Summary
Rapid convergence that can be prescribed by a user is appealing for many applications with high requirements. This stimulates finite‐time stabilization with arbitrarily prescribed ...settling‐time and so‐called prescribed‐time stabilization. But their continuous realizations had to restrict uncertainties and/or to bear truncated run of controllers. This paper, for nonlinear systems with large uncertainties, realizes not only the convergence within the prescribed time, but also the non‐truncated run. First, by lending finite‐time stabilization to prescribed‐time stabilization and integrating dynamic compensation, an adaptive controller with time‐varying components is devised such that the system state reaches the origin at a finite time less than the prescribed time, while exhibiting local asymptotic stability (of the origin). Then by monitoring the finite time online, the time‐varying components of the adaptive controller are frozen as their values at the finite time. The asymptotic stability guarantees the frozen adaptive controller can make the system state remain at the origin for all future time. But the above finite time could not be detected in practice, due to ubiquitous disturbances. We thus modified the detection to ensure that the system state enters a vicinity of the origin before the prescribed time and stays there afterwards under some conditions on uncertainties and disturbances. Two simulation examples illustrate the effectiveness of the proposed controller.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
This paper investigates the finite-time and fixed-time stabilization (FFTS) of switched systems with discontinuous dynamics, external disturbances and delays. Firstly, a new parameterized ...discontinuous stabilizer is designed to ensure the FFTS of switched discontinuous systems in the sense of Filippov solutions. Secondly, a detailed analysis is provided on how to regulate the power parameters to determine the settling time is finite or fixed. Thirdly, a new adaptive controller is further designed to stabilize the considered system in a finite time, and the corresponding settling time is estimated as well. Finally, two examples are given to demonstrate the efficiency of the proposed method.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
The formation and stabilization of soil organic matter (SOM) are major concerns in the context of global change for carbon sequestration and soil health. It is presently believed that lignin is not ...selectively preserved in soil and that chemically labile compounds bonding to minerals comprise a large fraction of the SOM. Labile plant inputs have been suggested to be the main precursor of the mineral‐bonded SOM. Litter decomposition and SOM formation are expected to have temperature sensitivity varying with the lability of plant inputs. We tested this framework using dual 13C and 15N differentially labeled plant material to distinguish the metabolic and structural components within a single plant material. Big Bluestem (Andropogon gerardii) seedlings were grown in an enriched 13C and 15N environment and then prior to harvest, removed from the enriched environment and allowed to incorporate natural abundance 13C–CO2 and 15N fertilizer into the metabolic plant components. This enabled us to achieve a greater than one atom % difference in 13C between the metabolic and structural components within the plant litter. This differentially labeled litter was incubated in soil at 15 and 35 °C, for 386 days with CO2 measured throughout the incubation. After 14, 28, 147, and 386 days of incubation, the soil was subsequently fractionated. There was no difference in temperature sensitivity of the metabolic and structural components with regard to how much was respired or in the amount of litter biomass stabilized. Only the metabolic litter component was found in the sand, silt, or clay fraction while the structural component was exclusively found in the light fraction. These results support the stabilization framework that labile plant components are the main precursor of mineral‐associated organic matter.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
Areas contaminated with heavy metals can pose major risks to human health and ecological environments. The aims of this study are to assess human health risk and pollution index for heavy metals in ...agricultural soils irrigated by effluents of stabilization ponds in Birjand, Iran. The results revealed that the levels of Cr, Mn, Zn, Fe, Cu, Cd, and Pb were in range of 70.3–149.65, 355–570, 31.15–98.45, 23,925–29,140, 22.75–25.95, 0.17–6.51, and 8.5–23.5 mg/kg in topsoils, respectively. Total hazard index values from heavy metals through three exposure routes for adults and children were 9.13E−01 and 1.10, respectively, indicating that there was non-carcinogenic risk for children. The total risk of carcinogenic metals (Cr, Cd, and Pb) through the three exposure routes for adults and children was 1.06E−04 and 9.76E−04, respectively, which indicates that the metals in the soil will not induce carcinogenic risks to these age groups. Pollution levels of heavy metals in soil samples including enrichment factor (EF), contamination factor (CF), pollution load index (PLI), and geo-accumulation index (
I
geo
) showed heavy metal contamination of agricultural soils. The results of the present study provide basic information about heavy metal contamination control and human health risk assessment management in the study area.
We study the modulus stabilization in an A4 model whose A4 flavor symmetry is originated from the S4 modular symmetry. We can stabilize the modulus so that the A4 invariant superpotential leads to ...the realistic lepton masses and mixing angles. We also discuss the phenomenological aspect of the present model as a consequence of the modulus stabilization.
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CMK, CTK, FMFMET, IJS, NUK, PNG, UM
Summary
This paper investigates the finite‐time robust simultaneous stabilization problem of a set of nonlinear time‐delay systems with general forms and proposes some new simultaneous stabilization ...results. First, by developing an equivalent form and applying augmented technique, this paper obtains an augmented equivalent form of the original systems. Secondly, based on the equivalent form, we study finite‐time simultaneous stabilization problem and present some new stabilization results by constructing some suitable Lyapunov functionals. Thirdly, using the simultaneous stabilization results obtained, this paper investigates the finite‐time robust simultaneous stabilization problem for the set systems and proposes a delay‐dependent robust simultaneous stabilization result. Finally, the study of an illustrative example shows that the results obtained by this paper work well in the finite‐time robust simultaneous stabilization the set systems. It is shown that, by using the method in this paper, the developed conditions do not contain delay terms, which can avoid solving nonlinear mixed matrix inequalities and reduce effectively computational burden in studying nonlinear time‐delay systems.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
“Prescribed-time” stabilization addresses the problem of regulating the state to the origin in a fixed (prescribed) time irrespective of the initial state. While prior results on prescribed-time ...stabilization considered specific classes of systems such as a chain of integrators with uncertainties matched with the control input (i.e., normal form), we address here a general class of nonlinear systems in a generalized strict-feedback-like structure with state-dependent nonlinear uncertainties throughout the system dynamics. The proposed control design is based on our dynamic high gain scaling technique along with a novel temporal transformation and form of the scaling dynamics with temporal forcing terms. We show that the proposed control design achieves prescribed-time stabilization for the considered general class of uncertain nonlinear systems.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
In this paper, a novel first‐ and second‐order stabilization‐free virtual element method is proposed for two‐dimensional elastoplastic problems. In contrast to traditional virtual element methods, ...the improved method does not require any stabilization, making the solution of nonlinear problems more reliable. The main idea is to modify the virtual element space to allow the computation of the higher‐order L2$$ {L}_2 $$ projection operator, ensuring that the strain and stress represent the element energy accurately. Considering the flexibility of the stabilization‐free virtual element method, the elastoplastic mechanical problems can be solved by radial return methods known from the traditional finite element framework. J2$$ {J}_2 $$ plasticity with hardening is considered for modeling the nonlinear response. Several numerical examples are provided to illustrate the capability and accuracy of the stabilization‐free virtual element method.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
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