Fast predictions of liquid-phase acid-catalyzed reaction rates using molecular dynamics simulations and convolutional neural networks

The rates of liquid-phase, acid-catalyzed reactions relevant to the upgrading of biomass into high-value chemicals are highly sensitive to solvent composition and identifying suitable solvent mixtures is theoretically and experimentally challenging. We show that the complex atomistic configurations of reactant–solvent environments generated by classical molecular dynamics simulations can be exploited by 3D convolutional neural networks to enable accurate predictions of Brønsted acid-catalyzed reaction rates for model biomass compounds. We develop a 3D convolutional neural network, which we call SolventNet, and train it to predict acid-catalyzed reaction rates using experimental reaction data and corresponding molecular dynamics simulation data for seven biomass-derived oxygenates in water–cosolvent mixtures. We show that SolventNet can predict reaction rates for additional reactants and solvent systems an order of magnitude faster than prior simulation methods. This combination of machine learning with molecular dynamics enables the rapid, high-throughput screening of solvent systems and identification of improved biomass conversion conditions.

Solvent-mediated, acid-catalyzed reaction rates relevant to the upgrading of biomass into high-value chemicals are accurately predicted using a combination of molecular dynamics simulations and 3D convolutional neural networks.     

Polymerization of Methyl Methacrylate and Isobutyl Methacrylate in Ternary-Component Emulsions and Microemulsions: Effect of Surfactant Concentration

Abstract

The similarities and differences in the polymerization of MMA (methyl methacrylate) and iBMA (isobutyl methacrylate) in a ternarycomponent system have been investigated from a turbid emulsion to a transparent microemulsion by increasing the surfactant concentration. In spite of the difference in the solubilities of these two monomers in the aqueous phase, the rate dependencies on the surfactant concentration of both monomers were found to be about 0.30 for the emulsion polymerization and about 0.60 for the microemulsion polymerization with monomer concentrations higher than 5 wt%. However, at a low monomer concentration (3 wt%), different negative rate dependencies of ?0.93 and ?1.20 were obtained for microemulsion polymerization of MMA and iBMA, respectively. The results are discussed in terms of particle nucleation mechanisms.     

Resource allocation for end-to-end QoS provisioning in a hybrid wireless WCDMA and wireline IP-based DiffServ network

In the future UMTS network, the heterogeneous traffics of multimedia services demand various QoS provisioning. At the same time, the seamlessly conveying of information between mobile users and a hybrid network requires the networking from wireless to wireline domains. However, in both academia and industries, the end-to-end QoS provisioning in the integration of wireline and wireless networks remains a challenge. In this paper, a modeling of a hybrid wireless WCDMA and wireline IP-based DiffServ network is presented to investigate the resource allocation for end-to-end QoS provisioning for multimedia services. In the wireless domain, the mathematical modeling of the cross-layer model including the physical layer, the link layer and the network layer is built. The connection admission control scheme is implemented based on the cross-layer model to determine the amount of resource for different services. In the wireline domain, we define the mapping of QoS classes between UMTS and DiffServ networks according to different QoS requirements. We propose a bandwidth allocation scheme to provide satisfactory packet loss and delay guarantee in DiffServ networks. The final end-to-end admission control scheme combines the resource allocation and admission control in both wireless and wireline domains. The analytical and simulation results show that the proposed resource allocation and admission control schemes work cooperatively in the presented hybrid wireless and wireline networks to guarantee the end-to-end QoS requirements for multimedia services.     

Intense short-pulse lasers irradiating wire and hollow plasma fibers

When an intense laser pulse irradiates a solid-density foil target, electrons produced at the relativistic critical density can be accelerated to relativistic energy by the ponderomotive force. When a plasma fiber is attached to the back of the foil, the produced relativistic electrons are guided to propagate along the fiber for a long distance, because the high-current electron beam induces strong radial electric fields in the fiber. Transport and heating of intense laser-driven relativistic electrons in both wire and hollow plasma fibers are compared theoretically and numerically. We found that the coupling efficiency from the laser to the plasma fiber depends on the fiber structure. Because of the enhanced return currents in the wire fiber, the temperature in the wire fiber is higher than that in the hollow fiber.     

Double-pomeron prediction for colliding beam experiments

It is shown that recent ISR measurements of double-pomeron cross sections contain a special kinematic constraint that forces the cross section to decrease with increasing energy, in contrast to the natural constraint which corresponds to an increasing cross section. The observed energy dependence is shown to be in agreement with theoretical expectation.     

Asymptotic-planarity prediction of a pomeron-like unnatural parity trajectory

The asymptotic-planarity argument that explains the pomeron as a cylinder-shifted f, when applied to unnatural parity, predicts near t = 0 a high-lying small-slope H trajectory, with the corresponding I = 0, 1⁺, C = ? meson mass near 1 GeV. H couplings near t = 0 will be close to pure SU₃ singlet.