Prediction of Stress Intensity Factor on Precracked Composite Wing Rib Made up of Carbon-Epoxy IM7-8552

Journal of Failure Analysis and Prevention - The stress intensity factor (SIF), K, is an important parameter to predict the stress state (“stress intensity”) near the tip of a crack...     

Outage analysis of SWIPT‐based full‐duplex cognitive NOMA downlink system over Nakagami‐m fading channels

Cognitive nonorthogonal multiple access (NOMA) technique allows multiple users to share the same time and same frequency resources to fulfil the reliability and spectral efficiency requirements of 5G communication standards. In this paper, simultaneous wireless information and power transfer (SWIPT)–based full‐duplex cognitive NOMA downlink system is proposed. In this system, secondary source (SS) serves as a relay to far primary user as there is no direct link from the primary source. NOMA technique is used at SS to transmit information to far primary user and secondary user. The time switching mechanism is adopted at SS for harvesting energy and information decoding. Analytical closed‐form expressions are derived for the outage probabilities of both primary and secondary users. Outage analysis is carried out in Nakagami‐ fading environment in the presence of self‐interference at SS. In addition to that, the optimal harvesting time to maximize the instantaneous throughput of the far primary user is also derived. Numerical results are plotted to validate the derived expressions. It is inferred that the outage probability of the proposed system depends on the fading environment, harvesting parameters, and self‐interference at SS.     

Effect of high or low molecular weight of components of feed on transmembrane flux during forward osmosis

The possible mechanism of water transport from feed to osmotic agent side during forward osmosis in situation when feed contains high or low molecular weight compounds and their combination has been presented. The orientation of membrane was found to influence the transmembrane flux. When the feed contains mixture of low and high molecular weight compounds mode I (feed towards the support layer) was found to result in lower flux values as compared to Mode II (feed towards active layer) due to significant external concentration polarization. Forward osmosis resulted in the concentration of betalains content in beetroot juice and anthocyanin content in grape juice from 50.92 mg/L to 2.91 g/L (57.1 fold) and from 104.85 mg/L to 715.6 mg/L (6.8 fold), respectively. Total soluble solids in case of beetroot, grape and pineapple juice were found to increase from 2.3 to 52 °Brix, from 8.0 to 54.6 °Brix from 4.4 to 54 °Brix, respectively.     

Work stealing for GPU‐accelerated parallel programs in a global address space framework

Task parallelism is an attractive approach to automatically load balance the computation in a parallel system and adapt to dynamism exhibited by parallel systems. Exploiting task parallelism through work stealing has been extensively studied in shared and distributed‐memory contexts. In this paper, we study the design of a system that uses work stealing for dynamic load balancing of task‐parallel programs executed on hybrid distributed‐memory CPU‐graphics processing unit (GPU) systems in a global‐address space framework. We take into account the unique nature of the accelerator model employed by GPUs, the significant performance difference between GPU and CPU execution as a function of problem size, and the distinct CPU and GPU memory domains. We consider various alternatives in designing a distributed work stealing algorithm for CPU‐GPU systems, while taking into account the impact of task distribution and data movement overheads. These strategies are evaluated using microbenchmarks that capture various execution configurations as well as the state‐of‐the‐art CCSD(T) application module from the computational chemistry domain. Copyright © 2016 John Wiley & Sons, Ltd.     

Rubbers Based on Conjugated Soybean Oil: Synthesis and Characterization

A range of bio‐based rubbery thermosets have been synthesized by the cationic copolymerization of conjugated soybean oil, styrene, and 1,5‐hexadiene or isoprene as flexible crosslinkers. The thermal, and mechanical properties, as well as the wear behavior, of these new bio‐rubbers are reported. The amount of styrene and the type of diene incorporated have the greatest influence on the properties of the final materials. The largest variations are found in glass transition temperature, storage modulus, tan δ values, crosslink density, and abrasive wear depth, while thermal degradation and extraction analyses showed minimal variations with changes in composition.

     

A test method for determining adhesion forces and Hamaker constants of cementitious materials using atomic force microscopy

A method for determining Hamaker constant of cementitious materials is presented. The method involved sample preparation, measurement of adhesion force between the tested material and a silicon nitride probe using atomic force microscopy in dry air and in water, and calculating the Hamaker constant using appropriate contact mechanics models. The work of adhesion and Hamaker constant were computed from the pull-off forces using the Johnson–Kendall–Roberts and Derjagin–Muller–Toropov models. Reference materials with known Hamaker constants (mica, silica, calcite) and commercially available cementitious materials (Portland cement (PC), ground granulated blast furnace slag (GGBFS)) were studied. The Hamaker constants of the reference materials obtained are consistent with those published by previous researchers. The results indicate that PC has a higher Hamaker constant than GGBFS. The Hamaker constant of PC in water is close to the previously predicted value C₃S, which is attributed to short hydration time (≤ 45 min) used in this study.     

Modulation aware cluster size optimisation in wireless sensor networks

Wireless sensor networks (WSNs) play a great role because of their numerous advantages to the mankind. The main challenge with WSNs is the energy efficiency. In this paper, we have focused on the energy minimisation with the help of cluster size optimisation along with consideration of modulation effect when the nodes are not able to communicate using baseband communication technique. Cluster size optimisations is important technique to improve the performance of WSNs. It provides improvement in energy efficiency, network scalability, network lifetime and latency. We have proposed analytical expression for cluster size optimisation using traditional sensing model of nodes for square sensing field with consideration of modulation effects. Energy minimisation can be achieved by changing the modulation schemes such as BPSK, 16-QAM, QPSK, 64-QAM, etc., so we are considering the effect of different modulation techniques in the cluster formation. The nodes in the sensing fields are random and uniformly deployed. It is also observed that placement of base station at centre of scenario enables very less number of modulation schemes to work in energy efficient manner but when base station placed at the corner of the sensing field, it enable large number of modulation schemes to work in energy efficient manner.     

Carbon Dioxide Laser Cutting of a Carbon-Fiber–Silicon Carbide-Matrix Composite

CO₂ laser scribing and cutting were studied on a carbon-fiber-silicon carbide-matrix (C/SiO) composite nominally containing 45 vol% of carbon fibers. The scribing and cutting were performed in continuous-wave (CW) mode using laser powers between 750 and 1500 W, and specimen translation velocities between 0.5 and 4 cm/s. The laser spot size was 300 μm in diameter. The groove width and depth were measured as functions of power and velocity. The results were compared to theoretically predicted values obtained by solving the quasi-steady-state heat conduction equation in three dimensions for a moving body. Reasonably good agreement between theory and experiment was found. The microstructures of the laser-cut surfaces indicated the formation of redeposit by condensation from the vapor phase. X-ray diffraction and Raman spectroscopy analyses of the redeposit showed the presence of β-SiC and graphitic carbon. The four-point bending strength of the laser-cut composite was found to be approximately 20% lower than the corresponding strength of the diamond-cut composite. The strength was fully recovered after removing 180 ± 10 μm of the material from the lased surface by grinding. The oxidation resistance of the laser-cut and diamond-cut composites was studied with a thermogravimetric balance at 1103°, 1304°, and 1402°C in air. The oxidation behavior at all investigated temperatures for both materials was dominated by a rapid initial mass loss due to the oxidation of carbon and a possible active oxidation of SiC, followed by a slow mass gain due to the passive oxidation of SiC. At 1304°C the rate of passive oxidation of SiC in the laser-cut material was somewhat higher than in the diamond-cut material. At 1402°C, the diamond-cut surface oxidized more rapidly than the taser-cut surface. The differences in oxidation rates were attributed to the differences in microstructure.     

A design methodology for fractal layout organization

Venkatadri el a.(HE Transactions, 29, 911-924, 1997) have proposed a new methodology for shop floor layout that involves the use of fractal cells and have compared the performance of their new layout with those obtained using the function, group and holographic layouts. A few inconsistencies are present in their results, expressed as flow scores. This note points out these inconsistencies through the use of appropriate examples.