African Linguistics in Central and Eastern Europe, and in the Nordic Countries

Non peer reviewe

High-Order Sliding Mode-Based Fixed-Time Active Disturbance Rejection Control for Quadrotor Attitude System

This article presents a fixed-time active disturbance rejection control approach for the attitude control problem of quadrotor unmanned aerial vehicle in the presence of dynamic wind, mass eccentricity and an actuator fault. The control scheme applies the feedback linearization technique and enhances the performance of the traditional active disturbance rejection control (ADRC) based on the fixed-time high-order sliding mode method. A switching-type uniformly convergent differentiator is used to improve the extended state observer for estimating and attenuating the lumped disturbance more accurately. A multivariable high-order sliding mode feedback law is derived to achieve fixed time convergence. The timely convergence of the designed extended state observer and the feedback law is proved theoretically. Mathematical simulations with detailed actuator models and real time experiments are performed to demonstrate the robustness and practicability of the proposed control scheme

Electrocatalytic evaluation of liquid phase deposited methylene blue/TiO2 hybrid films

Methylene blue (MB)/TiO2 hybrid thin films were prepared on glassy carbon (GC) electrode surface by the liquid phase deposition (LPD) process. The electrochemical measurements indicated that MB retained its electrochemical activity in the hybrid films. The linear dependence of the reduction peak current for MB upon the scan rate and linear relationship between the middle point potential of MB and pH revealed the surface-confined two-proton two-electron electrochemical characteristics of MB entrapped in hybrid LPD films. Although the electron transfer of K3[Fe(CN)6] on GC surface was inhibited by TiO2 film, the catalytic reduction of K3[Fe(CN)6] by MB was observed on the MB/TiO2 hybrid films. The electrocatalytic activity of hybrid films was also demonstrated as an “artificial peroxidase” for the catalytic reduction of H2O2. Keywords: Methylene blue/TiO2 film, Electrocatalytic activity, Liquid phase depositio

Treatment of wastewater containing polyacrylamide using three dimensional electrodes

A method using three-dimensional electrode is applied to treat wastewater in oil fields, which contains polyacrylamide (PAM), for analogue. A best condition for electrolysis (I = 1.0 A, t=90 min, c=0.1%, m=980 g, =5 mm, d=5.0 cm) has been determined, under which the COD removal efficiency reached 96.0%, COD containing in wastewater reduced to 64.3 mg/L from 1 622.9 mg/L, the figure before treatment. Three categories of PAM-containing wastewater in production practice have been treated with the COD removal ratios being 87.5%, 82.4% and 84.7% respectively. Presence of H2O2 and •OH are detected by means of Ti(IV)-5-Br-PADAP technique and colorimetry respectively. The concentration is positively proportional to the COD removal ratio and increases in accordance with increment of time of electrolysis and current

Research on One-Time Pouring Construction Technology of Side-Span Cast-In-Situ Section and Closed Section

In recent years, in the construction process of closed-bridge side spans, construction has often been carried out in accordance with the construction sequence of, first, pouring the cast-in-place section, then preburying strong bone and pouring the closed section, and finally tensioning the closure steel bundle. However, the temperature change during the construction process of the conventional hinges leads to a large deformation of the hinges’ strong bone, which disturbs the concrete of the hinged section, and, at the same time, its high stiffness means that the concrete of the hinged section will not be sufficiently precompressed, thus resulting in the loss of prestressing force. Therefore, it is necessary to study the one-time casting construction technology of the side-span’s cast-in-place and closed sections. In this study, on the basis of introducing the conventional side-span joint-construction technology, the one-time pouring joint-construction technology was adjusted. In order to eliminate the sunlight temperature factor, which has a great influence on the process of joining, finite element analysis was used to further compare and analyze the changes in the internal force and the linearity of the structure under different joining methods. The results of this study show that, by adjusting the counterweight, the adverse effect of the disturbance of the main girder on the concrete at the joint end under the effect of sunshine temperature can be effectively controlled. Also, one-time joint construction is more reasonable for the internal force and deflection deformation of the structure compared with the conventional side-span joining method of a continuous rigid bridge, which is more favorable to the structure. The research methods and conclusions of this paper can provide a reference for the improvement of closed side-span one-time casting construction technology

Electrochemical Determination of Nitrite Using a Gold Nanoparticles-modified Glassy Carbon Electrode Prepared by the Seed-mediated Growth Technique

Seed-mediated growth of gold nanoparticles on glassy carbon (GC) surfaces was developed. The field emission scanning electron microscopy (FE-SEM) and electrochemical characterization confirmed the effective attachment of gold nanoparticles on GC surface with such a wet-chemical method. The as-prepared gold nanoparticles attached glassy carbon electrode (Au/GCE) presented excellent catalytic ability toward the oxidation of nitrite. Compared with bare GCE and planar gold electrode, the Au/GCE obviously decreased the overpotential of nitrite oxidation and improved the peak current. The catalytic current was found to be linearly proportional to the nitrite concentration in the range of 1 × 10-5 - 5 × 10-3 M, with a detection limit of 2.4 × 10-6 M. The Au/GCE was successfully applied to the electrochemical determination of nitrite in a real wastewater sample, showing excellent stability and anti-interference ability

Application of Xanthan-Gum-Based Edible Coating Incorporated with Litsea cubeba Essential Oil Nanoliposomes in Salmon Preservation

Salmon is prone to be contaminated by Vibrio parahaemolyticus (V. parahaemolyticus), leading to the deterioration of salmon quality and the occurrence of food-borne diseases. In this study, we aimed to develop a novel xanthan-gum-based edible coating embedded with nano-encapsulated Litsea cubeba essential oil (LC-EO) for salmon preservation at 4 °C. First, the results of the growth curves and scanning electron microscopy (SEM) showed that LC-EO displayed potent antibacterial activity against V. parahaemolyticus; the optimal concentration of LC-EO in the liposomes was 5 mg/mL, and the maximal encapsulation efficiency (EE) was 37.8%. The particle size, polydispersity coefficient (PDI), and zeta potential of the liposomes were 168.10 nm, 0.250, and −32.14 mV, respectively. The rheological test results of xanthan-gum-based edible coatings incorporating liposomes showed that the prepared coating was suitable for applying on food surfaces. The results in the challenge test at 4 °C demonstrated that the treatment of 1:3 (liposome: xanthan gum, v/v) coating performed the best preservative properties, the coating treatment delayed the oxidation of salmon, and controlled the growth of V. parahaemolyticus. These findings suggest that the coatings formulated in this study could be used as a promising approach to control V. parahaemolyticus contamination and maintain salmon quality