关键词： Electrochemical microdrilling   In-process monitoring   Material removal rate   Microtool   Microhole  

摘要： The electrochemical micromachining appears to be a promising candidate as a future micromachining technique that utilizes high frequency pulses for micron- to nanoscale material dissolution. This article presents a step towards the in-process monitoring based on waveforms generated during electrochemical micromachining. An attempt has been taken to correlate between the waveforms generated during machining and experimental outcomes such as material removal rate, machining time, and the dimensions of the microholes fabricated on commercially available nickel plate with prefabricated tungsten microtools. An electrical function generator is used as a signal source and a digital storage oscilloscope is provided for observing the nature of electrical pulses used and recording the waveforms generated during machining. The waveforms are subgrouped depending on the parameters used and analyzed to correlate the waveform shape and the machining outcomes. The digital storage oscilloscope also facilitates for observing the short-circuit condition which may occur during microdrilling. These results show that the shape of the waveforms and their corresponding values are in good agreement with the material removal rate, machining time, and on the dimension of fabricated microholes. Therefore, the proposed monitoring technique can be employed as a predictive tool in electrochemical micromachining.

关键词： 中国铁路   电气化铁路   发展  

摘要： 根据铁路部门多年的统计数据,对我国30多年来电力机车保持量、电气化铁路里程、电力机车牵引工作量、电力机车单位耗能和电力机车年耗电量的变化特征进行了解读。1970年至2007年,我国铁路电力机车的保持量年均增加160台,电气化铁路里程年均增加642km,电力机车牵引工作量年均增长542亿t·km。从1975到2007年,我国电力机车牵引耗电量年均增加6.8亿kw·h,但其单位耗能强度呈明显的降低趋势,年均降低1.12kw·h/万t·km。

关键词： Wire electrochemical turning (WECT)   Statistical process control (SPC)   Design of experiments (DOE)   Response surface methodology (RSM)   Control chart  

摘要： Design of experiments (DOE) and statistical process control (SPC) have been separately used in many traditional and non-traditional machining processes, but recently these two approaches are being combined and reevaluated for more effective use and accurate conclusions. DOE and SPC are very efficient tools to maintain the process on target and within boundaries of natural variations and to achieve the maximum accuracy and effectiveness of an experimental program. This paper proposes an integrated framework of SPC and DOE to execute the experimental procedures and to investigate a reliable mathematical model for optimizing the wire electrochemical turning process (WECT). WECT is a non-traditional machining process which has tremendous applications in modern industries especially in the aerospace and military industries. Response surface methodology is used to determine the sufficient number of experiments and also the recommended values of the input parameters. Univariate and multivariate control charts are used to assess the statistical control of the output parameters. Multi-objective optimization is conducted for determining the optimum values of the input parameters.

关键词： 电动汽车   电机驱动技术   数字化  

摘要： 电动汽车分为纯电动、混合动力和燃料电池三类,上述三类电动汽车都需要至少一套电机驱动系统提供动力。文章综述了电动汽车电机驱动系统的发展现状,指出电动汽车电机驱动的技术发展趋势是永磁高效化、数字化和集成化。

关键词： Cr(VI) reduction   Cr(VI) adsorption   Precipitation   Current efficiency   Electrode deposit  

摘要： This work experimentally investigates aqueous Cr(VI) reduction/removal by electrotreatment with mild steel electrode in a batch stirred reactor. Cr(VI) removal is due to simultaneous reduction to Cr(III) followed by precipitation and adsorption of Cr(VI) on Fe(OH)(3)(s)/Cr(OH)(3)(s) sludge formed. Cr(VI) adsorbed on sludge increases to maximum 10% and decreases to negligible level with diminishing concentration of Cr(VI) in solution. Concentration of Cr(VI) can be decreased to its discharge limit (0.5 mg/l) in a single process step without addition of any precipitating agent. The highest reduction rate of Cr(VI) was found to be 3.8 mgl(-1) min(-1) at lowest initial pH 2 at the beginning (treatment time <1 min) of the run, but Cr(III) in solution remains high due to its high solubility. The Cr(VI) reduction rate varies between 1.38 and 0.89 mgl(-1) min(-1) at higher initial pH (4.9-10). Among the anions Cl-, NO3-, SO42- and PO43-, PO43- is found to inhibit Cr(VI) reduction significantly by around 27% as it enhances oxidation of Fe(II) by dissolved oxygen. Stoichiometry of Cr(VI) reduction was experimentally determined at lower pH (2-3.1) range, where oxidation of Fe(11) by dissolved oxygen and its precipitation can be neglected. Against stoichiometric ratio of similar to 3 in case of reduction of Cr(VI) by Fe(II), the observed overall molar ratio varies from 2.49 to 2.92. Participation of Fe-0 on the electrode surface(s) in reducing Cr(VI) and accumulation of deposit on electrodes explain the observations including progressive variation. (C) 2010 Elsevier B.V. All rights reserved.

关键词： Nitrate   Electrochemical reduction   Sodium chloride   Optimization   Box-Behnken design  

摘要： Electrochemical reduction of nitrate in an undivided cell was studied in the present experiments. The optimization of the influencing factors on electrochemical reduction of nitrate by response surface methodology (RSM) was also studied. An ideal condition of performing both cathodic reduction of nitrate and anodic oxidation of the formed by-product in the presence of NaCl was achieved in the present experiment. The Box-Behnken design can be employed to develop mathematical models for predicting electrochemical nitrate removal geometry. The removal is sensitive to the current density and time in the present study. The value of R-2 > 0.99 for the present mathematical model indicates the high correlation between observed and predicted values. The optimal NaCl dosage, current density and electrolysis time for nitrate removal in the present experiment are 0.47 g L-1, 26.06 mA cm(-2), and 111.88 min, respectively, at which the nitrate nitrogen (nitrate-N) and ammonia nitrogen (ammonia-N) concentration in the treated solution are 9.80 and 0 mg L-1, respectively, which will meet the standards for drinking water. (C) 2010 Elsevier Ltd. All rights reserved.

关键词： decolorization   electrocoagulation   reactive dye   textile wastewater   upflow reactor  

摘要： This study presents an investigation of electrochemical variables in the operation of a continuous upflow electrocoagulation process in treating textile wastewater. Reactive Blue 140, which is porphyrin-based, was used as a representative dye in the experiments. The optimal values of the design and operating parameters were found, from a batch mode, to be the following: iron anode, distance between electrodes of 8 mm, current density of at least 30 A/m(2), and contact time of at least 5 minutes. These optimal values were used to design a continuous upflow electrocoagulation reactor. The pattern of liquid flow within the upflow reactor was studied using a computational fluid dynamics (CFD) program, which simulated the flow behavior inside the reactor using the finite volume method. For optimal parameter values, the water passing the electrode plates had a uniform distribution, and the reactor performance was satisfactory, with >90% color removal and energy consumption of approximately 1.4 kWh/m(3). Water Environ. Res., 82, 2325 (2010).

关键词： MOLECULES   ABSORPTION spectra   EXCITON theory   BACTERIA   ELECTRIC fields   FIELD theory (Physics)  

摘要： The article focuses on the measurement of the rates of intramolecular relation in the B[b] molecule and energy migration from B[b] to P. The rates are measured using the effect of electrochromic shift of the absorption spectrum of the Car molecule located in Rhodobacter sphaeroides. The electric field that influence the Car molecule is also calculated. It is determined by the rate of electron shells in alternating electric field of the excited BCh1 molecule.

关键词： Degradation   Power conversion efficiency   Electrodes   Electrolysis   Materials  

摘要： An extensive study of the influence of the operational variables in the electrochemical degradation of perchloroethylene in water has been carried out using an electrochemical filter-press reactor. The influences of the initial concentration, volumetric flow, and electrode geometry and nature on the kinetics, degradation efficiency, and mechanism have been analyzed by determining the values of process performance parameters such as fractional conversion, degradation efficiency, mass balance error, and selectivity. The best results obtained were a fractional conversion higher than 85%, degradation efficiencies of 65%, selectivities close to 0.8, and energetic consumption around 3 kWh m(-3) obtained with two-dimensional electrodes. Three-dimensional carbon electrodes did not provide a more competitive option.

关键词： Stainless steel   Electrochemical noise   Pitting corrosion   Oxygen reduction  

摘要： The use of electrochemical noise (EN) measurements for the investigation and monitoring of corrosion has allowed many interesting advances in the corrosion science in recent years. A special advantage of EN measurements includes the possibility to detect and study the early stages of localized corrosion. Nevertheless, the understanding of the electrochemical information included in the EN signal is actually very limited. The role of the cathodic process on the EN signals remains uncertain and has not been sufficiently investigated to date. Thus, an accurate understanding of the influence of the cathodic process on the EN signal is still lacking. On the basis of different kinetics of the oxygen reduction it was established that the anodic amplitude of transients arising from pitting corrosion on stainless steel can be decreased by the corresponding electron consumption of the cathodic process. Therefore, the stronger the electron consumption, the weaker the anodic amplitude of the EN signal becomes. EN signals arising from pitting corrosion on stainless steel can be measured because the cathodic process is inhibited by the passive layer. This was confirmed by means of EN measurements under cathodic polarisation. Since the cathodic process plays a decisive role on the form of transients arising from pitting corrosion, its influence must be considered in the evaluation and interpretation of the EN signals. (C) 2009 Elsevier Ltd. All rights reserved.