1,542 research outputs found
High-energy, curable polycyclopentadiene binder for solid rocket propellants
Diels Alder polymerization of cyclopentadiene ( CPD ) has been carried out at 170Ā°C under inert atmosphere. The resulted polymer has a low bulk viscosity, 7.4 cps, and a number average molecular weight Mn up to 3000. This liquid Prepolymer is curable with maleic anhydride. With ammonium perchlorate, aluminum, and maleic anhydride, a high energy solid propellant has been formulated with this polymer. Via bomb calorimeter, Instron, and density measurement, it was found that this propellant has a better heat of combustion, tensile strength, and solid loading than that of the commercial rocket propellant based on hydroxyl terminated polybutadiene
A constitutive model for particulate-reinforced titanium matrix composites subjected to high strain rates and high temperatures
Quasi-static and dynamic tension tests were conducted to study the mechanical
properties of particulate-reinforced titanium matrix composites at strain
rates ranging from 0.0001/s to 1000/s and at temperatures ranging from 20 Ā°C
to 650 Ā°C Based on the experimental results, a constitutive model, which
considers the effects of strain rate and temperature on hot deformation
behavior, was proposed for particulate-reinforced titanium matrix composites
subjected to high strain rates and high temperatures by using Zener-Hollomon
equations including Arrhenius terms. All the material constants used in the
model were identified by fitting Zener-Hollomon equations against the
experimental results. By comparison of theoretical predictions presented by
the model with experimental results, a good agreement was achieved, which
indicates that this constitutive model can give an accurate and precise
estimate for high temperature flow stress for the studied titanium matrix
composites and can be used for numerical simulations of hot deformation
behavior of the composites
Biomimetic Polymer Film with Brilliant Brightness Using a OneāStep Water VaporāInduced Phase Separation Method
The scales of the white Cyphochilus beetles are endowed with unusual whiteness arising from the exceptional scattering efficiency of their disordered ultrastructure optimized through millions of years of evolution. Here, a simple, oneāstep method based on water vaporāinduced phase separation is developed to prepare thin polystyrene films with similar microstructure and comparable optical performance. A typical biomimetic 3.5 Āµm PS film exhibits a diffuse reflectance of 61% at 500 nm wavelength, which translates into a transport mean free path below 1 Āµm. A complete optical characterization through Monte Carlo simulations reveals how such a scattering performance arises from the scattering coefficient and scattering anisotropy, whose interplay provides insight into the morphological properties of the material. The potential of brightāwhite coatings as smart sensors or wearable devices is highlighted using a treated 3.5 Āµm film as a realātime sensor for human exhalation
The extended BLMSSM with a 125 GeV Higgs boson and dark matter
To extend the BLMSSM, we not only add exotic Higgs superfields
to make the exotic lepton heavy, but also introduce
the superfields(,) having couplings with lepton and exotic lepton
at tree level. The obtained model is called as EBLMSSM, which has difference
from BLMSSM especially for the exotic slepton(lepton) and exotic
sneutrino(neutrino). We deduce the mass matrices and the needed couplings in
this model. To confine the parameter space, the Higgs boson mass and
the processes , are
studied in the EBLMSSM. With the assumed parameter space, we obtain reasonable
numerical results according to data on Higgs from ATLAS and CMS. As a cold dark
mater candidate, the relic density for the lightest mass eigenstate of and
mixing is also studied
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