Summary
This paper considers the problem of state feedback finite‐time stabilization for a class of high‐order nonlinear systems with an output constraint. By proposing a novel tan‐type barrier ...Lyapunov function combined with manipulating sign functions, the technique of adding a power integrator is skillfully revamped to develop a systematic approach that guides us to construct a state feedback finite‐time stabilizer for high‐order nonlinear systems while preventing the violation of a prespecified output constraint during operation. The proposed approach is a unified tool in the sense that it can provide a finite‐time stabilizer design even when the constraint is infinite, or equivalently, there is no need for a constraint. A simple example is presented to demonstrate the effectiveness of the proposed strategy.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
•Humic acid residue (HAS) is currently a wasted resource.•We modified HAS with NH4H2PO4 to improve its heavy metal stabilization capacity.•N-HAS reduces the mobility of Hg and Pb in soils.•Addition ...of N-HAS alters soil physicochemical properties.•N-HAS was an industrially produced heavy metal passivator.
Humic acid residue (HAS), as a waste product from the extraction of humic acid from low-rank coal such as weathered coal and lignite, is characterized by its abundant yield and low price. However, the low efficiency and high pH value of HAS in passivating heavy metals limit their application in the passivation of heavy metals in soils. To improve the passivation efficiency of humic acid residues against heavy metals, in this study, modified humic acid residues (N-HAS) were prepared by pretreatment with HNO3 and modification with NH4H2PO4. The results showed that the passivation efficiency of N-HAS was up to 87.75% and 57.07% for Hg and Pb in the effective state, and the adsorption kinetics were under the pseudo-second-order model. The addition of N-HAS to the soil resulted in a change in the morphology of the heavy metals, with the acid extractable state of Hg and Pb reduced by 66.92% and 30.44% respectively, and the results of the Toxicity Leaching Test (TCLP) showed that the addition of N-HAS significantly reduced the leaching toxicity and potential ecological risk index (RI). The soil physicochemical properties changed after the addition of N-HAS and there was a correlation between the soil physicochemical properties and the effective state of Hg and Pb content. In conclusion, N-HAS has a positive effect on the remediation of heavy metal-contaminated soil and has a broad application prospect.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
This article addresses the event-triggered stabilization for continuous-time stochastic systems. Due to stochastic effects, the system state is hard to predict and dominate, and the system behavior ...would vary with every trial (i.e., sample path) even for the same initial condition. This gives rise to substantial challenges, especially, in determining the execution/sampling times and assessing the closed-loop performance, which urges us to develop powerful and sophisticated tools/methods for the analysis and design of stochastic event-triggered control. In this article, basic theorems, particularly a stochastic convergence theorem, are first proposed for stochastic event-triggered controlled systems. Then, a framework of event-triggered stabilization is established for the stochastic systems without applying the well-known Lyapunov theorems. Specifically, we present conditions under which event-triggered stabilization is feasible for the systems. Accordingly, static and dynamic event-triggering mechanisms are proposed with enforcing a fixed positive lower bound for the interexecution times. While avoiding infinitely fast execution/sampling, both asymptotic stabilization and exponential stabilization are achieved for the systems by the proposed stochastic convergence theorem. The involved analysis is helpful to form a pattern for stochastic event-triggered controlled systems. As the direct application of the established framework, the constructive design of event-triggered controller is realized, respectively, for two representative classes of stochastic systems.
The paper provides a comparative investigation on accuracy and conservation properties of two particle regularization schemes, namely, the Dynamic Stabilization (DS) 1 and generalized Particle ...Shifting (PS) 2 schemes in simulations of both internal and free-surface flows in ISPH (Incompressible SPH) context. The paper also presents an Optimized PS (OPS) scheme for accurate and consistent implementation of particle shifting for free-surface flows. In contrast to PS, the OPS does not contain any tuning parameters for free-surface, consistently resulting in perfect elimination of shifting normal to an interface and resolves the unphysical discontinuity beneath the interface, seen in PS results.
•Accuracy and conservation properties of two particle regularization schemes are comparatively investigated.•The considered particle regularization schemes are dynamic stabilization and particle shifting.•An optimized particle shifting is proposed for free-surface flows.•The optimized particle shifting is free of tuning parameters and eliminates shifting normal to an interface.•The optimized particle shifting outperforms dynamic stabilization in terms of accuracy and energy conservation.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Aqueous dispersions of graphene oxide are inherently unstable in the presence of electrolytes, which screen the electrostatic surface charge on these nanosheets and induce irreversible aggregation. ...Two complementary strategies, utilizing either electrostatic or steric stabilization, have been developed to enhance the stability of graphene oxide in electrolyte solutions, allowing it to stay dispersed in cell culture media and serum. The electrostatic stabilization approach entails further oxidation of graphene oxide to low C/O ratio (∼1.1) and increases ionic tolerance of these nanosheets. The steric stabilization technique employs an amphiphilic block copolymer that serves as a noncovalently bound surfactant to minimize the aggregate-inducing nanosheet–nanosheet interactions. Both strategies can stabilize graphene oxide nanosheets with large dimensions (>300 nm) in biological media, allowing for an enhancement of >250% in the bioconjugation efficiency of streptavidin in comparison to untreated nanosheets. Notably, both strategies allow the stabilized nanosheets to be readily taken up by cells, demonstrating their excellent performance as potential drug-delivery vehicles.
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IJS, KILJ, NUK, PNG, UL, UM
Traditional macroeconomic stabilization policies seek to moderate swings in economic activity through measures that primarily augment aggregate demand. Such measures are, however, inadequate in ...mitigating the comprehensive effects of crisis such as the COVID-19, which affects both the demand and supply sides of the economy. Moreover, monetary policies are presently close to a liquidity trap combined with weakened transmission links to the real economy. Fiscal policies have been reactivated, albeit in an ad hoc and experimental manner. Based on a literature review and the policy responses following the COVID-19 crisis, the objective is to present a modified and extended framework for stabilization policies. In particular, the importance of microeconomic supply-side measures that promote entrepreneurial processes and knowledge-upgrading efforts are emphasized. Furthermore, a coherent realigning of policies at the micro- and macro-levels is argued to enhance the potential for long-term growth and to facilitate the restructuring of an economy that normally follows a crisis.
Plain English Summary
The COVID-19 crisis makes traditional stabilization policies obsolete. Reinstate the market and redirect policy from interest rates and unconditional state support toward providing employees and firms with adequate knowledge for future challenges. Traditional crises policies seek to moderate swings in economic activity by primarily lowering interest rates and increase governmental expenditure to stimulate demand and economic activity. However, the effectiveness of both of these measures has been questioned, in particular, further reductions in already extremely low-interest rates. The present COVID-19 crisis has highlighted the importance of taking firms, entrepreneurs, trade, etc., into account, i.e., the supply side of the economy. It is argued that traditional policies should partly be replaced by measures targeting entrepreneurial processes, firm growth, innovation, and knowledge upgrading. Corporate taxes should be used to increase firms’ crisis resilience, increase investment, and encourage start-ups, while state support should be conditioned on employees engaging in knowledge upgrading. Hence, the main conclusion of this study is that such redirection of policies will more effectively level out swings in the business cycle, increase the potential for long-term growth, and make it easier for employees and firms to adjust to new economic conditions.
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CEKLJ, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
This paper considers the problem of sampled-data adaptive output feedback fuzzy stabilization for switched uncertain nonlinear systems associated with asynchronous switching. A state observer is ...designed to estimate the unmeasured states and fuzzy logic systems are employed to deal with the unknown nonlinear terms. Sampled-data controller and novel switched adaptive laws are constructed based on the recursive design method and an average dwell time constraint is given to ensure that the closed-loop system is stable. The proposed scheme is employed in a mass-spring-damper system to demonstrate its effectiveness.
Modern society needs to address the major societal challenges related to human health, safety and the environment by developing new safe and environmentally friendly polymers and biopolymer-based ...materials and technologies. With this in mind, the present overview provides an integrated approach to understanding when and how polymers and biopolymers are subject to degradation phenomena throughout their life cycle, taking into account their specific conditions of synthesis, manufacture, use and end-of-life. It also discusses what kind of stabilization strategies could be applied to prevent the degradation of polymers and biopolymers.
The term “degradation” is therefore used in a broad sense to include all processes that lead to a change in the properties and overall performance of polymers and biopolymers, from synthesis to end-of-life. The main experimental techniques used to follow the degradation phenomena of polymers and biopolymers and to evaluate their structural and property changes are also briefly mentioned.
The work attempts to provide points for reflection on the importance of understanding degradation, which is directly related to the failure of polymers and biopolymers in-service conditions. It also briefly discusses the application of a controlled degradation strategy to solve the negative environmental impact of polymers and biopolymers and to implement an integrated circular approach for material recovery. Therefore, today with significant advances in polymer science and technology, understanding, tuning and controlling the degradation of polymers and biopolymers is of paramount importance, especially considering the environmental sustainability and biocompatibility of the degradation products.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
We solve the prescribed-time mean-square stabilization and inverse optimality control problems for stochastic strict-feedback nonlinear systems by developing a new nonscaling backstepping design ...scheme. A key novel design ingredient is that the time-varying function is not used to scale the coordinate transformations and is only suitably introduced into the virtual controllers. The advantage of this approach is that a simpler controller results and the control effort is reduced. By using this method, we design a new controller to guarantee that the equilibrium at the origin of the closed-loop system is prescribed-time mean-square stable. Then, we redesign the controller and solve the prescribed-time inverse optimal mean-square stabilization problem, with an infinite gain margin. Specifically, the designed controller is not only optimal with respect to a meaningful cost functional but also globally stabilizes the closed-loop system in the prescribed-time. Finally, two simulation examples are given to illustrate the stochastic nonlinear prescribed-time control design.
•Recent progress in flame stabilization methods for micro-combustors was reviewed.•Flame anchoring approaches are divided into single, combined, and other methods.•Single methods include flame ...holders, heat recirculation, catalyst, and additives.•The combined methods are combinations of two or more of these single methods.•Future directions towards the development of micro-combustors were presented.
The microscale combustion-based energy and power generation systems are potential alternatives to traditional batteries owing to the much higher energy density of hydrogen and hydrocarbon fuels. However, the surface-area-to-volume ratio of the micro-combustors is very large, which makes the flame difficult to sustain stable owing to the large heat-loss. Therefore, it is very necessary to develop effective flame stabilization technologies for combustion-based micro energy and power systems. Great progress has been made in the past decade, which was reviewed in this article. The flame stabilization technologies for micro- and meso-scale combustors are divided into three categories, namely, single flame stabilization technologies, combined flame stabilization technologies, and other flame stabilization technologies that could not be included in the former two. The single flame stabilization technologies include flame holders (e.g., bluff body, wall cavity), heat recirculation strategy (e.g., porous media, thermally orthotropic wall), catalyst, and additives in the fuel. The combined flame stabilization technologies consist of two or more of these single flame stabilization methods, such as Swiss-roll combustor with a bluff-body, micro catalytic combustor with a bluff-body, and so on. The underlying mechanisms of these flame anchoring strategies were also discussed. The guidelines to develop micro-combustors with excellent flame stabilization ability were summarized at the end of this review article.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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