The investigation of fibre reinforcement effects in thermoplastic materials: interfacial bond strength and fibre end parameter

Glass fibres used in the manufacture of fibre reinforced thermoplastic composites (FRTP) are normally sized with a film former which includes a silane coupling agent to improve the interfacial bond strength between glass fibre and matrix . However, during composite failure even an optimized interface cannot stop the initia tion of cracks at the fibre ends, which can lead to large transverse cracks in the matrix or failure by fibre pull-out. In order to help better understand the failure mechanisms of FRTP, thermoplastic microbond tests and photoelasticity experiments have been used to study the interface in model single fibre composites

Viscoelastic Properties of Foam Under Hydrostatic Pressure and Uniaxial Compression

AbstractFoam is a lightweight material suitable for aerospace applications for load bearing structures or noise reduction media. The microstructure of the foam, which is constructed with cell ribs, allows its unique mechanical properties. In this work, commercial polyurethane foams with a pore size on the order of a few hundred microns were subjected to quasi-static hydrostatic and uniaxial compression at low strain rates, as well as dynamic sinusoidal loading for studying their loss tangent and storage modulus. The identified incremental negative modulus depends on deformation modes, and it is been shown hydrostatic compression may trigger the negative bulk modulus mode, while uniaxial compression may not. The use of negative modulus in composite materials may lead to extreme high damping and high stiffness materials. Furthermore, by finite element calculations on a dodecahedral unit cell with different elastic constant, it is found that high elastic constant of the cell ribs may give rise to larger negative stiffness effects, when the cell in under hydrostatic compression

Repulsion and attraction in high Tc superconductors

The influence of repulsion and attraction in high-Tc superconductors to the gap functions is studied. A systematic method is proposed to compute the gap functions using the irreducible representations of the point group. It is found that a pure s-wave superconductivity exists only at very low temperatures, and attractive potentials on the near shells significantly expand the gap functions and increase significantly the critical temperature of superconductivity. A strong on-site repulsion drives the $A_{1g}$ gap into a $B_{1g}$ gap. It is expected that superconductivity with the $A_{1g}$ symmetry reaches a high critical temperature due to the cooperation of the on-site and the next-nearest neighbor attractions.Comment: 4 pages, 5figure

Field Driven Pairing State Phase Transition in d_x^2-y^2+id_xy-Wave Superconductors

Within the framework of the Ginzburg-Landau theory for $d_{x^2-y^2}+id_{xy}$-wave superconductors, we discuss the pairing state phase transition in the absence of the Zeeman coupling between the Cooper pair orbital angular momentum and the magnetic field. We find that above a temperature $T_{\ast}$, the pairing state in a magnetic field is pure $d_{x^{2}-y^{2}}$-wave. However, below $T_{\ast}$, the pairing state is $d_{x^{2}-y^{2}}+id_{xy}$-wave at low fields, and it becomes pure $d_{x^{2}-y^{2}}$-wave at higher fields. Between these pairing states there exists a field driven phase transition . The transition field increases with decreasing temperature. In the field-temperature phase diagram, the phase transition line is obtained theoretically by a combined use of a variational method and the Virial theorem. The analytical result is found to be in good agreement with numerical simulation results of the Gingzburg-Landau equations. The validity of the variational method is discussed. The difference to the case with the Zeeman coupling is discussed, which may be utilized to the detection of the Zeeman coupling.Comment: 5 pages, 2 figures, submitted to PRB Brief Repor

Seed dimorphism nutrients and salinity differentially affect seed traits of the desert halophyte Suaeda aralocaspica via multiple maternal effects.

Background: Maternal effects may influence a range of seed traits simultaneously and are likely to be context-dependent. Disentangling the interactions of plant phenotype and growth environment on various seed traits is important for understanding regeneration and establishment of species in natural environments. Here, we used the seed-dimorphic plant Suaeda aralocaspica to test the hypothesis that seed traits are regulated by multiple maternal effects.Results: Plants grown from brown seeds had a higher brown:black seed ratio than plants from black seeds, and germination percentage of brown seeds was higher than that of black seeds under all conditions tested. However, the coefficient of variation (CV) for size of black seeds was higher than that of brown seeds. Seeds had the smallest CV at low nutrient and high salinity for plants from brown seeds and at low nutrient and low salinity for plants from black seeds. Low levels of nutrients increased size and germinability of black seeds but did not change the seed morph ratio or size and germinability of brown seeds. High levels of salinity decreased seed size but did not change the seed morph ratio. Seeds from high-salinity maternal plants had a higher germination percentage regardless of level of germination salinity.Conclusions: Our study supports the multiple maternal effects hypothesis. Seed dimorphism, nutrient and salinity interacted in determining a range of seed traits of S. aralocaspica via bet-hedging and anticipatory maternal effects. This study highlights the importance of examining different maternal factors and various offspring traits in studies that estimate maternal effects on regeneration. © 2012 Wang et al.; licensee BioMed Central Ltd

SMA Observations on faint submillimeter galaxies with S 850 < 2 mJy: ultra dusty low-luminosity galaxies at high redshift

We obtained Submillimeter Array (SMA) observations of eight faint (intrinsic 850 μm fluxes < 2 mJy) submillimeter galaxies (SMGs) discovered in SCUBA images of the massive lensing cluster fields A370, A2390, and A1689 and detected five. In total, we obtain five SMA detections, all of which have de-lensed fluxes <1 mJy with estimated total infrared luminosities 1010-1012 L ☉, comparable to luminous infrared galaxies and normal star-forming galaxies. Based on the latest number counts, these galaxies contribute ~70% of the 850 μm extragalactic background light and represent the dominant star-forming galaxy population in the dusty universe. However, only 40$^{+30}_{-16}$% of our faint SMGs would be detected in deep optical or near-infrared surveys, which suggests many of these sources are at high redshifts (z gsim 3) or extremely dusty, and they are not included in current star formation history estimates

A Co-axial Multi-tube Heat Exchanger Applicable for a Geothermal ORC Power Plant

AbstractThe study proposes a Co-axial multi-tube heat exchanger (CMTHE) applicable to geothermal heat extraction. The heat exchanger is integrated with a 50kW geothermal ORC power plant having a working fluid of R-245fa. Two field tests were performed to examine the system response of the ORC system subject to change of CMTHE. In case 1 where the flow rate in the shell-side of CMTHE is maintained, the pressure variation in the shell-side of CMTHE casts minor variations on heat extraction, ORC power generation, and ORC efficiency during the transient. Moreover, the effect of pressure has barely any influence of the final states of heat extraction, ORC power generation, and ORC efficiency. In case 2 where the pressure is preserved in the CMTHE, it is found that a decrease of flow rate in the CMTHE results in degradation of heat extraction, ORC power generation and ORC system efficiency. On the contrary, increasing the flow rate in the CMTHE leads to a rise of heat extraction, ORC power generation and ORC system efficiency. Unlike that in case 1, the effect of flow rate has a detectable effect on the final states of heat extraction, ORC power generation, and ORC efficiency

Cooler Magnetic Spectrometer

This research was sponsored by the National Science Foundation Grant NSF PHY-931478