Stabilized methods, which have been very common in flow computations for many years, typically involve stabilization parameters, and discontinuity-capturing (DC) parameters if the method is ...supplemented with a DC term. Various well-performing stabilization and DC parameters have been introduced for stabilized space–time (ST) computational methods in the context of the advection–diffusion equation and the Navier–Stokes equations of incompressible and compressible flows. These parameters were all originally intended for finite element discretization but quite often used also for isogeometric discretization. The stabilization and DC parameters we present here for ST computations are in the context of the advection–diffusion equation and the Navier–Stokes equations of incompressible flows, target isogeometric discretization, and are also applicable to finite element discretization. The parameters are based on a direction-dependent element length expression. The expression is outcome of an easy to understand derivation. The key components of the derivation are mapping the direction vector from the physical ST element to the parent ST element, accounting for the discretization spacing along each of the parametric coordinates, and mapping what we have in the parent element back to the physical element. The test computations we present for pure-advection cases show that the parameters proposed result in good solution profiles.
Full text
Available for:
DOBA, EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, IZUM, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UILJ, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
This paper investigates the fixed-time stabilization problem for a class of nonlinear systems via event-triggered control. The event-triggered mechanism can be applied to the nonlinear system with ...the coexistence of low-order and high-order nonlinearities. In order to deal with these low-order and high-order terms as well as achieve the objective of fixed-time stabilization, the initial value of the system is divided into two cases, and then the event-triggered controller is designed, respectively. By switching control theory, it is proved that the nonlinear system is globally fixed-time stable under the designed controller and the Zeno behavior can be excluded. Finally, two simulations show that the proposed technology is effective.
In this contribution, the problem of fixed-time stabilization in multi-weighted complex networks via the novel adaptive pinning nonchattering control based on the linear matrix inequality (LMI) ...method, as well as its application to image protection is addressed. Different from the traditional methods, a novel fixed-time stable form is proposed and the convergence time is estimated based on beta function. Next, utilizing the designed continuous adaptive control strategy, a sufficient LMI condition is presented to ensure the fixed-time stabilization of multi-weighted complex networks. Furthermore, the novel nonchattering adaptive pinning control protocol is given to guarantee the fixed-time stabilization of the system only by controlling a small number of nodes. Note that a scheme of how to select the number of control nodes is put forward accordingly. Finally, the effectiveness of the proposed method is verified by the actual financial model. Meanwhile, a number of encryption experiments are carried out based on three networks, and the mean and variance of the encryption performance are calculated to show the stability and robustness of image encryption different from the existing research works.
The traditional preparation methods of nitrocellulose emulsion have many problems, such as high emulsifier content, complex preparation processes, or the need for high energy‐consuming emulsification ...equipment. To address these issues, in this paper, the emulsifier‐free NC dispersion was successfully prepared by a simple, low‐energy solvent displacement method for the first time and the formation and stabilization mechanism of NC nanoparticles was also thoroughly investigated. The formation mechanism of the NC particles based on the “nucleation and aggregation” and the stabilization mechanism of the NC aqueous dispersions based on the electrostatic repulsion of anions were proposed and supported by experimental results. At the same time, we achieved effective control of the solid content of the NC dispersion by vacuum concentration. The obtained NC dispersion had a large range of adjustable sizes (63.82–143.43 nm), uniform size distribution (PDI < 0.2), a wide range of tunable solid content (0.5%–16%), and good stability (zeta potential < −20 mV), which has potential application in adhesives and coatings as promising candidates for traditional NC organic coatings.
In this paper, the emulsifier‐free NC dispersion was successfully prepared by a simple, low‐energy solvent displacement method for the first time and the formation and stabilization mechanism of NC nanoparticles was also thoroughly investigated.
Full text
Available for:
BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Nowadays, chemically defined cell culture media (CCM) have replaced serum‐ and hydrolysate‐based media that rely on complex ingredients, such as yeast extracts or peptones. Benefits include a ...significantly lower lot‐to‐lot variability, more efficient manufacturing by reduction to essential components, and the ability to exclude components that may negatively influence growth, viability, or productivity. Even though current chemically defined CCMs provide an excellent basis for various mammalian biotechnological processes, vitamin instabilities are known to be a key factor contributing to the variabilities still present in liquid CCM as well as to short storage times. In this review, the chemical degradation pathways and products for the most relevant vitamins for CCM will be discussed, with a focus on the effects of light, oxygen, heat, and other CCM compounds. Different approaches to stabilize vitamins in solution, such as replacement with analogs, encapsulation, or the addition of stabilizing compounds will also be reviewed. While these vitamins and vitamin stabilization approaches are presented here as particular for CCM, the application of these concepts can also be considered relevant for pharmaceutical, medical, and food supplement purposes. More precise knowledge regarding vitamin instabilities will contribute to stabilize future formulations and thus decrease residual lot‐to‐lot variability.
The use of chemically‐defined cell culture media in place of serum‐ or hydrolysate‐based media has significantly enhanced the robustness of cell culture in the biomanufacturing of therapeutic proteins. However, some of these essential chemical compounds, such as vitamins, still contribute to cell culture inconsistency via chemical degradation upon storage. This review highlights the likely chemical degradation pathways for vitamins in cell culture media, factors contributing to this degradation, and potential strategies to stabilize these vitamins in complex cell culture media.
Full text
Available for:
BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
•Identification of modal parameters automatically.•Variational Gaussian mixture model for soft classification.•Using only two user-specified thresholds.•Automatically determine the optimal number of ...clusters.
Automated operational modal analysis is essential for online structural health monitoring without human intervention. It remains a challenging issue due to the need of processing a large number of datasets and the involvement of many user-specified thresholds. This paper proposes a novel automated modal identification approach based on stochastic subspace identification and variational Gaussian mixture model that involves the analysis of the stabilization diagram to automatically identify modal parameters. Two validation criteria are first adopted to eliminate the spurious modes in the stabilization diagram. A Gaussian mixture model (GMM) is then used to probabilistically classify each pole in the stabilization diagram to a specific cluster. The parameters of GMM are estimated using variational inference, giving representatives of each mode, and the optimal number of clusters is automatically determined through the Dirichlet Process. The proposed framework automatically distinguishes physical modes from spurious modes with only two verified and widely used thresholds. Results of a four-story shear and a footbridge with continuous measurements demonstrate the efficacy and robustness of the proposed approach. It shows that the proposed approach can automatically identify modal parameters with high accuracy, including weakly excited and closely spaced modes.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
The Fe(II)-induced phase transformation of iron (hydr)oxides is an important process in the geochemical iron cycle and is one in which the coexisting metal cations inhibit the phase transformation ...rates. However, the underlying affecting mechanisms by metal cations and the critical property of metal cations that is responsible for the inhibition remain unclear. In this study, we focus on the cation effect of seven divalent cations (denoted as Me(II), including Mg(II), Ca(II), Ba(II), Mn(II), Co(II), Ni(II), and Zn(II)) and their influencing mechanisms on Fe(II)-catalyzed transformation processes of ferrihydrite. At initial reaction conditions (i.e. pH6.5 and 2.0mM Fe(II)), the binding ability (the affinity of cations for ferrihydrite surface) of Me(II) was found to affect the ferrihydrite transformation. Me(II) with higher binding abilities reduced the bound-Fe(II) amount on ferrihydrite and decreased the redox potentials of the Fe(II)-catalyzed system to inhibit the transformation rates of ferrihydrite. In addition to the inhibition effect, the Me(II) was partly stabilized in the formed secondary iron minerals. The binding abilities of Me(II) also affected the Fe(II)-induced transformation pathways of ferrihydrite by affecting the amount of bound-Fe(II) on ferrihydrite. Ferrihydrite was first transformed to lepidocrocite and later to goethite and magnetite with Me(II) that had lower binding ability than Fe(II), whereas it was directly transformed to goethite and magnetite when with Me(II) that had higher binding ability than Fe(II).
•Fe(II)-induced phase transformation of ferrihydrite is inhibited by the presence of divalent metal cations in solution.•Binding abilities of cations affect the phase transformation rate of ferrihydrite at a constant pH of 6.5.•Different divalent metal cations result in different pathways of Fe(II)-induced ferrihydrite transformation.•Metals were stabilized through occlusion/incorporation in the formed secondary iron minerals from transformed ferrihydrite.
Display omitted
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Grassland restoration across the world increases soil organic carbon (SOC) sequestration which is critical for global C cycling and CO2 removal from the atmosphere. However, the relative importance ...of plant- and microbially-derived C for SOC is still an open question for temperate grasslands. Here, amino sugars and lignin phenols were used as biomarkers to investigate the relative microbial and plant residue contribution to SOC in a 30-year (1-, 5-, 10-, 15-, 25-, 30-year) restoration chronosequence of temperate grassland. The contribution of microbially-derived C (from 4.9 to 13 g kg−1) to SOC was much greater than that of plant-derived C (from 1.3 to 2.3 g kg−1). At the early stage of restoration (<15 years), grassland soils accumulated more C in the form of plant-derived C. In contrast, grassland soils at the late stage of restoration (>15 years) accumulated more microbially-derived C, and less from plant residues. These findings highlight the dominance of microbial contribution to SOC stabilization compared with plant residues. The contribution of bacteria-derived C to SOC gradually increased from 29% to 50% with progress of grassland restoration, while the contribution of fungal C to SOC decreased from 30% to 21%. Consequently, microbial residue contribution to SOC shifts from fungal and bacterial to mainly bacterial residues during grassland restoration. This shift may be due to the faster bacterial growth and a increasing living biomass during grassland restoration, leading to higher accumulation of bacterial residues. Correlation analysis and random forest models showed that belowground plant biomass, soil pH, and living microbial biomass were the main factors regulating plant-derived C. The microbially-derived C in SOC, however, was dependent on living microbial biomass, soil pH and dissolved organic C. Concluding, grassland restoration increased soil C sequestration primarily by microbial necromass (mainly bacterial necromass), and is affected by abiotic and biotic factors, as well as plant C input.
Display omitted
•Both microbial and plant-derived C contents increased with grassland restoration age.•Microbial-derived C contributed more to SOC than plant-derived C.•Microbial residue contribution to SOC shifted from fungal-to bacterial residue.•Soil pH and living microbial biomass were driving factors for plant- and microbial-derived C.
Full text
Available for:
GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Nitrogen removal is an important process for wastewater ponds prior to effluent release. Bacteria and archaea can drive nitrogen removal if they possess the genes required to metabolize nitrogen. In ...the tropical savanna of northern Australia, we identified the previously unresolved microbial communities responsible for nitrogen cycling in a multi-pond wastewater stabilization system by measuring genomic DNA and cDNA for the following:
nifH
(nitrogen fixation);
nosZ
(denitrification);
hzsA
(anammox); archaeal
AamoA
and bacterial
BamoA
(ammonia oxidation);
nxrB
(nitrite oxidation); and
nrfA
(dissimilatory NO
3
reduction to NH
3
). By collecting 160 DNA and 40 cDNA wastewater samples and measuring nitrogen (N)-cycling genes using a functional gene array, we found that genes from all steps of the N cycle were present and, except for
nxrB
, were also expressed. As expected, N-cycling communities showed daily, seasonal, and yearly shifts. However, contrary to our prediction, probes from most functional groups, excluding
nosZ
and
AamoA
, were different between ponds. Further, different genes that perform the same N-cycling role sometimes had different trends over space and time, resulting in only weak correlations between the different functional communities. Although N-cycling communities were correlated with wastewater nitrogen levels and physico-chemistry, the relationship was not strong enough to reliably predict the presence or diversity of N-cycling microbes. The complex and dynamic response of these genes to other functional groups and the changing physico-chemical environment provides insight into why altering wastewater pond conditions can result an abundance of some gene variants while others are lost.
Full text
Available for:
EMUNI, FZAB, GEOZS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
PDF
