The distribution characteristics of phosphorus （P） forms in the sediment profile of Lake Erhai, in southwestern China has been investigated by sequential extraction and 31p nuclear magnetic resonance ...spectroscopy （NMR） of NaOH extracts to understand P dynamics and its potential contribution to lake eutrophication. Contents of P fractions varied in the order of NH4C1 extracted P （NH4C1- P） 〈 bicarbonate-dithionite extracted P （BD-P） 〈 HC1-P, Residual-P 〈 NaOH extracted P （NaOH-P）. The highly available NH4C1-P represented less than 1% of total P （TP）. BD-P and NaOH extracted reactive P （NaOH-rP） averaged 39%, while the ratio of Fe/P was higher than 15, indicating low P release from the sediments under permanent oxic condition. The less bio-available HC1-P, NaOH extracted nonreactive P （NaOH-nrP） and residual-P contributed 61% of TP. Regression analysis revealed that BD-P, NaOH-rP and HC1-P were positively correlated with the contents of Fe and Mn, A1 and Fe, and Ca, respectively. The investigation of P compound groups in NaOH extracts by 31p NMR showed that ortho-P and monoester-P were the largest two constituents of the P pool, followed by diester-P, phosphonate and pyro-P. A comparison of vertical variations of P groups in the sediment profile suggested that these compounds were involved in the P recycling to different extents in Lake Erhai. In particular, the lake exhibits high potential for labile P release from the surface sediments, which should be taken into consideration even after the outsourced P runoff ceased.
The removal of algal organic matter (AOM) through water treatment processes is a major approach of reducing the formation of disinfection by-products (DBP). Here, the formation of DBP from AOM in ...karst water under different combination of potassium permanganate (KMnO4) and polyaluminium chloride (PACl) was investigated. The effect of divalent ions (Ca2+ and Mg2+) on DBP formation was traced by AOM chemistry variations. For DBP formation after KMnO4 preoxidation, total carbonaceous DBPs (C-DBPs) decreased by 12.9% but nitrogen-containing DBPs (N-DBPs) increased by 18.8%. Conversely, the C-DBPs further increased by 3.3% but N-DBPs reduced by 10.7% after the addition of PACl besides KMnO4 preoxidation. The variations of aromatic protein-like, soluble microbial products-like compounds and ultraviolet absorbance at 254 nm (UV254) were highly correlated with the formation of DBPs, which suggest aromatic substances strongly affect DBP behaviors at different treatment conditions. In the presence of divalent ions (Ca2+=135.86 mg/L, Mg2+=18.51 mg/L), the combination of KMnO4 and PACl was more effective in controlling DBP formation compared to the situation without Ca2+ and Mg2+. Specifically, trichloromethane formation was largely inhibited compared to the other tested DBPs, which may refer to complexation of electron-donating groups via divalent ions. While Ca2+ and Mg2+ may not affect the nature of α-carbon and amine groups, so the variation of haloacetonitriles (HANs) was not obvious. The study enhances the understanding of the DBP formation patterns, transformation of carbon and nitrogen by preoxidation-coagulation (KMnO4-PACl) treatment in algae-laden karst water.The removal of algal organic matter (AOM) through water treatment processes is a major approach of reducing the formation of disinfection by-products (DBP). Here, the formation of DBP from AOM in karst water under different combination of potassium permanganate (KMnO4) and polyaluminium chloride (PACl) was investigated. The effect of divalent ions (Ca2+ and Mg2+) on DBP formation was traced by AOM chemistry variations. For DBP formation after KMnO4 preoxidation, total carbonaceous DBPs (C-DBPs) decreased by 12.9% but nitrogen-containing DBPs (N-DBPs) increased by 18.8%. Conversely, the C-DBPs further increased by 3.3% but N-DBPs reduced by 10.7% after the addition of PACl besides KMnO4 preoxidation. The variations of aromatic protein-like, soluble microbial products-like compounds and ultraviolet absorbance at 254 nm (UV254) were highly correlated with the formation of DBPs, which suggest aromatic substances strongly affect DBP behaviors at different treatment conditions. In the presence of divalent ions (Ca2+=135.86 mg/L, Mg2+=18.51 mg/L), the combination of KMnO4 and PACl was more effective in controlling DBP formation compared to the situation without Ca2+ and Mg2+. Specifically, trichloromethane formation was largely inhibited compared to the other tested DBPs, which may refer to complexation of electron-donating groups via divalent ions. While Ca2+ and Mg2+ may not affect the nature of α-carbon and amine groups, so the variation of haloacetonitriles (HANs) was not obvious. The study enhances the understanding of the DBP formation patterns, transformation of carbon and nitrogen by preoxidation-coagulation (KMnO4-PACl) treatment in algae-laden karst water.
We study the stationary points and local geometry of gradient play for stochastic games (SGs), where each agent tries to maximize its own total discounted reward by making decisions independently ...based on current state information which is shared between agents. Policies are directly parameterized by the probability of choosing a certain action at a given state. We show that Nash equilibria (NEs) and first-order stationary policies are equivalent in this setting by establishing a gradient domination condition for SGs. We characterize the structure of strict NEs and show that gradient play locally converges to strict NEs within finite steps. Further, for a subclass of SGs called Markov potential games, we prove that strict NEs are local maxima of the total potential function, thus locally stable under gradient play, and fully-mixed NEs are saddle points, thus unstable under gradient play.
Sodium ion batteries (SIBs) are considered promising alternatives to lithium ion batteries for grid‐scale and other energy storage applications because of the broad geographical distribution and low ...cost of sodium relative to lithium. Here, fabrication and characterization of high gravimetric and volumetric capacity 3D Ni‐supported Sb2O3 anodes for SIBs are presented. The electrodes are prepared by colloidal templating and pulsed electrodeposition followed by heat treatment. The colloidal template is optimized to provide large pore interconnects in the 3D scaffold to enable a high active materials loading and accommodate a large volume expansion during cycling. An electrodeposited loading of 1.1 g cm−3 is chosen to enable a combined high gravimetric and volumetric capacity. At this loading, the electrodes exhibit a specific capacity of ≈445 mA h g−1 and a volumetric capacity of ≈488 mA h cm−3 with a capacity retention of 89% after 200 cycles at 200 mA g−1. The stable cycling performance can be attributed to the 3D metal scaffold, which supports active materials undergoing large volume changes, and an initial heat treatment appears to improve the adhesion of the Sb2O3 to the metal scaffold.
3D Ni‐supported Sb2O3 electrodes show high gravimetric and volumetric capacity anodes for sodium ion batteries. The electrodes show considerable specific and volumetric capacities with good cycling performance, demonstrating that a 3D conductive scaffold with an engineered‐free volume can accommodate volume changes during cycling and increase active materials loading.
In this paper, a self-organizing RBF (SORBF) neural network with an adaptive threshold is proposed based on improved particle swarm optimization (IPSO) and neural strength (NS). The parameters and ...structure of SORBF can be optimized simultaneously and dynamically. Moreover, the tiresome problem of threshold setting is solved. Firstly, the network size and parameters of SORBF are mapped into the particle information of PSO. Secondly, an IPSO algorithm, based on diversity inertia weight and elite knowledge guiding, is proposed to reduce the probability of the population falling into the local optimum. Then, IPSO is used for optimizing the parameters of SORBF. Based on neuron growth intensity and competition intensity, SORBF can realize the hidden neuron addition and deletion adaptively. Moreover, the thresholds during the structure adjustment can be provided adaptively based on the network scale and neuron strength, which avoids the subjectivity setting and can improve the adaptive ability. Finally, the convergence analysis of IPSO is provided to ensure the performance of SORBF. Experiment results show that the proposed SORBF has good self-organizing ability and compact network structure compared with other methods.
As functionally gradient materials (FGMs) reveal innovative mechanical properties, they have aroused huge interest in multiple industry areas. In this study, a hybrid manufacturing (HM) technique ...that combines a directed energy deposition (DED)-type additive manufacturing (AM) fabrication process with milling-type machining is investigated. In the DED process examined, Inconel 718 (IN718) and stainless steel 316L (SS316L) metal powders were blown into the molten pool at different and varying respective flow rates to achieve specific composition ratios for different printed layers so that a smooth gradient transition from SS316L to IN718 was achieved. Due to the attendant generation of rough surfaces common to such FGMs, partition milling was employed after fabrication, and the cutting temperatures and forces were simultaneously recorded considering the significant anisotropy in mechanical properties. The surface roughness of each FGM gradient section and tool wear mechanism were also measured after machining. Through analysis of the experimental results, the machining mechanism was revealed, which provides new insights into the machinability of SS316L/IN718 FGMs.
Low-molecular-weight organic acids (LMWOAs) in eutrophic lake water of Dianchi, Southwestern China Plateau were investigated diurnally and vertically using ion chromatography. Two profiles (PI and ...P2) were studied due to the difference of hydrochemical features. Lactic, formic, pyruvic and oxalic acid were detected as major components at PI and P2 which were on average 7.98 and 6.53 μmol/L, respectively, corresponding to their proportions of 2.68% and 2.48% relative to DOC. Pyruvic acid was regarded as the uppermost species at PI and P2, reaching up to 3.82 and 3.35 μmol/L and accounting for 47.9% and 51.3%, respectively, in individual TOA. Although humus were of biogenetic production at both sites, the significant negative correlation between diurnal variations of TOAs, fluorescence intensity (FI) of protein-like components and humic-like components at PI indicated LMWOAs were greatly originated from bacterioplankton excretion and degradation. However, correlations between diurnal variations of humic-like FI and physicochemical parameters demonstrated algal origination of LMWOAs at P2. Although content of humus was high, TOA at P2 was 1.45 μmol/L lower than that at PI, due to the co-influence of more intense photo-oxidation and aggregation at P2. Therefore, TOAs exhibited quite opposite diurnal variation trends of increasing-decreasing and decreasing-increasing at PI and P2, respectively. Except for impact of solar radiation, bacterial decomposition and assimilation rendered shifts of maximal LMWOAs along water column at PL Covering with massive algae, UV rays penetrated shallower depth that LMWOAs assembled in surface layer water before 18:00 at P2 and represented decreasing profiles.
Model predictive control (MPC) offers promising solutionsfor the smart control of natural ventilation. However, challenges arise in constructing precise models for such nonlinear systems, preserving ...accuracy over a long-prediction horizon while capturing short-term dynamics, and handling disturbances uncertainties. This study proposes a novel Ensembled Multi-time scale deep-learning-based Adaptive Model Predictive Control (EMA-MPC) system. It integrates an ensembled Long-Short-Term Memory (ensembled-LSTM) model, comprising two LSTM models for fast and slow time-scale dynamics, respectively, and continuously evolving to changing conditions through online model adaptation. A bound control module is incorporated as an additional safety mechanism ensuring the environmental control within the desired threshold during unforeseen scenarios. A multi-objective optimization problem is formulated to maintain indoor air temperature and CO2 concentration within the predefined comfort range while optimizing energy efficiency by controlling automated windows in a naturally ventilated room in winter. The EMA-MPC system demonstrates superior performance in balancing indoor air quality, temperature regulation, and energy efficiency. The ensembled-LSTM model significantly reduces the mean absolute error by 78.6% and 88.9% for CO2 and indoor air temperature predictions respectively, against a single LSTM model. The proposed EMA-MPC system achieves an 86% reduction in unmet CO2 hours compared to rule-based control and reduces occupied hours with temperature below 19 °C by 44% and 93% compared to enhanced MPC and basic MPC, respectively, while maintaining similar heating demand as other controllers. In conclusion, the proposed EMA-MPC system reduces modeling efforts and provides an effective approach towards reliable use of ML models in smart building control.
•Multi-objective optimal control of automatic windows for natural ventilation.•Ensembled multi-time scale deep-learning-based adaptive Model Predictive Control.•Online model adaptation and bound control to enhance robustness and reliability.
In this study, disinfection by-products (DBP) formation from dissolved organic matter (DOM) and its fractions, including both hydrophilic and hydrophobic components, were investigated at a typical ...karst surface water. The subsequent DBP formation potential was evaluated by deducing chemical characteristics of DOM fractions and representative algal organic matter (Chlorella sp. AOM) under the influence of divalent ions (Ca2+ and Mg2+) via spectra analysis. Both terrigenous and autochthonous DOM performed as critical DBP precursors, and DBP formation patterns were tightly correlated to organic matter chemical variations. DBP formation was significantly higher in drought period compared to that in wet period (P < 0.05). Particularly, trichloromethane (TCM) and dichloroacetonitrile (DCAN) showed distinct formation patterns compared to the scenarios in non-karst water. For DOM fractions, hydrophobic components showed higher DBP formation compared to hydrophilic counterparts, hydrophilic neutral enriched more reactive organic nitrogen for N-DBPs production. It was preferable to enrich humic-like substances after Ca2+ and Mg2+complexation in Chlorella sp. AOM, TCM formation increased whereas DCAN production remained unchanged in the presence of divalent ions. This study innovatively provided a linkage between chemical characteristics of DOM and understanding of DBP formation in karst surface water.
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•DBP formation from DOM and its fractions were investigated at karst surface water.•DOM characteristics responded to spatiotemporal DBPs formation.•TCM and DCAN formation was significantly higher in drought period than post-wet period.•Both flushed terrestrial and endogenous organic matter were important DBP precursors.•Ca2+ and Mg2+ complexation in AOM affects DBP formation.
This paper studies network LQR problems with system matrices being spatially-exponential decaying (SED) between nodes in the network. The major objective is to study whether the optimal controller ...also enjoys a SED structure, which is an appealing property for ensuring the optimality of decentralized control over the network. We start with studying the open-loop asymptotically stable system and show that the optimal LQR state feedback gain K is 'quasi'-SED in this setting, i.e. \left\| {{{K}_{ij}}} \right\|\sim O\left( {{e^{ - \frac{\beta }{{{\text{poly }}\ln (N)}}\operatorname{dist} (i,j)}}} \right). The decaying rate β depends on the decaying rate and norms of system matrices and the open-loop exponential stability constants. Then the result is further generalized to unstable systems under a stabilizability assumption. Building upon the 'quasi'-SED result on K, we give an upper-bound on the performance of κ-truncated local controllers, suggesting that distributed controllers can achieve near-optimal performance for SED systems. We develop these results via studying the structure of another type of controller, disturbance response control, which has been studied and used in recent online control literature; thus as a side result, we also prove the 'quasi'-SED property of the optimal disturbance response control which serves as a contribution on its own merit.
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