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This paper presents a novel approach to stabilizing two-wheeled balancing mobile robots (2WBMR) using hierarchical sliding mode control (HSMC) combined with sliding mode control (SMC). The 2WBMR system, an inherently unstable underactuated mechanical system, is modeled and analyzed for its dynamic properties. The controller of the 2WBMR is divided into two main components due to the independent control of state variables: the HSMC controller performs velocity control and stabilizes the vehicle body, while the SMC controller manages the vehicle’s tilt angle. Moreover, our simulations demonstrate that the HSMC-SMC approach significantly outperforms the SMC method, particularly in terms of response time and error reduction during stable control of position, pitch angle, and rotation angle. Additionally, a rapidly exploring random tree (RRT) algorithm is implemented for trajectory planning, enabling the robot to navigate complex environments. Simulation results demonstrate that the proposed control strategy effectively stabilizes and trajectory tracking for the 2WBMR.

This article introduces a method that simplifies the process of designing an observer for Takagi-Sugeno (T-S) fuzzy models with unmeasured premise variables. By incorporating an adjustment parameter into the simplified Linear Matrix Inequality (sLMI) conditions, the dynamic error of the system can be controlled to remain within a specified region, ensuring better system performance. Through a basic linear algebra analysis, the relationship between the system’s membership functions and the estimated ones is established. Lyapunov’s theorem is employed to formulate the sLMI condition. Additionally, to optimize the sLMI conditions with the aim of minimizing dynamic error, an optimization problem is formulated. Finally, numerical simulations were executed on the Rotary Inverted Pendulum (RIP) system to validate the proposed control approach.

The present study aimed to evaluate the antioxidant activity and antithrombotic effect of the n-hexane extract from rhizomes Distichochlamys citrea(DC-R), an endemic ginger species of Vietnam. Results showed that DC-R expressed a more potent antioxidative effect against ABTS than DPPH radical (p< 0.05). DC-R contained a total phenolic content of 3.41 g GAE/100 g and a total flavonoid content of 18.33 g QE/100 g of the dried extract. At concentrations of 1, 2 and 4 mg/mL, DC-R reduced the percentage of platelet aggregation triggered by ADP, collagen and ristocetin in a dose-dependent manner (Pearson’s correlation, r> 0.95, p< 0.05). DC-R also exhibited anticoagulant activity by significantly prolonging the activated prothrombin time (APTT) at all concentrations tested (p< 0.05 compared to DMSO 0.1%). GC–MS revealed 41 volatile components in DC-R, in which several compounds were firmly bound to receptors COX-1 and P2Y12 of the platelet aggregation and factors X and II of the blood coagulation cascades. Using response surface methodology with central composition design, the extraction yield of DC-R reached the highest value (1.011 ± 0.008%) at optimized conditions: liquid/ solid ratio 13.5 mL/g, ultrasonic power level 80%, extraction time 30 min, and extraction temperature 34 °C.

Graphical Abstract:

Graphical Abstract:

5-O-Methylnorbergenin (5-OMB), a natural compound isolated from Rourea harmandiana, is a compound with potential antioxidant activity based on its chemical structure; however, this activity has not been investigated thus far. In this study, the antioxidant activity of 5-OMBwas evaluated by experimental and computational methods. 5-OMBexhibited high activity in DPPH (IC50= 7.25 ± 0.94 μM) and ABTS•+(IC50= 4.23 ± 0.12 μM) assays, higher than the reference compound Trolox. The computational results consistently show that 5-OMBis an excellent HOO•radical scavenger (koverall= 8.14 × 108M–1s–1) in water at physiological pH, however it only exerts weak activity in lipid medium (koverall= 3.02 × 102M–1s–1). The reaction follows the formal hydrogen transfer mechanism in nonpolar solvents, whereas both the sequential proton loss electron transfer and the formal hydrogen transfer pathways contribute to the activity in aqueous solution. There is a good agreement between experimental and computational data, suggesting that 5-OMBis a promising natural radical scavenger in aqueous physiological environment.

In the article, based on empirical research using the VAR model, the authors examine the influence of monetary policy on growth and inflation in Vietnam in the period 2008-2017. The results show that, when applying broad monetary policy, interest rates will reduce, the currency devaluated in the first quarter in accordance with the theory. CPI remained unchanged in the first quarter then rose in the next quarter, output declined slightly in the first quarter and then rose in the next quarter, then reversed and fluctuated little, which may be explained by the delay in policy enforcement. The model results also confirm that past inflation plays an important role in determining inflation in Vietnam. Therefore, the government and the State Bank of Vietnam need to maintain the target of inflation control, thus contributing to macroeconomic stability and rational growth support.

AbstractThe stability of allyl sulfide, an organosulfur compound present in garlic oil, in its α-, β-, and γ-cyclodextrin inclusion complexes was investigated under various storage conditions. The complexes of cyclodextrins and allyl sulfide were prepared by spray drying. The storage temperature, relative humidity, and initial moisture content of the inclusion complex had different effects on the release rate of allyl sulfide. Allyl sulfide in α-cyclodextrin complexes had a lower release rate than in β- and γ-cyclodextrin complexes at 100 °C and at 50 °C under 6, 40, 54, and 73% relative humidity. The initial moisture content affected only the release rate of allyl sulfide from α-cyclodextrin complexes. The release behavior of allyl sulfide can be correlated with the first-order release rate equation with a normal Gaussian distribution of free energy of activation of release rate constant. The results indicated α-cyclodextrin is a suitable material for controlled release of allyl sulfide.

This study presents a novel approach to enhance the control of Pneumatic Artificial Muscle (PAM) systems by combining Sliding Mode Control (SMC) with the Radial Basis Function Neural Network (RBFNN) algorithm. PAMs, when configured antagonistically, offer several advantages in creating human-like actuators. However, their inherent nonlinearity and uncertainty pose challenges for achieving precise control, especially in rehabilitation applications where control quality is crucial for safety and efficacy. To address these challenges, we propose an RBF-SMC approach that leverages the nonlinear elimination capability of SMC and the adaptive learning ability of RBFNN. The integration of these two techniques aims to develop a robust controller capable of effectively dealing with the inherent disadvantages of PAM systems under various operating conditions. The suggested RBF-SMC approach is theoretically verified using the Lyapunov stability theory, providing a solid foundation for its effectiveness. To validate its performance, extensive multi-scenario experiments were conducted, serving as a significant contribution of this research. The results demonstrate the superior performance of the proposed controller compared to conventional controllers in terms of convergence time, robustness, and stability. This research offers a significant contribution to the field of PAM system control, particularly in the context of rehabilitation. The developed RBF-SMC approach provides an efficient and reliable solution to overcome the challenges posed by PAMs’ nonlinearity and uncertainty, enhancing control quality and ensuring the safety and efficacy of these systems in practical applications.

The effects of anode composition and temperature on anode electrochemical properties, the passivation layer’s structure, and ferrate(VI) generation in 14 M NaOH were investigated. Cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and galvanostatic polarization (GP) were used to analyze the electrochemical processes involving the electrosynthesis of ferrate using some low-cost anode materials: ductile iron, grey cast iron, and mild steel. The results proved that the presence of silicon and graphite with sphere form in the ductile iron anode significantly increased ferrate electro-generation. The optimal temperature for the electro-generation of ferrate was 30 °C–40 °C. The current efficiency using the ductile iron anode was constantly at least about 30% superior to that of the grey cast iron and mild steel electrodes. The ductile iron anode material was the most feasible option because it provides the highest ferrate concentration (1.58 g L−1) with the highest current efficiency of 74% and the lowest specific energy consumption of 1.2 kWh kg−1ferrate.

An additive mixture of nanoTiO2(n-TiO2in sol form), nano fumed SiO2(nf-SiO2, NFS), propylene glycol (PPG) and polyacryl amide (PAM) was used for preparation of gelled electrolytes. They were characterized by some physicochemical and electrochemical methods to consider their effect on the capacity of lead acid battery during working process. The material property of samples was observed by scanning electron microscopy, thermal analysis, FTIR study, and X-ray diffraction. The resistance of electrolyte was considered by electrochemical impedance spectroscopy. The capacity of battery were observed by charge-discharge at constant current density (0.8 mA cm−2) and charge-discharge according to the international recognized standards (IEC 61056–1:2012; 2.35 V/6 h–0.25 C/1.7 V or 0.5 C/1.7 V) for anodized PbO2cells and VRLA cells (Gel-VRLA cells, AGM Gel-VRLA cells, and AGM flooded-VRLA cells), respectively. The results showed that a suitable content of n-TiO2should be 0.2 wt% combined with ternary additive (PAM/PPG/NFS, 0.2/0.1/0.6 wt%, respectively). The discharge capacity of the VRLA cells with 0.2 wt% n-TiO2was higher than that without n-TiO2at both discharge rates 0.25 and 0.5 C. In particular, their service life reaches more than 225 cycles at 0.25 C discharging thanks to the use of AGM separator, meeting the IEC 61056–1:2012 standard (200 cycles).

Previous studies have reported no or only a very poor correlation between 6-methylmercaptopurine6-thioguanine nucleotide (6-MeMPN6-TGN) and azathioprine (AZA) dose in the treatment of inflammatory bowel disease (IBD). However, metabolite levels are often repeatedly measured yielding a hierarchical data structure that requires more appropriate data analysis.

In this study, the pulse-voltage-driven dynamical switching of perpendicular exchange bias in a Pt/Co/Au/Cr2O3/Pt thin film observed at pulse amplitudes exceeding the DC switching threshold is investigated. The switching time decreases with increasing pulse amplitude, reaching values below 10 ns at an amplitude two times higher than the above threshold. Conversely, several hundreds of nanoseconds is required for switching at amplitudes close to the threshold, suggesting that the switching mechanism is dominated by the motion of magnetic domains of the antiferromagnetic layer.

We propose a method of discriminating whether the gating effect is electrostatic or electrochemical on an electric double-layer transistor (EDLT), which can be a good guideline for examining the nature of EDLTs. The electrochemical effect between a channel and an ionic liquid depends on the gate voltage (VG). Our study on the dependence of the transport properties of a (La0.525Pr0.1Ca0.375)MnO3(LPCMO) EDLT on VGrevealed that the electrostatic effect is dominant below |VG| = 2 V, whereas the electrochemical effect is dominant at higher voltages. The modulation of the insulator-to-metal transition property of LPCMO was realized through the electrostatic effect.