In the light of increasing energy demand and environmental pollution, it is urgently required to find a clean and renewable energy source. In these years, photocatalysis that uses solar energy for ...either fuel production, such as hydrogen evolution and hydrocarbon production, or environmental pollutant degradation, has shown great potential to achieve this goal. Among the various photocatalysts, covalent organic frameworks (COFs) are very attractive due to their excellent structural regularity, robust framework, inherent porosity and good activity. Thus, many studies have been carried out to investigate the photocatalytic performance of COFs and COF-based photocatalysts. In this critical review, the recent progress and advances of COF photocatalysts are thoroughly presented. Furthermore, diverse linkers between COF building blocks such as boron-containing connections and nitrogen-containing connections are summarised and compared. The morphologies of COFs and several commonly used strategies pertaining to photocatalytic activity are also discussed. Following this, the applications of COF-based photocatalysts are detailed including photocatalytic hydrogen evolution, CO
2
conversion and degradation of environmental contaminants. Finally, a summary and perspective on the opportunities and challenges for the future development of COF and COF-based photocatalysts are given.
This review summarises the recent advances of covalent organic framework photocatalysts including structures and applications.
Soil contamination in some areas of southern China has resulted in elevated dietary intake of cadmium (Cd), posing a potential risk to human health. A survey of paired soil-rice (n = 200) and ...soil-vegetable (n = 142) samples was conducted in Xiangtan county of Hunan province, southern China. The concentrations of Cd in all the samples were determined by inductively coupled plasma mass spectrometry. Dietary intakes of Cd from the consumption of locally produced rice and vegetables were estimated for different age groups. Among the 342 crop samples collected in the survey, 88% and 29% of rice grain and vegetable samples, respectively, exceeded the Chinese maximum permissible limit for Cd (0.2 mg dry weight kg−1, 0.2 mg fresh weight kg−1 and 0.1 mg fresh weight kg−1 for rice, leafy vegetables and for rootstalk and legume vegetables, respectively). The median dietary Cd intake varied from 66.5 to 116 μg Cd kg−1 body weight (BW) month−1, with children (4–11 years) exhibiting the highest intake. These values are 2.7–4.6 times the tolerable dietary intake of 25 μg kg−1 BW month−1 recommended by the Joint FAO/WHO Expert Committee on Food Additives. For the general population in Xiangtan county, rice contributed the majority (81%) of the Cd intake with vegetables contributing only 19%. The median hazard quotient calculated from dietary Cd intake was 2.4 times the permissible level, indicating a high risk to the local residents. This study highlights an urgent need to reduce the transfer of Cd from soil to the food chain in the investigated region.
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•A paired soil-crop survey was conducted in a county in southern China.•82% of the soil samples exceeded the Chinese soil Cd threshold.•88% and 29% of rice and vegetable samples exceeded the Chinese limits for Cd.•Median Cd intake from rice and vegetables was 2.7–4.6 times the FAO/WHO guideline.
Two-dimensional (2D) semiconductors, in particular transition metal dichalcogenides (TMDCs), have attracted great interest in extending Moore's law beyond silicon
. However, despite extensive efforts
..., the growth of wafer-scale TMDC single crystals on scalable and industry-compatible substrates has not been well demonstrated. Here we demonstrate the epitaxial growth of 2 inch (~50 mm) monolayer molybdenum disulfide (MoS
) single crystals on a C-plane sapphire. We designed the miscut orientation towards the A axis (C/A) of sapphire, which is perpendicular to the standard substrates. Although the change of miscut orientation does not affect the epitaxial relationship, the resulting step edges break the degeneracy of nucleation energy for the antiparallel MoS
domains and lead to more than a 99% unidirectional alignment. A set of microscopies, spectroscopies and electrical measurements consistently showed that the MoS
is single crystalline and has an excellent wafer-scale uniformity. We fabricated field-effect transistors and obtained a mobility of 102.6 cm
V
s
and a saturation current of 450 μA μm
, which are among the highest for monolayer MoS
. A statistical analysis of 160 field-effect transistors over a centimetre scale showed a >94% device yield and a 15% variation in mobility. We further demonstrated the single-crystalline MoSe
on C/A sapphire. Our method offers a general and scalable route to produce TMDC single crystals towards future electronics.
-- With the rapid development of the energy internet, integrated energy system (IES) has become a topic of interest in the field of energy research. In light of energy interconnection system ...containing multiple communities, this paper proposes a hierarchically partitioned coordinated operation method for distributed integrated energy system (DIES) based on a master-slave game. First, based on the concept of "distributed autonomy and centralized coordination", a hierarchically partitioned structure of urban integrated energy system is given, and a variety of energy equipment are modeled and analysed. Next, in considering the energy and interest interactions among different communities, the urban manager and community operators are taken as the game leader and game followers, respectively, to establish a hierarchically partitioned master-slave game optimization model of DIES based on game theory, and a mixed integer linear programming method is applied to solve the model. Finally, a typical case of urban integrated energy system is taken as an example to verify the optimization model. Simulation results show that the proposed method can effectively promote the balance of energy supply and demand, and reconcile the benefits of leader and followers, while further realizing the economic, flexible and efficient operation of DIES.
•Clarified the interest game pattern based on the hierarchically partitioned structure.•Established the master-slave game based bilevel optimization model of DIES.•Proposed a hierarchically partitioned coordinated operation method for DIES.•Analysed the effects of energy interaction constraints and source-load uncertainties.
Metal-organic frameworks (MOFs) derived nanomaterials have attracted widespread interest due to their unique properties. This article emphasizes the primary routines to improve the performance of MOF ...derivatives. Their environmental applications in particular for wastewater treatment, air purification and target-specific sensing are comprehensively summarized. In addition, the challenges and perspectives in future work are proposed.
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•An overview of the primary strategies to improve the performance of MOF-derived nanomaterials.•General discussion on recent progress of environmental cleaning and monitoring over MOF-derived nanomaterials.•The challenges and prospects related to MOF-derived porous materials for environmental applications.
Metal–organic frameworks (MOFs) as a new class of crystalline porous materials, composing of metal nodes and organic linkers, have been extensively used as versatile precursors or sacrificial templates for the preparation of numerous nanomaterials. The advantages of these MOF-derived nanomaterials such as controllable composition, tunable structure and high porosity endow them with enormous potential in many areas, including catalysis, sensors, energy storage and conversion. Herein, MOF derivatives in environment related fields are highly emphasized. The fundamental properties and general background of these nanomaterials are summarized. The primary strategies involved in compositional manipulation, pre-synthetic modulation, morphology control and post-synthetic treatment to improve the performance of MOF-derived nanomaterials are highlighted. In addition, we systematically discuss their recent progress in environmental cleaning and monitoring, especially for the wastewater treatment, air purification and target-specific sensing. Finally, the challenges and prospects of MOF-derived nanomaterials are also proposed. This article gives a comprehensive overview of MOF-derived nanomaterials for environmental applications and is expected to shed light on the further study in this highly exciting area.
With the rapid advancement of the Internet of Things, network security has garnered increasing attention from researchers. Applying deep learning (DL) has significantly enhanced the performance of ...Network Intrusion Detection Systems (NIDSs). However, due to its complexity and “black box” problem, deploying DL-based NIDS models in practical scenarios poses several challenges, including model interpretability and being lightweight. Feature selection (FS) in DL models plays a crucial role in minimizing model parameters and decreasing computational overheads while enhancing NIDS performance. Hence, selecting effective features remains a pivotal concern for NIDSs. In light of this, this paper proposes an interpretable feature selection method for encrypted traffic intrusion detection based on SHAP and causality principles. This approach utilizes the results of model interpretation for feature selection to reduce feature count while ensuring model reliability. We evaluate and validate our proposed method on two public network traffic datasets, CICIDS2017 and NSL-KDD, employing both a CNN and a random forest (RF). Experimental results demonstrate superior performance achieved by our proposed method.
A new electrochemical synthesis route was developed for the fabrication of Fe-containing layered double hydroxide (MFe-LDHs, M = Ni, Co and Li) hierarchical nanoarrays, which exhibit highly-efficient ...electrocatalytic performances for the oxidation reactions of several small molecules (water, hydrazine, methanol and ethanol). Ultrathin MFe-LDH nanoplatelets (200-300 nm in lateral length; 8-12 nm in thickness) perpendicular to the substrate surface are directly prepared within hundreds of seconds (<300 s) under cathodic potential. The as-obtained NiFe-LDH nanoplatelet arrays display promising behavior in the oxygen evolution reaction (OER), giving rise to a rather low overpotential (0.224 V) at 10.0 mA cm
with largely enhanced stability, much superior to previously reported electro-oxidation catalysts as well as the state-of-the-art Ir/C catalyst. Furthermore, the MFe-LDH nanoplatelet arrays can also efficiently catalyze several other fuel molecules' oxidation (
, hydrazine, methanol and ethanol), delivering a satisfactory electrocatalytic activity and a high operation stability. In particular, this preparation method of Fe-containing LDHs is amenable to fast, effective and large-scale production, and shows promising applications in water splitting, fuel cells and other clean energy devices.
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•N-doped biochars activated with ammonium chloride and ammonium acetate were prepared through microwave radiation.•N-doped biochars showed higher adsorption capacities of acid red 18 ...than non-doped biochar.•The π-π EDA interaction was attributed to the adsorption capacity increment.
Nitrogen-doped biochars derived from Phragmites australis (PA) were prepared using ammonium chloride (AC) and ammonium acetate (AA) as nitrogen sources by phosphoric acid activation via microwave assisted treatment. Their physicochemical properties, acid red 18 (AR18) adsorption performance and possible mechanisms were systematically evaluated. Nitrogen was successfully doped onto the biochar’s surface in the formation of pyrrole-N, pyridine-N and oxidized-N with pyridine-N being the major component (64%). The pHiep and basic foundational groups of the biochars increased consequently however their surface areas slightly decreased. The adsorption kinetic data were best fit to the pseudo-second order model and the equilibrium data were well simulated by Freundlich model for all biochars, indicating the important role of chemical interactions. The maximum AR18 adsorption capacities of PAB-AA and PAB-AC were 1.41 and 1.18 times higher compared with the non N-doped biochar, which were mainly attributed to the π-π EDA interaction between the pyridine-N and AR18 as revealed by the comparison of XPS analyses before and after AR18 adsorption. Meanwhile, other mechanisms such as pore filling effect, Lewis acid-base interaction, electrostatic attraction and hydrogen bonding also existed as demonstrated by BET, XPS and FTIR analyses.
We propose a generalization of the linear panel quantile regression model to accommodate both sparse and dense parts: sparse means that while the number of covariates available is large, potentially ...only a much smaller number of them have a nonzero impact on each conditional quantile of the response variable; while the dense part is represent by a low-rank matrix that can be approximated by latent factors and their loadings. Such a structure poses problems for traditional sparse estimators, such as the ℓ1 -penalized quantile regression, and for traditional latent factor estimators such as PCA. We propose a new estimation procedure, based on the ADMM algorithm, that consists of combining the quantile loss function with ℓ1 and nuclear norm regularization. We show, under general conditions, that our estimator can consistently estimate both the nonzero coefficients of the covariates and the latent low-rank matrix. This is done in a challenging setting that allows for temporal dependence, heavy-tail distributions and the presence of latent factors. Our proposed model has a "Characteristics + Latent Factors" Quantile Asset Pricing Model interpretation: we apply our model and estimator with a large-dimensional panel of financial data and find that (i) characteristics have sparser predictive power once latent factors were controlled and (ii) the factors and coefficients at upper and lower quantiles are different from the median.
Genetic pleiotropy refers to the simultaneous association of a gene with multiple phenotypes. It is widely distributed in the whole genome and can help to understand the common genetic mechanism of ...diseases or traits. In this study, a multivariate response best-subset selection (MRBSS) model based pleiotropic association analysis method is proposed. Different from the traditional genetic association model, the high-dimensional genotypic data are viewed as response variables while the multiple phenotypic data as predictor variables. Moreover, the response best-subset selection procedure is converted into an 0-1 integer optimization problem by introducing a separation parameter and a tuning parameter. Furthermore, the model parameters are estimated by using the curve search under the modified Bayesian information criterion. Simulation experiments show that the proposed method MRBSS remarkably reduces the computational time, obtains higher statistical power under most of the considered scenarios, and controls the type I error rate at a low level. The application studies in the datasets of maize yield traits and pig lipid traits further verifies the effectiveness.
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Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
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