For open systems derived from quadratic total Hamiltonians, we derive a dynamic fluctuationadissipation (FD) inequality valid for any total initial state and without regard to the sign of the ...dissipation. With the added constraint that this state be factorized with the reservoir in thermal equilibrium, an uncertainty relation arises naturally from the FD inequality that can be stronger than the usual uncertainty principle in the form aq2aap2aaCO34a2/4aq2aap2aaCO34a2/4. We discuss some of the properties of the uncertainty relation relevant to decoherence.
SUMMARY Copositive linear Lyapunov functions are used along with dissipativity theory for stability analysis and control of uncertain linear positive systems. Unlike usual results on linear systems, ...linear supply rates are employed here for robustness and performance analysis using L sub(1)-gain and L sub(infin)-gain. Robust stability analysis is performed using integral linear constraints for which several classes of uncertainties are discussed. The approach is then extended to robust stabilization and performance optimization. The obtained results are expressed in terms of robust linear programming problems that are equivalently turned into finite dimensional ones using Handelman's theorem. Several examples are provided for illustration. Copyright copy 2012 John Wiley & Sons, Ltd.
For any α < 1/3, we construct weak solutions to the 3D incompressible Euler equations in the class
CtCx
α
that have nonempty, compact support in time on R × T3 and therefore fail to conserve the ...total kinetic
energy. This result, together with the proof of energy conservation for α < 1/3 due to Eyink and Constantin, E, Titi, solves Onsager's conjecture that the
exponent α = 1/3 marks the threshold for conservation of energy for weak solutions in the class
Lt
∞Cx
α. The previous best results were solutions in the class
CtCx
α
for α < 1/5, due to Isett, and in the class
Lt
1
Cx
α
for α < 1/3 due to Buckmaster, De Lellis, Székelyhidi, both based
on the method of convex integration developed for the incompressible Euler equations by De Lellis, Székelyhidi. The present proof combines the method of convex integration and a
new “Gluing Approximation” technique. The convex integration part of the proof relies on the “Mikado flows” introduced by Daneri, Székelyhidi and the framework of estimates
developed in the author's previous work.
We prepared poly(vinylidene fluoride) (PVDF)/carbon/Ni-chain composites by dispersing Ni chains, and either carbon nanotubes (CNTs) or graphene nanoplatelets (GNPs) into a PVDF solution. The ...electrical conductivity and the electromagnetic interference (EMI) shielding properties of the PVDF/CNT/Ni-chain and the PVDF/GNP/Ni-chain composites were increased by increasing the Ni-chain filler content. The electrical conductivity of the PVDF/CNT/10 wt%Ni-chain composite was lower than the PVDF/CNT/6 wt%Ni-chain composite. We attributed this abnormality to the Ni chains having blocked the CNT connections, when there was a high Ni-chain content. Furthermore, the PVDF-based composites' EMI shielding properties were effectively tuned by controlling the films' thicknesses. The total shielding of the PVDF/CNT/6 wt%Ni-chain and the PVDF/GNP/8 wt%Ni-chain composite films increased from 23.6 to 57.3 dB and from 22.7 to 55.8 dB, as their thicknesses were increased from 0.3 mm to 0.6 mm, respectively. The synergetic relationship between the Ni chains and the carbon materials (CNT or GNP), meant that the main EMI shielding mechanisms of the PVDF/carbon/Ni-chain composites had resulted from the absorption process. Moreover, these composites possessed high thermal conductivity, which can convert microwave energy into Joule heating systems. Thus, these PVDF-based composite films can be used to make high-efficiency EMI shielding devices that can rapidly dissipate heat.
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•New nonlinear wind input source term.•Negative wind input for adverse winds.•New wave breaking and whitecapping dissipation source term.•New swell attenuation source term.
Measurements collected ...during the AUSWEX field campaign, at Lake George (Australia), resulted in new insights into the processes of wind wave interaction and whitecapping dissipation, and consequently new parameterizations of the input and dissipation source terms. The new nonlinear wind input term developed accounts for dependence of the growth on wave steepness, airflow separation, and for negative growth rate under adverse winds. The new dissipation terms feature the inherent breaking term, a cumulative dissipation term and a term due to production of turbulence by waves, which is particularly relevant for decaying seas and for swell. The latter is consistent with the observed decay rate of ocean swell. This paper describes these source terms implemented in WAVEWATCH III ®and evaluates the performance against existing source terms in academic duration-limited tests, against buoy measurements for windsea-dominated conditions, under conditions of extreme wind forcing (Hurricane Katrina), and against altimeter data in global hindcasts. Results show agreement by means of growth curves as well as integral and spectral parameters in the simulations and hindcast.
Aluminum/graphene (Al/G) composites with enhanced heat-dissipation and mechanical properties were prepared by the powder metallurgy (P/M) technique. Graphene was first uniformly coated on the surface ...of micro-sized aluminum (Al) powders by an in-situ reduction reaction of GO and Al. Al/G bulk composites with uniform graphene dispersion in Al matrix were fabricated by the simple conventional P/M technique. Enhancements of 15.4% in thermal conductivity, 9.1% in specific heat capacity, 21.1% in hardness, and 25.6% in compressive strength were achieved with only 0.3 wt% graphene addition into pure Al.
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•Dispersion of graphene in aluminum matrix by in-situ reduction of graphene oxide on aluminum particles.•Alcohol washing was adopted to avoid the hydrolysis reaction of aluminum and guarantee the purity of the composites.•Enhancement of heat-dissipation and mechanical properties by adding graphene into aluminum matix.
The use of existing large pumping station equipment for upstream residual water reverse power generation is an unrealized yet valuable renewable energy project. At present, some large axial flow pump ...stations have begun to perform reverse power generation operations; however, related research has not yet started. In this paper, entropy generation theory is applied to a large-scale axial flow pump station system in reverse power generation operations, and the entropy generation method is used to investigate the accurate size and distribution of the mechanical energy dissipation of each component under different flow conditions. First, the energy characteristics and pressure fluctuations in the pump of the large axial flow pump station system are experimentally tested under reverse power generation conditions. The reliability of the entropy generation numerical calculation is verified both experimentally and theoretically. Then, the proportion of each component in the total entropy production is compared to illustrate how each component contributes to the total entropy production of the system and how this contribution changes as operating conditions vary. Then, the type of entropy production of each component is accurately determined under different flow conditions, revealing the changes in the proportions of the different types of entropy production of each component. Finally, components with large mechanical energy dissipations are selected, and the changes and causes of the energy dissipation distribution of the components are thoroughly analysed under different flow conditions. The research results can aid in better understanding the energy dissipation mechanism of large axial flow pump systems in reverse power generation operations.
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