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Forming behavior and microstructural evolution during single point incremental forming process of AA-6061 aluminum alloy sheet
No full textAA-6061 aluminum alloy is extensively used in automobile and aerospace industries due to its high strength-to-weight ratio. However, this material shows limited formability in age-hardened condition at room temperature. Therefore, a new forming method known as single point incremental forming (SPIF) to deform the sheet was adopted. The SPIF experiments and finite element method (FEM) simulation were performed to form the sheet into the desired conical shape. Digital image correlation (DIC) method was used to measure the major and minor strains post deformation experimentally, and results were compared with FEM results. Detailed microstructural study was performed to understand the deformation behavior of AA-6061 aluminum alloy sheets during SPIF. It is observed that plastic anisotropy has strong effect on microstructure and texture development in different directions of AA-6061 alloy sheet during SPIF. It is also observed that volume fraction of goss and S texture components remains stable, whereas volume fraction of cube and brass texture changes significantly
Advances in point-of-care diagnostic devices in cancers
No full textThe early diagnosis and monitoring of the progress of cancers are limited due to the lack of adequate screening tools. Ultrasensitive and precise point-of-care cancer diagnostic tools are required for the early detection and screening of cancer biomarkers at the bedside with accuracy and specificity of diagnosis. Recent advances in nano- and microfabrication based technologies integrated with different sensing platforms are accelerating the development of rapid, low-cost and reliable point-of-care cancer diagnostic devices. These technologies allow low volumes of reagents and samples, reduced analysis time, are disposable and portable, and provide ultrasensitive multiplexed analysis to improve diagnostic and prognostic evaluations. Networking for communicating and transferring the results through wireless networks provides additional opportunities for remote telemedicine-based diagnosis and planning of treatment regimens, even in semi-urban and rural areas. This review focuses on recent advances in point-of-care cancer diagnostics for efficient treatment along with the key challenges, opportunities and future scope of these technologies for clinical translation
Dynamic near-field heat transfer between macroscopic bodies for nanometric gaps
No full textThe dynamic heat transfer between two half-spaces separated by a vacuum gap due to the coupling of their surface modes is modeled using the theory that describes the dynamic energy transfer between two coupled harmonic oscillators, each separately connected to a heat bath and with the heat baths maintained at different temperatures. The theory is applied for the case when the two surfaces are made up of a polar crystal that supports surface polaritons that can be excited at room temperature and the predicted heat transfer is compared to the steady-state heat transfer value calculated from the standard fluctuational electrodynamics theory. It is observed that for small time intervals the value of heat flux can be significantly higher than that of steady-state value
Insights on the Origin of Regiodivergence in the Parallel Kinetic Resolution of rac-Aziridines Using a Chiral Lanthanum-Yttrium Bimetallic Catalyst
No full textParallel kinetic resolution of racemic mixtures is an important method used in asymmetric synthesis of chiral compounds. In a recent example, a rac-cis-2,3-substituted chiral N-benzoyl aziridine was reacted with dimethyl malonate, in the presence of a La-Y heterobimetallic chiral BINAM Schiff base (L) catalyst, to form enantiomerically pure (ee > 98%) gamma-amino acid derivatives through a ring-opening reaction in near quantitative yields from both the enantiomers (similar to 48%). High regio- and enantioselectivities even with a rac-aziridine, having C2 and C3 substituents as similar as ethyl and n-propyl. Through a comprehensive computational investigation, we delineate the origin of regio-divergent and enantioselective formation of gamma-amino ester derivatives. The Gibbs free energy of the transition state for the ring-opening at the propyl substituted C2 carbon leading to 3-benzamidoheptan-4-yl malonate is found to be 7.2 kcal/mol lower than that at the ethyl substituted C3 carbon in the case of (2R,3S)-aziridine. A reversal of the regio-chemical preference for its enantiomeric (2S,3R)-aziridine is noted where the ring-opening occurs at the ethyl substituted C3 carbon. The La Y catalyst is found to initially "recognize" both the enantiomers of the rac-aziridine rather indiscriminately. The activation barriers for the most-preferred ring-opening for each enantiomer are found to be closely similar, suggesting that both enantiomers would react. The high regio-selectivity in the addition of lanthanum-bound malonate to the aziridine anchored onto the yttrium center is due to a unique geometric disposition of the aziridine in the stereocontrolling ring-opening transition state. The lowest-energy ring-opening transition state for each enantiomer of aziridine exhibited very similar geometries, while notable geometric distortions is identified in the malonate addition to less-preferred site of the same enantiomer
Design and development of a low-cost angular sky luminance measurement system
No full textEnergy efficient building design requires simulated assessment of overall performance through reliable models, taking into account the daylight variations along with other significant parameters such as ventilation, plug loads and occupant behaviour. A robust indoor daylight model applicable to locations across the globe needs to incorporate local variations of sky luminance on a spatial and temporal basis, and needs an affordable system for dynamic angular daylight measurement to be used as part of a wider distributed network. In the present work, a low-cost prototype based on Light Dependent Resistors for measurement of angular daylight luminance distribution is developed and analyzed. This device was used to capture the angular analog data for 221 sky segments (20 azimuthal x 11 altitudinal segments and Zenith). The analog data was further converted to luminance data, and the visualized data was compared with sky-dome photographs and also with simulated polar daylight maps for a few Commission International de l'Eclairage (CIE) skies. The repeatability of the experiment was assessed by comparing the luminance data for selected sky segments over multiple time-segments for consecutive days. Measured data was found to be an acceptable fit with the CIE-models over various time segments, validating the prototype
Lithium assisted enhanced hydrogenation of reduced graphene oxide-PANI nanocomposite at room temperature
No full textPresent study, first time, reveals that lithium and ethylenediamine assisted Benkeser reaction enhanced the hydrogenation process where reduced graphene oxide-PANI (G-PANI) nanocomposites act as storage medium. Varying the weight ratio of graphene and PANI, several samples were synthesized and hydrogenated. The reduced grapheme oxide-PANI (G-PANI) and hydrogenated reduced grapheme oxide-PANI (HG-PANI) nano-composites were characterized by high resolution transmission electron microscopy (HRTEM), field emission scanning electron microscopy (FESEM), Fourier transform infrared spectra (FTIR) analysis and thermo gravimetric analysis (TGA). The electrical conductivity with the variation of temperature for the nanocomposites has also been studied. The reduced values of electrical conductivity and percent weight loss in TGA suggested that the hydrogenation occurs. The degree of hydrogenation of reduced graphene oxide-PANI estimated by TGA, revealed 11% (30% reduced graphene oxide-PANI) and 16.04% (50% reduced graphene oxide-PANI), hydrogen storage, which is considerably higher than the reported values of hydrogen storage in individual storage materials like, PANI, graphene and carbon nano tube
Di, tri and tertanuclear ruthenium complexes of a heterocyclic and quinonoid bridging ligand: Valence and spin alternatives for the metal/Ligand/ metal arrangement, non-innocence and mixed valency
No full textCharting the protomap of the human telencephalon
No full textThe cerebral cortex is divided stereotypically into a number of functionally distinct areas. According to the protomap hypothesis formulated by Rakic neural progenitors in the ventricular zone form a mosaic of proliferative units that provide a primordial species-specific cortical map. Positional information of newborn neurons is maintained during their migration to the overlying cortical plate. Much evidence has been found to support this hypothesis from studies of primary cortical areas in mouse models in particular. Differential expansion of cortical areas and the introduction of new functional modules during evolution might be the result of changes in the progenitor cells. The human cerebral cortex shows a wide divergence from the mouse containing a much higher proportion of association cortex and a more complicated regionalised repertoire of neuron sub-types. To what extent does the protomap hypothesis hold true for the primate brain? This review summarises a growing number of studies exploring arealised gene expression in the early developing human telencephalon. The evidence so far is that the human and mouse brain do share fundamental mechanisms of areal specification, however there are subtle differences which could lead us to a better understanding of cortical evolution and the origins of neurodevelopmental diseases. (C) 2017 Elsevier Ltd. All rights reserved
Efficiency of Open and Infill Trenches in Mitigating Ground-Borne Vibrations
No full textIn the present-day context, man-made sources of ground-borne vibration are rising at a very rapid rate due to increasing construction work, blasting activities, and rapidly expanding rail and road traffic systems. As a consequence, amplified levels of ground-borne vibration occur, causing annoyance to residents living in nearby areas, posing a threat to the stability of old structures, and interfering with instrumentation works in industries. This paper discusses an investigation into the use of trenches as a means of mitigating ground vibration caused by propagation of surface (Rayleigh) waves. Two- and three-dimensional (2D and 3D) finite-element models were developed using PLAXIS for identifying key factors affecting the vibration isolation efficiency of open and infill trenches. Parametric studies were carried out, and the results were analyzed to arrive at optimum values of geometrical and material properties of trenches. Numerical analysis showed that, for open trenches, normalized depth is the decisive factor and width is of importance in trenches that are very shallow. For infill trenches, it was observed that low-density materials perform exceedingly well as infill materials but their performance is highly sensitive to the relative shear-wave velocity between the infill material and the in situ soil. Finally, an in-depth analysis was carried out to investigate the performance of polyurethane foam trenches in mitigating vibrations caused by harmonic loads. The analysis was extended to study the effectiveness of these geofoam barriers in damping out the vibrations generated by a moving train. In this case, barrier efficiency was shown to increase with increasing train speed. The key findings suggest that trenches are a simple and effective solution for reducing ground-borne vibrations. (C) 2018 American Society of Civil Engineers
Aquifer parameter and zonation structure estimation using meshless local Petrov-Galerkin method and particle swarm optimization
No full textThe simulation-optimization (SO) modeling approach can be effectively used for aquifer parameter estimation. In this study, a numerical approach based on meshless local Petrov-Galerkin (MLPG) method is used for groundwater flow simulation and coupled with particle swarm optimization model for optimization. The study deals with the identification of the most suitable model structure for a hypothetical heterogeneous confined aquifer from a number of alternate models using zonation method of parameter estimation. A range of alternate models starting from homogeneous to more complex model structures are considered for the zonation. Inverse modeling of different model structures is carried out based on weighted least square performance criterion. The suitable models are selected and reliability analysis ascertained by computing three parameters of composite scaled sensitivity, coefficient of variation, and confidence interval, and the best model is selected. Sensitivity of estimated parameters is investigated by considering different sets of head data involving possible measurement errors. The solutions are compared with another inverse model using the MLPG and Levenberg-Marquardt algorithm. Based on the results, it is found that the proposed methodology can be utilized in the estimation of different unknown parameters in a regional groundwater system