Electromagnetic Metrology on Concrete and Corrosion

To augment current methods for the evaluation of reinforcing bar (rebar) corrosion within concrete, we are exploring unique features in the dielectric and magnetic spectra of pure iron oxides and corrosion samples. Any signature needs to be both prominent and consistent in order to identify corrosion within concrete bridge deck or other structures. In order to measure the permittivity and propagation loss through concrete as a function of temperature and humidity, we cut and carefully fitted samples from residential concrete into three different waveguides. We also poured and cured a mortar sample within a waveguide that was later measured after curing 30 days. These measurements were performed from 45 MHz to 12 GHz. Our concrete measurements showed that the coarse granite aggregate that occupied about half the sample volume reduced the electromagnetic propagation loss in comparison to mortar. We also packed ground corrosion samples and commercially available iron-oxide powders into a transmission-line waveguide and found that magnetite and corrosion sample spectra are similar, with a feature between 0.5 GHz and 2 GHz that may prove useful for quantifying corrosion. We also performed reflection (S₁₁) measurements at various corrosion surfaces and in loose powders from 45 MHz to 50 GHz. These results are a first step towards quantifying rebar corrosion in concrete.     

Effect of selected aromatic medicinal plant sancho (Zanthoxylum schinifolium) on osteoblastic MC3T3-E1 cells

This study was performed to investigate the bioactivity of sancho (Zanthoxylum schinifolium) essential oil (EO) on bone metabolism and its function of osteoblastic MC3T3-E1 cells. The volatile aroma components of sancho EO were collected using a Clevenger-type apparatus by steam distillation extraction method, and determined by GC-MS. β-Phellandrene (22.54%) was the most abundant volatile compound in sancho EO, followed by citronellal (16.48%) and geranyl acetate (11.39%). It increased the collagen and mineralization of osteoblasts (p<0.05), indicating that sancho may help prevent osteoporosis.     

Microstructural features, texture and strengthening mechanisms of nanostructured AA6063 alloy processed by powder metallurgy

Nanostructured AA6063 (NS-Al) powder with an average grain size of ∼100 nm was synthesized by high-energy attrition milling of gas-atomized AA6063 powder followed by hot extrusion. The microstructural features of the consolidated specimen were studied by transmission electron microscopy (TEM) and electron backscatter diffraction (EBSD) techniques and compared with those of coarse-grained AA6063 (CG-Al) produced by hot powder extrusion of gas-atomized powder (without using mechanical milling). The consolidated NS-Al alloy consisted of elongated ultrafine grains (aspect ratio of ∼2.9) and equiaxed nanostructured grains. A high fraction (∼78%) of high-angle grain boundaries with average misorientation angle of 33° was noticed. Microtexture evaluation by plotting pole-figures and orientation distribution function (ODF) analysis showed Copper and P texture components for both the consolidated Al alloys. Tensile test at room temperature and microhardness measurement revealed that a significant improvement in the strength of AA6063 alloy is obtained through refinement of the grain structure. The strengthening mechanisms are discussed based on the dislocation-based models. The role of high-angle and low-angle grain boundaries on the strengthening mechanisms is discussed.     

A simple method to prepare indium oxide nanoparticles: Structural,microstructural and magnetic properties

Indium oxide nanoparticles of ～12 nm were synthesized by a simple chemical route using indium(III) nitrate. Nanoparticles are formed after calcining the dried precursor in air at 400 °C for 10 h. TEM analysis showed that the morphology and size of the In₂O₃ samples were affected by ultrasonication. FTIR and Raman studies reveal that the nanoparticles are single-phase cubic structure of In₂O₃. NEXAFS study was used to quantify the Indium and oxygen valence state. Magnetic behavior of indium oxide nanoparticles was found to be diamagnetic. UV spectra show a weak band at ～308 nm corresponds to optical band gap energy of 4.03 eV.     

pH-sensitive photocatalytic activities of TiO2/poly(vinyl alcohol)/poly(acrylic acid) composite hydrogels

The pH-sensitive photocatalytic system was prepared by embedding TiO₂ into poly(vinyl alcohol)/poly(acrylic acid) hydrogel. Two different type TiO₂/hydrogel composites, such as matrix and nanofiber, were prepared to investigate the morphological effects on the photocatalytic activity. TiO₂ was distributed uniformly in the composite hydrogel and kept the original anatase structure without any structural change. The photocatalytic activity of TiO₂ was evaluated based on the efficiency of photobleaching of dye. The photobleaching of dye was improved greatly as the pH was changed into basic condition and the larger surface area of hydrogel was available for TiO₂ by using nanofiber supports.     

Quantitative measurement of cementite dissociation in drawn pearlitic steel

Fractional dissociation of cementite was quantified as a function of strain by measuring the volume change of cementite in the pearlitic steel. The amount of carbon dissolved into the ferrite was estimated from the decrease of cementite volume, to correlate with the hardness in different strain level. The hardness showed linear relationship with the carbon dissolved into the ferrite matrix, which is believed to contribute in strengthening the drawn wire. Defects introduced from the deformation were believed to lower the energy barrier of cementite break-ups and to enhance the dissolution of carbon into ferrite.     

Molecular dynamics study on nanotube-resonators with mass migration applicable to both frequency-tuner and data-storage-media

We investigated the cantilevered carbon-nanotube-resonator including electromigratively movable nanoparticle via classical molecular dynamics simulations and continuum model. The change of the effective mass value, which was closely correlated with the position change of the encapsulated nanoparticle, could be regressed by a power function, the resonance frequency of the carbon-nanotube-resonator could be tuned by controlling the nanoparticle’s position, and the possible frequency-shift-ranges then reached 18–85%. The suggested device could be served as a data-storage-media for electromechanical nonvolatile-memory as well as a frequency-tuner.     

Thermoreversible behavior of κ-carrageenan and its apatite-forming ability in simulated body fluid

Osteoconductive materials with self-setting ability have received much attention because their properties allow developing injectable materials for bone defects. Thermosensitive hydrogel with ability of bone-like apatite formation in a body environment is a candidate of injectable bone fillers with osteoconductivity because the apatite formation on materials is an essential to show osteoconduction. The present study focused on the development of a thermosensitive hydrogel through modifications of the sulphonic groups of the polysaccharide, κ-carrageenan, with potassium chloride (KCl) and calcium chloride (CaCl₂). We found that the gelation temperature of κ-carrageenan solutions increased with increasing amounts of K⁺ ions. Apatite formation was observed on the gel after exposure to simulated body fluid for 0.5 day when the gel was prepared with a molar ratio of Ca²⁺/sulfonic groups = 1.5. These results indicate that a thermosensitive κ-carrageenan hydrogel with apatite-forming ability was obtained through the incorporation of K⁺ and Ca²⁺ ions into the solution.     

The Navier–Stokes-αβ equations as a platform for a spectral multigrid method to solve the Navier–Stokes equations

This paper describes a spectral multigrid method for spatially periodic homogeneous and isotropic turbulent flows. The method uses the Navier–Stokes-αβ equations to accelerate convergence toward solutions of the Navier–Stokes equations. The Navier–Stokes-αβ equations are solved on coarse grids at various levels and the Navier–Stokes equations are solved on the “nest grid”. The method uses Crank–Nicolson time-stepping for the viscous terms, explicit time-stepping for the remaining terms, and Richardson iteration to solve linear systems encountered at each time step and on each grid level. To explore the computational efficiency of the method, comparisons are made with results obtained from an analogous spectral multigrid method for the Navier–Stokes equations. These comparisons are based on computing work units and residuals for multigrid cycles. Most importantly, we examine how choosing different values of the length scales α and β entering the Navier–Stokes-αβ equations influence the efficiency and accuracy of these multigrid schemes.