Influence of electric parameters on MAO of AZ91D magnesium alloy using alternative square-wave power source

Micro-arc oxidation （MAO） process was carried out on AZ91D alloy in alkaline borate solution using an alternative square-wave power source with different parameters. The effects of voltage, frequency and duty cycle on the coatings were investigated by orthogonal experiment. It is found that the thickness of coatings increases with the increase of voltage and duty cycle, but decreases with the increase of frequency. The structure and morphology of the coatings also depend on voltage, frequency and duty cycle. The coatings become more porous and crack with increasing voltage and duty cycle. The coating is thin and transparent when the voltage is lower than 120 V. The corrosion resistances of different coatings were evaluated by polarization curves and electrochemical impedance spectroscopy （EIS） in 3.5% NaCl （mass fraction） solution. When the optimized values of voltage, frequency and duty cycle are 140 V, 2 000 Hz and 0.4, respectively, the anodic coating shows the best corrosion resistance.

Square-Wave Drive for Synchronous Reluctance Machine and its Torque Ripple Analysis

Synchronous reluctance machine(SynRM)can be perceived as a special type of permanent magnet synchronous machine(PMSM),and shares similar control method,i.e.the sine-wave current drive with sinusoidal phase currents.In this paper,square-wave drive,which is employed for permanent magnet brushless(BLDC)motors,is employed for the SynRM,in order to economically reduce the cost of rotor position sensor.It is revealed that the torque density and efficiency are slightly sacrificed,whereas torque ripple is deteriorated,proving the SynRM with square-wave drive still promising for the cost-sensitive application if torque ripple is not considered as a critical issue.To further investigate the additional pulsating torque under square-wave drive,mathematical model based on a-b-c phase inductance and d-q axis inductance are established,together with the time-stepping FE calculated currents.It is concluded that the harmonics in the currents tend to cause non-sinusoidal variation of the magnetic reluctance,which can be represented as additional inductance harmonics.The harmonics of the current and inductance interact with each other,thus undesirable torque ripple components are produced.

Polarographic Analysis of Diosgenin in Dioscorea zingiberensis C.H.Wright

目的:研究采用线性扫描极谱技术,测定薯蓣皂苷元(C_(27)H_(42)O_3,简称皂素)的分析方法。方法:用硫酸水解黄姜粉末,以乙醇提取薯蓣皂苷元,再用线性扫描极谱法进行测定。结果:在 pH=5.3±0.5的 B-R 缓冲溶液和0.1 mol·L^(-1)氯化钾底液中,薯蓣皂苷元产生极谱还原波,其一阶导数波的峰电位在-1.05 V(vs.SCE)处,峰电流与薯蓣皂苷元的浓度在一定浓度范围内有良好的线性关系,r=0.9989。建立了薯蓣皂苷元的极谱分析方法,成功地测定了黄姜中的薯蓣皂苷元,并讨论了极谱波的产生机理。结论:方法简便可行,结果准确可靠。本方法对黄姜中薯蓣皂苷元的测定结果与 Liebermann-Barcharad 光度法一致。

Determination of Stability Constants of Cadmium-Glycine Complexes by a Unified Treatment for Potentiometric and Polarographic Data

The cadmium（Ⅱ）-glycine system was studied by the two experimental techniques, ion sensitive electrode （ISE） and differential pulse polarography （DPP）, and the experimental data obtained were used by a unified mathematical treatment to calculate the complex stability constants. The combination of the two techniques is of many advantages as ISE can be performed at low [LT]：[MT] ratios and significantly higher [MT], whereas DPP could be used well at large [LT]：[MT] ratios and much smaller [MT]. This makes it possible to study a metal-ligand system in a relatively broader range of experimental conditions that, in turn, provides more information about the metakligand system of interest. Applying the unified mathematical treatment to the cadmium-glycine system, two new complexes MHL and ML2（OH） as well as three complexes ML, ML2 and ML3, reported in literatures, could be modeled and all their stability constants have been refined.

Determination of Naphthalene by Single Sweep Polarography

A second derivative polarographic wave of naphthalene is observed in 50% N, N-dimethylformamide and ammonia-ammonium chloride medium. The peak potential is about ?1.05 V (vs. SCE). The concentration of naphthalene is linear with peak current in the range of 5.00×10?6 mol/L to 5.00×10?4 mol/L, The detection limit is 2.00×10?6 mol/L. This method can be used to determine naphthalene content of the sample such as coal, mothball and asphaltic bitumen. The relative standard deviation (RSD) are in the range of 0.38%≈1.30%. The determined recoveries by adding known amounts of naphthalene to sample solution are in the range of 92%≈101%. This paper also study on the polarographic behavior of naphthalene.

Catalytic Kinetic Determination of Micro Amounts of Oxalic Acid by Second-Order Derivative Oscillopolarography

It was found that micro amounts of oxalate showed a very strong catalytic effect on the slow reaction between K 2Cr 2O 7 and Orange Ⅳ in a diluted sulfuric acid medium in a water bath at 70 ℃ . Orange Ⅳ exhibited a sensitive second order derivative polarographic wave at -0 50 V( vs . SCE). This provides the basis for a sensitive and selective catalytic kinetic method for oxalate determination with second order derivative oscillopolarography. The effects of sulphuric acid, K 2Cr 2O 7, and orange Ⅳ concentrations, reaction temperature and reaction time were investigated. A calibration curve of oxalate in the range of 0 1-2 0 μg/mL was obtained by the fixed time procedure. The detection limit was 0 03 μg/ mL. The possible interference from co existing substances or ions was examined. The new method has a high sensitivity and a good selectivity compared to other existing methods for oxalic acid determination. It has been applied to the determination of micro amounts of oxalate in real urine samples with satisfactory results.

Polarographic Studies on Associations of Midecamycin and Chloroquine with Hydrogen Peroxide

The associations of each of midecamycin and chloroquine phosphate to hydrogen peroxide were studied by using linear-potential scan polarography. In a 0.15 mol/L KH 2PO 4-NaOH(pH 7.4) buffer, the association ratio of the association complex of midecamycin to hydrogen peroxide is 1∶1, and the apparent association constant is 7.18. While in a 0.04 mol/L NH 3·H 2O-NH 4Cl(pH 9.5) buffer, the association ratio and the apparent association constant of the association complex of chloroquine phosphate to hydrogen peroxide are 1∶1 and 45.4, respectively. The formation of the association complexes stabilizes H 2O 2 and results in the accumulation of H 2O 2, which is baneful to human body.

SIMULTANEOUS DETERMINATION OF Cu(Ⅱ),Zn(Ⅱ),Fe(Ⅱ),Mn(Ⅱ),Co(Ⅱ) AND Ni(Ⅱ) WITH A SINGLE SWEEP POLAROGRAPHY

A new method of simultaneous determining Cu(Ⅱ), Zn(Ⅱ), Fe(Ⅱ), Mn(Ⅱ), Co(Ⅱ)and Ni(Ⅱ) with a single sweep polarography was developed. The experiment condition was studied and the results shou that the optimum base solution is that the residue got from evaporating 25 mL mixed solution, 2.5 mL 1.0 mol/L ethylenediamine, 3.0 mL 1 .0 mol/L ammonia-ammonium chloride,5.0mL, 10 % sodium sulfite and 0.5 mL 0.5 % gelatin were mixed and diluted to 25 mL, with water.Under the condition of this base solution, the polarography wave shapes of the six cations are ideal and without overlap of the peaks. In this base solution, Cu(Ⅱ), Zn(Ⅱ), Fe(Ⅱ), Mn(Ⅱ). Co(Ⅱ) and Ni(Ⅱ)in synthetic samples were determined with relative errors 0.4-9.4 % and relative standard deviations 0.8%- 12.2%. Under this experiment condition, one fold of Pb(Ⅱ), Cr(Ⅵ) and Mo(Ⅵ ) do not interere with the determination for Cu(Ⅱ). This method has been used to the simultaneous determination of the amount of the six cations in the samples of soil and Beiqi Tea. The relative standard deviations were 0.1%-2.1 % and recoveries were 93.5%-99.0 %.

Determination of Consuming Rate for Pb－Ag－Ca Anode in Preparation of Electrolytic MnO＿2 by Differential Pulse Polarography

The determination of trace element Pb in electrolyte MnSO_4H_2SO_4 was studied with differential pulse po-larography. The trace Pb was originated from new type Pb-Ag-Ca alloy anode being used in preduction processof electrolytic MnO_2 (EMD). The KCl was added as background of electrolyte. The differential pulse polarco-gram obtained for Pb(Ⅱ) is well in peak contour and is easy to determination. The peak potential is -0. 44 V(vs Ag-AgCl potential , experimental valuel). The Pb content may be determined by standard addition methodwhich is simple , reliable and fast. This study presents some foundamental data for Pb-Ag-Ca anode (abbreviated to PAC anede). The consuming rate for PAC anode is evaluated as 4. 82% annually.

Studies on Quantitative Determination of Active Principles in Chinese Herbal Medicine by Second Derivative Differential Pulse Polarography

The second derivative differential pulse polarography was developed for the quantitative determination of active principles in medicinal herbs (baicalin in Scutellaria baicalensis Georgi, indigo in Baphicacanthus cusia (Nees) Bremek, paeonol in Paeonia suffruticosa Andr and piperine in Piper longum L ) The C O group in baicalin, indigo, paeonol and piperine could be reduced to CH OH in acidic solution at the dropping mercury electrode, and showed very good second derivative differential pulse polarographic peak at 1 550V, 1 300V, 1 630V and 0 860V (vs Ag/AgCl) respectively The linear relationship between concentration of baicalin, indigo, paeonol, piperine and peak height was obtained in the concentration range of 4 5×10 5 ～ 2 7×10 4 mol·L 1 , 3 8×10 5 ～ 4 2×10 4 mol·L 1 , 1 0～6 0×10 4 mol·L 1 and 7 0×10 5 ～2 5×10 4 mol·L 1 and the determination limits were 9 0×10 8 mol·L 1 , 8 4×10 9 mol·L 1 , 9 2×10 9 mol·L 1 and 8 7×10 9 mol·L 1 respectively This method is simple, rapid and sensitive, and the results are accurate

Determination of Vitamin B12 Using Differential Pulse Polarography

Vitamin B12 is a type of vitamin also known by the name cobalamin. B12 is involved in many metabolism activities, including DNA synthesis, nervous system, red blood formation and immune system. Therefore, we chose the Differential Pulse Polarography (DPP) method is that has a high sensitivity for the determination of vitamin B12. This determination was possible with cobalt present in vitamin B12 structure. Since Co(III) is formed from the oxidation of the vitamin, its polarographic behavior had to be determined in various electrolytes such as acetate, borate, phosphate and ammonia. The polarograms of Co(III) were taken in these electrolytes in which 1.0 M NH3/ (pH = 9.8) and 1.0 M AcOH/AcO- (pH = 4.0) were found as the most suitable electrolytes. This method was successfully applied vitamin of B12 determination in a 1 mL ampoule with high precision. The LOD was found as 3.7 × 10-7 for instead of (S/N = 3). Besides Co(III), interference effects of Zn(II), Ni(II), Cr(III), Fe(III), Cu(II), Cd(II) and Se(IV) were also studied. It was found that only Zn(II) peak had an overlap Co(III) peak in ammonium buffer. This problem could be solved by working in 1.0 M AcOH/AcO- (pH = 4.0) buffer. B12, which is 1000 μg in 1 mL vitamin ampoule, was found for 4 measurements as 999 ± 15 μg as a result of 95% confidence interval.

STUDY ON DATA PROCESSING WITH DERIVATIVE IN DIFFERENTIAL PULSE POLAROGRAPHY——PART Ⅰ: THEORY

The formulas of current of first and second derivative of differential pulse polarography (DPP) which has been deduced in this paper indicate that derivative may be enhance the sensitivity of DPP. By the analogy/data transformation, smoothing, and numerical differentiation,we can obtain the derivative current of DPP.

伏安极谱法同时检测有色企业工业生产用水中的锌、镉、铅、铜四种离子

有色企业工业生产用水样品采用吸附溶出伏安极谱仪的悬汞模式(HMDE),使用标准加入法进行检测,Zn、Cd、Pb、Cu这四种元素的检出限均能达到10ng/L,回收率分别为:Cu:100.6%;Zn:100.8%;Cd:92.70%;Pb:104.0%。本研究开辟了在水分析领域中电化学方法检测有色企业工业生产用水中痕量重金属残留的新途径。

极谱络合吸附催化波测定人发中微量锗的研究

用Ge(Ⅳ)-邻苯二酚—澳酸钠极谱络合吸附催化波测定人发中微量锗,并对发样的消化处理方法进行了较详细的研究。测定结果令人满意。

石油馏分及产品中元素硫的示波极谱测定

提出了采用示波极谱法测定馏分油及石油产品中元素硫的方法。支持电解液是含有０．５ｍ ｏｌ／Ｌ醋酸和０．３ ｍ ｏｌ／Ｌ醋酸铵体积比为１∶１的甲苯－甲醇溶液。在此介质中，饱和甘汞电极的峰电位为－ ０．６１Ｖ。该方法灵敏度高，当元素硫浓度为０．１ ｍ ｇ／Ｌ时仍可以看到明显峰电流；精密度和准确度较好，对１ ｍ ｇ／Ｌ元素硫的测定，标准偏差为０．０２；元素硫浓度在０～４ ｍ ｇ／Ｌ浓度范围与极谱峰电流呈线性关系。

极谱法测定地质样品中痕量氯

提出了０．１％ＨＣＯＯＨ－８×１０－３％百里香酚兰－０．４ｍｏｌ／ＬＨＣｌＯ４－０．４％ＴｒｉｔｏｎＸ－１００极谱法测定痕量氯离子的新体系，检出限为０．１８μｇ／ｇ，ＲＳＤ为７．６％。标准样品测定结果与推荐值相吻合。

Fenton反应产生的羟自由基及其清除的电化学方法测定

建立了一种新的测定羟自由基的电化学方法 ,Fenton反应产生的羟自由基氧化二甲亚砜 (DMSO)生成的甲醛与乙酰丙酮、氨发生Hantzsch反应 ,产物3,5_二乙酰基_1,4_二氢吡啶在 -1.20V(vsSCE)处有一灵敏的二阶导数极谱波 ,通过峰电流变化可间接测定羟自由基 ;拟定的方法测定了数种清除剂与羟自由基反应的反应速率常量和清除羟自由基的IC50;该法简便可靠 。

催化极谱法快速测定硫磺中微量砷

采用硫化铵分解硫磺试样 ,在 1 .46mol/L H3 PO4 、0 .8mol/L KI和 4.0 7× 1 0 -5mol/L Te( )体系中以催化极谱法测定微量砷。极谱峰电位为 - 0 .63V(相对饱和甘汞电极 )。砷浓度在 4～1 0 0 ng/m L范围内与峰电流有良好的线性关系 ,检出限为 2 ng/m L。方法的 RSD为 3.6%～ 4.6% ,加标回收率为 94%～ 97%。该法操作简便快速 ,用于硫磺样品测定 。

甲醛存在下阿米卡星的单扫描示波极谱法测定

研究了在Ｂｒｉｔｔｏｎ－Ｒｏｂｉｎｓｏｎ（ｐＨ８．０）介质中，阿米卡星（ＡＭＫ）甲醛衍生物的单扫描示波极谱行为，并对其电极反应机理作了研究。在选定条件下，ＡＭＫ浓度在６．０×１０￣（－７）～５．０×１０￣（－５）ｍｏｌ·Ｌ￣（－１）范围内与峰电流呈线性，相关系数为０．９９９８，检测限为２．４×１０￣（－７）ｍｏｌ·Ｌ￣（－１）．方法无需前处理即可用于针剂、尿及血清样品中痕量ＡＭＫ测定，回收率９０％～１１０％，相对标准偏差小于４．１％。

极谱法测定钒钛磁铁矿中钒

在pH 4.5的HAc-NaAc缓冲溶液中,邻菲罗啉在-0.82V（v.sSCE）处出现一灵敏极谱峰。加入钒,邻菲罗啉极谱峰减小,且减小的峰电流与钒的加入量在0.05~5.0μg/mL范围内呈线性关系,由此建立了极谱法测定钒的新方法。优化了试剂及仪器条件,考察了共存元素的干扰。在优化条件下,钒的检出限为0.004 2μg/mL。测定0.8μg/mLV（,除Fe,Ti,Mn外,钒钛磁铁矿中其它元素没有干扰。Fe,Ti可以通过控制溶液的pH值用沉淀方法分离,Mn和溶液中残留Fe,Ti可加入F-络合消除其对钒测定的干扰。方法用于钒钛磁铁矿标准样品中钒的测定,测定值与认定值相符,测定结果的相对标准偏差小于1.1%。