Estimation of the superhigh-frequency magnetic permeability of alsifer from the measured permeability of composites

The magnetic permeability of alsifer was restored from the frequency dependences of the dielectric and magnetic permeabilities of powder alsifer (AlSiFe alloy)–wax matrix composites. The permeabilities were measured using the coaxial line technique within a frequency range of 0.05–20 GHz. The effect of the concentration, shape, and size of powder particles on the microwave magnetic properties of composites was considered. A good agreement between the measurement results and the Maxwell–Garnett formula generalized with consideration for the particle shape, the percolation threshold, and the skin-effect was obtained. The found sizes of particles agreed with electron microscopy and granulometry data. Both the frequency and the ferromagnetic resonance line figure of merit (FOM) for lamellar particles proved to be higher than for spherical ones. Alsifer powders were shown to be promising fillers for radioabsorbing materials.     

Measurement of electrode overpotentials for direct hydrocarbon conversion fuel cells

Cathodic and anodic overpotentials were measured using current interruption and AC impedance spectroscopy for two separate solid oxide fuel cells (SOFCs). The fuel cells used yttria-stabilized zirconia (YSZ) as the electrolyte, strontium-doped lanthanum manganite (LSM) as the cathode, and a porous YSZ layer impregnated with copper and ceria as the anode. The Cu/CeO₂/YSZ anode is active for the direct conversion of hydrocarbon fuels. Overpotentials measured using both current interruption and impedance spectroscopy for the fuel cell operating at 700 °C on both hydrogen and n-butane fuels are reported. In addition to providing the first electrode overpotential measurements for direct conversion fuel cells with Cu-based anodes, the results demonstrate that there may be significant uncertainties in measurements of electrode overpotentials for systems where there is a large difference between the characteristic frequencies of the anode and cathode processes and/or complex electrode kinetics.     

Electrode processes of LaCoO3+La2Zr2O7 cathodes deposited onto GCO

A combination of dc and ac results was used to study the electrode processes of LaCoO₃+La₂Zr₂O₇ cathodes deposited onto a GCO electrolyte, in air and in the range 600–800 °C. Steady state polarisation results showed that the overpotential values are very dependent on the electrode microstructures, which might be optimised by changes in the deposition and/or firing conditions of the electrodes. Tafel plots suggest different mechanisms under low and relatively high cathodic polarisation, with a transition at about −0.2 V at 700 °C. The transition tends to be displaced towards higher cathodic overpotentials with decreasing temperatures. The exchange current density is higher in the high polarisation regime (high values of |η|) than under low polarisation, and the exchange coefficient is lower in the range of high |η| The changes in pseudocapacitance and electrode resistance extracted from ac results also indicate a change in the regime. Paper presented at the 6th Euroconference on Solid State Ionics, Cetraro, Calabria, Italy, Sept. 12–19, 1999.     

Information-Corrected Estimation: A Generalization Error Reducing Parameter Estimation Method

Modern computational models in supervised machine learning are often highly parameterized universal approximators. As such, the value of the parameters is unimportant, and only the out of sample performance is considered. On the other hand much of the literature on model estimation assumes that the parameters themselves have intrinsic value, and thus is concerned with bias and variance of parameter estimates, which may not have any simple relationship to out of sample model performance. Therefore, within supervised machine learning, heavy use is made of ridge regression (i.e., L2 regularization), which requires the the estimation of hyperparameters and can be rendered ineffective by certain model parameterizations. We introduce an objective function which we refer to as Information-Corrected Estimation (ICE) that reduces KL divergence based generalization error for supervised machine learning. ICE attempts to directly maximize a corrected likelihood function as an estimator of the KL divergence. Such an approach is proven, theoretically, to be effective for a wide class of models, with only mild regularity restrictions. Under finite sample sizes, this corrected estimation procedure is shown experimentally to lead to significant reduction in generalization error compared to maximum likelihood estimation and L2 regularization.     

Carbon-to-metal bonds: Electrochemical reduction of 2-butenenitrile

2-Butenenitrile belongs to the large family of electron deficient vinylic monomers that usually form 100 to 500 nm thick grafted polymer films by electroreduction. However, 2-butenenitrile exhibits a slightly acidic hydrogen atom on its CH₃ group that inhibits the anionic polymerization usually observed with ‘classical’ organic monomers such as its isomer methacrylonitrile. 2-Butenenitrile thus gives nanometer thick grafted film by electroreduction, essentially composed of a mixture of monomers, dimers and trimers and in the same way, allows an easy observation by XPS of the chemical signature of the grafting, i.e. the carbon-to-nickel bond, observed at 283.6 eV.     

Adjustable microwave permeability of nanorings: A micromagnetic investigation

Based on the three-dimensional micromagnetic simulations, we present a method to tailor the microwave permeabilities of magnonic metamaterials cells by a designed nanoring structure. The results show that the permeabilities and resonant frequency are depended on the wall?s thickness of nanorings. The underlying mechanism is ascribed to the presence of strong demagnetization fields, which are associated to the ring?s wall. In addition, the products of magnetic susceptibility and resonant frequency are larger than that predicted from Snoek?s law in polycrystalline particles. These results are direct manifestations of the bi-anisotropy model.     

Electrochemical evaluation of ultrasonic cleaning: the Galvani potential

We show that measurements of the Galvani potential between two titanium electrodes can give a quantitative on-line measure of ultrasonic cleaning efficiency. One titanium electrode is the reference (clean) electrode, and the other has adsorbed contaminant to be evaluated. The potential between them is read by using a high impedance millivoltmeter. The method is capable of detecting small fractions of protein or lipid monolayers, and is about as sensitive as the radioactive tracer technique to which it is compared. The Galvani potential method can only be used on a restricted number of electrode materials, including titanium, gold, platinum and vitalium, but not including stainless steel, nickel alloys or aluminium.     

Electrochemical solid state gas sensors: An overview

Gas sensors has been currently in great demand because of serious concern over environmental pollution and public health considerations resulting from tremendous growth of industrialisation. Concurrently, there have been continuous efforts to obtain sensors with improved performance. The performance of any solid-state electrochemical gas sensor has been always rated on its response time, thermodynamic stability, operating temperature, gas sensing ability, sensitivity and gas concentration range, which is to be sensed. This article reviews the factors contributing towards a gradual development of electrochemical solid-state gas sensors in terms of a continuous tailoring of its two basic components, i.e. solid electrolyte and reference electrode. Invited paper presented at the Third International Conference on Ionic Devices (ICID 2006), Chennai, Tamilnadu, India, Dec. 7–9, 2006.     

Statistical mechanics of networks: Estimation and uncertainty

Exponential random graph models (ERGMs) are powerful tools for formulating theoretical models of network generation or learning the properties of empirical networks. They can be used to construct models that exactly reproduce network properties of interest. However, tuning these models correctly requires computationally intractable maximization of the probability of a network of interest—maximum likelihood estimation (MLE). We discuss methods of approximate MLE and show that, though promising, simulation based methods pose difficulties in application because it is not known how much simulation is required. An alternative to simulation methods, maximum pseudolikelihood estimation (MPLE), is deterministic and has known asymptotic properties, but standard methods of assessing uncertainty with MPLE perform poorly. We introduce a resampling method that greatly outperforms the standard approach to characterizing uncertainty with MPLE. We also introduce ERGMs for dynamic networks—temporal ERGM (TERGM). In an application to modeling cosponsorship networks in the United States Senate, we show how recently proposed methods for dynamic network modeling can be integrated into the TERGM framework, and how our resampling method can be used to characterize uncertainty about network dynamics.     

阻隔材料的气体渗透率

对气体渗透阻隔材料的渗透率与气体温度、气体压强的关系进行了理论分析,得到了在不同温度和气体压强条件下渗透率的加速因子的计算式,理论计算结果与相关文献中实验测量结果比较一致。根据加速条件下进行的水蒸气、氧气和二氧化碳对聚对苯二甲酸（PET）和环氧树脂渗透率测量的结果,计算得到在常温常压条件下这些气体对0.155 mm厚PET塑料的渗透率和对0.065 mm厚环氧树脂的渗透率。     

阻隔材料的气体渗透率

对气体渗透阻隔材料的渗透率与气体温度、气体压强的关系进行了理论分析,得到了在不同温度和气体压强条件下渗透率的加速因子的计算式,理论计算结果与相关文献中实验测量结果比较一致。根据加速条件下进行的水蒸气、氧气和二氧化碳对聚对苯二甲酸（PET）和环氧树脂渗透率测量的结果,计算得到在常温常压条件下这些气体对0.155 mm厚PET塑料的渗透率和对0.065 mm厚环氧树脂的渗透率。     

Validity of the permeability Carman-Kozeny equation: A volume averaging approach

A volume averaging approach is used to estimate the porous media permeability. Contrary to traditional methods that rely on solving the Navier-Stokes equations for laminar flow, this approach has the advantage that it does not require the specification of some physical conditions and parameters (pressure drop and viscosity). Numerical results on synthetic models of porous media showed that (i) the local porous medium configuration has an important effect on the permeability value, and (ii) the Carman-Kozeny equation cannot describe the permeability behavior as a function of porosity and characteristic lengths. In turn, our results indicate that simple empirical equations, commonly used in practice, are unable to describe the permeability functionalities over a broad range of porous media configurations.     

Electrochemical cleaning of metallic surfaces

The aim of this research is to investigate the feasibility of depleting or modifying solid steel’s surface layer by electrochemically affecting the non-metallic inclusions, such as oxides and sulphides, thus providing zero calibration and modified surface properties. It has been shown that this is possible by decomposing or modifying non-metallic inclusions. This is achieved by the application of cathodic refining of the surface of solid steel, utilising molten salt as the electrolyte. The thermodynamic and electrochemical basis of the experimental results is presented, along with SEM/EDX information. Paper presented at the 6th Euroconference on Solid State Ionics, Cetraro, Calabria, Italy, Sept. 12–19, 1999.     

Electrochemical synthesis and characterization of a new conducting polymer: Polyrhodanine

An antimicrobial drug, rhodanine (Rh), was electrochemically polymerized on a Pt electrode using cyclic voltammetry (CV). The high quality and homogeneous polyrhodanine (pRh) films with a dark-purple color were obtained. The chemical structure characterization was investigated by Fourier transform infrared spectroscopy (FTIR) and UV-vis spectroscopy techniques. Further, thermogravimetric analysis (TGA) and differential thermal analysis (DTA) techniques used to investigate thermal properties of the film. It is found that thermal stability of pRh films is relatively high. It is also observed that tetrahydrofurane (THF) and N-methyl-2-pyrrolidone (NMP) are good solvents for the polymer.     

Electrochemical characterization of nanostructured zirconias

Redox stability of cubic nanostructured zirconia ceramics, free of any secondary phases, has been investigated experimentally as a function of grain size. Pure 8 mol% Y₂O₃-doped ZrO₂ powders were synthesized by a spray pyrolysis process and then compacted by uniaxial pressing, followed by cold isostatic pressing. Using appropriate thermal treatments, average grain sizes ranging from 25 to 242 nm and relative densities from 71% up to 98% were obtained. An electrochemical characterization was performed with comparison on ceramics of 3.2 and 7.6 μm and 98% of theoretical density starting from commercial YSZ powder.     

Electrochemical promotion of environmental catalysis

Electrochemical catalysts were used for environmental applications, such as the clean production of energy from propane and propene combustion, the elimination of VOC's like propene and the NOx abatement All the selected electrochemical catalysts were composed of a Pt film deposited on YSZ, NASICON or CGO. It was found that all these chemical reactions can be electropromoted. Moreover, the reaction rates can be in-situ tuned by applying a polarisation. Furthermore, the selectivity of Pt-based electrochemical catalysts can be modified in order to avoid the formation of pollutant. Finally, EPOC can improve the lifetime of a catalyst by inhibiting its poisoning by carbonaceous species. Paper presented at the Patras Conference on Solid State Ionics — Transport Properties, Patras, Greece, Sept. 14–18, 2004.     

Electrochemical detection of bubble oscillation

The interaction of a tethered bubble with sound is demonstrated using novel electrochemical characterisation technology. A 25 microm diameter microelectrode, positioned close to the gas/liquid interface is used to monitor the motion of the bubble wall as a function of time in the presence and absence of sonic irradiation. Evidence for 'breathing' mode oscillation of the bubble and its effect on mass transfer to the microelectrode is presented.     

High-frequency magnetic permeability of nanocomposite film

The high-frequency magnetic permeability of nanocomposite film consisting of the single-domain spherical ferromagnetic particles in the dielectric matrix is studied. The permeability is assumed to be determined by rotation of the ferromagnetic inclusion magnetic moments around equilibrium direction in AC magnetic field. The composite is modeled by a cubic array of ferromagnetic particles. The magnetic permeability tensor is calculated by solving the Landau–Lifshits–Gilbert equation accounting for the dipole interaction of magnetic particles. The permeability tensor components are found as functions of the frequency, temperature, ferromagnetic inclusions density and magnetic anisotropy. The obtained results show that nanocomposite films could have a rather high value of magnetic permeability in the microwave range.