Electrocatalytic two‐electron oxygen reduction has emerged as a promising alternative to the energy‐ and waste‐intensive anthraquinone process for distributed H2O2 production. This process, however, ...suffers from strong competition from the four‐electron pathway leading to low H2O2 selectivity. Herein, we report using a superhydrophilic O2‐entrapping electrocatalyst to enable superb two‐electron oxygen reduction electrocatalysis. The honeycomb carbon nanofibers (HCNFs) are robust and capable of achieving a high H2O2 selectivity of 97.3 %, much higher than that of its solid carbon nanofiber counterpart. Impressively, this catalyst achieves an ultrahigh mass activity of up to 220 A g−1, surpassing all other catalysts for two‐electron oxygen reduction reaction. The superhydrophilic porous carbon skeleton with rich oxygenated functional groups facilitates efficient electron transfer and better wetting of the catalyst by the electrolyte, and the interconnected cavities allow for more effective entrapping of the gas bubbles. The catalytic mechanism is further revealed by in situ Raman analysis and density functional theory calculations.
Honeycomb carbon nanofibers behave as a superb electrocatalyst for selective H2O2 production (97.3 %) via 2 e− oxygen reduction, capable of attaining an ultrahigh mass activity of 220 A g−1 with a H2O2 yield rate of 6.37 mmol L−1 h−1. The catalytic mechanism is revealed by in situ Raman analysis and DFT calculations.
When rock samples are loaded until macroscopic fractures develop, the failure process can be divided into several stages based on axial and lateral strain responses or the acoustic emission sequence ...during uniaxial compression tests. Several stress thresholds may be identified: the crack closure stress
σ
cc
, crack initiation stress
σ
ci
, crack damage stress
σ
cd
, and uniaxial compressive strength
σ
ucs
; these may be used as a warning indicator for rock rupture. We investigated the crack damage stress
σ
cd
, its threshold, and a possible relationship between
σ
cd
and the uniaxial compressive strength. The
σ
cd
of different rock types were compiled from previous studies based on uniaxial compression tests. The results showed that the overall averages and standard deviations of
σ
cd
/σ
ucs
for igneous, metamorphic, and sedimentary rocks were ~0.78 (±0.11), ~0.85 (±0.11), and ~0.73 (±0.18), respectively. There were no significant differences in
σ
cd
/σ
ucs
between the different rock types, except that the sedimentary rock had a slightly larger standard deviation attributed to the variation of porosity in the samples, while the metamorphic rock had higher average
σ
cd
/σ
ucs
resulting from the small statistical sample size. By excluding the higher-porosity (>10 %) rock samples, the averages and standard deviations of
σ
cd
/σ
ucs
for igneous, metamorphic, and sedimentary rocks were ~0.78 (±0.09), ~0.85 (±0.09), and ~0.78 (±0.11), respectively. The results imply that the rock origin process (i.e., igneous, metamorphic, and sedimentary) has a minimal effect on
σ
cd
/σ
ucs
. The ratio
σ
cd
/
σ
ucs
could be an essential intrinsic property for low-porosity rocks, which could be used in rock engineering for predicting the failure process.
This article focuses on a proportional-derivative (PD) feedback controller to control a Neimark–Sacker bifurcation for a Mackey–Glass system by the Euler method. It has been shown that the onset of ...the Neimark–Sacker bifurcation can be postponed or advanced via a PD controller by choosing proper control parameters. Finally, numerical simulations are given to confirm our analysis results and the effectiveness of the control strategy. Especially, a derivative controller can significantly improve the speed of response of a control system.
•A holistic water quality assessment was conducted in the Erdao Songhua River Basin.•The IWPI showed “Good” water quality with spatiotemporal variations in studied basin.•PI, DO, CODcr, and BOD5 are ...the most important parameters in this basin.•The potential risks of point source and non-point source pollution in middle-downstream should be of concern.
The Erdao Songhua River provides drinking water for 16.82 million people; therefore, ensuring that the water quality adequate is of particular concern. In this study, an improved water pollution index (IWPI) and multiple statistical methods were employed to assess the overall water pollution situation and investigate spatiotemporal variations of seven physicochemical parameters such as the permanganate index (PI), dissolved oxygen (DO), chemical oxygen demand (CODcr), five-day biochemical oxygen demand (BOD5), total nitrogen (TN), total phosphorus (TP) and ammonia nitrogen (NH3-N), which were collected monthly at 20 sites within the mainstream and major tributaries of the Erdao Songhua River Basin (ESRB) from 2015 to 2020. Stepwise regression analysis was conducted to build a minimum improved water pollution index (IWPImin) model consisted of four key elements (PI, DO, CODcr, and BOD5) proposed from seven parameters. The results demonstrated water quality within the ESRB was considered to be “Good” with the mean IWPI values <40. However, the water quality deteriorated from the upstream to the downstream within the basin, manifested as the mean value of IWPI of the downstream is 1.7 times of upstream. Seasonally, an improving trend of water quality was observed during the monitoring period and the mean IWPI value decreased by 23%. Furthermore, Seasonal variation in the IWPI value was evident, and the best water quality was found in winter (lowest IWPI value of 14.1) and the worst in summer (highest IWPI value of 21.7). The proposed IWPImin model uses the selected four crucial parameters and the weights of those parameters has exhibited excellent performance in the water quality assessment, with the highest coefficient of determination (R2) and lowest Root Mean Square Error (RMSE) values of 0.996 and 0.51, respectively, which can be used to optimize water quality assessment strategies at a lower cost. For future management, the water quality of middle and downstream should be carefully inspected, and strictly control the effects of point source and non-point source pollution in the ESRB.
Urban Heat Island (UHI) leads to increased energy consumption, aggravated pollution and threatened health of citizens. Urban green spaces mitigate UHI effects, however, it is still unclear how the ...green space characteristics and its surrounding environment affects the green space cool island (GCI). In this study, land surface temperature (LST) and land cover types within the outmost ring road of Shanghai, China were obtained from Landsat 8 data and high-resolution Google Earth data. The GCI effects were defined in three aspects: GCI range (GR), amplitude of temperature drop (TA) and temperature gradient (TG). Pearson correlation analysis was processed to get the relationship between the aspects and impact factors. The results indicated that the GCI principle could be explained by the thermal conduct theory. The efficient methods to decrease LST of green spaces include increasing green space area while staying below the threshold, adding complexity of green space shape, decreasing impervious surfaces and enlarging the area of water bodies. For the surrounding environment of the green spaces, increasing vegetation and water body fractions or decreasing impervious surfaces will help to strengthen GCI effects. The findings can help urban planners to understand GCI formation and design cool green spaces to mitigate UHI effects.
NiCo2O4 nanowire array on carbon cloth (NiCo2O4/CC) is proposed as a highly active electrocatalyst for ambient nitrate (NO3−) reduction to ammonia (NH3). In 0.1 m NaOH solution with 0.1 m NaNO3, such ...NiCo2O4/CC achieves a high Faradic efficiency of 99.0% and a large NH3 yield up to 973.2 µmol h−1 cm−2. The superior catalytic activity of NiCo2O4 comes from its half‐metal feature and optimized adsorption energy due to the existence of Ni in the crystal structure. A Zn‐NO3− battery with NiCo2O4/CC cathode also shows a record‐high battery performance.
NiCo2O4 nanowire array on carbon cloth is an efficient electrocatalyst for NO3− to NH3 conversion under ambient conditions, achieving a high Faradic efficiency of 99.0% and a large NH3 yield up to 973.2 µmol h−1 cm−2 in 0.1 m NaOH with 0.1 m NO3−. The catalytic mechanism is investigated by theoretical calculations.
Corruption is one of the most pervasive obstacles to economic and social development. However, in the existing literature it appears that corruption seems to be less harmful in some countries than in ...others. The most striking examples are well known as the “East Asian paradox”: countries displaying exceptional growth records despite having thriving corruption cultures. The aim of this paper is to explain the high corruption but fast economic growth puzzle in China by providing firm-level evidence of the relation between corruption and growth and investigating how financial development influences the former relationship. Our empirical results show that corruption is likely to contribute to firms' growth. We further highlight the substitution relationship between corruption and financial development on firm growth. This means that corruption appears not to be a vital constraint on firm growth if financial markets are underdeveloped. However, pervasive corruption deters firm growth where there are more developed financial markets. This implies that fast firm growth will not be observed until a later stage of China's development when financial markets are well-functioning and corruption is under control. Furthermore, the substitution relationship exists in the private and state-owned firms. Geographically, similar results can be seen in the Southeast and Central regions.
► This paper provides a possible explanation for the corruption-growth puzzle in China. ► The evidence is addressed from the micro level survey data. ► Corruption is likely to contribute to firm growth, though the benefit is transitory. ► A substitution relationship exists between corruption and financial development. ► Similar results can be observed across types of ownership and regions.
Over the past few decades, the synthetic development of ultra-small nanoparticles has become an important strategy in nano-medicine, where smaller-sized nanoparticles are known to be more easily ...excreted from the body, greatly reducing the risk caused by introducing nano-theranostic agents. Gold nanorods are one of the most important nano-theranostic agents because of their special optical and electronic properties. However, the large size (diameter > 6 nm) of most obtained gold nanorods limits their clinical application. In recent years, more and more researchers have begun to investigate the synthesis and application of small gold nanorods (diameter < 6 nm), which exhibit similar optical and electronic properties as larger gold nanorods. In this review, we summarize the recent advances of synthesis of the small gold nanorods and their application for near-infrared light-mediated bio-imaging and cancer therapy.
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