The peridynamic motion equation was investigated once again. The origin of incompatibility between boundary conditions and peridynamics was analyzed. In order to eliminate this incompatibility, we ...proposed a new peridynamic motion equation in which the effects of boundary traction and boundary displacement constraint were introduced. The new peridynamic motion equation is invariant under the transformations of rigid translation and rotation. Meanwhile, it also satisfies the requirements of total linear and angular momentum equilibrium. By this motion equation, three kinds of boundary value problems containing the displacement boundary condition, the traction boundary condition and mixed boundary condition are characterized in peridynamics. As examples, we calculated static tension and longitudinal vibration of a finite rod. The acquired solutions exhibit obvious nonlocal features, and the vibration has the dispersion similar to one dimensional atom chain vibration.
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•Cu13, Cu38, Cu55 clusters and Cu(111) surface are used to model different sizes of Cu cluster.•The preferable path of C2H2 selective hydrogenation depends on the size of Cu ...catalyst.•The larger the Cu cluster size is, the higher the selectivity of C2H4 is.•Beginning with Cu55 cluster, Cu cluster size is beneficial to form C2H4.•The activity of C2H4 formation is related to the d-band center of Cu catalysts.
In order to probe into the size effect of Cu catalyst on the selectivity and activity of ethylene formation in acetylene selective hydrogenation, different sizes of Cu catalysts including Cu13, Cu38, Cu55 clusters and the periodic Cu(111) surface have been employed to systematically investigate the selective hydrogenation of C2H2 using density functional theory calculations. The results show that the adsorption ability of C2H2 is stronger than that of C2H4 on different sizes of Cu catalysts, which is in favor of C2H2 activation and hydrogenation. On Cu13 and Cu38 clusters, C2H2 easily undergoes over-hydrogenation to form ethane via CHCH2 and CHCH3 intermediates, namely, both clusters exhibit a poor selectivity towards C2H4 formation. However, on Cu55 cluster, C2H2 is easily hydrogenated to form C2H4via CHCH2 intermediate, and C2H4 prefers desorption over its hydrogenation, suggesting that Cu55 cluster exhibits a good selectivity towards C2H4 formation. Further, the periodic Cu(111) surface regarded as the large Cu particle sizes has the same results with Cu55 cluster. Therefore, among different sizes of Cu cluster, the size of Cu cluster affects the preferred pathway of C2H2 selective hydrogenation, and alters the selectivity towards C2H4 formation; moreover, beginning with Cu55 cluster, Cu cluster is beneficial to C2H2 hydrogenation to C2H4. The activity of C2H4 formation follows the order of Cu(111) > Cu38> Cu55 >> Cu13, which corresponds to the d-band center of these catalysts. The identifications about the relationship of the intrinsic selectivity and activity with cluster size effect would provide a clue for designing highly-efficient Cu-based catalysts in C2H2 hydrogenation to C2H4.
Biogenic CBM is an important component of detected CBM, which is formed by coal biodegradation and can be regenerated by anaerobic microorganisms. One of the rate-limiting factors for microbial ...degradation is the bioavailability of coal molecules, especially for anthracite which is more condense and has higher aromaticity compared with low-rank coal. In this paper, NaOH solution with different concentrations and treating time was employed to pretreat anthracite from Qinshui Basin to alter the coal structure and facilitate the biodegradation. The results showed that the optimal pretreatment conditions were 1.5 M NaOH treating for 12 h, under which the biomethane production was increased by 17.65% compared with untreated coal. The results of FTIR and XRD showed that NaOH pretreatment mainly reduced the multi-substituted aromatics, increased the C-O in alcohols and aromatic ethers and the branching degree of aliphatic chain, and decreased the aromatic ring structure, resulting in the improvement of coal bioavailability and enhancement of biomethane yield. And some organics with potential to generate methane were released to filtrate as revealed by GC-MS. Our results suggested that NaOH was an effective solution for pretreating coal to enhance biogenic methane production, and anthracite after treating with NaOH could be the better substrate for methanogenesis.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
•The singular solutions to the stress and displacement in the local uniaxial tension are acquired in the framework of non-ordinary state-based peridynamics.•The stress solution of peridynamics is ...smoother than the displacement solution.
We solve the local uniaxial tension of an infinite rod in the framework of non-ordinary state-based peridynamics. The singular solutions of stress and displacement are acquired. When the influencing range of the window function approaches zero, these two solutions will return to the solutions of the classical elasticity. The analysis shows that the singularities of the solutions stem from such a feature of the window function that must be represented by a rapidly decreasing function in physics. Contrary to the classical elasticity, the stress solution of peridynamics is smoother than the displacement solution. In addition, a criterion used to select the window function is proposed in this paper.
We solve the local uniaxial tension of an infinite rod in the framework of non-ordinary state-based peridynamics. The singular solutions of stress and displacement are acquired. When the influencing range of the window function approaches zero, these two solutions will return to the solutions of the classical elasticity. The analysis shows that the singularities of the solutions stem from such a feature of the window function that must be represented by a rapidly decreasing function in physics. Contrary to the classical elasticity, the stress solution of peridynamics is smoother than the displacement solution. In addition, a criterion used to select the window function is proposed in this paper.
How to prescribe traction on boundary surface is still an open question in peridynamics. This problem is investigated in this paper. Through introducing the induced body force defined by boundary ...traction, the Silling's peridynamic motion equation is extended to a new formulation called the traction-associated peridynamic motion equation, which is verified to be compatible with the conservation laws of linear momentum and angular momentum. The energy conservation equation derived from the traction-associated peridynamic motion equation has the same form as that in the original peridynamics advanced by Silling. Therefore, the constitutive models of the original peridynamics can be directly applied to the traction-associated peridynamic motion equation. Some benchmark examples in the plane stress problems are calculated. The numerical solutions agree well with the classical elasticity solutions, and the volume correction and the surface correction are no longer needed in the numerical algorithm. These results show that the traction-associated peridynamic motion equation not only retains all advantages of the original peridynamics, but also can conveniently deal with the complex traction boundary conditions.
Based on a energy flux vector associated with surface energy, the Lagrangian field theory is used to derive a new mixed boundary condition of solid concerned with surface effects. The prediction ...given by it agrees well with experimental data on the lattice contraction of palladium nanoparticles. Comparison with various existing versions of traction boundary condition is discussed. The results show that the new version is concise in theory and verifiable in experiment.
Celotno besedilo
Dostopno za:
BFBNIB, DOBA, GIS, IJS, IZUM, KILJ, KISLJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
Hydrocarbon contamination due to anthropogenic activities is a major environmental concern worldwide. The present study focuses on biochar prepared from fruit and vegetable waste and sewage sludge ...using a thermochemical approach and its application for the enhanced bioremediation (biostimulation and bioaugmentation) of diesel-polluted soil. The biochar was characterized using FTIR (Fourier-transform infrared spectroscopy), elemental analysis, surface area analysis, and pore analysis. Adsorption experiments showed that hydrocarbon degradation was attributed to biological processes rather than adsorption. The study found that various biochar amendments could significantly increase the rate of hydrocarbon biodegradation with removal efficiencies > 70%. Bioaugmentation using cow dung further improved the removal efficiency to 82%. Treatments showing the highest degree of removal efficiency indicated the presence of 27 different bacteria phyla with Proteobacteria and Actinobacteria as the most abundant phyla. The present study concludes that biochar amendments have great potential for enhancing the bioremediation of soils contaminated with diesel range hydrocarbons.
Abstract
Brown blotch disease in
Agaricus bisporus
reduces its commercial value, resulting in significant economic losses. The pathogens of brown blotch disease are diverse. Current research on the ...biological characteristics and toxins has been limited to
Pseudomonas tolaasii
but lacks understanding of other pathogens. Understanding the biological characteristics of the pathogens and identifying their toxins are essential prerequisites for disease prevention and control. This study isolated two pathogens from brown discoloration in
A. bisporus
in Guangxi, China, and identified them as
Pseudomonas tolaasii
and
Cedecea neteri
.
C. neteri
exhibited stronger resistance to sodium dodecyl sulfate (SDS) and H
2
O
2
and a broader pH adaptation range than
P. tolaasii
.
P. tolaasii
showed higher swimming motility than
C. neteri
.
C. neteri
produces two toxins identified as phenylacetic acid and p-hydroxybenzoic acid, causing browning symptoms in
A. bisporus
at 20 μg and 10 μg, respectively. The present study compared various biological characteristics between
P. tolaasii
and
C. neteri
. The toxins produced by
C. neteri
were extracted and identified, and their toxicity to
A. bisporus
was evaluated, which is the first report on
C. neteri
toxins. These discoveries have enhanced our understanding of the biological characteristics and biotoxins of
C. neteri
. The research findings offer new insights for developing novel disease prevention and control strategies.
In situ bioconversion of low rank coal to natural gas is an attractive approach to reduce greenhouse gas emissions and utilize underexploited coal recourses. Hydrogen peroxide pretreatment followed ...by microbial conversion of coal to methane proved effective. However, what maceral component is more susceptible to solubilization and microbial conversion remains elusive. In this study, the dissolution of huminite-enriched Shengli lignite by hydrogen peroxide and its effects on the subsequent methane production by a microbial assemblage were investigated. The huminite was enriched and separated by a combination of hand-picking and floating-sink (isopycnic centrifugation) separation and treated with hydrogen peroxide. Both solid and liquid fractions of the treated coal were subjected to microbial conversion. Various analyses including Fourier Transform Infrared Spectroscopy (FTIR), Gas Chromatography/Mass Spectrometry (GC/MS), High-Performance Liquid Chromatography (HPLC), Gel Permeation Chromatography (GPC), and DNA sequencing were conducted for both solid and liquid fractions as well as samples after biomethanation. The study demonstrated unequivocally that the enrichment of huminite can improve solubilization and methane production, and that huminite is more accessible and biodegradable compared to other macerals. Microbial analysis revealed that the dominance of methanogens was associated with huminite. Overall, this study provides insight into the bioconversion of lignite to natural gas and suggests that huminite plays a crucial role in this process.
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The coal-degrading ability of microorganisms is essential for the formation of biogenic coalbed methane. The ability to degrade the aromatic compound of coal is more important because it is perceived ...as the main refractory component for bioconversion. In this paper, a polycyclic aromatic hydrocarbon (PAH) degrading fungal community (PF) was enriched from produced water using phenanthrene as sole carbon source. The goal was to improve both the microbial structure of the methanogenic microflora and its coal-degrading ability. Two strategies were pursued. The first used coal pretreatment with PF (PP), followed by methane production by methanogenic microflora; the second used methane production directly from coal by mixed culture of PF and methanogenic microflora (PM). The results showed that methane productions of PP and PM increased by 29.40 and 39.52%, respectively. After 7 days of cultivation, the fungal community has been altered in PP and PM, especially for
Penicillium
the proportions of which were 67.37 and 89.81% higher than that in methanogenic microflora, respectively. Furthermore, volatile fatty acid accumulations increased by 64.21 and 58.15%, respectively. The
13
C-NMR results showed that PF addition promoted the transformation of aromatic carbons in coal to carboxyl and carbonyl carbons, which contributed greatly to the production of methane together with oxygen-containing functional groups. These results suggest that methane production can be increased by indigenous PAH-degrading fungi by improving the fermentation of aromatics in coal and the generation of volatile fatty acids. This provided a feasible method for enhancing biomethane generation in the coal seam.
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