Coherent quantum transport in disordered systems: II. Temperature dependence of carrier diffusion coefficients from the time-dependent wavepacket diffusion method

The time-dependent wavepacket diffusion method for carrier quantum dynamics (Zhong and Zhao 2013 J. Chem. Phys. 138 014111), a truncated version of the stochastic Schrödinger equation/wavefunction approach that approximately satisfies the detailed balance principle and scales well with the size of the system, is applied to investigate the carrier transport in one-dimensional systems including both the static and dynamic disorders on site energies. The predicted diffusion coefficients with respect to temperature successfully bridge from band-like to hopping-type transport. As demonstrated in paper I (Moix et al 2013 New J. Phys. 15 085010), the static disorder tends to localize the carrier, whereas the dynamic disorder induces carrier dynamics. For the weak dynamic disorder, the diffusion coefficients are temperature-independent (band-like property) at low temperatures, which is consistent with the prediction from the Redfield equation, and a linear dependence of the coefficient on temperature (hopping-type property) only appears at high temperatures. In the intermediate regime of dynamic disorder, the transition from band-like to hopping-type transport can be easily observed at relatively low temperatures as the static disorder increases. When the dynamic disorder becomes strong, the carrier motion can follow the hopping-type mechanism even without static disorder. Furthermore, it is found that the memory time of dynamic disorder is an important factor in controlling the transition from the band-like to hopping-type motions.National Natural Science Foundation (China) (Grant no. 91333101)National Natural Science Foundation (China) (Grant no. 21073146)National Natural Science Foundation (China) (Grant no. 21133007)National Natural Science Foundation (China) (973 Program)National Science Foundation (U.S.) (Grant no. CHE-1112825)United States. Defense Advanced Research Projects Agency (DARPA grant N99001-10-1-4063)United States. Dept. of Energy (Office of Science, Office of Basic Energy Sciences, Center of Excitonics, an Energy Frontier Research Center, award no. DE-SC0001088

Nonequilibrium quantum dynamics of partial symmetry breaking for ultracold bosons in an optical lattice ring trap

A vortex in a Bose-Einstein condensate on a ring undergoes quantum dynamics in response to a quantum quench in terms of partial symmetry breaking from a uniform lattice to a biperiodic one. Neither the current, a macroscopic measure, nor fidelity, a microscopic measure, exhibit critical behavior. Instead, the symmetry memory succeeds in identifying the point at which the system begins to forget its initial symmetry state. We further identify a symmetry energy difference in the low lying excited states which trends with the symmetry memory

Macroscopic Quantum Tunneling Escape of Bose-Einstein Condensates

Recent experiments on macroscopic quantum tunneling reveal a non-exponential decay of the number of atoms trapped in a quasibound state behind a potential barrier. Through both experiment and theory, we demonstrate this non-exponential decay results from interactions between atoms. Quantum tunneling of tens of thousands of 87 Rb atoms in a Bose-Einstein condensate is modeled by a modified Jeffreys-Wentzel-Kramers-Brillouin model, taking into account the effective time-dependent barrier induced by the mean-field. Three-dimensional Gross-Pitaevskii simulations corroborate a mean-field result when compared with experiments. However, with one-dimensional modeling using time-evolving block decimation, we present an effective renormalized mean-field theory that suggests many-body dynamics for which a bare mean-field theory may not apply

An optimal gear-shifting strategy for heavy trucks with trade-off study between trip time and fuel economy

© Inderscience Enterprises Ltd. The original source of publication is available at InderScience. Zhao, X. x., Ing, A. h., Azad, N. l., & McPhee, J. (2015). An optimal gear-shifting strategy for heavy trucks with trade-off study between trip time and fuel economy. International Journal of Heavy Vehicle Systems, 22(4), 356–374. https://doi.org/10.1504/IJHVS.2015.073205We show how the fuel efficiency of heavy mining trucks can be improved by optimising the gear-shifting strategy. Using characteristic tests of the diesel engine, a high-fidelity model of a mining truck was built in MapleSim and a consistent low-order model was developed in Matlab. Dynamic programming was used to optimise the low-order model of the specialised off-road 30-tonne truck over a fixed route in a mining area. There were two competing objectives: fuel use and trip time, which were combined in a single objective function using weighting coefficients. A Pareto curve was created to analyse the effect of the weights on the fuel use and trip time. Applying the control strategy obtained from dynamic programming to the high-fidelity model, it is estimated that 40,000 L of fuel can be saved annually for a mine that produces 110 kilotonnes of coal per day

Potential biomarkers of Parkinson’s disease revealed by plasma metabolic profiling

The plasma of Parkinson's disease (PD) patients may contain various altered metabolites associated with the risk or progression of the disease. Characterization of the abnormal metabolic pattern in PD plasma is therefore critical for the search for potential PD biomarkers. We collected blood plasma samples from PD patients and used an LC-MS based metabolomics approach to identify 17 metabolites with significantly altered levels. Metabolic network analysis was performed to place the metabolites linked to different pathways. The metabolic pathways involved were associated with tyrosine biosynthesis, glycerol phospholipid metabolism, carnitine metabolism and bile acid biosynthesis, within which carnitine and bile acid metabolites as potential biomarkers are first time reported. These abnormal metabolic changes in the plasma of patients with PD were mainly related to lipid metabolism and mitochondrial function

Interface and Energy Efficiency of Organic Photovoltaics

As a promising new technology, organic photovoltaics (OPVs) have been widely studied recently. To improve the device efficiency for commercial use of 10%, a number of attempts have been made in my research. The ultra-low frequency AC field was first employed, to align p/n polymers during fabrication. The resulting devices showed 15% increase in device efficiency, attributed to the optimized morphology and enlarged p/n interface. During the improvement process, dual nanostructures of the polymers were found, the highly oriented layer and the randomly distributed part, which provided a better understanding of the OPVs under the AC field alignment. The OPV stability was then studied by impedance measurements, to track multi-interface degradation without breaking the device. It was found the degradation of p/n junction was attributed to the deteriorated morphology and oxidized polymers, whereas the semiconductor/metal interface changed by producing metal oxides as degradation products. The dramatic contrast between the bilayer and bulk heterojunctions (BHJ) was at last investigated by capacitance measurements in vacuum. The existing models of the BHJs had difficulty explaining the higher overall capacitance, compared with that from the bilayer devices. The resulting puzzling charge density was clarified by separating the measured capacitance into two parallel components, one from the space charge of the proposed Schottky junction, and the other from the dark dipoles presumably formed spontaneously across the donor/acceptor interface.Doctor of Philosophy (PhD

Extra Current Uncovered in Alkaline Biofuel Cells

p.p1 {margin: 0.0px 0.0px 0.0px 0.0px; font: 11.0px Times} Due to the environmental burden of fossil fuel combustion, a major strategic shift towards renewable green sources and environmentally benign power generation technology makes biofuel cells a possible alternative, though their extremely low current density remains a bottleneck for the further practical applications. Recent progress shows some promise to increase the current by platinum (Pt) electrodes, and alkaline solution to replace the enzymes/microbes. However, the approach involves high cost of noble metals as well as their poisoning effect. We report here a glucose biofuel cell based on nickel (Ni) electrodes and alkaline medium without the catalyst poisoning found in Pt systems. Surprisingly, a six-fold current increase over time, and a final current density equivalent to 1.5 times that of Pt have been achieved. They are found to be caused by the transformation of glucose to an enediol form, the expansion of triple phase boundaries where cathode reactions take place, and the enhancement of reaction kinetics by alkaline solution. The results not only provide a dramatic increase in current and overall biofuel cell performance, but also demonstrate a low cost approach to renewable source utilization, if corresponding designs can be implemented.Master of Applied Science (MASc

Le regole del gioco: Primo incontro con l'ingegneria strategica

Cu particles decorated carbon composite microspheres (CCMs) with a unique sesame ball structure have been prepared by combining the mass-producible spray drying technique with calcinations. The conventional cuprammonium cellulose complex solution obtained by dissolving cellulose in a cuprammonia solution has been applied as raw materials for the preparation of Cu­(NH₃)₄²⁺/cellulose complex microspheres via a spray drying process. The resulted Cu­(NH₃)₄²⁺/cellulose complex microspheres are then transformed into the Cu particles homogeneously decorated porous carbon spheres <i>in situ</i> by calcinations at 450 or 550 °C. The coordination effect between the Cu­(NH₃)₄²⁺ species and the hydroxyl groups of the cellulose macromolecules has been exploited for directing the dispersion of the Cu particles in the resultant composite CCMs. The antimicrobial effects of the CCMs are evaluated by determining the minimum growth inhibitory concentrations using Staphylococcus aureus and Escherichia coli as representatives, respectively. The CCMs show high efficiency catalytic properties to the conversion of 4-nitrophenol to 4-aminophenol using NaBH₄ as a reductant in a mild condition. The recyclability and stability of the CCM catalysts have also been studied

RURAL RESIDENTS SATISFACTION AND INFLUENCING FACTORS IN THE SUPPLY OF PUBLIC GOODS IN CHINA

The satisfaction of farmers with the supply of rural public goods is an importantindicator of the effectiveness of rural public goods investment. Using cross-sectionaldata on 400 farmers in five counties of China’s Shaanxi province, this study adoptsordinal logit and probit models to investigate rural residents’ satisfaction and theinfluencing factors in the supply of public goods. The empirical results indicate thatthe income of farmers has a significantly negative impact on their satisfaction, farmerswho were consulted in the process of public goods supply have higher satisfactionlevels than farmers who were not, and farmers who profited from the supply of publicgoods are more satisfied than those who did not. Additionally, other factors have asignificant impact on the satisfaction of certain public products. For example, the olderthe respondents, the higher their satisfaction with medical hygiene service and highereducation levels among the respondents reduce their satisfaction with compulsoryeducation. Our empirical results provide a relevant reference for governmentdepartments in China.The satisfaction of farmers with the supply of rural public goods is an importantindicator of the effectiveness of rural public goods investment. Using cross-sectionaldata on 400 farmers in five counties of China’s Shaanxi province, this study adoptsordinal logit and probit models to investigate rural residents’ satisfaction and theinfluencing factors in the supply of public goods. The empirical results indicate thatthe income of farmers has a significantly negative impact on their satisfaction, farmerswho were consulted in the process of public goods supply have higher satisfactionlevels than farmers who were not, and farmers who profited from the supply of publicgoods are more satisfied than those who did not. Additionally, other factors have asignificant impact on the satisfaction of certain public products. For example, the olderthe respondents, the higher their satisfaction with medical hygiene service and highereducation levels among the respondents reduce their satisfaction with compulsoryeducation. Our empirical results provide a relevant reference for governmentdepartments in China