Engineering Science and Materials Commons^™

Studies On Coordination Behavior Of Dimethyl Sulfoxide In Complex Of Rare Earth With Cryptand, Shichang Liu, Tianpei Zhu

Journal of Electrochemistry

Electrochemical reduction reaction in the course of the titration of Eu(2.2.2) and Eu(2.2) using strong bonding solvent, DMSO, in C₂H₄Cl₂ has been investigated by cyclic voltammetry. The greater the concentration of strong bonding solvent, the more negative the half-wave potentials for the reduction reaction are. The coordination number of Eu(2.2.2) and Eu(2.2) which are 2 and 3 respectively, with DMSO can be calculated, according to the relations between half-wave potentials and the variety of concentration of DMSO.

Distortion And Evolution Of A Localized Vortex In An Irrotational Flow, Joseph F. Lingevitch, Andrew J. Bernoff

All HMC Faculty Publications and Research

This paper examines the interaction of an axisymmetric vortex monopole, such as a Lamb vortex, with a background irrotational flow. At leading order, the monopole is advected with the background flow velocity at the center of vorticity. However, inhomogeneities of the flow will cause the monopole to distort. It is shown that a shear‐diffusion mechanism, familiar from the study of mixing of passive scalars, plays an important role in the evolution of the vorticity distribution. Through this mechanism, nonaxisymmetric vorticity perturbations which do not shift the center of vorticity are homogenized along streamlines on a Re1/3 time scale, much faster …

Studies Of Elecctrochcmical Oscillation Of Au/Hcl In Presence Of ″Positive Feedback″Of Substrate Electrodes, Bin Ren, Bingwei Mao, Xiongwei Cai, Tao Jiang, Jiqian Mu

Journal of Electrochemistry

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A Photoelectrochemical Investigation Of Zirconium Oxide Film, Maizhi Yang, Ping Wei, Di Quarto F., Piazza S., Sunseri C.

Journal of Electrochemistry

A photoelectrochemical investigation has been carried out on zirconium initialoxide film and its oxide film grownanodically at constant rate up to different thickness. Both anodicand cathedic photocurrents on the photocurrent spectrum depended on the potential, but had littlerelation with the forming anedic films or measuring solutions. Photocurrent spectrum and photocurrenttransients suggested that the oxide films on zirconium were duplex layers structure. The internal layerwas ZrO₂ and the external layer ZrO₂·(H₂O)_n. The photocurrent included photogenerated carrier ininternal and external oxide films, as well as internal photoinjection process for electrons from thesubstrate metal into the …

Application Of Inhibitor To Improve The Anticorrosion Performance Of Electrophoretic Coating, Changshou Cai, Fangteng Su, Bihuan Liu, Guomou Wen, Jingdong Guo, Renxin Liu, Weidong Tian

Journal of Electrochemistry

To improve the anti-corrosion performance of electrocoating, organic andinorganic inhibitors are applied in an anodic electrophoretic-coating. The results show that the deposition of polymer with zinc phospate exhibits a high inbihition efficiency. The inhibition mechanism of the inhibitor in electrocoating has been studied.

A Investigation Of Hydrogen-Storage Alloy As Catalytic Electrode For Hydrogenation Of Nitrobenzene, Shigang Lu, Hanxi Yang, Changfa Wan

Journal of Electrochemistry

Since hydrogen-storage alloy ean not only absorb hydrogen atoms to form highlyreactive metal hydride as hydrogen source by electrolysis but also possesses a certain catalytic activityfor hydrogenation,it is thus feasible to utilize the allov as a novel electrode for electrolvtichydrogenation in organic electroreduction. This work employed misch metal AB₅ type alloy as acatalytic electrode and studied the electrochemical hydrogenation of nitrobenzene.

The hydrogen-storage electrode (MH) was a plastic bonded electrode sheet made from a paste of Mm(NiCoMnAl)₅ alloy powder and teflon emulsion. The electrolysis was performed at constantcurrent and controlled potential in a three electrode cell of H-type …

Transient Photocurrent Behavior Of Multiple Quantum Well Gaas/AlXGa(1-X)As Electrode, Liu Yao, Xurui Xiao, Yuan Lin, Yiping Zeng, Dianzhao Sun, Haiqun Zheng

Journal of Electrochemistry

Transient photocurrents induced by short light pulses at lattice-matched multiplequantum well (MQW)GaAs/Al_0.3)Ga_0.7 As electrodes were studied in the 1 ×10^-2 mol·dm^-3 ferrocene([Fc⁰]/[Fc⁺]=9/1)-0.1 mol·dm^-3 tetrabutylammonium tetrafluoroborate acetonitrile solutionin order to examine the relaxation photoprocesses and to evaluate kinetic parameters of superlattice electrodes.

GaAs/Al_0.3Ca_0.7 As MQW electrode consisting of 10 periods with each of GaAs well (5.3 nm) and Al_0.3Ga_0.7. As barrier (10 nm) showed two pronounced and well-resolved peak structures located at 1.503 eV and 1.699 eV in the photocurrent spectrum, corresponding to the …

Synthesis Of LiXCoo2 And Its Behaviour In Rechargeable Lithium Battery, Mingfeng Guo, Ruimin Yang, Zebo Zhang, Jincao Ye

Journal of Electrochemistry

The Variations of crystal lattice parameters of Li_xCoO₂ during charge anddischarge have been st ud ied by XRD and AAR spectroscopy. It was found that the Li_xCoO₂ crystalvolume expanded during charge and contracted during discharge. The crystal lattice structure was broken because of the formation of Co₃O₄ when deeply charge.The variation of lattice parameter C₀ value in cycling process was similar to that in charge process.The variation of 006 peak was the mostsensitive in every case. In case of preheating for 20 hours at 700℃ before operating high temperature, the …

The Effect Of Some Ions On Cr2O72- Anodic Formation Process At Pt And Pbo2 Electrodes, Shixiong Jin, Zhigang Zhou, Lan Wang

Journal of Electrochemistry

The influence of Ag₂SO₄, Li₂SO₄, Na₂SO₄, K₂SO₄, (NH₄)₂SO₄,MgSO₄ and KF on the evolution of O₂ and the formation of Cr₂O at Pt and PbO₂ anodes was investigated in mixed H₂SO₄-Cr₂(SO₂)₃ solutions. The kinetic data related respectively to Cr₂O formation and O₂ evolution at Pt and PbO₂ anodes were measured by method of resolving the steady-state polarization curve. The Tafel slope …

Self Assembly Via Layer By Layer Surface Reaction On Gold Electrodes And The Electrochcmical Characterization, Xiandui Dong, Juntao Lu, Chuanxin Cha

Journal of Electrochemistry

The self-assembled monolayers,which were built by spontaneous adsorption of ω-carboxylic acid thiols on gold surface,were used as substrate for further modification through later bylayer amide surface reactions. At each stage of modification,the gold surface was characterizedelectochemieally. The results demonstrated that the strategies of layer by layer self assembly is ofsignificant potential for fabrieating functionalized ultrathin layers.

Electroreduction Of The Nittobenzene On Titanium Electrode Implanted With Palladium, Zhongda Wu, Xianjun Zhu, Hongsen Wang

Journal of Electrochemistry

The titanium substrates were bombarded with 1×10¹⁷～5×10¹⁷ ions·cm^-2 ofpalladium at the room temperature. The surface composition of implanted electrode and concentration-depth profiles of various elements were measured by AES. The electrored uction processes ofnitrobenzene (NB) in 0.1 mol/L NaOH solution at Pd/Ti electrodes have been investigated by cyclicvoltaivimetry. The results show that the palladium implanted titanium electrodes exhibit a high catalyticactivity in the electroreduction of NB. The NB radical anion, which is the product of one-electronelectroreduction of NB, was detected by ESR in-situ in conjunction with electrochemical methods. Aniline was also detected as a product of …

Electroreduction Of Holmium Ion On Iron Electrde In Molten Cholorides, Qiqin Yang, Guankun Liu, Yuzhi Su

Journal of Electrochemistry

The cyclic voltammetry, open circuit potential-time curve after poteritiostatic electrolysis, current-time curve at potential step, X-ray diffraction and electron probe microanalysiswere used to investigate the electrode process of Ho(Ⅲ) reduced on iron electrode in molten chloridesand the phases of surface alloy layer. The Ho-Fe alloys are formed at first, and then the metallic holmium is deposited when Ho(Ⅲ) is reduced on iron electrode. The charge transfer is reversible. The free energies of formation for the four inter metallic compounds of Ho-Fe system, the diffusion coefficients and diffusion activation energy of Ho in alloyed cathode are determined.

Electrocatalytic Oxidation Of Formaidehyde And Formic Acid On A Pt/SbAd Electrode, Hong Li, Lincai Jiang, Xiong Jiang

Journal of Electrochemistry

The electrocatalytic activity for the oxidation of formaldehyde and formic acid ona Sb-modified platinum (Pt/Sb_ad) was investigated. Results showed that the Pt/Sb_ad electrode was electrocatalytically more active than a Pt electrode in the anodic oxidation of formaldehyde and formicacid. In the case of formaldehyde, an oxidation peak appeared at a potential of ca. 0.7V. During the oxidation of formic acid, a 4-fold increase in the 1st peak current was observed. The Sb-modified platinum electrode was found to be most electrocatalytically active at a coverage of 0.75±0.05. The electrocatalytic activity of the Pt/Sb_ad electrode can be best …

The Study Of The Growth Processes Of The Oxides On Lead Electrodes In Sulfuric Acid Solution, Hesheng Zhai, Xuguang Chen, Jinkua You, Yong Yang, Zugeng Lin

Journal of Electrochemistry

The growth processes of PbO and PbO₂ on lead electrodes have been investigatedby using in-situ methods that are combined with temporary AC resistance measurment technique and in-situ laser scanning photoelectrochemical microscopy. It is found that a linear relationship existsbetween the electrode resistance(R) and^1/2 after the electrode is oxidized at +0.6 V(vs.Hg/H₂SO₄/35% H₂SO₄) for more than 5 min. This result suggests that the growth of PbO is well distributed during the early stage of oxidation. The study by using laser scanning photoelectrochemical microscopy has further proved this point. The results also …

The Electrode Process Of Y(Ⅲ) On Copper Electrode And Its Surface Metallizing, Chungen Zhou, Shuzhen Duan

Journal of Electrochemistry

The reduction of yttrium ion on copper electrode in NaCl-KCl-YCl₃ molten saltshas been investigated. The results indicate that the formation of intermetallic compounds is occuredbefore the metallic yttrium to be formed. The formation of intermetallic compounds is controlled bythe process of which yttrium atoms are diffusing into copper electrode. The kinetic characters todiffusion of yttrium atoms were also discussed.

The Catalytic Behavior For Ni-W Electrode Modified By Carbon Ion Beam Implantion, Jishuang Zhang, Yaojiao Lv, Qinglian Li, Baoen Shen

Journal of Electrochemistry

The hydrogen evolution activity in acidic and basic mediums for Ni-W electrodemodified by carbon ion bean implantation was investigated. The experimental results show thiselectrode has superior catalytic activity for the hydrogen evolution reaction than that of the unmodified Ni-electrode. Long period testing of electrolysis under high current density show that this electrode hasalonger useful life hence it is a practical electrode material. The temperature effect of electrocatalytic property was also inverstigated. The experimental regularities are explained on the basis of the formation of surface multialloys of Ni-W-WC.

Model For Complete Drawdown Of Floating Solids In Stirred Tank Reactors, J Mmbaga

Tanzania Journal of Engineering and Technology (TJET)

A Semi-empirical model has been developed on the basis of Kolmogoroff's theory of isotropic turbulence to determine the minimum drawdown speed for floating solids in a mechanically agitated vessel. An adjustable pa- rameter in the model is found to be afunction of impeller type and position in a vessel. A simplified representation of macroscopicflow pattern, rep- resenting the circulation flow in a vessel depending on impeller pumping characteristic is developed to account for recirculation pattern.

Rapid Relaxation Of An Axisymmetric Vortex, Andrew J. Bernoff, Joseph F. Lingevitch

All HMC Faculty Publications and Research

In this paper it is argued that a two‐dimensional axisymmetric large Reynolds number (Re) monopole when perturbed will return to an axisymmetric state on a time scale (Re^1/3) that is much faster than the viscous evolution time scale (Re). It is shown that an arbitrary perturbation can be broken into three pieces; first, an axisymmetric piece corresponding to a slight radial redistribution of vorticity; second, a translational piece which corresponds to a small displacement of the center of the original vortex; and finally, a nonaxisymmetric perturbation which decays on the Re^1/3 time scale due to a shear/diffusion …

Investigation Of Computational And Spectral Analysis Methods For Aeroacoustic Wave Propagation, Florence Odile Vanel

Mechanical & Aerospace Engineering Theses & Dissertations

Most computational fluid dynamics (CFD) schemes are not adequately accurate for solving aeroacoustics problems, which have wave amplitudes several orders of magnitude smaller yet with frequencies larger than the flow field variations generating the sound. Hence, a computational aeroacoustics (CAA) algorithm should have minimal dispersion and dissipation features. A dispersion relation preserving (DRP) scheme is, therefore, applied to solve the linearized Euler equations in order to simulate the propagation of three types of waves, namely: acoustic, vorticity, and entropy waves. The scheme is derived using an optimization procedure to ensure that the numerical derivatives preserve the wave number and angular …

Influence Of Turbulence On Methane-Air Flame Speed, E Mushi

Tanzania Journal of Engineering and Technology (TJET)

Experimental study Of the influence qfturbulence on flame speed for meth- ane-air mixtures has been conducted in afan stirred bomb using schlieren photography. It has been observed that turbulence increases flame speed but above KLe=O. 18 (KLe is the product Of the dimensionless Karlovitz flame stretch factor and the Lewis number) turbulence quenches the flame. Inminarflame kernel is observed to prevail in the early stages of flame development in a turbulent mixture. Further, the laminar burning velocity plays a significant role in turbulent combustion. It is proposed that the increase in flame speed is a result of flame wrinkling.

A Direct Numerical Simulation Of Vortex Breakdown Induced Tail Buffet, Steven James Massey

Mechanical & Aerospace Engineering Theses & Dissertations

A simulation of tail buffet is presented for a delta wing-vertical tail configuration. Flow conditions are chosen such that the wing primary-vortex cores experience vortex breakdown and the resulting turbulent wake flow impinges on the vertical tail. The dimensions and material properties of the vertical tail are chosen such that the deflections are large enough to insure interaction with the flow, and the natural frequencies are high enough to facilitate a practical computational solution. This multidisciplinary problem is solved sequentially for the fiuid flow, the elastic deformations and the grid displacements. The fluid flow is simulated by time accurately solving …

Simulation Of Vertical Tail Buffet In Internal Vortex Breakdown Flows, Mark William Flanagan

Mechanical & Aerospace Engineering Theses & Dissertations

Computational simulation of vertical tail buffet in an internal vortex breakdown flow is considered. The fiuid-flow problem is formulated using the full, compressible, unsteady Navier-Stokes equations which are solved using an implicit, flux-difference splitting, finite volume scheme. The fluid-flow problem is solved in a configured circular duct using quasi-axisymmetric assumptions to simplify the flow equations. A plate is placed transverse to the incoming flow. Solution of the flow in the duct is performed with and without a rigid plate, and with and without an elastic plate. The elastic response of the plate is calculated assuming that it is a cantilever …

Optimum Design For Spring With Orthogonal Design Method, Han Fu - Jie

Tanzania Journal of Engineering and Technology (TJET)

Orthogonal design method is a sort of direct optimum method, by which the op- timal result may be obtained through simple computation and analysis. This method has gained increasingly extensive interest in scientific research, engineering design, end production management as well. The orthogonal table is the basic instrument for carrying out optimum design with orthogonal design method. It is a mathernatical table established On the basis Of the idea of isostatic distribution. As various levels may appear in any column, it makes a partial experiment contain levels of all factors furthermore. RII combina- tions of any two columns may appear …

Hierarchical Flux-Based Thermal-Structural Finite Element Analysis Method, Sandra P. Polesky

Mechanical & Aerospace Engineering Theses & Dissertations

A hierarchical flux-based finite element method is developed for both one- and two-dimensional thermal-structural analyses. Derivation of the finite element equations is presented. The resulting finite element matrices associated with the flux-based formulation are evaluated in closed-form. The hierarchical finite elements include additional degrees of freedom in the approximation of the element variable distributions by the use of nodeless variables. The nodeless variables offer increased solution accuracy without the need for defining actual nodes and rediscretizing the finite element model. Thermal and structural responses obtained using the hierarchical flux-based method are compared with results obtained from a conventional linear finite …

Numerical Investigation Of A Non-Newtonian Material Through A Sudden Pipe Expansion, V. G. Masanja

Tanzania Journal of Engineering and Technology (TJET)

A numerical method for solving two dimensional elliptic boundary-value problems of fourth order is used for finding stationary solutions of the equations of motion for a laminar flow through a sudden pipe expansion of an incompressible non-Newtonian fluid with a constitutive equation of the Reiner-Rivlin (R-R) type. Results for the Newtonian fluid, which is a special case, are in excellent agreement with those by previous investigators and they demonstrate the reliability, superiority and accuracy of the method. Results for the non-Newtonian cases could be of value for fixing ideas about visco-elastic behaviour although the R-R fluid allows only inelasticity: this …

Application Of Shape Sensitivity Analysis For Computation Of Transient Free-Surface Flows, Frank Nicolas Michel

Mechanical & Aerospace Engineering Theses & Dissertations

Shape sensitivity analysis is introduced into a numerical scheme simulating a transient free-surface flow and applied to the case of a fluid advancing through a bed of cylinders. For this incompressible Newtonian flow, viscous forces are dominant. A penalty function finite element formulation is used to solve the problem. Coordinates of nodes on the moving boundary are chosen as design variables and an analytical formulation of the gradient of the finite element algebraic system, with respect to these variables, is derived.

In a numerical example, the results obtained with and without sensitivity analysis are compared. The efficiency and accuracy of …

An Application Of Global Optimization Algorithm For Modal Parameter Identification, Chung-Men Chen

Mechanical & Aerospace Engineering Theses & Dissertations

Single-mode projection filters for modal parameter identification for flexible structures are introduced. An effective two-dimensional global optimization method using interval analysis is combined with the projection filters to facilitate identification for modal frequency and damping. A numerical simulation of a ten-mode structure is presented to illustrate the feasibility of the new method. The projection filters are practical for parallel processing implementation.

Finite Element Thermal-Structural Analysis Of Cable-Stiffened Space Structures, Ajay Kumar Pandey

Mechanical & Aerospace Engineering Theses & Dissertations

Finite element thermal-structural analyses of cable-stiffened space structures are presented. A computational scheme for calculation of prestresses in the cable-stiffened structures is also described. The determination of thermal loads on orbiting space structures due to environmental heating is described briefly. Three finite element structural analysis techniques are presented for the analysis of prestressed structures. Linear, stress stiffening and large displacement analysis techniques are investigated.

The three techniques are employed for structural analysis of prestressed cable structures at different prestress levels. The three analyses produce similar results at small prestress. but at higher prestress differences between the results become significant. For …

An Apparatus For Measuring The Thermal Conductivity Of Cast Insulation Materials, Christine A. Wilkins, Robert L. Ash

Mechanical & Aerospace Engineering Faculty Publications

A steady-state apparatus has been developed for measuring the thermal conductivity of cast materials. The design has employed a novel thermal symmetry arrangement which can permit total electrical isolation of the test material from its surroundings. © 1980 American Institute of Physics

Effect Of Compliant Wall Motion On Turbulent Boundary Layers, Dennis M. Bushness, Jerry N. Hefner, Robert L. Ash

Mechanical & Aerospace Engineering Faculty Publications

A critical analysis of available compliant wall data which indicated drag reduction under turbulent boundary layers is presented. Detailed structural dynamic calculations suggest that the surfaces responded in a resonant, rather than a compliant, manner. Alternate explanations are given for drag reductions observed in two classes of experiments: (1) flexible pipe flows and (2) water-backed membranes in air. Analysis indicates that the wall motion for the remaining data is typified by short wavelengths in agreement with the requirements of a possible compliant wall drag reduction mechanism recently suggested by Langley. Copyright © 1977 American Institute of Physics.