5,751 research outputs found
Development of polymer network of phenolic and epoxies resins mixed with linseed oil: pilot study
Epoxy resin was mixed with phenolic resins in different percentages by weight. Composite 40/60 means the proportion by weight of epoxy resin is 40 percent. It was found that only composites 50/50 and 40/60 could be cured in ambient conditions. Dynamic mechanical analysis showed that only these two composites form interpenetrating polymer network. The addition of linseed oil to the two resins results also in the formation of interpenetrating network irrespective of proportion by weight of the resins; the mechanical properties will only be better when the percentage by weight of epoxy resin is higher; the aim of reducing cost and at the same time maintaining the mechanical properties cannot be fully achieved because epoxy resin is much more expensive than its counterpart
Variable frequency microwave (VFM) processing facilities and application in processing thermoplastic matrix composites
Microwave processing of materials is a relatively new technology advancement alternative that provides new approaches for enhancing material properties as well as economic advantages through energy savings and accelerated product development. Factors that hinder the use of microwaves in materials processing are declining, so that prospect for the development of this technology seem to be very promising. The two mechanisms of orientation polarisation and interfacial space charge polarisation, together with dc conductivity, form the basis of high frequency heating. Clearly, advantages in utilising microwave technologies for processing materials include penetration radiation, controlled electric field distribution and selective and volumetric heating. However, the most commonly used facilities for microwave processing materials are of fixed frequency, e.g. 2.45 GHz. This paper presents a state-of-the-art review of microwave technologies, processing methods and industrial applications, using variable frequency microwave (VFM) facilities. This is a new alternative for microwave processing
EFFICIENCY OF ENERGY UTILIZATION OF VOLATILE FATTY ACIDS BY MATURE CATILE GIVEN A HAY OR HIGH-CONCENTRATE DIET
High-temperature phase transitions in SrBi_2Ta_2O_9 film: a study by THz spectroscopy
Time-domain THz transmission experiment was performed on a film deposited on sapphire substrate. Temperatures between 300
and 923 K were investigated and complex permittivity spectra of the film were
determined. The lowest frequency optic phonon near 28 cm reveals a slow
monotonic decrease in frequency on heating with no significant anomaly near the
phase transitions. We show that the dielectric anomaly near the ferroelectric
phase transition can be explained by slowing down of a relaxational mode,
observed in the THz spectra. A second harmonic generation signal observed in a
single crystal confirms a loss of center of symmetry in the ferroelectric phase
and a presence of polar clusters in the intermediate ferroelastic phase.Comment: subm. to J. Phys.: Condens. Matte
Coercive Field and Magnetization Deficit in Ga(1-x)Mn(x)As Epilayers
We have studied the field dependence of the magnetization in epilayers of the
diluted magnetic semiconductor Ga(1-x)Mn(x)As for 0.0135 < x < 0.083.
Measurements of the low temperature magnetization in fields up to 3 T show a
significant deficit in the total moment below that expected for full saturation
of all the Mn spins. These results suggest that the spin state of the
non-ferromagnetic Mn spins is energetically well separated from the
ferromagnetism of the bulk of the spins. We have also studied the coercive
field (Hc) as a function of temperature and Mn concentration, finding that Hc
decreases with increasing Mn concentration as predicted theoretically.Comment: 15 total pages -- 5 text, 1 table, 4 figues. Accepted for publication
in MMM 2002 conference proceedings (APL
Rabi oscillations of a qubit coupled to a two-level system
The problem of Rabi oscillations in a qubit coupled to a fluctuator and in
contact with a heath bath is considered. A scheme is developed for taking into
account both phase and energy relaxation in a phenomenological way, while
taking full account of the quantum dynamics of the four-level system subject to
a driving AC field. Significant suppression of the Rabi oscillations is found
when the qubit and fluctuator are close to resonance. The effect of the
fluctuator state on the read-out signal is discussed. This effect is shown to
modify the observed signal significantly. This may be relevant to recent
experiments by Simmonds et al. [Phys. Rev. Lett. 93, 077003 (2004)].Comment: 4 pages, 4 figure
Riemann-Hilbert problems for monogenic functions in axially symmetric domains
We consider Riemann-Hilbert boundary value problems (for short RHBVPs) with variable coefficients for axially symmetric monogenic functions defined in axial symmetric domains. This is done by constructing a method to reduce the RHBVPs for axially symmetric monogenic functions defined in four-dimensional axial symmetric domains into the RHBVPs for analytic functions defined over the complex plane. Then we derive solutions to the corresponding Schwarz problem. Finally, we generalize the results obtained to null-solutions of (Dâα)Ï=0, αâR, where R denotes the field of real numbers
Superconductivity and Field-Induced Magnetism in PrCeCuO Single Crystals
We report muon-spin rotation/relaxation (muSR) measurements on single
crystals of the electron-doped high-T_c superconductor PrCeCuO.
In zero external magnetic field, superconductivity is found to coexist with Cu
spins that are static on the muSR time scale. In an applied field, we observe a
Knight shift that is primarily due to the magnetic moment induced on the Pr
ions. Below the superconducting transition temperature T_c, an additional
source of static magnetic order appears throughout the sample. This finding is
consistent with antiferromagnetic ordering of the Cu spins in the presence of
vortices. We also find that the temperature dependence of the in-plane magnetic
penetration depth in the vortex state resembles that of the hole-doped cuprates
at temperatures above ~ 0.2 T_c.Comment: 4 pages, 5 figure
A homeostatic function of CXCR2 signalling in articular cartilage
Funding This work was funded by Arthritis Research UK (grants 17859, 17971, 19654), INNOCHEM EU FP6 (grant LSHB-CT-2005-51867), MRC (MR/K013076/1) and the William Harvey Research FoundationPeer reviewedPublisher PD
- âŠ