distribution is random and difficult to verify in the field,we designed an improved stray current experimental platform by replacing the simulated aqueous solution with a real soil environment and by calculating the transition resistance by measuring the soil resistivity,which makes up for the defects in the previous references.Firstly,the mathematical models of rail-drainage net and rail-drainage netground were established,and the analytical expressions of current and voltage of rail,drainage net and other structures were derived.In addition,the simulation model was built,and the mathematical analysis results were compared with the simulation results.Secondly,the accuracy of the improved stray current experimental platform was verified by comparing the measured and simulation results.Finally,based on the experimental results,the influence factors of stray current were analyzed.The relevant conclusions provide experimental data and theoretical reference for the study of stray current in urban rail transit.

一“新颖解法”引起的思考——兼谈比值法定义物理量

在复习《交流电》一节时，讲到正弦式交流电有效值与最大值的关系是：U=√2/2Um，我曾说了一句话：有兴趣的同学可以课外去作数学证明．确有很多同学作了探索，有一种证明方法看起来很简洁、新颖，他的证法如下：

Anodic behavior and microstructure of Al/Pb-Ag anode during zinc electrowinning

Anodic behaviors and oxygen evolution kinetics of Pb-0.8%Ag and Al/Pb-0.8%Ag anodes during the initial 24 h zinc electrowinning were investigated with cyclic voltammetry （CV） curves and electrochemical impedance spectroscopy （EIS）. The results reveal that the anodic behaviors and reaction kinetics of the two anodes vary a lot during the anodic polarization which indicate the formation and stabilization of anodic layer. Compared with conventional Pb-0.8%Ag anode, A1/Pb-0.8%Ag anode has longer time of anodic polarization. At the very beginning of anodic polarization, the two anodes all exhibit higher potential of oxygen evolution reaction （OER） since the reaction is controlled by the transformation step of intermediates. Then, its OER potential is largely diminished and OER rate is deduced from the formation and adsorption of the first intermediate （S-OHms）. In the prolonged anodie polarization, the anodie potential of A1/Pb-0.8%Ag gradually decreases and the final value is more stable than that of conventional Pb-0.8%Ag anode. On the anodic layer after 24 h of anodic polarization, the OER potential is controlled by the formation and adsorption of intermediate. The microstructures of A1/Pb-0.8%Ag and Pb-0.8%Ag anodes after 24 h of anodie polarization were analyzed by scanning electron microscope （SEM）.

Electrochemical hydrogen storage properties of non-equilibrium Ti_(2-x)Mg_xNi alloys

Amorphous Ti2?xMgxNi (x=0?0.3) alloys were prepared by mechanical milling of elemental powders. Charge and discharge test, linear polarization (LP) and potential-step measurement were carried out to investigate the electrochemical hydrogen storage properties of the alloys before and after heat treatment. The results show that the maximum discharge capacity of heat-treated Ti2?xMgxNi alloy can reach 275.3 mA·h/g, which is 100 mA·h/g higher than that of the amorphous Ti2?xMgxNi alloy. The heat-treated Ti1.9Mg0.1Ni alloy presents the best cycling stability with a high discharge capacity of 210 mA·h/g after 30 cycles. The results of LP and potential-step measurement of the Ti1.9Mg0.1Ni alloy show that the exchange current density increases from 101.1 to 203.3 mA/g and the hydrogen diffusion coefficient increases from 3.20×10?11 to 2.70×10?10 cm2/s after the heat treatment, indicating that the heat treatment facilitates both the charge-transfer and hydrogen diffusion processes, resulting in an improvement in electrochemical hydrogen storage properties of Ti2?xMgxNi (x=0?0.3) alloys.

Electrical conductivity of MO(MO=FeO,NiO)-containing CaO-MgO-SiO_2-Al_2O_3 slag with low basicity

As a fundamental study on recovery of valuable metals from nonferrous metallurgical slags,electrical conductivity values of MO（MO=FeO,NiO）-containing CaO-MgO-SiO2-Al2O3 slag with a low basicity were measured at different temperatures using AC impedance spectroscopy.The result shows that the electrical conductivity increased from 1.4 S/m to 14.4 S/m with the increase of the temperature from 1 573 to 1 773 K and the content of MO which is less than 12% under the constant mass ratio of （CaO＋MgO） to （SiO2＋Al2O3） of 0.47.Moreover,the increase magnitude of the electrical conductivity was also promoted with the increase of the content of MO.The electrical conductivity of FeO-containing slags was close to that of NiO-containing slags when the content was less than 8%;however,it was obviously larger than that of NiO-containing slags when the content was 12%.The activation energy of the electrical conductivity decreased with the increase of MO content.

In situ investigation of atmospheric corrosion behavior of PCB-ENIG under adsorbed thin electrolyte layer

The effects of relative humidity (RH) on a printed circuit board finished with electroless nickel immersion gold (PCB-ENIG) under an adsorbed thin electrolyte layer (ATEL) were investigated in situ via the measurement of cathodic polarization curves, electrochemical impedance spectroscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy to clearly elaborate the corrosion behavior of PCB-ENIG in the atmospheric environment. Results indicated that the cathodic process of PCB-ENIG under ATEL was dominated by the reduction of dissolved oxygen, corrosion products, and H2O. The cathodic current density of PCB-ENIG increased progressively with increasing RH. Moreover, its cathodic current density in the solution was greater than that under ATEL. This result demonstrated that the diffusion process was not the controlling step during the limiting reduction of cathodic oxygen. When the polarization potentials were located in a more negative region, the cathodic polarization current density gradually decreased under 75% and 85% RH. Notably, the anodic process became the controlling step in the extremely thin liquid film during the remainder of the experiment.

A New AC Driving Method for a Current-Programmed AM-OLED Pixel Circuit

A new,improved pixel-driving circuit is presented based on a current-programmed pixel circuit in order to achieve an AC-driving mode. This driving method realizes an AC-driving mode,removes the threshold voltage variation of the driving TFT due to the process variation or long-term operation,which can bring about brightness non-uniformity, and eliminates high peak pulse currents at the beginning and end of recovery time. Simulation is done with AIM-SPICE,and simulation results demonstrate that the OLED is in the reverse-biased state during recovery time.

LOAD FLOW CALCULATION FOR FLEXIBLE AC TRANSMISSION SYSTEMS

In this paper, a synthetic mathematical model of load flow for flexible AC transmission systems (FACTS) with unified power flow controller (UPFC) is presented based on the analysis of basic principle and operation state of UPFC. The model can use the fast P Q decoupled load flow method. Examples of test systems show that the proposed model and method have good convergence. An effective tool is provided by the load flow computer program to analyze the load flow and initial valve calculation of the dynamic state of FACTS.

Development and Prospect of China Power Grids

In this paper the growing process of China power grid from formation of local power grids to nationwide interconnection is reviewed. The scale and structure of power grid construction in the near future, especially the planning on sending power from west to east, North-South supplementation and nationwide interconnection are introduced. In addition, the technologies to be extended in future grid development are briefed, such as HVDC, FACTS and compact transmission line, etc.

IMPROVEMENT IN WAVEFORM OF SWITCHING POINT-PRESET SPWM INVERTERS

Total harmonic distortion (THD) is one of the key technical indexes of inverter output voltage. Optimization o f switching points and filter parameters could ensure the switching-point-preset sinusoidal pulse width modulation (SPWM) inverters with low harmonyic content in theory.The THD value would be increased by switching time delay of power devices and control circuit. A new control coecuit with delay time compensation is presented in this paper. With this control scheme, the output of the inverter could be basically identified with the theory given.Test results of experimental circuit verify that the control circuit presented in this paper is feasible. The THD of the inverter output voltage could be reduced to a certain extent by this method.

Material Design and Experimental Analysis of a New Type of Semiconductor ER Fluids

To improve the electrorheological effect of electrorheological fluid (ERF), a new type of the electrosensitive particle material, polynaphthalene quinone was prepared, whose molecules contain blended atoms of nitrogen, oxygen, sulphur and big π bond conjugate system. In both DC and AC electric fields, the ERF material showed a distinct ER effect. Especially, in the alternating electric field, the shear stress of this material versus AC voltage has a better quadratic relation than that of the other materials. The experimental data showed that organic semiconductor polymers with big π bond conjugate system are a new type of electrosensitive particle materials which are worth well developing.

Ionic Conduction and Fuel Cell Performance of Ba0.98Ce0.8Tm0.2O3-α Ceramic

The perovskite-type oxide solid solution Ba0.98Ce0.8Tm0.2O3-α was prepared by high temperature solid-state reaction and its single phase character was confirmed by X-ray diffraction. The conduction property of the sample was investigated by alternating current impedance spectroscopy and gas concentration cell methods under different gases atmospheres in the temperature range of 500-900 ℃. The performance of the hydrogen-air fuel cell using the sample as solid electrolyte was measured. In wet hydrogen, the sample is a pure protonic conductor with the protonic transport number of 1 in the range of 500-600 ℃, a mixed conductor of proton and electron with the protonic transport number of 0.945-0.933 above 600 ℃. In wet air, the sample is a mixed conductor of proton, oxide ion, and electronic hole. The protonic transport numbers are 0.010-0.021, and the oxide ionic transport numbers are 0.471-0.382. In hydrogen-air fuel cell, the sample is a mixed conductor of proton, oxide ion and electron, the ionic transport numbers are 0.942 0.885. The fuel cell using Ba0.98Ce0.8Tm0.2O3-α as solid electrolyte can work stably. At 900 ℃, the maximum power output density is 110,2 mW/cm2, which is higher than that of our previous cell using Ba0.98Ce0.8Tm0.2O3-α （x〈≤1, RE=Y, Eu, Ho） as solid electrolyte.

Manipulation of nanoparticles by AC electrothermal effect in laboratory-on-a-chip applications

Microflow driven by AC electrothermal pumping electrolytes with high conductivity fluid （ACET） effect is explored in order to seek new methods for （more than 0. 02 S/m） at microscale. Based on the ACET theory, a physical model for particle trapping is established by a set of electrostatics, heat transfer and fluid dynamic equations. Further, fluid velocity fields are predicted using the software FEMLAB. Experiments are performed which verify the numerical results. The experimental results show that with appropriate electrode design, ACET effect can work on fluids with conductivity up to I. 53 S/m and trap particles at a low voltage. ACET devices can be readily integrated on chip into a microsystem. This offers insight into designing ACET lab-chips.

对教材中一道例题的重新设计

全日制普通高级中学教科书(必修)《物理》第二册(人教版)中第114页的(原题略)给出了一个交流发电机的原始模型，从教材编写意图来看本例题一方面给学生展示了一个应用公式E=BLv来计算感应电动势的实例，同时为以后学习《交流电》一章中的发电机原理打下基础，

Effects of spinal cord stimulation on cerebrovascular flow: role of sym-pathetic and parasympathetic innervations

Objective Cervical spinal cord stimulation （SCS） has been found to augment cerebral blood flow （CBF） in a number of animal models. However, the effective use of SCS is hampered by a lack of understanding of its mechanism（s） of action. In this paper, we focus on the sympathetic and parasympathetic effects of SCS on CBF. Method SpragueDawley rats were selected for the experimental series. The animals were divided into 5 groups to underwent SCS and laser Doppler flowmeter （LDF） recordings. Control group, the animal underwent SCS and LDF recordings without any surgery of the nerve fibers and ganglia. V 1 group, the animal underwent bilateral resection of the nasociliary and post-ganglionic parasympathetic nerve fibbers. SCG group, the animal underwent bilateral resection of supper cervical ganglion. V 1 ＋ SCG group, the animal underwent both surgeries as V1- and SCG-group animals did. Sham group, the animal underwent the carotid manipulation with blunt-tipped forceps as well as the dissection of nasociliary and post-ganglionic parasympathetic nerve fibers around the ethmoidal foramen, but without cutting any nerves. Results During the SCS, the LDF was no statistical difference between the V 1 or SCG group and the control group. Yet, the effects of SCS on CBF are completely abolished in V1＋ SCG group. Conclusions Surgical interruption of both the parasympathetic and sympathetic pathways has the contradict effect on SCS-induced CBF augmentation.

Direct Synthesis of High Purity Silicon Wires by Electrorefining in Molten KF-NaF Eutectic

The electrochemical synthesis silicon wires by electrorefining metallurgical grade silicon in thermally dried and pre-electrolyzed molten KF-NaF eutectic were studied at temperatures 800-900 ℃ using cyclic voltammetry and ac impedance. One oxidation peak at -0.14 V could be attributed to the reaction of Si to Si4＋. A cathodic peak occurred at -0.56 V in the cyclic voltammogram and one response semicircle in the ac impedance spectrum was observed, supporting a one-step electrochemical reduction process of Si4＋-→Si. The electrochemical reaction of silicon was controlled by the diffusion process. The purity of electrorefined silicon wires was up to 99.999% by ICP-MS analysis.

APPLICATION OF INTELLIGENCE FORECASTING METHOD IN TRAFFIC ANALYSIS OF EGCS

Traffic flow forecasting is an important part of elevator group control system (EGCS).This paper applies time series prediction theories based on neural networks(NN) to EGCSs traffic analysis,and establishes a time series NN traffic flow forecasting model.Simulation results show its validity.

Application of Developed Grid-GA Distributed Hydrologic Model in Semi-Humid and Semi-Arid Basin

A grid and Green-Ampt based （Grid-GA）distributed hydrologic physical model was developed for flood simulation and forecasting in semi-humid and semi-arid basin. Based on topographical information of each grid cell extracted fi＇om the digital elevation model （DEM） and Green-Ampt infiltration method, the Grid-GA model takes into consideration the redistribution of water content, and consists of vegetation and root interception, evapotranspiration, runoff generation via the excess infiltration mechanism, runoff concentration, and flow routing. The downslope redis- tribution of soil moisture is explicitly calculated on a grid basis, and water exchange among grids within runoff routing along the river drainage networks is taken into consideration. The proposed model and Xin＇anjiang model were ap- plied to the upper Lushi basin in the Luohe River, a tributary of the Yellow River, with an area of 4 716 km2 for flood simulation. Results show that both models perform well in flood simulation and can be used for flood forecasting in semi-humid and semi-arid region.

A new dimmer for alternating-current directly driven light-emitting-diode lamp

A new dimmer using a mental-oxide-semiconductor field-effect transistor (MOSFET) for alternating-current (AC) directly driven light-emitting-diode (LED) lamp was presented. The control method of proposed dimmer is pulse width control (PWM) method. Compared with the conventional phase-controlled dimmer, the proposed PWM dimmer can produce sine wave and did not cause harmonics problem. Furthermore, the proposed control method did not amplify the light flicker due to the independence of input voltage. Therefore, the PWM dimmer can be used as the dimmer of the AC LED lamp instead of the conventional phase-controlled dimmer. The experimental result shows that the proposed PWM dimmer has good performances.