Effect of nanoclay addition on the displacement-controlled flexural fatigue behavior of a polymer

Reinforcing polymers with nanoclay improves the stiffness and decreases the dissipative nature of polymer matrix. This article describes the effect of nanoclay addition on the flexural fatigue response of Polyamide6 (PA6). The emphasis was on temperature rise, temperature-induced stiffness drop, and flexural fatigue life. The fatigue performance has been investigated under displacement-controlled flexural loading conditions at room temperature. The samples were subjected to same displacement amplitude and same initial force amplitude (force amplitude in the first fatigue cycle) flexural fatigue conditions. Under the same displacement amplitude conditions, PA6NC samples exhibited marginally lesser percentage drop in the initial force amplitude (temperature-induced stiffness change) compared to PA6. Due to the addition of nanoclay, a marginal improvement in fatigue life (~64,000 cycles) was also observed under these conditions. Under the same initial force amplitude conditions, PA6NC samples exhibited significantly lesser percentage drop in its initial force compared to PA6 and retained the stiffness throughout the fatigue life. In addition to this, a significant improvement in fatigue life (>150,000 cycles) was observed. The performance improvement due to nanoclay addition can be attributed to enhanced modulus coupled with reduced dissipation factor (tan δ) and improved surface hardness. The fibrillated appearance of the PA6NC fracture surface suggests that the clay addition promotes toughening and influences the crack propagation characteristics of PA6.     

Combined multiuser signal classification and blind equalization

A multiuser automatic modulation classifier (MAMC) is an important signal processing component of a multiantenna cognitive radio (CR) receiver that helps the radio in identifying modulation format employed by multiple users in a frequency band simultaneously. In a typical wireless communication, transmitted signals are subjected to multipath fading and interference from other users. Multipath fading not only affects symbol detection performance but also affects the performance of the automatic modulation classifier. A multi input multi output (MIMO) blind equalizer is another important component of a multiantenna CR receiver that improves symbol detection performance by reducing inter symbol interference and inter user interference. In a CR scenario it is preferable to consider the performance of the AMC also while adapting the parameters of the blind equalizer. In this paper we propose MIMO blind equalizers that improves the performance of both multiuser symbol detection and cumulants based MAMC. Computer simulations are provided to illustrate this concept and the proposed algorithm.     

Nitroxide Radicals@US‐Tubes: New Spin Labels for Biomedical Applications

The encapsulation of nitroxide radicals within ultrashort (ca. 50 nm) single‐walled carbon nanotubes (US‐tubes) is achieved. Tempo‐ and Iodo‐Tempo@US‐tubes are characterized by thermogravimetric analysis (TGA), X‐ray photoelectron spectroscopy (XPS), and Raman spectroscopy. Electron paramagnetic resonance (EPR) spectra display characteristic signals due to the detection of the spin probes within the US‐tubes. Longitudinal proton relaxivities (r₁) of both nitroxide@US‐tubes samples are 7 to 13 times greater than the free nitroxide radicals in solution, giving relaxivities comparable to the clinical contrast agent (CA) Magnevist. In addition, transverse proton relaxivities (r₂) show unprecedented proton relaxation enhancement in comparison to any other reported nitroxide radical‐based system or the clinically approved T₂ CA, Resovist, under the same conditions. T₂‐weighted magnetic resonance imaging (MRI) phantom images show that the encapsulation of nitroxide radicals within the US‐tubes produces good contrast enhancement due to their high r₂ relaxivities. The nitroxide radicals@US‐tube agents are a new promising class of spin probes for MRI and electronic paramagnetic resonance imaging (EPRI) labeling, tracking, and diagnosis.     

A blockchain-based approach for a multi-echelon sustainable supply chain

Blockchain technology is destined to revolutionise supply chain processes. At the same time, governmental and regulatory policies are forcing firms to adjust their supply chains in response to environmental concerns. The objective of this study is therefore to develop a distributed ledger-based blockchain approach for monitoring supply chain performance and optimising both emission levels and operational costs in a synchronised fashion, producing a better outcome for the supply chain. We propose the blockchain approach for different production allocation problems within a multi-echelon supply chain (MESC) under a carbon taxation policy. As such, we couple recent advances in digitalisation of operations with increasingly stringent regulatory environmental policies. Specifically, with lead time considerations under emission rate constraints (imposed by a carbon taxation policy), we simultaneously consider the production, distribution and inventory control decisions in a production allocation-based MESC problem. The problem is then formulated as a Mixed Integer Non-Linear Programming (MINLP) model. We show that the distributed ledger-based blockchain approach minimises both total cost and carbon emissions. We then validate the feasibility of the proposed approach by comparing the results with a non-dominated sorting genetic algorithm (NSGA-II). The findings provide support for policymakers and supply chain executives alike.     

Effective removal of Cr(VI) and methyl orange from the aqueous environment using two-dimensional (2D) Ti3C2Tx MXene nanosheets

Industrial use of heavy metals and dyes critically depends on the effective handling of industrial effluents. Effective remediation of industrial effluents using various adsorbent materials has thus become critical. In this paper, we study two-dimensional MXenes as an adsorbent for removing Cr(VI) and methyl orange (MO) in waters. The physico-chemical performance of MXenes was studied using X-ray diffraction, Fourier transform infrared spectroscopy, Brunauer?Emmett?Teller, scanning electron microscopy, high resolution-transmission electron microscopy, thermogravimetric analysis, and X-ray photoelectron spectroscopy techniques. The adsorption system, including influence of contact time, pH of solutions, co-ions, and desorption experiments were performed for effective Cr(VI) and MO removal. The Cr(VI) and MO removal rate of the MXenes was very fast, and the kinetic system was driven by pseudo-second-order kinetics. The sorption isotherm closely well-tailored with the Langmuir isotherm, and the maximum removal efficiencies were 104 and 94.8 mg/g for Cr(VI) and MO, respectively. The MXenes was successfully regenerated by 0.1 M NaOH aqueous solution and can be repeatedly recycled. The uptake of Cr(VI) and MO by the MXenes was mainly due to chemical adsorption, namely electrostatic adsorption, complexation, surface interactions, and ion exchange mechanisms. This investigation demonstrates the selectivity and feasibility of the MXenes as a real adsorbent for eliminating Cr(VI) and MO from the aqueous environment.     

Growth of titanium oxide overlayers by thermal oxidation of titanium

This paper describes a theoretical model for the growth of titanium oxide by thermal oxidation of titanium. It is shown that this model can explain the formation of layers of different oxides of titanium and the changes in these layers with variations in the conditions of oxidation. Some experimental X-ray diffraction results which support the model are also given.     

Multiparty gaze preservation through perspective switching for interactive elearning environments

Multimedia Tools and Applications - Existing live tele-teaching systems enable eye-contact between interacting participants, however, they are often incomplete as they neglect finer levels of...     

EFFECT OF MICROWAVE TREATMENT ON WC INSERTS FOR DRILLING OF GFRP COMPOSITES

Due to excellent properties such as high specific strength, high specific modulus, and corrosion resistance, Glass Fiber Reinforced Plastics (GFRP) find wide applications particularly in the aerospace and automotive industries. In order to fabricate structural components of GFRP to near-nett shape, machining of GFRP composites is necessary. Drilling is the most common machining operation for GFRP composites. The fiber pull-out, cracking of matrix during the entry and exit of drill, rapid tool wear, and hole shrinkage are problems associated with machining of GFRP. The present study attempts an innovative idea of improving the cutting performance of Tungsten carbide (WC) inserts (K-20) by post-sintering using microwave irradiation.     

Experimental investigations on the SiO<Subscript>2</Subscript> flux-assisted GTA welding of super-austenitic stainless steels

Analyzed in this paper are barrier properties of wood specimens treated by ball burnishing. For the purpose of experimental investigation, special device was designed which allows continuous monitoring of the volume of water absorbed by specimen within particular time intervals. The device allows water pressurized at 3 bar to efficiently penetrate specimen internal structure over its burnished/non-burnished surface interface. The experimental investigation encompassed six types of wood—beech, acacia, walnut, oak, linden, and ash tree. Comparative analysis was performed to establish relative resistance to water penetration in burnished and non-burnished specimens, as well as the quantities of water volume absorbed over time. The results indicate that ball burnishing is capable of enhancing barrier properties in all of the examined types of wood.     

Experimental and theoretical investigation of a polymer subjected to cyclic loading conditions

There are many machine components made of polymeric materials, such as gears, which are subjected to cyclic loading conditions. To design such components, it is necessary to arrive at a suitable mathematical model that can describe the mechanical response of polymeric materials. In this paper, we derive a mathematical model for rate-type solids using thermodynamical framework developed by Rajagopal and Srinivasa (K.R. Rajagopal, A.R. Srinivasa, A thermodynamic frame work for rate type fluid model, Journal of Non-Newtonian Fluid Mechanics 88 (2000) 207-227) (also see Section 5 of Kannan and Rajagopal (K. Kannan, K.R. Rajagopal, A thermomechanical framework for the transition of a viscoelastic liquid to a viscoelastic solid, Mathematics and Mechanics of Solids 9 (2004) 37-59)), which was used by Rajagopal and Srinivasa to derive a mathematical model for isotropic, rate-type liquids. Uniaxial cyclic loading and stress relaxation experiments were conducted. The predictions of the model agreed well with the experimental data.