Rather than incoherent hopping between chromophores, experimental evidence suggests that the excitation energy transfer in some biological light harvesting systems initially occurs coherently, and ...involves coherent superposition states in which excitation spreads over multiple chromophores separated by several nanometers. Treating such delocalized coherent superposition states in the presence of decoherence and dissipation arising from coupling to an environment is a significant challenge for conventional theoretical tools that either use a perturbative approach or make the Markovian approximation. In this paper, we extend the recently developed iterative linearized density matrix (ILDM) propagation scheme E. R. Dunkel et al., J. Chem. Phys. 129, 114106 (2008) to study coherent excitation energy transfer in a model of the Fenna-Matthews-Olsen light harvesting complex from green sulfur bacteria. This approach is nonperturbative and uses a discrete path integral description employing a short time approximation to the density matrix propagator that accounts for interference between forward and backward paths of the quantum excitonic system while linearizing the phase in the difference between the forward and backward paths of the environmental degrees of freedom resulting in a classical-like treatment of these variables. The approach avoids making the Markovian approximation and we demonstrate that it successfully describes the coherent beating of the site populations on different chromophores and gives good agreement with other methods that have been developed recently for going beyond the usual approximations, thus providing a new reliable theoretical tool to study coherent exciton transfer in light harvesting systems. We conclude with a discussion of decoherence in independent bilinearly coupled harmonic chromophore baths. The ILDM propagation approach in principle can be applied to more general descriptions of the environment.
The drying stage of ceramic green body is crucial in the production process, and the equilibrium moisture content achieved by green body drying is very important for the green body firing stage. ...Based on the modified Oswin equilibrium moisture model, the influence of hot air temperature and relative humidity on the equilibrium moisture content of SiO2 and Al2O3 ceramic composite green body drying was studied through hot air drying experiments, and according to the experimental data, the equilibrium moisture content data was fitted by the least squares method to determine the equilibrium moisture content model.
Fluctuations of conserved quantities such as baryon number, charge, and strangeness are sensitive to the correlation length of the hot and dense matter created in relativistic heavy-ion collisions ...and can be used to search for the QCD critical point. We report the first measurements of the moments of net-kaon multiplicity distributions in Au+Au collisions at sNN=7.7, 11.5, 14.5, 19.6, 27, 39, 62.4, and 200 GeV. The collision centrality and energy dependence of the mean (M), variance (σ2), skewness (S), and kurtosis (κ) for net-kaon multiplicity distributions as well as the ratio σ2/M and the products Sσ and κσ2 are presented. Comparisons are made with Poisson and negative binomial baseline calculations as well as with UrQMD, a transport model (UrQMD) that does not include effects from the QCD critical point. Within current uncertainties, the net-kaon cumulant ratios appear to be monotonic as a function of collision energy.
Al 6061/Ti–6Al–4V/Al 6061 laminated composites were fabricated by hot-roll bonding. The effect of rolling temperature and reduction on the microstructure and mechanical properties of Al/Ti/Al ...laminated composites was investigated. The results show that the Al/Ti/Al laminated composites exhibited a good Al/Ti interfacial bonding. The reduction ratio of Ti to Al layer decreased with increasing rolling temperature and reduction. The development of microstructure through the thickness of Al layer was inhomogeneous. The number of high-angle boundaries and the misorientation angle across low-angle boundaries increased as the thickness position moved towards the surface of Al layer from the interface of Al/Ti. The initial grains near the surface of Al layer were markedly elongated at a certain angle to the RD and then fragmented into the equiaxed fine grains at larger rolling reductions. This inhomogeneity of microstructure can be attributed to the effect of the friction between the roll and sheet surface and the uncoordinated deformation between Al and Ti layers. The deformation inhomogeneity increased with increasing rolling reduction. For the laminated composites fabricated with rolling reductions of 27% and 38%, the yield and tensile strength increased to a maximum value at about 400°C and then decreased with increasing rolling temperature. The laminated composites fabricated with a 45% reduction possessed lower strength in the temperature range from 400°C to 450°C than those with a 38% reduction due to the fracture of Ti layer.
The first (v_{1}^{fluc}), second (v_{2}), and third (v_{3}) harmonic coefficients of the azimuthal particle distribution at midrapidity are extracted for charged hadrons and studied as a function of ...transverse momentum (p_{T}) and mean charged particle multiplicity density ⟨N_{ch}⟩ in U+U (sqrts_{NN}=193 GeV), Au+Au, Cu+Au, Cu+Cu, d+Au, and p+Au collisions at sqrts_{NN}=200 GeV with the STAR detector. For the same ⟨N_{ch}⟩, the v_{1}^{fluc} and v_{3} coefficients are observed to be independent of the collision system, while v_{2} exhibits such a scaling only when normalized by the initial-state eccentricity (ϵ_{2}). The data also show that ln(v_{2}/ϵ_{2}) scales linearly with ⟨N_{ch}⟩^{-1/3}. These measurements provide insight into initial-geometry fluctuations and the role of viscous hydrodynamic attenuation on v_{n} from small to large collision systems.
In order to accurately predict the flow stress of Mg-Zn-Zr-Y alloy at high temperature, the hot compression test of Mg-Zn-Zr-Y alloy was carried out on Gleeble-1500 thermal / mechanical simulator. ...The deformation temperature was 523 K, 573 K, 623 K, and the strain rate was 0,01 ~ 1 s-1. By obtaining the true stress-strain curve, the strain compensation factor Z parameter was introduced into the Arrhenius equation to establish a more accurate strain coupling constitutive model. The results show that the theoretical value of the peak stress calculated by the constitutive model is in good agreement with the experimental results, and the average relative error is 5,67 %, which verifies the feasibility of the model.
The high temperature compression experiments of 2209 duplex stainless steel were carried out by using Gleeble3800 thermal simulator, the rate was 0,01~10 s–1, and the deformation temperature was ...950~1 100°C. The strain rate and deformation temperature were analyzed and the effect of strain rate and deformation temperature were analyzed. The high-temperature rheological behavior of 2209 duplex stainless steel was investigated, and the effects of strain rate and deformation temperature on the two-phase relationship of 2209 duplex stainless steel were analyzed, the strain rate compensation factor Z was introduced, and the Arrhenius eigenmodel equation was established. The results show that the theoretical value of peak stress calculated numerically by this constitutive model fits well with the experimental results, and the correlation is 97,3 %, which verifies the feasibility of the model.
In order to accurately describe the high temperature deformation behavior of GGG70L ductile iron, the thermal simulation experiments with deformation rate of 0,01~10 s-1 were carried out at 800~1 100 ...°C by Gleeble-1500D thermal simulation machine. The deformation behavior of GGG70L ductile iron was studied. The temperature compensated strain rate Zener-Hollomon parameter was introduced, and the constitutive model of GGG70L ductile iron was established based on the strain compensated Arrhenius model. The results show that the theoretical value of peak stress calculated by the constitutive model is in good agreement with the experimental results, and the correlation is 97,8 %, which can accurately describe the high temperature deformation behavior of GGG70L ductile iron
The hot compression test of as-cast P91 alloy steel was carried out by Gleeble3500 multi-functional thermal simulation test machine under the deformation conditions of temperature of 900 ~ 1 100 ...°Cand strain rate of 0, 1~5 s-1. The high temperature flow behavior of as-cast P91 alloy steel was studied. The effects of strain rate and deformation temperature on the two-phase relationship of as-cast P91 alloy steel were analyzed. The strain rate compensation factor Z was introduced, and the Arrhenius constitutive model equation was established. The results show that the theoretical value of the peak stress calculated by the constitutive model is in good agreement with the experimental results, and the correlation is 96, 8 %, which verifies the feasibility of the model.
In this letter, measurements of the shared momentum fraction (zg) and the groomed jet radius (Rg), as defined in the SoftDrop algorithm, are reported in p+p collisions at s=200 GeV collected by the ...STAR experiment. These substructure observables are differentially measured for jets of varying resolution parameters from R=0.2−0.6 in the transverse momentum range 15<pT,jet<60 GeV/c. These studies show that, in the pT,jet range accessible at s=200 GeV and with increasing jet resolution parameter and jet transverse momentum, the zg distribution asymptotically converges to the DGLAP splitting kernel for a quark radiating a gluon. The groomed jet radius measurements reflect a momentum-dependent narrowing of the jet structure for jets of a given resolution parameter, i.e., the larger the pT,jet, the narrower the first splitting. For the first time, these fully corrected measurements are compared to Monte Carlo generators with leading order QCD matrix elements and leading log in the parton shower, and to state-of-the-art theoretical calculations at next-to-leading-log accuracy. We observe that PYTHIA 6 with parameters tuned to reproduce RHIC measurements is able to quantitatively describe data, whereas PYTHIA 8 and HERWIG 7, tuned to reproduce LHC data, are unable to provide a simultaneous description of both zg and Rg, resulting in opportunities for fine parameter tuning of these models for p+p collisions at RHIC energies. We also find that the theoretical calculations without non-perturbative corrections are able to qualitatively describe the trend in data for jets of large resolution parameters at high pT,jet, but fail at small jet resolution parameters and low jet transverse momenta.
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