Design parameters for an electrochemical cell with porous electrode to treat metal-ion solution

An electrochemical reactor was designed and operated to treat the solution containing copper ions. Design parameters for the electrochemical reactor using the porous cathode and RuO2/IrO2/Ti anode were investigated. The porous cathode was prepared by the electroless nickel deposition on polyurethane. The apparent current, the gap between cathode and anode, and hydraulic retention time (HRT) were selected as design parameters. The copper removal rate increased with an increase in apparent current. It was not affected by the gap between the cathode and the anode. A reduction in hydraulic retention time stimulated the mass transfer toward the electrode and increased the cathodic current efficiency. Dimensional analysis was conducted to obtain the design equation for scale-up of the electrochemical reactor. The dependence of Sh on Re, Sc, and characteristic lengths, DC/A/L and DW/C/L, was described in the form of a power series. The coefficients were obtained from experimental data.     

Asymmetric wave propagation in a transversely isotropic half-space in displacement potentials

With the aid of a complete representation using two displacement potentials, an efficient and accurate analytical derivation of the fundamental Green’s functions for a transversely isotropic elastic half-space subjected to an arbitrary, time-harmonic, finite, buried source is presented. The formulation includes a complete set of transformed stress-potential and displacement-potential relations that can be useful in a variety of elastodynamic as well as elastostatic problems. The present solutions are analytically in exact agreement with the existing solutions for a half-space with isotropic material properties. For the numerical evaluation of the inversion integrals, a quadrature scheme which gives the necessary account of the presence of singularities including branch points and pole on the path of integration is implemented. The reliability of the proposed numerical scheme is confirmed by comparisons with existing solutions.     

The use of MWCNT to enhance oxygen reduction reaction and adhesion strength between catalyst layer and gas diffusion layer in polymer electrolyte membrane fuel cell

The pore structure and pore volume of catalyst layer (CL) were controlled by utilizing multi-walled carbon nanotube (MWCNT). According to the increase in MWCNT ratio in CL, the primary pore (below 100 nm) volume concerning with the phosphoric acid penetration to the reaction site was decreased and the secondary pore (approximately 1 μm) volume relating with oxygen gas transportation was increased, respectively. However, the excessive addition of MWCNT was detrimental to electrochemical properties due to the difficulty of phosphoric acid penetration to the reaction site and the opposite influx of phosphoric acid to the secondary pore. Furthermore, the adhesion strength between CL and gas diffusion layer (GDL) was improved by only 10% addition of MWCNT. Therefore, it is suggested that the ratio of MWCNT in CL can be key role for obtaining the optimized pore volume, enhanced adhesion strength, and good performance of polymer electrolyte membrane fuel cell (PEMFC).     

The heat capacity of cadmium telluride at medium and high temperatures

The modified Schomeit method for processing enthalpies (H _T ⁰ -H _298.15 ⁰ ) is suggested, which provides for agreement between high-temperature data on C _p both with a reliably measured value of C _{p, 298.15} ⁰ and with derivative $\left( {\frac{{\partial C_p^0 }}{{\partial T}}} \right)_{298.15} $ . The latter gives a “smoother” joining of dependences C _p (T) obtained experimentally with different accuracy. The suggested procedure is applied to analysis of experimentally obtained distributions of heat capacity of cadmium telluride as a function of temperature, and a new approximating equation is obtained for the most reliable data in the range from 298 K to the melting point of CdTe. This procedure is compared to other known methods of simultaneous processing of C _p (T) data. It is demonstrated that the values of heat capacity of CdTe recommended by us agree with reliably determined coefficients of thermal expansion (CTE) of this compound. The characteristic Debye temperature of cadmium telluride is estimated in a wide temperature range, and the pattern of its variation with temperature is analyzed.     

Algal wastewater treatment systems for seasonal climates: application of a simple modelling approach to generate local and regional design guidelines

Algal waste stabilisation ponds (WSP) provide a means of treating wastewater, and also a potential source of water for re-use in irrigation, aquaculture or algal biomass cultivation. The quantities of treated water available and the periods in which it is suitable for use or discharge are closely linked to climatic factors. This paper describes the application, at a continent-wide scale, of a modelling approach based on the use of readily available climate datasets to provide WSP design and performance guidelines linked to geographical location. Output is presented in regionally-based contour maps covering a wide area of Russia and central Asia and indicating pond area, earliest discharge date, discharge duration, wastewater inflow:outflow ratio and salinity under user-specified conditions. The results confirm that broad-brush discharge guidelines of the type commonly used in North America can safely be applied; but suggest that a more detailed approach is worthwhile to optimise operating regimes for local conditions. The use of long-series climate data can also permit tailoring of designs to specific sites. The work considers a simple 2-pond system, but other configurations and operating regimes should be investigated, especially for the wide range of locations across the world that are intermediate between the ‘one short discharge per year’ mode and year-round steady-state operation.     

Electrocatalytic performance of Ba-doped TiO2 hollow spheres in water electrolysis

Barium doped titania hollow sphere catalysts of various compositions were prepared and their electrocatalytic performance was evaluated in acidic media. Titania hollow sphere particles were prepared using poly (styrene–methacrylic acid) latex as template material, and BaCl₂ was used precursor material during barium doping over spheres. The morphology and structure of Ba/TiO₂ hollow spheres were characterized by BET, XRD, TGA and TEM analysis. XRD results had confirmed the presence of rutile TiO₂ and BaTiO₃ phases in the catalysts. The catalysts have shown almost similar surface area values (around 97 m²/g) irrespective of their compositions. On the other hand, surface area values were diminished remarkably with rise in the calcination temperatures. In TEM images, hollow sphere formation with uniform layer of barium over the spheres could clearly be observed. Diameter of Ba-doped TiO₂ hollow sphere was found 0.4–0.5 μm irrespective of the variation in calcination temperatures. In cyclic voltammograms, both the hydrogen and oxygen evolution peaks were present for all the hollow sphere samples; although the peak positions had changed to some extent for few samples. Anodic polarization curves have shown 60 mA cm⁻² current density for 20 wt% Ba/TiO₂ hollow sphere sample. Tafel slope is revealed as 122 mV for the same electrocatalyst. Barium doped titania hollow spheres have also shown long time electrocatalytic stability in acid solution.     

Continuous-time optimal unbiased FIR filter for input-delayed systems

Most existing finite impulse response (FIR) filters are restricted to models without delays. This paper proposes an continuous-time optimal unbiased FIR filter for input-delayed systems (CTOUFFID). A new integral transformation relation was introduced to derive the FIR filter. By applying this relation, the CTOUFFID problem is represented as an optimal control problem with zero terminal state. The filter gain function is obtained by solving two coupled matrix differential equations using initial conditions. The paper also offers discussion on the horizon size and a few special cases. The main benefit of the proposed solution is that it provides the maximum likelihood estimate with no requirements for the initial values. Finally, an application with the $F$-404 turbofan engine model is presented to demonstrate the highly robust nature of the proposed FIR filer against incomplete noise information and unspecified model uncertainties.