科研成果

Effective removal of dyes has been widely investigated by the adsorption of powder activated carbon and photodegradation by titanate nanotubes (TNTs). In this study, a facile one-step alkaline-hydrothermal method was applied to synthesize powder activated charcoal–supported TNTs (TNTs@PAC). Adsorption of three representative dyes, i.e., cationic methylene blue (MB), cationic rhodamine B (RhB), and anionic methyl orange (MO), onto TNTs@PAC was evaluated by the adsorption kinetic experiments and adsorption isotherms. The first 30 min is the main time phase of adsorption, and MB, RhB, and MO obtained the experimental equilibrium uptake of 173.30, 115.06, and 106.85 mg/g, respectively, indicating their final removal efficiencies of 100%, 69.36%, and 64.11%, respectively. The increase of pH value reduced adsorption capacity of MO (from 149.35 mg/g at pH of 2 to 96.99 mg/g at pH of 10), but facilitated MB adsorption, which was attributed to the charge distribution on the surface of TNTs@PAC and the charge of dyes at different pH. Furthermore, good capacity recoveries of MB by TNTs@PAC (>þinspace}99%) were observed after UV irradiation treatment, indicating the used TNTs@PAC can be easily recycled for the adsorption of MB by UV irradiation. Overall, TNTs@PAC is an effective process for remediation of dye-contaminated water because of its adsorption performance for all selected dyes and good regeneration capacity for MB.

The traditional eigen beam based localization algorithms are usually not employed on the non-spherical microphone array, for which the eigen beam is hard to be obtained. In this paper, the transfer functions are introduced to calculated the eigen beam on the non-spherical microphone array. Based on it, three localization algorithms including the eigen beam based intensity vector, eigen beam based beamforming, eigen beam based MUSIC, are employed and their performance on localization are evaluated.

Personalized recommendation has important implications in raising online shopping efficiency and increasing product sales. There has been wide interest in finding ways to provide more efficient personalized recommendations. Most existing studies focus on how to improve the accuracy of the recommendation algorithms, or are more concerned on ways to increase consumer satisfaction. Unlike these studies, our study focuses on the process of decision-making, using long tail theory as a basis, to reveal the mechanisms involved in consumers' adoption of recommendations. This paper analyzes the effect of personalized recommendations from two angles: product sales and ratings, and tries to point out differences in consumer preferences between mainstream products and niche products, high rating products and low rating products, search products and experience products. The study verifies that consumers demand diversity in the recommended content, and also provides suggestions on how to better plan and operate a personalized recommendation system. © 2019 IEEE Computer Society. All rights reserved.

Scholars commonly regard the Comintern as having played a critical role in the emergence of the communist movement in late-colonial Malaya. When discussing the Comintern’s early influence, existing scholarships often use the arrest of Joseph Ducroux — alias Serge Lefranc, a French agent of the Comintern — in Singapore in June 1931 to illustrate the Comintern-China-Malaya connection. Additionally, historians have attached special meanings to the Ducroux Case, primarily because of the more significant repercussions it caused internationally. Laurent Metzger has conducted detailed research on Ducroux’s arrest in and eventual exile from Singapore between 1931 and 1932. While such an account is useful in demonstrating the incident’s international significance, little is known as to what immediate impression it created in the cosmopolitan port city. Moreover, it is also unclear how Singapore’s general public perceived communism when communist organizations had yet firmly established themselves in the British colony. This article seeks to make sense of such issues by investigating how the Singapore press reported on the Ducroux Case.

As the common saying goes: All's well that ends well. This research was the first to explore whether the end effect could be observed in the perception of air pollution and further examined the effect of perceived difference on the end effect. In Experiment 1, participants went through a short trial of 30 severe air pollution pictures and a long trial of 45 pollution pictures containing 15 extra moderate pollution pictures at the end. The results showed preference for the long trial as well as more willingness to experience it again, which verified the end effect. In Experiment 2, the long trial was adjusted to 45 severe air pollution pictures, which caused the end effect to disappear. In Experiment 3, it was confirmed that perceived difference had an impact on the end effect, as the end effect worked when subjects cognitively focused on the variated pollution extent but disappeared when they focused on the air pollution quality. These results advance our understanding by directly demonstrating the influence of perceived difference on the end effect as well as providing a useful view to intervene in people's perception of air pollution. Further theoretical and practical implications are discussed.

© 2019 Elsevier Ltd Effective policy requires comprehensive analysis of many factors. But presently there does not exist a sufficiently comprehensive research on the interrelationship between energy input and output, carbon emissions, and water use in the oil and gas extraction process. To more comprehensively measure this phenomenon, this paper constructs an assessment model of energy return on energy, carbon, and water investment for the development of oil and gas resources using the Daqing and Shengli oilfields as practical examples. The results show that the method for evaluating energy input and output (energy return on energy invested) can be made more comprehensive for covering the resources required in the oilfield extraction process; this method ignores the environmental impacts of carbon emissions (energy return on carbon) and water use (energy return on water). However, the energy return evaluation method, which considers energy, carbon, and water inputs, is more comprehensive and practically used to evaluate the development status of oil and gas resources as well as other types of energy development processes. Policy implications for biophysical input accounting and the management of energy resource extraction are given accordingly.

Sulfur-modified zero valent iron (S-ZVI) particles have been reported to show improved reactivity and selectivity than conventional ZVI. However, current methods for ZVI sulfidation do not fully utilize the advantages of the material, and S-ZVI has not been tested for U(VI) immobilization. In this work, we synthesized a new type of FeS-modified ZVI core-shell particles (FeS@Fe0) through a facile two-step reaction approach, and then tested for reductive sequestration of U(VI) in water. X-ray diffraction, Scanning transmission electron microscopy, and physical property analyses confirmed the formation of the core-shell structure, surface compositions and magnetic properties. Batch kinetic tests showed that FeS@Fe0 with an Fe0/FeS molar ratio of 1:1 offered the highest U(VI) reduction rate, prolonged reactive life than pristine ZVI, and the reduced uranium was most resistant to re-oxidation when exposed to oxygen. The retarded first-order kinetic model was able to adequately interpret the experimental rate data. FeS@Fe0 performed well over the pH range 5.5–9.0, with higher pH more favoring the reaction. High concentrations (5–10 mg/L) of humic acid, bicarbonate (1–5 mM) and Ca2+ (1 mM) showed only modest inhibition to the U(VI) reduction. Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and extraction studies indicated that U(VI) was immobilized via both direct adsorption and reductive precipitation, where Fe0 was the main electron source, with Fe0, sorbed Fe(II) and structural Fe(II) acting as the electron donors. FeS@Fe0 may serve as an improved material for efficient immobilization of U(VI) and other redox-active contaminants in water.

Current air quality models usually underestimate the concentration of ambient air sulfate, but the cause of this underestimation remains unclear. One reason for the underestimation is that the sulfate formation mechanism in the models is incomplete, and does not adequately consider the impact of the synergistic effects of high concentrations of multiple pollutants on sulfate formation. In this work, the roles of gaseous NO2, NH3 and solution ionic strength in the formation of sulfate in the aqueous phase were quantitatively investigated using a glass reactor and a 30 m(3) smog chamber, separately. The results showed that sulfate formation was enhanced to different degrees in the presence of gas-phase NO2, NH3 and their coexistence as solutes in both liquid solution and aerosol water. NH3 enhances the aqueous oxidation of SO2 by NO2 mainly by accelerating the uptake of SO2 through increased solubility. More importantly, we found that high ionic strength in aerosol water could significantly accelerate the aqueous oxidation of SO2, resulting in unexpectedly high S(VI) formation rates. We estimate that under severe haze conditions, heterogeneous oxidation of SO2 by NO2 on aerosols may be much shorter than that through gas phase oxidation by OH, aided by high ionic strengths in aerosols. Considering the existence of complex air pollution conditions with high concentrations of NO2, NH3 and aerosol water, as expected in typical urban and suburban settings, the sulfate formation mechanisms revealed in the present work should be incorporated into air quality models to improve the prediction of sulfate concentrations. (C) 2019 Elsevier Ltd. All rights reserved.

Two-dimensional (2D) metal–semiconductor transition-metal dichalcogenide (TMDC) vertical heterostructures play a crucial role in device engineering and contact tuning fields, while their direct integration still challenging. Herein, a robust epitaxial growth method is designed to construct multiple lattice-matched 2D metal–semiconductor TMDC vertical stacks (VSe2/MX2, M: Mo, W; X: S, Se) by a two-step chemical vapor deposition method. Intriguingly, the metallic VSe2 preferred to nucleate and extend from the energy-favorable edge site of the semiconducting MX2 underlayer to form VSe2/MX2 vertical heterostructures. This growth behavior was also confirmed by density functional theory calculations of the initial adsorption of VSe2 adatoms. In particular, the formation of Schottky-diode or Ohmic contact-type band alignments was detected for the stacks between VSe2 and p-type WSe2 or n-type MoSe2, respectively. This work hereby provides insights into the direct integration, band-alignment engineering, and potential applications of such 2D metal–semiconductor stacks in next-generation electronics, optoelectronic devices, and energy-related fields.