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Articles 25771 - 25800 of 27337

Full-Text Articles in Engineering

Electrochemical Behavior Of Chemically Prepared Ring-Substituted Polyanilines, Li-Zong Dai, Hui-Huang Wu Aug 1998

Electrochemical Behavior Of Chemically Prepared Ring-Substituted Polyanilines, Li-Zong Dai, Hui-Huang Wu

Journal of Electrochemistry

Polyaniline (PAn) has been known as a promising conducting polymer for technological applications. In research work elecrochemically synthesized PAn has been frequently used since electropolymerization is convenient to prepare the polymer film with controllable thickness or dopingon electrodes. However , the processibility of elecrosynthesized PAn is too poor to produce largearea devices because of its insolubility and infusibility. Recently, therefore, chemical polymerization has attracted a considerable attentionfl-3],  especially suitably derivatized ring substituted (e.g. alkyl or alkoxy) polyanilines have been synthesized, and their appreciable solubility in commonorganic solvents enable the preparation of film on industrial scale by casting. Moreover, emulsionpolymerization reduces …

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Studies On The Preparation Of Nanophase Electrode Materials And Its Electrochemical Properties(Ⅲ)—Performance Of Nm-Γ-Mno2 Obtained By Microemulsion Method, Ling Liu, Xi Xia Aug 1998

Studies On The Preparation Of Nanophase Electrode Materials And Its Electrochemical Properties(Ⅲ)—Performance Of Nm-Γ-Mno2 Obtained By Microemulsion Method, Ling Liu, Xi Xia

Journal of Electrochemistry

A nanophase MnO2 was synthesized using w/o microemulsion as reation media, The most favorable experiment conditions for the preparation of nm MnO2 were researched. XRD,TEM,AC impedance, cyclic voltammetry etc. examinations were used to characterize the sample comparison with the classical MnO2 (I.C.No.1EMD,electrolytic manganese dioxide). Sample shows that the crystal styucture of the synthesized samples are mainly γ-MnO2, with average particle size in the nanometer as shown by TEM. It was found that the discharge capacity of nm MnO2 obtained is significantly higher than that of the I.C.No.1 EMD.

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Electrooxidation Of Benzene To Benzoquinone In A Packed Bed Reactor, Xin-Sheng Zhang, Ping Ding, Ying-Chun Dai, Wei-Kang Yuan Aug 1998

Electrooxidation Of Benzene To Benzoquinone In A Packed Bed Reactor, Xin-Sheng Zhang, Ping Ding, Ying-Chun Dai, Wei-Kang Yuan

Journal of Electrochemistry

A packed electrode reactor was used to oxidize to benzoquinone. Anode bed of the reactor has a size of 10～30 mm×450 mm×50 mm(thickness×length×width),and was packed porous lead alloy. A dispersion of benzene in 1 mol/L aqueous sulfuric acid was passed through the reactor. Current efficiency for benzoquinone generation is 62.9% at optimal operating condition: velocity of electrolyte flow, 0.19 ms -1 ;current, 10 A; thickness of anode bed, 10 mm, and percentage of benzene, 24%.

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Study Of Proton Exchange Membrane Fuel Cells(Pemfc), Shan-Hai Ge, Bao-Lian Yi, Hong-Fen Xu, Ming Han, Zhi-Gang Shao Aug 1998

Study Of Proton Exchange Membrane Fuel Cells(Pemfc), Shan-Hai Ge, Bao-Lian Yi, Hong-Fen Xu, Ming Han, Zhi-Gang Shao

Journal of Electrochemistry

The electrode kinetic parameters for proton exchange membrane fuel cells(PEMFC) were investigated by measuring the relations of cell potential and current density. An experimental stack of PEMFC which can be operated at E cell =0.7V, I =0.55A/cm2 steadily is presented, and the effects of electrode structure and operation conditions such as temperature, pressure, humidification, flow rate on the performance of PEMFC are discussed.

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40th Rocky Mountain Conference On Analytical Chemistry Jul 1998

40th Rocky Mountain Conference On Analytical Chemistry

Rocky Mountain Conference on Magnetic Resonance

Final program, abstracts, and information about the 40th annual meeting of the Rocky Mountain Conference on Analytical Chemistry, co-sponsored by the Colorado Section of the American Chemical Society and the Rocky Mountain Section of the Society for Applied Spectroscopy. Held in Denver, Colorado, July 25 - August 1, 1998.

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Bs News Jul 1998

Bs News

Building Services Engineering

No abstract provided.

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Sustaina Bility Of Irrigation Schemes For Small-Scale Farmers: A Case Study Of Irrigation Scheme At Buleya Malima, Gwembe Valley, Zambia, Masinja R Jul 1998

Sustaina Bility Of Irrigation Schemes For Small-Scale Farmers: A Case Study Of Irrigation Scheme At Buleya Malima, Gwembe Valley, Zambia, Masinja R

Tanzania Journal of Engineering and Technology (TJET)

A study to determine facrors influencing sustainability of smallholder irrigation schemes was carried our a! Buleya Malima, Southern Province, 7_nnzbia. These factors included technical and socio-economic factors. found Out that the technical factors were 26.5, 64.5 and 9.2 percent for application efficiency, tailwater ratio and deep percolation, respectively, indicating that farmers wasted water mainly through tailwater runoff.From socio-economic point of view, the study indicated that the scheme lacked (i) farmer participation in designing and planning operation of the scheme (ii) managerial ability and innovativeness to form their own viable organisation: and (iii) formal training in technical operations of irrigation, infrastructure …

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Trends Of Microcomputer Technology In Developing Countries, With More Focus On Tanzanian Experiences: Achievements And Problems, Satoki Mahenge Jun 1998

Trends Of Microcomputer Technology In Developing Countries, With More Focus On Tanzanian Experiences: Achievements And Problems, Satoki Mahenge

Tanzania Journal of Engineering and Technology (TJET)

Trends of microcomputer technology in developing countries, including Tanzanian. is like a 'mixed bag' of achievement and problems. Although rhe technology has been available for many years in developed world, developing countries are responding to it differently due to differences in political and economic policies. Some countries have acrimonious policies on the technology, some not. There are countries which utilize fully the technology in work places and others are still at dilemma on the importation of the technology due to what is 'claimed to be a weak economy in the presence Of many other pressing needs'. Other countries seem to …

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Experimental Study Of Rural Brick Burning In Iringa And Mbeya Regions, E Mushi Jun 1998

Experimental Study Of Rural Brick Burning In Iringa And Mbeya Regions, E Mushi

Tanzania Journal of Engineering and Technology (TJET)

In this paper results are presented Of a study conducted between June and December 1997. on nine brick firing kilns in Iringa and Mbeya. The locations for rhe study were Mahenje and Iloniba in Mbeya Region and Igumbilo in Iringa region. Three kilns were investigated in each location. For each kiln the process was followed from the laying Of the bricks into a kiln to the opening Of thc kiln for renu)val Of the bricks in preparation for the selling. Different weights and tenperatures were Taken a,' different times. Firing wet bricks results in consumption of 33.63 % of the …

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Design Considerations For A Three-Phase Fluidized-Bed Bioreactor, S Manyele Jun 1998

Design Considerations For A Three-Phase Fluidized-Bed Bioreactor, S Manyele

Tanzania Journal of Engineering and Technology (TJET)

The design Of a three-phase fluidized bed bioreactor using novel biomass support for industrial wastewater treatment is reported in this paper. A column of 0.20 m diameter with variable height up to 6.60 m equipped with a foam breaker tank was designed, commissioned and operated. A novel biomass support, KMTR support, has been used Separate gas and liquid feeding systems were designed to facilitate proper bioreactor operation. A flat distriburor plate with 4 mm holes- diameter was desined A study on the hydrodynamic properties of the three-phase fluidized bed bioreactor revealed high values of bed expansion and air hold-ups. Purification …

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Kiln Design And Fuel Wood Consumption In Fish Smoking, E Mushi Jun 1998

Kiln Design And Fuel Wood Consumption In Fish Smoking, E Mushi

Tanzania Journal of Engineering and Technology (TJET)

In this paper. a load flow solution for the Medium Voltage (MY) three-phase radial distribution in delta-delta (A — A) connected network supplying different line topologies such as three phase, phase to phase and single-wire earth return (SWER) networks is presented. The general voltage related network equations are developed using Kirchhoff's voltage and current laws. Development ofa solution to the loadflow analysis applying the developed general voltage related network equations is proposed in order to evaluate the network voltage profile. Various numbers of arrays are developed for the identification of the network under study. The proposed method is a new …

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Development And Evaluation Of A New Soil Erosion- Productivity Index Model (Sepim), Metthew Mulengera Jun 1998

Development And Evaluation Of A New Soil Erosion- Productivity Index Model (Sepim), Metthew Mulengera

Tanzania Journal of Engineering and Technology (TJET)

A soil erosion-productivity model which considers rhe effect of soil water storage Capacity. crop evapotranspiration, soil chemical and physical properties inrporrantfor Crop growth has been developed. The model is shown to give good predictions and it promises to be an improvement over the former productivity Index (PI). It also promises to give more reliable results than the currently used /nodels which consider only soil water storage capacity and crop e ' 'apotransp iration.

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Use Of Dissolved Oxygen Concentration Probes In Biological Wastewater Treatment Plants, S Manyele Jun 1998

Use Of Dissolved Oxygen Concentration Probes In Biological Wastewater Treatment Plants, S Manyele

Tanzania Journal of Engineering and Technology (TJET)

A study on use Of dissolved oxygen probes (DOP) for measurement Of oxygen concentration in warer and wastewater treatment is presented. The principles Of operation, design considerations and selection criteria for Two types of probes, viz. galvanic and polarographic, are discussed Use of polarographic probes in n rhree-phase fluidized bed bioreactor and in laboratory experiments is presented and discussed. The effect of airflow rate and treatment time on dissolved oxygen concentration was found to be significant. It was found that polarographic probes are important equipment in determining the pollution of the industrial effluents. Finally, the use of the DOC probes …

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Near-Field Source Localization Using Music With Polynomial Rooting, Hsien-Sen Hung, Shun-Hsyung Chang, Chien-Hsing Wu Jun 1998

Near-Field Source Localization Using Music With Polynomial Rooting, Hsien-Sen Hung, Shun-Hsyung Chang, Chien-Hsing Wu

Journal of Marine Science and Technology–Taiwan

In this paper, the bearing, elevation, and range estimation of near-field narrow-band sources from data observed across an array of sensors is considered. For high-resolution source localization, the multiple signal classification (MUSIC) algorithm is modified and extended to its 3-D version by accounting for spherical curvature and spreading factor in the array manifold. However, the simultaneous estimation of bearing, elevation, and range from 3-D MUSIC spectrum requires exhaustive multidimensional search. As to alleviate computational load, an alternative algorithm is proposed. The proposed algorithm involves search in the range domain combined with polynomial rooting, which replaces the search in the azimuth-elevation …

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Frequency Selection Of Wake Flow Behind A Naca 0012 Wing, Han-Wen Lee, Rong-Fung Huang Jun 1998

Frequency Selection Of Wake Flow Behind A Naca 0012 Wing, Han-Wen Lee, Rong-Fung Huang

Journal of Marine Science and Technology–Taiwan

The oscillating flow modes, frequency selection, and response of periodic frequency to change of characteristic flow modes behind a NACA 0012 wing model are studied experimentally. The functional relationships of the dominant mechanisms in limiting ranges of Reynolds number are justified analytically. The oscillating instabilities in wake region possess four characteristic modes: laminar, subcritical, transitional, and supercritical. In viscous effect dominated regime of laminar mode, Strouhal number is inversely proportional to Reynolds number. In inertial effect or pressure gradient dominated regime of supercritical mode, Strouhal remains constant. In regime between limiting cases, Strouhal number increases nonlinearly with Reynolds number and …

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Investigation Of Longitudinal Elastic Wave At Right-Angle Joint Of Two Rods, Ming-Te Liang, Chiou-Jenn Chen Jun 1998

Investigation Of Longitudinal Elastic Wave At Right-Angle Joint Of Two Rods, Ming-Te Liang, Chiou-Jenn Chen

Journal of Marine Science and Technology–Taiwan

The right-angle welded joint is usefully and frequently used in the welded type for the steel structures. The present study is focused on the longitudinal elastic waves propagating through the right-angle welded joint of two rods. One uses the theory and numerical calculation to identify the consequence of the problems of reflection and transmission. The present study indicates that the incident longitudinal elastic waves are almost reflected in the horizontal rod while the values of 3% of the generated pulse are transmitted in the vertical rod.

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Routing And Broadcasting Algorithms For The Root-Folded Petersen Etworks, Ming-Bo Lin, Grene-Eu Jan Jun 1998

Routing And Broadcasting Algorithms For The Root-Folded Petersen Etworks, Ming-Bo Lin, Grene-Eu Jan

Journal of Marine Science and Technology–Taiwan

Petersen networks have been proposed as the alternatives for interconnecting highly parallel computers. The main advantages of Petersen networks are: regular topology, high scalability, and smaller diameters. In this paper, we propose a new node naming scheme for Petersen networks. Based on this scheme, two Petersen graph related networks, called root-folded Petersen network in type-I and type-II, are constructed. Furthermore, both O(1ogio N) routing and broadcasting algorithms for the proposed networks are developed, where N is the number of nodes.

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The Estimation Of Direction-Of-Arrivals Of Wideb And Sources By Signal Subspace Focusing Approach, Lena Chang, Chung-Fan Twu Jun 1998

The Estimation Of Direction-Of-Arrivals Of Wideb And Sources By Signal Subspace Focusing Approach, Lena Chang, Chung-Fan Twu

Journal of Marine Science and Technology–Taiwan

A novel signal subspace focusing (SSF) approach for the wideband array processing is proposed in this paper. The method is based on the transformation of the signal subspaces by using focusing matrices. The focusing matrix is designed to align the signal subspaces for different frequencies in the bandwidth of the sources, and is constructed without the preliminary angle estimation. Hence, the SSF can avoid the inherent sensitivity to focusing error. Simulation results validate the effectiveness of the SSF in the estimation of the direction-of-arrivals (DOAs) of wideband sources.

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Complete Solution Of The Five-Position Synthesis For Spherical Four-Bar Mechanisms, Chen-Chou Lin Jun 1998

Complete Solution Of The Five-Position Synthesis For Spherical Four-Bar Mechanisms, Chen-Chou Lin

Journal of Marine Science and Technology–Taiwan

The objective of this paper is to synthesis spherical four-bar motion and path generators using continuation method (homotopy method). Using continuation method, we may obtain a complete set of the solutions to the problems, and provide mechanism designers with all possible choices which meet the kinematic specifications. In contrast to other local numerical schemes such as Newton method and Powell method which are sensitive to initial guess, continuation method is a global convergence method that guarantee to find all solutions to the equations. In this paper, the problems with four and five precision points will be formulated, solved, and compared …

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Analysis Of The Pivot Point For A Turning Ship, Ching-Yaw Tzeng Jun 1998

Analysis Of The Pivot Point For A Turning Ship, Ching-Yaw Tzeng

Journal of Marine Science and Technology–Taiwan

An approximate method based on the steady state linearized sway-yaw equations is proposed to estimate the pivot point of a turning ship. The location of the pivot point is directly related to the ratio of the "sway-rudder" and "yaw-rudder" gain coefficients. which can be readily computed from six linear hydrodynamic coefficients. Hence, estimation of the pivot point for a ship at the design stage is made possible with minimum hydrodynamic coefficients information required. Numerical results indicate that based on the proposed method, the estimated pivot point position for a turning ship correlates well with the solution obtained from a full …

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A Unified Approach For The Robust Spr Property Of A Parametric Uncertainty System, Chih-Yung Cheng, Chao-Fong Chang Jun 1998

A Unified Approach For The Robust Spr Property Of A Parametric Uncertainty System, Chih-Yung Cheng, Chao-Fong Chang

Journal of Marine Science and Technology–Taiwan

In this paper, we adopt a unified approach based on the concept of value set to analyze the robust strict positive real (SPR) property of uncertain systems with interval, affine linear or multilinear uncertainty structures.

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A Study Of Along Wind Speed Power Spectrum For Taiwan Area, Jing-Jong Jang, Yu-Lin Lee Jun 1998

A Study Of Along Wind Speed Power Spectrum For Taiwan Area, Jing-Jong Jang, Yu-Lin Lee

Journal of Marine Science and Technology–Taiwan

The Purpose of this paper is to formulate the wind speed power spectrum by time history data of strong wind speed in Taiwan area. By utilizing random vibration theory and statistical regression analysis, a systematic analysis and discussions of along wind turbulence effects for wind speed power spectrum is performed. This study includes the time history data collection of along wind speed for typhoon in Taiwan and the regression analysis of wind speed spectral formulas. The strong wind speed data was first transformed from time domain to frequency domain. Then, the statistical analysis methods were applied for spectrum formulation and …

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Robust Multiple Constrained State Feedback Controller Design With Minimum Auxiliary Entropy For Linear Discrete Systems, Wen-Jer Chang Jun 1998

Robust Multiple Constrained State Feedback Controller Design With Minimum Auxiliary Entropy For Linear Discrete Systems, Wen-Jer Chang

Journal of Marine Science and Technology–Taiwan

Existence of a state feedback controller with minimized auxiliary entropy design problem will be explained in this paper. This state feedback controller will achieve multiple performance constraints for linear discrete systems. These constraints include individual state variance constraints. H.. norm constraints and regional pole assignment constraints. By achieving the previous three requirements, the state feedback controller can then be solved through use of the singular value decomposition (SVD) techniques and the theory of generalized inverses. An example will be provided to demonstrate the effectiveness of the present methodology.

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In-Situ Raman Spectroscopic Study Of The Oxidation And Reduction Of Ag Electrode In Na2So4, Yan-Xia Chen, Kai-Qi Huang, Zhong-Qun Tian May 1998

In-Situ Raman Spectroscopic Study Of The Oxidation And Reduction Of Ag Electrode In Na2So4, Yan-Xia Chen, Kai-Qi Huang, Zhong-Qun Tian

Journal of Electrochemistry

In-situ Raman spectroscopy combined with cyclic voltammogram measurements was used to investigate formation of oxygen species at Ag electrode surfaces during the oxidation and reduction process in 0.1 mol/L Na2SO4 solution. The time dependent Raman spectra show that at potentials positive of 0.2 V, adsorption of oxygen atom occurs, while at the potentials positive of 0.4 V, some oxygen atoms migrate into subsurface of the Ag electrode and the other form strongly bound oxygen on the surface through chemical bond. At the same potentials, part of the silver atoms are oxidized and form Ag2SO4 …

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An Investigation On Galvanic Corrosion Behavior Of Co-Cr-Mo Alloy And Ti-6al-4v Alloy, Zhi-Jun Bai, Yin-Shun Wu, Tian-Cheng Zhang May 1998

An Investigation On Galvanic Corrosion Behavior Of Co-Cr-Mo Alloy And Ti-6al-4v Alloy, Zhi-Jun Bai, Yin-Shun Wu, Tian-Cheng Zhang

Journal of Electrochemistry

The combination of Co-Cr-Mo alloy and Ti-6Al-4V alloy is widely used as total hip prostheses. The objective of this work is to quantify the possibility of the acceleration of corrosion due to the galvanic effect. Electrochemical tests based on mixed potential and protection potential theories were used to study the galvanic corrosion behavior of coupling these alloys. The results indicated that the galvanic potential between two alloys always was in the passive potential zone of the isolated alloy respectively, and that the galvanic current of the couple is same as the corrosion current of isolated alloy under passive state. The …

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Investigation Of Pb/Pb2+ And Polypyrrole Electrodes By Use Of Ac Electrochemical-Thermal Method, Ji-Hua Zhuang, Jie Zhang, Liang-Jun Dong, Hong Xie, Zhi-Yu Jiang May 1998

Investigation Of Pb/Pb2+ And Polypyrrole Electrodes By Use Of Ac Electrochemical-Thermal Method, Ji-Hua Zhuang, Jie Zhang, Liang-Jun Dong, Hong Xie, Zhi-Yu Jiang

Journal of Electrochemistry

The values of entropy change for Br-/Br2 and Pb/Pb2+ electrode reactions were measured by use of the ac electrochemical-thermal method. The influence of alkaline pretreatment on the electrochemical behavior for a polypyrrole electrode was also investigated by this method. It was found that after alkaline pretreatment the eletrochemical activity of polypyrrole electrode was decreased obviously, but it kept partly electrochemical-thermal characteristic as same as that before pretreatment.

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Studies On Impedance Of Acid-Copper Electroplating System, Wen Deng, Zhao Liu, Xiang-Min Lin, He-Tong Guo May 1998

Studies On Impedance Of Acid-Copper Electroplating System, Wen Deng, Zhao Liu, Xiang-Min Lin, He-Tong Guo

Journal of Electrochemistry

The impedance characteristics of elementary solution (0.3 mol/L CuSO4+1.94 mol/L H2SO4) and that with the addition of 60 mg/L Cl-, 300 mg/L OP-21, 30 mg/L PEG, 10 mg/L 2thiazolinyldithiopropane sulfate (self-synthesized additive) are investigated and interpreted in terms of equivalent circuit. The results indicated: (1) Cl- ion can increase cathodic polarization. (2) A twostep reaction mechanism corresponds to Cu2+ reduction, that is: Cu2+→Cu+, Cu+→Cu(adsorption)→Cu(lattice), Cu2+ react in different forms of complex ion in sulfuric acidcupric sulfate solution with or without Cl- ion. …

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New Esr-Electrochemical Cell Designs For Coaxial Microwave Cavity, Lin Zhuang, Jun-Tao Lu May 1998

New Esr-Electrochemical Cell Designs For Coaxial Microwave Cavity, Lin Zhuang, Jun-Tao Lu

Journal of Electrochemistry

New cell designs for simultaneous electrochemical (EC) and electron spin resonance (ESR) measurements are reported for coaxial microwave cavity. Adjustable shieldings are introduced so that the working electrode can be much shorter than the full height of the cavity. Besides the traditional helical electrode, the working electrode can be cylinders made from metal plates, metallic meshes or even composite materials. The counter electrode can be placed either inside or outside the cavity. These features make the new designs more flexible than that previously reported. With a nonperforated cylindrical electrode, this cell can be used to determine the standard potential and …

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Application Of Electrochemical Process To Recycling Waste Water From Flotation Of Phosphate Ores, Shi-Xin Yu, Wen Sun May 1998

Application Of Electrochemical Process To Recycling Waste Water From Flotation Of Phosphate Ores, Shi-Xin Yu, Wen Sun

Journal of Electrochemistry

The waste water from flotation of phosphate ores can be used to recycling by electrochemical process. The suitable factors of electrochemical process is made by measuring ζ potential and transmittance of the waste water in modified way.

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Studies Of Surface Alloy As High Efficient Electrocatalyst For Glyoxylic Acid Synthesis, Sheng-Pei Chen, Sheng-Qing Xia, Shi-Gang Sun May 1998

Studies Of Surface Alloy As High Efficient Electrocatalyst For Glyoxylic Acid Synthesis, Sheng-Pei Chen, Sheng-Qing Xia, Shi-Gang Sun

Journal of Electrochemistry

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