Huge amounts of by-products are generated from industrial processes which affect the environment adversely. Production process of conventional cement is energy demanding and it also emits enormous ...amounts of greenhouse gases. Geopolymers are the new generation green material that has a great potential of replacing the conventional cementitious materials. The fresh and hardened properties of sodium hydroxide activated binary blends of slag and fly ash based geopolymer paste and mortars are reported in this paper. Experimental outcomes on fresh and hardened properties such as normal consistency, flow value, setting time, drying shrinkage, soundness, and compressive strengths of the geopolymer binders are presented. Additionally, the chemical products, bonding and microstructural changes occurring during the setting and hardening course are examined. The experimental outcomes showed that the physical and mechanical properties of the binders are very much akin to that of conventional cement and the same is significantly influenced by the chemical composition of the source materials, concentration of the activator and the processing environment. The consistency and setting times of geopolymers are found to be within the ranges that are prescribed for ordinary Portland cement. Highest compressive strength of around 44 MPa is obtained for slag based geopolymer mortar that is activated using 8 M sodium hydroxide solution. Fly ash and slag geopolymers exhibited excellent stability against expansion and shrinkage. Raw materials are optimized by design of experiment and the fitted model shows a good relation with the experimental data.
AbstractGranular soils are sensitive to internal erosion due to the presence of lesser fines and need to be stabilized to improve their geoengineering properties. An investigation is made to explore ...the efficacy of fly ash-slag (FA-GGBS) geopolymer in stabilizing granular soil through a set of experimental studies. The experimental program focused on compaction characteristics, unconfined compressive strength, bearing resistance, and durability of geopolymer stabilized granular soil to assess its suitability as a construction material. Microstructural analysis has been carried out and correlated with strength development. Based on the test results, a maximum unconfined compressive strength of about 7 MPa and California bearing ratio (CBR) ranging from 52% to 416% is obtained. The geopolymer stabilized soil showed excellent stability against wetting–drying and freezing–thawing cycles, slaking water, and aggressive chemical environments. The microstructural developments are greatly influenced by the geopolymer content and curing period, indicating the formation of hydration and geopolymeric reaction products.
This paper reports the influence of delay time on the index and engineering properties of geopolymer-, cement-, and lime-treated expansive soil. Locally available expansive soil was treated with ...different doses of slag-based geopolymer, cement, and lime. The index and engineering properties like Atterberg’s limits, free swell index, grain-size distribution, compaction properties, and unconfined compressive strength (UCS) were evaluated at delay periods of 0, 6, 12, 24, 48, 72, and 168 h. Further, the mineralogical characteristics and microstructure of the stabilized materials were examined using X-ray diffraction (XRD) and scanning electron microscopic (SEM) images. It was observed that with an increase in delay time, the plasticity and swelling characteristics of the treated soil reduced with improvement in the soil grain size along with the formation of hydration and geopolymeric compounds. The delay in compaction results in the decline of the compacted density and UCS. The formation of hydrated products and flocs during the delay period caused loose packing under dynamic loading and affects the mechanical properties. A significant improvement in plasticity and engineering properties of the expansive soil was observed with geopolymer stabilizers. Thus, it is noteworthy to consider geopolymers as a new generation eco-friendly stabilizer for treating expansive clays for geotechnical constructions.
•Significance of slag-based geopolymer as soil stabilizer was examined.•Plasticity characteristics, strength, and durability properties of the treated soil were reported.•Geopolymer stabilized soil ...showed superior strength and durability compared tocement and lime stabilized soil.•A correlation is established between the microstructure with mechanical behaviour.
This paper reports the strength and durability properties of expansive soil treated with slag-based geopolymer, hydrated lime, and Portland cement. The slag content in the soil-slag mix is varied as 5%, 10%, and 20% by dry weight of soil and activated with NaOH solutions of 2 M, 6 M, and 8 M concentrations, respectively. Whereas cement and lime contents in the mix are varied as 4%, 12%, and 15%. The plasticity and compaction properties of the mixes are evaluated. Further, the unconfined compressive strength of specimens, compacted to their respective maximum dry density at optimum moisture content, is determined after 0, 3, 7, and 30 days of curing. Durability studies such as freezing-thawing, slaked durability, modified durability, and resistance to water immersion are determined on 30-days cured stabilized soil specimens. X-ray diffraction and scanning electron microscopic analysis are carried out for identifying the reaction products and microstructure of the stabilized specimens. The results indicate that the expansive soil can be effectively stabilized with slag-based geopolymer. The geopolymer stabilized soil has superior strength and durability compared to the conventional stabilizers. Geopolymer stabilized soil attains dense and compact structures with the better formation of cementitious products.
The XOR operation has improved the recovery effect of the visual secret sharing schemes. Various visual secret sharing schemes based on XOR operation are available in the literature with some ...limitations, e.g. direct non-applicability of the scheme to the gray-scale images and reduced quality of the reconstructed secret image. Many existing visual secret sharing schemes in the literature, firstly converts grayscale secret image into a halftone image then creates the shares. This paper proposes XOR-based (
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visual secret sharing scheme using pixel vectorization. It diffuses and disguise secret information into multiple meaningless shares prior to allocating participants of the group having no clue about the secret information. The scheme also resolves various problems like pixel expansion, contrast-loss, explicit codebook requirement, limitation on number of participants and lossy recovery of the secret image. The proposed scheme makes use of implicit codebook and pixel vectorization to encode gray secret image directly without converting to halftone image, into multiple random looking shares. Also applicable to binary image. Reveal a secret image perfectly by XOR-ing all share. The efficacy of the proposed scheme is verified by numerical illustrations, experimental results and comparative analysis. We found that proposed scheme outperform in comparison to the state-of-the-art approaches.
Microwave-vacuum dehydration characteristics of button mushroom (
Agaricus bisporus) were evaluated in a commercially available microwave oven (0–600
W) modified to a drying system by incorporating a ...vacuum chamber in the cavity. The effect of drying parameters, namely microwave power, system pressure and product thickness on the drying kinetics and rehydration characteristics were investigated. The drying system was operated in the microwave power range of 115–285
W, pressure range of 6.5–23.5
kPa having mushroom slices of 6–14
mm thickness. Convective air drying at different air temperatures (50, 60 and 70
°C) was performed to compare the drying rate and rehydration properties of microwave-vacuum drying with conventional method. Microwave-vacuum drying resulted in 70–90% decrease in the drying time and the dried products had better rehydration characteristics as compared to convective air drying. The rate constants of the exponential and Page’s model for thin layer drying were established by regression analysis of the experimental data which were found to be affected mainly by the microwave power level followed by sample thickness while system pressure had a little effect on the drying rate. Rehydration ratio was significantly affected by the system pressure. Empirical models are also developed for estimating the drying rate constant and rehydration ratio as a function of the microwave-vacuum drying process parameters.
It is well known that cancer cells are heterogeneous in nature and very distinct from their normal counterparts. Commonly these cancer cells possess different and complementary metabolic profile, ...microenvironment and adopting behaviors to generate more ATPs to fulfill the requirement of high energy that is further utilized in the production of proteins and other essentials required for cell survival, growth, and proliferation. These differences create many challenges in cancer treatments. On the contrary, such situations of metabolic differences between cancer and normal cells may be expected a promising strategy for treatment purpose. In this article, we focus on the molecular determinants of oncogene-specific sub-organelles such as potential metabolites of mitochondria (reactive oxygen species, apoptotic proteins, cytochrome c, caspase 9, caspase 3, etc.), endoplasmic reticulum (unfolded protein response, PKR-like ER kinase, C/EBP homologous protein, etc.), nucleus (nucleolar phosphoprotein, nuclear pore complex, nuclear localization signal), lysosome (microenvironment, etc.) and plasma membrane phospholipids, etc. that might be exploited for the targeted delivery of anti-cancer drugs for therapeutic benefits. This review will help to understand the various targets of subcellular organelles at molecular levels. In the future, this molecular level understanding may be combined with the genomic profile of cancer for the development of the molecularly guided or personalized therapeutics for complete eradication of cancer.
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Characterization of physiological traits affected by rice breeding for grain yield under drought conditions shows that atmospheric and soil stresses strengthen the relationship between leaf traits ...and yield across extensive trials in South Asia.
Abstract
Direct selection for yield under drought has resulted in the release of a number of drought-tolerant rice varieties across Asia. In this study, we characterized the physiological traits that have been affected by this strategy in breeding trials across sites in Bangladesh, India, and Nepal. Drought- breeding lines and drought-tolerant varieties showed consistently longer flag leaves and lower stomatal density than our drought-susceptible check variety, IR64. The influence of environmental parameters other than drought treatments on leaf traits was evidenced by close grouping of treatments within a site. Flag-leaf length and width appeared to be regulated by different environmental parameters. In separate trials in the Philippines, the same breeding lines studied in South Asia showed that canopy temperature under drought and harvest index across treatments were most correlated with grain yield. Both atmospheric and soil stress strengthened the relationships between leaf traits and yield. The stable expression of leaf traits among genotypes and the identification of the environmental conditions in which they contribute to yield, as well as the observation that some breeding lines showed longer time to flowering and higher canopy temperature than IR64, suggest that selection for additional physiological traits may result in further improvements of this breeding pool.
Abstract
The influence of inorganic salt solutions on the physical and mechanical properties of bentonite based liner materials is highlighted. Compacted pond ash-bentonite (PAB) and sand-bentonite ...(SB) liners, prepared at their respective maximum dry unit weight (MDD) and optimum moisture content (OMC) are permeated with NaCl, CaCl2, and FeCl3 solutions of concentrations from 0.1 to 1 M. The physical and mechanical properties are determined after permeations of 7, 14, and 21 days. The consistency limits, free swell indices, and volumetric shrinkage strain are found to reduce and the hydraulic conductivity increased as the concentration of salt solutions and their permeation time increased. Permeation of lower concentration salt solutions increases the unconfined compressive strength (UCS) value and this reduces substantially as the concentration increases. Salt solutions of polyvalent cations have more impact than those of monovalent cations. PAB specimens are less vulnerable to these changes compared with those of SB specimens. The concentration of permeating cations increases substantially in the liner materials with an increase in salt concentration and permeation time, and the concentration of inherently adsorbed elements decreases.
Abstract
This research focuses on the potentiality of calcium hydroxide (Ca(OH)2) and sodium hydroxide (NaOH) columns in augmenting the geoengineering and geoenvironmental properties of sedimented ...ash beds. Model ash beds were prepared and stabilized with NaOH and Ca(OH)2 of 9 M concentration. The bearing resistance, collapse potential, hydraulic conductivity, pore characteristics, concentration of elements, and pH of the pore fluid were measured. The strength contours formed around chemical columns were found to be bell-shaped. The magnitude of strength development in the Ca(OH)2 column was relatively insignificant and limited to the peripheral region of the column, whereas it spread to a greater extent in a NaOH-treated ash bed. Calcium-based hydration compounds were found in a Ca(OH)2 column-treated ash bed whereas an ash bed column treated with NaOH displayed both geopolymeric as well as calcium-based hydration compounds. The encapsulation of leached elements in the reaction matrix reduced their concentrations in leachate. The concentration of elements in leachate was identified to be influenced by the pH value and stabilization period. Both the chemical columns were found to be effective. However, the NaOH column showed a significant improvement in bearing resistance and in situ dry unit weight along with reducing the hydraulic conductivity, collapsibility, and migration of leachable elements.
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