The association of organic carbon (OC) with ferrihydrite (Fh) is critical for regulating soil carbon persistence. However, the reduction of Fh compromises the stability of Fh-bound OC. So far, little ...is known about the impact of formation pathway (adsorption versus coprecipitation) of Fh-OC association (FOA) on the mobilization of Fh-bound OC during Fh reduction. In this study, we examined the release of Fh-adsorbed and Fh-coprecipitated OC during the abiotic reduction of FOA by hydroxylamine hydrochloride, to elucidate processes regulating the stability of OC during the redox processes. Using ESI-FT-ICR-MS, combustion-derived condensed polycyclic aromatic and vascular plant-derived polyphenols were found to be preferentially adsorbed and coprecipitated by Fh compared with aliphatics, and this structural preference was more pronounced for adsorption. Adsorbed and coprecipitated OC showed different release patterns during reduction: all the adsorbed OC was rapidly released initially, while the coprecipitated OC was slowly mobilized for almost the entire reduction period. The reductive release of OC depended upon the C/Fe ratio, with high C/Fe ratio inhibiting the release of OC. For both adsorption and coprecipitation, aliphatics were preferentially released from FOA into solution during Fe reduction. Our results are valuable for a better understanding of the role of Fh in OC stabilization in natural environments with fluctuating redox conditions.
•Reductive release of ferrihydrite - adsorbed and -co-precipitated DOC was tested.•Adsorbed and co-precipitated OC showed different release patterns during ferrihydrite reduction.•Ferrihydrite preferentially associated with aromatics compared with aliphatics.•Aliphatics were preferentially reductively released during Fe reduction.
Extremely high energy density and environment friendly reaction make Li-O2 batteries a promising energy storage system. In order to improve the energy efficiency and cycle life of Li-O2 battery, ...spinel mesoporous CuCo2O4 was successfully synthesized by a facile hydrothermal method and investigated in Li-O2 batteries. The electrochemical measurements show that mesoporous CuCo2O4 possess higher oxygen reduction and oxygen evolution activity than bulk CuCo2O4 both in alkaline and non-aqueous solution. Owing to the inherent catalytic activity, high conductivity and facile mass transfer of mesoporous CuCo2O4, Li-O2 battery shows enhanced electrochemical performances, including much lower charge overpotential and a high capacity up to 5288 mAh g−1. When restricting the discharge capacity at 500 mAh g−1, it could operate over 80 cycles and exhibit superior cycle stability. These results indicate that mesoporous CuCo2O4 nanoparticles are appropriate bifunctional catalysts for Li-O2 batteries.
•Mesoporous CuCo2O4 are prepared and investigated in Li-O2 batteries.•Mesoporous CuCo2O4 possess superior catalytic activity than bulk CuCo2O4.•The specific capacity and cycling life were increased.•Mesoporous CuCo2O4 significantly decreased the overpotential.
•Combined floating platform and WECs system can provide a cost-effective solution.•An accurate method is developed to optimize size and layout of WECs on a platform.•Larger WECs capture more wave ...energy in a limited region and a specific sea state.•Added WECs reduce the maximum horizontal force and pitch moment on the platform.•The synergy between wave and wind energy utilization on floating platform is shown.
Combined floating offshore wind platform and Wave Energy Converters (WECs) systems have the potential to provide a cost-effective solution to offshore power supply and platform protection. The objective of this paper is to optimize the size and layout of WECs within the hybrid system under a given sea state with a numerical study. The numerical model was developed based on potential flow theory with viscous correction in frequency domain to investigate the hydrodynamic performance of a hybrid system consisting of a floating platform and multiple heaving WECs. A non-dimensional method was presented to determine a series of variables, including radius, draft, and layout of the cylindrical WEC at a typical wave frequency as the initial design. WECs with larger diameter to draft ratio were found to experience relatively smaller viscous effects, and achieve more wave power, larger effective frequency range and similar wave power per unit weight compared with those with the smaller diameter to draft ratio in the same sea state. The addition of WECs reduced the maximum horizontal force and pitch moment on the platform, whereas the maximum vertical force increased due to the increasing power take-off force, especially at low frequencies. The results presented in this paper provide guidance for the optimized design of WECs and indicate the potential for synergies between wave and wind energy utilization on floating platforms.
In this work, we have prepared a p-type semiconductor of Cu2O decorated with MoS2 nanosheets as cocatalyst for efficient solar hydrogen production under visible light. Results show that Cu2O ...decorated with 1.0 wt % MoS2 presents the maximum reduction photocurrent density of 0.17 mA cm–2, which is 7-fold higher than pristine Cu2O. Furthermore, the as-prepared MoS2@Cu2O exhibits remarkable photostability with only 7% loss of its original photocurrent after 9 h of continuous work. The excellent performance of MoS2@Cu2O is ascribed to the introduction of active sites of MoS2 nanosheets as cocatalyst to the surface of Cu2O nanoparticles, which activates the photocatalyst by lowering the electrochemical proton reduction overpotential and also inhibits photoinduced corrosion during the measurement.
•Automatic integrating sphere system was built for measurement of optical properties.•Optical properties at 400–1050 nm of apple flesh during storage were measured.•μa and μ's in different ...wavelengths were related to soluble solid and soluble sugar.•Prediction models were used to verify the relationship of μa, μ's and soluble sugar.
Soluble solids (SS) in fruit are mainly composed of soluble sugars. This research aims to further the understanding of the detection mechanism of soluble solid content (SSC) based on optical technology by exploring the relationship between optical properties and soluble sugar contents. The total reflectance and total transmittance at 400–1050 nm of Fuji apple flesh stored at 25 °C for 50 d and 0 °C for 150 d were collected by an automatic integrating sphere system. The absorption coefficient (μa) and reduced scattering coefficient (μ's) were obtained by iteratively solving the radiative transfer equation using the inverse adding doubling algorithm. The relationship of μa and μ's with the contents of SS, total soluble sugars, fructose, glucose and sucrose were quantitatively analyzed at different wavelengths, and prediction models were established by partial least squares regression (PLSR). The results showed that the changes in μa, μ's, SSC and soluble sugar content presented similar trends during storage at the two test temperatures. As the storage time increased, the decreases in μa and μ's were accompanied by declines in SSC and soluble sugar content. In addition, μa and μ's at 550–1050 nm were both positively correlated with SSC and soluble sugar content, with correlation coefficients (r) of 0.834-0.992 and 0.737-0.981, respectively. Compared with the correlations at 550–780 nm, the correlations at 780–1050 nm between μa and SSC and soluble sugar content were enhanced, while the corresponding correlations with μ's were gradually weakened. In addition, SS was most strongly correlated with sucrose among the three types of soluble sugars. SS and sucrose had closer relationship with μa and μ's than fructose and glucose with μa and μ's. Moreover, their prediction models also performed better than the models for fructose and glucose, with Rp2 values of 0.731-0.804. Thus, the prediction of SSC based on Vis-NIR optical technology may be related to the high correlations between the absorption and scattering properties and the sucrose content.
In recent years, vision-aided inertial odometry for state estimation has matured significantly. However, we still encounter challenges in terms of improving the computational efficiency and ...robustness of the underlying algorithms for applications in autonomous flight with microaerial vehicles, in which it is difficult to use high-quality sensors and powerful processors because of constraints on size and weight. In this letter, we present a filter-based stereo visual inertial odometry that uses the multistate constraint Kalman filter. Previous work on the stereo visual inertial odometry has resulted in solutions that are computationally expensive. We demonstrate that our stereo multistate constraint Kalman filter (S-MSCKF) is comparable to state-of-the-art monocular solutions in terms of computational cost, while providing significantly greater robustness. We evaluate our S-MSCKF algorithm and compare it with state-of-the-art methods including OKVIS, ROVIO, and VINS-MONO on both the EuRoC dataset and our own experimental datasets demonstrating fast autonomous flight with a maximum speed of 17.5 m/s in indoor and outdoor environments. Our implementation of the S-MSCKF is available at https://github.com/KumarRobotics/msckf_vio.
Abstract
To solve the problem that the traditional hyperspectral image classification method cannot effectively distinguish the boundary of objects with a single scale feature, which leads to low ...classification accuracy, this paper introduces the idea of guided filtering into hyperspectral image classification, and then proposes a multi-scale guided feature extraction and classification (MGFEC) algorithm for hyperspectral images. Firstly, the principal component analysis theory is used to reduce the dimension of hyperspectral image data. Then, guided filtering algorithm is used to achieve multi-scale spatial structure extraction of hyperspectral image by setting different sizes of filtering windows, so as to retain more edge details. Finally, the extracted multi-scale features are input into the support vector machine classifier for classification. Several practical hyperspectral image datasets were used to verify the experiment, and compared with other spectral feature extraction algorithms. The experimental results show that the multi-scale features extracted by the MGFEC algorithm proposed in this paper are more accurate than those extracted by only using spectral information, which leads to the improvement of the final classification accuracy. This fully shows that the proposed method is not only effective, but also suitable for processing different hyperspectral image data.
Plant-residue derived biochars from walnut shell, corn cob, corn straw, and rice straw obtained at three heat treatment temperatures (HTTs) (250 °C, 400 °C, and 600 °C) were applied in an incubation ...experiment to investigate how feedstocks, HTTs, and biochar properties affect the quantity of microorganisms, microbial community shift, enzyme activity, and biodegradation of polycyclic aromatic hydrocarbons (PAHs) in an aged contaminated soil. The microbial quantities (bacteria and fungi) and enzyme activities (catechol 2,3-dioxygenase and ligninolytic enzymes) generally decreased with the increase in HTTs. Microbial quantities had significantly positive correlations with the aliphatic carbon (C) (p < 0.01) but negative correlations with the aromatic C of biochars (p < 0.01). Similar findings were observed with enzyme activities, which had significantly positive correlations with microbial quantities (p < 0.05). Meanwhile, there were significantly positive correlations between C23O activity and bacterial quantity (p < 0.01) and between ligninolytic enzyme activities and the quantity of fungi (p < 0.05). These results indicate that the increase in recalcitrant aromatic C in biochars that occurs with the increase in HTT is unfavorable for the microbial growth and enzyme activity in the soil studied. Generally, application of biochars had little influence on the biodegradation rates of total PAHs. However, the effects of biochars on the biodegradation rates of major individual PAH (e.g., Nap, Phe, Pyr, and Chr) depended on both the types of biochars and the PAH properties such as benzene ring number and angular pattern of the ring linkage.
•Microbial quantity and enzyme activity generally decreased with the increase in HTTs.•Recalcitrant aromatic C is unfavorable for the microbial growth and enzyme activity.•Application of biochars had little impact on the biodegradation rates of total PAHs.•PAH molecular structure affect the biodegradation rates of PAHs in biochar-treated soil.
Object recognition is among the basic survival skills of human beings and other animals. To date, artificial intelligence (AI) assisted high-performance object recognition is primarily visual-based, ...empowered by the rapid development of sensing and computational capabilities. Here, we report a tactile-olfactory sensing array, which was inspired by the natural sense-fusion system of star-nose mole, and can permit real-time acquisition of the local topography, stiffness, and odor of a variety of objects without visual input. The tactile-olfactory information is processed by a bioinspired olfactory-tactile associated machine-learning algorithm, essentially mimicking the biological fusion procedures in the neural system of the star-nose mole. Aiming to achieve human identification during rescue missions in challenging environments such as dark or buried scenarios, our tactile-olfactory intelligent sensing system could classify 11 typical objects with an accuracy of 96.9% in a simulated rescue scenario at a fire department test site. The tactile-olfactory bionic sensing system required no visual input and showed superior tolerance to environmental interference, highlighting its great potential for robust object recognition in difficult environments where other methods fall short.
The accurate theoretical interpretation of ultrafast time-resolved spectroscopy experiments relies on full quantum dynamics simulations for the investigated system, which is nevertheless ...computationally prohibitive for realistic molecular systems with a large number of electronic and/or vibrational degrees of freedom. In this work, we propose a unitary transformation approach for realistic vibronic Hamiltonians, which can be coped with using the adaptive time-dependent density matrix renormalization group (t-DMRG) method to efficiently evolve the nonadiabatic dynamics of a large molecular system. We demonstrate the accuracy and efficiency of this approach with an example of simulating the exciton dissociation process within an oligothiophene/fullerene heterojunction, indicating that t-DMRG can be a promising method for full quantum dynamics simulation in large chemical systems. Moreover, it is also shown that the proper vibronic features in the ultrafast electronic process can be obtained by simulating the two-dimensional (2D) electronic spectrum by virtue of the high computational efficiency of the t-DMRG method.
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