•Various conventional and NDT tests of concrete are reviewed.•The MNDT techniques used in concrete applications are summarized.•MNDT techniques minimize processing time and preserve of energy.•The ...advantages of MNDT include instant measurements with monochromatic radiation.•The findings assist in the selection of suitable methods for concrete repair.
Every year, a massive amount of literature is published on many aspects of microwave applications. Over the past few years, the need for progressive methods for assessing different properties of concrete, as well as for maintenance and monitoring of structures, has led to the development of microwave non-destructive testing (MNDT) techniques for preserving the civil infrastructure. MNDT has many advantages, including good penetrability in nonmetallic materials, instantaneous measurements, monochromatic radiation, low power requirements, substantial energy savings, and easy-to-interpret data. Additionally, with the potential to overcome the limits of both conventional testing and non-destructive testing (NDT), MNDT has received much interest.
In this paper, a comprehensive review of the most common MNDT techniques for material assessment is conducted based on a detailed literature survey. Furthermore, the basics of MNDT techniques are explored to contribute to its use in the concrete industry. The conventional tests and NDTs on concrete, including the applications of different MNDT methods, are discussed. The outcomes of this review can assist in using the MNDT methods in concrete structures, structural health monitoring, and enhancement of microwave-based techniques. Finally, this work provides a summary of MNDT techniques used in concrete applications, which can lead to advancements in this field.
Understanding how plant species coexist in tropical rainforests is one of the biggest challenges in community ecology. One prominent hypothesis suggests that rare species are at an advantage because ...trees have lower survival in areas of high conspecific density due to increased attack by natural enemies, a process known as negative density dependence (NDD). A consensus is emerging that NDD is important for plant-species coexistence in tropical forests. Most evidence comes from short-term studies, but testing the prediction that NDD decreases the spatial aggregation of tree populations provides a long-term perspective. While spatial distributions have provided only weak evidence for NDD so far, the opposing effects of environmental heterogeneity might have confounded previous analyses. Here we use a novel statistical technique to control for environmental heterogeneity while testing whether spatial aggregation decreases with tree size in four tropical forests. We provide evidence for NDD in 22% of the 139 tree species analyzed and show that environmental heterogeneity can obscure the spatial signal of NDD. Environmental heterogeneity contributed to aggregation in 84% of species. We conclude that both biotic interactions and environmental heterogeneity play crucial roles in shaping tree dynamics in tropical forests.
Aims: With the aim of understanding why some of the world's forests exhibit higher tree beta diversity values than others, we asked: (1) what is the contribution of environmentally related variation ...versus pure spatial and local stochastic variation to tree beta diversity assessed at the forest plot scale; (2) at what resolution are these beta-diversity components more apparent; and (3) what determines the variation in tree beta diversity observed across regions/continents? Location: World-wide. Methods: We compiled an unprecedented data set of 10 large-scale stem-mapping forest plots differing in latitude, tree species richness and topographic variability. We assessed the tree beta diversity found within each forest plot separately. The non-directional variation in tree species composition among cells of the plot was our measure of beta diversity. We compared the beta diversity of each plot with the value expected under a null model. We also apportioned the beta diversity into four components: pure topographic, spatially structured topographic, pure spatial and unexplained. We used linear mixed models to interpret the variation of beta diversity values across the plots. Results: Total tree beta diversity within a forest plot decreased with increasing cell size, and increased with tree species richness and the amount of topographic variability of the plot. The topography-related component of beta diversity was correlated with the amount of topographic variability but was unrelated to its species richness. The unexplained variation was correlated with the beta diversity expected under the null model and with species richness. Main conclusions: Because different components of beta diversity have different determinants, comparisons of tree beta diversity across regions should quantify not only overall variation in species composition but also its components. Global-scale patterns in tree beta diversity are largely coupled with changes in gamma richness due to the relationship between the latter and the variation generated by local stochastic assembly processes.
Selective logging that is commonly conducted in tropical forests may change tree species diversity. In rarely disturbed tropical forests, locally rare species exhibit higher survival rates. If this ...non-random process occurs in a logged forest, the forest will rapidly recover its tree species diversity. Here we determined whether a forest in the Pasoh Forest Reserve, Malaysia, which was selectively logged 40 years ago, recovered its original species diversity (species richness and composition). To explore this, we compared the dynamics of secies diversity between unlogged forest plot (18.6 ha) and logged forest plot (5.4 ha). We found that 40 years are not sufficient to recover species diversity after logging. Unlike unlogged forests, tree deaths and recruitments did not contribute to increased diversity in the selectively logged forests. Our results predict that selectively logged forests require a longer time at least than our observing period (40 years) to regain their diversity.
The abrasive blasting industry is identified as the most unsafe operation in terms of potential exposure to airborne crystalline silica. This is due to the free silica content in the common abrasives ...that are used for blasting activities. This paper will identify a sustainability-based or green blasting media to replace free silica content abrasives for blasting activities. The characteristics of sustainability-based abrasives are determined based on systematic review procedure. The combination keywords of “Abrasive blasting”, “Garnet’’, “Free Silica Media”, “Sustainable blasting”, “Eco-friendly blasting”, “Glass Bead blasting” and “Green blasting” were used to collect the existing studies on abrasive blasting operations. Six characteristics of green abrasives were identified: (1) zero content of free silica, (2) high efficiency and productivity, (3) low consumption media (4) low amount of waste generation and emission potentials (5) high recyclability and (6) environmentally friendly in line with sustainable development goals SDG3, SDG12, SDG13, SDG14 and SDG15. The application of green abrasives as substitution to free silica media is therefore important not only for safety and health reasons, but also for the environmental protection and sustainable business operations.
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•Corrosion inhibitors yield high inhibidtion efficiency at low concentration.•Maximal adsorption coverage of inhibitors on metal surface in planar orientation.•High negative value of ...adsorption energy indicates high metal-inhibitor interaction.•Inhibition efficiency of inhibitor on metal surface is affected from heteroatoms.•Computational method discovers the adsorption mechanism in corrosion system.
Corrosion of metal pipelines is a huge industrial concern, with potential environmental pollution and economic loss. The implementation of a cost-effective technology in using waste palm oil as biobased corrosion inhibitors (CIs) has risen. However, the inhibition mechanism of CIs remains unclear due to the lack of comprehensive review and a small number of existing experimental data. Density functional theory (DFT) and molecular dynamics (MD) simulation provided significant insights into the adsorption mechanism. The influence of fatty hydrazide derivatives as effective CIs on ferrous (110) metal surface in 1.0 M HCl medium at a temperature ranging from 298 to 383 K was studied. DFT predicted inhibition efficacies of these CIs based on electronic/molecular properties and reactivity induced through the band gap energy between the HOMO and LUMO in the range of 7.290 to 7.480 eV. Results from MD simulation showed that the inhibition efficiency increased at low concentration of CIs (0.04 M) and increasing temperature, which was suggestive of chemical adsorption mechanism with the adsorption energy from −200 to −400 kJ/mol. . The result further suggested that thermal stability of CIs at high temperature increased due to adsorption energy of CI-metal interaction from heat supplied. All the findings were consistent with the experimental data reported earlier. Understanding the adsorption mechanism of fatty hydrazide derivatives on the metal surface could be used as a basis for future development of specific biobased CIs for cost-effective corrosion control technology.
1. Masting, the production of large seed crops at intervals of several years, is a reproductive adaptation displayed by many tree species. The predator satiation hypothesis predicts that starvation ...of seed predators between mast years and satiation during mast years decreases seed predation and thus enhances tree regeneration. 2. Mast fruiting comes at demographic costs such as missed reproduction opportunities and increased density-dependence of recruits, but it remains unknown if predator satiation constitutes a sufficiently large benefit for masting to evolve as a viable life-history strategy. So far, no studies have quantified the net fitness consequences of masting. 3. Using a long-term demographic data set of the dipterocarp Shorea leprosula in a Malaysian forest, we constructed stochastic matrix population models and performed a demographic cost-benefit analysis. 4. For observed values of mast frequency and seed predation rates, we show that strict masting strongly increases fitness compared with fruiting annually. Model results also show that the demographic costs of mast fruiting are very low compared to the demographic losses due to seed predation in a scenario of annual fruiting. Finally, we find that mast fruiting would still be selected for even at low levels of seed predation and when including additional costs such as decreased adult growth rates, limiting crop size and density-dependent seedling survival. 5. Synthesis. Our results are consistent with the predictions of the predator satiation hypothesis: mast fruiting increases fitness for a range of seed predation levels. Under seed predation pressure annually fruiting species are at a strong disadvantage and as a result a mast fruiting strategy may swiftly confer a fitness advantage. Our study shows that demographic modelling allows the weighing of fitness benefits and costs of life-history phenomena such as strict masting.
We investigate the dynamics of high energy dual regime unidirectional Erbium-doped fiber laser in ring cavity, which is passively Q-switched and mode-locked through the use of an environmentally ...friendly graphene filament-chitin film-based saturable absorber. The graphene-chitin passive saturable absorber allows the option for different operating regimes of the laser by simple adjustment of the input pump power, yielding, simultaneously, highly stable and high energy Q-switched pulses at 82.08 nJ and 1.08 ps mode-locked pulses. The finding can have applications in a multitude of fields due to its versatility and the regime of operation that is on demand.
Accurate estimation of tree biomass is necessary to provide realistic values of the carbon stored in the terrestrial biosphere. A recognized source of errors in tree aboveground biomass (AGB) ...estimation is introduced when individual tree height values (H) are not directly measured but estimated from diameter at breast height (DBH) using allometric equations. In this paper, we evaluate the performance of 12 alternative DBH:H equations and compare their effects on AGB estimation for three tropical forests that occur in contrasting climatic and altitudinal zones. We found that fitting a three-parameter Weibull function using data collected locally generated the lowest errors and bias in H estimation, and that equations fitted to these data were more accurate than equations with parameters derived from the literature. For computing AGB, the introduced error values differed notably among DBH:H allometric equations, and in most cases showed a clear bias that resulted in either over- or under-estimation of AGB. Fitting the three-parameter Weibull function minimized errors in AGB estimates in our study and we recommend its widespread adoption for carbon stock estimation. We conclude that many previous studies are likely to present biased estimates of AGB due to the method of H estimation.
Water-in-diesel (W/D) emulsion is one of the promising alternative fuel that improves the combustion efficiency of a diesel engine and simultaneously reduces harmful exhaust emissions. To ensure a ...stable emulsion, surfactant is used during the formation of W/D emulsion which causes additional costs for this alternative fuel. A device called as Real-Time Non-Surfactant Emulsion Fuel Supply System (RTES) was invented to eliminates the use of surfactant and rapidly supply the W/D emulsion to the engine. The efficiency of 1-ton light-duty diesel truck fueled with W/D emulsion fuel produced by RTES was tested. Two types of the experimental method were used which chassis dynamometer testing and on-road are testing. The optimum water percentage and vehicle speed were evaluated from the result of exhaust emissions and fuel consumption measurement. Chassis dynamometer testing showed that the optimum water percentage for DE2 were 6.5% and vehicle speed aimed at 52 km/h was selected as the optimum vehicle speed. In on-road testing, the urban route gave the deficient results for both exhaust emissions and fuel consumption which agree with chassis dynamometer testing result where emulsion fuel is not suitable to be used at low speed vehicle operation.
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