3D microwave printing temperature control of continuous carbon fiber reinforced composites

Continuous carbon fibers show dramatic promise as reinforcement materials to improve the stiffness, strength properties and design ability of 3D printed polymer parts. Current 3D printing methods have a low printing speed because the intrinsic slow and contact needed heat transfer disadvantages of the traditional resistive heating approach. We present a 3D microwave printing method by using the microwave for instantaneous and volumetric heating the continuous carbon fiber reinforced polymer (CCFRP) filament. This allows fabricating CCFRP components with much higher speed compared to traditional 3D printing technologies. To utilize the benefit of high printing speed, the speed-variation 3D microwave printing is applied to adapt the diverse printing path and reduce the printing period. In this paper, a new 3D microwave printing temperature control method by combining the prediction-model and step-proportional-integral-derivative control is researched to reduce the printing temperature difference of the CCFRP filaments during the speed-variation printing process. Three different CCFRP specimens with variation printing speed are tested, including a spanner, an aircraft and a spider from Nazca lines. The experimental results indicate that the new printing temperature control method for 3D microwave printing process dramatically reduces the temperature deviation. Further mechanical testing results indicate that the CCFRP printed with this method has a high tensile strength up to 358 MPa. This technology solved a key problem of 3D microwave printing of continuous carbon fiber reinforced polymer composites and can be used to manufacture complex polymer-matrix composite material

Sensitivity of an image plate system in the XUV (60 eV < E < 900 eV)

Phosphor imaging plates (IPs) have been calibrated and proven useful for quantitative x-ray imaging in the 1 to over 1000 keV energy range. In this paper we report on calibration measurements made at XUV energies in the 60 to 900 eV energy range using beamline 6.3.2 at the Advanced Light Source at Lawrence Berkeley National Laboratory. We measured a sensitivity of ~25 plus or minus 15 counts/pJ over the stated energy range which is compatible with the sensitivity of Si photodiodes that are used for time-resolved measurements. Our measurements at 900 eV are consistent with the measurements made by Meadowcroft et al. at ~1 keV.Comment: 7 pages, 2 figure

Hotspot Prevention Through Runtime Reconfiguration in Network-On-Chip

Abstrac

Pulsar Constraints on Neutron Star Structure and Equation of State

With the aim of constraining the structural properties of neutron stars and the equation of state of dense matter, we study sudden spin-ups, glitches, occurring in the Vela pulsar and in six other pulsars. We present evidence that glitches represent a self-regulating instability for which the star prepares over a waiting time. The angular momentum requirements of glitches in Vela indicate that at least 1.4% of the star's moment of inertia drives these events. If glitches originate in the liquid of the inner crust, Vela's `radiation radius' must exceed ~12 km for a mass of 1.4 solar masses. Observational tests of whether other neutron stars obey this constraint will be possible in the near future.Comment: 5 pages, including figures. To appear in Physical Review Letter

High-pressure transport properties of CeRu_2Ge_2

The pressure-induced changes in the temperature-dependent thermopower S(T) and electrical resistivity \rho(T) of CeRu_2Ge_2 are described within the single-site Anderson model. The Ce-ions are treated as impurities and the coherent scattering on different Ce-sites is neglected. Changing the hybridisation \Gamma between the 4f-states and the conduction band accounts for the pressure effect. The transport coefficients are calculated in the non-crossing approximation above the phase boundary line. The theoretical S(T) and \rho(T) curves show many features of the experimental data. The seemingly complicated temperature dependence of S(T) and \rho(T), and their evolution as a function of pressure, is related to the crossovers between various fixed points of the model.Comment: 9 pages, 10 figure

Ring-Pattern Dynamics in Smectic-C* and Smectic-C_A* Freely Suspended Liquid Crystal Films

Ring patterns of concentric 2pi-solitons in molecular orientation, form in freely suspended chiral smectic-C films in response to an in-plane rotating electric field. We present measurements of the zero-field relaxation of ring patterns and of the driven dynamics of ring formation under conditions of synchronous winding, and a simple model which enables their quantitative description in low polarization DOBAMBC. In smectic C_A* TFMHPOBC we observe an odd-even layer number effect, with odd number layer films exhibiting order of magnitude slower relaxation rates than even layer films. We show that this rate difference is due to much larger spontaneous polarization in odd number layer films.Comment: 4 RevTeX pgs, 4 eps figures, submitted to Phys. Rev. Let

Positive parity pentaquark towers in large Nc QCD

We construct the complete set of positive parity pentaquarks, which correspond in the quark model to {\bar s} q^{Nc+1} states with one unit of orbital angular momentum L=1. In the large Nc limit they fall into the K=1/2 and K=3/2 irreps (towers) of the contracted SU(4)c symmetry. We derive predictions for the mass spectrum and the axial couplings of these states at leading order in 1/Nc. The strong decay width of the lowest-lying positive parity exotic state is of order O(1/Nc), such that this state is narrow in the large Nc limit. Replacing the antiquark with a heavy antiquark {\bar Q} q^{Nc+1}, the two towers become degenerate, split only by O(1/mQ) hyperfine interactions. We obtain predictions for the strong decay widths of heavy pentaquarks to ordinary baryons and heavy H(*)_{\bar Q} mesons at leading order in 1/Nc and 1/mQ.Comment: 21 pages, 2 figures, 5 table

Observations of Six Glitches in PSR B1737-30

Six glitches have been recently observed in the rotational frequency of the young pulsar PSR B1737-30 (J1740-3015) using the 25-m Nanshan telescope of Urumqi Observatory. With a total of 20 glitches in 20 years, it is one of the most frequently glitching pulsars of the about 1750 known pulsars. Glitch amplitudes are very variable with fractional increases in rotation rate ranging from 10^{-9} to 10^{-6}. Inter-glitch intervals are also very variable, but no relationship is observed between interval and the size of the preceding glitch. There is a persistent increase in |\dot\nu|, opposite in sign to that expected from slowdown with a positive braking index, which may result from changes in the effective magnetic dipole moment of the star during the glitch.Comment: 7 pages, 10 figure

Slowly Rotating General Relativistic Superfluid Neutron Stars with Relativistic Entrainment

Neutron stars that are cold enough should have two or more superfluids/supercondutors in their inner crusts and cores. The implication of superfluidity/superconductivity for equilibrium and dynamical neutron star states is that each individual particle species that forms a condensate must have its own, independent number density current and equation of motion that determines that current. An important consequence of the quasiparticle nature of each condensate is the so-called entrainment effect, i.e. the momentum of a condensate is a linear combination of its own current and those of the other condensates. We present here the first fully relativistic modelling of slowly rotating superfluid neutron stars with entrainment that is accurate to the second-order in the rotation rates. The stars consist of superfluid neutrons, superconducting protons, and a highly degenerate, relativistic gas of electrons. We use a relativistic $\sigma$ - $\omega$ mean field model for the equation of state of the matter and the entrainment. We determine the effect of a relative rotation between the neutrons and protons on a star's total mass, shape, and Kepler, mass-shedding limit.Comment: 30 pages, 10 figures, uses ReVTeX