First-principles investigation of F-functionalized ZGNR/AGNR for nanoscale interconnect applications

Journal of Computational Electronics - Zigzag and armchair graphene nanoribbons (ZGNR and AGNR) have been investigated using the density functional theory (DFT) and nonequilibrium Green’s...     

Kinetics of Iododeoxyuridine release from sodium alginate hydrogel in vitro

Objective To investigate the kinetics of Iododeoxyuridine (IUdR)release from sodium alginate hydrogel cross-linked with varying amounts of calcium chloride, and to optimize sustained release for further periadventitial I125-labeled IUdR     

On-Demand Local Modification of High-Tc Superconductivity in Few Unit-Cell Thick Bi2Sr2CaCu2O8+δ

High-temperature superconductors (HTSs) are important for potential applications and for understanding the origin of strong correlations. Bi₂Sr₂CaCu₂O_8+δ (BSCCO), a van der Waals material, offers a platform to probe the physics down to a unit-cell. Guiding the flow of electrons by patterning 2DEGS and oxide heterostructures has brought new functionality and access to new science. Similarly, modifying superconductivity in HTS locally, on a small length scale, is of immense interest for superconducting electronics. A route to modify superconductivity locally by depositing metal on the surface is reported here by transport studies on few unit-cell thick BSCCO. Deposition of chromium (Cr) on the surface over a selected area of BSCCO results in insulating behavior of the underlying region. Cr locally depletes oxygen in CuO₂ planes and disrupts the superconductivity in the layers below. This technique of modifying superconductivity is suitable for making sub-micrometer superconducting wires and more complex superconducting devices.     

Correlation between spin–phonon coupling and magneto-electric effects in CoFe2O4/PMN-PT nanocomposite: Raman spectroscopy and XMCD study

We have investigated strain-induced spin lattice coupling in the CoFe₂O₄/0.65Pb (Mg_1/3Nb_2/3)O₃–0.35PbTiO₃(PMN-PT) composite system, evident by temperature-dependent Raman spectroscopy and magnetization measurements. The strain interactions lead to magneto-electric coupling, and the measured magneto-electric voltage coefficient is 40 mV/cm^?1Oe^?1 for the CoFe₂O₄/PMN-PT composite samples. X-ray magnetic circular dichroism (XMCD) analysis establishes modified spin structure in the electrically poled CoFe₂O₄/PMN-PT composite, further validating the coupling between magnetic and electric ordering in the composite. The magneto-electric coupling coefficient α vs dc magnetic field curves revealed hysteretic behavior and enhanced α values after electric poling, which originates from the strain-induced modifications in the magnetic structure of composite in the electrically poled samples. These findings suggest that the existence of spin lattice coupling may lead to the mechanism of strong magneto-electric effects via strain interactions in CoFe₂O₄/PMN-PT composite.

     

Optimisation of tensile membrane structures under uncertain wind loads using PCE and kriging based metamodels

Tensile membrane structures (TMS) are light-weight flexible structures that are designed to span long distances with structural efficiency. The stability of a TMS is jeopardised under heavy wind forces due to its inherent flexibility and inability to carry out-of-plane moment and shear. A stable TMS under uncertain wind loads (without any tearing failure) can only be achieved by a proper choice of the initial prestress. In this work, a double-loop reliability-based design optimisation (RBDO) of TMS under uncertain wind load is proposed. Using a sequential polynomial chaos expansion (PCE) and kriging based metamodel, this RBDO reduces the cost of inner-loop reliability analysis involving an intensive finite element solver. The proposed general approach is applied to the RBDO of two benchmark TMS and its computational efficiency is demonstrated through these case studies. The method developed here is suggested for RBDO of large and complex engineering systems requiring costly numerical solution.     

Signatures of molecular magnetism in single-molecule transport spectroscopy

We report single-molecule-transistor measurements on devices incorporating magnetic molecules. By studying the electron-tunneling spectrum as a function of magnetic field, we are able to identify signatures of magnetic states and their associated magnetic anisotropy. A comparison of the data to simulations also suggests that sequential electron tunneling may enhance the magnetic relaxation of the magnetic molecule.     

Structural,microstructural and magneto-electric properties of single-phase BiFeO3 nanoceramics prepared by auto-combustion method

Polycrystalline nano BiFeO₃ powders were synthesized by auto-combustion method using urea as fuel and metal nitrates (Fe(NO₃)₃·9H₂O, Bi(NO₃)₃·5H₂O) as oxidizers. In order to optimize the single-phase synthesis condition of BiFeO₃, different fuel to oxidizer ratios have been investigated. The preliminary structural investigation using X-ray diffraction shows the samples were of single phase and crystallize in rhombohedral structure (R3c). The ferroelectric and antiferromagnetic ordering temperatures of BiFeO₃ were found to be 832 °C and 364 °C respectively, from differential thermal analysis. The temperature dependent dielectric study shows an anomaly around 215 °C which corresponds to magneto-electric coupling in the material. Field-emission scanning electron micrographs show effect of fuel to oxidizer ratio on grain size evolution. The ferroelectric hysteresis loops for all the samples were measured at a frequency of 100 Hz confirming the ferroelectric nature. An evidence of magneto-electric coupling was also observed at room temperature from magneto-capacitance measurements.     

Hands-On Undergraduate Geotechnical Engineering Modules in the Context of Effective Learning Pedagogies, ABET Outcomes, and Our Curricular Reform

Hands-on inquiry-based educational modules were designed for two undergraduate geotechnical engineering courses at the University of Vermont. The modules were designed to achieve three objectives: (1) meet the goals of our ongoing civil and environmental engineering curricular reform (e.g., inquiry-based experiential learning and civic engagement through service-learning); (2) reach higher levels of Bloom’s taxonomy in specific topical areas addressed by the modules; and (3) help achieve Accreditation Board for Engineering and Technology (ABET) outcomes for civil and environmental engineering programs. All four modules were conducted within team settings and required students to write formal technical papers or reports followed by presentations. An additional underlying objective was the development of students’ interpersonal and communication skills. The educational modules included: (1) Atterberg limits using Casagrande and fall cone devices; (2) physical, analytical, and numerical modelings of steady-state seepage; (3) validation of undrained slope stability, bearing capacity of shallow foundations, and active and passive lateral earth pressure analytical solutions using centrifuge modeling; and (4) service-learning projects related to foundations, retaining structures, or slope stability for rehabilitation of historic structures. Student reflection and self-assessment activities were conducted. The student self-assessment results and assessments of student work indicated that many of the curricular reform objectives, ABET outcomes, and higher levels of Bloom’s taxonomy could be reached through these modules. Modules similar to these could be effective in other engineering disciplines and subdisciplines.     

Experimental investigation of convective heat transfer coefficient of Al2O3/water nanofluid at lower concentrations in a car radiator

For many years, water and ethylene glycol were used as conventional coolants in automotive car radiators, but these coolants offer lower thermal conductivity than is required. This study is focused on the application of water‐based Al₂O₃ nanofluid at lower concentrations in a car radiator. The Al₂O₃ nanoparticles with an average diameter of 50 nm are dispersed in demineralized water at four different volume concentrations (0.1 vol. % to 0.4 vol. %) without any dispersant or stabilizer. Flow rate is varied in the range of 2 l/min to 5 l/min and inlet coolant temperature to the radiator is set to 50 °C, 60 °C, and 70 °C. The results show that the heat transfer coefficient increases with an increase in particle concentration, flow rate, and inlet temperature of coolant and the maximum increase in heat transfer coefficient is 45.87 % compared to pure water. However, the Nusselt number increases with the increase in particle concentration, Reynolds number, and inlet temperature of the coolant. In addition with the experimental study, a regression analysis is performed by using the ANOVA method and generates a correlation for the convective heat transfer coefficient.     

An Embedding Based IR Model for Disaster Situations

Twitter (http://twitter.com) is one of the most popular social networking platforms. Twitter users can easily broadcast disaster-specific information, which, if effectively mined, can assist in relief operations. However, the brevity and informal nature of tweets pose a challenge to Information Retrieval (IR) researchers. In this paper, we successfully use word embedding techniques to improve ranking for ad-hoc queries on microblog data. Our experiments with the ‘Social Media for Emergency Relief and Preparedness’ (SMERP) dataset provided at an ECIR 2017 workshop show that these techniques outperform conventional term-matching based IR models. In addition, we show that, for the SMERP task, our word embedding based method is more effective if the embeddings are generated from the disaster specific SMERP data, than when they are trained on the large social media collection provided for the TREC (http://trec.nist.gov/) 2011 Microblog track dataset.