4.2 V Stack of metal oxide-polypyrrole-based composite electrodes and their power management

Polypyrrole (PPy)-based composites containing nanostructured VO _x, PbO _x, and MnO _x are galvanostatically synthesized on exfoliated graphite papers (1.0 and 6.25 cm²) formed as a result of the intercalation with their metals. Both intercalation and synthesis are performed in the synthesis solution containing metal(II)tetrafluoroborate salts, pyrrole monomer, HBF₄, H₂O, Triton-X 100 (TX100), and carboxymethyl cellulose (CMC). The mass loading of the composite at the electrode is maintained at 10 mg cm⁻². Symmetric and asymmetric unit cells are prepared in polyvinyl alcohol (PVA)/H₂SO₄ (1:1) gel electrolyte using composites synthesized on the treated graphite paper electrode. The electrical properties of these cells are examined by electrochemical impedance spectroscopy and their capacitive properties by cyclic voltammetry and galvanostatic-charge discharge test. The asymmetrical cell, prepared with PPy/PbO _x/CMC composite having energy density and cycle life better than others, exhibits 7.77 Wh kg⁻¹ and 0.51 kW kg⁻¹ at a working voltage of 1.4 V, considering the total mass of all sub-components. The three-cell asymmetric stack design, which is prepared using these composite-coated electrodes, achieves a coulombic efficiency of 76% at 4.2 V. Finally, an electronic control system (DC/DC buck-boost converter) is designed and implemented to manage the charge and discharge cycles of single-cell and bipolarly connected stack to operate the asymmetric supercapacitor arrays with high performance.     

Resource recovery as a sustainable perspective for the remediation of mining wastes: rehabilitation of the CMC mining waste site in Northern Cyprus

Bulletin of Engineering Geology and the Environment - This paper highlights resource recovery and stabilization as the novel approach adopted in the rehabilitation strategy of the abandoned copper...     

Phase detector for tuning circuit of resonant inverters

The tuning circuit in a resonant inverter determines the inverter frequency and makes it track the load resonant frequency. Current phase detectors have some serious drawbacks for this application. A new phase detector circuit is presented which can overcome these drawbacks.     

Decision making with epistemic uncertainty under safety constraints: An application to seismic design

The problem of accounting for epistemic uncertainty in risk management decisions is conceptually straightforward, but is riddled with practical difficulties. Simple approximations are often used whereby future variations in epistemic uncertainty are ignored or worst-case scenarios are postulated. These strategies tend to produce sub-optimal decisions. We develop a general framework based on Bayesian decision theory and exemplify it for the case of seismic design of buildings. When temporal fluctuations of the epistemic uncertainties and regulatory safety constraints are included, the optimal level of seismic protection exceeds the normative level at the time of construction. Optimal Bayesian decisions do not depend on the aleatory or epistemic nature of the uncertainties, but only on the total (epistemic plus aleatory) uncertainty and how that total uncertainty varies randomly during the lifetime of the project.     

Investigation of relation between both sulfur removal and adsorption capacity with surface morphology of a pyrolysed Turkish lignite

In considering with morphological physicochemical transformations of the coal samples pyrolysed in CO₂ atmosphere at different temperatures, the change of their adsorptive capacities have been investigated. It was seen that the change occurred in the monolayer adsorption capacities as parallel to morphological transformations of the coal surface is particularly connected with the amount of organic sulfur present in the coal matrix. Adsorption capacity is not affected from the contents of pyritic sulfur and ash of coal samples. The measurements of zeta potential of the pyrolysed coal samples also showed that pyrolysis modified the functional groups on surface of the coal, depending on the pyrolysis temperature.