Nano/Submicro-Structured Iron Cobalt Oxides Based Materials for Energy Storage Application

Supercapacitors, as promising energy storage devices, have been of interest for their long lifespan compared to secondary batteries, high capacitance and excellent reliability compared to conventional dielectric capacitors. Transition metal oxides can be applied as the electrode materials for pseudocapacitors and offer a much higher specific capacitance. Co3O4 is one of the most investigated transition metal oxides for supercapacitor. Besides simple monometallic oxides, bimetallic transition oxides have recently drawn growing attention in electrochemical energy storage. They present many unique properties such as achievable oxidation states, high electrical conductivities because of the coexistence of two different cations in a single crystal structure. This study focuses on the bimetallic iron cobalt oxide based materials for the application of energy storage. We selected iron as the substituent in spinel Co3O4, by virtue of its abundant and harmless character. Four types of iron cobalt oxides based electrode materials with different morphologies and components have been synthesized for the first time. The hydrothermal method was the main strategy for the synthesis of iron cobalt based materials, which achieved the control of morphology and ratio of components. Multiple characterization methods, including SEM, TEM, XRD, XPS, TGA, BET, have been applied to study the morphologies and nano/submicron structures. The electrochemical properties of as-fabricated samples were performed by electrochemical workstation. In addition, in order to investigate the practical application of electrode materials, asymmetric supercapacitors have been assembled by using as-prepared samples as the positive electrodes and activated carbon as the negative electrodes

Local Freeway Ramp Metering using Self-Adjusted Fuzzy Controller

A self-adjusted fuzzy local ramp metering strategy is proposed to keep the mainline traffic state and the on-ramp queue length at reasonable levels. The fuzzy ramp metering strategy (FRMS) takes the following variables as inputs: error between desired density and measured density, change-in-error and on-ramp queue length. On-ramp metering flow is decided by these variables. It is difficult to construct fuzzy rules for a three-dimension inputs fuzzy controller based on expert knowledge, so the proposed FRMS generates fuzzy control rules by an analytic expression with correction factors. The correction factors reflect the weights upon linguistic variables of inputs and can be regulated according to actual traffic state of mainline and on-ramp. The proposed FRMS not only simplifies the process of rules definition for a multi-dimension fuzzy controller, but also has function of self-adjusted control rules. To examine the proposed FRMS, a freeway stretch in Los Angeles is simulated with distributed models. The proposed FRMS is also compared with an existing T-S FRMS and PI-ALINEA in the simulation experiments which cover different on-ramp inflow scenarios. Simulation results show the proposed FRMS provides improved adaptation to various scenarios and superiority in striking a balance between the mainline and on-ramp performances

Comparisons of mutation rate variation at genome-wide microsatellites: evolutionary insights from two cultivated rice and their wild relatives

<p>Abstract</p> <p>Background</p> <p>Mutation rate (μ) per generation per locus is an important parameter in the models of population genetics. Studies on mutation rate and its variation are of significance to elucidate the extent and distribution of genetic variation, further infer evolutionary relationships among closely related species, and deeply understand genetic variation of genomes. However, patterns of rate variation of microsatellite loci are still poorly understood in plant species. Furthermore, how their mutation rates vary in di-, tri-, and tetra-nucleotide repeats within the species is largely uninvestigated across related plant genomes.</p> <p>Results</p> <p>Genome-wide variation of mutation rates was first investigated by means of the composite population parameter θ (θ = 4Nμ, where N is the effective population size and μ is the mutation rate per locus per generation) in four subspecies of Asian cultivated rice <it>O. sativa </it>and its three related species, <it>O. rufipogon</it>, <it>O. glaberrima</it>, and <it>O. officinalis</it>. On the basis of three data sets of microsatellite allele frequencies throughout the genome, population mutation rate (<b><it>θ</it></b>) was estimated for each locus. Our results reveal that the variation of population mutation rates at microsatellites within each studied species or subspecies of cultivated rice can be approximated with a gamma distribution. The mean population mutation rates of microsatellites do not significantly differ in motifs of di-, tri-, and tetra-nucleotide repeats for the studied rice species. The shape parameter was also estimated for each subspecies of rice as well as other related rice species. Of them, different subspecies of <it>O. sativa </it>possesses similar shape parameters (<b><it>α</it></b>) of the gamma distribution, while other species extensively vary in their population mutation rates.</p> <p>Conclusion</p> <p>Through the analysis of genome-wide microsatellite data, the population mutation rate can be approximately fitted with a gamma distribution in most of the studied species. In general, different population histories occurred along different lineages may result in the observed variation of population mutation rates at microsatellites among the studied <it>Oryza </it>species.</p

Analysis of internal crack healing mechanism under rolling deformation

A new experimental method, called the \u27hole filling method\u27, is proposed to simulate the healing of internal cracks in rolled workpieces. Based on the experimental results, the evolution in the microstructure, in terms of diffusion, nucleation and recrystallisation were used to analyze the crack healing mechanism. We also validated the phenomenon of segmented healing. Internal crack healing involves plastic deformation, heat transfer and an increase in the free energy introduced by the cracks. It is proposed that internal cracks heal better under high plastic deformation followed by slow cooling after rolling. Crack healing is controlled by diffusion of atoms from the matrix to the crack surface, and also by the nucleation and growth of ferrite grain on the crack surface. The diffusion mechanism is used to explain the source of material needed for crack healing. The recrystallisation mechanism is used to explain grain nucleation and growth, accompanied by atomic migration to the crack surface

Bioinspired and bristled microparticles for ultrasensitive pressure and strain sensors

Biological sensory organelles are often structurally optimized for high sensitivity. Tactile hairs or bristles are ubiquitous mechanosensory organelles in insects. The bristle features a tapering spine that not only serves as a lever arm to promote signal transduction, but also a clever design to protect it from mechanical breaking. A hierarchical distribution over the body further improves the signal detection from all directions. We mimic these features by using synthetic zinc oxide microparticles, each having spherically-distributed, high-aspect-ratio, and high-density nanostructured spines resembling biological bristles. Sensors based on thin films assembled from these microparticles achieve static-pressure detection down to 0.015 Pa, sensitivity up to 121 kPa−1, and a strain gauge factor \u3e104, showing supreme overall performance. Other properties including a robust cyclability \u3e2000, fast response time ~7 ms, and low-temperature synthesis compatible to various integrations further indicate the potential of this sensor technology in applying to wearable technologies and human interfaces