Stability Matrix Research Articles

Synthesis of Selenium Sulfide Nanoparticles in Polysaccharide Arabinogalactan and Starch Matrices

New water-soluble SeS2 containing nanocomposites are obtained via ion-exchange interaction between selenous acid and ammonium sulfide in water using natural arabinogalactan and starch polysaccharides as nanoparticle stabilizers. The transmission electron microscopy, X-ray diffraction analysis, and dynamic light scattering data show that nanocomposites are formed as spherical crystalline SeS2 nanoparticles 5–140 nm in size, dispersed in polysaccharide matrices. The type of stabilization matrix and ratio of reactants have a decisive influence on the nanomorphological properties of the materials obtained.

Event-triggered Consensus Control of Nonlinear Multi-agent Systems based on First-order Hold

In this paper, consensus problem is studied for the first-order nonlinear multi-agent systems under directed topology, and a novel event-triggered consensus protocol is proposed. Different from the existing results with general zero-order hold, the first-order hold is adopted to construct the event-triggered control signal so as to reduce the triggering rate. By using Lyapunov stability method and matrix theory, a sufficient consensus condition is derived for the agents to reach the asymptotic consensus, and Zeno-behavior can be avoided. Finally, a numerical example is presented to demonstrate the effectiveness of our proposed protocol.

High-gain observer-based integral sliding mode tracking control for heavy vehicle electro-hydraulic servo steering systems

The electro-hydraulic servo steering system (EHSSS) is the key element to determine the handling and stability of heavy vehicles. Accurate steering control is challenged due to its complicated structure and a wide range of steering loads. In this paper, an output feedback integral sliding mode control (ISMC) method based on high-gain observer is proposed to solve this issue. First, a new Hurwitz matrix design method is presented for EHSSS with non-chain integrator, in order to prove the convergence of the observer error dynamics. Then, the Lyapunov stability of the observer-based controller is verified. Finally, a test bench is established to experimentally validate the proposed method's effectiveness through multiple test scenarios. The results show the tracking error of the proposed method is significantly smaller than PI and similar to full-state feedback integral sliding mode controller. This paper provides a valuable reference for high-gain observer-based nonlinear control applied to a typical electro-hydraulic servo steering system.

Influence of guabiroba pulp (campomanesia xanthocarpa o. berg) added to fermented milk on probiotic survival under in vitro simulated gastrointestinal conditions

In fermented milks inoculated with two thermophilic strains (Lactobacillus bulgaricus and Streptococcus thermophilus), guabiroba pulp (Campomanesia xanthocarpa O. Berg) was added in different concentrations: 5% (I5 sample) and 10% (I10 sample), compared to a control sample, with no pulp addition. In these fermented milks, Bifidobacterium BB-12 was added and the samples were submitted to a progressive gastrointestinal simulation in vitro. The cells count was performed, including the survival rates for all the progressive steps of the simulated digestion. Total phenolic content (TPC) and antioxidant activity analysis by FRAP (Ferric Reducing Antioxidant Power) and DPPH (2,2-diphenyl-1-picrylhydrazyl) were performed in all the gastrointestinal steps. Before and during the entire gastrointestinal tract, the Bifidobacterium BB-12 count was 8–9 log CFU g−1, above the recommended for a probiotic product, with a highlight in intestinal colon steps. The I10 sample showed the highest viable cell count, the highest total phenolic content and antioxidant activity throughout the entire gastric steps (p < 0.05). The fermented milk proved to be an effective matrix for the probiotic stability and incorporation of guabiroba components. Bioactive compounds present in the guabiroba pulp may have occasioned a prebiotic and protective effect on Bifidobacterium BB-12 after gastric conditions. The possible bioconversion of these compounds in more active forms can contribute to the absorption in epithelial cells, enhancing fermented milks with guabiroba pulp as important sources of dietary accessible bioactive compounds.

Observer Design for Positive Uncertain Discrete-time Lipschitz Systems

Abstract For positive uncertain discrete-time Lipschitz systems this paper proposes a way to reflect matched uncertainties, structural system parameter constraints, positiveness and Lipschitz continuity in solving the problem of the state observer quadratic stability. The design conditions are proposed in the set of linear matrix inequalities to guarantee the observer strict positiveness, system parameter constraint representation and estimation error bounding in terms of achieved quadratic stability and nonnegative feedback gain matrix. It follows from the results obtained that the impact of nonnegative system matrix structures can be reflected in uncertainty matching problems. A numerical example is included to assess the feasibility of the technique and its applicability.

Passive control for a class of T-S fuzzy systems with memory controller

Taking the advantage of fuzzy systems, a class of T-S fuzzy models used to describe nonlinear systems. Firstly, by designing a memory state feedback controller, we draw the conclude of robust stability and the conditions of passive control. Secondly, using Lyapunov stability and linear matrix inequality technology in MATLAB, we can utilize the gain matrix about the controller of the memory state feedback. Finally, a simulation example is given to illustrate the effectiveness of the proposed method.

Freshness constraints of an age of information based event-triggered Kalman consensus filter algorithm over a wireless sensor network

This paper presents the design of a new event-triggered Kalman consensus filter (ET-KCF) algorithm for use over a wireless sensor network (WSN). This algorithm is based on information freshness, which is calculated as the age of information (AoI) of the sampled data. The proposed algorithm integrates the traditional event-triggered mechanism, information freshness calculation method, and Kalman consensus filter (KCF) algorithm to estimate the concentrations of pollutants in the aircraft more efficiently. The proposed method also considers the influence of data packet loss and the aircraft’s loss of communication path over the WSN, and presents an AoI-freshness-based threshold selection method for the ET-KCF algorithm, which compares the packet AoI to the minimum average AoI of the system. This method can obviously reduce the energy consumption because the transmission of expired information is reduced. Finally, the convergence of the algorithm is proved using the Lyapunov stability theory and matrix theory. Simulation results show that this algorithm has better fault tolerance compared to the existing KCF and lower power consumption than other ET-KCFs.

Cluster consensus of multi-agent systems with general linear and nonlinear dynamics via intermittent adaptive pinning control

This paper investigates the cluster consensus of multi-agent systems (MASs) with general linear and nonlinear dynamics via intermittent adaptive pinning control, where each cluster has a virtual leader whose state can be sensed by only a small part of followers on some disconnected time intervals because of communication constraints. The communication topology is considered to be weakly connected, that is, it is not necessary to be in-degree balanced, strongly connected or contain a directed spanning tree. To realise the cluster consensus, a class of intermittent adaptive pinning control protocols is proposed according to difference that the agents receive information source. The pinning gains are designed to be intermittent adaptive and with an exponential convergence rate, which will effectively reduce communication costs, avoid the pinning gains being larger than those needed in practice. Meanwhile, it guarantees that the pinning gains quickly converge to steady value. Correspondingly, some sufficient consensus criteria are derived to guarantee that the agents in the same cluster asymptotically can reach consensus while the agents in different clusters can reach different consensus. Rigorous proofs are given by the aid of Lyapunov stability theory and matrix theory. Finally, a numerical simulation example is presented to validate the main results.

State bounding for fuzzy memristive neural networks with bounded input disturbances

This paper investigates the state bounding problem of fuzzy memristive neural networks (FMNNs) with bounded input disturbances. By using the characters of Metzler, Hurwitz and nonnegative matrices, this paper obtains the exact delay-independent and delay-dependent boundary ranges of the solution, which have less conservatism than the results in existing literatures. The validity of the results is verified by two numerical examples.

Effect of Carbonation on the Water Resistance of Steel Slag-Magnesium Oxysulfate (MOS) Cement Blends.

Magnesium oxysulfate (MOS) cement has the advantages of lightweightedness, high strength, and low thermal conductivity, but the utilization of MOS cement is limited due to low water resistance. This paper studied the influence of steel slag and CO2 treatment on the compressive strength and water resistance of MOS cement. The hydration products and microstructures were characterized by X-ray diffraction (XRD), thermogravimetric analysis–differential scanning calorimetry (TG–DSC), scanning electron spectroscopy (SEM), and Fourier transform infrared spectroscopy (FTIR). The results showed that the strength of MOS cement reached 89.7 MPa with steel slag and CO2 treatment; the water-resistance coefficients of the control and samples containing 10%, 20%, and 30% reached 0.91, 0.81, 1.01, and 1.08 MPa, respectively. The improvement in the strength and water resistance coefficients was because of carbonation that accelerated the hydration of C2S in the steel slag and formed a Ca–Mg–C amorphous substance. The carbonation products contributed to better water stability and denser matrix denser while inhibiting the hydration of MgO, which led to improving the water resistance of the sample.

Algae Growth Stabilization and Prediction Model Matrix of Soil Sludge

Algae Growth Stabilization and Prediction Model Matrix of Soil Sludge

Algae Growth Stabilization and Prediction Model Matrix of Soil Sludge

Algae Growth Stabilization and Prediction Model Matrix of Soil Sludge

Improved IMU Preintegration with Gravity Change and Earth Rotation for Optimization-Based GNSS/VINS

IMU preintegration technology has been widely used in the optimization-based sensor fusion framework, in order to avoid reintegrating the high-frequency IMU measurements at each iteration and maintain the ability of bias correction when bias estimation changes. Since IMU preintegration technology was first proposed, several improved versions have been designed by changing the attitude parameterization or the numerical integration method in the most current related research. However, all of these versions have failed to take the change of gravity and the earth rotation into consideration. In this paper, we redesign the IMU preintegration algorithm in which the earth rotation and gravity vector are calculated from the geodetic position. Compared with the covariance matrix form, in this paper, the uncertainty of the preintegrated IMU measurements is propagated in the form of a square root information matrix (SRIM) for better numerical stability and easy use in the optimization-based framework. We evaluate the improved IMU preintegration algorithm by using the dataset collected by our sensor platform equipped with two different-grade IMUs. The test results show that the improved IMU preintegration algorithm can cope well with the gravity change and earth rotation. The earth rotation must be taken into consideration for the high-grade IMU that can effectively sense the earth rotation. If the change of gravity is omitted, the root-mean-square error (RMSE) of the horizontal attitude is about 1.38 times greater than the geodetic displacement. Additionally, the positioning RMSE does not increase obviously within a limited range, which means tens of kilometers and several hundred meters for the low-grade and high-grade IMU used in the experiment, respectively.

Event-triggered control for coupled reaction–diffusion complex network systems with finite-time synchronization

In this paper, a class of coupled nonlinear reaction–diffusion complex network system are investigated with finite-time synchronization based on the event-triggered control. The study aims to develop nonlinear complex network systems with partial differential terms under Dirichlet’s boundary conditions by combining the distributed event-triggered control protocol with the Lyapunov stability theorem, Green formula, matrix inequality, and partial differential equation theory. Several sufficient conditions for the system to achieve finite-time synchronization with or without time delay are obtained. Furthermore, the upper bound of time can be estimated to achieve synchronization. Finally, numerical simulation is used to prove the effectiveness of the theory.

Scaled group consensus in multi-agent networks with high-order continuous dynamics

We investigate scaled group consensus problems of high-order multi-agent systems with directed information exchanges. As one of multiple consensus, the scaled group consensus focuses on both cooperations and competitions among multi-agent sub-networks and cooperations among agents belonging to a sub-network. Two distributed protocols are designed to solve the scaled group consensus problems. The (generalised) Routh–Hurwitz stability criterion and matrix theory are utilised to establish necessary and sufficient conditions guaranteeing the agents reaching the scaled group consensus. Finally, several simulations are presented to demonstrate the effectiveness of the theoretical results.

In situ synthesis and long-term stabilization of nanosilver in poly(vinyl acetate-co-butyl acrylate-co-neodecanoate) matrix for antibacterial applications

Although the synthesis and the study of properties of silver nanoparticles (AgNP) have been the subject of much research, it is also of great interest the development of new hybrid nanomaterials based on AgNP and the corresponding stabilization by means of new substrates, especially polymeric ones like vinylacrylic and derivatives, extensively used in industrial applications. These types of substrates in addition to stabilizing these nanoparticles take advantage of the synergy of properties between both types of materials. The purpose of this research is the in situ synthesis of AgNP in poly (vinyl acetate-co-butyl acrylate-co-neodecanoate) (VAVTD) terpolymer water emulsion as stabilization matrix and the corresponding characterization. UV-VIS, X-ray photoelectron spectroscopy (XPS), transmission (TEM) and scanning electron microscopy (SEM) were used to characterize these AgNP polymer hybrids. Additionally, preliminary work was carried out to assess the biofilm formation of a multiple antibiotic resistance (MAR) strain of Pseudomonas aeruginosa on these AgNP/VAVTD hybrids in order to explore their use in antibacterial applications. The results show that VAVTD terpolymer water emulsion, in low concentrations, is a very good substrate to stabilize AgNP particles as evidenced by the SEM and TEM studies, and the relatively small displacement in the corresponding UV spectra of AgNP particles, even after 45 d of ageing. It was also found a significant reduction of P. aeruginosa cell viability in biofilms formed at 1 and 7 d (p < 0.05) on VAVDT/AgNP hybrid materials, suggesting potential antibacterial properties. Our results also provide important insights to the current knowledge in control strategies for MAR bacterial infections, such as those caused by P. aeruginosa, while avoiding the spreading of resistant strains in healthcare facilities and multiple environments related to human everyday live, especially for surfaces that require antibacterial protection.

On generalization of classical Hurwitz stability criteria for matrix polynomials

In this paper we associate a class of Hurwitz matrix polynomials with Stieltjes positive definite matrix sequences. This connection leads to an extension of two classical criteria of Hurwitz stability for real polynomials to matrix polynomials: tests for Hurwitz stability via positive definiteness of block-Hankel matrices built from matricial Markov parameters and via matricial Stieltjes continued fractions. We obtain further conditions for Hurwitz stability in terms of block-Hankel minors and quasiminors, which may be viewed as a weak version of the total positivity criterion.

Cluster Synchronization in Delayed Networks With Adaptive Coupling Strength via Pinning Control

Many previous studies have indicated that pinning control and adaptive feedback control are two of most effective strategies for achieving synchronization. In this paper, we present a mixed method integrating the two control strategies to realize cluster synchronization in delayed networks with directed couplings. Based on Lyapunov stability theory and matrix theory, several criteria on cluster synchronization are obtained. Compared with the previous results on cluster synchronization, the obtained criteria can be applied to delayed network with nonidentical nodes, directed couplings and time-varying coupling strength. Finally, numerical simulations are performed to verify the theoretical results.

An effort towards hard and tough coatings by cathodic arc deposition of Zr-Cr-O coating system

A new coating system of Zr-Cr-O in which tetragonal ZrO2 acts as toughening agent and Cr2O3 can act as stabilizer and hard matrix was proposed. The coatings were obtained by cathodic arc deposition of Zr and Cr in gas mixture of oxygen and argon. Pure ZrO2 coatings were also deposited as control group to verify the stabilizing effect of Cr in tetragonal ZrO2. Various substrate biases were applied to modify the properties of the coatings. The result showed that monoclinic phase dominated in pure ZrO2 coating, whereas only tetragonal phase can be detected in ZrO2 coating with low Cr content. Increasing of Cr content resulted in more and more amorphous phase until crystal Cr2O3 was obtained when Cr content was higher than 90.27%. The phase composition was also affected by substrate bias. It was found that tetragonal phase in pure ZrO2 was destroyed when substrate bias was applied, whereas tetragonal phase in Cr-doped ZrO2 was very stable, and the crystallinity of the co-deposited coatings was enhanced by substrate bias. The hardness of the coatings was affected by composition, substrate bias and crystallinity. It was regretful that Cr doped t-ZrO2 coatings showed relatively low hardness due to high amount of amorphous phase. However, a remarkable plastic deformation capability was found in all the co-deposited coatings, and the coating with high Cr content and high bias voltage exhibited relatively high hardness, H/E and plastic deformation.

LC-MS/MS method for quantitation of the CK2 inhibitor silmitasertib (CX-4945) in human plasma, CSF, and brain tissue, and application to a clinical pharmacokinetic study in children with brain tumors

Silmitasertib (CX-4945) as a potent and selective inhibitor of CK2 exhibited promising in vitro and in vivo anti-cancer activity. An assay employing cation-exchange solid phase extraction (SPE) followed by LC-MS/MS analysis was successfully developed and validated for the quantitation of silmitasertib in human plasma, brain tissue, and human cerebrospinal fluid (CSF). Reverse phase chromatographic separation was achieved using Synergi™ hydro-RP column (4 μm, 75 × 2.0 mm) and gradient elution with 5 mM ammonium formate aqueous solution (pH 6.5) as mobile phase A and 0.1% formic acid in acetonitrile as mobile phase B. Multiple reaction monitoring (MRM) transition of m/z 350.2 → 223.2 and m/z 316.2 → 223.2 were chosen for detection of silmitasertib and internal standard (CX-4786) respectively. Since silmitasertib concentration in patient plasma is expected to be in a wide range due to the study design, two calibration curves with range 0.2–125 ng/ml and 32–20,000 ng/ml were established. A different curve ranging from 2 to 40 ng/g was used for measurement of silmitasertib in brain tissue, while another calibration curve ranging from 0.2 to 20 ng/ml was established for CSF. All these calibration curves corresponding to different matrices showed good linearity (R2 > 0.99) over the concentration range. This assay demonstrated excellent precision below 15% and accuracies between 85% and 115% within–day and between–day for all the concentration levels in each matrix. This assay was also validated for each matrix for selectivity, sensitivity, matrix effects, recovery, and stability. We applied the validated method to the analysis of plasma silmitasertib for a clinical study.