A reliable system simulation to relate socioeconomic development with water environment and to comprehensively represent a watershed's dynamic features is important. In this study, after identifying lake watershed system processes, we developed a system dynamics modeling framework for managing lake water quality at the watershed scale. Two reinforcing loops (Development and Investment Promotion) and three balancing loops (Pollution, Resource Consumption, and Pollution Control) were constituted. Based on this work, we constructed Stock and Flow Diagrams that embedded a pollutant load model and a lake water quality model into a socioeconomic system dynamics model. The Dianchi Lake in Yunnan Province, China, which is the sixth largest and among the most severely polluted freshwater lakes in China, was employed as a case study to demonstrate the applicability of the model. Water quality parameters considered in the model included chemical oxygen demand (COD), total nitrogen (TN), and total phosphorus (TP). The business-as-usual (BAU) scenario and three alternative management scenarios on spatial adjustment of industries and population (Si), wastewater treatment capacity construction (S2), and structural adjustment of agriculture (S3), were simulated to assess the effectiveness of certain policies in improving water quality. Results showed that S2 is most effective scenario, and the COD, TN, and TP concentrations in Caohai in 2030 are 52.5, 10.9, and 0.8 mg/L, while those in Waihai are 9.6, 1.2, and 0.08 mg/L, with sustained development in the watershed. Thus, the model can help support the decision making required in development and environmental protection strategies. (C) 2015 Elsevier Ltd. All rights reserved.
We report the interface characterization of Al2O3/AlN/GaN MOS (metal-oxide-semiconductor) structures with an AlN interfacial layer. A thin monocrystal-like interfacial layer (AlN) is formed at the Al2O3/GaN to effectively block oxygen from the GaN surface and prevent the formation of detrimental Ga-O bonds. The suppression of Ga-O bonds is validated by X-ray photoelectron spectroscopy of the critical interface. Frequency-dispersion in C-V characteristics has been significantly reduced, owing to improved interface quality. Furthermore, using the conventional conductance method suitable for extracting the interface trap density D-it in MOS structures, Dit in the device with AlN was determined to be in the range of 10(11)-10(12) eV(-1) cm(-2), showing one order of magnitude lower than that without AlN. Border traps near the gate-dielectric/GaN interface were identified and shown to be suppressed by the AlN interfacial layer as well. (C) 2015 AIP Publishing LLC.
Formic acid (HCOOH) is one of the most abundant carboxylic acids in the atmosphere. However, current photochemical models cannot fully explain observed concentrations and in particular secondary formation of formic acid across various environments. In this work, formic acid measurements made at an urban receptor site (Pasadena) in June-July 2010 during CalNex (California Research at the Nexus of Air Quality and Climate Change) and a site in an oil and gas producing region (Uintah Basin) in January-February 2013 during UBWOS 2013 (Uintah Basin Winter Ozone Studies) will be discussed. Although the VOC (volatile organic compounds) compositions differed dramatically at the two sites, measured formic acid concentrations were comparable: 2.3 +/- 1.3 in UBWOS 2013 and 2.0 +/- 1.0 ppb in CalNex. We determine that concentrations of formic acid at both sites were dominated by secondary formation (> 99 %). A constrained box model using the Master Chemical Mechanism (MCM v3.2) underestimates the measured formic acid concentrations drastically at both sites (by a factor of > 10). Compared to the original MCM model that includes only ozonolysis of unsaturated organic compounds and OH oxidation of acetylene, when we updated yields of ozonolysis of alkenes and included OH oxidation of isoprene, vinyl alcohol chemistry, reaction of formaldehyde with HO2, oxidation of aromatics, and reaction of CH3O2 with OH, the model predictions for formic acid were improved by a factor of 6.4 in UBWOS 2013 and 4.5 in CalNex, respectively. A comparison of measured and modeled HCOOH / acetone ratios is used to evaluate the model performance for formic acid. We conclude that the modified chemical mechanism can explain 19 and 45% of secondary formation of formic acid in UBWOS 2013 and CalNex, respectively. The contributions from aqueous reactions in aerosol and heterogeneous reactions on aerosol surface to formic acid are estimated to be 0-6 and 0-5% in UBWOS 2013 and CalNex, respectively. We observe that air-snow exchange processes and morning fog events may also contribute to ambient formic acid concentrations during UBWOS 2013 (similar to 20% in total). In total, 53-59 in UBWOS 2013 and 50-55% in CalNex of secondary formation of formic acid remains unexplained. More work on formic acid formation pathways is needed to reduce the uncertainties in the sources and budget of formic acid and to narrow the gaps between measurements and model results.
Threshold voltage drift under gate bias stress was investigated in gate-recessed enhancement mode (E-mode) GaN MOSFET and depletion mode (D-mode) GaN MOS high-electron-mobility transistor (MOSHEMT) with Al2O3 gate dielectric layer. Besides the positive shift of threshold voltage in both devices under positive gate stress, it is also found that positive shift could also exist in E-mode GaN MOSFET under negative gate bias stress, while negative shift is observed in D-mode MOSHEMT. A three-step trapping and detrapping process was observed in the drain current transient of the device after negative gate bias stress. It was suggested that gate electron injection and the following trapping in the ``damaged'' gate recessed GaN channel layer is the dominant mechanism for the positive shift of the threshold voltage under negative gate bias in the enhancement mode GaN MOSFET. (c) 2015 The Japan Society of Applied Physics
We develop a model of firms' auditor choices when presented with a heterogeneous group of investors. We show that firms' auditor choices in equilibrium depend on the composition of investors in the market. The signaling effect of choosing a high-quality auditor exists only when there is at least a certain proportion of sophisticated investors. If there is a sufficiently high proportion of sophisticated investors, then all firms will choose high-quality auditors. We also show that the overall audit quality in the market increases with an increasing proportion of sophisticated investors. When the audit market is differentiated and investors are heterogeneous, an increase in the penalty for firms that receive a qualified opinion will lead to a decrease in the overall audit quality in the market. Our conclusions remain valid even after taking audit fees, auditor quality change, and firm heterogeneity into consideration.
We report on the role of hydrogen (forming gas) post-metal annealing to passivate border traps in Al2O3/In0.53Ga0.47As (100) gate stacks and of bias temperature stress treatments to generate/depassivate such traps. Experiments are carried out with Pd metal gates that efficiently dissociate molecular hydrogen during forming gas annealing, and they make use of InGaAs epitaxial layer substrates that are capped with arsenic after completion of their growth, to avoid unintentional oxide formation and disorder at the channel surface prior to atomic layer deposition of the Al2O3 gate dielectric. We find that forming gas anneal (FGA) greatly reduces both the interface trap density and border trap density measured in the gate stacks, but that the effectiveness of FGA for border trap passivation saturates for anneals with thermal budgets greater than 450°C/30 min. Both negative and positive bias temperature stress treatments are found to have no effect on the extracted border trap densities compared to non-treated capacitors.
Laser proton acceleration can be enhanced by using target ablation, due to the energetic electrons generated in the ablation preplasma. When the ablation pulse matches main pulse, the enhancement gets optimized because the electrons' energy density is highest. A scaling law between the ablation pulse and main pulse is confirmed by the simulation, showing that for given CPA pulse and target, proton energy improvement can be achieved several times by adjusting the target ablation. (C) 2015 AIP Publishing LLC.
In multiphase particulate composites, the deviation and mismatch of the elastic moduli of different particles may significantly affect the overall mechanical performance of the composites. This study investigates the effects of such deviations on the macroscopic properties of multiphase composites via an iterative micromechanics-based method. The elastic properties of the particles are assumed to obey certain statistical distributions. In the proposed iterative method, the composites are divided into multiple two-phase composites and their strain concentration tensors are derived by means of the inclusion matrix-reference medium model, which is a modification of the generalized self-consistent method. Iterative solutions are established that take into account the effects of the variation in the elastic properties of the particles in terms of the effective shear and bulk moduli. The findings show that the proposed iterative method converges quickly and that the results agree well with the experimental data for three-phase composites. In addition, the model indicates that the variation in the elastic properties of the particles does have a significant effect on the effective moduli of the composites. (C) 2015 American Society of Civil Engineers.
In multiphase particulate composites, the deviation and mismatch of the elastic moduli of different particles may significantly affect the overall mechanical performance of the composites. This study investigates the effects of such deviations on the macroscopic properties of multiphase composites via an iterative micromechanics-based method. The elastic properties of the particles are assumed to obey certain statistical distributions. In the proposed iterative method, the composites are divided into multiple two-phase composites and their strain concentration tensors are derived by means of the inclusion matrix-reference medium model, which is a modification of the generalized self-consistent method. Iterative solutions are established that take into account the effects of the variation in the elastic properties of the particles in terms of the effective shear and bulk moduli. The findings show that the proposed iterative method converges quickly and that the results agree well with the experimental data for three-phase composites. In addition, the model indicates that the variation in the elastic properties of the particles does have a significant effect on the effective moduli of the composites. (C) 2015 American Society of Civil Engineers.
Heterogeneous reaction of SO2 on mineral dust seems to be an important sink for SO2. However, kinetic data about this reaction on authentic mineral dust are scarce and are mainly limited to low relative humidity (RH) conditions. In addition, little is known about the role of hydrogen peroxide (H2O2) in this reaction. Here, we investigated the uptake kinetics of SO2 on three authentic mineral dusts (i.e., Asian mineral dust (AMD), Tengger desert dust (TDD), and Arizona test dust (ATD)) in the absence and presence of H2O2 at different RHs using a filter-based flow reactor, and applied a parameter (effectiveness factor) to the estimation of the effective surface area of particles for the calculation of the corrected uptake coefficient (γc). We found that with increasing RH, the γc decreases on AMD particles, but increases on ATD and TDD particles. This discrepancy is probably due to the different mineralogy compositions and aging extents of
these dust samples. Furthermore, the presence of H2O2 can promote the uptake of SO2 on mineral dust at different RHs. The probable explanations are that H2O2 rapidly reacts with SO2 on mineral dust in the presence of adsorbed water, and OH radicals, which can be produced from the heterogeneous decomposition of H2O2 on the mineral dust, immediately react with adsorbed SO2 as well. Our results suggest that the removal of SO2 via the heterogeneous reaction on mineral dust is an important sink for SO2 and has the potential to alter the physicochemical properties (e.g., ice nucleation ability) of mineral dust particles in the atmosphere.
He W, Feng Y, Zou L, Zhao D. Knowledge Base Completion Using Matrix Factorization, in Web Technologies and Applications - 17th Asia-PacificWeb Conference, APWeb 2015, Guangzhou, China, September 18-20, 2015, Proceedings.; 2015:256–267.