In order to improve cloud detection capabilities under small sample conditions, in this paper, a cloud detection and evaluation method was proposed. First, a multi-feature channel weighting and feature fusion structure based on U-net was designed to more effectively extract and integrate key information. Secondly, the quantity of cloud cover differences greater than $\mathrm{X} \%$ has been proposed as a key indicator for performance evaluation, which is closer to actual application needs. Thirdly, a method for constructing small sample datasets was designed to improve the efficiency of model training. Several experimental cases show that the dataset constructed combined with the proposed multi-feature channel weighting and feature fusion structure significantly improved the performance of cloud detection under the evaluation metrics.

The Fenton process is widely used in the advanced treatment of municipal wastewater (such as waste leachate) with complex organic compositions because of its high efficiency in removing dissolved organic matter (DOM). However, actual wastewater contains high concentrations of Cl- , the effect of which on the Fenton process mechanism is unclear. We investigated the effect of Cl-on the formation mechanism of chlorinated DOM (ClDOM) during advanced treatment of biologically treated waste leachate (BTL) by the Fenton process via Fourier transform ion cyclotron resonance mass spectrometry. We found that increased Cl- concentration decreases the effectiveness of DOM mineralization and produces many species of Cl-DOM, both known and unknown. Elevated Cl-concentration decreases the amount of center dot OH, the reactive oxygen species in the Fenton process, producing radical chlorine species instead. This weakens the demethylation, (de)carboxylation, and (de)hydroxylation pathways for DOM degradation while enhancing chlorine substitution and addition reactions, which generate ClDOM. Increasing the amount of H2O2 to provide more available center dot OH increases the vigor of the degradation reactions, but Cl-DOM is still primarily transformed from macromolecules to smaller ones. This study provides theoretical support for the prevention and control of Cl-DOM in Fenton processes on complex DOM in BTL with high concentrations of Cl-.

Although hydroxyl radicals ( OH) degrade organic pollutants nonselectively, their mineralization rate during the treatment of waste leachate biological treatment effluent (BTL) using Fenton or Fenton-like systems is not high, and the reason is unknown. In this study, we investigated three typical Fenton-like systems that act on dissolved organic matter (DOM) in BTL. We analyzed the molecular composition of DOM resistant to OH, using ultrahigh resolution mass spectrometry. We find that DOM resistant to OH is more oxidized, less unsaturated/aromatic, has higher molecular weights, and contains more unsaturated oxygen-containing functional groups than does DOM reactive to OH. Resistant-DOM is further categorized into DOM derived by the action of OH (DOMderived) and DOM initially present (DOMintrinsic), whose quantities account for approximately 20% and 80 %, respectively. The DOMderived is gradually removed under extended reaction time, while DOMintrinsic is relatively unreactive with OH and is always present in the treated effluent. Based on the molecular composition of resistant-DOM, we propose a method to increase the mineralization rate (up to 95 % TOC removal with only 5 mM persulfate). This study provides direct evidence for the first time that the presence of resistant-DOM (mainly stemming from DOMintrinsic) in BTL is an important reason for the unideal mineralization rate in the advanced treatment of Fenton or Fenton-like systems.

To improve the yield and quality of rice grown on saline-alkali soil, a meta-analysis combined with micro-district experimental studies was conducted in China to examine the impact of humic acid-based organic fertilizer and chemical fertilizer on rice yield and quality. This study employed a two-factor fully randomized experimental design, incorporating four levels of humic acid (F0, 0.0 g/pot; F1, 4.8 g/pot; F2, 12.0 g/pot; and F3, 19.2 g/pot) and three levels of chemical fertilizer (A1, full conventional dosage; A2, 85% of conventional dosage; and A3, 70% of conventional dosage). The meta-analysis revealed that the application of organic fertilizer (at a rate of 1500-3000 kg/hm2) combined with chemical fertilizer had a significantly positive effect on the theoretical yield, tiller number, partial factor productivity, and SPAD value of rice. Temperature, organic fertilizer application, and chemical fertilizer levels were identified as critical factors affecting rice yield. The micro-experiments demonstrated that the application of humic acid organic fertilizer with treatment F3 significantly elevated the SPAD value at the full heading and grain filling stages. Increased panicle number and seed-setting rate were the main contributors to the rise in yield, with the F3 treatment yielding the highest overall. The effective leaf area, high-efficiency leaf area, and dry matter accumulation in rice treated with F3 were all higher compared with the F0 treatment. Our findings indicated that the addition of humic acid organic fertilizer can markedly improve the partial factor productivity and agronomic efficiency of rice. In conclusion, the application of F3 organic fertilizer combined with A3 chemical fertilizer (F3A3) significantly increased the yield of saline-alkali rice, which was 6.62% higher than that of the F0A1 treatment, thereby validating the meta-analysis outcomes. We propose that the combined use of humic acid organic fertilizer and chemical fertilizer can promote the growth of rice in saline-alkali soils. Consequently, these management practices provide a means to foster the green and healthy development of rice in saline-alkali regions across China.

Investigating the critical role of carbon cycling feedback to warming is essential for understanding future biosphere development. One of the current challenges is that the warming effect on carbon cycling is inconsistent across various aquatic ecosystems. It was postulated that the composition of dissolved organic matter (DOM) and the microbial community influenced the response of carbon metabolism to warming. To test our hypothesis, we conducted a microcosm study in which three key factors were manipulated: initial DOM composition (adjusting the ratio of autochthonous and allochthonous substrates), bacterioplankton community history (characterized by two distinct sources of bacterioplankton community), and temperature (ambient and 4 °C warming). The results demonstrated that the initial composition of DOM exerted a dominant influence on carbon metabolism. In contrast, the history of bacterioplankton community influenced the active taxa and functional traits. The log-response ratio approach revealed that the warming treatment affected bacterial carbon demand (BCD) and bacterial growth efficiency (BGE). A piecewise structural equation model further validated the paths by which warming altered BCD, particularly by changing the consumption of fluorescent DOM, and altered BGE, by affecting the active bacterioplankton. Our study demonstrated that the impact of warming on carbon cycling was context-dependent, with particular relevance to the history and dynamics of bacterioplankton community in this process. Given ongoing changes in lacustrine environments, a more comprehensive understanding of the interactions between DOM and microbes is essential for the accurate prediction of future carbon cycling.

Dissolved organic matter (DOM), the most reactive fraction of forest soil organic matter, is increasingly impacted by wildfires worldwide. However, few studies have quantified the temporal changes in soil DOM quantity and quality after fire. Here, soil samples were collected after the Qipan Mountain Fire (3-36 months) from pairs of burned and unburned sites. DOM contents and characteristics were analyzed using carbon quantification and various spectroscopic and spectrometric techniques. Compared with the unburned sites, burned sites showed higher contents of bulk DOM and most DOM components 3 months after the fire but lower contents of them 6-36 months after the fire. During the sharp drop of DOM from 3 to 6 months after the fire, carboxyl-rich alicyclic molecule-like and highly unsaturated compounds had greater losses than condensed aromatics. Notably, the burned sites had consistently higher abundances of oxygen-poor dissolved black nitrogen and fluorescent DOM 3-36 months after the fire, particularly the abundance of pyrogenic C2 (excitation/emission maxima of <250/∼400 nm) that increased by 150% before gradually declining. This study advances the understanding of temporal variations in the effects of fire on different soil DOM components, which is crucial for future postfire environmental management.

High altitude platform (HAP), known as line-of-sight dominated communications, effectively enhance the spectral efficiency of wireless networks. However, the line-of-sight links, particularly in urban areas, may be severely deteriorated due to the complex communication environment. The reconfigurable intelligent surface (RIS) is employed to establish the cascaded-link and improve the quality of communication service by smartly reflecting the signals received from HAP to users without direct-link. Motivated by this, the joint precoding scheme for a novel RIS-aided beamspace HAP with non-orthogonal multiple access (HAP-NOMA) system is investigated to maximize the minimum user signal-to-leakage-plus-noise ratio (SLNR) by considering user fairness. Specifically, the SLNR is utilized as metric to design the joint precoding algorithm for a lower complexity, because the isolation between the precoding obtainment and power allocation can make the two parts be attained iteratively. To deal with the formulated non-convex problem, we first derive the statistical upper bound on SLNR based on the random matrix theory in large scale antenna array. Then, the closed-form expressions of power matrix and passive precoding matrix are given by introducing auxiliary variables based on the derived upper bound on SLNR. The proposed joint precoding only depends on the statistical channel state information (SCSI) instead of instantaneous channel state information (ICSI). NOMA serves multi-users simultaneously in the same group to compensate for the loss of spectral efficiency resulted from the beamspace HAP. Numerical results show the effectiveness of the derived statistical upper bound on SLNR and the performance enhancement of the proposed joint precoding algorithm.

Organosulfates (OSs) are an important component of secondary organic aerosols (SOA), accounting for ~30% of total organic aerosol. In this study, OSs in eastern China were investigated to understand their diurnal evolution, source, and volatility using high-resolution mass spectrometry. In polluted days, we identified a total of 5147 organic molecules, including 1206 OS molecules. The average molecular weight (m.w.) and carbon chain length of OSs in this study exceeded the commonly recognized range (500 Da). OSs were mostly composed of newly formed low oxidation state compounds as well as aged aliphatic and aromatic ones. The number and abundance of aromatic and aliphatic OSs with low saturation, volatility, O/Cw as well as H/Cw increased greatly with rising PM2.5 concentrations. The daytime photo-oxidation resulted in a large number of high m.w. (HMW, > 500 Da) OSs. OSs with m.w. <500 Da, and many oxygen atoms were newly generated during the nighttime, mainly dominated by liquid-phase oxidation processes. The result of OSs with higher m.w. and lower volatility was due to increased dimerization and oligomerization. During pollution formatting, OSs with small DBE values (between 0 and 6) appeared; meanwhile, the number of highly unsaturated OSs with DBE > 7 (mainly aromatic OSs) increased by about 34%. This study is useful for clarifying the secondary formation and properties of HMW OSs in a polluted environment in China.

This paper analyzes and optimizes the average Age of Information (AAoI) of Frame Slotted ALOHA with Reservation and Data slots (FSA-RD) in a multi-access network, where multiple users transmit their randomly generated status updates to a common access point in a framed manner. Each frame consists of one reservation slot and several data slots. The reservation slot is further split into several mini-slots. In each reservation slot, users that want to transmit a status update will randomly send short reservation packets in one of the mini-slots to contend for data slots of the current frame. The reservation is successful only if one reservation packet is sent in a mini-slot. The data slots are then allocated to those users that succeed in the reservation slot. In the considered FSA-RD scheme, one user with a status update for transmission, termed active user, may need to perform multiple reservation attempts before successfully delivering it. As such, the number of active user(s) in different frames are dependent and thus the probability of making a successful reservation varies from frame to frame, making the AAoI analysis non-trivial. We manage to derive an analytical expression of AAoI for FSA-RD by characterizing the evolution of the number of active user(s) in each frame as a discrete-time Markov chain. We then consider the FSA-RD scheme with one reservation attempt per status update, termed FSA-RD-One. Thanks to the independent frame behaviors of FSA-RD-One, we attain a closed-form expression for its AAoI, which is further used to find the near-optimal reservation probability. Our analysis reveals the impact of key protocol parameters, such as frame size and reservation probability, on the AAoI. Simulation results validate our analysis and show that the optimized FSA-RD outperforms the optimized slotted ALOHA.

热活化过硫酸盐(Heat/PDS)体系因能有效去除垃圾渗滤液浓缩液中溶解性有机物(DOM)而备受关注,但限于此类实际废水组分极其复杂.其转化机理尚需进一步研究.本文采用具有超高分辨率的静电场轨道阱质谱从分子组成的角度研究了垃圾渗滤液浓缩液中DOM在Heat/PDS体系的转化特性.结果表明,经Heat/PDS体系处理后,垃圾渗滤液浓缩液中DOM分子式从3732种减少至2984种,出水中DOM具有低芳香性、高饱和程度和高氧化程度的特性,降解途径包括:去芳香化、去甲基化、氢提取和羧化反应等.此外,出水中DOM包含1837种未知氯代有机物(CHOCl、CHONCl、CHOSCl和CHONSCl类),其前驱体主要为垃圾渗滤液浓缩液中DOM氧化降解的中间产物,如低氧高度不饱和酚类及脂肪族DOM.本研究可为垃圾渗滤液浓缩液中DOM的处理和氯代有机物的阻控提供一定理论依据.

Heating temperature (HT) during forest fires is a critical factor in regulating the quantity and quality of pyrogenic dissolved organic matter (DOM). However, the temperature thresholds at which maximum amounts of DOM are produced (TTmax) and at which the DOC gain turns into net DOC loss (TT0) remain unidentified on a component-specific basis. Here, based on solid-state 13C nuclear magnetic resonance, absorbance and fluorescence spectroscopies, and Fourier transform ion cyclotron resonance mass spectrometry, we analyzed variations in DOM composition in detritus and soil with HT (150-500 °C) and identified temperature thresholds for components on structural, fluorophoric, and molecular formula levels. TTmax was similar for detritus and soil and ranged between 225 and 250 °C for bulk dissolved organic carbon (DOC) and most DOM components. TT0 was consistently lower in detritus than in soil. Moreover, temperature thresholds differed across the DOM components. As the HT increased, net loss was observed initially in molecular formulas tentatively associated with carbohydrates and aliphatics, then proteins, peptides, and polyphenolics, and ultimately condensed aromatics. Notably, at temperatures lower than TT0, particularly at TTmax, burning increased the DOC quantity and thus might increase labile substrates to fuel soil microbial community. These composition-specific variations of DOM with temperature imply nonlinear and multiple temperature-dependent wildfire impacts on soil organic matter properties.

This paper describes the design and characteristics of a three-chamber electromagnetic-driven peristaltic micropump based on 3D-printing technology. The micropump is composed of an NdFeB permanent magnet, a polydimethylsiloxane (PDMS) film, a 3D-printing pump body, bolts, electromagnets and a cantilever valve. Through simulation analysis and experiments using a single chamber and three chambers, valved and valveless, as well as different starting modes, the results were optimized. Finally, it is concluded that the performance of the three-chamber valved model is optimal under synchronous starting conditions. The measurement results show that the maximum output flow and back pressure of the 5 V, 0.3 A drive source are 2407.2 μL/min and 1127 Pa, respectively. The maximum specific flow and back pressure of the micropump system are 534.9 μL/min∙W and 250.4 Pa/W, respectively.

利用三维荧光和高分辨质谱等手段分析某炼油化工企业炼化废水处理厂不同来源污水(炼油废水、酸性废水、化工废水)可溶有机质(DOM)的分子组成.结果表明,炼油废水DOM浓度低且极性化合物以含氧类化合物为主;酸性废水、化工废水DOM浓度较高,检测到高丰度的表面活性剂及其衍生物为主的聚合物类等多氧含硫类化合物.对不同来源废水在水解酸化、生化和臭氧催化氧化单元工艺中的DOM变化规律进行研究,发现分子缩合度较低的化合物及多氧含硫类化合物在水解酸化工艺中能得到有效降解;生化处理后86％的DOM得到降解,其中分子缩合度低,在荧光光谱中显示类酪氨酸类特征的化合物在生化单元中得到有效去除;臭氧催化氧化工艺对类腐殖酸具有良好去除效果.此外研究发现,废水经生化单元处理,其DOM去除效率、荧光基团及极性化合物变化规律不受进水水质影响;类色氨酸类和多氧含硫类化合物等难降解有机物,是影响废水可生化性能及处理达标的关键因素.

溶解性有机质(Dissolved organic matter, DOM)在全球碳循环中扮演重要角色, 对其化学组成的深入分析是研究其环境及生物地球化学行为及意义的基础. DOM是一类组成十分复杂的有机质混合物, 其分子组成研究一直是分析化学领域的难题. 傅里叶变换离子回旋共振质谱(Fourier transform ion cyclotron resonance mass spectrometry, FT-ICR MS)作为目前分辨率最高的质谱, 其发展与应用为分子水平识别DOM的化学组成提供了变革性的支撑. 本文从FT-ICR MS技术、DOM样品前处理方法、质谱电离技术、数据采集、数据处理与表达、分子结构表征等方面总结了基于FT-ICR MS研究DOM分子组成的进展, 重点围绕本课题组的相关工作, 介绍该技术在地球科学、环境科学及环境工程等领域的应用情况, 并展望了未来的研究方向.

Quantum digital signatures (QDS) are able to verify the authenticity and integrity of a message in modern communication. However, the current QDS protocols are restricted by the fundamental rate-loss bound and the secure signature distance cannot be further improved. We propose a twin-field quantum digital signature (TF-QDS) protocol with fully discrete phase randomization and investigate its performance under the two-intensity decoy-state setting. For better performance, we optimize intensities of the signal state and the decoy state for each given distance. Numerical simulation results show that our TF-QDS with as few as six discrete random phases can give a higher signature rate and a longer secure transmission distance compared with current quantum digital signatures (QDSs), such as BB84-QDS and measurement-device-independent QDS (MDI-QDS). Moreover, we provide a clear comparison among some possible TF-QDSs constructed by different twin-field key generation protocols (TF-KGPs) and find that the proposed TF-QDS exhibits the best performance. Conclusively, the advantages of the proposed TF-QDS protocol in signature rate and secure transmission distance are mainly due to the single-photon interference applied in the measurement module and precise matching of discrete phases. Besides, our TF-QDS shows the feasibility of experimental implementation with current devices in practical QDS system.

In this article, we propose a low-complexity quantum principal component analysis (qPCA) algorithm. Similar to the state-of-the-art qPCA, it achieves dimension reduction by extracting principal components of the data matrix, rather than all components of the data matrix, to quantum registers, so that the samples of measurement required can be reduced considerably. Both our qPCA and Lin’s qPCA are based on quantum singular-value thresholding (QSVT). The key of Lin’s qPCA is to combine QSVT, and modified QSVT is to obtain the superposition of the principal components. The key of our algorithm, however, is to modify QSVT by replacing the rotation-controlled operation of QSVT with the controlled-not operation to obtain the superposition of the principal components. As a result, this small trick makes the circuit much simpler. Particularly, the proposed qPCA requires three phase estimations, while the state-of-the-art qPCA requires five phase estimations. Since the runtime of qPCA mainly comes from phase estimations, the proposed qPCA achieves a runtime of roughly 3/5 of that of the state of the art. We simulate the proposed qPCA on the IBM quantum computing platform, and the simulation result verifies that the proposed qPCA yields the expected quantum state.

A 64-channel detection system for laser-induced fluorescence (LIF) detection at the cell level is established and applied to single event counting. Generally, fluorescence detection at the cellular level requires a dyeing label to enhance the scattered light intensity for the photodetector. However, the dyeing labels, such as fluorophores, probes, and dyes, complicate sample preparation and increase cytotoxicity in the process. Therefore, label-free detection becomes essential for in vivo research. The presented 64-channel detection system is designed for label-free detection with the ability to record feeble emissions. Two linear photodetector devices are included in the system, extending the wavelength detection range to 366-680 nm with an improved spectral resolution at an average of 4.9 nm. The performance of the system was validated by detecting unlabeled human hepatocytes (L-02) and other cell-level biologic samples. In addition, the 64-channel detection system was also used for particle counting with a quartz microfluidic chip. The counting method is based on fluorescence spectra differs from those of other devices (i.e., flow cytometry and cell-sorting equipment), which use isolated irradiance intensities.

Dissolved organic matter (DOM) in soils drives biogeochemical cycling and soil functions in different directions depending on its molecular signature. Notably, there is a distinct paucity of information concerning how the molecular signatures of soil DOM vary with different degrees of weathering across wide geographic scales. Herein, we resolved the DOM molecular signatures from 22 diverse Chinese reference soils and linked them with soil organic matter and weathering-related mineralogical properties. The mixed-effects models revealed that the yields of DOM were determined by soil organic carbon content, whereas the molecular signature of DOM was primarily constrained by the weathering-related dimension. The soil weathering index showed a positive effect on the lability and a negative effect on the aromaticity of DOM. Specifically, DOM in highly weathered acidic soils featured more amino sugars, carbohydrates, and aliphatics, as well as less O-rich polyphenols and condensed aromatics, thereby conferring a higher DOM biolability and lower DOM aromaticity. This study highlights the dominance of the weathering-related dimension in constraining the molecular signatures and potential functions of DOM in soils across a wide geographic scale.

Currently, most scene classification algorithms are trained and evaluated based on a single dataset. However, practical applications are not usually restricted to specific satellite platforms or datasets. Researchers generally train a model on one dataset and require the model to perform tasks with another dataset, leading to a data shift problem and performance decrease in practical applications. To address this problem, this study presents a metric-based few-shot classification method with L-2-norm prototypical networks. Specifically, a carefully designed L-2-norm layer was introduced into prototypical networks. The proposed L-2-norm layer applies L-2-norm operations to prototypes and query features to mitigate the length fluctuations caused by the data shift problem. With this layer, the L-2-norm prototypical networks maintain the ability to identify novel classes and limit the effects of data discrepancies. The proposed L-2-norm layer improves the classification accuracy by 0.42% to 2.41% on various public datasets. Moreover, L-2-norm prototypical networks outperform other methods by 0.02% to 34.38%. Comprehensive experiments consistently demonstrate the advantages of the proposed method in tackling the data shift problem.

A kind of electric and pneumatic joint control system for transport robot was proposed, and the system implementation was given. A transport robot and a 3D model built by SolidWorks were provided to illustrate the control system. The control system adopted the driving method of motor and cylinder, and took STM32 microcontroller as the control core. In order to improve the control precision and compliance of the system, the position loop and speed loop were used to establish the double closed loop PID control. In order to verify the performance of the system, 25 handling experiments were carried out for four kinds of box workpiece with mass of 1kg, 2kg, 3kg and 4kg respectively. The results show that the system can control the transport robot to complete the handling of the box workpiece. The system has a fast response and it is stable.