Proton acceleration during the interaction of an ultraintense (6 x 10(19) W/cm(2)) femtosecond (fs) laser pulse with a thin (2.5 mu m) foil target pre-ablated by a picosecond (ps) pulse is experimentally and numerically investigated. Enhancements in both proton cut-off energy and charge are observed with the target ablation due to a large number of energetic electrons generated from the preformed preplasma in front of the target. The enhanced proton beams are successfully collected at 4-9 MeV with +/- 4% energy spread and then transported to the irradiating platform. The results show that for the interaction between fs laser pulse and mu m-thickness target, proton energy and charge can be enhanced by target ablation using a ps laser pulse, which is valuable for application like cancer radiotherapy. Published by AIP Publishing.
In this study, the performances of nitrogen removal in constructed wetlands using solid carbon source with limited aeration were investigated. The blends of poly-3-hydroxybutyrate-co-3-hydroxyvalerate (PHBV) and polyacetic acid (PLA) were used as the carbon source and biofilm support. The performances of nitrogen removal, microbial abundance and microbial community structure in the biofilm attached on PHBV/PLA were investigated. Higher ammonia removal efficiency (91.00%) and total nitrogen removal efficiency (97.03%) than non-aerated constructed wetland (System NA) were achieved in constructed wetland with limited aeration (System A). The limited aeration decreased the average concentrations of COD in effluent. And, System A had higher microbial abundance than System NA. Pyrosequencing analysis showed that denitrifying bacteria Brevinema (41.85%) and Thiothrix (12.33%) were the predominant genus in the biofilm attached on the carbon source in System NA and System A, respectively.
The photodynamic properties involving both intra-and intermolecular triplet energy transfers (ET) of a bichromophoric photosensitizer having a tris-cyclometalated Ir(III) tethered with a pyrene derivative are studied. Due to the triplet energy gap of the two chromophores, a reversible intramolecular triplet ET equilibrium is quickly established upon photoexcitation, with the triplet exciton mainly residing on the acceptor side in the photostationary state. By virtue of the very small decay rate of triplet pyrene, a considerably extended triplet lifetime (2 ms) is observed. Next, the intermolecular triplet-triplet ET properties are investigated. Using steady-state and time-resolved spectroscopy, the ET rate constants from the Ir complex and pyrene unit in the sensitizer to an external triplet acceptor (unattached, free pyrene derivative) in solution are found to be around 10(9) s(-1) and 10(8) M-1 s(-1), respectively. In spite of a lower ET rate constant, the tethered pyrene serves as the main intermolecular ET channel because of the large, favorable intramolecular ET equilibrium (K similar to 10(3)). Importantly, this cascade ET process, from Ir complex to linked pyrene, and then to free pyrene, offers an overall improved ET efficiency than a direct ET from Ir complex to free pyrene, by virtue of the much smaller spontaneous decay rate compared to that of the metal complex. Finally, the more efficient ET ability is demonstrated experimentally by applying the molecule as sensitizer in a triplet-triplet annihilation upconversion. The bichromophoric sensitizer achieved upconverted emission intensity S times higher than a monochromophoric Ir-complex analogue.
Industrial GHG mitigation policies are prevalent across the world to realize global greenhouse gas (GHG) emissions targets. It is essential to simulate the impacts of different policies on various industries in the socio-economic system to find out the most effective emission reduction pathways. In this study, an Environmentally-Extended Input-Output Simulation (EEIOS) model is developed to facilitate integrated GHG mitigation policy development for multiple industries from both production and consumption sides. In addition, a Production-Consumption Rate is proposed to reflect the differences between Production-Based Policies (PBP) and Consumption-Based Policies (CBP) for a certain industry, which further supports the optimized and systematic emission reduction strategy development. A special case study of the Province in Saskatchewan, Canada, is conducted to illustrate the applicability and superiority of the Environmentally-Extended Input-Output Simulation model. It is found that Production-Based Policies applied to primary industries will lead to larger GHG reductions, and that Consumption-Based Policies should be applied to industries that are located at the end of industrial chains. The results provide a solid scientific basis for supporting industrial greenhouse gas mitigation policy development for each industry and identifying the optimized emission reduction pathways for the entire socio-economic system.
Estimates of potential harmful effects on ecosystems in the Canadian provinces of Alberta and Saskatchewan due to acidifying deposition were calculated, using a 1-year simulation of a high-resolution implementation of the Global Environmental Multiscale-Modelling Air-quality and Chemistry (GEM-MACH) model, and estimates of aquatic and terrestrial ecosystem critical loads. The model simulation was evaluated against two different sources of deposition data: total deposition in precipitation and total deposition to snow-pack in the vicinity of the Athabasca oil sands. The model captured much of the variability of observed ions in wet deposition in precipitation (observed versus model sulfur, nitrogen and base cation R-2 values of 0.90, 0.76 and 0.72, respectively), while being biased high for sulfur deposition, and low for nitrogen and base cations (slopes 2.2, 0.89 and 0.40, respectively). Aircraft-based estimates of fugitive dust emissions, shown to be a factor of 10 higher than reported to national emissions inventories (Zhang et al., 2018), were used to estimate the impact of increased levels of fugitive dust on model results. Model comparisons to open snow-pack observations were shown to be biased high, but in reasonable agreement for sulfur deposition when observations were corrected to account for throughfall in needleleaf forests. The model-observation relationships for precipitation deposition data, along with the expected effects of increased (unreported) base cation emissions, were used to provide a simple observation-based correction to model deposition fields. Base cation deposition was estimated using published observations of base cation fractions in surface-collected particles (Wang et al., 2015). Both original and observation-corrected model estimates of sulfur, nitrogen, and base cation deposition were used in conjunction with critical load data created using the NEG-ECP (2001) and CLRTAP (2017) methods for calculating critical loads, using variations on the Simple Mass Balance model for terrestrial ecosystems, and the Steady State Water Chemistry and First-order Acidity Balance models for aquatic ecosystems. Potential ecosystem damage was predicted within each of the regions represented by the ecosystem critical load datasets used here, using a combination of 2011 and 2013 emissions inventories. The spatial extent of the regions in exceedance of critical loads varied between 1 x 10(4) and 3.3 x 10(5) km(2), for the more conservative observation-corrected estimates of deposition, with the variation dependent on the ecosystem and critical load calculation methodology. The larger estimates (for aquatic ecosystems) represent a substantial fraction of the area of the provinces examined. Base cation deposition was shown to be sufficiently high in the region to have a neutralizing effect on acidifying deposition, and the use of the aircraft and precipitation observation-based corrections to base cation deposition resulted in reasonable agreement with snowpack data collected in the oil sands area. However, critical load exceedances calculated using both observations and observation-corrected deposition suggest that the neutralization effect is limited in spatial extent, decreasing rapidly with distance from emissions sources, due to the rapid deposition of emitted primary dust particles as a function of their size. We strongly recommend the use of observation-based correction of model-simulated deposition in estimating critical load exceedances, in future work.
In this paper, four different injection schemes, i.e., CO2 continuous gas injection (CGI), gas injection (GI) + soaking, pulse injection, and injection-alternating-production (IAP), for the high-temperature and pressure CO2 immiscible flooding in low-permeability formations are experimentally studied. A series of comprehensive and optimum practical strategies with respect to the four immiscible CO2 injection processes in the low-permeability formations can be determined from this study. More specifically, a total of 10 immiscible coreflood tests are conducted at the injection pressure of 20.0 MPa and reservoir temperature of 130.0 °C by means of the four different injection schemes. The oil viscosity and density are experimentally measured to be reduced with the temperature increase and the minimum miscibility pressure is measured to be 30.0 MPa at 130.0 °C from the vanishing interfacial tension (VIT) technique. Among Tests No. 1–10 with the same experimental conditions, the measured oil recovery factor (ORF) of Test No. 9, which is the CO2 IAP with the injection rates of 0.5 cm3/min, is the highest at 69.06%. In Test No. 4, the CO2 GI + soaking at the injection rate of 0.5 cm3/min has the second highest ORF of 65.21%. Tests No. 1, 4, 7, and 9 at the injection rate of 0.5 cm3/min outperform other tests with the same injection scheme in terms of the ORF under the same experimental conditions but at larger injection rates. Thus, a small CO2 injection rate is beneficial to increase the ORF for all schemes except for the CO2 pulse injections. It is found that soaking is an important step for CO2 enhanced oil recovery at the immiscible conditions. Moreover, the smaller injection rate also contributes to the delay of CO2 breakthrough so that a higher ORF can be reached at a lower cost. Finally, the measured asphaltene and wax contents in the produced oil are found to reduce in the percentages of 33–51% and 14–25% from the beginning period to the end of the oil production.
The many-body ground state wave function of a fractional Chern insulator (FCI) can be constructed by mapping a fractional quantum Hall state to a FCI state through a substitution of the Bloch state of the flat Chern band for the magnetic Bloch state of the Landau level. There is a gauge freedom in choosing the single particle Bloch basis of the flat Chern band. Instead of considering only one form of interaction in FCI when choosing the gauge as done in previous works, we determine the optimal gauges for FCIs with different forms of interaction, including a short-range interaction, the Coulomb interaction, and an interpolation between them, by applying the variational principle proposed by Zhang et al. [Phys. Rev. B 93, 165129 (2016)]. We find that the optimal gauge strongly depends on the form of interaction. It contradicts with the common belief that the wave function of FCI is not sensitive to the interaction. In comparing the optimal gauge with the previous gauges proposed by Qi [Phys. Rev. Lett. 107, 126803 (2011)] and Wu et al. [Phys. Rev. B 86, 085129 (2012)], we find Wu et al.'s gauge is close to the optimal one when the interaction is a certain mixture of the Coulomb interaction and the short-range interaction, while Qi's gauge is qualitatively different from the optimal gauge in all the cases.
Experimental and simulation I–V characteristics of the cap gate high electron mobility transistor (HEMT) are reported. The two-dimensional simulations results are in conformity with the realistic HEMT perfectly, indicating reliable and acceptable of the TCAD simulation method in GaN-based devices. Depending on this, further researches on the cap gate HEMT are carried out by TCAD software, which analyzes the impact of recessed depth of gate barrier, the dimension of LG and cap gate structure on GaN HEMT performances.