F-LEACH: a fuzzy-based data aggregation scheme for healthcare IoT systems

The Journal of Supercomputing - Internet of Things (IoT) is an emerging paradigm that consists of numerous connected and interrelated devices with embedded sensors, exchanging data with each other...     

Effects of thermal and mechanical activation methods on compressive strength of ordinary Portland cement–slag mortar

Activation methods and curing regimes have crucial effects on the strength of mortars and concretes. The objective of this investigation is to examine the early and later compressive strength of activated ordinary Portland cement (OPC)–ground granulated blast-furnace slag (GGBFS) mortars and identify the most effective activation technique. The methods of activation used were thermal, mechanical and thermal–mechanical combined. Two curing regimes were adopted and five groups of mortars were prepared. It was observed that OPC–GGBFS mortars have greater sensitivity to OPC mortars against the curing regimes. However, the study revealed that there was no particular activation method which when used gave the best results for both early and later strengths and did not cause strength loss. It also proved that the most effective activation method for early strength is a combination of both the thermal and mechanical, while for later strengths, none of the activation methods was recommended.     

An Investigation of Mechanical Properties of Polyurethane Nanocomposites with Various Silicas: Experimental Study and Modeling of Finite Deformation Response

It is well-known that polymer nanocomposites can bring about superior mechanical, thermal, optical, physical, and chemical properties in comparison with pure polymers. In this study, different contents of unmodified silica nanoparticles (Si-Un), surface modified nano-silica by octylsilane (Si-OS), and surface modified nano-silica by polydimethylsiloxane (Si-PDMS) are added to the polyurethane (PU) matrix and their effects on the physical properties of the polymer examined. The experimental results indicate that most of the nanocomposites have a higher tensile strength and elongation. In addition, hyperelastic energy function models have been used to model the stress-strain relation of the nanocomposites. In this study, Mooney-Rivlin, neo-Hookean, Rivlin general polynomial, and Davies-De Thomas (DDT) models have been investigated, possessing respectively, two, one, eight, and three constants to be determined. The differential evolution (DE) optimization method, a strong heuristic optimization algorithm, has been used to find the constants; in which the absolute summation of the differences between the models’ predictions and experimental data is taken into account as the objective function and the models’ constants are considered as the decision variables. Moreover, equation constants are found by using regression, an indicator of DE optimization superiority. The results show that even though the Rivlin general polynomial model provides the most accurate prediction, the DDT model, consisting of three constants, can be considered as the most acceptable one.     

Effect of Foliar-Applied Silicon on Flower Yield and Essential Oil Composition of Damask Rose (Rosa damascena Miller) under Water Deficit Stress

Silicon - A field experiment was conducted to investigate the effect of silicon on the flower yield and essential oil composition of damask rose under water deficit stress. Silicon was applied as...     

Ensemble Boosting and Bagging Based Machine Learning Models for Groundwater Potential Prediction

Water Resources Management - Due to the rapidly increasing demand for groundwater, as one of the principal freshwater resources, there is an urge to advance novel prediction systems to more...     

Effects of curing regimes and cement fineness on the compressive strength of ordinary Portland cement mortars

Curing techniques and curing duration have crucial effects on the strength and other mechanical properties of mortars. Proper curing can protect against moisture loss from fresh mixes. The objective of this experimental work is to examine the compressive strength of ordinary Portland cement mortars (OMs) under various curing regimes and cement fineness. Six different curing methods including water, air, water heated, oven heated, air–water, and water–air were applied to the specimens and also six groups of mortars were used. The results showed that the highest and lowest compressive strengths are attributed to the specimens of OPC mortar water cured using grounded OPC for duration of 6 h (OM–G6–wc) and OPC mortar air cured under room temperature with oven heated after demoulding of the specimens at 60 °C for duration of 20 h (OM–OH–ac), respectively. The maximum levels obtained of compressive strengths at 7, 28, and 90 days are 57.5, 70.3, and 76.0 MPa, respectively.     

Comparison of different methods for activation of ordinary Portland cement-slag mortars

This paper compares three methods for activation of OPC-slag mortars (OSM): (1) prolonged grinding of binders (mechanical method), (2) elevated temperature curing of mortars (thermal method), and (3) use of chemical activators such as NaOH, KOH, and Na₂SiO₃, 9.35H₂O (chemical method). The proper reactivity of OSM was evaluated using a mixture of 50% OPC and 50% slag. Early and ultimate strengths were compared. All three activation methods accelerated both the slag reaction and strength development rates. However, the chemical method did not show a significant effect on the ultimate strength, while thermal activation increased the early strength by 3 days. Mechanical activation increased the early strengths of the mortar significantly, but about 6% strength loss occurred in the ultimate strength. Although, the application of mechanical and thermal activation methods needs extra equipment and energy, due to more significant of strength improvement; based on current test results, it can be said that mechanical activation is the most efficient and feasible method for the activation of OSMs.     

Fragile Watermarking Based on QR Decomposition and Fourier Transform

Wireless Personal Communications - In this study, a fragile watermarking technique is introduced for verifying images based on QR decomposition and Fourier Transform (FT). At first, we apply the FT...     

Frame‐type load bearing system for long‐span cantilevers

Cantilevers experience high risks of vulnerability against progressive collapse and vertical ground motion effects. In addition, despite common engineering practice that regards cantilevers dominated by vertical loads, it is shown that while subjected to lateral forces, they might undergo large deflections due to the formation of plastic hinges in the supporting structural subassemblage; even if cantilevers satisfy deflection limits proposed by design codes. To overcome such vulnerabilities, successive cantilever beams can be coupled in the height of the structure using vertical elements to develop a framed cantilever system. Frame behavior in cantilevers is formulized using spring models and by employing optimization procedures, economic efficiency is compared to the conventional method. The optimization results for 6 2‐D steel moment frames showed that employing framed cantilever system has the potential to reduce required material weight up to 40%. Furthermore, nonlinear pushdown and incremental dynamic analyses were conducted to extract capacity and fragility curves. The results reveal the superior performance of framed cantilevers in both lateral and vertical loads while offering better resistance against the progressive collapse.     

Using contourlet transform and cover selection for secure steganography

In this paper, we present a new adaptive contourlet-based steganography method that hides secret data in a specific or automatically selected cover image. Our proposed steganography method primarily decomposes the cover image by contourlet transform. Then, every bit of secret data is embedded by increasing or decreasing the value of one coefficient in a block of a contourlet subband. Contourlet coefficients are manipulated relative to their magnitudes to hide the secret data adaptively. In addition to proposing contourlet-based steganography method, this work investigates the effect of cover selection on steganography embedding and steganalysis results. We demonstrate, through the experiments, that choosing suitable cover image by a proper selection measure could help the steganographer reduce detectability of stego images. The proposed technique is examined with some state-of-the-art steganalysis methods, and the results illustrate that an image can successfully hide secret data with average embedding capacity of 0.02 bits per pixel in a random selected cover image. Cover selection improves the embedding capacity up to 0.06 bits per pixel. Several experiments and comparative studies are performed to show the effectiveness of the proposed technique in enhancing the security of stego images, as well as to demonstrate its gain over the previous approaches in literature.