Synthesis of ferromagnetic nickel ferrite nanofibers via electrospinning with iron acetate as an iron precursor

We report the synthesis of nickel ferrite nanofibers via an elecrospinning technique particularly using iron (II) acetate as an iron precursor. Nanofibers of a single-phase nickel ferrite with a uniform diameter of ??90 nm were successfully synthesized by adopting a properly prepared solution and calcination condition. Individual nickel ferrite nanofibers synthesized by electrospinning were made up of nanograins of ??20 nm in diameter. In addition, the hysteresis observed in a magnetization measurement confirmed their ferromagnetism, supporting their potential use in magnetic devices. These results demonstrate that the use of iron (II) acetate as an iron precursor is another way to synthesize ferromagnetic nickel ferrite nanofibers.     

Nano-sized particles formed by pulsed discharge of powders

Exploding wire and pulsed wire discharge are effective methods to form nano-sized particles. They are based on evaporation of thin metal wires by applied large electric current as the principle to form particles. Many kinds of wires have been used to form nano-sized particles so far. However, materials which are not sufficiently ductile to form thin wires are unsuitable for the methods. We have developed a method for powders to be held between electrodes by using heat-shrinkable tubes and discharged for evaporation. Nano-sized intermetallic NiAl compound particles were synthesized from mixed powders of Al and Ni. Si powder could be discharged by sealing with a thin Al wire, and nano-sized Si particles were formed. Utilizing this technique, various metal powders can be used for raw materials in pulsed discharge.     

Local thermal degradation behavior of heterophasic polypropylene copolymers

Polypropylene (PP) impact copolymer is one of the heterophasic PP systems that is improved by rubber modification. Because the copolymer is a complicated polymer blend, which mainly consists of PP and ethylene–propylene rubber (EPR) components, the degradation behavior has hardly been studied. In this study, the thermal degradation of the copolymer was studied through direct observation by atomic force microscopy, which is a powerful tool for observing a local domain in a polymer blend. The degradation behavior was visually captured by the mapping of topological changes. Although the EPR phase was hardly degraded, the neighboring PP matrix was degraded selectively. The degradation behavior of the copolymer was found to be heterogeneous. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1831–1835, 2006     

OPTIMAL CONTROL OF AN ACTIVE SUSPENSION SYSTEMEMPLOYING HIGH SPEED ON/OFF SOLENOID VALVE

Conventionalpassivesuspensionistypicallycomposedofcoilspringandhydraulicdampers.Toimproveridecomfort,thesepassiveelementsmustbesetonthesoftside,buttoimprovehandling,springsanddampersmustbemadestiffertodampwheelvibrationandreducebodyrollingandpitchingmotions.Thesecontrarypurposesformtheclassicsuspensiondesigncompromise.Differingfromapassivesuspension,anactivesuspensionhasitsownpowersource,andcancontinuallysupplyandmodulatetheflowofenergyandgeneratethecontrolforcewhichcanbeafunctionsofanyvariabl…     

Studies of thermal oxidative degradation of polypropylene impact copolymer using the temperature rising elution fractionation method

Thermal oxidative degradation of polypropylene impact copolymer has been studied with its fractions obtained using the temperature rising elution fractionation method. The fractions were analyzed using ¹³C NMR, Fourier transform infrared and differential scanning calorimetry measurements, and the chemical structure, isotacticity, conformation and melting point were investigated. It is found that these fractions are composed of a homopolymer or a polymer blend of polypropylene, polyethylene and ethylene–propylene copolymer. The thermal oxidative degradation of each fraction was carried out at 130 °C, and the degradation progress was estimated by the change of molecular weight distribution (from gel permeation chromatography curves). The rate of degradation is found to be dominated by the content of tertiary C? H bonds (propylene unit) and the existence of 3₁ helix conformation corresponding to a crystalline polypropylene part in each fraction. The latter is more evident leading to the degradation reaction path with a lower activation energy. Copyright © 2007 Society of Chemical Industry     

A Markov basis for conditional test of common diagonal effect in quasi-independence model for square contingency tables

In two-way contingency tables we sometimes find that frequencies along the diagonal cells are relatively larger (or smaller) compared to off-diagonal cells, particularly in square tables with the common categories for the rows and the columns. In this case the quasi-independence model with an additional parameter for each of the diagonal cells is usually fitted to the data. A simpler model than the quasi-independence model is to assume a common additional parameter for all the diagonal cells. We consider testing the goodness of fit of the common diagonal effect by the Markov chain Monte Carlo (MCMC) method. We derive an explicit form of a Markov basis for performing the conditional test of the common diagonal effect. Once a Markov basis is given, MCMC procedure can be easily implemented by techniques of algebraic statistics. We illustrate the procedure with some real data sets.     

Dependence of tacticity distribution in thermal oxidative degradation of polypropylene

Summary Thermal oxidative degradation behavior of two kinds of polypropylene (PP) with different tacticity distribution was investigated based on the data obtained by NMR, temperature rising elution fractionation (TREF) and thermogravimetric analysis (TGA). Although these PPs have similar molecular weights and tacticity, the behavior of degradation was considerably different. The differences were found to be due to the tacticity distribution by TREF measurement. In order to investigate the effect of tacticity distribution on the degradation in more detail, the more stable PP having a broad tacticity distribution was divided into four kinds of tacticity fraction by TREF, and each of degradation behavior was investigated by TGA. The results indicated that the rate of degradation systematically depended on the tacticity. The higher stability of PP with the broader tacticity distribution would be originated from the abstraction reaction of tertiary hydrogen, which was the rate-determining step in PP degradation reaction.     

Operational wavelength range of GaInAs(P)-InP intersectionaloptical switches using field-induced electrooptic effect inlow-dimensional quantum-well structures

Operational wavelength range for low insertion loss and high extinction ratio of GaInAs(P)-InP intersectional optical switches consisting of low-dimensional quantum-well structures, such as quantum-box, quantum-wire, and quantum-film structures, is theoretically analyzed. It is found that superior operation characteristics can be attained with the lower-dimensional quantum-well structure. For instance, an operational wavelength range of around 10 nm for an insertion loss less than 1 dB and an extinction ratio higher than 50 dB can be obtained with the device using a quantum-box structure     

Magnetic Properties of CsxC60

Magnetic properties of Cs_xC₆₀ have been studies by the magnetic susceptibility and ESR. The observation of Pauli and Curie-Weiss susceptibilities implies the existence of a metallic phase Cs₁C₆₀ and a paramagnetic phase Cs₄C₆₀.