It is important to detect floating oil slicks after spill accidents, and hyperspectral remote sensing technology is capable of achieving this task. Traditional methods mainly utilize the spectral ...indices of hydrocarbons to detect floating oil slicks, but are poor at distinguishing the thickness of oil slicks and cannot detect sheens. Since the spectra of oil slicks should be affected by seawater as well as oil, this paper investigated the use of spectral indices of hydrocarbons and seawater to identify different thicknesses of oil slicks. In this research, a measurement, called index separability (IS), was proposed for quantitatively evaluating the identification ability of these spectral indices. Based on the evaluation results, experiments were conducted to validate the applicability of these spectral indices. The results show that the spectral indices of hydrocarbons are more suitable for detecting continuous true color oil slicks and emulsions and that spectral indices of seawater are more suitable for sheens and seawater. In addition, the spectral indices of hydrocarbons and seawater are complementary for detecting oil slicks. Finally, combining the spectral indices of hydrocarbons and seawater is conducive to achieving more accurate oil slick recognition results.
A new metal–organic polyhedron Cu-MOP with octahedral geometry was constructed by 2,8-dibenzothiophenedicarboxylic acid and dicopper paddlewheel. Cu-MOP exhibited H2 and CO2 sorption behavior. ...Furthermore, Cu-MOP revealed reductive properties towards TCNQ, DDQ, CR and MB due to the electron-donating nature of DBT ligand.
A new metal organic polyhedron Cu-MOP based on a dibenzothiophene ligand showing gas sorption and reductive properties. Display omitted
•A new metal organic polyhedron Cu-MOP based on a dibenzothiophene ligand has been synthesized and characterized.•Cu-MOP showed H2 and CO2 sorption behavior over N2.•TCNQ, DDQ, CR and MB could be reduced in the presence of Cu-MOP.
•The full debonding strain between steel fibers and the UHPC matrix is about 0.32%.•The maximum strain for generating cracks is about 3.25%.•The crack initiation strain rate varies linearly with ...time.•The relationship between crack length and temporal crack evolution is described by an exponential function.
This study investigates the crack propagation behavior of UHPC blended with straight steel fibers of different lengths (6, 13, and 20 mm), at varying replacement ratios (0.5%, 1.0%, and 1.5%) and a constant total fiber volume fraction (Vf = 2.0%), under flexural loading. The results indicate that blending with 0.5% medium length fibers and 1.5% long fibers yields the best flexural behavior compared to other investigated specimens. Using digital image correlation (DIC) technique, the evolution of surface deformation and strain field was analyzed. Based on the recorded images and corresponding analyses, the full debonding strain between the fibers and the matrix was determined to be about 0.32%. Moreover, the maximum strain for generating cracks was approximately 3.25%, irrespective of the fiber length. When longer fibers were replaced with shorter fibers at 0.5% or 1.0% replacement ratios, Crack opening displacement (COD) variations along the beam presented a linear shape. However, at higher replacement ratios (1.5% and 2.0%), the profile showed an abrupt change, and COD variations were non-constant. The samples comprising hybrid fibers presented a faster decline in the crack initiation strain rate at higher replacement ratios of the longer fibers. In the initial stage of cracking, the crack propagated rapidly; however, the crack propagation speed dropped dramatically during crack evolution before it stabilizes.
This study presents the meso-mechanics models of the multi-scale fiber bridging constitutive law of ultra high-performance concrete (UHPC) under cyclic loading. First, an analytical fiber pullout ...model was improved by considering the effect of fiber inclination angle and embedded length. Second, the flexural behavior of the UHPC with various fiber volume fractions under quasi-static loading was predicted by performing meso-mechanics-based sectional analysis. Third, the relation between a single steel fiber and the crack opening displacement amplitude (ΔCOD) under cyclic loading was simulated. Importantly, regardless of the state of the single fiber in (debonding or sliding), the evolution of ΔCOD with different inclination angles and embedded lengths could be quantitatively analyzed during a cycle. Finally, the multi-scale fiber bridging constitutive law of the UHPC under cyclic loading was obtained, and the theoretical relation for the fiber bridging stress amplitude (Δσf) and ΔCOD during the entire cycle process could be quantitatively estimated. There was a slight of deviation between the predicted and experimental results for the UHPC under cyclic loading, because the effect of the UHPC matrix on the fatigue crack was neglected. Overall, the fiber bridging theoretical analysis model for the UHPC under cyclic loading showed good agreement with the experimental data.
•CCR could be used as a potential replacement of NaOH to activate coal gangue geopolymer.•Optimal CCR content and NaOH:Na2SiO3 mass ratio = 20% and 50:50.•The compressive strength depended on the ...types and amounts of reaction products and pore structure.•CG-CCR geopolymer is feasible to enhance the strength of soft soil.•The exponential correlation between strength of stabilized soil and CG-CCR geopolymer content is proposed.
This study investigates the use of calcium carbide residue (CCR) as a potential alternative to NaOH for activating coal gangue (CG) geopolymers, both of industrial waste. A series of experiments were carried out to evaluate the effects of CCR content, NaOH:Na2SiO3 mass ratios, liquid to solid ratio (L/(CG + CCR)), and curing time on the strength development of CG-CCR geopolymers. Moreover, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), mercury intrusion porosimetry (MIP), and field emission scanning electron microscopy (FESEM) were used to analyze the reaction products and microstructural characteristics of CG-CCR geopolymer. Accordingly, the CG-CCR geopolymers were applied to stabilize soft soil. Experimental results indicate that CCR could significantly enhance the compressive strength of CG-CCR geopolymer. A CCR content of 20% correlates to the greatest increase in 3-d compressive strength (327.6%) compared with pure CG geopolymer (CCR = 0%). The optimal NaOH:Na2SiO3 mass ratio is 50:50, while the compressive strength increases with decreasing L/(CG + CCR) and increasing curing time. Based on the analysis of microstructure (XRD, FTIR, TGA, MIP, and FESEM), it was inferred that CCR could promote the polymerization reaction and increase the reaction products (primarily N-A-S-H and C-A-S-H gels) of CG-CCR geopolymers, which are responsible for the strength development. Additionally, CG-CCR geopolymer has a positive impact on the stress–strain relationship and strength of stabilized soil. This study demonstrates that CCR can be used as a partial replacement for NaOH in generating CG geopolymer, which can provide an effective path for disposing of CG and CCR as well as lead to more practical applications for geopolymer in soil stabilization.
The design and construction of highly effective circularly polarized luminescence (CPL)-active materials has aroused considerable attention due to their widespread applications in sensors, optical ...devices, and asymmetric synthesis. However, the exploration of novel CPL-active materials with high luminescence dissymmetry factor (
g
lum
) values is still a challenge. Herein, we describe a new approach for the preparation of supramolecular metallacycles with amplified CPL promoted by hierarchical self-assembly involving Pt···Pt interactions. Notably, the resultant metallacycles exhibited strong CPL signals with high
g
lum
values, while their corresponding precursors were CPL silent. The CPL amplification mechanism was comprehensively validated by ultraviolet-visible absorption, emission spectroscopy, nuclear magnetic resonance spectroscopy, scanning electron microscopy, transmission electron microscopy, atomic force microscopy, coarse-grained molecular dynamics simulations, and time-dependent density functional theory calculations. This work thus provides the first example of preparing highly effective CPL-active materials based on hierarchical self-assembly involving Pt···Pt interactions.
Fatigue crack propagation behavior in ultra-high-performance concrete (UHPC) containing different volume fractions of steel fibers is investigated under cyclic flexural loading at various stress ...levels. Evolutions of the crack mouth opening displacement, crack tip strain, and crack propagation length are characterized during continuous loading cycles via digital image correlation. Test data are fit to smooth, continuous logarithmic functions to discern relationships between evolving crack length and the number of loading cycles. The crack propagation rates of different UHPC specimens are then determined from the first derivative of these logarithmic functions. A critical crack length of approximately 20 mm is found in UHPC containing a fiber volume fraction (Vf) of 0.5%, while that of other specimens (Vf = 1.0%, 1.5%, and 2.0%) is found to approach 60 mm under the stress levels of 0.80, 0.75, 0.70 and 0.65. Strain diagrams obtained via DIC reveal no obvious changes for the crack growth along the y-direction in UHPC specimens containing fiber volume fractions of 0.5% and 1.0%, while a tendency for strain concentrations oriented at 45° characterizes crack development in specimens containing 1.5% and 2.0% volume fractions of fiber. Crack propagation rates during the stable stage of crack propagation decrease upon reducing applied stress level and with increased content of steel fiber reinforcement, providing predominant means to enhance fatigue life.
•The fibers number per unit area for S0.5, S1.0, S1.5, and S2.0 were 7, 14, 21, and 31, respectively. The fiber pull-out length in cracked zone with different fiber-volume fractions was about ...3.56 mm.•The fiber orientation factor (ηθ) of S0.5, S1.0, S1.5, and S2.0 were 0.80, 0.79, 0.69 and 0.61 respectively.•A linear relationship between fiber pull-out number and equivalent bending stress, as well as between total fiber pull-out length and toughness, was established.•A quadratic relationship between the ηθ and the fiber pull-out number is proposed. The flexural-tensile strength ratio (β) is about 2.52 for UHPFRC exhibiting deflection hardening behavior.•The tri-linear softening curve analysis exhibited good agreement with the experimental results.
This paper investigated the effect of steel fiber-volume fraction (0.5%, 1.0%, 1.5%, and 2.0%) and distribution on the flexural behavior of ultra-high performance fiber reinforced concrete (UHPFRC). Digital image correlation (DIC) was used to obtain the crack propagation behavior of UHPFRC under bending load. With increasing fiber-volume fraction, the crack-propagation path becomes more zigzagged. Based on the flexural response of UHPFRC and fiber distribution on the crack plane, a correlation between fiber distribution characteristics and flexural behavior was discussed. The fibers number per unit area for S0.5, S1.0, S1.5, and S2.0 were 7, 14, 21, and 31, respectively. The fiber pull-out length in cracked zone with different fiber-volume fractions was about 3.56 mm. The fiber orientation factor (ηθ) of S0.5, S1.0, S1.5, and S2.0 were 0.80, 0.79, 0.69 and 0.61 respectively. A quadratic relationship between the ηθ and the fiber pull-out number is proposed. The flexural-tensile strength ratio (β) is about 2.52 for UHPFRC exhibiting deflection hardening behavior. Finally, the post-cracking tensile behavior of UHPFRC was analyzed based on the matrix softening and fiber bridging curve models by the inverse analysis method. The tension softening curves obtained from the tri-linear softening curve analysis exhibited good agreement with the experimental results.
One of the primary purposes of the innovative development of ethnomedicines is to use their excellent safety and significant efficacy to serve a broader population. To achieve this purpose, modern ...scientific and technological means should be referenced, and relevant national laws and regulations as well as technical guides should be strictly followed to develop standards and to perform systemic research in producing ethnomedicines. Finally, ethnomedicines, which are applied to a limited extent in ethnic areas, can be transformed into safe, effective, and quality-controllable medical products to relieve the pain of more patients. The innovative development path of ethnomedicines includes the following three primary stages: resource study, standardized development research, and industrialization of the achievements and efforts for internationalization. The implementation of this path is always guaranteed by the research and development platform and the talent team. This article is based on the accumulation of long-term practice and is combined with the relevant disciplines, laws and regulations, and technical guidance from the research and development of ethnomedicines. The intention is to perform an in-depth analysis and explanation of the major research thinking, methods, contents, and technical paths involved in all stages of the innovative development path of ethnomedicines to provide useful references for the development of proper ethnomedicine use.
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